CA1203143A - Crack-resistant detergent bar - Google Patents

Abstract

CRACK-RESISTANT DETERGENT BAR

ABSTRACT OF THE DISCLOSURE

A fatty acid soap bar is disclosed containing one or a mixture of hydrocarbyl or hydroxyhydrocarbyl polycarboxylic acids such as adipic or azelaic acid in an amount effective to inhibit wet cracking, and a nonionic surfactant of the polyoxyethylene in an amount effective to improve processing, inhibit embrittlement, and further inhibit wet cracking.

Description

~3~ 3 This invention relates to detergent bars an~ especially to the provision o~ detergent bars having a basis of fatty acid soap as the predominant wash-active agent nnd having improved resistance to wet cracking and embrittlement.
There exist a number of prior art disclosures o~ soap bars in which polycarboxylic acids, including aliphatic dicarboxylic acids, have been incorporated for various purposes.
Thus, U.S. 1,6O4,336 of ~ept. 11, 1928 discloses a medicinal soap bar containing rectified amber oil and about 2~ of succinic acid to provide hyperaemia with consequent heating. U.S. 2,792,348 of May 14, 1~57 discloses the addition of 1% to 10'~ of aliphatic dibasic acids of 3 to 10 carbon atoms as a hardness - incrensing agent in soap bars, especially those derived from unsaturated fatty acids,U.S. 3,o85,066 of April ~, 1963 discloses the use of about 0.01% to 0.5%, up to lO~o ~ of an alkanedioc acid of 2 to 10 carbon atoms a5 a color stabilizer in an antisepti~ soap bar containing a discolorin~ type of bacteriostat. U.S. 3,557,()06 of Jan. 1~, 1971 discloses the very same dibasic acid-containing soap bars as U.S. 2,792,348 but the acid is relied upon to provide on tlle skin the normal acidic skin p~ ritish 481,481 accepted March 11, 1~38 discloses the addition to soap bars bleached with boric acid of a very small amount (about 0.1%) of a hydroxypoly basic aliphatic acid such as tartaric or citric acid for neu-trali-zation of excess alkali and to provide resistance to discoloration 9 cracking and embrittlement. British 1,460,442 published Jan. 6, 1977 discloses soap bars containing, as skin moisturizersl 5 to 55%
of C4 10 aliphatic dicarboxylic acids and/or hydroxy polycarboxylic acids. U.K. Patent Application GB 2,oo4,5~4A published Apr. 4, 1~7 discloses the concept of reacting a neutral fatty acid soap wi-th about O.l~o to 3% of a C3 10 aliphatic dicarboxylic acid which ~Z~3~3 yields the corresponding soap o the dicarboxylic acid and con-currently releases an equivalent desired amount of free (super-fatting) fatty acid. In South African Patent No. 80/7894 issued July 28, 1982 soap bars are disclosed containing, as anti-wet cracking agent, about 1% to about 5% of adipic, azelaic or tartaric acid. In South African Patent No. 80/7779 issued July 28, 1982 soap bars are disclosed containing, as anti-wet crack-ing agent, about 1~ to about 5~ of a mixture of C4 20 poly-carboxylic acids, at least 20% of the mixture comprising straight chain dicarboxylic acid of no more than 9 carbon atoms.
Wet-cracking refers to the known defect of soap bars in develop-ing cracks when repeatedly moistened and dried.
Such soap bars containing polycarboxylic, and especi-ally dicarboxylic, acids are however more or less disadvantage-ous for several reasons. Thus, it has been found that these acids tend to make the soap "short" or brittle upon extrusion, thus showing its non-plasticity. Furthermore, these acids have high melting points and in their original state are hard dry particles not readily miscible with the soap during processing.
This reduced miscibility not only renders the processing more difficult and costly, but also reduces the anti-wet cracking efficiency of the acid in the soap bar. These acids also tend to reduce the water solubility and/or lathering properties of the soap bar, especially in cold, hard water. Further, these soap bars, being still on the alkaline side because of the rela-tively small amount of acid contained therein, exert a recognized degree of skin irritation in use.
It is an object of this invention to provide soap bars and methods of making them which will not be subjec-t to one or more of the above disadvantages. Other objects and advantages `' 3l2~ 3 will appear as the description proceeds.
The attainment o~` the above ob~ects is ma~e possible by this invention which includes the provision of a detergent bar comprising, approximately by weight, at least 70~ of a C8 20 fatty acid salt, 0.5% to less than 5% of one or a mixture of hydrocarbyl or hydroxyhydrocarbyl polycarboxylic acids of 2 to about 20 carbon atoms, and 1% to less than 25% of one or a mixture of ethoxameric nonionic surface active agents.
According to another aspect of this invention, a preferred method for making the aforementioned detergent bar cornprises dissolving the polycarboxylic acid in the nonionic surface active agent and mixing the resulting sclution with the fatty acid salt.
According to yet another aspect of this invention, a washing method is provided comprising contacting the human body with the aforementioned detergent bar in the presence of water.
The nonionic surface active agent included in the poly-carboxylic acid-containing detergent bars of this invention reduces or eliminates the tendency of the bars to become brittle, furtller improves their resistance to wet-cracking, improves their solubility and la-thering properties in use in water, especîally cold, hard water, exerts an emollient or anti-irritation effect on the skin, and renders the soap composition more pl~stic and more easily and economically processed into bars. Pre-dissolving the polycarboxylic ncid nnti-wet cracking agent in the nonionic surface active agent further facilitates uniform mixin~ into the soap composition and improves the efficiency of the anti-wet cracking agent in the bar.
~he predominant wnsh-active n~ent in the detcreent bnrs 3 ol this illVClll;iOIl m/ly be nlly COIIIVelltiOnal sonp, Ol,ll^L'WiS(' I`CI`('rl`eU

~l2C~3~43 to as fatty acid .;alt. The soap may be derived from one or a mixture of C8-20~ preferably C12_18, straight or branched chain, saturated or unsatura-ted monocarboxylic acids, of nnturnl or synthetic origin. Natural sources, e.g. animal, marine or ,vegetable fats and oils, almost always yield mixtures of these fatty acids, all of which may be employed. Examples thereof include the fatty acids derived from coconut oil, olive oil, palm kernel oil, tall oil, soy bean oil, cottonseed oil, peanut oil, safflower oil, sunflower seed oil, corn oil, Pish oils, tallow, and the like. Illustratively, indiv;dual fatty acids include capric, lauric, myristic, stearic, oleic, palmitoleic, ricinoleic, linoleic, linoleric acids and tile like. The fatty aolds may also be derived synthetically by paraffin oxidation, Oxo-synthesis, or the like. The cation or salt portion of the soap is preferably an alkali metal such as potassium and, especially, sodium, but may alternatively be an alkaline earth metal such as calcium or magnesillm, ammonium, substituted ammonium, or organic amine such as lower alkylamines and lower alkanolamines. Mixtures of the fatty acids may be employed.
Preferred are 4/1 to 7/1, especinlly nbout 3/1 to 5/1, tallow/coco sodium soaps. The fatty acid salt typically constitutes a-t least about 70%, preferably at least about 80%, by weight of the detergent bars of this invention.
The polycarboxylic acid component may be unsaturated but preferably saturated, and aromatic, alicyclic but preferably aliphatic, branched but pre~erably straight chain, and hydroxy-substituted but preferably unsubstituted, and hexa-, penta-, tetra--, tri- but preferably di-carboxylic, and of 2 to about 20, preferably

2 to a,bout 10, carbon atoms. Alkanedioc and hydroxyalkanedioc acids of 2 to about 10 carbon atoms are especin1ly ~reI'erre(l, particularly adipic nnd a~elaic acids. ~s illustratlve of other suitable hydrocarbyl and hydroxyhydrocarbyl polycarboxylic acids, there may be mentioned oxalic, malonic, succinic, glutaric, pimelic, suberic, sebacic, methyl adipic, citric, malic, tartaric, dihydroxy~ar-taric, fulllaric, maleic, itaconic, aconitic, hexerledioc, heptenedioc, phthalic, 3-hydroxyphthalic, cyclohexyldicarboxyli

3-cyclohexyl- dicarboxylic, melli~ic, hexahydromellitic, mello-phanic and the like. Mixtures of two or more such acids may be employed. The polycarboxylic acid component, which may optionally be in anhydride form and/or at least partiallY in salt form, typically constitutes about 0.5% to less than 5S', preferably about lS~ to about 3%, by weight of the detergent bars of this invention.
The nonionic surfactants (sur*ace active agents) useful in the present invention are well known materials and may be broadly defined as water soluble products derived from the condensation of a plurality of moles of a C2_3 alkylene oxide or equivalent reactant (hydrophilic in nature) with n reactive hydrogen-containing organic llydropllobic compound which may be aliphatic, aromatic, alicyclic or heterocyclic. The length of the hydrophilic polyoxyall~ylene chain in the condensation product derived from any particular hydrophobe can be readily adjusted to provide water solubility and the desired degree of balance between hydrophilic and hydrophobic or lipophilic elements 5 (HLB factor). Although propylene oxide may be employed as the alkylene oxide reactant, ethylene oxide is most commonly emp'oyed, more effective and preferr~d herein. These polyoxyethylene-containing condensation products have been referred to as ethoxamers or ethoxameric 0 nonionic surfactants.

"` ~ZO;3:143 The precursor hydrophobe of the nonionic surfactant may contain from about 6, preferably from about 8, up to 50 or more carbon atoms and at least one reactive hydrogen~containing moiety as present for example in aliphatic alcohols, alkyl phenols, carboxylic acids, carboxylic acid amides, sulfonamides, amines, and the like. As a general rule, at least about 4 moles of ethylene oxide should be reacted per mole of hydrophobe, but up to 200 moles of ethylene oxide may be so reacted depending on the hydrophobe, desired water solubility, surface activity, emolliency, plasticity and melting point, and the like. The non-ionic surfactant should be liquifiable, e.g. at elevated tempera-tures up to about 90C, to facilitate processing o the soap com-position into bar form.
Representative operative nonionic surfactants include polyoxyethylene polyoxypropylene block polymers ~Pluronics)* and other types as disclosed for example in the portion of U.S.

4,140,641 issued February 20, 1979 to Ramachandran from line 3 to line 63 of column 2. As exemplary of specific nonionic sur-factants, mention is made of dinonyl phenol + 15 E.O. (1 mole of dinonyl phenol reacted with 15 moles of ethylene oxide), dodecyl mercaptan + 10 E.O., lauramide + 8 E.O., stearic acid + 20 E.O., tetradecyl amine + 14 E.O., dodecyl sulfonamide + 6 E.O., and myristyl alcohol + 10 E.O. Preferred are condensation products of one mole of an alkanol, preferably straight chain and primary, of about 9 to 20, especially 10 to 18, carbon atoms ~ith about 4 to 20, especially 5 to 15, moles of ethylene oxide, as repre-sented for example by Neodol* 23-65 (C12 13 alkanol + 6.5 E.O.) and Neodol 45-13 (C14_15 alkanol + 13 E.O.). The nonionic sur-factant component typically constitutes about 1% to less than 25%, preferably about 2 to less than 10%, more preferably about 2.5% to less than 5%, * Trade Mark '~i 3l203:1~3 by weight of the detergent bars of this invention. As indicated in the examples below, inclusion of this nonionic surfactant component in polycarboxylic acid--containing detergent (soap) bars enables the attainment of equal or better resistance to wet cracking with a substantially lower proportion of the polycarboxylic acid.
The nonionic surfactant/polycarboxylic acid weight ratio preferably ranges from about 0.5/1 to about 5/1, more preferably about 1/1 to about 2/1, especially about 1.5/1.
The detergent bars of this invention generally contain about 8% to about 16%, more usually about 10% to about 14~, by weight of water, and optionally other conventionnl additives suc~h as super-fatting agents, perfumes, coloring matter, anti-oxidants, non-soap organic anionic surfactants, proteins, binding agent~ sequestrants, foam boosters, optical brighteners, preservatives, bacteriostats, and inorganic salt fillers and builders and the like in conventional proportions of about 0.01% to about 25% by weight of the detergent bar.
In preparing the detergent bars of this invention, the polycnrboxylic acid and nonionic surfactant components may be incorporated into the sonp nt nny stnee of processi~g into bal forrll, preferably by admixture with -the previously prepared soap chips in the crutcher or, more preferably, the amalgamator.
According to a further feature of the invention, the polycarboxylic acid component is first dissolved or dispersed in the liquid or liquified nonionic surfactant (e.g. by heating up to about ~0C. if needed) and the resulting solution (or dispersion) then admixed with the fatty acid salt-containing soap composition, followed by conventional extrusion and pressing into bar form.
The wet cracking test, results of which are given in the following ex~mplcs, lnvolvcs immersing the bar (Or a~out :L0() grams) 3~'~3 in water at llbou~ 24C~ for l~ hours, removine and hanging the bnr to dry and thell evaluating for cracks. The severity of the cracks are rated on a scale of 0 to 5, no cracks of any kind being assigned a severity rating of 0~ very tiny cracks being assigned a severity rating of 1, larger cracks 2 to 4 depending on size, and 5 when the bar is badly cracked or split. The severity rating multiplied by the number of cracks is the cracking rating, averaged for reliability on a substantial number (e.g. 31) of bars concurrently produced from the same composition.
The following examples are only illustrative. ~11 amounts and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.
Example 1 A solution of 2 parts by weight of adipic acid in 3 parts by weight of Neodol 23-6.5 (C12_13 alkanol + 6.5 EØ) is prepared at about 65C. The solution is then processed in a conventional amalgamator with, approximately by weight, ~2 parts of 5/1 tallow/
coco sodium soap chips of 11% moisture content, 0.1 parts of 50%
aqueous stannic chloride (color and fragrance stabilizer), 0.5 parts of titanium dioxide, 1.25 parts of bacteriostat, 0.5 parts of glycerin, 1.5 parts of' perfume, and 0.5 parts of A 10~ color solution. The mixture is then shaped into bars of about 100 grams each in conventional manner including extrusion and pressing, and tested for wet cracking as described above, together with control bars made in similar manner but withou-t the Neodol nonionic surfactant and adipic acid. The control bars are found to have an average cracking rating of 51 compared with an average cracking rating of 0 for the bars containing nonionic surfactant and adipic acid. By comparison, in Example 2 Or the above-mentioned application Serial No. 105,806 filed Dec. 20, 1~7~, a substantially similar soap bar _5._ ~l203143 con-taining 2% adipic acid but no nonionic suractant is indi-cated to have an average cracking rating of 3.
Example 2 Example 1 is repeated substituting 2 parts of azelaic acid for the adipic acid. These bars are likewise found to have an average cracking rating of 0. By comparison, in Example 1 of said South African Patent No. 80/7894 a substantially similar soap bar containing 3.5~ azelaic acid but no nonionic surfactant is indicated to have an average cracking rating of 1.
Example 3 When Examples 1 and 2 are repeated using Neodol 45-13 (C14 15 alkanol + 13 E.O.) instead of Neodol 23-6.5, substanti-ally similar results are obtained.
Example 4 When Examples 1, 2 and 3 are repeated using as the soap chips 3/1 tallow/coco sodium soap chips of 13% moisture con-tent, substantially similar results are obtained.
This invention has beèn disclosed with respect to pre-ferred embodiments thereof and it will be understood that modi-fications and variations thereof obvious to those skilled in theart are to be included within the spirit and purview of this application and the scope of the appended claims.

Claims (9)

WE CLAIM:

1. A detergent bar comprising, approximately by weight, at least 70% of n C8-20 fatty acid salt, 0.5% to less than 5% of one or a mixture of hydrocarbyl or hydroxyhydrocarbyl poly-carboxylic acids of 2 to about 20 carbon atoms, and 1% to less than 25% of one or a mixture of ethoxameric nonionic surface active agents.

2. A detergent bar according to Claim 1 containing about 1 to 3% of the polycarboxylic acid and about 2 to less than 10% of the nonionic surface active agent.

3. A detergent bar according to Claims 1 or 2,wherein the polycarboxylic acid is an alkanedioc or hydroxyalkanedioc acid of about 2 to 10 carbon atoms.

4. A detergent bar according to Claims 1 or 2 wherein the nonionic surface active agent is the condensation product of one mole of a C9-20 alkanol with about 4 to 20 moles of ethylene oxide.

5. A detergent bar according to Claims 1 wherein the polycarboxylic acid is adipic acid or azelaic acid and the nonionic surface active agent is the condensation product of one mole of a C10-18 alkanol with about 5 to 15 moles of ethylene oxide.

6. A method of preparing a detergent bar as defined in Claims 1 or 2 comprising dissolving the polycarboxylic acid in the nonionic surface active agent and mixing the resulting solution with the fatty acid salt.

7. A method of preparing a detergent bar as defined in Claim 5 comprising dissolving the polycarboxylic acid in the nonionic surface active agent and mixing the resulting solution with the fatty acid salt.

8. A washing method comprising contacting the human body with a detergent bar as defined in Claims 1 or 2 in the presence of water.

9. A washing method comprising contacting the human body with a detergent bar as defined in Claim 5 in the presence of water.