Silicone surfactants

Abstract: Certain polysiloxane surface active agents containing radial organic polyether groups provide for improved stability of silicone emulsions, particularly antiperspirant stick compositions.

Description: The present invention relates to surface active agents of polysiloxane. More particularly, the present invention relates to polysiloxane surface active agents having radial organic polyether groups for use in stabilizing silicone emulsions. It also relates to antiperspirant stick compositions comprising such surface active agents. Background of the Invention The use of polysiloxane surface active agents containing radial organic polyether groups to stabilize silicone emulsions is well known. U.S. Pat. No. 4,265,878 uses a polysiloxane surface active agent to stabilize polish formulations. U.S. Pat. No. 4,268,499 uses these surface active agents to stabilize antiperspirant emulsion compositions. Further, U.S. Pat. No. 4,311,695 uses such surface active agents in personal care creams and the like. EP-A-0 125 779 discloses a polysiloxane surface active agent which contains alkyl radicals having from 6 to 16 carbon atoms. It also discloses skin care formulations comprising a water-in-mineral oil emulsion containing such an agent. WO 85/03641 discloses water-in-volatile silicone emulsions useful in personal-care formulations. The subject polysiloxane surface active agents are generically known and are sometimes referred to as siloxane-oxyalkylene copolymers. However, their use to date as stabilizers for silicone emulsions has not been completely satisfactory because the variables effecting their function are not well understood. It is the object of the present invention to produce novel polysiloxane surface active agents containing radical organic polyether groups. It is another object of the present invention to produce such polysiloxane surface active agents for polishes, sun screen oils, antiperspirant lotions, body lotions, and particularly for improved antiperspirant stick compositions. It is another object of the present invention to produce such polysiloxane surface active agents for antiperspirant stick compositions having improved stability, remelt stability, and low wax content. Summary of the Invention Briefly, there is provided by the present invention a surface active agent of polysiloxane consisting of (a) units of the formula: R₂SiO 2/2 where R is hydrogen, methyl, ethyl, vinyl trifluoropropyl or phenyl and (b) units of the formula RR¹SiO 2/2 where R¹ is a polyalkylene ether of the formula: - R 3 / a -(OR²)- n OR⁴ where R² is a -CH₂-CH₂-group, R³ is a substituted or unsubstituted alkylene group of from 1 to 20 carbon atoms, R⁴ is the same as R, n has a value of from about 5 to 20, and "a" is 0 or 1, with the proviso that the polysiloxane absent R¹ has a molecular weight of from 25,000 to 35,000 and the weight ratio of R¹ to polysiloxane absent R¹ is from greater than 15/85 to less than 35/65. These surface active agents may be combined with water, cyclic polysiloxane fluid, organic waxes and active ingredient, to produce antiperspirant sticks of improved properties. In addition to the (a) and (b) units described above, the polysiloxane surface active agent also includes (c) units of the formula RSiO 3/2 and will of course include end capping units which are preferably R₃SiO 1/2 but may have one or more of the R groups replaced with R¹, hydroxy or alkoxy. Units of (c) should constitute from about 0.1 to about 1% by number of siloxane units. Suitable R groups include hydrogen, methyl, ethyl, vinyl, phenyl, trifluoropropyl, etc. Preferably, at least about 80% by number of all R groups are methyl. It is critical herein that the number of repeating units of R¹, i.e. the value of n be between 5 and 20. Thus, in the case of ethylene oxide as the repeating unit, the molecular weight of R¹ should be less than 900. The preferred value of n is from 10 to 15, which likewise for ethylene oxide provides a molecular weight for R¹ of no more than 700. R³ is the group which bonds the polyoxyalkylene segment to the polysiloxane. Preferably, this group is derived from alpha-beta unsaturated carboxylic acids or alcohols. Thus, R³ may be -CH₂CH₂CH₂-, -CH₂CH₂-, -CH₂CH₂CH₂CH₂-, -(CH₂)₁₀(C=O)- etc. Preferably, R³ is -CH₂CH₂CH₂-. Otherwise, "a" could be O and the segments joined by -O- which is the product of a condensation reaction between a condensable substituent on the polysiloxane and a condensable end group on polyalkylene oxide. R⁴ is the terminal group of the polyalkylene ether. The type Of R⁴ is not critical and may be selected from hydrogen, methyl, ethyl, propyl, butyl, phenyl, alkenyl, acetyl, etc. Preferably, R⁴ is hydrogen. The polysiloxane absent R¹ has a molecular weight between 25,000 and 35,000. Further, the weight ratio of R¹ to polysiloxane absent R¹ should range from greater than 15/85 to less than 35/65 on a weight basis. Preferably, this ratio is between about 20/80 to 30/70. Given this ratio and a value for n above, it is possible to calculate the ratio of (b) siloxane units to all other siloxane units for any given surfactant. It is preferred herein that this ratio be greater than about 10/400 and preferably greater than about 15/400. The upper limit of this ratio is not as important and can be generally determined from ratios already given. The polysiloxane surface active agent may be prepared by well known methods. The preferred method is to introduce an alpha-beta unsaturated alcohol or carboxylic acid into the polymerization of alkylene glycols to produce a terminally unsaturated polyalkylene oxide. These terminally unsaturated polyalkylene glycols are subsequently added to silicon bonded hydrogens on suitable polysiloxanes. The addition reaction proceeds best in the presence of an active metal catalyst such as platinum. The manufacture of the polysiloxane surface active agents is well known and understood. Methods of preparation are taught in U.S. Pat. Nos. 4,265,878; Re 25,727; 3,174,987; 4,122,029; 3,172,899. Antiperspirant stick compositions having improved properties may be formulated using the polysiloxane surface active agent. Such compositions contain (A) from about 100 to 200 parts by weight water having the desired amount of active ingredient dissolved or dispersed therein as a discontinuous phase in about 100 parts by weight of a continuous oil matrix containing (B) at least 50% by weight cyclic polysiloxane fluid, (C) at least 25% by weight of an organic wax, and (D) about 0,25 to 5% by weight of polysiloxane surface active agent. The active ingredient may be an aluminum salt for antiperspirant effect, etc., so long as it is soluble or dispersible in water or oil. Preferably, there should be no more than about 1 part by weight active ingredient dissolved or dispersed in each 1 part by weight of water. Cyclic polysiloxane fluid for use herein is a fluid of the formula where b is 3, 4, 5, 6 or 7 and R is given above. It is important herein that the fluid evaporate from the skin at a rate which is slow enough not to make evaporative cooling noticeable but which is rapid enough that the skin quickly feels dry. Thus R and b should be chosen such that the boiling point of the cyclic polysiloxane fluid or blend of fluids is between about 175 and 250C. Preferred polysiloxanes are octamethylcyclotetrapolysiloxane and decamethylcyclopentapolysiloxane. Suitable organic waxes include mineral waxes, such as paraffin, etc; vegetable waxes, such as carnauba, flax, candelilla, etc.; and animal waxes such as bees wax. Chemically these waxes are branched or straight chain hydrocarbons, high molecular weight fatty acid, high molecular weight alcohols, or high molecular weight fatty acid esters. Characteristically waxes have low viscosities just above their melting point. For use herein the waxes should have a melting point between about 40 and 65°C. Such a melting point allows for proper application rates and prevents melting upon storage under ambient conditions. Preferably the organic wax is a mixture of waxes to control the hardness of the stick composition. Thus, a preferred organic wax is a mixture of a waxy ester for hardness, such as methyl hydroxystearate, and a solid alkanol such as stearyl alcohol. Where such a mixture of waxes is used, the organic wax might contain 10 to 50% by weight solid alkanol and 50 to 90% by weight waxy ester. Hardness is also greatly effected by the proportion of organic wax in the stick composition. Preferably, the continuous oil matrix contains about 25 to 40% by weight organic wax. The antiperspirant stick is easily prepared by methods well known in the art. Herein the cyclic polysiloxane, organic wax, and polysiloxane surface active agent are heated until all components are liquid and then mixed. Generally the components will liquify between about 40 and 70°C. Subsequently the water solution with active ingredient is warmed and emulsified into the molten wax as is known. The warm emulsion is poured as close to solidification temperature as possible into molds and allowed to cool. The solid stick compositions containing the polysiloxane surface active agent described herein have improved stability and are drier than described in the prior art. Other surfactants and additives may be included in the stick composition as experience has taught to be beneficial for specific formulations. For example, talc may be added to the oil phase and incorporated into the stick composition. Further, it may be known that further surfactants are beneficial to certain formulations, i.e. surfactants such as polyalkylene ethers, diglycerides, sorbitan monopalmitate, polyoxyethylene (20) sorbitan trioleate, complex fatty acid condensate, etc. The requied or proper amount is well known to persons skilled in the art. The following examples are offered by way of illustration and not by way of limitation. All parts are in parts by weight. Surfactants 1 to 6 These examples illustrate the production of different polysiloxane surface active agents. Production requires as the principal inputs a polysiloxane hydride fluid and polyalkylene oxide having terminal unsaturation. Identification of the polysiloxane hydride fluid is based on the following nomenclature: T = methyltrisiloxy unit D = dimethyldisiloxy unit M = trimethylsiloxy unit D¹ = methylhydrogendisiloxy unit The polysiloxane hydride fluids shown herein are produced by acid equilibration of appropriate input materials. The molecular weight and structure for the base polysiloxane hydride fluid is shown for each surface active agent in Table I. The polyalkylene oxide having terminal unsaturation is an allyl alcohol initiate polymerization of ethylene oxide or a 50/50 by weight mixture of ethylene oxide with propylene oxide. The final molecular weight and monomer input for the polyalkylene oxide portion are indicated for each surface active agent in Table I. The functional polyalkylene oxide was diluted with toluene and azeotroped to eliminate water. Subsequently a platinum catalyst was added along with a stoichiometric amount of polysiloxane hydride fluid and the mixture was heated to 100°C for 4 to 5 hours to insure complete reaction. The toluene was stripped and the resultant polysiloxane surface active agent was diluted to 10% by weight solution with cyclic D₄ and D₅ silicone fluid. Examples 1 through 6 Antiperspirant sticks were manufactured using each of surface active agents in surfactants 1 through 6. Table II shows compositions for Part A and Part B. Part A contains as the surface active agent the corresponding surfactant 1 through 6. Part A is heated to 57 to 60°C until all wax is melted and stirred to a homogeneous mixture. Likewise, Part B is heated to 57 to 60°C. Part B is added to Part A with continued mixing, and the resultant water in oil emulsion is cooled to just above melting. The emulsion is poured into commercially available stick containers which have been cooled in an ice box. Observations of each stick compositions are noted in Table I. 1 2 3 4 5 6 Part A Surfactant 1.0 1.0 1.0 1.0 1.0 1.0 D₄ Fluid 9.0 9.0 9.0 9.0 9.0 9.0 D₅ Fluid 15.0 15.0 15.0 15.0 15.0 15.0 Stearyl Alcohol 12.0 12.0 12.0 12.0 12.0 12.0 Methyl Hydroxystearate 3.0 3.0 3.0 3.0 3.0 3.0 Sorbitan Mono-oleate 0.1 0.1 0.1 0.1 0.1 0.1 Part B Aluminum Zirco<-> 25.0 25.0 25.0 25.0 25.0 25.0 nium Chloride Water 34.9 34.9 34.9 34.9 34.9 34.9 Observations Stick Hardness firm soft soft firm soft soft Stick Leakage leak leak leak w/use no leak leak leak Stick Remelt -- -- emulsion broken mixing does not restore stable emulsion restored with mixing -- --

Claims: A polysiloxane surface active agent consisting of: (a) units of the formula R₂SiO 2/2 where R is hydrogen, methyl, ethyl, vinyl, trifluoropropyl or phenyl; (b) units of the formula: RR¹SiO 2/2 where R¹ is a polyalkylene ether of the formula: -R 3 / a-(OR²) n -OR⁴ where R² is -CH₂CH₂-, R³ is a substituted or unsubstituted alkylene group of 1 to 20 carbon atoms, R⁴ is the same as R, n has a value of from 5 to 20, and "a" is 0 to 1; and (c) endcapping units; with the proviso that the polysiloxane absent R¹ has a molecular weight of from 25,000 to 35,000 and the weight ratio of R¹ to polysiloxane absent R¹ is from greater than 15/85 to less than 35/65. The polysiloxane surface active agent of Claim 1 wherein about 80% by number of R is methyl. The polysiloxane surface active agent of Claim 1 wherein n has a value of from 10 to 15. The polysiloxane surface active agent of Claim 1 wherein R¹ has a maximum molecular weight of less than 900. The polysiloxane surface active agent of claim 3 wherein R¹ has a maximum molecular weight of 700. The polysiloxane surface active agent of Claim 1 wherein R³ is derived from a compound selected from the group consisting of alpha-beta unsaturated carboxylic acids and alpha-beta unsaturated alcohols. The polysiloxane surface active agent of Claim 1 wherein R³ is selected from the group consisting of -CH₂CH₂CH₂-, -CH₂CH₂-, -CH₂CH₂CH₂CH₂-, and -(CH₂)₁₀(C = O)-. The polysiloxane surface active agent of Claim 1 wherein the weight ratio of R¹ to polysiloxane absent R¹ ranges from 20/80 to 30/70. The polysiloxane surface active agent of Claim 1 wherein the ratio of (b) units to all other siloxane units is greater than 10/400. The polysiloxane surface active agent of Claim 1 wherein the ratio of (b) units to all other siloxane units is greater than 15/400. An antiperspirant stick composition comprising: (A) from 100 to 200 parts by weight of water having an active ingredient dissolved or dispersed therein, in a discontinuous phase in 100 parts by weight of a continuous oil matrix containing: (B) at least 50% by weight cyclic polysiloxane fluid; (C) at least 25% by weight of an organic wax; and (D) 0.25 to 5% by weight of a polysiloxane surface active agent consisting of: (a) units of the formula: R₂SiO 2/2 where R is hydrogen, methyl, ethyl, vinyl, trifluoropropyl or phenyl; (b) units of the formula: RR¹SiO 2/2 where R¹ is a polyalkylene ether of the formula: -R 3 / a-(OR²) n -OR⁴ where R² is a -CH₂-CH₂- group, R³ is a substituted or unsubstituted alkylene group of 1 to 20 carbon atoms, R⁴ is the same as R, n has a value of from 5 to 20, and "a" is 0 to 1; and (c) endcapping units; with the proviso that the polysiloxane absent R¹ has a molecular weight of from 25,000 to 35,000 and the weight ratio of R¹ to polysiloxane absent R¹ is from greater than 15/85 to less than 35/65. The stick composition of Claim 11 wherein said polysiloxane surface active agent has an R² of 100% by number -CH₂CH₂-. The stick composition of Claim 11 wherein said polysiloxane surface active agent has an n with a value of from 10 to 15. The stick composition of Claim 11 wherein said polysiloxane surface active agent has a weight ratio of R¹ to polysiloxane absent R¹ of from 20/80 to 30/70. The stick composition of Claim 11 wherein said polysiloxane surface active agent has a ratio of (b) units to all other siloxane units greater than 10/400. The stick composition of Claim 11 wherein said organic wax is a mixture comprising from 50 to 90% by weight solid alkanol. The stick composition of Claim 11 wherein said active ingredient is an aluminum salt for antiperspirant effect. The stick composition of Claim 11 wherein said cyclic polysiloxane fluid boils between 175 and 250°C. The stick composition of Claim 11 wherein said organic wax has a melting point between 40 and 65°C. The stick composition of Claim 11 wherein R³ is derived from a compound selected from the group consisting of alpha-beta unsaturated carboxylic acids and alpha-beta unsaturated alcohols.

Inventors: RALEIGH WILLIAM JOHN, THIMINEUR RAYMOND JOSEPH, ZOTTO ANTHONY ARTHUR, RALEIGH, WILLIAM JOHN, THIMINEUR, RAYMOND JOSEPH, ZOTTO, ANTHONY ARTHUR
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1988
Main classification: C08G77
IPC codes: A61Q15, A61K8, B01F17, C08G77, C08L83