JPS59215810A - Manufacture of thermosetting resin composition for forming - Google Patents

Abstract

PURPOSE:To form granular pieces of a thermosetting resin by reducing the generation of fine particles through such an arrangement wherein the thermosetting resin is melted and then it is converted into a sheet between cooled rollers, and lastly the sheet-like resin is crushed into pieces. CONSTITUTION:A thermosetting resin such as phenol resin, epoxy resin or polyester resin is homogenized by rollers, kneaders, etc. at a temperature higher than its melting point and then it is converted into a sheet between cooled rollers arranged so that their space is kept less than 4mm.. The sheet body thus obtained is changed into pieces of a resin composition for forming by being crushed by a crusher. When the thickness of the sheet exceeds 4mm., pieces of the thermosetting resin composition for forming to be obtained by being crushed in a later stage of processing contain much fine particles and tend to be easily scattered around.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermosetting resin composition for molding, particularly a granular composition suitable for injection molding, and a composition with little generation of fine particles.

The thermosetting resin composition for molding is made into a suitable solid material for handling and transformation into molded products.
It is common to form the composition into granular or powdered form. Conventionally, a thermosetting resin composition containing fillers, lubricants, pigments, etc. is homogenized using a mixer such as a suitable roll or co-kneader, and then crushed using a crusher, or by other methods, the composition is homogenized. Generally, the extrudate is melted and homogenized in an extruder, and the extrudate is cooled and cut into desired sizes.

The above method has the disadvantage that many fine particles are produced and are easily scattered. Although uniform particles can be obtained in the latter method, the viscosity of the thermosetting resin composition during extrusion must be sufficiently low due to the processing in an extruder, and the viscosity of the thermosetting resin composition during extrusion must be low enough to slow the rate of formation during subsequent molding. There are disadvantages such as a large amount of gas and a decrease in the dimensional accuracy of the final product.

An object of the present invention is to provide a thermosetting resin composition for molding, which generates fewer fine particles and is less likely to scatter, and which does not impair the properties of molding and final products.

The present invention involves homogenizing a thermosetting resin composition at a temperature equal to or higher than the melting point of the resin, and then applying the homogenized composition to a cooled surface with a surface distance of 4 m or less at a temperature at which the composition exhibits plasticity. The method is characterized in that it is fed between a pair of rollers to produce a sheet of calendering, and the resulting sort is crushed.

Thermosetting resins used in the present invention include phenol resins, epoxy resins, polyester resins, melamine resins, silicone resins, and the like. The thermosetting resin composition is made of commonly existing fillers such as wood flour, pulp, asbestos, glass fiber, talc, silica, calcium carbonate, wax, stearic acid and its esters, zinc stearate, calcium or Contains a lubricant such as magnesium salt, other dyes, and pigments as appropriate. The mixed resin composition is homogenized using a roll, co-kneader, etc. at a temperature higher than the melting point of the resin, is supplied to the gap between a pair of rollers, and is formed into a sheet by calendering. The distance between the surfaces must be 4 or less, and if it exceeds 4n, the thermosetting resin composition for molding obtained by crushing in the subsequent step will contain many fine particles and will be easily scattered.

The temperature of the thermosetting resin composition supplied to the roller must be such that the composition exhibits plasticity; if the temperature is lower than that, it will not be bitten by the roller and calendar linking will not be possible. In addition, the rollers need to be cooled, and if they are not cooled, the temperature will rise rapidly and stable calendering will not be possible.

Next, the present invention will be explained in detail.

Examples 40 parts by weight of phenolic resin, 6 parts by weight of hexamethylenetetramine, 30 parts by weight of glass fiber, 20 parts by weight of glass powder, 1 part by weight of magnesium oxide, 1 part by weight of stearic acid,
Mix the carbon black 1 layered part thoroughly and roll it with a hot roll.
The mixture was kneaded for ~5 minutes to obtain a sheet material having a thickness of 5~1 Otnm.

The composition is rotated in mutually opposite directions at a circumferential speed of 1-2 m/min, and the distance between the rotating surfaces is 05-1 v.
The material was quickly fed between a pair of internally cooled roasting ovens maintained at a temperature of 200 m, and the obtained sheet material having a thickness of about 1 mm was crushed using a crusher to obtain a phenolic resin composition for molding.

The drawing shows the particle size distribution of this phenolic resin composition for molding.

COMPARATIVE EXAMPLE The sheet-like material having a thickness of 5 to 10 mm, which had been kneaded with hot rolls in the example, was crushed as it was with a crusher to obtain a phenolic resin composition for molding.

The drawing shows the particle size distribution of this phenolic resin composition for molding.

As is clear from the drawings, according to the present invention, a thermosetting resin composition for molding that contains fewer fine particles and is therefore less likely to scatter can be obtained. In addition, since calendering can be carried out at a temperature at which the resin composition exhibits plasticity, there is no need to lower the viscosity of the resin composition as in the case of processing with an extruder, which may impair moldability and properties of the final product. The industrial value of this method is extremely great in that it is possible to obtain a thermosetting resin composition for molding.

[Brief explanation of drawings]

The drawing is a line diagram showing the particle size distribution of the obtained phenolic resin composition for molding. patent applicant

Claims (1)

[Claims] A thermosetting resin composition is homogenized at a temperature equal to or higher than the melting point of the resin, and the homogenized composition is supplied between at least a pair of cooled rollers having a surface distance of 4n or less at a temperature at which the composition exhibits plasticity. A method for producing a thermosetting resin composition for molding, which comprises producing a sheet by rendering and crushing the obtained sheet.