JPH0479801B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a novel photocurable resin composition for coating wood. [Prior art] Various wood coatings have been used for the purpose of making wood beautiful and giving it durability, and thermosetting amino alkyd resin coatings have been widely used mainly due to cost. . However, aminoalkyd resin coatings have drawbacks such as a long curing time and the generation of formalin odor not only during curing but also after being left to cure. In recent years, photocurable coatings have been actively investigated and used in an attempt to overcome the above-mentioned drawbacks. Although photocurable coatings themselves are generally expensive, the application of an ultraviolet curing system makes it relatively easy to streamline the coating process and improve productivity.
After all, if the total cost is taken into account, the drawbacks of the coating material itself in terms of price can be overcome. In particular, polyurethane-based photocurable resins are expected to be suitable as binders for wood coatings because they have excellent coating film properties after curing, such as flexibility, abrasion resistance, and chemical resistance. However, it has been pointed out that polyurethane-based photocurable resins generally have poor wettability to wood during coating, and in extreme cases may cause repellency on the coated surface. Therefore, there is a demand in this field for the development of a polyurethane-based photocurable resin composition that has excellent coating suitability for wood. [Problems to be Solved by the Invention] The present invention has been made in order to solve the above-mentioned problems that could not be solved by the prior art. Therefore, the present inventors have conducted extensive research in order to develop an excellent photocurable resin composition for wood coating that can simultaneously satisfy all of the performances of curing speed, physical properties of the coating film, and coating suitability. As a result, it has been found that all of the above problems can be solved by using a specific polyfunctional compound having a rosin component. The present invention was completed based on this new knowledge. [Means for solving the problems] The present invention provides a reaction product (a) of (meth)acrylic acid and rosin glycidyl ester, diisocyanates
(b) and a (meth)acrylic acid ester monomer (c) containing a hydroxyl group, consisting of a reaction product (a) of (meth)acrylic acid and rosin glycidyl ester and a (meth)acrylic acid containing a hydroxyl group. The total amount of ester monomer (c) charged is 1.8 to 2.2 mol per 1 mol of diisocyanate (b), and the reaction product (a) of (meth)acrylic acid and rosin glycidyl ester is charged. Photocuring for wood coating characterized by containing as a main component a reaction product in an amount of 0.5 to 2.0 mol per 1 mol of the (meth)acrylic acid ester monomer (c) containing a hydroxyl group. The present invention relates to a synthetic resin composition. [Example] The photocurable resin composition for wood coating of the present invention contains a reaction product of (meth)acrylic acid and rosin glycidyl ester (hereinafter referred to as component (a)), diisocyanates (hereinafter referred to as component (b)). ) and a (meth)acrylic acid ester monomer containing a hydroxyl group (hereinafter referred to as component (c)).
It contains as a main component a produced resin). The above component (a) is a reaction product of (meth)acrylic acid and rosin glycidyl ester, and has the general formula
(1)： (In the formula, R ¹ is a rosin residue, and R ² is a hydrogen atom or a methyl group.) The rosins used here are determined by considering the UV curing speed of the resulting resin, the color tone, etc., and are usually treated to stabilize conjugated double bonds, such as hydrogenated rosin or disproportionated rosin. rosin is suitable. As mentioned above, component (a) can be obtained by esterifying (meth)acrylic acid and rosin glycidyl ester. In addition, known polymerization inhibitors such as phenols, quinones, and phenothiazine can be appropriately selected and used. The molar ratio of (meth)acrylic acid to rosin glycidyl ester is stoichiometrically set to 1:1, but industrially it may range from 1:0.9 to 1:1.1. The amount of esterification catalyst used is (meth)
0.1 to 2 parts by weight per 100 parts by weight of the total amount of acrylic acid and rosin glycidyl ester, and the amount of polymerization inhibitor used is 0.001 parts by weight per 100 parts of the total amount.
The amount is preferably 0.5 parts by weight. The reaction temperature is usually
The temperature may be 80 to 130°C, and the reaction time is determined by monitoring the oxidation of the product, and is usually 3 to 10 hours. The component (b) is a diisocyanate, and any conventionally known one can be used as is. Specific examples of these include isophorone diisocyanate,
Examples include diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, phenylene diisocyanate, hydrogenated xylylene diisocyanate, and xylylene diisocyanate. However, in order to obtain a highly pure compound having a free isocyanate group at the end by selectively reacting with component (a), one of the isocyanate groups in component (b) is required to react with component (a). It is desirable that the isocyanate groups present in component () are not equivalent, and in view of this, isophorone diisocyanate and tolylene diisocyanate are preferred among the above. The component (c) is a (meth)acrylic acid ester monomer containing a hydroxyl group, and specific examples thereof include 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxyethyl acrylate.
- Mono(meth)acrylates with one hydroxyl group in the molecule, such as hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, glycerin diacrylate, glycerin dimethacrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate. , di(meth)acrylate, tri(meth)acrylate, etc. The usage amounts of component (a), component (b) and component (c) are as follows:
It can be appropriately selected within the following ranges. That is, the total amount of components (a) and (c) is 1.8 to 2.2 moles, preferably 1.9 moles per mole of component (b).
-2.1 mol, and the amount of component (a) charged is 0.5 to 2.0 mol, preferably 0.8 to 1.2 mol, per 1 mol of component (c) charged. If the former molar ratio is less than 1.8, free isocyanate groups will remain at the molecular ends of the resulting resin, and if it exceeds 2.2, components (a) and (b) will remain unreacted in the resulting resin. Both are undesirable as they will remain as they are. On the other hand, if the latter molar ratio is less than 0.5,
The amount of rosin contained in the produced resin becomes too small,
In the end, it is not preferable because the coating suitability, which is a characteristic of the photocurable resin composition of the present invention, cannot be fully exhibited.
If it exceeds 2.0, the flexibility and abrasion resistance of the resulting photocurable resin composition tend to decrease, so both are unfavorable. Next, a method for producing the resulting resin, which is the main component of the composition of the present invention, will be explained. That is, it can be produced according to the following method using each of the components (a), (b), and (c) within the ranges described above. That is, after obtaining a compound having a free isocyanate group at the end by adding and reacting component (b) in the presence of component (a), the compound is then reacted with component (c). The resulting resin is obtained. Since this reaction is essentially a reaction between an isocyanate group and a hydroxyl group, if the reactivity of the isocyanate group in component (b) is equivalent, component (a) will react with both ends of component (b). Therefore, it is not always easy to selectively leave free isocyanate groups at the ends of the molecules, resulting in the production of some by-products. However, if tolylene diisocyanate, isophorone diisocyanate, etc. are used as component (b), the desired intermediate can be easily obtained due to the difference in reactivity of both isocyanate groups. The reaction conditions at this time are determined as appropriate by monitoring the NCO value, and usually the reaction temperature is 50-100℃ and the reaction time is 1.
~5 hours. Then the intermediate and (c)
In such a case, the same conditions as those for producing the intermediate can be set. Of course, in the above method, the order of adding components (a) and (c) can also be reversed. It is also possible to react the components (a), (b) and (c) at the same time. In addition, when any reaction method is adopted, the viscosity can be adjusted during the reaction by using a reactive diluent such as trimethylolpropane triacrylate or tetraethylene glycol diacrylate, if necessary. The coating material of the present invention can be easily prepared from the resulting resin thus obtained by appropriately adding known formulations. For example, trimethylolpropane triacrylate, tetraethylene diacrylate, bisphenol A tetraoxyethylene diacrylate, etc. can be used as a reactive diluent, and benzophenone, 1-hydroxycyclohexyl phenyl ketone, etc. can be used as a photosensitizer. 2,2-dimethoxy-2-phenylacetophenone and the like can be used. Further, a coloring agent, a matting agent, a defoaming agent, a leveling agent, etc. may be used as appropriate. The thus obtained coating material of the present invention can be suitably used as a wood coating material by utilizing its photocurability. Of course, conventional urethane-based photocuring resins can also be used in combination without impairing the features of the present invention. Furthermore, the coating material of the present invention can be used in a wide range of applications other than those described above, such as printing ink, overprint varnish for paper coating, solder resist, etc. Hereinafter, the present invention will be explained in detail with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to these examples. In each example, all parts and percentages are based on weight unless otherwise specified. Reference example (manufacture of rosin epoxy acrylate) Into a reaction vessel equipped with a thermometer, a cooling tube, a nitrogen introduction tube, and a stirrer, 2568 parts (5.81 mol) of disproportionated rosin glycidyl ester after nitrogen substitution, 98
% acrylic acid (5.81 mol), 3.0 parts of benzyl trimethyl chloride as an esterification catalyst, 3.0 parts of hydroquinone monomethyl ether (hereinafter referred to as HQME) as a polymerization inhibitor, and 3.0 parts of phenolthiazine, and heated at 105 to 115°C under a nitrogen stream.
The reaction was completed over 6 hours. The reaction product had an acid value of 4.8 and a brown transparent balsamic appearance.
The molecular weight of the obtained rosin epoxy acrylate is
It was 514. Example 1 The rhodiepoxy acrylate as component (a) was placed in a reaction vessel equipped with a thermometer, a cooling tube, and a stirrer.
521.5 parts, 223.3 parts of isophorone diisocyanate (hereinafter referred to as IPDI) as component (b), and tetraethylene diacrylate (hereinafter referred to as
4EGA) and HQME1.2 and heated to 50℃.
The mixture was reacted for 0.5 hour, then the temperature was raised to 80°C, and the reaction was further continued at the same temperature for 1 hour. Next, as component (c), 58.3 parts of 2-hydroxyethyl acrylate (hereinafter referred to as 2HEA) and pentaerythritol triacrylate (hereinafter referred to as PETA)
Add 196.9 parts and add 0.4 parts of stannous octylate.
absorption of NCO group (2300cm ^-1 ) by IR measurement
The reaction was carried out until it disappeared, and after completion of the reaction, 1000 ppm of HQME was added and mixed to the total amount charged to obtain a resin product. The resulting resin had a pale yellow, transparent appearance and a viscosity of 15,200 cP at 25°C. Next, the physical properties of the resulting resin include the smoothness of the coating film, the number of curing irradiations, stain resistance, pencil hardness, and adhesion.
Water resistance (membrane condition and adhesion), moisture resistance (membrane condition and adhesion) and weather resistance (membrane condition and adhesion) were examined according to the following methods. The results are shown in Table 1. (Performance evaluation) A sample was prepared by mixing 3 parts of 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Geigy, trade name: "Irgakiure 184") as a photosensitizer with 97 parts of the produced resin. This was applied to Shina plywood (manufactured by Murai Plywood Co., Ltd.) using an applicator so that the dry film thickness was approximately 50 μm (dry film weight: 90 g/m ² ), and sample pieces were prepared. Various performances were evaluated as follows. (Coating suitability (smoothness of coating film)) The surface smoothness of the sample piece obtained above was visually inspected immediately after coating. (Curing speed) The number of irradiations until the sample became tack-free was measured by keeping one 80 W/cm ultraviolet lamp at an irradiation distance of 10 cm and moving the sample piece at a belt speed of 20 m/min. (Stain resistance) Irradiation was performed 5 times at the above (curing speed),
Lines were drawn on the cured film with black, blue, and red felt pens, and after being left for 10 minutes, the film was wiped off with petroleum benzine and the state of contamination of the film was observed. (Pencil hardness) The sample was applied to a steel plate instead of the china plywood used when making the sample piece, and then irradiated 5 times at the above (curing speed) to harden it, and then pencil hardened according to JIS K5400. I conducted an oyster test. (Adhesion) Using the sample piece obtained above, irradiation was performed five times at the above-mentioned (curing rate) to cure it, and then it was evaluated according to JIS K5400. (Water resistance) Using the sample piece obtained above, it was irradiated 5 times at the above (curing speed) to cure it, then immersed in hot water at 80°C for 1 hour, and then dried at 60°C in a circulating air dryer. After repeating 10 cycles of drying for 2 hours, the surface condition of the coating film was visually observed and secondary adhesion was measured and evaluated. (Moisture resistance) Using the sample piece obtained above, it was then cured by irradiation 5 times at the above (curing speed), and then placed in a constant temperature and humidity chamber at 50°C and 98% RH for 120 hours. After standing, the surface condition of the coating film was visually observed, and secondary adhesion was further measured and evaluated. (Weather resistance) Using the sample piece obtained above, it was then cured by irradiation 5 times at the above (curing rate), and then exposed for 100 hours using a sunshine type weather meter to test the coating film. The surface condition was visually observed and secondary adhesion was measured and evaluated. Examples 2 to 5 In Example 1, at least one of (a) the amount used of the component, (b) the type or amount of the component used, and (c) the type or amount of the component used is as shown in Table 1. The reaction was carried out in the same manner as in Example 1 except that the reaction mixture was changed to obtain a resin. The physical properties of the resulting resin were measured in the same manner as in Example 1. The results are shown in Table 1. Examples 6 to 7 Example 1 was repeated except that the amount of component (a) used, the amount of component (b) used, and the amount of component (c) used were changed as shown in Table 1. A similar reaction was carried out to obtain a resin. The physical properties of the resulting resin were measured in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 1 In a reaction vessel equipped with a thermometer, a cooling tube, and a stirrer, 329.8 parts of diphenylmethane diisocyanate (hereinafter referred to as MDI) as component (b), 517.2 parts of PETA, 200.0 parts of 4EGA as component (c), and HQME1.2
1 part was charged, reacted at 50°C for 0.5 hour, then heated to 80°C, and further reacted at the same temperature for 1 hour. Next, 153.0 parts of 2HEA was added as component (c), and after further reaction at 80°C for 1 hour, 0.4 parts of stannous octylate was added, and the absorption of NCO groups (2300 cm ^-1 ) disappeared by IR measurement. The reaction continued for about 1 hour. After completion, 1.2 parts of HQME was added to obtain the resulting resin. This product had a pale yellow transparent appearance and a viscosity of 37,000 cP at 25°C. Next, the physical properties of the resulting resin were measured in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 2 In Comparative Example 1, hydrogenated xylylene diisocyanate (hereinafter referred to as H ₆ XDI) was used instead of MDI.
367.7 copies were used, and PETA 280.6 copies,
Resins were obtained in the same manner as in Comparative Example 1, except that the amounts used were changed to 351.7 parts of 2HEA. Next, the physical properties of the resulting resin were measured in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 3 In a reaction vessel equipped with a thermometer, a cooling tube, and a stirrer, 1000.0 parts of the above-mentioned rosin epoxy acrylate and 200.0 parts of 4EGA were charged as components (a), and mixed with stirring to obtain a pale yellow transparent mixture. Next, the physical properties of the obtained mixture were measured in the same manner as in Example 1. The results are shown in Table 1.

【table】

[Table] [Effects of the Invention] The photocurable resin composition for wood coating of the present invention can be applied to a wide range of uses by utilizing its photocurability, but it is particularly effective when used as a wood coating. In addition to having the physical properties of a cured film such as flexibility, abrasion resistance, and chemical resistance, which are the characteristics of conventional urethane photocurable resins, it also has the properties of conventional urethane photocurable resins. The coating suitability for wood, which had been a drawback of previous products, has been greatly improved, and by adopting an ultraviolet curing system,
In the end, it can compete with thermosetting aminoalkyd resin-based coatings in terms of price, and has the effect of not producing formalin odor, which is a drawback of aminoalkyd resin-based coatings.

Claims (1)

[Claims] 1 Consisting of a reaction product (a) of (meth)acrylic acid and rosin glycidyl ester, diisocyanates (b) and a (meth)acrylic acid ester monomer (c) containing a hydroxyl group, (meth)acrylic acid and rosin glycidyl ester (a) and the (meth)acrylic acid ester monomer (c) containing a hydroxyl group in a total amount of 1.8 to 2.2 mol per 1 mol of the diisocyanate (b). Yes, and reaction product (a) of (meth)acrylic acid and rosin glycidyl ester
The amount charged is 0.5 to 1 mole of the (meth)acrylic acid ester monomer (c) containing a hydroxyl group.
A photocurable resin composition for coating wood, characterized in that it contains 2.0 mol of a reaction product as a main component.