JPH0422655B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an oxidizing agent used when forming a mold by adding sulfur dioxide to a granular refractory aggregate mixture containing an acid-curable resin and an oxidizing agent. More particularly, it relates to certain aqueous organic peroxide compositions used as oxidizing agents for the curable molds. Conventionally, for high-speed mold production applications such as automobile castings, the cloning method, which uses novolak-type phenolic resin as a binder and heat-cures it, or the hot-boxing method, which heats and cures liquid phenolic resin or furan-based resin, have been widely used. It's here. All of these are normally fired and hardened at 200°C to 300°C, which causes various problems such as energy consumption, hardening time, distortion of the mold, poor dimensions of the casting due to deformation, and working environment. In recent years, the so-called cold box method, in which a mold is formed by blowing a gaseous or aerosol-like substance at room temperature, has been attracting attention and becoming popular as a molding method to improve these drawbacks. As a cold box method, there is a urethane-based cold box method in which curing is performed using a polyol compound and a polyisocyanate as a binder and a tertiary amine as a catalyst. However, in the urethane cold box method, even if the granular refractory mixture containing polyol and polyisocyanate is left to stand, the curing reaction proceeds gradually, resulting in a short pot life of the mixture or problems such as soot defects, gas defects, etc. There are drawbacks such as many casting defects. Another cold box method currently available is an acid curing cold box method in which an acid curing resin and an oxidizing agent are added to a granular refractory, and then sulfur dioxide is blown into the refractory to form a mold. In this method, the curing reaction does not proceed unless the granular refractory mixture and sulfur dioxide come into contact with each other, so the pot life of the mixture is long, and acid-curing resins with excellent heat resistance, such as furan-based resins, are used as the binder. Therefore, there are advantages such as fewer casting defects. However, this acid-curing cold box method requires the use of expensive organic peroxides as oxidizing agents.
In addition, there is a problem of concern about the safety of organic peroxides, and there is a demand for inexpensive and highly safe peroxides. Hydrogen peroxide is an inexpensive and highly safe peroxide, but hydrogen peroxide easily decomposes due to the alkali content, metal oxides, and other impurities contained in the granular refractory aggregate. The usable time after mixing of a mixture obtained by adding and kneading a resin and peroxide to a fire-resistant aggregate, the so-called pot life, is so short that it is practically unusable. Under such circumstances, the inventors of the present invention have conducted extensive research and have come up with the invention of a peroxide composition for curable molds that is inexpensive, highly safe, and has excellent performance. That is, the present invention is a peroxide composition that is used as an oxidizing agent when producing a mold by injecting gaseous or aerosolized sulfur dioxide into a granular refractory aggregate mixture to which an acid-curing resin and an oxidizing agent have been added. It consists of 35-60% by weight of a ketone peroxide, 35-60% by weight of a carrier agent consisting of water or a dialkyl ester of water and an aliphatic or aromatic dibasic acid, and 0.1-5% by weight of a surfactant. The present invention relates to a peroxide composition for molds, characterized in that it is a hydrous ketone peroxide composition prepared homogeneously by emulsifying and dispersing or solubilizing with an activator. Normally, ketone peroxide compositions are reacted by dropwise reacting hydrogen peroxide with a mineral acid such as sulfuric acid as a catalyst, an aliphatic or alicyclic ketone and an aliphatic or aromatic dibasic acid diester as a carrier agent under cooling, and the reaction is completed. This is a non-aqueous peroxide composition produced by separating the aqueous layer and neutralizing, washing, drying and purifying the non-aqueous layer. The manufacturing process for this product is complicated and takes many man-hours, and considering the amount of raw materials used, the yield is significantly reduced, making it expensive, and it is also dangerous because it is non-aqueous. On the other hand, there are hydrous homogenized ketone peroxide compositions that use polyhydric alcohols such as glycerin or nitrogen-containing water-soluble solvents such as N-methyl-2-pyrrolidone as carrier agents, but these carrier agents are acid-curable resins. It is a curing retardant and is inexpensive and highly safe, but when used as an oxidizing agent for acid-curing cold boxes, it causes poor curing of the mold, making it practically unusable. The peroxide composition of the present invention improves these drawbacks, does not contain a solvent that acts as a curing retarder for homogenization, and is water-containing, so it has excellent performance as an oxidizing agent for acid-curing cold boxes. , which does not require complicated manufacturing processes, is inexpensive, and has excellent safety against fires and the like due to its water-containing properties, providing practically satisfactory results. As a preferred method for producing the hydrous ketone peroxide composition of the present invention, at least one of an aliphatic ketone having 4 to 8 carbon atoms or an alicyclic ketone having 6 to 10 carbon atoms is mixed with hydrogen peroxide under an acid catalyst. Ketone peroxide produced by oxidation with water is emulsified and dispersed using a surfactant without separating water during or after production using a dialkyl ester of an aliphatic dibasic acid or an aromatic dibasic acid as a carrier agent. Alternatively, there is a method of solubilization. As the surfactant, it is preferable to use at least one type of nonionic or anionic surfactant. If the number of carbon atoms in the aliphatic ketone or alicyclic ketone that is the raw material for the ketone peroxide used in the present invention is greater than the above range, curing will be delayed by the obtained peroxide. If the amount is less than the above range, there is a problem with the safety of the peroxide, and both are not preferred. The proportions of each component in the peroxide composition of the present invention are appropriately within the range of 35 to 60% by weight of ketone peroxide, 35 to 60% by weight of water or water and carrier agent, and 0.1 to 5% by weight of surfactant. By selecting, a ketone peroxide composition that is water-containing and homogeneous and has excellent safety and performance can be obtained.When the proportion of ketone peroxide exceeds 60% by weight, the active oxygen concentration becomes high; The tendency for spontaneous decomposition will be accelerated and the danger will be significantly increased. Also, the proportion of ketone peroxide is 35% by weight
When the refractory granular aggregate and peroxide composition are kneaded, some of the ketone peroxide decomposes due to the impurities present in the refractory granular aggregate, and the absolute If the amount is insufficient, the curing speed will suddenly slow down. Next, if the ratio of water or water and carrier agent is less than 35% by weight, the ketone peroxide becomes unstable.
The tendency for spontaneous decomposition will be accelerated and the danger will be significantly increased. Also, the ratio of water or water to carrier agent is 60
If the weight percentage is exceeded, water essentially acts as a retarder for this curing reaction, and the curing rate becomes impractically slow. Generally, when forming a mold, silica sand containing quartz as a main component, zircon sand, and chromite sand are used as granular refractory aggregates, but the present invention is not limited to this. Acid-curable resins include furan resin, phenol resin, urea resin,
Examples include melamine resins or their co-condensates or mixtures, and these resins can be used as granular refractory aggregates.
It is usually used in an amount of 5 to 20 parts by weight per 1000 parts by weight. The peroxide composition of the present invention is usually used in an amount of 3 to 10 parts by weight per 1000 parts by weight of aggregate. Examples will be described below to explain the present invention in more detail, but the scope of the present invention is not limited by the Examples. Examples 1 to 3 and Comparative Examples 1 to 2 Hydrous ketone peroxide composition according to the present invention containing 50% by weight of ketone peroxide, 33% by weight of carrier agent, 1% by weight of surfactant, and 16% by weight of water. In order to evaluate the performance of a commercial hydrous ketone peroxide composition as an oxidizing agent in acid-curable cold boxes, molds were molded and the mechanical properties of the molds were investigated. A mixture of 3000 parts by weight of Australian flattery silica sand, 35 parts by weight of furan resin, and 14 parts by weight of peroxide composition was added and kneaded into a 25 x 25 x 250 m/m mold, gaseous sulfur dioxide was blown into it, and then compressed. The mold was molded after cleaning with air. After molding, the bending strength of the mold was measured over time. The results are shown in Table 1.

[Table] *1 Sodium dodecylbenzenesulfonate/Polyethylene glycol *2 Polyoxyethylene cetyl ether/Sodium lauryl sulfate Examples 4-6 and Comparative Examples 3-4 3000 parts by weight of Iwami silica sand, 45 parts by weight of furan resin, peroxide Examples 1 to 3 were prepared by adding and kneading 15 parts by weight of the composition.
A mold was molded in the same manner as in Comparative Examples 1 and 2, and after molding, the bending strength of the mold was measured to examine practical performance. At the same time, the added kneaded product was allowed to stand for 1 hour, and then a mold was molded in the same manner to measure the pot life of the kneaded product. The results are shown in Table 2. The composition of the peroxide composition of the present invention is 50% by weight of ketone peroxide, 32% by weight of carrier agent, 1% by weight of surfactant, and 17% by weight of water.

【table】

Claims (1)

[Claims] 1. A peroxide used as an oxidizing agent when producing a mold by injecting gaseous or aerosolized sulfur dioxide into a granular refractory aggregate mixture to which an acid-curing resin and an oxidizing agent have been added. A composition comprising 35-60% by weight of a ketone peroxide, 35-60% by weight of a carrier agent consisting of water or a dialkyl ester of water and an aliphatic or aromatic dibasic acid, and 0.1-5% by weight of a surfactant.
% by weight, and is a hydrous ketone peroxide composition homogeneously prepared by emulsifying and dispersing or solubilizing with a surfactant. 2. The composition according to claim 1, wherein the surfactant is at least one of a nonionic surfactant and an anionic surfactant. 3. The composition according to claim 1 or 2, wherein the ketone peroxide is at least one of peroxides of aliphatic ketones having 4 to 8 carbon atoms or peroxides of alicyclic ketones having 6 to 10 carbon atoms. thing.