JPS62263843A - Binder for shell mold - Google Patents

Abstract

PURPOSE:To improve the characteristics of a novolack type phenolic resin formed by controlling the ortho rate of tetranuclide and higher nuclides to a specific % range and limiting the total content of dinuclide and trinuclide components. CONSTITUTION:The novolack type phenolic resin is formed by dehydrating and concentrating a phenol and formaldehyde respectively at prescribed ratios by an acidic catalyst, bivalent metallic salt catalyst, etc., heating and mixing two kinds of the resultant resins and further dehydrating and concentrating the mixed resins. The ortho rate of the tetranuclide and higher nuclide components of the phenolic resin is controlled to >=40% and <50% in this stage; at the same time, the ratio of the ortho rate of the dinuclide and trinuclide components to the tetranuclide and higher nuclide components is controlled to <1.05 and further the total content of the dinuclide and trinuclide components is controlled to >=20% and <45%. The strength and curing speed characteristics of the casting mold are both improved by using such phenolic resin as the essential component for the binder.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a resin binder for shell molds,
In particular, the present invention relates to a resin binder for shell molds that has a fast curing speed for resin-coated sand by hot marling and has excellent mold strength.

(Prior Art) In the -ff shell mold method, a novolac type phenol resin obtained by reacting phenol and formaldehyde with an acidic catalyst is used as a binder, and hexamine is used as a curing agent.

Recently, from the viewpoint of energy saving, so-called fast-curing type resin binders for shell molds have been praised because they can lower molding temperatures and shorten molding cycles.

It is known to use a high ortho resin that reacts quickly with hexamine in order to speed up the curing speed of the mold. High-ortho resins are obtained by polymerizing phenols and formaldehyde using metal salts such as zinc acetate and cobalt chloride as catalysts.

(Problems to be Solved by the Invention) However, in the conventional method, although the hardening speed of the mold was improved, there was a problem that the strength of the mold was thickened (decreased).

The present invention provides a resin binder 1 for shell molds that is excellent in both mold hardening speed and mold strength.

(Means for Solving the Problems) In order to obtain a resin binder for shell molds that has a fast mold hardening speed and excellent mold strength, the present inventors investigated the mold hardening mechanism and found that the resin caking The custom flow during curing of the agent greatly affects the curing speed and mold strength.
Furthermore, we carefully investigated the molecular weight and ortho ratio of the novolak type phenolic resin, which is a resin binder, and the curing properties and flow characteristics of hexamine, and found that the binuclear and trinuclear components of the phenolic resin have excellent fluidity. It has been found that the phenol/L-resin has the disadvantage of being slow to cure, and that the proportion of phenol/L-resin having four or more nuclear bodies has a disadvantage of having poor fluidity although the curability is 4&n. Therefore, the dinuclear body of phenolic resin and 5
In order to improve the curability of the core components, it was discovered that both fluidity and curability could be improved by increasing the ortho ratio of these components, leading to the present invention. type phenolic resin, the ortho rate of components with four or more nuclei is 40% or more and less than 50%, and the ratio of (ortho rate of dinuclear + hexanuclear components) / (ortho rate of components with four or more nuclei) is 1 .05 or more, and (2
The resin binder for shell molds has a content of 20% or more and less than 45% of nuclear bodies + 5 nuclear bodies).

The present invention will be explained in detail below.

The ortho rate of the phenolic resin in the present invention is 0th position/(0th position + Pth position), and the infrared absorption spectrum of the resin was measured by the KBr method using Hitachi Model 270-30, and according to the method of Tsuchinaka et al. Reference: Relationship between binding mode and curing speed of novolak resin: Kouka 13, 93 (1] 56)) Calculated using the following formula. However, the transmittance of benzene nuclei clustered around 160 Qcm-1 was adjusted to 40 to 50%.

The binuclear + trinuclear components and the tetranuclear and higher components of phenol sesame were analyzed using a preparative high-performance liquid chromatography model HLC-635 manufactured by Hitachi/91 (solvent: THF, column:
TSK-GEL, G2500HG: 2 bottles (trade name of Toyo Soda Koso Co., Ltd.) were used for fractionation.

In addition, the content of binuclear + hexanuclear components of phenol resin is:
Toyo Soda High Performance Liquid Chromatograph 4-HLC-802
Using URfJt (bath a: THF, column: TSK-G
EL, G2000H8: 3 pieces, G3000H8: 1 piece,
The chart obtained from Toyo Soda Koka Co., Ltd.
It was determined by the cut weight method. What's that like? Figures 1 and 2
As shown in the figure. FIG. 1 is an analysis chart showing an example of the molecular weight distribution state of the novolak type 2-enol resin according to the present invention, and FIG. 2 is an analysis chart of the resin obtained in Comparison 1('lJ1).

■, ■, ■, and ■ in the figure represent regions of high molecular weight components of phenol monomer, dinuclear, pentanuclear, and tetranuclear or more, respectively. A vertical line was drawn between each displacement point on the analysis chart, and each vertical layer was regarded as a region for each polynuclear body to which it belonged.

That is, measure the distances @a and bf from the center point of the phenol monomer beak to the 0 point and 0 point, and draw vertical lines at distances a and b from the phenol monomer to identify dinuclear bodies, ■trinuclear bodies■, and 4 nuclear bodies, respectively. We decided to divide it into regions with high molecular weights larger than the nuclear body.

The phenols used in the present invention include phenol, cresol, xylenol, and bisphenol. Formaldehyde includes paraform,
Formalin and the like are used.

The method for producing the novolac type phenolic resin of the present invention is not particularly limited, but the following method is preferred.

Formaldehyde 0.6 to α per mole of phenol
After adding 9 mol and an acidic catalyst such as hydrochloric acid and reacting at reflux temperature for 4 hours, dehydration and concentration were performed by a conventional method to obtain a softening point of 80°C.
As the end point, a resin (4) is obtained in which the ortho rate is 42% and the content i of dinuclear and trinuclear components is 15%.

In another flask, 3 to 0.6 moles of formaldehyde (cL) and a divalent metal salt catalyst such as cobalt acetate were added to 1 mole of phenol, and the mixture was reacted at reflux temperature for 4 hours, followed by dehydration and concentration using a conventional method. Resin tBJ is obtained with a content of 70% and 40% of dinuclear + pentanuclear components.

The resins tA), tB) obtained in this way were added to 100
The mixture was poured in portions into a flask, heated and mixed, and dehydrated and concentrated using a conventional method. When the softening point reached 80° C., the end point was determined.

Among phenolic resins, ortho''4 of components with four or more nuclear bodies
is preferably 40% or more and less than 50%, especially when the ortho rate is 45%.
% to 48% is preferred. If it is less than 4a%, curing will be slow (and if it is more than 50%, the mold strength will be low).

The ratio of (ortho ratio of 2-nuclear + 3-nuclear component)/(ortho ratio of 4-nuclear or higher component) is preferably 1.05 or more. @ If it is less than 1.05, the rapid curing effect will be small. 1.08 to 1
．． 20 is particularly preferred.

The content of dinuclear bodies + trinuclear fraction is preferably 20% or more and less than 45%. If it is less than 20%, fluidity decreases and mold strength decreases. Moreover, if it exceeds 45%, the mixing sand will become blocked, which is not preferable. A more preferable range is 25% to 30%.

A preferred method is to add a silane coupling agent to the phenol resin in order to improve mold strength.

γ-Glycidoxypropyltrimethoxysilane, N-β(aminoethyl/L-nγ-aminopropyltrimethoxysilane, T-aminoglopyltrimethoxysilane, etc.) can be used as a silane coupling agent. The amount of the silane coupling agent to be added is preferably 05 to 50 parts by weight of phenolic resin 1001.If it is less than 05, the effect will be small! If it is more than LO, the cost will be high, so it is preferable. do not have.

It is also preferable to add aromatic organic r1k to the phenolic resin in order to further speed up the curing speed of the mold. As an aromatic organic acid, naliteric acid, benzoic acid, etc. are used. The aromatic organic acid is preferably added in an amount of 4.0 parts by weight to αa5 based on 100 parts by weight of the phenolic resin. α0
If it is less than 5, the effect will be small, and if it is more than 4.0, it will cause blocking of the kneaded sand, which is not preferable.

The obtained phenolic resin may be added with t-acetic acid, a lubricant usually used as a resin binder for shell molds. As lubricants, ethylene bisstearamide, oxystearamide, stearamide, meso α-
Ruamite, methylene bisstearamide, calcium stearate, polyethylene wax, paraffin wax, montan wax, carnauba wax, etc. are used. The amount of lubricant used is not particularly limited, but it is preferably 5.0 parts by weight for α5 per 100 parts by weight of the resin binder.

(Function) The phenol resin according to the present invention contains many components having ortho bonds consisting of binuclear bodies and hexanuclear bodies as shown below as resin components, and has improved reactivity with curing agents such as hexamine. Therefore, the curability is improved. Moreover, since the molecular weight of these dinuclear and trinuclear fractions is small, it is thought that the fluidity will not be impaired even if the ortho ratio is large.

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

(Example) Example 1 1880 g of phenol and 300 g of 80% paraform were placed in a four-way flask equipped with a stirrer, a reflux condenser, and a thermometer.
, 160 g of 37% formalin and 4 g of cobalt acetate were weighed, heated on an oil bath without stirring, allowed to react at reflux temperature for 4 hours, and then concentrated under reduced pressure of 700 °C until the internal temperature reached 150 °C. phenolic resin as the end point)
I got it. Resin (4) had an ortho rate of 69% and a content of components (binary bodies + trinuclear bodies) of 37%.

Next, in a four-way flask equipped with a stirrer, reflux condenser, and thermometer, 1880 g of phenol and 45 g of 80% paraform were added.
0g, 57% formalin and 4g of IN hydrochloric acid were weighed, heated on an oil bath without stirring and reacted at reflux temperature for 4 hours, and then dehydrated and concentrated using a conventional method until the softening point was 80.
The end point was 0.degree. C. to obtain resin (B). The ortho rate of the resin was 41%, and the content of dinuclear + trinuclear components was 15%.

Next, the above resin (500 g of AJ and 40 g of the above resin (B)
0gt - Weigh and heat on an oil bath without stirring to bring the internal temperature to 1.
When the temperature reaches 00°C, perform depressurization III #l until the softening point reaches 8.
The end point was 0°C. After that, KBM-60 was heated at the same temperature of 140℃.
9 g of 3 (N-β (amino ether) γ-aminopropyltrimethoxysilane, trade name of Shin-Etsu Chemical Co., Ltd.) was added through a sieve, stirred for 30 minutes, and subjected to corrugation to obtain a resin (C).

Furthermore, after kneading flattary silica sand 8- heated to 150°C and the above resin (Q140gt-speed mixer for 60 seconds,
100 g of quinamine water bath solution was added to the 20% solution and kneaded until the sand disintegrated, and further 8 g of calcium stearate was added, kneaded for 20 seconds and discharged to obtain resin-coated sand. Table IK shows resin properties and sand mold properties.

Example 2 300 g of resin (5) and 600 g of resin (B) were weighed into a four-ring flask equipped with a stirrer, reflux condenser, and thermometer, heated on an oil bath while stirring, and when the temperature reached 100°C, the pressure was reduced. Concentration was carried out, and the end point was a softening point of 83°C. Furthermore, 10 g of ethylene bisstearamide was added.
IKBM-403 (r-g17) stirred at 40°C for 60 minutes.
7) 5 gt-m of "dipropyltrimethoxysilane (trade name, Shin-Etsu Chemical Co., Ltd.) was added, stirred at 140° C. for 30 minutes, and subjected to corrugation to obtain a resin (DJ).

Using the above resin tD+, 5Jj! , 71i1 Resin-coated sand was obtained in the same manner as in Example 1. Table 1 shows resin properties and sand mold properties.
Shown below.

Example 3 Resin obtained in Example 2 (Tell acid 2 with a D of 1300 g)
Resin IEI was obtained by heating and sweetening 1 g.

Tree 11ti coated sand was obtained in the same manner as in Example 1 using the resin tEl. Table 1 shows the resin percentage and sand mold properties.

Comparative Example 1 940 g of phenol, 225 g of 80% paraform,
80 g of 37% formalin and IN hydrochloric acid were weighed out, stirred, and heated on an oil bath for 4 hours at reflux temperature. did.

Furthermore, 10 g of ethylene bisstearamide was scuttled and stirred at 140°C for 60 minutes, and then 5 g of KBM-403 was added.
After adding ff5 and stirring for 30 minutes, add t4 fat (F
I got it. Resin-coated sand was obtained in the same manner as in Example 1 using the above resin. Table 1 shows the resin customization and sand mold characteristics.

Comparative Example 2 IN salt of Comparative Example 1 #! Resin (H) was obtained in the same manner as in Comparative Example 1 except that 2 g of zinc chloride was used instead of 2 g.

Resin encrusted sand was obtained in the same manner as in Example 1 using the above resin. Resin characteristics Sand mold custom order complete table-1.

Comparative Example 3 500 g of resin in Example 1, 100 g of resin (resin 1A instead of 400 g of BJ), and resin t1 in the same manner as resin tQ of Example 1 except that 700 g of Bl was used.
I got it. Resin-coated sand was obtained in the same manner as in Example 1 using the above resin.

Comparative Example 4 1880 g of phenol and 200 g of 80% paraform were placed in a four-ring flask equipped with a stirrer, reflux condenser, and thermometer.
and 4 g of acetic acid were weighed and synthesized in the same manner as in Example 1 to obtain a resin (J). The ortho rate was 69%, and the content of fractions (binary and trinuclear) was 75%.

Using 500 g of resin (J) and 400 g of resin IB), the resin (IQ) was synthesized in the same manner as the resin (Cl) of Example 1. Using the above resin, resin-coated sand was obtained in the same manner as in Example 1.Resin Table 1 shows the characteristics and custom made sand mold.

Below margin fusion point: 0 according to JACT Shell Sakuto standards Strength: J
Based on ACT shell work standards.

Pend: Flat mold 70x140m set at 260℃
Place a U-shaped mold with inner dimensions 50 x 120 ffi 11 height 5 on top of n+, fill it with resin-coated sand, and heat it to a furnace temperature of 350°C.
It was left for 40 seconds, then taken out and placed on a jig with a distance between fulcrums of 10 Qma+ after 10 seconds, and the amount of deflection was measured when a load of 500 g was applied. It is shown that the smaller the amount of deflection, the faster the curing property.

(Effects of the Invention) As is clear from the above description, the present invention makes it possible to provide a resin binder for shell molds that has a fast curing speed for resin-covered sand and excellent mold strength. .

[Brief explanation of drawings]

FIG. 1 is an analysis chart showing the molecular weight distribution of the novolak phenol resin according to the present invention, and FIG. 2 is an analysis chart of the novolak phenol resin obtained in Comparative Example 1.

Claims (1)

[Scope of Claims] 1. (a) The ortho rate of the tetranuclear or higher component of phenol is 40% or more and less than 50%, and (b) (ortho rate of the dinuclear + trinuclear component)/(tetranuclear (c) The novolac type phenolic resin has a ratio of 1.05 or more (ortho ratio of components larger than 3-nuclear body), and the content of (2-nuclear body + 3-nuclear body component) is 20% by weight or more and less than 45% by weight. A binder for shell molds that is produced as a component. 2. The binder for shell molds according to claim 1, wherein the novolac type phenolic resin contains a silane coupling agent and/or an aromatic organic acid.