KR950010586B1 - Primed polyalefin base material - Google Patents

Abstract

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Description

Primed Polyolefin Substrate

FIELD OF THE INVENTION The present invention relates to primed polyolefin substrates with improved adhesion to epoxy resin adhesives and also to methods for bonding primed polyolefin substrates using epoxy resin adhesives.

For many years, there has been a desire for polyolefin materials that can be bonded to other materials such as metals, ceramics and wood using epoxy resin adhesives or to themselves. It may sometimes be necessary to combine the above materials with epoxy resin adhesives, especially when the combined materials are subjected to high temperature and high humidity conditions.

Untreated polyolefin bases such as polyallomers, polypropylenes or polyethylenes, which are copolymers of polyolefins and polypropylenes, generally do not adhere well to epoxy adhesives, so that the properties of the substrate are easily adhered without significantly altering the properties of the substrate. Many efforts have been made in the study of techniques to increase the number and reliably. Unfolding to improve the adhesive bonds that have been studied is the treatment with helium gas plasma, oxygen gas plasma and chromic acid. This treatment and other methods of surface modification have a common drawback of poor durability. Slightly rubbing the surface causes a reduction in effectiveness, and the deformed surface is easily worn.

Irradiation of polyolefin-based substrates by electronic loads, etc., to improve the adhesion of various coatings is also known, which is described in U.S. Pat. Described in the essay.

The polyolefin substrate had a treated surface for improved adhesion of the pressure sensitive adhesive. Such pressure sensitive adhesives include rubber-like adhesives such as those based on natural rubber and synthetic rubber, such as styrene-butadiene, chloroprene, neoprene and isobutylene rubber and synthetic resinous adhesives such as acrylic, polyvinyl chloride, polyvinyl Acetate and polyvinyl butyrate adhesives. U.S. Patent No. 3,628,987 (Nakata et al.) Discloses a pressure-sensitive adhesive wherein the film surface to which the adhesive is bonded has a graft-polymerized vinyl monomer or diene monomer to which the polymer is a polymer of vinyl or diene monomer. It has a solubility similar to U.S. Patent No. 4,563,388 (Bunk et al.) Includes acrylic acid, methacrylic acid and esters thereof; Acrylamide; Methacrylamide; Sterically unterminated tertiary alkylamides and methacrylamides having 3 or less carbon atoms in the alkyl group; And a polyolefin substrate having graft polymerized at least one monomer selected from the group consisting of N-vinylpyrrolidone and in which a normal adhesive pressure-sensitive adhesive of acrylic type is bonded to such graft polymerized monomer.

The following documents describe methyl acrylate, vinyl acetate, acrylic acid, acrylamide and methylol acrylamide by liquid preliminary irradiation or vapor phase cross graft with graft monomer thicknesses of 10 macrometers or more to improve the adhesion of epoxy adhesives. A method of grafting a polyethylene to polyethylene is described (in the case of the above methyl acrylate, it saponifies later).

"Surface Modification of Polyethylene by Radiation-Induced Grafting for Adhesive Bonding. I. Relationship Between Adhesive Bond Strength and Surface Composition," (S. Yamakawa, J. Appl. Polym Sci. 20, 3057-3072 (1976);

"II. Relationship Between Adhesive Bond Strength and Surface Structure," (S. Yamakawa et al., Macromolecules, 9, 754-758, (1976);

"III. Oxidative Degradation and Stabilization of Grafted Layer," (S. Yamakawa, et al., J. Appln. Plym. Sci., 22, 2479-2470 (1978);

"IV .. Improvement in Wet Peel Strength," (S. Yamakawa et al., J. Appl. Polym. Sci., 25, 25-39 (1980);

"V. Comparison with Other Surface Treatments," (S. Yamakawa et al., J. Appl. Polym. Sci., 25, 4049 (1980).

The present invention provides a polyolefin first substrate that is firmly adhered to a second substrate by an epoxy resin adhesive, wherein the polyolefin first substrate is a carboxylic acid and a sulfonic acid and an alkylester thereof (the alkyl ester is an ester group). Of up to 5 carbon atoms), mono- and di-substituted amides, alcohols, amines, epoxides and 5-, 6-, and 7-membered containing at least one oxygen and / or nitrogen atom in the ring At least one monomer selected from the group consisting of heterocyclic rings is graft polymerized to the substrate and is in contact with the epoxy resin adhesive, provided that the monomer contains an ethylenically unsaturated polymerizable moiety; The graft-polymerized monomer is in a layer having a thickness of 5 micrometers or less.

The present invention provides a method of attaching a polyolefin first substrate to a second group using an epoxy resin adhesive, which method comprises: a) carboxylic acids and sulfonic acids and their alkyl esters (the alkyl esters being no more than 8 in the ester group); Containing carbon number). Selected from the group consisting of mono- and di-substituted amides, alcohols, amines, epoxides and 5-, 6- and 7-membered heterocyclic rings containing at least one oxygen and / or nitrogen atom in the ring Coating a liquid monomer, wherein said monomer contains an ethylenically unsaturated polymerizable moiety, on said polyolefin first substrate in a layer of 5 micrometers or less; b) irradiating the coated substrate with ionizing radiation to graft polymerize the monomer onto the substrate; c) coating an epoxy resin adhesive on at least one of (i) the graft-polymerized monomer surface on the first substrate and (ii) the surface of the second substrate; d) connecting said surfaces (i) and (ii); e) curing the epoxy resin adhesive.

Surprisingly, excellent peel values of 25 1b / in (440 N / dm) or more are obtained when the thickness of the grafted monomer layer is 5 micrometers or less.

The substrate of the present invention is a polyolefin material, ie polyethylene, polyalkyl-α-olefins and combinations thereof, such as polyalomers which are polyethylene, polypropylene or ethylene / propylene copolymers. These polyolefin materials may also contain small amounts, or about 10% by weight, of modifying monomers, and examples of such monomers are crosslinkable terpolymers such as dicyclopentadiene and norbornene, and ionomers that enhance binding strength, such as acrylic acid. (jonomer), etc. Terpolymers and ionomers are not present on the surface of the polyolefin material in an amount sufficient to affect the epoxy resin adhesive to the polyolefin material.

The thickness of the polyolefin material is determined by the end use of the adhesive-coated product, which generally has a thickness of about 0.025 to about 5.0 ml. Polyolefin materials may also contain additives such as carbon black, calcium carbonate, silica, titanium dioxide, crosslinking agents, dispersants and extrusion aids known in the art.

Suitable monomers for graft polymerization on polyolefin substrates in order to improve the adhesion of the epoxy adhesive to the substrates are as follows; Acrylic acid, dimethyl acrylamide, diethyl acrylamide, dipropyl acrylamide, hydroxyethyl acrylate, butanediol diacrylate, hexanediol diacrylate, diethylaminoethyl acrylate, glycidyl methacrylate, isobutyl meta Acrylate, cyclohexyl methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tol acrylate, hydantoin hexaacrylate, 2-vinyl-4 , 4-dimethylazlactone and N-minyl-pyrrolidone.

The monomer composition generally contains about 60 to 100 weight percent monomer. The monomer composition applied to the polyolefin substrate may contain various additives such as crosslinkers, surfactants, alcohols and acids and the like.

Crosslinking agents, which may be suitable monomers for grafting on the substrate, may be added to further improve the heat resistance of the product. Useful crosslinking agents include polyethylene glycol diacrylate, pentaerythritol tetraacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, allyl methacrylate, 1,6- Hexanediol diacrylate, 1,6-hexanediol dimethacrylate, thiodiethylene glycol diacrylate, trialkyl cyanurate, and the like. Preferred crosslinkers include polyethylene glycol diacrylate, tetraethylene glycol dimethacrylate, trimethylol propane triacrylate and thiodiethylene glycol diacrylate. The crosslinking agent may be present in the monomer composition at about 0 to about 80 weight percent, preferably 0 to about 40 weight percent.

Surfactants may be present in the monomer composition to increase the uniformity of the coating on the substrate.

The thickness of the monomer composition is preferably about 5 micrometers or less, more preferably about 1 micrometer or less and most preferably about 0.5 micrometer or less.

In order to uniformly apply the monomer to the polyolefin substrate, it is preferable to treat the substrate so that the polar liquid wets the surface of the substrate. This can be accomplished by treating the substrate with an oxidizing agent such as nitric acid or chromic acid or treating the substrate with a flame, plasma discharge or corona discharge. Preferred method is corona discharge treatment.

The monomers are graft polymerized onto the substrate by the use of actinic radiation such as X-rays, beta rays, gamma rays, ultraviolet rays, visible light and electron beam radiation. Preferred graft polymerization method is a method of radiation calculation by electron beam. The electron beam capacity is generally at least about 0.05 Mrads, preferably at least about 0.5 Mrads, more preferably between about 2 and about 10 Mrads.

The substrate to which the polyolefin material is to be bonded may be anything that bonds well with the epoxy adhesive. Examples of such substrates include metals such as aluminum, steel, galvanized steel, stainless steel, copper and titanium, plastics other than polyolefins, such as polycarbonates, polyvinyl chlorides, polyesters and fiber-reinforced polyesters, poly Methyl methacrylate and acrylonitrile-butadiene-styrene, especially plastics with improved impact resistance, natural and synthetic rubbers such as polychloroprene, styrene-butadiene rubber and nitrile rubber, ceramics, wood, painted surfaces, primed with silane Glass and polyolefins containing monomers graft polymerized according to the invention.

The epoxy adhesive useful in the present invention may be any 1- or 2-part epoxy adhesive as long as the required curing temperature does not exceed the softening temperature of the polyolefin substrate. In use, the epoxy adhesive may be applied to the polyolefin substrate or the substrate to which the polyolefin material is to be attached or both. Typical epoxy adhesives are Epoxy Adhesivews 1838 and 2216B / A under the trademark Sootch-Weld ^R, each of which is available from 3M.

The advantages of the invention are illustrated by the following examples, and various modifications are possible to those skilled in the art.

Example 1

The polyalomer resin, available from Tennessee Eastman as "Tenite" 5321 E, was milled with carbon black by weight percent. The composition was then extruded into a sheet about 0.5 ml thick and then one surface of the sheet was corona-treated by passing the sheet through a 1 ml air gap between the chlorinated polyethylene-coated electrode and the crushed aluminum cylinder. The frequency is 16 kHz, the total input is 1.5 kw, and the exposure time is 0.6-1.0 seconds. The corona-treated surface was then subjected to 80 parts by weight of N, N-dimethyl acrylamide, 20 parts by weight of trimethylol propane triacrylate, and 0.5 parts by weight of fluoro chemical acrylate oligomer (from 3M to "FC 430"). And a mixture of commercially available wetting and leveling agents). The mixture having a viscosity of 2.3 cps at 25 ° C. was prepared so that the coating thickness was 1 micrometer or less. 200 quadrant knurled gravure rolls and doctor blades were applied to the corona-treated polyalomer surface. The coated surface was then exposed to an application amount of about 4Mards and electron beam radiation of 150-250kV under nitrogen atmosphere. The thickness of the grafted layer was found to be less than 0.4 micrometer as measured by reduced total radiation-infrared spectroscopy.

Cold-rolled steel (4 "x 12" x 0.32 "(10 cm x 30 cm x 0.8 cm) commercially available from Advanced Coating Technologies, Inc., Hillside, Michigan, 80-730 F cold-rolled steel, B40 , Unpolished, 17603001) three times with methyl ethyl ketone to remove surface oils 6 parts by weight of base and 5 parts by weight of accelerator are mixed with Epoxy Adhesive 1838-LB / A under the Scotch-Weld ^R brand name. The translucent body was prepared by coating the adhesive on a steel sheet and placing a strip of N, N-dimethyl acrylamide / trimethyl on propane triacrylate-grafted 1 "x 6" polyalomer onto the adhesive, where the graft was The coated surface was in contact with the adhesive and the polyalomer end extended past the plate.The steel / adhesive / polyalomer composite was rolled twice with a 4.5 lb (2 kg) roller.The epoxy adhesive layer was approximately 0.004 inches (thick). 0.1 mm) into the oven at 170 ° F. (77 ° C.) for 2 hours. The oven was then turned off and the composite was cooled overnight (16 hours) The adhesive force was measured by pulling the polyalomer from the steel sheet at a 90 ° angle at a rate of 12 inches (30 cm) per minute. There was no failure The bonded polyalomer was destroyed at a force of about 40 1b / in (700 N / dm).

Comparative Example 1-3

For Comparative Examples 1-3, each of the untreated polyalomer, the corona-treated polyalomer as in Example 1, each of the corona-treated and electron beam irradiated but no monomer monomers as in Example 1 Was tested for adhesion as in Example 1.

The results are shown in Table 1.

Example 2-19

The various methods listed in Table 1 in Examples 2-19, except that the monomer was applied by rubbing the polyalomer with a paper towel moistened with the monomer and the electron beam radiation application amount was about 5 Mars. The monomer was graft polymerized onto the polyalomer. In Examples 2-12 and 14-19, respectively, 95 parts by weight of the indicated monomers were mixed with 5 parts by weight of trimethylolpropane triacrylate as a crosslinking agent, and in Example 13, 50 parts by weight of trimethylolpropane triacrylate in acetone. It was applied as a solution of%. The composite was prepared as in Example 1 and tested for adhesion.

The results are shown in Table 1 below.

TABLE 1

* Destroying Bonded Polyalomers

[Examples 20 and 21]

To a 20 mil (0.5 mm) thick polyalomer sheet material, a monomer mixture of 80 parts by weight of diethylacrylamide, 20 parts by weight of trimethylolpropane triacrylate, and 0.5 parts by weight of FC430 was grafted according to the method of Example 1. It was. Cold-rolled steel sheet (3 "x 7" x 1/8 (7.5 cm x 17.5 cm x 2.2 cm), Type 1018, available from Paper Calmenson & Co., Minn., St. Paul, After wear by hand, rub with a grade 80 bristle abrasive brush and degreased with methyl ethyl ketone. The steel sheet was then coated with a thickness of about 1-2 mils (0.025-0.5 mm) with 3M Scotch-Weld ^R brand Epoxy Primer 1945 and dried for about 10 minutes.

In Example 20, Scotch-Weld ^R brand Epoxy Adhesive 1838-LB / A Tramslucent, commercially available on 3M, was prepared by mixing the same volume of base and accelerator. The adhesive was coated on the primed steel plate.

The grafted surface of the 1 "x 8" polyalomer was placed on the adhesive as in Example 1 and a second steel sheet was placed on top of the polyalomer to make uniform contact between the polyalomer material and the adhesive. . The composite thus formed was cured for 3 days at room temperature (73 ° F., 23 ° C.). After removing the upper steel sheet, the composite was immersed in water at room temperature for 13 days. When the composite was subjected to a 90 ° peel test as in Example 1, the adhered polyalomer was first broken before any bond breakage occurred.

In Example 21, the composite was prepared as in Example 20 except that the adhesive used was 2216 B / A Structural Adhesive of the Scotho-Weld ^R brand (accelerator of 3 parts volume mixed with a base of 2 parts volume). Was prepared and tested. Before any bond failure occurred, the adhered polyalomer was first broken.

It will be readily apparent to one skilled in the art how to modify the invention without departing from the scope of the invention and the invention is not to be construed as illustrative herein.

Claims (10)

A product consisting of a first substrate of polyolefin adhered onto a second substrate coated with an epoxid adhesive, wherein the polyolefin first substrate comprises carboxylic acids and sulfonic acids and their alkyl esters (which have up to 8 carbon atoms in the ester group). Group) consisting of mono- and di-substituted amides, alcohols, amines, epoxides and 5-, 6- and 7-membered heterocyclocycles containing at least one oxygen and / or nitrogen atom in the ring At least one monomer selected from is graft-polymerized to the first substrate and the first substrate is in contact with an epoxy resin adhesive, the monomer containing an ethylenically unsaturated polymerizable moiety, the graph The article of claim 1, wherein the t-polymerized monomer is in a layer having a thickness of less than 5 microns. The article of claim 1 wherein the graft polymerized monomer is dimethylacrylamide and trimethyl propanetriacrylate. The article of claim 1 wherein the first substrate of polyolefin is a polyalomer. The article of claim 1, wherein said second substrate is a metal. The product of claim 1, wherein the peel value is at least 251 b / in (440 N / dm). a) carboxylic acids and sulfonic acids and their alkyl esters, which contain up to 8 carbon atoms in the ester group, mono- and di-substituted amides, alcohols, amines, epoxides and at least one oxygen in the ring and / or A liquid monomer selected from the group consisting of 5-, 6-, and 7-membered heterocyclic rings containing nitrogen atoms, wherein the monomers contain ethylenically unsaturated polymerizable moieties, is 5 micrometers or less in thickness. Coating on a polyolefin first substrate with a layer of; b) irradiating the coated substrate with ionizing radiation to graft polymerize the monomer onto the substrate; (c) coating an epoxy resin adhesive on at least one of (i) the graft-polymerized monomer surface of the first substrate and (ii) the surface of the second substrate; c) contacting said surfaces (i) and (ii); e) The method of claim 1 comprising curing the epoxy resin adhesive. 7. The method of claim 6, wherein the ionizing radiation is electron beam radiation. 8. The method of claim 7, wherein the electron beam radiation application amount is about 0.05Mards to 0.5Mards. 7. The method of claim 6 further comprising a humectant coated with said liquid monomer. 7. The method of claim 6, further comprising corona-treating the first substrate of polyolefin prior to coating the first substrate of polyolefin with the liquid monomer.