CA1051743A - Liquid alkaline builder for liquid laundry detergent systems - Google Patents

Abstract

LIQUID ALKALINE BUILDER FOR
LIQUID LAUNDRY DETERGENT SYSTEMS

Abstract of the Disclosure In a 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.

Description

~0~7~a3 BACKGROUND

- l. Field of the Invention This invention relates to an improved liquid alkaline builder for liq~id laundry detergent ~ystems. The new builder is particularly u~eful for wash-and-wePr typ2 Qf fabrics containing high amounts of polyeste ~ibers.

2. Description of the Prior Art The increasing use o~ industri~l wasn~ng machines equipped with automatic liquid supply injection systems constitutes an impoxtant change iD the laundry and chemieal supply industries. No longer will it be pcssible to use solid products, but rather stock solutions of the detergent, builder, bleach, sour and the like will ~,e requi~d to keep ' ~he supply systems operationa1. Builders arè''included` iD `~ .
laundry formulations to enhance the cleaning capacity of - the detergent bein~ used. For ex~mple, alkaline builders extend detergent capacity by so1ubili~'ng~so11s~'hydro1yzing fats, pr~moting~foam formation and the lil.~e. ~ne of the most effective, and once extensively used, 1aundry builders is sodium hydroxide, c~mmonly called caustic soda. In addition, caustic~soda is also economical, very so1uble in water and germicidally effective. Therefore, people have ~- attempted for many years to utilize this builder'despite its~~ ~caustio nature which, in some respects, is a major drawback.
; Am~ng the alkali metal sal s which have been used as builders,~either as complete or partial replacement for the -~alkali metal hydroxides, have been the borates, phosphates, ~; silicates, carbonates~and the like.~
The detergent art is replete with many~ instances ~ ~' 30 - ~ ofl~ttempts~to use these various alkali~metal salts-~n the -: ~ .

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varîo~s branches of detergency. For instance, United States Pat~tl,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 com~irlation. ~he dis closed solution contains abou~ l/2 tc 1~ of a salt and water because a~ that concentration the h~7drolysis is substantially complete and continuous. At h gher concen-trations there is an increa3ing amount of salt whieh is not hydrolyzed. Another patent is U. S. ~,~97,193 -;elating to ~: wood bleaching wherein the bleaching composition consists of about one volume of an alkali compoQent con~.isting ~
substantially of one par~ Dy weight borax~ two parts by weight caustic soda, and one p~rt 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. 3,142,531, disclosing an industrial process for bleaching of gray cotton knit goo~s~
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 ~mmersed in the peroxide bleaching~solution at a temperature of : ~ :
170~F. to 190 F. for a period of 280 to 320 minutes. A
still later U. S. patent, ~,529,999, ~iscloses a method ~or .
cleaning natural and;artificial stones~by the use of an aqueous solution consisting of an alkali metal h~droxide, 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 , 5~ 3 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. patent 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 ~. 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 carbona-te, 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 reductlon in the concentration of the primary germicidal component, namely, sodium hydroxide.
The present invention relates to 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 in-cluded in said aqueous solution in an amount from about 5 to 15 weight percent of the amount of said hydroxide present, there-by 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, so that the available hydroxyl ion concentra-tio~ of said solution is decreased but its alkalinity and detcryency are increascd.
In a liquid laundry detergent system employing an alkaline builder solution, the preferred alkallne 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 ~5~ 43 even though there is a technical advantage in the use of the potassium hydroxide solutions. These solutions on a weight per-cent of total basis contain from lO 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 concentra-tion.
An effective means has now been found for reducing caustie soda or caustic potash available hydroxyl ion concen-tration, while increasing its detergency by in situ reacting it with the alkali salt sodium borate (Na2B4O7), .:

5~ ~ ~ 3 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 th~ builder. Based on the amount of caustic solids initially in the solution, it has been ~ound advantageous to add fro~ about 5 to about 15 weight ~ercent o~ b~rax and preferably from about 8 to 12 weight percent of bora.~ with 10~ by weighc being preferred. Eight weight percent of borax with yield 10.~ weight percent sodiur~l metaborate, 10~ borax yie~ds 13 ~eight percent sodium metaborat~ while 12 weight percent borax yields 1~.7 w_igh~ percent soditm m2tabcrate.
Although ~he total alkali concentration of the system is increased, the net available hydroxyI ion co~centration has been reduced. When 2fi 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 ~s achieved, namely, that the 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 llquid alkaline builder containing the same amount of caustic soda plus 20% borax (by weight of the initially present caustic soda) .
had the same cleaning effi~iency. Whereas lesser amounts of borax added to the alkaline builder in the same liquid ~ _6_ .
'.

~ 3 cleaning system had increasing amounts of efficieney 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 ~oil wnich hcs been re~.oved from th~ fabric being redeposited on the ~Çabric during ~he sub-sequent period of washing. H~wever, in a liquia system the ~ypical surfactant employed is not readily compatible with - an anti-redeposition agent ~nd, thexefore, must be injected into the wash via a different cond~it. 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 ~uilder solution of this invention in no way inhlbits 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 abou 1.5 weight percent with a typical amount being 0.75 to 110.: Typical anti~redeposition agents employed include the alkali and ammonium salts of carboxymethylcellulose, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl Gellulose and the like.
The alkaline buiIder solution of this invention is added to thé wash in the conventional manner for utilizing liquid detergent systems. -The amoullt of alkaline builder to be addëd, 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 .
.
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S~L~79t3 than those which would be immediately obvious to those of ordinary skill in the art. Therefore, for the sake of .
brevity further elucidation oE the obvious will not be made at this time The practice of this invention is illustrated by, but not limited by, the examples g;ven below. Unless otherwise noted, temperature is ex~ress~d in degrees centigrade and parts are parts by weight.

EXAMPLE I
A liquid alkaline builder solution was prepared containing ~0% by weight caustic soda and 80~o 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-~i~ration 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 w s 11.9.
~ 20 The solution required 17.~ milliliters of 0.3 N hydro-; chloric 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 o~ 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 li~wid builder solution to a marked amount inasmuch-as less ~ ` .
;
.~

1/~517g~3 acid was required to achieve the same pH. The alkaline builder solution containing the anti-redeposition agent required only 16.L milliliters ~o reach the pH of 4. It is believed that the slight fllrther reduction in alkalinity in tha~ solution over the caustic/borax solution was due to the physical entrapment of thle hydroxyl ion~s 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 d termined ~y washing crank-case oil soiled swatches of polyester-cotton cloths in an aqueous solution of the li~uid laundry ~letergen~ system ~ containing the alkaline builder to be~evaluated under the following conditions: -(1) water temperature - 180~ F., ~ ;
(2) detergent eoncentration~-~
0.2510 by weight c~mmercial nonicnic ~-liquid detergent mi-~ture, 0.~510 liquid alkaline buil~er a~ -~
- ~ ~ specified, ~ ~-

(3)~ time - 20 minutes.
The liquid nonionic c~mmercial detergent used in the examples contained a nonionic liquid detergent poly-ethylene glycol ether of linear alcohol having a HLB value :
of 13.3 (45'~ of the total), a nonionic modified alkylene -~
oxide condensation o~a linear alcohol having a HLB
; value of 15.0 (constituting 15% of the total composition~
optioal~brightener, O.lqo of the total composition, aliphatic . , ~ , , .
~0 solvent, c~nprising 34.9~o of the total composition and the ~
~, .
~ remaining 5'1~ was water.~

51~43 The swatches w~re 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 of frame so constructed that 20 one-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, rising and drying the amounts of soil removal, that is, the amount of cleaning performed on ~ 20 each swatch was determined by use of the Reflectometer, ; manufactured by ~unter Associates Laboratory, using the Hunterlab D-40 green Reflectometer readings as the final result. Three swatches were wa~hed 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 u~ed crankcasa oils were used to soil the various swatches by placing one drop of oil - lû
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~ 7 ~3 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 4-1/4" x 4-1/4" in size. The Reflectome~er readings (an average of ~ 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 ~8.6; and No. 5 oil was 12.8 for a summation of the readings vallle of 177.8.

EXAMPLES III-VI
Following t~e procedure of Example~ II except for di~ference in the liquid alkaline builder solution employed, Examples III through VI were performed and the test data is noted undern~ath each example heading. Throughou~ all tests the same identificatio~ was maintained or each lot of use~
- ~ crankcase oil.

EXAMPLE III
The liquid alkaline builder used in this~example contained 20~ sodium hydroxlde, l~o borax (that is, 5%~by weight of the sodium hydroxide initially employed) and~
79~0 water. The~resulting sodiùm metaborate content of~the ;`~
solution was 6.5~ o~ the sodium~hydroxide used.~ The Reflectometer readings for the oils were as follows:
Oil No. 1 - 44.2; oil No. 2 - `44.~, oil No. 3 - 42.6; oil No. 4 - 41.5; and oil No. 5 - 13.1 for a sum of reflectanc~
. ~
readings value~of 185.7 ~ ~
:
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;EXAMPLE IV ~
The liquid alkaline builder o~ thi~ example contained 20~;by;weighè sodium hydroxide,~1.3% borax (that is, 6-2/3%~by weight~based on the amount of initially`
present sodium~hydroxide),;and~78.7% water.~ ;The res~l~ting , , , ; . , , : . . . ~ , . .

sodium metaborate content of the solution was 1.7% of the total solution. The Reflectome~er readings were: Oil No. 1 ~ 45. 8; oil No. 2 - 43.5; oil No. 3 _ I~ O; oil No. 4 - 40.7; and oil No. 5 - 12.0 for a sum of reflectance readings value or 185Ø
EXAM]?LE V
~.. .
In Lhis exampLe the liquid alkaline builder sol~tion contained 20~ sodium hydroxide, 2qo borax (that is, - 10% by weight when based on sodium hydroxide initially present), and`~78~0 water. The resulting sodium metaborate con~ent of the solu~ion -was 13.0~a of the sodium hydroxide~
used. The Re~lectometer readings were as follows~: Oil No. 1 _ 46.2; oil No. 2 - 45.2; oil No. 3 - 44.5; oil o,--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 sybstituted for~ the sodium hydroxide~above.

EXAMPLE VI
~; In~this example~he~Iiquid alkaline builder .
solution contained 20~ by weight sodium hydroxide,`4~ borax (that is, 20% by weight when bas~d on sodium hydroxide used), and 76~ water.~ The resulting sodium metaborate-coDtent of the solution is 5 . 2qo o f the total solution or 26~ of the sodium hydroxide used. The Reflect~ometer , readings were as ollows:~ Oil~No. 1 ~44.1; oil No. 2 -~
.
. . 38-3; oil NoO ~ - 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 o~
reflecta~ce va~ues, w~ich ;s the more indicative figure ~-~

! ' ' , . 1 ~ 5~ 7 4 o the Reflectomete~ values obtained, in Examples II through VI that the detergency value or efect 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 i.3~, respectively, has a material effect on the cleaning abiLlty c 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 i. ~he - reflectance value was 194.6, a 10~ incre~se in cleaning ver the similar situ~tion where no borax,or t-~ice as m;uch borax, was employed. In view o~ th~ prior art, it was surprising to find such 2 material d-flerenc~ conc~ntrated in such a short range of borax addition va'ues. I~ scanning ~he individual oil values, it will be noted that the 2 borax addition of Example V in each instance is substan ially above the values for no borax or for 4~ bora~.
.
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 ~" x 1-1/2" dimensions (0 0~3" thickness) were prepared for use by boiling for one-half hour in a 3~ hydrochloric acid - solution. The scoured samples were then placed in weighing bottles, dried or one hour at 110-120 C. and then weighed.
The pre-treated and weighed polyester samples WerQ added to - 500 milliliters wide mouthed, conical ~lask containing 250 grams of alkali sol~tion indicated below. The units 3Q were equipped to maintain reflux conditions and the film :.
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1~ 5~ ~ ~ 3 samples were processed for a period of 2.~82 hours at 100 C. After treatment the film samples were again scoured with 3~ hydrochloric acid solutions, dried, rooled 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 ha~ a weigh~ loss of o.67~..
The second solution had a molarity of 0.4089 ~or a weight loss of 3.81~. The third solution had a molarity of 0.8360 for a weight loss of 13.5~. The fourth solut.ion had a molarity of 1.8140 for a weight loss of ~8.12~. Thus, it can be collcluded that the progressive efrect or strong-alkali solutions is to degrade the p~lyeste- in the . wash-and-wear fabric over a perioa oE time..
For solutions 5 and 6 the ti~e was changed ~o 2.012 hours and the molarity was 2.1727, the temperature being varied. Solution 5 a~ a temperature of 60Q C. had a polyester weight loss of 1.~1~ and solution 6 a~ 90 C. had a p~lyester weight loss of 14.7~.
For solution5 7 and 8 the temperature was 100 C., the molarity was 1.~160 and the time was varied. With - solution 7 the time of exposure was 4 hours and t~e poly-ester weight loss was ~3.75~. 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 temyerature dependent as well as dependent upon the molarity of the alkaline builder. .The greater the exposure time to the ;
~0 caustic, i.e., the greater the number of washings of the : -14-.

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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..:~herefore, 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 elean-ng ~ility.
The foregoing e~amples have ~een descri~ed in the above specification for the purpose of illustration and not iimitation. Many other modifications and ra~ifications '~ased on this disclosure will naturally suggest themselves to tkose skilled in the art. The~e are int~nded to be comprehended as within the s~ope of this invent.on.

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Claims (9)

The embodiments 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 solu-tion in an amount from about 5 to 15 weight percent of the amount of said hydroxide present, thereby 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.

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 meta-borate 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, the sum of all components equals 100%.

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, poly-vinyl 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.