JPH06239910A - Photopolymerization initiator - Google Patents

Abstract

PURPOSE:To obtain a new water-soluble photopolymerization initiator, composed of a benzoin derivative having a specific structure, having a high curing rate without using an amine and useful as a printing plate material, a resist, an ultraviolet curing coating, an ultraviolet curing ink, etc. CONSTITUTION:1,4-Dioxane, water and selenium dioxide are placed in a flask and the resultant mixture is then heated at 50-55 deg.C to provide a uniform solution. Acetophenones of formula I (R1 is H, alkyl, alkoxy, halogen, etc.) are subsequently added to the prepared solution and the resultant mixture is then subjected to oxidizing reaction while being heated. Thereby, a phenylglyoxal derivative is obtained. Toluene is subsequently made to react therewith in the presence of aluminum chloride to afford a 4'-methylbenzoin derivative of formula II. The hydroxyl group is then etherified and the obtained compound is subsequently made to react with N-bromosuccinimide and benzoyl peroxide and brominated. Furthermore, a tertiary amine such as triethylamine is then allowed to react therewith to provide a quaternary salt. As a result, the objective photopolymerization initiator of formula III [R2 and R3 are alkyl; Y<+> is quaternary ammonium; X<-> is monovalent anion; (n) is 1-5] or formula IV is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel photopolymerization initiator, and more particularly to a water-soluble photopolymerization initiator.

[0002]

2. Description of the Related Art A composition which is polymerized and cured by irradiation with light and its technique are used in a wide variety of fields such as printing plate-making materials, various resists, ultraviolet curable paints and ultraviolet curable inks. Taking UV curing paint as an example, the transparent top coat layer of the printing paper is coated with a gravure coater as a thin film of several micrometers or less. In this case, a composition having a low viscosity such as 10 centipoise or less is required to obtain a thin film, and in order to achieve this, a composition in which an organic solvent (e.g., methyl ethyl ketone, toluene) accounts for more than half of the total weight of the composition is used. There is.

However, in recent years, water-soluble photosensitive materials have been demanded due to environmental problems and the like. In order to avoid the harmful effects of organic solvents, the design of a water-soluble photosensitive composition is considered as a measure. Therefore, it is necessary to make the photopolymerization initiator water-soluble as well as making the resin water-soluble.

Examples of water-soluble photopolymerization initiators include substituted benzophenones (Journal of Photochemistry).
(Journal of Photochemistry) No. 36, 1987, No. 347-
363), substituted thioxanthones (Journal of Photochemistry No. 36, 1987, pp. 99-112;
2-132880; and 58-80301), substituted anthraquinones and substituted hydroxyacetophenones. However, benzophenone, thioxanthone and anthraquinone undergo a hydrogen abstraction type reaction and thus require the presence of an amine as a co-initiator. As a result, the use of amine causes odor and irritation, which poses a safety problem in the environment and work. Further, the currently known substituted hydroxyacetophenone which causes an α-decomposition type reaction without using an amine has an essential problem that the curing rate is low.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and an object thereof is to:
It is to provide a water-soluble photopolymerization initiator that does not use an amine and has a high curing rate.

[0006]

The present invention is based on the formula

[0007]

[Chemical 3]

The present invention is to provide a photopolymerization initiator having a structure shown by the above, by which the above object is achieved.

In the formulas (I) and (II), R ₁ is hydrogen, alkyl group, substituted alkyl group, alkoxy group, cyano group, nitro group, benzoyl group, acetyl group, hydroxy group or halogen. The alkyl group, the substituted alkyl group and the alkoxy group preferably have 1 to 6 carbon atoms. This is because if the carbon number exceeds 6, the hydrophobicity of the photopolymerization initiator will increase, resulting in a decrease in water solubility. In addition, a preferable substituent of the substituted alkyl group is a hydrophilic group such as a hydroxy group. R ₂
And R ₃ are the same or different alkyl groups. Preferred alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-
Examples thereof include hydrocarbon groups having 1 to 4 carbon atoms such as a butyl group and a tert-butyl group.

Y ⁺ is a quaternary ammonium group and is not particularly limited.

[0011]

[Chemical 4]

It is preferable to have a structure represented by: This is because such a structure can be easily synthesized as a quaternary salt and is stable.

In the formula (III), R ₄ , R ₅ and R ₆ are the same or different alkyl groups or substituted alkyl groups, and R ₇ and R ₉ are hydrogen, an alkyl group, a substituted alkyl group, an alkoxy group and a cyano group. Group, nitro group, benzoyl group, acetyl group, hydroxy group or halogen. R ₈ is an alkyl group or a substituted alkyl group. The reason why such a group is preferable and specific examples are as described above.

X ⁻ is not particularly limited as long as it is a monovalent anion, but is preferably an anion such as chloride ion and bromide ion which does not impair the water solubility. Other anions such as perchlorate and borofluoride may be used.

N is an integer from 1 to 5. When n exceeds 5, hydrophobicity increases and water solubility decreases, which is not preferable.

The inventors of the present invention focused on the fact that an α-alkylbenzoin alkyl ether derivative in which the hydrogen at the α-position of benzoin, which is susceptible to hydrolysis, was substituted with an alkyl group, could be easily synthesized, and as a result of trying to make it water-soluble, It was found that the above-mentioned quaternary ammonium salt of α-alkylbenzoin alkyl ether is a photopolymerization initiator which is water-soluble and exhibits a high curing rate, and has completed the present invention.

The photopolymerization initiators (I) and (II) of the present invention are usually obtained according to the following Reaction Example 1 or 2. The reaction conditions, separation and purification method, and identification method of the obtained compound are well known to those skilled in the art.

Reaction Example 1

[Chemical 5]

Reaction Example 2

[Chemical 6]

[In the formula, R _{1 to} R ₃ have the same meanings as described above. ]

The photopolymerization initiator of the present invention comprises a monomer having an ethylenically unsaturated group (hereinafter abbreviated as an ethylenically unsaturated monomer) and a polymer having an ethylenically unsaturated group (hereinafter abbreviated as an ethylenically unsaturated polymer). ) Is photopolymerized. Examples of the ethylenically unsaturated monomer and the ethylenically unsaturated polymer suitable for using the photopolymerization initiator of the present invention are described in "UV Curing System", Kiyomi Kato, 1989, General Technology Center, No. 151. ~ 331.

The amount of the photopolymerization initiator used in the present invention is preferably in the range of 0.1 to 10% by weight based on the total amount of the ethylenically unsaturated monomer and the ethylenically unsaturated polymer. If it is less than 0.1% by weight, the photo-curing will be insufficient,
If the amount exceeds 5% by weight, the resulting polymer has a low molecular weight, which is not preferable.

In addition to the above components, other polymer components such as thermoplastic acrylic resin, polyester resin and styrene resin may be added if necessary. Further, a polymerization inhibitor (for example, 2,6-di-t-butyl-p-cresol, hydroquinone and p-methoxyphenol), if necessary,
Dyes (e.g. eosin, methylene blue and malachite green), other sensitizers (e.g. 2,4-diethylthioxanthone and 2-ethylanthraquinone), and other initiators (e.g. benzyl dimethyl ketal and benzoin isopropyl ether) are included. May be.

The amount of the polymerization inhibitor blended is 0 to 5% by weight, preferably 0 to 1% by weight, based on the total amount of the ethylenically unsaturated monomer and the ethylenically unsaturated polymer.
The blending amount of the sensitizer and the other initiator is 0 to 10% by weight, preferably 0 to 3% by weight, based on the total amount of the ethylenically unsaturated monomer and the ethylenically unsaturated polymer. Further, a copolymerization initiator such as amine may be added if necessary. The blending amount of the copolymerization initiator is preferably 0 to 10% by weight, particularly preferably 0 to 5% by weight based on the total amount of the ethylenically unsaturated monomer and the ethylenically unsaturated polymer.

An aqueous photosensitive composition is obtained by using the photopolymerization initiator of the present invention in combination with a water-soluble one of the above-mentioned ethylenically unsaturated monomer and the above-mentioned ethylenically unsaturated oligomer. It can be prepared. Examples of preferred water-soluble ethylenically unsaturated monomers include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, N-acryloylmorpholine and N-vinylpyrrolidone. Further, examples of preferable water-soluble ethylenically unsaturated oligomers include polyethylene glycol diacrylate and polyethylene glycol dimethacrylate. In that case, the usage-amount of the photoinitiator of this invention is as above-mentioned.

In addition, water-soluble polymer components such as polyvinyl alcohol, polyvinylpyrrolidone and sodium polyacrylate can be added in amounts well known to those skilled in the art. If necessary, the above-mentioned polymerization inhibitor, dye, other sensitizer and other initiator can be used in the above-mentioned proportions.

Such an aqueous photosensitive composition is usually irradiated with ultraviolet rays after evaporation of water after coating, but it is desirable to cure even in the state where water remains.

[0028]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0029]

[Synthesis Example 1] (i) In a 500 ml eggplant-shaped flask equipped with a cooling tube, 250 ml of 1,4-dioxane, 8.3 ml of water and 46.3 g of selenium dioxide were placed, and
Heated to ~ 55 ° C to dissolve the selenium dioxide. Acetophenone (48.4 ml) was added to the solution and the mixture was refluxed for 5 hours. After that, the reaction solution was cooled to room temperature, the precipitated black solid selenium was filtered, and the filtrate was concentrated to obtain a yellow liquid phenylglyoxal (yield 48.8 g, yield 87.4%).

(Ii) 1.74 liters of anhydrous toluene and aluminum chloride were placed in a 3 liters three-necked flask equipped with a calcium chloride tube, a condenser tube with an acid trap and a 500 ml dropping funnel.
97 g was added and stirred. To this, a yellow solution of anhydrous toluene 433 ml and phenylglyoxal 48.8 g was added dropwise over 30 minutes under ice cooling. The color of the solution changed from light brown to milky white. After stirring for 17 hours under ice cooling, the solution turned blackish brown.
To this solution, 1 liter of 20% HCl aqueous solution was added to treat excess aluminum chloride, and the toluene layer was separated with a separating funnel. The toluene layer was concentrated to a solution of about 300 ml, 300 ml of petroleum ether was added and ice-cooled to precipitate crystals. White needle-like 4'-methylbenzoin was obtained by recrystallization from ethanol (yield 31.0 g, yield 3
7.7%).

(Iii) 41.0-Methylbenzoin (31.0 g) and DMSO (274 ml) were placed in a 1-liter two-necked flask and the atmosphere was replaced with N _2.
% NaOH aqueous solution 64.9ml, followed by methyl iodide 18.1ml
Was added and stirred at room temperature for 18 hours, the solution changed from dark green to yellow. 1 liter of water was added to this solution, and 100 ml of chloroform was added to the suspended liquid for extraction. The chloroform layer is washed with water, dried and concentrated to give 4- and 4'-methyl-
A mixture of α-methylbenzoin methyl ether was obtained as a yellow liquid (yield 33.8 g, yield 97.1%).

(Iv) In a 1 liter eggplant-shaped flask equipped with a condenser, 33.8 g of a mixture of 4- and 4'-methyl-α-methylbenzoin methyl ether, 500 ml of carbon tetrachloride, 23.7 g of N-bromosuccinimide and a mixture of Put a catalytic amount of benzoyl oxide 4
Reflux for hours. The reaction solution was cooled to room temperature, the precipitated succinimide was filtered off, and the filtrate was concentrated to give 4- and 4 '.
A mixture of -bromomethyl-α-methylbenzoin methyl ether was obtained as a yellow liquid (yield 50.8 g, yield 100
%).

(V) A 100 ml eggplant-shaped flask was equipped with a calcium chloride tube, 1 g of a mixture of 4- and 4'-bromomethylbenzoin methyl ether, 10 ml of anhydrous triethylamine and 20 ml of anhydrous benzene were added, and the mixture was stirred at room temperature for 3 days. The solvent was distilled off, and the residue was washed with ether and dried to obtain a mixture of 4- and 4′-triethylammoniomethyl bromide-α-methylbenzoin methyl ether as a yellow viscous solid (yield 1.09 g,
Yield 83%, ¹ H-NMR (270 MHz, CDCl ₃ ) δ 8.03 to 7.94 (m, 2H),
7.57 ~ 7.26 (m, 7H), 5.30, 4.90 (S, 2H), 3.31 ~ 3.28 (m, 3
H), 3.52 to 3.37, 3.15 to 3.07 (m, 6H), 1.72, 1.70 (s, 3
H), 1.46 to 1.38, 1.23 to 1.18 (m, 9H)).

[0034]

[Synthesis Example 2] 4 obtained by the same operation as (i) to (iv) of Synthesis Example 1
1 g of a mixture of -and 4'-bromomethyl-α-methylbenzoin methyl ether, 10 ml of anhydrous pyridine and 30 ml of anhydrous acetonitrile were subjected to the same operation as in (v) of Synthesis Example 1 for 24 hours. A mixture of 4- and 4'-pyridiniomethyl-α-methylbenzoin methyl ether bromide was obtained as a yellow viscous solid (yield 1.18 g, 95.2%, ¹ H-NMR (270 MHz, CDCl
₃ ) δ 9.58 to 9.49 (m, 2H), 8.36 to 8.31 (m, 1H), 7.65 to 7.61
(m, 2H), 8.09 to 7.93, 7.54 to 7.19 (m, 9H), 6.37 to 6.26
(m, 2H), 3.29 to 3.24 (m, 3H), 1.71 to 1.66 (m, 3H)).

[0035]

[Synthesis Example 3] 4 obtained by the same operation as (i) to (iv) in Synthesis Example 1
3 g of a mixture of -and 4'-bromomethyl-α-methylbenzoin methyl ether, 30 ml of anhydrous benzene and 9.26 ml of anhydrous diethylamine were placed in a 50 ml eggplant-shaped flask and allowed to stand at room temperature for 24 hours.
Stir for hours. This solution was extracted with 30 ml of 3N aqueous HCl and made alkaline with 20% aqueous KOH. This was extracted with 30 ml of ether, dried over anhydrous Na ₂ SO ₄ and the solvent was removed to obtain 1.65 g of a brown viscous liquid. A silica gel column chromatograph (developing solvent ether: petroleum ether = 3:
2-diethylaminomethyl-α-
Methyl benzoin methyl ether (A) and 4′-diethylaminomethyl-α-methyl benzoin ether (B) were obtained as brown liquids ((A) yield 670 mg, yield 22.9%;
(B) yield 380 mg, 12.9% yield).

500 m of (A) or (B) thus obtained
50 g of anhydrous acetonitrile 10 ml and ethyl iodide 1.23 ml
The mixture was placed in a l-shaped eggplant-shaped flask and stirred at room temperature for 7 days. After distilling off the reaction solvent, washing with ether and drying,
4- or 4'-triethylammoniomethyl-α-methylbenzoin methyl ether iodide was obtained as a yellow viscous solid (4-triethylammoniomethyl iodide-α-
Methyl benzoin methyl ether yield 740 mg, yield 100
%, Mp. 33 to 36 ° C, ¹ H-NMR (CDCl ₃ ): δ8.02 (d, J = 8.25Hz, 2
H), 7.54 to 7.29 (m, 7H), 4.81 (s, 2H), 3.39 (q, J = 7.26Hz,
6H), 3.29 (s, 3H), 1.72 (s, 3H), 1.45 (t, J = 7.26Hz, 9H;
Yield 4'-triethylammoniomethyl-α-methylbenzoin methyl ether yield 640 mg, yield 86.5%, mp. 32
~ 35 ° C, ¹ H-NMR (CDCl ₃ ): δ7.96 (d, J = 8.25Hz, 2H), 7.60
~ 7.25 (m, 7H), 4.70 (s, 2H), 3.42 (q, J = 6.93Hz, 6H), 3.3
1 (s, 3H), 1.71 (s, 3H), 1.46 (t, J = 6.93Hz, 9H)).

[0037]

Synthesis Example 4 (i) In a 100 ml eggplant-shaped flask, 5 g of a mixture of 4- and 4′-bromomethyl-α-methylbenzoin methyl ether obtained in the same manner as in (i) to (iv) of Synthesis Example 1 was added. 50 ml anhydrous benzene
And 2.60 ml of morpholine were added, and the mixture was stirred at room temperature for 43 hours. The solution was extracted with 50 ml of 3N aqueous HCl and made alkaline with 20% aqueous KOH. This was extracted with 50 ml of ether, dried over anhydrous Na ₂ SO ₄ , the solvent was distilled off and the residue was vacuum dried to obtain 2.64 g of a yellow viscous liquid.

TLC separation (developing solvent chloroform: n-
Purification with hexane = 3: 1) gave a mixture of 4- and 4'-morpholinomethyl-α-methylbenzoin methyl ether as brown viscous liquid (1.25 g, 24.4% yield,
₁ H-NMR (100 MHz, CDCl ₃ ) δ 7.98 to 7.80 (m, 2H), 7.48 to 7.10
(m, 7H), 3.75 to 3.56 (m, 4H), 3.38 (s, 2H), 3.21 (s, 3H),
2.46 ~ 2.26 (m, 4H), 1.62 (s, 3H)).

(Ii) 500 mg of a mixture of 4- and 4'-morpholinomethyl-α-methylbenzoin methyl ether thus obtained, 10 ml of anhydrous acetonitrile and methyl iodide
1.20 ml and 50 ml eggplant flask were put and stirred at room temperature for 5 days. After the reaction solvent was distilled off, the residue was washed with ether and dried to give 4- and 4'-N-methylmorpholiniomethyl iodide-α.
A mixture of -methylbenzoin methyl ether was obtained as a brown viscous liquid (650 mg, 91.7% yield).

[0040]

EXAMPLE The following photopolymerization initiators (A) to (E) obtained in Synthesis Examples 1 to 4 and commercially available water-soluble initiators (F) to (H) were used.
Sample liquids A to H were prepared by dissolving 0.05 mol of each in 1 liter of a mixture of 2-hydroxyethyl methacrylate: water = 8: 2. However, the sample solutions F and H further contained 0.1 mol of N-methyldiethanolamine (MDEA) as a co-initiator.

Expression (A)

[0042]

[Chemical 7]

A mixture of 4- and 4'-triethylammoniomethyl-α-methylbenzoin methyl ether bromide of the structure:

Expression (B)

[0045]

[Chemical 8]

4- and 4'-pyridiniomethyl bromide represented by
-A mixture of methyl benzoin methyl ether.

Expression (C)

[0048]

[Chemical 9]

4-triethylammoniomethyl-α-methylbenzoin methyl ether iodide represented by

Expression (D)

[0051]

[Chemical 10]

Iodide 4'-triethylammoniomethyl-α-methylbenzoin methyl ether represented by

Expression (E)

[0054]

[Chemical 11]

4- and 4'-N-methylmorpholiniomethyl-α-methylbenzoin methyl ether iodide represented by

Formula (F)

[0057]

[Chemical 12]

Cantacure QTX (manufactured by WARD BLENKINSOP) which is a commercially available water-soluble initiator represented by formula (G)

[0059]

[Chemical 13]

Darocur 2959 (manufactured by MERCK), which is a commercially available water-soluble initiator represented by.

Expression (H)

[0062]

[Chemical 14]

Sodium anthraquinone 2-sulfonate (manufactured by Wako Pure Chemical Industries, Ltd.), which is a commercially available water-soluble initiator represented by

Then, 10 mg of each sample solution was placed in an aluminum can having a diameter of 5 mm, and a 200 W Hg-Xe lamp (manufactured by Ushio Inc.) was used as a light source to irradiate light at a light intensity of 20 W / cm ² for differential scanning calorie. The heat of polymerization was measured with a meter (manufactured by DBC220 Seiko Denshi Kogyo). Then, the irradiation time (T) until reaching the maximum calorific value was measured and used as a standard for the curing rate of each initiator.

[0065]

[Table 1]

From the results shown in Table 1, the water-soluble photopolymerization initiators (A) to (E) of the present invention are commercially available initiators (G) containing no other amine.
It has about 4 times faster curing rate and uses amine
It was shown to have a curing speed equal to or higher than that of (F) / MDEA.

[0067]

Industrial Applicability A water-soluble photopolymerization initiator which does not use an amine and has a high curing rate is provided.

Claims (2)

[Claims] 1. The formula: [In the formula, Y ⁺ is a quaternary ammonium group, X ⁻ is a monovalent anion, n is an integer of 1 to 5, and R ₁ is hydrogen, an alkyl group, a substituted alkyl group, an alkoxy group, It is a cyano group, a nitro group, a benzoyl group, an acetyl group, a hydroxy group or a halogen, and R ₂ and R ₃ are the same or different alkyl groups. ] The photoinitiator of the structure shown by. 2. The Y ⁺ is of the formula: [Wherein R ₄ , R ₅ and R ₆ are the same or different alkyl groups or substituted alkyl groups, and R ₇ and R ₉ are hydrogen, alkyl groups, substituted alkyl groups, alkoxy groups, cyano groups, nitro groups, benzoyl A group, an acetyl group, a hydroxy group or halogen, and R ₈ is an alkyl group or a substituted alkyl group. ] The photoinitiator of the structure shown by.