JPS60197736A - Bonding of porous thin-sheet material - Google Patents

Abstract

PURPOSE:To bond cellulose-based porous thin-sheet materials together firmly, without wrinkles, by glueing said materials together through a particular photoreactive adhesive in a sheet form and curing said adhesive by photo-irradiation. CONSTITUTION:In bonding two adherends comprising cellulose-based porous thin- sheet materials at least one of which has a mean transmittance of light in a range of wavelengths between 200 and 500nm of 10% or more, these adherends are glued together through a photocurable adhesive in a sheet form contg. a photoreactive compd. having one or more hydroxyl groups and one or more (meth)acryloyl groups, a base polymer, and a photosensitizer. Then, said adhesive is cured by photo-irradiation from the side of the thin-sheet material having said mean transmittance to bond the adherends together firmly. Photoreactive compds. to be used include hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adhering cellulose-based porous thin materials such as crepe paper, Japanese paper, paraffin paper, tray sink paper, and Krashin paper.

Conventionally, for adhering cellulose-based porous thin materials such as Japanese paper and glassine paper, we have used this solution-type adhesive that uses starch, polyvinyl alcohol, etc. as an adhesive base, or natural rubber, synthetic rubber, or polyvinyl acetate as an adhesive base. Water-based adhesives such as emulsion-type adhesives have been used. However, these water-based adhesives have drawbacks in that the thin sheet material swells and wrinkles during application and has poor water resistance.

Therefore, hot-melt adhesives and sheet-like adhesives that do not have these drawbacks have come to be used for bonding the above-mentioned thin materials. However, hot-melt adhesives have the disadvantage that their adhesive strength decreases at high temperatures, and sheet adhesives have low cohesive strength, so they tend to peel off when subjected to long-term stress.

In view of the above-mentioned state of the prior art, the inventors have discovered that it is possible to firmly bond a cellulose-based porous thin sheet material not only at room temperature but also at high temperatures, without causing wrinkles in the thin sheet material, and As a result of intensive research into adhesion methods that provide good water resistance, we found that
The inventors have discovered that the desired adhesion can be achieved by using a photocurable sheet-like adhesive having a specific composition, leading to the present invention.

In other words, this invention provides a method for reducing the number of
The average transmittance of light in the wavelength range of 00 nm is 10%.

In bonding two adherends which are the above cellulose-based porous thin leaf materials, these adherends are bonded using a photoreactive compound having at least one hydroxyl group and at least one (meth)acryloyl group in the molecule. After bonding via a photocurable sheet-like adhesive containing a base polymer and a photosensitizer, the adhesive is cured by irradiating light from the side of the porous thin sheet material having the above-mentioned average transmittance. The present invention relates to a method for bonding a porous thin material, which is characterized in that the above-mentioned adherend is firmly bonded to the adherend.

The above-mentioned photocurable sheet-like adhesive has fluidity before being irradiated with light and has adhesive strength comparable to that of ordinary pressure-sensitive adhesives, so at least one of them has the above-mentioned light-transmitting properties. Temporary adhesion of two adherends made of a thin, porous cellulose material can be achieved by pressing the adhesive between the two adherends through the adhesive. Since this adhesive is not water-based, it does not cause wrinkles in the thin sheet material.

After this temporary adhesion, if light is irradiated from the side of the thin sheet material, the adhesive hardens and loses its initial fluidity, forming a cured material layer that firmly adheres to the two adherends. For this reason, these adherends are firmly adhered, and the adhesive strength does not decrease even at high temperatures and does not decrease due to moisture.

The two adherends to which the method of the present invention is applied include crepe paper, Japanese paper, tracing paper, glassine paper, and at least one of which has an average transmittance of 10% or more for light in the wavelength range of 200 to 500 nm. It is a cellulose-based porous thin material such as paraffin paper. The average transmittance above is 0% per month
If it is less than this, the photocurable sheet-like adhesive will not be sufficiently cured by light irradiation, making it impossible to firmly bond two adherends together, and the adhesive strength will decrease at high temperatures, which is not preferable.

As long as one of the above two adherends is the thin sheet material mentioned above, the material and shape of the other one are not particularly limited and various materials can be used depending on the purpose, but cellulose materials and glass are preferred. , plastic, metal, etc.

The photocurable sheet-like adhesive used in the method of this invention has at least one, preferably two to three, hydroxyl groups and at least one, preferably two or more (meth)acryloyl groups in the molecule. It contains a chemical compound, a base polymer, and a photosensitizer as essential components.

The hydroxyl group in the above-mentioned photoreactive compound has a function of increasing the adhesive strength of the photocurable sheet-like adhesive to the cellulose-based porous thin sheet material before and after light irradiation. Although the reason for this is not clear, it is thought to be as follows.

In other words, cellulose is a polymer in which D-glucose is linearly linked through β-1.4 bonds, and each glucose unit has three hydroxyl groups, so it is highly hydrophilic. For this reason,
When the adhesive contains a hydroxyl group, the adhesive has good affinity with the above-mentioned thin sheet material, and the hydroxyl group in the cellulose and the hydroxyl group on the adhesive form a hydrogen bond, making the adhesive and the thin sheet material stronger. Can be glued.

Specific examples of the above-mentioned photoreactive compounds include hydroxybutyl (meth)acrylate, hydroxy to 1xyl (
meth)acrylate, hydroxyneopentyl (meth)
acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxyprobyl(meth)acrylate, pentaerythritol triacrylate and the following formula; In formula 1, R1 is H or CH3, R2 is C2H4, CH
2CH (CH3) Mataha CH (CH3) CH20-G-
C(CH3)2-G-OCH2CH(CH3).

] Examples include compounds represented by
One species or two or more species may be used. The (meth)acryloyl group in these photoreactive compounds is activated by light irradiation to perform a photopolymerization reaction.

Next, the above base polymers include alkyl (meth)acrylates in which the alkyl group has several carbon atoms to 12 carbon atoms, vinyl alkyl esters in which the alkyl group has carbon atoms in the range from 1 to 12 carbon atoms, and alkyl groups in which the carbon atoms in the alkyl group have 1 to 12 carbon atoms. Examples include polymers obtained by polymerizing one or more monomers having an ethylenic double bond, such as vinyl alkyl ether, dimethylaminoethyl (meth)acrylate, (meth)acrylonitrile, and vinylpyridine. .

Preferably, a copolymer obtained by copolymerizing these monomers with a copolymerizable monomer having a functional group such as a carboxyl group, a hydroxyl group, a glycidyl group, an amide group, or a phosphoric acid group is used. Good. Copolymerizable monomers having this functional group include (meth)acrylic acid, maleic acid, itaconic acid, crotonic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl methacrylate, (,meth)acrylamide, N-methylol(meth)acrylamide, acryloyloxyethyl phosphate, etc., and one or more of these are added to 100 parts by weight of the above monomer having an ethylenic double bond. Generally, it may be used in a proportion of 15 parts by weight or less.

It is advantageous to use a copolymer obtained by using a copolymerizable monomer having these functional groups as a base polymer because it improves the compatibility of the photocurable sheet-like adhesive with the cellulose-based porous thin sheet material.

To obtain a polymer using the above monomers, polymerization may be performed by various known polymerization methods such as emulsion polymerization, solution polymerization, and bulk polymerization, and the average molecular weight of the resulting polymer is is preferably about 10,000 or more.

The base polymer is a component that gives the photocurable sheet-like adhesive the desired tackiness before and after irradiation, and a photoreactive carbon-carbon double bond is introduced into this base polymer. By doing so, it is possible to further improve the photocuring properties of this pressure-sensitive adhesive. As a means for this, for example, a polymerizable carbon-based polymer having a functional group such as a carboxyl group, a hydroxyl group, or a glycidyl group present in the above-mentioned polymer has a group that can react directly or indirectly with these functional groups.
A photoreactive monomer containing a carbon double bond may be reacted. Examples of such photoreactive monomers include monomers that react with hydroxyl groups such as (meth)acrylic acid chloride, (meth)acrylic acid bromide, N-methylolacrylamide, N-butoxymethylacrylamide, etc. Glycidyl (meth)acrylate and the like are examples of monomers that can react with groups and hydroxyl groups.

Another method for introducing photoreactive polymerizable carbon-carbon double bonds into the base polymer is to use a monomer having two or more (meth)acryloyl groups as a copolymerizable monomer when obtaining the polymer. Examples of this monomer include polyethylene glycol di(meth)acrylate and pentaerythritol tri(meth)acrylate.

Next, the above-mentioned photosensitizer is not particularly limited as long as it promotes the photopolymerization reaction of the above-mentioned photoreactive compound, but examples include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, Contains benzoins such as α-methylbenzoin, anthraquinones such as 1-chloroanthraquinone and 2-chloroanthraquinone, benzophenones such as benzophenone, p-chlorobenzophenone, and p-dimethylaminobenzophenone, diphenyl disulfide, and tetramethylthiuram disulfide. Examples include sulfur compounds.

The blending ratio of these essential components in the photocurable sheet-like adhesive is usually 10 to 300 parts by weight, preferably 20 to 200 parts by weight, of the photoreactive compound to 100 parts by weight of the base polymer, and 20 to 200 parts by weight of the photosensitive compound. It is recommended that the amount of the adhesive be 0.05 to 30 parts by weight. If the amount of the photoreactive compound is too small, the adhesive will not be cured sufficiently by light irradiation, making it difficult to firmly adhere the adherend. It is not preferable because it cannot be used and the adhesive force decreases at high temperatures. On the other hand, if this amount is too large, the cured product formed by light irradiation becomes too hard and sufficient adhesive strength cannot be obtained, which is not preferable. In addition, if the amount of the photosensitizer is too small, the effect of promoting the photopolymerization reaction will be insufficient, and the adhesive will be likely to be insufficiently cured by light irradiation, while if it is too large, the promoting effect will not be increased any further, making it less economical. It is also disadvantageous.

The photocurable sheet-like adhesive has each of the above components as essential components, but in addition to these components, there are other ingredients that can be used, such as increasing the adhesive properties of the adhesive before irradiation with light and further increasing the water resistance of the cured product after irradiation with light. Therefore, a compound having a (meth)acryloyl group in the molecule may be blended. This compound is
For example, 1,4-butylcatechol di(meth)acrylate, 1,6-hexanegelicoldi(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate Examples include acrylate, urethane-modified acrylate, and oligoester acrylate.

In addition, in order to prevent the above-mentioned photoreactive compounds from thermally polymerizing during storage of this adhesive, for example, hydroquinone, hydroquinone 7-methyl ether, tert-butylcatechol, p-benzoquinone, 2,5-tert-butylhydroquinone, phenothiazine, etc. A thermal polymerization inhibitor such as 5 to 1.00 lppm can be added to the photoreactive compound.

A photocurable sheet-like adhesive having such a composition is usually obtained by applying an organic solvent solution or emulsion containing each of the above components onto a release-treated release paper and drying it. The thickness of the agent is usually 5 to 3
It is preferable to set it to about 00μ. In addition, in order to increase the mechanical strength of this adhesive sheet, a base material such as a woven or non-woven fabric such as rayon or nylon may be interposed as an intermediate layer in this adhesive. usually 5
The thickness may be ~300μ.

In the method of the present invention, the above-mentioned photocurable sheet-like adhesive is coated with two covers, at least one of which is a cellulose-based porous thin sheet material having an average transmittance of 10% or more for light in the wavelength range of 200 to 500 nm. These adherends are crimped and bonded together by applying a pressure of usually about 5 to 50 kg/cI/I between the adherends, and then light is irradiated from the side of the thin sheet material having the above-mentioned average transmittance. The above adhesive is cured.

During this bonding, wrinkles do not occur in the thin sheet material before and after irradiation with light.

As a light source used for light irradiation, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a carbon arc lamp, a xenon lamp, etc. may be used, and the light irradiation time is usually 0.3 seconds or more, preferably 3 seconds or more.

Due to the above light irradiation, a cured product is formed between the two adherends that adheres well to the adherends, resulting in strong adhesion between the adherends and even under high temperatures. This adhesive strength does not decrease and water resistance is also good.

Examples of this invention will be described below. In addition, in the following, parts mean parts by weight.

Example 1 90 parts of 2-ethylhexyl acrylate 7 parts of 2-hydroxyethyl acrylate 3 parts of alylic acid 0.1 part of benzoyl peroxide 200 parts of ethyl acetate The mixture of each of the above components was charged into 11 flasks. , the temperature of the reaction system was increased to 65°C while stirring while introducing nitrogen into the system.
After polymerizing for about 15 hours while maintaining the temperature at 80 DEG C., the temperature of the reaction system was raised to 80 DEG C. and maintained for 2 hours to completely polymerize the remaining upper layer. This results in a weight average molecular weight of 5.8×105
A polymerization product containing an acrylic copolymer (according to GPc) was obtained.

To this polymerization product, 6 parts of pentaerythritol triacrylate (1 part of benzyl dimethyl ketal, 5 parts of hydroquinone monomethyl ether, 0.005 parts of hydroquinone monomethyl ether) were added to 100 parts of the solid content and mixed uniformly to obtain an adhesive solution. This solution was applied onto release paper that had been subjected to release treatment so that the thickness after drying was 50 mm.
/'I and dried at 100° C. for 3 minutes to obtain a photocurable sheet-like adhesive.

Spread this adhesive on two sheets of glassine paper (thickness: 2Q Q, i
s.

Average transmittance of light in the wavelength range of 200-500 nm; 1
5%) at a pressure of 20 kg/cJ, then a high-pressure mercury lamp (80 W) was placed on one glassine paper side.
>> ) was irradiated with light for 5 seconds from a distance of 10 mm to cure the adhesive and firmly adhere the two sheets of glassine paper.

There were no wrinkles in the two sheets of glassine paper that were glued together.

Example 2 85 parts of n-butyl acrylate 10 parts of 2-hydroxyethyl acrylate 5 parts of methoxylic acid 0.2 parts of ammonium persulfate After charging the flask and purging it with nitrogen for about 30 minutes while stirring, it was polymerized for 2 hours under heating at 65°C. After the polymerization was completed, the reaction system was heated to 75°C and aged for 1 hour, and the average particle size was 0. An acrylic copolymer emulsion with a pH of about 3 was obtained. The weight average molecular weight of this acrylic copolymer is 8.0×10 (GP
According to C).

Next, while stirring this emulsion, 10 parts of trimethylolpropane triacrylate, 5 parts of benzoin isobutyl ether, 0.005 parts of hydroquinone, and 100 parts of ion-exchanged water are added to 100 parts of the solid acrylic copolymer. An adhesive emulsion was obtained.

A photocurable sheet-like adhesive was obtained using this emulsion in the same manner as in Example 1, and two sheets of glassine paper were bonded together using this adhesive in the same manner as in Example 1. There were no wrinkles in the two sheets of glassine paper that were glued together.

Example 3 To the polymerization product in Example 1, 3 parts of acrylic acid chloride and 3.3 parts of triethylamine were added to 100 parts of the solid content of the acrylic copolymer, and the mixture was reacted at 5° C. for 2 hours. Acryloyl groups were introduced into this copolymer. After thoroughly washing this reaction product with water, its solid content 1
Each component described in Example 1 was added to 00 parts and mixed uniformly to obtain an adhesive solution. A photocurable sheet-like adhesive was obtained using this solution in the same manner as in Example 1, and two sheets of glassine paper were bonded together using this adhesive in the same manner as in Example 1. There were no wrinkles in the two sheets of glassine paper that were glued together.

Example 4 Using the photocurable sheet adhesive obtained in Example 1,
Sheet of crepe paper (thickness: 1oolDn12oo~500
The average transmittance of light in the nm wavelength range; 3Q%) was adhered in the same manner as in Example 1. There were no wrinkles in the two pieces of crepe paper that were glued together.

Comparative Example 1 The polymerization product in Example 1 was added to 100 parts of the solid content of the acrylic copolymer.

60 parts of trimethylolpropane triacrylate, 5 parts of benzyl dimethyl ketal, and 0.005 parts of hydroquinone monomethyl ether were blended and mixed uniformly to obtain an adhesive solution. Using this solution, a photocurable sheet-like adhesive was obtained in the same manner as in Example 1,
Using this adhesive, two sheets of glassine paper were adhered in the same manner as in Example 1. There were no wrinkles in the two sheets of glassine paper that were glued together.

Comparative Example 2 A 1=3 (molar ratio) adduct of trimethylolpropane and tolylene diisocyanate was added to the polymerization product in Example 1 based on 100 parts of the solid content of the acrylic copolymer.
The components were blended and mixed uniformly to obtain an adhesive solution. A photocurable sheet-like adhesive was obtained using this solution in the same manner as in Example 1, and two sheets of glassine paper were bonded together using this adhesive in the same manner as in Example 1. There were no wrinkles in the two sheets of glassine paper that were glued together.

Comparative Example 3 Two sheets of crepe paper (the same as in Example 4) were adhered in the same manner as in Example 1 using the photocurable sheet-like adhesive obtained in Comparative Example 1. There were no wrinkles in the two pieces of crepe paper that were glued together.

The adhesive properties of the adhesives obtained in the above Examples and Comparative Examples were investigated as follows. The results are shown in the table below.

T-Peel Adhesive Strength: The adhesive was cut into 25mm width pieces, the adherend at one end of the adhesive was peeled off at a constant temperature, and the adhesive strength was measured when the two adherends were pulled from side to side.

Misaligned crepe; the bonded area between the two adherends is 10 mm wide;
The length 2ON1 was further cut so that the unbonded parts were 30 pieces each, one side of the adhesive was fixed to a Bakelite plate, and the Bakelite plate was further fixed and a load of 500y was applied to the other end at a constant temperature. The distance of deviation was measured.

(The crepe paper was torn.) Also, the adhesives obtained in Examples 1 to 4 were heated to 95% at 40°C.
After being left in an RH atmosphere for 48 hours, the above T-peel adhesive strength was measured at 20°C and 80°C, and the same results as in the table above were obtained.

As is clear from the above results, the method of the present invention can bond thin cellulose-based materials without causing wrinkles, firmly at room temperature as well as at high temperatures, and with good water resistance. I understand.

Patent applicant: Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] When bonding two adherends, at least one of which is a cellulose-based porous thin film material with an average transmittance of light in the wavelength range of 200 to 500 nm of 10% or more, these adherends are (Both are bonded together via a photocurable sheet adhesive containing a photoreactive compound having one hydroxyl group and at least one (meth)acryloyl group, a base polymer, and a photosensitizer, and then A method for adhering a porous thin sheet material, characterized in that the adhesive is cured by irradiating light from the side of the porous thin sheet material having an average transmittance to firmly adhere the adherend.