JPH03288629A - Manufacture of composite molder product - Google Patents

Abstract

PURPOSE:To obtain a composite molded product having excellent productivity and workability by making reinforcing fibers exist in the vicinity of the inner surface of a mold, and also making heat expansion particles and solid heat melting matrix resin or the mixed substance with the material thereof exist in the part to be a porous core after the molding and, after that, heating the mold. CONSTITUTION:By using matrix resin or the material thereof to be softened and liquified by heating in combination with expansive particles, these raw material composites are put into the mold wrapping with reinforcing fibers, or put into the central part of the mold that is preliminarily placed with reinforcing fibers in the proximity of the inner surface of the mold so as to be heated therein, whereby the matrix resin or raw material constituting the raw material composites is softened or melted and the heat expansive particles are expanded, and thus, by the expansion forces thereof, a part of the matrix resin is impregnated in the layer of the reinforcing fibers and, by pressing the layer into the inner surface of the mold so as to be solidified under the state, thereby forming it into the configuration of the inner surface of the mold. Such heat expansive particles are increased in volume by heating and, for such foaming expansive particles, foaming expansive particles in which foaming agents are wrapped with vinylidene chloride, polystyrene or the like are is given for example.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a lightweight composite molded article mainly comprising a porous core and a fiber-reinforced resin composite material surrounding it.

[Prior Art] Porous molded products are industrially a type of resin molded products. Conventionally, this has been manufactured industrially by a method of molding using a foamable resin, that is, by foam molding.

This method can be roughly divided into two methods: a method in which a resin or resin raw material that foams when heated or reduced pressure is placed in a mold and molded into a predetermined shape, and a method in which a specific resin is foam-molded into particles and primary foaming is performed. This can be divided into two methods: putting it into a mold, expanding it further (secondary foaming), and molding it into a predetermined shape. As a method of manufacturing lightweight structures such as Sanderutsch timber using such foam molding, a pre-formed foam molding is used as a skin material such as a pre-formed fiber reinforced resin molding (hereinafter abbreviated as FRP). Usually, the foam molded product is bonded with a material (sometimes referred to as a foam material), the foam molded product is covered with a prepreg or the like, or a foamable resin is injected into a pre-formed hollow outer shell to perform foam molding. In addition, in recent years, methods have been developed in which internal pressure molding using foaming expansion and methods using thermally expandable molded products as materials for porous bodies have been developed. (
For example, Japanese Patent Application Publication No. 1-255530, Japanese Patent Application No. 1-179
No. 830, JP-A No. 63-162207, etc.) [Problem to be solved by the invention] A composite molded product whose surface is molded into a predetermined shape using a fiber-reinforced resin composite material and whose core is porous is subjected to thermal expansion. These molding methods using plastic resins are generally excellent methods that yield good molded products. However, the process is far from simple and the productivity is far from particularly high.

Specifically, among these methods, the Foam RTM method (a method in which a pre-formed foam core is wrapped with reinforcing fibers, placed in a mold, and a liquid curable resin is injected into the reinforcing fiber layer), the Foam TEM method (a method in which a foam core is wrapped in a liquid TERTM method (wrapping a foam molded core with reinforcing fibers, placing it in a mold and applying liquid hardening to the reinforcing fiber layer) In both methods, a foam core with a shape similar to the final molded product is molded in advance, and then a liquid hardening resin for the FRP layer is separately molded using this as a core. do. These problems not only require the separate molding of a core similar to the molded product, but also the need to handle liquid resin in addition to making the foam core.

The present inventors have developed and proposed a method for molding sand german materials using a thermally expandable balloon and a liquid curable resin as a method that does not require preforming a form core. (For example, Japanese Patent Application No. 1-179830, 1-255
No. 305, No. 1-229425, etc.). However, even with these methods, the molding operation remains complicated because the resin is in a liquid state and is in the process of being cured.

The present invention aims to further improve the previously proposed method and provide a method for manufacturing composite molded articles with even better productivity and workability.

[Means for Solving the Problems] The present inventors have conducted extensive studies on means for achieving the above-mentioned problems, and have developed the simple molding method of the present invention.

That is, in manufacturing a composite molded article containing at least a surface layer and a porous core formed into a predetermined shape from a fiber-reinforced resin composite material, at least the inner surface of the mold is formed in a mold for molding. Reinforcing fibers are placed nearby, and a mixture of heat-expandable particles and a solid heat-fusible matrix resin or its raw material is present in the portion that will become the porous core after molding, and then the mold is heated to form the solid material. This method of manufacturing a composite molded article is characterized in that the surface layer portion is molded while melting the matrix resin or its raw material and foaming and expanding the thermally expandable particles.

In the method of the present invention, foam RTM, foam TEM, T
Unlike the method using a series of foam cores called ERTM, there is no need to pre-shape the core, there is no need to use a separate resin in addition to the core, and there is no need to use liquid hardening resin, which softens or liquefies when heated. The main feature is that the matrix resin or its raw material is used in combination with thermally expandable particles to be molded all at once. Therefore, these raw material compositions are wrapped in reinforcing fibers and placed in a mold, or placed in the center of a mold in which reinforcing fibers have been placed near the inner surface of the mold, and heated to form the raw material compositions. The matrix resin or raw material to be used is softened or melted, and the thermally expandable particles are expanded, and the expansion force causes part of the matrix resin to penetrate into the reinforcing fiber layer, and the core layer is pressed against the inner surface of the mold, and solidified in that state. This is a method of molding the material into the shape of the inner surface of the mold. At this time, the thermally expandable particles and the matrix resin are wrapped in advance in a separation layer that does not allow the particles to pass through, but allows the melted or softened matrix resin to pass through, and the thermal expansion pressure of the particles is used to allow only the molten resin or its raw materials to pass through. A preferred method is to form a Sanderutsch material by passing through a separation layer and penetrating a fibrous reinforcing material to form FRP.

This solid matrix resin or its raw material is a thermoplastic resin or a raw material for a partially polymerized thermosetting resin that solidifies at room temperature, and can be melted and fluidized at a temperature below the expansion start temperature of the thermally expandable particles. . That is, by heating the matrix resin after placing it in a mold, the matrix resin becomes soft or liquid and has a relatively low viscosity, and the heat-expandable particles mixed therein expand, causing the matrix resin to flow. It is molded to match the shape of the inner surface of the mold. Such a matrix resin is usually preferably used in powder form at room temperature.

In the method of the present invention, a mixture of heat-expandable particles and a heat-melt matrix resin is placed in a position that will become the porous core of a target molded product, and heated to melt or soften the resin and foam and expand the heat-expandable particles. By using this force to spread the thermally expandable particles and liquefied matrix resin to every corner of the mold and perform internal pressure molding, it is possible to avoid contaminating the working environment when handling unlike liquid hardening resins. It can be reduced. In addition, in the case of thermoplastic resins, after melting, if the resin spreads through the reinforcing fiber layer due to the expansion of thermally expandable particles, it can be immediately cooled and recovered.Thermosetting resins are partially polymerized in advance and become solid at room temperature. In the case of raw materials, the amount of additional reaction can be reduced.

During molding, it may be preferable to release some of the resin or its raw materials that have returned to a liquid state and discharge them from the mold. It is possible to spread the resin even to areas where the injection is defective, reduce the amount of resin between the thermally expandable particles, and help correct variations in the presence of the thermally expandable particles within the cavity. Therefore, pressure relief can also be applied according to its purpose.

When making Sanderutsch material, the resulting molded product is a seamless molded product in which the core of the porous portion and the skin made of FRP are integrated.

Thermally expandable particles may exist as blocks, but
Even distribution is even more desirable. From the point of view of homogeneous dispersion, thermally expandable particles have an average particle size of IIIi.
It is preferable to use small particles of 1 or less, and when used in combination with other hollow bodies (for example, inorganic hollow particles), it is preferable to sufficiently mix and disperse these and thermally expandable particles.

The heat-expandable particles used in the present invention increase in volume when heated, and examples thereof include foam-expandable particles containing a blowing agent, such as particles called "microspheres" in which the blowing agent is wrapped in vinylidene chloride. particles, expanded expanded particles such as commonly used polystyrene, and foamed particles (
For example, polyethylene, polypropylene, polyurethane,
(primary expanded particles such as rubber) etc. In the case of the latter foam-molded thermally expandable particles, particles obtained by pressurizing and heating molded particles □ to fix them are also included.

0 A non-expandable hollow body can also be mixed with this.

Such hollow bodies are inexpensive and convenient for obtaining lightweight porous bodies. In consideration of economic efficiency, suitable non-expandable hollow bodies include inorganic hollow particles such as glass balloons and glass balloons.

Such a hollow body, for example, may be smaller than the thermally expandable particles, and by replacing a portion of the matrix resin between the thermally expandable particles, it is possible to further reduce the weight of the molded product. For example, if the thermally expandable particles are spherical with a relatively large diameter,
It is possible to replace a part of the matrix resin corresponding to the space of close packing with a sphere smaller than the gap in the case of close packing.

On the other hand, as the molding resin, a thermoplastic resin or a curable liquid resin that is solid at room temperature is used. As the latter, among generally well-known liquid molding resins that are solid at room temperature, such as epoxy resins, unsaturated polyester resins, non-foaming urethane resins, or their precursors, those that are solid at room temperature are preferably used. As a thermoplastic resin, it is necessary to have fluidity by softening or melting at a temperature (usually around 150°C) that does not expand due to thermal expansion particles, and for such a resin it has a relatively low melting point. Polyolefins, polystyrene, etc., phenoxy resins, some liquid crystal resins, etc. are preferably used.

The development of heat-expandable particles for this resin is progressing, and the scope of its application is also expanding as thermoplastic resins are being developed.

When producing Sanderutsch material by the method of the present invention, reinforcing fibers are used near the surface layer of the molded product, and the reinforcing fibers may be either inorganic fibers or organic fibers.

For example, inorganic fibers such as glass fiber, carbon fiber, boron fiber, silicon carbide fiber, and alumina fiber, organic synthetic fibers such as polyester, aramid, polyolefin, polyamide, and arylate, and natural fibers such as cotton and hemp may be used alone or in combination. It will be done. In addition to woven fabrics and knitted fabrics, it can also be constructed of filament windings as strands, yarns, etc., and can also be used as short fiber webs, mats, etc.

A preform may be used as the reinforcing fiber. When a separation layer is substantially used in combination, the opening of the reinforcing fiber sheet or preform can be freely selected, and for example, unidirectional fiber array prepreg, three-dimensional woven fabric, or knitted preform can also be used.

In addition, the separation layer (separation membrane) used in a preferred embodiment includes at least a part or all of the part containing a separation function that substantially does not pass particles after thermal expansion but allows liquefied molded resin to pass through, and the remainder is made of a material that does not allow the liquid molding resin to pass through. Examples of materials constituting the separation function of such a separation layer include a fiber sheet and/or a porous sheet. As the fiber sheet, woven fabrics, knitted fabrics, braided fabrics, non-woven fabrics, paper, etc. made of various natural fibers, synthetic fibers, metal fibers, inorganic fibers such as carbon or ceramics, etc. are used. The porous sheet contains continuous pores,
Foam sheets such as polyurethane, polystyrene, or polypropylene, or porous membranes such as polypropylene or polysphone made by stretching, extraction, or coagulation methods are used.

The opening size is selected depending on the type of thermally expandable particles used and the foamability of the particles. A sheet of glass fiber, carbon fiber, aramid fiber, etc., which itself has a reinforcing function, can also be used for this separation layer. These sheets may be colored or patterned on the surface. Furthermore, it is also possible to select an elastic material for the separation layer so that it can be easily adapted to the shape of the molded product.

Materials that do not allow the liquefied matrix resin to pass through may be composed of fiber sheets and/or materials used in the separation function-containing area, in addition to joining with materials different from those used in the separation function-containing area. Alternatively, a porous sheet whose openings have been sealed in advance with a resin, etc., or a fiber sheet whose openings have been closed by a fusion process if the fiber sheet can be fused by heat treatment, such as polypropylene fibers, and a film, etc. There are things etc.

In addition, in the case of a flat plate or a planar molded product with front and back surfaces, the separation layer can be provided only on one side of the inner surface of the mold. In this case, there are examples in which no separation layer is provided on the other side, and examples in which a material such as a film that does not allow even liquefied resin to pass is provided in place of the separation layer, but the choice may be made depending on the purpose. For example, in the case of a motorcycle cowling, by installing a printed film on the front side and using a separation layer made of glass fiber on the back side, it is possible to simplify the work of painting the front side and applying decals after molding.

Since the present invention involves mixing solid materials, especially at least two types of powder materials, as raw materials and heating and melting the mixture, heat transfer may be one of the factors. As a remedy for this, it may be preferable to use microwave heating and/or electromagnetic heating. In the former case, it is preferable to use a material that absorbs microwaves and generates heat, such as silicon carbide, in the raw material composition, and in the latter case, it is preferable to use an electromagnetic induction material such as iron powder or wire in combination.

[Effects of the Invention] By the method of the present invention, a lightweight and strong composite molded article, especially a sandwich structure, whose inner layer is a porous core and outer layer is a fiber-reinforced resin, can be easily and inexpensively obtained.

5 The molded product produced by the method of the present invention can be widely applied to various structural materials such as architecture and vehicles, sports goods, electrical parts, and other fields.

That is, as already mentioned, according to the method of the present invention,
Unlike liquid hardening resins, there is less pollution of the working environment when handling them, and in the case of thermoplastic resins, after melting,
The expansion of the thermally expandable particles spreads to the resin or reinforcing fiber layer and can be immediately cooled and recovered, and in the case of thermosetting resin raw materials that have been partially polymerized in advance and become solid at room temperature, the additional reaction scene can be reduced. It is effective.

In addition, when releasing or discharging a part of the liquid resin or its raw materials during molding, be sure to do so in areas where the resin does not spread, especially in areas where the resin has not been properly injected, such as reinforcing material preforms used in advance. It is also useful for distributing resin, reducing the amount of resin between thermally expandable particles, and correcting for variations in the presence of thermally expandable particles within the cavity.

[Example] Next, Examples and Comparative Examples of the present invention will be given.The present invention is not limited to these. In addition, unless otherwise specified, "parts" in each example are parts by weight.

Example 1 Heat-expandable foam beads [Matsumoto Microspheres-F-80SDJ] manufactured by Matsumoto Yushi ■ were obtained. These foam beads begin to expand at temperatures above 140°C and have the property of expanding up to about 70 times. Hereinafter, this particle will be abbreviated as F-80SD.

On the other hand, epoxy resin and curing agent made by Shell, namely [70 parts of Epikote 1001J (this resin itself is thermoplastic), 30 parts of "Epicoat 348", 30 parts of phthalic anhydride, 1 part of "Evomate YLH185," Part, 8
Mixed at 0°C. After cooling and solidifying, it was crushed into powder.

This is referred to as solid powder resin A.

100 parts of the above F-80SD, 10 parts of solid powder resin A
0 part was used, and both were mixed in solid phase. The obtained mixture is referred to as mixture B.

Unicell's polyester nonwoven fabric "Unicell" B T
-0404 was used to create a bag with a size corresponding to the reinforcing fiber layer (described later) being made smaller to fit the cavity of the mold. This contained the mixture B described above.

A mold was made with a Teflon frame sandwiched between two aluminum plates, and nozzles were installed at the top and bottom ends. A glass fiber cloth WF-181-1008■ made by Nittobo was prepared, and two pieces of the mold-cup crow cloth were prepared, along with 10 strips of glass cloth whose length matched the mold and whose width was sized to cover the nozzle. A sheet was made, used together with a large glass cloth, and placed in a mold in the following order: glass cloth/bagging mixture B/glass cloth. The position that covers the nozzle, that is, the upper and lower ends of the mold, is filled with small glass cloth, and F-80 is used in this position.
Prevented SD molded particles from entering. Air was sucked in using both nozzles to create a vacuum inside the mold. Then the mold is 145
Place in a silicone oil bath and heat. A small amount of liquefied resin and gas were allowed to overflow from the nozzle, and the nozzle was sequentially closed. After 1 hour, the mold was removed from the silicone oil bath, cooled, and the molded product was taken out from the mold. In this way, a good lightweight sandwich structure was obtained consisting of a glass fiber-reinforced epoxy resin on the surface and a foam-like body in which F-80SD foamed in the epoxy resin matrix was dispersed in the inner layer. The resulting molded product is F-80SD except for the part where the small glass cloth was inserted.
was distributed evenly, and the density was (1.56 g/).

Example 2 F-80SD, solid powder resin A,
Mixture B was prepared.

A set of two molds for making a serpentine model with a maximum width of 120 mm, a maximum length of 350 mm, and a thickness of 14 cm was prepared.

Nozzles were provided at the top and bottom of the mold. Four leaves of glass cloth and carbon cloth were also prepared to fit this mold. The glass cloth was glass fiber cloth WF-180-100BV manufactured by Nittobo Co., Ltd., which is the same as in Example 1, and the carbon cloth was carbon fiber 1111i product C06304 manufactured by Toshi Co., Ltd.

In addition, Unicell ■ polyester nonwoven fabric “Unicell,
BT-0404 was made into a bag according to the mold.

Mixture B was placed in a "Unicell" bag, sandwiched between glass cloth and carbon cloth, and placed in a mold.

9 The inside of the mold was evacuated and placed in a hot bath of silicone oil at 145°C. After confirming that liquefied resin and gas were coming out of each nozzle, the nozzles were closed.

After holding for 1 hour, the molded product was taken out from the hot bath, cooled, and taken out. A good snake-shaped model with a specific gravity of 0.8 was obtained.

Example 3 Nozzles are provided at both ends and the cross section is 20rnm x 20+n
Prepare a mold with a length of 500 m.

Polypropylene and a blowing agent such as freon are mixed under pressure and discharged under normal pressure, and the obtained pre-expanded particles are aged at normal pressure, then placed in a pressure vessel at an external temperature of 160°C to produce 6 kg/
It was compressed for 1 hour at a pressure of cIiI. After returning to room temperature, the pressure was returned to normal pressure to obtain expanded polypropylene particles. These foamed particles have a particle size of 1 to 2 mm, and have the property that when heated to 100° C., the particles immediately expand in volume by 20%, but no volume contraction is observed even when the particles are returned to room temperature.

These polypropylene particles are abbreviated as PPB.

A tube with a circumference of 80 mm was made using the polyester nonwoven fabric [UNICEL J BT-0404] used in Example 2, and
PB100 parts and solid powder particles A100 used in Example 1
The parts were mixed and packed.

A cylinder made from "Unicell" containing PPB and solid powder resin A was covered with two layers of carbon fiber braid and one layer of glass fiber braid. The blade used was a carbon fiber blade.
Trading card J T-3964, T-3484, glass fiber braid "Adkins & Pierce, $927
3, each blade is T-3484, $9273,
They were stacked in the order of T-3964.

This was placed in the mold described above, and the mold was closed. The mold was placed horizontally, and then the pressure was reduced using a vacuum pump to create a nearly vacuum. Next, in substantially the same manner as in Example 1.2, the resin was cured by placing it in a hot bath at 110° C. while removing excess resin and debris.

The mold was removed from the hot bath after one hour, cooled, and the molded product was taken out from the mold. In this way, a lightweight square timber was obtained whose surface was made of carbon/glass fiber-reinforced epoxy resin and whose inner layer was a foam of epoxy resin and polypropylene. FRP surface
The specific gravity including the layer was 0.56 g/-.

1 Example 4 Polyethylene resin was obtained. When this resin is thermally analyzed, it begins to endotherm at about 70°C and softens, and the endothermic rate reaches its maximum at 98°C.

50 parts of the same microspheres as in Example 1, 30 parts of Asahi Glass's hollow balloon M28, and 100 parts of the above polyethylene resin were mixed. This is called mixture B.

A mold was made with a Teflon J frame sandwiched between two aluminum plates. Nozzles were provided at the top and bottom ends of this mold. - On the other hand, the mold - 6 pieces of cup glass cloth and 8 pieces of rectangular crow cloth whose length was matched to the mold and whose width was sized to cover the nozzle were made.

A bag was made using the polyester/polypropylene nonwoven fabric "Unicell" of Example 1, matching the inner dimensions of the mold, and considering the possibility of inserting smaller glass cloths at the top and bottom. In this bag, the same PPB and solid powder resin A as in Example 3 were added.
I put it in. Using a large crow cloth, glass cloth/PPB and bagging of solid powder resin A/crow cloth were placed in the mold in this order. I layered small pieces of glass cloth to cover the nozzle, i.e. the top and bottom edges. This was placed in a hot bath at 150°C.

After 10 minutes, the molded product was taken out from the hot bath, cooled, and taken out from the mold. A light and good sand german material was obtained in which the surface layer was made of glass fiber reinforced polyethylene and the inner layer was made of 1 microsphere foam and polyethylene.

Example 5 A phenoxy resin having the following structure was prepared. This resin exhibited fluidity at 140°C in experiments.

A molded article was similarly produced using this phenoxy resin in place of the polyethylene resin of Example 4.

However, without using the crow balloon M28, the same product can be used. After shaping, a good lightweight sandwich material was obtained.

Example 6 Epoxy resin used in Example 1 [Epicote 1001J
itself is a thermoplastic resin with a pour point of 80°C or lower. A similar trial production was conducted using only this resin as the matrix resin.

[Epicote 1ooi was mixed with the same PPB as in Example 3 in a 1:1 weight ratio to form a mixture, and the mixture was placed in a bag made by "Unicell". This was sandwiched between crow cloth, placed in a mold, placed in a 145°C hot bath, and heated. The obtained molded product was similar to Example 1, and its specific gravity was 0.45 t/ai.
It was smaller than Example 1.

[When 100 parts of Epicoat 1001J, 100 parts of PPB, and 50 parts of Karasbeads M28 were mixed, the molded product had a specific gravity of 0.52 and was lightweight. This is thought to be because the size of the foam and the hollow body were significantly smaller, and the latter filled the filling gap of the former.

Claims (5)

[Claims] (1) When manufacturing a composite molded product having at least a surface layer and a porous core molded into a predetermined shape from a fiber-reinforced resin composite material, reinforcement is provided at least near the inner surface of the mold in the mold for molding. A mixture of heat-expandable particles and a solid heat-melting matrix resin or its raw material is present in the fiber for use in the porous core and in the portion that will become the porous core after molding, and then the mold is heated to form the matrix resin or its raw material. A method for producing a composite molded article, which comprises molding the surface layer while melting the heat-expandable particles and foaming and expanding the heat-expandable particles. (2) The manufacturing method according to claim (1), characterized in that a thermally expandable foam balloon is used as the thermally expandable particles. (3) Claim (1) or (2) characterized in that a thermoplastic resin is used as the matrix resin or its raw material.
The manufacturing method described in. (4) In manufacturing a composite molded product containing at least a surface layer portion molded into a predetermined shape and a porous core made of a fiber-reinforced resin composite material, (a) In a mold for molding, foamability after expansion is (b) Installing a separation layer made of a porous sheet that does not substantially allow resin particles to pass through, but allows molten matrix resin or its raw materials to pass; (b) in a portion surrounded by the separation layer that will become a porous core after molding; (c) providing a separation layer and a mixture of the heat-expandable particles and the solid heat-fusible matrix resin or its raw material in a mold; (d) heating the mold to a sufficiently high temperature to melt the solid thermofusible matrix resin or its raw material and to raise the temperature of the thermoexpandable particles to cause volumetric expansion, thereby forming a separation layer and (e) solidifying the molten liquid matrix resin and/or its raw materials; and (f) removing the resulting composite molding from the mold. The method for producing a composite molded article according to claim (1), (2) or (3). (5) Claim (1), (2), (3) or (4) characterized in that the mold is heated by microwaves or electromagnetic induction.
) The method for producing a composite molded article.