JPH0446142A - Production of aminomethylated phenols - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject substances at a low cost while suppressing side reaction by reacting phenols with aldehydes and an ammonium salt in an aqueous solvent, carrying out oil-water separation of the reaction mixture, then recycling the aqueous layer and neutralizing the oily layer. CONSTITUTION:Phenols are reacted with aldehydes and an ammonium salt (e.g. ammonium chloride) in an aqueous solvent at 20-100 deg.C for 0.1-10hr in an aminomethylation step and oil-water separation of the reaction mixture is carried out. The aqueous layer is then recycled to the aminomethylation step and the oily layer, as necessary, is washed with water and subsequently neutralized with an aqueous solution of an alkali (e.g. NaOH). The oil-water separation is further performed to afford a mixture consisting essentially of the subject substances. The contained unreacted phenols are recovered by vacuum distillation and recycled to afford the objective substances in high yield. Since the ammonium salt can be previously removed by the oil-water separation, a small amount of the alkali required for the neutralization is sufficiently used. The subject substances are useful as a raw material for heat-resistant epoxy resins.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing aminomethylated phenols.

The aminomethylated phenols produced in the present invention are useful compounds as raw materials for various chemical products or as epoxy resin curing agents.

In particular, epoxy resins made from aminomethylated phenols have good workability because they are low-viscosity liquid resins.
Moreover, since it provides a cured product with excellent heat resistance, it has a wide range of applications such as various molding materials, encapsulating agents and substrates for electronic parts, matrix resins for composite materials, adhesives, and coating materials.

(Prior art) In the FW method (filament winding method), a reinforcing fiber base material such as glass fiber or carbon fiber is impregnated with a thermosetting resin and wound around a mandrill, and after the resin is cured, the mandrel is removed ( In some cases, the mandrill is left in the product as it is), making it possible to produce FRP, which is a composite material product.
(fiber-reinforced plastic).

According to the FW method, properties such as strength and rigidity can be imparted by arranging fibers in any direction, so this method is particularly suitable for manufacturing high-strength FRP.

Typical thermosetting resins include phenolic resins and epoxy resins, but none of the phenolic resins has been able to satisfy both the fluidity and curing properties required for the FW method. On the other hand, epoxy resins are low viscosity liquids that easily impregnate fiber base materials, and have excellent curing properties such as short curing times.

Among epoxy resins, glycidyl ether of bisphenol A is particularly frequently used in the FW method.

However, since the resulting cured product has a low glass transition temperature,
It cannot be used in fields that require heat resistance of 100"C or higher.

Epoxy resins obtained by epoxidizing the active hydrogen of the amino group of an aromatic amine compound are known as those used in fields where heat resistance is required. Specifically, tetraglycidyldiaminodiphenylmethane (TG[lDM), triglycidyl-para-aminophenol (TGPAP), triglycidyl-methaminophenol (TGMAP),
Tetraglycidyl metaxylylene diamine (TGMχA
) are glycidylamino group-containing epoxy resin compounds. Among these, TGDDM and TGPAP are low viscosity liquid resins, and by selecting the curing conditions, a cured product with a heat distortion temperature of over 200'C can be obtained.
It is particularly suitable for application to the W method. However, since these are made from special amine compounds, they are currently expensive and are not suitable for large-scale use. In addition, since rapid heat generation occurs when the aromatic amine compound as a raw material is glycidylated, sufficient temperature control is required to prevent undesirable side reactions such as polymerization of the resin.

(Problems to be Solved by the Invention) In order to solve the problems of the above-mentioned epoxy resin raw materials, the present inventors first devised a method for producing epoxy resins using aminomethylated phenols as raw materials. .

Furthermore, as a method for producing aminomethylated phenols, a method in which phenols, aldehydes, and ammonium salts are reacted is effective in suppressing side reactions such as polymerization, and is useful as a method for producing low-viscosity epoxy resin raw materials. I also discovered something and filed an application first.

In this method, when phenol is selected as the phenol, formaldehyde is selected as the aldehyde, and ammonium chloride is selected as the ammonium salt, aminomethylated phenol is synthesized as follows.

Nine-arc reaction il n・1-3 raw m R(JIzN)12・I(C++MO)l → I'
lCH,N[12+gate C1+8.0M=Na K
... In this case, aminomethylated phenol is made from general-purpose chemicals such as phenol, formaldehyde, and monoammonium monide, so the raw material cost can be reduced.

When synthesizing an epoxy resin using this aminomethylated phenol as a raw material, it can be used as a mixture, but in order to obtain an epoxy resin with excellent heat resistance, it is desirable to separate unreacted phenols.

Traditionally, in the Mannich reaction of phenols, secondary amines such as dimethylamine were used to synthesize 2,4.6-tri(dimethylaminomethyl)phenol.
It was used as a curing agent for epoxy resins.

The present inventors have demonstrated that by utilizing this Mannich reaction and using ammonium salts in place of secondary amines, it is possible to synthesize aminomethylated phenols useful as chemical raw materials including epoxy resin raw materials and as epoxy resin curing agents. This is what we discovered.

When synthesizing an epoxy resin from the aminomethylated phenols obtained in this way by a glycidylation reaction, since the glycidylation reaction is a reaction of aliphatic amines, conventional glycidylation of aromatic amines such as aminophenol, etc. Compared to conventional reactions, the reaction is easy to repeat without generating rapid heat generation.

However, in order to lower the viscosity of the epoxy resin obtained through the glycidylation reaction, it is necessary to improve the yield of primary amines during the production of aminomethylated phenols, but in this case, there are disadvantages as described below. .

That is, if the amount of ammonium salt is less than the equivalent amount to formaldehyde, the primary amine, which is the target product, will further react with phenol and formaldehyde to form secondary amine, tertiary amine, etc.
Since a class amine is produced and polymerization occurs, it is usually necessary to use an amount of ammonium salt equal to or more than that of formaldehyde.

By using an equivalent amount or more of ammonium salt in this manner, undesirable side reactions can be prevented from proceeding, but on the other hand, unreacted ammonium salt remains in the reaction product.

When this ammonium salt is neutralized by a neutralization reaction, the amount of alkali used for neutralization increases, which is not desirable in terms of cost reduction. In addition, efficient use of raw materials and solvents is desired from the viewpoint of reducing raw material costs and disposal costs.

Therefore, an object of the present invention is to provide a method for efficiently carrying out the reaction in a method for producing aminomethylated phenols from phenols, aldehydes, and ammonium salts.

(Means for Solving the Problems) The gist of the present invention is to aminomethylate phenols with aldehydes and ammonium salts in an aqueous solvent, move the resulting reaction mixture into oil and water, and then neutralize the oil layer. A method for producing aminomethylated phenols, characterized in that the aminomethylated phenols are obtained by

In a preferred embodiment, the aqueous layer after oil and water separation is recycled to the aminomethylation step. Furthermore, it is also preferable to neutralize the oil layer after oil-water separation, recover unreacted phenols, and circulate this to the aminomethylation step.

The present invention will be explained in detail below.

In the present invention, aminomethylated phenols are produced as follows.

Phenols include phenol, cresol, xylenol, ethylphenol, phenylphenol, catechol, resorcinol, hydroquinone, naphthol,
Compounds having at least one phenolic hydroxyl group such as methylnaphthol can be used alone or in combination of two or more. In the following, phenol will be used as a representative of phenols.

As the aldehydes, aliphatic or aromatic aldehydes such as formaldehyde, acetaldehyde and benzaldehyde, and aldehyde generating substances such as trioxane and paraformaldehyde can be used alone or in combination of two or more. In the following, formaldehyde will be used as a representative example of aldehydes. As formaldehyde, formalin, which is an aqueous solution thereof, can also be used.

The amount of formaldehyde used is 0.0% relative to phenol.
It is preferably in the range of 5 to 5 (molar ratio). If it is less than 0.5 or more than 5, the yield of the desired aminomethylated phenol will decrease.

As the ammonium salt, ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium acetate, etc. are used. Alternatively, ammonia and an inorganic acid may be added during the reaction so that these ammonium salts are generated during the reaction.

The amount of ammonium salt used is preferably in the range of 1 to 10 (molar ratio) relative to formaldehyde; if it is less than 1, undesirable side reactions tend to proceed, while if it exceeds 10, the reaction efficiency will decrease.

Preferably, the ammonium salt is added as an aqueous solution. The concentration of ammonium salt in the aqueous solution is preferably at least below the concentration at which the ammonium salt is dissolved under the reaction conditions. This is because if the concentration exceeds the soluble concentration, ammonium salt will precipitate during the reaction, making it impossible to carry out the reaction efficiently.

The reaction conditions for the aminomethylation reaction are not particularly limited, and are appropriately determined depending on the properties of the desired aminomethylated phenol product. Preferred specific examples will be explained below.

The reaction temperature is preferably in the range of 20 to 100°C. If the reaction temperature is less than 20° C., the aminomethylation reaction will not proceed sufficiently, requiring a long reaction time, and the reaction efficiency will tend to decrease. On the other hand, if the temperature exceeds 100°C, undesirable side reactions will proceed.

The reaction time is preferably in the range of 0.1 to 10 hours. 0.1
If the reaction time is less than 1 hour, the aminomethylation reaction will not proceed sufficiently and the reaction efficiency will be low. On the other hand, if the reaction time exceeds 10 hours, undesirable side reactions will proceed.

The aminomethylation reaction produces acid addition salts of aminomethylated phenols as shown in the above formula ( ]).

For ammonium salts other than ammonium chloride, acid addition salts of aminomethylated phenols corresponding to the respective ammonium salts are produced by a similar reaction. Also,
When an aldehyde other than bomaldehyde is used, a phenol containing an aminomethyl group having a substituent depending on the type of aldehyde is obtained.

An aqueous solvent is used as a reaction solvent during the aminomethylation reaction. The aqueous solvent may contain alcohol.

Before separating the reaction mixture from oil and water after the completion of the aminomethylation reaction, it is desirable to add alcohol and leave it for a certain period of time in order to prevent undesirable side reactions. There are no particular restrictions on the type of alcohol to be added, but methanol, which can be easily separated from water by distillation, is preferred. Although the amount used is not limited, it is desirable that the entire amount of the reaction product and unreacted raw material be dissolved at a temperature below the reaction temperature at which the aminomethylation reaction was performed.

If alcohol is added, the alcohol is removed from the reaction product by distillation or the like after it is left for a certain period of time. Note that when alcohol is added, ammonium salt crystals may precipitate in the reaction product, but it is preferable to remove these crystals by filtration or the like before distilling off the alcohol.

This is because after the alcohol is distilled off, the crystals and the oil layer coexist, making it difficult to separate the crystals.

After the alcohol has been distilled off, the reaction mixture is left to cool, and then oil and water are separated.

During oil-water separation, ammonium salt crystals may precipitate again in the water layer. In that case as well, it is desirable to remove the precipitated crystals in order to prevent the crystals from coexisting with the oil layer.

After oil and water separation, ammonium salt and other unreacted raw materials such as phenol and formaldehyde are present in the water layer. This aqueous layer can be recycled to the aminomethylation step again. At that time, the amount of raw materials to be charged may be adjusted based on the analytical value of this aqueous layer. In addition, the ammonium salt crystals that have been removed can also be circulated together with the water layer.

The oil layer after oil-water separation contains acid addition salts of aminomethylated phenols and unreacted phenol. This oil layer is washed with water if necessary, and then neutralized with an aqueous alkaline solution. The type of alkali used for neutralization is not limited, but sodium hydroxide, potassium hydroxide, etc. can be used. It is desirable to add it in an amount that makes it slightly alkaline. In the present invention, since the ammonium salt is removed in advance, the amount of alkaline aqueous solution required to neutralize the oil layer can be reduced.

After neutralization with an alkaline aqueous solution, oil and water separation is performed.
By washing with water if necessary, a mixture containing the target aminomethylated phenol as a main component is obtained. Unreacted phenols can be recovered from this mixture by distillation or the like. Although there are no particular restrictions on the conditions for distilling unreacted phenols, it is desirable to carry out the distillation under reduced pressure in order to prevent undesirable side reactions. The recovered unreacted phenols can be recycled to the aminomethylation step.

According to the present invention, aminomethylated phenols, which are primary amines, can be obtained in high yield as described above,
Suitable as a raw material for producing low-viscosity epoxy resins. Furthermore, raw materials can be used efficiently in the production of aminomethylated phenols, and the burden of waste treatment can be reduced. Specifically, since the ammonium salt used in an equivalent or more amount in the aminomethylation reaction can be removed in advance by oil-water separation, the amount of alkali required for neutralization can be reduced. Further, by recycling the water layer after oil-water separation and the recovered unreacted phenols to the aminomethylation step, it is possible to reduce the raw material cost and the cost required for these treatments. Furthermore, if the ammonium salts that have precipitated as crystals are separated from the oil layer before oil/water separation, the amount of alkali required to neutralize the oil layer can be reduced, and furthermore, it is possible to prevent ammonium salts from being mixed into the oil layer. Therefore, it also improves the quality of aminomethylated phenol products. Moreover, by removing unreacted phenols, it can be used as a raw material for obtaining an epoxy resin with excellent heat resistance.

The aminomethylated phenols obtained by the present invention are
It is used as a raw material for various chemicals and as a curing agent for epoxy resins. In particular, aminomethylated phenols are reacted with epihalohydrin in the presence of an alkali metal hydroxide by a conventional method to epoxidize some or all of the phenolic hydroxyl groups and N-aminomethyl groups of the aminomethylated phenols. Suitable for obtaining low viscosity liquid epoxy resin.

The epoxy resin thus obtained is a liquid resin with low viscosity at room temperature and has excellent moldability, and can be cured in a short time using a commonly used curing agent to form a cured product with excellent heat resistance.

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

Example 1 Phenol 94 was added to a 50 flask of capacity 11 equipped with a stirrer, reflux condenser, nitrogen inlet tube, temperature needle and dropping funnel.
g (1 mol), 40% ammonium chloride aqueous solution 270
g (2 mol) was charged, and the temperature was raised to 50°C while stirring.

At that temperature, 108g (1 mol) of 37% formalin aqueous solution
was gradually added dropwise. 6 while being careful to avoid heat generation due to reaction heat.
The temperature was raised to 0°C and held at that temperature for 1 hour. After the reaction is complete, transfer the reaction mixture to a beaker and add 30 methanol
After adding 0 cc and stirring for 1 hour, the mixture was allowed to stand overnight.

Ammonium chloride crystals were deposited in the beaker and were filtered out. Methanol was completely distilled off from the filtrate using an evaporator, and the mixture was allowed to stand still. Ammonium chloride crystals were deposited again, so the crystals were filtered to the filter side and oil and water were separated. The weight of the precipitated ammonium chloride was about 30 g.

The aqueous layer after oil and water separation weighed about 150 g, and contained about 30% by weight of ammonium chloride.

A 5% NaOH aqueous solution was added to the oil layer until the pH reached 8, and then the oil and water were separated. The amount of 5% NaOH aqueous solution used is approximately 1
It was 20g. Furthermore, the oil layer was repeatedly washed with water, and the target product, aminomethylated phenol (formula (1))
85 mixtures based on n=1 product)
I got g. This mixture was distilled under reduced pressure to separate about 8 g of distillate oil mainly composed of unreacted phenol, yielding about 77 g of an aminomethylated phenol product.

The yield of the aminomethylated phenol product based on the starting phenol was about 82% by weight, and the product contained about 5% by weight of unreacted phenol.

Example 2 42 g of ammonium chloride and 48 g of water were added to 30 g of the ammonium chloride crystals obtained in Example 1 and 150 g of the water layer to prepare 270 g (2 moles) of a 40% ammonium chloride aqueous solution. Capacity 1 with stirrer, reflux condenser, nitrogen inlet tube, thermometer and dropping funnel! 94 g (1 mol) of phenol and 270 g (2 mol) of the above ammonium chloride aqueous solution were placed in a 50 flask, and while stirring,
The temperature was raised to 0''C.

At that temperature, 108 g (1 mol) of a 37°C formalin aqueous solution was gradually added dropwise. The temperature was raised to 60°C while being careful to avoid heat generation due to reaction heat, and maintained at that temperature for 1 hour.

After the reaction was completed, the reaction mixture was transferred to a beaker, 300 cc of methanol was added thereto, and the mixture was stirred for 1 hour and then allowed to stand overnight.

Thereafter, the same operation as in Example 1 was performed to obtain about 70 g of an aminomethylated phenol product (product where n=1 in formula (1)).

The yield of the aminomethylated phenol product based on the starting phenol was about 82%, and the product contained about 4% by weight of unreacted phenol.

Comparative Example 1 Phenol 94 was added to a 50 flask with a capacity of 11 equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel.
g (1 mol) and 20% ammonium chloride aqueous solution 58
5 g (2 mol) was charged, and the temperature was raised to 50°C while stirring.

At that temperature, 108 g (1 mol) of a 37°C formalin aqueous solution was gradually added dropwise.6 The temperature was raised to 60°C, being careful not to generate heat due to the reaction heat, and the temperature was maintained at that temperature for 1 hour.After the reaction was completed, the reaction mixture was Transfer to a beaker and add 300 methanol
After adding cc and stirring for 1 hour, the mixture was left standing for 1 day and night.
Methanol was completely distilled off from the compound using an evaporator, and the mixture was neutralized with 1600 g of 5% NaOH aqueous solution (2 morphs).

After neutralization, oil and water separation was performed, and water washing was further performed to obtain 80 g of a mixture containing aminomethylated phenol as a main component.

This mixture contained about 15% by weight of unreacted phenol.

Reference example (Epoxidation of aminomethylated phenol) Stirrer, thermometer, nitrogen inlet tube, dropping funnel, and condensation separation of an azeotrope of shrimp chlorohydrin and water to remove the lower shrimp chlorohydrin layer. Approximately 70 g of aminomethylated phenol obtained in Example 1, 660 g of shrimp chlorohydrin, were placed in a 50 flask equipped with a separator for returning to the reactor.
60 g of a 50% aqueous tetramethylammonium chloride solution was charged, the temperature was raised while stirring, and addition reaction was carried out at 60'C for 1 hour.

Furthermore, after reducing the pressure to the boiling pressure of shrimp chlorohydrin at the same temperature, while returning the shrimp chlorohydrin in the lower layer from the azeotropic mixture of shrimp chlorohydrin and water to the reactor,
102 g of sodium hydroxide was added over 4 hours to carry out a dehydrochlorination reaction.

After distilling shrimp chlorohydrin with an evaporator,
300 g of toluene was added and filtered to separate toluene-soluble components. Furthermore, toluene was distilled off using an evaporator, and about 150 g of toluene-soluble epoxy resin was recovered.

The epoxy equivalent of this epoxy resin was about 150 g/mol, and when it was mixed with an aromatic amine, ancamine, in a theoretical amount and cured at 190°C for 3 hours, a cured product with excellent heat resistance was obtained.

(Effects of the Invention) According to the method of the present invention, aminomethylated phenols can be produced efficiently and at low cost while suppressing side reactions.

In the present invention, since ammonium salts can be removed in advance by oil-water separation, the amount of alkali required for neutralization is small, making it economical. Furthermore, since the aqueous layer containing ammonium salt after oil and water separation can be reused, and unreacted phenol recovered from the oil layer can also be reused, raw material costs and disposal costs can be reduced.

From the aminomethylated phenols obtained according to the present invention, an epoxy resin with excellent moldability and curing properties can be produced, and this epoxy resin can form a cured product with excellent heat resistance.

Claims (3)

[Claims] (1) It is characterized by aminomethylating phenols with aldehydes and ammonium salts in an aqueous solvent, separating the resulting reaction mixture from oil and water, and then neutralizing the oil layer to obtain aminomethylated phenols. , a method for producing aminomethylated phenols. (2) The production method according to claim 1, wherein after oil and water separation, the obtained aqueous layer is recycled to the aminomethylation step. (3) Recovering unreacted phenols from the oil layer after neutralization,
3. The method according to claim 1, wherein the recovered unreacted phenols are recycled to the aminomethylation step.