JPS6149740A - Production of resin-coated sand for casting - Google Patents

Abstract

PURPOSE:To improve the collapsing property of resin-coated sand by adding and kneading simultaneously respectively specific weight ratios of solid phenolic resin and phosphate to and with silica sand at a prescribed temp. and adding and mixing further a specific weight ratio of lubricant to and with such mixture. CONSTITUTION:1.0-2.0pts.wt. novolak or resol type phenolic resin and 0.15- 1.0pt.wt. phosphate such as triphenyl phosphate are simultaneously added and kneaded to and with 100pts.wt. silica sand heated to 100-200 deg.C. The lubricant such as olefin wax is added and mixed at 0.05-0.3pt.wt. to and with such mixture, by which the resin-coated sand for a casting is obtd. The solid phenolic resin and phosphate coat simultaneously the silica sand according to the above-mentioned method; at the same time, the lubricant decreases the tackiness among the sand grains and increases the welding point thereof. The collapsing property and blocking property of the coated sand are thus improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing resin-coated sand for foundries, and is particularly applicable to the production of castings with relatively low casting temperatures, such as aluminum castings and alloy castings. The present invention relates to a method for producing resin-coated foundry sand that significantly improves the collapsibility of the mold after casting.

[Conventional technology]

Generally, the binder used in resin-coated sand for foundries is a resin obtained by reacting phenol and formaldehyde in an acidic or alkaline solution. When used for this purpose, a very large amount of cost and labor is required to remove sand after casting.

In other words, when these phenolic resins are used, even after casting, the mold still maintains its strength due to the low pouring temperature, and is then heat treated at a high temperature of about 500°C for 6 to 12 hours. The cast base will not collapse unless an impact is applied after casting, and post-casting treatment requires a great deal of cost and labor.

100~200℃ in Japanese Patent Application Laid-Open No. 57-209741
After coating 1.5 to 3 parts by weight of a solid phenol resin on 100 parts by weight of silica sand heated to
5 to 1.5 parts by weight, and further 0.05 to 0.0 parts by weight of lubricant.
A method for producing resin-coated sand for foundries is described, which includes adding and mixing 3 parts by weight.

The resin-coated sand produced by such a method has a disadvantage in that the disintegrability is insufficient because the phenol resin and the phosphoric acid ester are difficult to mix and fuse.

Furthermore, Japanese Patent Application Laid-Open No. 58-3745 describes a resin binder for castings which is a mixture of a phosphoric acid ester and a solid phenol resin. However, when phosphoric acid ester is melted in 100 parts by weight of phenol resin, if 7.5 parts by weight or more is added, the resin will block during storage, which is not preferable.

[Problem that the invention seeks to solve]

The present invention provides a method for producing resin-coated sand for foundries which does not require long-term heat treatment during casting and has extremely excellent disintegration properties that disintegrates only by mechanical impact. be.

[Means for solving problems]

In the present invention, silica sand heated to 100 to 200°C
After adding and kneading 1.0 to 2.0 parts by weight of a solid phenol resin and 0.15 to 1.0 parts by weight of a phosphoric acid ester to 0 parts by weight, 0.05 to 0.05 parts by weight of a lubricant is added. A resin-coated sand for foundry is manufactured by adding and mixing 0.3-layered part. This resin-coated sand coats the silica sand with the solid phenol resin and the phosphate ester at the same time, so the phosphate ester and the 7-dinol resin are well mixed on the sand, improving the collapsibility. There is also no need to worry about resin blocking.

Furthermore, in the present invention, it is essential to add and mix a lubricant after coating the phenol resin and phosphoric acid ester.

In other words, coated sand in which 100 parts by weight of silica sand is coated with 1.0 to 2.0 parts by weight of solid phenol tJJ AM and 0.15 to 1.0 parts by weight of phosphoric acid ester has a low melting point, so it is difficult to use in summer. Blocking during storage of the coated sand is a problem, but the lubricant should be added to 100 parts by weight of silica sand from 0.05 to 0.05 parts by weight.
By adding 0.3 parts by weight, the tackiness between sand grains decreases and the fusion point increases, so blocking can be prevented.

The present invention will be explained in more detail.

As the solid phenolic resin used in the present invention, novolac type phenolic resins, resol type phenolic resins, and mixtures and melts thereof can be used.

As the novolak resin, in addition to the commonly used phenol and formaldehyde novolak resins, so-called high ortho type novolak resins, novolak resins modified with alkylphenols, etc. can be used.

It is highly preferred to use a solid resol type phenolic resin as the 7-enol resin in the present invention. In the example using a solid resol type phenolic resin, a higher disintegration rate was obtained than in the example using a novolac type phenol resin. This is because the so-called anthoniaresol resin, which is obtained using ammonia or amines as a catalyst, has a window-containing element bond called N-methylene in its molecule, compared to novolak-type phenol resin, which only has methylene bonds. It is thought that this is because the heat resistance is low and the disintegration property is improved.

The resol type phenolic resin that can be used in the present invention includes a monosol type phenol resin using ammonia or amines as a catalyst, and a resol type obtained by a combined catalyst of ammonia or amines and an alkali metal or alkaline earth metal hydroxide. Phenol resin etc. can be used.

In the present invention, it is a more preferable example to use a mixture or a mixture of a novolac type phenol resin and a resol type phenol resin as the solid phenol resin because mold strength is improved.

The blending ratio of novolac type phenolic resin and resol type phenolic resin is preferably 1/9 to 4/6. If it is less than 1/9, the effect of improving mold strength will be small, and if it exceeds 4/6, the curing speed will be slow, which is not preferable.

Phosphate ester is 0 per 100ffiffi parts of silica sand.
．． 15 to 1.0 parts by weight are used. If it is less than 0.15 parts by weight, the effect of improving disintegration is small, and if it exceeds 1.0 parts by weight, the melting point becomes too low, which is not preferable. Phosphate esters include trimethyl phosphate, triethyl phosphate, triglythyl phosphate, trioctyl phosphate,
Tributoxyethyl phosphate, trischloroethylene phosphate, trischlorofurobyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, octyldiphenyl phosphate, xylenyl Orthophosphoric acid esters such as diphenyl phosphate, trilauryl phosphate, tricetyl phosphate, tristearyl phosphate, trioleyl phosphate, trimethyl phosphite, tributyl phosphite, triphenyl phosphite, tridodecyl phosphite, trisnonylphenyl Phosphite triesters such as phosphite, trischloroethyl phosphite, tristridecyl phosphite, phosphorous diesters such as dimethyl phosphite, diethyl phosphite, dibutyl phosphite, dibutylcuptylphosphonate f, di(2-ethylhexyl) ) Phosphonate esters such as 2-ethylhexylphosphonate can be used.

The solid phenol resin and the phosphoric acid ester are added and kneaded to the heated silica sand simultaneously or substantially simultaneously.

Here, "substantially simultaneously" means that the interval between the addition of both, that is, the interval between the introduction of one and the start of introduction of the other, is within 10 seconds.

By rubbing in this manner, both are uniformly mixed and fused on the sand.

As lubricants, ethylene bisstearamide, ethylene bisoleic acid amide, methylene bisstearamide, oxystearamide, stearamide, balmitic acid amide, oleic acid amide, valmitic acid amide, calcium stearate,
Fatty acid waxes such as zinc stearate and olefin waxes such as carnauba wax and Kist wax can be used.

Examples and comparative examples of the present invention will be described below.

〔Example〕

Example 1 1880 g of phenol, 375 g of 8096 paraformaldehyde, 405 g of 37% formalin and 4 g of IN hydrochloric acid were weighed into a four-way flask equipped with a stirrer, a reflux condenser, and a thermometer, and heated on an oil bath without stirring until the reaction solution was heated to reflux temperature. React until emulsified. Thereafter, the reflux reaction was further carried out for 2 hours, and then concentrated under reduced pressure to obtain a novolak type phenol resin having a softening point of 85°C.

8 pieces of Fremantle silica sand heated to 140°C and 144 g of the above novolak type phenolic resin (1.8 g per silica sand)
96) and 24 g of triphenyl phosphate at the same time.
ζ was added, mixed for 40 seconds with a speed mixer, 144 g of 1596 hexamethylenetetramine aqueous solution was added, kneaded for 30 seconds, and 8 g of calcium stearate was added.
Mix for seconds and discharge to obtain resin coated sand.

Example 2 Phenol 940g 3796 formalin 1460 in a Yotsuro flask equipped with a stirrer, reflux condenser, and thermometer
．． Weighed out 136 g of 25% ammonia water, stirred, heated on an oil bath, reacted at 70°C for 1 hour, and gradually raised the temperature while concentrating under reduced pressure. When the internal temperature reached 90°C, the reaction started. The material was taken out and allowed to cool to obtain a solid resol type phenol resin.

8 Kf of Freemantle silica sand heated to 140° C., 144 g of the above solid resol type phenol resin, and 24 g of triphenyl phosphate were added at the same time, and kneaded for 40 seconds with a speed mixer.

120 g of water was added, kneaded for 30 seconds, 8 g of calcium stearate was added, mixed for 20 seconds and discharged to obtain resin-coated sand.

Example 3 Fremantle silica sand 8b heated to 140°C and Example 1
44g of solid novolak type phenolic resin obtained in 1 100g of solid resol resin obtained in Example 2 and 24g
g of talesyl diphenyl phosphate was added at the same time and kneaded for 40 seconds with a speed mixer. 120 g of water was added, kneaded for 30 seconds, 12 g of ethylene bisstearamide was added, mixed for 20 seconds, and discharged to obtain resin-coated sand.

Comparative Example 1 Novolac type phenolic resin 200 obtained in Example 1
After melting the mixture by heating it up to -150° C. in a flask, 8 g of triphenylphosphor was added and dissolved to obtain a phenol resin containing 496 phosphate esters.

Fremantle silica sand 8 heated to 140°C and 144 g of the above resin were kneaded for 40 seconds with a speed mixer, and then 1
Add 144 g of 5% hexamethylenetetramine aqueous solution and mix for 30 seconds, then add 8 g of calcium stearate.
Mixing was performed for 0 seconds to obtain resin-coated sand.

Comparative Example 2 Fremantle silica sand 8~ heated to 140°C and Example 1
After kneading 144 g of the novolak type phenol resin obtained in 1596 for 40 seconds with a speed mixer, 24 g of triphenyl phosphate was added and kneaded for 20 seconds.
Add 144 g of hexamethylenetetramine aqueous solution and
After mixing for seconds, 8 g of calcium stearate was added, mixed for 20 seconds, and discharged to obtain resin-coated sand.

Comparative Example 3 One experiment was carried out in the same manner as in Example 1 except that calcium stearate was not added.

The properties of the resin-coated sand obtained in Examples and Comparative Examples are shown in the table below. It can be seen that Example 1 of the present invention has greatly improved disintegration properties compared to Comparative Example 1.

In Comparative Example 2, the disintegration rate was low because the phenol resin and phosphoric acid ester were difficult to mix and melt.

Example 2 has higher disintegrability than Example 1 and is a preferable example. Example 3 has high mold strength.

The lubricant used is 0.3 parts by weight of O, OS per 100 parts by weight of silica sand. If it is less than 0.05 parts by weight, blocking may occur, which is not preferable (if it exceeds 0.3 parts by weight, it is not preferable because the curing speed becomes slow and the adhesive force between sand grains is inhibited.

Measuring method Fusion point j Based on JAOT shell work standards.

Bending strength: 5JXs Based on x-6910.

Disintegration rate: 30φX heated to 250℃ Resin-coated sand in a 50mmH mold Place in electric furnace at 400℃ for 3 minutes Let it harden and make a test piece. Ru. 500 kept in anoxic condition Enclose it in a mold heated to ℃, Bake for 20 minutes in a 500℃ oven. After that, let it cool. This test piece Place the rice on a 28-mesh sieve. -Using a tap sieve shaker 1~ Shake for 5 minutes and see if the amount decreases. The disintegration rate was calculated using the following equation.

[Effects of the Invention] According to the present invention, resin-coated sand for foundry use having excellent collapsibility and blocking properties was obtained. It also prevents resin blotting during the manufacturing process of resin-coated sand for foundries.

Claims (1)

[Claims] 1. 1.0 to 2.0 parts by weight of solid phenol resin and 0.15 to 1.0 parts by weight of phosphoric acid ester are added to 100 parts by weight of silica sand heated to 100 to 200°C. Lubricant 0.05 to 0.3 after addition and kneading at the same time or substantially simultaneously
A method for producing resin-coated sand for foundries, characterized by adding and mixing parts by weight. 2. The method for producing resin-coated sand for foundries according to claim 1, wherein the solid phenolic resin is a novolac type phenolic resin. 3. The method for producing resin-coated sand for foundries according to claim 1, wherein the solid phenolic resin is a resol type phenolic resin. 4. The method for producing resin-coated sand for foundries according to claim 1, wherein the solid phenolic resin is a mixture of a novolac type phenolic resin and a resol type phenolic resin. 5. The method for producing resin-coated sand for foundries according to claim 1, wherein the solid phenolic resin is a mixture of a novolac type phenolic resin and a resol type phenolic resin. 6. The method for producing resin-coated sand for foundries according to claim 4 or 5, characterized in that the blending ratio of novolac type phenolic resin and resol type phenolic resin is 1/9 to 4/6. .