JP3004857B2 - 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 molded article having a desired inner surface shape 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 molded body that is a non-foamed resin member having a hollow portion is arranged in a molding die, and a cavity of the molding die is filled with expandable resin particles to be a foamed resin member. By foaming,
This is a method in which the hollow thin-walled molded article and the foamed resin particles are integrally molded to form a disappearing model molded article.

[0003] By the way, the amount of the resin of the above-mentioned disappearing model molded article 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 wall thickness is formed thin. 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 molded article, deformation of the hollow thin molded article due to the foaming pressure of the foamed resin particles is prevented.

[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). That is, if the air pressure is adjusted to be too high with respect to the foaming pressure of the foamed resin particles, the hollow thin-walled molded product swells due to the air pressure, or undergoes deformation such as bursting, while the air pressure is adjusted too low with respect to the foaming pressure. In addition, the foaming pressure causes deformation such as denting of the hollow thin-walled molded product, and in any case, it is impossible to obtain a good disappearing model molded product.

[0005] Therefore, conventionally, when a vanishing model molded article is molded, the material, thickness, mechanical strength (impact resistance), etc. of the hollow thin molded article, or the material and expansion ratio of the foamed resin particles are different. Each time, it is necessary to determine the air pressure to be supplied to the hollow portion by performing a trial production several times, and therefore, there is a problem that a long time is required for molding and the molding process becomes complicated. Was.

On the other hand, it is conceivable to improve the strength by increasing the thickness of the hollow thin-walled molded product. However, in this case, the amount of resin of the disappeared model molded product increases, and the disappeared model molded product becomes large. It does not completely disappear due to 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.

[0007] From the above, in forming a vanishing model molded article, it is necessary to provide a strong hollow thin molded article having impact resistance without changing the thickness of the hollow thin molded article (in a thin state). desired. That is, while being able to be processed into the desired inner surface shape, when performing integral molding with the foamed resin particles, do not burst by the air put into the hollow portion,
There is a demand for the development of a hollow thin-walled molded article having the property of having sufficient strength not to be damaged during molding.

[0008] Generally, the material of the hollow thin-walled molded product is as follows.
Polypropylene, polyethylene, ABS resin, polystyrene, vinyl chloride, polystyrene terephthalate and other synthetic resins in general are used alone or in copolymers. A simple substance or a copolymer is used.

When the material of the hollow thin molded article and the material of the foamed resin particles are made the same, the advantage that the hollow thin molded article and the foamed resin particles are bonded without using an adhesive at the time of integral molding is obtained. As a material of the model molded product, a polystyrene resin or a polymethyl methacrylate resin is used. However, polystyrene resin or polymethyl methacrylate resin alone does not have impact resistance, and when a hollow thin molded article having a complicated shape is manufactured, deburring is required. There is a problem such as breakage.

[0010]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to obtain a hollow thin molded article having a desired inner surface shape and foamed resin particles simultaneously. By changing the material of the hollow thin-walled molded article without increasing the thickness of the hollow thin-walled molded article, the strength of the hollow thin-walled molded article (impact resistance)
The object of the present invention is to provide a vanishing model molded article having improved.

[0011]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, the present inventors have found that a hollow thin-walled molded article containing a rubber component in a base material and foamed resin particles are simultaneously molded to form a hollow thin-walled molded article. We succeeded in providing a vanishing model molded article with improved body impact resistance, and completed the present invention. That is, the present invention relates to a vanishing model molded article obtained by simultaneously molding a hollow thin molded article having a desired inner surface shape and foamed resin particles, wherein the material of the hollow thin molded article is a polystyrene resin or polymethyl methacrylate. A vanishing model molded product comprising a base material selected from a series of resins and a rubber component.

Further, the present invention provides the vanishing model molded article characterized in that the rubber component is butadiene and the content of butadiene is 0.01% or more and 20% or less. Hereinafter, the present invention will be described in detail. Examples of a material constituting a base material of the hollow thin molded body (hereinafter, referred to as a core) include a polystyrene resin or a polymethyl methacrylate resin. Polystyrene-based resins include, in addition to styrene homopolymer, styrene as a main component, copolymerizable with acrylonitrile, copolymers with other ethylenically unsaturated monomers, and the like. The methyl methacrylate-based resin includes, in addition to methyl methacrylate homopolymer, a copolymer of acrylonitrile having methyl methacrylate as a main component, copolymerizable therewith, and other ethylenically unsaturated monomers. It is a thing.

The rubber component contained in the base material may be any of natural rubber or synthetic rubber, a blend of natural rubber and synthetic rubber, and the like, for example, butadiene. Here, if the content of the rubber component is too large, the elasticity, which is a characteristic of the rubber, increases, causing deformation due to steam pressure or foaming pressure of the foamed resin at the time of integral molding, and casting defects (gas defects) at the time of casting. Cause. On the other hand, if the rubber content is too small, a molded article with improved core impact resistance cannot be obtained.

Therefore, the content of butadiene as a rubber component is preferably 0.01% to 20%. The rubber content can be contained in the base material by a method of copolymerizing the resin at the time of producing the resin or a method of blending the resin before being extruded by an extruder and kneading the resin inside the extruder. Examples of the expanded resin particles (hereinafter referred to as expanded beads) include a polystyrene resin and a polymethyl methacrylate resin.

The hollow molding and the integral molding 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.

[0016]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Example 1 A shape of an intake manifold for an automobile engine as shown in FIG. 1 using a material obtained by mixing polystyrene and high impact polystyrene (polystyrene containing about 8% butadiene) at a ratio of 1: 1. Was molded by blow molding. The average thickness of core 3
1.0 mm.

Next, the core obtained as described above was inserted into a mold for molding foam beads, and was integrally molded. That is, foamable beads for casting (manufactured by Sekisui Chemical Co., Ltd .; trade name: Eslenbeads LFK), which is made of polystyrene and has an average particle diameter before foaming of 0.3 mm, are used as a raw material of the foam beads 4. Increase the expansion ratio of expanded beads 4 to 40
The thickness of the foamed portion was set to 2.5 mm, and integral molding was performed to produce a vanishing model molded product 1.

As a result, the core 3 maintained the shape of the hollow portion 2 without causing deformation or rupture, and the shape accuracy of the disappearing model molded product 1 was good. The material is aluminum alloy (AC-
As a result of performing the casting as 4A), the finished cast product had good shape accuracy, and the surface and the inner surface were smooth and beautiful.

[0019]

According to the present invention, deformation and rupture of the core due to the foaming pressure of the expanded beads and the like can be achieved by changing the material of the core including rubber, without increasing the thickness of the core. This can be prevented. As a result, it is possible to provide a vanishing model molded article in which the impact resistance of the core is improved.

[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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Kubota 1-10-26 Sangenya Higashi, Taisho-ku, Osaka City, Osaka Prefecture References JP-A-62-156913 (JP, A) JP-A-63-162776 (JP, A) JP-A-2-63636 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name ) B22C 7 / 02,9 / 04 B29C 39/00-39/44 B29C 43/00-43/58

Claims (2)

(57) [Claims] 1. A vanishing model molded article obtained by simultaneously molding a hollow thin molded article having a desired inner surface shape and foamed resin particles, wherein the material of the hollow thin molded article is a polystyrene resin or a polymethyl methacrylate series. A vanishing model molded product comprising a base material selected from a resin and a rubber component. 2. The vanishing model molded article according to claim 1, wherein the rubber component is butadiene, and the content of the butadiene is 0.01% or more and 20% or less.