JPH07107151B2 - Radiation curable pressure sensitive adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radiation-curable pressure-sensitive adhesive composition used in pressure-sensitive adhesive tapes and the like, and particularly to a radiation-curable pressure-sensitive adhesive suitable for a surface protective film. It relates to an adhesive composition.

[Conventional technology]

Conventionally, pressure-sensitive adhesive tapes have been produced mainly by dissolving a high molecular weight polymer such as natural rubber or synthetic rubber in an appropriate organic solvent, applying this solution to a substrate such as a plastic film, and drying. It was However, it was necessary to lower the solution viscosity due to coating restrictions, and therefore a large amount of diluting solvent was required.

In recent years, solvent-free methods have been studied from the viewpoints of resource saving, energy saving, pollution-free and safety. One of the countermeasures that is solvent-free is a radiation-curable adhesive that uses a liquid oligomer. Such an adhesive is one in which a liquid oligomer having a relatively low molecular weight is coated on a base material and is irradiated with ionizing radiation to have a high molecular weight on the base material.

However, in this method, since the main component is a low-molecular weight oligomer in which functional groups are randomly added in the molecule, the elongation at break and the tensile elastic modulus are smaller than those of a polymer having a high degree of polymerization, resulting in adhesiveness. Only the adhesive tape with poor quality was obtained. Further, addition of a chain transfer agent having a mercapto group or the like to such an oligomer has been attempted (Patent No. 1307060). In addition, it has been attempted to add a small amount of a polymer (Japanese Patent Laid-Open No. 60-255873) or a polar monomer (Japanese Patent Publication No. 60-25070).

[Problems to be solved by the invention]

However, when a low molecular weight oligomer having a functional group at random in the molecule is used, even if a chain transfer agent or a polar monomer is added, not only the adhesive strength but also its temperature characteristics,
In terms of properties such as peeling speed dependency, it was far behind that of a high degree of polymerization.

Further, the method of adding a small amount of a polymer cannot essentially solve these problems, and since the viscosity becomes extremely high, it has become a major obstacle to solventless coating.

Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide a radiation-curable pressure-sensitive adhesive that has a low viscosity, a high adhesive force, and particularly exhibits favorable properties in drawing processability.

[Means for solving problems]

The present invention solves the above problems by blending a pressure-sensitive adhesive composition containing a liquid oligomer having a specific structure as a main component with a specific chain transfer agent and a thermal polymerization inhibitor in a specific ratio. is there.

That is, the present invention has an unsaturated double bond having an electron-donating substituent at both ends of the molecule, and has a liquid side chain having a vinyl group of 70
% To 50% by weight or more of hydrogenated 1,2-polybutadiene oligomer, 100 parts by weight of an adhesive composition containing 0.5 to 50 parts by weight of a thiol compound having 3 or more functional groups in one molecule, The present invention relates to a radiation-curable pressure-sensitive adhesive composition containing 0.001 to 10 parts by weight of a polymerization inhibitor.

Next, the components used in the adhesive composition of the present invention will be described in detail.

The 1,2-polybutadiene oligomer having an unsaturated double bond having an electron-donating substituent at both ends of the molecule and having 70% or more of a liquid side chain vinyl group hydrogenated is used in the present invention. A compound whose structure is polybutadiene obtained by ordinary living anionic polymerization or the like, and which has an unsaturated double bond having an electron-donating substituent with hydroxyl groups present at both ends of the molecule through a diisocyanate, for example, It is obtained by reacting with allyl alcohol, allyl mercaptan and the like. Examples of the unsaturated double bond having an electron-donating substituent include unsaturated double bonds such as those possessed by vinyl thioether, vinyl ether, propenyl ether, allyl ether, vinyl carbamate, allyl carbamate, and styrene. .

Among these unsaturated double bond-containing oligomers,
Particularly good results are obtained with allyl ether, which has high reactivity with a mercapto group, and those having a double bond like allyl thioether, and these should be introduced using allyl alcohol, allyl mercaptan, etc. You can

As the diisocyanate used for chain extension, trimethylhexamethylene diisocyanate and tolylene diisocyanate, which have a glass transition temperature suitable as an adhesive and have flexibility, are particularly excellent. When hexamethylene diisocyanate is used as a substitute for these, for example, the adhesive strength and drawability at high temperature may deteriorate.

You may use these oligomers individually or in combination of 2 or more types. These oligomers are applied to the base material as it is without solvent, and in order to be radiation-cured, the temperature is from room temperature to 80 ° C
It must be liquid at the temperature of. And the viscosity is 50 ℃
Those with 50,000 cps or less are more suitable for coating. The weight average molecular weight of the oligomer is 1,000 to 10,
It is preferably 000. When the weight average molecular weight of the oligomer exceeds 10,000, it becomes difficult to be liquid at the upper limit of the coatable temperature of 80 ° C. When it is less than 1,000, the adhesive force and the like become smaller than those of the polymer.

The pressure-sensitive adhesive composition in the present invention is an additive such as a tackifier, a regulator, a stabilizer or a diluent, which is used by blending the oligomer or the oligomer with the ordinary pressure-sensitive adhesive composition.
A composition comprising a compounding agent. As such, for example, an acidic group-containing monomer for the purpose of improving interfacial properties, a monomer for dilution, an additive such as a tackifier, a stabilizer such as an antioxidant, a radiation curing accelerator, and an ultraviolet absorber. , Solvents and the like. These can be used by appropriately selecting and adjusting the type, combination, usage amount and the like according to the tenacity.

The chain transfer agent used in the present invention has 3 functional groups in one molecule.
A thiol compound having at least one, for example, trimethylolpropane tris- (β-thiopropionate), trimethylolpropane tris- (thioglycolate),
Examples thereof include pentaerythritol tetrakis- (β-thiopropionate) and pentaerythritol tetrakis- (thioglycolate). These may be used alone or in combination of two or more.

These chain transfer agents are added to disperse the crosslinks during radiation curing. For that purpose, it is usually preferable to select the addition amount in the range of 0.5 to 50 parts by weight, preferably 1 to 30 parts by weight, based on 100 parts by weight of the pressure-sensitive adhesive composition. If this amount is less than 0.5 parts by weight, the effect of cross-linking dispersion will be insufficient, and if it exceeds 50 parts by weight, curing will be insufficient and cohesive force will be insufficient, which may adversely affect adhesive properties.

Examples of the thermal polymerization inhibitor that can be used in the present invention include nitroso-based polymerization inhibitors such as nitrosophenylhydroxylamine aluminum salt and nitrosophenylhydroxylamine ammonium salt, hydroquinone, hydroquinone monomethyl ether, hydroquinone monoethyl ether, and benzoquinone. Radical scavengers such as quinones, N, N-diphenylpicrylhydrazyl (DPPH) and triphenylmethyl, and benzotriazole-based antioxidants are available. These thermal polymerization inhibitors may be used alone or in combination of two or more, but the total addition amount thereof is 0.001 to 10 parts by weight, preferably 100 parts by weight of the resin solid content. , 0.01 to 3 parts by weight.

If the amount is too small, the prohibition period becomes too short, and if it is too large, the radiation-polymerizable property may be impaired, or the unreacted material may deteriorate the cohesiveness of the adhesive.

The adhesive composition of the present invention is obtained by blending the above-mentioned various components. This adhesive composition can be applied to a base film such as a polyethylene film so as to have an appropriate application thickness, and then irradiated with radiation to be cured to form an adhesive tape.

The radiation referred to in the present invention is an active energy ray and α
Ionizing radiation such as rays, β rays, γ rays, neutron rays and accelerated electron rays. The dose of this ionizing radiation is typically 0.5-5.
It can be used in the range of 0 Mrad, but 1 to 10 Mrad is preferable. In addition, when irradiating, it may be necessary to pay attention to the irradiation atmosphere. That is, since the generated radicals are normally inhibited by oxygen in the air, it may be necessary to use an inert gas such as nitrogen to obtain an appropriate oxygen concentration in some cases.

[Action]

The adhesive tape obtained by using the adhesive composition of the present invention has a high adhesive strength and exhibits particularly good properties for drawability. The reason for this expression is not always clear, but the reaction with the thiyl radical is very fast because the electron-donating substituents are added to the unsaturated double bonds at both ends of the oligomer.
It is presumed that this is due to the linear increase in the molecular weight. Therefore, at this time, in a case where the unsaturated double bond has a high polymerizability alone, for example, an acrylic or methacrylic unsaturated double bond, homopolymerization occurs in a considerable ratio, and as a result, the reaction with the thiol is reduced. Therefore, it is difficult to obtain a polymer having a long dynamic chain length.

〔Example〕

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

Radiation-curable oligomer production method (Oligomer A) Liquid hydrogenated 1,2-polybutadiene at both ends hydroxyl group (manufactured by Nippon Soda Co., Ltd., trade name GI-1000, molecular weight about 2600, hydrogenation rate of side chain vinyl group 95 % Or more) 1 mol, and mixed with 2 mol tolylene diisocyanate (hereinafter abbreviated as TD1),
After heating at 80 ° C for 5 hours using dibutyltin dilaurylate as a catalyst, 2 mol of allyl alcohol was added, and the mixture was heated at 80 ° C again.
Heated for 4 hours. The resulting oligomer (hereinafter referred to as oligomer A) has a viscosity of 8,000 cps at 50 ° C., M _n = 3,100,
It had a molecular weight of M _w = 5,300.

(Oligomer B) It was synthesized in the same manner as in the case of oligomer A except that 2 mol of TMDI (trimethylhexamethylene diisocyanate) was added instead of TDI. The M _n and M _w of the obtained oligomer were almost the same as those of the oligomer A.

(Oligomer C) Tolylene diisocyanate 3 against 2 mol of GI-1000
Oligomer C was synthesized in the same manner as in the case of oligomer A at a ratio of 2 moles of allyl alcohol. This oligomer has a viscosity of 50,000 cps at 50 ° C., M _n = 5,900, M _w = 9,00.
It had a molecular weight of 0.

(Oligomer D) An oligomer D was obtained in the same manner as in the case of the oligomer A except that the mixing amount of allyl alcohol was reduced from 2 mol to 1 mol.

(Oligomer E) Oligomer E was obtained in the same manner as in the case of Oligomer A using GI-1000 with a hydrogenation rate of the side chain vinyl group of 60%.

(Examples 1 and 2) 15 parts by weight of trimethylolpropane tris- (β-thiopropionate) with respect to 100 parts of each of the oligomers A and B,
Nitrosophenylhydroxylamine aluminum salt 0.
An adhesive composition was prepared by adding 1 part by weight. (Examples 1 and 2) (Example 3) An adhesive composition was obtained in the same manner as in Example 1 except that 30 parts by weight of trimethylolpropane tris- (β-thiopropionate) was used.

Example 4 An adhesive composition was obtained in the same manner as in Example 1 except that 10 parts by weight of pentaerythritol tetrakis- (β-thiopropionate) was added to 100 parts by weight of oligomer A.

(Example 5) 10 parts by weight of trimethylolpurpantris- (β-thiopropionate) and 0.3 parts by weight of nitrosophenylhydroxylamine ammonium salt were added to 100 parts by weight of oligomer C to prepare an adhesive composition.

(Comparative Examples 1 and 2) To 100 parts by weight of each of the oligomers D and E, 10 parts by weight of trimethylolpurpantris- (β-thiopropionate) and 0.1 part by weight of nitrosophenylhydroxylamine aluminum salt were added. A part was added to give an adhesive composition.

(Comparative Example 3) A formulation was obtained in the same manner as in Example 1 except that the adhesive composition was prepared by not blending trimethylolpropane tris- (β-thiopropionate).

(Comparative Example 4) A formulation was obtained in the same manner as in Example 1 except that the adhesive composition was prepared by not incorporating the nitrosophenylhydroxylamine aluminum salt.

Application example Polyethylene film (thickness 60μm) with these compositions
The solvent was applied without solvent to a coating thickness of 10 μm, and an electron beam irradiation device (linear filament type, Energy Science Inc., product name Electro Curtain) with an accelerating voltage of 200 kV and a beam current of 10 mA was used to generate a nitrogen gas atmosphere (O. ₂ concentration 500pp
m) was irradiated under 6 Mrad to prepare an adhesive film. This adhesive film was attached to a SUS-430BA plate, and an adhesive strength test was performed using a Tensilon tensile tester (measurement temperature 20 ° C, tensile speed
200 mm / min). Further, this sample was subjected to a drawing test with an Erichsen drawing tester to compare the degree of floating of the film 1 hour after drawing (drawing depth was 5 mm). The results are shown in Table 1.

[Advantages of the Invention] The radiation-curable pressure-sensitive adhesive composition of the present invention has low viscosity, high adhesive strength, and particularly excellent drawability.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Dobashi 1500 Ogawa, Shimodate, Ibaraki Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (72) Hiroyuki Hagiwara 1500 Ogawa, Shimodate, Ibaraki Hitachi Chemical Co., Ltd. Shimodate Research Center (56) References Japanese Patent Publication Sho-56-53596 (JP, B2) Japanese Patent Publication Sho-56-53597 (JP, B2)

Claims (7)

[Claims] 1. At least 50 wt.% Of a 1,2-polybutadiene oligomer having an unsaturated double bond having an electron-donating substituent at both ends of the molecule and having 70% or more of a liquid side chain vinyl group hydrogenated. % With respect to 100 parts by weight of the adhesive composition containing 1% or more
A thiol compound with three or more functional groups in the molecule is 0.5
A radiation-curable pressure-sensitive adhesive composition comprising -50 parts by weight and 0.001-10 parts by weight of a thermal polymerization inhibitor. 2. The composition according to claim 1, wherein the unsaturated double bond having an electron-donating substituent is an allyl ether group, an allyl thioether group, a vinyl ether group or a vinyl thioether group. 3. The composition according to claim 1 or 2, wherein the liquid hydrogenated 1,2-polybutadiene oligomer is an oligomer having a viscosity of 50,000 cps or less at 50 ° C. 4. The composition according to any one of claims 1 to 3, wherein the liquid hydrogenated 1,2-polybutadiene oligomer is an oligomer having a weight average molecular weight of 1,000 to 10,000. 5. A liquid hydrogenated 1,2-polybutadiene oligomer is used as a chain extender and tolylene diisocyanate or trimethylhexamethylene diisocyanate is used as an unsaturated 2
The composition according to any one of claims 1 to 4, which is an oligomer obtained by using allyl alcohol as a heavy bond-providing agent. 6. A thiol compound having three or more functional groups in one molecule is trimethylolpropane tris- (β-thiopropionate) or pentaerythritol tetrakis-.
The composition according to any one of claims 1 to 5, which is (β-thiopropionate), trimethylolpropane tris- (thioglycolate) or pentaerythritol tetrakis- (thioglycolate). object. 7. The composition according to any one of claims 1 to 6, wherein the thermal polymerization inhibitor is a nitrosophenylhydroxylamine aluminum salt or a nitrosophenylhydroxylaminoammonium salt.