JPH0667998B2 - Method for producing phenol resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for producing a phenolic resin having a light hue.

(Prior Art) Phenolic resin is used as molded products, adhesives, paints, impregnating materials, etc. by taking advantage of its characteristics such as heat resistance, corrosion resistance, and water resistance, electrical parts, machine parts, acid resistant equipment, electrical insulating materials, It is widely used as an adhesive for woodworking and as a corrosion resistant paint.

However, phenolic resin has a major drawback that its hue becomes yellow or blackish brown during its formation reaction or curing reaction by heat or acid.
Applications were limited in fields such as paints where hue is important.

Various clarifications have been made to clarify the phenomenon that the hue changes from yellow to blackish brown. The color development mechanism differs depending on the type of raw materials such as phenols, aldehydes or catalysts, or the progress of formation reaction or curing reaction, and it is extremely complicated. One of the major causes is that phenol is converted into an aromatic quinoid by oxidation. It is mentioned that it will become.

Various attempts have been made to remedy the drawback of such hue change.

For example, 1) acetylation with acetic anhydride, silylation with trimethylchlorosilane, esterification with methyl acetate, etc. to mask phenolic hydroxyl groups, 2) co-condensation of phenols and ureas with aldehydes, Alternatively, a method of using a phenol / aldehyde resin and a urea / aldehyde resin together, 3) a method of co-condensing triazines and phenols such as melamine and benzoguanamine with an aldehyde, or a resin obtained by condensing a triazine and an aldehyde, and a phenol / aldehyde resin There is a method of using and together.

However, in the masking method of 1), the curing speed is slow, and high temperature is required to obtain a sufficient cured state,
It is disadvantageous in terms of energy and has a drawback that the base material is limited when applied to paints, adhesives, etc. In addition, this method has a drawback in that the reaction device and the reaction process are complicated and the resulting phenol resin is expensive.

According to the methods 2) and 3), water resistance, heat resistance, corrosion resistance, etc., which are the original characteristics of the cured phenolic resin, are reduced, and when used as a paint or adhesive, the adhesion to the base material is reduced. There was a flaw.

(Problems to be Solved by the Invention) The present invention has improved the above-mentioned various drawbacks and has a light or colorless hue without impairing the inherent properties of a phenolic resin such as water resistance, heat resistance and corrosion resistance. A method for producing a phenolic resin is provided.

[Structure of Invention]

(Means for Solving Problems) The present invention relates to a method for producing a phenol resin by reacting phenols and aldehydes in the presence of a basic catalyst, wherein dissolved oxygen is repeatedly supplied by repeatedly reducing pressure and introducing an inert gas. To the mixed solution of phenols and aldehydes with reduced amount, add basic catalyst solution with reduced dissolved oxygen content by repeating depressurization and introduction of inert gas, and further depressurize and inert gas as necessary. This is a method for producing a phenol resin, which is characterized in that the amount of dissolved oxygen in the reaction system is made less than 300 ppm by repeating the introduction and then the reaction is carried out in an inert gas atmosphere.

In the present invention, any phenol may be used, but p
One or more selected from the group consisting of phenols having a saturated alkyl group having 1 to 18 carbon atoms at the -position, phenols having a phenyl group at the p-position, bisphenol F, bisphenol A and bisphenol B are preferable. ，
More preferably p-isopropylphenol, p-tert
-Butylphenol or bisphenol A.
Further, it is preferable to use highly pure phenols, for example, carbonate grade phenols.

In the present invention, formaldehyde, acetaldehyde, benzaldehyde, paraformaldehyde and the like can be used as the aldehydes, but among these, because they are inexpensive, the reaction products cure rapidly with acid or heat, and have little discoloration. , Formaldehyde and paraaldehyde are preferably used. Formaldehyde is used as an aqueous solution or butanol solution.

Aldehydes are added to 1 mol of bifunctional phenol such as p-alkylphenols and p-phenylphenols.
Bisphenol F, bisphenol at a ratio of 6 to 6.0 mol
The aldehydes are reacted in a ratio of 1.2 to 12.0 mol with respect to 1 mol of the tetrafunctional phenol such as A and bisphenol B. If the reaction rate of the aldehydes is small, the storage stability tends to be poor, or the compatibility of the generated phenolic resin with other resins tends to be poor. There is no particular advantage.

Phenols and aldehydes, water and / or
It is used by dissolving it in an organic solvent.

As the basic catalyst in the present invention, a conventionally known basic catalyst used in the production of a phenol resin, for example, a hydroxide or alkoxide of an alkali metal or an alkaline earth metal, ammonia, an alkanolamine, an aromatic amine or the like can be used. However, among them, lithium, sodium,
One or more selected from the group consisting of potassium hydroxide and alkoxide, and magnesium and calcium hydroxide are preferable. In order to promote the reaction smoothly, it is preferable to use the basic catalyst in an amount of 200 ppm or more based on the total amount of phenols, aldehydes and basic catalysts. The basic catalyst is used by dissolving it in water and / or an organic solvent. In the case of hydroxide, the basic catalyst is water or a mixture of water and a small amount of an organic solvent, and in the case of alkoxide, an organic solvent, especially a monohydric alcohol, or a mixture thereof with a small amount of water, respectively. Used by dissolving. Even at room temperature, a solution of a mixture of phenols and alcohols is not easily oxidized by oxygen in the air or in the solution before the basic catalyst is added to it, but when the basic catalyst is added, the solution is not oxidized in the air. It is easily oxidized by the oxygen in the solution or the solution and the discoloration proceeds rapidly. Therefore, in the present invention, the dissolved oxygen amount is reduced by repeating the reduced pressure and the introduction of the inert gas to the solution of the mixture of phenols and aldehydes in which the reduced oxygen amount is reduced by repeating the reduced pressure and the inert gas conduction. Add a basic catalyst solution, and if necessary, further reduce the pressure and conduct inert gas to reduce the amount of dissolved oxygen in the reaction system to less than 300 ppm, preferably 10
After adjusting the amount to less than 0 ppm, the reaction is performed in an inert gas atmosphere. The smaller the amount of dissolved oxygen in the reaction system, the better.

In the present invention, the inert gas includes fluorine gas, carbon dioxide gas, helium gas, argon gas, etc.
Inexpensive nitrogen gas is preferably used.

In the present invention, a solution of a mixture of phenols and aldehydes, in which the amount of dissolved oxygen is reduced by repeatedly reducing the pressure and introducing an inert gas, is added to a base in which the amount of dissolved oxygen is reduced by repeatedly reducing the pressure and introducing the inert gas. A reactive catalyst solution was added, and pressure reduction and inert gas introduction were repeated as necessary, resulting in a dissolved oxygen content in the reaction system of 300 p
less than pm, preferably less than 100 ppm,
It is preferable that the amount of dissolved oxygen in both the solution of the above-mentioned mixture of phenols and aldehydes and the basic catalyst solution is less than 300 ppm, preferably less than 100 ppm, because the oxygen concentration does not increase locally even temporarily. . In this way, the amount of dissolved oxygen in the reaction system is set to less than 300 ppm, preferably less than 100 ppm, and then the reaction is performed in an inert gas atmosphere. The inert gas may flow through the space above the reactor or may be blown into the reaction system, but it is preferable to blow it into the reaction system because the discoloration preventing effect is high.

By repeating the depressurization and the introduction of the inert gas in this manner, in the present invention, the dissolved oxygen amount in the reaction system can be made extremely small in a much shorter time than in the case of simply blowing the inert gas.

Further, in the present invention, when the reaction between phenols and aldehydes progresses and the molecular weight increases, discoloration tends to become remarkable. In addition, when a high molecular weight substance with low solubility in a solvent or other resin is generated, and it is used for paints or adhesives,
It may cause deterioration of physical properties. Therefore, the molecular weight of the obtained phenol resin is preferably 200 to 150. If the molecular weight of the resulting phenol resin is less than 200, it may not be possible to obtain sufficient physical properties when used in molded products, paints, adhesives, etc. In order to control the molecular weight of the obtained phenol resin to 200 to 1500, it is preferable to use a monohydric alcohol together. These monohydric alcohols include methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol monoethyl ether and ethylene glycol monoethyl ether acetate. These monohydric alcohols can also be added to the reaction system as part or all of the organic solvent that dissolves the phenols and aldehydes, and / or as part or all of the organic solvent that dissolves the basic catalyst. A monohydric alcohol whose dissolved oxygen amount is less than 300 ppm, preferably less than 100 ppm by repeating reduced pressure and introduction of an inert gas can be added before or during the reaction.
Alternatively, these methods can be combined appropriately. Monohydric alcohols that azeotrope with water under reduced pressure, such as isopropyl alcohol and ethanol, are used in large amounts when they are used together with water and the amount of dissolved oxygen in the system containing them is reduced by repeating reduced pressure and introduction of an inert gas. Must be added in excess.

(Examples) Hereinafter, the present invention will be described with reference to Examples. In the examples, “part” means “part by weight” and “%” means “% by weight”. Example 1 p-tert-butylphenol (carbonate grade)
A reactor was charged with 150 parts, 429 parts of 35% aqueous formaldehyde solution and 300 parts of butanol. Next, the inside of the reactor was depressurized and kept at 12 mmHg for 5 minutes, and then nitrogen was introduced into the reactor to return it to atmospheric pressure. The operation of depressurizing and introducing nitrogen was repeated again.

On the other hand, sodium hydroxide (purity 93%) 21.5 was added to the dropping tank.
And 150 parts of water were charged, the inside of the dropping tank was depressurized and kept at 20 mmHg for 5 minutes, and then nitrogen was introduced into the dropping tank to return to atmospheric pressure. The operation of depressurizing and introducing nitrogen was repeated again.

Next, 171.5 parts of aqueous sodium hydroxide solution was gradually dropped from the dropping tank into the reactor. Then, the inside of the reactor was depressurized and kept at 8 mmHg for 3 minutes, and then nitrogen was introduced to return it to atmospheric pressure, and the amount of dissolved oxygen in the reaction system was adjusted to 93 ppm.
While flowing nitrogen in the reactor, the reaction system was heated to 60 ° C in 30 minutes.
The temperature was raised to 60 ° C., and the reaction was carried out at 60 ° C. for 1 hour and then at 90 ° C. for 3 hours. After cooling the reaction product, phosphoric acid (purity 85
%) 19.2 parts and 150 parts of water were added to neutralize, and then washed with 500 parts of water four times.

Next, dehydration was performed at 40 ° C and 15 mmHg to obtain a colorless transparent phenol resin solution (average molecular weight: 450).

Comparative Example 1 A black-brown colored phenol resin solution (average molecular weight of about 600) was obtained in the same manner as in Example 1 except that the operation of depressurization and introduction of fluorine and the introduction of fluorine during the reaction were not carried out. .

Example 2 p-tert-butylphenol (carbonate grade)
150 parts, 225 parts of 40% formaldehyde butanol solution and ethylene glycol monoethyl ether acetate 15
Charge 0 parts into the flask, then depressurize the inside of the flask to 12 mm.
After maintaining at Hg for 5 minutes, nitrogen was introduced and the pressure was returned to atmospheric pressure. The operation of depressurization and introduction of nitrogen was repeated once again.

On the other hand, the dropping funnel was charged with 38.6 parts of 28% sodium methylate methanol solution, and the pressure inside the dropping funnel was reduced to 20 mmHg.
After holding for 5 minutes, nitrogen was introduced into the dropping funnel and the pressure was returned to atmospheric pressure. The operation of depressurizing and introducing nitrogen was repeated again.

Next, a methacrylic solution of sodium methylate was gradually dropped into the flask from the dropping funnel, and after the dropping was completed, the inside of the flask was depressurized and kept at 8 mmHg for 3 minutes, and then nitrogen was introduced to increase the inside of the flask. The pressure was returned to atmospheric pressure and the amount of dissolved oxygen in the reaction system was adjusted to 78 ppm. While blowing nitrogen into the reaction system, the temperature of the reaction system was raised to 90 ° C in 30 minutes, and the temperature was raised to 90 ° C.
And reacted for 6 hours. After cooling the reaction product, it was neutralized by adding 7.7 parts of phosphoric acid (purity 85%) and 60 parts of water, and then adding 3 parts of water.
It was washed 4 times with 00 parts. Then, dehydration was performed at 30 ° C and 15 mmHg to obtain a colorless transparent phenol resin solution (average molecular weight 300).

Comparative Example 2 A flask was charged with 150 parts of p-tert-butylphenol, a 40% formaldehyde butanol solution and 150 parts of ethylene glycol monoethyl ether acetate, and the mixture was blown with nitrogen to prevent dropping.
A% sodium methylate methanol solution was gradually added dropwise. After the dropping was completed, blowing of nitrogen was continued for 40 minutes. At this time, the amount of dissolved oxygen in the reaction system was about 800 ppm.
Then, in the same manner as in Example 2, the reaction was carried out while blowing in nitrogen, and neutralization, washing and dehydration were carried out to obtain a solution of a brown phenol resin (average molecular weight about 400).

Example 3 120 parts of p-tert-butylphenol, bisphenol A
(Carbonate grade) 45.6 parts, 225 parts of 40% formaldehyde butanol solution and 150 parts of ethylene glycol monoethyl ether acetate were charged into the reactor, and then the pressure inside the reactor was reduced and kept at 12 mmHg for 5 minutes, and then reacted with nitrogen. It was introduced into the vessel and returned to atmospheric pressure. The operation of depressurizing and introducing nitrogen was repeated again.

On the other hand, the dropping tank was charged with 38.6 parts of 28% sodium methylate methanol solution, and the pressure inside the dropping tank was reduced to 20 mmHg.
After maintaining for 5 minutes, nitrogen was introduced to return the inside of the dropping tank to atmospheric pressure. The depressurization and the introduction of nitrogen were repeated once again.

Next, the sodium methylate methanol solution was gradually dropped from the dropping tank into the reactor, and after the dropping was completed, the inside of the reactor was depressurized and kept at 8 mmHg for 3 minutes, and nitrogen was introduced to increase the inside of the reactor. It returned to atmospheric pressure. At this time, the amount of dissolved oxygen in the reaction system was 75 ppm. While blowing nitrogen into the reaction system, the reaction system was heated to 90 ° C. in 30 minutes and reacted at 90 ° C. for 6 hours. The obtained reaction product is cooled, neutralized by adding 7.7 parts of phosphoric acid (purity 85%) and 60 parts of water, and then water 3
It was washed 4 times with 00 parts. Next, dehydration was performed at 50 ° C and 15 mmHg to obtain a colorless transparent solution of phenol resin (average molecular weight: 700).

Comparative Example 3 p-tert-butylphenol 120 parts, bisphenol A
(Carbonate grade) 45.6 parts, 40% formaldehyde butanol solution 225 parts, ethylene glycol monoethyl ether acetate 150 parts and 28% sodium methylate methanol solution 38.6 parts were charged into the reactor, and nitrogen was blown into the reaction system for 40 minutes. At this time, the amount of dissolved oxygen in the reaction system was about 700 ppm. Next, in the same manner as in Example 3, the reaction was carried out while blowing in nitrogen to carry out 3 neutralization, washing and dehydration to obtain a blackish brown phenol resin (average molecular weight).
1300) solution was obtained.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY According to the present invention, a phenol resin whose hue is pale or colorless can be obtained by a simple and short-time operation without deteriorating the excellent performance of phenol resin such as water resistance, heat resistance, and corrosion resistance. .

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Claims (5)

[Claims] 1. A method for producing a phenol resin by reacting phenols and aldehydes in the presence of a basic catalyst, wherein phenols and aldehydes having reduced dissolved oxygen content by repeatedly reducing pressure and introducing an inert gas. The basic catalyst solution, in which the amount of dissolved oxygen is reduced by repeating reduced pressure and introduction of an inert gas, is added to the solution of the mixture of kinds,
If necessary, further reduce the pressure and introduce an inert gas to reduce the amount of dissolved oxygen in the reaction system to less than 300 ppm.
A method for producing a phenol resin, which comprises reacting in an inert gas atmosphere. 2. A phenol is selected from the group consisting of a phenol having a saturated alkyl group having 1 to 18 carbon atoms at the p-position, a phenol having a phenyl group at the p-position, bisphenol F, bisphenol A and bisphenol B. 1 chosen
The method for producing a phenol resin according to claim 1, wherein the phenol resin is one kind or two or more kinds. 3. The method for producing a phenol resin according to claim 1 or 2, wherein the aldehydes are formaldehyde and / or paraformaldehyde. 4. The basic catalyst is one or more selected from the group consisting of lithium, sodium and potassium hydroxides and alkoxides, and magnesium and calcium hydroxides. Item 4. A method for producing a phenolic resin according to any one of Items 3 to 3. 5. In addition to phenols, aldehydes and basic catalysts, a monohydric alcohol is used, and the resulting phenol resin has a molecular weight of 200 to 1500.
Item 5. A method for producing a phenolic resin according to any one of Items 4 to 4.