The present invention relates to a radiation hardening type resin composition which is outstanding in its coating suitability and in its coated film properties. Radiation hardening resins are widely used in various fields both on account of their outstanding productivity and also because of the recent increased awareness of environmental issues.

The generally-used radiation hardening resin compositions, which are a combination of oligomers of various kinds and ethylenically-unsaturated monomer, suffer from the problem of a lack of compatibility between the viscosity of compositions suitable for coating and the properties of the coated substrate and, additionally, the adhesion to the coated substrate is impaired by cure shrinkage at the time of curing especially when the substrate is poly ethylmethacrylate such as for Fresnel lenses Therefore a resolution of such problems is desirable.

The aforesaid problems can be overcome by a combination of at least an oligomer (A) selected from urethane (meth)acrylates, epoxy (meth)acrylates and polyester (meth)acrylates, and at least a polymer (B) of number average molecular weight in the range from about 500 to about 20,000 obtained by polymerizing at least one monomer selected from the group consisting of styrene, (meth)acrylonitrile and (meth)acrylate esters

The urethane (meth)acrylate oligomer (A) may be obtained by the reaction between an organic isocyanate and a (meth)acrylate monomer having at least one hydroxyl group, optionally in the presence of a polyol. Specifically reaction can be carried out at normal pressure, at a temperature from about 60 to 80°C, and in the absence of a catalyst, but in order to promote the reaction there may be used from about 50 to 2000 ppm of a catalyst such as dibutyltin dilaurate. As examples of the organic isocyanate, there can be cited aromatic, aliphatic and alicyclic dusocyanates such as tolylene dusocyanate, 4, 4-dιphenylmethane dusocyanate, 1, 6-hexamethylene dusocyanate, xylylene dusocyanate and isophorone dusocyanate As examples of the (meth)acrylate monomer having at least one hydroxyl group there can be cited 2-hydroxyethyl (meth)acrylate, 2- hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxy-butyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethyleneglycol mono(meth)acrylate, pentaerythritol di (meth)acrylate pentaerythπtol tri (meth)acrylate and lactone-modifled 2-hydroxyethyl (meth) acrylate

As examples of the optional polyol there can be cited polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene glycol, propylene glycol, 1, 6-hexanedιol, polyester-polyols obtained by the reaction between a polyhydric alcohol and adipic acid or a similar polybasic acid, polycarbonate-polyols, and lactone-based polyester-polyols such as polycaprolactone and polybutyrolactone

The epoxy (meth)acrylate oligomer (A) may be obtained by the reaction between an epoxy resin and a (meth)acrylate monomer with at least one functional group in the molecule which possesses reactivity for epoxy groups Specifically, such reaction may be carried out at normal pressure, at a temperature from about 100°C to about 140°C, using from about 0.5 to 3% of a catalyst such as triethylamme or triethylbenzylammonium chloride to promote the reaction. As the aforesaid epoxy resin mention may be made of bisphenol- A type epoxy resins, novolak type epoxy resins, alicyclic epoxy resins and their modified derivatives. Further, as examples of the (meth)acrylate monomer with at least one functional group n the molecule which possesses reactivity for epoxy groups, may be mentioned acrylic acid, methacrylic acid, β-carboxyethyl acrylate, and the like

The polyester (meth)acrylate oligomer (A) may be obtained by the reaction between (a) a polyol, (b) an organic acid with at least two carboxyl groups in the molecule, or the anhydride of such organic acid, and (c) a (meth)acrylate monomer with at least one carboxyl group in the molecule. Specifically, (a) , (b) and a solvent such as dichloroethane or a hydrocarbon used for the azeotropic removal of water, are introduced into a reactor and an esterification reaction is carried out under reduced pressure, at a temperature from about 80°C to about 150°C From about 50 to 2000 ppm of a catalyst such as dibutyltin oxide may be used to promote the reaction When (b) is an acid anhydride, the reaction may be performed at normal pressure, and no solvent for azeotropic removal of water is required. Following the esterification, (c) is added, and further reaction is carried out at a temperature of about 80°C to about 120°C. From 0 1 to 1% of a strong acid catalyst such as sulphuric acid or methanesulphonic acid may be added for promoting the reaction.

As examples of the polyol (a) , there can be cited polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene glycol, propylene glycol, 1, 6-hexanedιol, polyester-polyols, polycarbonate-polyols, and lactone-based polyester-polyols such as poly-caprolactone and polybutyrolactone.

As examples of the organic acid (b) or anhydrides thereof, there can be cited phthalic acid, adipic acid, phthalic anhydride, pyromellitic anhydride tπmellitic anhydride, isophthalic acid, terephthalic acid and the like Again, as examples of the (meth)acrylate monomer (c) , there can be cited acrylic acid, methacrylic acid, β-carboxyethyl acrylate, and the like

It is essential that the oligomer (A) component comprises from about 95 to about 10 wt%, and preferably from 80 to 40 wt% of the composition of the invention With more than about 95 wt% of the oligomer (A) , there is considerable cure shrinkage at the time of curing, and the adhesion to the coating substrate is lowered. Conversely, with less than about 10 wt% of the oligomer (A) , properties of the coated film such as the tensile strength are markedly lowered

Polymer (B) thus preferably comprises from 20 to 60 wt% of the composition of the invention As examples of the starting material monomer used for polymer (B) , there can be cited styrene, acrylonitrile, methacrylonitrile, ethyl acrylate butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2- hydroxypropyl acrylate, methyl methacrylate, butyl methacrylate, 2- hydroxyethyl methacrylate and the like. These starting material monomers are subjected to a polymerization reaction until a number average molecular weight in the range from about 500 to about 20,000 is obtained, and preferably in the range from 2,000 to 10,000 If the number average molecular weight is more than about 20,000, the final viscosity of the composition of the present invention is too high and therefore unsuitable for practical application Conversely, with a number average molecular weight of less than about 500, the adhesion of the composition of the present invention to the coating substrate is markedly reduced.

Further, in the present invention, it is possible to use a polymer (B) where terminal or side chain portions of the aforesaid polymer molecules have been modified (capped) by means of hydroxyl groups or polymerizable groups such as acryloyl groups, methacryloyl groups, allyl groups, styryl groups, vinyl benzyl groups, vinyl ether groups, vinyl silyl groups, dicyclopentadienyl groups, isopropenylphenyl groups, 5-norbornen-2-yl groups, or di ethylsiloxanyl groups, thus constituting what is commonly named a macromer.

Further, m the present invention, any ethylenically unsaturated monomer can be added to the composition with the objective of adjusting the viscosity of the composition or improving the properties of the coated f lm

As specific examples of such monomer, there can be cited styrene, acrylonitrile, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, cyclohexyl acrylate, 2-chlorostyrene, 2,4- dichlorostyrene, acrylic acid, 2-hydroxyethyl acrylate, methacrylic acid, butyl methacrylate, 2-hydroxyethyl methacrylate, 1, 6-hexanedιol diacrylate, trimethylolpropane triacrylate, penta-erythπtol triacrylate, dipentaerythritol hexaacrylate, and mixtures thereof

The radiation hardening resin composition of the present invention can be cured by ultraviolet radiation, electron beam, etc, and in the case of curing by ultraviolet radiation there can be added a photopolymerization initiator such as benzoin, benzoin methyl ether, benzyl dimethyl ketal, 2- hydroxy-2-methyl-1-phenylpropan-l-one and benzophenone, etc Further, where required, there can also be used a photoactivator such as amines ureas, sulphur-containing compounds, phosphorus-containing compounds and sulphur- containing compounds, etc

The radiation-cured resin composition thus obtained constitute a second object of the present invention.

The radiation hardening and radiation cured resin compositions obtained by the present invention, can be used in wide-ranging fields of industry such as for example in the composition of various kinds of coating agents, inks and paints

In the following examples, reference to 'parts' shall mean 'parts by weight'

Example 1 444 g (2 mole) of isophorone dusocyanate (IPDI) and 0.05 g of stannous chloride were introduced into a reaction vessel provided with a stirrer, thermometer, dropping funnel and dry air supply inlet, and which was immersed m an oil bath When IPDI had reached 70°C, 530 g (1 mole) of Placcel 205, a polycaprolactone diol of molecular weight 530 marketed by Daicel Chemical Industries was added from the dropping funnel

Following this addition, polycaprolactone urethane prepolymer was produced by maintaining the internal temperature of the reaction vessel at 70°C until the residual NCO concentration reached the stoichiometric value. Subsequently, 232 g (2 mole) of 2-hydroxyethyl acrylate was added, after which maturation/ageing was carried out while maintaining the reaction vessel interior at 70°C, until the residual NCO concentration m a sample of extracted reaction product reached 0 1% or less In this way, a urethane acrylate oligomer (Al) was obtained

Example 2

Urethane acrylate oligomer (A2) was obtained in the same way as in Example 1 except that the IPDI was changed to 336 g (2 mole) of 1,6- hexamethylene dusocyanate.

Examples 3 to 8

Radiation hardening resin compositions were prepared by mixing the urethane acrylate oligomers obtained in Examples 1 and 2 with the amount of the various other components specified in Table 1.

Examples 7 and 8 are comparative.

Table 1

Example 3 4 5 6 7 8

Al 60 50 60

A2 60 50 60 macromer B *2 20 30 20 30 0 0

IBOA *2 20 20 20 20 40 40 photoinitiator *3 5 5 5 5 5 5

"1 Macromonomer HN-6, marketed by Toagosei Chemical Industry Co.

"2 isobornyl acrylate

*3 2-hydroxy-2-methyl-l-phenylpropan-l-one (Dalocure 1173, marketed by Ciba Geigy)

The performance of the radiation hardening resin compositions and the properties of their coated films, were measured by the following methods. The results are shown in Table 2. (1) UV curability UV irradiation conditions:- high pressure mercury lamp 1 lamp lamp output 120 W/cm lamp irradiation distance 10 cm conveyor speed 10 m/min The compositions were respectively coated to a thickness of 100 μm on glass plates, then UV irradiation carried out under the aforesaid conditions, after which in each case the surface of the coated film was assessed by touch for any tackiness .

(2) Mechanical properties

A 100 μm thickness coated film was produced under the aforesaid UV irradiation conditions, and then tensile testing carried out based on standard method JIS K7113. The breaking strength, elongation at break, and Young's modulus were thus measured.

Table 2

Example UV Curability Breaking Elongation Young's

Strength at break Modulus

[g/mm2] [kg/mπι2]

3 good 1050 85 1210

4 good 1100 105 1550

5 good 910 95 1090

6 good 980 120 1440

7 good 720 25 700

8 good 560 35 570