BACKGROUND OF THE INVENTION
Molded plastic parts are widely used in automobiles, trucks, household appliances, graphic arts and the like. Frequently these plastic parts are made from polyolefins such as polyethylene, ethylene copolymers, polypropylene, propylene copolymers and polyolefin blends with other polymers. One such blend is a thermoplastic polyolefin (TPO), which is a rubber-modified polypropylene. Frequently, these plastic parts have to be painted to match the color of painted metal parts that are also present in the automobile, appliance or other items. Typical paints do not adhere well to these plastic parts. Thus, adhesion-promoting primers are needed to improve the adhesion of the paints to the polyolefin materials.
Chlorinated polyolefins, particularly chlorinated, maleated crystalline polypropylene polymers are effective as adhesion-promoting primers and they have very limited solubility in anything other than aromatic or chlorinated solvents. The U.S. Federal Clean Air Act of 1990 limits the amounts of solvents that are on the Hazardous Air Pollutants (HAPs) list that can be used in some areas, and most practical aromatic and chlorinated solvents for use in coatings applications are on the HAPs list. There are some applications where a non-chlorinated adhesion promoter is desired. Other systems proposed for use as primers are based on maleated amorphous polyolefins, which are dissolved in aromatic solvents such as xylene and toluene.
Attempts have been made to provide water based paints and primers for the automotive and appliance industries but these systems generally are not thought to be as effective as solvent based systems. For example, the polymers used in water based systems must be emulsified or dispersed in water using a nonionic, cationic or anionic surfactant and a primary, secondary or tertiary amine, which can lend water-sensitivity to the applied coating.
U.S. Pat. No. 4,286,047 describes pressure-sensitive adhesives that are readily detackifiable by exposure to ultraviolet radiation. These adhesive systems contain a normally tacky and pressure-sensitive adhesive having an epoxy equivalent value of about 400-900 and including an effective amount of an ionic photoinitiator. These adhesives show a decrease in adhesion to surfaces such as glass, aluminum, circuit boards, silicon wafers, and enamel after exposure to ultraviolet radiation.
U.S. Pat. No. 4,303,697 discloses a process for improving the adhesion of paint to polyolefin surfaces. In this process polyolefin surfaces, such as polyethylene, polypropylene, ethylene/propylene copolymers, and EPDM copolymers (TPOs), are primed with a chlorinated polyolefin, which comprises chlorinated polypropylene and chlorinated polypropylene containing carboxylic anhydride groups, and then exposed to ultraviolet radiation. This treatment improves both the dry and wet adhesion of paint to the polyolefin surfaces.
U.S. Pat. No. 4,880,849 describes a coating composition which crosslinks upon exposure to ultraviolet radiation. This composition consists of (a) from 1 to 5 percent of a saturated, chlorinated polymeric material selected from the group consisting of (1) a chlorinated polyolefin containing about 5 to 75 percent by weight of chlorine and having a number average molecular weight of about 5,000 to 50,000, (2) a chlorinated polyolefin containing carboxylic anhydride groups and about 5 to 25 percent by weight of chlorine and having a number average molecular weight of about 5,000 to 50,000, and (3) a mixture thereof; (b) from 20 to 80 percent of a radiation sensitive monomer having at least two addition polymerizable unsaturated bonds; (c) from 0.1 to 5.0 percent of a photopolymerization initiator; and (d) from 80 to 20 percent of an acrylic addition polymer having at least one amino group and having a number average molecular weight of about 8,000 to 70,000. This patent discloses a method of coating comprising (1) applying a film of the coating composition of the invention to a plastic substrate, and (2) curing the film by exposing the film to ultraviolet radiation.
U.S. Pat. No. 4,968,559 describes an adhesive film comprising (a) a base film permeable to ultraviolet light, (b) a layer of a pressure sensitive adhesive formed on one side of the film. The pressure sensitive adhesive layer comprises (1) an elastic polymer selected from the group consisting of a polymer mainly composed of acrylic acid ester copolymers and a saturated copolyester mainly composed of dibasic carboxylic acids and dihydroxy alcohols, (2) an ultraviolet light polymerizable acrylic acid ester having not less than two acryloyl or methacryloyl groups in the molecule in amounts of about 15-200 parts by weight in relation to 100 parts by weight of the elastic polymer, and (3) a photopolymerization initiator in amounts sufficient to induce the photopolymerization of the ultraviolet light polymerizable acrylic acid ester. This adhesive film can be utilized as a dicing film in dicing a semiconductor wafer to dices. The semiconductor wafer is fixed on the film with a relatively large adhesive force and thereafter the film is irradiated with ultraviolet light from the other side thereof, which reduces the adhesive force of the film so that the dice is loosely adhered onto the film.
U.S. Pat. No. 5,118,567 describes an adhesive tape comprising an energy beam transmittable base sheet and an adhesive layer formed on the surface of the said base sheet. The adhesive layer comprises (a) an acrylate or methacrylate polymer substantially free from C—C double bonds and having at least 50 mole % of units derived from at least one acrylate or methacrylate and a molecular weight from about 40,000 to 1,500,000, (b) an epoxy resin having an average of at least 1.8 vicinal epoxy groups per molecule and an average molecular weight from about 100 to 10,000, (c) a photopolymerizable low molecular weight compound having at least one C—C double bond and having a molecular weight from about 100 to 30,000, (d) a heat activatable potential curing agent for said epoxy resin, and (e) a photopolymerization initiator for the said low molecular weight compound. The adhesive layer is curable by irradiation with an energy beam and the cured adhesive layer is also capable of developing tackiness again by heating. These adhesive tape compositions can be utilized as dicing tape for holding semiconductor wafers in place during the dicing step.
U.S. Pat. No. 5,373,048 discloses a composition for a water based adhesion promoter that consists of a non-chlorinated polyolefin, a nonionic surfactant, a primary, secondary or tertiary amine, and water.
U.S. Pat. No. 5,728,767 describes an aqueous resin composition comprising (a) 80 to 10 parts by weight of a modified polyolefin; and (b) 20 to 90 parts by weight of an acrylic or methacrylic monomer or mixture thereof. The modified polyolefin (a) is said to have a weight average molecular weight of 1,000 to 100,000 and is modified by copolymerizing polypropylene, polyethylene, a copolymer of propylene or ethylene with an α-olefin or degradation products thereof under heat or with an oxidizing agent, a radical-generating agent or the like, with 0.1 to 20% by weight of an acid anhydride, carboxylic acid, an alcohol with a radically polymerizable double bond, or a mixture thereof. This patent also describes the process for preparing the aqueous resin composition. In this process component (a) and component (b) are mixed or dissolved and polymerized in water in the presence of a surfactant and a polymerization initiator. These compositions are shown to provide good adhesion of a two-component urethane coating on polypropylene.
U.S. Pat. No. 6,184,264 describes “switchable” adhesive compositions, which are capable of being transformed from a tacky to a non-tacky state. These compositions comprise an adhesive polymeric moiety and a plurality of bound in visible light curable groups, which are chemically bound to the adhesive polymeric moiety. The curing reaction of these adhesive compositions is initiated by visible light. These adhesive compositions show a decrease in peel strength upon irradiation with visible light. These adhesives are said to be especially advantageous when used in medical dressings and which allow for their easy removal when irradiated with visible light. This technology is also disclosed in WO 97/06836.
U.S. Pat. No. 6,262,182 describes a solution process for the modification of certain polyolefins with an unsaturated anhydride, unsaturated acid or unsaturated ester. These modified polyolefins are reported to have good utility as primers for polyolefins substrates when top coated with melamine based and two-part polyurethane paints. Although the modified polyolefins provide good initial crosshatch adhesion of melamine based topcoats and good solvent resistance after application, they are deficient in water resistance, especially under high temperature and humidity conditions.
Thus, there exists a need to provide both solvent based and water-based primers which provide for good adhesion of paints to polyolefin substrates, which are environmentally acceptable and which provide good solvent and water resistance when top coated with urethane or melamine top coats.
SUMMARY OF THE INVENTION
This invention relates to modified polyolefins containing unsaturated pendant groups prepared by reacting a functionalized polyolefin with one or more ethylenically unsaturated compounds having a functional group reactive with the functional group on the polyolefin. These modified polyolefins polymerize in the presence of a photoinitiator upon exposure to ultraviolet radiation and also are capable of copolymerizing in the presence of a photoinitiator with other ethylenically unsaturated crosslinking agents upon exposure to ultraviolet radiation. The modified polyolefins of the present invention significantly improve the adhesion of paints, inks, and adhesives to various plastic and metal substrates. In addition, the modified polyolefins may also contain pendant carboxyl groups, which have the propensity to form hydrophilic salts with amines, therefore rendering the modified polyolefins water-dispersible.
The solvent-based and water-based primer compositions disclosed in this invention are excellent adhesion promoters for polyolefin and other types of plastic substrates. These compositions also provide good solvent and water resistance when top coated with a variety of paint topcoats and are environmentally acceptable.
DETAILED DESCRIPTION OF THE INVENTION
The modified polyolefins of the present invention contain unsaturated pendant groups and are prepared by reacting a functionalized polyolefin with one or more ethylenically unsaturated compounds having a functional group reactive with the functional group on the polyolefin. These compositions have been found to be useful as adhesion promoters for paints and/or melamine or urethane based topcoats applied to various plastic and metal substrates.
Useful polyolefin polymers for practice of the invention include, but are not limited to, polyethylene, ethylene copolymers containing alpha olefins having 2 to about 10 carbon atoms, polypropylene, propylene copolymers containing ethylene or alpha olefins having from 4 to about 10 carbon atoms, poly(1-butene), 1-butene copolymers containing ethylene or alpha olefins having 3 to about 10 carbon atoms and the like. The term copolymer means that the olefin polymer may contain one or more comonomers. In addition, mixtures of the previously mentioned polyolefins may be used in this process as opposed to using a single polyolefin. The polymers may be crystalline, semi crystalline or amorphous but the amorphous ones are preferred because of their improved solubility in typical coating solvents.
Monomers useful in the initial step of functionalizing the polyolefin include unsaturated esters, unsaturated acids, unsaturated anhydrides, and vinyl or acrylic monomers such as hydroxyalkyl acrylates, hydroxyalkyl methacrylates or mixtures thereof and the like. Useful monomers include, but are not limited to, maleic anhydride, citraconic anhydride, itaconic anhydride, glutaconic anhydride, 2,3-dimethylmaleic anhydride, maleic acid, fumaric acid, citraconic acid, mesaconic acid, glutaconic acid, acrylic acid, methacrylic acid, crotonic acid, 2-pentenoic acid, 2-methyl-2-pentenoic acid, dimethyl maleate, diethyl maleate, di-n-propyl maleate, diisopropyl maleate, dimethyl fumarate, diethyl fumarate, di-n-propyl fumarate, diisopropyl fumarate, dimethyl itaconate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, polyethylenglycol monoacrylate, polyethyleneglycol monomethacrylate, polyalkyleneglycol monomethacrylate, polypropyleneglycol monoacrylate, polypropyleneglycol monomethacrylate, and the like.
Preferably, the concentration of the unsaturated anhydride, unsaturated acid, unsaturated ester, vinyl monomer or acrylic monomer is in the range of about 1 to about 30 weight percent based on the weight of the polyolefin. A more preferable range is from about 2 to about 15 weight percent. A range of about 4 to about 12 weight percent is most preferred.
These monomers are readily grafted to polyolefins either in the melt phase or in solution using radical initiators, such as organic peroxides or azo compounds, as the catalyst. A preferred method includes the grafting of the monomers in a solution process according to the procedure described in U.S. application Ser. No. 09/453,892, incorporated herein by reference.
The reaction temperature is usually controlled by the half-life of the peroxide initiator. The half-life of the initiator at a given reaction temperature should be about one third to about one sixth of the reaction time. By knowing the half-life of the initiator at a specific temperature, a suitable reaction time can be quickly determined. The more stable the initiator, the longer the reaction time will be. For example, a peroxide may be suitable if its half-life at a given reaction temperature is 10 hours or less.
Examples of organic peroxides, which may be used, include, but are not limited to, dibenzoyl peroxide, tert-amylperoxy 2-ethylhexanoate, tert-butylperoxy 2-ethylhexanoate, tert-butylperoxy isobutyrate, and tert-butylperoxy isopropyl carbonate, tert-butylperoxy 3,5,5-trimethylhexanoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxy acetate, tert-butylperoxy benzoate, n-butyl 4,4-di(tert-butyl)valerate, dicumyl peroxide, tert-butylcumyl peroxide, di(2-tert.butylperoxy isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di(tert-butyl) peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, tert-butyl hydro peroxide, cumyl hydroperoxide and mixtures thereof.
Examples of suitable azo compounds include, but are not limited to, 2,2′-azobisisopropionitrile, 2,2′-azobisisobutryonitrile (AIBN), dimethyl azoisobutyrate, 1,1′azobis(cyclohexanecarbonitrile), 2,2′-azobis(2-methylpropane) and mixtures thereof. Typical concentrations of radical initiators range from about 0.1 to about 20-weight %, based on the weight of the polyolefin. A more preferable range is from about 0.2 to about 10-weight %.
The addition of the monomers and a radical initiator can be carried out under numerous scenarios. For example, these monomers can be added before the radical initiator, concurrent with the radical initiator or subsequent to the radical initiator. The monomer can be added in either the molten state or as a solution in a solvent that does not interfere with the grafting reaction. Likewise the radical initiator can be added in either solid or liquid form. It is also possible to charge a solution of the grafting monomer containing the initiator in a solvent that does not interfere with the desired reaction. The solvent used for this purpose can be the same or different from the reaction solvent. Preferably the solvent has a low volatility such that it flashes off and does not dilute or contaminate the reaction solvent. Preferred solvents for dissolving the grafting monomer include ketone solvents such as acetone and methyl ethyl ketone. In general, the ketone solvents are used in amounts that do not cause the polyolefin to precipitate.
The grafting process is typically conducted in solution at temperatures ranging from about 50° C. to about 300° C., depending on the choice of solvent. The reaction may be carried out at temperatures up to and including the boiling point of the solvent. A more preferable temperature range is from about 70° C. to about 240° C.; and a most preferred range is from about 80° C. to about 220° C.
Following the completion of the grafting reaction, the solvent used in the grafting reaction may be removed by distillation at either ambient pressure or more preferably at reduced pressure. As a way of reducing cost in the process, the solvent may be recovered and recycled in subsequent batches. Solvents with relatively low boiling points are typically easier to remove and consequently more desirable for use in this process. Preferred solvents include tert-butylbenzene (b.p. 169° C.) and anisole (b.p. 154° C.) because of their lack of reactivity and ease of removal.
In the process of the present invention, the functionalized (grafted) polyolefin is further reacted (fully or partially) with one or more ethylenically unsaturated compounds having a functional group reactive with the functional group on the polyolefin. Useful ethylenically unsaturated compounds include, but are not limited to, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, unsaturated anhydrides, unsaturated esters, unsaturated acids, or mixtures thereof and the like. Useful hydroxyalkyl acrylates or methacrylates include, but are not limited to, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, polyethylenglycol monoacrylate, polyethyleneglycol monomethacrylate, polyalkyleneglycol monomethacrylate, polypropylene-glycol monoacrylate, polypropyleneglycol monomethacrylate and the like. Useful unsaturated anhydrides, unsaturated esters, and unsaturated acids include, but are not limited to, maleic anhydride, citraconic anhydride, itaconic anhydride, glutaconic anhydride, 2,3-dimethylmaleic anhydride, maleic acid, fumaric acid, citraconic acid, mesaconic acid, glutaconic acid, acrylic acid, methacrylic acid, crotonic acid, 2-pentenoic acid, 2-methyl-2-pentenoic acid, dimethyl maleate, diethyl maleate, di-n-propyl maleate, diisopropyl maleate, dimethyl fumarate, diethyl fumarate, di-n-propyl fumarate, diisopropyl fumarate, dimethyl itaconate and the like.
The reaction of the functionalized, ethylenically unsaturated compound with the functionalized (grafted) polyolefin may be carried out in the presence or absence of a solvent. However, it is preferred to conduct the reaction in a solvent at temperatures in the range of 40° C. to 250° C. Any solvent in which the functionalized polyolefin is soluble or partially soluble may be used. Suitable solvents include aromatic hydrocarbon solvents such as benzene, toluene, xylene, tert-butylbenzene, chlorinated solvents, aliphatic hydrocarbon solvents such as naphtha, mineral spirits, and hexane, ester solvents such as propyl acetate and butyl acetate as well as ketones such as methyl amyl ketone. Mixtures of solvents may be used if desired. It may or may not be desirable to conduct this reaction in the reaction solvent from the initial grafting reaction. It also may be desirable to conduct this reaction in the solvent to be used for dissolving the final resin. The amount of functionalized, ethylenically unsaturated compound used will generally be in the range of about 0.01 to about 25-weight % based on the weight of the functionalized polyolefin.
In some instances a catalyst may be used to promote the reaction of the functionalized polyolefin with the functionalized, ethylenically unsaturated compound. There are a variety of acid and base catalysts that may be employed, such as sulphuric acid, p-toluenesulfonic acid, perchloric acid, zinc chloride, sodium acetate, sodium hydroxide, tertiary aliphatic amines, pyridine, and the like. Other types of catalysts that may be employed are ion exchange resins, which are usually sulfonic acid cation exchangers in the hydrogen form, metallic catalysts such as aluminum oxide, lead, tin, and zinc hydroxides as well as tetraalkyl titanates and zirconates such as titanium tetraisopropoxide, titanium tetraisobutoxide and the like.
The functionalized polyolefin may be fully or partially reacted with the functionalized, ethylenically unsaturated compound to yield a modified polyolefin composition having pendant acrylate groups and at least one other pendant functional group. For example, it may be desirable to only partially react the functionalized polyolefin with the functionalized, ethylenically unsaturated compound to provide for a balance of properties and functional groups. Depending on how the functionalized polyolefin is prepared and the corresponding modification with the ethylenically unsaturated compound, a variety of pendant functional groups are possible. In some instances it is possible to have two or more pendant functional groups on the polyolefin, with at least one of those groups being a pendant acrylate group. For example, it is possible to have pendant acrylate, carboxyl, and hydroxyl functionality present on the modified polyolefin. In other instances, one may desire to fully react the functionalized polyolefin with the functionalized, ethylenically unsaturated compound to yield a polyolefin containing mostly pendant acrylate groups. In this instance, a catalyst may or may not be required to complete the reaction.
These modified polyolefin resins are readily soluble in typical coating solvents such as toluene, xylene, naphtha, mineral spirits, hexane, and ester solvents such as propyl acetate and butyl acetate as well as ketones such as methyl amyl ketone. Mixtures of solvents may be used if desired.
The modified polyolefins of the present invention may also contain pendant carboxyl groups, which have the propensity to form hydrophilic salts with amines and therefore may allow the modified polyolefins to be rendered water-dispersible. The modified polyolefin may contain a combination of both pendant acrylate and pendant carboxylic acid groups. For example, this can be accomplished by reacting an anhydride functional polyolefin (functionalized polyolefin) with one mole of a hydroxyl-functional, ethylenically unsaturated compound to yield a modified polyolefin containing both acrylate and carboxyl functionality.
It is readily understood by one skilled in the art that these modified polyolefins may also be rendered water-dispersible. The acrylate modified polyolefins, which contain pendant carboxyl groups, may be dispersed by emulsifying the modified polyolefin in the presence of a nonionic surfactant, amine, and water. The total amount of modified polyolefin in this composition is not significant as long as the relative amounts of surfactant and amine are within typically used ranges for these materials.
The surfactants useful in this invention may be broadly described as nonionic surfactants. The surfactants may have a molecular weight of up to 500 or greater and may include polymeric materials. The surfactants include materials which contain groups of varying polarity whereby one part of the molecule is hydrophilic and the other part of the molecule is hydrophobic. Examples of such materials include polyethyleneoxy polyols and ethoxylated alkyl phenols. Particularly preferred classes of surfactants include alkyl phenoxy poly(ethyleneoxy) alcohols, primary ethoxylated alcohols and secondary ethoxylated alcohols. Preferably the surfactant is a primary ethoxylated alcohol having 12 to 15 carbon atoms or a secondary ethoxylated alcohol having 11 to 15 carbon atoms. Examples of alkyl phenoxy poly(ethyleneoxy) alcohols include Igepal CO-710 sold by Rhone Poulenc. Examples of primary ethoxylated alcohols include Neodol 25-9 and Neodol 25-12 sold by Shell Chemical Company. Examples of secondary ethoxylated alcohols include Tergitol 15-S-9 and Tergitol 15-S-15 sold by Union Carbide Company. The amount of surfactant is broadly in the range of 18 to 50 weight percent and is preferably in the range of 20 to 25 weight percent, based on the weight of the modified carboxylated polyolefin.
The amine component may be a primary, secondary, or tertiary amine. The amine may be aromatic or aliphatic, but aliphatic amines are preferred. The amount of amine may be in the range of 4 to 30 weight percent and preferably is in the range of 8 to 10 weight percent, based on the weight of the modified polyolefin. The amount of water may vary widely and there is no upper limit on the amount of water used. There may be a lower limit on the amount of water because there should be sufficient water in the composition to result in the formation of an admixture of the four components. Generally, there should be at least 50 weight percent water in the composition, based on the weight of the total composition.
The modified polyolefins of the present invention may be readily used as primers for plastic and metal substrates prior to painting. The modified polyolefins may be applied to the plastic or metal substrate as prepared or they may be further diluted with any of the solvents listed previously. The water-dispersible versions may also be applied to the substrate as prepared or they may be further diluted with water. Both the solvent and water-based materials may be applied to the substrate by spray application, dipping, or any other means available, which allows for a uniform coating of the modified polyolefin onto the substrate. These modified polyolefins may also be readily used as additives for commercially available radiation curable top coats or thermally cured topcoats. In this instance, the modified polyolefin adhesion promoter may be added to the coating prior to application on a substrate.
Before application of the modified polyolefin to the substrate, a photoinitiator may be added to the modified polyolefin or modified polyolefin solution or dispersion. The amount of photoinitiator added is typically in the range of 0.01 to 8.0 weight percent based on the non-volatile, ethylenically unsaturated content of the coating composition; preferably about 0.05 to 5.0 weight percent of the non-volatile, ethylenically unsaturated content of the coating composition. The photoinitiator can be any photoinitiator known to one skilled in the art. Suitable photoinitiators include, but are not limited to acetophenone and benzophenone/tertiary amine combinations, dialkoxyacetophenone derivatives, organic peroxides, benzoin and its ethers, and benzil and benzil ketals. A typical photoinitiator is 1-hydroxycyclohexyl-phenyl-ketone or IrgacureŽ 184, available from Ciba Specialty Chemicals, Inc.
The modified polyolefin or modified polyolefin solution or dispersion may also contain auxiliary polymerizable monomers and/or oligomers such as, but not limited to, vinyl acetate, N-vinyl pyrrolidone methyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, neopentylglycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, trimethylolpropane triacrylate, (meth)acrylated urethanes such as EbecrylŽ 220, SartomerŽ CN 964 and CN 965, (meth)acrylated epoxies such as SartomerŽ CN 104, and (meth)acrylated polyesters and polyethers.
After application of the modified polyolefin to the substrate, the modified polyolefin may be cured (i.e. polymerized and crosslinked) in the liquid or solid state (i.e. as a dry film) using methods known in the art. The modified polyolefin may be cured in the presence of a photoinitiator by an amount of ultraviolet radiation sufficient to affect the degree of curing. Depending upon thickness of the coating film, product formulation, photoinitiator type, radiation flux, and source of radiation, exposure times to ultraviolet radiation for about 0.5 seconds to about 30 minutes are typically used for curing the coating composition. Curing may also occur by exposure to sunlight.
After application of the modified polyolefin to the substrate, it may then be topcoated. The topcoat may be applied before or after the modified polyolefin has been cured. If the topcoat is applied after the modified polyolefin has been cured, then the topcoat may or may not have to go through a thermal or radiation curing process. If the topcoat is applied before the modified polyolefin has been cured, then the topcoat and modified polyolefin may go through a radiation curing process together.
These modified polyolefins may also be used as adhesives for polyolefins and other types of plastic substrates. In this instance the modified polyolefin/photoinitiator mixture may be applied to a substrate in which adherence or bonding of a coating, film, fabric, or other material is needed. The adhesive/photoinitiator mixture may be applied to the substrate by roller coating or other methods of application. The adhesive may then be cured before or after application of the coating, film, or fabric by an amount of ultraviolet radiation sufficient to affect the degree of curing. These types of adhesives may be especially effective when the coating, film, fabric, or other materials are pre-coated with resins that are capable of copolymerizing with the modified polyolefin adhesive compositions on the substrate upon exposure to ultraviolet radiation.
Other auxiliary polymerizable monomers and/or oligomers may also be used in conjunction with the modified polyolefin adhesive composition as described above. In this instance the modified polyolefin, containing auxiliary polymerizable monomers or oligomers and a photoinitiator, may be applied to the substrate to which adherence or bonding of a coating, film, fabric, or other material is needed. This mixture may be applied to the substrate by roller coating or other methods of application. The adhesive composition may then be cured before or after application of the coating, film, or fabric by an amount of ultraviolet radiation sufficient to affect the degree of curing. These adhesive compositions may also be especially effective when the coating, film, fabric, or other materials are pre-coated with resins that are capable of copolymerizing with the adhesive composition on the substrate upon exposure to ultraviolet radiation.
The invention disclosed herein can be further described by the following examples. It will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.