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
  • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
  • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
  • C08F299/06—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from polyurethanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/67—Unsaturated compounds having active hydrogen
  • C08G18/671—Unsaturated compounds having only one group containing active hydrogen
  • C08G18/672—Esters of acrylic or alkyl acrylic acid having only one group containing active hydrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/67—Unsaturated compounds having active hydrogen
  • C08G18/68—Unsaturated polyesters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/04—Coating
  • C08J7/0427—Coating with only one layer of a composition containing a polymer binder
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/04—Coating
  • C08J7/046—Forming abrasion-resistant coatings; Forming surface-hardening coatings
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2475/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers

Definitions

• the invention relates to a process for treating a substrate with a radiation curable coating composition based on a polyester resin esterified with acrylic acid and/or methacrylic acid, a vinyl compound and a photoinitiator, the coating composition being dried under the influence of ultraviolet light having a wave length of 200 to 600 nm.
• a process of the type indicated above is known from Britsh Patent Specification 1 286 591, in which, however, the coating composition is subjected to ionizing radiation by means of an electron beam and the presence of a photoinitiator is not required.
• the ionizing radiation is carried out with the aid of ultraviolet light, the man skilled in the art with usually incorporate a photoinitiator into the coating composition.
• the present invention has for its object to provide a process which is technically feasible with the aid of simple devices.
• use may further be made of a solvent-free composition which, after having been applied to a substrate, will be dry to the touch upon being exposed to a few minutes radiation with a UV lamp, so that the coated substrate can immediately be subjected to further treatment.
• the coating layer will have the same hardness as after being baked.
• a further important advantage consists in that the coating layer combines good hardness with satisfactory flexibility.
• the process according to the invention is now characterized in that the polyester resin esterified with (meth)acrylic acid has a hydroxyl number in the range of 50 to 250 and an ethylenic unsaturation equivalent weight in the range of 200 to 10,000 grammes, and in that the coating composition also contains a polyisocyanate in an amount of 0.7 to 1.3 equivalents of isocyanate per equivalent of hydroxyl contained in the composition.
• the unmodified polyester resin may be prepared in any convenient manner and is generally built up from one or more aliphatic and/or cycloaliphatic mono-, di- and/or polyvalent alcohols and one or more aliphatic, cycloaliphatic and/or aromatic divalent or polyvalent carboxylic acids and, optionally, one or more monovalent carboxylic acids and/or esters thereof.
• suitable alcohols may be mentioned benzyl alcohol, ethylene glycol, propylene glycol, neopentyl glycol, hexane diol, dimethylolcyclohexane, 2,2-propane-bis(4-hydroxycyclohexane), 2,2- bis(p-phenyleneoxyethanol)-propane, diethylene glycol, glycerol, trimethylol ethane,trimethylolpropane, pentaerythritol and/or dipentaerythritol.
• one or more epoxy compounds may be used, for instance ethylene oxide, propylene oxide, epoxy propanol and isodecanoic glycidyl ester.
• suitable di- or polyvalent carboxylic acids may be mentioned maleic acid, fumaric acid, itaconic acid, citraconic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, phthalic acid, dichlorophthalic acid, isophthalic acid, terephthalic acid and/or trimellitic acid.
• the carboxylic acid also may be used in the form of an anhydride, for instance maleic anhydride or phthalic anhydride. It is preferred that as dicarboxylic acid phthalic acid should be used.
• the polyester resin may further contain monocarboxylic acids such as synthetic and/or natural fatty acids having 4 to 36 carbon atoms or esters of these carboxylic acids and polyvalent alcohols such as glycerol.
• monocarboxylic acids such as synthetic and/or natural fatty acids having 4 to 36 carbon atoms or esters of these carboxylic acids and polyvalent alcohols such as glycerol.
• suitable monocarboxylic acids may be mentioned fatty acid precondensates having 5 to 10 carbon atoms, heptanoic acid, pelargonic acid, isonoanoic acid, lauric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, cerotic acid, benzoic acid and/or tert.butylbenzoic acid.
• the fatty acid content of the polyester resin may generally be in the range of 0 to 60, and preferably in the range of 0 to 35 per cent by weight, based on the polyester resin. It is, of course, also possible to employ mixtures of 2 or more polyester resins.
• the hydroxyl number of the polyester resin(sl not esterified with acrylic acid and/or methacrylic acid is generally in the range of 55 to 550, and preferably in the range of 100 to 400.
• the polyester resin may be prepared in any convenient manner, for instance by the so-called melting process in which reaction of the components takes place with evaporation of the water evolved in the reaction. If desired, however, use may be made of the solvent process, in which the water is removed azeotropically with the aid of, for instance, an organic solvent such as toluene or xylene and generally the volatile constituents are to the desired extent removed in vacuo. Esterification of the polyester containing hydroxyl groups may be effected in some convenient manner. Usually first of all a polyester resin is prepared which has such a high hydroxyl number, for instance a hydroxyl number in the range of 55 to 550, that after esterification the modified polyester resin has the desired hydroxyl number in the range of 50 to 250.
• Esterification can be effected in an organic solvent, for instance toluene or xylene, use being made of an esterification catalyst, for instance p-toluene sulphonic acid, naphthalene sulphonic acid and sulphuric acid.
• an esterification catalyst for instance p-toluene sulphonic acid, naphthalene sulphonic acid and sulphuric acid.
• the polyester-forming components together with acrylic acid and/or methacrylic acid may be subjected to polycondensation, so that the preparation of the modified polyester resin can be effected in one step.
• the modifiedpolyester resin has an ethylenic unsaturation equivalent weight in the range of 200 to 10,000 grammes, and preferably in the range of 250 to 3,500 grammes.
• ethylenic unsaturation equivalent weight of the polyester is to be understood here the number of grammes of polyester corresponding to 1 equivalent of the ethylenically unsaturated groups in the polyester. It is preferred that this unsaturation should for 35 to. 100%, and preferably for 45 to 100%, be caused by the presence of the acrylic acid and/or methacrylic acid groups.
• the radiation curable coating composition generally also contains one or more vinyl compounds for instance in amounts of 5 to 1900, and preferably of 25 to 900 parts by weight per 100 parts by weight of the modified polyeater resin.
• suitable vinyl compounds may be mentioned styrene, divinyl benzene, diallylphthalate and acrylic or methacrylic (hydroxyl esters of alcohols having 1 to 12 carbon atoms, such. as methanol, ethanol, butanol, ethylene glycol, propylene glycol, neopentyl glycol, butane diol, hexane diol, polyethylene glycol, glycerol, trimethylol ethane, trimethylol propane and pentaerythritol.
• the radiation curable coating composition further contains one or more photoinitiators in a usual amount of 0.1 to 10% by weight, based on the modified polyester resin and the vinyl compound(sl.
• photoinitiatiors may be mentioned aromatic carbonyl compounds such as benzoin and ethers thereof, such as the methyl ether, the ethyl ether, the propyl ether and the tert.butyl ether, benzil, benzildimethylketal, acetophenone, substituted acetophenones such as diethoxyacetophenone, benzophenone, substituted benzophenones, Michler's ketone and chlorothioxanthone. It is preferred that use should be made of benzildimethylketal.
• coloured compounds such as aromatic azo compounds may be employed.
• the coating composition still contains one or more polyisocyanates, by which are to be understood here compounds having at least 2 and not more than 10, and preferably 2 or 3 isocyanate groups per molecule.
• the polyisocyanate may be of aliphatic, cycloaliphatic or aromatic nature and generally contains 6 to 100 carbon atoms and preferably 20 to 50 carbon atoms.
• suitable (ar)aliphatic or cycloaliphatic diisocyanates may be mentioned tetramethylene diisocyanate, hexamethylene diisocyanate, ⁇ , ⁇ '-dipronylethe diisocyanate, thiodipropyl diisocyanate, cyclohexyl-1,4-diisocyanate, isophoron diisocyanate, dicyclohexyl methane-4,4'-diisocyanate, dicyclohexyldimethyl methane-4,4'-diisocyanate, xylylene diisocyanate, 1,5-dimethyl (2,4-w-diisocyanato- methyl)benzene, 1,5-dimethyl-(2,4-w-diisocyanatoethyllbenzene, 1,3,5-trimethyl-(2,4-w-diisocyanatomethyllbenzene and 1,3,5-triethyl-
• aromatic diisocyanates may be mentioned toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthalene diisocyanate, 3,3'-bistoluene diisocyanate and 5,5'-dimethyldiphenylmethane-4,4'-diisocyanate.
• suitable triisocyanates may be mentioned the adduct of 3 molecules of hexamethylene diisocyanate and 1 molecule of water (marketed by Bayer under the trade name Desmodur N), the adduct of 1 molecule of trimethylol propane and 3 molecules of toluene diisocyanate (marketed by Bayer under the trade name Desmodur Ll and the adducts of 1 molecule of trimethylol propane or 1 molecule of water and 3 molecules of isophoron diisocyanate.
• a suitable tetraisocyanate may be mentioned the adduct of 1 molecule of pentaerythritol and 4 molecules of hexamethylene diisocyanate.
• Use also may be made of mixtures of two or more of the above - envisaged polyisocyanates. More particularly, use may be made of the adducts based on hexamethylene diisocyanate, toluene diisocyanate or isophoron diisocyanate.
• the polyisocyanate is present in the radiation curable composition in such an amount that per equivalent of hydroxyl not more than 1.3 equivalents of isocyanate are available in the composition.
• per equivalent of hydroxyl not more than 1.3 equivalents of isocyanate are available in the composition.
• 'per equivalent of hydroxyl at least 0.7 equivalents of isocyanate should be available. It is preferred that per equivalent of hydroxyl 0.9 to 1.1 equivalents of isocyanate should be available.
• the coating compositon may, if desired, still contain other additives, for instance: pigment dispersing agents, levelling agents, fillers, colourants, solvents, polymerization inhibitors such as a quinone or a hydroquinone or alkyl ether thereof, p.tert.-butyl catechol, phenothiazine and copper, accelerators for the UV-curing step, for instance tertiary amines such as triethanolamine and N-methyldiethanolamine and catalysts for accelerating the reaction between the polyester and the polyisocyanate after the composition has been applied to the desired substrate.
• additives for instance: pigment dispersing agents, levelling agents, fillers, colourants, solvents, polymerization inhibitors such as a quinone or a hydroquinone or alkyl ether thereof, p.tert.-butyl catechol, phenothiazine and copper
• accelerators for the UV-curing step for instance tertiary amines such as triethanolamine
• coating composition to the substrate may be carried out in any convenient manner, for instance by calendering, rolling, spraying, brushing, sprinkling, flow coating, dipping, electrostatic spraying or by some printing process such as offset printing. It is preferred that the composition sbould be applied by rolling, spraying, flow coating or offset printing.
• the coating composition may with advantage be applied to a substrate of a synthetic material such as polyvinyl chloride, polystyrene, polyester and to metal substrates, for instance as automobile paint or automobile repair paint, and as coil coating or can coating.
• the composition may further be applied as lacquer to, for instance, timber and plywood, wood-like materials such as chipboard, hardboard, softboard and veneered core board; and to cardboard and paper.
• hardening of the radiation curable coating composition is effected in stages.
• the composition after it has been applied to a particular substrate, is subjected to ultraviolet radiation having a wave length of 200 to 600 nm, and preferably of 300 to 400 n-m.
• UV-radiation source there may serve, for instance, a mercury or xenon lamp, which works at high, medium or low pressure.
• Lamps that are commonly used are those of the Hannovia and HOK types, having a radiant energy of BOW/cm and HTQ lamps with a radiant energy of 29W/cm.
• lamps of a lower or higher energy may be employed, such as lamps having an energy of, for instance, 20W/cm or of 200W/cm or 250W/cm.
• the composition needs to be exposed to ultraviolet radiation only for a fraction of a second up to a few seconds in order to ensure such drying that the coating layer is tack-free and already displays some degree of hardness.
• the coating layer is given its final hardness as a result of the progressing reaction between the isocyanate groups of the polyisocyanate (s) and the hydroxyl groups of the polyester resin and the vinyl compound(sl, provided that it(they) contain(s) a hydroxyl group.
• the second curing step may take place at a temperature in the range of, say, 130° to 200°C over a period of 5 to 10 minutes. It is also possible, however, for this curing to take place over a period of several days at ambient temperature. It is found that after the coating has been cured for seven days at ambient temperature, the coating layer generally has about the same hardness as after a curing treatment of 10 minutes at 160°C. Carrying out the second curing step at room temperature offers the considerable advantage that it does not require any energy nor any capital expenditure.
• the polyesters obtained were esterified with 1.1-5.9 moles of acrylic acid per mole of-polyester at a temperature of 100°-130°C in the presence of 4 mmoles of p-toluene sulphonic acid per mole of acrylic acid and hydroquinone in an amount of 0.2% by weight, based on the total reaction mixture.
• 0.18 grammes of lithium carbonate per mole of originally present acrylic acid were added and the toluene and the excess acrylic acid were removed by distillation in vacuo.
• the hydroxyl numbers and the number average moleculare weights of the modified polyesters obtained are given in Table 1.
• the acrylic acid content (in molesl of the polyesters is also given in Table 1.
• the coating compositions according to the invention were prepared by admixing the compounds given in Table 2 in the amounts mentioned, in addition to 4 parts by weight of benzildimethylketal as photoinitiator.
• the vinyl monomer used in the examples I-VII and X-XIV was polyethylene glycol diacrylate, the glycol having a number average molecular weight of 200; in Example VIII hydroxyethyl acrylate was used and in Example IX a mixture of diallyl succinate (25%), diallyl glutarate (50%) and diallyl adipate (25%).
• the polyisocyanate used in the Examples I-X was the adduct of 3 molecules of hexamethylene diisocyanate and 1 molecule of water.
• the polyisocyanates in the Examples I-X were used as a 75% by weight solution in-a mixture of equal parts by weight of ethylglycol acetate and xylene, the one in Examgle XI as a 75% by weight solution in ethyl acetate, and the one in Example XIII as a 70% by weight solution in a mixture of equal parts by weight of ethylglycol acetate and toluene, whereas in the Examples XII and XIV the polyisocyanate was used as such.
• the resulting coating compositions were applied to tinplate and glass, respectively, to a layer thickness (measured in the wet state) of 10 ⁇ m in Example I and of 60 ⁇ m in the other examples.
• the coating layers were then exposed to radiation with a UV lamp of the HOK 5 type manufactured by Philips) over the periods given in Table 2 (in seconds). After radiation with the ultraviolet light the coated substrates were left at a temperature of 20°C over the periods mentioned in Table 3, after which the hardness values were measured. The flexibility was determined after the samples had been kept at 20°C for 7 days after radiation. Furthermore, some other part of the coating layers were baked for 10 minutes at a temperature of 160°C to find out whether the resulting hardness deviated considerably from the hardness obtained after about 3 weeks at 20°C. This was found not to be the case.
• Example II For comparison Example II was repeated, with the exception however that either the photoinitiator was left out and the coated object was not exposed to radiation (Example XV) or the polyisocyanate was left out and the coated object was radiated for 1.5 seconds (Example XVI).
• Example XV the photoinitiator was left out and the coated object was not exposed to radiation
• Example XVI the polyisocyanate was left out and the coated object was radiated for 1.5 seconds

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Paints Or Removers (AREA)
• Macromonomer-Based Addition Polymer (AREA)
• Polyurethanes Or Polyureas (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Polymerisation Methods In General (AREA)

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Cited By (12)

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• 1977
  • 1977-07-08 NL NL7707669A patent/NL7707669A/xx not_active Application Discontinuation
• 1978
  • 1978-06-27 EP EP78200061A patent/EP0000407B1/de not_active Expired
  • 1978-06-27 DE DE7878200061T patent/DE2862023D1/de not_active Expired
  • 1978-07-07 JP JP53082870A patent/JPS5829976B2/ja not_active Expired
  • 1978-07-10 US US05/923,353 patent/US4212901A/en not_active Expired - Lifetime

Patent Citations (1)

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