JP3104915B2 - Novolak resin manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a novolak resin having a low softening point, which is useful as a raw material of an epoxy resin which gives a cured product having excellent moisture resistance and heat resistance, and which is useful as a curing agent for an epoxy resin.

[0002]

2. Description of the Prior Art JP-A-3-717 discloses a novolak resin obtained by reacting a dimethylol compound with naphthol in the presence of an acid catalyst.

[0003]

In the embodiment of JP-A-3-717, the reaction between a dimethylol compound and naphthol is 9
The reaction is carried out at 0 to 95 ° C., and excess naphthol in the reaction mixture is removed by steam distillation.

However, in this method, a reaction product is decomposed or recondensed by an oxidation reaction under steam distillation or the like, so that the ratio of the trinuclear compound described below in the novolak-type resin decreases, Further, the content of the compound having a lower molecular weight than that of the trinuclear compound increases, and the obtained novolak-type resin and its epoxidized product have a high softening point, and a low-viscosity product that is easy to handle cannot be obtained.

Further, a cured product using an epoxy resin obtained by epoxidizing this novolak type resin has moisture resistance,
Although excellent in heat resistance, further improvement in moisture resistance and heat resistance is desired.

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive studies to solve the above problems, the present invention has been completed. That is, the present invention relates to formula (A)

[0007]

(Wherein R represents an alkyl group having 1 to 4 carbon atoms) The dimethylol compound (A) is reacted with naphthol at a temperature of 40 to 85 ° C. in the presence of an acid catalyst. Remove excess naphthol in the solution at 200 ° C under reduced pressure
The present invention relates to a method for producing a novolak resin, which is removed by heating and distillation at the following temperature.

[0009]

[0010]

[0011]

[0012]

Hereinafter, the present invention will be described in detail. In the dimethylol compound (A), examples of R include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group. Is preferred.

Specific examples of the dimethylol compound (A) include, for example, 2,6-dimethylol-4-methylphenol, 2,6-dimethylol-4-t-butylphenol, 4,6-dimethylol-2-methylphenol,
4,6-dimethylol-2-t-butylphenol and the like. Naphthol includes α-naphthol and β-naphthol.

The novolak-type resin (hereinafter referred to as the novolak-type resin of the present invention) obtained by the production method (1) is obtained by reacting a dimethylol compound (A) with naphthol in the presence of an acid catalyst (dehydration condensation). Equation (C)

[0016]

(Wherein R has the same meaning as described above, and n takes a value of 0-2), but contains at least 30% by weight of a trinuclear compound (B). The content is preferably at least 35% by weight, particularly preferably at least 40% by weight.

In the novolak resin of the present invention, by-products such as decomposed products and recondensates generated in the course of distillation and the like are contained, and the following general formula (B) in the novolak resin is contained. (Wherein R represents the same meaning as described above), the content of the compound having a lower molecular weight than the trinuclear compound (B) (such as the above by-product) is 10% by weight or less, preferably 7% by weight or less, Particularly preferably, it is at most 5% by weight.

The total content of polynuclear compounds having seven or more nuclei is preferably 25% by weight or less, more preferably 20% by weight or less. The X-nuclear compound is defined as the sum of the numbers of benzene nuclei and naphthalene nuclei in one molecule is X
Is a compound.

In the process for producing a novolak resin according to the present invention, it is preferable to use 2 to 10 moles of naphthol with respect to 1 mole of the dimethylol compound (A), and it is particularly preferable to use 3 to 6 moles.

The acid catalyst includes hydrochloric acid, sulfuric acid, phosphoric acid, p
-Various compounds such as toluenesulfonic acid and oxalic acid can be used, but p-toluenesulfonic acid is preferred in view of increasing the smoothness of the reaction and increasing the yield of the trinuclear compound (B). The amount of the acid catalyst used is preferably 0.01 to 10% by weight based on the dimethylol compound (A), but it is sufficient to use 0.1 to 1% by weight.

The reaction temperature is from 40 to 85 ° C.,
80 ° C. is particularly preferred. The reaction can be carried out without solvent or in a solvent such as methanol, ethanol, propanol, butanol, benzene, toluene and methyl isobutyl ketone. The reaction time is preferably 2 to 15
Time, particularly preferably 4 to 10 hours.

It is effective to carry out the reaction sufficiently to prevent the polymerization at the time of removing excess unreacted naphthol to be performed subsequently. After carrying out the reaction in this way, the acid catalyst is removed by washing with water to make it neutral.

Next, the removal of excess unreacted naphthol, which is an important point of the present invention, is carried out at 200 ° C. or less under reduced pressure. At this time, if the reaction is performed at a temperature exceeding 200 ° C., the trinuclear compound (B) causes a high differentiation reaction, and the purpose of lowering the viscosity of the novolak resin is lost.

In the case of steam distillation, which is a method for generally removing phenols and naphthols, the novolak resin deteriorates due to side reactions such as decomposition and recondensation due to the oxidation state. Therefore, in the method of the present invention,
It is extremely important to heat distill at 200 ° C. or less under reduced pressure.

According to the method of the present invention, side reactions are suppressed and the resulting novolak-type resin does not undergo the above-mentioned alteration, so that it contains at least 30% by weight of the trinuclear compound (B). Become.

The novolak resin of the present invention is easy to handle and has excellent workability because of its low softening temperature and low viscosity, and the epoxy resin obtained by epoxidizing the novolak resin of the present invention also has low viscosity and low workability. The cured product using the epoxy resin is excellent in moisture resistance and heat resistance.

The epoxidation of the novolak type resin of the present invention can be carried out by a conventional method. For example, it can be obtained by reacting the novolak type resin with epichlorohydrin in the presence of a basic compound. The obtained epoxy resin can be cured by a conventional method using a known curing agent such as the novolak resin of the present invention or phenol novolak. The novolak resin of the present invention can also be used as a curing agent for ordinary epoxy resins, and gives a cured product having excellent moisture resistance and heat resistance.

[0029]

The present invention will be described more specifically below with reference to examples and application examples.

Example 1 108 g (1 mol) of paracresol, 60 g (2 mol) of paraformaldehyde and 100 ml of water were charged into a 1-liter flask equipped with a thermometer, a cooling tube, a dropping funnel and a stirrer, and nitrogen was blown into the flask. Stirred.

80 g of a 15% aqueous sodium hydroxide solution at room temperature
(0.3 mol as caustic soda) was slowly added dropwise while paying attention to heat generation so that the liquid temperature did not exceed 50 ° C. Thereafter, the mixture was heated to 50 ° C. in a water bath and reacted for 10 hours. After completion of the reaction, 200 ml of water was added, the mixture was cooled to room temperature, and neutralized gradually with a 10% aqueous hydrochloric acid solution while paying attention to heat generation.
An aqueous solution of hydrochloric acid was added until H was 4.

Thereafter, the precipitated crystals were separated by filtration, and the crystals were further washed with water. The obtained crystals were removed under reduced pressure (10 mm
Hg) dried at 50 ° C. to give white 2,6-dimethylol-4
-Methylphenol was obtained. The yield was 143 g.
(Yield from paracresol is 85%)

168 g of 2,6-dimethylol-4-methylphenol was charged into a glass container equipped with a thermometer and a stirrer, 576 g of α-naphthol and 1000 ml of methyl isobutyl ketone were added, and the mixture was stirred at room temperature under a nitrogen atmosphere. Then, 1 g of p-toluenesulfonic acid (2, 6
0.6 with respect to dimethylol-4-methylphenol
(% By weight) was carefully added so that the liquid temperature did not exceed 50 ° C. while paying attention to heat generation.

After the addition, the mixture was heated to 50 ° C. on an oil bath and reacted for 2 hours, and further heated to 70 ° C. and reacted for 7 hours, and then transferred to a separating funnel and washed with water. After washing with water until the washing water shows neutrality, remove the unreacted naphthol from the organic layer using an evaporator under reduced pressure (10 mmHg or less).
The bath temperature was reduced to 195 ° C., and the mixture was distilled under reduced pressure. Distillation time is 2
It took time.

By this operation, the novolak resin (A-
1) 372 g was obtained. The softening temperature of the product (A-1) is 1
At 12 ° C., the hydroxyl equivalent (g / mol) was 137. or,
The amount of unreacted naphthol in the product (A-1) was 1% by weight or less as a result of analysis by gas chromatography.

The product (A-1) was analyzed by GPC analysis.
The content of the trinuclear compound (B) was 52% by weight, and the content of the compound having a lower molecular weight than the trinuclear compound (B) was 3.5.
% By weight, and the total content of polynuclear compounds having seven or more nuclei was 15% by weight. The viscosity of the product (A-1) is 25
Poise.

Example 2 In Example 1, the amount of α-naphthol used was changed to 504 g.
Otherwise in the same manner as in Example 1, 375 g of novolak resin (A-2) was obtained. The softening temperature of the product (A-2) was 118 ° C and the hydroxyl equivalent (g / mol) was 138. The amount of unreacted naphthol in the product (A-2) was 1% by weight or less as a result of analysis by gas chromatography.

The product (A-2) was analyzed by GPC analysis.
The content of the trinuclear compound (B) was 45% by weight, and the content of the compound having a lower molecular weight than the trinuclear compound (B) was 3.2%.
%, And the total content of polynuclear compounds of seven or more nuclei was 17% by weight. The viscosity of the product (A-2) is 27
Poise.

Comparative Example 1 In Example 1, after the water was washed with a separating funnel until the washing water became neutral, the amount of unreacted naphthol (1% by weight or less) was the same as in Example 1 by steam at 150 ° C. Steam distillation was carried out until. Steam distillation took 5 hours. (The amount of unreacted naphthol after 2 hours, the same operation time as in Example 1, was 3.5% by weight.)

Thus, 365 g of the product (A-3) was obtained. The softening temperature of the obtained product (A-3) is 135 ° C,
The hydroxyl equivalent was 143. The unreacted naphthol in the product (A-3) was 1% by weight or less as a result of analysis by gas chromatography.

According to GPC analysis, the content of the trinuclear compound (B) in the product (A-3) was 25% by weight, and the content of the compound having a lower molecular weight than the trinuclear compound (B) was 15%. weight%
And the total content of polynuclear compounds of seven or more nuclei is 30.
% By weight. The viscosity of the product (A-3) was 39 poise.

Application Example 1 137 g of the product (A-1) of Example 1 was charged into a reactor equipped with a thermometer, a stirrer, and a vacuum recovery device, and 374 g (3.5 mol) of epichlorohydrin and 68 g of dimethyl sulfoxide were further added. Was added and dissolved. During this time, nitrogen has been introduced into the system.

After dissolution, while maintaining the reaction temperature at 40 ° C.
40 g (1 mol) of solid caustic soda was slowly added.
The addition time required one hour. After the addition of caustic soda, the reaction was further performed at 40 ° C. for 1 hour, then the reaction temperature was increased to 70 ° C., and the reaction was further performed for 1 hour. As a result, the total reaction time was 3 hours.

Then, the bath temperature of the reactor was raised to 130 ° C., and the pressure was gradually reduced while paying attention to bumping, so that unreacted epichlorohydrin, dimethyl sulfoxide and produced water were expelled at once. The final degree of vacuum was 5 mmHg, during which it took 2 hours.

Thereafter, 500 ml of methyl isobutyl ketone
To dissolve the resin component, and add 20% aqueous sodium hydroxide solution 20
g was added and reacted at a reaction temperature of 70 ° C. for 2 hours. After the completion of the reaction, washing with water was repeated with a separating funnel to return the aqueous phase to neutral. Then, the methyl isobutyl ketone phase was heated under reduced pressure to remove methyl isobutyl ketone.

As a result, 175 g of a pale yellow solid (B-1) as an epoxy resin was obtained. The softening temperature of the product (B-1) is 75 ° C., the epoxy equivalent (g / mol) is 212,
The viscosity was 10 poise, the amount of free chlorine was 1 ppm or less, the amount of hydrolyzable chlorine was 230 ppm, the total amount of chlorine was 510 ppm, and the concentration of chloride ions in the water extracted by PCT was 3 ppm.

Application Example 2 The same operation as in Application Example 1 was carried out except that 139 g of the product (A-2) obtained in Example 2 was used instead of the product (A-1), and an epoxy resin was used. (B-2) 17 which is
2 g were obtained.

Application Example 3 Instead of the product (A-1), the product (A
-3) Using 143 g, dimethyl sulfoxide 68 g
Was performed in the same manner as in Application Example 1 except that 68 g of methanol was used instead of
3) 150 g was obtained.

The properties of the products (B-1) to (B-3) are shown in Table 1.

[0050]

In Examples, Comparative Examples and Application Examples, the free chlorine amount, hydrolyzable chlorine amount, viscosity, softening temperature, total chlorine amount, chlorine amount by PCT (pressure cooker test), and GPC analysis are as follows. Was measured as follows.

(Amount of Free Chlorine) About 10 g of a sample (epoxy resin) was precisely weighed in a 200 ml beaker, dissolved in 100 ml of acetone, further added with 2 ml of distilled water and 1 ml of glacial acetic acid, and added with an aqueous solution of silver nitrate. Potentiometric titration was performed to determine the amount.

(Amount of Hydrolyzable Chlorine) About 0.5 g of a sample (epoxy resin) is precisely weighed in a 100 ml stoppered flask and dissolved in 30 ml of dioxane. After dissolution, 5 ml of a 1N-KOH ethanol solution is added, and the mixture is boiled under reflux for 30 minutes. Thereafter, this solution was completely transferred to a 200 ml beaker, 100 ml of an 80% strength aqueous acetone solution was added, and 2 ml of concentrated nitric acid was further added.

(Viscosity) The viscosity at 150 ° C. was measured with an ICI viscometer (cone plate type). (Softening temperature) It was measured by JIS K2425 ring and ball method.

(Total Chlorine Content) About 1 g of a sample (epoxy resin) was precisely weighed into a 100 ml stoppered flask, and n-butyl carbitol 2 was added.
Add 5 ml and heat to dissolve. After dissolution, 1N-
Add 25 ml of KOH propylene glycol solution and heat to reflux for 10 minutes. Thereafter, this solution was completely transferred to a 200 ml beaker, 50 ml of glacial acetic acid was added, and the solution was quantified by potentiometric titration with an aqueous silver nitrate solution.

(Amount of chlorine by PCT) 50 g of ion-exchanged water was added to 5 g of epoxy resin,
The chlorine ion concentration in the extraction water when kept at 20 ° C. for 20 hours was quantified by ion chromatography.

(GPC analysis) GPC apparatus; Shimadzu Corporation (Column: TSK-G-3000XL (one) + TSK-G-2000XL (two)) Solvent: Tetrahydrofuran 1 ml / min Detection: UV (254 nm)

Application Examples 4 to 6 Phenol novolak (manufactured by Nippon Kayaku Co., Ltd., softening temperature 85 ° C., hydroxyl equivalent (g / mol) 10
5) and products (B-1) to (B) obtained in application examples 1 to 3.
-3) and 2-methylimidazole were blended to obtain a composition.

The composition was roll-kneaded at 70-80 ° C. for 15 minutes, cooled, pulverized, tableted, molded by a transfer molding machine, pre-cured at 160 ° C. for 2 hours, and 180 ° C. for 8 hours Post-curing was performed to obtain a cured product (test piece). The glass transition temperature (Tg), heat distortion temperature (HDT) and water absorption of the cured product were measured under the following conditions.

Glass transition temperature Thermomechanical instrument (TMA): Vacuum Riko Co., Ltd. TM-7000 Heating rate: 2 ° C./min Heat deformation temperature Conditions specified in JIS K7207

Water absorption test piece Diameter: 50 mm (cured product) Thickness: 3 mm Disk condition Weight increase after boiling in water at 100 ° C. for 50 hours (% by weight) The evaluation results of the cured product are shown in Table-2. Indicated.

[0062]

[0063]

The novolak type resin obtained by the present invention has a low viscosity and excellent workability, and the epoxy resin obtained therefrom has a low viscosity and excellent workability. Further, the cured product of this epoxy resin has moisture resistance and heat resistance. Is excellent.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-110287 (JP, A) JP-A-56-98229 (JP, A) JP-A-4-211422 (JP, A) JP-A-4-112 155939 (JP, A) JP-A-3-717 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 8/12 C08G 59/06

Claims (1)

(57) [Claims] 1. The formula (A) (Wherein R represents an alkyl group having 1 to 4 carbon atoms), the dimethylol compound (A) is reacted with naphthol at a temperature of 40 to 85 ° C in the presence of an acid catalyst, and the excess in the reaction mixture. And removing the naphthol by heating distillation at a temperature of 200 ° C. or less under reduced pressure.