GB2126243A - Process for dispersing hydroxypropyl methyl cellulose - Google Patents

Abstract

A method of facilitating the incorporation of hydroxypropyl methyl cellulose (HPMC) into a liquid formulation containing water which comprises forming a liquid premix of hydroxypropyl methyl cellulose dispersed in an aqueous-free organic liquid medium in which it does not swell or dissolve, selected from the group consisting of liquified nonionic surfactants, fatty acids, anionic surfactants and mixtures thereof, by dispersing HPMC in said liquified organic medium with mild agitation; adding said premix to an aqueous- containing liquid formulation and dispersing therein. This method has particular utility in the preparation of liquid shampoos, liquid dishwashing detergents, liquid hand soaps and other aqueous-containing liquid formulations wherein it is desirable or necessary to include hydroxypropyl methyl cellulose as a viscosity modifier.

Description

SPECIFICATION Process for dispersing hydroxypropyl methyl cellulose The present invention relates to a process for dispersing hydroxypropyl methyl cellulose in a nonaqueous liquified organic medium in which it does not swell or dissolve, and subsequently adding said dispersion to an aqueous-containing liquid formulation wherein it is readily solubilised.

Hydroxypropyl methyl cellulose is often used as a thickening agent in aqueous-containing liquid formulations such as liquid detergents, shampoos, liquid hand soaps and the like. However, processing difficulties are encountered when dispersing and incorporating hydroxypropyl methyl cellulose into liquid formulations containing water, using conventional methods of dispersion. These known methods include dispersion in hot water at temperatures of 80-1 000C (176-21 2 F); dispersion in water miscible organic solvents such as alcohol or glycol; and dispersion by dry blending with dry powders.

The disadvantages of the aforesaid conventional methods are the use of large amounts of energy in the form of heat and long mixing cycles; and the presence of flammable solvents such as alcohol which creates the danger of inflammability.

Still another difficulty encountered with the aforesaid dispersion methods is the formation of lumps of undissolved hydroxypropyl methyl cellulose in the aqueous medium, which do not dissolve even after protracted periods of agitation (about 2-3 hours). This lumping problem requires an additional filtration step to rid the liquid formulation of the said undissolved material. In addition, it is necessary to heat the water to high temperatures of about 75-1000C to effect dispersion of the hydroxypropyl methyl cellulose therein. This is shown in U.S.Patent No. 3,953,591 wherein is disclosed a method of preparing a skin conditioning emulsion by separately heating the oil phase and the water phase containing the hydroxypropyl methyl cellulose, each to a temperature of 75--1000C, and slowly adding the heated oil phase to the water phase with stirring (column 4, lines 21-34).

U.S. Patent No. 3,549,542 also discloses the necessity of using hot water heated to a temperature of 1 80-2000F (82 to 93by) for dispersing the hydroxypropyl methyl cellulose in water prior to the addition of an aqueous solution of a cationic polymer to form a premix, which is subsequently dispersed in an aqueous solution of an anionic detergent, followed by milling in a colloid mill, to form a homogeneous liquid detergent composition.

U.S. Patent No. 3,998,761 also discloses the necessity of using water heated to a temperature of about 1 85-1 900F (85 to 880 C) to slowly disperse hydroxypropyl methyl cellulose powder under rapid lightning agitation and the addition, with agitation of a formaldehyde solution in the formation of a lump free mucilage. This mucilage is prepared a day prior to its addition to a shampoo formulation.

U.S. Patent No. 4, 1 74,305, discloses the preparation of a granular detergent composition by combining all the components except the cellulose ether (Methocel HB 1 5000) in an aqueous crutcher slurry, spray drying to granule form and adding the cellulose ether to the granules as a dry admix. The liquid compositions are prepared by mixing the components in a liquid carrier of water or water and alcohol.

However, there is no disclosure of the preparation of a premix of hydroxypropyl methyl cellulose dispersed in an aqueous-free liquified organic medium in which it does not swell or dissolve, the organic medium consisting of liquified nonionic surfactants, fatty acids, anionic surfactants or mixtures thereof, prior to its incorporation into an aqueous-containing liquid formulation, using a short mixing cycle.

The present invention aims to provide an improved method for dispersing hydroxypropyl methyl cellulose in an aqueous-containing liquid formulation.

It also aims to provide an improved method for overcoming processing difficulties when dispersing and incorporating hydroxypropyl methyl cellulose into liquid formulations containing water.

The invention also aims to provide an improved method of dispersing hydroxypropyl methyl cellulose into liquid formulations containing water, by first dispersing with mild agitation, in an aqueousfree organic medium in which it does not swell or dissolve, prior to its addition to said aqueouscontaining liquid.

The invention also aims to provide a method of preparing a premix of a dispersion of hydroxypropyl methyl cellulose in an aqueous-free liquified organic medium selected from the group consisting of nonionic surfactants, fatty acids, anionic surfactants and mixtures thereof.

The invention also aims to provide a method of readily dispersing hydroxypropyl methyl cellulose in an aqueous-containing liquid formulation utilising a short mixing cycle.

According to the present invention a method of incorporating hydroxypropyl methyl cellulose into water or liquid formulations containing water comprises dispersing, preferably by means of a short mixing cycle, hydroxypropyl methyl cellulose in an aqueous-free organic liquid medium in which it does not swell or dissolve, the said organic medium consisting of liquified nonionic surfactants, fatty acids, anionic surfactants and mixtures thereof, to form a liquid premix. This dispersion can be maintained at a temperature sufficiently high to retain its fluidity for incorporation into a water-containing liquid formulation; or said premix dispersion can be allowed to solidify upon cooling to room temperature; and be remelted when needed.The hydroxypropyl methyl cellulose may be dispersed into the said nonaqueous or water free liquid organic medium at a ratio of 1 part hydroxypropyl methyl cellulose to about 1 to 10 parts of organic medium, and preferably the formula amount of the said organic dispersant ingredients.

More specifically, the present invention relates to an improved method of dispersing hydroxypropyl methyl cellulose into liquid formulations containing water, which comprises: 1. liquifying, if said organic medium is not liquid at room temperature, and blending (if necessary) an aqueous-free organic medium in which hydroxypropyl methyl cellulose does not swell or dissolve, the said organic medium consisting of nonionic surfactants, fatty acids, anionic surfactants and mixtures thereof, by heating to a temperature of about 75-1 200F (24 to 490C); 2. adding hydroxypropyl methyl cellulose to the said organic liquified medium and dispersing it therein with mild agitation to form a premix dispersion;; 3. adding the said premix dispersion to water or a water containing formulation, and dispersing the premix therein, e.g. by means of a short mixing cycle of about 5-10 minutes, to form a homogeneous liquid. The premix dispersion of hydroxypropyl methyl cellulose (HPMC) and nonaqueous organic medium, when made in the ratio required for processing, such as in the preparation of a shampoo, can be readily added to the formula amount of water, wherein it is readily solubilised. For example, a premix of Methocel (HPMC) dispersed in a blended liquid mixture of lauric diethanolamide, lauric acid and polyoxyethylene lauryl ether phosphate liquified at 1 00F (430C), can readily be pumped into the formula amount of water in the formation of a homogeneous liquid, free of lumps.This premix which is a paste at 770F (250C), can similarly be added to the formula amount of water to form a homogeneous liquid, free of lumps. Thus, it is apparent that the said premix dispersion is equally effective in the form of a liquid or a paste.

Hydroxypropyl methyl cellulose is a cellulosic polymer in the form of a white or off-white granular product, typically commercially available from the Dow Chemical Co. as Methocel, in the form of a fine powder. This polymer dissolves in water and in certain organic solvents by swelling and successive hydration of the structurai layers of each particle. Accordingly, in order to make gel-free solutions of Methocel, it is necessary to first disperse the particles in the water or organic solvent with continuous agitation so that each particle is wetted, after which time it hydrates and builds viscosity.

It has been unexpectedly found that the premix of hydroxypropyl methyl cellulose dispersed in a nonaqueous organic medium in which it does not swell or dissolve, can be readily mixed with water or a liquid formulation containing water, to form a homogeneous liquid free of particles or lumps, using a short mixing cycle of about 5-10 minutes, as opposed to a 2 or 3 hour mixing period heretofore utilised. In a comparative test using a Methocel/urea blend, the two powders were blended for 2 2 hours on rollers prior to the addition of the said blend to a mixer containing an aqueous shampoo formulation, and agitated for 2 hours. The resultant liquid shampoo still had lumps.

It has additionally been unexpectedly found that the hydroxypropyl methyl cellulose premix of the present invention, which may solidify at room temperature, has the capability of being reliquified at temperatures of about 85-1 050F (29 to 41 OC), and is equally effective in the preparation of a homogeneous, lump-free liquid formulation containing water, after only a short mixing cycle. Freshly made hydroxypropyl methyl cellulose premix and 24 hours old remelted premix give identical final products.

It has additionally been found that the addition of perfume, an ingredient often found in aqueous liquid formulations such as shampoos, to the premix dispersion of nonaqueous organic liquid medium and hydroxypropyl methyl cellulose, retains the liquidity of the said premix at room temperature. This is advantageous in that heat is not required to reliquify such a premix which would otherwise solidify at room temperature into a pasty material. Although the liquid or paste form of the said premix can be incorporated into the aqueous-containing liquid formulation, it is preferable to utilize the liquid form because of the pumping equipment generally used in the preparation of liquid formulations. The perfume ingredient, which is solubie in organic liquids, is readily blended with the nonaqueous organic medium of the premix.The hydroxypropyl methyl cellulose does settle on standing, but agitation disperses it readily. The dual advantage of including the perfume in the premix is the elimination of the use of heat to liquify the pasty unperfumed premix, and the necessity of maintaining the said mix at an elevated temperature in order to pump it into the aqueous-containing liquid formulation.

The nonionic surfactants suitable for use as a dispersing agent for the hydroxypropyl methyl cellulose are preferably liquid, or capable of being liquified at low temperatures of about 75-1 200F (240 to 490C). The nonionic synthetic organic detergents are generally the condensation product of an organic aliphatic or alkyl aromatic hydrophobic compound and hydrophilic ethylene oxide groups.

Practically any hydrophobic compound having a carboxy, hydroxy, amido, or amino group with a free hydrogen attached to the nitrogen can be condensed with ethylene oxide or with the polyhydration product thereof, polyethylene glycol, to form a nonionic detergent. A preferred nonionic surfactant for use in the present invention is ethylene glycol distearate.

Suitable nonionic detergents include the polyethylene oxide condensate of one mole of alkyl phenol containing from about 6 to 12 carbon atoms in a straight -- or branched -- chain configuration with about 5 to 30 moles of ethylene oxide, for example, nonyl phenol condensed with 9 moles of ethylene oxide, dodecyl phenol condensed with 1 5 moles of ethylene and dinonyl phenol condensed with 1 5 moles of ethylene oxide. Condensation products of the corresponding alkyl thiophenols with 5 to 30 moles of ethylene oxide are also suitable.

Also included in the nonionic detergent class are the condensation products of a high alcohol (e.g.

an alkanol containing about 8 to 1 8 carbon atoms in a straight or branched -- chain configuration) condensed with about 5 to 30 moles of ethylene oxide, for example, lauryl-myristyl alcohol condensed with about 1 6 moles of ethylene oxide.

One group of nonionics is marketed under the trade name "Pluronic" (Registered Trade Mark).

The compounds are formed by condensing ethylene oxide with a hydrophobic base formed by the condensation of propylene oxide with propylene glycol.

Other suitable nonionic surfactants include polyethoxylated hexitan fatty acid esters such as polyoxyethylene (20 or 80) sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan or mannitan palmitate or oleate, with the number of ethoxy groups varying from 1 5 to 80.

A preferred group of nonionic surfactants particularly useful herein are the mono- and diethanolamides of higher fatty acids having 10 to 1 8 carbon atoms, such as cocomonoethanolamide, cocodiethanolamides, lauric myristic diethanolamide, lauric monoethanolamide and lauric diethanolamide. Polyacrylamides may also be utilised.

The aliphatic amine oxides of the general formula R1R2R3N-O are nonionic at a pH of 6.5 to 7.5 and may also be used herein. R1 may represent an alkyl, alkenyl, or monohydroxyalkyl radical having about 10 to 1 6 carbon atoms, R2 and R3 may each represent a methyl, ethyl, propyl, ethanol, or prnpano radical. Examples of suitable amine oxides include dimethyl lauryl amine oxide, dimethyl cetyl amine oxide and dimethylmyristyl amine oxide.

Another group of suitable organic dispersants for the hydroxypropyl methyl cellulose are the higher fatty acids containing 10 to 31 carbon atoms in their chain, preferably which can be liquified at low temperatures of about 75 to 1 200F (24 to 49"C). Examples of suitable fatty acids include lauric acid, palmitic acid, stearic acid, oleic acid, lanolin fatty acids, capric acids, and undecylic acid.

Still another group of suitable organic dispersants for hydroxypropyl methyl cellulose are the anionic surfactants which are liquid at room temperature or can be liquified at low heat, temperatures of about 75 to 1 200F (24 to 490C). Examples of suitable anionic surfactants are the water soluble salts, e.g. sodium, potassium, ammonium, alkylolammonium and triethanolammonium salts of higher alkyl benzene sulphonates and phosphonates, higher alkyl toluene sulphonates and phosphonates, higher alkyl phenol sulphonates and phosphonates and higher naphthalene sulphonates and phosphonates; paraffin sulphonates and phosphonates containing about 10 to 20 carbon atoms; sodium and potassium sulphates and phosphates of higher alcohols containing 8 to 1 8 carbon atoms such as sodium lauryl sulphate or phosphate and sodium tallow alcohol sulphate or phosphate, sodium and potassium salts of a-sulphofatty or phosphofatty acid esters containing about 10 to 20 carbon atoms in the acyl group, for example, methyl a-sulpho- or phospho-myristate and methyl a-sulphotallowate, ammonium sulphates and phosphates of mono- or diglycerides of higher (C,0C,8) fatty acids, for example, stearic monoglyceride monosulphate or phosphate; sodium higher alkyl (C1OC,8) glyceryl ether sulphates and phosphonates; and sodium or potassium alkyl phenol polyethenoxy ether sulphates and phosphates with about 1 to 6 oxyethylene groups per molecule and in which the alkyl radicals contain about 8 to 12 carbon atoms.

Other suitable anionic surface active agents include the C8 to C,8 acyl sarcosinates (for example sodium lauroyl sarcosinate); sodium and potassium salts of the reaction product of higher fatty acids containing 8 to 18 carbon atoms in the molecule esterified with isethionic acid; and sodium and potassium salts of the C8 to C,8 acyl N-methyl taurides, for example sodium cocoyl methyl taurate and potassium stearoyl methyl taurate.

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.

EXAMPLE 1 Pre-Mix Blend Yo Lauric diethyanolamide 3.0 Lauric Acid 1.0 MUP-1 031 0.5 Methocel E4M2 1.0 ' Polyoxyethylene lauryl ether phosphate.

2 Hydroxypropyl methyl cellulose powder having a methoxyl content of 2830%, a hydroxypropyl content of 7-12% and a viscosity at 200C (2% soln.), of 3,500 cps-5,600 cps supplied by Dow Chemical Company.

The first three ingredients were mixed together and heated to 1 200F (490 C) to ensure liquifaction of the lauric acid flakes, and formed a melted liquid mixture thereof. Then Methocel was added to these liquid ingredients with mixing. The resulting premix was a thin liquid at 1 200F (490C), and on cooling it remained a thin fluid at 1 1 OOF (43 OC) and at 1 000 F (380) and whilst it was thickening at 900F (320C) it was still pourable, as it was at 800F (270C) and 70"F (21 OC) but at 650F (1 80C) it has become pasty.

The premix at a temperature of 870F (31 OC) was added to the aqueous mixture of the remaining ingredients of a typical shampoo formulation, using mild agitation. Small clumps or lumps seemed to form but within 5 minutes of good agitation, the shampoo formulation was a homogeneous liquid with no particles or lumps.

EXAMPLE 2 The premix of Example 1 was allowed to cool over night to room temperature, and it solidified into a paste. The solidified premix was completely liquified by heating to 1 050F (41 OC). The remelted premix at 900F (320C) was added to the aqueous mixture of the other shampoo ingredients, and mixed for 10 minutes with strong agitation.

The resulting shampoo formulation was a homogeneous liquid having no undissolved particles.

Both Examples 1 and 2 processed identically. There was no difference in using a freshly made or a remelted premix dispersion of hydroxypropyl methyl cellulose in an aqueous-free organic medium.

EXAMPLE 3 The premix of Example 1 was allowed to cool to 77"F (250C) and formed a paste. This paste was added to the formula amount of water in a shampoo formulation. No lumping occurred. The aqueous mixture remained fluid. Although the paste form of the premix was not pumpable, it can be used where processing does not depend upon pumps as a means of addition to the liquid formulations.

EXAMPLES 4 and 5 Premix (in formula amount) 4 5 Ingredient % % % Lauric diethanolamide 3.000 5.000 Lauric Acid 1.000 1.000 MEP-103' 0.500 0.500 Methocel E4M2 1.010 0.825 Perfume 0.800 0.800 Viscosity at 770F (250C) 1170 cps 900 cps The first three ingredients were heated until liquid, approximately 1 200F (490 C). The Methocel was added to the liquid medium, and mixed thoroughly. The perfume was then added to the above dispersion and also mixed thoroughly. The perfume or fragrance may be added to the liquid medium, wherein it dissolves, prior to the addition of the Methocel. Both premixes remained liquid after cooling to room temperature. The Methocel did settle on standing but mild agitation dispersed it readily.

These examples show that the premix containing perfume retains its liquid state at room temperature, as compared to a pasty consistency without the perfume. Although the presence of perfume in the premix is not essential, it is a preferred optional ingredient. The advantage of the perfumed premix is the elimination of the necessity of heating the premix in order to liquify the pasty unperfumed premix and to maintain it at an elevated temperature in order to pump it.

EXAMPLE 6 3 g Neodol (Registered Trade Mark) 25-7 (ethoxylated C1215 alcohol containing 7 moles ethylene oxide per mole) which is a nonionic liquid at room temperature, was mixed with 0.5 g HPMC to form a nonaqueous liquid dispersion at room temperature.

This liquid premix was added to a warm (1 200F) (490C) aqueous solution containing 60 9 triethanolamine lauryl sulphate and 40 g water, and mixed weli for about 5 minutes. The HPMC readily dissolved in the said aqueous solution and formed a homogeneous liquid free of lumps, which may be used in the laundering of fabrics.

EXAMPLE 7 3 g ethylene glycol distearate was heated to 1 200F (490C) to liquify it. 0.5 g HPMC was added to HPMC was added to, and mixed with the liquid stearic acid to form a warm nonaqueous liquid dispersion of HPMC.

This warm premix was added to an aqueous solution of 40 g water and 60 g triethanolamine sulphate and 40 g water, and mixed well for 5 minutes. The HPMC dissolved readily in the said aqueous solution and formed a lump-free homogeneous liquid detergent formulation.

EXAMPLE 8 3 g ethylene glycol distearate was heated to 1 200F (490C) to liquidy it. 0.5 g HPMC was added to the said nonaqueous liquid medium with mixing. The HPMC readily dispersed therein, to form a warm premix.

This warm premix was added to an aqueous solution of 40 g water and 60 g triethyanolamine lauryl sulphate and mixed for 5 minutes. The HPMC readily dissolves in the said aqueous medium and formed a lump-free homogeneous liquid detergent.

Other nonaqueous organic dispersing mediums may be substituted for the specific dispersants recited in the examples, provided the hydroxypropyl methyl cellulose does not swell or dissolve therein.

This novel method may be used to incorporate hydroxypropyl methyl cellulose in aqueouscontaining liquid formulations, such as shampoos, liquid soaps, liquid detergents including dishwashing liquids, fabric laundering liquids and the like. The resulting products are stable, homogeneous liquids, free of lumps of hydroxypropyl methyl cellulose.

The present method is more economical, uses less energy (heat), eliminates the filtration step and avoids the use of flammable solvents such as alcohol, heretofore used. The use of perfumed and unperfumed premix has overcome processing difficulties and facilitated the incorporation of hydroxypropyl methyl cellulose into aqueous-containing liquid formulations.

Claims (21)

1. A method for incorporating hydroxypropyl methyl cellulose into water or liquid formulations containing water, which comprises forming a premix of hydroxypropyl methyl cellulose dispersed in a water-free organic medium dispersant in which it does not swell or dissolve, the said organic medium consisting of nonionic surfactant, a higher fatty acid, or an anionic surfactant or a mixture thereof, by dispersing, preferably with mild agitation, hydroxypropyl methyl cellulose in the said organic medium when in a liquid state; and dispersing the said premix in water or an aqueous or water containing liquid formulation.

2. A method as claimed in Claim 1, in which the said organic medium dispersant is liquified by heating to a temperature of about 75-1 200F (24 to 490C).

3. A method as claimed in Claim 1 or Claim 2 in which the ratio of hydroxypropyl methyl cellulose to the said organic dispersant in the premix is one part hydroxypropyl methyl cellulose to about 1 to 10 parts water-free organic dispersant.

4. A method as claimed in any one of Claims 1 to 3 in which the said premix dispersion is in the form of a warm liquid which is readily dispersed in water or a water-containing liquid formulation, to form a homogeneous liquid free of particles or lumps.

5. A method as claimed in any one of Claims 1 to 3 in which the said premix is allowed to cool to room temperature and solidify into a paste which is readily incorporated into water or an aqueouscontaining liquid formulation to form a lump-free homogeneous liquid.

6. A method as claimed in Claim 5 in which the said solidified premix is aged and then reliquified by heating to a temperature of about 850 to 1 050F (290 to 41 OC), prior to addition to water or a water containing liquid formulation.

7. A method as claimed in any one of Claims 1 to 6 in which the dispersion is carried out by a short mixing cycle.

8. A method as claimed in Claim 7, in which the mixing cycle is as short as about 5 to 10 minutes.

9. A method as claimed in one of Claims 1 to 8 in which a perfume is added to the said premix to form a perfumed premix which retains its liquid state upon cooling to room temperature.

10. A method as claimed in any one of Claims 1 to 9 in which the water-containing liquid formulation is a shampoo, and the premix constitutes the said formula amount of hydroxypropyl methyl cellulose and water-free organic dispersant ingredients.

11. A method as claimed in any one of Claims 1 to 10 in which the nonaqueous organic dispersant for the hydroxypropyl methyl cellulose is a blend of lauric diethanolamide, lauric acid, and polyoxyethylene lauryl ether phosphate.

12. A method as claimed in Claim 1 substantially as specifically described herein with reference to any one of the Examples.

1 3. A composition of matter comprising a blend dispersible in water or an aqueous formulation the blend comprising a lump-free dispersion of hydroxypropyl methyl cellulose in a water free organic medium dispersant in which it does not swell or dissolve.

14. A composition as claimed in Claim 1 3 in which the organic medium is a nonionic surfactant, a higher fatty acid or an anionic surfactant or a mixture thereof.

1 5. A composition as claimed in Claim 13 or Claim 14 in which the organic medium is one which is liquid in the range 75 to 1 200F (24 to 490C).

16. A composition as claimed in Claims 13, 14 or 1 5 in which the organic medium is a blend of lauric diethanolamide, lauric acid and polyoxyethylene lauryl ether phosphate.

17. A composition as claimed in any one of Claims 13 to 1 6 in which the ratio of HPMC to organic medium is in the range 1:1 to 1:10.

18. A composition as claimed in any one of Claims 13 to 17 which contains perfume and is liquid at room temperature.

1 9. A composition as claimed in Claim 18 containing in the range 4.5 to 6.5 parts organic medium, 1 to 0.8 parts HPMC and 0.8 parts perfume.

20. A composition as claimed in any one of Claims 1 3 to 1 9 in which the aqueous formulation in which the composition is dispersible, is a shampoo, a liquid soap, a liquid detergent, or a dishwashing or a fabric laundry liquid formulation.

21. A composition as claimed in Claim 13 substantially as specifically described herein with reference to the Examples.