JPH0625427A - Method for postcuring thermosetting resin - Google Patents

Abstract

PURPOSE:To produce a cured molding greatly improved in water resistance, chemical resistance, and electrical insulating property. CONSTITUTION:A thermosetting resin obtained by thermally reacting a condensed aromatic compound, such as naphthalene or a component of a tar or pitch, along with di(hydroxymethyl)benzene or a di(halomethyl)benzene as a crosslinking agent in the presence of an acid catalyst is molded and cured. The molding is postcured by heating it in the absence of oxygen (e.g. by embedding in a carbon powder).

Description

Detailed Description of the Invention

[0001]

This invention relates to water resistance, chemical resistance,
The present invention relates to a post-curing method for obtaining a molded and cured product of a thermosetting aromatic hydrocarbon resin having excellent electric insulation and heat resistance.

[0002]

2. Description of the Related Art Thermosetting resins include phenol resins, urea resins, melamine resins, epoxy resins, unsaturated polyester resins, polyimide resins, polyurethane resins,
Silicone resin, furan resin, xylene resin and the like are known. Generally, such a thermosetting resin exhibits superior heat resistance to a thermoplastic resin, but even if the polyimide resin is excluded, the long-term usable temperature is up to 150 to 200 ° C.
It is a degree. On the other hand, the polyimide resin has a very long-term usable temperature of 200 to 300 ° C., which is extremely excellent in heat resistance, but on the other hand, it has a drawback that it has poor moldability.

Recently, as a new thermosetting resin, a condensed polycyclic aromatic compound such as naphthalene or a mixture containing it as a main component, and at least two hydroxymethyl groups and / or halomethyl groups bonded to an aromatic ring are used. When a cross-linking agent comprising an aromatic compound is heated and reacted in the presence of an acid catalyst, a condensed polycyclic polynuclear aromatic hydrocarbon resin showing extremely excellent heat resistance comparable to that of polyimide can be easily obtained. It was reported that they were obtained (Japanese Patent Laid-Open Nos. 62-521 and 62-522). This thermosetting resin is COPN
It is named A resin and is being industrialized as a heat resistant resin. In the present specification, this resin will be referred to as COP hereinafter.
Abbreviated as NA resin.

Generally, a thermosetting resin is shaped by using a mold or the like, and is cured during molding to obtain a molded and cured product, and then the resulting molded product is improved in heat resistance and dimensional stability. Post-curing treatment is often performed for the purpose of removing residual stress during molding. Post-curing treatment is usually under normal pressure,
It is carried out by heat treatment in air, and the heating temperature is generally within the range of 150 to 350 ° C, although it varies depending on the resin species.
Also in the above-mentioned COPNA resin, it is known that such a post-curing treatment is a very effective means for improving the heat resistance and dimensional stability of the molded body.

[0005]

Since the heat resistance of COPNA resin is improved by post-curing treatment, post-curing treatment is often required when it is used as a heat-resistant resin. As a result of investigating the behavior of the post-curing treatment of the COPNA resin, the present inventors found that the post-curing treatment of the COPNA resin is effective in improving the heat resistance and the dimensional stability of the molded product, but at the same time, the water resistance and the It was discovered that it causes a phenomenon that the chemical property and the electrical insulating property are deteriorated. This invention is capable of producing a molded and cured product of a COPNA resin which is excellent in heat resistance, water resistance, chemical resistance, and electrical insulation by post-curing treatment and can be used for a long time in high-temperature air. An object is to provide a curing treatment method.

[0006]

Means for Solving the Problems As a result of repeated studies aimed at achieving the above object, the present inventors have found that it is effective to post-cure the molded product of the COPNA resin in a state where oxygen is blocked. And completed this invention.

Here, the gist of the present invention is a COPNA resin (that is, a condensed polycyclic aromatic compound or a mixture containing it as a main component, and at least two hydroxymethyl groups and / or halomethyl groups bonded to an aromatic ring. A thermosetting resin obtained by heating and reacting a cross-linking agent composed of an aromatic compound having an acid catalyst in the presence of an acid catalyst) is molded and cured, and then the molded body is heat-treated in a state in which oxygen is blocked and post-cured. It is a post-curing method for obtaining a thermosetting resin cured product having excellent water resistance, chemical resistance, and electrical insulation properties.

[0008]

The structure of the present invention will be described in detail below together with its operation. The present inventors have found that when a molded product of a COPNA resin is subjected to a post-curing treatment by a usual method, that is, a method of heating to 150 to 350 ° C. in air under normal pressure, the molded cured product has water resistance and chemical resistance. It has been found that the electrical conductivity and the electrical insulation are deteriorated. In order to investigate the cause of this, IR spectrum analysis before and after the post-curing treatment of COPNA resin, and volume resistivity and surface resistivity among electrical properties were investigated.

As a result, when the COPNA resin is subjected to the usual post-curing treatment, the peak attributed to the oxygen-containing functional group in the IR spectrum is increased and only the surface resistivity is greatly reduced as compared with the volume resistivity. I found a thing. From these facts, it was clarified that the reason why the water resistance, chemical resistance and electric insulation of the COPNA resin are deteriorated by the post-curing treatment is the remarkable oxidation of the surface of the molded article by the post-curing treatment in air. Furthermore, the dimethyl ether bonds and hydroxymethyl groups remaining on the surface of the molded body are preferentially oxidized, and sulfonic acid used as an acid catalyst and its decomposition products.
It was also found that (for example, SO ₃ ) acts as an oxidation initiator.

According to the present invention, since the molding of the COPNA resin is post-cured in a state where oxygen is blocked, introduction of oxygen-containing functional groups (surface oxidation) on the surface of the molding is prevented,
The deterioration of water resistance, chemical resistance, and electric insulation of the molded and cured product is prevented.

Even more surprisingly, the molded and cured product once subjected to the post-curing treatment by the method of the present invention does not undergo oxidation on the surface of the molded product even if it is subsequently left at high temperature in air,
As a result, it has an unexpected effect of being able to maintain extremely excellent water resistance, chemical resistance, and electrical insulation.

CO post-cured by the method of the present invention
The reason why the molded and cured product of the PNA resin can retain water resistance, chemical resistance, and electrical insulation without being oxidized even if it is left at high temperature in an oxidizing atmosphere thereafter is that Dimethyl ether bond and hydroxymethyl group are converted to methylene bond between aromatic rings, which is stable against oxidation, by post-curing treatment with oxygen blocked according to the present invention, and further decomposition derived from sulfonic acid used as an acid catalyst. SO _{3 which} can be an initiator of oxidation
It is conceivable that the material may escape to the outside of the system by the post-curing treatment by the method of the present invention.

The main raw materials used in the production of the thermosetting resin of the present invention are a condensed polycyclic aromatic compound or a mixture containing it as a main component, and a crosslinking agent for crosslinking it.

The condensed polycyclic aromatic compound includes any hydrocarbon compound having two or more aromatic rings and at least two of which are condensed. As a concrete example,
Examples include naphthalene, acenaphthene, acenaphthylene, phenanthrene, anthracene, pyrene, chrysene, naphthacene, coronene, perylene, fluoranthene, picene, various benzopyrenes, various benzoperylenes, and alkyl derivatives of these compounds, and these alone or It can be used in a mixture of two or more kinds.
In addition, these condensed polycyclic aromatic compounds, methylene group,
A hydrocarbon compound having a structure in which a divalent group such as a phenylene group, a xylylene group and an ether group is linked (eg, dinaphthylmethane) is also included. Furthermore, the fused polycyclic aromatic compound may be substituted with a hydroxyl group. That is, naphthol, hydroxyanthracene and the like are also included in this compound.

The fused polycyclic aromatic compound need not be pure. That is, coal-based or petroleum-based heavy oils, tars, and pitches containing a polycyclic aromatic compound as a main component can also be used as a raw material. Also, a mixture of a condensed polycyclic aromatic compound and a small amount of a monocyclic aromatic compound such as phenol, alkylphenol, or alkylbenzene can be used.

It is an aromatic compound having at least two hydroxylmethyl and / or halomethyl groups attached to the aromatic ring that is used as a crosslinker in the process of this invention. Examples of such cross-linking agents include poly (hydroxymethyl) derivatives and poly (halomethyl) derivatives of aromatic hydrocarbon compounds such as benzene, xylene, naphthalene, anthracene, pyrene or alkyl derivatives thereof. As the crosslinking agent, one kind or two or more kinds can be used. Preferred cross-linking agents are aromatic compounds having two or more hydroxymethyl groups, with di (hydroxymethyl) benzene and di (hydroxymethyl) xylene being particularly preferred.

The above-mentioned condensed polycyclic aromatic compound and the crosslinking agent are subjected to polycondensation reaction in the presence of an acid catalyst to obtain a thermosetting resin. As the acid catalyst, sulfuric acid, organic sulfonic acid or the like can be used. Among them, organic sulfonic acids such as toluene sulfonic acid, xylene sulfonic acid, phenol sulfonic acid and naphthalene sulfonic acid are preferable. Resins containing sulfonic acid groups such as polystyrene sulfonic acid resins and phenol sulfonic acid resins are also useful as catalysts.

The blending ratio of the cross-linking agent to the condensed polycyclic aromatic compound (in the case of a mixture, the condensed polycyclic aromatic compound in the mixture) as the main raw material is appropriately in the range of 0.7 to 6 in terms of molar ratio. . If the molar ratio is less than 0.7, the thermosetting property of the product will be insufficient, and conversely, if the molar ratio is greater than 6, the crosslinking agent will be in excess, giving a somewhat inhomogeneous product. A more preferable range is 1 to 3.

The addition amount of the acid catalyst is in the range of 0.2 to 20% by weight, preferably 0.5 to 10% by weight, based on the total weight of the condensed polycyclic aromatic compound and the crosslinking agent.

The condensed polycyclic aromatic compound as the main raw material and the cross-linking agent are mixed with an acid catalyst in a predetermined ratio, and the mixture is heated and reacted preferably in a non-oxidizing atmosphere to easily prepare a thermosetting prepolymer. Aromatic hydrocarbon resins can be produced.

The reaction temperature is about 50 to 300 ° C., preferably about
80 to 200 ° C. The reaction pressure is usually normal pressure or slightly increased pressure, but in order to remove the condensed water (or hydrogen chloride) by-produced in the reaction from the reaction system to enhance the reaction efficiency, the reaction may be performed under reduced pressure. it can. The reaction is easy to carry out in a molten state (melt polymerization), but can also be carried out in a suitable solvent or dispersion medium (solution polymerization or suspension polymerization).

In the case of melt polymerization, the viscosity of the reaction product increases as the reaction proceeds, and the thermosetting prepolymer B is used.
A stage resin is obtained. If the reaction proceeds further from this stage, it becomes an insoluble and infusible cured product, so the temperature of the reaction mixture is lowered at an appropriate stage in the B stage state to stop the reaction so as to obtain a thermosetting resin that can be molded. Let The thermosetting resin thus obtained is an uncured intermediate polycondensate (prepolymer) at a stage where the heat meltability and the solvent solubility still remain.

The thermosetting prepolymer has a viscosity of about 100-35.
By heating to 0 ° C., a thermosetting product is easily obtained. Therefore, shaping and curing are performed by shaping and heating by an appropriate method to obtain an insoluble and infusible shaped product. Molding and hardening can be performed, for example, by a compression molding method in which a powder is formed and heated and pressed, a casting molding method in which the material is poured into a molding die in a molten state or a solution state dissolved in a solvent and then heated, and further, a transfer molding method or the like. It can be carried out by utilizing various known thermosetting resin molding methods.

At the time of molding and curing, various fibrous, granular, and flake-like ceramic, carbonaceous, organic or metallic materials are added to the resin as an aggregate (that is, a filler or a reinforcing material). As a result, a desired characteristic function can be imparted. Examples of useful aggregates are glass fibers, carbon fibers, graphite and the like.

The molded body thus obtained has improved heat resistance,
A post-curing treatment is performed to improve dimensional stability and remove residual stress during molding. A feature of the present invention is to carry out a post-curing treatment in a state where oxygen is blocked in order to bring out the excellent water resistance, chemical resistance and electric insulation of this resin. Specifically, a method of embedding the molded body in a solid or liquid having reducing properties such as carbonaceous powder and heat-resistant oil and performing heat treatment for post-curing is simple. Alternatively, it is also possible to perform a heat treatment while flowing a non-oxidizing gas such as nitrogen or argon gas, or enclosing the compact in this gas.

The heat treatment is usually carried out under normal pressure, but it may be carried out under a slight reduced pressure in order to accelerate the curing reaction and removal of the sulfonic acid decomposition product from the outside of the system. Heat treatment conditions differ depending on the combination of temperature and time, but when heat treatment is insufficient due to low heat treatment temperature or short heat treatment time, not only the improvement of heat resistance and dimensional stability becomes insufficient, but also post-curing If the treated product is used at high temperature in the air (oxidizing atmosphere), the water resistance, chemical resistance, and electric insulation will be deteriorated, so that the object of the present invention cannot be achieved. On the other hand, when the heat treatment conditions are excessive, the resin is thermally decomposed, resulting in deterioration of mechanical properties and the like. The preferred post-curing heat treatment conditions are from about 180 to about
It is 1 to 30 hours in the temperature range of 350 ° C.

COPN produced by the method of the present invention
Molded and cured products of resin A have better water resistance, chemical resistance, and electrical insulation than those obtained by the conventional post-curing treatment method, and moreover, compared with cured products not subjected to post-curing treatment. Also,
When used, it is not susceptible to oxidative deterioration when exposed to high temperature air, and the resin properties (water resistance, chemical resistance, electrical insulation) are not easily deteriorated, which is a very advantageous property. For example, the COPNA resin produced by the method of the present invention is treated with an alkali (soaked in 10% NaOH at 23 ° C. for 5 weeks).
The flexural strength retention rate by 90% or more is preferably 90% or more, preferably 95% or more, and the change in weight after this treatment is 0.1% or less, preferably 0.05% or less. Then, in the air,
Even if the sample is heated to 0 ° C for 500 hours and subjected to the same alkali treatment, neither the flexural strength retention rate nor the weight change after the alkali treatment is substantially the same as before the heat treatment, and the product is kept in air for a long time. No deterioration of characteristics due to heating.

[0028]

EXAMPLES The present invention will be specifically described below based on examples. [Example 1] 64.0 parts by weight of naphthalene in a glass reactor
(0.5 mol), p-di (hydroxymethyl) benzene 110.
4 parts by weight (0.8 mol), and p-toluenesulfonic acid 1
Charge 8.72 parts by weight of the hydrate, and stir in a nitrogen stream at 110 ° C for 120 minutes with stirring to give a C having a pour point of 99 ° C.
An OPNA resin prepolymer (B stage resin) was obtained.
The pour point of the resin is determined by measuring the apparent viscosity using a flow tester while raising the temperature of the resin at 6 ° C / min.
The temperature at which 10 ⁵ poise was reached was defined as the pour point.

This COPNA resin prepolymer was crushed to 3 mm or less to obtain a thermosetting resin molding material. This molding material was compression molded at 180 ° C and 300 kg / cm ² for 2 minutes to obtain the diameter
A disc-shaped insoluble and infusible cured molded product having a thickness of 100 mm and a thickness of 2 mm was obtained. This compact was then embedded in coke fine powder having a particle size of 1 mm or less, and post-cured by heating at 250 ° C. for 12 hours in an oven to obtain a post-cured molded cured product. Table 1 shows the results of measuring the volume resistivity and surface resistivity of the post-cured molded cured product according to JIS K-6911.

Comparative Example 1 A cured molded product was obtained in the same manner as in Example 1 except that the cured product was subjected to post-curing treatment without being embedded in coke fine powder. The volume resistivity and surface resistivity of this cured molded product are also shown in Table 1.

[0031]

[Table 1]

From Table 1, as compared with the cured product of Comparative Example 1 post-cured by the conventional method, the cured product of Example 1 post-cured by the method of the present invention has a surface resistivity of about 1000 times. It can be seen that it is large and has excellent electrical insulation.

Example 2 The molding material obtained in the same manner as in Example 1 was compression-molded at 180 ° C. and 300 kg / cm ² for 5 minutes to obtain a rectangular molded body having a size of 20 mm × 40 mm × 10 mm. Obtained. The compact was then embedded in fine coke powder having a particle size of 1 mm or less, heat-treated at 230 ° C for 4 hours in an oven, and then further heat-treated at 260 ° C for 12 hours while slightly reducing the pressure. A molded cured product was obtained.

After the test piece for insulation resistance measurement shown in JIS K-6911 was prepared from the post-cured product, it was placed in boiling distilled water and boiled for 2 hours. Table 2 shows the results of measuring the insulation resistance of the test pieces before and after boiling according to JIS K-6911.
In addition, this post-cured product (test piece before boiling) was placed in air.
Even after heat treatment at 250 ° C for 500 hours, no significant decrease in insulation resistance after boiling was observed.

[Comparative Example 2] Molding and post-curing treatment were carried out in the same manner as in Example 2 except that the post-curing treatment was carried out without embedding the compact in coke fine powder. The insulation resistance before and after boiling of the obtained post-curing test piece is also shown in Table 2, and a significant decrease in insulation resistance was observed by the boiling treatment. The post-cured product (before boiling) should be heated at 250 ° C in air at 50 ° C.
After the heat treatment for 0 hour, the insulation resistance after boiling was further decreased. For reference, after boiling the cured product without post-curing treatment (compression molding only) and in air 250
The insulation resistance after treatment at 500 ° C for 500 hours is also shown in Table 2.

[0036]

[Table 2]

As can be seen from the results shown in Table 2, the cured molded article of Example 2 obtained by the post-curing treatment method of the present invention has a very small change in insulation resistance before and after boiling, and has insulation even after boiling. The resistance remains on the same order and the water resistance is very good. In addition, no noticeable deterioration of insulation is observed even when used at high temperature for a long time. On the other hand, in Comparative Example 2, the insulation resistance was greatly reduced to 1/1000 after boiling and the water resistance was low. In addition, when post-curing was not performed, deterioration of water resistance and insulating property was observed when exposed to high temperature for a long time.

[Example 3] From a molding material obtained in the same manner as in Example 1, transfer molding was carried out at 180 ° C and 500 kg / cm ² for 5 minutes to give a 80 mm × 10 mm × 4 mm thin plate-shaped cured molded article. Obtained. This molded body is placed in an oven with a nitrogen stream for 23
After heat treatment at 0 ° C. for 4 hours, heat treatment was further performed at 280 ° C. for 5 hours under slightly reduced pressure to obtain a post-cured molded cured product.

After this, the cured product was immersed in a 10% aqueous sodium hydroxide solution and left at 23 ° C. for 5 weeks. Table 3 shows the results of measuring the flexural strength retention rate and the weight change due to the alkali treatment.

[Comparative Example 3] Test pieces were prepared under the same conditions and conditions as in Example 3, except that the post-curing treatment was carried out in air. Was measured. The results are also shown in Table 3.

[Example 4] The post-cured product obtained in Example 3 was further heat-treated in air at 250 ° C for 500 hours. This test piece was subjected to the same method and conditions as in Example 3 to measure the bending strength retention rate and weight change when treated with alkali. The results are shown in Table 3.

[0042]

[Table 3]

As can be seen from Table 3, the molded and cured product (Example 3) which was post-cured under oxygen blocking by the method of the present invention substantially maintained the flexural strength even after the alkali treatment, and Weight gain is also minimal. That is, it is resistant to alkalis and has excellent chemical resistance. On the other hand, in Comparative Example 3 in which the atmosphere of the post-curing treatment is changed to air, the bending strength after the alkali treatment is reduced to almost half, and the weight increase is large, it is clear that it does not have chemical resistance. . Even more unexpectedly, the molded and cured product of Example 4, which was obtained by subjecting the molded and cured product post-cured by the method of the present invention to high temperature in air for a long time, retained the same chemical resistance as that of Example 3. Therefore, it can be seen that after the post-curing treatment with the air shut off by the method of the present invention, the deterioration of the characteristics does not occur even when exposed to high temperature air.

[0044]

As described above, by performing the post-curing treatment according to the method of the present invention under the condition of blocking oxygen, water resistance is higher than that of the post-curing treatment cured product in normal air (oxidizing atmosphere). It is possible to produce a cured product having significantly improved properties, chemical resistance, and electrical insulation. Further, the molded and cured product thus obtained does not undergo significant deterioration in properties even if it is subsequently left to stand in high temperature air for a long time, so that it can be sufficiently used in applications exposed to high temperatures. Therefore, the present invention is effective in improving the properties of COPNA resin and expanding its applications, and also exhibits excellent heat resistance comparable to that of polyimide resin and supplies heat resistant resin excellent in various physical properties at low cost. And is extremely useful in industry.

Claims (2)

[Claims] 1. A condensed polycyclic aromatic compound or a mixture containing the same as a main component, and a cross-linking agent comprising an aromatic compound having at least two hydroxymethyl groups and / or halomethyl groups bonded to an aromatic ring, Thermosetting resin obtained by heating reaction in the presence of an acid catalyst, after molding and curing, characterized by heat-treating the molded body in a state of blocking oxygen, post-curing, water resistance, chemical resistance and A post-curing method for obtaining a thermosetting resin cured product having excellent electric insulation. 2. The method according to claim 1, wherein the thermosetting resin is mixed with an aggregate and then molded and cured.