WO2016119848A1

WO2016119848A1 - Method for the preparation of cycloaliphatic epoxy resins

Info

Publication number: WO2016119848A1
Application number: PCT/EP2015/051785
Authority: WO
Inventors: Ligang Zhao; Verónica De la Fuente; Marcos CHAS PEDREIRA; Aurora PEREZ BRIONES; Nélida GIMENO GORMAZ
Original assignee: Henkel Ag & Co. Kgaa
Priority date: 2015-01-29
Filing date: 2015-01-29
Publication date: 2016-08-04

Abstract

The present invention relates to a method for preparing a cycloaliphatic epoxy resin and the thus prepared cycloaliphatic epoxy resins. The method includes the oxidiation of a cycloalkene compound with hydrogen peroxide in the presence of a base, a stabilizer and acetonitrile to form the cycloaliphatic epoxy resin.

Description

..Method for the preparation of cycloaliphatic epoxy resins"

The present invention relates to a method for preparing a cycloaliphatic epoxy resin and the thus prepared cycloaliphatic epoxy resins.

Mono-, di- or poly-epoxide compounds have been used as plasticizers and/or stabilizers for polymers, especially for halogen-containing vinyl polymers, as intermediate products for organic syntheses and as starting material for the manufacture of plastic substances.

Epoxidation reactions of cycloaliphatic resins have traditionally been carried out using meta- chloroperoxybenzoic acid (m-CPBA) as oxidizing agent. Generally, mild reaction conditions are used, and relatively high yields may be obtained after about 1 to 18 hours, in particular when the substrate in low molecular weight bears an internal double bond and an ester function group. High processing costs, excess of oxidants and tedious work-up and purification, however, render this method unsuitable for industrial scale operations.

Alternative processes for epoxidation of cycloaliphatic resins involve the use of peracetic acid as oxidizing agent. Generally, the reactions are carried out at a temperature ranging from room temperature to 45 °C. Even though high yields have been reported using this process, one disadvantage of this process relates to a need to neutralize the acetic acid by-product that is produced. In some cases, some substrates or their functional groups are also not stable in such acid medium.

Epoxidation of cycloaliphatic resins has also been carried out using hydrogen peroxide as oxidant. Such processes may be carried out using a metal-catalyzed system or a metal-free system. Metal-catalyzed epoxidation processes using hydrogen peroxide as oxidant involve the use of metals, such as tungsten, aluminum, rhenium, molybdenum, vanadium, and iron, as catalysts. These processes suffer from drawbacks relating to color change in the resins produced, and the metal complex residue in resins might make themselves not suitable for many specific applications. Metal-free epoxidation processes using hydrogen peroxide as oxidant, on the other hand, usually require use of high temperatures in the range of 70 °C to 140 °C and presence of a catalyst or cocatalyst in the form of a phase transfer catalyst or an acid. One example of such a process includes the use of hydrogen peroxide, sodium chloride and cetyl dimethyl ammonium chloride as reagents.

Other reported epoxidation processes include use of a) t-BuOOH in the presence of a vanadium complex or a quaternary ammonium salt; b) urea with hydrogen peroxide; c) dimethyldioxirane; d) nucleophilic substitution; e) O3; and f) metal-02. These processes suffer from drawbacks such as moderate conversions and selectivities towards epoxides, as well as inefficient waste management. In view of the above, there exists a need for methods of preparing cycloaliphatic epoxy resins that address one or more of the above-mentioned problems.

The inventors of the present invention have now found that cycloaliphatic epoxy resins can be prepared by a process that avoids the known drawbacks by a method comprising the oxidiation of a cycloalkene compound with hydrogen peroxide in the presence of a base, a stabilizer and acetonitrile.

In a first aspect, the present invention therefore relates to a method for the preparation of a cycloaliphatic epoxy resin and includes the oxidiation of a cycloalkene compound with hydrogen peroxide in the presence of a base, a stabilizer and acetonitrile.

In a second aspect, the invention relates to a cycloaliphatic epoxy resin prepared according to a method according to the first aspect.

Using this method the oxidation of a cycloalkene compound can performed high effectively achieving high conversation and yield. This method does not need any metal catalyst and can even be performed at temperatures below 70 °C. Therefore, the advantages of this newly developed process are that the procedure can be applied to a wide range of different compounds, no metal catalysts are required in any step, the oxidation conditions are very mild and the reaction is easily scalable, and the side product of this reaction is only water, which simplifies the work up. Since no metal catalysts are required, the reaction mixture is preferably essential free of any metal catalyst. Essential free means that the reaction mixture contains less than 0,01 % by weight of a metal catalyst, preferably less than 0,0001 % by weight.

The cycloalkene compound can be any known compound having at least one cycloalkene group per molecule, preferably at least two, more preferred 2 to 4, most preferably exactly 2 cycloalkene groups per molecule. The cycloalkene can be part of the backbone or attached to the backbone of a polymer in a side chain. Preferably the cycloalkene group is attached to the cycloalkene group in a terminal position, which means that e.g. the cycloalkene group is at the end of polymer backbone or attached at the end of a side chain.

Generally, the term "cycloaliphatic" refers to organic compounds having arrangement of carbon atoms in saturated or unsaturated non-aromatic closed ring structures. Accordingly, the term "cycloaliphatic epoxy resin" as used herein refers to a resin having cycloaliphatic structural units comprising an epoxy group. "Cycloalkene alcohol", as used herein, relates to cycloalkenes substituted with a hydroxyl group or a hydroxyl-group containing group, such as hydroxymethyl. "Cycloalkene carboxylic acid", as used herein, relates to a cycloalkenes substituted with a carboxylic acid group or a carboxylic acid-group containing group, such as an acetic acid or propionic acid group. Preferred as cycloalkene compound are cycloalkene esters, preferably cycloalkene terminated esters. These cycloalkene esters have at least one cycloalkene group per molecule, preferably at least two, more preferred 2 to 4, most preferably exactly 2 cycloalkene groups per molecule.

The preferred cycloalkene esters can be prepared before their oxidation by first carrying out an esterification reaction between (i) a cycloalkene carboxylic acid and an alcohol, preferably a polyol or (ii) a cycloalkene alcohol and a carboxylic acid, preferably a polyacid. The next step is than the oxidation of the ester with hydrogen peroxide as the oxidant as described. The advantages of this combined developed process are that the procedure can be applied to a wide range of polyols, no metal catalysts are required in any step, the oxidation conditions are very mild and the reaction is easily scalable, and both reaction steps proceed to completion so that no purification is necessary.

In a preferred aspect, the present invention therefore relates to a combined method for the preparation of a cycloaliphatic epoxy resin and includes a) reacting (i) an alcohol, preferably a polyol, with a cycloalkene carboxylic acid, or (ii) a carboxylic acid, preferably a polyacid, with a cycloalkene alcohol, in the presence of an acid catalyst to form a cycloalkene ester, preferably a cycloalkene terminated ester; and b) oxidizing the cycloalkene terminated ester with hydrogen peroxide in the presence of a base, a stabilizer and acetonitrile to form the cycloaliphatic epoxy resin.

For this preferred method, a wide range of polyols/polyacids may be used to produce cycloaliphatic epoxy resins using the preferred two-step process. By varying the polyol used, properties of the epoxy resin produced may be tuned accordingly, resulting in a wide range of cycloaliphatic epoxy resins being produced. The methodology described herein affords synthesis of cycloaliphatic epoxy resins under mild and safe conditions. Metal catalysts are not required in the epoxidation step. By using hydrogen peroxide as oxidant, costs of manufacturing are significantly reduced, which renders the method suitable and easily scalable for industrial scale operations. Furthermore, high product yields may be achieved due to absence of observable side reactions. The reaction steps in the method proceed to completion, thus negating the need for product purification.

The esterification includes reacting an alcohol, preferably a polyol, with a cycloalkene carboxylic acid in the presence of an acid catalyst to form a cycloalkene ester, preferably a cycloalkene terminated ester. The term "alcohol", as used herein, refers to compounds having at least one hydroxyl (-OH) group.

Similarly, the term "polyol", as used herein, refers to compounds having more than one hydroxyl (-OH) group per molecule. For example, the polyol may have two or more hydroxyl groups, such as 3, 4, 5, 6, 7, 8, 9, 10 or more hydroxyl groups. The term "carboxylic acid", as used herein, refers to compounds having at least one carboxylic acid (-COOH) group. Similarly, the term "polyacid", as used in connection with carboxylic acids, refers to compounds having more than one carboxylic acid groups, for example two or more, such as 3, 4, 5, 6, 7, 8, 9, 10 or more. The esterification also includes the option of reacting a carboxylic acid, preferably a polyacid, with a cycloalkene alcohol in the presence of an acid catalyst to from a cycloalkene ester, preferably a cycloalkene terminated ester.

In preferred embodiments, the reaction employs a polyol and a cycloalkene carboxylic acid as educts.

In various embodiments, the polyol or polyacid, preferably polyol, has an average molecular weight in the range of about 60 to about 6000, such as about 60 to about 4000, about 60 to about 2000, about 60 to about 1000, about 500 to about 6000, about 500 to about 5000, about 500 to about 3000, about 500 to about 2000, about 100 to about 6000, about 1000 to about 3000, about 100 to about 3000, about 100 to about 2000, about 500 to about 2500, or about 62 to about 2500.

Generally, "about", as used herein, relates to ± 20 %, preferably ± 10 %, or most preferably to the exact value of the numerical value to which it refers. "About 200" thus relates to 200 ± 40, preferably 200 ± 20, most preferably 200.

The polyol may be a polyether polyol, a polyester polyol, or mixtures thereof. In various embodiments, the polyol is a polyether polyol, preferably polyalkylene glycols. Examples of polyether polyol include, but are not limited to, polyoxyalkylene polyol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol.

Examples of polyester polyol include, but are not limited to, polyadipate diols such as polyethylene adipate diol, polybutylene adipate diol and polyethylenebutylene adipate diol; polyethylene terephthalate polyols, polycaprolactone polyols, and polybutadiene polyols.

The polyol is reacted with a cycloalkene carboxylic acid in the presence of an acid catalyst to form a cycloalkene terminated ester. In various embodiments, the cycloalkene carboxylic acid is selected from the group consisting of cyclopropene carboxylic acid, cyclobutene carboxylic acid, cyclopentene carboxylic acid, cyclopentadiene carboxylic acid, cyclohexene carboxylic acid, 1 ,3-cyclohexadiene carboxylic acid, 1 ,4-cyclohexadiene carboxylic acid, cycloheptene carboxylic acid, cycloheptadiene carboxylic acid, cyclooctene carboxylic acid, cyclooctadiene carboxylic acid and mixtures thereof. The position of the double bond(s) relative to the carboxylic acid group can be any possible position, but preferably is the 2-, 3- or 4-position. The cycloalkene moieties are preferably monocyclic with 3- to 8-ring carbon atoms. In various embodiments the cycloalkene carboxylic acids can be substituted, but preferably are unsubstituted.

The polyacids may be diacids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, fumaric acid, maleic acid and the like. The cycloalkene alcohols may have the same cycloalkene moieties described above in connection with the cycloalkene carboxylic acids with the difference lying in that they have an hydroxyl group instead of the acid group.

In the following, the invention is described in greater detail by reference to a concrete embodiment, namely a method that uses a cycloalkene carboxylic acid and a polyol as educts. It is however understood that the present invention is not limited to such an embodiment, but can easily be adapted to use the other educts described above, namely cycloalkene alcohols and acids or polyacids. Such alternative embodiments are also encompassed by the scope of the instant invention.

The cycloalkene carboxylic acid may be used in molar excess relative to the hydroxy groups of the polyol. In embodiments where the polyol is a diol, i.e. the polyol has two hydroxyl groups, the molar ratio of the cycloalkene carboxylic acid to diol is in the range of about 2.5:1 to about 4: 1 , preferably about 2.9:1 to about 3.1 : 1. Generally, it is preferred that the ratio of carboxylic acid groups to hydroxyl groups is greater than 1 , preferably 1.25: 1 to 2: 1. This ensures that all hydroxyl groups present are esterified.

In various embodiments, the acid catalyst comprises or consists of p-toluenesulfonic acid. Alternatively, a variety of other acid catalysts suitable for esterification reactions and readily known to those skilled in the art may be used.

In various embodiments, the esterification reaction of reacting a polyol with a cycloalkene carboxylic acid in the presence of an acid catalyst to form a cycloalkene ester is carried out in a suitable solvent, preferably an organic solvent. Suitable solvents include, but are not limited to toluene.

In some embodiments, the esterification reaction of reacting a polyol with a cycloalkene carboxylic acid in the presence of an acid catalyst to form a cycloalkene ester is carried out at elevated temperature, preferably in a solvent under reflux. Accordingly, the esterification reaction may be carried out at elevated temperatures, such as a temperature in the range from about 40 °C to about 100 °C, or about 40 °C to about 80 °C. The temperature can be adapted based on the solvent used to achieve reflux conditions.

The esterification reaction of polyol with cycloalkane carboxylic acid may be carried out for a length of time sufficient to form a cycloalkane ester. In various embodiments, the esterification reaction is conducted for about 2 hours to about 24 hours, such as about 2 hours to about 20 hours, about 2 hours to about 12 hours, about 2 hours to about 6 hours, about 6 hours to about 24 hours, about 6 hours to about 12 hours, or about 8 hours to about 15 hours. In various embodiments, the esterification reaction is conducted for about 2 hours to about 6 hours.

Preferably the cycloalkene ester, preferably the cycloalkene terminated ester resulting from the described esterification are oligomeric or polymeric. Most preferably the cycloalkene terminated ester have a molecular weight between 200 and 10000, more preferably between 300 and 5000, even more preferably between 1000 and 3000 g/mol. In the case of higher molecular weights, e.g. for oligomic or polymeric structures, the molecular weight refers to the number average molecular weight Mn measured by GPC against a polystylrol standard (in accordance to DIN 55672-1 )

According to the first aspect of the invention the cycloalkene compounds, especially the preferred ones as described above, are oxidized by hydrogen peroxide in the presence of a base, a stabilizer and acetonitrile. Advantageous, hydrogen peroxide is used as the oxidant of choice due to its high oxygen content and generation of water as its only by-product in heterolytic oxidation.

In various embodiments, hydrogen peroxide as the oxidant is used in molar excess relative to the olefinic double bonds of the cycloalkene compound. The molar ratio of hydrogen peroxide as oxidant used per double bond may thus range from about 1.1 to about 5, beneficial from about 2 to 5, preferably from about 2 to 4, most preferably from about 2,5 to 3,5.

The oxidation is carried out in the presence of at least one stabilizer. Preferred stabilizers are ammonium salts, especially quaternary ammonium salts. These quaternary ammonium salts preferably have the formula R4NX, wherein R is independently chosen from substituted or no substituted, linear or branched alkyi groups or aryl groups with 1 to 20, preferably 1 to 10 carbon atoms and X is CI^", Br, I^", SO4^2", NO2^", NO3^", PO4^3", BF4^", SbF6^" PF6^", CIO4^", preferred CI^", Br. Preferably the ammonium salt has at least one residue R with more than 1 , preferably more than 4 carbon atoms. Preferably the ammonium salt is a quaternary ammonium salt with four alkyi groups or with three alkyi groups and one aryl group, preferably benzene. Especially preferred as stabilizer are tetrabutylammonium chloride (TBAC) and bromide (TBAB), trioctylmethylammonium chloride (TOMAC), trimethylbenzylammonium choride (TMBAC) and mixtures thereof.

The molar ratio of stabilizer used per double bond may thus range from about 0.001 to about 0.1 , preferably from about 0.005 to about 0.05. Furthermore, the oxidation is carried out in the presence of at least one base. Preferably the base is selected from Na2C03, NaOH, tBuONa, NaHCCb or mixtures thereof. The preferred base is NaHCCb. In preferred embodiments, the base is used in molar excess relative to the olefinic double bonds of the cycloalkene compound, preferably the molar ratio of the base per double bond may be in the range of about 1 to about 5, preferably about 1 , 1 to about 2, most preferred about 1 ,2 to 1 ,5.

The oxidation reaction of oxidizing the cycloalkene compound to form the cycloaliphatic epoxy resin may be conducted for a suitable length of time. In preferred embodiments, the reaction may be carried out for about 1 hours to about 48 hours, such as about 2 hours to about 36 hours, preferably about 5 hours to about 24 hours. In various embodiments, the oxidation reaction using hydrogen peroxide as oxidant is conducted for about 7 hours to about 24 hours.

Oxidizing the cycloalkene compound with hydrogen peroxide may be carried out at a temperature in the range of about 15 °C to about 90 °C, such as about 20 °C to about 80 °C, preferably about 30 °C to about 70 °C, most preferably about 40 °C to about 70 °C.

Further, oxidizing the cycloalkene compound is performed in the presence of acetonitrile as organic solvent. Acetonitrile can be used alone as organic solvent or in a mixture of various solvents, preferably organic solvents. Suitable other solvents include methanol, iso-propanol, tetrahydrofuran (THF), dimethylformamide (DMF) or mixtures thereof, but are not limited thereto. Preferably acetonitrile is used alone as organic solvent or in a mixture with methanol, most preferably alone. The total amount of organic solvent (does not include the water content of the hydrogen peroxide) is at least 30 % by volume of the total reaction mixture, preferably at least 40 % by volume, most preferable at least 50 % by volume. The total amount of organic solvent is preferably in the range from 30 to 90 % by volume of the total reaction mixture, more preferably from 40 to 80 % by volume, most preferably from 50 to 70 % by volume. In the event acetonitrile is used in a mixture of solvents, the mixture of the organic solvents contains at least 30 % by volume, preferably at least 40 % by volume, most preferable at least 50 % by volume of the total amount of organic solvents. In various preferred embodiments the total amount of acetonitrile is at least 15 % by volume of the total reaction mixture, preferably at least 30 % by volume, most preferable at least 50 % by volume. The total amount of acetonitrile is preferably in the range from 15 to 90 % by volume of the total reaction mixture, more preferably from 30 to 80 % by volume, most preferably from 50 to 70 % by volume. The preferred ranges of the amount of acetonitrile have a beneficial effect on the conversion rate.

In a second aspect, the invention relates to a cycloaliphatic epoxy resin prepared by a method according to the first aspect or any preferred embodiment.

The epoxy resins produced may form the basis of epoxy thermosets, adhesives and coatings. For example, the epoxy resins may be used to replace, supplement, or improve existing epoxy resins that are used as thermoset adhesives in pure format or as additives. As mentioned above, a wide range of cycloaliphatic epoxy resins may be produced using methods disclosed herein, and properties of the formed product may depend on the nature of the backbone of the resin, and are mainly affected by the preferably used starting polyol.

In the following, the invention is described in greater detail by reference to concrete embodiments. It is however understood that the present invention is not limited to such embodiments, but may easily be adapted to use other starting compounds for polyols, cycloalkane carboxylic acids, and acid catalysts. Such alternative embodiments are also encompassed by the scope of the instant invention.

Example

Example 1 : Esterification of a polyol with 3-cyclohexene-1 -carboxylic acid to form a cycloalkane terminated ester, with subsequent epoxidation to form a cycloaliphatic epoxy resin

(1 .1 )

CH.CN

(1.2)

Reaction scheme in 1.1 depicts an esterification reaction, where a polyol is reacted with a carboxylic acid using p-toluenesulfonic acid as catalyst in toluene under reflux conditions. Full conversion is obtained.

Reaction scheme in 1.2 depicts an epoxidation reaction of the cycloalkane terminated ester formed in 1.1. The epoxidation is carried out using hydrogen peroxide. Hydrogen peroxide is the oxidant of choice due to its high oxygen content and generation of water as its only by-product in heterolytic oxidation.

Example 2: Epoxidation of tetraethylene glycol-based 3-cyclohexene-1-carboxylate 1

Tetraethylene glycol (TEG)-based 3-cyclohexene-1-carboxylate (TEG-carboxylate) 1 with structure as shown below was epoxidized with hydrogen peroxide following a method described herein.

Firstly, required amounts of TEG-carboxylate 1 were prepared according to the synthesis method depicted in reaction scheme 2.1.

PTSA = p-toluenesulfonic acid monohydrate (2.1 ) Following esterification, a standard procedure (Dean-Starks distillation in toluene) was used. Average batch size that may be prepared using this method was 1.0 to 1 .5 kg (2.4 to 3.7 mol) using 0.5 to 0.8 kg of TEG (average yield of 99 %).

Epoxidation of 1 was carried out in a 60 litre reactor correlating to the method depicted in reaction scheme 2.2 and described in greater detail below with the amounts specified in the following table.

(2.2)

Reagents and amounts used:

Procedure:

A 60 litre reactor was used to contain TEG-carboxylate 1 (5.00 kg, 12.2 mol), CH₃CN (17 I), solid NAHC0₃ (2.58 kg, 30.6 mol), and benzyltrimethylammonium chloride 12 (TMBAC; 45.0 g, 0.24 mol). Subsequently, the reaction mixture was heated to 65 °C and the addition of hydrogen peroxide (4.85 I, Hyprox® 500, 50 wt%, purchased from Evonik) was started as soon as temperature stability was reached. In the process, hydrogen peroxide was added in portions. After the addition was completed (after ca. 5 hours), the reaction mixture was stirred at 65 °C for additional 2 hours. The thermostat was then set to 20 °C and the mixture was left stirring overnight at that temperature.

Subsequently, the mixture was heated again to 65 °C and one last portion of hydrogen peroxide was added (ca. 0.4 I) and the mixture was stirred for 2 hours.

Work up:

For the work up procedure, the reaction mixture was cooled down to 25 °C and 10 I EtOAc and 15 I H2O were added (20 minutes stirring). After phase separation was reached (ca. 10 minutes), 20 I of a CH3CN/H2O mixture were removed and the organic layer was washed with further 10 I H2O (15 I of the CH3CN/H2O mixture were removed). The remaining organic layer (ca. 22 I) was left standing overnight over solid Na2S03 whereas the combined aqueous layers were poured in the reactor and extracted with 5 I EtOAc. Subsequently, the organic layers were combined and washed free of peroxide using aqueous Na2S03 (ca. 2.0 kg in 10 I H2O). Al the wash waters were combined and disposed of after demonstrating the absence of peroxides. The peroxide free organic layer (ca. 30 I) was dried over MgSC and freed of the solvent by vacuum evaporation at 35 °C (thermostat had to be set to 65 °C). Finally, 4.4 kg of a product in which 84 % of the double bonds were oxidized, was recovered.

Example 3 - 16: Epoxidation of tetraethylene glycol-based 3-cyclohexene-1-carboxylate 1

In correlation to experiment 2 the following experiments 3 to 16 have been conducted as trial experiments using only 2 g of TEG-carboxylate 1. 2 g (4.9 mmol) of TEG-carboxylate 1 were mixed with 12,2 mmol of a base, 0,2 mmol of a stabilizer and a solvent. The used base, stabilizers (tetrabutylammonium chloride (TBAC) trioctylmethylammonium chloride (TOMAC) and trimethylbenzylammonium choride (TMBAC)) and solvent are shown in table 1. The addition of 3 equivalents of hydrogen peroxide (-2.1 mL Hyprox® 500, 50 wt%) per double bond was performed as described in example 2 using a parallel reactor (Multimax). Only example 17 differs therefrom, since the total reaction time was set to 7 hours. After the evaporation of the solvent the conversion of the reaction has been determined by H-NMR. The results are shown in Table 1.

Table 1 : Summary of the experiments

12 NaHCOs TMBAC AcOEt 7,8 <5

13 NaHCOs TMBAC Hexane 7,8 <5

14 NaHCOs TMBAC Toluene 7,8 <5

15 NaHCOs TMBAC Xylenes 7,8 <5

16 NaHCOs TMBAC ACN 7,8 95

As can be seen from examples 11 to 15 it is necessary for the reaction and to achieve high yield that acetonitrile and a stabilizer is present. As shown by example 6 a mixture of acetonitrile and Methanol leads also to a high conversion. Additionally, faster reaction times are possible as example 15 shows.

Example 6: Other examples were prepared according to the method described herein and shown below.

Claims

1. Method of preparing a cycloaliphatic epoxy resin, the method comprising the oxidiation of a

cycloalkene compound with hydrogen peroxide in the presence of a base, a stabilizer and acetonitrile.

2. The method according to claim 1 , wherein the cycloalkene compound is a cycloalkene ester, preferably a cycloalkene terminated ester prepared by reacting (i) an alcohol, preferably a polyol, with a cycloalkene carboxylic acid, or (ii) a carboxylic acid, preferably a polyacid, with a cycloalkene alcohol in the presence of an acid catalyst to form a cycloalkene ester;.

3. The method according to claim 2, wherein polyol has an average molecular weight in the range of about 60 to about 6000, preferably about 62 to about 2500 and/or the polyol is selected from the group consisting of polyether polyols, preferably polyalkylene glycols, polyester polyols and mixtures thereof.

4. The method according to any one of claims 2 to 3, wherein the cycloalkene carboxylic acid is selected from the group consisting of cyclopropene carboxylic acid, cyclobutene carboxylic acid, cyclopentene carboxylic acid, cyclopentadiene carboxylic acid, cyclohexene carboxylic acid, 1 ,3- cyclohexadiene carboxylic acid, 1 ,4-cyclohexadiene carboxylic acid, cycloheptene carboxylic acid, cycloheptadiene carboxylic acid, cyclooctene carboxylic acid, cyclooctadiene carboxylic acid and mixtures thereof.

5. The method according to any one of claims 2 to 4, wherein the cycloalkene carboxylic acid is used in molar excess relative to the hydroxy groups of the polyol.

6. The method according to claim 5, wherein the polyol is a diol and the molar ratio of the

cycloalkene carboxylic acid to diol is in the range of about 2.5:1 to about 4: 1 , preferably about 2.9: 1 to about 3.1 :1.

7. The method according to any one of claims 2 to 5, wherein

(i) the acid catalyst comprises or consists of p-toluenesulfonic acid; and/or

(ii) the esterification reaction of step a) is carried out in a suitable solvent, preferably toluene; and/or

(iii) the esterification reaction of step a) is carried out at elevated temperature, preferably in a solvent under reflux.

8. The method according to any one of claims 1 to 7, wherein hydrogen peroxide as the oxidant is used in molar excess relative to the olefinic double bonds of the cycloalkene compound, preferably the molar ratio of hydrogen peroxide as oxidant used per double bond ranges from about 2 to about 4.

9. The method according to any one of claims 1 to 8, wherein the stabilizer is at least one

ammonium salt, especially the stabilizer is selected from the group of tetrabutylammonium chloride (TBAC) and bromide (TBAB), trioctylmethylammonium chloride (TOMAC),

tnmethylbenzylammonium choride (TMBAC) and mixtures thereof, and/or the molar ratio of the stabilizer used per double bond ranges from about 0.001 to about 0.1 , preferably from about 0.005 to about 0.05.

10. The method according to any one of claims 1 to 9, wherein the base is selected from Na2C03, NaOH, tBuONa, NaHCCb or mixtures thereof, especially NaHCCb, and/or the base is used in molar excess relative to the olefinic double bonds of the cycloalkene compound, preferably the molar ratio of the base per double bond may be in the range of about 1 , 1 to about 2.

1 1. The method according to any one of claims 1 to 10, wherein the acetonitrile is used alone as organic solvent or in a mixture with methanol, most preferably alone, and/or the total amount of acetonitrile is in the range from 15 to 90 % by volume of the total reaction mixture, more preferably from 30 to 80 % by volume, most preferably from 50 to 70 % by volume.

12. The method according to any one of claims 1 to 1 1 , wherein the oxidation reaction is carried out at a temperature in the range of about 15 °C to about 90 °C, preferably about 40 °C to about

70 °C.

13. Cycloaliphatic epoxy resin prepared by a method according to any one of claims 1 to 12.