JPH0474644A - Manufacture of lightweight composite molding - Google Patents

Abstract

PURPOSE:To obtain a sandwiched foam core material at low cost and efficiently by deforming elastically a soft foam such as soft slab material impregnated with resin to a specified shape, solidifying the foam with resin, using a die with its porosity maintained as it is, molding a skin FRP with the same resin simultaneously and forming some internal pressure utilizing the elastic recovery force of the soft foam. CONSTITUTION:A soft foam is used as a core member, and the foam is obtained by cutting it out of a large foam almost to a shape and size matching the internal profile of a die or forming it preliminarily. In this case, it is recommended that the foam be slightly larger than the internal profile of the die. Next, the core member is impregnated with an unsaturated liquid resin and squeezed, then it is allowed to recover almost its original form elastically. After that, when inserting the core member in the die, the soft foam containing resin should be compressed to be deformed elastically into the die and the core member should be introduced into the cavity of the die together with a reinforcing fiber material, utilizing the elastic deformation and elastic recovery force of the soft foam.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a lightweight composite molded product made of a sandwich foam core material, which has been widely used in aerospace materials, sporting goods, and other fields in recent years. Regarding.

[Conventional technology 1] Conventionally, sandwich foam core materials mainly consisting of a foam core and a surface layer made of resin and reinforcing fibers are made by bonding a foam-molded core and a fiber-reinforced plastic (hereinafter referred to as FRP). After that, there are methods of molding FRP on the surface of a foam core that has been pre-foamed, methods of molding an FRP outer shell in advance and injecting foamable resin into it, and reinforcing. A method has been proposed in which fibers are attached to the inner surface of a mold and foamed resin is injected to mold a foamed core and an FRP skin at the same time.

The method of making the foam core and FRP skin separately in advance and gluing them together is as follows:
Although a good product can be obtained, the process is complicated and requires skillful skill because individual molded products are molded into a predetermined shape and then assembled and bonded in a predetermined manner. Various practical methods have been devised for foam-molding a core in advance and molding FRP on the outside, but the basic method is to mold a specified foam core, put it into a mold, and mold the skin FRP. This is the way to do it. If this core does not have a predetermined shape, it will not fit into the mold, or a gap will be created so that the core will not be located at the predetermined position of the desired molded product, making it impossible to obtain a good sandwich material. In the method called Form RTM, reinforcing material is wrapped around the outside of the foam core, placed in a mold, and resin is injected. However, if the core is made precisely and the gap between it and the mold is not small, the position of the core may be incorrect. However, in a method called foam TEM, a foam that retains its expansion force is wrapped in a reinforcing material soaked in resin and then heated and expanded in a mold to compensate for this drawback, but the expansion temperature and the curing temperature of the resin must approximately match. Further, the core is also hard and the expansion period may be limited, making it impractical if the core differs from a predetermined shape. In the method of molding an outer FRP shell in advance and injecting foamed resin into it, the first problem is to mold the FRP to fit a predetermined mold. In the method of placing reinforcing fibers on the wall of a mold and injecting foamed resin, the primary problem is fixing the reinforcing fibers, and another problem is that the foamed air bubbles infiltrate the reinforcing material. In any case, although pre-forming the core reduces the problem, making this core is also a challenge in itself and is unlikely to lead to a method of obtaining inexpensive sand german wood.

[Problem to be Solved by the Invention] The problem to be solved by the present invention is to solve the problems of the conventional method as described above and to provide a method for manufacturing sand inch foam core material at low cost and efficiently. .

[Means for Solving the Problems] The present inventor has made extensive research into means for solving the above-mentioned problems, and has found, for example, the effective use of general-purpose soft foams such as inexpensive so-called slab materials as form core materials. After thinking about it, I arrived at the present invention.

That is, in the method of the present invention, a soft foam such as a soft slab material is impregnated with resin, elastically deformed into a predetermined shape, and solidified with resin while maintaining porosity in a mold to form a core. At the same time, the skin FRP is molded using the same resin, and at this time, the internal pressure molding of the seeds is performed using the elastic recovery force of the compressed soft foam.

In other words, in the method of the present invention, a soft foam is prepared approximately to the size of the desired core, impregnated with uncured resin (sucked or infiltrated), and then squeezed.
This is a method for producing a lightweight composite molded product, which consists of elastically recovering almost its original shape, inserting it into a mold in a laminated state with reinforcing fiber material coated with resin, and then curing the resin.

In the method of the present invention, a soft foam is used as the core member, and this is done by cutting or preforming a large foam into a shape and size that roughly matches the internal shape of the mold. At this time, it is preferable to make the mold slightly thicker than the inner shape of the mold.

This core member is impregnated with uncured liquid resin and squeezed to elastically restore it to almost its original shape, and when it is inserted into a mold, the soft foam containing the resin is compressively and elastically deformed and inserted into the mold. However, it is preferable to insert the reinforcing fiber material together with the reinforcing fiber material into the mold cavity by utilizing its elastic deformation and elastic recovery force.

Pushing the soft foam into the mold in this way means that there is no need to precisely manufacture the foam core.
At the same time, utilizing the recovery power means that it is freed from the constraint of matching the expansion conditions and resin curing conditions as in the case of using thermally expandable foam. In addition, within the mold, the reinforcing fiber material is pressed against the inner surface of the mold by the elastic recovery force of the foam, so that the problem of fixation during installation on the inner surface of the mold is also solved. There is also no problem of the foamed resin penetrating into the reinforcing m-wire material.

To set a reinforcing material, a fiber sheet that has been pre-impregnated or coated with resin, in a mold, apply the resin to a mold that has been split into two, and then layer the fiber sheet on top of it.Apply the resin to the fiber sheet in advance. A method of impregnating the fiber sheet and placing it in a mold, a method of setting a fiber sheet in the mold in advance and applying resin, etc. are adopted. In particular, it is convenient to overlay the fiber sheet set in this way with a soft foam impregnated with resin and recovered by squeezing. Further, the soft foam can be added with reinforcing fibers and pressed into a mold, and then resin can be injected. Furthermore, a combination of these methods can also be implemented. Gel coats are often used to improve the surface of molded articles, but it is also preferable to use them in combination or in combination. The temperature of the laminate housed in a mold is raised by heating the mold or by heat generation due to a reaction of the resin itself, and the resin in the laminate hardens to become an integrally molded product. Note that it is preferable to gel part or all of the resin before putting it into the mold in order to shorten the curing time.

The soft foam used as the core member in the method of the present invention is preferably cut out from a commercially available slab material or the like into a general shape that fits a mold, but a preformed core may also be used. The material of the soft foam is not particularly limited, and any material that is soft and elastic, such as foamed rubber such as polyurethane, polyvinyl chloride, polyolefin, and polyisoprene, can be used successfully. Particularly preferred are those having open cells. A foamed balloon or the like may be used in combination, or a core made of a foamed elastic balloon may be used. An elastic form made by using a combination of an inorganic material hollow balloon and an elastic resin is also preferable, and glass hollow balloons, glass balloons, etc. are used for this.

On the other hand, uncured resin is preferably a resin that is liquid at least when impregnated into the foam, and that hardens (or solidifies) in the mold in the later stage of molding, such as epoxy resin.

Unsaturated polyester resins, vinyl ester resins, and raw materials thereof are preferred. Polyurethane, polyamide resin, raw materials thereof, etc. may also be used. A resin with a low melting point and low viscosity, such as a melt of methacrylic acid resin, may also be used. Thermoplastic resins that flow during molding are also used. When considering the strength of the molded product, epoxy resins are preferred, and unsaturated polyester resins and vinyl ester resins are preferred for general use.

The soft foam used in the present invention needs to be impregnated with resin, and by squeezing and recovering the resin after impregnation, it is useful for fixing the soft foam with the resin and leaving pores as the foam. The profits of impregnation and compression 9 recovery are adjusted from this point of view. The weight increase (resin impregnation amount) of the foam after impregnation and compression recovery is apparently 0 when the specific gravity is changed.
．． 0.05 to 0.8 < g/ml), preferably 0.05 to 0.8 < g/ml).
1 to 0.5 < 9/m1). If this value is too large, the weight of the core of the molded product increases, making it difficult to reduce the weight; if this value is too small, it becomes difficult and weak to fix the core.

The resin to be impregnated or applied to the fiber sheet and the resin to be absorbed into the soft foam are preferably the same, and should be at least of the same type and at least have good adhesion to each other. This concerns the strength and durability of the molded product.

The material for the reinforcing fiber sheet is glass fiber.

Carbon fibers, aramid fibers, polyester fibers, polyolefin fibers, etc. are used, and glass l1Ilt is particularly preferred. Carbon fiber is used for high-end products. The sheet may be in the form of a woven fabric or a non-woven fabric, and is usually a woven fabric.

The mold is not limited to a metal mold, and may be made of resin, ceramics, wood, or other materials.

[Effects of the Invention] According to the method of the present invention as described above, a lightweight and inexpensive sandwich foam core composite material whose core portion is a foam hardened with a cured resin and whose surface layer is a fiber-reinforced resin can be efficiently manufactured. Ru. Therefore, the resulting molded products can be used as various lightweight structural materials and sporting goods.

Can be widely used for electrical equipment housing, medical equipment, household use, etc.

[Example 1 Next, Examples and Comparative Examples of the present invention will be given, but the present invention is not limited thereto. In addition, unless otherwise specified, "1 part" in each example means part by weight.

Example 1 100 parts of an epoxy resin manufactured by Shell [Epicoat 8071] and 31 parts of a curing agent "Epomate" were mixed. This is called resin A.

A mold for a flat plate was constructed in advance from two aluminum plates and a 1" Teflon spacer. A liquid drain was provided at both ends of this mold, and the thickness of the spacer was set to 3111 mm.

A commercially available Utaren foam slab material (manufactured by Toyo Rubber Co., Ltd.) with a thickness of 3IIIL was obtained and cut to match the inner shape of the mold. This was impregnated with resin A, squeezed to a thickness of 1+u, and allowed to recover its elasticity.

Nittobo glass fiber cloth WF-181-100
Add resin A to a sheet cut from 8V (twill weave) to fit the mold.
It was impregnated with water and placed in one of the two halves of the mold.

On top of this was placed the soft foam that had been cut out and recovered by impregnating it with resin A. The same sheet as described above was similarly impregnated with resin A and substantially pasted onto the other mold, and the foam was placed upside down on the mold.

After tightening the mold while expelling excess resin and air,
One drain was closed, and the container was placed in a hot bath at 80° C. with the open drain facing upward, and heated. After 1 hour, the molded product was taken out from the hot bath, cooled, and taken out from the mold. A lightweight and good flat plate was obtained, the surface of which was made of epoxy resin, the outer core made of glass fiber-reinforced epoxy resin, and the inside made of polyurethane foam fixed with epoxy. The specific gravity of the molded product is 0.60
, the strength by bending test is 8.2 kO/si, the elastic modulus is 6
It was 43 kg/-. The apparent specific gravity of the elastic foam used was 0.08 (9/Il+), and the specific gravity of the core portion of the molded product was 0.36. This is an example in which the specific gravity of the core increased by 0.28 (9/1) due to molding.

Examples 2 and 3 Flat plates were created in the same manner as in Example 1. However, the glass fiber fabric used as the reinforcing material is M manufactured by Asahi Fiberglass.
S 253E -1040-2N T -10F S(
plain weave). Resin A was applied to the mold, the glass cloth was placed and pasted, resin A was further applied, and a soft foam prepared in advance by sucking and squeezing the resin A was placed thereon. The other mold to which resin A was applied and the glass cloth was attached was placed upside down and closed.

The resin was cured by heating in the same manner as in Example 1, cooled, and taken out. The specific gravity of this sample was 0.581, the bending strength was 7.8k (1/aj), and the elastic modulus was 567 parts M-.

Glass cloth, non-woven fabric [UNICELL B T 0404J
A sample made in exactly the same way using a combination of
It was 93 kg/-.

Example 4 Similarly to Example 1, 100 parts of the epoxy resin "Epicoat 807J" manufactured by Shell and the curing agent "Epomate YL" were added.
31 parts of HOO6J were mixed. This is called resin A.

In advance, I made a mold for a fin (skeg) for a sailing board out of resin. Liquid handles are provided at both ends.

The mold was made into two parts.

A commercially available soft and elastic Utaren 7-ohm slab material (manufactured by Toyo Rubber Co., Ltd.) was obtained and cut to fit the outline of the fin. This is soaked in resin and squeezed to a thickness of 3 mm.
I let it recover.

Nittobo glass fiber cloth WF-181-100
Three sheets of 8V were cut to fit the mold, impregnated with resin A, and placed in one of the two molds.

On top of this was placed the soft foam that had been cut out, impregnated with the resin, squeezed, and recovered in elasticity.

Three of the same sheets were impregnated with resin A and substantially pasted on the other mold, and the foam was placed upside down on the mold. The foam was cut out to mount the fins, and 18 sheets of the glass cloth cut out to fit the fins were placed in place of the foam.

After tightening the mold while expelling excess resin and air,
One drain was closed, and the container was placed in a hot bath at 80° C. with the open drain facing upward, and heated. After 1 hour, the molded product was taken out from the hot bath, cooled, and taken out from the mold. A lightweight and good quality fin was obtained whose surface was made of epoxy resin, the outplant was made of glass fiber-reinforced epoxy resin, and the inside was made of polyurethane foam fixed with epoxy. The total specific gravity was 0.83.

Former Patent Attorney 1) Sumihiro (N)

Claims (3)

[Claims] (1) When manufacturing a lightweight composite material consisting of an integrally molded product having a hard porous core in which a soft foam is fixed with a resin, and a skin made of the resin and reinforcing fibers, it is necessary to use the soft foam as the target core. After preparing the flexible foam to approximately the same size and impregnating it with uncured resin, it is squeezed to remove excess resin, and then the resin-impregnated foam thus obtained is elastically restored to approximately its original shape. manufacturing a lightweight composite molded article, which is characterized in that this and a reinforcing fiber material impregnated or coated with a resin are substantially laminated together in a mold for molding, and then the resin is cured. Method. (2) When inserting the reinforcing fiber material impregnated or coated with resin and the soft foam that has been impregnated with uncured resin and squeezed and then elastically recovered to almost its original shape into a mold, the soft foam 2. The method for manufacturing a lightweight composite molded article according to claim 1, wherein the lightweight composite molded article is compressively deformed to fit the inner shape of a mold. (3) The lightweight composite molding according to claim (1) or (2), characterized in that the reinforcing fiber material and the resin impregnated or applied to the soft foam are gelled in advance and placed in a mold. How things are manufactured.