JP3007519B2 - Lost model molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vanishing model molded article obtained by simultaneously molding a hollow thin-walled thermoplastic resin molded article and foamed resin particles.

[0002]

2. Description of the Related Art Conventionally, a synthetic resin molded article having a hollow portion has been used as a vanishing model molded article for producing a cast article having a complicated shape. The vanishing model molded article is molded, for example, by a method disclosed in Japanese Patent Application Laid-Open No. 4-305331. In this molding method, a hollow thin-walled thermoplastic resin molded body which is a non-foamed resin member having a hollow portion is arranged in a molding die, and foamable resin particles to be a foamed resin member are placed in a cavity of the molding die. This is a method in which the hollow thin-walled thermoplastic resin molded article and the foamed resin particles are integrally molded by filling and foaming to form a disappearance model molded article.

By the way, in the above-mentioned vanishing model molded product,
Since the amount of the resin is reduced as much as possible so that the resin can be completely eliminated (decomposed) by the heat of the molten metal to be cast, the thickness of the hollow thin-walled thermoplastic resin molded article is reduced. I have. Therefore, at the time of molding the disappearing model molded article, by supplying air at a predetermined pressure to the hollow portion of the hollow thin-walled thermoplastic resin molded article, deformation of the hollow thin-walled thermoplastic resin molded article due to the foaming pressure of the expanded resin particles is prevented. ing.

[0004] However, when molding a vanishing model molded article having a large hollow portion, there is a problem that it is very difficult to adjust the pressure of supplied air (hereinafter referred to as air pressure). In other words, if the air pressure is adjusted too high with respect to the foaming pressure of the foamed resin particles, the hollow thin-walled thermoplastic resin molded body may be deformed such as swelling or bursting by the air pressure, while the air pressure is adjusted to be low relative to the foaming pressure If it is performed too much, there is a problem that the hollow thin thermoplastic resin molded article is deformed by the foaming pressure, such as denting, and in any case, a good disappearing model molded article cannot be obtained.

Therefore, conventionally, when a vanishing model molded article is formed, every time the material, thickness, mechanical strength, etc. of the hollow thin-walled thermoplastic resin molded article, or the material, foaming ratio, etc. of the foamed resin particles are different, It is necessary to determine the air pressure to be supplied to the hollow portion by performing a trial production several times, and thus there is a problem that a long time is required for molding and the molding process is complicated.

On the other hand, in order to solve the above-mentioned problems caused by the reduced thickness of the vanishing model molded product, it is considered to increase the thickness of the hollow thin-walled thermoplastic resin molded product to improve its strength. Can be However, when the thickness of the hollow thin-walled thermoplastic resin molded article is increased, the amount of resin in the disappeared model molded article increases, and the disappeared model molded article is not completely eliminated by the heat of the molten metal. For this reason, the synthetic resin and its decomposed product remain in the mold and are mixed with the molten metal, so that a pure and good cast product cannot be obtained, which is not preferable.

Therefore, there is a demand for the development of a vanishing model molded product that can be completely vanished by the heat of the molten metal during casting even if the wall thickness is increased.

[0008]

DISCLOSURE OF THE INVENTION The present invention is directed to a synthetic resin and its decomposed product, in which even if the thickness of the hollow thin-walled thermoplastic resin molded article is increased, the disappeared model molded article completely disappears due to the heat of the molten metal. The purpose of the present invention is to provide a vanishing model molded product that does not remain in the mold.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies on the above-mentioned problems, and examined the thickness of a hollow thin-walled thermoplastic resin molded product, the expansion ratio, the thickness of a disappearing model molded product, and the like. As a result, the present invention succeeded in forming a vanishing model molded product that can be integrally molded under a certain condition and can cast a good casting.

That is, the present invention relates to a vanishing model molded article obtained by simultaneous molding of a hollow thin-walled thermoplastic resin molded article and foamed resin particles, wherein the hollow thin-walled thermoplastic resin molded article has the entire thickness of the vanishing model molded article. Not more than 25% of the thickness and the following formula [I]: Y = {C (AX) + X} / A [I] (where Y is the density of the disappearing model molded product, and A is the disappearing model) The thickness of the molded product, X is the thickness of the hollow thin thermoplastic resin molded product, C
Is the density of the foamed resin particles), and the density Y of the disappeared model molded product is 0.28 or less.

Hereinafter, the present invention will be described in detail. In general,
Since the density of the resin is around 1, the formula [I] can be derived as follows. Y = {(A−X) / A} × C + [{A− (A−X)} / A] × 1 = {C (A−X) + X} / A [I] Elimination model molded article of the present invention In the formula (I), if the value of Y is 0.28 or less, the thickness A of the vanishing model molded product and the thickness of the hollow thin thermoplastic resin molded product (hereinafter, referred to as core) The value of X and the density C of the expanded resin particles (hereinafter referred to as expanded beads) is not particularly limited, and can be set arbitrarily. However, since it is necessary to keep the shape of the disappearing model molded product, the minimum thickness of A is 0.1 mm or more, preferably
It is desirable that it is 1.0 mm or more.

The density C of expanded beads means the reciprocal of the expansion ratio of expanded beads. For example, when the expansion ratio is 45, the density C of expanded beads is 0.022. The ratio of the thickness X of the core to the thickness A of the disappeared model molded product (hereinafter, referred to as “the thickness A”)
Is preferably 25% (0.25) or less. If the wall thickness ratio exceeds 0.25, the disappearing model molded product is not completely replaced with the molten metal, resulting in poor casting.

The core and foam beads of the present invention may be composed of styrene, methyl methacrylate homopolymer, styrene or methyl methacrylate as a main component, acrylonitrile copolymerizable therewith, and other ethylene. And a copolymer with a unsaturated monomer. Further, a rubber component may be added to the core, if necessary, in order to increase the impact resistance of the core. The rubber component may be any of natural rubber or synthetic rubber, a blend of natural rubber and synthetic rubber, and the like. For example, butadiene is preferable, and its content is preferably 0.01% to 20%.

The rubber content can be contained in the core by a method of copolymerizing the resin at the time of producing the resin, or a method of blending the resin before extruding with an extruder and kneading the resin inside the extruder. The hollow molding of the core and the integral molding of the core and the expanded beads can be performed by a known method.
For example, the method of hollow molding includes blow molding, injection molding, sheet molding and the like, and the method of integral molding includes the method described in JP-A-4-305331.

[0015]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. [Example 1] In molding a vanishing model molded article 1 having an automobile intake manifold shape shown in Fig. 1, first, as shown in Table 1 below, the core thickness was set and the core 3 was removed. Molded. That is, in addition to the conventionally used core thickness of 0.5 to 0.8 mm, the core thickness was set to be thicker (0.8 to 1.0 mm), and the core 3 was formed. The molding was carried out by blow molding, and a resin obtained by mixing high impact polystyrene (polystyrene containing about 8% butadiene in polystyrene) at a ratio of 1: 1 was used as a material.

The cores 3 having various thicknesses obtained by the above-mentioned molding were inserted into a foamed bead molding die, and integrally molded by changing the foaming ratio to produce a disappearing model molded product.
The core 3 at the time of production of the disappearing model molded product (at the time of integral molding) maintains the shape of the hollow portion 2 without deformation or rupture, and the shape accuracy was good in any of the disappearing model molded products. .

The foam beads 4 are made of polystyrene and have an average particle diameter of 0.3 mm before foaming. The foam beads for casting (manufactured by Sekisui Plastics Co., Ltd .; trade name: Eslen Bead LFK) used. Also, the thickness of the foamed part is
It was kept constant at 2.5 mm. Next, using the obtained vanishing model molded product, casting was performed using aluminum alloy (AC-4A) as the material.

As a result, as shown in Table 1, when the Y value is 0.28 or less and the thickness ratio is 0.25 or less, a good cast product is obtained.
That is, the shape accuracy is good, and the surface and inner surface are smooth,
A beautiful casting was obtained.

[0019]

[Table 1]

[0020]

According to the present invention, even when the thickness of the core is increased, the disappeared model molded product is completely disappeared by the heat of the molten metal, and the synthetic resin and its decomposition products do not remain in the mold. It is possible to provide a vanishing model molded product capable of casting a simple cast product.

[Brief description of the drawings]

FIG. 1 is a front view showing a vanishing model molded product partially broken away.

[Explanation of symbols]

1: molded model disappeared 2: hollow part 3: core
4: foam beads

Continued on the front page (72) Inventor Yutaka Kubota 1-10-26 Sangenya Higashi, Taisho-ku, Osaka-shi, Osaka (72) Inventor Hiroshi Hasegawa 726-26, Yagai, Miwa-cho, Sarushima-gun, Ibaraki Prefecture 19 (56) References Special JP-A-5-138292 (JP, A) JP-A-5-237590 (JP, A) JP-A-61-199545 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22C7 / 02,9 / 04 B29C 39/00-39/44

Claims (1)

(57) [Claims] 1. A vanishing model molded article obtained by simultaneously molding a hollow thin-walled thermoplastic resin molded article and foamed resin particles, wherein the hollow thin-walled thermoplastic resin molded article has a thickness of 25% of the total wall thickness of the vanishing model molded article. % Or less and the following formula [I]: Y = {C (A−X) + X} / A [I] (where Y is the density of the disappearing model molded article, and A is the Thickness, X is the thickness of the hollow thin thermoplastic resin molding, C
Is the density of the foamed resin particles), and the density Y of the disappeared model molded product is 0.28 or less.