JPH01294723A - Thermosetting sheet for coating - Google Patents

Abstract

PURPOSE:To obtain a thermosetting sheet for coating, improved in coating workability and impact resistance by mixing a specified acrylpolyol with a blocked isocyanate crosslinking agent and molding the mixture. CONSTITUTION:A (meth)acrylate monomer (a) is copolymerized with a styrene monomer (b) and a hydroxyl group-containing (meth)acrylate monomer (c) to obtain a normally solid acrylpolyol (A) of a weight-average MW of 200000-800000. Separately, an isocyanate compound (d) having at least two NCO groups in the molecule (d) is reacted with a blocking agent (e) to block the NCO groups of component (d) to obtain a blocked isocyanate crosslinking agent (e.g., an oxime-blocked product of hydrogenated diphenyl methane diisocyanate) (B). Component A is mixed with component B in an amount to give a ratio of the OH groups of component to the NCO groups of component B of 0.5-1.5 and, optionally, a filler, an antioxidant, a colorant, etc., (C), to obtain an uncured thermoplastic resin sheet. This composition is applied to the surface of a substrate and dried, and the product is released from the substrate to obtain the subject sheet.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a thermosetting coating sheet that is coated on an article and then thermally cured to form a uniform hardened coating on the article. The present invention relates to a thermosetting coating sheet that is flexible and can be easily coated, and can form a hard coating with excellent impact resistance after curing.

(Prior Art) Paints have generally been used to coat plastic molded bodies, metal molded bodies, etc. for the purpose of improving their appearance and preventing corrosion, or for various markings.

However, when painting with a paint, it is necessary to adjust the viscosity and concentration of the Wl material, which makes the work complicated. Paints using organic solvents cause contamination of the work environment and health and safety problems. Water-based solvent-based paints require a long time to dry, require drying equipment to dry quickly, and require a lot of energy such as heating and blowing air. There are drawbacks.

In order to solve these problems, sheet-like coating materials have been proposed in place of paint. for example.

A sheet-like coating material mainly made of polyvinyl chloride is used. Such a sheet material does not contaminate the work environment or cause health and safety problems, and does not require drying after application, which simplifies the work. However, since the main component of the material is soft polyvinyl chloride, the resulting coating has poor impact resistance and is prone to cracking.

As an alternative to these soft polyvinyl chloride sheet materials, heat or photo-curable sheet materials have been proposed. This sheet material cures to form a hard coating when heated or irradiated with light, either when or after it is applied to an article.

For example, Japanese Patent Publication No. 57-13425 discloses a thermosetting composite sheet having a structure in which a layer containing a direactive unsaturated polymer, an oligomer, a monomer, etc. and a layer containing a radical reaction initiator are laminated. There is.

(Problem to be solved by the invention) However, in such sheet materials, the component that causes the 9-polymerization reaction and the 9-reaction initiator are contained in different layers, making it difficult to control heating and pressure during curing. Therefore, a uniformly cured film cannot be obtained.Furthermore, paper, woven fabric, non-woven fabric, etc. are used as the sheet-like base material to be impregnated with the radical reaction initiator. When coating a film, it is difficult to apply it while stretching, and a good cured film cannot be obtained.

There are drawbacks such as.

The present invention solves the above-mentioned conventional problems, and its purpose is to provide a hard coating that is flexible before curing, is easy to coat, and is uniform and has excellent impact resistance. It is an object of the present invention to provide a thermosetting coating sheet capable of forming a coating film.

(Means for Solving the Problems) The thermosetting coating sheet of the present invention is an uncured sheet made of a thermosetting resin composition.

The thermosetting resin composition has a weight average molecular weight of 200.0.
00 to 800.000 and is solid at room temperature, and a blocked isocyanate crosslinking agent are the main components.

The thermosetting coating sheet of the present invention is composed of a thermosetting resin composition containing the above two components as main components.

At a temperature lower than the curing temperature of the acrylic polyol contained, it is in an uncured state and is in the form of a solid or solid solution with excellent flexibility.

The acrylic polyol contained in the resin composition is an acrylic polymer having a plurality of hydroxyl groups, and is a solid polymer at room temperature. Such acrylic polyols include, for example, a (meth)acrylic ester monomer and a styrene monomer.

It is obtained by copolymerizing a (meth)acrylic acid ester monomer having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate. The molecular weight of the acrylic polyol can be changed depending on the conditions when performing a polymerization reaction using an initiator.One acrylic polyol used in the present invention is as follows.

Its weight average molecular weight (print) is 200,000 to 80
A range of 0,000 is selected. When the weight average molecular weight is less than 200,000, it becomes difficult for the obtained coating sheet to maintain its sheet shape. Therefore, for example, sufficient elongation cannot be obtained for stretching during pasting work.

In some cases, cracks or cracks may occur. On the other hand, if the 2 weight average molecular weight exceeds 800,000, the resin composition will have poor moldability and it will be difficult to prepare a coating sheet.

The thermosetting resin composition containing the above-mentioned acrylic polyol has viscosity characteristics necessary to maintain its shape during storage and use when formed into a coating sheet. In other words, a thermosetting coating sheet made of a thermosetting resin composition has flexibility before curing and is hard enough to maintain its sheet shape.

To cure the above acrylic polyol.

A blocked isocyanate crosslinking agent is used as a heat-reactive curing agent. Here, the block isocyanate crosslinking agent refers to the isocyanate group of an isocyanate compound having two or more isocyanate groups in two molecules, such as phenol,
Refers to compounds blocked with blocking agents such as oximes, ε-caprolactam, and malonic acid esters. Examples of the above-mentioned isocyanate compounds include monomers such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and trimethylolpropane adducts, isocyanurate-modified products, and carbodiimide-modified products of these monomers. . The blocked isocyanate crosslinking agent is a heat-reactive curing agent in which the blocking agent is removed by heating and the resulting isocyanate group causes a crosslinking reaction with the hydroxyl group of the acrylic polyol. The content of the blocked isocyanate crosslinking agent is such that the ratio of the hydroxyl groups contained in the acrylic polyol to the isocyanate groups contained in the blocked isocyanate crosslinking agent is 0.5 to 1.5°, preferably 0.
．． The amount is adjusted to be within the range of 8 to 1.2.

The thermosetting resin composition further contains a filler, if necessary.
Contains an anti-aging agent, a coloring agent, etc.

The coating sheet of the present invention has an adhesive layer 1 on one side of the thermosetting coating sheet 1, for example, as shown in FIGS. 1 to 3.
may be provided, and/or a support layer 3 may be provided on the other side.

When the thermosetting coating sheet 1 does not have sufficient adhesive strength to the article to be coated.

An adhesive layer 2 is provided on one side of the covering sheet 1, and the adhesive layer 2
By attaching it to the article through the adhesive, it is possible to improve the adhesion between the hard coating and the article after hardening.

When the thermosetting resin composition constituting the covering sheet 1 has a low viscosity at room temperature, it becomes difficult for the covering sheet 1 to maintain its shape. In such a case, by providing the support layer 3 on one side of the covering sheet 1, the shape retention of the covering sheet 1 can be improved. As shown in FIG. 3, the adhesive layer 2 may be provided on one side of the thermosetting resin sheet 1, and the support N3 may be provided on the other side.

As described above, the adhesive layer 2 is formed to adhere the covering sheet 1 to the article when covering the article with the covering sheet 1. Therefore, it is necessary to have high adhesiveness and excellent durability in the bonded state. Adhesives for forming such an adhesive layer 2 include pressure-sensitive adhesives,
Hot-melt adhesives, post-curing adhesives, and the like are preferably used. Mixtures of these adhesives can also be used.

It is also possible to sequentially laminate a plurality of different types of adhesives to provide excellent adhesion to both the thermosetting coating sheet 1 and the article to be coated.

Among the above adhesives, pressure-sensitive adhesives include rubber-based, acrylic-based, urethane-based, and silicone-based adhesives. Hot melt adhesives include, for example, ethylene-vinyl acetate copolymer systems.

Styrene-isoprene-styrene block copolymer system,
There are adhesives such as acrylic. 1 for post-curing adhesives
For example, there is a microcapsule curing adhesive. Examples of the material include uncrosslinked unsaturated polyester adhesives, self-crosslinked acrylic adhesives, and the like.

Further, the support layer 3 is formed to improve the shape retention of the covering sheet 1 during storage and use. The covering sheet 1 is attached to an article by stretching it as necessary. Therefore, it is preferable that the support N3 is made of at least a film that is malleable under heating (for example, a thermoplastic resin film or a rubber film). Examples include acrylic resin, polyester, ethylene-vinyl acetate copolymer, polyethylene, and polypropylene. Examples of materials for the rubber film include natural rubber, styrene-butadiene rubber, and nitrile-butadiene rubber.

Isoprene rubber, butadiene rubber, chloroprene rubber,
Examples include urethane rubber, silicone rubber, and acrylic rubber. Mixtures of these thermoplastic resins and rubbers can also be used. or.

These can also be laminated to form a film layer. Thermoplastic resin films often become malleable under heating, but if a rubber film is used.

Spreadability can be obtained even at room temperature.

The adhesive layer 2 and the support layer 3 further contain a filler, an anti-aging agent, a colorant, and the like, if necessary.

The coating sheet of the present invention is prepared, for example, as follows. First, an acrylic polyol, a blocked isocyanate crosslinking agent, and, if necessary, a suitable organic solvent are mixed. The above-mentioned acrylic polyol and the like are often commercially available as an organic solvent solution, and in that case, the above-mentioned organic solvent is not required.

The resulting mixture is applied to the surface of a release-treated base material such as a film, and then dried.

A thermosetting coating sheet 1 is obtained by peeling the formed sheet from the base material. Thermosetting coating sheet 1
The thickness of typically ranges from 10 to 500 g rm.

Any method can be used to laminate the adhesive layer 2, but for example, the thermosetting coating sheet 1 is prepared on a releasable base layer by the same method as described above, and then the thermosetting coating sheet 1 is prepared on the releasable base layer.

A solution containing the above adhesive is applied to the surface of different releasable base materials and heated and dried to form adhesive N2, and the thus obtained thermosetting coating sheet 1 and adhesive By pressing the agents N2 against each other by applying pressure, for example, with a roll press, and removing the releasable base material.

A sheet for lamination is prepared. What is the thickness of adhesive layer 2?

It is typically in the range of 30-100 μm.

For the support layer 3, the above-mentioned base material may be used as is, or after forming the covering sheet 1, the support J! The above thermoplastic resin film or rubber film constituting 3 may be laminated.
The layer thickness of the support layer 3 is typically about 10 to 500 μm.

The thermosetting coating sheet of the present invention can be used to form a hard coating on a desired article, for example, by using it in the following manner. Since the covering sheet has a certain degree of flexibility at room temperature, it can be stretched without heating and attached to the surface of the article to match the shape of the article. Heating above the curing temperature of the acrylic polyol contained.

Allow the coating sheet to completely cure. In this way, a hard coating is formed on the surface of the article. Alternatively, the covering sheet may be cured at the same time as the covering sheet is applied to the article by hot pressing using a mold that fits the article. According to this method, even a three-dimensional solid with unevenness can be obtained.

It can be easily coated.

Even when the above-mentioned thermosetting coating sheet has poor adhesion to the article to be coated, if a sheet having the adhesive layer 2 is used, sufficient adhesion to the article can be obtained.

Even when the thermosetting coating sheet is in the form of a solid solution, the sheet having the support layer 3 can be used when the sheet is attached to or heated on the surface of the article.

This prevents the shape of the sheet from deforming more than necessary. When attaching the sheet having the support layer 3, heating is performed as necessary to impart flexibility to the support layer 3 and ensure desired malleability. After the covering sheet is applied to the article and cured by heating, the support layer 3 may be peeled off and removed.

(Example) Examples of the present invention will be described below. In addition.

Hereinafter, "part" means 9 parts by weight.

Yo Uratanemasu (^) Preparation of thermosetting coating sheet: Thermosetting acrylic polyol (manufactured by Nippon Shokubai ■, Arotan 2040-14
5, Tg = 40°C9 shoes = 339.0OO) 10
0 parts, and a blocked isocyanate crosslinking agent (manufactured by Takeda Pharmaceutical Company Ltd.).

B-815N, oxime block of hydrogenated diphenylmethane diisocyanate) 25 parts (this crosslinking agent is based on the hydroxyl group of the acrylic polyol).

1.0 equivalents of isocyanate groups) were mixed with stirring. This mixture is applied to the release surface of a silicone release-treated polyethylene terephthalate film (manufactured by Soken Kako ■, film thickness 50 μm), and after drying at 80°C for 5 minutes, the polyethylene terephthalate film is peeled off. In this way, an uncured coating sheet was prepared. The layer thickness of the resulting coating sheet was about 50 μI.

(B) Performance evaluation of thermosetting coating sheet: A strip-shaped test piece (20X
100cm) was cut and subjected to a tensile test in the longitudinal direction at 80°C. Even for 100% stretching.

It showed uniform elongation without any cracks or cracks.

Next, a coating test was conducted on the above-mentioned coating sheet.

Steel plate curved like a convex lens (curvature radius 50c+++;
Covering sheet (2
0x20cm) were vacuum-pressed at 80°C with their resin layers facing each other. The coated steel plate was coated well without wrinkles.Next, this coated steel plate was heated at 160'C for 30 minutes to harden the acrylic polyol, forming a strong coating (film thickness of about 40 μm). Obtained. The pencil hardness of the coating was 2H.

Miniwa Madagei acrylic polyol (manufactured by Nippon Shokubai ■, Arotan 2040)
-140. Tg=20°C, 6=369,000)
For 100 copies.

Example 1 except that 35 parts of a blocked isocyanate crosslinking agent (this crosslinking agent has 1.0 equivalent of isocyanate groups with respect to the hydroxyl group of the acrylic polyol) was used.
A thermosetting coating sheet was prepared in the same manner as above.

The obtained covering sheet was tested in the same manner as in Example 1. In tensile tests, even for 100% stretching.

It showed uniform elongation without any cracks or cracks. In addition, in the coating test, the convex surface of a steel plate curved into a convex lens shape was successfully coated without wrinkles. The pencil hardness of the film after heating and curing was H.

Acrylic polyol (manufactured by Nippon Shokubai ■, Arotan 2040)
-144. Tg=20°C2 cap=104,000)
For 100 copies.

Example 1 except that 37 parts of a blocked isocyanate crosslinking agent (this crosslinking agent has 1.0 equivalent of isocyanate groups with respect to the hydroxyl group of the acrylic polyol) was used.
A thermosetting coating sheet was prepared in the same manner as above.

The obtained covering sheet was tested in the same manner as in Example 1. In the tensile test, it was not possible to obtain 100% elongation with respect to stretching. In addition, in the coating test, the sheet shape retention was poor and it was difficult to apply by vacuum pressure bonding.

(Effects of the Invention) When the thermosetting coating sheet of the present invention is used, a hard coating having excellent thermosetting properties, uniformity, and excellent impact resistance can be easily formed. This is because the thermosetting resin contained in the sheet is in an uncured state.

This sheet is flexible at room temperature or at least below the curing temperature. Therefore, it has excellent pasting workability and can easily form a uniform hard coating not only on flat articles but also on articles having some unevenness or curved surfaces. Such covering sheets can be used for furniture.

It is used in a wide range of applications, including as decorative or display sheet materials that are attached to the surfaces of plastic molded objects, steel plates, etc.

4. Figures 1 to 3 are sectional views showing an example of the thermosetting coating sheet of the present invention.

1... Thermosetting coating sheet, 2... Adhesive layer, 3
...Supporting layer.

that's all

Claims (1)

[Claims] 1. Weight average molecular weight is 200,000 to 800,000
1. A thermosetting coating sheet comprising a thermosetting resin composition mainly comprising an acrylic polyol that is solid at room temperature and a blocked isocyanate crosslinking agent, and is in an uncured state.