JPS61199545A - Consumable pattern material for casting - Google Patents

Abstract

PURPOSE:To reduce the cost of a product by forming a pattern material of a crosslinked foamed-in-place molding of which the resin consists of a PP resin and high density polyethylene and which has specific density. CONSTITUTION:The pattern material is formed of the crosslinked foamed-in- place molding of which the resin consists of the PP resin and/or high density polyethylene and which has 0.025-0.012g/cm<2> density. The PP resin to be used for such full mold pattern material is exemplified by an ethylene/propylene random copolymer, ethylene/propylene block copolymer, propylene homopolymer, etc. Since the resin and the density are specified in the above-mentioned manner, the resin is easily gasified when the resin contacts with the molten metal poured into the mold. No soot is generated in such a stage. The resultant casting has no surface defects such as 'gas pockets' and 'wave-like surface folding' owing to the unevaporated residue and is free from the carburization in the casting. The casting has excellent dimensional accuracy as well.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention provides a method for eliminating casting defects caused by the chemical properties of synthetic resin foam in a vanishing model casting method in which casting is produced by replacing the molten metal with injected metal. The present invention also relates to a disappearing model material for casting made of a synthetic resin foam that easily disappears.
[Prior Art] The use of synthetic resin foam as a vanishing model for casting has been known as the full mold method.

In the full mold method, a model is usually made from a plastic foam made of polystyrene, which is then buried in a mold and molten metal is injected into the mold.

This is a method in which the plastic foam model is gasified and disappeared by the heat of the molten metal, and the cavity is filled with hot water and cooled to obtain a casting. Therefore, in this full mold method, the process from making the model to making the mold is extremely simple.
It can be said to be a simplified and innovative casting method.

However, polystyrene, which has traditionally been used as a disappearing model material for casting, has a chemical property that makes it difficult to thermally decompose. In case of surface defects such as "gas wrinkles" or "wavyness" due to vaporized residue, and carburization inside the casting, there were problems in which gas defects were generated due to entrainment of decomposed gas. Therefore, in the past, such castings required an extra step of mechanically finishing the surface of the casting to make them into products, or had to be discarded if they had gas defects. It had been.

〔the purpose〕

The present invention solves these problems seen in conventional vanishing model materials for casting, and provides a synthetic resin that produces castings that do not cause casting defects due to the chemical properties of the synthetic resin foam and do not require post-processing steps such as surface finishing. The object of the present invention is to provide a disappearing model material for casting made of resin foam.

[Configuration] In the present invention, the constituting resin is a polypropylene resin and l
Or made of high density polyethylene, with a density of 0.025~
The gist of the present invention is a disappearing model material for casting, which is characterized by a cross-linked foamed in-mold molded product having a density of 0.012 g/cl.

The casting model material resin of the present invention, that is, the polypropylene resin used as the full mold model material, includes ethylene-propylene random copolymer, ethylene-propylene block copolymer, propylene droplet monopolymer, propylene-1- Examples include butene random copolymers. In particular, among these polymers, ethylene content of 1°0
It is preferable to use an ethylene-propylene random copolymer having a content of 1% by weight to 10% by weight and a proportion of n-hebutane extraction residue of 50% by weight or less. In this case, the n-heptane extraction residue ratio means stereoregularity and is expressed by the following formula.

R (%) = -xto.

R: n-heptane extraction residue ratio A: weight of insoluble matter after 8 hours of n-heptane extraction B: n-
Weight before hebutane extraction In the present invention, as a model material for full mold,
High-density polyethylene is also used, but in this case, high-density polyethylene is generally obtained by a low-pressure method, and usually includes those having a density of 0.94 g/C1f or more.

In the present invention, the polypropylene resin and high-density polyethylene may be used alone or in a blend of the two, and in the case of a blend, the blending ratio is arbitrary.

The disappearing model material for casting of the present invention is composed of a cross-linked and foamed in-mold body formed from so-called cross-linked pre-expanded particles, which are formed by cross-linking the resin particles and foaming the obtained cross-linked particles. In this case, the crosslinked particles are prepared by mixing resin particles, water, an anti-fusing agent, and a crosslinking agent in an autoclave, raising the temperature to the softening temperature of the resin while stirring, impregnating the resin with the crosslinking agent, and then crosslinking. Obtained by raising and maintaining the temperature. Examples of the crosslinking include dicumyl peroxide, 1,1-bis(t-butylperoxy) 3,3°5
-trimethylcyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, thi-butylcumyl peroxide, 2,5-dimethyl-2,5-di(
Organic peroxides such as t-butylperoxy)hexane are used. In addition, in the case of resin particles containing polypropylene resin, it is preferable to use divinylbenzene as a crosslinking aid in addition to the crosslinking agent. 05 to 5 parts by weight, and the amount of divinylbenzene used is 100 parts by weight of the resin.
By weight.

The proportion is 0.05 to 5 parts by weight. In addition, for pre-foaming of cross-linked particles, the cross-linked particles, water, anti-fusing agent, and blowing agent are mixed in an autoclave, the temperature is raised to the foaming temperature under pressure, and one end of the container is opened to transfer the contents to a low-pressure zone. This can be done by releasing it.

In this case, examples of the anti-fusing agent include aluminum oxide, titanium oxide, and aluminum hydroxide.

Basic magnesium carbonate, basic zinc carbonate, zinc carbonate, etc. are mentioned, and blowing agents include organic ones such as propane, butane, pentane, trichlorofluoromethane, dichlorodifluoromethane, carbon dioxide, nitrogen, etc. , and inorganic gases such as air.

The crosslinked pre-expanded particles obtained as described above are as follows.

This is placed in a mold and heated and foamed to form a crosslinked foam molded product, which is used as a model material for full molding. The density of the crosslinked foamed in-mold body of the present invention thus obtained is 0.025 to 0.012 g/c! , preferably within the range of 0.024 to 0.014 g/cur. Foams with a density smaller than this have weak mechanical strength and are unsuitable as a model material for full molds, while foams with a density larger than this have a weak mechanical strength.

When it comes into contact with the molten metal and gasifies, the amount of gas generated is too large, which is undesirable as the hot water blows up and develops. Further, the degree of crosslinking of the crosslinked foamed in-mold body of the present invention is as follows: gel fraction o, o
It is preferable to specify i to 40%.

If the gel fraction exceeds 40%, the molded article will have many voids, which is not preferable. The gel fraction in this case indicates the proportion of insoluble matter obtained after immersing the crosslinked pre-expanded particles in boiling xylene for 8 hours, and is expressed by the following formula.

P (%) = -xlOO P gel fraction (%) L: Weight of cross-linked pre-expanded particles M: Weight of insoluble matter The casting model according to the present invention is made of a special full-mold model material. bury something in a mold,
When molten metal is poured into this.

The model comes into contact with the molten metal and is gasified and eliminated by combustion or thermal decomposition, and the remains of the model are filled with the molten metal. And the molten metal that filled the remains of this model.

It is then cooled and solidified to obtain a casting having the same shape and dimensions as the model.

〔effect〕

As described above, the disappearing model material for casting of the present invention is made of a polypropylene resin and/or high-density polyethylene, and is a crosslinked foam molded body having a density of 0.025 to 0.012 g/ad. , when it comes into contact with the injected molten metal, it is easily gasified and no soot is generated at that time, and the resulting casting has ``gas wrinkles'' or ``wavy shapes'' on its surface due to unvaporized residue. There are no problems such as surface defects, carburization inside the casting, or gas defects sometimes caused by entrainment of decomposed gas, and the dimensional accuracy is excellent. Therefore, in the case of a casting obtained using the disappearing model material for casting of the present invention, unlike the conventional case, there is no need to finish the surface of the casting, and it can be used as a product as it is. Significant cost reductions can be achieved.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 In an autoclave, ethylene content 3.8% by weight, n-
100 parts by weight of ethylene-propylene random copolymer particles with a heptane extraction residue ratio of 5%, 300 parts by weight of water, 0.3 parts by weight of finely divided aluminum oxide as an anti-fusing agent,
1,1-bis(butylperoxy)- as a crosslinking agent
0.30 parts by weight of 3,3,5-)-limethylcyclohexane and 0.3 parts by weight of divinylbenzene were blended, and the mixture was heated to 100° C. with stirring, and maintained at this temperature for 1 hour.

Thereafter, the temperature was raised to 150° C. to perform a crosslinking reaction, and then the container was once cooled and the crosslinked resin particles were taken out.

Next, the crosslinked resin particles 100 were placed in the autoclave again.
parts by weight, 300 parts of water, 0.3 parts by weight of finely divided aluminum oxide as an anti-fusing agent, and 18 parts by weight of dicrowag fluoromethane as a blowing agent. ! Blend the following amounts and heat to 150°C while stirring.
After raising the temperature to 15 hours and holding it at this temperature for 15 hours, one end of the container was opened while pressurizing the inside of the container with air to 40 kg/aJG, and the crosslinked particles and water were released to atmospheric pressure to perform foaming.
Pre-expanded crosslinked particles were obtained.

Next, the pre-expanded crosslinked particles are placed in a pressure container.

Pressurize with air and place 1.5 kg inside the pre-expanded crosslinked particles.
The particles had an internal pressure of /aIG. The particles were placed in a mold, heated and foamed at a vapor pressure of 3.2 kg/dG, and then cooled to obtain a foamed molded article in which each particle was fused, that is, a disappearing model material for casting.

Example 2 In Example 1, the ethylene content was 2.8% by weight.

Ethylene-propylene random copolymer particles with an n-heptane extraction residue ratio of 28% were used, and the amount on the cross side was 0.35 parts by weight, divinylbenzene 0.35 parts by weight,
A vanishing model material for casting was obtained in the same manner as in Example 1 except that 19 parts by weight of dichlorofluoromethane was used.

Example 3 In Example 1, the ethylene content was 1.5% by weight, n-
Ethylene-propylene random copolymer particles with a hebutane extraction residue ratio of 40% were used, and the amount of crosslinking agent was 0.
A vanishing model material for casting was obtained in the same manner as in Example 1, except that the amounts were 25 parts by weight, 0.25 parts by weight of divinylbenzene, and 220 parts by weight of dichloromethane.

Example 4 In an autoclave, XI (density 0.958 g/cd,
100 parts by weight of high-density polyethylene particles with a melt index of 0.40, 300 parts by weight of water, 0.3 parts by weight of finely divided aluminum oxide, and 0.32 parts by weight of dicumyl peroxide as a crosslinking agent were mixed, and while stirring, The temperature was raised to 100°C and maintained at this temperature for 1 hour. After that, 150℃
After raising the temperature to 90 minutes and holding it for 90 minutes, the container was cooled and the crosslinked resin particles were taken out.

Next, 100 parts by weight of crosslinked resin particles, 300 parts by weight of water, and 0.3 parts of fine aluminum oxide were placed in the autoclave again.
parts by weight, 28 parts by weight of dichlorofluoromethane,
The temperature was raised to 150°C while stirring, and after holding at that temperature for 15 minutes, one end of the container was opened while pressurizing the inside of the container to 40 kg/dG with air, and the crosslinked resin particles and water were released to atmospheric pressure. Foaming was performed to obtain pre-foamed crosslinked particles.

Next, the obtained pre-expanded crosslinked particles were placed in a pressure container and pressurized with air to give 5 particles an internal pressure of 1.5 kg/CiG. The particles were put into a mold and weighed 3.2 kg/
After heating at the vapor pressure of alG and foaming.

A foamed molded product in which particles are fused to each other after cooling.

A vanishing model material for casting was obtained.

Example 5 In Example 4, density 0.952 g/a#, MIo
A vanishing model material for casting was obtained in the same manner as in Example 4, except that high-density polyethylene particles of No. Ta.

Example 6 In Example 4, density 0.968 g/aj, MI5
．． In addition to using high-density polyethylene particles of No. 5, the amount of crosslinking agent was 0.28 parts by weight, and the amount of dichlorodifluoromethane was 3 parts by weight.
A vanishing model material for casting was obtained in the same manner as in Example 4 except that the amount was 0 parts by weight.

Example 7 In Example 1, the ethylene content was 2.8% by weight, n-
30% by weight of ethylene-propylene random copolymer with hebutane extraction residual liquid ratio of 28% and density of 0.958 g/cj
, MIo, 70% by weight of high-density polyethylene blend particles of 4 were used, and the crosslinking agent was 0.35 parts by weight of dicumyl peroxide, 0.35 parts by weight of divinylbenzene, and the amount of dichlorodifluoromethane was 23 parts by weight. A vanishing model material for casting was obtained in the same manner as in Example 1 except for the following.

Example 8 In Example 1, the ethylene content was 2.8% by weight, n-
70% by weight of ethylene-propylene random copolymer with hebutane extraction residue ratio of 30% and density of 0.954 g/cd
, using blend particles of 30% by weight of high-density polyethylene of MI 2, and the amount of dichlorodifluoromethane was 2.
A vanishing model material for casting was obtained in the same manner as in Example 1 except that the amount was 0 parts by weight.

Comparative Example 1 In an autoclave, 100 parts by weight of the crosslinked particles shown in Example 2, 300 parts by weight of water, and 0.0 parts by weight of finely divided aluminum oxide were added.
3 parts by weight and 216 parts by weight of dichlorone fluorometa were mixed, heated to 150°C while stirring, held at that temperature for 15 minutes, and then closed one end of the container while pressurizing the inside of the container to 40 kg/cdG with air. The container was opened, and the crosslinked particles and water were discharged under atmospheric pressure to perform foaming, thereby obtaining pre-foamed crosslinked particles.

Next, the obtained pre-foamed crosslinked particles were placed in a pressure container and pressurized with air to give an internal pressure of 1.5 kg/c+JG within the expanded particles. Place the particles into a mold for molding; 3.
After heating and foaming at a steam pressure of 2 kg/aJG.

A foam molded product in which each particle is fused together after cooling.

A vanishing model material for casting was obtained.

Comparative Example 2 The pre-expanded crosslinked particles obtained in Comparative Example 1 were pressurized with air in a pressure-resistant container so that each expanded particle had an internal pressure of about 3 kg/cdG of air. The particles were heated with steam at 1.3 kg/aJG to obtain expanded particles with a bulk density of 0.01 g/cii.

The particles were placed in a pressure-resistant container and pressurized with air to give the expanded particles an internal pressure of 1.5 kg/aJG. These particles were placed in a mold, heated and foamed with steam to 3.2 kg/a#G, and then cooled to obtain a foam molded product in which each particle was fused to each other, that is, a disappearing model material for casting. Ta.

Comparative Example 3 A vanishing model material for casting was obtained in the same manner as in Example 4, except that the amount of dichlorodifluoromethane was changed to 25 parts by weight.

Comparative Example 4 The pre-expanded crosslinked particles shown in Example 4 were pressurized in a pressure-resistant container so that each expanded particle had an internal pressure of about 2 kg/aJG of air. These particles were heated and foamed with steam at 1.5 kg/aJG to obtain second pre-expanded crosslinked particles having a bulk density of 0.01 g/cIl. The particles were placed in a pressure-resistant container and pressurized with air to provide an internal pressure of 1.5 kg/dG within the expanded particles. The particles were put into a mold and weighed 3.2 kg/aiG.
After heating and foaming with steam, the mixture was cooled to obtain a foamed molded product in which each particle was fused to each other, that is, a disappearing model material for casting.

Next, using the vanishing model material obtained as described above, a model having a shape as shown in Figure 1 was created, and Mh.

After applying the system coating to the entire surface until the foamed particles are no longer visible to the naked eye, it is buried in the mold (furan material is used) together with the sprue system, and molten cast iron (carbon 3.24% by weight) is poured through a weir installed above the sprue. , 2.7% by weight of silicon, 0.65% by weight of manganese, and the balance iron and impurities) were cast at a casting temperature of 1350° C., and the quality of this casting was evaluated. On the other hand, when casting molten cast steel (0.18% by weight of carbon, 0.40% by weight of silicon, 0.70% by weight of manganese, balance iron and impurities), the same model (the coating mold is based on zircon powder) This was applied in the same manner as above using a coating mold with a diameter of 5 mm.
153 in a mold with a blind feeder of 0m x height 50w+m
It was cast at 0° C., and the presence or absence of carburization and gas defects inside the casting was determined as quality evaluation defects. The results are shown in the table below.

In the quality evaluation shown in the table, "carbon residue" refers to the presence or absence of carbon residue adhering to the surface of the casting, and "defects" refer to "gas wrinkles" on the surface of the casting.
The presence or absence of "wavyness" or "gas defects", "gas defects" inside the casting, or "occurrence of carburization" is determined. "Deformation" refers to the shape of the casting when compared with the model dimensions.
It is determined whether or not there is any deformation in the dimensions.

In addition, in the model shown in the drawing, the dimension a:
200mm, b: 30w+m, c: 30n
++w, d: 30+sm, e: 200mm
.

f: 200mm.

[Brief explanation of drawings]

The drawings show the model used in the casting test, of which figure A shows a front view and figure B shows a plan view. Patent applicant: Nippon Styrene Paper Co., Ltd. (and one other person)

Claims (4)

[Claims] (1) The constituent resin is made of polypropylene resin and/or high-density polyethylene, and has a density of 0.025 to 0.
1. A vanishing model material for casting, characterized in that it is made of a cross-linked foamed in-mold body having a weight of 0.012 g/cm^3. (2) Polypropylene resin has an ethylene content of 1 to 10
% by weight of an ethylene-propylene random copolymer, as claimed in claim 1. (3) The disappearing model material for casting according to claim 1 or 2, wherein the n-heptane extraction residue ratio of the polypropylene resin is 50% or less. (4) Gel fraction of cross-linked foamed in-mold body is 0.01% to 4
The disappearing model material for casting according to claim 1 or 2, which has a content of 0%.