JPS6227899B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, a reaction product or mixture of a phenolic resin and a polyfunctional compound is mixed with refractory granules such as sand, the mixture is packed into a mold of a desired shape and molded, and then heated with a gaseous curing agent at room temperature. The present invention relates to a method of manufacturing a mold by contacting the mold. Traditionally, mold making methods that harden at room temperature include the Dical method, carbon dioxide gas method, FS method, cement method, etc. for inorganic systems, and in particular, the carbon dioxide molding method that hardens by blowing carbon dioxide gas using water glass as a binder. has been widely used, but it has problems such as poor disintegration of the sand mold after pouring, poor regeneration of recovered sand, and alkaline content leached from waste sand, which causes pollution. However, its use is on the decline. On the other hand, so-called organic self-hardening binders such as furan resins, phenolic resins, and polyurethane resins have been in the spotlight as a way to overcome these drawbacks and have been greatly developed. Among these, conventional furan resins include furfuryl alcohol alone, or an initial condensate of furfuryl alcohol, urea, and formaldehyde, and phosphoric acid, toluenesulfonic acid, xylene sulfonic acid, benzenesulfonic acid, sulfuric acid, etc. alone or in combination.
A mixture of seeds or more is stirred on the sand to bind the sand grains. Further, as phenolic resins, novolak type and resol type are used for this type of use. Novolak resin is a condensate of phenol nuclei connected by methylene bonds, and is soluble in organic solvents and exhibits thermoplasticity. This resin is produced by an addition condensation reaction using a molar excess of phenol to aldehyde in the presence of an acid catalyst. The novolak resin thus obtained can be cured into an insoluble and infusible resin by adding a formaldehyde source such as urotropin and heating it to 200 to 300°C, and the shell mold mold is made by utilizing such a reaction. be. On the other hand, resol resin, which is used as a self-hardening molding binder at room temperature, contains an excess of aldehyde relative to phenol in the presence of an alkaline catalyst [usually phenol:aldehyde = 1:1 to 1:3].
(molar ratio)].
Under these conditions, addition reactions occur primarily, resulting in polymers containing high concentrations of terminal alkylol groups. Since such an alkylol group has a latent crosslinking ability, it is cured by heating or at room temperature using a curing agent such as sulfuric acid or organic sulfonic acid like furan resin. Furthermore, urethane-based binders use active hydrogen components such as polyols and polyisocyanates together with amine-based catalysts to similarly solidify sand. However, in these self-hardening molding methods, the resin and curing agent or catalyst are kneaded with sand and then filled into the mold, so there is a drawback that the pot life is limited due to the curing reaction that occurs immediately after kneading. Furthermore, if the pot life is set to a sufficient length, a large amount of time is required from mold filling to mold removal, which worsens the rotation of the wooden mold and significantly reduces work efficiency. Therefore, a gas curing method has been developed to solve these problems. The first to appear was the Isokure method for urethane binders.
32820). That is, a polyol component and a polyisocyanate component are kneaded with sand, the mixture is filled into a mold, and then amine gas is passed through it to instantly cure the mixture. Also, the SO ₂ process for furan resins and phenolic resins was subsequently developed (Japanese Patent Publication No. 35121/1983, etc.)
There is. That is, after kneading resin and peroxide with sand and filling it into a mold, SO ₂ gas is passed through it, so that SO ₂ is oxidized to sulfuric acid, sulfonic acid, etc., and this becomes a hardening agent. This is a method of curing in a short time. However, when using furan resins and phenolic resins, these methods have certainly solved the problem of pot life in new sand, but when it comes to reclaimed sand, the pot life is shortened due to residual catalyst or curing agent. The question of what happens is unresolved.
Furthermore, since the chemical reaction mode is the same, problems arising from this remain unsolved. In other words, since sulfuric acid or sulfonic acid is used as a hardening agent, the work environment and pollution problems caused by the generation of SO ₂ gas during pouring, and the adverse effects on product castings such as poor spheroidization and sulfurization in ductile castings due to the sulfur content. It has the same drawbacks as conventional self-hardening binders. On the other hand, as a phenolic mold binder that does not contain a sulfur component and has been widely used in the past, there is a shell mold method. However, as mentioned above, this method requires a large amount of thermal energy to create the mold.
It is extremely uneconomical. Furthermore, ammonia and formaldehyde generated during thermal decomposition are also harmful to occupational health.
This is not desirable in terms of both pollution. In view of these circumstances, the present inventors have conducted various studies and studies to solve these difficulties, and as a result, have completed the present invention. That is, the present invention is a curing method in which a sand mold is cured in a short time at room temperature using a liquid phenolic resin as a binder component that does not contain a sulfur component. Specifically, a reaction product or mixture of a polyfunctional compound highly reactive with aldehydes and a phenolic resin is mixed with molding aggregate mainly composed of sand, packed into a mold, and then an aldehyde-containing gas is poured into the mold. The present invention relates to a mold manufacturing method characterized by hardening a sand mold through the inside of the frame. The object of the present invention is to have the ability to harden in a short time at room temperature when used as a mold, and to have moisture resistance and
To manufacture molds that have one or more of the following properties: large resistance pressure, adhesion to various foundry refractory particles, good moldability as a mold, sufficient pot life, and elimination of adverse effects caused by sulfur components. to provide a binder. The phenolic resin referred to in the present invention has the formula (R ₁ , R ₂ , R ₃ represent a hydrogen atom, a hydrocarbon group, an oxyhydrocarbon group, a hydroxyl group) Phenols such as phenol,
m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 2,3,4-
trimethylphenol, 3-ethylphenol,
Alkyl substituted phenols such as 3,5-diethylphenol, p-butylphenol-3,5-dibutylphenol, aryl substituted phenols such as p-phenylphenol, cycloalkyl substituted phenols such as p-cyclohexylphenol, 3,5- Dimethoxyphenol, 3,4,5
- One or more mixtures of alkoxy-substituted phenols such as trimethoxyphenol, p-ethoxyphenol, p-butoxyphenol, p-phenoxyphenol, naphthol, etc. Formula RCHO (R is a hydrogen atom, 1 to 3 It is an initial condensation product with aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and furfural, and the usage ratio is aldehyde:phenol=1. :2
~1:0.8 (molar ratio) is preferred. Phenol is generally preferred as the phenol, and formaldehyde is generally preferred as the aldehyde. Further, as the polyfunctional compound to be reacted or mixed with this phenolic resin, a compound having two or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, a hydraside group, and a hydroxyl group is used. , specifically m-phenylenediamine, 1,4
-Diaminobutane, 2,4-diaminoacetanilide, 1,3,5-triaminobenzene, 4,
Polyamino compounds such as 4'-methylene dianiline, aminophenols such as m-aminophenol, p-aminophenol, and 1-amino-5-naphthol, polyhydroxybenzenes such as resorcin and phloroglucin, isophthalic acid dihydrazide, adipic acid Examples include hydrazine derivatives such as dihydraside and succinic dihydraside. The amount used is 3 to 70% of the phenolic resin.
% by weight, preferably from 5 to 40% by weight, and from 0.15 to 14% by weight relative to the aggregate. Further, the amount of phenolic resin used is 0.5 to 10% by weight based on the sand. A preferred embodiment of the invention consists of the following two steps. That is, a reaction product of a phenol resin and the above polyfunctional compound is kneaded with sand, and the sand uniformly coated with the resin is filled into a mold. Next, aldehyde is blown into the kneaded sand filled in this mold in the form of a gas or spray. This method includes blowing aldehydes that are gaseous at room temperature, such as formaldehyde and acetaldehyde, as they are or as a mixture with an inert gas (e.g., air, nitrogen, etc.); In the case of aldehydes, the aldehydes are contained in an inert gas stream, or are passed in a gaseous state or as fine droplets by a method such as being atomized into an inert gas stream, or by introducing an inert gas into a liquid and bubbling it. The aldehyde used as the curing agent is an aldehyde having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms, such as formaldehyde, acetaldehyde, and propionaldehyde, and preferably has at least one hydrogen at the α-position carbon relative to the carbonyl group. Higher aldehydes with a large number of carbon atoms tend to slow down curing and make the mold soft. These aldehydes can be used alone or as a mixture of two or more. In the present invention, both novolac type and resol type phenolic resins can be used. When using the novolak type, it is dissolved in an organic solvent to form a liquid. Conventional resol resins as self-hardening phenolic resins have a major drawback of increasing viscosity over time, but the resol resins reacted with polyfunctional compounds according to the present invention have improved viscosity stability over time. Furthermore, unlike conventional acid-curing resins (e.g., furan resins, resol resins), this method has the great feature of being applicable to most types of sand. In the present invention, as described above, it is most preferable to perform gas curing using a reaction product obtained by reacting a polyfunctional compound with a phenolic resin in advance. It goes without saying that aldehyde gas or aldehyde fine droplets may be passed through a sand mold formed by adding appropriately and kneading the mixture. Note that the gas amount, ventilation time, gas concentration, etc. vary depending on the shape, size, etc. of the mold, and are appropriately selected. Next, the content of the present invention will be specifically explained using examples. In the examples, all parts and percentages are based on weight unless otherwise specified. Example 1 The charging ratio of phenol and paraformaldehyde
1.6 (molar ratio), and to this, calcium benzoate was added 0.007 times the mole of phenol, and 105
Stir at ~110°C for 3 hours. Add 0.21 times m-aminophenol to this composition and further
After stirring at 105-110℃ for 2 hours, cool and add 0.2 times the total weight of methanol to give a viscosity of 95cp (25℃).
A resin composition with a water content of 10.3% was obtained. This is resin
It is called (A). Further, a resin composition similarly modified with resorcinol instead of m-aminophenol is referred to as resin (B). Example 2 Using m-cresol instead of phenol,
The reaction was carried out according to the method of Example 1 except that isophthalic acid dihydrazide was used instead of m-aminophenol, and the viscosity was 3000 cp (25°C) and the water content was 10.3%.
A resin composition was obtained. This is called resin (C). Example 3 20g of resin (A) was added to 1kg of Freemantle sand and stirred for 1 minute. This was packed into an iron mold (see Figure 1) to form a 50mm x 50mmφ sand mold.
g of gaseous acetaldehyde were passed through with the air. Thereafter, air was further passed through the test piece to drive out the acetaldehyde remaining in the test piece, and the test piece was immediately taken out. This lasted about 2 minutes. The test piece taken out had no foul odor and had a resistive pressure of 23 kg/cm ² . Example 4 20 g of resol resin [viscosity 360 cp (25°C), residual phenol 7%, formaldehyde 0.4%, water 22%] obtained by a conventional method was added to 1 kg of freemantle sand and kneaded, and powdered m-amino Approximately 10g of phenol
After adding and stirring for another 60 seconds, Example-3
The mold was filled in the same manner as above, and 8 g of acetaldehyde was blown in with air at 25°C. After that, the test piece was immediately taken out and the resistance pressure was measured to be 9.1Kg/cm ²
I got it. Incidentally, acetaldehyde gas was blown into the mold under the same conditions as above except that m-aminophenol was not added, but no change was observed and the sand mold could not be taken out. Example 5 Add 20g of resin (C) to 1kg of Freemantle sand,
After stirring for 1 minute, 6 g of gaseous acetaldehyde was passed through according to the method of Example-3. Immediately take out the test piece and measure the anti-pressure, 6.1
Kg/ ^cm2 was obtained. Example 6 The test piece prepared according to the method of Example 4 except that 4.9 g of 1,4-diaminobutane was used instead of m-aminophenol had a counterpressure of 16 Kg/cm ² . Example 7 The influence of casting sand on the present caking method was investigated. That is, after adding and kneading 20 g of resin (A) to 1 kg of the various types of sand shown in Table 1, 5 g of gaseous acetaldehyde was passed through it for 30 seconds according to the method of Example 3, and the sand mold was immediately taken out and resisted. Pressure was measured. It was found that sufficient strength could be obtained as a mold no matter which type of sand was used.

[Table] Example 8 After adding and kneading 20 g of resin (A) to 1 kg of Freemantle sand, 10 g of propionaldehyde was passed in a gaseous state together with air into a sand mold filled according to the method of Example 3. Propionaldehyde is generated by blowing air into the aldehyde and evaporating it. The sand mold thus obtained weighs 14Kg/cm ²
showed a resistance to pressure. Example 9 20 g of resin (B) was added to 1 kg of freemantle sand, kneaded, and placed in a sand mold according to the method of Example 3. Gaseous formaldehyde, which was generated by thermally decomposing about 15 g of paraformaldehyde, was placed in a sand mold. After passing through the sand with air and replacing the formaldehyde by further blowing air, the sand mold was taken out from the mold and the resistance pressure was measured. The counter pressure was 9.8Kg/cm ² . Example 10 50% Novolac resin in 1 kg of Freemantle sand
40g methanol solution and 6g m-aminophenol
was added and kneaded, and about 30 g of acetaldehyde was gasified and passed through a sand mold filled in the mold according to the method of Example 3, thereby obtaining a sand mold having a counter pressure of 5.8 Kg/cm ² . However, without the addition of m-aminophenol, the sand mold did not harden at all. Example 11 A 2.9% solution of novolac resin/methyl ethyl ketone/m-aminophenol mixed in a ratio of 4/4/2 was added to Freemantle sand, kneaded for 1 minute, and molded according to the method of Example 3. It was packed in a frame and 10 c.c. of acetaldehyde was blown in gaseous form over a period of 2 minutes. After leaving it for another 3 minutes, cut out the mold.
The counter pressure was measured. The counter pressure was 10.4Kg/cm ² .

[Brief explanation of the drawing]

FIG. 1 shows an iron gas passing device used in an embodiment of the present invention. 1 is an inlet for aldehyde-containing gas, 2 is an outlet, and 3 is sand. Also X, Y
indicates the dimensions and each is 50mm.

Claims (1)

[Claims] 1 formula (R ₁ , R ₂ , R ₃ represent a hydrogen atom, a hydrocarbon group, an oxyhydrocarbon group, or a hydroxyl group.) Phenols represented by the formula RCHO (R is a hydrogen atom, 1 to 3 carbon atoms A phenol resin (a) which is a condensation product with an aldehyde represented by (a hydrocarbon group having a furan ring), a primary amino group, a secondary amino group, a hydrazide group, and a hydroxyl group. A reaction product or mixture with a compound (b) having two or more functional groups selected from the group is kneaded with a molding aggregate (c) whose main component is sand, and the mixture is filled into a mold, and A method for manufacturing a mold, which is characterized by curing by passing aldehyde (d) in gaseous or fine droplet form into the mold. 2 Compound (b) is m-aminophenol, 1,4-
The method according to claim 1, which is diaminobutane, isophthalic acid dihydrazide, adipic acid dihydrazide, 4,4'-methylene dianiline, 1-amino-5-naphthol, resorcinol, and phloroglucin. 3 The amount of compound (b) used is 0.15 to 14 per aggregate (c)
% by weight. 4. The method according to claim 1, wherein the aldehyde (d) is one or a mixture of two or more of formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, and isobutyraldehyde.