JPH0798925B2 - Radiation curable pressure sensitive adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to pressure-sensitive adhesive tapes, and particularly to a pressure-sensitive adhesive composition used for a surface protective film of a glass plate or a metal plate.

[Conventional technology]

Conventionally, the pressure-sensitive adhesive film has been produced by applying a pressure-sensitive adhesive obtained by dissolving a high-molecular polymer such as natural rubber or synthetic rubber in an organic solvent onto a support such as a plastic film and drying it. However, in recent years, solvent-free adhesives have been studied from the viewpoints of resource saving, energy saving, and pollution-free. Radiation-curable adhesives that use liquid oligomers are one of the measures to eliminate solvent. Such an adhesive is one in which a liquid oligomer having a relatively low molecular weight is coated on a support to have a high molecular weight on the support by irradiating with ionizing radiation.

It is already known that a polybutadiene oligomer obtained by polymerizing butadiene to a low degree can be used as such a liquid oligomer.

Polybutadiene oligomers include 1.4-bond type and 1.2-
There is a combined type, but the viscosity is usually low and 1.4 is convenient for handling.
-A combined type is used. (Japanese Patent Publication No. 56-53596, 5)
6-53597) Japanese Patent Publication No. 49-48190 discloses a resin having a high glass transition temperature as a 1.2-bonding polybutadiene oligomer.

However, when a polybutadiene oligomer (hereinafter referred to as polybutadiene) having a 1.4-bond structure is used, the glass transition temperature is too low, so that the adhesive properties such as high-speed peelability and high-temperature adhesiveness required for the surface protection film are particularly high. I can't give it. The 1.2-bond type polybutadiene has a molecular weight (3,000 or more) of an oligomer usually used and its viscosity is too high, so that the work such as coating is difficult. It also has a low molecular weight and low viscosity.
The use of 2-engaging type polybutadiene has drawbacks such as not having desired adhesive properties and poor water resistance, light resistance and heat resistance.

Therefore, the present inventors previously proposed Japanese Patent Application No. 62-30088,
A composition was proposed in which a thiol compound was added to a modified polybutadiene or a modified polybutadiene copolymer having an unsaturated double bond at the end of the molecule.

[Problems to be Solved by the Invention]

However, when an adhesive film of the above composition is produced, it has drawbacks such as lack of flexibility and low adhesive strength per coating thickness.

The present invention has been made in view of such a situation, and has good adhesive properties such as high-speed peelability and high-temperature adhesiveness and a relatively low viscosity, and is excellent in water resistance, light resistance, and heat resistance per coating thickness. It is an object of the present invention to provide a radiation-curable pressure-sensitive adhesive having high adhesive strength.

[Means for Solving the Problems]

This object is achieved by the combination of the modified polybutadiene specified according to the invention and a thiol compound.

That is, the present invention consists of 90% or more of 1.2-bond structure, the main chain or side chain vinyl double bond is hydrogenated, and the number average molecular weight of introducing an unsaturated double bond at the terminal is 500 to 5000. Which is a modified polybutadiene or a modified polybutadiene copolymer having a terminal unsaturated double bond
20 to 60% is an electron-withdrawing substituent group, and 80 to 40% is an electron-donating substitution rate. 100 parts by weight of the modified polybutadiene or modified polybutadiene copolymer has two or more mercapto groups in one molecule. 0.2 to 20 thiol compounds
The present invention relates to a radiation-curable pressure-sensitive adhesive composition characterized by being mixed in parts by weight. As a preferred embodiment of the present invention, (i) a modified polybutadiene in which 95% or more of the main chain or side chain vinyl double bonds are hydrogenated (ii) introduction of terminal unsaturated double bonds It is preferable that there is one or more molecules in one molecule on average.

The present invention will be described in detail below.

The modified polybutadiene or modified polybutadiene copolymer used in the present invention is obtained by hydrogenating vinylic double bonds in the main chain and side chains and introducing unsaturated double bonds at both ends of the molecule.

The raw material polybutadiene or polybutadiene copolymer has the following general formula [1] [1] In the formula, R ¹ and R ² each represent a hydrogen atom, a hydrocarbon group such as an alkyl group, a cycloalkyl group, an aryl group or an aryl group, or a substituent such as a halogen atom. Here, R ¹ is preferably a hydrogen atom C _{1 to} C ₁₀ alkyl group, a chlorine atom or the like, particularly preferably a hydrogen atom, a methyl group or a chlorine atom, and R ² is a hydrogen atom or a methyl group. Preferred are hydrogen atoms and the like. ) 1,4-cis polymerization, 1,4-trans polymerization, etc., of one or more selected from the butadienes
-Polymerization, 1,2-polymerization, 3,4-polymerization, or a butadiene polymer obtained by homopolymerization or copolymerization by various polymerization modes by any combination thereof, or by the above formula [1]. A so-called butadiene polymer or a butadiene copolymer such as a butadiene copolymer obtained by copolymerizing one or more kinds of the butadienes represented and a small amount of olefins by various polymerization modes. It has a polymer skeleton.

In general, anion living polymerization is preferable because it contains 90% or more of 1.2-bond structure.

Here, specific examples of the butadiene polymers serving as the skeleton or the matrix of the polybutadienes are not limited, and for the purpose of illustration, for example, 1,2-polybutadiene, 1,4
-Cis-polybutadiene, 1,4-trans-polybutadiene, polyisoprene, poly-2-ethyl-1,3-butadiene, poly-2,3-dimethyl-1,3-butadiene, poly-2-propyl-1, 3-butadiene, poly-2-isopropyl-1,3 butadiene, poly-2-butyl-1,3-butadiene, poly-2-isobutyl-1,3-butadiene, poly-2-tert-butyl-1,3 -Butadiene, poly-
2-pentyl-1,3-butadiene, poly-2-isohexyl-1,3-butadiene, poly-2-cyclohexyl-
1,3-butadiene, poly-2-n-heptyl-1,3-butadiene, poly-2-n-decyl-1,3-butadiene, poly-2-isodecyl-1,3-butadiene, polychloroprene, poly Polybutadiene or substituted butadiene polymer such as -2,3-dichloro-1,3-butadiene; Polybutadiene or butadiene having two or more structural units selected from repeating structural units constituting these polybutadiene or substituted butadiene polymer Examples thereof include copolymers. Among these, polybutadiene having a 1,2-polybutadiene polymer as a skeleton structure is particularly preferable.

In addition, the introduction rate of unsaturated double bonds introduced at both ends of the molecule is preferably 1 or more in one molecule on average, and if it is 1 or less, the curability becomes poor.

The hydrogenation rate of polybutadiene or polybutadiene copolymer is preferably 70% or more of the vinyl groups contained.
95% or more. If the hydrogenation rate is less than 70%, the adhesive strength will change significantly over time, making it brittle.

Further, the number average molecular weight of the polybutadiene used in the present invention is
If it is less than 500, it lacks flexibility as an adhesive, and the adhesive strength per coating thickness is small. If it is more than 5000, the viscosity becomes too high and it is difficult to make it solvent-free.

The terminal unsaturated double bond, which is a feature of the present invention, will be described in detail. That is, the unsaturated double bond is composed of two types, an electron-withdrawing substituent and an electron-donating substituent.

The mixing ratio of the electron-withdrawing substituent is 20 to 60% and the electron-donating substituent is 80 to 40%.

Here, the unsaturated double bond having an electron-withdrawing substituent is, for example, an acryloyl or methacryloyl group. As the unsaturated double bond having an electron donating substituent,
Examples thereof include an allyl ether group, an allyl thioether group, a vinyl ether group and a vinyl thioether group.

Next, a method for introducing the above-mentioned two types of unsaturated double bonds will be specifically shown.

That is, vinyl of the main chain and side chain of polybutadiene or a copolymer thereof having active hydrogen such as hydroxyl group, carboxyl group, amino group, etc. at both ends of the molecule (these can be commercially available). 0.5 equivalent or more, preferably 0.6 to 1.0 equivalent, as an isocyanate group of the isocyanate compound having the unsaturated heavy bond in the molecule, relative to 1 equivalent of active hydrogen of the intermediate obtained by hydrogenating the organic double bond. It can be introduced after the reaction.

Examples of the isocyanate compound having an unsaturated double bond in the molecule include those having an unsaturated double bond and an isocyanate group directly bonded to the main chain or ring constituting the compound, and those having an isocyanate group A compound having a saturated double bond also includes a product obtained by chemically bonding it through an appropriate functional group. In general, the latter has a different kind, and a compound suitable for the purpose is obtained. be able to. In the above, the number of unsaturated double bonds and isocyanate groups per molecule is not particularly limited, but it is generally preferable that each of them be present at 1 to 2.

Preferred examples of the compound having an unsaturated double bond and an isocyanate group directly bonded to the main chain or ring include acryloyl isocyanate, vinyl isocyanate, vinylphenyl isocyanate, vinylphenyl diisocyanate, allyl isocyanate, and 2-butene-1. 4-diisocyanate, trans-vinylene diisocyanate and the like are included.

As a product obtained by chemically bonding a compound having an unsaturated double bond with a compound having an isocyanate group through an appropriate functional group, for example, a polyisocyanate compound having an unsaturated double bond and active hydrogen Both of the functional groups, obtained by reacting with a compound having in the molecule, the polyisocyanate compound used in the reaction, ethylene diisocyanate, ethylidine diisocyanate, propylene diisocyanate, lower aliphatic such as butylene diisocyanate Alicyclic polyisocyanates such as polyisocyanates, cyclopentylene diisocyanate and cyclohexylene diisocyanate, 2,4-tolylene diisocyanate, 2.6
-Tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, p- or m-phenylenediisocyanate , Naphthylene diisocyanate, pyrene diisocyanate, chrysene diisocyanate, nitrodiphenyl diisocyanate, 1-
Aromatic polyisocyanates such as methylbenzene-2,4,6-triisocyanate and mixtures thereof are included, and as a compound having both an unsaturated double bond and a functional group having active hydrogen in the molecule, Allyl alcohol, methallyl alcohol, cinnamic alcohol, ethylene glycol monovinyl ether vinylphenyl methacrylic acid, cinnamic acid, crotonic acid, maleic acid monoester, fumaric acid monoester, paravinyl benzoic acid, acrylamide, methacrylamide, maleic anhydride amide, 2 -Acrylic acid esters such as aminoethyl vinyl ether, vinylaniline, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, hydroxyputyl acrylate, 2-carboxypropyl acrylate, 2- Mino ethyl acrylamide, 2-
Aminopropyl acrylamide, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, hydroxyputyl methacrylate, 2-carboxypropyl methacrylate, 2-aminoethyl methacrylamide, 2-aminopropyl methacrylamide, etc. are used. A compound having an electron-withdrawing substituent such as 2-hydroxyethyl acrylate or 2-hydropropyl methacrylate alone or a mixture of two or more kinds of these compounds, and an electron-donating substituent such as allyl alcohol ethylene glycol monovinyl ether. The compound having the above or a mixture of two or more kinds of these compounds can be blended and used in the above ratio.

In the above, the reaction of the compound having an isocyanate group with the compound having both a functional group having active hydrogen and an unsaturated double bond, the isocyanate group per active hydrogen equivalent of 1.1 equivalents or more, preferably 1.5 to 2.5 equivalents It is carried out by mixing both so as to react and reacting at 50 to 100 ° C. for 0.5 to 6 hours.

The modified polybutadiene or modified polybutadiene copolymer according to the present invention comprises a polybutadiene intermediate obtained by hydrogenating the main chain and side chain vinylic double bonds having the above active hydrogen, and an isocyanate compound containing an unsaturated double bond. Isocyanate groups are mixed in an amount of 0.4 to 1.2 equivalents per 1 equivalent of active hydrogen of the polybutadiene intermediate,
It is manufactured by reacting at 0 ° C for 0.5 to 6 hours.

Examples of the thiol compound having two or more mercapto groups in one molecule used in the present invention include 1,4-butanediol dithiopropionate, 1,6-hexanediol dithiopropionate and ethylene glycol dithioglycolate. , Trimethylolpropane tris- (thioglycolate) trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakis-
(Thioglycolate), pentaerythritol tekirakis- (β-thiopropionate) and the like. These may be used alone or in combination of two or more.

These thiol compounds are added for the purpose of suppressing excessive crosslinking at the time of radiation curing, and as a result, adhesiveness and the like are dramatically improved. It is necessary to select the addition amount in the range of 0.2 to 20 parts by weight, more preferably 2 to 15 parts by weight. If this amount is less than 0.2 parts by weight, the effect of suppressing crosslinking will be insufficient, and if it exceeds 20 parts by weight, the cohesive force will be insufficient due to insufficient curing, and the adhesive properties will be adversely affected.

Radiation in the present invention is an active energy ray, such as α ray and β
Rays, γ rays, neutron rays, accelerating electron rays and other ionizing radiation, as well as ultraviolet rays, the dose of ionizing radiation is 0.5 to 50 Mra
It can be used in the range of d, but 1 to 10 Mrad is preferable.
In the case of ultraviolet rays, a high-pressure mercury lamp or the like is suitable as a generation source in the wavelength range of about 180 to 460 nm.

When irradiating, it is the irradiation atmosphere that requires attention. That is, the generated radicals are polymerized and inhibited by oxygen in the air, so that it is necessary to use an inert gas such as nitrogen to obtain an appropriate oxygen concentration in some cases.

If necessary, the resin composition according to the present invention may contain additives such as a diluent, a crosslinkable monomer, a plasticizer, a tackifier, an antioxidant, and a thermal polymerization inhibitor.

Since the obtained adhesive composition has a low viscosity, it is crosslinked by being irradiated with radiation after being applied to a support such as a plastic film by a usual coating method.

[Action]

The pressure-sensitive adhesive tape obtained using the adhesive composition having the present invention has a small polymerization shrinkage, an excellent cohesive force, and a high adhesive force.

Although the reason for its manifestation is not clear, in the case of an electron-withdrawing substituent, the reactivity of the thiol compound produced by irradiation with the thiyl radical is high, but since its own vinyl polymerization also occurs at a high ratio, its cross-linking structure. Becomes three-dimensional and does not show rubber-like properties, but high cohesive force can be obtained.

On the other hand, in the case of an electron-donating substituent, on the contrary, although it has a high selective reactivity with a thiyl radical, it hardly undergoes vinyl polymerization, and its crosslinked structure is two-dimensional and shows a rubber-like structure.

In the present invention, it is considered that different kinds of reactive substances are generated in the same system, and a network structure is generated as a kind of polymer alloy in a short time of irradiation of radiation.

〔Example〕

The present invention will be described in more detail and specifically with reference to the above examples. In the above description, parts and% are based on weight unless otherwise specified.

Examples 1, 2, 3 <Synthesis of modified polybutadiene> 1.2-bonded polybutadiene (trade name NISSO PBG-100
0, diol at both ends, molecular weight about 1,000, Nippon Soda Co., Ltd.
Produced in an autoclave under a platinum catalyst at 150 ° C. and 10 kg / cm ² for 3 hours to react with hydrogen to give vinylic properties in polybutadiene 2.
Hydrogen bonds were added to the heavy bonds to make hydrogenated polybutadiene with an addition rate of 95%. The specified hydrogenation rate is 1600 cm of IR
^It was confirmed by absorption of ^-1 .

Next, a mixture having a molar ratio of 2-hydroxyethyl acrylate and allyl alcohol of 20/80 (Example 1), 40/60 (Example 2), and 60/40 (Example 3) was prepared, and the respective mixtures were prepared. In the same manner, tolylene diisocyanate was mixed in an equimolar amount, and the isocyanate compound containing three unsaturated two-bonds obtained by stirring and reacting at 70 ° C. for 4 hours was mixed in an amount of 2 mol with respect to 1 mol of hydrogenated polybutadiene. , 80 ° C
After reacting for 5 hours, 3 types of modified polybutadiene having an acryloyl group and an allyl ether group respectively at the molecular ends were obtained.

<Preparation of surface protection film> 100 parts of the synthesized modified polybutadiene was mixed with 10 parts of trimethylolpropane tris- (β-thiopropionate) as a thiol compound, and three kinds of compositions were applied to a polyethylene film (thickness: 60 μm). Electron beam irradiation equipment (linear filament type, Energy Science Inc) with a coating thickness of 5 μm and an acceleration voltage of 200 KV and a beam current of 10 mA
A surface protection film was prepared by irradiating a nitrogen gas atmosphere (oxygen concentration (500 ppm) at a dose of 8 Mrad with a trade name of Electrocurtain) manufactured by SUS-430.
It was attached to a BA plate and various tests were conducted.

The characteristics are shown in Table 1.

Comparative Examples 1 and 2 2-hydroxyethyl acrylate alone (Comparative Example 1) was used as the active hydrogen-containing compound having an unsaturated double bond of the Examples.
A modified polybutadiene was synthesized by the same reaction using allyl alcohol alone (Comparative Example 2). Furthermore, the same thiol compound as that in the example was blended, and a comparative example protective film was prepared by electron beam irradiation.

The characteristics are also shown in Table 1.

[Effects of the Invention] As is clear from the results of the above-mentioned examples, according to the present invention, the adhesive strength per coating thickness is large, the radial characteristics are excellent, and the water resistance, light resistance, and heat resistance are excellent. An adhesive composition was obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeru Nakamura Inventor Nihon Soda Co., Ltd. 2-2-1 Otemachi, Chiyoda-ku, Tokyo (72) Inventor Keiji Nishio 2-2-1 Otemachi, Chiyoda-ku, Tokyo Issue Nihon Soda Co., Ltd. (56) Reference Japanese Patent Publication Sho 56-53596 (JP, B2) Japanese Publication Sho 56-53597 (JP, B2) Japanese Publication Sho 49-48190 (JP, B2)

Claims (5)

[Claims] 1. A number-average molecular weight comprising 90% or more of 1.2-bond structure, hydrogenated main chain or side chain vinyl double bond, and introduction of unsaturated double bond at the terminal, and a number average molecular weight of 500 to 5.
The modified polybutadiene or modified polybutadiene copolymer of 000, wherein 20 to 60% of the terminal unsaturated double bond is an electron-withdrawing substituent and 80 to 40% is a ratio of electron-donating substitution, or A radiation-curable pressure-sensitive adhesive composition, characterized in that 0.2 to 20 parts by weight of a thiol compound having two or more mercapto groups in one molecule is blended with 100 parts by weight of a modified polybutadiene copolymer. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the electron-withdrawing substituent is an acroyl group or a metalliloyl group. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the electron-donating substituent is an allyl ether group, an allyl thioether group, a vinyl ether group or a vinyl thioether group. 4. The modified polybutadiene or modified polybutadiene copolymer has 70 or more vinylic double bonds in the main chain or side chains.
The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is hydrogenated in an amount of at least%. 5. The pressure-sensitive adhesive composition according to claim 1, wherein the introduction rate of terminal unsaturated double bonds in the modified polybutadiene or the modified polybutadiene copolymer is 1 or more in one molecule on average.