JP7303713B2 - UV curable resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultraviolet curable resin composition having excellent storage stability.

Acrylic photocurable resins are used in many fields to impart special properties to the surfaces of plastic films and plastic moldings. For example, a hard coat film that is applied on a PET (polyethylene terephthalate) film to impart high hardness is used in large quantities in touch panel products, and an adhesive film that imparts viscosity to the film is a final product in flat panel display products. It is also used as a protective film in the manufacturing process.

In addition to the application of a thin film to the surface of plastics to impart special properties, acrylic resin is also used as a casting resin for making accessories such as brooches and small items, taking advantage of its hardness and transparency. (Patent Document 1). In the past, the applicant has used a bifunctional urethane (meth)acrylate resin having a polyether skeleton with a number average molecular weight of 1,000 to 7,000 and a monofunctional methacrylate monomer or aromatic acrylate monomer or a polar group for the same application. We have invented a composition consisting of an aliphatic acrylate monomer that does not have a photopolymerization initiator (Patent Document 2).

This invention is excellent in that it can be sufficiently cured without leaving stickiness or the like even when cured with a black light source. However, it is not sufficient in terms of storage stability, and there is a problem that it tends to thicken especially in a high temperature environment. There was room for improvement in terms of reconciling the different required performance of high

JP-A-10-264184 Japanese Patent No. 6335853

The subject of the present invention is a UV curable resin suitable for casting molds for self-made accessories such as brooches and small articles. To provide a resin composition having excellent properties.

The invention according to claim 1 comprises a polyfunctional urethane (meth)acrylate oligomer (A), a (meth)acrylate monomer (B), a photopolymerization initiator (C), a phosphate ester (D), and a tetrafunctional The above primary thiol (E) and a stabilizer (F) are included , the (A) includes a bifunctional urethane (meth)acrylate oligomer, and the blending ratio of the bifunctional urethane (meth)acrylate oligomer in (A) is 30% by weight or more, (B) is a difunctional or less (meth)acrylate monomer, and (D) is added in an amount of 0.3 to 4 parts by weight per 100 parts by weight of the radically polymerizable component. and 1.5 to 15 parts by weight per 100 parts by weight of the radically polymerizable component (E) .

The invention according to claim 2 is characterized in that the bifunctional or less (meth)acrylate monomer (B) contains a (meth)acrylate monomer containing a hydroxyl group and/or a linear skeleton (meth)acrylate monomer. The photocurable resin composition according to claim 1 is provided.

Further, the invention according to claim 3 provides the photocurable resin composition according to claim 1 or 2, which is a casting molding resin .

The composition of the present invention has excellent curability even when the ultraviolet irradiation light source is an LED, and is resistant to thickening even in a high-temperature environment and has excellent storage stability. It is useful as a curable composition for casting molds.

The structure of the ultraviolet curable resin composition of the present invention comprises a polyfunctional urethane (meth)acrylate oligomer (A), a (meth)acrylate monomer (B), a photopolymerization initiator (C), and a phosphate ester (D). , a tetrafunctional or higher primary thiol (E), and a stabilizer (F). In addition, in this specification, (meth)acrylate includes both acrylate and methacrylate.

The polyfunctional urethane (meth)acrylate oligomer (A) used in the present invention is one of the main components constituting the cured film. Examples include structures produced by reacting (meth)acrylates and having two or more (meth)acryloyl groups and urethane bonds in one molecule. As for the number of functional groups, it is preferable to include a bifunctional urethane (meth)acrylate oligomer in view of the balance of reactivity, cure shrinkage, and storage stability.

The blending ratio of the bifunctional urethane (meth)acrylate oligomer in (A) is preferably 30 to 100% by weight, more preferably 80 to 100% by weight, particularly 90 to 100% by weight. preferable. Sufficient storage stability can be ensured by making it 30% by weight or more, and stability can be further improved by making it 80% by weight or more.

The weight average molecular weight (hereinafter referred to as Mw) of (A) is preferably 1,000 to 20,000, more preferably 1,500 to 10,000, and particularly preferably 1,500 to 5,000. By setting it to 1000 or more, a cured product having sufficient hardness can be obtained, and by setting it to 20000 or less, it becomes easy to adjust the viscosity to be suitable for 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 amount of (A) is preferably 40 to 75% by weight, more preferably 45 to 70% by weight, based on the total solid content. When the amount is 40% by weight or more, sufficient curability can be ensured, and when the amount is 75% by weight or less, it becomes easy to adjust the viscosity to be suitable for workability.

The (meth)acrylate monomer (B) used in the present invention is blended as a reactive diluent for adjusting the viscosity for good workability, and the ratio of the bifunctional or less (meth)acrylate monomer is 80% by weight or more. is. If the content is less than 80% by weight, the curability is lowered and the surface of the cured product tends to be sticky.

Examples of the bifunctional or less (meth)acrylate monomer include, for example, linear (branched) alkyl skeletons, aliphatic cyclic skeletons, ether skeletons, aromatic ring-containing, hydroxyl group-containing, amino group-containing, heterocyclic (meth) Examples include acrylate monomers, which can be used alone or in combination of two or more. Among these, hydroxyl group-containing (meth)acrylate monomers and straight-chain skeleton (meth)acrylate monomers are preferred from the viewpoint of good curability. For example, 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, particularly 2-hydroxypropyl methacrylate, 1.6-hexanediol diacrylate, polyethylene glycol diacrylate. (n<10) is preferred.

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 curability can be ensured. The amount of (B) added to 100 parts by weight of (A) is preferably 20 to 75 parts by weight, more preferably 25 to 70 parts by weight. When the amount is 20 parts by weight or more, the viscosity can be easily adjusted to suit workability, and when the amount is 75 parts by weight or less, sufficient curability can be ensured.

The photopolymerization initiator (C) 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 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 a benzyl ketal system, and 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2- hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1 as α-aminoacetophenone -on includes acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, either alone or in combination of two or more can be used in combination.

Among the above (C), it is preferable to include an α-hydroxyacetophenone type that is resistant to yellowing and an acylphosphine oxide type that is excellent in internal curability. In particular, when the cured film is thickened to 100 μm or more as in a casting mold, the combination of acylphosphine oxide is effective, and the combination of both is preferable. Commercially available products include α-hydroxyacetophenone type Omnirad 184 and phosphine oxide type Omnirad TPO H (trade name: manufactured by iGM Resins).

The content of (C) is preferably 1 to 25 parts by weight, more preferably 10 to 20 parts by weight, particularly preferably 12 to 18 parts by weight, per 100 parts by weight of the radically polymerizable component. By blending in this range, the composition can be efficiently cured. When the α-hydroxyacetophenone system and the acylphosphine oxide system are used in combination, the mixing ratio is preferably 20 to 60 parts by weight of the acylphosphine oxide system to 100 parts by weight of the α-hydroxyacetophenone system.

The phosphate ester (D) used in the present invention is blended to play a role in suppressing an increase in viscosity during storage at a high temperature such as 60°C. It preferably 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 Nippon Kayaku Co., Ltd.).

The amount of (D) per 100 parts by weight of the photoreactive component is preferably 0.2 to 5 parts by weight, more preferably 0.3 to 4 parts by weight, and 0.4 to 3.5 parts by weight. Parts by weight are particularly preferred. 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 tetrafunctional or higher primary thiol (E) used in the present invention is blended with the role of promoting the ultraviolet curing reaction, and is capable of enthiol reaction that can suppress curing inhibition due to oxygen, and has a large number of functional groups such as tetrafunctional or higher. , In addition, it is a thiol with very high reactivity because it is a first-class thiol with low steric hindrance. For example, tetrafunctional pentaerythritol tetrakis(3-mercaptopropionate) and hexafunctional dipentaerythritol hexa-3-mercaptopropionate can be used alone or in combination of two or more. A thiol having less than tetrafunctionality or a secondary or higher functionality is insufficient in reactivity, and stickiness cannot remain on the surface of the cured product after UV irradiation.

The blending amount of (E) per 100 parts by weight of the photoreactive component is preferably 1.0 to 15 parts by weight, more preferably 1.5 to 12 parts by weight, and particularly preferably 2.0 to 5.0 parts by weight. If it is 1.0 part by weight or more, the curability can be improved and the surface of the cured film will not be sticky. Commercially available products include PEMP (trade name: manufactured by SC Organic Chemical Co., Ltd., tetrafunctional) and DPMP (trade name: manufactured by SC Organic Chemical Co., Ltd., hexafunctional).

The stabilizer (F) used in the present invention, like the above (D), is blended to play a role in suppressing an increase in viscosity during high-temperature storage. Types of stabilizers include light stabilizers and antioxidants, and specific examples include UV absorbers represented by benzotriazoles and triazines, hindered amines, hindered phenols, phosphites, and thioethers. and can be used alone or in combination of two or more.

The blending amount of (F) per 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 composition of the present application preferably further contains a polymerization inhibitor (G) for the role of suppressing an increase in viscosity during high-temperature storage. By adding a small amount of (G), it becomes possible to effectively bring out the performance of (D) and (F), and the blending amount thereof 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 contains various additives such as leveling agents, plasticizers, tackifiers, pigments, dyes, antifoaming agents, thickeners, and wettability modifiers, if necessary, within a range that does not impair performance. It's okay if it is.

The viscosity of the present composition at 25° C. is preferably 500 to 15,000 mPa·s, more preferably 1,000 to 10,000 mPa·s. When the viscosity is 500 mPa·s or more, the workability is improved and the casting work becomes easier, and when the viscosity is 15000 mPa·s or less, the reproducibility of the casting mold and air bubble removal are improved.

The storage stability of the composition can be judged by measuring the viscosity increase rate in an environment of 60° C. as an accelerated test. Specifically, the increase rate of the viscosity of the composition after standing at 60° C. for 14 days is preferably 20% or less, more preferably 10% or less, relative to the initial viscosity. If it is 20% or less, it is judged that there is sufficient storage stability 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, a bifunctional urethane (meth) acrylate oligomer (Mw.3000) and a hexafunctional urethane (meth) acrylate oligomer are used as (A), and light ester HOP (N) (trade name: Kyoeisha Chemical Co., Ltd.) is used as (B). (manufactured by iGM, 2-hydroxypropyl methacrylate) as (C), Omnirad 184 (manufactured by iGM, α-hydroxyacetophenone type) and Omnirad TPO H (G) (manufactured by iGM, acylphosphine oxide type) as (D) PM-21 (trade name: manufactured by Nippon Kayaku Co., Ltd.), PEMP (trade name: manufactured by SC Organic Chemical Co., Ltd., pentaerythritol tetrakis (3-mercaptopropionate)) as (E), and Tinuvin249 (F) as Trade name: Hindered amine type manufactured by BASF Japan), dibutyl hydroxytoluene as (G), and KL-700 as a leveling agent (trade name: Kyoeisha Chemical Co., Ltd., organic group-containing polydimethylsiloxane) are shown in Table 1. The resin composition of Example 1 was prepared by weighing and stirring for 15 minutes or more until uniform using a stirring deaerator.

Examples 2-12
In addition to the materials used in Example 1, 1.6HX-A (trade name: manufactured by Kyoeisha Chemical Co., Ltd., 1.6 hexanediol diacrylate) and M-240 (trade name: manufactured by Toa Gosei Co., Ltd., Polyethylene glycol (n≈4) diacrylate) as (D), PM-2 (trade name: manufactured by Nippon Kayaku Co., Ltd.), and DPMP (trade name: manufactured by SC Organic Chemical Co., Ltd., dipenta) as (E) Erythritol hexa-3-mercaptopropionate) was stirred for 15 minutes or more until uniform using a stirring deaerator according to the formulation shown in Table 2 to prepare resin compositions of Examples 2 to 12.

Comparative Examples 1-11
In addition to the materials used in the examples, PET-30 (trade name: Nippon Kayaku Co., Ltd., pentaerythritol triacrylate) and DPHA (trade name: Nippon Kayaku Co., Ltd., dipentaerythritol hexa TMMP-LV (trade name: SC Organic Chemical Co., Ltd., trimethylolpropane tris (3-mercaptopropionate)) and TEMPIC (trade name: SC Organic Chemical Co., Ltd., Tris- [(3-Mercaptopropionyloxy)-ethyl]-isocyanurate) as a tetrafunctional secondary thiol PE1 (trade name: Showa Denko Co., Ltd., pentaerythritol tetrakis (3-mercaptobutyrate)), 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 11 were prepared.

Preparation of cured product 3 g of the resin composition at room temperature was placed in a silicone mold (manufactured by Herbert, silicone motif RSSD-2, 20 mm x 32 mm x t5 mm), and irradiated with an LED from a height of 4 cm above the resin surface. Using a machine SUN mini (manufactured by Parts Club), an output of 6 W and an illuminance of 6 mW/cm 2 (365 nm) (13 W/cm 2 (405 nm)) was used for 1 minute, followed by irradiation from the back surface for 1 minute for curing. After that, the cured product was taken out from the silicone mold and left at 23±2° C. for 30 minutes to prepare.

Table 1

Table 2

The evaluation method was as follows.

Viscosity: Using a cone plate type viscometer RC-550 manufactured by Toki Sangyo Co., Ltd., 25 ± 1 ° C with a cone angle of 3 ° R 17.65, the rotation speed is 20 rpm for 500 to 2000 mPa s, 10 rpm for 2000 to 5000 mPa s, 5000 to 10000 mPa·s was measured at 5 rpm.

Curability: The degree of tackiness of the surface of the cured product irradiated with the LED light was checked by finger touch.

Appearance: The transparency and color of the cured product were visually confirmed, and colorless and transparent was evaluated as ◯, and abnormalities such as cloudiness and discoloration were observed as x.

Cure shrinkage: The cured product was visually checked for warpage and air bubbles.

Storage stability: 20 g of the resin composition is weighed into a 50 mL light-shielding bottle, stored in a constant temperature bath at 60 ° C. for 14 days, and then the viscosity is measured. 20% was rated as ◯, and more than 20% was rated as x.

Table 2 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 had good viscosity, curability, appearance, cure shrinkage, and storage stability.

On the other hand, Comparative Examples 1 and 2 in which (E) is not blended (or less), Comparative Examples 3 to 5 using different thiols, and Comparative Examples 10 and 11 with a high ratio of trifunctional or higher monomers in (B) are all cured. Comparative Examples 6 and 7 in which the amount of (D) is not blended (or less) are inferior in storage stability, Comparative Example 8 in which the amount of (D) is large, and Comparative Example 9 in which (F) is not blended Both of them were inferior in preservability and were not suitable for the present invention.

The ultraviolet curable resin composition of the present invention has excellent curability even when using an LED light source, has a low viscosity increase rate at high temperatures, and has good storage stability. It is useful as a casting mold resin suitable for handicraft applications.

Claims (3)

Polyfunctional urethane (meth)acrylate oligomer (A), (meth)acrylate monomer (B), photopolymerization initiator (C), phosphate ester (D), and tetrafunctional or higher primary thiol (E) and a stabilizer (F), wherein (A) contains a bifunctional urethane (meth)acrylate oligomer, and the blending ratio of the bifunctional urethane (meth)acrylate oligomer in (A) is 30% by weight or more; (B) is a bifunctional or less (meth)acrylate monomer, the amount of which is 0.3 to 4 parts by weight per 100 parts by weight of the radically polymerizable component of (D) , and the radical polymerization of (E). 1.5 to 15 parts by weight per 100 parts by weight of the photocurable resin composition. 2. The photocuring according to claim 1 , wherein the (B) bifunctional or less (meth)acrylate monomer comprises a (meth)acrylate monomer containing a hydroxyl group and/or a linear skeleton (meth)acrylate monomer. elastic resin composition. 3. The photocurable resin composition according to claim 1, which is a casting mold resin.