KR101191974B1 - Method of improving adhesion strengths between metal and polymer substrate - Google Patents

Abstract

The present invention relates to a method for improving adhesion between metals and resins, and more particularly, to expose a hydroxy group on a metal surface, and attach a vinyl group to a surface by sol-gel reaction with vinyltrimethoxysilane, followed by metal and primer, It relates to a method of improving the adhesion between the metal and the resin by forming a chemical bond between the primer and the polymer resin by UV curing. According to the method for improving adhesion between metals and resins according to the present invention, since the adhesion between metals and plastics that are not compatible is greatly increased, the present invention can be usefully applied to various incompatible metal-resin coating layers.

Description

Method of improving adhesion strengths between metal and polymer substrate}

The present invention relates to a method for improving adhesion between metal and resin by forming a chemical bond between metal and primer, primer and polymer resin to improve adhesion between metal and polymer resin in metal layer-primer layer-polymer resin type coating film. will be.

Metallized painting, which embodies the metallic feel of plastic parts, has a number of advantages such as smooth texture, excellent appearance and increased durability. Accordingly, the demand for plasticized metallized painting on interior and exterior materials for creating a luxurious atmosphere is increasing. In particular, research on metallized painting related to interior and exterior materials for automobiles is being developed.

In general, the metal and the polymer resin have little compatibility because there is no compatibility. Therefore, metallizing painting is performed by forming a primer layer having compatibility with both components on the polymer resin supporter, forming a metal layer on the primer layer, and then forming a top coat layer with a transparent paint or the like on the metal layer for durability of the coating film. Doing. That is, it has a structure of a "top layer-metal layer-primer layer-polymer resin support body." Therefore, primers that are compatible with both metal and polymer resins are essential factors in determining the performance of coating films, and molecular design and synthesis of these primers are very important.

Conventionally, the primer layer was formed using the thermosetting paint containing acrylic polyol, a urethane resin, a hardening | curing agent, a solvent, an additive, etc. However, when the thermosetting paint is used, the shape and physical properties of the polymer resin, which are weak in heat resistance, may change during the heating and curing process.As a crack occurs in the primer layer, the adhesion between the metal and the polymer resin is decreased, and the thermosetting paint is heat resistant. There was a problem of being vulnerable. Accordingly, in Korean Patent Laid-Open Publication No. 10-2010-0055172, the primer layer was formed by using a UV-curable paint, but there was a limit in adhesion between the metal and the polymer resin because it did not form a chemical bond between the primer layer and the metal layer.

Accordingly, the present inventors have tried to solve the above problems, chemically attach the vinyl group on the surface of the metal plate, and then apply a primer composition compatible with the metal and the polymer resin, and then apply the polymer resin to the primer composition coating layer The present invention was completed by knowing that the adhesion between the metal and the polymer resin can be greatly improved by attaching and UV curing the primer composition. That is, an object of the present invention is to provide a method for improving the bonding force between a metal and a polymer resin having no compatibility.

The present invention

Impregnating the metal plate with a phosphoric acid solution to expose a hydroxyl group on the surface;

Sol-gel reacting the hydroxy group-exposed metal plate with vinyltrimethoxysilane to attach a vinyl group to the metal plate surface;

Reacting a polyol, a diol having a carboxyl group, and a diisocyanate to prepare an isocyanate terminated prepolymer;

Reacting the isocyanate terminated prepolymer with 2-hydroxyethylacrylate to prepare a vinyl terminated prepolymer;

Dispersing the vinyl terminal prepolymer to prepare an aqueous polyurethane primer, and then mixing the photoinitiator to prepare a primer composition; And

Applying the primer composition to a metal plate having a vinyl group attached to the surface, and then attaching the polymer resin to the coating layer, and then UV curing the primer composition;

Characterized in that the metal-resin adhesion improving method comprising a.

According to the method of improving adhesion between metals and resins according to the present invention, since a chemical bond is formed between a metal surface and a primer, a primer, and a polymer resin, adhesion between metals and plastics having incompatibility is greatly increased, and various incompatible metal-resins It can be usefully applied to the coating layer manufacturing field.

Figure 1 shows the synthesis of the aqueous polyurethane primer.
Figure 2 shows the data confirmed by the XPS measurement of the vinyl group on the surface after the sol-gel reaction of the aluminum plate.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a method of modifying a metal plate surface to attach a vinyl group, and then forming a chemical bond with an aqueous polyurethane primer to improve the bonding strength between the metal and the polymer resin having no compatibility.

In the step of exposing the metal plate to the phosphoric acid solution to expose the hydroxy group on the surface, the metal may be a metal of high oxidizing properties such as aluminum, zinc, iron or alloys thereof, preferably aluminum. In addition, the phosphoric acid solution is a mixture of phosphoric acid, 1-propanol, 1-butanol and water. The impregnation lasts until the contact angle does not change by measuring the contact angle between the metal surface and water, and the optimum impregnation time is about 180 seconds.

In the step of attaching the vinyl group to the surface of the metal plate by performing a sol-gel reaction between the metal plate exposed to the hydroxyl group and the vinyltrimethoxysilane, the metal plate is impregnated with the vinyltrimethoxysilane solution. The vinyl trimethoxysilane solution is a mixture of vinyltrimethoxysilane, water, ethanol and hydrochloric acid, and the mixing ratio is preferably 1: 0.8 to 1: 2.3 to 2.5: 0.3 to 0.5. When the content of water and hydrochloric acid is out of the above range, there may be a problem that the reaction does not occur because it is out of the pH range where the sol-gel reaction may occur, and when the content of ethanol is out of the above range, vinyltrimethoxy as a solvent There may be a problem of not sufficiently dissolving the silanes. The sol-gel reaction usually takes place in a two-step reaction, the first being a hydrolysis reaction in which an alkoxy group is substituted with a hydroxy group, and the second is a condensation reaction between the hydroxy groups. Generally, the sol-gel reaction is performed using an acid catalyst or a base catalyst. In order for the sol-gel reaction to occur, the pH corresponding to each catalyst and the reaction temperature must be appropriately adjusted. In the present invention, since hydrochloric acid as an acid catalyst is used, the pH was adjusted to 2.

On the other hand, the process of preparing the primer composition is as follows.

First, an isocyanate terminated prepolymer is prepared by reacting a polyol, a diol having a carboxyl group, and a diisocyanate. When these three materials are reacted at once, non-polar polyols and diisocyanates react first to form urethane groups. Accordingly, when polarized, the diols having carboxyl groups react. In general, when the anion center is located at the center of the aqueous polyurethane, the dispersion particle size is larger and the storage stability is lowered after water dispersion than the position at the chain end. However, in the present invention, the location of the anion center is not the hard segment center. Does not significantly affect

The polyol is generally used in the art and is not particularly limited. Specifically, it is preferable to use a low molecular weight diol system having a molecular weight of 1000 or less, preferably 400 to 800. When the molecular weight exceeds 1000, it is preferable to maintain the above range because the polyol may form crystals, thereby limiting the movement of the molecular chain and causing a decrease in adhesion. Such polyol may specifically use polytetramethylene glycol, polycaprolactone diol, polypropylene glycol, or mixtures thereof.

The diisocyanate is generally used in the art, and is not particularly limited. Specifically, 1,6-hexamethylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate, isophorone diisocyanate or a mixture thereof may be used. It is more preferable to use isophorone diisocyanate which has an asymmetric structure and is difficult to form crystals.

The diol having the carboxyl group is generally used in the art, but is not particularly limited, and specifically, dimethylolpropionic acid, dimethylolbutanoic acid or a mixture thereof may be used. In general, it is preferable to use dimethylolbutanoic acid, which has a low melting point and high reactivity so that the reaction can be performed at a low temperature, so that the side reactions of the carboxyl group are less likely to be reduced. It is also more structurally stable. The amount of diol having a carboxyl group is preferably 4 to 9 parts by weight based on 100 parts by weight of the polyol, but if the amount is too small, there may be a problem that the dispersion is not properly due to a small ion center. There may be a problem that does not dry properly.

In preparing the isocyanate terminated prepolymer, dibutyltin dilaurate is used as a reaction catalyst, and the amount of the isocyanate terminated prepolymer is preferably used in the range of 0.1 to 0.3 parts by weight based on 100 parts by weight of the polyol. If the amount is less than 0.1 part by weight, the reaction rate is too slow. If the amount is more than 0.3 part by weight, the reaction rate is too fast, causing problems in viscosity control during polymerization.

Next, the isocyanate terminated prepolymer is reacted with 2-hydroxyethyl acrylate to prepare a vinyl terminated prepolymer. The isocyanate terminated prepolymer and 2-hydroxyethylacrylate react in a molar ratio of 1: 2 to produce a vinyl terminated prepolymer.

The prepared vinyl terminal prepolymer is water-dispersed to prepare an aqueous polyurethane primer, and then a photoinitiator is mixed with the aqueous polyurethane primer to obtain a primer composition. The water used for water dispersion is used in the range of 150 to 300 parts by weight based on 100 parts by weight of the vinyl terminal prepolymer, and when the amount is less than 150 parts by weight, it may not be possible to obtain stable particles after the dispersion, and the amount used is 300 parts by weight. When the amount is exceeded, it is preferable to maintain the above range because there is little solid content, the film thickness decreases after drying, and the drying time may be long. The aqueous polyurethane primer prepared by the above method has an content of 3% by weight of anion center, 30% by weight of solid content, which shows the same stability as the conventional aqueous polyurethane. In addition, the photoinitiator is generally used in the art, but is not particularly limited. Specifically, since the solvent is water, it is preferable to use 2-hydroxy-2-methyl-1-phenyl-1-propanone. The addition amount is preferably 3 to 6 parts by weight based on 100 parts by weight of the vinyl terminal prepolymer. If the amount is less than 3 parts by weight, the photoinitiator is vaporized in the film drying step, which is the primer composition coating layer before UV curing, there may be a problem that a sufficient amount does not exist and the initiation reaction does not occur completely. There may be a problem that the remaining amount is present inside to act as an impurity to lower the film properties.

Thereafter, the primer composition is applied to the metal plate attached to the vinyl group on the surface, the polymer resin is attached to the coating layer, and then the UV curing of the primer composition is performed. The polymer resin may be a polycarbonate, polyester or a mixture thereof in which the main chain capable of chemical bonding with the vinyl terminal prepolymer contained in the primer composition is composed of a carbonate bond, an ester bond. Through UV curing, the double bond of the vinyl group on the surface of the metal plate and the vinyl group derived from the vinyl terminal prepolymer contained in the primer composition is broken to form a carbon bond between the metal surface and the primer, and also the vinyl group derived from the vinyl terminal prepolymer. As the double bonds and the multiple bonds contained in the polymer resin are broken, a carbon bond is formed between the primer and the polymer resin to enhance the metal-resin adhesion.

According to the method of improving adhesion between metals and resins according to the present invention, a chemical bond is formed between a metal surface and a primer, a primer, and a polymer resin, thereby greatly increasing adhesion between metal and plastic having no compatibility.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

[Example]

Production Example 1

Inject a nitrogen into a 500 mL round four-necked flask equipped with a thermometer and a stirrer, inject polycaprolactonediol, isophorone diisocyanate and dimethylolbutanoic acid in a weight ratio of 100: 42.7: 4.93 and stir at 80 ° C for about 30 minutes. After dibutyltin dilaurate was injected 0.25 parts by weight based on 100 parts by weight of polycaprolactone diol and reacted for about 6 hours to prepare an isocyanate terminated prepolymer. Thereafter, after the temperature was lowered to 50 ° C., 7.63 parts by weight of 2-hydroxyethyl acrylate was added to 100 parts by weight of polycaprolactone diol, and reacted for about 24 hours to prepare a vinyl terminal prepolymer having a molecular weight of 5,000 g / mol. After the temperature was lowered to 30 ° C, 2.05 parts by weight of triethylamine, a tertiary amine, was added to 100 parts by weight of the vinyl terminal prepolymer, neutralized by stirring at 500 rpm for 3 hours, and water-dispersed by adding 233.33 parts by weight of water. Primers were prepared. Thereafter, 2-hydroxy-2-methyl-1-phenyl-1-propanone was added to the aqueous polyurethane primer at 4 parts by weight based on 100 parts by weight of the vinyl terminal prepolymer to prepare a primer composition.

Production Example 2

A primer composition was prepared in the same manner as in Preparation Example 1, using polypropylene glycol instead of polycaprolactone diol as a polyol.

Production Example 3

A primer composition was prepared in the same manner as in Preparation Example 1, using polytetramethylene glycol instead of polycaprolactone diol as a polyol.

Production Example 4

In the same manner as in Example 1, polycaprolactone diol, isophorone diisocyanate and dimethylol butanoic acid were injected at a weight ratio of 100: 42.08: 4.68 to prepare an isocyanate terminated prepolymer, and 2-hydroxyethyl acrylate was prepared in poly A vinyl terminated prepolymer having a molecular weight of 10,000 g / mol was prepared by injecting 3.62 parts by weight based on 100 parts by weight of caprolactonediol. After the dispersion in the same manner as in Preparation Example 1 to prepare a primer composition.

Production Example 5

A primer composition was prepared in the same manner as in Preparation Example 4, using polypropylene glycol instead of polycaprolactone diol as a polyol.

Production Example 6

A primer composition was prepared in the same manner as in Preparation Example 4, using polytetramethylene glycol instead of polycaprolactone diol as a polyol.

division Weight portion Preparation Example 1 Preparation Example 2 Production Example 3 Production Example 4 Production Example 5 Production Example 6 Polyol Polycaprolactone diol 100 - - 100 - - Polypropylene glycol - 100 - - 100 - Polytetramethylene glycol - - 100 - - 100 Isophorone diisocyanate 42.7 42.7 42.7 42.08 42.08 42.08 Dimethyl Butanoic Acid 4.93 4.93 4.93 4.68 4.68 4.68 Dibutyl tin dilaurate 0.25 0.25 0.25 0.25 0.25 0.25 2-hydroxyl ethyl acrylate 7.63 7.63 7.63 3.62 3.62 3.62

division Preparation Examples 1 to 6 (parts by weight) Vinyl terminated prepolymer 100 Triethylamine 2.05 water 233.33 2-hydroxy-2-methyl-1-phenyl-1-propanone 4

Preparation Example 7

After washing the surface of the aluminum plate with acetone, it was impregnated into a solution mixed with phosphoric acid, 1-propanol, 1-butanol and deionized water in a mass ratio of 1: 1.94: 1.39: 1.22 as shown in Table 3 to expose the hydroxyl group on the surface. I was. As a result of measuring the contact angle with different impregnation times, the optimum impregnation time was found to be 180 seconds.

An aluminum plate having a hydroxyl group exposed on the surface was immersed in a solution containing vinyltrimethoxysilane, distilled water, ethanol, and hydrochloric acid in a weight ratio of 1: 0.97: 2.49: 0.49, and the sol-gel reaction was performed at 60 ° C. and 2pH for about 24 hours. It was attached to the vinyl group on the surface of the aluminum plate, it was confirmed through the XPS measurement. XPS measurement results are shown in FIG.

division Production Example 7 (parts by weight) Phosphoric Acid 100 1-propanol 194 1-butanol 139 Deionized water 122

division Production Example 7 (parts by weight) Vinyltrimethoxysilane 100 Distilled water 97 ethanol 249 Hydrochloric acid 49

Examples 1-6

After applying the primer composition prepared in 1 to 6 to the aluminum panel (4.4 × 6.0 cm) modified with a vinyl group, the surface prepared in Preparation Example 7 was covered with a polycarbonate resin for 2 days in a 60 ℃ vacuum oven After drying, UV curing was performed for 2 hours.

Comparative Examples 1 to 6

Using the primer composition prepared in Preparation Examples 1 to 6 as it is, a sample for adhesion experiments was prepared as in Example 1 using an aluminum plate not subjected to surface modification.

Test Example

50 mm (length) × 4 mm (width) × 0.5 mm (thickness) specimens were fabricated by film casting to measure the mechanical properties of the primer compositions themselves prepared in Preparation Examples 1 to 6, followed by breaking strength with UTM. Was measured. In addition, the adhesive strength test of Examples 1 to 6 and Comparative Examples 1 to 6 was measured through the lap shear test. The test results are shown in Table 5 below.

division Production Example 1 Production Example 2 Production Example 3 Breaking strength (MPa) 15.13 8.15 11.71 Elongation at Break (%) 363 496 438 Adhesive Strength (kgf / cm ² ) Example 1 Comparative Example 1 Example 2 Comparative Example 2 Example 3 Comparative Example 3 5.488 2.158 3.536 1.297 4.163 1.575 division Production Example 4 Production Example 5 Production Example 6 Breaking strength (MPa) 9.36 3.87 5.62 Elongation at Break (%) 548 625 583 Adhesive Strength (kgf / cm ² ) Example 4 Comparative Example 4 Example 5 Comparative Example 5 Example 6 Comparative Example 6 3.930 1.088 1.935 0.425 2.483 0.618

As shown in Table 5, it can be seen that the mechanical strength of the primer composition using the polycaprolactone diol of the three types of polyols is the best, which may be due to the strong hydrogen bond of the ester group in the polyol.

In addition, the adhesive strength was the best primer composition using polycaprolactone diol, the structural compatibility of the most similar to polycarbonate. In addition, the smaller the molecular weight of the prepolymer, the better the penetration into the resin and showed better adhesion strength.

As a result, when the surface of the aluminum plate was modified with vinyl groups from each example and the comparative example, the surface and the primer were adhered through chemical bonding, so that the adhesive strength was significantly higher.

Claims (8)

Impregnating the metal plate with a phosphoric acid solution to expose a hydroxyl group on the surface;
The metal plate exposed to the hydroxyl group is impregnated with a vinyltrimethoxysilane solution containing vinyltrimethoxysilane, water, ethanol and hydrochloric acid, and the metal plate is subjected to a sol-gel reaction between the hydroxy group and the vinyltrimethoxysilane exposed to the metal plate. Attaching a vinyl group to a surface;
Reacting a polyol, a diol having a carboxyl group, and a diisocyanate to prepare an isocyanate terminated prepolymer;
Reacting the isocyanate terminated prepolymer with 2-hydroxyethylacrylate to prepare a vinyl terminated prepolymer;
Dispersing the vinyl terminal prepolymer to prepare an aqueous polyurethane primer, and then mixing the photoinitiator to prepare a primer composition; And
Applying the primer composition to a metal plate having a vinyl group attached to the surface, and then attaching the polymer resin to the coating layer, and then UV curing the primer composition;
Metal-resin adhesive strength improvement method comprising a.
The method of claim 1, wherein the metal plate is aluminum, zinc, iron, or an alloy thereof.
The method of claim 1, wherein the phosphoric acid solution is a mixture of phosphoric acid, 1-propanol, 1-butanol, and water.
The method of claim 1, wherein the polyol is polytetramethylene glycol, polycaprolactonediol, polypropylene glycol, or a mixture thereof.
The method of claim 1, wherein the diol having a carboxyl group is dimethylolpropionic acid, dimethylolbutanonic acid, or a mixture thereof.
The method of claim 1, wherein the diisocyanate is 1,6-hexamethylene diisocyanate, 4,4-dicyclohexyl methane diisocyanate, isophorone diisocyanate or a mixture thereof. .
The method of claim 1, wherein the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.
The method of claim 1, wherein the polymer resin is polycarbonate, polyester, or a mixture thereof.

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