JPH0532748A - Photosetting resin composition - Google Patents

Abstract

PURPOSE:To provide the title composition capable of giving tough, flexible, weatherable cured products, comprising a reaction product from a specific polyisocyanate, polyol, and a monomer having active hydrogen and acryloyl group, an acrylate and photopolymerization initiator. CONSTITUTION:The objective composition comprising (A) a (meth)acryloyl group-terminated urethane (meth)acrylate oligomer produced by reaction among (1) a tetramethylxylylene diisocyanate-contg. polyisocyanate, (2) a polyoxyalkylene glycol-contg. polyol and (3) a monomer having active hydrogen and (meth)acryloyl group (e.g. 2-hydroxypropyl acrylate), (B) a (meth)acrylate monomer compatible with the oligomer (e.g. tetrahydrofurfuryl acrylate), (C) a photopolymerization initiator (e.g. methylphenyl glyoxalate), and (D) an antioxidant (e.g. 2,6-di-t-butyl-phydroxytoluene).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocurable resin composition which is cured by irradiation with light to form a cured film which is tough and has excellent flexibility and weather resistance.

[0002]

A photocurable resin comprising a urethane acrylate oligomer obtained by reacting a polyisocyanate, a polyether polyol and an acrylate having a hydroxyl group, an acrylic monomer compatible with the urethane acrylate oligomer, and a photopolymerization initiator. The composition is known (see, for example, JP-A-61-281051).

Heretofore, a photocurable resin composition of this kind has not been found to have excellent flexibility and weather resistance. That is, if the flexibility of the cured film is emphasized, the weather resistance is lowered, and conversely, if the weather resistance of the cured film is emphasized, the flexibility is deteriorated. If anything, the weather resistance is often insufficient.

The photocurable resin composition disclosed in the exemplified prior art is used for the primary coating (inner layer) of an optical fiber. A cured film formed from this resin composition has good flexibility but insufficient weather resistance. That is, the weather resistance is not so important.

[0005]

This type of photocurable resin composition is often used outdoors as a paint, a coating agent, or an adhesive, and is flexible enough to follow the contraction / expansion of an object to be coated. There is a demand for a photocurable resin composition that forms a tough cured film excellent in both heat resistance and weather resistance. Therefore, an object of the present invention is to provide a photocurable resin composition which is tough and forms a cured film excellent in both flexibility and weather resistance.

[0006]

In order to solve the above-mentioned problems, the present inventor has conducted various studies on combinations of polyisocyanates and polyols and acrylic monomers added to urethane acrylate oligomers.

As a result, when the polyisocyanate comprises tetramethylxylylene diisocyanate, the polyol comprises polyoxyalkylene glycol and the acrylic monomer comprises preferably a monofunctional acrylate monomer, it is tough and flexible. It was found that a photocurable resin composition that produces a film excellent in both weather resistance and weather resistance can be obtained.

That is, the photocurable resin composition of the present invention reacts a polyisocyanate containing tetramethylxylylene diisocyanate, a polyol containing polyoxyalkylene glycol, and a monomer having active hydrogen and a (meth) acryloyl group. It is characterized by comprising a urethane (meth) acrylate oligomer having a (meth) acryloyl group at the terminal obtained in this way, a (meth) acrylate monomer compatible with this oligomer, and a photopolymerization initiator.

Here, the expressions (meth) acryloyl group and (meth) acrylate are used to include both an acryloyl group and a methacryloyl group, and both an acrylate and a methacrylate, and also in the following description. Similarly, both shall be included.

The urethane (meth) acrylate oligomer used in the present invention is obtained by reacting a specific polyisocyanate, a specific polyol, and three components of a monomer having active hydrogen and a (meth) acryloyl group. This oligomer has a (meth) acryloyl group at the terminal of the urethane type skeleton, and its molecular weight is generally several hundreds to several thousands.

In the production of this oligomer, it is necessary to use tetramethylxylylene diisocyanate as the polyisocyanate. This tetramethylxylylene diisocyanate (TMXDI) has an ortho isomer, a meta isomer, and a para isomer, and any of them can be used. Generally, the meta and para forms are used.

The tetramethylxylylene diisocyanate may be mixed with other polyisocyanates such as isophorone diisocyanate and hexamethylene diisocyanate. When these other polyisocyanates are mixed, the mixing amount is preferably 50% by weight or less.

Further, it is necessary to use polyoxyalkylene glycol as the polyol. This is called a polyether polyol. This polyoxyalkylene glycol preferably has an alkylene carbon number of 2 to 4, and includes polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, and copolymers of two or more of these, such as ethylene oxide and propylene. A copolymer with oxide or the like is used.

Although this polyoxyalkylene glycol is bifunctional, it can be used as a mixture of trifunctional or higher functional compounds. The number of this functional group depends on the initiator used in the synthesis of polyoxyalkylene glycol, and the synthetic method using such an initiator is well known. For example, to synthesize a trifunctional one, a trifunctional alcohol such as glycerin or trimethylolpropane is used as an initiator.

The polyoxyalkylene glycol may be mixed with other polyols such as polyester polyol, polyolefin polyol, polybutadiene polyol, polycarbonate polyol, siloxane polyol, thioether polyol and alkylene polyol. When these other polyols are mixed, the mixing amount is preferably 50% by weight or less.

The monomer having active hydrogen and a (meth) acryloyl group has a hydroxyl group of 2-
Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate and their modified products, and (meth) acrylic acid having a carboxyl group and its modified products are used.

The urethane (meth) acrylate oligomer used in the present invention is synthesized from the above-mentioned three-component compound by a conventional method, for example, in the following procedure. The first method can be obtained by first reacting a polyisocyanate with a polyol to prepare a urethane oligomer having an isocyanate group at a terminal, and reacting this with a monomer having an active hydrogen and a (meth) acryloyl group. it can.

In the second method, first, a polyisocyanate is reacted with a monomer having active hydrogen and a (meth) acryloyl group to prepare a compound having an isocyanate group and a (meth) acryloyl group, and a polyol is reacted therewith. Can be obtained.

In this case, when the number of moles of the polyol is (a), the number of moles of the polyisocyanate is (b), and the number of moles of the monomer having active hydrogen and the (meth) acryloyl group is (c), the molar ratio is Is generally (a) / (c) = 0.5-
2, [2 (a) + (c)] / 2 (b) = 0.8 to 1.2 are used and synthesized so as to satisfy the relationship.

In the present invention, the urethane (meth) acrylate oligomer obtained by the above method is mixed with a (meth) acrylic acid ester having compatibility with the urethane (meth) acrylate oligomer. The (meth) acrylic acid ester is mainly used for improving the flexibility and toughness of the cured film and adjusting the viscosity of the composition, and is necessary in the present invention.

In this case, when a monofunctional (meth) acrylic acid ester is used, the flexibility of the cured film is generally improved.
Further, when a polyfunctional (meth) acrylic acid ester is used, the toughness of the cured film is generally improved. In this invention,
Since both toughness and flexibility and weather resistance are problems, it is preferable to use a monofunctional (meth) acrylic acid ester alone or to mix it with a polyfunctional (meth) acrylate. When the polyfunctional (meth) acrylate is mixed, the mixing amount is 70% by weight or less.

Such (meth) acrylic acid ester is generally mixed in the range of 20 to 200 parts by weight with respect to 100 parts by weight of the urethane (meth) acrylate oligomer. If the amount is less than 20 parts by weight, the viscosity of the composition becomes too high, making it difficult to handle, and the cured film becomes hard. On the other hand, if the amount is more than 200 parts by weight, the toughness of the cured film may be deteriorated.

As the monofunctional (meth) acrylate,
Aliphatic monomers such as methyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate; ether-based monomers such as methoxymethyl (meth) acrylate, carbitol (meth) acrylate; cyclohexyl (meth) acrylate, tetrahydro Cyclic monomers such as furfuryl (meth) acrylate, isobornyl (meth) acrylate, phenoxy (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4
A monomer having a hydroxyl group such as hydroxybutyl (meth) acrylate; other 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl acid phosphate, dimethylaminoethyl (meth) acrylate and the like are used.

Of these, cyclic monomers, ether monomers and monomers having a hydroxyl group are preferable from the viewpoint of toughness, flexibility and weather resistance of the cured film. Hexanediol (meth) is a polyfunctional (meth) acrylate.
Acrylate, neopentyl glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (Meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like are used.

Further, in the present invention, a photopolymerization initiator is mixed. As the photopolymerization initiator, any known radical-type photopolymerization initiator that produces razyl by light can be used.
The radical type photopolymerization initiators are often acetophenone-based, benzoin-based, benzophenone-based, and thioxanthone-based in terms of chemical structure, and in addition, acylphosphine oxide, glyoxyester, diketone, and the like are used. Such photopolymerization initiators are well known.

The photopolymerization initiator is generally mixed in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the total amount of the urethane (meth) acrylate oligomer and the (meth) acrylate monomer. If it is less than 0.1 part by weight, the curability of the composition will be poor. On the other hand, if the amount is more than 10 parts by weight, the curability of the composition is deteriorated and the cured film is colored. Thus, the photocurable resin composition of the present invention is obtained.

Furthermore, when an ultraviolet absorber is added to the above photocurable resin composition, the weather resistance can be further improved. As the ultraviolet absorber, for example, benzotriazole-based, benzophenone-based, salicylic acid-based, and cyanoacrylate-based ones are used. Such UV absorbers are well known. The ultraviolet absorber is generally added in the range of 0.01 to 5 parts by weight to the above composition.

In this case, the combination of the photopolymerization initiator and the ultraviolet absorber is selected so that the activation of the photopolymerization initiator is not hindered by these ultraviolet absorbers. An example of the selection method is as follows.

The photopolymerization initiator and the ultraviolet absorber are selected from the relationship between the molar extinction coefficient and the wavelength. That is, the wavelength region in which the molar extinction coefficient of the photopolymerization initiator is 10 or more and the wavelength region in which the molar extinction coefficient of the ultraviolet absorber is 1000 or less are selected so as to overlap each other only in the range of the light wavelength of 430 nm or less. It

Here, the molar extinction coefficient is the Lambert-Beer equation log (I ₀ / I) = εcd for a solution.
The value of ε (M ^-1 cm ^-1 ) defined by
Here, I is the intensity of transmitted light, I ₀ is the intensity of transmitted light of a pure solvent, c is the molar concentration (M), and d is the thickness (cm) of the solution layer. ε is a constant determined only by the substance and the wavelength.

In the above selection, the overlapping of wavelength regions means the following state. Figure 1
Is a photopolymerization initiator and an ultraviolet absorber, which are dissolved in a solvent to form a solution, and the solution is irradiated with light of various wavelengths to measure the intensity I of the transmitted light. Is a graph created by putting in the above equation, and schematically shows the relationship in which the molar extinction coefficient of the photopolymerization initiator and the ultraviolet absorber changes with the wavelength of light.

In FIG. 1, it is assumed that the photopolymerization initiator has a molar extinction coefficient as shown by the curve A and the ultraviolet absorber has a molar extinction coefficient as shown by the curve B. A wavelength x of the molar extinction coefficient epsilon _A curve A is 10, with the wavelength y of molar extinction coefficient epsilon _B of the curve B is 1000, y is x
If the relationship is smaller than
That is, they overlap in the wavelength region of <x.

The wavelength region where the molar extinction coefficient of the photopolymerization initiator is 10 or more, and the molar extinction coefficient of the ultraviolet absorber are 100.
The wavelength region of 0 or less is selected so as to overlap only in the range of light wavelength of 430 nm or less. Where 43
0 nm is a boundary wavelength set by experiments by the inventor based on ultraviolet rays.

Among them, the overlapping wavelength region is 410
It is desirable that the thickness is less than or equal to nm. The overlapping wavelength region is preferably 280 nm or more. The reason is that the light having a wavelength of 280 nm or less is absorbed by the resin component and therefore is utilized for curing near the surface layer but not for curing inside.

If desired, various compounding agents may be added to the photocurable resin composition of the present invention.
For example, in order to obtain further excellent weather resistance, a phenol-based, amine-based, phosphorus-based, sulfur-based antioxidant or hindered amine-based light stabilizer can be added. Further, a leveling agent, a thickener, a filler, a coloring agent and the like can be added.

The photocurable resin composition of the present invention is coated with
When it is used as a coating agent or an adhesive, it is applied by various known methods such as brush coating, flow coating and dipping, and then it is irradiated with light to be cured. Alternatively, it can be formed into a sheet by applying it to a suitable mold-releasing plate or the like, irradiating it with light to cure it, and peeling off the cured film.

As a light source for irradiating light to cure it, any light source which emits light having a wavelength of about 250 to 450 nm may be used. For example, a high pressure or ultra high pressure mercury lamp,
Metal halide lamp, fluorescent lamp, xenon lamp,
Either sunlight or the like can be used. When an ultraviolet absorber is added, it is preferable to use the above-mentioned light source that abundantly emits light in the overlapping wavelength ranges of both wavelength regions.

This photocurable resin composition exhibits excellent adhesion to synthetic resins such as vinyl chloride resins, but in order to further improve the adhesion to various materials, an undercoat primer is used. To be

In this case, as a primer, a monofunctional (meth) acrylate monomer alone or a (meth) acrylate monomer obtained by mixing a polyfunctional (meth) acrylate monomer into the main component is used as a main component, and a photopolymerization initiator is added thereto. After applying this primer, the primer is reacted with light by irradiating light to such an extent that the primer is tacky. Then, a method of applying the photocurable resin composition of the present invention thereon and irradiating it with light to cure the resin composition is suitable.

For inorganic materials such as glass, earthenware, aluminum and iron, it is preferable to use a primer containing a silane coupling agent such as (meth) acryloxyalkoxysilane as a component. in this case,
After the primer is heat-cured, the photocurable resin composition of the present invention is applied onto the primer and irradiated with light to be cured.

[0041]

In the present invention, a poly (isocyanate) containing tetramethylxylylene diisocyanate, a polyol containing polyoxyalkylene glycol, and a monomer obtained by reacting active hydrogen and a monomer having a (meth) acryloyl group are added to a terminal (meth). When a urethane (meth) acrylate oligomer having an acryloyl group is used, it is copolymerized and cured by the action of light and a photopolymerization initiator,
A tough, cured film with improved weather resistance and flexibility is formed. In this case, it is considered that tetramethylxylylene diisocyanate contributes to the improvement of weather resistance and polyoxyalkylene glycol contributes to the improvement of flexibility.

When the urethane (meth) acrylate oligomer is mixed with a (meth) acrylate monomer compatible with the oligomer, the monomer is mixed with the oligomer by the action of light and a photopolymerization initiator. It is polymerized and cured to further improve the flexibility or toughness of the cured film.

Further, when an ultraviolet absorber is added,
Due to the action of this ultraviolet absorber, a cured film having further improved weather resistance in addition to the above-mentioned improvements in toughness, weather resistance and flexibility is formed.

[0044]

EXAMPLES Examples and comparative examples of the present invention will be shown below. Example 1 Tetramethylxylylene diisocyanate (molecular weight 24
4) 440 g and 2700 g of bifunctional polytetramethylene glycol having a molecular weight of 3000 were reacted at 80 ° C. for 10 hours. To this, 209 g of 2-hydroxyethyl acrylate (molecular weight 116) was added, and the mixture was further reacted for 10 hours to obtain a urethane acrylate oligomer.

This urethane acrylate oligomer 10
0 g to 30 g of tetrahydrofurfuryl acrylate,
30 g of 2-hydroxypropyl acrylate, 1.6 g of methylphenylglyoxylate as a photopolymerization initiator, and 0.3 g of 2,6-di-t-butyl-p-hydroxytoluene (BHT) as an antioxidant were added, mixed and dissolved. A photocurable resin composition was prepared.

This photocurable resin composition was cast on a glass plate to a thickness of 0.5 mm and irradiated with a 80 W / cm high pressure mercury lamp for 30 seconds to obtain a cured film. This cured film has 1
It was flexible and tough without bending even when bent at an angle of 80 degrees. Further, the above cured film was exposed for 400 hours using a sunshine weatherometer,
The yellowing index (ΔYI) was measured by the method described in K 7103. Its yellowness index (ΔYI) was 10, showing excellent weather resistance.

Example 2 The photo-curable resin composition prepared in Example 1 was supplemented with 2- (2'-hydroxy-5'-methylphenyl) as an ultraviolet absorber.
0.4 g of benzotriazole was added and mixed. Other than that was performed like Example 1. Also in this case, the cured film is 18
Even if it was bent at an angle of 0 degree, it did not crack and was flexible and tough. The degree of yellowing (ΔYI) was 1, showing extremely excellent weather resistance.

The ultraviolet absorber exhibits the molar extinction coefficient curve of B in FIG. 1, and has a molar extinction coefficient of 1000 or less in the wavelength range of 381 nm or more. Further, the photopolymerization initiator (methylphenylglyoxylate) shows the molar extinction coefficient curve of A in FIG. 1 and has a wavelength of 398 nm or less and 280 n or less.
The molar extinction coefficient is 10 or more in the range of m or more.

Therefore, the wavelength region in which the molar extinction coefficient of this ultraviolet absorber is 1000 or less and the wavelength region in which the molar extinction coefficient of the photopolymerization initiator is 10 or more are 381n.
They overlap in the wavelength range of m to 398 nm.

Comparative Example 1 440 g of tetramethylxylylene diisocyanate (molecular weight 244) used in Example 1 was replaced with 310 g of 2,4-tolylene diisocyanate (molecular weight 166). Other than that was performed like Example 1. In this case, the cured film does not break even when bent at an angle of 180 degrees,
It was flexible and tough. However, the degree of yellowing (ΔYI) is 4
The weather resistance was inferior.

Comparative Example 2 2700 g of the bifunctional polytetramethylene glycol having a molecular weight of 3000 used in Example 1 was synthesized by polycondensation from isophthalic acid and ethylene glycol to give a molecular weight of 300.
It was replaced with 2700 g of the polyester polyol of No. 0. Other than that was performed like Example 1. In this case, the cured film was broken into two when bent at an angle of 180 degrees, and the flexibility and toughness were poor. Yellowing degree (ΔYI) is 1
It was 5, and the weather resistance was good.

[0052]

As described above, the photocurable resin composition of the present invention has a polyisocyanate containing tetramethylxylylene diisocyanate, a polyol containing polyoxyalkylene glycol, active hydrogen and a (meth) acryloyl group. It is composed of a urethane (meth) acrylate oligomer having a (meth) acryloyl group at the terminal obtained by reacting a compound, a (meth) acrylic acid ester, and a photopolymerization initiator, whereby it is tough and flexible. A cured film excellent in both weather resistance can be formed.

Further, the weather resistance can be further improved by adding an ultraviolet absorber to the above photocurable resin composition. The photocurable resin composition of the present invention has the advantages described above, and in particular, a coating material for outdoor use,
It is suitably used as a coating agent and an adhesive.

[Brief description of drawings]

FIG. 1 is a graph schematically showing a relationship in which the molar absorptivity of a photopolymerization initiator and an ultraviolet absorber used in the present invention changes with the wavelength of light.

[Explanation of symbols]

A Molar extinction coefficient curve of photopolymerization initiator B Molar extinction coefficient curve of UV absorber

Claims (2)

[Claims] 1. A polyisocyanate containing tetramethylxylylene diisocyanate, a polyol containing polyoxyalkylene glycol, active hydrogen and (meth).
It comprises a urethane (meth) acrylate oligomer having a (meth) acryloyl group at the terminal obtained by reacting with a monomer having an acryloyl group, a (meth) acrylate monomer compatible with this oligomer, and a photopolymerization initiator. Photocurable resin composition. 2. An ultraviolet absorber is added to the composition.
The photocurable resin composition described.