JPH01252682A - Production of pressure-sensitive adhesive member - Google Patents

Abstract

PURPOSE:To produce a pressure-sensitive adhesive member having excellent tack and a retentive force in good efficiency, by applying a pressure-sensitive adhesive comprising an epoxy acrylic polymer and an onium salt compound to the surface of a substrate and curing the formed pressure-sensitive adhesive layer. CONSTITUTION:A pressure-sensitive adhesive comprising an epoxy acrylic polymer and an onium salt compound (e.g., diazonium, sulfonium or iodonium salt) is applied to at least either surface of a substrate (e.g., paper, cloth, plastic film or metallic foil), and the formed pressure-sensitive adhesive layer is cured by heating or by ultraviolet irradiation to produce a pressure-sensitive adhesive member composed of the substrate and the adhesive layer formed thereon. According to the above, the curing can be performed within a short time without any oxygen control. After-curing for a long time need not be performed, and therefore the efficiency of production is excellent. The obtained pressure- sensitive adhesive member has a small curing shrinkage, excellent retentivity of adhesion of the adhesive layer to the substrate and is excellent in tack and retentive force.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for efficiently manufacturing an adhesive member having excellent tack and holding power by curing an epoxy group-containing acrylic polymer with an onium salt compound.

PRIOR ART AND PROBLEM Applications of adhesive members formed by providing an acrylic adhesive layer on a supporting base material include packaging materials, masking materials, electrical insulation materials, surface protection materials, anti-corrosion materials, bonding materials, etc. When manufacturing the adhesive member, if the polymerized acrylic polymer is used as an adhesive as it is, it will cause cohesive failure and the problem of insufficient holding power such as the adhesive state with the adherend will not be maintained. It is said to be a pressure-sensitive adhesive with a hardened composition.

Traditionally, acrylic adhesives have been cured using heat curing methods such as the chestnut sulfur method using sulfur, the crosslinking method using chestnut linking agents made of peroxides, isocyanate compounds, epoxy compounds, and melamine compounds, and the crosslinking method using metal ions. was known. However, during the curing process of the adhesive layer, the supporting base material is left at high temperatures for a long period of time, resulting in problems such as a decrease in strength and dimensional changes. In addition, due to the time required for heat curing, a long heating zone is required to achieve high-speed processing, and the length of the heating zone may restrict the speed of the production line or require a long time for after-cure. There were also problems with manufacturing efficiency.

On the other hand, acrylic pressure-sensitive adhesives are also known in which radically reactive functional groups such as acryloyl groups are introduced into acrylic polymers and can be efficiently crosslinked by treatment with ultraviolet rays or electron beams. However, curing is inhibited by oxygen, and to prevent this, there are curing problems such as the need to replace the irradiation zone with nitrogen, and it is difficult to introduce radically reactive functional groups into acrylic polymers, making them difficult to obtain. In addition, the adhesive layer shrinks due to curing, resulting in poor adhesion to the supporting substrate.
There were problems such as a significant decrease in

Means to Solve the Problems The inventors of the present invention have attempted to overcome the above problems (as a result of extensive research, they have developed an adhesive that incorporates epoxy groups into acrylic polymers and cures them with onium salt compounds). The inventors have found a way to achieve this objective and have come up with the present invention.

That is, the present invention uses an adhesive containing an acrylic polymer having an epoxy group and an onium salt compound as components to produce an adhesive member in which an adhesive layer is provided on a supporting substrate, and the adhesive is applied to the supporting substrate. Attached to one or both sides of the
The present invention provides a method for producing an adhesive member, characterized in that the formed adhesive layer is cured by ultraviolet irradiation or heating.

Effect As mentioned above, by introducing an epoxy group into an acrylic polymer and using an adhesive that is cured using an onium salt compound, the adhesive can be cured by ultraviolet irradiation or heating. The purpose of the period is achieved. In other words, it is easy to introduce epoxy groups into acrylic polymers, so they are highly available, and since they are not inhibited by oxygen, there is no need to replace the curing zone with nitrogen, and the time required for curing can be reduced. In addition, in the case of heat curing, low-temperature treatment is possible and long-term after-curing is not required.

In addition, the curing reaction described above is a ring-opening reaction of the epoxy group based on the cationic reaction mechanism of the epoxy group-containing acrylic polymer using an onium salt compound as a reaction initiation catalyst, so it is different from the conventional curing reaction based on radically reactive functional groups. Compared to the case of , there is less curing shrinkage and excellent ability to maintain adhesion between the adhesive layer and the supporting base material.

Examples of Constituent Elements of the Invention The adhesive used in the present invention contains an acrylic polymer having an epoxy group as a component. The epoxy group may be within the molecular chain of the acrylic polymer,
It may be present on the side chain or terminal of a molecular chain, and there are no particular limitations on its form of existence or method of introduction.

Typical preparation methods for acrylic polymers having epoxy groups include acrylic acid ester, glycidyl methacrylate, 3,4-epoxycyclohexylmethyl-3
Epoxy group-containing copolymerizable monomers such as acryloyl-4'-hydroxycyclohexanecarboxylate are polymerized using known methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization using a radical polymerization initiator. A method of copolymerizing to obtain an acrylic polymer having an epoxy component in the molecular chain, or a method of preparing a polymer containing an acrylic acid ester as a raw monomer component in advance, and then adding and modifying it as appropriate by an addition reaction or a modification reaction. Examples include a method of introducing an epoxy group-containing compound to have an epoxy component in the side chain or terminal of the molecular chain. Monomer concentration during polymerization, type and amount of chain transfer agent added, polymerization temperature,
There are no particular limitations on the processing conditions such as the solvent, and they can be appropriately determined depending on the desired molecular weight of the polymer, etc.

There is no particular limitation on the content of epoxy groups in the acrylic polymer, and in general, from the viewpoint of the balance between tack and cohesive force in the resulting adhesive, one or more epoxy groups, especially acrylic acid ester units, are added to the acrylic polymer. 1-10 based on degree of polymerization? , ; is appropriate.

Note that, if necessary, an acrylic polymer copolymerized with a modifying monomer may be used.

The weight average molecular weight of the acrylic polymer is 1.00.
Generally 0 to 5,000.000, preferably 2.
000 to 3,000,000. A material having a low weight average molecular weight and fluidity at room temperature has the advantage that a pressure-sensitive adhesive that can be applied without a solvent can be prepared. In addition, if the fluidity is poor, it may be used as a solution type using an organic solvent or a type dispersed in water or the like as usual.

Examples of the acrylic ester used in the preparation of the acrylic polymer described above include n-propyl group, n-butyl group, n-amyl group, n-hexyl group, 2-ethylhexyl group, n-octyl group, Examples include esters such as acrylic acid and methacrylic acid, which usually have an alkyl group having 30 or less carbon atoms, represented by isooctyl group, n-nonyl group, isononyl group, n-decyl group, etc.

Typical examples of modifying monomers that may be used as necessary include acrylic acid, methacrylic acid, vinyl acetate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl acrylate, and acrylonitrile. The amount of the modifying monomer used is generally 30 parts by weight or less per 100 parts by weight of acrylic ester, but is not limited thereto.

The adhesive used in the present invention contains an onium salt compound. The appropriate amount is 0.2 to 20 parts by weight per 100 parts by weight of the acrylic polymer.
0.5 to 10 parts by weight are preferred. If the amount is less than 0.2 parts by weight, crosslinking will be insufficient, and if it exceeds 20 parts by weight, tackiness etc. will be poor, which is not preferable in terms of adhesive properties.

The onium salt compound to be used may be one that can cause a ring-opening reaction of the epoxy group by ultraviolet irradiation or heating. Typical examples include - formula, ArN2
"X-1RIS X % R21X (However, Ar
is an aryl group, R is an alkyl group or an aryl group, X″″
is B F4-1PF, -1A s F6-1SbF&-
, 5bC16-1HS 04-1C104- and the like. ), diazonium salts, sulfonium salts, iodonium salts, etc. can be mentioned, among which sulfonium salts are preferably used.

The adhesive used in the present invention may contain an epoxy group-functional crosslinking agent having one or more epoxy groups in the molecule, if necessary, in order to increase the crosslinking efficiency. The appropriate amount is 200 parts by weight or less per 100 parts by weight of the acrylic polymer. Examples of epoxy functional crosslinkers include vinylcyclohexene dioxide, limonene dioxide, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bis-(6-methyl-3,4- Examples include epoxycyclohexyl) adipate and ethylene glycol diglycidyl ether.

Furthermore, the adhesive used in the present invention may contain conventional acrylic polymers that do not contain epoxy groups, as well as tackifiers, softeners, antioxidants, fillers, pigments, extenders, etc., as necessary. It may also contain certain additives. Further, it may contain an adhesion improver typified by an isocyanate compound. The adhesion improver is used to improve the adhesion or adhesion to an adherend or supporting substrate.

In the method of the present invention, an adhesive comprising an acrylic polymer having an epoxy group and an onium salt compound is spread and attached to one or both sides of a supporting base material, and the formed adhesive layer is cured by ultraviolet irradiation or heating. It is processed to make adhesive members such as adhesive tapes and adhesive sheets. Adhesive tape is
For example, like a surface protection material, a supporting base material is attached to an adherend integrally with an adhesive layer. The adhesive sheet uses a supporting base material as a separator so that the adhesive layer can be easily peeled off from the supporting base material, so that the adhesive can be used as a sheet-like material.

When applying the adhesive to the supporting base material, even if solvent-free coating is possible, it may be used as a solution or dispersion in a medium consisting of a solvent, water, etc., if necessary.

In that case, drying treatment is performed after application, if necessary.

The amount of adhesive applied varies depending on the application, but in general, a solid content of 2 to 2000 g/rj is appropriate.

Supporting substrates include paper, plastic laminated paper, cloth, plastic laminated cloth, plastic film,
Generally, a thin sheet made of metal foil or the like with a thickness of 1 to 500 um, a foam sheet with a thickness of 10 μff1 to 10 cII, etc. are used. In addition, as a support base material (separator) for making the adhesive layer easy to peel off, one or both sides of the thin film is coated with a ml agent made of a silicone compound or a long-chain alkyl compound. Processed materials or thin sheets with poor adhesion to adhesives are used.

The adhesive layer can be cured by ultraviolet irradiation using an ultraviolet irradiation device such as a mercury lamp or a metal halide lamp. The amount of ultraviolet rays irradiated may be determined as appropriate depending on the desired adhesive properties such as the required adhesive strength to the adherend.

Curing of the adhesive layer by heating can be performed using an appropriate heating device such as a thermal oven, an infrared heater, a far-infrared heater, or a heating furnace. Heating conditions may be determined as appropriate depending on desired adhesive properties. -Generally 0 at 80-200℃
．． The heating conditions are 1 to 30 minutes.

Effects of the Invention According to the present invention, since an easily available epoxy group-containing acrylic polymer is cured by ultraviolet irradiation or heating in the presence of an onium salt compound, it can be cured in a short time without the need for oxygen control. It has excellent manufacturing efficiency because it can be processed and does not require long after-curing. In addition, the obtained adhesive member has a small amount of shrinkage upon curing, has excellent ability to maintain adhesion between the adhesive layer and the support base material, and has excellent tack and holding power.

Examples Reference Examples Using a four-eye flask equipped with a stirring blade, a thermometer, a cooling tube, and a gas introduction tube, under nitrogen atmosphere, 100 parts of 2-ethylhexyl acrylate (parts by weight, the same applies hereinafter), 3 parts of acrylic acid, and 3 parts of glycidyl methacrylate were dissolved in 106 parts of ethyl acetate in the presence of 0.6 parts of azobisisobutyronitrile.
After polymerization treatment was carried out under stirring for 8 hours while adjusting the internal temperature to 70° C. using 53 parts of ethyl acetate as a solvent to obtain a solution of an epoxy group-containing acrylic polymer. The epoxy group-containing acrylic polymer has a number average molecular weight of 48,000 and a weight average molecular weight of 380. based on polystyrene conversion determined by gel permeation chromatography.
It was 000.

Example 1 100 parts (solid content) of the epoxy group-containing acrylic polymer obtained in Reference Example was mixed with 2 parts of a sulfonium salt-based ultraviolet curing catalyst, and then applied onto a polyester film having a thickness of 38 mm. The coating amount was 40 g/d in terms of solid content. Next, the coated material was placed in a heating oven at 50°C for 10 minutes to evaporate and dry the ethyl acetate, and then the adhesive layer was cured by irradiating ultraviolet rays of 300 mJ/c- using a high-pressure mercury lamp. An adhesive tape was obtained.

Example 2 100 parts (solid content) of the epoxy group-containing acrylic polymer obtained in Reference Example was mixed with 2 parts of a sulfonium salt thermosetting catalyst, and then applied onto a polyester film having a thickness of 38 uIIl. The coating amount was 40 g/'d in terms of solid content. Next, the coated material was placed in a heating oven at 50° C. for 10 minutes to evaporate the ethyl acetate, and then placed in a heating oven at 100° C. for 2 minutes for curing treatment to obtain an adhesive tape.

Comparative Example 1 An adhesive tape was obtained in accordance with Example 1, except that an adhesive not containing a sulfonium salt ultraviolet curing catalyst was used.

Comparative Example 2 An adhesive tape was obtained according to Example 2, except that an adhesive containing diphenylmethane diisocyanate was used instead of the sulfonium salt-based thermosetting catalyst.

20IIIll1 from the adhesive tapes obtained in the evaluation test examples and comparative examples.
Pieces of the tape were cut out and subjected to the following tests. In addition,
The test was started within 2 hours after the curing process of the adhesive layer.

[Holding force 1 23℃, 65% R, H, lower, the tape piece is attached to a stainless steel plate (
After adhering it to SUS304) with a length of 15IIIll, it was pressed with a rubber roller weighing 2 kg back and forth once, and heated to 40°C.
After being left for 20 minutes, a load of 1 kg was applied to the free end of the tape piece and the tape piece was hung down, and the time until the tape piece peeled off was measured.

[Tack I PSTC-6 (, US Pressure 5ensit
ive TapeCount ii6), 2
3°C, 65% 11.11. Below, the rolling distance of the ball on the adhesive surface of the tape piece was measured.

The results are shown in the table. Note that the numerical value is the average value of 4 measured values.

From the table, it can be seen that the adhesive member of the present invention exhibits excellent initial tack and high holding power even after a short curing treatment.

Patent applicant: Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. When manufacturing an adhesive member in which an adhesive layer is provided on a supporting base material, an adhesive containing an acrylic polymer having an epoxy group and an onium salt compound as components is used, and this is applied to one or both sides of the supporting base material. 1. A method for producing an adhesive member, which comprises spreading the adhesive layer on the adhesive member and curing the formed adhesive layer by irradiating ultraviolet rays or heating.