JPH0569619B2 - - 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 method 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. This invention relates to an improved binder composition for use in boxes. [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 foundry 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 as Among these, molds using urethane cold boxes have poor disintegration of casting sand during casting production.
It has drawbacks such as 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] Acid-curable cold boxes save energy during mold production, are faster in mold production, and have superior quality of manufactured molds and castings, etc., compared to conventional cloning methods and urethane. It has many features superior to cold boxes. On the other hand, acid-curable resins used in acid-curable cold boxes include furan resins, phenol resins, urea resins, and mixtures or cocondensates thereof. However, in practical use, resins other than furan-based resins have a drawback in that the initial strength of the mold is low in the acid-curing cold box method. On the other hand, automatic molding machines are used to manufacture medium to large quantities of molds, in which acid-curing resin and peroxide are added and kneaded to the refractory granular material to coat the surface of the refractory granular material, and air pressure etc. Since filling, molding, curing, and ejection are automatically performed continuously in a cycle of less than one minute, the low initial strength of the mold is a fatal drawback in the cold box method. Therefore, in the acid-curable cold box method, acid-curable resins other than furan-type resins have not yet been put into practical use. The present invention uses a phenolic resin or a furan resin mixed or co-condensed with a phenolic resin, which greatly improves the initial strength of the mold and significantly improves mold productivity in the acid-curing cold box method. The object of the present invention is to provide a binder composition for molds based on the present invention. [Means for Solving the Problems] As a result of intensive research, the present inventors have found that, in the acid-curing cold box method, a phenol resin or a furan resin mixed or co-condensed with a phenol resin is used as the main ingredient. We found that there is a close relationship between the weight average molecular weight of the acid-curing resin and the initial strength of the mold, and by adjusting the weight-average molecular weight of the acid-curing resin within an appropriate range, we were able to increase the initial strength of the mold. The present inventors have discovered that the present invention is greatly improved and the productivity of molds is significantly improved, leading to the completion of the present invention. That is, the present invention uses an acid-curable resin as a binder,
A binder composition used in a gas-curing mold manufacturing method in which a mold is molded with sulfur dioxide using peroxide as an oxidizing agent, in which an acid-curing resin is mixed or co-condensed with a phenolic resin or a phenolic resin. The present invention relates to a binder composition for molds, which is mainly composed of a furan-based resin and has a weight average molecular weight of 300 to 5,000. The binder composition of the present invention significantly improves the initial strength of molds, significantly improves mold productivity, and makes it possible to practically use phenolic resins in acid-curing cold box methods. Ta. The weight average molecular weight of the acid-curing resin with respect to the initial strength of the acid-curing cold box mold is determined by the interaction of complex factors such as curing speed, wettability, filling properties, and SO ₂ diffusivity. It is thought to be closely related to balance. Therefore, by adjusting the weight average molecular weight of the acid-curable resin to an appropriate range, that is, from 300 to 5,000, preferably from 300 to 3,000, the initial strength of the mold can be significantly improved. If the weight average molecular weight is outside the above range, the initial strength will decrease significantly. Note that the weight average molecular weight of the acid-curable resin is determined by GPC (gel permeation chromatography). However, the average molecular weight may show different values depending on the measurement conditions such as column conditions and standard substances, so it is important to specify the conditions. The measurement conditions in the present invention are shown in the Examples below. In addition, there is a close relationship between the number of moles of aldehyde, the number of furan rings, the number of moles of phenol compound, and the number of reaction points contained in the form of reactants or monomers in the acid-curing resin and the initial strength of the mold. There is.
That is, the initial strength of the mold is determined by a complex balance of various factors, such as wettability, fillability, curing reaction rate, and molecular structure during the curing process. Conditional formula (A + B) / (3 × B + k × C) However, A: Number of moles of aldehyde contained in 100 g of the composition in the form of a reactant or monomer B: Number of furan rings contained in 100 g of the composition C: Number of phenolic hydroxyl groups contained in 100 g of the composition k: The total number in one molecule of the above-mentioned phenolic compound at the ortho and para positions in a state capable of addition reaction with formaldehyde is determined by the curing reaction rate and curing process molecule among the above factors. It seems to be closely related to the structure and has a great influence on the initial strength of the mold. The appropriate range is 0.3 to 1.0, preferably 0.4 to 0.7, and if it is outside this range, the initial strength will be extremely low. The phenolic resin and the furan resin mixed or co-condensed with the phenolic resin in the present invention are resins mainly composed of a condensate of a phenol compound and an aldehyde, and the phenolic compound used is, for example, phenol, cresol,
These include xylenol, resorcinol, methylenebisphenol, and catechol, and preferably at least one selected from phenol, cresol, and xylenol. Furthermore, examples of the aldehyde used in the phenolic resin in the present invention include aromatic aldehydes and aliphatic aldehydes, but aliphatic aldehydes are preferred. Preferred aliphatic aldehydes are at least one of formaldehyde, paraformaldehyde, glyoxal, and acetaldehyde, and more preferred are:
Paraformaldehyde, at least one type of formaldehyde or a part thereof, glyoxal,
It is an aldehyde modified with other aldehydes such as acetaldehyde. In the present invention, the furan-based resin mainly includes furfuryl alcohol, furfuryl alcohol/aldehyde condensate, furfuryl alcohol condensate, furfuryl alcohol/urea/aldehyde condensate, furfuryl alcohol/melamine/aldehyde condensate, etc. It is an acid-curable resin that is not particularly limited. The binder composition of the present invention is mainly composed of a phenolic resin or a furan resin mixed or co-condensed with a phenolic resin, but it may be mixed or co-condensed with, for example, urea or a urea/aldehyde condensate as a modifier. Alternatively, at least one of conventionally known modifiers can be mixed or co-condensed. Specific examples of conventionally known modifiers include coumaron/indene resin, petroleum resin, polyester, alkyd resin, polyvinyl alcohol, epoxy resin, ethylene/vinyl acetate, polyvinyl acetate, polybutadiene, polyether, polyethyleneimine, and polychloride. Vinyl, polyacrylic acid ester, polyvinyl butyral, phenoxy resin, cellulose acetate,
Polymers and oligomers such as xylene resin, toluene resin, polyamide, styrene resin, polyvinyl formal, acrylic resin, urethane resin, nylon, lignin, lignin sulfonic acid, rosin, ester gum, vegetable oil, bitumen, heavy oil, cashew nut shell liquid, vanillin. , natural products such as tannins, saccharides and their derivatives such as starch, corn starch, glucose, dextrin, resorcin residues, cresol residues, 2,2,4-trimethyl-4-(hydroxyphenyl)coumarone and isopropenyl. Reaction residues and by-products such as reaction by-products of phenol, reaction by-products of terephthalic acid and ethylene glycol, polyhydric alcohols such as polyethylene glycol, condensates with ketones and aldehydes such as acetone, cyclohexanone, and acetophenone, These include amino or imino compounds such as dicyandiamide, acrylamide, and thiourea, and their aldehyde condensates; aldehyde compounds such as furfural and glyoxal; and ester compounds such as isocyanuric acid esters and unsaturated fatty acid esters. The modification rate of these modifiers is preferably 20% or less. Furthermore, the viscosity of the binder composition in the present invention can be adjusted to 1 to 1 at 25°C by controlling the reaction conditions and using a diluent.
By setting it to 1000 cps, the initial strength of the mold can be further improved. If the viscosity is too low, the resin will be adsorbed into the microscopic pores on the surface of the sand grains, which will prevent the resin from effectively coating the surface of the sand grains. If the viscosity is too high, the wettability and uniform dispersibility of the resin to foundry sand will decrease. Specific examples of diluents that can be used for the above purpose include aromatic hydrocarbons such as benzene and xylene;
Alcohols such as methanol, ethanol and furfuryl 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, 2-methoxyethyl acetate,
Examples include at least one of cellosolve acetates such as 2-ethoxyethyl acetate, 2-butoxyethyl acetate, and 2-phenoxyethyl acetate, and carbitol acetates such as diethylene glycol monoethyl ether acetate. The diluent may be mixed into the binder composition in advance or may be mixed into the composition immediately before kneading the foundry sand. It is preferable that the blending amount is 20% or less based on the composition. Further, the amount of water contained in the composition of the present invention is preferably 10% or less. If more water is contained, the effects of the present invention will be significantly reduced. Further, the amount of monomer phenol compounds contained as unreacted substances is preferably 10% or less. If more monomer phenol compounds are contained, the initial strength will be significantly lowered or the storage stability will be deteriorated. Further, the amount of monomer aldehyde contained as unreacted substances is also preferably 10% or less. If more monomer aldehyde is contained, workability will be significantly deteriorated due to the odor caused by the monomer aldehyde. Furthermore, a silane coupling agent may be added for the purpose of further improving the strength of the mold. Examples of the silane coupling agent include γ-(2-amino)aminopropylmethyldimethoxysilane,
Examples include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane. The binder composition of the present invention may be kneaded and added to the foundry sand either before or after peroxide addition and kneading, but since the pot life of the kneaded sand is longer, peroxide It is preferable to use it before addition and kneading. In order to manufacture the mold, silica sand mainly composed of quartz, zircon sand, chromite sand, 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 is not something that will be done. 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. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples. In addition, the weight average molecular weight in the present invention is
Measured by GPC under the following conditions, it is the weight average molecular weight in the region on the polymer side from the negative peak due to water. (a) Sample preparation: The composition is prepared without any special treatment.
Soluble in THF solvent. Concentration: 1%. Insoluble matter;
Attach a 0.5μm membrane filter (made of Teflon) to the syringe and filter. Injection volume: 20μ. (b) Column: Guard column TSK (manufactured by Toyo Soda Kogyo Co., Ltd.)
1 HXL (6.5mmφ×4cm) and TSK3000HXL
(7.8mmφ×30cm) and TSK2500H×L (7.8mm
φ×30cm) 1 piece. Guard column from the inlet side →
3000HXL → 2500HXL connection. (c) Standard substance: Polystyrene (manufactured by Toyo Soda Kogyo Co., Ltd.) (d) Eluent: THF. Flow rate: 1 ml/min (pressure 40 to 70 kg/min)
^cm2 ). (e) Column temperature: Room temperature (20-25℃) (f) Detector: RI (differential refractometer) (g) Division method for molecular weight calculation: Time division (2 seconds) However, in the case of an RI detector, As shown in FIG. 1, a negative peak due to water appears, and the peak of low molecular weight compounds such as formaldehyde is also included in this negative peak. The weight average molecular weight of the binder composition in the present invention refers to the positive peak (area A) on the polymer side excluding the negative peak (area B) shown in FIG.
is the weight average molecular weight of The measurement equipment and connection method used for GPC measurements are shown in Figure 2. In the figure, 1 is a solvent,
2 is a pump, 3 is a sample injection valve, 4 is a pulsation/pressure/flow control circuit, 5 is a guard column, and 6 is a
3000HXL column, 7 is 2500HXL column, 8 is RI
9 is a data processing device, and 10 is a waste liquid. Examples 1 to 5 and Comparative Examples 1 to 2 Phenol and paraformaldehyde were reacted for a predetermined time under a NaOH basic catalyst by a conventional method,
After the reaction was completed, the mixture was neutralized with an aqueous para-toluenesulfonic acid solution, 10% methanol was added, and the weight average molecular weight was determined by the above measurement method to obtain various binder compositions shown in Table 1. 1.2 parts by weight of the obtained binder composition was added to 100 parts by weight of Australian flattery silica sand, and kneaded.
Mixed sand mixed with 0.4 parts by weight of MEKPO peroxide was blown into a 25 x 25 x 250 m/m mold with pressurized air, and then sulfur dioxide gas was added to the mold filled with the mixed sand. A mold test piece was formed by blowing into the frame, and the mold bending strength was measured 30 seconds after the sulfur dioxide gas was blown into the frame. The results are shown in Table 1.

[Table] Examples 6 to 9 and Comparative Examples 3 to 4 Phenol, furfuryl alcohol, and paraformaldehyde were reacted for a predetermined time under a NaOH basic catalyst by a conventional method, and after the reaction was completed, neutralized with an aqueous solution of para-toluenesulfonic acid. 10% methanol was added to obtain a binder composition having the weight average molecular weight shown in Table 2. Using the obtained binder composition, a mold test piece was molded by the method shown in Examples 1 to 5, and the mold bending strength was measured after 30 seconds. The results are shown in Table-2.

[Table] Examples 10 to 12 Phenol and paraformaldehyde were reacted in the presence of a KOH catalyst using a conventional method, and after the reaction was completed, the viscosity at 25°C was neutralized with an aqueous solution of paratoluenesulfonic acid.
A binder composition having a weight average molecular weight of 560 and a weight average molecular weight of 4200 cps was obtained. This was diluted with a predetermined amount of ethyl cellosolve acetate to obtain a composition having a viscosity shown in Table 3. Using the obtained binder composition, mold test pieces were molded in the same manner as shown in Examples 1 to 5,
Bending strength was measured. The results are shown in Table-3.

[Table] Examples 13 to 18 Various reaction amounts of phenol, furfuryl alcohol, and paraformaldehyde were reacted for a predetermined time using a conventional method, and after the reaction was completed, the mixture was neutralized with an aqueous solution of paratoluenesulfonic acid, 5% methanol was added, and the weight average Molecular weight and conditional formula (A+B)/(3×B+k×
Various binder resin compositions having the values of C) shown in Table 4 were obtained. Using the obtained binder composition, mold test pieces were molded in the same manner as shown in Examples 1 to 5,
Bending strength was measured. The results are shown in Table 4.

[Table] Examples 19 to 24 Phenol and paraformaldehyde were reacted under NaOH basic catalyst by a conventional method, and after the reaction was completed, neutralized with an aqueous solution of para-toluenesulfonic acid, 10% methanol was added, and the weight average molecular weight and conditional formula ( A
Various binder resin compositions having the values of +B)/(3×B+k×C) shown in Table 5 were obtained. Using the obtained binder composition, mold test pieces were molded in the same manner as shown in Examples 1 to 5,
Bending strength was measured. The results are shown in Table-5.

〔Effect of the invention〕

As is clear from this example, in the acid-curing cold box method using an acid-curing resin mainly composed of a phenolic resin or a phenol-furan resin as a binder, the present invention particularly reduces other performances. It is possible to significantly improve the initial strength of the mold, and the productivity of the mold can be significantly improved.

[Brief explanation of drawings]

Figure 1 is a typical GPC chart of the binder composition of the present invention obtained by the molecular weight measuring method used in the Examples, and Figure 2 is the measuring equipment used in the molecular weight measurement by GPC in the present invention. and a process diagram showing a connection method. In the figure, 1 is the solvent, 2 is the pump, 3 is the sample injection valve, 4 is the pulsation/pressure/flow control circuit, 5 is the guard column, 6 is the 3000HXL column, and 7 is the
2500HXL column, 8 is an RI detector, 9 is a data processing device, and 10 is a waste liquid.

Claims (1)

[Scope of 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 a peroxide as an oxidizing agent, which The curable resin is mainly composed of a phenol resin or a furan resin mixed or co-condensed with a phenol resin, and the weight average molecular weight is 300.
A binder composition for molds, characterized in that it has a molecular weight of 5000 to 5000. 2 The weight average molecular weight of the acid-curing resin is 300 to 3000
The composition according to claim 1. 3. The composition according to claim 1, wherein the acid-curable resin satisfies the conditions shown in the following formula. (A+B)/(3×B+k×C)=0.3-1.0 However, A: Number of moles of aldehyde contained in 100 g of the composition in the form of a reactant or monomer B: Number of furan rings contained in 100 g of the composition C: Number of phenolic hydroxyl groups contained in 100 g of composition k: Total number in one molecule of the above phenolic compound at ortho and para positions capable of addition reaction with formaldehyde 4 The phenolic resin consists of phenol, cresol and xylenol. The composition according to claim 1, which is mainly composed of a condensate of at least one selected from the group consisting of an aldehyde and an aldehyde. 5. The composition according to claim 4, wherein the aldehyde is an aliphatic aldehyde. 6. The composition according to claim 5, wherein the aliphatic aldehyde is at least one of formaldehyde, paraformaldehyde, glyoxal, and acetaldehyde.