JP4119515B2 - Resin coated sand for mold - Google Patents

Description

【００４０】
【表２】

【００４１】
表１及び表２にみられるように、フェノール樹脂にリン酸エステル、酸化剤、および有機カルボン酸金属塩としてシュウ酸カリウムや酒石酸カリウムを含有させて調製した粘結剤を被覆して調製した各実施例のレジンコーテッドサンドは、各比較例のものよりも曝熱後強度保持率が低く、鋳型の崩壊性が良好であることが確認される。
【００４２】
【発明の効果】
上記のように本発明は、フェノール樹脂にリン酸エステル、酸化剤、および有機カルボン酸金属塩を配合して調製される粘結剤で、砂粒の表面が被覆された鋳型用レジンコーテッドサンドであって、有機カルボン酸金属塩として、シュウ酸カリウム、酒石酸カリウムから選ばれるものを用いて成ることを特徴とするものであり、粘結剤に配合したリン酸エステル、酸化剤、および有機カルボン酸金属塩の作用でフェノール樹脂は炭化分解され易くなっており、アルミニウム鋳造やマグネシウム鋳造など鋳込み温度が低い鋳造を行なうにあたっても、粘結剤は容易に分解して鋳型の崩壊性が良好になり、砂落としの作業を容易に行なうことができるものである。
【００４３】
また請求項２の発明は、酸化剤として、酸素酸の塩を用いるようにしたので、酸素酸の塩は安定であって取り扱いが容易であり、レジンコーテッドサンドを調製するうえでの作業性が高まるものである。
また請求項３の発明は、酸素酸の塩として、硝酸塩を用いるようにしたので、鋳型の崩壊性を一層良好にすることができるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin-coated sand for a mold used for casting.
[0002]
[Prior art]
The casting mold is produced by molding refractory sand grains such as silica sand by binding them with a binder. Castings that are shaped and cast by the shell mold method are frequently used because they have excellent characteristics such as a smooth casting surface and good dimensional accuracy. As the binder for the shell mold, a novolak-type or resol-type phenol resin is generally used. By coating this phenol resin binder on the surface of sand particles, a resin-coated sand is produced. The resin-coated sand can be sprinkled or filled into a heated mold to melt and cure the binder, thereby forming a casting mold.
[0003]
And when casting by casting the molten metal into the mold, the binder is decomposed by the high temperature action of the molten metal, the binding action of the sand particles by the binder disappears, and the mold can be collapsed, Casting can be removed.
[0004]
[Problems to be solved by the invention]
However, when using a metal with a high casting temperature, the binder can be easily decomposed, but when casting using a metal with a low casting temperature as in the case of castings such as aluminum and magnesium. Since the casting temperature is low, the binder is not sufficiently decomposed, and it is necessary to take out the casting from the mold in a state where the binding action of the sand particles by the binder is maintained.
[0005]
For this purpose, the mold is struck with a hammer, shot blasting or vibration is repeatedly applied, or the mold is placed in a furnace at 300 to 500 ° C. for a long time to reduce the binding force of the binder. As a result, there has been a problem that a great amount of labor and cost are required for the so-called sand removal operation of removing the mold.
The present invention has been made in view of the above points, and an object of the present invention is to provide a resin-coated sand for a mold which can obtain a mold having good disintegration even in casting at a low casting temperature.
[0006]
[Means for Solving the Problems]
The resin coated sand for a mold according to the present invention is a resin for a mold in which the surface of sand grains is coated with a binder prepared by blending a phenolic resin with a phosphate ester , an oxidizing agent, and an organic carboxylic acid metal salt. Coated sand, characterized in that the organic carboxylic acid metal salt is selected from potassium oxalate and potassium tartrate .
The invention of claim 2 is characterized in that a salt of oxygen acid is used as the oxidizing agent.
[0007]
The invention of claim 3 is characterized in that nitrate is used as the salt of oxygen acid.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
In the present invention, as the phenolic resin, it is preferable to use a solid phenolic resin obtained by reacting phenols and formaldehyde in the presence of a reaction catalyst and dehydrating the reaction product.
[0009]
Here, the above phenols mean phenol and phenol derivatives. For example, in addition to phenol, trifunctional compounds such as m-cresol, resorcinol, 3,5-xylenol, bisphenol A, dihydroxy Tetrafunctional ones such as diphenylmethane, 2 such as o-cresol, p-cresol, p-ter-butylphenol, p-phenylphenol, p-cumylphenol, p-nonylphenol, 2,4 or 2,6-xylenol Functional o- or p-substituted phenols can be mentioned, and halogenated phenols substituted with chlorine or bromine can also be used. Of course, one type can be selected and used, or a plurality of types can be mixed and used.
[0010]
As the formaldehyde, formalin in the form of an aqueous solution is optimal, but forms such as paraformaldehyde, acetaldehyde, benzaldehyde, trioxane, and tetraoxane can be used. In addition, some formaldehyde is furfural. It is also possible to replace it with furfuryl alcohol.
[0011]
The blending ratio of phenols to formaldehydes is preferably set so that the molar ratio of phenols to formaldehyde is in the range of 1: 0.6 to 1: 3.5.
When preparing a novolak type phenolic resin, the reaction catalyst is an inorganic acid such as hydrochloric acid, sulfuric acid or phosphoric acid, or an organic acid such as oxalic acid, paratoluenesulfonic acid, benzenesulfonic acid or xylenesulfonic acid, or zinc acetate. Can be used. Moreover, when preparing a resol type phenol resin, an alkaline earth metal oxide or hydroxide can be used, and aliphatic dimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, diethylenetriamine, dicyandiamide and the like can be used. Primary amine, secondary amine, tertiary amine, aliphatic amines having aromatic rings such as N, N-dimethylbenzylamine, aromatic amines such as aniline and 1,5-naphthalenediamine, ammonia, hexamethylenetetramine, etc. In addition, other divalent metal naphthenic acid, divalent metal hydroxide, and the like can also be used.
[0012]
Said novolak-type phenol resin and resol-type phenol resin can also be mixed and used in arbitrary ratios as needed.
In the present invention, a phosphoric acid ester , an oxidizing agent, and an organic carboxylic acid metal salt are blended with this phenol resin and used as a binder.
Phosphate esters and oxidizers have long been known as combustion accelerators for phenol resins, etc., and their combustion promotion mechanism has not been elucidated, but it has the effect of promoting the carbonization of phenol resins. It is believed that. Therefore, it is expected that the disintegration of the template can be promoted by carbonizing the phenol resin even at a relatively low temperature by blending the phosphate ester and the oxidizing agent with the phenol resin. In this way, the knowledge that the disintegration of the template can be further improved by blending the organic carboxylate metal salt in combination with the phosphate ester and the oxidizing agent has been obtained and completed. is there.
[0013]
Here, as the phosphoric acid ester , trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, tributoxyethyl phosphate, trioleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, Cresyl diphenyl phosphate, xylenyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate, trischloroethyl phosphate, trisdichloropropyl phosphate, tris β chloropropyl phosphate, tris (tribromophenyl) phosphate, bis-2-ethylhexyl phosphate, phosphorus Examples include diisododecyl acid, dibutyl butyl sulfonate, dibutyl butyl phosphonate, etc. . This phosphate ester is desirably used in the range of about 0.1 to 15 parts by weight with respect to 100 parts by weight of the phenol resin. The blending amount varies depending on the performance required as a mold, but generally, when the amount is less than 0.1 part by weight, the disintegration of the mold tends to be insufficient. There is a tendency that the fusion point of the sand is lowered and the handling property is deteriorated.
[0014]
Examples of the oxidizing agent include peroxides such as benzoyl peroxide and ammonium peroxide, oxides of elements having a higher valence than ordinary valences such as lead peroxide, manganese dioxide, and cesium dioxide, copper oxide, Examples thereof include iron oxides or salts of oxygen acids such as potassium dichromate, potassium chromate, potassium permanganate, potassium nitrate, lithium nitrate, sodium nitrate, and cesium nitrate.
[0015]
Of these, oxygen acid salts are preferred. Peroxides are often in liquid form at room temperature and are extremely unstable, so they must be handled with great care and are easily decomposed. Therefore, storing resin-coated sand for a long period of time is effective as an oxidizing agent. Although there is a risk of lowering the fusion point of the resin-coated sand, it is preferable to use an oxygen acid salt since the salt of oxygen acid is stable and easy to handle.
[0016]
Of the oxygen acid salts , nitrate is particularly preferred. Oxygen acid salt facilitates the decomposition of the binder and promotes carbonization, but nitrate has the effect of further decomposing carbide carbon bonds compared to other salts , so it is particularly preferable to use nitrate. is there.
The blending amount of the oxidizing agent is preferably set in the range of about 0.1 to 15 parts by weight with respect to 100 parts by weight of the phenol resin. This amount varies depending on the performance required for the mold, but generally, when the amount of the oxidizing agent is less than 0.1 parts by weight, the mold disintegration tends to be insufficient, and conversely, it exceeds 15 parts by weight. And the strength of the binder tends to be lowered, and the handleability of the mold tends to deteriorate.
[0017]
The organic carboxylic acid constituting the above organic carboxylic acid metal salt includes formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid Fatty acids such as linoleic acid and elaidic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, o-toluic acid, m-toluic acid, p-toluic acid, o-chlorobenzoic acid, m-chlorobenzoic acid, p- Chlorobenzoic acid, o-bromobenzoic acid, m-bromobenzoic acid, p-bromobenzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, salicylic acid, p-hydroxybenzoic acid, o- Aminobenzoic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-methoxybenzoic acid, m-methoxybenzoic acid, -Aromatic carboxylic acids such as methoxybenzoic acid, or saturated dibasic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, tartaric acid, phthalic acid, Aromatic dibasic acids such as isophthalic acid and terephthalic acid can be exemplified.
[0018]
Examples of the metal constituting the organic carboxylic acid metal salt include lithium, sodium, magnesium, aluminum, potassium, calcium, titanium, manganese, iron, nickel, copper, zinc, barium, and tin. In the dibasic acid, at least one carboxyl group is a metal salt.
The amount of the organic carboxylic acid metal salt is preferably set in a range of about 0.1 to 15 parts by weight with respect to 100 parts by weight of the phenol resin. Although the blending amount varies depending on the performance required as a mold, generally, when the blending amount of the organic carboxylic acid metal salt is less than 0.1 parts by weight, the disintegration of the mold tends to be insufficient. If it exceeds 15 parts by weight, the strength of the binder tends to decrease and the mold handling property tends to deteriorate.
[0019]
The above phosphoric acid ester , oxidizing agent, and organic carboxylic acid metal salt may be added at the initial stage of synthesis in which the phenol resin is subjected to a condensation reaction, and further, the binder of the phenol resin is coated on the surface of the sand particles. You may make it add at the time. Further, the phosphate ester , the oxidizing agent, and the organic carboxylic acid metal salt may be simply mixed with the phenol resin, or may be partially reacted with the phenol resin and incorporated into the molecule.
[0020]
As described above, a binder can be prepared by blending a phosphate ester , an oxidizing agent, and an organic carboxylic acid metal salt with a phenol resin, but it is preferable to further blend a lubricant with the binder. Examples of lubricants include aliphatic waxes such as ethylene bisoleic acid amide, ethylene bis stearic acid amide, methylene bis stearic acid amide, oxystearic acid amide, palmitic acid amide, calcium stearate, aluminum stearate, zinc stearate, and carnauba wax. Olefin wax or the like can be used. By blending the lubricant, the tackiness of the binder can be reduced and the fusion point can be increased, so that blocking can be prevented from occurring.
[0021]
And the resin-coated sand for casting molds according to the present invention can be obtained by coating the binder prepared as described above on the surface of fire-resistant sand grains such as silica sand.
The sand particles can be coated with a binder by a dry hot coating method, a cold coating method, a semi-hot coating method, a powder solvent method, or the like.
[0022]
In the dry hot coating method, a solid binder made of a solid phenol resin is added to and mixed with sand heated to 130 to 180 ° C., and the solid binder is melted by heating with sand to form the surface of the sand with the binder. And then cooling with this mixture kept, to obtain a granular and free-flowing resin-coated sand.
[0023]
The cold coating method is a method in which a resin-coated sand is obtained by dissolving a binder in a solvent such as methanol to form a liquid, adding it to sand grains, mixing the mixture, and volatilizing the solvent.
The semi-hot coating method is a method for obtaining a resin-coated sand by adding and mixing a liquid binder dissolved in the above solvent to sand heated to 50 to 90 ° C.
[0024]
The powder solvent method is a method of obtaining a resin-coated sand by pulverizing a solid binder, adding the pulverized binder to sand grains, adding a solvent such as methanol, and mixing them.
In any of the above methods, a granular and smooth resin-coated sand can be obtained, but the dry hot coating method and the semi-hot coating method are preferable in terms of workability.
[0025]
The mixing ratio of the sand particles and the binder varies depending on the performance required as a mold, and is not particularly limited. However, the binder is 0.5 in terms of resin solid content with respect to 100 parts by weight of the sand particles. About 4 parts by weight is preferred. In addition, a curing agent and other various coupling agents such as a silane coupling agent for making the sand particles and the binding agent compatible with each other can be blended if necessary.
[0026]
The resin-coated sand thus obtained is sprinkled or filled into a heated mold in accordance with a conventional method, and the binder phenolic resin is melted and cured to bond the sand particles with the binder. A mold is formed by action. And casting can be performed by casting a molten metal in the casting_mold | template produced in this way. Here, since the binder contains a phosphate ester , an oxidizing agent, and an organic carboxylic acid metal salt , the phenol resin is easily carbonized and decomposed, and the casting temperature is low such as aluminum casting or magnesium casting. In casting, the binder is easily decomposed and the mold has good disintegration, and the sand removal operation can be easily performed.
[0027]
【Example】
Next, the present invention will be specifically described with reference to examples.
First, a phenol resin was prepared as follows.
(Preparation of novolak type phenolic resin I)
A reaction vessel was charged with 940 parts by weight of phenol, 649 parts by weight of 37% formalin, and 4.7 parts by weight of oxalic acid, refluxed for about 60 minutes, and allowed to react for 120 minutes. This was dehydrated at normal pressure to an internal temperature of 160 ° C. and then dehydrated under reduced pressure at 100 Torr to obtain a novolac type phenol resin (phenol resin I) having a softening point of 95 ° C.
[0028]
(Preparation of resol type phenolic resin II)
A reaction vessel was charged with 680 parts by weight of phenol, 880 parts by weight of 37% formalin and 101 parts by weight of hexamethylenetetramine. The temperature was raised to 70 ° C. in about 60 minutes, and the reaction was continued for 5 hours. This was dehydrated under reduced pressure to 90 ° C. at 100 torr, then discharged into a vat and cooled to obtain a resol type phenol resin (phenol resin II) having a softening point of 80 ° C.
[0029]
(Preparation of novolak type phenol resin III)
The novolac type phenol resin I prepared as described above was mixed with 5% by weight of tributyl phosphate to obtain a novolac type phenol resin (phenol resin III) having a softening point of 90 ° C.
(Preparation of resol type phenol resin IV)
In the operation of synthesizing the phenol resin II, 5% by weight of tributyl phosphate is added immediately before the resin is discharged from the reaction vessel, and then discharged and cooled, whereby a resol type phenol resin (phenol resin having a softening point of 76 ° C.). IV) was obtained.
[0030]
(Example 1)
30 kg of fluttered silica sand heated to 145 ° C. is placed in a whirl mixer, 600 g of novolak type “phenol resin III” is added and kneaded for 30 seconds, and then 90 g of hexamethylenetetramine, 30 g of potassium nitrate and 30 g of potassium oxalate are dissolved in 450 g of water. Was added and kneaded until the sand grains collapsed. Next, 30 g of calcium stearate was further added thereto, and after kneading for 30 seconds, this was discharged and aerated to obtain a resin-coated sand having a resin amount of 2% by weight.
[0031]
(Example 2)
In the same manner as in Example 1, 30 kg of heated fluttered silica sand was put in a whirl mixer, and after adding 600 g of novolak-type “phenol resin III” and kneading for 30 seconds, 90 g of hexamethylenetetramine, 30 g of potassium nitrate and 60 g of potassium oxalate were 450 g. What was dissolved in water was added and kneaded until the sand grains collapsed. Thereafter, in the same manner as in Example 1, a resin-coated sand having a resin amount of 2% by weight was obtained.
[0032]
(Example 3)
Resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Example I except that 30 g of potassium tartrate was used instead of 30 g of potassium oxalate.
Example 4
Resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Example I except that 60 g of potassium tartrate was used instead of 30 g of potassium oxalate.
[0033]
(Example 5)
Add 30 kg of fluttered silica sand heated to 140 ° C. into a whirl mixer, add 600 g of resole type “phenol resin IV” and knead for 30 seconds, then add 30 g of potassium nitrate and 30 g of potassium oxalate dissolved in 300 g of water. A resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Example 1 except that the kneading was continued until the sand grains collapsed.
[0034]
(Comparative Example 1)
In the same manner as in Example 1, 30 kg of heated fluttered silica sand was put in a whirl mixer, 600 g of novolak type “phenolic resin I” was added and kneaded for 30 seconds, and then 90 g of hexamethylenetetramine dissolved in 450 g of water was added. The mixture was kneaded until the sand grains collapsed. Thereafter, in the same manner as in Example 1, a resin-coated sand having a resin amount of 2% by weight was obtained.
[0035]
(Comparative Example 2)
Add 30 kg of fluttered silica sand heated to 145 ° C. to a whirl mixer, add 600 g of novolak type “phenolic resin III” and knead for 30 seconds, then add 90 g of hexamethylenetetramine and 30 g of potassium nitrate dissolved in 450 g of water. Thereafter, in the same manner as in Comparative Example I, a resin-coated sand having a resin amount of 2% by weight was obtained.
[0036]
(Comparative Example 3)
Resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Comparative Example 1 except that a resol-type “phenol resin II” was used.
(Comparative Example 4)
Resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Comparative Example 1, except that resol-type “phenol resin IV” was used and 30 g of potassium nitrate was dissolved in 450 g of water and added.
[0037]
(Comparative Example 5)
A resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Comparative Example 1 except that a novolak-type “phenol resin III” was used.
(Comparative Example 6)
Resin-coated sand having a resin amount of 2% by weight was obtained in the same manner as in Comparative Example 2 except that a novolak-type “phenol resin I” was used.
Using the resin-coated sand obtained in Examples 1 to 5 and Comparative Examples 1 to 6 as described above, the fusion point, the room temperature bending strength, and the bending strength after heating were measured. The fusion point was measured according to JACT test method SM-1, and the normal temperature bending strength was measured according to JACT test method C-1. Also, the bending strength after heat exposure was wrapped with aluminum foil using the same specimen as the normal temperature bending strength, placed on a stainless steel bat and placed in a blower dryer set at 350 ° C, 400 ° C, 450 ° C 30 minutes later. After taking out, it waited until it became normal temperature, and tested by measuring the bending strength after heat exposure using a bending strength tester. These results are shown in Tables 1 and 2. Tables 1 and 2 show the strength retention after exposure calculated by the following equation.
[0038]
Strength retention after exposure (%) = (Bending strength after heating / bending strength at room temperature) × 100
[0039]
[Table 1]

[0040]
[Table 2]

[0041]
As seen in Tables 1 and 2, each prepared by coating a phenolic resin with a binder prepared by adding potassium oxalate or potassium tartrate as a phosphate ester , an oxidizing agent, and an organic carboxylic acid metal salt. It is confirmed that the resin coated sands of the examples have lower strength retention after heating than those of the respective comparative examples, and the mold disintegration is good.
[0042]
【The invention's effect】
The present invention as described above, phenol resin phosphoric acid ester, oxidizing agents, and organic carboxylic acid metal salt binder to be prepared by blending, there in the mold resin-coated sand the surface of the sand grains coated The organic carboxylate metal salt is selected from potassium oxalate and potassium tartrate, and is composed of a phosphate ester , an oxidizing agent, and an organic carboxylate metal compounded in a binder. Due to the action of salt, phenolic resin is easily carbonized and decomposed, and even when casting at low casting temperatures such as aluminum casting and magnesium casting, the binder easily decomposes and the mold disintegration becomes good, and sand is lost. The dropping operation can be easily performed.
[0043]
In the invention of claim 2, since an oxygen acid salt is used as the oxidizing agent, the oxygen acid salt is stable and easy to handle , and the workability in preparing the resin-coated sand is improved. It will increase.
In the invention of claim 3, since nitrate is used as the salt of oxygen acid, the disintegration property of the template can be further improved.

Claims (3)

A binder prepared by blending a phenolic resin with a phosphate ester , an oxidant, and an organic carboxylic acid metal salt , and a resin-coated sand for a mold with the surface of sand grains coated, and as an organic carboxylic acid metal salt A resin-coated sand for molds, comprising a material selected from potassium oxalate and potassium tartrate . 2. The resin-coated sand for a mold according to claim 1, wherein a salt of oxygen acid is used as the oxidizing agent. The resin-coated sand for a mold according to claim 2, wherein nitrate is used as the salt of oxygen acid.