CA1166925A - Soap compositions of improved resistance to cracking - Google Patents

Abstract

ABSTRACT
Soap compositions in solid form such as bars or tablets or the like, are provided with improved resistance to cracking by the addition thereto of from about 1 to about 5% by weight of a mixture of polycarboxylic acids of 4 to 20 carbon atoms and wherein at least about 20% by weight of the mixture comprises di-carboxylic acid of not more than 9 carbon atoms in a straight chain. Better lathering is also obtained with such compositions.

Description

B~CKGROUND OF TIIE_INVENTION
The wet cracking of soap, i.e.3 the tendency of soap to form cracks when moistened and dried, particularly during use, has been an ever present problem. In United States patent 2,414,098 wet cracking is discussed but it is alleged to be minimi~ed by mechanical processing techniques, In United States patent 4,814,807 there is disclosed the use of branched chain C12 to C20 alkanols as well as di-octyl adipateJ the latter having up to 50% of n-octyl groups to improve wet cracking. In United States patent 2,792,348 there is disclosed the use of sodium salts of C3 to C10 di-basic acids as an additive to soap to produce a harder soap from a given fatty acid or fat and at a given moisture content. In United States patent 3,557,006 certain low molecular weight di-basic acids are disclosed as a basis for a soap to be used as an additive to soap to produce a harder soap product. In United States patent 4,151,105 lactic acid and citric acid are disclosed as useful organic acid to adjust downward the pH of a synthetic detergent-containing ~other than soap) bar to within a pH of 5.0 to 7Ø In British 1,460,442 there are dis-closed detergent bars containing as a moisturi~ing component inter alia, 5 to 50% by weight of an acyclic C2 to C8 hydrocarbon dicarboxylic acid which may be linear or branched. It is an object of this invention to provide soap com-positions in shaped form and particularly in bar form which have improved wetcracking resistance.
It is a further object of this invention to provide soap compositions of improved wet cracking resistance and otherwise acceptable for personal washing.
Ano~her object of this invention is to provide soap bars of impro~ed resistance to wet cracking and of improved lathering characteristics.
Still another object of this invention is to provide processing for making soap bars of improved lathering properties.
Accordi.ng to the present invention, there is provided in a detergent bar comprising a C8 to C20 fatty acid salt, the improvement wherein from about 1% to about 5% by weight based on the weight of detergent of a mixture of at least two polycarboxylic acids of 4 to 20 carbon atoms and wherein at least 20% by weight of the mixture comprises dicarboxylic aci.d of not more than 9 carbon atoms in a straight chain is included as an anti-cracking agent.
:[n another aspect, the invention provides a process for preparing a detergent bar as defined above, the process comprising addi.ng the anti-cracking agent to a soap mix in at least one of a crutcher and amalgamator.
DESCRIPTION OF INVENTION
This invention provides soap compositions, and particularly soap bars of improved and outstanding resistance to wet cracking by the incorporation into the soap at any stage of ma~ing and/or processing, but preferably in the amalgamator, of about 1 to 5% by weight, preferably 2 to 4% and more preferably

2 to 3.5% of a mixture of at least two polycarboxylic acids or anhydrides of 4 to 20 carbon atoms; at least about 20% by weight of the mixture, preferably at least about 30% by weight of the mixture and more preferably about 50% of the mi.xture comprises a dicarboxylic acid of no more than nine carbon atoms in a straight chain. Illustrative dicarboxylic acids are succinic acid, glutaric, adiptic acid, pimelic, suberic and azelaic acid and their anhydrides. As the polycarboxylic acid component in addition to the foregoing one may use any C4 to C20 dicarboxylic, tricarboxylic, tetracarboxylic or pentacarboxylic acid, but a dicarboxylic of C4 to C20 or a tricarboxylic acid is preferred.
Substituted acids are also operable such as citric, malic and tartaric acids.
Unsaturated acids as well as the aforementioned saturated acids may be used.
Within the parameters of C4 to C20 and the requirement for an acid of no more than C9 in a chain, one may use, as illustrative of the unsaturated acids~

fumaric, maleic, and the higher acids such as hexenedioic, heptenedioic and the like.
The soap compositions contemplated herein are the conventional salts of fatty acids of C8 to C20 and pre~erably C12 to C18. The salts may be alkali metal or alkaline earth salts, wherein the cation, illustratively may be sodium, potassium, lithium, calcium, magnesium, etc.. The sodium salts are - 2a -$

preferred. Particular examples of fatty acids are those derived from natural fats and oils and include the coconut and tallow fatty acids, fatty acids from olive oil, palm kernel oil, cotton seed oil, peanut oil and tall oil. The fatty acids may also be derived synthetically by paraffin oxidation, oxo-synthesis or the like.
The soap composition of this invention may also include the usual additive and adjuncts such as super-fatting agents, perfumes, coloring matter, anti-oxidants, proteins, binding agents, sequestrants, foam boosters, optical brighteners, anti-bacterial agents, inorganic salts as fillers and builders and the like. Generally, such additives are used in conventional amounts (e.g. 0.1% to about 50%). In addition to the soap as the wash-active sub-stance, other synthetic detergents may be used in admixture with the soap.
These include paraffin sulfonates (C8 to C20~, olefin sulfonates (C8 to C20), sulfosuccinates, alkyl sulfonates (C8 to C20), alkyl sulfates (C~ to C20), ethoxylated (1 to 100 moles ethylene oxide) alkyl sulfates ~C8 to C20), alkyl aryl sulfonates, iso~hionates (alkyl of C8 to C18), taurides (C8 to Cl~ alkyl), nonionics and the like. In general, such other detergents are employed to constitute from about 1% to about 75% by weight and preferably about 5 to 50%
by weight of the total detergent (including soap) present.
The following examples will serve to illustrate the present inven-tion without being deemed limitative thereof; parts are by weight unless otherwise indicated.

To 92.1 parts of soap chips at 13% moisture level (soap is a 17/83 coco/tallow soap) in a conventional amalgamator are added 1.0 part of azelaic acid, 1.0 part sebacic acid, 0.8 parts titanium dioxide and 1.0 part perfume.
Soap bars (about 100 grams each) are formed in a conventional manner by extru-sion and pressing. The bars are tested for wet cracking. The test involves immersing the bar in water at 75F for 4 hours, removing~ hanging to dry and evaluating after about 24 hours. The severity of the cracks are determined on a scale of 0 to 5; very tiny cracks being assigned a severity value o~ 1, larger cracks 2 to 4 depending on size and when the bar is badly cracked or split a value of 5 is given. The number of cracks is also counted and the product of severity and number of cracks is the cracking rating. When the rating is 0, obviously the bar has no cracks of any kind at all. The bars (average of 31 bars) have a cracking rating of < 9. This compares with a rat-ing of 51 obtained using 3.5% of coco acids in the same procedure and a ratingof 40 using 2% sebacic; a rating of 37 using 2% citric acid and an average value of about 60 using no free acids.
F.XAMPLE 2 When Example 2 is repeated with 1.5% of each dibasic acid, the cracking rating is 2.

Example 1 is repeated except the acids are first dispersed in a liquid carrier comprising about 40% water, 30% glycerin and 20% propylene glycol. qual parts of acid and carrier are used. Excellent results are ob-tained.
XAMPL~ 4 Example 1 is again repeated using 1.2 parts each of adipic andazelaic acids. A superior cracking rating is obtained.

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a detergent bar comprising a C8 to C20 fatty acid salt, the improvement wherein from about 1% to about 5% by weight based on the weight of detergent of a mixture of at least two polycarboxylic acids of 4 to 20 carbon atoms and wherein at least 20% by weight of the mixture comprises dicarboxylic acid of not more than 9 carbon atoms in a straight chain is included as an anti-cracking agent.

2. In a detergent bar as defined in claim 1, the improvement wherein the mixture of acids comprises equal weights of adipic and azelaic acids.

3. In a detergent bar as defined in claim 1, the improvement wherein the mixture of acids comprises equal weights of adipic and sebacic acids.

4. In a detergent bar as defined in claim 2, wherein the weight of the mixture is about 2 to 4%.

5. In a detergent bar as defined in claim 3, wherein the weight of the mixture is about 2 to 4%.

6. A process for preparing a detergent bar as defined in claim 1 compris-ing adding the anti-cracking agent to a soap mix in at least one of a crutcher and amalgamator.

7. A process as defined in claim 6, wherein the said agent is added as a solid.

8. A process as defined in claim 6, wherein the said agent is added as a suspension or solution in a liquid carrier.