Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/46—Polymerisation initiated by wave energy or particle radiation
  • C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
  • C08F2/50—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light with sensitising agents
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D4/00—Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F230/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal
  • C08F230/04—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing a metal
  • C08F230/08—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing a metal containing silicon
  • C08F230/085—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing phosphorus, selenium, tellurium or a metal containing a metal containing silicon the monomer being a polymerisable silane, e.g. (meth)acryloyloxy trialkoxy silanes or vinyl trialkoxysilanes

Definitions

• This invention relates to an ultraviolet radiation curable protective coating composition. More particularly, it relates to a silicone coating composition which, when applied to a substrate, forms a protective, abrasion-resistant coating thereon.
• While transparent plastics provide the major advantage of being more resistant to shattering and lighter than glass, a serious drawback lies in the ease with which these plastics mar and scratch, due to everyday contact with abrasives, such as dust, cleaning equipment and/or ordinary weathering. Continuous scratching and marring results in impared visibility and poor aesthetics, and often times requires replacement of the glazing or lens or the like.
• One of the most promising and widely used transparent plastics for glazing is polycarbonate, such as that known as Lexan ® sold by General Electric Company. It is a tough material, having high impact strength, high heat deflection temperature, good dimensional stability, as well as being self-extinguishing, and is easily fabricated. Acrylics, such as polymethyimethacrylate, are also widely used transparent plastics for glazing.
• the present invention offers a significant advantage over many of the heretofore known coating compositions in that it does not require heat in order to initiate the cure reaction.
• the radiation cure system of the present invention expends considerably less thermal energy than conventional heat cure systems.
• Ultraviolet light is one of the most widely used types of radiation because of its relatively low cost, ease of maintenance, and low potential hazard to industrial users. Rapid photo-induced polymerization utilizing UV light rather than thermal energy for the curing of hard coating offer several other significant advantages. First, faster curing coatings offer substantial economic benefits. Furthermore, heat sensitive materials can be safely coated and cured with UV light without the use of thermal energy which could damage the substrate. Additionally, the essentially solvent free media reduces the necessity for expensive and time consuming pollution abatement procedures.
• a coating composition comprising a mixture of ingredient (A) which is the acid hydrolysis product of an alkoxy-functional si lane and ingredient (B) which is the acid hydrolysis product of an acryloxy-functional si lane or the acid hydrolysis product of a glycidoxy-functional silane, or mixtures thereof.
• ingredient (A) which is the acid hydrolysis product of an alkoxy-functional si lane
• ingredient (B) which is the acid hydrolysis product of an acryloxy-functional si lane or the acid hydrolysis product of a glycidoxy-functional silane, or mixtures thereof.
• a catalytic amount of a cationic photoinitiator which is effective for facilitating a cure reaction of the hydrolysis products.
• a cationic photoinitiator can be a radiation sensitive halonium, phosphonium or sulfonium salt.
• a radical type photoinitiator as opposed to the above- described cationic type can be combined with the cationic photoinitiator.
• This radical photoinitiator facilitates a cure reaction on the part of the acryloxy-functional portions of the hydrolyzed silanes, thereby providing a hard coating having an even tighter cure and exhibiting improved abrasion-resistance.
• ingredient (A) is the hydrolysis product of an alkoxy-functional si lane.
• Such a si lane will ordi- rily have the following general formula:
• R 1 and R 2 are the same or different monovalent hydrocarbon radicals, including halogenated species of such radicals.
• R 1 and R 2 will be lower alky! radicals such as methyl, ethyl, propyl, etc., but may include other saturated and unsaturated species including vinyl, aryl, etc.
• the letter a is aninteger from
• the hydrolysis product of such silanes is obtained by contacting the silanes with an excess of water in the presence of a catalytic amount of acid. When less than a stoichiometric amount of water is utilized, a partial-hydrolyzate is obtained. Such partial-hydrolyzates can also be used to obtain the hard coatings of present invention.
• alkoxy- functional silanes are the following: Tetraethoxysilane, ethyl triethoxysi 1 ane , diethyl di ethoxsi 1 ane , tri ethy1 ethoxysi 1 ane, tetramethoxysilane, methyl trimethoxysi lane, dimethyl dimethoxysi lane, and trimethylmethoxysilane.
• the second major ingredient is ingredient (B) which is the acid hydrolysis product of a acryloxy-functional si lane or the acid hydrolysis product of a glycidoxy-functional si lane or mixtures thereof.
• the acryloxy-functional si lane has a general formula given by
• R 3 and R 4 are the same or different monovalent hydrocarbon radicals as described above for R 1 and R 2 .
• R 5 is a divalent hydrocarbon radical having from 2 to 8 carbon atoms.
• R 6 is a hydrogen or a monovalent hydrocarbon radical.
• the letter b is an integer from 1 to 3
• c is an integer from 0 to 2
• d is an integer equaling 4-b-c. In many of the embodiments of the present invention, b will ordinarily be 3, c will be 0 and d will equal 1.
• acryloxy-functional silanes include:
• Such acryloxy-functional silanes are cor ⁇ merically available.
• 3-methacryloxypropyl tri methoxysi lane can be obtained from Union Carbide.
• the second major constituent (Ingredient B) of the coating composition may also be a glycidoxy-functional silane instead of the acryloxy-functional silane just described, or it may be a combination or mixture of both types of silanes.
• a glycidoxy-functional silane has the general formula given by (III)
• R 7 and R 8 are the same or different monovalent hydro carbon radicals, as described above for R 1 and R 2 R 9 is a divalent hydrocarbon radical having from 2 to 8 carbon atoms
• the letter e is an integer from 1 to 3
• f is an integer from 0 to 2
• g is an integer equaling 4-e-f.
• Specific examples of useful glycidoxy-functional silanes are the following:
• the ultraviolet radiation curable coating composition of the present invention will be comprised of 100 parts by weight of the acid hydrolysis product of the alkoxy-functional silane given by formula I which is combined with from approximately 10 to 1000 parts by weight. of either the acid hydrolysis product of the acryloxy-functional silane given by formula II or the glycidoxy-functional silane given by formula III, or combinations thereof. To this mixture must be added a catalytic amount of a cationic photoinitiator.
• Effective photpinitiators are radiation sensitive aromatic halonium, sulfonium or phosphonium salts which have been described in the literature.
• Cationic photoinitiators have been described by Crivello in numerous U.S. Patents and applications, such as the following, for example, which are hereby incorporated by reference: U.S. 4,136,102 issued.January 23, 1979 and U.S. 3,981,897 issued September 21, 1976.
• Such cationic photoinitiators can have the general formula given by (IV In this formula, X is a radical selected from I, P or S. M is a metal or metalloid and Q is a halogen radical selected from Cl, F, Br, or I. R 10 is hydrogen or a monovalent hydrocarbon radical having from 1 to 12 carbon atoms.
• the letter h is an integer having the value of 4 to 6 inclusive, an n is an integer having the value of 2 or 3.
• the expression[MO h ] applies to any number of ionic species but preferably will be selected from SbF 6 -, AsF 6 , BF 4 - and PF 6 -.
• the amount of the photoinitiator can range from approximately .01 to 5 parts by weight per 100 parts of the mixture of ingredient A and B.
• the cationic photoinitiators are particularly effective for initiating a cross-linking reaction between the hydrolyzed alkoxy groups of the compositions given by formulas I, II, and III upon exposure to ultraviolet radiation. Good hard coatings having excellent adhesion can thus be obtained when the coating composition is applied to a substrate and exposed to radiation such as that provided by UV lamps.
• radical-type initiator which is effective for cross-linking or self-condensing the acryloxy-functional portions of the silanes contained in the composition.
• radical photoinitiators include among others, benzoin ethers, alpha-acyloxime esters, acetophenone derivatives, benzil ketals and ketone-amine derivatives. Specific examples of these photoinitiators include ethyl benzoin ether, isopropyl be ⁇ soin ether, and dimethoxyphenyl acetophenone.
• the acid hydrolysis products of ingredients A and B can be effectively catalyzed to form satisfactory radiation curable hard coatings by combining 100 parts by weight of such hydrolysis products and mixtures with from approximately, 0.5 to 5.0 parts by weight of a combination of photoinitiators.
• the photoinitiator combination will be comprised of, approximately, 10 to 90% by weight of a cationic-type initiator such as diphenyliodonium- hexafluoroarsenate and the remaining portion is a radical -type initiator such as ethyl benxoin ether.
• Alternative embodiments of the present invention are achieved when the coating composition as discussed above is optionally further combined with from 5 to 50 parts by weight of additional acryloxy-functional.
• the UV-curable coating composition of the present invention is ordinarily coated on at least one surface of some solid substrate.
• the solid substrate may be comprised of. a synthetic organic polymer or a metal or even glass, also included are synthetic organic polymer substrates which themselves have a metallized surface.
• a priming step wherein a primer such as a thermosetting acrylic emulsion could first be applied to the substrate. After the coating composition is applied to the substrate or the primed substrate, the coating may be cured thereon by an effective amount of UV-radiation, which may be obtained from for example, a. Hanovia 550 watt lamp or a PPG Processor, Model QC1202.
• the coating compositions of the present invention can be applied to a variety of solid substrates, by conventional methods, such a flowing, spraying or dipping, to form a continuous surface film. Optimum coating thicknesses are obtained by slow dip coating procedures.
• Substrates which are especially contemplated herein are transparent and non-transparent plastics and metals. More particularly, these plastics are synthetic organic polymeric substrates such as acrylic polymers like poly-(methylmethacrylate), polyesters, such as poly(ethylene terephthalate), poly(butyl ene terephthalate), etc, polyamices, polyimides, acrylonitrile- styrene copolymers, styrene-acrylonitrile-butadiene copolymers,.
• coating compositions of this invention are especially useful as coatings for polycarbonates, such as poly(bisphenol-A carbonate) and those polycarbonates known as lexan ® , sold by General Electric
• Metal substrates on which the present protective coatings are also effective include bright and dull metals like aluminum and bright metal ized surfaces like sputtered chromium alloy.
• Other solid substrates contemplated herein include wood, painted surfaces, leather, glass, ceramics and textiles.
• Coating thicknesses may vary but for improved abrasion- resistance coating thicknesses of 3-10 microns and preferably 5 microns, are utilized.
• Example 1 Into a 200 ml three-necked flask equipped with a thermometer, a magnetic stirring bar and ice bath, was placed a mixture of 52 grams (0.25 mole) of tetraethoxysilane (TES) and 9 grams (0.5 mole of water. This heterogeneous solution was cooled to approximately 0 to 3 C whereupon 0.4 grams of perchloric acid was added. The reaction mixture was stirred as the ice melted away. After removal of some insoluble particles by filtration, a clear solution of TES-hydrolyzate having a viscosity of 5.6 centisstokes was obtained.
• TES tetraethoxysilane
• a second emulsified solution was obtained by mixing 24.8 grams (0.1 mole) of 3-methacryloxypropyltrimethoxysilane (MPTMS) and 2.7 grams (0.15 mole) of water to which 2 drops of perchloric acid were added at room temperature. After stirring overnight at room temperature, a pale, greenish solution of MPTMS-hydrolyzate was obtained having a viscosity of 8.6 centi- stokes. Into a mixture of 5 grams of TES-hydrolyzate and 4 grams of MPTMS-hydrolyzate was added 60 mg of a cationic catalyst, diphenyliodo ⁇ iumhexafluoroarsenate.
• MPTMS 3-methacryloxypropyltrimethoxysilane
• Example 2 To a mixture of eight parts of tetraethoxysilane, four parts by weight of 3-methacryloxypropyltrimethoxysilane (MPTMS), and a catalytic amount of perchloric acid, was added three molar equivalents of water at ice-bath temperature. The reaction mixture was sitrred overnight at room temperature. One hundred parts of the resultant hydrolyzate was combined With 16 parts by weight trimethyl opropanetriaerylate and 2.0 parts of a mixture of photoinitiators comprising 50% by weight ethylbenzoin ether. This catalyzed mixture was flow coated on lexan ® and subsequently air dried for 30 minutes whereupon it was cured on a UV processor. The cured composition showed good adhesion and it was cured on a UV processor. The cured composition showed good adhesion and abrasion-resistance, and required only 3 to 6 seconds to cure.
• MPTMS 3-methacryloxypropyltrimethoxysi
• Example 3 To a mixture of 152.2 g (1 mole) of tetramethoxysilane (TMS) and 36 g (2 mole) of water was added 1 g of perchloric acid at ice-bath temperature. The reaction mixture was then stirred overnight (approximately 16 hours) as the ice melted. To 50 parts by weight of this TMS-hydrolyzate was added 40 parts MPTMS-hydrolyzate as obtained in Example 1. To the resulting hydrolyzate mixture was added 1.5 parts by weight of a mixture of photoinitiators comprising 40% by weight diphenyliodonium hexafluoroarsenate and 60% by weight ethyl benzoin ether.
• TMS tetramethoxysilane
• Example 4 A mixture of 104 g (0.5 mole) of tetraethoxysilane and 18 g (1 mole) of water was cooled in an ice-bath. 0.5 g trifluoroacetic acid was then added. A clear TES-hydrolyzate was obtained after stirring overnight at room temperature. To 100 grams of this hydro lyzate was added 80 grams MPTMS hydrolyzate as obtained in Example 1. To 100 parts of this resulting hydrolyzate-was added 1.5 parts by weight of the 50-50 photoinitiator combination of Example 1. After the mixture was coated and air-dried upon lexan ® it cured to an abrasion resistant hard coating showing good adhesion upon exposure to ultra-violet radiation.
• Example 5 Into a 500 ml, three-necked flask equipped with a thermometer, mechanical stirr ⁇ r, and ice-bath was placed 236 g (1 mole) of glycidoxypropyltrimethoxysilane (GPTMS) and 54 g (3 mole) of water. The suspension mixture was. cooled at the ice-bath temperature while 0.5 g of perchloric acid was added. This mixture was filtered and a.GPTMS-hydrolyzate was obtained. A mixture of 208 g (1 mole) of tetraethoxysilane, 27 g (1.5 mole) of water and 1 g of perchloric acid was heated to 80 C for 4 hrs.
• GTMS glycidoxypropyltrimethoxysilane

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• Engineering & Computer Science (AREA)
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• Wood Science & Technology (AREA)
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• Coating Of Shaped Articles Made Of Macromolecular Substances (AREA)
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• 1981
  • 1981-03-02 JP JP56501131A patent/JPS6365115B2/ja not_active Expired
  • 1981-03-02 WO PCT/US1981/000252 patent/WO1981002579A1/en not_active Ceased
  • 1981-03-02 EP EP19810900791 patent/EP0047299A4/en not_active Ceased
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