Solvent-free coating composition

Abstract

To provide a solvent-free coating agent which has good abrasion resistance and adhesion and is less likely to crack even when subjected to bending to form a curved surface. [Solution] This is a solventless coating composition that is a photocurable resin composition containing a multifunctional urethane (meth)acrylate, a phosphate ester compound, a reactive diluent, and a photopolymerization initiator, wherein the multifunctional urethane (meth)acrylate contains a urethane (meth)acrylate having a polycaprolactone-based polyester skeleton, and the ratio of the polyfunctional urethane (meth)acrylate to the polyfunctional urethane (meth)acrylate is 40 to 85% by weight.

Description

[Technical Field]

[0001] The present invention relates to a solventless coating composition that can be used on polyvinyl chloride substrates and the like. [Background technology]

[0002] PVC resin is a general-purpose plastic with excellent chemical and mechanical stability, and excellent processability and moldability. As a result, processed products made from it have many practical properties, such as excellent mechanical strength, creep resistance, durability, flame retardancy, weather resistance, and chemical resistance, and are therefore widely used in building materials such as flooring, wall materials, window frames, and roofing materials.

[0003] For example, vinyl chloride tiles have moderate hardness and durability as flooring materials, and are used in a wide range of buildings, from office buildings and commercial facilities to ordinary homes. However, although they are relatively hard, their surfaces are prone to scratches and wear, so they are often coated with a coating agent to improve scratch resistance and heel mark resistance. For example, vinyl chloride tiles that form a glassy inorganic protective coating layer on their surfaces have been proposed (Patent Document 1).

[0004] Meanwhile, resin siding is becoming increasingly popular as a wall material, primarily in the renovation market, due to its excellent durability and economy. Its lightweight construction makes it easy to install, and it maintains its aesthetic appearance for a long time with virtually no maintenance. Its widespread use is expected to continue. Unlike flooring, this field requires bending to enhance aesthetics. In such cases, using coatings similar to those used for flooring as is can result in defects such as microcracks during bending. Therefore, there was room for improvement in creating a coating that could be used for both PVC flooring, which requires scratch resistance, and wall materials, which require curved surfaces. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6065247 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a solvent-free coating agent that has good scratch resistance and adhesion, and is less likely to crack even when subjected to bending processing. [Means for solving the problem]

[0007] In order to solve the above problems, the invention of claim 1 provides a solventless coating composition, which is a photocurable resin composition containing a polyfunctional urethane (meth)acrylate (A), a phosphate ester compound (B), a reactive diluent (C), and a photopolymerization initiator (D), wherein (A) contains a urethane (meth)acrylate (a1) having a polycaprolactone-based polyester skeleton, and the proportion of (a1) in (A) is 40 to 85% by weight.

[0008] The invention of claim 2 provides the solventless coating composition of claim 1, characterized in that (A) contains an aliphatic urethane (meth)acrylate (a2).

[0009] The invention of claim 3 provides the solventless coating composition of claim 1 or 2, which is a coating agent for polyvinyl chloride substrates.

[0010] The invention as set forth in claim 4 provides a polyvinyl chloride building material coated with the solventless coating composition as set forth in claim 1 or 2. [Effects of the Invention]

[0011] The solvent-free coating agent of the present invention has sufficient adhesion to polyvinyl chloride substrates, as well as good scratch resistance, and is less likely to crack even when subjected to bending processing, making it useful as a coating agent for use on flooring materials such as PVC tiles and PVC wall materials. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] The solventless coating composition of the present invention comprises a polyfunctional urethane (meth)acrylate (A), a phosphate ester compound (B), a reactive diluent (C), and a photopolymerization initiator (D). In this specification, "(meth)acrylate" encompasses both acrylate and methacrylate. Solvent-free refers to the absence of intentionally blended solvents for dilution purposes in the coating agent, but does not include the elimination of trace amounts of volatile components contained in each component of the coating agent. This refers to a solvent content of 5% by weight or less, typically 1% by weight or less.

[0014] The polyfunctional urethane (meth)acrylate (hereinafter referred to as polyfunctional ureac) (A) used in the present invention is one of the main components constituting the cured coating, and has abrasion resistance and toughness due to the cohesive force of hydrogen bonds derived from urethane bonds. Ureac can be obtained, for example, by reacting a urethane prepolymer obtained by reacting a polyol with an excess of polyisocyanate with a (meth)acrylate having a hydroxyl group, or by reacting a polyisocyanate with a (meth)acrylate having a hydroxyl group, and is not particularly limited.

[0015] The synthesis method of the urea is not particularly limited, and known methods can be used. The reaction can be carried out without a solvent; however, as the molecular weight increases, the viscosity increases, making stirring difficult. Therefore, ketones such as butanone, or aromatic inert solvents such as xylene can be used. Furthermore, it is preferable to use a catalyst for the reaction between the hydroxyl group of the (meth)acrylate and the isocyanate group. Examples of such a catalyst include tin-based catalysts such as dibutyltin dilaurate, and metal alkoxide-based catalysts such as cobalt naphthenate. The reaction temperature can be set as appropriate, but is preferably 40 to 120°C, and more preferably 60 to 100°C.

[0016] Polyisocyanates used in the synthesis of ureac include hexamethylene diisocyanate, isophorone diisocyanate (hereinafter referred to as IPDI), diphenylmethane diisocyanate (hereinafter referred to as MDI), tolylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, hydrogenated xylylene diisocyanate, methylcyclohexylene diisocyanate, HDI isocyanurate, IPDI isocyanurate, etc., and these may be used alone or in combination of two or more. Among these, aliphatic and alicyclic diisocyanates are preferred because they have high weather resistance and are resistant to yellowing, and IPDI is particularly preferred because of its high rigidity.

[0017] Examples of (meth)acrylates having a hydroxyl group used in the synthesis of urea include monofunctional (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, bifunctional (meth)acrylates such as glycerin di(meth)acrylate, trifunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate, and tetrafunctional (meth)acrylates such as dipentaerythritol tetra(meth)acrylate. These can be used alone or in combination of two types. Among these, bifunctional or less functional compounds are preferred, and monofunctional compounds are more preferred, as they can suppress excessive curing and ensure sufficient bending processability. Among the monofunctional compounds, 2-hydroxyethyl acrylate (hereinafter referred to as 2-HEA) is particularly preferred.

[0018] The number of functional groups in (A) is preferably 2 to 8, more preferably 2 to 6, and particularly preferably 2 to 4. By making it 2 or more functional, sufficient curability and adhesion to the adherend can be ensured, and by making it 8 or less functional, excessive curing can be prevented and sufficient bending workability can be ensured.

[0019] The (A) contains a urethane (meth)acrylate (a1) having a polycaprolactone (PCL)-based polyester skeleton. (a1) has good adhesion to polyvinyl chloride (PVC) substrates and, due to its high crystallinity, is excellent in water resistance, weather resistance, and heat resistance. Furthermore, the partial insertion of polyester chains slightly disrupts the crystallinity of the PCL, strengthening the crystalline crosslinks with isocyanate, resulting in excellent elastic recovery.

[0020] In addition to (a1), (A) may contain, for example, aliphatic urethane (meth)acrylate, aromatic urethane (meth)acrylate, polycarbonate-skeleton urethane (meth)acrylate, polyether-skeleton urethane (meth)acrylate, isocyanurate-skeleton urethane (meth)acrylate, silicone-modified urethane (meth)acrylate, etc., which can be used alone or in combination of two or more. Among these, aliphatic urethane (meth)acrylate (a2) is preferred because of its good compatibility with (a1) and excellent scratch resistance.

[0021] The weight molecular weight (hereinafter referred to as Mw) of (a1) and (a2) is preferably 500 to 30,000, more preferably 1,000 to 15,000, and particularly preferably 3,000 to 10,000. A weight molecular weight of 500 or more ensures sufficient bending processability, while a weight molecular weight of 30,000 or less facilitates adjustment of the composition viscosity to a level suitable for workability. Mw was measured and calculated by gel permeation chromatography using a column with a styrene-divinylbenzene-based packing material and a tetrahydrofuran eluent, relative to standard polystyrene.

[0022] The blending amount of (a1) is 40 to 85 wt % of the total amount of (A), preferably 43 to 80 wt %, more preferably 45 to 75 wt %, and particularly preferably 48 to 65 wt %. A blending amount of 40 wt % or more ensures sufficient bending workability, while a blending amount of 85 wt % or less ensures sufficient scratch resistance. The blending amount of (a1) is preferably 10 to 45 wt %, more preferably 15 to 35 wt %, of the total composition.

[0023] The blending amount of (A) is preferably 20 to 55% by weight, more preferably 25 to 50% by weight, and particularly preferably 30 to 45% by weight, based on the total weight of the composition. By making it 20% by weight or more, sufficient scratch resistance can be ensured, and by making it 55% by weight or less, sufficient bending workability can be ensured.

[0024] The phosphate ester compound (B) used in the present invention is blended for the purpose of improving adhesion to the substrate. A (meth)acrylate monomer having a phosphate ester group is preferred due to its compatibility with (A) and excellent curing properties. Examples include 2-(meth)acryloyloxyethyl dihydrophosphate and dipentaerythritol penta(meth)acryloyloxydihydrogen phosphate. Bis[2-(methacryloyloxy)ethyl] hydrogen phosphate, represented by the following chemical formula (1), produced by the reaction of 2-hydroxyethyl methacrylate with phosphoric anhydride, is particularly suitable. Chemical formula (1) JPEG2026040844000001.jpg3252

[0025] The blending amount of (B) is preferably 0.3 to 5.0 wt % of the total solid content, and more preferably 0.5 to 3.0 wt %. Blending within this range can improve the adhesive strength to the substrate. Commercially available (meth)acrylate monomers having a phosphate ester group include KAYAMER PM-2 and PM-21 (trade names: manufactured by Nippon Kayaku Co., Ltd.).

[0026] The reactive diluent (C) used in the present invention is blended for the purpose of reducing the viscosity of the composition and improving its curability. In order to obtain good bending workability, it is preferably trifunctional or less, more preferably bifunctional or less, and particularly preferably monofunctional. For example, examples of chain alkyl monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and butyl (meth)acrylate; examples of alicyclic monomers include cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; examples of aromatic ring-containing monomers include benzyl (meth)acrylate and phenoxyethyl acrylate; examples of ether skeleton monomers include ethoxyethoxyethyl (meth)acrylate; and examples of amide compounds include N,N-dimethyl (meth)acrylamide and acryloylmorpholine. These can be used alone or in combination of two or more. Among these, hydroxyl group-containing (meth)acrylates and ether skeleton (meth)acrylates are preferred in terms of improving adhesion to vinyl chloride. Furthermore, 2-hydroxypropyl methacrylate and ethoxyethoxyethyl acrylate are particularly preferred because they have good compatibility with (A) and (B) and are highly dilutable.

[0027] The blending amount of (C) is preferably 30 to 55% by weight, more preferably 35 to 50% by weight, and particularly preferably 38 to 48% by weight, based on the total solid content. By making it 30% by weight or more, it is possible to expect adjustment to a viscosity that is excellent in workability and at the same time ensure sufficient scratch resistance, and by making it 55% by weight or less, sufficient bending workability can be ensured.

[0028] The photopolymerization initiator (D) used in the present invention generates radicals upon irradiation with ultraviolet light or an electron beam, and these radicals trigger the polymerization reaction, and general-purpose photopolymerization initiators such as benzyl ketals, acetophenones, and phosphine oxides can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, it is possible to impart curability over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, benzyl ketals include 2,2-dimethoxy-1,2-diphenylethan-1-one, α-hydroxyacetophenones include 1-hydroxycyclohexylphenyl ketone and 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, α-aminoacetophenones include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, and acylphosphine oxides include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, which can be used alone or in combination. Among these, α-hydroxyacetophenones, which are less prone to yellowing, are preferred.

[0029] The amount of (D) is preferably 3 to 15 parts by weight, more preferably 5 to 12 parts by weight, per 100 parts by weight of the photopolymerizable component. By adding 3 parts by weight or more, sufficient curability can be ensured, while by adding 15 parts by weight or less, an excessive amount can be avoided and a sufficient molecular weight can be ensured even after curing. Commercially available α-hydroxyacetophenone-based products include JRCURE 1103 (trade name: manufactured by Daido Chemical Industry Co., Ltd.).

[0030] Furthermore, the solventless coating composition of the present invention (hereinafter referred to as the present coating composition) can contain additives such as leveling agents, slip agents, inorganic fillers, light stabilizers, surfactants, antioxidants, ultraviolet absorbers, flame retardants, antifoaming agents, wettability adjusters, organic fine particles, and antistatic agents, within the range that does not impair performance.

[0031] The leveling agent improves the leveling properties during application and also improves the scratch resistance and stain resistance of the cured coating. Examples include fluorine-based, silicone-based, and fluorine-silicone-based leveling agents, which can be used alone or in combination of two or more types.

[0032] Among these, silicone-based polysiloxane compounds are preferred because they can equalize large differences in surface tension on the coating surface. Examples include polyalkylsiloxanes, polyarylsiloxanes, polyalkylarylsiloxanes, polyester-modified siloxanes, and polyether-modified siloxanes, and these can be used alone or in combination of two or more.

[0033] The amount of the leveling agent to be added is preferably 0.1 to 3 wt % of the total solid content, and more preferably 0.3 to 2 wt %. By using this range, sufficient leveling properties can be ensured, resulting in a stable coating film appearance, and it is also possible to improve scratch resistance and stain resistance. Commercially available products include TEGO Glide 410 (trade name: polyether-modified siloxane copolymer, manufactured by EVONIK INDUSTRIES).

[0034] The slip agent adjusts the coefficient of friction of the cured coating, improving its slipperiness and thereby improving its abrasion resistance. Depending on whether or not a reactive functional group is present, slip agents are classified as reactive and non-reactive. Examples include reactive slip agents such as silicone-modified acrylates and fluorine-modified acrylates, and non-reactive slip agents such as polyglycerol-modified silicones and paraffins. These can be used alone or in combination of two or more. Among these, reactive slip agents are preferred because they can prevent the slip effect from decreasing over time.

[0035] The amount of slip agent added is preferably 0.1 to 3% by weight, more preferably 0.3 to 2% by weight, based on the total solid content. By using this range, it is possible to sufficiently improve slip properties and scratch resistance. Commercially available products include TEGORAD 2700 (trade name: silicone-modified acrylate, manufactured by EVONIK INDUSTRIES).

[0036] The inorganic filler can improve the appearance of the coating film and the hardness of the cured coating film. Examples include silica particles, alumina particles, and titanium oxide particles, which can be used alone or in combination of two or more. The incorporation of such components can cause diffuse reflection of light and reduce the gloss of the coating film surface. In addition, it is preferable to treat the surface with an organic component to improve adhesion to the coating film.

[0037] In particular, when adjusting the glossiness of the coating film appearance, it is preferable to incorporate amorphous silica with a secondary particle size of 0.5 to 10 μm. Furthermore, by incorporating silica whose surface has been treated with polyethylene, a very smooth matte surface can be obtained. The amount to be incorporated depends on the desired glossiness, but examples include 1 to 20 wt % based on the total solid content. Commercially available products include ACEMATT OK607 (trade name: manufactured by EVONIK INDUSTRIES, secondary particle size 4.4 μm, surface treated with polyethylene).

[0038] The method for applying the coating composition of the present invention is not particularly limited, and any known method may be used. When applying the coating composition to the entire surface of an adherend, for example, a roll coater, a reverse roll coater, a knife coater, an air knife coater, a bar coater, a slot die coater, a lip coater, a gravure coater, a reverse gravure coater, etc. may be used.

[0039] The present coating composition is applied to a substrate and then cured using light such as ultraviolet light. Examples of light sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, LED lamps, and electrodeless ultraviolet lamps. The curing conditions are 50 mW / cm.2 ~3000mW / cm 2 The irradiation intensity is 100 to 2,000 mJ / cm as the cumulative light amount. 2 The irradiation atmosphere may be air or an inert gas such as nitrogen or argon.

[0040] The coating composition may be applied to a polyvinyl chloride substrate. For example, when used as a coating on the surface of a vinyl chloride tile, the coating composition has excellent scratch resistance and the cured film is less likely to crack when bent to form a curved surface.

[0041] The present invention will be described in detail below based on examples and comparative examples, but these are intended to be specific examples and are not intended to limit the scope of the invention. Unless otherwise specified, measurements were taken at a room temperature of 25°C and a relative humidity of 65%. The blend amounts are in parts by weight.

[0042] Multifunctional urethane (meth)acrylate Ureac 1: Bifunctional urethane acrylate obtained by reacting PCL-based polyester diol with IPDI and then with 2-HEA, Mw 6,800 Urea 2: Difunctional urethane acrylate obtained by reacting polytetramethylene glycol with hydrogenated MDI and then with 2-HEA, Mw 7,300

[0043] Examples and Comparative Examples Ureacl 1 and Ureacl 2 were used as (A), KAYAMER PM-2 (trade name: manufactured by Nippon Kayaku Co., Ltd.) was used as (B), Light Ester HOP(N) (trade name: manufactured by Kyoeisha Chemical Co., Ltd., hydroxypropyl methacrylate) and MIRAMER M170 (trade name: manufactured by Kyoeisha Chemical Co., Ltd., ethoxyethoxyethyl acrylate) were used as (C), JRCURE1103 (trade name: manufactured by Daido Chemical Industry Co., Ltd., α-hydroxyacetophenone system) was used as (D), TEGO Glide 410 (trade name: manufactured by EVONIK INDUSTRIES, polyether-modified siloxane copolymer, 100% solids) was used as a leveling agent, TEGORAD 2700 (trade name: manufactured by EVONIK INDUSTRIES, silicone-modified acrylate, 100% solids) was used as a slip agent, and ACEMATT OK607 (trade name: manufactured by EVONIK INDUSTRIES, silicone-modified acrylate, 100% solids) was used as a filler. The solventless coating compositions of Examples 1 to 7 and Comparative Examples 1 to 3 were prepared by mixing the formulations shown in Tables 1 and 2 with Tinuvin 249 (trade name: BASF, hindered amine type) as a light stabilizer.

[0044] Table 1 JPEG2026040844000002.jpg87135

[0045] Table 2 JPEG2026040844000003.jpg140132

[0046] The evaluation method was as follows.

[0047] Curing: A photocurable resin composition was applied to an unpainted vinyl chloride tile with a thickness of 3 mm to a film thickness of 20 μm, and an electrode high-pressure mercury lamp (trade name: iGrandage ECS4011GX / N, manufactured by iGraphics Co., Ltd.) was used to apply the composition to the tile with an irradiation intensity of 100 mW / cm. 2 , cumulative light intensity 800mJ / cm 2 The coating film was irradiated with ultraviolet light at 100°C, and the tackiness of the coating film surface to the touch was checked. Those that were cured without tackiness were rated as ◯, and those that were tacky but not cured were rated as x.

[0048] Viscosity: Using a Toki Sangyo BM type viscometer TVB-10, the viscosity was measured after 1 minute at 25±1°C with a rotor No. 3 and a rotation speed of 60 rpm. Viscosity of 300 to less than 5000 mPa·s was marked as ◯, and viscosity outside this range was marked as ×.

[0049] Adhesion: In accordance with JIS K5600-5-6, a 10x10 grid of 1mm squares was created and a cross-cut test was performed, and the peeling state of the coating film was checked using cellophane tape (specified in JIS Z1522). When the cellophane tape attached to the coating side was peeled off, if 0 squares peeled off, it was marked as ○, and if even 1 square peeled off, it was marked as ×.

[0050] Glossiness: 60° glossiness was measured in accordance with JIS Z 8741 using Micro Trigloss (manufactured by Byck-Gardner Co.).

[0051] Taber abrasion test: Using Taber Abrasion Tester Model 1750, in accordance with JIS K 7204, a load of 250 g, a rotation speed of 60 rpm, and an abrasion wheel CS-17, the number of rotations at which the exposed area of ​​the substrate within the abraded area reached 50% was marked as × if it was less than 300, 300 to 1000 was marked as ○, and more than 1000 was marked as ◎.

[0052] Bending workability: A photocurable resin composition was applied to an unpainted PVC board measuring 100 mm in length, 100 mm in width, and 2 mm in thickness to a film thickness of 10 μm, and an electrode high-pressure mercury lamp (product name: iGrandage ECS4011GX / N, manufactured by iGraphics Co., Ltd.) was used to irradiate the composition with an irradiation intensity of 100 mW / cm. 2 , cumulative light intensity 800mJ / cm 2 The film was then cured by irradiating it with ultraviolet light at 150°C. It was then left in a thermostatic chamber at 150°C for 30 minutes, and immediately after removal, it was folded 180° so that the coated surface formed a valley fold, allowed to cool naturally to room temperature, and the presence or absence of cracks or breaks on the coating surface was confirmed using an electron microscope at 139x magnification. The evaluation was rated as ◯ if there were no cracks or breaks, and × if there were any.

[0053] Table 3 JPEG2026040844000004.jpg77135

[0054] Table 4 JPEG2026040844000005.jpg139142

[0055] Each of the resin compositions of the Examples gave good results in the evaluations of curability, viscosity, adhesion, Taber test, and bending processability.

[0056] On the other hand, Comparative Example 1, in which the blending amount of (A) was less than 40% by weight, exhibited poor bending workability, Comparative Example 2, in which the blending amount of (A) was more than 85% by weight, exhibited poor results in the Taber abrasion test, and Comparative Example 3, which did not contain (B), exhibited poor adhesion, and none of these were suitable for the present invention.

Claims

1. A solventless coating composition comprising a photocurable resin composition comprising a polyfunctional urethane (meth)acrylate (A), a phosphoric acid ester compound (B), a reactive diluent (C), and a photopolymerization initiator (D), wherein (A) comprises a urethane (meth)acrylate (a1) having a polycaprolactone-based polyester skeleton, and the proportion of (a1) in (A) is 40 to 85% by weight.

2. 2. The solventless coating composition according to claim 1, wherein (A) comprises an aliphatic urethane (meth)acrylate (a2).

3. 3. The solventless coating composition according to claim 1, which is a coating agent for polyvinyl chloride substrates.

4. 3. A polyvinyl chloride building material coated with the solventless coating composition according to claim 1.

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