Patent Publication Number: US-6670320-B1

Title: Wash cycle unit dose softener containing a disintegrating agent

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     This invention relates to wash cycle unit dose laundry compositions for softening or conditioning fabrics. More particularly, this invention relates to unit dose fabric softening compositions which are compacted granular compositions suitable for use in the wash cycle of an automatic washing machine. 
     2. Background of the Invention 
     Detergent compositions manufactured in the form of compacted detergent powder are known in the art. U.S. Pat. No. 5,225,100, for example, describes a tablet of compacted powder comprising an anionic detergent compound which will adequately disperse in the wash water. 
     Although detergent compositions in the form of compacted granular tablets of various shapes have received much attention in the patent literature, the use of such tablets to provide a unit dose fabric softener which will soften or condition fabrics in the wash cycle without impairing detergency or otherwise compromise the cleaning benefits provided by the detergent composition is not known. 
     Another possible option for providing a unit dose softener apart from the wash cycle is to introduce the softening ingredients directly into the rinse cycle. But, for this type of product to be effective several practical requirements must be met. To begin with, the size and shape of the unit dose container must be readily compatible with the geometry of a wide variety of rinse cycle dispensers designed for home washing machines in order to insure its easy introduction into the dispenser. Moreover, in common with the general use of rinse cycle softeners, it is necessary to clean the rinse dispenser on a regular basis to avoid residue from accumulating within the dispenser or even, at times, prevent bacterial growth from occurring. 
     Still further, a unit dose composition for the rinse cycle must be formulated to readily dispense its contents upon contact with water in a period of time corresponding to the residence time of the unit dose in the dispenser, namely, the period of time during which water enters and flows through the rinse cycle dispenser. The aforementioned practical requirements have to date not been successfully met with any commercially available product and hence there remains a need in the art for a unit dose softener capable of activation in the rinse cycle. 
     Laundry detergent compositions which further include a fabric softener to provide softening or conditioning of fabrics in the wash cycle of the laundering operation are well-known in the art and described in the patent literature. See, for example, U.S. Pat. No. 4,605,506 to Wixon; U.S. Pat. No. 4,818,421 to Boris et al. and U.S. Pat. No. 4,569,773 to Ramachandran et al., all assigned to Colgate-Palmolive Co., and U.S. Pat. No. 4,851,138 assigned to Akzo. U.S. Pat. No. 5,972,870 to Anderson describes a multi-layered laundry tablet for washing which may include a detergent in the outer layer and a fabric softener, or water softener or fragrance in the inner layer. But, these type of multi-benefit products suffer from a common drawback, namely, there is an inherent compromise which the user necessarily makes between the cleaning and softening benefits provided by such products as compared to using a separate detergent composition solely for cleaning in the wash cycle and a separate softening composition solely for softening in the rinse cycle. In essence, the user of such detergent softener compositions does not have the ability to independently adjust the amount of detergent and softener added to the wash cycle of a machine in response to the cleaning and softening requirements of the particular wash load. 
     Some attempts have been made in the art to develop wash cycle active fabric softeners, typically in powder form. But, these type products are characterized by the same inconvenience inherent with the use of powered detergents, namely, problems of handling, caking in the container or wash cycle dispenser, and the need for a dosing device to deliver the desired amount of active softener material to the wash water. 
     The use of a unit dose wash cycle fabric softening composition in the form of a compacted granular tablet offers numerous advantages, but it is important that such tablets be sufficiently hard and not friable so as to withstand handling and transportation without breaking or fragmenting. In order to achieve the desired level of hardness, tablet makers generally tend to increase the compacting pressure. But, a high compacting pressure, if favorable to the hardness of the tablet, lowers the disintegration rate of such tablet. 
     To be effective, the unit dose fabric softening compositions, which are compacted granular compositions, must be able to disperse in the wash liquor in a short period of time to avoid any residue at the end of the wash cycle. 
     Typically, the wash cycle time can be as short as 12 minutes and as long as 90 minutes (in typical European washers) depending on the type of washer and the wash conditions. Therefore, to make sure that the compacted unit dose is properly dispersed in the wash liquor before the end of the cycle, disintegrating materials must be added to the granules before compacting. This need for disintegrating agents is well-known in the art and the most popular materials used for this purpose are water swelling polymers such as polyvinylpyrrolidone, cellulosic polymers or a blend of citric acid and bicarbonate salt that provide an effervescent matrix. 
     The problem with these disintegrating materials and swelling polymers when used to disperse a compacted unit dose is that they are not very efficient in dispersing a unit dose tablet containing predominantly insoluble materials. Furthermore they constitute a significant weight and cost of the overall composition and they serve only the single purpose of dispersion of the tablet. Also the use of a typical effervescent matrix results in a typical feel of the tablet surface that can be described as dry and stony, which is generally not favored by consumers. 
     A particular treated montmorillonite-containing clay (such as described in WO 00/03959) is known to enhance dispersibility of a unit dose softening composition. U.S. Pat. No. 6,291,421 to Colgate describes a unit dose wash cycle fabric softening composition containing a treated montmorillonite-containing clay. 
     It has now been surprisingly discovered that when disintegrating materials such as swelling polymers and cellulose are combined with the aforementioned treated clay, a synergy of activity is evidenced which significantly accelerates the disintegration speed of unit dose tablets containing predominantly insoluble materials. 
     SUMMARY OF INVENTION 
     There is provided herein a unit dose wash cycle fabric softening composition for softening or conditioning fabrics in the wash cycle of an automatic washing machine, said unit dose comprising a compacted granular fabric softener composition in an amount sufficient to form a unit dose capable of providing effective softening or conditioning of fabrics in the wash cycle of said washing machine, and wherein said fabric softener composition comprises (A) a treated montmorillonite-containing clay selected to have initial properties as follows: (i) a montmorillonite content of at least 85%; and (ii) when said clay is activated with sodium ions, dried and ground to particles, said ground particles do not swell more than about 2.5 fold over a period of 24 hours when added to deionized water at room temperature; and wherein said montmorillonite-containing clay is treated by the process comprising the following sequential steps: (a) drying said clay to a moisture content of from about 25 to about 35%, by weight; (b) extruding the dried material through a die to form a paste; (c) drying said paste to a moisture content of from about 10% to about 14% by weight; and (d) calcining at a temperature of about 120° C. to about 250° C.; and (B) at least one disintegration agent selected from the group consisting of swelling polymers; cellulose; and electrolytes, to enhance the dispersibility of said compacted granular composition in water. 
     The term granular as used herein in describing the fabric softener is intended to encompass relatively coarser granules varying in size from about 150 to 2,000 microns as well as finer powder having a size as small as 30 to 50 microns. 
     The term fabric softener is used herein for purposes of convenience to refer to materials which provide softening and/or conditioning benefits to fabrics in the wash cycle of a home or automatic laundering machine. 
     The term “disintegration agent” as used herein refers to materials selected from among swelling polymers; cellulose; and electrolytes which agent when used in combination with the aforementioned particular grade of clay, significantly enhances the speed of disintegration of the compacted granular fabric softener composition as herein described. The swelling polymers include most notably polyvinyl pyrrolidone (PVP) such as Kollidon CL from BASF, polyacrylate such as Acusol 771 from Rohm &amp; Haas, and polyethylene glycol (PEG). Cellulose disintegration agents include crystalline and amorphous varieties of cellulose such as Technocel 150 Tab from CFF, and useful electrolytes include sodium acetate, urea, and potassium carbonate. 
     The present invention is predicated on the use of a treated montmorillonite-containing clay, preferably a treated bentonite, as herein defined, as an active disintegrating ingredient in a unit dose softening composition for the wash cycle in combination with a disintegration agent to significantly enhance the speed of disintegration of the compacted granular composition. The resultant unit dose composition has reduced tendency to gel on contact with water so that when used in conjunction with laundry detergent compositions it manifests improved dispersion properties in the wash water without having any adverse effect on its softening properties. 
     In accordance with the process aspect of the invention there is provided a process for softening or conditioning laundry, which comprises contacting the laundry with an effective amount of the unit dose laundry composition defined above. 
     DETAILED DESCRIPTION 
     The clays that are useful components of the invented products are those that cooperate with the organic fatty softener materials to provide enhanced softening of laundry. Such clays include the montmorillonite-containing clays which have swelling properties (in water) and which are of smectite structure, so that they deposit on fibrous materials, especially cotton and cotton/synthetic blends, such as cotton/polyester, to give such fibers and fabrics made from them a surface lubricity or softness. The best of the smectite clays for use in the present invention is bentonite and the best of the bentonites are those which have a substantial swelling capability in water, such as the sodium and potassium bentonites. Such swelling bentonites are also known as western or Wyoming bentonites, which are essentially sodium bentonite. Other bentonites, such as calcium bentonite, are normally non-swelling and usually are, in themselves, unacceptable as fabric softening agents. However, it has been found that such non-swelling bentonites exhibit even better fabric softening in combination with PEC&#39;s than do the swelling bentonites, provided that there is present in the softening composition, a source of alkali metal or other solubilizing ion, such as sodium (which may come from sodium hydroxide, added to the composition, or from sodium salts, such as builders and fillers, which may be functional components of the composition). Among the preferred bentonites are those of sodium and potassium, which are normally swelling, and calcium and magnesium, which are normally non-swelling. Of these it is preferred to utilize calcium (with a source of sodium being present) and sodium bentonites. The bentonites employed may be produced in the United States of America, such as Wyoming bentonite, but also may be obtained from Europe, including Italy and Spain, as calcium bentonite, which may be converted to sodium bentonite by treatment with sodium carbonate, or may be employed as calcium bentonite. Also, other montmorillonite-containing smectite clays of properties like those of the bentonites described may be substituted in whole or in part for the bentonites described herein and similar fabric softening results will be obtained. 
     The swellable bentonites and similarly operative clays are of ultimate particle sizes in the micron range, e.g., 0.01 to 20 microns and of actual particle sizes in the range of No&#39;s. 100 to 400 sieves, preferably 140 to 325 sieves, U.S. Sieve Series. The bentonite and other such suitable swellable clays may be agglomerated to larger particle sizes too, such as 60 to 120 sieves, but such agglomerates are not preferred unless they include the PEC(&#39;s) too (in any particulate products). 
     For purposes of providing a treated bentonite in accordance with the invention, the initial bentonite starting material is selected to have relatively low gelling and swelling properties. Specifically, the starting material bentonite is selected to have the following initial properties: (a) a montmorillonite content of at least 85%; and (b) when the bentonite is activated with sodium ions, dried and ground to particles, the ground particles do not swell more than about 2.5 fold over a period of 24 hours when added to deionized water at room temperature. The ground particles of bentonite for purposes of determining swelling herein are particles at least 90% of equal to or less than about 75 microns in diameter. 
     The chemical composition of the starting material bentonite is preferably comprised by weight of the following: SiO 2  55.0 to 61.0%; Al 2 O 3  14.5 to 17.6%; Fe 2 O 3  1.45 to 1.7%CaO 2.8 to 7.0%; MgO 5.0 to 6.3%; K 2 O 0.5 to 0.85%; Na 2 O 0.25 to 0.30%; Mn 3 O 4  0.04 to 0.25%. The process of treating the bentonite comprises the following sequential steps: (a) drying said clay to a moisture content of from about 25 to about 35%, by weight; (b) extruding the dried material through a die to form a paste; (c) drying said paste to a moisture content of from about 10% to about 14% by weight; and(d) calcining at a temperature of about 120° C. to about 250° C. 
     A detailed description of the process for treating bentonite in accordance with the present invention is disclosed in WO 00/03959 filed in the name of Colin Stewart Minchem, Ltd., the disclosure of which is incorporated herein by reference. 
     A main component of the invented compositions and articles of the present invention, and which is used in combination with the fabric softening clay is an organic fatty softener. The organic softener can be anionic, cationic or nonionic fatty chains (C 10 -C 22  preferably C 12 -C 18 ) Anionic softeners include fatty acids soaps. Preferred organic softeners are nonionics such as fatty esters, ethoxylated fatty esters, fatty alcohols and polyols polymers. The organic softener is most preferably a higher fatty acid ester of a pentaerythritol compound, which term is used in this specification to describe higher fatty acid esters of pentaerythritol, higher fatty acid esters of pentaerythritol oligomers, higher fatty acid esters of lower alkylene oxide derivatives of pentaerythritol and higher fatty acid esters of lower alkylene oxide derivatives of pentaerythritol oligomers. Pentaerythritol compound is often abbreviated as PEC herein, which description and abbreviation may apply to any or all of pentaerythritol, oligomers, thereof and alkoxylated derivatives thereof, as such, or more preferably and more usually, as the esters, as may be indicated by the context. 
     The oligomers of pentaerythritol are preferably those of two to five pentaerythritol moieties, more preferably 2 or 3, with such moieties being joined together through etheric bonds. The lower alkylene oxide derivatives thereof are preferably of ethylene oxide or propylene oxide monomers, dimers or polymers, which terminate in hydroxyls and are joined to the pentaerythritol or oligomer of pentaerythritol through etheric linkages. Preferably there will be one to ten alkylene oxide moieties in each such alkylene oxide chain, more preferably 2 to 6, and there will be one to ten such groups on a PEC, depending on the oligomer. At least one of the PEC OH groups and preferably at least two, e.g., 1 or 2 to 4, are esterified by a higher fatty acid or other higher aliphatic acid, which can be of an odd number of carbon atoms. 
     The higher fatty acid esters of the pentaerythritol compounds are preferably partial esters. And more preferably there will be at least two free hydroxyls thereon after esterification (on the pentaerythritol, oligomer or alkoxyalkane groups). Frequently, the number of such free hydroxyls is two or about two but sometimes it may by one, as in pentaerythritol tristearate. The higher aliphatic or fatty acids that may be employed as esterifying acids are those of carbon atom contents in the range of 8 to 24, preferably 12 to 22 and more preferably 12 to 18, e.g., lauric, myristic, palmitic, oleic, stearic and behenic acids. Such may be mixtures of such fatty acids, obtained from natural sources, such as tallow or coconut oil, or from such natural air materials that have been hydrogenated. Synthetic acids of odd or even numbers of carbon atoms may also be employed. Of the fatty acids lauric and stearic acids are often preferred, and such preference may depend on the pentaerythritol compound being esterified. 
     Examples of some esters (PEC&#39;s) within the present invention follow: Monopentaerythritol Esters                    
     Monopentaerythritol Dilaurate 
     R 1 ═CH 3 —(CH 2 ) 10 —COO— 
     R 2 ═CH 3 —(CH 2 ) 10 —COO— 
     R 3 ═OH 
     R 4 ═OH 
     Monopentaerythritol Monostearate 
     R 1 ═CH 3 —(CH 2 ) 16 —COO— 
     R 2 ═OH 
     R 3 ═OH 
     R 4 ═OH 
     Monopentaerythritol Distearate 
     R 1 ═CH 3 —(CH 2 ) 16 —COO— 
     R 2 ═CH 3 —(CH 2 ) 16 —COO— 
     R 3 ═OH, 
     R 4 ═OH 
     Monopentaerythritol Tristearate 
     R 1 ═CH 3 —(CH 2 ) 16 —COG— 
     R 2 ═CH 3 —(CH 2 ) 16 —COO— 
     R 3 ═CH 3 —(CH2) 16 —COO— 
     R 4 ═OH 
     Monopentaerythritol Monobehenate 
     R 1 ═CH 3 —(CH 2 ) 20 —COO— 
     R 2 ═OH 
     R3═OH 
     R 4 ═OH 
     Monopentaerythritol Dibehenate 
     R 1 ═CH 3 —(CH2) 20 —COO— 
     R 2 ═CH 3 —(CH 2 ) 20 —COO— 
     R 3 ═OH 
     R 4 ═OH 
     Dipentaerythritol Esters 
     
       
         
         
             
             
         
       
     
     Dipentaerythritol Tetralaurate 
     R 1 ═CH 3 —(CH 2 ) 10 —CO 
     R 2 ═CH 3 —(CH 2 ) 10 —CO 
     R 3 ═CH 3 —(CH 2 ) 10 —CO 
     R 4 ═CH 3 —(CH 2 ) 10 —CO 
     Dipentaerythritol Tetrastearate 
     R 1 ═CH 3 —(CH 2 ) 16 —CO 
     R 2 ═CH 3 —(CH 2 ) 16 —CO 
     R 3 ═CH 3 —(CH 2 ) 16 —CO 
     R 4 ═CH 3 —(CH 2 ) 16 —CO 
     Pentaerythritol 10 Ethylene Oxide Ester 
     
       
         
         
             
             
         
       
     
     Monopentaerythritol 10 Ethylene Oxide Distearate 
     R 1 ═CH 3 —(CH 2 ) 16 —COO— 
     R 2 ═CH 3 —(CH 2 ) 16 —COO— 
     Pentaerythritol 4 Propylene Oxide Esters 
     
       
         
         
             
             
         
       
     
     Monopentaerythritol 4 Propylene Oxide Monostearate 
     R 1 ═CH 3 —(CH 2 ) 16 —COO— 
     R 2 ═OH 
     Monopentaerythritol 4 Propylene Oxide Distearate 
     R 1 ═CH 3 —(CH 2 ) 16 —COO— 
     R 2 ═CH 3 —(CH 2 ) 16 —COO— 
    
    
     Although in the formulas given herein some preferred pentaerythritol compounds that are useful in the practice of this invention are illustrated it will be understood that various other such pentaerythritol compounds within the description thereof may also be employed herein, including such as pentaerythritol dihydrogenated tallowate, pentaerythritol ditallowate, pentaerythritol dipalmitate, and dipentaetythritol tetratallowate. 
     To enhance the softening efficacy of the unit dose compositions described herein, cationic softeners such as conventional quaternary ammonium softening compounds may optionally be added in minor amounts. 
     The combination of bentonite and organic fatty softening material is generally from about 10% to about 100% bentonite and from about 1% to about 100% fatty softening material, preferably from about 50% to about 95% bentonite and about 5% to about 50% fatty softening material, and most preferably from about 80% to 90% bentonite and from about 10% to about 20% fatty softening material. 
     Other useful ingredients for the unit dose compacted granular compositions of the invention include disintegration materials to enhance the disintegration of the unit dose in the wash water. Such materials include an effervescent matrix such as citric acid combined with baking soda, or materials such as PVP polymer and cellulose. Granulating agents may be used such as polyethylene glycol; bactericides, perfumes, dyes and materials to protect against color fading, dye transfer, anti-pilling and anti-shrinkage. For purposes of enhancing the aesthetic properties of the final composition, cosmetic ingredients such as dyes, micas and waxes may be used as coating ingredients to improve the appearance and feel of the unit dose. 
     Clay/PDT granules and tablets are conveniently made following five major steps: a)PDT oversprayed onto Clay powder b)Agglomeration of Clay PDT powder to make granules c)Fragrances and color dyes addition to Clay PDT granules d)Blending with disintegration system to form a particulate composition e)Compaction into tablets 
     The first step of the process is to spray molten PDT onto the clay powder in a rotary drum. 
     Fragrances and color dye solutions are then applied to the clay PDT granules. Preferred mixing devices include both batch and continuous rotary mixers (i.e. rotary drums, twin shell mixers). 
     To prepare the product for tableting, the disintegration system is blended to the clay PDT granules using both continuous and batch mixing systems, with the preferred ones having minimum shear on the granules. 
     The blended granules are finally compacted into tablets using alternative or high speed rotative presses. Ideal tableting conditions balance tablet hardness which promotes consumer preferred disintegration and durability to survive the shipping process. 
     Example 1 Compacted granular unit dose compositions (A and B) were prepared from the following ingredients to demonstrate the effect on dispersibility resulting from the use of a treated bentonite clay such as described in the present invention. 
     
       
         
           
               
               
               
            
               
                   
                   
               
               
                   
                 Weight Percent 
                   
               
            
           
           
               
               
               
            
               
                   
                 A 
                 B 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Clay/Pentaerythritol ditallowate (PDT) in a 
                 80.0 
                 80.0 
               
               
                   
                 ratio of 83%: 17% 
               
               
                   
                 Effervescent matrix of baking soda and citric 
                 17.0 
                 — 
               
               
                   
                 acid 
               
               
                   
                 Polyvinylpyrrolidone 
                 1 
                 — 
               
               
                   
                 Perfume 
                 2 
                 2.0 
               
               
                   
                 Treated bentonite 
                 — 
                 18.0 
               
               
                   
                   
               
            
           
         
       
     
     Both Compositions A and B are comparative compositions not in accordance with the invention. Composition A contained a disintegrating system comprised of a disintegration agent but did not contain any treated bentonite clay while Composition B contained the treated bentonite clay of the invention but did not contain a disintegration agent as required by the present invention 
     The tablets were manufactured by the method described above. The weight of the spherical unit dose was 60 g and such unit dose dispersed in water within 20 minutes when introduced in the wash load at the beginning of the wash in a European Miele W832 front loading washing machine set a Program White Colors at 40° C. 
     The softness provided by the unit dose compositions of A and B on terry towels, cotton tee-shirts and cotton kitchen towels was evaluated after cumulative washes and compared with a commercial liquid fabric softener. A 3 Kg laundry ballast was used in the machine. Softness was evaluated by a panel of six judges using 9 replicates. The results were as follows: 
     The softness performance of Compositions A and B were essentially equivalent. 
     As compared to a commercial liquid fabric softener, Compositions A and B provided equivalent softness after one wash cycle with regard to cotton tee-shirts and cotton kitchen towels. 
     A comparison of Compositions A and B with regard to physical properties and dispersion in water is shown below: 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Composition 
                 Friability (1)   
                 Hardness (2)   
                 Dispersion time in water (3)   
               
               
                   
               
             
            
               
                 A 
                 57% 
                  75 gr 
                 50 min. 
               
               
                 B 
                 12% 
                 100 gr 
                  9 min. 
               
               
                   
               
               
                   (1) Friability: Measurement of the residues in the bottom receptacle after sieving during 15 minutes (amplitude 4) on a vibrating 4 mm meshes sieve; the lower, the less friable.  
               
               
                   (2) Hardness: Resistance to breakage when various weights are falling onto the sphere; the higher, the more resistant.  
               
               
                   (3) Dispersion in beaker: Dispersion time of 1 sphere in 1 cold water beaker under moderate agitation; the shorter, the better.  
               
            
           
         
       
     
     Composition B provided a significantly smoother feel and texture to the touch as evaluated by a panel of judges as compared to Composition A. 
     Example 2 The compacted granular unit dose composition B described in Example 1 was compared to compositions of the invention C and D which are identical to B except they replaced the 18% treated bentonite with 1 5% treated bentonite, 2% cellulose and 1% PVP (Composition C) and 15% treated bentonite, 2% cellulose and 1% Acusol 771 from Rohm &amp; Haas, a polyacrylate polymer (Composition D). The weight of the tablets was around 19 gr. Compositions B, C and D were put in separate beakers containing water and the speed of dispersion or disintegration of the tablet was measured. The results are noted below: 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Composition B 
                 Composition C 
                 Composition D 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Disintegrants 
                 18% Treated 
                 15% Treated 
                 15% Treated 
               
               
                   
                 Bentonite 
                 Bentonite 
                 Bentonite 
               
               
                   
                   
                 2% Cellulose 
                 2% Cellulose; 
               
               
                   
                   
                 1% PVP 
                 1% Acusol 771 
               
               
                 Dispersion 
                 15 minutes 
                 4 minutes 
                 4 minutes 
               
               
                 Time in 
               
               
                 the Beaker 
               
               
                   
               
            
           
         
       
     
     Based on the above data, it was clearly evidenced that the combination of disintegration agents (cellulose and polymers) with the treated bentonite clay significantly improved the dispersion speed of the tablets in water.