JPH0740503Y2 - Intermediate material for composite moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a novel intermediate material used when molding a sandwich composite molded article mainly composed of a porous core.

[Prior Art] A composite molded article mainly composed of a porous core is used for various applications as a lightweight material as it is or in combination with other materials.

A molded product mainly composed of such a porous core is industrially a kind of resin molded product. Conventionally, this is industrially manufactured by a method of molding using a foamable resin, that is, foam molding. This method is roughly classified into a mold in which a resin or resin raw material that foams when heated or depressurized is put into a mold, or a specific one of these resins is foam-molded into particles (primary foam), and this is It can be divided into a method of molding in a mold and further expanding (secondary foaming). As a method of making this into a lightweight structure such as a sandwich composite material, the foamed molded product is bonded to a skin material, for example, a preformed fiber-reinforced resin molded product (hereinafter, abbreviated as FRP as necessary), or foamed. It is usual that the molded product is covered with a prepreg or the like for molding, or the expandable resin is injected into a preformed outer shell hollow body for foam molding.

In recent years, methods for improving these methods have been developed, such as internal pressure molding using foam expansion of resins and a method of using a heat-expandable molded product as a raw material of a porous body (for example, JP-A 1-25).
5530, JP-A-63-162207). As an example of further improving these methods, the present inventors previously developed a method for molding a sandwich core composite material using heat-expandable particles and a liquid curable resin (Japanese Patent Application No. 1-179830, etc.). ). Even in these methods, since the liquid curing resin is handled during molding, the work remains complicated. To improve this, a method using a specific intermediate material was proposed (Japanese Patent Application No. 2-95069).
issue).

[Problems to be Solved by the Invention] Although the above-mentioned intermediate materials are useful for the production of composite molded products, they have some problems in handling.

That is, the above-mentioned intermediate material is either a hard plate or a flexible molded product in the process of curing, but the former has poor handleability, and the latter is difficult to match with appropriate physical properties if starting from a liquid resin raw material. However, there is a problem that it is easy to change.

The present invention is intended to improve the above intermediate material to make it easier to use.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to improve the above problems, and have developed a new intermediate material. This intermediate material is generally plate-shaped, but is preferably soft in handling. That is, in many cases, it is preferable that the material is not rigid during handling because of damage during handling and fitability to the mold.

Thus, in the present invention, the heat-expandable particles are an intermediate material that is solidified with an epoxy resin that is solid at room temperature, and are placed at a position in the mold that will become the porous core of the target molded product and heated. The epoxy resin is melted or softened and at the same time the heat-expandable particles are expanded, and this force is used to spread the heat-expanded particles and the epoxy resin to the inside of the outer shell or to every corner of the mold at a predetermined location to form an internal pressure. In doing so, the intermediate material is intended to be a plastic material.

Therefore, in the present invention, phthalic anhydride, which is a plasticizer, is added to the intermediate material also as a raw material curing agent, so that curing of the epoxy resin and expansion of heat-expandable particles do not substantially occur in a sheet form (or It has a predetermined shape such as a plate shape. Phthalic anhydride is known as a curing agent for epoxy resins and is also known as a plasticizer.

FIG. 1 shows an example of a sheet-shaped intermediate material according to the present invention, in which the heat-expandable particles 2 are uniformly dispersed in the resin composition 1 including the matrix-forming epoxy resin and phthalic anhydride. There is.

In the molding method using the intermediate material of the present invention, it is not necessary to use a liquid resin or its raw material in addition to the solid intermediate material to be inserted into the mold or the outer shell, and the intermediate material is flexible and easy to handle. It is easy to put in. Therefore, when a core made from this intermediate material and, if necessary, a skin FRP are integrally formed at the same time to make a sandwich material, the productivity can be greatly improved. In some cases, it may be preferable to release and discharge from the mold a part of the resin or its raw material that has returned to a liquid state at the time of molding. By this means, a place where the resin does not reach at the time of molding, for example, a reinforcing material in a sandwich material. It is also useful for spreading the resin to a portion where the resin is poorly injected, such as a preform, reducing the amount of resin between the thermal expansion particles, and correcting the presence of the thermal expansion particles in the cavity. Therefore, the operation of releasing the pressure during molding can be added according to the purpose.

When making a sandwich composite material, the molded product obtained by using the intermediate material of the present invention is a seamless molded product in which the core of the porous part and the skin made of FRP are integrated. The thermal expansion particles may be present as a block in the molded product,
It is even more desirable that the particles are evenly dispersed as shown in FIG. It is also preferable to use heat-expandable particles as fine particles, and when used in combination with other non-expandable hollow particles, these and heat-expandable particles are sufficiently mixed and dispersed to obtain an intermediate material. It is preferable.

The heat-expandable particles used in the intermediate material of the present invention include particles containing a foaming agent, such as (a) vinylidene chloride, which is a so-called heat-expandable microsphere containing a foaming agent. b) Expandable expandable particles of polystyrene or the like which are generally used, and (c) expanded and molded particles such as primary expanded particles of polyethylene, polypropylene, polyurethane, rubber or the like. In the case of foam-expanded heat-expandable particles, particles obtained by pressing and fixing the molded particles are also included.

In the present invention, these may be mixed with non-expandable hollow particles. The combination of such hollow particles is inexpensive and convenient for obtaining a lightweight porous body. Glass balloons, shirasu balloons and the like can be mentioned as preferable hollow particles including economical efficiency. Such hollow particles may be smaller than the thermally expanded particles after expansion, and a part of the resin existing between the thermally expanded particles may be replaced with the hollow particles to further reduce the weight. For example, in the case where the thermally expanded particles are spherical, if the hollow particles are formed into spheres smaller than the gap when the particles are closely packed, the resin corresponding to the closely packed space can be replaced.

On the other hand, the epoxy resin is one that has fluidity by being softened or melted at a temperature at which the thermally expandable particles do not expand (foam), and it is preferable to start the polymerization, and the thermally expandable particles before the completion of the polymerization. Need to expand. Such a resin is determined according to the selection of the heat-expandable particles, but under the present circumstances, a resin that normally undergoes fluidization and initiation of polymerization at about 150 ° C. or lower is suitable.

The ratio between the epoxy resin and phthalic anhydride is determined from the composition ratio as a raw material and the required amount as a plasticizer. Although an epoxy resin is selected, it can be adjusted by using a resin other than phthalic anhydride, which does not show much plasticizing property.
Generally, the amount of phthalic anhydride in the intermediate material is 10
5 to 70 parts by weight per 0 parts by weight. If it deviates from this range, the plasticizing effect and the curing will be adversely affected. The ratio of the heat-expandable particles and the epoxy resin is determined from the characteristics of the core part as a syntactic foam, the required amount of foaming and the internal pressure of the mold at the time of foaming, etc. 5-40 parts by weight is suitable. If it is less than this range, the amount of foaming will be insufficient, and if it is more than this range, the resin will be insufficient when making a sandwich material.

The intermediate material of the present invention is formed into an arbitrary shape such as a sheet (or plate) by an appropriate method such as mixing these components and pressing. At this time, molding conditions are selected so that the entire curing of the resin and the substantial thermal expansion (foaming) of the particles do not occur. However, the resin may be gelled to some extent as long as it exhibits fluidity during subsequent molding.

The reinforcing fibers used when forming a fiber-reinforced sandwich composite using this intermediate material may be inorganic fibers or organic fibers. For example, inorganic fibers such as glass fiber, carbon fiber, boron fiber, silicon carbide fiber, alumina fiber, etc., organic synthetic fibers such as polyester, aramid, polyolefin, nylon, arylate, etc., natural fibers such as cotton, hemp etc., alone or in combination. Used. Textiles, knits, strands,
The yarn may be formed by filament winding, or may be used as a short fiber web or mat.

In the case of a sandwich composite material, it is usually preferable that the lightweight elastic particles do not penetrate into the reinforcing fiber layer, and it may be preferable to place a separation layer between the reinforcing fiber and the intermediate material. As the separation layer, the curable liquid molding resin that does not substantially pass through the particles after thermal expansion and has a separating function that allows the curable liquid molding resin to form at least a part or all of the part, and the rest is a material that does not pass the liquid molding resin. Use A fiber sheet and / or a porous sheet may be used as a material that constitutes the separation function of the separation layer. As the fiber sheet, various kinds of natural fibers, synthetic fibers, metal fibers, woven fabrics of inorganic fibers such as carbon or ceramics, knits, braids, non-woven fabrics,
Paper or the like is used. The porous sheet has open pores, and a foam sheet such as polyurethane, polystyrene, or polypropylene, or a porous membrane such as polypropylene or polysulfone formed by a drawing, extraction, or coagulation method is used. The openings are selected depending on the type of the particulate foaming resin used and its foaming property. As the separation layer, a sheet having a small opening such as glass fiber, carbon fiber or aramid fiber, which itself has a reinforcing function, can be used. These sheets may have their surfaces colored or patterned. Further, a material having elasticity can be selected as the separation layer so that it can be easily matched with the shape of the molded product.

As a material that does not pass the liquid molding resin,
In addition to joining with a material different from the material used in the part having the separating function, the fiber sheet and / or the porous sheet used in the part having the separating function are pre-sealed with resin etc. In the case where the fibrous sheet can be fused by heat treatment such as polypropylene fiber, there are those in which the openings are crushed by the fusion treatment and those in which a film or the like is attached.

A preform may be used as the reinforcing fiber. When the separating layer is substantially used together, the openings of the reinforcing fiber sheet and the preform can be freely selected, and for example, a unidirectional fiber array prepreg, a three-dimensional woven fabric or a knit preform can also be used.

Thus, as illustrated in FIG. 2, a sandwich consisting of a skin layer 3, 3 ′ made of fiber reinforced epoxy resin, a separation layer 4, 4 ′ and a core portion in which thermally expanded particles 6 expanded in a cured epoxy resin 5 are dispersed. The material is obtained.

[Effects of the Invention] The present invention provides an intermediate material for a composite molded product, which is easy to handle. Therefore, by using this intermediate material, a sandwich composite material or the like having good workability can be obtained.

[Examples] Next, examples of the present invention and comparative examples will be given, but the present invention is not limited thereto. Unless otherwise specified, "part" in each example is part by weight.

Example 1 The thermally expandable expandable beads “Matsumoto Microsphere F-80SD” manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. were obtained. The expandable beads start to expand at 140 ° C or higher and expand up to about 70 times.
(Hereinafter, this is abbreviated as F-80SD.) 100 parts of epoxy resin "Epicoat 1001" made of shell,
And 30 parts of curing agent "Epicoat 348" and 3 parts of phthalic anhydride
0 parts were mixed. This is designated as resin composition A.

20 parts of F-80SD and 100 parts of resin composition A were mixed at 80 ° C. This was poured into a mold preheated to 80 ° C. and immediately cooled. The mold was opened to obtain a thin plate with a thickness of about 3 mm.
The obtained thin plate is used as an intermediate material B. This intermediate material B is
It showed flexibility and was easy to handle.

Next, a mold was made by sandwiching a "Teflon" frame between two aluminum plates. Nozzles were provided at the upper and lower ends of this mold. On the other hand, a glass fiber cloth WF-181-100BV manufactured by Nitto Bosh Co., Ltd. with a small opening was prepared. Make two glass cloths full of molds and ten strip-shaped glass cloths that match the length with the mold and have a width that covers the nozzle, and use the larger glass cloth to make a glass cloth / intermediate Material B / glass cloth were placed in the mold in this order. Instead of the intermediate material B, a small glass cloth was piled up at the position where the nozzle was covered, that is, at the upper and lower ends inside the mold so that F-80SD particles would not enter this position. The inside of the mold was evacuated using both nozzles. The mold was then placed in a 145 ° C. silicon oil bath and heated. A small amount of resin and gas were overflowed to the position of the nozzle, and the nozzle was sequentially closed. These were almost simultaneous. After 2 hours, the mold was taken out of the warm bath, cooled, and the molded product was taken out from the mold. Thus, a good lightweight composite sandwich material was obtained in which the surface was glass fiber reinforced epoxy resin and the inner layer was epoxy resin in which foamed particles were dispersed. The obtained molded product had foamed particles evenly distributed except for the portion containing the small glass cloth, and had a density of 0.54 g / cm ³ .

Example 2 F-80SD and resin A were prepared in the same manner as in Example 1.

F-80SD and resin composition A were mixed and extruded using a 25 mmφ extruder. In the extruder, the lower part of the hopper was water-cooled, and thereafter, a non-heating zone, a zone of 50 ° C., a zone of 70 ° C., and a die temperature of 65 ° C. were set.

The obtained extruded mixture was formed into a sheet having a thickness of 3 mm to obtain an intermediate material C.

On the other hand, maximum width 120 mm, maximum length 350 mm, maximum thickness 14 mm,
Two male dies for making a rudder model were prepared. Nozzles were provided above and below the mold. 4 leaves of glass cloth and 2 leaves of carbon cloth were prepared according to this mold. The glass cloth is the glass fiber cloth WF-180-1 manufactured by Nitto Boseki of Example 1.
It is 00BV and the carbon cloth is a carbon fiber woven fabric C063 made by Toray.
04. Polyester non-woven fabric "Unicel BT-0404" manufactured by Unicell Co., Ltd. was put into a bag in accordance with the mold.

The above-mentioned intermediate material C having a thickness of 3 mm was cut into a small size in a shape substantially similar to that of a mold. This intermediate material is "Unicel BT
-0404 "bag, sandwiched with glass cloth and put in the mold.

The mold was evacuated and then placed in a warm bath of silicone oil at 145 ° C. After confirming that resin and gas were discharged to each nozzle, the nozzle was closed. After holding for 1 hour, the molded product was taken out from the warm bath and cooled. A good model with a specific gravity of 0.8 was obtained.

[Brief description of drawings]

FIG. 1 shows an example of an intermediate material according to the present invention. In the figure, 1 is a resin composition comprising an epoxy resin and phthalic anhydride, and 2 is expandable particles. FIG. 2 is a sectional view showing an example of a sandwich core composite molded product molded using the molded product of the present invention. In the figure
3, 3'is a skin layer made of fiber reinforced epoxy resin, 4, 4'is a separation layer, 5 is a hardened epoxy resin which constitutes the matrix of the core portion, and 6 is foamed particles.

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Claims (2)

[Scope of utility model registration request] 1. Phthalic anhydride and heat-expandable particles are added to an epoxy resin or a raw material thereof that is solid at room temperature but softens or liquefies when heated, and these particles are in an unexpanded state. An intermediate material for a composite molded article, characterized by being formed into a predetermined shape as it is. 2. A non-expandable lightweight hollow particle is included in addition to the epoxy resin, phthalic anhydride, and thermally expandable particles (1).
Intermediate material for the composite molded article described in.