WO1995009724A1 - Dual cure, in-mold process for manufacturing abrasion resistant, coated thermoplastic articles - Google Patents

Dual cure, in-mold process for manufacturing abrasion resistant, coated thermoplastic articles Download PDF

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Publication number
WO1995009724A1
WO1995009724A1 PCT/EP1993/002725 EP9302725W WO9509724A1 WO 1995009724 A1 WO1995009724 A1 WO 1995009724A1 EP 9302725 W EP9302725 W EP 9302725W WO 9509724 A1 WO9509724 A1 WO 9509724A1
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WO
WIPO (PCT)
Prior art keywords
coating composition
initiator
process according
acrylic monomer
mold
Prior art date
Application number
PCT/EP1993/002725
Other languages
French (fr)
Inventor
Rudolph H. Boeckeler
Original Assignee
Cook Composites And Polymers
Cray Valley S.A.
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 Cook Composites And Polymers, Cray Valley S.A. filed Critical Cook Composites And Polymers
Priority to PCT/EP1993/002725 priority Critical patent/WO1995009724A1/en
Priority to AU51112/93A priority patent/AU5111293A/en
Publication of WO1995009724A1 publication Critical patent/WO1995009724A1/en

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Classifications

    • 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
    • C09D4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09D159/00 - C09D187/00
    • 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
    • B29C37/00—Component parts, details, accessories or auxiliary operations, not covered by group B29C33/00 or B29C35/00
    • B29C37/0025—Applying surface layers, e.g. coatings, decorative layers, printed layers, to articles during shaping, e.g. in-mould printing
    • B29C37/0028—In-mould coating, e.g. by introducing the coating material into the mould after forming the article
    • B29C37/0032—In-mould coating, e.g. by introducing the coating material into the mould after forming the article the coating being applied upon the mould surface before introducing the moulding compound, e.g. applying a gelcoat
    • 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
    • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
    • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
    • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
    • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
    • B29C2035/0827—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using UV radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2033/00—Use of polymers of unsaturated acids or derivatives thereof as moulding material
    • B29K2033/04—Polymers of esters
    • B29K2033/12—Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2061/00—Use of condensation polymers of aldehydes or ketones or derivatives thereof, as moulding material
    • B29K2061/20—Aminoplasts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0037—Other properties
    • B29K2995/0087—Wear resistance

Definitions

  • This invention relates to coated, molded articles.
  • this invention relates to coated, molded articles comprising a plastic laminated to an abrasion resistant coating while in another aspect, this invention relates to a dual cure, in-mold process for making these articles.
  • thermoplastic articles such as those made from polymethylmethacrylate, polycarbonate, polyester carbonates, polyester and polystyrene, are commonly used in a wide variety of applications including automotive head and tail lamps, glazing, optical lenses, aircraft parts, signs, display and store fixtures and furniture, to name but a few. Since the surfaces of these thermoplastics are quite soft and are easily scratched and marred during normal use, these surfaces are commonly treated with an abrasion resistant coating.
  • Any acid catalyst that is blocked, i.e. inactive, at a temperature of less than about 95°C, preferably less than about 120°C, but will unblock, i.e. activate, at temperatures in excess of 95°C, preferably in excess of 120°C, to catalyze the condensation reaction of the aminoplast resin can be used in the practice of this invention to increase the rate of cure.
  • these catalysts are blocked polymeric dodecylbenzene sulfonic acid ester, dinonylnaphtalene
  • Representative acids include linoleates, naphthenates, octoates, and resinates.
  • Preferred metallic salt driers include the octoates, naphtenates and neodecanoates of cobalt, manganese, vanadium, potassium, zinc and copper.
  • Especially preferred metallic salt driers are the cobalt-based driers such as cobalt octoate, cobalt naphtenate and the organo- complexes of cobalt and potassium.
  • UV Photoinitiator 0.2 - 6 1 3 If the first stage cure is by heat, then typically the relative amounts, in weight percent based on the weight of the coating composition, are about : Component °ref erred More Pre ⁇ ferred
  • the coating is applied by any conventional technique at thicknesses ranging from about 1 ⁇ m to about 75 ⁇ m, preferably from about 5 ⁇ m to about 25 ⁇ m, and then it is exposed to UV radiation of wavelengths ranging from about 180 nm to about 450 nm.
  • the sources of UV radiation include medium or high pressure mercury vapor lamps, metal halide lamps and xenon discharge lamps. Generally exposures of 1 to about 5 seconds are used to provide the first stage cure.
  • the coating After UV curing, the coating is relatively soft, possibly even tacky, and is easily marred on the surface exposed to the atmopshere. Continued exposure to UV radiation does not significantly increase the hardness of the film.
  • the thermoplastic material is fiber-reinforced.
  • the reinforcing fiber can vary to convenience, and typical reinforcing fibers include glass, polyethylene, metal, ceramic and the like. While the fiber can be admixed with the thermoplastic material prior to its application to the cured coating composition, more commonly the fiber is applied to the cured coating composition as a preform. Under this circumstance, the mold is usually a matched mold. The preform is inserted over the cured coating composition, the mold is closed, and the thermoplastic material injecied. Upon cure, a fiber-reinforced plastic article is formed.
  • the resulting film had a very slight surface tack.
  • a cell was constructed with the coated plate and acrylic syrup was cast as in Example 1. The coated casting was then cured in the mold for 12 hours at 60°C.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Laminated Bodies (AREA)

Abstract

Laminated, molded plastic articles having an excellent abrasion resistant coating are prepared by a two-step process comprising: A) applying to a mold surface a 100 % reactive coating composition comprising: 1) a polyfunctional acrylic monomer having at least three acryloloxy groups, 2) a monofunctional acrylic monomer, 3) an acrylic-soluble thermoplastic having hydroxy functionality, 4) an aminoplast resin, and 5) a free radical initiator; B) at least partially curing the coating composition by either UV or IR radiation; C) applying to the exposed surface of the cured coating composition a thermoplastic material; and D) during the thermoplastic material to form the laminated molded article.

Description

DUAL CURE, IN-MOLD PROCESS FOR MANUFACTURING ABRASION RESISTANT, COATED THERMOPLASTIC ARTICLES.
This invention relates to coated, molded articles. In one aspect, this invention relates to coated, molded articles comprising a plastic laminated to an abrasion resistant coating while in another aspect, this invention relates to a dual cure, in-mold process for making these articles.
Molded thermoplastic articles, such as those made from polymethylmethacrylate, polycarbonate, polyester carbonates, polyester and polystyrene, are commonly used in a wide variety of applications including automotive head and tail lamps, glazing, optical lenses, aircraft parts, signs, display and store fixtures and furniture, to name but a few. Since the surfaces of these thermoplastics are quite soft and are easily scratched and marred during normal use, these surfaces are commonly treated with an abrasion resistant coating.
Many coatings have been proposed for post-application onto the finished molded articles. These materials are applied by conventional coating methods such as spraying, dipping, brushing and roll coating. One common type of a post-application coating is the solvent -based, thermally crosslinkable type, such as polysiloxanes, fluorocarbonvinyl ether copolymers, and polyurethanes. These materials, when cured, offer various degrees of abrasion resistance, gloss, weatherability, chemical resistance, and adhesion to the thermoplastic substrate. However, these materials suffer certain disadvantages, some serious, such as slow cure, high energy requirements to convert and/or eliminate solvent, emission of environment damaging solvents, and comestically undesirable features, e.g. orange peel, craters, fish eyes and the presence of airbone dust particles.
Another type of post-application coating is the 100 % solids, UV radiation-curable coating type. These materials overcome some of the disadvantages associated with the solvent-based materials, such as high energy consumption and solvent emissions but because of their higher viscosities, they suffer even more from the previously described surface defects as well as poor adhesion to some thermoplastic compositions. These materials also have a tendency to stress crack when applied at higher film thickness. The addition of nonreactive thermoplastic polymers or monofunctional monomers can reduce or eliminate cracking, but only with a diminished resistance to abrasion, chemicals and weathering. In addition, the cure of these coatings by UV radiation is inhibited by atmospheric oxygen, and this results in lower molecular weight polymers at the surface and thus a coating with less hardness, abrasion resistance, chemical resistance, gloss and weatherability than would otherwise be the case. This inhibition can be overcome by conducting the cure in an inert atmopshere, but this is comparatively costly and impractical when the article is large and of a complex shape.
Therefore the purpose of this invention is to remedy the prior art disadvantages relating to molded articles comprising a thermoplastic laminated to an abrasion resistant coating.
According to this invention, plastic articles having an abrasion resistant coating are prepared by a two-stage, in-mold curing process comprising the steps of :
A Providing a mold having a surface corresponding to the article in negative relief ;
B. Applying to at least a portion of the surface of the said mold a 100 % reactive coating composition comprising : 1. A polyfunctional acrylic monomer having at least three acryloloxy groups, 2. A monofunctional acrylic monomer,
3. An acrylic-soluble thermoplastic having hydroxy functionality,
4. An aπiinoplast resin,
5. A free radical initiator, and optionally
6. A blocked acid catalyst ; C Curing the coating composition ;
D. Applying to the cured coating composition an at least partially uncured thermoplastic composition to form a laminate ;
E. Curing the laminate to form the plastic article ; and
F. Removing the cured plastic article from the mold. In one embodiment of this invention, the free radical initiator is a photoinitiator, and the coating composition is cured by ultraviolet (UV) radiation. In another embodiment of this invention, the free radical initiator is an initiator system comprising a metallic salt drier, a polyallylic crosslinker-initiator, and optionally, a non- polyallylic peroxide initiator, and the coating composition is cured by heat (typically induced by infrared radiation). In either cure embodiment, the laminated, molded plastic article exhibits a coating that has excellent abrasion resistance and adhesion to the plastic substrate, a smooth, blemish-free surface, and sufficient flexibility to resist thermal stress cracking even in those instances in which the coating is relatively thick.
The polyfunctional acrylic monomers used in the practice of this invention have at least three, and preferably at least five, acryloloxy groups, i.e.
CH2 = CR - C - O- O
(where R is H or CH^), and include the acrylic acid esters and methacrylic acid t ers of polyhydric alcohols. Preferred polyfunctional acrylic monomers include the polyacrylates and methacrylates of pentaerythritol and dipentaerythritol such as pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, pentaerythritol trimethacrylate, and the like. These materials are further described in US-A-4,902,578 and US-A- 4,800, 123. The monofunctional acrylic monomers used in the practice of this invention include any of the well known alkyl and cycloalkyl acrylates and methacrylates. Preferred monofunctional acrylic monomers are those monofunctional monomers which bear hydroxy groups such as hydroxyethylmethacrylate, hydroxypropyl- methacrylate, caprolactone acrylate, and caprolactone methacrylate. These materials are also further described in US-A-4,902,578.
Any acrylic-soluble thermoplastic polymer that will readily condense at an elevated temperature with an aminoplast resin can be used in the practice of this invention. These polymers are characterized by the presence of hydroxy g ups, good solubility in the poly- and monofunctional acrylic monomers and upon cure, the ability to impart clarity and flexibility to the coating. These polymers also improve the flow and leveling characteristics of the cured coating composition.
The molecular weights of these acrylic-soluble thermoplastic polymers can vary over a wide range, but in general are both low enough to provide good solubility in the monomers and reasonable solution working viscosity, and yet high enough to provide the desired flow, leveling and flexibility characteristics to the cured coating. Preferred are those thermoplastic polymers with a weight average molecular weight of at least about 3,000, more preferably at least about 9,000. Preferably, the weight average molecular weight of these polymers does not exceed about 90,000. Exemplary polymers include the various cellulose esters, e.g. cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate, and the various polyesters and acrylics. These polymers are further described in
USP 4,308, 119.
Any aminoplast resin that condenses at an elevated temperature with the acrylic-soluble thermoplastic polymer and hydroxy functional monomer described above can be used in the practice of this invention. Exemplary resins include alkylated melamine-formaldehyde, urea-formaldehyde, benzoquanamine and glycouril, with the melamine-formaldehyde resins being preferred. These resins do not participate to any significant extent in the first curing stage, namely the free radical cure, since the low or moderate temperatures reached for brief periods of time during this stage are insufficient to provide cure and to unblock the blocked acid catalyst (if present) which is used to catalyze the condensation reaction of the aminoplast resin.
Any acid catalyst that is blocked, i.e. inactive, at a temperature of less than about 95°C, preferably less than about 120°C, but will unblock, i.e. activate, at temperatures in excess of 95°C, preferably in excess of 120°C, to catalyze the condensation reaction of the aminoplast resin can be used in the practice of this invention to increase the rate of cure. Examples of these catalysts are blocked polymeric dodecylbenzene sulfonic acid ester, dinonylnaphtalene
SUBSTITUTE SHEET disulfonic acid ester, and dinonylnaphtalene disulfonic acid reacted with an epoxy resin.
The free radical initiators that are used in the first stage UV cure embodiment of this invention include any of the well known UV photoinitiators such as benzophenone; acetophenone and its derivatives, benzoin, benzoin ethers, thioxanthones, halogenated compounds, oximes, and acyl phosphine oxides. Preferred are those photoinitiators which do no strongly discolor when exposed to sunlight, e.g. the acyl phosphine oxides and 2 -hydroxy-2 -methyl- 1- phenyl propan-1-one.
The free radical initiators that are used in the first stage thermal cure embodiment of this invention are a system compri ig a metallic salt drier, a polyallylic crosslinker-initiator, and optionally, a nonpolyallylic peroxide initiator. Representative of the polyallylic crosslinker-initiators are polyester resins based on trimethylolpropane mono- or diallyl ethers and polyallylglycidyl ether alcohol resins. Those crosslinker-initiators that function both as initiators for low temperature, free radical polymerization of the mono- and polyfunctional acrylic monomers and as a multifunctional crosslinker are the preferred crosslinker-initiators. Polyallylic ethers having the general formula
Figure imgf000007_0001
wherein n is an integer from 2 to 10 are representative of these preferred crosslinker-initiators. The polyallylic ethers are representative of these preferred crosslinker-initiators.
Any metallic salt drier that will promote or accelerate the rate of cure of the mono- and polyfunctional acrylic monomers, acrylic- soluble thermoplastic having hydroxy functionality, and crosslinker- initiator and, if present, monomer, can be used in the practice of this invention. Typical of these driers are salts of metals with a valence of two or more and unsaturated organic acids. Representative metals include cobalt, magnesium, cerium, lead,
SUBSTITUTE SHEET chromium, iron, nickel, uranium and zinc. Representative acids include linoleates, naphthenates, octoates, and resinates. Preferred metallic salt driers include the octoates, naphtenates and neodecanoates of cobalt, manganese, vanadium, potassium, zinc and copper. Especially preferred metallic salt driers are the cobalt-based driers such as cobalt octoate, cobalt naphtenate and the organo- complexes of cobalt and potassium.
The rate of cure, especially at relatively low temperatures, e.g. 21° to 38°C, can be further accelerated through the use of one or more co -initiators. These co-initiators are typically non-polyallylic peroxides, and include any of the common peroxides such as benzoyl peroxide ; dialkyl or aralkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, cumylbutyl peroxide, l, l-di-t-butylperoxy-3,5,5- trimethylcyclohexane, 2,5-dimethyl-2,5-di-t-butylperoxy hexane and bis (α-t-butylperoxy isopropylbenzene) ; peroxyesters such as t- butylperoxy pivalate, t-butyl peroctoate, t-butyl perbenzoate, 2,5- dimethylhexyl-2,5-di (perbenzoate), dialkylperoxymonocarbonates and peroxydicarbonates ; hydroperoxides such as t-butyl hydroperoxide, p-methane hydroperoxide, pentane hydroperoxide and cumene hydroperoxide ; and ketone peroxides such as cyclohexanone peroxide and methyl ethyl ketone peroxide.
Other additives, such as fillers, thixotropic agents, rheological control additives, UV absorbers, solvents and the like, can be incorportated into the coating composition as desired. The at least partially uncured thermoplastic composition used in step D of the process of this invention can vary to convenience.
Representative resins include acrylics, polycarbonates, vinyls, polyesters and polyurethanes. Preferred thermoplastic resins are those that readily polymerize at the temperatures of the second stage cure.
The relative amounts of the individual components present in the coating composition will vary with the nature of the first stage cure. If the first stage cure is by UV radiation, then typically the relative amounts, in weight percent based on the weight of the coating composition, are about : Component Preferred More preferred
Polyfunctional Monomer 30 - 85 55 75
Monofunctional Monomer 10 - 40 10 20
Acrylic-soluble Thermo¬ 2 - 15 4 10 plastic having hydroxy functionality
Aminoplast Resin 5 - 20 7 12
Blocked Acid Catalyst 0.5 - 5 1 2
UV Photoinitiator 0.2 - 6 1 3 If the first stage cure is by heat, then typically the relative amounts, in weight percent based on the weight of the coating composition, are about : Component °ref erred More Pre ϊferred
Polyfunctional Monomer 30 - 70 50 - 65 Monofunctional Monomer 10 - 40 10 - 20 Acrylic-soluble Thermo¬ 2 15 4 10 plastic having hydroxy functionality Aminoplast Resin 5 20 7 12 Blocked Acid Catalyst 0 5 0 2 Crosslinker-initiator 5 25 10 20 Metallic Salt Drier 0.05 - 0.5 0.1 - 0.3 Co-initiator 0.2 - 3 1 2
In the process of this invention for molding a laminated article comprising a plastic substrate and an abrasive resistant coating, a mold surface corresponding to the article in negative relief is at least partially, preferably completely, covered with the coating composition. Typically, this composition is formulated from its constituent components just prior to its application to the mold surface. The monomers, acrylic- soluble thermoplastic, aminoplast resin and blocked acid catalyst are blended with one another prior to the addition of the free radical initiator. If the initiator is a UV photoinitiator, then it can be blended with the other components at any time prior to exposing the uncured composition to UV radiation. If the initiator is a thermal cure system, then the metallic salt drier is mixed with the monomers, etc. prior to blending that mix with the crosslinker-initiator and, if present, co-initiator.
In those compositions in which a UV photoinitiator is employed, the coating is applied by any conventional technique at thicknesses ranging from about 1 μm to about 75 μm, preferably from about 5 μm to about 25 μm, and then it is exposed to UV radiation of wavelengths ranging from about 180 nm to about 450 nm. The sources of UV radiation include medium or high pressure mercury vapor lamps, metal halide lamps and xenon discharge lamps. Generally exposures of 1 to about 5 seconds are used to provide the first stage cure.
After UV curing, the coating is relatively soft, possibly even tacky, and is easily marred on the surface exposed to the atmopshere. Continued exposure to UV radiation does not significantly increase the hardness of the film.
For those compositions in which a thermally activated cure system is employed, the coating is applied in thicknesses ranging from about 1 μm to about 75 μm, preferably from about 5 μm to about 25 μm. The coating is then typically subjected to infrared radiation for 1 to about 5 minutes in order to complete the first stage cure.
After curing, the coating is relatively soft, possibly even tacky, and is easily marred on the surface exposed to the atmosphere. The coating of this embodiment may also be cured simply by exposing it to heat.
After the first stage curing is complete, regardless of the method of cure, the thermoplastic material is applied, usually in the form of a syrup, to the exposed surface of the cured coating composition. This material can be applied in any conventional manner, e.g. spraying, brushing, injection, etc. The thermoplastic material is then subjected to a temperature of at least 65°C, preferably a temperature between about 70° and 150°C, for at least about 30 minutes, preferably at least about 60 minutes. Once this second stage curing is complete, the molded is removed from the mold.
The mold may be an open mold or a matched mold, i.e. a two component mold comprising a female mold surface and a male mold surface that when joined, define a volume with the shape of the desired molded product. If an open mold, then once the plastic has been applied to the exposed surface of the cured coating composition, then it is cured as described above, typically by placing it, an oven. If a matched mold, then once the coating composition has cured the mold is closed and the plastic injected under pressure into the mold to completely fill the volume formed by the two mated mold surfaces. The mold is retained in this closed position at the curing temperature for a sufficient period of time to allow the molded article to complete cure. The mold is then opened, and the molded article removed. Mold release agents can be used with both open and matched molds as desired.
In one embodiment of this invention, the thermoplastic material is fiber-reinforced. The reinforcing fiber can vary to convenience, and typical reinforcing fibers include glass, polyethylene, metal, ceramic and the like. While the fiber can be admixed with the thermoplastic material prior to its application to the cured coating composition, more commonly the fiber is applied to the cured coating composition as a preform. Under this circumstance, the mold is usually a matched mold. The preform is inserted over the cured coating composition, the mold is closed, and the thermoplastic material injecied. Upon cure, a fiber-reinforced plastic article is formed.
The laminated, plastic molded articles of this invention exhibit a coating film that has resistance to scratching with No. 00 steel wool, solvent resistance, and excellent adhesion to the thermoplastic substrate.
The following examples are illustrative of certain embodiments of this invention. Unless indicated to the contrary, all parts and percentages are by weight. Example 1
An abrasion resistant coating was prepared by combining 65 grams of dipentaerythritol monohydroxypentaacrylate (SR-399 from SARTOMER Co.), 15 grams 98.0 % purity grade 2- hydroxyethylmethacrylate, 10 grams of methylated melamine- formaldehyde resin (Cymel 303 from the MONSANTO Co.), 7.4 grams of cellulose acetate butyrate (CAB 551.1 for EASTMAN CHEMICAL Co.), 1.5 grams polymeric dodeylbenzene sulfonic acid ester (Nacure XP-314 from KING INDUSTRIES, and 2 grams acyl phosphine oxide (Lucirin TPO from BASF Corp.).
The resulting solution was clear and had a viscosity of 200 Pa.s at 25°C.
This solution was applied with a glass rod to a clean, unwaxed glass plate at a film thickness of 30 μm.
The film was exposed for 1.5 seconds to ultraviolet radiation from a mercury vapor lamp with an output of 79 W/cm. The resulting film had a very slight tack and marred easily.
A cell casting mold was constructed with the coated glass plate, a 3,2 mm thick Telfon® spacer and a clean uncoated glass plate. A thermoplastic syrup consisting of an acrylic resin, methylmethacrylate and a peroxide initiator was cast between the glass plates and the coated casting was placed in a oven held at 65°C for 60 minutes. Then the coated casting was removed from the mold and post cured for 60 minutes at 120°C.
The resulting cast article had excellent clarity, was not scratched with No. 00 steel wool and was not removed or dulled by 100 double rubs with methyl ethyl ketone. The coating did not lose adhesion when crosshatched and subjected to No. 600 Scotch® Brand adhesive tape pull. Example 2
An abrasion resistant coating composition was prepared by combining 60 grams of dipentaerythritol monohydroxypentaacrylate, 0.2 grams of cobalt-potassium complex drier (Nuocure CK from HUELS Corp.), 0.3 grams of methyl ethyl ketoxime, 15 grams 98.0 % purity 2-hydroxyethyl-methacrylate, 7.4 grams cellulose acetate butyrate (CAB 551.01), 1.5 grams 2,5 dihydroxyperoxy-2,5- dimethylhexane (Luperox 2,5 - 2,5 from PENNWALT Corp.), and 10 grams polyallylglycidyl ether crosslinker-initiator (Santolink XI- 100 from MONSANTO Co.).
This solution was applied at 30 μm to a clean, unwaxed glass plate and the film was exposed for 3 minutes to infrared radiation produced by 40 W/cm high intensity tungsten quartz tube.
The resulting film had a very slight surface tack. A cell was constructed with the coated plate and acrylic syrup was cast as in Example 1. The coated casting was then cured in the mold for 12 hours at 60°C.
After demolding the resulting article was optically clear. The coated side was not scratched after 25 rubs with No. 00 steel wool and the coating was not removed by cross hatching and tape pulling. Example 3
An abrasion resistant coating was prepared by combining 65 grams dipentaerythritol monohydroxypentaacrylate, 18 grams 98.0 purity 2-hydroxyethylmethacrylate, 7.4 grams CAB 551.01, 10 grams Cymel 303 and 2.0 grams acyl phosphine oxide photoinitiator.
25 μm of this solution were applied to a clean glass plate and subjected to UV radiation from as 79 W/cm mercury vapor lamp for 1.5 seconds. The resulting film had a slight tack and marred easily. Into the cell constructed with the coated glass plate, 3,2 mm
Teflon® spacer and a clean, waxed glass plate was cast an acrylic syrup consisting of acrylic resin, methylmethacrylate and 2,2'-azobis (2-methylpropane nitrile) initiator. The cell was placed in a 60°C oven for 12 hours. The resulting article was optically clear, and was not scratched on the coated side with No. 00 steel wool. The coating could not be removed by cross hatching and tape pulling.

Claims

1. A two-stage, in-mold process for preparing a laminated thermoplastic article with an abrasion resistant coating, the process comprising the steps of :
A Providing a mold having a surface corresponding to the article in negative relief ; R Applying to at least a portion of the surface of the said mold a 100 % reactive coating composition comprising : 1. A polyfunctional acrylic monomer having at least three acryloloxy groups,
2. A monofunctional acrylic monomer,
3. An acrylic-soluble thermoplastic having hydroxy functionality, 4. An aminoplast resin, and
5. A free radical initiator ; C At least partially curing the coating composition ;
D. Applying to the at least partially cured coating composition an at least partially uncured thermoplastic composition to form a laminate ;
E. Curing the laminate to form the plastic article ; and
F. Removing the plastic article from the mold.
2. The process of Claim 1 in which the 100 % reactive coating composition contains a blocked acid catalyst.
3. A process according to any of Claims 1 and 2, in which the polyfunctional acrylic monomer has at least five acryloloxy groups.
4. A process according to any of Claims 1 to 3, in which the monofunctional acrylic monomer is selected from the group consisting of alkyl and cycloalkyl acrylates and methacrylates.
5. A process according to any of Claims 1 to 4, in which the acrylic-soluble thermoplastic has a weight average molecular weight of at least about 3,000.
6. A process according to any of Claims 1 to 5, in which the aminoplast resin is a melamine-formaldehyde resin.
7. The process of Claim 2 in which the blocked acid catalyst remains inactive at temperatures less than about 95°C.
8. A process according to any of Claims 1 to 7, in which the free radical initiator is a UV photoinitiator and the reactive coating composition is at least partially cured by UV radiation.
9. A process according to any of Claims 1 to 7, in which the free radical initiator is a system comprising a metallic salt drier, and a polyallylic crosslinker-initiator.
10. The process of Claim 9, in which the crosslinker-initiator is a polyallylic ether, and the metallic salt drier is selected from the group consisting of the octoates, naphtenates and neodeconates of cobalt, manganese, vanadium, potassium, zinc and copper.
11. The process of Claim 9 or Claim 10, in which the system includes a co-initiator.
12. A process according to Claim 2 and Claim 8, in which the coating composition comprises, in weight percent based on the total weight of the coating composition :
A 30 85 % polyfunctional acrylic monomer,
B 10 40 % monofunctional acrylic monomer,
C 2 15 % acrylic-soluble thermoplastic having hydroxy functionality, D D.. 5 5 - - 20 % Aminoplast resin,
E. 0 - 5 % Blocked acid catalyst, and
F. 0.2 - 6 % UV photoinitiator.
13. The process of Claim 11, in which the coating composition comprises, in weight percent based on the total weight of the coating composition :
A 30 - 70 % polyfunctional acrylic monomer, B. 10 - 40 % monofunctional acrylic monomer, C 2 - 15 % acrylic-soluble thermoplastic having hydroxy functionality, D. 5 - 20 % Aminoplast resin,
E. 0 - 5 % Blocked acid catalyst,
F. 5 - 25 % polyallylic crosslinker-initiator,
G. 0.05 - 0.5 % Metallic salt drier, and H. 0 - 3 % Co-initiator.
14. A process according to any of Claims 9, 10, 11 and 13, in which the coating composition is cured by infrared radiation.
15. A laminated thermoplastic article with abrasion resistant coating prepared by a process according to any of Claims 1 to 14.
PCT/EP1993/002725 1993-10-06 1993-10-06 Dual cure, in-mold process for manufacturing abrasion resistant, coated thermoplastic articles WO1995009724A1 (en)

Priority Applications (2)

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PCT/EP1993/002725 WO1995009724A1 (en) 1993-10-06 1993-10-06 Dual cure, in-mold process for manufacturing abrasion resistant, coated thermoplastic articles
AU51112/93A AU5111293A (en) 1993-10-06 1993-10-06 Dual cure, in-mold process for manufacturing abrasion resistant, coated thermoplastic articles

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP1993/002725 WO1995009724A1 (en) 1993-10-06 1993-10-06 Dual cure, in-mold process for manufacturing abrasion resistant, coated thermoplastic articles

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US6848986B2 (en) 2001-03-28 2005-02-01 3M Innovative Properties Company Dual cured abrasive articles
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AU2007247775B2 (en) * 2001-12-14 2012-07-19 Carl Zeiss Vision Australia Holdings Ltd Methods for forming coated high index optical elements
AU2007247775B8 (en) * 2001-12-14 2012-09-20 Carl Zeiss Vision Australia Holdings Ltd Methods for forming coated high index optical elements
US9453950B2 (en) 2001-12-14 2016-09-27 Carl Zeiss Vision Australia Holdings Ltd. Photochromic coating process
DE10222574A1 (en) * 2002-05-08 2003-11-27 Global Science Patent Gmbh Production of multi-layer systems, e.g. for sensors, reflectors or coatings, involves forming a chemical bond between adjacent layers by polymerising monomers contained therein
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WO2007128071A1 (en) 2006-05-09 2007-11-15 Carl Zeiss Vision Australia Holdings Ltd Methods for forming coated high index optical elements

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