US 3433667 A
Description (OCR text may contain errors)
United States Patent 3,433,667 POLISHING CLOTH Richard C. Gergle and James A. Merricks, Greensboro,
N.C., assignors to Dow Corning Corporation, Midland,
Mich., a corporation of Michigan No Drawing. Filed Jan. 22, 1964, Ser. No. 339,325 U.S. Cl. 117-161 2 Claims Int. Cl. C09d 3/48; C08g 47/04 ABSTRACT OF THE DISCLOSURE A polish cloth containing a partially cured methyl or ethylmethylpolysiloxane which possesses the combination of good polishing activity and resistance to repeated laundering. For example, cotton flannelette is impregnated with 33% by weight of a methylpolysiloxane fluid cured to such an extent that from 85 to 95% by weight of the fluid is extracted from the fabric by immersing the fabric in benzene at room temperature for two days.
This application relates to an article of manufacture comprising a fabric impregnated with an organopolysiloxane as hereinafter defined.
These articles are especially useful as polish or dust cloths.
The usefulness of organopolysiloxanes, especially the methylpolysiloxanes, as polishing agents has long been established. These materials when used alone or in conjunction with waxes, impart a high degree of gloss to most surfaces such as furniture, automobiles, glass, plastie, and ceramic surfaces. Fabric impregnated with methylpolysiloxanes, either with or without wax have been employed as polish cloths.
Repeated use of a polish cloth invariably results in it becoming extremely dirty and further use necessitates cleaning of the cloth. At times this can be accomplished by merely shaking the cloth but generally it requires washing in order to remove sufficient amount of dirt so that the cloth can be used again. With the organopolysiloxane impregnated polish cloths previously employed, washing removed practically all of the siloxane fluid and therefore destroyed the polishing quality of the cloth. Thus, heretofore employed polysiloxane polish cloths had limited life.
It is the object of this invention to provide a new article of manufacture which is useful as a polish cloth and which can be washed repeatedly without losing its polishing ability.
Applicants have found that the above objective can be accomplished by employing a fabric which is impregnated with a partially cured organopolysiloxane fluid. The state of cure is critical since if the cure proceeds too far one will obtain an impregnated fabric from which the siloxane is not removed by washing, but which will no longer serve as a polishing cloth. On the other hand, if the state of cure is not sufficient substantially all of the siloxane is removed after one or two washings, and the cloth is useless for polishing because there is no more fluid left therein to exude onto the surface being polished.
The article of this invention comprises a fabric which can be washed repeatedly without losing its ability to polish, said fabric being impregnated with an organopolysiloxane fluid which has been cured to such an extent that from 85 to 95 of said siloxane is extracted from the fabric by immersing the fabric in benzene at room temperature for two days.
For the purpose of this invention the siloxane should be either a methylpolysiloxane or an ethylmethylpolysiloxane in which there is on the average no more than 3,433,667 Patented Mar. 18, 1969 about one ethyl group per silicon atom. It has been found that if the polysiloxane is cured so that less than of the siloxane is extracted under the above conditions, the impregnated fabric will no longer function as a polishing cloth. On the other hand, if more than 95% of the siloxane is extracted, under said conditions, the polishing nature of the fabric is lost when it is washed. Best results are obtained when the cure is such that from to 94% of the siloxane is extracted.
It is to be understood that it is the state of cure and not the manner of cure which is critical for the purpose of this invention. Thus, the siloxane can be cured on the fabric in any conventional manner. For example, the siloxane can be cured with any of the known siloxane catalysts such as peroxides, amine salts, metal salts of carboxylic acids, quaternary ammonium hydroxides or alkyl titanates.
As is well known, peroxide catalyst cure by free radical mechanisms involving the hydrocarbon substituents on the silicon atoms. Thus, when peroxides are employed completely condensed (i.e. hydroxyl-free) siloxanes can be applied to the fabric and thereafter cured to the desired extent by heating to a temperature above the decomposition temperature of the peroxide. Many siloxane catalysts, however, cure by means of SiOH condensation. Thus when such catalysts are employed the siloxane should contain silicon-bonded hydroxyl groups. If desired, one can employ cross-linking agents such as siloxanes having the SiH groups or alkyl silicates in conjunction with the silanol condensation catalyst to facilitate cure. However, when such cross-linkers are employed care must be taken that the cure does not proceed too far.
A third method of curing the siloxane involves the reaction of SiH groups with alkenyl groups on the silicon in presence of platinum catalyst. Here again, the balance of the SiH groups and vinyl groups should be such that an over-cure is not obtained.
The preferred method of preparing the articles of this invention involves using a mixture of from 5 to 13% by weight of alkylsiloxane fluid containing Si-OH groups and from 87 to 95% by weight of siloxane fluid which is substantially free of SiOH groups. This mixture is allowed to cure on. the fabric employing a tin salt of a carboxylic acid such as stannous octoate or dibutyl tin dilaurate. The curing can be carried out at room temperature or at elevated temperatures. In order to facilitate crosslink-ing it is desirable that the hydroxylated siloxane fluid contain some trifunctional silicon atoms so as to more easily introduce branching into the system.
Preferably, this hydroxyl fluid should contain from .5 to 5 mol percent monoorgano-substituted silicon atoms. In other words, the rat-i0 of organic groups to silicon atoms in the preferred fluid ranges from 1.95 to 1.995.
The fabric used in this invention can be any fabric suitable for polishing such as tissue paper, flannel or other soft cloths.
The amount of organosiloxane in the fabric is not critical although, in general, "best results are obtained when the fabric is impregnated from 25 to 50% by weight of the siloxane based on total weight of siloxane and fabric.
In order to obtain acceptable results for polishing, the viscosity of the siloxane fluid, which is free of silanol groups should be below 1500 cs. and preferably between 200 and about 800 cs. at 25 C. This viscosity range gives the best gloss and depth of color to the polishing surface. If desired, this fluid can be a blend of two or more fluids, some of which may have viscosities outside the preferred range, so long as the blend itself falls within the range.
The wash fastness of the articles of this invention was tested by washing them in a standard household automatic washer using a standard commercial detergent and then drying the treated cloth in a standard household dryer. This is to show that the articles of this invention will withstand ordinary household laundering conditions.
The polishing test consisted of wiping the fabric on oak and maple test panels which had lacquer, varnish and oil finishes. After the fabric was wiped across the panels, the gloss was observed visibly and also measured with a gloss meter. The gloss was also checked after 24 hours in order to test the lasting quality of the finish. In addition, each cloth was rated subjectively on ease of polishing.
The benzene extraction tests were run as follows:
An 8 by 8 in. sample was maintained in a vacuum desiccator for several hours. It was then weighed and the sample is placed in a 12 cm. crystallization dish which was full of benzene and allowed to remain immersed at 72 F. for two days. The sample is then removed, air dried and again placed in a vacuum desiccator and finally weighed. The difference in weight of the sample before and after extraction gives the percent of siloxane extracted with cold benzene.
Example 1 The following mixtures were applied to cotton flannelete in amount so that the cloth contained 33 /s% by weight organosiloxane. In each case the fabric was allowed to age 4 days and then heated 4 min. at 230 F.
(a) 8% by weight of a hydroxylated dimethylsiloxane fluid of about 40 cs. viscosity at C. which fluid contained about 3% copolymerized monomethylsiloxane and (b) 92% by weight of a 350 cs. trimethylsiloxy endblocked dimethylpolysiloxane fluid.
Each of these formulations was catalyzed with 2% by weight based upon the weight of the hydroxylated fluid of stannous octoate. The cloths were each tested for polishing as described above and each was found to give excellent results both with respect to gloss and ease of polishing. Each cloth was then washed twice in an automatic washer using Tide as a detergent and the cloth thereafter dried in an automatic dryer. After each washing the cloths still gave excellent polishing by the above test. This shows that the polish cloths of this invention can be washed free of dirt in a conventional manner without ruining their polishing action.
Example 2 (1) Percent (d) 3.2 (a) 4.8 (c) 22.88 (b) 68.67
4 (d) 3.2 (e) Hydroxyl endblocked polydimethylsiloxane fluid (920 cs.) 7.6 (a) 4.8 (c) 15.28 (b) 68.67
(d) 3.2 (b) 15.2 (a) 4.8 (c) 7.68 (b) 68.67
Each formulation contained 0.45% of stannous octoate catalysts.
The percent silicone extracted by the benzene in each case and the polishing action of the cloth are shown in the table below.
Sample No. Percent silicone Percent silicone Polishing action extracted remaining before extraction 91. 3 8. 7 Excellent. 64. 3 35. 7 No good. 72. 0 28. 0 Do. 66.1 33. 9 Do.
Example 3 Equivalent results are obtained when a 350 cs. ethyldimethylsiloxy endblocked ethylmethylpolysiloxane fluid is substituted for fluid b) in mixture (1) of Example 1.
Example 4 Equivalent results are obtained when a hydroxylated ethylmethylsiloxane fluid of about 40 cs. at 25 C. which contained about 2% copolymerized monomethylsiloxane is substituted for fluid (a) in mixture (1) of Example 1.
That which is claimed is:
1. A polish cloth which can be washed repeatedly without losing its ability to polish comprising a fabric impregnated with a partially cured fluid mixture consisting essentially of (1) from 5 to 13% by weight of hydroxylated methylsiloxane fluid and (2) from 87 to 95% by weight of dimethylpolysiloxane fluid which is substantially free of silicon-bonded hydroxyl groups, having a viscosity of from 200 to 800 cs. at 25 C., said fluid mixture being cured to such an extent that from to 95% by weight of total siloxane is extracted from the fabric by immersing same in benzene at room temperature for two days.
2. A polish cloth which can be washed repeatedly without losing its ability to polish comprising a fabric impregnated with a partially cured fluid mixture consisting essentially of (1) from 5 to 13% by weight of hydroxylated methylsiloxane fluid and (2) from 87 to 95% by weight of dimethylpolysiloxane fluid which is substantially free of silicon-bonded hydroxyl groups, having a viscosity of from 200 to 800 cs. at 25 C., said fluid mixture being cured to such an extent that from 90 to 94% by weight of total siloxane is extracted from the fabric by immersing same in benzene at room temperature for two days.
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