JPH06218830A - Manufacture of composite molded piece - Google Patents

Abstract

PURPOSE:To shorten a molding cycle and obtain excellent quality by a method wherein a surface layer molding material is arranged in a mold, a mixture of foaming resin and liquid molding resin system is supplied to a part of foaming core by mixing them immediately before the supply of it, the foaming resin is foamed by heating after the mold is closed and the surface layer molding material is pushed to the inner wall of the mold so as to cure. CONSTITUTION:A surface layer molding material is arranged in a forming mold and a mixture of foaming resin and liquid molding resin system is supplied to a part which is to be a foaming core. At this time, the component which reacts due to the mixing is mixed immediately before the mixture is supplied to the mold. That is, the one is led to a dynamic mixing part 5 equipped with a spindle 1 from a supplying opening 3 of the device and the other is led from a supplying opening 4, which are led to a microwave irradiation part 2 by an exhaust-pipe 6 and heated by microwave coming from a microwave generator 7. The temperature is set to be above room temperature and below the temperature where cubic expansion occurs in the foaming resin particle. After the mold is closed, the foaming resin in the core is foamed by heating, the surface layer molding material is pushed to the inner wall of the mold so as to cure.

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, an integrated, lightweight and tough body including (i) a surface layer portion made of a resin layer containing a fibrous reinforcing material, and (ii) a lightweight core portion (core portion) containing a foamed resin. The present invention relates to a method for efficiently producing various composite molded articles.

[0002]

2. Description of the Related Art FRP (fiber reinforced resin) composite molded products having a foam core in the core are excellent in lightness and toughness, and are therefore structural materials for transportation equipment such as sports equipment, automobiles, trains, aircraft and ships. It has an extremely wide range of uses such as interior and exterior members, medical equipment, and structural materials and housings for communication equipment.

As a method for producing an FRP composite molded article having a foam core in the core, for example, a foam core is preformed in the core, wrapped with a woven cloth 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-61-61)
No. 279517), or FRP of the outer shell is preformed, and a foaming urethane resin or the like is injected into the void at the center of the FRP 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, JP-A-3-
183511, JP-A-3-180329, JP-A-3
-45315, JP-A-3-288629, JP-A-4
-The 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 foamable resin and a liquid molding resin system proposed in No. 27532 and the like is an improvement of the above-mentioned drawbacks. Is.

[0005]

However, even in this molding method, it is very important to further improve the production efficiency. Therefore, an object of the present invention is to provide a method for shortening a molding cycle in order to increase production efficiency in a method for producing the above-mentioned composite molded article using a foamable resin and a liquid molding resin system. It is in.

[0006]

DISCLOSURE OF THE INVENTION The present invention is directed to the production of a composite molded article having at least a surface layer portion made of a fiber reinforced resin layer molded into a predetermined shape by a liquid molding resin system and a core portion made of a foam core. , (A) placing a material for molding a surface layer in a molding die, and (b) a mixture containing at least a foaming resin and a liquid molding resin system in a portion which becomes a foamed core after molding in the mold. Supply
And, at that time, at least the components which react by mixing such as the liquid molding resin and the curing agent thereof are mixed immediately before being supplied to the mold, and the mixture is kept at room temperature or higher and at a temperature below which the expandable resin particles cause volume expansion. After heating by microwave to the mold, (c) after closing the mold, heating a predetermined region of the mold to a sufficiently high temperature and / or increasing the temperature by the reaction heat of the liquid molding resin system. Due to
The foamable resin located in the core part is heated and foamed to cause volume expansion, thereby pressing the material for forming the surface layer part against the inner wall surface of the mold, and (d) curing the liquid molding resin system in that state. And (e) removing the obtained composite molded article from the mold. In particular, in the above step (b), the foamed core is formed on the portion to be the foamed core after molding in the mold. When a mixture containing a polymerizable resin and a liquid molding resin system is supplied, at least components of the liquid molding resin system that react by mixing, such as the liquid molding resin and its curing agent, are mixed immediately before being supplied to the mold. The most feature is that the mixture is rapidly heated to a temperature below the temperature at which the foamable resin causes volume expansion at room temperature or higher by using microwaves and supplied to the mold.

In the method of the present invention, first, a molding die is 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. In the mold, that is, along the inner wall surface of the cavity of the mold, one or more layers of the reinforcing fiber material and / or the separation layer forming the surface layer portion are provided.

Here, as the separating layer, at least a part or all of the separating layer, which has a separating function to allow the liquid molding resin system to pass substantially without passing the expandable resin after thermal expansion, and the rest is the liquid molding resin. Use a material that does not pass through the system.

As a material capable of exhibiting the separating function of the separating layer, for example, a fiber sheet and / or a porous sheet having a small opening can be mentioned. 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 of polyurethane, polystyrene, polypropylene or the like, or a porous membrane of polyethylene, polypropylene, polysulfone or the like produced 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 separation 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 portion. 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 the separation layer, a layer partially made of a material that does not pass through the liquid molding resin system may be used. 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. If the openings are sealed, if the fibrous sheet can be fused by heat treatment such as polypropylene fiber, then some of the openings are crushed by the fusion treatment, or some of which the film or the like is attached. is there.

Instead of the above-mentioned separation layer or in addition to the separation layer, a reinforcing fiber sheet or preform having a poor separation function and having a large opening may be used together. in this case,
The openings of the reinforcing fiber sheet or preform can be freely selected, for example, unidirectional fiber array prepreg or three-dimensional fabric /
Knit preforms can also be used, and when the separation layer is not used, these become the surface layer molding material. When the separating layer and the reinforcing fiber sheet or preform having a large opening are overlapped and used, it is preferable to arrange the separating layer so as to be located on the core side.

The separating layer and / or the reinforcing fibrous sheet or preform as described above may be treated with a resin in the form of a prepreg in advance.

In the method of the present invention, as described above, for example, a surface layer forming material such as a separation layer is placed along the inner wall surface of the cavity of the mold, and then the portion in the mold where the foam core is to be formed (usually) Is a part surrounded by the surface layer forming material),
A foamable resin, a liquid molding resin system, and optionally a third component described below are added. Each of the above components may be previously mixed as a mixture at the time of supply or may be mixed immediately before the supply. At least the resin and the curing agent constituting the liquid molding resin system are mixed immediately before the supply.

The foamable resin used in the method of the present invention has a volume of at least twice when heated, preferably 3 to.
6 times, more preferably 6 times or more,
It does not dissolve in the molding liquid resin system used. Further, as the resin, one in which the foam is closed cells is used so that the liquid resin does not enter the foam space.

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

For the foaming of the foamable resin, any method such as a foaming agent decomposition method, a solvent vaporization method, a chemical reaction method and a gas mixing method 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 having a particle diameter of about 10 μm to 1 mm, which contains a heat-expandable or foamable substance known by trade names such as “Microsphere”, “Expancel”, and “Ethren 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 well 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. However, they often consist of a combination of a liquid molding resin and a curing agent.

In addition to the above two components, non-expandable inorganic hollow particles such as silica balloons and shirasu balloons may be mixed in the mixture of the foamable resin and the liquid molding resin system. As these inorganic hollow particles, those which do not basically pass through the separation layer are used, and those having an average particle size of about 1 μm to about 1 mm are preferable.

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 if necessary, pigments and the like can be added. It can also be added. In any case, it is appropriate to mix the components so that the density of the foamed core portion after molding is 0.8 g / cm ³ or less.

Further, a crushed product of the FRP molded product can be added in consideration of recovery and reuse. In this case, even if the density of the foamed core 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, and the above-mentioned JP-A-4-27532. Are described in detail in.

In the method of the present invention, the above mixture is preheated to a temperature not lower than room temperature and not higher than the temperature at which the expandable resin causes volume expansion, and is supplied into the mold. 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.

At this time, as described above, among the liquid molding resin systems, the liquid molding resin and its curing agent, or in the case of the urethane resin system, the one that starts the reaction by mixing like isocyanate and polyol, It is effective not to mix until just before supply.

Therefore, in the method of the present invention, at least components constituting the liquid molding resin system that start the reaction upon mixing (for example, the liquid molding resin and its curing agent).
Is mixed immediately before being supplied to the mold, and immediately after mixing, is rapidly heated by using a microwave to preheat the mixture to a predetermined temperature and then is supplied to the mold. For example, a method in which a slurry-like mixture of fine-particle foaming resin and liquid molding resin is prepared, a curing agent is added to this mixture immediately before being supplied to a mold, and then the mixture is rapidly heated to a predetermined temperature by using a microwave. Is adopted.

FIG. 1 shows an example of an apparatus for mixing a foaming resin and a liquid molding resin system and heating the mixture. In the liquid molding resin system, at least the resin and the curing agent are separated into two liquids. After being prepared, one is introduced from a supply port 3 of the apparatus and the other is introduced from another supply port 4 into a dynamic mixing section 5 equipped with a spindle 1, respectively, and after being uniformly mixed therein, they are arranged side by side in the downstream section. It is guided to the microwave irradiation unit 2 by the discharge pipe 6 and is heated directly to a predetermined temperature by the microwave from the microwave oscillation unit 7.

It is desirable that the amount of the mixture at the time of supply is 40% or more and 95% or less of the volume of the completed composite molded article on a volume basis. If it is less than 40%, the amount of heat brought 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. Is large, and voids tend to increase in the finished molded product. In a more extreme case, defective resin impregnation is observed on the side of the molded product facing the lower mold. If it exceeds 95%, there is little room for volume expansion of the expandable resin particles, and there are cases where the weight reduction of the core of the finished molded product is not sufficient.

Generally, when preparing a mixture of at least a foamable resin and a liquid molding resin system as described above, a large amount of non-condensable gas such as air or nitrogen is likely to be contained. These non-condensable gases permeate the separation molding layer and / or other surface layer forming materials together with the liquid molding resin system, and a part of them penetrates through the material to form the surface layer of the molded article, so that it is particularly preferable for molding. When the cycle is shortened, this process is also accelerated, so that the gas is left behind and tends to remain as a void in the molded product or the surface layer portion. Voids in molded parts and surface layers To prevent this, make sure that the mixture contains as little non-condensable gas as possible when preparing the mixture, or temporarily put the mixture under reduced pressure before feeding it to the mold. It is desirable to supply air to the mold after degassing by, for example.

The mixture supplied to the portion of the mold where the core is to be formed is heated to a sufficiently high temperature due to the reaction of the liquid molding resin system, heat generated by the reaction, or heat transfer from a predetermined region of the mold. The heating causes expansion of the foamable resin while the liquid molding resin system maintains fluidity.

The expansion pressure of the expandable resin causes the separation layer and / or other surface forming material to be pressed against the inner wall surface of the mold to form an outer contour along the inner wall surface, while the liquid molding resin system forms the separation layer and It penetrates into the other surface layer forming material, and a part of it penetrates 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.

Thus, the curing of the liquid molding resin system progresses in parallel at the same time, and at the stage of sufficient curing, the mold is opened,
The composite molded article containing the obtained foam core is taken out of the mold.

If the molded product is not properly cooled, it may be deformed when the resulting composite molded product is taken out of the mold. In order to prevent this, a predetermined region of the mold is kept below the heat deformation temperature of the liquid molding resin system. It is necessary to lower it to and remove it from the mold.

It is preferable to minimize the operation of raising and lowering the temperature of the predetermined region of the mold during the molding cycle.
In the method of the present invention, the temperature of a predetermined region of the mold is kept constant only by the heat generated by the reaction heat of the liquid molding resin system by selecting the temperature condition for microwave heating the mixture of the foaming resin and the liquid molding resin system. be able to.

As described above, the method of the present invention is efficiently controlled by strictly controlling the conditions for supplying the mixture containing at least the foamable resin and the liquid molding resin system to the portion to be the foamed core after molding. (A) As a means of promoting molding, among liquid molding resin systems that make up the mixture to be fed into the mold, liquid molding resins and their curing agents, or in the case of urethane resin systems, react by mixing like isocyanate and polyol What is started is left unmixed until just before feeding, and mixed at the stage immediately before feeding to the mold. (B) Using a microwave just before feeding the mixture to the mold at room temperature or above The main feature is that the material is rapidly heated to the following temperature at which volume expansion occurs and is supplied to the mold. By these, not only the time required for molding can be greatly shortened, but also a good quality composite molded product can be efficiently produced.

[0035]

As described above, according to the method of the present invention, the molding cycle can be greatly shortened, and a composite molded article of good quality can be obtained, which is industrially very useful.

Since the composite molded article obtained by the method of the present invention is lightweight and tough, for example, canoe paddles, masts, rudders, windsurfing fins (skegs), human hydrofoil, skis (boards, poles), hockey sticks. , Baseball bats, non-spoke wheels, bicycle frames, skateboards and other sporting goods fields, automobile (passenger cars, buses, trucks) and other outer skin materials, spoilers, drive shafts, interior and exterior products, railroad vehicle doors Fields such as automobiles and structural members, end plates of heat exchangers, air conditioners,
Industrial fields such as compressor blades, stirring blades, electrical insulation support beams, fittings, wheelchairs (hydrim, side panels), X-ray projection tables, medical equipment fields such as artificial hands and artificial legs, and propellers, seats, furniture, controls It is effective in a wide range of fields such as surfaces, secondary structural materials, and reflectors for satellite broadcasting antennas.

[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 addition, "part" in an example represents a weight part unless there is particular notice.

[0038]

Example 1 An epoxy resin was prepared as a liquid molding resin system. That is, “Epicoat 828” and isophoronediamine (curing agent “Epicure T”) manufactured by Yuka Shell Co., Ltd.

A glass mat (8609-300 manufactured by Asahi Fiber Class Co., Ltd.) was obtained as a reinforcing fiber material. The basis weight is about 300 g / m ² . In addition, a non-woven fabric "UNICEL BT605W" mainly made of polyester manufactured by Unicell was obtained as a separation layer.

As the expandable resin, "Matsumoto Microsphere F-82D" manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. was obtained. These are resin particles that expand and expand at 105 ° C. Furthermore, "Silica Balloon Q-CEL" manufactured by Asahi Glass Co., Ltd. was obtained as a third component.

Then, 100 parts of "Epicote 828",
24 parts of isophorone diamine, 40 parts of expandable resin and 15 parts of silica balloon were mixed and heated as described below to prepare a slurry mixture A.

That is, first, "Epicoat 828",
The foaming resin and silica balloon were mixed in advance after quantitative determination. This mixed liquid is referred to as a slurry liquid B. On the other hand, the isophoronediamine is separately set, and this is liquid C. These liquids B and C are supplied to the mixing and heating device shown in FIG. 1, and the liquids B and C measured by the gear pump are supplied to the dynamic mixing section 5 from the supply ports 3 and 4, respectively. Both liquids are mixed by the spindle 1 in the dynamic mixing section 5, and the mixture A is discharged to the discharge pipe 6. The discharge pipe 6 is guided to the inside of the microwave irradiation unit 2, and the mixture A
Was heated directly in the tube by microwave while flowing to obtain a mixture A having a predetermined temperature.

On the other hand, a pair of upper and lower inner dimensions having a jacket through which a heat medium can pass for heating and cooling has a width of 210 m.
A mold having m, a length of 300 mm and a thickness of 10 mm was prepared.

The above-mentioned reinforcing fiber material and the separation layer were laid in a mold in which the temperature of the inner wall surface of the cavity was kept at 80 ° C., and the mixture A having the temperature shown in Table 1 and mixed and heated as described above was immediately added thereto. Supplied.

Then, the separating layer and the reinforcing fiber material were immediately placed on the mold in this order, and the mold was closed.

When the mold is closed and the condition is maintained for 2 minutes, the temperature of the center of the mold jacket and the mold is 100.
Since the temperature reached to 0 ° C, it was immediately cooled by passing through a heating medium for cooling at 30 ° C. After cooling, the molded product was taken out when the center temperature in the mold reached 60 ° C.

[0047]

Example 2 An experiment was conducted in exactly the same manner as in Example 1 except that the mold was positively heated under the following conditions during molding. That is, in this example, as soon as the mold is closed, a heating medium of 150 ° C. is passed through the mold jacket to heat the mold, and the temperature of the central portion in the mold reaches 100 ° C. I switched to the heat medium for. After cooling, the molded product was taken out when the temperature of the central portion in the mold reached 60 ° C.

[0048]

Comparative Example 1 For comparison, in Example 1, the mixture A was used.
A molded article was produced in exactly the same manner as in Example 2 except that the mixture A was fed into the mold at room temperature (25 ° C.) without heating.

The molding conditions and the required molding time in each of these experiments are shown in Table 1.

[0050]

[Table 1]

[Brief description of drawings]

FIG. 1 is a simplified sectional view showing an example of a mixing and heating apparatus used in the method of the present invention.

[Explanation of symbols]

 1 Spindle 2 Microwave Irradiation Device 3 Supply Port 4 Supply Port 5 Dynamic Mixing Section 6 Discharge Path 7 Microwave Transmission Section

Claims (1)

[Claims] 1. A mold for molding (a) for producing a composite molded article having at least a surface layer portion made of a fiber reinforced resin layer molded into a predetermined shape by a liquid molding resin system and a core portion made of a foamed core. And (b) supplying a mixture containing at least a foamable resin and a liquid molding resin system to a portion which becomes a foam core after molding in the mold, and at that time, , At least the components that react by mixing are mixed just before feeding to the mold,
The mixture is heated to a temperature not lower than room temperature and at a temperature not higher than that at which the expandable resin particles cause volume expansion by microwave, and then supplied into a mold, (c) after closing the mold, a predetermined region of the mold is sufficiently high. By heating to a temperature and / or temperature rise due to the reaction heat of the liquid molding resin system, the expandable resin located in the core part is heated and foamed to cause volume expansion, whereby the material for forming the surface layer part is molded. Manufacturing of a composite molded article, characterized by pressing against the inner wall surface of (5), (d) curing the liquid molding resin system in that state, and (e) removing the obtained composite molded article from the mold. Method.