JPH0417740B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a gas-curable binder composition for molds. More specifically, the present invention is a so-called acid-curing cold box in which a mold is manufactured by adding and kneading an acid-curing resin and an oxidizing agent to refractory granules, molding the mixture into a mold, and then injecting gaseous or aerosol sulfur dioxide into the mold. The invention relates to an improved binder composition for use in. [Prior Art] Conventionally, in order to manufacture molds at medium to high speeds, a cloning method has been widely used in which a mold is manufactured by heating and curing so-called coated sand in which granular refractories are coated with phenolic resin. However, in order to save energy during mold manufacturing, mold production speed, and improve the quality of molds and castings, the cold box mold manufacturing method, which hardens at room temperature using gaseous or aerosol substances, has been introduced as a mold manufacturing method that replaces the cloning method. Serious attempts are being made to introduce it in the industry. The cold box method involves curing acid-curing resins, typically furan-based resins, with sulfur dioxide using peroxide as an oxidizing agent, and curing polyols and polyisocyanates with an aerosol of tertiary amine as a catalyst. There is a urethane cold box that hardens. Among these, molds using urethane cold boxes have drawbacks such as poor disintegration of casting sand during production of castings, and easy occurrence of casting defects such as sand trapping, scooping, pinholes, and soot defects. On the other hand, acid-curing cold boxes have been rapidly attracting attention in recent years as a method for solving the above-mentioned difficulties. [Problems to be Solved by the Invention] The present invention relates to a binder composition suitable for use in this acid curing cold box method. This invention relates to a binder composition containing an acid-curable resin as a main ingredient, which is used to improve curing behavior such as initial strength, mold flexibility, and casting surface finish (surface stability). Conventionally, automatic molding machines have been used to manufacture medium to large quantities of molds, in which acid-curing resin and peroxide are added and kneaded to fire-resistant granular material to coat the surface of the fire-resistant granular material, and air pressure, etc. Filling, molding, curing, and removal are automatically performed continuously in a cycle of less than one minute. Therefore, in the cold box method, in order to further improve mold productivity, it is desired to improve the initial strength so that the mold can be sufficiently mechanically handled within one minute after molding. In addition, there are increasing demands regarding the surface stability of molds, which is closely related to the quality of the casting surface. [Means for Solving the Problems] As a result of intensive research, the present inventors have developed a method to significantly improve the initial strength within one minute after molding, the surface stability of the mold, etc., and to improve mold productivity. The inventors have discovered a binder composition for cold boxes, which comprises an acid-curable resin containing rosin and a monomer or polymer having a phenolic hydroxyl group, and have arrived at the present invention. That is, the present invention relates to a binder composition used in a method for producing a gas-curable mold in which a mold is formed using sulfur dioxide using an acid-curable resin as a binder and a peroxide as an oxidizing agent. The resin is mainly composed of furan-based resins, urea-based resins, and melamine-based resins, each singly or mixed or co-condensed together, and contains 5 to 30% by weight of rosin and phenolic hydroxyl groups. This invention relates to a binder composition characterized in that it contains 5 to 30% by weight of a monomer or polymer, respectively. If the rosin content in the binder composition of the present invention is less than 5% by weight, there will be no effect of improving initial strength or mold surface stability, and if it exceeds 30% by weight, there will be problems with solubility. In addition, if the content of monomers or polymers having phenolic hydroxyl groups in the binder composition is less than 5% by weight, there will be no rosin solubilizing effect or initial strength improvement effect, and if it exceeds 30% by weight, the content of the monomer or polymer having a phenolic hydroxyl group will not increase after the mold is left standing. The final strength is reduced and the surface stability of the mold is also reduced. This improves initial strength immediately after molding, mold flexibility, and
The finish of the cast surface has been greatly improved. In addition, in the present invention, by combining rosin and a monomer or polymer having a phenolic hydroxyl group, problems such as poor solubility and storage stability, which are found in acid-curing resins containing only rosin, can be overcome. I was able to make a huge improvement. As for forms in which acid-curable resin is used in combination with rosin and monomers or polymers having phenolic hydroxyl groups, they may be stirred and mixed separately together with acid-curable resin in fire-resistant granular material during mold production. When producing a binder composition, rosin and a monomer or polymer having a phenolic hydroxyl group may be incorporated into the reaction system for producing the binder, or may be mixed after production. In the present invention, the binder composition may contain a silane coupling agent for the purpose of improving the surface stability and moisture resistance of the mold, and a known solvent or diluent for improving the viscosity, workability, etc. It is also possible to use additives in combination. In order to manufacture the mold, in addition to silica sand mainly composed of quartz, zircon, chromite, olivine sand, etc. are used as refractory granular materials together with the binder according to the present invention, but there are no particular limitations. It's not a thing. Further, as the peroxide, organic peroxides such as ketone type and aromatic type, and inorganic peroxides such as hydrogen peroxide are used, but are not particularly limited. [Examples] Hereinafter, in order to explain the present invention in more detail, the advantages of the present invention will be described using Examples, but the scope of the present invention is not limited by the following Examples. Examples 1 to 5 To 3000 parts by weight of silica sand, 40 parts by weight of urea-formalin-modified furan resin containing the substances according to the present invention shown in Table 1 and 15 parts by weight of methyl ethyl ketone peroxide were mixed in advance in a Shinagawa rotary-revolution type batch mixer. After filling into a 25 x 25 x 250 m/m mold mold bending strength measurement test piece mold, sulfur dioxide gas was blown in for 1 second, excess sulfur dioxide was washed away with pressurized air for 5 seconds, and the mold was mixed. was molded. 30 from the start of sulfur dioxide injection
After a few seconds, the initial strength is measured using a bending strength tester.
A mold was similarly molded using a urea-formalin-modified furan resin that did not contain the substance according to the present invention, and the initial strength of the measured product was expressed as a ratio with the initial strength as 100. The results are shown in Table-1.

[Table] Examples 6 to 10, Comparative Example 1 Molds were molded in the same manner as in Example 1, except that a 50φ×50 m/mH mold was used. Immediately after molding, the mold was placed on a 10-mesh sieve and vibrated for 1 minute using a rotary shaking sieve to measure the surface stability of the mold. The results are shown in Table-2.

【table】

[Table] (Note)
Surface stability (〓)〓Mold weight after sieving (g)〓Casting before sieving
Mold weight (g)〓100
Examples 11 to 16, Comparative Examples 2 to 8 A mold was made in the same manner as in Example 1, except that 30 parts by weight of the acid-curing resin listed in Table 3 and the stated amount of the substance according to the present invention listed in Table 3 were added. Molded. The initial bending strength and surface stability of the obtained mold were measured in the same manner as in the above example. The results are shown in Table 3.

[Table] * ○: Dissolution ×: Separation or precipitation [Effects of the invention] As shown in Table-1 and Table-2, both the initial bending strength and surface stability were improved in all Examples compared to the blank. , sufficiently remarkable effects were seen on the expression of these template properties.

Claims (1)

[Claims] 1 A binder composition used in a gas-curable mold manufacturing method in which a mold is formed using sulfur dioxide using an acid-curable resin as a binder and peroxide as an oxidizing agent, wherein the acid-curable resin is The main components are furan-based resins, urea-based resins, and melamine-based resins, each singly or mixed or co-condensed together, containing 5 to 30% by weight of rosin and a monomer or polymer having a phenolic hydroxyl group. 5
A binder composition characterized by containing up to 30% by weight of each.