CRYSTALLINE SODIUM POTASSIUM SILICATES

Abstract: The present invention pertains to a crystalline silicate material containing both sodium and potassium cations within the crystalline matrix. The composition of the material is SiO2 / (xNa2O + yK2O) = Z where x + y = 1, 0.75 < x < 1.0 (and therefore 0.0 < y < 0.25), and 1.3 </= Z </= 3.22. The material possesses predetermined superior hardness ion sequestration properties determined by the composition and processing of the material. The material can be made by any one of several processes which are also set forth.

Description: CRYSTALLINE SODIUM POTASSIUM SILICATES FIELD OF THE INVENTION This invention relates to crystalline alkali silicates that exhibit the ability to reduce the activity of hardness ions in laundry wash water, as well as to supply alkalinity and buffer the laundry wash water. In particular, this invention relates to crystalline sodium/potassium silicate materials useful as detergent ingredients. BACKGROUND OF THE INVENTION It is known that hard water ions, specifically calcium and magnesium, adversely affect the activity of soaps and detergents. These ions deactivate detergents and can form undesirable precipitates. Thus it is desir¬ able to remove these ions before reaction with the detergent. One way to do this is to soften the water before it enters the washing machine. In many parts of the world, this is impractical or impossible, and even where it can be done, in most localities it is expensive. Another approach to removing hard water ions is by reaction with another material in situ in the washer. Materials useful for removing hard water ions include alkali silicates (noncrystalline silicates, crystalline silicates, and zeolites) , particularly hydrated layered alkali silicates. Layered silicates are materials chemically comprising Si0 2 organized into layers (sheets) having a negative charge, with alkali cations for charge compensation. Layered sodium silicates have been known for a number of years, either synthetically produced or naturally occurring (McCulloch J. Am . Chem . Soc . 75, 2453 (1952)). In recent years, use of crystalline layered sodium silicates, especially crystalline sodium disilicates, as detergent builders has been suggested (see US Patents 4,585,642; 4,806,327; 4,950,310; 4,820,439; 4,664,839; and 4,959,170). While these patents claim that crystalline sodium disilicates function when incorporated into detergents, the disclosed crystalline layered sodium silicates have not been accepted readily by the worldwide detergent industry due to their poor ability to remove hardness ions from wash water at temperatures below about 30°C. Furthermore, there are circumstances where it may be necessary or desirable to remove only one hardness ion or the other (Ca 2+ or Mg 2+ ) . Some detergent formulations have been developed which work synergistically with one hardness ion. Accordingly, it may be undesirable to remove that ion, or it may be desirable to reduce it to a particular concentration to optimize detergent performance while removing the other ion. Finally, where only one ion is present in the water of a particular geographic region, it is only that ion (either calcium or magnesium) which can be removed from the wash water. In the past, tailoring builder materials to selectively sequester hardness ions was difficult or impossible. It is an object of this invention to provide a material that is more suitable as a detergent ingredient than previously suggested materials, and which can be made easily and efficiently. It is a further object of this invention to provide the chemistry and the processing necessary to tailor the detergent builder and ion sequestering properties of these crystalline sodium/potassium silicate materials. SUMMARY OF THE INVENTION The present invention pertains to a crystalline silicate material containing both sodium and potassium cations within the crystalline matrix. The composition of the material is Siθ2 / (xNa2θ + yK2θ) - Z where x + y « 1, 0.75 < x < 1.0 (and therefore 0.0 < y < 0.25), and 1.3 < Z < 3.22. The material possesses predetermined hardness ion sequestration properties determined by the composition and processing of the material. The material can be made by any one of several processes. The first process route includes the production of an amorphous Na/K silicate glass in a furnace using conventional means. This amorphous glass is then milled and optionally mixed with water. The mixture is calcined to produce the product of the present invention. The calcination is generally performed at temperatures- between about 500°C and 800°C, although calcination temperatures outside this range may be effective with specific formulations. Temperatures outside this range generally yield either an amorphous alkali silicate or undesirable crystalline alkali silicates. The material can then be milled to the appropriate particle size. In the second process, the amorphous Na/K silicate glass is dissolved in soft water and then spray dried to produce a hydrated Na/K silicate, followed by calcination to produce the product of the present invention. The third process involves the production of a sodium silicate glass by conventional means. This glass is then milled and mixed with water and a suitable potassium compound such as potassium hydroxide. This mixture is calcined to produce the product of the present invention. In each process, product can be recycled into the calciner to seed the formation of the desired product. The resulting material has a structure unlike prior art alkali silicates, as shown by X-ray diffraction. The different processes, when operated with different ratios of starting materials, produce materials with differing properties and differing abilities to sequester magnesium and calcium ions in solution. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed toward the production of crystalline layered silicates having a particular crystal structure effective in the sequestration of hardness ions from solution. The silicates are designed to sequester ions specifically in conjunction with laundry detergents in the laundry wash water. The silicates are alkali oxide silicates including both sodium and potassium oxides. The sodium/potassium silicates of the present invention have a unique crystal structure, as evidenced by a unique X-ray diffraction pattern. The silicates generally have superior hardness ion sequestration properties as compared to prior art crystalline layered sodium silicates. Furthermore, the sodium/potassium silicates of the present invention are cheaper and easier to produce than certain prior art crystalline sodium silicates. Crystalline sodium silicates and sodium/potassium silicates can be produced having different crystal structures (or phases) for the same chemical composition. The crystal phase of the crystalline silicate depends on the method used to produce it, along with any subsequent treatment. Particularly, sodium disilicates can be produced in either the alpha or delta phases. Generally, the delta phase is preferred for detergent formulations due to its increased hardness ion sequestration abilities. Similarly, the preferred form of sodium/potassium silicate is a crystal phase which was heretofore unknown. That crystal phase has been named DB-1. The presence of this unique phase was determined by X-ray diffraction. The d-spacings of alpha phase sodium disilicate, delta phase sodium disilicate, and DB- 1 phase sodium/potassium disilicate as determined by X- ray diffraction will be set forth in conjunction with the examples hereto, specifically in Table 3. The term "disilicate" indicates that the Siθ2:Na2θ ratio (or Siθ2:(Na2θ + 2O) ratio) is 2.0. Similarly, the term "polysilicate" refers to a polymer of silicon dioxide and alkali oxide in any proportions. Since both alpha and delta phase silicates are crystalline materials, their compositions are fixed. Particularly, alpha, delta, and DB-1 phase silicates are disilicates. The DB-l phase crystalline sodium/potassium silicates produced by the present invention are useful as detergent builders due to their hardness ion sequestering properties. The silicates can be used alone as a builder in detergents or in conjunction with other hardness ion sequestering detergent builders as well as other commonly used detergent ingredients (in which case, each is a co- builder) . Other detergent builders include anionic, non- ionic and zwiterionic materials. Co-builders such as crystalline alumino silicates, including clays, zeolites, such as Zeolite NaA and Zeolite MAP (maximum aluminum NaP phase), organic sequesterants, and condensed polyphosphates are also compatible with the material of the present invention, as are other conventional detergent ingredients. Zeolites are particularly preferred as co-builders for use with the DB-1 sodium/potassium silicates of the present invention. Spray drying, agglomeration and dry blending methods can be utilized to form stable and efficient detergents containing the products of the present invention. Conventionally, alpha phase sodium disilicate has been produced by heating a mixture of ground sodium silicate glass and water to about 700°C to 800°C. However, to produce the desired delta phase, a sodium silicate and water solution must be used as the starting material. The solution is spray dried to produce a hydrous sodium polysilicate. This material is then crushed and calcined at about 700°C to produce delta phase sodium disilicate. If the starting material for the alpha or delta phase disilicates has a silica:soda (Siθ2:Na2θ) ratio other than 2.0, some material will remain in an amorphous state. Similarly, if the starting material for the DB-l phase disilicate has a silica:alkali oxide ratio other than 2.0, some material will remain in an amorphous state. The crystalline layered sodium/potassium silicates of the present invention can be produced by any of three processes. The first process is similar to the process for producing the unpreferred alpha phase disilicate. A glass of sodium and potassium silicate is first produced by any conventional means. As used herein, the term "glass" refers to an amorphous silicate. The glass should have a composition of ZSiθ2: (xNa2θ + y 2θ) where 1.3 < Z < 3.22, 0.75 < x < 1.0, and x + y - 1.0, making 0.0 < y < 0.25. A preferred composition is 2.0 SiO 2 :(0.90 Na 0 + 0.10 K 2 0) . The glass is cooled and ground. The ground sodium/potassium silicate glass may be mixed with soft water in an amount up to about 25% of the weight of the glass. As referred to herein, the term "soft water" refers to water which is substantially free of hardness ions. Such water may be obtained through distillation, ion exchange, or other standard purification method. The mixture, or the glass alone, is heated (calcined) to between 500°C and 800°C, preferably between 700 β C and 770°C for a sufficient time to form DB-l phase silicate. Without seeding the mixture, calcination should take place for at least about one hour. This time can be reduced to below fifteen minutes by adding about 10% seed to the mixture before calcination. Generally, the resulting DB-l phase silicate is milled to produce particles of below 50 microns in size for use in detergent formulations. Since the addition of seed for calcination is commonly accomplished by recycle of the finished product, such addition reduces the amount of new material in the calciner. This reduces the production rate. However, this is balanced by a shorter residence time in the calciner, which increases production. These two competing effects can be optimized to achieve maximum production rate under the particular process conditions chosen. The DB-l material resulting from this process should have a silica:alkali oxide ratio of 2.0. If the silica:alkali oxide ratio of the starting material is anything other than 2.0, the resulting material will include amorphous silicate along with crystalline DB-l phase silicate. The material used as a seed should have the crystal phase desired to be formed from the • starting material. Preferably the seed would also have the same composition as the starting material. Since the seed in the present application is normally taken as recycle from the product stream, the seed may include both crystalline and amorphous material, but should have the same overall composition as the starting material. The second process for the production of the DB-l silicates of the present invention is similar to the process for producing delta phase disilicate. A glass of sodium and potassium silicate is first produced by any conventional means. Generally, this is accomplished by introducing pot ash (potassium carbonate) , soda ash (sodium carbonate) , and sand (silicon dioxide) into a furnace and heating to between 1100°C and 1300°C until a uniform fused melt is produced. The proportions of pot ash, soda ash, and sand introduced should be calculated to produce a glass having the composition set forth above. The glass from the furnace is cooled and dissolved in soft water. The resulting solution is spray dried to produce a hydrous sodium/potassium polysilicate. The concentration of glass in water should therefore be chosen to produce a material which can be easily spray dried. The spray dried hydrous sodium/potassium polysilicate is calcined as set forth by the first process, to produce a DB-l phase disilicate of the present invention. The third process for the production of the DB- 1 silicates of the present invention has previously been unknown. First, a sodium silicate glass is produced by any conventional method. The glass is milled and mixed with water and a potassium source. Generally, any potassium source such as a potassium halide, potassium nitrate, etc. can be used. However, potassium hydroxide is preferred as the potassium source. The proportions of sodium silicate glass and potassium hydroxide are selected to produce a mixture having the desired composition of the final product, as set forth above, since the addition of potassium to the sodium silicate glass adds alkali to the system, if a disilicate material is desired, the starting silica to soda ratio of the sodium silicate glass should be somewhat greater than 2.0. Ten molar KOH solution can be added in an amount up to 25% of the weight of the sodium silicate glass to produce a DB-l silicate having desirable hardness ion sequestration properties. Once the sodium silicate glass has been mixed with the potassium source and water, the mixture is calcined as set forth above, to produce the DB-l phase silicate of the present invention. The following examples illustrate the methods of producing the DB-l phase sodium/potassium silicates of the present invention. The examples are not intended to limit the scope of the invention in any way, but rather to illustrate the different methods of producing the DB-l phase silicate of the present invention and the effect of the different methods of production and materials used on the properties of the final product. EXAMPLES The proportions for all examples are in parts by weight (pbw) , percent weight (%) , parts per million (ppm) , moles or equivalents unless otherwise indicated. The notation, DI -water, refers to double distilled water . The calcium and magnesium ion exchange rates and capacities were determined for various products and are reported as the calcium exchange rate (CER) , calcium exchange capacity (CEC) , magnesium exchange rate (MgER) , and magnesium exchange capacity (MgEC) . The results shown in the tables are expressed as milligrams (mg) of CaCθ3 per gram (g) of anhydrous product for both calcium and magnesium. For brevity, the calcium and magnesium exchange capacities of the products of this invention, as described in the disclosure and recited in the claims, can also be (and frequently are) expressed in units of milliequivalents of Ca (or Mg) per gram of anhydrous product. The calcium and magnesium performance (CER, CEC, MgER, and MgEC) were determined as follows. The product (0.5 grams on an anhydrous basis) was reacted with 250 milliliters (ml) of a solution containing either calcium or magnesium ions. The concentration of these solutions was 1000 ppm expressed as CaCθ3. The stirred reaction mixture was buffered at a pH of 10 with 2 to 3 ml of a solution of NH 4 CI and NH4OH. The temperature was held at 25°C unless otherwise noted during the exchange reaction. An aliquot (15 ml) was removed after 2 minutes to determine the calcium and magnesium exchange rates (CER and MgER) by pulling the suspension through a 1.0 micron filter into a syringe. A second aliquot was removed at 15 minutes to determine the calcium and magnesium exchange capacities (CEC and MgEC) . The filtrates from the calcium exchange reaction were analyzed for calcium in solution as follows. A 5 ml aliquot of filtrate was combined with 5 ml of 1 molar NaOH and about 100 milligrams of Hydroxy Naphthol Blue indicator. A titration to a definite blue endpoint was carried out with 0.005 molar ethylene diaminetetracetic acid (EDTA) and the volume of EDTA recorded. A blank titration using 5 ml of the 1000 ppm CaCθ3 solution was carried out using the same method and the volume of EDTA recorded. Filtrates from the magnesium exchange reaction were analyzed in the same manner except that 5 ml of an NH4OH/NH4CI buffer and about 100 mg of Erichrome Black T (3-hydroxy-4- [ (1- hydroxy-2-naphthalenyl)azo] -7-nitro-l-naphthalenesulfonic acid monosodium salt, available from Sigma Chemical Co. of St. Louis, Mo.) were used. The rates and capacities for calcium and magnesium ions removed by the product were calculated as mg of CaC03/g of anhydrous product as follows: milligrams CaC0 3 . (B-V) -M-FW-50 gram anhydrous [ (100-LOI)/100] *W product where: B = volume of EDTA for blank titration (ml) V « volume of EDTA for sample titration (ml) M = Molarity of EDTA solution FW = Formula Weight of CaCθ3 (100.1 g/mole) LOI - Loss on Ignition of product at 800°C (%) W = Weight of product (grams) Phase identification of the examples was determined using standard x-ray diffraction techniques. A 5-50 two-theta scan was used. To determine precise d- spacings, physical mixtures of a mica standard from the National Bureau of Standards and Testing and products synthesized according to the processes disclosed in this patent were used. Unit cell parameters were determined using a least squares analysis program from the National Bureau of Standards and Testing. The standard parameters for examples 1-46 are as follows: 20 weight % DI -water; 80 weight % alkali silicate ground glass wherein the alkali is 90 mole % sodium oxide and 10 mole % potassium oxide and the silica:alkali oxide molar ratio is 2.0; calcined at 700°C for 1 hour with no seed. For experimental purposes, each parameter was varied while keeping the others constant to determine the effect of a change in any single parameter. Headings for each set of experiments indicate which parameters were varied for that set of experiments, as do the headings for tables. All unspecified parameters for each set of examples have the values set forth above. Examples 1-4: No water, varying proportions of sodium and potassium. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2:(xNa2θ + yK2θ) where Z « 2.0, 1 > x > 0.75, and x + y ■ 1, (and therefore, 0 < y < 0.25) . Specifically, the following compositions were made: 2Siθ2:Na2θ (comparative example) , 2Siθ2:(0.95 Na2θ + 0.05 K2O) , 2Siθ2: (0.90 Na2θ + 0.10 K 0) , and 2Siθ2:(0.80 N 2θ + 0.20 K2O) . Material having the composition 2Siθ2 (0.75 Na2θ + 0.25 2O) was also made, but was not tested. It was therefore excluded from Table 1. The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica at between 1100°C to 1300°C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. The ground amorphous sodium/potassium glass was heated to 700°C at a heating rate of 5 β C/minute and held at this temperature for 1 hour. The resulting product was ball milled to produce particles of less than 50 micron diameter. The crystalline silicate phases present in the products as identified by x-ray diffraction is shown in Table 1. The hardness ion binding performance results for the crystalline sodium/potassium silicates are also shown in Table 1. As can be seen from Table 1, the DB-l crystalline silicate is preferentially produced as the proportion of potassium increases in the amorphous sodium/potassium glass. In Table 1, as well as all other tables herein, where x-ray analysis indicates that more than one crystalline phase is present, the predominant phase is listed first. Thus "alpha & DB-l" indicates that alpha phase disilicate predominates, whereas "DB-l & alpha" indicates that the DB-l phase predominates. Table 1 Crystalline products from silicate having varying proportions of potassium and sodium, with no water Examples 5a-9: Varying proportions of sodium and potassium. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2: (xNa2θ + yK2θ) where Z « 2.0, l > x > 0.75, and x + y ■ 1, (and therefore, 0 < y < 0.25). The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300 β C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of 8 pbw of the ground amorphous sodium/potassium glass and 2 pbw of DI 2 -water was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for 1 hour. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. The crystalline sodium/potassium silicate phases present in the products as identified by x-ray diffraction are shown in Table 2. The d-spacings for crystalline materials are shown in Table 3. Example 5a is alpha phase sodium disilicate and was produced according to the process set forth above. Example 7 is DB-phase sodium/potassium disilicate. Example 5d is delta-phase sodium disilicate and was produced according to the following process. A spray dried sodium silicate having 2 moles of Si0 2 for each mole of Na 2 0 and 18% water was heated to 700°C for 1 hour. The crystalline mass was pulverized by ball milling. The product was identified by X-ray diffraction as delta-phase sodium disilicate. The unit cell parameters of the various crystalline silicates, examples 5a-9, as determined by X-ray diffraction are shown in Table 4. The hardness ion binding performance results for DB-l silicates are shown in Table 2. As the concentration of potassium increases, the DB-l silicate is observed to be preferentially synthesized from the amorphous sodium/potassium glass/ water mixture. A highly crystalline DB-l silicate was produced by heating amorphous sodium/potassium glass having a Si0 2 / (0.9Na 2 O + 0.1KO) - 2 mole ratio composition at 700°C, as shown in example 3. The crystallization of a DB-l silicate from an amorphous sodium/potassium glass and water mixture at 700°C, as shown in example 7, had superior hardness ion binding properties when compared to the DB-l silicate crystallized from an amorphous sodium/ potassium glass at 700°C shown in example 3. The CER and CEC improved by 275% and 29%, respectively, and the MgER and MgEC improved by 11% and 25%, respectively. Table 2 Crystalline products from silicate having varying proportions of potassium and sodium Example SiO2/(xNa2O+yK_2O) = 2.0 CER CEC MgER MgEC X-ray No. Analysis 55 103 111 184 Alpha 105 270 110 300 Delta 209 239 326 400 DB-l & Alpha 240 285 330 405 DB-l 187 247 283 357 DB-l t 72 97 o 270 369 Phase Unknown Table 3 d-spacings of examples 5a, 5d, and 7 [Siθ2/(xNa2θ+yK_2θ) = 2] t-o Table 4 Unit cell parameters for examples 5-9 Examples 10-12: Varying silicate to alkali oxide ratios. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiC>2:(xNa2θ + VK2O) where 1.7.> Z > 3.22, x •= 0.90, and x + y « 1, (and therefore, y - 0.10) . The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300 β C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of 8 pbw of the ground amorphous sodium/potassium glass and 2 pbw of DI 2 -water was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for 1 hour. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. The crystalline sodium/potassium silicate phases present in the products as identified by x-ray diffraction are shown in Table 5. Table 5 also shows the hardness ion binding performance results for these DB-l silicates including the DB-l silicate produced in example 7. The material from example 7 had the highest hardness ion binding performance, based on calcium ion binding. The unit cell parameters of these various DB-l silicates, examples 7 and 10-12, as determined by x-ray diffraction are shown in Table 6. Table 5 Crystalline products from silicate having varying ratios of silica to alkali oxide = Z Am. denotes amoφhous material isj Table 6 Unit cell parameters for examples 5, 7, and 10-12 Examples 13-21: Varying proportions of sodium and potassium and varying calcination temperatures. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2: (xNa2θ + yK2θ) where Z » 2.0, 1 > x .> 0.80, and x + y ■ 1, (and therefore, 0 < y <.0.20) . The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300 β C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of 8 pbw of the ground amorphous sodium/potassium glass and 2 pbw of DI 2 -water was heated to a temperature between 500 β C and 800°C, as set forth in Table 7, at a heating rate of 5°C/minute and held at this temperature for 1 hour. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. The crystalline sodium/potassium silicate phases present in the products as identified by x-ray diffraction are shown in Table 7. The hardness ion binding performance results for the DB-l silicates are also shown in Table 7. Generally, DB-l silicates prepared at 700°C, examples 7 and 8, were considered to be very crystalline and these products exhibited the highest hardness ion binding performances. The DB-l phase sodium/potassium crystalline silicates have considerably higher affinity to bind calcium and magnesium ions in solution when compared to pure sodium crystalline silicates. This was concluded by comparing examples 5a and 15 which are the pure alpha phase sodium crystalline silicates to examples 7, 8, and 18 which are the pure sodium/potassium crystalline silicates. Table 7 Crystalline products from silicate having varying proportions of sodium and potassium, calcined at various temperatures Examples 22-36: Varying proportions of sodium and potassium and varying calcination times. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2: (xNa2θ + yK2θ) where Z - 2.0, X «= 1.0, 0.90, and 0.80, and x + y = 1.0, (and therefore, Y = 0.20, 0.10, and'0.0). The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300°C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of 8 pbw of the ground amorphous sodium/potassium glass and 2 pbw of DI -water was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for a period of time as described in Table 8. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. The crystalline silicate phases present in the products as identified by x-ray diffraction are shown in Table 8. The hardness ion binding performance results for the DB-l silicates can also be found in Table 8. The results indicate that the crystallization time to synthesize the DB-l silicate does not significantly affect the hardness ion binding properties, or crystallize more undesirable sodium/potassium silicate phases. Table 8 Crystalline products from silicate having varying proportions of sodium and potassium, calcined for varying time periods. to Examples 37-39: Varying amounts of seed, no water. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2:(xNa2θ + yK2θ) where Z ■ 2.0, x ■= 0.90, and x + y « 1, (and therefore, y = 0.10). The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300°C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of ground amorphous sodium/potassium glass and DB-l silicate seed having a mole composition identical to that of the amorphous sodium/potassium glass, was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for 1 hour. The amount of seed added is shown in Table 9. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. A DB-l silicate phase was identified by x-ray diffraction. The hardness ion binding performance results for the DB-l silicates are shown in Table 9. Crystallization of the amorphous sodium/potassium glass in the presence of a DB-l silicate seed increased the hardness ion binding performance compared to crystallization with no seed. Comparing example 3 (no seed) to example 39 (10% seed) , it may be seen that the addition of 10% seed during calcination increased the CER and CEC by 252% and 20%, respectively, and increased the MgER and MgEC by 24% and 30%, respectively. Table 9 Crystalline products from silicate with no water and having various amounts of seed Example 40-42: Varying amounts of seed. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2:(xNa2θ + yK2θ) where Z = 2.0, x « 0.90, and x + y « 1, (and therefore, y = 0.10). The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300°C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of 8 pbw of the ground amorphous sodium/potassium glass, 2 pbw of DI -water, and a DB-l silicate seed having a mole composition identical to that of the amorphous sodium/potassium glass, was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for 1 hour. The amount of seed added is shown in Table 10. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. A DB-l silicate phase was identified by x-ray diffraction. The hardness ion binding performance results for the DB-l silicates are shown in Table 10. The use of DB-l seed during calcination of the amorphous sodium/potassium glass and water mixture appeared to have negligible effect on the hardness ion binding properties of the resulting material. Table 10 Crystalline products from silicate having varying amounts of seed. Examples 43-46: Varying calcination times in the presence of 10 weight % seed. Preparation of DB-l silicates according to the process of the present invention began with the preparation of an amorphous sodium/potassium silicate glass. The glass had a composition of ZSiθ2:( Na2θ + yK2θ) where Z - 2.0, x « 0.90, and x + y = 1, (and therefore, y = 0.10) . The glass was formed by the fusion of a sodium carbonate, potassium carbonate, and silica between 1100°C to 1300°C followed by rapid cooling of the molten sodium/potassium glass in an ice bath. The cool amorphous sodium/potassium glass was ball milled to produce particles of less than 200 microns. A mixture of 8 pbw of ground amorphous sodium/potassium glass, 2 pbw of DI -water, and 10 weight percent of DB-l silicate seed having a mole composition identical to that of the amorphous sodium/potassium glass was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for a period of time as described in Table 11. The resulting material was cooled and ball milled to produce particles of less than 50 microns diameter. A DB-l silicate phase was identified by x-ray diffraction. The hardness ion binding performance results for DB-l silicates are shown in Table 11. Excellent hardness ion binding performances were observed when an amorphous sodium/potassium glass was calcined in the presence of 10% DB-l seed for 15 minutes or more. No data for calcination times shorter than 15 minutes was collected. Accordingly, shorter times may also result in effective calcination when using seed. Table 11 Crystalline products from silicate with varying calcination times and 10% seed SECOND PROCESS Examples 47 and 48 demonstrate the production of sodium/potassium silicates in accordance with the second process of the present invention. In this process, amorphous Na/K silicate glass is dissolved and spray dried to produce a hydrous sodium/potassium polysilicate. The hydrated silicate is then calcined to produce the product of the present invention. Example 47: Hydrous polysilicate having 16% to 22% water content, calcined for 3 hours. Preparation of DB-l silicates according to the process of the present invention was accomplished by heating an amorphous hydrous sodium/potassium polysilicate having a composition of 2.0 Siθ2 (0.90 Na2θ + 0.10 K2O) and a water content between 16 to 22%. The mixture was heated to 700°C at a 5°C/minute and held at this temperature for 3 hours. The cool crystalline sodium/potassium silicate was ball milled to produce particles of less than 50 microns. A DB-l silcate phase was identified by x-ray diffraction. The hardness ion binding performance results for the crystalline sodium/potassium silicates are shown in Table 12. Example 48: Liquid sodium/potassium silicate having 60% to 70% water content and no added water, calcined for 3 hours. Preparation of DB-l silicates according to the process of the present invention was accomplished by heating an amorphous hydrous sodium/potassium polysilicate having a composition of 2.0 Siθ2/(0.90 Na2θ + 0.10 2O) and a water content between 60% to 70%. The mixture was heated to 700 β C at a 2°C/minute and held at this temperature for 3 hours. The crystalline sodium/potassium silicate was cooled and ball milled to produce particles of less than 50 microns. A DB-l phase was identified by x-ray diffraction. The hardness ion binding performance results for the DB-l silicates are shown in Table 12. Table 12 Crystalline product from silicates having a variable water content, calcined for 3 hours _£*. ■ fc*. THIRD PROCESS Examples 49 to 75 show the production of the crystalline silicate material of the present invention by the third process of the present invention. In the third process, conventional sodium silicate glass is milled and mixed with a potassium source, such as potassium hydroxide, and water. Other potassium sources (such as a potassium halide or potassium peroxide) may also be used. The mixture is then calcined to produce the crystalline product of the present invention. Comparative Examples 49-56: Preparation of sodium silicate by treatment of silicate with NaOΞ, no potassium present. Preparation of a crystalline sodium silicate was accomplished by heating a mixture of a ground glass having a Siθ2/Na2θ mole ratio of 2.0 with 10 molar NaOH solution and DI 2 -water in various weight ratios as set forth in Table 13. The mixture was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for 1 hour. The cooled crystalline sodium silicate was ball milled to produce particles of less than 50 microns. The crystalline sodium silicate phases present in the products as identified by x-ray diffraction are shown in Table 13. The hardness ion binding performance results for the crystalline sodium silicates are also shown in Table 13. Decreasing the Siθ2/Na2θ ratio of the ground amorphous sodium silicate glass by the addition of NaOH to the ground glass had a negligible effect in preferentially synthesizing the delta phase crystalline silicate instead of the alpha phase sodium crystalline silicate. Table 13 Comparative examples of crystalline products from silicate treated with varying amounts of 10M NaOH and DI -water and calcined. Exam le 57-68: Varying ratios of 10M KOH and water. Preparation of DB-l silicates according to the process of the present invention was accomplished by heating a mixture of a ground glass having a Siθ2/Na2θ mole ratio of 2.0 with 10 molar KOH solution and DI - water in various weight ratios as described in Table 14. The mixture was heated to 700°C at a rate of 5°C/minute and held at this temperature for 1 hour. The cooled crystalline sodium/potassium silicate was ball milled to produce particles of less than 50 microns. The crystalline silicate phases present in the products as identified by x-ray diffraction are shown in Table 14. The hardness ion binding performance results for the DB-l silicates are also shown in Table 14. The unit cell parameters for the DB-l silicates shown in Table 14 are consistent with example 3. The presence of potassium during the crystallization of the amorphous sodium silicate/water mixture resulted in alpha phase and/or DB-l phase silicates to be crystallized. As the potassium concentration increased, the desired DB-l phase crystalline silicates were preferentially produced. Even adding as much as 20 grams 10M KOH resulted in the formation of DB-l phase silicate. At 20 grams 10M KOH, the Siθ2: (Na2θ + K2O) ratio will change significantly from the initial 2.0 value. The initial 80 grams 2.0 Siθ2:Na2θ should have about .44 moles Na2θ and .88 moles Siθ2« The addition of 20 grams of 10M KOH should add 0.20 moles 2O, making a total of .64 moles alkali oxide. The Siθ2: (Na2θ + yK2θ) ratio then becomes .88:.64 or 1.375. Thus even Siθ2 (Na2θ + yK2θ) ratios as low as 1.375 yield DB-l phase silicate. Table 14 Crystalline products from mixtures with varying proportions of sodium silicate, potassium hydroxide, and water Examples 69-72: Varying calcination times Preparation of DB-l silicates according to the process of the present invention was accomplished by heating a mixture of 80 weight % of ground glass having a Siθ2/Na2θ mole ratio of 2.0, 11 weight % of 10 molar KOH solution, and 9 weight % of DI -water. The mixture was heated to 700°C at a heating rate of 5°C/minute and held at this temperature for a period of time as described in Table 15. The cooled DB-l silicate was ball milled to produce particles of less than 50 microns. The crystalline silicate phases present in the products as identified by x-ray diffraction are shown in Table 15. The hardness ion binding performance results for the DB-l silicates are also shown in Table 15. The results show that the crystallization time of an 80 weight % ground glass/11 weight % KOH/9 weight % DI 2 - water mixture had negligible effect on the hardness ion binding performance. For long crystallization times, i.e. greater than 6 hours, no additional phases are crystallized, and no decrease in the hardness ion binding properties are observed. Table 15 Crystalline products from mixtures of sodium silicate, potassium hydroxide, and water with various calcination time. CER CEC MgER MgEC X-ray Analysis 255 305 400 440 DB-l 245 299 406 426 DB-l 240 290 397 427 DB-l 245 295 395 425 DB-l 230 290 388 433 DB-l Examples 73-75: Varying calcination temperatures. Preparation of DB-l silicates according to the process of the present invention was accomplished by heating a mixture of 80 pbw of ground glass having a Siθ2/Na2θ mole ratio of 2.0, 11 pbw of 10 molar KOH solution, and 9 pbw of DI 2 -water. The mixture was heated to a temperature between 500 β C and 800°C as described in Table 16, at a heating rate of 5°C/minute and held at that temperature for 3 hours. The cooled DB-l silicate was ball milled to produce particles of less than 50 microns. The crystalline silicate phases present in the products as identified by x-ray diffraction are shown in Table 16. The hardness ion binding performance results for the DB-l crystalline sodium/potassium silicates are shown in Table 16. Excellent hardness ion binding performances were obtained when the crystallization temperature was around 700 β C. Table 16 Crystalline products from mixtures of sodium silicate, 10M KOH, and DI -water with varying calcination temperatures

Claims: What is Claimed: 1. A process for the production of a crystalline sodium/potassium silicate comprising: producing a sodium/potassium glass having a composition of ZSiθ2:(xNa2θ + yK2θ) where 1.3 < Z <.3.22, 1 > x > 0.75, 0 < y < 0.25, and x + y « 1; and calcining said glass at a temperature between 500°C and 800 β C for at least one hour to produce a crystalline silicate. 2. The process of claim l wherein said step of producing a sodium/potassium glass comprises fusing sodium carbonate, potassium carbonate, and silica at a temperature between 1100°C and 1300°C. 3. The process of claim 2 including the further step of milling said crystalline silicate sufficient to produce particles of 50 microns or smaller in size. 4. The process of claim l further including the step of mixing said glass with water in an amount of up to 25 % of the weight of said glass, prior to said step of calcining. 5. The process of claim 4 including the further step of milling said crystalline silicate sufficient to produce particles of 50 microns or smaller in size. 6. The process of claim 4 wherein said step of calcining includes the further step of adding crystalline sodium/potassium silicate seed to said glass prior to calcining. 7. The process of claim 6 wherein said seed has the same composition as said glass. 8. The process of claim 1 wherein said step of calcining includes the further step of adding crystalline sodium/potassium silicate seed to said glass prior to calcining. 9. The process of claim 8 wherein said seed has the same composition as said glass. 10. A process for the production of a crystalline sodium/potassium silicate comprising: producing a sodium/potassium silicate glass having a composition of ZSiθ2: (xNa2θ + yK2θ) where 1.3 <. Z < 3.22, l > x > 0.75, 0 < y < 0.25, and x + y = 1; dissolving said glass in water to produce a liquid sodium/potassium silicate; spray drying said liquid sodium/potassium silicate to produce a hydrous sodium/potassium polysilicate; and calcining said hydrous sodium/potassium polysilicate at a temperature between 500°C and 800°C to produce a crystalline silicate. 11. The process of claim 10 wherein said step of producing a sodium/potassium glass comprises fusing sodium carbonate, potassium carbonate and silica at a temperature between 1100°C and 1300 β C. - ° 12. The process of claim 11 including the further step of milling said crystalline silicate sufficient to produce particles of 50 microns or smaller in size. 13. The process of claim 10 wherein said step of calcining includes the further step of adding crystalline sodium/potassium silicate seed to said hydrous polysilicate prior to calcining. 14. The process of claim 13 wherein said seed has the same composition as said hydrous polysilicate. 15. A process for the production of a crystalline sodium/potassium silicate comprising: producing an amorphous sodium silicate glass having a composition of ZSiθ2 Na2θ where 1.7 > Z >.3.22; mixing said glass with a potassium hydroxide and water solution to form a mixture; and calcining said mixture at a temperature between 500°C and 800°C for at least one hour. 16. The process of claim 15 wherein said step of producing a sodium silicate glass comprises fusing sodium carbonate, and silica at a temperature between 1100°C and 1300 β C. 17. The process of claim 16 including the further step of milling said crystalline silicate sufficient to produce particles of 50 microns or smaller in size. 18. The process of claim 15 wherein said step of calcining includes the further step of adding crystalline sodium/potassium silicate seed to said glass prior to calcining. 19. The process of claim 18 wherein the composition of said seed is chosen to approximate the composition of the final crystallized silicate. 20. The process of claim 15 wherein Z-2.0. 21. The crystalline phase sodium/potassium silicate produced by the process of claim 1. 22 The crystalline phase sodium/potassium silicate of claim 21 wherein said silicate has a hardness binding capacity of up to 5.8 meq Ca 2+ per gram anhydrous product and up to 8.9 meq Mg 2+ per gram anhydrous product. 23. The crystalline phase sodium/potassium silicate produced by the process of claim 10. 24 The crystalline phase sodium/potassium silicate of claim 23 wherein said silicate has a hardness binding capacity of up to 5.9 meq Ca 2+ per gram anhydrous product and up to 8.5 meq Mg 2+ per gram anhydrous product. 25. The crystalline phase sodium/potassium silicate produced by the process of claim 15. 26 The crystalline phase sodium/potassium silicate of claim 25 wherein said silicate has a hardness binding capacity of up to 6.1 meq Ca 2+ per gram anhydrous product and up to 9.0 meq Mg 2+ per gram anhydrous product. 27. A detergent builder comprising a crystalline DB-l phase sodium/potassium silicate. 28. The detergent builder of claim 27 wherein said crystalline phase sodium/potassium silicate has a composition of ZSiθ2: ( N 2θ + y 2θ) where 1.7 < Z <.3.22, l > x > 0.75, 0 < y < 0.25, and x + y = i. 29. The detergent builder of claim 28 wherein said crystalline phase sodium/potassium silicate has a hardness binding capacity of up to 6.1 meq Ca per gram anhydrous product and up to 9.0 meq Mg 2+ per gram anhydrous product. 30. A cleaning composition containing effective amounts of surfactant and a builder wherein said builder comprises a DB-l crystalline phase sodium/potassium silicate. 31. The cleaning composition of claim 30 further including 5% to 95% by weight of a co-builder. 32. The cleaning composition of claim 31, wherein said co-builder is a zeolite. 33. The cleaning composition of claim 30 wherein said DB-l crystalline phase sodium/potassium silicate has a hardness binding capacity of up to 6.1 meq C Caa 22++ ppeerr ggrraamm aannhhyyddrroouuss pprroo<duct and up to 9.0 meq Mg per gram anhydrous product. 34. A cleaning composition containing effective amounts of surfactant and a builder wherein said builder comprises a DB-l crystalline phase sodium/potassium silicate which is the product of the process of claim 1. 35. The cleaning composition of claim 34 wherein said DB-l crystalline phase sodium/potassium silicate has a hardness binding capacity of up to 5.8 meq Ca 2+ per gram anhydrous product and up to 8.9 meq Mg 2+ per gram anhydrous product. 36. A cleaning composition containing effective amounts of surfactant and a builder wherein said builder comprises a DB-l crystalline phase sodium/potassium silicate which is the product of the process of claim 10. 37. The cleaning composition of claim 36 wherein said DB-l crystalline phase sodium/potassium silicate has a hardness binding capacity of up to 5.9 meq Ca 2+ per gram anhydrous product and up to 8.5 meq Mg 2+ per gram anhydrous product. 38. A cleaning composition containing effective amounts of surfactant and a builder wherein said builder comprises a DB-l crystalline phase sodium/potassium silicate which is the product of the process of claim 15. 39. The cleaning composition of claim 38 wherein said DB-l crystalline phase sodium/potassium silicate has a hardness binding capacity of up to 6.1 meq Ca 2+ per gram anhydrous product and up to 9.0 meq Mg per gram anhydrous product.

Inventors: BORGSTEDT ERIC VON REHREN, DENKEWICZ RAYMOND P JR, DENKEWICZ, RAYMOND, P., JR., VON REHREN BORGSTEDT, ERIC
Applicants: PQ CORP, PQ CORPORATION
Application year: 1995
Main classification: C11D3
IPC codes: B01J20, C01B33, C11D3, C11D7