JP2735785B2 - Sheet-shaped thermosetting resin molding material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like thermosetting resin molding material and a method for producing the same. More specifically, the present invention is a reinforcing material obtained by cutting fibers such as glass fiber or carbon fiber into a thermosetting resin, fillers and pigments such as calcium carbonate and aluminum hydroxide,
The present invention relates to a sheet-shaped molding material containing a curing accelerator and the like, and a method for producing the same. In particular, the present invention provides a sheet-shaped molding material which can be cured to obtain a cured molded product having a smooth surface and no whitening, pinholes, color unevenness, and the like.

[0002]

2. Description of the Related Art Conventionally, a sheet-like thermosetting resin molding material known as SMC generally includes a thermosetting resin, a filler,
A paste of a mixture of a pigment, a curing accelerator, and other additives mixed with a reinforcing material such as glass fiber is sandwiched between two carrier films such as polyethylene to form an appropriately sized sheet. It is manufactured by For example,
When a sheet-like molding material is manufactured using the conventional apparatus shown in FIG. 2, a liquid thermosetting resin, for example, an unsaturated polyester, a filler such as calcium carbonate or aluminum hydroxide, A liquid mixture (called a paste) is prepared by mixing a pigment, a curing accelerator, and other additives. This is applied to the surfaces of two rolls rotating in opposite directions using a doctor knife or the like so as to have a uniform thickness (referred to as a paste film). Immediately, that is, a part of the styrene in the paste film is volatilized. While the mixing ratio does not change, a reinforcing fiber such as glass fiber or carbon fiber cut short to a certain length is dropped on the paste film so as to have an arbitrary ratio with the paste, and the gap between the two rolls is reduced. To apply pressure to the paste and the reinforcing fibers, and discharge the molding material impregnated with the paste into the reinforcing fibers from the opposite side.

[0003] The scraper is scraped off the surface of the roll with a scraper, and the scraped-off material (referred to as impregnated material) is extruded using an extruder to form a sheet. It is made into a sheet by receiving it continuously. At this time,
When the impregnated sheet is used as a molding material, a film is used as a carrier for producing the impregnated sheet so that they do not stick to each other, and sandwiches the impregnated sheet. In this way, the sheet-like molding material is manufactured by being sandwiched between two films.

According to Japanese Patent Publication No. 52-17903,
After passing the viscous substance and the solid substance between at least a pair of rollers facing each other, the viscous substance and the solid substance are generated by rotating a rotating body close to the roller and provided with a gap at a high speed in the same direction as the roller. The mixture is scraped off, and the resulting mixture falls between two polyethylene sheets, is sandwiched, and is evenly leveled by a conveyor and shaping rollers to form a sheet-shaped molding material product.
The sheet-shaped molding material product thus manufactured is
A molded product is obtained by peeling the carrier film on both sides and as it is, or after laminating several sheets, and then pressurizing and heating with a mold to cure.

[0005]

However, the prior art as described above has the following problems. That is, a continuous layer of the paste is not uniformly present on the surface of the molding material after the carrier film is peeled off, and it is difficult to obtain a smooth surface after curing the paste.
When impregnating the reinforcing fiber with the paste between the two rolls described above, if the viscosity of the paste is increased, the impregnation becomes worse,
In addition, even if the content of the reinforcing fibers is increased or the production rate is increased, the impregnation becomes worse, and the range of these three conditions is naturally limited. In addition, these three conditions are such that even when only one protrudes, even if each of the three slightly exceeds the appropriate value, the impregnation property is adversely affected. This insufficiency of the impregnation becomes more and more apparent from the degree that, when the sheet-shaped molding material product is observed from the surface, a fine fiber (glass) is slightly visible on the surface. When press molding is performed using such a sheet-shaped molding material product, whitening, pinholes, and the like occur to some extent in the molded product, resulting in a defective product in many cases. When the impregnating property of the paste becomes worse, fibrous grains (glass grains) on the surface gradually increase. Needless to say, in this case, the defective rate of the molded article increases.

Considering the cause of these adverse effects on impregnation, the following is obtained. That is, the molding material impregnated in the gap between the two rolls rotating relatively inward is scraped off from the roll surface by the scraper as described above,
Alternatively, it is scraped off from the roll surface by a rotating body that rotates at a high speed. Thereafter, the molding material is sandwiched between two carrier films and shaped into a sheet. The molding material at this time is impregnated with the reinforcing fibers with a paste, but is strongly sandwiched between the two carrier films. Even so, the paste that forms the paste skin layer on the inner surfaces of the two carrier films is not squeezed out.

In other words, since the molding material sandwiched between the carrier films has no paste layer on the carrier film surface and remains as it is, if there is even a slight impregnation failure, the time passes on the carrier film contact surface. However, impregnation failure is not improved. If some reinforcing fiber eyes (glass eyes) remain, they do not improve over time. In addition, since the molding material is in contact with the carrier film as it is, the roughness due to the reinforcing fibers and the filler becomes partial unevenness and remains in the molding material product. If the molding material is of the thickening type, it will go through a thickening step. In this case, the impregnation failure and the presence of the reinforcing fiber (glass) may be improved to some extent, but this is not the case. Absent. The molding material having the reinforcing fiber eyes (glass eyes), impregnation defects and irregularities,
When this is press-molded, the molded product often becomes defective due to whitening and pinholes.

[0008]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention relates to a two-carrier carrier for sandwiching a molding material scraped from the surfaces of two rolls rotating relatively inward from both surfaces thereof. A thin skin layer of paste is previously formed on the inner surface of the film. That is, the present invention provides a molding material in which reinforcing fibers are impregnated with a paste in which additives such as a thermosetting resin and a filler are mixed,
In a method for producing a sheet-shaped thermosetting resin molding material, which is sandwiched between two carrier films in a sandwich shape, another paste-like material is previously formed into a thin film on each surface of the carrier film in contact with the molding material. To provide a method characterized in that the method is applied to a substrate. The paste of this paste skin layer is a mixture of the same thermosetting resin used for the molding material and an additive such as a filler.

[0009] The paste skin layer passes through the molding material sandwiched therein between rolls and between upper and lower belts in a subsequent process, and is impregnated,
It penetrates and solves the manifestation of impregnated fibrous grains (glass eyes) and impregnation, and also serves to smooth the surface by compensating for surface irregularities. In addition, even if the paste skin layer is impregnated and penetrated, a very thin layer remains uniformly on the surface in contact with the inner surface of the carrier film. The material has no irregularities on both planes, no reinforcing fiber eyes (glass eyes),
Of course, there is no impregnation failure, and there is no unevenness in color, and there is gloss with uniform flatness. Therefore, by heating and pressurizing this with a mold to form a cured product, it is possible to obtain a molded product having a beautiful surface free from whitening, pinholes, color unevenness, and the like with a high yield.

[0010]

The present invention will be further described below with reference to examples. FIG. 1 shows one embodiment of the present invention.
In FIG. 1, (3) and (3 ′) are a pair of impregnating rollers arranged at a constant interval in the horizontal direction, and the impregnating rollers are mutually inward at the same speed as indicated by arrows. It is designed to turn over. Above each of these impregnating rollers, there are first doctor knives (1) and (1 '), by which a so-called paste (2) in which a thermosetting resin, a filler, an additive, etc. are mixed, flows out, It is applied uniformly on the surface of the impregnated roller to form a paste film (4). On the other hand, above the impregnating roller, the roving (5) of the reinforcing fiber (glass fiber) is cut into a chopped strand (6), which is evenly spread on the surface of the paste uniformly applied to the roller.

Thereafter, the paste film (4) on the surface of the impregnating roller and the chopped strands (6) of the reinforcing fibers pass through a narrow gap (7) between the rollers, and the paste has an action of wetting (impregnating) the chopped strands. I do. The mixture of the paste and the chopped strand (6) generated by the impregnation is called a thermosetting resin molding material. This thermosetting resin molding material is scraped off by the scraper (8), falls, and temporarily accumulates above the take-up rollers (9) and (9 ').

On the other hand, the carrier films (10) and (10 ') are unwound from both right and left, and take-up rollers (9),
At (9 '), the direction is changed from horizontal to vertical. At this time, there is a temporary pool of the thermosetting resin molding material above the take-up rollers (9) and (9 '), and this is taken down while being sandwiched between two carrier films. At this time, the carrier film is taken off by the take-up roller (9),
Before reaching (9 '), put a second doctor knife on top
The paste (12) (the same as the paste (2)) is thinly and uniformly applied by (11) and (11 '). On the two carrier films on which the thinly applied paste (12) is placed, a thermosetting resin molding material is placed on top of the take-up rolls (9) and (9 ') and sandwiched in a sandwich shape. And proceed between the guide plates (13) and (13 ') to form a thermosetting resin molding material (14).
Is shaped into a sheet.

The paste (12) thinly applied to the two carrier films penetrates into the sandwiched thermosetting resin molding material to improve the impregnation effect, and the paste (12) is applied to the surface in contact with the carrier film inner surface. It remains as a skin layer. The thickness of the paste applied on the carrier film is preferably from 0.1 to 1.5 mm. 0.
If the thickness is less than 1 mm, impregnation is poor, and glass grains and irregularities may remain. If the thickness is more than 1.5 mm, a paste-rich portion is formed, which is not preferable.

Example 1 A molded article made of a thermosetting resin was obtained by the above-described apparatus under the mixing and shaping conditions shown in the following table.

[0015]

(Table 1) (Blending composition) Paste weight% unsaturated polyester resin (Lycolac M-411 *) 20 Filler (calcium carbonate) 45 Additive (park mill etc. **) 10 Glass fiber 25 * Showa Polymer Co., Ltd. ) Unsaturated polyester ** Curing agent of NOF Corporation

[0016]

[Table 2] (Shaping conditions) Impregnating roll radius 300 mm 〃 Peripheral speed 16 m / min ギ ャ ッ プ Gap (7) 0.55 mm Length of chopped strand 13 mm Gap of first doctor knife (1), (1 ') 0.25 mm No. 2 (11), (11 ') 0.15mm Speed of take-off rollers (9), (9') 1m / min Viscosity of paste 1200PS Thickness of sheet-like thermosetting resin molding material 10mm Specific gravity of product 1.9

(Evaluation of Obtained Molding Material) When the carrier film of the molding material obtained as described above was peeled off and inspected, there was no fibrous grain (glass grain) on the surface and the unimpregnated portion was not. Of course, there were very few surface irregularities, the entire surface was covered with a very thin paste skin layer, and the film was shiny and shiny. The impregnation state inside the entire thickness was also very good. Using this molding material, electrical parts were molded by a compression molding machine. The finished molded product had no defects such as whitening, pinholes, and uneven color, and the yield was as good as 99%. .

Comparative Example 1 FIG. 2 shows an embodiment of a comparative example. The embodiment up to the carrier film is the same as that in FIG. 1 of the embodiment. In FIG. 2, two carrier films are taken up by a take-up roll (9),
The molding material is placed on the upper part of (9 '), the molding material is sandwiched in a sandwich shape, the sheet material is formed, and the process proceeds to the subsequent process. The composition and the shaping conditions were the same as in Example 1, and only the application of the paste onto the carrier film by the second doctor knife was not performed.

(Evaluation of Obtained Molding Material) When the carrier film of the molding material obtained as described above was peeled off and inspected, fibrous grains (glass grains) on the surface were slightly generated in some places. I was No noticeable impregnation failure was found on the surface, but the roughness of the base material of the thermosetting resin molding material was uneven as it was, and the overall appearance was not good. Also,
In the impregnation state inside the entire thickness, a whitish impregnation defect was observed at a part of the end. Using this molding material, electric parts were molded by a compression molding machine, but the finished molded product was slightly whitened and pinholes occurred, and the yield was not as good as 95.5%.

[0020]

According to the prior art, the paste has a high viscosity. The reinforcing fiber (glass fiber) has a high content rate. The production rate has a high speed. There were restrictions. The present invention eliminates these problems, improves the quality of the resulting thermosetting resin molding material, and greatly advances productivity. The thermosetting resin molding material produced by the method of the present invention is mainly used for compression molding, but is also used for transfer molding. As for the quality of the molded product, high quality could be obtained without defects such as whitening, pinholes, and color unevenness, and a high yield was also guaranteed.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram of a prior art device used in a comparative example.

[Explanation of symbols]

 1, 1 'first doctor knife 2 paste 3, 3' impregnating roller 4 paste application surface 5 glass roving 6 chopped strand 7 roller gap 8 scraper 9, 9 'take-up roller 10, 10' carrier film 11, 11 'second doctor Knife 12 Paste 13, 13 'Guide plate 14 Sheet-shaped thermosetting resin molding material

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 16

Claims (3)

(57) [Claims] 1. A sheet-like material obtained by sandwiching a molding material impregnated with reinforcing fibers with a paste-like material obtained by mixing a thermosetting resin and an additive such as a filler between two carrier films. A method for producing a thermosetting resin molding material, characterized in that another paste-like material is applied in advance to each surface of the carrier film in contact with the molding material in a thin film form. 2. The method according to claim 1, wherein the thickness of the paste applied in the form of a thin film is 0.1 to 1.5 mm. 3. A sheet in which a thin film of the paste is formed on both surfaces of a sheet of a molding material in which reinforcing fibers are impregnated with a paste in which a thermosetting resin and an additive such as a filler are mixed. Thermosetting resin molding material.