JPS6119331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold binder that has high mold strength when hot and has good thermal disintegration properties of the mold when pouring molten metal.

Traditionally, novolak type or resol type phenol formaldehyde resins have been widely used in mold molding, but the thermal decomposition properties of the molds when pouring molten metal are poor, especially for low-temperature materials such as aluminum alloys using core molds. In casting molten metal,
Since it is difficult to remove sand from the core mold, it is necessary to post-heat the cast product (called sand baking) to remove the sand, and drastic improvements are desired from the viewpoint of energy and labor savings. From this point of view, attempts have been made to develop various types of binders with excellent heat disintegration properties, but even if they meet these requirements, it is almost impossible to obtain a binder with sufficient hot mold strength immediately after molding. The appearance of this is eagerly awaited.

The present invention is a mold binder which greatly improves the drawbacks of the prior art, has high mold strength when hot and has excellent heat disintegration properties, and is particularly suitable for aluminum alloy casting cores.

That is, the present invention provides at least one compound selected from the group consisting of (a) triglycidyl isocyanurate and/or tri(β-methylglycidyl) isocyanurate, and (b) dicyandiamide and its derivatives, organic acid hydrazides, and imidazole derivatives. A mold caking composition comprising a curing agent and a curing agent.

Diglycidyl isocyanurate and di(β-methylglycidyl)isocyanurate can also be used, and addition reactions of triglycidyl isocyanurate or tri(β-methylglycidyl)isocyanurate with polyhydric carboxylic acids, polyhydric phenols, etc. Oligomers having two or more glycidyl groups in one molecule obtained by this process and mixtures of two or more selected from the above can also be used.

The curing agent used in the present invention includes various dicyandiamide derivatives such as dicyandiamide, guanidine, guanidine salts, biguanide, guanidine or aryl group-substituted products of biguanide, such as succinic acid dihydrazide, adipic acid dihydrazide, isophthalic acid dihydrazide, paraoxylic acid dihydrazide, etc. Organic acid hydrazides such as benzoic acid dihydrazide, salicylic acid dihydrazide, and phenylaminopropionic acid hydrazide, imidazole derivatives such as cyanoethyl-substituted imidazole organic acid salts, azine-substituted imidazole, and imidazole metal salts, and one or more of these. can be used. These curing agents do not react with the above-mentioned polyvalent glycidyl compound having an isocyanuric ring at room temperature, but react in a short time when heated, and usually form glycidyl groups within a few minutes at a temperature of 150°C or higher. It is a curing agent that can complete the reaction with. These curing agents can be used from the viewpoints of mold strength and heat disintegration property when heated.

Furthermore, in order to adjust the reaction rate of the polyglycidyl compound having an isocyanuric ring and the curing agent during mold making, a curing accelerator may be used in combination, such as aminophenol such as dimethylaminophenol, diazabicyclo Undecene and its salts, urea derivatives such as 3(p-chlorophenyl)-1,1-dimethylurea, etc. are used as curing accelerators, and imidazole derivatives and organic acid hydrazides, which also act as curing agents, are used as dicyandiamide derivatives. It is also effective as a curing accelerator. Among these, the above-mentioned urea derivatives are effective.

The mold binder used in the present invention, which is composed of the above-mentioned polyvalent glycidyl compound having an isocyanuric ring and its curing agent, and optionally also contains a curing accelerator, is added to the casting sand in an amount that is normal to that of the casting sand. 1 to 10% by weight, preferably 1.5 to 5% by weight, particularly preferably
It is 1.5 to 3% by weight. In general, increasing the amount of binder improves the strength of the mold when hot, but it not only decreases the thermal decay properties but also increases the amount of gas generated when pouring molten metal into the mold, causing defects in the casting. Cheap. However, the mold binder of the present invention is preferable from this point of view because it can impart extremely high mold strength when hot even when added to a small amount of foundry sand.

The optimum blending ratio of the above-mentioned polyvalent glycidyl compound having an isocyanuric ring and the above-mentioned curing agent differs depending on the individual combination, but usually the reactive active hydrogen groups of the curing agent are equal to the equivalent number of glycidyl groups. It is used in an amount of 0.5 to 4.0 times equivalent, preferably 1.0 to 2.5 times equivalent. The reason why it is recommended that the active hydrogen of the curing agent is excessive in terms of the equivalent ratio is because it is rapidly heated during mold making and the molding is completed in a short time, so that the active hydrogen is consumed effectively during the reaction. This is thought to be because there is a limit to the amount of curing agent that can be used.

In addition, when using a curing accelerator in the present invention,
When the curing accelerator simultaneously acts as a curing agent,
That is, for example, when imidazole derivatives or organic acid hydrazides are used, they are generally included in the above-mentioned curing agent and used in the above-mentioned mixing ratio. On the other hand, when using a substance that acts only as a curing accelerator, it is usually 1 to 10, preferably 1 to 10, based on the total amount of the polyvalent glycidyl compound and curing agent, although it depends on the individual combination and desired conditions. It is used in a range of 3 to 8% by weight. If the amount added is small, reaction promotion tends to be insufficient,
If the amount is too high, the reaction may be too fast or the tensile strength at high temperature may decrease.

It should be noted that the mold binder composition of the present invention may be mixed with a polyvalent epoxy resin such as a glycidyl ether of a polyvalent phenol, a glycidyl ester of a polyvalent carboxylic acid, or an alicyclic epoxy resin, or a phenol such as novolak or resol. It is also possible to mix and cast the formaldehyde resin together with its curing agent if necessary, as long as this does not impede the object of the present invention. In addition, auxiliaries for the purpose of improving the slipperiness of casting sand, silane coupling agents and titanium coupling agents for improving the adhesion between sand and binder, or inorganic fillers other than silica sand. It is also possible to use them together.

When putting into practical use the binder composition for molds of the present invention, the binder for molds of the present invention is added to preheated casting sand and mixed, and the mixture is cooled to fuse the binder to the surface of the casting sand. A method of dissolving or dispersing the binder composition for molds of the present invention in an organic solvent, water, etc., mixing with preheated or not preheated casting sand, and drying; or a binder composition for molds of the present invention. Various methods of mixing with casting sand are used, such as the method of finely pulverizing the material and mixing it with casting sand at room temperature, but from the viewpoint of uniformity of the mixing state, the method of mixing with appropriately preheated casting sand is also used. A method that does not use a liquid medium is particularly preferable in terms of reducing the number of materials and operations and further saving energy and resources. Usually, the polyvalent glycidyl compound of the present invention is added to casting sand preheated to at least 150°C or higher, and the fine powder of the mixture with the curing agent or curing accelerator of the present invention, or a solution or dispersion thereof, is poured into the casting while cooling. It is common to add sand after it has reached a temperature of 130°C or less.

The foundry sand coated with the mold caking composition of the present invention thus obtained is usually heated at a temperature of 150°C or higher.
Preferably, the mixture is poured into a mold heated to 180 to 250°C, and removed from the mold after 30 seconds to 3 minutes to obtain a mold.
The mold thus obtained has excellent mold strength at high temperatures, so the defect rate during mold production is extremely low, and it also has excellent thermal disintegration properties when used for casting light alloys such as aluminum, so it is easy to remove sand. The sand baking process is completely unnecessary.

EXAMPLES The present invention will be specifically explained below with reference to Examples.

Note that Example 1 uses dicyandiamide and Example 2 uses dicyandiamide.
Examples 3 and 4 use imidazole derivatives, and Example 5 uses an organic acid hydrazide as a curing agent.

Example 1 1 kg of No. 6 silica sand preheated to 200°C was placed in a stirring mixing tank equipped with a cooling jacket and stirred while cooling. When the silica sand temperature was 160°C, 20 g of triglycidyl isocyanurate was added and melted onto the surface of the silica sand. let him wear it,
Subsequently, at 110°C, 4g of fine powder of dicyandiamide (average particle size 40μ) and 3-
(p-chlorophenyl)-1,1-dimethylurea 1
g and calcium stearate 1 as a slip aid.
g was added thereto, and the mixture was stirred and cooled to obtain a coated sand coated with the mold caking composition of the present invention.

The above-mentioned coated sand was molded at 200° C. for 60 seconds using a high-temperature tensile test, and the tensile strength at the warm temperature was immediately measured. As a result, the tensile strength at the warm temperature was 21 Kg/cm ² .

Next, a thermal collapse test was conducted using the above coated sand. Thermal decay test was performed by pouring the above coated sand into a cylindrical mold with an inner diameter of 30 mm and a height of 30 mm that had been preheated to 200°C, heating it at 200°C for 60 seconds, removing it from the mold to create a core, and making Bennatoite. A cylindrical main mold with an inner diameter of 70 mm and a depth of 70 mm, which was separately prepared as a system mold, was equipped with an outlet with a diameter of 10 mm and a length of 10 mm, the above core was set, and the molten aluminum alloy at 650°C was poured into it and cooled. After solidification, the main mold was broken and vibration was applied using a rotor-tap tester to determine the state of the core being discharged from the aluminum casting outlet. was completely expelled.

Example 2 The mixing tank used in Example 1 was filled with 1000 g of No. 6 silica sand preheated to 200°C and stirred while cooling.
When the temperature of the silica sand reached 150°C, 22 g of a mixture of 90% by weight of tri(β-methylglycidyl)isocyanurate and 10% by weight of di(β-methylglycidyl)isocyanurate was added and fused to the surface of the silica sand.
At 100°C, 3 g of fine powder of phenyl biguanide (average particle size 40 μm) and 1 g of calcium stearate as a sliding aid were added and cooled with stirring to obtain coated sand coated with the mold caking composition of the present invention. .

Next, in the same manner as in Example 1, the tensile strength at high temperature was measured and the thermal disintegration test was conducted. Tensile strength at temperature is 17
Kg/cm ² , and the heat disintegration property was completely ejected by shaking the rotor tap for 5 minutes without any sand baking process.

Example 3 The mixing tank used in Example 1 was preheated to 200°C.
Add 1000g of silica sand and stir while cooling.
When the temperature of the silica sand reached 160℃, 80% by weight of triglycidyl isocyanurate, 2 moles of triglycidyl isocyanurate and bisphenol A1
Tetrafunctional polyglycidyl compounds that are molar adducts
Add 25g of a mixture of 20% by weight and fuse it to the silica sand surface, and heat it at 100°C with 3g of fine powder (average particle size 35μ) of 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate and a sliding aid. 1 g of calcium stearate was added as an agent, and the mixture was stirred and cooled to obtain coated sand coated with the caking composition of the present invention.

Next, in the same manner as in Example 1, the tensile strength at high temperature was measured and the thermal disintegration test was conducted. Tensile strength at temperature is 18
Kg/cm ² , and the heat disintegration property was determined by the fact that the core was completely ejected by shaking the rotor-tap tester for 5 minutes without any sand baking process.

Example 4 The mixing tank used in Example 1 was preheated to 200°C.
Add 1000g of No. silica sand, stir while cooling, and when the temperature of the silica sand reaches 160°C, add 20g of a mixture of 95% by weight of triglycidyl isocyanurate and 5% by weight of diglycidyl isocyanurate to the surface of the silica sand. Fuse 5 g of guanidine carbonate and azine-substituted imidazole (Kyuazole) at 100℃.
C11 Z-Azine (trade name manufactured by Shikoku Kasei Co., Ltd.) 1 g of mixed fine powder (average particle size 50μ) and 1 g of calcium stearate as a sliding aid were added, stirred and cooled, and coated with the mold binding composition of the present invention. Got a sandwich.

Next, in the same manner as in Example 1, the tensile strength at high temperature was measured and the thermal disintegration test was conducted. Tensile strength at temperature is 20
Kg/cm ² , and the heat disintegration property was determined by the fact that the core was completely ejected by shaking the rotor-tap tester for 5 minutes without any sand firing process.

Example 5 1000 g of No. 6 silica sand preheated to 200°C was placed in the mixing tank used in Example 1, and stirred while cooling.
When the temperature of the silica sand reaches 160℃, add 20g of triglycidyl isocyanurate and fuse it to the surface of the silica sand. At 100℃, add 3g of fine powder of adipic acid dihydrazide (average particle size 40μ) and 1g of calcium stearate as a sliding aid. The mixture was stirred and cooled to obtain coated sand coated with the mold binder composition of the present invention.

Next, in the same manner as in Example 1, the tensile strength at high temperature was measured and the thermal disintegration test was conducted. Tensile strength at temperature is 18
Kg/cm ² , and the heat disintegration property was determined by the fact that the core was completely ejected by shaking the rotor-tap tester for 5 minutes without any sand firing process.

Comparative Example 1 The mixing tank used in Example 1 was preheated to 200°C.
Add 1000g of No. silica sand, stir while cooling, and when the temperature of the silica sand reaches 160℃, add 22g of novolac type phenolic resin and let it fuse to the surface of the silica sand.
At 110° C., 15 g of a 20% aqueous solution of hexamethylenetetramine and 1 g of calcium stearate as a sliding aid were added, and the mixture was stirred and cooled to obtain a coated sand coated with the mold binder composition of the comparative example.

Next, in the same manner as in Example 1, the tensile strength at high temperature was measured and a thermal decay test was performed. However, the molding conditions were 230℃, which showed the highest temperature strength when using the coated sand of this comparative example in a separate experiment.
I did it under the conditions of 90 seconds. The tensile strength at high temperatures was 18 Kg/cm ² , and in a thermal collapse test, only 5% of the cores could be ejected during 10 minutes of vibration using a rotor-tap tester without sand baking.

Comparative Example 2 [Polymerization of unsaturated polyester resin] 1126 g of fumaric acid, 44 g of phthalic anhydride, 617 g of ethylene glycol, and 56 g of diethylene glycol
The mixture was charged into a four-necked flask and subjected to an esterification condensation reaction using a conventional method to obtain an unsaturated polyester having an acid value of 25. Cool this to 120℃ and use Hydroquine.
0.42 g of dicumyl peroxide, 56 g of dicumyl peroxide, and 140 g of diallyl phthalate were added thereto, thoroughly stirred and mixed, and cooled to room temperature to obtain an unsaturated polyester resin composition.

[Production and evaluation of coated sand]

The mixing tank used in Example 1 was preheated to 200°C.
Add 1000g of No. silica sand, stir while cooling, and when the temperature of the silica sand reaches 160°C, add 25g of the unsaturated polyester resin composition obtained by the above method.
Then, 0.03 g of a silane coupling agent (manufactured by Nippon Unicar Co., Ltd., trade name A-174), 2.5 g of zinc carbonate, and 1 g of calcium stearate were added, and the mixture was cooled and discharged to obtain coated sand.

Next, in the same manner as in Example 1, the tensile strength at high temperature was measured and a thermal decay test was conducted. However, the tensile strength at temperature when molding was performed at 230℃ for 70 seconds is
The heat disintegration property was 10.5 Kg/cm ² , and as in Example 1, the core was completely ejected by vibration of a rotor-tap tester for 5 minutes without the sand baking step.

Claims (1)

[Claims] 1 (a) triglycidyl isocyanurate and/or
or tri(β-methylglycidyl)isocyanurate; and (b) one or more curing agents selected from the group consisting of dicyandiamide and its derivatives, organic acid hydrazides, and imidazole derivatives.