JPH082596B2 - Surface treatment method for patch sheets - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface treatment method for a sheet attached to an adherend.

(Prior Art) In recent years, a sheet is attached to an adherend such as a steel plate or furniture, and the adherend is often decorated with the sheet to change the appearance. Various sheet materials that are used for such purposes and have excellent hardness and scratch resistance have been proposed.

For example, in Japanese Examined Patent Publication (Kokoku) No. 57-13425, one or two selected from polymers, oligomers or monomers in which a porous sheet-shaped substrate is impregnated with a radical initiator and a radical-reactive unsaturated bond is present on one or both sides thereof. A sheet material comprising a thermosetting composite sheet in which layers of a mixture of one or more kinds are laminated is disclosed.

Further, Japanese Patent Publication No. 21630/1985 discloses that thermoplasticity and / or
Alternatively, in a self-supporting continuous layer made of rubber, a powder containing a radical-reactive unsaturated compound solid at room temperature and a powder containing a radical reaction initiator solid at room temperature are dispersed and held in the form of solid particles. A heat-curable sheet material is disclosed.

On the other hand, in order to control the surface of the sheet material, a method in which an embossing roll, a mirror surface roll, a gloss calender, or the like is pressed against the sheet has been conventionally used. For example, JP-A-56-10
Japanese Patent Publication No. 7098 proposes a method of obtaining a marking paper having excellent gloss and smoothness by applying a water-based coating liquid on a predetermined paper, drying it, and then contacting it with a gloss calender.

(Problems to be solved by the invention) These sheet materials and the like, when controlled using a gloss calendar or a mirror-like roll as in the method disclosed in Japanese Patent Laid-Open No. 56-107098, at the time of sticking to unevenness or a stage There is a problem that the sheet is partially stretched and the surface gloss and image clarity are not uniform in each part.

An object of the present invention is to provide a surface treatment method for an adhesive sheet, which can form an excellent coating layer on an adherend having irregularities or curved surfaces.

(Means for Solving the Problems) The surface treatment method of the patch sheet according to the present invention comprises a reactive acrylic resin having a weight average molecular weight of 100,000 to 1,000,000 and a blocked isocyanate or melamine, which is attached to an adherend. The uncured or semi-cured thermosetting sheet is brought into contact with a pressing die to mirror-finish the surface of the sheet, and then the sheet is cured by heating, thereby achieving the above-mentioned object. To be done.

The thermosetting sheet is a sheet that has flexibility and is flexible enough to be easily attached to an adherend having a three-dimensional curved surface (unevenness, etc.) in an uncured or semi-cured state. When the surface of the uncured or semi-cured thermosetting sheet attached to the adherend is brought into contact with the mirror surface provided in the pressing die to mirror-finish the surface of the sheet, the surface state of the coating layer is changed. Gloss control (gloss control) and sharpness control are performed.

The curable sheet used in the present invention is made of an acrylic resin, has at least one kind of a hydroxyl group, an amino group, and a carboxyl group, and has a weight average molecular weight of 100,000 to
Unhardened consisting of 1,000,000 reactive acrylic resin and blocked isocyanate, crosslinking agent such as melamine, or
It is a thermosetting sheet in a semi-cured state. This thermosetting sheet has unblocked isocyanate, melamine,
It is also possible to use a thermosetting sheet in a state (B stage) which has undergone an initial curing reaction to some extent by including a crosslinking agent such as epoxy.

The initial curing rate is determined, for example, by the reaction rate (crosslinking rate) of the total functional groups of hydroxyl group, amino group and carboxyl group contained in the reactive acrylic resin. For example, when a sheet is spread and pasted on a three-dimensional curved surface as in vacuum contact molding or pressure forming, the spreadability of the sheet should be improved, for example, there should be about 100% elongation at the sheet forming temperature. Preferably, the reaction rate of the functional group is about 0.01 to 0.4. In the case of a molding method in which pressure is applied to the sheet such as press molding or insert injection, it is preferable to set the reaction rate of the functional group to about 0.2 to 0.8. The appropriate range of these values may change to some extent depending on the Tg (glass transition point) of the reactive acrylic resin and the molding temperature.

A reactive acrylic resin having at least one or more functional groups of a hydroxyl group, an amino group and a carboxyl group means a reactive acrylic resin having at least one of a hydroxyl group, a primary amino group and a carboxyl group. And is a solid polymer at room temperature. Examples of such reactive acrylic resin include 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth).
(Meth) acrylic acid ester monomer having a hydroxyl group such as acrylate and (meth) acrylic acid ester monomer having an amino group such as 2-aminoethyl (meth) acrylate and 3-aminopropyl (meth) acrylate and (meth) acrylic acid A monomer material selected from the combination of at least one functional group among (meth) acrylic acid having a carboxyl group such as, and other (meth) acrylic acid ester, styrene derivative monomer, etc., and maleic acid-based monomer And the like are polymerized with various peroxides and chain transfer agents as catalysts.

The reactive acrylic resin used in the present invention has a weight average molecular weight (▲ ▼) of 100,000 to 1,000,000. When the weight average molecular weight is less than 100,000, it is difficult for the obtained sheet material to maintain a sheet shape. When the weight average molecular weight exceeds 1,000,000,
The obtained sheet material is inferior in moldability (for example, in the case of solvent casting, the solution viscosity is high, the resin can be cast only at a low concentration, and it is difficult to control the film thickness of the sheet and remove irregularities). Becomes difficult to prepare. In addition, these reactive acrylic resins,
From the relationship of hardness after curing, for example, when the pencil hardness method is B or more, Tg is within the range of −20 to 80 ° C., and the functional group value [OH group value and
NH ₂ group value (NH ₂ value: the amount of NH ₂ groups added at the time of polymerization was calculated by the same calculation as the OH value, or the NH ₂ group was reacted with nitrous acid to be converted into an OH group and quantified) COOH base value (COOH
Value: The amount of COOH groups added at the time of polymerization is calculated by the same calculation as the OH value, or the total value of titrated COOH groups with KOH)] is preferably in the range of 20 to 200. However, the surface hardness is not too high, for example, 2B or less (23 ℃) by the pencil hardness method.
In the case of, it is applicable even if it is outside this range.

As for the blocked isocyanate, isocyanate groups having two or more isocyanate groups in the molecule, for example, isocyanate groups of monomers or modified products such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diamine diisocyanate, and isophorone diisocyanate are blocked (masked). In addition, phenols, oximes, lactams, malonic esters and the like are used as the block components.
The block isocyanate is released from the block by heating, and the isocyanate group reacts for the first time to exhibit a role as a curing agent. The blending ratio of the broken isocyanate and the reactive acrylic resin is the number of functional groups (functional group value) / the number of isocyanate groups (NCO value) =
It is set to 0.5 to 2.0, preferably 0.8 to 1.2.

Unblocked isocyanates are isocyanate compounds having two or more isocyanate groups in the molecule, such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, triphenylmethane triisocyanate, tris (isocyanatophenyl) thiophosphite, P-phenylene diisocyanate, xylylene diisocyanate, bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, and other monomers, or trimethylolpropane adducts of these monomers , Isocyanurate modified product, biure DOO modified products, carbodiimide-modified compounds, urethane modified product, there is allophanate modified product, or the like. The addition amount of this isocyanate varies depending on the sheet molding method, but NCO is functional group value: NCO = 1: 0.01 to 0.9 with respect to the functional group value of the reactive acrylic resin.

Melamine-based cross-linking agents include trimethylol melamine, hexamethylol melamine, and dimethylol urea obtained by reacting formaldehyde with a material having a polyfunctional amino group such as melamine, urea, thiourea, guanidine, guanamine, acetoguanamine, benzoguanamine, and dicyandiamide. It is an etherified melamine resin obtained by reacting dimethylolguanidine, dimethylolacetoguanamine, dimethylolbenzoguanamine and the like with an alcohol such as butyl alcohol and propyl alcohol. The addition amount of these melamine-based cross-linking agents is difficult to take a fixed value with respect to the functional group value of the reactive acrylic resin such as isocyanate, and when adding, determine the addition amount by conducting a preliminary experiment before making a sheet. Is preferred. For this sheeting, it is preferable that the functional group value: OR (ether value) = 1: 0.1 to 1.2 relative to the functional group value of the reactive acrylic resin.

The epoxy-based cross-linking agent is a glycidyl compound of a polyhydric alcohol containing a plurality of epoxy groups and is used together with a Lewis acid catalyst. For example, butadiene dioxide,
Hexazine dioxide, diglycidyl ester of phthalic acid, bisphenol-A diglycidyl ether, bisphenol-F diglycidyl ether, paraaminophenol triglycidyl ether amine, aniline diglycidyl ether, phenylenediamine tetraglycidyl ether, sulfonamide Glycidyl compounds such as diglycidyl ether of glycerin, triglycidyl ether of glycerin, polyether-modified diglycidyl, polyester-modified diglycidyl, urethane-modified diglycidyl compound (polymer), vinylcyclohexenedioxide, and dicyclopentadiene oxide. The amount of the epoxy added is preferably about 0.01 to 0.9 of functional group: CH ₂ CH ₂ O (epoxy group) with respect to the functional group value of the reactive acrylic resin.

The amount of the initial curing cross-linking agent to be added is preferably the above-mentioned amount, but in reality, the functional groups of the reactive acrylic resin and the cross-linking agent are mixed depending on the reactivity of the reactive acrylic resin used, for example, the melamine cross-linking agents Since the reaction between the melamine-based cross-linking agent and the epoxy-based cross-linking agent occurs, it is preferable to determine the actual amount to be added after conducting a preliminary experiment.

The thickness of the thermosetting sheet varies depending on the sticking property of the sheet to the adherend and the function imparting to the adherend, but from a viewpoint of sticking the sheet to the uneven surface from 20 to 500.
A range of about μm is preferable, but 5 to 5
A range of about 1,000 μm is also preferable.

Various adherends can be used for attaching these. For example, steel plates, aluminum plates, galvanized metal such as tin plate, tin plate, gypsum board, cement, ceramics such as pottery, steel plates and ceramics, coated plates mainly composed of resin components on resin, and further polyolefin, ABS resin,
Thermoplastic resin such as polyphenylene sulfide (PP4) and polyetherimide, melamine resin, epoxy resin,
The material is a thermosetting resin such as phenol resin or polyimide. For these attachments, there are cases where the sheet itself is used and cases where an adhesive layer is laminated.
Adhesiveness to the thermosetting sheet (good interface familiarity) as a material when these adhesive layers are laminated on the sheet
Excellent in, for example, EVA-based HM (hot melt) adhesive, SIS
Examples thereof include a system HM adhesive, an acrylic HM adhesive, an unsaturated polyester non-crosslinked product, an acrylic adhesive, a silicone adhesive, and a post-cured acrylic adhesive. As the property of the adherend, for example, in the case of a hydrophilic surface, the thermosetting sheet is used directly or the one provided with these adhesive layers is used.

In addition, the thermosetting sheet material may contain a coloring agent such as a pigment or a dye. As the colorant, pigments, dyes and the like used in ordinary painting can be used. For example, pigments include titanium oxide, iron oxide, carbon black, and cyanine pigments, and dyes include azo dyes, anthraquinone dyes, indigoid dyes, stilbene dyes, and the like, and aluminum flakes, nickel powder, gold powder, There is metal powder such as silver powder. With respect to the amount of the colorant, when it has a high hiding property, the total amount of the colorant is preferably in the range of 2 to 500 parts based on 100 parts of the solid content of the sheet material.

These thermosetting sheet materials may further contain an inorganic filler, a metal material, a deterioration preventing agent, a rust preventive agent, etc. for surface control and high functionality.

This thermosetting sheet is coated on process paper (usually PET released with silicone: polyethylene terephthalate, paper, etc.) by a casting method such as comma roll or comma reverse after sufficiently dissolving and stirring the above materials in organic solvent etc. Then, it is prepared by performing drying for removing the solvent.

The thermosetting sheet is attached to an adherend by the following method.

Various methods can be used for attaching to the adherend. For example, there are methods such as hand pasting method, laminator method, (vacuum) press, insert injection, vacuum adhesion molding (vacuum packaging molding), etc., but to improve the adhesion to the adherend and rust prevention Is preferably vacuum contact molding or vacuum pressing in which a vacuum is applied between the adherend and the thermosetting sheet.

 After sticking, the surface of the sheet is processed by a pressing die.

The pressing die used in the present invention is one that fits the adherend to which the thermosetting sheet is attached (it does not have to be fitted when controlling a part of the surface of the sheet), and the sheet The surface in contact with is made of various plastic materials, metal materials, and inorganic materials, and the surface is used after being smoothed (mirror-finished). In some cases, the surface of a die used during pressing such as a vacuum press is processed so that the surface of the sheet is processed simultaneously with the attachment. When the thermosetting sheet surface is processed by this pressing die, the sheet and / or the pressing die is heated or cooled and / or sprays a solvent capable of swelling or dissolving the sheet, swelling only the surface portion of the sheet, It may soften and improve the transfer of the surface of the die. In this case, it is better to skip the solvent before bringing the sheet to the curing temperature.

The pressure at the time of treating the sheet surface with a pressing die is usually 5 kg f / cm ² or less, but this value is determined by the material used and the required surface state of the sheet.

Then, by heating, the thermosetting sheet is completely cured. The heating temperature is determined by the curing agent used, and curing is performed for the predetermined time.

Example 1 Acrylic polyamine (methyl methacrylate, butyl methacrylate and acrylic acid-2 was added to 300 parts of ethyl acetate.
-Aminoethyl copolymer, Mw = 492,000, Tg 35 ° C, NH ₂
Value 80) Solid content 100 parts, Broke isocyanate (Takeda Yakuhin Kogyo, Takenate B-870N, ketoxime block NCO = 12.6%) 23 parts (This cross-linking agent is 0.8 equivalent of isocyanate group to the amino group of the acrylic polyamine. ), Epoxy (made by Ciba Geigy, Araldide CY
175, epoxy equivalent 160, epoxy value 220 corresponding to functional group value) 4.9 parts (10% of amino groups of acrylic polyamine are initially cured) were mixed with good stirring. This mixture was applied to the mold release surface of a polyethylene release-treated polyethylene terephthalate (PET) film with an applicator and dried at 80 ° C. for 5 minutes to prepare a thermosetting sheet.
The thickness of the sheet was 80 μm.

Next, this sheet was attached to a hemisphere having a radius of 10 cm and subjected to alkyd melamine coating treatment by vacuum contact molding (vacuum packaging molding) at a temperature of 60 ° C. when the ultimate vacuum reached 6 Torr.

Furthermore, the surface in contact with the sheet is mirror-finished (Mirror surface clarity GD
Polished to a value of 1.0, treated with chrome) and heated to 30 ° C with a die that can be fitted to the hemisphere with the above sheet attached.
It was pressed at 0.5 kg f / cm ² for 5 minutes. Then, the sheet was heated at 140 ° C. for 20 minutes to cure the sheet. Of this hemispherical surface sheet
The GD was 1.0 and the surface gloss was 85%, which was uniform.

(Example 2) Acrylic polyol (manufactured by Nippon Shokubai Co., Ltd., Arotane 20)
40-139, Tg = 20, Mw = 321,300, solid content 28%, solid content 100
% Hydroxyl group 100) and blocked isocyanate cross-linking agent (Nippon Polyurethane Industry Co., Ltd., Coronate 25)
15, hexamethylene diisocyanate isocyanurate ε-caprolactam block, isocyanate 1
0.6%, solid content 80%) 57 parts (equivalent) were mixed with stirring.

This mixture was applied to the mold release surface of a polyethylene release-treated polyethylene terephthalate (PET) film with an applicator and dried at 80 ° C. for 5 minutes to prepare a thermosetting sheet. The thickness of the sheet was 80 μm.

Next, this sheet was attached to a hemisphere having a radius of 10 cm and subjected to alkyd melamine coating treatment by vacuum contact molding (vacuum packaging molding) at 60 ° C. when the ultimate vacuum reached 6 Torr.

Furthermore, the surface in contact with the sheet is mirror-finished (Mirror surface clarity GD
Polished to a value of 1.0, chrome-plated), and heat the pressing die fitted to the hemisphere with the above sheet attached to 30 ° C,
It was pressed at 5 kg f / cm ² for 5 minutes. Then, it was heated at 140 ° C. for 20 minutes to cure the sheet. GD of this hemispherical surface sheet
Was 1.0 and the surface gloss was 87%, which was uniform.

(Comparative Example) The thermosetting sheets prepared in Examples 1 and 2 were attached in the same manner as in Example, and the sheet was heated at 140 ° C for 20 minutes without being processed with a pressing die to cure the sheet. It was

The surface of the same sheet as in Example 1 had a GD value of 0.5 to 0.9 and a 60 ° θ gloss of 50 to 85%, which was nonuniform.

The surface of the same sheet as in Example 2 had a GD value of 0.4 to 0.9 and a 60 ° θ gloss of 50 to 85%, which was nonuniform.

(Effect of the Invention) According to the present invention, the weight average molecular weight is 100,000 to 1,000,0.
By using an uncured or semi-cured thermosetting sheet made of a reactive acrylic resin of 00 and a blocked isocyanate or melamine, the sheet shape can be maintained and the film thickness can be controlled and unevenness can be removed. It is easy to mold and has excellent moldability, and the surface of the coating layer made of the thermosetting sheet is mirror-finished by a pressing die to obtain a coating layer with a high-definition and high-gloss surface condition.

Claims (1)

[Claims] 1. A weight average molecular weight of 10 applied to an adherend.
000 to 1,000,000 reactive acrylic resin, and a block isocyanate or melamine, a thermosetting sheet in an uncured or semi-cured state, the surface of the sheet is mirror-finished by contacting a pressing die, then, A surface treatment method for a patch sheet, which comprises curing the sheet by heating.