JPH05186664A - Molding material of thermosetting resin - Google Patents

Abstract

PURPOSE:To obtain the subject material having excellent moldability, capable of extremely reducing post-processing man-hour of molded article because of greatly excellent filling properties to mold and extremely slight occurrence of burr by blending a thermosetting resin with a filler and a specific compound. CONSTITUTION:(A) A thermosetting resin (preferably phenol resin of type obtained by curing novolak with hexamethylenetetramine) is blended with (B) a filler (e.g. wood flour or silica) and (C) a compound selected from 1,3,2,4- dibenzylidene sorbitol, 1,3,2,4-ditolylidene sorbitol, 1,3,2,4-dibenzylidene xylitol and 1,3,2,4-tribenzylidene sorbitol to give the objective material. The blending ratio is preferably 20-70wt.% component A, 30-80wt.% component B and 0.5-3wt.% component C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting resin molding material excellent in molding processability, and particularly to a thermosetting resin molding material which has extremely few burrs generated in injection molding. ..

[0002]

2. Description of the Related Art Thermosetting resin molding materials are used in a wide range of applications such as automobile parts, electronic / electrical parts and mechanical parts because of their excellent heat resistance, electric performance and mechanical performance. However, the thermosetting resin molding material has a problem that burrs are more likely to occur during the molding process than the thermoplastic resin molding material. Burrs are caused by the overflow of molten molding material from narrow gaps such as the parting surface of the mold and air vents during molding of molding material, and it is very useful to remove this burr from the molded product after molding. Therefore, it is strongly desired to reduce or suppress the occurrence of burrs in the thermosetting resin molding material.

Conventionally, as a method of solving these problems, a method of blending a molding material with a filler of fine powder has been known. Since the filling of the molding material is insufficient, it is difficult to satisfy both the suppression of burrs and the filling property into the mold. Also, many solutions have been proposed in terms of mold design, molding machine design and control, but practical solutions are difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made as a result of various studies in order to obtain a thermosetting resin molding material in which burrs are hardly generated during molding. It is intended to provide a thermosetting resin molding material, particularly a phenol resin molding material, which is extremely excellent in mold filling property and in which burr generation is extremely suppressed.

[0005]

[Means for Solving the Problems] The present invention comprises (a) a thermosetting resin, (b) a filler, (c) 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-. Zitoylidene sorbitol,
1,3,2,4-dibenzylidene xylitol and 1,3,2,4,5,6-
A thermosetting resin molding material containing one or more compounds selected from tribenzylidene sorbitol (hereinafter referred to as "the specific compound").

As the thermosetting resin in the present invention, a resin which can be melted and fluidized by heating and cured by a crosslinking reaction is used. Examples of such a resin include a phenol resin, an epoxy resin, a diallyl phthalate resin, an unsaturated polyester resin, a maleimide-based polyimide resin, a urea resin, and a melamine resin. Among these thermosetting resins, the preferred resin is phenol resin. Examples of the phenol resin include ordinary novolac type resins and resol type resins obtained by reacting phenols with formaldehydes. Examples of the phenols of the phenol resin include monovalent or polyvalent phenols such as phenol, cresol, xylenol, naphthol, pt-butylphenol, bisphenol A, resorcin, and their substitution products, and one or two of them. More than one species can be used. Examples of formaldehydes include formalin and paraformaldehyde. Further, as the present phenol resin, those modified appropriately with aromatic hydrocarbon resin, dimethoxyparaxylene, dicyclopentadiene, etc. can be used. Among these resins, the phenol resin of the type in which novolak is cured with hexamethylenetetramine is most preferable.

As the filler in the present invention, organic substances such as wood powder, pulp powder, various pulverized products of woven fabric, pulverized powder of thermosetting resin laminates and molded products, silica, alumina, aluminum hydroxide, glass, Inorganic powder such as talc, clay, mica, calcium carbonate and carbon, and inorganic fibers such as glass fiber, carbon fiber and asbestos are used.

In the present invention, the mixing ratio of the thermosetting resin in the molding material is 20 to 70% by weight, the filler is 30 to 80% by weight,
The specific compound is 0.5 to 3.0% by weight. If the blending ratio of the specific compound is less than 0.1% by weight, the effect of suppressing burr is not exerted, and if it exceeds 3.0% by weight, the effect is not increased, and various properties of the molded article are rather deteriorated.

The thermosetting resin molding material of the present invention is produced by blending a thermosetting resin, a filler, the specific compound and various additives, kneading them with a roll mill, a twin-screw kneader or the like, and pulverizing them. You can The specific compound is used in the form of a powder, but if it is used by being mixed and dispersed in the resin in advance, a better burr suppressing effect can be imparted. As an example of the mixing method, there is a method in which a novolac and the specific compound are charged into a Henschel mixer equipped with a heating jacket, heated to 150 ° C., and mixed at a high speed in a molten state of the resin. In the present invention, additives such as a flame retardant, a colorant, a curing accelerator, and a release agent can be appropriately blended and used as necessary.

[0010]

The thermosetting resin molding material of the present invention has excellent moldability in filling in a mold and excellent moldability with extremely reduced burrs, and particularly has molding characteristics suitable for injection molding. is doing. The reason for this is not fully clear, but the specific compound forms clusters in the molten resin, and the molten thermosetting resin molding material is plasticized during molding, and has a low viscosity and good fluidity in the high shear rate region of the filling process. However, it is considered that the viscosity becomes high and the fluid does not flow in the low shear rate region of the narrow gap where burr is generated.

[0011]

The present invention will be described below with reference to examples. Here, "parts" represent parts by weight.

(Example 1) Novolak resin (average molecular weight 800) obtained by the reaction of phenol and formaldehyde 44
And 0.8 parts of 1,3,2,4-ditoluylidene sorbitol were placed in a Henschel mixer equipped with a heating jacket, heated to 145 ° C and mixed for 30 minutes. This is taken out, cooled and pulverized into a powder. Hexamethylenetetramine powder 7
Parts, calcium hydroxide 3 parts, wood flour 32 parts, calcium carbonate 1
1 part and 3 parts of a release agent were mixed, melt-kneaded with a two-roll mill, cooled and pulverized to obtain a phenol resin molding material.

(Example 2) 44 parts of a solid resol resin obtained by reacting phenol and formaldehyde with an ammonia catalyst, 1,3,2,4-dibenzylidene xylitol 0.5
Part, calcium hydroxide 3 parts, wood flour 30 parts, calcium carbonate 1
1 part and 3 parts of a release agent were mixed, melt-kneaded with a two-roll mill, cooled and pulverized to obtain a phenol resin molding material.

Example 3 100 parts of ortho-cresol novolac type epoxy resin and 2 parts of 1,3,2,4-dibenzylidene sorbitol were placed in a Henschel mixer equipped with a heating jacket and heated to 150 ° C. and mixed for 30 minutes. This was taken out, cooled and pulverized into a powder form, 51 parts of phenol novolac resin, 1 part of 2-methylimidazole, 3 parts of fused silica powder.
50 parts, 5 parts of a releasing agent and 5 parts of epoxysilane were mixed, kneaded by a twin-screw extruder, cooled and pulverized to obtain an epoxy resin molding material.

Comparative Example 1 Novolak resin (average molecular weight 800) obtained by the reaction of phenol and formaldehyde 44
Parts, 7 parts of hexamethylenetetramine powder, 3 parts of calcium hydroxide, 32 parts of wood powder, 11 parts of calcium carbonate, 3 parts of release agent, melt-kneaded with a two-roll mill, crushed after cooling and crushed phenol resin A molding material was obtained.

(Comparative Example 2) Orthocresol novolac type epoxy resin 100 parts, phenol novolac resin 51
Parts, 2-methylimidazole 1 part, fused silica powder 350 parts,
5 parts of a releasing agent and 5 parts of epoxysilane were mixed, kneaded by a twin-screw extruder, cooled and pulverized to obtain an epoxy resin molding material.

The fluidity (melt viscosity) of each of the obtained thermosetting molding materials was measured by a Koka type flow tester. Further, molding was carried out by a transfer molding machine under the following conditions, and the state of burrs generated was measured. The results are shown in Table 1. (Molding conditions by transfer molding machine) 20 g of tabletized thermosetting resin molding material is preheated to about 100 ° C,
Using the transfer mold of the shape shown in FIG.
Molded at ℃ for 3 minutes. The burr generation state was visually determined for burr in the air vent portion of the mold.

[0018]

[Table 1]

From Table 1, the molding materials obtained in the respective examples have the same fluidity as compared with the conventional thermosetting resin molding materials of the comparative example, but the occurrence of burrs during molding occurs. It can be seen that is extremely small.

[0020]

EFFECTS OF THE INVENTION As is clear from the above examples, the thermosetting resin molding material of the present invention is capable of satisfying both the filling property in the mold during molding and the suppression of burrs. The number of processing steps can be significantly reduced, and it can be widely used as a thermosetting molding material having excellent moldability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a transfer molding die used in an example.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 1: Circular Cavity 2: Square Cavity 3, 4, 5: Air Vent 6: Pot 7: Plunger

Claims (2)

[Claims] 1. (a) Thermosetting resin, (b) Filler,
(C) 1,3,2,4-dibenzylidene sorbitol, 1,3,2,4-
Characterized by containing one or more compounds selected from ditoluylidene sorbitol, 1,3,2,4-dibenzylidene xylitol and 1,3,2,4,5,6-tribenzylidene sorbitol A thermosetting resin molding material. 2. The thermosetting resin molding material according to claim 1, wherein the thermosetting resin is a phenol resin.