JP5731742B2 - Energy ray curable elastomer composition - Google Patents

Description

  The present invention relates to an energy beam curable elastomer composition, and more specifically, by adopting an ene-thiol-based energy beam curable system, the type of energy beam curable compound, preferably oligomer, before curing is changed. The present invention relates to an energy beam curable elastomer composition that can increase the molecular weight between cross-linking points and provides an elastomer cured product having both elongation at break and processability.

  In general, a composition that imparts so-called rubber properties such as flexibility, stretchability, and elasticity is called an elastomer, and its fatigue durability against vibration is far superior to that of other polymer materials. Applicable as sealing members for structures such as members, civil engineering and construction, packing members such as O-rings, gasket members, acoustic members such as speakers, sheet members such as key sheets for mobile phones, anti-vibration materials, various mechanism members, etc. Has been.

By the way, in recent years, HDDs (hard disk drives) of computers have been improved in performance and size and have a complicated circuit configuration, and even a small amount of dust causes a failure. There is a growing need, and it is common practice to use a gasket to prevent dust from entering.
As a method for manufacturing an HDD gasket, a method of injection-molding a thermoplastic elastomer or the like, a method of punching a sheet made of EPDM (ethylene propylene diene rubber) or fluorine rubber into a predetermined shape, and adhering it is adopted. I came.
On the other hand, in recent years, in order to reduce capital investment and processing costs, a photocurable sealant composition is applied to an adherend using a dispenser, molded, and then cured mainly by ultraviolet rays to produce a gasket. The method of doing has come to be taken (for example, refer patent document 1). In order to obtain sufficient sealing properties as a gasket, a urethane acrylate oligomer is used as a main component in the composition for a photocurable sealing material so that the cured product has a low hardness.

  In an elastic body using such a composition for a photocurable sealing material, it is necessary to increase the molecular weight between crosslinking points in order to increase the elongation at break. In order to increase the molecular weight between cross-linking points, it is conceivable to increase the molecular weight of the urethane acrylate oligomer. In this case, however, the viscosity of the photocurable sealing material composition increases, for example, in application using a dispenser. This technique is unavoidable due to a decrease in workability, and this method is difficult to adopt. Moreover, as a method of increasing the elongation at break, a method of blending oil or the like is conceivable, but there is contamination due to bleed out, and this method is not sufficient. Therefore, it has been difficult to control the mechanical properties of the elastic body made of a cured product of the sheet material composition by ultraviolet irradiation.

  On the other hand, the ene-thiol photocurable resin composition, which is a radical polymerization type photocuring system, regenerates active thiyl radicals even when radical deactivation occurs due to oxygen, and thus is found in acrylic materials. There is no polymerization inhibition by oxygen, the amount of photoinitiator used can be reduced, the volumetric shrinkage during curing is small, curing in a few seconds to several minutes from the start of polymerization, extremely hardness It has attracted attention as a photo-curing material because it has advantages such as the ability to design a wide range of materials from high-cured cured products to flexible cured products and the ability to produce cured products with a thickness of 1 mm or more. (Refer nonpatent literature 1).

  Examples of the ene-thiol-based photocurable resin composition include (1) polyene, polythiol, and a compound having a bromine-substituted aromatic ring having a specific structure, and the mass ratio of polyene to polythiol is 49: (1) 1:49 photocurable resin composition (see Patent Document 2), and (2) a polyene compound, and a (poly) thiol monomer comprising a reaction product of a polyamine compound and a mercaptocarboxylic acid compound An ene-thiol-based photocurable resin composition (see Patent Document 3) is disclosed.

JP 2003-7047 A Japanese Patent No. 4034098 JP 2007-70417 A

“Prospects for UV / EB Curing Technology”, CMC Publishing, 2002, pages 39-50

However, the technique disclosed in Patent Document 2 is a technique for providing a photocurable resin composition having a high refractive index and capable of adjusting the refractive index with high accuracy. No mention is made of processability. In addition, the technique disclosed in Patent Document 3 has no inhibition of polymerization due to oxygen, can be cured in a short time, has a small volume shrinkage, can reduce the amount of photoinitiator used, and greatly improves moisture resistance. This is a technique for providing a cured product, and no mention is made of the elongation at break and workability of the cured product.
The present invention was made under such circumstances, and without changing the type of the energy beam curable compound before curing, the molecular weight between the crosslinking points could be increased, and both elongation at break and workability were compatible. An object of the present invention is to provide an energy ray curable elastomer composition that provides an elastomer.

  As a result of intensive studies to achieve the above object, the inventors of the present invention include an energy ray-curable compound having a (meth) acryloyl group and a polythiol compound having 2 to 6 mercapto groups, It was found that the object can be achieved by an energy ray curable elastomer composition in which the ratio of the number of functional groups of acryloyl groups and mercapto groups is within a specific range. The present invention has been completed based on such findings.

That is, the present invention
[1] An energy ray curable elastomer composition comprising (A) an energy ray curable compound having a (meth) acryloyl group and (B) a polythiol compound having 2 to 6 mercapto groups in the molecule, The functional group number ratio of the (meth) acryloyl group in the composition to the mercapto group in the component (B) is 100: 0.1 to 100: 5n (n is the number of mercapto groups in one molecule of the polythiol compound). An energy ray curable elastomer composition, characterized in that:
[2] The energy beam curable elastomer composition according to the above [1], wherein the cured product by energy beam irradiation has a molecular weight between crosslinks calculated from the Flory-Rehner formula of 4,000 to 55,000. ,
[3] Energy according to [1] or [2] above, wherein the energy ray-curable compound having (A) (meth) acryloyl group is a compound having at least two (meth) acryloyl groups in the molecule. Wire curable elastomer composition,
[4] The energy ray curable elastomer composition according to the above [3], wherein the energy ray curable compound having a (meth) acryloyl group is an energy ray curable oligomer,
[5] The energy ray curable oligomer is a urethane (meth) acrylate oligomer, a polyester (meth) acrylate oligomer, a polyether (meth) acrylate oligomer, an epoxy (meth) acrylate oligomer, or a conjugated diene polymer system (meth). The energy ray-curable elastomer composition according to the above [4], which is at least one selected from an acrylate oligomer and a hydrogenated product thereof,

[6] (B) In the above [1] to [5], the polythiol compound having 2 to 6 mercapto groups in the molecule is a polyhydric alcohol β-mercaptopropionic acid ester having 2 to 6 hydroxyl groups. The energy ray curable elastomer composition according to any one of the above,
[7] The polyhydric alcohol having 2 to 6 hydroxyl groups is an alkanediol having 2 to 20 carbon atoms, poly (oxyalkylene) glycol, glycerol, diglycerol, trimethylolpropane, ditrimethylolpropane, pentaerythritol or dipentaerythritol. The energy ray curable elastomer composition according to the above [6],
[8] The energy ray-curable elastomer composition according to any one of the above [1] to [7], wherein the energy ray is ultraviolet light and (C) contains a photoradical polymerization initiator, and [9] a photoradical The energy ray-curable elastomer composition according to [8] above, wherein the polymerization initiator is an intramolecular cleavage type and / or a hydrogen abstraction type,
Is to provide.

The energy ray curable elastomer composition of the present invention has the following effects.
(1) By adopting an ene-thiol energy beam curing system, the molecular weight between crosslink points of the cured product can be increased without changing the type of energy beam curable compound before curing, and the elongation at break It is possible to provide a cured elastomer that has both good processability.
(2) When the molecular weight between cross-linking points of the cured product by irradiation with energy rays is in the range of 4,000 to 55,000, the effect (1) is exhibited well.
(3) If the energy ray-curable compound has at least two (meth) acryloyl groups, preferably an oligomer, the effect of the above (1) is more satisfactorily exhibited.
(4) As the polythiol compound, a β-mercaptopropionic acid ester of a polyhydric alcohol having 2 to 6 hydroxyl groups is easily available and exhibits the excellent effect (1).
(5) By irradiating ultraviolet rays as energy rays in the presence of a photopolymerization initiator, an elastomer having both elongation at break and workability can be obtained with high productivity.

  The energy beam curable elastomer composition of the present invention (hereinafter sometimes simply referred to as an elastomer composition) includes (A) an energy beam curable compound having a (meth) acryloyl group, and (B) a mercapto in the molecule. A functional group number ratio of (meth) acryloyl group in the composition to mercapto group in the component (B) is 100: 0.1 to 100: 5n (n Is the number of mercapto groups in one molecule of the polythiol compound.

[(A) Energy beam curable compound]
In the elastomer composition of the present invention, an energy ray curable compound having a (meth) acryloyl group is used as the component (A). As this energy ray curable compound, those having at least two (meth) acryloyl groups in the molecule can be suitably used from the viewpoint of the performance and processability of the resulting elastomer. The number of (meth) acryloyl groups in one molecule is usually about 2 to 6, preferably 2 to 4, particularly preferably 4.
The (meth) acryloyl group refers to an acryloyl group or a methacryloyl group.
Such an energy ray curable compound is preferably an energy ray curable oligomer having a (meth) acryloyl group.

(Energy beam curable oligomer having (meth) acryloyl group)
There is no restriction | limiting in particular as an energy-beam curable oligomer which has a (meth) acryloyl group, For example, a urethane type (meth) acrylate oligomer, a polyester type (meth) acrylate oligomer, a polyether type (meth) acrylate oligomer, an epoxy type (meta ) Acrylate oligomers, conjugated diene polymer (meth) acrylate oligomers and hydrogenated products thereof.
Here, the urethane-based (meth) acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by a reaction between a polyether polyol or a polyester polyol and a polyisocyanate with (meth) acrylic acid. .
Polyester (meth) acrylate oligomers can be obtained by, for example, esterifying the hydroxyl groups of polyester oligomers having hydroxyl groups at both ends with (meth) acrylic acid, obtained by condensation of polyvalent carboxylic acids and polyhydric alcohols. It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding an alkylene oxide to a carboxylic acid with (meth) acrylic acid.

The polyether (meth) acrylate oligomer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid, and the epoxy (meth) acrylate oligomer is, for example, a bisphenol type having a relatively low molecular weight. It can be obtained by reacting (meth) acrylic acid with an oxirane ring of an epoxy resin or a novolak-type epoxy resin for esterification. A carboxyl-modified epoxy acrylate oligomer obtained by partially modifying this epoxy-based (meth) acrylate oligomer with a dibasic carboxylic acid anhydride can also be used.
Examples of the conjugated diene polymer (meth) acrylate oligomer include SBR diacrylate obtained by acrylic modification of liquid styrene-butadiene copolymer, and polyisoprene acrylate obtained by acrylic modification of polyisoprene. The hydrogenated conjugated diene polymer (meth) acrylate oligomer can be obtained, for example, by esterifying the hydroxyl group of hydrogenated polybutadiene or hydrogenated polyisoprene having hydroxyl groups at both ends with (meth) acrylic acid. .
In addition, (meth) acrylate refers to acrylate or methacrylate, and (meth) acrylic acid refers to acrylic acid or methacrylic acid.

  In the present invention, the energy ray-curable oligomer having the (meth) acryloyl group may be used alone or in combination of two or more. For example, for use in sealing members such as gaskets. When used, among the oligomers, a bifunctional urethane-based (meth) acrylate oligomer is preferable from the viewpoint of performance and processability of the obtained elastomer. The bifunctional urethane-based (meth) acrylate oligomer means that two (meth) acryloyl groups are contained in one molecule of the urethane-based (meth) acrylate oligomer.

[(B) polythiol compound]
In the energy ray-curable elastomer composition of the present invention, the polythiol compound used as the component (B) is a compound having 2 to 6 mercapto groups in the molecule.
Such a polythiol compound is not particularly limited as long as it has 2 to 6 mercapto groups in the molecule. For example, aliphatic polythiols such as alkanedithiol having about 2 to 20 carbon atoms, xylylene diene Aromatic polythiols such as thiols, polythiols obtained by substituting halogen atoms of halohydrin adducts of alcohols with mercapto groups, polythiols consisting of hydrogen sulfide reaction products of polyepoxide compounds, and 2-6 hydroxyl groups in the molecule. And polythiols composed of esterified products of polyhydric alcohols having thioglycolic acid, β-mercaptopropionic acid, or β-mercaptobutanoic acid.

Among these polythiols, a polyhydric alcohol having 2 to 6 hydroxyl groups in the molecule, which has good reactivity and easy chemical structure control, thioglycolic acid, β-mercaptopropionic acid, or β- Preference is given to polythiols comprising esterified products with mercaptobutanoic acid, in particular esterified products with β-mercaptopropionic acid, and esterified products with β-mercaptobutanoic acid.
Examples of the polyhydric alcohol having 2 to 6 hydroxyl groups in the molecule include alkanediol having 2 to 20 carbon atoms, poly (oxyalkylene) glycol, glycerol, diglycerol, trimethylolpropane, ditrimethylolpropane, and pentaerythritol. And dipentaerythritol.

The alkanediol having 2 to 20 carbon atoms may be linear, branched or cyclic, for example, ethylene glycol, trimethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butane. Examples include diol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,12-dodecanediol, cyclohexane-1,4-dimethanol, hydrogenated bisphenol A, and the like. It is done.
Examples of the poly (oxyalkylene) glycol include diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, polytetramethylene ether glycol, cyclohexane-1,4-dimethanol ethylene oxide adduct, water Examples thereof include a bisphenol A ethylene oxide adduct, a cyclohexane-1,4-dimethanol propylene oxide adduct, and a hydrogenated bisphenol A propylene oxide adduct.

  In the present invention, as the polythiol compound of component (B), for example, ethylene glycol di (thioglycolate), ethylene glycol di (β-mercaptopropionate), ethylene glycol di (β-mercaptobutanate), trimethylene glycol Di (thioglycolate), trimethylene glycol di (β-mercaptopropionate), trimethylene glycol di (β-mercaptobutanoate), propylene glycol di (thioglycolate), propylene glycol di (β-mercaptopropioate) Nate), propylene glycol di (β-mercaptobutanate), 1,3-butanediol di (thioglycolate), 1,3-butanediol di (β-mercaptopropionate), 1,3-butanediol di (Β-mercaptobutanate ), 1,4-butanediol di (thioglycolate), 1,4-butanediol di (β-mercaptopropionate), 1,4-butanediol di (β-mercaptobutanate), neopentyl glycol di (Thioglycolate), neopentyl glycol di (β-mercaptopropionate), neopentyl glycol di (β-mercaptobutanate), 1,6-hexanediol di (thioglycolate), 1,6-hexanediol Di (β-mercaptopropionate), 1,6-hexanediol di (β-mercaptobutanate), 1,8-octanediol di (thioglycolate), 1,8-octanediol di (β-mercaptopro) Pionate), 1,8-octanediol di (β-mercaptobutanate), 1,9-nonanediol di (Thioglycolate), 1,9-nonanediol di (β-mercaptopropionate), 1,9-nonanediol di (β-mercaptobutanate), cyclohexane-1,4-dimethanoldi (thioglycolate), Cyclohexane-1,4-dimethanol di (β-mercaptopropionate), cyclohexane-1,4-dimethanol di (β-mercaptobutanate), diethylene glycol di (thioglycolate), diethylene glycol di (β-mercaptopropionate), Diethylene glycol di (β-mercaptobutanate), triethylene glycol di (thioglycolate), triethylene glycol di (β-mercaptopropionate), triethylene glycol di (β-mercaptobutanate), polyethylene glycol di (t Oglycolate), polyethylene glycol di (β-mercaptopropionate), polyethylene glycol di (β-mercaptobutanoate), dipropylene glycol di (thioglycolate), dipropylene glycol di (β-mercaptopropionate), Dipropylene glycol di (β-mercaptobutanate), tripropylene glycol di (thioglycolate), tripropylene glycol di (β-mercaptopropionate), tripropylene glycol di (β-mercaptobutanate), polypropylene glycol di (Thioglycolate), polypropylene glycol di (β-mercaptopropionate), polypropylene glycol di (β-mercaptobutanate), polytetramethylene ether glycol di (thioglycolate) ), Polytetramethylene ether glycol di (β-mercaptopropionate), polytetramethylene ether glycol di (β-mercaptobutanate), di (thioglycolate) of cyclohexane-1,4-dimethanol ethylene oxide adduct Di (β-mercaptopropionate) of cyclohexane-1,4-dimethanol ethylene oxide adduct, di (β-mercaptobutanoate) of cyclohexane-1,4-dimethanol ethylene oxide adduct, hydrogenated bisphenol A Di (thioglycolate) of ethylene oxide adduct, di (β-mercaptopropionate) of hydrogenated bisphenol A ethylene oxide adduct, di (β-mercaptobutanate) of hydrogenated bisphenol A ethylene oxide adduct, cyclohexane -1 Di (thioglycolate) of 4-dimethanol propylene oxide adduct, di (β-mercaptopropionate) of cyclohexane-1,4-dimethanol propylene oxide adduct, cyclohexane-1,4-dimethanol propylene oxide addition (Β-mercaptobutanoate), hydrogenated bisphenol A propylene oxide adduct di (thioglycolate), hydrogenated bisphenol A propylene oxide adduct di (β-mercaptopropionate), hydrogenated bisphenol A propylene Dioxide (β-mercaptobutanate), glycerol tri (thioglycolate), glycerol tri (β-mercaptopropionate), glycerol tri (β-mercaptobutanate), diglycerol tetra (thioglycolate) ), Diglycerol tetra (β-mercaptopropionate), diglycerol tetra (β-mercaptobutanate), trimethylolpropane tri (thioglycolate), trimethylolpropane tri (β-mercaptopropionate), trimethylol Propanetri (β-mercaptobutanate), ditrimethylolpropanetetra (thioglycolate), ditrimethylolpropanetetra (β-mercaptopropionate), ditrimethylolpropanetetra (β-mercaptobutanoate), pentaerythritoltetra (thiol) Glycolate), pentaerythritol tetra (β-mercaptopropionate), pentaerythritol tetra (β-mercaptobutanate), dipentaerythritol hexa (thioglycolate), dipenta Risuri Tall hexa (beta-mercaptopropionate), dipentaerythritol hexa (beta-mercapto pig titanate) can be preferably used.

  Among these polythiol compounds, poly (β-mercaptopropionate) and poly (β-mercaptobutanate) are preferred, and in particular, polyethylene glycol di (β-mercaptopropionate), pentaerythritol tetra (β- Mercaptopropionate), dipentaerythritol hexa (β-mercaptopropionate), polyethylene glycol di (β-mercaptobutanate), pentaerythritol tetra (β-mercaptobutanate) and dipentaerythritol hexa (β-mercaptobutane) Nate) is preferred from the standpoint of availability and performance of the resulting elastomer.

As the polythiol compound as the component (B), one type may be used alone, or two or more types may be used in combination. The content of the polythiol compound of the component (B) in the elastomer composition of the present invention is such that the functional group number ratio between the (meth) acryloyl group in the elastomer composition and the mercapto group in the component (B) is 100. : 0.1 to 100: 5n (n is the number of mercapto groups in one molecule of the polythiol compound).
That is, when a bifunctional compound having two mercapto groups in the molecule is used as the polythiol compound, the (meth) acryloyl group / mercapto group functional group ratio is 100: 0.1 to 100: 10. When a tetrafunctional compound having 4 groups is used, the ratio of the number of functional groups of (meth) acryloyl group / mercapto group is 100: 0.1 to 100: 20, and a hexafunctional compound having 6 mercapto groups is used. In this case, the functional group number ratio of (meth) acryloyl group / mercapto group is 100: 0.1 to 100: 30.
When the mercapto group is less than 0.1 with respect to the (meth) acryloyl group 100, the effect of blending the polythiol compound is not sufficiently exhibited, and the object of the present invention cannot be achieved. On the other hand, if the mercapto group exceeds the upper limit value that is added to the (meth) acryloyl group 100 according to the polythiol compound to be used, the resulting elastomer cured body will be fluidly broken. From the above viewpoint, the ratio of the number of functional groups of (meth) acryloyl group / mercapto group is preferably in the range of 100: n to 100: 5n, and more preferably in the range of 100: 2n to 100: 5n.

The elastomer composition of the present invention is an energy ray curable type, and as the energy ray, ionizing radiation such as ultraviolet rays, electron rays, α rays, β rays, γ rays and the like can be used. From the viewpoint of productivity, productivity and economy, it is preferable to use ultraviolet rays. When ultraviolet rays are used, the elastomer composition preferably contains a radical photopolymerization initiator as the component (C). In addition, when using ionizing radiation like an electron beam and a gamma ray, hardening can be rapidly advanced even if it does not contain a photoinitiator.
The amount of the radical photopolymerization initiator to be contained in the elastomer composition of the present invention is usually about 0.1 to 10 parts by mass, preferably about 100 to 10 parts by mass, preferably 100 parts by mass of the total energy ray curable compound contained in the composition. 0.5 to 3 parts by mass. Moreover, in this invention, a well-known photosensitizer can be used together with the said radical photopolymerization initiator.

[(C) Photoradical polymerization initiator]
As the radical photopolymerization initiator of component (C), an intramolecular cleavage type and / or a hydrogen abstraction type can be used.
Examples of the intramolecular cleavage type include benzoin derivatives, benzyl ketals [for example, Ciba Specialty Chemicals Co., Ltd., trade name: Irgacure 651], α-hydroxyacetophenones [for example, Ciba Specialty Chemicals Co., Ltd.] Product name: Darocur 1173, Irgacure 184, Irgacure 127, Irgacure 2959], α-aminoacetophenones [for example, Ciba Specialty Chemicals, Inc., product names: Irgacure 907, Irgacure 369], α-aminoacetophenone And thioxanthones (for example, isopropylthioxanthone, diethylthioxanthone), acylphosphine oxides [for example, Ciba Specialty Chemicals, Inc., trade name: Irgacure 819] Etc., and the like.

  Examples of the hydrogen abstraction type include a combined use of benzophenones and an amine, and a combined use of thioxanthone and an amine. Further, an intramolecular cleavage type and a hydrogen abstraction type may be used in combination. Of these, oligomerized α-hydroxyacetophenone and acrylated benzophenones are preferred. More specifically, oligo [2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone] [for example, Lamberti S. et al. p. A product, trade name: ESACURE KIP150, etc.], acrylated benzophenone [for example, trade name: Ebecryl P136, etc., manufactured by Daicel UCB Co., Ltd.], imide acrylate, and the like.

  As the radical photopolymerization initiator of component (C), in addition to these, 1- [4- (2-hydroxyethoxy) phenyl] -2-methyl-1-propan-1-one, 1-hydroxy-cyclohexyl- Phenyl-ketone, mixture of 1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2,4,6-trimethylbenzoylphenylphosphine oxide, 2,4 , 6-Trimethylbenzoylphenylphenylethoxyphosphine oxide, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one 2-methyl-1-[(4-methylthio) phenyl] -2-morpholino Lopan-1-one, benzoyl methyl ether, benzoyl ethyl ether, benzoyl butyl ether, benzoyl isopropyl ether, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, 2-hydroxy-2-methyl- [4- (1- Methylvinyl) phenyl] propanol oligomer, mixture of 2-hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propanol oligomer and 2-hydroxy-2-methyl-1-phenyl-1-propanone, isopropylthioxanthone , Methyl o-benzoylbenzoate and [4- (methylphenylthio) phenyl] phenylmethane can also be used.

[Optional ingredients]
In the elastomer composition of the present invention, as necessary, for example, a monofunctional (meth) acrylate monomer, an inorganic filler, an organic thickener, a coupling agent, as long as the object of the present invention is not impaired. Antioxidants, light stabilizers, adhesion improvers, reinforcing agents, internal mold release agents, softeners, colorants, leveling agents, flame retardants, antistatic agents, and the like can be used.

(Monofunctional (meth) acrylate monomer)
The monofunctional (meth) acrylate monomer is a compound having one (meth) acryloyl group in the molecule, and is necessary for adjusting the viscosity of the elastomer composition of the present invention and adjusting the physical properties of the resulting elastomer. The compound is used in an appropriate amount.
Examples of the monofunctional (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and tert-butyl (meth). Acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, tridecyl (meth) acrylate, behenyl (meth) acrylate, methoxyethyl ( (Meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate , Methoxytriethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxytetraethylene glycol (meth) acrylate, phenoxyhexaethylene glycol (meth) acrylate , Methoxydipropylene glycol (meth) acrylate, methoxytripropylene glycol (meth) acrylate, cyclohexyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, dicyclopenta Nyl (meth) acrylate, dicyclopentenyl (meth) acrylate, bornyl (meth ) Acrylate, isobornyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, allyl (meth) acrylate. These may be used individually by 1 type and may be used in combination of 2 or more type.

(Inorganic filler)
By blending an inorganic filler or an organic thickener described later in the elastomer composition of the present invention, thickening and thixotropy can be imparted to the composition, and the moldability of the composition can be improved. it can.
Examples of the inorganic filler include silica (SiO ₂ ), alumina, titania, viscosity mineral, and the like, and among these, silica powder, hydrophobically treated silica powder, or a mixture thereof is preferable. More specifically, a silica fine powder pulverized by a dry method [for example, product name: Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.], a fine powder obtained by modifying this silica fine powder with trimethyldisilazane [for example, Japan Aerosil Co., Ltd., trade name: Aerosil RX300, etc.] and fine powder obtained by modifying the above silica fine powder with polydimethylsiloxane [for example, Nippon Aerosil Co., Ltd., trade name: Aerosil RY300, etc.].
The average particle diameter of the inorganic filler is preferably 5 to 50 μm, more preferably 5 to 12 μm, from the viewpoint of thickening and thixotropy.

(Organic thickener)
As the organic thickener, hydrogenated castor oil, amide wax or a mixture thereof is preferable. Specifically, as an organic thickener, hydrogenated castor oil which is a hydrogenated product of castor oil (non-drying oil whose main component is ricinoleic acid) [for example, product name: ADVITROL100, Enomoto Kasei Co., Ltd. Product name: Disparon 305, etc.] and higher amide waxes that are compounds in which hydrogen of ammonia is substituted with an acyl group [for example, trade name: Disparon 6500, manufactured by Enomoto Kasei Co., Ltd.].
These may be used alone or in combination of two or more, or may be used in combination with the inorganic filler.

(Coupling agent)
The coupling agent is used in an appropriate amount as needed in the elastomer composition of the present invention in order to improve the adhesion between the obtained elastomer and the substrate. Examples of the coupling agent include a silane coupling agent, a titanate coupling agent, and an aluminum coupling agent. Among these coupling agents, a silane coupling agent is preferable.
The silane coupling agent is not particularly limited, but examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropyltriethoxysilane. Saturated group-containing silane coupling agents; glycidyl group-containing silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane; γ-aminopropyltrimethoxysilane, γ-aminopropyltri Amino group-containing silane coupling agents such as ethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane; γ-mercaptopropyl Trimethoxysilane, γ- Mercapto group-containing silane coupling agents such as Le mercaptopropyl triethoxysilane, and the like. These silane coupling agents may be used singly or in combination of two or more.

(Antioxidant)
Examples of the antioxidant used in the elastomer composition of the present invention include phenol-based, sulfur-based, and phosphorus-based antioxidants.
Examples of phenolic antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4- Hydroxy-5-tert-butylphenylbutane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis -[Methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis- (4′-hydroxy-3′-t-butyl) Phenyl) butyric acid] glycol ester, 1,3,5-tris (3 ′, 5′-di-t-butyl-4′-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H , 5H) trione, α-tocopherol and the like.

  Examples of sulfur-based antioxidants include dilauryl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3′-thiodipropionate, and phosphorus-based oxidation. Examples of the inhibitor include triphenyl phosphite, diphenylisodecyl phosphite, phenylisodecyl phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, 2,2 ′. -Methylenebis (4,6-di-t-butylphenyl) octyl phosphite and the like are exemplified.

These antioxidants may be used individually by 1 type, and may be used in combination of 2 or more type, Among these, a phenolic antioxidant is suitable.
The blending amount of the antioxidant is appropriately selected according to the type of the antioxidant. The energy ray-curable compound (A), the polythiol compound (B), and the monofunctional (meta) used as desired. ) It is usually 0.01 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass as a total amount with the acrylate monomer.

(Light stabilizer)
Examples of the light stabilizer used in the elastomer composition of the present invention include benzophenone-based, benzotriazole-based, benzoate-based, and triazine-based ultraviolet absorbers, hindered amine light stabilizers, and the like. System light stabilizers are preferred.
Examples of the hindered amine light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 4- Benzoyloxy-2,2,6,6-tetramethylpiperidine, 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethyl-4-piperidinyl-methacrylate, Bis (1,2,2,6,6-pentamethyl-4-piperidinyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] Tilmalonate, decanedioic acid bis (2,2,6,6-tetramethyl-1- (octyloxy) -4-piperidinyl) ester, N, N ′, N ″, N ″ ′-tetrakis- (4,6- Bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine -1,3,5-triazine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6- Polycondensate of tetramethyl-4-piperidyl) butylamine, poly [[6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl] [(2 , 2,6,6-Tetramethyl-4-piperidyl ) Imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl) imino]], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol Polymer, 2,2,4,4-tetramethyl-20- (β-lauryloxycarbonyl) ethyl-7-oxa-3,20-diazadispiro [5.1.1.12] heneicosane-21-one, β -Alanine, N,-(2,2,6,6-tetramethyl-4-piperidinyl) -dodecyl ester / tetradecyl ester, N-acetyl-3-dodecyl-1- (2,2,6,6-tetra Methyl-4-piperidinyl) pyrrolidine-2,5-dione, 2,2,4,4-tetramethyl-7-oxa-3,20-diazadispiro [5.1.1.12] heneicosane-21 -One, 2,2,4,4-tetramethyl-21-oxa-3,20-diazadicyclo- [5.1.1.12] -heneicosane-20-propanoic acid dodecyl ester / tetradecyl ester propanedioic acid , [(4-Methoxyphenyl) -methylene] -bis (1,2,2,6,6-pentamethyl-4-piperidinyl) ester, higher fatty acid ester of 2,2,6,6-tetramethyl-4-piperidinol 1,3-benzenedicarboxamide-N, N′-bis (2,2,6,6-tetramethyl-4-piperidinyl) and the like.

  These may be used individually by 1 type and may be used in combination of 2 or more type. The blending amount of the light stabilizer is appropriately selected according to the type of the light stabilizer. The energy ray-curable compound (A), the polythiol compound (B), and a monofunctional (meta) compound used as desired. ) It is usually 0.01 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass as a total amount with the acrylate monomer.

(Adhesion improver, etc.)
In the elastomer composition of the present invention, examples of the adhesion improver used as desired include terpene resins, terpene phenol resins, coumarone resins, coumarone-indene resins, petroleum hydrocarbons, rosin derivatives, and the like. A seed may be used independently and may be used combining two or more sorts.
In addition, the elastomer composition may optionally comprise a reinforcing agent such as glass fiber or carbon fiber; a dripping agent such as hydrogenated castor oil or succinic anhydride fine particles; a fatty acid such as stearic acid; a fatty acid metal salt such as calcium stearate; Fatty acid amides such as stearic acid amide, fatty acid esters, polyolefin waxes, paraffin waxes and other internal mold release agents; process oils and other softeners; colorants; leveling agents; flame retardants;
The elastomer composition of the present invention is basically solvent-free, but a solvent may be added as necessary.

[Preparation of Elastomer Composition]
There is no restriction | limiting in particular in the preparation method of the elastomer composition of this invention, A well-known method is applicable. For example, a kneader capable of adjusting the temperature of the component (A), the component (B) and each additive component used as required, for example, a single screw extruder, a twin screw extruder, a planetary mixer, a twin screw mixer, a high shear It can be prepared by kneading using a mold mixer or the like.
The viscosity of the elastomer composition thus obtained is preferably 1 to 1000 Pa · s at 50 ° C. If it is 1 Pa · s or more, it can be prevented that a molded article having a desired shape is obtained due to liquid leakage or the like. On the other hand, if it is 1000 Pa · s or less, filling can be performed easily, and when the mold is used, the mold is not pushed up, so that a cured body having a desired shape can be easily obtained. From the above viewpoint, the viscosity of the elastomer composition at 50 ° C. is more preferably in the range of 10 to 500 Pa · s.

[Production of cured elastomer]
In the present invention, a cured elastomer can be obtained by irradiating the energy ray-curable elastomer composition prepared as described above with energy rays.
As described above, ultraviolet rays are preferable as the energy rays from the viewpoints of operability, productivity, economy, and the like. In addition, when using an ultraviolet-ray, it is preferable to use what contains radical photopolymerization initiator as an elastomer composition of this invention.
Examples of the ultraviolet light source include a xenon lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, and a microwave excimer lamp. The atmosphere for irradiation with ultraviolet rays is preferably an inert gas atmosphere such as nitrogen gas or carbon dioxide gas, or an atmosphere with a reduced oxygen concentration, but can be sufficiently cured even in a normal air atmosphere. The irradiation atmosphere temperature can usually be 10 to 200 ° C.
The curing method by irradiation with energy rays of the elastomer composition, preferably ultraviolet rays, can be appropriately selected depending on the use of the obtained elastomer cured body.

Next, when the elastomer composition is used to produce a member with a sealing layer, such as a gasket for a hard disk drive (HDD) of a computer, and an independent elastomer cured body (without a support or an adherend), an optical type The example in the case of using as an adhesive for bonding disks etc. is given, and the preferable aspect of the hardening method in each is demonstrated.
The use of the elastomer composition of the present invention will be described later.

(Member with seal layer)
A member with a seal layer can be produced by applying the energy ray-curable elastomer composition of the present invention to an adherend and curing it by irradiation with energy rays, preferably ultraviolet rays. As the adherend, for example, one made of a hard resin can be used, but a metal one is preferable from the viewpoint of workability. There are no particular restrictions on the metal, for example, cold-rolled steel sheet, galvanized steel sheet, aluminum / zinc alloy plated steel sheet, stainless steel sheet, aluminum plate, aluminum alloy plate, magnesium plate, magnesium alloy plate, etc. Can be used. Moreover, what injection-molded magnesium can also be used. From the viewpoint of corrosion resistance, a nickel-plated metal is preferred.
Examples of the member with a seal layer include a seal material, a gasket for HDD, an ink tank seal, a liquid crystal seal, and the like. The thickness of the seal layer can be appropriately selected depending on the application, but is usually about 0.1 to 2.0 mm.

  Application of the composition to an adherend can be performed by any method using a coating liquid that is temperature-adjusted as necessary and adjusted to a constant viscosity, such as gravure coating, roll coating, Methods such as spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating, dipping, and dispensing can be used. After apply | coating and shaping | molding the said composition, an application layer is hardened by irradiating an energy ray, Preferably an ultraviolet-ray, and a member with a sealing layer can be obtained.

(Independent cured elastomer)
The independent elastomer cured body refers to the elastomer cured body itself having no support or adherend.
When the above independent elastomer cured product is produced by ultraviolet irradiation, various methods can be adopted as the means. Preferably, (1) at least one set of molding die including an upper die and a lower die is used. Either one is formed of a material that transmits ultraviolet rays, and a predetermined amount of the elastomer composition before curing is dropped. Next, the upper mold and the lower mold are pressure-bonded, the mold is closed, and the composition is cured by irradiating ultraviolet rays from the outside of the mold made of a material that transmits ultraviolet rays, and (2) At least one of a set of upper and lower molds is made of a material that transmits ultraviolet light, and then the upper and lower molds are crimped, closed, and then pre-formed on the mold. A predetermined amount of the elastomer composition before curing is injected from the injection port. And the method of irradiating an ultraviolet-ray from the outer side of the type | mold which consists of a material which permeate | transmits an ultraviolet-ray, hardening a composition, and obtaining the target elastomer hardening body is preferable.

  Examples of materials used for the mold that transmits ultraviolet rays include glass materials such as quartz, quartz glass, borosilicate glass, and soda glass, acrylic resin, polycarbonate resin, polystyrene resin, polyester resin, polyethylene resin, polypropylene resin, fluororesin, Although resin materials, such as a cellulose resin, a styrene-butadiene copolymer, and a methyl methacrylate-styrene copolymer, can be illustrated, it is not limited to these. Particularly preferred is an acrylic resin such as polymethyl methacrylate.

(Adhesive for optical bonded discs)
The energy beam curable elastomer composition of the present invention can reproduce information between disk members on which information is optically recorded, or between a disk member on which information is recorded and another disk member having the same shape. When using as an adhesive for optically bonded discs, the following operations are usually performed.
The elastomer composition is applied onto the bonded surface of a disk member based on a plastics substrate such as polycarbonate or polymethyl methacrylate by spin coating, roll coater, silk screen, etc. After laminating the disk member, a method of curing the elastomer composition by irradiating energy rays, preferably ultraviolet rays, from one side or both sides of the disk member is performed. The coating thickness is preferably about 20 to 50 μm after irradiation with energy rays.

[Properties of cured elastomer]
As described above, the energy ray curable elastomer composition of the present invention contains an energy ray curable compound as the component (A) and a polythiol compound as the component (B), and is an ene-thiol-based energy ray curable. By adopting the system, it is possible to increase the molecular weight between cross-linking points of the cured product without changing the type of the energy beam curable compound before curing, and to achieve a cured elastomer that has both elongation at break and workability. Can be provided.
The cured elastomer obtained by curing the elastomer composition by energy ray irradiation has a molecular weight between crosslinking points calculated from the following Flory-Rehner formula in the range of 4,000 to 55,000. It is preferable. If the molecular weight between crosslinks is 4,000 or more, the effect of improving the elongation at break in the cured elastomer is satisfactorily exhibited. On the other hand, if the molecular weight between crosslinks is 55,000 or less, the cured elastomer has excellent workability. It is excellent and has practical strength as an elastomer.

(Molecular weight Mc between cross-linking points)
The molecular weight Mc between the crosslinking points of the elastomer cured product can be calculated by the following method.
Flory-Rehner equation

[However, Mc: molecular weight between cross-linking points [g / mol], ρ: density [g / cm ³ ], ν ₁ : molar volume of solvent (toluene) [cm ³ / mol], ν ₂ : volume swelling ratio [− ], Χ ₁ : Flory χ parameter [−] (estimated from sp value of solvent and cured elastomer). ]
Thus, the molecular weight Mc between the crosslinking points can be calculated.
In the present invention, a value calculated from the Flory-Rehner equation is adopted as the molecular weight Mc between the crosslinking points.

The molecular weight Mc between the crosslinking points is controlled by selecting the type of the polythiol compound as the component (B) to be used and selecting the ratio of the polythiol compound to the energy ray curable compound having the (meth) acryloyl group as the component (A). And thus the elongation at break can be controlled.
In the present invention, as described above, a 2-6 functional thiol compound having 2-6 mercapto groups in the molecule is used as the polythiol compound of the component (B), and the energy ray of the component (A). The ratio of the number of functional groups between the (meth) acryloyl group in the curable compound and the mercapto group in the component (B) ([CH = C (R) -COO] / SH ratio, where R is a hydrogen atom or a methyl group) By selecting so that it may be in the range of 100 / 0.1 to 100 / 5n (n is the number of mercapto groups in one molecule of the polythiol compound), the molecular weight Mc between the crosslinking points of the obtained elastomer cured product is 4, It can be controlled to a desired value within the range of 5,000 to 55,000.

For example, as shown in Examples described later, a bifunctional urethane acrylate oligomer is used as the component (A), a bifunctional thiol compound is used as the component (B), and the [CH═C (R) —COO] / SH ratio is used. Is changed from 100/2 to 100/10, the molecular weight Mc between the crosslinking points is increased from about 5,600 to 31,900, and the elongation at break Eb at room temperature of the cured elastomer is from 360% to 875%. To increase.
On the other hand, in the same manner as described above, a bifunctional urethane acrylate oligomer was used as the component (A), a tetrafunctional thiol compound was used as the component (B), and the [CH = C (R) -COO] / SH ratio was 100. When the ratio is changed from / 5 to 100/20, the molecular weight Mc between the crosslinking points increases from about 6,500 to 51,000, and the elongation at break Eb of the cured elastomer at room temperature increases from 400% to 955%. .
Similarly to the above, a bifunctional urethane acrylate oligomer is used as the component (A), a hexafunctional thiol compound is used as the component (B), and the [CH = C (R) -COO] / SH ratio is 100 / When changed from 5 to 100/30, the molecular weight Mc between the crosslinking points increases from about 4,900 to 36,000, and the elongation at break Eb of the elastomer cured body at room temperature increases from 335% to 775%.
A method for measuring the elongation at break Eb will be described later.

As described above, even when any of the 2 to 6 functional thiol compounds is used, the molecular weight between cross-linking points of the cured elastomer is increased by adding a small amount, and as a result, the elongation at break at room temperature can be greatly improved. The same tendency can be seen for the elongation at break at 80 ° C.
In addition, when a bifunctional thiol compound having the smallest crosslink density among 2 to 6 functional thiol compounds is used, the effect of improving the elongation at break is large, and the number of mercapto groups in one molecule is 4 (tetrafunctional). , 6 (6-functional), the improvement in breaking elongation tends to decrease.
In general, when the molecular weight between crosslink points increases, C.I. S. (Compression set: compression set) is deteriorated, but in the present invention, since an ene-thiol-based energy ray curing system is employed, even if the molecular weight between cross-linking points is increased, it is greatly deteriorated. Can be suppressed.
Note that C.I. S. The measurement method will be described later.

[En-thiol energy beam curing system]
The energy ray curable elastomer composition of the present invention is an ene-thiol-based energy produced by the (meth) acryloyl group-containing energy ray curable compound of the component (A) and the 2-6 functional thiol compound of the component (B). Before describing this ene-thiol-based energy beam curing system, first, radical polymerization of a general (meth) acryloyl group-containing compound and ene-thiol-based energy beam curing system The reaction mechanism will be described.

(1) Radical polymerization of (meth) acryloyl group-containing compound and reaction mechanism of ene-thiol-based energy ray curing system As (meth) acryloyl group-containing compound, a bifunctional acryloyl group-containing oligomer and a monofunctional acryloyl group-containing monomer are used. In addition, the crosslinking reaction by ultraviolet irradiation of the system using the photoradical polymerization initiator is a chain reaction, and the polymerization proceeds in the steps shown in the following scheme 1.
<Scheme 1>

(R ¹ represents an organic group.)
First, the photopolymerization initiator (PI) excited by ultraviolet irradiation is cleaved to generate a radical, and this radical attacks the acryloyl group, thereby moving the excited end (initiating reaction), and the oligomers and monomers are successively formed. Polymerization proceeds (growth reaction) while reacting with the excited end. In addition, description of a stop reaction and a chain reaction is abbreviate | omitted.

On the other hand, the reaction between ene and thiol is a sequential reaction as shown in Scheme 2 below.
<Scheme 2>

(R ² and R ³ each represents an organic group.)
First, a thiol excited by ultraviolet irradiation releases a hydrogen radical to generate a thiol radical. After this thiol radical and ene react with each other, a hydrogen atom is extracted from another thiol to complete the reaction.
When a radical polymerization ultraviolet curing system and an ene-thiol system are used in combination, the polymerization of acryloyl group-containing compounds and the reaction of the acryloyl group-containing compound and thiol proceed almost simultaneously. In many cases, the reaction rate between ene and thiol is faster, but the order of magnitude is not changed. Since no further polymerization of the acryloyl group-containing compound occurs at the site where the thiol has reacted, as a result, when comparing the cured product containing only the acryloyl group-containing compound and the cured product using the ene-thiol system, ene-thiol The cured product combined with the system has a shorter polymerization chain. Thus, when a polymer chain becomes short, the effect which suppresses the production | generation of a microgel (hard part in an elastomer) can be anticipated.
From the above, it can be said that the combined use of the ene-thiol system has an effect of increasing the flexibility of the cured product.

(2) Mechanism of increase in molecular weight between cross-linking points by reaction of bifunctional (meth) acrylate oligomer and polythiol compound Next, bifunctional urethane methacrylate acrylate oligomer as bifunctional (meth) acrylate oligomer, bifunctional as polythiol compound An example of using a thiol compound will be described to explain the mechanism for increasing the molecular weight Mc between the crosslinking points. This reaction proceeds according to Scheme 3 below.
<Scheme 3>

When two molecules of a bifunctional urethane acrylate oligomer react with one molecule of a bifunctional thiol compound, one new oligomer with an extended molecular chain is generated as shown in Scheme 3 above. That is, by adding the polythiol compound, the oligomer chain can be extended in the reaction process without changing the molecular weight of the bifunctional urethane acrylate oligomer to be used.
Thereafter, when the polymerization of the bifunctional urethane acrylate oligomer with the extended oligomer chain proceeds by ultraviolet irradiation, a cured elastomer having a large molecular weight between cross-linking points is obtained.
In addition, when a tetrafunctional or hexafunctional compound is used as the polythiol compound, since the site of a normal crosslinking point exists in the structure of these polythiol compounds, the increase in the molecular weight between the crosslinking points is bifunctional. Small compared to thiol compounds. However, when a tetrafunctional or hexafunctional polythiol compound reacts with a urethane acrylate oligomer, a star branch oligomer having a long side chain is generated, and this part acts as a soft segment in the cured elastomer, resulting in The elastomer composition is considered to increase the elongation at break in the same manner as when the molecular weight between crosslinks is increased.

[Use of energy ray curable elastomer composition]
The energy ray-curable elastomer composition of the present invention employs an ene-thiol-based energy ray curing system, so that the molecular weight between crosslink points of the cured product can be changed without changing the type of energy ray-curable compound before curing. Thus, a cured elastomer having both elongation at break and processability can be provided.
This elastomer cured body has applications such as gaskets for HDDs, sealing materials for ink tanks, sealing materials for various display devices, sealing materials for structures such as civil engineering and construction, packing for O-rings, vibration isolating members, and the like. I can expect.
In addition, the elastomer composition reproduces information between plastic adhesives, for example, optically recorded disk members, or a disk member on which information is recorded and another disk member having the same shape. In addition, it can be expected to be used for an adhesive for an optically bonded disk and the like used for an ink composition for inkjet recording.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the various characteristics in each example were calculated | required according to the method shown below.
(1) Molecular weight Mc between the crosslinking points of the cured elastomer
The molecular weight Mc between crosslinking points of the cured elastomer was calculated by the Flory-Rehner equation described in the specification. The volume swelling rate in the formula was measured by the following method.
(Volume swelling rate)
A test piece of 25 × 12 × 2 mm was immersed in 50 mL of toluene for 24 hours, and the dimensions before and after the immersion were measured.
(2) Tensile test Using a tensile tester [ORITENTEC, model name “Tensilon RTC-1225A”] on a 2 mm thick elastomer sheet punched into DIN3 dumbbell shape, test temperature in accordance with JIS K 6251 A tensile test was performed under the conditions of 23 ° C. and 80 ° C. and a tensile speed of 200 mm / min, and the breaking strength Tb and the breaking elongation Eb were measured.
(3) Compression set (C.S.)
Five cured elastomer sheets having a thickness of 2 mm cut into 2 cm squares were used as measurement samples, and compression set was measured at a test temperature of 70 ° C. in accordance with JIS K 6262.

Examples 1-6, Comparative Examples 1 and 2
An ultraviolet curable elastomer composition having the composition shown in Table 1 was prepared, and an elastomer cured body sheet was prepared according to the method shown below, and further cut into a shape used in each test.
First, two 15 cm × 15 cm × 3 mm glass plates and two 15 cm × 15 cm × 0.06 mm releasable polyethylene terephthalate (PET) films were prepared.
While maintaining a predetermined thickness with a spacer, the ultraviolet curable elastomer composition obtained above is sandwiched between a releasable PET film and further sandwiched between glass plates, and then ultraviolet rays (manufactured by Sen Engineering Co., Ltd.) are used. And an ultraviolet irradiator “UV1501BA-LT” and a metal halide lamp “SE-1500M” manufactured by the same company were used under the conditions of an illuminance of 150 mW / cm ² and an irradiation time of 60 seconds to cure the elastomer composition.
Next, the elastomer cured body sheet was peeled off from the glass plate and the releasable PET film, subjected to an annealing treatment at 120 ° C. for 4 hours, and then cut into a shape used for each test, and used for measurement of various properties. Table 1 shows the measurement results of various characteristics. In addition, the ultraviolet curable elastomer compositions of Examples 1 to 6 and Comparative Examples 1 and 2 all had an appropriate viscosity at room temperature and were homogeneous compositions.

[note]
1) Energy beam curable oligomer A: manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Tack PUA-KH32M” (bifunctional urethane acrylate oligomer, isobornyl acrylate, phenoxyethyl acrylate, and Irgacure 2959 (photopolymerization initiator) Mixture)
2) Hexafunctional thiol compound: manufactured by SC Organic Chemical Co., Ltd., trade name “DPMP”, dipentaerythritol hexa (β-mercaptopropionate)

Examples 7 to 10 and Comparative Example 3
An ultraviolet curable elastomer composition having the composition shown in Table 2 was prepared. Hereinafter, the same operations as in Examples 1 to 6 and Comparative Examples 1 and 2 were performed, and the cured elastomer sheet was cut into a shape used for each test and used for measurement of various properties. The measurement results of various characteristics are shown in Table 2 together with Comparative Example 1. Note that each of the ultraviolet curable elastomer compositions of Examples 7 to 10 and Comparative Example 3 had a proper viscosity at room temperature and was a homogeneous composition.

[Note] 1) is the same as the footnote in Table 1.
3) Tetrafunctional thiol compound: manufactured by SC Organic Chemical Co., Ltd., trade name “PEMP”, pentaerythritol tetra (β-mercaptopropionate)

Examples 11-13
Ultraviolet curable elastomer compositions having the composition shown in Table 3 were prepared. Hereinafter, the same operations as in Examples 1 to 6 and Comparative Examples 1 and 2 were performed, and the cured elastomer sheet was cut into a shape used for each test and used for measurement of various properties. The measurement results of various characteristics are shown in Table 3 together with Comparative Example 1. In addition, all of the ultraviolet curable compositions of Examples 11 to 13 had an appropriate viscosity at room temperature and were homogeneous compositions.

[Note] 1) is the same as the footnote in Table 1.
4) Bifunctional thiol compound: manufactured by SC Organic Chemical Co., Ltd., trade name “EGMP4”, tetraethylene glycol di (β-mercaptopropionate)

Comparative Example 4
Except that the number average molecular weight of the urethane-based acrylate oligomer (bifunctional) in the light tack PUA-KH32M (supra) is about twice as the energy ray curable oligomer, the same as in Example 1 was used. Thus, an ultraviolet curable elastomer composition was prepared. The energy ray curable oligomer was water-like at room temperature, and handling was extremely poor. Further, the ultraviolet curable elastomer composition had a high viscosity, and a homogeneous composition could not be obtained.
Hereinafter, the same operations as in Examples 1 to 6 and Comparative Examples 1 and 2 were performed, and the cured elastomer sheet was cut into a shape used for each test, and used for measurement of various properties. The measurement results of various characteristics are shown below.
Molecular weight between cross-linking points Mc = 12585
23 ° C tensile test Tb = 3.52 MPa
Eb = 533%
Compression set [70 ° C.] = 14.3%

The energy beam curable elastomer composition of the present invention can increase the molecular weight between cross-linking points of the cured product without changing the type of energy beam curable compound before curing, and has both elongation at break and workability. A cured elastomer can be provided.
This cured elastomer is, for example, a gasket for HDD, a sealing material for ink tank, a sealing material for various display devices, a sealing material for structures such as civil engineering and construction, a packing such as an O-ring, a vibration isolating member, and various adhesives. Applications such as can be expected.

Claims (5)

(A) An energy beam comprising a bifunctional urethane-based (meth) acrylate oligomer having a (meth) acryloyl group, (B) a polythiol compound having six mercapto groups in the molecule, and (C) a photoradical polymerization initiator. A curable elastomer composition having a functional group number ratio of (meth) acryloyl group in the composition to mercapto group in component (B) of 100: 4n to 100: 5n (n is one molecule of polythiol compound) The amount of the photoradical polymerization initiator is 0.1 to 10 parts by mass with respect to 100 parts by mass of the total energy ray curable compound contained in the composition. An energy ray-curable elastomer composition characterized by being.   The energy ray-curable elastomer composition according to claim 1, wherein the cured product by energy ray irradiation has a molecular weight between crosslink points of 4,000 to 55,000 calculated from the Flory-Rehner equation. (B) The energy ray-curable elastomer composition according to claim 1 or 2 , wherein the polythiol compound having 6 mercapto groups in the molecule is a β-mercaptopropionic acid ester of a polyhydric alcohol having 2 to 6 hydroxyl groups. object. The polyhydric alcohol having 2 to 6 hydroxyl groups is alkanediol having 2 to 20 carbon atoms, poly (oxyalkylene) glycol, glycerol, diglycerol, trimethylolpropane, ditrimethylolpropane, pentaerythritol or dipentaerythritol. The energy ray-curable elastomer composition according to claim 3 . The energy ray-curable elastomer composition according to any one of claims 1 to 4 , wherein the photo radical polymerization initiator is an intramolecular cleavage type and / or a hydrogen abstraction type.