JPH04234610A - Sheet molding compound material - Google Patents

Abstract

PURPOSE:To shorten a curing time, and to prevent the generation of warpage, etc., at the time of thermocompression molding and improve the quality of molding by holding the core section of a quick-curable sheet molding compound material and the core section of said core section and using the core section as the surface layer section of a slow-curable sheet molding compound material. CONSTITUTION:A two-layer catalyst type SMC is composed of a core section 1 consisting of a quick-curable SMC material having a curing time of sixty sec and surface layer sections 2 made up of a slow-curable SMC material having a curing time of ninety section. The two-layer catalyst type SMC material is manufactured in such a manner that the SMC materials 1a of a tabular quick-curable resin extruded from a mold under the state having preheat and the SMC materials 2 of a slow-curable resin are compressed by rollers and the two resins are bonded, and the SMC materials 1a of the quick-curable resin are laminated mutually and compressed by rollers again. Each surface layer section 2 is 0.5mm thick respectively, the core section 1 is 2.5mm thick, and the whole is 3.5mm thick.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a semi-soft sheet material, a so-called sheet molding compound material (hereinafter referred to as SMC material), which is made of a thermosetting resin material such as an unsaturated polyester resin and a reinforcing material such as glass fiber. Regarding.

0002

2. Description of the Related Art SMC materials are made into molded products by hot compression molding. This thermal compression molding involves placing the SMC material on a lower mold that has been preheated to a predetermined temperature, then clamping the upper mold to compress (shape) the SMC material and allow it to harden for several minutes. This is done by In recent years, from the perspective of improving productivity, SMC
There is a need to shorten the molding cycle, and in particular, there is a strong desire to shorten the curing time, which occupies a large proportion of one cycle.

[0003] In order to shorten the curing time, it is conceivable to use an SMC material that has a fast curing speed. However, the SMC material placed in the lower mold begins to gel immediately after being charged due to the heat from the lower mold, and the longer the standing time or the faster the SMC material is used, the more the gelation will occur. As the gelation progresses, so-called pre-gel phenomenon, in which gelation progresses too much, is likely to occur. When molding is performed using SMC that has undergone this pregel phenomenon, various molding defects such as underfilling, rough skin, blisters, cracks, and pinholes occur. Therefore, in order to shorten the curing time by using an SMC material that has a fast curing speed, it must be done under the constraint that the above-mentioned pregel phenomenon does not occur, and there is a limit.

0004

[Problem to be solved by the invention] The above pregel phenomenon is
The longer the time from the moment the SMC material is introduced into the lower mold until the mold clamping is completed (hereinafter referred to as set time), the more likely it is to occur. Therefore, there is a limit to increasing the curing speed of the SMC material used depending on the setting time. This relationship is shown in Table 1 using SMC materials for automobile interior parts as an example. In addition, in the table, ◎ indicates the required curing time of the SMC material that does not cause the pregel phenomenon and has the fastest curing speed, that is, the limit of increasing the curing speed (limit of shortening the curing time). This indicates that the phenomenon does not occur, and × indicates that the pregel phenomenon occurs. Furthermore, the mold temperature was 140° C. for both the upper mold and the lower mold, and the wall thickness of the molded product was 2.5 mm.

[0005]

[Table 1] In Table 1, for example, if the set time is 25 seconds, the limit for shortening the curing time is 90 seconds. (If the pre-gel phenomenon occurs). Note that the setting time is determined by constraints such as press functionality and SMC loading method.

[0006] In addition, in Japanese Patent Application Laid-Open No. 58-158220, a slow-curing SMC material is first placed in the lower mold,
By layering a fast-curing SMC material on top of that,
A technique has been disclosed that prevents the SMC material from gelling at an early stage, thereby preventing the occurrence of the pre-gel phenomenon, and shortening the curing time. However, even with this method, it is impossible to cure the material at a faster rate than the slow-curing SMC material placed directly on the lower mold, and it is not possible to further shorten the required curing time. In addition, since two types of SMC materials with different hardening speeds are laminated, when both materials harden, relative tensile stress acts between them due to the different hardening speeds, causing warping and other problems. Another problem is that molding defects are likely to occur.

The present invention has been made in view of the above-mentioned circumstances, and the technical problem to be solved is to shorten the curing time, which has hitherto been considered the limit, without causing molding defects. It is.

[0008]

[Means for solving the problems] The SMC material of the present invention is
It is characterized by comprising a core made of a fast-curing SMC material, and a surface layer sandwiching the core and made of a slow-curing SMC material. As the thermosetting matrix resin for the above-mentioned fast-curing SMC material and slow-curing SMC material, in addition to unsaturated polyester resin, vinyl ester resin, epoxy resin, acrylic resin, phenol resin, etc. can be used. . In addition, peroxycarbonate-based, peroxyester-based, perpercale-based, etc. can be used as the hardening agent, and by changing the type and amount of this hardening agent, the curing speed of the SMC material can be changed. can.

[0009] It is preferable that the surface layer portion is made of an SMC material having the fastest curing speed, which is considered to be the usable limit at the setting time when the SMC material of the present invention is thermally compression molded. Further, it is preferable that the core portion is made of an SMC material having a curing speed of 30 to 100% of the curing speed of the SMC material constituting the surface layer portion. Further, the thickness of the surface layer is preferably 10 to 30% of the thickness of the core, and is preferably 15 to 2% of the thickness of the core.
It is particularly preferable to set it to 5%. If the thickness of the surface layer is too thin, the pre-gel phenomenon cannot be effectively prevented, and if the thickness of the surface layer is too thick, the effect of shortening the curing time cannot be expected. Note that the ratio of the wall thickness between the surface layer and the core depends on the mold temperature,
It varies depending on the hardenability of the SMC material used.

0010

[Function] Since the SMC material of the present invention has a surface layer that is in direct contact with the mold and is composed of a slow-curing SMC material, it is possible to reliably prevent the pregel phenomenon during hot compression molding. Moreover, if the SMC material of the present invention is subjected to hot compression molding, it becomes possible to cure the material in a faster curing time than the curing speed of the slow-curing SMC material constituting the surface layer. This is because the SMC material that makes up the core is fast-curing SMC.
It is thought that this is because the internal heat generation effect is improved because the core is made of such a material, that is, the amount of reaction heat generated from the core per unit time during the curing reaction can be increased.

Furthermore, since the SMC material of the present invention has a sandwich structure in which the core is sandwiched between the surface layers, the materials are symmetrical in the thickness direction, and warpage is less likely to occur during hot compression molding.

0012

EXAMPLES The implementation of the present invention will be explained in detail below. The SMC material used is an SMC material for automobile interior parts. It is composed of a core part 1 made of a fast-curing SMC material with a curing time of 60 seconds, and surface layer parts 2, 2 sandwiching the core part 1 and made of a slow-curing SMC material with a curing time of 90 seconds. A two-layer catalytic SMC material was prepared. This two-layer catalytic SMC material is produced by compressing SMC material 1a made of a plate-shaped fast-curing resin and SMC material 2 made of a slow-curing resin, which are taken out of a mold in a preheated state, with a roller. After adhering the resin, the SMC materials 1a, which are fast-curing resins, were bonded together and compressed again using a roller. Note that the thickness of each surface layer 2 is 0.5 mm,
The thickness of the core part 1 is 2.5 mm, and the overall thickness is 3.5 mm.
It is mm.

[0013] The above two-layer catalyst type SMC material was heated to a mold temperature of 14
After placing the mold in the lower mold at 5℃, the upper mold, which also has a mold temperature of 145℃, was clamped with a pressure of 100 tons, and the curing time was changed to 60 seconds, 70 seconds, 80 seconds, and 90 seconds. By doing so, 4 pieces with a thickness of 2.5 mm and a size of 300 mm x 300 mm
Various types of flat molded products were obtained. Incidentally, all setting times were 25 seconds.

The physical properties of the four types of molded products having different curing times were measured, and the molding quality of the molded products, such as underfilling and roughness, was evaluated. The results are shown in Table 2. The bending elastic modulus and bending strength are in accordance with JIS K7203.
According to the regulations, Rockwell hardness and Barcol hardness are J
Each was measured according to the provisions of IS K6911. In addition, as Comparative Example 1, fast-curing S with a curing time of 60 seconds was used.
Flat molded products were obtained in the same manner as above for those made only of MC material, and for those made only of slow-curing SMC material with a curing time of 90 seconds as Comparative Example 2, and the same measurements and evaluations as above were carried out. I did it. Table 2 shows the results.
Shown below.

[0015]

[Table 2] From the results shown in Table 2, the two-layer catalyst type SM according to the present invention
By using C material, when the set time is 25 seconds,
The curing time could be shortened from the conventional 90 seconds to 70 seconds without causing any pre-gel phenomenon or deterioration of physical properties.

Note that no warping or the like occurred in these molded products.

[0017]

As described in detail above, according to the SMC material of the present invention, the curing time, which was conventionally considered to be a limit, can be further shortened without causing the pregel phenomenon. In addition, since the material has a symmetrical structure in the thickness direction, warping is less likely to occur during hot compression molding.
Good molding quality.

Furthermore, when cutting the material, it can be done in one go, and the workability is good.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the sheet molding compound material of this example.

[Explanation of symbols]

1 is a core portion, and 2 is a surface layer portion.

Claims (1)

[Claims] 1. A sheet molding compound material comprising a core made of a fast-curing sheet molding compound material, and a surface layer sandwiching the core and made of a slow-curing sheet molding compound material. .