Photocurable composition, photocurable foam composition, urethane (meth)acrylate compound, and method for producing foam

Abstract

To provide a photocurable composition capable of forming a sealant formed of a foam combining excellent elongation and excellent tensile strength by curing while foaming, a photocurable foam composition containing foam of a gas in the photocurable composition, an urethane (meth)acrylate compound used suitably as a component of the photocurable composition, and a manufacturing method of a foam using the photocurable composition.SOLUTION: In a photocurable composition containing an urethane (meth)acrylate (A) and a photopolymerization initiator (C), as the urethane (meth)acrylate (A), an urethane (meth)acrylate compound of a specific structure that contains an urethane bond, has a polyether chain having a molecular weight in a specific range at a center, and has a (meth) acryloyloxy group at both ends of a straight chain polyether chain.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photocurable composition, a photocurable foam composition containing gas bubbles in the photocurable composition, a urethane (meth)acrylate compound that is suitably used as a component of the photocurable composition, and a method for producing a foam using the photocurable composition. [Background technology]

[0002] In the manufacture of various electrical and mechanical product parts and automotive parts, when multiple parts are assembled or parts with gaps are used, the mating surfaces and gaps of the parts are often sealed. A known sealing method for this purpose is to apply and harden a liquid material for forming a gasket called FIPG (Formed In Place Gasket) to the mating surfaces and gaps while foaming it with a gas. According to this method, the mating surfaces and gaps of the parts are sealed with a sealant formed by foaming and hardening the FIPG.

[0003] Known examples of curable compositions that can be used as FIPG include a photocurable sealing material that contains (A) an oligomer having a (meth)acryloyl group and having a weight-average molecular weight of 10,000 to 30,000, (B) a (meth)acrylate monomer, and (C) a polythiol compound in specific ratios (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5693799 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a conventionally known curable composition such as that described in Patent Document 1 is applied to produce a foam, it is difficult to form a sealant consisting of a foam that has both good elongation and good tensile strength.

[0006] The present invention has been made in consideration of the above problems, and has an object to provide a photocurable composition that can form a sealant consisting of a foam that has both good elongation and good tensile strength by being foamed and cured at the same time; a photocurable foamable composition that contains gas bubbles in the photocurable composition; a urethane (meth)acrylate compound that is preferably used as a component of the photocurable composition; and a method for producing a foam using the photocurable composition. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by using, as the urethane (meth)acrylate (A) in a photocurable composition containing a urethane (meth)acrylate (A) and a photopolymerization initiator (C), a urethane (meth)acrylate compound having a specific structure that contains a urethane bond, has a polyether chain having a molecular weight in a specific range at the center, and has (meth)acryloyloxy groups at both ends of the linear polyether chain, and have completed the present invention. Specifically, the present invention provides the following (1) to (22).

[0008] (1) A photocurable composition comprising a urethane (meth)acrylate (A) and a photopolymerization initiator (C), The urethane (meth)acrylate (A) is represented by the following formula (A1): (CH2=CR 5 -CO-OR 4 -O-CO-NH) a -R 2 -NH-CO-(OR 1 ) n -O-CO-NH-R 3 -(NH-CO-OR 4 -O-CO-CR 5 =CH2) b (A1) (In formula (A1), R 1 is an alkylene group having 2 to 4 carbon atoms, R 2 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of a+1, and R 3 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of b+1, a and b each independently represent 1 or 2, and R 4 is an alkylene group having 1 to 8 carbon atoms; R 5 is a hydrogen atom or a methyl group, and in formula (A1), -(OR 1 ) n The molecular weight of the unit represented by -O- is 3,000 to 30,000, and n is -OR 1 - is the number of repetitions of the oxyalkylene group represented by the formula A photocurable composition comprising a urethane (meth)acrylate compound represented by the formula: (2) The photocurable composition according to (1), wherein a and b are each 1. (3) The photocurable composition according to (1) or (2), in which the ratio of the mass of the urethane (meth)acrylate compound represented by formula (A1) to the mass of the urethane (meth)acrylate (A) is 60 mass% or more. (4)R 1 is a propane-1,2-diyl group. (5) The photocurable composition according to any one of (1) to (4), further comprising a photopolymerizable monomer (B), the photopolymerizable monomer (B) being at least one selected from the group consisting of a tri(meth)acrylate (B1), a di(meth)acrylate (B2), and a mono(meth)acrylate (B3). (6) The photocurable composition according to any one of (1) to (5), wherein the photopolymerizable monomer (B) is at least one selected from the group consisting of linear aliphatic tri(meth)acrylates (B1-1), linear aliphatic di(meth)acrylates (B2-1), linear aliphatic mono(meth)acrylates (B3-1), and alicyclic mono(meth)acrylates (B3-2). (7) The photocurable composition according to any one of (1) to (6), wherein the photopolymerization initiator (C) includes at least one selected from the group consisting of alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime ester-based photopolymerization initiators. (8) The photocurable composition according to any one of (1) to (10), which is used for producing a foam through mixing with a gas and photocuring. (9) A photocurable foaming composition comprising the photocurable composition according to any one of (1) to (8) above and gas bubbles (E) dispersed in the photocurable composition. (10) The photocurable foamable composition according to (9), wherein the gas is at least one selected from the group consisting of nitrogen, argon, xenon, krypton, and carbon dioxide gas. (11) The photocurable foamable composition according to (9) or (10), wherein the size of the gas bubbles (E) in a cured product cured under atmospheric pressure is 5 μm or more and 200 μm or less. (12) Formula (A1): (CH2=CR 5 -CO-OR 4 -O-CO-NH) a -R 2 -NH-CO-(OR 1 ) n -O-CO-NH-R 3 -(NH-CO-OR 4 -O-CO-CR 5 =CH2) b (A1) (In formula (A1), R 1 is an alkylene group having 2 to 4 carbon atoms, R 2 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of a+1, and R 3 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of b+1, a and b each independently represent 1 or 2, and R 4 is an alkylene group having 1 to 8 carbon atoms; R 5 is a hydrogen atom or a methyl group, and in formula (A1), -(OR 1 ) nThe molecular weight of the unit represented by -O- is 3,000 to 30,000, and n is -OR 1 - is the number of repetitions of the oxyalkylene group represented by the formula A urethane (meth)acrylate compound represented by the formula: (13) Mixing the photocurable composition according to any one of (1) to (8) with a gas to produce a photocurable foamable composition containing bubbles; and photocuring the photocurable foam composition by exposure to light. (14) Producing a photocurable foam composition, a first step of supplying a photocurable composition pumped through a first pipeline and a gas pumped through a second pipeline by a first pump to mix the photocurable composition and the gas to generate a mixture; a second step of dispersing a gas into the photocurable composition in a dispersion line while the mixture is under pressure; and a third step of discharging the mixture that has passed through the dispersion pipeline to foam the mixture, thereby producing a photocurable foam composition. (15) The method for producing a foam according to (13) or (14), wherein the exposure is LED exposure. (16) The method for producing a foam according to any one of (13) to (15), wherein the oxygen concentration on the surface of the photocurable foamable composition during exposure is 3 volume % or less. (17) The method for producing a foam according to any one of (13) to (16), wherein, of (I) producing a photocurable foam composition, (II) reducing the oxygen concentration on the surface of the photocurable foam composition to 1 volume % or less, and (III) curing the photocurable foam composition by exposure to light, (I) and (III) or all of (I) to (III) are achieved simultaneously or continuously using one or more manipulators. (18) The method for producing a foam according to any one of (13) to (17), wherein the oxygen concentration on the surface of the photocurable foamable composition is reduced to 3 volume % or less by spraying a gas other than oxygen onto the surface of the photocurable foamable composition. (19) The method for producing a foam according to any one of (13) to (18), wherein the oxygen concentration at the surface of the photocurable foamable composition is adjusted to 3 volume % or less by releasing a gas other than oxygen from the photocurable foamable composition during production of the photocurable foamable composition. Effect of the Invention

[0009] According to the present invention, there can be provided a photocurable composition that can form a sealant consisting of a foam that has both good elongation and good tensile strength by being foamed and cured at the same time; a photocurable foamable composition that contains gas bubbles in the photocurable composition; a urethane (meth)acrylate compound that is preferably used as a component of the photocurable composition; and a method for producing a foam that uses the photocurable composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <<Photocurable composition>> The photocurable composition includes a photocurable composition containing a urethane (meth)acrylate (A) and a photopolymerization initiator (C). The urethane (meth)acrylate (A) contains a urethane (meth)acrylate compound represented by the following formula (A1). (CH2=CR 5 -CO-OR 4 -O-CO-NH) a -R 2 -NH-CO-(OR 1 ) n -O-CO-NH-R 3 -(NH-CO-OR 4 -O-CO-CR 5 =CH2) b (A1) (In formula (A1), R 1 is an alkylene group having 2 to 4 carbon atoms, R 2 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of a+1, and R 3 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of b+1, a and b each independently represent 1 or 2, and R 4is an alkylene group having 1 to 8 carbon atoms; R 5 is a hydrogen atom or a methyl group, and in formula (A1), -(OR 1 ) n The molecular weight of the unit represented by -O- is 3,000 to 30,000, and n is -OR 1 - is the number of repetitions of the oxyalkylene group represented by the formula

[0011] When the photocurable composition contains the urethane (meth)acrylate compound represented by the above formula (A1), the photocurable composition can be foamed and cured at the same time to form a sealant consisting of a foam that has both good elongation and good tensile strength.

[0012] For this reason, the photocurable composition is suitable for use in producing foams by mixing with a gas and undergoing photocuring.

[0013] The viscosity of the photocurable composition, measured using a BH type viscometer with a No. 7 rotor at 20°C and a rotation speed of 20 rpm, is preferably from 10,000 mPa·s to 300,000 mPa·s, more preferably from 20,000 mPa·s to 250,000 mPa·s, and even more preferably from 50,000 mPa·s to 150,000 mPa·s. If the viscosity of the photocurable composition is too high, it may be difficult to apply the composition at room temperature, whereas if the viscosity of the photocurable composition is too low, it may be difficult to maintain the desired shape of the bead when the bead is formed using the photocurable composition. The method of adjusting the viscosity of the photocurable composition is not particularly limited. The viscosity of the photocurable composition is typically adjusted by adjusting the viscosity of the urethane (meth)acrylate (A). The viscosity of the photocurable composition can also be adjusted by blending a low-viscosity monomer component into the photocurable composition or by adjusting the blending amount of a filler.

[0014] Essential and optional components of the photocurable composition will be described below.

[0015] <Urethane (meth)acrylate (A)> The photocurable composition contains a urethane (meth)acrylate (A) as a curable component. The urethane (meth)acrylate (A) is represented by the following formula (A1): (CH2=CR 5 -CO-OR 4 -O-CO-NH) a -R 2 -NH-CO-(OR 1 ) n -O-CO-NH-R 3 -(NH-CO-OR 4 -O-CO-CR 5 =CH2) b (A1) The composition essentially contains a urethane (meth)acrylate compound represented by the following formula: (In formula (A1), R 1 is an alkylene group having 2 to 4 carbon atoms, R 2 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of a+1, and R 3 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of b+1, a and b each independently represent 1 or 2, and R 4 is an alkylene group having 1 to 8 carbon atoms; R 5 is a hydrogen atom or a methyl group, and in formula (A1), -(OR 1 ) n The molecular weight of the unit represented by -O- is 3,000 to 30,000, and n is -OR 1 - is the number of repetitions of the oxyalkylene group represented by the formula

[0016] When the photocurable composition contains a urethane (meth)acrylate compound represented by the above formula (A1) as the urethane (meth)acrylate (A), the photocurable composition can be foamed and cured to form a sealant consisting of a foam that has both good elongation and good tensile strength. The photocurable composition may contain, together with the urethane (meth)acrylate compound represented by the above formula (A1), a urethane (meth)acrylate compound having a structure other than that of formula (A1), within the scope of not impairing the object of the present invention.

[0017] In addition, in the specification and claims of the present application, "(meth)acrylate" means both "acrylate" and "methacrylate", "(meth)acryloyl" means both "acryloyl" and "methacryloyl", and "(meth)acrylic acid" means both "acrylic acid" and "methacrylic acid".

[0018] In formula (A1), R 1 is an alkylene group having 2 to 4 carbon atoms. 1 ) n The molecular weight of the unit represented by -O- is 3000 or more and 30000 or less. Therefore, the urethane (meth)acrylate compound represented by formula (A1) is 1 In other words, in formula (A1), R 1 There are multiple. In formula (A1), 1 may be only one type of alkylene group, or may be two or more types of alkylene groups.

[0019] -(OR 1 ) n The unit represented by -O- is typically H-(OR 1 ) n A polyoxyalkylene glycol represented by -OH is used to introduce it into the urethane (meth)acrylate compound represented by formula (A1). Therefore, by appropriately selecting the molecular weight of the polyoxyalkylene glycol, the molecular weight of the urethane (meth)acrylate compound represented by formula (A1) can be adjusted.

[0020] In order to ensure that the viscosity of the photocurable composition falls within the above-mentioned preferred range, the viscosity of the urethane (meth)acrylate (A) is preferably from 30,000 mPa·s to 300,000 mPa·s, and more preferably from 35,000 mPa·s to 200,000 mPa·s, as measured with a BH type viscometer using a No. 7 rotor at 20°C and a rotation speed of 20 rpm. As a method for adjusting the viscosity of the urethane (meth)acrylate (A), there can be mentioned a method for appropriately adjusting the molecular weight of a urethane (meth)acrylate compound included in the urethane (meth)acrylate compound such as the urethane (meth)acrylate compound represented by formula (A1).

[0021] R in formula (A1) 1 Specific examples of include an ethane-1,2-diyl group (ethylene group), a propane-1,3-diyl group, a propane-1,2-diyl group, and a butane-1,4-diyl group. Among these, one or more selected from the group consisting of an ethane-1,2-diyl group (ethylene group), a propane-1,3-diyl group, and a propane-1,2-diyl group are preferred, and a propane-1,2-diyl group is more preferred, because the urethane (meth)acrylate compound represented by formula (A1) can be easily synthesized and a photocurable composition that gives a cured product exhibiting desired physical properties can be easily obtained. R 1 If the number of carbon atoms is too small, the polyoxyalkylene structure will contain a large amount of ether bonds, which may impair the water resistance of the cured product or increase the water absorption of the cured product, tending to reduce the sealing properties when used as a sealant. R 1 If the number of carbon atoms is too large, the viscosity of the photocurable composition tends to be high and processability such as coatability tends to be reduced. From the above points, R 1 Most preferably, the number of carbon atoms is 3.

[0022] In formula (A1), R 2 is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of a+1. 3is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of (b+1). a and b each independently represent 1 or 2. In other words, R 2 and R 3 are residues derived from divalent or trivalent aliphatic isocyanate compounds, respectively. R 2 and R 3 The divalent or trivalent aliphatic isocyanate compound capable of providing the above is not particularly limited as long as it does not impair the object of the present invention. Specific examples of suitable divalent or trivalent aliphatic isocyanate compounds include 1,6-hexane diisocyanate (1,6-hexamethylene diisocyanate), oligomers of 1,6-hexane diisocyanate, isophorone diisocyanate (3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate), methylene bis(4-cyclohexyl isocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 1, Aliphatic diisocyanates such as 4-hexamethylene diisocyanate, bis(2-isocyanatoethyl) fumarate, and lysine diisocyanate (hexanoic acid-2,6-diisocyanate); and aliphatic triisocyanates such as 1,6,11-undecane triisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, and bicycloheptane triisocyanate. Trimers of the above diisocyanates are also preferred as trivalent aliphatic isocyanates. Examples of the trimers include isocyanurates, adducts, and biuret.

[0023] Among these aliphatic isocyanates, 1,6-hexane diisocyanate (1,6-hexamethylene diisocyanate), an oligomer of 1,6-hexane diisocyanate, and isophorone diisocyanate are preferred, and isophorone diisocyanate is more preferred, because it is easy to obtain a photocurable composition that gives a cured product exhibiting desired physical properties. In particular, when isophorone dicyanate is used, the viscosity of the composition can be reduced and a long-chain polyol can be selected, and when the cured product is a foam, the cured product tends to have good elongation.

[0024] H-(OR 1 ) n By reacting a polyoxyalkylene glycol represented by -OH with the above-mentioned divalent or trivalent aliphatic isocyanate in a conventional manner, a polyisocyanate compound represented by the following formula (A1-1) can be obtained. 1 , R 2 , R 3 , a, b, and n are the same as those in formula (A1). (OCN) a -R 2 -NH-CO-(OR 1 ) n -O-CO-NH-R 3 -(NCO) b (A1-1)

[0025] The urethane (meth)acrylate compound represented by formula (A1) can be obtained by reacting the polyisocyanate compound represented by formula (A1-1) above with the hydroxyalkyl (meth)acrylate represented by formula (A1-2) below. 4 , R 5 are similar to those in formula (A1). H.O.R. 4 -O-CO-CR 5 =CH2 (A1-2)

[0026] R in formula (A1) 4 R is an alkylene group having 1 to 8 carbon atoms. 4 The alkylene group as R may be a linear alkylene group or a branched alkylene group. 4 The alkylene group as is preferably a linear alkylene group. R 4Specific preferred examples of the alkylene group as include a methylene group, an ethane-1,2-diyl group (ethylene group), a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diyl group, a heptane-1,7-diyl group, and an octane-1,8-diyl group. Among these groups, an ethane-1,2-diyl group (ethylene group) and a propane-1,3-diyl group are preferred, and an ethane-1,2-diyl group (ethylene group) is more preferred.

[0027] In addition, the hydroxyalkyl (meth)acrylate represented by the above formula (A1-2) may be used in combination with the above R 2 and R 3 and reacting the resulting isocyanate compound represented by the following formula (A1-3) with an isocyanate compound represented by the following formula (A1-4) by reacting the resulting isocyanate compound represented by the following formula (A1-3) and the isocyanate compound represented by the following formula (A1-4) by H-(OR 1 ) n The urethane (meth)acrylate compound represented by formula (A1) can also be obtained by reacting with a polyoxyalkylene glycol represented by --OH. In formula (A1-3) and formula (A1-4), R 2 , R 3 , R 4 , R 5 , a, and b are the same as those in formula (A1). (CH2=CR 5 -CO-OR 4 -O-CO-NH) a -R 2 -NCO···(A1-3) (CH2=CR 5 -CO-OR 4 -O-CO-NH) b -R 3 -NCO···(A1-4)

[0028] R in formula (A1) 5is a hydrogen atom or a methyl group. R is a photocurable composition having low hardness and good flexibility such as high elongation. 5 is preferably a hydrogen atom.

[0029] Since it is easy to form a cured product exhibiting desired physical properties using the photocurable composition, it is preferable that a and b are each 1 in the above-described formula (A1). In particular, it is preferable that a and b are each 1 in terms of ease of obtaining a photocurable composition with a viscosity suitable for application and in terms of good flexibility, such as low hardness and high elongation, of the cured product of the photocurable composition.

[0030] The ratio of the mass of the urethane (meth)acrylate compound represented by formula (A1) to the mass of the urethane (meth)acrylate (A) is not particularly limited as long as it does not impair the object of the present invention. In order to easily form a cured product exhibiting desired physical properties, the ratio of the urethane acrylate compound represented by Formula (A1) to the mass of the urethane acrylate (A) is preferably 60 mass% or more, more preferably 80 mass% or more, even more preferably 90 mass% or more, and most preferably 100 mass%.

[0031] When the urethane (meth)acrylate (A) contains a urethane (meth)acrylate compound other than the urethane (meth)acrylate compound represented by formula (A1), the other urethane (meth)acrylate compound is not particularly limited as long as it does not impair the object of the present invention. As other urethane (meth)acrylate compounds, for example, urethane (meth)acrylate compounds that can be produced by reacting a polyol such as polyester polyol or carbonate diol with a known polyisocyanate compound and a hydroxyalkyl (meth)acrylate represented by the above formula (A1-2) can be used.

[0032] The ratio of the mass of the urethane (meth)acrylate (A) to the mass of the photocurable composition is preferably from 50 to 95% by mass, more preferably from 60 to 94% by mass, and even more preferably from 70 to 93% by mass. When the mass ratio of the urethane (meth)acrylate (A) is within the above range, a cured product exhibiting good flexibility and elongation is obtained, and it is easy to obtain a photocurable composition having a low viscosity suitable for application.

[0033] <Photopolymerizable monomer (B)> The photocurable composition may contain a photopolymerizable monomer (B) which is a compound having an ethylenically unsaturated double bond, and preferably contains a photopolymerizable monomer (B). The photopolymerizable monomer (B) is not particularly limited as long as it has one or more ethylenically unsaturated double bonds and does not fall under the category of the above-mentioned urethane (meth)acrylate (A). As the photopolymerizable monomer (B), one type of compound may be used alone, or two or more types of compounds may be used in combination.

[0034] Suitable photopolymerizable monomers (B) include (meth)acrylate compounds not corresponding to the above-mentioned urethane (meth)acrylate (A) and compounds having a (meth)acryloyl group such as (meth)acrylamide compounds. As the photopolymerizable monomer (B), (meth)acrylate compounds are preferred.

[0035] The number of (meth)acryloyl groups in the photopolymerizable monomer (B) having a (meth)acryloyl group is not particularly limited. The number of (meth)acryloyl groups in the photopolymerizable monomer (B) having a (meth)acryloyl group may be any of 1, 2, 3, and 4 or more, and is preferably 1, 2, or 3. When the number of (meth)acryloyl groups in the photopolymerizable monomer (B) is within the above range, the photocurable composition has good photocurability and is easy to obtain a photocurable composition with a low viscosity suitable for application.

[0036] As the photopolymerizable monomer (B), one or more compounds selected from the group consisting of tri(meth)acrylate compounds (B1), di(meth)acrylate compounds (B2), and mono(meth)acrylate compounds (B3) are preferred, since they are easily available and synthesized, and can easily form a cured product exhibiting desired physical properties.

[0037] Preferred specific examples of the tri(meth)acrylate compound (B3) include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tris((meth)acryloyloxyethyl)isocyanurate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and propoxylated pentaerythritol tri(meth)acrylate.

[0038] Preferred specific examples of the di(meth)acrylate compound (B2) include di(meth)acrylates of aliphatic glycols such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 2-methyl-1,3-propanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate; diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, di(meth)acrylates of oligo- or polyalkylene glycols such as acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate; di(meth)acrylates of ethoxylated aliphatic glycols such as ethoxylated dipropylene glycol di(meth)acrylate, ethoxylated 2-methyl-1,3-propanediol di(meth)acrylate, ethoxylated 1,6-hexanediol di(meth)acrylate, and propoxylated neopentyl glycol di(meth)acrylate; ethoxylated bisphenol A di(meth)acrylate; isocyanurate di(meth)acrylate; and tricyclodecane dimethanol di(meth)acrylate.

[0039] Preferred specific examples of the mono(meth)acrylate compound (B3) include C1-C20 alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; menthyl (meth)acrylate, Alicyclic (meth)acrylates such as norbornyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and tetracyclodecanyl (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate; 2-hydroxyethyl (meth)acrylate; ethoxylated 2-hydroxyethyl (meth)acrylate; 2-phenoxyethyl (meth)acrylate; 2-(2-ethoxyethoxy)ethyl acrylate; benzyl (meth)acrylate; and (2-(meth)acryloyloxyethyl) phosphate.

[0040] Of the above photopolymerizable monomers (B), at least one selected from the group consisting of chain aliphatic tri(meth)acrylates (B1-1), chain aliphatic di(meth)acrylates (B2-1), chain aliphatic mono(meth)acrylates (B3-1), and alicyclic mono(meth)acrylates (B3-2) is preferred.

[0041] When the chain aliphatic tri(meth)acrylate (B1-1) is used, the surface curability of the photocurable composition and the heat resistance of the cured product are improved. Examples of the linear aliphatic tri(meth)acrylate (B1-1) include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and propoxylated pentaerythritol tri(meth)acrylate.

[0042] Examples of the linear aliphatic di(meth)acrylate (B2-1) include di(meth)acrylates of aliphatic glycols such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 2-methyl-1,3-propanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate; diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, Di(meth)acrylates of oligo- or polyalkylene glycols, such as ricol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate; di(meth)acrylates of ethoxylated aliphatic glycols, such as ethoxylated dipropylene glycol di(meth)acrylate, ethoxylated 2-methyl-1,3-propanediol di(meth)acrylate, ethoxylated 1,6-hexanediol di(meth)acrylate, and propoxylated neopentyl glycol di(meth)acrylate.

[0043] Examples of the linear aliphatic mono(meth)acrylate (B3-1) include C1-C20 alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, n-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, n-heptyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, lauryl(meth)acrylate, and stearyl(meth)acrylate; 2-hydroxyethyl(meth)acrylate; ethoxylated 2-hydroxyethyl(meth)acrylate; 2-phenoxyethyl(meth)acrylate; 2-(2-ethoxyethoxy)ethyl acrylate; and (2-(meth)acryloyloxyethyl)phosphate.

[0044] When an alicyclic mono(meth)acrylate (B3-2) is used, the viscosity of the photocurable composition can be reduced while improving the curability, without decreasing the flexibility (elongation) of the cured product. Examples of the alicyclic mono(meth)acrylate (B3-2) include alicyclic (meth)acrylates such as menthyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecanyl (meth)acrylate, tetracyclodecanyl (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate.

[0045] The ratio of the mass of the photopolymerizable monomer (B) to the mass of the photocurable composition is preferably from 1 to 20% by mass, more preferably from 2 to 18% by mass, and even more preferably from 5 to 15% by mass. When the ratio of the mass of the photopolymerizable monomer (B) to the mass of the photocurable composition is within the above range, it is easy to obtain a photocurable composition that has both good curability and low viscosity, and it is easy to form a flexible cured product.

[0046] <Photopolymerization initiator (C)> The photocurable composition contains a photopolymerization initiator (C) as a component for reacting the urethane acrylate (A) and the photopolymerizable monomer (B) to cure the photocurable composition. The type of the photopolymerization initiator (C) is not particularly limited as long as it does not impede the object of the present invention. The photocurable composition may contain one type of photopolymerization initiator (C) alone or two or more types in combination.

[0047] From the viewpoint of achieving both deep curability of the photocurable composition and suppression of surface tackiness of the cured product, it is preferable that the photocurable composition contains, as the photopolymerization initiator (C), at least one selected from the group consisting of alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime ester-based photopolymerization initiators.

[0048] Examples of the alkylphenone-based photopolymerization initiator include an α-hydroxyalkylphenone compound, an α-aminoalkylphenone compound, and an α-benzi-ketal compound. The α-hydroxyalkylphenone compound is a compound having an alkylphenone skeleton with a hydroxyl group bonded to the α-position relative to the carbonyl group. The α-aminoalkylphenone compound is a compound having an alkylphenone skeleton with an optionally substituted amino group bonded to the α-position relative to the carbonyl group.

[0049] Specific examples of the α-hydroxyalkylphenone compound include 1-hydroxycyclohexyl phenyl ketone (IGM Resins BV, Omnirad 184), 2-hydroxy-2-methyl-1-phenylpropanone (IGM Resins BV, Omnirad 1173), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxymethylpropanone (IGM Resins BV, Omnirad 2959), and 2-hydroxy-1-(4-(4-(2-hydroxypropionyl)benzyl)phenyl)-2-methylpropan-1-one (IGM Resins BV, Omnirad 127). Specific examples of α-aminoalkylphenone compounds include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IGM Resins BV, Omnirad 907) and 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (IGM Resins BV, Omnirad 369). A specific example of an α-benzyl ketal compound is 2,2-dimethoxy-2-phenylacetophenone (Omnirad 651, manufactured by IGM Resins BV).

[0050] The acylphosphine oxide photopolymerization initiator is a pentavalent phosphorus compound having a P=O bond and at least one acyl group bonded to the phosphorus atom constituting the P=O bond. As the acylphosphine oxide photopolymerization initiator, any pentavalent phosphorus compound having a P=O bond and at least one acyl group bonded to the phosphorus atom constituting the P=O bond that has been conventionally used as a photopolymerization initiator can be used without any particular limitation.

[0051] Preferred specific examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (manufactured by IGM Resins BV, Omnirad TPO-H), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (manufactured by IGM Resins BV, Omirad 819), ethyl (2,4,6-trimethylbenzoyl)phenylphosphineate (manufactured by IGM Resins BV, Omirad TPO-L), and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide (manufactured by Ciba, CGI403).

[0052] Examples of photopolymerization initiators that can be suitably used other than the alkylphenone-based photopolymerization initiators and the acylphosphine oxide-based photopolymerization initiators include benzoin-based photopolymerization initiators such as benzoin, benzoin methyl ether, and benzoin ethyl ether; anthraquinone-based photopolymerization initiators such as 2-methylanthraquinone, 2-amylanthraquinone, 2-tert-butylanthraquinone, and 1-chloroanthraquinone; thioxanthone-based photopolymerization initiators such as 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, and 2-chlorothioxanthone; benzophenone, 4-(1-tert-butyldioxy-1-methylethyl)benzophenone, and 3,3',4,4'-tetrakis(tert-butyldioxycarbonyl)benzophenone; phenyl glyoxylate-based photopolymerization initiators such as alkylphenyl glyoxylate; oxime ester-based photopolymerization initiators such as 1,2-octanedione, 1-[4-(phenylthio)phenyl]-, 2-(O-benzoyloxime) (manufactured by BASF Japan, OXE01), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime) (manufactured by BASF Japan, OXE02), OXE03 (manufactured by BASF Japan), and OXE04 (manufactured by BASF Japan); and titanocene compound-based photopolymerization initiators such as bis(5,2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium.

[0053] The ratio of the mass of the photopolymerization initiator (C) to the mass of the photocurable composition is preferably from 0.01 to 10 mass%, more preferably from 0.05 to 5 mass%, and even more preferably from 0.1 to 2 mass%.

[0054] <Wax (D)> The photocurable composition preferably contains a wax (D) from the viewpoint of suppressing tackiness on the surface of the cured product. From the viewpoint of high suppression of tackiness, the wax (D) is preferably a wax made of a hydrocarbon having a melting point of 60° C. or more and 75° C. or less. Examples of the wax made of a hydrocarbon having a melting point of 60° C. or more and 75° C. or less include paraffin wax and microcrystalline wax.

[0055] The ratio of the mass of the wax (D) to the mass of the photocurable composition is preferably from 0.1 to 8% by mass, more preferably from 0.5 to 5% by mass, and even more preferably from 1 to 3% by mass.

[0056] <Other ingredients> The photocurable composition may or may not contain various additives that have conventionally been blended into photocurable compositions as other components, as long as the object of the present invention is not impaired. Such other components include polythiol compounds, carbodiimide compounds, viscosity adjusters, sensitizers, thickeners, polymerization inhibitors, pigments, adhesion improvers, antioxidants, curing accelerators, fillers, foam stabilizers, plasticizers, surfactants, lubricants, and antistatic agents. The amounts of these other components to be used are appropriately determined taking into consideration the amounts of each component that are usually used.

[0057] As described below, the photocurable composition is preferably used for preparing a photocurable foaming agent containing gas bubbles, and therefore the photocurable composition preferably contains a foam stabilizer. As the foam stabilizer, a silicone-based foam stabilizer is preferred because it has a good foam stabilizing effect on the photocurable composition. As the silicone-based foam stabilizer, a polyorganosiloxane having a siloxane structure and an ester structure, or a polyorganosiloxane having a siloxane structure and an ether structure is preferred. The polyorganosiloxane preferred as the foam stabilizer may have two or more ester structures per molecule, or may have two or more ether structures per molecule. As the ester structure, an aliphatic polyester structure is preferred. As the ether structure, a polyoxyalkylene structure is preferred. The structure of the polyorganosiloxane may be a chain structure or a structure containing a cyclic structure. The structure of the polyorganosiloxane may be a combination of one or more chain structures and one or more cyclic structures, or may be a structure in which one or more cyclic polyorganosiloxanes are linked by siloxane bonds (Si-O-Si). The molecular weight of the silicone-based foam stabilizer is preferably such that it contains polyorganosiloxane having a number average molecular weight of 800 or more and 3,000 or less, and more preferably 1,000 or more and 2,000 or less, as a main component. The silicone foam stabilizer preferably contains a high molecular weight polyorganosiloxane having a number average molecular weight of 5,000 or more and 20,000 or less in addition to the above main component.

[0058] The photocurable composition can be prepared by uniformly mixing the desired amounts of each of the above-described components using a known mixer.

[0059] ≪Photocurable foam composition≫ As described above, the photocurable composition is preferably used for forming a foam by being mixed with a gas and then cured. Therefore, a photocurable foaming composition containing the photocurable composition and gas bubbles (E) dispersed in the photocurable composition is preferably used for forming a foam. The method for producing the photocurable foam composition will be described later as a method for producing a foam.

[0060] The gas contained in the photocurable foaming composition is preferably an inert gas from the viewpoint of suppressing inhibition of curing of the photocurable composition by oxygen. The inert gas is preferably at least one selected from the group consisting of nitrogen, argon, xenon, krypton, and carbon dioxide gas.

[0061] The content of the bubbles (E) in the photocurable foaming composition is not particularly limited and is appropriately determined according to the expansion ratio of the foam obtained by curing the photocurable foaming composition. The expansion ratio is, for example, preferably 1.5 times or more and 5 times or less, more preferably 2.5 times or more and 4 times or less. The expansion ratio is defined by the following formula. Expansion ratio A=V1 / V0 V1: Volume per unit mass of the photocurable foam composition under atmospheric pressure. V0: Volume per unit mass of the photocurable composition under atmospheric pressure.

[0062] The size of the bubbles (E) in the photocurable composition is measured as the size of the bubbles (E) in the cured product of the photocurable composition cured under atmospheric pressure. Typically, the photocurable composition is discharged from a nozzle under atmospheric pressure to form a bead, and then the formed bead is exposed to light and cured to obtain a cured product, and the size of the bubbles (E) is measured using the cured product. The size of the gas bubbles (E) is not particularly limited as long as it does not impede the object of the present invention. The size of the gas bubbles (E) is preferably, for example, 5 μm or more and 200 μm or less, more preferably 20 μm or more and 100 μm or less. The size of the gas bubbles can be adjusted by adjusting the strength of the shear force applied to the mixture of the photocurable composition and the gas, the amount of gas blended into the photocurable composition, the pressure applied to the photocurable composition in the nozzle before the photocurable composition is discharged from the nozzle when forming a cured product, etc. The magnitude of the shear force can be adjusted by adjusting the cross-sectional area of ​​the flow path that transports the mixture, the flow rate of the mixture in the flow path, etc. The size of the gas bubbles (E) can be measured by observing under a microscope a cross section of the cured product of the photocurable composition cured under atmospheric pressure.

[0063] <Method of manufacturing foam> The method for producing the foam is not particularly limited as long as the above-mentioned photocurable composition is used. Typically, the foam is produced by mixing the photocurable composition with a gas to produce a photocurable foam composition containing gas bubbles; and photocuring the photocurable foam composition by exposure to light. A specific example of such a method is described in Japanese Patent No. 3482309. The method for producing a foam will be described in detail below.

[0064] In the typical foam manufacturing method described above, forming a photocurable foam composition includes: a first step of supplying a photocurable composition pumped through a first pipeline and a gas pumped through a second pipeline by a first pump to mix the photocurable composition and the gas to generate a mixture; a second step of dispersing a gas into the photocurable composition in a dispersion line while the mixture is under pressure; and a third step of foaming the mixture that has passed through the dispersion pipeline by discharging it to produce a photocurable foam composition.

[0065] In the first step, a piston pump connected to the first and second pipes is preferably used as the first pump. First, the piston of the piston pump operates to evacuate the space in the cylinder housing the piston. The compressed gas is filled into the space in the vacuum cylinder from the second pipe. The pressure of the gas at this time is not particularly limited, but is preferably 0.05 MPa or more and 0.3 MPa or less, and more preferably 0.1 MPa or more and 0.2 MPa or less. Next, the photocurable composition is supplied from the first pipe, and a mixture of the photocurable composition and the gas is generated in the cylinder. The pressure of the mixture generated in the cylinder is not particularly limited. The pressure of the mixture generated in the cylinder is preferably 5 MPa or more and 25 MPa or less, and more preferably 15 MPa or more and 20 MPa or less.

[0066] The mixture thus produced in the first step is extruded in the second step into a dispersion line connected to the cylinder by the action of the cylinder, where shear forces are applied to the mixture in the dispersion line, which promotes the dispersion of gas bubbles into the photocurable composition.

[0067] Next, in the third step, the mixture that has passed through the dispersion pipe is discharged. The mixture is usually discharged from a nozzle connected to the dispersion pipe. The pressure applied to the mixture in the nozzle is, for example, preferably 5 MPa or more and 20 MPa or less, more preferably 8 MPa or more and 15 MPa or less. When the pressurized mixture is discharged under an atmospheric pressure environment, the compressed bubbles in the mixture expand to produce a photocurable foam composition. The pressurized mixture is typically dispensed from the nozzle in such a manner that a bead of the photocurable foamable composition is formed at the site where the foam sealant is to be applied.

[0068] The photocurable foam composition thus formed is exposed to light to form a cured foam. The type of light source used for exposure is not particularly limited, and is appropriately selected in consideration of the absorption wavelength of the photopolymerization initiator (C). As the light source used for exposure, an LED is preferred because of various advantages such as a long light source life, energy saving, space saving, output stability, and low maintenance cost.

[0069] The oxygen concentration on the surface of the photocurable foamable composition during exposure is preferably 3% by volume or less, which suppresses inhibition of the effect of the photocurable foamable composition on the surface by oxygen and tends to suppress tackiness of the foam formed.

[0070] The oxygen concentration on the surface of the photocurable foamable composition during exposure is measured, for example, by the following method. First, gas is collected from a space 1 cm to 3 cm away from the surface of the photocurable foamable composition immediately before exposure or at the start of exposure. The concentration of the collected gas is then measured using an oxygen detector or an oxygen concentration meter. For measuring the oxygen concentration, a detector tube 31B manufactured by Gastec Corporation, a digital oxygen concentration meter manufactured by New Cosmos Corporation, an oxygen concentration meter manufactured by Iijima Electronics Co., Ltd., or the like can be used.

[0071] When performing exposure, the method of making the oxygen concentration on the surface of the photocurable foamable composition 3 volume % or less is not particularly limited. For example, the oxygen concentration on the surface of the photocurable foamable composition may be reduced by spraying a gas other than oxygen onto the surface of the photocurable foamable composition. In addition, when producing the photocurable foamable composition, the oxygen concentration on the surface of the photocurable foamable composition may be reduced by releasing a gas other than oxygen from the photocurable foamable composition. As the gas other than oxygen, an inert gas such as nitrogen, argon, xenon, krypton, or carbon dioxide is preferably used.

[0072] Of the steps of (I) producing a photocurable foamable composition, (II) reducing the oxygen concentration on the surface of the photocurable foamable composition to 3 volume % or less, and (III) curing the photocurable foamable composition by exposure to light, it is preferred to achieve (I) and (III), or all of (I) to (III), simultaneously or consecutively using one or more manipulators.

[0073] When the operations (I) to (III) are carried out continuously, the interval between each operation is, for example, preferably 1 minute or less, more preferably 30 seconds or less, still more preferably 10 seconds or less, and particularly preferably 5 seconds or less.

[0074] For example, the above steps (I) and (III) can be carried out simultaneously or successively by using a single manipulator equipped with a nozzle for ejecting a mixture to produce a photocurable foamable composition and a light source for exposing the photocurable foamable composition. The above steps (I) and (III) can also be carried out simultaneously or successively using a manipulator equipped with a nozzle for discharging a mixture to produce a photocurable foamable composition, and a manipulator equipped with a light source for exposing the photocurable foamable composition to light.

[0075] In addition, the above steps (I) to (III) can be carried out simultaneously or continuously by using a single manipulator equipped with a nozzle for discharging a mixture to produce a photocurable foamable composition, a gas supply device for supplying a gas other than oxygen to the surface of the photocurable foamable composition, and a light source for exposing the photocurable foamable composition.

[0076] The above (I) to (III) can also be performed simultaneously or consecutively by using a method of combining a manipulator capable of performing (I) and (II) with a manipulator capable of performing (III), a method of combining a manipulator capable of performing (I) and (III) with a manipulator capable of performing (II), a method of combining a manipulator capable of performing (II) and (III) with a manipulator capable of performing (I), or a method of combining a manipulator capable of performing (I), a manipulator capable of performing (II), and a manipulator capable of performing (III).

[0077] When the above (I) and (III) are carried out by a manipulator, (II) of reducing the oxygen concentration at the surface of the photocurable foamable composition to 3 volume % or less may be carried out by a manipulator or by other means without using a manipulator. For example, the oxygen concentration can be reduced by enclosing the vicinity of the position where the photocurable foaming composition discharged from the manipulator is exposed to light and supplying an inert gas to the enclosed space. EXAMPLES

[0078] The present invention will be described in more detail below by showing examples, but the scope of the present invention is not limited to these examples.

[0079] [Examples 1 to 7, Comparative Example 1, and Comparative Example 2] In Examples 1 to 7, Comparative Example 1, and Comparative Example 2, the following PO1 to PO6 were used as glycols or triols. PO1: Polypropylene glycol (molecular weight 2000, number of hydroxyl groups 2) PO2: Polypropylene glycol (molecular weight 3000, number of hydroxyl groups 2) PO3: Polypropylene triol (molecular weight 5100, number of hydroxyl groups 3, branched triol obtained by adding propylene oxide to glycerin) PO4: Polypropylene glycol (molecular weight 10,000, number of hydroxyl groups 2) PO5: Polypropylene glycol (molecular weight 15,000, number of hydroxyl groups 2) PO6: Polypropylene glycol (molecular weight 8000, number of hydroxyl groups 2)

[0080] In Examples 1 to 7, Comparative Example 1, and Comparative Example 2, the following I1 or I2 was used as the polyisocyanate. I1: Hexamethylene diisocyanate oligomer (isocyanate functional group number 2, NCO content 17.2 mass%, Asahi Kasei Corporation Duranate A201H) I2: Isophorone diisocyanate

[0081] In Examples 1 to 7, Comparative Example 1, and Comparative Example 2, 2-hydroxyethyl acrylate (HEA) was used as the hydroxyalkyl (meth)acrylate.

[0082] In Examples 1 to 7, Comparative Example 1, and Comparative Example 2, the following CA1 or CA2 was used as the catalyst. CA1: Stannous octoate CA2: Dibutyltin laurate

[0083] The urethane (meth)acrylate compounds of each Example and Comparative Example were synthesized according to the following method using the raw materials in the amounts shown in Table 1. The viscosity of the obtained urethane (meth)acrylate compounds and the molecular weight of the polyoxyalkylene unit in the urethane (meth)acrylate compounds are shown in Table 1. The viscosity was measured with a BH type viscometer using a No. 7 rotor at 20°C and a rotation speed of 20 rpm.

[0084] Specifically, first, nitrogen was flowed into the reaction vessel to remove moisture from the vessel. After that, dehydrated HEA was added to the reaction vessel, and polyisocyanate was further added. Next, the contents of the reaction vessel were stirred. Half of the catalyst was added to the reaction vessel to start the reaction, and the reaction was carried out by stirring the contents of the reaction vessel for 2 hours at room temperature (reaction started at about 20°C). After confirming that the remaining amount of isocyanate groups was a predetermined amount, polyol was further added, and the contents of the reaction vessel were stirred while heating to 80°C. When the temperature in the reaction vessel reached 80°C, half of the catalyst was added, and the reaction was carried out by stirring the contents of the reaction vessel for 6 hours to obtain a urethane (meth)acrylate compound.

[0085] [Table 1]

[0086] [Examples 8 to 23 and Comparative Examples 3 to 5] In Examples 8 to 23 and Comparative Examples 3 to 5, the urethane (meth)acrylate compounds obtained in Examples 1 to 7, Comparative Example 1, and Comparative Example 2 were used as the urethane (meth)acrylate (A).

[0087] In Examples 8 to 23 and Comparative Examples 3 to 5, the following M1 to M5 were used as the photopolymerizable monomer (B). M1: Isobornyl acrylate M2: Trimethylolpropane triacrylate M3: Polytetramethylene glycol diacrylate M4: 1,9-nonanediol diacrylate M5: Lauryl acrylate

[0088] In Examples 8 to 23 and Comparative Examples 3 to 5, the following PI1 to PI4 were used. PI1: 2,4,6-Trimethylbenzoyl-diphenyl-phosphine oxide (manufactured by IGM Resins B.V., Omnirad TPO-H) PI2: 1-Hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins B.V., Omnirad 184) PI3: 1,2-Octanedione, 1-[4-(phenylthio)phenyl]-, 2-(O-benzoyloxime) (manufactured by BASF Japan Ltd., OXE01)

[0089] The urethane (meth)acrylate (A), photopolymerizable monomer (B), and photopolymerization initiator (C) of the types and amounts described in Tables 2 to 4, respectively, and 1.4 parts by mass of a foam stabilizer (SF-8427, 0.7 part by mass and SZ-1923, 0.7 part by mass. Both are manufactured by The Dow Chemical Company) were uniformly mixed using a planetary mixer to obtain the photocurable compositions of Examples 8 to 23 and Comparative Examples 3 to 5, respectively.

[0090] The viscosity of the obtained photocurable composition was measured. The viscosity is the viscosity measured at 20 °C and a rotation speed of 20 rpm using a No. 7 rotor with a BH type viscometer. Also, according to the following method, the Asker C hardness, elongation, M50 (tensile stress at an elongation of 50%), M100 (tensile stress at an elongation of 100%), and Tb (breaking point stress) of the cured product which is a foam were measured. Furthermore, according to the following method, the heat resistance, deep part curability, and surface tack (N2 spraying) of the photocurable composition were evaluated. These evaluation results and measurement results are shown in Tables 2 to 4.

[0091] <Asker C hardness measurement> A cylindrical polypropylene cup having a circular opening with an inner diameter (diameter) of 50 mm, an inner depth of 12 mm, and one bottom closed was filled with a photocurable foam composition using a mechanical foaming device (FOAMPLY-ST, manufactured by Sansuta Giken Co., Ltd.). The photocurable foam composition was prepared by adjusting the supply gas pressure using the aforementioned mechanical foaming device so that the foaming ratio was 4 times. Next, the photocurable foam composition filled in the cup was exposed for 2 seconds at a distance of 10 mm from the surface of the photocurable composition foam using an exposure device (firejet240, wavelength 395 nm, manufactured by Phoseon) with an LED output of 12 W / cm 2 to form a photocured foam. After the photocured foam was allowed to stand at room temperature for 24 hours, its hardness was measured using an Asker C hardness tester in accordance with JIS K 6253 (ASTM D2240).

[0092] <Measurement of M50, M100, and Tb> While discharging the photocurable foam composition at a discharge rate of 30 cc / min from the nozzle provided in the aforementioned mechanical foaming device onto a Teflon (registered trademark) sheet, the nozzle was moved at a robot speed of 100 mm / sec to form a strip-shaped bead having a semicircular cross-section with a radius of 4 mm made of the photocurable foam composition. The photocurable foam composition was prepared by adjusting the supply gas pressure using the aforementioned mechanical foaming device so that the foaming ratio was 4 times. Next, at a distance of 15 mm from the strip-shaped bead, using an exposure device (firejet240, wavelength 395 nm, manufactured by Phoseon) with an LED, at an output of 12 W / cm 2 while moving the manipulator at a speed of 50 mm / sec for exposure to form a photocured strip-shaped foam. Note that exposure was performed on the strip-shaped bead while blowing N2 gas at a flow rate of 20 L / sec toward the front in the moving direction of the nozzle. Using the obtained strip-shaped foam as a test piece, M50, M100, and Tb were measured in accordance with JIS K 6251 (ASTM D412) under the conditions of a test speed of 200 mm / min and a chuck distance of 20 mm.

[0093] <Heat resistance evaluation> A band-shaped cured bead formed in the same manner as in the M50, M100, and Tb measurements was placed in an atmosphere at 140° C. for 24 hours. After 24 hours, the appearance of the cured bead was observed, and the heat resistance was evaluated according to the following criteria. ◎: No change in appearance. ○: No change in appearance, but stickiness was observed on the surface. Δ: The edge of the cured product melted. ×: The cured product melted.

[0094] <Deep section curing evaluation> The curable composition was filled into a cup having a circular opening with a diameter of 15 mm and a depth of 23 mm, with the sides made of aluminum and the bottom made of glass. From a height of 10 mm above the curable composition filled in the cup, an exposure device (firejet240 (wavelength 395 nm, manufactured by PhoSeon)) was used to expose the curable composition to an LED with an output of 12 W / cm. 2 After exposure to light while moving the manipulator at a speed of 150 mm / sec, the curing depth from the position on the opening side of the cup was measured using a scale.

[0095] <Surface tack evaluation> The photocurable composition was filled into a cylindrical polypropylene cup having a circular opening with an inner diameter of 50 mm, an inner depth of 12 mm, and one bottom portion closed. Next, an exposure device (firejet 240 (wavelength 395 nm, manufactured by PhoSeon)) was used to expose the photocurable foam composition filled in the cup from a height of 10 mm, with an output of 12 W / cm 2 using LEDs. 2 The photocurable composition was exposed to light while moving the manipulator at a speed of 150 mm / sec to form a cured product of the photocurable composition. A test was conducted in which the photocurable composition in the cup was exposed to light while N2 gas was sprayed at a flow rate of 20 L / sec, and a test was conducted in which the photocurable composition was exposed to light without spraying N2 gas. The surface of the cured product was touched with a finger and then visually observed, and the surface tackiness was evaluated according to the following criteria. No sticky feeling when touched with fingers. ○There is a sticky feeling but no fingerprints. △Fingerprints on the surface. × Liquid is attached.

[0096] [Table 2]

[0097] [Table 3]

[0098] [Table 4]

[0099] It can be seen from Tables 2 to 4 that a foam having both good elongation and good tensile strength can be formed by foaming and curing a photocurable composition containing a urethane (meth)acrylate compound represented by formula (A1) satisfying the above-mentioned constituent requirements and a photopolymerization initiator (C).

Claims

1. A photocurable composition comprising a urethane (meth)acrylate (A) and a photopolymerization initiator (C), The urethane (meth)acrylate (A) is represented by the following formula (A1): (CH ２ =CR ５ ---O-R ４ -O---++) ａ -R ２ -+----(O-R １ ) ｎ -O---NH-R ３ --------R ４ -O---CR ５ =CH ２ ) ｂ ・・・(A1) (In formula (A1), R １ is an alkylene group having 2 to 4 carbon atoms; R ２ is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of a+1, and R ３ is a group obtained by removing an isocyanate group from an aliphatic isocyanate compound having a valence of (b+1), a and b each independently represent 1 or 2, R ４ is an alkylene group having 1 to 8 carbon atoms; R ５ is a hydrogen atom or a methyl group, and in formula (A1), -(O-R １ ) ｎ The molecular weight of the unit represented by -O- is 3,000 to 30,000, and n is -O-R １ is the number of repetitions of the oxyalkylene group represented by the formula: The urethane (meth)acrylate compound is represented by the formula: the photocurable composition contains a photopolymerizable monomer (B), the photopolymerizable monomer (B) is at least one selected from the group consisting of a chain aliphatic tri(meth)acrylate (B1-1), a chain aliphatic di(meth)acrylate (B2-1), a chain aliphatic mono(meth)acrylate (B3-1), and an alicyclic mono(meth)acrylate (B3-2); the photopolymerization initiator (C) is one or more selected from the group consisting of alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, benzoin-based photopolymerization initiators, anthraquinone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, benzophenone-based photopolymerization initiators, phenylglyoxylate-based photopolymerization initiators, oxime ester-based photopolymerization initiators, and titanocene compound-based photopolymerization initiators; a ratio of the mass of the urethane (meth)acrylate (A) to the mass of the photocurable composition is 50 mass% or more; A photocurable composition, wherein a ratio of the mass of the urethane (meth)acrylate compound represented by Formula (A1) to the mass of the urethane (meth)acrylate (A) is 90 mass% or more.

2. A photocurable composition comprising a urethane (meth)acrylate (A) and a photopolymerization initiator (C), and not containing a thermoplastic polymer having a carboxy group, The urethane (meth)acrylate (A) is represented by the following formula (A1): (CH 2 =CR 5 -CO-O-R 4 -O-CO-NH) a -R 2 -NH-CO-(O-R 1 ) n -O-CO-NH-R 3 -(NH-CO-O-R 4 -O-CO-CR 5 =CH 2 ) b ... (A1) (In formula (A1), R 1 is an alkylene group having 2 to 4 carbon atoms, R 2 is a group obtained by removing an isocyanate group from an a+1-valent aliphatic isocyanate compound, R 3 is a group obtained by removing an isocyanate group from an a+1-valent aliphatic isocyanate compound, a and b are each independently 1 or 2, R 4 is an alkylene group having 1 to 8 carbon atoms, R 5 is a hydrogen atom or a methyl group, the molecular weight of the unit represented by -(O-R 1 ) n -O- in formula (A1) is 3,000 to 30,000, and n is the number of repetitions of the oxyalkylene group represented by -O-R 1 -.) The urethane (meth)acrylate compound is represented by the formula: The photocurable composition may or may not contain a photopolymerizable monomer (B); When the photocurable composition contains the photopolymerizable monomer (B), the photopolymerizable monomer (B) is a (meth)acrylate compound, the photopolymerization initiator (C) is one or more selected from the group consisting of alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, benzoin-based photopolymerization initiators, anthraquinone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, benzophenone-based photopolymerization initiators, phenylglyoxylate-based photopolymerization initiators, oxime ester-based photopolymerization initiators, and titanocene compound-based photopolymerization initiators; a ratio of the mass of the urethane (meth)acrylate (A) to the mass of the photocurable composition is 50 mass% or more; A photocurable composition, wherein a ratio of the mass of the urethane (meth)acrylate compound represented by Formula (A1) to the mass of the urethane (meth)acrylate (A) is 90 mass% or more.

3. The photocurable composition according to claim 1 or 2, wherein a and b are each 1.

4. A photocurable composition described in any one of claims 1 to 3, wherein the ratio of the mass of the urethane (meth)acrylate (A) to the mass of the photocurable composition is 70 mass% or more.

5. The R １ The photocurable composition according to any one of claims 1 to 3, wherein is a propane-1,2-diyl group.

6. The photocurable composition described in claim 2, comprising the photopolymerizable monomer (B), wherein the photopolymerizable monomer (B) is one or more selected from the group consisting of tri(meth)acrylates (B1), di(meth)acrylates (B2), and mono(meth)acrylates (B3).

7. The photocurable composition according to claim 6, wherein the photopolymerizable monomer (B) is at least one selected from the group consisting of linear aliphatic tri(meth)acrylates (B1-1), linear aliphatic di(meth)acrylates (B2-1), linear aliphatic mono(meth)acrylates (B3-1), and alicyclic mono(meth)acrylates (B3-2).

8. The photocurable composition according to any one of claims 1 to 7, wherein the photopolymerization initiator (C) comprises at least one selected from the group consisting of alkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime ester-based photopolymerization initiators.

9. The photocurable composition according to any one of claims 1 to 8, which is used to produce a foam by mixing with a gas and photocuring.

10. A photocurable foaming composition comprising the photocurable composition according to any one of claims 1 to 9 and gas bubbles (E) dispersed in the photocurable composition.

11. The photocurable foamable composition according to claim 10, wherein the gas is at least one selected from the group consisting of nitrogen, argon, xenon, krypton, and carbon dioxide gas.

12. The photocurable foamable composition according to claim 10 or 11, wherein the size of the gas bubbles (E) in a cured product cured under atmospheric pressure is 5 μm or more and 200 μm or less.

13. mixing the photocurable composition according to any one of claims 1 to 9 with a gas to produce a photocurable foamable composition containing bubbles; and photocuring the photocurable foam composition by exposure to light.

14. Producing the photocurable foam composition comprises: a first step of supplying the photocurable composition pumped through a first line and the gas pumped through a second line by a first pump to mix the photocurable composition and the gas to generate a mixture; a second step of dispersing the gas into the photocurable composition in a dispersion line while the mixture is under pressure; and a third step of discharging the mixture that has passed through the dispersion conduit to foam the mixture and generate the photocurable foam composition.

15. The method for producing a foam according to claim 13 or 14, wherein the exposure is LED exposure.

16. The method for producing a foam according to any one of claims 13 to 15, wherein an oxygen concentration on the surface of the photocurable foamable composition during exposure is 3 volume % or less.

17. The method for producing a foam according to any one of claims 13 to 16, wherein (I) and (III), or all of (I) to (III), among (I) producing the photocurable foam composition, (II) reducing the oxygen concentration on the surface of the photocurable foam composition to 3 volume% or less, and (III) curing the photocurable foam composition by exposure to light, are achieved simultaneously or continuously using a manipulator.

18. The method for producing a foam according to any one of claims 13 to 17, wherein the oxygen concentration on the surface of the photocurable foamable composition is set to 3 volume % or less by spraying a gas other than oxygen onto the surface of the photocurable foamable composition.

19. The method for producing a foam according to any one of claims 13 to 18, wherein the oxygen concentration on the surface of the photocurable foamable composition is set to 3 volume % or less by releasing a gas other than oxygen from the photocurable foamable composition when generating the photocurable foamable composition.

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