EP0870008B2 - Process for producing granular detergent components or compositions - Google Patents

Description

• The present invention relates to a process for the continuous preparation of a granular detergent composition or component having a high bulk density and good flow properties. In such compositions and components it is known to use crystalline Zeolite A which is a water-insoluble, crystalline material well-known in the detergent art as a builder which is particularly suited to removing cations such as calcium and magnesium from hard water.
• Crystalline Zeolite A is a very finely divided powder. It has been common practice to process the finely divided powder into the form of larger granules (typically 400 to 1000 micrometers) before incorporation into finished products, especially finished detergent compositions. Various granulation processes are known including spray drying and agglomeration. Conventional agglomeration processes in which Zeolite A is used as one of the components have long been known in the prior art :
• GB2005715, published on 25th April 1979 describes an agglomeration process based upon Zeolite A. The Zeolite A is agglomerated along with carbonate/bicarbonate to make nonionic surfactant agglomerates.
• US-A-5 468 516 describes a process for producing nonionic detergent granules which have a high bulk density, excellent powder fluidity and non-caking property, wherein (inter alia) 20 to 95 parts by weight of a builder, 1 to 20 parts by weight of a porous oil absorbent carrier and from 10 to 60 parts by weight of a nonionic surfactant are processed.
• WO93/25378, published on 23rd December 1993, discloses a process for making granular detergents comprising Zeolite A. The Zeolite A is agglomerated with a high active, neutralised surfactant paste in a high speed mixer and a moderate speed mixer/agglomerator to make anionic surfactant agglomerates.
• One of the factors which limits the surfactant activity of the prior art mentioned above is the capacity of Zeolite A to absorb liquid organic materials. It has been suggested that replacing Zeolite A by Zeolite P (specifically Zeolite MAP) could address this problem :
• EP521635, published on 7th January 1993, discloses granular detergents made using from 10% to 100% of Zeolite MAP. Zeolite MAP has a different chemical composition to Zeolite A. In Example 1 of this patent application it is reported that the oil absorbing capacity of Zeolite MAP is 41.6 ml/100g, and that this is higher than measured samples of Zeolite A for which it is 26 to 35.5 ml/100g.
  However modifying the chemical structure of conventional crystalline Zeolite A (i.e. modifying the stoichiometric ratios of Si, Al, Na, O, H) is not always desirable because other properties and characteristics cf the Zeolite are necessarily affected.
• The object of the invention is to provide a granulation process for making granular detergents which incorporates highly absorbent crystalline Zeolite into granular agglomerates, without losing any of the builder capabilities, especially calcium exchange capacity and calcium exchange rate.
• According to the invention this object is achieved by using a modified crystalline Zeolite A having higher oil absorption capacities in a process as specified in claim 1. The Zeolite A has modified physical characteristics (i.e. crystallinity, surface area characteristics, moisture level etc.) rather than a modified chemical structure in order to achieve an oil absorbing capacity of at least 40 ml/100g. In this way the excellent builder properties of Zeolite A may still be utilised.
• It is a further object of the present invention to provide a granulation process for making granular detergents having improved processability, and amount of oversize particles (or "lumps") being formed in the process being reduced.
Summary of the Invention
• The objects of the invention are achieved by a process for the preparation of a granular detergent composition or component having a bulk density greater than 650 g/l, from 20% to 70% by weight of crystalline zeolite A having an oil absorbing capacity of at least 40ml/100g, at least 30% by weight of anionic surfactant, the ratio of the crystalline zeolite A to the anionic surfactant being less than 1:1, which comprises the step of dispersing a liquid binder, which is a paste comprising at least 10% by weight of a neutralised anionic surfactant and having a viscosity of at least 10000mPas, throughout a powder stream in a high speed mixer to form granular agglomerates, wherein the powder stream comprises crystalline zeolite A having an oil absorbing capacity of at least 40 ml/100g, preferably at least 45 ml/100g and most preferably at least 50 ml/100g.
• In a preferred embodiment of the invention the granular agglomerates are formed by mixing in the high speed mixer for a residence time of from 2 seconds to 30 seconds, followed by the step of
  further mixing in a moderate speed mixer/agglomerator for a residence time through the moderate speed mixer of less than 5 minutes, preferably less than 2 minutes, in which, optionally, a finely divided powder may be added.
Detailed Description of the Invention
• Granulation in the context of the present invention is defined as a process of making a granulated product which is an agglomerate of particles that itself behaves as a particle (according to S.A. Kuti, "Agglomeration - The Practical Alternative", published in Journal American Oil Chemists' Society, Volume 55, January 1978). The granular agglomerate is defined herein as the product of such a granulation process. Kuti goes on to state that "the agglomerate is usually formed by blending solids with liquids that serve as adhesive agents. But a lump-free liquid-solids blend is often a difficult task to produce."
• In the present invention the "solids" referred to by Kuti will comprise crystalline Zeolite A having certain physical characteristics to be defined in more detail below. It has now been found that this choice of "solids" contributes greatly to fulfilling the task of producing a lump-free liquid-solids blend.
• The essential component of the granular agglomerate of the present invention is crystalline Zeolite A of the formula
  
          (Na2O) . (Al2O3) . x (SiO2) . wH2O
  
  wherein x is from 1 to 2, and w is from 0 to 6.
• Hydrated, or partially hydrated sodium Zeolite A with a particle size of up to 10 microns is preferred.
• In an especially preferred embodiment, x=2, the Zeolite A material has the formula
  
          Na₁₂ [(AlO₂)₁₂ (SiO2)₁₂] · (6w') H₂O
  
  wherein (6w') is from about 20 to about 30, especially about 27, and has a particle size generally less than about 5 microns.
• The Zeolite A materials herein may contain up to about 28% water. Preferred builder materials are in hydrated form and contain from about 5% to about 28% of water by weight. Highly preferred crystalline aluminosilicate ion exchange materials contain from about 10% to about 22% water in their crystal matrix. The crystalline Zeolite A materials are further characterized by a particle size diameter of from about 0.1 micron to about 10 microns. Preferred ion exchange materials have a particle size diameter of from about 0.2 micron to about 4 microns. The term "particle size diameter" herein represents the average particle size diameter by weight of a given ion exchange material as determined by conventional analytical techniques such as, for example, microscopic determination utilizing a scanning electron microscope. The crystalline Zeolite A materials herein are usually further characterized by their calcium ion exchange capacity, which is at least about 200 mg equivalent of CaCO₃ water hardness/g of aluminosilicate, calculated on an anhydrous basis, and which generally is in the range of from about 300 mg eq./g to about 352 mg eq./g. The Zeolite A materials herein are still further
  characterized by their calcium ion exchange rate which is at least about 2 grains Ca⁺⁺/gallon/minute/gram/gallon (0.13g Ca⁺⁺/litre/minute/gram/litre) of aluminosilicate (anhydrous basis), and generally lies within the range of from about 2 grains/gallon/minute/gram/gallon(0.13g Ca⁺⁺/litre/minute/gram/litre) to about 6 grains/gallon/minute/gram/gallon (0.39g Ca⁺⁺/litre/minute/gram/litre), based on calcium ion hardness. Optimum aluminosilicate for builder purposes exhibit a calcium ion exchange rate of at least about 4 grains/gallon/minute/gram/gallon (0.26g Ca⁺⁺/litre/minute/gram/litre).
• Zeolite A materials useful in the practice of this invention are commercially available. The aluminosilicates useful in this invention are crystalline in structure and can be naturally occurring aluminosilicates or synthetically derived. A method for producing aluminosilicate ion exchange materials is discussed in U.S. Pat. No. 3,985,669, Krummel et al., issued Oct. 12, 1976, incorporated herein by reference.
• It is an essential feature of the present invention that the Zeolite A used in the formation of the granular agglomerates has an oil absorption capacity of at least 40 ml/100g, preferably at least 45 ml/100g and most preferably at least 50 ml/100g. The method for determining the oil absorption capacity is defined below under the heading "Test Methods".
• Optionally other forms of zeolite may be present in combination with the zeolite A, such as zeolite P, zeolite X, and zeolite HS.
• The granular agglomerates of the present invention also comprise other detergent ingredients.
• Water-soluble salts of the higher fatty acids, i.e., "soaps", are useful anionic surfactants in the compositions herein. This includes alkali metal soaps such as the sodium, potassium, ammonium, and alkylammonium salts of higher fatty acids containing from about 8 to about 24 carbon atoms, and preferably from about 12 to about 18 carbon atoms. Soaps can be made by direct saponification of fats and oils or by the neutralization of free fatty acids. Particularly useful are the sodium and potassium salts of the mixtures of fatty acids derived from coconut oil and tallow, i.e., sodium or potassium tallow and coconut soap.
• Useful anionic surfactants also include the water-soluble salts, preferably the alkali metal, ammonium and alkylolammonium salts, of organic sulfuric reaction products having in their molecular structure an alkyl group containing from about 10 to about 20 carbon atoms and a sulfonic acid or sulfuric acid ester group. (Included in the term "alkyl" is the alkyl portion of acyl groups.) Examples of this group of synthetic surfactants are the sodium and potassium alkyl sulfates, especially those obtained by sulfating the higher alcohols (C₈-C₁₈ carbon atoms) such as those produced by reducing the glycerides of tallow or coconut oil; and the sodium and potassium alkyl benzene sulfonates in which the alkyl group contains from about 9 to about 15 carbon atoms, in straight or branched chain configuration, e.g., those of the type described in U.S. Pat. Nos. 2,220,099 and 2,477,383; and methyl ester sulphonates. Especially valuable are linear straight chain alkyl benzene sulfonates in which the average number of carbon atoms in the alkyl group is from about 11 to 13, abbreviated as C₁₁-C₁₃ LAS.
• Other anionic surfactants herein are the sodium alkyl glyceryl ether sulfonates, especially those ethers of higher alcohols derived from tallow and coconut oil; sodium coconut oil fatty acid monoglyceride sulfonates and sulfates; sodium or potassium salts of alkyl phenol ethylene oxide ether sulfates containing from about 1 to about 10 units of ethylene oxide per molecule and wherein the alkyl groups contain from about 8 to about 12 carbon atoms; and sodium or potassium salts of alkyl ethylene oxide ether sulfates containing from about 1 to about 10 units of ethylene oxide per molecule and wherein the alkyl group contains from about 10 to about 20 carbon atoms.
• Other useful anionic surfactants herein include the water-soluble salts of esters of alpha-sulfonated fatty acids containing from about 6 to 20 carbon atoms in the fatty acid group and from about 1 to 10 carbon atoms in the ester group; water-soluble salts of 2-acyloxy-alkane-1-sulfonic acids containing from about 2 to 9 carbon atoms in the acyl group and from about 9 to about 23 carbon atoms in the alkane moiety; alkyl ether sulfates containing from about 10 to 20 carbon atoms in the alkyl group and from about 1 to 30 moles of ethylene oxide; watersoluble salts of olefin sulfonates containing from about 12 to 24 carbon atoms; and beta-alkyloxy alkane sulfonates containing from about 1 to 3 carbon atoms in the alkyl group and from about 8 to about 20 carbon atoms in the alkane moiety. Although the acid salts are typically discussed and used, the acid neutralization cam be performed as part of the fine dispersion mixing step.
• Water-soluble nonionic surfactants are also useful as surfactants in the compositions of the invention. Indeed, preferred processes use anionic/nonionic blends. Such nonionic materials include compounds produced by the condensation of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound, which may be aliphatic or alkyl aromatic in nature. The length of the polyoxyalkylene group which is condensed with any particular hydrophobic group can be readily adjusted to yield a water-soluble compound having the desired degree of balance between hydrophilic and hydrophobic elements.
• Suitable nonionic surfactants include the polyethylene oxide condensates of alkyl phenols, e.g., the condensation products of alkyl phenols having an alkyl group containing from about 6 to 16 carbon atoms, in either a straight chain or branched chain configuration, with from about 4 to 25 moles of ethylene oxide per mole of alkyl phenol.
• Preferred nonionics are the water-soluble condensation products of aliphatic alcohols containing from 8 to 22 carbon atoms, in either straight chain or branched configuration, with from 1 to 25 moles of ethylene oxide per mole of alcohol, especially 2 to 7 moles of ethylene oxide per mole of alcohol. Particularly preferred are the condensation products of alcohols having an alkyl group containing from about 9 to 15 carbon atoms; and condensation products of propylene glycol with ethylene oxide.
• Other preferred nonionics are polyhydroxy fatty acid amides which may be prepared by reacting a fatty acid ester and an N-alkyl polyhydroxy amine. The preferred amine for use in the present invention is N-(R1)-CH2(CH2OH)4-CH2-OH and the preferred ester is a C12-C20 fatty acid methyl ester. Most preferred is the reaction product of N-methyl glucamine (which may be derived from glucose) with C12-C20 fatty acid methyl ester.
• Methods of manufacturing polyhydroxy fatty acid amides have been described in WO 9206073, published on 16th April, 1992. This application describes the preparation of polyhydroxy fatty acid amides in the presence of solvents. In a highly preferred embodiment of the invention N-methyl glucamine is reacted with a C12-C20 methyl ester. It also says that the formulator of granular detergent compositions may find it convenient to run the amidation reaction in the presence of solvents which comprise alkoxylated, especially ethoxylated (EO 3-8) C12-C14 alcohols (page 15, lines 22-27). This directly yields nonionic surfactant systems which are suitable for use in the present invention, such as those comprising N-methyl glucamide and C12-C14 alcohols with an average of 3 ethoxylate groups per molecule.
• Semi-polar nonionic surfactants include water-soluble amine oxides containing one alkyl moiety of from about 10 to 18 carbon atoms and 2 moieties selected from the group consisting of alkyl groups and hydroxyalkyl groups containing from 1 to about 3 carbon atoms; water-soluble phosphine oxides containing one alkyl moiety of about 10 to 18 carbon atoms and 2 moieties selected from the group consisting of alkyl groups and hydroxyalkyl groups containing from about 1 to 3 carbon atoms; and water-soluble sulfoxides containing one alkyl moiety of from about 10 to 18 carbon atoms and a moiety selected from the group consisting of alkyl and hydroxyalkyl moieties of from about 1 to 3 carbon atoms.
• Ampholytic surfactants include derivatives of aliphatic or aliphatic derivatives of heterocyclic secondary and tertiary amines in which the aliphatic moiety can be either straight or branched chain and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and at least one aliphatic substituent contains an anionic water-solubilizing group.
• Zwitterionic surfactants include derivatives of aliphatic quaternary ammonium phosphonium, and sulfonium compounds in which one of the aliphatic substituents contains from about 8 to 18 carbon atoms.
• Useful cationic surfactants include water-soluble quaternary ammonium compounds of the form R₄R₅R₆R₇N⁺X^-, wherein R₄ is alkyl having from 10 to 20, preferably from 12-18 carbon atoms, and R₅, R₆ and R₇ are each C₁ to C₇ alkyl preferably methyl; X^- is an anion, e.g. chloride. Examples of such trimethyl ammonium compounds include C_12-14 alkyl trimethyl ammonium chloride and cocalkyl trimethyl ammonium methosulfate.
• The granular detergents of the present invention can contain neutral or alkaline salts which have a pH in solution of seven or greater, and can be either organic or inorganic in nature. The builder salt assists in providing the desired density and bulk to the detergent granules herein. While some of the salts are inert, many of them also function as detergency builder materials in the laundering solution.
• Examples of neutral water-soluble salts include the alkali metal, ammonium or substituted ammonium chlorides, fluorides and sulfates. The alkali metal, and especially sodium, salts of the above are preferred. Sodium sulfate is typically used in detergent granules and is a particularly preferred salt. Citric acid and, in general, any other organic or inorganic acid may be incorporated into the granular detergents of the present invention as long as it is chemically compatible with the rest of the agglomerate composition.
• Other useful water-soluble salts include the compounds commonly known as detergent builder materials. Builders are generally selected from the various water-soluble, alkali metal, ammonium or substituted ammonium phosphates, polyphosphates, phosphonates, polyphosphonates, carbonates, silicates, borates, and polyhyroxysulfonates. Preferred are the alkali metal, especially sodium, salts of the above.
• Specific examples of inorganic phosphate builders are sodium and potassium tripolyphosphate, pyrophosphate, polymeric metaphosphate having a degree of polymerization of from about 6 to 21, and orthophosphate. Examples of polyphosphonate builders are the sodium and potassium salts of ethylene diphosphonic acid, the sodium and potassium salts of ethane 1-hydroxy-1,1-diphosphonic acid and the sodium and potassium salts of ethane, 1,1,2-triphosphonic acid. Other phosphorus builder compounds are disclosed in U.S. Pat. Nos. 3,159,581; 3,213,030; 3,422,021; 3, 422, 137; 3,400,176 and 3,400,148, incorporated herein by reference.
• Examples of nonphosphorus, inorganic builders are sodium and potassium carbonate, bicarbonate, sesquicarbonate, tetraborate decahydrate, and silicate having a molar ratio of SiO₂ to alkali metal oxide of from about 0.5 to about 4.0, preferably from about 1.0 to about 2.4. The compositions made by the process of the present invention does not require excess carbonate for processing, and preferably does not contain over 2% finely divided calcium carbonate as disclosed in U.S. Pat. No. 4,196,093, Clarke et al., issued Apr.1, 1980, and is preferably free of the latter.
Polymers
• Also useful are various organic polymers, some of which also may function as builders to improve detergency. Included among such polymers may be mentioned sodium carboxy-lower alkyl celluloses, sodium lower alkyl celluloses and sodium hydroxy-lower alkyl celluloses, such as sodium carboxymethyl cellulose, sodium methyl cellulose and sodium hydroxypropyl cellulose, polyvinyl alcohols (which often also include some polyvinyl acetate), polyacrylamides, polyacrylates and various copolymers, such as those of maleic and acrylic acids. Molecular weights for such polymers vary widely but most are within the range of 2,000 to 100,000. Other suitable polymers are polyamine N-oxide polymers, copolymers of N-vinylpyrrolidone and N-vinylimidazole, polyvinylpyrrolidone polymers, polyvinyloxazolidones and polyvinylimidazoles or mixtures thereof.
• Polymeric polycarboxyate builders are set forth in U.S. Patent 3,308,067, Diehl, issued March 7, 1967. Such materials include the water-soluble salts of homo-and copolymers of aliphatic carboxylic acids such as maleic acid, itaconic acid, mesaconic acid, fumaric acid, aconitic acid, citraconic acid and methylenemalonic acid.
Silicone Oils
• Particulate suds suppressors may also be incorporated either directly in the agglomerates herein by way of the powder stream into the agglomerating unit, or in the finished composition by dry adding. Preferably the suds suppressing activity of these particles is based on fatty acids or silicones.
  In one embodiment of the present invention the silicone oil is adsorbed onto the specified Zeolite A.
Optionals
• Other ingredients commonly used in detergent compositions can be included in the compositions of the present invention. These include flow aids, color speckles, bleaching agents and bleach activators, suds boosters or suds suppressors, antitarnish and anticorrosion agents, soil suspending agents, soil release agents, dyes, fillers, optical brighteners, germicides, pH adjusting agents, nonbuilder alkalinity sources, hydrotropes, enzymes, enzyme-stabilizing agents, chelating agents and perfumes.
• These optional ingredients, especially optical brighteners, may be incorporated either directly in the agglomerates herein or may be components of separate particles suitable for dry adding to the agglomerates of the present invention.
Processing
• Useful agglomeration processes are defined in EP-A-510746, published on 28th October 1992, and in WO93/25378, published on 23rd December 1993. These applications describe the agglomeration of solids with a high active neutralised surfactant paste. However it will be appreciated that the high active neutralised paste could be replaced fully or in part by other surfactants, especially nonionic surfactants (as in EP643130, published on 15th March 1995), or by organic polymers or silicone oils. Preferred embodiments of the process are described in more detail in the Examples below.
TEST METHOD
• Oil absorption values can be determined by following British Standards, BS3483 : Part 7 :1982 (corresponding to ISO 787/5-1980). A 5 gram sample of Zeolite A having a free alkalinity of less than 0.5% should be used. Oil absorption value (OAV) is expressed as :$$\mathrm{OAV}=\frac{\mathrm{Volume\; of\; oil}\left(\mathrm{ml}\right)}{\mathrm{Wt}\mathrm{.}\mathrm{of\; Zeolite\; sample}\left(\mathrm{g}\right)}$$

  
EXAMPLES
• All values are expressed in % by weight. Zeolite levels are expressed on a hydrated basis (including 15% by weight of bound water)

  	Ex. 1	Comp. Ex. A
  Zeolite A *	32	-
  Zeolite A #	-	32
  C12-15 AS	24	24
  C12-15 AE3S	6	6
  Sodium	25	25
  Carbonate
  Co-polymer	-	-
  Nonionic Surfactant	-	-
  Water	5	5
  Misc.	8	8

  Zeolite A* has an oil absorption capacity of 45.5 ml/100g supplied by Industrial Zeolites (UK) Ltd. of Thurrock, Essex, England. Zeolite A # has an oil absorption capacity of 36 ml/100g supplied by Degussa under the Trade Name Wessalith®. C12-15AS is sodium alkyl sulphate, the alkyl chains principally comprising C12 to C15. C12-15AE3S is sodium alkyl ether sulphate, the alkyl chains principally comprising C12 to C15, and with an average of 3 ethoxy groups per molecule. Co-polymer is a co-polymer of acrylic and maleic acid. Nonionic surfactant comprises 7 parts of ethoxylated alcohol, the alkyl chains principally comprising C12 to C15, and with an average of 3 ethoxy groups per molecule; and 3 parts of C12-14 polyhydroxy fatty acid amide. Misc is mainly sulphate with some other minor impurities.

• Granular agglomerates having the composition of Example 1 were prepared by the following process. The powdered raw materials (Zeolite A and sodium carbonate) were added to the pan of an Eirich® mixer rotated at 64 rpm and mixed for 10 seconds. The mixer pan was then stopped and preheated surfactant paste (50°C), 80% surfactant active in aqueous solution, was then added in slices into a hollow formed in the middle of the powder. Loose powder being scooped over the paste to completely cover it. The mixer was then started again with pan rotating at 64 rpm, and choppers set at 2500 rpm. The mixing was stopped when granular agglomerates started to form (at this point the current drawn by the Eirich rose from 2.8 to 3 amps.
• The resulting granular agglomerates were free-flowing and had less than 25% by weight of oversized particles (oversized particles be considered as those having particle size of greater than 1600 micrometers).
• Granular agglomerates having the composition of Comparative Example A were prepared by the same process as Example 1, using the same time of mixing the powders and paste as that used in Example 1. The resulting granular agglomerates had greater than 25% by weight of oversized particles (oversized particles be considered as those having particle size of greater than 1600 micrometers).

Claims (3)

1. A process for the preparation of a granular detergent composition or component having a bulk density greater than 650 g/l, which comprises the step of dispersing a liquid binder throughout a powder stream in a high speed mixer to form granular agglomerates,characterised in that
   the powder stream comprises crystalline zeolite A having an oil absorbing capacity of at least 40 ml/100g
   the liquid binder is a paste which comprises at least 10% by weight of a neutralised anionic surfactant, the paste having a viscosity of at least 10000 mPas, and
   the granular detergent composition or component comprises:

   a) from 20% to 70% by weight of crystalline zeolite A having an oil absorbing capacity of at least 40 ml/100g;

   b) at least 30% by weight of anionic surfactant;

   the ratio of the crystalline zeolite A to the anionic surfactant being less than 1:1.
2. A process according to claim 1, wherein the granular agglomerates are formed by mixing in the high speed mixer for a residence time of from 2 seconds to 30 seconds, followed by the step of
   further mixing in a moderate speed mixer/agglomerator for a residence time through the moderate speed mixer of less than 5 minutes, preferably less than 2 minutes, in which, optionally, a finely divided powder may be added.
3. Process according to claim 1 wherein the liquid binder is a surfactant paste which comprises at least 70% by weight of anionic surfactant.