DE69421172T2 - SYNTHETIC DETERGENT PIECE AND PRODUCTION THEREOF - Google Patents

Description

SYNTHETIC DETERGENT COMPOUND AND PRODUCTION THEREOF

The invention relates to synthetic detergent bars and detergent compositions that can be formed into bars.

Detergent bars can be divided into soap bars, mixed active bars which contain a significant amount of soap and thirdly synthetic detergent bars which contain only a small amount of soap or none at all.

Typical soap bars contain a large proportion, generally 60-80% by weight, of fatty acid soap. Fatty acid soaps are selected to provide a balance of soluble and insoluble soaps that provide the required functional properties in terms of lathering and bar structure. Typical soap bars are made by milling, extruding and molding a semi-solid mass of soap and other components.

Bars containing a mixture of soap and synthetic detergent, in which the amount of soap is less than the amount of synthetic detergent, but nevertheless contributes substantially to the content of the bar, are known. In such bars, as in conventional soap bars, the proportion of soap, particularly the insoluble soap, contributes to the structure and physical properties of the bar.

The third category are synthetic detergent bars, often known as "syndet" bars, in which no or only a small amount of soap is present and the detergent active is mostly or entirely a synthetic, non-soap detergent. Generally, such bars contain a substantial proportion of non-detergent material which serves to give structure to the bar. Such "structurants" are normally water-insoluble and include such materials as starch and kaolin. The bars also frequently contain a plasticizer: known plasticizers include stearic acid and cetyl alcohol. WO-A-92/13060 discloses a syndet bar comprising a long chain alkyl sulfate, water and a three component plasticizer system containing free fatty acid, monoglyceride and polyethylene glycol. Bars containing polyethylene glycol are also known from US-A-3 687 855 and 2 987 484. US-A-3 687 855 discloses iodine-containing germicidal bars in which the polyethylene glycol facilitates the homogeneous distribution of the active germicidal compound and detergent throughout the bar. Polyethylene glycol is used as a filler in US-A-2 987 484 for bars by a closed die molding process involving the use of molten mixture of the active components.

GB-A-1 294 754 discloses the use of polyethylene oxide with very high molecular weight (100 000-600 000) in amounts of not more than 10%.

Common surfactants for syndet bars include primary alkyl sulfates, alkyl ether sulfates, betaines, sarcosinates, sulfosuccinates and isethionates. These syndet bars, which contain no soap or only a small amount of soap, are usually made by vigorously processing a physical mixture of structurant, plasticizer and surfactant, i.e. both the soluble and insoluble components, in a high shear mixer to an end point where the product is not gritty. The mixture is then formed into "syndet" bars.

The known processes have various disadvantages in that the physical mixing step is carried out batchwise and requires a powerful mixer.

In contrast to known compositions and methods, the invention is based on ingredients that are melted at conveniently achievable temperatures, but above those normally encountered during use of "syndet" bars. As a result, the necessary intimate mixing of the components of the piece can be accomplished by simple mixing while the piece composition is liquid, rather than relying on forceful work to achieve intimate mixing of a mixture of solids.

Accordingly, the present invention provides a detergent composition which is, or can be formed into, a synthetic detergent bar composition comprising:

(a) 10-60% by weight of a synthetic non-soap detergent,

(b) 20-50% by weight of water soluble material comprising one or more polyethylene glycols having a molecular weight in the range of 1500 - 10,000 and a melting point in the range of 40ºC to 100ºC,

(c) 5-50% by weight of water-insoluble C₁₂-C₂₄ fatty acid, C₈-C₂�0 alkanols or mixtures thereof having a melting point in the range of 40°C to 100°C and

(d) 3-20% by weight water.

It is desirable that the proportion (if present) of material other than the synthetic non-soap detergent (a) which does not melt below 100°C be less than 20% by weight of the composition.

In many embodiments of this invention, the level of synthetic detergent (a) will be in the range of 10 to 50% by weight. Preferably, the composition will contain some water in an amount of 3% or 5% to 20%, most preferably 15% by weight of the composition.

From the foregoing, it will be appreciated that a significant component of the composition of the invention is a water soluble material which melts at a temperature in the range of 40-100°C and acts as a bar structuring agent. Such a material assists in imparting the desired properties, preferably so that the bar has a rigid, solid form.

It can be seen from the foregoing that the bar compositions can tolerate the presence of some material which does not melt at temperatures below 100°C. Such material can also serve as a structuring agent. Such material is not an essential requirement and need not be present at all. If such material is present, the molten composition will not be completely liquid at a temperature of up to 100°C unless the non-melting material dissolves in the other materials present. We have found that a moderate amount of material which does not melt can be dispersed in the molten composition while remaining sufficiently liquid to be stirred without the need for vigorous operation. Again, as mentioned below, this material which disperses but does not melt may be at least a part of the synthetic non-soap detergent (a) and/or the material other than this category.

Suitable synthetic detergents (a) are: alkyl ether sulfates, alkyl ethoxylates, alkyl glyceryl ether sulfonates, α-olefin sulfonates, acyl taurides, methyl acyl taurates, N-acyl glutamates, acyl isethionates, anionic acyl sarcosinates, alkyl phosphates, methyl glucose esters, protein condensates, ethoxylated alkyl sulfates, alkyl polyglucosides, alkyl amine oxides, betaines, sultaines, alkyl sulfosuccinates, dialkyl sulfosuccinates, acyl lactylates and mixtures thereof. The detergents mentioned above are preferably those based on C8-C24, more preferably those based on C10-C18 alkyl and acyl units.

For many embodiments of this invention, the amount of synthetic detergent (a) may range from 10 to 50% by weight. Other preferences are at least 20% and not more than 40%.

Among the above synthetic detergents, some acyl isethionates are particularly less water-soluble than others. If a detergent of low solubility is used, it is preferably mixed with other synthetic detergent. Thus, inventive Detergent compositions may exclude acyl isethionates from the synthetic detergent (a) or may include it along with other synthetic detergent. In some embodiments of this invention, acyl isethionate is not more than 10% by weight of the composition, for example 5% to 9.5%. However, other embodiments of the invention include larger amounts of acyl isethionate, for example up to 30% by weight of the composition.

The water-soluble structurant (b) is required to melt in the temperature range of 40°C to 100°C, so that it may be molten to form the bar composition, but in a solid state at a temperature at which the bar is used. Preferably it has a melting point of at least 50°C, preferably in the narrower range of 50°C to 90°C.

Although structurant (b) comprises one or more polyethylene glycols (PEG) having a molecular weight in the range of 1500 - 10,000, in some embodiments of this invention it is preferred to include a further relatively small amount of polyethylene glycol having a molecular weight in the range of 50,000 to 500,000, particularly having molecular weights of around 100,000. The possible addition of such higher molecular weight polyethylene glycols has been found to improve the wear rate of the bars. This is believed to be due to their long polymer chains remaining entangled even when the bar composition becomes wet during use.

When such higher molecular weight polyethylene glycols (or other high molecular weight water-soluble polyalkylene oxides) are used, the amount is preferably from 1% to 5%, more preferably from 1% or 1.5% to 4% or 4.5% by weight of the composition. These materials are generally used together with a larger amount of other water-soluble structurant (b), such as the above-mentioned polyethylene glycol having a molecular weight of 1500 to 10,000.

Some polyethylene oxide-polypropylene oxide block copolymers melt at temperatures in the required range of 40 to 100°C and can be used as part or all of the water-soluble structurant (b). Preferred herein are block copolymers in which polyethylene oxide provides at least 40% by weight of the block copolymer. Such block copolymers can be used in blends with polyethylene glycol or other water-soluble structurant.

The water-insoluble structurants (c) are also required to have a melting point in the range of 40-100°C, more preferably at least 50°C to 90°C. Particularly preferred are fatty acids having a carbon chain of 12 to 24 carbon atoms. Examples are lauric, myristic, palmitic, stearic, arachidonic and behenic acids and mixtures thereof. Sources of these fatty acids are coconut, topped coconut, palm, palm kernel, babassu and tallow fatty acids and partially or fully hydrogenated fatty acids or distilled fatty acids. Other suitable water-insoluble structurants include alkanols having 8 to 20 carbon atoms, particularly cetyl alcohol. These materials generally have a water solubility of less than 5 g/l at 20°C.

The relative proportions of water-soluble polyethylene glycol structurants (b) and water-insoluble structurants (c) determine the rate at which the piece wears during use. The presence of water-insoluble structurant typically results in a delay in the dissolution of the piece when exposed to water during use and consequently a delay in the rate of wear.

Preferably, the total amount of component (c) is 10% to 40% by weight of the composition.

A water-insoluble material which does not melt below 100ºC may act as a further piece structuring agent. It may be specified as a requirement that the proportion (if any) of water-insoluble material which does not melt below 100ºC, is less than 20% by weight of the composition.

If a water-insoluble structuring agent (c) which does not melt below 100ºC is present, it may well be selected from plant materials or minerals. Starches, including corn starch, are preferred among the plant materials, while kaolin and calcite are preferred mineral materials. The ratio of water-soluble structuring agent (b) to the total amount of water-insoluble structuring agents may possibly be in a range of from 2:3 or 1:1 up to 3:1 or 5:1.

Some soap, i.e. salts of monocarboxylic fatty acids having chain lengths of 8 to 22 carbon atoms, may be included in the bar compositions of the invention. The amount is desirably not greater than 10 percent by weight of the composition.

We have found that when water insoluble soap is included it is beneficial to reduce the wear rate of the bars. Such water insoluble soaps are salts of saturated fatty acids having chain lengths of 16 to 22, especially 16 and 18, carbon atoms. Preferably these salts are sodium salts. They melt at temperatures above 100ºC and therefore fall within a category (e) representing material distinct from synthetic detergent which melts above 100ºC.

When water-insoluble soap is present in the composition, the amount thereof desirably does not exceed 10% by weight of the composition, for example in the range of 3% to 9.5% by weight, more preferably 5% to 9%.

It is preferred to use a combination of polyethylene glycol having a molecular weight of 50,000 to 500,000 as at least a portion of the soluble structuring agent (b) and water-insoluble soap as at least a portion of the insoluble material (c). The use of these materials in combination improves the wear rate of the pieces while also providing a good feel when handled during use.

When such a combination of materials is employed, the preferred amounts are by weight of the composition: 4 to 9.5% of the water-insoluble soap and 1.5 to 4.5% of polyethylene glycol having a molecular weight in the range of 50,000.

Materials that can be enclosed but do not melt at temperatures below 100ºC can be

synthetic non-soap detergents that do not become completely liquid at temperatures below 100ºC, e.g. acyl isethionates;

Soap, especially water-insoluble soap that does not melt below 100ºC;

other water-insoluble materials that do not melt below 100ºC.

Materials other than synthetic detergent, which are water soluble but do not melt below 100ºC, are preferably not present or are present only in amounts that are small, such as not more than 10%, more preferably not more than 5% by weight of the composition.

It is desirable that the total amount of material in the second and third of these categories (i.e., materials other than synthetic non-soap detergent) be no more than 20% by weight of the composition. The total amount of material that does not melt below 100°C should not exceed 50% by weight of the composition, preferably less, such as no more than 40% or no more than 30% or even 20%, and should not be so high that the molten composition cannot be stirred.

Bar compositions of this invention usually contain water, but the amount of water is only a fairly small proportion of the bar. Larger amounts of water reduce the hardness of the bars. It is preferred that the amount of water not exceed 15% by weight of the bars;

for example in a range of 3% or 5% to 14.9 percent by weight.

The bars of the invention may optionally include so-called adjuvants - materials included in relatively small proportions which impart some benefit to the bars in addition to the basic cleaning action. Examples of such agents are: skin conditioning agents, including emollient agents such as fatty alcohols and vegetable oils, essential oils, waxes, phospholipids, lanolin, antibacterial and anti-germicidal agents, opacifiers, pearlescent agents, electrolytes, perfumes, sunscreen, fluorescers and colorants. Preferred skin conditioning agents include silicone oils, mineral oils and/or glycerin.

In a further aspect, the present invention provides a process for preparing a synthetic detergent bar comprising the steps of:

(i) preparing a liquid mixture comprising the components (a) to (d) mentioned in claim 1

(ii) cooling the product of step (i) to a temperature at which it solidifies and

(iii) forming the product of step (ii) into pieces.

The liquid mixture may be a single or multiphase system. The single phase may be an isotropic mixture, whereas the multiphase system comprises either an emulsion or liquid crystal dispersion. The mixture may be prepared by mixing the components followed by heating the mixture to the molten state where further mixing will take place, or by heating the components followed by mixing the components.

Step (i) can be carried out in a stirred, heated vessel.

For a composition containing fatty acid or a mixture of soap and fatty acid and also containing polyalkylene oxide, a useful process begins with melting the fatty acid in a heated vessel with a stirrer. The stirrer is started and the polyalkylene oxide is At this stage, the soap is produced in situ by partial neutralization of the fatty acid.

Now the non-soap detergent is added. The end result is a macroscopically homogeneous melted mixture, with no more than 50% solids present.

Preferably, step (ii) is carried out with a cooled doctor roll, which may be part of a cooled mill.

Minor ingredients and auxiliaries may be added at this stage between steps (ii) and (iii).

In an alternative embodiment of the invention, the liquid mixture of step (i) is poured into moulds. The pouring step can be used to produce a block which is further processed into pieces or to directly form pieces. If the product is poured into pieces, process steps (ii) and (iii) are combined; the moulds used can form the final packaging of the pieces, or the pieces can be removed from the moulds and repackaged.

In order to further understand the present invention, it will be described with reference to the following illustrative examples.

In the examples, "Aerosol OT", "Pluronic F87" and "Dove" are trademarks.

EXAMPLE 1

The components listed in Table 1 below are melted together at 80°C to produce a material consisting predominantly of a liquid phase. All amounts are in weight percent. After cooling to room temperature, solid, generally cubic, pieces were formed from compositions (A) and (B) using a one-piece press. Similar compositions were also formed into pieces using a hot melt casting process. TABLE 1

* SLES 3E0 means sodium lauryl ether sulfate with an average of 3 ethylene oxide residues.

** PEG 4000 means polyethylene glycol medium molecular weight 4000.

Both the melt-cast and pressed pieces had acceptable properties for "syndet" pieces.

EXAMPLE 2

The materials listed in Table 2 below, where all amounts are given as weight percent, were melted together at 60°C to produce a pumpable, stirrable liquid. The liquid melt was poured into piece-formed molds and allowed to cool to solid pieces, that is, the pieces were cast from the melt. Acceptable pieces were obtained. TABLE 2

* Aerosol OT is dioctyl sulfosuccinate

EXAMPLE 3

The materials listed in Table 3 below were melted together at 80ºC to produce a pumpable, stirrable liquid. All amounts are in Ge The liquid melt was cast into pieces as in Example 2.

A portion of each melt was processed into bars by a different route. The melt was cooled by passing it through a chilled three-roll mill. Small amounts of perfume, opacifier and fluorescer were added, totaling less than 2% by weight of the composition. The resulting composition was reground, passed through a vacuum extruder and formed into the desired bar shape using a hand press. TABLE 3

Acceptable pieces were obtained by both processing routes.

EXAMPLE 4

Components listed in Table 4 below were prepared in bars by the method of Example 2. All amounts are in weight percent. These bars contained a mixture of two detergent actives. TABLE 4

* Fatty alcohol with 16 and 18 carbon atom chain lengths mixed, ethoxylated with an average of 20 ethylene oxide residues.

** Directly esterified fatty acyl isethionate, which is a mixture containing approximately 70% by weight fatty acyl isethionate, 15-20% fatty acid and small amounts of other materials, from Lever Brothers, USA

*** Cocoamidopropyl betaine, from Albright and Wilson, GB.

EXAMPLE 5

Materials listed in Table 5 below were molded into pieces by the method of Example 2. All amounts are in weight percent. In these pieces, the water-soluble structurant was a mixture of polyethylene glycol and a block copolymer of polyethylene oxide and polypropylene oxide available from Pluronic F87, from BASF Germany. TABLE 5

EXAMPLE 6

The materials listed in Table 6 below were melted together at 80ºC. All amounts are given in weight percent.

PEG 4000 and stearic acid were the first materials to be heated and melted. Once these were melted, a small amount of sodium hydroxide was added to neutralize the stearic acid to sodium stearate. Then the remaining materials were added and stirred to produce a pumpable, homogeneous liquid.

Each melt was cooled by passing it over a chilled three-roll mill. 1% perfume and 0.3% titanium dioxide as an opacifier were then added, followed by milling and extruding the resulting composition and molding into the desired bar shape using a hand press. TABLE 6

EXAMPLE 7

The materials listed in Table 7 below were formed into bars by the procedure of Example 3, wherein the melt was cooled on a mill, extruded and formed into bars. All amounts are in weight percent. These bars contained a mixture of three detergent actives. TABLE 7

Compositions 7C and 7F gave compositions that were too soft to be processed, whereas the remaining compositions could be processed into hard pieces.

EXAMPLE 8

A variety of compositions from the previous examples were evaluated for mildness using a zein test, generally as described by Gotte, Proc. Int. Cong. Surface Active Subs., 4th ed., Brussels, 3, 89-90 (1964). This test determines the amount of amino acid under specific conditions that is solubilized from zein. The solubilized material is determined by a nitrogen evaluation. The results were as below.

Composition Number Solubilized Nitrogen

3A 0.08

3B 0.13

3C 0.16

4D 0.11

4G 0.1

4K 0.11

6A 0.12

6C 0.05

6D 0.05

7D 0.2

80/20 Coconut/Tallow Soap 0.73

"DOVE"R commercial "Syndet" piece, based on DEFI 0.22

The low values of zein solubilization for the inventive pieces indicate very good mildness.

Claims (8)

1. A detergent bar composition comprising: (a) 10-60% by weight of a synthetic non-soap detergent, (b) 20-50% by weight of water-soluble material comprising one or more polyethylene glycols having a molecular weight in the range of 1500 - 10000 and a melting point in the range of 40ºC to 100ºC, (c) 5-50% by weight of water-insoluble C₁₂-C₂₄ fatty acid, C₈-C₂�0 alkanols or mixtures thereof having a melting point in the range of 40°C to 100°C and (d) 3-20% by weight water. 2. A detergent bar composition according to claim 1, wherein the amount of component (a) is 10 to 50% by weight. 3. A detergent bar composition according to claim 1 or claim 2, wherein the amount of water is 5 to 14.9 weight percent. 4. A detergent bar composition according to any one of claims 1 to 3, which additionally comprises less than 20 percent by weight of the composition of a material other than the synthetic non-soap detergent which does not liquefy below 100°C. 5. A detergent bar composition according to any one of claims 1 to 4, which additionally comprises 1-4.5% by weight of the composition of a polyethylene glycol having a molecular weight of 50,000 to 500,000. 6. A detergent bar composition according to any one of claims 1 to 5, wherein component (c) is selected from the group consisting of lauric, myristic, palmitic, stearic, arachidic and behenic acid and mixtures thereof. 7. A detergent bar composition according to any one of claims 1 to 6, which additionally comprises 3% to 10% of the composition of a water-insoluble soap. 8. A process for preparing a synthetic detergent bar comprising the steps of: (i) preparing a liquid mixture comprising the components (a) to (d) mentioned in claim 1 (ii) cooling the product of step (i) to a temperature at which it solidifies and (iii) forming the product of step (ii) into pieces.