WO2004014990A1 - Procede de revetement d'articles thermoplastiques moules - Google Patents

Procede de revetement d'articles thermoplastiques moules Download PDF

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Publication number
WO2004014990A1
WO2004014990A1 PCT/US2003/024716 US0324716W WO2004014990A1 WO 2004014990 A1 WO2004014990 A1 WO 2004014990A1 US 0324716 W US0324716 W US 0324716W WO 2004014990 A1 WO2004014990 A1 WO 2004014990A1
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WO
WIPO (PCT)
Prior art keywords
mold
coating
coating composition
alkyl
thermoplastic
Prior art date
Application number
PCT/US2003/024716
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English (en)
Inventor
David Sizer
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Omnova Solutions Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Omnova Solutions Inc. filed Critical Omnova Solutions Inc.
Priority to AU2003258138A priority Critical patent/AU2003258138A1/en
Publication of WO2004014990A1 publication Critical patent/WO2004014990A1/fr

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    • 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
    • C09D131/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid, or of a haloformic acid; Coating compositions based on derivatives of such polymers
    • C09D131/02—Homopolymers or copolymers of esters of monocarboxylic acids
    • C09D131/04—Homopolymers or copolymers of vinyl acetate
    • 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
    • C08F263/00—Macromolecular compounds obtained by polymerising monomers on to polymers of esters of unsaturated alcohols with saturated acids as defined in group C08F18/00
    • 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
    • C08F263/00—Macromolecular compounds obtained by polymerising monomers on to polymers of esters of unsaturated alcohols with saturated acids as defined in group C08F18/00
    • C08F263/02—Macromolecular compounds obtained by polymerising monomers on to polymers of esters of unsaturated alcohols with saturated acids as defined in group C08F18/00 on to polymers of vinyl esters with monocarboxylic acids
    • 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
    • C08F263/00—Macromolecular compounds obtained by polymerising monomers on to polymers of esters of unsaturated alcohols with saturated acids as defined in group C08F18/00
    • C08F263/02—Macromolecular compounds obtained by polymerising monomers on to polymers of esters of unsaturated alcohols with saturated acids as defined in group C08F18/00 on to polymers of vinyl esters with monocarboxylic acids
    • C08F263/04—Macromolecular compounds obtained by polymerising monomers on to polymers of esters of unsaturated alcohols with saturated acids as defined in group C08F18/00 on to polymers of vinyl esters with monocarboxylic acids on to polymers of vinyl acetate
    • 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
    • C08F290/00—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups
    • C08F290/02—Macromolecular compounds obtained by polymerising monomers on to polymers modified by introduction of aliphatic unsaturated end or side groups on to polymers modified by introduction of unsaturated end groups
    • C08F290/06—Polymers provided for in subclass C08G
    • 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
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • 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
    • C08J7/043—Improving the adhesiveness of the coatings per se, e.g. forming primers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
    • C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
    • 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
    • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
    • C09D133/04—Homopolymers or copolymers of esters
    • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09D133/062—Copolymers with monomers not covered by C09D133/06
    • C09D133/068—Copolymers with monomers not covered by C09D133/06 containing glycidyl groups
    • 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
    • C09D151/00—Coating compositions based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Coating compositions based on derivatives of such polymers
    • C09D151/003—Coating compositions based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Coating compositions based on derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/16—Making multilayered or multicoloured articles
    • B29C45/1679—Making multilayered or multicoloured articles applying surface layers onto injection-moulded substrates inside the mould cavity, e.g. in-mould coating [IMC]
    • 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
    • C08J2433/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L31/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid; Compositions of derivatives of such polymers
    • C08L31/02—Homopolymers or copolymers of esters of monocarboxylic acids
    • C08L31/04—Homopolymers or copolymers of vinyl acetate

Definitions

  • Sheet molded articles are made by a compression molding process.
  • the coating of such articles while they remain in the mold has been performed for some time.
  • the process of compression molding lends itself to such an in- mold coating process for at least two reasons.
  • First, the compression molding process results in a shear edge that, in effect, provides a seal to prevent the coating composition from escaping the mold.
  • Second, compression molding processes typically are performed at relatively high temperatures. These high temperatures are optimal for quickly curing a coating composition introduced into the mold.
  • thermoplastic articles typically are performed at temperatures significantly lower than those used in compression molding operations. These lower temperatures mean that the coating composition either does not cure in the same amount of time as it would in a compression molding operation or, in some cases, insufficiently cures.
  • a need for an in-mold coating composition that can cure in a commercially reasonable amount of time at temperatures typically used in injection molding operations for the production of thermoplastic articles remains.
  • the present invention provides a method for providing a thermoset coating on a molded thermoplastic article.
  • a coating composition that includes at least one ethylenically unsaturated compound and a free radical initiating system which has an activation temperature of from about 60° to about 105°C is applied to the article prior to it being removed from its mold.
  • the initiating system is allowed to initiate at least one of polymerization and cross- linking of the unsaturated compound(s) so as to form the thermoset coating.
  • the interior of the mold is maintained at a temperature of at least about 60°C.
  • the coating composition optionally can include a polyvinyl ester and/or an adhesion promoter.
  • a novel coating composition for use in the foregoing method as well as a molded laminate made thereby.
  • macromolecule means an oligomer or polymer
  • (alkyl)acrylic means acrylic and/or alkylacrylic
  • (alkyl)acrylate means acrylate and/or alkylacrylate.
  • FIG. 1 is a side view of a molding apparatus suitable for utilizing the composition and method of the present invention.
  • FIG. 2 is a cross section through a vertical elevation of a mold cavity.
  • the present method employs a coating composition that allows a coating to be formed at the relatively low temperatures encountered in, for example, the injection molding of thermoplastics.
  • the coating composition includes one or more ethylenically unsaturated compounds and an initiating system that has an activation temperature of from about 60° to about 105°C.
  • Ethylenically unsaturated compounds that can be used in the coating composition include, but are not limited to, one or more of epoxy acrylate macro- molecules, hydroxyalkyl (alkyl)acrylates, and vinyl-substituted aromatic compounds.
  • Epoxy acrylate macromolecules typically involve an epoxy- derived intermediate reacted with an (alkyl)acrylic acid to produce an (alkyl)acrylateterminated epoxy; they have at least one and preferably have at least two terminal (alkyl)acrylate groups.
  • the epoxy intermediate can be an aromatic epoxy derived from bisphenol A or a phenolic novalak epoxy, or can be an epoxy derived from alkylene oxide resins or other diglycidyl functional resin.
  • Biphenyl epoxy intermediates predominantly involve the coreaction product of polynuclear dihydroxy phenols or bisphenols with halohydrins to produce epoxy resin intermediates containing up to 3 or 4 but preferably 2 terminal epoxy functional groups per intermediate molecule.
  • the most common bisphenols are bisphenol-A, bisphenol-F, bisphenol-S and 4,4'-dihydroxy bisphenol-A.
  • Useful halohydrins include epichlorohydrin, dichlorohydrin, and 1 ,2-dichlorohydrin 3-hydropropane, with epichlorohydrin being preferred.
  • an exemplary epoxy resin intermediate includes the reaction of an excess of epichlorohydrin with bisphenol-A (typically in a 2:1 equivalent ratio, although somewhat less also can be used) to produce a linear chain that includes mer units of the diglycidyl ether of bisphenol-A and that is terminated with an epoxide group.
  • Preferred epoxy intermediates are polyglycidyl ethers of bisphenol A having two terminal 1 ,2-epoxide groups and epoxide-terminated epoxy novolac resins.
  • the epoxy-terminated intermediate can be reacted with excess equivalents of an (alkyl)acrylic acid to provide an (alkyl)acrylate-terminated epoxy compound having ethylenic unsaturation at one or preferably both ends, thereof.
  • Desirable (alkyl)acrylic acids include acrylic acid, methacrylic acid, ethacrylic acid, and higher homologues, with the first two being most preferred.
  • An example of a commercially available epoxy acrylate macromolecule is EbecrylTM 9125 resin (UCB Chemical Corp.; Smyrna, Georgia).
  • hydroxyalkyl (alkyl)acrylates particularly those where the alkyl ester group contains up to 12, preferably up to 10, more preferably up to about 8, and most preferably up to about 4 carbon atoms.
  • alkylacrylate C 1 -C 3 alkyl groups (particularly methyl groups) are preferred.
  • a preferred such material is hydroxypropyl methacrylate.
  • Hydroxyalkyl (alkyl)acrylates can be used in conjunction with an epoxy acrylate macromolecule. For example, based on 100 parts by weight (pbw) of the latter, from about 30 to about 80 pbw, preferably from about 40 to about 70 pbw, and more preferably from about 45 to about 65 pbw of the former can be used.
  • Yet another ethylenically unsaturated material that can be used is a vinylsubstituted aromatic.
  • Those vinyl-substituted aromatic compounds containing from about 8 to 12 carbon atoms, as well as macromolecules made from such compounds, are preferred.
  • Representative examples include styrene and ⁇ -methyl styrene, with the former being preferred.
  • an epoxy acrylate macromolecule preferably is in monomeric form.
  • a vinyl- substituted aromatic monomer can be present (based on 100 pbw of the epoxy acrylate macromolecule) at from about 20 to about 80 pbw, preferably from about 30 to about 70 pbw, more preferably from about 40 to about 60 pbw.
  • the coating composition needs to include an initiator or catalyst system that will allow the ethylenically unsaturated compound(s) to at least one of polymerize and cross-link.
  • an ethylenically unsaturated polymer is chosen as one of the components, it need not be polymerized. However, to provide a durable coating, such a polymer is preferably crosslinked.
  • initiator or catalyst system can be called upon to do one or both of polymerization and cross-linking and because the surface of the molded thermoplastic article sometimes can need to be made receptive to the coating to be applied thereto, initiator systems capable of generating free radicals are preferred.
  • the initiator system preferably has an activation temperature of from about 6O° to about 105°C, more preferably from about 65° to about 95°C, and most preferably from about 70° to about 85°C.
  • a peroxide is chosen as the source of free radicals, it preferably has or is made to have an activation temperature in this range.
  • a family of alkylperoxy alkyl esters is available from Akzo Nobel Chemicals Inc. (Chicago, Illinois), including TrigonoxTM 141 2,5-dimethyl-2,5- di(2-ethylhexanoylperoxy) hexane; TrigonoxTM 121 tert-amyl peroxy-2- ethylhexanoate; TrigonoxTM 21 tert-butyl peroxy-2-ethylhexanoate; TrigonoxTM 127 tert-amyl peroxybenzoate; TrigonoxTM BPIC tert-butylperoxy isopropyl carbonate; and TrigonoxTM C tert-butyl peroxybenzoate.
  • TrigonoxTM KSM or 161 peroxyester/peroxyketal
  • TrigonoxTM 29-1375 1,1 -di-(tert-butylperoxy)-3,3,5-trimethylcyciohexane
  • an accelerator to the initiating system can be desirable.
  • Such accelerators can promote or catalyze decomposition of the peroxide initiator.
  • Typical accelerators include cobalt napthenate and octoate, zinc napthenates, manganese napthenates, soluble Co and Mn salts of linoleic acid, various amines, and the like; mixtures of such accelerators also can be used.
  • a preferred accelerator is cobalt naphthenate, which typically is commercially available as a salt of 2-ethylhexonic acid in mineral spirits.
  • the ordinarily skilled artisan can select one or more accelerators, as well as identifying proper relative amounts thereof, such that a reasonable rate of peroxide decomposition is promoted so that formation of the thermoset coating is relatively fast but not so rapid that the coating composition starts to set prior to being fully and evenly dispersed across the surface of the thermoplastic article to be coated.
  • a typical initiating system might constitute, per 100 parts by weight of the epoxy acrylate material, (a) from about 5 to about 50 pbw, preferably about 7.5 to about 40 pbw, and more preferably from about 10 to about 30 pbw of peroxide initiator and (b) from about 0.01 to about 5 pbw, preferably about 0.05 to about 2, and more preferably from about 0.1 to about 1 pbw accelerator.
  • the components of the coating composition can be divided into two or more parts so as to keep the initiator separate from the accelerator until just prior to introduction into the injection mold. This is not required where, for instance, the coating composition is to be used very quickly or is to be stored at relatively low temperatures; however, keeping the initiator and accelerator separate until just prior to introduction into the injection mold is preferred.
  • the amount of one part to the other part(s) is subject to no particular limit. If desired, the separate parts can be formulated so as to have similar viscosities to aid in mixing.
  • the coating composition can include one or more adhesion promoters.
  • Such promoters can be especially desirable depending on the particular thermoplastic resin(s) from the article to be coated is made.
  • Exemplary promoters include (alkyl)acrylic acid where the alkyl substituent includes from 1 to 3 carbon atoms. Methacrylic acid is a preferred adhesion promoter. From about 1 to about 15 pbw, preferably from about 2 to about 12 pbw, more preferably from about 3 to about 8 pbw adhesion promoter can be used per 100 parts by weight of (for example) epoxy acrylate macromolecule. If a multi-part coating composition is employed, the adhesion promoter (when used) can be present in any one or more of the parts.
  • Various low profile additives which generally aid in forming a thermoset coating with a smooth surface and possibly function as plasticizers, also optionally can be included in the coating composition.
  • Such additives include polymers of vinyl esters wherein the ester portion contains from 2 to about 5 carbon atoms. Examples include polyvinyl butyrate, polyvinyl propionate, and polyvinyl acetate.
  • the low profile additive(s) can be present at from about 0.1 to about 15 pbw, preferably from about 1 to about 10 pbw, more preferably from about 1.5 to about 8 pbw, and most preferably from about 2 to about 6 pbw per 100 pbw of (for example) epoxy acrylate macromolecule.
  • One commercially available additive is LP 90 polyvinyl acetate in styrene (Dow Chemical Co.; Midland, Michigan).
  • the coating composition can include other additives including opacifying pigments, tinting pigments or colorants, and inert fillers.
  • Useful opacifying agents such as carbon black, Ti0 2 , ZnO, and the like; tinting pigments such as any of a variety of metal oxides, Cr, Cd, and the like; and fillers such as clays, silicas, talc, mica, wood flour, BaS0 4 , calcium and magnesium silicates or carbonates, aluminum hydroxide, and the like.
  • the amount of such additives can vary widely.
  • a pigment such as Ti0 2 can be utilized at from about 1 to about 10 pbw per 100 pbw of (for example) epoxy acrylate macromolecule whereas a filler such as talc can be used at from about 45 to about 100 pbw per 100 pbw of (for example) epoxy acrylate macromolecule.
  • surfactants include various cationic, anionic or nonionic materials such as these listed in M. Allured, McCutc neon's 2001 Emulsifiers & Detergents; vol. 1 , Int'l Ed. (1992).
  • An exemplary commercially available material is Disperse-AYDTM 6 or 8 surfactant (Elementis Specialties; Jersey City, NJ).
  • Other suitable surfactants include the DisperbykTM 160 family of high molecular weight block copolymers (BYK-Chemie USA; Wallingford, Connecticut). The amount of such surfactants are generally low, typically just enough to disperse the particulate material(s) to the desired degree.
  • additives that can be present in the coating composition include lubricants and mold release agents such as zinc or calcium stearate, phosphoric acid esters, and zinc salts of fatty acids. Mold release agents can also be used to control the cure rate, where zinc fatty acids tend to moderately accelerate the cure time, while calcium fatty acids tend to moderately retard the cure time.
  • the coating composition can be introduced directly into a mold containing an injection molded thermoplastic substrate.
  • a fully cured thermoset coating has been achieved in approximately 2 minutes or less at temperatures of from about 60° to about 105°C, preferably from about 65° to about 95°C, more preferably from about 70° to about 85°C.
  • the coating composition can be used on a variety of thermoplastic substrates.
  • Suitable thermoplastics include, but are not limited to, various polyesters (optionally containing glass fiber reinforcement) such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), copolymers of PET and PBT, etc.; polyolefins including polyolefin homopolymers, copolymers of a polyolefin and another monomer, polyolefins grafted with functional groups such as (meth)acrylate, acids, halogens, etc, and blends thereof; acrylonitrile- butadienestyrene copolymers (i.e., ABS); polycarbonate; alloys of polycarbonate; and blends or mixtures of ABS and polycarbonate such as CycoloyTM MC8800 (GE Plastics; Pittsfield, Massachusetts); high impact polystyrene (HIPS); thermoplastic polyurethane, and the like.
  • various polyesters such as polyethylene
  • Figure 1 shows a molding apparatus or injection molding machine 10, in who's operation the present invention finds particular utility.
  • the molding apparatus 10 includes a first mold half 20 which preferably remains in a stationary or fixed position relative to a second moveable mold half 3O.
  • Figure 1 shows the movable mold half 30 in an open position.
  • the first mold half 20 and second mold half 30 are adapted to mate with one another to form a contained mold cavity 40 therebetween (See Figure 2).
  • the mold halves 20,30 mate along surfaces 24 and 34 ( Figure 1) when the molding apparatus is in the closed position, forming a parting line 42 ( Figure 2) therebetween and around the cavity 40.
  • the moveable mold half 14 reciprocates generally along a horizontal axis relative to the first or fixed mold half 20 by action of a clamping mechanism 70 with a clamp actuator 72 such as through a hydraulic or pneumatic actuator as known in the art.
  • the clamping pressure exerted by the clamping mechanism 70 should have a clamping pressure in excess of the pressures generated or exerted by either of a pair of composition injectors 50,60.
  • the pressure exerted by the clamping mechanism 7O ranges generally from about 14 MPa (2,000 pounds per square inch (psi)) to about 103 MPa (15,000 psi), preferably from about 28 MPa (4,000 psi) to about 83 MPa (12,000 psi), and more preferably from about 41 MPa (6,000 psi) to about 69 MPa (10,000 psi) of the mold surface.
  • the mold halves 20,30 are shown in a closed position abutting or mating with one another along the parting line 42 to form the mold cavity 40.
  • the mold cavity 40 generally has a first surface 44 on the second mold half 30 and a corresponding or opposite second surface 46 on the first mold half 20.
  • the mold cavity 40 also contains separate orifices 38,62 to allow the composition injectors 50,60 to inject their respective compositions thereinto.
  • the coating composition desirably is used to coat injection molded substrates. Accordingly, the drawings and following description are based on injection molding. However, the ordinarily skilled artisan will recognize that molded articles made by other known methods, such as resin or transfer molding, rotational molding, blow molding and thermoforming, likewise can be coated using the described process.
  • the first composition injector 50 is that of a typical injection molding apparatus which is well known to those of ordinary skill in the art.
  • the first composition injector 50 is generally capable of injecting a thermoplastic composition, generally a resin or polymer, into the mold cavity 40. Owing to space constraints, the first injector 50 used to inject the thermoplastic composition is positioned to inject material from the fixed half 20 of the mold. It is to be understood that the first composition injector 50 could be reversed and placed in the movable mold half 30. Likewise, it is to be understood that the second injector 60 which is shown positioned in the movable mold half 30 could be alternatively positioned in the stationary mold half 20.
  • the first composition injector 50 is shown in a "backed off' position, but it is readily understood that the same can be moved in a horizontal direction so that a nozzle or resin outlet 58 of the first injector 50 mates with the mold half 20. In the mated position, the injector 50 is capable of injecting its contents into the mold cavity 40.
  • the first composition injector 50 is shown as a reciprocating-screw machine wherein a first composition can be placed in a hopper 52 and a rotating screw 56 can then move the composition through a heated extruder barrel 54, where the first composition or material is heated above its melting point.
  • the screw 56 acts as an injection ram and forces the material through the nozzle 58 and into the mold cavity 40.
  • the nozzle 58 generally has a nonreturn valve (not shown) at the open end thereof, and the screw 56 has a nonreturn valve (not shown), to prevent the backflow of material.
  • the first composition injector 50 is not meant to be limited to the embodiment shown in Figure 1 but can be any apparatus capable of injecting a thermoplastic composition into the mold cavity 40.
  • the injection molding machine can have a mold half movable in a vertical direction such as in a "stack-mold" with center injection.
  • Other suitable injection molding machines include many of those available from Cincinnati-Milacron, Inc. of Cincinnati, Ohio; Battenfeld Injection Molding Technology of Meinlerzhagen, Germany; Engel Machinery Inc. of York, Pennsylvania; Husky Injection Molding Systems Ltd. of Bolton, Canada; BOY Machines Inc. of Exton, Pennsylvania and others.
  • thermoplastic first composition is placed in the hopper 52 of the molding apparatus 10.
  • the first injector 50 is moved into nesting or mating relation with the fixed mold half 20.
  • the first injector 50 heats the first composition above its melting point and directs the heated first composition toward the nozzle 58 of the first injector 50.
  • the mold halves 20, 30 are closed thereby creating the contained molding cavity 40.
  • the molding process continues and a nozzle valve (not shown) of the nozzle 58 is moved to an open position for a predetermined amount of time to allow a corresponding quantity of the first thermoplastic composition to enter the mold cavity 40 through the orifice 38.
  • the screw 56 provides a force or pressure that urges the first composition into the mold cavity 40 until the nozzle valve is returned to its closed position.
  • the first composition is filled and packed into the mold cavity 40 as is well known in the art. Once the mold cavity 40 is filled and packed, the molded first composition is allowed to cool to a temperature below its melting point.
  • the thermoplastic will not cool uniformly, with the thermoplastic forming the interior of the molded article generally remaining molten while the surface begins to harden as it cools more quickly.
  • the injection of the thermoplastic used to form the substrate in the mold can be viewed as a three-stage process.
  • the first stage is referred to as the filling stage. In this stage, an amount of thermoplastic is injected into the mold to nearly fill the mold cavity 40, preferably to at least about 75% of its capacity.
  • the second stage is referred to as the packing stage. In this stage, additional thermoplastic is packed into the mold to fill the mold cavity, preferably to at least about 99% of its capacity.
  • the third stage is referred to as the cooling stage. In this stage, the thermoplastic begins to solidify as it starts to cool.
  • thermoplastic in the packing stage, packing pressure rises as a result of injecting more thermoplastic mate ⁇ al into the mold and then is kept constant for a while to compensate for the material shrinkage caused by the temperature decrease as the thermoplastic begins to cool.
  • thermoplastic cooling stage the pressure in the mold cavity decreases as the thermoplastic continues to cool and begins to shrink. It is during the thermoplastic cooling stage that the IMC coating is injected into the mold.
  • the IMC coating should be injected during the cooling stage. One must wait until the surface of the substrate has sufficiently cooled and hardened such that the IMC and the thermoplastic will not excessively intermingle. Also, the longer the period between the end of the thermoplastic filling and the coating injection, the lower the packing pressure needed to inject the coating and the easier the injection. However, because the IMC coating generally relies on the residual heat of the cooling thermoplastic to cure, one risks inadequate curing of the IMC coating if the waiting period is too long. In addition, the thermoplastic needs to remain sufficiently molten both to allow for sufficient adhesion between the IMC and the substrate as well as to provide sufficient compressability to allow adequate flow of the IMC around the surface of the substrate in the mold. Thus, the ease of coating injection needs to be balanced with the need for sufficient residual heat to obtain an adequate curing of the IMC.
  • a predetermined amount of an IMC is ready to be introduced into the mold cavity from the nozzle 62 ( Figure 2) of second composition or in-mold coating injector 60.
  • a supply pump (not shown) is generally utilized to supply the coating composition into the injector 60 from a storage vessel (not shown).
  • the coating composition is injected from the metering cylinder into mold cavity 40 through orifice 62 with a pressurizing device utilizing hydraulic, mechanical, or other pressure.
  • coating injector 60 When coating injector 60 is activated during injection mode, coating composition flows through orifice 62 and into mold cavity 40 between surface 44 and the exterior of the molded article.
  • coating apparatus 60 is deactivated via a nozzle valve (not shown) or by some other means, thus causing the flow of coating composition to cease.
  • the coating composition flows around the molded article and adheres to its surface.
  • the IMC should be injected soon after the surface of the thermoplastic has cooled enough to reach its melt temperature.
  • the determination of when the melt temperature is reached can be determined directly by observation of the internal mold temperature if the melt temperature of the specific thermoplastic is known, or indirectly by observation of the internal mold pressure. As noted, when the molded part reaches its melt temperature and begins to solidify, it contracts somewhat, thus reducing the pressure in the mold, which may recorded through the use of a pressure transducer (not shown) in the mold.
  • the mold is generally not opened or undamped before the in-mold coating is applied. That is, the mold halves maintain a parting line and generally remain substantially fixed relative to each other while both the first and second compositions are injected into the mold cavity.
  • the in-mold coating composition spreads out from the mold surface and coats a predetermined portion or area of the molded article.
  • the nozzle valve or deactivation means of the second injector 60 is engaged, thereby preventing further injection of the in-mold coating into the mold cavity 40.
  • the coated substrate can be removed from the mold.
  • the in-mold coating is typically cured by components present within the coating composition.
  • the cure is optionally heat activated, from sources including the substrate or mold halves which are at or above the curing temperature of the in-mold coating. Cure temperature will vary depending on the in-mold coating utilized. As mentioned above, it is important to inject the in-mold coating before the molded article has cooled to the point below where proper curing of the coating can be achieved.
  • the in-mold coating requires a minimum temperature to activate the catalyst present therein which causes a cross-linking reaction to occur, thereby curing the coating and melt-bonding it to the thermoplastic substrate.
  • the coating composition can cure at a relatively low temperature is advantageous in that it permits the use of moderate mold temperatures without sacrificing good adhesion of the coating to the molded article. Also, intermingling of the coating composition with the thermoplastic article, which is undesirabte, is abated or even eliminated. Additionally, a coating of a fairly constant thickness is obtained. Still further, by avoiding the use of more typical higher-temperature initiation systems, the cure time is reduced significantly. In this respect, although such more typical systems will work in lower temperature molds, the amount of time to achieve satisfactory cross-linking is, in many cases, commercially impractical.
  • a two-part coating composition was prepared.
  • Parts A and B were separately mixed in a dynamic mixer and then blended in a dynamic mixing head. Subsequently, the blended mixture of Part A and Part B was added to an injection molding nozzle and then injected into a mold containing an article formed from CycoloyTM MC8800 ABS/polycarbonate resin. The coated article remained in the mold for approximately two minutes where it experienced temperatures of from about 71° to about 82°C. [0052] A laminate of cured, cross-linked coating on the molded article was tested and the results thereof were as follows:

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Wood Science & Technology (AREA)
  • Manufacturing & Machinery (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

Selon cette invention, une composition de revêtement renferme une macromolécule d'époxy acrylate, un monomère d'hydroxylalkyl (alkyl)acrylate, un composé aromatique substitué par vinyle, et facultativement un monomère d'ester de polyvinyle. La polymérisation et/ou la réticulation sont initiées par un système radicalaire libre qui comprend un accélérateur, un initiateur de peroxyde et, facultativement, un promoteur d'adhésion. La polymérisation et/ou la réticulation peuvent se produire à des températures relativement basses, telles que celles d'un système de moulage à injection.
PCT/US2003/024716 2002-08-10 2003-08-08 Procede de revetement d'articles thermoplastiques moules WO2004014990A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003258138A AU2003258138A1 (en) 2002-08-10 2003-08-08 Method for coating molded thermoplastic articles

Applications Claiming Priority (2)

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US40242602P 2002-08-10 2002-08-10
US60/402,426 2002-08-10

Publications (1)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0733668A2 (fr) * 1995-03-23 1996-09-25 DAI NIPPON TORYO CO., Ltd. Procédé pour enduire dans un moule
WO2002004187A2 (fr) * 2000-07-12 2002-01-17 Omnova Solutions Inc. Procede de revetement d'un article en polyolefine dans son moule
US20020039656A1 (en) * 2000-07-12 2002-04-04 Omnova Solutions Inc. Optimization of in-mold coating injection molded thermoplastic substrates
EP1207031A1 (fr) * 1999-07-27 2002-05-22 Dai Nippon Toryo Co., Ltd. Procede de formation d'un revetement sur les surfaces internes d'un moule metallique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0733668A2 (fr) * 1995-03-23 1996-09-25 DAI NIPPON TORYO CO., Ltd. Procédé pour enduire dans un moule
EP1207031A1 (fr) * 1999-07-27 2002-05-22 Dai Nippon Toryo Co., Ltd. Procede de formation d'un revetement sur les surfaces internes d'un moule metallique
WO2002004187A2 (fr) * 2000-07-12 2002-01-17 Omnova Solutions Inc. Procede de revetement d'un article en polyolefine dans son moule
US20020039656A1 (en) * 2000-07-12 2002-04-04 Omnova Solutions Inc. Optimization of in-mold coating injection molded thermoplastic substrates
WO2003031138A1 (fr) * 2001-10-09 2003-04-17 Omnova Solutions Inc. Optimisation de substrats thermoplastiques moules par injection revetus dans le moule

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