JPH07113048B2 - Method for producing radiation curable resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a radiation curable resin that is cured by radiation such as ultraviolet rays, electron beams, infrared rays, and the like. The present invention relates to a method for producing a radiation-curable resin, which is a coating film having less surface hardness and excellent heat resistance.

2. Description of the Related Art Conventionally, radiation curable resins that are cured by ultraviolet rays have been widely used because of their energy saving and space saving properties.

As these radiation curable resin materials, unsaturated polyester resins, various acrylic esters or acrylic oligomers, and some epoxy resins have been used.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the above-mentioned conventional radiation-curable resins each have drawbacks, and improvements have been desired.

That is, unsaturated polyester resins and various acrylic esters or acrylic oligomers are prone to deterioration due to hydrolysis, and have insufficient heat resistance. On the other hand, epoxy resin-based resins do not have the above-mentioned drawbacks, but are suitable for electrical applications. When used, there was a problem that the deterioration of insulation due to residual fragments of the photopolymerization initiator cannot be avoided.

Bisphenol A (2,
A radiation-curable coating having excellent performance is obtained by using a resin containing a polymer of a compound obtained by esterifying a tetramethylol compound of 2'-bis (4'-oxyphenyl) propane) in a specific ratio. The application of the film was first disclosed (Japanese Patent Laid-Open No. 60-001209).
Has been done. Although this radiation-curable resin gives a radiation-cured coating film with excellent performance, the stability of the precursor oligomer is not always good, and as shown by the broken line in Fig. 4, when stored at 30 ° C, 20 It had a problem of gelation in about a day.

Means for Solving the Problems The method for producing a radiation-curable resin of the present invention is a compound represented by the following structural formula in which a compound obtained by reacting a bisoxyphenyl compound with formaldehyde is reacted with acrylic acid or methacrylic acid. Is produced as a monomer unit.

However, R ₁ is CH ₂ , C (CH ₃ ) ₂ or alkylene R ₂ , R ₃ is a methylol group or an acrylic acid or methacrylic acid ester of a methylol group, and the sum of X and Y is 2 to 3 What is.

By using a radiation-curing resin with the above structure as a monomer unit, a radiation-curing resin with low hygroscopicity, surface hardness, heat resistance, and chemical resistance, and storage stability is provided. A resin is obtained.

Examples Hereinafter, examples of the present invention will be described.

First, FIG. 1 shows a production flow sheet of a radiation curable resin according to the present invention.

In FIG. 1, a bisoxyphenyl compound (I) Add 2 to 3 parts of formaldehyde to 1 mol.
By adjusting the amount to be mol, the di- or trimethylol compound (II) of (I) can be obtained.

Formaldehyde can usually be added as formalin which is an aqueous solution thereof, but it is known to add it to the reaction system as other paraform. Then, (II) is reacted with acrylic acid or methacrylic acid to carry out the condensation of the methylol group and the esterification reaction at the same time. The charging amount of acrylic acid or methacrylic acid is 1 to 7 mol per 1 mol of (II). If the amount of acrylic acid or methacrylic acid is small during the reaction, the system may gel.

The ratio of the methylol group and the acrylic acid or methacrylic acid ester of the methylol group can be arbitrarily changed depending on the use of the resin. That is, it is preferable to increase the ratio of the methylol group particularly when importance is attached to the heat resistance and chemical resistance of the cured resin, and to increase the amount of the ester when priority is given to fast curability and curability at low dose. . In normal use, if the ratio of the methylol group and the acrylic acid or methacrylic acid ester of the methylol group is in the range of 10: 1 to 1: 6, the hygroscopicity is low, and the surface hardness, heat resistance, chemical resistance and radiation A resin having excellent curability can be obtained.

The esterification rate can be determined by infrared spectroscopic analysis as described in the examples below.

The resin of the present invention can obtain good characteristics only by being cured by radiation, but the post-curing can remarkably improve the surface hardness.

The resin which has reached a predetermined esterification rate stops the reaction, unreacted acrylic acid or methacrylic acid is removed from the reaction system, washed with water and dehydrated to complete the radiation curable resin.

As R _{1 in} the structure of the starting material (I), CH ₂ (bisphenol F), C (CH ₃ ) ₂ (bisphenol A), etc. are easily available, but they improve toughness and reactivity of the cured resin. Therefore, a long-chain methylene group or alkylene group can also be used. Bisphenol-based resoles using these long-chain methylene groups or alkylene groups are known (Higashi et al., Industrial Chemistry Magazine, Vol. 61, p. 439, Darashenko et al., Plastieskie-Massi, pp. 19658, p. 9).

Specific examples will be described below with reference to FIGS. 2, 3, and 4.

FIG. 2 is a diagram showing the result of infrared spectroscopic analysis of the radiation curable resin, FIG. 3 is a diagram showing the same molecular weight distribution, and FIG. 4 is a radiation curable resin according to the present invention and a conventional radiation curable resin. It is a figure which shows the viscosity change at the time of storage.

Example 1 1 mol of bisphenol A and 38% formalin (3.0 mol of formaldehyde) were placed in a four-necked flask equipped with a thermometer, an agitator, a reflux condenser, and a dropping funnel, and 2.2 mol of a 6N caustic soda aqueous solution was added at 60 ° C. from the dropping funnel. Drop it while not exceeding it. After completion of dropping, the mixture is reacted at 60 ± 1 ° C. for 2 hours, then neutralized with 6N sulfuric acid aqueous solution, washed with water and concentrated under reduced pressure to prepare an 85% solution mainly containing trimethylolated bisphenol A. To 9 parts by weight of this solution, 1 part by weight of n-propyl alcohol and 7 parts by weight of isophorone were added and completely dissolved, and then 8 parts by weight of acrylic acid (molar ratio of trimethylolated bisphenol A to 4.6) and p-toluene. Add 0.02 parts by weight of sulfonic acid and depressurize with an aspirator at 60 ℃.
React at ± 1 ° C for 4 hours.

After the reaction, the system is cooled to 40 ° C., unreacted acrylic acid is removed under reduced pressure, washed with water and dehydrated to obtain 20 parts by weight of a resin solution.

The infrared absorption spectrum of the resin thus obtained is shown in FIG. From the absorption ratio of the benzene ring at 1485 cm ^{−1 and} the vinyl at 1405 cm ^{−1 in} the same spectrum, it was confirmed that the resin in this example contained 2.0 mol of acrylic acid ester in the monomer unit.

When this resin was stored at 30 ° C and the shelf life was measured, as shown by the solid line in Fig. 4, about 2 months later,
It showed only 50% change in viscosity. For comparison, when the oligomer according to the above invention, in which X + Y was 4 in the above structural formula, was used, it gelled in 22 days when stored at 30 ° C.

The results of liquid chromatography analysis of this resin are shown in FIG. From this result, it can be seen that the present resin contains a large amount of components having a considerably high molecular weight.

Add 2% of benzoin ethyl ether to the above resin solution, apply it on an alumina substrate using a 25μ doctor blade, and after drying, irradiate from a high pressure mercury lamp of 120W / cm energy at a distance of 10cm for 30 seconds. did. The coating film obtained here was very smooth and hard showing a pencil hardness of 6H. When this product was dipped in solder at 350 ° C for 10 seconds, it turned only brown and no peeling or cracking of the coating film was observed. For comparison, a commercially available UV curable resin was subjected to a solder dipping test at 350 ° C., and the resin was decomposed to generate a gas.

In this example, when the ultraviolet irradiation time was 1 minute, the pencil hardness increased to 8H.

Next, this resin solution was directly applied on an iron plate in an amount of 50 μm, dried, and then irradiated with an electron beam having an energy of 165 eV at 10 Mrad to obtain a hard coating film having a pencil hardness of 7H. This coating is then post-cured at 190 ° C for 5 minutes,
Pencil hardness increased to 9H.

The cured resin showed remarkable resistance to general acids and alkaline solutions.

Example 2 In Example 1, when the charged amount of acrylic acid was 8 mol per 1 mol of trimethylolated bisphenol A and the esterification reaction time was 6 hours, a resin having an esterification rate of 2.6 mol per monomer unit was obtained. Was obtained. Although a cured resin having the same degree as in Example 1 was obtained by ultraviolet curing with this resin, generation of microcracks was observed on the surface in the solder immersion test at 350 ° C.

Example 3 In Example 1, when the esterification reaction time was 1 hour, a resin having an esterification rate of 0.5 mol per monomer unit was obtained. This resin showed a pencil hardness of 4H upon UV curing for 30 seconds, and the surface hardness increased to 9H or more after postcuring at 190 ° C. for 5 minutes.

Example 4 In Example 1, methacrylic acid was used instead of acrylic acid. In this case as well, a resin containing 1.8 mol of methacrylic acid ester per monomer unit was obtained. The esterification rate for methacrylic ester is around 1480 cm ^-1 and 12
It was determined from the ratio of infrared absorption around 95 cm ^-1 .

A coating film having a surface hardness of 5H was obtained from this resin by irradiating it with ultraviolet rays in the air for 30 seconds. It can be seen that the present resin exhibits unique properties, considering that it is difficult to cure in air in the case of ordinary methacrylic acid ester.

The surface hardness of this resin was increased to 9H by post-curing at 190 ° C for 5 minutes.

Example 5 In Example 1, a dimethylol compound was produced by setting the amount of formaldehyde charged to 2 mol per 1 mol of bisphenol A, the amount of acrylic acid charged to 4 mol per 1 mol of dimethylolated bisphenol A, and the esterification reaction time was 2 hours. If it is, the esterification rate per monomer unit is 1.4.
A mole of resin was obtained. A cured resin having the same properties as in Example 1 when obtained by ultraviolet curing was obtained from this resin.

As described above, the radiation curable resin according to the production method of the present invention is cured by ultraviolet rays, infrared rays or electron beams in a short time to give a coating film which is smooth and has high surface hardness, and is particularly suitable as a coating resin. As shown in FIG. 3, these preferable characteristics are presumed to be because the precursor oligomer contains a large amount of high molecular weight components. Further, the present resin is not only preferable for general paints, but also exhibits a remarkable effect on the dispersion of magnetic powder when used for paints for magnetic recording media. For this reason, it is also optimal as a resin for addition to electron beam curable magnetic ink.

In addition, in the present specification, the radiation curing capable of maximizing the characteristics of the resin according to the present invention has been described, but the present resin is not only cured only by radiation curing but also easily cured by heating. It cures over time to give a very hard coating.

As described above, the radiation curable resin according to the production method of the present invention has excellent heat resistance, chemical resistance, surface hardness, and excellent storage stability of the precursor. The effect is great.

[Brief description of drawings]

FIG. 1 is a view showing a production sheet of a radiation curable resin according to the present invention, FIG. 2 is a view showing a result of infrared spectroscopic analysis of an embodiment of the radiation curable resin according to the present invention, and FIG. 3 is a view showing the present invention. FIG. 4 is a diagram showing a molecular weight distribution of an example of the radiation curable resin according to the present invention, and FIG. 4 is a diagram showing a viscosity change during storage of the radiation curable resin according to the present invention and a conventional example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takuya Yagasaki Takuya Yagasaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Noboru Nakatani 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Suzuki Katake 20 Meiwa Kasei Co., Ltd., 1988, Ogushi, Ube City, Yamaguchi Prefecture (72) Inventor Katsuhiko Okazaki 20 Meiwa Kasei Co., Ltd., 1988, Kobe, Obe, Yamaguchi Prefecture

Claims (1)

[Claims] 1. A polymer having a structure represented by the following structural formula as a monomer unit is produced by reacting a compound obtained by reacting a bisoxyphenyl compound with formaldehyde and acrylic acid or methacrylic acid. And a method for producing a radiation curable resin. Provided that R ₁ is CH ₂ , C (CH ₃ ) ₂ or alkylene R ₂ , R ₃ is a methylol group or an acrylic acid or methacrylic acid ester of a methylol group, and the sum of X and Y is 2 to 3
What is.