JPS5927671B2 - Manufacturing method for resin-coated sand - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing resin-coated sand.

When forming molds or cores for foundries, resin-coated sand is used, and phenolic resin has conventionally been used as a binder for this resin-coated sand.

However, when phenolic resin is used as a binder, hexamethylenetetramine is used as a hardening agent, which causes an ammonia odor during firing, and when casting metals with low casting temperatures such as aluminum and copper alloys, phenolic resin-coated sand may not be used in the mold. When used as a core, it has drawbacks such as poor disintegration after casting. In order to solve this drawback, we have previously proposed a resin composition for bonding foundry sand grains, which is made by adding diallyl phthalate monomer as a crosslinking agent to unsaturated polyester. This resin composition is an extremely excellent binder for foundry sand, as it does not generate unpleasant odors or harmful gases during firing, and has good disintegration properties after casting because the unsaturated polyester contains ester bonds. . In order to sufficiently increase the strength of the unsaturated polyester used in such a binder when molded into a mold or core, a silane coupling agent, a catalyst for polymerizing the unsaturated polyester, and a liquid crosslinking agent are added. Among these additives, the catalyst has the property of polymerizing the unsaturated polyester when heated after addition, and once added to the unsaturated polyester, the catalyst cannot be heated for forming molds, cores, etc. Furthermore, the silane coupling agent has the property that it evaporates rapidly at high temperatures above the softening point of the unsaturated polyester. Furthermore, since the amount of these silane coupling agents and polymerization catalysts added to the unsaturated polyester is small, it has been difficult to uniformly mix them into the unsaturated polyester. The aforementioned difficulty is further compounded by the fact that a hot-melt method is generally used to coat sand with binder, in which the sand is heated to a temperature above the binder's softening point, and then the binder is added and stirred. was.
In other words, if these additives are added to unsaturated polyester in advance to create an unsaturated polyester composition, if a hot melt method is used to coat sand with these unsaturated polyester compositions, the sand will be heated at this point. As a result, the catalyst acts and the unsaturated polyester is polymerized, so that when molds, cores, etc. are molded, almost no polymerization takes place and the strength of the molds, cores, etc. is insufficient.

If you add the silane coupling agent, catalyst, etc. to the heated sand first and then add the unsaturated polyester and stir, the addition of the silane coupling agent and catalyst will lower the sand temperature, which will reduce the unsaturated polyester. The temperature is too low to add polyester. Also, conversely, it is possible to raise the sand temperature at the time of adding the silane coupling agent etc. to make the temperature at the time of coating the unsaturated polyester appropriate, but it is possible to There is a problem that the silane coupling agent evaporates during the process, producing a strange odor and reducing the amount of the silane coupling agent.

There is also a method of producing coated sand by dissolving these unsaturated polyesters and all other additives in a solvent, kneading this solution with foundry sand, and volatilizing the solvent. Polyester has problems such as being insoluble or poorly soluble in common solvents and causing environmental deterioration due to volatilization of the solvent. As a result of various research into a method for producing resin-coated sand that improves the conventional drawbacks when using such an unsaturated polyester resin composition as a binder, the present inventors have developed a specific uncured unsaturated polyester resin described below. The present inventors have discovered that an excellent method for producing resin-coated sand can be obtained by coating sand grains using a silane coupling agent, a catalyst, and a crosslinking agent as a starting material, and separately adding a silane coupling agent, a catalyst, and a crosslinking agent during kneading. .

Therefore, the method for producing resin-coated sand of the present invention involves using an unsaturated polyester alone or a liquid copolymerizable with the unsaturated polyester, which is solid at room temperature, has no tackiness, and has a viscosity of 500 poise or less above its softening point. After the uncured product of unsaturated polyester mixed with a crosslinking agent becomes molten during the process of coating the foundry sand grains by the hot melt method, a silane coupling agent and a polymerization catalyst are respectively applied. It is characterized in that a solution dissolved in a liquid crosslinking agent alone or together is added, stirred and the sand grains are coated with the resin.

The amount of the silane coupling agent is 0.1 to 5 parts by weight based on 100 parts by weight of the uncured polyester, and the amount of the polymerization catalyst is 0.1 to 5 parts by weight based on 100 parts by weight of the uncured polyester.
．． The total amount of the liquid crosslinking agent is 5 to 50 parts by weight based on 100 parts by weight of the uncured polyester. In addition, the meaning of the total amount here means the total amount including the liquid crosslinking agent, if the liquid crosslinking agent has already been added to the uncured polyester material. In the method of the present invention, the step of coating the foundry sand grains with resin is usually carried out in a mixer, and after the sand grains are coated with the resin, the sand grains are thoroughly mixed until the sand temperature drops below the softening point. The coating resin solidifies and the sand grains separate from each other, so if the sand is discharged from the mixer at this point, the desired resin-coated sand can be obtained. The invention will be described in further detail below.

In the present invention, unsaturated sand is solid at room temperature, has no viscosity, has a viscosity of 500 poise or less at a softening point or higher, particularly at a softening point of 60°C or higher, preferably 80°C or higher, and is capable of producing coated sand by a hot melt method. Examples of the uncured polyester include crystalline unsaturated polyester.

Raw materials for the crystalline unsaturated polyester include α,β unsaturated dibasic acids such as maleic anhydride, citraconic acid, fumaric acid, mesaconic acid, and substituted products thereof, all of which react at room temperature. It is solid and has crystallinity. Among these, those exhibiting steric symmetry, such as fumaric acid and mesaconic acid, are particularly preferred in order to increase the crystallinity of the unsaturated polyester. Examples of saturated dibasic acids include terephthalic acid, dimethyl terephthalate, adipic acid, sebacic acid, azelaic acid, isophthalic acid, endomethylenetetrahydrophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, anthracene maleic anhydride, and their like. Examples include adducts and substitution products. Among these, those exhibiting steric symmetry, such as terephthalic acid, dimethyl terephthalate, and adipic acid, are particularly preferred in order to enhance the crystallization of unsaturated polyesters. Glycols include ethylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol, hexanediol-1.6
, neopentyl glycol, hydrogenated bisphenol A,
Examples include meta-xylene glycol and substituted products thereof. All of these are solid and crystalline at room temperature, or exhibit steric symmetry. When replacing at least one α,β-unsaturated dibasic acid among these groups and, if necessary, a part of the α,β-unsaturated dibasic acid, by a saturated dibasic acid, at least a saturated dibasic acid is used. Select a type of dibasic acid as the acid component,
On the other hand, at least one type from the glycol group is selected and polyesterified by a known method, heated above the melting point, and the degree of crystallinity is adjusted by cooling rate, addition of crystal nuclei, etc., and the average molecular weight is 1000 to 2000 and viscous at room temperature. It is possible to obtain a solid without coagulation.

For the unsaturated polyester thus obtained,
Furthermore, it is possible to make the crosslinking agent's unsaturated monomer and unsaturated prepolymer singly or as an uncured resin by blending both to 500 poise or less in a temperature range of 30°C or more from the upper limit of the softening temperature range at room temperature. be.

Here, "non-adhesive solids" are those that can be made into small pieces with a maximum dimension of 4 mm or less, and that these small pieces do not stick together to form large lumps, and that these small pieces can be sieved using a standard 4-mesh sieve. This refers to a block of 1009 that completely passes a rotor tap tester manufactured by Tokuju Seisakusho within 10 seconds.

Although the crystalline unsaturated polyester has been explained above, in the present invention, for the "uncured unsaturated polyester product that is solid at room temperature, has no stickiness, and exhibits a viscosity of more than the softening point and less than 500 poise", the unsaturated polyester is crystalline. It is not limited to only sexually unsaturated polyesters.

The liquid crosslinking agent for the uncured unsaturated polyester used in the present invention preferably has good reactivity during curing, high heat resistance strength, and low volatility, such as chloromethylene diaryl phthalate, triaryl Examples include lucyanurate, diallylbenzenesulfonate, and the like.

Regarding this liquid crosslinking agent, 5 to 10
Parts by weight may be added in advance. The amount of liquid crosslinking agent to be added separately later is 10% of the uncured unsaturated polyester.
It is necessary that the amount of the crosslinking agent be 5 parts by weight or more based on 0 parts by weight, and the total amount of the crosslinking agent should not exceed 50 parts by weight. In this case, if the amount of liquid crosslinking agent to be separately added is less than 5 parts by weight, the catalyst and silane coupling agent will not be uniformly dispersed in the coating resin due to the small amount of added solution, and the firing strength will decrease.
If the amount exceeds 0 parts by weight, seepage will occur from the surface of the crystalline resin-coated sand, worsening sand clogging and reducing firing strength. Examples of catalysts for polymerizing the uncured unsaturated polyester in the present invention include benzoyl peroxide, lauroyl peroxide, ditertiary butyl peroxyadipate, dicumyl peroxide, tertiary butyl peroxybenzoate, methyl ethyl ketone peroxide, Examples include organic peroxides such as menhydroperoxide. These polymerization catalysts may be used alone or in combination of two or more, and when actually used, they need to be added to the post-addition solution. In other words, the method of adding a polymerization catalyst to the uncured resin in advance is preferable because polymerization and curing progresses during melting and stirring, and cooling is slow, especially in mass production, and curing may be completed during production. do not have. The amount of the catalyst added is 0 parts by weight per 100 parts by weight of the uncured unsaturated polyester (including the amount of crosslinking agents such as unsaturated monomers and unsaturated prepolymers).
．． 1 to 5 parts by weight, preferably 0.5 to 3 parts by weight,
If it is less than 0.1 parts by weight, it will not cure, and if it is added more than 5 parts by weight, the effect will not change, which is not preferable in terms of cost. Next, the silane coupling agent used in the present invention has the following general formula (in the formula, Y represents an organic functional moiety, Xl, X2 and X3
is a hydrolyzable group selected from the group consisting of an alkoxyl group, an acetoxy group, an alkoxyethoxy group, and a halogen atom, and R represents an alkyl group, and includes, for example, the following.

The amount of the silane coupling agent added is 0.1 to 5 parts by weight per 100 parts by weight of the uncured unsaturated polyester (including the amount of crosslinking agents such as unsaturated monomers and unsaturated prepolymers when added). Parts by weight, preferably 0.5 to 3 parts by weight. If the amount of the catalyst added is less than 0.1 parts by weight, there is no effect of adding the catalyst, while if it is added more than 3 parts by weight, there is no effect, which is not preferable in terms of cost. In the present invention, resin-coated sand can be manufactured as follows.

First, silica sand, which is foundry sand, is heated (for example, 170° C.) and charged into a mixer, and then an uncured unsaturated polyester resin is charged.

Next, when the uncured unsaturated polyester resin is in a molten state, a solution of additives such as a catalyst and a silane coupling agent dissolved in a liquid crosslinking agent is added and stirred, and waxes, such as waxes, are added to improve fluidity. Add calcium stearate, etc., and stir until the temperature drops below the softening temperature of the resin, solidifying the resin and separating the sand grains to produce resin-coated sand. The present invention will be explained in more detail using the following examples and reference examples.

Example 1 Fumaric acid 11269, phthalic anhydride 449, ethylene glycol 6179 and diethylene glycol 569 were placed in 21 L-shaped flasks, and an unsaturated polyester having an acid value (AV) of -25 was obtained by an esterification condensation reaction using a conventional method.

The product was cooled to 140°C and 0.0% of hydroquinone was added.
339, diallyl phthalate monomer 2479, ultrafine silicic anhydride (Aerosil 200, Nippon Aerosil Co., Ltd.)
16.5 g (manufactured by ) company, trade name) were added, mixed and dissolved, and cooled to room temperature to obtain solid crystalline unsaturated polyester uncured product 1. The viscosity of this uncured product was measured at 130°C and found to be 50 poise. The uncured material is crushed and 16
It was made into a powder with a size smaller than 100g. Next, 18
4 kg of Nikko silica sand heated to 0°C was charged, followed by 120 kg of the uncured crystalline unsaturated polyester powder, and the uncured product was melted. Immediately add a solution of dicumyl peroxide 4.29 and silane coupling agent Nippon Unica KK A-174 (trade name) 4.29 dissolved in diallyl phthalate monomer 309, continue stirring for about 3 minutes, and remove the sand block. When the sand was loosened, 4.29 g of calcium stearate was added, and after 30 seconds, the sand was discharged from the kneader to obtain resin-coated sand 1. Example 2 Nikko silica sand No. 5 4 heated to 180°C in a kneader during stirring
K9 was added, and then 1209 powder of crystalline unsaturated polyester uncured material 1 of Example 1 was added, and the uncured material was melted.

Immediately add a solution of dicumyl peroxide 4.2f1 and silane coupling agent A-1744.29 dissolved in triallyl cyanurate 309, continue stirring for about 3 minutes, and when the sand block has loosened, calcium stearate After 30 seconds, the sand was discharged from the kneader to obtain resin-coated sand 2. Reference Example 1 Uncured crystalline unsaturated polyester of Example 1 1120
9 at 120℃, dicumyl peroxide 4.2
g, silane coupling agent A-1744.2 g, and diallyl phthalate monomer 309 were added and stirred, cooled and solidified to produce a resin composition, which was then ground into powder of 16 mesh or less.

Next, Nikko silica sand 5 heated to 180℃ was placed in the kneader while stirring.
No. 4k9 was added, followed by the above resin composition powder, stirring was continued for about 3 minutes, and when the sand block became loose, 4.2 g of calcium stearate was added. After 30 seconds, the sand was removed from the kneader and the resin was mixed. Coated sand 3 was obtained. Resin-coated sands 1, 2, and 3 of Examples 1 and 2 and Reference Example 1 were fired and molded for 70 seconds at a temperature of 230° C. using the molds shown in FIGS. 1A and 1B to prepare test pieces.

The mold A consists of plate-like pieces Al and A2, and an array-shaped cavity B is formed at the abutting portion of both pieces Al and A2. The width at the waist is 1 inch, and the thickness of the plates Al and A2 is 2 inches. To create a test piece, resin-coated sand is poured into cavity B, and both sides of mold A are brought into contact with heater C. The hot tensile strength of the prepared test piece was immediately measured at this temperature. After cooling these test pieces to room temperature, the room temperature tensile strength was measured. The results obtained are shown in Table 1. From the results shown in Table 1, it is clear that the resin-coated sand produced by the method of the present invention exhibits higher strength than the coated sand coated with the resin composition produced by the conventional method.

Further, using the resin-coated sand of Example 1, the automobile intake manifold port air shown in FIG. Cast the intake manifold. As a result, there are no casting defects,
The entire port core was ejected with just a simple impact of sand. Example 3 11379 of fumaric acid, 299 of adipic acid, and 6529 of ethylene glycol were charged into 21 four-bottle flasks, and A was prepared by an esterification condensation reaction using a conventional method.
An unsaturated polyester resin of V-30 was obtained.

This was cooled to 145°C, and parabenzoquinone 0.33
g, diallyl phthalate 2479, ultrafine particle silicic anhydride (
16.5 g of Aerosil 200) was added, mixed, dissolved, and cooled to room temperature to obtain uncured crystalline unsaturated polyester 2. The viscosity of this unsaturated polyester was measured at Cl3O°C and found to be 80 poise. Also, the softening point is 10
It was 0℃. Resin-coated sand 4 was obtained in the same manner as in Example 1 using this uncured crystalline unsaturated polyester.

Example 4! 11,269 g of fumaric acid, 449 g of phthalic anhydride, 617 g of ethylene glycol, 5879 diethylene glycol, and 809 g of trimethylene glycol were charged into a 21 four-bottle flask, and AV-23 was obtained by an esterification condensation reaction using a conventional method.
, unsaturated polyester 14 with number average molecular weight Jl75O
I got 009. This was cooled to 145°C, and 0.319 g of hydroquinone, 0.169 g of parabenzoquinone, 1569 g of diallyl phthalate, 15.69 g of ultrafine silicic anhydride (Aerosil 200), and 1.1 g of zinc stearate were added.
The mixture was mixed and dissolved, and cooled to room temperature to obtain uncured crystalline unsaturated polyester material 3. The viscosity of this unsaturated polyester was measured at 130°C and found to be 105 poise. Moreover, the softening temperature was 95°C. Resin-coated sand 5 was obtained in the same manner as in Example 1 using this crystalline unsaturated polyester uncured product 1. Example 5 10459 of fumaric acid, 1669 of terephthalic acid, 587 g of ethylene glycol, and 809 of trimethylene glycol were charged into a 21 four-bottle flask and subjected to an esterification reaction using a conventional method to obtain an unsaturated polyester having an AV of 35 and a number average molecular weight of 1850.

This was cooled to 145°C, and 0.29g of hydroquinone was added.
, diallyl phthalate 749, ultrafine silicic anhydride (Aerosil 200) 5.6f! and zinc stearate 0.
569 was added, mixed and dissolved, and cooled to room temperature to obtain uncured crystalline unsaturated polyester resin 4. When the viscosity of this unsaturated polyester was measured at 130°C, it was 110
It was poise. Further, the softening temperature was 98°C. Resin-coated sand 6 was produced in the same manner as in Example 1 using this uncured crystalline unsaturated polyester.

Reference Examples 2, 3, 4 After producing resin compositions in the same manner as in Reference Example 1 for the unsaturated polyester uncured products 2, 3, and 4 produced in Examples 3, 4, and 5, Reference Examples 2, 3, and 4 were prepared. Resin coated sand was obtained.

The resin-coated sands of Examples 3, 4, and 5 and Reference Examples 2, 3, and 4 were fired and molded at a temperature of 230°C for 70 seconds in mold A shown in Fig. 1 to prepare a test piece, and immediately heated to this temperature. Hot tensile strength was measured.

Furthermore, after cooling this test piece to room temperature, the room temperature tensile strength was measured. The results obtained are shown in Table 2. From the results shown in Table 2, resin-coated sand 4, 5, and 6 by the method of the present invention
It is clear that the sand exhibits higher strength than the resin-coated sand of Reference Examples 2, 3, and 4.

[Brief explanation of the drawing]

Figure 1a is a side view of the mold for making test pieces, Figure 1b
is a cross-sectional view along line I-1 in Figure 1a (7), and Figure 2 is 1
．． FIG. 2 is a front view of an intake manifold port core for a No. 81 automobile engine. A... Mold, Al, A2... Plate piece of the mold, B... Cavity, C... Heater.

Claims (1)

[Scope of Claims] 1. A liquid cross-linked polyester that is solid at room temperature, has no stickiness, and is composed of an unsaturated polyester that exhibits a viscosity of 500 poise or less at a softening point or higher, or is copolymerizable with the polyester. After the uncured product becomes molten during the process of coating the uncured unsaturated polyester containing the agent on the foundry sand grains by a hot melt method, a silane coupling agent and a polymerization catalyst are respectively applied. A method for producing resin-coated sand, which comprises adding alone or together with a solution dissolved in a liquid crosslinking agent, stirring, and coating sand grains with a resin. 2. The method for producing resin-coated sand according to claim 1, in which an unsaturated prepolymer, an unsaturated monomer, or a mixture thereof is used as a liquid crosslinking agent.