JPH0598231A - Adhesive composition for decorative laminated steel - Google Patents

Abstract

PURPOSE:To prepare the title compsn. excellent in adhesiveness, resistance to hot water, hardness of an adhesive layer, etc., by using, as the main component, a specific copolyester having an m.p., a Shore D hardness, and a reduced viscosity each of a specified value. CONSTITUTION:The title compsn. is prepd. by using, as the main component, a copolyester which has an m.p. of 100-180 deg.C, a Shore Dhardness of at least 60 deg., and a reduced viscosity of 0.4-1.2 and which is prepd. by reacting an acid component comprising 40-80mol% terephthalic acid, 20-60mol% isophthalic acid, 2-15mol% arom. dicarboxylic acid having a metal sulfonate group, and 0-20mol% 4-36C aliph. dicarboxylic acid with a glycol component comprising a 2-10C alkylene glycol. If necessary, the copolyester may be compounded with an inorg. filler such as talc or kaolin. a pigment, a stabilizer, a nucleating agent, etc. The title compsn. is excellent in adhesion to a steel sheet and a surface material of, e.g. polyethylene terephthalate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot melt adhesive for decorative steel sheets for coating and adhering a film or sheet of polyvinyl chloride resin, polyethylene terephthalate, melamine resin or the like on the surface of a steel sheet.

[0002]

Decorative steel sheets are widely used for home appliances, office equipment such as desks and cabinets, furniture, building materials and the like. Conventionally, the following two are the mainstream methods of manufacturing decorative steel sheets. The first is a method of applying paint on the surface of the steel sheet. However, this method is suitable for mass production of monotone, but has a drawback of poor cosmetic appearance.

The second is a method of adhering a skin material composed of a film or sheet of polyvinyl chloride resin, polyethylene terephthalate, melamine resin or the like to a steel plate. This method can change the design by appropriately selecting the skin material, and has been remarkably used in recent years. However, most of the adhesives used in this method are chloroprene-based and urethane-based solvent-based adhesives,
After applying these adhesives to a skin material or a steel plate, the solvent is volatilized and the adhesives are bonded within a pot life, so-called open time, and then heat-cured under pressure. Therefore, there is a big problem in working environment, and there is another problem in appearance such as wrinkles on the bonded surface during thermosetting.

[0004]

The present invention is based on the above-mentioned second aspect.
The present invention provides a novel adhesive that solves the problems of the method. That is, a polyvinyl chloride resin, polyethylene terephthalate, a skin material made of a film or sheet of melamine resin, solves the problem of the working environment when adhering to a steel plate, and further retains a high designability,
It is intended to provide a hot melt adhesive having excellent heat resistance, hot water resistance, etc. of the obtained decorative steel sheet and having little scratches on the surface such as imprints.

The hot-melt adhesive is easily melted by heating without using a solvent, has a low melt viscosity and is easy to flow, so that it can be smoothly and easily applied to a substrate, and can be rapidly cooled only by cooling. Finish the bonding. Furthermore, the bonding operation is simple and can be automated, and if one substrate is coated with a hot-melt adhesive in advance, it can be bonded simply by heating when necessary, and it is solvent-free and pollution-free. For these reasons, it has recently been used in various assembly fields.

However, conventional ethylene-vinyl acetate copolymers, polyamide-based, polyester-based hot-melt adhesives have insufficient adhesiveness with a steel plate or a skin material, and a decorative steel plate after lamination. Since it has insufficient durability such as heat resistance, hot water resistance and wet heat resistance, and has a problem that the hardness of the adhesive layer is insufficient and it is easily scratched, it cannot be used for decorative steel sheet applications. In particular, there has been no excellent hot-melt adhesive for a decorative steel sheet having a polyethylene terephthalate film or sheet as a skin material.

[0007]

Means for Solving the Problems The present inventors have found that a steel plate and polyethylene terephthalate, polyvinyl chloride resin,
As a result of diligent research to develop a hot melt adhesive having excellent adhesiveness to skin materials such as melamine resin, excellent durability such as heat resistance, hot water resistance, and moist heat resistance, and having sufficient hardness of the adhesive layer. The present invention has been completed.

That is, the present invention provides (a) terephthalic acid 40
~ 80 mol%, (b) isophthalic acid 20 to 60 mol%,
(C) Aromatic dicarboxylic acid containing sulfonic acid metal base 2 to
15 mol%, (d) 0 to 20 mol% of an aliphatic dicarboxylic acid having 4 to 36 carbon atoms as an acid component, and 2 to 1 carbon atoms
The alkylene glycol of 0 is used as a glycol component, the melting point is 100 to 180 ° C., the Shore D is 60 or more,
The present invention relates to an adhesive for decorative steel sheet, which contains a copolyester having a reduced viscosity of 0.4 to 1.2 as a main component.

In the present invention, the copolyester is
As the acid component, terephthalic acid, isophthalic acid and sulfonic acid metal group-containing aromatic dicarboxylic acid are essential. The ratio of terephthalic acid to all the acid components is preferably 40 to 80 mol%, particularly preferably 40 to 70 mol%. If it is less than 40 mol%, the melting point of the copolyester will be low and the crystallinity will be low, resulting in insufficient heat resistance. On the other hand, when the proportion of the terephthalic acid component increases, the melting point increases and the crystallinity also improves,
Although effective for heat resistance, the adhesiveness is slightly reduced and the adhesive temperature is also increased, damaging the skin material. Therefore, 8
0 mol%, preferably 70 mol% or less is suitable. The ratio of isophthalic acid to all the acid components is preferably 20 to 60 mol%, particularly preferably 20 to 50 mol%. If it is less than 20 mol%, the adhesion to the skin material, especially to polyethylene terephthalate, will be poor. As the proportion of the isophthalic acid component increases, the crystallinity of the polyester decreases, the polyester becomes brittle, the adhesiveness deteriorates, and heat resistance, hot water resistance, and the like become unreasonable. Therefore, 60 mol%, preferably 50 mol% or less is suitable. The ratio of the metal sulfonate-containing aromatic dicarboxylic acid to all the acid components is preferably 2 to 15 mol%, particularly preferably 2 to 10 mol%. If it is less than 2 mol%, the adhesiveness to the steel sheet is poor. As the proportion of the sulfonic acid metal group-containing aromatic dicarboxylic acid component increases, the initial adhesion with the steel sheet increases, but the hot water resistance decreases. Examples of the aromatic dicarboxylic acid containing a metal sulfonate group include sulfoterephthalic acid, alkali metal salts of 5-sulfoisophthalic acid and ester-forming derivatives thereof, and sodium or potassium salts of 5-sulfoisophthalic acid are particularly preferable. .. In addition to the above acid component, an aliphatic dicarboxylic acid having 4 to 36 carbon atoms can be used in an amount of 0 to 20 mol% based on the total acid component. When it is 20 mol% or more, the hardness of the copolyester is lowered, the adhesive layer is softened, and when a hard steel sheet hits the decorative steel sheet, the portion is dented or scratched. Examples of the aliphatic dicarboxylic acid having 4 to 36 carbon atoms include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dimer acid and the like.

The glycol component used in the present invention is mainly composed of an alkylene glycol having 2 to 10 carbon atoms, for example, ethylene glycol, 1.2-propanediol, 1,3-propanediol, 1,4-. Examples include butanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, diethylene glycol and triethylene glycol. These glycols may be used alone or as a mixture of two or more kinds. As a particularly preferable glycol, 1,4-butanediol can be mentioned.

The copolymerized polyester in the present invention preferably has a melting point of 100 to 180 ° C. If it is less than 100 ° C, the heat resistance is insufficient, and if it exceeds 180 ° C, it is difficult to use as a hot melt adhesive. The hardness of the copolyester is preferably Shore D of 60 or more, particularly 70 or more. If it is less than 60, the adhesive layer becomes soft,
If a hard product hits a decorative steel sheet during the laminating process or during transportation after the laminating, or after being assembled into a final product, for example, a home electric appliance, the portion is dented or damaged.
Further, the copolyester has a reduced viscosity of 0.4 to 0.4 when measured in a 1.0% orthochlorophenol solution at 35 ° C.
The thing of 1.2 is preferable. When it is 0.4 or less, the so-called polymerization degree is too low to exhibit sufficient adhesive strength. on the other hand,
When it is 1.2 or more, the melt viscosity becomes too high, the wetting with the adherend becomes non-uniform, and sufficient adhesive strength cannot be exhibited.

As the method for producing the copolyester in the present invention, the usual synthetic method for the copolyester can be applied as it is. For example, the acid component is directly esterified with the glycol component, or the ester-forming derivative of the acid is transesterified with the glycol component, and this is heated under reduced pressure to remove the excess glycol component, thereby copolymerization. Polyester can be obtained. At this time, any of various commonly used catalysts, stabilizers, additives and the like can be used.

The polyester hot melt adhesive of the present invention can be used by appropriately blending the above-mentioned copolymerized polyester with various additives. For example, talc, kaolin, inorganic fillers such as calcium carbonate, pigments, stabilizers,
You may mix | blend a crystal nucleating agent etc. Further, in order to enhance the effect of the polyester hot melt adhesive of the present invention, various epoxy compounds, isocyanate compounds, polyolefin polymers and the like which are commonly used may be blended.

To apply the hot melt adhesive of the present invention,
A method in which the copolyester is formed into various forms such as powder, tape, film or sheet, sandwiched between a steel plate and a skin material, and heat-bonded at a temperature not lower than the melting point of the copolyester, or a T-die type extruder. Alternatively, using a hot-melt roll coater or an adhesive applicator, one of the base materials, for example, a steel sheet is coated with the molten copolyester, and the other base material, for example, a polyethylene terephthalate film as a skin material is laminated and bonded. One of the base materials, for example, a polyethylene phthalate film is coated with the copolyester in advance, and when necessary, the steel plates are overlaid, and heat bonding is performed at a melting point of the copolyester or more. The method can be adopted.

[0015]

EXAMPLES Next, the present invention will be further described with reference to Examples and Comparative Examples. In addition, various measurements and tests followed the following methods. O Melting point Scanning differential calorimeter (Perkin-Elmer, D
SC7 type). ○ Measured according to Shore D ASTM D2240. ○ Reduced viscosity A solution of polymer-1 g / orthochlorophenol 100 ml was prepared and measured at 35 ° C. ○ 180 degree peeling adhesion strength A copolyester film (thickness 0.1 mm) is sandwiched between a steel plate (thickness 0.5 mm) and a polyethylene phthalate film (thickness 0.1 mm), and the melting point of the adhesive is 2 or more.
Bonding was carried out at a temperature higher by 0 ° C. under a load of 1 kgf / cm ² .
Then, after cooling to room temperature, a tensile test was performed at a tensile speed of 200 mm / min in an atmosphere of 23 ° C. and 50%. ○ Hot water resistance test The above 180 ° peeling test sample was divided into 100 mm × 10 mm into 100 parts with an NT cutter, soaked in boiling water at 100 ° C. for 2 hours, and then attached with cellophane tape, and a peeling test was conducted to remain on the steel plate. I counted the crosses.

[0016]

Example 1 103 parts of dimethyl terephthalate (0.5
3 mol), 8 parts (0.03 mol) of 5-sodium sulfodimethylisophthalate and 18 of 1,4-butanediol.
0 part (2.00 mol) and tetraisopropyl titanate as a catalyst 0.05 part (0.0006 mol), lithium acetate as a stabilizer 0.37 part (0.0002 mol)
Was added and the mixture was heated to 180 to 220 ° C. in a reaction can under a nitrogen stream to reflux 1,4-butanediol while completely distilling methanol to carry out a transesterification reaction. Then, 73 parts (0.44 mol) of isophthalic acid was added,
While refluxing 1,4-butanediol for 3 hours at 0 ° C., water was distilled out of the system to carry out an esterification reaction. Further, tetraisopropyl titanate 0.07 part (0.000
(3 mol), and the temperature is raised from 220 ° C to 240 ° C over 1 hour, and in parallel with this, gradually reducing the pressure to 1 mm.
Polycondensation reaction was carried out for 3 hours under the condition of Hg to obtain polyester. The melting point of this polyester is 140 ° C, Shore D
Was 75 and the reduced viscosity was 0.50. Further, as shown in Table 1, the 180 ° T-type peeling adhesion strength between the steel sheet and the polyethylene terephthalate film and the hot water resistance test result were extremely good, and it was found that the hot melt adhesive for decorative steel sheet can be effectively used.

[0017]

Examples 2 to 9 and Comparative Examples 1 to 4 Next, polyesters were synthesized in the same manner as above except that the carboxylic acid component and the glycol component were changed. The composition and properties of this polyester are shown in Table 1. It was found that the copolyesters of Examples 2 to 9 can be effectively used as a hot melt adhesive for decorative steel sheets. On the other hand, the copolyesters of Comparative Examples 1 to 2 and 4 are particularly difficult in hot water resistance and cannot be applied to this application. Further, the copolymerized polyester of Comparative Example 3 has a low Shore D of 57 and is not suitable for this application because it leaves a nail mark when pressed with a nail from above the skin material.

[0018]

Example 10 The copolymerized polyesters obtained in Example 1 and Comparative Example 1 were coated with a polyethylene terephthalate film (thickness) at a resin temperature of 160 ° C. using a 45 mm extruder having a coat hanger type T-die (slit width 600 mm). 0.1 mm) and a soft polyvinyl chloride resin sheet (thickness 0.3 mm) were extruded to a thickness of 0.05 mm and laminated. The laminated material was bonded to a steel plate (thickness 0.5 mm) preheated to 200 ° C. via a hot roller and bonded. Table 2 shows the results of the 180 ° peel adhesion strength and the hot water resistance test after adhesion.

As is clear from this table, it was found that the copolyester obtained in Example 1 can be effectively applied as a decorative steel sheet adhesive.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

EFFECT OF THE INVENTION The adhesive of the present invention has excellent adhesiveness to steel sheets and skin materials such as polyethylene terephthalate and polyvinyl chloride resin, and also has excellent durability represented by hot water. In addition, the adhesive layer has a high hardness even after the steel sheet and the skin material are attached to each other, and there is no scratch such as a pressing mark, and the hot melt adhesive for a decorative steel sheet can be effectively applied.

Claims (1)

[Claims] (A) 40-80 mol% of terephthalic acid,
(B) 20 to 60 mol% of isophthalic acid, (c) 2 to 15 mol% of a metal sulfonate-containing aromatic dicarboxylic acid,
(D) 0 to 2 aliphatic dicarboxylic acid having 4 to 36 carbon atoms
0 mol% is an acid component, alkylene glycol having 2 to 10 carbon atoms is a glycol component, and the melting point is 10
0 to 180 ° C, Shore D of 60 or more, and reduced viscosity of 0.
An adhesive for decorative steel sheets, which comprises a copolyester main component of 4 to 1.2.