JPH04318017A - Novolak type epoxy resin - Google Patents

Abstract

PURPOSE:To provide the subject resin containing multi-nuclear compounds, having low viscosity and excellent workability and giving heat-resistant cured products by reacting an o-cresol dimethylol compound with a phenol compound in the presence of an acidic catalyst and subsequently reacting the reaction product with an epihalohydrin. CONSTITUTION:A polyhydric phenol compound containing a phenolic novolak compound obtained by reacting an o-cresol dimethylol compound of formula I with a phenol compound (e.g. o-cresol) of formula II (R<1>, R<2> are H, 1-4C alkyl) in the presence of an acrdic catalyst is reacted with a compound of formula III (X is halogen; Z is H methyl) (e.g. epichlorohydrin) to produce the objective novolak epoxy resin containing >=20wt.% of a tri-nuclear phenolic novolak epoxy compound of formula IV and >=20wt.% of a dinuclear phenolic novolak epoxy compound of formula V and having an average glycidyl group number of 2.1-3.9 per molecule.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novolac type epoxy resin which provides a cured product with low viscosity and excellent heat resistance.

0002

BACKGROUND OF THE INVENTION Epoxy resins are widely used as thermosetting resins in various fields such as coating, lamination, painting, adhesion, sealing, and molding.

[0003] In recent years, as requirements for polymeric materials have become stricter and usage conditions have become more severe, epoxy resins made from commonly used bisphenol A and epichlorohydrin are required to have higher heat resistance, moisture resistance, etc. In many cases, the characteristics cannot be fully satisfied.

Conventionally, novolac type epoxy resins such as phenol novolac epoxy resins have been widely used to improve heat resistance, and o-cresol novolac type epoxy resins have been particularly frequently used from the viewpoint of moisture resistance. However, these novolak-type epoxy resins are simply epoxidized phenolic novolaks obtained by condensing phenols and aldehydes under acidic conditions, so they can vary from polynuclear bodies with 10 or more aromatic nuclei to low molecular weight bodies. It contains many types of phenolic novolac type epoxy compounds, has a wide molecular weight distribution, high melt viscosity, and has the drawbacks of poor workability and handling.

On the other hand, there are novolac type epoxy resins in which the molar ratio of phenols and aldehydes is changed and condensed to lower the melt viscosity and improve handling properties. It contained a large amount of epoxy compounds and had the disadvantage of insufficient heat resistance.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novolak-type epoxy resin that has a low viscosity, has excellent workability and handling properties, and provides a cured product with excellent heat resistance.

[0007]

[Means for Solving the Problems] The novolac type epoxy resin of the present invention is produced by combining an o-cresol dimethylol compound represented by the following structural formula (1) and a phenol represented by the following general formula (2) in the presence of an acidic catalyst. An epoxy resin obtained by reacting a polyhydric phenol compound containing a phenolic novolak compound obtained by the reaction below with a compound represented by the following general formula (■), Contains 20% by weight or more of a trinuclear phenol novolac type epoxy compound represented by the following general formula (2) and 20% by weight or less of a dinuclear phenol novolac type epoxy compound represented by the following general formula (2), and has an average glycidyl content per molecule. It is a novolac type epoxy resin having a base number of 2.1 to 3.9.

[0008]

[C6]

[0009]

embedded image (In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, and R1 and R2 may be the same or different.)

0010

[Chemical formula 8] (In the formula, X is a halogen atom, and Z is a hydrogen atom or a methyl group.)

[0011]

[Image Omitted] (In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, and R1 and R2 may be the same or different. Z is a hydrogen atom or a methyl group. be.)

0012

(In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, and R1 and R2 may be the same or different. Z is a hydrogen atom or a methyl group. be.)

The novolac type epoxy resin of the present invention has a content of a trinuclear phenol novolak type epoxy compound represented by the above general formula (2) of 20% by weight or more, and a content of a dinuclear phenol type novolak type epoxy compound. The amount is 20% by weight or less. This is because if the content of the trinuclear epoxy compound is too low and the content of the dinuclear epoxy compound is too high, that is, if the molecular weight distribution is widened in the low molecular weight range, the cured product will not have sufficient heat resistance. This is because it no longer shows.

Further, the novolac type epoxy resin of the present invention has an average number of glycidyl groups per molecule of 2.1 to 3.9.
within the range of . This is because if the average number of glycidyl groups is less than 2.1, the heat resistance of the cured product will be insufficient, and if it exceeds 3.9, the molecular weight distribution of the epoxy resin will become wide and the melt viscosity will increase. This is because the workability of the resin deteriorates.

In order to produce the novolac type epoxy resin of the present invention, first, an o-cresol dimethylol compound represented by the above structural formula (1) and a phenol represented by the above general formula (2), such as phenol, o-cresol, etc. , m-cresol, p-cresol, p-(t-butyl)phenol, etc. are reacted in the presence of an acidic catalyst. By this reaction, the phenol novolak represented by the following general formula (1) is contained at least about 20% by weight or more, the dinuclear phenol novolak represented by the following general formula (1) is contained at least about 20% by weight, and 1 A phenolic novolac having an average number of hydroxyl groups per molecule of about 2.1 to 3.9 is obtained.

[0016]

embedded image (In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, and R1 and R2 may be the same or different.)

[0017]

embedded image (In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, and R1 and R2 may be the same or different.)

Next, the phenolic novolak compound obtained as described above is subjected to an addition reaction and a ring-closing reaction with a compound represented by the above general formula (2) to obtain the novolac type epoxy resin of the present invention. In this reaction, the phenolic novolac compound obtained as described above may be reacted with a relatively small amount of other polyhydric phenol compounds. The addition reaction and ring closure reaction can be carried out according to conventional methods. Below, a typical example of a reaction mode when epichlorohydrin is used as the compound represented by the above general formula (1) will be described in detail.

First, the phenolic novolac compound is dissolved in epichlorohydrin in an amount corresponding to 2 to 20 moles per mole of phenolic hydroxyl group to form a homogeneous solution. Next, while stirring the solution, an alkali metal hydroxide in an amount of 1 to 2 moles per mole of phenolic hydroxyl group is added in the form of a solid or aqueous solution and reacted. This reaction can be carried out under normal pressure or reduced pressure, and the reaction temperature is usually about 60 to 105°C under normal pressure, and about 50 to 80°C under reduced pressure. The reaction is
The reaction is carried out by azeotropically distilling the reaction liquid while maintaining a predetermined temperature as necessary, cooling the volatile vapor, separating the resulting condensate from oil/water, and returning the oil with water removed to the reaction system. Perform this while dehydrating the system. The alkali metal hydroxide is added intermittently or continuously in small amounts over 1 to 8 hours in order to suppress rapid reaction. NaOH or KOH is usually used as the alkali metal hydroxide. The total reaction time is usually about 1 to 10 hours.

After completion of the reaction, insoluble by-product salts are removed by filtration or washing with water, and unreacted epichlorohydrin is removed by distillation under reduced pressure to obtain the desired novolac type epoxy resin.

In this reaction, quaternary ammonium salts such as tetramethylammonium chloride and tetraethylammonium bromide; benzylmethylamine,
Tertiary amines such as 2,4,6-(trisdimethylaminomethyl)phenol; Imidazoles such as 2-ethyl-4-methylimidazole and 2-phenylimidazole; Phosphonium salts such as ethyltriphenylphosphonium iodide ; Catalysts such as phosphines such as triphenylphosphine may be used.

Furthermore, in this reaction, alcohols such as ethanol and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane and ethylene glycol dimethyl ether; aprotic polar solvents such as dimethyl sulfoxide and dimethyl formamide; Inert organic solvents may also be used.

In order to obtain a curable epoxy resin composition using the novolac type epoxy resin of the present invention, it is desirable to use the novolac type epoxy resin alone as the epoxy resin, but if two or more epoxy resins are present in one molecule, Other epoxy resins having groups can also be used in combination.

Examples of epoxy resins that can be used in combination include glycidyl ether type epoxy resins such as bisphenol A type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, Examples include various polyfunctional epoxy resins such as linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and halogenated epoxy resins.

Examples of the curing agent include aromatic polyamines, dicyandiamide, acid anhydrides, and various phenol novolac resins.

Examples of the curing accelerator include amines such as benzyldimethylamine and various imidazole compounds, and tertiary phosphines such as triphenylphosphine.

[0027]

[Examples] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Moreover, "parts" described in these examples mean parts by weight.

Example 1 In a glass container equipped with a stirrer, 84 g of 2,4-bishydroxymethyl-o-cresol and 1 g of o-cresol were added.
After adding 62 g (1.5 mol) and further adding 1 g of oxalic acid and reacting at 75° C. for 4 hours, dehydration was performed under reduced pressure and steam distillation to obtain 115 g of novolac resin.

Next, 115 g of this novolak resin and 595 g of epichlorohydrin were placed in a glass container equipped with a stirrer, and the temperature was raised from 30° C. to 50° C. at a rate of 1° C./3 minutes, during which time a 48.5% NaOH aqueous solution was added. 1g/2
After the temperature reached 50°C, the reaction was carried out for 60 minutes while maintaining the same temperature. After the reaction was completed, unreacted epichlorohydrin was removed under reduced pressure and washed with water to obtain 169 g of a novolac type epoxy resin.

The gas permeation chromatography (GPC) pattern of this epoxy resin is shown in FIG.
The epoxy equivalent, the melt viscosity at 150°C, the average number of glycidyl groups per molecule determined by GPC, the content of the trinuclear phenol novolac type epoxy compound represented by the general formula (■), and the general formula (■) The content of the dinuclear phenol novolak type epoxy compound represented by is as shown in Table 1. Hereinafter, this epoxy resin will be referred to as "epoxy resin A1."

Comparative Example 1 126 g of o-cresol (
1 mol), 37% formalin 61g (0.75 mol),
and 1.3 g of oxalic acid, reacted at reflux temperature for 3 hours, then dehydrated under reduced pressure, and further removed o-cresol by steam distillation, resulting in an unreacted o-cresol content of 0.5% by weight. 121 g of the following novolac resin was obtained.

Next, 121 g of this novolac resin and 643 g of epichlorohydrin were placed in a glass container equipped with a stirrer, and reacted in the same manner as in Example 1. The same treatment was carried out to obtain 176 g of a novolac type epoxy resin.

[0033] This novolak type epoxy resin is
The pattern diagram is as shown in Figure 2, and its epoxy equivalent, melt viscosity at 150°C, average number of glycidyl groups per molecule determined by GPC, and content of trinuclear phenol novolac type epoxy compound represented by the general formula (■) The amount and the content of the dinuclear phenol novolac type epoxy compound represented by the general formula (2) were as shown in Table 1. Hereinafter, this epoxy resin will be referred to as "epoxy resin B".
1”.

Comparative Example 2 130 g of novolak resin was obtained in the same manner as in Comparative Example 1 except that the amount of 37% formalin used was changed to 75 g (0.93 mol). Next, 130 g of this novolac resin and 726 g of epichlorohydrin were placed in a glass container equipped with a stirrer, and a reaction was carried out in the same manner as in Example 1 to obtain 185 g of a novolac type epoxy resin.

[0035] This novolak type epoxy resin is
The pattern diagram is as shown in Figure 3, and its epoxy equivalent, melt viscosity at 150°C, average number of glycidyl groups per molecule determined by GPC, and content of trinuclear phenol novolac type epoxy compound represented by general formula (■) The amount and the content of the dinuclear phenol novolac type epoxy compound represented by the general formula (2) were as shown in Table 1. Hereinafter, this epoxy resin will be referred to as "epoxy resin B".
2”.

[0036]

[Table 1]

Experimental Example Each of the epoxy resins A1, B1 and B2 obtained in Example 1, Comparative Example 1 and Comparative Example 2 above was used, and methyltetrahydrophthalic anhydride was used as a curing agent as shown in Table 2. 2-methyl-4-ethylimidazole was added as a curing accelerator, and the resulting curable resin composition was cured by heating at 180° C. for 6 hours. The results of measuring the glass transition temperature, bending strength and bending modulus of the obtained cured product are as shown in Table 2.

[0038]

[Table 2]

[0039]

[Effects of the Invention] The epoxy resin of the present invention has a low melt viscosity, is excellent in workability, and can provide a cured product with excellent heat resistance.

[Brief explanation of the drawing]

FIG. 1 is a gas permeation chromatography (GPC) pattern diagram of epoxy resin A1 produced in Example 1. The columns used for the measurement were one TSK gel G4000HXL manufactured by Toyo Soda Co., Ltd. and one TSK gel G30 column manufactured by Toyo Soda Co., Ltd.
Two 00HXL and one G2000HXL, total 4
The books were arranged in series and used.

FIG. 2 is a similar GPC pattern diagram of epoxy resin B1 produced in Comparative Example 1.

FIG. 3 is a similar GPC pattern diagram of epoxy resin B2 produced in Comparative Example 2.

Claims (1)

[Claims] Claim 1: A phenolic novolak compound obtained by reacting an o-cresol dimethylol compound represented by the following structural formula (1) with a phenol represented by the following general formula (2) in the presence of an acidic catalyst. An epoxy resin obtained by reacting a compound represented by the following general formula (1) with a polyhydric phenol-based compound contained therein, the trinuclear phenol novolac type epoxy compound represented by the following general formula (2) is Weight% or more, and the following general formula ■
A novolak-type epoxy resin containing 20% by weight or less of a dinuclear phenol novolak-type epoxy compound represented by the following, and having an average number of glycidyl groups per molecule of 2.1 to 3.9. [Formula 1] [Formula 2] (In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, and R1 and R2 may be the same or different.) [Formula 3 ] (In the formula, X is a halogen atom, Z is a hydrogen atom or a methyl group.) [In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, (Z may be the same as or different from .Z is a hydrogen atom or a methyl group.) [Formula 5] (In the formula, R1 and R2 are each a hydrogen atom or an alkyl group having 4 or less carbon atoms, R1 and R2 may be the same or different. Z is a hydrogen atom or a methyl group.)