JPH08174580A - Manufacture of molded item of thermosetting resin - Google Patents

Abstract

PURPOSE: To provide a method for manufacturing a molded item whose strength is stabilized and a thick wall portion of which is free from bubbles, in which a molding time can be shortened and productivity can be improved when a molded item of a thermosetting resin having a thick wall portion is manufactured. CONSTITUTION: A method for manufacturing a molded item of a thermosetting resin having partially thick wall portions is provided, wherein a molding material of the thermosetting resin is fed into a mold 1 having thick wall forming parts 13 to cure it by heat under pressure. A step wherein pieces 2 of a thermosetting resin molding material having been preheated beforehand are put into the parts 13 of the mold 1 and a step wherein a molding material 3 of a thermosetting resin is fed onto the pieces 2 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermosetting resin molded product having a partially thick portion using a thermosetting resin molding material such as sheet molding compound (SMC).

[0002]

2. Description of the Related Art Conventionally, as a method for producing a thermosetting resin molded product using SMC, a glass fiber mat or chopped strand is used for thermosetting resin such as unsaturated polyester resin, a curing agent, a thickener, and a filling agent. After impregnating a paste-like mixture in which agents, pigments, etc. are mixed, both sides are covered with a film such as polyethylene to form a sheet, which is left at a predetermined temperature for a certain period of time to be thickened by a chemical reaction, Create a sheet-shaped SMC stock that is less sticky,
A method is generally employed in which a film is peeled from this SMC original fabric, a predetermined weight of SMC cut into a predetermined size is weighed, and the SMC is fed to a heated matched die and pressure-cured by a press molding machine or the like.

The press molding cycle consists of 5 steps of material supply, mold closing, curing, mold opening, and product removal.
It consists of steps. Of these, the one with the longest cycle time is the curing step of, and in order to shorten that time, in recent years, attempts have been made to shorten the molding cycle by SMC using a fast curing agent (low temperature decomposition catalyst). ing.

[0004]

However, this curing time is governed by the wall thickness of the molded product, and as a matter of course, the larger the wall thickness, the longer the curing time. For example, as in a fiber reinforced resin (FRP) bathtub or waterproof pan, the ribs on the back of the bottom and the bosses for mounting feet have a thick portion of about 15 mm even if the overall thickness is 4 to 7 mm. In the case of a product, there is a problem that a curing time corresponding to the wall thickness of a very small portion of the product is required, and finally the molding cycle becomes long and the productivity is lowered.

In view of this point, for example, “Reinforced Plastic Molding Material” issued by the Japan Reinforced Plastics Association on October 1, 1989, (2) Mold temperature on page 66, and 9.1 on the same page. .3 Technical Issues (1) In the column of shortening the molding cycle, it has been proposed to use a material having high thermal conductivity for the mold, but it is not yet sufficient for shortening the molding cycle.

The present invention solves the above-mentioned conventional problems and shortens the molding time in the case of producing a thermosetting resin molded product having a thick portion, improves the productivity and The object of the present invention is to provide a method for producing a thermosetting resin molded product that is stable in strength without bubbles remaining in the meat portion.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a thermosetting resin having a partially thick portion, in which a thermosetting resin molding material is supplied into a mold having a thick portion to be heated and pressure cured. A method of manufacturing a molded product, comprising a step of supplying a thermosetting resin molding material piece which has been preheated in advance to a thick-wall forming portion of a mold, and a step of supplying a thermosetting resin molding material thereon. And a method for producing a thermosetting resin molded article having:

In the present invention, SMC or bulk molding compound (BMC) is usually used as the thermosetting resin molding material. Among these, as a method for producing SMC as a thermosetting resin molding material which is a typical material, inorganic particles, a thickener, a curing agent, an internal mold release agent are added to a thermosetting resin such as an unsaturated polyester resin. A resin composition containing a stabilizer, a colorant, a low-shrinking agent, etc. is prepared.

Next, the resin composition is applied to a support film, and short fibers obtained by cutting reinforcing fibers such as glass rovings are accumulated on the applied surface in a sheet form. After that, the coated surface of the support film coated with the same resin composition as described above is superposed on the aggregate of the short fibers, and this is passed through a gap of a transfer device including a pair of endless belts and a plurality of pairs of rolls. Then, this is wound and then aged to prepare an SMC original fabric.

The unsaturated polyester resin is a mixture of an unsaturated polyester obtained by polycondensing an unsaturated dibasic acid, a glycol, and a saturated dibasic acid optionally added, and a copolymerizable monomer. Is.

As the resin component contained in the unsaturated polyester resin, there may be mentioned, in addition to the unsaturated polyester, a thermoplastic resin added for the purpose of reducing the shrinkage. Examples of such a thermoplastic resin include polystyrene,
Polyvinyl acetate, polymethyl methacrylate, polyethylene, poly ε-caprolactone, saturated polyester, polyvinyl chloride, polybutadiene, polystyrene-acrylonitrile copolymer, polystyrene-polyvinyl acetate copolymer, ethylene-vinyl acetate copolymer, vinyl chloride ─
A vinyl acetate copolymer or the like is used.

As the inorganic particles, for example, calcium carbonate, calcium sulfate, aluminum hydroxide, glass powder, clay, talc, silica sand and the like are used.

As the reinforcing fibers, generally, a glass roving having a monofilament diameter of 1 to 50 μm and a length of 5 to 150 mm, chopped strands obtained by cutting the strands to a certain length, and chopped strands bonded with a binder to form a mat-like shape. Chopped strand mats etc. are used. The addition amount of the reinforcing fiber is appropriately determined depending on the required physical properties of the molded product, but in general,
The reinforcing fiber in SMC is added so as to be 5 to 70% by weight.

As a curing agent, a 10-hour half-life temperature is 1
Organic peroxides around 00 ° C., such as t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, methyl ethyl ketone peroxide,
Organic peroxides having a 10-hour half-life temperature of about 75 ° C., such as t-amylperoxy-2-ethylhexanoate and t-butylperoxy-2-ethylhexanoate, are used. These organic peroxides may be used alone or in combination.

As the release agent, for example, zinc stearate, calcium stearate or the like is used. As the chemical thickener, for example, magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide or the like is used. As the stabilizer, for example, hydroquinone, parabenzoquinone or the like is used.

The present invention includes the steps of supplying a thermosetting resin molding material piece that has been preheated in advance to the thick portion, and supplying the thermosetting resin molding material thereon.

In the former process, for example, first, 10
In order to prevent the decomposition of the organic peroxide, SMC containing an organic peroxide having a time half-life temperature of 70 to 105 ° C. is cut into small pieces, and the temperature is 50 to 60 lower than the decomposition temperature.
Preheating is carried out by placing it in a preheating device such as a gear oven heated to ℃ for a predetermined time. Then, FIG.
As shown in, the upper mold 11 which has been heated to a predetermined temperature in advance.
The preliminarily preheated SMC piece 2 is supplied to the thick-wall forming portion 13 of the lower die 12 of the mold 1 including a matched die including

In the latter process, for example, the lower mold 12
And the preheated S supplied to the thick-wall forming part 13
SM containing the same organic peroxide that has been cut and weighed in advance so as to be stacked on the MC piece 2.
Supply C3.

Subsequent to this step, the upper mold 11 is lowered, the mold is clamped, the pressure is held, the pressure is hardened, and the mold is opened. As shown in FIG. A thermosetting resin molded product 4 having is obtained. Mold temperature is generally 12
0 to 160 ° C., mold clamping pressure is generally 3 to 20 MPa
Is. The pressure holding time after mold clamping varies depending on the molding conditions such as the type of organic peroxide contained in SMC, the mold temperature, and the size (particularly the thickness) of the molded product, but generally 200 to
400 seconds.

[0020]

The method for producing a thermosetting resin molded article of the present invention comprises a step of supplying a thermosetting resin molding material piece which has been preheated in advance to a thick-wall forming portion of a die, and a thermosetting process. Since it has a step of supplying a resin molding material, it is possible to complete the curing of the thick-walled portion at the same time as the portion other than the thick-walled portion, so that the molding cycle can be shortened and the productivity is excellent. ing. In addition, since the SMC piece supplied in advance to the thickness forming portion does not move much, air traps or cavities are hardly formed in the thick portion,
It is possible to manufacture a thermosetting resin molded product that is stable in strength.

[0021]

[Example] as in Example following, was engaged in the manufacture of FRP bathtub. 32 parts by weight of unsaturated polyester resin, 47 parts by weight of styrene monomer, 9 parts by weight of polystyrene, 120 parts by weight of calcium carbonate, 4.2 parts by weight of zinc stearate, 12.3 parts by weight of pigment composed of titanium oxide, para. 0.03 parts by weight of benzoquinone were mixed.

0.8 parts by weight of methylethylketone peroxide and 0.4 parts by weight of t-butylperoxy-2-ethylhexanoate were mixed with the mixture, and 0.85 parts by weight of magnesium oxide was further added to the mixture. Fiber (filament diameter 13 μm, cut length 25.4 mm)
And aged at 40 ° C. for 24 hours to prepare a sheet molding material.

From this molding material, length × width = 600 mm
Wrap several sheets cut to 40 mm into a polyester film so that the styrene monomer will not volatilize, and heat at 50 ° C.
Preheating was carried out by placing in a heating box whose temperature was controlled.

Then, as shown in FIG. 1, the pre-heated SMC piece 2 is placed in the thick-wall forming portion 13 of the lower die 12 of the die 1 in which the upper die 11 and the lower die 12 are heated to 145 ° C.
Is supplied, and SMC3 containing the previously cut and weighed organic peroxide similar to the above is supplied to the upper mold 1.
1, the mold was clamped at a pressure of 13 MPa, pressure-hardened, and then the mold was opened to partially have a 12 mm thick portion 41 as shown in FIG. A bath made of FRP having a bottom portion thickness of 8 mm was obtained. At this time, the mold clamping time required for the SMC to be completely cured was 100 seconds.

Comparative Example An SMC piece without preheating (20 ° C.) was used as a lower mold 12
An FRP bath similar to that in the example was obtained in the same manner as in the example, except that the bath was supplied to the thick-walled forming portion 13. At this time, the mold clamping time required for the SMC to completely cure is 1
It was 50 seconds.

[0026]

EFFECTS OF THE INVENTION Since the method for producing a thermosetting resin molded product of the present invention is configured as described above, the molding cycle can be shortened, the productivity is excellent, and air bubbles remain in the thick portion. It is possible to produce a thermosetting resin molded product that is stable in strength without causing any damage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating steps of an example of a method for manufacturing a thermosetting resin molded product of the present invention.

FIG. 2 is a sectional view showing an example of a thermosetting resin molded product manufactured according to the present invention.

[Explanation of symbols]

 1 Mold 2 SMC Piece 3 SMC 4 Thermosetting Resin Molded Product 13 Thick Wall Forming Section 41 Thick Wall Section

Claims (1)

[Claims] 1. A method for producing a thermosetting resin molded product having a partially thick portion, in which a thermosetting resin molding material is fed into a mold having a thick portion to be heated and pressure-hardened. hand,
A heat treatment comprising a step of supplying a thermosetting resin molding material piece that has been preheated in advance to a thick-wall forming portion of a mold, and a step of supplying a thermosetting resin molding material thereon. A method for producing a curable resin molded product.