Patent Application
20200078759
The present disclosure is generally related to methods and systems for forming microcapsules having a liquid core and a solid shell, and, more particularly, to methods for forming such microcapsules using a drying chamber.
Microencapsulation refers to a process in which a first material or composition is enveloped by one or more second materials or compositions. The material inside the microcapsule is often referred to as the core, whereas the outer surface/layer of the microcapsule is sometimes also referred to as the shell. Microencapsulation of materials can provide a number of benefits, including protecting reactive substances in the core from the environment, separation of incompatible components, and/or controlling the release of the core material. Microencapsulation processes have been widely adopted in a variety of industries, including the agricultural, consumer goods, food, chemical and pharmaceutical industries.
A variety of microencapsulation processes exist, including solvent evaporation and extraction, cryogenic solvent extraction, interfacial polymerization, polyectrolyte complexation, and coacervation (which may occur by non-solvent addition, temperature change, incompatible polymer or salt addition, or polymer to polymer interaction), spray drying, spray chilling, spray desolvation, and supercritical fluid precipitation. See, e.g., Yeo, et. al, “Microencapsulation Methods for Delivery of Protein Drugs”, Biotechnol. Bioprocess Eng. (2001), 6:213-230 and Umner et al., “Microencapsulation: Process, Techniques, and Applications”, International Journal of Research in Pharmaceutical and Biomedical Sciences, (2011).
Spray drying is one of the more popular microencapsulation processes, particularly in the food industry. Poshadri et al., “Microencapsulation Technology: A Review”, J. Res. ANGRAU (2010). Some examples of spray drying processes and systems are described in U.S. Pat. Nos. 2,824,807; 4,187,617; 4,352,718; 4,963,226; 5,547,540; 5,487,916; and U.S. Publ. Nos.: 2012/0167410; 2014/0079747; and 2014/0086965.
There have been some attempts to use spray drying techniques to form microcapsules comprising a liquid core surrounded by a solid shell. For example, U.S. Publ. No. 2014/0342972 describes a process in which a polymeric shell solution comprising a mixture of water and ethanol is dried in heated air between 80° C. and 120° C. (in the examples). However, ethanol is a flammable material that can contribute to high volatile organic compounds (VOCs) in a drying process. Evaporation of ethanol at high temperatures in a spray dryer may also create explosion risks if the drying facility is not properly constructed. These facilities can be expensive to construct for commercial scale-up.
There are other challenges with forming liquid core microcapsules in a spray dryer. As the desired microcapsule size decreases, it can become increasingly difficult to control the kinetics, thermodynamics and hydrodynamics of liquid droplet formation in transient conditions in the time frame of 1 to 2 seconds (or less) during which the liquid droplets form. It is presently believed that some of the factors include: i) the fast time frame over which the liquid droplets form, ii) the small amount of water present, which may quickly evaporate from the shell liquid when forming small liquid droplets and microcapsules, iii) the presence of heat which can accelerate evaporation of the water from the shell liquid, iv) the changing make-up of the shell liquid as water evaporates, and v) turbulence of the gas in which liquid droplet formation occurs. As such, it would be advantageous to provide improved systems and methods for producing microcapsules comprising a liquid core and a solid shell.
The present disclosure may fulfill one or more of the needs described above by, in one embodiment, a method for producing microcapsules comprising providing a core liquid comprising one or more oils and one or more surfactants and providing a shell liquid comprising water, one or more surfactants and at least one wall forming material. The method further comprises forming a plurality of liquid droplets in a formation zone, wherein each of the plurality of liquid droplets comprise a core formed from the core liquid and a shell surrounding the core formed from the shell liquid, wherein the core liquid and shell liquid have a dynamic spreading coefficient greater than zero at 0.03 seconds, preferably at 0.1 seconds, and most preferably at 1 second. Water is evaporated from the plurality of liquid droplets within a drying zone of a drying chamber and microcapsules formed from the plurality of liquid droplets are collected.
Reference within the specification to “embodiment(s)” or the like means that a particular material, feature, structure and/or characteristic described in connection with the embodiment is included in at least one embodiment, optionally a number of embodiments, but it does not mean that all embodiments incorporate the material, feature, structure, and/or characteristic described.
Furthermore, materials, features, structures and/or characteristics may be combined in any suitable manner across different embodiments, and materials, features, structures and/or characteristics may be omitted or substituted from what is described. Thus, embodiments and aspects described herein may comprise or be combinable with elements or components of other embodiments and/or aspects despite not being expressly exemplified in combination, unless otherwise stated or an incompatibility is stated.
All percentage and ratios are calculated by weight unless otherwise stated. All percentages and ratios are calculated based on the total composition unless otherwise stated.
All ranges are inclusive and combinable. Every maximum numerical limitation given throughout this specification includes every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.
The number of significant digits conveys neither a limitation on the indicated amounts nor on the accuracy of the measurements. All numerical amounts are understood to be modified by the word “about” unless otherwise specifically indicated.
Unless otherwise indicated, all measurements are understood to be made at approximately 25° C. and at ambient conditions, where “ambient conditions” means conditions under about 1 atmosphere of pressure and at about 50% relative humidity.
“Benefit Agent” refers to the material, mixture or composition that forms at least part of a core of a microcapsule and provides an intended benefit to a target surface (e.g., skin, hair or fabrics) and/or delivers a benefit to a consumer.
“Benefit Agent Loading” refers to a weight average amount of benefit agent across a population of microcapsules measured using the Core Liquid Loading Test Method described herein.
“Bi-component Liquid Stream” refers to two liquid streams that are disposed in close proximity to one another. In some instances, the two liquid streams may be co-dispensed from a microfluidic device and/or are arranged in whole or partial contact with each other and/or are substantially concentric with respect to each another.
“Consumer Goods Composition” refers to any surfactant containing liquid composition intended for end use by a consumer.
“Core” refers to the inner volume of a liquid droplet or microcapsule that is bounded completely or almost completely by either a liquid or solid shell. The core and shell share an interface that defines the boundary of each. A non-limiting example of a microcapsule 10 having a core 12, shell 14 and interface 16 is shown in
“Core Liquid” refers to the liquid used to form the core of a liquid droplet. The core liquid may be a mixture of liquids.
“Core Liquid Loading” refers to a weight average amount of core liquid across a population of microcapsules measured using the Core Liquid Loading Test Method described herein. If the core liquid is also the benefit agent (e.g., the core liquid consists of or consists essentially of a perfume oil or a sensate oil), then the Core Liquid Loading may be the same as the Benefit Agent Loading.
“Core/Shell Ratio” refers to the ratio of the weight of the core of a microcapsule to the weight of the shell of a microcapsule.
“Depressed Glass Transition Temperature” or “Tgd” refers to the Glass Transition Temperature of the combination of a wall forming material of the shell liquid and the surfactant(s) of the shell liquid measured using the Depressed Glass Transition Temperature Test Method described herein.
“Drying Gas” refers to the gas within the drying zone. The drying gas may or may not be heated.
“Drying Zone” refers to a gaseous zone within a drying chamber. In certain embodiments, the drying gas is heated to facilitate evaporation of substantially all of the water from the shell of the liquid droplets.
“Dynamic Interfacial Tension” refers to an interfacial tension value, IFT (mN/m), that has an absolute (i.e., with the sign omitted) instantaneous rate of change /
(or line slope)>X at a particular time, T, wherein X is greater than 0.05 mN/m·s and T is the elapsed time from bubble formation (i.e., bubble surface age). In some instances, X may be greater than 0.5 mN/m·s, 1 mN/m·s, 2 mN/m·s or greater than 4 mN/m·s. In some instances, the interfacial tension is dynamic from time T=0.03 or 0.1 seconds to T=1, 0.75, 0.5 or 0.25 seconds.
“Dynamic Spreading Coefficient” refers to a spreading a coefficient value, S (mN/m), that has an absolute (i.e., with the sign omitted) instantaneous rate of change /
(or line slope)>X at a particular time, T, wherein X is greater than 0.05 mN/m·s and T is the elapsed time from bubble formation (i.e., bubble surface age). In some instances, X may be greater than 0.5 mN/m·s, 1 mN/m·s, 2 mN/m·s, or 4 mN/m·s. In some instances, the spreading coefficient is dynamic from time T=0.03 or 0.1 seconds to T=1, 0.75, 0.5 or 0.25 seconds. Dynamic spreading coefficient values may be positive or negative.
“Dynamic Surface Tension” refers to a surface tension value, γ (mN/m), that has an absolute (i.e., with the sign omitted) instantaneous rate of change /
(or line slope)>X at a particular time, T, wherein X is greater than 0.05 mN/m·s and T is the elapsed time from bubble formation (i.e., bubble surface age). In some instances, X may be greater than 0.5 mN/m·s, 1 mN/m·s, 2 mN/m·s, or 4 mN/m·s. In some instances, the surface tension is dynamic from time T=0.03 or 0.1 seconds to T=1, 0.75, 0.5 or 0.25 seconds.
“Dynamic Vapor Sorption” (DVS) refers to how much water is absorbed by a material sample according to the DVS Water Sorption Test Method described herein.
“Flammable” refers to a material having a flash point below 38° C.
“Formation Zone” refers to a gaseous zone in which a liquid stream and/or liquid droplets are formed, in whole or part, and wherein: i) the temperature of the formation zone is less than or equal to the temperature of the drying zone, and/or ii) flow conditions of the formation zone are less turbulent than the flow conditions within the drying zone.
“Glass Transition Temperature” or “Tg” refers to the reversible transition from a hard and relatively brittle “glassy” state into a molten or rubber-like state, as the temperature of a material (or combination of materials) is increased. The glass transition temperature, or Tg, of a material characterizes the range of temperatures over which this glass transition occurs. It is always lower than the melting temperature, Tm, of the crystalline state of the material, if one exists. As used herein, Glass Transition Temperature refers to the Tg of the wall forming material(s) of the shell liquid measured using the Glass Transition Temperature Test Method described herein.
“Interfacial tension” refers to the surface tension (mN/m) at a surface separating two non-miscible liquids. Interfacial tension is measured using the IFT Test Method described herein.
“Liquid” refers to a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. Some materials may be a liquid under some conditions and a solid under others. For example, a material (e.g., shell liquid) is preferably a liquid when flowing thru a microfluidic device but may become a solid during or after microcapsule formation.
“Liquid Droplet” refers to a discrete liquid or semi-liquid volume bounded completely or almost completely by a free surface. Liquid droplets may or may not be substantially spherical. A liquid droplet has a core comprising one or more liquids surrounded by a shell comprising one or more liquids. In some instances, the core of the liquid droplet is formed substantially or completely from liquids and the shell of the liquid droplet is formed substantially or completely from liquids. In some instances, the core, the shell or both may also contain solid materials.
“Microcapsule” refers to a core-shell particle having a solid or semi-solid shell bounding or encapsulating a core comprising one or more liquids and having a mean, equivalent diameter of less than 150 μm, or less than 100 μm, or less than 75 μm or less than 50 μm. Microcapsules may have any shape, including spherical or irregular.
“Microfluidic Device” refers to a device having one or more fluid channels having a cross-sectional dimension less than 1 mm, or less than 900 microns, or less than 800 microns or less than 600 microns or less 400 microns, or less than 300 microns through which the core liquid and/or the shell liquid flow and/or exit the device to form liquid droplets. The cross-sectional dimension need not be constant through the entire length of a fluid channel.
“Micro-Liquid Droplets” refers to liquid droplets having a mean diameter of less than 350 μm, 250 μm or less than 100 μm, or less than 75 μm or less than 50 μm measured approximately 5 cm from the exit of the device. The liquid droplet diameter may be measured using optical microscopy.
“Rayleigh Break-up” refers to a liquid stream, including a bi-component liquid stream, which breaks-up into liquid droplets due to Rayleigh instability. Rayleigh break-up is characterized by liquid droplets having a diameter larger than the stream diameter and the break-up occurring further downstream of the exit compared to first wind induced, second wind induced and atomization. Some non-limiting examples of Rayleigh Break-up, First Wind Induced, Second Wind Induced and Atomization are shown in Erriguible et al, Numerical investigations of liquid jet breakup in pressurized carbon dioxide: Conditions of two phase flow in supercritical antisolvent process, J. of Supercritical Fluids 63, p 17 (2012).
“Oil” refers to any hydrophobic liquid. An oil may be derived from any animal, plant or mineral source. An oil may be volatile or non-volatile.
“Shell” refers to the outer portion or layer of a liquid droplet or a microcapsule. One non-limiting example of a microcapsule illustrating a core and shell is shown in
“Shell Liquid” refers to a liquid used to form the shell of a liquid droplet. The shell liquid may be a mixture of liquids.
“Shell Liquid/Core Liquid Flow Rate Ratio” refers to the ratio of the volumetric flow rate of the shell liquid to the volumetric flow rate of the core liquid through a liquid droplet forming device, such as, for example, a microfluidic device.
“Spreading Coefficient” refers to the measure of the ability of a liquid to spread on the surface of another liquid. Spreading coefficient is defined by the formula:
S=γ
CORE−γSHELL−γINTERFACIAL
wherein S=The spreading coefficient value (mN/m);
“Steady State Interfacial Tension” refers to an interfacial tension value, IFT (mN/m), having an absolute (i.e., with the sign omitted) instantaneous rate of change /
(or line slope)=Y at a particular time, T, wherein Y is between 0 and 0.05 and T is the elapsed time from bubble formation (i.e., bubble surface age). In some instances, the interfacial tension is steady state at T>1, 1.5, 2, 5 or 10 seconds.
“Steady State Spreading Coefficient” refers to a spreading coefficient value, S (mN/m), having an absolute (i.e., with the sign omitted) instantaneous rate of change /
(or line slope)=Y at a particular time, T, wherein Y is between 0 and 0.05 mN/m·s and T is the elapsed time from bubble formation (i.e., bubble surface age). In some instances, the spreading coefficient is steady state at T>1, 1.5, 2, 5, or 10 seconds.
“Steady State Surface Tension” refers to a surface tension value having an absolute (i.e., with the sign omitted) instantaneous rate of change /
(or line slope)=Y at a particular time, T, wherein Y is between 0 and 0.5 mN/m·s and T is the elapsed time from bubble formation (i.e., bubble surface age). In some instances, the surface tension is steady state at T>1, 1.5, 2, 5, or 10 seconds. Steady state surface tension values may be positive or negative.
“Substantially Free” means a material is present at concentration of less than 2%, 1%, 0.5%, 0.1%, 0.01% or 0.001% by weight of the shell, core, liquid droplet or microcapsule as dictated by the context.
“Surface Tension” refers to the elastic tendency of a liquid that tends to minimize the surface area of the liquid. Surface tension values may be either dynamic or steady state positive or negative and is measured using the Surface Tension Test Method described herein.
“Tower” refers to any structure or combination of structures enclosing, at least partially, a formation zone.
“Viscosity Modifier” refers to a material (or materials) that reduces the viscosity of the core liquid to less than 200 centipoise (cP), 150 cP or 100 cP.
“Water Absorbing Polymer” refers to a polymer having a DVS sorption value greater than 3%, 5%, 6%, 7% or 8% at 80% relative humidity and 30° C.
Various methods and systems will now be described in which liquid droplets are formed and water is evaporated from the liquid droplets to form microcapsules.
Referring to
A tower 46 having a passage 48 is shown. The tower 46 has a proximal end 50 and a distal end 52. The passage 48 has an opening 54 and an opening 56 disposed at the proximal end 50 and the distal end 52, respectively. In certain embodiments, the passage 48 extends from the proximal end 50 to the distal end 52, as shown by way of example in
In certain embodiments, the distal end 52 and opening 56 of the passage 48 thereat are partially, substantially or wholly closed to the ambient environment. In other embodiments, the distal end 52 and the opening 56 of the passage 48 there at may be partially, substantially or wholly exposed to the ambient environment, an example of the passage 48 being exposed to the ambient environment being shown in
Tower 46 is disposed outside (preferably wholly outside) of the drying chamber 34, its drying zone 60 and otherwise upstream of an opening or hole 62 in a top portion 64 of the drying chamber 34. The opening 62 is in communication with drying zone 60 of the drying chamber 34. Likewise, formation zone 58 is also disposed wholly outside of the drying chamber 34, its drying zone 60 and upstream of the opening 62 of the drying chamber 34. The drying zone 60 is considered to be the interior volume of the drying chamber less that volume occupied by the portion of a tower disposed therein (see, e.g.,
The liquid droplets enter the drying chamber 34 through the opening 62 of the drying chamber. The opening 54 of the tower 46 is located at or adjacent to the inlet 62 of the drying chamber 34. The bi-component liquid stream and/or liquid droplets pass through the opening 54 of the tower 46 and enter the drying zone 60 of drying chamber 34. Preferably, the liquid droplets fully form within the formation zone 58. When the bi-component liquid stream and and/or liquid droplets are formed within a tower, the formation zone may be regarded as the gaseous interior volume of the tower 46. This is shown schematically in
While the opening 62 of the drying chamber 34 is shown in
In certain embodiments, gas flow within a formation zone is less turbulent than the gas flow within the drying zone. Whether gas flow is less turbulent in a formation zone compared to a drying zone may be demonstrated by in-silico modeling using computational fluid dynamics (CFD). Some examples of such CFD modeling for spray dryers are described, for example, in Saleh, CFD simulations of a co-current spray dryer, International Journal of Chemical, Molecular, Nuclear Materials and Metallurgical Engineering, Vol. 4, No. 2 (2010); Fletcher et al., What is important in simulation of spray dryer performance and how do current CFD models perform?, Applied Mathematical Modelling 30 (2006); Gabities et al., Air flow patterns in an industrial milk powder sprayer, Fifth International Conference on CFD in the Process Industries (2006). Visualization of flow fields may be accomplished by, for example, hot wire anemometry, laser Doppler anemometry or other technique known in the art.
In certain embodiments, the formation zone comprises a laminar gas flow within which at least a portion of the bi-component liquid stream and/or the liquid droplets reside for a period of time. Laminar flow in the formation zone may be provided by: i) a tower that does not have a swirling gaseous flow introduced thereto (other than from the liquid droplet forming device), ii) a tower that does not have a high velocity gaseous flow introduced thereto (other than from the liquid droplet forming device), and/or iii) a tower that does not induce recirculation zones or eddies by utilizing a passage that is substantially straight and/or of substantially constant cross-sectional area. In contrast, a turbulent drying zone may be provided by: i) swirling the drying gas (typically air) as it is introduced to the drying chamber, ii) introducing the drying gas at a high velocity and/or flow rate, iii) the drying chamber contains a conically shaped bottom portion or other shape that contributes to the creation of recirculation zones or eddies, and/or iv) temperature gradients within the drying chamber. The formation zone has a temperature Temp1 and the drying zone has a temperature Temp2. Temp2 is greater than or equal to Temp1. Temp1, which is the gas temperature within the formation zone at a mid-point along its longest dimension, may be at ambient temperature. In some instances, the Temp1 may between about 20° C., 21° C. or 22° C. and about 30° C., 28° C., or 25° C. Temp2 of the drying zone, which is the temperature of the drying gas as it enters the drying chamber, may be between about 30° C., 40° C., 50° C., 75° C. and 100° C. and about 700° C., 200° C., 150° C. or 125° C. in instances where Temp2 is greater than Temp1. In these instances, the drying gas is typically heated by a heater (e.g., electrical resistive heater, a heat exchanger employing a heated liquid or other means known in the art) prior to entering the drying chamber. The drying gas may be heated to Temp2 by the heater.
In certain embodiments, the tower is in the form of a hollow cylinder formed by a wall 66 as shown by way of example in
When the drying gas has a temperature greater than that of the formation zone, some or substantially all or all of the water may evaporate from the shell of the liquid droplets in the drying zone. While it is often desirable for the drying gas to be heated in order to evaporate substantially all of the water from the liquid droplet shell (thereby forming microcapsules which may be more stable than those retaining water in the shell), in certain embodiments it may be desirable for the drying gas to have a temperature equal to or close to ambient, in which case less water will evaporate from the liquid droplet shell. Microcapsules may exit the drying chamber 34 at exit 70. The microcapsules exiting the drying chamber 34 may be transferred to a cyclone chamber 72 or other device which separates/collects the microcapsules. The cyclone chamber 72 uses a cyclonic action to separate the microcapsules from the gas. The separated microcapsules may then be collected in a collection chamber. Other arrangements, components and structures may be provided or substituted for those shown in the FIGS or otherwise described herein as known in the art.
Following collection of the microcapsules, some or all of the collected microcapsules may be subjected to further processing as known in the art (e.g., sieving, coating, dispersion into other liquids, admixing with other powders, etc.), after which the microcapsules may be incorporated into a consumer goods composition or an article of manufacture, such as, for example, a web, non-woven or other substrate.
The liquid droplet forming device 32 may be provided in a variety of forms. In some instances, it may be desirable to maximize the flow rate of the core liquid compared to the shell liquid in order to form liquid droplets and microcapsules that maximize, rather than minimize, the core-shell ratio and therefore the amount of benefit agent delivered per microcapsule. The shell liquid/core liquid flow rate ratio through the liquid droplet forming device may be less than 30:1, 20:1, 10:1, 8:1, 6:1, 4:1, 3:1 or 2:1. The liquid droplet forming device typically comprises a housing, one or more (typically two) inlets to receive the core liquid and the shell liquid and one or more channels, passages or tubes within the housing for transporting the core liquid and the shell liquid within the device. The device also comprises one or more exits from which the core liquid and shell liquid are discharged.
Preferably, the core liquid and the shell liquid are discharged as a bi-component liquid stream from co-axial exits. The device may or may not utilize pressurized air or other means to assist with the liquid droplet formation. For example, in certain embodiments, the device may comprise an inlet for receiving a pressurized gas and an exit for the same near or adjacent to the exits for the core liquid and/or the shell liquid. Alternatively or in addition thereto, the liquid droplet forming device may be connected to an electrical power supply and utilize a transducer (e.g., a piezoelectric transducer or the like) or other electrically driven, vibrating surface to assist with forming the liquid droplets (e.g., model ACCUMIS™ available from Sonotek, Inc.).
While a variety of liquid droplet forming devices may be utilized, a microfluidic device is preferred in order to achieve more uniform liquid droplet/microcapsule sizes and distributions. Some non-limiting examples of microfluidic devices will be described hereafter for purposes of illustration. In some instances, one or more of the channels of a microfluidic device may have an exit, or the microfluidic device may have an exit, with a cross-sectional dimension from about 10 microns, 50 microns or 200 microns to about 300 microns, about 400 microns, about 600 microns, about 800 microns, about 900 microns or about 1 mm. Due to the small channel dimension and/or exit dimension that may be employed in a microfluidic device, it may be desirable for the shell liquid and/or the core liquid to have a viscosity less than 200 centipoise (cP), 150 cP, 125 cP or 100 cP. One or more viscosity modifiers may sometimes be added to one or both of these liquids in order to reduce their viscosity to a desired level, so long as the dynamic spreading coefficient is greater than zero.
The flow rate of a core liquid through a channel of a microfluidic device may be greater than 2 ml/hr, 4 ml/hr, 6 ml/hr, 8 ml/hr, 10 ml/hr or 12 ml/hr and/or less than 150 ml/hr, 125 ml/hr, 100 ml/hr or less than 80 ml/hr. In some instances, the flow rate of the core liquid through a channel of a microfluidic device is from about 2 ml/hr to about 150 ml/hr. The flow rate of the shell liquid thru a channel of the microfluidic device may be greater than 5 ml/hr, 10 ml/hr, 15 ml/hr, 30 ml/hr, 40 ml/hr, or 50 ml/hr and/or less than about 450 ml/hr, 250 ml/hr, or 100 ml/hr. In some instances, the flow rate of the shell liquid through a channel of a microfluidic device may be from about 30 ml/hr to about 450 ml/hr. A bi-component liquid stream exiting a microfluidic device may break-up into liquid droplets in less than 0.75 milliseconds, less than 0.5 milliseconds or less than 0.3 milliseconds after exiting a microfluidic device. The liquid droplets typically formed from a microfluidic device are micro-liquid droplets. In some embodiments, the bi-component liquid stream undergoes Rayleigh Break-Up to form the stream of liquid droplets. It is presently believed that the Rayleigh Break-Up regime balances (as compared to first wind induced, second wind induced or atomization regimes) core/shell liquid throughput, liquid droplet size control and liquid droplet morphology, especially when combined with a separate formation zone and dynamic spreading coefficient greater than zero.
Referring to
In use, a bi-component liquid stream exits the capillary tubes of the device 32 and is accelerated and stretched by the pressurizing gas, resulting in reduction of the diameter of the bi-component liquid stream. Upon exiting the device 32, the bi-component liquid stream begins to break-up as it decelerates, Rayleigh instability sets in and the pressurized gas also exiting the device 32 diffuses. In this particular microfluidic device, the time period from when the liquid bi-component stream exits the capillary tubes to break-up of the bi-component liquid stream into liquid droplets may be less than about 0.5 milliseconds.
The drying chamber 34 may be provided in a wide variety of shapes, sizes and configurations. The drying chamber may be also referred to as a spray dryer in the art, and various models are available from manufactures such as the GEA Group. The drying chamber 34 utilizes a turbulent gas (typically ambient air or heated air) to evaporate water from the shell liquid. Referring again to
Referring to
Without intending to be bound by any theory, it is believed to be highly desirable for the core liquid and shell liquid to have a dynamic spreading coefficient that is greater than zero to aid formation of liquid droplets during the short time period of droplet formation and prior to evaporation of too much water from the shell liquid. The dynamic spreading coefficient may be calculated from the dynamic surface tensions of the core liquid and the shell liquid and the dynamic interfacial tension between them. While steady state spreading coefficient is widely discussed in the art, it is believed that a dynamic spreading coefficient greater than zero may be a more important consideration for successful formation of liquid core microcapsules due to the short time period over which the liquid droplets (particularly micro-liquid droplets) have to successfully form once a bi-component liquid stream has broken up.
The shell liquid and/or the core liquid comprise one or more surfactants to achieve the desired surface tension values that result in a dynamic spreading coefficient greater than zero. Sometimes, depending on the nature of the core liquid and the shell liquid, it may be desirable to include 2 or more surfactants: one or more for lowering the dynamic interfacial tension and one or more for lowering the dynamic surface tension of the shell liquid. In some instances, the one or more surfactants reduce the dynamic surface tension of the shell liquid by greater than 25%, 30%, 35%, 40%, 45%, 50%, 55% and or 60% at T=0.03, 0.1, 0.25, 0.5, 0.75 and/or 1 second of the bubble surface age. In some instances, the one or more surfactants reduce the dynamic surface tension of the shell liquid by greater than 40% or 50% at T=0.1 seconds of the bubble surface age. One example of a dynamic surface tension reduction is shown in
Without intending to be bound by any theory, it is presently believed that the dynamic interfacial tension should be low enough to contribute to a dynamic spreading coefficient greater than zero but not too low that the core liquid becomes miscible in the shell liquid of the liquid droplet (i.e., interfacial surface tension equal greater than zero). In some instances, the dynamic interfacial surface tension is greater than 0, 0.25, 0.5, or 1 mN/m and/or less than 12, 10, 5, 3, 2 or 1 mN/m at T=0.03, 0.1, 0.25, 0.5 0.75 and/or 1 second of the bubble surface age. In some instances, the one or more surfactants reduce the dynamic interfacial tension between the shell liquid and the core liquid (as compared to a shell liquid without the surfactant(s) with the wt % of surfactant being replaced by water, and a core liquid without the surfactant(s) with the wt % of surfactant being replaced by the oil of the core liquid) by greater than 40%, 50%, 60%, or 70% at T=0.03, 0.1, 0.25, 0.5, 0.75 and/or 1 second of the bubble surface age. In some instances, the one or more surfactants reduce the dynamic interfacial tension between the shell liquid and the core liquid by greater than 40% or 50% at T=0.1 second of the bubble surface age. One example of a dynamic interfacial tension reduction is shown in
a. Dynamic Spreading Coefficient, Dynamic Surface Tension and Dynamic Interfacial Tension
The core liquid and the shell liquid have a dynamic spreading coefficient greater than zero. In some instances, the dynamic spreading coefficient is greater than zero at T=0.03, 0.1, 0.25, 0.5, 0.75 and/or 1 second of bubble surface age. In some instances, the core liquid and the shell liquid have a dynamic spreading coefficient great than zero from about 0.03 seconds to about 1 second of bubble surface age. In some instances, the dynamic spreading coefficient may be greater than 0, 2.5, 5, 7.5, 10, 15, or 20 mN/m during at least some of these time periods. For example, the dynamic spreading coefficient might be greater than 10 mN/m at T=0.1 seconds and greater than 0 or 5 mN/m at T=0.25, 0.75 and 1 second of bubble surface age.
Incorporating one or more surfactants in the shell liquid and, optionally the core liquid, used to form the liquid droplets may assist in providing a dynamic spreading coefficient greater than zero within time periods that enable rapid envelopment or spreading of the shell liquid about the core liquid during liquid droplet formation. It is believed that rapid envelopment of the core liquid by the shell liquid during formation of the liquid droplets may contribute to core-shell ratios greater than 2.5:1, 3:1, 4:1 by weight of the microcapsule. In some instances, the microcapsule comprises greater than 40%, 50%, 60%, 70% or 80% of one or more oils by weight of the microcapsule, as determined by thermogravimetric analysis averaged across a population of microcapsules. In some instances, the core liquid consists essentially of or consists of just the one or more oils. In some instances, the core liquid comprises greater than 50%, 80%, 90%, 95%, or 99% by weight of one or more oils.
More than one surfactant may be incorporated in the shell liquid, wherein one of the surfactants decreases the surface tension of the shell liquid and the other surfactant decreases the interfacial tension between the core liquid and the shell liquid. The surfactant that lowers the interfacial tension may be added to the core liquid and/or the shell liquid. The shell liquid may comprise from about 0.1%, 0.2% or 0.3% to about 3%, 2%, 1%, 0.75% or 0.5% of one or more surfactants by weight of the shell liquid. In some instances, the shell liquid comprises from about 0.3% to about 1% by weight of the one or more surfactants. The core liquid may comprise from about 0.1%, 0.2% or 0.3% to about 2%, 1%, 0.75% or 0.5% of one or more surfactants by weight of core liquid. In some instances, the core liquid comprises from about 0.3% and about 1% by weight of the one or more surfactants.
In some instances, the shell liquid may have a dynamic surface tension less than 50, 40 or 30 mN/m at T=0.03, 0.1, 0.25, 0.5 and/or 1 second of bubble surface age. In some instances, the dynamic surface tension of the shell liquid may be between about 25 mN/m and about 45 mN/m at T=0.1 seconds and/or between about 25 mN/m and about 30 mN/m at T=1 second of bubble surface age.
In some instances, the core liquid may have a dynamic surface tension greater than 20 mN/m, 30 mN/m, 40 mN/m or greater than 50 mN/m at T=0.03, 0.1, 0.25, 0.5, 0.75 and/or 1 second of bubble surface age. In some instances, the dynamic surface tension of the core liquid may be between about 30 mN/m and about 45 mN/m at T=0.1 seconds and/or between about 28 mN/m and about 32 mN/m at T=1 second of bubble surface age. The lower the dynamic surface tension of the core liquid at a given time T, the lower the dynamic surface tension of the shell liquid and/or the dynamic interfacial tension will need to be at time T in order to provide a dynamic spreading coefficient value greater than zero. More preferably, the difference between the dynamic surface tension of the core liquid and the dynamic surface tension of the shell (difference=γCORE−γSHELL) at a given time T of bubble surface age is greater than +1, +2, +4, +6, +8 or +10 mN/m.
As an example, it is possible to calculate spreading coefficients from the surface tensions and interfacial tensions shown in
b. Surfactants
A variety of surfactants may be incorporated into the shell liquid and/or core liquid to achieve the desired dynamic spreading coefficient within the ranges described herein. As discussed above, the shell liquid and/or the core liquid may comprise one or more surfactants. The shell liquid and/or the core liquid may include one or more surfactants selected from anionic surfactants, amphoteric surfactants, cationic surfactants, non-ionic surfactants, zwitterionic surfactants, and mixtures thereof.
Anionic Surfactants
In some instances, the anionic surfactants may be present in acid form or in neutralized (e.g., salt) form. In some instances, the anionic surfactants may be linear, branched, or a mixture thereof. Non-limiting examples of anionic surfactants are the alkali metal salts of C10-C18 alkyl sulfonic acids, such as sodium dodecyl sulfate, and the alkali metal salts of C10-C18 alkyl benzene sulfonic acids the C11-C14 alkyl benzene sulfonic acids, or dialkyl sulfosuccinates, such as dioctyl sulfosuccinate. In some aspects, the alkyl group is linear, and such linear alkyl benzene sulfonates are known as “LAS.” Alkyl benzene sulfonates, and particularly LAS, are well known in the art. Such surfactants and their preparation are described in, for example, U.S. Pat. Nos. 2,220,099 and 2,477,383.
Amphoteric Surfactants
Non-limiting examples of amphoteric surfactants include: aliphatic derivatives of secondary or tertiary amines, or aliphatic derivatives of heterocyclic secondary and tertiary amines in which the aliphatic radical can be straight- or branched-chain. One of the aliphatic substituents contains at least about 8 carbon atoms, typically from about 8 to about 18 carbon atoms, and at least one contains an anionic water-solubilizing group, e.g. carboxy, sulfonate, sulfate. Examples of compounds falling within this definition are sodium 3-(dodecylamino)propionate, sodium 3-(dodecylamino) propane-1-sulfonate, sodium 2-(dodecylamino)ethyl sulfate, sodium 2-(dimethylamino) octadecanoate, disodium 3-(N-carboxymethyldodecylamino)propane 1-sulfonate, disodium octadecyl-imminodiacetate, sodium 1-carboxymethyl-2-undecylimidazole, and sodium N,N-bis(2-hydroxyethyl)-2-sulfato-3-dodecoxypropylamine. Illustrative amphoteric surfactants are shown and described in U.S. Pat. No. 3,929,678 at column 19, lines 18-35.
Cationic Surfactants
Non-limiting cationic surfactants include quaternary ammonium surfactants, which can have up to about 26 carbon atoms. Additional examples include a) alkoxylate quaternary ammonium (AQA) surfactants as discussed in U.S. Pat. No. 6,136,769; b) dimethyl hydroxyethyl quaternary ammonium as discussed in U.S. Pat. No. 6,004,922; c) trimethyl quaternary ammonium such as lauryl trimethyl quaternary ammonium d) polyamine cationic surfactants as discussed in WO 98/35002, WO 98/35003, WO 98/35004, WO 98/35005, and WO 98/35006; e) cationic ester surfactants as discussed in U.S. Pat. Nos. 4,228,042, 4,239,660 4,260,529 and U.S. Pat. No. 6,022,844; and e) amino surfactants as discussed in U.S. Pat. No. 6,221,825 and WO 00/47708, specifically amido propyldimethyl amine (APA).
Non-Ionic Surfactants
Non-limiting examples of nonionic surfactants include: a) C12-C18 alkyl ethoxylates, such as, NEODOL® nonionic surfactants from Shell; b) C6-C12 alkyl phenol alkoxylates where the alkoxylate units are a mixture of ethyleneoxy and propyleneoxy units; c) C12-C18 alcohol and C6-C12 alkyl phenol condensates with ethylene oxide/propylene oxide block polymers such as PLURONIC® from BASF; d) Alkylpolysaccharides as discussed in U.S. Pat. No. 4,565,647; specifically alkylpolyglycosides as discussed in U.S. Pat. Nos. 4,483,780 and 4,483,779; e) Polyhydroxy fatty acid amides as discussed in U.S. Pat. No. 5,332,528, WO 92/06162, WO 93/19146, WO 93/19038, and WO 94/09099; and f) ether capped poly(oxyalkylated) alcohol surfactants as discussed in U.S. Pat. No. 6,482,994 and WO 01/42408.
Zwitterionic Surfactants
Non-limiting examples of zwitterionic surfactants include: derivatives of secondary and tertiary amines, derivatives of heterocyclic secondary and tertiary amines, or derivatives of quaternary ammonium, quaternary phosphonium or tertiary sulfonium compounds. Illustrative zwitterionic surfactants are disclosed in U.S. Pat. No. 3,929,678 at column 19, line 38 through column 22, line 48 such as, for example, betaines, including alkyl dimethyl betaine and cocodimethyl amidopropyl betaine, C8 to C18 (for example from C12 to C18) amine oxides and sulfo and hydroxy betaines, such as N-alkyl-N,N-dimethylammino-1-propane sulfonate where the alkyl group can be C8 to C18 and in certain embodiments from C10 to C14.
The one or more surfactants may also include any of the surfactants or combinations thereof shown and described in the following: Handbook of Surfactants, 1991, M. R. Porter, published by Springer Science+Business Media, LLC, M. R. Porter, 1991, U.S. Pat. Publ. Nos.: 2014/0349908, 2015/093347, and 2015/182993, EP0006655, and/or EP0320219, which are all hereby incorporated by reference herein.
The shell liquid may comprise one or more surfactants that reduce the dynamic surface tension of the shell liquid by greater than 25%, 30%, 40% or 50% or more, preferably from T=0.03 or 0.1 seconds to T=1, 0.75, 0.5 or 0.25 seconds compared to the shell liquid without the surfactant(s) (i.e., the surfactants being replaced by water). As one example,
In some instances, the shell liquid comprises one or more surfactants comprising a siloxane functional group having the following formula:
Si—O—Si
Some preferred siloxane containing surfactants are available: i) under the brand name DYNOL™ Superwetting Surfactants (Air Products and Chemicals, Inc.), ii) under the brand name SILWET® (Momentive Performance Materials), and iii) from BYK USA, Inc. under the BYK brand name. It is believed one or more of these surfactants may be particularly useful for lowering dynamic surface tensions of a shell liquid. In some instances, this shell liquid comprises a polyester wall forming material. In some instances, one or more surfactants comprising a siloxane functional group are included at a concentration less than 1% or less than 0.75% by weight of the shell liquid. In some instances, one or more surfactants containing a siloxane functional group have a concentration from about 0.1 wt % to 0.5 wt % of the shell liquid.
In some instances, the shell liquid and/or the core liquid may comprise two or more surfactants to achieve the desired dynamic surface tension and/or dynamic interfacial tensions to yield a dynamic spreading coefficient greater than zero, preferably from T=0.03 or 0.1 seconds and/or to T=1, 0.75, 0.5 or 0.25 seconds. Some preferred surfactant combinations, include, but are not limited to: i) a surfactant having a siloxane functional group and an anionic surfactant, ii) a surfactant having a siloxane functional group and a sulfosuccinate surfactant (e.g., having both carboxylate and sulfonate groups), and iii) a first surfactant having a siloxane functional group and a second surfactant having a siloxane functional group. In some instances, the shell liquid comprises 2 or more surfactants selected from the group consisting of a surfactant having a siloxane functional group, a second surfactant having a siloxane functional group, a sulfosuccinate surfactant, an anionic surfactant and mixtures thereof. In some instances, the core liquid may comprise a sulfosuccinate surfactant.
c. Core Liquids
The core liquid may be stored in a tank or reservoir and pumped to a liquid droplet forming device, although it is also envisioned that a plurality of liquids may be stored in a plurality of tanks and the liquids are pumped to the liquid droplet forming device and mixed in the device to form the core liquid.
The core liquid comprises one or more oils and one or more surfactants. In some instances, the core liquid comprises greater than 50%, 60%, 70%, 80%, 90%, 95% or 99% by weight of the one or more oils. In some instances, the core liquid consists essentially of or consists of the one or more oils. The one or more oils may also be a benefit agent, such as in the case of perfume oils or sensates (e.g., warming sensates, tingling sensates, or cooling sensates). The one or more oils may also be a carrier for one or more benefit agents that are soluble or dispersible in the oil(s). Optionally, the core liquid may comprise one or more other materials that are benefit agents. In some instances, the one or more oils are organic oils. Some non-limiting examples of oils include mineral oil and/or petrolatum (when melted), essential oils, vegetable oils, perfume oils and mixtures thereof.
Essential oils are those oils derived from parts of plants, such as the bark, berries, flowers, leaves, peel, resin, rhizome, root, seeds or wood thereof. Some non-limiting examples of essential oils, include, but are not limited to agar oil, ajwain oil, angelica root oil, anise oil, asafoetida, balsam, basil oil, bay oil, bergamot oil, black pepper essential oil, buchu oil, birch, camphor, cannabis flower essential oil, caraway oil, cardamom seed oil, carrot seed oil, cedarwood oil, chamomile oil, calamus root, cinnamon oil, cistus, citron, citronella oil, clary sage, clove oil, coffee, coriander, costmary oil, costus root, cranberry seed oil, cubeb, cumin oil/black seed oil, cypress, cypriol, curry leaf, davana oil, dill oil, elecampane, eucalyptus oil, fennel seed oil, fenugreek oil, fir, frankincense oil, galangal, galbanum, geranium oil, ginger oil, goldenrod, grapefruit oil, henna oil, helichrysum, hickory nut oil, horseradish oil, hyssop, idaho tansy, jasmine oil, juniper berry oil, laurus nobilis, lavender oil, ledum, lemon oil, lemongrass, lime, litsea cubeba oil, linaloe, mandarin, marjoram, melaleuca or tea tree oil, melissa oil (lemon balm), mentha arvensis oil/mint oil, moringa oil, mountain savory, mugwort oil, mustard oil, myrrh oil, myrtle, neem oil or neem tree oil, neroli, nutmeg, orange oil, oregano oil, orris oil, palo santo, parsley oil, patchouli oil, perilla essential oil, peppermint oil, petitgrain, pine oil, ravensara, red cedar, roman chamomile, rose oil, rosehip oil, rosemary oil, rosewood oil, sage oil, sandalwood oil, sassafras oil, savory oil from satureja species, schisandra oil, spearmint oil, spikenard, spruce oil, star anise oil, tangerine, tarragon oil, tea tree oil, thyme oil, tsuga, turmeric, valerian, vetiver oil (khus oil), western red cedar, wintergreen, yarrow oil, ylang-ylang, and zedoary.
A vegetable oil comprises a triglyceride extracted from a plant material. Common vegetable oils include, but are not limited to, coconut oil, corn oil, cottonseed oil, olive oil, palm oil, peanut oil, rapeseed oil, safflower oil, sesame oil, soybean oil and sunflower oil. Nut oils include oils derived from at least one part of or known as the oil of: almond, beech nut, brazil nut, cashew, hazelnut, macadamia, mongongo nut, pecan, pine nut, pistachio, and walnut. Citrus Oils include grapefruit seed oil, lemon oil and orange oil. Melon and gourd seed oils include: bitter gourd oil, bottle gourd oil, buffalo gourd oil, butternut squash seed oil, egusi seed oil, pumpkin seed oil, and watermelon seed oil. Some other oils include acai oil, black seed oil, blackcurrant seed oil, borage seed oil, evening primrose oil, and flaxseed oil (aka linseed oil) and oil derived from amaranth, apricot, apple seed, argan, avocado, babassu, ben, borneo tallow nut, cape chestnut, carob pod oil, chestnut, cocoa butter, cohune, coriander seed, date seed, dika, false flax, grape seed, hemp, kapok seed, kenaf seed, lallemantia, mafura, marula, meadowfoam seed, mustard, niger seed, nutmeg butter, okra seed, papaya seed, perilla seed, persimmon seed, pequi, pili nut, pomegranate seed, poppyseed, pracxi, prune kernel, quinoa, ramtil, rice bran, royle, sacha inchi, sapote, seje, shea butter, taramira, tea seed, thistle, tigernut, tobacco seed, tomato seed, and wheat germ.
The term “perfume oil” refers to any perfume raw material, or mixture of perfume raw materials, that comprise oils and is/are intended to deliver a fragrance experience to a consumer, inclusive of carriers, solvents, etc., that are customarily provided with the perfume raw material by a supplier thereof. A wide variety of perfume oils may be incorporated in the core liquid. In some instances the perfume oil may comprise a material selected from the group consisting of prop-2-enyl 3-cyclohexylpropanoate, (4aR,5R,7aS,9R)-octahydro-2,2,5,8,8,9a-hexamethyl-4h-4a,9-methanoazuleno(5,6-d)-1,3-dioxole, (3aR,5aS,9aS,9bR)-3a,6,6,9a-tetramethyl-2,4,5,5a,7,8,9,9b-octahydro-1H-benzo[e][1]benzofuran, 4-methoxybenzaldehyde, benzyl 2-hydroxybenzoate, 2-methoxynaphthalene, 3-(4-tert-butylphenyl)propanal, 3a,6,6,9a-tetramethyl-2,4,5,5a,7,8,9,9b-octahydro-1H-benzo[e][1]benzofuran, 3,7-dimethyloct-6-en-1-ol, 3,7-dimethyloct-6-enenitrile, 3-(4-tert-butylphenyl)butanal, 3-(4-propan-2-ylphenyl)butanal, (E)-1-(2,6,6-trimethyl-1-cyclohexa-1.3-dienyl)but-2-en-1-one, decanal, (E)-1-(2,6,6-trimethyl-1-cyclohex-3-enyl)but-2-en-1-one, (5E)-3-methylcyclopentadec-5-en-1-one, 2,6-dimethyloct-7-en-2-ol, ethyl 2-methylpentanoate, ethyl 2-methylbutanoate, 1,3,3-trimethyl-2-oxabicyclo[2,2,2]octane, 2-methoxy-4-prop-2-enylphenol, 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-indenyl acetate, 3-(3-propan-2-ylphenyl)butanal, a,4,5,6,7,7a-hexahydro-1H-4,7-methanoinden-1-yl propanoate, (2E)-3,7-dimethylocta-2,6-dien-1-ol, (12E)-1-oxacyclohexadec-12-en-2-one. [2-[1-(3,3-dimethylcyclohexyl)ethoxy]-2-methylpropyl]propanoate, hexyl acetate, 2-(phenylmethylidene)octanal, hexyl 2-hydroxybenzoate. (E)-4-(2,6,6-trimethyl-1-cyclohex-2-enyl)but-3-en-2-one, (E)-4-(2,6,6-trimethyl-1-cyclohexenyl)but-3-en-2-one, (E)-3-methyl-4-(2,6,6-trimethyl-1-cyclohex-2-enyl)but-3-en-2-one, 1-(2,3,8,8-tetramethyl-1,3,4,5,6,7-hexahydronaphthalen-2-yl)ethanone, propan-2-yl 2-methylbutanoate, (1R,2S,5R)-5-methyl-2-propan-2-ylcyclohexan-1-ol, (E)-2-ethyl-4-(2,2,3-trimethyl-1-cyclopent-3-enyl)but-2-en-1-ol, 2,4-dimethylcyclohex-3-ene-1-carbaldehyde, 3,7-dimethylocta-1,6-dien-3-ol, 3,7-dimethylocta-1,6-dien-3-yl acetate, 1-((3R,3aS,7R,8aS)-2,3,4,7,8,8a-hexahydro-3,6,8,8-tetramethyl-1H-3a,7-methanoazulen-5-yl)-ethanone, methyl 3-oxo-2-pentylcyclopentaneacetate, 2-methylundecanal, 2-[2-(4-methyl-1-cyclohex-3-enyl)propyl]cyclopentan-1-one, 1-(5,5-dimethyl-1-cyclohexenyl)pent-4-en-1-one, 2-cyclohexylidene-2-phenylacetonitrile, 2-phenylethanol, 3,7-dimethyloctan-3-ol, 5-heptyloxolan-2-one, (2-tert-butylcyclohexyl) acetate, (E)-4-methyldec-3-en-5-ol, (4-tert-butylcyclohexyl) acetate, decahydro-2,2,6,6,7,8,8-heptamethyl-2H-indeno(4,5-b)furan, 17-oxacycloheptadec-6-en-1-one, pentyl 2-hydroxybenzoate, benzyl acetate, 4-phenylbutan-2-one, 2-methoxynaphthalene, 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one, 1,1,2,3,3-pentamethyl-2,5,6,7-tetrahydro-inden-4-one, 1H-3a,7-Methanoazulene, octahydro-6-methoxy-3,6,8,8-tetramethyl, [(Z)-hex-3-enyl]acetate, [(Z)-hex-3-enyl]2-hydroxybenzoate, (9Z)-cycloheptadec-9-en-1-one, chromen-2-one, cyclohexyl 2-hydroxybenzoate, ethyl 3-methyl-3-phenyloxirane-2-carboxylate, 3-ethoxy-4-hydroxybenzaldehyde, 1,4-dioxacycloheptadecane-5,17-dione, 16-oxacyclohexadecan-1-one, diethyl cyclohexane-1,4-dicarboxylate, 1-(5,5-dimethyl-1-cyclohexenyl)pent-4-en-1-one, [(2E)-3,7-dimethylocta-2,6-dienyl]acetate, 3-(1,3-benzodioxol-5-yl)-2-methylpropanal, 1,3-benzodioxole-5-carbaldehyde, 6-(pent-3-en-1-yl)tetrahydro-2H-pyran-2-one, [(1R,2S)-1-methyl-2-[[(1R,3S,5S)-1,2,2-trimethyl-3-bicyclo[3.1.0]hexanyl]methyl]cyclopropyl]methanol, (Z)-3,4,5,6,6-pentamethyl-hept-3-en-2-one, dodecanal, 3,7-dimethylnona-2,6-dienenitrile, (2S)-2-aminopentanedioic acid, methyl 2,4-dihydroxy-3,6-dimethylbenzoate, 2,6-dimethyloct-7-en-2-ol, 4-(4-hydroxy-4-methylpentyl)cyclohex-3-ene-1-carbaldehyde, 1-naphthalen-2-ylethanone, 4-methyl-2-(2-methylprop-1-enyl)oxane, 1H-Indene-ar-propanal, 2,3-dihydro-1,1-dimethyl-(9CI), nonanal, octanal, 2-phenylethyl 2-phenylacetate, 3-methyl-5-phenylpentan-1-ol, 4-methyl-2-(2-methylpropyl)oxan-4-ol, 1-oxacycloheptadecan-2-one, 1-(spiro[4.5]dec-7-en-7-yl)pent-4-en-1-one, 2-(4-methyl-1-cyclohex-3-enyl)propan-2-ol, 1-methyl-4-propan-2-ylidenecyclohexene, (4-methyl-1-propan-2-yl-1-cyclohex-2-enyl) acetate, 1,2-dimethylcyclohex-3-ene-1-carbaldehyde, undec-10-enal. [(4Z)-1-cyclooct-4-enyl]methyl carbonate, 8-methyl-1,5-benzodioxepin-3-one, nona-2,6-dienal, (SZ)-cyclohexadec-5-en-1-one, 2,6,10-trimethylundec-9-enal, prop-2-enyl hexanoate, (E)-1-(2,6,6-trimethyl-1-cyclohex-2-enyl)but-2-en-1-one, 3-phenylprop-2-en-1-ol, 3,7-dimethylocta-2,6-dienal, 3,7-dimethyloct-6-enyl acetate, [2-(2-methylbutan-2-yl)cyclohexyl]acetate, 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-5-yl 2-methyl propanoate, 2-pentylcyclopentan-1-ol, (E)-dec-4-enal, 2-pentylcyclopentan-1-one, 2-methoxy-4-propylphenol, methyl 2-hexyl-3-oxocyclopentane-1-carboxylate, phenoxybenzene, ethyl 3-phenylprop-2-enoate, (E)-2-ethyl-4-(2,2,3-trimethyl-1-cyclopent-3-enyl)but-2-en-1-ol, 3-(4-ethylphenyl)-2,2-dimethyl-propanal, 4-methyl-2-(2-methylpropyl)oxan-4-ol, 2-methyldecanenitrile, 5-hexyloxolan-2-one, 5-(diethoxymethyl)-1,3-benzodioxole, 7-hydroxy-3,7-dimethyloctanal, (E)-4-(2,5,6,6-tetramethyl-1-cyclohex-2-enyl)but-3-en-2-one. [(1R,4S,6R)-1,7,7-trimethyl-6-bicyclo[2.2.1]heptanyl]acetate, 6-butan-2-ylquinoline, 2-methoxy-4-prop-1-en-2-ylphenol, (NE)-N-[(6E)-2,4,4,7-tetramethylnona-6,8-dien-3-ylidene]hydroxylamine, (4-propan-2-ylcyclohexyl)-methanol, 2,6-dimethylhept-5-enal, (1R,2S,5R)-5-methyl-2-propan-2-ylcyclohexan-1-ol, ethyl 2-(2-methyl-1,3-dioxolan-2-yl)acetate, 1-phenylethyl acetate, 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone, 6-butyloxan-2-one, 2,4-dimethyl-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1,3-dioxolane, (2R,4S)-2-methyl-4-propyl-1,3-oxathiane, 4-(4-hydroxyphenyl)butan-2-one, 3-methyl-5-phenylpentan-1-ol, 4-((1R,5S)-6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl)-3,3-dimethylbutan-2-one, 3-methylbut-2-enyl acetate, dec-9-en-1-ol, 5-(3-methylphenyl)pentan-1-ol, 3,7-dimethyloctan-3-ol, 1-methoxy-4-[(E)-prop-1-enyl]benzene, 4-hydroxy-3-methoxybenzaldehyde, 9-acetyl-2,6,6,8-tetramethyltricyclo(5.3.1.01,5)undec-8-ene, 2,5-dioxacyclohexa-decane-1,6-dione and mixtures thereof.
d. Shell Liquids
The shell liquid may be stored in a tank or reservoir and pumped to a liquid droplet forming device, although it is envisioned that a plurality of liquids may be stored in a plurality of tanks which are pumped to the liquid droplet forming device and mixed in the device to form the shell liquid.
The shell liquid comprises water, one or more surfactants, and a wall forming material. In some instances, the shell liquid comprises greater than 60%, 70%, 80% or 85% of water by weight of the shell liquid. While the shell liquid may comprise other carriers, it is preferred that the shell liquid comprises less than 20%, 10%, 5% or 3% by weight of the shell liquid of flammable liquids. Preferably, the shell liquid is substantially or completely free of flammable liquids, such as alcohols (e.g., ethanol), due to the explosive risks when used with a drying chamber.
The shell liquid comprises one or more wall forming materials that form a solid shell upon evaporation of the water in the shell liquid. Some examples include water soluble or water dispersible organic materials, typically oligomers or polymers that form a film or are otherwise capable of forming a solid shell upon evaporation of the water. The wall forming material may have a concentration in the shell liquid of greater than 5%, 10%, 15% and/or less than 40% or 30% or 20% by weight of the shell liquid. In some instances, it may be desirable for the concentration of the one or more wall forming materials be less than 20 wt % so that the viscosity of the shell liquid is less than 200 cP, 150 cP, or 100 cP and is flowable through the small passages of microfluidic devices.
Some non-limiting examples of wall forming materials include synthetic polymeric materials or natural polymers. Synthetic polymers can be derived from petroleum oil, for example. Some non-limiting examples of synthetic polymers include polyesters, polyacrylates and mixtures thereof. Some non-limiting examples of natural polymers includes polysaccharides. In some instances, the wall forming material may be selected from the group consisting of shellacs, polyesters and mixtures thereof, which are believed particularly suited use in consumer goods compositions comprising one or more surfactants.
It is presently believed that surfactant concentrations sufficient to provide a dynamic spreading coefficient greater than zero may also depress the Tg of the wall forming material sufficiently that it is difficult to form microcapsules in a heated drying chamber if the temperature Temp2 of the drying zone is greater than the Tgd of the wall material. In these instances, exceeding the Tgd temperature in the drying zone of the drying chamber may lead to microcapsule agglomeration, and/or the wall forming material sticking to the interior surfaces of the drying chamber, and/or microcapsules sticking to the interior surfaces of the drying chamber.
In accordance with one aspect of the invention, the wall forming material of the shell liquid has a Tg greater than 50° C., or greater than 75° C. or greater than 100° C. in combination with a heated drying gas. In accordance with another aspect of the invention, the Tgd of combination of the wall forming material and shell liquid surfactants is greater than 40° C., 50° C., 60° C., 70° C., 80° C. or 90° C. in combination with a heated drying gas. Preferably, the temperature Temp2 of the drying zone is less than the Tg and/or Tgd of the wall forming material.
Turning to
In some instances, formulations in Quadrant I may have total concentrations of the surfactants of the shell liquid that are less than 1%, 0.75% or 0.5% by weight of the shell liquid in combination with a wall forming material having a Tg greater than 50° C., 75° C. or 100° C. In some instances, formulations in Quadrant II may have total concentrations of surfactants of the shell liquid that are greater than 1% in combination with a wall forming material having a Tg greater than 50° C., 75° C. or 100° C. In some instances, formulations in Quadrant III may have total concentrations of surfactants of the shell liquid that are less than 1%, 0.75%, or 0.5% by weight of the shell liquid in combination with a wall forming material having a Tg less than 50° C. In some instances, formulations in Quadrant IV may have total surfactant concentrations greater than 1% in combination with a forming material having a Tg less than 50° C.
Still further, for Quadrant I, it may in some instances be desirable for the combination of surfactants and wall forming material to have a Tgd greater than 30° C., or greater than about 45° C., greater than about 75° C., or greater than about 90° C., optionally in combination with a drying chamber having a drying zone Temp2 that is less than the Tgd. In some instances, the temperature Temp2 of the drying zone for Quadrant I is between about 30° C. and about 100° C. or between about 40° C. and about 75° C. Table 1 below lists the measured Tgd for various combinations of wall forming materials and surfactants.
Water Absorbing Polymers
Polyvinyl alcohol, may act as both a surfactant/emulsifier and a wall forming material. Polyvinyl alcohol is also a water absorbing polymer, which is believed to hinder evaporation of water from the shell liquid in a drying chamber. As such, it is believed that the concentration of water absorbing polymers in the shell liquid are preferably less than 5%, 4%, 3%, 2% or 1% by weight of the shell liquid. This may reduce or eliminate the need to include an alcohol in the shell liquid as a water evaporative aid. Preferably, the shell liquid comprises a primary wall forming material (e.g., a wall forming material having the highest wt % of the shell liquid relative to any other wall forming material in the shell liquid) that is a water soluble or water dispersible oligomer or polymer having a DVS water sorption less than 5%, or less than 4%, or less than 3% or less than 2% or less than 1%.
Microcapsules
A population of the microcapsules may be produced by the materials, compositions, devices, and systems described herein. The population of microcapsules may be collected at an exit of the drying chamber or downstream of the exit. In some instances, the population of microcapsules may have a mean equivalent diameter from 0.5 μm, or 1 μm, 5 μm or 10 μm to about 150 μm, or 100 μm, or 75 μm or 50 μm. A population of microcapsules may have a mean equivalent diameter coefficient of variation from 1% to 35%, preferably from 1% to 25%, more preferably from 1% to 10%. In some instances, this population of microcapsules may be produced from microfluidic device, which uses small dimensions to facilitate the production of small microcapsule sizes and more uniform microcapsule diameters.
In some instances, a population of microcapsules made according to the teachings herein may be incorporated in a composition or deposited upon or incorporated into an article of manufacture (e.g., a substrate, non-woven, etc.). The composition may be a consumer goods composition, such as a hair care composition (e.g., a shampoo or conditioner), a personal cleansing composition (e.g., a body wash), a fabric care composition or dish care composition. These compositions typically include a surfactant and one or more of an emulsifier, a chelating agent, a conditioning agent, a carrier and/or various other optional ingredients. Polyester and shellac wall forming materials are believed to be particularly well suited for use in these types of compositions for stability. Some non-limiting examples of various compositions are described in Publication Nos.: US2014/0179586; US2015/0267155; US2015/0267156; US2012/0297551; US2015/0376552; US2014/0026331; US2013/0061402; U.S. Pat. No. 8,729,007; and WO 2014/18309.
a. Composition Surfactants
In some instances, the composition may comprise one or more surfactants, including but not limited to an anionic surfactant, amphoteric or zwitterionic surfactants, or mixtures thereof. Various examples and descriptions of detersive surfactants are set forth in U.S. Pat. No. 6,649,155; U.S. Patent Application Publication No. 2008/0317698; and U.S. Patent Application Publication No. 2008/0206355, which are incorporated herein by reference in their entirety
Some examples of anionic surfactants include alkyl and alkyl ether sulfates. Other suitable anionic surfactants include water-soluble salts of organic, sulfuric acid reaction products. Still other suitable anionic surfactants include the reaction products of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide. Other similar anionic surfactants are described in U.S. Pat. Nos. 2,486,921; 2,486,922; and 2,396,278, which are incorporated herein by reference in their entirety. Some exemplary anionic surfactants include ammonium lauryl sulfate, ammonium laureth sulfate, triethylamine lauryl sulfate, triethylamine laureth sulfate, triethanolamine lauryl sulfate, triethanolamine laureth sulfate, monoethanolamine lauryl sulfate, monoethanolamine laureth sulfate, diethanolamine lauryl sulfate, diethanolamine laureth sulfate, lauric monoglyceride sodium sulfate, sodium lauryl sulfate, sodium laureth sulfate, potassium lauryl sulfate, potassium laureth sulfate, sodium lauryl sarcosinate, sodium lauroyl sarcosinate, lauryl sarcosine, cocoyl sarcosine, ammonium cocoyl sulfate, ammonium lauroyl sulfate, sodium cocoyl sulfate, sodium lauroyl sulfate, potassium cocoyl sulfate, potassium lauryl sulfate, triethanolamine lauryl sulfate, triethanolamine lauryl sulfate, monoethanolamine cocoyl sulfate, monoethanolamine lauryl sulfate, sodium tridecyl benzene sulfonate, sodium dodecyl benzene sulfonate, sodium cocoyl isethionate and combinations thereof. In a further embodiment, the anionic surfactant is sodium lauryl sulfate or sodium laureth sulfate.
Some examples of amphoteric or zwitterionic surfactants include those which are known for use in shampoo or other personal care cleansing products. Concentrations of such amphoteric surfactants may range from about 0.5 wt % to about 20 wt %. Some non-limiting examples of suitable zwitterionic or amphoteric surfactants are described in U.S. Pat. Nos. 5,104,646 and 5,106,609, which are incorporated herein by reference in their entirety.
Some examples of amphoteric surfactants suitable include those surfactants broadly described as derivatives of aliphatic secondary and tertiary amines in which the aliphatic radical can be straight or branched chain and wherein one of the aliphatic substituents contains from about 8 to about 18 carbon atoms and one contains an anionic group such as carboxy, sulfonate, sulfate, phosphate, or phosphonate. Exemplary amphoteric detersive surfactants for use in a personal care composition include cocoamphoacetate, cocoamphodiacetate, lauroamphoacetate, lauroamphodiacetate, and mixtures thereof.
Some examples of zwitterionic surfactants include those surfactants broadly described as derivatives of aliphatic quaternaryammonium, phosphonium, and sulfonium compounds, in which the aliphatic radicals can be straight or branched chain, and wherein one of the aliphatic substituents contains from about 8 to about 18 carbon atoms and one contains an anionic group such as carboxy, sulfonate, sulfate, phosphate or phosphonate. In another embodiment, zwitterionics such as betaines are selected.
Some non-limiting examples of other anionic, zwitterionic, amphoteric or optional additional surfactants suitable for use in the personal care composition are described in McCutcheon's, Emulsifiers and Detergents, 1989 Annual, published by M. C. Publishing Co., and U.S. Pat. Nos. 3,929,678, 2,658,072; 2,438,091; 2,528,378, which are incorporated herein by reference in their entirety.
b. Conditioning Agents
In some instances, the composition may comprise a conditioning agent. Some examples include organic conditioning material and silicone conditioning agents. A silicone conditioning agent may comprise volatile silicone, non-volatile silicone, or combinations thereof. The concentration of the silicone conditioning agent may range from about 0.01% to about 10%, by weight of the composition. Some non-limiting examples of silicone conditioning agents, and optional suspending agents for the silicone, are described in U.S. Reissue Pat. No. 34,584, U.S. Pat. Nos. 5,104,646, and 5,106,609. Additional material on silicones including sections discussing silicone fluids, gums, and resins, as well as manufacture of silicones, are found in Encyclopedia of Polymer Science and Engineering, vol. 15, 2d ed., pp 204-308, John Wiley & Sons, Inc. (1989), incorporated herein by reference.
The conditioning agent may also comprise at least one organic conditioning material such as oil or wax, either alone or in combination with other conditioning agents, such as the silicones described above. The organic material can be non-polymeric, oligomeric or polymeric. It may be in the form of oil or wax and may be added in the formulation neat or in a pre-emulsified form. Some non-limiting examples of organic conditioning materials include, but are not limited to: i) hydrocarbon oils; ii) polyolefins, iii) fatty esters, iv) fluorinated conditioning compounds, v) fatty alcohols, vi) alkyl glucosides and alkyl glucoside derivatives; vii) quaternary ammonium compounds; viii) polyethylene glycols and polypropylene glycols having a molecular weight of up to about 2,000,000 including those with CTFA names PEG-200, PEG-400, PEG-600, PEG-1000, PEG-2M, PEG-7M, PEG-14M, PEG-45M and mixtures thereof.
c. Emulsifiers
In some instances, the composition may comprise an emulsifier. Anionic and nonionic emulsifiers can be either monomeric or polymeric in nature. Monomeric examples include, by way of illustrating and not limitation, alkyl ethoxylates, alkyl sulfates, soaps, and fatty esters and their derivatives. Polymeric examples include, by way of illustrating and not limitation, polyacrylates, polyethylene glycols, and block copolymers and their derivatives. Naturally occurring emulsifiers such as lanolins, lecithin and lignin and their derivatives are also non-limiting examples of useful emulsifiers.
d. Chelating Agents
In some instances, the composition may comprise a chelant. Suitable chelants include those listed in A E Martell & R M Smith, Critical Stability Constants, Vol. 1, Plenum Press, New York & London (1974) and A E Martell & R D Hancock, Metal Complexes in Aqueous Solution, Plenum Press, New York & London (1996) both incorporated herein by reference. When related to chelants, the term “salts and derivatives thereof” means the salts and derivatives comprising the same functional structure (e.g., same chemical backbone) as the chelant they are referring to and that have similar or better chelating properties. This term include alkali metal, alkaline earth, ammonium, substituted ammonium (i.e. monoethanolammonium, diethanolammonium, triethanolammonium) salts, esters of chelants having an acidic moiety and mixtures thereof, in particular all sodium, potassium or ammonium salts. The term “derivatives” also includes “chelating surfactant” compounds, such as those exemplified in U.S. Pat. No. 5,284,972, and large molecules comprising one or more chelating groups having the same functional structure as the parent chelants, such as polymeric EDDS (ethylenediaminedisuccinic acid) disclosed in U.S. Pat. No. 5,747,440.
e. Carriers
The compositions may be in the form of pourable liquids (under ambient conditions). Such compositions will therefore typically comprise a carrier, which is present at a level of from about 20 wt % to about 95 wt %, or even from about 60 wt % to about 85 wt %. The carrier may comprise water, or a miscible mixture of water and organic solvent, and in one aspect may comprise water with minimal or no significant concentrations of organic solvent, except as otherwise incidentally incorporated into the composition as minor ingredients of other essential or optional components.
f. Articles of Manufacture
In some instances, a population of microcapsules made using the teachings herein may be applied to and/or deposited onto one or more substrates. A substrate may comprise woven or non-woven materials, typically made from a plurality of fibers, films and similar materials. The population of microcapsules may be applied to the article of manufacture using any means known to one skilled in the art. In some instances, the microcapsules are embedded between fibers. A water insoluble adhesive composition may be used to bind the microcapsules to the substrate. As an alternative to embedding the microcapsules into the core of a substrate, the microcapsules may be coated on an outer surface of the substrate. Non-limiting examples of microcapsules deposited on substrates of personal care products are shown and described in the following: U.S. Publ. No. 2013/0239344, U.S. Publ. No. 2006/270586, U.S. Pat. Nos. 8,329,223, 6,774,063, 4,988,557, 4,186,743, 5,923,412. Non-limiting examples of such personal care products may include cleansing/cleaning wipes, paper towels, tissues, toilet paper, sanitary napkins, diapers, sponges, and other similar personal care products.
It is understood that the methods that are disclosed herein should be used to determine the respective values of the parameters of Applicants' invention as such invention is described and claimed herein. Furthermore, it is obvious to those skilled in the art that a population of microcapsules may in some instances need to be isolated from an end product (e.g., skin care composition, hair care composition or fabric care composition) prior to using a method involving a microcapsule parameter (e.g., microcapsule equivalent diameter). These methods are well known in the art. The method of isolation will depend not only on the type and form of the product but also on the nature of the microcapsule. For example, microcapsules dispersed in a liquid product (e.g., a shampoo) might be isolated by centrifugation and re-dispersion in a non-solvent, while microcapsules in a solid product might be separated using a solvent for the binder and non-solvent for the microcapsules.
Interfacial tension (IFT) measurements between a pair of test liquids, such as the core liquid material and the shell liquid material, are obtained using the pendant drop method. Within this method the more hydrophilic liquid is dispensed as a hanging drop, and the more hydrophobic (oily) liquid is the bulk liquid into which the drop is hung. Suitable instrument systems for dispensing and imaging the pendant drop include equipment such as the Contact Angle Tensiometer model DCA-100, or General Drop Shape Instrument model FTA 1000 (both available from First Ten Angstroms Inc. (Portsmouth, Va., U.S.A.), or similar instruments. Such systems are equipped with a high performance digital video camera capable of capturing 50 frames/sec. Suitable cameras include the Prosilica GT model 1930 or 2000, (available from Allied Vision Technologies GmbH, Stadtroda, Germany). Interfacial Tension (IFT) values and the Drop Volumes are calculated from each captured image using the specialized video drop shape analysis software FTA32 Video Software Version 2.1 (available from First Ten Angstroms Inc., Portsmouth, Va., U.S.A.). For the purposes of this invention, the term “dynamic” is not to be inherently associated with the measured IFT values reported by the drop shape analysis software, regardless of how that terminology is used by the software or in common language. Rather, for IFT values the term “dynamic” is only to be associated with predicted IFT values that are output from the curve fitting and modelling procedures specified here, and which additionally meet the slope value criteria also specified herein.
Both liquids in the pairing to be tested are equilibrated to approximately 25° C. prior to their use in the analysis. The more hydrophilic liquid is dispensed from a 1 mL syringe using an automatic syringe pump at a rate of 13 to 15 μL/sec, until the drop has a total volume of between 5 to 6 μL. The drop is allowed to hang in the bulk liquid, and video images are taken of the pendant drop during its growth and hang for a period of at least 10 sec, at a frame rate of 50 frames/sec. At least two replicate drops are measured with the image analysis software and the resulting replicate IFT values are averaged at each time point. The average data points obtained are plotted on a graph wherein IFT values (mN/m) and Drop Volume values (μL) are plotted on the two vertical y-axes, while time (sec) is plotted on the horizontal x-axis. Within the drop volume data series, the time point at which the growth in drop volume slows (just prior to stopping) is determined. This slowing-of-growth time point is defined as the “time zero” time point for Surface Age of the drop. All IFT values and drop volume values that were captured prior to this surface age time zero are discarded, and the plots' vertical y-axes are rescaled for the remaining data point ranges. The horizontal x-axis and its associated data values are transformed to represent the surface age values, commencing with the first remaining data point (which possesses a drop surface age of zero seconds). For IFT data points, the Surface Age values are deemed to be directly equivalent to the Bubble Lifetime values of Surface Tension (ST) data points from the Surface Tension method contained herein.
A curve is fitted to the remaining data points of IFT (mN/m) plotted versus surface age (sec), and subsequently the slope of the fitted curve at any given time point is determined, The procedures for fitting a curve to the measured surface tension values, and the subsequent determination of the slope of the curve at any given time point are both procedures that are conducted in accordance with the teachings of Hua, X., Rosen, M. J. Dynamic Surface Tension of Aqueous Surfactant Solutions 1: Basic Parameters, J. Colloid Interface Sci. 124, 2 (1988), as described in the following two equations.
The curve equation to be fitted is:
wherein:
The constant values for the four fitted parameters in the curve equation are determined via the reiterative non-linear process of least sum of squares (of the residual errors). This modeling process is conducted by fitting to find constant values for the fitted curve equation parameters which yield the lowest Sum of Squares. This approach aims to minimize the difference between the input values (i.e. the measured IFT values) and the output values (i.e., the predicted IFT values). This curve fitting process is conducted using the “Solver” module within the spreadsheet software Microsoft Excel (such as version #14.0, 32-bit, available from Microsoft Corp. Redmond, Wash., U.S.A.). Within the Solver module of the Excel program, the following options are selected: Solver Method is set as GRG Nonlinear; and Convergence is set at 0.0001. The numerical constraints for each of the four parameters (as specified respectively alongside the equation) are imposed within the Excel program, in order to restrict the range of acceptable values for the parameter constants being determined. Additionally, the reiterative fitting process is seeded with starting values for each of the four parameter values being determines. These starting seed values are selected as follows: γ0 is set as 110% of the highest measured IFT value; γe is set as equal to the IFT value measured at the longest time point; t is set as 1; and n is set as 1,
Once the least sum of squares process has determined constant values for the four fitted parameters in the curve equation, those fitted parameter values are substituted into the curve equation so that the equation can then be used to produce predicted values of IFT for any time point of interest. Using the equation of the fitted curve, predicted IFT values may be extrapolated to time points for which measured surface tension data were not collected.
Whether a predicted IFT value on the fitted curve is a dynamic value or a steady state value is determined as follows. The point on the fitted IFT curve at the time point of interest is identified. Next, the slope of the line at that time point is determined using the slope equation below (first derivative of the previous curve equation).
wherein:
The fitted curve may be extrapolated to extend beyond the range of measured values contained within the plotted data set. The value of the slope of the fitted curve at any given surface age time point indicates whether the predicted IFT value at that time point on the fitted curve is considered to be a Dynamic value or a Steady State value. At a given surface age time point, the predicted IFT value of the fitted curve is defined as being a Dynamic Interfacial Tension (DIFT) value if the absolute value (i.e. with the sign omitted) of the slope of the curve at that time point is greater than 0.05 mN/m·s. DIFT values at any time point along the fitted curve are reported in units of mN/m, at their respective surface age time point.
Predicted IFT values are also generated from the fitted curve equation from at least 25 time points (i.e., bubble lifetime or drop surface age), namely, the time points within the range of 0 sec to 10.8 sec, at intervals of 0.02 sec, and these values are used as specified for calculations within the Spreading Coefficient Test Method.
The surface tension of a given test liquid, such as the core liquid material or the shell liquid material, is measured using the bubble tensiometer instrument model SITA science line t60, and accompanying software SITA-Lab Solution v.1.4.1 (both available from SITA Messetechnik GmbH, Dresden, Germany), or equivalent. This instrument measures the surface tension of a liquid according to the bubble pressure approach, which involves injecting air into the test liquid via a capillary that is immersed within the test liquid, thereby forming a bubble within the test liquid. For the purposes of this invention, the term “dynamic” is not to be inherently associated with the measured SFT values reported by the tensiometer or accompanying software, regardless of how that terminology is used by the software or in common language. Rather, for SFT values the term “dynamic” is only to be associated with predicted SFT values that are output from the curve fitting and modelling procedures specified here, and which additionally meet the slope value criteria also specified herein.
The tensiometer is used to obtain surface tension measurements for the test liquid at multiple bubble lifetime time points, using the Auto function within the software. Between each sample tested the instrument is cleaned by rinsing the capillary tube and temperature probe with DI water, followed by their immersion in 20 mL of ethanol for 15 min, followed by their immersion in 20 mL of DI water. Instrument calibration is subsequently conducted with 20 mL of deionized (DI) water within the temperature range of 20-30° C. The instrument parameter values used during analysis are as follows. Mode is set as Auto-Measurement Mode; Start Bubble is set at 15 ms; End bubble is set at 50 s; Tolerance is set at 8%; Resolution is set at Medium; Average is set as 1; Skip is set as 0; Bar min (graph display) is set at 20; Bar max (graph display) is set at 80. The resolution selected is set to have 25 measurement points within the range of bubble lifetimes described in the parameters. The auto-measurement of the surface tension is conducted by placing the tip of the capillary tube and the temperature probe of the tensiometer into about 20 mL of the test liquid held in a glass vial. The temperature of the test liquid is held steady and within the range of 20-30° C. Three replicates samples are analyzed, and the average result is reported as the Surface Tension of the test material, expressed in units of mN/m, for each measurement time point within the range of 0.03-50 sec of bubble lifetimes. For SFT data points, the Bubble Lifetime values are deemed to be directly equivalent to the drop Surface Age values of Interfacial Tension data points from the IFT method contained herein.
A curve is fitted to the data points of SFT (mN/m) plotted versus surface age (sec), and subsequently the slope of the fitted curve at any given time point is determined,
The procedures for fitting a curve to the measured surface tension values, and the subsequent determination of the slope of the curve at any given time point are both procedures that are conducted in accordance with the teachings of Hua, X., Rosen, M. J. Dynamic Surface Tension of Aqueous Surfactant Solutions 1: Basic Parameters, J. Colloid Interface Sci. 124, 2 (1988), as described in the following two equations. The curve equation to be fitted is:
wherein:
The constant values for the four fitted parameters in the curve equation are determined via the reiterative non-linear process of least sum of squares (of the residual errors). This modeling process is conducted by fitting to find constant values for the fitted curve equation parameters which yield the lowest Sum of Squares. This approach aims to minimize the difference between the input values (i.e. the measured SFT values) and the output values (i.e., the predicted SFT values). This curve fitting process is conducted using the “Solver” module within the spreadsheet software Microsoft Excel (such as version #14.0, 32-bit, available from Microsoft Corp. Redmond, Wash., U.S.A.). Within the Solver module of the Excel program, the following options are selected: Solver Method is set as GRG Nonlinear; and Convergence is set at 0.0001. The numerical constraints for each of the four parameters (as specified respectively alongside the equation) are imposed within the Excel program, in order to restrict the range of acceptable values for the parameter constants being determined. Additionally, the reiterative fitting process is seeded with starting values for each of the four parameter values being determines. These starting seed values are selected as follows: γ0 is set as 110% of the highest measured SFT value; γe is set as equal to the SFT value measured at the longest time point; t is set as 1; and n is set as 1,
Once the least sum of squares process has determined constant values for the four fitted parameters in the curve equation, those fitted parameter values are substituted into the curve equation so that the equation can then be used to produce predicted values of SFT for any time point of interest. Using the equation of the fitted curve, predicted SFT values may be extrapolated to time points for which measured surface tension data were not collected.
Whether a predicted SFT value on the fitted curve is a dynamic value or a steady state value is determined as follows. The point on the fitted SFT curve at the time point of interest is identified. Next, the slope of the line at that time point is determined using the slope equation below (first derivative of the previous curve equation).
wherein:
The value of the slope of the fitted curve at any given bubble lifetime time point indicates whether the predicted SFT value at that time point on the fitted curve is considered to be a Dynamic value or a Steady State value. At a given bubble lifetime time point, the predicted SFT value of the fitted curve is defined as being a Dynamic Surface Tension (DSFT) value if the absolute value (i.e. with the sign omitted) of the slope of the curve at that time point is greater than 0.05 mN/m·s. DSFT values at time points along the fitted curve are reported in units of mN/m, at their respective bubble lifetime time point.
Predicted SFT values are also generated from the fitted curve equation from at least 25 time points (i.e., bubble lifetime or drop surface age), namely, the time points within the range of 0 sec to 10.8 sec, at intervals of 0.02 sec, and these values are used as specified for calculations within the Spreading Coefficient Test Method.
Spreading Coefficient (SC) values for a particular combination of core liquid and shell liquid are determined as follows. First, Surface Tension (SFT) values are collected for the core liquid and the shell liquid according to the Surface Tension Test Method set forth herein. Next, Interfacial Tension (IFT) values are collected for the core liquid and the shell liquid combination according to the Interfacial Tension Test Method set forth herein. The Bubble Lifetime values of Surface Tension data points are deemed to be directly equivalent to the drop Surface Age values of Interfacial Tension data points from the IFT method contained herein. Spreading Coefficient (SC) values are next generated as follows. The initial calculated spreading coefficient values are calculated according to the initial spreading coefficient equation below at each of at least 25 time points (i.e., bubble lifetime or drop surface age) using the predicted values of IFT and SFT which are generated by the respective curve equations fitted via the least sum of squares modeling procedures specified in the respective test methods. The time points at which predicted values for IFT and SFT, and the initial spreading coefficient values are calculated are the time points within the range of 0 sec to 10.8 sec, at intervals of 0.02 sec.
Initial Spreading Coefficient (at a given time point T)=γCORE−γSHELL−γINTERFACIAL
wherein:
In a process similar to the curve fitting procedures specified within the IFT and SC test methods, a curve is also fitted to these initial calculated spreading coefficient values, and subsequently the slope of the curve at any given time point is determined, with both procedures conducted in accordance with the teachings of Hua, X., Rosen, M. J. Dynamic Surface Tension of Aqueous Surfactant Solutions 1: Basic Parameters, J. Colloid Interface Sci. 124, 2 (1988), as described in the following two equations. The curve equation to be fitted is:
wherein:
The constant values for the four fitted parameters in the curve equation are determined via the reiterative non-linear process of least sum of squares (of the residual errors). This modeling process is conducted by fitting to find constant values for the fitted curve equation parameters which yield the lowest Sum of Squares. This approach aims to minimize the difference between the input values (i.e. the initial calculated spreading coefficients) and the output values (i.e., the predicted SC values). This curve fitting process is conducted using the “Solver” module within the spreadsheet software Microsoft Excel (such as version #14.0, 32-bit, available from Microsoft Corp. Redmond, Wash., U.S.A.). Within the Solver module of the Excel program, the following options are selected: Solver Method is set as GRG Nonlinear; and Convergence is set at 0.0001. The numerical constraints for each of the four parameters (as specified respectively alongside the equation) are imposed within the Excel program, in order to restrict the range of acceptable values for the parameter constants being determined. Additionally, the reiterative fitting process is seeded with starting values for each of the four parameter values being determines. These starting seed values are selected as follows: γ0 is set as 110% of the highest initial calculated SC value; γe is set as equal to the initial calculated SC value at the longest time point calculated (i.e. 10.8 sec); t is set as 1; and n is set as 1,
Once the least sum of squares process has determined constant values for the four fitted parameters in the curve equation, those fitted parameter values are substituted into the curve equation so that the equation can then be used to produce predicted values of SC for any time point of interest. Using the equation of the fitted curve, predicted spreading coefficient values may be extrapolated for time points of bubble lifetime or drop surface age for which measured surface tension and measured interfacial tension data were not collected.
Whether a predicted Spreading Coefficient value on the fitted curve is a dynamic value or a steady state value is determined as follows. The point on the fitted spreading coefficient curve at the time point of interest is identified. Next, the slope of the line at that time point is determined using the slope equation below (first derivative of the previous curve equation).
wherein:
If the slope of the curve of predicted spreading coefficient values, at a selected time point of interest, is greater than 0.05 mN/m·s, then the predicted spreading coefficient value at that time point on the curve is defined as being a Dynamic Spreading Coefficient (DSC) value. If the slope of the spreading coefficient curve at a selected time point of interest is less than or equal to 0.05 mN/m·s, then the predicted spreading coefficient value at that time point on the curve is defined as being a Steady State Spreading Coefficient value.
A population of microcapsules is characterized by their Mean Equivalent Diameter (D) value, which is obtained using the computerized image analysis software ImageJ version 1.46r, (available from the National Institutes of Health, Bethesda, Md. USA, http://imagej.nih.gov/ij/, 1997-2012), to analyze images of microcapsules obtained via microscopy. The type of microscope instrument, along with the illumination source and geometry, detector type and geometry, and any instrument or software options affecting image contrast, are all carefully selected and set up such that the combined configuration of the instrument yields images of the microcapsules that display an evenly illuminated background and are substantially free from side-directional shadowing and highlighting, or other illumination effects which hinder accurate rendering of the object perimeter when processed through the ImageJ automatic thresholding function. One such suitable microscope is the Scanning Electron Microscope (SEM) model Hitachi TM-1000 Table Top SEM (available from Hitachi High-Technologies Europe GmbH. Germany).
A sample of about 30 mg of the microcapsule powder test material is prepared for examination under the microscope, by dispersing the sample of microcapsules as a uniform monolayer having minimal agglomerations of particles. In using SEM, the sample may be adhered to a stub (such as a 12.5 mm diameter Aluminum Pin Stub G301, mounted with 12 mm diameter Leit Adhesive Carbon tab, as available from Agar Scientific. Essex. UK). The microscope is operated at a magnification of approximately 100× and is used to obtain images of at least 500 randomly selected microcapsules per sample preparation, via capturing at least ten images per sample of the test material. From the ten or more images captured, at least three images are selected for image analysis, while ensuring that sufficient images are selected to depict a monolayer of at least 300 microcapsules in total. Each of the images to be analyzed is calibrated for linear scale and the scale used is in micrometers (μm). Each image is captured as, or converted to, 8-bit grayscale pixel depth, and then automatically thresholded to create a binary (black and white) image. The grey level value to be used as the threshold value is obtained by applying the ImageJ software's automatic threshold function independently to each grey scale image. This automatic thresholding function yields a binary image wherein pixels representing the microcapsules become the foreground objects and regions-of-interest, and which are separated from the background pixels. The area (in square micrometers) of each region-of-interest object representing an individual microcapsule is then measured with the ImageJ software by selecting “Area” on the “Set Measurement” menu, and within “Area” selecting “Exclude Edge Particles” and “circularity”. Then for “circularity” entering the range of values from about 0.4 to about 1 on the “Analyze Particles” menu.
The obtained areas (A, in sq. μm) are recorded and used to calculate the equivalent diameters of perfect circles, according to following formula:
d
i=√(4Ai/π)
wherein:
Then, equivalent diameters (di) are rank-ordered from largest to smallest size and the mean microcapsule equivalent diameter is obtained and reported using following formula:
wherein:
Additionally, the 5th, 50th and 95th percentile values are also calculated and reported for these equivalent diameter data points.
A population of microcapsules (or encapsulated benefit agent particles) is characterized by a coefficient of variation (CoV) of the equivalent diameters, corresponding to the ratio between the distribution of equivalent diameters in said population of microcapsules (i.e., the standard deviation) and the mean microcapsule equivalent diameter. CoV is obtained as follows. First, the Standard Deviation (STD) of the mean microcapsules' equivalent diameter is obtained using following formula:
wherein:
Finally, the coefficient of variation (CoV) of the equivalent diameters of a population of microcapsules is obtained using following formula:
wherein:
Dynamic Vapor Sorption (DVS) water sorption is a gravimetric technique that measures the mass of a sample as it changes in response to changes in humidity. The Dynamic Vapor Sorption water sorption percentage of a test material (e.g. polymer) when exposed to humidity is measured by using a ProUmid SPS-DVS Instrument (available from ProUmid GmbH & Co. KG, Ulm, Germany), or equivalent. The instrument is capable of resolving changes in sample weight as small as 0.1 μg. The accuracy of the system conditions is ±0.5% for the relative humidity (RH), and ±0.3° C. for temperature. A 100 to 200 mg sample of the test material is placed onto the specimen chamber microbalance of the DVS instrument and the instrumental temperature is fixed at 30° C. The test material sample is held at 30° C. and 30% RH until the mass was stable over time (i.e. a change in mass per unit time that is lower than 0.02 mg/h). The precise initial weight of the equilibrated sample is determined and recorded. The relative humidity that the sample is exposed to within the instrument is then raised in a single step from 30% to 80% RH (sorption). The sample weight is monitored until the change in mass per unit of time is less than 0.02 mg/h, at which time the stabilized final weight is determined and recorded. For each sample, the DVS water sorption percentage value is the difference between the initial sample weight and the final sample weight, calculated as a percentage of the initial weight. For each test material, three replicate samples are measured using a new fresh sample for each replicate. The DVS water sorption percentage value reported for the test material is the average of the DVS water sorption percentage values obtained from the three replicate samples.
Viscosity measurements of a test material are obtained using a model ARG2 stress-controlled rheometer having a 40 mm 1° cone and plate geometry (available from TA Instruments, Inc. (New Castle, Del., U.S.A.). This geometry has an inherent nominal cone truncation distance of 26 μm. All measurements are performed after 3 minutes of equilibration at 20° C. under a constant shear rate of 0.01 l/s, preceded by a pre-shear stage of 10 seconds at a shear rate of 10 l/s. Shear viscosity versus shear rate profiles are acquired in continuous ramp mode from 0.01 to 1,200 l/s taking at least 30 points per shear rate decade in logarithmic distribution. The viscosity value for each analysis is calculated as the average of the shear viscosity values measured during the shear rates ranging from 10 to 1000 s−1. For each test material, the analysis is conducted in triplicate using a new fresh sample for each replicate. The viscosity value reported for the test material is the average viscosity value calculated from the triplicate analyses, reported in units of cP (centipoise).
Thermogravimetric analysis (TGA) is conducted using a TGA analyzer such as the model Q-5000 available from TA Instruments, Inc. (New Castle, Del., U.S.A.) or equivalent, to determine the average Core Liquid Loading for a population of microcapsules. The Q-5000 has a weighing precision of 0.01%; a sensitivity of 0.1 g; an isothermal temperature accuracy of 1° C.; and isothermal temperature precision of 0.1° C. TGA is used to measure the weight change of a population of microcapsules as a function of temperature and time, under a controlled atmosphere. A gas purge system removes the decomposition materials during testing.
The sample of microcapsules is heated to a temperature which is both higher than the boiling point of the core material and is also lower than the degradation temperature of the shell material, such that the core material is vaporized and released while the mass of the shell material is principally left behind. One of skill will of course recognize however that such a temperature may not exist for all combinations of core and shell materials. For the purposes of this test method the temperature of 250° C. is specified. This value has been shown to be broadly suitable for many relevant combinations of core and shell materials.
The microcapsules to be sampled for testing is preconditioned by equilibrating it to the laboratory's ambient atmospheric conditions (approximately 25° C. and 50% RH) prior to being weighed. Open platinum pans are used to hold the test sample during analysis, and the precisely known sample weight is within the range of 15 to 20 mg of microcapsule powder. All analyses are conducted with the test sample under a nitrogen atmosphere with a flow rate of 25 mL/min. The TGA instrument is configured to run the following temperature profile conditions for the initial analysis: Initial Ramp at 20° C./minute to 250° C., followed by an Isothermal Hold at 250° C. for 30 minutes. The percent weight loss value reported is the value measured at the time point when the derivative “% loss/minute” drops below 0.05%/min. Measurements are collected from two replicate samples, using a new fresh sample for each replicate. The results from the replicate samples are averaged. The average measured result is reported as the Core Liquid Loading (as % by weight of the microcapsules).
The Glass Transition Temperature, Tg, for a material may be determined using Differential Scanning Calorimetry (DSC) according to the method described herein in the event the glass transition temperature for a material of interest is not otherwise available from the material's supplier or manufacturer. The Depressed Glass Transition Temperature, Tgd, for a combination of materials (e.g., the combination of a wall forming material and surfactant(s)) may also be determined using DSC according to the method described herein. A differential scanning calorimeter is utilized, such as a TA Instruments Inc. DSC Q2000 (or equivalent device) with a Standard Cell RC and auto sample changer.
A test sample is prepared by placing the material(s) of interest in an oven at 100° C. for at least 12 hours followed by cooling the material(s) to ambient temperature followed by placement in a desiccator where the material(s) remain until placement in the DSC device. In preparation for placement in the DSC device, the material(s) of interest is removed from the desiccator and a sample (between 9 and 22 mg) is added to a tared TZero Pan (TA product #150710) and a TZero Hermetic Lid (TA product #151008) is crimped on top. Preferably, the material(s) of interest completely cover the bottom of the pan to ensure good thermal contact. The pan is loaded into the autosampler of the DSC device together with a reference pan.
Following calibration of the DSC device according to manufacturer's instructions, two temperature cycles are performed as follows. The pan containing the test sample is allowed to equilibrate at −50° C. followed by a first temperature cycle which consists of increasing the pan temperature at a rate of 10° C./minute until the pan temperature reaches 150° C. followed by decreasing the pan at a rate of 20° C./minute until the pan temperature reaches −50° C. The test sample is allowed to equilibrate at −50° C. and then a second temperature cycle is performed which consists of increasing the pan at a rate of 10° C./minute until the pan temperature reaches 200° C. followed by decreasing the pan temperature at a rate of 20° C./minute until the pan temperature reaches a temperature of −50° C.
Experimental data may be analyzed with TA “Universal Analysis” Software V4.5A or equivalent. Tg and Tgd are determined from the heat flow curve, which is an X-Y curve of heat flow (mw) v. temperature (° C.). While Tg and Tgd occur over a temperature range, Tg and Tgd are determined according to the mid-point temperature, Tm (° C.), definition found in Section 3 of ASTM E1356-08 titled “Standard Test Method for Assignment of the Glass Transition Temperatures by Differential Scanning Calorimetry” (Reapproved 2014), the substance of which is incorporated herein by reference.
The following examples are given solely for the purpose of illustration and are not to be construed as limitations of the invention as many variations are possible without departing from the spirit and the scope of the invention.
A shell liquid and core liquid were prepared as follows. The core liquid comprised a 50:50 by weight mixture of L-menthol (available from Symrise AG) and menthyl lactate (also available from Symrise AG), which are initially solids but form an oil when mixed and melted. This mixture remains a liquid when cooled to room temperature. The core liquid was prepared by mixing both solids and then heating them to approximately 50° C. until a transparent oil formed. Once the mixture was a liquid, 1% by weight of sodium dioctyl sulfosuccinate (available from Cytec Industries, Inc. under the name AEROSOL™ OT) was added to the liquid.
The shell liquid was prepared by mixing 10 wt % of Eastman AQ™38S (available from Eastman Chemical Company), 0.5 wt % of SDS (available from Sigma-Aldrich GmbH) and 0.5 wt % of DYNOL™ 960 (available from Air Products and Chemicals, Inc.) in water.
A shell liquid and core liquid were prepared as follows. The core liquid comprised a perfume oil mixture. The shell liquid was prepared by mixing 10 wt % PLASCOAT™ Z-687 (available from Goo Chemical Co., Ltd.), 0.3 wt % of DYNOL™ 960 (available from Air Products and Chemicals, Inc.), 0.15 wt % SDS (available from Sigma-Aldrich GmbH) in water. The shell liquid and the core liquid were each loaded into a separate syringe pump, such as, for example a programmable syringe pump model PHD 4400 available from Harvard Apparatus (USA). The syringe pumps were connected to a concentric flow microfluidic device, such as, for example, Flow Focusing® device model # PSC0350F available from Ingeniatrics SA. This microfluidic device has fundamentally the same configuration as that shown in
The shell liquid and the core liquid were pumped through the microfluidic device using the syringe pumps The flow rates of the shell liquid was adjusted to 7 ml/hr, and the flow rate of the core liquid was adjusted to 3 ml/hr. Ambient air was used as the pressurizing gas for the pressurizing chamber. A population of microcapsules was collected at the exit of the spray dryer. The population of microcapsules were observed to have retained their shell integrity within 24 hrs of collection.
A shell liquid and core liquid were prepared as follows. The core liquid comprised a 50:50 by weight mixture of L-menthol (available from Symrise AG) and menthyl lactate (also available from Symrise AG), which are initially solids but form an oil when mixed and melted. This mixture remains a liquid when cooled to room temperature. The core liquid was prepared by mixing both solids and then heating them to approximately 50° C. until a transparent oil formed. The shell liquid was prepared by mixing 10 wt % PLASCOAT™ Z-687 (available from Goo Chemical Co., Ltd.), 0.3 wt % of DYNOL™ 960 (available from Air Products and Chemicals, Inc.), 0.15 wt % SDS (available from Sigma-Aldrich GmbH) in water. The shell liquid and the core liquid were each loaded into a separate syringe pump, such as, for example a programmable syringe pump model PHD 4400 available from Harvard Apparatus (USA). The syringe pumps were connected to a concentric flow microfluidic device, such as, for example, Flow Focusing® device model # PSC0350F available from Ingeniatrics SA. This microfluidic device has fundamentally the same configuration as that shown in
The shell liquid and the core liquid were pumped through the microfluidic device using the syringe pumps. The flow rate of the shell liquid was adjusted to 80 ml/hr, and the flow rate of the core liquid was adjusted to 5 ml/hr, with a target core:shell ratio of 35:65. Ambient air was used as the pressurizing gas for the pressurizing chamber. A population of microcapsules was collected at the exit of the spray dryer. The population of microcapsules were observed to have retained their shell integrity within 24 hrs of collection.
A shell liquid and core liquid were prepared as follows. The core liquid comprised a 50:50 by weight mixture of L-menthol (available from Symrise AG) and menthyl lactate (also available from Symrise AG), which are initially solids but form an oil when mixed and melted. This mixture remains a liquid when cooled to room temperature. The core liquid was prepared by mixing both solids and then heating them to approximately 50° C. until a transparent oil formed. Once the mixture was a liquid, 1% by weight of sodium dioctyl sulfosuccinate (available from Cytec Industries, Inc. under the name AEROSOL™ OT) was added to the liquid.
The shell liquid was prepared by mixing 10 wt % of Eastman AQ™38S (available from Eastman Chemical Company), 0.5 wt % of SDS (available from Sigma-Aldrich GmbH) and 0.5 wt % of DYNOL™ 960 (available from Air Products and Chemicals, Inc.) in water.
The shell liquid and the core liquid were each loaded into a separate syringe pump, such as, for example a programmable syringe pump model PHD 4400 available from Harvard Apparatus (USA). The syringe pumps were connected to a concentric flow microfluidic device, such as, for example, Flow Focusing® device model # PSC0350F available from Ingeniatrics SA. This microfluidic device had fundamentally the same configuration as that shown in
The shell liquid and the core liquid were pumped through the microfluidic device using the syringe pumps The flow rates of the shell liquid was adjusted to 15.4 ml/hr, and the flow rate of the core liquid was adjusted to 4.6 ml/hr. Ambient air was used as the pressurizing gas for the pressurizing chamber.
A population of microcapsules was collected at the exit of the spray dryer. Thermogravimetric analysis indicated an average core liquid loading of approximately 60% (compared to approximately 28% for Comparative Example 5).
The shell liquid and the core liquid of Example 1 were each loaded into a separate syringe pump, such as, for example a programmable syringe pump model PHD 4400 available from Harvard Apparatus (USA). The syringe pumps were connected to a concentric flow microfluidic device, such as, for example, Flow Focusing® device model # PSC0350F available from Ingeniatrics SA. This microfluidic device has fundamentally the same configuration as that shown in
The shell liquid and the core liquid were pumped thru the microfluidic device using the syringe pumps. The flow rates of the shell liquid was adjusted to 15.4 ml/hr, and the flow rate of the core liquid was adjusted to 4.6 ml/hr. Ambient air was used as the pressurizing gas for the pressurizing chamber.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
| Number | Date | Country | |
|---|---|---|---|
| 62728128 | Sep 2018 | US |
