Anhydrous curing agent composition, method for producing same and use for curing epoxy resins

Abstract

An anhydrous curing agent composition contains: a) an adduct of 2-methylbutadiene-1,3 and maleic anhydride (MAH), including 4-methyltetrahydrophthalic anhydride (4-MTHPA), in an amount of from 50 to 90 parts by mass, b) an adduct of trans-1,3-pentadiene and MAH, including 3-methyltetrahydrophthalic anhydride (3-MTHPA), in an amount of from 10 to 40 parts by mass, and c) an adduct of 1,3-cyclopentadiene and MAH, including 5-norbornene-endo-2,3-dicarboxylic anhydride, in an amount of from 2.6 to 7 parts by mass. Also proposed are a method for producing said composition and a use of said composition to cure epoxy resins. The composition is characterized by a consistently liquid state and a solidification temperature of not more than -20°C, inclusive, and also makes it possible to increase the strength properties of epoxy resins produced using the claimed composition.

Description

[0001] COMPOSITION OF ANHYDRIDE HARDENERS, METHOD OF ITS PRODUCTION AND ITS APPLICATION FOR CURING EPOXY RESINS

[0002] Field of technology to which the invention relates

[0003] The present invention relates to a composition of anhydride hardeners, as well as to an improved method for producing a composition of anhydride hardeners. Such a composition of anhydride hardeners can be used for polymerizing an epoxy binder, synthesizing unsaturated esters and polyesters.

[0004] State of the art

[0005] According to the state of the art, the main method for obtaining anhydrides of dibasic carboxylic acids is the Diels-Alder reaction, which occurs during the interaction of maleic anhydride and a diene reactive with it.

[0006] The main requirement for hardeners of epoxy resins based on anhydrides is to ensure a stable liquid state at the temperature of transportation and operation of the hardener. Compliance with this requirement allows mixing the hardener without an additional preliminary stage of heating it for the purpose of melting it.

[0007] FR 1600836 (Hitachi Chemical Company LTD, published 08.03.1970) discloses a method for producing methyl-1,2,3,6-tetrahydrophthalic anhydride from the C4-C6 fraction of hydrocarbons of pyrolysis products by a selective Diels-Alder reaction between maleic anhydride with isoprene and trans-1,3-pentadiene. To prevent the formation of solid reaction products and further separation, the content of cyclopentadiene in the hydrocarbon mixture does not exceed 0.5 wt%.

[0008] From US 3976590 (Yax Emile, Zander Mechthild, published 24.08.1976) a mixture of anhydrides of homologues of tetrahydrophthalic anhydride with a melting point from 40 to 60°C is known, consisting of endomethylenetetrahydrophthalic anhydride, 4-methyltetrahydrophthalic anhydride and 3-methyltetrahydrophthalic anhydride and obtained by the interaction of a diene-containing Cd fraction of hydrocarbons with maleic anhydride. From SU 308006 (published 03.05.1972) it is known that isomerization of a mixture of 3-methyltetrahydrophthalic anhydride and 4-methyltetrahydrophthalic anhydride leads to stabilization of the liquid state of the mixture due to the formation of endo- and exo-isomers of the corresponding anhydrides.

[0009] The essence of the invention

[0010] The present invention is based on the task of proposing stable liquid anhydride hardeners that would satisfy the requirements for the efficiency of their use in the production of finished products.

[0011] The technical result consists in obtaining a composition of anhydride hardeners with a solidification temperature of no higher than -20°C inclusive.

[0012] Another technical result consists in increasing the strength properties of cured epoxy resins obtained during the curing process using the composition proposed in the invention.

[0013] An additional technical result consists in reducing energy costs during transportation to the consumer and during the operation of the anhydride hardener composition.

[0014] The specified technical problem is solved and the specified technical result is achieved by using heteropoly acids as catalysts for the structural isomerization of adducts of the interaction of by-products of hydrocarbon raw material pyrolysis with maleic anhydride (hereinafter referred to as MAH) and purification of the resulting mixture of diene adducts and MAH by distillation under heating and reduced pressure using a method known from the prior art, where the by-products of hydrocarbon raw material pyrolysis are predominantly a mixture of diene hydrocarbons with a number of carbon atoms in the molecule structure from 4 to 6, preferably 5 (diene-containing SD fraction of hydrocarbons). The diene-containing SD fraction of hydrocarbons according to the proposed method predominantly contains the following active dienes: 2-methylbutadiene-1,3, trans-1,3-pentadiene, 1,3-cyclopentadiene, 1,3-butadiene.

[0015] The present inventors have unexpectedly found that the use of heteropoly acids as structural isomerization catalysts significantly reduces the pour point of the anhydride hardener composition. Detailed description of the invention

[0016] The following is a description of the objects of the present invention and various embodiments thereof.

[0017] The first object of the present invention is a composition of anhydride hardeners for curing epoxy resins, which is a liquid mixture with the following components: a) an adduct of 2-methylbutadiene-1,3 and MAN, including 4-methyltetrahydrophthalic anhydride, in an amount of 50 to 90 parts by weight, b) an adduct of trans-1,3-pentadiene and MAN, including 3-methyltetrahydrophthalic anhydride, in an amount of 10 to 40 parts by weight; c) an adduct of 1,3-cyclopentadiene and MAN, including 5-norbornene-endo-2,3-dicarboxylic anhydride, in an amount of 2.6 to 7 parts by weight.

[0018] 4-Methyltetrahydrophthalic anhydride (hereinafter referred to as 4-MTHPA) is used in an amount of 50 to 90 parts by weight, preferably 55 to 80 parts by weight, most preferably 60 to 70 parts by weight.

[0019] 4-MTHF is formed by the interaction of 2-methylbutadiene-1,3 in the diene-containing Cs fraction of hydrocarbons and MAN with subsequent catalytic isomerization predominantly in the form of two structural isomers - 4-methyl-D4-tetrahydrophthalic (4-M-D4-THF) and 4-methyl-D3-tetrahydrophthalic (4-M-D3-THF) anhydrides. In one embodiment of the invention, the anhydride hardener composition contains 4-M-D3-THF in an amount of 50 to 80 wt.%, preferably 60 to 77 wt.%, most preferably 70 to 75 wt.%, in each case based on the total amount of 4-MTHF isomers. A decrease in the content of 4-M-DZ-THFA leads to an increase in the freezing temperature, and the upper limit of more than 80 wt.% is not achievable, since thermodynamic equilibrium between the isomeric forms occurs.

[0020] 3-Methyltetrahydrophthalic anhydride (hereinafter referred to as 3-MTHPA) is used in an amount of 10 to 40 parts by weight, preferably 15 to 37 parts by weight, most preferably 25 to 35 parts by weight. 3-MTHPA is formed by the interaction of trans-1,3-pentadiene in the diene-containing Cs fraction of hydrocarbons and MAN, followed by catalytic isomerization. 5-Norbornene-endo-2,3-dicarboxylic anhydride (or endic anhydride) is a product of the interaction of 1,3-cyclopentadiene in the diene-containing Cs fraction of hydrocarbons and MAN. 5-Norbornene-endo-2,3-dicarboxylic anhydride is used in an amount of 2.6 to 7 parts by weight, preferably 2.8 to 6 parts by weight. parts, most preferably from 3 to 5 parts by weight. Excess content of 5-norbornene-endo-2, 3-dicarboxylic anhydride more than 7 parts by weight.parts in the composition proposed in the invention would lead to an increase in the solidification temperature of the hardener due to the precipitation of an insoluble precipitate, which is 5-norbornene-endo-2,3-dicarboxylic anhydride, as well as to additional energy costs to achieve homogeneity of the anhydride hardener composition by melting. When the content of 5-norbornene-endo-2,3-dicarboxylic anhydride in the anhydride hardener composition is less than 2.6 mass parts, the physical and mechanical properties, in particular the strength characteristics of the cured epoxy resins, deteriorate.

[0021] The anhydride hardener composition in one embodiment of the invention optionally contains anhydrides selected from phthalic anhydride, maleic anhydride, trimellitic anhydride, methyl hexahydrophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride and mixtures thereof.

[0022] The anhydride hardener composition in one embodiment of the invention comprises antioxidants selected from the group of compounds comprising alkylhydroxybenzenes, preferably 2,2-methylenebis(4-methyl-6-tert-butylphenol) and 4-tert-butylbenzene-1,2-diol. The antioxidant content is typically from 0.01 to 1 parts by weight, preferably from 0.05 to 0.5 parts by weight, most preferably from 0.1 to 0.2 parts by weight.

[0023] The anhydride hardener composition in one embodiment of the invention may contain cycloalkenes selected from the group of compounds comprising dicyclopentadiene and tricyclo-3-decene, in a total amount of no more than 0.02 parts by weight, preferably no more than 0.01 parts by weight, most preferably no more than 0.005 parts by weight. The content of cycloalkenes greater than 0.02 parts by weight in the anhydride hardener composition leads to deterioration of the physical and mechanical properties of the cured epoxy resins, in particular the tensile strength, as illustrated in the examples.

[0024] The anhydride hardener composition in one embodiment of the invention may contain oligomeric anhydrides selected from the group of compounds comprising a mixture of adducts of 1,3-cyclopentadiene and methyltetrahydrophthalic anhydride, 1,3-cyclopentadiene and 5-norbornene-endo-2,3-dicarboxylic anhydride, in a total amount of from 1 to 15 parts by weight, preferably from 5 to 12 parts by weight, most preferably from 7 to 10 parts by weight.

[0025] The second object of the present invention is a method for producing the above-described composition of anhydride hardeners proposed in the invention.

[0026] This method for obtaining a composition of anhydride hardeners consists of performing the following stages: a) the diene-containing Cd fraction of hydrocarbons and MAN are mixed at a temperature in the range from 40 to 120°C to obtain a reaction mixture of adducts of dienes with MAN, b) the reaction mixture of adducts of dienes with MAN obtained in stage a) is purified by heating, c) the reaction mixture of adducts of dienes with MAN purified in stage b) is subjected to isomerization in the presence of a heteropoly acid as a catalyst to obtain a composition of anhydride hardeners.

[0027] The diene-containing SD fraction of hydrocarbons in one embodiment of the invention contains hydrocarbons with a number of carbon atoms in the structure of the molecule from 4 to 6, preferably 5. The diene-containing SD fraction of hydrocarbons contains 1,3-cyclopentadiene, which, when interacting with dienophiles, forms undesirable reaction products, in particular 5-norbornene-endo-2,3-dicarboxylic anhydride, as well as dicyclopentadiene, tricyclo-3-decene. Under the influence of elevated temperature, in particular during the curing of the epoxy binder, dicyclopentadiene and tricyclo-3-decene are destroyed to monomers, releasing low-boiling SD hydrocarbons. In this case, micropores are formed in the polymer structure, which lead to deterioration of the physicomechanical characteristics of the cured epoxy binder.In order to reduce the content of 1,3-cyclopentadiene, as a rule, its dimerization is carried out by preliminary processing of pyrolysis by-products, which involves heating with subsequent distillation of light hydrocarbons and obtaining a diene-containing Cd-fraction of hydrocarbons with a reduced content of 1,3-cyclopentadiene.

[0028] The amount of 2-methylbutadiene-1,3 in the diene-containing Cd fraction of hydrocarbons in one embodiment of the invention is from 30 to 70 parts by weight, preferably from 40 to 60 parts by weight.

[0029] The amount of trans-1,3-pentadiene in the diene-containing Cd fraction of hydrocarbons in one embodiment of the invention is from 10 to 40 parts by weight, preferably from 15 to 30 parts by weight.

[0030] The amount of 1,3-cyclopentadiene in the diene-containing Cd fraction of hydrocarbons in one embodiment of the invention is from 1 to 15 parts by weight, preferably from 5 to 10 parts by weight.

[0031] MAI can generally be loaded into the reactor as a melt or in a solid phase.

[0032] The reactor is a capacitive apparatus known from the prior art, equipped with a heat exchange jacket and a mixing device.

[0033] The mixing of MAN and the diene-containing Cd fraction of hydrocarbons in stage a) is carried out at a temperature of 40 to 120°C, preferably 50 to 110°C, most preferably 60 to 100°C. The temperature of the reaction mixture is usually maintained by any method known from the prior art, in particular by heat exchange with a coolant through the reactor wall or by evaporation of a portion of the reaction mass.

[0034] In one embodiment of the invention, the mixing of MAN and the diene-containing SD fraction in step a) is carried out with intensive stirring, ensuring a high reaction rate. In one embodiment of the invention, in step a), an antioxidant known from the prior art is additionally introduced into the reactor in an amount of 0.01 to 1 parts by weight, preferably 0.05 to 0.5 parts by weight, most preferably 0.1 to 0.2 parts by weight. The antioxidants are selected from a group of compounds including alkylhydroxybenzenes, preferably 2,2-methylene-bis(4-methyl-6-tert-butylphenol) and 4-tert-butylbenzene-1,2-diol. After adding the entire amount of the diene-containing SD fraction of hydrocarbons, the reaction mass in step a) is usually maintained with constant stirring until the evolution of heat ceases. The duration of such maintenance is usually from 0.25 to 3 hours, preferably from 0.5 to 2 hours.

[0035] After completion of the reaction, the resulting reaction mixture of diene adducts with MAN is purified from unreacted reagents in step b) by heating the reaction mass to a temperature in the range from 160 to 220°C, preferably from 180 to 210°C, most preferably from 190 to 200°C, and distilling off the cycloalkenes, optionally at a pressure in the range from 700 mbar to 1200 mbar, preferably from 800 mbar to 1100 mbar, most preferably from 900 mbar to 1000 mbar.

[0036] Next, at stage c), catalytic isomerization of the reaction mixture of MAN adducts and the diene-containing Cd-fraction of hydrocarbons purified at stage b) is carried out. Isomerization is carried out in order to reduce the freezing point and stabilize the liquid state of the product mixture containing isomers of diene adducts with maleic anhydride.

[0037] Heteropoly acids of the general formula Hk[X n+ MiO m ]^ n ' 8^pH2O, where X is selected from the group of elements including phosphorus, silicon, arsenic, preferably silicon,

[0038] M is selected from the group of elements comprising molybdenum, tungsten, titanium, vanadium, preferably tungsten, k is a number from 3 to 10, preferably from 7 to 8, 1 is a number from 10 to 15, preferably from 11 to 13, w is a number from 38 to 44, preferably from 40 to 42, n is a number from 0 to 20, preferably from 1 to 10, p is a number from 0 to 7, preferably from 1 to 5.

[0039] The amount of isomerization catalyst in step c) in one embodiment of the invention is from 250 to 750 mass ppm, more preferably from 400 to 600 mass ppm.

[0040] The isomerization temperature in step c) is typically from 160 to 220°C, preferably from 180 to 210°C, most preferably from 190 to 200°C.

[0041] In one embodiment of the method for producing an anhydride hardener composition proposed in the invention, it is preferable to simultaneously carry out distillation and isomerization at the above-discussed stages b) and c), respectively.

[0042] To complete the isomerization reaction and remove the by-products of cycloalkene decomposition, the anhydride hardener composition obtained in stage c) is usually maintained at the reaction temperature for a period of time ranging from 0.5 to 12 hours.

[0043] The anhydride hardener composition obtained in step c) containing isomers of diene adducts with MAI is then optionally subjected to distillation to separate high-boiling compounds, including compounds of the oligomeric anhydride group, in particular from the adduct of 1,3-cyclopentadiene and methyltetrahydrophthalic anhydride and the adduct of 1,3-cyclopentadiene and methylenetetrahydrophthalic anhydride, and from the catalyst residues.

[0044] The distillation is carried out by vacuum distillation under reduced pressure in a manner known from the prior art. The pressure is usually from 15 to 60 mbar, preferably from 25 to 35 mbar. This stage allows for the complete removal of oligomeric anhydrides from the composition of the anhydride hardener composition obtained according to the invention and for its viscosity to be reduced, which ensures the acceleration of the homogenization of the hardener / resin mixture during the preparation of the epoxy resin composition.

[0045] The process of obtaining the anhydride hardener composition is usually carried out in a periodic or continuous mode with the supply of raw material flows of maleic anhydride and diene-containing Cs-fraction of hydrocarbons in countercurrent. The anhydride hardener composition obtained by the method proposed in the invention has a solidification temperature of no higher than -20°C inclusive, which allows maintaining a stable liquid state during transportation to the consumer and during operation for the purpose of curing epoxy resins without an additional heating stage, as well as increasing the strength properties of the final products.

[0046] A third object of the present invention is the use of the anhydride hardener composition described above or obtained by the method described above for curing epoxy resins.

[0047] The epoxy resin is cured by mixing it with the anhydride hardener composition proposed in the invention under stirring conditions until the resulting mixture is homogenized. In a preferred embodiment, mixing is carried out sequentially in any order of adding the components to be mixed. The weight ratio between the anhydride hardener composition and the epoxy resin is preferably from 0.75 to 0.95, most preferably from 0.8 to 0.85. In a preferred embodiment, polymerization accelerators selected from the group of amines, preferably tertiary amines, most preferably 2,4,6-tris(dimethylaminomethyl)phenol (grade UP-606 / 2) are added to the resulting mixture. The mixture is thoroughly stirred until homogeneous. In order to obtain finished products, the resulting mixture is formed by filling fluoroplastic forms and maintained at a temperature ranging from 120 to 150°C for a period of time ranging from 4 to 48 hours, followed by cooling.

[0048] Implementation of the invention

[0049] Tensile strength tests are carried out in accordance with ASTM D 638 at a speed of 5.1 mm / min.

[0050] To determine the pour point, a sample of at least 50 ml is kept in a thermostatically controlled container for at least 72 hours at a given temperature. The temperature is changed in 5°C increments from 25°C to -25°C. Visual assessment of the appearance is carried out every 24 hours. The test is considered to be failed if the sample becomes cloudy. Dynamic viscosity is determined in accordance with ASTM D 7042.

[0051] Example 1 (according to the invention)

[0052] 100 parts by weight of crystalline MAI and 0.1 parts by weight of an antioxidant, which is 2,2-methylene-bis(4-methyl-6-tert-butylphenol), are placed in a metal reactor equipped with a stirrer. 50 parts by weight of 2-methylbutadiene-1,3, 20 parts by weight of trans-1,3-pentadiene, 8 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing Cs-fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 60°C and with stirring for 2 hours. Then 500 parts by weight of h.p. / million of crystalline hydrate of silicotungstic acid of formula H^SiW^C^o^^O and the reaction mass is stirred for another 6 hours at a temperature of 200°C and a pressure of 900 mbar under conditions of simultaneous isomerization of adducts of dienes with MAI and purification by distillation of by-products of decomposition of cycloalkenes. In this way a stable liquid product of dark brown color is obtained.

[0053] This product is a composition of anhydride hardeners, which contains 60 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 72% by weight based on the total amount of 4-MTHF isomers, 27.5 parts by weight of 3-MTHF, 3 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride, 9 parts by weight of oligomeric anhydrides, 0.019 parts by weight of cycloalkenes and 0.1 parts by weight of antioxidant.

[0054] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0055] Example 2 (according to the invention)

[0056] In this example, the process is similar to example 1, except that the product after isomerization in stage c) is distilled at a pressure of 25 mbar. In this way, a stable, liquid, colorless product is obtained.

[0057] This product is a composition of anhydride hardeners which contains 68 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 70% by weight based on the total amount of 4-MTHF isomers, 29 parts by weight of 3-MTHF, 2.6 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.01 parts by weight of cycloalkenes.

[0058] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0059] Example 3 (according to the invention)

[0060] 100 parts by weight of crystalline MAN and 0.2 parts by weight of an antioxidant, which is 2,2-methylene-bis(4-methyl-6-tert-butylphenol), are placed in a metal reactor equipped with a stirrer. 53 parts by weight of 2-methylbutadiene-1,3, 23 parts by weight of trans-1,3-pentadiene, 7 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing Cd fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 55°C and with stirring for 3 hours. Then 600 parts by weight of 1,3-methylbutadiene-1,3, 23 parts by weight of trans-1,3-pentadiene, and 7 parts by weight of 1,3-cyclopentadiene are added to the reactor as part of the diene-containing Cd fraction of hydrocarbons. h.p. / million of phosphotungstic acid crystal hydrate of formula Н3СТЦУ^О^'бНгО and the reaction mass is stirred for another 6 hours at a temperature of 195°С and at a pressure of 950 mbar under conditions of simultaneous isomerization of diene adducts with MAN and purification by distillation of by-products of cycloalkene decomposition. Then the product obtained after isomerization in stage c) is distilled at a pressure of 25 mbar. In this way a stable liquid colorless product is obtained.

[0061] This product is a composition of anhydride curing agents which contains 64 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 72% by weight based on the total amount of 4-MTHF isomers, 32 parts by weight of 3-MTHF, 3.2 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.012 parts by weight of cycloalkenes.

[0062] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0063] Example 4 (comparative)

[0064] The anhydride hardener composition is obtained similarly to example 2, except that purification by distillation of cycloalkenes is not carried out. In this way, a stable liquid colorless product is obtained.

[0065] This product is a composition of anhydride hardeners, which contains 63 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 73% by weight based on the total amount of 4-MTHF isomers, 33 parts by weight of 3-MTHF, 3.1 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.03 parts by weight of cycloalkenes.

[0066] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0067] Example 5 (according to the invention)

[0068] 100 parts by weight of crystalline MAN and 0.2 parts by weight of an antioxidant, which is 2,2-methylene-bis(4-methyl-6-tert-butylphenol), are placed in a metal reactor equipped with a stirrer. 45 parts by weight of 2-methylbutadiene-1,3, 27 parts by weight of trans-1,3-pentadiene and 9 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing Cd fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 100°C and with stirring for 3 hours. Then 600 parts by weight of 1,3-methylbutadiene-1,3, 27 parts by weight of trans-1,3-pentadiene and 9 parts by weight of 1,3-cyclopentadiene are added to the reactor as part of the diene-containing Cd fraction of hydrocarbons. The reaction is carried out at a temperature of 100°C and with stirring for 3 hours. Then 600 parts by weight of 1,3-methylbutadiene-6-tert-butylphenol are added. h.p. / million of crystalline hydrate of silicotungstic acid of formula H^SiWi O^' HO and the reaction mass is stirred for another 6 hours at a temperature of 195°C and a pressure of 950 mbar under conditions of simultaneous isomerization of adducts of dienes with MAN and purification by distillation of by-products of decomposition of cycloalkenes. Then the product obtained after isomerization in stage c) is distilled at a pressure of 25 mbar. In this way a stable liquid colorless product is obtained.

[0069] This product is a composition of anhydride curing agents which contains 59 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 74% by weight based on the total amount of 4-MTHF isomers, 35 parts by weight of 3-MTHF, 5 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.011 parts by weight of cycloalkenes.

[0070] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0071] Example 6 (comparative)

[0072] The anhydride hardener composition is obtained similarly to Example 3, except that the amount of 1,3-cyclopentadiene is 15 parts by weight. In this way, a stable liquid colorless product is obtained.

[0073] This product is a composition of anhydride curing agents which contains 64 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 72% by weight based on the total amount of 4-MTHF isomers, 27 parts by weight of 3-MTHF, 8 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.012 parts by weight of cycloalkenes.

[0074] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0075] Example 7 (comparative)

[0076] The anhydride hardener composition is obtained similarly to Example 3, except that the amount of 2-methylbutadiene-1,3 is 50 parts by weight, the amount of trans-1,3-pentadiene is 20 parts by weight, and the amount of 1,3-cyclopentadiene is 0 parts by weight. In this way, a stable liquid colorless product is obtained.

[0077] This product is a composition of anhydride curing agents which contains 72 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 70% by weight based on the total amount of 4-MTHF isomers, 27 parts by weight of 3-MTHF, 0 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0 parts by weight of cycloalkenes.

[0078] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0079] Example 8 (according to the invention)

[0080] 100 parts by weight of crystalline MAN and 0.02 parts by weight of an antioxidant, which is 4-(1,1-dimethylethyl)-1,2-benzenediol, are placed in a metal reactor equipped with a stirrer. 30 parts by weight of 2-methylbutadiene-1,3, 10 parts by weight of trans-1,3-pentadiene and 2 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing C5 fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 65 °C and with stirring for 20 min. Then 300 parts by weight of 1,3-methylbutadiene-1,3, 10 parts by weight of trans-1,3-pentadiene and 2 parts by weight of 1,3-cyclopentadiene are added to the reactor as part of the diene-containing C5 fraction of hydrocarbons ... h.p. / million of crystalline hydrate of silicotungstic acid of formula H^SiWi C^o^HO and the reaction mass is stirred for another 12 hours at a temperature of 165°C and a pressure of 1100 mbar under conditions of simultaneous isomerization of adducts of dienes with MAN and purification by distillation of by-products of cycloalkene decomposition. Then the product obtained after isomerization in stage c) is distilled at a pressure of 16 mbar. In this way a stable liquid colorless product is obtained.This product is a composition of anhydride hardeners, which contains 70 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 55% by weight based on the total amount of 4-MTHF isomers, 25 parts by weight of 3-MTHF, 4.8 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.005 parts by weight of cycloalkenes.

[0081] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0082] Example 9 (according to the invention)

[0083] 100 parts by weight of crystalline MAN and 0.45 parts by weight of an antioxidant, which is 4-(1,1-dimethylethyl)-1,2-benzenediol, are placed in a metal reactor equipped with a stirrer. 68 parts by weight of 2-methylbutadiene-1,3, 37 parts by weight of trans-1,3-pentadiene and 12 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing C5 fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 95°C and with stirring for 30 min. Then 750 parts by weight of 1,3-methylbutadiene-1,3, 37 parts by weight of trans-1,3-pentadiene and 12 parts by weight of 1,3-cyclopentadiene are added to the reactor as part of the diene-containing C5 fraction of hydrocarbons ... h.p. / million of crystalline hydrate of silicotungstic acid of formula H^SiWi O^'SH O and the reaction mass is stirred for another 3 hours at a temperature of 215°C and a pressure of 750 mbar under conditions of simultaneous isomerization of adducts of dienes with MAN and purification by distillation of by-products of decomposition of cycloalkenes. Then the product obtained after isomerization in stage c) is distilled at a pressure of 55 mbar. In this way a stable liquid colorless product is obtained.

[0084] This product is a composition of anhydride curing agents which contains 60 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 76% by weight based on the total amount of 4-MTHF isomers, 33 parts by weight of 3-MTHF, 6.5 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.045 parts by weight of cycloalkenes.

[0085] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0086] Example 10 (according to the invention)

[0087] 100 parts by weight of crystalline MAN and 0.2 parts by weight of an antioxidant, which is 2,2-methylene-bis(4-methyl-6-tert-butylphenol), are placed in a metal reactor equipped with a stirrer. 53 parts by weight of 2-methylbutadiene-1,3, 23 parts by weight of trans-1,3-ientadiene, 7 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing Cs-fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 55°C and with stirring for 3 hours. Then 600 parts by weight of 1,3-methylbutadiene-1,3, 23 parts by weight of trans-1,3-ientadiene, and 7 parts by weight of 1,3-cyclopentadiene are added to the reactor as part of the diene-containing Cs-fraction of hydrocarbons. h. / million of phosphomolybdic acid crystal hydrate of formula H3[P(MO3O10)4]*5H2O. The reaction mass is stirred for another 12 hours at 200°C and 950 mbar under conditions of simultaneous isomerization of diene adducts with MAN and purification by distillation of cycloalkene decomposition by-products. Then the product obtained after isomerization in stage c) is distilled at 25 mbar. In this way, a stable, liquid, colorless product is obtained.

[0088] This product is a composition of anhydride curing agents which contains 65 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 70% by weight based on the total amount of 4-MTHF isomers, 32 parts by weight of 3-MTHF, 2.2 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.01 parts by weight of cycloalkenes.

[0089] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0090] Example 11 (according to the invention)

[0091] 100 parts by weight of crystalline MAN and 0.2 parts by weight of the antioxidant 2,2-methylene-bis(4-methyl-6-tert-butylphenol) are placed in a metal reactor equipped with a stirrer. 53 parts by weight of 2-methylbutadiene-1,3, 23 parts by weight of trans-1,3-pentadiene, 7 parts by weight of 1,3-cyclopentadiene in the composition of the diene-containing Cd fraction of hydrocarbons are added to the reactor. The reaction is carried out at a temperature of 55 °C and with stirring for 3 h. Then 600 parts by weight of 2-methylbutadiene-1,3, 23 parts by weight of trans-1,3-pentadiene, and 7 parts by weight of 1,3-cyclopentadiene are added to the reactor as part of the diene-containing Cd fraction of hydrocarbons. The reaction is carried out at a temperature of 55 °C and with stirring for 3 h. Then 600 parts by weight of 2-methylbutadiene-1,3, 23 parts by weight of trans-1,3-pentadiene, and 7 parts by weight of 1,3-cyclopentadiene are added to the reactor in the composition of the diene-containing Cd fraction of hydrocarbons. h.p. / million of phosphonovandium molybdic acid crystal hydrate of formula NDPROMonVO^' O and the reaction mass is stirred for another 12 hours at a temperature of 190°C and a pressure of 950 mbar under conditions of simultaneous isomerization of diene adducts with MAN and purification by distillation of by-products of cycloalkene decomposition. Then the product obtained after isomerization in stage c) is distilled at a pressure of 25 mbar. In this way a stable liquid colorless product is obtained.

[0092] This product is a composition of anhydride curing agents which contains 65 parts by weight of 4-MTHF, including the isomer 4-M-D3-THF in an amount of 67% by weight based on the total amount of 4-MTHF isomers, 32 parts by weight of 3-MTHF, 2.2 parts by weight of 5-norbornene-endo-2,3-dicarboxylic anhydride and 0.01 parts by weight of cycloalkenes.

[0093] The characteristics of the obtained composition are given in Table 1. The strength of the cured epoxy resin is presented in Table 2.

[0094] Table 1: Properties of anhydride hardener compositions

[0095] Table 2: Properties of cured epoxy resin

[0096] As follows from examples 1-11, the implementation of the invention under the stated conditions ensures the production of a composition of anhydride hardeners that is stably liquid at negative temperatures. Failure to comply with the stated conditions leads to the production of a composition of anhydride hardeners with an increased solidification temperature (example 6) or to a decrease in the strength properties of the cured epoxy resins obtained during the curing process using the compositions from examples 4 and 7.

Claims

CLAUSES OF THE INVENTION 1. A composition of anhydride hardeners for curing epoxy resins with the following components: a) an adduct of 2-methylbutadiene-1,3 and maleic anhydride (MAI), including 4-methyltetrahydrophthalic anhydride (4-MTHPA), in an amount of 50 to 90 parts by weight, b) an adduct of trans-1,3-pentadiene and MAI, including 3-methyltetrahydrophthalic anhydride (3-MTHPA), in an amount of 10 to 40 parts by weight, c) an adduct of 1,3-cyclopentadiene and MAI, including 5-norbornene-endo-2,3-dicarboxylic anhydride, in an amount of 2.6 to 7 parts by weight.

2. The anhydride hardener composition according to claim 1, in which 4-MTHF is contained in an amount of 55 to 80 parts by weight, preferably 60 to 70 parts by weight.

3. The anhydride hardener composition according to claim 1, wherein 4-MTHF comprises the isomer 4-M-DZ-THHF, the content of which is from 50 to 80 wt.%, preferably from 60 to 77 wt.%, most preferably from 70 to 75 wt.%, in each case based on the total amount of 4-MTHF isomers.

4. The anhydride hardener composition according to claim 1, in which 3-MTHF is contained in an amount of 15 to 37 parts by weight, preferably 25 to 35 parts by weight.

5. The anhydride hardener composition according to claim 1, in which the content of 5-norbornene-endo-2,3-dicarboxylic anhydride is from 2.8 to 6 parts by weight, preferably from 3 to 5 parts by weight.

6. The anhydride hardener composition according to claim 1, which further comprises anhydrides selected from phthalic anhydride, maleic anhydride, trimellitic anhydride, methyl hexahydrophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride and mixtures thereof.

7. The anhydride hardener composition according to claim 1, which further comprises antioxidants selected from the group of compounds comprising alkylhydroxybenzenes, preferably 2,2-methylene-bis(4-methyl-6-tert-butylphenol) and 4-tert-butylbenzene-1,2-diol.

8. The composition according to claim 7, wherein the antioxidant content is from 0.01 to 1 part by weight, preferably from 0.05 to 0.5 parts by weight, most preferably from 0.1 to 0.2 parts by weight.

9. The anhydride hardener composition according to claim 1, which further comprises cycloalkenes selected from the group of compounds including dicyclopentadiene and tricyclo-3-decene.

10. The anhydride hardener composition according to claim 9, wherein the content of cycloalkenes is no more than 0.02 parts by weight, preferably no more than 0.01 parts by weight, most preferably no more than 0.005 parts by weight.

11. The anhydride hardener composition according to claim 1, which further comprises oligomeric anhydrides selected from the group of compounds comprising a mixture of adducts of 1,3-cyclopentadiene and methyltetrahydrophthalic anhydride, 1,3-cyclopentadiene and 5-norbornene-endo-2,3-dicarboxylic anhydride.

12. The anhydride hardener composition according to claim 11, wherein the content of oligomeric anhydrides is from 1 to 15 parts by weight, preferably from 5 to 12 parts by weight, most preferably from 7 to 10 parts by weight.

13. A method for producing a composition of anhydride hardeners according to any of paragraphs 1-12, comprising performing the following steps: a) a diene-containing Cs-fraction of hydrocarbons and MAN are mixed at a temperature in the range from 40 to 120°C to obtain a reaction mixture of adducts of dienes with MAN, b) the reaction mixture of adducts of dienes with MAN obtained in step a) is purified by heating, c) the reaction mixture of adducts of dienes with MAN purified in step b) is subjected to isomerization in the presence of a heteropoly acid as a catalyst to obtain a composition of anhydride hardeners.

14. The method according to item 13, in the implementation of which a diene-containing Cs-fraction of hydrocarbons is used, containing hydrocarbons with a number of carbon atoms in the structure of the molecule from 4 to 6, preferably 5.

15. The method according to item 13, in the implementation of which a diene-containing Cd fraction of hydrocarbons is used, containing 2-methylbutadiene-1,3 in an amount of from 30 to 70 parts by weight, preferably from 40 to 60 parts by weight.

16. The method according to claim 13, in the implementation of which a diene-containing Cd fraction of hydrocarbons is used, containing trans-1,3-pentadiene in an amount of 10 to 40 parts by weight, preferably from 15 to 30 parts by weight.

17. The method according to item 13, in the implementation of which a diene-containing Cs-fraction of hydrocarbons is used, containing 1,3-cyclopentadiene in an amount of from 1 to 15 parts by weight, preferably from 5 to 10 parts by weight.

18. The method according to item 13, in which step a) is carried out at a temperature of 50 to 110°C, preferably 60 to 100°C.

19. The method according to claim 13, wherein in step a) an antioxidant is additionally added in an amount of 0.01 to 1 part by weight, preferably 0.05 to 0.5 parts by weight, most preferably 0.1 to 0.2 parts by weight.

20. The method according to claim 19, in which the antioxidants are selected from the group of compounds comprising alkylhydroxybenzenes, preferably 2,2-methylene-bis(4-methyl-6-tert-butylphenol) and 4-tert-butylbenzene-1,2-diol.

21. The method according to item 13, in which the holding time in step a) is from 0.25 to 3 hours, preferably from 0.5 to 2 hours.

22. The method according to item 13, in which the purification of the resulting reaction mixture of diene adducts with MAN in step b) is carried out at a temperature in the range from 160 to 220°C, preferably from 180 to 210°C, most preferably from 190 to 200°C.

23. The method according to claim 13, wherein step b) is carried out at a pressure in the range from 700 mbar to 1200 mbar, preferably from 800 mbar to 1100 mbar, most preferably from 900 mbar to 1000 mbar.

24. The method according to item 13, in the implementation of which heteropoly acids of the general formula H are used as an isomerization catalyst. k [X n+ MiO m ] (n ' 8) -pH2O, where X is selected from the group of elements comprising phosphorus, silicon, arsenic, preferably silicon, M is selected from the group of elements including molybdenum, tungsten, titanium, vanadium, preferably tungsten, k is a number from 3 to 10, preferably from 7 to 8, 1 represents a number from 10 to 15, preferably from 11 to 13, w represents a number from 38 to 44, preferably from 40 to 42, n represents a number from 0 to 20, preferably from 1 to 10, p represents a number from 0 to 7, preferably from 1 to 5.

25. The method according to claim 13, in which the isomerization catalyst is used in an amount of 250 to 750 mass parts per million, preferably 400 to 600 mass parts per million.

26. The method according to claim 13, in which the isomerization in step c) is carried out at a temperature in the range from 160 to 220°C, preferably from 180 to 210°C, most preferably from 190 to 200°C.

27. The method according to claim 13, in the implementation of which the composition of anhydride hardeners is obtained under conditions of simultaneous distillation and isomerization at stages b) and c), respectively.

28. The method according to item 13, in which the holding time at stage c) is from 0.5 to 12 hours.

29. The method according to item 13, in the course of which the anhydride hardener composition obtained in step c) is distilled.

30. The method according to claim 29, in which the distillation pressure is from 15 to 60 mbar, preferably from 25 to 35 mbar.

31. Use of an anhydride hardener composition according to any of paragraphs 1-12 or an anhydride hardener composition obtained by the method according to any of paragraphs 13-30 for curing epoxy resins.

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