JPH08127606A - Thermosetting composition and method for curing - Google Patents

Abstract

PURPOSE: To obtain a thermosetting composition, capable of promoting the thermosetting reaction by photoreaction and efficiently initiating the thermosetting reaction, curable with a small amount of a catalyst in a short time and useful for resists, etc., by combining a light absorbing compound with a thermosetting compound. CONSTITUTION: This composition contains (A) a thermosetting compound and (B) a light absorbing compound. Furthermore, a mixture of (i) any of an isocyanate compound, a polyorganic acid compound, a polyorganic acid anhydride, an epoxy compound and a melamine compound with (ii) any of a polyol compound, a polyphenol compound, a polyamine compound and a compound containing polymercapto groups, a mixture of the polyorganic acid compound with the isocyanate compound or the epoxy compound, etc., are preferably used as the component (A) and a compound, having the absorption in the region of near infrared rays and represented by the formula D<+> .A<-> (D<+> is a cation having the absorption in the region of near infrared rays; A is various anions) is preferably used as the component (B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting composition and a curing method for curing by a new system in which a light absorbing compound and light irradiation are combined with a widely used thermosetting reaction. More specifically, a curable composition and a curing method in which a light-absorbing compound is added to a conventional thermosetting compound and light irradiation is performed, and the light-absorbing compound converts light energy into heat energy to accelerate a heat-curing reaction. Regarding

[0002]

2. Description of the Related Art Conventionally, a curing reaction by heat has been widely used in the production of cured products such as paints, printing inks, adhesives and various molded products. It causes a crosslinking reaction such as a urethane bond, a polyester bond, a melamine bond, and a siloxane bond by heating, and is widely used because of its easy availability of raw materials, economy, and good physical properties of the cured product. Is used for. However, the thermosetting reaction is generally carried out at a high temperature of 100 ° C. or higher, and from the viewpoint of energy saving and resource saving, it is desired that the storage stability is good and the curing reaction is as low as possible and as short as possible. Further, as a problem of the thermosetting reaction, in the case of a composition having a large volume, it is difficult to uniformly heat the composition, and the curing reaction may be uneven.

On the other hand, the photopolymerization reaction is used in various fields such as curing and printing of coating film, resin convex printing, print substrate preparation, resist or photomask, black and white or color transfer coloring sheet or coloring sheet preparation. In particular, recently, from the viewpoint of global environment problems, energy saving, labor saving in response to rising labor costs, etc., attention has been paid to the fact that photopolymerization is possible even at room temperature, that it can be dried quickly and that it is solvent-free. Have been developed. In particular, the photopolymerization reaction using long-wavelength near-infrared light, etc. is different from conventional ultraviolet curing, and it is possible to apply photo-curing to systems containing pigments by applying high near-infrared light transmission. (For example, JP-A-5-194619).

However, the curing reaction by ultraviolet light or near infrared light cures the composition by photopolymerization by radicals generated by the photoreaction, and the raw material is a polymerizable unsaturated compound, which is more than thermosetting compound. Since it is expensive and its type is limited, it is the present situation that it is not generally used as much as a thermosetting compound.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a thermosetting composition and a curing method capable of promoting a thermosetting reaction by combining a photocuring reaction with a thermosetting reaction which has been generally performed conventionally. To aim.

[0006]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have added a light absorbing compound to a thermosetting compound and have a spectrum at the absorption wavelength of the light absorbing compound. It was found that when light is irradiated, the absorbed light energy is converted into heat energy, and the thermosetting reaction is effectively promoted by functioning as a molecular heating element.
The present invention has been completed. That is, according to the present invention,
The composition comprises a combination of a light absorbing compound and a thermosetting compound to form a composition, which accelerates the thermosetting reaction by a photoreaction to efficiently cause the thermosetting reaction.

The light absorbing compound used at that time is 200
Any compound can be used as long as it has absorption in an arbitrary wavelength region of nm to 2000 nm and converts a part or all of light energy into heat energy, and examples thereof include a light absorber such as an ultraviolet absorber and various dye compounds. Among them, compounds having absorption in the visible light or near-infrared light region are preferable from the viewpoints of light transmittance, availability of irradiation source, and the like, and particularly preferable are compounds represented by the general formula (1). It is a cationic dye that absorbs in the infrared region. General formula (1); D ⁺ · A ⁻ (In the formula, D ⁺ is a cation having absorption in the near infrared light region, and A ⁻ represents various anions.)

Since near-infrared light has a longer wavelength than visible light, it has excellent light-transmitting properties, and contains various pigments and other shielding materials that cannot be transmitted by the ultraviolet light that has been conventionally used in photocuring reactions. Even a thick composition can sufficiently transmit light and uniformly heat the entire composition. The light absorbing dyes described above are conventionally colored compounds. When it is not preferable that the color of the dye remains in the cured product, a decoloring agent represented by the following general formula (2) can be used. General formula (2);

[0009]

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(In the formula, Z ⁺ represents a cation, and R ₁ , R
₂ , R ₃ and R ₄ are each independently an alkyl group, aryl group, allyl group, aralkyl group, alkenyl group, alkynyl group, silyl group, heterocyclic group, halogen atom, substituted alkyl group, substituted aryl group, substituted allyl group. Group, substituted aralkyl group, substituted alkenyl group, substituted alkynyl group or substituted silyl group)

The above decolorizing agent has a function of converting a dye into a colorless compound by a reaction with the photoexcited dye,
The addition of the decolorizer prevents the dye from impairing the color tone of the curable composition. Alternatively, near-infrared light absorbing dye (D ⁺ A
^The same effect can be obtained by using a dye in which the anion portion (A ⁻ ) of ⁻ ) is a quaternary boron salt represented by the general formula (3). General formula (3);

[0012]

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(In the formula, R ₅ , R ₆ , R ₇ and R ₈ are the same as the substituents of the general formula (2).) As an example of the use of the composition in the present invention, a conventional thermosetting material is used. The fields that have been developed are listed. For example, coating of resists, adhesives, dental materials, woodworking, furniture, etc., coating of metals, plastics, etc., coating of automobile bodies, interiors, bumpers, etc., inorganic material coating, molding of various thermosetting FRP, etc. The body etc. are mentioned. The shape of the curable composition is arbitrary, and not only a general solvent-dilutable thermosetting composition but also a solid thermosetting composition such as a powder coating can be used as the composition of the present invention.

Preferred cations (D ⁺ ) having absorption in the near infrared light region of the general formula (1) are, for example, cyanine, xanthene, oxazine, thiazine, diallylmethane, triallylmethane and pyrylium cations. Examples include cations of dyes. Typical examples of such cation dyes include cations shown in Table 1. The cation having absorption in near infrared light as used herein is a cation having absorption in the wavelength region of 740 nm or more, and preferably a compound having absorption in the wavelength region of 780 nm or more.

[0015]

[Table 1]

[Table 1]

Examples of visible light absorbing dyes include cations shown in Table 2.

[0017]

[Table 2]

A ⁻ in the general formula (1) which is a counter anion is an arbitrary anion, but as described above, from the viewpoint of not leaving the color tone of the dye in the cured product, 4 represented by the general formula (3) is used. Coordinated boron anions are particularly preferred.

Specific examples include n-butyltriphenylboron ion, n-octyltriphenylboron ion, n-butyltrianisylboron ion, di-n-dodecyldiphenylboron ion, tetraphenylboron ion, triphenylnaphthylboron ion. , Tetrabutylboron ion, tri-n-butyl (dimethylphenylsilyl) boron ion, and the like. More specifically, they have been previously filed (JP-A-5-194619 and JP-A-6-75).
No. 374) Anions and the like described in the patent specification can be mentioned. The cation (Z ⁺ ) of the decoloring agent represented by the general formula (2) is represented by the general formula (4), the general formula (4);

[0020]

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(In the formula, R ₉ , R ₁₀ , R ₁₁ and R ₁₂ are each independently a hydrogen atom, an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkenyl group, an alkynyl group, a heterocyclic group or a substituted alkyl group. Group, a substituted aryl group, a substituted allyl group, a substituted aralkyl group, a substituted alkenyl group, or a substituted alkynyl group), a quaternary ammonium cation or a quaternary pyridinium cation, a quaternary quinolinium cation, a phosphonium cation, or a sulfonium Examples thereof include cations, metal cations such as sodium, potassium, lithium, magnesium, calcium, etc., and specific examples of the decolorizing agent of the present invention have been previously filed (JP-A-6-75).
No. 374) Compounds described in detail in patent specifications and the like as sensitizers. These cationic dyes and decolorizers can be used alone or in admixture of two or more.

The thermosetting compound of the present invention is a polymer having a reactive functional group capable of being crosslinked and cured by a chemical reaction,
It is a mixture of oligomers or monomers. That is, the cured product is a group of compounds known as polyurethane resin, melamine resin, epoxy resin, polyester resin, silicone resin and the like. Examples of thermosetting compounds include blocked isocyanate, melamine, epoxy, organic acid,
Examples thereof include a compound having a functional group such as an acid anhydride, a mixture of a hydroxyl group capable of forming a chemical bond with the functional group and a compound capable of forming a chemical bond, an amino group-containing compound, and a compound capable of forming a silanol bond.

Specifically, a mixture of a (block) isocyanate compound capable of forming a urethane bond and forming a polyurethane resin and a polyol compound, and a mixture of a melamine compound and a polyol compound capable of forming a melamine bond and forming a melamine resin. , A polyorganic acid compound capable of forming an ester bond to form a polyester resin, a mixture of a polyorganic acid anhydride or a polyorganic acid ester compound and a polyol compound, an epoxy compound and a polyol compound capable of forming an epoxy resin, a polyamine compound Alternatively, a mixture with a polyorganic acid compound, a silanol group capable of forming a silanol bond, and a silanol group (having a protecting group) capable of forming a silanol group or a trialkoxysilyl group-containing compound and a polyol compound capable of forming a silanol group at the time of reaction Or poly Mixtures of amine compounds.

The compounds having two kinds of the reactive functional groups in the above combination in one molecule can be used alone, or two or more of the above combinations can be mixed and used. For example, it is possible to allow three types of functional groups, an epoxy group-containing compound, a silanol group-containing compound, and a hydroxyl group-containing compound, to be mixed in the reaction system and reacted. In the case of a compound capable of self-condensation such as a silanol group, it is not always necessary to mix a compound containing another functional group.

As the compound having the above-mentioned functional group, an acrylic resin, urethane resin, epoxy resin or the like in which the above-mentioned functional group is bonded, or an oligomer may be used. In the above combination, a polyphenol compound or a polymercapto compound may be used instead of the polyol compound. Compounds that are cured by these cross-linking reactions are described, for example, in the Coloring Materials Society, Vol. 65, August issue, page 511 (1
(1992 issue) and the like.

The curable composition of the present invention can be easily produced by adding and mixing a light absorbing compound to the above-mentioned conventionally known thermosetting compound. The curing reaction of the composition of the present invention is achieved by accelerating the cross-linking reaction by irradiation with light having a spectrum in the light absorption region of the light absorbing compound such as a mercury lamp, a metal halide lamp, a halogen lamp, a xenon lamp, and sunlight, and heating. However, especially when a near-infrared light absorbing compound is used, since the near-infrared light contains heat rays, it is possible to heat the composition to some extent without performing a special heating operation. Can achieve the object of the present invention only by irradiation with near infrared light. Further, it is of course possible to use external heating together to obtain a desired temperature, if necessary.

According to the curing method of the present invention, the heating energy is reduced, the curing time is shortened, and the curing reaction is uniform throughout the composition, as compared with the conventional curing method using only heating.
In the case of solid thermosetting compounds such as powder coatings, generally, the compound is heated and melted and then heated to a higher temperature to cause a thermosetting reaction, but an undesired curing reaction occurs during heating and melting. The problem is that the curing reaction temperature is high. The heating of the present invention at the molecular level to which the photoreaction is applied suppresses the thermosetting reaction before light irradiation and achieves a decrease in the curing temperature, thereby solving the above-mentioned problems in the thermosetting of a solid composition. .

Any pigment may be added to the composition of the present invention,
A coloring dye or the like can be added. As the pigments and coloring dyes to be added, various commercially available pigments such as black pigments such as carbon black and titanium black, white pigments such as titanium white and clay, aluminum powder, aluminum paste, titanium compounds, metal pigments such as silver powder. Other than pigments,
Known materials and the like described in various documents (for example, "Dye Handbook" edited by The Society of Synthetic Organic Chemistry, published in 1970, "Latest Pigment Handbook" edited by Japan Pigment Technology Association, published in 1976) can be used. When an additive such as a pigment having a high light shielding property is added, it is preferable to use light having a long wavelength as much as possible. When light having a short wavelength is used, the light may not sufficiently reach the inside of the effect product due to the shielding effect of the additive, and the effect of the present invention may not be sufficiently exhibited.

Further, optional additives and fillers can be added to the composition of the present invention. Examples of the additive here include a thickener, a leveling agent, a thixotropic agent, a dispersant and the like which are generally used as an additive for paints, and the filler includes powder, spherical and fibrous. Examples include organic substances, inorganic substances, and composites and mixtures of various shapes such as flakes, flakes, and scales.

Examples of the organic filler include those obtained by finely pulverizing a polymer, and examples of the inorganic filler include silica, silica-alumina, alumina, quartz, calcium carbonate, kaolin, talc and aluminum sulfate. , Barium sulphate, calcium sulphate, titanium oxide, calcium phosphate, etc. powder and the surface of these powders are polyfunctional (meta)
Examples thereof include those coated with an acrylate monomer or a silane coupling agent, and fibrous fillers such as glass fiber and carbon fiber. In the composite, the above inorganic filler is mixed with an ethylenically unsaturated compound,
Those finely pulverized after polymerization and curing may be mentioned. Further, two or more different kinds of fillers may be added separately, or may be added after mixing, without any problem.

The object of the present invention can be achieved by using the cationic dye represented by the general formula (1) in the present invention in an amount of 0.001% by weight or more based on the whole composition. If it is less than that, the thermosetting promoting function may be insufficiently completed. It is preferably in the range of 0.01 to 10% by weight. Even if a large amount of the cationic dye is used in excess of the solubility of the composition, the effect of adding the large amount is not sufficiently manifested, which is not preferable from the economical point of view. It is also possible to use two or more cationic dyes in combination.

When a boron compound which is a decoloring agent is used, it is preferably used in the range of 1: 1 to 1:10 (molar ratio) with respect to the dye. The decoloring effect can be sufficiently achieved by using an excessive amount with respect to the dye. Also,
The order of compounding the materials of the present invention is not particularly limited. It may be used as a so-called one-pack type compound, or as a so-called two-pack type compound, a thermosetting compound is separately prepared and a light absorbing compound (and a decoloring agent) is added to either or both compositions. There is no problem even if a mode of adding and mixing immediately before use is adopted.

[0033]

EXAMPLES The present invention will be described below with reference to examples. (Example 1) Polyol compound (trade name: Desmophen 67
0-80B) 25 g, ethyl acetate 20 g, 1% butyl acetate solution of dibutyl tin dilaurate as a curing agent 100 m
After thoroughly mixing g, 10.0 g of an isocyanate compound (trade name Sumidur N-3500, manufactured by Sumitomo Chemical Co., Ltd.), a near-infrared light absorbing cation dye (Table 1, complex number 3, anion is p-toluene sulfone). 0.1 g of acid anion) was added and stirred to prepare Sample 1. Aluminum substrate (15cm x 7c
m) was coated with the above sample to a thickness of 30 μm. The obtained test piece was provided with 30 halogen lamps having an output of 1500 W and having a spectral distribution in the wavelength range of 800 nm to 950 nm.
Irradiated for minutes. The temperature of the substrate surface is about 80 by light irradiation.
It has reached ℃. A blue colored cured product of a cationic dye was obtained.

Example 2 Sample 2 was prepared and a curing test was conducted in the same manner as in Example 1 except that 0.3 g of tetrabutylammonium n-butyltriphenylboron, a boron compound, was added to the composition of Example 1. . The temperature of the substrate surface became about 80 ° C. by the light irradiation. Due to the effect of the added boron salt in the cured product, the dye was decolored and a colorless and transparent coating film was obtained.

Comparative Example 1 Comparative sample 1 was prepared in the same manner as in Example 1 except that the near infrared absorptive cationic dye was not added.
Was prepared and a curing test was conducted to obtain a cured product. The surface temperature during curing was about 80 ° C. as in Example 1.

Reference Example 1 A reference sample was prepared in the same manner as in Comparative Example 1 except that the amount of a 1% butyl acetate solution of dibutyltin dilaurate as a curing agent was changed to 300 mg, and a curing test was conducted. It was heated at 80 ° C. for 30 minutes to obtain a cured product.

Example 3 A sample was prepared in the same manner as in Example 1 except that the amount of a 1% butyl acetate solution of dibutyltin dilaurate as a curing agent was changed to 300 mg, and a curing test was conducted. The irradiation time was 20 minutes. The surface temperature of the cured product was about 75 ° C. A cured product colored in blue of the dye was obtained.

[Evaluation of Curability] Curability evaluation tests of the coating films obtained in the above Examples and Comparative Examples were carried out. 1) Surface hardness Pencil hardness was measured. (measuring equipment:
HEIDON14) 2) Gel Fraction A part of the coating film was peeled off, and the mixture was heated under reflux in acetone for 2 hours for extraction. The percentage of insoluble matter was taken as the gel fraction. 3) Isocyanate reaction rate Changes in isocyanate groups before and after the reaction were measured by FT-IR. Reaction rate = (peak area before reaction) / (peak area after reaction) The results are shown in Table 3.

[0039]

[Table 3]

Equivalent curability can be obtained with a catalyst amount of 1/3 of Reference Example 1 (standard thermosetting formulation) (Examples 1 and 2).
With the same amount of catalyst (Comparative Example 1), curing is insufficient with heat alone. In Examples 1 and 2 and Comparative Example 1, the surface temperature during curing was 80.
It is presumed that the difference in curability despite the temperature being at the same level as ° C is because the dye of the present invention functions as a molecular heating element in the composition as described in the specification. Further, with the same catalyst amount, it is possible to shorten the curing time and the reaction temperature (Example 3).

Reference Example 2 Melamine-based thermosetting coating material (mixture of hydroxyl group-containing acrylic resin / melamine compound, product name Bellcoat 6000 manufactured by NOF Corporation, solid content 35%) 4
3 g of aluminum paste (trade name: 561PS, Showa Aluminum Powder Co., Ltd., aluminum content: 65%) was mixed with 7 g, and this coating material was applied to the same substrate as in Example 1 by the same method and cured. Heating at 140 ° C. for 30 minutes was required to fully cure.

(Example 4) A near-infrared light absorbing cation dye (Table 1 complex No. 1, anion is p-) was added to the coating material of Reference Example 2.
0.1 g of toluenesulfonic acid anion was added to prepare Sample 4. This coating material was applied to an aluminum substrate in the same manner as in Reference Example 2 and a curing test was conducted. When the substrate was heated to 140 ° C. and irradiated with near-infrared light, the curing time was shortened to about 20 minutes due to the effect of photoreaction, even though the aluminum paste having a high concealing property was contained.

[0043]

EFFECTS OF THE INVENTION The present invention provides a thermosetting composition and a curing method which can be cured in a short time or with a small amount of a catalyst as compared with the conventional thermosetting composition.

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Claims (4)

[Claims] 1. A thermosetting composition comprising a thermosetting compound and a light absorbing compound. 2. The thermosetting composition according to claim 1, wherein the light absorbing compound is a compound represented by the general formula (1) having absorption in the near infrared light region. General formula (1); D ⁺ · A ⁻ (In the formula, D ⁺ is a cation having absorption in the near infrared light region, and A ⁻ represents various anions.) 3. The thermosetting compound is at least one selected from an isocyanate compound, a polyorganic acid compound, a polyorganic acid anhydride, an epoxy compound and a melamine compound, and a polyol compound, a polyphenol compound, a polyamine compound or a polyamine compound. Mixture with at least one selected from mercapto group-containing compounds; Mixture of polyorganic acid compound with isocyanate compound or epoxy compound; or siloxane bond having silyl group bonded to silanol group or hydrolyzable protecting group The curable composition according to claim 1, which is at least one selected from the compounds capable of forming crosslinks according to 1. 4. The method of curing a composition according to claim 1, 2 or 3, wherein heat curing is accelerated by irradiating light having an absorption wavelength of the light absorbing compound.