JPH09176255A - Thermosetting resin molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molding material which is excellent in thermal stability in injection molding, cures quickly, and gives a molded item excellent in mechanical strengths and high-temp. stiffness. SOLUTION: This molding material mainly comprises a resin component comprising 100 pts.wt. (meth)acryloylated novolak resin and 0.1-30 pts.wt. org. peroxide and a filler component comprising org. and inorg. fillers. The novolak resin has phenolic hydroxyl groups and is obtd. by reacting phenolic hydroxyl groups of a novolak resin with an at most equivalent of glycidyl (meth)acrylate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a very large temperature dependence of a curing reaction, that is, it is stable without being substantially cured at a relatively low temperature of 130 ° C. or lower, and is rapidly cured at a high temperature of 150 ° C. or higher. It is a thermosetting resin that has features and is particularly excellent in thermal stability in the cylinder of the injection molding machine in injection molding, and the resulting molded product is excellent in rigidity when heated, mechanical strength, and electrical characteristics. Regarding molding material.

[0002]

2. Description of the Related Art Generally, thermosetting resin molding materials include:
Examples thereof include a phenol resin represented by a condensation curing type and an unsaturated polyester resin and an epoxy (meth) acrylate resin represented by a radical curing type. Among these, many of the phenolic resin molding materials (condensation curing type) use a novolak type phenol resin as a resin component and add a hexamethylenetetramine (hexamine) as a curing agent to cause a curing reaction. Although the phenol resin molding material using such a novolac type phenol resin has good curability in injection molding, the thermal stability in the injection cylinder is insufficient, and the filling property in the molding die is also good. However, it has been required to improve in terms of continuous moldability, and water, ammonia, formaldehyde, lower amine, etc. are generated at the time of curing, resulting in defective gas deficiency and formation of many voids in molded products. , Improvement was required. Regarding curability,
It has been studied and improved by using a high ortho novolac type phenol resin having a high ratio of ortho bonds in the methylene bond to the phenol nucleus, but it has been implemented, but the thermal stability during injection molding is insufficient. Yes, and further improvements were desired.

On the other hand, since unsaturated polyester resins and epoxy (meth) acrylate resins are cured by a radical reaction, voids are not generated, and the curing temperature and the curing speed can be easily controlled. And the moldability is good. However, since it does not have a phenolic hydroxyl group, the characteristics attributable to the phenolic hydroxyl group, that is, the strength due to the intermolecular interaction of the phenolic hydroxyl group in the cured resin, the adhesion to the base material, etc., are lower than those of the phenol resin.

[0004] Epoxy (meth) acrylate resins are generally synthesized by reacting epoxy resins with (meth) acrylic acid. A method is also known in which a compound having a phenolic hydroxyl group such as a bisphenol or a novolak resin is reacted with glycidyl (meth) acrylate. The latter method is not generally used because it is disadvantageous in terms of cost.
It is known that the ratio can be controlled to an arbitrary ratio of up to 100% (JP-A-5-57828). However, curing a resin alone with a radical initiator with a phenolic hydroxyl group remaining has not been studied because it is believed that the phenolic hydroxyl group does not undergo radical polymerization due to its polymerization inhibiting action.

Further, regarding the filler, wood powder, pulp, organic fibers, cloth strips, thermoplastic resin powder, etc. are used as the organic filler depending on the application. Among the organic fillers, ordinary ones such as wood flour are not sufficient in mechanical strength and electric properties (particularly after boiling), and are not suitable for powders of thermoplastic resin powders or thermosetting resin cured products or inorganic fillers. The above properties have been improved to some extent by blending the material. However, since the heat resistance of a thermoplastic resin powder generally decreases, there is a limit to its blending. Further, attempts have been made to improve molding shrinkage and electrical characteristics by using a thermosetting resin powder or wood powder in combination (Japanese Patent Application Laid-Open Nos. 57-78444 and 59-105049). However, if the thermosetting resin powder is used in a large amount, the molded product becomes hard and brittle, and other characteristics are not improved much.

On the other hand, as the inorganic filler, powders of calcium carbonate, clay, silica, alumina, aluminum hydroxide, glass and the like, glass fiber and the like are used. Inorganic fillers include hard materials such as silica, alumina, and glass, and relatively soft materials such as calcium carbonate and clay, which are selected and used according to the application and required characteristics. Excellent performance in electrical characteristics and the like.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of various studies in order to solve such problems of the conventional phenol resin molding material. Even in a resin system in which a phenolic hydroxyl group remains, radical curing is possible by using an appropriate amount of the initiator. Furthermore, because of this, the temperature dependence of curing is extremely large, so that it has excellent thermal stability during injection molding and fast curing, and the resulting molded product has excellent mechanical strength and rigidity during heating. This led to the development of molding materials.

[0008]

SUMMARY OF THE INVENTION The present invention has a phenolic hydroxyl group in a molecule obtained by reacting a phenolic hydroxyl group of a novolak resin with glycidyl (meth) acrylate in an equivalent amount or less. (Meth) acryloylated novolak resin (A) (100 parts by weight) and organic peroxide (B) 0.1 to 3
It is a thermosetting resin molding material characterized by mainly comprising a resin component consisting of 0 parts by weight and an organic filler and / or an inorganic filler as a filler.

In the present invention, the (meth) acryloylated novolak resin has curability due to a radical reaction despite the fact that it contains a phenolic hydroxyl group. The reason is considered as follows.

Generally, the polymerization inhibitor is a monomeric phenol compound having one or two hydroxyl groups in the molecule and has a high radical scavenging ability because it is easy to move in the reaction system, but the (meth) acryloylated novolak resin is , A large molecular weight makes it difficult to move and a functional group derived from a relatively long chain glycidyl (meth) acrylate is often present at a position adjacent to a phenolic hydroxyl group, so that the hydroxyl group is difficult to effectively capture a radical, and therefore ( The phenolic hydroxyl groups of the (meth) acryloylated novolak resin have a small inhibiting effect on the polymerization of vinyl groups. 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 undergoes a radical reaction despite the presence of a phenolic hydroxyl group, and a cured product excellent in various properties can be obtained. In particular, it is excellent in rigidity when heated. This is because the phenolic hydroxyl group, which is a polar group, remains in the cured resin.
Alternatively, when a base material, a reinforcing material, etc. are present, it is considered that the interaction between the molecule and these base materials is strong. From the above, the resin composition of the present invention radically cures despite having a phenolic hydroxyl group in the molecule, has excellent rigidity at the time of heat, and has extremely large temperature dependence of curing. It is a thing.

The novolak resin used in the present invention is obtained by reacting a phenol compound with formaldehyde in the presence of an acidic catalyst. The phenol compound used in the novolak resin may be any compound having a hydroxyl group in an aromatic nucleus, such as phenol, alkyl phenols such as cresol, xylenol, butyl phenol, and nonyl phenol; further, catechol, resorcinol, polyhydric phenols such as hydroquinone, and bisphenol A, bisphenol F, bisphenol S
Examples thereof include polynuclear phenols and the like, and one or more of these may be combined. 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.

The molar ratio (F / P) of formaldehyde to be reacted with these phenolic compounds is 0.4 to 0.1.
9, preferably 0.65-0.9, free phenol 2
% By weight or less is preferred. If the amount of free phenol is large, it acts as a radical polymerization inhibitor.

In the present invention, the (meth) acryloylated novolak resin comprises the above-mentioned novolak resin and glycidyl (meth)
The acrylate is prepared in the presence of a basic catalyst such as amines or the like by a known and conventional method at 70 to 150 ° C., preferably 75 to 10 ° C.
Obtained in a temperature range of 0 ° C. A polymerization inhibitor may be used for the purpose of preventing gelation of the resin during synthesis, controlling storage stability of the product, and adjusting curability.

Examples of the polymerization inhibitor include hydroquinone, hydroquinone such as pt-butylcatechol, mono-t-butylhydroquinone, hydroquinone monomethyl ether, phenols such as di-p-cresol, p-benzoquinone, naphthoquinone, and p-toluquinone. Such as quinones 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 preferably in the range of 1: 9 to 9: 1, and more preferably 2: 8 to 5: 5. When the amount of the (meth) acryloyl group is larger than the above range, the softening point of the resin is lowered, and the resin becomes a starch syrup or a sticky solid. Also (meta)
If the 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 number average molecular weight of the (meth) acryloylated novolak resin (A) is preferably from 500 to 2,000. When it is less than 500, the softening point of the resin is lowered and the workability is lowered in various applications. On the other hand, when it is more than 2000, application to a molding material becomes difficult due to an increase in softening point, a decrease in fluidity, an increase in viscosity of a solution and the like. A more preferred molecular weight range is from 700 to 1500.

The amount of the organic peroxide (B) used in the present invention is (meth) acryloylated novolac resin (A).
It is 0.1 to 30 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight. If the amount is less than 0.1 part by weight, the curability is significantly impaired, and the curability comparable to that of conventional unsaturated polyester and epoxy (meth) acrylate cannot be obtained. If the amount is more than 30 parts by weight, the curing will be too fast, and the residue due to the curing agent will have an adverse effect, which is not practical.
The thermal decomposition temperature (half-life of 10 hours) of organic peroxide is 100.
C. or higher is suitable. If the temperature is lower than 100 ° C., one of the objects of the present invention is that the advantage of high temperature dependence of the curing reaction is not sufficiently exhibited. As the organic peroxide having a thermal decomposition temperature of 100 ° C. or higher, dicumyl peroxide, t-butylperoxybenzoate and di-t-butylperoxide are generally and preferably used. These organic peroxides may be used alone or in combination of two or more.

Next, the filler will be described. In the present invention, it is particularly preferable to use an organic filler and an inorganic filler in combination, and to use a powder of a cured thermosetting resin as a part of the organic filler. The powder of the cured thermosetting resin includes not only the cured product powder of the resin alone but also the cured product of the thermosetting resin molding material, or the crushed thermosetting resin laminate or decorative board. Examples of the thermosetting resin include a phenol resin, a melamine resin, an epoxy resin, a urethane resin, and an unsaturated polyester resin, and a phenol resin, a melamine resin, and an epoxy resin are generally used.

The hardness of the molded product is not sufficient, the dimensional accuracy is not sufficient, and it is difficult to obtain a satisfactory product in terms of strength and wear only by using an ordinary organic filler such as wood powder. Therefore, these disadvantages can be greatly improved by blending a powder of a cured thermosetting resin as a part of the organic filler. The powder of the thermosetting resin cured product is harder than other organic fillers, but it is softer than metals such as iron and aluminum, so it wears the counterpart drill and metal during drilling and sliding. Never. The compounding ratio of the powder of the cured thermosetting resin is 10 to 4 in the organic filler.
0% by weight. If it is less than 10% by weight, the effect of the compounding is small, and if it exceeds 40% by weight, the molded article becomes hard and brittle, which is not preferable.

As the organic filler, in addition to the powder of the thermosetting resin cured product, wood powder, pulp, organic fibers, cloth strips, thermoplastic resin powder and the like are used depending on the application. Next, an inorganic filler is used together with the above organic filler. By using an inorganic filler together, strength, dimensional accuracy, electrical characteristics, etc. are improved. As an inorganic filler,
Calcium carbonate, talc, clay, silica, alumina,
Aluminum hydroxide, glass, etc. can be used, but the molded product may become hard and brittle depending on the type and the amount used.

The thermosetting resin molding material of the present invention comprises, as a resin component, a phenolic hydroxyl group in which a (meth) acryloylated novolak resin can serve as a radical polymerization inhibitor and a radical reaction type phenolic resin sharing a (meth) acryloyl group. By using an organic peroxide as a radical initiator, improvement of thermal stability in a cylinder at the time of injection molding and quick curing property in a mold are achieved. Further, as a filler, an organic filler and an inorganic filler are used in combination, and the thermosetting resin cured product powder is used as a part of the organic filler to improve mechanical strength and rigidity at the time of heating. You can

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. <Example 1> As a resin component, the ratio of a phenolic hydroxyl group to a methacryloyl group was 5: 5, and 3 parts of dicumyl peroxide was added to 40 parts of a methacryloylated phenol novolac resin having a number average molecular weight of 1000. Then, pulp, thermosetting resin cured product powder, and calcium carbonate were mixed as a filler and kneaded with a heating roll to obtain a thermosetting resin molding material. The curing behavior (curing speed) of this molding material at 120 ° C. and 175 ° C. was measured by a curast meter. At 120 ° C., the curing reaction was extremely slow, and at 175 ° C., the curing rate was high and the curing was rapid. A test piece was prepared from the molding material by transfer molding, and the properties of the cured product were measured. As a result, it was found that both the mechanical strength and the rigidity when heated were good.

Example 2 The same method as in Example 1 was carried out except that a methacryloylated phenol novolac resin having an equivalent ratio of phenolic hydroxyl groups to methacryloyl groups of 3: 7 and a number average molecular weight of 1000 was used. <Example 3> The same method as in Example 2 was carried out except that t-butylperbenzoate was used instead of dicumyl peroxide.

<Comparative Example 1> As a resin component, only a novolac type phenol resin was used, hexamethylenetetramine was used as a curing agent, and a filler was compounded in the same material and compounding amount as in Example 1. A method similar to Example 1 was performed. Table 1 shows the composition of each example.

[0026]

[Table 1]

With respect to the molding materials obtained in the respective examples and comparative examples, the curing speed and the characteristics of the cured product were measured. Table 2 shows the results.

[0028]

[Table 2]

(Measuring method) (1) Curing speed (kgf · cm / min): The curing speed was defined as the slope of the straight line portion of the torque increase curve of the curast meter. (2) Bending strength, insulation resistance: Measured according to JIS K 6911. (3) Barcol hardness: A Barcol hardness meter 935 type was used, and after 20 seconds from molding, the hardness was measured 10 seconds after being taken out of the mold.

From Table 2, the thermosetting resin molding materials of the present invention shown in Examples 1 to 3 are extremely excellent in heat stability and curability as compared with the conventional phenol resin molding material of Comparative Example 1. It can be seen that is equal to or higher than. Further, Examples 1 to
3 and Comparative Example 1 were injection-molded, the molding machine was stopped midway, and the molding material in the plasticized and molten state in the cylinder was allowed to stand as it was. When the molding machine was restarted after being left standing, molding was possible, but when the material of Comparative Example 1 was left standing for 20 minutes, it hardened in the cylinder, and restarting was difficult.

[0031]

EFFECTS OF THE INVENTION According to the present invention, the obtained molding material has extremely excellent thermal stability in the plasticized and molten state and curability at high temperature. That is, the temperature dependence of curing is extremely large, and 1
It is possible to obtain a radical-curable resin molding material that has a characteristic that it is not substantially cured at a relatively low temperature of 10 ° C. or lower and is stable, and that it is rapidly cured at a high temperature of 150 ° C. or higher, and that it has high rigidity when heated. it can. For this reason, particularly in injection molding, the progress of the curing reaction of the plasticized molten resin in the cylinder of the injection molding machine is significantly suppressed, and it rapidly cures in the mold, so it can be applied to a wide range of molding conditions and is extremely Excellent workability. Furthermore, by using an organic filler and an inorganic filler in combination as the filler, the mechanical strength and electrical characteristics are maintained as in the conventional phenol resin molding material.

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 resin composition comprising 100 parts by weight of an acryloylated novolak resin (A) and 0.1 to 30 parts by weight of an organic peroxide (B), and an organic filler and / or an inorganic filler as a filler. Characteristic thermosetting resin molding material. 2. Residual phenolic hydroxyl group (a) of (meth) acryloylated novolak resin (A) as a resin component
The thermosetting resin molding material according to claim 1, wherein the ratio of the (meth) acryloyl group (b) to the equivalent ratio is 1: 9 to 9: 1. 3. The resin component (meth) acryloylated novolak resin (A) has a number average molecular weight of 500 to 20.
The thermosetting resin molding material according to claim 1 or 2, which is not more than 00.