Liquid laundry builder containing alkali hydroxide and borax
United States Patent 3927970
In an liquid laundry detergent system for the washing of fabrics, clothes and the like, particularly those of the wash-and-wear type, wherein an aqueous solution of alkali metal hydroxide is employed as the alkaline builder, the improvement of adding to the alkaline builder solution borax in an amount of from about 5 to 15 weight percent of the amount of said hydroxide initially present, so as to form in situ alkali metal metaborate, e.g., sodium metaborate when the builder is sodium hydroxide, so that the available hydroxyl ion concentration of said alkaline builder solution is decreased but its alkalinity and detergency are increased.
US Patent References:
Composition and a process for electrolytic cleaning of metals
Webster - August 1956 - 2760927
/2791562.html
Diffley - May 1957 - 2791562
Enameling of aluminum alloys
Hubbell - April 1960 - 2932584
Method for inhibiting corrosion of ferrous metals
Krueger - June 1962 - 3039970
Composition and a process for electrolytic cleaning of metals
Webster - August 1956 - 2760927
/2791562.html
Diffley - May 1957 - 2791562
Enameling of aluminum alloys
Hubbell - April 1960 - 2932584
Method for inhibiting corrosion of ferrous metals
Krueger - June 1962 - 3039970
Inventors:
Ciko, John D. (Allen Park, MI)
Cramer, John J. (Wyandotte, MI)
Cramer, John J. (Wyandotte, MI)
Application Number:
05/415238
Publication Date:
12/23/1975
Filing Date:
11/12/1973
View Patent Images:
Export Citation:
Assignee:
BASF Wyandotte Corporation (Wyandotte, MI)
Primary Class:
Other Classes:
510/420, 510/345, 510/339, 510/435, 510/531
International Classes:
C11D3/02; C11D7/06; D06L1/12; C11D7/02; D06L1/00; C11D7/10; C11D9/16; C11D7/06
Field of Search:
252/99,103,109,135,156,189 8/125,127,137
Other References:
F L. Wells et al.: "Manufacture of Dissolving Pulps by Extraction in Sodium Hydroxide-Borax Solutions" Tappi, Vol. 54, No. 4, Apr. 1971, pp. 525-529..
Primary Examiner:
Talbert Jr., Dennis E.
Assistant Examiner:
Albrecht, Dennis L.
Attorney, Agent or Firm:
Swick, Bernhard Michaels Joseph Dunn Robert R. D. E.
Claims:
The embodiment of the invention in which an exclusive property or privilege is claimed are defined as follows
1. In a method of cleaning fabrics with an aqueous solution containing alkali metal hydroxide builder selected from the group consisting of sodium hydroxide and potassium hydroxide, the improvement wherein borax is included in said aqueous solution in an amount from about 5 to 15 weight percent of the amount of said hydroxide present, thereby forming in situ alkali metal mataborate in an amount from about 6.5 to 19.5 weight percent of the amount of said hydroxide initially present.
2. The improvement of claim 1 wherein said alkali metal hydroxide is sodium hydroxide.
3. The improvement of claim 1 wherein the amount of said borate present is about 13 percent by weight of the amount of said alkali metal hydroxide.
4. The improvement of claim 1 wherein the amount of said borax is from about 8 to 12 percent by weight of the amount of said alkali metal hydroxide.
5. An aqueous alkaline builder solution consisting essentially of 10 to 30 percent by weight alkali metal hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide, borax in an amount from about 5 to 15 weight percent of said hydroxide and forming in situ alkali metal metaborate in an amount from about 6.5 to 19.5 weight percent of the amount of said hydroxide initially present, and from about 0.25 to about 1.5 weight percent of anti-redeposition agent, balance water.
6. The solution of claim 5 wherein said alkali metal hydroxide is sodium hydroxide.
7. The solution of claim 5 wherein said anti-redeposition agent is selected from the group consisting of the alkali and ammonium salts of carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone and hydroxyethyl cellulose.
8. The solution of claim 7 wherein the amount of said borax is from about 8 to 12 percent by weight of said hydroxide.
9. The solution of claim 6 wherein the amount of said anti-redeposition agent is from about 0.75 to 1 percent.
1. In a method of cleaning fabrics with an aqueous solution containing alkali metal hydroxide builder selected from the group consisting of sodium hydroxide and potassium hydroxide, the improvement wherein borax is included in said aqueous solution in an amount from about 5 to 15 weight percent of the amount of said hydroxide present, thereby forming in situ alkali metal mataborate in an amount from about 6.5 to 19.5 weight percent of the amount of said hydroxide initially present.
2. The improvement of claim 1 wherein said alkali metal hydroxide is sodium hydroxide.
3. The improvement of claim 1 wherein the amount of said borate present is about 13 percent by weight of the amount of said alkali metal hydroxide.
4. The improvement of claim 1 wherein the amount of said borax is from about 8 to 12 percent by weight of the amount of said alkali metal hydroxide.
5. An aqueous alkaline builder solution consisting essentially of 10 to 30 percent by weight alkali metal hydroxide selected from the group consisting of sodium hydroxide and potassium hydroxide, borax in an amount from about 5 to 15 weight percent of said hydroxide and forming in situ alkali metal metaborate in an amount from about 6.5 to 19.5 weight percent of the amount of said hydroxide initially present, and from about 0.25 to about 1.5 weight percent of anti-redeposition agent, balance water.
6. The solution of claim 5 wherein said alkali metal hydroxide is sodium hydroxide.
7. The solution of claim 5 wherein said anti-redeposition agent is selected from the group consisting of the alkali and ammonium salts of carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone and hydroxyethyl cellulose.
8. The solution of claim 7 wherein the amount of said borax is from about 8 to 12 percent by weight of said hydroxide.
9. The solution of claim 6 wherein the amount of said anti-redeposition agent is from about 0.75 to 1 percent.
Description:
BACKGROUND
1. Field of the Invention
This invention relates to an improved liquid alkaline builder for liquid laundry detergent systems. The new builder is particularly useful for wash-and-wear type of fabrics containing high amounts of polyester fibers.
2. Description of the Prior Art
The increasing use of industrial washing machines equipped with automatic liquid supply injection systems constitutes an important change in the laundry and chemical supply industries. No longer will it be possible to use solid products, but rather stock solutions of the detergent, builder, bleach, sour and the like will be required to keep the supply systems operational. Builders are included in laundry formulations to enhance the cleaning capacity of the detergent being used. For example, alkaline builders extend detergent capacity by solubilizing soils, hydrolyzing fats, promoting foam formation and the like. One of the most effective, and once extensively used, laundry builders is sodium hydroxide, commonly called caustic soda. In addition, caustic soda is also economical, very soluble in water and germicidally effective. Therefore, people have attempted for many years to utilize this builder despite its caustic nature which, in some respects, is a major drawback. Among the alkali metal salts which have been used as builders, either as complete or partial replacement for the alkali matal hydroxides, have been the borates, phosphates, silicates, carbonates and the like.
The detergent art is replete with many instances of attempts to use these various alkali metal salts in the various branches of detergency. For instance, U.S. Pat. No. 1,869,057 discloses a shaving aid to remove oil film from hair by the use of a dilute aqueous solution of a salt composed of a strong base and a weak acid, e.g., a dilute aqueous solution of potassium or sodium carbonate or borate, either singularly or in combination. The disclosed solution contains about 1/2 to 1 percent of a salt and water because at that concentration the hydrolysis is substantially complete and continuous. At higher concentrations there is an increasing amount of salt which is not hydrolyzed. Another patent in U.S. Pat. No. 2,397,193 relating to wood bleaching wherein the bleaching composition consists of about 1 volume of an alkali component consisting substantially of one part by weight borax, 2 parts by weight caustic soda, and one part by weight of waterglass plus twenty parts by weight of water. Hydrogen peroxide is then added before being used as the bleach.
A later patent, U.S. Pat. No. 3,142,531, disclosing an industrial process for bleaching of gray cotton knit goods suggests as the second bath of a three-bath series the use of a bleaching solution containing hydrogen peroxide, sodium hydroxide and borax while keeping the goods immersed in the peroxide bleaching solution at a temperature of 170° to 190° F. for a period of 280 to 320 minutes. A still later U.S. Pat. No. 3,529,999, discloses a method for cleaning natural and artificial stones by the use of an aqueous solution consisting of an alkali metal hydroxide, a salt from the same alkali metal with a weak acid coming from the group of formic, acetic, propionic, lactic, citric, boric, carbonic, hydrofluoric, sulfurous tetraboric and phosphoric acids, a thickening agent and water. In this mixture the alkali metal salt of the weak acid content is from 5 to 60% by weight of total composition and preferably from 5 to 40%. Another recent U.S. Pat. No. 3,530,071, discloses the use of borax as a stabilizer for chlorinated trisodium phosphate which is used in conjunction with up to 30% by weight alkaline detergency builder in an abrasive scouring cleaner.
S. Bernstein and M. Levine in an article published in Food Technology, Volume 3, pages 375-378, November, 1949, note that the addition of alkaline salt, such as sodium chloride, sodium carbonate, or sodium phosphate, to a solution of sodium hydroxide appreciably increases the germicidal properties of the caustic solution. Furthermore, sodium metaborate acts in an analogous manner but, in contrast to the foregoing, the addition of borax causes a marked reduction in germicidal efficiency. This is due to interaction of borax with the caustic to form sodium metaborate with a corresponding reduction in the concentration of the primary germicidal component, namely, sodium hydroxide.
SUMMARY OF THE INVENTION
In accordance with this invention there is provided a liquid laundry detergent system for the washing of fabrics, clothes and the like, particularly those of the wash-and-wear type containing polyester fibers, wherein an aqueous solution of alkali metal hydroxide is employed as the builder, the improvement comprising adding to said solution borax in an amount of from about 5 to 15 weight percent of the amount of said hydroxide initially present, said borax forming in situ alkali metal metaborate, so that the available hydroxyl ion concentration of said solution is decreased but its alkalinity and detergency are increased.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a liquid laundry detergent system employing an alkaline builder solution, the preferred alkaline material is either sodium hydroxide which is often called caustic soda or potassium hydroxide which is often called potash. Because of cost considerations sodium hydroxide solutions are widely used even though there is a technical advantage in the use of the potassium hydroxide solutions. These solutions on a weight percent of total basis contain from 10 to 30% alkali metal hydroxide and preferably 18 to 22 weight percent alkali metal hydroxide with a 20% solution being ideal. In the past, the presence of relatively high concentration of hydroxyl ion in liquid wash formulas has not constituted any real threat to fabric tensile strength, since the preponderance of garments consisted of cotton. However, with the advent of garments consisting of polyester-cotton blends, i.e., wash-and-wear fabrics, the effects of caustic upon modern synthetic fibers became increasingly important. It has been shown that the extent of damage caused to polyester structures is directly proportional to the independent variables of exposure time, temperature and molar hydroxyl ion concentration.
An effective means has now been found for reducing caustic soda or caustic potash available hydroxyl ion concentration, while increasing its detergency by in situ reacting it with the alkali salt sodium borate (Na 2 B 4 O 7 ), commonly called borax. The borax reacts with the caustic liquor to form alkali metal borate, e.g., sodium metaborate when caustic soda is used. A mixed alkali metal borate is obtained in the case where potash is the builder. Based on the amount of caustic solids initially in the solution, it has been found advantageous to add from about 5 to about 15 weight percent of borax and preferably from about 8 to 12 weight percent of borax with 10% by weight being preferred. Eight weight percent of borax with yield 10.4 weight percent sodium metaborate, 10% borax yields 13 weight percent sodium metaborate while 12 weight percent borax yields 15.7 weight percent sodium metaborate. Although the total alkali concentration of the system is increased, the net available hydroxyl ion concentration has been reduced. When 2% by weight of borax is added to a 20 weight percent aqueous solution of caustic soda (sodium hydroxide liquor), the available hydroxyl ions are reduced by approximately 25%. While the borax did reduce the hydroxyl ion concentrations and, therefore, it would be expected to proportionately reduce its cleaning efficiency, it has been found that just the opposite effect is achieved, namely, that that alkalinity and detergency of the alkali builder solution are increased.
It was quite surprising to find the cleaning efficiency of a liquid laundry formulation utilizing an alkaline builder of only caustic soda and a liquid alkaline builder containing the same amount of caustic soda plus 20% borax (by weight of the initially present caustic soda) had the same cleaning efficiency. Whereas lesser amounts of borax added to the alkaline builder in the same liquid cleaning system had increasing amounts of efficiency and this synergistic effect approached the maximum when the amount of borax was 10% by weight of the amount of caustic initially in the alkaline builder solution.
In the liquid detergent system it is conventional and desirable to add to the formulation an anti-redeposition agent so as to prevent the soil which has been removed from the fabric being redeposited on the fabric during the subsequent period of washing. However, in a liquid system the typical surfactant employed is not readily compatible with an anti-redeposition agent and, therefore, must be injected into the wash via a different conduit. It has been found practical and useful to add the anti-redeposition agent in the alkaline builder solution. The presence of the anti-redeposition agent in the alkaline builder solution of this invention in no way inhibits or materially changes the invention which has been discovered. The amount of anti-redeposition agent added to the alkaline builder solution can range from about 0.25 weight percent to about 1.5 weight percent with a typical amount being 0.75 to 1%. Typical anti-redeposition agents employed include the alkali and ammonium salts of carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose and the like.
The alkaline builder solution of this invention is added to the wash in the conventional manner for utilizing liquid detergent systems. The amount of alkaline builder to be added, of course, will be varied according to the total detergency desired in the particular wash. These variations and ratios are well known in the art and the use of this invention does not entail any modifications other than those which would be immediately obvious to those of ordinary skill in the art. Therefore, for the sake of brevity further elucidation of the obvious will not be made at this time.
The practice of this invention is illustrated by, but not limited by, the examples given below. Unless otherwise noted, temperature is expressed in degrees centigrade and parts are parts by weight.
EXAMPLE I
A liquid alkaline builder solution was prepared containing 20% by weight caustic soda and 80% by weight of water. The pH of a 0.2% aqueous solution of this builder was 11.8. The solution when titrated with hydrochloric acid had a typical strong acid-strong based titration curve. The amount of 0.3 N hydrochloric acid required to reduce the pH to 4 was 20.5 mils. A second liquid alkaline builder was prepared containing 20% by weight sodium hydroxide, 2% by weight borax, and 78% by weight water. The pH of a 0.2% aqueous solution of this builder was 11.9. The solution required 17.3 milliliters of 0.3 N hydrochloric acid to obtain the pH 4 level. A third liquid alkaline builder was prepared containing 20% by weight sodium hydroxide, 2% borax, 1% of an anti-redeposition agent which was the sodium salt of carboxymethylcellulose, the remainder of the builder being water. The initial pH of a 0.2% aqueous solution of this builder was 11.8. This solution required 16.1 milliliters of the same hydrochloric acid to reach the same pH point of 4. It will thus be seen that the addition of borax reduced the alkalinity of the liquid builder solution to a marked amount inasmuch as less acid was required to achieve the same pH. The alkaline builder solution containing the anti-redeposition agent required only 16.1 milliliters to reach the pH of 4. It is believed that the slight further reduction in alkalinity in that solution over the caustic/borax solution was due to the physical entrapment of the hydroxyl ions by the anti-redeposition agent rather than further chemical reduction of the hydroxyl ion concentration.
EXAMPLE II
The detergency effectiveness of the alkaline builder of this invention was determined by washing crankcase oil soiled swatches of polyester-cotton cloths in an aqueous solution of the liquid laundry detergent system containing the alkaline builder to be evaluated under the following conditions:
1. water temperature -- 180° F.,
2. detergent concentration -- 0.25% by weight commercial nonionic liquid detergent mixture, 0.5% liquid alkaline builder as specified,
3. time -- 20 minutes.
The liquid nonionic commercial detergent used in the examples contained a nonionic liquid detergent polyethylene glycol ether of linear alcohol having a HLB value of 13.3 (45% of the total), a nonionic modified alkylene oxide condensation of a linear alcohol having a HLB value of 15.0 (constituting 15% of the total composition), optical brightener, 0.1% of the total composition, aliphatic solvent, comprising 34.9% of the total composition and the remaining 5% was water.
The swatches were washed in an apparatus often referred to as the "Launder-Ometer" which is the official method of American Association of Textile Chemists and Colorists which may be found in the association's Monograph No. 3, First Edition, published 1949, Second Edition published 1968. The apparatus consists essentially of a thermostatically controlled waterbath in which is mounted a rotary rack or frame so constructed that 20 1-pint Mason jars may be clamped to it in rows of five opposite to each other. A sample of cloth soiled with a standard artificial soil is placed in each jar along with a measured volume of detergent solution and a number of small rubber or stainless steel balls. The total volume of water, detergent and builder is 100 milliliters. As the jar holder rotates, each jar describes a complete circle causing the balls in the solution to tumble about. This supplies the mechanical action needed for good detergency.
After washing, rinsing and drying the amounts of soil removal, that is, the amount of cleaning performed on each swatch was determined by use of the Reflectometer, manufactured by Hunter Associates Laboratory, using the Hunterlab D-40 green Reflectometer readings as the final result. Three swatches were washed and individually read to determine an average value. It should be noted that the detergent solution used in washing no thickener or anti-redeposition agent was used in the formulation.
In this test the liquid alkaline builder was a solution containing 20% by weight sodium hydroxide and 80% by weight water. Five different used crankcase oils were used to soil the various swatches by placing one drop of oil from each near the edge of a polyester-cotton 65/35 blend swatch in a pentagonal form leaving the center of the swatch unsoiled. The swatches were 41/4 inches × 41/4 inches in size. The Reflectometer readings (an average of 3 tests) for oil No. 1 was 43.9; the reading for oil No. 2 was 42.3; No. 3 oil was 40.2; No. 4 oil was 38.6; and No. 5 oil was 12.8 for a summation of the readings value of 177.8.
EXAMPLES III-VI
Following the procedure of Example II except for difference in the liquid alkaline builder solution employed, Examples III through VI were performed and the test data is noted underneath each example heading. Throughout all tests the same identification was maintained for each lot of used crankcase oil.
EXAMPLE III
The liquid alkaline builder used in this example contained 20% sodium hydroxide, 1% borax (that is, 5% by weight of the sodium hydroxide initially employed) and 79% water. The resulting sodium metaborate content of the solution was 6.5% of the sodium hydroxide used. The Reflectometer readings for the oils were as follows: Oil No. 1 -- 44.2; oil No. 2 -- 44.3; oil No. 3 1 /8 42.6; oil No. 4 -- 41.5; and oil No. 5 -- 13.1 for a sum of reflectance readings value of 185.7
EXAMPLE IV
The liquid alkaline builder of this example contained 20% by weight sodium hydroxide, 1.3% borax (that is, 62/3% by weight based on the amount of initially present sodium hydroxide), and 78.7% water. The resulting sodium metaborate content of the solution was 1.7% of the total solution. The Reflectometer readings were: Oil No. 1 -- 45.8; oil No. 2 -- 43.5; oil No. 3 -- 43.0; oil No. 4 -- 40.7; and oil No. 5 -- 12.0 for a sum of reflectance readings value of 185.0.
EXAMPLE V
In this example the liquid alkaline builder solution contained 20% sodium hydroxide, 2% borax (that is, 10% by weight when based on sodium hydroxide initially present), and 78% water. The resulting sodium metaborate content of the solution was 13.0% of the sodium hydroxide used. The Reflectometer readings were as follows: Oil No. 1 -- 46.2; oil No. 2 -- 45.2; oil No. 3 -- 44.5; oil No. 4 -- 41.5; and oil No. 5 -- 17.2 for a sum of reflectance readings value of 194.6.
Similar results will be obtained when potassium hydroxide is substituted for the sodium hydroxide above.
EXAMPLE VI
In this example the liquid alkaline builder solution contained 20% by weight sodium hydroxide, 4% borax (that is, 20% by weight when based on sodium hydroxide used), and 76% water. The resulting sodium metaborate content of the solution is 5.2% of the total solution or 26% of the sodium hydroxide used. The Reflectometer readings were as follows: Oil No. 1 -- 44.1; oil No. 2 -- 38.3; oil No. 3 -- 40.4; oil No. 4 -- 40.3; and oil No. 5 -- 13.5 for a summation of reflectance readings value of 176.6.
It will be seen in comparing the sum of reflectance values, which is the more indicative figure of the Reflectometer values obtained, in Examples II through VI that the detergency value or effect of no borax and 4% borax in the builder of Example VI is substantially the same and that under these conditions the borax has no effect. However, Examples III and IV point out increasing the amount of borax 1% and 1.3%, respectively, has a material effect on the cleaning ability of the solution. The highest cleaning effect is obtained in Example V wherein 2% borax was added to the alkaline builder, that is, the ratio of sodium hydroxide to borax was 10 to 1. The reflectance value was 194.6, a 10% increase in cleaning over the similar situation where no borax, or twice as much borax, was employed. In view of the prior art, it was surprising to find such a material difference concentrated in such a short range of borax addition values. In scanning the individual oil values, it will be noted that the 2% borax addition of Example V in each instance is substantially above the values for no borax or for 4% borax.
EXAMPLE VII
To indicate the seriousness of the breakdown of polyesters on exposure to caustic in solution, the following test was prepared. Polyester film samples, cut to 3 inches × 11/2 inches dimensions (0.003 inch thickness) were prepared for use by boiling for one-half hour in a 3% hydrochloric acid solution. The scoured samples were than placed in weighing bottles, dried for one hour at 110°-120° C. and then weighed. The pre-treated and weighed polyester samples were added to 500 milliters wide mounted, conical flask containing 250 grams of alkali solution indicated below. The units were equipped to maintain reflux conditions and the film samples were processed for a period of 2.382 hours at 100° C. After treatment the film samples were again scoured with 3% hydrochloric acid solutions, dried, cooled and weighed to a constant weight. The difference between the original weight and the final weight is stated below as a percent of the original weight. Solution 1 had a molarity of 0.1234 and the polyester film had a weight loss of 0.67%. The second solution had a molarity of 0.4089 for a weight loss of 3.81%. The third solution had a molarity of 0.8360 for a weight loss of 13.5%. The fourth solution had a molarity of 1.8140 for a weight loss of 23.12%. Thus, it can be concluded that the progressive effect of strong alkali solutions is to degrade the polyester in the wash-and-wear fabric over a period of time.
For solutions 5 and 6 the time was changed to 2.012 hours and the molarity was 2.1727, the temperature being varied. Solution 5 at a temperature of 60° C. had a polyester weight loss of 1.41% and solution 6 at 90° C. had a polyester weight loss of 1.41% and solution 6 at 90° C. had a polyester weight loss of 14.7%.
For solutions 7 and 8 the temperature was 100° C., the molarity was 1.3160 and the time was varied. With solution 7 the time of exposure was 4 hours and the polyester weight loss was 33.75%. With solution 8 the time of exposure was 6 hours and the polyester weight loss was 50.56%.
Therefore, the rate of weight loss of the polyester in the wash-and-wear fabric is also temperature dependent as well as dependent upon the molarity of the alkaline builder. The greater the exposure time to the caustic, i.e., the greater the number of washings of the garment or fabric, and the higher the temperature used, which is often the case in white goods or flat goods, the quicker the fabric will be disrupted by the caustic alkaline builder. Therefore, the invention confers a real and valuable result by decreasing the hydroxyl exposure time (the caustic quality of the alkaline builder) while at the same time increasing the amount of cleaning ability.
The foregoing examples have been described in the above specification for the purpose of illustration and not limitation. Many other modifications and ramifications based on this disclosure will naturally suggest themselves to those skilled in the art. These are intended to be comprehended as within the scope of this invention.
1. Field of the Invention
This invention relates to an improved liquid alkaline builder for liquid laundry detergent systems. The new builder is particularly useful for wash-and-wear type of fabrics containing high amounts of polyester fibers.
2. Description of the Prior Art
The increasing use of industrial washing machines equipped with automatic liquid supply injection systems constitutes an important change in the laundry and chemical supply industries. No longer will it be possible to use solid products, but rather stock solutions of the detergent, builder, bleach, sour and the like will be required to keep the supply systems operational. Builders are included in laundry formulations to enhance the cleaning capacity of the detergent being used. For example, alkaline builders extend detergent capacity by solubilizing soils, hydrolyzing fats, promoting foam formation and the like. One of the most effective, and once extensively used, laundry builders is sodium hydroxide, commonly called caustic soda. In addition, caustic soda is also economical, very soluble in water and germicidally effective. Therefore, people have attempted for many years to utilize this builder despite its caustic nature which, in some respects, is a major drawback. Among the alkali metal salts which have been used as builders, either as complete or partial replacement for the alkali matal hydroxides, have been the borates, phosphates, silicates, carbonates and the like.
The detergent art is replete with many instances of attempts to use these various alkali metal salts in the various branches of detergency. For instance, U.S. Pat. No. 1,869,057 discloses a shaving aid to remove oil film from hair by the use of a dilute aqueous solution of a salt composed of a strong base and a weak acid, e.g., a dilute aqueous solution of potassium or sodium carbonate or borate, either singularly or in combination. The disclosed solution contains about 1/2 to 1 percent of a salt and water because at that concentration the hydrolysis is substantially complete and continuous. At higher concentrations there is an increasing amount of salt which is not hydrolyzed. Another patent in U.S. Pat. No. 2,397,193 relating to wood bleaching wherein the bleaching composition consists of about 1 volume of an alkali component consisting substantially of one part by weight borax, 2 parts by weight caustic soda, and one part by weight of waterglass plus twenty parts by weight of water. Hydrogen peroxide is then added before being used as the bleach.
A later patent, U.S. Pat. No. 3,142,531, disclosing an industrial process for bleaching of gray cotton knit goods suggests as the second bath of a three-bath series the use of a bleaching solution containing hydrogen peroxide, sodium hydroxide and borax while keeping the goods immersed in the peroxide bleaching solution at a temperature of 170° to 190° F. for a period of 280 to 320 minutes. A still later U.S. Pat. No. 3,529,999, discloses a method for cleaning natural and artificial stones by the use of an aqueous solution consisting of an alkali metal hydroxide, a salt from the same alkali metal with a weak acid coming from the group of formic, acetic, propionic, lactic, citric, boric, carbonic, hydrofluoric, sulfurous tetraboric and phosphoric acids, a thickening agent and water. In this mixture the alkali metal salt of the weak acid content is from 5 to 60% by weight of total composition and preferably from 5 to 40%. Another recent U.S. Pat. No. 3,530,071, discloses the use of borax as a stabilizer for chlorinated trisodium phosphate which is used in conjunction with up to 30% by weight alkaline detergency builder in an abrasive scouring cleaner.
S. Bernstein and M. Levine in an article published in Food Technology, Volume 3, pages 375-378, November, 1949, note that the addition of alkaline salt, such as sodium chloride, sodium carbonate, or sodium phosphate, to a solution of sodium hydroxide appreciably increases the germicidal properties of the caustic solution. Furthermore, sodium metaborate acts in an analogous manner but, in contrast to the foregoing, the addition of borax causes a marked reduction in germicidal efficiency. This is due to interaction of borax with the caustic to form sodium metaborate with a corresponding reduction in the concentration of the primary germicidal component, namely, sodium hydroxide.
SUMMARY OF THE INVENTION
In accordance with this invention there is provided a liquid laundry detergent system for the washing of fabrics, clothes and the like, particularly those of the wash-and-wear type containing polyester fibers, wherein an aqueous solution of alkali metal hydroxide is employed as the builder, the improvement comprising adding to said solution borax in an amount of from about 5 to 15 weight percent of the amount of said hydroxide initially present, said borax forming in situ alkali metal metaborate, so that the available hydroxyl ion concentration of said solution is decreased but its alkalinity and detergency are increased.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a liquid laundry detergent system employing an alkaline builder solution, the preferred alkaline material is either sodium hydroxide which is often called caustic soda or potassium hydroxide which is often called potash. Because of cost considerations sodium hydroxide solutions are widely used even though there is a technical advantage in the use of the potassium hydroxide solutions. These solutions on a weight percent of total basis contain from 10 to 30% alkali metal hydroxide and preferably 18 to 22 weight percent alkali metal hydroxide with a 20% solution being ideal. In the past, the presence of relatively high concentration of hydroxyl ion in liquid wash formulas has not constituted any real threat to fabric tensile strength, since the preponderance of garments consisted of cotton. However, with the advent of garments consisting of polyester-cotton blends, i.e., wash-and-wear fabrics, the effects of caustic upon modern synthetic fibers became increasingly important. It has been shown that the extent of damage caused to polyester structures is directly proportional to the independent variables of exposure time, temperature and molar hydroxyl ion concentration.
An effective means has now been found for reducing caustic soda or caustic potash available hydroxyl ion concentration, while increasing its detergency by in situ reacting it with the alkali salt sodium borate (Na 2 B 4 O 7 ), commonly called borax. The borax reacts with the caustic liquor to form alkali metal borate, e.g., sodium metaborate when caustic soda is used. A mixed alkali metal borate is obtained in the case where potash is the builder. Based on the amount of caustic solids initially in the solution, it has been found advantageous to add from about 5 to about 15 weight percent of borax and preferably from about 8 to 12 weight percent of borax with 10% by weight being preferred. Eight weight percent of borax with yield 10.4 weight percent sodium metaborate, 10% borax yields 13 weight percent sodium metaborate while 12 weight percent borax yields 15.7 weight percent sodium metaborate. Although the total alkali concentration of the system is increased, the net available hydroxyl ion concentration has been reduced. When 2% by weight of borax is added to a 20 weight percent aqueous solution of caustic soda (sodium hydroxide liquor), the available hydroxyl ions are reduced by approximately 25%. While the borax did reduce the hydroxyl ion concentrations and, therefore, it would be expected to proportionately reduce its cleaning efficiency, it has been found that just the opposite effect is achieved, namely, that that alkalinity and detergency of the alkali builder solution are increased.
It was quite surprising to find the cleaning efficiency of a liquid laundry formulation utilizing an alkaline builder of only caustic soda and a liquid alkaline builder containing the same amount of caustic soda plus 20% borax (by weight of the initially present caustic soda) had the same cleaning efficiency. Whereas lesser amounts of borax added to the alkaline builder in the same liquid cleaning system had increasing amounts of efficiency and this synergistic effect approached the maximum when the amount of borax was 10% by weight of the amount of caustic initially in the alkaline builder solution.
In the liquid detergent system it is conventional and desirable to add to the formulation an anti-redeposition agent so as to prevent the soil which has been removed from the fabric being redeposited on the fabric during the subsequent period of washing. However, in a liquid system the typical surfactant employed is not readily compatible with an anti-redeposition agent and, therefore, must be injected into the wash via a different conduit. It has been found practical and useful to add the anti-redeposition agent in the alkaline builder solution. The presence of the anti-redeposition agent in the alkaline builder solution of this invention in no way inhibits or materially changes the invention which has been discovered. The amount of anti-redeposition agent added to the alkaline builder solution can range from about 0.25 weight percent to about 1.5 weight percent with a typical amount being 0.75 to 1%. Typical anti-redeposition agents employed include the alkali and ammonium salts of carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose and the like.
The alkaline builder solution of this invention is added to the wash in the conventional manner for utilizing liquid detergent systems. The amount of alkaline builder to be added, of course, will be varied according to the total detergency desired in the particular wash. These variations and ratios are well known in the art and the use of this invention does not entail any modifications other than those which would be immediately obvious to those of ordinary skill in the art. Therefore, for the sake of brevity further elucidation of the obvious will not be made at this time.
The practice of this invention is illustrated by, but not limited by, the examples given below. Unless otherwise noted, temperature is expressed in degrees centigrade and parts are parts by weight.
EXAMPLE I
A liquid alkaline builder solution was prepared containing 20% by weight caustic soda and 80% by weight of water. The pH of a 0.2% aqueous solution of this builder was 11.8. The solution when titrated with hydrochloric acid had a typical strong acid-strong based titration curve. The amount of 0.3 N hydrochloric acid required to reduce the pH to 4 was 20.5 mils. A second liquid alkaline builder was prepared containing 20% by weight sodium hydroxide, 2% by weight borax, and 78% by weight water. The pH of a 0.2% aqueous solution of this builder was 11.9. The solution required 17.3 milliliters of 0.3 N hydrochloric acid to obtain the pH 4 level. A third liquid alkaline builder was prepared containing 20% by weight sodium hydroxide, 2% borax, 1% of an anti-redeposition agent which was the sodium salt of carboxymethylcellulose, the remainder of the builder being water. The initial pH of a 0.2% aqueous solution of this builder was 11.8. This solution required 16.1 milliliters of the same hydrochloric acid to reach the same pH point of 4. It will thus be seen that the addition of borax reduced the alkalinity of the liquid builder solution to a marked amount inasmuch as less acid was required to achieve the same pH. The alkaline builder solution containing the anti-redeposition agent required only 16.1 milliliters to reach the pH of 4. It is believed that the slight further reduction in alkalinity in that solution over the caustic/borax solution was due to the physical entrapment of the hydroxyl ions by the anti-redeposition agent rather than further chemical reduction of the hydroxyl ion concentration.
EXAMPLE II
The detergency effectiveness of the alkaline builder of this invention was determined by washing crankcase oil soiled swatches of polyester-cotton cloths in an aqueous solution of the liquid laundry detergent system containing the alkaline builder to be evaluated under the following conditions:
1. water temperature -- 180° F.,
2. detergent concentration -- 0.25% by weight commercial nonionic liquid detergent mixture, 0.5% liquid alkaline builder as specified,
3. time -- 20 minutes.
The liquid nonionic commercial detergent used in the examples contained a nonionic liquid detergent polyethylene glycol ether of linear alcohol having a HLB value of 13.3 (45% of the total), a nonionic modified alkylene oxide condensation of a linear alcohol having a HLB value of 15.0 (constituting 15% of the total composition), optical brightener, 0.1% of the total composition, aliphatic solvent, comprising 34.9% of the total composition and the remaining 5% was water.
The swatches were washed in an apparatus often referred to as the "Launder-Ometer" which is the official method of American Association of Textile Chemists and Colorists which may be found in the association's Monograph No. 3, First Edition, published 1949, Second Edition published 1968. The apparatus consists essentially of a thermostatically controlled waterbath in which is mounted a rotary rack or frame so constructed that 20 1-pint Mason jars may be clamped to it in rows of five opposite to each other. A sample of cloth soiled with a standard artificial soil is placed in each jar along with a measured volume of detergent solution and a number of small rubber or stainless steel balls. The total volume of water, detergent and builder is 100 milliliters. As the jar holder rotates, each jar describes a complete circle causing the balls in the solution to tumble about. This supplies the mechanical action needed for good detergency.
After washing, rinsing and drying the amounts of soil removal, that is, the amount of cleaning performed on each swatch was determined by use of the Reflectometer, manufactured by Hunter Associates Laboratory, using the Hunterlab D-40 green Reflectometer readings as the final result. Three swatches were washed and individually read to determine an average value. It should be noted that the detergent solution used in washing no thickener or anti-redeposition agent was used in the formulation.
In this test the liquid alkaline builder was a solution containing 20% by weight sodium hydroxide and 80% by weight water. Five different used crankcase oils were used to soil the various swatches by placing one drop of oil from each near the edge of a polyester-cotton 65/35 blend swatch in a pentagonal form leaving the center of the swatch unsoiled. The swatches were 41/4 inches × 41/4 inches in size. The Reflectometer readings (an average of 3 tests) for oil No. 1 was 43.9; the reading for oil No. 2 was 42.3; No. 3 oil was 40.2; No. 4 oil was 38.6; and No. 5 oil was 12.8 for a summation of the readings value of 177.8.
EXAMPLES III-VI
Following the procedure of Example II except for difference in the liquid alkaline builder solution employed, Examples III through VI were performed and the test data is noted underneath each example heading. Throughout all tests the same identification was maintained for each lot of used crankcase oil.
EXAMPLE III
The liquid alkaline builder used in this example contained 20% sodium hydroxide, 1% borax (that is, 5% by weight of the sodium hydroxide initially employed) and 79% water. The resulting sodium metaborate content of the solution was 6.5% of the sodium hydroxide used. The Reflectometer readings for the oils were as follows: Oil No. 1 -- 44.2; oil No. 2 -- 44.3; oil No. 3 1 /8 42.6; oil No. 4 -- 41.5; and oil No. 5 -- 13.1 for a sum of reflectance readings value of 185.7
EXAMPLE IV
The liquid alkaline builder of this example contained 20% by weight sodium hydroxide, 1.3% borax (that is, 62/3% by weight based on the amount of initially present sodium hydroxide), and 78.7% water. The resulting sodium metaborate content of the solution was 1.7% of the total solution. The Reflectometer readings were: Oil No. 1 -- 45.8; oil No. 2 -- 43.5; oil No. 3 -- 43.0; oil No. 4 -- 40.7; and oil No. 5 -- 12.0 for a sum of reflectance readings value of 185.0.
EXAMPLE V
In this example the liquid alkaline builder solution contained 20% sodium hydroxide, 2% borax (that is, 10% by weight when based on sodium hydroxide initially present), and 78% water. The resulting sodium metaborate content of the solution was 13.0% of the sodium hydroxide used. The Reflectometer readings were as follows: Oil No. 1 -- 46.2; oil No. 2 -- 45.2; oil No. 3 -- 44.5; oil No. 4 -- 41.5; and oil No. 5 -- 17.2 for a sum of reflectance readings value of 194.6.
Similar results will be obtained when potassium hydroxide is substituted for the sodium hydroxide above.
EXAMPLE VI
In this example the liquid alkaline builder solution contained 20% by weight sodium hydroxide, 4% borax (that is, 20% by weight when based on sodium hydroxide used), and 76% water. The resulting sodium metaborate content of the solution is 5.2% of the total solution or 26% of the sodium hydroxide used. The Reflectometer readings were as follows: Oil No. 1 -- 44.1; oil No. 2 -- 38.3; oil No. 3 -- 40.4; oil No. 4 -- 40.3; and oil No. 5 -- 13.5 for a summation of reflectance readings value of 176.6.
It will be seen in comparing the sum of reflectance values, which is the more indicative figure of the Reflectometer values obtained, in Examples II through VI that the detergency value or effect of no borax and 4% borax in the builder of Example VI is substantially the same and that under these conditions the borax has no effect. However, Examples III and IV point out increasing the amount of borax 1% and 1.3%, respectively, has a material effect on the cleaning ability of the solution. The highest cleaning effect is obtained in Example V wherein 2% borax was added to the alkaline builder, that is, the ratio of sodium hydroxide to borax was 10 to 1. The reflectance value was 194.6, a 10% increase in cleaning over the similar situation where no borax, or twice as much borax, was employed. In view of the prior art, it was surprising to find such a material difference concentrated in such a short range of borax addition values. In scanning the individual oil values, it will be noted that the 2% borax addition of Example V in each instance is substantially above the values for no borax or for 4% borax.
EXAMPLE VII
To indicate the seriousness of the breakdown of polyesters on exposure to caustic in solution, the following test was prepared. Polyester film samples, cut to 3 inches × 11/2 inches dimensions (0.003 inch thickness) were prepared for use by boiling for one-half hour in a 3% hydrochloric acid solution. The scoured samples were than placed in weighing bottles, dried for one hour at 110°-120° C. and then weighed. The pre-treated and weighed polyester samples were added to 500 milliters wide mounted, conical flask containing 250 grams of alkali solution indicated below. The units were equipped to maintain reflux conditions and the film samples were processed for a period of 2.382 hours at 100° C. After treatment the film samples were again scoured with 3% hydrochloric acid solutions, dried, cooled and weighed to a constant weight. The difference between the original weight and the final weight is stated below as a percent of the original weight. Solution 1 had a molarity of 0.1234 and the polyester film had a weight loss of 0.67%. The second solution had a molarity of 0.4089 for a weight loss of 3.81%. The third solution had a molarity of 0.8360 for a weight loss of 13.5%. The fourth solution had a molarity of 1.8140 for a weight loss of 23.12%. Thus, it can be concluded that the progressive effect of strong alkali solutions is to degrade the polyester in the wash-and-wear fabric over a period of time.
For solutions 5 and 6 the time was changed to 2.012 hours and the molarity was 2.1727, the temperature being varied. Solution 5 at a temperature of 60° C. had a polyester weight loss of 1.41% and solution 6 at 90° C. had a polyester weight loss of 1.41% and solution 6 at 90° C. had a polyester weight loss of 14.7%.
For solutions 7 and 8 the temperature was 100° C., the molarity was 1.3160 and the time was varied. With solution 7 the time of exposure was 4 hours and the polyester weight loss was 33.75%. With solution 8 the time of exposure was 6 hours and the polyester weight loss was 50.56%.
Therefore, the rate of weight loss of the polyester in the wash-and-wear fabric is also temperature dependent as well as dependent upon the molarity of the alkaline builder. The greater the exposure time to the caustic, i.e., the greater the number of washings of the garment or fabric, and the higher the temperature used, which is often the case in white goods or flat goods, the quicker the fabric will be disrupted by the caustic alkaline builder. Therefore, the invention confers a real and valuable result by decreasing the hydroxyl exposure time (the caustic quality of the alkaline builder) while at the same time increasing the amount of cleaning ability.
The foregoing examples have been described in the above specification for the purpose of illustration and not limitation. Many other modifications and ramifications based on this disclosure will naturally suggest themselves to those skilled in the art. These are intended to be comprehended as within the scope of this invention.