JPH0940847A - Curable resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a curable resin composition which has temperature dependency in the curing behavior and rapid curing properties and gives a cured resin excellent in heat stability and electric properties with reduced void development on curing. SOLUTION: This resin composition comprises (A) 100 pts.wt. of a (meth)- acryloyl novolak resin prepared by reaction of the phenolic hydroxyl group in the novolak resin with less than the equivalent amount of glycidyl (meth) acrylate, (B) 0.1-15 pts.wt. of radical initiator and (C) the following pts.wt. of hexamethylenetetramine: 3×(remaining phenolic hydroxyl groups/the phenolic hydroxyl groups in the starting novolak)-20×(remaining phenolic hydroxyl groups/the phenolic hydroxyl groups in the starting novolak).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a radical curable resin composition suitable for applications such as adhesives, paints, laminates, molding materials, and binders for organic or inorganic materials.

[0002]

BACKGROUND OF THE INVENTION Conventionally, curable resins that have been used in many fields such as adhesives, paints, laminated materials and molding materials include condensation-curable phenol resins, radical-curable unsaturated polyester resins and epoxies. (Meth) acrylate resin etc. are mentioned.

Phenolic resins are roughly classified into novolac type phenolic resins which are cured with a crosslinking agent typified by hexamethylenetetramine and resole type phenolic resins which are self-curable by a crosslinking group such as a methylol group and / or a dimethylene ether group. To be done. However, these phenolic resins have the following drawbacks associated with condensation curing. (1) Water, ammonia, formaldehyde,
Since lower amines are generated, minute gas holes are formed in the cured product. (2) Since the curing of the resin mainly depends on the activation temperature of hexamethylenetetramine, methylol group and / or dimethylene ether group, the curing conditions such as the curing temperature and the curing rate are naturally limited. In fact, in the case of hexamethylenetetramine curing of novolac resin, the temperature at which the curing reaction begins vigorously is around 120 ° C, but an increase in viscosity is observed even at 100 ° C or less. (3) In the novolak resin using hexamethylenetetramine, impurities such as unreacted hexamethylenetetramine and lower amine are present in the cured product, so it is used as an electric / electronic component such as deterioration of insulation and corrosion of insert metal. When doing, inconvenient problems are likely to occur. In particular, a resol-type phenol resin is used to solve the third problem, but the resol-type phenol resin generally has a slow curing rate, and a fast curing agent is thermally unstable and has a problem in workability. is there.

On the other hand, since the unsaturated polyester resin is cured by a radical reaction, no voids are generated, the curing temperature and speed can be easily controlled, and the electric characteristics are good. However, it lacks thermal stability and is unsuitable for use at high temperatures.

Epoxy (meth) acrylate resins have good thermal stability but contain a large amount of highly reactive (meth) acrylic groups, so that crosslinking tends to be non-uniform during curing and bending strength tends to decrease. . Epoxy (meth) acrylate resin is generally synthesized by a method of reacting an epoxy resin and (meth) acrylic acid. Also known is a method of reacting a compound having a phenolic hydroxyl group such as bisphenols or novolac resins with glycidyl (meth) acrylate. The latter method is not generally used because it is disadvantageous in terms of cost, but it is known that the residual amount of phenolic hydroxyl group can be controlled to an arbitrary ratio from 0 to 100% (JP-A-5-57).
828). However, curing of a resin having a phenolic hydroxyl group left alone with a radical initiator has not been studied because it is believed that the phenolic hydroxyl group does not undergo radical polymerization because it has a polymerization inhibiting action. It is considered that in such a resin, the number of (meth) acryloyl groups contained in the molecule is reduced, so that the crosslinking becomes uniform and the bending strength is improved. However, due to the decrease in crosslink density,
A decrease in thermal stability is inevitable.

[0006]

The present invention has been made as a result of various studies in order to solve such problems of the conventional phenol resin, unsaturated polyester resin and epoxy (meth) acrylate resin. The inventors have found that a (meth) acryloylated novolak containing a phenolic hydroxyl group can be cured using an appropriate amount of a radical initiator and hexamethylenetetramine in combination.
The present invention has been achieved. It is an object of the invention to provide a curable resin composition which has a temperature dependency of curing and a rapid curing property, has few voids during curing, and gives a cured resin excellent in thermal stability and electric characteristics.

[0007]

The present invention has a phenolic hydroxyl group in a molecule, which is obtained by reacting a phenolic hydroxyl group of a novolac resin with an equivalent amount or less of glycidyl (meth) acrylate. (Meth) acryloylated novolak resin 10 characterized by
The present invention relates to a curable resin composition comprising 0 parts by weight, 0.1 to 15 parts by weight of a radical initiator, and hexamethylenetetramine in an amount of the range determined by the following formula. 3 × (residual phenolic hydroxyl group / phenolic hydroxyl group in raw novolak) to 20 × (residual phenolic hydroxyl group /
(Phenolic hydroxyl group in raw novolac)

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material novolak resin used for synthesizing the (meth) acryloylated novolak having a phenolic hydroxyl group used in the present invention is obtained by condensing a phenol compound and formaldehyde.
The phenol compound used in the novolac resin may be a compound having a hydroxyl group in the aromatic nucleus, for example, phenol, cresol, xylenol, butylphenol, alkylphenols such as nonylphenol, catechol, resorcin, hydroquinone, polyphenols, Examples thereof include bisphenol A, bisphenol F, bisphenol S, polynuclear phenols, and the like, and one kind or a combination of two or more kinds thereof may be used. Further, these novolak resins may be modified for the purpose of imparting flexibility. Examples of the modifying agent include aromatic hydrocarbons such as toluene, xylene and mesitylene, drying oils such as tung oil and linseed oil, and dicyclopentadiene.
Further, the molar ratio (F / P) of formaldehyde to be condensed with these phenol compounds is 0.4 to 0.9, preferably 0.65 to 0.9, and unreacted phenol compound may be present, but is not present. Is better.

The (meth) acryloylated novolak resin used in the present invention is obtained by using the above-mentioned novolak resin and glycidyl (meth) acrylate in the presence of a basic catalyst such as amines at 70 to 150 ° C. Desirably, it is obtained in the temperature range of 75 to 100 ° C. In synthesizing the resin, a polymerization inhibitor may be used for the purpose of preventing gelation during the reaction, storage stability of the product, and preparation of the curability.

Examples of such a polymerization inhibitor include hydroquinone, pt-butylcatechol, hydroquinones such as mono-t-butylhydroquinone, hydroquinone monomethyl ether, phenols such as di-p-cresol, p-benzoquinone, naphthoquinone, p. -There are quinones such as toluquinone and copper salts such as naphthene copper.

The residual phenolic hydroxyl group of the (meth) acryloylated novolak resin used in the present invention and (meth)
The ratio with the acryloyl group is 2: 9 in the range of 9: 1.
8-5: 5 is more desirable. When the number of (meth) acryloyl groups is more than the above, the number of reaction points with hexamethylenetetramine decreases, and sufficient strength cannot be obtained. Further, since the softening point of the resin is lowered and the resin becomes a starch syrup or a sticky solid, it becomes difficult to handle and the workability deteriorates. On the other hand, if the (meth) acryloyl group is less than the above range, the number of cross-linking points becomes too small, and a good cured product cannot be obtained.

The amount of the radical initiator according to the present invention is 0.1 to 15 parts by weight, preferably 0.5 to 1 part by weight, based on 100 parts by weight of the (meth) acryloylated novolak resin.
0 parts by weight. If the amount is less than 0.1 part by weight, the composition will cure, but the curability comparable to that of conventional unsaturated polyester and epoxy (meth) acrylate cannot be obtained. If the amount is more than 15 parts by weight, the curing will be too fast, and the residue due to the curing agent will have a bad effect, which is not practical.

The radical initiator used in the present invention is preferably an organic peroxide having a thermal decomposition temperature (half-life of 10 hours) of 100 ° C. or higher. If the temperature is lower than 100 ° C., the advantage that the temperature dependence of the curing reaction is large, which is one of the objects of the present invention, cannot be sufficiently exhibited.

Examples of the radical initiator include peroxyesters such as 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate and t-butylperoxybenzoate, and 2,2. -Bis (t-butylperoxy) octane, 2,2-bis (t-butylperoxy)
Butane, 2,5-dimethyl-2,5-di (t-butylperoxy)
Peroxyketals such as hexane, dicumyl peroxide, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di-t-
There are dialkyl peroxides such as butyl peroxide and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, and these can be mixed if necessary.

The amount of hexamethylenetetramine used in the present invention is a part by weight determined by the following formula according to the amount of phenolic hydroxyl groups remaining in the resin. 3 × (residual phenolic hydroxyl group / phenolic hydroxyl group in raw novolak) to 20 × (residual phenolic hydroxyl group /
Raw material novolac phenolic hydroxyl group) Desirably 10 x (residual phenolic hydroxyl group / raw material novolac phenolic hydroxyl group) to 15 x (residual phenolic hydroxyl group / raw material novolac phenolic hydroxyl group) If less than the above range, hexamethylene tetramine is used in combination. If the amount is more than the above range, the characteristics of the cured product will be impaired and it will not be practical.

The curable resin composition of the present invention has curability due to a radical reaction despite the fact that the (meth) acryloylated novolak resin contains a phenolic hydroxyl group which can serve as a radical polymerization inhibitor. The reason is as follows. It is thought to be as follows. Generally, the polymerization inhibitor is a monomeric phenol compound having one or two hydroxyl groups in the molecule and is considered to suppress the polymerization by the hydrogen abstraction reaction from the hydroxyl groups, but the (meth) acryloylated novolak resin is a phenol. In many cases, a bulky (meth) acryloyl group is present at a position adjacent to the functional hydroxyl group, so that the active radical is difficult to effectively extract hydrogen, and thus has a small inhibiting effect on the polymerization of the vinyl group. Furthermore, the radical on the oxygen atom generated when the phenolic hydroxyl group captures the radical reacts with the other terminal radical contributing to the crosslinking, and a new crosslinking is generated. (In the case of a monomer having one or two hydroxyl groups in a molecule such as a polymerization inhibitor, a polymerization termination reaction is induced and crosslinking does not proceed.) For the above reasons, the resin composition of the present invention is a radical It is thought that it is cured by the reaction.

The resin composition of the present invention does not cure at 100 ° C. or lower, and rapidly cures at 150 ° C., which shows extremely high temperature dependence. The reason is that two different curing systems, radical curing and condensation curing, proceed in two stages. That is, the radical curing starts according to the decomposition temperature of the initiator, and then the curing with hexamethylenetetramine proceeds. The curing with hexamethylenetetramine has a low activation energy and can occur even at a low temperature of 100 ° C., but the influence can be suppressed by reducing the amount used. Further, reduction of the amount of hexamethylenetetramine leads to reduction of voids and improvement of electrical characteristics. Furthermore, by reducing the amount of the (meth) acryloyl group contained in the (meth) acryloylated novolac resin, uniform radical curing proceeds, and heat treatment is used to compensate for the low crosslinking density by methylene crosslinking with hexamethylenetetramine. The stability is also good.

[0018]

The following examples are given to illustrate the present invention in detail, but the present invention is not limited thereto.

Synthesis Example 1 A separable flask equipped with a thermometer and a stirrer was placed in a phenol novolac resin (F / P =
0.8) 100 parts by weight, glycidyl methacrylate (hereinafter abbreviated as GMA) 90 parts by weight, 2-methylimidazole 1 part by weight, and hydroquinone 0.05 part by weight were charged.
By reacting at 5 ° C. for 4 hours, a methacryloylated novolak resin was obtained as a dark red solid substance. According to comparison of ¹ H NMR integral values, the ratio of the phenolic hydroxyl group and the methacryloyl group was 4: 6.

(Synthesis Example 2) A separable flask equipped with a thermometer and a stirrer was placed in a phenol novolac resin (F / P =
0.8) 100 parts by weight, GMA 90 parts by weight, methyl ethyl ketone 100 parts by weight, triethanolamine 3 parts by weight,
Hydroquinone (0.05 parts by weight) was charged and refluxed for 5 hours. The reaction product was poured into a large amount of water and the resulting precipitate was filtered off.
By drying, a methacryloylated novolac resin in which the ratio of the phenolic hydroxyl group and the methacryloyl group was 4: 6 was obtained as a dark red solid substance.

(Synthesis Example 3) Synthesis was carried out under the same conditions as in Synthesis Example 1 except that the amount of GMA was changed to 60 parts by weight. As a result, a methacryloylated novolak resin having a ratio of phenolic hydroxyl groups and methacryloyl groups of 6: 4 was concentrated. Obtained as a red solid.

(Synthesis Example 4) Synthesis was carried out under the same conditions as in Synthesis Example 1 except that the amount of GMA was changed to 140 parts by weight and the ratio of phenolic hydroxyl group to methacryloyl group was 0.5: 9.5.
Was obtained as a dark red solid substance.

(Example 1) 5 parts by weight of dicumyl peroxide and 5 parts of hexamethylene tetramine per 100 parts by weight of the methacryloylated novolak resin synthesized in Synthesis Example 1
Parts by weight were added and mixed in a mortar. After this mixture was melted at 90 ° C. in an aluminum vat, bubbles contained in the resin were removed under reduced pressure. Curing behavior (curing speed,
The maximum degree of cure) was measured and the appearance of the resulting cured product piece was observed. Also, 100 and 17 of this compound by a kneader
The torque rise time at 0 ° C was measured. An insulation resistance test piece, a bending test piece, and a TMA test piece are prepared by compression molding using this composition, and the insulation resistance, boiling insulation resistance, bending strength,
The glass transition temperature by TMA was measured according to JIS C6481.

Example 2 The same method as in Example 1 was carried out except that the radical initiator was changed to di-t-butyl peroxide.

Example 3 The same method as in Example 1 was carried out except that the resin synthesized in Synthesis Example 3 was used and the amount of hexamethylenetetramine was changed to 9 parts by weight.

Comparative Example 1 The same method as in Example 1 was carried out except that hexamethylenetetramine was not used.

Comparative Example 2 The same procedure as in Example 1 was carried out except that 30 parts by weight of hexamethylenetetramine was used.

Comparative Example 3 The same method as in Example 1 was carried out except that the resin synthesized in Synthesis Example 4 was used.

Comparative Example 4 15 parts by weight of hexamethylenetetramine was added to 100 parts by weight of a phenol novolac resin having F / P = 0.85 and mixed in a mortar. The same operation as in Example 1 was carried out except that this formulation was used.

(Comparative Example 5) Unsaturated polyester resin 10
5 parts by weight of dicumyl peroxide was added to 0 parts by weight and mixed in a mortar. Example except using this formulation
The same operation as in 1 was carried out.

[0031]

[Table 1]

[0032]

According to the present invention, there is provided a curable resin composition which gives a cured resin having a large temperature dependence of curing, a rapid curing property, little void generation during curing, and excellent thermal stability and electrical properties. A resin composition that can be obtained and is useful in various applications such as adhesives, paints, laminates, molding materials, binders of organic materials or inorganic materials can be provided.

Claims (3)

[Claims] 1. A phenolic hydroxyl group of a novolac resin, which is obtained by reacting a glycidyl (meth) acrylate in an equivalent amount or less with respect to the phenolic hydroxyl group, and has a phenolic hydroxyl group in the molecule (meth). A curable resin composition comprising 100 parts by weight of an acryloylated novolak resin, 0.1 to 15 parts by weight of a radical initiator, and parts by weight of hexamethylenetetramine calculated by the following formula. 3 x (residual phenolic hydroxyl group / phenolic hydroxyl group in raw material novolak) to 20 x (residual phenolic hydroxyl group / phenolic hydroxyl group in raw material novolac) 2. The curable resin composition according to claim 1, wherein the ratio of the residual phenolic hydroxyl group to the (meth) acryloyl group of the (meth) acryloylated novolac resin is 1: 9 to 9: 1. 3. The thermal decomposition temperature (half-life 10
The curable resin composition according to claim 1, wherein the time) is 100 ° C or higher.