JPS592814A - Manufacture of sheet molding compound - Google Patents

Abstract

PURPOSE:To obtain the titled compound which is completely free from any electrostatic interference in cutting as well as excellent in hot water resistance, adhesive properties and so forth, by employing as a glass fiber used for reinforcement, one which is positively charged when cut for use. CONSTITUTION:A polyethylene film is uniformly coated with a compound formed by uniformly mixing generally a liquid unsaturated polyester resin, a filler, a hardener, etc. Then, a glass fiber, which is positively charged when cut, is cut and uniformly dispersed on the compound. Further, another polyethylene film coated with the compound is overlaid thereon and pressed to obtain a desired compound. It is to be noted that to positively charge the glass fiber, it is preferable to treat the glass fiber, in spinning, with, for example, a surface treating agent consisting essentially of polyvinyl acetate emulsion, epoxy resin emulsion, acrylic silane, amino silane, polyethylene glycol and paraffin emulsion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a sheet molding compound (hereinafter referred to as SMC) using glass fibers. More specifically, by using glass fibers that are positively charged when they are cut and used,
The present invention relates to a method for manufacturing 5IViC that improves process failures caused by static electricity generation (hereinafter referred to as static electricity failures) such as non-uniform dispersion of glass strands during cutting and adhesion of charged glass strands to the periphery of the cutting machine.

Generally, as shown in Figure 1, SMC is a polyethylene compound made by uniformly mixing a liquid unsaturated polyester resin, a filler, an internal mold release agent, a curing agent, a coloring agent, a thickener, etc. After coating the film uniformly and dispersing the glass strands cut to a certain length using a cutting machine on top of the film, the compound is coated on another polyethylene film, which is then layered so that it is in contact with the compound-coated surface of another polyethylene film. It is produced by a process in which the film is pressed together in an appropriate manner from above and below to promote impregnation of the compound into the glass strands and to sufficiently remove air bubbles.

) A cutting machine for cutting glass fiber usually has 1 cutter barrel,
It consists of a presser roll and a rubber roll, and 2,310 rolls are placed at regular intervals on the part corresponding to the required width of the rolls.
Several dozen glass rovings of 4,630 tex or 4,630 tex are provided. Here, the glass roving is 1
Cut into ~2 inches and drop onto the compound coated onto the film. When most glass rovings are cut, they are charged with static electricity due to friction with the rubber row 5 of the cutting machine and friction between the glass fibers. Cut glass strands (hereinafter referred to as "chirobutsu strands") charged with static electricity (1) repel each other or are attracted to side walls, etc., resulting in an unevenly dispersed state. ■It adheres and accumulates around the roll of the cutting machine, significantly impeding cutting performance.

■As a result of the falling of the chimney strands accumulated on the side walls of the equipment, creating areas with extremely high glass content in the SMC, static electricity problems such as unimpregnated areas of glass fibers may occur. Cause. When SMC made by a process that has these static electricity problems is hot-pressed in a press or the like, the strength distribution of the resulting molded product may become uneven, and the air layer of unimpregnated strands may cause blisters on the surface of the molded product. or stains on the surface of the molded product due to burnt unimpregnated strands.

Conventionally, in order to eliminate static electricity damage caused by this charging,
Efforts are being made to bring the electrical charge of glass fibers as close to zero as possible by adding inorganic or organic antistatic agents to surface treatment agents for glass fibers. Known antistatic agents utilize the moisture absorption function of substances, and include salts such as ammonium chloride, magnesium chloride, lithium chloride, and sodium chloride as inorganic agents, and anionic alkyl phosphate esters as organic agents.

Examples include cationic alkyl quaternary ammonium salts and nonionic polyethylene glycols. When an antistatic agent is used, it is added in a relatively large amount to the glass fiber surface treatment agent, which increases the adsorbed moisture content of the glass fiber itself.
The disadvantage is that the hot water resistance of the SMC molded product using this product and the adhesion between the glass fiber and the resin deteriorate.

In addition, in order to avoid static electricity problems, a method has been used in which the inside of the SMω factory is kept at high humidity to reduce the generation of static electricity. However, the thickening agent in the compound absorbs moisture and changes its thickening properties, making it impossible to obtain SMC of a constant quality, and using glass roving that has absorbed too much moisture in high humidity may result in uneven dispersion after cutting. It has been found that this can cause molded product defects such as the aforementioned deterioration in hot water resistance due to moisture adsorption of glass fibers.

In addition to these methods, there is also a method of installing a high-pressure discharge machine or a straight cutter with a large number of small needles planted in series near the cutting machine, but this method is not suitable for SM cutting a large number of rovings at once.
In the manufacturing process of C, a large amount of static electricity is generated, ranging from several a to several tens of K.
Since the V and voltage are also high, it is difficult to completely remove it. Moreover, it is not actually used because the styrene vapor generated from the compound may explode due to electrical discharge. The present inventors recognized that removing static electricity damage during roving cutting is most important in the SMC manufacturing process, and as a result of various studies on methods for removing static electricity damage from glass fibers that do not impede the hot water resistance of SMC1. We have arrived at the present invention. In other words, by using glass fibers that are positively charged when cut and used for reinforcing the fibers, the present inventors completely eliminate static electricity damage and eliminate the occurrence of the aforementioned strand agglomeration. I discovered that. In this case, there is little effect on the voltage level.

It is fine as long as it is positive. According to the present invention, there is no need to use moisture-absorbing glass fibers, and therefore, it has become possible to supply glass fibers for SMCs that do not cause blisters during molding of SMCs and have good hot water resistance in molded products.

It has been found that "C" can be achieved by selecting an appropriate surface treatment agent during spinning, which is a method of positively charging glass fibers. Although it is influenced by the material of the rubber roll used for cutting, etc. The present invention is not limited to the following examples.

<Examples and Comparative Examples> While applying the surface treatment agent of the composition shown in Table 1 to the glass fibers being spun, the strands were wound around a high-speed rotating drum (
cake). This cake was dried at 125°C for 10 hours, then tied into 9 yarns and wound up.

Obtained roving of 4.630 tex. The 40 rolls of this roving were cut into 1-inch pieces using the cutting machine of the SMC coating apparatus shown in FIG. 1, and at the same time, a compound having the composition shown in Table 2 was uniformly coated and dispersed. At this time, the charged polarity (plus (positive) or minus (negative)) and generated voltage (Kv) of the cut glass fiber were measured. Furthermore, the state of adhesion to the rubber roll and barrel peripheral equipment of the glass fiber cutting machine was visually observed. The results are shown in Table 4.

After sufficiently impregnating and degassing the SMC, a plate was molded under the molding conditions shown in Table 3. In order to check the hot water resistance of the obtained molded product, it was left in boiling water for 300 hours.
The appearance of the molded products was observed and the results are also shown in Table 4.

From the results shown in Table 4, it is clear that according to the method of the present invention, there is no electrostatic damage during cutting of glass fibers, and the molded products using this SMC also have excellent hot water resistance.

Table 2 Table 3 Table 4

[Brief explanation of drawings]

FIG. 1 is a schematic side view of SMC being manufactured using a glass roving according to the present invention using a coating device.

Claims (1)

[Claims] A sheet molding compound that uses glass fibers that are positively charged when cut (
SMC) manufacturing method