JPH0818102B2 - Method for producing phenol-formaldehyde resin binder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a self-hardening binder for sand mold molding required for casting, and particularly to a phenol / formaldehyde resin that can be cured while remaining alkaline. The present invention relates to a method for producing a self-hardening phenolic resin binder for castings, which comprises mixing with an improved organic ester-based curing agent.

[Conventional technology]

It is known that highly alkaline phenol-formaldehyde resins cure with certain esters,
When this was used as a binder for molding, the performance was too poor. However, the seed binding property has also been improved, and it has become possible to put it to practical use alone. These improved techniques are described in JP-A-49-16793 and JP-A-49-16793.
50-130627, JP-A-58-154433 and JP-A-58-154434.

It is not fully understood why the highly alkaline phenol-formaldehyde resin is cured with an ester, but it is a phenol-formaldehyde resin suitable for molding that can be cured with an ester (hereinafter referred to as an ester-curable phenol resin). ) Are described in detail in JP-A-58-154433.

However, the present situation is that the amount of resin added to the molding sand required for molding is very large as seen in the examples of the prior art. The fact that a large amount of resin component is added results in a large amount of decomposition gas generated during pouring and causes gas defects, which is not desirable and is not economical, so the development of a binder that reduces the amount of resin added as much as possible Has been.

[Problems to be solved by the invention]

The present inventors have earnestly studied to solve the above-mentioned problems of the ester-curable phenol resin as a binder. At the stage of investigation, the present inventors have found that the ester-curable phenol resin contains a large amount of alkali metal, and the component that can be a substantial binder is about 2/3 of its solid content, which is effective. It was considered that the characteristics were poor because the amount that could be a binder component was small in absolute amount. Then, the present inventors have noticed that the organic ester used as the curing agent requires 20 to 80 parts by weight with respect to the ester-curable phenol resin, and the organic ester is not merely a curing agent component. By devising it so that it can also be used as a binder component, the absolute binder amount can be increased, the performance can be improved, and the addition amount can be reduced. As a result, they have found that when a phenol / formaldehyde resin dissolved with an ester is used as a curing agent component, the absolute amount of the binder increases, thereby improving the strength performance, and completed the present invention.

[Structure of Invention]

(Means for Solving Problems) The present invention can be summarized as follows. (1) Formaldehyde of phenol is reacted with a molar ratio of phenol: formaldehyde = 1.0: 0.85 to 1.0: 3.0, and then, The molar ratio of potassium hydroxide and / or sodium hydroxide to the phenol is:
(Potassium hydroxide and / or sodium hydroxide) = 1.0:
A phenol-formaldehyde resin aqueous solution having a number average molecular weight of 600 to 1,800 and a solid content of 40 to 70%, which is obtained by adding at a ratio of 0.5 to 1.0: 1.5, and (2) the phenol and the formaldehyde. , Phenol-formaldehyde resin having a number average molecular weight of 300 to 1,500 obtained by reacting at a molar ratio of phenol: formaldehyde = 1.0: 0.6 to 1.0: 3.0 as a solid content of 20
The present invention relates to a method for producing a phenol / formaldehyde resin binder, which comprises mixing an organic ester solvent contained in an amount of -60% by weight with a ratio of (2) to 20-80% by weight with respect to (1).

 Hereinafter, the configuration of the present invention will be described in detail.

First, the ester-curable phenol resin used in the present invention will be described.

As the phenol source, all phenol sources such as phenol, cresol, xylenol, bisphenol A, bisphenolde F, and resorcinol can be used. However, phenol is preferable in terms of performance and economy. If economy is ignored, resorcinol is fast-curing and has good performance.

As the aldehyde source, formaldehyde, acetaldehyde, benzaldehyde, glyoxal and the like can be used, but formaldehyde has good performance and is inexpensive.
However, partial replacement with glyoxal is preferable because it results in rapid hardening.

Further, as the phenol resinous material, by-products of isopropenylphenol and the residue produced during the production of bisphenol A can be used, but the use of up to about 30 parts by weight is limited,
Above that, the performance will be inferior. From the above points, the phenol-formaldehyde resin containing phenol as the phenol source and formaldehyde as the aldehyde source is the most excellent in the balance of performance and economy. This ester-curable phenol resin (1) component has a solid content of 40
An aqueous solution containing ~ 70% has a viscosity that is easy to handle. The higher the solid content concentration is, the more preferable it is, but if the viscosity is too high, the handling becomes rather difficult, the kneading property deteriorates, and the performance decreases. On the contrary, when the solid content is low, the viscosity is low and the kneading property is good, but the performance is inferior due to the decrease in the amount of the active ingredient. The preferred solid content concentration is 45 to 55%, and the viscosity is preferably 200 cps / 25 ° C, max.

Next, the molar ratio, alkali amount, and molecular weight will be described.

(1) Molar ratio In the present invention, as the curing agent for the ester-curing type phenol resin, the one in which a specific phenol / formaldehyde resin is dissolved using the organic ester as a solvent as described above is used. As the phenol / formaldehyde resin, a resol type resin or a novolac type resin is used. On the other hand, from the viewpoint of curing reaction, the bond molar ratio of phenol and formaldehyde is both (ester curable phenol resin and phenol resin in organic ester).
It is preferable that the total resol type is 1.0 or more when calculated from the total amount. Therefore, the combined molar ratio of phenol and formaldehyde is the sum of the two.
If the bond molar ratio of the ester-curable phenolic resin is 1.0 or more, it may be a novolac type lower phenol-formaldehyde resin having a bond molar ratio of less than 1.0, but if the bond molar ratio is too low, the required high molecular weight The performance is inferior because it is not good, and if it is too high, the odor of formalin becomes strong. From the above points, an appropriate molar ratio of phenol to formaldehyde in ester-curable phenol resin is phenol: formaldehyde = 1.0: 0.85 to 1.0 to 3.0
Is.

(2) Regarding the amount of alkali, in the ester-curable alkali phenol-formaldehyde resin used in the present invention, all alkali metals can be applied as the alkali component, and if it is a small amount, it is a mixture of alkaline earth and other metals. Although it is not a problem, it is essentially necessary to contain an alkali metal.
The alkali metal having a small ionic potential energy is preferable, but in view of economy, the most appropriate alkali metal is potassium, and then sodium. It is preferable to use a general-purpose hydroxide.
As the hydroxide, a molar ratio to phenol of phenol: alkali metal hydroxide = 1.0: 0.5 to 1.0: 1.5 is appropriate, and it may be used alone or in combination, or may be added later. When the molar ratio is 0.5 or less, not only slow curing but also phenol /
The viscosity of the formaldehyde resin becomes too high.
On the contrary, the higher the molar ratio, the lower the viscosity, but if the amount is too large, the performance will be inferior due to an increase in metal hydroxide as a contaminant. The valid range is 1.0: 0.5 to 1.0:
It is 1.5.

(3) Molecular Weight The average molecular weight (number average) is preferably as high as possible in terms of balance between concentration and viscosity. However,
From the balance of concentration and viscosity, there is a constraint that it should be 600 to 1,800, and more preferably 800 to 1,200.

Of the phenol / formaldehyde resins that meet the above-mentioned conditions, only when it is a resol-type phenol / formaldehyde resin, it can be cured with an organic ester.

That is, it can be cured in a short time at room temperature with organic esters such as methyl formate, ethyl formate, diethyl oxalate, diacetin, triacetin, propion lactone, butyrolactone, ethylene glycol diacetate. If several days are spent, a general-purpose ester solvent such as methyl acetate or ethyl acetate, a vinyl acetate polymer, or a low molecular weight polyester resin can be cured. The higher molecular weight esters are only slow-curing, and the polymers described above have only some binder capacity.

Next, the phenol / formaldehyde resin (hereinafter referred to as ester solvent phenol resin) component contained in the ester solvent as the curing agent used in the present invention will be described.

It is considered that the ester solvent phenol resin component remains in the system as a binder and reacts with the ester-curable phenol resin to increase the absolute amount of the binder and contribute to the improvement of strength. When the ester-curable phenol resin and the ester-solvent phenol resin are used together, if the total bond molar ratio is 1.0 or more, one of the ester-curable phenol resin or the ester-solvent phenol resin may be a novolac type. I don't care. However, the bond molar ratio at which strength is high is phenol: formaldehyde = 1.0: 1.5 to 1.0: 2.5. If it is too low, slow curing will occur, and if it is too high, the formalin odor will be strong.
Eventually, the ester-curing phenolic resin has a bond molar ratio of phenol: formaldehyde = 1.0: 2.0 to 1.0: 2.5, which is a resol-type phenol-formaldehyde resin. If it is designed to be a formaldehyde resin, it can be said to be a preferable design method because it does not have to be complicated in the calculation of the molar ratio in the case of combination and can be contained within the bond molar ratio which gives good strength.

In preparing the ester solvent phenol resin, the phenol source, the formaldehyde source, and other requirements can be considered almost the same as the ester-curable phenol resin, but the presence of the alkaline substance decomposes the organic ester. In addition, it is better to have as few as possible. In addition, high molecular weight and high concentration are preferable, but the viscosity suitable for workability is naturally constrained, and the appropriate amount of organic ester used for ester-curable phenol resin is almost determined by its type. There are restrictions on the concentration depending on the type of ester.

The appropriate amount of the organic ester used as the curing agent in the present invention is mainly determined by the bond molar ratio of the ester-curable phenol resin, the molecular weight, and the amount of alkali metal. Depends on. As a general usage amount, if it is around 20-25 ° C,
Formic acid ester is around 10% by weight, γ-butyrolactone is around 20% by weight, and diethylene glycol diacetate is around 50% by weight.
-In the case of butyrolactone, at 0 ° C, 25-30% by weight, 40
At 15 ° C, 10 to 15% by weight is a preferable blending amount. Dilute the organic ester concentration to a fixed amount to make this necessary amount, and
20-80% by weight based on ester-curable phenol resin
It is used by changing the compounding amount. If the amount is small,
Since it is soaked in foundry sand and is not uniformly dispersed, and if it is too large, it becomes uneconomical. Therefore, a blending amount which is suitable for mixing and has good economic compatibility is preferably 30 to 50% by weight. When 30 to 50% by weight is blended, the organic ester curing agent can be prepared by diluting it with a solvent or mixing it with other esters so that the required amount of the organic ester is exactly obtained.

The present invention is intended to adjust the concentration of an organic ester as a curing agent with a phenol-formaldehyde resin and at the same time to improve the strength.

Therefore, the organic ester itself is a good curing agent for the ester-curable phenol resin, and is also a good solvent for the ester-solvent phenolic resin, and when the ester-solvent phenolic resin is compounded under an appropriate viscosity, it is just used as a curing agent. Most preferably, it is designed so that the required amount of organic ester is maintained. A simple organic ester capable of curing the ester-curable phenol resin can serve as a solvent for the phenol-formaldehyde resin, and a preferable organic ester is γ-butyrolactone. γ−
Butyrolactone, for example, as an aqueous solution with a concentration of 30 to 80% and 40 to 50% of the ester-curable phenolic resin, can be demolded for 30 to 60 minutes under temperature conditions between -10 ° C and 50 ° C. It is possible to obtain the curing conditions suitable for the working conditions. A high concentration is suitable for low temperature curing conditions, and a low concentration is suitable for high temperature curing conditions. The content of γ-butyrolactone is constant, for example, 40% concentration, 40% as an ester solvent phenol resin, the remaining 20% portion by using an ester other than the γ-butyrolactone to delay the curing conditions, or It can be promoted. First
The curing speed of organic esters is shown in the table. On the other hand, at the time of adjusting the concentration, if the amount of the ester solvent phenol resin is not kept constant, the performance varies.However, the ester solvent phenol resin has a high molecular weight as much as possible. It is high and the workability and kneading property are poor. Therefore, if you limit the viscosity to 200 cps / 25 ° C or less,
Due to the viscosity restriction, the molecular weight of the ester solvent phenol resin is regulated to 300 to 1,500 cps, preferably 500 to 1,100, and the content thereof is regulated to 30 to 50%.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.

<Synthesis example> 1. Synthesis of ester-curable phenol resin (Example-1) 940 g (10 mol) of phenol, 41.5% formalin 72.3 g
(1 mol) and 5 g of oxalic acid are put into a four-necked flask equipped with a reflux condenser and a stirrer and gradually heated. Stop heating at 85 ° C and heat up to reflux temperature. 100 ° C
When the temperature reaches, 578 g (8 mol) of 41.5% formalin is applied for 30 minutes, and the reaction is carried out while applying. Cooling is started after a suitable period of time, and 80% ℃ 48% potassium hydroxide 585g
(5 mol), followed by 48% sodium hydroxide 41.7 g (5
(Mol) is added dropwise and cooled to room temperature. Then the weight 23
Add 0g. This is designated as (resin-1).

(Resin-1) is a novolac-type ester-curing phenol resin having a solid content of 55%, a viscosity of 165 cps / 25 ° C., a bond molar ratio of 0.90 (F / P molar ratio), and an average molecular weight of about 900.

(Example-2) 1807 g of 41.5% formalin to 940 g (10 mol) of phenol
(25 mol) is added and the temperature is raised to 85 ° C. Then, 1169 g (10 mol) of 48% potassium hydroxide was added dropwise over about 1 hour, and the reaction was continued at 85 ° C. After the dropping was completed, the temperature was kept at 85 ° C. for 5 hours. Then 370 g of water are removed while lowering the temperature by vacuum distillation. This is designated as (resin-2).

(Resin-2) is a resole-type ester-curable phenol resin having a solid content of 54%, a viscosity of 130 cps / 25 ° C., a bond molar ratio of 2.30 (F / P molar ratio), and an average molecular weight of about 750.

2. Synthesis of Ester Solvent Phenol Resin (Example-3) Synthesis was carried out in exactly the same manner as in (Example-1), and the reflux temperature was adjusted to 2
After keeping for a while, the temperature was raised to 150 ° C. by vacuum distillation 700 mmHg. This phenol-formaldehyde resin was a novolac type phenol-formaldehyde resin, and had a bond molar ratio of 0.90 (F / P molar ratio) and an average molecular weight of about 1,000.
This phenol-formaldehyde resin is γ-
It was dissolved in butyrolactone to a concentration of 35%. Viscosity is 150cps
/ 25 ° C. This is designated as (ester solvent phenol resin-3).

(Example-4) Phenol 940g (10mol), 41.5% formalin 1229g
Then, 337 g of 48% aqueous sodium hydroxide solution is added, and the temperature is gradually raised to 90 ° C. Hold at 90 ℃ for 5 hours, vacuum degree 700mmH
Distilled to above 80 ° C in g. This resol-type phenol-formaldehyde resin contained 83% solids and 7% water, had a viscosity of 14,000 cps / 25 ° C, a binding molar ratio of 1.55 (F / P molar ratio), and a molecular weight of about 600. This phenol / formaldehyde resin was adjusted to a resin: γ-butyrolactone: triacetin = 45: 45: 10 weight composition ratio. Viscosity is 80cps /
It was 25 ° C. This (ester solvent phenol resin-
4).

1. Preparation Example of Ester-Curing Phenolic Resin Ester-curing Phenolic Resin
Was prepared as follows.

(Main agent-1) (Resin-1 of Example-1): (Resin-2 of Example-2) = 1: 1
The mixture in the weight ratio is referred to as (main ingredient-1).

(Main ingredient-2) (Resin-2 of Example-2) itself is referred to as (main ingredient-2).

2. Preparation Example of Ester Solvent Phenolic Resin Ester solvent phenol resin (hereinafter referred to as curing agent) was prepared as follows.

(Curing agent-1) The (resin-3) itself of (Example-3) is (curing agent-1)
And

(Curing agent-2) The (resin-4) of (Example-4) itself is (curing agent-2).
And

3. Preparation of Ester Curing Agent (Comparative Curing Agent) As a comparative example, a curing agent containing only ester was prepared as follows.

(Comparative Curing Agent-1) γ-butyrolactone was dissolved in water to have a concentration of 65% as the curing agent of (Comparative Example-5).

(Comparative curing agent-2) A mixture of 45% γ-butyrolactone and 55% diacetin is used as a curing agent for (Comparative Example-6) in a 60% aqueous solution.

Main Agent-1, Main Agent-2 and Curing Agent-1, Curing Agent-
No. 2 was used, and as comparative examples, comparative curing agent-1 and comparative curing agent-2 were used for performance evaluation.

<Performance evaluation> 3000g of freemantle fresh sand with a sand temperature of 15 ° C was added to a small mixer with a capacity of 5l and a rotation speed of 90rpm, and then the required amount of curing agent (18g when the main agent was added 1.5%, 12g when the main agent was 1.0%) Stir and knead for 10 seconds. Next, the main agent (4 at 1.5%
Add 5g, 30g when 1.0%), knead for 45 seconds, immediately add 5
It is strongly molded in a mold of 0 mmH x 50 mmφ, and after a lapse of time, it is demolded and the strength is measured. The leaving temperature at this time is 15 ° C, and the humidity is
It was 60% RH.

 The results are shown in Table 2 (1) and (2).

As is clear from the strength test results in Table 2 (2), when a curing agent containing an ester solvent phenol resin was used, the strength was remarkably high, and the final strength (after 24 hours) was the addition of the main agent. Even if the amount is reduced by about 30%, the strength is almost the same as that of the comparative example.

〔The invention's effect〕

The self-hardening binder for castings obtained by mixing the alkali phenol / formaldehyde resin as the main agent and the organic ester solvent containing the phenol / formaldehyde resin as the curing agent according to the present invention is compared with the conventional one. It has excellent strength characteristics even if the resin component is significantly reduced.

Therefore, the self-hardening phenolic resin binder for casting according to the present invention is extremely effective in the casting industry.

Claims (1)

[Claims] (1) Phenol and formaldehyde in a molar ratio of phenol: formaldehyde = 1.0: 0.85
To 1.0: 3.0, and then potassium hydroxide and / or sodium hydroxide in a molar ratio with the phenol: phenol: (potassium hydroxide and / or sodium hydroxide) = 1.0: 0.5 to 1.0: 1.5 The number average molecular weight is 600 to 1,800 and the solid content is 40.
˜70% phenol / formaldehyde resin aqueous solution and (2) the phenol and formaldehyde are reacted at a molar ratio of phenol: formaldehyde = 1.0: 0.6 to 1.0: 3.0 to obtain a number average molecular weight of 300 to 1,500 phenol / formaldehyde resin as solid content
A method for producing a phenol-formaldehyde resin binder, which comprises mixing 20 to 60% by weight of an organic ester solvent with 20 to 80% by weight of (2) relative to (1).