Siloxanes with betaine groups, their synthesis and use in cosmetic preparations
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to novel organopolysiloxanes with betaine groups and to processes for the synthesis of these compounds. It also relates to the use of these compounds in cosmetic preparations. 
     2. Description of the Prior Art 
     The use of organopolysiloxanes for the preparation of hair care products is well known. However, in &#34;Chemie und Technologie der Silicone&#34; (Chemistry and Technology of the Silicones) by Water Noll, Chemie Publishing House, 2nd edition, 1968, page 536, it is stated that normal polydimethylsiloxanols are unable to maintain the hairdo independently of the effects of moisture. Rather, the silicone would have to be fixed on the hair with the help of functional groups. 
     German Auslegeschrift No. 14 93 384 discloses organosiloxane compounds or mixtures of compounds of the formula: ##STR4## in which R represents hydrogen or CH 3 , X represents halogen, x=1 to 10, and y=0 to 8.5, and the ratio of y:x is not greater than 8.5:1. 
     These organosiloxanes with quaternary ammonium groups can be synthesized by reacting an epoxysiloxane compound having the formula ##STR5## in a known manner with dimethylamine, and converting the dimethylamino organosiloxane compound obtained which has the formula ##STR6## in a known manner with a hydrogen halide or with a methyl halide into the quaternary ammonium compound of the aforementioned formula. 
     According to U.S. Pat. No. 4,185,087, the aforementioned organopolysiloxanes with quaternary ammonium groups can be used for hair care products. As disclosed therein, simple aqueous shampoos may release soil from hair and remove an excess of grease. With most shampoos, however, degreasing of the hair would be carried out so thoroughly that damage to the hair could be observed. After washing, the hair becomes electrostatically charged and therefore difficult to comb. While the addition of lanolin derivatives, glycol, fatty esters or proteins improves the ability to handle the hair after washing, it does interfere with foaming. The hair would become somewhat sticky and feel unnatural. According to U.S. Pat. No. 4,185,087, the specific organpolysiloxanes with the quaternary ammonium groups should eliminate these disadvantages and improve the combability of the washed hair, give better hold to the hair set, and improve the gloss. 
     Similar teachings are contained in European Pat. Nos. 0 017 121 and 0 017 122 which describe organopolysiloxanes with quaternary ammonium groups for use in shampoos and hair conditioners to improve the combing properties of the hair. The compounds correspond to the general formula: ##STR7## in which R 1  and R 2  represent an alkyl radical with 1 to 4 carbon atoms or an aryl radical, p represents the numbers 0 to 50, and R the radicals: ##STR8## in which R 3  represents an alkyl or hydroxyalkyl radical with 1 to 3 carbon atoms, R 4  represents a radical identical with R 3 , aryl--CH 2  --, or the allyl radical, R 5  represents hydrogen or the methyl radical, X.sup.⊖  represents the anions Cl.sup.⊖, Br.sup.⊖, I.sup.⊖, CH 3  SO 4 .sup.⊖  or C 2  H 5  SO 4 .sup.⊖  and m the numbers 2 to 10 and n the numbers 2 to 4. 
     Finally, published European Patent Application No. 0095 238 discloses a composition which essentially comprises the following components: 
     (A) a siloxane of the general formula 
     
         R.sub.a X.sub.3-a Si(OSiX.sub.2).sub.n (OSiX.sub.b R.sub.2-b).sub.m OSiX.sub.3-a R.sub.a 
    
     in which R is only described functionally as a group which brings about adhesion to the hair, for example, an amino, carboxyl or quaternary ammonium group, X is a hydrogen radical or a phenyl, hydroxyl or saturated hydrocarbon group with 1 to 8 carbon atoms, a has a value of 0 to 3, b has a value of 0 to 1 and n+m has a value of 1 to 1999, n having a value from 0 to 2000 and m a value of 1 to 2000; 
     (B) a surfactant; 
     (C) an additive for improving the freeze/thaw stability, and 
     (D) water. 
     It therefore follows from the state of the art that organopolysiloxanes with quaternary ammonium groups have a strong substantivity on hair and endow it with good combability and gloss. However, their poor compatibility with anionic components, especially with anionic surfactants, is a disadvantage in hair care preparations. Moreover, they may also lead to irritation of the skin, especially of the mucous membrane, and to irritation of the eye which is extremely undesirable, especially in shampoos. 
     SUMMARY OF THE INVENTION 
     We have discovered additives for hair cosmetics which have the good properties of the organopolysiloxanes with quaternary ammonium groups, but are compatible with anionic additives, especially with anionic surfactants. At the same time, the inventive siloxane derivatives are less irritating to the skin than prior art compounds. 
     More particularly, the compounds having these properties are organopolysiloxanes which have one or more betaine groups. The object of the invention therefore are compounds having the general formula ##STR9## in which 
     R 1  can represent the same or different groups in the molecule and may be an alkyl radical with 1 to 18 carbon atoms, an aryl radical or a polyoxyalkylene radical with the proviso that at least 70% of the R 1  radicals are methyl radicals, 
     R 2  may be the same as R 1 , with the proviso that at least one R 2  radical represents the ##STR10## in which R 3  and R 4  are different, one radical representing a hydroxyl group, and the other the ##STR11## in which R 5  and R 6  are the same or different and represent an alkyl radical with 1 to 4 carbon atoms or a benzyl radical, and n=1, 2, or 3, 
     x has a value of 0 to 200, and 
     y has a value of 1 to 50. 
     It is evident from the general formula I that the betaine group(s) may be linked terminally or laterally. 
     At least 70% of the R 1  radicals are methyl radicals. Especially preferred are those polysiloxanes in which all the R 1  radicals are methyl radicals. Up to 30% of the R 1  radicals may be alkyl radicals, with 2 or more and, preferably, with 12  to 18 carbon atoms, or aryl radicals. Examples of such alkyl radicals are the ethyl, propyl, isopropyl, butyl, hexyl, isooctyl, decyl, dodecyl or stearyl radicals. The aryl radical generally is a phenyl radical. The alkyl radicals as well as the aryl radicals may be substituted. 
     It is also possible that up to 30% of the R 1  radicals are polyoxyalkylene radicals and especially those having the general formula: 
     
         --(CH.sub.2).sub.3 O(C.sub.m H.sub.2m O).sub.p Q 
    
     in which the --(C m  H 2m  O) p  group is built up from ethylene oxide and propylene oxide and m has an average value of 2.0 to 2.6, p has a value of 1 to 25, and Q is a hydrogen or alkyl radical with 1 to 4 carbon atoms. Compounds are preferred in which 3 to 10% of the R 1  radicals are polyoxyalkylene radicals. 
     At least one R 2  radical must represent the ##STR12## in which one of the R 3  and R 4  radicals is a hydroxyl radical. The other radical is the ##STR13## in which R 5  and R 6  preferably are methyl radicals. They may, however, also be ethyl, propyl, isopropyl or butyl radicals or a benzyl radical. In this formula, n has a value of 1, 2 or 3, with n=1 being preferred. 
     The value of x preferably is 2 to 100, and especially, 5 to 50, while the value of y is 1 to 25, and especially, 2 to 10. 
     Examples of inventive organopolysiloxanes with betaine groups are: ##STR14## 
     The inventive compounds generally are viscous to highly viscous, oily to pasty, and colorless to yellow products. The solubility of the inventive compounds is essentially determined by the ratio of the number of betaine groups to the number of siloxy units (R 2   1  SiO) as well as by the nature of the R 1  radicals. Higher betaine group contents and/or the presence of polyoxyalkylene radicals with a predominant proportion of oxyethylene units results in products, which are soluble in water and lower alcohols or glycols. On the other hand, oil compatible or oil dispersible products can be obtained by incorporating alkyl radicals with 12 to 18 carbon atoms. Products which are soluble in water or glycols, are generally preferred for use in hair care products. 
     We also have discovered an inventive method for the synthesis of the inventive compounds. In this process, compounds of the general formula ##STR15## in which R 7  may be the same as R 1  with the proviso that at least one of the R 7  radicals is the ##STR16## group, are reacted in a known manner with, based on the ##STR17## group, equimolar amounts of compounds of the general formula ##STR18## in which R 8  may be the same as R 1 , with the proviso that at least one of the R 8  radicals is the ##STR19## group, in which R 3  and R 9  are different, one being a hydroxyl radical and the other the ##STR20## group, are reacted in a known manner with, based on the ##STR21## group, equimolar amounts of compounds of the general formula 
     
         X--(CH.sub.2).sub.n --COOY 
    
     in which X is a chlorine or bromine radical and 
     Y is an alkali radical. 
     Those skilled in the art are familiar with the synthesis of compounds of Formulas II and III, which serve as starting compounds in the inventive process, and this synthesis is not an object of this invention. For example, the appropriate allyl compounds, e.g., ##STR22## can be added to hydrogen siloxanes corresponding to Formula II, in which, however, the R 7  radicals are hydrogen radicals, and, for synthesizing compounds III, these initially obtained addition products can be reacted with amines of the formula HNR 5  R 6 . 
     The reaction of compounds of the general Formula II with compounds of the general formula ##STR23## or the reaction of compounds of the general Formula III with compounds of the general formula X--(CH 2 ) n  --COOY is, in each case, carried out by known methods. Preferably, the reaction is conducted at elevated temperatures, especially at temperatures ranging from 40° to 160° C. The reaction can also be carried out in the presence of solvents, in which case the upper temperature limit is determined by the boiling point of the solvent used. Examples of suitable solvents are water, lower alcohols or glycols. 
     The inventive compounds exhibit the desired combination of properties. They are compared in the following table with similar products used according to the state of the art. 
     
                       TABLE                                                       
______________________________________                                    
                    Comb-            Compati-                             
           Substan- ability          bility with                          
           tivity   and Gloss Skin   Anionic                              
Additive   on Hair  of Hair   Irritation                                  
                                     Additives                            
______________________________________                                    
Siloxane with                                                             
           weak     weak      none   good                                 
polyether groups                                                          
Siloxane with                                                             
           none     none      weak   good                                 
anionic groups                                                            
Siloxane with                                                             
           average  average   average                                     
                                     good                                 
amino groups                                                              
Siloxane with                                                             
           strong   good      weak   poor                                 
quaternary amino                                                          
groups                                                                    
Siloxane with                                                             
           average  good      none   good                                 
betaine groups                                                            
Siloxane-free                                                             
           average  weak      none   good                                 
betaine                                                                   
______________________________________                                    
 
    
     It can be seen from the table that the organpolysiloxanes with betaine groups have the desired combination of properties, which is not exhibited by any of the other compounds. 
     It is therefore a further object of the invention to use the inventive compounds in cosmetic preparations, especially in preparations for the care of hair. In this connection, hair cosmetics can be shampoos or hair conditioner, depending on whether the emphasis is on the cleansing effect or on the care effect and the effect of better combability. Shampoos to which the inventive organopolysiloxane with betaine groups have been added in amounts of 0.1 to 10 weight percent, and which contain up to 30 weight percent of substances with detergent activity, besides water and possibly other additives, cause the washed hair to have fullness and an agreeable handle, to show the desired gloss and to be easily combable. Practically no electrostatic charging of the hair is to be observed. In hair care products, such as, hair tonics or hair sprays, the inventive compounds in amounts of 0.1 to 5% already bring about a significant improvement in combability of the hair and develop fullness and gloss. 
     Conventional additives, such as, solvents, thickeners, perfumes, preservatives, complexing agents, foam stabilizers, opacifiers, luster developing agents or other conventional additives, such as, dyes, may be added to the hair care products. Examples of formulations are: 
     
         ______________________________________                                    
Material for a Cream-Treatment Rinse                                      
Cetyl alcohol         6     parts by weight                               
TEGINACID ® H (mixture of                                             
                      6     parts by weight                               
glycerin monostearate and glycerin                                        
distearate with polyglycol fatty alcohol                                  
ethers, a commercial product of                                           
Th. Goldschmidt AG)                                                       
Glycerin              3     parts by weight                               
Betaine siloxane (Example 1)                                              
                      1     part by weight                                
Water                 84    parts by weight                               
Conditioning Shampoo                                                      
(a) Sodium lauryl ether sulfate                                           
                          3     parts by weight                           
    Ammonium alkyl ether sulfate                                          
                          6     parts by weight                           
    TAGAT ® KL 141    5     parts by weight                           
    (a polyoxyethylene-propylene                                          
    glycol dioleate, a commercial                                         
    product of Th. Goldschmidt AG)                                        
    Betaine siloxane (Example 1)                                          
                          2     parts by weight                           
    Water                 84    parts by weight                           
(b) Coconut fatty acid diethanolamide                                     
                          0.5   parts by weight                           
    Sodium lauryl ether sulfate                                           
                          30    parts by weight                           
    Salt                  1.5   parts by weight                           
Betaine L 7 (alkyl-                                                       
    8                     parts by weight                                 
    amidobetaine), a commercial                                           
    product of Th. Goldschmidt AG                                         
    Betaine siloxane (Example 1)                                          
                          2     parts by weight                           
    Water                 58    parts by weight.                          
______________________________________                                    
 
    
     The inventive compounds may also be added to skin care products. As a component of soap or skin creams, they form a fine, non-irritating, non-greasy film on the skin. In contrast to dimethylsiloxanes of low viscosity, especially the cyclic dimethylsiloxanes, they do not evaporate on the skin and therefore provide a constant protection. 
     A liquid soap may moreover have the following composition: 
     
         ______________________________________                                    
TAGAT ® 0 2 (polyoxyethylene                                          
                      1      part by weight                               
ether of the oleic acid monoester of                                      
glycerin, a commercial product of                                         
Th. Goldschmidt AG)                                                       
Coconut fatty acid diethanolamide                                         
                      0.5    parts by weight                              
Sodium lauryl ether sulfate                                               
                      30     parts by weight                              
betaine L 7 (alkylamido-                                                  
                      7      parts by weight                              
betaine), a commercial product                                            
of Th. Goldschmidt AG                                                     
Salt                  2      parts by weight                              
Betaine siloxane (Example 2)                                              
                      2      parts by weight                              
Water                 57.5   parts by weight                              
______________________________________                                    
 
    
    
    
     The inventive process is explained in greater detail in the following examples. Furthermore, application-related tests are shown for comparison with products of the state of the art. 
     EXAMPLE 1 
     In an autoclave, 214.6 g (=0.1 mole) of a siloxane having the average formula ##STR24## and 110 g (approximately 100% excess) of a 40% aqueous dimethylamine solution, are reacted for 3 hours at 120° C. with stirring. At the same time, the pressure increases to about 4.5 bar. The yellow, two-phase reaction mixture obtained is freed from water and excess amine by distillation (bath temperature: up to 90° C., pressure: 20 mbar). The brown, liquid residue obtained is slightly cloudy and is filtered. A clear product is obtained with a nitrogen content of 2.85% (theoretical: 2.95%). 
     The previously synthesized siloxane that contains tertiary amine groups (172 g=0.35 moles of amino groups) is stirred for 5 hours at 100° C. with 40.8 g (=0.35 moles) of ClCH 2  COONa in 230 g of water in a 3-neck flask equipped with thermometer, stirrer and reflux condenser. The initially cloudy formulation becomes clear after about 1 hour. At the end of the reaction, 2.75% of ionic chlorine can be determined in the solution. This value corresponds to a 98.2% conversion. The water is subsequently distilled off in a rotary evaporator (bath temperature: 90° C., pressure: 20 mbar). A cloudy residue remains, which is still capable of flowing at 90° C., but is almost solid at room temperature. In order to remove the sodium chloride formed, the residue is taken up in 150 ml of i-propanol and filtered. The solution is subsequently concentrated once again in a rotary evaporator. A clear, light brown product is obtained, which is barely able to flow at room temperature. Analysis reveals a betaine nitrogen content of 2.4% (theoretical: 2.55%). 
     The substance is dissolved in water to form a 1% and a 0.1% solution and the surface tensions are measured at 20° C. 
     1% solution: 28.1 mN/m 
     0.1% solution: 29.0 mN/m 
     EXAMPLE 2 
     A 30% ethanolic solution of dimethylamine (140 g) is added at 20° C. to a flask equipped with thermometer, stirrer and reflux condenser. Over a period of 30 minutes, 236.2 g (=0.05 moles) of a siloxane having the average composition ##STR25## are added dropwise to this solution. At the same time, the temperature rises to about 40° C. After 1 hour, the solution is heated to the refluxing temperature and stirred for a further 5 hours. The clear, yellowish solution is freed from excess amine and from ethanol in a rotary evaporator (bath temperature: 80° C., pressure 22 mbar). A clear, yellow, slightly viscous liquid is obtained as residue, the nitrogen content of which is 2.7% (theoretical: 2.71%). 
     The siloxane obtained (207.5 g=0.4 moles of amino groups), which contains tertiary amino groups, together with 46.6 g (0.4 moles) of ClCH 2  COONa in 207.3 g of water and 307.6 g of 1,2-propylene glycol are added to a 3-neck flask equipped with thermometer, reflux condenser, and stirrer and stirred for 5 hours at 100° C. After about 1 hour, the formulation becomes clear. At the end of the reaction, 1.8% of ionic chloride may be determined in the clear, yellow, slightly viscous solution. This value corresponds to a 97.8% conversion. In addition, the analysis reveals that the solution contains 0.7% betaine nitrogen (theoretical: 0.73%). 
     The solution obtained consists of 30% of the desired siloxane that contains betaine groups, 3% of sodium chloride, 27% of water, and 40% of 1,2-propylene glycol. 
     By diluting with water, 1 and 0.1% solutions are prepared, whose surface tensions are determined (at 20° C.): 
     1% solution: 25.5 mN/m 
     0.1% solution: 26.5 mN/m. 
     EXAMPLE 3 
     A 33% ethanolic solution of dimethylamine (70 g) is added at room temperature to a flask equipped with thermometer, stirrer and reflux condenser. Over a period of 25 minutes, 372.2 g (=0.1 moles) of a siloxane having the average composition ##STR26## are added dropwise to this solution. This siloxane which has polyoxyalkylene radicals in addition to epoxy groups, can be synthesized according to known procedures by the addition, in the presence of platinum catalysts, of 
     
         CH.sub.2 ═CH--CH.sub.2 --O--(C.sub.2 H.sub.4 O--).sub.13 (C.sub.3 H.sub.6 O--).sub.3 H 
    
     and allyl glycidyl ether to the appropriate siloxane 
     
         (CH.sub.3).sub.3 SiO[(CH.sub.3).sub.2 SiO].sub.13 [(CH.sub.3)HSiO].sub.5 Si(CH.sub.3).sub.3 
    
     that carries SiH groups. 
     After the addition of the siloxane to the dimethylamine solution, the temperature is raised to 75° C. and stirring is continued for 6 hours. Subsequently, the excess amine and the ethanol are distilled off in a rotary evaporator (bath temperature: 80° C., pressure: 15 mbar). A clear yellow, viscous product with a nitrogen content of 0.87% (theoretical: 0.91%) is obtained. 
     The product obtained (322 g=0.2 moles of amino groups), together with 23.3 g (=0.2 moles) of ClCH 2  COONa in 321.9 g of water and 166.8 g of 1,2-propylene glycol is added to a 3-neck flask equipped with thermometer, stirrer and reflux condenser and stirred for 6 hours at 100° C. The formulation becomes clear after about 15 minutes. At the end of the reaction, 0.8% ionic chlorine can be detected in the clear, yellow solution. This corresponds to a 94.1% conversion. In addition, the analysis reveals a betaine nitrogen content of 0.31% (theoretical: 0.34%). 
     The solution obtained consists of 40% of a siloxane modified with betaine groups and polyoxyalkylene radicals, 1.4% of sodium chloride, 38.6% of water, 20% of 1,2-propylene glycol. 
     By diluting with water, 1% and 0.1% solutions are prepared for surface tension measurements (at 20° C.). The following values are obtained: 
     1% solution: 25.7 mN/m 
     0.1% solution: 26.4 mN/m 
     EXAMPLE 4 
     Testing the Inventive Compounds in Hair Care Products A conditioning shampoo of the following composition: 
     
         ______________________________________                                    
Sodium laurylether sulfate                                                
                     3     parts by weight                                
Ammonium alkylether sulfate                                               
                     6     parts by weight                                
TAGAT ® KL 141 (monoleic                                              
                     5     parts by weight                                
acid ester of the polyoxyethylen                                          
ether of propylene glycol, a                                              
commercial product of                                                     
Th. Goldschmidt AG)                                                       
Betaine siloxane (Example 1)                                              
                     2     parts by weight                                
Water                84    parts by weight                                
______________________________________                                    
 
    
     is compared in respect to its action with a shampoo formulation in which the inventive betaine siloxane is replaced by a cationic organosiloxane compound as described in German Auslegeschrift No. 14 93 384, wherein x=15, y=5 and X=Cl.sup.⊖. 
     The preparation with the betaine siloxane is clear, while the cationic siloxane leads to cloudiness. 
     The half-side comparison of the practical application on human hair resulted in the following evaluation: 
     With respect to foaming, the creaminess of the foam, the dry combability, the anti-electrostatic effect and the fullness of the hair, the inventive betaine siloxane is superior. The cationic siloxane gives a somewhat better result only with respect to the wet combability. This is, however, associated with a heavier loading and therefore a lesser fullness of the hair.