JP2731006B2 - Manufacturing method for composite molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a lightweight sandwich-like composite molded product having a surface layer (skin) made of a tough reinforcing material and a core (core) made of a foam. It is about.

[Prior Art] Sandwich-shaped fiber-reinforced resin composite molded products having a foamed core at the core are excellent in lightness and toughness, and thus have been applied to various uses such as surfboards and turbine blades.

As a method of producing a fiber-reinforced resin (hereinafter sometimes referred to as FRP) composite molded article having a foam core in a core, for example, a foam core to be a core is preliminarily molded and wrapped in a woven cloth as a reinforcing material. A method of forming the outer shell by re-inserting into a mold and injecting a liquid molding resin (see JP-A-55-82612, JP-A-61-279517, JP-A-63-162207); A method is known in which FRP is molded in advance, and a foamable urethane resin or the like is injected into a void at the center of the FRP and foamed in the void (see JP-A-1-255530).

However, each of these methods has a problem that the steps are diversified and the operation is complicated, and as a result, the production efficiency of the molded article is low and the cost must be high.

On the other hand, there is a method of installing a skin on the cavity surface of a mold, injecting a foamable liquid molding resin such as foamable urethane into the inside of the skin, and producing a foam with a skin by foaming in a-process. In the method, a low density (for example, a density of 0.
When trying to obtain a foam core (less than 8 g / cm ³ ), it is difficult to use foaming pressure during molding to press the reinforcement against the inner wall of the mold to give it a shape. Therefore, this method
Practically, the present invention is limited to molding of soft pads for automobiles using a skin material having sufficient extensibility that can be applied even at a low foaming pressure, or molding of a skin material in which the skin material is preliminarily shaped in accordance with a mold.

There is also a method in which foamable thermoplastic resin particles such as polystyrene are used in place of the foamable liquid molding resin, the skin of the particles is softened by heating, and the volume expansion is formed by mutual fusion to form a foamed core. The molded article has a problem in that when the use conditions approach the molding temperature, the foamed core softens, and the molded article lacks stable toughness.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems, and in producing a sandwich-like composite molded article having a low-density foamed core in a core portion, forming a foamed core, a surface layer containing a cured resin. An object of the present invention is to provide a method capable of simultaneously forming a portion in a single step, and efficiently producing a lightweight and rigid composite molded article having an arbitrary shape.

[Means for Solving the Problems] An object of the present invention is to provide a lightweight composite molded product in which the surface layer is formed of a tough reinforcing material and the core is formed of a foamed core, and the density of the foamed core is reduced. (A) Reinforcing material (excluding those that have the function of separating resin and particles) that constitutes the surface layer of the molded product is installed on the cavity surface of the mold when manufacturing products with 0.8 g / cm ³ or less. (B) having foamable resin particles and a liquid molding resin present in a portion to be a foamed core after molding; (c) heating a predetermined region of a mold to a sufficiently high temperature and / or the liquid Due to the temperature rise due to the heat of reaction of the molding resin, the expandable resin particles are heated and foamed to cause volume expansion, and the foaming core is formed by using the expansion force due to the foaming, and the reinforcing material is pressed against the internal constraint surface of the mold. Pressing (d) liquid in that state It is cured form the resin and is accomplished by a method according to the invention, characterized in, taking out from the mold a composite molded article obtained (e).

According to the method of the present invention, a mold for molding is first prepared. This mold is appropriately selected and used from a mold, a wooden mold, a resin mold and the like according to the molding temperature. A reinforcement is placed inside the mold, i.e., along the inner surface of the cavity of the mold. Reinforcing materials include airtight sheets such as paper and film, and generally FR
A fibrous sheet (for example, a woven or knitted fabric, a nonwoven fabric, or the like) made of an organic fiber, an inorganic fiber, a metal fiber, or the like, which is a reinforcing material used in P, has a function of separating resin and particles (Japanese Patent Application Laid-Open No. 7-1261).
No. 3) is used.
These reinforcing materials may be colored, patterned or printed in advance. Further, two or more sheets may be laminated and used. The reinforcing material may be preformed in advance or may be resin-treated in the form of a prepreg. In this case, a preform that has appropriate flexibility and can be spread over the inner wall of the mold by the expansion force of the expandable resin particles is convenient.

In the method of the present invention, at least the portion where the foam core is to be formed in the cavity of the mold in which the reinforcing material is installed along the inner surface as described above, the foamable resin particles and the curable liquid molding resin and, if necessary, A third component as described below is added. In this case, it is preferable to inject both the third component and the third component in advance as a mixture. The injection is usually performed at room temperature. In the injection, when the mixture is fluid, the inside of the mold may be kept at atmospheric pressure.However, when the mixture is poured under reduced pressure vacuum, the mixture can be spread all over the mold and become uniform. .

However, when the amount of the expandable resin particles or the third component increases, the mixture often becomes a paste or a block having low fluidity, and in such a case, these can be injected or packed with the mold opened.

Alternatively, the reinforcing material may be prepared in a bag shape in advance so as to fit the mold, and a mixture of the expandable resin particles and the liquid molding resin may be put in the bag and then placed in the mold.

The expandable resin particles used here are those whose volume increases at least twice, preferably 3 to 6 times, and more preferably 6 times or more by heating, and are insoluble in the liquid curable resin used. . In addition, in order to prevent the liquid resin from entering the foaming space portion, one in which foaming becomes closed cells is preferably used.

Examples of such foamable resin particles include curable foams such as polyurethane, phenol, polyurea, melamine, and polyimide, and precursors thereof, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polystyrene, polyethylene, polypropylene, PPO, polyamide, and the like.
Examples include those made of thermoplastic resins such as polycarbonate, PBT, and polyimide. For foaming of the expandable resin particles, any method such as a foaming agent decomposition method, a solvent diffusion method, a chemical reaction method, and a gas mixing method can be applied. Among these, a foaming agent decomposition method and a solvent air diffusion method are preferably used.

In the present invention, the shape of the expandable resin particles is preferably because the homogeneity of the molded product can be increased by mixing with the liquid molding resin as the size is appropriately fine, and the homogeneity of the molded product is improved.
The particle size according to the purpose is selected in consideration of the relationship with the cost. Hollow heat-expandable resin particles such as expandable beads or microcapsules are originally fine particles that are not expanded, and closed cells are used because expansion occurs due to expansion inside the hollow space of beads or capsules. Therefore, it is preferably used in the present invention.

On the other hand, as the liquid molding resin, generally well-known curable liquid molding resins such as epoxy resin, unsaturated polyester resin, vinyl ester resin, dicyclopentadiene resin, and urethane resin are preferably used. The resin may be used in the state of a raw material before reaction curing.

The compounding ratio of the expandable resin particles and the liquid molding resin varies depending on the density and toughness of the obtained molded product, ease of molding, and the like, but generally ranges from 5/95 to 60/40 by weight. preferable. In addition to the above components, non-expandable inorganic hollow particles such as silica balloons and shirasu balloons, non-thermally expandable elastic particles, pigments, and the like may be mixed into the mixture as the third component. In order to increase the strength of the molded product, carbon fibers, aramid fibers, fibers of silicon carbide, potassium titanate, boron and the like, whiskers, and the like can be added. Further, a flame retardant, a stabilizer and the like can be added as needed.

The amount of the mixture injected or packed into the mold is determined in consideration of the mixing ratio of the expandable resin particles and the volume expansion rate during heating.
It should be selected appropriately.

Next, the mold is heated from the outside or the temperature is raised by curing heat of the liquid molding resin or both, and the expandable resin particles in the cavity are expanded in volume by foaming or the like.

At this time, by causing the volume expansion of the expandable resin particles while the liquid molding resin maintains the fluidity, the reinforcing material is pressed against the internal constraint surface of the mold by the expansion pressure of the expandable resin particles, and the molded product is formed. To the desired skin. Curing is usually performed by heating a predetermined portion of the mold to a temperature equal to or higher than the curing temperature of the liquid molding resin, and may be post-cured depending on the type of the liquid molding resin.

In this case, if a fiber sheet impregnated with a curable liquid resin is used as the reinforcing material, the above resin is impregnated into the reinforcing material due to the expansion pressure of the expandable resin particles and hardened, and the surface layer of the molded product is
Become FRP.

Thus, a sandwich in which the surface layer (skin) is made of a tough reinforcing material (FRP when the reinforcing material is a fiber sheet) and the core is made of a foam core with a density of 0.8 g / cm ³ or less A lightweight composite molded article is obtained.

[Effect of the Invention] In the method for producing a composite molded article of the present invention as described above, in producing the molded article in the form of a foam with a skin in the-step, the foamable resin particles and the liquid molding resin are combined as a foam core. By using (1) a foamable liquid molding resin such as a foamable urethane resin, the strength required for pressing the reinforcing material against the inner wall of the mold by utilizing the properties of the foamable resin particles is improved. A low-density foamed core can be formed by pressure; (2) a foamed core in which expanded foamable resin particles are solidified with a thermosetting resin whose periphery is cured, as compared with a case where foamable resin particles are used alone. Therefore, a stable foamed core can be obtained even if it is exposed to a temperature near the molding temperature again, etc., and it is a tough lightweight composite sandwich / foam core composite molded product that was difficult to manufacture by the conventional method. The efficiency And can be produced economically.

Such composite molded articles can be widely used in various fields such as various lightweight structural materials, sporting goods, vehicle and aircraft members, mechanical parts, electric parts, civil engineering materials and the like.

EXAMPLES Hereinafter, the method of the present invention will be described in detail with reference to the drawings by way of examples, but the present invention is not limited to the examples.

Example 1 As shown in FIG. 1, a polypropylene-based synthetic paper 3 is placed in a cavity 1 of a mold. At this time, the synthetic paper 3 does not necessarily have to be in close contact with the inner surface of the cavity. on the other hand,
A preform 5 shaped along the core of a mold made of chopped glass is placed on the mold core 2. Next, on the polypropylene synthetic paper 3, expandable particles of polystyrene ("Eslen beads" HE type manufactured by Sekisui Plastics Co., Ltd.) and an epoxy resin ("Epicoat" manufactured by Yuka Shell Epoxy Co., Ltd.)
Composition 4 in which the "epomate" 100/31 mixture) was mixed in a weight ratio of 50/50 was injected and the mold was closed. By heating from the mold, the expandable particles of polystyrene expand and the epoxy resin reacts and cures. Remove the molding from the mold,
By removing burrs, a second layer comprising a skin 11 made of synthetic paper, a core 12 made of foam, and a glass fiber reinforced resin layer 13
A product having the cross section shown in the figure is obtained.

Example 2 Using the same mold as in Example 1, a 3D knitted glass fiber knitted according to the shape of the skin of a molded product in which a sheet of polyvinyl chloride was adhered to the skin with an adhesive was used. Install so that it faces the cavity mold. At this time, it is not always necessary to closely contact the cavity. After the mold is closed, expandable resin particles of polyacrylonitrile (“Matsumoto Microsphere” manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) on the knitted fabric
And inorganic hollow microspheres ("Silica Balloon" Q-CEL manufactured by Asahi Glass Co., Ltd.) and epoxy resin (mixture of "Epicoat" / "Epomate" 100/31 manufactured by Yuka Shell Epoxy) at a weight ratio of 15:15:70. Inject the mixture. Next, the foamable particles of polyacrylonitrile are expanded by heating from the mold, and the epoxy resin reacts and cures. The molded product is removed from the mold, and burrs are removed to obtain a product.

[Brief description of the drawings]

FIG. 1 shows one embodiment of the present invention, and is a simplified cross-sectional view showing a state where a raw material or the like is installed in a mold.
FIG. 2 is a simplified cross-sectional view of the lightweight composite molded article obtained in the embodiment of FIG. In the figure, 1 ... cavity type, 2 ... core type, 3 ... synthetic paper, 4 ... mixture of expandable resin particles and liquid molding resin, 5 ... preform made of glass fiber, 11 ... synthetic paper An epidermis consisting of ...
... Foam core, 13 ... Glass fiber reinforced resin layer

Claims (2)

(57) [Claims] 1. A lightweight composite molded article having a surface layer made of a tough reinforcing material and a core made of a foamed core, wherein the foamed core has a density of 0.8 g / cm ³ or less. In manufacturing, (a) installing a reinforcing material constituting a surface layer portion of a molded article on a cavity surface of a mold; (b) forming a foamed resin particle and a liquid molding resin in a portion to be a foamed core after molding; (C) heating a predetermined region of the mold to a sufficiently high temperature and / or increasing the temperature due to the heat of reaction of the liquid molding resin, thereby causing the expandable resin particles to expand by heating and causing volume expansion; Forming the foamed core and pressing the reinforcing material against the inner constraining surface of the mold by utilizing the expansion force due to foaming; Curing the liquid molding resin, And (e) removing the obtained composite molded product from the mold. 2. The method according to claim 1, wherein the expandable resin particles are hollow heat-expandable resin particles, and the liquid molding resin is a thermosetting resin composition that is liquid at room temperature. Manufacturing method.