JPH01263182A - Production of pressure-sensitive adhesive tape - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an acrylic pressure-sensitive adhesive tape having a multilayer adhesive layer with excellent shear resistance.

[Conventional technology]

Conventionally, pressure-sensitive adhesive tapes such as double-sided tapes have been required to have contradictory properties such as high wettability and adhesion to adherends, and high cohesive strength. Furthermore, if the adherends have different surface properties,
It is difficult for pressure-sensitive adhesives with the same composition to exhibit good adhesion properties for both wave-bound bodies.
It is often processed in a way that balances the characteristics between the two.

In order to improve these points, by creating a multilayer structure using two or more types of pressure-sensitive adhesives with different compositions, it is possible to improve adhesion and anchoring properties to different adherends and supports, and to By changing the composition and physical properties of the surface layer, which requires strong bonding with the adherent, and the inner layer, which requires high cohesive force,
There are attempts to control the characteristics.

For example, JP-A-54-139946 discloses a pressure-sensitive adhesive tape having a multilayered adhesive layer composed of two or more compositions having different shear creep compliances. It is said to be particularly useful for diaper tapes and cloth display labels where the adherend has an irregular surface and is subjected to various external stresses during use.

[Problems to be Solved by the Invention] However, in pressure-sensitive adhesive tapes in which the adhesive layer has a multilayer structure as described above, the bonding force between each layer is weak, and the layers may peel off due to external stress such as shear force. It has the disadvantage of being easy to use.

This is because the multilayer structure described above (which is simply a stack of film-like adhesive layers made by the 8-component Toyast method) allows for sufficient mixing, penetration, and bonding of molecules between each layer. It is presumed that this is because the eyebrows are held together only by comparatively weak forces such as <<, intermolecular force, and ionic bond force.

In view of the above-mentioned circumstances, the present invention provides the following features when forming an adhesive layer into a multilayer structure using two or more different pressure sensitive adhesives:
The object of the present invention is to provide a method for producing a pressure-sensitive adhesive tape that has strong bonding strength between layers and exhibits high resistance to shear stress.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the inventors included unreacted monomers in a polymer film for each layer to form a multilayer structure, and then deposited the unreacted monomers on a carrier. The inventors discovered that if the Japanese film roof tiles were polymerized while they were laminated and pressed together, the bonding strength between each layer could be greatly increased, and the present invention was completed.

That is, this invention provides an alkyl (meth)acrylic acid ester with an alkyl group having 2 to 14 carbon atoms on a carrier.
Partial polymerization of an acrylic monomer consisting of 0 to 100% by weight and 50 to 0% by weight of a vinyl monomer copolymerizable with this monomer has a monomer residual rate in the range of 1 to 60% by weight. At least two partial polymer films are laminated and pressed so that the monomer compositions of adjacent films are different from each other, and then the remaining monomers in each film are polymerized. This invention relates to a method for manufacturing a pressure-sensitive adhesive tape.

In this way, in this invention, a film-like partial polymer is obtained from two or more types of acrylic monomers, and these films are laminated and pressure-bonded on a carrier to sufficiently remove the residual monomer at the layer interface. The above-mentioned monomers are then polymerized (hereinafter, such polymerization on a carrier is referred to as in-situ polymerization) to create a multilayer structure that eliminates layer interfaces, so it is resistant to shear stress. It has a high resistance to and can be used against.

This is because each adhesive layer during lamination and pressure bonding is a partial polymer and some monomer remains, so monomers and even polymers easily mix and penetrate between each layer of tiles. In addition, since polymerization after lamination starts with the monomers in both layers mixed, the polymer produced is a copolymer of the components of both layers. This is thought to be due to the fact that the interfacial portion of the layers disappears and an IPN (interpenetrating polymer network) is formed.

In this specification, (meth)acrylic acid alkyl ester means acrylic acid alkyl ester and/or methacrylic acid alkyl ester.

[Structure and operation of the invention]

The acrylic monomer used in this invention is a (meth)acrylic acid alkyl ester in which the alkyl group has 2 to 14 carbon atoms, preferably 50 to 10% by weight, preferably 80 to 9
9% by weight and 50% by weight of a vinyl monomer capable of copolymerizing with this
-0% by weight, preferably 20-1% by weight.

(Meth)acrylic acid alkyl ester requires at least 50% by weight of all monomers in order to take advantage of the characteristics of acrylics such as weather resistance and heat resistance, and from the viewpoint of adhesive properties, Alkyno+; carbon number of JJ is 2
-15 is used. Specific examples thereof include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, ethyl methacrylate, butyl methacrylate, and lauryl methacrylate.

Vinyl monomers are used to improve adhesive properties and cohesive strength, and specific examples include ethylenically unsaturated vinyl monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. Carboxylic acids, divinylhenzene, trimena L-nolpropane triacrylate,
Polyfunctional monomers such as ethylene glycol diacrylate, as well as acrylonitrile, methacrylonitrile,
Examples include vinyl acetate, sunalene, and derivatives thereof.

As the acrylic monomer in this invention, the above (
One or more of the meth)acrylic acid alkyl esters may be used alone, or this and one or more of the above vinyl monomers may be used in combination at the above ratio. Good too.

In addition, known additives such as colorants, fillers, and tackifiers can be appropriately blended into such acrylic monomers as necessary. However, as these additives, it is necessary to select substances that do not inhibit the polymerization of the acrylic monomer.

In this invention, in order to obtain a partial polymer film using such an acrylic monomer, for example, a) a method in which the acrylic monomer is formed into a film on a carrier and then partially polymerized by in-situ polymerization; ) A method in which a part of the acrylic monomer is polymerized by a conventional method, and then mixed with the remaining monomer to form a partial polymer, which is then formed into a film on a carrier. What is necessary is to adopt a method of further in-situ polymerizing the partial polymer film obtained in 2 to obtain a predetermined monomer residual rate.

In these methods, to form a film of the monomer or partial polymer on the carrier, it is sufficient to use a conventional coating method. After coating, the solvent may be dried and evaporated.

The monomer residual rate in the partial polymer film thus obtained is 1 to 60% by weight, preferably 5 to 50% by weight.
It is necessary that it is set within the range of . If the monomer residual rate is less than 1% by weight, the above-mentioned mixing and penetration of molecules between each layer will be insufficient, and sufficient resistance to shear core force will not be obtained after complete polymerization. If it exceeds %, molecules will mix and permeate between each layer more than necessary, and after complete polymerization, the entire layer structure will be uniform, making it impossible to obtain the effect of a multilayer structure, and both are inappropriate.

In this invention, at least two of the above partial polymer films are prepared, and these films are laminated and pressure bonded together. When laminating and pressing three or more films, it goes without saying that after laminating and pressing two films, one side of the carrier is removed, and the process of laminating and pressing and removing the carrier is repeated to create three or more layers. It becomes possible to create multiple layers.

Here, it is important that adjacent partial polymer films have different monomer compositions from each other. This is because there is no particular significance in laminating two films having the same monomer composition to form a multilayer structure.

From this, when forming an adhesive layer with a two-layer structure, two types of polymer films having different monomer compositions are naturally used. On the other hand, for example, in the case of a three-layer adhesive layer, three types of films with different monomer compositions can be used, and two types of films, that is, only one of the three films can have a monomer composition. Films having different body compositions may be used, such that one type of film having a different composition is used for the middle layer, and two films of the other type are used for the upper and lower layers.

Note that the above-mentioned monomer compositions being different means that the types of acrylic monomers are different, or in the case of a monomer mixture, the mixing ratio thereof is different.

Lamination and pressure bonding of the above-mentioned partial polymer films is usually carried out at room temperature with a pressure of about finger pressure, but if necessary, it can be carried out at a temperature of up to about 60°C, or by applying a pressure higher than finger pressure using an appropriate pressure means. You can also do this in addition.

The partial polymer film laminated and pressure-bonded in this way is
By being directly subjected to in-situ polymerization on the carrier to completely polymerize the residual monomers in the film, a multilayer adhesive layer with a high interlayer bond strength and high resistance to shear stress is created. It is said to be an acrylic pressure-sensitive adhesive tape.

This tape has a multi-layered adhesive layer and each adjacent layer has a different monomer composition, so each layer can exhibit different adhesive properties. The layer can be made to have a large cohesive force, and the surface layer can be made to have a multipurpose function, such as having a large adhesive force or adhesive force.

In this invention, the polymerization methods used to obtain the above-mentioned partial polymer film and to completely polymerize this film include thermal polymerization, ultraviolet polymerization, electron beam polymerization, and the like.

To perform thermal polymerization, a known thermal polymerization initiator such as hendyl peroxide, lauroyl peroxide, ditertiary butyl peroxide, abbisisobutyronitrile, etc. is added to the acrylic monomer, and the mixture is What is necessary is just to heat it at a predetermined temperature for a predetermined time.

In order to carry out ultraviolet polymerization, a known photopolymerization initiator such as henzine, \enduine methyl ether, henduine ethyl ether, henzoin isopropyl ether, 2-methylanthraquinone, acetophenone is added to the acrylic monomer. , benzophenone, etc. are added to this mixture, and ultraviolet X14 with a wavelength of 200 to 450 r+m is applied to this mixture using a high-pressure mercury lamp, tungsten lamp, metal halide lamp, xenon lamp, etc.→! <(Just shoot.

To carry out electron beam polymerization, 0.0.
An electron beam having an irradiation dose of 1 to 50 Mrad may be irradiated.

The above polymerization methods can be selected and used in combination depending on the conditions such as partial polymerization, complete polymerization, and in-situ polymerization, but from the viewpoint of ease of polymerization control, ultraviolet polymerization It is preferable to use That is, in ultraviolet polymerization, by appropriately adjusting the amount of photopolymerization initiator added and the amount of ultraviolet ray irradiation, it is relatively easy to obtain a partial polymer film with a desired monomer residual rate, or It is possible to completely polymerize the polymer film.

〔Effect of the invention〕

As described above, according to the present invention, there is provided an acrylic pressure-sensitive adhesive tape that has a multilayered adhesive layer but is strongly bonded between layers and exhibits strong resistance against shear stress. can do.

〔Example〕

Examples of the present invention will be described below to explain it more specifically. In the following, % means % by weight, and parts means parts by weight. Further, the T-peel adhesive strength and shear retention strength were measured by the methods shown below.

Peel Adhesive Strength Cut the double-sided adhesive tape to 1Qam x 5Qmm, and bond the other ends of two aluminum plates measuring 15mm x 50mm to each other with the above adhesive tape. The other end of the aluminum plate is bent outward on both sides perpendicular to the adhesive tape to form a sample piece. This sample piece was stretched in a direction perpendicular to the adhesive tape at a speed of 1 lm/min, and the force required for peeling at this time was measured.

<Shear holding power> Cut a double-sided adhesive tape into a size of 1010 mm x 1 O, and attach the other ends of two aluminum plates to each other with this adhesive tape. One aluminum plate was fixed, a 500 g load was applied to the other aluminum plate in the horizontal direction of the adhesive tape, the plate was left in an atmosphere at 40°C, and the time until the aluminum plate fell was measured.

Example 1 A polymerization raw material consisting of 90 parts of n-bunal acrylate, 1 part of acrylic acid, and 0.5 part of benzphenone was irradiated with ultraviolet rays using a high-pressure mercury lamp to partially polymerize, and a plastic film was then mold-released. The film was coated to a coating thickness of 50 μm and further irradiated with ultraviolet rays to obtain a partial polymer film A having a monomer residual rate of 20%.

In addition, 100 parts of n-butyl acrylate, 0.2 parts of trimethylolpropane triacrylate, and 0 parts of hensifhenone.
．． A partial polymer film B with a coating thickness of 50 μm and a monomer residual rate of 40% was prepared in the same manner as above from a polymerization raw material consisting of 5 parts.
I got it.

After laminating and pressing the above partial polymer films A and B, this is irradiated with ultraviolet rays to completely polymerize the remaining monomers in each film, resulting in a double-sided adhesive with a two-layer adhesive layer. manufactured the tape.

Comparative Example 1 Using the same polymerization raw material as in Example 1, two types of polymer films with a coating thickness of 50 μrn that were completely polymerized from the beginning were obtained, and these were laminated and pressure-bonded to form a double-sided film with a two-layer adhesive layer. An adhesive tape was manufactured.

Comparative Example 2 A monomer mixture consisting of 90 parts of n-butyl acrylate and 10 parts of acrylic acid, and a monomer mixture consisting of 100 parts of n-butyl acrylate and 0.2 parts of trimethylolpropane triacrylate were separately prepared. , solution polymerization was carried out in toluene using azoisobutyronitrile as a polymerization initiator.

The obtained complete polymer was coated on a release-treated plastic film and dried to obtain two types of polymer films each having a coating thickness of 50 μm, which were laminated and pressed together to form a two-layer adhesive layer. A double-sided adhesive tape was manufactured.

Example 2 A polymerization raw material consisting of 95 parts of isodecyl acrylate, 5 parts of acrylic acid, and 0.2 parts of benzoin methyl ether was partially polymerized by irradiating it with ultraviolet rays using a metal halide lamp, and then it was placed on a plastic film that had been subjected to mold release treatment. Coating thickness 25
The film was coated so as to have a thickness of .mu.m, and further irradiated with ultraviolet rays to obtain a partial polymer film C with a monomer residual rate of 5%.

Further, from a polymerization raw material consisting of 85 parts of 2-ethylhexyl acrylate, 10 parts of vinyl acetate, 5 parts of acrylic acid, and 0.4 parts of benzoin isopropyl ether, a coating thickness of 250 μm and a monomer residual rate of 50% were prepared in the same manner as above. Partial polymer film D was obtained.

After the above partial polymer films C and D were laminated and pressure bonded, they were irradiated with ultraviolet rays to completely polymerize the remaining monomers, thereby producing a double-sided adhesive tape having a two-layered adhesive layer.

Comparative Example 3 Two types of polymer films with coating thicknesses of 25 μrn and 250 μm that were completely polymerized from the beginning were obtained using the same polymerization raw materials as in Example 2, and these were laminated and pressed together to form an adhesive layer with a two-layer structure. A double-sided adhesive tape was manufactured.

Comparative Example 4 Monomer mixture consisting of 95 parts of isodecyl acrylate, 5 parts of acrylic acid, and 8 parts of 2-ethylhexyl acrylate
A monomer mixture consisting of 5 parts of vinyl acetate, 10 parts of vinyl acetate, and 5 parts of acrylic acid was separately subjected to solution polymerization in ethyl acetate using benzoyl peroxide as a polymerization initiator.

The obtained completely polymerized product was coated on a release-treated plastic film and dried to give a coating thickness of 25 μm and 2 μm, respectively.
Two types of 50 μm polymer films were obtained and laminated and pressure-bonded to produce a double-sided adhesive tape having a two-layer adhesive layer.

The results of examining the T#Jiii adhesive strength and shear holding strength of the pressure sensitive adhesive tapes produced in Example 1.2 and Comparative Examples 1 to 4 above were as shown in the table below. In addition, when observing the peeled surface after measurement, it was found that both T-peel adhesive force and shear holding force were peeled at the interface between the adhesive layer and the aluminum plate in Example 1.2.
In Comparative Examples 1 to 4, the two-layer adhesive layer peeled off between the eyebrows.

was recognized.

As is clear from the above results, it can be seen that the pressure-sensitive adhesive tape having a multilayered adhesive layer obtained according to the present invention has significantly stronger resistance to stress in the shear direction.

Claims (1)

[Claims] (1) On the carrier, the alkyl group has 2 to 14 carbon atoms (
50-100% by weight of meth)acrylic acid alkyl ester
A partial polymer film having a monomer residual rate in the range of 1 to 60% by weight, obtained by partially polymerizing an acrylic monomer consisting of 50 to 0% by weight of a vinyl monomer copolymerizable with this. A method for producing a pressure-sensitive adhesive tape, which comprises laminating and press-bonding at least two adjacent films such that their monomer compositions differ from each other, and then polymerizing the remaining monomers in each film.