JPH09157622A - Adhesive for decorative sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive, comprising a specific polyester resin, useful for bonding a decorative sheet to a building material made of aluminum with excellent adhesive strength without using a primer or a special solvent and hardly causing heat-resistant creep. SOLUTION: This adhesive for a decorative sheet comprises one or more polyester resins having two or more hydroxyl groups, containing terephthalic acid as a dicarboxylic acid component and soluble in organic solvents. A linear dicarboxylic acid such as adipic acid is preferred as the polycarboxylic acid used in addition to the terephthalic acid. When two or more polyester resins of different compositions are used in combination, at least either of the polyester resins has <=55 deg.C glass transition temperature. The molecular weight of the polyester resins used is preferably 3,000-5,000. A polyfunctional isocyanate compound such as hexamethylene diisocyanate is preferably blended as a cross- linking agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aluminum building material, and more particularly to an adhesive for adhering a decorative sheet to the surface of a residential aluminum sash.

[0002]

2. Description of the Related Art Aluminum has a surface which is easily oxidized by oxygen in the air to form an aluminum oxide layer. For this reason, it is necessary to coat or bond aluminum building materials.
The use of special primers such as so-called wash primers was essential. In recent years, coatings, especially electrodeposition coatings, have been applied to improve the weather resistance, durability, and corrosion resistance of aluminum building materials, but their cosmetic properties are limited. For this reason, it is considered that a decorative sheet is further attached to the interior surface of the building in order to improve its cosmetic properties. However, the conventional adhesives cannot sufficiently satisfy the peel strength and the heat-resistant creep resistance. Therefore, the following inventions have been made. a. Method using chlorinated rubber as a primer (JP-A-62-3943). b. A method of swelling a part of the coating film on the aluminum base material to strengthen the adhesive force by controlling the solvent in the adhesive (Japanese Patent Publication No. 3-41345). c. A method of using an adhesive in which polyester urethane rubber is blended with a polymer obtained by quaternizing a copolymer of an alkoxysilyl compound having an unsaturated bond and a dialkylaminoalkyl methacrylate with benzyl chloride as an adhesive (Japanese Patent Publication No. -271641). Also known is a method in which an anodized film is directly formed on an aluminum substrate and then a decorative sheet is adhered using an acrylic resin or a polyurethane resin (JP-A-59-1).
No. 23656).

[0003]

With respect to the above proposal,
First, the method of using a primer is not preferable for cost reduction because it increases the number of steps for adhesion, and it is a method of swelling the coating surface with ethyl acetate or methylene chloride to improve the adhesive strength. Has a problem that the swollen state is easily affected by the drying conditions. Further, the method of using an adhesive compounded with a polymer in which a copolymer of an alkoxysilyl compound and a dialkylaminoalkyl methacrylate is quaternized with benzyl chloride has a complicated adhesive structure.

According to the method of directly forming the anodized film on the aluminum base material and then bonding the decorative sheet using an acrylic resin, a polyurethane resin or the like, there is no problem in the adhesive force. (Japanese Patent Publication No. 3-41345, No. 1
Page 39, right column. ) However, in order to change the color tone of the exposed parts of the building and the exposed parts of the building to match each side, the interior of the building has been processed differently from the exterior such as wood grain. It is necessary to attach a decorative sheet. However, an adhesive capable of obtaining sufficient adhesive force without applying any pretreatment to an aluminum base material coated with acrylic-melamine or the like having excellent weather resistance has not been obtained so far, and therefore, a cosmetic For the adhesion of the sheet, it is necessary to use an aluminum base material at the stage where the anodized film is formed at the sacrifice of the performance or to provide a pretreatment step such as a primer treatment as described in the prior art. It was

The object of the present invention is to coat the entire aluminum base material, even when the aluminum base material is used as it is, and in particular to an acrylic resin usually used for aluminum building materials.
An object of the present invention is to provide an adhesive that can bond a decorative sheet without using a primer or a special solvent even when melamine coating is applied.

[0006]

The present invention is an adhesive for adhering a decorative sheet to a building material made of aluminum, which has two or more hydroxyl groups in one molecule and contains terephthalic acid as a dicarboxylic acid component. The present invention relates to an adhesive containing at least one polyester resin soluble in a solvent. The polyester resin may have a single composition or a combination of different compositions, but it has a glass transition temperature of 55 ° C.
It is preferable to contain at least one of the following polyester resins. In addition, it is preferable to use a polyfunctional isocyanate compound as a crosslinking agent together with the polyester resin.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The base material to which the present invention is adhered is an aluminum building material and a decorative sheet. In addition, as a decorative sheet example, a thermoplastic resin mixed with various fillers and colorants and formed into a film, paper, metal foil, or a sheet formed by printing a pattern or the like on them is used. To be done. A typical resin for such a decorative sheet is polyvinyl chloride,
It is not limited to this. The decorative sheet may be embossed. The aluminum material used for the aluminum building material may be formed of aluminum alone or an aluminum alloy. Here, a base material used for an aluminum building material, which is an object of adhesion, is referred to as an aluminum base material including an untreated one, anodized one, and a coated one.

The polyester resin used in the present invention contains terephthalic acid as an essential component. Other polycarboxylic acid components used include aromatic carboxylic acids such as isophthalic acid, phthalic acid, and their nuclear substitution derivatives, and aliphatic polycarboxylic acids such as glutaric acid, malonic acid, and adipic acid. Examples include linear dicarboxylic acids such as sebacic acid and side chain substituted derivatives thereof. In consideration of the solubility of the polyester resin in a solvent, it is preferable to use a linear difunctional dicarboxylic acid, but from the viewpoint of improving the heat-resistant creep resistance of the adhesive, a small amount of polyfunctional polyfunctional trifunctional or higher is used. Carboxylic acids may be used, for which purpose for example trimellitic acid or the like may be used.

As the glycol component of the polyester resin used in the present invention, ethylene glycol, 1,
Linear glycols such as 3-propylene glycol and 1,4-butanediol, glycols having side chains such as neopentyl glycol, alicyclic glycols such as cyclohexane-1,4-diol and spiroglycol, and others. Xylylene glycol (Mitsubishi Gas Chemical Industry Co., Ltd.)
Manufactured) can also be used. As in the case of the polycarboxylic acid component, trifunctional or higher functional alcohols, for example, polyols such as trimethylolpropane, glycerin and pentaerythritol can be copolymerized. Furthermore, it is also possible to use hydroxycarboxylic acids such as hydroxyacetic acid, ε-oxycaproic acid and the like. These acids, glycols, and hydroxycarboxylic acids are used in arbitrary combination in consideration of various properties such as the glass transition temperature of the polyester resin, the solubility, and the adhesive strength as an adhesive.

As the polyester resin used in the present invention, a resin having a single composition may be used alone, or two or more resins having different compositions may be used in combination. In this case, at least one of the polyester resins preferably has a glass transition temperature of 55 ° C. or lower. Further, the molecular weight of the polyester resin used is not particularly limited as long as the adhesive force can be obtained, but generally, the balance of the amount of the polyisocyanate compound used as the curing agent, the dissolution in the solvent Considering the properties and the viscosity of the solution when dissolved, it is preferably about 3,000 to 50,000.

As such polyester resins, the Byron series (manufactured by Toyobo Co., Ltd.), the Stafix series (manufactured by Fuji Film Co., Ltd.), the Elitel series (manufactured by Unitika Co., Ltd.) and the like are commercially available. The same effect as that of the present invention can be obtained even when the polyester resin is previously reacted with a diisocyanate compound and used as a urethane-modified polyester resin having a molecular weight of about 20,000 to 50,000. As such a urethane-modified polyester resin, Byron UR-3
200 (manufactured by Toyobo Co., Ltd.) and the like are commercially available.

The polyester resin is preferably used in combination with a polyfunctional isocyanate compound. When used in combination with such an isocyanate compound, the isocyanate group and the hydroxyl group of the polyester resin react and crosslink to form a three-dimensional network, whereby the adhesive strength and the heat creep resistance of the adhesive strength are improved. Further, when the aluminum building material is coated with acrylic-melamine, active hydrogen groups such as hydroxyl groups remaining in the resin of the coating film also participate in the crosslinking reaction and contribute to the improvement of adhesive strength.

As a component of the adhesive of the present invention, it is possible to add other resin in addition to the polyester resin to improve the characteristics. Examples of such a resin include polyvinyl butyral, a thermoplastic polyurethane, and an acrylic resin, which are resins excellent in affinity with metals and metal oxides.

Examples of polyfunctional isocyanate compounds that can be used in the present invention include, as bifunctional isocyanates, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate and the like. As trifunctional isocyanate, triphenylmethane triisocyanate (Desmodur RE (Bayer)), Desmodur RF, Desmodur N (both are Bayer), Duranate series compounds (Asahi Kasei Co., Ltd.), Coronate L
(Nippon Polyurethane Co., Ltd.) can be exemplified. These isocyanate compounds are selected in consideration of reaction rate, adhesive strength, cost, etc., but when discoloration of the adhesive is a problem, in order to prevent this, an aliphatic system which is difficult to discolor is used. It is preferable to select the compound of

The organic solvent used for the adhesive is not particularly limited as long as it dissolves the polyester resin, but esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and other cellosolves. Acetate, polyethylene glycol dimethyl ether, etc. can be used, and one or more kinds or a mixture thereof are used in consideration of the viscosity of the adhesive composition, the drying speed, the degree of swelling of the coating film applied to the aluminum substrate, and the like. .

As other substances to be added to the adhesive composition, a tackifier for increasing the adhesive strength, a discoloration preventing agent for preventing discoloration, a viscosity adjusting agent for adjusting the solution viscosity, etc. are required. You may add arbitrarily according to it.

The adhesive of the present invention can be a two-component adhesive containing a liquid containing a polyester resin as a main component and a liquid containing a polyfunctional isocyanate compound. In this case, the adhesive is used in the bonding step. The two liquids are mixed and used in advance. A liquid containing a polyester resin as a main component may absorb moisture in the air when left standing, and the use of a liquid having an increased moisture content causes a problem that the adhesive layer foams. In order to prevent this, it is also preferable to add methyl orthoformate (trade name Permflow OF) or the like to the liquid containing the polyester resin as a main component in order to remove water.

When the aluminum building material and the decorative sheet are bonded by using the adhesive of the present invention, as the method of applying the adhesive, all of the methods generally known as the method of applying the adhesive are used. This is possible, and examples of such a method include a method using a coater such as a roll coater and a knife coater, spray coating, and brush coating.

The adhesion method is generally performed by applying adhesion to the surface to be adhered of the decorative sheet, volatilizing the solvent appropriately, and then press-bonding the aluminum substrate. The adhesive may be applied to the decorative sheet or the aluminum base material. In order to promote the volatilization of the solvent and accelerate the process speed, it is preferable to pass the decorative sheet coated with the adhesive or the aluminum base material through a heating and drying oven. In this case, the temperature of the drying oven is 40 ° C. or higher. The upper limit temperature varies depending on the material passed through the drying furnace, but is about 120 ° C. for a decorative sheet using a thermoplastic resin and about 160 ° C. for an aluminum base material. After adhering the base material and the decorative sheet, it is possible to further heat the isocyanate group and the hydroxyl group in order to completely carry out the reaction and crosslinking of the isocyanate group and the hydroxyl group.

The coating amount of the adhesive is not particularly limited as long as the adhesive strength is sufficiently obtained, but the coating thickness in the wet state is 5 to 500 μm, particularly preferably 10 to 100 μm.

[0021]

[Materials used]

Polyester resin: Byron 550, 500, 30
0, 103, 200 (all manufactured by Toyobo Co., Ltd.). Urethane Modified Polyurethane Resin: Byron UR 320
0 (manufactured by Toyobo Co., Ltd.). (This resin is a polyurethane oligomer obtained by binding a hydroxyl group-terminated polyester resin containing terephthalic acid as an acid component with a diisocyanate compound.) Polyurethane resin: Pandex T-5202, T-5
201 (all manufactured by Dainippon Ink and Co., Ltd.). Tackifier: Synthetic resin AP (ketone resin) Tamanor 100S (phenolic resin) Hardener: Desmodur-RE (manufactured by Bayer) Properties of polyester resin and polyurethane resin [Table 1]
Are shown together.

[0022]

[Table 1]

[Experimental Example] A polyester resin or a polyurethane resin was dissolved in a predetermined solvent, and a tackifier was added as necessary to obtain a solid content of 30% or 25%.
Solution A was prepared and used as Solution A. Prior to bonding, 5% by weight of a hardening agent was added to the liquid A and stirred, and the resulting adhesive composition was applied to a PVC decorative sheet (thickness 170 μm),
It is coated with a knife coater so as to have a thickness of 50 μm in a wet state, and then dried at 60 ° C. for 30 seconds. The adhesive-coated decorative sheet was attached to an acrylic-melamine electrodeposition-coated aluminum substrate.

The evaluation of the adhesive performance was carried out for two items, a 180 ° peel strength test and a 60 ° C. heat creep test. The 180 ° peel strength test was performed at a measurement temperature of 20 ° C. and a pulling speed of 50 mm / min. Further, in the 60 ° C. heat resistance creep test, a load of 500 g was applied to a sample having a width of 25 mm in the direction of 180 degrees, and the sample was allowed to stand at 60 ° C. for 24 hours,
The peeled length was measured. The evaluation results are summarized in [Table 2] together with the composition of the adhesive.

[0025]

[Table 2]

The results of plotting the glass transition temperature and the peel strength are shown in FIG. From this result, it is necessary to use a polyester resin having a glass transition temperature of 55 ° C. or lower in order to achieve a peel strength of 3.0 kgf / inch which is generally required for bonding a base material and a decorative sheet. It turns out that

[0027]

【The invention's effect】

As is clear from the results shown in [Table 1], according to the present invention, it is practically necessary to adhere such a base material to 3.
A 180 ° peel strength of 0 kg / inch was obtained, and heat creep did not occur, or occurred only slightly. Further, by using the adhesive of the present invention, it is not necessary to use an aluminum base material in the anodizing treatment stage, and it is not necessary to take out the base material during a series of anodizing treatment / painting processes. The secondary effect is that production control and inventory control of coating materials are significantly simplified.

Claims (3)

[Claims] 1. An adhesive for adhering a decorative sheet to an aluminum building material, which has two or more hydroxyl groups in one molecule,
An adhesive containing terephthalic acid as a dicarboxylic acid component and at least one polyester resin soluble in an organic solvent. 2. The adhesive according to claim 1, wherein at least one of the polyester resins has a glass transition temperature of 55 ° C. or lower. 3. The adhesive according to claim 1, wherein a polyfunctional isocyanate compound is used as a crosslinking agent together with the polyester resin.