JPH0580921B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a photocurable resin composition, particularly a resin composition that is photocurable even when containing a white pigment such as titanium white, and is mainly used in the field of coatings such as paints and inks. , used for pure white or light-colored painted objects based on white. [Prior art] In a photocurable system, when using a paint that uses a large amount of white pigment such as titanium white, for example 10% or more, the ultraviolet absorption region of titanium white is used for photocuring. Because it overlaps with the decomposition wavelength range of the initiator, curing is severely inhibited.
In order to prevent this, a photocuring system that uses a thioxanthone-based initiator and an amine-based sensitizer in combination has been put into practical use. However, although this system is certainly effective when the titanium white concentration is not high, unfortunately, when the amount of sensitizer that can be cured is high, it becomes yellowish and has the disadvantage that a pure white coating cannot be obtained. . In recent years, there has been a report from West German BASF that photocuring is possible even when titanium white is mixed in using acylophosphine oxide (for example,
(Refer to Japanese Patent Publication No. 60-8047 and Japanese Patent Application Publication No. 55-15471). Compared to previous initiators, this type of initiator was superior in whiteness and curability of coating films containing titanium white, and improvements were observed. However, titanium white with high concentration, e.g. 20
It has also become clear that if titanium white is mixed in at a concentration of more than 5%, curing is significantly inhibited and sufficient curability cannot be obtained. [Problems to be Solved by the Invention] The present invention solves the problem by using a large amount of titanium white pigment (for example, 10
% or more) and which is not cured or is only insufficiently cured with general photoinitiators, and which can photocure in a short time a (meth)acryloyl group-containing polymer or oligomer. There is something to do. [Means for solving the problem] That is, the photocurable resin composition of the present invention comprises (A) a curable polymer or oligomer having one or more (meth)acrylonyl groups in one molecule; It consists of the combined use of B) a white titanium pigment and (C) a compound capable of generating radicals whose decomposition temperature at a half-life of 10 hours is 60°C or lower, particularly when the decomposition temperature at a half-life of 10 hours is 60°C or lower. The present invention was completed based on the discovery that photocuring is possible in a short time even in the presence of a large amount of white pigment by using a radical-generating compound such as an azo compound or an organic oxide. It was done. [Function] In the present invention, the decomposition temperature with a half-life of 10 hours (hereinafter simply referred to as half-life temperature) is 60°C or less, which is insufficient to heat cure the (meth)acryloyl group-containing oligomer or polymer within a short time. For some reason, when a compound capable of generating radicals is used in combination with a white pigment, a polymer or oligomer having a (meth)acryloyl group can be photocured in a short period of time. Although the details of the reason for this are not known, it is assumed that a synergistic effect is exerted because the compound capable of generating radicals is photodecomposed by ultraviolet irradiation and thermally decomposed by the heat generated from the device. Ru. Compounds that can generate radicals and have a half-life temperature of 60°C or less include azo compounds and organic peroxides. As an azo compound, 2,2'-azobis(4-
methoxy-2,4-dimethylvalerylonitrile)
(half-life temperature (same below) 30℃), 2,2'-azobis(2,4-dimethylvaleronitrile) (51℃)
are cited as representative examples. Further suitable organic peroxides include peroxy esters and peroxy carbonates. For example: Acetyl cyclohexyl sulfonyl peroxide (half-life temperature 26.5°C), isobutyryl peroxide (32.5°C), cumyl peroxyneodecanoate (36.6°C), diisopropyl peroxydicarbonate (40.5°C), diallyl peroxydicarbonate ( 38.8°C), di-n-propyl peroxycarbonate (40.5°C), dimyristyl peroxycarbonate (40.9°C), di(2-ethoxyethyl) peroxydicarbonate (43.4°C),
Di(methoxyisopropyl) peroxydicarbonate (43.4℃), di(2ethylhexyl peroxydicarbonate (43.5℃), t-hexyl peroxyhexanoate (44.7℃), t-butylperoxyneohexanoate (46.5℃), di(3methyl-3-methoxybutyl) peroxydicarbonate (46.5℃), t-hexyl peroxyneohexanoate (46.5℃), t-hexyl peroxyneohexanoate (51.3℃) ), t
-butyl peroxyneohexanoate (53°C),
t-hexyl peroxypivalate (53.2°C),
t-Butyl peroxypivalate (55°C), bis(4-t-butylcyclohexyl) peroxydicarbonate (44°C). Practically speaking, in consideration of the storage stability of the mixture, the speed of curing, the handling properties of organic peroxides at room temperature, peroxycarbonate-based materials, especially bis(4-t-butylcyclohexyl) peroxydicarbonate, are preferred. (Kayaku Nury Co., Ltd. trade name: Parkadox #16) is available as a typical example. Of course, the present invention is not limited to these representative examples. The amount used is per 100 parts by weight of the (meth)acryloyl group-containing polymer or oligomer.
The amount is 0.03 to 5 parts by weight, preferably 0.1 to 2 parts by weight.
If the amount is less than this range, photocuring will be difficult, and if the amount is more than this range, the effect will be poor and foaming will occur, which is not preferred. High-temperature decomposable radical-generating compounds with half-life temperatures exceeding 60°C, such as benzoyl peroxide and azobisisobutyronitrile, which are commonly used as radical polymerization catalysts, have poor effects. The curable polymer or oligomer having one or more (meth)acryloyl groups in the molecule used in the present invention has a molecular weight of 200, preferably 500 or more, preferably 200,000 or more, although it varies depending on the type.
100,000 or less, and representative examples thereof are as follows. (a) Vinyl ester resin (epoxy-(meth)acrylate) This is an oligomer obtained by reacting an epoxy resin and (meth)acrylic acid such that the epoxy groups and carboxyl groups are substantially equimolar. Typical epoxy resins include bisphenol diglycidyl ether type, novolac polyglycidyl ether type, polybasic acid polyglycidyl ester type, and epoxy resins obtained by oxidizing intramolecular double bonds with peracetic acid. Can be mentioned. (b) Polyurethane (meth)acrylate Synthesized using an unsaturated monoalcohol having a hydroxyl group and a (meth)acryloyl group in the molecule, a polyhydric isocyanate compound, and, if necessary, a polyether polyol or a polyester polyol. It is an oligomer. Examples of unsaturated monoalcohols include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and 2-hydroxyethyl methacrylate. In addition, examples of polyvalent isocyanate compounds include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthylene diisocyanate, and polyisocyanate of polyvalent phenol. can be mentioned. (c) Polyester (meth)acrylate This is an oligomer synthesized by condensation of (meth)acrylic acid and any polybasic acid or polyhydric alcohol. It can also be synthesized by a transesterification method using (meth)acrylic acid ester, or by reacting glycidyl (meth)acrylate with a polyester containing a terminal carboxyl group. There are no particular restrictions on the polybasic acids and polyhydric alcohols used, and maleic acid, fumaric acid, terephthalic acid, isophthalic acid, ethylene glycol, propylene glycol, butadiol, neopentyl glycol, etc., which are commonly used as raw materials for polyester resins, can be used. is given as a representative example. (d) Spiroacetal-(meth)acrylate A spiroacetal structure is obtained by reacting an unsaturated monoalcohol that shares a hydroxyl group and a (meth)acryloyl group in the molecule with diarylidene pentaerythrite. It is an oligomer with As the unsaturated monoalcohol, the same one as mentioned in (b) is used. The (meth)acrylate oligomers (a) to (d) above may be used as they are, or may be used in combination with a (meth)acrylate monomer such as methyl methacrylate. (Meth)acrylate oligomer has a molecular weight of
Desirably 200 or more. If the molecular weight is less than 200, the physical properties of the cured film will be poor, which is not preferable. (e) Polymer having a (meth)acryloyl group in the side chain There are several synthesis methods and types, but in general, the following polymerizable monomer (i) and the introduction of a (meth)acryloyl group into the monomer are used. A polymerizable monomer (ii) having a functional group (for example, an acid anhydride group, a carboxylic acid group, a hydroxyl group, an epoxy group) and a polymerizable double bond, and a reactive group with the functional group of the monomer (ii). (e.g. hydroxyl group,
It is synthesized from compound (iii) having an epoxy group, an NCO group) and a (meth)acryloyl group. Monomer (i) forming part of the polymer backbone
Although there is no need to place any particular restrictions on them, typical examples include styrene, vinyltoluene, chlorostyrene, acrylic esters, methacrylic esters, acrylonitrile, vinyl chloride, vinylidene chloride, vinylpyrrolidone, and vinyl acetate. . The monomer (ii) which forms a part of the polymer main chain and has a functional group for introducing a side chain (meth)acryloyl group into the main chain is, for example, acrylic acid, methacrylic acid; maleic anhydride, itaconic anhydride: (b) Typical examples of the unsaturated monoalcohols mentioned above include methylol acrylamide, glycidyl (meth)acrylate, and epoxy resin mono(meth)acrylate. Compound (iii) that introduces a (meth)acryloyl group in a side chain into a polymer is an unsaturated compound described in (b) above that introduces a (meth)acryloyl group into a side chain by reacting with an acid anhydride group in the polymer. Monoalcohols: unsaturated epoxy compounds that react with side chain carboxyl groups of polymers to introduce (meth)acryloyl groups, such as glycidyl (meth)acrylate, especially glycidyl methacrylate, mono(meth)acrylates of epoxy resins: side of polymers Isocyanates opposite to the chain OH groups include ethyl methacrylate, unsaturated isocyanates, and the like. The above-mentioned unsaturated isocyanate can be obtained by reacting the unsaturated monoalcohol described in (b) with a polyhydric isocyanate. In this case, it is necessary to react 1 mol or more of unsaturated monoalcohol per 1 mol of polyvalent isocyanate. For example, it is necessary to react in a range of 1.1 to 1.8 moles of unsaturated alcohol per mole of diisocyanate to leave an NCO group, and this residual NCO group can be used to form monomers (i) and (ii).
It is used for the reaction with the hydroxyl group of the polymer main chain obtained in . A typical example of the polymer (A) having a (meth)acryloyl group in the side chain is produced, for example, as follows: (a) A polymer having an acid anhydride structure in its structure has a (meth)acryloyl group React alcohol:

[Chemical formula] (b) Reacting a polymer having a carboxyl group in its structure with an epoxy compound having a (meth)acryloyl group:

[C] (c) Reacting a polymer having a hydroxyl group in its structure with an unsaturated isocyanate compound containing an isocyanate group and a (meth)acryloyl group in the molecule:

〔Example〕

Next, the following examples are presented to aid in understanding the present invention. Example 1 (1) Synthesis of vinyl ester resin (A) In a separable flask equipped with a stirrer, a reflux condenser, and a thermometer, 350 g of Dow's DER-332 as an epoxy resin and 144 g of acrylic acid were added.
g, trimethylbendialmonium chloride
When 1.5g of methylhydroquinone and 0.15g of methylhydroquinone are charged and heated to 120-130℃ for 3 hours, the acid value becomes
14.1, so we stopped heating, added 206 g of trimethylolpropane triacrylate and 200 g of phenoxyethyl acrylate, and added vinyl ester resin (A) with a Hazen color number of 350 and a viscosity of approx.
Obtained for 14 poise. (2) Synthesis of polyurethane-acrylate (B) In a 2-separable flask equipped with a stirrer, reflux condenser, gas inlet tube, and thermometer, 2-
232g of hydroxyethyl acrylate, 600g of phenoxyethyl acrylate, and 348g of 2,4-tolylene diisocyanate were charged and reacted at 60℃ for 3 hours in a stream of dry air.As a result of infrared analysis, 57 (%) of the isocyanate groups were It was determined that there was a reaction. Next, 220g of dipropylene glycol, 2g of dibutyltin dilaurate, and 0.2g of parabenizoquinone.
When the reaction mixture was further reacted at 60° C. for 5 hours, infrared analysis showed that the free isocyanate groups had completely disappeared. The obtained polyurethane-acrylate (B) was pale reddish brown and had a viscosity of 29 poise. (3) Synthesis of polyester-acrylate (C) In a separable flask equipped with a stirrer, reflux condenser, and thermometer, add 280 g of glycidyl methacrylate, 296 g of phthalic anhydride, 104 g of neopentyl glycol, 2 g of trimerylbenzylammonium chloride, and hydroquinone.
After charging 0.5g and reacting at 130-135℃ for 3 hours, the acid value reached 9.1, so the reaction was stopped, 420g of cresol ethyl alrylate was added, and polyester acrylate (C) had a Hazen color number of 450,
A viscosity of 11.4 poise was obtained. (4) Synthesis of spiroacetal acrylate (D) In a separable flask equipped with a stirrer, a reflux condenser, and a thermometer, add 222 g of diarylidene pentaene slit, 232 g of 2-hydroxyethyl acrylate, and para-toluenesulfonic acid.
When 4.5g was charged and reacted at 60-65℃ for 10 hours,
As a result of infrared analysis, it was confirmed that the unsaturated bonds in diarylidene pentaerythrite had disappeared. After adding 5 g of triethylamine to remove the odor from free acrolein, it was washed three times with 300 g of 1% sodium carbonate solution and then with 200 g of distilled water. Next, the reflux condenser was replaced with a fractionation condenser, and water was removed by heating to 10 to 12 mmHg and 65 to 70°C. trimethylolpropane triacrylate
400 g and 0.1 g of methylhydroquinone were added to obtain spiroacetal acrylate (D) with a Hazen color number of 300 and a viscosity of 5.4 poise. (5) Polymer with methacryloyl group in side chain
Synthesis of (E) 104 g of styrene, 26 g of 2-hydroxyethyl methacrylate, 115 g of isobutyl methacrylate,
2.4 g of tertiary decyl mercaptan, 2.4 g of azobisisobutyronitrile, and 240 g of methyl ethyl ketone were charged and polymerized at 65 to 70°C in a nitrogen stream for 12 hours. During the process, 1.2 g of azobisisobutyronitrile was added twice every 4 hours. 0.2 g of hydroquinone was added to stop the polymerization.
The polymerization rate was 91%. As a result of GPC analysis,
A polymer containing side chain hydroxyl groups with a peak at a molecular weight of 27,000 was obtained. To this were added 31 g of isocyanate ethyl methacrylate and 1 g of dibutyltin dilaurate from Dow Chemical Company, USA, and the mixture was reacted at 75 to 80°C for 6 hours. As a result of infrared analysis, the absorption of isocyanate groups completely disappeared. After changing the reflux condenser to a fractionation condenser and distilling out about 100 c.c. of methyl ethyl ketone at normal pressure, phenoxyethyl acrylate 330
g, under reduced pressure of 100-150mmHg, 70-75℃
and distilled off until the remaining amount of methyl ethyl ketone was 0.2 (%) or less as determined by gas chromatography analysis. The obtained polymer (E) (monomer solution) having a methacryloyl group in its side chain has a Hazen color number.
200, with a viscosity of 21.7 poise. 100 parts of each of the resins mentioned above, 80 parts of titanium white, [2,
2-Azobis(4-methoxy-2,4-dimethylvaleronitrile)] (Product name: V- manufactured by Wako Pure Chemical Industries, Ltd.)
70) 0.3 parts were kneaded with three rolls to prepare resin samples for coatings (a) to (e). Separately, as a comparative example, instead of V-70, 2,2
A thread was prepared by adding 2 parts of -dimethoxy-2-phenyl-acetophenone (Irugakyure #651 manufactured by Ciba) and 0.5 part of dimethylaminoethanol to 100 parts of each of the above-mentioned resins. The above samples (a) to (e) were placed on a bonderite steel plate.
Paint with a bar coater to make it 100μ thick.
A 50μ polyester film was attached. The temperature of the plate was kept constant at 30-35℃. Output this
Inside the 50kW ultraviolet irradiation device, 15cm below the lamp, 2
It was passed at a speed of m/min. The required irradiation time was about 1 minute. The temperature of the painted board leaving the irradiation device was in the range of 60 to 65°C. The results obtained, excluding the film, are shown in Table 1, and only the system containing V-70 was completely cured and was suitable for practical use.

[Table] Similarly, add 0.3 parts of V-70 to sample (A).
A bonderite steel plate coated with a film coated to a thickness of 100μ was left in a constant temperature bath at 60°C, but
Even after several minutes had elapsed, it did not cure at the gelation stage, which was definitely different from photocuring. Example 2 Synthesis of polymer (F) having a (meth)acryloyl group in the side chain Production of unsaturated epoxy resin (a) 1 separable flask equipped with a stirrer, a thermometer with a gas introduction tube, a reflux condenser, and a dropping funnel 360g (1 mol) of Mitsubishi Yuka-Ciel's Epicote 827 as an epoxy resin and 43g of methacrylic acid.
(0.5 mol), benzyldimethylamine, 1.2 g, and rosebenzoquinone, 0.08 g, and reacted for 3 hours under air blowing conditions at 120 to 130°C. The acid value became almost zero, and the unsaturated epoxy resin (a) turned into a light reddish brown syrup. Obtained as follows. Resin (a) is calculated using the following formula [1] as 223g.

It is a mixture with 180g of free epoxy resin. Synthesis of side chain epoxy resin (b) Into the same apparatus as above, 250 g of methyl ethyl ketone,
173 g (0.2 mol) of unsaturated epoxy resin (a), 100 g of styrene, and 3.5 g of azobisisobutyronitrile were charged, and 87 g of styrene (total amount of styrene: 1.8 mol) was added dropwise at 75° C. in a nitrogen stream. After 6 hours, add 2 more azobisisobutyronitrile
g was added, and the polymerization was further continued for 10 hours. When the polymerization rate reaches 96%, hydroquinone
Polymerization was stopped by adding 0.2 g. A solution of side chain epoxy resin (b) in methyl ethyl ketone (solid content 40%) was obtained in the form of a pale yellowish brown liquid. As a result of GPC analysis, it was confirmed that it was a mixture of a polymer with a peak at a molecular weight of about 50,000 and unreacted epoxy resin. Synthesis of side chain unsaturated bond type resin (F) 52 g (0.60 mol) of methacrylic acid was added to the entire methyl ethyl ketone solution of the side chain epoxy resin (b) mentioned above.
When 0.8 g of triphenylphosphine is charged and reacted for 16 hours at the boiling point of methyl ethyl ketone, the acid value is
10.4, 620 g of phenoxyethyl acrylate was added and heated under reduced pressure of 400 to 450 mmHg to remove methyl ethyl ketone. After about 6 hours, gas chromatographic analysis showed that the methyl ethyl ketone content was 0.3%, so heating was stopped and a side chain unsaturated bond type resin (F) was obtained with a yellowish brown color and a viscosity of 8.5 poise. After adding and kneading 50 parts of titanium white and 50 parts of calcium carbonate to 100 parts of resin (F), the liquid was divided into two parts, and one part was mixed with [2,2'-azobis(2,4-dimethylvaleronitrile)] ( 0.5 part of V-65 (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and this was used as a sample (f). Separately, 0.5 part of gazebisisobutyronitrile (65°C) was added to the other, and this was used as a sample (g).
Both were coated with a bar coater to a thickness of 70μ on a slate board with a board temperature of 30℃ and a thickness of 5m/m, and immediately placed 15cm below the lamp of a UV irradiation device with an output of 50kW.
was passed at a speed of 1 m/min. It took about 100 seconds to pass through, and the temperature when it left the irradiator was 65-70°C. The coating film using sample (f) was completely cured, and its physical properties were as shown in Table 2.

[Table] Sample (F) was left in a constant temperature bath at 65°C in the same way, but after 30
It turned into a gel after a few minutes had elapsed, and an essential difference from photocuring was observed. Example 3 Vinyl ester resin (A) 100 produced in Example 1
100 parts of titanium white and 1 part of bis(4-t-butylcyclohexyl) peroxydicarbonate (trade name: Percadox #16, manufactured by Kayaku Nouri Co., Ltd.) were uniformly kneaded with a roll, and the mixture was rolled to a thickness of 100μ on a Bonderite steel plate at a temperature of 30°C. After painting, the material was passed 20 cm under an ultraviolet irradiation device with an output of 50 kW at a rate of 1 m/min. It took about 100 seconds to pass. The temperature of the coating film that came out of the irradiation machine was 67℃, the coating film was completely cured, the hardness at 23℃ was 3-4H, the cross cut adhesion was passed, and the goblin test was 100/100.
It was hot. When a similar painted board was left in a constant temperature bath at 60-65°C, the paint gelled after 30 minutes, but it was still hard enough to be scratched with a fingernail (2B or less), and it was difficult to reach the same hardness as photocuring. Further curing was required at 80°C for 1 hour. Example 4 100 parts of the spiroacetal acrylate (D) produced in Example 1, 90 parts of titanium white, and (i) sample (h), t-butyl peroxypivalate {NOF Corporation)
Perbutyl PV} (ii) Sample (2): t-butyl peroxyneodecanoate (Perbutyl ND) (iii) Sample (N): 1.5 parts each of dimyristyl peroxydicarbonate (Perloyl MSP) The mixture was added one by one and kneaded with three rolls to form a uniform paste. The surface of a paper-based phenolic resin laminate with a thickness of 1.6 m/m and 300 x 300 m/m was polished with #300 abrasive paper, and a moisture-curable urethane primer was applied with 20 mm of vinyl roll #1300X manufactured by Showa Kobunshi Co., Ltd. I painted it to a thickness of ~25μ and left it overnight. After coating the samples (J) to (N) to a thickness of approximately 200μ, a polyethylene film with a thickness of 50μ is adhered, and after squeezing with a roll to make a coating film with a thickness of approximately 100μ, ultraviolet rays with an output of 50kW are applied. 20cm below the irradiation device 1
It was passed at a speed of m/min. The temperature of the plate before entering the irradiation machine was 34°C, and the temperature immediately after leaving it was 68°C. All of the coating films were completely cured, and the physical properties of the coating films after peeling off the films were as shown in Table 3.

〔Effect of the invention〕

The photocurable composition of the present invention can form a photocurable coating film with whiteness and hiding power that is difficult to achieve with conventional photocurable resins, regardless of the type or color of the object to be coated. This makes it extremely useful in the field of coatings such as paints and inks.

Claims (1)

[Scope of Claims] 1. (A) a curable polymer or oligomer having one or more (meth)acryloyl groups in one molecule, (B) a white titanium pigment, and (C) a decomposition temperature with a half-life of 10 hours. A photocurable resin composition characterized in that three compounds capable of generating radicals having a temperature of 60°C or less are used in combination.