JPS62230815A - Quick-curing novolak type phenolic resin and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled resin which is a high-strength and high-ortho type resin suitable for shell molding, by reacting a phenolic compound with a formaldehyde compound while specifying the molar ratio and pH. CONSTITUTION:(A) A phenolic compound, e.g. phenol, etc., is mixed with (B) a compound, e.g. paraformaldehyde, etc., at 0.4-0.9mol ratio of the components (B) to (A) and <=3pH and reacted until the weight-average molecular weight attains 300-1,800. The pH is then adjusted to 3-7 and a bivalent metal salt, e.g. Mg chloride, etc., is added to react the unreacted phenolic compound. The reaction solution is then concentrated while heating and resinified to afford the aimed resin having 1,200-2,000 weight-average molecular weight, 1.5-2.3 ratio thereof to the number-average molecular weight and 3.5-4.5 ratio of the ortho-bonds to the para-bonds at the bonding position of methylene groups to the hydroxyl groups of the phenolic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a fast-curing novolac type phenolic resin and a method for producing the same. The fast-curing Tuvolac type phenolic resin according to the present invention is used for resin-coated sand grains for shell molds.

[Prior Art] It is known that high ortho novolac type resins with a high content of A-ruso conjugates in phenolic resins have a fast curing speed (Japanese Patent Publications No. 53-35596, Japanese Patent Publication No. 46-887).
8, JP-A-54-127997, etc.). As a method for this synthesis, methylolation is carried out under a weak acidic catalyst or in the presence of divalent metal ions to form an ortho-bonded methylolation.

A method is known in which methylenation is then carried out by adding an acid or perchloric acid or the like or by a reaction at elevated temperature, followed by concentration.

[Problems to be Solved by the Invention] When the above-mentioned high-ortho-novolac type resin is used for shell molding, the curing speed is fast, but the strength of the mold tends to be low. It is thought that the reaction control in the methylenation reaction following the methylenation reaction causes the resulting resin to randomly increase in molecular weight and become a resin with a large molecular weight distribution. Therefore, when this resin is used for shell molds, The decline becomes larger.

The present invention overcomes this drawback, and aims to provide a fast-curing novolac type phenolic resin that has high strength and a fast curing speed, and a method for producing the same.

Means for Solving Problem E] The fast-curing novolak phenolic resin of the present invention has m
The suspended average molecular weight is 1200 to 2000, the ratio of the molded average molecular ffi (Mw) to the number average molecular species (Mn) (Mw/Mn) is 1.5 to 2°3, and the phenol The ratio (o/p) of the ortho bond (0) to the para bond (p) indicating the bonding position of the methylene group to the hydroxyl group of
is 3.5 to 4°5.

Novolac type phenolic resin is composed of phenols such as phenol, xylenol, and cresol, formalin,
A resin synthesized by a synthetic reaction with aldehydes such as paraformaldehyde under an acid catalyst.

In this phenolic resin, the average molecular weight of severe cases is 1200.
If it is less than 2,000, the melting point of the resin or the melting point of the resin-coated sand will be low, and if it is more than 2,000, the coating properties at the time of crosstalk will be reduced and the strength will be low, and neither of these is included in the scope of the present invention. Moreover, when the Mw/Mn ratio exceeds the range of 1.5 to 2.3, the molecule/f1 distribution becomes wide and is not included in the scope of the present invention. Also, if the O/p ratio is less than 3.5, A
If the number of rusomethylene groups decreases and the curing rate is sufficiently high, it will be 4. If the 0/p ratio exceeds 4.5, the number of paramethylene groups will decrease and the strength will not improve sufficiently.

The method for producing a fast-curing novolac-type phenolic resin of the present invention is to combine phenols and formaldehyde with a saw,
The ratio of formaldehydes to nols is 0.4.
~0.9 range, PH is 3 or less, weight average molecular fil
1st stage reaction step of reacting until 300-1800;
7, add a divalent metal salt, and use this as a catalyst to react 50% or more of the unreacted phenol at the end of the first reaction step; It is characterized by consisting of a resin-forming culm that heats and condenses the reaction solution to form a resin.

As the phenol, phenol, xylenol, cresol, etc. can be used, and phenol is usually used. The formaldehyde may be formaldehyde present as an aqueous solution or paraformaldehyde.

In the first stage reaction step, if the molar ratio of formaldehyde to phenol is less than 0.4, the yield will be low and uneconomical, and if it exceeds 0.9, the reaction will be radical and polymerization or gelation will occur. In addition, in the same process, if the pH exceeds 3, the methylenation reaction will not proceed sufficiently, and ff1
If the fEi average molecular weight is less than 300, methylenation is insufficient and gelation tends to occur during dehydration, and if it exceeds 1800, the strength decreases.

In the second stage reaction, the pH is adjusted to 3 to 7 in the culm in order to suppress the methylenation reaction and facilitate the addition of methylol groups to the ortho(+/neck).Divalent metals used in the same process As the divalent metal of the salt, alkaline earth metals such as Mg and Ca, or Zn, 1yln, etc. can be used, and the metal salt can be chloride, acetate, etc. Also, in the same step, If less than 50% of the unreacted phenol is reacted by the end of the first stage reaction step, the methylol group at the ortho position is insufficient and the degree of curing is high (hardening), so it is not included in the scope of the present invention.

In the first stage reaction, the mixture can be reacted under reflux for 60 to 90 minutes, and in the second stage reaction step, it can be reacted under reflux for 2 to 3 hours.

[Effect of the invention] The fast-curing novolac type phenol resin of the present invention is ff
1ffi average molecule ^) is 1200 to 2000 and M
W, '1vln is 1.5 to 2.3, and the ratio (0/p) of ortho bond to para bond, which indicates the bonding position of the medilene group to the hydroxyl group of the phenol, is 3.5 to 4.5. characterized by something. Therefore, this phenol resin has a narrow molecular weight distribution and a moderately large number of ortho bonds, so it is highly reactive and has high strength.

The method for producing the 381i curable novolac type phenolic resin of the present invention is characterized in that the molar ratio of phenols and formaldehydes to phenol is 0.
4 to 0.9, the pH is 3 or less, and the first stage reaction step is to react until the average molecular weight of drunkenness is 300-1800. ? The pH of the reaction solution was 3 to 7.
A divalent metal salt is added, and this is used as a catalyst for the first
a second stage reaction step in which 50% or more of the unreacted phenol at the end of the stage reaction step is reacted; and 1. 166 to have
51. Therefore, according to this ¥J manufacturing method, the initial reaction product produced in the first stage reaction step has a random novolak skeleton, low molecular weight, and narrow molecular distribution, and this is then used as a raw material for the second reaction product. When the step reaction step is carried out under the above conditions, it is possible to produce a resin having many ortho bonds on the outside of the random novolak skeleton and having a uniform molecular weight. Therefore, this manufacturing method produces a fast-curing novolac-type phenolic resin that has high strength and a fast curing speed! I can do that.

[Example] The present invention will be explained below with reference to Examples.

(1) Production of novolac type phenolic resin ゛(a) Example Amount No. 1 Production 100 parts of phenol, 56 parts of 37% formalin, and 0.3 part of concentrated hydrochloric acid were mixed and reacted for 60 minutes under reflux. At this point, when the weighted average molecular weight was measured, the value was 530, and the amount of unreacted phenol was 25%. .

Next, sulfurium hydroxide was added to adjust P[-1 to 4.0, and then 0.5 part of zinc chloride was added. When the reaction was continued for another 3 hours under reflux, the amount of unreacted phenol was 12%, so the mixture was heated to 170°C under reduced pressure, and 95 parts of the resin (No. 1), which is solid at room temperature, was heated to 11%. The amount of unreacted phenol was measured using GPC.

(B) Production of Example Amount No. 2 100 parts of phenol, 85% rose formaldehyde 26
1 part, and 0.5 part of Shu-FiQ were added and reacted under reflux for 60 minutes. At this point, the average molecular weight of Juebu was 730, and the amount of unreacted phenol was 19%.

Next, dimethylamine was added to this reaction mixture and I) l-1
was set at 4.5, 0.3 part of zinc acetate was added, and the reaction was further carried out under reflux for 2 hours, resulting in 8% of unreacted phenol. Therefore, water was heated under reduced pressure to 160°C, and the resin that was solid at room temperature (No. 2 > 98 parts was 17. Measurements for Φ5 average molecular weight and unreacted phenol were carried out in the same manner as No. 1.゜(c) Production of Example Amount N003 Phenol 100 parts, 37% Formalin 43 parts, 65%
Contains 0.4 part of phenolsulfonic acid;! The reaction was carried out for 90 minutes under flowing conditions. At this point, the average molecular weight of f'fl was 450, and unreacted phenol was 21%.

Next, heptanoethanolamine was added to this reaction mixture to adjust the pH to 5.1, 1.0 part of manganese chloride was added, and the mixture was allowed to react under reflux for an additional 4 hours, resulting in 9% unreacted phenol. Therefore, vacuum dehydration was carried out to 180° C. to obtain a resin (No. 3>94 parts) that was solid at room temperature.

The average molecular weight and the amount of unreacted phenol were measured in the same manner as in No. 1.

(d) Manufacture of comparative example amount The following two types of resins were produced as comparative examples.

One is a mixture of 100 parts of phenol, 28 parts of 85% paraformaldehyde, and 0.5 W of zinc acetate, and 2
After reacting for 1 hour, 0.8 parts of oxalic acid was added and the reaction was continued for 1 hour under reflux, followed by dehydration under reduced pressure to 170° C., and 104 parts of resin (comparative example amount N0.1) was reduced to 10.

The resin of another comparative example was prepared by blending 100 parts of phenol, 60 parts of 37% formalin, and 0.3 parts of zinc acetate.
After reacting for an hour, then adding hydrochloric acid to 1) 1-1 to almost zero, reacting at 120°C for 1 hour while removing water at normal pressure,
After that, dehydration was carried out under reduced pressure to 170°C, and 99 parts of the resin (
A comparative example amount N0.2> was obtained.

(2) Characteristics of Example Amounts and Comparative Example Amounts For the above Example Amounts N091 to 3 and Comparative Example Amounts N011.2, frlh1 average molecular weight (MW), number average molecular weight 1 (
The ratio of MW to Mn (Mw/Mn, Ql direct) and the ratio of A-para bond to para bond (o/p) were measured, and the results are shown in the table.

J3MW and Mn were measured by GPCr, and the O/P ratio was measured by infrared absorbance ratio.

(3) Sand Test Characteristics of the resin-coated sand of Example products Nos. 1 to 3 and Comparative Example 1.2 were evaluated as follows.

First, the resin-coated sand was prepared as follows.

Speed mixer (N5C-2 type manufactured by Enshu Tekko), 16
8 kg of Tsuka sand heated to 0 ° C. was added, 1,609 kg of each example and comparative example were added, and the mixture was stirred and kneaded for 30 seconds.
Next, an aqueous solution of Bexamine 24G dissolved in water 1209 was added and stirred until the sand grains disintegrated, and then 89 calcium stearate was added and stirred roughly for 20 seconds, and the sand was drained to obtain coated sand.

The fusion point, room temperature bending strength, and warm bending strength of each coated sand were measured, and the results are shown in the table. This F! The first score was determined by JACT test method C-1, and the room temperature bending strength was determined by JrsK-
6910, the warm bending strength is J ACT test method 5M-5.
This was done in accordance with the.

(4> Performance evaluation of phenolic resin According to the results in the above table, the molecule ω is smaller and the Q value is smaller in the example amount No. 1 to 3 than the comparative example amount No. 1.2, so the molecular weight distribution is shallow. t'-p, and the ortho/balance ratio was equal to or even smaller than that of the comparative example, and the A-ortho form was relatively large.

The performance of the resins in the sand test for Example Amounts No. 1 to 3 was as follows: room temperature bending strength, J,
It has high bending strength and warm bending strength. In particular, the warm bending strength reaches a large value in a short time.

From the above, the resins of Examples Nos. 011 to 3 have high strength and fast curing speed. -Patent applicant: Aisin Kako Co., Ltd. Agent: Ben 111j specialist Anama Okawa Patent attorney: Akio Maruyama

Claims (4)

[Claims] (1) Weight average molecular weight is 1200 to 2000,
Weight average molecular weight (Mw) relative to number average molecular weight (Mn)
The ratio (Mw/Mn) is 1.5 to 2.3, and the ratio (o/p) of the ortho bond (o) to the disjoint bond (p) indicating the bonding position of the methylene group to the hydroxyl group of the phenol.
3.5 to 4.5. (2) Phenols and formaldehyde are mixed in a molar ratio of formaldehyde to phenol of 0.4 to
0.9 range, PH is 3 or less, weight average molecular weight is 30
A first stage reaction step in which the pH of the reaction solution obtained in the first stage reaction step is adjusted to 3 to 7, a divalent metal salt is added, and this is used as a catalyst in the first stage reaction step. Consisting of a second reaction step in which 50% or more of the unreacted phenol at the end of the step reaction step is reacted, and a resinization step in which the reaction liquid obtained in the second reaction step is heated and concentrated to become a resin. A method for producing a fast-curing novolac type phenolic resin, characterized by: (3) The method for producing a fast-curing novolak phenolic resin according to claim 2, wherein the phenol is phenol, and the formaldehyde is formaldehyde or paraformaldehyde present as an aqueous solution. (4) In the first stage reaction step, 60 to 90
In the second stage reaction step, 2 to 2 minutes of
The method for producing a fast-curing novolac type phenolic resin according to claim 2, wherein the reaction is carried out for 3 hours.