JPH04247918A - Thermocompression molding method of thermosetting-fiber-reinforced resin sheet material - Google Patents

Abstract

PURPOSE:To improve productivity by shortening a molding cycle without deterio rating a quality, in a thermocompression molding method of a thermosetting fiber-reinforced resin sheet. CONSTITUTION:A sheet molding compound (SMC) 50 having a thickness of about 2mm is manufactured by infiltrating thermosetting unsaturated polyester resin paste containing t-butyl peroxy isopropyl cabonate into a glass fiber as a curing catalyst. A top force 10 and bottom force 20 are heated at 130 deg.C by circulating heating oil within the top force and bottom force by making use of a heating and control device 40 of the heating oil. Thirty sheets of the SMCs 50 are charged to the bottom force 20 by piling them upon one another, onto which the top force 10 is lowered and mold clamping is performed. Immediately after that, high-temperature heating oil is cerculated within the top force and bottom force by changing over to a heating and control device 30 of the heating oil, the top force 10 and bottom force 20 are heated at 150 deg.C and the SMC 50 is cured. A mold clamping time is 205 seconds and a good quality bathtublike molded product is obtained in a comparatively short time.

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for thermocompression molding thermosetting fiber reinforced resin sheet materials such as sheet molding compounds (SMC). [0002] Thermosetting fiber-reinforced resin sheet materials such as SMC are molded into various product shapes by a thermocompression molding method. Specifically, a mold consisting of a lower mold and an upper mold that have been heated to a predetermined temperature is used, a plurality of the above-mentioned materials are stacked and loaded onto the lower mold of the mold, and the upper mold is loaded onto the lower mold. By lowering the mold and clamping it, various product shapes are formed. [0003] In this case, particularly when a fast-curing material is used, the material loaded onto the lower mold begins to gel until the mold is completely closed due to heat from the lower mold. If the gelled material is in contact with the lower mold surface for a long time, the so-called pre-gelation phenomenon will cause roughness and roughness on the surface of the molded product.
Defects such as pockmarks and cloudiness occur. [0004] Therefore, in conventional hot compression molding methods, the temperature of the lower mold is generally lowered by about 20°C than the temperature of the upper mold, or a material that gels slowly is used. This prevents gelation from starting before the material is filled and the mold is completely closed, thereby preventing the pre-gelation phenomenon. However, if the temperature of the lower mold is kept low until the completion of molding or if a material that hardens slowly is used, the molding time becomes longer and productivity deteriorates. The present invention solves the above problems, and its purpose is to:
It is an object of the present invention to provide a method for thermocompression molding of a thermosetting fiber-reinforced resin sheet material, which can shorten molding time, improve productivity, and produce molded products of good quality. [0006] Means for Solving the Problems The method of thermocompression molding of a thermosetting fiber reinforced resin sheet material of the present invention includes supplying a heating medium into an upper mold and a lower mold, The lower mold is heated and held at a lower temperature than the molding temperature, and after the lower mold is loaded with a thermosetting fiber-reinforced resin sheet material and the mold is clamped, the heat medium is switched to a higher temperature heat medium and supplied. The method is characterized in that the temperature of the upper mold and the lower mold is kept at the molding temperature to harden the material, thereby achieving the above object. [0007] In the present invention, sheet molding compound (SMC) is usually used as the thermosetting fiber-reinforced resin sheet material. This SMC is manufactured, for example, by a known method as described below. First, a curing catalyst is added to a conventional liquid unsaturated polyester resin made by diluting an unsaturated polyester with a resin crosslinking monomer such as a styrene monomer, and if necessary, a chemical thickener,
An unsaturated polyester resin paste is prepared by blending a filler, a shrinkage prevention resin, a mold release agent, a stabilizer, a coloring agent, etc. [0008] Next, this paste is applied to a support film, and short fibers obtained by cutting glass rovings etc. into short lengths are accumulated in the form of a sheet on the applied surface. Thereafter, the coated surface of a support film coated with the same paste as above is superimposed on this aggregate of short fibers, and then it is passed through the gap of a transfer device consisting of a pair of endless belts and multiple pairs of rolls, and then wound. It will ripen after being harvested. The thickness of SMC is generally 1 to 1
It is about 0 mm. As a curing catalyst, organic peroxides with a 10-hour half-life temperature lower than 100°C, such as t-butylperoxyisopropyl carbonate (10-hour half-life temperature 97°C), t-butylperoxy-2- Organic peroxides such as ethylhexanoate (10-hour half-life temperature: 74°C), benzoyl peroxide (10-hour half-life temperature: 72°C), or a mixture thereof, are preferably used. [0010] As the chemical thickener, magnesium oxide, magnesium hydroxide, etc. are used. As the filler, calcium carbonate, clay, aluminum hydroxide, etc. are used. Further, as a mold release agent, zinc stearate, calcium stearate, etc. are used. As the stabilizer, hydroquinone, parabenzoquinone, etc. are used. As the reinforcing fibers, glass fiber rovings having a monofilament diameter of 1 to 50 μm and a length of 5 to 150 mm are generally suitably used. The mixing ratio of the above-mentioned thermosetting resin paste and reinforcing fibers is appropriately determined depending on the required physical properties of the molded product, but in general, SMC
The reinforcing fibers are mixed in an amount of 5 to 70% by weight. In addition, the supporting film generally has a thickness of 10 to 1
00 μm polyethylene film, polypropylene film, nylon film, polyester film, etc. are used. The present invention will be specifically explained below with reference to the drawings. FIG. 1 is an explanatory diagram showing one embodiment of the present invention. In FIG. 1, 10 is an upper mold, and 20 is a lower mold. Inside the upper mold 10 and the lower mold 20, a large number of pipes 11 and 21 are arranged, respectively, for supplying a heat medium such as steam or oil. 30 is a heating control device for a heating medium at a molding temperature to be supplied to the upper mold 10 and the lower mold 20; 40 is a heating control device for the heating medium at the molding temperature; 40 is the upper mold 10 and the lower mold 2;
This is a heating control device for a heat medium at a temperature lower than the molding temperature supplied to the heat transfer medium. The heating control device 30 and the plurality of pipe lines 11 are connected by flexible piping 31. The multiple conduits 11 and the multiple conduits 21 are connected by flexible piping 32. The multiple pipe lines 21 and the heating control device 30 are connected by flexible piping 33. Then, the heat medium heated to the molding temperature is heated to the heating control device 30,
Piping 31, multiple pipelines 11, piping 32, multiple pipelines 21
, and piping 33 in this order to circulate in the direction of the arrow. This heating medium heats and maintains the upper mold 10 and the lower mold 20 at the molding temperature. Further, a flexible pipe 41 is connected to the heating control device 40, and this pipe 41 is connected to the middle of the pipe 31. A flexible pipe 42 is connected to the middle of the pipe 33, and this pipe 42 is connected to a heating control device 40. The heat medium heated to a temperature lower than the molding temperature circulates in the direction of the arrow through the heating control device 40, piping 41, multiple pipe lines 11, piping 32, multiple pipe lines 21, and piping 42 in this order. It is done like this. This heating medium heats and maintains the upper mold 10 and the lower mold 20 at a temperature lower than the molding temperature. Note that the pipes 31 and 41 are provided with heat medium supply pumps 34 and 43, respectively. Also, valves 35, 3 are provided in the pipes 31, 33, 41 and 42.
6, 44 and 45 are provided, respectively. In the heat compression molding apparatus configured in this way, first, the valve 3
5 and 36 are closed, valves 44 and 45 are opened, and a heat medium heated to a temperature lower than the molding temperature (for example, 110 to 130°C) is transferred to the heating control device 40, piping 41, a large number of conduits 11, and the piping. 32, the upper mold 10 and the lower mold 20 are heated and maintained at a temperature lower than the molding temperature by circulating in the direction of the arrow through a large number of conduits 21 and piping 42 in this order. Next, a thermosetting fiber-reinforced resin sheet material 50 such as SMC is loaded into the lower mold 20. A plurality of thermosetting fiber-reinforced resin sheet materials 50 are usually stacked and loaded. Then, the upper mold 10 is lowered onto the lower mold 20 under a constant pressure (generally 70 to 150 kgf/cm2).
Clamp the mold with. Thereafter, the valves 44 and 45 are closed, the valves 35 and 36 are opened, and the molding temperature (for example, 145 to
155° C.), and this heat medium is transferred to the heating control device 30, piping 31, a large number of conduits 11,
The upper mold 10 and the lower mold 20 are heated and maintained at the molding temperature by circulating in the direction of the arrow through the pipe 32, a large number of pipes 21, and the pipe 33 in this order. In this way, the sheet material 50 is heated and maintained at the molding temperature, and the resin in the sheet material is cured. Thereafter, the mold is demolded to obtain a fiber-reinforced resin molded body. In this case, the mold clamping time (time from the start of mold clamping to demolding) varies depending on the hardenability of the sheet material 50, but is generally 10 to 3
00 seconds. [Operation] In this way, a heating medium is supplied into the upper mold and the lower mold to heat and maintain the upper mold and the lower mold at a temperature lower than the molding temperature, and heat is applied to the lower mold. After loading the curable fiber-reinforced resin sheet material and clamping the mold, the heat medium is switched to a higher temperature heat medium and the upper and lower molds are heated and maintained at the molding temperature to harden the material. The material loaded into the mold is
Since the temperature of the lower mold is low, gelation is prevented from starting until the mold is completely tightened. After the mold is clamped, a higher temperature heat medium is switched and supplied into the upper mold and the lower mold to heat the upper mold and the lower mold to the molding temperature. The lower mold is quickly heated and maintained at the molding temperature by this heating medium. [Examples] Examples and comparative examples of the present invention will be shown below. Example 1 40 parts by weight of unsaturated polyester, 60 parts by weight of styrene monomer
parts by weight, 10 parts by weight of polystyrene, t-butyl peroxyisopropyl carbonate (10 hour half-life temperature: 9
7° C.), 140 parts by weight of calcium carbonate, 1 part by weight of magnesium oxide, and 4 parts by weight of zinc stearate to prepare a thermosetting resin paste. In addition, glass roving (monofilament diameter approximately 13 μm, count 4630 g/km) was prepared as a reinforcing fiber. First, the above-mentioned large number of glass rovings are
The fibers were cut into short fibers with a length of about 25 mm using a rotary cutter and allowed to fall downward. On the other hand, upper and lower supporting films made of nylon films having a thickness of 50 μm were supplied while being supported by a pair of upper and lower endless belts. Then, the above thermosetting resin paste was applied to the inside of the upper and lower support films. Next, the inner coating surface (top surface) of the lower support film is coated with this thermosetting resin paste.
The above-mentioned short fibers were dropped, and the short fibers were transferred while being accumulated in a sheet form. Subsequently, the inner coated surface (lower surface) of the upper support film coated with the thermosetting resin paste was superimposed on the short fiber layer accumulated in the sheet form. Thereafter, this laminate was passed through a gap in a transfer device consisting of a pair of upper and lower endless belts and a plurality of pairs of rolls, and wound up into a roll. In this case, the sheet manufacturing speed is 3 m/
The thickness of the sheet is approximately 2 mm, and the glass fiber content is approximately 2 mm.
It was 8% by weight. The thus produced SMC scroll (approximately 100 kg) was left to mature in a thermostatic chamber at approximately 50° C. for approximately one day. Thirty sheets of aged SMC were cut and prepared. By the method shown in FIG. 1, heating oil is circulated in the upper mold and the lower mold to heat the upper mold and the lower mold to 130.
The temperature was maintained at ℃. Then, 30 sheets of the above-described cut SMC were stacked and loaded into the lower mold, and the upper mold was lowered thereto and the molds were clamped at a pressure of 100 kgf/cm2. Immediately thereafter, another heated oil was supplied and circulated into the upper mold and the lower mold to maintain the temperature of the upper mold and the lower mold at 150°C. Mold clamping time 20
The SMC in the mold was heated and hardened for 5 seconds, and then removed from the mold to obtain a bathtub-shaped molded product. [0024] The surface of this bathtub-shaped molded product was free from defects such as rough skin, pockmarks, and cloudiness, and was of good quality. Furthermore, the mold clamping time was relatively short at 205 seconds. Comparative Example 1 In Example 1, both the upper mold and the lower mold were heated and maintained at 150° C. from the beginning. Other than that, the same procedure as in Example 1 was carried out. In this case, the mold clamping time was 180 seconds, which was relatively short. However, rough skin and cloudiness occurred on the surface of the obtained bathtub-shaped molded product, resulting in poor quality. Comparative Example 2 In Example 1, after the mold clamping, the upper mold and the lower mold were heated and maintained at 130° C. without switching and circulating another heating oil in the upper mold and the lower mold. In addition, the mold clamping time was changed to 300 seconds. Other than that, the same procedure as in Example 1 was carried out. In this case, defects such as rough skin, pockmarks, and cloudiness did not occur on the surface of the obtained bathtub-shaped molded product, and the quality was good. However, the mold clamping time was relatively long at 300 seconds. Comparative Example 3 In Example 1, 1 part by weight of t-butylperoxyisopropyl carbonate (10-hour half-life temperature: 97°C) was replaced with 1 part by weight of t-butylperoxybenzoate (10-hour half-life temperature: 105°C). I changed it. Also,
Both the upper mold and the lower mold were heated and maintained at 150°C from the beginning. Other than that, the same procedure as in Example 1 was carried out. In this case, defects such as rough skin, pockmarks, and cloudiness did not occur on the surface of the obtained bathtub-shaped molded product, and the quality was good. However, the mold clamping time was relatively long at 220 seconds. [0028] As described above, according to the heat compression molding method of the present invention, even if a fast-curing material is used, the material loaded into the lower mold will not be able to harden until the mold is completely closed. Since the temperature of the lower mold is low during this period, gelation is prevented from starting before the mold is completely tightened. Therefore, defects such as rough skin, pockmarks, and cloudiness on the surface of the molded product due to the so-called pre-gelation phenomenon do not occur, and a fiber-reinforced resin molded product of good quality can be produced. In addition, the above-mentioned fast-curing material loaded into the lower mold can be quickly cured because the temperatures of the upper mold and lower mold quickly reach the same molding temperature after the mold has been completely tightened. It hardens quickly when heated. Therefore, molding time can be shortened and productivity can be improved.

[Brief explanation of the drawing]

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

[Explanation of symbols]

10 Upper mold 11 Pipe line in the upper mold 20 Lower mold 21 Pipe line in the lower mold 30 Heating control device for heat medium 40 Heating control device for heat medium

Claims (1)

[Claims] Claim 1: A heating medium is supplied into the upper mold and the lower mold to heat and maintain the upper mold and the lower mold at a temperature lower than the molding temperature, and the lower mold is reinforced with thermosetting fibers. After the resin sheet material is loaded and the mold is clamped, the heat medium is switched to a higher temperature heat medium and the temperature of the upper mold and the lower mold is maintained at the molding temperature to harden the material. A method for thermocompression molding of thermosetting fiber-reinforced resin sheet materials.