JPH0236130B2 - AKURIRUSANMOSHIKUHAMETAKURIRUSANGURISHIJIRUESUTERUKEIJUGOTAINOSHIGAISENKOKAHOHO - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for curing glycidyl ester polymers of acrylic acid or methacrylic acid (hereinafter referred to as "(meth)acrylic acid") with ultraviolet light,
More specifically, the present invention relates to a method of curing the copolymer with ultraviolet light using a specific organic sulfur compound as a curing catalyst. Conventionally, methods are known in which polyfunctional vinyl (mainly acrylic) monomers and polyfunctional oligomers are cured by irradiating them with ultraviolet rays in the presence of a radical initiator (or photosensitizer). These methods have recently been widely applied to ultraviolet curing paints, inks, adhesives, photoresists, and the like. However, when using the ultraviolet curing method using the above-mentioned radical-based initiator, the polymerization of the vinyl-based compound, etc. proceeds by a radical mechanism, so the effect of inhibiting polymerization due to oxygen in the air is large, and the optimum curing conditions must be determined. It is difficult to do so, and the handling workability is often inferior. Furthermore, the obtained product is susceptible to the effects of oxygen, temperature, etc. even during storage, and has a problem with its pot life. In response to this, methods of ultraviolet curing using ionic polymerization initiators are currently being actively studied. Among these, the method using cationic polymerization species has a cationic polymerization mechanism, so it is not inhibited by oxygen when using the radical initiation species, and can be noted as an excellent curing method, and is particularly useful for epoxy resins. has been changed. The cationic starting species that can be used in this method are aryldiazonium salts, diaryliodonium salts, and triarylsulfonium salts, and salts such as boron fluoride, phosphorous fluoride, arsenic fluoride, and antimony fluoride are used as cationic catalysts. I am using it. However, these salts themselves have poor miscibility with (meth)acrylic acid glycidyl ester polymers, and furthermore, they decompose upon irradiation with ultraviolet rays, producing nitrogen gas and Lewis acids corresponding to the above salts, such as boron trifluoride. , phosphorus pentafluoride, etc. Such Lewis acids are corrosive and coloring, and therefore products obtained by blending them have the disadvantage that their uses are limited, and that they are particularly difficult to apply to metal substrates. More importantly, the nitrogen gas generated by the decomposition causes bubbles and pinholes to form in the resulting cured product; therefore, the use of the known cationic initiator species provides a high quality cure. Things have a fatal flaw that makes them difficult to obtain. Furthermore, products containing the above-mentioned starting species had the disadvantage that their pot lives were too short. In view of the above-mentioned current situation, the present inventors have discovered the drawbacks observed in methods using various conventionally known reagents (initiating species) in the ultraviolet curing of epoxy compounds, especially (meth)acrylic acid glycidyl ester polymers. We have conducted extensive research with the aim of providing a new ultraviolet curing method that can eliminate all problems. As a result, surprisingly, a specific organic sulfur compound, completely different from conventional starting species, has excellent miscibility with the above polymer, and does not generate any gas even when irradiated with ultraviolet rays. It has been found that it can function as a very effective cationic initiating species without producing Lewis acids that have corrosive properties, coloring properties, etc. The present invention was completed based on the above findings. That is, the present invention uses a catalyst having the general formula A-X-B-() (where A and B each represent an alkyl group having 1 to 3 carbon atoms) when curing a (meth)acrylic acid glycidyl ester polymer with ultraviolet light. X is -S-, -SO- or _-SO2-
shows. ) and/or the general formula D-Y-E() (in the formula, D and E each represent a phenyl group that may have an alkyl group having 1 to 3 carbon atoms as a substituent, and Y represents -SS-, _-SO2 The present invention relates to an ultraviolet curing method characterized by using an organic sulfur compound represented by S- or -SO ₂ SO ₂ -. According to the method of the present invention, the above general formula () and /
By using the specific organic sulfur compound represented by () as a catalyst, the following excellent effects are exhibited. (1) Since the catalyst used functions as a cationic initiator, polymerization is not inhibited by oxygen in the air, unlike methods using radical initiators, and the process is easy to work with and has good storage stability. A desired cured product with excellent properties can be obtained. (2) The above catalyst has excellent miscibility with polymers, and also removes any gas by UV irradiation.
Does not produce decomposition products that are corrosive or colored,
It can be effectively used in a wide range of applications and can provide cured products of excellent quality. (3) The polymer containing the above catalyst has a long pot life and is extremely easy to handle and apply. Although the reason why the above-mentioned excellent effects are exhibited by the method of the present invention has not yet been elucidated in detail, the organic sulfur compounds represented by the above general formulas () and () are decomposed by ultraviolet irradiation, resulting in certain types of It is thought that the cationically polymerized species attacks the oxirane rings of the (meth)acrylic acid glycidyl ester, and a polyether-type crosslinked structure is generated between the oxirane rings, thereby obtaining a cured product. In the present invention, any of various known polymers can be used as the (meth)acrylic acid glycidyl ester polymer. The polymer is prepared using, for example, a radical polymerization initiator, in the presence or absence of an organic solvent, a (meth)acrylic acid glycidyl ester monomer or other copolymerizable monomers with the monomer. It can be obtained by adding it dropwise or simultaneously with an α,β-unsaturated monomer and polymerizing it while appropriately heating or cooling. As the radical initiator, any known radical initiator can be used without particular limitation. Typical examples include azo type compounds such as azobisisobutyronitrile, peroxides such as benzoyl peroxide, and the like. Preferred examples of organic solvents that can be used in the polymerization reaction include aromatic hydrocarbons such as benzene, toluene, and xylene; esters such as ethyl acetate; and ethers such as dioxane. In addition, other α, β that can be copolymerized with the above (meth)acrylic acid glycidyl ester
- The unsaturated monomer can be appropriately determined on the condition that it is inert to the oxirane ring of the (meth)acrylic acid glycidyl ester and has high copolymerizability with the monomer. Preferred specific examples include styrene, vinyl acetate,
Examples include acrylonitrile, acrylic esters, methacrylic esters, and the like. The amount of other α,β-unsaturated monomers that can be copolymerized with (meth)acrylic acid glycidyl ester is not particularly limited, but (meth)acrylic acid glycidyl ester is usually included in the copolymer obtained. The content of the component should be at least 5 mol %, preferably 20 mol % or more. The above radical initiator, (meth)acrylic acid glycidyl ester or other α,β-
The proportion of unsaturated monomers used, polymerization reaction conditions, etc. can be arbitrarily determined depending on the desired polymer, and are no different from known polymerization reactions of this type. The details are as shown in the reference examples described later. In the present invention, it is essential to use specific organic sulfur compounds represented by the above general formulas () and () as a catalyst. General formulas () and () above
Preferred specific compounds included in the organic sulfur compounds represented by the formulas include, for example, dibenzyl sulfone, dibenzyl sulfide, phenyl phenacyl sulfide, phenyl phenacyl sulfoxide, phenyl phenacyl sulfone, 4 -ethyl phenyl phenacyl sulfone, diphenyl disulfide, phenylbenzenethiol sulfonate,
Diphenyldisulfone, phenyl-4-methylphenyldisulfone, di-(4-methylphenyl)
Examples include disulfone and the like. Among these, phenyl phenacyl sulfone and diphenyl disulfone are particularly preferred. These have a particularly excellent sensitizing effect and can cure glycidyl (meth)acrylate ester by short-term ultraviolet irradiation. Furthermore, these materials exhibit a strong sensitizing effect even when irradiated in the far ultraviolet region (254 nm).
The organic sulfur compounds represented by the above general formulas () and () can be advantageously used in the present invention either singly or in combination of two or more. The proportion of the (meth)acrylic acid glycidyl ester polymer used as the raw material is usually about 0.05 to 20% by weight, preferably about 0.5 to 10% by weight, based on the solid weight of the polymer. It is better to The method for curing the above-mentioned polymer of the present invention, except for using the above-mentioned specific organic sulfur compound as a catalyst, is basically a curing reaction method of this kind of polymer by ultraviolet irradiation using other known catalysts. It can be carried out under similar operations and conditions. That is, a solvent solution containing (meth)acrylic acid glycidyl ester to be cured and the above-mentioned specific organic sulfur compound in a predetermined ratio, such as a tetrahydrofuran solution, is prepared, and the solution is irradiated with suitable ultraviolet rays for a predetermined period of time. More specifically, the above-mentioned solvent solution is usually coated onto a predetermined base material by an appropriate means and then dried, and then the resulting dry film is irradiated with ultraviolet rays, thereby curing (gelling) the film. It is done. In the above, the ultraviolet irradiation can be carried out in the same manner as a conventional method, for example, using a commercially available low-pressure mercury lamp, high-pressure mercury lamp, etc., without any particular limitation. In particular, in the method of the present invention, based on the use of a specific organic sulfur compound as a catalyst, short-wavelength light in the deep ultraviolet region can be used as the ultraviolet rays, which allows for excellent increase in a shorter time. It has the advantage of forming a cured film with sensitization (resolution). In order to explain the present invention in more detail, the production examples of the (meth)acrylic acid glycidyl ester polymer used in the present invention and the production examples of typical organic sulfur compounds contained in the general formulas () and () are used as reference examples. Examples of the method of the present invention will be given below, but the present invention is not limited to these examples. Reference Example 1 Synthesis of methacrylic acid glycidyl ester polymer 500 ml of benzene, 150 g of methacrylic acid glycidyl ester, and 30 mg of azobisisobutyronitrile were charged into a reaction container equipped with a stirrer, a nitrogen gas introduction port, and a cooler, and the mixture was heated under a nitrogen stream. Mix and stir. Thereafter, the temperature was raised until the internal temperature of Kolben reached 70°C, and the temperature was kept at the same temperature for 2 hours to complete the polymerization.
The reaction solution was poured into methanol to precipitate the polymerization reaction product, and the precipitate was further overdried to obtain a white powdery polymer of glycidyl methacrylate. The yield was 35%. The molecular weight of the obtained polymer was measured by gel permeation chromatography, and the results were as follows. Number average molecular weight (Mn) 194000 Weight average molecular weight (Mw) 321000 (Mw/Mn) 1.65 Both Mn and Mw were calculated in terms of polystyrene. Reference Example 2 Synthesis of methacrylic acid glycidyl ester/acrylic acid ethyl ester copolymer Using the same reaction apparatus as in Reference Example 1, 500 g of benzene, 142 g (1 mol) of methacrylic acid glycidyl ester, and 100 g (1 mol) of acrylic acid ethyl ester and 2 g of azobisisobutyronitrile were added, and the mixture was mixed and stirred under a nitrogen stream. Thereafter, the internal temperature of the Kolben was raised to 60°C and kept at the same temperature for 3 hours to complete polymerization. The reaction solution was poured into n-hexane to precipitate the polymerization reaction product, and the precipitate was further overdried to obtain a copolymer of glycidyl methacrylate/ethyl acrylate. The molecular weight of the obtained copolymer was measured by gel permeation chromatography, and the results are shown below. Mn 48100 Mw 122000 Mw/Mn 2.54 Reference example 3 Phenyl phenacyl sulfide (hereinafter referred to as “PPS”)
Synthesis of phenacyl bromide (199 g (1 mole), 132.2 g (1 mole) of thiophenol, and sodium ethylate (1 mole) were reacted in absolute ethanol for 2 hours under ice cooling, and then at room temperature for 12 hours. After standing, the precipitated sodium bromide was separated, and the liquid was concentrated and dried to obtain crude crystals. This was further recrystallized with ethanol to obtain PPS. Melting point (mp) 50.5-51.5 (℃) IR 1670, 1264 (cm ^-1 ) Elemental analysis Actual value (*) C: 58.89%, H: 3.72%, N: 13.39% Theoretical value (as C ₁₄ H ₁₂ SO) C: 58.81%, H: 3.93%, N: 13.60% (*) 2,4-dinitrophenylhydrazone was recrystallized using a mixed solvent of ethyl acetate/ethanol (volume ratio 1:1). there was. Reference example 4 Phenyl phenacyl sulfone (hereinafter referred to as “PPSO ₂ ”)
) Synthesis of 50g of PPS obtained in Reference Example 3 was added to ice-cooled glacial acetic acid.
After dissolving in 200 g, excess 30% hydrogen peroxide solution is added dropwise. This was left at room temperature for 12 hours to oxidize, and the solvent was distilled off under reduced pressure to obtain crude crystals.
This was reconsolidated with 95% ethanol to obtain PPSO ₂ as crystals. The crystal gave the following measurements. mp; 92.5-94.0 (℃) IR (CHCl ₃ ); 1690, 1328, 1274, 1157 (cm ^-1 ) Elemental analysis; Actual values C: 64.59%, H: 4.63% Theoretical values (as C ₁₄ H ₁₂ SO ₃ ) C: 64.60%, H: 4.65% Reference Example 5 Synthesis of phenyl phenacyl sulfoxide (hereinafter referred to as "PPSO") 200 g of glacial acetic acid obtained by ice-cooling 50 g of PPS obtained in Reference Example 3
After dissolving in the solution, equimolar 30% hydrogen peroxide solution is added dropwise. This was left at room temperature for 12 hours to oxidize.
Further, the solvent was distilled off under reduced pressure to obtain a yellow oil.
This was cooled on ice to obtain PPSO as crystals. mp; 76-77 (℃) IR; 1685, 1276, 1047 (cm ^-1 ) Elemental analysis; Actual value C: 68.72%, H; 5.00% Theoretical value (as C ₁₄ H ₁₂ O ₂ S) C: 68.83% , H: 4.94% Reference Example 6 Synthesis of phenylbenzenethiol sulfonate (hereinafter referred to as "PSSO ₂ ") Diphenyl disulfide (hereinafter referred to as "DPDS", manufactured by Tokyo Kasei Co., Ltd., reagent grade 1) was added with ice-cold ice. The mixture was oxidized by adding 30% hydrogen peroxide solution in the presence of acetic acid, and further concentrated under reduced pressure to obtain crude crystals. This is petroleum ether/ethanol (volume ratio 10:3)
Recrystallization was performed using a mixed solvent of to obtain PSSO ₂ . mp; 43-44℃ Elemental analysis; Actual value C: 57.79%, H: 4.15% Theoretical value (as C ₆ H ₅ SO ₂ SC ₆ H ₅ ) C: 57.85%, H: 4.03% Reference example 7 Diphenyldisulfone (hereinafter referred to as "DPDSO ₄ ") Benzene sulfuric acid was oxidized using potassium permanganate to obtain DPDSO ₄ . This was recrystallized from benzene. mp; 165-167 (℃) Elemental analysis; Actual value C: 51.78%, H: 3.33% Theoretical value (C ₆ H ₅ SO ² SO ₂ C ₆ H ₅ ) C: 51.05%, H: 3.57% Example 1 Solid content of 100 parts by weight of the methacrylic acid glycidyl ester polymer obtained in Reference Example 1 and that obtained in Reference Example 4
A solution for ultraviolet curing test was prepared by dissolving 1 part by weight of PPSO ₂ in tetrahydrofuran so that the solid content was 10% by weight. The solution was applied to a stainless steel plate using a film applicator so that the dry film thickness was about 20 μm, and dried at 80° C. to prepare a test plate. UV lamp (SHL-) manufactured by Tokyo Shibaura Electric Co., Ltd.
100UV (75W)), 10cm from the center of the lamp.
The test plates, which were held apart, were irradiated with ultraviolet light for 30 seconds. In order to prevent polymerization due to heat, the back side of the test plate was cooled with water during irradiation. The test plate obtained after the above irradiation was immersed in tetrahydrofuran at room temperature for 3 hours, the undissolved film was carefully taken out, and after drying, the weight was measured, and the gelation rate was determined according to the following formula. The results are shown in Table 1. Gelation rate = weight of undissolved film/weight of film before dipping x 100 (%) Furthermore, the state of the film obtained after the above-mentioned ultraviolet irradiation was visually observed to check for the presence of bubbles and the degree of coloring. The results are shown in Table 1. Examples 2 to 4 Example 1 except that the type of organic sulfur compound and the ultraviolet irradiation time were changed as shown in Table 1.
The gelation rate and film condition were determined in the same manner as above. The results are shown in Table 1. Comparative Examples 1 and 2 As the organic sulfur compound in Example 1,
Using benzene siazonium tetrafluoroborate (hereinafter referred to as "BDA"), a known cationic polymerization initiator, instead of PPSO ₂ , and setting the ultraviolet irradiation time to 30 seconds (Comparative Example 1) or 60 seconds (Comparative Example 2). Test plates were prepared for each, and the same tests as in Example 1 were conducted on each of them. The results are shown in Table 1.

[Table] Examples 5 to 16 As shown in Table 2, the gelation rate and film condition of the obtained film were measured in the same manner as in Example 1 except that the type of organic sulfur compound and the ultraviolet irradiation time were changed. Or observed. The results are shown in the second section below.
Shown in the table. In each example, the organic sulfur compound is
Each was used in an amount of 2% by weight based on the solid content of the polymer. Further, the distance between the ultraviolet lamp and the test plate was 5 cm.

[Table] Examples 17 to 20 In Example 1, the methacrylic acid glycidyl ester/acrylic acid ethyl ester copolymer obtained in Reference Example 2 was used instead of the methacrylic acid glycidyl ester polymer, and the Test plates were prepared using 4% by weight (based on solid content) of each of the organic sulfur compounds shown in Table 3, and the plates were irradiated with ultraviolet light for a predetermined period of time at a distance of 5 cm from the center of the ultraviolet lamp to obtain a cured film. The physical properties of the obtained film were determined by the same test as in Example 1, and the results are shown in Table 3. Comparative Examples 3 and 4 The same procedure was carried out using BDA instead of the organic sulfur compound used in Examples 17 to 20 above. The results are shown in Table 3 below.

【table】

Claims (1)

[Claims] 1. When curing a glycidyl ester polymer of acrylic acid or methacrylic acid with ultraviolet light,
An ultraviolet curing method characterized by using an organic sulfur compound represented by the following general formula () and/or () as a catalyst. A - or _-SO2- ) D-Y-E () (In the formula, D and E each represent a phenyl group that may have an alkyl group having 1 to 3 carbon atoms as a substituent, and Y represents -SS-, -SO ₂ S- or -SO ₂ SO ₂ -.) 2 Claims in which the organic sulfur compound represented by the general formula () and/or () is phenyl phenacyl sulfone and/or diphenyl disulfone. Curing method according to item 1.