Патент USA US2404426код для вставки
Patented July 23, 1946 v ‘ um'rao STATE s - PATENT _~ onucs 2,404,420 , CHARACTERISTICS or soup summonoaomo ronmaas Max Fredrick Bechtold and Paul Swithin Pinkney, Wilmington, Del., assignors to E. 1. du Pont de Nemours & Company, Wilmington, Del., a cor- poration of Delaware No Drawing. Application July 15,1944, erial No. 545,196 11 Claims.‘ (01117-121) A ' 1 "\ This invention relates to an improvement in the surface characteristics of solid organic poly mers and, more particularly, to increasing the scratch resistance and decreasing‘ the tackiness ' ' of the surface of solid organic polymers by de prising an acid polysilicic acid ester and a volatile organic solvent therefor. The term “acid poly silicic acid ester" is used herein in its normal meaning to denote an ester of a polymeric silicic acid, which ester contains -OH groups attached to- S1. positing a ?lm thereon from polysilicic acid ester ‘ Polysilicic acid and esters thereof are . . characterized by containing solutions. This application is a continuation-in part of application Serial No. 484,062, ?led April 22, 1943, and now abandoned. - ‘ Application Serial No. 507,591, ?led October 25, 1943, in the name of M. F. Bechtold and en 10 titled “Coated methyl methacrylate polymer” is ‘ -0-+-o-§%1 groups. I ‘ ,- More particularly the invention is carried out by applying to the surfaces of the solid organic polymer the solution of ‘an acid polysilicic acid also a continuation-in-part of application Serial No. 484,062 and relates more speci?cally to scratch resistant and weather resistant coatings ll ester in a volatile organic solvent, in a thin uni form ?lm, allowing the solvent to evaporate, and for methyl methacrylate polymer. ' _ then baking the. coated surface at an elevated Heretofore methods have been proposed for im-' temperature usually not exceeding the softening’ proving the surface characteristics such‘ as the point of the organic polymer, temperatures of scratch resistance, of solid organic polymers, par about 75° C. to 100° C. generally being satisfac ticularly transparent polymeric materials. One tory; by the use of certain expedients consid method has involved the vaporization of silica at erably higher temperatures may be used with suc low pressures followed by condensation on the cess. The. coating composition may advanta polymer surface to form a coating said to have geously contain. an organic liquid which is a sol improved resistance to‘ scratching. A second - vent ‘for the organic polymer being treated, in‘ method has depended on the incorporation of a addition to the volatile organic solvent for, the‘ solid, insoluble material such as amorphous. di ods requires elaborate equipment and the process polysilicic acid ester, and from 5% to 25%, by weight of the combined S102, of an organic poly mer which is compatible with the polysilicic acid tory for use with transparent polymers because resin and relative proportions of the components atomaceous silicaon the surface‘ of the'polymer ' to render it less tacky. The ?rst of these meth . is costly and inconvenient to operate on a com 80~ ester in the solvent-free ?lm. The speci?c choice of solvent, ?lm-modifying mercial scale. The‘ second method is unsatisfac- ' the insoluble material detracts from the clarity, gloss, and brilliance of the surface. , An object of the present invention is to provide a convenient, economical method of treating the , surfaces of solid organic polymers to improve their scratch resistance, decrease their tackiness, - ofvthe coating-composition, as well as the con ditions of application, depend, as explained here inafter, on the degree of esteri?cation and poly merization of the acid polysilicic acid ester, the nature of the esterifying alcohol, the resin being coated, and the e?ects desired. When the in vention is properly carried out, a uniform, clear, and reduce their tendency to collectdust, all ?lm is obtained ' without detracting from their gloss, brilliance, 40 transparent, glossy polysilica‘te glossy, colored ?lm is or, if a dye is included, a and clarity. A more particular object is to pro vide such a method suitable for treatment of obtained. ' _ invention given hereinafter. To the resulting solution, 196 parts of tributyl Speci?c embodiments of the invention are il transparent, solid organic polymers.‘ A further lustrated in the following examples wherein all object is to provide‘ solid organic polymers with 45 parts are by weight unless otherwise speci?ed. improved scratch resistance and non-tacky sur Example I faces. A still further and more speci?c object is to provide transparent methyl methacrylate A predominantly n-butanol solution, of poly polymer with an improved surface characterized silicic acid partially esteri?ed- with n-butanol is by its scratch resistance and yet at least equal 50 prepared as follows. An aqueous solution of polysilicic acid is prepared by adding 900 parts to the uncoated polymer with respect to clarity of a 15.5% solution of sodium silicate and brilliance. A further object is to provide on ' solid organic polymers and the like. glossy, col- ' (SiOa:NasO=3.25:1 by weight) cred coatings which are highly resistant to chip ping or cracking with rough usage. Other ob 55 tov860 parts. of'a vigorously stirred solution of 1% sulfuric acid over a period of ten minutes. jects will be apparent from the description of the - The above objects are accomplished according to the present invention by coating the surface of a solid organic polymer with a solution com phosphate and 460 parts of sodium chloride are added, Stirring is continued for one hour and 60 then the mixture is allowed to stand for one hour." 'Thefupper, .3 tributy'l' phosphate layer 2,404,42c is silicate. ' separated, centrifuged. and .dried over anhydrous -_resulting_ clear, tributyl sulfate. Heat ' is used-to .4‘accelerate' the harden- _ _ ‘ing ofthe coating. . 7 ~ . A portion. of oneside of‘ a. sample ‘of cast _ phosphate solution contains 116.5% $102 as n ' butyl acid polysilicate of a relatively low degree methyl methacrylate polymer shooting is coated of esteri?cationr To 1 volume of this solution are added rapidly and with stirring 1 volume of methanol and 2.5 volumes of benzene. The methanol solution of partially esteri?ed P01! silicic acid ‘which separates as a lower layer when .the mixture is allowed to stand for ?fteen ‘min utes contains 50% to 60% combined $102. It as butyl acid polysilicate. 'I‘his'solution is p'ré with a butanol solutionrcontaining 10.5% SiO: pared by the procedure described in Example 1.‘ V The coating is allowed to 'dry for twenty minutes. 7 v - Then the sample is baked for ?fteen minutes at 75° C. ‘The resulting coating is clear and much more resistant to scratching with dryvBon Ami than is the uncoated surface. However, it is ‘_ isseparated and dissolved-in n-butanol.‘ The ' ?nal solution contains 10.4%810: as n-butyl acid . polysillcate'oi a relatively low degree of eateri 15 ?cation (0.15 to 0.25 butyl ester group per silicon atom). _ , A coating solution is prepared by mixing 25 parts or the n-butyl acid polysilicate solution tendency to lose 7 - amoopzc a This example shows the coating ‘of ‘a methyl’ methacrylate polymer with a tert.-butyl polysilicate. ' ' prepared as described above with 2.6. parts of a 20 15%’ solution of polyvinyl butyral resin (10% by ~ droxyl) in butanol. slightly crazed and shows some adhesion when wet. The resulting solution con ' A tert.-butyl alcohol solution: of tert._-butyl° acid . polysilicate is prepared as follows: An aqueous solution of polysilicic acidis prepared by adding " tains combined S10: and'polyvinyl butyral resin 900 parts of a 15.5% solution of sodium silicate . . in a ratio of 87:13. It is ?owed on a portion (SiOo:Na-.~O=3.25:1 by weight) to- 860 partsof of one surface of a sample of each of the poly 25 a vigorously stirred solution of 7% sinfuric acid meric materials listed below. The sample is held .over a period of ten minutes. with the coated surface in a vertical position‘ to To the resulting ~ solution 200 parts of'tert.~butyl alcohol and 450 permit the excess solution to run oil. The coat parts of sodium chloride are added and the mix ing is allowed to dry at room temperature and ture is stirreduntil the sodium-chloride is dis is examined after twenty-four hours. The rel 30 solved (about ?ve minutes). The upper, tert. ative scratch resistance of the coated portion of butyl alcohol layer, which separates when the a surface is determined by wiping the whole - mixture is allowed to stand for forty-?ve minutes, surface several times with cheesecloth on which is centrifuged to remove occluded water and im dry Bon Ami, (a cleansing powder commonly used purities. The resulting clear, tert.-butyl alcohol .. for cleaning glasssurfaces) , hasmbeen placed, and solution of tert.-butyl acid polysilicate is dried comparing qualitatively the numbers and depth over anhydrous sodium sulfate. Further esteri of scratches in the coated and uncoated portions ~?cation is effected by azeotropic distillation of of the surface. water from the solution, ?rst with tert.-butyl It was round that the coating on each of the alcohol at a pressure of 75 mm. of mercury’ and polymeric materials listed below gave a surface 40 then for about twelve hours with benzene at a which was markedly superior to the uncoated pressure of 135 mm. of mercury. Duringthe surface in resistance to‘ scratching and. in some distillation the solution is. not heated above instances, possessed improved slip character istics; Cast methyl methacrylate polymer sheeting. 35° C. The ?nal product, ?ltered to remove sodium chloride which separates on removal of 45 water from the solution, contains 10.3% SiO: as Viny1 chloride/vinyl acetate interpolyiner ?lm (95:5). ' tert.-butyl acid polysilicate. one side of a sample of cast methyl methacrylate Vinyl chloride/diethyl fumarate interpolymer ?lm (86:14). polymer sheeting and allowed to dry for twenty 50 minutes at room temperature._ ' Polyvinyl chloride ?lm. The resulting clear coating is much more resistant to scratch Ethylene polymer ?lm. ing with dry Bon Ami than is the uncoatcd - Ethylene/vinyl acetate interpolym'er ?lm (8:1). Polystyrene injection molded bar. , . surface. Polyvinyl butyrate resin ?lm (10% hydroxyl). Polyvinyl alcohol ?lm plasticized with 15% 55 glycerol. Neoprene sheeting. . Y ' v - . Example 4 This example shows the coating of a methyl methacrylate polymer with a tertgbutyl acid F Coated fabric with a topcoat- of unvulcanized rubber. . ' The solution is spread thinly on a portion of > ' polysilicate prepared from silicon tetrachloride ' and'tert.-butyl alcohol. A tert.-butyl alcohol solution of tert.-butyl acid 60 Rubber hydrochloride ?lm polysilicate is prepared in the following manner. Av ?lm of an interpolymer obtained by inter» _ To 296 parts of tert.-butyl alcohol 42.5 parts of polymerization of hexamethylene diammonium . adipate, hexamethylene diammonium sebacate, and caprolactam- ' - A ?lm of N-methoxymethylpolyhexamethylen adipamide (10.67% N, 5.85% CHaO). Cellophane. ‘ ‘ . Ethyle cellulose ?lm plasticized with 11% dibutyl Dhthalate. ' ' Cellulose acetate ?lm. Nitrocellulose?lm. ‘Example 2 This example shows v‘the coating of a methyl ‘ _ methacrylate polymer with a n-butyl acid poly silicon tetrachloride is added‘over a period of ' ten minutes with stirring and cooling to keep the 65 temperature of the reaction mixture below 30° C. The mixture is warmed slowly to 65° C.,' where a vigorous reaction sets in. The tert.-butyl chlo-. ride, formed in quantitative yield, is distilled from the reaction mixture together with su?icient tert. 70 butyl alcohol to leave a solution which, after _ ?ltration, contains 12.0% 81% as tert.-butyl aci polysilicate. _ , - - ' A portion of one side of a sample of cast methyl methacrylate polymer sheeting is wet with the 75 solution, dried, and baked at 100° C. for ?fteen _ , 2,404,428 , minutes. The resulting clear coating is more ‘ resistant to scratching with dry Bon Ami than ' is the uncoated surface. This example shows the coating of a methyl _. methacrylate polymer with a butyl- polysilicate ?lmirom asolution containing a polymerizable V Example 5 _ carboxylic acid. A coating composition is prepared by mixing 10 parts of the n-butyl‘ acid polysilicate solution described in Example '6 with 1 part of methacrylic acid, 0.0015 part of lauroyl peroxide, and 0.0015 This example shows the coating of a methyl methacrylate polymer with an ethyl acid poly silicate prepared by partial hydrolysis of tetra- , ethyl silicate. , 6 Example 8 i _ A coating composition is prepared by mixing 10 parts or tetraethyl silicate,‘ 2 parts of water, part 01' benzoin. The resulting solution is spread thinly on a portion or one side of a sample of cast 2 parts or ethanol, 15 parts of butanol and a trace methyl methacrylate polymer sheeting and dried ' or concentrated hydrochloric acid and allowing for three hours at 75° C. The resulting'clear, the solution to stand at room temperature for craze-tree coating is much more scratch resistant twenty-four hours. The resulting solution is 15 than isthe uncoated surface. On the other hand, spread thinly on a portion 01 one side of a sample a coating prepared from a similar solution con taining no lauroyl peroxide or benzoin is crazed of cast methyl methacrylate polymer sheeting. It is dried in thr‘ee minutes at 75° C. to a clear and shows less improvement in scratch resistance. coating which is much more resistant to scratch Example 9 ' ing with dry Bon Ami than is the uncoated 20 surface. ' _ . . v Example 6 This example shows the coating 01' a methyl . methacrylate polymer with a polyvinyl butyral ' ~ resin-modi?ed butyl polysilicate ?lm hardened , This example shows the coating of a methyl under pressure at'a relatively high temperature. methacrylate polymer with a butylacid poly 25 A coating composition is prepared by mixing 10 parts oi the n-butyl acid polysilicate solution silicate from a solution containing toluene in addition to butanol. _ > ' described in Example 6 with 1 part of a 15% A coating composition is prepared by adding 2 solution of a polyvinyl butyral resin (10% hy parts of toluene to 10 partsof n-butanol solution droxyl) in ethanol, 1 part of methacrylic acid, and containing 9.9% 510: as nl-butyl acid polysilicate .80 5 parts of butanol. The ratio of polyvinyl butyral prepared by the procedure described in Exam resin to combined SiOa in the resulting solution is ple l. The resulting solution is spread thinly on 13:87. The solution is spread thinly on a portion a portion of one side or a sample of cast methyl of one side of a sample of cast methyl meth methacrylate polymer sheeting, dried, and baked acrylate polymer sheeting. After the‘ coating has . for sixteen hours at 75° C. The clear coating is 35 dried for ?fteen minutes at room temperature, free of craze and is much more resistant to it is covered with a smooth glass plate and heated , scratching with dry Bon Ami than is the uncoated for ?ve minutes at 150° C. to 165° C. under a pres sure of 1000 - lbs/sq. in, The resulting clear, craze-‘free coating shows unusually good adhesion ' surface. Example 7 to the methyl methacrylate polymer surface and ‘This example shows the coating of a methyl methacrylate polymer with a butyl polysilicate ?lm containing a polyvinyl butyral resin and, in some cases, a carboxylic acid. , is much more scratch resistant than is the un coated surface. , Example 10 - A coating composition is prepared by mixing 45 This example shows the coating of a methyl» 10 parts of the n-butyl acid polysilicate solution methacrylate polymer with a polyvinyl butyral described in Example 6, 6.67 parts of a 15% solu resin modi?ed polysilicate ?lm prepared from tion of apolyvinyl-butyral resin -(10% hydroxyl) ethyl silicate. in ethanol, and 8.1 parts of n-butanol. The ratio A coating composition is prepared by mixing of polyvinyl butyral resin to combined ‘S10: in the 10 parts of the partially hydrolyzed ethyl silicate solution is 1:1. A portion of one side of a sample solution described in Example 5 with 2'parts of a or cast methyl methacrylate polymer sheeting is coated with this solution. After forty-three hours at 75° C., the clear, craze-tree coating shows im proved resistance to scratching with dry Bon Ami in comparison with the uncoated surface. When the ratio of polyvinyl'butyral resin to combined 15% solution of apolyvinyl butyral resin (10% hydroxyl) in ethanol and'5 parts of butanol. The ratio of polyvinyl butyral resin to combined' S102 in the resulting solution is 23:77. A portion of a sample of cast methyl methacrylate polymer sheeting is dipped in this solution for one min 810: in the coating solution is lowered to 1 :3 and ute and'dried at room temperature for ten min utes. The sample is baked, ?rst at 75° C. for ‘75° C., a clear, craze-free coating is obtained 00 ?ve hours, and then at 100° C. for sixteen hours. the baking period ‘is reduced to sixteen hours at which shows a greater improvement in scratch ' The resulting coating is clear and shows improved resistance. When the ratio or these ingredients is lowered further to 12.5:87.5 and glacial acetic acid equivalent to 16.7% of the ?nal coating com position is added and the baking period is reduced to one hour at 75° C., a clear, craze-tree coating is obtained which shows an even greater improve scratch resistance in comparison with the un ment in scratch resistance. when the acetic acid ' hyde resin-modi?ed alkyl polysilicate ?lm pre- , coated surface. * - . Example 11 This example shows the coating of a methyl methacrylate polymer with a phenol-formalde in the above coating composition is replaceduby pared from ethyl silicate. ' isobutyric acid and the sheeting is baked for 70 A coating composition is prepared by mixing 10 parts of the partially hydrolyzed ethyl silicate sixteen hours at ‘70° C., a clear coating is obtained which shows a still greater improvement in scratch resistance. However, in the last instance the coating and the polymer surface are both a slightly cracked. solution described in Example 5 with 1 part of a 50% solution '01 a diphenyl-olpropane-formalde hyde resin in ethanol. ‘The ratio of phenol 78 iormaldehyde resin to combined $10: in the ' 2,404,426 10 ‘scratch resistant coatings having more-satisfac any form including sheet, rod, tube, supported ?lm, unsupported film, .molded article, cast ar ticle, powder, and the like. 'The clarity and scratch resistance of the coatings ‘obtainable by tory weather resistance are ,obtained- when the coating composition contains partially hydro lyzed polyvinyl acetate or a hydrolyzed ethyl ene/vinyl acetate (1:3) inixerpolymer in a ratio of 1 part to from 2 to'6 parts of silica. the process of this invention are of great advan tage when the polymers to which the coating are applied are transparent. ,However, as shown'in Optimum , coating thickness is obtained most conveniently by use of coating solutions containing from 4% to 8% solids (silicaplus modifying resin). The Example 14, excellent glossy colored coatings may be produced in which case transparency of the pressing step, when coating polyméthyl meth base polymer-is not necessarily of especial bene ‘ acrylate, is carried out preferably at from 125° C. ?t. The colored coatings are‘obtained by adding to 180° C. under a pressure of at least 150 lbs/sq. a dye to the coating composition. The dye should in. between highly polished rigid surfaces which preferably be soluble in the coating solution em may be of metal or glass. , I ployed, for example, a mixture of alcohol, water In general the surface characteristics of any or 15 and acetic acid. Du Pont fuchsine, concentrated ganic"-'polymer can be improved by application powder, Colour Index 677 is a suitable dye for thereto of a coating'comprising an organic poly this purpose. ' l silicate from a solution comprising any acid poly silicic acid ester and a volatile solvent. ' , I A solution of an acid polysilicic acid ester in ‘a solvent may also be advantageously applied to The term “organic polymer” is used herein to 20 glass. In this instance, the hardness of the sur include both natural and synthetic polymeric ma face is not improved but the coating deposited terials. ‘Organic polymers adapted to be ‘coated tends to reduce the re?ection of light by the glass by the Process of this invention include; cuma; which, in turn, tends to make the glass less visible. rone resins; indene resins; acetylene polymers, The application of the colored solutions to glass including their halogenated derivatives; ole?n 25 is particularly advantageous. hydrocarbon polymers, including polymers of _ In addition to the acid polysilicic acid esters ethylene and butadiene and their homologs, and prepared as described in the examples, acid poly~ halogen substituted derivatives thereof; ole?n silicic acid esters prepared by any other processes sulfur dioxide resins; petroleum resins, including are suitable for use in this invention. These in resins formed by oxidation of petroleum and 30 clude acid polysilicic acid esters prepared as de resins formed by reaction of petroleum constitu scribed in the following references: U. S. Applica ents with such materials as formaldehyde, tion Serial N0. 439,549, ?led April 18, 1942, by methylal, metallic halides, sulfur. and sulfur chlo Joseph S. Kirk; U. 8. application Serial No. ride; ‘resinousv halogenated ‘petroleum hydrocar 439,548, filed April 18, 1942, by Ralph K. Iler and bons; resins from halogenated petroleum hydro 35 Joseph S. Kirk, also assigned to the assignee of carbons; resins from cracked hydrocarbons; poly styrene and polymers from styrene derivatives; the present application; U. S. Patent 1,809,755; German Patent 568,545 and German, Patent 659,814. Suitable solutions can also be made by controlled hydrolysis of ethyl silicate. phenol-aldehyde resins; aldehyde resins; furufral resins; ketone’ resins; urea-formaldehyde type resins, including thioureai’ormaldehyde, mel 40 The formation of a hard, adherent polysilicate amine-formaldehyde, and dicyandiamide-formal ?lm appears to depend in large part on the ability dehyde resins; amine-aldehyde resins; sulfonaé of acid polysilicic acid esters to polymerize fur mide-aldehyde resins; nitro, resins; resins from ther until a highly polymeric structure results. such nitrogen-containing materials as hydrazine ' Therefore it is preferable that the polysilicic acid and related substances, pyrazoles, pyridine, quin 45 ester contain free silicic acid hydroxyl groups, oline. pyrrole, indole, and carbazole; resins from ‘wood and from carbohydrates; natural resins and which make possible the formation of high poly mers through condensation. It may be desirable their esters, including rosin, shellac, and ester in some cases to prepare the acid polysilicic acid‘ gum; condensation polyester resins, including ester from a neutral polysilicic acid ester in situ resins obtained from polyhydric alcohols and 60 by adding a suitable amount of water and a hy polybasic acids, and from hydroxy-acids; poly drolysis catalyst such as a strong mineral acid to amide resins and derivatives thereof; mixed the ester solution just beforev application. polyester-polyamide resins; polyether resins; The acid polysilicic acid esters may vary in polyvinyl ethers; polyvinyl alcohols; polyvinyl molecular weight from esters containing only two esters, including esters of inorganic‘ acids; poly 55 silicon atoms per molecule to those whose mole vinyl acetals; polyacrylic acids, anhydrides, esters, ' cules are of colloidal dimensions and whose sols amides, and homologs thereof; rubber and its de are approaching the gel state. In general, esters rivatives, including rubber hydrochloride and hal of relatively low molecular weight are preferred ogenated. rubber; condensation resins from halo since they areimore soluble and more compatible genated compounds; olefin-sul?de resins such as 60 with organic materials than are the relatively the reaction product of ethylene dichloride and high molecular weight esters. alkali polysul?de; phenol-sulfur and phenol-sul The acid polysilicic acid esters may vary also fur chloride resins; sulfur-aromatic amine resins; in the ratio of silicic acid ester groups to silicon » factice; drying oil'resins; cellulose and its deriva- - atoms from 0.01:1 or less to 2:1. Although the ‘ tives, including ‘Cellophane, cellulose esters, and 65 solubility of the ester inorganicsolvents and its . cellulose ethers; and proteins such as casein, zein, soybean protein, and leather. These may be mod i?ed with any of the usual modifying agents in- ' compatibility with organic polymers increase with increase in degree of esteri?cation of the poly silicic acid, the ester tends to polymerize more eluding plasticizers, pigments, ?llers, dyes, and , readily‘at lower temperatures and in a shorter materials which combine chemically with the 70 time (i. e., it forms a tack-free, hard film under . polymer ingredients either during formation of the polymeror during an after treatment. Thus, copolymers, interpolymers, and mixtures of poly milder conditions) as the degree of esteri?cation ,is' decreased. In general, the hardness of the coating obtained from an acid polysilicic~acid mers can advantageously be coated by the process ester solution decreases with increase in the de of this invention. The organic polymer may be in 75 gree of esteri?cation of the polysilicic acid. As 2,404,420 11 12 illustrated by the, above‘ examples, a butyl acid polysilicate in which the ratio of butyl groups to silicon atoms is 0.2:1 forms a hard, scratch re sistant coating merely on drying at room tem . in the acid polysilicic acid ester solution a liquid which will soften, or even better, dissolve the sur face polymer. Improved anchorage of the highly perature. As the ratio of butyl silicate groups to ' polymeric silicic acid ester coating to the polymer surface is-bften obtained in this way. Organic silicon atoms increases to 05:1 the ?lm obtained polymers vary widely, of course, in their solubili becomes softer; when the ratio reaches 0.821, the filmiwithout modi?cation) remains tacky; and ‘ing agents are well known to those who are at all" ties, but in most cases suitable solvents or swell-. when it is 1:1 or greater, the ?lm obtained re familiar with the resin ?eld. In many cases a mains oily‘unless suitably modi?ed. The pre mixture of solvents including both a relatively volatile liquid and a less volatile solvent for the organic polymer is preferable. Acid polysilicic, acid ester and organic polymer solvents useful in ferred ratio of silicic acid ester groups to silicon " atoms, depends, of course, on the nature of the‘ ester group, the nature of the polymer surface to be coated, and the characteristics desired in the this application includealcohols, ketones, esters coating. Acid polysilicic acid esters in which the 15 of organic or inorganic acids, ethers, amides, and ratio of silicic acid ester groups to silicon atoms acids. In ~general, it is preferable to include in ‘ varies from 0.1:1 to 1:1 include those useful in. the solvent composition at least 20% of an alco most polymer-coating applications. -Butyl acid hol of they group consisting of ethyl, propyl, and polysilicates containing from 0.1. to.0.3 butyl sili butyl alcohols. In the coating of methyl meth cate groups per silicon atom and ethyl acid poly 20 acrylate polymer good adhesion of the polysilicate ‘ silicates containing from 0.1 to 0.7 ethyl silicate ?lm to the polymer, particularly'lon immersion ‘ groups per silicon atom are among the preferred in water, is promoted by including in the solvent polysilicic acid esters for use in improving the composition 1 to 50% of a carboxylic acid con scratch resistance of polymeric materials. The taining 2, 3, 4, or 5 carbon atoms per molecule. optimum degree of esteri?cation for each partic Amines are not ordinarily suitable as constituents ular application can readily be determined by a of the coating composition since they cause rapid few preliminary tests. . gelation of acid polysilicicacid esters. The alcohol from which the acid polysilicicvacid In many cases the desired change in surface characteristics can be obtained more satisfac tertiary, aliphatic or aromatic, cyclic or alicyclic, 80 torily if a suitable organic polymer is included in ‘ ester is derived may be primary, secondary, or ‘ mono- or polyhydric, saturated or unsaturated, and straight chain or branched chain. It may contain additional functional groups provided such groups do not a?ect the stability of the ester. the coating composition. In general, the hard- ' ness and scratchresistance ofthe resulting coat ing are intermediate between those of the modi fying polymer and. an unmodified polysilicate' I Suitable fimctional groups include ether, halide, 35 coating. The modifying polymer must be soluble ‘ ‘mercaptan, sul?de, ketone, ester, amide, nitro, in the solvent composition used and is preferably compatible with the acid polysilicic acid ester both in the coating solution and in the solvent ‘ perior to unsubstituted esters in solubility in cer free ?lm. The compatibility of a particular or tain organic solvents and compatibility with cer 40 ganic polymer with an acid polysilicic acid ester 1 tain polymers. The alcohol from which the acid depends, as indicated'above, on the ratio of silicic ‘ In some cases acid polysilicic acid esters containing such groups may be‘ su and nitrile groups. ‘ polysilicic acid ester is derived may vary in chain length from 1 to 12 or more carbon atoms. ‘ In general the solubility of acid polysilicic acid acid ester groups to silicon atoms, the nature of ' the esterifying group, and the molecular weight of the acid polysilicic acid ester. The choice of esters in solvents in which the ratio of carbon to 45 modifying polymer and ratio of modifying poly oxygen is high (e. g., long-chain alcohols and mer to acid polysilicic acid ester in the coating esters, hydrocarbons, and halogenated hydrocar composition depends in each case on the polymer . bons), the compatibility of acid polysilicic acid which is being coated, the acid polysilicic acid 1 esters with polymeric materials in which the ratio ester being used, and the characteristics desired ‘ of carbon to omgen is high, and the softness of 50 in the coating. The modifying polymer content coatings obtained from these esters appear to in . crease with increase in the ratio of carbon to silicon in the acid polysilicic acid ester. Thus, of the coating composition solids may vary from 5% or less to 90% or more. In order to take fuller advantage‘ of the effect of the polysilicate, the modifying polymer content of the coating com-_ to silicon atoms, the preference as to which par-' 65 position ‘solids is- usually limited to 50% ‘and in ticular acid polysilicic acid ester to use in a given many cases the best results are obtained by- using" ‘ given a de?nite ratio of silicic acid ester groups 7 ‘ application depends on the polymer to be coated ' 30% or less. ‘ and the characteristics desired in the coating. A polymer which is insoluble in the preferred ‘ In the coating of methyl methacrylate polymer acid polysilicic acid ester solvents when com to improve its 'scratch resistance, acid polysilicic 60 pletely polymerized may often advantageously be . acid esters derived from alcohols containing less than six carbon atoms per molecule are preferred. Coatings with improved scratch resistance can be I obtained from longer chain esters of very low de , gree of esteri?cation.' However, the lower stabil . ity of such esters detracts from their utility. The choice of the solvent from which the acid ' polysilicic acid ester is applied depends on a 1 number of variables. One is the solubility of the acid polysilicic acid ester, which varies, as pointed _ out above, with degree of esteri?cation, nature of esterifying group, and molecular weight. The ‘ ester should, of course, be soluble in the solvent added to the coating composition while it is in- ' completely polymerized and still soluble, and then polymerized further after application of the coat ing composition. Examples ofv polymers which are preferably used in this manner are urea formaldehyde and phenol-aldehyde type poly- ' mers. In some cases it is preferable to add the ingredients of the modifying polymer and a suit able polymerization catalyst to the coating com position and carry out the polymerization either in the coating composition before application, during the evaporation of the solvent from the . ?lm, or in the solvent-free ?lm. For example, used. Another variable is the solubility of the ‘ ‘monomeric or partially polymerized methyl polymer being coated. It is preferable to include 75 methacrylate can be used in this manner. It is V 2,404,426 I 13 . probable that in some cases copolymer-s involving both the acid polysilicic acid ester and the modi fying polymer are formed. Some of the advantages of including an organic polymer in the coating composition are brought out in the above examples which illustrate the application of polysilicate coatings containing organic polymers to methyl methacrylate poly mer sheeting to form a more scratch resistant 14 'i give cracked surfaces when high temperature cur-' ing of the coatings is ‘attempted. It has now been discovered that high temperature curing of acid polysilicic acid ester containing coatings can be performed successfully on the vinyl polymers if the polymer is modified by copolymerization with a relatively small amount of bifunctional or p'olyfunctional cross linking agent.’ For example, the addition of '7 parts of methacrylic anhydride surface. \In this application a polyvinyl butyral 10 to 93 parts of methyl methacrylate in a casting resin is particularly useful. This resin decreases syrup will yield a high softening Point cast sheet the tendency of the coating to crack or craze resistant to cracking during the curing of coat- . and improves its ?exibility, adhesion to the poly ings at unusually high temperatures around 150° mer surface, resistance to deterioration on im C. In the case of styrene, a copolymer with mersion in water, and outdoor durability. 15 2%-4%, by weight of the copolymer, of meth-' It may in some cases be desirable to pretreat acrylic anhydride is more'suitable than unmodi the polymer surface which is to be coated. Thus fled polystyrene as a base material for the high" it may be softened or even made tacky by use temperature curing of the coatings. of a solvent or swelling agent before the coating In some cases improved adhesion of me poly composition is applied. Such pretreatment assists 20 silicate coating to the surface of the organic penetration of the acid polysilicic acid ester into polymer can be obtained by placing a smooth the polymer surface and leads to formation of a more [adherent coating. The acid polysilicic acid ester coating compo ' plate, such. as a piece of plate glass. over the coating after evaporation of the volatile solvent and pressing the plate-against the surface dur sition may be applied in any suitable manner, 25 ing the heating step. This technique permits use‘ of higher baking'temperatures (up to 200° C. or using a doctor knife or applicator roll. Its or 250° C.) without deformation of the polyme viscosity can be adjusted to suit the method of surface. ' application by varying the solids content of the There is evidence indicating that when the solution. The thickness of the film of ester, modi 30 modifying organic polymer in the coating solu fying polymer, and non-volatile solvent for the tition contains free alcohol hydroxyl groups, re such as by spraying, dipping, brushing, ?owing, polymer being coated‘ can be varied by varying action takes place ‘during baking between the, the proportion of volatile solvent and by varying the thickness of the ?lm of coating solution ap polymer and the acid polysilicic acid ester. The ‘ness. It may vary from 0.5% or less to 60% or orester interchange _(reaction between an alco hol hydroxyl group of the polymer and a silicic reaction probably involves either direct esteri? plied. Thus the solids content of the coating solu 35 cation (reaction between an alcoh'ol hydroxyl tion is governed by the method of application to group of the polymer and a silicic acid hydroxyl the polymer surface and the desired film thick group with formation of_ a molecule of water) more. After application of the coating solution to the 40 acid ester group with formation of a molecule polymer surface, the volatile solvent is allowed to of the alcohol from which the silicic acid ester evaporate. The time required for the evaporation is derived). A crossllnking reaction of this type depends, of course, on several factors including could conceivably take place between an acid the volatility of the solvent, temperature, the cir polysilicic acid ester and any organic polymers culation of air over the polymer surface, the which ordinarily contain free alcohol-hydroxyl thiclmess oi’ the coating applied, and the nature groups, such as polyvinyl alcohols, polyvinyl ace of the modifying polymer in the solution. The tals, cellulose ethers and esters, nitrocellulose, ‘rate of polymerization of acid polysilicic acid condensation polyesters, and any other types of polymers prepared from ingredients contain esters increases as the concentration of ester in creases. Accordingly, as solvent evaporates from 60 ing free alcohol hydroxyl groups not involved in the coating the acid polysilicic acid ester poly formation of ‘the polymer. The e?ect of this reaction is to reduce the solubility of the modify merizes more and more rapidly. The rate of ing polymer and increase the hardness of the polymerization increases also with‘ risev in tem ?lm obtained. Usually, particularly when the perature. Thus, while it may take several hours for. an acid polysilicicacid ester in which the 55 degree of esteri?cation of the acidpolysilicic acid ester is relatively high and the alcohol from ratio of silicic acid ester groups to silicon atoms which the ester is derived has a boiling point is low (0.25 or less to 1) to polymerize to a hard, above about 80° 0., it is necessary to bake the scratch resistant ?lm at room temperature, poly film at temperatures of 80° C. to 200° C.‘ for ?f merization is usually relatively complete within a few minutes at higher temperatures (100° C. 60 teen minutes to two hours-to promote the cross linking reaction to the fullest extent. It is pos to 150° (3.). A curing period of one minute to sible that a reaction of this type is involved ‘in twenty-four hours at temperatures varying from 25° C. to 150°‘ C. is normally 'su?icient to produce _'the formation of a strong bond between a poly; silicate coating and, the surface of a polymer the desired e?ect. ' , \ In addition to increasing the rate of polymer 65 which contains alcoh‘ol hydroxyl groups. The extent to which an acid polysilicic acid ization, it has been found that the scratch re-. ester polymerizes on heating depends on the ex sistance and exposure resistance of acid polysilicic tent to which it is esterifled (the ratio of silicic acid esters-hydroxylated organic polymer coat acid ester groups to silicon atoms). If, as pointed ings baked on plastics increases appreciably with increasing curing temperatures. However, the 70 out above, the degree of esteri?cation is low, the ?lm obtained is usually very hard and the hard temperature at wl'iichthe coatings canbe baked is limited by the softening temperature .of the ' ness decreases as the degree of esteriflcation in-‘ polymer being coated. This is‘ especially true of creases. The silicic acid esters of lower alcohols,v the thermoplastic resins such as methyl'methi such as methanol or ethanol, are more easily acrylate polymer and polystyrene which tend to 76 hydrolyzed by moisture in the atmosphere than 1's 2,404,426 16 ‘ are the esters of high'er alcohols, such as butanol ing from‘ 1 to 12 carbon atoms, inclusive, said ‘ or octanol. Therefore, the extent of polymeriza . tion during drying, baking, or subsequent aging ‘ increases more in the cases of the methyl and ester having from .01 to 2.0 silicic acid ester groups per silicon atom, and an organic solvent -' for said polymer whose surface is being coated. 5. A solid organic polymer having, a surface ethyl esters than with the higher esters wh'en ?lm thereon obtained by coating a surface of the polymer with a, coating solution comprising. an acid polysilicic acid ester of an alcohol'con-v ‘ these operations are carried out in an atmos phere containing appreciable amounts of mois ture. , Since amines accelerate both hydrolysis of taining from 1 to 12 carbon atoms, inclusive, said ester having, from .01 to 2.0 silicic acid ester groups per silicon atom, an organic polymeric polysilicate coating may be promoted by carrying material compatible with said ester in the sol out the drying, baking, or aging operations in a vent-free ?lm, and'an organic solvent for said moist atmosphere containing an amine such as polymer whose surface is being coated. ‘ ammonia or by ?ushing the dry, coated surface 6. A solid organic polymer having a surface , with an aqueous solution of an amine. 15 ?lm thereon obtained by coating a surface of the Through use of this invention the surface polymer with a coating solution comprising an characteristics of solid organic polymeric ma acid polysilicic acid ester of an alcohol contain~ terials are changed to enhance the utility of the ' polymeric materials in a given application- The ing from 1 to 12 carbon atoms, inclusive, said invention is particularly useful‘ for improving 20 ester having from .01 to 2.0 silicic acid ester silicicacid esters and polymerization of silicic acid, rapid formation of a 1118b]! polymerized ‘ th'e serviceability of transparent plastic mate- - groups per silicon atom, and a polymer contain " rials through application to the surface of the - - ing hydroxyl groups, dissolved in a volatile or ganic solvent. , plastic a clear, transparent coating which is more 7. A' transparent, solid organic polymer from ‘ resistant to marring and scratching than is the ‘ uncoated surface. .The invention is also useful .25 the group consisting of poiyacrylic esters and :polymethylacrylic’ esters, having a surface ?lm for decreasing the tackiness of polymer surfaces, . , thereon obtained by coating a surface of the polymer with an acid polysilicic acid ester of an the tendency of polymer surfaces to collect dust, alcoholcontaining from 1 to 12 carbon atoms, I and decreasing the re?ection, of light from the surfaces of transparent plastic materials. Fur 80 inclusive, said ester containing from 0.1 to 1.0 ther, the invention is adapted to provide glossy. silicic‘ acid ester groups per silicon atom, dis solved in a volatile organic solvent. ' colored coatings, both scratch resistant and ex 8. Process of providing a solid organic polymer posure ' sistant, on organic polymeric materials 1 and on glass. with’ improved‘ surface characteristics which comprises coating a surface of the polymer with Plastics coated in accordance with this inven ‘ particularly at elevated temperatures, decreasing tion show a reduced tendency to acquire a static charge and, therefore, are highly useful in en closing and panelling instruments subject to stat an acid polysilicic acid ester of an alcohol con taining from 1 to 12 carbon atoms, inclusive, said ester having from .01 to 2.0 silicic acid ester ic aberration, for example, galvanometers, volt groups per silicon atom, dissolved in a volatile . meters, aircraft instruments, and the like. 40 organic solvent and drying said coating. As many apparently widely different embodi -9. Process of providing a solid organic polymer I ments of this invention may be made without de- . with improved surface characteristics which ‘ parting from the spirit and scope thereof, it is comprises coating 9. surface of the polymer with to be understood that the invention is not limited an acid polysilicic acid ester of an alcohol con to the speci?c embodiments thereof except as taining from 1 to 12 carbon atoms, inclusive, defined in the appended claims. , said ester having from .01 to 2.0 silicic acid ester ' . groups per silicon atom, dissolved in a volatile 1. A solid organic poLvmer having a surface organic solvent, drying said coating at approxi- .. ?lm thereon obtained by coating 0. surface of the mately room temperature and, thereafter, bak polymer with an acid polysilicic acid ester of an 60 ing said coating at an elevated temperature. alcohol containing from 1 to 12 carbon atoms, 10. Process of providing a solid organic poly‘- . inclusive, said ester having from .01 to 2.0 silicic me'r with‘ improved surface characteristics which acid ester groups per silicon atom, dissolved in comprises coating a surface of the polymerv with ' a volatile organic solvent. a butyl acid polysilicate containing from 0.1 to 2. A transparent, solid organic polymer hav 55 0.3 butyl silicate groups per silicon atom, dis We claim: ‘ ing a. surface ?lm thereon obtained by coating solved in a volatile organic solvent, drying said . a, surface of the polymer with a butyl acid poly silicate containing from 0.1 to 0.3 butyl silicate groups per silicon atom, dissolved in a volatile ‘ organic solvent. - - . _ 3. A transparent, solid organic polymerhav ing a surface iilm thereon obtained by coating a surface of the polymer with a coating solution coating at approximately room temperature and, thereafter, baking said coating at an elevated temperature not\in excess of the softening point 60 of said polymer.. ' comprising an acid‘ polysilicic acid ester of an a 11. Process of providing a solid organic polymer with improved surface characteristics which comprises coating a surface of the polymer, with a coating solution comprising an acid polysilicic 0 alcohol containing from 1 to 12 carbon atoms, 65 acid ester of an alcohol containing from 1 to 12 inclusive, said ester having from .01 to 2.0 silicic , acid ester groups per- silicon atom, and an or-, ‘ ganic polymeric materialcompatible with said ‘ ester in the solvent-free ?lm, dissolved in a vola carbon atoms, inclusive, said ester having from , .01 to 2.0 silicic acid ester groups per silicon atom, a polymer containing hydroxyl groups, and a volatile organic solvent, drying said coating at tile organic solvent. ' ' ‘ 70 approximately room temperature and, there 4. Asolid organic polymer having a surface after, baking said coating at an elevated tempera ‘ ?lm thereon obtained by coating a surface of the polymer with a coating solution comprising an acid polysilicic acid ester of an alcohol contain ture. - MAX FY'REDRICK BECH'I'OLD. PAUL SWITHIN PINKNEY. 17 I c '18 v Certi?cate of Correction Patent No. 2,404,426. , MAX FREDRIOK BEOHTOLD v July 23, 1946. ‘It is hereby certi?ed that errors appear in the printed speci?cation of the above numbered patent requiring correction as follows: Column 8, line 43, after “hydro— lyzed” insert high; column 9, line 38, for “furufral” read furfaml; column '14, line 31, for the syllable “tition" read tion; and that the said Letters Patent should be read with these corrections therein that same may conform to the record of the case in the Patent O?‘ice. Signed and sealed this 8th day of October, A. D. 1946. [mm] ' LESLIE FRAZER. . First Assistant Commissioner of Pateiits. Certi?cate of Correction Patent No. 2,404,426. , _ ' July 23, 1946. MAX FREDRICK BEOHTOLD ET AL. It is hereby certi?ed that error appears in the printed speci?cation of the above numbered patent requiring correction'as follows: Column 7, line 24, Example 12, for “alkyl” read alkyd; and that the said Letters Patent should be read with this cogection therein that the same may conform to the record of the case in the Patent ce. ' Signed and sealed this 13th day bf May, A. D. 1947. [mm] LESLIE FRAZER. , First Assistant Commissioner of Patents.