JP2023169917A - Photocurable resin composition - Google Patents

Abstract

To provide a photocurable resin composition that has optical properties, reliability, surface hardness, and adhesiveness equivalent to those of two-part polyurethane resins, while having adequate hardness and slip-resistance for pleasant grip feel, and an article including the same.SOLUTION: A photocurable resin composition includes an allophanate urethane (meth)acrylate, a (meth)acrylate monomer, an allyl ether compound, a thiol compound, a phosphoester compound, and a photopolymerization initiator. The urethane (meth)acrylate constitutes 40-70 wt.% of the total solid content, and its average weight molecular weight is 2,000-30,000.SELECTED DRAWING: None

Description

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

Potting resin for decorative purposes can create a three-dimensional finish, and the lens effect adds volume and depth, increasing the sense of luxury, so it is widely used in home appliances, automobile interiors and exteriors, ornaments for miscellaneous goods, touch switches, etc. It is used. In addition, 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-component polyurethane resins, which are excellent in weather resistance and durability, have been generally used as such potting resins. However, this two-component polyurethane resin requires mixing two components before use, and is not easy to handle.It also takes a long time to cure, resulting in a long production lead time. Since it is necessary to cure in a highly clean environment to avoid adhesion of foreign substances, etc., there is a problem of putting pressure on production costs.

In order to deal with these problems, we have developed an ultraviolet curable resin that is made by reacting a urethane acrylate with an average number of functional groups in the range of 2.0<f≦2.5, a reactive diluent, and a photopolymerization initiator. A composition has been proposed (Patent Document 1). This composition is a photo-curing type that can be cured instantly with a single component, so it can overcome the above problems, but when used as a non-slip material in automobile interior applications, it has a suitable hardness but is also non-slip. The grip feeling (touch) was not sufficient, and there was room for improvement.

JP 9-48830

The object of the present invention is to create a photocurable resin composition that has the same optical properties, reliability, surface hardness, and adhesive strength as a two-component polyurethane resin, and at the same time has a grip feeling with appropriate hardness and anti-slip properties. , and to provide products using it.

In order to solve the above problem, the invention of claim 1 comprises an allophanate type urethane (meth)acrylate (A), a (meth)acrylate monomer (B), an allyl ether compound (C), and a thiol compound (D). , a phosphoric acid ester compound (E) and a photopolymerization initiator (F), the blending amount of (A) is 40 to 70% by weight based on the total solid content, and the average weight molecular weight is 2,000. 30,000 to 30,000.

Moreover, the invention of claim 2 provides the photocurable resin composition according to claim 1, wherein the (B) contains a monofunctional (meth)acrylate having a hydroxyl group.

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

Furthermore, the invention of claim 4 provides the photocurable resin composition according to claim 1 or 2, which is used as a casting resin, a sealing resin, or a potting agent. .

Moreover, the invention according to claim 5 provides an article that is cast, sealed, or potted with the photocurable resin composition according to either claim 1 or 2.

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 two-component polyurethane resins, and at the same time, it has a grip feeling of moderate hardness and anti-slip properties. Therefore, it is useful as a resin composition used as a casting resin, a sealing resin, a potting agent, etc.

The composition of the ultraviolet curable resin composition of the present invention is: allophanate-type urethane (meth)acrylate (A), (meth)acrylate monomer (B), allyl ether compound (C), thiol compound (D), and phosphorus. They are an acid ester compound (E) and a photopolymerization initiator (F). In addition, in this specification, (meth)acrylate includes both acrylate and methacrylate.

Allophanate-type urethane (meth)acrylate (hereinafter referred to as allophanate-type ureac) (A) used in the present invention is one of the main components constituting the cured film, and is resistant to wear due to the cohesive force of hydrogen bonds derived from urethane bonds. It has strength and toughness. The urethane bond has an allophanate bond (-NH-CO-NCOO- group) that has reacted with an isocyanate group, and the hydrogen bond interaction between O-H, which has a large effect on viscosity, occurs within the molecule. It is possible to lower the viscosity compared to urethane (meth)acrylate of the same composition that does not have an allophanate bond. In addition, even in thick films, it has a fast curing speed, good curing properties without stickiness, high hardness, and low curing shrinkage. The number of functional groups is preferably 2 to 8 functional groups, more preferably 4 to 6 functional groups. By setting it within this range, the curing properties and curing shrinkage can be balanced, and the adhesion to the adherend can be more stabilized.

The weight average molecular weight (hereinafter referred to as Mw) of the above (A) is 2,000 to 30,000, preferably 2,500 to 20,000, and more preferably 3,000 to 10,000. preferable. If it is less than 2,000, it may be difficult to ensure sufficient holding power or the hardness may become too high, and if it exceeds 30,000, it becomes difficult to adjust the viscosity to a value suitable for workability. Note that 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 the above (A) is preferably 500 to 5,000, more preferably 600 to 3,000, and particularly preferably 700 to 2,000. By setting it to 500 or more, sufficient holding power can be ensured without making the hardness too high, and by setting it to 5,000 or less, sufficient curability can be ensured. Note that the equivalent weight is a value obtained by dividing Mw by the number of functional groups based on the acryloyl group that the urethane (meth)acrylate has.

The blending amount of (A) is 40 to 70% by weight, preferably 45 to 68% by weight, and more preferably 50 to 65% by weight based on the total solid content. If it is less than 40% by weight, it will be difficult to ensure sufficient holding power or adjust the viscosity to be suitable for workability, and if it exceeds 70% by weight, it will be difficult to adjust the viscosity to be suitable for workability.

The (meth)acrylate monomer (B) used in the present invention is a reactive diluent for adjusting the viscosity to suit workability, and is blended for the purpose of improving curability. It is preferable that it is difunctional or less, and more preferably monofunctional, since curing shrinkage does not become large.

Examples of the (meth)acrylate monomer having less than two functional groups include (meth)acrylate monomers having a linear (branched) alkyl skeleton, an aliphatic cyclic skeleton, an ether skeleton, an aromatic ring-containing, a hydroxyl group-containing, an amino group-containing, a heterocycle-containing, etc. Examples include acrylate monomers, which can be used alone or in combination of two or more. Among these, hydroxyl group-containing (meth)acrylate monomers are preferred from the viewpoint of good water resistance, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 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 blending amount of (B) is preferably 10 to 40% by weight, more preferably 15 to 35% by weight based on the total solid content. By setting the content to 10% by weight or more, the viscosity can be easily adjusted to suit workability, and by setting the content to 40% by weight or less, sufficient holding power can be ensured.

Allyl ether (C) used in the present invention is a reactive diluent for adjusting the viscosity for good workability, and is also blended for the purpose of suppressing yellowing of the cured product and odor under moist heat conditions. . By using (B) and (C) together, the viscosity of the composition can be lowered, and at the same time, by incorporating (C), it can reduce the imbalance in the partial reaction rate of radical polymerization and the resulting stickiness of the coating film surface. Defects on the surface of the coating film due to polymerization inhibition caused by oxygen can be suppressed or buffered.

The above (C) preferably contains an allyl ether having two or more functionalities, and more preferably contains an allyl ether having three or more functionalities in terms of good reactivity. Examples of the bifunctional or more functional compounds 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, and pentaerythritol diallyl ether; glycerin triallyl; Examples include ether, triallyl ether compounds such as trimethylolpropane triallyl ether and pentaerythritol triallyl ether, and tetraallyl ether compounds such as pentaerythritol tetraallyl ether, which can be used alone or in combination of two or more types. . Among these, pentaerythritol triallyl ether is preferred in terms of compatibility and reactivity with other components.

The blending amount of (C) is preferably 2 to 25 parts by weight, more preferably 3 to 20 parts by weight, and more preferably 3.5 to 20 parts by weight, based on the total of 100 parts by weight of (A) and (B). Particularly preferred is 10 parts by weight. 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, the generation of odor can be similarly suppressed. Further, the blending ratio with respect 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 an enethiol reaction that can suppress curing inhibition caused by oxygen, and is blended for the purpose of accelerating the ultraviolet curing reaction and improving grip feeling. For example, n-octyl-3-mercaptopropionate is monofunctional, tetraethylene glycol bis(3-mercaptopropionate) is bifunctional, and trimethylolpropane tris(3-mercaptopropionate) is trifunctional. Tetrafunctional examples include pentaerythritol tetrakis (3-mercaptopropionate) and pentaerythritol tetrakis (3-mercaptobutyrate), and hexafunctional examples include dipentaerythritol hexa-3-mercaptopropionate, which can be used alone or in combination. can be used in combination. Among these, those having two or more functionalities are preferred from the viewpoint of accelerating curing.

The blending amount of (D) is preferably 5 to 35 parts by weight, more preferably 6 to 30 parts by weight, based on 100 parts by weight of the photoreactive components (A), (B), and (C). Particularly preferred is 7 to 28 parts by weight. When the weight is 5 parts or more, curing properties can be improved and a sufficient grip feeling can be ensured, and when the weight is 35 parts or less, odor can be sufficiently suppressed in a high-temperature, humid, heat environment. 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 phosphoric acid ester (E) used in the present invention is blended for the purpose of improving storage stability. It is preferable to have a photoreactive functional group such as a (meth)acryloyl group that can firmly bond to (A) and (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 blending amount of (E) is preferably 0.2 to 5 parts by weight, and preferably 0.3 to 5 parts by weight, based on 100 parts by weight of the photoreactive components (A), (B), and (C). More preferably, the amount is 4 parts by weight, and particularly preferably 0.4 to 3 parts by weight. By keeping it within this range, it is possible to suppress an increase in viscosity even when stored 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, etc., and these radicals trigger the polymerization reaction. General-purpose photopolymerization initiators can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, 2,2-dimethoxy-1,2-diphenylethan-1-one is used as a benzyl ketal type, and 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2- hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is converted into 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1 as an α-aminoacetophenone system. -one is acylphosphine oxide, such as 2.4.6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2.4.6-trimethylbenzoyl)-phenylphosphine oxide, either singly or in combination. Can be used in combination.

Among the above (F), it is preferable to include an acylphosphine oxide type having excellent internal curability. In particular, when the cured film is thicker than 100 μm, such as in a cast molding type, the formulation of acylphosphine oxide is effective. Commercially available products include Omnirad TPO H (trade name: manufactured by iGM Resins).

The blending amount of (F) is preferably 0.1 to 10 parts by weight, and 0.1 to 10 parts by weight, based on 100 parts by weight of the photoreactive components (A), (B), and (C). It is more preferably 3 to 5 parts by weight, particularly preferably 0.5 to 3 parts by weight. By blending within this range, the composition can be efficiently cured.

It is preferable that the composition of the present invention further contains a polymerization inhibitor to suppress an increase in viscosity during high-temperature storage. By adding a small amount of a polymerization inhibitor, it becomes possible to effectively bring out the above-mentioned performance (E), and the amount of the polymerization inhibitor added can also be reduced. A specific example is dibutylhydroxytoluene, and the amount thereof 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 optionally contain various additives such as stabilizers, leveling agents, plasticizers, tackifiers, pigments, dyes, antifoaming agents, thickeners, and wettability regulators, to the extent that they do not impair performance. It may also contain an agent.

Examples of the stabilizers include light stabilizers and antioxidants, including ultraviolet absorbers such as benzotriazole and triazine, hindered amine, hindered phenol, phosphite, and thioether. Examples include antioxidants, which can be used alone or in combination of two or more.

The amount of the stabilizer added 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. Setting the amount to 0.2 parts by weight or more has the effect of suppressing an increase in viscosity at high temperatures, and setting the amount to 2.0 parts by weight or less makes it possible to suppress surface stickiness during curing. Commercially available hindered amine products include Tinuvin 123 and Tinuvin 249 (trade name: manufactured by BASF Japan).

The solid content of the present composition is preferably 80% by weight or more, more preferably 95% by weight or more, and particularly preferably 99% by weight or more, which is substantially solvent-free. When it is 80% by weight or more, thick coating is possible by sufficiently volatilizing the solvent before photocuring.

The viscosity of the present composition at 25° C. is preferably 300 to 5,000 mPa·s, more preferably 1,000 to 3,000 mPa·s. Setting the pressure to 300 mPa·s or more improves workability and makes potting work easier, and setting the pressure to 15,000 mPa·s or less improves mold reproducibility and air bubble removal when casting.

The hardness of the cured product of the present 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, the number is 15 to 45. When the hardness is within this range, there is no stickiness, and the grip has a good holding power (see Examples for the evaluation method), the grip feeling is good.

The storage stability of the present composition can be determined by measuring the viscosity increase in an environment of 60°C as an accelerated test. Specifically, if it does not gel after being left at 60°C for 7 days, it is judged that it has 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 intended to be specific examples and are not particularly limited to these. Unless otherwise specified, the measurements were performed at a room temperature of 25° C. and a relative humidity of 65%. Further, the blending amount indicates parts by weight.

Example 1
In a light-shielding bottle, as (A), ureac 1 (pentafunctional, Mw 7,900, equivalent weight 1,580, allophanate type) was added, and as (B), light ester HOP (N) (trade name: manufactured by Kyoeisha Chemical Co., Ltd., 2- hydroxypropyl methacrylate) as (C), P-30M (trade name: manufactured by Osaka Soda Co., Ltd., pentaerythritol triallyl ether) as (D), PEMP (trade name: manufactured by SC Organic Chemical Co., Ltd., pentaerythritol tetrakis (3)). -Mercaptopropionate)), PM-2 (trade name: manufactured by Nippon Kayaku Co., Ltd.) as (E), and Omnirad TPO H (G) (manufactured by iGM, acylphosphine oxide type) as (F). Add Tinuvin 249 (trade name: manufactured by BASF Japan, hindered amine type) as a stabilizer and BHT (dibutylhydroxytoluene) as a polymerization inhibitor in the amounts shown in Table 1, and stir using a stirring defoamer for 15 minutes until uniform. The resin composition of Example 1 was prepared by stirring for more than a minute.

Examples 2 to 11
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 4,100, equivalent weight 820, allophanate type) are used as (A) in addition to the materials used in Example 1. As (D), Karenz MTPE1 (trade name: manufactured by Showa Denko K.K., pentaerythritol tetrakis (3-mercaptobutyrate)) and Karenz MT BD1 (trade name: manufactured by Showa Denko K.K., 1,4-bis(3-mercaptobutyrate) Resin compositions of Examples 2 to 11 were prepared by stirring (Ryloxy)butane) according to the formulation shown in Table 1 using a stirring defoaming machine for 15 minutes or more until it became uniform.

Comparative examples 1 to 6
In addition to the materials used in the examples, binder resins include Ureac A (trifunctional, Mw 800, equivalent weight 266, allophanate type) and Ureac B (bifunctional, Mw 6,600, equivalent weight 3,300, polypropylene glycol skeleton non-allophanate type) and Using Ureac C (9 functional, Mw 2,500, equivalent weight 277, non-allophanate type with hexamethylene diisocyanurate skeleton), the formulation shown in Table 2 was stirred for 15 minutes or more until uniform using a stirring defoamer and compared. Resin compositions of Examples 1-7 were prepared.

Preparation of test piece A: diameter 23 mm x thickness 6 mm
Pour the photocurable resin into a silicone mold (diameter 23mm x depth 6mm) and cure it by irradiating it with a metal halide lamp under the conditions of 300mW/cm ² and 6,000mJ/cm ² , then remove the cured resin from the silicone mold. , and left at 23±2° C. for 30 minutes.

Preparation of test piece B: 30 mm x 30 mm x thickness 2 mm
A 30 mm x 30 mm hole was made in a silicone mat (40 mm x 40 mm x 2 mm thick), a photocurable resin was poured in, and the resin was irradiated with a metal halide lamp at 300 mW/cm ² and 6,000 mJ/cm ² to cure. Thereafter, the cured product was removed from the silicone mat and left at 23±2° C. for 30 minutes.

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 mPa・s: 20 rpm, 2000 to 5000 mPa・s s was measured at 10 rpm. Cases of 300 to 1,000 mPa·s or less and 3,000 to 5,000 mPa·s were marked as ○, cases of 1,000 to less than 3,000 mPa·s were marked as ◎, and cases outside of this range were marked as ×.

Color: The b* value of test piece B was measured in accordance with JIS K 0062 using a color difference measuring instrument SD-6000 manufactured by Nippon Denshoku Industries. - 1.2 or less was rated as ○, and over 1.2 was rated as ×.

Appearance: The transparency and color of test specimens A and B were visually confirmed, and a colorless and transparent specimen was rated ○, and a case where an abnormality such as cloudiness or discoloration was observed was rated ×.

Curability: The degree of stickiness of test pieces A and B was confirmed by touching with fingers, and if there was no transfer of stickiness, it was rated ○, and if there was, it was rated ×.

Holding power: A 1 mm thick silicone mat with a 20 mm x 20 mm cutout was placed on a 76 mm x 26 mm x 1 mm thick glass plate, a photocurable resin was poured, and it was cured under the same conditions as the above test piece. . Thereafter, the silicone mat was removed, and the same glass plates were overlapped with the cured material in between so as to form a cross shape, and a load of 500 g was applied from above the glass and left to stand at room temperature for 1 minute. Thereafter, the load was removed, and the upper glass was lifted, and the case where the glass did not come off for 30 seconds or more was marked as ○, and the case where it came off in less than 30 seconds was marked as ×.

Hardness: Using a durometer hardness tester, in accordance with JIS K 6253, with a load of 1Kgf for types A and E and 5Kgf for type D, the needle is slowly dropped from the irradiated surface side of test piece A, and the value is measured after 60 seconds. was measured. Cases of 50 to 95 for type A, 60 to 95 for type E, and 10 to 50 for type D were marked as ○, and other cases were marked as ×.

Cured product odor: The odor of test piece A was checked immediately after curing, and the case where there was no odor was rated as ○, and the case where there was odor was rated as ×.

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. If the resin composition was fluid, it was rated ○, and if it gelled, it was rated x.

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 evaluated favorably in terms of viscosity, color, appearance, curability, holding power, hardness, cured product odor, and storage stability.

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

Claims (5)

Allophanate-type urethane (meth)acrylate (A), (meth)acrylate monomer (B), allyl ether compound (C), thiol compound (D), phosphate ester compound (E), and photopolymerization initiator (F), the amount of (A) blended is 40 to 70% by weight based on the total solid content, and the average weight molecular weight is 2,000 to 30,000. Resin composition. The photocurable resin composition according to claim 1, wherein the (B) contains a monofunctional (meth)acrylate having a hydroxyl group. 3. The photocurable resin composition according to claim 1, wherein the (C) contains triallyl ether. 3. The photocurable resin composition according to claim 1, which is used as a casting resin, a sealing resin, or a potting agent. An article cast, sealed, or potted with the photocurable resin composition according to claim 1 or 2.