JPS628254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful foundry sand composition, which is intended for molding molds with good collapsibility after casting, especially for light alloy castings. To provide a sand composition. In mold making methods that use phenolic resin as the main binder, such as the shell mold method, when making castings of metals such as aluminum and copper alloys whose molten metal temperature is lower than that of cast iron, Disintegratability after casting is particularly required. To this end, various proposals have been made in the past, but none have yet been found to be sufficiently effective. For example, there is a method of adding compounds such as urea or zinc carbonate, but such methods not only have insufficient disintegration properties but also have drawbacks such as lowering the fusion point and lowering strength. ing. However, in view of the existence of various drawbacks in the prior art, the present inventors conducted intensive studies in order to obtain a foundry sand composition with particularly excellent disintegration properties and good strength properties. A binder containing specific dicarboxylic acid metal salts and a specific halogen-containing polymer compound not only has excellent disintegration properties after casting, that is, it disintegrates easily at low temperatures, but also has high The present invention was completed by discovering that a strong mold can be provided. That is, the present invention provides a foundry sand composition for shell molds containing a phenolic resin as a main binder component, in which a metal salt of oxalic acid or tartaric acid or a water thereof is added to 100 parts by weight of the binder component. A polymer compound containing 1 to 15 parts by weight of at least one compound (A) and chlorine or bromine.
The present invention provides a composition containing at least one of (B) in a proportion of 0.5 to 20 parts by weight. Here, typical examples of the above-mentioned phenolic resins include novolak type phenolic resins and resol type phenolic resins, but these resins include phenol, cresol, resorcinol, bisphenol A, or oligomers of bisphenols. It is obtained by reacting a phenol compound or a substance having the same effect with an aldehyde supplying substance such as formaldehyde, paraformaldehyde, acetaldehyde or butyraldehyde or a substance having the same effect by a known and commonly used method. The binder is mainly composed of such a phenol resin, and a compound such as hexamethylenetetramine, urea resin, furan resin or polyester resin is also used in combination. On the other hand, typical components (A) used in obtaining the composition of the present invention include copper oxalate, ferrous oxalate, potassium oxalate, nickel oxalate, and ferrous oxalate. In addition to strontium acid or potassium tartrate, there are also hydrates of these metal salts. The component (A) is thermally decomposed to create an oxidizing atmosphere,
It has the function of accelerating the thermal decomposition of sand binders. Separately, typical examples of component (B) include vinyl chloride resin, vinylidene chloride resin, chlorinated polyether resin, chlorinated polyethylene, chlorinated polypropylene, chlorinated paraffin, vinyl chloride/propylene copolymer resin, or brominated resin. Examples include epoxy resins, but it goes without saying that resins obtained by chlorinating or brominating organic polymer compounds can also be used. Among these polymer compounds (B), the content of the element chlorine or bromine - expressed as the composition ratio of the element in one molecule in weight percent - is at least 5%,
A high value, preferably 20% or more, is suitable for the purposes of the present invention. The reason why a high molecular compound is suitable for the purpose of the present invention is that a low molecular compound inevitably has a strong odor, has a decomposition point and boiling point lower than the casting temperature, and is highly toxic. When contained in foundry sand, such as inhibiting the hardening of the binder component, it is unsuitable because it tends to cause some of the harmful effects that must be avoided. This is because there are fewer such concerns. The high molecular weight compound (B) used in the present invention suitably has an average molecular weight of at least about 500. In addition, the component (B) is triggered by the chlorine gas or bromine gas generated when they are decomposed, promoting carbonization due to dehydrogenation of the binder molecules such as the phenol resin, and weakening the sand grain adhesion of the binder. It has a function. In the relatively low temperature region where the mold temperature is 200 to 400℃, component (A) mainly promotes thermal decomposition, and
When the temperature exceeds .degree. C., the decomposition of the binder component by the component (B) becomes particularly significant. Therefore, by using both components (A) and (B) in combination, the decomposition of the binder component is promoted in a wide temperature range, and the disintegration properties of the template are improved. The amount of the metal salt of oxalic acid or tartaric acid or hydrate thereof, which is the component (A), is usually 1 to 15 parts by weight per 100 parts by weight of the binder component. , preferably in a proportion of 3 to 7 parts by weight. On the other hand, the amount of the polymer compound containing chlorine or bromine, which is component (B), should be determined based on the amount of the binder component.
0.5 to 20 parts by weight, preferably 2 parts by weight per 100 parts by weight
~10 parts by weight. If the amount of these components (A) or (B) added is too small, it will not be possible to improve the collapsibility after casting, and conversely, if the amount of each component added is too large, the strength of the mold will decrease. The amount of both components (A) and (B) added should be adjusted as appropriate depending on the type and amount of the binder component. Therefore, in order to obtain the composition of the present invention by adding both components (A) and (B) to the foundry sand using the binder component containing phenolic resin as the main binder component, (1) Either the components (A) and (B) are dispersed or dissolved in the binder in advance and then added to the sand, or (2) both components are added during the process of mixing the sand and the binder. (3) Adding both components to sand in advance and mixing the binder therein; or (4) Adding both components to sand that has previously contained a binder. be. Furthermore, one or more compounds selected from the component (A) and one or more compounds selected from the component (B) are separately added to each of the above (1) to (4). It is possible to adopt either method of adding the compounds, or it is also possible to add each compound at the same time. In particular, as a method for adding compounds belonging to component (B) above, during the manufacturing process of foundry sand, the component (B) is dissolved in an appropriate solvent in advance and added to foundry sand, and then the solvent is evaporated. One of the effective methods is to remove it by using In obtaining the composition of the present invention, substantially the same effects can be obtained by using any of the above-mentioned methods. The thus obtained composition of the present invention can provide foundry sand and molds with good disintegrability after casting, but is especially suitable for foundry sands or molds for so-called light alloys containing aluminum or copper. It is useful as a. Next, the present invention will be specifically explained with reference to Examples, Comparative Examples, Application Examples, and Comparative Application Examples. In the following, parts and percentages are all based on weight unless otherwise specified, and silica sand is _SiO2
At least 99% pure with an American Foundry Men's Society (AFS) particle size index of 60
±3 was used. Example 1 100 parts of "Foundrets TD-3402-B" (novolac resin manufactured by Dainippon Ink and Chemicals Co., Ltd.)
Melt it at 150℃, add 5 parts of ferrous oxalate dihydrate and 5 parts of "Epicron 152" (brominated epoxy resin manufactured by the same company), and stir well to mix uniformly. Then, it was cooled to obtain a resin composition. Thereafter, 2.2 parts of this composition was passed through a 3-mesh sieve and coarsely crushed so as to remain on a 20-mesh sieve, and then added to 100 parts of silica sand that had been previously heated to 150°C. The mixture was then kneaded in a whirl mixer for 1 minute to obtain resin-coated sand. Next, an aqueous solution of 0.3 parts of hexamethylenetetramine (hereinafter abbreviated as hexamine) dissolved in 1.3 parts of water was added and kneaded for 1 minute, and then 0.1 part of calcium stearate was added and kneaded for 20 seconds. The mixture was kneaded to obtain the desired foundry sand composition. Example 2 100 parts of silica sand preheated to 150°C,
2.0 parts of "Foundrets TD-3402-B", 0.1
part of ferrous oxalate dihydrate and 0.1 part of "Epicron 152" were added. Thereafter, the same operations as in Example 1 were repeated starting with coarse crushing to obtain a foundry sand composition. Example 3 Add 100 parts of silica sand preheated to 150°C,
2.0 parts of "Foundrets TD-3402-B" was added and kneaded in a whirl mixer for 1 minute. Thereafter, resin-coated sand was obtained in the same manner as in Example 1. Next, 0.1 part of ferrous oxalate dihydrate and 0.1 part of "Epicron 152" were added to this coated sand and mixed uniformly to obtain a foundry sand composition. Example 4 100 parts of phenol, 120 parts of 37% formaldehyde aqueous solution and 12 parts of 25% ammonia aqueous solution were
The reaction was carried out at 65°C for 2 hours, and then low-boiling substances such as water and unreacted substances in the reaction product solution were removed by vacuum distillation, and when the gelation time at 150°C reached 90 seconds, the product was taken out. was immediately cooled to obtain a solid resol type phenolic resin with a softening point of 85°C. After that, 2.0 parts of this resin was passed through a 3-mesh sieve, and then coarsely crushed so that it remained on the 20-mesh sieve, and then 100 parts of silica sand, which had been preheated to 150°C, was added. Mixed for 1 minute in a whirl mixer. Thereafter, 1.3 parts of water, 0.1 part of ferrous oxalate dihydrate, and 0.1 part of "Epicron 152" were added thereto and kneaded for an additional minute to obtain a foundry sand composition. Example 5 100 parts of silica sand was heated to 150℃ in advance.
2.0 parts of "Foundrets TD-3402-B", 0.1
1 part ferrous oxalate dihydrate and 0.1 part vinyl chloride resin were added. Thereafter, a foundry sand composition was obtained in the same manner as in Example 1, starting from coarse crushing. Example 6 100 parts of silica sand preheated to 150°C
Add 2.0 parts of "Foundrets TD-3402-B" and 0.1 part of ferrous oxalate dihydrate and mix in a Whirl mixer for 1 minute, then mix 0.1 part of chlorinated paraffin with a chlorine content of 40%. A solution obtained by dissolving 1 part of hexamine in twice the amount of acetone and a solution obtained by dissolving 0.3 parts of hexamine in 1.3 parts of water were added and kneaded for 1 minute, and then kneaded for 1 minute.
0.1 part of calcium stearate was also added and kneaded for 20 seconds to obtain a foundry sand composition. Example 7 The same amount of potassium oxalate monohydrate was used instead of ferrous oxalate dihydrate, and the amount of "Epicron 152" was changed to 0.15 parts.
A foundry sand composition was obtained in the same manner as in Example 2. Comparative Example 1 100 parts of silica sand preheated to 150℃,
Add 2.0 parts of "Foundlets TD-3402-B" and 0.2 parts of ferrous oxalate dihydrate,
A foundry sand composition for comparison was obtained in the same manner as in Example 1, except that no component of the polymer compound (B) containing chlorine or bromine was used. Comparative Example 2 100 parts of silica sand preheated to 150℃,
2.0 parts of "Foundrets TD-3402-B" and 0.2 parts of "Epicron 152" are added, but metal salts of oxalic acid or tartaric acid or their hydrates are added.
Example 1 except that no component (A) was used.
A foundry sand composition for comparison was obtained in the same manner as in the above. Comparative Example 3 100 parts of silica sand preheated to 150°C,
Add 2.0 parts of "Foundrets TD-3402-B", but you can also use metal salts of oxalic acid or tartaric acid or their hydrates (A), or polymer compounds containing chlorine or bromine (B). A comparative sand composition was obtained in the same manner as in Example 1, except that no component was used. Comparative Example 4 Ferrous oxalate dihydrate and “Epiclon”
A comparatively bright foundry sand composition was obtained in the same manner as in Example 4, except that "152" was not used at all. Application Examples 1 to 7 and Comparative Application Examples 1 to 4 First, Examples 1 to 7 were placed in a mold heated to 230°C.
After pouring each foundry sand composition obtained in Comparative Examples 1 to 4 and holding for 2 minutes,
A mold was obtained by firing for 1 minute in a furnace at 250°C. Next, a disk-shaped test piece with a diameter of 85 mm and a height of 10 mm was made using this fired foundry sand, which was then wrapped twice in aluminum foil and heated at 350℃ and 400℃.
℃ and 450℃ for 20 minutes in each oven for heat treatment. Afterwards, each heat-treated test piece is passed through a 10-mesh sieve using a rotor-tap sieve to remove sand, and if the sand is removed in 4 minutes, no test pieces will be on the sieve. It is expressed as the time (in seconds) until no sand remains, and if the sand does not come off in 4 minutes, this sand removal start time is 4.
We decided to measure the ratio (% value) of the amount of sand falling after 10 minutes to the weight of the test piece before sand removal started and express it as a % value. The measurement was repeated twice and the average of the measured values was taken as the disintegration value. The results are summarized in Table 1. The same table also shows the results for the fusion point and bending strength, of which the fusion point was determined according to "JACT (Casting Technology Promotion Association) Test Method C-1". On the other hand, the bending strength is determined according to the test method of JIS K-6910. 【table】

Claims (1)

[Scope of Claims] 1. In a foundry sand composition for shell molding containing a phenolic resin as a main binder component, (A) a metal salt of oxalic acid or tartaric acid, or At least one of these hydrates is contained in a proportion of 1 to 15 parts by weight, and (B) at least one of the polymer compounds containing chlorine or bromine is contained in a proportion of 0.5 to 20 parts by weight. A foundry sand composition consisting of: