JP2558798B2 - Radiation curable resin composition and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radiation curable resin that is cured by radiation such as ultraviolet rays, electron beams, infrared rays, etc., and particularly has low hygroscopicity when used as a coating film, hardness,
The present invention mainly relates to a solventless type radiation curable resin which forms a coating film having excellent heat resistance.

2. Description of the Related Art Conventionally, a radiation curable resin that is cured by ultraviolet rays has been widely used because of its 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.

However, the above-mentioned conventional radiation-curable resins each have drawbacks, and improvement has 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.

As means for solving the above problems, bisphenol A
There is a resin using a polymer of a compound obtained by converting a tetramethylol compound of (2,2'-bis (4'-oxyphenyl) propane) into an acrylic acid or methacrylic acid ester at a specific ratio (JP-A-60-001209). However, although the radiation-cured resin gives a radiation-cured coating film with excellent performance, the stability of the precursor oligomer is not always good, for example, when stored at 30 ° C, it takes about 20 days. It had a problem of gelation.

As means for solving the above-mentioned problem, a polymer of a compound obtained by converting a di- or trimethylol compound of a bisoxyphenyl compound into a specific ratio of acrylic acid or methacrylic acid ester is used in place of the tetramethylol compound of bisphenol A. Resin is newly proposed.

Problems to be Solved by the Invention The radiation-curable resin has a long shelf life and exhibits excellent characteristics.However, during the manufacturing process, a solvent is included, and therefore when a coating film of the resin is to be formed, it is not exposed to radiation. The drying step was indispensable in advance, and there was a drawback that the rapid curing, which is one of the features of radiation curing, was hindered.

Means for Solving the Problems As a means for solving the drawbacks of the above-mentioned conventional radiation-curable resins, the present invention has a formaldehyde resin characterized by having the following structure as a monomer unit, and at least one formaldehyde resin in the structure. The radiation-curable resin composition is characterized by containing at least one kind of monomer or oligomer having a photopolymerizable unsaturated double bond.

Provided that R ₁ is CH ₂ , C (CH ₃ ) ₂ or alkylene having 1 to 6 carbon atoms, R ₂ and R ₃ are methylol groups or acrylic acid or methacrylic acid esters of methylol groups, and X and Y are The sum of is 2 or 3.

By using the radiation curable resin composition described above,
It is possible to obtain a solventless radiation-curable resin which has a low hygroscopicity, provides a coating film having excellent surface hardness, heat resistance and chemical resistance, and has excellent storage stability.

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

A production flow sheet of the radiation curable resin according to the present invention is shown in FIG.

In FIG. 1, for 1 mol of the bisoxyphenyl compound represented by the chemical formula (I) below, Mixing 2 to 3 mol of muraldehyde, and dropping caustic soda aqueous solution to react. After the reaction, the product is neutralized with an aqueous solution of sulfuric acid, washed with water and dehydrated to obtain the di- or trimethylol compound (II) of (I).

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.

R _{1 in} the structure of the starting material (I) is CH ₂ (bisphenol F), C (CH ₃ ) ₂ (bisphenol A)
Etc. are easily available, but a long-chain methylene group or alkylene group can be used for improving the toughness and reactivity of the cured resin. Bisphenolic resoles using these long-chain methylene groups or alkylene groups are known (Higashi et al., Industrial Chemistry Magazine, Vol. 61, 469 pages, Darashenko et al., Plaschezkie Massi, August 1965, 9).
Page etc.).

Next, in (II), at least one monomer or oligomer having at least one photopolymerizable unsaturated double bond in the structure is added, and if necessary, a solvent is further added and mixed,
Acrylic acid or methacrylic acid and a catalyst are added and reacted to carry out the condensation of the methylol group and the esterification reaction at the same time. The charge amount of acrylic acid or methacrylic acid is (II) 1
An amount of 1 to 8 mol is used with respect to mol. If the amount of acrylic acid or methacrylic acid is small during the reaction, the system may gel.

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 composition.

By the reduced pressure reaction step and the final dehydration step, the solvent in the reaction system is removed and the final resin becomes virtually solvent-free, but a solvent may be added for the purpose of controlling the viscosity of the resin and other purposes.

The esterification rate can be calculated from the absorption rate in infrared spectroscopic analysis and the amount of the charged monomer or oligomer.

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 ester when priority is given to fast curability and curability at low doses. . 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 9: 1 to 1: 2, there is little hygroscopicity, surface hardness, heat resistance, chemical resistance and radiation. A resin composition having excellent curability can be obtained.

The mixing ratio of the resin having the above structure as a monomer unit and the monomer or oligomer having at least one photopolymerizable unsaturated double bond in the structure is the property of the above monomer or oligomer and the required coating film properties. Although it can be changed arbitrarily depending on the composition, it is a feature of a resin having the above-mentioned structure as a monomer unit. It has low hygroscopicity, and if surface hardness, heat resistance and chemical resistance are to be particularly utilized, the proportion of the monomer or oligomer blended. It is preferable to reduce However, if the blending ratio of the above-mentioned monomer or oligomer is low, the viscosity of the resin composition will be high, so it is necessary to determine the blending ratio in accordance with the purpose of use and the application or the equipment used.

Examples of monomers or oligomers that can be used here include monofunctional or polyfunctional acrylic or methacrylic esters, oligoester acrylates, epoxy acrylates, polyester acrylates, urethane acrylates, various unsaturated polyesters, polybutadiene and modified products thereof. Examples thereof include, but are not limited to, any compound having a photopolymerizable unsaturated double bond and having compatibility with the resin having the above structure.

Since the present resin composition is substantially solvent-free, good properties can be obtained only by curing with radiation, but post-curing can significantly improve the surface hardness.

 Hereinafter, a specific example will be described.

(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 6 mol of 6N caustic soda aqueous solution (2.2 mol) was added from the dropping funnel to 60 mol. Add dropwise while keeping the temperature below ℃. 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 7.6 parts by weight of trimethylolpropane were added and completely dissolved, and then 7 parts by weight of acrylic acid (molar ratio of trimethylolated bisphenol A to 4.6),
0.02 parts by weight of p-toluenesulfonic acid is added, and the mixture is reacted at 60 ° C. ± 1 ° C. for 4 hours under reduced pressure with an aspirator. After the reaction,
After cooling the system to 40 ° C., unreacted acrylic acid was removed under reduced pressure, washed with water and dehydrated to obtain a resin composition.

From the ratio of absorption near 1485cm ^-1 vicinity and 1405cm ^-1 in infrared spectroscopic analysis, the resin composition is methylol group 2 molar in trimethylol bisphenol A was found to contain an acrylic esterified resin.

When this resin composition was stored at 30 ° C. and the shelf life was measured, only about 20% of the viscosity change was shown even after 2 months, and it was confirmed that the storage stability was excellent even when the solvent was removed. Was done.

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.

2% of benzoin ethyl ether was added to the above resin composition, which was applied onto an alumina substrate using a 25 μ doctor blade, and irradiated with a high pressure mercury lamp of 120 W / cm energy at a distance of 10 cm for 30 seconds. The coating film obtained here was very smooth and hard showing a pencil hardness of 6H. When this was further post-cured at 120 ° C. for 5 minutes, the pencil hardness increased to 9H.

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

Next, this resin composition was mixed with an extender pigment and titanium oxide for coloring, and the mixture was kneaded with a three-roll mill to obtain 50 on an iron plate.
When μ was applied and an electron beam with an energy of 165 eV was applied for 3 Mrad, a hard coating film having a pencil hardness of 7H was obtained. After this coating film was post-cured at 190 ° C. for 5 minutes, the pencil hardness increased to 9H or higher.

(Example 2) In Example 1, when the esterification reaction time was set to 1 hour, a composition containing a resin having an esterification rate of 1.2 mol per 1 mol of trimethylolated bisphenol A was obtained. This resin showed a pencil hardness of 4H upon UV curing for 15 seconds, and the surface hardness increased to 9H or more by post-curing at 120 ° C. for 5 minutes.

When this product was dipped in solder at 350 ° C for 10 seconds, it was only discolored brown, and peeling and cracks of the coating film were not observed. For comparison, in this example, the amount of acrylic acid charged was 8 with respect to 1 mol of trimethylolated bisphenol A.
When the amount was 6 mol and the esterification reaction time was 6 hours, a composition containing a resin having an esterification rate of 2.6 mol per 1 mol of trimethylolated bisphenol A was obtained. A cured resin having the same degree as in Example 1 was obtained from this resin in ultraviolet curing, but cracks were generated on the surface in the solder immersion test at 350 ° C. Therefore, it is considered to be sufficiently practical except under the above high temperature.

Similarly, for comparison, a commercially available ultraviolet curable resin was subjected to ultraviolet curing under the same conditions as in Example 2 above. The surface hardness was 5H, there was no post cure effect, and the resin decomposed in the 350 ° C solder dip test. , Gas was generated.

(Example 3) In Example 1, the amount of p-toluenesulfonic acid was adjusted to 0.
When 005 parts by weight and the esterification reaction time was 1 hour, a composition containing a resin having an esterification rate of 0.3 mol per 1 mol of trimethylolated bisphenol A was obtained. This resin exhibits a pencil hardness of 4H upon 15 seconds of UV curing,
The surface hardness is 9 by post-curing at 190 ℃ for 5 minutes.
It rose above H.

When this product was immersed in solder at 350 ° C. for 10 seconds, it only changed to brown, and no peeling or cracking of the coating film was observed.

(Example 4) In Example 1, methacrylic acid was used instead of acrylic acid. Also in this case, a composition containing 1.8 mol of a methacrylic acid ester resin with respect to 1 mol of trimethylolated bisphenol A was obtained. The esterification rate in the case of methacrylic ester was determined from the ratio of infrared absorption around 1480 cm ^-1 and 1295 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, and the amount of acrylic acid charged was 4 mol per 1 mol of dimethylolated bisphenol A, and the esterification reaction time was 2 times.
When the time was used, a composition containing a resin having an esterification rate of 1.4 mol per mol of dimethylolated bisphenol A was obtained. This resin composition was used in Example 1 in ultraviolet curing.
A cured resin having the same properties as was obtained.

(Example 6) In Example 1, even when pentaerythritol triacrylate was used instead of trimethylolpropane triacrylate, a cured resin having a very high surface hardness was obtained as in Example 1.

(Example 7) A cured resin having a very high surface hardness was obtained as in Example 1 even when 5.0 parts of 2-phenoxyethyl acrylate was used in place of trimethylolpropane triacrylate in Example 1.

As described above, the radiation curable resin according to the present invention is an ultraviolet ray,
It is cured by infrared rays or electron rays in a short time to give a coating film which is smooth and has high surface hardness, and is particularly suitable as a resin for paints. It is speculated that these preferable characteristics are due to the precursor oligomer containing a large amount of high molecular weight components, as shown in FIG. 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. Therefore, it is also most suitable as a resin for addition to electron beam curable magnetic ink.

In this specification, the radiation curing capable of maximizing the characteristics of the resin according to the present invention has been described. However, the present resin is not only cured by the radiation curing but easily cured by heating. Since it cures over time to give a very hard cured resin, it can be used as a thick coating film or for casting.

As described above, the radiation curable resin according to the present invention has excellent heat resistance, chemical resistance, and surface hardness, and
The precursor has excellent storage stability, and since it is solvent-free, it has a high curing speed, and is industrially effective.

[Brief description of drawings]

FIG. 1 is a diagram showing a production sheet of a radiation curable resin according to the present invention, and FIG. 2 is a diagram showing a molecular weight distribution of an example of the radiation curable resin according to the present invention.

 ─────────────────────────────────────────────────── ─── 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 Matsushita Electric Industrial Co., Ltd. (72) Inventor Katake Suzuki 20 Meiwa Kasei Co., Ltd., Obeshi, Ube, Yamaguchi Prefecture, 1988 20 Meiwa Kasei Co., Ltd. (72) Inventor Katsuhiko Okazaki, 20 Meiji Kasei Co., Ltd., Obeshi, Ube, Yamaguchi Prefecture

Claims (3)

(57) [Claims] 1. A formaldehyde resin having the following structure as a monomer unit, and at least one monomer or oligomer having at least one photopolymerizable unsaturated double bond in the structure. Radiation curable resin composition. Provided that R ₁ is CH ₂ , C (CH ₃ ) ₂ or alkylene having 1 to 6 carbon atoms, R ₂ and R ₃ are methylol groups or acrylic or methacrylic acid esters of methylol groups, and X
And the sum of Y and Y is 2 or 3. 2. The radiation curable resin composition according to claim 1, wherein the composition does not contain a solvent. 3. The acrylic or methacrylic esterification reaction of a di- or trimethylolated bisoxyphenyl compound is carried out in the presence of a monomer or oligomer having at least one photopolymerizable unsaturated double bond in the structure. A method for producing a radiation curable resin composition, comprising: