JPH0351753B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a new and useful wood coating composition, and more particularly, the present invention relates to a novel and useful wood coating composition. The present invention relates to a composition that has excellent adhesion to wood materials and contains as an essential component a specific urethane acrylate compound obtained by reacting a (meth)acrylic acid ester with a polyhydric alcohol. The object of the present invention is that it does not require any undercoat for the purpose of providing adhesion to wooden materials, which is applied to wooden flooring materials, wooden wall materials, wooden furniture, etc. An object of the present invention is to provide a composition for coating wood materials, which can form a film having excellent adhesion upon irradiation with active energy rays. [Prior Art] To date, many paints have been proposed for the purpose of improving the durability and aesthetic appearance of such wood materials, and various coating methods and curing methods have also been proposed and put into practical use. Of these, most of the paints used for painting wood materials are various synthetic resin paints such as lacquer, aminoalkyd, urethane, polyester, or emulsion, and even if they are cured at room temperature, they cure at room temperature (naturally). Various methods are used, ranging from dry curing to heat curing. [Problems to be Solved by the Invention] With the conventional paints and curing methods as described above, excessive space is required for drying and curing, the production line becomes long,
In addition, there were various problems such as the long time required for curing, and there was a desire for the development of fast-curing paints and coating systems. Therefore, as UV-curable paint systems were developed to meet these demands, the curing time changed from a few seconds to several hours, compared to 30 minutes to 2 hours for heat curing and 12 to 72 hours for room temperature curing. The time has been shortened to about a minute, and along with this, the space and line length have also been significantly reduced. However, UV-curable coating systems to date have had major drawbacks. In other words, it was not possible to obtain a cured coating film by directly painting the wood material.
The reason for this is "Painting and Paints"'77 New (No.
278), pages 53 to 57 of the paper "Forced drying of wood coatings - especially UV and IR curing" is the most likely theory. Even today, eight years have passed since this document was published, according to the documents and product introductions published during that time, the paper from pages 99 to 110 of the November 1981 issue of "Painting Technology" Part 1 of “Technological trends of air-drying unsaturated polyester in wood coatings”
Pages 108 and 109, issues 69-74 of the same magazine, October 1983.
``Figure 1'' on page 73 of the article ``Coating film curing by ultraviolet rays'' and the article ``UV plywood for furniture'' on pages 50 to 62 of the December 1983 issue of ``Paints and Coatings.''
As can be seen in Figures 5 and 6 in ``Coating Systems,'' non-energy ray-curable non-coating agents are still being used on wood materials, which significantly impedes productivity. , which hinders such improvements in productivity. [Means for Solving the Problems] However, as a result of intensive studies by the present inventors in order to solve the problems in the prior art as described above, the present inventors have developed a method that contains a specific urethane acrylate compound as an essential component as described below. The present invention was completed by discovering a coating material composition that has excellent adhesion to wood materials. That is, the present invention is an essential component obtained by reacting a polyisocyanate having two or more isocyanate groups in one molecule with a hydroxyl group-containing acrylic ester or methacrylic ester, or Acrylic ester or methacrylic ester,
In the resin solid content obtained by reacting with a polyhydric alcohol having two or more hydroxyl groups in one molecule.
The present invention provides a coating composition with excellent adhesion to wood, comprising a urethane acrylate compound containing 1.5 to 15% by weight of free isocyanate groups. First, the polyhydric alcohols mentioned above are ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,
3-butylene glycol, 1,4-butylene glycol, neopentyl glycol, 1,6-hexanediol, 2,2,4-trimethyl-1,3
-pentanediol, cyclohexanediol,
In addition to bisphenol A, hydroxypivalyl hydroxypivalate, hydrogenated bisphenol A, trimethylolethane, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol or dipentaerythritol, these alcohols It refers to a compound obtained by chlorination or bromination, a compound obtained by converting the alcohol or bisphenol A into a polyoxyalkylene ether with ethylene oxide, propylene oxide, tetrahydrofuran, etc. Polyester polyols obtained by esterifying one or more of the various polyhydric alcohols or polyols listed above with one or more known and commonly used polybasic acids are also the same as the polyhydric alcohols referred to in the present invention. Of course, it can be used for. Typical such polybasic acids include adipic acid, succinic acid, sebacic acid, azelaic acid,
Maleic acid, fumaric acid, itaconic acid, 2,2,4
- Trimethyladipic acid, orthophthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, citraconic acid, muconic acid, oxalic acid, malonic acid, glutaric acid or trimellitic acid or anhydrides thereof. In carrying out the above-mentioned esterification, polyols such as those listed above, as well as bisphenol A diglycidyl ether, neopentyl glycol diglycidyl ether, triglycidyl ether, which is a condensate of bisphenol A, a polybasic acid, and epichlorohydrin, are used. Monovalent or polyvalent epoxy compounds such as methylolpropane triglycidyl ether, phthalic acid diglycidyl ether, butyl glycidyl ether, phenyl glycidyl ether, benzoic acid glycidyl ester, etc. can also be used as a component of the polyhydric alcohol. Of course, it can also be used. Further, as the polyhydric alcohol, compounds obtained by polycondensation of the aforementioned polyols and/or polyester polyols with lactones such as ε-caprolactone or γ-butyrolactone can also be used. Among these polyhydric alcohols as mentioned above,
When considering the balance between curability, adhesion to the wood material base, and physical properties of the coating film, it is particularly preferable that the number of hydroxyl groups contained in one molecule is within the range of 3 to 5 on average. On the other hand, when the number of such hydroxyl groups is 2 on average, the curability decreases and the physical properties of the coating film tend to deteriorate, but the adhesion can be maintained, which is one of the objects of the present invention. It goes without saying that such polyhydric alcohols can be used satisfactorily from the viewpoint of adhesion to wood materials. Further, when the number of hydroxyl groups in one molecule is 6 or more, there is a problem in practical terms because viscosity increases or gelation occurs during synthesis, so special care must be taken. The molecular weight of the polyhydric alcohol is 100~
It is preferably within the range of 3,000, and particularly preferably within the range of 200 to 2,000 in order to obtain fast curing properties and tough coating film properties. By the way, when comparing polyether-based compounds and polyester-based compounds among the polyhydric alcohols, the latter has excellent adhesion to the substrate and toughness of the coating film, and in particular, polycaprolactone Ester can control the molecular weight distribution and the number of hydroxyl groups contained in one molecule, and as a result, it is a urethane that has low viscosity, fast curing, strong coating properties, and even better adhesion. Polyhydric alcohols are particularly desirable because they provide acrylate compounds. Next, typical examples of the above-mentioned hydroxyl acrylic esters or methacrylic esters include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl (meth)acrylate. Hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate
Mono(meth)acrylates of dihydric alcohols such as acrylates; trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, di(meth)acrylate of tris(hydroxyethyl)isocyanuric acid, pentaerythritol tri(meth)acrylate Partial (meth)acrylates of trihydric or higher alcohols such as acrylates; epoxy esters of (meth)acrylic acid and monoepoxy compounds such as butyl glycidyl ether, allyl glycidyl ether, glycidyl methacrylate or benzoic acid glycidyl ester; or There are lactone-modified hydroxyl group-containing compounds obtained by reacting each compound with ε-caprolactone or γ-butyrolactone. Among these hydroxyl group-containing (meth)acrylic esters, 2-hydroxyethyl (meth)acrylate , 2-hydroxypropyl (meth)acrylate, caprolactone-modified products of 2-hydroxybutyl (meth)acrylate, or (meth)acrylic acid esters of monoepoxy compounds are urethane because the number of hydroxyl groups in one molecule is one. During the preparation of the acrylate compound, the molecular weight does not increase, and therefore a low viscosity product can be obtained, which is particularly desirable in terms of controlling the various performances of the composition of the present invention. Furthermore, typical polyisocyanates mentioned above include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isophorone diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and diphenylmethane. -4,4'-diisocyanate, 3-methyl-diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4-diisocyanate or lysine diisocyanate, or each of these diisocyanates Diisocyanates such as hydrogenated xylylene diisocyanate or hydrogenated diphenylmethane-4,4'-diisocyanate obtained by hydrogenating aromatic diisocyanates; or "Burnok DN-970"
[Dainippon Ink & Chemicals Co., Ltd. product]
24A-100 [produced by Asahi Kasei Industries, Ltd.], [Sumideur L-100] [produced by Sumitomo Bayer Co., Ltd.], or "Coronate EH" [produced by Nippon Polyurethane Industries Co., Ltd.]. Among them, 2,4-tolylene diisocyanate or isophorone diisocyanate is suitable for the desired urethane acrylate because the reaction rate of each isocyanate group contained in the molecule is significantly different. It is possible to carry out the urethanization reaction selectively at the stage of compound preparation, and is therefore particularly desirable for obtaining urethane acrylate compounds with low viscosity and excellent curability and coating properties. be. In contrast, other polyisocyanates, i.e.
When using isocyanate groups with little difference in reactivity, unreacted isocyanate tends to remain in the end, resulting in health problems.
In terms of safety, it is harmful, the type and molar ratio of the polyhydric alcohols to be combined are severely restricted, and furthermore, it tends to become extremely viscous.
In some cases, it may even gel, so special care must be taken. Therefore, in the reaction between polyisocyanate having isocyanate groups having almost the same reactivity and the polyhydric alcohol, there is not much difference in the reactivity of each isocyanate group. but
It is particularly desirable to use it in a proportion of 1.5 mol or more, preferably 2.0 mol or more, and to react with the hydroxyl group-containing (meth)acrylic acid ester after removing unreacted isocyanate after the completion of the reaction. In addition, when a monomeric polyisocyanate is used to prepare the desired urethane acrylate without using the polyhydric alcohol,
This is undesirable since unreacted isocyanate inevitably comes out, and it goes without saying that it is also desirable to use purified polyisocyanate in this case as well. The above-described isocyanate group-containing urethane acrylate compound, which is an essential component of the composition of the present invention, can be prepared using the raw material components listed above according to known and commonly used methods.
First, the polyisocyanate is 0.8 to 1 equivalent of the hydroxyl group in the polyhydric alcohol or the hydroxyl group-containing (meth)acrylic ester.
in a proportion of 2.0 mol, preferably 1.0 to 1.2 mol,
After obtaining the intermediate by a conventional method, the amount of the hydroxyl group-containing (meth)acrylic ester is determined by adjusting the free isocyanate group concentration (isocyanate group content) in the solid content of the target urethane acrylate compound.
is determined to be within a range of 1.5 to 15% by weight, preferably 1.5 to 12% by weight, particularly preferably 2.0 to 10% by weight, and added to the above intermediate to continue the urethanization reaction, The reaction may be completed when the concentration of the remaining isocyanate groups no longer changes, or the polyisocyanate and the hydroxyl group-containing (meth)acrylic ester may be reacted in advance, and then the polyhydric alcohol may be reacted with the polyisocyanate. Alternatively, a method may be used in which a hydroxyl group-containing (meth)acrylic ester is added and the reaction is caused. Furthermore, it is also possible to react the polyisocyanate and the hydroxyl group-containing (meth)acrylic ester at the same time, or to react the polyisocyanate and the hydroxyl group-containing (meth)acrylic ester at the same time. Of course, it is also possible to use a method in which the meth)acrylic acid ester and the polyhydric alcohol are reacted at the same time, that is, in one urethanization reaction step. However, when using polyhydric alcohol,
As described above, 2,4-tolylene diisocyanate or isophorone diisocyanate is suitable as the polyisocyanate, but if such a polyisocyanate is not used, a large excess of polyisocyanate is used to remove unreacted polyisocyanate after the reaction. It is desirable to remove the polyisocyanate before proceeding to the next step in order to obtain the desired urethane acrylate compound suitable for practical use. In addition, if one-time urethanization reaction step is desired, the amount of polyhydric alcohol used should be kept as low as possible, or it should not be used at all. It is necessary to avoid viscosity. In preparing the urethane acrylate compound, a known and commonly used catalyst such as an organotin compound such as dibutyltin diacetate or dibutyltin dilaurate can be used to accelerate the urethanization reaction. In order to inhibit polymerization of the (meth)acryloyloxy groups in the urethane acrylate compound, polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, catechol, phenothiazine or benzoquinone can also be added. In addition, the preparation of the urethane acrylate compound does not require any special operations and can be done very easily as long as the well-known and commonly used method as described above is followed, but unreacted polyisocyanate remains until the end. From this point on, one must be very careful about the occurrence of side reactions. In other words, never add substances that are reactive to polyisocyanate or that promote side reactions that cannot be predicted with common knowledge, such as water in the system or amines. This means that it must not be done. The urethanization reaction during the preparation of the urethane acrylate compound is monitored according to the amount of residual isocyanate groups (unreacted polyisocyanate) detected. It is also possible to use a calibration curve method using absorption near 2240 cm ^-1 in the absorption spectrum. Therefore, unless there is any abnormality in each raw material component itself or in the urethanization reaction itself, once the hydroxyl groups that should react with the polyisocyanate disappear, the isocyanate group concentration will no longer change, and the urethanization reaction will stop. However, if any abnormality is observed, the isocyanate group concentration will continue to decrease, and it will remain largely unknown using both amine back titration and infrared absorption spectroscopy. The result is completely different from the isocyanate group-containing urethane acrylate compound desired in the present invention, and therefore has no properties in terms of adhesion to wood substrates, viscosity, curing properties, etc. In order to prevent the product from showing any superiority, the management of each raw material component and the urethanization reaction process must be strictly checked. The isocyanate group-containing urethane acrylate compound thus obtained, which is an essential component of the wood material coating composition of the present invention, has a resin solid content of 1.5
~15% by weight, preferably 1.5-12% by weight, particularly preferably 2.0-10% by weight of free isocyanate groups should be contained; if this isocyanate group concentration is less than 1.5% by weight, this is unavoidable. Adhesion to wood materials, which is one of the purposes of the invention, will be significantly reduced, and conversely, 15% by weight
If it exceeds 20%, the curing speed becomes low and the physical properties of the coating film also deteriorate, which is not preferable. The coating material composition of the present invention may further contain various substances required to make the composition of the present invention more practical, if necessary. That is, for example, (1) organic solvents inert to isocyanate groups - acetate esters such as ethyl acetate, propyl acetate, butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, dibutyl ketone, isophorone; Aromatic hydrocarbons such as toluene and xylene; Alkyl (poly)alkylene glycol acetates such as cellosolve acetate and carbitol acetate; "Solbetsuso #100, #150" [products of Exxon Chemical Co., Ltd.] and "Swazol # Various mixed solvents such as ``310'' [product of Maruzen Sekiyu Co., Ltd.]; and aliphatic hydrocarbons that are mixed solvents, have tolerance, and do not impair the transparency of the coating film when evaporated. Known and commonly used organic solvents used in general-purpose paints, which can be used without impairing the excellent properties of the isocyanate group-containing urethane acrylate compound, which is an essential component of the composition of the present invention, (2) ) A monomer or prepolymer that is inert to isocyanate groups and radically polymerizable with the urethane acrylate compound which is an essential component - an aliphatic, alicyclic or araliphatic (ether bond-containing) polyvalent Alcohol (meth)acrylates; aromatic divalent ~
(meth)acrylates of alkylene oxide adducts of hexahydric polyhydric alcohols; mono- or poly(meth)acryloyloxyalkyl phosphates; polyester (meth)acrylates; polyurethane (meth)acrylates; polyamide (meth)acrylates Class; polysiloxane (meth)
Acrylates; vinyl or diene low molecular weight (co)polymers having (meth)acryloyloxy groups at the end or side chain of the main chain; modified products of various polymerizable (meth)acrylates as listed above; or allyl compounds etc., and the amount of such monomers or prepolymers to be used is 100 parts by weight or less per 100 parts by weight of the solid content of the isocyanate group-containing urethane acrylate compound, which is an essential component of the present invention, especially for adhesion to wood materials, curing, etc. In order not to impair the properties and physical properties of the coating film.
(Meth)acrylic acid; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl, which is used in a proportion of 80 parts by weight or less. (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate , ethoxydiethylene (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene Glycol (meth)acrylate, Alkylphenoxyethyl (meth)acrylate, Alkylphenoxypolyalkylene glycol (meth)acrylate, Tetrahydrofurfuryloxypolyalkylene glycol (meth)acrylate, Dicyclopentenyl (meth)acrylate, Dicyclo Pentenyloxyalkyl (meth)acrylate, dicyclopentenyloxypolyalkylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate ) acrylate, hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol ester di(meth)
Acrylate, di(meth)acrylate of ethylene oxide adduct of bisphenol A, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, lactone-modified product of polyhydric alcohol (meth)
various (meth)acrylic acid esters such as acrylate, carbamoyloxyalkyl (meth)acrylate, polyfluoroalkyl (meth)acrylate, cyclohexyl (meth)acrylate or benzyl (meth)acrylate; or specific examples such as vinyl acetate or vinyl propionate. In addition to known and commonly used reactive diluents, (3) compounds known as radically polymerizable oligomers or prepolymers as described in various literature and catalogs; Photopolymerization initiator and/or photosensitizer used in polymerization - benzoin methyl ether, benzoin ethyl ether, benzoin n-(iso-)
Propyl ether, benzoin n-(iso-)butyl ether, benzyl, benzophenone, p-
Chlorbenzophenone, p-methoxybenzophenone, 4'-isopropyl-2-methyl-propiophenone, α,α-dichloro-4-phenoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal ,2,
Known and commonly used photopolymerization methods such as 2-diethoxyacetophenone, chlorothioxanthone, isopropylthioxanthone, diethylthioxanthone, diisopropylthioxanthone, "Juvecryl P36" (radically polymerizable high molecular weight benzophenone manufactured by UCB, Belgium), etc. is an initiator, and 4
-Ethyl dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 4,4-bisdiethylaminobenzophenone, "Uvecryl P104"
(Radical polymerizable high molecular weight tertiary amine compound manufactured by the same company), N-methyldiethanolamine,
A urethane acrylate compound which is a known and commonly used photosensitizer, specific examples of which include diethylaminoethyl methacrylate, triethylamine, etc., and which is an essential component of the composition of the present invention, is used in the amount of the photopolymerization initiator and/or photosensitizer. 0.01 to 10 parts by weight, preferably 0.05 to 8 parts by weight per 100 parts by weight of solid content.
(4) Radical polymerization initiator used in thermosetting the composition of the present invention - ketone peroxide, hydroperoxide, dialkyl hydroperoxide, diacyl peroxide or peroxy ester; Typical examples include organic peroxides such as those described above, or diazo compounds. However, when heat curing and photocuring (photopolymerization) are used together, photopolymerization initiators such as those listed above and organic peroxides such as those described above are used. (5) Synthetic resins that are inert to isocyanate groups and do not have radical copolymerizability - typified by acrylic resins, ketone resins, petroleum resins, etc. (6) organic or inorganic extender pigments, fillers such as erasing agents or sanding aids, and (7) other various additives used in general-purpose paints.
Examples include leveling agents, pigment dispersants, brightening agents, slip agents, and thixotropic agents. After coating, the thus obtained composition for coating wood materials of the present invention is rapidly cured by exposure to heat, ultraviolet rays, or electron beams after pre-drying if necessary, and is effective against wood materials. It not only provides good adhesion, but also provides good physical properties of the coating film. Here, wood materials include cherry, red oak,
Chinese rosewood, Chinese quince, mahogany, lauan, mulberry, boxwood, Japanese oak, yellowfin tuna, Japanese oak, wig, zelkova, walnut, camphor tree, oak, teak, persimmon, Japanese wig, Japanese cedar, black oyster, ebony, striped ebony, horse chestnut, maple, willow, Natural wood such as ash, processed wood itself such as plywood, laminate, particle board, or printed plywood, or building materials and furniture made from such natural or processed wood such as flooring, furniture, and wall materials. This refers to what is used in the field. In addition, ultraviolet rays include sunlight, xenon lamps, metal halide lamps, low pressure mercury lamps, medium pressure mercury lamps,
Various light sources such as high-pressure mercury lamps or ultra-high-pressure mercury lamps are used as radical sources, while electron beams use, for example, 20 to 2000 kV electron beam sources as radical sources.Active energy rays such as ultraviolet rays and electron beams are The irradiation atmosphere is an inert gas atmosphere such as nitrogen gas or carbon dioxide gas,
Alternatively, an atmosphere with a reduced oxygen concentration is of course preferable, but a normal air atmosphere may also be used. The temperature of the irradiation atmosphere may be room temperature, or heat may be used for the curing reaction by actively heating, but in order to use the composition of the present invention,
Usually, an irradiation atmosphere temperature in the range of 0 to 200°C is suitable. Of course, each of the above radical sources may be used alone or in combination of two or more in any order. The composition of the present invention has groundbreaking significance in that it can beautifully solve the current problems mentioned above, especially when used after being painted and cured on wood materials. The target objects to be used are by no means limited to only wood materials, and can of course be applied to various materials other than wood materials such as metal, plastic, glass, or paper, as well as various materials other than wood materials and the wood material concerned. The composition of the present invention is coated on the surface of a treated material that has been previously treated with a plurality of materials to be combined with the material, for example, by a known and commonly used means such as printing, painting, vapor deposition, or ion plate, and then dried and hardened. It is also possible to apply the composition of the present invention to a material that has been once coated with the composition of the present invention and cure it, or to apply another coating agent other than the composition of the present invention. Of course, it is also possible to apply multiple coats of paint. As a method for applying the composition of the present invention, known and commonly used means such as brush coating, roll coater method, flow coater method, spraying method or dipping method can be employed. [Example] Next, the present invention will be specifically explained using reference examples, examples, and comparative examples. In the following, all parts and percentages are based on weight unless otherwise specified. Reference Examples 1 to 29 Polyhydric alcohols (PO-1 to PO-11) and polyisocyanates (PI-1 to PI-6) as shown in Table 1 were prepared using a flask equipped with a stirrer, thermometer, and condenser. ), using hydroxyl group-containing (meth)acrylic esters (HA-1 to HA-6),
Various isocyanate group-containing urethane acrylate compounds were prepared according to reaction method A or B as described below. Reaction method A: Charge the amount of polyisocyanate shown in Table 2 and react with stirring for about 50 minutes.
℃, then gradually add the amount of polyhydric alcohol shown in the table while being careful not to generate heat, maintain the temperature at 70℃ for 4 hours, and then add the amount of polyhydric alcohol shown in the table. A method in which a hydroxyl group-containing (meth)acrylic acid ester is added, and the reaction is continued at the same temperature until the isocyanate group concentration no longer changes.Reaction method B: Polyisocyanate in the amount shown in Table 2 about 50 minutes while stirring.
The temperature was raised to 70°C, and then the amount of hydroxyl group-containing (meth)acrylic ester shown in the table was gradually added while being careful not to generate heat. Then, at a temperature of 70°C, the isocyanate group concentration no longer changed. A method that allows the reaction to continue until it runs out. In the same table, the type and amount of each raw material component, the reaction method as listed above, and the isocyanate concentration per solid content of the obtained urethane acrylate compound are collectively shown. As is clear from the results shown in the same table, in the cases of Reference Examples 6, 8, 9, and 10, gelation occurred during the first stage reaction, and the target urethane acrylate compound could not be obtained. First, in Reference Example 6, the number of functional groups in the polyhydric alcohol was 6, which is considered to be because the risk of gelation exceeded the limit, and in Reference Examples 8 to 10, the polyhydric alcohol used This is thought to be because the reactivity of the isocyanate groups in the isocyanates was the same or the number of functional groups was high, which was also outside the allowable limit for synthesis.

【table】

【table】

【table】

【table】

[Table] Examples 1 to 26 and Comparative Examples 1 to 8 Obtained in each reference example (containing isocyanate groups)
A photopolymerizable composition was prepared using a urethane acrylate compound according to the proportions shown in Table 5, and was coated on beech veneer plywood as a material using a No. 28 bar coater. After drying, it was irradiated with ultraviolet light. Each of the thus obtained painted plates was used as a test piece, and each of these test pieces was heated to 23℃±2℃.
After being left for 24 hours at room temperature and humidity of 73±5%, an adhesion test was conducted. At that time, the beech wood used was coated with #240 sandpaper, and pre-drying was performed at room temperature for 3 minutes, then at 40℃ for 1 minute, and then exposed to ultraviolet light. The irradiation was carried out twice using a high-pressure mercury lamp with an intensity of 80 W/cm at a distance of 20 cm below the lamp and at a conveyor speed of 5 m/min. Then, the adhesion test was done using a cutter knife for 2mm.
Create 25 squares on the painted surface of the painted board (test piece) so that the six grooves are perpendicular to the interval.
When "Scotchi Tape" (product of Sumitomo 3M Ltd.) is pasted on these squares and then peeled off, the following results are obtained based on the number of squares where the film remains on the material (veneer plywood). It is evaluated on a five-point scale. 1...The number of squares remaining as a film is 0-5 2... 〃 〃 6-10〃 3... 〃 〃 11-15〃 4... 〃 〃 16-20〃 5... 〃 〃 21-25〃 Regarding the results of the adhesion test (Table 3), in the case of Examples 4 to 6 using polycaprolactone polyol, overall the effect was remarkable, and the free isocyanate group concentration was within a specific range. Remarkable effects are also shown in Examples 8 to 13 and Examples 21 to 25. On the other hand, all of the comparative examples in which the concentration of isocyanate groups deviates from the specific isocyanate group concentration range are bad, and as in the case of comparative examples 6 to 8, the reaction diluent and polyisocyanate were not added properly. It is known that it is not possible to improve this adhesion.

【table】

〔Effect of the invention〕

By using the composition for coating wood materials of the present invention, it becomes possible to cure the paint without requiring the conventional two-component or one-component undercoat, and it exhibits excellent adhesion to the substrate. Moreover, since these can be carried out in an extremely short time, it is possible to shorten long lines and eliminate stockyards, which have been desired to be solved, especially in the painting industry mainly related to wood materials and processing. We can expect a great contribution to the industry.

Claims (1)

[Claims] 1. A polyisocyanate having two or more isocyanate groups in one molecule and a hydroxyl group-containing acrylic ester or a hydroxyl group-containing methacrylic ester, or the above polyisocyanate and the acrylic ester or methacrylic acid. Contains as an essential component a urethane acrylate compound containing 1.5 to 15% by weight of isocyanate groups in the resin solid content, which is obtained by reacting an ester and a polyhydric alcohol having two or more hydroxyl groups in one molecule. A coating material composition with excellent adhesion to wood materials. 2. The composition according to claim 1, wherein the polyisocyanate having two or more isocyanate groups in one molecule is 2,4-tolylene diisocyanate. 3. The composition according to claim 1, wherein the polyisocyanate having two or more isocyanate groups in one molecule is isophorone diisocyanate. 4 The hydroxyl group-containing acrylic ester or hydroxyl group-containing methacrylic ester described above has the general formula [However, R ₁ and R ₂ in the formula represent a hydrogen atom or a methyl group, which may be the same or different. ] The composition according to claim 1, characterized in that it is a 2-hydroxyalkyl (meth)acrylate represented by the following. 5 The hydroxyl group-containing acrylic ester or hydroxyl group-containing methacrylic ester described above has the general formula [However, R ₁ and R ₂ in the formula represent a hydrogen atom or a methyl group, which may be the same or different, m is an integer from 3 to 5, and n is an integer from 1 to 5. shall be. ] The composition according to claim 1, characterized in that it is a caprolatone modified product of 2-hydroxyalkyl (meth)acrylate. 6 The hydroxyl group-containing acrylic ester or methacrylic ester described above has the general formula [However, R ₁ in the formula represents a hydrogen atom or a methyl group, and X represents a monovalent organic group such as an acryloyl group, a methacryloyl group, a phenyl group, an alkylphenyl group, a benzoyl group, or an alkylbenzoyl group. Claim 1, characterized in that it is at least one compound selected from the group consisting of (meth)acrylic esters of monoglycidyl ethers and (meth)acrylic esters of monoglycidyl esters represented by The composition described in Section. 7. The composition according to claim 1, wherein the polyhydric alcohol having two or more hydroxyl groups in one molecule is a trifunctional or higher functional polycaprolactone ester.