The present invention relates to foaming hand sanitizers which utilize a linear polysiloxane polyether as the foaming agent and an alcohol as the virucidal agent.
Viruses cause about 5% of all healthcare associated infections, and the use of ethanol-based hand rubs can prevent such infections. However, the efficacy of ethanol-based hand rubs with respect to various types of viruses depends on the concentration of ethanol. By way of example, ethanol concentrations of less than 75% (by weight) were effective within 30 seconds against enveloped viruses, however, a concentration of up to 95% was necessary to kill certain non-enveloped viruses within 30 seconds. See, e.g., Kampf, Guenter, Efficacy of Ethanol against Viruses in Hand Disinfection, J
Ethanol-based hand rubs can be dispensed as liquids, gels, and foams. For a number of usability reasons, including fast absorption, reduced drying time, low smell, gentleness to the skin, clean/non-sticky feel, and dosage control, foam-based hand sanitizers are viewed as superior to liquid- and gel-based hand sanitizers. See, e.g., Greenaway, R. E. et al., Impact of Hand Sanitizer Format (Gel/Foam/Liquid) and Dose Amount on its Sensory Properties and Acceptability for Improving Hand Hygiene Compliance, J
Alcohol-based foaming hand sanitizers known in the art typically include an alcohol such as ethanol or isopropanol, water, and a linear polysiloxane polyether foaming agent. For example, U.S. Pat. No. 8,058,315 discloses the combination of an alcohol (ethanol, propanols, or butanols), water, and a polyethylene glycol (PEG) linear dimethicone surfactant with a length of PEG-8, PEG-10, or PEG-12. Similarly, U.S. Pat. Pub. No. 20150297728 discloses the combination of ethanol, water, and a linear dimethicone copolyol with a polyethylene glycol of PEG-8, PEG-10, or PEG-12. However, the inventors of the present invention have experimentally determined that the foams based on such prior art formulations do not exhibit high foaming quantity, quality, and stability when the alcohol content exceeds 85% by weight; in particular, less foam is produced, the foam breaks down more quickly, the foam is less dense, and the air bubbles are bigger and non-uniform in size.
Therefore, what is needed is a foaming hand sanitizer that has an alcohol content sufficient to kill most viruses within 30 seconds that still provides high foam quantity, quality, and stability comparable to foaming hand sanitizers having a lower alcohol content.
Embodiments of the present invention relate to formulation of a foaming alcohol-based hand sanitizer that (a) has an alcohol content high enough to kill most viruses within 30 seconds and (b) has foam properties of comparable quantity, quality, and stability to that of lower alcohol content foaming hand sanitizers. More particularly, the embodiments of the present invention utilize a linear polysiloxane polyether having a polysiloxane backbone with between 20 and 40 repeating dimethyl siloxane units and blocked by propyl segments, polyethyl ether chains (each having between 10 and 20 repeating ethyl ether units), polypropyl ether chains (each having between 0 and 10 repeating propylene oxide units), and terminal hydroxyls. Embodiments of the present invention comprise between 0.01 and 5% by weight of the linear polysiloxane polyether, at least 85% alcohol by weight, and the remainder being water.
In the following embodiments of the present invention, polymer segments are expressed in terms of the number of repeating monomer units. These numbers should be interpreted as referring to the statistical average number of monomer units in each molecule and not an exact numerical requirement.
Embodiments of the present invention utilize a linear polysiloxane polyether comprising a polysiloxane segment having between 20 and 40 —OSi(CH3)2— units, blocked on each side by a propyl segment, a polyethyl ether segment having between 10 and 20 —CH2CH2O— units, an optional polypropyl ether segment having between 1 and 10 —CHCH3CH2O— units and a terminating hydroxy.
The foregoing linear polysiloxane polyethers 100 and 200 are combined with ethanol and water to form the inventive foaming hand sanitizer, where the foaming hand sanitizer contains at least 85% ethanol, between 0.01% and 5% linear polysiloxane polyether, with the balance of foaming hand sanitizer being water (all percentages measured by weight).
In a preferred embodiment utilizing linear polysiloxane polyether 200, the inventive foaming hand sanitizer comprises:
In order to evaluate the foaming characteristics of foaming hand sanitizers, the inventors have adapted techniques known in the art for measuring foam quality and quantity. By comparing various formulations of foaming hand sanitizers under controlled procedures, the inventors have identified which formulations produce the highest quality and quantity of foam.
To measure foam quantity, the inventors poured a 50 g sample of the subject foam hand sanitizer into a woo-watt Oster® Classic Series Heritage Blender, blended the sample at the highest speed for 10 seconds, poured the sample into a 100 ml graduated cylinder, and measured the total volume of the foam and any un-foamed liquid immediately, after 30 seconds, and after 5 minutes.
To measure foam quality, the inventors placed a sample of the subject foam hand sanitizer into a 250 ml PET bottle with a foamer pump, commercially available from SKS Bottle & Packaging Inc. (item #0043-12), priming the foaming pump head with several pumps, performing one additional pump onto a flat, black, circular plastic surface 58 mm in diameter, and then photographing the surface immediately and again after 30 seconds. Three panelists independently graded the foam quality on a 1 to 5 scale defined as follows:
1.0 (poor). This foam exhibits few to no visible bubbles of random sizes, and the black surface area is completely visible through the liquid/foam. See
1.5 (poor to low). This foam exhibits few visible bubbles of small sizes, and the black surface area is nearly completely visible through the foam. See
2.0 (low). This foam exhibits loosely-packed bubbles of random sizes, and less than half of the black surface area is covered with foam. See
2.5 (low to average). This foam exhibits low density, random-sized bubbles, and about half of the black surface area is covered with foam. See
3.0 (average). This foam exhibits loose-to-dense, large, and tightly-packed bubbles, and more than half of black surface area is covered with foam. See
3.5 (average to good). This foam exhibits mostly small, homogenous-sized bubbles size with a few larger bubbles and little to no volume, and nearly all of the black surface area is covered with foam. See
4.0 (good). This foam exhibits loose to dense, nearly same-sized, tightly packed bubbles, with low volume, and the black surface area is completely covered with foam. See
4.5 (good to excellent). This foam exhibits loose to dense, lacy bubbles in high volume, and the black surface area is completely covered with foam. See
5.0 (excellent). This foam exhibits densely-packed, mostly or completely same-sized bubbles, in high volume, and the black surface is mostly or completely covered with foam. See
Based on the inventors' empirical observations using these qualitative and quantitative techniques, compositions having an initial foam volume of at least 95 ml have the best potential to generate foams with enough quantity, quality, and stability when dispensed with non-propellent foam packaging. Further, a foam quality score of at least 3.5 is needed to fully cover the consumer's hand with foam, and a foam quality score of 4.5 to 5.0 provides higher spreadability and hand coverage, reducing the occurrences of un-foamed liquid dripping through the consumer's fingers upon application.
To evaluate the performance of the embodiments of the present invention using these qualitative and quantitative techniques, the inventors first established a baseline using a prior art linear polyethyl polysiloxane surfactant comprising 20 dimethyl siloxane units and two terminal polyethylene glycol segments, each having 12 ethyl ether units. This prior art linear polyethyl polysiloxane is commercially-available from Ele′ Corporation under the brand name PEL-SIL™ Bis-PEG-12. The inventors tested two foaming hand sanitizer formulations using this prior art surfactant, one with 65% ethanol and the other with 90%; both formulations used 1.75% prior art surfactant with the balance being water. As shown by the table in
Next, the inventors prepared hand sanitizer formulations using embodiments of the linear polyethyl polysiloxane surfactant of the present invention; all formulations had 90% ethanol, 1.75% surfactant, and 8.25% water (all percentages measured by weight). As can be seen in from the table in
The foaming hand sanitizers described in the foregoing embodiments of the present invention may be modified and/or extended by one of ordinary skill without departing from the spirit of the present invention, so long as (a) the virucidal efficacy after 30 seconds achieves≥log10 reduction of viral infectivity in suspension tests or the limit of detection is reached, (b) the foam quality using the foregoing techniques indicated a foam quality score ≥3.5, and (c) the foam quantity using the foregoing techniques indicated a foam volume of 95 ml. Selection of some of these modifications and extensions may affect the quality of the general characteristics of the present invention in terms of performance when used for particular applications. Other modifications and extensions may be driven by costs of manufacture, availability of materials, physical constraints, and other factors which may be independent of the general characteristics of the present invention. The following variations represent a non-exclusive list of examples of other embodiments which may be mixed and matched as needed and as technically feasible without affecting the general characteristics of the present invention.
In the foregoing foaming hand sanitizer embodiments, ethanol acts as the virucidal agent. In other embodiments, methanol, isopropanol, butanol, or other water-miscible alcohols may be used, either alone or in combination.
In the foregoing foaming hand sanitizer embodiments, the polysiloxane backbone is separated from the propyl ether backbone by a linear propyl segment. In other embodiments, this segment could be non-linear and it could include a different number of carbons (typically between 1 and 5).
In the foregoing foaming hand sanitizer embodiments, the disclosed formulation comprises ethanol, water, and the inventive linear polysiloxane polyether. In other embodiments, the foaming hand sanitizer may include additional components typically found in foaming hand sanitizer products, including additional surfactants, foam stabilizers, fragrances, coloring agents, terpenoids, humectants, skin conditioning agents, chelating agents, preservatives, thickeners, skin feel enhancers, and antioxidants. Such additional components would typically take the place of a portion of the water.
The procedures used to evaluate the quality and quantity of foam for any given formulation of the foaming hand sanitizer in comparison to prior art foaming hand sanitizers may be modified as needed, provided that the same procedures and scales are used for all samples in the comparison.
In the embodiment shown in
This application claims the benefit of U.S. App. No. 63/136,893 titled “Foaming Hand Sanitizer with High Alcohol Content” which was filed on Jan. 13, 2021.
Number | Date | Country | |
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63136893 | Jan 2021 | US |
Number | Date | Country | |
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Parent | PCT/US2022/011271 | Jan 2022 | US |
Child | 18220101 | US |