WO2004035697A1

WO2004035697A1 - Coating for providing a tactile surface to molded articles

Info

Publication number: WO2004035697A1
Application number: PCT/US2003/030093
Authority: WO
Inventors: Douglas Mcbain; Guillermina Garcia; Raymond Weinert
Original assignee: Omnova Solutions Inc.; Sizer, David
Priority date: 2002-10-16
Filing date: 2003-09-24
Publication date: 2004-04-29
Also published as: AU2003270875A1; AU2003270875A8

Abstract

A composition for the manufacture of a thermosetting in-mold coating includes one or more ethylenically unsaturated materials and a thermally activated initiator. The resultant cured coating has a soft feel and appearance independent of any macroscopic texture imparted by the substrate to which it is applied.

Description

COATING FOR PROVIDING A TACTILE SURFACE TO MOLDED ARTICLES

BACKGROUND INFORMATION

The invention pertains to coatings that provide a tactile, thermosetting surface coating for molded thermoplastic and thermoset substrates.

Injection molded articles can be coated to provide a variety of decorative or protective surfaces. Often, this is done to hide surface imperfections such as porosity, sink marks, waviness, and the like, which frequently require additional labor and costs to rework. Ordinarily, such coatings provide hard, smooth surfaces that are free of surface defects and imperfections while, at times, simultaneously providing desired properties such as, for example, resistance to actinic radiation degradation, scratching, and the like.

For certain end use applications, a molded article having something other than a hard, smooth surface is desired. For example, automotive manufacturers typically desire that vehicular interiors - including such components as dashboards, instrument panels, air bags covers, glove boxes, consoles, headliners, flooring components, and the like - include surfaces that are, or at least give the impression of being, soft. This impression can be achieved in several ways. For example, the human mind tends to perceive shiny surfaces as being hard and, conversely, to perceive matte or macroscopically textured surfaces as being soft, regardless of the actual pliancy of the surface material. Accordingly, molded articles used in automotive interiors often are made in molds that impart a macroscopically textured surface such as, for example, a grain similar to that seen in leather. For purposes of this document, this type of surface is referred to as visually soft.

In situations where a user is likely to touch (as opposed to merely receive a visual impression of) a surface, a visually soft surface is inadequate. For these types of surfaces, the actual tactility of the surface needs to be altered, i.e., the surface must be made less hard. To make a molded article having a less hard surface feel, one can apply a composition that includes a particulate material of sufficient size to provide a discontinuous surface and/or a material that alters the properties of the polymeric material that forms the bulk of the surface (e.g., a solvent or plasticizer). These solutions work adequately in situations where, for example, an article is spray coated after being removed from the mold in which it was made. The situation changes drastically if one wishes to provide a soft feel coating to a mold article while the article remains in the mold, however.

Injection molding processes ordinarily consist of heating a molding resin to form a viscous melt, injecting the melt under pressure into a closed mold cavity maintained at a temperature below that of the introduced melt, allowing the molten resin to harden so as to form a solid molded substrate conforming to the interior configuration of the mold cavity, and then ejecting the mold part from the mold cavity. The same general description also holds true for the production of thermoset articles with the proviso that a crosslinking reaction is initiated and/or promoted by thermally activated chemical compounds added to the melt.

The use of a mold cavity during this type of molding process creates a problem where one desires to impart a surface coating having a soft feel. For example, the addition of particulate material to a coating composition is pointless because the interior surface of the mold (i.e. the surface that defines the mold cavity) necessarily defines the macroscopic texture of the coating surface, and the discontinuity that particles normally would impart cannot be obtained. Likewise, introduction of volatile materials into a defined volume mold cavity that is essentially filled with resin results in undesired effects to the coating being applied thereto such as, for example, macroscopic voids or porosity caused by the inability of the volatile materials to escape from the coating as it gels or foams and/or continuity disruptions in the coating due to the volatile material finding a pathway to a point in the mold parting line where it can vent.

According, one wishing to impart a coating having a soft feel to a molded article which remains in its mold during the coating process must be able to formulate a composition that incorporates materials which, upon curing, result in a polymer network that itself possesses a soft feel.

The process whereby an article is coated while remaining in its mold commonly is referred to as in-mold coating or IMC. Historically, IMC has been accomplished by spraying a composition onto the surface of a mold prior to inject- tion of molten resin or by injection of a liquid composition into a slightly opened mold to coat the mold cavity surfaces and/or the molded or partially molded substrate followed by reapplication of molding pressure. Recently, however, others have described a process whereby the necessity to manipulate the mold before or during the mold process has been eliminated. Even with this development, provision of a liquid composition capable of forming a coating having a soft feel without reliance on particulate materials or migratory materials (e.g., solvents) has remained desirable yet elusive.

SUMMARY OF THE INVENTION

Briefly, the present invention involves a thermoset coating which is formed on a molded article while the article remains in the mold in which it was formed. The coating includes the reaction product of one or more ethylenically unsaturated materials each of which has a number average molecular weight (M_n) of no more than about 10,000 and is capable of thermally initiated polymerization. The coating includes a surface which has a soft feel independent of any macroscopic texture imparted thereto by the mold from which the molded article is produced. In another aspect, the present invention provides a composition capable of being initiated so as to form a thermoset network having a soft feel. The composition includes a thermally activatable initiator and at least two materials containing terminal ethylenic unsaturation. None of the ethylenically unsaturated materials has a M_n of more than about 10,000, at least one has a M_n of at least about 4000, at least one has a M_n of less than about 4000, and at least one includes more than one point of ethylenic unsaturation.

In a further aspect, the present invention provides a process for providing an injection molded article with a thermoset coating which is derived from a curable composition. The process employs a mold defining a mold cavity having a shape of the article to be formed; the mold cavity is maintained at an elevated temperature throughout the process. Into the mold cavity is injected a first composition that includes one or more polymers and allowing this first composition to at least partially solidify before injecting into the mold cavity the curable composition and allowing the curable composition to contact at least a part of a surface of the partially solidified first composition and at least partially curing the curable composition so as to form the thermoset coating. The coating includes a surface which has a soft feel independent of any macroscopic texture imparted by the surface of the mold cavity. The thermosetting surface coating can provide molded articles with a soft touch surface coating integrally fused or adhered to the surface of the molded substrate and form a soft matte appearance. The cured, soft, matte surface coating on the molded part or article can provide a finished appearance free of surface defects and imperfections and a surface of limited hardness having an excellent soft matte appearance and soft touch feel yet which is resistant to scuffing, scratching, abrasion, and similar surface damage. The cured soft touch coating can have a pencil hardness of from HB to H, a Shore A hardness no greater than 90, and a Hoffman scratch above about 300 and preferably from about 450 to about 1000 g, and Taber abrasion above about 1000 cycles per 25.4 μm (mil) of coating thickness.

Hereinthroughout, the following definitions apply unless a contrary intention is expressly indicated:

"(meth)acrylate" means acrylate or methacrylate; "cure" means to at least one of polymerize and crosslink;

"soft feel" means that a human tester, upon touching a surface, recognizes the surface in question to be non-hard and/or non-smooth; and "oligomer" means a polymer having a relatively low M_n such as, for example, no more than about 20,000.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

ILLUSTRATIVE EMBODIMENTS FOR CARRYING OUT THE INVENTION

A soft touch-type coating can be derived from a composition that includes one or more ethylenically unsaturated materials. The composition is capable of uniformly coating an article and providing the same with a soft feel that is indepen- dent of any macroscopic texture that might be imparted by the mold. This soft feel can be accomplished without the need to include particulate and/or migratory materials (e.g., solvents) in the composition. This is extremely advantageous in that the composition can be used to coat a molded article while such article remains in the mold in which it is made. This ability to in-mold coat thermoplastic and thermoset articles has many advantages such as, for example, a large reduction in the amount of coating composition that must be used (because essentially none is lost due to, e.g., venting (as occurs with solvent-based coatings) or over- spray (as occurs with paint).

The present composition employs one or more ethylenically unsaturated materials. An example of a useful ethylenically unsaturated material is a (meth)acrylate-terminated oligomer, particularly such an oligomer that includes at least two terminal (meth)acrylate groups. Such ethylenically unsaturated materials can be cured thermally, which is highly desirable because of the environment in which IMC typically occurs (i.e., elevated temperatures but an absence of other sources of energy to initiate curing). To expedite curing, inclusion of a thermally activated initiator is desirable. Examples of such initiators are given below.

In one embodiment, the composition includes no ethylenically unsaturated materials with a M_n of more than about 10,000. Within this type of composition, it can be desirable to include at least one ethylenically unsaturated oligomer that has a M_n of at least about 4000 and at least one ethylenically unsaturated material that has a M_n of less than about 4000. By doing so, the result upon initiation is a polymer backbone that includes side chains of varying length. Where one of the side chains itself includes ethylenic unsaturation (e.g., where the material from which it was derived included at least two terminal (meth)acrylate groups), that side chain unsaturation becomes a point for separate chain growth or for attachment to another chain, i.e., crosslinking. This results in a polymer network that includes primary and secondary chains which are linked in numerous places. Although not wishing to be bound by a particular theory, providing a polymer network having a soft feel is believed to be possible through a combination of crosslink density, glass transition temperature (T_g) of the component material(s), an ability of one or more of the component polymers to retain heat and/or moisture so as to provide a warmer-than-expected feel when the polymer network is touched, and possibly other factors. For example, inclusion of oligo- mers in the ethylenically unsaturated materials results in a polymer network having a crosslink density that is less than if one were to use only ethylenically unsaturated monomers. Additionally, materials having relatively low T_g are relatively flexible, and this is believed to contribute to the soft feel of a polymer network which incorporates such materials.

A composition that includes one or more oligomers can produce, upon thermal initiation, a polymer backbone having relatively long side chains. If at least one of the oligomers is difunctional (e.g., includes at least a second point of unsaturation), the relatively long side chains derived from that oligomer then become points of possible branching in a polymer network structure. Several different oligomers can be used so as to provide side chains of multiple lengths. However, this may not be necessary where a proper blend of oligomer and mono- mer is used so as to achieve a desired combination of primary polymer chain length and crosslink density.

With respect to ethylenically unsaturated materials, (meth)acrylates are preferred due to their commercial availability and tendency to cure easily and quickly in thermally initiated systems. For oligomeric ethylenically unsaturated materials, the polyurethane (meth)acrylates are preferred. These are made from polyethers or polyesters of a desired M_n by reacting the same with isocyanate and then end-capping the chain with one or more functional (meth)acrylate groups. Where both ends of a straight chain oligomer are capped, the resulting material is said to be a di(meth)acrylate. Such materials can be represented by the formula A-B-C-B-A Formula 1 where each A is a (meth)acrylate-derived moiety, each B is a polyisocyanate derived moiety, and C is a polyol-derived moiety. A specific example of such a material can be represented by the general formula

O O O O O O ιι ₁ || II II I II

CH₂=CRCOR¹O-CNH-T-NHC-O-L-O-CNH-T-NHC-OR¹CRC=CH₂ (A) (B) (C) (B) (A) where each R independently is H or a methyl group, each R¹ independently is a

C Cι₂ alkyl group, each T independently is the residual portion of a polyisocyanate from which B of Formula 1 is derived, and L is the residual portion of a hydroxy- terminated oligomer (e.g., a polyester or polyether) from which C of Formula 1 is derived.

A representative composition includes a polyurethane-(meth)acrylate oligomer as well as a polymerizable di(meth)acrylate and/or monoethylenically unsaturated monomer. Using this representative composition as an example, the various potential reactants can be described in detail.

The polyurethane-(meth)acrylate oligomer includes a polyurethane "backbone" with at least one (meth)acrylate capping group. A preferred polyurethane can be obtained by reacting an excess number of equivalents of an isocyanate, preferably a diisocyanate, with a lesser number of equivalents of a polyol, preferably a diol. The resulting material is an isocyanate-terminated low molecular weight linear polyurethane. The terminal isocyanate groups of this polyurethane can be further reacted with a hydroxyalkyl (meth)acrylate to produce a polyurethane oligomer having terminal ethylenic unsaturation.

Polyols from which the foregoing polyurethane can be formed include hydroxyl-terminated polyethers and polyesters, commonly known as polyether or polyester diols, respectively. The manufacture of such hydroxyl-terminated materials is a known procedure which need not be repeated here. Polyester- derived polyurethane oligomers can be preferred for certain end-use applications. These hydroxyl-terminated polyethers or polyesters are reacted with an excess of isocyanate, preferably a diisocyanate, to provide a polyurethane with terminal isocyanate groups. Examples of diisocyanates that can be used include one or more of hexamethylene diisocyanate, 2,2,4- and/or 2,4,4-trimethyl hexa- methylene diisocyanate, p- and m-tetraethyl diisocyanate, methylene bis(4-cyclo- hexyl) diisocyanate (sometimes referred to as hydrogenated MIDI), 4,4-methylene diphenyl diisocyanate (sometimes referred to as MIDI), p- and m-phenylene diisocyanate, 2,4- and/or 2,6-toluene diisocyanate (sometimes referred to as TDI), isophorone diisocyanate (sometimes referred to as IPDI), 1 ,5-naphthalene diiso- cyanate, ethylene or propylene diisocyanate, 1 ,4-dimethyl cyclohexane diphenyl- methane diisocyanate, and the like. Relatively small amounts of triisocyanate can be used as well in the reaction with the hydroxyl-terminated polyethers or polyesters. This reaction typically is carried out at a temperature of from about 125° to about 210°C or higher, preferably from about 140° to about 175°C. The polyurethane oligomers that result from this type of reaction can have a

T_g of from about -50° to about 100°C, preferably from about -10° to about 35°C.

An isocyanate-terminated polyurethane can be further reacted with a hydroxyl-functional (meth)acrylate to form an oligomer that includes two terminal (meth)acrylate groups linked by a polyurethane, preferably a linear polyurethane. Useful hydroxyl-functional (meth)acrylates include, for example, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, hydroxyoctyl, and similar hydroxy-functional (meth)acrylates. Hydroxyl-functional lower alkyl acrylates are preferred to produce preferred diacrylate.

The resulting (meth)acrylate-terminated polyurethane oligomers have a M_n of from about 4000 to about 10,000, preferably from about 5000 to about 8000, and desirably have a T_g from about -55° to about 50°C and preferably from about -10° to about 35°C. Another oligomer of this type involves a (meth)acrylic ester-linked urethane intermediate that includes (meth)acrylic acid esterified with a hydroxyl-terminated linear urethane intermediate to form an ester-linked polyurethane (meth)acrylate oligomer. A hydroxyl-terminated urethane intermediate involves the reaction of excess equivalents of a polyether or polyester diol with lesser equivalents of a diisocyanate to form a hydroxyl-terminated linear urethane intermediate. The hydroxyl-terminated intermediate is further reacted with excess equivalents of (meth)acrylic or ethacrylic acid to provide an ester-linked acrylate terminated polyurethane oligomer, where polyurethane diacrylates are preferred. The resulting ester-linked polyurethane (meth)acrylate oligomers are comparable in physical properties and performance to the other polyurethane (meth)acrylate oligomers described above.

These primary polyurethane-(meth)acrylate oligomers can be used alone or in combination with one or more ethylenically unsaturated oligomers. When used in conjunction with other materials, the primary type polyurethane-(meth)acrylate oligomer constitutes from about 20 to about 80%, preferably from about 30 to about 45%, of the IMC composition with balance being coreactive polymerizable acrylate(s) and/or mono-ethylenic monomer(s).

Where a second type of ethylenically unsaturated oligomer is used, it preferably has a M_n that is lower than that of the primary type polyurethane- (meth)acrylate oligomer; specifically, the secondary type of oligomer, when used, can have a M_n of from about 500 to about 3000. The relative amounts of the two types of oligomers can be varied to adjust the crosslink density of the resulting polymer network as well as any other properties that might enhance the soft feel thereof. When a mixture of oligomers is utilized, the additional low molecular weight polyurethane-acrylate oligomer(s) can constitute up to about 80% (by wt.) of the composition, but preferably is from about 10 to about 50% (by wt.) thereof. The IMC composition also can contain a coreactive, low molecular weight polyoxylated glycol di(meth)acrylate which includes a glycol-initiated diester of a polyoxylate alkylene chain involving 2 to 12, preferably 2 to 10, repeat units of a C₂-C₆ alkylene oxide such as ethylene oxide and/or propylene oxide, where the polyoxylate chains extending from the glycol are each terminated with a (meth)- acrylate group to provide a poly(alkylene oxide) di(meth)acrylate. Preferred polyoxylated glycol (meth)acrylates are di(meth)acrylates including an ethoxylated glycol di(meth)acrylate, a propoxylated glycol di(meth)acrylate, or an ethyl- or propyloxylated glycol di(meth)acrylate. Useful glycol initiators include ethylene glycol, propylene glycol, butylene glycols, pentane diols, neopentyl glycol, 1 ,6- hexanediol, diethylene glycol, dipropylene glycol, and the like, with neopentyl glycol and 1 ,6 hexanediol being preferred. Preferred polyoxylated glycol di(meth)- acrylates are poly-ethoxylated and -propoxylated neopentyl glycol (or 1,6- hexanediol) diacrylate having from 4 to 8 repeat units.

Where use of this type of polyoxylated material is desired, it can be present in the composition in an amount of from about 10 to 50% (by wt.), preferably from about 15 to about 40% (by wt.).

In addition to the aforementioned relatively large ethylenically unsaturated materials, smaller ethylenically unsaturated materials also can be included. These include ethylenically unsaturated vinyl aromatic monomers including, for example, styrene, lower alkyl-substituted styrenes such as α-methyl styrene, vinyl toluene, halo-substituted styrenes such as α-chlorostyrene, and the like, with styrene being preferred in certain end-use applications. Other ethylenically unsaturated alkyl or alicyclic monomers include vinyl monomers such as vinyl esters (e.g., vinyl acetate, vinyl propionate, vinyl butyrates, vinyl benzoates, vinyl isopropyl acetates and similar vinyl alkyl esters); acrylic monomers such as lower alkyl esters of (meth)acrylic acid having a C Cι₂ alkyl ester moiety as well as aromatic derivatives of (meth)acrylic acid (e.g., methyl, ethyl, propyl, butyl, 2-ethyl hexyl, cyclo- hexyl; decyl, isodecyl, benzyl, and similar lower alkyl or cyclic esters of (meth)- acrylic acid) and hydroxyl-functional lower alkyl (meth)acrylates such as hydroxyl- propyl methacrylate; and (meth)acrylamides having lower (C C₄) alkyl groups, as well as N-alkoxymethyl derivatives.

Where one or more monomers are desired, the composition preferably contains from about 10 to about 60, preferably from about 15 to about 40 parts by weight (pbw) monomer per 100 pbw of other type(s) of ethylenically unsaturated materials (e.g., oligomers).

Often, polyurethane-(meth)acrylate oligomers of the type described previously are commercially available as blends with ethylenically unsaturated monomers just described. For example, Ebecryl™ 841 1 urethane blend (UCB Chemicals Corp.; Smyrna, Georgia) is about 80% (by wt.) polyurethane-acrylate oligomer having a M_n of about 5000 and about 20% (by wt.) isobornyl acrylate. Similar materials can be obtained from, for example, Sartomer Co. (Exton, Pennsylvania), Cognis (Cincinnati, Ohio), and BASF Corp. (Mt. Olive, New Jersey). An exemplary composition of this type could include, for example, (with all percentages being by weight) from about 20 to about 80%, preferably from 30 to about 45%, polyurethane oligomer(s) having terminal (meth)acrylate groups; from about 10 to about 50%, preferably from about 15 to about 40% polyoxylated glycol di(meth)acrylate; up to about 45%, preferably from about 5 to about 20%, isobornyl (meth)acrylate; up to about 45%, preferably from about 5 to about 25%, vinyl aromatic monomer; with the balance (if any) being other ethylenically unsaturated materials. (The sum of the foregoing will equal 100% for any given composition).

The coating composition can further include a coreactive polymerizable linear (meth)acrylate ester of an alkyl or an alkyl ether diol or triol or higher polyol to provide a di- or tri(meth)acrylate or polyol ester. Di(meth)acrylates are preferred. Useful alkyl diols include up to about 30 alkyl carbon atoms, preferably from

2 to about 10 carbon atoms, including alkylene and branched alkyl diols such as ethylene glycol, propylene glycol, butylene glycols, pentane diol, neopentyl glycol, 1 ,6-hexanediol, and similar lower alkyl diols, as well as higher alkyl diols, where a preferred diol is propylene glycol. Useful alkyl polyols include alkyl triols such as trimethylol ethane and propane, although linear alkyl (meth)acrylate diesters are preferred. Poly(meth)acrylate esters of higher polyols such as pentaerythritol are possible. Useful alkyl ether glycols include diethylene glycol, dipropylene glycol, and triethylene glycol, and similar lower alkyl ether diols. Preferred ether glycols are diethylene and dipropylene glycols. Esters are formed from the foregoing diols, triols and/or higher polyols by esterification of the respective diol, triol or polyol with an unsaturated acid such as (meth)acrylic acid or similar lower alkyl acrylic acid. The composition can include from about 20 to about 100 pbw, and preferably from about 60 to about 80 pbw, diacrylate ester based on 100 pbw polyurethane-(meth)acrylate oligomer(s), and from about 5 to about 50%, preferably from about 15 to about 35%, based on all components.

To assist the foregoing reactive components of the composition to cure when introduced into, for example, a heated mold, one or more thermally activated initiators typically are included. Such thermally activated initiators typically employ a free radical mechanism. Free radical initiators include, inter alia, peroxide and azo compounds. Exemplary peroxides include t-butyl peroxide, t-butyl perbenz- oate, t-butyl peroctate, dibenzoyl peroxide, methyl ethyl ketone peroxide, diacetyl peroxide, t-butyl hydroperoxide, ditertiary butyl peroxide, benzoyl peroxide, t-butyl peroxypivalate, 2,4-dichlorobenzoyl peroxide, decanoylperoxide, propionyl peroxide, hydroxyheptyl peroxide, cyclohexanone peroxide, dicumyl peroxide, cumene hydroperoxide, and the like. Exemplary azo initiators include azo bis- isobutyro nitrite, dimethyl azobis-isobutyrate, and the like. Preferred initiators are tertiary butyl peroxy benzoate, tertiary alkyl hydroperoxides, and tertiary amyl peroxides. Other preferred initiators include tert-amylperoxy-2ethylhexanoate, di- (4-tert-butylcyclohexyl)peroxydicarbonate, and blends of the two, which allowed for a lower cure temperature for the coating.

Initiators are added at a level above about 0.5%, desirably from about 1 to about 5%, and preferably from about 2 to about 4%, by weight based on the weight of the polymerizable components of the composition.

In conjunction with the free radical initiator, an accelerator or inhibitor can be added to accelerate or retard curing. Exemplary accelerators include one or more of cobalt naphthenate or octoate and other metal naphthenates such as zinc, lead, and manganese naphthenates. Ordinarily minimal amounts of accelerator are used, e.g., levels of from about 0.01 to about 1%, preferably from about 0.01 to about 0.5%, based on the weight of the curable components in the composition. Inhibitors such as quinones can control and delay cure times and, if used, are present at very low levels (e.g., as low as parts per million). The composition can include a variety of additives, if desired, such as opacifying pigments, tinting pigments or colorants, and inert fillers. Useful opacifying pigments include TiO₂, ZnO, and the like, while tinting pigments include a variety of oxides, Cr, Cd, and other tinters. Useful fillers include clays, silicas, talc, mica, wood flower, BaSO , calcium and magnesium silicates, aluminum hydroxide, and magnesium and calcium carbonates. Opacifying pigments, tinting pigments or colorants, and inert fillers can be used at up to about 25 pbw, preferably up to about 2 pbw, per 100 pbw of curable components. Use of such adjuvants can result in an IMC that is opaque, tinted, or otherwise modified. Other additives can 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 be used to control the cure rate of the composition. A low profile additive, such as polyvinyl acetate, can be added if desired to avoid molding shrinkage of the coating. Defoamers, flattening agents, wetting agents, stabilizers, scratch-resistant additives, etc., also can be added.

The composition can be prepared by mixing the curable components to form a uniform, fluid blend. Initiator can be added to this mixture as a separate step or can be carried with one of the polymerizable components (e.g., vinyl aromatic monomer where one is used). Additives can be added similarly. Additives commonly used with such resins (e.g., tinting pigments, colorants, heat stabilizers, impact modifiers, lubricants, mold release agents, UV stabilizers, plasticizers, fibers, reinforcing materials, fillers, and the like) can be present without deleterious effect on the coating.

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, compression molding, rotational molding, blow molding and thermoforming, likewise can be coated using the described process. Injection molding processes involve heating a resinous compounding composition to a temperature above the melting point of the component resin(s) and injecting the molten composition into a mold cavity and maintained under heat and pressure until the resins have at least partially solidified into the form of the desired article. Molding temperatures for thermoplastics typically range from about 35° to about 150°C, more commonly from about 65° to about 120°C, while molding temperatures for thermoset resins range from about 115° to about 150°C.

While the molded article is solidifying, the mold pressure preferably is partially released to permit injection of the coating composition under relatively low pressure; alternatively, the coating composition can be injected while the mold is maintained under relatively high pressure. In the former, a metered amount of the coating composition is injected into a nozzle located within the parting line of the mold cavity and preferably disposed opposite from the point where the molten resin composition was injected. Pressure can be applied as needed and ordinarily can be from about 3.5 to about 35 MPa, and preferably from about 13.5 to about 27.5 MPa, but ordinarily at a pressure considerably less than the pressure applied while molding the substrate itself. The applied pressure can increase as the coating composition is injected between the partially molded substrate and the mold cavity surfaces.

The coating composition is allowed to cure so as to provide a thermoset soft touch surface coating advantageously fused to the substrate. Curing temperatures can vary dramatically depending on the components of the coating composition and the desired operational speed of the molding process. In general, however, temperatures typically used for injection molding processes (e.g., about 60° to about 250°C, preferably from about 100° to about 190°C, and more preferably from about 150° to about 180°C) are adequate to cure the coating composition within a reasonable amount of time. The heat curing intervals can be as long as about 180 seconds, although times of from about 25 to about 50 seconds generally are sufficient. After curing is complete, the mold is opened and the coated article removed from the mold cavity.

Referring now to the drawings which are provided to illustrate an embodiment of the invention, FIG. 1 shows a molding apparatus or injection molding machine 10. 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 30. FIG. 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 FIG. 2). The mold halves 20,30 mate along surfaces 24 and 34 (FIG. 1) when the molding apparatus is in the closed position, forming a parting line 42 (FIG. 2) therebetween and around the cavity 40.

The moveable mold half 30 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 70 ranges generally from about 14 to about 103 MPa (i.e., 2000 to 15,000 pounds per square inch (psi)), preferably from about 28 to about 83 MPa (4000 to 12,000 psi), and more preferably from about 41 to about 69 MPa (6000 to 10,000 psi).

With reference to FIG. 2, 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. It should be readily understood by those skilled in the art that the design of the cavity 40 can vary greatly in size and shape according to the desired end product or article to be molded. 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.

Referring back to FIG. 1 , 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 may be positioned to inject material from stationary mold half 20. The first composition injector 50 can be reversed and placed in movable mold half 30. Likewise, second injector 60, which is shown positioned in movable mold half 30, alternatively can be positioned in stationary mold half 20.

The first composition injector 50 is shown in a "backed off' position but can be moved in a horizontal direction so that a nozzle or resin outlet 58 of first injector 50 mates with mold half 20. In the mated position, injector 50 is capable of injecting its contents into mold cavity 40. For purposes of illustration only, 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. As the heated material collects near the end of the barrel, the screw 56 acts as an injection ram and forces the material through the nozzle 58 and into the mold cavity 40. Nozzle 58 generally has a nonreturn valve (not shown) at the open end thereof, and screw 56 has a non-return valve (not shown), to prevent backflow of material.

First composition injector 50 is not meant to be limited to the embodiment shown in FIG. 1 but can be any apparatus capable of injecting a thermoplastic composition into mold cavity 40. For example, 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. (Cincinnati, Ohio), Battenfeld Gloucester Engineering Co, Inc. (Gloucester, Massachusetts), Engel Machinery Inc. (York, Pennsylvania), Husky Injection Molding Systems Ltd. (Bolton, Canada), BOY Machines Inc. (Exton, Pennsylvania), and others. To make an in-mold coated thermoplastic article, with reference to FIG. 1 , a thermoplastic first composition is placed in hopper 52 of the molding machine 10. First injector 50 is moved into nesting or mating relation with the fixed mold half 20. Through conventional means, i.e., using heated extruder barrel 54 and rotating screw 56, first injector 50 heats the first composition above its melting point and directs the heated first composition toward nozzle 58 of first injector 50. Mold halves 20,30 are closed thereby creating the contained molding cavity 40. The molding process continues and a nozzle valve (not shown) of 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 mold cavity 40 through orifice 38. Screw 56 provides a force or pressure that urges the first composition into mold cavity 40 until the nozzle valve is returned to its closed position. The first composition is filled and packed into mold cavity 40 as is known in the art. Once mold cavity 40 is filled and packed, the molded first composition is allowed to cool to a temperature below its melting point. As understood by those in the art, 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. After injection, the resin in the mold cavity begins to solidify, at least to an extent such that the substrate can withstand injection and/or flow pressure subsequently created by introduction of the coating composition. During this solidification, the forming article cools somewhat and this is believed to result at least a slight shrinkage, i.e., a small gap is created between the forming article and surfaces 44 and 46. Some type of active movement of the forming article away from surfaces 44 and 46 could be undertaken but has not proven necessary. After the injected thermoplastic has achieved a suitable modulus, the coating composition can be injected. A predetermined amount of coating composition is utilized so as to provide a coating having, for example, a desired thickness and density. As described above, the surface of the substrate preferably cools and hardens sufficiently 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, generally 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 compressibility 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.

After the first composition has been injected into mold cavity 40 and the surface of the molded article to be coated has cooled below the melt point or otherwise reached a temperature or modulus sufficient to accept or support an IMC but before the surface has cooled too much such that curing of the IMC would be inhibited, a predetermined amount of an IMC is ready to be introduced into the mold cavity from nozzle 62 (FIG. 2) of second composition or IMC injector 60. Injection systems for fluid materials are known in the art and need not be described in detail here; nevertheless, a description of such a system is provided for the convenience of the reader. Coating apparatus 60 includes a coating injector having a shut off pin which supplies a metered amount of a coating material. A supply pump (not shown) is generally utilized to supply the coating composition into a metering cylinder from a storage vessel. 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. When coating apparatus 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 composition typically is injected into mold cavity 40 at a pressure of from about 3.5 to about 35 MPa, preferably from about 10 to about 30 MPa, and more preferably from about 12.5 to about 27.5 MPa.

As shown, a single orifice 62 is used in this description, although clearly two or more orifices can be used if desired. The location of this type of orifice as well as the coating composition injectors communicating therewith (60 in FIG. 1) obviously can vary from apparatus to apparatus, and from part to part, and can be based on a variety of practical and/or aesthetic factors.

Because a typical coating composition is a liquid of relatively low viscosity, it can escape mold cavity 40 at typical clamping pressures through most any opening including, for example, parting line 42. While some equipment manufacturers sell injection molding equipment that employs extremely high clamping pressures (e.g., UBE Industries, Ltd.; Ube City, Japan), alternative means for retaining the composition in mold cavity 40 after introduction but prior to complete cure are available.

For example, one or both of mold halves 20 and 30 can be adapted to provide a lip or track into which molten resin flows and, upon solidification, form a rib for retaining the coating composition. For additional information on this technique, see, for example, PCT publication WO 01/81065 or US 2003-0090035 A1. Another alternative is to adapt one or both of mold halves 20 and 30 to provide a decrease in thickness of the molded article at or near the openings where escape of the coating composition is possible. At those points where the article to be coated includes regions of decreased thickness, the article becomes less compressible and, accordingly, acts to prevent escape of the coating composition. The ordinarily skilled artisan will understand that the gross compressibility of an article does not change but rather its relative compressibility. For example, where the compressibility of an article made from a given polymer or polymer blend is 5%, a region of that article which is 1 mm thick will result in a gap or pulling away from the walls of mold cavity 40 of 0.05 mm; however, another region having a thickness of 0.1 mm will result in a gap of only 0.005 mm. By reducing the thickness of the article to be coated at strategic points, one can achieve gap sizes that are sufficiently small so as to prevent escape of the coating composition. For additional information on this type of technique, see, for example, US 2002- 0039656 A1 , 2003-0077426 A1 , 2003-0082344 A1 , or 2003-0099809 A1.

Once coating composition has been injected into mold cavity 40, coating apparatus 60 is deactivated, thus causing the flow of coating composition to cease. The coating composition flows around the molded article and adheres to its surface. Curing or crosslinking of the coating composition can be caused by the residual heat of the substrate or mold halves, or by reaction of the composition components. The in-mold coating subsequently cures in the mold cavity and adheres to the substrate surface to which the same was applied. The curing can be caused by the residual heat of the substrate or mold halves and/or by reaction between the coating composition components. The IMC is injected into the mold cavity at a pressure ranging generally from about 3.5 to about 35 MPa, desirably from about 10 to about 31 MPa, and preferably from about 13.5 to about 28 MPa. As detailed above, 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.

In the process, the mold is generally not opened or undamped before the in-mold coating is applied. That is, the mold halves maintain a parting line 42 and generally remain substantially fixed relative to each other while both the first and second compositions are injected into the mold cavity. The IMC composition spreads from the mold surface and coats a predetermined portion of the molded article. Immediately or very shortly after the IMC composition is fully injected into mold cavity 40, the nozzle valve or deactivation means of second injector 60 is engaged, thereby preventing further injection of IMC into mold cavity 40.

After the predetermined amount of in-mold coating is injected into mold cavity 40 and it covers or coats the predetermined area of the article or substrate, the coated substrate can be removed from the mold. However, before the mold halves are parted, the IMC 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 IMC composition utilized. As mentioned above, the IMC composition should be injected before the molded article has cooled to the point below which proper curing of the coating can be achieved. The IMC composition requires a minimum temperature to activate the catalyst present therein which causes a crosslinking reaction to occur, thereby curing the coating and melt-bonding it to the thermoplastic substrate.

As described above, the IMC composition is typically heat cured to copolymerize the ethylenically unsaturated oligomer(s) and possibly other components to form an at least partially cured in-mold primer surface coating advantageously molded integrally with and fusion adhered to the fully formed substrate. Depending on the identity of the components in the surface coating as well as the initiator, the in-mold coating curing temperatures may be, for example, from about 60 to about 250°C, preferably from about 150 to about 180°C, for a time sufficient to cure the in-mold coating. The heat curing intervals typically are from about 30 to about 180 seconds and preferably from about 60 to about 90 seconds. The mold is then opened and the surface coated molded part or article can be removed from the mold cavity. The cured surface coating provides an excellent soft touch coating on a variety of substrate surfaces. The in-mold coatings of the present invention are generally flexible and can be utilized on a variety of injection molded substrates, including thermoplastics and thermosets. Thermoplastic molding resins that can be used to make articles capable of being coated include acrylonitrile-butadiene-styrene (ABS), phenolics, polycarbonate (PC), thermoplastic polyesters, polyolefins, PVC, epoxies, silicones, and similar thermoplastic resins, as well as alloys of such molding resins. Preferred thermoplastic resins include PC and PC alloys, ABS, and alloy mixtures of PC/ABS. Useful alloy mixtures of PC/ABS ordinarily have a PC/ABS weight ratio of about 20/80.

Polyolefins which may be coated using the process of the present invention include, among others, polypropylene, polyethylenes, polystyrenes, polybutylenes, substituted polyolefins and mixtures thereof.

More generally, and as used herein, the term "polyolefin" is intended to be expansive and non-limiting. As such, it encompasses polyolefin homopolymers, polyolefin copolymers including copolymers of two or more olefin monomers (including block, alternating, and random configurations), blends of two or more polyoefin homopolymers or copolymers, functionalized or substituted polymers containing monomer or polymer side units grafted onto an olefinic polymeric backbone, as well as blends of any of the above with each other or other polymers. The polyolefins for use herein may conventionally be described as thermoplastics, plastomers, thermoplastic elastomers (TPEs) or thermoplastic olefins (TPOs), depending on the exact structure and composition of the compound. While typically not crosslinked, the polyolefin may have a small amount of crosslinking to impart desired properties to the substrate.

Suitable polyolefins also include polyolefins blended or filled with a lesser amount of another polymer or filler, such as impact modified polypropylene, which typically includes an elastomeric additive or a halogenated polyolefin.

Still other compositions useful as substrates in the present invention include polycarbonate alloys comprising major amounts of polycarbonate mixed with minor amounts of nylon, ABS, PET, PBT, and/or HIPS. The polycarbonate and alloying copolymer can be heated to make the two polymeric material miscible or partially miscible depending on the alloying polymer. The polymers may or may not interact, such as by ester interchange, during the heat alloying process. The polycarbonate ordinarily is the dominant matrix polymer but need not be. On a weight basis, polycarbonate alloys comprise by weight from about 40 to about 95% polycarbonate, preferably from about 50 to about 80% polycarbonate, with the balance being blend or alloying polymer(s). Other suitable materials include nylons, which can be used either alone or alloyed with polycarbonate and compounded with fillers and additives in much the same manner as polycarbonates. Still other materials include ABS, which is a polymeric material comprising copolymerization of acrylonitrile, butadiene, and styrene in various ratios to form a terpolymer comprising butadiene rubber grafted with styrene-acrylonitrile and provide a thermoplastic exhibiting various physical and strength properties, as desired. A fourth monomer can be copolymerized with the ABS if desired to provide special properties, such as alpha-methyl styrene for high heat deflection. ABS can be alloyed with polycarbonate to form a polycarbonate alloy which can be compounded with pigments, filler and other additives in much the same manner as polycarbonates to form a thermoplastic molding composition for injection molding of thermoplastic substrates.

Polyethylene terephthalate (PET) is a polycondensation polymer of ethylene glycol and terephthalic acid, or ethylene glycol transesterified with dimethyl terephthalate. Ordinarily ethylene glycol is esterified or transesterified using a continuous melt phase condensation polymerization process, or trans esterification process, and can be followed by solid-state polymerization at higher temperatures to obtain higher molecular weight PET, if desired. PET can be alloyed with polycarbonate and compounded with other compounding ingredients to provide a thermoplastic injection molding compound useful as an injection molded substrate capable of achieving good surface adhesion with the in-mold primer coating in accordance with this invention.

Polybutylene terephthalate (PBT) or polytetramethylene terephthalate is made by direct esterification of 1 ,4-butanediol with dimethyl terephthalate in much the same manner as PET. PBT can be alloyed with polycarbonate and compounded with filler, pigments, and other additives similar to polycarbonate compounding. High impact styrene (HIPS) is polystyrene reinforced with a rubber compound comprising a non-crystalline polystyrene thermoplastic toughened by incorporating a rubber additive without diminishing other properties. The rubber additive component comprises a large number of small gel particles with a modulus much lower than the matrix polystyrene. The rubber gel particles are added to avoid brittle fracture by absorbing impact energy through micro-craze formation at the gel particles, while preventing craze propagation cracks, to provide a thermoplastic substrate that does not bend or crack under stress due to high flexural modulus. HIPS thermoplastic resins can be alloyed with polycarbonate and compounded with other additives and compounding components in much the same manner as polycarbonates to provide an injection molded substrate. The alloy of polycarbonate with HIPS provides an injection molded substrate having good adhesion with the IMC.

The coating composition is similarly useful for compression molding of thermoplastic substrates. Thermoplastic molding materials for compression molding can be compounded in a manner similar to injection molding thermoplastic molding materials, typically supplied in the form of coarse granules often referred to as molding powder, which ordinarily comprises thermoplastic resin, a filler(s), along with minor amounts of additives such as dye, colorant, and lubricants. Thermoplastic molding powders can be placed in a mold cavity and, on the application of heat and pressure, the thermoplastic resin melts and the compounding material flows to conform to the shape of the mold cavity and form into a molded part. The mold and molded part are then cooled to solidify the molded part. In- mold coatings can be injected into the compression mold to form an in-mold cured thermoset surface coating on the molded part in a manner similar to injection molding in-mold coating. The IMC compositions of the present invention can also be utilized on a surface of a fiber reinforced plastic substrate which can be a thermoplastic or a thermoset, on compression molded sheet molded compounds (SMCs) which are generally thermosets, on low pressure molding compounds (LPMC), and the like. In-mold coatings essentially eliminate porosity and sink marks as well as "orange peel" effect associated with wet post-molding coatings for SMC products. Compression molded parts and articles can be based on thermoplastic or thermosetting molding resins. SMCs ordinarily are fiber reinforced plastics which primarily consist of thermosetting resin glass fiber reinforcement, and fillers, as well as low profile additives, cure initiators, and mold release agents, as desired. During the SMC molding process, a pre-measured molding compound is placed in the mold cavity typically heated to about 130° to about 160°C and cured for time sufficient, typically around 50 seconds more or less, and ordinarily at a pressure from about 3.5 to about 7 MPa. Thermosetting substrate molding resins usually comprise unsaturated polyesters coreactive with styrene or other polymerizable monomer, while thermosetting epoxies can be useful substrate resins for specific high performance molding applications. Thermosetting resins can be compounded with pigments, colorants, fillers, deglossing agent to thermoplastic molding compounds, and frequently further contain reinforcing materials such as strand or chopped fibers.

A cured coating made from the coating composition of this invention exhibits a matte surface having a non-smooth, soft, appearance. The surface of the coating has limited hardness but retains substantial resistance to scratching and other surface abrasions. The surface also has stain resistance and low gloss.

EXAMPLES

Test procedures indicated below were conducted on an in-mold coating heat cured on a substrate at 1 10°C for 140 seconds to provide a dry cured film. Cured films had a thickness of about 35 to about 50 μm.

Pencil Film Hardness (ASTM D3363-92a). A coated panel with a cured film was placed on a horizontal surface. The pencil was held firmly against the dried film at a 45° angle (point away from operator) and pushed away in a 5.5 mm stroke. The hardest pencil lead was used first, followed by pencils having decreasingly hard leads to either of two end points: (a) where a pencil lead did not cut or gouge the film, i.e., "pencil hardness", or (b) where a pencil lead did not scratch the film, i.e. "scratch hardness".

Hoffman Scratch Resistance (STP 500 5.1.6.1 .4). Scratch resistance was measured with a "Balanced Beam Scrape Adhesion and Mar Tester" (Paul N. Gardner Co., Inc.; Pompano Beach, Florida). A Hoffman stylus was used to scratch the cured film. Scratch resistance was determined by the highest stylus load the cured film was able to withstand without scratching.

Taber Abrasion (ASTM D 4060-90). Taber abrasion was measured by abrading a cured coating film on a test panel using 500 g abrasive wheels for a predetermined number of cycles. Abrasion was calculated as loss in weight at a specific number of cycles per mil (25.4 m) of cured film.

Tape Adhesion (ASTM D 3359). Tape adhesion was measured in accordance with method B for the appropriate cured film thickness. Burnish Mar Resistance (ASTM D 5178). This was determined by firmly rubbing a polished porcelain pestle on a cured film surface and visually observing the severity of a mark on the film using the following scale: severe - mark visible at all angles; moderate - mark visible at some angles; slight - mark visible only at grazing angles; or none - no perceptible mark. Solvent Resistance (ASTM D 5402). A cloth towel was soaked with MEK and gently rubbed on the cured film surface. (One back and forth movement counts as one rub.) The cured film surface was rubbed until a break in the cured film surface became visible (but no more than 100 rubs).

Humidity Aging Test (GM No. 4465P). This test was performed at 96 hours at 100% relative humidity and 38°C (100°F).

Softness Method. Comparative subjective evaluation by hand or tactile feel of cured in-mold coating and compared to a standard hard surface appearance IMC designated as "Control".

Examples 1 and 2 were compositions in accordance with this invention. Example 1 was clear whereas Example 2 included pigment. The control is a standard hard surface appearance coating not exhibiting soft touch properties. All amounts are in pbw.

The compositions of Examples 1 and 2 were cured at 1 10°C for 140 seconds and physical properties of the cured films are shown in Table 2. Samples were molded from a Cycoloy™ MC8800 polycarbonate/ABS alloy (GE Plastics; Pittsfield, Massachusetts), in a mold of cavity dimensions 14.0 * 52.0 x 0.33 cm, using a Cincinnati-Milacron injection molding machine. The composition was injected at an 80 second delay from mold close, with a cure time of 140 seconds.

Table 2: Physical Properties of Cured Coatings

Characteristic Comparative Sample* Example 1 Example 2

Gloss 3-5 68 52

Taber abrasion 350-500 >1000 >1000

Subjective softness determination Hard Ultra-soft Ultra-soft

Hoffman scratch (g) 200-300 700 >1000

Solvent resistance (0=poor, 100 100 (50 haze) 50 100=best)

Pencil hardness H H 3B

Adhesion after humidity aging 90-95% 90-95% 100%

Tape adhesion 4B-5B 4B-5B 5B

Mar resistance Slight Slight Slight

* Comparative sample was a 2-part soft touch paint applied after the injection molded article had been removed from its mold.

The ability of each of the coatings to resist stains was nearly identical. Thus, the composition of the present invention can provide coatings that are softer than those derived from "soft touch" painted coatings without compromising other types of performance (e.g., scratch resistance).

Claims

We claim:

1. A thermoset coating for a molded article comprising the reaction product of one or more ethylenically unsaturated materials, each of said materials having a number average molecular weight of no more than about 10,000 and being capable of thermally initiated polymerization, said coating comprising a surface which has a soft feel independent of any macroscopic texture imparted thereto by the mold from which said molded article is produced, and said coating being formed on said molded article while said article remains in the mold in which it was formed.

2. A composition capable of being initiated so as to form a thermoset network having a soft feel, said composition comprising: a) a thermally activatable initiator, and b) at least two materials comprising terminal ethylenic unsaturation, wherein none of said materials has a number average molecular weight of more than about 10,000, at least one of said materials has a number average molecular weight of at least about 4000, at least one of said materials has a number average molecular weight of less than about 4000, and at least one of said materials comprises more than one point of ethylenic unsaturation, said composition optionally being essentially solvent-free.

3. A process for providing an injection molded article with a thermoset coating which is derived from a curable composition, said process comprising: a) providing a mold (20,30) defining a mold cavity (40) having a shape of the article to be formed, said mold cavity (40) being maintained at an elevated temperature throughout said process; b) injecting into said mold cavity (40) a first composition comprising one or more polymers and allowing said first composition to at least partially solidify; c) injecting into said mold cavity (40) said curable composition and allowing said curable composition to contact at least a part of a surface of the partially solidified first composition; and d) at least partially curing said curable composition so as to form said thermoset coating, said coating comprising a surface which has a soft feel independent of any macroscopic texture imparted by the surface of the mold cavity.

4. The process of claim 3 wherein said mold (20,30) is modified so as to comprise one or more means for retaining said first composition and said curable composition.

5. The process of claim 3 wherein said curable composition comprises one or more ethylenically unsaturated materials and an initiator.

6. The coating of claim 1 or the process of claim 5 wherein said one or more ethylenically unsaturated materials comprises oligomers having at least two terminal (meth)acrylate groups.

7. The coating or process of claim 6 wherein one of said oligomers has a number average molecular weight of from 4000 to 10,000 and another of said oligomers has a number average molecular weight of less than 4000.

8. The coating or process of claim 6 wherein said at least one of said oligomers is a (meth)acrylate-terminated polyurethane oligomer.

9. The coating or process of claim 8 wherein said (meth)acrylate- terminated polyurethane oligomer has the formula A-B-C-B-A where each A is a (meth)acrylate-derived moiety, each B is a polyisocyanate-derived moiety, and C is a polyol-derived moiety.

10. The coating of claim 1 , the composition of claim 2, or the process of claim 5 wherein said ethylenically unsaturated materials comprise, by weight, from

20 to 80% polyurethane (meth)acrylate oligomers; from 10 to 50% polyoxylated glycol di(meth)acrylate; up to 45% isobornyl (meth)acrylate; up to 45% vinyl aromatic monomer; and, optionally, additional ethylenically unsaturated materials.