Abstract:
Disclosed are novel polyglycerine polyricinoleates as emulsifiers obtained by the esterification of polyricinoleic acid with a natural condensation rate of from 2 to 10 with a polyglycerine mixture comprising 5-35 wt. % glycerine, 15-40 wt. % diglycerines, 10-30 wt. % triglycerines, 8-20 wt. % tetraglycerines, and 3-10 wt. % pentaglycerines, and the remainder being oligoglycerines. The materials have improved emulsifying capacity.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to new polyglycerol polyricinoleates obtainable by esterification of polyricinoleic acid with technical polyglycerol having a certain composition, to a process for their production, to formulations containing these substances and to the use of the new polyglycerol polyricinoleates as w/o emulsifiers. 
     2. Statement of Related Art 
     Polyglycerol polyricinoleates have long been known as w/o emulsifiers and may be used for the formulation of low-viscosity w/o emulsions  cf. EP-A1 0559013 (Th. Goldschmidt), EP-A1 044203 (Lotte Co.) and WO 85/04346 (Meiji Milk Prods.)!. However, it has been found that commercial polyglycerol polyricinoleates do not form emulsions with all the oils typically used in cosmetics, but only with those having a certain polarity range. In addition, these emulsions show only limited stability in storage. 
     Now, the problem addressed by the present invention was to provide new w/o emulsifiers which would form low-viscosity and storage-stable emulsions with a broad range of oils. 
     DESCRIPTION OF THE INVENTION 
     The present invention relates to polyglycerol polyricinoleates obtained by esterifying polyricinoleic acid having a degree of autocondensation of 2 to 10 with a polyglycerol mixture of the following composition: 
     
         ______________________________________glycerol:   5 to 35 (25 to 25)                       % by weightdiglycerols:       15 to 40 (20 to 32)                       % by weighttriglycerols:       10 to 35 (15 to 25)                       % by weighttetraglycerols:       8 to 20 (10 to 18)                       % by weightpentaglycerols:       3 to 10 (5 to 9)                       % by weightoligoglycerols:       to 100          % by weight______________________________________ 
    
     (the figures in brackets represent preferred ranges) by methods known per se. 
     It has surprisingly been found that the composition of the polyglycerol component has a critical bearing on the performance properties of the emulsifiers. The invention includes the observation that polyglycerol polyricinoleates containing less than 5% by weight or more than 35% by weight of glycerol in their polyglycerol component have significantly poorer emulsifying power. 
     The present invention also relates to a process for the production of polyglycerol polyricinoleates, in which polyricinoleic acid having a degree of autocondensation of 2 to 10 is esterified with a polyglycerol mixture of the following composition: 
     
         ______________________________________glycerol:   5 to 35 (25 to 25)                       % by weightdiglycerols:       15 to 40 (20 to 32)                       % by weighttriglycerols:       10 to 35 (15 to 25)                       % by weighttetraglycerols:       8 to 20 (10 to 18)                       % by weightpentaglycerols:       3 to 10 (5 to 9)                       % by weightoligoglycerols:       to 100          % by weight______________________________________ 
    
     (the figures in brackets represent preferred ranges) by methods known per se. 
     Production of the polyqlycerol polyricinoleates 
     The polyglycerol polyricinoleates may be produced in known manner. Preferably, the polyglycerol is prepared in a first step and the polyricinoleic acid in a second step and, finally, the two are condensed. 
     The preparation of a polyglycerol having the composition shown above may be carried out by autocondensation of glycerol in the presence of suitable catalysts, for example silicates according to DE-A1 4029323 (Henkel) or borates according to DE-A1 4117033 (Henkel), at temperatures in the range from 200° to 260° C. 
     The polyricinoleic acid is prepared, for example, by controlled thermal polycondensation of castor oil fatty acid of which around 90% by weight consists of ricinoleic acid. Linear esterification products containing 2 to 10 and, more particularly, 4 to 6 fatty acid units are preferably formed. 
     A complex mixture of homologous polyesters is formed in the subsequent condensation of the technical polyglycerol with the polyricinoleic acid. The percentage contents of mono-, di-, tri- and oligoesters in the polyglycerol polyricinoleates according to the invention are determined by the ratios in which the starting compounds are used. In one preferred embodiment of the process according to the invention, a polyglycerol polyricinoleate with particularly favorable performance properties is obtained by subjecting around 1000 kg of castor oil fatty acid to autocondensation until a product with an acid value of 50 to 55 is obtained and the product thus obtained is then further condensed with around 150 kg of technical polyglycerol having the composition shown above until the acid value has fallen to below 2. 
     Cosmetic and Pharmaceutical Formulations 
     The present invention also relates to cosmetic and/or pharmaceutical formulations containing the new polyglycerol polyricinoleates. 
     Suitable auxiliaries and additives are oils, co-emulsifiers, fats and waxes, stabilizers, thickeners, biogenic agents, film formers, fragrances, dyes, pearlescers, preservatives, UV filters, pigments, electrolytes (for example magnesium sulfate) and pH regulators. 
     Suitable oil components are, for example, Guerbet alcohols based on fatty alcohols containing 6 to 18 and preferably 8 to 10 carbon atoms, esters of linear C 6-20  fatty acids with linear C 6-20  fatty alcohols, esters of branched C 6-13  carboxylic acids with linear C 10-18  fatty alcohols, esters of linear C 10-18  fatty acids with branched alcohols, more particularly 2-ethylhexanol, esters of linear and/or branched fatty acids with dihydric alcohols and/or Guerbet alcohols, triglycerides based on C 6-10  fatty acids, vegetable oils, branched primary alcohols, substituted cyclohexanes, Guertbet carbonates and/or dialkyl ethers. Of particular importance in this regard is the fact that the polyglycerol polyricinoleates according to the invention are suitable for the formation of emulsions using both polar and medium-polar to nonpolar oils with dipole moments in a range from &lt;1 to &gt;5 Debye. 
     Suitable co-emulsifiers are preferably known w/o and also o/w emulsifiers such as, for example, polyglycerol esters, sorbitan esters or partly esterified glycerides. Typical examples of fats are glycerides while suitable waxes include inter alia beeswax, paraffin wax or microwaxes, optionally in combination with hydrophilic waxes. Suitable stabilizers are metal salts of fatty acids such as, for example, magnesium, aluminium and/or zinc stearate. Suitable thickeners are, for example, crosslinked polyacrylic acids and derivatives thereof, polysaccharides, more particularly xanthan gum, guar guar, agar agar, alginates and tyloses, carboxymethyl cellulose and hydroxyethyl cellulose, fatty alcohols, monoglycerides and fatty acids, polyacrylates, polyvinyl alcohol and polyvinyl pyrrolidone. In the context of the invention, biogenic agents are, for example, plant extracts, protein hydrolyzates and vitamin complexes. Typical film formers are, for example, hydrocolloids, such as chitosan, polyvinyl pyrrolidone, vinyl pyrrolidone/vinyl acetate copolymers, polymers of the acrylic acid series, quaternary cellulose derivatives and similar compounds. Suitable preservatives are, for example, formaldehyde solution, p-hydroxybenzoate or sorbic acid. Suitable pearlescers are, for example, glycol distearic acid esters, such as ethylene glycol distearate, and also fatty acids and fatty acid monoglycol esters. The dyes used may be selected from any of the substances which are permitted and suitable for cosmetic purposes, as listed for example in the publication &#34;Kosmetische Farbemittel&#34; of the Farbstoffkommission der Deutschen Forschungsgemeinschaft, published by Verlag Chemie, Weinheim, 1984, pages 81-106. These dyes are typically used in concentrations of 0.001 to 0.1% by weight, based on the mixture as a whole. 
     The total percentage content of auxiliaries and additives may be 1 to 80% by weight and is preferably 5 to 40% by weight, based on the formulation, while the non-aqueous component (&#34;active substance&#34;) makes up 20 to 80% by weight and preferably 30 to 70% by weight of the formulation. The formulations may be produced in known manner, i.e. for example by hot, cold, hot-hot/cold or PIT emulsification. These are purely mechanical processes which do not involve a chemical reaction. 
     Commercial Applications 
     The polyglycerol polyricinoleates according to the invention are distinguished by improved emulsifying power. The resulting emulsions are preferably low in viscosity and have higher stability in storage and, in particular, thermal stability by comparison with known products. 
     Accordingly, the present invention also relates to the use of the polyglycerol polyricinoleates according to the invention as w/o emulsifiers for the production of cosmetic and/or pharmaceutical formulations, for example skin cremes, body lotions, sunscreens and the like, in which they may be present in concentrations of 1 to 30% by weight and preferably 2 to 10% by weight, based on the particular formulation. 
    
    
     EXAMPLES 
     I. Polyqlycerol polyricinoleates used 
     The composition of the polyglycerol component is shown in Table 1. 
     The emulsifiers had a degree of condensation of 5 through their polyricinoleic acid component. 
     
                       TABLE 1______________________________________Composition of polyglycerol polyricinoleates        Emulsifier A                Emulsifier B        % by weight                % by weight______________________________________Glycerol       20         0Diglycerols    30        21Triglycerols   20        22Tetraglycerols 15        20Pentaglycerols  5        11Oligoglycerols 10        26______________________________________ 
    
     Emulsifier A corresponds to the invention while emulsifier B is a commercial product intended for comparison. 
     II Performance Tests 
     The properties of emulsifiers A and B were tested in various w/o emulsions according to Tables 2a and 2b. Formulations F1 to F4 correspond to the invention while formulations F5 to F8 are intended for comparison. Myritol® 318 is a C 8-10  triglyceride, Cetiol® V is decyl oleate and Cetiol® SN is cetearyl isononanoate. The viscosity of the products was determined after storage (1 day and 1 week) using a Brookfield RVF viscosimeter (spindle 5, 10 r.p.m., 23° C.). The results are set out in Table 3 below. 
     
                       TABLE 2a______________________________________Formulations according to the invention          F1 % F2 %     F3 %   F4 %______________________________________Emulsifier A     7.0    7.0      7.0  7.0Paraffin oil, low-viscosity            20.0   --       --   --Myritol 318      --     20.0     --   --Cetiol V         --     --       20.0 --Cetiol SN        --     --       --   20.0Glycerol, 86% by weight            5.0    5.0      5.0  5.0MgSO.sub.4.7H.sub.2 O            0.5    0.5      0.5  0.5Formaldehyde     0.1    0.1      0.1  0.1Water            To 100%______________________________________ 
    
     
                       TABLE 2b______________________________________Comparison formulations          F5 % F6 %     F7 %   F8 %______________________________________Emulsifier B     7.0    7.0      7.0  7.0Paraffin oil, low-viscosity            20.0   --       --   --Myritol 318      --     20.0     --   --Cetiol V         --     --       20.0 --Cetiol SN        --     --       --   20.0Glycerol, 86% by weight            5.0    5.0      5.0  5.0MgSO.sub.4.7H.sub.2 O            0.5    0.5      0.5  0.5Formaldehyde     0.1    0.1      0.1  0.1Water            To 100%______________________________________ 
    
     
                       TABLE 3______________________________________Performance resultsViscosity  mPas · s!Formulation   After 1 d            After 1 w                     Remarks______________________________________F1      24800    24000    Stable emulsions even after storageF2      22800    22000    for more than 1 weekF3      16000    15200F4      30000    29000F5      --       --       No emulsion formedF6      --       --       Separates after 1 dF7      16000    19000    Unstable emulsionF8      --       --       Separates after 1 d______________________________________ 
    
     The Examples show that stable and low-viscosity w/o emulsions are only reliably obtained, i,e. over a broad range of oils to be emulsified, where the polyglycerol polyricinoleates according to the invention are used.