JP2000154234A - Flame-retardant epoxy resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin being excellent in flame retardancy, heat resistance, water resistance, and chemical resistance and evolving a reduced quantity of noxious gases if burnt by using the reaction product of an epoxy resin with a resorcinol-derivative-type organophosphorus compound. SOLUTION: This resin comprises the reaction product of an epoxy resin with organophosphorus compounds of formulae I and/or II and desirably contains the organophosphorus compounds in an amount in the range of 0.1-6.0% in terms of the P atoms. In the formulae, X is a P-containing substituent represented by formula III; n is 1-3; and l and m are each 0-2, provided that l and m can not be simultaneously 0. A organophosphorus compound of formula I can be produced, for example, by condensing resorcinol with an organophosphorus compound of formula IV under heating. An organophosphorus compound of formula II can be produced by condensing a resorcinol/HCHO condensate with an organophosphorus compound of formula IV under heating or by condensing a compound of formula I with resorcinol and HCHO. The resin is useful as e.g. a coating material or an electrical insulation material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a flame-retardant epoxy resin. More specifically, the present invention relates to a flame-retardant epoxy resin containing a novel organic phosphorus compound as a reactive flame retardant.

[0002]

2. Description of the Related Art Epoxy resin, which is one of thermosetting resins, has features such as excellent mechanical strength, heat resistance, chemical resistance, electrical insulation, adhesiveness, or ease of processing.
It is widely used as a structural material, laminate, paint or adhesive in various fields such as coating, electrical or civil engineering.

On the other hand, organic compounds usually have a property of easily burning, and epoxy resins are no exception. Suppressing the combustibility of organic materials and improving the safety of the materials is called flame retardancy, and one technical field is currently being formed. In general, adding a flame retardant to an organic material is a technology that has already been widely put into practical use, but there are still many problems.

Although a large number of flame retardants are known to be added to organic materials depending on the type of organic material, in the case of epoxy resins only, organic halogen compounds, particularly organic bromo compounds, are mainly flame retardants. It can be said that the study for putting an organic phosphorus compound into practical use as a flame retardant has just begun.

Conventionally, many types of epoxy resins can react as an epoxy compound from the viewpoints of flame retarding cost and maintenance of properties of the epoxy resin by adding a flame retardant for the purpose of making the epoxy resin flame retardant. , Reactive halogenated compounds, especially tetrabromobisphenol-A
Alternatively, diglycidyl ether thereof has been used as a flame retardant. However, epoxy resins to which these organic halogen compounds are added may generate harmful halogen compounds when burned, or may generate organic halogen compounds that may significantly contaminate the environment when the epoxy resin is discarded or incinerated. Became problematic. Therefore, it is a recent situation that the tendency to shift the flame retardant of the epoxy resin from the organic halogen compound to the organic phosphorus compound has increased.

[0006]

The organic phosphorus compound is added as a flame retardant to many organic high molecular compounds such as polyphenylene oxide, polyester or polycarbonate. Recently, it has recently been recognized that the epoxy resin has a high flame retardant effect.

There are roughly two types of organophosphorus compounds as flame retardants that can be used in epoxy resins. One of them is a so-called addition type flame retardant which has no reactivity with an epoxy compound and is simply mixed with an epoxy resin, and examples thereof include triphenyl phosphate and tricresyl phosphate. The drawback of these additive-type flame retardants is that if they are added to the epoxy resin in a considerable amount, that is, in such an amount that the flame retardancy is sufficiently exhibited, the heat resistance (glass transition) of the epoxy resin is increased due to the plasticizing effect. Temperature). Therefore, these addition-type organophosphorus compounds are generally rarely used in applications where the physicochemical properties of the epoxy resin are important, despite being inexpensive and most economical. The other is a reactive flame retardant which has a group reactive with the epoxy group of the epoxy compound, that is, a functional group, and in which the organophosphorus compound is incorporated into the chain after the curing reaction of the epoxy polymer. The reactive group with the epoxy group of the reactive organophosphorus compound is usually a PH group, a hydroxy group, an amino group, a carboxy group or an acid anhydride thereof. It can also be classified by the number of functional groups that can react. According to this classification, the addition-type flame retardant could be said to be zero-functional.

The monofunctional organophosphorus compound has one group that reacts with an epoxy group, and includes structural formula 2, structural formula 3, or structural formula 4. However, these monofunctional flame retardants are linked to the epoxy resin chain, so that migration or volatility from the epoxy resin is prevented, as well as reaction with the epoxy group, In the meantime, the crosslinking density of the epoxy resin decreases to form a so-called pendant, the curing rate is retarded, adverse effects such as a decrease in heat resistance or a decrease in mechanical strength are large, and the degree of sufficient flame retardancy is exhibited. It is difficult to use the quantity.

[0009]

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[0010]

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[0011]

Embedded image Examples of organic phosphorus compounds that are bifunctional with respect to epoxy compounds include JP-A-4-11662 and JP-A-6-80765.
Or the organic phosphorus compounds disclosed in JP-A-10-87786. Since these do not have curability with respect to an epoxy compound having two epoxy groups, a thermosetting epoxy resin is usually finished by further adding an epoxy curing agent having three or more functionalities. Japanese Patent Application Laid-Open No. 6-80765 or 10
Although the organophosphorus compound described in JP-A-88786 can provide an excellent flame-retardant epoxy resin, it is generally recognized that it has poor water resistance or alkali resistance due to formation of an ester bond in the resin. .

As an organic phosphorus compound having three or more functionalities with respect to an epoxy resin, a phosphoric acid ester of bisphenol-A or a condensate thereof is known. These are also evaluated to have poor water resistance or alkali resistance because they also have a phosphate group.

Although an overview of the organophosphorus compound has been given above only based on the number of functional groups with respect to the epoxy group, in reality, it is difficult to finish the epoxy resin, the physical strength of the finished epoxy resin, heat resistance, and water resistance. The organophosphorus compound as a flame retardant should be determined in view of the effects on various properties such as the properties, chemical resistance, and the amount of harmful gas generated during combustion.

When the organophosphorus compound found in JP-A-4-11652 is processed as an epoxy resin,
It has been recognized that it has the best properties in terms of excellent flame retardancy, mechanical strength, heat resistance, water resistance, chemical resistance, and low generation of harmful gases during combustion. However, this organophosphorus compound has a slower reaction rate with the epoxy group than other epoxy curing agents, and if it is mixed and cured with the epoxy compound and the epoxy curing agent suddenly, the reaction between the organophosphorus compound and the epoxy group is delayed. Despite being difunctional, they tend to be left unreacted in the epoxy resin and function only zero or monofunctional. In order to solve this problem, it is necessary to prepare a prepolymer which has been heated and reacted with a sufficient excess of a difunctional epoxy compound in advance, and then add an epoxy curing agent to cure the prepolymer. At the same time, this organophosphorus compound has the drawback that it is difficult to spread in general because expensive parabenzoquinone is used as one of the raw materials, which raises the cost required for flame retardancy.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to use a specific organic phosphorus compound in place of an organic halogen compound, which has been widely used as a flame retardant, to provide excellent flame retardancy, physical strength and heat resistance. Offers epoxy resin that has good properties such as electrical insulation, water resistance, chemical resistance or low generation of harmful gas when burning, yet provides easy-to-process epoxy resin. Materials, electrical insulation materials, laminates,
To provide structural materials or civil engineering materials.

According to the present invention, the compound represented by the general formula 1 or the general formula 2
And a flame-retardant epoxy resin characterized by containing an organic phosphorus compound represented by the following formula (hereinafter simply referred to as general formula 1 or general formula 2).

[0017]

Embedded image (In the general formula 1, X is a phosphorus-containing substituent represented by the structural formula 1, and n is an integer of 1 to 3.)

[0018]

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[0019]

Embedded image (In the general formula 2, X is the same as defined in the general formula 1,
l and m are integers from 0 to 2. Where l and m
Are never zero. General formula 1 is a novel compound, and is produced by heat-condensing resorcinol and an organic phosphorus compound represented by the structural formula 5 (hereinafter, simply referred to as structural formula 5). The general formula 2 is also a novel compound, and is prepared by heat-condensing a formaldehyde condensate of resorcin and structural formula 5, or condensing general formula 1 or general formula 1 and resorcin with formaldehyde. Usually, it is difficult to manufacture only the general formula 2 alone, and a considerable amount of the general formula 1
Or an organic phosphorus compound comprising a higher-order resorcinol condensate. Therefore, it is easily understood that an organophosphorus compound comprising a higher-order resorcinol condensate is also included in the scope of the present invention.

[0020]

Embedded image Formula 1 is bifunctional with respect to the epoxy group. Accordingly, a divalent epoxy compound having two epoxy groups usually does not have curability, and thus requires the use of another epoxy curing agent in combination. However, since the compound has curability with respect to a polyvalent epoxy compound having three or more epoxy groups, it is not always necessary to use another curing agent in combination depending on the amount used in the general formula 1. Formula 2 is tetrafunctional to the epoxy group and has a curing effect on the epoxy resin, and the addition of the curing agent to the bifunctional epoxy resin within an appropriate addition amount. Is not required. However, the amount of the general formula 1 or the general formula 2 required for ordinary flame retardation is small, and is insufficient to fulfill the function as a curing agent, and it is inevitable to use it in combination with another curing agent. .

Commercially available epoxy compounds include monofunctional (monovalent) epoxy compounds, difunctional (divalent) epoxy compounds, and trifunctional or higher polyfunctional (polyvalent) epoxy compounds. . As a monovalent epoxy compound,
Examples include n-butyl glycidyl ether, styrene oxide or phenyl glycidyl ether,
These are used for the purpose of lowering the viscosity by mixing with a divalent or higher epoxy compound. And it is generally called a diluent, and it is difficult to form an epoxy resin alone. Examples of the divalent epoxy compound include diglycidyl ethers of bisphenol-A, and diglycidyl ethers of bisphenol-A and bisphenol- Diglycidyl ether of F, bisphenol-S
, The diglycidyl ether of tetrabromobisphenol-A or many alicyclic epoxy compounds. As polyvalent epoxy compounds,
Triglycidyl ether of glycerin, tetraglycidyl diaminodiphenylmethane, epoxidized soybean oil, glycidyl ether of formaldehyde polycondensate of phenols (novolak epoxy) or polyphenol,
That is, glycidyl ethers such as condensates of glyoxal and phenol are known. It is difficult to use a monovalent epoxy compound alone for the purpose of the present invention, but all divalent or higher epoxy compounds are used.

The organophosphorus compound represented by the general formula 1 also has a function as a curing agent for a polyvalent epoxy compound, but is not expected to be curable for a divalent epoxy compound. Therefore, it is necessary to separately add a chemical called an epoxy curing agent. The organic phosphorus compound represented by the general formula 2 is a tetravalent phenol, and is expected to have curability with respect to a bifunctional or higher epoxy compound. But,
When the addition amount is small relative to the epoxy compound, it is preferable to add another epoxy curing agent to the extent calculated from the epoxy equivalent.

There are many types of commercially available epoxy curing agents, but polyhydric phenol compounds, amines, polyamide resins, tertiary amines which are catalysts for promoting ring-opening polymerization of organic acids and their anhydrides or epoxy groups, and Amine complexes of Lewis acids and the like are known. Examples of these curing agents include bisphenol-A, bisphenol-
F, novolak resin of paracresol, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, N-diethylaminopropylamine, N-
Aminoethylpiperazine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, menthanediamine, bisaminopropyltetraoxaspiroundecane adduct, dicyandiamide, xylylenediamine, polyamide resin, phthalic anhydride, dodecylsuccinic anhydride, maleic anhydride, Tetrahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride,
Benzyldimethylamine, ethylmethylimidazole,
Trisdimethylaminophenol, tetramethylammonium chloride or boron trifluoride / monoethylamine complex may, for example, be mentioned. The reaction rate or curing rate of these epoxy curing agents with epoxy groups is not uniform depending on the type thereof, but is generally selected finely at the epoxy resin production site.

The functional groups of the general formulas 1 and 2 are hydroxy groups, and the rate at which they react with the epoxy groups is almost the same as other epoxy curing agents. Therefore, if the usual method of use is used, the hydroxy group of the general formula 1 or the general formula 2 remains in the zero-functional or monofunctional function without being reacted with the epoxy group and is left in the resin. As a result, there is little danger of lowering heat resistance or mechanical strength. This applies to general formulas 1 and 2
This is one of the features of

There are two methods for applying General Formula 1 to an epoxy resin as a flame retardant. The general formula 1 is considered as one of the curing agents for polyvalent epoxy compounds, and only the necessary amount for flame retardancy is added, and if necessary, other curing agents are added to cure at once. Then, a method of obtaining an epoxy resin is employed. However, the other epoxy curing agent used at this time is selected to have an extremely large reaction rate as compared with the reaction rate with the epoxy group of the general formula 1, and the use amount thereof is not excessively increased. Is good. Similarly, in the case of a divalent epoxy compound, the compound of the general formula 1, the divalent epoxy compound and the epoxy curing agent are mixed and then cured at once. At this time, it is preferable that the selection and the use amount of the epoxy curing agent are similarly limited. Other methods are mainly applied with a combination of a divalent epoxy compound and the general formula 1. After preliminarily reacting a divalent epoxy compound represented by diglycidyl ether of bisphenol-A with a required amount of general formula 1 to prepare a prepolymer containing an epoxy group at a terminal, an epoxy curing agent Is added and cured. In order to prepare a prepolymer having an epoxy group at the terminal, the molar ratio of the general formula 1 to the divalent epoxy compound is preferably from 0.08 to 0.6, more preferably from 0.1 to 0.5. Is added. At this time, since the general formula 1 is already completely linked to the epoxy compound, any other epoxy curing agent may be selected.

Formula 2 is formally tetrafunctional with respect to the epoxy group, and has curability with respect to divalent or higher-valent epoxy compounds. Accordingly, the epoxy resin can be cured only by the general formula 2 without using another epoxy curing agent. However, if the amount of use of the general formula 2 is limited to a level necessary for making the resin flame-retardant, the amount of the curing agent is generally insufficient. At this time, the use of another epoxy curing agent is inevitable, and it is preferable that the selection and use amount of the other epoxy curing agent be limited as in the case of the general formula 1.

As mentioned above, it is difficult to produce the general formula 2 in a pure form due to the process. Therefore, the general formula 2 generally contains the general formula 1 and an organophosphorus compound in which the resorcinol nucleus is further polynuclear. General formula 1 and general formula 2
Are almost the same, and the general formulas 1 and 2 can be mixed at an arbitrary ratio according to the purpose and applied to an epoxy resin.

Since the flame retardant effect on the epoxy resins of the general formulas 1 and 2 is significantly higher than that of other organic phosphorus compounds, the phosphorus content in the epoxy resin may be relatively small. Usually, the phosphorus content is 0.1 to 6.0, depending on the degree of flame retardancy required of the epoxy resin.
%, More preferably from 0.3 to 4.0%, is added to the epoxy resin with the pre-calculated general formulas 1 and 2.

A first object of the present invention is to provide a flame-retardant epoxy resin using only the novel organophosphorus compound specified by the general formula 1 or 2 as a flame retardant. Other flame retardants such as other organic phosphorus compounds, organic halogen compounds, antimony trioxide or aluminum hydroxide can be added as long as the properties of the epoxy resin are not deteriorated.

In the flame-retardant epoxy resin according to the present invention, additives usually used, such as animal and plant fibers, synthetic fibers, mineral fibers, glass fibers, fiber cloth, quartz powder, calcium carbonate, clay minerals , Titanium oxide, alumina, pigments or dyes can be added.

When manufacturing a laminate or the like mainly made of a woven fabric such as glass fiber as a core material, an uncured epoxy resin composition, that is, an epoxy compound, a general formula 1 or a general formula 2, another epoxy curing agent, The accelerator and, if necessary, other additives can be dissolved and mixed in an organic solvent to impregnate the fabric. After drying the organic solvent, the resin is cured. The organic solvent used at this time is MEK (methyl ethyl ketone), MIBK (methyl isobutyl ketone), DMF (dimethyl formamide), DMAC
(Dimethylacetamide) or ethylene glycol ethers.

[0032]

EXAMPLES In order to further clarify the present invention, general formula 1
The present invention will be described with reference to Production Examples of General Formula 2, specific examples of the present invention, and Comparative Examples.

[Production Example 1] (Production Example of General Formula 1) 165 g of resorcinol was placed in a 1,000 ml four-necked flask equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser capable of separating water. 1.5 mol), structural formula 5
(10-hydroxymethyl-9,10-dihydro-9-
554 g (1.5 mol × 1.5) of oxa-10-phosphaphenanthrene-10-oxide) and 0.8 g of potassium carbonate were charged. Since the contents were dissolved by heating the flask, stirring was started. Toluene was appropriately added dropwise from the dropping funnel to raise the temperature of the contents to 120 ° C to 13 ° C.
At 0 ° C., toluene was refluxed and, at the same time, generated water could be removed. After about 20 hours, the amount of water generated and separated became 40 ml, which was almost the theoretical amount. The product was analyzed by liquid chromatography. As a result, the area ratio of the peaks was 0.2% for resorcin, 36% for n of the general formula 1 was 1 and 56% for n was 2 in the general formula 1. And 8% of unidentified substances (though the number of n in the general formula 1 is considered to be 3 but not confirmed). The flask was then connected to a vacuum and the used toluene was distilled off to give a slightly yellowish glassy solid. This had a phosphorus content of 10.26% and a hydroxyl value of 248.7, and it was confirmed that the product was mainly a mixture of general formula 1 in which the number of n was 1 and 2.

[Production Example 2] (Production Example of General Formula 2) In the same flask as in Production Example 1, 165 g of resorcin, 443 g of Structural Formula 5, and 0.5 g of potassium carbonate were charged, and almost the same as in Production Example 1 was prepared. In the area ratio of liquid chromatography, resorcin was 0.5%, n of the general formula 1 was equivalent to 1, 56%, and n was 2 for 37.
% And 7% of unidentified material. After the content was cooled to 90 ° C., 0.5 mol of formalin was gradually added dropwise from a dropping funnel. During the reaction, the reaction was monitored by liquid chromatography.
Although it was observed that the compound corresponding to the above was polycondensed sequentially with formaldehyde, the number of peaks was large and complicated, and it was difficult to specify the structure of the finished product for each peak. After completion of the reaction, the flask was connected to a decompression device, and water and toluene were distilled off to obtain a pale yellow glassy solid. It has a phosphorus content of 9.60.
% And a hydroxyl value of 337.3, and it was mainly confirmed that the mixture was a mixture of the general formulas 1 and 2.

[Production Example 3] (Experiment for confirming the formation of General Formula 2) Production Example 1 was prepared by charging 550 g of resorcin, 123 g of Structural Formula 5, and 0.8 g of potassium carbonate in the same flask as in Production Example 1. The reaction was carried out in the same manner as Analysis revealed that resorcinol and a product having X, that is, structural formula 1 in the 4-position of resorcinol were mainly contained, and a small amount of 2-substituted product was contained. This reaction mixture was dissolved in ethyl acetate and washed repeatedly with water to remove unreacted resorcinol. Ethyl acetate and toluene were distilled off under reduced pressure to give a pale yellow glassy solid 161.
g was obtained. The phosphorus content was 9.18%, the hydroxyl value was 333.6, and the analysis by a mass spectrometer revealed that the compound had a molecular weight of 338. Next, 101 g (0.3 mol) of this compound, 50 g of dioxane and 0.2 g of metal sulfonic acid were charged into a 200 ml four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel. Then, the contents were heated to 90 ° C. Formalin was gradually dropped from the dropping funnel in an amount corresponding to 0.02 mol. The reaction rate was sufficiently high, and the process of polycondensation of the resorcinol ring was confirmed by liquid chromatography following the reaction in detail. The number of peaks in the finished reaction mixture was simpler than that in Preparation Example 2. According to this experiment, the mixture was found to be a compound in which the number of n in the general formula 1 was 1 and the number of l and m in the general formula 2 was both 1. It was confirmed that the compound consisted of: Therefore, although the composition of the mixture prepared in Production Example 2 is complicated and difficult to analyze by comparing this experiment and the process in detail, it must be a mixture of the general formulas 1 and 2. Was confirmed. [Example 1] Epicoat 828 (epoxy equivalent: 19)
(0) 190 g (manufactured by Shell Sekiyu KK), 65 g of the general formula 1 obtained in Production Example 1 and 0.1 g of tetramethylammonium chloride were mixed and melted, and reacted at 120 ° C. for 5 hours. To this, 35 g of 4,4'-diaminodiphenylmethane was added and cured at 150 ° C. for 5 hours to obtain an epoxy resin test piece. The phosphorus content of this resin is 2.29%
Met. Example 2 190 g of Epicoat 828, 65 g of the formula 1 obtained in Production Example 1, 35 g of 4,4'-diaminodiphenylmethane and 0.1 g of tetramethylammonium chloride were added, and cured at 150 ° C. for 5 hours. Thus, an epoxy resin test piece was obtained. The properties of this resin were almost similar to the resin obtained in Example 1, and the phosphorus content was exactly the same as that obtained in Example 1. [Example 3] A phenol novolak epoxy compound (average molecular weight: 650, epoxy equivalent: 178) was converted to 178.
g, 75 g of the general formula 1 obtained in Production Example 1, 70 g of a phenol novolak resin (average molecular weight: 350, hydroxyl number: 530) and 0.1 g of tetramethylammonium chloride were mixed and cured in the same manner as described above. A resin test piece was obtained. The phosphorus content of this resin is 2.3
7%. Example 4 190 g of Epicoat 828 and 60 parts of the mixture of Formulas 1 and 2 obtained in Production Example 2
g, 34 g of 4,4'-diaminodiphenylmethane and 0.1 g of tetramethylammonium chloride were added and cured at 150 ° C. for 5 hours to obtain an epoxy resin test piece. The phosphorus content of this resin was 3.02%. [Example 5] 178 g of the phenol novolak epoxy compound used in Example 3, 60 g of the mixture of General Formulas 1 and 2 obtained in Production Example 2, and 72 g of the phenol novolak resin used in Example 3 were melted. Then, 0.1 g of tetramethylammonium chloride was added and cured in the same manner to obtain an epoxy resin test piece. The phosphorus content of this resin was 2.84%. [Comparative Example 1] 190 g of Epicoat 828, 4,4'-
50 g of diaminodiphenylmethane and 0.1 g of tetramethylammonium chloride were mixed and cured in the same manner to obtain an epoxy resin test piece. This resin did not contain phosphorus. Comparative Example 2 190 g of Epicoat 828, 80 g of tricresyl phosphate, 50 g of 4,4'-diaminodiphenylmethane and 0.1 g of tetramethylammonium chloride were melt-mixed and cured in the same manner to obtain an epoxy resin test piece. Was. The phosphorus content of this resin is 2.09%
Met. Comparative Example 3 190 g of Epicoat 828 and 45 g of an organic phosphorus compound (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) represented by the structural formula 2 (manufactured by Sankosha) 39 g of 4,4'-diaminodiphenylmethane and 0.1 g of tetramethylammonium chloride were added and cured in the same manner to obtain an epoxy resin test piece. The phosphorus content of this resin is 2.35%
Met.

[Evaluation of Examples and Comparative Examples] The epoxy resins obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated and determined by the following methods and summarized in Table 1.

A Tg (glass transition temperature): Measured at a heating rate of 2 ° C./min using a viscoelastic spectrometer DMA980 (manufactured by DuPont) and the temperature was indicated.

B: Water absorption at boiling: The test piece was immersed in boiling water at 100 ° C. for 1 hour to show the rate of weight increase.

C Pressurized hot water absorption: The rate of weight increase of the test piece when exposed to pressurized water at 120 ° C. for 1 hour.

D Alkali resistance: After heating a 10% aqueous solution of caustic soda to 80 ° C. and immersing the test piece for 2 hours, observing the surface condition, ◎ indicates no change, ○ indicates slight erosion, Δ
Was considerably eroded and X was very eroded.

E Flame resistance (flame retardancy): Evaluated by the method of an underwriter UL-94, and the average value of the duration of framing was shown.

[0042]

[Table 1]

[0043]

As will be understood from the results of Examples 1 to 5 and Comparative Examples 1 to 3, according to the method of the present invention, high flame resistance and high heat resistance can be obtained without using any organic halogen compound. It is clear that a water-resistant and chemical-resistant epoxy resin can be provided, which is extremely useful in industry.

Continued on the front page (72) Inventor Hiroshi Sumitomo 1-10-24, Itikaichi, Ibaraki-shi, Osaka F-term in Sanko Development Research Institute Co., Ltd. (reference) 4J036 AA01 CC02 DA01 DA05

Claims (3)

[Claims] 1. A flame-retardant epoxy resin comprising a reaction product of an epoxy resin and an organic phosphorus compound represented by general formula 1 and / or general formula 2. Embedded image (In the general formula 1, X is a phosphorus-containing substituent represented by the structural formula 1, and n is an integer of 1 to 3.) Embedded image (In the general formula 2, X is the same as defined in the general formula 1,
l and m are integers from 0 to 2. Where l and m
Are never zero. ) 2. The flame-retardant epoxy resin according to claim 1, wherein the organic phosphorus compound in the flame-retardant epoxy resin is contained in a range of 0.1 to 6.0% as a phosphorus atom. 3. An organic phosphorus compound represented by the general formula 1 and / or the general formula 2 is reacted with an epoxy compound having at least two epoxy groups in a ratio of 0.08 to 0.6 mol. A flame-retardant epoxy resin obtained by further curing the obtained organic phosphorus compound with an epoxy curing agent.