Patent Application
20080292569
Method for increasing the efficiency of surfactants, suppressing lamellar mesophases, temperature stabilization of the monophase area, and method for reducing the interfacial surface tension in microemulsions that contain silicone oils, by means of additives and surfactant/oil mixture
The invention relates to a method for increasing the efficiency of surfactants, suppressing lamellar mesophases, temperature stabilization of the monophase, and method for reducing the interfacial surface tension in microemulsions that contain silicone oils, by means of additives and a surfactant/oil mixture.
In the following, microemulsions are construed as mixtures of water, oil, and surfactant that are thermodynamically stable. An oil is construed to be a liquid that is not miscible with water.
Normally hydrocarbon oils are used for oils in microemulsions. However, microemulsions with other oils such as ester oils are known. Microemulsions that contain silicone oils represent a special case. Such microemulsions are known in the prior art. Surfactants whose hydrophobic component is a silicon-containing organic residue, e.g. an oligodimethylsiloxane, are particularly suitable for these silicone oil microemulsions. The microemulsions can be liquids or solid gels. The following publications can be cited as examples: U.S. Pat. Nos. 5,705,562, 5,707,613; U.S. Pat. No. 5,707,613; EP 0 789 610 A1; and U.S. Pat. No. 6,616,934.
The disadvantage of these silicone oil microemulsions lies in the high price for the required silicone oil surfactants.
Alternatively, mixtures of silicone surfactants and conventional surfactants that do not contain silicon can be used (US 2003/0040571 A1).
Also known are silicone oil microemulsions that do not use silicon-containing surfactants. In this case, the usual non-ionic or ionic surfactants or mixtures thereof are used (U.S. Pat. No. 6,013,683; U.S. Pat. No. 6,071,975). The disadvantage with these systems is that very high proportions of surfactants are required to maintain microemulsions.
It is also possible to use for the oil functional silicones that contain e.g. vinyl groups, Si—H, amino groups, Si—OH. The microemulsions can also be used as reaction media (EP 1 221 455 A1; U.S. Pat. No. 5,518,716; U.S. Pat. No. 5,661,215; U.S. Pat. No. 5,684,085; U.S. Pat. No. 6,207,781 B1; U.S. Pat. No. 6,201,091 B1; U.S. Pat. No. 5,017,297; U.S. Pat. No. 5,891,954).
The efficiency of the surfactants is expressed in the amount of a surfactant that is needed to mix a certain portion of oil in water or vice versa in the form of a microemulsion. Increasing efficiency thus also means widening the temperature window in which the microemulsion is stable.
However, undesired lamellar mesophases frequently occur in the technical formulation of microemulsions. Lamellar mesophases cause optical anisotropy and increased viscosity.
Temperature behavior represents another problem in the technical formulation of microemulsions. In particular, adding an additive generally leads to a shift of the monophase areas that are important for the technical application to other temperature ranges. These shifts can be on the order of magnitude of 10° C. or more. However, the consequence of this is that e.g. formulas must be altered in order to adapt them to the new temperature behavior that prevails in the monophase area.
In addition there is the need to achieve a formulation that is at least equally good while saving on surfactants. In addition to costs, saving on surfactants is also advantageous for ecological and health reasons. These requirements are particularly pronounced for silicone oil microemulsions because the silicone surfactants used in this case are expensive or very high concentrations of the conventional surfactants have to be used.
German patent application 198 39 054.8-41 discloses a method for increasing the efficiency of surfactants while simultaneously suppressing lamellar mesophases, a method for stabilizing the temperature behavior of the temperature of the monophase area for oil, water, and surfactant mixtures, a method for enlarging the structure size of emulsified liquid particles in microemulsions, and a method for reducing the interfacial surface tension of oil/water mixtures in which AB block copolymers having a water-soluble block A and a water-insoluble block B are added.
It is therefore the object of the invention also to increase the efficiency of surfactants in microemulsions that contain silicone oils and to reduce the interfacial surface tension. Silicone oil-containing microemulsions are to be stabilized with smaller amounts of surfactant, i.e. there is to be savings on surfactants, and the temperature window of the thermodynamic stability is to be widened. Moreover, the occurrence of lamellar phases in silicone oil-containing microemulsions is to be suppressed and the interfacial surface tension is to be reduced. The temperature behavior of silicone oil-containing microemulsions should remain unaffected by additives, that is, the position of the monophase area in the phase diagram should be largely unaffected by the addition of additives in terms of the temperature.
In addition, an additive is to be provided that effects the aforesaid advantages and e.g. that can be added to a microemulsion without it being necessary to significantly modify the formula. Moreover, an additive is to be provided that can be used in detergents and/or in silicone oil-containing microemulsions and that effects a reduction in the amount of surfactant required for efficacy. Among these are hair-care and personal hygiene products and cosmetic products such as deodorants, skin care products, sunscreens, lotions, shampoos, shower gels, bath preparations, lubricants, slip agents, release agents, plant protection products, pharmaceuticals, textile care products, leather and fur care products, automobile care products, cleaners and polishes, and products for household, commercial, and industrial applications. It should also provide an opportunity to produce microemulsions the size of which corresponds to the emulsified liquid particles in emulsions. The temperature window for the microemulsion stability should be enlarged for the same surfactant content if silicone oils are added.
Surprisingly, proceeding from the preamble to claim 1 all of the objects are inventively attained in that a block copolymer having a water-soluble block A and a block B that is either a polyalkylene oxide having at least 4 C atoms in the monomer component or a polydiene, a partially or completely hydrogenated polydiene having very small content of 1,4 microstructure or a high content of short-chain branching is used as an additive.
Block A is preferably not soluble in silicone oil and Block B is preferably not soluble in water.
Block A preferably comprises PEO, but copolymers made of ethylene oxide with higher alkylene oxides such as for instance propylene oxide and/or butylene oxide are also possible without Block A losing its solubility in water.
However, all blocks A can be used that are water-soluble so that they form an amphiphile in conjunction with block B. Moreover, examples for block A can be polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid and their alkali metal salts in which there has been at least a partial substitution of the acid function by alkali metal cations, polyvinylpyridine and polyvinyl alcohol, polymethylvinyl ether, polyvinylpyrrolidine, polysaccharides, and mixtures thereof.
The monomer components can occur in any sequence within block A. The individual components preferably alternate at least in part.
In one further preferred embodiment the monomer components of block A have a stochastic sequence.
Block A should preferably not be soluble in silicone oil.
In contrast, block B is preferably a polyalkylene oxide having at least 4 carbon atoms in the monomer component, preferably polybutylene oxide, polypentylene oxide, and polyhexylene oxide, but also other polyalkylene oxides having at least four carbon atoms in the monomer component. 1,2 butylene oxide is particularly preferred for the monomer component.
A block B can comprise at least two components from the group of polybutylene oxide, polypentylene oxide, and polyhexylene oxide, but also other polyalkylene oxides having at least four carbon atoms in the monomer component.
Block B can also include ethylene oxide and propylene oxide if there is solubility in silicon oil.
Moreover, Block B should preferably not be soluble in water.
Furthermore, triblocks with the structure ABA or BAB can be used as well as star-shaped polymers with the structure (AB)n or (BA)n, n symbolizing the number of arms in the star polymer. In the case of polyalkylene oxide block copolymers, the center of the star structure can be for instance an n-functional alcohol where n=number of OH groups or an m-functional amine where m=number of amino groups and n=number of H atoms bonded to nitrogen. In the case of (AB)n the component A is connected to the center of the star and in the case of (BA)n the component B is connected to the center of the star.
Another embodiment of block B are polydienes having a very small portion of 1,4 microstructure or its partially hydrogenated or completely hydrogenated polyalkane variants. Possible monomers for block B are: 1,3 butadiene, isoprene, 1,3 pentadiene, 2,3-dimethyl-1,3-butadiene, 1,3-hexadiene, and myrcene. Mixtures of the corresponding diene monomers are also possible in the block B. The number of C atoms in 1,3 diene monomers is between 4 and 20, preferably 4 and 10, particularly preferred 4 or 5. Butadiene and isoprene are particularly preferred. The diene is preferably anionically polymerizable. The branching in the polyalkanes can be attributed to the branching in the polydiene. However, the short-chain branched polyalkane blocks can also be produced without hydrogenating polydienes from other monomers as dienes, e.g. poly(1,2-butene) from 1-butene.
The microstructure of the polymer block B should be such that the 1,4 content is as small as possible. Ideally it should not exceed 10%. Other preferred ranges that lead to good results also extend however to a 1,4 content of 25% or, less preferred, 50%. Block B can be partially or completely hydrogenated.
The polymers obtained in this manner are inter alia poly(1-butene) (from 1,2 polybutadiene) or poly(1-hexene) (from 1,2 poly(1,3-hexadiene)).
The stereochemical structure of the hydrogenated variants should be as atactic as possible.
The same structures as for the polyalkylene oxide block copolymers are possible.
Surprisingly, it has been found that the inventive AB block copolymers are created such that their block B is soluble in silicone oils.
Advantageous further developments of the invention are provided in the subordinate claims.
Blocks A and B can have molecular weights between 500 and 100,000, preferably between 1000 g/mol and 50,000 g/mol, and particularly preferably between 3000 g/mol and 20,000 g/mol.
A polyethylene oxide block is preferably used for block A. Moreover, a copolymer of ethylene oxide and propylene oxide that is soluble in water can be used for block A.
A polyalkylene oxide block having at least 4 C atoms in the monomer component is preferably used for block B. These blocks B have the advantage that they are better producible and better miscible with the surfactants than polymers having blocks B=polydiene, partially/completely hydrogenated polydiene.
The inventively used AB block copolymers having block B=polyalkylene oxide can preferably be obtained from an alkoxylation using sequential polymerization of the blocks.
Block B is advantageously soluble in mineral oils or silicone oils.
Particularly advantageous properties of the inventively used AB block copolymers are observed in application products when the molecular weights of blocks A and B are on the order of magnitude of 3000-20,000 g/mol for blocks A and B. Thus the polymers having these relatively low molecular weights dissolve rapidly and well, i.e. the polymers are easy to work into a surfactant.
In one preferred embodiment, block A has ½ to 2-times the molecular weight of block B.
In the inventively used AB block copolymers, the two blocks A and B should have the greatest possible difference in their polarity. Block A is as polar as possible and Block B is as non-polar as possible. This increases the amphiphilic behavior.
Block A is water-soluble and block B is preferably soluble in non-polar media.
Block B is advantageously soluble in mineral oils, high-boiling esters, or aliphatic hydrocarbons or in silicone oils. This also preferably applies at room temperature.
Moreover, the AB triblock copolymers having the ABA or the BAB pattern and the star-shaped polymers of this monomer sequence have the same inventive effect and are therefore included in the invention.
Moreover, star-shaped polymers with the structure (AB)n or (BA)n are also included in the invention, n symbolizing the number of arms in the star polymer. In the case of polyalkylene oxide block copolymers, the center of the star structure can be for instance an n-functional alcohol where n=number of OH groups or an m-functional amine where n=number of H atoms bonded to nitrogen. These star-shaped polymers also have the inventive effect.
As an example, but not a limitation, the following surfactants (C) and their mixtures can be used with the inventive additives:
Non-ionic surfactants of the alkyl alkoxylate class, especially alkyl alkoxylates having a narrow molecular weight distribution and/or a low residual alcohol content.
Non-ionic surfactants of the alkyl polyglucoside (APG, “sugar surfactants”, CiGj where i≧8) class having cosurfactant alcohol (Cx—OH, x≧6)
Anionic surfactants, e.g. fatty alcohol sulfates, alkylbenzene sulfonates, alkylether sulfates, AOT (sodium bis-(2-ethylhexyl)sulfosuccinate)
Mixtures of surfactants, in particular non-ionic/anionic or non-ionic/cationic or silicone surfactant having non-silicon-containing surfactant.
In accordance with the invention, the efficiency of surfactants can now also be increased in microemulsions that contain silicone oils.
As an example, but not a limitation, the invention can be applied to microemulsions that contain silicone oils of the following structure types: linear, cyclic, and branched siloxanes.
R=organic group, preferably an aliphatic or aromatic hydrocarbon group, particularly preferred CH3.
Other organic groups that have for instance functional groups are also possible for R, such as: OH groups, amino groups, epoxy groups.
There can also be a plurality of different groups R.
Some of the R groups can also be —H or —OH.
a can preferably be 0-1000.
b can particularly preferred be between 3 and 10, a and b being distribution-related means. In particular a=0-10 and b=3-6.
The following compounds are cited as examples of silicone oils:
R═CH3, a ═O hexamethyldisiloxane (M2)
R═CH3, a=1 octamethyltrisiloxane (MDM)
R═CH3, a=2 decamethyltetrasiloxane (MD2M)
R═CH3, b=3 hexamethylcyclotrisiloxane (D3)
R═CH3, b=4 octamethylcyclotetrasiloxane (D4)
R═CH3, b=5 decamethylcyclopentasiloxane (D5)
The silicone oils are generally industrial products that are not monodisperse in their compositions.
Mixtures having different values for a and b are also possible, as are mixtures of linear and/or cyclic and/or branched silicone oils.
The aqueous phase of the microemulsion can contain additives like salts or water-soluble organic compounds such as e.g. glycols.
The oil phase can also contain adjuvants. However, the additives and adjuvants should not destroy the microemulsion.
For instance, glycerin can be added to the water in order to match the refractive index of the aqueous component to that of the oil component. Because of this microemulsions with increased efficiency that are visually turbid become transparent again. This method is particularly important for microemulsions that are used in the fields of cosmetic products, hair care, and personal hygiene products.
The inventive microemulsions do not absolutely have to be liquid. They can also include gel-like solid mixtures provided these are microemulsions in the thermodynamic sense. The solid form can therefore be obtained, e.g. by adding additives to the aqueous and/or oily component or by mesophases present in the microemulsion.
The ratio of the weight of the aqueous phase to the oil phase is for instance 0.01-100, preferably 0.1-10, particularly preferred 0.3-3.
The block copolymer weight proportion in the surfactant block copolymer mixture is for instance preferably 0.01-0.25, particularly preferred 0.05-0.15.
The surfactant/block copolymer mixture weight proportion in the microemulsion is preferably 0.03-0.3, preferably 0.05-0.2, depending on the temperature window.
In accordance with the invention, by adding the inventive AB block copolymers to the water/oil/surfactant mixture, the position of the monophase area remains in the same temperature range in the phase diagram, the efficiency of the surfactant mixture is significantly increased, lamellar mesophases are controlled in microemulsions, and the interfacial surface tension is reduced. In addition, microemulsions retain the properties characteristic of them while enlarging their structure; thus the emulsified structures can be up to approx. 2000 Angstroms. The size of the emulsified liquid particles is largely a function of the surfactant concentration.
A few terms shall be defined in the following:
C=Any surfactant or emulsifier, such as anionic, cationic, non-ionic surfactant or sugar surfactant, or mixtures thereof that contain at least two surfactants.
D=Additive that is inventively added to the surfactant C.
γ=Total surfactant concentration (weight fraction) of C and D
where
In the formula above,
m=weight in g
γ=dimensionless weight fraction
mges=total weight from mwater+moil+m(C)+m(D)
{tilde over (γ)}=total surfactant concentration at point of intersection at which the monophase area meets the three-phase area in the phase diagram. This is equal to the total minimum surfactant concentration that is required at a given water/oil ratio to completely mix the water and oil.
δ=Mass fraction of the additive D in the surfactant C+additive D mixture,
equals
where
m=weight in g and
δ=weight fraction (dimensionless)
PIH13: Hydrogenated polyisoprene
PEP5: Hydrogenated polyisoprene
PB05 and PB010: Poly(1,2-butylene oxide)
PEO: Polyethylene oxide
The associated microstructures for the non-polar blocks 1,2PB6, PIH13, PEP5 are provided in Table 1, the values for the hydrogenated variants, PIH13 and PEP5, being related to the non-hydrogenated polyene variants.
The efficiency of the surfactants is expressed in the amount of surfactant that is needed to solubilize a certain portion of oil in water or vice versa. The smaller the amount of surfactant needed for the same effectiveness, the higher the efficiency is. There has also been an increase in efficiency when the microemulsion is stabilized at the same surfactant concentration across wider temperature ranges.
Microemulsions are produced without adding a large amount of energy. The components can fundamentally be added to one another in any sequence.
The block copolymer and the surfactant do not have to be considered as a unit, but it can make sense to add them to a formulation together.
The following surfactants were used for the examples: Pentaethylene glycol monododecyl ether (C12E5), triethylene glycol monododecyl ether (C12E3), didodecylammonium bromide (DDAB), hydroxy(polyethyleneoxy)propyl-terminated polydimethyl siloxane [with] molecular weight 550-650 g/mol: 50% (CH2—CH2—O) (Gelest Inc. Morrisville, Pa., USA) (C4D3E8). Silicone polyether surfactants that contain a heptamethyltrisiloxane group for the hydrophobic unit, whereby a hydroxyl(polyethyleneoxy)propyl group is attached to the center silicon atom.
For M(DE10.3)M, mean ethoxylation of 10.3 and for M(DE9.7)M mean ethoxylation of 9.7 were found by means of NMR spectroscopy.
The behavior of the inventive microemulsions is depicted in
In these diagrams, the curves are each drawn in at a δ value that characterizes the limit of the monophase area associated with a δ value. The peak of each curve is the point at which different multiphase areas meet. This point is also called the fishtail point. The farther the peak of a curve is at low surfactant concentrations, i.e. γ values, the greater the efficiency of the surfactant C is by adding the block copolymer D.
The label 1 characterizes the areas of monophase microemulsion, 2 describes an oil in water microemulsion coexisting with an oil phase, and
Table 1 characterizes the block copolymers from the examples.
Table 2 provides the measured values from the characterization of the microemulsions by means of small-angle neutron scattering.
Table 2 provides the weights for the polymer content δ and for the surfactant content γ near the fishtail point. The position of the maximum scatter intensity qmax largely characterizes the domain size dTS—2π/qmax, but a more refined evaluation of the scattered intensity is based on the Teubner-Strey formula, and a more precise value is found for dTS and in addition a correlation length ξ that is approximately half the value of dTS.
The T/γ diagrams depicted in
The efficiency of the total surfactant is also increased in the example illustrated in
The water-insoluble block in the block copolymer PEP5-PEO5 has a lower portion of short chain branching and a high portion of 1,4 microstructure in the basic polydiene. While PEP5-PEO5 is suitable for increasing efficiency in the smallest dimethylsiloxane M2, the increase in efficiency from PEP5-PEO5 in the next higher dimethylsiloxane MDM is much smaller than that of 1,2PB6-PEO6, however, which has only 9% of 1,4 microstructure in the hydrophobic block. PEP5-PEO5 does not attain any increase in efficiency for higher molecular weight siloxanes.
Lamellar phases can be detected in the microemulsion with polymers and in the microemulsion without polymers. Here, as well, it would be expected that the lamellar phases in efficient systems would come closer to the fishtail point than is the case.
Table 2 and
The inventive reduction in the interfacial surface tension is illustrated in the example of the polymer PBO10-PEO10 in the system water-M2-C12E5. Using the spinning drop tensiometer, at 56° C. an interfacial surface tension σab between water and silicone oil of 3.58*10−2 is obtained in the polymer-free system. If 5% of the surfactant is now replaced with PBO10-PEO10, the interfacial surface tension is reduced to 2.2*10−2 mNm. This reduction can be reproduced for all of the illustrated examples.
In the examples, a 5% polymer portion in the surfactant is equal to δ=0.05; however, other polymer contents can be used. The increase in efficiency is more pronounced in particular with high polymer contents. δ is preferably between 0.01 and 0.25.
The interfacial surface tension of surfactants such as for instance anionic, cationic, and non-ionic surfactants, sugar surfactants, silicone surfactants, in particular industrial surfactant mixtures, is reduced with the inventively used AB block copolymers. The occurrence of lamellar mesophases is suppressed. The temperature behavior of the microemulsions remains unchanged, that is, the addition of the inventively used additive does not affect the position of the monophase area with respect to the temperature in the phase diagram. Therefore the formulas do not have to be changed in order to ensure that the position of the monophase area remains the same with respect to the temperature in the monophase diagram.
The inventive AB block copolymers, ABA, BAB, and the star-shaped co-block polymers can preferably be used for stabilizing cosmetic products containing microemulsions. Moreover, they can preferably be used as lubricants in the field of textiles, in pharmaceuticals, or as release agents.
Among possible applications are hair and personal care products and cosmetic products such as deodorants, skin care products, sunscreens, lotions, shampoos, shower gels, bath preparations, lubricants, slip agents, release agents, plant protection products, pharmaceuticals, textile care products, leather and fur care products, automobile care products, cleaners and polishes, and products for household, commercial, and industrial applications. An opportunity is also provided to produce microemulsions, the sizes of which correspond to those of the emulsified liquid particles in emulsions. The temperature window for the stability of the microemulsions should be enlarged for the same surfactant content if silicone oils are added.
Microemulsions can also be used as reaction media, they can absorb hydrophobic impurities or form by absorbing hydrophobic impurities, for instance when used as washing agents or detergents. The inventive microemulsions can give off hydrophobic components and/or wet solid or liquid surfaces. Silicone oils are suitable for this in particular due to their spreading action.
The silicone-oil containing microemulsions produced by means of the inventive addition of the AB block copolymers have emulsified liquid volumes that equal those of emulsions.
The increase in efficiency is also concurrently associated with an increase in the temperature interval within which the microemulsion is thermodynamically stable. This is particularly advantageous for industrial applications where stability must be assured across large temperature ranges.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 023 762.2 | May 2005 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2006/000842 | 5/17/2006 | WO | 00 | 1/10/2008 |
