LIQUID BUFFER SYSTEMS

Abstract: A liquid buffer composition comprises either or both of monsodium phosphate, in a concentration of 13-40 percent by weight, and tripotassium phosphate, in a concentration of 20-50 percent by weight, in aqueous solution. Combination of these two ingredients provides liquid buffer mixes for use in place of solid phosphate buffers.

Description: This invention relates to the use of liquid ingredients to provide a pH setting and/or buffering system which is beneficial to the preparation, treating, dyeing, printing and finishing of textile materials, such as fibre, yarn, fabric and carpet. The invention also has utility in non-textile industrial operations where processing in water systems occurs, as a replacement and improvement for solid phosphate pH setting and/or buffer ingredients. For proper treatment in the dyeing and finishing of textile materials, it is the practice to select a pH range which is best suited to the particular operation. These operations can be carried out in water at various temperatures or by the application of water-suspended or dissolved ingredients directly on to the material pH is a term used to express a measure of acidity or alkalinity. The pH in these operations can fluctuate widely and, if not controlled, can cause erratic results. In order to control pH fluctuation, chemicals are added to the liquid treating bath. Such chemicals are used to set or control pH fluctuations and are called "buffers". The preparation, treating, dyeing, printing and finishing of textile material, such as fibre, yarn, fabric and carpet, involve placing the textile material in a vessel containing water and various compounds dispersed, dissolved, emulsified or suspended in the water, for the purpose of creating the desired effects on the textile material. This water-based mixture is called the bath. The specific process may require a short term immersion in the bath, such as a padding operation in the finishing or preparation area. In this case, the material is run continuously through a trough containing the bath with a dwell time of only a few seconds. The material is then often squeezed dry by means of nip rolls. In other cases, the material is left immersed in the bath for long periods of time (up to 12 hours) to allow chemicals in the bath to act on the textile substrate. Various conditions of temperature, acidity, alkalinity, etc. may be used to produce the desired effects on the material. Some examples of typical chemicals which may be contained in a textile bath are listed below: Preparation : surfactants hydrogen peroxide sodium hydroxide silicates stabilizers pH neutralizers (buffers) Finishing : resin finishes hand builders softeners lubricants pH control agents (buffers) Printing : acrylic polymers thickeners pH control agents (buffers) dyestuffs or pigments surfactants oils softeners Dyeing : surfactants solvent swelling agents pH control agents (buffers) salt softeners lubricants dyestuffs thickeners defoamers Among the commonly used materials for buffering and/or setting pH are monosodium phosphate (MSP), disodium phosphate (DSP) and trisodium phosphate (TSP). These materials are solids and users face difficulties in measuring, handling and dissolving these materials. for example, these solid products are commonly packaged in 22.5 or 45 kg (50 or 100 pound) bags. These bags must be manually lifted and opened, a procedure which often results in strained muscles, spill waste from broken bags and poor control over material usage. These powders must then be diluted in a premixing tank before being fed into the textile processing equipment. This is a time-consuming operation and, unless those involved in the powder dilution are very conscientious, lumps of undissolved product may flow into the equipment or drain lines can become clogged with solid particles. These difficulties associated with the handling of solid phosphates - spillage, lost time from physical strain, disposal of empty bags, time spent in dividing operating difficulties because of incompletely dissolved solids - are of great concern and have been a long-standing problem in dyehouse operations. GB-A-1515103 discloses aqueous solutions of monosodium phosphate and, optionally, phosphoric acid, in the context of a process and apparatus for intermixing liquids. EP-A-0041240 discloses a dyeing agent containing a buffer which may comprise tripotassium phosphate. US-A-3058917 discloses a dishwashing agent containing an alkali metal hypochlorite, tripotassium orthophosphate, another phosphate or mixture of phosphates, a silicate and potassium hydroxide. US-A-415104 discloses a water-based bleaching composition containing sodium hypochlorite, an alkali metal orthophosphate buffer and an alkali metal pyrophosphate builder. It has been discovered that the above-noted prior art problems with respect to solid phosphate buffers can be eliminated by the use of liquid buffer ingredients which are easy to handle and measure and which mix readily with water. Three known liquid buffer compositions consists of (1) tripotassium phosphate, potassium hydroxide and water, (2) monosodium phosphate, phosphoric acid and water and (3) monosodium phosphate and water. The liquid buffer system of the present invention is designed to use a high pH liquid buffer ingredient, either alone or in combination with a low pH liquid buffer ingredient, which will provide a pH and buffering action in a preselected range, the desired preselected pH range being considered the optimum for the particular processing operation in question. The high pH liquid buffer ingredient performs in the range where solid TSP (trisodium phosphate) is used. By a combination of the high pH liquid ingredient and the low pH liquid ingredient, the pH range of DSP (disodium phosphate) can be covered. Thus the use of the high pH buffer ingredient and low pH buffer ingredient serves to cover the full range in which solid trisodium and disodium phosphate buffers are used. TSP is not soluble enough to be considered a suitable ingredient for a high pH liquid buffer ingredient, particularly for cold temperature storage. However, tripotassium phosphate, TPP, (also called "potassium phosphate, tribasic") has good solubility in water and is a suitable ingredient for a high pH liquid buffer ingredient. In carrying out the present invention, it is important to make the liquid buffer ingredients with high concentrations, in order to achieve product economy versus the solid phosphate buffer ingredients. The suitability of tripotassium phosphate as a high pH buffer ingredient, because of its high solubility in water, is critical to the practicality of the invention. High concentrations of a high pH liquid buffer ingredient would not be possible using TSP, the usual solid high pH buffer ingredient. According to one aspect of this invention, therefore, a composition is provided which is suitable for addition to a textile bath as a buffer for the control of pH and which comprises an alkali metal phosphate, characterised in that (a) the composition is in the form of a premixed high pH liquid which is usable alone and is therefore suitable for direct addition to a textile bath, (b) the composition consists essentially of an aqueous solution containing tripotassium phosphate, potassium hydroxide and sodium hydroxide, the remainder of the composition being water, and (c) the tripotassium phosphate and the potassium and sodium hydroxides are present in the following amounts in weight percent: tripotassium phosphate: 20 to 50 potassium hydroxide: 2.5 to 20 sodium hydroxide: 0.4 to 7 water: balance. The invention also resides in several method aspects, details of which are given below, and in several forms of liquid buffer composition, details of which are also given below. The liquid buffer compositions of the present invention can be formulated over wide ranges of concentration. For reasons of economy in preparation, storage and shipping, the concentration of the tripotassium phosphate is at least 20 and up to 50 percent by weight in water. The concentration of the monosodium phosphate, when used in combination with the buffer of the invention, is from 13 to 40 percent by weight in water. The liquid buffer ingredients can be constituted so as to provide for the formation of additional buffering chemicals in situ, by incorporating chemicals in the two liquid buffer ingredients which will react chemically on mixing to provide additional buffering material in solution. The high pH liquid buffer ingredient is formulated so as to contain free potassium hydroxide, in addition to the tripotassium phosphate. A small amount of sodium hydroxide is also added to enhance the temperature stability of the high pH liquid buffer ingredient. The low pH liquid buffer ingredient for use with the buffer of the invention is formulated so as to contain free phosphoric acid, in addition to the monosodium phosphate. When the high pH liquid buffer ingredient is mixed with the low pH liquid buffer ingredient, the free potassium hydroxide and free phosphoric acid preferably present react to form a potassium phosphate which is therefore a buffer formed in situ. This reinforces the buffering action of the tripotassium phosphate present in the high pH liquid buffer ingredient and the monosodium phosphate present in the low pH liquid buffer ingredient. The reaction of the free phosphoric acid and the free potassium hydroxide can be represented as an example by the following: KOH + H₃PO₄ ----> KH₂PO₄ + H₂O 2KOH + H₃PO₄ ----> K₂PHO₄ + 2H₂O 3KOH + H₃PO₄ ----> K₃PO₄ + 3H₂O Any free sodium hydroxide present would react in a similar way to form comparable sodium phosphates in addition to the potassium phosphates. The solid phosphates of the prior art give inferior buffering in the pH range from 8 to 10. When desired, the liquid buffer ingredients can be modified by the addition of borax and/or ethanolamines, to improve the buffering of the system in the pH range form 8 to 10. When used with the high pH buffer composition or ingredient, the concentration of borax pentahydrate should preferably be in the range from 4 to 10 percent by weight. The monoethanolamine, diethanolamine and/or triethanolamine, alone or in combination, should preferably be in the range from 4 to 8 percent by weight. The liquid buffers of the present invention are usually added in amounts in the range from 0.1 to 0.3 percent by weight of the dye bath. This range is on the "as-is" basis and is the combined total for the low pH and high pH liquid buffers. This range applies for dyes other than fibre-reactive dyes, where the liquid buffers are preferably added in the range from 0.25 to 1.5 percent by weight of the dye bath. The concentration of dyes in the dye bath usually ranges from 0.1 to 1 percent by weight. Salt usually ranges from 0 to 10 percent by weight. Levellers and surfactants customarily range from 0 to 0.3 percent. Sequestering agents usually range from 0 to 0.05 percent. All percentages are by weight of the dye bath. A typical method which may be used for making the low pH liquid buffer for use with the high pH liquid buffer is as follows: Add 55.0 parts of water to a mixer and stir. Then add 31.0 parts of sodium phosphate, monobasic (MSP) and stir until dissolved. Then add 14.0 parts of phosphoric acid. Stir until uniform and then transfer the material to a suitable container. The high pH buffer can be made as follows: Add 56.6 parts of water to a mixer and stir. Then add 31.6 parts of potassium phosphate tribasic (TKP) and stir to dissolve. Then add 7.9 parts of potassium hydroxide and stir to dissolve. Cool and transfer to a suitable container. The chemicals used are corrosive and should be handled with proper precautions and with proper safety equipment. Examples of seven buffer formulations, which have been found suitable for low pH liquid buffer ingredients and for high pH liquid buffer ingredients, are tabulated below in parts by weight, the final formulation being a formulation according to the present invention: 1. Low pH Liquid Buffer Ingredient sodium phosphate, monobasic 15.3 parts water 56.5 parts monoethanolamine 1.9 parts phosphoric acid 26.3 parts 2. Low pH Liquid Buffer Ingredient sodium phosphate, monobasic 31.0 parts phosphoric acid 14.0 parts water 55.0 parts 3. High pH Liquid Buffer Ingredient potassium phosphate, tribasic 42.9 parts water 57.1 parts 4. High pH Liquid Buffer Ingredient potassium phosphate, tribasic 30.1 parts borax pentahydrate 4.0 parts triethanolamine 7.1 parts water 58.8 parts 5. High pH Liquid Buffer Ingredient potassium phosphate, tribasic 21.4 parts potassium hydroxide 2.9 parts borax pentahydrate 8.4 parts triethanolamine 6.2 parts water 61.1 parts 6. High pH Liquid Buffer Ingredient, potassium phosphate, tribasic 29.2 parts potassium hydroxide 12.3 parts water 58.5 parts 7. High pH Liquid Buffer Ingredient potassium phosphate, tribasic 31.6 parts potassium hydroxide 7.9 parts sodium hydroxide 3.9 parts water 56.5 parts A high pH liquid buffer ingredient may be used alone with certain fibre-reactive dyes for the dyeing of rayon and cotton as a replacement for TSP (trisodium phosphate). In the reactive dyeing of cellulosic textile materials, an alkaline material is needed to provide conditions which promote formation of a chemical bond between the reactive dye and the cellulosic textile material. The firm chemical bond between the dye and the cellulosic textile material is responsible for the excellent wash fasteness produced on cellulosics with reactive dyes. The commonly used alkaline materials include sodium hydroxide, trisodium phosphate (TSP), sodium silicate, sodium carbonate and sodium bicarbonate. A high pH liquid buffer may be used as a replacement for the commonly used alkaline materials in the reactive dyeing of cellulosic textile materials (e.g. rayon, cotton, flax) and blends of cellulosic textile materials with other natural or synthetic textile materials. The high pH liquid buffer performs comparably with the commonly used alkaline materials in creating the necessary reaction conditions and in producing level full-shade dyeings. In addition, less of the high pH liquid buffer on a weight basis is needed to do the same job as the optimum amount of the commonly used alkaline material. The following example illustrates the use of a high pH liquid buffer in a reactive dyeing operation. EXAMPLE I Into a suitable dyeing beaker containing an agitator, 5 grams of bleached 100% cotton fabric are placed in a bath containing 125 ml of water, 6.25 grams of common salt and 0.2 gm Remazol Red 3FB dye (American Hoechst Company). The bath is stirred for 15 minutes, warmed to 40°C (104°F) and held for 15 minutes. Then 1.25 gm of high pH liquid buffer ingredient No. 6 are added to the bath. The bath is heated to 60°C (140°F) and held for one (1) hour and then allowed to cool to room temperature. The cotton is removed from the bath and washed thoroughly. The use of 1.25 gm of liquid buffer No. 6 in this procedure results in a dyeing of equal shade depth and fastness properties as compared with using 2.50 gm of TSP as the high pH buffer in the same procedure. The high pH liquid buffer ingredient and the low pH liquid buffer ingredient may be used together to set and hold a pH level between 5.0 and 9.0 for a dyeing operation. The following example illustrates an application of the two buffer ingredients in a typical dyeing operation. EXAMPLE II Into a suitable dyeing beaker containing an agitator, 10 grams of "Nylon 6" tufted carpet are placed in a bath containing 150 ml water, 0.1 gm of leveller (migrassist NEW) (Sybron Chemicals Inc.), 0.01 gm of Nylosan Red F2R (Sandoz Color & Chemical) (0) and 0.01 gm of low pH liquid buffer ingredient No. 1 plus 0.14 gm of high pH liquid buffer ingredient No. 5, to control the pH in the range from 8.3 to 8.6. The use of low pH liquid buffer ingredient No. 1 and high pH liquid buffer ingredient No. 5 in this manner produces a dyed carpet of similar colour yield and appearance to dyeings where MSP, TSP, diammonium phosphate, ammonium sulphate and other solid pH buffer ingredients are used, whether separately or in conjunction with another solid or liquid pH buffer ingredient, to influence dye bath pH. A high pH liquid buffer ingredient may be used to control the pH of a scouring bath used to remove waste and oils from fibre or fabric. The desired pH for this operation is 8-9.5. The following example illustrates this operation. EXAMPLE III Into a suitable dyeing beaker containing an agitator, 25 grams of 50% polyester, 50% cotton knit are placed in a bath of 500 ml of water. Then surfactant (Tanaterge WFF) (Sybron Chemicals, Inc.), and 0.15 gm of high pH liquid buffer ingredient No. 3 are added. The bath is then heated to 82.2°C (180°F) and held for 10 minutes. The cloth scoured by this procedure using high pH liquid buffer ingredient No. 3 to control pH is of comparable cleanliness, brightness and whiteness to cloth scoured in baths where solid phosphate pH control agents are used. A low pH liquid buffer ingredient may be used alone to set the final pH of a bleaching bath in the range from 6.0 to 8.0. The following example illustrates this operation: EXAMPLE IV Into a suitable dyeing beaker containing an agitator, 10 grams of cotton knit are placed in a bath of 200 ml water. Next are added 0.2 gm of a sequestering agent (Plexene 280) (Sybron Chemicals Inc.) and 1.2 gm of 35% hydrogen peroxide. The bath is heated to boil at 100°C (212°F) and held for one (1) hour. The bath is drained and the cotton washed with 200 ml of water and 0.2 gm of low pH liquid buffer ingredient No. 2. Then the cotton knit is washed again in 200 ml of water. Neutralizations carried out in this manner with low pH liquid buffer ingredient No. 2 produce comparable results and fabric to neutralizations done with acetic acid or with other solid phosphate pH buffer agents. The high pH buffer ingredient of the invention may be used in a wide variety of textile wet processing operations (bleaching, scouring, dyeing, printing or finishing) to neutralize the bath or the fabric. The high pH buffer ingredient is used to raise an existing low pH. One example of this type of use is to neutralize the fabric and dye bath of a polyester/cotton blend after dyeing with disperse dyes and before dyeing with direct dyes. In addition to the above applications of the present invention, the high pH liquid buffer ingredients find usage in a wide variety of industrial non-textile applications where processing in water systems occurs and setting and/or maintaining a desired pH is necessary. For example, solid buffer agents such as MSP or TSP are often used as ingredients in metal-working lubricants which are water-based. Low pH liquid buffer ingredients Nos. 1 and 2 and/or high pH liquid buffer ingredients Nos. 3 and 6 may be used as the pH controls in these systems and they produce comparable results when substituted for MSP or TSP. Solid buffer agents such as MSP or TSP are commonly used as pH control agents and/or buffers in the wet processing of wood pulp in the paper industry. Low pH liquid buffer ingredients Nos. 1 and 2 and/or high pH liquid buffer ingredients Nos. 3 and 6 may be used as the pH control agents and/or buffers in pulp processing and produce comparable results when substituted for MSP or TSP.

Claims: A composition which is suitable for addition to a textile bath as a buffer for the control of pH and which contains an alkali metal phosphate, characterised in that (a) the composition is in the form of a premixed high pH liquid which is usable alone and is therefore suitable for direct addition to a textile bath, (b) the composition consists essentially of an aqueous solution containing tripotassium phosphate, potassium hydroxide and sodium hydroxide, the remainder of the composition being water, and (c) the tripotassium phosphate and the potassium and sodium hydroxides are present in the following amounts in weight percent: tripotassium phosphate: 20 to 50 potassium hydroxide: 2.5 to 20 sodium hydroxide: 0.4 to 7 water: balance. A premixed liquid buffer composition according to claim 1, which also contains in solution, in replacement for some of the water, at least one of monoethanolamine, diethanolamine and triethanolamine. A premixed liquid buffer composition according to claim 2, which contains 4 to 8 percent by weight of monoethanolamine, diethanolamine or triethanolamine alone or in combination. A premixed liquid buffer composition according to any preceding claim, which contains 2 to 5 percent by weight of potassium hydroxide and which also contains in solution, in replacement for some of the water, 4 to 9 percent by weight of borax pentahydrate. A method of controlling the alkali content of a dye bath used in a reactive dye bath process, in which a cellulose-containing textile material to be dyed is placed in a liquid reactive dye bath solution, containing water, surfactant, salt and a dye, and the dye bath is heated for a prescribed period of time, characterised in that a premixed high pH liquid buffer composition according to any preceding claim is added in an amount sufficient to control the alkali concentration of the dye bath at a level sufficient to allow the reactive dye to form a firm chemical bond with the cellulose-containing textile material when heated for a prescribed period of time. A method of controlling the pH of a scouring bath in the range from 8.0 to 9.5 for removing waste and oils from fibre or fabric, characterised in that a premixed high pH liquid buffer composition according to any of claims 1 to 4, is added to a scouring bath which contains water and a surfactant and a fibre or fabric to be scoured is placed in the bath at an elevated temperature for a time sufficient to scour the fibre or fabric. A method of controlling the pH of a dye bath in the range from 5.0 to 7.0 in a dyeing operation which employs a liquid due bath solution which contains water, a leveller and a dye characterised in that a premixed low pH liquid buffer composition, comprising an aqueous solution containing 13 to 40 weight percent monosodium phosphate and 5 to 30 weight percent phosphoric acid, and a premixed high pH liquid buffer composition according to any of claims 1 to 4, are added to the dye bath, the concentration of the low pH and the high pH buffer compositions are controlled so as to maintain the pH of the dye bath within the range from 5.0 to 7.0 and a textile material to be dyed is placed in the dye bath for a time and at a temperature sufficient to carry out the dyeing operation. A premixed high pH liquid buffer composition, characterised by comprising in percent by weight: tripotassium phosphate: 20 to 50 borax pentahydrate: 4 to 10 mono-, di- and/or tri-ethanolamine: 4 to 8 sodium hydroxide: 0.4 to 7 water: balance. A premixed high pH liquid buffer composition, characterised by comprising in percent by weight: tripotassium phosphate: 20 to 50 potassium hydroxide: 2 to 5 borax pentahydrate: 4 to 9 mono-, di and/or tri-ethanolamine: 3 to 8 sodium hydroxide 0.4 to 7 water: balance.

Inventors: MORAN, JAMES C.
Applicants: SYBRON CHEMICALS INC
Application year: 1985
Main classification: C01B25
IPC codes: D06M13, D06P3, D06M11, D06M101, D06P1, D06L3, D06P5, D06M23