GB2114145A - Crack-resistant detergent bar - Google Patents

Abstract

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 type in an amount effective to improve processing, inhibit embrittlement, and further inhibit wet cracking.

Description

SPECIFICATION Crack-resistant detergent bar The present invention relates to detergent bars and expecially to the provision of detergent bars having a basis of fatty acid soap as the predominant wash-active agent and having improved resistance to wet cracking and embrittlement.

There exist a number of prior art disclosures of soap bars in which polycarboxylic acids, including aliphatic dicarboxylic acids, have been incorporated for various purposes. Thus, U.S.

1,684,336 of 1 itch September, 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 14th May, 1957 discloses the addition of 1% to 10% of aliphatic dibasic acids to 3 to 10 carbon atoms as a hardness-increasing agent in soap bars, especially those derived from unsaturated fatty acids. U.S. 3,085,066 of 9th April, 1963 discloses the use of about 0.01% to 0.5%, up to 10%, of an alkanedioc acid of 2 to 10 carbon atoms as a colour stabilizer in an antiseptic soap bar containing a discolouring type of bacteriostat. U.S. 3,557,006 of 19th January, 1 971 discloses the very same di-basic acidcontaining soap bars as U.S. 2,792,348 but the acid is relied upon to provide on the skin the normal acidic skin pH.British 481,481 accepted 1 itch March, 1 938 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 neutralization of excess alkali and to provide resistance to discolouration, cracking and embrittlement. British 1 ,460,442 published 6th January, 1977 discloses soap bars containing, as skin moisturizers, 5 to 55% of C4~,0 aliphatic dicarboxylic acid and/or hydroxy polycarboxylic acids. U.K.Patent Application G.B. 2,004,564A published 4th April, 1 979 discloses the concept of reacting a neutral fatty acid soap with about 0.1% to 3% of a C31o aliphatic dicarboxylic acid which yields the corresponding soap of the dicarboxylic acid and concurrently releases an equivalent desired amount of free (superfatting) fatty acid. In U.S. Application Serial No. 105,806 filed 20th December, 1 979 which corresponds to copending published G.B. Application No.

2068997 soap bars are disclosed containing, as anti-wet cracking agent, about 1% to about 5% of adipic, azelaic or tartaric acid. In U.S. Application Serial No. 105,808 filed 20th December 1979 which corresponds to copending published G.B.

Application No. 2075044 soap bars are disclosed containing, as anti-wet cracking agent, about 1% to about 5% of a mixture of C42o polycarboxylic 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 developing cracks when repeatedly moistened and dried.

Such soap bars containing polycarboxylic, and especially dicarboxylic, acids are however more or less disadvantageous 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, expecially in cold, hard water. Further, these soap bars, being still on the alkaline side because of the relatively small amount of acid contained therein, exert a recognized degree of skin irritation in use.

The present invention aims to provide soap bars and methods of making them which will have at least a reduced incidence of or not be subject to at least one of the above disadvantages.

According to a first aspect of the present invention a detergent bar comprises, approximately by weight, at least 70% of a C82o fatty acid salt, 0.5% to less than 5% of one or a mixture of hydrocarbyl or hydroxycarbyl 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 comprises dissolving the polycarboxylic acid in the nonionic surface active agent and mixing the resulting solution 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 polycarboxylic acid-containing detergent bars of the present invention reduces or eliminates the tendency of the bars to become brittle, further improves their resistance to wet-cracking, improves their solubility and lathering properties in use in water, especially cold, hard water, exerts an emollient or anti-irritation effect on the skin, and renders the soap composition more plastic and more readily and economically processed into bars. Pre-dissolving the polycarboxylic acid antiwet cracking agent in the nonionic surface active agent further facilitates uniform mixing into the soap composition and improves the efficiency of the anti-wet cracking agent in the bar.

The predominant wash-active agent in the detergent bars of the present invention may be any conventional soap, otherwise referred to as fatty acid salt. The soap may be derived from one or a mixture of Cs2o, preferably C,2~,8, straight or branched chain, saturated or unsaturated monocarboxylic acids, of natural 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, fish oils, tallow, and the like. lilustratively, individual fatty acids include capric, lauric, myristic, stearic, oleic, palmitoleic, ricinoleic, linoleic, and linoleric acid and the like. The fatty acids 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 alternativbly be an alkaline earth metal such as calcium or magnesium, or ammonium, substituted ammonium, or organic amine such as a lower alkylamine or a lower alkanolamine.

Mixtures of the fatty acids may be employed.

Preferred are 4/1 to 7/1, especially about 3/1 to 5/1, tallow/coco sodium soaps. The fatty acid salt typically constitutes at least about 70%, preferably at least about 80%, by weight of the detergent bars of the present invention.

The polycarboxylic acid component may be unsaturated but preferably saturated, and aromatic, alicyclic but preferably aliphatic, branched but preferably 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 about 10, carbon atoms. Alkanedioc and hydroxyalkanedioc acids of 2 to about 10 carbon atoms are especially preferred, particularly adipic and azelaic acids.As illustrative of other suitable hydrocarbyl and hydroxyhydrocarbyl polycarboxylic acids, there may be mentioned oxalic, malonic, succinic, glutaric, pimelic, suberic, sebacic, methyl adipic, citric, malic, tartaric, dihydroxytartaric, fumaric, maleic, itaconic, aconitic, hexenedioic, heptenedioic, phthalic, 3-hydroxy: phthalic, cyclohexyldicarboxylic, 3-cyclohexyldicarboxylic, mellitic, hexahydromel litic, mellophanic 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 lesu than 5%, preferably about 1% to about 3%, by weight of the detergent bars of the present invention.

The nonionic surfactants (surface 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 a reactive hydrogen-containing organic hydrophobic compound which may be aliphatic, aromatic, alicyclic or heterocyclic. The length of the hydrophilic polyoxyalkylene 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 (HLB factor). Although propylene oxide may be employed as the alkylene oxide reactant, ethylene oxide is most commonly employed, more effective and preferred herein.

The polyoxyethylene-containing condensation products have been referred to as ethoxamers or ethoxameric nonionic surfactants.

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, sulphonamides, 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 nonionic surfactant should be liquifiable, e.g. at elevated temperatures up to about 900C, to facilitate processing of the soap composition 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 20th February, 1979 to Ramachandran from line 3 to line 63 of column 2, which portion is incorporated herein by reference thereto. As exemplary of specific non ionic surfactants, mention is made of dinonyl phenol +15 E.O. (1 mole of dinonyl phenol reacted with 1 5 moles of ethylene oxide), dodecyl mercaptan + 10 E.O., lauramide +8 E.O., stearic acid +20 E.O., tetradecyl amine + 1 4 E.O., dodecyl sulphonamide +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 with about 4 to 20, especially 5 to 15, moles of ethylene oxide, as represented for example by Neodol 23-65 (C,2~13 aikanol +6.5 E.O.) and Neodol 4513 (C1415 alkanol + 13 E.O.). The nonionic surfactant 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%, by weight of the detergent bars of the present invention. As indicated in the examples below, inclusion of this nonionic surfactant component in polycarboxylic acidcontaining detergent (soap) bars enables the attainment of equal or better resistance to wet cracking with a substantially lower proportion of the polycarboxylic acid.

The non ionic 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 the present invention generally contain about 8% to about 16%, more usually about 10% to about 14%, by weight of water, and optionally other conventional additives such as superfatting agents, perfumes, colouring matter, anti-oxidants, non-soap organic anionic surfactants, proteins, binding agents, 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 the present invention, the polycarboxylic acid and nonionic surfactant components may be incorporated into the soap at any stage of processing into bar form, 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 components is first dissolved or dispersed in the liquid or liquified nonionic surfactant (e.g. by heating up to about 900C 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 examples, involves immersing the bar (weighing about 100 grams) in water at about 240C for 4 hours, removing and hanging the bar to dry and then 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 invention may be put into practice in various ways and a number of specific embodiments will be described to illustrate the invention with reference to the accompanying examples.

All 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 E.O.) was prepared at about 650C.

The solution was then processed in a conventional amalgamator with, approximately by weight, 92 parts of 5/1 tallow/coco sodium soap chips of 11% moisture content, 0.1 parts of 50% aqueous stannic chloride (colour and fragrance stabilizer),0.5 parts of titanium doxide, 1.25 parts of bacteriostat, 0.5 parts of glycerin, 1.5 parts of perfume, and 0.5 parts of a 10% colour solution.

The mixture was 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 without the Neodol nonionic surfactant and adipic acid.

The control bars were 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 of the abovementioned published G.B. Application Serial No.

2068997, a substantially similar soap bar containing 2% adipic acid but no nonionic surfactant is indicated to have an average cracking rating of 3.

Example 2 Example 1 was repeated substituting 2 parts of azelaic acid for the adipic acid. These bars were likewise found to have an average cracking rating of 0. By comparison, in Example 1 of the said application Serial No. 105,806, a substantially similar soap bar containing 3.5% azelaic acid but no non ionic surfactant is indicated to have an average cracking rating of 1.

Example 3 When Examples 1 and 2 were repeated using Neodol 45-13 (C14~15 alkanol + 13 E.O.) instead of Neodol 23-6.5, substantially similar results were obtained.

Example 4 When Examples 1,2 and 3 were repeated using as the soap chips 3/1 tallow/coco sodium soap chips of 13% moisture content, substantially similar results were obtained.

Reference has been made to U.S.P. 4140641 for details of nonionic surfactants.

The nonionic surfactants for use in compositions according to the present invention are commercially known and comprise the water soluble products which are derived from the condensation of an alkylene oxide or equivalent reactant and a reactive-hydrogen hydrophobe.

The hydrophobic organic compounds may be aliphatic, aromatic, or heterocyclic, although the first two classes are preferred. Then preferred types of hydrophobes are higher aliphatic alcohols and alkyl phenols, although others may be used such as carboxylic acids, carboxamides, mercaptans or sulphonamides. The ethylene oxide condensates with higher aliphatic alcohols represent a preferred class of nonionic compounds.

Usually the hydrophobic moiety should contain at least about 6 carbon atoms and preferably at least about 8 carbon atoms, and may contain as many as about 50 carbon atoms or more. The amount of alkylene oxide will vary considerably depending upon the hydrophobe, but as a general rule at least about 5 moles of alkylene oxide per mole of hydrophobe should be used. The upper limit of alkylene oxide will vary also, but no particular criticality can be ascribed thereto. As much as 200 or more moles of alkylene oxide per mole of hydrophobe may be employed. While ethylene oxide is the preferred and predominating oxyalkylating agent, other lower alkylene oxides such as propylene oxide, butylene oxide, and the like may be used or substituted in part for the ethylene oxide.

Other nonionic compounds which are suitable are the polyoxyalkylene esters of the organic acids such as the higher fatty acids, the resin acids, tall oil acids, or acids from petroleum oxidation products. These esters will usually contain from about 10 to about 22 carbon atoms in the acid moiety and from about 12 to about 30 moles of ethylene oxide or its equivalent.

Still other nonionic surfactants are the alkylene oxide condensates with the higher fatty acid amides. The fatty acid group will generally contain from about 8 to about 22 carbon atoms, and this will be condensed with about 10 to about 50 moles of ethylene oxide. The corresponding carboxamides and sulphonamides may also be used as substantial equivalents.

The oxyalkylated higher aliphatic alcohols are the preferred nonionic surfactants for compositions according to the present invention.

The fatty alcohols should contain at least 6 carbon atoms, and preferably at least about 8 carbon atoms. The most preferred alcohols are lauryl, myristyl, cetyl, stearyl, and oleyl alcohols, and the said alcohols should be condensed with at least about 6 moles of ethylene oxide. A typical nonionic product is C12-C13 aliphatic alcohol condensed with about 6.5 moles of ethylene oxide. The corresponding alkyl mercaptans when condensed with ethylene oxide are also suitable in the compositions of the present invention.

The alkoxylated higher aliphatic alcohols are particularly well suited for these formulations because they are readily biodegradable and compatible with most other adjuvants.

Claims (11)

Claims

1. A detergent bar comprising, approximately by weight at least 70% of a C820 fatty acid salt, 0.5% to less than 5% of one or a mixture of hydroca rbyl or hydroxyhydrocarbyl polycarboxylic acids of 2 to about 40 carbon atoms, and 1% to less than 25% of one our a mixture of ethoxameric nonionic surface active agents.

2. A detergent bar as claimed in 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 as claimed in Claim 1 or Claim 2 in which the polycarboxylic acid is an aikanedioc or hydroxyalkanedioc acid of about 2 to 10 carbon atoms.

4. A detergent bar as claimed in Claim 1,2 or 3 in which the nonionic surface active agent is the condensation product of one mole of a C9~20 aikanol with about 4 to 20 moles of ethylene oxide.

5. A detergent bar as claimed in any one of Claims 1 to 4 in which the polycarboxylic acid is adipic acid or azelaic acid.

6. A detergent bar as claimed in any one of Claims 1 to 5 in which the nonionic surface active agent is the condensation product of one mole of a C10-a8 alkanol with about 5 to 1 5 moles of ethylene oxide.

7. A detergent bar as claimed in Claim 1 substantially as specifically described herein with reference to any one of the Examples.

8. A method of preparing a detergent bar as claimed in any one of Claims 1 to 7 comprising dissolving the polycarboxyiic acid in the nonionic surface active agent and mixing the resulting solution with the fatty acid salt.

9. A method as claimed in Claim 8 substantially as specifically described herein with reference to any one of the accompanying Examples.

1 0. A detergent bar whenever made by a method as claimed in Claim 8 or Claim 9.

11. A washing method comprising contacting the human body with a detergent bar as claimed in any one of Claims 1 to 7 or 10 in the presence of water.