Claims
- 1. A process for perparing a mold by hardening molding materials by CO.sub.2 gas which comprises mixing refractory particles with a binder material comprising a caustic alkali-neutralized product of at least one copolymer selected from the group consisting of .alpha.-olefin-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and methylvinyl ether-maleic anhydride copolymer, and calcium hydroxide, thereby preparing molding materials, filling the molding materials around a pattern, and blowing CO.sub.2 gas into the molding materials, thereby hardening the molding materials.
- 2. A process according to claim 1, wherein 0.2-2.0 parts by weight of the copolymer as solid matters is added to 100 parts by weight of the refractory particles.
- 3. A process according to claim 1, wherein 0.2-4.0 parts by weight of the calcium hydroxide is added to 100 parts by weight of the refractory particles.
- 4. A process according to claim 1, wherein 0.2-2.0 parts by weight of the copolymer as solid matters and 0.2-4.0 parts by weight of the calcium hydroxide are added to 100 parts by weight of the refractory particles.
- 5. A process for preparing a mold by hardening molding materials by CO.sub.2 gas, which comprises mixing refractory particles with a binder material comprising a caustic alkali-neutralized product of at least one copolymer selected from the group consisting of .alpha.-olefin-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and methylvinyl ether-maleic anhydride copolymer, calcium hydroxide, and polyvinyl alcohol, thereby preparing molding materials, filling the molding materials around a pattern, and blowing CO.sub.2 gas into the molding materials, thereby hardening the molding materials.
- 6. A process according to claim 5, wherein not more than 2 parts by weight of the polyvinyl alcohol is added to 100 parts by weight of the refractory particles.
- 7. A process for preparing a mold by hardening molding materials by CO.sub.2 gas, which comprises mixing refractory particles with a binder material comprising a caustic alkali-neutralized product of at least one copolymer selected from the group consisting of .alpha.-olefin-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and methylvinyl ether-maleic anhydride copolymer, calcium hydroxide, and at least one member selected from the group consisting of calcium oxide and hydroxides of zinc, aluminum, barium, magnesium and iron, thereby preparing molding materials, filling the molding materials around a pattern, and blowing CO.sub.2 gas into the molding materials, thereby hardening the molding materials.
- 8. A process for preparing a mold by hardening molding materials by CO.sub.2 gas, which comprises mixing refractory particles with a binder material comprising a caustic alkali-neutralized product of at least one copolymer selected from the group consisting of .alpha.-olefin-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and methylvinyl ether-maleic anhydride copolymer, calcium hydroxide, and SBR styrene-butadiene rubber latex, thereby preparing molding materials, filling the molding materials around a pattern, and blowing CO.sub.2 gas into the molding materials, thereby hardening the molding materials.
Priority Claims (2)
| Number |
Date |
Country |
Kind |
| 52-37621 |
Apr 1977 |
JPX |
|
| 52-37622 |
Apr 1977 |
JPX |
|
Parent Case Info
This is a continuation-in-part application of Ser. No. 893013 filed on Apr. 3, 1978 and now abandoned.
The present invention relates to a process for preparing a mold which is hardened by CO.sub.2 gas.
In practical molds for molding metals, there have heretofore been used inorganic binder materials such as sodium silicate and organic binder materials such as phenol resins and furan resins. All the molds using these binder materials have properties which can endure pressure or heat of molten metals. However, the molds using inorganic binder materials have a weak point in the operation that it is very difficult to remove castings and it takes a lot of time to produce the castings owing to the poor collapsibility of molds after pouring. Also, the molds using organic binder materials have not such a weak point. As a method for hardening a mold, there are self-hardening process by chemical reaction of the binder material components in the molding materials and cold setting process which comprises hardening a mold by blowing CO.sub.2 gas or an amine gas into the molding materials after molding materials containing binder materials has been filled around pattern. The former hardening method is limited in the time during which molding materials can be effectively used, that is, bench life since chemical reaction starts simultaneously with the addition of the binder materials to molding materials. As the latter hardening method, there are so-called CO.sub.2 process which comprises blowing CO.sub.2 gas into molding materials containing, for example, sodium silicate as a binder material to effect hardening, a method which comprises blowing an amine gas into molding materials containing a hydroxyl group-containing resin (for example, a phenol resin) and a polyisocyanate as a binder material to effect hardening, and a method which comprises blowing CO.sub.2 gas into molding materials containing a combination of an acrylic copolymer or a phenol resin and calcium hydroxide as binder materials to effect hardening. These methods can give a good mold production efficiency since the bench life of molding materials is longer than by the former hardening method by the chemical reaction of the binder material components contained in molding materials and the molding materials begin to harden as soon as the gas is blown into the molding materials. However, the CO.sub.2 process has a weak point in the mold collapsibility. Also, in the method using an amine gas the toxicity and bad odor of amine gases give rise to trouble. Further, the method using a combination of a copolymer of an acrylic acid ester, ammonium acrylate and sodium acrylate, calcium hydroxide and CO.sub.2 gas has the following defects:
(1) The ammonia gas is let loose by the preparation of molding materials and it pollutes working environment.
(2) The strength of a mold immediately after blowing CO.sub.2 gas is unsatisfactory. Further, the method using a phenol resin does not cause the pollution of working environment by the release of ammonia gas, but an increase in the strength of a mold is small since the hardening of molding materials after blowing CO.sub.2 gas is carried out only by drying.
The present inventors previously proposed, as a technique for solving the above-mentioned problems in the CO.sub.2 process and the other prior art processes for producing a mold, a process for producing a mold by using a combination of polyvinyl alcohol, calcium hydroxide or calcium oxide and CO.sub.2 gas. This process greatly improved prior art, but when a large mold is produced, it was difficult to harden molding materials uniformly to its inside.
Therefore, an object of the present invention is to provide a process for preparing a mold by hardening molding materials by CO.sub.2 gas, wherein the advantages of prior art have been retained, whereas the above-mentioned defects of the prior art have been obviated, and more specifically the object of this invention is to provide a process for preparing a mold having a high compressive strength and good collapsibility at a good mold production efficiency.
The other objects and advantages of the present invention will be apparent from the following description.
The present invention provides a process for preparing a mold by hardening molding materials by CO.sub.2 gas, which comprises mixing refractory particles with a binder material comprising a caustic alkali-neutralized product of at least one copolymer selected from the group consisting of .alpha.-olefin-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and methyl vinyl ether-maleic anhydride copolymer, and calcium hydroxide, thereby preparing molding materials, filling the molding materials around a pattern, and blowing CO.sub.2 gas into the molding materials, thereby hardening the molding materials, where 0.2-2.0 parts by weight of the copolymer and 0.2-4.0 parts by weight of the calcium hydroxide are added to 100 parts by weight of the refractory particles, and polyvinyl alcohol, calcium oxide, at least one hydroxide of zinc, aluminum, barium, magnesium and iron, and SBR (styrene-butadiene rubber) latex can be added thereto, when desired.
US Referenced Citations (13)
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 42-25527 |
Dec 1967 |
JPX |
| 432964 |
Nov 1974 |
SUX |
Continuation in Parts (1)
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Number |
Date |
Country |
| Parent |
893013 |
Apr 1978 |
|
Patent Grant
4269256
