JP2005153251A - Method of molding pulley made of phenol resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of molding a pulley made of a phenol resin excellent in cold heat impact strength or mechanical strength, especially in weld strength and dimensional precision, in a side gate type method of injection molding the pulley made of the phenol resin. <P>SOLUTION: In the method for molding the pulley made of the phenol resin by injection compression molding using a mold having a side gate structure, a low viscosity phenol resin molding material of which the Brabender melt-torque at 150°C is 0.5-1.0 kg×m is used as a phenol resin molding material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of molding a phenolic resin pulley by injection compression molding.

Phenolic resin pulleys have been used for automobile parts, general-purpose machine parts, home appliance parts, OA equipment, and peripheral parts because of the advantage of light weight and low noise compared to metal pulleys. For the pulleys made of phenol resin used for these materials, a material in which glass fiber is blended and mechanical strength is increased due to its necessary characteristics has been used.
Conventionally, a pulley made of phenol resin is generally formed by compression molding or injection molding. In the case of molding by compression molding, products having no practical problems such as strength and dimensional accuracy can be obtained. However, it takes a long time to mold and it is difficult to obtain a large number of products, so that there is a great disadvantage that productivity is low.

  On the other hand, injection molding is a molding method with good productivity. In this case, a pin having several gates from the disk part of the pulley is used in order to prevent a decrease in strength due to welds and to maintain dimensional accuracy. It is usual to mold with a point gate. However, in this case, the molding cycle can be shortened, but the problem that a large number cannot be obtained has not been solved.

  In order to improve productivity, it has also been proposed to form by a side gate method that allows easy multi-cavity (see, for example, Patent Documents 1 and 2). However, in this system, since the resin injected from the gate flows around the insert fitting or along the circumferential direction of the pulley, the glass fibers are easily oriented in that direction. On the other hand, in the vicinity of the gate, it is oriented in the injection direction, and in the weld part, it is oriented in the direction perpendicular to the flow due to the flow characteristics of the flow front end. In this way, when the orientation of the fiber is different at each location of the pulley, warping is likely to occur due to the anisotropic difference in the shrinkage rate of the molded body. This warpage causes a V-groove swing during pulley rotation, which is a serious practical problem.

JP 07-329103 A Japanese Patent Laid-Open No. 08-276465

  The present invention provides a method for molding a phenolic resin pulley excellent in thermal shock resistance, mechanical strength, particularly weld strength, and dimensional accuracy in a side gate type injection molding method of a pulley made of phenolic resin.

Such an object is achieved by the following present invention (1).
(1) A method of molding a pulley made of phenol resin by injection compression molding using a mold having a side gate structure, and as a phenol resin molding material, a Brabender melting torque at 150 ° C. is 0.5 kg · m or more 1 A method for molding a phenol resin pulley, comprising using a phenol resin molding material having a low viscosity of 0.0 kg · m or less.

When molding a pulley made of phenolic resin, by combining injection compression molding with a mold with a side gate structure and a low viscosity phenol resin molding material as described above, using a normal mold with a side gate structure, thermal shock It is possible to efficiently form a phenolic resin pulley that is excellent in properties and mechanical strength and has little warpage.

Hereinafter, the injection compression molding method of the phenol resin pulley of the present invention will be described in detail.
FIG. 1 shows an example of a mold for pulley injection compression molding according to the present invention. The insert metal fitting (1) is set in advance on the metal fitting set pin (3) of the fixed side cavity (2) and fixed by the metal fitting pressing pin (4). FIG. 1A shows a state in which the movable cavity (5) is retracted from a predetermined position and filled with a molding material. FIG. 1B shows a state in which the gate seal pin (6) is advanced to seal the gate, and then the movable side cavity (5) is advanced to a predetermined position. When the gate seal pin is not attached to the mold, backflow from the gate can be prevented by applying a screw holding pressure. Thereafter, the mold is opened and the molded pulley is taken out. FIG. 1 (c) shows the mold opened.

  An example of a mold structure and an operating mechanism for moving the movable cavity (5) backward or forward from a predetermined position will be described with reference to FIG. 2 (a) and 2 (b), the bottom surface (the left surface in FIG. 2) is inclined on the back surface of the movable side template (7) integrally attached to the outside of the movable side cavity (5). A block (8) is arranged, and a cam slide (10) that moves forward and backward by external force is arranged between the movable side template (7) and the receiving plate (9) provided below (left side in FIG. 2). . The cam slide (10) slides on the inclined back surface of the locking block (8) to adjust the clearance (14) between the movable side mold plate (7) and the receiving plate (9). In FIG. 2, (11) is a slide core, (12) is a fixed-side template, and (13) is a slide-core moving angular pin fixed to the fixed-side template.

As a molding method of the phenol resin pulley, the cam slide (10) is inserted forward by an external force, and a clearance (14) of 1 to several millimeters is generated between the movable side mold plate (7) and the receiving plate (9). With the movable cavity retracted, the mold is closed and the cavity is filled with a molding material (FIG. 2 (a)). Thereafter, the cam slide (10) is retracted by external force, and the movable side mold plate (7) and the receiving plate (9) are brought into close contact with each other by re-pressurization in this state, and the movable side cavity fixed to the receiving plate (9). (5) rises to a predetermined position of the final shape of the pulley and compresses the phenol resin molding material filled in the cavity (FIG. 2 (b)). By this method, a flow in the circumferential direction is generated in the entire molded body, and reorientation in the circumferential direction is performed even in the gate portion and the weld portion in which the fibers are oriented in the direction perpendicular to the circumference. As a result, the difference in the degree of orientation of the glass fibers in the molded body is reduced, and warpage due to shrinkage anisotropy is reduced.

  Even with a side gate structure mold that easily warps, warping can be reduced by injection compression molding, but the effect of internal residual stress, which is the cause of warping independent of the orientation of the substrate such as glass fiber, is It cannot be excluded. The internal residual stress is caused by the viscosity of the molding material, and the higher the melt viscosity, the larger the internal residual stress. Therefore, the warping can be further reduced by molding using a low viscosity material. When molding a material with low viscosity, there is a concern that a large amount of burrs will occur if molding is performed by normal injection molding, but in injection compression molding, the movable side cavity forms the final molded body shape of the pulley. When the mold is closed by a certain distance from the predetermined position and the molding material is injected and filled, the internal pressure of the resin is hardly generated in the cavity and no burrs are generated. Thereafter, when the movable cavity is advanced to the predetermined position, filling is completed and a shape is given. At that time, an internal pressure of the resin is generated, but by setting a holding time before compression, the curing reaction is advanced, and the resin viscosity on the surface of the molded body is increased to suppress burrs.

The viscosity of the phenol resin molding material used in the present invention is preferably such that the Brabender melting torque at 150 ° C. is 0.5 kg · m or more and 1.0 kg · m or less. Even if a mold with a side gate structure that easily warps is used, injection compression molding using a molding material having a Brabender melting torque in this range has a small orientation difference due to the base material such as glass fiber and the inside. By relieving the residual stress, warping can be effectively prevented and the occurrence of burrs is substantially prevented. When the viscosity is greater than 1.0 kg · m, the internal residual stress is not relaxed and the warpage cannot be reduced. If it is less than 0.5 kg · m, excessive burrs are generated, and the internal pressure of the resin does not reach the inside of the cavity sufficiently, resulting in a complete molded body.

  As a technique for lowering the viscosity of a phenolic resin molding material, a method of lowering the molecular weight of the resin is generally used as long as there is no practical problem such as strength and dimensions. Generally, the molecular weight of the phenol resin used for the molding material is 500 to 900 in terms of number average molecular weight, but the viscosity at the time of melting in the mold can be lowered by making the molecular weight relatively small as 350 to 500. If the molecular weight is less than 350, the resin is difficult to be solid and workability in the molding material is deteriorated. On the other hand, if the molecular weight exceeds 500, the viscosity of the molding material becomes high and the dimensional accuracy is insufficient. Other techniques for reducing the viscosity of the molding material include techniques such as shortening the thermal history during the kneading process of the material to lower the progress of the reaction, and are not particularly limited.

  The molding material used in the present invention usually contains a fiber substrate such as glass fiber as a filler, and is used in combination with one or more inorganic substrates such as silica powder, calcium carbonate, clay, mica and talc. You may do it. As an effect of blending such an inorganic base material, since the thermal expansion coefficient of the inorganic base material is generally small, dimensional stability with respect to the temperature of the molded body is improved. Moreover, various additives, such as an elastomer, a lubricant, a coloring agent, a hardening accelerator, a flame retardant, can be suitably mix | blended with the phenol resin molding material of this invention as needed.

  The phenolic resin molding material of the present invention is blended with a resin component, a filler, and other additives, kneaded with a kneader such as a roll mill, twin screw extruder, and kneader alone or in combination with a roll and another kneader, and cooled. It can be manufactured by crushing.

  In the molding of phenol resin pulleys, a combination of injection compression molding and low viscosity phenol resin molding material as described above can be used to mold phenol resin pulleys with low warpage using a normal side gate mold. Can do.

Hereinafter, the present invention will be described with reference to examples and comparative examples.
45 parts by weight of phenolic resin (resol type phenolic resin), 40 parts by weight of glass fiber (fiber diameter 11 μm, fiber length 3 mm), 10 parts by weight of inorganic substrate (calcium carbonate, average particle size 10 μm), release agent (stearic acid) A blending composition consisting of 1.5 parts by weight, pigment (carbon black) 1.5 parts by weight, and curing aid (calcium hydroxide) 2 parts by weight is heated with a mixing roll at 90 ° C. for 3 minutes (Comparative Example 1 is 2 minutes). It knead | mixed and grind | pulverized and the phenol resin molding material was obtained.

  Using this molding material, using a side gate mold (FIG. 2) heated to 175 ° C., the movable side cavity is retracted by 1 mm from the predetermined position by moving the cam slide forward (clearance 14 = 1 mm). The injection was performed with an injection time of 8 seconds. Immediately after the injection, the cam slide was started to be extracted, and after 5 seconds, it was compressed with a clamping force of 100 tons, and a pulley molded body having the shape shown in FIG. 3 was obtained in a curing time of 60 seconds.

<Example 1>
Using a phenol resin having a number average molecular weight of 400, a molding material having a Brabender melting torque at 150 ° C. of 0.6 kg · m was obtained. A pulley molded body was injection compression molded with this molding material.
When the thermal shock test was conducted as the thermal shock resistance, no changes such as cracks were observed up to 1000 cycles. It was confirmed that the warpage was at a low level with no practical problems.

<Example 2>
Using a phenol resin having a number average molecular weight of 500, a molding material having a Brabender melting torque at 150 ° C. of 0.8 kg · m was obtained. A pulley molded body was injection compression molded with this molding material.
When the thermal shock test was carried out, no changes such as cracks were observed up to 1000 cycles. It was confirmed that the warpage was a low level with no practical problem.

<Comparative Example 1>
Using a phenol resin having a number average molecular weight of 400, kneading with a mixing roll was shortened to 2 minutes, and a molding material having a Brabender melting torque at 150 ° C. of 0.3 kg · m was obtained. A pulley molded body was injection compression molded with this molding material.
When the thermal shock test was carried out, no change such as cracks was observed up to 1000 cycles, and it was confirmed that the warp was at a low level with no practical problem, but a large amount of burrs occurred and continuous molding was impossible. .

<Comparative example 2>
Using a phenol resin having a number average molecular weight of 900, a molding material having a Brabender melting torque of 1.2 kg · m at 150 ° C. was obtained. A pulley molded body was molded from this molding material by injection compression molding.
When the thermal shock test was carried out, cracks occurred at the weld position in 650 cycles.

Table 1 shows the characteristics of the molded body together with the measured value of the Brabender melting torque of the molding material.

(Measuring method)
1. Brabender melting torque: The minimum melting torque of the molding material at 150 ° C. was measured using a Laboplast mill manufactured by Toyo Seiki Seisakusho.
2. Thermal shock test: The thermal cycle in which the pulley molded body was alternately exposed to −40 ° C. and 150 ° C. for 30 minutes was repeated, and the occurrence of cracks was confirmed every 50 cycles.
3. Warpage: The thickness of the flange portion of the pulley molded body was measured 12 points concentrically with a three-dimensional measuring instrument, and the difference between the maximum value and the minimum value was defined as the warp.
4). Burrs: Twenty pulley molded bodies were molded, and burrs generated on the parting line surface of the mold and the mating surface of the slide were visually observed to evaluate the state of occurrence of burrs.
○: There is little burr generation, burr remains on the product side, and does not substantially remain on the mold.
X: A large amount of burrs is generated and adheres to the mold when the mold is opened.

  The present invention relates to a method of molding a pulley made of phenol resin by injection compression molding. As described above, injection compression molding with a mold having a side gate structure that can be easily obtained in large numbers and a low viscosity phenol resin molding material are provided. By combining them, a phenol resin pulley having excellent thermal shock resistance and mechanical strength and small warpage can be efficiently produced. Therefore, the present invention is particularly suitable for pulleys used for automobiles that require high productivity and high quality.

Schematic sectional view showing an example of a mold for pulley injection compression molding of the present invention An example of a mold structure and an operating mechanism for moving the movable side cavity (cross-sectional view in a direction perpendicular to FIG. 1) The pulley molded object obtained by the Example and the comparative example is shown, (a) is a top view, (b) is AA sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insert metal fitting 2 Fixed side cavity 3 Metal fitting set pin 4 Metal fitting holding pin 5 Movable side cavity 6 Gate seal pin 7 Movable side template 8 Locking block 9 Receiving plate 10 Cam slide 11 Slide core 12 Fixed side template 13 Angular pin 14 Clearance

Claims (1)

A method of molding a pulley made of phenol resin by injection compression molding using a side gate structure mold, and as a phenol resin molding material, a Brabender melting torque at 150 ° C. is 0.5 kg · m to 1.0 kg · A method for molding a phenol resin pulley, comprising using a low viscosity phenol resin molding material of m or less.

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