Skin pH freezer bar and process

A skin pH freezer bar comprising:

• (A) from about 10% to about 50% of essentially free monocarboxylic acid;
• wherein no more than about 15% by weight of said essentially free monocarboxylic acid is neutralized;
• (B) from about 15% to about 65% of anionic and/or nonionic bar firmness aid, said bar firmness aid comprising at least 10% synthetic surfactant by weight of said bar;
• and
• (C) from about 15% to about 40% water by weight of said bar;
• wherein said skin pH is from about 4.8 to about 6.0:
• wherein said bar firmness aid is selected from the group consisting of:
• (I) from about 10% to about 50% by weight of a synthetic surfactant wherein said synthetic surfactant is selected from the group consisting of:
• alkyl sulfates, paraffin sulfonates, alkyl glyceryl ether sulfonates, anionic acyl sarcosinates, methyl acyl taurates, linear alkyl benzene sulfonates, N-acyl glutamates, alkyl glucosides, alpha sulfo fatty acid esters, acyl isethionates, glucose amide alkyl sulfosuccinates, alkyl ether carboxylates, alkyl phosphate esters, ethoxylated alkyl phosphate esters, methyl glucose esters, protein condensates, the alkyl ether sulfates with 1 to 12 ethoxy groups, and mixtures thereof, wherein said surfactants contain C.sub.8 -C.sub.22 alkylene chains;
• and mixtures thereof;
• and
• (II) form zero to about 40% by weight of a co-solvent wherein said co-solvent is selected from the group consisting of:
• (a) non-volatile, water-soluble nonionic organic solvents selected from the group consisting of:
• a polyol of the structure:
• ##STR4## where R.sub.3 .dbd.H, C.sub.1 -C.sub.4 alkyl;
• R.sub.4 .dbd.H, CH.sub.3 ;
• and k=1-200;
• C.sub.2 -C.sub.10 alkane diols;
• sorbitol;
• glycerine;
• sugars;
• sugar derivatives;
• urea;
• and
• wherein said monocarboxylic acid X.dbd.H and a+b+12-20 or said monocarboxylic acid is 12-hydroxy stearic acid;
• and wherein said water is from about 20% to about 30% by weight of said bar;
• and
• (III) mixtures of said (I) and (II);
• wherein said freezer bar is made by the following process steps:
• (I) mixing a molten mixture comprising said essentially free carboxylic acid;
• said water;
• and said bar firmness aid at a temperature of 170.degree.-205.degree. F. (76.degree.-96.degree. C.);
• (II) cooling said mixture to a semi-solid in a scraped wall heat exchanger freezer at a cooled outlet temperature of 110.degree.-195.degree. F. (43.degree.-91.degree. C.);
• and
• (III) extruding said semi-solid as a soft plug;
• and further cooling and crystallizing said soft plug until firm to provide said skin pH personal cleansing freezer bar;
• wherein said molten mixture of Step I comprises a liquid crystalline middle phase;
• said molten mixture has:
• a viscosity of from about 100,000 cps to about 1,000,000 cps at a shear rate of about 1 sec.sup.-1 ;
• wherein said viscosity is from about 5,000 cps to about 100,000 cps at a shear rate of about 5 sec.sup.-1 ;
• a viscosity of from about 1,000 cps to about 50,000 cps at a shear rate of about 20 sec.sup.-1 ;
• a viscosity of from about 500 cps to about 12,000 cps at a shear rate of about 50 sec.sup.-1 and
• wherein the ratio of synthetic surfactant to water is from about 2:1 to about 1:2;
• and
• wherein said freezer bar has a 25.degree. C. penetration value of from zero up to 12 mm;
• wherein said bar comprises a rigid crystalline phase skeleton structure comprising an interlocking, open, three-dimensional mesh of elongated crystals comprising:
• (a) said free monocarboxylic acid, or (b) said mixture of said free and neutralized carboxylic acid;
• wherein said bar also comprises an aqueous phase mix;
• said mix (when measured alone) having a penetration value of greater than 12 mm to complete penetration at 25.degree. C.