The invention relates to a halogen free flame/fire retardant epoxy resin composition with excellent mechanical properties, thermal resistance, low smoke release and good processability.

The invention also refers to the process of obtaining said epoxy resin composition. Moreover, the present invention relates to the use of the halogen free flame/fire retardant epoxy resin composition as adhesive.

Furthermore, the present invention relates to articles comprising halogen free flame/fire retardant epoxy resin composition and their uses as an electric or electronic circuit component or a structural element for transportation and building.

BACKGROUND ART Epoxy resins are widely-used matrix resins due to their superior thermal, chemical-resistance, electrical-resistance and mechanical properties. However, the flammability of epoxy resins greatly restricts their applications. As the awareness of fire security increased, improving the flame retardancy has been the key challenge for epoxy resins research.

Although adding halogenated flame retardants to epoxy resins matrices, such as tetrabromobisphenol A (TBBPA), is quite effective method for improving the flame retardancy of epoxy resins with electrical and electronic applications, they produce a poisonous and corrosive smoke and may generate super-toxic halogenated dibenzodioxins and dibenzofurans during combustion, which is forbidden in the new environmental legislations Registration, Evaluation, Authorisation and Restriction of Chemical substances (REACH), Waste Electrical and Electronic Equipment Directive (WEEE) and Restriction of Hazardous Substances (RoHS).

Since the implementation of environmental directives banning or limiting the use of halogenated compounds, the development of flame retardants based on epoxy resins has focused on more environmentally friendly alternatives. In recent years, a broad range of new halogen free flame retardants have been developed. Flame retardants can either be physically mixed with the base material (additive flame retardants) or chemically bonded to it (reactive flame retardants). New additive non-halogen flame retardants formulations are, for example, ammonium polyphosphate (APP), triphenyl phosphate (TPP), dimethyl methylphosphonate (DMMP), tricresyl phosphate (TCP), cresyldiphenyl phosphate (CDP), resorcinol bis(diphenyl phosphate) (RDP) and bisphenol A bis(diphenyl phosphate) (BDP), which are described in the corresponding patents US5945467, US5919844, US4918122, US5932637, US6348523, US6713163 and EP1359174. Here, the flame retardancy of epoxy resins has been improved in some extent; however, this effect sacrifices application performances such as water resistance, mechanical resistance and transparency due to the high percentage addition and the poor chemical compatibility with the polymer structure.

The main disadvantage of the additive flame retardant has been overcome by a great number of the reactive type formulations. For example, organophosphoruses compounds are commonly incorporated to epoxy resins due to its thermal and hydrolytic stability [US6353080 and US6403690]. Moreover, other phosphorus element-containing compounds are described as difunctional or trifunctional phosphine oxide crosslinkers, that is, as effective curing agents [US0065869]. Reactive flame retardants as 9, 10-Dihydro-9-oxa- 10-phosphaphenanthrene 10-oxide (DOPO) and their derivatives are also examples to mention [US4280951]. A plastics flammability standard released UL 94-VO rating of approximately 3 mm, was reached incorporating about 12 wt% DOPO in the DGEBA/DDS system [D. Sunand Y. Yao, Polymer Degradation and Stability, 96, 1720-1724 (201 1 )]. However a decrease of the Glass Transition Temperature (Tg) is also observed herein. Main disadvantages of the reactive flame retardants relate to decreases of mechanical performances, thermal resistance, and processability of the epoxy resins composition containing them. Moreover, the flame retardant efficiency is low and the combustion produces a big amount of smoke. For the reasons stated above, it is needed to develop new halogen free flame retardant epoxy resin composition with excellent thermal resistance, superior mechanical properties and low smoke release.

SUMMARY OF THE INVENTION

The present invention discloses a novel halogen free flame retardant epoxy resin composition with excellent mechanical properties, thermal resistance, fire retardancy, low smoke release and good processability. Its flame retardancy derives from the flame retardant halogen free phosphorous ingredient.

The invention also refers to the process of obtaining said epoxy resin composition.

Moreover, the present invention relates to the use of the halogen free flame/fire retardant epoxy resin composition as adhesive.

Furthermore, the present invention relates to articles comprising halogen free flame/fire retardant epoxy resin composition and their uses as an electric or electronic circuit component or a structural element for transportation and building. Therefore, a first aspect of the present invention relates to a halogen free cured epoxy resin composition that comprises the following components:

• at least one epoxy resin matrix selected from the list comprising a glycidyl ether/ester type epoxy resin, a glycidyl amine type epoxy resin and a combination thereof, wherein the glycidyl amine type epoxy resin has at least one of the following molecular group,

• at least one flame retardant phosphorous compound, wherein the flame retardant compound is in a weight percent between 0.5 and 15% based on the weight of the cured composition,

• and at least a hardener of the epoxy resin matrix in a stoichiometric amount based on the weight of the cured composition, which comprises an amine group, an anhydride group, an aryl group, a sulfhydryl group or a combination thereof.

Thus a preferred embodiment of the present invention provides a cured epoxy resin composition, wherein the glycidyl ether/ester type epoxy resin is selected from the list consisting of

Bisphenol A epoxy resin

II

>-CHr-CH-CHr+-0- ^■ O-CH ₂ -CH-CH ₂

H OH H Bisphenol F epoxy resin

Bisphenol S epoxy resin

and Novolac epoxy resin,

wherein n is a value between 0 and 10. More preferably, the glycidyl ether/ester type epoxy resins have n values between 1 a 5.

In another preferred embodiment, the glycidyl amine type epoxy resin of the cured epoxy resin composition described above, is selected from the list comprising Tris(2,3-epoxypropyl) isocyanurate, 4,4'-Methylenebis(N,N- diglycidylaniline), bis(N,N-diglycidylaminomethyl)cyclohexane, N,N-Diglycidyl-4- glycidyloxyaniline and a combination thereof.

A further embodiment of the present invention provides a cured epoxy resin composition, wherein the flame retardant phosphors compound is a compound of formula I

wherein Ri and R3 are independently selected from the list comprising epoxides, -XR ₄ , -alkyl(Ci-C ₄ )-COO-R ₅ , -COOR ₆ and -Y-NH ₂ ,

X is selected from O, -NH, -S-,

Y is selected from the list comprising hydrogen, alkyl (C1-C10), cycloalkyl, aryl and aralkyl,

R ₄ , R ₅ and R6 are independently selected from the list comprising hydrogen, alkyl (Ci-C ₄ ), aryl and diol,

and R2 is selected from the list comprising hydrogen, alkyl (Ci-C ₄ ), cycloalkyl, aryl and aralkyl,

In the present invention, the term "epoxide" relates to is cyclic ether with three ring atoms. As a functional group, epoxides feature the epoxy prefix, such as in the compound 1 ,2-epoxycycloheptane, which can also be called cycloheptene epoxide, or simply cycloheptene oxide.

The term "alkyl (Ci-C ₄ )" as used herein relates to a linear or branched aliphatic chains, which have from 1 to 4 carbon atoms, for example, methyl, ethyl, n- propyl, i-propyl, n-butyl, tert-butyl and sec-butyl. Preferably the alkyl group has between 1 and 3 atoms, more preferably between 1 and 2 atoms, more preferably is methyl. The term "alkyl (C1-C10)" as used herein relates to a linear or branched aliphatic chains, which have from 1 to 10 carbon atoms, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl and sec-butyl. Preferably the alkyl group has between 1 and 6 atoms. In the present invention, the term "aryl" relates to an aromatic carbocyclic chain, which has from 6 to 18 carbon atoms, and can be a single or multiple ring, in this last case with separated and/or condensed rings. In the present invention, preferably the aryl group is a phenyl. Non-limiting examples of aryl grupos are phenyl, naphthyl and indenyl groups. Preferably the aryl group is a phenyl, wherein the phenyl group may contain 1 or more substituents such as alkyl, hydroxyl, nitro and amine groups. The term "diol" as used herein relates to a chemical compound containing two hydroxyl groups (— OH groups), which can be geminal, this means, the diol has two hydroxyl groups bonded to the same atom or vicinal (glycols), wherein the two hydroxyl groups occupy vicinal positions, that is, they are attached to adjacent atoms. An example of a diol group is -CH ₂ -CHOH-CH ₂ OH.

The term "cycloalkyl" relates to a stable monocyclic or bicyclic radical of 3 to 10 members that is saturated or partially saturated, and which only consists of carbon and hydrogen atoms, such as cyclopentyl, cyclohexyl or adamantyl

The term "aralkyl" relates, in the present invention, to an aliphatic chain wherein at least one of the hydrogen has been substituted by an aryl group, with the previous senses but without being limited to, a benzyl or phenethyl group. In a more preferred embodiment, Ri and R3 are -OH and R ₂ is a phenyl group.

In another more preferred embodiment, Ri is an -OH, R ₂ is a phenyl group, R3 is a alkyl(Ci-C ₄ )-COO-R ₅ and R ₅ is a hydrogen. In another more preferred embodiment, Ri and R3 are -OH and R ₂ is a methyl group.

In another more preferred embodiment, Ri and R3 are -OH and R ₂ is hydrogen. These reactive phosphorous compounds provide flame retardancy and consequently fire retardancy to the cured epoxy resin compositions. Furthermore, they enhance the mechanical properties of the cured epoxy resin compositions. In another more preferred embodiment, the compound of formula I is the compound of formula II.

Another preferred embodiment, the compound of formula I is the compound of formula III.

Another preferred embodiment refers to a cured epoxy resin composition, wherein the flame retardant phosphors compound is a compound of formula IV havin n values between 0 and 10.

[IV]

Another preferred embodiment refers to a cured epoxy resin composition, wherein the flame retardant phosphors compound is a compound of formula V having n between 0 and 10.

[V]

Another preferred embodiment refers to a cured epoxy resin composition, wherein the flame retardant phosphors compound is a compound of formula VI having n values between 0 and 10.

[VI]

Another preferred embodiment refers to a epoxy resin composition, wherein the flame retardant phosphors compound is a compound of formula VII havingn values between 0 and 5.

[VII] Another preferred embodiment refers to a cured epoxy resin composition, wherein the flame retardant phosphors compound is a compound of formula VII having n values between 0 and 5.

[VIII]

A further embodiment of the present invention provides a cured epoxy resin composition, wherein the flame retardant phosphorous compound is in a weight percent between 0.5 and 5% based on the total weight of the cured composition. More preferably is in a weight percent between 0.5 and 4% based on the total weight of the cured composition. Another preferred embodiment relates to a cured epoxy resin composition, wherein the hardener of the epoxy resin matrix comprises an aryl group. This aryl group has been defined above. More preferably, the hardener is selected from the list comprising aminophenyl sulfone (DDS), diaminodiphenylmethane (DDM) and a combination thereof.

In the present invention, the term "hardener" as used herein refers to compounds that serve as crossi inkers of the epoxy resins so that the mechanical properties as well as high temperature and chemical resistance are improved. In another preferred embodiment, the hardener of the epoxy resin composition described above is in a weight percent between 10 and 40% based on the total weight of the cured composition. A further embodiment of the present invention relates to the cured epoxy resin composition described previously, which further comprises a nanofiller. More preferably, the nanofiller is selected from the list comprising nanoclay, carbon nanotubes and nanofibers, nanodiamonds, nano zirconium phosphate, graphite, and a combination thereof.

In the present invention, the term "nanofiller" relates to a doping agent distributed in the matrix of an epoxy resin composition, whose individual elements have at least one of their dimensions in the nanoscale. Examples of nanofillers include nanoclays, carbon nanotubes and nanofibres, nanodiamonds, nano zirconium phosphate and graphite.

Moreover, the second aspect of the present invention refers to a process for obtaining the cured epoxy resin composition described previously that comprises following steps:

a) mixing at least one epoxy resin matrix and at least a hardener at a temperature value between 60 and 150°C,

b) adding at least one flame retardant phosphorous compound to the mixture of step (a),

c) transferring the mixture obtained in step (b) into a mold, and

d) curing the mixture inside a mold of step (c) at least once at a temperature value between 120 and 220°C.

In a preferred embodiment, the invention relates to the above mentioned process, wherein the curing step (d) is carried out in one step at a temperature of 180°C and maintaining said temperature for 2 hours. In another preferred embodiment, the invention refers to the process described previously, wherein the curing step (d) is carried out in three steps at temperatures values between 120°C and 220 ^a c and maintaining said temperature for between 30 and 150 minutes.

Another preferred embodiment refers to the above mentioned process, wherein the curing step (d) is carried out by following continuously the next three steps: i) curing the mixture obtained in step (c) at a temperature of 150 °C and maintaining the temperature for 1 hour,

ii) curing the mixture obtained in (ii) at a temperature of 180 °C and maintaining the temperature for 2 hours, and

iii) curing the mixture obtained in (iii) at a temperature of 200°C and maintaining the temperature for 1 hour. A further embodiment of the present invention relates to the the above mentioned process described previously, wherein flame retardant phosphorous compound of step (b) is further combined with a nanofiller. More preferably, the nanofiller is selected from the list comprising nanoclay, carbon nanotubes and nanofibers, nanodiamonds, nano zirconium phosphate, graphite, and a combination thereof.

A third aspect of the present invention relates to the use of the cured epoxy resin composition described before as adhesive. A fourth aspect of the present invention relates to an article comprising the above mentioned cured epoxy resin composition.

A fifth aspect of the present invention refers to an article coated by the cured epoxy resin composition described above.

A sixth aspect of the invention relates to a fiber reinforced composite article comprising the previously described cured epoxy resin composition. In a preferred embodiment, the fiber reinforced composite article is a laminate or a prepreg. Pre-preg as used here is a term for "pre-impregnated" composite fibres where a material, such as epoxy is already present. Usually the pre-preg takes the form of a weave or is unidirectional. The epoxy resin is only partially cured to allow easy handling and requires cold storage to prevent complete curing until complete polymerization is done, most commonly by heat.

A seventh aspect of the invention refers to the above mentioned article which is an electric or electronic circuit component or a structural element for transportation and building. In the present invention the term "transportation" refers to aircrafts, ships, rails, cars, bicycles and the like.

The term "building" relates to any structural element forming any kind of building. Furthermore, the term refers to any element taking part of the indoor decoration of a building.

An eighth aspect of the invention relates to an electric or electronic circuit component having an insulating coating of the cured epoxy resin composition described previously.

A ninth aspect of the invention is a compound of formula II, which is obtained by reaction of phenylphosphonic acid with glycidol at temperatures between 30 and 70°C.

A tenth aspect of the invention is a compound of formula III, which is obtained by reaction of 2-carboxyethyl(phenyl)phosphonic acid with glycidol

at temperatures between 30 and 70°C.

An eleveth aspect of the invention is a compound of formula IV, which is obtained by reaction of phenylphosphonic acid with ethylene glycol diglycidyl ether at temperatures between 30 and 70°C.

[IV] A twelfth aspect of the present invention is a compound of formula V, which is obtained by reaction of phenylphosphonic acid with diglycidyl ether at temperatures between 30 and 70°C.

[V]

A thirteenth aspect of the present invention is a compound of formula VI, which is obtained by reaction of 2-carboxyethyl(phenyl)phosphinic acid with diglycidyl ether at temperatures between 30 and 70°C.

[VI]

A fourteenth aspect of the present invention refers to a compound of formula VII, which is obtained by reaction of phenylphosphomic acid with phenylene diisocyanate at temperatures between 30 and 70 °C.

-N=C=0

[VII]

A fifteenth aspect of the present invention relates to a compound of formula VIII, which is obtained by reaction of phosphorous acid with tolyene diisocyanate at temperatures between 30 and 70 °C.

[VIM]

A sixteenth aspect of the invention relates to the use of a compound selected from the list comprising the compound of formula II

the compound of formula

the compound of formula VII

[VII] and the compound of formula VIII

[VIII],

as flame retardants.

The compounds of formulas II, III, IV, V, VI, VII and VIII described previously as flame retardants. These compounds can be also considered as flame retardants diluents, as shown in the examples, they reduce the viscosity of the epoxy resin compositions to values below 30 mPa-s. Common values of viscosities are 30- 70 mPa-s when other phosphorous flame retardants are used.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. Methods and materials similar or equivalent to those described herein can be used in the practice of the present invention. Throughout the description and claims the word "comprise" and its variations are not intended to exclude other technical features, additives, components, or steps. Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples are provided by way of illustration and are not intended to be limiting of the present invention.

EXAMPLES

Example 1 : Synthesis of the compound of formula II.

[II]

Into a 1 L flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 142.3 g (0.9 mol) of phenylphosphonic acid and 300 ml of acetone were put to obtain a solution. Then, 133.4 g (1 .8 mol) of glycidol was dropped into the acetone solution of phenylphosphonic acid over 30 min. After the dropping, the reaction was further performed at 50°C for another 6 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove acetone leaving 273 g of a colorless, transparent liquid product at a yield of 99%.

Example 2 Synthesis of the compound of formula III

Into a 1 L flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 192.7 g (0.9 mol) of 2-carboxyethyl(phenyl)phosphinic acid and 300 ml of ethanol were put to obtain a solution. Then, 133.4 g (1 .8 mol) of glycidol was dropped into the ethanol solution of 2- carboxyethyl(phenyl)phosphinic acid over 30 min. After the dropping, the reaction was further performed at 50oC for another 8 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove ethanol leaving 319.6 g of a colorless, transparent liquid product at a yield of 98%.

Example 3 Synthesis of the compound of formula IV

Into a 1 L flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 142.3 g (0.9 mol) of phenylphosphonic acid and 300 ml of acetone were put to obtain a solution. Then, 142.4 g (0.9 mol) of ethylene glycol diglycidyl ether was dropped into the acetone solution of phenylphosphonic acid over 30 min. After the dropping, the reaction was further performed at 50°C for another 6 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove acetone leaving 281 .9 g of a colorless, transparent liquid product at a yield of 99%.

Example 4 Synthesis of the compound of formula V

Into a 1 L flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 142.3 g (0.9 mol) of phenylphosphonic acid and 300 ml of acetone were put to obtain a solution. Then, 1 17.1 g (0.9 mol) of diglycidyl ether was dropped into the acetone solution of phenylphosphonic acid over 30 min. After the dropping, the reaction was further performed at 50°C for another 6 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove acetone leaving 256.9 g of a colorless, transparent liquid product at a yield of 99%. Example 5 Synthesis of the compound of formula VI

Into a 1 L flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 192.7 g (0.9 mol) of 2-carboxyethyl(phenyl)phosphinic acid and 300 ml of ethanol were put to obtain a solution. Then, 1 17.1 g (0.9 mol) of diglycidyl ether was dropped into the ethanol solution of 2- carboxyethyl(phenyl)phosphinic acid over 30 min. After the dropping, the reaction was further performed at 50°C for another 6 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove acetone leaving 303.5 g of a colorless, transparent liquid product at a yield of 98%.

Example 6 Synthesis of the compound of formula VII

Into a 1 L flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 142.3 g (0.9 mol) of phenylphosphonic acid, 1 .5 g of 1 ,4- diazabicyclo[2.2.2]octane, and 300 ml of acetone were put to obtain a solution. Then, 144.1 g (0.9 mol) of phenylene diisocyanate was dropped into the acetone solution of phenylphosphonic acid over 30 min. After the dropping, the reaction was further performed at 50°C for another 8 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove acetone leaving 282.9 g of a colorless, transparent liquid product at a yield of 99%.

Example 7 Synthesis of the compound of formula VIII

Into a 500 ml flask equipped with a reflux condenser, a thermometer, a stirrer, a dropping funnel, 73.8 g (0.9 mol) of phosphorus acid, 1 .5 g of 1 ,4- diazabicyclo[2.2.2]octane, and 300 ml of acetone were put to obtain a solution. Then, 156.7 g (0.9 mol) of tolyene diisocyanate was dropped into the acetone solution of phenylphosphonic acid over 30 min. After the dropping, the reaction was further performed at 50°C for another 8 hours to complete the reaction. After the reaction ended, the flask was connected to a vacuum system to remove acetone leaving 225.9 g of a colorless, transparent liquid product at a yield of 98%. Example 8:

A curable epoxy resin composition was made by mixing:

100 parts by weight of 4,4'-Methylenebis(N,N-diglycidylaniline);

59 parts of 4-aminophenyl sulfone; 8 parts of the flame retardant compound of formula II described in example 1 , that is, the product of phenylphosphonic acid and glycidol (4.8wt% based on the total weight of the cured product) Curing process:

100 g of 4,4'-Methylenebis(N,N-diglycidylaniline) and 59 g of 4-aminophenyl sulfone was mixed at 80°C by removal of air bubbles and moisture under vacuum. 8 g of the flame retardant compound of formula II described in example 1 , that is, the product of phenylphosphonic acid and glycidol was added as a flame retardant. The mixture was cured at 180°C for 2 hours.

LOI: Limited Oxygen Index

The limiting oxygen index (LOI) is the minimum concentration of oxygen (expressed as a percentage) that will support combustion of a polymer. It was measured by passing a mixture of oxygen and nitrogen over a burning specimen, and reducing the oxygen level until a critical level was reached. LOI values for the composites were determined by standardized tests, according to the ASTM D2863 (samples of dimensions 130 * 6.5 * 3.2 mm ³ ).

UL 94 is a plastics flammability standard released by Underwriters Laboratories of the USA. The standard classifies plastics according to how they burn in various orientations and thicknesses. From lowest (least flame-retardant) to highest (most flame-retardant), the classifications are: HB: slow burning on a horizontal specimen; burning rate < 76 mm/min for thickness < 3 mm and burning stops before 100 mm

V2 burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.

· V1 : burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

V0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

5VB: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.

5VA: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole

Cone Calorimeter Test (CCT): p-HRR: peak Heat Release Rate, THR: Total Heat Release and TSP: Total Smoke Production.

The cone calorimeter test (CCT) is the most significant bench scale instrument to study the fire behavior of small specimen of various materials, following the procedures in ISO 5660 (without the use of the "frame and grid") using an FTT cone calorimeter. Square specimens (100x100^3 mm ³ ) were irradiated at a heat flux of 50 kW/m ² . This method is able to investigate some important parameters in a fire, like heat release rate (HRR), peak of heat release rate (p- HRR), total heat release (THR), total smoke production (TSP), among others.

Tg (Glass transition temperature)

The glass-liquid transition (or glass transition for short) is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or rubber-like state. In this invention all Tg have been measured by dynamic mechanical analysis (DMA).

Example 9: A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332), a transparent super-cooled liquid which has an epoxide equivalent weight of 171 - 175 and is commercially available from the DOW Chemical Company;

30 parts of tris(2,3-epoxypropyl) isocyanurate;

43 parts of 4-aminophenyl sulfone;

1 .5 parts of phenylphonic acid (1wt% based on the total weight of the cured product) Curing process:

70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 43 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 1 .5 g of phenylphosphonic acid was added as a flame retardant. The mixture was stirred at 120°C until phenylphosphonic acid had completely dissolved, and then the mixture was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 10

A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

30 parts of tris(2,3-epoxypropyl) isocyanurate;

42 parts of 4-aminophenyl sulfone;

2.9 parts of phenylphonic acid (2wt% based on the total weight of the cured product) Curing process:

70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 42 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 2.9 g of phenylphosphonic acid was added as a flame retardant. The mixture was stirred at 120°C until phenylphosphonic acid had completely dissolved, and then the mixture was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 11 A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

30 parts of tris(2,3-epoxypropyl) isocyanurate;

40 parts of 4-aminophenyl sulfone;

5.8 parts of phenylphonic acid (4wt% based on the total weight of the cured product)

Curing process:

70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 40 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 5.8 g of phenylphosphonic acid was added as a flame retardant. The mixture was stirred at 120°C until phenylphosphonic acid had completely dissolved, and then the mixture was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 12

A curable epoxy resin composition was made by mixing:

75 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

25 parts of tris(2,3-epoxypropyl) isocyanurate;

38 parts of 4-aminophenyl sulfone;

7.2 parts of phenylphonic acid (5wt% based on the total weight of the cured product)

Curing process:

75 g of high purity bisphenol A diglycidylether (D.E.R. 332), 25 g of tris(2,3- epoxypropyl) isocyanurate, and 38 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 7.2 g of phenylphosphonic acid was added as a flame retardant. The mixture was stirred at 120°C until phenylphosphonic acid had completely dissolved, and then the mixture was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 13 A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

30 parts of tris(2,3-epoxypropyl) isocyanurate;

44 parts of 4-aminophenyl sulfone;

16 parts of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol (10wt% based on the total weight of the cured product) Curing process:

70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 44 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 16 g of the product of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol was added as a flame retardant. The mixture was stirred at 120°C until a homogeneous solution was obtained, and then the solution was transferred in to mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 14

A curable epoxy resin composition was made by mixing:

80 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

20 parts of tris(2,3-epoxypropyl) isocyanurate;

42 parts of 4-aminophenyl sulfone; 20 parts of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol (12wt% based on the total weight of the cured product) Curing process:

80 g of high purity bisphenol A diglycidylether (D.E.R. 332), 20 g of tris(2,3- epoxypropyl) isocyanurate, and 42 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 20 g of of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol was added as a flame retardant. The mixture was stirred at 120°C until a homogeneous solution was obtained, and then the solution was transferred in to mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 15

A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

30 parts of tris(2,3-epoxypropyl) isocyanurate;

40 parts of 4-aminophenyl sulfone;

7.4 parts of 2-carboxyethyl(phenyl)phosphinic acid (5wt% based on the total weight of the cured product)

Curing process: 70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 40 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 7.4 g of 2- carboxyethyl(phenyl)phosphinic acid was added as a flame retardant. The mixture was stirred at 120°C until 2-carboxyethyl(phenyl)phosphinic acid had completely dissolved, and then the mixture was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 16

A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

30 parts of tris(2,3-epoxypropyl) isocyanurate;

44 parts of 4-aminophenyl sulfone;

16 parts of the flame retardant compound of formula III described in Example 2, that is, the product of 2-carboxyethyl(phenyl)phosphinic acid and glycidol (10wt% based on the total weight of the cured product)

Curing process:

70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 44 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 16 g of the flame retardant compound of formula III described in Example 2, that is, the product of 2-carboxyethyl(phenyl)phosphinic acid and glycidol was added as a flame retardant. The mixture was stirred at 120°C until a homogeneous solution was obtained, and then the solution was transferred in to mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 17

A curable epoxy resin composition was made by mixing:

50 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

50 parts of 4,4'-methylenebis(N,N-diglycidylaniline);

48 parts of 4-aminophenyl sulfone;

16.5 parts of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol (10wt% based on the total weight of the cured product)

Curing process:

50 g of high purity bisphenol A diglycidylether (D.E.R. 332), 50 g of 4,4'- methylenebis(N,N-digylcidylaniline), and 48 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 16.5 g of the flame retardant compound of formula II described in Example 1 , that is, product of phenylphosphonic acid and glycidol was added as a flame retardant. The mixture was stirred at 120°C until a homogeneous solution was obtained, and then the solution was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Viscosity LOI UL94 p-HRR THR TSP Tg

(mPa-s at 80°C) (%) (3.2±0.3 mm) (kW/m ² ) (MJ/m ² ) (m ² ) (°C)

<30 33.7 VO 463 58 17 229 Example 18

A curable epoxy resin composition was made by mixing:

50 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

50 parts of N,N-diglycidyl-4-glycidyloxyaniline;

50 parts of 4-aminophenyl sulfone;

16 parts of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol (10wt% based on the total weight of the cured product)

Curing process:

50 g of high purity bisphenol A diglycidylether (D.E.R. 332), 50 g of N,N- digylcidyl-4-glycidyloxyaniline, and 50 g of 4-aminophenyl sulfone was mixed at 120oC by removal of air bubbles and moisture under vacuum. 16 g of the flame retardant compound of formula II described in Example 1 , that is, the product of phenylphosphonic acid and glycidol was added as a flame retardant. The mixture was stirred at 120oC until a homogeneous solution was obtained, and then the solution was transferred into mold and cured at 150oC for 1 hour, 180oC for 2 hours, and finally postcured at 200oC for 1 hour.

Example 19

A curable epoxy resin composition was made by mixing:

70 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

30 parts of tris(2,3-epoxypropyl) isocyanurate; 44 parts of 4-aminophenyl sulfone;

16 parts of the flame retardant compound of formula V described in Example 4, that is, the product of phenylphosphonic acid and phenylene diisocyanate (10wt% based on the total weight of the cured product)

Curing process:

70 g of high purity bisphenol A diglycidylether (D.E.R. 332), 30 g of tris(2,3- epoxypropyl) isocyanurate, and 44 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 16 g of the flame retardant compound of formula V described in Example 4, that is, the product of phenylphosphonic acid and phenylene dissocyanate was added as a flame retardant. The mixture was stirred at 120°C until a homogeneous solution was obtained, and then the solution was transferred in to mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Example 20 A curable epoxy resin composition was made by mixing:

50 parts by weight of high purity bisphenol A diglycidylether (D.E.R. 332);

50 parts of 4,4'-methylenebis(N,N-diglycidylaniline);

48 parts of 4-aminophenyl sulfone;

16 parts of the flame retardant compound of formula V described in Example 4, that is, the product of phenylphosphonic acid and phenylene diisocyanate (10wt% based on the total weight of the cured product)

Curing process: 50 g of high purity bisphenol A diglycidylether (D.E.R. 332), 50 g of 4, 4'- methylenebis(N,N-digylcidylaniline), and 48 g of 4-aminophenyl sulfone was mixed at 120°C by removal of air bubbles and moisture under vacuum. 16 g of the flame retardant compound of formula V described in Example 4, that is, the product of phenylphosphonic acid and phenylene diisocyanate was added as a flame retardant. The mixture was stirred at 120°C until a homogeneous solution was obtained, and then the solution was transferred into mold and cured at 150°C for 1 hour, 180°C for 2 hours, and finally postcured at 200°C for 1 hour.

Viscosity LOI UL94 p-HRR THR TSP Tg

(mPa-s at 80°C) (%) (3.2±0.3 mm) (kW/m ² ) (MJ/m ² ) (m ² ) (°C)

<30 29.7 VO 563 69 23 208