JPH04200838A - Production of molding sand, core, and molded body made of fiber-reinforced resin using same - Google Patents

Abstract

PURPOSE:To lighten the weight of a core and to facilitate the removal of the core by collapse by mixing a solvent-soluble thermoplastic resin, previously dissolved in a solvent, with molding sand for core. CONSTITUTION:A thermoplastic resin which can be easily dissolved in a solvent of low boiling point and has superior property of joining with molding sand is dissolved in a solvent, which is mixed with molding sand whose average grain size is regulated to a value in the prescribed range. It is preferable that the solvent is the one capable of easily dissolving various thermoplastic resins and having low boiling point.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to foundry sand and cores used for manufacturing hollow objects, and a method for manufacturing fiber-reinforced resin molded objects of irregular hollow shapes using the same.

<Prior art> Fiber-reinforced resins (hereinafter sometimes referred to as FRP), especially fiber-reinforced resins using high-performance reinforcing fibers such as carbon fibers and aramid fibers, are characterized by their light weight, high strength, and high elasticity. Taking advantage of this, it is being developed into a variety of applications, and there is a remarkable expansion into fields where metals have traditionally been used.

This is because FRP has superior specific strength (strength/density) and specific elasticity (modulus/density) compared to metals such as steel and aluminum, and by changing the orientation of the fibers, the strength characteristics can be freely adjusted. This is because it can be done.

In recent years, there has been an increasing demand for converting irregularly shaped hollow molded bodies having complex external shapes into fiber-reinforced resins. Specific examples include surge tanks for automobile parts and various pressure vessels.

If the irregularly shaped hollow molded body is made of metal, it can be easily manufactured by casting, deep drawing, etc. Conventionally, to mold irregularly shaped hollow molded bodies using fiber-reinforced resin, prepreg is laminated around a mold, or a lay-up method is used in which reinforced fiber fabric is laminated around a mold while impregnated with resin. It was made. , - molds were usually made of low melting point alloys, foundry cores, or thin-walled metals.

<Problems to be solved by the invention> 1. The low melting point alloy mold is heavy and difficult to handle, and has a large heat capacity. The drawback is that it takes a long time to cure certain thermosetting resins.

Foundry cores are made by heating and hardening foundry river sand coated with thermosetting resin such as Fugnol resin.No heating is required for curing, and the core can be removed after molding the irregularly shaped hollow molded body. There were problems such as difficulty.

Thin-walled metal mold cores have problems such as requiring a separate mold for molding them, and secondly, residual ζ remains inside the molded product after molding, making it impossible to achieve weight reduction.

<Means for solving the problem 2 The present invention has been made to solve the problems of the above-mentioned conventional method, and is a lightweight and collapsible method for producing a deformed hollow molded body made of FRP. The present invention relates to a method for manufacturing a deformed FRP hollow molded body using molding sand, a core, and the core, which can be easily removed by removing the molding sand.

That is, the present invention provides: (1) Foundry sand for cores made by dissolving a solvent-soluble thermoplastic resin in a solvent and mixing it with foundry sand.

(2) A core made of foundry sand using a solvent-soluble thermoplastic resin as a binder.

(3) A core formed by dissolving a solvent-soluble thermoplastic resin in a solvent, mixing it with foundry sand, placing the mixture in a mold, and solidifying it by substantially removing the solvent using -). A fiber-reinforced resin characterized in that a film having mold releasability (5) is coated on the surface of the core, and a fiber-reinforced resin layer is further formed on the surface of the fiber-reinforced resin, and then a solvent is injected into the core Y to disintegrate and remove the core. Method for manufacturing a molded object.

It's something to do with.

The present invention will be explained in detail below.

The foundry river sand used in the present invention is not particularly limited as long as it is sand used for shell molding F, but the preferred average particle size range is 20 to 150 mesh. If it is less than 20 mesos, the fluidity is poor when it is charged into a mold, and the solvent poured into the fiber-reinforced resin to disintegrate it with a solvent after hardening does not easily penetrate between the sand grains. When the mesh size is 150 or more, there are problems in that the surface of the formed core collapses, the bonding force between the sand grains is weak, and the strength of the core cannot be maintained.

The solvent-soluble thermoplastic resin used in the present invention is preferably one that is easily dissolved in a low-boiling point solvent and has excellent bondability with foundry sand.

Specifically, polycarbonate-F, polymethyl methacrylate-1, polyacrylate-1, polyvinyl chloride, polystyrene, polyvinyl acetate, BS resin, polyamide,
Examples include polyester, polyphenyl ether, polyether sulfone, and polyphenylene sulfide. Among these, polycarbonate-1- is preferably used because it is easily dissolved in a solvent and has good heat resistance.

The solvent used in the present invention is preferably one that can easily dissolve the various thermoplastic resins described above and has a low boiling point. For example, those having a boiling point of 100°C or less are more preferable. Further, it is preferable to use a material having a small latent heat of vaporization.

The mixing ratio of thermoplastic resin to foundry sand is 0.5 to 20
It is used in a range of % by weight.

When the amount is less than 0.5% by weight, the bonding force of the foundry sand is so weak that a core cannot be formed. If the amount exceeds 20% by weight, it is difficult to remove the solvent, and communicating holes may be formed in the casting.
- cannot be used for the purpose of the present invention.

The material for the releasable film formed on the surface of the core is preferably one that has good mold releasability and can form a film in a short time. Examples of such materials include unsaturated polyester resins, vinyl ester resins, epoxy resins, alkyd resins, urethane resins, phenol resins, xylene resins, melamine resins, furan resins, and silicone resins.

In order to improve mold release properties, it is also effective to use an internal mold release agent or to apply a mold release agent on the formed film.

In the method of the present invention, in the step of removing the solvent when forming the core, the solvent may remain to an extent that does not cause any problems in the subsequent steps.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

<Example> 0.4 kg of polycarbonate resin and 2 kg of methylene chloride
A binder solution was prepared by dissolving it in

20 kg of foundry sand (Freemantle, manufactured by Yamakawa Sangyo Co., Ltd.) was placed in a concrete mixer, and while stirring, the above binder solution was added to produce surface-treated foundry sand.

On the other hand, a gel coat agent (epoxy resin: Sumitomo Chemical Co., Ltd.) "A IE" was applied to the inner surface of the female split mold made of aluminum.
I-Δ128.100 parts by weight, Aerosil = 8 parts by weight,
After applying triethylenetetramine and assembling a split mold, molding sand whose surface has been treated with a binder is filled into the mold, and then heated under vacuum at 100°C for 2 hours to harden the gel coat agent and cure the solvent. (methylene chloride) was removed.

Open the split mold, take out the completed core, apply a mold release agent (Dai-free manufactured by Daikin Corporation) to its surface,
After laminating carbon fiber fabric prepreg on the outside and wrapping it in a vacuum bag, it was heated at 120° in an autoclave.
C. for 2 hours. After the autoclave was taken out, methylene chloride was poured into the mouth to break up the foundry sand forming the core, and the molding sand was taken out to the outside. By mechanically destroying and removing the gel coat layer, a desired irregularly shaped hollow molded body was obtained.

<Comparative example> Phenol resin (94 parts by weight of phenol,
A core was formed using foundry sand prepared using a resol-type solid phenolic resin (condensed with 100 parts by weight of 50% formalin and 12 parts by weight of 35% ammonia) in the same manner as in the example, and a fiber-reinforced resin was formed. An irregularly shaped hollow molded body was molded, but the core could not be taken out.

(9 complete)

Claims (3)

[Claims] (1) Foundry sand for cores made by dissolving a solvent-soluble thermoplastic resin in a solvent and mixing it with foundry sand. (2) Core made of foundry sand using solvent-soluble thermoplastic resin as a binder (3) A solvent-soluble thermoplastic resin is dissolved in a solvent and mixed with foundry sand, the mixture is placed in a mold, and then the solvent is removed, allowing it to solidify and be easily released on the surface of the formed core. Manufacture of a fiber-reinforced resin molded article, which comprises covering with a film having moldability and further forming a fiber-reinforced resin layer on the surface thereof, and then injecting a solvent into the core to disintegrate and remove the core. Method.