JP5247733B2 - Plastic molded product - Google Patents

Description

  The present invention relates to a thermosetting resin molded product using a sheet molding compound (SMC) or a bulk molding compound (BMC), and particularly relates to a thermosetting resin molded product having a thick portion of 15 mm or more. is there.

Thermosetting resin such as SMC is a composite material reinforced with glass fiber, etc., so it has high strength and has the advantage of being able to form complex shapes relatively easily compared to metals, so it can be used in various products. It is used.
Most SMC molded products are manufactured by compression molding. In the compression molding method, an appropriate amount of resin material is put into a mold (lower mold and upper mold) that is attached to a press machine and controlled (heated) to a predetermined temperature, and the upper mold is clamped by a press machine. By compressing while heating the resin material in the lower mold, it is molded into a shape along the mold, and is held in this state for a certain period of time. After the resin material is cured, a molded product is obtained from the mold. Is the method.
In the case of a molded product by compression molding using SMC, a thick part may be partially provided in the molded product depending on the function required for the product. SMC often causes distortion in the molded product due to curing shrinkage during curing, heat generation due to a curing reaction, and thermal contraction due to subsequent cooling. In particular, in the case of a molded product having a large thickness, internal distortion is large, and molding defects such as internal cracks, sink marks, and deformation occur.

  As a technique for suppressing the occurrence of such molding defects, a core material made of ABS resin or the like is placed in advance in the center of the mold cavity, and a thermosetting resin liquid is injected into the outer periphery of the mold. When heating, a volume expansion amount corresponding to the curing shrinkage volume amount of the thermosetting resin is generated in the core material, and the expansion of the core material and the curing shrinkage of the thermosetting resin are synchronized, thereby forming A technique for suppressing sink marks on the product surface is disclosed (for example, Patent Document 1).

JP 2000-079620 A

However, the technique disclosed in Patent Document 1 can suppress sink defects occurring on the surface of the molded product, but the core material, which is a thermoplastic resin inserted inside, expands more than expected. There is a problem that defects such as cracks may occur at the interface between the curable resin and the thermoplastic resin.
The present invention has been made to solve the above-described problems, and occurs when a molded product having a thick portion is molded using a thermosetting resin such as SMC. The object is to suppress crack defects and obtain a sound resin molded product free from defects.

  The resin molded product according to the present invention is a resin molded product that is formed by heating and compressing a thermosetting resin material, and in which a thin-walled portion and a thick-walled portion are integrally provided, and the thin-walled portion is an SMC. It is formed by either the molded part or the LSMC molded part, the thick part has a thickness of 15 mm or more, and a BMC molded part is provided at the center in the thickness direction, and the BMC molded part Either the SMC molded part or the LSMC molded part is formed so as to surround the part.

  Since the present invention adopts the above-described configuration, it is excellent in suppressing the occurrence of cracks, sink marks, and deformation inside the molded product, despite being a resin molded product having a thick portion. There is an effect that a quality resin molded product can be obtained.

It is a figure explaining the manufacturing process of SMC. It is a figure which shows the characteristic measurement result of SMC, LSMC, and BMC and the number of internal crack generation of a molded article. It is a figure explaining the bending test method of a SMC molded article. It is an external view which shows the molded article of a reference example. It is a figure which shows the cross section of the molded article of a reference example. It is a figure explaining the material charge pattern of a reference example. It is a figure which shows the orientation model of the molded article of a reference example. It is a schematic diagram which shows the internal crack of a molded article. It is a schematic diagram which shows the heat_generation | fever condition inside a molded article. It is a figure which shows the resin temperature change at the time of compression molding. 3 is a diagram showing a cross section of a molded product according to Embodiment 1. FIG. FIG. 3 is an alignment schematic diagram of a thick portion according to the first embodiment. FIG. 3 is a diagram for explaining a material charge pattern according to the first embodiment. 6 is a view showing a cross section of a molded product according to Embodiment 2. FIG. It is a figure explaining the material charge pattern of Embodiment 2. FIG. FIG. 5 is an orientation schematic diagram of a thick part in the second embodiment. FIG. 10 is a diagram showing a cross section of a molded product according to another example of the second embodiment.

Embodiment 1 FIG.
In order to make it easier to understand the excellent characteristics of the resin molded product according to Embodiment 1 of the present invention, first, a method for producing an SMC (Sheet Molding Compound) sheet and a strength investigation result of a test product cut out from the SMC molded product will be described below. To do.

The SMC sheet is usually manufactured by the process shown in FIG. In ST1 shown in FIG. 1, a liquid resin material in which an unsaturated polyester is used as a main material and a viscosity modifier, a release agent, a curing agent and the like are mixed is applied on a lower sheet having a width of about 1000 mm. The resin material applied in ST2 is extended to a certain thickness using a blade. In ST3, a reinforcing material such as glass fiber having a diameter of about 1 mm and a length of about 25 mm is formed by twisting about 1000 fibers having a diameter of several microns on the resin material. In ST4, a resin material is applied to the upper sheet, and is extended to a certain thickness with a blade. In ST5, the lower sheet and the upper sheet are overlapped, and the resin material and the reinforcing fiber are sandwiched between the sheets. In ST6, the resin between the sheets is pressed and rolled using a roller to obtain a constant thickness. In ST7, the sheet is wound up.
Since the SMC sheet is manufactured in such a process, the reinforcing material such as glass fiber is oriented in the surface direction of the sheet. Since the SMC sheet is often charged (charged) along the surface of the mold, the glass fiber is often oriented in a direction orthogonal to the thickness of the molded product even when it is a molded product. Therefore, the strength can be improved, for example, when bending stress is applied to the surface (plane portion) in the direction orthogonal to the thickness direction of the molded product.

FIG. 2 is a diagram showing the result of measuring the characteristics of SMC, LSMC, and BMC and the number of internal cracks generated in the molded product.
FIG. 2 (a) shows the result of cutting out a test piece from the molded product molded using SMC and measuring the bending strength. The description of FIG. 2B showing the number of internal cracks will be described later. The bending test is carried out as shown in FIGS. 3 (a) and 3 (b), and the bending strength in the surface direction indicates the strength when bending stress is applied in the direction shown in FIG. 3 (b). The bending strength indicates the strength when bending stress is applied in the direction of FIG. As can be seen from FIG. 2A, the strength in the plane direction is about 20 times the strength in the stacking direction.
Although it is manufactured in the same process as SMC, the characteristics of LSMC using glass fibers with a length of about 1000 mm and BMC (bulk molding compound), which is a material obtained by kneading a resin material and glass fibers with a fiber length of about 25 mm, are also shown. 2 (a).
Further, the fluidity shown in FIG. 2A is an index indicating the ease of flow. For example, when SMC, LSMC, and BMC are pressurized with a certain pressure, how much the area of the resin material is. It indicates whether it spreads (how much the thickness can be rolled (thinned)). Further, as shown in FIG. 2 (a), LSMC (long SMC) has a long fiber length, and thus has a higher strength in the surface direction than SMC, but the fluidity is inferior. Since BMC is only kneaded in the material state, the glass fiber is not oriented, but the glass fiber is oriented in the plane direction by the resin material flow when compression molding in the mold, There is a difference in strength between the surface direction and the lamination direction. However, the difference is smaller than SMC and about 3 times. In addition, this test has revealed that BMC can exhibit greater strength than SMC in the stacking direction.

Next, a prototype manufactured to obtain the thermosetting resin molded product of the present invention will be described as a reference example.
FIG. 4 is a view showing the appearance of the thermosetting resin molded product 20 of the reference example, which has a width of 1000 mm, a depth of 1200 mm, a height of 700 mm, and a thickness of 5 to 50 mm.
FIG. 5 is a cross-sectional view of FIG. 4. As can be seen from these drawings, the thick portion 21 having a thickness of 50 mm and the thin portion 22 having a thickness of 5 mm are integrally formed. Next, the manufacturing method of this molded product 20 is demonstrated based on figures.
As shown in FIG. 6, first, a necessary number of SMC sheet materials 2 cut in advance to the shape of the lower die are stacked and put into the lower die 1, and in that state, the upper die is removed by the mechanism of the press machine not shown. 3 is lowered, the SMC 2 is compressed and fluidized (deformed), the inside of the mold cavity (the space formed by the upper mold 3 and the lower mold 1) is filled with the SMC material 2, and then heated and cured to form the cavity. The molded product 20 has a shape along the shape.

FIG. 7 is a detailed cross-sectional view showing an orientation pattern of the thick portion 21 of the molded product 20. The line in the figure indicates the orientation of the glass fiber 2a. When the SMC 2 is charged as shown in FIG. 6, the glass fiber 2a is strongly oriented in the plane direction as shown in FIG. 7 in the thick portion 21, and thus has a very strong strength in the plane direction. However, an internal crack as shown in FIG. 8 is generated in the central portion of the thick portion 21 having a thickness of 20 mm or more of such a molded product 20, causing a defect that deteriorates the quality of the molded product 20.
FIG. 2 (b) shows the result of confirming the occurrence of internal cracks by molding 50 sample molded products (100 mm long and 100 mm wide test pieces) each having a thickness of 5 to 50 mm using SMC2. . Cracks did not occur when the thickness was 15 mm or less, but cracks occurred in all of the 35 pieces out of 50 pieces at 20 mm and 25 mm or more. When SMC2 was used, it turned out that it is difficult to shape | mold the molded product which has a thickness of 20 mm or more with sufficient quality.
Here, the result of having measured the temperature of the inside of a molded article and the surface at the time of compression molding is shown in FIG. Molding was performed at a mold temperature of 140 ° C. The surface portion in the thickness direction of the molded product is slightly higher than the mold temperature 140 ° C. and then the temperature is equal to the mold temperature 140 ° C., but the central portion in the thickness direction of the molded product 17 It was found that the temperature reached 200 ° C. or higher in ˜18 minutes. Such a high temperature was caused by heat generated by the curing reaction of the resin.

The high temperature region inside the molded product thickness direction is generally as shown in FIG. At this point (17-18 minutes after the start of pressurization), the resin is cured. During cooling of the molded product, the central part in the thickness direction is cooled from 200 ° C. or more to room temperature, but the vicinity of the surface is cooled from 140 ° C. to room temperature, and the heat shrinkage amount in the central part in the thickness direction is more than the surface part. Becomes larger. For this reason, a crack was generated inside due to the tensile stress generated in the central portion in the thickness direction. When the wall thickness is reduced, the high temperature region (dimension in the thickness direction of the high temperature region) is reduced, so that the difference in thermal shrinkage from the surface portion is also small, the tensile stress is small, and cracks are not generated.
Moreover, the heat transfer from a metal mold | die is so quick that it is near the metal mold | dies 1 and 3, and it becomes quick to harden | cure. Since it takes time for the central portion to rise in temperature, the vicinity of the molds 1 and 3 (side view) is heated and cured to become an elastic body, and then a curing reaction is started (see above) When the surface portion is cured, the central portion is still in an uncured state), and tensile stress is generated even by curing shrinkage of the central portion, causing cracks.
Thus, in the molding of the thick product 21 using SMC2, the generation of internal cracks could not be suppressed with a thickness of 20 mm or more.

The thermosetting resin molded product according to Embodiment 1 is created based on various data obtained from the prototype described above. First, the manufacturing method will be described.
The shape and dimensions of the thermosetting resin molded product (hereinafter referred to as a molded product) 20 according to Embodiment 1 are the same as those shown in FIGS. However, the molded product 20 according to the first embodiment has a cross-sectional configuration as shown in FIG. 11 in which the structure of the thick portion 21 is different from the thick portion of the prototype described above. That is, in FIG. 11, a thick portion 21 having a thickness of 15 mm or more and a 50 mm thick portion 21 is provided with a BMC molding portion 21b at the center in the thickness direction, and an SMC molding portion 21a is provided surrounding the BMC molding portion 21b. An orientation schematic diagram of the thick part 21 is shown in FIG. As can be seen from FIG. 12, a BMC 21b is provided at the center part having a thickness of 50 mm, and an SMC 21a is provided on the lower surface.

  FIG. 13 shows a charge pattern of the SMC material and the BMC material for forming the molded product 20 having such a configuration. The uncured SMC sheet material 2A is put into a portion corresponding to the thin portion 22 having a finished thickness of 15 mm or less, which constitutes most of the molded product 20 shown in FIG. In a portion corresponding to the thick portion 21 having a finished thickness of 15 mm or more, an amount necessary for charging the upper portion 1a of the lower mold 1 with the SMC sheet material 2B and filling the upper portion with the central portion of the thick portion 21. After the BMC 2C in a semi-solid state before being cured is charged, the thick SMC sheet material 2B is charged so as to surround the BMC 2C. This SMC sheet material 2B may be obtained by stretching the SMC sheet material 2A charged into the lower mold 1. Here, the thickness of the SMC sheet material 2A introduced so that the dimension of the thin-walled portion 22 after compression molding is 15 mm or less is 21 mm (15 / 0.7) assuming that the thickness is compressed by 30% after compression molding. = 21 mm) or less. In this manner, with the lower mold 1 charged with the SMC materials 2A, 2B, and BMC material 2C, the upper die 3 was lowered by a press material mechanism (not shown) and compression molded, so that it was put before compression molding. The SMC material 2A of the thin portion 22 is compression-molded with the SMC molding portion 22a of the thin portion, the SMC 2B of the thick portion 21 is compression-molded with the SMC molding portion 21a of the thick portion, and the BMC material 2C is compression-molded with the BMC molding portion 21b of the thick portion. Thus, the molded product 20 shown in FIG. 11 is obtained. The lower mold 1 and the upper mold 3 are both heated to a predetermined temperature.

As shown in the SMC / BMC of FIG. 2 (b) described above, in the case of BMC, the strength in the surface direction is small, but the strength in the stacking direction is three times that of SMC. Even if a tensile stress is generated due to heat generation in the central portion of the steel plate, cracks are not generated in the thick portion 21, and a molded product with a stable quality with improved sink and deformation and an improved yield can be obtained. it can. In addition, since the SMC 21a is disposed on the surface portion of the thick portion 21 and the SMC 22a is disposed on the thin portion 22 having a thickness of 15 mm or less, the bending strength in the surface direction is larger than when only BMC is used, and heat with excellent strength and quality. A curable resin molded product can be obtained.
Moreover, LSMC (long SMC) can also be used for the surface portion of the thick portion 21 or a portion of 15 mm or less. In this case, the strength can be further improved.
Further, according to the manufacturing method of the first embodiment, SMC or LSMC is used for the thin portion 22 and the thick portion 21 is configured to surround the BMC with either SMC or LSMC, as shown in FIG. It becomes easy to manufacture a thermosetting resin molded product excellent in strength and quality of a shape having the thin portion 22 and the thick portion 21 in various shapes as well as the shape.

Embodiment 2. FIG.
Next, the molded product 20 of Embodiment 2 is demonstrated.
The molded product 20 according to the second embodiment is the same as the molded product 20 shown in FIGS. 4 and 5 described in the first embodiment except that a thick portion 21 as shown in FIG. 14 is provided. It is the same. That is, the thick portion 21 of the second embodiment is provided with an insert work 21C such as a metal workpiece at the center of the thick portion 21, and is formed by SMC molding of the thick portion 21 on the side of the insert work 21C. The BMC molding part 21b is provided so that the insert work 21C is sandwiched between the space part and the part 21a.
The molded product in which the insert part 21C is simply provided in the thick part 21 has an internal shape as shown in FIG. Cracks occur. However, the molded product 20 having the structure manufactured by the material charge pattern as shown in FIG. 15 according to the second embodiment has no occurrence of internal cracks.
The material charge pattern will be described below with reference to FIG. First, the uncured SMC sheet material 2A is introduced into a portion corresponding to the thin portion 22 having a finished thickness of 15 mm or less in the lower mold 1. The amount to be charged is the same as in the first embodiment. In a part corresponding to the thick part 21 having a finished thickness of 15 mm or more, the SMC sheet material 2B is introduced into the upper surface 1a of the lower mold 1, and an insert work 21C such as a metallic workpiece is introduced into the upper part.
Next, after a sufficient amount of semi-solid BMC2C is filled to fill the space between the insert work 21C and the SMC sheet material 2B, the SMC sheet material 2B is charged so as to surround the insert work 21C and the thick part BMC2C. To do. This SMC sheet material 2B may be obtained by stretching the SMC sheet material 2A charged into the lower mold 1. Thereafter, the molded product 20 shown in FIG. 14 is obtained by compression molding in the same manner as in the first embodiment. FIG. 16 shows an orientation model (cross-sectional view) of the thick portion 21 after molding.

As described above, in the second embodiment, as in the first embodiment, since the BMC molding portion 21b is arranged at the central portion in the thickness direction of the thick portion, the thickness direction of the molded product at the time of compression molding is arranged. Even if tensile stress is generated due to heat generation in the central portion, a molded product having a stable quality can be obtained without causing cracks in the thick portion 21. Further, since the SMC material 22a is disposed in the thin portion 22 of 15 mm or less shown in FIG. 14, the bending strength in the surface direction is larger than that in the case of using only BMC, and the thermosetting resin having excellent strength and quality. A molded product can be obtained.
Further, as shown in FIG. 2A, BMC has a fluidity that is three times that of LSMC and 1.5 times that of SMC, and the resin pressure during resin flow is small (flows (deforms) with a small pressure). ). By disposing BMC 2C around the insert work 21C as in the second embodiment, the insert work 21C is deformed or the position of the insert work 21C is changed due to resin (BMC) flow during compression molding. Can be prevented. That is, when the charge pattern of the material is not uniform, the material flows in the molds 1 and 3 so that the density of the material in the molds 1 and 3 becomes uniform during compression molding. When the SMC having a large resistance flows greatly, the position of the insert work 21C may change with the flow or the insert work 21C may be deformed. However, when the BMC 2C having high fluidity is arranged around the insert work 21C, only the BMC 2C flows, so that the position of the insert work 21C does not fluctuate or deform. Further, as in the first embodiment, LSMC can be used for the surface portion of the thick portion 21 or a portion of 15 mm or less. In this case, the strength can be further improved.
Instead of the configuration of the thick portion 21 of FIG. 14 described above, a thick portion 21 as shown in FIG. 17 may be used.
That is, the thick portion 21 shown in FIG. 14 has a configuration in which the BMC molding portion 21b is provided so as to sandwich the insert workpiece 21C. However, as shown in FIG. 17, the BMC molding portion is provided only on one side of the insert workpiece 21C. Even if it is the structure which provided 21b, there exists the same effect. In addition, although the example which provides the BMC shaping | molding part 21b on the outer side of the insert work 21C was shown here, you may provide not only in this but on the inner side.

1 Lower mold, 2A Thin part SMC material, 2B Thick part SMC material,
2C BMC material, 3 upper mold, 20 molded product, 21 thick part,
21a thick part SMC molding part, 21b BMC molding part, 21C insert work,
22a Thin part SMC molding part.

Claims (2)

It is a resin molded product formed by heating and compressing a thermosetting resin material, and a thin-walled portion and a thick-walled portion are integrated. The thin-walled portion is either an SMC molded portion or an LSMC molded portion. On the other hand, the thick part has a thickness of 15 mm or more, and a BMC molding part is provided at the central part in the thickness direction, and an SMC molding part or a so as to surround the BMC molding part. One of the LSMC molding part is formed, The resin molded product characterized by the above-mentioned. A metal material insert work is provided at a central portion in the thickness direction of the thick part, and the BMC molding part is provided on a side part of the insert work, and either the SMC molding part or the LSMC molding part is provided. 2. The resin molded product according to claim 1, wherein either one is formed so as to surround the insert work and the BMC molding part.

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