KR830002156B1 - Resin composition for molding sand - Google Patents

Abstract

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Description

Resin composition for molding sand

The present invention relates to a resin composition for molding sand bond.

Phenolic resins are now widely used as binders for sand in casting molds. However, this resin has proved to be very inadequate for labor hygiene and pollution control because it emits toxic or odorous gases when heated during coating, molding and injection of sand. In addition, when the core material is used in an aluminum caste, the sealing of the core material after casting is poor.

Therefore, studies on the possibility of using other materials such as unsaturated polyester resins as binders have been continued. By using unsaturated polyester resins as binders for sand, the aforementioned drawbacks can be eliminated. However, since these resins have basically lower heat resistance strength (heat strength) than phenolic resins, a larger amount of resin is used in resin-coated sand (hereinafter simply referred to as coated sand) than in the case of phenolic resins. It is necessary to compensate for the heat resistance strength of the unsaturated polyester resin. This will certainly improve the strength, but ideal casting is difficult to obtain because bubbles or pores tend to be formed by the gases produced during injection. Moreover, in this case, manufacturing costs increase. It is an object of the present invention to provide a novel composition for foundry sand bonding without this drawback.

According to the present invention, a crystalline unsaturated polyester composition for molding sand bonds is obtained.

(A) 100 parts by weight (weight) of crystalline unsaturated polyester, which is usually solid and basically not tacky, and an unsaturated prepolymer or monomo copolymerizable with the aforementioned unsaturated polyester, or 0 to 50 parts of these two components. 100 parts by weight (weight) of an unsaturated polyester resin composed of a mixture with (weight) (preferably 10 to 30 parts)

(B) (1) radical polymerization catalysts requiring a temperature of 70 ° C. or higher and lower than 90 ° C. in order to obtain a half-period value of 10 hours, and (2) 90 ° C. or higher and 110 ° C. to have a half life of 10 hours. 0.1-10 parts (weight) (1.0-3.0 parts) of a mixture of two or more of radical polymerization catalysts requiring a lower temperature and (3) a radical polymerization catalyst requiring a temperature of 100 ° C. or higher and lower than 130 ° C. in order to obtain a half-life of 10 hours. (Weight) is preferred).

Crystalline unsaturated polyesters used in the present invention can be prepared from materials having a symmetric molecular structure, and examples of such materials include unsaturated acids such as fumaric acid or mesaconic acid, terephthalic acid, dimethyl terephthalate, adipic acid, sebacic acid or Aromatic or saturated acids such as succinic acid, ethylene glycol, 1, 3-propanediol, diethylene glycol, 1, 4-butanediol, dipropylene glycol, neopentyl glycol, hydrogenated bisphenol A, 2, 2-bis [4- ( Hydroxyethoxy) phenyl propane] and glycols such as 2, 2-bis [4-hydroxypropoxy) phenyl] propane and the like. Other substances, for example unsaturated acids such as maleic anhydride, citraconic acid or itaconic acid, aromatic acids such as phthalic acid, isophthalic acid tetrahydro anhydrophthalic acid and endo methylenetetrahydro phthalic acid, propylene glycol, or 1, 3 -Glycol such as butanediol, glycerin, trimethylolpropane or derivatives thereof may be used in an amount that does not adversely affect the crystallinity of the unsaturated polyester.

The crystalline unsaturated polyesters contain a small amount of an unsaturated fatty acid having a symmetric molecular structure or a mixture of a saturated acid in one or more thereof, and a glycol or a mixture thereof having one or more of the aforementioned symmetric molecular structures. It is preferable to make it by esterifying with the glycol component which has the glycol which has a subsidiary molecular structure. A polymerization inhibitor such as p-benzoquinone, hydroquinone or catechol is added to the reaction system in an amount of about 100 to 1000 ppm.

Examples of suitable prepolymers or monomoles which can be crosslinked or copolymerized with the aforementioned polyesters include styrene, divinylbenzene, vinyltoluene, α-methylstyrene, diallylphthalate prepolymer, diallyl isophthalate prepolymer, ethylene glycol dimethacrylate , Diethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylol propanetrimethacrylate, diallyl phthalate, diallyl isophthalate, triallyl cyanurate, triallyl isocyanurate, triallyl tree Meritate, diacetoneacrylamide and N-methylol

An unsaturated polyester resin (A) is obtained by adding 0-50 parts (weight) (preferably 10-30 parts weight) of the prepolymer or monomole 1 to 100 parts (weight) of crystalline unsaturated polyester. If the amount of prepolymer or polymer exceeds 30% (by weight), the coated sand produced using the final product exhibits significant stickiness and the bulk density of the coated sand is reduced. The strength of the molded product produced therefrom therefore decreases. Examples of catalysts that require a temperature of 70 ° C. or more and less than 90 ° C. in order to obtain a half-life of 10 hours are t-butylperoxy-2-ethylhexanoate, benzoyl peroxide and t-butyl peroxyisobutylate, and the like. Examples of the catalyst requiring a temperature of 90 ° C. or more and 110 ° C. or lower to obtain the same half-life include t-butylperoxylaurate, cyclohexanone peroxide, t-butylperoxybenzoate and di-butylperoxyphthalate. Examples of the catalyst requiring a temperature of 100 to 130 ° C. in order to obtain the same half-life include dicumyl peroxide, t-butyl cumyl peroxide, t-butyl hydroperoxide and di-t-butyl peroxide.

The half-life is measured by preparing a solution having a peroxide concentration of 0.1-0.2 mol / l using a solvent that is relatively inert to the resulting radicals, sealing the solution in a glass tube filled with nitrogen gas, and then pyrolyzing at a predetermined temperature. do.

The catalyst mixture (B) consisting of two or more of the radical polymerization catalysts (1), (2) and (3) is 0.1 to 10 parts (weight) per 100 parts (weight) of crystalline unsaturated polyester resin (A) (1 to 3 parts (weight) is preferred). If the amount of the catalyst mixture (B) is less than 0.1 part (weight), sufficient strength of the mold and the core material cannot be obtained using the resultant composition. Even if the amount of the catalyst mixture (B) exceeds 10 parts (weight), an increase in strength corresponding to the increase amount of the catalyst mixture (B) cannot be obtained, and furthermore, it is economically disadvantageous. There is no particular limitation on the ratio between the constituent catalysts (two or more of the catalysts (1), (2) and (3)) in the catalyst mixture (B), but it preferably contains at least 0.1% (weight).

If only one of the three catalysts is used, local and solidified (thin sections) or local inadequate solidified (thick sections) can be obtained from complex structures and cores obtained using the final product when heating the mold and core at homogeneous temperatures. Tends to occur. Therefore, the production rate of the mold and the core of the complicated structure is reduced. In order to avoid this difficulty, it is possible to keep the temperature of a part which is easy to clog low, and to maintain a high mold temperature at a part where insufficient solidification is likely to occur. However, it is very difficult to control the mold temperature in such a way, and there is no economic advantage. When producing molds and cores of complex structure, it is effective to use the catalysts of the three types of catalysts (1), (2) and (3) described above. A silane coupling agent may be added to the resin composition of the present invention in order to enhance the strength of the mold or core material after molding, and a suitable silane coupling agent may be represented by the following general structural formula.

Wherein R ₁ is an organic functional group containing at least one group selected from the group consisting of alkenyl, alkenylphenylalkyl, acryloxyalkyl, methacryloxyalkyl, glycidoxyalkyl, epoxycyclohexylalkyl and haloalkyl groups, R ₂ , R ₃ and R ₄ are hydrolyzable groups selected from the group consisting of alkoxy, alkoxy ethoxy, acetoxy groups and halogen atoms. Examples of the silane coupling agent include γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyl-tris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3, 4 -Epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-amino-propyltriethoxysilane, N- (β-aminoethyl) -gamma -aminopropyltrimethoxysilane, gamma -ureidopropyltriethoxysilane, and the like. At least one of these silane coupling agents is added at an amount of 0.1 to 10 parts by weight (preferably 0.5 to 5 parts by weight) per 100 parts (weight) of the unsaturated polyester resin (A). If the amount of silane coupling agent is added less than 0.1 (weight), it is not added to show the effect of increasing the strength.

In using the compositions of the present invention, it is also possible to add known rheology enhancers such as waxes, higher fatty acids or salts of higher fatty acids.

Other additives such as disintegration enhancers, crystallization promoters or weighting agents can also be combined.

The use of the resin composition of the present invention as a binder for the shell mold has the advantage that no toxic or odorous gases are generated during operation, and molds and cores of a complicated structure can be homogeneously solidified and a good yield can be obtained. During injection, processing and the generation of pupils are reduced, and casting can be obtained with good yield. In addition, the core material produced using the resin composition of the present invention has excellent disintegration after injection.

The following examples illustrate the invention in more detail. However, this embodiment does not limit the scope of the present invention.

Example 1

In a 2-liter four-necked flask, 1137.5 g of fumaric acid, 33.2 g of isophthalic acid, and 651.7 g of ethylene glycol were added and esterified by a conventional method to prepare an unsaturated ester having an acid value of 25.

Unsaturated polyester was cooled to 140 degreeC, 95 parts (weight) of produced unsaturated pulley esters were made into 10 parts (weight) of diallyl phthalate, (gamma)-methacryloxypropyl trimethylsilane ((A-174, the brand name of the Japan Unika company make) ) 2 parts (by weight) and 0.8 parts (by weight) of ultrafine silicic anhydride (Aerosil # 200, trade name of Japan Aerosil Co., Ltd.), and the mixture is cooled to room temperature, crystallized and solidified. Powder I to obtain Sample I.

Coated sand is prepared by the following method using Sample I.

Nikko silica sand (# 5,1000 g heated to 170 ° C.) was placed in an all-purpose mixing-stirrer (5DWM, product name of Shinagar Co., Ltd.), mixed with 29.5 g of sample I and melt-bonded to the surface of sand. Next, 0.35 g of t-butylperoxy-2-ethylhexanoate, 0.35 g of dicumyl peroxide and 0.35 g of t-butylperoxybenzoate dissolved in 5.5 g of acetone while maintaining the temperature of sand at 60 to 100 ° C. The solution of is mixed with sand.

Comparative Example 1

In the same manner as in Example 1, 1000 g of Nikko silica sand # 5 heated to 170 ° C. was placed in a universal mixing-stirrer (5DWM, trade name) and mixed with 29.5 g of sample I. It is then mixed and dispersed with a solution of 1.05 t-butylperoxy-2-ethylhexanoate dissolved in 5.5 g of acetone to obtain coated sand.

Comparative Example 2

In the same manner as in Comparative Example 1, 1.05 g of t-butyl p-oxybenzoate was prepared in place of the catalyst used in Comparative Example 1 to prepare coated sand.

Comparative Example 3

In the same manner as in Comparative Example 1, 1.05 g of dicumylperoxide was used instead of the catalyst used in Comparative Example 1 to prepare coated sand.

Example 2

In the same manner as in Example 1, coated sand was prepared using 0.525 g of t-butylperoxy-2-ethylhexanoate and 0.525 g of dicumylperoxide instead of the catalyst used in Example 1.

Example 3

In the same manner as in Example 1, coated sand was prepared using 0.525 g of t-butylperoxabenzoate and 0.525 g of dicumylperoxide instead of the catalyst used in Example 1.

[Test Example 1]

Each of the coated sands obtained in Examples 1-3 and Comparative Examples 1-3 was placed in a mold (maintained at 250 ° C.) of sizes 10 mm ψ 80 mm, 20 mm ψ 150 mm and 30 mm ψ 150 mm, respectively, and heated for 40 seconds. At room temperature, the flexural strength and volume fraction of the resulting test sample were measured and the results are listed in Table 1.

TABLE 1

From the results in Table 1, it can be seen that using only one type of catalyst makes it difficult to obtain homogeneous strength for molded products of different diameters.

This is because each catalyst has its own optimum activity temperature, and if this temperature is not observed, sufficient strength cannot be obtained due to the excess of activity or lack of activity. On the other hand, in the part having a large diameter in the test sample, the increase in temperature during molding is small, and in the part in which the diameter of the test sample is small, the rise in temperature during molding is large. In contrast, the composition of the present invention does not have such drawbacks because it contains two or three kinds of catalysts.

Example 4

1102.6 g of fumaric acid, 83.1 g of terephthalic acid, 614.5 g of ethylene glycol and 147.6 g of neopentylglycol were added to a 2-liter four-neck flask, and esterified by a conventional method to prepare an unsaturated polyester having an acid value of 30. The resulting unsaturated polyester was cooled to 135 ° C., and 90 parts (weight) of the cooled unsaturated polyester was converted into 10 parts (weight) of diallyl phthalate and vinyltris (β-methoxyethoxy) silane (A-172 Japan). 3 parts by weight of UNICA's product (weight) and 0.8 micro parts (weight) of ultra fine anhydrous silicic acid (Aerosil # 200, trade name of Japan Aerosil)

The mixture is cooled to room temperature to crystallize and solidify, and then powdered to 10 mesh or less to obtain Sample II.

In the same manner as in Example 1, Sample II was used to produce coated sand. Nikko Sand # 5,100g heated to 170 ° C is placed in a universal mixing-stirrer (5DWM, product name), mixed with 31.1 g of Sample II, and the resin is melted and adhered to the surface of the sand. Furthermore, the temperature of the sand was maintained at 60 to 100 ° C., 0.2 g of t-butylperoxy-2-ethylhexanoate dissolved in 3.9 g of acetone, 0.2 g of t-butylperoxylaurate, and t-butyl hydroper Coated sand is prepared by mixing with a solution of oxide and dispersing.

Example 5

In the same manner as in Example 4, Nikko Silica Sand # 5,1000g heated to 170 ° C was placed in a universal mixing-stirrer (5DWM, trade name), mixed with 31.1 g of Sample II, and the resin was melt-bonded to the sand surface. . Coated sand was prepared by mixing and dispersing with a solution of 0.3 g t-butylperoxy-2-ethylhexanoate and 0.3 g t-butylperoxylaurate dissolved in 3.9 g of acetone.

Example 6

In the same manner as in Example 4, instead of the catalyst used in Example 4, 0.3 g of t-butylperoxy-2-ethylhexanoate and 0.3 g of t-butylhydroperoxide were prepared to produce coated sand. do.

Example 7

In the same manner as in Example 4, instead of the catalyst used in Example 4, 0.3 g of t-butylhydroperoxide and 0.3 g of t-butylperoxylaurate were used to prepare coated sand.

Comparative Example 4

In the same manner as in Example 4, 0.6 g of t-butylhydroperoxide was used instead of the catalyst used in Example 4 to prepare coated sand.

[Test Example 2]

The same test as in Experimental Example 1 was carried out by changing only the temperature of the mold to 260 ° C, and the results are shown in Table 2.

TABLE 2

Claims (1)

(A) Unsaturated, usually composed of 100 parts by weight (weight) of crystalline unsaturated polyesters, which are generally solid and essentially non-tacky, and unsaturated prepolymers or copolymers of 0 to 50 parts (weights) of monomers copolymerizable with this unsaturated polyester. Polyester resin 100 (weight) and (B) (1) radical polymerization catalyst which requires a temperature of 70 ° C or more and less than 90 ° C in order to have a half life of 10 hours, (2) 90 ° C or more in order to have a half life of 10 hours (3) 0.1-10 parts (by weight) of a mixture of two or more of radical polymerization catalysts requiring a temperature of less than 110 ℃ and (3) a radical polymerization catalyst requiring a temperature of 110 ℃ or more and less than 130 ℃ to have a half-life of 10 hours Crystalline unsaturated ester composition for molding sand bond.