Patent Publication Number: US-6221829-B1

Title: Particulate polymeric materials and their use

Description:
This invention relates to liquid detergent concentrates which include polymeric particles (ie particles having an external surface of organic polymer) which give improved stability when dispersed in the concentrate. 
     Processes are described in PCT/GB96/03233 now WO 97/24179 for forming particulate compositions comprising particles having a hydrophilic core within a shell comprising a membrane comprising an association product of (a) an interfacial condensation (IFC) product formed by reaction in a non-aqueous liquid between a first IFC reactant having at least two first condensation groups and the second IFC reactant having at least two second condensation groups and (b) an amphipathic polymeric stabiliser which will concentrate at the interface between oil and water and which has recurring hydrophobic groups and recurring reactive hydrophilic groups which associate with the second condensation groups. After formation in the non-aqueous liquid, the particles are then dispersed in aqueous electrolyte. 
     It is explained in that application that the association may comprise a condensation reaction and, in particular, condensation may occur when the stabiliser is a copolymer of an ethylenically unsaturated carboxylic anhydride such as maleic anhydride and the second condensation groups are amino groups. It is also explained, however, that the association preferably comprises forming an internal, ring-formed salt between the adjacent carboxylic groups of a stabiliser formed from a monomer such as maleic acid or maleic anhydride with an IFC reactant which is a polyamine. 
     We have found that the best performance is generally achieved when the formation of the IFC shell does depend on the use of a polycarboxylic stabiliser which is in hydrolysed acid form rather than anhydride form, and this is probably due to the fact that internal salt formation occurs and that covalent reaction between the amine and the carboxylic acid groups does not occur during normal processing. 
     We have also found that when particles are made in this way, the resultant particles sometimes have less dispersion-stability than is desirable, especially when they are subsequently dispersed in an aqueous electrolyte solution (such as a liquid detergent concentrate). 
     We have found that, when developing these unpublished processes, it is difficult simultaneously to optimise the shell formation and the stability of the particles in the final liquid dispersion. We believe that this may arise because of there being different requirements for optimum shell formation and for optimum stability, and because of the differences in the continuous phase. We believe that optimum shell formation may often be promoted by some degree of ionic association between the stabiliser and IFC reactant groups, but we believe that materials which are optimum for undergoing this ionic association may give less satisfactory stability in the final dispersion. Conversely, materials which may give optimum stability in the final dispersion appear to give less adequate shell formation. 
     Our object, arising out of this unpublished work, is to try to obtain a better combination of properties during manufacture and during long term storage in the electrolyte. 
     Different types of dispersions are known from, for instance, GB-A-1,198,052, GB-A-1,231,634, GB-A-1,268,692, GB-A-2,207,681, AU-A-455,165, U.S. Pat. No. 3,580,880, U.S. Pat. No. 3,875,262, EP-A-707,018 and EP-A-719,085. 
     According to the invention, we provide a liquid detergent concentrate containing a dispersion of particles having a size below 30 μm wherein the particles have a shell core configuration, the shell has been made by interfacial condensation and has an outer surface which includes reactive groups, and a reactive stabilizer is covalently bonded with some of the reactive groups on to the surface of the particles. The dispersion is preferably substantially stable. The reactive stabiliser is preferably polymeric. 
     By saying that we covalently react the stabiliser material with some of the reactive groups, we mean that there is sufficient covalent bonding between the stabiliser material and the reactive groups to ensure that the stabiliser is attached to the particles by sufficient covalent bonding to hold the stabiliser material in place despite reasonable changes in the continuous phase in which the particles may be dispersed. For instance the stabiliser material should remain in place, and give a stabilising effect, even though the continuous phase may change from a first liquid which is a non-aqueous, predominantly hydrocarbon, liquid to the aqueous detergent concentrate. There can additionally be some ionic bonding or other forms of association but there must be sufficient covalent bonding to dominate the performance of the particles when the continuous phase is changed. 
     The number of reactive groups which remain unreacted after covalently reacting the stabiliser material on to the particles is often unimportant but in practice there will always be some reactive groups that do not react covalently with the stabiliser. For instance some of the reactive groups will be prevented from reacting because of steric hindrance between the stabiliser and the particle surface. Some of the reactive groups will be prevented from reacting covalently because they may react in another manner, for instance forming an ionic complex in practice some of the reactive groups may remain unreacted because there is a stoichiometric excess of reactive groups on the polymer particles over groups on the stabiliser that can react with them. 
     The particles have a size at least 90% by weight below 30 μm, preferably below 10 or 20 μm. The invention reduces or eliminates the risk of the particles sedimenting and/or aggregating, both at low concentrations (e.g., down to 0.1% by weight) and at higher concentrations (e.g., 5% or even much higher such as 30% or 50% in some liquids used for introducing the particles into the detergent concentrate. 
     Generally a substantially stable dispersion of the particles may be formed in a first liquid (usually a non-aqueous liquid) and then these particles may be dispersed into the liquid detergent concentrate and the dispersion would have been less stable in this if the covalent bonding of the invention had not been applied. In particular, by the invention the dispersion in the detergent concentrate is preferably more stable than if the same stabiliser material is simply mixed into the final dispersion of particles in the second liquid, without the covalent reaction. Generally the covalent reaction is conducted in the first (usually non-aqueous) liquid and the resultant self-stabilised particles are dispersed in the second liquid. However if desired the first liquid may be exchanged with another non-aqueous liquid (or some other liquid such as a surfactant) before the covalent reaction or even before adding the reactive stabiliser. 
     The change of the continuous phase from the first liquid to another liquid, and in particular to the detergent concentrate can be conducted in various ways, for instance as described in PCT/GB96/03233. 
     The particles may be made by interfacial condensation (IFC) in a first liquid as described in PCT/GB96/03233 and which is incorporated herein by reference. 
     The reactive groups on the polymer particles can be epoxide or hydroxyl groups (in which even the covalent bond will be an ether). They can be carboxylic groups (free acid, water soluble salt, anhydride or acid halide) in which event the covalent linkage can be an ester or amide linkage. Preferably, however, the reactive groups are amino groups in which event the covalent linkage is preferably an amide linkage, formed by reaction between these amino groups and carboxylic groups which can be covalently bonded with them. 
     Although covalent bonding can be achieved between carboxylic free acid, salt or halide groups and amino groups, the covalent reaction generally occurs much more easily if the carboxylic groups are in the form of anhydride groups and thus preferably the reactive groups are amino groups and the stabiliser provides dicarboxylic anhydride groups. 
     We believe that one reason why some existing stabiliser systems are less effective in, for instance, detergent concentrate is that the reactive groups on many of the particles that are under consideration are ionisable (for instance being cationic or anionic) and the stabiliser is counterionic so that the attraction between the stabiliser and the particle is primarily ionic. This ionic attraction can be displaced by, for instance, changes in the electrolyte concentration. 
     In the invention, it is preferred that the reactive groups on the polymer particles are ionisable and the stabiliser is a counterionic material or a derivative (such as an anhydride) of a counterionic material and which is now covalently bonded to the particles in contrast to being ionically attached, as in prior processes. 
     In another embodiment, the outer surface of the particles is substantially free of ionisable groups by which the stabilising material could be ionically associated with the particles. 
     The stabiliser material can be a monomeric material which achieves the self-stabilising effect merely by covalently blocking sufficient of the ionisable reactive groups on the polymer particles that the stabilising effect is not significantly altered by moderate changes in electrolyte concentrate. For instance, amino reactive groups on the particles would normally be ionisable, but if they are reacted with a monomeric anhydride or acid halide they are covalently blocked and so cannot ionise. This prevention of ionisation is, in some environments, sufficient to maintain self-stabilising properties when the continuous phase is changed. 
     Accordingly the invention includes processes in which the stabilising material is a monomeric anhydride or acid halide such as acetic anhydride, acetyl chloride, maleic anhydride or succinic anhydride and which is covalently reacted on to polymer particles having free amino groups so as to form amide groups. When these particles carrying amide groups are dispersed into a detergent or other electrolyte liquid, optionally in the presence of additional polymeric stabiliser which is unreactive with the particles, the particles are self stabilising. 
     By this we mean that improved stability is obtainable compared to the stability that is achieved when the same particles are dispersed into the same liquid (in the presence of the same extra stabiliser if that is used) but without the prior reaction with the anhydride or acid halide. 
     Preferably, however, the stabilising material which is used in the invention is a reactive copolymer of hydrophilic monomer units and hydrophobic monomer units, i.e., it is an amphipathic polymer. The hydrophilic units are attracted to the shell, which is usually hydrophilic, and the hydrophobic units are attracted to the non-aqueous liquid. Suitable hydrophobic monomers and hydrophilic monomers and their amounts (except for the groups which are to react) are given in PCT/GB96/03233. The hydrophilic monomer units should provide groups which will react covalently with the reactive groups on the particles. Preferably the stabiliser is a copolymer of dicarboxylic anhydride monomer units and the reactive groups on the particles are amino groups. 
     The preferred aspects of the invention are those in which the dispersion in the first liquid is formed by IFC polymerisation in the presence of a first stabiliser which is a copolymer of hydrophobic units with hydrophilic units which preferably include dicarboxylic units and wherein the dicarboxylic units (if present) are in the hydrolysed form (free acid, acid salt or acid halide) and a second stabiliser is reacted with amino groups from the IFC polymerisation and the second stabilizer is a copolymer of hydrophobic monomer units with hydrophilic monomer units which include dicarboxylic acid units and wherein the dicarboxylic units include anhydride groups, whereby they will enter into covalent amide formation with the amino groups. Other stabilisers which have hydrophilic monomer units which can react covalently with the amino groups may be used. 
     In PCT/GB96/03233 we described a process in which IFC particles containing amine groups are made in the presence of one such stabiliser, either free dicarboxylic acid or anhydride, and preferably the invention does not include such an IFC process using, as the sole stabiliser, such a polymer which is hydrolysed (so that all the dicarboxylic acid groups are free acid or salt form) or mainly unhydrolysed anhydride, mainly meaning preferably above 80%. 
     We can obtain useful results using a polymer which is partially hydrolysed eg 20-80% anhydride and 80-20% dicarboxylic acid or acid salt, preferably 30-80% dicarboxylic acid. 
     We have now found that best results are achieved by. using a combination of stabilisers (generally amphipathic stabilisers) wherein the first will predomfinantly enter into ionic association with the amino IFC reactant (so as to promote shell formation) and the other will enter into covalent reaction with the amino groups, so as to bond stabiliser to the surface of the particles and so as to block some or all of the ionisable amino groups. The first may have free dicarboxylic acid groupswithout anhydride, and the second may have anhydride groups. 
     The second carboxylic stabiliser, or other stabilising material which is to react with the reactive groups, may be added at any time such that it achieves the desired effect and blocks the ionisable groups in the final particles. For instance the particles may be formed initially with the reactive groupe on them (optionally in the presence of a polymeric stabiliser) and then the stabilising material may be reacted covalently on to the particles having the reactive groups. Thus the particles may be formed in the presence of one stabiliser (which is unreactive) and then the reactive stabiliser is added and reacted on to the particles. As another example, the stabiliser which is to react with the reactive groups may be added before the formation of the particles is completed. 
     Good results are also obtained when the amount of anhydride monomer units is low, e.g., 1 to 10% by weight of the monomers or when 1 to 10% glycidyl monomer units are included instead of the anhydride units. 
     The remaining hydrophilic units in the stabiliser can be mono- or di-carboxylic acid monomer units and/or hydroxyalkyl monomer units, generally to provide 10 to 30 mole % ionic or other hydrophilic units, with the balance being hydrophobic (see PCT/GB96/03233). Suitable hydrophobic groups include fatty (C8-24) alkyl (meth)acrylates, C1-4 alkyl (meth)acrylates and styrenes. 
     The stabiliser which is to be covalently reacted on to the reactive groups may be incorporated before the interfacial condensation reaction is started. For instance both a dicarboxylic acid stabiliser and a dicarboxylic anhydride stabiliser may be present before the IFC is initiated. For instance the stabiliser which is to promote wall formation (e.g., the dicarboxylic acid stabiliser) may be present during the emulsification of the aqueous core phase into a non-aqueous liquid, and the stabiliser which is to react covalently with amino or other reactive groups is then added, for instance with the other IFC reactant. 
     Irrespective of when the various materials are added, the process of the invention preferably includes a reaction stage at the end of the particle formation (or subsequently) in order to allow the reaction which forms the covalent linkages. For instance the dispersion may be left to react at ambient temperature for, for instance 3 to 48 hours, but preferably the reaction is driven by heating, e.g., to 30 to 90° C., preferably 35° C. to 60° C. or 70° C., for 1 to 18 hours, e.g., 3 to 16 hours at 35-55° C. 
     The invention also includes detergent concentrates made as in PCT/GB96/03233 (for instance using a single stabiliser) wherein the amine reactant has less tendency to undergo displaceable ionic association with the stabiliser. In particular the amine is preferably a cyclic amine, such as piperazine, the other IFC reactant may be an aromatic acid halide and the stabiliser may include carboxylic acid, acid salt, acid halide or anhydride groups. 
     The active ingredients which may be present in the core of a shell core particles, can be any active ingredient which is useful in detergent concentrates, as described in PCT/GB96/03233. The core is usually hydrophilic. Preferably the active ingredient is an enzyme such as one or more proteases, lipases, eutinases, amylases, cellulases, peroxidases or oxidases (e.g. laccases). 
     The core is hydrophilic, and often includes water. 
     The detergent concentrates may be as described in PCT/GB96/03233 and PCT/GB96/03231 (WO97/24177 and WO97/24179) which are incorporated herein by reference. The detergent concentrate may comprise one or more surfactants, e.g. anionic, nonionic, cationic, ampholytic, zwitterionic, or semi-polar surfactants, and may be aqueous or substantially non-aqueous. Other ingredients normal for detergent concentrates or compositions may also be included, e.g. builder systems, suds suppressors, soil-suspending agents, soil-releasing agents, bleaching agents, optical brighteners, abrasives, bacterides, tarnish inhibitors, coloring agents and/or perfumes. 
     It is preferable to encapsulate active ingredients such as proteolytic enzyme e.g. Savinase by using the process of this invention. The protease enzyme will remain within the interior of the IFC microcapsules in concentrated liquid detergent and only be released after dilution of the detergent formulation into wash water. This allows other enzyme types (for instance lipases, amylases, cellulasee) to be incorporated into liquid detergents containing the degrading proteolytic enzymes. 
    
    
     The following are examples of the invention. 
     EXAMPLE 1 
     This example shows that the Savinase microcapoules obtained in Example 1 of PCT/GB96/03233 when using hydrolysed maleic acid copolymer stabiliser can be post treated to improve the capsules from aggregating in liquid detergent formulations. 
     Acetic anhydride (2.5 parts) was added to 50 parts of Savinase microcapsules dispersion in surfactant (Capsules A) under stirring. The mixture formed was allowed to react for 1 hour at room temperature (20° C.) to give Capsules B. 
     Capsules B showed no loss of enzyme activity nor alteration of performance properties. 
     The enzyme capsules A and B were separately dosed into commercial heavy duty liquid detergents at 0.10 KNPU/g protease activity. Each one of the detergent mixtures was placed in an oven at 40° C. and subjected to the accelerated storage test. 
     After 24 hours, the detergent mixture containing Capsules A had aggregated and settled to the bottom of the container. The acetic anhydride treated microcapsules (capsule B) remained dispersed and showed no signs of instability. After, further 3 days at 40° C., Capsules B showed formation of fine aggregates. 
     EXAMPLE 2 
     Savinase enzyme microcapsules were prepared according to Example 1 of PTJ/GB96/03233 except that an oil-soluble stabilizer having a proportion (about 25%) of unhydrolysed (maleic anhydride) groups in the stabilising polymer was employed instead of the fully hydrolysed version. 
     The resulting capsules (Capsules C) were dosed in liquid detergent at 0.10 KNPU/g enzyme activity and placed in an oven at 40° C. Also, a comparative detergent mixture was made with Capsules A (Example 1 of PCT/GB96/03233). Capsules A aggregated and settled to the bottom of the container after 1 day storage. Capsules C remain dispersed and showed no signs of instability after 1, 4 and 7 days storage. 
     EXAMPLE 3 
     A dispersion of microcapoules was prepared as in Example 1 of PCT/GB96/03233 using a polymeric stabiliser in which the hydrophilic groups are hydrolysed to maleic acid groups. The dispersion was then treated as in that Example first to dehydrate the dispersion to provide anhydrous particles in hydrocarbon, then to exchange the hydrocarbon with a non-ionic surfactant to provide an anhydrous dispersion in non-ionic surfactant, and then to mix this dispersion into a heavy duty liquid detergent at 0.10 KNPU/g enzyme activity. 
     When an addition of the same polymeric stabiliser, but in the unhydrolysed, anhydride form, was made to the wet or dry dispersion in hydrocarbon or the dispersion in non-aqueous liquid, it was found that storage stability was improved compared to the process without the addition of this extra, anhydride stabiliser. 
     Even better results are obtained when adding the anhydride stabiliser with the initial oil phase or with the TPC oil phase. 
     EXAMPLE 4 
     Protection of Lipase Enzyme From Degrading Protease Enzyme 
     This example demonstrates that non-protective enzymes such as Lipolase, a lipase enzyme can be protected from proteases such as Savinase enzyme by use of product formed in Example 2 (Capsule C). 
     To three separate concentrated liquid detergent samples containing liquid Lipolase enzyme at 1.0 KLU/g enzyme activity. One of the following Savinase formulations is added at 0.10 KNPU/g protease enzyme activity. 
     (a) Liquid Savinase enzyme (16.OL) 
     (b) Savinase Capsules A (Example 1 of PCT/GB96/03233) 
     (c) Savinase Capsules C (Example 2 of present patent) 
     Each of the detergent samples is subjected to an accelerated test at 30° C. After the storage test each detergent mixture is analysed for lipase enzyme activity. 
     The percentage of Lipolase enzyme activity remaining after 1, 2; 4 weeks in detergent samples is given in Table 1. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 % Lipolase 
               
               
                 Savinase 
                 % Lipolase 
                 % Lipolase 
                 After 4 
               
               
                 Formulation 
                 After 1 Week 
                 After 2 Weeks 
                 Weeks 
               
               
                   
               
             
            
               
                 Liquid 
                  8 
                  0 
                  0 
               
               
                 Savinase 
               
               
                 Capsules A 
                 94 
                 81 
                 56 
               
               
                 Capsules C 
                 94 
                 82 
                 57 
               
               
                   
               
            
           
         
       
     
     The above results clearly demonstrates that the Capsules C of this invention gives the same performance as Capsules A and protects the lipase enzyme from the degrading Savinase enzyme compared to the un-encapsulated liquid formulation. 
     EXAMPLE 5 
     Sample A 
     A capsule dispersion in Isopar was prepared according example 6B in PCT/GB96/03233 where the polymer was replaced with a sodium polyacrylate homopolymer of similar molecular weight, the stabiliser was replaced by a copolymer of styrene, stearyl methacrylate and maleic acid. For analysis 0.44 g capsules A was mixed with 50.0 g Detergent 1 and left stirring for one hour. 
     Sample B 
     16.3 g Triethanolamine (TE) was emulsified into 500.0 g capsules A using a high shear Silverson mixer (trade name) for 5 minutes. The capsules were left stirring 3 hours at 40° C. 178.2 g hereof was mixed with 20.2 g of a 20% solution in hydrocarbon of a copolymer of 65% stearyl methacrylate, 17.5% styrene, 15% maleic acid and 2.5% maleic anhydride (by weight), under stirring. The capsules were left stirring overnight at 40° C. For analysis 0.47 g capsules B was mixed with 50.0 g Detergent 1 and left stirring for one hour. 
     Sample C 
     3.1 g capsules B were mixed with 3.1 g non-ionic surfactant (Softanol 50). The capsules were left stirring at 40° C. for one hour. For analysis 0.94 g capsules C was mixed with 50.0 g Detergent 1 and left stirring for one hour. 
     Detergent 1 in A-C is a comnmercially available U.S. liquid detergent (WISK Free Clear). 
     The detergents with capsules were placed at 40° C. and inspected visually as a function of time, the results are given in the following table. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Sample A 
                 Sample B 
                 Sample C 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                  0 days 
                 No aggregates 
                 No aggregates 
                 No aggregates 
               
               
                  1 day 
                 Small aggregates 
                 No aggregates 
                 No aggregates 
               
               
                  2 days 
                 Large aggregates 
                 Small aggregates 
                 No aggregates 
               
               
                  3 days 
                 Large aggregates 
                 Small aggregates 
                 No aggregates 
               
               
                  6 days 
                 Large aggregates 
                 Small aggregates 
                 Small aggregates 
               
               
                 13 days 
                 Large aggregates 
                 Large aggregates 
                 Small aggregates 
               
               
                   
               
            
           
         
       
     
     The above results demonstrates that reaction with the reactive polymeric stabiliser improve the physical stability of the capsules, and even better results can be obtained by adding a non-ionic surfactant. 
     EXAMPLE 6 
     1050.0 g capsules A from example 5 was mixed with 30.3 g Triethanolamine using a high shear Silverson mixer for 10 minutes. The capsules were left stirring overnight at 40° C. Concentrates capsules were produced by centrifugation of 108 g of the capsules, removing 55 g of the oil phase, leaving 53 g concentrated capsules. 
     Sample D 
     53.0 g concentrated capsules were mixed with 8.1 g of a 20% solution in hydrocarbon of a copolymer of 55% stearyl methacrylate, 33% methyl methacrylate, 10% methacrylic acid and 2% glycidyl methacrylate and 8.3 g Isopar and left stirring overnight at 40° C. 31.9 g non-ionic surfactant (Softanol 50) was added and stirred overnight at 40° C. For analysis 0.45 g capsules D was mixed with 50.0 g Detergent 2 and left stirring for 1 hour. 
     Sample E 
     53.0 g concentrated capsules were mixed with 16.8 g of the same dissolved reactive polymeric stabiliser as in Sample D and left stirring overnight at 40° C. 35.6 g non-ionic surfactant (Softanol 50) was added and stirred overnight at 40° C. For analysis 0.45 g capsules E was mixed with 50.0 g Detergent 2 and left stirring for 1 hour. 
     Detergent 2 in D-E is a commercially available U.S. liquid detergent (Ultra Tide Free). 
     The detergents with capsules were placed at 40° C. and inspected visually as a function of time, the results are given in the following table. 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Sample D 
                 Sample E 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 0 days 
                 No aggregates 
                 No aggregates 
               
               
                   
                 1 day 
                 No aggregates 
                 No aggregates 
               
               
                   
                 5 days 
                 Large aggregates 
                 No aggregates 
               
               
                   
                 12 days 
                 Large aggregates 
                 No aggregates 
               
               
                   
                   
               
            
           
         
       
     
     The above results demonstrates that increasing the amount of reactive polymeric stabilizer further improves the physical stability of the capsules.