US 3625890 A
Description (OCR text may contain errors)
United States Patent  inventor John A. Sramek Racine, Wis.
[21 Appl. No. 830,093
 Filed June 3, I969  Patented Dec. 7, I971  Assignee S. C. Johnson & Son, Inc.
 PROCESSES AND COMPOSITIONS FOR THE TREATMENT OF TEXTILE MATERIALS 17 Claims, No Drawings  0.8. CI 252/8.6, l17/l38.8 A, 117/1395 CQ, 252/305  Int. Cl ....D06m 13/20  Field of Search 252/86, 305; 117/1395 CQ, 138.8 A; 260/80 M, 80 P, DIG. l7,D1G. 19
 References Cited UNITED STATES PATENTS 2,504,049 4/1950 Richards 260/80 Primary Examiner-Richard D. Lovering Assistant Examiner-Harris A. Pitlick Attorneys-Joseph T. Kivlin, Jr. and Thomas A. Hodge ABSTRACT: Processes for reducing or eliminating the accumulation of static electric charges on carpeting and other textile fibers which comprise treating such fibers with an alkaline polymethacrylic acid mixture, the mixture being prepared by admixing polymethacrylic acid with an alkali metal hydroxide to provide a pH of at least about 9; compositions containing such polymethacrylic acid mixtures adapted to effect such reduction or elimination of static electric charges, and methods for preparing and using such compositions.
PROCESSES AND COMPOSITIONS FOR THE TREATMENT OF TEXTILE MATERIALS BACKGROUND OF THE INVENTION The buildup of static electrical charges on textile fabrics, especially in winter climates where the relative humidity is low, is a well-recognized phenomenon. Such a static electrical charge can range from an occasional nuisance to a very severe and hazardous problem in atmospheres containing explosive mixtures of gases, vapors, and/or dusts. While the problem can occur in just about any textile fiber at very low relative humidity, it is severest in natural and manmade fibers having low moisture absorption capabilities. Thus, the problem is frequently not acute with a cellulosic material such as cotton, but it is quite noticeable with relatively hydrophobic fibers such as nylon, polyester, the polyolefins, and similar fibers.
A number of methods of dealing with the reduction of static electrical charges on fabric have been discussed at length in the literature, and various compositions have been prepared to ameliorate the problem. Thus, attempts have been made, especially in textile treatment plants, to soak the fiber in some sort of an aqueous solution which will deposit a moisture-absorbing or other conductive film on the surface of the fiber. The difficulty with most of these formulations is that they are too easily removed when the fabric made from the fibers is washed or cleaned, and the antistatic substance may even be removed from the textile by physical abrasion.
Another method for dealing with this problem involves cross-linking certain substances to the surface of the fiber. While some of these methods are more or less successful, the consumer using an article made from textile fibers and finding a static buildup does not have the facilities for treating fibers and cross-linking materials to them. Moreover, even such treatments of the fiber surface frequently do not provide a fabric which combines good antistatic properties with resistance to washing, cleaning, or abrasion.
There are a number of compositions known which can be applied by the consumer to confer some immunity from the buildup of static electrical charges. Here again, durability is frequently a problem. Moreover, many such treatments so adversely affect the hand or other properties of the textile product that they are of little practical advantage.
While static electrical charge buildup is a problem with textiles in virtually all uses, it is especially manifest in carpeting, particularly in the popular synthetics which have very low moisture regain. The treatment of carpeting provides a special challenge in that it perforce is subjected to very heavy wear and accumulations of dirt and other soil. Many of the treatments which are of the greatest assistance in lowering the buildup of static electricity either have extremely low durability or, more seriously, actually exacerbate the buildup of soil on car etings. What is worse, after the carpet does become soiled many antistatic finishes frequently are virtually uncleanable by ordinary cleaning methods. This means that an extremely vigorous and wear-producing cleaning must be given to the carpet or else that the entire carpet must be removed from the home, building, or ofiice and taken to a plant for cleaning with special solvents or methods.
THE INVENTION Briefly, the present invention provides methods for reducing or eliminating the accumulation of static electrical charges on carpeting and other textile fibers, which method comprises treating textile fibers with an alkaline polymethacrylic acid mixture having a pH of at least about 9 and containing an alkali metal hydroxide. The invention also provides compositions containing such polymethacrylic acid mixtures, together with vehicles for depositing the mixture on textile fibers. ln one particularly preferred embodiment of the invention, the antistatic composition is in an aerosol propellant form which is particularly adapted for ease of application on carpeting and like textile floor coverings.
As further shown hereinafter, the processes are characterized by their ease of use, as are the compositions. The compositions and methods of the present invention further provide very good durability when used on carpeting. Thus, a particularly outstanding feature of the invention is the greatly reduced soiling of carpets. Moreover, when the carpeting does become soiled, as is inevitably the case with carpets subject to ordinary domestic and commercial use, the soil can readily be removed with common cleaning agents, particularly with anionic detergent compositions which do a good job of removing ingrained dirt and soil from a carpet.
The polymethacrylic acid utilized in the present invention is a relatively short chain polymer. Such polymethacrylic acid is prepared by the use of a bulk charge redox emulsion polymerization system utilizing an initiator and a reducing agent component to rapidly provide a large number of free radicals and form the requisite low molecular weight polymer. It will be understood by those skilled in the art that polymethacrylic acid can also include quantities of other substances in the polymer chains. Thus, it is possible to incorporate minor quantities of materials such as methylmethacrylate, but such a material will not substantially react with the alkali metal hydroxides as herein described and generally should be limited to not more than about 10 percent of the weight of the polymer. if such materials are present, higher usages of the polymer are required than when substantially pure methacrylic acid is used. Accordingly, it is preferred that the polymethacrylic acid be substantially homopolymeric.
The methacrylic acid starting material is preferably free of any substantial quantities of dimers and trimers. it is also preferred that relatively low levels of inhibitors be present. Thus, a level of monomethyl ether of hydroquinone not greatly in excess of I00 p.p.m. would be satisfactory. Lower inhibitor levels would be desirable, but it is customary that some inhibitor be present in the methacrylic acid so that it can be handled and shipped without polymerizing in an uncontrolled manner.
The polymerization is desirably carried out in aqueous or aqueous alkanol systems, lower alkanols having from two to four carbon atoms being desirable. Water is a preferred reaction vehicle. In general, the quantity of methacrylic acid in the reaction vehicle ranges from 10 to 20 percent. All parts, proportions, percentages and ratios herein are by weight unless otherwise stated.
As disclosed above, the reaction mixture contains an initiator component and a reducing component. The initiators are peroxy compounds, desirably inorganic peroxygen compounds. Preferred initiators are the alkali metal persulfates, particularly the alkali metal or ammonium persulfates such as sodium persulfate, potassium persulfate, and the like. The quantity of initiator used is preferably from l to 5 percent of the weight of methacrylic acid.
Reducing compounds are added to accelerate the formation of polymer chains. Lower oxyacids of sulfur are desirable reducing agents. Thus, alkali metal bisulfites, metabisulfites, hydrosulfites and thiosulfites can be used, as can organic sulfur oxyacids. A preferred reducing agent in the practice of this invention is alkali metal formaldehyde sulfoxylate. particularly sodium formaldehyde sulfoxylate. The amount of reducing agent used is from 20 to 60 percent of the amount of initiator.
After the methacrylic acid is dissolved in the reaction vehicle, the temperature is preferably brought into the range of 50 to C. When the desired temperature is reached the initiator and reducing agent are added. lt is particularly preferred to carry out the reaction so that a relatively low viscosity, low molecular weight polymethacrylic acid is obtained. Thus. the polymethacrylic acid prepared according to the process for use in the practice of this invention desirably has a solution viscosity of less than 650 centipoises at 15 percent solids level and a temperature of 25 C. The viscosity is desirably not less than about 50 centipoises, so the preferred range is from 50 to 600 cp., and about 600 cp. provides excellent results.
The polymerization reaction can be carried out over a wide range of pressures, including both subatmospheric and superatmospheric pressures. When water is used as the reaction vehicle. however, the use of pressures considerably below atmospheric will result in undesirable ebullition at the desired reaction temperatures set forth above. Generally, it is preferred to utilize atmospheric pressure for the reaction.
The polymerization reaction is carried out until polymerization of the methacrylic acid is substantially complete. This can be determined by gas chromatographic analysis of a sample of the reaction mixture. Generally, it is preferred that the free monomer content be less than about 0.005 percent, and this is a useful criterion of reaction completeness. The polymethacrylic acid can be used in the aqueous reaction vehicle in which it was prepared or it can be dried, as by spraydrying, to recover the pure material. if an aqueous alkanol system was used the alcohol can be stripped off, and the polymethacrylic acid can be used in that form.
The polymethacrylic acid so produced is then treated with an alkali metal hydroxide to obtain a pH of at least about 9. Generally, the preferred range pH in the practice of this invention is determined by the antistatic properties of the alkaline polymethacrylic acid on the one hand and the need to avoid excess alkalinity on the other. Moreover, operation outside of the desired range can also result both in poor cleanability of the textile fibers and in excessive dirt and soil accumulation in the textile. It is accordingly desirable that the pH range be from 9 to about 10.5. The preferred pH range for use herein is 9.6 20.2.
The treatment with alkali metal hydroxide is desirably carried out with an alkali metal having an atomic number of at least 1 1, since in most uses lithium does not have as great an effect in preventing the accumulation of static electrical charges as to the higher alkali metals. From the standpoint of antistatic activity, potassium. rubidium and cesium hydroxides provide the best results. However, in many instances, agents prepared with sodium hydroxide are found to provide slightly better cleanability. Accordingly, while sodium, potassium, rubidium and cesium hydroxides can be used, it is generally preferred to use the sodium or potassium hydroxides for treating the polymethacrylic acid. It is particularly preferred to use potassium hydroxide.
it will be understood by those skilled in the art from the present disclosure that other alkali metal substances of high alkalinity are equivalent to the hydroxides specifically described herein and are contemplated within the scope of the present invention. As is well known, many salts of the alkali metals with weak bases provide sufiicient hydroxyl ions in aqueous solutions to be substantially equivalent to such hydroxides. An outstanding example of such materials would be the alkali metal carbonates and bicarbonates.
The quantity of alkaline polymethacrylic acid utilized in the compositions of this invention for application to carpets ranges from about 3 to about percent. At lower concentrations, the excess vehicle can be troublesome, and the viscosity of higher concentrations can pose difficulties in obtaining uniform coatings on textile fibers at desirable usage levels.
To carry out the process of this invention, the alkaline polymethacrylic acid mixture is broadcast over the surface of the textile so as to form a film or coating on the fibers. lt will be understood that while a substantial improvement is obtained by distribution ofa reticulate film on the surfaces of the fibers, it is desirable that a substantially continuous film be formed on the fibers to insure maximum surface conductivity and minimum accumulation of static electrical charges.
Distribution of a greater quantity of the polymethacrylic acid mixture on the textile fibers will tend to insure continuity of the film. On the other hand, the use of excessive quantities of the polymethacrylic acid material is wasteful, needlessly costly, and at very high relative humidities can result in abnormully high soil pickup. It has accordingly been found that the best results are obtained by utilizing at least about 0.20 gram of the alkaline polymer per square foot of carpeting. On the other hand, the use of substantially more than 0.50 gram of alkaline polymethacrylic acid per square foot of carpeting provides little benefit by way of further prevention of static electrical buildup. It is accordingly desirable in the practice of this invention to distribute from about 0.20 to about 0.50 grams of the alkaline polymethacrylic acid on each square foot of carpeting.
it will accordingly be appreciated that one ounce of the alkaline polymethacrylic acid is sufficient to treat about square feet of carpeting. Less polymer is required for a cloth or other smooth textile material, whereas somewhat greater amounts may be sometimes required for very rough material such as a very deep pile carpet.
The alkaline polymer can be distributed on the carpet to be treated by sponging, soaking, sprinkling, spraying, and like techniques to provide a relatively uniform distribution of the polymer. Compositions for application to carpets are desirably aqueous and can comprise the mixture obtained directly after the polymer is treated with the hydroxide. It is desirable that the vehicle in which the polymer is distributed over the textile fibers be as volatile as possible; however, the vehicle must of course be inert with respect to the polymer and to the textile fibers upon which the polymer is to be distributed. Moreover, the vehicle in the composition for application to carpets should neither constitute a fire hazard nor provide noisome or noxious odors or vapors. it is accordingly desirable that compositions for applying the polymer to the surface of the textile fibers contain a lower alkanol, preferably one having from one to three carbon atoms in the molecule. A preferred material for use in the compositions of this invention is ethanol. Generally it is desirable that the composition contain up to about 20 percent of the alkanol.
It is found that better distribution can be obtained in some cases if the compositions of the invention contain wetting or other agents to lower the surface tension of the composition. Anionic surface active agents are preferred in the compositions, although nonionic surface active agents can also be used. Preferred surface active agents include sulfonated alkylaryl ethers such as sodium dodecyldiphenylether disulfonate, alkyl sulfates, sulfonates and the like, ethoxylated alkanol sulfates, alkanols, alkylphenols, and the like. The preferred alkyl groups contemplated in such use are the higher alkyl groups such as those obtained from triglycerides or synthesized from petroleum hydrocarbons. Thus, the chain length is from about eight to about 22 carbon atoms. A preferred dispersing agent for use in the practice of this invention is sodium dodecyldiphenylether disulfonate which material is sold under the trade name Dowfax 2A 1.
It will be appreciated from the present description that it can also be desirable to include other additives in the composition. Thus, brighteners, pigments or dyes (for carpeting of a particular color), or other materials can be incorporated in the compositions of this invention. The use of Dispal alumina or Ludox colloidal silica can retard soiling under high humidity conditions.
While the foregoing compositions can readily be distributed upon carpeting or other substrates by spraying, sponging, and the like, it has been found particularly convenient to provide the compositions of this invention in admixture with a suitable propellant for packaging in pressurized aerosol containers. it is accordingly possible for a consumer to purchase a product ready to use and apply it directly to a carpeting or other textile fabric upon which it is desired to prevent the accumulation of static electric charges. Such preferred carpet treatment compositions contain, in addition to the alkaline polymethacrylic acid, vehicle, and any other ingredient such as surface-active agent, a propellant. Such propellants include nitrogen oxides such as nitrous oxide, low-boiling hydrocarbons such as butane, isobutane, and propane, and low-boiling halogenated hydrocarbons such as dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, difluorotetrachloroethane, and the like. Such propellant preferably comprises from about 2 to about 50 percent of the total aerosol formulation.
A convenient method for measuring the antistatic properties of the processes and compositions of this invention takes advantage of the effect of the polymethacrylic acid materials upon the surface resistivity of a treated fiber or fabric made from treated fiber. Thus, one test utilized to evaluate the accomulation of static electricity involves prewashing 2-inch square samples of acetate fabrics in a 50 percent aqueous ethanolic solution of an anionic detergent such as Tide so that any antistatic agents or sizers are removed from the fabric. The prewashed fabric is then dried and dipped into a solution of the material to be tested. The excess solution is drained off for 30 seconds, and any remaining excess material is removed by absorption onto absorbent cellulose. The fabric is then air dried for 30 minutes and ironed at the synthetic temperature setting to smooth its surface and remove any remaining moisture.
The resistance measurement is made with a piece of Plexiglas methylmethacrylate plastic containing two embedded parallel copper wires. The wires are l /4inches long and are spaced one-half inch apart. The resistance is read on a General Radio Type 544-B megohm bridge. A load of approximately 650 grams is placed on the resistance-measuring plate to insure reproducibility of results. Readings are taken twice on each side of the material, the first reading on each side being taken in a first position and the second reading being taken with the plate turned at right angles to the position of the first reading. The average of the four readings is reported as the resistance of the material per unit square.
An additional advantage conferred according to the present invention is that after treatment with the neutralized polymethacrylic acid of this invention, a carpeting is much easier to clean than is the case with untreated carpets. The cleaning tends to remove the properties of the antistatic agent, but the properties are easily obtained again by a simple retreatment according to this invention.
According to the foregoing tests, it is desirable that a resistance not substantially greater than l X ohms per unit square be conferred on textile fibers to provide antistatic electrical properties. Values of resistance lower than this are of course also useful, lower values generally conferring greater freedom from accumulation of static electrical charges. The tests carried out herein indicate that the present invention confers nearly constant resistance to current flow over the range of from to 50 percent relative humidity. This will be recognized as an additional advantage of the invention in that resistance is lowered at low relative humidities, whereas excess surface moisture does not accumulate as the relative humidity is increased to and above 50 percent. This is important in eliminating soiling at high relative humidities.
The following examples are given to illustrate embodiments of the invention as it is now preferred to practice it. It will be understood that these examples are illustrative, and the invention is not to be considered as restricted thereto except as indicated in the appended claims.
EXAMPLE I Methacrylic acid in the amount of 15 parts is dissolved in 85 parts of water in a mixing vessel, and the mixture is heated to 65 C. At this temperature 1 mole percent (2.65 weight percent) of ammonium persulfate initiator and 40 percent Formapon sodium formaldehyde sulfoxylate, based upon the weight of initiator, are charged to the reaction vessel. There is a rapid exotherm of about 16 C., and the temperature of the reaction mixture is held at 80-85 C. for 1 hour to obtain a low-viscosity polymethacrylic acid. At the end of this time the reaction mixture is cooled to C. and the polymer is transferred to a holding tank.
The product is a clear, colorless liquid containing 15.5 percent solids and having a viscosity of about 600 C. at 25 C. The free monomer level is less than 0.005 percent.
The polymethacrylic acid solution so obtained in the amount of 51 grams is placed in a mixing vessel and 5.8 grams of potassium hydroxide pellets is added to obtain a pH of about 9.6.
EXAMPLE II A 2-inch square of acetate fabric is prewashed in a 50 percent ethanolic aqueous solution of Tide anionic detergent to remove any agents or sizing which may be present on the fabric. A 5 percent solution of the potassium hydroxide treated polymethacrylic acid prepared according to example I is prepared, and the square sample of acetate fabric is dipped in the solution. The fabric is then removed from the solution and excess liquid is allowed to drain ofi". The saturated fabric is then placed on absorbent paper to dry and aged overnight before performing the resistance test.
The fabric is then held at a temperature of 23 C. and 20 percent relative humidity overnight, and its resistance is measured according to the method set forth above. The resistance of this sample is about 0.81 X10 ohms. This compares with a resistance of more than 2,000 l0 ohms for an untreated acetate square.
EXAMPLE "I The following formulation is prepared:
Ingredient Amount (Parts) Alkaline polymethacrylic acid-15.54%
solids (as prepared in Example I) 5|.02 Deionized water 31.69 Solid potassium hydroxide (to give pH 9.6) 5.80 Ethanol 1 L09 "Dowfax" 2Al sulfonate (45% solids) 0.40
EXAMPLE IV Samples of the polymethacrylic acid as prepared in example I are treated with lithium, sodium, potassium, rubidium, and cesium hydroxides to obtain a pH of 9.6. Five percent of a 2- to-l mixture of sodium lauryl sulfate and sodium lauroyl sarcosinate is added to each sample for wetting. Samples of acetate fabric are washed in 5 percent solutions of each of the alkaline polymethacrylic acids and tested according to the procedure set forth in example II. After drying fabric treated in each solution is maintained at 23 C. and 20 percent relative humidity for 15 minutes and another sample of each is so maintained overnight. The results of this test are set forth in table I.
EXAMPLE V A polymethacrylic acid is prepared and treated to obtain a pH of 9.6 with potassium hydroxide as set forth in example I. Six percent of Dowfax 2A1 liquid sodium dodecylidiphenylether disulfonate is added and the mixture is sprayed onto new white nylon carpet at various use levels. After spraying the color of the carpet is measured with a photoelectric device.
The static electrical propensities of the carpet are measured by shuffling on the carpet while the testers right index finger is held in front of a Simco static locater. After these initial measurements are taken, the samples of white nylon carpet are placed in a traffic area where the carpet receives about 800-900 passes each day. The carpet is left in the traffic area for 5 days, whereupon the color and static buildup measurements are repeated. After the color has been measured the carpet is cleaned with a commercial carpet cleaning product sold under the trademark Glory, and the color is measured again. The results of such a test are set forth in table ll. The higher the color reading in table II, the lighter is the color.
What is claimed is:
1. A process for reducing the accumulation of static electrical charges on textile fibers, which process comprises applying a polymethacrylic acid mixture to the surface of textile fibers, said mixture having a pH of at least about 9 and comprising polymethacrylic acid, an alkali metal hydroxide and water or an aqueous lower alkanol.
2. A process according to claim 1 wherein the pH is from 9.2 to 10.5.
3. A process according to claim 1 wherein the alkali metal has an atomic number of at least 1 l.
4. A process according to claim 1 wherein the alkali metal is sodium or potassium.
5. A process according to claim 1 wherein the alkali metal is potassium.
6. A process according to claim 1 wherein the resistance of the textile fibers after application of the polymethacrylic acid mixture is less than l0' ohms per unit square.
7. A process for reducing the accumulation of static electrical charges on textile fibers, which process comprises providing a film of an alkaline polymethacrylic acid mixture on the surface of textile fibers, said mixture having a pH of at least about 9 and comprising polymethacrylic acid, at least one metal hydroxide, and water or an aqueous lower alkanol.
8. A process according to claim 7 wherein the polymethacrylic acid has a solution viscosity, at 25 C. and a polymethacrylic acid solids content of 15 percent, not greater than about 650 centipoises.
9. A process according to claim 7 wherein the amount of polymethacrylic acid mixture, based upon the surface area of the textile, is from about 0.2 to about 0.5 grams per square foot.
10. A composition for reducing the accumulation of static electrical charges on textile fibers, which composition consists essentially of a mixture of polymethacrylic acid, an alkali metal hydroxide, and water or an aqueous lower alkanol, the
mixture having a pH of at least about 9 11. A composition according to claim 10 wherein the alkali metal has an atomic number of at least I l.
12. A composition according to claim 10 wherein the alkali metal is sodium or potassium.
13. A composition according to claim 10 wherein the alkali metal is potassium.
14. A composition according to claim 10 wherein the pH is from 9.2 to l0.
15. A composition according to claim 10 which additionally contains an amount of a surface-active agent to lower the surface tension of the composition.
16. A package consisting of a pressurized aerosol container and containing a mixture of polymethacrylic acid, an alkali metal hydroxide, and water or an aqueous lower alkanol, the mixture having a pH of at least about 9, and additionally, a quantity of propellant sufficient to provide a sufficient pressure to discharge the mixture from said aerosol container.
17. A package according to claim 16 wherein the propellant is a hydrocarbon having from two to four carbon atoms in the molecule.
' UNITED STATES PATENT ()FFICE QE'HHCATE QEQTEN Patent No. 3,625,890 Dated December 7, 1971 Invent John A.u Sramek It is Certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 5, line 72, "600 C." should read 600 centipoises Signed and sealed this 19th day of December 1972.
EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 60876-P69 w uts. eovsnnuzur PRINTING omca mu O-!60-3M.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,625 890 Dated December 7, 1971 Inv n John A. Sramek It is certified that error appears in the above-identified patent and that said Lettersv Patent are hereby corrected as shown below:
Column 5, line 72, "600 C." should read 600 centipoises Signed and sealed this 19th day of December 1972.
EDWARD M.FLETCHER,JR. ROBERT GO'I'TSCHALK Attesting Officer Commissioner of Patents FORM PO-lOSO (10-69) uscoMM-oc 60376-P69 v US. GOVERNMENT PRINTING OFFICE: 19.9 0-55l34, Z