JPH03290488A - Radiation curing type pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, excellent in water, light and heat resistance and useful especially as surface protective films for glass or metal plates by blending respective specific modified polybutadiene (copolymer) with a specified thiol compound in a specific amount. CONSTITUTION:The objective composition is obtained by blending (A) 100 pts.wt. modified polybutadiene (copolymer), composed of >=90% 1,2-bond structure and having hydrogenated vinylic double bonds in the backbone chain or side chain, unsaturated double bonds introduced into the terminals, 500-5000 number- average molecular weight, electron attractive substituent groups such as (meth) acryloyl group in an amount of 20-60% based on terminal unsaturated double bonds and electron donative substituent groups such as allyl ether or vinyl thioether group in an amount of 80-40% based on the terminal unsaturated double bonds with (B) 0.2-20 pts.wt. thiol compound having >=2 mercapto groups in one molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to pressure-sensitive adhesive tapes, particularly pressure-sensitive adhesive compositions used in surface protection films for glass plates and metal plates.

(Prior art) Adhesive films have traditionally been produced by applying an adhesive prepared by dissolving a high molecular weight polymer such as natural rubber or base rubber in an organic solvent onto a support such as a plastic film and drying it. . However, in recent years, consideration has been given to making adhesives solvent-free from the viewpoint of saving resources, saving energy, and eliminating pollution. One of the measures to eliminate solvents is radiation-curable adhesives that use liquid oligomers. Such an adhesive is made by coating a relatively low molecular weight liquid oligomer on a support and irradiating it with ionizing radiation to increase the molecular weight on the support.

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

As polybutadiene oligomers, 1,4-bond type and 1
．． There is a 2-bond type, but 1. usually has a low viscosity and is easy to handle. A 4-bond type is used.

(Special Publication No. 56-53596, No. 56-53597
1. Japanese Patent Publication No. 49-48190 discloses a method using a 2-bonded polybutadiene oligomer aimed at a resin having a high glass transition point.

However, when polybutadiene oligomers (hereinafter referred to as polybutadiene) with a 1,4-bond structure are used, the glass transition temperature is too low, which is particularly important for the high-speed peelability and high-temperature adhesion required for surface protection films. It cannot exhibit adhesive properties such as strength. 1.2 = Polybutadiene with a bonded structure has a molecular weight of a commonly used oligomer (3,000 or more) and a viscosity that is too high, making it difficult to perform coating operations. Furthermore, when 1,2-bonded polybutadiene having a low molecular weight and low viscosity is used, there are drawbacks such as not achieving the desired adhesive properties and poor water resistance, light resistance, and heat resistance.

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

[Problem to be solved by the invention]

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

Therefore, we have developed a radiation-curable pressure-sensitive adhesive that has good adhesive properties such as high-speed peelability and high-temperature adhesion, is relatively low in viscosity, has excellent water resistance, light resistance, and heat resistance, and has high adhesive strength per coating thickness. The purpose is to provide.

[Means to solve the problem]

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

That is, the present invention has a 1,2-bond structure of 90% or more, the vinyl double bond in the main chain or side chain is hydrogenated, and the number average molecular weight is 500 with an unsaturated double bond introduced at the terminal. Modified polybutadiene or modified polybutadiene copolymer with a molecular weight of 5,000 to 5,000, in which 20 to 60% of the terminal unsaturated double bonds are electron-withdrawing substituents, and 80 to 40% are electron-withdrawing substituents.
0.2 to 20 parts by weight of a thiol compound having two or more mercapto groups in one molecule is blended to 100 parts by weight of the modified polybutadiene or modified polybutadiene copolymer in which is the proportion of electron-donating substitution. The present invention relates to a radiation-curable pressure-sensitive adhesive U acid characterized by: Also,
In a desirable embodiment of the present invention, (i) the vinyl double bond in the main chain or side chain in the modified polybutadiene is 95
% or more of hydrogenation (■) It is preferable that one or more terminal unsaturated double bonds are introduced in one molecule on average.

The present invention will be explained in detail below.

The modified polybutadiene or modified polybutadiene copolymer used in the present invention has vinyl double bonds in the main chain and side chains hydrogenated to introduce 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' and R'' are carbonized hydrogen atoms, alkyl groups, cycloalkyl groups, aryl groups, aryl groups, etc., respectively. Represents a substituent such as a hydrogen group or a halogen atom, where R1 is preferably a hydrogen atom, a C2-C1o alkyl group, a chlorine atom, etc. In particular, a hydrogen atom,
A methyl group or a chlorine atom is preferable, and as R2, a hydrogen atom or a methyl group is preferable, and a hydrogen atom is particularly preferable.

) 1,4-cis polymerization of one or more selected from the butadienes represented by (l).

Butadiene polymers obtained by homopolymerization or copolymerization by various polymerization formats such as 1.4-polymerization, 1.2-polymerization or 3,4-polymerization, or any combination thereof, such as 4-trans polymerization, Or, the above [
1] So-called butadiene polymers or butadienes such as butadiene copolymers obtained by copolymerizing one or more butadienes represented by the formula and a small amount of olefins by various polymerization methods It has a copolymer as a polymer skeleton.

In general, anionic living polymerization is preferred because it contains 90% or more of the 1°2-bond structure.

Here, specific examples of the butadiene polymer serving as the skeleton or base of the polybutadiene are shown for the purpose of illustration rather than limitation, such as 1.

2-polybutadiene, 1,4-cis-polybutadiene,
1.4-trans-polybutadiene, polyisoprene,
Poly-2-ethyl-13-butadiene, poly-23-dimethyl-13-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-tertiarybutyl-1,3- Butadiene, poly-2-pentyl-1,3-butadiene, poly-2-isohexyl-1
, 3-butadiene, poly-2-cyclohexyl-1,3
-butadiene, poly-2-n-hebutyl-1,3-butadiene, poly-2-n-decyl-1,3-butadiene,
Polybutadiene or substituted butadiene polymers such as poly-2isodecyl-1,3-butadiene, polychloroprene, poly-2,3-dichloro-1,3-butadiene; Examples include polybutadiene and butadiene copolymers having two or more types of structural units selected from among them. Among these, 1.
Particularly suitable are polyphtadiene having a 2-polybutadiene polymer as a skeleton structure.

Further, the introduction rate of unsaturated double bonds introduced at both ends of the molecule is preferably one or more per molecule on average, and if there is less than one unsaturated double bond, the curability deteriorates.

Further, the hydrogenation rate of the polybutadiene or polybutadiene copolymer is 70% or more, preferably 95% or more of the vinyl groups contained. If the hydrogenation rate is less than 70%, the adhesive strength changes greatly over time and becomes brittle.

Furthermore, if the number average molecular weight of the polybutadiene used in the present invention is less than 500, it will lack flexibility as an adhesive, and
The adhesive strength per coating thickness is low, and if it is 5,000 or more, the viscosity becomes too high, making it difficult to make it solvent-free.

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

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

Here, examples of the unsaturated double bond having an electron-withdrawing substituent include acryloyl and methacryloyl groups.

Examples of the unsaturated double bond having an electron-donating substituent 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 two types of unsaturated double bonds will be specifically shown.

That is, the main chain and side chain of polybutadiene or a copolymer thereof (commercially available products can be used) having active hydrogens such as hydroxyl groups, carboxyl groups, and adanino groups at both ends of the molecule. 0.5 equivalent or more, preferably 0.6 to 1 equivalent of the isocyanate group of the isocyanate compound having the unsaturated double bond in the molecule, per equivalent of active hydrogen of the intermediate obtained by hydrogenating the vinyl double bond of ．．
An amount corresponding to 0 equivalents can be reacted and introduced.

Isocyanate compounds having an unsaturated double bond in the molecule include those in which an unsaturated double bond and an isocyanate group are directly bonded to the main chain or ring constituting the compound, as well as compounds having an isocyanate group and an isocyanate group. Also included are products obtained by chemically bonding a compound with a saturated double bond via an appropriate functional group. In general, the latter type has a greater variety of types and can yield compounds suitable for different uses. In the above, the number of unsaturated double bonds and isocyanate groups per molecule is not particularly limited, but it is generally preferable that 1 to 2 of each are present.

Preferred examples of compounds in which an unsaturated double bond and an isocyanate group are directly bonded to the main chain or ring include acryloyl isocyanate, vinyl isocyanate, vinyl phenyl isocyanate, vinyl phenyl diisocyanate, allyl isocyanate, and 2-butene 4- Diisocyanate, trans-vinylene diisocyanate, etc. are included.

A product obtained by chemically bonding a compound having an isocyanate group with a compound having an unsaturated double bond through an appropriate functional group is, for example, a polyisocyanate compound having an unsaturated double bond and an active hydrogen. Polyisocyanate compounds that are obtained by reacting both functional groups with a compound that has both functional groups in the molecule include lower aliphatic compounds such as ethylene diisocyanate, ethyridine diisocyanate, propylene diisocyanate, and butylene diisocyanate. Polyisocyanates, cycloaliphatic polyisocyanates such as cyclobenzeni 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-phenylene diisocyanate , naphthylene diisocyanate, pyrene diisocyanate, chrysene diisocyanate, nitrodiphenyl diisocyanate, 1-
This includes aromatic polyisocyanates such as methylhenzene-2,4,6-dolyisocyanate [and mixtures thereof, etc.] Compounds having both an unsaturated double bond and a functional group having active hydrogen in the molecule include allyl, Alcohol, methallyl alcohol, cinnamic alcohol, ethylene glycol monovinyl ether vinyl phenyl methacrylic acid, cinnamic acid, crotonic acid, maleic acid monoester, fumaric acid monoester, paravinylbenzoic acid, acrylamide, methacrylamide, maleic anhydride, 2- Aminoethyl vinyl ether, vinylaniline, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, hydroxybutyl acrylate,
Acrylic acid esters such as 2-carboxypropyl acrylate, 2-aminoethyl acrylamide, 2-aminopropylacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, hydroxybutyl methacrylate, 2-carboxypropyl methacrylate, 2-aminoethyl methacrylamide , 2-aminoethylmethacrylamide, etc. are used,
Among these, for example, a compound having an electron-withdrawing substituent such as 2-hydroxyethyl acrylate or 2-hydropropyl methacrylate alone or a mixture of two or more of these compounds, for example, allyl alcohol ethylene glycol monovinyl ether, etc. A compound having an electron-donating substituent may be used alone or a mixture of two or more of these compounds may be used in the above-mentioned proportions.

In the above, in the reaction between the compound having an isocyanate group and the compound having both a functional group having active hydrogen and an unsaturated double bond, the amount of isocyanate group per 1 equivalent of active hydrogen is 1.1 equivalent or more, preferably 1.5 The reaction is carried out by mixing the two in an amount of ~2.5 equivalents and reacting at 50-100°C for 0.5-6 hours.

The modified polybutadiene or modified polybutadiene copolymer according to the present invention comprises a polybutadiene intermediate obtained by hydrogenating the vinyl double bonds in the main chain and side chain having active hydrogen, and an isocyanate compound containing an unsaturated double bond. Mixing so that the isocyanate group is 0.4 to 1.2 equivalents per equivalent of active hydrogen of the polybutadiene intermediate,
It is produced by reacting at 50-100°C for 0.5-6 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-hexanesioldithioprobionate, ethylene glycol dithioglycolate, Trimethylolpropane tris-(thioglycolate) trimethylolpropane tris-(β-
thiopropionate), pentaerythritol tetrakis (thioglycolate), pentaerythritol tetrakis (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 during radiation curing, and as a result, adhesive properties etc. are dramatically improved. The amount added needs to be selected within 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, curing will be insufficient and cohesive force will be insufficient, which will adversely affect adhesive properties.

The radiation referred to in the present invention refers to active energy rays, including α rays and β rays.
The dose of ionizing radiation is 0.5 to 5.
It can be used in the range of 0 Mrad, but it is preferably about 1 to 10 Mrad, and in the case of ultraviolet rays, it is about 180 to 460 nm.
am wavelength range, and the source is a high-pressure mercury lamp.

Furthermore, when irradiating, care must be taken in the irradiation atmosphere. That is, since the generated radicals are inhibited from polymerization by oxygen in the air, it may be necessary to use an inert gas such as nitrogen to maintain an appropriate oxygen concentration.

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

Since the obtained adhesive composition has a low viscosity, it is applied to a support such as a plastic film by a conventional coating method and then crosslinked by irradiation with radiation.

[Function] The pressure-sensitive adhesive tape obtained using the adhesive composition of the present invention has small snow shrinkage, excellent cohesive force, and high adhesive strength.

The reason for this phenomenon is not clear, but in the case of electron-withdrawing substituents, the reactivity with the thiyl radical of the thiol compound generated by radiation irradiation is high, but a high proportion of its own vinyl polymerization also occurs, so the crosslinked structure of the electron-withdrawing substituent is three-dimensional and does not exhibit rubber-like properties, but high cohesive strength can be obtained.

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

The present invention considers that different types of reactive substances occur within the same system, and a network structure is formed as a kind of polymer alloy in a short period of time when irradiated with radiation.

[Example] The present invention will be explained in more detail and concretely using the above example. In the above description, unless otherwise specified, parts and percentages are based on weight.

Example 1. 2. 3 <Bottom of modified polybutadiene> 1.2-bonded polybutadiene (trade name Nl5So
PBG-1000, diol at both ends, molecular weight approximately 1000
, manufactured by Nippon Soda ■) in an autoclave under a platinum catalyst.
``Hydrogen was reacted at 110 kg/cj for 3 hours to hydrogenate the vinyl double bonds in polybutadiene, and the addition rate was 9.
A 5% hydrogenated polybutadiene was made. Obtaining the predetermined hydrogenation rate was confirmed by IR absorption at 1600 cm-'.

Then, the molar ratio of 2-hydroxyethyl acrylate and allyl alcohol was 20/80 (Example 1) and 40/6.
0 (Example 2) and 60/40 (Example 3) were prepared, equimolar amounts of tolylene diisocyanate were mixed with each mixture, and three kinds of mixtures were obtained by stirring and reacting at 70°C for 4 hours. Two moles of each of the isocyanate compounds containing two unsaturated bonds were mixed with 1 mole of the hydrogenated polybutadiene, and the mixture was reacted at 80'C for 5 hours to form three kinds of isocyanate compounds each having an acryloyl group and an allyl ether group at the molecular end. A modified polybutadiene was obtained.

<Preparation of surface protection film> Three types of compositions containing 100 parts of the synthesized modified polybutadiene and 10 parts of trimethylolpropane tris(β-thiopropionate) as a thiol compound were applied to a polyethylene film (thickness: 60 μm). The coating was applied to a coating thickness of 5 μm, and the beam was applied at an acceleration voltage of 200 amps and a beam current of 10 µm.
＋＊＾ electron beam irradiation device (linear filament type, En
manufactured by Ergy 5science Inc., product name Electro Curtain) in a nitrogen gas atmosphere (oxygen concentration 500 pp).
A surface protection film was prepared by irradiating the sample with a dose of 8 Mrad under m). The surface protection film is 5O3-430
It was attached to a BA board and various tests were conducted.

Its characteristics are shown in Table 1.

Comparative Example 1.2 The active hydrogen-containing compound having an unsaturated double bond of Example was used as 2-hydroxyethyl acrylate alone (Comparative Example 1),
Modified polybutadiene was synthesized using allyl alcohol alone (Comparative Example 2) in a similar reaction. Furthermore, a comparative protective film was prepared by blending the same thiol compound as in the example and irradiating it with an electron beam.

Its characteristics are also shown in Table 1.

Table 1 Characteristics of surface protection film Time until transfer (ATLAS CllMC type closed carbon arc type) (5) 80°C, 100kgf/cd lh Ratio of adhesive strength after hot pressing and initial adhesive strength [One effect of the invention] As is clear from the results of the above examples, according to the present invention, an adhesive composition can be obtained which has high adhesive strength per coating thickness, excellent aging properties, and excellent water resistance, light resistance, and heat resistance. It was done.

Tensile speed 2001/win, ambient temperature 20'C (2
) After 7 days of heating and pressurizing at 65°C and 30 kgf/c-d, peel off the surface protective film and observe the surface condition of the 5O5-430BA board. It is shown as follows.

・Adhesive transfer

Claims (1)

[Claims] A number-average compound consisting of a 1,2-bond structure of 90% or more, with hydrogenated vinyl double bonds in the main chain or side chain, and with an unsaturated double bond introduced at the terminal. Molecular weight is 500 to 5
000 modified polybutadiene or modified polybutadiene copolymer having 20 to 6 terminal unsaturated double bonds.
A thiol compound having two or more mercapto groups in one molecule, based on 100 parts by weight of the modified polybutadiene or modified polybutadiene copolymer, in which 0% is an electron-withdrawing substituent and 80-40% is an electron-donating substitution. A radiation-curable pressure-sensitive adhesive composition comprising 0.2 to 20 parts by weight of the following. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the electron-withdrawing substituent is an acroyl group or a methallyloyl 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 pressure-sensitive adhesive composition according to claim 1, wherein 70% or more of the vinyl double bonds in the main chain or side chain of the modified polybutadiene or modified polybutadiene copolymer are hydrogenated. 5. The pressure-sensitive adhesive composition according to claim 1, wherein the modified polybutadiene or modified polybutadiene copolymer has an average introduction rate of one or more terminal unsaturated double bonds per molecule.