JPS5947041A - Production of resin coated sand for casting - Google Patents

Abstract

PURPOSE:To obtain resin coated sand for castings having the mold moldability equal to the moldability of phenolic resin coated sand by adding oxides of I -III, IVor VIII group metals of periodic table during production of polyester resin coated sand to improve the low melt sticking point which is the disadvantage of the abovd-described resin coated sand. CONSTITUTION:Unsatd. polyester which is solid at ordinary temp. e.g.,; alpha, beta- unsatd. polyester (e.g.; the resulted product of reaction of alpha, beta-unsatd. dibasic acid and polyhydric alcohol), an unsatd. monomer having >=1 unsatd. bonds (e.g.; styrene) or a prepolymer and a catalyst for polymn. are coated on molding sand grains by a hot melt liquid. Oxides of metals belonging to I -III, IV or VIII groups of periodic table of elements are required to be added particularly at 1- 30pts.wt. based on 100pts.wt. the unsatd. polyester during the manufacture of said polyester resin coated sand. As a result, the polyester resin coated sand having the above-described characteristics of >=90 deg.C melt sticking point is obtd. The oxides of the above-mentioned metals are exemplified by, for example, MgO, ZnO, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing JfiJ oil-coated sand for foundries used in forming molds and cores for foundries.

Currently, the shell molding method is the mainstream method for manufacturing molds and cores for 9g production, and phenolic resin is generally used as the resin for covering the sand grains. However, phenolic position 1 fat is.

During the coating, molding, and pouring processes of the shell molding process, gases with harmful and unpleasant odors such as phenol, ammonia, aldehyde, and carbon oxide are generated during heating, and when the casting temperature is low, such as aluminum casting. There are drawbacks such as poor mold disintegration properties when ((i 50 to 750°C)).

These drawbacks of phenolic resins are summarized as 116 (good-4-).

Recently, unsaturated polyester resins have begun to attract attention as resins for coating sand grains in castings, and are published in JP-A-49-48520, JP-A-50-30114, and JP-A-50-104721.
No. 1, JP-A-51-29318, JP-A-54-
Although it is disclosed in Japanese Patent Application Laid-open No. 80234 and Japanese Patent Application Laid-Open No. 56-595fiO, it is still used in only a few cases.

Although polyester resin-coated sand using unsaturated polyester resin as a coating agent for foundry sand grains improves the above-mentioned drawbacks of phenolic resin-coated sand using phenolic resin as a coating agent, it also has the disadvantage of poor moldability. There is. That is, using a blow-in shell mold making machine, 28
When molds heated to 0 to 300°C are filled with resinous sand and molded into 7-L cores, the magazine of the mold-making machine is densified and the filling performance is reduced as a result. Sand with polyester resin? However, the practical use of polyester resin-coated sand has been delayed due to the inability to utilize conventional mold-forming methods as is.

This is one of the characteristics required for the mold making machine magazine's "soil", which is one of the characteristics required for sand production, and is related to melting.

Since the temperature of the mold used to form the core and mold is as high as 28 +1 to 3 ()0"C, the temperature of the mold making machine magazine also rises by about 70 to 9 (1 °C). If the landing point is low, the sand grain coating agent will melt in the magazine of the mold making machine, and it will stick to the magazine or block the resin-coated sand, resulting in cracks.

The problem is that the commonly used phenolic resin-coated sand has a melting point of 90 to 115°C, whereas the melting point of polyester-coated sand made using known technology is as low as 85°C or lower. .

The melting point of resin-coated sand is influenced by the softening point of the resin used as the coating material. Therefore, in order to raise the melting point of the polyester resin-coated sand, it is conceivable to raise the softening point of the unsaturated polyester that is the coating material.

According to the studies conducted by the present inventors, the melting point of polyester resin-coated sand was determined by phenol (☆・[melting point of fat-coated sand (90°C
In order to increase the softening point to 1208CbJ or higher, the softening point of the unsaturated polyester must be 1208CbJ or higher.
Molds using polyester resin-coated sand using polyester as a coating agent have low strength, and in order to raise the softening point of monounsaturated polyester to 120°C or higher, it is necessary to increase the degree of condensation. There is a problem that there is a high probability of gelation during synthesis of 9, making it difficult to supply it in a stable state.

In view of the disadvantages of polyester resin-coated sand, the inventors of the present invention conducted intensive research to obtain polyester resin-coated sand with a melting point of 90°C, and found that during the production of resin-coated sand, periodic laws of elements were observed. ■Table.

n,,11. They discovered that by adding an oxide of a metal belonging to Group IV or Group II, it was possible to obtain polyester resin-coated sand at 90°C by fusion bonding.1.The present invention was completed. It arrived.

In other words, the present invention provides a catalyst for combining unsaturated monomers or prepolymers having one or more unsaturated, In the process of coating the sand grains with 1ir15 particles using the melt method, 1.
I, l'1. of the original asynchronous table. IIl, IV or ■
Total addition of oxides of metals belonging to the group 4-ru trace 111471
This invention relates to a method for producing oil-coated sand. ) 9 In this specification, the hot-melt method is a process in which the sand grains are heated to a temperature above the softening temperature of the resin to be coated, and the resin is applied to the heated sand. This refers to a method of coating by heating and melting the resin by stirring and mixing.

The unsaturated polyester that is solid at room temperature used in the present invention is an α,β-unsaturated dibasic acid.

It can be obtained by reacting its anhydride or its mixture, optionally a saturated dibasic acid, its hydrate or a mixture thereof, with a polyhydric alcohol by a known method.

α,β-Unsaturated dibasic acid or its anhydride and 17 include maleinoic acid, maleic anhydride, -f taconic acid, fumaric acid,
Citraconic acid, chloromaleic acid, etc. are used. As the saturated dibasic acid or anhydride of -t, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, succinic acid, adipic acid, hivacic acid, methylsuccinic acid, etc. are used.

Examples of polyhydric alcohols include propylene glycol, ciglopylene glycol, 1.2-7' CI] undiol, ethylene glycol, diethyl glycol, 1.3
-butanediol, neopentyl glycol, 1,6-
Glycols such as hexanediol and hydrogenated bisphenol A, glycerin, trimethylolpronol, pentaerythyl alcohol, etc. are used, and if necessary, a monohydric alcohol is used in combination.

In order for the unsaturated polyester to be solid at room temperature, it is sufficient if the softening point measured by the ring and ball method is 50°C or higher, but it is preferably in the range of 80°C to 110°C. If the softening point is less than 80°C, the amount of metal oxide added will increase, and if it exceeds 110"C", the strength of the mold or core will tend to decrease.

Styrene is an unsaturated monomer or prepolymer having one or more unsaturated bonds in its molecule.

Chlorstyrene, divinylbenzene', 271)
/ phthalate, methyl methacrylate, =ac 1 nor
Decline.

Vinyl acetate, acrylamide, Fenyl/L/maleimide, maleimide, styrene bromide, Tarja 1-butylstyrene, triallylino'/Anu 1/-t.

N-methylacrylamide, N,N'-dimethylacrylamide, N-methylolcrylamide.

N,N'-dimethylmethacrylamide, N-methylolmethacrylamide, N,N'-methylenebis-f-1-norami)
”, N, N'-methylene bismethacrylamide zinc acrylate. acrylic acid Cal/Uno., f aluminum acrylate, zinc methacrylate. lead, calcium methacrylate, diallyl phthalate prepolymer, triallyl isodunurate brepolymer , epoxy resin alkyl acrylic 1 note, etc.

As the unsaturated monomer or prepolymer having one or more unsaturated bonds in the molecule, it is preferable to use a monomer or prepolymer having a melting temperature of 60°C or higher, and the amount added is usually Polyester 100'+. A preferable range is 5 parts by weight to 100 parts by weight based on 1[Ff+° parts.

When using an unsaturated monomer or premelon aggregate with a melting point of less than 60°C, the melting point of the resin-coated sand tends to decrease, so the amount of unsaturated sand added should be 100 parts by weight of the diester. The amount is preferably 5 parts or less.

One type of unsaturated monomer, polymer or prepolymer may be used alone. Two or more types may be used in combination.

The polymerization catalyst used in the present invention includes:

Dicumyl peroxide, benzoyl peroxide.

Tert-butyl perbenzoate, di-tert-butyl perbenzoate, cumene hydroperoxide, 1,3-bis-(tert-butyl peroxyinocropyl)benzene, 1,1-bis-(tert-butyl perbenzoate) -oxy)-3.

3, 5-trimethylcyclohexane, 2.5-dimethyl-(2.5-cyhenzoylnokoxy)heginane, 2.2-bis-(4.4-di-tert-butylveroxinchlorohexyl)pronokane, 2.

5-dimethyl-2,5-di(tert-butyl);-oxy)-hexyne-;1,n-butyl-1,4-bis-
Examples include (tertiarybutyl-relate), lauroyl peroxide, and clohexanone peroxide.

The polymerization catalyst has curing properties, 4. c) The unsaturated polyester is preferably used in the range of 0.5 to 20 stitches for a 100 stitch needle, more preferably from a 1 stitch to a 10 stitch. These polymerization catalysts may be used alone or in combination of two types.

Metal oxides and L2 are I and H of the periodic table of elements.

Oxides of metals belonging to the ■, ■, or ■ groups are used. In particular, considering the price and the effect on the fusion point of the resin-coated sand, magnesylano oxide, zinc oxide, and calcium oxide are preferable.

The amount of metal oxide added depends on the type of metal oxide used, the softening point of the unsaturated polyester, and the unsaturated monomer or reserve (1
7It varies depending on the melting point of the coalescence.

Traditionally, unsaturated polyester 1 n (] trrp
It is used in the rli'ii four of the 30-ichi Kuibu section. For example, &-1' in magnesylano oxide\
0. ! For zinc oxide, it ranges from the commercial weight part to the 5-claw needle part, and for zinc oxide, it ranges from the double shell part to the 15-claw needle part. Metal oxides can be used alone or in combination of two or more. , but that's fine.

The unsaturated polyester used in the production method of the present invention contains a lubricant, a curing accelerator, a polymerization inhibitor, and a filler as necessary. It may contain a silane coupling agent or the like, and these additives may be added and mixed during the manufacturing process of the resin-coated sand.

(As the agent, calcium stearate, zinc stearate, methylolamide, bisamide, etc. are used.

Cobalt naphthenate is used as a curing accelerator.

There are naphthene metal salts such as cobalt octenoate, metal octenoate salts, amines, etc. -Polymerization inhibitors include nohydroquinone, p-benzoquinone, 2. ', +-sinoenylparabenzoquinone, tolbenzoquinone, seven-turcyybutylhydroginone, etc. are used.

The filler and 1.1''' are Cal/Rum carbonate, barium sulfate, Fre-F, silica, and talc.

6ri:, vinyltriethoxy/lane, vinyl-tris-(β-methoxyethoxy)silane, γ-aminopropyltriethoxysilane>7.
N-β-(aminoethyl)-γ-amine, allobyltrimethoxysilane. 1. Vinyltrichlorosilane etc. are used. Ru.

The present invention will be explained and explained below with reference to Examples. Parts are by weight.

Example 1 7 moles of maleic anhydride, 3 moles of inophthalic acid.

6 moles of glopylene glycol and 3 moles of glycerin were reacted by heating at 210°C in an inert gas stream.

A softening point (measured by ring-and-ball method; same as in 1 below) of 100° C. and an unsaturated polyester with an acid value of 50) was obtained.

The resin-coated sand was preheated to 180°C.
3 kg of shiitake silica sand was put into a N5C-] type speed mixer manufactured by Enshu Tekko ■, and while stirring, unsaturated -1 and reester (5) 200! i', diallyl phthalate pre' is 60g of limmer, magnesium oxide 2? , zinc oxide 10%, dicumyl peroxide 61. It was obtained by sequentially adding and mixing 8 r of calcium stearate and stirring for a total of 5 minutes.

About this resin-coated sand JACT (Casting Technology Promotion Association)
The fusion point and bending strength were measured based on the resin-coated sand standard test method. The results are shown in Table 1.

Comparative Example 1 Resin-coated sand was obtained in the same manner as in Example J, except that the metal oxides, hismagnesium/ium oxide and lead oxide, were omitted.

Table 1 shows the measurement results for the melting point and room temperature bending strength.

Example 2 7 moles of maleic anhydride, 3 moles of terephthalate.

3 moles of glycerin, water, 3 moles of nitride bisphenol A,
3 moles of propylene glycol in a stream of inert gas at 21
The softening point is 100°C when heated to 0°C.

An unsaturated polyester (13+e) having an acid value of 6() was obtained.

The resin-coated sand is preheated to 1) 10'C and heated to 7
Bamboo sand (81) was placed in a N5C-1 type speed mixer made by Enshu Tekko WQ, and while stirring, unsaturated primary polyester (B12007.N, N'-methinone bisacrylamide 205'-, zinc oxide 20V- , dicumyl] 6g of nitric oxide, 8f of calcium stearate
were sequentially added and mixed and stirred for a total of 5 minutes. The fusion breath room temperature bending strength was measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 Resin-coated sand was obtained in the same manner as in Example 2, except that the metal oxide zinc oxide was removed during the production of resin-coated sand. The melting point and room temperature bending strength were measured in the same manner as in Example 1, and the results are shown in Table 1.

Table 1 Castings I'll ff produced by the manufacturing method of the present invention
/4 fat-covered sand improves the low fusion point, which was a drawback of conventional polyester resin-coated sand, and has mold formability equivalent to that of phenolic resin-coated sand. Furthermore.

The manufacturing process for resin-coated sand may be the same as that for phenolic resin-coated sand, and does not require any modification of the equipment.

Claims (1)

[Claims] ■Unsaturated polyester that is solid at room temperature, an unsaturated monomer or prepolymer having one or more unsaturated bonds in the molecule, and a polymerization catalyst are coated on casting sand grains using a hot melt method. Rule 1. if, IIl, I
Adding oxides of metals belonging to group V or ■! A method for producing resin-coated sand for castings using blue mold.