JPH03180329A - Manufacture of lightweight composite formed product - Google Patents

Abstract

PURPOSE:To obtain composite formed product, which has favorable surface and is useful for lightweight structural material such as honeycomb material, by a method wherein non-thermally expandable lightweight elastic body particles are used in combination with thermally expandable foamable resin particles. CONSTITUTION:Liquid curable resin and/or its stock are introduced in a forming mold. The introduction of the resin and its stock is stopped after their overflowing is confirmed. When foamable resin particles are expanded by being heated under the condition that a nozzle above the mold is opened, a separating layer is pushed against the inner surface of a mold and, at the same time, liquid resin and/or its stock are permeated in the separating layer and some part of it reaches the outside front layer part of formed product. And the liquid curable resin and/or its stock are hardened while being overflown through the nozzle. Elastic particles are once contracted by the pressure developed through the expansion of the foamable resin. When the contraction of the formed particles starts after the peak of expansion, the elastic particles expand so as to compensate the contraction of the foamed particles, resulting in acting so as to prevent resin starved part from developing in the formed product. After the hardening of the resin, the formed product is cooled and removed from the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a lightweight composite molded article mainly composed of a porous core and a surface layer made of a hardened molded resin.

[Prior Art] Porous molded products, which are a type of synthetic resin molded products, have conventionally been manufactured industrially by foam molding. As a way to make this into a lightweight II body, such as sand german wood,
Usually, a foamed product is covered with a 7-repreg or the like and then molded, or a foamable resin is injected into a previously molded hollow outer shell to perform foam molding.

In recent years, internal pressure molding using foam expansion has been devised (Japanese Unexamined Patent Publication No.
No. 3-162207, etc.], and the present inventors have also developed and proposed a new method for simultaneously molding a porous core and a fiber-reinforced resin surface using expandable resin particles and a curable liquid resin. Hei 1-179830>.

[Problem to be solved by the invention] A composite molded article whose core is porous and whose surface is molded into a predetermined shape using a fiber-reinforced resin composite material is integrally molded using a thermally expandable resin such as a foamable resin. These molding methods are efficient and superior.

However, the thermally expandable resin usually expands to a predetermined temperature for a predetermined time at that temperature, maintains the expansion pressure within the mold for some time, and then the expansion pressure decreases. For example, JP-A-1-255530 No. 8
Figures 9 and 10 on the page show an example of this, and other examples include, for example, foamable resin particles (FMC-00
3.004) catalog etc. Therefore, in these molding methods, thermally expandable resin, curable resin,
If the form of the molded product is not selected appropriately, the curable resin will not harden even after the expansion of the thermally expandable resin has finished, and the curable resin will harden only after the expansion of the thermally expandable resin has finished and it begins to shrink. Problems arise, such as a molded product containing a portion lacking in curable resin. This problem is particularly likely to occur as the thickness of the molded product increases.

[Means for Solving the Problems] As a result of intensive research to solve these problems, the present inventors have discovered that non-thermally expandable lightweight elastic particles are used in combination with thermally expandable foamable resin particles. After thinking about it, I arrived at the present invention.

That is, the present invention includes at least a surface layer portion molded into a predetermined shape using a cured molding resin, a porous core portion,
In producing a lightweight composite molded article having a separation layer interposed between a surface layer and a core, (a) heat-stretched foamable resin particles and non-thermally expandable resin particles are placed in a mold for molding; fb) installing a separation layer that is substantially impermeable to lightweight elastic particles but permeable to a curable liquid molding resin and/or its raw materials; (c) Injecting liquid curable resin into the mold as necessary; (d) Predetermined setting of the mold. By heating the region to a sufficiently high temperature and/or increasing the temperature due to the reaction heat of the resin raw material,
The foamable resin particles are heated and foamed to create volume tension.
thereby pressing the separation layer against the inner surface of the mold, allowing the curable liquid molding resin and/or its raw material to permeate the separation layer, and allowing at least a portion of it to pass through the separation layer to reach the surface layer; (e) curing the liquid molding resin and/or its raw material; and (f) removing the obtained composite molding from the mold.

In the present invention, when molding is performed while applying internal pressure to the molded product by utilizing the foaming expansion caused by heat of the foamable resin, this expansion compresses the coexisting lightweight elastic particles and expands the resin before it hardens. When the foamable resin particles begin to contract, the lightweight elastic particles are expanded due to a pressure change (pressure drop) within the system to compensate for the overall expansion force. For example, some of the porous pores in uncured Sanderutsch wood may be filled with an elastic material, compressed during initial molding, and then used when other pores begin to contract and the pressure in the mold decreases. It attempts to compensate by expanding.

Therefore, it is desirable that the thermally expandable body made of expandable resin particles and the particulate lightweight elastic body are evenly dispersed and mixed together. For example, it is a preferred embodiment that the thermally expandable body is a foamable balloon and the lightweight elastic body is foam-molded small particles.

The lightweight elastic particles used in the present invention are foam-molded particles, such as polyethylene, polypropylene, polyurethane, etc., which are lightweight particles containing air bubbles, which shrink when compressed and return to almost their original shape when the pressure is released. is a particle that does not expand further due to heat. Also,
Of course, the particles may also be elastic hollow balloons or the like.

The elastic particles preferably have a specific gravity of 0.5 or less.

Furthermore, an inelastic hollow body can also be mixed therein.

Such inelastic hollow bodies are inexpensive and convenient for obtaining lightweight porous bodies. Considering economic efficiency, glass balloons, glass balloons, etc. are preferable as such hollow bodies.

On the other hand, at least a part or all of the separation layer has a separation function that substantially does not allow the expandable resin particles to pass through after thermal expansion but allows the curable liquid molding resin to pass through, and the rest is made up of the above-mentioned liquid molding resin. Use a material that is impermeable to water.

A fiber sheet and/or a porous sheet may be used as a material constituting the separation function of such a separation layer. 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.As the porous sheet, membranes with continuous pores are used. Alternatively, it is in the form of a film, such as a foam sheet of polyurethane, polystyrene, or polypropylene, or a porous membrane of polypropylene or polysulfone made by stretching, extraction, or coagulation. The opening size is selected depending on the type of expandable resin particles used and their expandability. 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, a material having elasticity may be selected for the separation layer so that it can be easily adapted to the shape of the desired molded product.

Materials that do not pass through the liquid molded resin that may form part of the separation layer include parts that have a separation function, in addition to being joined with a material different from the material that makes up the part that has a separation function. The fiber sheet and/or porous sheet used in the above are sealed in advance with resin etc., or if the fiber sheet can be fused by heat treatment such as polypropylene fiber, the opening is sealed by fusion treatment. There are crushed ones and ones with a film pasted on them.

Further, a reinforcing fiber sheet or preform may be used in combination with the separation layer. In this case, 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.

It is also possible to pre-treat the separation layer and/or the reinforcing fiber sheet or preform in the form of a prepreg with a resin, as long as the separation layer does not lose its intended function in the present invention.

In addition, when manufacturing flat plates or planar molded products with front and back sides,
The separating layer can also be placed on only one side of the inner surface of the mold. In this case, a separation layer may not be provided on the other side, or a material such as a film that does not allow liquid molding resin to pass through may be provided instead of the separation layer, but this may be selected 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 glass fiber separation layer on the back side, it is possible to simplify the work of painting the front side and applying decals after molding.

The expandable resin particles used here have a volume that increases by at least 2 times, preferably 3 times, more preferably 6 times by heating.
The amount increases by more than twice as much, and it does not dissolve in the resin used for molding. Further, it is preferable that the foam be formed into closed cells so that the liquid resin does not enter the foaming space. Examples of materials for such expandable resin particles include curable foams such as polyurethane, phenol, polyurea, melamine, and polyimide, and precursors thereof, polyvinyl chloride,
Polyvinylidene chloride, polystyrene, polyethylene, P
Examples include thermoplastic resins such as PO, polyamide, polycarbonate, PBT, and polyimide. Foaming of such expandable resin particles can be carried out by a blowing agent decomposition method, a solvent volatilization method, a chemical reaction method,
Any method such as gas mixing method can be applied. Among these, the blowing agent decomposition method and the solvent volatilization method are preferably used.

In the method of the present invention, the foamable resin can also be used in the form of fine particles and mixed with the liquid curable resin. In this case, the finer the particles, the higher the quality of the molded product obtained, which is preferable. This also applies to the lightweight elastic particles used in combination. In this sense, the foamable resin particles are preferably hollow thermally expandable resin particles, that is, resin particles whose volume increases by at least twice, preferably three times or more when heated. For example, they can be foamed by heating to form microcapsules. Particularly preferred are polyvinylidene chloride particles containing low-boiling hydrocarbons.

On the other hand, thermoplastic resins can also be used as molding resins, but
Curable liquid resins are preferred, and generally well-known liquid molding resins such as epoxy resins, unsaturated polyester resins, dicyclopentadiene resins, and non-foaming urethane resins are preferably used.

The method of the present invention, which is characterized by the combined use of expandable (thermally expandable) resin particles and non-thermally expandable lightweight elastic particles, will be described in detail below, step by step.

According to the present invention, a mold for molding is first prepared.

The material for this mold is selected depending on the molding temperature, etc.

A sheet serving as the above-mentioned separation layer is installed along the inner surface of a mold which is appropriately selected from a so-called narrow-sense mold, a wooden mold, a resin mold, etc. In addition to the sheet, reinforcing fibers may be added separately, or the separation layer itself may be composed of reinforcing fibers. This separation layer can also serve as a release sheet. In some cases, a porous sheet such as a woven fabric may be added to serve as a resin outlet portion.

This mold has a nozzle for removing gas and liquid, and a device is provided between the nozzle and the mold body to allow the liquid resin and its raw materials to pass through without passing through the lightweight elastic particles and foamable resin particles.

This mold is filled with lightweight elastic particles, expandable resin particles, and, if necessary, a hollow balloon and curable resin, and the mold is closed, leaving a space. At this time, it is preferable to evacuate the inside of the mold. Next, a liquid curable resin and/or its raw material is introduced into the mold. Preferably, the introduction is stopped after confirming that the resin and its raw materials overflow. When heating is performed with the nozzle above the mold open to expand the foamable resin particles, the separation layer is pressed against the inner surface of the mold, and the liquid resin and/or its raw material permeates into the separation layer, causing a part of it to expand. reaches the outer surface layer of the molded product. Then, the liquid curable resin and/or its raw material is cured while overflowing from the nozzle. If necessary, close the nozzle to stop the overflow. The elastic particles temporarily shrink due to the pressure caused by the foaming of the foamable resin, but when the foaming reaches its peak and the foamed particles shrink, the elastic particles expand to compensate for the shrinkage, resulting in areas lacking resin in the molded product. It works to prevent. After the resin hardens, it is cooled and the molded product is removed from the mold. For example, a large amount of liquid curable resin may be included in the reinforcing fiber sheet, and injection may be omitted.

[Effects of the Invention] According to the method of the present invention, a composite molded product having a good surface and useful as a lightweight structural material such as a honeycomb material can be obtained.

That is, in molding by heating and expanding the foamable resin particles and applying internal pressure, even if the foamable resin particles and the curable resin that forms the matrix shrink, there is no shortage of cured resin on the surface of the molded product or in specific parts. The quality stability of the molding process and molded products is also good.

The original purpose of the present invention was to provide a countermeasure against shrinkage of expandable resin particles and the like before completion of molding. However, when the method of the present invention is actually implemented, the weight of the molded product is reduced more than when molding is performed by adding an inorganic hollow body such as a glass balloon. This is thought to be because the specific gravity of polypropylene foams and the like used as elastic particles is generally lower than that of inorganic hollow bodies. Furthermore, even if some repulsion force remains in the elastic particles of a molded product, once the resin in the core cell has completely cured, the elastic particles contained therein may not cause problems such as deformation of the molded product. confirmed.

[Actual Rejection Examples] Next, examples and comparative examples of the present invention will be explained.
The present invention is not limited thereby. Incidentally, unless otherwise specified, "parts" herein are parts by weight.

Example 1 31 parts of an epoxy resin "Epikote 807" manufactured by Shell Co., Ltd. and a curing agent "Evomate YLHOO7J" were mixed. This was referred to as a liquid curable resin A.

On the other hand, polypropylene has a dispersant and a foaming agent Kufreon 12.
) and water were added, heated and pressurized. This was discharged into a low pressure zone to obtain expanded particles. Although the particles contained a large number of bubbles inside, they did not substantially expand even when heated further, and were elastic particles that contracted when compressed and recovered when the pressure was released.

Matsumoto Yushi's foam balloon "Microsphere-J F-" was added as foamable resin particles in 100 parts of liquid curable resin A.
44 parts of 30D and 10 parts of the above elastic particles (polypropylene beads) were mixed.
shall be.

Using Unicell, a long-fiber nonwoven fabric made from polyethylene terephthalate fibers and polypropylene fibers, a slightly smaller bag was made to match the inner dimensions of the mold described below. Effervescent mixture in this bag! I packed IIJB.

Meanwhile, a mold was made with a Teflon frame sandwiched between two aluminum plates. This mold was provided with nozzles at the top and bottom ends. Mold - Make 6 pieces of goblet glass cloth and 8 strips of glass cloth whose length matches the mold and whose width is sized to cover the nozzle, and use the large glass cloth to mix the glass cloth/foam mixture B. The material was placed in a mold in the following order: bagging and glass cloth. On the other hand, I layered small pieces of glass cloth to cover the nozzle, that is, to fill in the top and bottom edges. A vacuum was created inside the mold using the upper nozzle. Next, liquid curable resin A was press-fitted from the lower nozzle, and it was confirmed that it overflowed from the upper nozzle. After leaving the mold for a while, the mold was placed in a hot water bath at 70° C. and heated to expand the foaming balloon, and after the internal pressure became positive, the nozzle was slightly opened. Internal pressure 6Kg/ail
The curable resin was removed and cured while maintaining the temperature.

After 1 hour, the molded product was taken out from the hot bath, cooled, and taken out from the mold. In this way, a lightweight and good sandwich-like structural material having a glass fiber-reinforced epoxy resin surface and an epoxy resin foam inner layer was obtained. The results of repeating this operation were all the same, and the average specific gravity of the molded products was 0.52.

For comparison, when 22 parts of glass beads Q-Cell 575 manufactured by Asahi Glass were used in place of the above polypropylene beads, 30% of the resin was missing in the center.
The average specific gravity of the molded product was 0.62.

Kunao, 10 parts of polypropylene beads and glass beads Q
-Cell 57522 parts have the same volume. ) Example 2 Liquid resin A was prepared in the same manner as in Example 1.

However, the total amount of resin was 575 parts. On the other hand, polypropylene beads PB-MG15P, which are elastic particles, were obtained.

These particles had a bulk specific gravity of 0.05 g/-, and 8 parts were prepared. On the other hand, Matsumoto Yushi's foam balloon F-30D
48 copies were prepared.

Maximum width 120mm, maximum length 350mm, tIl
Two male molds were made to make a serpentine model with a thickness of 14 mm. Nozzles were installed at the top and bottom of the mold. Six leaves of glass cloth were also prepared to match the internal dimensions of this mold. A polyester nonwoven fabric "Unicell BT-0404J" was formed into a bag shape according to the inner dimensions of a mold, and the polypropylene beads and foam balloons described above were placed in the bag and sealed.

The bag containing polypropylene beads and foam balloons was covered with glass cloth, placed in a mold, and closed. The inside of this mold was evacuated, and the liquid curable resin (epoxy resin) was press-fitted from the lower nozzle and overflowed from the upper nozzle.

The mold containing the curable resin was placed in a hot bath at 70° C., and the foaming balloon was expanded to cause the liquid resin to flow out. The nozzle was closed while the flow continued. After holding for 1 hour, the molded product was taken out from the hot bath, cooled, and taken out. A good composite molded product with a specific gravity of 0.8 was obtained.

For comparison, when 24 parts of glass beads M28 manufactured by Asahi Glass Co., Ltd. were used instead of polypropylene beads and molded in the same manner, the surface of the thickest part of the molded product lacked the cured resin. (The amount of glass beads is the same as that of polypropylene beads on a volume basis.) Also, in place of polypropylene beads and Matsumoto Yushi's foam balloons, only polystyrene expanded beads were used. The resulting molded product lacked resin on the surface of the thickest part.

Example 3 A raw material prepared by mixing 100 parts of Incyanate C-46 manufactured by Nedo Kogyo and 80 parts of Soflan R1109-50FS manufactured by Toyo Tire & Rubber Co., Ltd. was molded in a first mold. The obtained foamed molded product is used as a core material.

On the other hand, in the same manner as in Example 1, a curable liquid resin was prepared by mixing "Epicote 807" and "Epomate YLHOO6J" at a weight ratio of 100:31.

Similar to Example 1, a long-fiber nonwoven fabric made of polyethylene terephthalate and polypropylene fibers "Unicell J B"
Using T4040, 10 parts of polypropylene beads were prepared using the above core material, 10 parts of polypropylene beads, and the foam balloon "Microsphere-J F-30D 4" manufactured by Matsumoto Yushi used in Example 1.
A slightly smaller bag was made by wrapping the four parts to match the inner dimensions of the second mold.

This wrapper is made of Nittobo glass cloth WE-181-10.
Wrapped in 0BV. This was placed in a second mold. The interior of the mold was evacuated using an upper nozzle provided on the mold.

Next, the liquid curable resin was introduced from the lower nozzle, and it was confirmed that it overflowed from the upper nozzle.

Next, in exactly the same manner as in Example 1, the second mold was placed in a hot bath and cured while removing the resin. After 1 hour, the molded product was taken out from the hot bath, cooled, and taken out from the mold. In this way, a lightweight and good sandwich-like structural material was obtained, the surface of which was made of glass fiber-reinforced epoxy resin and the inner layer made of polyurethane, polypropylene, and epoxy resin foam.

Claims (3)

[Claims] (1) Produce a lightweight composite molded article having at least a surface layer molded into a predetermined shape using a hardened molding resin, a porous core, and a separation layer interposed between the surface layer and the core. (a) Separation in which the thermally expanded foamable resin particles and non-thermally expandable lightweight elastic particles are not substantially passed through the mold, but a curable liquid molding resin and/or its raw material is passed through the mold. (b) Presence of foamable resin particles, non-thermally expandable lightweight elastic particles, and, if necessary, a curable resin in a region surrounded by the separation layer that will become a foamed core after molding. (c) injecting a liquid curable resin into the mold as necessary; (d) heating a predetermined area of the mold to a sufficiently high temperature and/or increasing the temperature due to reaction heat of the resin raw material,
The foamable resin particles are heated and foamed to cause volumetric expansion,
thereby pressing the separation layer against the inner surface of the mold, allowing the curable liquid molding resin and/or its raw material to permeate the separation layer, and allowing at least a portion of it to pass through the separation layer to reach the surface layer; (e) curing the liquid molding resin and/or its raw material; and (f) removing the obtained composite molded product from the mold. (2) The manufacturing method according to claim (1), wherein the expandable resin particles are hollow thermally expandable resin particles. (3) the separation layer is composed of a fibrous sheet and/or a porous sheet, at least in part or in whole, which does not allow the thermally expanded expandable resin particles to pass through, but allows the curable liquid molded resin to pass through; 3. The manufacturing method according to claim 1, wherein the remaining portion is made of a material that does not allow the liquid resin to pass through.