JPH06143441A - Method for manufacturing composite molded article - Google Patents

Abstract

(57) [Summary] [Objective] An FRP composite molded article having a foam core in the core is manufactured in a short molding cycle. [Structure] A material for forming a surface layer such as a reinforcing fiber sheet and / or a separating layer such as a woven fabric or a non-woven fabric having a small opening is placed in a molding die, and a core portion inside thereof is exposed to a specific temperature. By supplying a mixture of preheated foamable resin and liquid molding resin, and closing the mold to perform heat molding, a lightweight and rigid useful FRP having at least a surface layer part made of resin and a core part made of a foam core. Obtain a composite molded article.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a composite molded article. More specifically, a composite molding that is composed of a surface layer portion made of a resin layer (FRP layer) containing a fibrous reinforcing material and a lightweight core portion (foam core) made of a resin containing bubbles and is integrated as a whole. The present invention relates to a method for efficiently manufacturing a product with good productivity.

[0002]

2. Description of the Related Art FRP composite molded products having a foamed core in the core are excellent in lightweight and toughness, and are therefore used in the field of sports equipment, structural materials for transportation equipment such as automobiles, trains, aircraft and ships, interior and exterior members, It has an extremely wide range of applications such as medical equipment and communication equipment.

In the manufacture of an FRP composite molded article having a foam core in the core, for example, a foam core to be the core is preformed, wrapped with a woven fabric as a reinforcing material, and then inserted into a mold again. A method for forming an outer shell by injecting a liquid molding resin system (JP-A-55-82612, JP-A-61-2).
No. 79517), or FRP of the outer shell is molded in advance, and a foaming urethane resin or the like is injected into the void at the center thereof to foam in the void.

However, each of the above-mentioned techniques has a drawback that the steps for obtaining the composite molded product are various and the operation is complicated, so that the production efficiency of the molded product is low and the cost is high. On the other hand, Japanese Patent Laid-Open No. 3-1
No. 83511, JP-A-3-180329, and JP-A-3-180329.
45315, JP-A-3-288629, JP-A-4-
No. 27532, etc. proposes a method of simultaneously molding a foam core and a surface layer portion made of a resin layer containing a fibrous reinforcing material by using a foaming resin and a liquid molding resin, which is an improvement of the above drawbacks. Is.

[0005]

However, even in this molding method, it is very important to further increase the production efficiency, and the present inventors have proposed a method of shortening the molding cycle in order to increase the production efficiency. As a result of earnest research, the present invention has been achieved.

[0006]

Means for Solving the Problems The present invention is intended to produce a composite molded article having at least a surface layer portion molded in a predetermined shape by a liquid molding resin system and a core portion composed of a foamed core. A material for forming a surface layer portion is placed in the mold of (b), and a mixture containing at least a foamable resin and a liquid molding resin system at a temperature of 50 ° C. or higher and a foamable resin is provided in a portion to be a foamed core after molding (b). Is preheated to a temperature below the temperature at which volume expansion occurs,
(C) After the mold is closed, a predetermined region of the mold is heated to a sufficiently high temperature and / or the temperature is raised by the reaction heat of the liquid molding resin system to heat and foam the foamable resin located in the core portion. Causing a volume expansion, thereby pressing the surface layer forming material against the internal constraining surface of the mold, (d) curing the liquid molding resin system, and (e) removing the resulting composite molded article from the mold. In particular, in the step (b), a mixture containing at least a foamable resin and a liquid molding resin system at a temperature of 50 ° C. or higher and foaming property is formed in a portion to be a foamed core after molding in the step (b). The greatest feature is that the resin is preheated and supplied to a temperature below the temperature at which volume expansion occurs.

In 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. At the time of molding, it is preferable to preheat a predetermined region of this mold for molding at a temperature not lower than room temperature and at a temperature not deformed when the obtained composite molded product is taken out of the mold.

In the mold, that is, along the inner wall surface of the cavity of the mold, one or a plurality of layers of reinforcing fiber material and / or separation layers constituting the surface layer portion are provided.

As the reinforcing fiber material, high-strength and high-modulus fibers such as woven fabric, knitted fabric, non-woven fabric or unidirectional fiber array sheet made of carbon fiber, glass fiber, silicon carbide fiber, aramid fiber and the like are preferably used. It

On the other hand, as the separation layer, at least a part or all of the part having a separating function which allows the liquid molding resin system to pass substantially without passing the foamable resin after thermal expansion, and the remaining part is the liquid molding resin. Use a material that does not pass through the system.

Examples of materials capable of exhibiting the separating function of the separating layer include a fiber sheet and / or a porous sheet having a small opening. As the fibrous sheet for the separation layer, woven fabric, knitted fabric, braid, non-woven fabric, paper or the like of various natural fibers, synthetic fibers, inorganic fibers or the like is used, and the porous sheet is a sheet or film having continuous ventilation holes. For example, a foam sheet such as polyurethane, polystyrene or polypropylene or a porous membrane such as polyethylene, polypropylene or polysulfone formed by a stretching, extraction or coagulation method is used. The openings are selected in a range that does not allow them to pass, depending on the type of the expandable resin and the expandability. As the separating layer, a sheet having a small opening such as glass fiber, carbon fiber or aramid fiber, which itself has a function as a reinforcing material, can be used. in this case,
The separation layer itself also serves as a reinforcing material for the surface layer. 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.

The separation layer may be made of a material partially impervious to the liquid molding resin system. For example, in addition to joining a part made of a material having a separating function and a material different from the material used in the part, a part of the fiber sheet and / or the porous sheet having a separating function is previously made of a resin. Sealed opening,
When the fibrous sheet can be fused by heat treatment such as polypropylene fiber, there are those in which a part of the openings are crushed by the fusion treatment and those in which a film or the like is partially stuck.

Instead of the above-mentioned separating layer or in addition to the separating layer, a reinforcing fiber sheet or preform having a poor separating function may be used together. In this case, the openings of the reinforcing fiber sheet or preform can be freely selected. For example, a unidirectional fiber array prepreg or a three-dimensional woven / knit preform can also be used. If a separation layer is not used, these are the surface layer part. It becomes a molding material.

It is also possible to subject the separating layer and / or the surface layer molding material (such as a reinforcing fiber sheet or preform) to resin treatment in the form of a prepreg in advance.

In the method of the present invention, as described above, for example, the foamed layer surrounded by the separation layer and / or the reinforcing fiber sheet in the mold in which the separation layer and / or the reinforcing fiber sheet is installed along the inner wall surface of the cavity. A foamable resin, a liquid molding resin system, and, if necessary, a third component described later are put in a portion where a core is to be formed.

Each of the above components may be previously mixed as a mixture when it is supplied to a predetermined place in the mold, or may be mixed immediately before the supply.

The expandable resin used in the method of the present invention is
Volume is at least doubled by heating, preferably 3-6
And more preferably 6 times or more,
It does not dissolve in the molding liquid resin used. Further, in order that the liquid resin does not enter the foaming space portion, a material in which foaming becomes closed cells is used.

Examples of the foamable resin include curable foams such as polyurethane, phenol, polyurea, melamine and polyimide, precursors thereof, polyvinyl chloride,
Examples thereof include thermoplastic resins such as polyvinylidene chloride, polyacrylonitrile, polystyrene, polyethylene, polypropylene, PPO, polyamide, polycarbonate, PBT, and polyimide.

For the foaming of the foamable resin, any of a foaming agent decomposition method, a solvent vaporization method, a chemical reaction method, a gas mixing method and the like can be applied. Of these, the foaming agent decomposition method and the solvent vaporization method are preferably used.

Particularly preferred as the foamable resin is
It is a heat-expandable resin particle containing a heat-expandable or foamable substance known by trade names such as "Microsphere", "Expancel", and "Eslen beads". Examples of such resin particles are described in detail in the above-mentioned JP-A-4-27532.

On the other hand, as the liquid molding resin system, generally known liquid molding resin systems such as epoxy resin, unsaturated polyester resin, vinyl ester resin, curable dicyclopentadiene resin, non-foaming urethane resin are preferably used. To be

In the present invention, a slurry-like or paste-like mixture is prepared from the expandable resin and the liquid molding resin system. In this mixture, in addition to the above-mentioned two components, a silica balloon or a silas balloon is further contained as a third component. You may mix non-expandable inorganic hollow particle like this. As these inorganic hollow particles, those which basically do not penetrate the separation layer are used.

Further, in order to increase the strength of the molded product, carbon fibers, aramid fibers, short fibers such as silicone carbide, potassium titanate and boron, whiskers and the like can be added, and pigments and the like are added as necessary. You can also do it. In any case, it is appropriate to mix the components so that the density of the foamed core after molding is 0.8 g / cm ³ or less.

Further, a crushed product of an FRP molded product can be added in consideration of recovery and reuse. In this case, even if the density of the foamed core portion is 0.8 g / cm ³ or more, it may be useful depending on the economic effect.

The amount of the above mixture to be supplied into the mold should be appropriately selected in consideration of the compounding ratio of the foamable resin and the volume expansion coefficient during heating. -275
No. 32, the details are described.

In the method of the present invention, in order to shorten the molding cycle, the above mixture is preheated and supplied at a temperature of 50 ° C. or higher and a temperature at which the foamable resin causes volume expansion or less. A higher preheating temperature is preferable in the molding cycle, but if the temperature is too high, the volumetric expansion of the expandable resin may start and overflow may occur when the mold is closed. It is inconvenient if it interferes with.

In order to stabilize the mixture in the preheated state, the reaction is initiated by mixing the liquid molding resin and the curing agent thereof in the liquid molding resin system, or the isocyanate and the polyol in the case of the urethane resin system. It is effective to keep things unmixed until just before feeding, and such a method is recommended.

The amount of the mixture at the time of supply is preferably 40 to 95% of the volume of the finished composite molded article on a volume basis. If it is 40% or less, the amount of heat carried into the mixture and the amount of heat generated by the reaction tend to be insufficient, and the heat transfer from a predetermined region of the mold is small, and the proportion of the gas layer portion that needs to be replaced by volume expansion is occupied. The voids tend to increase in the finished product. In more extreme cases, impregnation defects are seen on the side of the molded product that faces the lower mold. On the other hand, when it is 95% or more, there is little room for volume expansion of the expanded particles, and there are cases where the weight reduction of the core of the finished molded product is not sufficient.

The mixture supplied into the mold is heated to a sufficiently high temperature by the reaction of the liquid molding resin system starting to generate heat due to reaction heat and / or heat transfer from a predetermined region of the mold, whereby the liquid molding resin system is heated. The expansion of the foamable resin occurs while the fluidity is maintained. Thus, the expansion pressure of the expandable resin causes the separation layer and / or other surface forming material to be pressed against the internal constraining surface of the mold to form an outline along the constraining surface while the liquid molding resin system causes the separation layer and / or Alternatively, it penetrates into other skin layer forming materials, and a part thereof passes through the material to form the surface layer of the molded article. Excess resin is either collected in the mold reservoir or withdrawn from the vent.

Generally, when preparing a mixture of at least a foamable resin and a liquid molding resin system as described herein, a large amount of non-condensable gas such as air or nitrogen is likely to be contained.
These non-condensable gases penetrate the separating layer and / or other skin layer forming materials with the liquid molding resin system,
Some of them pass through the material to form the surface layer of the molded product, which causes voids and the like. In particular, when the molding cycle is shortened, this process is also accelerated, so that it is likely to be left behind and left as voids in the molded product or on the surface layer surface. Therefore, in order to prevent voids in the molded product and the surface layer, it is desirable that the mixture contain as little non-condensable gas as possible at the time of supply. Therefore, when preparing the mixture, it is preferable to prepare the mixture so that the non-condensable gas is contained as little as possible, or the once prepared mixture is defoamed to remove the non-condensable gas contained in the mixture. preferable.

Thus, the liquid molding resin system is cured simultaneously with the expansion of the foamable resin in the mold, and the composite molded product obtained at the sufficiently cured stage is taken out of the mold.

If the molded product in the mold is not properly cooled,
Since the obtained composite molded article may be deformed when it is taken out of the mold, it is necessary to lower a predetermined region of the mold to a temperature not higher than the heat deformation temperature of the liquid molding resin system in order to prevent this.

It is preferable that the operation of raising and lowering the temperature of a predetermined region of the mold during the molding cycle is minimized, and depending on the temperature condition for supplying the mixture of the foamable resin and the liquid molding resin system, the reaction heat of the liquid molding resin system may be used. Molding can be performed by keeping the temperature of a predetermined region constant only by heat generation.

As described above, according to the method of the present invention, molding is efficiently proceeded by strictly controlling the conditions for supplying at least the mixture of the foamable resin and the liquid molding resin system to the portion to be the foamed core after molding. As a means therefor, the basic feature is that the mixture to be supplied is preheated to a temperature of 50 ° C. or higher and lower than or equal to the temperature at which the expandable resin causes volume expansion. ) Among the liquid molding resin systems that make up the mixture to be supplied, in the case of a liquid molding resin and its curing agent or urethane resin system, do not mix the ones that start the reaction by mixing such as isocyanate and polyol until just before the supply. (A) The amount of the mixture at the time of supply is set to 40 to 95% of the volume of the composite molded article completed on a volume basis,
(C) At least one of non-condensable gas may not be contained in the mixture at the time of supply.

As a result, according to the method of the present invention, it is possible to significantly shorten the molding cycle and improve the productivity.

[0036]

As described above, according to the method of the present invention, an FRP composite molded article having a dense cured resin layer containing a reinforcing material on the surface layer and a foamed resin layer on the core can be stably manufactured in a short time. It becomes possible to do. Moreover, the surface properties of the obtained FRP composite molded product are good, and this molded product is useful for various applications.

[0037]

EXAMPLES The present invention will now be described in detail with reference to examples, but these are for explaining the present invention and the present invention is not limited to these examples.

In the examples, "part" means "part by weight" unless otherwise specified.

[0039]

Examples 1 to 3 and Comparative Examples 1 and 2 As a reinforcing fiber material, a glass mat (M8609-300 manufactured by Asahi Fiber Glass Co., Ltd.) having a basis weight of about 300 g / m ² was obtained. Also, an epoxy resin was prepared as a liquid resin system.
"Epicote 828" manufactured by Yuka Shell Co., Ltd., isophorone diamine (curing agent), and "Epicure T".

As a separation layer, a non-woven fabric "UNICEL BT605W" manufactured by Unicell Co., Ltd. mainly containing polyester was obtained. Then, "Matsumoto Microsphere F-82D" manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. was obtained as a foaming resin. The resin fine particles expand and expand at 105 ° C. As a third component, Asahi Glass Co., Ltd. silica balloon Q-CE
100 parts of the above "Epicoat 828", 12 parts of isophoronediamine, 10 parts of "Epicure T", and the foaming resin 40
And 15 parts of silica balloon were mixed. This is mixture A
And On the other hand, 100 parts of "Epicoat 828", 12 parts of isophoronediamine, 10 parts of "Epicure T", 30 parts of a foaming resin, and 5 parts of silica balloon were mixed. This is mixture B.

On the other hand, as a mold for molding, a mold having a pair of upper and lower jackets having a jacket through which a heat medium can be passed so that heating and cooling can be performed, and the inner dimensions are 210 mm in width, 300 mm in length and 10 mm in thickness was prepared.

Then, the temperature of the inner wall surface of the cavity is set to 80.degree.
The reinforcing fiber material (glass mat) and the separation layer (nonwoven fabric) were laid in the mold which was kept, and the mixture A having the temperature and the amount shown in Table 1 was rapidly supplied thereon. With respect to the inert gas such as air mixed in the mixture A, only the one that was previously removed under reduced pressure in Example 3 was used.

Then, the separating layer and the reinforcing fiber material were immediately placed in the mold so as to cover the layer of the mixture, the mold was closed, and the mold was heated under the temperature conditions shown in Table 1 to perform molding.

Table 1 shows the molding conditions, the required molding time, and the surface properties of the molded products obtained in these experiments. In addition, the reason that the molding required time in Examples 1 and 2 is longer than that in Example 3 is that it took time to cool the mold because of heating.

[0045]

[Table 1]

Claims (6)

[Claims] 1. When producing a composite molded article having at least a surface layer part molded into a predetermined shape by a liquid molding resin system and a core part made of a foam core, (a) forming a surface layer part in a molding die. Installing materials for
(B) 50 parts of a mixture containing at least a foaming resin and a liquid molding resin system is added to a part which becomes a foamed core after molding.
Preheated to a temperature not lower than ℃ and not higher than the temperature at which the expandable resin causes volume expansion, (c) heating the predetermined region of the mold to a sufficiently high temperature after closing the mold, and / or the above liquid The temperature rise due to the reaction heat of the molding resin system causes the foamable resin located in the core portion to heat-foam and cause volume expansion, thereby pressing the surface layer forming material against the inner constrained surface of the mold, (d) ) A method for producing a composite molded article, which comprises curing a liquid molding resin system, and (e) removing the obtained composite molded article from a mold. 2. In producing a composite molded article having at least a surface layer portion molded in a predetermined shape by a liquid molding resin system and a core portion made of a foam core, (a) a predetermined region of a molding die is kept at room temperature. Preheating the composite molded article obtained above and below at a temperature at which it does not deform when taken out of the mold; (b) installing a material for forming the surface layer in the mold; and (c) forming the foamed core 5 parts of the mixture containing at least the foamable resin and the liquid molding resin system.
Preheating and supplying to a temperature not lower than 0 ° C. and not higher than the temperature at which the expandable resin causes volume expansion, (d) after closing the mold,
The temperature rise due to the reaction heat of the liquid molding resin system without actively increasing the temperature of the predetermined region of the mold causes the foamable resin located in the core portion to be heat-foamed to cause volume expansion. A composite characterized in that the surface layer forming material is pressed against the internal constrained surface of the mold, (e) the liquid molding resin system is cured, and (f) the obtained composite molded article is taken out of the mold. Molded article manufacturing method. 3. Immediately before the supply of the liquid molding resin constituting the liquid molding resin system and the curing agent thereof in the mixture containing at least the foamable resin and the liquid molding resin system, which is supplied to the portion to be the foamed core after molding. Mixing to
The manufacturing method in any one of -2. 4. A mixture containing at least a foamable resin and a liquid molding resin system, which is supplied to a portion to be a foamed core after molding, in a state where the mixture does not contain a non-condensable gas such as air or nitrogen. The manufacturing method according to claim 1. 5. A non-condensable gas such as air or nitrogen is prevented from being mixed in or removed from the mixture containing at least the foamable resin and the liquid molding resin system supplied to the portion to be the foamed core after molding by decompression vacuum. Item 4. The manufacturing method according to any one of Items 1 to 3. 6. A mixture containing at least a foamable resin and a liquid molding resin system to be supplied to a portion which will be a foamed core after molding, and the amount at the time of supply is 40 to 95% of the volume of the completed composite molded article on a volume basis. The manufacturing method according to any one of claims 1 to 5.