JPS61209281A - Radiation-curable pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To provide the titled composition having excellent adhesivity, cohesivity and weather-resistance, by adding a specific amount of an ultraviolet absorber having unsaturated double bond to a liquid oligomer having unsaturated double bond in the molecule. CONSTITUTION:The objective composition is composed of (A) 100pts.(wt.) of a liquid oligomer having unsaturated double bond in the molecule (preferably imparted with acrylic double bond having high reactivity), (B) 0.1-30pts. of an ultraviolet absorber imparted with an unsaturated double bond, preferably containing phenyl salicylate, hydroxybenzophenone, or hydroxyphenyl benzotriazole in the molecular skeleton, (C) a chain transfer agent (e.g. butyl mercaptan) and (D) a reactive monomer having polar group (preferably imparted with phosphoric acid radical).

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a radiation-curable adhesive composition.

[Conventional technology]

Conventionally, adhesive films have been manufactured by dissolving a high molecular weight polymer such as natural rubber or synthetic rubber in an organic solvent, applying a thin adhesive onto a web 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 resource saving, energy saving, and pollution-free production.

Since the tetrapolymer chain used in this case has a low molecular weight due to viscosity constraints, the rubber elasticity inherent in the polymer is impaired when used alone, and the adhesive force and other properties required as an adhesive cannot be achieved. Therefore, efforts have been made to supplement these properties by adding chain transfer agents and monomers having polar groups.

However, it is used here! Even if the combined component has excellent weather resistance, the weather resistance of the adhesive film obtained by incorporating the above-mentioned low molecular weight substances and curing with radiation tends to be significantly impaired.

That is, when this adhesive film is attached to an adherend and exposed to sunlight, the adhesive transfers to the adherend, and if this is large enough, the film cannot be peeled off. Further deterioration may result in the film spontaneously peeling off from the adherend.

[Problem that the invention seeks to solve]

Therefore, as a measure to improve weather resistance, we attempted to add an ultraviolet absorber, which is a conventional method. However, if the amount is less than the CLI part, which is the usual amount, there is little effect on improving the UV absorber, and since conventional UV absorbers have poor compatibility with radiation-curable oligomers, 1 part or more of α is added and radiation-cured products are obtained. When the adhesive film is attached to an adherend, there is a problem that the adhesive film bleeds out onto the adherend.

The present invention was developed in view of the situation, and the object is to provide a radiation-curable adhesive for adhesive films that does not cause bleeding of ultraviolet absorbers and has excellent adhesive properties, weather resistance, etc. .

[Means for Solving the Problems] That is, the present invention provides an adhesive composition mainly composed of a liquid oligomer having unsaturated double bonds in its molecules, by adding unsaturated double bonds that are polymerized by radiation. It is characterized by containing a UV absorber.

The ultraviolet absorbers provided with unsaturated double bonds that undergo radiation polymerization used in the present invention have molecular skeletons such as phenylsalicylate%2-(seriously, 4-)human-xybenzophenone, 2(2'- It must have a molecular structure that can absorb light energy and convert it into thermal energy, such as benzotriazole (hydroxyfer), and must have at least one unsaturated double bond per molecule. Examples of unsaturated double bonds include vinyl, vinyl ether, vinyl ester, acrylic, methacrylic groups, etc. In the present invention, particularly good results are obtained with acrylic, which has high reactivity and particularly excellent weather resistance. It is an ultraviolet absorber with a methacrylic group added. These may be used alone or in a mixture of 211 or more, but the total amount added is a1 to 30 weight fI per 100 parts by weight of oligomer.
Selected within a km range.

If the amount is less than 0.1 part by weight, the effect of improving weather resistance will be insufficient, and if it is added in excess of 30 parts by weight, the adhesive properties (adhesive force, radiation curability) will deteriorate.

A more preferable range of addition amount is 1 to 15 parts by weight.

The oligomers having an unsaturated double bond in the molecule used in the present invention include alkyl acrylates, alkyl methacrylates, polyol acrylates, polyester acrylates, urethane acrylates, epoxy acrylates, and other unsaturated main chains. These are prepolymers such as acrylic oligomers, polybutadiene, polychloroprene, and polyisoprene that have one or more double bonds per molecule at the terminal or side chain. The oligomer is usually in liquid form, and its viscosity is in the range of 102 to 5 x 10' cps at room temperature. In the present invention, particularly good results can be obtained with highly reactive acrylic oligomers having 2N bonds.

Chain transfer agents used in the adhesive composition other than Manen oligomer include thiol compounds such as butyl mercaptan, lauryl mercaptan, octyl thioglycolate, ethylene glycol dithioglycolate, pentaerythritol tetrakis ÷ β-thiopropionate), Examples include disulfides such as diphenyl disulfide, and halides such as carbon tetrachloride, carbon tetrabromide, chloroform, and dichlorobenzene. These may be used alone or in combination of two or more. These chain transfer agents are added to suppress excessive crosslinking during radiation curing. For that purpose, the amount added should be 0.
It is necessary to select it in the range of 2 to 20% by weight, preferably 2 to 15% by weight. If this amount is less than 12% by weight, the effect of suppressing crosslinking will be insufficient, and if it exceeds 20% by weight, curing will be insufficient and cohesive force will be insufficient, which will adversely affect adhesive properties.

On the other hand, the polar group-containing motumer used in the present invention includes acrylic acid and methacrylic acid.

Itacone R11% maleic acid, crotonic acid, acryloyloxyethyl hydrogen phthalate, 2-acrylamide-2
-Methylpropane-sulfonic acid, 3-chloro-2-acid phosphoxyglobyl methacrylate, 2-acid phosphooxyethyl acrylate, 2-acid phosphooxybu Ωpyr methacrylate, di(2-methacryloyloxyethyln) phosphate, phosphorus Examples include acid di(2-acryloyloxyethyl), etc. Particularly advantageous is heptamine having a phosphate group having a large dissociation constant.

The amount of these monomers having acidic groups added is α5~30!
Selected within the range of quantity. If this amount is less than 15% by weight,
The effect of interfacial force is insufficient, and if it exceeds 30% by weight, the curability of the radiation door and the physical properties of the cured coating film will deteriorate, which is not preferable.

In carrying out the present invention, in addition to the compositions described above, cage additives such as diluent monomers and tackifiers may be added, and a small amount of solvent may also be freely added.

The radiation referred to in the present invention refers to active energy rays.

It refers to ionizing radiation such as α-rays, β-rays, rlfM, neutron beams, accelerated electron particles, and ultraviolet radiation. In the case of ionizing radiation, the dose can be used in the range of α5 to 50 Mrad,
Approximately 1 to 10 Mrad is desirable. In most cases, ultraviolet rays have a wavelength range of 180 to 460 nm, and a high-pressure mercury lamp or the like is suitable as a source. Also, when irradiating, care must be taken in the irradiation atmosphere. In other words, the generated radicals are inhibited by oxygen in the air.

In some cases, it may be necessary to use an inert gas such as nitrogen to achieve an appropriate oxygen concentration.

[Effect]

The adhesive tape obtained by the present invention has good rubber elasticity, excellent adhesive properties, and excellent weather resistance. The reason for the improved weather resistance is that as a result of adding unsaturated double bonds to ordinary ultraviolet absorbers, their compatibility with adhesive compositions such as oligomers has improved, making it possible to add them in large quantities. In addition, most of the additives are radiation-cured and incorporated into the system through covalent bonds, so they have excellent cohesive strength and do not easily bleed out.

Furthermore, the introduction of unsaturated double bonds into the UV absorber does not adversely affect the light ← heat conversion function of the UV absorber.

The present invention will be further explained below with reference to Examples.

(1) Synthesis of radiation-curable oligomer (1-a) 10 parts of ethyl acrylate, 70 parts of butyl acrylate, and 20 parts of metaglycidyl acrylate were solution-polymerized in a 30% solution, and the viscosity was reduced by removing the solvent. 50℃-I
A solvent-free copolymer of X 10'cp@ was synthesized. Next, this copolymerized pre-oligomer was subjected to an addition reaction with 5 parts of acrylic acid to impart double bonds to the side chains.

(1-b) α-ethylhexyl acrylate) 75II
S, 15 parts of methyl methacrylate, and 10 parts of metaglycidyl acrylate were copolymerized in the same manner as in (1-a) above to impart a double bond to the side chain.

(2) Synthesis of unsaturated double bond-added ultraviolet absorber (2
-a) 2.2; 4.4' ~ 1 mol of tetrahydroxybenzophene is reacted with 2 mol of sodium hydroxide in methanol 300111 at 50°C, and after completely removing water, s 10 wt% in MEK 2 at 10℃
mol of acrylic acid chloride, and the reaction product was purified by distillation.

<2-b) % for 2:C-dihydroxyphenylnaliterate Synthesis was performed in the same manner as (2-!I) ◎ Example 1 Pentaerythritol was added to 100 parts by weight of the oligomer synthesized in (1-a). 10 parts by weight of di(2-acryloyloxyethyl) phosphate, and 1 part by weight of the ultraviolet absorber α synthesized in (2-a) were added to form an adhesive composition. did.

Example 2 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the t of the ultraviolet absorber was 10 parts by weight.

Comparative Example 1.2.3 Comparative Example 1.2.3 was prepared by removing the ultraviolet absorber from the formulation of Example 1. Comparative Example 2.05 parts by weight of 2.2;4.4'-teto2hydroxybenzophenone α0 was added as an ultraviolet absorber. Comparative Example 3 was prepared by adding 1 part by weight of α.

Example 3 100 parts by weight of the oligomer synthesized in (1-b), 5x parts by weight of butyl mercaptan, 15 parts by weight of acroyloxyethyl hydrogen phthalate, and 5 parts by weight of the ultraviolet absorber synthesized with CF<2-b) was added to prepare an adhesive composition.

Example 4 Example 3 except that the amount of ultraviolet absorber was t-15 parts by weight
An adhesive composition was prepared according to the following.

Comparative Example 4.5.6 Comparative Example 4 was the formulation of Example 3 except that the evening ultraviolet absorber was removed, and Comparative Example 5 was the formulation of Example 3 except that α05 parts by weight of γ4'-dihydroxyphenyl salicylate was added as an ultraviolet absorber.
(Comparative Example 6 was obtained by adding 11 parts by weight.

These compositions were applied to a polyethylene film (thickness 60 μm)
Apply K so that the thickness of the coating becomes 10 μm, and apply the acceleration voltage to 2.
00kV, beam ml, filmoA electron beam irradiation device (linear filament type, Energy 5cienc)
1 product manufactured by e Inc. Trade name: Electrocurtain, irradiated with 6 Mrad under nitrogen gas atmosphere (02 concentration 500 ppl) to create an adhesive film.

This adhesive film was subjected to an adhesive force test using a Tensilon type tensile tester. The tensile speed was 200 mIII/mf n (
20°C).

In addition, a hardenability test was performed by pasting it on a 5O5-45QBA board and peeling it off after 2 hours, and visually observing whether the adhesive had transferred to the board surface.

About the adhesive film with no abnormality in the curing test.

An accelerated weather resistance test was conducted using a sunshine weather meter. (ATLAS CDMC type, sealed carbon arc type)
The results are shown in Table 1.

Table 1 Adhesive film characteristics (*) Visually observe to determine whether the adhesive has transferred to the board surface.

(#) The time it takes for the destructive sea of adhesive to begin to transfer to the adherend in the accelerated weather resistance test of the Tensier 4 Weather Meter.

〔Effect of the invention〕

As is clear from the results of the above examples, according to the present invention, since the ultraviolet absorber having unsaturated double bonds is blended, it has excellent adhesive strength and cohesive strength.

In addition, it has become possible to provide a radiation-curable pressure-sensitive adhesive that can be added in large amounts and has excellent weather resistance.

Claims (1)

[Claims] 1. A liquid oligomer having an unsaturated double bond in its molecule;
In an adhesive composition comprising a chain transfer agent and a reactive monomer having a polar group, 0 parts of an ultraviolet absorber having an unsaturated double bond is added to 100 parts by weight of the liquid oligomer.
．． A radiation-curable pressure-sensitive adhesive composition characterized in that it contains 1 to 30 parts by weight. 2. The radiation-curable pressure-sensitive adhesive composition according to claim 1, wherein the ultraviolet absorber provided with an unsaturated double bond has phenyl salicylate, hydroxybenzophenone, or hydroxyphenylbenzotriazole in its molecular skeleton.