JP2608743B2 - Adhesive structure of adhesive thin layer development - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive which is obtained by applying a thin layer of an acrylic pressure-sensitive adhesive to an adherend and then subjecting it to a heat-curing treatment, whereby the adhesive strength to the adherend is excellent. The present invention relates to a sticking structure of a thin agent spread.

Conventional technology and problems Conventionally, thin-layered products such as pressure-sensitive adhesive tapes and sheets using acrylic pressure-sensitive adhesives are used for packaging materials, masking materials, electrical insulation materials, surface protection materials, anticorrosion materials, bonding materials, etc. However, in the case of a thin layer of an acrylic pressure-sensitive adhesive, the balance between tack and cohesion controls the aging characteristics of the adhesive force. A method of adjusting the temperature has been adopted.

However, tack and cohesion are incompatible with each other because they are incompatible with each other. If priority is given to cohesion by increasing the degree of cross-linking, etc., there is a sufficient effective adhesive area for rough surfaces such as cardboard. Will not be formed, and if tack is prioritized by lowering the elastic modulus, etc., the effective adhesive area to the rough surface may increase, but the adhesive will soften and cause cohesive failure, The state is not maintained, and in any case, there is a peeling problem.

Means for Solving the Problems As a result of intensive studies to overcome the above-described problems, the present inventor uses a special adhesive and performs a cross-linking process by applying a heat treatment after adhering to an adherend. As a result, the present inventors have found that the object can be achieved, and have accomplished the present invention.

That is, the present invention provides a thin layer spread of an adhesive comprising an acrylic polymer having an epoxy group and a sulfonium salt, and a heat-curing treatment after adhering to an adherend. It is to provide a sticking structure.

Action As described above, by adopting a method in which a thin layer spread of an adhesive comprising an epoxy group-containing acrylic polymer blended with a sulfonium salt is heat-cured after the adherend is attached,
The intended purpose is achieved. Known curing treatment methods such as sulfur crosslinking, peroxide crosslinking, isocyanate crosslinking, metal ion crosslinking, and radiation crosslinking have problems in reaction controllability, pot life, reproducibility, or curing treatment properties, and in any case, You cannot get satisfactory results.
That is, for example, in the case of a crosslinking method based on a radical reaction of a (meth) acryloyl group, it is difficult to introduce a (meth) acryloyl group into a base polymer of an adhesive,
There is a problem in its cross-linking property. In the case of a cross-linking method based on a radical reaction in which a (meth) acrylate group is introduced, the adhesion to an adherend and a supporting substrate is significantly reduced due to shrinkage of the pressure-sensitive adhesive layer due to curing. There is a problem to do.

Exemplary components of the invention In the present invention, an acrylic polymer having an epoxy group is used. The epoxy group may be in the molecular chain, or may be in the side chain or terminal of the molecular chain, and there is no particular limitation on the form of the epoxy group and the method of introduction.

As a typical method for preparing the acrylic polymer, acrylic acid esters, glycidyl methacrylate and 3,
Epoxy group-containing copolymerizable monomers such as 4-epoxycyclohexylmethyl-3'-acryloyl-4'-hydroxycyclohexanecarboxylate are prepared by using a radical polymerization initiator or the like in a solution polymerization system, bulk polymerization system, emulsion polymerization system, Copolymerization by a known polymerization method such as a turbid polymerization method to prepare an acrylic polymer having an epoxy component in the molecular chain, or a polymer containing an acrylic acid ester as a main monomer component in advance and adding to this A method in which an appropriate epoxy group-containing compound is introduced by a reaction or a modification reaction to have an epoxy component at a side chain or a terminal of a molecular chain, or the like. Monomer concentration during polymerization,
There are no particular restrictions on the processing conditions such as the type and amount of the chain transfer agent, the polymerization temperature, and the solvent, and they can be appropriately determined according to the desired molecular weight of the polymer.

The content ratio of the epoxy group in the acrylic polymer is not particularly limited, and is generally one or more in the acrylic polymer from the viewpoint of the balance between tack and cohesive force in the obtained pressure-sensitive adhesive. A ratio of 1 to 10% is appropriate based on the degree of polymerization.

An acrylic polymer obtained by copolymerizing a modified monomer as necessary may be used.

The weight average molecular weight of the acrylic polymer is 1,000
~ 5,000,000 is common, preferably 2,000 ~ 3,000,00
It is 0. Those having a small weight average molecular weight and fluidity at room temperature have the advantage that a pressure-sensitive adhesive that can be applied without solvent can be prepared. In general, those having poor fluidity may be used as a solution type using an organic solvent or a type dispersed in water or the like.

The acrylic acid ester used for preparing the above-mentioned acrylic polymer includes, for example, n-propyl group, n-
A butyl group, n-amyl group, n-hexyl group, 2-ethylhexyl group, n-octyl group, isooctyl group, n-nonyl group, isononyl group, n-decyl group, etc. And esters having an alkyl group such as acrylic acid and methacrylic acid.

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

The pressure-sensitive adhesive in the present invention contains a sulfonium salt. The compounding amount is suitably from 0.2 to 20 parts by weight, preferably from 0.5 to 10 parts by weight, per 100 parts by weight of the acrylic polymer. If the amount is less than 0.2 parts by weight, crosslinking will be insufficient, and 2
If the amount is more than 0 parts by weight, tackiness and the like become poor, which is not preferable in terms of adhesive properties.

The sulfonium salt of the general formula: R ₃ S ⁺ X ^- (where
R is an alkyl group or an aryl group, X ^- is ^{_{BF 4 -, PF 6 -,}} AsF 6
^{_{-, SbF 6 -, SbCl 6}} -, HSO - a ₄ such anion ^- _4, ClO. ). When an onium salt-based compound other than a sulfonium salt, such as a diazonium salt or an iodonium salt, is used, the conventional curing treatment described in the above-described operation can be used to explain the adhesive strength and the like developed by making the pressure-sensitive adhesive thin layer porous by gas generation. Therefore, the object of the present invention is not achieved.

The pressure-sensitive adhesive used in the present invention may optionally contain an epoxy group-functional cross-linking agent having one or more epoxy groups in the molecule in order to increase the cross-linking efficiency. The compounding amount is suitably 200 parts by weight or less per 100 parts by weight of the acrylic polymer. Examples of epoxy-functional crosslinkers include vinylcyclohexenedionoxide, limonenedoxide, 3,4-epoxycyclohexylmethyl-3 ',
4'-epoxycyclohexanecarboxylate, bis- (6-methyl-3,4-epoxycyclohexyl) adipate, ethylene glycol diglycidyl ether and the like.

Further, the pressure-sensitive adhesive used in the present invention may be, if necessary, commonly used in addition to a known acrylic polymer containing no epoxy group, a tackifier, a softener, an antioxidant, a filler, a pigment, a filler, and the like. May be contained. Further, it may contain an adhesion improver represented by an isocyanate compound or the like. The adhesion improver is for improving the adhesion or adhesion to an adherend or a supporting substrate.

The thin layer spread of the pressure-sensitive adhesive in the present invention is, for example, a spread layer obtained by directly applying the pressure-sensitive adhesive to an adherend, a pressure-sensitive adhesive tape spread on one or both surfaces of a support substrate, or a sheet of a pressure-sensitive adhesive material. Such a pressure-sensitive adhesive sheet is used to develop the above-mentioned pressure-sensitive adhesive using a supporting base material or the like, if necessary, to form a thin layer.

Incidentally, the production of the pressure-sensitive adhesive tape can be carried out by applying the pressure-sensitive adhesive as it is (solvent-free coating) or, if necessary, a solution or dispersion in a medium comprising a solvent, water or the like to the supporting substrate. In the latter case, a drying treatment is performed after the application, if necessary. The drying treatment is preferably performed at a low temperature for a short time from the viewpoint that the curing reaction of the adhesive is not prevented. The amount of adhesive applied varies depending on the application, but is generally 2 to 2 in solid content.
2000 g / m ² is appropriate. Paper, plastic laminated paper, cloth, plastic laminated cloth,
A thin leaf composed of a plastic film, a metal foil or the like and having a thickness of usually 1 to 500 μm is generally used.

The production of the pressure-sensitive adhesive sheet can be carried out by using a separator such as a release paper instead of the support base material in the pressure-sensitive adhesive tape. That is, the separator can be easily peeled off from the surface of the pressure-sensitive adhesive so that the separator can be used as a sheet of the pressure-sensitive adhesive.

The adhesive structure of the present invention is obtained by applying a thin layer of an adhesive to an adherend, heating the adhesive, and curing the adhesive layer. The heat treatment may be performed using an appropriate heating device such as a heat oven, an infrared heater, or a heating furnace. Heating conditions are appropriately determined according to desired adhesive properties such as adhesive strength. Generally, the heating condition is 80 to 200 ° C. for 0.1 to 30 minutes.

Effect of the Invention The adhesive structure of the present invention has a large effective adhesive area because the adhesive is attached to the adherend in a state of an uncured material having a low elastic modulus and is subjected to a heat curing treatment. Together with appropriate cohesion and excellent adhesive strength.

Therefore, the present invention can be advantageously applied to a corrugated cardboard, a veneer plate, or an embossed plastic plate or the like having a significantly rough surface.

EXAMPLES Reference Example Using a four-necked flask equipped with a stirring blade, a thermometer, a cooling pipe, and a gas introduction pipe, under nitrogen replacement, 100 parts of 2-ethylhexyl acrylate (parts by weight, the same applies hereinafter), 3 parts of acrylic acid and 3 parts of glycidyl methacrylate was polymerized in the presence of 0.6 part of azobisisobutyronitrile using 106 parts of ethyl acetate as a solvent while stirring at an internal bath temperature of 60 ° C. for 4 hours and then at 70 ° C. for 3 hours. The solution was added to obtain an epoxy group-containing acrylic polymer solution. The epoxy group-containing acrylic polymer had a number average molecular weight of 51,000 and a weight average molecular weight of 420,000 based on polystyrene by gel permeation chromatography.

Example 1 After 100 parts (solid content) of the epoxy group-containing acrylic polymer obtained in Reference Example was mixed with 3 parts of a sulfonium salt-based thermosetting catalyst, this was applied on a 38 µm-thick polyester film. The coating amount is 40 g / m ² in solid content. The coating was then placed in a heating oven at 50 ° C. for 10 minutes to evaporate and dry the ethyl acetate.

20 less than the resulting adhesive tape as an adhesive thin layer spread
Cut out a piece of tape with a width of mm and put it on a commercially available cardboard board or a 180-mm sandpaper surface so that the apparent adhesion area is 20 mm (width) x 15 mm (length) and the free end protrudes about 50 mm. In the case of (1), a rubber roller weighing 0.5 kg was applied, and in the case of sandpaper, a rubber roller weighing 2 kg was reciprocated once and bonded by pressure.

The obtained bonded article was placed in a heating oven at 110 ° C. for 5 minutes and heat-cured to obtain a predetermined bonded structure.

Example 2 A curing treatment was carried out in the same manner as in Example 1 except that an adhesive was further added with 2 parts of 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate.
It had a predetermined bonding structure.

Comparative Example 1 An adhesive structure was formed in the same manner as in Example 1 except that a pressure-sensitive adhesive containing no sulfonium salt-based thermosetting catalyst was used, and thus no heat-curing treatment was performed.

Comparative Example 2 An adhesive structure was formed in the same manner as in Example 1, except that a tape piece that had been heat-cured before application was applied to an adherend instead of the method of applying heat-curing treatment after application. .

Comparative Example 3 An adhesive structure was formed in the same manner as in Comparative Example 2 except that the same tape piece as in Example 2 was used.

Evaluation Test The following test was performed on the adhesive thin layer developed product in the adhesive structure formed in each of Examples and Comparative Examples.

[Shearing adhesive strength] For a piece of tape stuck on sandpaper,
After allowing the tape to stand at 20 ° C. and 65% RH for 20 minutes, the shearing adhesive strength of the portion where the tape piece was adhered was measured using a shopper at a pulling speed of 300 mm / min.

[Holding power] This is applied to a piece of tape attached to a cardboard board.
After being left in a constant temperature bath at 40 ° C. for 20 minutes, a 1 kg load was applied to the free end of the tape piece, suspended vertically, and the time required for the tape piece to peel off from the cardboard board was measured.

The results are shown in the table. The numerical values are average values of four measured values.

From the table, it can be seen that the adhesive structure of the present invention exhibits excellent adhesive strength even on a rough surface and excellent holding power.

Claims (3)

(57) [Claims] An adhesive thin-layer spread obtained by applying a thin-layer spread of an adhesive containing an acrylic polymer having an epoxy group and a sulfonium salt to an adherend and then heat-curing it. Wearing structure. 2. An amount of 0.2 to 100 parts by weight of the acrylic polymer.
2. The adhesive structure according to claim 1, wherein the adhesive comprises 20 parts by weight of a sulfonium salt. 3. The adhesive structure according to claim 1, wherein an adhesive containing not more than 200 parts by weight of an epoxy group functional crosslinking agent per 100 parts by weight of the acrylic polymer is used.