Mixed resins for high voltage applications

Abstract

The present invention relates to a composition comprising an epoxy and ester-based resin, a reactive diluent and a free-radical polymerization initiator. Furthermore, the invention relates to a method for providing such a composition, a method for applying the composition, the use of the composition as a coating material, and a material coated with the polymerized composition.

Description

[0001] This application is a divisional application of the international application PCT / EP2019 / 076883 filed by ELANTAS PDG GmbH and ELANTAS Europe GmbH on October 4, 2019, entitled “Hybrid Resins for High Voltage Applications”. The date of entry of the international application PCT / EP2019 / 076883 into the Chinese national phase is March 30, 2021, and the national application number is 201980064383.X. Technical Field

[0002] The present invention relates to a composition comprising an epoxy and ester based resin, a reactive diluent and a free radical polymerization initiator. In addition, the present invention relates to a method for providing such a composition, to a method for applying the composition, to the use of the composition as a coating material, to a substrate coated with the polymerized composition. Background of the Invention

[0004] The present invention relates to compositions useful as insulators in electrical machines, such as rotating and non-rotating machines.

[0005] In electric motors, especially those subjected to high voltages, the insulation material used for the coils is extremely important to their performance and service life.

[0006] Common insulation materials are organic thermosetting polymers, whose thermal, electrical, chemical and mechanical properties are key requirements for obtaining long-term machine performance.

[0007] US2012 / 0259039 discloses a resin composition for fiber-reinforced composite materials, which comprises an epoxy resin, a radical polymerizable monomer containing an acid group (such as acrylic acid or methacrylic acid), and an amine-based curing agent for the epoxy resin.

[0008] US2015 / 0306790 discloses a method for producing a storage-stable epoxy prepreg using at least one reactive resin having at least one acid group and at least one epoxy-based reactive resin component, and a composite material obtained by the method, wherein one or both of the reactive resins contain groups capable of free radical polymerization.

[0009] US 6,555,023 and US 6,680,119 disclose insulated electrical coils whose insulation is formed from a cured resin composition of an epoxy-anhydride resin which has been pre-reacted with an antioxidant oligomer selected from the group consisting of organophosphorus compounds, phenolics, thioesters, thiophosphites, thiazoles, lactones, hydroxylamines and maleimides.

[0010] Epoxy resins cured with anhydrides, for example, have a higher viscosity, which is disadvantageous during the impregnation process. Anhydrides also have potential health hazards and are sensitive to moisture. Unsaturated polyester resins have been used to obtain low viscosity solutions for easy penetration of mica tapes, but low viscosity solutions result in poor mechanical, thermal and / or chemical resistance. Styrene or vinyl toluene reactive diluents are also potentially toxic and flammable.

[0011] There is therefore a need to find new materials suitable for impregnation and / or coating which have a low viscosity and nevertheless have good mechanical, thermal and / or chemical properties, in particular for use as insulators in electric machines. Summary of the invention

[0012] These problems are solved by the composition of the present invention, which comprises a resin component, a reactive diluent and a free radical polymerization initiator.

[0013] One of the advantages of the composition of the present invention is that it provides a curing system that does not contain anhydride as a curing agent. In addition, the use of styrene or vinyl toluene can be significantly reduced or avoided.

[0014] In general, the composition of the invention combines the advantages of having a low viscosity, a property essential for its application to a substrate, with good mechanical, thermal and chemical properties of the polymer obtained after curing the composition.

[0015] In other aspects, the invention relates to methods of making the compositions of the invention and methods of applying the compositions of the invention.

[0016] The invention also relates to the use of the composition according to the invention as a coating on a substrate, in particular an insulating material for use in electric machines.

[0017] The present invention may include the following embodiments:

[0018] 1. A composition comprising:

[0019] A) a resin component comprising:

[0020] i. one or more identical or different groups of the formula

[0021]

[0022] wherein R is an organic group containing 2 to 40 carbon atoms;

[0023] ii. one or more groups comprising two ester groups and one ethylenically unsaturated group;

[0024] iii. one or more terminal or pendant groups comprising an ester group and an ethylenically unsaturated group;

[0025] B) at least one reactive diluent having at least one ethylenically unsaturated polymerizable group and having a boiling point above 200° C. at atmospheric pressure; and

[0026] C) a free radical polymerization initiator;

[0027] The resin component A has an acid value of not more than 50 mgKOH / g.

[0028] 2. The composition of embodiment 1, wherein R comprises the hydrocarbon portion of a bisphenol A or bisphenol F unit.

[0029] 3. The composition of embodiment 1 or 2, wherein the side or end group iii. comprises an acrylate, a methacrylate, or a mixture thereof.

[0030] 4. The composition of any one of embodiments 1 to 3, wherein group ii. comprises an ester group of fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, and mixtures thereof.

[0031] 5. A composition as described in any one of embodiments 1 to 4, wherein component A is the reaction product of

[0032] A1) Epoxy resin;

[0033] A2) a compound comprising a) two carboxylic acid groups or carboxylic anhydride groups and b) one ethylenically unsaturated group, and

[0034] A3) Compounds having one carboxylic acid group and one ethylenically unsaturated group.

[0035] 6. The composition according to embodiment 5, wherein the epoxy resin of component A1 further comprises bisphenol A and / or F units.

[0036] 7. The composition according to any one of embodiments 5 to 6, wherein component A3) is selected from acrylic acid, methacrylic acid and mixtures thereof.

[0037] 8. The composition of any one of embodiments 5 to 7, wherein component A2 is selected from fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, and mixtures thereof.

[0038] 9. The composition of any one of embodiments 1 to 8, wherein component B is present in an amount of 20 to 70 wt %, calculated on the total weight of the composition.

[0039] 10. The composition of embodiment 1, wherein the composition has a viscosity of 50 to 450 cP at a temperature of 25°C.

[0040] 11. A method of preparing a treated metal-containing substrate comprising the steps of:

[0041] a. Providing a composition according to any one of the preceding embodiments;

[0042] b. applying the composition to a substrate comprising a metal; and

[0043] c. Polymerizing the composition.

[0044] 12. The method of embodiment 11, wherein the substrate comprising metal further comprises a tape.

[0045] 13. A treated metal-containing substrate obtainable by the method of embodiment 11 or 12.

[0046] 14. A method for preparing the composition of any one of embodiments 1 to 10, comprising the steps of:

[0047] a. optionally in the presence of one or more free radical polymerization inhibitors, providing A1) an epoxy resin, A3) a compound having a carboxylic acid group and an ethylenically unsaturated group, and a catalyst in a reactor to obtain a mixture;

[0048] b. reacting the mixture of step a. to obtain a first reaction product until the acid value of the first reaction product is less than 50 mgKOH / g;

[0049] c. providing in a reactor A2) a compound comprising a) two carboxylic acid groups or carboxylic anhydride groups and b) an ethylenically unsaturated group;

[0050] d. further reacting the mixture of steps a. to c. to obtain a second reaction product until the acid value of the second reaction product is less than 50 mgKOH / g;

[0051] e. Add components B and C and optionally other components to component A.

[0052] 15. Use of the composition of any of embodiments 1 to 10 for coating and / or impregnating a substrate comprising a metal.

[0053] 16. Use of the treated substrate according to embodiment 13 for electrical insulation. DETAILED DESCRIPTION DETAILED DESCRIPTION OF THE INVENTION

[0055] In a first embodiment, the present invention relates to a composition comprising:

[0056] A) a resin component comprising:

[0057] i. one or more identical or different groups of the formula

[0058]

[0059] wherein R is an organic group having 2 to 40 carbon atoms;

[0060] ii. one or more groups comprising two ester groups and one ethylenically unsaturated group;

[0061] iii. one or more terminal or pendant groups comprising an ester group and an ethylenically unsaturated group;

[0062] B) at least one reactive diluent having at least one ethylenically unsaturated polymerizable group and having a boiling point above 200° C. at atmospheric pressure; and

[0063] C) Free radical polymerization initiator.

[0064] In another embodiment, the present invention relates to a composition comprising:

[0065] A) a resin component comprising:

[0066] i. one or more identical or different groups of the formula

[0067]

[0068] wherein R is an organic group containing 2 to 40 carbon atoms;

[0069] ii. one or more groups comprising two ester groups and one ethylenically unsaturated group;

[0070] iii. one or more terminal or pendant groups comprising an ester group and an ethylenically unsaturated group;

[0071] B) at least one reactive diluent having at least one ethylenically unsaturated polymerizable group and having a boiling point above 200° C. at atmospheric pressure; and

[0072] C) Free radical polymerization initiator.

[0073] Wherein the resin component A has an acid value of no more than 50 mgKOH / g. Within the meaning of the present invention, R is an organic group containing 2 to 40 carbon atoms, wherein the organic group comprises at least an aromatic group, an aliphatic group, a heteroaromatic group, a heteroaliphatic group or a mixture thereof. The aliphatic group can be linear, branched, cyclic or a mixture thereof.

[0074] In a further preferred embodiment, R comprises the hydrocarbon portion of a bisphenol A or bisphenol F unit.

[0075] Within the meaning of the present invention, brackets [ ] indicate the point of attachment of the group indicated in the brackets to the rest of the molecule.

[0076] In another preferred embodiment, in the composition of the present invention, the side or end groups iii. comprise acrylates, methacrylates or mixtures thereof.

[0077] Preferably, the ethylenically unsaturated group is a conjugated ethylenically unsaturated group.

[0078] The use of "consisting essentially of" or "consisting essentially of" in the context of a compound or composition means that certain other components may be present, ie, those components that do not materially affect the basic characteristics of the compound or composition.

[0079] In some embodiments, the resin component A comprises 90 wt %, preferably 95 wt %, more preferably 98 wt % of the groups i), ii) and iii) present in the resin component A, based on the total weight of the resin component A.

[0080] In some embodiments, the resin component A of the composition of the present invention consists essentially of the following components:

[0081] i. one or more identical or different groups of the formula

[0082]

[0083] Wherein R is an organic group containing 2 to 40 carbon atoms

[0084] ii. one or more groups comprising two ester groups and one ethylenically unsaturated group;

[0085] iii. One or more terminal or pendant groups comprising an ester group and an ethylenically unsaturated group.

[0086] In another preferred embodiment, in the composition of the present invention, group ii. comprises an ester group of fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid and mixtures thereof.

[0087] In another preferred embodiment, in the composition of the present invention, component A is the reaction product of

[0088] A1) Epoxy resin;

[0089] A2) a compound comprising a) two carboxylic acid groups or a carboxylic acid anhydride group and b) one ethylenically unsaturated group,

[0090] A3) Compounds having one carboxylic acid group and one ethylenically unsaturated group.

[0091] In a further preferred embodiment of the present invention, the epoxy resin of component A1 also comprises bisphenol A and / or F units.

[0092] In a further preferred embodiment of the present invention, component A3) is selected from acrylic acid, methacrylic acid and mixtures thereof.

[0093] In a further preferred embodiment of the present invention, component A2 is selected from fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride and mixtures thereof. Most preferably, component A2 is selected from fumaric acid, maleic acid and maleic anhydride.

[0094] In a further preferred embodiment, component A of the composition of the present invention has an acid value of at most 50 mgKOH / g, preferably component A of the composition of the present invention has an acid value of at most 40 mgKOH / g, more preferably component A of the composition of the present invention has an acid value of at most 30 mgKOH / g, most preferably component A of the composition of the present invention has an acid value of at most 20 mgKOH / g.

[0095] Preferably, component A of the composition of the present invention has an acid value of 0 to 50 mgKOH / g, preferably 1 to 50 mgKOH / g, more preferably, component A of the composition of the present invention has an acid value of 0 to 40 mgKOH / g, preferably 1 to 40 mgKOH / g. More preferably, component A of the composition of the present invention has an acid value of 0 to 30 mgKOH / g, preferably 1 to 30 mgKOH / g. Most preferably, component A of the composition of the present invention has an acid value of 0 to 20 mgKOH / g, preferably 1 to 20 mgKOH / g.

[0096] In a further preferred embodiment, component B of the composition according to the invention is liquid at a temperature of 25°C.

[0097] In a further preferred embodiment, component B of the composition of the present invention comprises up to 3 wt. % of styrene and / or vinyltoluene reactive diluents, calculated on the total weight of the composition. More preferably, component B of the composition does not contain styrene and / or vinyltoluene reactive diluents.

[0098] In a further preferred embodiment, component B of the composition of the present invention is present in an amount of 20 to 70 wt % based on the total weight of the composition. In a more preferred embodiment, component B of the composition is present in an amount of 30 to 70 wt %, more preferably 40 to 70 wt %, more preferably 40 to 60 wt %, more preferably 40 to 55 wt %, based on the total weight of the composition.

[0099] In a further preferred embodiment, the composition according to the invention is substantially free of epoxy groups.

[0100] In a further preferred embodiment, the composition of the invention has a viscosity of 50 to 450 mPa*s at a temperature of 25° C. More preferably, the composition of the invention has a viscosity of 100 to 450 mPa*s at a temperature of 25° C., more preferably of 150 to 450 mPa*s at a temperature of 25° C.

[0101] In another embodiment, the present invention is directed to a method of preparing a treated metal-containing substrate comprising the steps of:

[0102] a. Provide a composition of the present invention;

[0103] b. applying the composition to a substrate comprising a metal; and

[0104] c. Polymerizing the composition.

[0105] Within the meaning of the present invention, step c. of the process for preparing a cured substrate may also be referred to as a curing step. In fact, in this step, the ethylenically unsaturated groups of the resin of the composition of the invention are polymerized at a suitable temperature to achieve free radical polymerization in the presence of a catalyst suitable for free radical polymerization, such as a peroxide.

[0106] In another preferred embodiment, the metal-comprising substrate further comprises a tape, preferably a mica tape.

[0107] Typically, the tape is wound onto a substrate surface. Mica tape means that the tape comprises mica. Any type of tape commonly used to insulate metal rods or substrates used in electric machines is a suitable tape according to the present invention.

[0108] In another embodiment, the present invention relates to a treated metal-containing substrate obtainable by a method for preparing a treated substrate, preferably the treated substrate further comprises a tape, more preferably a mica tape.

[0109] In the meaning of the present invention, the substrate comprising metal is an electrical conductor. The metal can be copper, aluminum, iron, gold or other alloys used for electromechanical devices. The substrate is not limited to a rod comprising metal, but should also be understood to include one or more electrical conductors, such as wires or coils, wherein the wires or coils may be pre-coated or not pre-coated. The electrical conductor or the substrate may be at least partially coated on the metal surface, or other materials may be applied to the metal surface, or even another form of insulating material may be applied to the electrical conductor or substrate, such as the aforementioned band.

[0110] Optionally, the metal containing substrate is wrapped with mica tape for dielectric breakdown protection.Mica tape is most effective for dielectric breakdown protection when air voids and moisture are replaced with the impregnating material (ie, the composition of the present invention) by a vacuum pressure impregnation procedure.

[0111] In another embodiment, the present invention relates to a method for preparing the composition of the present invention, comprising the steps of:

[0112] a. optionally in the presence of one or more free radical polymerization inhibitors, providing component A1) an epoxy resin, component A3) a compound having a carboxylic acid group and an ethylenically unsaturated group, and a catalyst in a reactor to obtain a mixture;

[0113] b. reacting the mixture of step a. to obtain a first reaction product until the acid value of the first reaction product is less than 50 mgKOH / g;

[0114] c. providing component A2 in a reactor) comprising a) two carboxylic acid groups or carboxylic acid anhydride groups (a) twocarboxylic acid groups or a carboxylic acid anhydride group) and b) a compound of an ethylenically unsaturated group;

[0115] d. further reacting the mixture of steps a. to c. to obtain a second reaction product until the acid value of the second reaction product is less than 50 mgKOH / g;

[0116] e. Adding other components to the second reaction product.

[0117] According to the present invention, the second reaction product produces component A of the composition of the present invention, and preferably, the other components added to component A are components B and C of the composition of the present invention.

[0118] In a further preferred embodiment of the method for preparing the composition of the present invention, the acid value of the first reaction product may be the same as or different from the acid value of the second reaction product and is at most 50 mgKOH / g, preferably it is at most 40 mgKOH / g, more preferably it is at most 30 mgKOH / g, most preferably it is at most 20 mgKOH / g.

[0119] The above-defined ranges for the acid value of resin component A also apply to the reaction product of the process.

[0120] The advantage of lower acid numbers is better solubility in the monomer.

[0121] In a further embodiment, the present invention relates to the use of a composition according to the invention for coating and / or impregnating a substrate.

[0122] Preferably, the composition is used for coating and / or impregnating an electric machine, more preferably a high voltage electric machine.

[0123] In another embodiment, the present invention relates to the use of the treated substrate for electrical insulation, preferably in an electric machine.

[0124] Reactive diluents within the meaning of the present invention are diluents having at least one ethylenically unsaturated polymerizable group and a boiling point above 200° C. Non-limiting examples of reactive diluents include vinyl ethers, acrylates, methacrylates, allyl groups, olefins (and vinyl groups).

[0125] Preferably, the reactive diluents of the present invention have at least two ethylenically unsaturated polymerizable groups.Most preferably, the reactive diluents of the present invention have two ethylenically unsaturated polymerizable groups.

[0126] The most preferred reactive diluents are diallyl fumarate (DAF), tetraethylene glycol di(meth)acrylate (TEGDMA), hexanediol di(meth)acrylate (HDDMA), butanediol dimethacrylate or mixtures thereof.

[0127] Epoxy resins or epoxy-type resins within the meaning of the present invention are those resins which carry at least one epoxy group, preferably at least two epoxy groups per molecule. Preferred epoxy resins of the present invention contain one or more epoxy groups and bisphenol A or bisphenol F or a mixture of bisphenol A and F.

[0128] In a preferred embodiment, the composition is substantially free of epoxy groups. Substantially free of epoxy groups also encompasses free of epoxy groups and means that the epoxy equivalent weight of the material is at least 2000 g / eq, preferably at least 3000 g / eq, more preferably at least 4000 g / eq, and most preferably at least 5000 g / eq.

[0129] A free radical polymerization initiator within the meaning of the present invention is a compound suitable for initiating free radical polymerization. Preferred free radical polymerization initiators are peroxides. Most preferred is dicumyl peroxide.

[0130] Within the meaning of the present invention, applying the composition of the invention on a substrate means that the substrate may be coated and / or impregnated with the composition of the invention.

[0131] A coating is a covering applied to the surface of a substrate, wherein the coating itself may be a full-face coating, ie completely covering the substrate, or it may cover only part of the substrate.

[0132] A substrate is impregnated when it at least partially absorbs a liquid, in this case the composition used to impregnate the substrate. This means that the cavities or voids present in the substrate are at least partially covered by the composition of the invention.

[0133] Example

[0134] Measurement

[0135] Examples 1 to 11

[0136] 1. Preparation of Reactive Composition

[0137] A glass reactor equipped with a water-cooled condenser was used to synthesize the resin. A combination of nitrogen and air was bubbled into the reactor. Bisphenol F or bisphenol A type epoxy resin (Epon 824, 344 grams) and an inhibitor were added to the reactor and stirring was turned on. Glacial acrylic acid or methacrylic acid (140 grams) and Ancamine K54 (0.6 grams) catalyst were then added to the container and the reaction mixture was heated to 99°C. An exotherm was observed, which increased the reaction temperature to approximately 121°C. The solution was then maintained at 104-110°C until the acid value was reduced to less than 20 mg KOH per gram of reaction product. The material was then cooled to less than 82°C, and maleic anhydride (22 grams) was added. The reaction temperature was then increased to 104.4-110°C until an acid value of less than 20 mg KOH per gram of reaction product was reached. The reaction was then divided into multiple samples and allowed to cool to room temperature. The reaction product was then melted again, additional inhibitor was added, and thinned with diallyl fumarate (DAF, 415 g), tetraethylene glycol di(meth)acrylate (TEGDMA, 507 g), hexanediol di(meth)acrylate (HDDMA, 507 g), or butanediol dimethacrylate (BDDMA, 507 g) monomer until a viscosity of about 400 cP or less was obtained. The material was then cooled to below 49° C., and dicumyl peroxide (5-20 g) was added. Finally, the material was filtered through a 25 micron cloth. The chemical compositions of Examples 1-11 are detailed in Table 1.

[0138] Table 1

[0139]

[0140]

[0141] Table 2 - Physical properties

[0142]

[0143] Table 3 - Mechanical properties

[0144]

[0145] Table 4 - Electrical permittivity at different temperatures

[0146]

[0147] Table 5-Dissipation Factor at Different Temperatures

[0148]

[0149] Table 6- Dielectric strength before and after water immersion

[0150]

[0151] Description of material properties

[0152] Table 2 shows the details of the physical properties of each sample.

[0153] The viscosities of the compositions of Examples 1 to 11 were below 450 mPas.

[0154] Sunshine (SS) gel is a measure of reactivity and can be used for the desired curing schedule.

[0155] The glass transition temperature (Tg) of the cured material was measured using a modulated differential scanning calorimeter (MDSC). The Tg ranged from 69°C to 153°C, depending on the reactive diluent used.

[0156] Mechanical properties were examined by bond strength using a helical coil of MW35 magnet wire.

[0157] As shown in Table 3, the cured resin of the present invention exhibits good mechanical resistance. After a temperature increase of 125°C (from 25°C to 150°C), the bond strength only decreases by about 50% of the value measured at 25°C, still maintaining a good value, especially for such a high temperature of 150°C.

[0158] The electrical properties of the resins are shown in Tables 4-6.

[0159] Dielectric strength indicates the maximum voltage a material can withstand depending on its thickness. This value was measured before and after immersion in water. As shown in Table 6, dielectric strength was not affected by immersion in water, and in some cases this property was improved after immersion in water, which was unexpected.

[0160] All samples exhibited excellent electrical properties as the dissipation factor of all samples remained below 0.1 up to 150° C. The closer the dissipation factor is to zero, the less energy is lost in the insulating material.

[0161] The electrical permittivity (also called dielectric constant) measured at various temperatures ranging from 25°C to 200°C is shown in Table 4. Small changes in dielectric constant are an important feature of high voltage systems to avoid charge concentration that can cause damage during long term use.

[0162] Table 5 relates to the measurement of the dissipation factor, which represents the amount of energy lost in the insulating material. A constant and low dissipation factor at a certain temperature is essential to making a good high voltage insulation system; a value of 0.1 is usually considered a threshold at high temperatures (eg above 150°C).

[0163] method

[0164] The above-mentioned properties were measured according to the following methods.

[0165] Acid value

[0166] The acid number is the amount of KOH in mg required to neutralize 1 gram of a substance under defined conditions. The acid number is determined by neutralization reaction with 0.1 N KOH in ethanol in accordance with DIN EN ISO 2114.

[0167] Viscosity is measured according to ISO 3219 using a Brookfield LV viscometer at 25°C using spindle 6 at 25 rpm.

[0168] The dissipation factor and dielectric constant (DF / DC) were measured simultaneously according to ASTM D 150, with the samples cast in small capacitors.

[0169] Bond strength was measured on impregnated spiral coils according to ASTM D2519.

[0170] The dielectric strength was measured on steel panels coated with the resin samples according to ASTM D149.

[0171] GPC measurement was performed using Agilent Infinity 1260 GPC. The Infinity GPC was equipped with an Infinity 1260 degasser. The Infinity GPC was equipped with an isocratic pump, also of the Infinity 1260 model. The serial number was DEAB902598. Next, the Infinity GPC contained accessories for constant temperature GPC columns and autosampler functions. The solvent was tetrahydrofuran (THF), provided by Honeywell. The purity was 99.9%, and the peroxide content was less than 2 mg / L. First, the sample to be analyzed was dissolved in THF under gentle stirring. The sample was then filtered through a 5 ml syringe with a 0.5 micron filter housing. The solution was collected with a 5 ml vial suitable for an autosampler. The vial crimper provided by Agilent was then used to crimp a cap with a rubber septum onto the vial. After all samples were loaded into the autosampler, the method began. The method is set up with a THF flow rate of 1 ml / min through a mixed D column (2 in series) supplied by Phenomenex. The mixed D column is thermostated at 40°C and the refractive index detector baseline is zeroed. The effluent is collected in a suitable container with proper ventilation. Samples are injected on the column according to the method with an injection volume of 0.5 μl per injection. The refractive index detector is thermostated at 40°C to prevent signal drift. The signal polarity is positive. The maximum pressure allowed on the column set is 600 bar. Analysis is performed using Agilent Chemstation software. Polystyrene reference samples purchased from Agilent are run in a similar manner to establish a calibration curve. The molecular weight range of the standards is from 500 to 30,000 Daltons [g / mol]. The calibration curve can be a linear fit, or first or second order, depending on the column set used.

Claims

1. A composition comprising: A) a resin component, obtained by: A1. In a first step, a mixture comprising: -Epoxy resin - a compound having one carboxylic acid group and one ethylenically unsaturated group, and -catalyst, until a first reaction product is obtained, wherein the acid value of the first reaction product is less than 50 mgKOH / g, A2. In the next step, the first reaction product is reacted with a compound comprising: - two carboxylic acid groups or - a carboxylic anhydride group and an ethylenically unsaturated group, To obtain a second reaction product with an acid value of less than 50 mgKOH / g, B) at least one reactive diluent having at least one ethylenically unsaturated polymerizable group and having a boiling point above 200° C. at atmospheric pressure; and C) Free radical polymerization initiator.

2. The composition according to claim 1, wherein the epoxy resin of A1 further comprises bisphenol A and / or F units.

3. The composition according to claim 1 or 2, wherein the compound having one carboxylic acid group and one ethylenically unsaturated group component is selected from acrylates, methacrylates and mixtures thereof.

4. The composition according to any one of claims 1 to 3, wherein the compound comprising two carboxylic acid groups or carboxylic anhydride groups and one ethylenically unsaturated group is selected from fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride and mixtures thereof.

5. The composition according to any one of claims 1 to 4, wherein component B is present in an amount of 20 to 70 wt%, calculated on the total weight of the composition.

6. The composition according to claim 1, wherein the composition has a viscosity of 50 to 450 mPa.s (cP) at a temperature of 25°C, as measured according to ISO 3219 using a Brookfield LV viscometer using a No. 6 spindle at 25 rpm.

7. A method for preparing a treated metal-containing substrate comprising the steps of: a. Providing a composition according to any one of the preceding claims; b. applying the composition to a substrate comprising a metal; and c. Polymerizing the composition.

8. The method of claim 7, wherein the substrate comprising metal further comprises a tape.

9. A treated metal-comprising substrate obtainable by the method of claim 7 or 8.

10. Use of a composition according to any one of claims 1 to 6 for coating and / or impregnating a substrate comprising a metal.

11. Use of the treated substrate according to claim 10 for electrical insulation.

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