KR920004449B1 - Mould binding agents composition and mfg engineering - Google Patents

Abstract

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Description

Mold binder composition and method for producing casting mold

1 is a representative GPC diagram of a binder composition according to the present invention obtained by molecular weight determination used in the Examples.

2 is a process chart showing the measuring device and the connection method used for the measurement of the molecular weight according to the GPC of the present invention.

* Explanation of symbols for main parts of the drawings

1: solvent stand 2: pump

3: sample injection valve 4: pulse pressure flow control circuit

5: protective column 6: 3000 HXL column

7: 2500 HXL column 8: IR detector

9: Data Processor 10: Liquid Waste

The present invention relates to a method for producing a gas-curable mold binder composition and a casting mold.

In particular, the refinements used in so-called acid-cured cold boxes which introduce gaseous or aerosol sulfur dioxide after the formation of form boxes from dough mixtures of granular refractory and acid-curable resins and peroxides for the production of molds. Binder composition is provided. BACKGROUND OF THE INVENTION A cloning method consisting of thermosetting a so-called coated sand formed by coating a granular refractory material with a phenolic resin to prepare a mold has been widely used in medium or high speed manufacturing of the mold.

In order to save energy and improve mold and composition quality as well as mold manufacturing speed in the manufacture of molds, cold box mold making method which involves curing with gaseous or aerosol substance at normal temperature as a mold manufacturing method instead of the cloning method. Attempts have been made seriously in the molding industry.

The cold box method is an acid-cured cold box method comprising aging an acid-cured resin represented by a furan resin having sulfur dioxide by using a peroxide as an oxidizing agent, and a urethane consisting of curing polyol and polyisocyanate with an aerosol tertiary amine as a catalyst. Includes cold box method.

Among them, the urethane cold box method has disadvantages including the tendency of casting defects such as poor collapsibility of molding sand, sand inclusions, scabs, pinholes and gaps in casting production. Entails.

In contrast, the acid-cured cold box method has recently attracted attention as a method of avoiding the above-mentioned drawbacks.

The acid-cured cold box method has many superior features, such as energy saving, rapid mold making speed, excellent quality molds and excellent quality moldings, compared to the cloning and urethane cold box methods. Acid-curing resins that can be used in acid hardening cold boxes include furan resins, phenolic resins, urea resins, and mixtures and their intercondensates. These resins, except furan resins, are practically flawed in that the initial strength of the mold is low in the acid-cured cold box method. On the other hand, automatic molding machines are used in the medium or mass production of molds. In this case, the kneaded mass made of granular refractory material mixed and surface-coated with the acid-curing resin and the peroxide is automatically filled and molded, such as air pressure, cured, and obtained continuously in one minute or shorter cycles. In this respect, the low initial strength of the mold is a fatal disadvantage. Therefore, acid-curing resins other than furan resins have not yet been put to practical use in the acid-curing cold box method.

In summary, the present invention is as follows.

It is an object of the present invention to provide a mold binder composition comprising a phenolic resin or a furan resin mixed or intercondensed with a phenolic resin as a main component, which provides a mold having a greatly improved initial strength in an acid-cured cold box method. Significantly improve the productivity of the mold.

As a result of intensive studies, the inventors found that the acid-cured cold box method is particularly close between the weight-average molecular weight of the acid-cured resin mainly composed of a phenolic resin or a furan resin mixed and condensed with the phenolic resin and the initial strength of the mold. It was found that the initial strength of the mold can be greatly improved by adjusting the weight-average molecular weight of the acid-curing resin to an appropriate range, thereby significantly improving the productivity of the mold. Based on this finding, the present invention has been completed.

In order to overcome the problems discussed above in the state of the art, the present invention relates to (a) a resol resin obtained by condensation of a substituted or unsubstituted monovalent or divalent phenol compound, or a mixture thereof and an aldehyde compound, (b) the resol resin and Mixtures of furan resins, and (c) resins obtained by mutual condensation of furan resins, said phenolic compounds and aldehyde compounds, said resins being resins having a weight average molecular weight of 300 to 3000 and having at least one element selected from them. Provided is a mold binder composition composed mainly of an acid-cured resin.

The present invention also provides a method for making a mold using the composition described above.

It is preferable in the present invention that the binder composition has the conditions shown below having the general formula (II).

The use of the binder composition of the present invention not only greatly improves the initial strength of the mold, which significantly improves the productivity of the mold, but also the phenolic resin is practically used in the acid-curing cold box method. Regarding the initial strength of the mold, the weight-average molecular weight of acid-cured resins is believed to be closely related to the complex balance of factors such as cure rate, wettability, filling properties, dispersibility of SO ₂ and their interactions. In this respect, the initial strength of the mold is greatly improved when the weight average molecular weight of the binder composition is adjusted to an appropriate range, ie 300 to 3,000, preferably 400 to 3,000. When the weight average molecular weight is out of range, the initial strength of the mold decreases drastically.

The weight average molecular weight of the composition is determined by GPC (gel permeation chromatography). It is important to specify these conditions because the average molecular weight can often have different values when different measurement conditions such as column conditions and reference materials are used.

Measurement conditions used in the present invention will be mentioned in the Examples given later.

In the present invention, when the composition satisfies the condition (II) defined below, it provides a result template having a further improved initial strength.

(A + B) / (3 × B + k × C) = 0.4 to 0.7

Where A is the molar amount of the aldehyde contained in the reaction product as well as the monomer in 100 g of the composition, B is the number of furangos contained in 100 g of composition, C is the number of phenolic hydroxyl groups contained in 100 g of composition, k Is the total number of ortho and para positions of a molecule of phenolic compound which can be introduced by addition reaction with formaldehyde.

The initial strength of the mold is determined by the complex balance of several factors such as wetting force, filling properties, rate of cure, and molecular structure during cure. Stated conditional formula: (A + B) / (3 × B + k × C) is believed to be particularly closely related to light reaction rate and molecular structure during the cure process, and thus is believed to significantly influence the initial strength of the mold . Its suitable range is 0.4 to 0.7. If outside this range, the initial strength of the resulting mold is reduced. Thus, the present invention unexpectedly improves the mold using phenol-furan resin in initial strength.

In the present invention, the composition preferably has a weight-average molecular weight of 400 to 3000. The composition may be formed in two liquid forms. In addition, the composition has a water content of 10% by weight or less, has an alkali metal or alkaline earth metal content in the range of 1% by weight or less, and the pH value is preferably 5-7.

Specific examples of the unsubstituted or substituted monovalent or divalent phenolic compounds used in the present invention include phenol, cresol, xylenol, butylphenol, nonylphenol, resorcinol, methylenebisphenol and catechol.

[General Formula (Ⅰ)]

Phenol compounds represented by are preferred. (Wherein R ₁ and R ₂ are hydrogen atoms or hydrocarbon groups having 1 to 9 carbon atoms) It is preferable to use at least one phenolic compound selected from phenol, cresol and xylenol.

The value of k is the total number of ortho and para positions of a molecule of phenolic compound that can be entered by addition reaction with formaldehyde. The k value for phenol, m-cresol and 3.5-xylenol is 3. The k values for a mixture of two or more phenolic compounds are expressed as an average corresponding to the mixing ratio.

Furan resin in the present invention is an acid-curing mainly composed of furfuryl alcohol, furfuryl alcohol / aldehyde condensate, furfuryl alcohol condensate, furfuryl alcohol / urea / aldehyde condensate, furfuryl alcohol / melamine / aldehyde condensate Although it is resin, it does not restrict | limit especially to these.

Aldehydes usable in the present invention include aromatic and aliphatic aldehydes. Aliphatic aldehydes are preferred. Preference is given to using aliphatic aldehydes with at least one aldehyde selected from formaldehyde, paraformaldehyde, glyoxal, and acetaldehyde. More preferred is at least one aldehyde selected from paraformaldehyde, formaldehyde and an aldehyde consisting of other aldehydes such as glyoxal or acetaldehyde and at least one aldehyde moiety modified above. Aldehydes are usually included in furan resins as well as in their condensates with phenolic compounds. Therefore, the aldehyde accompanying the above conditional formula is contained in both of them.

The binder composition of the present invention consists mainly of a phenolic resin mixed or co-condensed with a furan resin, but such a resin may be mixed or co-condensed with, for example, a urea of an urea / aldehyde condensate as a modifier, or at least one known. It can be mixed or co-condensed with a transfer agent of. Specific examples of known denaturants include coumarone-indene resin, petroleum resin, polyester, alkyd resin, polyvinyl alcohol, epoxy resin, ethylene / vinylacetate, polyvinylacetate, polybutadiene, polyether, polyethyleneimine, polyvinyl chloride Polymers and oligomers such as polyacrylates, polyvinyl butyral, phenoxy resins, cellulose acetates, xylene resins, toluene resins, polyamides, styrene resins, polyvinyl formals, acrylic resins, urethane resins and nylons; Natural substances such as lignin, lignin sulfonic acid, rosin, ester rubber, vegetable oil, bitumen, heavy oil, cashew nut shell oil and vanillin and tannins; Polysaccharides and derivatives thereof such as starch, cornstarch, glucose and dextrin; Reaction residues and by-products such as resorcinol residues, cresol residues, reaction byproducts between 2,2,4-trimethyl-4- (hydroxyphenyl) coumarone and isopropylphenol, and reaction byproducts between terephthalic acid and ethylene glycol; Polyhydric alcohols such as polyethylene glycol; Condensates with ketones and their aldehydes, such as acetone, cyclohexanone and acetophenone; Amino or imino compounds such as dicyandiamide, acrylamide and thiourea and their condensates with aldehydes; Aldehyde compounds such as furfural and glyoxal; And ester compounds such as isocyanurates and esters of unsaturated fatty acids. The degree of denaturation with the modifier is preferably 20% or less.

By controlling the viscosity of the binder composition of the present invention by adjusting the reaction conditions or with a diluent at 1 to 1,000 cps at 25 ℃ can further improve the initial strength of the mold. Too high viscosity leads to a reduction in the wettability of the molding as well as uniform dispersibility.

Specific examples of diluents which can be used for the above purposes include aromatic hydrocarbons such as benzene and xylene; Alcohols such as methanol, ethanol and furfural alcohol; Ethers such as diethyl ether, anisole and acetal; Ketones such as acetone and methyl ethyl ketone; Heterocyclic hydrocarbons such as tetrahydrofuran and dioxane; Esters such as methyl acetate and ethyl acetate; Polyhydric alcohols such as ethylene glycol and glycerin; Cellosolves such as 2-methoxyethanol and 2-ethoxyethanol; Cellosolve acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, and 2-phenoxyethyl acetate and carbitol acetates such as diethylene glycol monoethyl ether acetate, At least one of these is used. The diluent may be incorporated into the binder composition in advance or just prior to kneading the composition with the foundry sand. The amount of diluent is preferably 20% or less based on the composition.

The content of water included in the composition of the present invention is preferably 10% or less.

When the water content is larger, the effect of the present invention is drastically reduced.

The amount of the monomer phenol compound included as the unreacted compound is preferably 10% or less. When a large amount of monomeric phenolic compounds is included, the initial strength is drastically reduced or the storage stability is reduced. The amount of monomer aldehyde included as unreacted mixture or the like is also preferably 10% or less. When a large amount of monomer aldehyde is included, the workability is severely weakened due to the odor from the monomer aldehyde.

Silane coupling agents may be incorporated for the purpose of further enhancing the strength of the mold. Examples of such silane coupling agents include r- (2-amino) aminopropylmethyl dimethoxysilane, r-aminopropyl trimethoxysilane, r-aminopropyltriethoxysilane, r-aminomercaptopropyltrimethoxysilane And α-glycidoxypropyltrimethoxysilane.

Curing agents that can be used in the self-curing casting method of the present invention include organic sulfonic acids such as p-toluenesulfonic acid and xylenesulfonic acid; Inorganic acids such as phosphoric acid and sulfuric acid and mixtures thereof. However, the curing agent is not particularly limited to those described above. Peroxides that can be used in the acid hardening cold box process include, for example, ketones and organic peroxides in aromatic form; And inorganic peroxides such as hydrogen peroxide. However, the peroxides used are not particularly limited to them.

In the production of molds, zircon yarns, chromite yarns and olivine yarns as well as silica yarns consisting mainly of quartz-like materials can be used together with the binder of the present invention as load-bearing granules. However, it is not limited to the above materials.

The addition time of the binder resin composition may be before or after kneading the curing agent or the peroxide with the foundry sand, but after the addition of the curing agent in the case of a self-curing mold and the addition of the peroxide and the kneading transition in the case of an acid-curing cold box. It is desirable because longer pot life is ensured.

The binder composition according to the invention can be effectively used in the casting mold manufacturing method. The process is practical consisting of mixing sand grains with the caking agent composition and peroxide as described above, introducing the mixture into the master and curing the formed mixture with sulfurized sulfur gas. This method is described in Japanese Patent Publication A (Unexamined) No. Published in 57-137051. It is preferable in this method to use 100 parts by weight of the particles, 0.4 to 3 parts by weight of the binder composition and 0.01 to 0.3 parts by weight of peroxide as the effective oxygen. Peroxides preferably include methylethylketone hydroperoxide and acetone hydroperoxide.

The following examples will illustrate the present invention in more detail, but should not be construed as limiting the scope of the invention.

The weight average molecular weight mentioned in the present invention is measured under the following conditions according to GPC. This is the weight average molecular weight in the region towards the higher molecular weight than that corresponding to the negative peak given to water.

(a) Preparation Example: The composition is dissolved in the solvent of THF without any special treatment.

Concentration: 1%

Insoluble matter: Filtered by syringe with attached 0.5 μm membrane filter (Teflon).

Injection volume: 20 μl.

(b) Column: Protective columns TSK (Toyo Soda Kogyo Kabukishiki) HXL (6.5 mm x 30 cm), TSK3000 HXL (7.8 mm x 30 cm), and TSK2500 HXL (7.8 mm x 30 cm). From the inlet side, it is connected in the order of protection column → 3000HXL → 2500HXL.

(c) Reference material: polystyrene (Toyo Soda Kogyo Kabuki Seiki Co., Ltd.)

(d) Eluent: THF. Flow rate: 1 ml / min (pressure: 40 to 70 kg / ㎠)

(e) Column temperature: room temperature (20-25 ° C.)

(f) Detector: RI (Differential Refractometer)

(g) Split plot experiment to calculate molecular weight: time split (2 seconds)

In the case of an RI detector, a negative peak given to water appears as shown in FIG. 1 and peaks for low molecular weight compounds such as formaldehyde are included within that negative peak. The weight average molecular weight of the binder composition as defined in the present invention is one of the peaks of the positive molecular weight (A region) side except the negative peak (B region) as shown in FIG.

The measuring apparatus and method used for the GPC measurement is shown in FIG. In the figure, numeral 1 represents a solvent, 2 a pump, 3 a sample injection valve, 4 a pulsed pressure flow control circuit, 5 a guard column, 6 a 3000HXL column, 7 a 2500HXL column. 8 denotes an IR detector, 9 a data processor, and 10 a liquid waste.

[Examples 1 to 5 and Comparative Examples 1 and 2]

Phenol and paraformaldehyde were reacted in the presence of a basic catalyst of NaOH for a predetermined time according to a conventional method. After completion of the reaction, the reaction mixture was neutralized with p-toluenesulfonic acid aqueous solution and mixed with 10% methanol. The weight average molecular weight of the product was found by the above measurement method. Various binder compositions listed in Table 1 were obtained.

1.2 parts by weight of each of the obtained compositions was added to 100 parts by weight of Flatty Silica yarn from Australia, kneaded together, and then 0.4 parts by weight of MEKPO peroxide was added and kneaded. The kneaded yarn was blown together with compressed air to fill a 25 x 25 x 250 m / m flask. Subsequently, the flask was filled with a flask kneaded with sulfur dioxide gas to form a mold test piece, and the bending strength thereof was measured at 30 seconds after the blowing of sulfur dioxide gas.

The results are shown in Table 1.

TABLE 1

[Examples 6 to 9 and Comparative Examples 3 and 4]

Phenol, furfuryl alcohol and paraformaldehyde were reacted in the presence of a NaOH basic catalyst for a designated time according to a conventional method. After completion of the reaction, the reaction mixture was neutralized with p-toluenesulfonic acid aqueous solution and mixed with 10% methanol. As listed in Table 2, a binder composition having a weight average molecular weight was obtained.

Using the obtained binder composition, the test piece was molded in the same manner as in Examples 1 to 5, and then its bending strength after 30 seconds was measured.

The results are shown in Table 2.

TABLE 2

[Examples 10 to 12]

According to the conventional method, phenol and paraformaldehyde were reacted in the presence of a KOH catalyst. After completion of the reaction, the reaction mixture was neutralized with an aqueous p-toluenesulfonic acid solution to obtain a binder composition having a viscosity of 4,200 cps and a weight average molecular weight of 560 at 25 ° C. The composition was diluted with a predetermined amount of ethyl cellosolve acetate to obtain a composition having the viscosity listed in Table 3.

Using the obtained binder composition, the mold test pieces were molded in the same manner as in Examples 1 to 5, and then the bending strength was measured.

The results are shown in Table 3.

TABLE 3

[Examples 13 to 18 and Comparative Examples 5 and 6]

According to the conventional method, phenol, furfuryl alcohol and paraformaldehyde were reacted in various amounts for a predetermined time. After completion of the reaction, each reaction mixture was neutralized with p-toluenesulfonic acid aqueous solution and mixed with 5% methanol. Thus, a binder resin composition each having the weight average molecular weight and the conditions defined by the formula (A + B) / (3 × B + k × C) was obtained as listed in Table 4. They were tested for their initial strength in accordance with acid-hardened cold boxes. Next, each composition was molded into a test piece of a mold, which was measured for bending strength.

The results are shown in Table 4.

TABLE 4

[Examples 19 to 24 and Comparative Examples 7 and 8]

In a conventional manner, phenol and para-formaldehyde were reacted with each other in the presence of a NaOH basic catalyst. After the reaction, the reaction mixture was neutralized with aqueous para-toluenesulfonic acid solution and mixed with 10% methanol. The compositions as listed in Table 5 were obtained. They were each tested in the same manner as shown in Example 1 regarding the initial strength.

TABLE 5

Claims (6)

(a) a phenolic compound of phenol, cresol or xylenol, or a mixture thereof and a resol resin obtained by condensation of an aliphatic aldehyde, (b) a mixture of said resol resin and furan resin, and (c) furan resin, Containing one or two or more constituents selected from the resins obtained by the co-condensation of the phenol compounds and aliphatic aldehydes as a main component, and having an acid-curable resin for sand casting having a weight average molecular weight of 300 to 3000 Mold binder composition characterized in that. The mold binder composition according to claim 1, wherein the following conditions are satisfied. (A + B) / (3 × B + k × C) = 0.4 to 0.7 Where: molar amount of the aldehyde contained in the form of the reaction product as well as the monomer in 100 g of the composition B: number of furango contained in 100 g of the composition C: number of phenolic hydroxyl groups contained in 100 g of the composition k: the total number of ortho and para positions of one molecule of the phenolic compound which can enter by addition reaction with formaldehyde The mold binder composition according to claim 1, wherein the aldehyde compound is selected from formaldehyde, paraformaldehyde, glyoxal and acetaldehyde. The mold binder composition according to claim 1, wherein the resin has a weight average molecular weight of 400 to 3000. A method for producing a casting mold, comprising mixing the four particles with the binder composition and the peroxide as defined in claim 1, introducing the mixture into a pattern, and curing the molded mixture with sulfur dioxide gas. The method for producing a casting mold according to claim 4, wherein 100 parts by weight of incorporating sand, 0.4 to 3 parts by weight of the binder composition, and 0.01 to 0.3 parts by weight of peroxide are used as effective oxygen.

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