JP2023101841A - Photo-curable resin composition - Google Patents

Abstract

To provide a resin composition which is ultraviolet-curable and has optical characteristics, reliability, surface hardness and adhesiveness equivalent to those of a two-liquid type polyurethane resin and at the same time has a grip feeling of suitable hardness and anti-slip property, and to provide an article using the same.SOLUTION: A photo-curable resin composition includes: a polyfunctional urethane (meth)acrylate with three or more functional groups; a (meth)acrylate monomer; an allyl ether compound; a thiol compound; a phosphoric acid ester compound; and a photoinitiator, wherein weight average molecular weight of the polyfunctional urethane (meth)acrylate is 3,000-10,000, an average acrylic equivalent thereof is 500-2,000, and a solid content thereof is 95 wt.% or more.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a photocurable resin composition that is cured by active energy rays such as ultraviolet rays.

Potting resin for decoration can be used for a three-dimensional finish, and the lens effect gives a sense of volume and depth, increasing the sense of luxury. In recent automotive interior applications, potting has been applied to the surfaces of center consoles and cup holders to provide anti-slip and motion control functions.

Conventionally, two-liquid polyurethane resins, which are excellent in weather resistance and durability, are generally used as such potting resins. However, this two-liquid polyurethane resin requires mixing of the two liquids before use, and is not easy to handle. In addition, it takes a long time to cure, resulting in a long production lead time. In addition, it is necessary to cure in a highly clean environment to avoid adhesion of foreign matter until it cures.

In order to deal with such problems, for example, an ultraviolet curable resin composition has been proposed in which a urethane acrylate having an average functional group number in the range of 2.0<f≦2.5, a reactive diluent and a photopolymerization initiator are reacted (Patent Document 1). Although this composition can solve the above-mentioned problems in that it is a one-component photocurable type that can be cured immediately, when it is used as an anti-slip in automotive interior applications, it has an appropriate hardness but has anti-slip properties.

Japanese Patent Laid-Open No. 9-48830

An object of the present invention is to provide a resin composition that is photocurable and has the same optical properties, reliability, surface hardness, and adhesive strength as those of a two-part polyurethane resin, and at the same time, has a grip feeling of moderate hardness and anti-slip properties, and an article using the same.

In order to solve the above problems, the invention of claim 1 comprises a trifunctional or higher polyfunctional urethane (meth)acrylate (A), a (meth)acrylate monomer (B), an allyl ether compound (C), a thiol compound (D), a phosphoric acid ester compound (E), and a photopolymerization initiator (F). Provided is a photocurable resin composition characterized by being 95% by weight or more.

In addition, the invention of claim 2 provides a photocurable resin composition according to claim 1, wherein the amount of (C) is 2 to 25 parts by weight with respect to the total solid content of 100 parts by weight of (A) and (B).

Further, the invention of claim 3 provides the photocurable resin composition of claim 1 or 2, wherein the (C) contains triallyl ether.

Further, the invention of claim 4 provides the photocurable resin composition according to any one of claims 1 to 3, characterized in that it is used as a casting resin, a sealing resin, or a potting agent.

Further, the invention of claim 5 provides an article molded, sealed, or potted with the photocurable resin composition of any one of claims 1 to 3.

The composition of the present invention is a photocurable type with a fast curing speed, and has optical properties, reliability, surface hardness, and adhesive strength equivalent to those of two-component polyurethane resins, and at the same time, has a grip feeling of moderate hardness and anti-slip properties.

The composition of the ultraviolet curable resin composition of the present invention comprises a polyfunctional urethane (meth)acrylate (A), a (meth)acrylate monomer (B), an allyl ether compound (C), a thiol compound (D), a phosphate ester compound (E), and a photopolymerization initiator (F). In this specification, (meth)acrylate includes both acrylate and methacrylate.

The polyfunctional urethane (meth)acrylate (hereinafter referred to as ureac) (A) used in the present invention is one of the main components constituting the cured film, and can be obtained, for example, by adding a (meth)acrylic compound having a hydroxyl group to an isocyanate group-terminated urethane prepolymer, and subjecting the isocyanate groups in the urethane prepolymer to addition reaction of the hydroxyl groups. Ureac having an allophanate bond in the molecule or having a polyether skeleton is preferable in terms of the possibility of lowering the viscosity. The number of functional groups in (A) is 3 or more, preferably 4- to 12-functional, more preferably 5- to 9-functional, from the balance of reactivity, curing shrinkage, and storage stability.

The weight average molecular weight (hereinafter referred to as Mw) of (A) is 3,000 to 10,000, preferably 3,500 to 9,000, and more preferably 4,000 to 8,000. If it is less than 3,000, it may be difficult to ensure sufficient holding power, and if it exceeds 10,000, it becomes difficult to adjust the viscosity to suit workability. The Mw was calculated by measuring the molecular weight in terms of standard polystyrene by gel permeation chromatography using a column using a styrene-divinylbenzene-based packing material and using a tetrahydrofuran eluent.

The average acrylic equivalent weight (hereinafter referred to as equivalent weight) of (A) is 500 to 2,000, preferably 600 to 1,800, and more preferably 700 to 1,700. If it is less than 500, the hardness tends to be too high, and if it exceeds 2,000, the hardness tends to be too low. The equivalent weight is a value obtained by dividing Mw by the number of acryloyl group-based functional groups of the urethane (meth)acrylate.

The content of (A) is preferably 40 to 75% by weight, more preferably 45 to 70% by weight, particularly preferably 50 to 68% by weight, based on the total solid content. When the content is 40% by weight or more, sufficient holding power and viscosity suitable for workability can be ensured.

The (meth)acrylate monomer (B) used in the present invention is a reactive diluent for adjusting the viscosity suitable for workability and is blended for the purpose of improving curability. It is preferably bifunctional or less, and more preferably monofunctional, in that curing shrinkage does not increase.

Examples of the bifunctional or less (meth)acrylate monomers include linear (branched) alkyl skeletons, aliphatic cyclic skeletons, ether skeletons, aromatic ring-containing, hydroxyl group-containing, amino group-containing, and heterocyclic (meth)acrylate monomers, which may be used alone or in combination of two or more. Among these, hydroxyl group-containing (meth)acrylate monomers are preferable in terms of good water resistance, and examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, ethylene glycol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, 1.4-butanediol di(meth)acrylate, 1.6-hexanediol di(meth)acrylate, and the like. Among these, 2-hydroxypropyl methacrylate is particularly preferred because of its good color and transparency.

The amount of (B) is preferably 10 to 40% by weight, more preferably 15 to 35% by weight, based on the total solid content. When the content is 10% by weight or more, the viscosity can be easily adjusted to suit workability, and when the content is 40% by weight or less, sufficient holding power can be secured.

The allyl ether (C) used in the present invention is a reactive diluent for adjusting the viscosity for good workability, and is blended for the purpose of suppressing yellowing of the cured product and odor under moist heat conditions. By using (B) and (C) in combination, the viscosity of the composition is reduced, and at the same time, by blending (C), it is possible to suppress or buffer the partial reaction rate imbalance of radical polymerization and the accompanying stickiness of the coating film surface, and the defects on the coating film surface due to polymerization inhibition by oxygen.

From the viewpoint of good reactivity, (C) preferably contains a bifunctional or higher allyl ether, and more preferably contains a trifunctional or higher functional allyl ether. Examples of the difunctional or higher include diallyl ether compounds such as glycerin diallyl ether, diethylene glycol diallyl ether, ethylene glycol diallyl ether, triethylene glycol diallyl ether, polyethylene glycol diallyl ether, trimethylolpropane diallyl ether, pentaerythritol diallyl ether, triallyl ether compounds such as glycerin triallyl ether, trimethylolpropane triallyl ether, pentaerythritol triallyl ether, and tetraallyl ether compounds such as pentaerythritol tetraallyl ether. More than one type can be used in combination. Among these, pentaerythritol triallyl ether is preferred in terms of compatibility and reactivity with other components.

The amount of (C) is preferably 2 to 25 parts by weight, more preferably 3 to 20 parts by weight, and particularly preferably 3.5 to 10 parts by weight with respect to a total of 100 parts by weight of (A) and (B). When the amount is 2 parts by weight or more, yellowing and odor can be sufficiently suppressed, and when the amount is 25 parts by weight or less, generation of odor can be similarly suppressed. Also, the blending ratio to the total solid content of the composition is preferably 1 to 20% by weight, more preferably 2 to 18% by weight.

The thiol (D) used in the present invention is capable of enthiol reaction capable of suppressing inhibition of curing by oxygen, and is blended for the purpose of promoting ultraviolet curing reaction and improving grip feeling. For example, n-octyl-3-mercaptopropionate is monofunctional, tetraethylene glycol bis(3-mercaptopropionate) is difunctional, trimethylolpropane tris (3-mercaptopropionate) is trifunctional, pentaerythritol tetrakis (3-mercaptopropionate) and pentaerythritol tetrakis (3-mercaptobutyrate) are tetrafunctional, and dipentaerythritol hexa-3-mercapto is hexafunctional. There are propionate and the like, which can be used alone or in combination of two or more. Among these, bifunctional or higher functional compounds are preferable from the viewpoint of curing acceleration.

The amount of (D) is preferably 5 to 35 parts by weight, more preferably 6 to 30 parts by weight, and particularly preferably 7 to 28 parts by weight with respect to a total of 100 parts by weight of the photoreactive components (A), (B) and (C). At 5 parts by weight or more, curability can be improved and sufficient grip feeling can be ensured, and at 35 parts by weight or less, odor can be sufficiently suppressed in a high-temperature, moist-heat environment. Commercially available products include PEMP (trade name: manufactured by SC Organic Chemical Co., Ltd., tetrafunctional) and DPMP (trade name: manufactured by the same company, hexafunctional).

The phosphate ester (E) used in the present invention is blended for the purpose of improving storage stability. It preferably has a photoreactive functional group such as a (meth)acryloyl group capable of firmly bonding with (A) or (B) 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 Nippon Kayaku Co., Ltd.).

The amount of (E) is preferably 0.2 to 5 parts by weight, more preferably 0.3 to 4 parts by weight, and particularly preferably 0.4 to 3 parts by weight, per 100 parts by weight in total of the photoreactive components (A), (B), and (C). By setting the viscosity within this range, it is possible to suppress an increase in viscosity even during storage at 60° C., and sufficient storage stability can be ensured.

The photopolymerization initiator (F) used in the present invention generates radicals when irradiated with ultraviolet rays, electron beams, or the like, and the radicals trigger a polymerization reaction. General-purpose photopolymerization initiators such as benzyl ketal, acetophenone, and phosphine oxide can be used. Curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region by arbitrarily selecting the light absorption wavelength of the polymerization initiator. Specifically, 2,2-dimethoxy-1,2-diphenylethan-1-one as the benzyl ketal, 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one as the α-hydroxyacetophenone, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one as the α-aminoacetophenone, Examples of acylphosphine oxides include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, which can be used alone or in combination of two or more.

Among the above (F), it is preferable to include an acylphosphine oxide system which is excellent in internal curability. In particular, when the cured film is thickened to 100 μm or more as in a casting mold, blending of acylphosphine oxide is effective. Commercially available products include Omnirad TPO H (trade name: manufactured by iGM Resins).

The amount of (F) is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, and particularly preferably 0.5 to 3 parts by weight, with respect to a total of 100 parts by weight of the photoreactive components (A), (B), and (C). By blending in this range, the composition can be efficiently cured.

The composition of the present application preferably further contains a polymerization inhibitor for the role of suppressing an increase in viscosity during high-temperature storage. By adding a small amount of the polymerization inhibitor, it becomes possible to effectively bring out the performance of (E), and the amount of the compound can also be reduced. A specific example is dibutylhydroxytoluene, and the amount to be added is preferably 0.03 to 0.3 parts by weight per 100 parts by weight of the photoreactive component.

The composition of the present invention may contain various additives such as stabilizers, leveling agents, plasticizers, tackifiers, pigments, dyes, antifoaming agents, thickeners, and wettability modifiers, as long as they do not impair performance.

Examples of the stabilizer include light stabilizers and antioxidants, and specific examples include UV absorbers represented by benzotriazole and triazine, hindered amine, hindered phenol, phosphite, and thioether antioxidants, which may be used alone or in combination of two or more.

The amount of the stabilizer to be blended with respect to 100 parts by weight of the photoreactive component is preferably 0.2 to 2.0 parts by weight, more preferably 0.5 to 1.5 parts by weight. A content of 0.2 parts by weight or more has the effect of suppressing an increase in viscosity at high temperatures, and a content of 2.0 parts by weight or less makes it possible to suppress surface stickiness during curing. Commercially available hindered amines include Tinuvin 123 and Tinuvin 249 (trade name: manufactured by BASF Japan Ltd.).

The solid content of the present composition is 95% by weight or more, preferably 98% by weight or more, and more preferably 99% by weight or more, which is substantially solvent-free. If the content is less than 95% by weight, the solvent must be sufficiently volatilized before photocuring, making it difficult to apply a thick coating, and the surface appearance tends to deteriorate due to poor leveling.

The viscosity of the present composition at 25° C. is preferably 300 to 5,000 mPa·s, more preferably 4000 to 3,000 mPa·s. When the viscosity is 300 mPa·s or more, the workability is improved and the potting work is facilitated.

The hardness of the cured product of this composition can be measured using a durometer hardness tester. The hardness is preferably 50 to 95 for type A, 60 to 95 for type E, and 10 to 50 for type D, more preferably 55 to 90 for type A, 65 to 90 for type E, and 15 to 45 for type D. When the hardness is within this range, the grip is good when there is no stickiness and the holding power (see Examples for the evaluation method).

The storage stability of the present composition can be judged by measuring the viscosity increase in a 60° C. environment as an accelerated test. Specifically, if it does not gel after being left at 60° C. for 7 days, it is judged that the storage stability is sufficient for practical use.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but these are specific examples and are not intended to limit the invention in particular. Unless otherwise specified, the measurement was performed at a room temperature of 25° C. and a relative humidity of 65%. Moreover, the compounding quantity shows a weight part.

Example 1
In a light-shielding bottle, Ureac 1 (pentafunctional, Mw 7,900, equivalent weight 1,580) as (A), light ester HOP (N) (trade name: Kyoeisha Chemical Co., Ltd., 2-hydroxypropyl methacrylate) as (B), P-30M (trade name: Osaka Soda Co., Ltd., pentaerythritol triallyl ether) as (C), and PEMP (trade name: SC Organic Chemical Co., Ltd., pentaerythritol tetrakis (D)). 3-mercaptopropionate)), PM-2 (trade name: Nippon Kayaku Co., Ltd.) as (E), Omnirad TPO H (G) (iGM, acylphosphine oxide type) as (F), Tinuvin249 (trade name: BASF Japan, hindered amine type) as a stabilizer, and BHT (dibutyl hydroxytoluene) as a polymerization inhibitor in the amount shown in Table 1, and stirred. The resin composition of Example 1 was prepared by stirring for 15 minutes or more until uniform using a deaerator.

Examples 2-12
In addition to the materials used in Example 1, ureac 2 (pentafunctional, Mw 7,300, equivalent weight 1,460, allophanate type) and ureac 3 (pentafunctional, Mw 7,600, equivalent weight 1,520, polyether skeleton) and ureac 4 (pentafunctional, Mw 4,000, equivalent weight 800) were used as (A), and Karenz MTPE1 (trade name: Showa Denko Co., Ltd., pentaerythritol) was used as (D). Tetrakis(3-mercaptobutyrate) and Karenz MT BD1 (trade name: 1,4-bis(3-mercaptobutyryloxy)butane manufactured by Showa Denko Co., Ltd.) were stirred for 15 minutes or more until uniform using a stirring deaerator according to the formulation shown in Table 1 to prepare resin compositions of Examples 2 to 12.

Comparative Examples 1-7
In addition to the materials used in the examples, Ureac A (9-functional, Mw 2,500, equivalent weight 277, nurate skeleton), Ureac B (bi-functional, Mw 6,600, equivalent weight 3,300), Ureac C (tri-functional, Mw 800, equivalent weight 266, allophanate type) and Ureac D (bi-functional, Mw 3,000, equivalent weight 1,500) are used as binder resins, and are listed in Table 2. The mixture was stirred for 15 minutes or longer using a stirring deaerator until it became uniform, and resin compositions of Comparative Examples 1 to 7 were prepared.

Preparation of test piece A: diameter 23 mm × thickness 6 mm
A photocurable resin was poured into a silicone mold (diameter 23 mm x depth 6 mm) and cured by irradiation under the conditions of 300 mW/cm ² and 6,000 mJ/cm ² using a metal halide lamp.

Preparation of test piece B: 30 mm × 30 mm × thickness 2 mm
A silicone mat (40 mm x 40 mm x 2 mm thick) was cut out to a size of 30 mm x 30 mm, a photocurable resin was poured in, and irradiated with a metal halide lamp at 300 mW/cm ² and 6,000 mJ/cm ² to cure.

Table 1

Table 2

The evaluation method was as follows.

Viscosity: Using an E-type viscometer RE-215R manufactured by Toyo Seiki Co., Ltd., using a rotor with a cone angle of 3 ° R17.65, 25 ± 1 ° C., rotation speed of 500 to 2000 Pa s at 20 rpm, 2000 to 5000 mPa s at 10 rpm.

Color: Using a color difference measuring instrument SD-6000 manufactured by Nippon Denshoku Industries Co., Ltd., the b* value of the test piece B was measured according to JIS K 0062.

Appearance: The transparency and color of the test pieces A and B were visually confirmed, and colorless and transparent was evaluated as ◯, and abnormalities such as white turbidity and discoloration were observed as x.

Curability: The degree of tackiness of the test pieces A and B was checked by touching with a finger.

Holding power: A 1 mm-thick silicone mat with a 20 mm x 20 mm cut-out was placed on a 76 mm x 26 mm x 1 mm-thick glass plate, and a photocurable resin was poured into the mat and cured under the same conditions as the above test piece. After that, the silicone mat is removed, and the same glass plates are crossed to form a cross shape, placed on top of each other with the cured product interposed therebetween, and a load of 500 g is applied from above the glass and allowed to stand at room temperature for 1 minute. After that, the load was removed, the upper glass was lifted, and ◯ was given when the glass did not peel off for 30 seconds or longer, and x was given when the glass was peeled off in less than 30 seconds.

Hardness: Using a durometer hardness tester, according to JIS K 6253, a load of 1 Kgf for types A and E, and 5 Kgf for type D, was slowly dropped from the irradiated surface of test piece A, and the values were measured after 60 seconds. The case where the type A type was 50 to 95, the type E type 60 to 95, and the type D type 10 to 50 was rated as ◯, and the others were x.

Odor of cured product: The odor of test piece A immediately after curing was confirmed.

Preservability: 20 g of the resin composition was weighed into a 50 mL light-shielding bottle and stored in a constant temperature bath at 60°C for 7 days.

Table 3 shows the evaluation results of the examples.
Table 3

Table 4 shows the evaluation results of the comparative examples.
Table 4

The resin compositions of Examples were all evaluated well in terms of viscosity, color, appearance, curability, holding power, hardness, odor of the cured product, and storage stability.

On the other hand, Comparative Example 1 that does not contain (C) has poor color, appearance, and odor, Comparative Example 2 that does not contain (D) has poor curability and hardness, and Comparative Example 3 that does not contain (E) has poor storage stability. Comparative Examples 4 to 7, in which binders different from (A) were blended, were inferior in some of the evaluation items, and were not suitable for the present invention.

Claims (5)

Trifunctional or higher polyfunctional urethane (meth)acrylate (A), (meth)acrylate monomer (B), allyl ether compound (C), thiol compound (D), phosphoric acid ester compound (E), and photopolymerization initiator (F), wherein (A) has an average weight molecular weight of 3,000 to 10,000, an average acrylic equivalent of 500 to 2,000, and a solid content of 95% by weight or more. Resin composition. 2. The photocurable resin composition according to claim 1, wherein the amount of (C) is 2 to 25 parts by weight per 100 parts by weight of the total solid content of (A) and (B). 3. The photocurable resin composition according to claim 1, wherein (C) contains triallyl ether. 4. The photocurable resin composition according to claim 1, which is used as a casting resin, a sealing resin, or a potting agent. An article molded, sealed, or potted with the photocurable resin composition according to any one of claims 1 to 3.