GB1116725A - Surface treatment of organic polymers - Google Patents

Abstract

The surface of a "vinylic polymer" is treated by applying a film comprising an organosilicon compound, free from aliphatic unsaturation, containing at least one HSR'Si­ radial, wherein R' is a divalent hydrocarbon radical free from aliphatic unsaturation, and applying energy to the surface whereby the organosilicon compound is irreversibly attached to the vinylic polymer. The term "vinylic polymer" refers to any organic polymer formed by the polymerisation of aliphatically unsaturated carbon-carbon bonds e.g. polyethylene, polypropylene, poly (acrylonitrilebutadiene-styrene), polystyrene, polymethylmethacrylate, poly (acrylonitrile-styrene), polyisobutene, polyvinyl chloride, polyvinyl acetate, poly (vinyl chloride-vinylidene chloride), and organic rubbers such as natural rubber, butyl rubber, ethylene-propylene-cyclohexadiene terpolymer, styrene-butadiene rubber, and butadiene-acrylonitrile rubber. The organo-silicon compound may be a silane of formula (HSR1-)mRn SiX4-m-n or partial hydrolysate thereof, where R is a monovalent hydrocarbon or halohydrocarbon radical free from aliphatic unsaturation, R' is a divalent hydrocarbon radical free from aliphatic unsaturation, m is 1, 2 or 3, n is 0, 1 or 2, and the sum of m and n is 1, 2 or 3, and X= is a hydroxyl radical or a hydrolysable substituent free from aliphatic unsaturation. More than one type of R and R' groups can be present. Examples of X are alkoxy radicals, halogen atoms, acyloxy groups, hydrocarbyl-substituted isocyanoxy groups, isocyanate groups. Examples of suitable silanes are listed. Energy may be applied to the surface in the form of heat in the absence of air, ultra-violet radiation. It is believed that the mercaptan groups on the organo-silicon molecules react with linkages in the organic polymeric surface. The vinylic polymer, say rubber, may be heated to the vulcanising temperature in a mould using the mercapto siloxane as a mould release fluid. There may be applied to the same surface of the treated vinylic polymer a film of a substance selected from compounds of formulae <FORM:1116725/B1-B2/1> and partial hydrolysates thereof, to impart oleophobicity to the surface, and X4-m-n <FORM:1116725/B1-B2/2> where R\yF is any alkylene radical containing not more than 4 carbon atoms, and is a positive integer, Q is a hydrogen atom or a R\yFNH2 radical, and partial hydrolysates thereof, to render the surface hydrophilic, silicic acid and partial condensates thereof to produce an essentially silica surface thus increasing the coefficient of friction, a polyglycol end blocked with a functional group that reacts with the hydrolysable groups on the surface to produce a hydrophilic or slightly hydrophilic surface. These substances may be applied simultaneously with those in the first treatment described. Water soluble dyes, inks and printing pastes, such as polyamide resins containing pigments, can be permanently affixed to the surface rendered hydrophilic as above, making possible the dyeing of thermoplastic fibres and printing on thermoplastic sheets. In another embodiment of the invention, a vinylic polymer surface is lubricated by treatment with a liquid siloxane polymer having a viscosity of at least 45cs. at 25 DEG C and consisting essentially of at least 2 units on the average of formula <FORM:1116725/B1-B2/3> per siloxane polymer molecule, at least five times as many these units of (HSR1-)mRk <FORM:1116725/B1-B2/4> units, where n is 0, 1 or 2, m is 1, 2 or 3, k is 0, 1 or 2 and the sum of m and k is not more than 3. The preferred siloxane is a linear dimethyl siloxane polymer with <FORM:1116725/B1-B2/5> groups as endblocking units. The oganosilicon compounds may be applied to the surface in pure, undiluted form or as solutions and emulsions. Methods of making the mercaptosilanes and mercaptosiloxanes are described. In Examples (1 to 4), various formulations of rubbers are vulcanised using mercapto-siloxane polymers as mould release agents, including in Example 1 a formulation comprising styrene-butadiene rubber, polybutadiene rubber, silica, zinc oxide, coumarone-indene resin, sulphur, stearic acid, and their characteristics compared with non-treated rubbers. In Example (5), steel panels primed with (CH3O)3SiCH2CH2CH2NHCH2 CH2NH2 are bonded to films of polyethylene, or acrylonitrile-butadiene-styrene terpolymer, and films of mercapto siloxanes are applied to the thermoplastic faces of the panels. In other Examples, (6) natural rubber is treated to form permanent lubricating characteristics, (7) polypropylene yarn is treated prior to dyeing with a solution of a water soluble dye, (8) a treated sheet of polyethylene was coated with (9) a thin film of 3, 3, 3-trifluoropropyltrimethoxy-silane to obtain an oleophobic surface (b) C7F15CH2CH2SiCl3 to obtain a hydrophobic surface, and a polyethylene container is treated and coated with (b), (9) a treated polyethylene sheet is further treated with (CH3O)3SiCH2CH2 CH2NHCH2CH2NH2 and coated with a polyamide resin useful as a printing paste, (10) two polyethylene sheets are treated and then coated with an aqueous dispersion of colloidal silica, the coefficients of friction then being measured, (11) a treated polyethylene sheet is treated with an ethylene-propylene polyglycol co-polymer end-blocked by reaction with <FORM:1116725/B1-B2/6> OCH2CH2CH2Si(CH3) to obtain an hydrophilic surface, (12) a ring of butadiene-acrylonitrile rubber is treated and then coated with <FORM:1116725/B1-B2/7> , a partial hydrolysate of (C4F9CH2CH2)2Si(OC2HS)2, <FORM:1116725/B1-B2/8> or <FORM:1116725/B1-B2/90> to obtain an oleophobic rubber ring resistant to swell in organic solvents.