Photocurable resin composition

Abstract

To provide a resin composition which has good storage stability even under a high-temperature environment and is excellent in depth curability even with an LED light source.SOLUTION: A photocurable resin composition contains an epoxy (meth)acrylate, a pentaerythritol acrylate, a photopolymerization initiator, a phosphate ester, a thiol compound, and a light stabilizer. The pentaerythritol acrylate has a hydroxyl value of 170-350 mg KOH / g. The thiol compound contains a primary thiol.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photocurable resin composition having excellent deep curability and storage stability. [Background technology]

[0002] Acrylic photocurable resins are used in many fields to impart special properties to the surfaces of plastic films and plastic moldings. For example, hard coat films that are applied to PET (polyethylene terephthalate) films to impart high hardness are used in large quantities as films for touch panels and molding films.

[0003] In addition to the fields where acrylic resins are applied as thin films to plastic surfaces to impart special properties, they are also used as casting resins for making accessories such as brooches and small items, taking advantage of their hardness and transparency (Patent Document 1).In the past, the applicant has invented a composition for the same purpose, consisting of a multifunctional urethane (meth)acrylate, a (meth)acrylate monomer, a photopolymerization initiator, a phosphoric ester, a primary thiol with 4 or more functional groups, and a stabilizer (Patent Document 2).

[0004] This invention was excellent in that it could simultaneously satisfy different required performances, namely, excellent curability even when using an LED light source, and resistance to thickening even in high-temperature environments, and extremely high storage stability. However, because the deep curability was insufficient, the center of a thick object was not cured well, and fluidity remained. Therefore, a composition that had good storage stability and extremely excellent deep curability was required. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-264184 [Patent Document 2] Patent No. 7303713 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a resin composition which has good storage stability even in a high-temperature environment and is excellent in deep curing even with an LED light source. [Means for solving the problem]

[0007] In order to achieve the above object, the invention of claim 1 provides a photocurable resin composition comprising an epoxy (meth)acrylate (A), a pentaerythritol acrylate (B), a photopolymerization initiator (C), a phosphate ester (D), a thiol compound (E), and a light stabilizer (F), wherein the hydroxyl value of (B) is 170 to 350 mgKOH / g, and (E) contains a primary thiol (e1).

[0008] The invention of claim 2 provides the photocurable resin composition according to claim 1, characterized in that the (E) further contains a secondary thiol (e2).

[0009] The invention of claim 3 provides the photocurable resin composition according to claim 1, characterized in that the (C) contains 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

[0010] The invention of claim 4 provides the photocurable resin composition according to claim 1, wherein the (A) contains bisphenol A epoxy diacrylate.

[0011] The invention of claim 5 provides the photocurable resin composition according to any one of claims 1 to 4, which is for use in cast molding. Effect of the Invention

[0012] The composition of the present invention has good storage stability in high-temperature environments and excellent deep curing properties even with LED light sources, making it useful as a photocurable cast molding composition suitable for making your own thick accessories. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The ultraviolet curable resin composition of the present invention is composed of an epoxy (meth)acrylate (A), a pentaerythritol acrylate (B), a photopolymerization initiator (C), a phosphoric ester (D), a thiol compound (E), and a stabilizer (F). In this specification, the term "(meth)acrylate" includes both acrylate and methacrylate.

[0014] The epoxy (meth)acrylate (A) used in the present invention is one of the main components constituting the cured coating, and is blended for the purpose of improving the deep curing property of the composition. For example, acrylates obtained by reacting conventionally known aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins, etc. with acrylic acid can be mentioned. Among these, acrylates of aromatic epoxy resins are preferred because of their high hardness and reaction curing property.

[0015] The acrylate of the aromatic epoxy resin is an acrylate obtained by reacting a polyglycidyl ether of a polyhydric phenol having at least one aromatic nucleus or its alkylene oxide adduct with acrylic acid. For example, an acrylate obtained by reacting a glycidyl ether obtained by reacting a bisphenol resin or its alkylene oxide adduct with epichlorohydrin with acrylic acid, an acrylate obtained by reacting an epoxy novolac resin with acrylic acid, etc. can be mentioned. Among these, bisphenol epoxy diacrylate is preferred because it has a good balance in terms of fast curing property, transparency and heat resistance of the cured product, and cost, and can impart appropriate hardness and toughness to the cured product, and bisphenol A epoxy diacrylate is particularly preferred because of its excellent curing property.

[0016] The amount of (A) is preferably 20 to 40% by weight, more preferably 22 to 35% by weight, and particularly preferably 25 to 32% by weight, based on the total solid content. By making it 20% by weight or more, sufficient deep curing can be ensured, and by making it 40% by weight or less, it is easy to adjust the viscosity to a level suitable for workability.

[0017] The pentaerythritol acrylate (B) used in the present invention is blended for the purpose of improving the reaction curing property of the composition and improving the storage stability. (B) is produced by reacting pentaerythritol with acrylic acid, and due to the manufacturing method, most of it becomes a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate. Since the characteristics can be changed by the ratio of triacrylate having a hydroxyl group, (B) with a different hydroxyl value can be selected depending on the purpose. The hydroxyl value is 170 to 350 mgKOH / g, preferably 180 to 320 mgKOH / g, and more preferably 180 to 300 mgKOH / g. If it is less than 170 mgKOH / g, sufficient storage stability may not be ensured, and if it exceeds 350 mgKOH / g, sufficient economic availability cannot be obtained.

[0018] The blending amount of (B) is preferably 1.0 to 10.0% by mass, more preferably 1.5 to 8.0% by weight, based on the total solid content. By making it 1.0% by weight or more, sufficient storage stability can be ensured, and by making it 10.0% by weight or less, cure shrinkage can be sufficiently suppressed.

[0019] The photopolymerization initiator (C) used in the present invention generates radicals when irradiated with ultraviolet light or an electron beam, and the radicals trigger the polymerization reaction, and general-purpose photopolymerization initiators such as benzyl ketal, acetophenone, and phosphine oxide photopolymerization initiators 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-hydroxy-cyclohexyl-phenyl-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-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, which may be used alone or in combination of two or more.

[0020] Among the (C) resins, it is preferable to use an acylphosphine oxide type resin, which has excellent internal curing properties, and an α-hydroxyacetophenone type resin, which is less likely to yellow. In particular, when the cured film is to be thickened to 100 μm or more, such as in a cast molding type resin, it is effective to use an acylphosphine oxide type resin. Commercially available products include Omnirad 184, which is an α-hydroxyacetophenone type resin, and Omnirad TPO H (product name: manufactured by iGM Resins), which is a phosphine oxide type resin.

[0021] The amount of (C) is preferably 0.5 to 5.0 parts by weight, more preferably 1.0 to 3.0 parts by weight, based on 100 parts by weight of the radical polymerizable component. By adding it in this range, the composition can be cured efficiently without decreasing the storage stability.

[0022] The phosphoric acid ester (D) used in the present invention is blended for the purpose of stabilizing the initial viscosity and improving the curability. The reason why the blending of (D) stabilizes the viscosity is unclear, but since compositions containing thiols tend to gel in a basic atmosphere, it is believed that the blending of the acidic (D) neutralizes the basicity, thereby suppressing a sudden increase in viscosity. It is preferable that the composition has a photoreactive functional group such as a (meth)acryloyl group so that bleeding from the cured film is less likely to occur. Commercially available products include PM-2 (trade name: manufactured by Nippon Kayaku Co., Ltd.) and PM-21 (trade name: manufactured by the same company).

[0023] The amount of (D) is preferably 0.1 to 5.0% by weight, more preferably 0.2 to 3.0% by weight, and particularly preferably 0.3 to 1.5% by weight, based on the total solid content. By adjusting the amount of (D) within this range, the initial viscosity can be stabilized and sufficient surface curability and deep curability can be ensured.

[0024] The thiol compound (E) used in the present invention is formulated to promote the ultraviolet curing reaction and contains a highly reactive primary thiol (e1). It is capable of an enethiol reaction that can suppress curing inhibition by oxygen, and can improve deep curing with low shrinkage. The number of functional groups is preferably three or more in terms of reactivity, and more preferably four or more. For example, a four-functional group is pentaerythritol tetrakis(3-mercaptopropionate), and a six-functional group is dipentaerythritol hexa-3-mercaptopropionate, which can be used alone or in combination of two or more types. A commercially available product of (e1) is PEMP (trade name: manufactured by SC Organic Chemicals, four-functional).

[0025] In the present invention, it is preferable that the secondary thiol (e2) is further contained. (e2) is characterized by being capable of enethiol reaction, and having better storage stability than (e1) due to steric hindrance. Therefore, by using (e1) and (e2) in combination, it is possible to improve both reactivity and storage stability. The number of functional groups is preferably three or more from the viewpoint of reactivity, and more preferably four or more. For example, trimethylolpropane tris(3-mercaptobutyrate) is a trifunctional group, and pentaerythritol tetrakis(3-mercaptobutyrate) is a tetrafunctional group, and these can be used alone or in combination of two or more kinds. A commercially available product of (e2) is Karenz MTPE-1 (trade name: manufactured by Resonac, four functional groups).

[0026] The blending amount of (E) including (e1) and (e2) is preferably 3.0 to 15% by weight, more preferably 3.0 to 12% by weight, and particularly preferably 5.0 to 10% by weight, based on the total solid content. By making it 3.0% by weight or more, sufficient deep curing can be improved, and by making it 15% by weight or less, storage stability in a high temperature environment can be ensured.

[0027] When (e1) and (e2) are used in combination, the blending ratio (e2) / (e1) is preferably 0.05 to 1.0, more preferably 0.1 to 0.8, and particularly preferably 0.3 to 0.6. By keeping the blending ratio within this range, the reactivity and storage stability can be improved and further stabilized.

[0028] The light stabilizer (F) used in the present invention is blended with the role of suppressing the increase in viscosity during high-temperature storage, similar to the above-mentioned (D). Types of stabilizers include light stabilizers and antioxidants, and specific examples include ultraviolet absorbers such as benzotriazoles and triazines, hindered amines, hindered phenols, phosphites, and thioethers, which can be used alone or in combination of two or more.

[0029] The amount of (F) is preferably 0.05 to 3.0% by weight, more preferably 0.1 to 2.0% by weight, and even more preferably 0.3 to 1.5% by weight, based on the total solid content. By making it 0.05% by weight or more, it is possible to suppress the increase in viscosity at high temperatures, and by making it 3.0% by weight or less, it is possible to suppress surface stickiness during curing. Commercially available products include Tinuvin 123 and Tinuvin 249 (product names: manufactured by BASF Japan) as hindered amine-based products, Irganox 1076 (product name: manufactured by BASF Japan) as hindered phenol-based products, and AO-503 (product name: manufactured by Adeka Corporation) as a thioether-based product.

[0030] The composition of the present invention preferably further contains a polymerization inhibitor (G) to suppress the increase in viscosity during high-temperature storage. By adding a small amount of (G), it is possible to effectively bring out the performance of the above-mentioned (D) and (F), and the amount of (G) can also be reduced. Specifically, dibutylhydroxytoluene can be mentioned, and the amount of dibutylhydroxytoluene is preferably 0.01 to 0.3 parts by weight per 100 parts by weight of the photoreactive component.

[0031] The composition of the present invention may contain various additives, such as reactive oligomers, reactive diluents, leveling agents, plasticizers, tackifiers, pigments, dyes, defoamers, thickeners, and wettability adjusters, as necessary, within the range that does not impair the performance.

[0032] The reactive oligomer is not particularly limited, but is preferably an acrylic resin in terms of compatibility with (A) to (E). For example, urethane (meth)acrylate (hereinafter referred to as ureac), polyester (meth)acrylate, polycarbonate (meth)acrylate, acrylic (meth)acrylate, diene (meth)acrylate, etc. can be mentioned, and they can be used alone or in combination of two or more kinds. Among these, ureac is preferred in terms of weather resistance and reactive curing. In addition, the number of functional groups is preferably 4 or less in terms of suppressing cure shrinkage, and more preferably 2.

[0033] The amount of reactive oligomer is preferably 20 to 50% by weight, more preferably 30 to 45% by weight, based on the total solid content. By making it 20% by weight or more, it is possible to ensure sufficient curability, and by making it 50% by weight or less, it is easy to adjust the viscosity to a level suitable for workability.

[0034] The reactive diluent is not particularly limited, but is preferably an acrylic resin in terms of compatibility with (A) to (E). The number of functional groups is preferably two or less in terms of suppressing cure shrinkage, and is more preferably monofunctional. Examples of the diluent include (meth)acrylates and acrylamide compounds having functional groups such as aliphatic, alicyclic, polyether skeletons, hydroxyl groups, and amino groups, and these can be used alone or in combination of two or more types. Among these, hydroxyl-containing (meth)acrylate monomers are preferred in terms of good cure properties and storage stability.

[0035] The amount of reactive diluent blended is preferably 25% by weight or less, more preferably 20% by weight or less, based on the total solid content. By keeping the amount within this range, it is possible to easily adjust the viscosity to a level suitable for workability, and to ensure sufficient curability and storage stability.

[0036] The present composition is preferably solvent-free. "Solvent-free" means that no solvent is intentionally blended into the composition for the purpose of dilution, and does not mean that even trace amounts of volatile components contained in each component of the composition are excluded, and refers to a solvent content of 5% by weight or less, typically 1% by weight or less.

[0037] The viscosity of the composition at 25° C. is preferably 500 to 15,000 mPa·s, and more preferably 1,000 to 10,000 mPa·s. A viscosity of 500 mPa·s or more improves workability and facilitates casting, while a viscosity of 15,000 mPa·s or less improves the reproducibility of the casting mold and improves the escape of air bubbles.

[0038] The storage stability of this composition was evaluated by measuring the viscosity increase rate in an accelerated test at 60°C. Specifically, the viscosity of the composition after standing at 60° C. for 14 days increases preferably by 500% or less, more preferably by 300% or less, based on the initial viscosity. If the increase is 500% or less, the composition is deemed to have sufficient storage stability for practical use.

[0039] The present invention will be described in more detail below with reference to examples and comparative examples, but these are illustrative and are not intended to be limiting. Unless otherwise specified, measurements were performed under conditions of room temperature of 25°C and relative humidity of 65%. The amounts of the ingredients are expressed in parts by weight. EXAMPLES

[0040] Example 1 In a light-shielding bottle, MIRAMER PE210 (trade name: Miwon, bisphenol A epoxy diacrylate) as (A), ARONIX M-933 (trade name: Toagosei, hydroxyl value 250 to 300 mg KOH / g) as (B), JRCURE TPO (trade name: TIANJIN JIURI NEW MATERIALS, acylphosphine oxide photopolymerization initiator) as (C), and KAYAMER PM-2 (trade name: phosphoric acid ester, manufactured by Nippon Kayaku Co., Ltd.), (E) PEMP (trade name: pentaerythritol tetrakis (3-mercaptopropionate), tetrafunctional primary thiol) and Karenz MTPE-1 (trade name: pentaerythritol tetrakis (3-mercaptobutyrate), tetrafunctional secondary thiol, manufactured by Resonac Co., Ltd.), (F) Tinuvin 249 (trade name: hindered amine light stabilizer, manufactured by BASF Japan Ltd.), (G) BHT (dibutylhydroxytoluene), The amounts shown in Table 1 were added to a bifunctional urethane (meth)acrylate oligomer (residue of reaction of hydroxy (meth)acrylate with a reactant of PTMG and IPDI, Mw. 3000), a reactive diluent, Light Ester HOP (N) (product name: Kyoeisha Chemical Co., Ltd., 2-hydroxypropyl methacrylate), and a leveling agent, Polyflow KL-700 (product name: Kyoeisha Chemical Co., Ltd., organic group-containing polydimethylsiloxane), and the mixture was stirred for 15 minutes or more using a stirring defoamer until uniform, to prepare a resin composition of Example 1.

[0041] Examples 2 to 6, Comparative Examples 1 to 7 In addition to the materials used in Example 1, Aronix M-934 (product name: manufactured by Toagosei Co., Ltd., hydroxyl value 180 to 220 mg KOH / g) was used as (B), and Aronix M-305 (product name: manufactured by Toagosei Co., Ltd., hydroxyl value 100 to 130 mg KOH / g) and Aronix M-306 (product name: manufactured by Toagosei Co., Ltd., hydroxyl value 150 to 165 mg KOH / g) were used as pentaerythritol acrylates with low hydroxyl values ​​in the formulations shown in Tables 1 and 2, and the mixtures were stirred for 15 minutes or more using a stirring and defoaming machine until uniform, to prepare resin compositions of Examples 2 to 6 and Comparative Examples 1 to 7.

[0042] Preparation of hardened material 3g of the resin composition at room temperature was poured into a silicone mold (Elber's silicone motif RSSD-2, 20mm x 32mm x t5mm) and cured by irradiating it from a height of 4cm above the resin surface with an LED lamp XSR-120LED&UV LAMP2 (Elber's) at an output of 6W and wavelengths of 365nm+405nm for 1 minute, and then for another 1 minute from the back of the silicone mold. The cured product was then removed from the silicone mold and left to stand for 30 minutes at 23±2°C.

[0043] Table 1 JPEG2025085106000001.jpg121135

[0044] Table 2 JPEG2025085106000002.jpg108134

[0045] The evaluation method was as follows.

[0046] Viscosity: Measurements were taken using a Toki Sangyo cone-plate viscometer RC-550 with a cone angle of 3°R17.65 at 25±1°C and a rotation speed of 10 rpm for 2,000 to 5,000 mPa·s, 5 rpm for 5,000 to 10,000 mPa·s, and 1 rpm for 10,000 mPa·s or more.

[0047] Surface curability: The stickiness of the surface of the cured product irradiated with the LED light was confirmed by touching with the fingers. If there was no stickiness, it was marked with ○, and if there was stickiness, it was marked with ×.

[0048] Deep curing: The center part of the cured product was cut and the degree of curing of the center part was confirmed. Complete curing was indicated by ◯, and uncured parts were indicated by ×.

[0049] Storage stability: 200 g of the resin composition was weighed out into a 250 mL light-shielding bottle and stored in a constant temperature bath at 60°C for 14 days. The viscosity was then measured. A viscosity increase rate of 300% or less from the initial viscosity was evaluated as ◎, a viscosity increase rate of more than 300 to 500% or less was evaluated as 〇, and a viscosity increase rate of more than 500% was evaluated as ×.

[0050] The evaluation results of the examples are shown in Table 2. Table 3 JPEG2025085106000003.jpg71135

[0051] The evaluation results of the comparative examples are shown in Table 4. Table 4 JPEG2025085106000004.jpg63135

[0052] The resin compositions of the examples were good in all respects of initial viscosity, surface curability, deep curability and storage stability.

[0053] On the other hand, Comparative Example 1, which does not contain (A), was inferior in deep section curing property and storage stability, Comparative Example 2, which does not contain (B), and Comparative Examples 3 and 4, which contain pentaerythritol acrylate with a low hydroxyl value, were inferior in storage stability. Comparative Example 5, which does not contain (D), had a high initial viscosity and inferior surface curing property and deep section curing property, and Comparative Example 6, which does not contain (E), was inferior in deep section curing property. Furthermore, Comparative Example 7, which does not contain (F), was inferior in storage stability, and all of them were not suitable for the present invention.

Claims

1. A photocurable resin composition comprising: an epoxy (meth)acrylate (A), a pentaerythritol acrylate (B), a photopolymerization initiator (C), a phosphoric acid ester (D), a thiol compound (E), and a light stabilizer (F); (B) having a hydroxyl value of 170 to 350 mgKOH / g; and (E) containing a primary thiol (e1).

2. 2. The photocurable resin composition according to claim 1, wherein the (E) further contains a secondary thiol (e2).

3. 2. The photocurable resin composition according to claim 1, wherein the (C) contains 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

4. 2. The photocurable resin composition according to claim 1, wherein the (A) contains bisphenol A epoxy diacrylate.

5. 5. The photocurable resin composition according to claim 1, which is for use in a cast molding process.

Images