JPH10130363A - Radiation hardenable powder composition, hardening and hardened material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of being hardened at a temperature lower than the case of the conventional one and sufficiently hardened even in a pigment-added system by formulating a specific onium salt as a photoinitiator of a cation polymerization to a solid cationically polymerizable material. SOLUTION: The subject composition comprises (A) a solid cationically polymerizable material (preferably a compound containing an epoxy group such as a bisphenol type epoxy resin), (B) a photoinitiator of a cation polymerization comprising an onium salt having >=100 maximum molar absorption coefficient at >=360nm wave length (e.g. the onium salt having a thioxanthone structure such as a compound of the formula), and optionally (C) a pigment. The each component is preferably formulated to be 49.7-99.7wt.% component A, 1-10wt.% component B and 10-60wt.% component C in the objective composition. The melting point of component A is preferably 60-130 deg.C. Further the objective composition has <=300μm particle diameter of the solid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-curable powder composition, a curing method, and a cured product thereof. More specifically, the composition is heated and melted and then polymerized by irradiating ultraviolet rays or an electron beam. The present invention relates to a curable powder composition, a curing method, and a cured product thereof. Particularly, the present invention relates to a radiation-curable powder composition excellent in curability, a curing method, and a cured product thereof in a composition containing a pigment.

[0002]

2. Description of the Related Art Conventionally, there are many types of materials used as coating materials in which a resin is overwhelmingly dissolved in a solvent.
That is, this is a method in which a paint containing a solvent is applied to the painted surface, and after the solvent is evaporated, a resin film is formed. However, the solvent used in this method is generally volatilized in the atmosphere and is difficult to recover and reuse. Therefore, improvement in cost, working environment and global environment is strongly demanded. As a method for solving the above-mentioned problems of the solvent-type paint, powder paint has attracted attention. Since the powder coating does not use any solvent, the above-mentioned problems caused by the solvent are solved, and the powder coating is an excellent technique in storage stability, simplicity of handling method, and the like. However, a powder coating is generally a solid powder coating, which is heated and melted to form a continuous film, and then heated to a high temperature to cause a curing reaction, which completely separates the melting and the curing reaction. It is difficult to achieve a sufficient coating finish in the melting process, and it is difficult to obtain a sufficient finish of the coating film. Further, the curing reaction is caused at a temperature higher than the melting temperature of the resin, so that the temperature required for curing is high. was there.

On the other hand, examples of a catalyst for curing a cationically polymerizable compound such as an epoxy compound by irradiation with ultraviolet rays and a composition thereof are described in JP-A-50-151997 and JP-A-50-151997.
No. 158680. However,
It is difficult to use a colored coating film containing a pigment with a high concealment ratio because it has low transmittance of ultraviolet light, and even in a transparent system that does not contain pigments, colored dyes, etc., the thickness of the cured system increases or the material has poor transparency Has a problem that curing is insufficient in a system containing.

[0004]

SUMMARY OF THE INVENTION The present invention is capable of curing at a lower temperature than conventional thermosetting powder materials, and is capable of sufficiently curing even in a pigment-added system or a thick-film system by irradiation of ultraviolet rays or electron beams. It is an object to provide a radiation cationic polymerizable powder composition.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a powder composition containing a solid cationically polymerizable substance has a wavelength of 360 nm.
The present inventors have found that the above problems can be solved by including a photocationic polymerization initiator which is an onium salt having a maximum molar extinction coefficient of 100 or more, and have completed the present invention. That is, the present invention

(1) It contains a solid cationically polymerizable substance (A), a cationic photopolymerization initiator (B) which is an onium salt having a maximum molar extinction coefficient of 100 or more at a wavelength of 360 nm or more, and a pigment (C) as an optional component. (2) The cationic photopolymerization initiator (B), which is the onium salt described in (1), is an onium salt having a thioxanthone structure. (1) the powder composition according to (1), wherein the solid cationically polymerizable substance (A) according to (1) has a melting point in the range of 20 ° C to 180 ° C; 4) After heating and melting the composition to form a continuous coating, the composition is polymerized and cured by irradiating ultraviolet rays or an electron beam (1).
(2) or the method for curing the powder composition according to the item (3), (5)
It relates to a cured product of the powder composition of (1), (2) or (3).

The powder composition of the present invention can be used for general paints for exterior and interior of automobile bodies, pumps, etc., various parts, woodwork, furniture, electronic materials, building materials, metals, plastic inorganic materials and the like. Although it is suitable for use, it can be used not only for paints but also for various uses such as various photocurable materials such as printing inks, adhesives, solid photosensitive materials, soldering masks, plating resists, and the like.

In the practice of the present invention, specific examples of preferred solid cationically polymerizable substance (A) include the following compounds. As a compound having an epoxy group, bisphenol-type epoxy resin which is a reaction product of bisphenol A such as bisphenol A, bisphenol F and bisphenol S and epichlorohydrin,
Biphenol-type epoxy resins such as bisphenol diglycidyl ether and tetramethyl biphenol diglycidyl ether; novolak resins such as triglycidyl isocyanate; Epoxy group-containing mono (meth) acrylates such as resins, solid alicyclic epoxy compounds and glycidyl methacrylate and monofunctional unsaturated compounds (eg, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate , 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth)
Acrylate, styrene, α-methylstyrene, etc.).

Examples of the vinyl ether compound include vinyl ether compounds of novolak resins such as phenol novolak and cresol novolak, bisphenol A divinyl ether, bisphenol A oxyethyl divinyl ether, and vinylphenol compounds of polyvinyl phenol. These can be used alone or in combination of two or more. In particular, compounds having an epoxy group are preferably used.

The above-mentioned solid cationically polymerizable substance is a main component that determines the physical properties of the cured product, and is selected according to the physical properties such as hardness, strength, durability, and adhesion required for various uses, Be blended. Because of the characteristics of powder materials,
Since it is necessary to be in a solid state at room temperature, the melting point is preferably 20 ° C. or higher, and more preferably 60 ° C. or higher in consideration of storage at a high temperature. Further, it is inconvenient that the melting point is too high because it is necessary to melt at the time of curing, and the temperature is preferably 180 ° C. or lower. Considering the viewpoint of energy saving required for heating, the temperature is more preferably 130 ° C. or lower.

The component (B) used in the present invention has a wavelength of 360 n.
Examples of the cationic photopolymerization initiator which is an onium salt having a maximum molar extinction coefficient of 100 or more and m or more include an onium salt having a thioxanthone structure represented by the general formula (1).

[0012]

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In the formula (1), X is a group represented by the formula (2)

[0014]

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(In the formula (2), R _{6 to} R ₁₅ each represent a hydrogen atom, a halogen atom, a nitro group, an alkoxy group, a C ₁
The structure of the -C _20, a hydroxyl group, an ether group, an ester group,
It is a group selected from an aliphatic group which may have a (meth) acryloyl group, an epoxy group or an allyl group, a phenyl group, a phenoxy group and a thiophenoxy group. ) R _{1 to} R ₅ each represent a hydrogen atom, a hydroxyl group,
_{1 to} C ₁₅ are a group selected from an aliphatic group, a halogen atom, a nitro group, an alkoxy group, an ester group, a phenyl group and a group represented by the formula (2), wherein n is 1 to 4, and Z is a group represented by the formula ( 3) or equation (4)

MQ _p (3) MQ _p-1 (OH) (4)

(Wherein M is a phosphorus atom, a boron atom, an arsenic atom or an antimony atom, Q is a halogen atom, and p is an integer of 4 to 6). More specifically, a cationic photopolymerization initiator which is an onium salt having a thioxanthone structure described in JP-A-8-165290 is exemplified.

[0018]

[Table 1] Table 1

These onium salts are considerably sensitive to ultraviolet light having a wavelength not absorbed by the pigment. If the onium salt has no absorption at a wavelength of 360 nm or more, or has a molar extinction coefficient of 100 or less, it does not cure or cure. Is a problem late. The component (B) used in the present invention has a maximum molar extinction coefficient at a wavelength of 360 nm or more of 100 or more, preferably 1000 or more, and particularly preferably 2 or more.
000 or more.

In the present invention, the pigment (C) is used as an optional component. Specific examples of the pigment (C) include, for example, inorganic pigments such as carbon black, graphite, molybdenum, red iron oxide, rutile type titanium dioxide coated with titanium dioxide or aluminum oxide, cyanine green, cyanine blue, and Hansa yellow benzidine yellow. And organic pigments such as Brilliant Carmine 6B, Lake Red C and Permanent Red F5R.

In the composition of the present invention, the use ratio of each component (A) to (C) is as follows.
It is preferably from 7 to 99.7% by weight, particularly preferably 49.
7 to 99.7% by weight. The component (B) is 0.3 to 1
It is preferably 5% by weight, particularly preferably 1 to 10% by weight. The component (C) is preferably from 0 to 65% by weight, particularly preferably from 10 to 60% by weight.

The radiation-curable powder composition of the present invention comprises
The components (A) to (C) are mixed, pulverized and classified. Alternatively, it can be prepared by mixing and melting and kneading the respective components, followed by cooling, followed by pulverization and classification.

The powder composition of the present invention is a composition that is in a solid state at room temperature, and is generally a solid composition having a solid particle diameter of 1 mm or less, preferably 300 microns or less.

In the curing reaction of the radiation-curable powder composition of the present invention, generally, the composition is heated and melted to a melting temperature or higher, and the powder particles are continuously connected without maintaining the original particle shape. Then, irradiation with ultraviolet rays from a high-pressure mercury lamp, a metal halide lamp, or the like, or irradiation with an electron beam from an electron beam irradiation device is achieved.

The composition of the present invention may further comprise, if necessary,
Oligomers such as urethane (meth) acrylate compounds, polyester (meth) acrylate compounds, unsaturated polyester resins, epoxy (meth) acrylate compounds, and silicon (meth) acrylate compounds that are solid at room temperature;
Monomers such as diacetacrylamide, acrylamide, methacrylate amide, acrylamide glycolic acid, 2-methoxy-2-acrylamide-glycolic acid methyl ester, and N, N-methylenebisacrylamide can also be used.

Further, optional additives, fillers and the like can be added to the powder composition of the present invention. Examples of the additive herein include a leveling agent, a dispersant, a light stabilizer, an antioxidant, an ultraviolet absorber, and a flow regulator generally used as an additive for powder coatings. As the filler, powder, spherical, fibrous, whisker-like,
Examples include organic substances and inorganic substances in various shapes such as flakes, and composites and mixtures thereof. As described above, the composition of the present invention is suitable as a radiation-curable material such as paints, inks, adhesives, and resists, and is expected to contribute to improving the global environment.

[0027]

The present invention will be described below with reference to examples. Examples 1 to 4 According to the composition shown in Table 2 (the numerical values are parts by weight), the powder composition was melt-kneaded, cooled and pulverized to 10 μm.
A powder having an average particle size of After applying each of the prepared compositions to an aluminum plate, the coating film was examined using an infrared lamp for 120 minutes.
℃ and melted (adjusted so that the thickness of the melted coating film becomes about 20 μm), and then irradiated with ultraviolet rays (metal halide lamp, 160 w / cm, under the lamp, 10 cm, conveyor speed 5 m / min). Was cured. The obtained cured coating film was evaluated for solvent resistance, adhesion, and pencil hardness. Evaluation method (solvent resistance): Soak methyl ethyl ketone in cloth,
The surface of the cured coating was rubbed 50 times and the surface of the coating was observed.・ ・ ・: No abnormality on the surface of the coating film. Δ: Surface gloss was lost and the coating film became thin. X: The coating film was dissolved. (Adhesion): Goban 1 according to JIS K5400
By the cellophane tape peeling test, 00 pieces, the number of streaks where the coating film was not peeled off was indicated. (Pencil hardness): Based on JIS K5400, the maximum hardness at which the coating film peeled off at room temperature with Mitsubishi Pencil "Uni" and did not reach the base was indicated.

[0028]

Table 2 Example 1 2 3 4 Epicoat 1004 * 1 20 40 10 20 Epicoat 1004 * 2 20 30 15 YX-4000 * 3 30 30 20 Triglycidyl isocyanurate 21 Photo-cationic polymerization initiator Compound (a) * 4 3 3 Cationic cationic polymerization initiator compound (b) * 5 3 Cationic cationic polymerization initiator compound (c) * 63 Polyester resin * 79 Diacetoneacrylamide (melting point 56 ° C) 15 Titanium dioxide 30 30 30 30 Trimethylbenzoyldiphenyl Phosphine oxide (radical polymerization initiator) 1 Solvent resistance ○ ○ ○ ○ Adhesion 100/100 100/100 100/100 100/100 Pencil hardness 5H 4H 5H 5H

Note) * 1. Epicoat 1004: manufactured by Yuka Shell Epoxy Co., Ltd., bisphenol A type epoxy resin, melting point ° C, epoxy equivalent * 2. Epicoat 1004: manufactured by NOF Corporation * 3. YX-4000: Yuka Shell Epoxy Co., Ltd.
Manufactured by Tetramethylbiphenyl diglycidyl ether,
Melting point * 4. Compound (a): Table 1, No. 5, molar extinction coefficient at wavelength nm * 5. Compound (b): Table 1, No. 6, molar extinction coefficient at wavelength nm * 6. Compound (c): Table 1, No. 8, molar extinction coefficient at wavelength nm, * 7. Polyester resin: manufactured by Toyobo Co., Ltd., product name
Byron, melting point ° C.

From the evaluation results shown in Table 2, the powder composition of the present invention is excellent in curability, solvent resistance, adhesiveness, and pencil hardness.

[0031]

According to the present invention, there is provided a radiation-curable powder composition, a curing method, and a cured product which can be cured at a lower temperature than the conventional one, does not cause a curing reaction upon melting, and has excellent curability even in a pigment-added system. Was done.

Claims (5)

[Claims] 1. A solid cationically polymerizable substance (A) having a wavelength of 3
A radiation-curable powder composition comprising a cationic photopolymerization initiator (B) which is an onium salt having a maximum molar extinction coefficient of not less than 60 nm and not less than 100 and a pigment (C) as an optional component. 2. A powder composition, wherein the cationic photopolymerization initiator (B) as the onium salt according to claim 1 is an onium salt having a thioxanthone structure. 3. The solid cationically polymerizable substance (A) according to claim 1, having a melting point in the range of 20 ° C. to 180 ° C.
Powder composition. 4. After heating and melting the composition to form a continuous film, the composition is polymerized by irradiation with ultraviolet rays or electron beams.
4. The method for curing a powder composition according to claim 1, wherein the composition is cured. 5. A cured product of the powder composition according to claim 1, 2 or 3.