JPS6119329B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to resin-coated sand suitable for casting cores, which has high mold strength when hot and has good thermal disintegration properties when pouring molten metal. Traditionally, resin-coated sand coated with novolac type or resol type phenol formaldehyde resin has been widely used for mold molding, especially for molding cores for casting, but when casting low-temperature melting metals such as aluminum alloys, cores It is difficult to remove the sand because it does not thermally disintegrate sufficiently, and the cast product must be heated (sand baked) after sand removal to remove the sand.Therefore, drastic improvements are desired from the viewpoint of energy and labor saving. From this point of view,
Attempts have been made to develop various types of resin-coated sand with excellent thermal decomposition properties, but even if these methods are met, it is not possible to obtain a material with sufficient hot strength immediately after core molding, and new binders have not yet been developed. desired. The present invention greatly improves the drawbacks of the prior art, and increases the strength of the mold when hot. The present invention also provides a resin-coated sand that has excellent thermal decomposition properties and is particularly suitable for casting aluminum alloys and the like. That is, one of the present inventions includes (A) triglycidyl isocyanurate and/or tri(β-methylglycidyl)isocyanurate, (B) one or more of dicyandiamide, dicyandiamide derivative, organic acid hydrazide, or imidazole derivative; C) phenol formaldehyde resin; Another aspect of the present invention is resin-coated sand coated with (A) triglycidyl isocyanurate and/or tri(β-methylglycidyl) isocyanurate, and ( B) one or more of dicyandiamide, a dicyandiamide derivative, an organic acid hydrazide, or an imidazole derivative; (C) a phenol formaldehyde resin; and (D) hexamethylenetetramine. It is a resin-coated sand coated with the following as a binder. Diglycidyl isocyanurate and di(β-methylglycidyl)isocyanurate can also be used, and those obtained by addition reaction of triglycidyl isocyanurate or tri(β-methylglycidyl)isocyanurate with polyhydric carboxylic acid or polyhydric phenol, etc. Oligomers having two or more glycidyl groups in one molecule and two or more glycidyl groups selected from the above.
It is also possible to use mixtures of more than one species. (B) used in the present invention is a curing agent that does not react with the above-mentioned (A) polyvalent glycidyl compound having an isocyanuric ring at room temperature, but reacts in a short time when heated, and is usually at temperatures above 150°C. It is a curing agent that can complete the reaction with glycidyl groups within several minutes at a temperature of . Examples of (B) above include dicyandiamide,
Various dicyandiamide derivatives such as guanidine, guanidine salts, biguanides, aryl group substituted products of guanidine or biguanides, such as succinic acid dihydrazide, adipic acid dihydrazide,
Organic acid dihydrazides such as isophthalic acid dihydrazide, paraoxybenzoic acid dihydrazide, salicylic acid dihydrazide, and phenylaminopropionic acid dihydrazide, imidazole derivatives such as cyanoethyl-substituted imidazole organic acid salts, azine-substituted imidazole, and imidazole metal salts, etc. One or more of these can be used.
These compounds can be used from the viewpoints of mold strength and disintegration at elevated temperatures. Furthermore, a curing accelerator may be used in combination with the above (A) polyvalent glycidyl compound having an isocyanuric ring and the above (B) curing agent in order to adjust the reaction rate during mold making, such as dimethylaminophenol. Aminophenol, diazabicycloundecene 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 dihydrazide is also effective as a curing accelerator for dicyandiamide derivatives. Among these, the above-mentioned urea derivatives are effective. Resin-coated sand coated with the components (A) and (B) above has excellent hot strength when molded into cores, etc., and also has good thermal disintegration properties, but resin-coated sand coated with the components (A) and (B) above has excellent hot strength when molded into cores, etc., and has good thermal disintegration properties. When coated sand is stored, there are drawbacks such as poor sliding between the sands, resulting in a decrease in the density and strength of the mold obtained from the sand, and an increase in the defective rate due to poor sand clogging in the details. In the present invention, in the above-mentioned components (A) and (B), (C)
By adding phenol formaldehyde resin and optionally (D) hexamethylenetetramine which functions as a curing agent as in (C) above, the above-mentioned drawbacks can be overcome and the strength of the mold can be stabilized under any storage conditions. We were able to maintain this property and achieve a thermal disintegration property sufficient for practical use. (C) Phenol formaldehyde resin used in the present invention includes phenol, cresol, xylenol, paratertiary butylphenol, catechol, resorcinol, phenylphenol,
A resin obtained by condensation of a monophenol compound or a diphenol compound such as bisphenol A, bisphenol F, bisphenol S, or isopropenylphenol with formaldehyde, which can be roughly divided into novolac type phenol formaldehyde resin and resol type phenol formaldehyde resin. It is classified as a resin, and any of them can be used in the present invention. When the phenol formaldehyde resin (C) above is a novolak type phenol formaldehyde resin, the above (D) is used. When the above-mentioned (C) phenol formaldehyde resin is a resol type phenol formaldehyde resin, (D) is not necessary because it has self-curing properties. but,
When using resol type phenol formaldehyde resin, in order to accelerate the reaction rate during mold making, for example, benzoic acid, acetylbenzoic acid, hydroxybenzoic acid, oxalic acid, succinic acid, p-toluenesulfonic acid, dodecylbenzenesulfonate. It is also possible to use organic acids such as acids and alkyl phosphoric acids as reaction promoters. The ratio of each component (A) to (D) used in the present invention is such that the total amount of (A) and (B) is 10 to 95% by weight, when the total amount is 100% by weight, and (C) and the total amount of (D) is 90-5
% by weight, preferably the total amount of (A) and (B) is 25-80% by weight, and the total amount of (C) and (D) is 75-20% by weight, particularly preferably (A) and (B). In order to achieve the effects of the present invention, it is preferable that the total amount of (C) and (D) be 65 to 30% by weight relative to the total amount of 35 to 70% by weight. Also, (A) and
The optimal blending ratio of (B) varies depending on the type of curing agent in (B) and the molding temperature, but the reactive activity of the curing agent in (B) is based on the number of polyvalent glycidyl compounds in (A). It is usually used at a blending ratio such that the amount of hydrogen groups is 0.5 to 4.0 times equivalent, preferably 1.0 to 2.5 times equivalent. The blending ratio of (C) and (D) is, if (C) is a novolak type, when the total amount of (C) + (D) is 100% by weight, (C) is
(D) is usually used in a proportion of 20 to 5% by weight relative to 80 to 95% by weight, and in the case of a resol type, usually no D curing agent is used. The total amount of each of the components (A) to (D) in the resin-coated sand of the present invention is usually 1 to 10% of the sand.
It is used in an amount of 1.5 to 4% by weight, preferably 1.5 to 4% by weight. Each of the above-mentioned components (A) to (D) of the present invention can be dissolved and/or suspended in an organic solvent or water, mixed with the sand at room temperature, and then dried to coat the sand, but in particular, the main components (A) and (C) are usually 150 to
It is desirable to add it in a solid state to sand preheated to 200°C, melt it, and coat the sand. Methods for obtaining the coated sand of the present invention coated with each of the above-mentioned components include () a method in which each sand grain is coated with all of (A), (B), and (C); () a method in which one sand grain is coated with (A); ) and (B), the other sand grain is coated with (C), and then both sand grains are mixed. () One sand grain is coated with (A), and the other sand grain is coated with (B) and (C). (A), (B), and (C) are individually coated on the sand grains, and then these sand grains are mixed. In addition, when (D) is further used, various methods can be adopted in addition to the above. For example, in the methods () and () above, at least a part of (D) is added to one of the sands, and the remaining part is added to the sand. Although it is sufficient to coat the other sand, it is usually sufficient to apply it to either one of the sands. The same applies when using a curing accelerator for (A) and (B) mentioned above or a reaction accelerator for (C),
It is more convenient for the purpose of the present invention to achieve the purpose of the present invention if the former is coated on (A) a different sand grain from the coated sand grain, and the latter is coated on a different sand grain from the coated sand grain (C), and then both sand grains are mixed. There are many things. However, in the method (), each component (A) to (D)
Although the order of addition of (A) and (C) is arbitrary, it is particularly necessary to perform the addition and mixing while cooling for a short time so that (A) and (C) do not react with each other during the mixing process with preheated sand. Since the curing agent components (B) and (D) are small in quantity, from the viewpoint of uniform mixing, they are usually dissolved or suspended in water or an organic solvent and added after coating (A) and (C). It is common to mix and dry. In addition, the resin-coated sand of the present invention also includes the above-mentioned (A).
In addition to the components (D), there are of course the various curing accelerators and reaction accelerators mentioned above, such as polyvalent epoxy resins, xylene resins, coumaron resins, petroleum resins, and polyesters with a structure different from that of (A). It is also possible to mix and use other resins such as resins within a range that does not impede the purpose of the present invention, and it is also possible to use auxiliary agents, sand and various resins that improve the slipperiness of casting sand and the ease with which it can be removed from molds. It is also possible to use adhesion promoters such as silane coupling agents and titanium coupling agents, or fillers other than sand, to improve the adhesion of the components. The resin-coated sand of the present invention thus obtained is filled into a mold heated to usually 150°C or higher, preferably 180°C to 300°C, and after being left for 30 seconds to 3 minutes, the mold is removed and a core etc. Obtain a mold. The mold thus obtained has stable and excellent mold strength when hot, regardless of the storage conditions of the resin-coated sand, so the defect rate during mold creation is extremely low. Even when used in sand, it has excellent thermal decomposition properties, so there is no need for a sand burning process for sand removal. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples. Production of resin-coated sand: Example 1 1 kg of No. 6 silica sand preheated to 200°C was placed in a stirring mixing tank with a cooling jacket, stirred while cooling, and heated to 180°C to prepare a novolak type phenol formaldehyde resin (softening point: 85°C). ), then 8 g of triglycidyl isocyanurate was added at 140°C, and after quenching, 2 g of dicyandiamide and 2 g of hexamethylenetetramine were added at 100°C.
The mixture was dispersed and dissolved in water, added and mixed, cooled and dried, and then discharged from the mixing tank to obtain resin-coated sand (1) of the present invention. Example 2 Using the same apparatus as in Example 1, a solid resol type phenol formaldehyde resin (softening point 84°C) at 160°C was added to 1 kg of preheated No. 6 silica sand.
After cooling and stirring at 140°C, add 15g of tri(β-methylglycidyl)isocyanurate, and after rapid cooling at 90°C, prepare fine powder of adipic dihydrazide 2.
g was suspended in 5 g of methanol, added and mixed, cooled and dried, and then discharged from the mixing tank to obtain resin-coated sand (2) of the present invention. Example 3 Using the same apparatus as in Example 1, 20 g of triglycidyl isocyanurate was added at 180°C to 1 kg of preheated No. 6 silica sand, stirred and cooled, and 5 g of dicyandiamide was added to 10 c.c. of water at 100°C. The coated sand (3A) was obtained by dispersing and mixing, cooling, drying, and removing the sand. On the other hand, for 1 kg of similarly preheated No. 6 silica sand,
At 180℃, add 22g of novolac type phenol formaldehyde resin (softening point 85℃), stir and cool, and add 3g of hexamethylenetetramine at 100℃.
It was dissolved in 10 g of water, added and mixed, cooled, dried, and then drained to obtain coated sand (3B). 500g of the above coated sand (3A) and the above coated sand (3B)
500g of the resin-coated sand (3) of the present invention was obtained. Example 4 Using the same equipment as in Example 1, a resol type phenol formaldehyde resin (softening point 84°C) which is solid at 160°C was added to 1 kg of preheated No. 6 silica sand.
g was added thereto, the mixture was quickly cooled, stirred, and the sand was discharged to obtain coated sand (4B). 350 g of the coated sand (3A) obtained in Example 3 and 650 g of the coated sand (4B) described above were mixed to obtain resin-coated sand (4) of the present invention. Example 5 22 g of triglycidyl isocyanurate was added at 160°C to 1 kg of No. 6 silica sand preheated using the same equipment as in Example 1, and the mixture was cooled to 100°C and 3 g of hexamethylenetetramine was dissolved in 10 g of water. Add, mix, cool and dry then drain and coat sand (5A)
I got it. On the other hand, for 1 kg of No. 6 silica sand preheated in the same way,
22 g of novolac type phenol formaldehyde resin (softening point 96° C.) was added at 180° C., and after cooling to 110° C., 3 g of phenyl biguanide was added and mixed, and after cooling, it was discharged to obtain coated sand (5B). 600g of the above coated sand (5A) and 400g of coated sand (5B)
g was mixed to obtain resin-coated sand (5) of the present invention. Example 6 Using the same apparatus as in Example 1, a reaction adduct of 2 moles of triglycidyl isocyanurate and 1 mole of isophthalic acid was prepared at 170°C with respect to 1 kg of preheated No. 6 silica sand.
After cooling to 100℃, add 23g of hexamethylenetetramine and 1-cyanoethyl-2-ethyl-
2g of 4-methylimidazole trimellitate for 10
The coated sand (6A) was obtained by dispersing and dissolving the mixture in 100 g of water, adding and mixing, cooling and drying, and then draining the sand. On the other hand, for 1 kg of similarly preheated No. 6 silica sand,
22 g of novolac type phenol formaldehyde resin (softening point 76°C) was added and mixed at 170°C, and after cooling, the sand was removed to obtain coated sand (6B). 500g of the above coated sand (6A) and 500g of coated sand (6B)
The resin-coated sand (6) of the present invention was obtained by mixing with g. Example 7 Triglycidyl isocyanurate was added to 1 kg of No. 6 silica sand preheated using the same equipment as in Example 1.
21 g was added and mixed at 160°C, cooled, and then drained to obtain coated sand (7A). On the other hand, resol type phenol formaldehyde resin (softening point
Add and mix 25g (78℃) at 160℃, cool, and heat to 100℃.
3 g of guanidine carbonate was dispersed in 10 g of water, added and mixed, cooled, dried, and then drained to obtain coated sand (7B). 500g of the above coating (7A) and 500g of coated sand (7B)
The resin-coated sand (7) of the present invention was obtained by mixing. Example 8 22 g of novolac-type phenol formaldehyde resin (softening point 85°C) was added and mixed at 180°C to 1 kg of No. 6 silica sand preheated using the same equipment as in Example 1, and the mixture was cooled at 100°C. 4 g of dicyandiamide and 3 g of hexamethylenetetramine were dispersed and dissolved in 10 g of water and added, mixed, cooled, dried, and then drained to obtain coated sand (8B). 500 g of the coated sand (7A) produced in Example 7 and 500 g of the above-mentioned coated sand (8B) were mixed to obtain resin-coated sand (8) of the present invention. Comparative Example 1 The coated sand (3A) produced in Example 3 was used as resin-coated sand (i) for comparative testing. Comparative Example 2 The coated sand (3B) produced in Example 3 was used as resin-coated sand (ii) for comparative testing. Evaluation of resin-coated sand: The resin-coated sands (1) to (8) of the present invention described above and the resin-coated sands (i) and (ii) as comparative examples were evaluated regarding the following items. (b) Measurement of strength at temperature The above-mentioned coated sands were tested at 230°C using a high-temperature tensile tester.
It was molded for 90 seconds, and the tensile strength at a temperature of 230°C was immediately measured. (b) Measurement of hot strength of resin-coated sand after storage After each coated sand described above was left in an environmental test chamber at 40°C and 95% relative humidity for one week, the hot tensile strength was measured in the same manner as in (a) above. did. (c) Thermal disintegration test Each of the above coated sands was preheated to 250℃ and had an inner diameter of 30 mm.
Pour the sand into a cylindrical mold with a height of 30 mm, heat it for 60 seconds, remove it to create a core, and place a core of sand with a diameter of 10 mm into a cylindrical main mold with an inner diameter of 70 mm and a depth of 70 mm, which was separately prepared using a bentonite mold. After attaching the discharge port and setting the above-mentioned core, pouring the 650°C aluminum light composite melt and cooling and solidifying it, the main mold was broken and vibrated for 5 minutes using a rotor-tap tester. The weight percent of sand discharged from the core from the outlet of the alloy casting was measured. The results of the evaluation tests (a), (b), and (c) above are listed in Table 1. 【table】

Claims (1)

[Scope of Claims] 1 (A) triglycidyl isocyanurate and/or tri(β-methylglycidyl)isocyanurate, (B) one or more of dicyandiamide, dicyandiamide derivative, organic acid hydrazide, or imidazole derivative, and (C) Resin-coated sand made by coating phenol formaldehyde resin as a binder. 2. Resin-coated sand according to claim 1, which is obtained by mixing sand coated with (A) and (B) and sand coated with (C). 3. Resin-coated sand according to claim 1, which is obtained by mixing sand coated with (A) and sand coated with (B) and (C). 4 (A) triglycidyl isocyanurate and/or tri(β-methylglycidyl)isocyanurate; (B) one or more of dicyandiamide, dicyandiamide derivative, organic acid hydrazide, or imidazole derivative; (C) phenol formaldehyde resin; D) Resin-coated sand made by coating hexamethylenetetramine with as a binder. 5 Sand coated with the above (A) and (B) and the above (C) and
The resin-coated sand according to claim 4, which is obtained by mixing sand coated with (D). 6 Sand coated with the above (A), (B) and (D) and the above (C)
The resin-coated sand according to claim 4, which is obtained by mixing the resin-coated sand with the sand coated with the resin-coated sand. 7 Sand coated with the above (A) and the above (B), (C) and (D)
The resin-coated sand according to claim 4, which is obtained by mixing the resin-coated sand with the sand coated with the resin-coated sand. 8 Sand coated with the above (A) and (D) and the above (B) and
The resin-coated sand according to claim 4, which is obtained by mixing the sand coated with (C).