JP2659749B2 - Bonding method between insert parts and injection resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a lamp socket, a distributor cap, an ignition coil, a heat case, various switches, a bracket, a bobbin, an intake temperature control valve, a bimetal vacuum switching valve, and a vacuum. Automotive parts such as control valves; resin-coated steel sheets, resin-coated metal tubes, connectors, block terminal plateaus, coil bobbins, tuner parts relays, sockets, switches, sewing machine motor cases, round mounting terminals, relay terminal mounting terminals, fuse cases , Condenser case, metal insert resin electric parts such as CD player chassis; metal insert resin parts such as pump casing, camera exterior parts and resin composite parts such as packing, gasoline tank, etc. The present invention relates to a method for bonding an insert component and a resin that can be used when manufacturing a layer body.

(Prior art)

In recent years, a variety of thermoplastics have appeared, and engineering plastics (polyamide,
Polyester, polycarbonate, polyacetal, polysulfone, polysilicon, polyphenylene oxide, polyimide, ABS, methacrylic, etc.) are manufactured and sold, and these resins have excellent mechanical strength, heat resistance, creep resistance, Chemical properties, electrical properties,
Under many conditions of use, not a few exhibit dimensional stability, etc., and are often replaced by metals such as iron, zinc, and aluminum.

For example, polyamide is used as a material for gasoline tanks.

Depending on the application of the product, some molds cannot be molded with a single mold.Metal or resin parts with metal inserted as insert parts are pre-molded, then mounted in the cavity of the injection mold, and then melted. Injecting resin to obtain a composite laminate, or inserting an insert member molded of a resin material such as a composite product in which a resin pipe and a resin joint are integrated, for example, a female screw or coil with a complicated shape in an injection mold , And then inject the molten resin to integrate them.

Conventionally, in order to improve the adhesion between the insert part and the injection resin, a liquid adhesive or primer is applied to the surface of the insert part, or the surface of the rubber molded part is treated with tricrene or trichloroisocyanuric acid before injection. Molded,
Combined.

Examples of the liquid adhesive and primer include a solvent-type polyester resin, a liquid epoxy resin, a metal salt of an ethylene / methacrylic acid copolymer (Zn ⁺⁺ , Na ⁺ , K ⁺ ), and maleic anhydride-grafted ethylene / vinyl acetate. Copolymers, aqueous polyester emulsions, aqueous polyvinyl acetate emulsions, liquid phenolic resins and the like are used.

[Problems to be solved by the invention]

Recently, as the insert part, in the field where metal is further enclosed, the shape is complicated, or depending on the application of the composite, pressure resistance and thermal shock are required, even if it is the same kind of resin, the adhesive strength is low. It has been pointed out that the resin is inadequate or made of a different kind of resin, and the adhesive strength is insufficient even when an adhesive or a primer is used. In particular, this problem has been pointed out in a field where a composite product is small-sized or precision is required.

At present, the adhesive parts of this composite product are covered with epoxy resin or vulcanized polysilicon, and this is dealt with. However, repeated changes in temperature due to the rise and fall of heat such as motor oil and temperature (thermal shock), and the precision of electric precision parts Electric shock during voltage load, motor oil, pressurization of water, etc. (0.5-3
kg / cm ² ), this coating is also useless in a short period of time, causing boundary peeling at the bonding surface and coating surface, causing liquid leakage, malfunctioning of precision mechanical parts and electronic parts, or inoperability .

[Specific means to solve the problem]

In the present invention, the fitting property between the insert component and the injection resin is further improved by providing a fitting groove or projection on at least the side wall surface that adheres to the injection resin of the component to be inserted.

This adhesiveness can be further improved by using an acrylic copolymer aqueous emulsion of a specific composition as a surface treatment primer for insert parts,
An injection-molded composite laminate resistant to electric shock can be manufactured.

That is, a first aspect of the present invention is to apply a primer made of an aqueous acrylic copolymer resin emulsion having a glass transition point (Tg) of 20 ° C. or less to the surface of an insert part having a fitting groove formed on a side wall surface. Inserting the dried product into the cavity of the injection mold, and then injecting the resin into the cavity to integrate the insert part and the injected resin molded product via the primer. It is intended to provide a bonding method.

A second aspect of the present invention is to apply a primer made of an aqueous acrylic copolymer resin emulsion having a glass transition point (Tg) of 20 ° C. or less to the surface of an insert part having a large number of irregularities on a side wall surface, and then drying the primer. Is inserted into the cavity of the injection mold, and then the resin is injected into the cavity to integrate the insert component and the injected resin molded product via the primer. To provide.

As the primer, (a) 35 to 75% by weight of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms (b) 10 to 50% by weight of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms (C) styrene and / or acrylonitrile 0 to 15
% (However, the sum of the components (b) and (c) is 15 to 55% by weight.
(D) From α, β-unsaturated acids or acid anhydrides thereof, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate or their methacrylate equivalents, acrylamide, methylolacrylamide or their methacrylamide equivalents Selected vinyl monomer 0
Aqueous acrylic copolymer resin emulsion having a glass transition point (Tg) of not more than 20 ° C. obtained by emulsion polymerization of a monomer mixture consisting of 5% by weight and (e) 0 to 30% by weight of another vinyl monomer. By using the primer, the adhesion between the insert component and the injection resin is further improved, and a composite laminate that is less likely to leak out can be obtained.

 Hereinafter, the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an injection mold, 1a denotes a fixed mold, 1b denotes a movable mold, the movable mold 1b includes a release pin, and the molds 1a and 1b form a cavity 3. Reference numeral 4 denotes an insert resin molded product provided with a copper wire coil 5. A thread groove 7 is provided on at least a peripheral surface of the side surface 6 which is bonded to the injection resin 9, as shown in FIG. A coated primer layer 8 is provided, and the insert resin molded product 4 is fixed to the cavity 3 of the movable mold 1b.

The fixed mold 1a is connected to the plasticized resin 11 from the resin passage 10, and the resin passage 10 is connected to the cavity 3.

The molten resin 9 injected by the injection molding machine at a resin pressure of 500 to 2,000 kg / cm ² fills the cavity 3 and is integrated with the insert resin molded product to form a composite molded body shown in FIG.

FIG. 5 is a perspective view of an insert resin molded product of another embodiment, in which a number of protrusions 7 ′ are provided on the side surface 6 of the insert component 4. This projection 7 'may be an annular 7'a or a number of small projections 7'b.

The material of insert parts is metal, ceramic, pottery,
A resin molded product is used. As the material resin of the resin molded product 4 to be inserted, polyamide, polyacetal,
It can withstand the injection resin temperature of 150 ° C or higher selected from polybutylene terephthalate, polyethylene terephthalate, polypropylene, polycarbonate, polysulfone, epoxy resin, polyimide, modified polyphenylene oxide, unsaturated polyester, thermoplastic polyurethane, and vulcanized rubber without deformation. One or a mixture of two or more resins is used.

These may contain fillers, pigments, stabilizers, flame retardants, ultraviolet absorbers and the like.

As the resin to be injected next, polyamide, polyacetal, polybutylene terephthalate, polyethylene terephthalate, polyolefin, polycarbonate, modified polyphenylene oxide, thermoplastic polyurethane,
Vulcanized rubber, polymethyl methacrylate, polystyrene,
Thermosetting resins such as thermoplastic resins such as ABS, reactive epoxy resins, and novolak resins are used.

Furthermore, the rubber component of the vulcanized rubber used in the present invention is a natural rubber (NR) and a synthetic rubber having a carbon-carbon double bond in the structural formula alone or a blend of two or more. The above synthetic rubber includes isoprene, butadiene,
Polyisoprene rubber (IR) and polybutadiene rubber (B), which are homopolymers of conjugated diene compounds such as chloroprene
R), styrene-butadiene copolymer rubber (SBR) which is a copolymer of the conjugated diene compound and a vinyl compound such as styrene, acrylonitrile, vinylpyridine, acrylic acid, alkyl methacrylates and alkyl methacrylates, such as polychloroprene rubber. ), Vinyl pyridine butadiene styrene copolymer rubber, acrylonitrile butadiene copolymer rubber, acrylate butadiene copolymer rubber, methacrylate butadiene copolymer rubber, methyl acrylate butadiene copolymer rubber, methyl methacrylate butadiene copolymer rubber, ethylene, propylene, Copolymers of olefins such as isobutylene and diene compounds, for example, isobutylene isoprene copolymer rubber (II
R), copolymers of olefins and non-conjugated dienes (EPD
M) For example, ethylene, propylene, cyclopentadiene terpolymer, ethylene propylene-5-ethylidene-
2-norbornene terpolymer, ethylene propylene
1,4-hexadiene terpolymer, polyalkenamer obtained by ring-opening polymerization of cycloolefin such as polypentenamer or rubber obtained by ring-opening polymerization of oxirane ring such as sulfur-vulcanizable polyepichlorohydrin rubber or polypropylene oxide Rubber and the like are included. Also included are halides of the various rubbers, for example, chlorinated isobutylene isoprene copolymer rubber (CI-IIR), brominated isobutylene isoprene copolymer rubber (Br-IIR), and the like.

 Further, a ring-opened polymer of norbornene may be used.

Vulcanized rubber can be vulcanized with organic sulfur compounds in addition to common and most important sulfur vulcanization, such as dithiodimorpholine, thiuram vulcanization, peroxide vulcanization, quinoid vulcanization, resin vulcanization, metal vulcanization It includes all those obtained by salt vulcanization, metal oxide vulcanization, polyamide vulcanization, radiation vulcanization, hexamethylenetetramine vulcanization and the like.

The insert component 4 may have a through hole into which the injection resin 8 can enter.

(Primer) The aqueous resin emulsion for forming the adhesive layer is preferably an acrylic resin, which is a non-crosslinked type or a room temperature crosslinked type emulsion (Japanese Patent Laid-Open Nos. 57-3850, 57-3857, 61).
-166848) or a heat-crosslinkable emulsion. In particular, the above-mentioned (a) 35 to 75% by weight of an acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms, Methacrylic acid alkyl ester having 1 to 4 alkyl groups 10 to 50% by weight (c) styrene and / or acrylonitrile 0 to 15%
% (However, the sum of the components (b) and (c) is 15 to 55% by weight.
(D) From an α, β-unsaturated acid or an acid anhydride thereof, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate or a methacrylate equivalent thereof, acrylamide, methacrylamide, methanol acrylamide, or methacryl methacrylamide An emulsion of a copolymer obtained by emulsion polymerization of a monomer mixture comprising 0 to 5% by weight of the selected vinyl monomer and (e) 0 to 30% by weight of another vinyl monomer. The copolymer has a glass transition point of 20 ° C. or lower, or in this copolymer, as component (e), diacetone acrylamide, acrolein, formyl styrene,
Aldo group (-CHO) such as vinyl methyl ketone, vinyl ethyl ketone, acryloxyalkyl (alkyl group has 1 to 3 carbon atoms) propanal, diacetone acrylate, etc.
Alternatively, an emulsion (A) of an acrylic copolymer having a CO group obtained by using 0.1 to 20% by weight of a vinyl monomer having a carbonyl group (C = O) is added to adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid. dihydrazide, cold crosslinking type aqueous emulsion obtained by blending hydrazine derivative (B) in which the -NH · NH ₂ group, such as hydrazine polymer having -NH · NH ₂ 2 or more having two or more are preferred.

As the acrylic acid alkyl ester of the component (a),
2-ethylhexane acrylate (-85 ° C), n-butyl acrylate (-54 ° C), ethyl acrylate (-22 ° C),
Isopropyl acrylate (-5 ° C), methyl acrylate (8 ° C) and the like. The temperatures in parentheses indicate the Tg of the alkyl acrylate homopolymer.

The component (a) imparts flexibility to a film formed from an emulsion copolymer obtained from a soft monomer. The flexibility of this film causes the expansion and contraction due to the difference in the coefficient of thermal expansion between the resins to follow the film.

Component (b) alkyl methacrylate and component (c) styrene (100 ° C.), acrylonitrile (1
(00 ° C.) is called a hard monomer and gives the film toughness and heat resistance. This hard monomer should account for 15-55% by weight of the monomer mixture giving the copolymer. As the component (b), methyl methacrylate (10
5 ° C), ethyl methacrylate (65 ° C), n-methacrylic acid
・ Butyl (20 ° C) etc. can be used. This component (b) must be contained in an amount of 10% by weight or more from the viewpoint of adhesiveness.

The upper limit of the alkyl methacrylate in the monomer mixture of the component (b) is 55% by weight. If it exceeds this, the hardness of the film becomes high and the film becomes brittle, and the film is easily peeled off by a thermal shock, or a pinhole is formed in the film.

The proportion of the component (c) in the monomer mixture of styrene and acrylonitrile is 15% by weight or less. If it exceeds 15% by weight, the adhesion of the film to the adherend will decrease. Further, in the case of acrylonitrile, when the amount used is large, emulsion polymerization is difficult to be performed.

The vinyl monomer having an acid or a hydroxyl group or an amino group as the component (d) improves the adhesion of the film to an adherend (injection resin, insert part). Such acids include:
Acrylic acid, methacrylic acid, itaconic acid, maleic acid,
An α, β-unsaturated acid such as maleic anhydride or an acid anhydride thereof can be used. The vinyl monomer having a functional group such as an acid, hydroxyalkyl acrylate, acrylamide, or methylol acrylamide is used in an amount of 5% by weight or less, preferably 0.3 to 3% by weight of the monomer mixture.

The component (e) is used as necessary to adjust the balance between the elasticity and toughness of the film and the glass transition point of the emulsion copolymer to 20 ° C. or lower, or to impart room temperature crosslinking to the emulsion.

Examples of such a monomer include butanediol diacrylate, butanediol monoacrylate, vinyl chloride, vinyl acetate (30 ° C.), glycidyl methacrylate, diacetone acrylamide, acrolein, and the like. The monomer of component (e) is used in a proportion of 30% by weight or less of the copolymer component.

The copolymer emulsion for forming the adhesive layer can be obtained according to a conventional method. That is, the emulsion polymerization may be performed using a monomer, a surfactant, a polymerization initiator and water. In this case, the monomer concentration is 40 to 60% by weight based on the total amount, and the surfactant is a monomer. Preferred amounts are 1 to 5 parts by weight and 0.1 to 0.6 parts by weight of the polymerization initiator based on 100 parts by weight. The surfactant should be selected so that emulsion polymerization can be carried out smoothly, and in particular, a polyoxyethylene alkyl ether or a polyoxyethylene alkyl phenol ether having an addition mole number of oxyethylene group in the range of 10 to 60 and a higher alcohol sulfate ester A mixed system of a salt or a polyoxyethylene alkyl sulfate salt or a polyoxyethylene alkyl phenyl sulfate salt is preferable. As the polymerization initiator, potassium persulfate, ammonium persulfate and a redox system obtained by combining these with a reducing agent are particularly preferable. In addition, it is preferable to adjust the pH value of the produced copolymer emulsion, such as ammonia water, to 7 or more from the viewpoint of improving the dispersion stability.

The glass transition point (Tg) of the copolymer in the copolymer emulsion is 20 ° C. or less. When the Tg exceeds 20 ° C., the drying time of the film becomes longer. In general, the higher the Tg of the copolymer, the higher the strength of the film, and the lower the Tg, the higher the elasticity and flexibility of the film.

(Composite laminate) 10 to 100 g / m of the above primer on the surface of the insert part
After applying in a ratio of ² and drying, install it in the cavity of the mold preheated to 40-120 ° C, then melt the thermoplastic resin (including vulcanizable rubber) or reactive thermosetting The composite laminate is obtained by injecting the resin into the cavity of the mold at an injection pressure of 500 to 1,500 kg / cm ² .

An example of a preferable injection temperature is as follows. Polyamide (250-290 ° C), polyacetal (190-220 ° C),
Polybutylene terephthalate (250-270 ° C), polycarbonate (260-300 ° C), polyethylene terephthalate (250-270 ° C), polypropylene (180-230 ° C), and polyvinyl chloride (180-230 ° C). The injection pressure of the reaction type thermosetting resin is 500 to 1,500 kg / cm ² , and the temperature is room temperature to 130 ° C.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

Production Example of Aqueous Acrylic Copolymer Resin Emulsion Example 1 The following materials were charged into a reaction vessel equipped with a temperature controller, an irrigating stirrer, a reflux condenser, a supply vessel, a thermometer, and a nitrogen inlet tube. .

Water 200 parts 35% aqueous solution of sodium salt of sulfuric acid half ester of p-nonylphenol (anionic emulsifier) reacted with 20 moles of ethylene oxide 5 parts 20% of p-nonylphenol (nonionic emulsifier) reacted with 25 moles of ethylene oxide 20 parts of the solution Then, after the inside of the reaction vessel was replaced with nitrogen gas, 10% of the following feed I was added, and the mixture was heated to 90 ° C.

Feed I Water 200 parts 35% aqueous solution of the anionic emulsifier 25 parts Methyl methacrylate 160 parts (40 wt%) n-butyl acrylate 204 parts (51 wt%) Acrylic acid 20 parts (5 wt%) Acrylamide 16 parts (4 wt% Further, after charging 10% of a solution prepared by dissolving 2.5 parts of potassium persulfate in 85 parts of water (Feed II), 40% is added to all the remaining Feed I and Feed II for 3.5 hours. After the completion of the supply, the feed I was polymerized at the same temperature for 2 hours to polymerize the anionic resin aqueous emulsion (Tg3
° C).

Examples 2 to 7 Copolymer aqueous emulsions were obtained in the same manner as in Production Example 1 except that the types and amounts of vinyl monomers to be subjected to emulsion polymerization were changed as shown in Table 1.

Example 8 (Normal-temperature-crosslinkable aqueous emulsion) 0.8 part by weight of adipic dihydrazide was added to 100 parts by weight of an aqueous emulsion of a carbonyl group-containing acrylic copolymer obtained by emulsion polymerization of a vinyl monomer shown in Table 1. A cold crosslinking aqueous emulsion was obtained.

Example 1 The emulsion obtained in Production Example 1 was applied to the side wall of FIG. 1 and FIG.
The solid component is applied to the peripheral surface of the side wall of the coil bobbin resin molded product (4) of an electromagnetic valve having four V-grooves having a width of 4 m so that the solid amount becomes 30 g / m ² , dried for 2 hours, and then injected. Mold (70
1), and then nylon 6 was injection-molded at 280 ° C. and a pressure of 500 kg / cm ² to obtain a composite laminate shown in FIG.

The dimensions of the composite laminate are an outer diameter of 25 mm, a height of 35 mm, a thickness of nylon 6 of 1 mm, and a cylindrical shape.

(A) Injection nylon 9 at 20 ° C of this composite laminate
And the airtightness of the inserted nylon 66, as shown in FIG. 3, the composite laminate is fastened with a stopper (15a) and a packing (14a).
Prevent water intrusion from the outside using a water tank (16) filled with water (17), pressurize air from above and check for bubbles in the primer layer (8) of the composite laminate As a result of the test, the test piece withstood a pressurized air pressure of 7 kg / cm ² .

Further, the airtightness of the composite laminate after dipping in (b) a motor oil bath at 100 ° C. for one day withstood an air pressure of 6 kg / cm ² .

Further, (c) the composite laminate was heated in a motor oil bath at 20 ° C. for 2 hours, then the motor oil bath was heated to 80 ° C. over 15 minutes, and immersed at the same temperature for 2 hours, and further over 30 minutes. To cool the motor oil bath to 20 ° C and again at 20 ° C for 2 hours.
After repeating the process of immersion for 5 hours, then heating to 80 ° C. and continuing immersion at the same temperature for 2 hours five times (thermal shock test), the airtightness of the composite laminate endured air pressure of 6 kg / cm ² .

Comparative Example 1 A composite laminate was obtained in the same manner as in Example 1 except that the primer was not applied. The anti-pressurized air pressure is shown below.

(A) 1 kg / cm ² or less (b) 1 kg / cm ² or less (c) 1 kg / cm ² or less Example 2 Other than changing the material resin and the injected resin of the coil bobbin 4 shown in FIG. Was obtained in the same manner as in Example 1.

 Table 2 shows the hermetic pressure of this product.

Examples 3 to 10 As insert parts, the material shown in FIG. 5 is a galvanized product, a stainless steel product or a brass product, having a large number of irregularities on the surface and side walls, a thickness of 1 mm, a body diameter of 60 mmφ,
A 30 mmφ bottom circular hole was used, and the acrylic aqueous emulsion obtained in Examples 1 to 9 or the following adhesive was used as a primer and applied so as to be 30 g / m ² (solid content). After air-drying for a time, this was magnetically held in an injection mold, and then nylon 6 was heated at 280 ° C. and 500 kg / cm ^2.
Injection molding was performed under pressure to obtain a composite laminate (the thickness of nylon 6 was 3 mm).

Comparative Example 2 Polyester resin emulsion manufactured by T Company (Tg-20 ° C)
(PS) Comparative Example 3 NBR SBR latex (Tg 6 ° C) Comparative Example 4 N NBR acrylonitrile butadiene latex (Tg -25 ° C) (ABR) Comparative Example 5 Y Y two component epoxy resin adhesive (EX Comparative Example 6 Phenolic Resin Adhesive (PH) manufactured by S Company The following airtight retention tests (a), (b) and (c) were performed on the obtained composite laminate.

(A) Airtight holding pressure at 20 ° C (kg / cm ² ) (b) Airtight holding pressure after immersing in a 100 ° C motor oil bath for one day (kg / cm ² ) (c) In a motor oil bath at 20 ° C 2 hours and then heat the motor oil bath to 80 ° C over 15 minutes,
Continue immersion for another hour, then take a motor oil bath for 30 minutes.
Cool to 20 ° C, immerse again at 20 ° C for 2 hours, then 80 ° C
Heating and continuing immersion at the same temperature for 2 hours.
Table 3 shows the results of the hermetic pressure (kg / cm ² ) after the repetition.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an injection molding apparatus, and FIG. 2 is a sectional view of a composite laminate. FIG. 3 is a partial sectional view of the apparatus used for the airtightness test, FIGS. 4 and 5 are perspective views of the insert part, and FIG. 6 is a sectional view of another composite laminate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeo Tsukamoto 1000 Kawajiri-cho, Yokkaichi, Mie Pref.

Claims (5)

(57) [Claims] 1. A primer comprising an aqueous acrylic copolymer resin emulsion having a glass transition point (Tg) of 20 ° C. or less is applied to the surface of an insert part having a groove for fitting provided on a side wall surface, and dried. A bonding method comprising: inserting a molded product into a cavity of an injection mold; and then injecting a resin into the cavity to integrate the insert component and the injected resin molded product via the primer. 2. The insert component is made of metal or 150
2. The bonding method according to claim 1, wherein the bonding method is a molded product of a resin or a vulcanized rubber that is resistant to deformation at an injection resin temperature of not less than ° C. 3. A primer comprising: (a) 35 to 75% by weight of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms; and (b) 10 to 50% by weight of an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms. % By weight (c) styrene and / or acrylonitrile 0 to 15% by weight (however, the sum of the components (b) and (c) is 15 to 55% by weight)
(D) From α, β-unsaturated acids or acid anhydrides thereof, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate or their methacrylate equivalents, acrylamide, methylolacrylamide or their methacrylamide equivalents Selected inyl monomers 0-5
An aqueous acrylic copolymer resin emulsion obtained by emulsion-polymerizing a monomer mixture consisting of 0% to 30% by weight of (e) another vinyl monomer and (e) another vinyl monomer. 2. The bonding method according to claim 1. 4. The resin to be injected is a resin selected from polyamide, polyacetal, polybutylene terephthalate, polyethylene terephthalate, polyolefin, polycarbonate, epoxy resin, novolak resin, modified polyphenylene oxide, thermoplastic polyurethane, and vulcanizable rubber. The bonding method according to claim 1, wherein the bonding method is provided. 5. A primer comprising an aqueous acrylic copolymer resin emulsion having a glass transition point (Tg) of 20 ° C. or less applied to the surface of an insert part having a large number of projections on a side wall surface, and dried. Is inserted into a cavity of an injection mold, and then a resin is injected into the cavity to integrate the insert component and the injected resin molded product via the primer.