JPH03139525A - Ultraviolet-curable composition - Google Patents

Abstract

PURPOSE:To obtain an ultraviolet-curable composition which is substantially free from curing shrinkage even when irradiated with ultraviolet rays and can give a cured product of a high hardness by mixing an allylated acrylic prepolymer with a polythiol and a photopolymerization initiator. CONSTITUTION:An ultraviolet-curable composition essentially consisting of 10 pts.wt. allylated acrylic prepolymer, usually 5-300 pts.wt. polyol and usually 0.5-30 pts.wt. photopolymerization initiator. As the allylated acrylic prepolymer, one having a number-average mol.wt. of 1000-5000 is desirable. A prepolymer having a number-average mol.wt. >5000 is so viscous that it is poor in workability and is problematic in actual use, while a prepolymer having a number-average mol.wt. <1000 can hardly give a cured product of a high hardness and a low curing shrinkage. As the polythiol, one having two or three mercapto groups in the molecule is desirable. One having above four mercapto groups is liable to give a brittle cured product or to be poor in storage stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultraviolet curable composition, and more particularly, to a coating composition that exhibits small volumetric shrinkage during curing after irradiation with ultraviolet rays and can yield a cured product with high hardness. , relates to an ultraviolet curable composition suitable for application to adhesives and the like.

[Conventional technology]

Recently, ultraviolet curable compositions have been attracting attention due to social demands such as pollution-free, resource saving, and energy saving.

This ultraviolet curable composition has traditionally been used as an image forming material for printing plate materials, photoresists, etc., and recently its uses have been applied to printing inks, paints,
It is also expanding into adhesives, potting agents, etc.

By the way, ultraviolet curable compositions are classified into radical polymerization type and ionic polymerization type, depending on the type of photopolymerization initiator contained. Among these, radical polymerization type ultraviolet curable compositions are composed of a system that essentially includes various ultraviolet polymerizable compounds having an unsaturated group and a photopolymerization initiator.

In such a radical polymerizable ultraviolet curable composition, the photopolymerization initiator is first activated into radicals by the chemical action of ultraviolet rays, the ultraviolet ray polymerizable compound is activated by these radicals, and then this activation The UV-polymerizable compounds are polymerized and cured one after another.

In addition, as the ultraviolet polymerizable compound, in order to shorten the curing time, oligomers (hereinafter referred to as
In addition to using a photopolymerizable prepolymer (referred to as a "photopolymerizable prepolymer"), a photopolymerizable monomer having an unsaturated group is often used in combination as a reactive diluent monomer (reactive solvent).

[Problem to be solved by the invention]

However, conventional ultraviolet curable compositions tend to undergo curing shrinkage in volume during curing, resulting in problems with the physical properties of the cured product, such as distortion and warpage.

As a method for reducing such curing shrinkage, for example, the following methods have been conventionally employed, but as described in each section, they have not yet achieved a sufficiently satisfactory effect.

■A method of incorporating a particulate polymer into a UV polymerizable compound in a non-aqueous dispersion.

However, since the particulate polymer does not react with the UV polymerizable compound and is merely dispersed in the UV polymerizable compound, curing shrinkage cannot be effectively prevented by this method.

■Polyester acrylate, urethane acrylate,
A method of relaxing internal stress by introducing soft segments into oligomers such as acrylic-modified maleated polybutadiene and acrylic acid-modified epoxidized polybutadiene.

According to this method, curing shrinkage can be reduced.

However, it is still difficult to say that it is sufficient for some uses, and the modulus of elasticity decreases due to softening, so the reality is that it is difficult to obtain a cured product with high hardness.

The present invention has been made in view of the above circumstances, and its purpose is to produce a cured product with almost no curing shrinkage upon irradiation with ultraviolet rays and with high hardness, such as paints and adhesives. An object of the present invention is to provide an ultraviolet curable composition suitable for use as an agent.

[Means to solve the problem]

The ultraviolet curable composition according to the present invention for achieving the above object contains as essential components an allyl group-containing acrylic prepolymer as a photopolymerizable prepolymer, polythiol as a photopolymerizable monomer, and a photopolymerization initiator. do.

The allyl group-containing acrylic prepolymer in the present invention is a prepolymer containing an allyl group at the end or side chain of the molecule, and by blending an allyl group-containing compound when polymerizing or copolymerizing an acrylic ester. can get.

Examples of the acrylic ester include ethyl acrylate, propyl acrylate, n-butyl acrylate, inbutyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, and the like.

In addition, acrylic esters other than the above, such as methyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate, which can be copolymerized with the acrylic ester; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, Isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl methacrylate, glycidyl methacrylate, 2-methoxyethyl methacrylate, 2
- Methacrylic acid esters such as ethoxyethyl methacrylate; methacrylic acid; acrylic acid; vinyl acetate; vinyl propionate; vinyl persatate (manufactured by Shell Chemical Co., Ltd., trade name "Beoba"); vinyl chloride; acrylonitrile; styrene; acrylamide ; N-methylolacrylic acid amide; vinyl pyridine; maleic anhydride; vinyl pyrrolidone; or butadiene, etc. may be used in combination with the above acrylic ester.

In addition, from the purpose of the present invention to obtain an ultraviolet curable composition that exhibits small curing shrinkage and provides a highly hard coating,
It is preferable to use as the prepolymer an acrylic copolymer obtained by copolymerizing a component with a high Tg (glass transition point) and a component with a low Tg at a molar ratio of, for example, 1:1.

The allyl group-containing compound (polymerizable compound having an allyl group) has at least one allyl group in one molecule and one
Compounds that have a group that can be copolymerized with (meth)acrylic acid esters, such as allyl (meth)acrylate, vinyl ester, addition reaction product of (meth)allylic acid and allyl glycidyl ether, allyl (meth)acrylic acid esters of compounds obtained by adding alkylene oxide to alcohols, copolymerizable unsaturated carboxylic acid esters of allyl alcohol (mono- or diallyl maleate, mono- or diallyl fumarate, mono- or diallyl itaconate, etc.), carboxyl groups Examples include, but are not limited to, allyl alcohol esters of excess unsaturated polyesters, compounds in which both ω-hydroxyalkyl (meth)acrylate and allyl alcohol are added to polyisocyanate compounds, etc.
These allyl group-containing compounds may be used alone or in combination of two or more.

Regarding the content of the allyl group and the group copolymerizable with the (meth)acrylic acid ester in the allyl group-containing compound,
Although it depends on its molecular weight, chemical structure, etc., if the allyl group content is too large, the cured product tends to become brittle. 1
Appropriately there are 1 to 5, preferably 1 to 3, in the molecule.

If it has two or more copolymerizable groups, it is undesirable because it has a strong tendency to gel when copolymerized with a (meth)acrylic acid ester.Normally, one is suitable.

The allyl group-containing acrylic prepolymer preferably has a number average molecular weight of 11,000 to 5,000, more preferably a number average molecular weight of 11,000 to 3,000.If the number average molecular weight exceeds 500, the viscosity will become too high. This results in poor workability and poses a practical problem. Furthermore, if the number average molecular weight is less than 1000, it is difficult to obtain a cured product with high hardness and low curing shrinkage.

The polythiol used in the present invention preferably has 2 or 3 mercapto groups in one polymer molecule.If it has more than 4 mercapto groups, the cured product may become brittle or have poor storage stability. There is a tendency to Note that if a monothiol having one mercapto group is used, a cured product with high hardness cannot be obtained because the crosslinking reaction is not sufficiently carried out.

Preferred examples of the polythiol as a photopolymerizable monomer in the present invention include ethylene glycol dithioglycolate, trimethylolpropane-tris (thioglycolate), and trimethylolpropane-tris (β-thiopropionate). Ru.

The polythiol is preferably used in an amount of 5 to 300 parts, and preferably 10 to 200 parts, based on 100 parts by weight (hereinafter abbreviated as "parts") of the allyl group-containing acrylic prepolymer. It is more preferable.

If it is less than 5 parts, only a product with low hardness after UV curing will be obtained, and if it exceeds 300 parts, curing shrinkage will occur during curing, and deformation, warpage, etc. will tend to appear.

Note that other photopolymerizable monomers may be blended to improve the physical properties of the cured product.

Such other photopolymerizable monomers include acrylic monomers or (meth)acrylic monomers (hereinafter, acrylic and methacrylic are collectively referred to as "
(abbreviated as "(meth)acrylic"), such as trimethylolpropane tri(meth)acrylate, penta-triacrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate ,
1.4-butanediol di(meth)acrylate, 16
-Hexanethiol di(meth)acrylate, neopentyl glycol di(meth)acrylate, diacryloxyethyl phosphate, N-vinylpyrrolidone, 2-
Hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, tetrahydrofurfuryl acrylate, butoxyethyl acrylate, ethyldiethylene glycol acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenoxyethyl acrylate, 2-hydroxy-3-phenyl Examples include oxypropyl acrylate and dicyclopentadiene acrylate.

The other photopolymerizable monomer is preferably used in an amount of 5 to 500 parts, more preferably 10 to 200 parts, based on 100 parts of the allyl group-containing acrylic prepolymer.

As the photopolymerization initiator in the present invention, various conventionally known initiators can be used as long as they have excellent solubility in the allyl group-containing acrylic prepolymer.
For example, benzophenone, diacetyl, benzyl, benzoin, ω-bromoacetophenone, chloroacetone,
Carbonyl photopolymerization initiators such as benzyl methyl ketal; diphenyl disulfide, dibenzyl disulfide,
Sulfide photopolymerization initiators such as tetraethylthiuram disulfide; Quinone photopolymerization initiators such as benzoquinone and anthraquinone; Azo photopolymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobispropane, and hydrazine A photopolymerization initiator; and a sulfochloride photopolymerization initiator can be used.

These photopolymerization initiators may be used in an amount of usually 0.5 to 30 parts, preferably 0.5 to 20 parts, based on 100 parts of the allyl group-containing acrylic prepolymer.
These photopolymerization initiators may be used alone, or two or more types may be used in combination as appropriate to enhance the effect as a photopolymerization initiator.

In addition, in the present invention, a sensitizer is not intentionally required, but an appropriate amount and type of sensitizer may be used provided that storage stability (pot life) and physical properties of the cured product are not impaired. .

Such sensitizers include aliphatic amines, aromatic amines,
Amines such as piperidine; Ureas such as allyl urea and 0-tolylthiourea; Sulfur compounds such as sodium diethyldithiopho, sulfate, S-benzyl-iso-thiuronium-P-)luenesulfinate; substitution-p
- Nitrile compounds such as aminobenzonitrile compounds;
Examples include phosphorus compounds such as tri-n-butylphosphine and sodium diethyldithiophosphate; chlorine compounds such as carbon tetrachloride and hexachloroethane; and nitrogen compounds such as N-nitrosohydroxyamine derivatives and Michlaken.

As described above, although the ultraviolet curable composition according to the present invention contains the allyl group-containing acrylic prepolymer, polythiol, and photopolymerization initiator as essential components in the above-mentioned predetermined proportions, it is possible to work by lowering the viscosity of the system. In order to improve the properties, it may be diluted with an appropriate organic solvent as necessary.

Examples of such organic solvents include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and butyl alcohol; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate; benzene, toluene, Aromatics such as xylene; chloromethane, dichloromethane,
Examples include halides such as trichloroethane; and heterocycles such as tetrahydrofuran.

Furthermore, various additives such as fillers, anti-aging agents, polymerization inhibitors, pigments, waxes, adhesion agents, modifiers, flow improvers, etc. may be added as necessary.

【Example〕

Hereinafter, the present invention will be explained in more detail based on examples, but the present invention is not limited to the following examples, and can be modified as appropriate without changing the gist thereof.

(Reference Example 1) <Production of allyl group-containing acrylic prepolymer> 38.4 g of n-butyl acrylate, 2 g of methyl methacrylate
7.0 g of allyl methacrylate, 46.7 g of allyl methacrylate, 15.0 g of lauryl mercaptan and 210 g of toluene, and after adding 1.5 g of AIBN (2,2°-azobisisobutyronitrile) to this mixture, the mixture was stirred. AIBN was dissolved.

Next, after polymerizing for 4 hours at a temperature of 70°C in a nitrogen atmosphere, toluene and unreacted monomers were collected to obtain an allyl group-containing methyl methacrylate/butyl acrylate copolymer (allyl group-containing acrylic prepolymer). I got it. The number average molecular weight of this copolymer was 2,500 in terms of polystyrene. Also, C=O(17
The production of an allyl group-containing acrylic prepolymer was confirmed from the absorption of C═C (1648 cl') and C═C (1648 cl').

(Reference Example 2) <Production of allyl group-containing acrylic prepolymer> 73.0 g of n-butyl acrylate, 46 allyl methacrylate
', 7 g, lauryl mercaptan, 15.0 g, and toluene 210 g, and to this mixture, AIBN (2,
After adding 1.5 g of 2'-7zobisisobutyronitrile, the mixture was stirred to dissolve AIBN.

Next, after polymerizing for 4 hours at a temperature of 70°C in a nitrogen atmosphere, toluene and unreacted monomers were collected to obtain an allyl group-containing methyl methacrylate/butyl acrylate copolymer (allyl group-containing acrylic prepolymer). I got it. The number average molecular weight of this copolymer was 3000 in terms of polystyrene. Also, C=O(17
30c+aI) and C=C(1648cm-') (
Formation of an allyl group-containing acrylic prepolymer was confirmed by D absorption.

(Examples 1 to 3 and Comparative Examples 1 to 4) <Preparation of ultraviolet curable composition> Each component in the number shown in the table was mixed to prepare an ultraviolet curable composition.

Physical property test of each UV curable composition> (1) A 111n thick polycarbonate plate was layered on a glass plate with a hardness of 5III, and each of the UV curable compositions obtained earlier was placed on top of a 111n thick polycarbonate plate with a dry film thickness of 100 μm. After coating and curing by irradiating ultraviolet rays, the pencil hardness of each cured film was measured according to JIS K5400.

In addition, ultraviolet rays are irradiated only when a cold mirror is installed.
The test was carried out using a KW high pressure mercury lamp under the following conditions.

Lamp height ・---10cra Conhair speed ・・・−1Om/min Number of passes −・・・−3 integrated light intensity −・・・−340W・sec/c4 The results are shown in the table 6 (2) Each of the previously obtained ultraviolet curable compositions was applied to a cured shrinkable 150 x 50 sheet, 75 μm thick PET (polyethylene terephthalate) film using a dry WIJ to a thickness of 100 μm, and the above (]
) After curing by irradiating with ultraviolet rays under the same conditions as (2), each cured film was visually observed for the presence or absence of warpage.

The results are shown in the table.

(Hereafter, blank spaces) Notes ■ to ■ in the table are as follows: ■: Allyl group-containing acrylic prepolymer obtained in Reference Example 1■: Allyl group-containing acrylic prepolymer obtained in Reference Example 2■: Showa Komunshi Manufactured by Nippon Kasei Co., Ltd., product code: rU-3000. ■Manufactured by Nippon Kasei Co., Ltd., product name: rTAI C.

■: Manufactured by Negami Kogyo Co., Ltd., product code: rUN1000EPJ ■Nitrimethylolpropane tristhiopropionate ■: Manufactured by Sanyo Chemical Industries, Ltd., product code: "Neomer TA-5"
05J ■: Manufactured by Ciba Geigy, product code “Irgacure #5
00 (1-hydroxycyclohexylphenyl ketone 5
0%, benzophenone 50%).

As shown in the table, the cured films obtained by irradiating the UV curable compositions of Examples 1 to 3 with UV rays had a pencil hardness of 2H (and no curing shrinkage was observed). Is the comparative example soft with a pencil hardness of 28-HB?
Comparative Examples 1.2 and 4), Warpage is observed (Comparative Example 3)
and 4).

〔Effect of the invention〕

As described above in detail, the ultraviolet curable composition according to the present invention exhibits excellent and unique effects, such as realizing a cured product with high hardness and almost no curing shrinkage upon irradiation with ultraviolet rays.

Claims (1)

[Scope of Claims] 1. An ultraviolet curable composition containing an allyl group-containing acrylic prepolymer, a polythiol, and a photopolymerization initiator as essential components. 2. 10 parts by weight of allyl group-containing acrylic prepolymer,
5 to 300 parts by weight of polythiol and 0.0 parts by weight of photopolymerization initiator.
The ultraviolet curable composition according to claim 1, which contains 5 to 30 parts by weight as an essential component. 3. The ultraviolet curable composition according to claim 2, which contains 5 to 500 parts by weight of a photopolymerizable monomer based on 100 parts by weight of the allyl group-containing acrylic prepolymer. 4. The ultraviolet curable composition according to any one of claims 1 to 3, which is diluted with an organic solvent.