KR100776312B1 - Primer composition for metal-plastic adhesion - Google Patents

Abstract

The present invention is a primer composition which is applied to the metal surface in the in-mold bonding method for bonding the metal and plastic by injecting a plastic with a melt injection temperature of 250 ~ 350 ℃ to the metal surface at 250 ~ 350 ℃, 20 ~ 30wt %, Thermoplastic resin 20-30 wt%, solvent 40-60 wt%, based on 95-97 wt% of a main ingredient, a metal-plastic adhesive primer composition prepared by adding 3-5 wt% of diphenylmethane diisocyanate as a curing agent. .

The composition of the present invention has an effect of obtaining a molded article having excellent adhesion between the metal and the plastic by applying to the metal surface when the metal-plastic is bonded in an in-mold manner.

Primer Composition, Metal-Plastic Bonding, In Mold Bonding, Thermosetting Resin, Thermoplastic Resin

Description

Primer composition for metal-plastic bonding

1 is a cross-sectional view of a plastic injection mold in a process of bonding a metal plate and a plastic in a conventional in-mold method.

-Explanation of symbols for important parts of drawings-

1: metal plate 4: plastic injection hole

2: adhesive film 5: mold

3: space to be filled with plastic

The present invention relates to a primer composition for metal-plastic adhesion.

Specifically, the present invention relates to a primer composition for metal-plastic adhesion, which is applied to a metal surface in order to facilitate the adhesion of metal and plastic when the metal and plastic are adhered by an inmold adhesion method.

The housing of small electronic products such as mobile phones, earphones, or MP3s is a box-shaped material formed by bonding metal and plastic together to form a unit. It is used.

The reason why the housing of small electronic products is composed of metal-plastic adhesive is to keep the strength while maintaining the strength while maintaining the strength. Metal-plastic composites are widely used in this field because there is a limit to the appearance of a soft and beautiful appearance, and it is difficult to obtain a product that can maintain a high strength with thin thickness only by plastic alone.

In the case of a mobile phone housing, a material composed by bonding a plastic having a thickness of 0.1 to 1.5 mm to a metal plate having a thickness of 0.1 to 0.4 mm is used.

In the conventional mobile phone housing, as shown in FIG. 1, the adhesive film 2 formed in the film form having a thickness of 0.05 to 0.1 mm is bonded to the metal plate 1 having a thickness of 0.1 to 0.4 mm, and then placed in the mold 5. Plastic is injected into the plastic inlet (4) so that the thickness of the plastic on the adhesive film surface 0.1 ~ 1.5mm to produce a housing in which metal and plastic are bonded.

The metal used here is mainly iron or copper or iron or copper plated with chromium, nickel, gold or silver.As plastics, heat resistance and mechanical properties such as polycarbonate resin, polyphthalamide resin, and polyphthalimide resin are used. Expensive resins with high strength are mainly used and the injection temperature of these resins is 200 ° C or higher.

The reason for using the adhesive film here is to improve the adhesion between the plastic and the metal to be injected.

As a raw material of the adhesive film, various kinds of synthetic resins having viscoelasticity at room temperature may be used.

However, a thin adhesive film having a thickness of 0.05 to 0.1 mm has a problem in that it is difficult to maintain heat resistance at an injection temperature of a high heat resistant plastic such as polycarbonate having an injection temperature of about 310 ° C.

As described above, the method of bonding the metal and the plastic in the mold is called in-mold bonding in this field.

When manufacturing a housing of a small electronic product by the conventional in-mold adhesive method, the adhesive film cut in the same shape as the shape of the metal plate is bonded to the metal plate, put it in a mold, and inject the molten plastic therein to bond the metal plate and the plastic. A housing is made of a metal-plastic composite.

Since the injection temperature of polycarbonate resin or polyphthalimide resin is 250 ~ 350 ℃ and the melting temperature of adhesive is 200 ℃ or less, the adhesive is partially burned and tends to be carbonized or dripping, resulting in poor adhesion between metal and plastic. In many cases, the metal plate is not flat but has a curved surface, so that the adhesive on the film is brought into close contact with the metal plate, which requires a lot of manual labor for the worker, thereby reducing productivity.

An object of the present invention is to provide a primer composition for metal-plastic adhesion.

The present inventors applied a primer composition formed by mixing a thermoplastic resin and a thermosetting resin in a predetermined ratio instead of a conventional film adhesive when the metal and plastic are to be bonded by an in-mold adhesive method on a metal surface and then applying the metal and plastic. When gluing, it was confirmed that the metal and plastic can be firmly bonded in a simple process without using a film adhesive, and completed the present invention.

The present invention relates to a primer composition for metal-plastic adhesion.

Specifically, the present invention relates to a primer composition applied to a metal surface in order to facilitate adhesion between a metal and a plastic in bonding a molten synthetic resin to a metal surface by an in-mold adhesive method.

In order to make the different kinds of objects adhere to each other easily when painting or painting by applying paint to a certain object, apply a small amount of adhesion initiator to the object and then use paint or adhesive. In this case, the adhesion initiator used in a small amount is called a pretreatment agent or a primer in this field.

The present invention will be described in detail with reference to the following Examples.

Example

<Production Example of Primer Composition>

Example 1

The primer composition of this invention is a two-component primer comprised from a main material and a hardening | curing agent.

residence

① Epoxy resin (equivalent to 850) 300g (19wt%)

② Methyl Cellulose 200g (12.5wt%)

③ Polyvinylacetate 200g (12.5wt%)

④ Methyl ethyl ketone 400g (25wt%)

⑤ 400g (25wt%) toluene

⑥ Melamine resin 100g (6wt%)

  (Aekyung Chemical Product Name L-117-60)

Put ④⑤ into the reactor of the above ingredients and slowly add ②③ while stirring and maintain the reactor temperature up to 60 ℃ for 3 hours, and then check whether the contents are completely dissolved. After cooling, ⑥ was added, stirred for 15 minutes, and filtered through 300-neck mesh to obtain 1600g of a weak yellow viscous transparent liquid.

The primer composition of the present invention is a two-component primer used by adding a curing agent in use.

As a hardening | curing agent used for the main material obtained above, diphenylmethane diisocyanate (Diphenylmethane-4,4'-diisocyanate: Aekyung Chemical, brand name AK-75) which is an isocyanate type compound is used.

The use ratio of the main material and the curing agent is suitable for the main material of 95 ~ 97wt% and 3 ~ 5wt% of the curing agent.

In the present invention, the primer composition is formed by adding 3 to 5 wt% of the curing agent to 95 to 97 wt% of the main ingredient, which is composed of 20 to 30 wt% of the thermosetting resin, 20 to 30 wt% of the thermoplastic resin, and 40 to 60 wt% of the solvent. have.

In general, thermoplastic resins have a low heat resistance and excellent adhesion to plastics but poor adhesion to metals.

In addition, the thermosetting resin has a high heat resistance temperature and excellent adhesion to the thermosetting resin or metal, but has a poor adhesive strength with the thermoplastic resin.

The present inventors can improve the adhesion between metal and plastic while maintaining a higher heat resistance than using a thermoplastic resin by using a primer formed by mixing a thermosetting resin or a thermoplastic resin at a predetermined ratio in bonding the metal and the plastic. The present invention was completed with the idea that it would be possible.

However, as the thermosetting resin is used, the use of a certain amount of curing agent is inevitable, and it is composed of a two-component primer that must be used by adding a curing agent to the main material when used.

In Example 1, the epoxy resin and the melamine resin are thermosetting resins, the methyl cellulose and polyvinylacetate resins are thermoplastic resins, and methyl ethyl ketone and toluene are used as solvents.

In particular, epoxy resins and urethane resins not only have excellent adhesion to metals but also have excellent heat resistance, thereby enhancing primer heat resistance. Cellulose resins and polyester resins exhibit excellent adhesion to plastics.

Example 2

residence

① Epoxy resin (equivalent to 850) 300g (19wt%)

② Thermosetting urethane resin 100g (6wt%)

③ Nitrocellulose (1/2 second) 100g (6wt%)

④ 300g (19wt%) polyester resin

⑤ Methyl ethyl ketone 400g (25wt%)

⑥ Toluene 400g (25wt%)

Of the above components, ⑤⑥ was added to the reactor while stirring, ③④ was slowly added, and the temperature inside the reactor was raised to 60 ℃ to maintain 3 hours, and then the contents were completely dissolved. The resultant was filtered through a 300-neck mesh to obtain 1600 g of a weak yellow viscous transparent liquid. 3.85 wt% of diphenylmethane diisocyanate (Aekyung Chemical, AK-75) was added as a curing agent to obtain a primer composition of the present invention.

Comparative Example 1

A thermoplastic acrylic resin primer prepared from an acrylic resin used as an adhesive film for in-mold adhesion was used.

Acrylic resin 300g (23wt%)

Methyl ethyl ketone 500g (38.5wt%)

Toluene 500g (38.5wt%)

The component was added to the reactor, the internal temperature was raised to 60 ° C. and maintained for 3 hours to completely dissolve the acrylic resin in a solvent to obtain an acrylic resin primer.

Comparative Example 2

A thermosetting epoxy resin primer was prepared.

Epoxy Resin 500g (33.3wt%)

Methyl ethyl ketone 500g (33.3wt%)

Toluene 500g (33.3wt%)

The component was added to a reactor, the internal temperature was raised to 60 ° C., and maintained for 3 hours. The epoxy resin was completely dissolved in a solvent to obtain an epoxy resin primer.

<Adhesion test>

Adhesion Test 1

The primer compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were dried on a metal (copper chromium plating) to be inserted into the mold by spraying, and then coated in a mold so that the coating thickness was 5 μm. Injected at an injection temperature of 250 ~ 350 ℃ it was shown in Table 1 the experiment.

TABLE 1

Flow during injection Impact after injection (1m drop in height) Impact after painting the thermosetting paint 5% aqueous hydrochloric acid solution after 24 hours 5% caustic soda solution after 24 hours deposition Untreated metal  ○  ×  ×  ×  × Example 1 ○ ○ ○ ○ ○ Example 2 ○ ○ ○ ○ ○ Comparative Example 1 × △ × × △ Comparative Example 2 ○ × × ○ ○

No change = ○, slight change = △, not available due to severe deformation = ×

Untreated metal: When metal without primer is used.

No change in [Table 1] means a complete adhesion state and a slight change represents the usable adhesion state, a severe deformation represents the unusable adhesion state.

Adhesion Test 2

In the same manner as in the adhesion test 1 except that the polycarbonate resin was changed to polyphthalamide resin and injected at an injection temperature of 250 ~ 350 ℃ is shown in Table 2.

 TABLE 2

Flow during injection Impact after injection (1m drop in height) Impact after painting the thermosetting paint 5% aqueous hydrochloric acid solution after 24 hours 5% caustic soda solution after 24 hours deposition Untreated metal  ○  ×  ×  ×  × Example 1 ○ ○ ○ ○ ○ Example 2 ○ ○ ○ ○ ○ Comparative Example 1 × △ × × △ Comparative Example 2 ○ × × ○ ○

No change = ○, slight change = △, not available due to severe deformation = ×

Observing the Table 1 and Table 2, the product which is made of the non-primed metal in the mold and extruded with polycarbonate resin or polyphthalamide resin is not used because of poor adhesion with the metal, Acrylic resin primers had poor flowability during injection, lost or flowed during the heat treatment process, and thermosetting epoxy primers were easily peeled off in the impact test.

However, in the results of Table 1 and Table 2, when the metal material coated with the composition of Example 1 and the composition of Example 2 is inserted into a mold and the plastic water such as polycarbonate or polyphthalamide is extruded, it does not flow down during molding. After molding, the impact resistance was strong, and after coating the thermosetting paint and applying heat for 30 minutes to 1 hour at 100 ° C. to 140 ° C., it was proved that a composition resistant to impact and excellent in chemical resistance was obtained.

As the resin which can be used in the present invention, thermosetting epoxy resins, urethane resins and thermoplastic resins such as butyl cellulose, nitrocellulose, carboxymethyl cellulose, hydroxy ethyl cellulose, hydroxy methyl cellulose and cellulose acetate butyrate can be used. As the polyvinyl hardener, isocyanate-based and amine compounds mixed with the main material immediately before use can be used.

Toluene, methyl ethyl ketone, butyl cellus solvate, ethyl acetate, butyl acetate, isopropyl alcohol, etc. are used as a solvent used for viscosity adjustment.

The preferred composition ratio is 20 to 30% by weight of epoxy resin and thermosetting urethane resin, 20 to 30% by weight of thermoplastic resin, vinyl resin and cellulose resin, 20 to 30% by weight of polyester resin, and methyl ethyl ketone and toluene as a thermosetting resin. 95 ~ 97wt% of the main material obtained by mixing in% ratio is suitable to configure in the range of 3 ~ 5wt% curing agent.

The composition of the present invention has an effect of obtaining a molded article having excellent adhesion between the metal and plastic when applied to the metal surface when the metal-plastic is bonded in an in-mold manner.

Claims (2)

In the in-mold bonding method in which a plastic having a melt injection temperature of 250 to 350 ° C. is injected to a metal surface at 250 to 350 ° C. to bond a metal to a plastic, the primer composition is applied to the metal surface, and the thermosetting resin is 20 to 30 wt%, thermoplastic. A primer composition for metal-plastic adhesion, which is prepared by adding 3 to 5 wt% of diphenylmethane diisocyanate as a curing agent to 95 to 97 wt% of a main ingredient composed of 20 to 30 wt% of a resin and 40 to 60 wt% of a solvent. The method of claim 1, Plastics with a melt injection temperature of 250 to 350 ° C are polycarbonate, polyphthalamide or polyphthalimide resins, and metals are metals in which chromium, nickel, gold and silver are plated with iron or copper or copper, and thermosetting resins are epoxy A resin composition, a melamine resin or a thermosetting urethane resin, wherein the thermoplastic resin is methyl cellulose, polyvinylacetate, nitrocellulose, the solvent is methyl ethyl ketone or toluene, and the curing agent is diphenylmethane diisocyanate.

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