Patent Publication Number: US-6335375-B1

Title: Concentrated fluid aqueous-alcoholic compositions of hydrogenated coconut or palm kernel oil alkylamidopropylbetaines

Description:
FIELD OF THE INVENTION 
     The invention relates to concentrated, aqueous-alcoholic, low-viscosity, clear, relatively colourless solutions which are stable over a temperature range of between 5 and 50° C. and which contain at least 50% by weight of alkylamido-propylbetaine corresponding to the general formula (I):                    
     in which R represents the alkyl radical of a fraction of fatty acids of hydrogenated coconut or palm kernel oil type, with an iodine number of not more than 1 (in grams of iodine per 100 g). The approximate composition of such a fraction is, in percentages by weight: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 50-65% 
                 lauric acid, 
               
               
                   
                 15-26% 
                 myristic acid, 
               
               
                   
                  8-14% 
                 palmitic acid, 
               
               
                   
                  7-15% 
                 stearic acid, 
               
               
                   
                   
               
            
           
         
       
     
     the unsaturated fraction responsible for the low iodine number being represented by less than 1% oleic acid. 
     In the specification hereinbelow, these alkylamidopropylbetaines will be referred to for simplicity as “betaines”. Their solutions display these qualities only if their composition is chosen precisely in a region of the betaine/ethanol/water diagram normalized to 100 by weight after correction of the NaCl present. 
     BACKGROUND OF THE INVENTION 
     Betaines corresponding to the general formula (I) are amphoteric surfactants that are very well tolerated by the skin, they have excellent cleansing and foaming properties and are entirely suitable for making a whole range of surfactant compositions, such as washing agents, cleansing agents (liquid products for washing up by hand), haircare compositions (shampoos) and bodycare compositions (shower gels and bubble baths). 
     The preparation of this type of betaine is described in many documents, and the processes are known to those skilled in the art, for example U.S. Pat. No. 3,225,074 (American Cyanamid). It consists in reacting a fatty acid or a fatty acid fraction with N,N-dimethyl-1,3-propanediamine (DMAPA) between 140 and 200° C., and then in quaternizing the tertiary amidoamine obtained, of general formula (II):                    
     with monochloroacetic acid in the presence of an alkaline salt or the corresponding salt of this acid, the quaternization reaction usually taking place in aqueous medium. The alkaline chloride, which is often sodium chloride, obtained as a by-product in the reaction, is generally left in this aqueous betaine solution. These aqueous betaines are sold at a concentration in the region of 30% by weight. 
     Attempts have often been made to prepare industrially betaine solutions that are as concentrated and as fluid as possible, for quite understandable reasons of reducing the transportation and storage costs, without, however, sacrificing the ease of their handling. 
     A person skilled in the art knows that when the concentration of an aqueous surfactant solution increases, its viscosity also increases. Nevertheless, certain authors have sought to concentrate, by evaporation under reduced pressure, betaine solutions obtained according to the usual processes, but their viscosity increases rapidly and they become pasty at about 40° C. by weight of betaine, then continue to solidify as water is removed therefrom: it is not possible to obtain concentrated solutions via this route. However, it is reported in EP 0,302,329 (Th. Goldschmidt) that it was possible partially to circumvent this difficulty by adjusting the pH of the solution to between 1 and 4.5 with an inorganic acid (hydrochloric, sulphuric or phosphoric acid). The authors thus obtained solutions containing 43 to 44% by weight of betaine (or 53 to 54% solids) with a viscosity in the region of 1000 mPa.s at 25° C. However, the problems of corrosion during storage and transportation, along with the atypical pH of these betaine solutions, limit their use and, moreover, they gel below 16° C. 
     Another route is that for obtaining betaine in powder form, by spraying fluid solutions at less than 30%. It may be thought to redissolve these powders in suitable solvents, but redissolving these powders is hampered by the formation, when the powder is placed in contact with the solvent, of lumps or gelled pastes which are virtually impossible to redissolve, or at least not within reasonable times that are compatible with industrial activity. 
     International patent application WO 97/12856 (Henkel) discloses and claims a process for manufacturing surfactants of betaine type with a low salt content (0.98 to 1.01% residual NaCl) by quaternization of tertiary amines and/or tertiary amidoamines with sodium monochloroacetate in an aqueous-alcoholic mixture composed of 5 to 10% by weight of water and 35 to 50% by weight of ethanol and/or isopropanol, this reaction being followed by removal of the salt fraction precipitated, total removal of the solvent and readjustment of the water in the reaction medium in order to bring the solution to the desired active material concentration—in this case 30%. The water/ethanol weight ratio claimed by the authors is typical for a process aimed at removing the NaCl formed during the reaction. A composition of this type formed the subject of U.S. Pat. No. 4,705,893 (KAO), represented by a pentagonal zone of the betaine/water/ethanol ternary diagram defined by the triangular coordinates (80/10/10), (80/15/5), (40/55/5), (40/27.5/32.5) and (52.5/10/37.5). Both of these cases involve processes whose essential aim is to obtain totally aqueous non-concentrated amphoteric surfactant solutions with low salt contents. 
     A person skilled in the art is familiar with the idea of the possible existence of domains of fluid phases in an amphoteric surfactant/water/solvent system. This idea is pursued in WO 95/14076 (Albright and Wilson), in reality without any concrete teaching other than that of the individual examples reported in that publication, which come closest to the conditions of the present problem, namely, compositions of coco- or lauryl-amidopropylbetaine-salt dissolved in a mixed solvent of water/glycol type. 
     The problem which still remains is to obtain solutions of hydrogenated coconut or palm kernel oil alkylbetaine which are as concentrated as possible, i.e. at least 50% by weight, clear and relatively colourless, fluid and pumpable (viscosity of less than 1000 mPa.s), stable between 5 and 50° C. for prolonged periods, in order to reduce the packaging, transportation and storage costs, readily manipulable, and which can be formulated in their given state with other surfactants, for example alkyl ether sulphates, alkanolamides or other starting materials forming part, in particular, of the formulations for liquid soaps, shampoos, shower gels and other cosmetic preparations. The use of hydrogenated coconut oil is a restriction imposed by the requirement for these compositions intended for cosmetic uses to have better stability to oxidation than that which might be hoped for the non-hydrogenated natural fractions. 
     SUMMARY OF THE INVENTION 
     The present invention provides a solution to this technical problem, which consists in preparing the alkylbetaine by quaternizing the product of reaction of dimethylaminopropylamine with a fatty acid of hydrogenated coconut or palm kernel oil in the presence of small amounts of ethanol, provided that, however, the system remains limited to a quite precise and narrow region of the phase diagram as will now be defined. 
     The system is determined on betaine/water/ethanol ternary compositions, represented on the ternary diagram in reduced coordinates 
     B*=[betaine/(betaine+water+ethanol)]·10 2    
     W*=[water/(betaine+water+ethanol)]·10 2    
     E*=[ethanol/(betaine+water+ethanol)]·10 2    
     where betaine has the sense of, and is measured as, betaine=solids−NaCl, 
     in which the 100% loop relationship applies for the composition B*+W*+E*=100, 
     all of the betaine, solids, water, ethanol and NaCl magnitudes being expressed on a weight basis, the reduced magnitudes B*, W* and E* appearing as weight %. 
     With this definition, the betaine considered is a raw betaine, i.e. one consisting of alkylamidobetaine as corresponds to formula I, with a few reactant residues and a few reaction by-products not exceeding 3% by weight (see Example 1). 
     The compositions of the invention are those which obey the following relationships 
     
       
         52%≦B*≦57% 
       
     
     
       
         E*≧21% 
       
     
     
       
         W*≧20% 
       
     
     
       
         W*/W*+E*≦54% 
       
     
     In the compositions of the invention, NaCl is present to a maximum level of 6% by weight, beyond which value these compositions become uncontrollable, if only by precipitation of the salt. 
     The compositions according to the invention are capable of prolonged storage over periods of at least three months, in the course of which no gelling, demixing, precipitation of salts or appreciable change in colour or clarity is observed in the temperature range between 5 and 50° C. These solutions also have the advantage of being relatively non-foaming in the concentrated state, which makes them easier to manipulate. Another advantage lies in the fact that these concentrated solutions are sufficiently resistant to microbial invasion, such that it is unnecessary to add preserving agents. These characteristics make these solutions particularly suitable for making cosmetic compositions. 
     Another subject of the present invention relates to the process for manufacturing these concentrated solutions, which consists in preparing the intermediate hydrogenated coconut or palm kernel oil dimethylamidopropylamides and in quaternizing them with monochloroacetic acid in the presence of sodium hydroxide or sodium monochloroacetate directly in the solvent medium chosen, i.e. obeying the composition rule 
     
       
         E*≧21% 
       
     
     
       
         W*≦20% 
       
     
     
       
         W*/W*+E*≦54% 
       
     
     defined above. 
    
    
     The examples and comparative examples which follow will allow a better understanding of the invention . 
     EXAMPLE 1 
     Manufacture of a hydrogenated coconut betaine containing about 52.4% by weight of betaine, i.e. 57.4% solids, whose reduced coordinates B*/W*/E* in the phase diagram are 55/22.5/22.5 (in weight %). 
     1/a—Preparation of the Coconut Aminoamide 
     (Mw=309 g) 
     731 kg of coconut fatty acid with an iodine number of ≦1, melted at 50° C., are loaded in a reactor. The reactor and its contents are bubbled with nitrogen and brought to 190° C. 347 kg of dimethylaminopropylamine (DMAPA) are added over 4 hours via a dip tube, the distillation waters being removed continuously. The mixture is maintained at 190° C. under a stream of nitrogen until the reaction product shows an acid number of less than 4.5 mg KOH/g. The mixture is cooled to 150° C., 100 kg of water are injected, via a dip tube, over 1 hour and the resulting mixture is dried at 150° C. while bubbling nitrogen through, to a water content of less than 0.1%. The system is cooled to 60° C., the bubbling of nitrogen is stopped and the reactor is emptied. 
     The usual characteristics of the tertiary amidoamine thus obtained are as follows: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 HClO 4  alkalinity 
                 3.28-3.32 
               
            
           
           
               
               
               
               
            
               
                   
                 IA 
                 4.4 
                 mg KOH/g 
               
            
           
           
               
               
               
            
               
                   
                 Free fatty acid 
                   1.6% 
               
            
           
           
               
               
               
               
            
               
                   
                 Free DMAPA 
                 57 
                 ppm 
               
            
           
           
               
               
               
            
               
                   
                 Water content 
                 &lt;0.1% 
               
               
                   
                   
               
            
           
         
       
     
     1/b—Manufacture of the Concentrated Coconut Betaine Solution 
     233.7 kg of ethanol and 127.4 kg of water are loaded into another reactor at room temperature, followed by 169 kg of monochloroacetic acid. The mixture is brought to 25° C. and 473 kg of the amidoamine prepared in 1/a are then added slowly, while controlling the exothermicity so that the temperature does not exceed 40° C. 153 kg of 50% sodium hydroxide are then added over about one hour, while maintaining the temperature at 40° C., after which it is raised slowly to 80° C. The mixture is maintained at this temperature until the amidoamine content reaches a stable value of 1%, taking care to ensure that the pH of a test sample prediluted to 5% in water is still between 10-10.5. After one hour, the mixture is cooled to 40° C. and the pH is adjusted to 6.5 with 31% HCl solution. The NaCl fraction precipitated is removed by decantation, filtration or centrifugation. 
     A concentrated betaine solution having the following main compositions is thus obtained: 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Weight 
                   
                 Reduced 
               
               
                   
                 values 
                   
                 coordinates   c     
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 Solids   a     
                 57.4 
                   
                   
               
               
                   
                 NaCl 
                  5.0 
                   
                   
               
               
                   
                 Betaine   b     
                 52.4 
                 B* 
                 55.0   c     
               
               
                   
                 Water 
                 21.3 
                 W* 
                 22.5   c     
               
               
                   
                 Ethanol 
                 21.3 
                 E* 
                 22.5   c     
               
               
                   
                   
               
               
                   
                     a   : 20 minutes at 105° C.  
               
               
                   
                     b   : Betaine active material = solids - NaCl (including glycolate, free fatty acid and free amidoamine)  
               
               
                   
                     c   : B*, W* and E* values in the ternary diagram, after correcting the NaCl content and then normalizing to 100 by weight and the following associated characteristics:  
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Sodium monochloroacetate 
                 &lt;3 
                 ppm 
               
               
                   
                 Free DMAPA 
                 &lt;5 
                 ppm 
               
            
           
           
               
               
               
            
               
                   
                 Sodium glycolate 
                 0.3% 
               
               
                   
                 Free fatty acid 
                 0.8 
               
               
                   
                 Free amidoamine 
                 1.0% 
               
               
                   
                 pH at 5% (23° C.) 
                 6.5 
               
            
           
           
               
               
               
               
            
               
                   
                 Hazen colour (t = 0) 
                 100 
                 Hz 
               
               
                   
                 Hazen colour (t = 6 weeks)    d     
                 110 
                 Hz 
               
               
                   
                   
               
               
                   
                     d    : Maturation at 45° C.  
               
               
                   
                 This is a fluid, clear; easily pumpable solution which is stable between 5 and 50° C.  
               
            
           
         
       
     
     COMPARATIVE EXAMPLE 1 
     The operating conditions of step 1/b of Example 1 are repeated, except for the loads of starting materials, which were adjusted to obtain a hydrogenated coconut betaine at approximately 55.6% betaine, i.e. 60.5% solids, for which the corrected triangular coordinates B*/W*/E* of NaCl in the phase diagram are 58.5/20.0/21.5 (in weight %). 
     A viscous, non-newtonian, birefringent gel of liquid crystal type which is difficult to manipulate and to formulate between 5 and 50° C. is obtained. 
     COMPARATIVE EXAMPLE 2 
     The operating conditions of step 1/b of Example 1 are repeated, except for the loads of starting materials, which were adjusted to obtain a coconut betaine at approximately 49.35% raw betaine, i.e. 63.75% solids, for which the corrected triangular coordinates B*/W*/E* of NaCl in the phase diagram are 51.5/27.0/21.5 (in weight %). 
     A fluid, clear solution which is a single phase in the region of room temperature (20-25° C.) but which, between 5 and 15° C., undergoes a rapid change to a two-phase mixture with a birefringent viscous gel phase and a supernatant liquid phase. This heterogeneous product is difficult to use in this state. 
     COMPARATIVE EXAMPLE 3 
     The same operating conditions as in step 1/b of Example 1 are repeated, except for the loads of starting materials, which were adjusted to obtain a coconut betaine at approximately 53.95% betaine, i.e. 58.75% solids, for which the corrected triangular coordinates B*/w*/E* of NaCl in the phase diagram are 65.5/17.75/25.75 (in weight %). 
     A solution which becomes heterogeneous on storage at 5° C. is obtained. 
     The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples. Also, the preceding specific embodiments are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. 
     The entire disclosure of all applications, patents and publications, cited above and below, and of corresponding French application 98/15398, are hereby incorporated by reference. 
     From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.