Method for producing urethane (meth)acrylate and urethane (meth)acrylate resin

Abstract

To provide a method for producing an urethane (meth)acrylate resin which does not generate an insoluble by-product, can suppress turbidity, and has good appearance.SOLUTION: A method for producing an urethane (meth)acrylate includes a step 1 of obtaining a resin precursor (P) that is a reactant of polyol (A), organic isocyanate (B) and a hydroxyl group-containing compound (C-1), and a step 2 of obtaining urethane (meth)acrylate (UM) that is a reaction adduct of the resin precursor (P) obtained in the step 1 and a hydroxyl group-containing compound (C-2). The organic isocyanate (B) is a compound that is solid under one atmospheric pressure in a temperature range of 0-4°C, the hydroxyl group-containing compound (C-1) is a compound that is liquid at one atmospheric pressure in a temperature range of 20-35°C, and the hydroxyl group-containing compound (C-2) contains a hydroxyl group-containing (meth)acrylic compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a urethane (meth)acrylate and a urethane (meth)acrylate resin. [Background technology]

[0002] Radical polymerizable resins are compounds that contain ethylenically unsaturated groups and undergo polymerization reactions via radicals. The cured products of radical polymerizable resins are materials with excellent mechanical strength and water resistance. By adjusting the curing agent and accelerator, the curing time of such radical polymerizable resins can be set independently of temperature. Therefore, unlike epoxy resins, they do not require long curing times and do not suffer from poor curing, especially when applied at low temperatures. For this reason, radical polymerizable resins have traditionally been widely used in paints, adhesives, and fiber-reinforced plastic (hereinafter sometimes abbreviated as FRP) materials. Examples of radically polymerizable resins include urethane (meth)acrylate resins, vinyl ester resins, unsaturated polyester resins, polyester (meth)acrylate resins, and (meth)acrylate resins. Among these, urethane (meth)acrylate resins are used to impart high flexibility and low modulus of elasticity to the cured product of the radically polymerizable resin composition. Furthermore, by mixing them with other resins, they can impart flexibility to the cured product and exhibit high strength and toughness when made into FRP. Examples of methods for producing urethane (meth)acrylate include a production method having a reaction step 1 in which a polyol component is reacted with an organic isocyanate compound to bond the organic isocyanate compound to both ends of the polyol component to obtain a resin precursor (P), and a reaction step 2 in which a monohydroxy(meth)acrylate is bonded to the terminal isocyanate group of the obtained resin precursor (P) (for example, Patent Document 1). The obtained urethane (meth)acrylate is usually dissolved in a monomer such as a diluent and stored as a low-viscosity solution (urethane (meth)acrylate resin). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-183345 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional methods for producing urethane (meth)acrylate, it is believed that excess organic isocyanate compounds react with hydroxyl-containing compounds (water, inhibitors, etc.) in reaction step 1 to produce insoluble substances. These insoluble substances precipitate in the diluent (radical polymerizable monomer) such as a monomer in which the resin obtained in reaction step 2 is dissolved, causing problems such as the resin solution becoming cloudy or the cloudy precipitate flocculating and settling.

[0005] The present invention aims to provide a method for producing a urethane (meth)acrylate resin with good appearance, which can prevent the generation of by-products resulting from excess organic isocyanate compounds in Reaction Step 1 to obtain a resin precursor (P) and Reaction Step 2. It has been found that the use of this technology is effective in suppressing the occurrence of cloudiness due to aggregation of crystalline substances. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides the following [1] to

[14] . [1] A polyol (A), an organic isocyanate (B); a hydroxyl group-containing compound (C-1); a hydroxyl group-containing compound (C-2); A method for producing a urethane (meth)acrylate (UM) which is a reaction product of Step 1 of obtaining a resin precursor (P) which is a reaction product of the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-1); Step 2 of obtaining a urethane (meth)acrylate (UM) which is a reaction adduct of the resin precursor (P) obtained in Step 1 with a hydroxyl group-containing compound (C-2); and The organic isocyanate (B) is a compound that is solid under 1 atmosphere at a temperature range of 0 to 4°C, The hydroxyl group-containing compound (C-1) is a compound that is liquid under 1 atmosphere at a temperature range of 20 to 35°C, The hydroxyl group-containing compound (C-2) includes a hydroxyl group-containing (meth)acrylic compound. A method for producing a urethane (meth)acrylate, comprising: [2] The method for producing a urethane (meth)acrylate according to [1], wherein in step 1, the molar ratio of the isocyanato groups of the organic isocyanate (B) to the hydroxyl groups of the polyol (A) is isocyanato groups / hydroxyl groups=1.2 or more. [3] The amount of the hydroxyl group-containing compound (C-1) used is The method for producing a urethane (meth)acrylate according to [1] or [2], wherein the amount of the hydroxyl group-containing compound (C-2) is 0.01 to 5 parts by mass per 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-2). [4] The method for producing a urethane (meth)acrylate according to any one of [1] to [3], wherein the hydroxyl group-containing compound (C-1) is at least one selected from the group consisting of monohydroxy compounds and dihydroxy compounds. [5] The method for producing a urethane (meth)acrylate according to any one of [1] to [4], wherein the hydroxyl group-containing compound (C-1) is the same compound as the hydroxyl group-containing compound (C-2). [6] The method for producing a urethane (meth)acrylate according to any one of [1] to [5], wherein the melting point of the organic isocyanate (B) is 5°C to 50°C. [7] The method for producing a urethane (meth)acrylate according to any one of [1] to [6], wherein the organic isocyanate (B) is diphenylmethane diisocyanate. [8] The method for producing a urethane (meth)acrylate according to any one of [1] to [7], wherein the polyol (A) is at least one selected from the group consisting of polyether polyols, polyester polyols, and polyoxyalkylene bisphenol A ethers. [9] The method for producing a urethane (meth)acrylate according to any one of [1] to [8], wherein the hydroxyl group-containing compound (C-2) is at least one selected from the group consisting of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

[10] A step A of obtaining a urethane (meth)acrylate by using the method for producing a urethane (meth)acrylate according to any one of [1] to [9]; A step B of mixing a urethane (meth)acrylate and a diluent (E); A method for producing a urethane (meth)acrylate resin, comprising: A method for producing a urethane (meth)acrylate resin, characterized in that the method for mixing the diluent (E) includes any one or two methods selected from the group consisting of a method for mixing during step A and a method for mixing after step A.

[11] A urethane (meth)acrylate obtained by the method for producing a urethane (meth)acrylate according to any one of [1] to [9].

[12] The urethane (meth)acrylate according to

[11] , a diluent (E); A urethane (meth)acrylate resin comprising:

[13] The urethane (meth)acrylate resin according to

[12] , wherein the diluent (E) is a radical polymerizable monomer having an ethylenically unsaturated bond.

[14] The urethane (meth)acrylate resin according to

[13] , having a transparency (haze value) of 20% or less. [Effects of the Invention]

[0007] According to the present invention, in reaction step 1 for obtaining the resin precursor (P), the excess organic isocyanate compound is reacted with the hydroxyl group-containing compound (C-1) and blocked, so that in reaction step 2, the production of insoluble by-products can be suppressed, turbidity can be suppressed, and a production method for producing a resin with a good appearance can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, as an embodiment of the present invention, a method for producing a urethane (meth)acrylate and a urethane (meth)acrylate resin obtained by the method for producing a urethane (meth)acrylate resin will be described.

[0009] "(Meth)acrylic" is a general term for acrylic and methacrylic, and "(meth)acrylate" is a general term for acrylate and methacrylate. Urethane (meth)acrylate resin is a general term for urethane acrylate resin and urethane methacrylate resin. In this specification, "urethane (meth)acrylate resin" may be simply referred to as "urethane (meth)acrylate resin" or "resin of the present invention."

[0010] "Urethane (meth)acrylate" is a resin obtained by introducing (meth)acryloyl groups into the hydroxyl groups or isocyanato groups at both ends of polyurethane obtained by reacting a polyisocyanate with a polyhydric alcohol, for example. The "urethane (meth)acrylate resin" is a composition obtained by adding a radical polymerizable monomer and a diluent such as a solvent to the above-mentioned "urethane (meth)acrylate" and adjusting the viscosity and physical properties of the cured product. An "organic isocyanate" is a compound having two or more isocyanato groups in its structure. A "polyol" is a compound having two or more alcoholic hydroxyl groups in its structure, and is also called a polyhydric alcohol. A "hydroxyl group-containing compound" (or "hydroxy group-containing compound") is a compound that has one or more hydroxyl groups in its structure.

[0011] A "monohydroxy unsaturated compound or hydroxyl group-containing (meth)acrylic compound" is a compound that has one hydroxy group and one or more ethylenically unsaturated bonds in one molecule. Unless otherwise specified, an "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond that is radically polymerizable.

[0012] [Urethane (meth)acrylate] The urethane (meth)acrylate (UM), which is the target of the production method of the present invention, will be described below. The urethane (meth)acrylate (UM) of the present invention is obtained by reacting a polyol (A), an organic isocyanate (B) having two or more isocyanato groups per molecule, a hydroxyl-containing compound (C-1) having one or more hydroxyl groups per molecule, and a hydroxyl-containing compound (C-2) having one or more hydroxyl groups per molecule. The hydroxyl-containing compound (C-2) includes a hydroxyl-containing (meth)acrylic compound. For example, a resin obtained by introducing (meth)acryloyl groups contained in a monohydroxy unsaturated compound into the isocyanato groups at both ends of a urethane (meth)acrylate precursor (P) (sometimes simply referred to as "resin precursor (P)") obtained by reacting the organic isocyanate (B) with the polyol (A) can be used.

[0013] <Polyol (A)> As the polyol (A) used as a raw material for the urethane (meth)acrylate, compounds described as "polyhydroxy compounds" or "polyhydric alcohols" in WO2018 / 135654 can be used without particular limitation. The polyol (A) is selected from polyether polyols, polyester polyols, polycarbonate polyols, and mixtures thereof. Among these, polyether polyols are preferred from the viewpoints of ease of reaction, cost, and the ability to reduce the modulus of elasticity when the radical-polymerizable resin composition is cured. The polyether polyol is not particularly limited, and examples thereof include polyethylene glycol, polypropylene glycol, polyoxyalkylene bisphenol A ether, polytetramethylene glycol, random copolymers or block copolymers of ethylene oxide and propylene oxide, ethylene oxide and butylene oxide, etc. Furthermore, polyether polyester polyols having an ether bond and an ester bond can also be used.

[0014] "Polyether polyol" The polyether polyol is not particularly limited, but preferably has a weight-average molecular weight of 300 to 5,000, more preferably 350 to 3,000, and even more preferably 400 to 2,500. A weight-average molecular weight of 300 or more can impart flexibility. On the other hand, a weight-average molecular weight of 5,000 or less provides good compatibility with radically polymerizable monomers and allows for low viscosity as a resin. Furthermore, within the above range, it can be mixed with other resins having ethylenically unsaturated bonds, such as vinyl ester resins and unsaturated polyester resins, and compatibility is also good. When a polyether polyol is used, the amount used is preferably 10 to 90 parts by mass, more preferably 30 to 85 parts by mass, relative to 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), the hydroxyl group-containing compound (C-1), and the hydroxyl group-containing compound (C-2), and from the viewpoints of toughness as a resin, low viscosity, and the ability to be mixed with other resins, the amount used is even more preferably 40 to 80 parts by mass.

[0015] Among polyether polyols, polyethylene glycol and polypropylene glycol are more preferably used from the viewpoints of versatility, availability, and cost. From the viewpoint of water resistance of the cured product during the reaction, it is even more preferable to use polypropylene glycol as the main skeleton. These may also be used in combination.

[0016] The polyethylene glycol is not particularly limited, but preferably has a weight-average molecular weight of 300 to 5,000, more preferably 350 to 4,000, and even more preferably 400 to 2,000. A weight-average molecular weight of 300 or more can impart flexibility. On the other hand, a weight-average molecular weight of 5,000 or less facilitates reaction in terms of melting point. Furthermore, compatibility with radically polymerizable monomers is good, allowing for low viscosity as a resin. Furthermore, within the above range, it can be used in combination with other resins having ethylenically unsaturated bonds, such as vinyl ester resins and unsaturated polyester resins. Using a certain amount of polyethylene glycol in the skeleton can improve compatibility with vinyl ester resins and unsaturated polyester resins. When polyethylene glycol is used, the amount used is preferably 1 to 90 parts by mass, more preferably 3 to 75 parts by mass, and even more preferably 5 to 60 parts by mass, per 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), the hydroxyl group-containing compound (C-1), and the hydroxyl group-containing compound (C-2). From the viewpoints of toughness and low viscosity as a resin, and the ability to be mixed with other resins, the amount used is preferably 1 to 90 parts by mass, even more preferably 3 to 75 parts by mass, and even more preferably 5 to 60 parts by mass.

[0017] The polypropylene glycol preferably has a weight-average molecular weight of 300 to 5,000, more preferably 350 to 3,000, and even more preferably 400 to 2,500. A weight-average molecular weight of 300 or more can impart flexibility. On the other hand, a weight-average molecular weight of 5,000 or less provides good compatibility with radically polymerizable monomers and allows for low viscosity as a resin. Furthermore, within the above range, good compatibility can be achieved even when mixed with other resins having ethylenically unsaturated bonds, such as vinyl ester resins and unsaturated polyester resins.

[0018] "Polyester polyol" Polyester polyols are synthesized by dehydration condensation of several carboxylic acids and polyhydric alcohols. Examples of carboxylic acids include adipic acid and phthalic acid, and examples of polyhydric alcohols include ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol. There are no particular restrictions on the raw materials. There are no particular restrictions on the polyester polyols, and examples include polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, polyhexamethylene isophthalate adipate diol, polyethylene succinate diol, polybutylene succinate diol, polyethylene sebacate diol, polybutylene sebacate diol, poly-ε-caprolactone diol, poly(3-methyl-1,5-pentylene adipate) diol, and polycondensates of 1,6-hexanediol and dimer acid. Among these, from the viewpoint of imparting flexibility to the urethane (meth)acrylate, adipate-based polyester polyols such as polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, and polyhexamethylene isophthalate adipate diol are preferred.

[0019] The adipate-based polyester polyol is not particularly limited, but preferably has a weight-average molecular weight of 300 to 5,000, more preferably 400 to 4,000, and even more preferably 500 to 3,000. A weight-average molecular weight of 600 or more can impart flexibility. On the other hand, a weight-average molecular weight of 4,000 or less can provide good compatibility with radically polymerizable monomers and can achieve low viscosity as a resin. Furthermore, within the above range, it can also be used in combination with other resins having ethylenically unsaturated bonds, such as vinyl ester resins and unsaturated polyester resins. When an adipate-based polyester polyol is used, the amount used is preferably 10 to 90 parts by mass, more preferably 30 to 85 parts by mass, per 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), the hydroxyl group-containing compound (C-1), and the hydroxyl group-containing compound (C-2). From the viewpoints of toughness and low viscosity as a resin, and good compatibility when mixed with other resins, the amount used is even more preferably 40 to 80 parts by mass.

[0020] "Polycarbonate polyol" The polycarbonate polyol is not particularly limited, and examples thereof include polytetramethylene carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, and poly(hexamethylene-1,4-cyclohexanedimethylene carbonate) diol. The use of polycarbonate polyols allows for the production of urethane (meth)acrylates with better water resistance, chemical resistance, durability, and weather resistance than polyether polyols or polyester polyols. Among these, 1,6-hexanediol- and 1,5-pentanediol-based polycarbonate polyols are preferred from the viewpoints of the versatility, availability, and ease of reaction of urethane acrylates.

[0021] The polycarbonate polyol is not particularly limited, but preferably has a weight-average molecular weight of 300 to 4,000, more preferably 400 to 3,500, and even more preferably 500 to 3,000. A weight-average molecular weight of 600 or more can impart flexibility. On the other hand, a weight-average molecular weight of 4,000 or less can provide good compatibility with radically polymerizable monomers and can achieve low viscosity as a resin. Furthermore, within the above range, it can also be used in combination with other resins having ethylenically unsaturated bonds, such as vinyl ester resins and unsaturated polyester resins. When an adipate-based polyester polyol is used, the amount used is preferably 10 to 90 parts by mass, more preferably 30 to 85 parts by mass, per 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), the hydroxyl group-containing compound (C-1), and the hydroxyl group-containing compound (C-2). From the viewpoints of toughness and low viscosity as a resin, and good compatibility when mixed with other resins, the amount used is even more preferably 40 to 80 parts by mass.

[0022] Polymer polyols and vegetable polyols (castor oil, linseed oil, etc.) can also be used. The polyol (A) may be any of the above polyols alone or a mixture of two or more of the above polyols, i.e., the polyol (A) may consist of one or more of the above polyols.

[0023] The polyol (A) may be a difunctional or trifunctional compound, or a mixture thereof. The average molecular weight of the difunctional compound is preferably 4000 or less, more preferably 2500 or less, and the average molecular weight of the trifunctional compound is preferably 1500 or less.

[0024] <Organic isocyanate (B)> The organic isocyanate (B) having two or more isocyanato groups per molecule and used as a raw material for the urethane (meth)acrylate resin is a compound that is solid at 1 atmosphere in the temperature range of 0°C to 4°C. This temperature range is preferably 0°C to 9°C, more preferably 0°C to 15°C, even more preferably 0°C to 19°C, and particularly preferably 0°C to 25°C. For example, it can be selected from those described in JP 2009-292890 A and WO 2016 / 171151 A, including aromatic and alicyclic organic isocyanates. These organic isocyanates may be used alone or in combination of two or more. From the viewpoints of versatility and safety, solid organic isocyanates (B) are preferred. Examples include MDI and TDI. However, in conventional production methods, when a solid organic isocyanate (B) is used, there are problems such as the tendency for turbidity due to by-products to occur. However, by using the production method of the present invention, it is possible to produce a urethane (meth)acrylate without turbidity occurring during the production process, even when an organic isocyanate (B) that is solid in the temperature range of 0°C to 4°C is used. As a result, it is possible to produce a resin with a good appearance, with reduced turbidity, while maintaining versatility and safety. Note that "being solid in the temperature range of a°C to b°C" means that it is sufficient that it is solid in the temperature range of a°C to b°C, and it does not matter whether it is solid or not outside that range. Examples of aromatic isocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), phenylene diisocyanate, naphthalene diisocyanate (NDI), etc. Among these, and among these organic isocyanates (B), diphenylmethane diisocyanate is preferred because of its excellent reactivity and low toxicity to the human body.

[0025] Examples of alicyclic isocyanates include cyclohexane-1,4-diisocyanate, cyclohexane-1,4-diylbis(methylene)diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 1,3-bis(isocyanatomethyl)hexane, and hydrogenated products of TDI. The above isocyanates may also be modified with carbodiimide or isocyanurate. The organic isocyanate (B) may be used alone or in combination of two or more kinds.

[0026] The amount of organic isocyanate (B) used is preferably 3 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 35 parts by mass, relative to 100 parts by mass of the total of polyol (A), organic isocyanate (B), hydroxyl group-containing compound (C-1), and hydroxyl group-containing compound (C-2). If the amount of isocyanate compound used is less than 3 parts by mass, the desired adhesive strength may not be obtained, which is undesirable. On the other hand, if the amount of isocyanate compound used is more than 50 parts by mass, the desired flexibility may not be obtained, which is undesirable. When the amount of the isocyanate compound used is 3 parts by mass or more, flexibility and a certain level of strength can be imparted. On the other hand, when the amount of the isocyanate compound used is 50 parts by mass or less, compatibility with the radical polymerizable monomer is good and the viscosity of the resin can be made low. Furthermore, within the above range, good compatibility can be obtained even when mixed with other resins having ethylenically unsaturated bonds, such as vinyl ester resins and unsaturated polyester resins.

[0027] <Hydroxyl group-containing compound (C-1)> The hydroxyl group-containing compound (C-1) having a hydroxyl group and used as a raw material for urethane (meth)acrylate is a compound that is liquid at 1 atmosphere in a temperature range of 20° C. to 35° C. This temperature range is preferably 15° C. to 35° C., more preferably 10° C. to 35° C., even more preferably 5° C. to 35° C., and most preferably −10° C. to 35° C. Examples of the hydroxyl group-containing compound (C-1) include monohydroxy compounds having one or more hydroxyl groups in one molecule, dihydroxy compounds having two or more hydroxyl groups in one molecule, and polyol compounds. Note that "being liquid in the temperature range of a°C to b°C" means that it is sufficient that the material is liquid in the temperature range of a°C to b°C, and it does not matter whether it is liquid or not in a temperature range outside that range.

[0028] The monohydroxy compound may be a compound containing one or more hydroxyl groups and one or more ethylenically unsaturated bonds in one molecule, as described later in connection with the hydroxyl group-containing compound (C-2). From the viewpoint of using a common raw material, it is preferable that the hydroxyl group-containing compound (C-1) is the same compound as the hydroxyl group-containing compound (C-2). For example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxy(meth)acrylate, 2-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-methacryloyloxy acid phosphate, 2-acryloyloxyethyl-phthalate, 2-acryloyloxyethyl-2-hydroxyethyl-phthalate, 2-hydroxy-3-acryloyloxypropyl methacrylate, pentaerythritol tri(meth)acrylate, 2-hydroxyethyl (meth)acrylamide, 2-hydroxyethyl-N-methyl(meth)acrylamide, 3-hydroxypropyl (meth)acrylamide, caprolactone-modified hydroxyalkyl (meth)acrylate, and the like can be used. Among these, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxy(meth)acrylate, and 2-hydroxybutyl (meth)acrylate are preferred in terms of versatility, availability, cost, and ease of reaction, and 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate are more preferred in terms of good reactivity with isocyanate, reactivity during production of a cured product, versatility, and cost, and 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate are even more preferred in terms of irritation resistance and safety in use.

[0029] Monohydroxy compounds include compounds containing one or more hydroxyl groups and ethylenically unsaturated bonds in one molecule, as well as compounds containing no ethylenically unsaturated bonds and one hydroxyl group in one molecule, such as lower alcohols that are liquid at room temperature and have a high boiling point, benzyl alcohol, and higher alcohols such as octanol, decyl alcohol, and lauryl alcohol, as well as lactic acid and ethyl lactate.

[0030] The dihydroxy compound having two or more hydroxyl groups in one molecule may be a compound having two hydroxyl groups and one or more ethylenically unsaturated bonds in one molecule.From the viewpoint of using common raw materials, it is preferable that the hydroxyl group-containing compound (C-1) is the same compound as the hydroxyl group-containing compound (C-2).For example, 2-acryloyloxyethyl acid phosphate can be used. Examples of dihydroxy compounds include compounds containing two hydroxyl groups and one or more ethylenically unsaturated bonds in one molecule, as well as polyol compounds, which are compounds containing two hydroxyl groups in one molecule but no ethylenically unsaturated bonds. Examples include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 2-methyl-1,3 propanediol, 1,3-butanediol, an adduct of bisphenol A with propylene oxide or ethylene oxide, 1,2,3,4-tetrahydroxybutane, glycerin, trimethylolpropane, 1,3-butanediol, 1,2-cyclohexane glycol, 1,3-cyclohexane glycol, 1,4-cyclohexane glycol, paraxylene glycol, bicyclohexyl-4,4-diol, 2,6-decalin glycol, and 2,7-decalin glycol. These polyhydric alcohols may be used singly or in combination of two or more.

[0031] Examples of polyol compounds include compounds having three hydroxyl groups, such as di(meth)acrylate of tris(hydroxyethyl)isocyanuric acid and glycerin. Among these, ethylene glycol and propylene glycol are preferred from the viewpoints of versatility, availability, and cost, and propylene glycol is more preferred from the viewpoint of physical properties such as water resistance.

[0032] The amount of the hydroxyl group-containing compound (C-1) used is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and even more preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-2). When the amount of the hydroxyl group-containing compound (C-1) used is 0.01 part by mass or more, turbidity of the resin can be suppressed. On the other hand, when the amount of the hydroxyl group-containing compound (C-1) used is 5 parts by mass or less, the reaction between the polyol and the isocyanate in step 1 is not inhibited, turbidity of the resin can be suppressed, and physical properties equivalent to those obtained when the hydroxyl group-containing compound (C-1) is not used can be obtained. On the other hand, the total molar ratio of the hydroxyl group-containing compounds derived from (C-1) relative to the total hydroxyl group-containing compounds (C-1) + (C-2) in the urethane (meth)acrylate is preferably 0.01 to <50%, more preferably 0.1 to 40%, and even more preferably 0.3 to 20%. When the amount of the hydroxyl group-containing compound (C-1) used is less than 50%, it does not inhibit the reaction between the polyol and the isocyanate in step 1, and it is possible to suppress turbidity of the resin and obtain physical properties equivalent to those obtained when no hydroxyl group-containing compound (C-1) is used.

[0033] <Hydroxyl group-containing compound (C-2)> The hydroxyl group-containing compound (C-2) includes a hydroxyl group-containing (meth)acrylic compound. Examples of the hydroxyl group-containing compound (C-2) having one or more hydroxyl groups in one molecule and used as a raw material for urethane (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxy (meth)acrylate, 2-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-hydroxypropyl acrylate ... 2-Methacryloyloxy acid phosphate, 2-acryloyloxyethyl-phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid, 2-hydroxy-3-acryloyloxypropyl methacrylate, pentaerythritol tri(meth)acrylate, 2-hydroxyethyl(meth)acrylamide, 2-hydroxyethyl-N-methyl(meth)acrylamide, 3-hydroxypropyl(meth)acrylamide, caprolactone-modified hydroxyalkyl(meth)acrylate, etc. can be used. Among these, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxy(meth)acrylate, and 2-hydroxybutyl (meth)acrylate are preferred in terms of versatility, availability, cost, and ease of reaction, and 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate are more preferred in terms of good reactivity with isocyanate, reactivity during production of a cured product, versatility, and cost, and 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate are even more preferred in terms of irritation resistance and safety in use. These hydroxyl group-containing (meth)acrylic compounds may be used alone or in combination of two or more.

[0034] The amount of the hydroxyl group-containing (meth)acrylic compound used is preferably 3 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 7 to 30 parts by mass, per 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-2). When the amount of the hydroxyl group-containing (meth)acrylic compound used is 3 parts by mass or more, high reactivity can be imparted, whereas when the amount of the (meth)acrylic compound used is 50 parts by mass or less, both high flexibility and high reactivity can be achieved.

[0035] The hydroxyl group-containing compound (C-2) may further contain a hydroxyl group-containing compound other than the hydroxyl group-containing (meth)acrylic compound. For example, a monohydroxyl group-containing compound having no unsaturated group may be used to adjust the reactivity and compatibility with other compounds. Examples of hydroxyl group-containing compounds other than hydroxyl group-containing (meth)acrylic compounds include hydroxyl group-containing compounds having no unsaturated group, which are described as hydroxyl group-containing compounds (C-1).

[0036] [Method for producing urethane (meth)acrylate (UM)] The method for producing the urethane (meth)acrylate (UM) of the present invention includes the following steps 1 and 2. Step 1: A step of obtaining a resin precursor (P) which is a reaction product of a polyol (A), an organic isocyanate (B), and a hydroxyl group-containing compound (C-1). Step 2: A step of obtaining a urethane (meth)acrylate (UM) which is a reaction adduct of the resin precursor (P) obtained in Step 1 with a hydroxyl group-containing compound (C-2). During the production, a diluent (E) can be used as needed.

[0037] The organic isocyanate (B), which is a raw material used in the method for producing the urethane (meth)acrylate (UM) of the present invention, is a compound that is solid within the above temperature range. Detailed examples of the organic isocyanate (B) are as described above in <Organic isocyanate (B)>.

[0038] The hydroxyl group-containing compound (C-1), which is a raw material used in the method for producing the urethane (meth)acrylate (UM) of the present invention, is a compound that is liquid within the above temperature range. Detailed examples of the hydroxyl group-containing compound (C-1) are as described above in <Hydroxyl group-containing compound (C-1)>. The polyol (A) and the hydroxyl group-containing compound (C-2), which are raw materials used in the method for producing the urethane (meth)acrylate (UM) of the present invention, can be those described above in <Polyol (A)> and <Hydroxyl group-containing compound (C-2)>, respectively.

[0039] "Process 1" In step 1, in which the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-1) are reacted to produce the resin precursor, the compounding ratio of the polyol (A) to the organic isocyanate (B) is such that the number of moles of isocyanato groups in the organic isocyanate (B) is greater than the number of moles of hydroxyl groups in the polyol (A), i.e., the organic isocyanate (B) is in excess.

[0040] Specifically, as the blending ratio of raw materials before synthesis, the molar ratio of the isocyanato groups of the organic isocyanate (B) to the hydroxyl groups of the polyol (A) (isocyanato groups / hydroxyl groups) is preferably 1.2 or more, and from the viewpoints of reaction control and ease, it is more preferably 1.4 or more.

[0041] If the compounding ratio of the polyol (A) to the organic isocyanate (B) is within the above range, the organic isocyanate (B) will be supplied in excess, and a resin precursor (P) consisting of the polyol (A) and the organic isocyanate (B) bonded to both ends thereof will be easily produced. For example, if polypropylene glycol (PPG) is used as the polyol (A) and diphenylmethane diisocyanate (MDI) is used as the organic isocyanate (B), a resin precursor (P)MDI-(PPG-MDI)n will be easily produced in which MDI is bonded to both ends of one PPG, or the above-mentioned process is repeated until MDI is finally bonded to both ends.

[0042] Furthermore, if the blending ratio is small, a composition with a large number of repeating units of resin precursor (P)MDI-(PPG-MDI)n is produced, and a resin precursor (P) consisting of organic isocyanate (B) bonded to both ends is more likely to be produced.

[0043] By increasing the amount of resin precursor (P) composed of polyol (A) and organic isocyanate (B) bonded to both ends of polyol (A), a urethane (meth)acrylate having a constant molecular weight can be produced, and the cured urethane (meth)acrylate resin can stably exhibit physical properties such as elongation and flexibility. Furthermore, within the above range, ease of reaction and workability when using a diluent are good.

[0044] In step 1, the inclusion of a hydroxyl group-containing compound (C-1) as a raw material is a feature of the present invention. In step 1, in which the polyol (A), organic isocyanate (B), and hydroxyl-containing compound (C-1) are reacted to produce the resin precursor, the amount of hydroxyl-containing compound (C-1) used is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and even more preferably 0.05 to 1 part by mass, per 100 parts by mass of the total of polyol (A), organic isocyanate (B), and hydroxyl-containing compound (C-2). When the amount of hydroxyl-containing compound (C-1) used is 0.01 part by mass or more, turbidity of the resin can be suppressed. On the other hand, when the amount of hydroxyl-containing compound (C-1) used is 5 parts by mass or less, the reaction between the polyol and isocyanate in step 1 is not inhibited, turbidity of the resin can be suppressed, and physical properties equivalent to those obtained when the hydroxyl-containing compound (C-1) is not used can be obtained. On the other hand, the total molar ratio of hydroxyl groups derived from (C-1) to the total hydroxyl groups of the hydroxyl group-containing compounds (C-1) + (C-2) in the urethane (meth)acrylate is preferably 0.01 to <50%, more preferably 0.1 to 40%, and more preferably 0.3 to 20%. When the amount of hydroxyl group-containing compound (C-1) used is less than 50%, it does not inhibit the reaction between the polyol and isocyanate in step 1, suppresses turbidity of the resin, and provides physical properties equivalent to those obtained when not used.

[0045] In step 1, the order in which the raw materials polyol (A), organic isocyanate (B), and hydroxyl-containing compound (C-1) are added is not particularly limited. For example, mixing method [1] includes mixing polyol (A), organic isocyanate (B), and hydroxyl-containing compound (C-1) first, followed by initiating the reaction. Mixing method [2] includes reacting polyol (A) with organic isocyanate (B) first, and then adding hydroxyl-containing compound (C-1) after a certain period of time. The method for adding the hydroxyl-containing compound (C-1) is not particularly limited, and may include adding it all at once or adding it in portions. From the viewpoint of workability, the mixing method (1) is preferred.

[0046] In step 1, by adding the hydroxyl group-containing compound (C-1), the unreacted organic isocyanate (B) is reacted with the hydroxyl group-containing compound (C-1), and the generation of insoluble matter due to the unreacted organic isocyanate (B) in a subsequent step can be suppressed, and the final resin can be obtained with reduced turbidity.

[0047] In the reaction of step 1, the reaction temperature and reaction time may be set appropriately, but the reaction temperature is preferably 40°C to 120°C, and the reaction time is preferably 0.5 to 24 hours, with 1 to 6 hours being more preferable from the viewpoint of the degree of reaction progress and the cost expected from the process time. If the reaction temperature is less than 40°C or the reaction time is less than 0.5 hours, the reaction may not proceed sufficiently and the desired resin precursor (P) may not be obtained, which is not preferable. On the other hand, if the reaction temperature exceeds 120°C or the reaction time exceeds 24 hours, it may be unfavorable in terms of cost, reaction control, and resin precursor (P).

[0048] "Process 2" In step 2, the resin precursor (P) obtained in step 1 is reacted with a hydroxyl group-containing compound (C-2). The hydroxyl group-containing compound (C-2) is added to the resin precursor (P), and the two are reacted to produce a urethane acrylate. This urethane acrylate is obtained by bonding a hydroxyl group-containing compound (C-2) to the terminal isocyanato group of the resin precursor (P). For example, MDI-(PPG-MDI)n, which is the resin precursor (P), can be reacted with 2-hydroxyethyl methacrylate (HEMA), which is the monohydroxy unsaturated compound (C-2), to produce HEMA-MDI(-PPG-MDI)n-HEMA, which is a urethane acrylate.

[0049] In the reaction of step 2, the reaction temperature and reaction time may be set appropriately, but the reaction temperature is preferably 40°C to 120°C, and the reaction time is preferably 1 to 24 hours, with 1 to 6 hours being more preferable from the viewpoint of the degree of reaction progress and the cost expected from the process time. If the reaction temperature is less than 40°C or the reaction time is less than 1 hour, the reaction may not proceed sufficiently, and the desired urethane (meth)acrylate resin may not be obtained, which is not preferable. On the other hand, if the reaction temperature exceeds 120°C or the reaction time exceeds 24 hours, it may be unfavorable in terms of cost, reaction control, and the stability of the urethane (meth)acrylate.

[0050] <Catalyst (D)> In the reaction of step 1 or step 2, a catalyst may be added. Examples of the catalyst (D) include organic tin compounds such as dibutyltin dilaurate, dibutyltin dioctate, dioctyltin dilaurate, dioctyltin dineodecanoate, and tin octoate; other organic metal compounds such as copper naphthenate, cobalt naphthenate, and zinc naphthenate; triethylamine, 1,4-diazabicyclo[2.2.2]octane, 2,6,7-trimethyl-1-diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0]undecene, N,N-dimethylcyclohexylamine, pyridine, N-methylmorpholine, and N,N,N',N'-tetramethylethylene. Examples of suitable reactive compounds include amine compounds and salts thereof, such as ethylenediamine, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N,N',N'-pentamethyldiethylenetriamine, N,N,N',N'-tetra(3-dimethylaminopropyl)-methanediamine, N,N'-dimethylpiperazine, and 1,2-dimethylimidazole; trialkylphosphine compounds, such as tri-n-butylphosphine, tri-n-hexylphosphine, tricyclohexylphosphine, and tri-n-octylphosphine; and compounds containing sodium, potassium, or the like, such as aqueous alkali solutions. Among these, dibutyltin dilaurate, dioctyltin dilaurate, dioctyltin dineodecanoate, and tin octoate are preferred because they can accelerate and control the reaction rate even with a small amount.

[0051] When catalyst (D) is used, its amount is preferably 0.0001 to 1 part by mass, and more preferably 0.001 to 0.5 parts by mass, per 100 parts by mass of the total of components (A), (B), and (C-2). If the amount of catalyst used is less than 0.0001 part by mass, the reaction may not proceed sufficiently, which is undesirable. On the other hand, if the amount of catalyst used exceeds 1 part by mass, it may become difficult to control the reaction and excessive metal content may result, which is undesirable. The timing of adding the urethanization catalyst is not particularly limited.

[0052] <Molecular weight of urethane (meth)acrylate> The weight-average molecular weight of the urethane (meth)acrylate (UM) thus obtained is preferably 1500 to 30000, more preferably 3000 to 25000, and even more preferably 4000 to 21000. When the weight-average molecular weight is within the above range, when a urethane (meth)acrylate resin (U) is prepared by blending the urethane (meth)acrylate (UM) with a radically polymerizable unsaturated monomer or the like, which will be described later, the resulting urethane (meth)acrylate resin has low viscosity, good compatibility, and good workability during use.

[0053] [Urethane (meth)acrylate resin (U)] The obtained urethane (meth)acrylate (UM) contains a diluent (E) and can be adjusted to have the desired physical properties, viscosity, etc.

[0054] <Diluent (E)> The diluent (E) may contain a radical polymerizable monomer having an ethylenically unsaturated bond or a solvent. From the viewpoint of being able to react with the urethane (meth)acrylate and to adjust the cured physical properties in a variety of ways, it is preferable to use a radical polymerizable monomer reactive with the urethane (meth)acrylate as the diluent (E). The radical polymerizable monomer is not particularly limited, but is preferably an ethylenically unsaturated monomer having a (meth)acryloyl group or a vinyl group, from the viewpoint of reducing the viscosity of the urethane (meth)acrylate of the present invention and being able to adjust the hardness, strength, chemical resistance, water resistance, etc. after curing.

[0055] Examples of the monomer having a (meth)acryloyl group include acrylic acid esters and methacrylic acid esters, and both monofunctional and polyfunctional monomers can be used. Specific examples of the monofunctional monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, ethylene glycol monomethyl ether (meth)acrylate, ethylene glycol monoethyl ether (meth)acrylate, ethylene glycol monobutyl ether (meth)acrylate, ethylene glycol monohexyl ether (meth)acrylate, ethylene glycol mono-2-ethylhexyl ether (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, diethylene glycol monobutyl ether (meth)acrylate, (meth)acrylate, diethylene glycol monohexyl ether (meth)acrylate, diethylene glycol mono 2-ethylhexyl ether (meth)acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, tricyclodecanyl acrylate, tricyclodecanyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxy (meth)acrylate, 2-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-methacryloyloxy acid phosphate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl-phthalate, 2-hydroxy-3-acryloyloxypropyl methacrylate,Examples of such compounds include pentaerythritol tri(meth)acrylate, 2-hydroxyethyl(meth)acrylamide, 2-hydroxyethyl-N-methyl(meth)acrylamide, and 3-hydroxypropyl(meth)acrylamide. Further examples include compounds such as caprolactone-modified hydroxyalkyl (meth)acrylate and caprolactone-modified tris(acryloxyalkyl) isocyanurate. From the viewpoint of reducing the viscosity of the radically polymerizable resin composition, examples include monomers having a polycaprolactone (meth)acrylate structure with 1 to 5 moles of caprolactone added (m=1 to 5). Further examples include monomers having a polycaprolactone (meth)acrylate structure with 1 to 3 moles of caprolactone added. Of these, caprolactone-modified hydroxyethyl (meth)acrylate is preferred.

[0056] Specific examples of polyfunctional monomers include neopentyl glycol di(meth)acrylate, PTMG dimethacrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-hydroxy-1,3-dimethacryloxypropane, 2,2-bis[4-(methacryloylethoxy)phenyl]propane, 2,2-bis[4-(methacryloxy-diethoxy)phenyl]propane, 2,2-bis[4-(methacryloxy-polyethoxy)phenyl]propane, tetraethylene glycol diacrylate, bisphenol A EO-modified (n=2) diacrylate, isocyanuric acid EO-modified (n=3) diacrylate, and pentaerythritol diacrylate monostearate. Further, as polyfunctional monomers, alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate; polyoxyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; Trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl (meth)acrylate, diallyl fumarate; Other examples of the compound include tris(2-hydroxyethyl)isocyanuracrylate. Specific examples of monomers having a vinyl group include styrene, p-chlorostyrene, vinyltoluene, α-methylstyrene, dichlorostyrene, divinylbenzene, t-butylstyrene, vinyl acetate, diallyl phthalate, triallyl phthalate, triallyl isocyanurate, vinylbenzyl butyl ether, vinylbenzyl hexyl ether, vinylbenzyl octyl ether, vinylbenzyl (2-ethylhexyl) ether, vinylbenzyl (β-methoxymethyl) ether, vinylbenzyl (n-butoxypropyl) ether, vinylbenzyl cyclohexyl ether, vinylbenzyl (β-phenoxyethyl) ether, vinylbenzyl dicyclopentenyl ether, vinylbenzyl dicyclopentenyloxyethyl ether, vinylbenzyl dicyclopentenyl methyl ether, and divinylbenzyl ether. These may be used alone or in combination of two or more.

[0057] As the ethylenically unsaturated monomer, from the viewpoints of cost and dilution ability, methyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, diethylene glycol di(meth)acrylate, lauryl (meth)acrylate, and styrene are preferred, and from the viewpoints of corrosion resistance and irritation resistance, methyl methacrylate, phenoxyethyl methacrylate, benzyl methacrylate, diethylene glycol dimethacrylate, lauryl methacrylate, and styrene are more preferred.

[0058] From the viewpoint of workability in adjusting the composition to the target physical property range, it is preferable to synthesize the urethane (meth)acrylate (UM) and then add and mix a portion of the diluent (E) to reduce the viscosity of the urethane (meth)acrylate (UM). Alternatively, it is preferable to use a portion of the diluent (E) during the synthesis of component (A), obtain a mixture of the urethane (meth)acrylate (UM) and a portion of the diluent (E), and then add and mix the remaining diluent (E) and other components. The mixing ratio (mass ratio) of the urethane (meth)acrylate (UM) to the portion of the diluent (E) when reducing the viscosity is not particularly limited, but is preferably 95:5 to 5:95, more preferably 85:15 to 15:85.

[0059] "Transparency (haze value) of urethane (meth)acrylate resin (U)" The haze of the resulting urethane (meth)acrylate resin (U) is preferably 0.1 to 20%, more preferably 0.3 to 10%. The method for measuring the haze is as described in the Examples.

[0060] <Other ingredients> "Polymerization inhibitor (F)" A polymerization inhibitor may be used during or after the reaction, as needed, to inhibit polymerization of the urethane (meth)acrylate (UM) or the urethane (meth)acrylate resin (U). Specific examples of the polymerization inhibitor (F) include known ones such as tertiary butyl catechol, p-methoxyphenol, hydroquinone, tertiary butyl hydroquinone, p-benzoquinone, chloranil, m-dinitrobenzene, nitrobenzene, p-phenyldiamine, sulfur, diphenylpicrylhydrazyl, di-p-fluorophenylamine, tri-p-nitrophenylmethyl, etc. In addition, examples of free radicals include TEMPO derivatives such as 2,2,6,6-tetramethylpiperidine 1-oxyl free radical (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (4H-TEMPO), and 4-oxo-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (4-Oxo-TEMPO). The amount of each of these components is preferably 0.0001 to 10 parts by mass, more preferably 0.001 to 10 parts by mass, relative to 100 parts by mass of the urethane (meth)acrylate resin (U). [Example]

[0061] In the following examples, a urethane (meth)acrylate (UM) and a urethane (meth)acrylate resin (U) are prepared as examples of the configuration of the present invention, and compared with a urethane acrylate resin (cUM) and a urethane (meth)acrylate resin (cU) according to comparative examples to confirm the effects of the present invention. However, the present invention is not limited to these.

[0062] <Weight average molecular weight measurement> The weight-average molecular weight was measured using gel permeation chromatography (Shodex GPC-101, manufactured by Showa Denko K.K.) The weight-average molecular weight was measured at room temperature (23°C) under the following conditions and calculated in terms of polystyrene.

[0063] (Measurement conditions) Column: Showa Denko LF-804, 2 columns Column temperature: 40℃ Sample: 0.4 mass% tetrahydrofuran solution of the substance to be measured Flow rate: 1ml / min Eluent: tetrahydrofuran The conditions for measuring viscosity and liquid specific gravity are the same as those for the samples in the examples described below.

[0064] <Viscosity measurement> The viscosity was measured at 50 rpm in an environment of 25°C using a Toki Sangyo RE-85 viscometer, cone-plate type, with a cone rotor of 1°34' x R24.

[0065] <Appearance and changes over time after 3 days> The appearance of the obtained resin was visually evaluated on the day of synthesis and after 3 days at 23°C for changes in appearance over time. 〇: No turbidity △: Slightly cloudy ×: Turbidity was observed

[0066] <Haze measurement> Haze measurements were performed using a Haze Meter Model HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd., and a glass cell manufactured by AS ONE Corporation, Glass Cell GS-40, with internal dimensions of 40 x 10 x 40 mm (optical path length x optical path width x height) and a capacity of 14 mL, in an environment of 23°C. ○: Less than 10% △: 10~20% ×: More than 20%

[0067] <Ingredients used in this example> As will be described later, the urethane (meth)acrylates (UM1) to (UM6) of the examples and the urethane (meth)acrylates (cUM1) to (cUM5) of the comparative examples were synthesized using the following raw materials.

[0068] (Polyol (A)) (1) Polypropylene glycol (weight average molecular weight 2000), manufactured by Mitsui Chemicals SKC Polyurethanes Co., Ltd., product name: Actocol D-2000 (2) Polypropylene glycol (weight average molecular weight 1000), manufactured by Mitsui Chemicals SKC Polyurethanes Co., Ltd., product name: Actocol D-1000 (3) Polyethylene glycol (weight average molecular weight 600), manufactured by Toho Chemical Industry Co., Ltd., product name: Toho Polyethylene Glycol 600

[0069] (Organic isocyanate (B)) Diphenylmethane diisocyanate / Form: Solid (melting point 39°C), manufactured by Tosoh Corporation, Product name: Millionate MT

[0070] (Hydroxy group-containing compound (C-1)) Monohydroxy compounds 2-Hydroxyethyl methacrylate (HEMA) / Form: Liquid (melting point -12°C), manufactured by Nippon Shokubai Co., Ltd., Product name: 2-hydroxyethyl methacrylate 2-Hydroxypropyl methacrylate (HPMA) / Form: Liquid (melting point -58°C), manufactured by Kyoeisha Chemical Co., Ltd., Product name: Light Ester HOP(N) Dibutylhydroxytoluene (BHT) / Form: Solid (melting point 70°C), manufactured by Kyodo Pharmaceutical Co., Ltd., Product name: K-NOX BHT n-Octadecyl (4'-hydroxy-3'-5'-di-t-butylphenyl)propionate / Form: Solid (melting point 54°C), ADEKA Corporation, Product name: ADK STAB AO-50

[0071] Dihydroxy Compounds Propylene glycol (PG) / Form: Liquid (melting point -59°C), manufactured by Dow Chemical Japan, Product name: Propylene glycol Hydroquinone (HQ) / Form: Solid (melting point 172°C), manufactured by Ube Industries, Ltd., Product name: Hydroquinone

[0072] (Hydroxy group-containing compound (C-2)) 2-Hydroxyethyl methacrylate (HEMA), manufactured by Nippon Shokubai Co., Ltd., product name: 2-hydroxyethyl methacrylate

[0073] (Catalyst (D)) Dibutyltin dilaurate, manufactured by Sakai Chemical Industry Co., Ltd., product name: KS-1260 (Diluent (E)) Methyl methacrylate, manufactured by Mitsubishi Rayon Co., Ltd., product name: Acryester M

[0074] Example 1 A 3 L four-neck flask equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer was charged with 2000 g (1.0 mol) of Actocol D-2000 (polypropylene glycol 2: weight average molecular weight 2000, manufactured by Mitsui Chemicals SKC Polyurethanes Inc.) as the polyol (A), 500 g (2.0 mol) of diphenylmethane diisocyanate as the organic isocyanate (B), 0.1 parts by mass (2.8 g) of 2-hydroxyethyl methacrylate as the hydroxyl group-containing compound (C-1), and 0.007 parts by mass (0.19 g) of dibutyltin dilaurate as the catalyst (D), and the mixture was stirred at 60°C for 4 hours to cause a reaction. Next, 273 g (2.1 mol) of 2-hydroxyethyl methacrylate as a hydroxyl group-containing compound (C-2) was added dropwise to the reaction mixture over 2 hours while stirring, and after the addition was completed, the mixture was stirred for 4 hours to allow the reaction to proceed, yielding a urethane (meth)acrylate resin (UM1). The raw materials used in the production of the urethane (meth)acrylate resin (UM1) are shown in Table 1. Next, 1190 g of methyl methacrylate as a diluent (E) was added to this urethane (meth)acrylate (UM1) to obtain a urethane (meth)acrylate resin (U1).

[0075] The weight average molecular weight of the urethane (meth)acrylate (UM1) was 9900. The viscosity of the urethane (meth)acrylate resin (U1) at 25°C was 6.6 dPa·s. The results are shown in Table 1. The appearance of the resulting urethane (meth)acrylate resin was visually evaluated on the day of synthesis and after 3 days at 23°C for changes in appearance over time. The results are shown in Table 1. The haze at 23°C after 3 days at 23°C after synthesis was 20% or less.

[0076] (Examples 2 to 6, Comparative Examples 2 to 5) For Examples 2 to 8, synthesis was carried out in the same manner as in Synthesis Example 1, except that the raw materials used were changed as shown in Table 1, to obtain urethane (meth)acrylates (UM2) to (UM6) and (cUM2) to (cUM5). Furthermore, as shown in Table 1, urethane (meth)acrylate resins (U2) to (U6) and (cU2) to (cU5) were obtained by adding methyl methacrylate to 70% by mass of each of the urethane (meth)acrylates (UM2) to (UM6) and (cUM2) to (cUM5) in an amount of 30% by mass. The weight-average molecular weights of the urethane (meth)acrylates (UM2) to (UM6) and (cUM2) to (cUM5) are also shown in Table 1. The liquid density and viscosity values ​​of the urethane (meth)acrylate resins (U2) to (U6) and (cU2) to (cU5) are also shown in Table 1. The appearance and change in appearance over time of the obtained urethane (meth)acrylate resin were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0077] (Comparative Example 1) A 3 L four-neck flask equipped with a stirrer, reflux condenser, gas inlet tube, and thermometer was charged with 2000 g (1.0 mol) of Actocol D-2000 (Mitsui Chemicals SKC Polyurethanes, Inc., polypropylene glycol 2, weight average molecular weight 2000) as polyol (A), 500 g (2.0 mol) of diphenylmethane diisocyanate as organic isocyanate (B), and 0.007 parts by mass (0.19 g) of dibutyltin dilaurate as catalyst (D). The mixture was stirred at 60 °C for 4 hours to react. Next, 273 g (2.1 mol) of 2-hydroxyethyl methacrylate as hydroxyl group-containing compound (C-2) was added dropwise to the reaction mixture over 2 hours with stirring. After the addition, the mixture was stirred for 4 hours to react, yielding urethane (meth)acrylate resin (cUM1). The raw materials used in the production of urethane (meth)acrylate resin (cUM1) are listed in Table 1.

[0078] Next, 1189 g of methyl methacrylate as a diluent (E) was added to this urethane methacrylate resin (cUM1) to obtain a urethane (meth)acrylate resin (cU1). The weight-average molecular weight of the urethane methacrylate resin (cUM1) was 9950. The viscosity of the mixture (cU1) at 25°C was 6.5 dPa·s. The appearance of the obtained resin, its change over time, and haze were evaluated in the same manner as in the examples, and the results are shown in Table 1.

[0079] [Table 1]

[0080] In Table 1, the meaning of each ingredient is as follows: (a1) Polypropylene glycol Molecular weight = 2000 (a2) Polypropylene glycol Molecular weight = 1000 (a3) Polyethylene glycol Molecular weight = 600 (b1) Diphenylmethane diisocyanate (MDI) (solid) Molecular weight = 250 (c1-1) 2-Hydroxyethyl methacrylate (HEMA) / Form: Liquid (c1-2) 2-Hydroxypropyl methacrylate (HPMA) (c1-3) Dibutylhydroxytoluene (BHT) / Form: Solid (c1-4) (4'-hydroxy-3'-5'-di-t-butylphenyl)propionic acid-n-octadecyl (AO-50) / Form: Solid (c1-5) Propylene glycol / form: liquid (c1-6) Hydroquinone / Form: Solid (c2-1) 2-hydroxyethyl methacrylate (HEMA) Molecular weight = 130 (d) Dibutyltin dilaurate (e) Methyl methacrylate

[0081] <Consideration> Looking at the evaluation results of each example, in all examples, turbidity was suppressed and a urethane (meth)acrylate resin with a good appearance could be produced.

[0082] In Comparative Example 1, no hydroxyl group-containing compound (C-1) was added in step 1, and the resulting resin consisting of a urethane (meth)acrylate resin, which is the reaction product of the resin precursor (P) and the hydroxyl group-containing compound (C-2), did not become cloudy on the same day of synthesis, but became cloudy after three days. In Comparative Examples 2 and 3, a hydroxyl-containing compound (C-1) that is solid in the temperature range of 20 to 35°C was used in step 1 instead of the hydroxyl-containing compound (C-1) that is liquid in the temperature range of 20 to 35°C used in Example 1. The resulting resin (cU) made of urethane (meth)acrylate (cUM), which is the reaction product of the resin precursor (P) and the hydroxyl-containing compound (C-2), was not cloudy on the day of synthesis, but became cloudy after 3 days. In Comparative Examples 4 and 5, a hydroxyl-containing compound (C-1) that is solid in the temperature range of 20 to 35°C was used in step 1 instead of the hydroxyl-containing compound (C-1) that is liquid in the temperature range of 20 to 35°C used in Example 1. The resulting resin (cU) consisting of a urethane (meth)acrylate resin (cUM), which is the reaction product of the resin precursor (P) and the monohydroxy compound unsaturated (C-2), became cloudy even on the same day of synthesis. [Industrial Applicability]

[0083] The present invention relates to a method for producing a urethane (meth)acrylate and a urethane (meth)acrylate resin that have a good appearance and exhibit high flexibility on their own, but can also achieve both elongation, flexibility, and strength when used in combination with various fibers and aggregates, such as hard resins and glass fibers. These materials are useful as repair and coating materials with excellent durability in locations subject to constant load, and as molding resins for FRP structural components with excellent fatigue resistance. Therefore, they are suitable for applications requiring design or transparency. Furthermore, even when used in combination with other materials in the aforementioned applications, they can be used without affecting the color of the other materials. Examples of applications include concrete and asphalt repair where the repaired area can be visually observed, FRP molded products requiring high transparency and design, and automotive FRP molded products, which require design.

Claims

1. Polyol (A), an organic isocyanate (B); a hydroxyl group-containing compound (C-1); a hydroxyl group-containing compound (C-2); A method for producing a urethane (meth)acrylate (UM) which is a reaction product of Step 1 of obtaining a resin precursor (P) which is a reaction product of the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-1); Step 2 of obtaining a urethane (meth)acrylate (UM) which is a reaction adduct of the resin precursor (P) obtained in Step 1 with a hydroxyl group-containing compound (C-2); and The organic isocyanate (B) is a compound that is solid under 1 atmosphere at a temperature range of 0 to 4°C, The hydroxyl group-containing compound (C-1) is a compound that is liquid at 1 atmosphere and in a temperature range of 20 to 35°C, the hydroxyl group-containing compound (C-2) includes a hydroxyl group-containing (meth)acrylic compound, The hydroxyl group-containing compound (C-1) is the same compound as the hydroxyl group-containing compound (C-2). A method for producing a urethane (meth)acrylate, comprising:

2. 2. The method for producing a urethane (meth)acrylate according to claim 1, wherein in step 1, a molar ratio of isocyanato groups of the organic isocyanate (B) to hydroxyl groups of the polyol (A) is isocyanato groups / hydroxyl groups = 1.2 or more.

3. The amount of the hydroxyl group-containing compound (C-1) used is 3. The method for producing a urethane (meth)acrylate according to claim 1, wherein the amount of the hydroxyl group-containing compound (C-2) is 0.01 to 5 parts by mass per 100 parts by mass of the total of the polyol (A), the organic isocyanate (B), and the hydroxyl group-containing compound (C-2).

4. The method for producing a urethane (meth)acrylate according to any one of claims 1 to 3, wherein the hydroxyl group-containing compound (C-1) is at least one selected from the group consisting of monohydroxy compounds and dihydroxy compounds.

5. The method for producing a urethane (meth)acrylate according to any one of claims 1 to 4, wherein the organic isocyanate (B) has a melting point of 5°C to 50°C.

6. The method for producing a urethane (meth)acrylate according to any one of claims 1 to 5, wherein the organic isocyanate (B) is diphenylmethane diisocyanate.

7. The method for producing a urethane (meth)acrylate according to any one of claims 1 to 6, wherein the polyol (A) is at least one selected from the group consisting of polyether polyols, polyester polyols, and polyoxyalkylene bisphenol A ethers.

8. The method for producing a urethane (meth)acrylate according to any one of claims 1 to 7, wherein the hydroxyl group-containing compound (C-2) is at least one selected from the group consisting of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

9. A step A of obtaining a urethane (meth)acrylate by using the method for producing a urethane (meth)acrylate according to any one of claims 1 to 8; Step B: mixing the urethane (meth)acrylate with the diluent (E); A method for producing a urethane (meth)acrylate resin having the following structure: A method for producing a urethane (meth)acrylate resin, characterized in that the method for mixing the diluent (E) includes any one or two methods selected from the group consisting of a method for mixing the diluent during the step A and a method for mixing the diluent after the step A.

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