One-component cationically polymerizable composition

Abstract

The present invention relates generally to a one-component cationically polymerizable composition comprising an aromatic epoxy resin, an epoxy reactive diluent, a cationic polymerization initiator, a radical forming compound, and optionally a carboxylic acid, and its use in impregnation processes.

Description

[0001] Cross-reference to related patents

[0002] This application claims the priority of EP22214069.1 filed on December 16, 2022. Technical field

[0003] The present invention generally relates to a one-component cationically polymerizable composition and its use in various applications, including impregnating electric motors, generators, and transformers in trickle impregnation, hot-dip rolling, and vacuum impregnation processes. Background art

[0004] The resin impregnation of rotor or stator coils is an important process in the production of electric motors. Traditional impregnation methods are the application of solvent-free base insulating resins for trickle impregnation and dip impregnation. In trickle impregnation, the insulating resin is dripped onto the heated winding rotating at a medium speed until it is completely impregnated. Depending on the resin applied, subsequent resin curing can be achieved at low or high temperatures. In dip impregnation, the rotor or stator is preheated and then fixed on the equipment and immersed in an impregnation bath filled with insulating resin while rotating. After the winding is completely impregnated, the rotor or stator is taken out of the impregnation bath while continuing to rotate until the resin gels. In some cases, post-curing may be required in an oven to completely cure the resin.

[0005] Unsaturated polyester resins and epoxy resins are often used in one-component insulating resin systems for trickle impregnation and dip impregnation processes. However, these prior art resin systems either lack sufficient storage stability, are too viscous, cannot cure due to oxygen inhibition when applied to surfaces exposed to air, or cure too slowly at medium temperatures, making them unsuitable for the fast production cycles in current highly industrialized processes (such as especially the impregnation of electric vehicle stators).

[0006] Therefore, there is a need to develop alternative non-toxic insulating resin systems that can be used in impregnation processes and have good impregnation ability, good adhesion to the main insulation layer, can react quickly at medium temperatures, and have long-term storage stability. Summary of the invention

[0007] The present invention generally provides a one-component cationically polymerizable composition comprising: (a) an epoxy component containing an aromatic epoxy resin and an epoxy-reactive diluent; (b) a cationic polymerization initiator; (c) a radical-forming compound; and optionally (d) a carboxylic acid.

[0008] In another embodiment, there is provided the use of the one-component cationically polymerizable composition as an impregnating or coating composition for electric motors, transformers, and generators.

[0009] In another embodiment, there is provided a method of forming an impregnated substrate, comprising the steps of applying the one-component cationically polymerizable composition of the present invention to a substrate by immersion impregnation, vacuum impregnation or trickle impregnation to form an impregnated substrate, and curing the applied composition.

[0010] In another embodiment, there is provided a rotating facility including a rotor and a stator, wherein the stator includes a coil conductor and an insulating layer covering the coil conductor, and the insulating layer includes a cured product of the one-component cationically polymerizable composition. Detailed Description

[0011] The present invention generally relates to a one-component cationically polymerizable composition comprising an epoxy component containing an aromatic epoxy resin and an epoxy reactive diluent, a cationic polymerization initiator, a radical-forming compound, and optionally a carboxylic acid. It has surprisingly been found that the one-component cationically polymerizable composition of the present invention can not only be rapidly cured at a temperature of about 120 - 140 °C, but also reduce the oxygen sensitivity known for radical-initiating compounds. Additionally, when a carboxylic acid is present, the one-component cationically polymerizable composition may increase the transition temperature range between a long surface gel time and a highly exothermic cure.

[0012] The following terms shall have the following meanings:

[0013] The term "comprising" and its derivatives are not intended to exclude the presence of any additional components, steps or processes, whether or not disclosed herein. To avoid doubt, unless otherwise stated, all compositions required by the term "comprising" as used herein may include any additional additives, adjuvants or compounds. Conversely, if the term "consisting essentially of" appears herein, it excludes the scope of any subsequent recited additional components, steps or processes, except those that are not operationally important, and if the term "consisting of" is applied, any components, steps or processes not specifically described or listed are excluded. Unless otherwise stated, the term "or" refers to elements listed individually or in any combination.

[0014] The indefinite article as used herein refers to one or more (i.e., at least one) of the grammatical subjects of said article. As an example, "an epoxy resin" refers to one or more epoxy resins. Statements such as "in one embodiment", "according to one embodiment" and similar phrases generally mean that the specific feature, structure or property following such phrase is included in at least one embodiment of the present invention, and may be included in multiple embodiments of the present invention. Importantly, such phrases do not necessarily refer to the same aspect. If the specification states that a component or feature "may", "can", "is capable of" or "might" be included or have a certain property, then the specific component or feature is not necessarily included or has the said property.

[0015] As used herein, the term "about" can permit a degree of variation for a numerical value or range, for example, it can be within 10%, within 5%, or within 1% or 0.5% of the numerical value or range limit.

[0016] Numerical values expressed as a range should be interpreted in a flexible manner, including not only the numerical values explicitly described as the range limits, but also all individual numerical values or sub-ranges included within that range, as if those numerical values and sub-ranges were explicitly described. For example, a range such as 1-6 should be considered to include the specifically disclosed sub-ranges such as 1-3, 2-4, 3-6, etc., as well as the individual numerical values within that range, such as 1, 2, 3, 4, 5, and 6. This applies regardless of the width of the range.

[0017] The terms "preferred" and "preferably" refer to embodiments that can provide certain benefits under certain conditions. However, under the same or other conditions, other embodiments may also be preferred. Additionally, the description of one or more preferred embodiments does not imply that other embodiments are useless, nor is it intended to exclude other embodiments from the scope of the invention.

[0018] The term "one-component" or "single-part" composition refers to a composition contained in a single container (preferably a moisture-proof container) and having a certain storage stability. In contrast, a "two-component" composition refers to a composition in which two components (A and B) are physically separated (e.g., contained in different cartridges, compartments, tote bags, cans, or other containers), and when the composition is applied to form a cured resin, components A and B are physically combined (mixed).

[0019] The term "storage stability" refers to the ability of a composition to be stored in a suitable container at ambient temperature for a certain time interval without exposure to moisture, such as at least three months, or at least four months, or at least five months, or at least six months, and without significant change in application or final use properties (e.g., having slight (such as less than about 5% or less than about 4% or less than about 3%) crystallization or no crystallization, and / or having slight (less than about 5% or less than about 4% or less than about 3%) increase in viscosity or no increase in viscosity).

[0020] The term "ambient temperature" refers to the temperature surrounding the working environment (e.g., the temperature of the area, building, or room where the composition is applied), excluding any temperature changes resulting from directly heating the composition to promote curing. The ambient temperature can be about 10-30 °C, more specifically about 15-25 °C.

[0021] The term "primary insulation" refers to electrical insulation, i.e., non-conductive insulation. The primary insulation may include, but is not limited to, polysulfone, polyphenylsulfone ("PPSU"), polysulfide, polyphenylene sulfide ("PPS"), polyether ketone ("PEK"), polyether ether ketone ("PEEK"), polyaryl ether ketone ("PAEK"), polyamide ether ketone, thermoplastic polyimide, and aromatic polyamide.

[0022] When substituents are written in their conventional chemical formula from left to right, they also include the chemically identical substituents resulting from writing the structure from right to left. For example, -CH2O- is equivalent to -OCH2-.

[0023] The term "optionally" or "optionally" means that the subsequently described event or situation may or may not occur, and the description includes the situation when the event or situation occurs and the situation when the event or situation does not occur.

[0024] The term "substantially free of" means that the amount of a specific compound or moiety present in the composition has no substantial effect on the composition. In some embodiments, "substantially free of" may mean that the amount of a specific compound or moiety present in the composition is less than 2 wt%, or less than 1 wt%, or less than 0.5 wt%, or less than 0.1 wt%, or less than 0.05 wt%, or even less than 0.01 wt% based on the total weight of the composition, or the specific compound or moiety is absent in the corresponding composition.

[0025] According to one embodiment, the present invention relates to a one-component cationically polymerizable composition comprising: (a) an epoxy component containing at least about 50 wt% of an aromatic epoxy resin and less than about 50 wt% of an epoxy-reactive diluent, where wt% is based on the total weight of the epoxy component; (b) a cationic polymerization initiator; (c) a radical-forming compound selected from benzoin, peroxides, and azo compounds; and optionally (d) a carboxylic acid; wherein the epoxy-reactive diluent is selected from monofunctional C4-C 30 glycidyl ethers of alcohols, difunctional C2-C 15 glycidyl ethers of alcohols, glycidyl ethers of trifunctional or polyfunctional alcohols, glycidyl ethers of phenolic compounds, glycidyl amines of aniline compounds or monofunctional or difunctional aliphatic or cycloaliphatic amines, and glycidyl esters of monocarboxylic or dicarboxylic acids. In one embodiment, the one-component cationically polymerizable composition is substantially free of basic fillers such as calcium carbonate, magnesium oxide, zinc oxide, silica, titanium oxide, and aluminum oxide.

[0026] The aromatic epoxy resins referred to in this text are epoxy resins containing at least one aromatic unit in the main chain or side chain (if any). Generally, aromatic epoxy resins contain at least one aromatic epoxide, such as phenyl glycidyl ether, preferably located at the terminal position of the resin backbone or side chain (if any). Aromatic epoxy resins that can be applied include, for example, the reaction products of phenols (phenol and formaldehyde) and epichlorohydrin, peracid epoxy resins, glycidyl esters, glycidyl ethers, the reaction products of epichlorohydrin and aminophenols, and the reaction products of epichlorohydrin and glyoxal tetraphenol. The phenols mentioned above include polynuclear phenols (i.e., compounds having at least two phenolic functional groups). Typical examples of polynuclear phenols are bisphenols.

[0027] The aromatic epoxy resins can be liquid, solid, or semi-solid, or blends thereof. Suitable aromatic epoxy resins can include blends of two or more aromatic epoxy resins selected from difunctional, trifunctional, and / or tetrafunctional epoxy resins.

[0028] Examples of difunctional epoxy resins include those based on bisphenol F, bisphenol A (optionally brominated), bisphenol S, phenol, phenol and cresol epoxy novolac resins, aromatic glycidylamines, naphthalene, or any combination thereof. Trifunctional epoxy resins include triglycidyl - p - aminophenol and triglycidyl - m - aminophenol. Tetrafunctional epoxy resins include N,N,N′,N′ - tetraglycidyl - m - xylylenediamine and N,N,N′,N′ - tetraglycidyl methylenedianiline (e.g., MY0720 and MY0721 from Huntsman Advanced Materials Americas LLC). Other suitable polyfunctional epoxy resins include phenol novolac epoxy resins and cresol novolac epoxy resins available under the trade names EPN and ECN (from Huntsman Advanced Materials Americas LLC).

[0029] The epoxy equivalent weight of the aromatic epoxy resin is preferably about 100 - 1000 g / equivalent, or about 200 - 600 g / equivalent, or about 300 - 400 g / equivalent (measured according to DIN 16945).

[0030] In one embodiment, based on the total weight of the epoxy component, the content of the aromatic epoxy resin in the epoxy component is at least about 60 wt%, or at least about 70 wt%, or at least about 80 wt%, at least about 90 wt%. In another embodiment, based on the total weight of the epoxy component, the content of the aromatic epoxy resin in the epoxy component is at least about 50 wt% to about 99 wt%, or at least about 60 wt% to about 95 wt%, or at least about 70 wt% to about 90 wt%.

[0031] The epoxy component also contains an epoxy-reactive diluent. In the context of the present invention, "epoxy-reactive diluent" refers to mono-, di- or polyfunctional, aliphatic or aromatic alcohols or alkylphenol low-viscosity glycidyl ethers, glycidylamines or glycidyl carboxylates, and is used to increase flexibility and processability by diluting high-viscosity epoxy resins. The application of epoxy-reactive diluents can improve the properties of pigments or fillers / additives such as processing viscosity, shelf life and wettability. The application of epoxy-reactive diluents can also optimize flammability and mechanical properties.

[0032] More specifically, the epoxy-reactive diluent is: (i) a glycidyl ether of a monofunctional saturated or unsaturated, branched or unbranched, cyclic or acyclic C4-C 30 alcohol, such as butyl glycidyl ether, hexyl glycidyl ether, 2-ethylhexyl ether, allyl glycidyl ether, tetrahydrofurfuryl and furfuryl glycidyl ether and trimethoxysilane glycidyl ether; (ii) a glycidyl ether of a difunctional saturated or unsaturated, branched or unbranched, cyclic or acyclic C2-C 15 alcohol, such as glycidyl ethers of ethylene glycol, butanediol, hexanediol and octanediol, cyclohexanedimethanol diglycidyl ether and neopentyl glycol diglycidyl ether; (iii) a glycidyl ether of a trifunctional or polyfunctional saturated or unsaturated, branched or unbranched, cyclic or acyclic alcohol, such as epoxidized castor oil, epoxidized trimethylolpropane, epoxidized pentaerythritol or polyglycidyl ethers of aliphatic polyols (such as sorbitol, glycerol and trimethylolpropane); (iv) glycidyl ethers of phenolic compounds, such as phenyl glycidyl ether, cresyl glycidyl ether, p-tert-butylphenyl glycidyl ether, nonylphenol glycidyl ether and 3-n-pentadecenyl glycidyl ether (derived from cashew nut shell liquid); (v) glycidylamines of aniline compounds or mono- or difunctional aliphatic or cycloaliphatic amines, such as N,N-diglycidylaniline and N,N-diglycidylcyclohexylamine; and (vi) glycidyl esters of monocarboxylic or dicarboxylic acids, such as glycidyl neodecanoate, glycidyl methacrylate, glycidyl benzoate, diglycidyl phthalate, tetrahydrophthalate and hexahydrophthalate and diglycidyl esters of dimer fatty acids.

[0033] In one embodiment, based on the total weight of the epoxy component, the content of the epoxy-reactive diluent in the epoxy component is less than about 40 wt%, or less than about 30 wt%, or less than about 20 wt%, or less than about 15 wt%, or less than about 10 wt%. In another embodiment, based on the total weight of the epoxy component, the content of the epoxy-reactive diluent in the epoxy component is from about 1 wt% to less than about 50 wt%, or from about 5 wt% to less than about 45 wt%, or from about 10 wt% to less than about 30 wt%.

[0034] In another embodiment, the epoxy component may further comprise additional epoxy resins such as vinyl cyclohexene dioxide, limonene dioxide, limonene monoxide, vinyl cyclohexene monoxide, 3,4-epoxycyclohexyl methacrylate, 3,4-epoxy-6-methylcyclohexylmethyl 9,10-epoxystearate, and 1,2-bis(2,3-epoxy-2-methylpropoxy)ethane.

[0035] The one-component cationically polymerizable composition further includes a cationic polymerization initiator. The cationic polymerization initiator may be: (i) an aromatic sulfonium salt-based thermal cationic polymerization initiator; (ii) a phosphonium salt-based thermal cationic polymerization initiator; (iii) a quaternary ammonium salt-based thermal cationic polymerization initiator; (iv) an aluminum complex-based thermal cationic polymerization initiator; (v) an aromatic iodonium salt-based thermal cationic polymerization initiator; (vi) an aromatic diazonium salt-based thermal cationic polymerization initiator; or (vii) a pyridinium-based thermal cationic polymerization initiator.

[0036] (i) Examples of aromatic sulfonium salt-based thermal cationic polymerization initiators include: hexafluoroantimonates such as (2-ethoxy-1-methyl-2-oxoethyl)methyl-2-naphthylsulfonium hexafluoroantimonate, 4-(methoxycarbonyloxy)phenylbenzylmethylsulfonium hexafluoroantimonate, 4-acetoxyphenyldimethylsulfonium hexafluoroantimonate, 4-hydroxyphenylbenzylmethylsulfonium hexafluoroantimonate, 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium hexafluoroantimonate, 4-hydroxyphenyl(α-naphthylmethyl)methylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluoroantimonate, bis[4-(bis(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bishexafluoroantimonate and bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluoroantimonate; hexafluorophosphates such as (2-ethoxy-1-methyl-2-oxoethyl)methyl-2-naphthylsulfonium hexafluorophosphate, 4-acetoxyphenylbenzylmethylsulfonium hexafluorophosphate, 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium hexafluorophosphate, 4-hydroxyphenyl(α-naphthylmethyl)methylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, bis[4-(bis(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bishexafluorophosphate and bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate; hexafluoroarsenates such as 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium hexafluoroarsenate and 4-hydroxyphenylbenzylmethylsulfonium hexafluoroarsenate; tetrafluoroborates (2-ethoxy-1-methyl-2-oxoethyl)methyl-2-naphthylsulfonium tetrafluoroborate, 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium tetrafluoroborate, 4-hydroxyphenylbenzylmethylsulfonium tetrafluoroborate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, triphenylsulfonium tetrafluoroborate, bis[4-(bis(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide bistetrafluoroborate and bis[4-(diphenylsulfonio)phenyl]sulfide bistetrafluoroborate; trifluoromethanesulfonates such as 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium trifluoromethanesulfonate and 4-hydroxyphenylbenzylmethylsulfonium trifluoromethanesulfonate; trifluoromethanesulfonates such as diphenyl-4-(phenylthio)phenylsulfonium trifluoromethanesulfonate; bis(trifluoromethanesulfonyl)imide salts such as 4-hydroxyphenyl(α-naphthylmethyl)methylsulfonium bis(trifluoromethanesulfonyl)imide and 4-hydroxyphenylbenzylmethylsulfonium bis(trifluoromethanesulfonyl)imide;Tetrakis(pentafluorophenyl)borates such as (2-ethoxy-1-methyl-2-oxoethyl)methyl-2-naphthalenesulfonium tetrakis(pentafluorophenyl)borate, 4-(methoxycarbonyloxy)phenylbenzylmethylsulfonium tetrakis(pentafluorophenyl)borate, 4-hydroxyphenyl(o-methylbenzyl)methylsulfonium tetrakis(pentafluorophenyl)borate, 4-hydroxyphenyl(α-naphthylmethyl)methylsulfonium tetrakis(pentafluorophenyl)borate, 4-hydroxyphenylbenzylmethylsulfonium tetrakis(pentafluorophenyl)borate, diphenyl-4-(phenylthio)phenylsulfonium tetrakis(pentafluorophenyl)borate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis[4-(bis(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide tetrakis(pentafluorophenyl)borate and bis[4-(diphenylsulfonio)phenyl]sulfide tetrakis(pentafluorophenyl)borate.;

[0037] Examples of phosphonium salt-based thermal cationic polymerization initiators include ethyltriphenylphosphonium hexafluoroantimonate and tetrabutylphosphonium hexafluoroantimonate.

[0038] Examples of quaternary ammonium salt-based thermal cationic polymerization initiators include N,N-dimethyl-N-benzylaniline hexafluoroantimonate, N,N-diethyl-N-benzylaniline tetrafluoroborate, N,N-dimethyl-N-benzylpyridinium hexafluoroantimonate, N,N-diethyl-N-benzylpyridinium trifluoromethanesulfonate, N,N-dimethyl-N-(4-methoxybenzyl)pyridinium hexafluoroantimonate, N,N-diethyl-N-(4-methoxybenzyl)pyridinium hexafluoroantimonate, N,N-diethyl-N-(4-methoxybenzyl)toluidine hexafluoroantimonate and N,N-dimethyl-N-(4-methoxybenzyl)toluidine hexafluoroantimonate.

[0039] Examples of aluminum complex-based thermal cationic polymerization initiators include aluminum carboxylate, aluminum alkoxide, aluminum chloride, (alkoxide)aluminum acetylacetonate chelate, aluminum acetylacetonate and aluminum ethylacetoacetate.

[0040] (v) Examples of aromatic iodonium salt-based thermal cationic polymerization initiators include phenyl iodonium hexafluorophosphate, diphenyl iodonium hexafluoroantimonate, diphenyl iodonium tetrafluoroborate, diphenyl iodonium tetrakis(pentafluorophenyl)borate, diphenyl iodonium hexafluorophosphate, diphenyl iodonium trifluoromethanesulfonate, bis(dodecylphenyl)iodonium hexafluorophosphate, bis(dodecylphenyl)iodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate, 4-methylphenyl-4-(1-methylethyl)phenyl iodonium hexafluorophosphate, 4-methylphenyl-4-(1-methylethyl)phenyl iodonium hexafluoroantimonate, 4-methylphenyl-4-(1-methylethyl)phenyl iodonium tetrafluoroborate, 4-isopropyl-4'-methyldiphenyl iodonium tetrakis(pentafluorophenyl)borate, and 4-methylphenyl-4-(1-methylethyl)phenyl iodonium tetrakis(pentafluorophenyl)borate.

[0041] (vi) Examples of aromatic diazonium salt-based thermal cationic polymerization initiators include phenyl diazonium hexafluorophosphate, phenyl diazonium hexafluoroantimonate, phenyl diazonium tetrafluoroborate, and phenyl diazonium tetrakis(pentafluorophenyl)borate.

[0042] (vii) Examples of pyridinium-based thermal cationic polymerization initiators include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, 1-benzyl-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluorophosphate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluoroantimonate, 1-(naphthylmethyl)-2-cyanopyridinium tetrafluoroborate, and 1-(naphthylmethyl)-2-cyanopyridinium tetrakis(pentafluorophenyl)borate.

[0043] These cationic polymerization initiators can be used alone or as a mixture of two or more. In a preferred embodiment, the polymerization initiator is an aromatic iodonium salt-based thermal cationic polymerization initiator. In another embodiment, the aromatic iodonium salt-based thermal cationic polymerization initiator is diphenyl iodonium hexafluorophosphate, bis(4-methylphenyl)iodonium hexafluorophosphate, diaryl iodonium hexafluoroantimonate, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluoroantimonate, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium hexafluorophosphate, (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium tetrafluoroborate, 4-octoxyphenylphenyl iodonium hexafluoroantimonate, 4-(2-hydroxytetradecyloxyphenyl)phenyl iodonium hexafluoroantimonate, or 4-isopropyl-4'-methyldiphenyl iodonium borate.

[0044] In one embodiment, based on the total weight of the one-component cationically polymerizable composition, the content of the cationic polymerization initiator in the one-component cationically polymerizable composition is less than about 5 wt%, or less than about 4 wt%, or less than about 3 wt%, or less than about 2 wt% or less than about 1 wt%. In another embodiment, based on the total weight of the one-component cationically polymerizable composition, the content of the cationic polymerization initiator in the one-component cationically polymerizable composition is about 0.01 - 3 wt%, or about 0.1 - 1 wt%.

[0045] The one-component cationically polymerizable composition further comprises a radical-forming compound. The radical-forming compound is typically a peroxide or benzoin, but other radical-forming compounds such as azo compounds can also be used. In some embodiments, the radical-forming compound is a compound having a half-life of 1 hour at a temperature of about 100 - 130 °C.

[0046] Any peroxide that is liquid or soluble in the one-component cationically polymerizable composition is suitable. Specific examples of such peroxides include methyl ethyl ketone peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, isopropyl peroxy dicarbonate, dichlorobenzoyl peroxide, lauroyl peroxide, acetyl peroxide, tert-butyl peroxyacetate, tert-butyl peroxybenzoic acid, diisopropyl peroxide, diethyl peroxide, di-tert-amyl peroxide, and cyclohexyl hydroperoxide. Specific examples of azo compounds include 2,2'-azobis[N-(2-propenyl)-2-methylpropanamide], 1-[(cyano-1-methylethyl)azo]formamide, 2,2'-azobis(N-butyl-2-methylpropanamide), 2,2'-azobis(N-cyclohexyl-2-methylpropanamide), 2,2'-azobis(2-methyl-N-[2-(1-hydroxybutyl)]propanamide), 2,2'-azobis(2-methyl-N-[2-(1-hydroxybutyl)]propanamide), and 2,2'-azobis(2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propanamide).

[0047] In one embodiment, based on the total weight of the one-component cationically polymerizable composition, the content of the radical-forming compound in the one-component cationically polymerizable composition is less than about 5 wt%, or less than about 4 wt%, or less than about 3 wt%, or less than about 2 wt% or less than about 1 wt%. In another embodiment, based on the total weight of the one-component cationically polymerizable composition, the content of the radical-forming compound in the one-component cationically polymerizable composition is about 0.01 - 5 wt%, or about 0.1 - 3 wt%.

[0048] In one embodiment, the one-component cationically polymerizable composition further comprises a carboxylic acid. The carboxylic acid includes carboxylic acids having 1-20 carbon atoms. Specifically, the carboxylic acid can be formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, n-valeric acid, pivalic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, acrylic acid, methacrylic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, benzoic acid, phenylacetic acid, o-, m-, p-toluic acid, o-, p-chlorobenzoic acid, o-, p-nitrobenzoic acid, salicylic acid, p-hydroxybenzoic acid, o-aminobenzoic acid, p-aminobenzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, trimesic acid, mellitic acid, and mixtures of two or more of them.

[0049] In one embodiment, based on the total weight of the one-component cationically polymerizable composition, the carboxylic acid content in the one-component cationically polymerizable composition is less than about 5 wt%, or less than about 4 wt%, or less than about 3 wt%, or less than about 2 wt%, or less than about 1 wt%. In another embodiment, based on the total weight of the one-component cationically polymerizable composition, the carboxylic acid content in the one-component cationically polymerizable composition is about 0.01-5 wt%, or about 0.1-3 wt%.

[0050] In another embodiment, the one-component cationically polymerizable composition can include one or more additives, including but not limited to plasticizers, chain extenders, pigments and dyes such as carbon black, oxide colorants and titanium oxide, and flame retardants, defoamers, thixotropic agents, flow control agents, adhesion promoters (such as epoxy silanes) and antioxidants (such as sterically hindered phenols). Other additives can include fillers, such as metal powders, wood powders, glass powders, glass beads, semimetals and metal oxides such as SiO2 (silica sand, silica powder, silanized silica powder, synthetic silica powder, silanized synthetic silica powder), semimetals and metal carbides (SiC and boron carbide), semimetals and metal nitrides (AlN and BN), metal carbonates (dolomite, chalk, CaCO3), metal sulfides (barite, gypsum), rock powders (such as from hydromagnesite and huntite) and natural or synthetic minerals mainly from silicate classes, such as zeolites (especially molecular sieves), talc, mica, kaolin, wollastonite, etc.

[0051] The additives can also include fungicides, defoamers, antistatic agents, lubricants, anti-settling agents, water repellents and mold release agents.

[0052] Optional additives can also be selected from toughening agents such as CTBN type toughening agents, core-shell toughening agents, block copolymers (such as silicone-butyrolactone type), and polyurethanes, for example phenol-terminated polyurethane adducts such as Flexibilizer DY 965 from Huntsman Advanced Materials LLC.

[0053] The one-component cationically polymerizable composition of the present invention can be prepared by mixing the components at ambient temperature or slightly elevated temperature, and if desired, using a suitable grinder such as a ball mill or a needle mill, a kneader or a mixer.

[0054] Curing of the one-component cationically polymerizable composition of the present invention can be carried out in a known manner. Generally, it can be carried out by heating the composition to a temperature of about 50 - 250 °C, preferably about 110 - 150 °C. Thus, according to another embodiment, there is provided a cured or crosslinked product obtained by curing a one-component epoxy resin-based composition.

[0055] According to another embodiment, there is provided a storage-stable packaged product comprising: a) a container having at least one outlet; and b) the one-component cationically polymerizable composition of the present invention.

[0056] According to one embodiment, the packaged product comprises a container having a closure means such as a top, lid, cap or plug for sealing the container. In another embodiment, the sealed container further has a nozzle or a pouring spout. The sealed container can be cylindrical, oval, round, rectangular, flat round box-shaped, barrel-shaped, square or jug-shaped, and contains the one-component cationically polymerizable composition of the present invention.

[0057] In yet another embodiment, the container can be made of any material such as steel, glass, aluminum, cardboard, tinplate, plastics including but not limited to high density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), oriented polypropylene (OPP), polyethylene (PE) or polyamide, including mixtures, laminates or other combinations of these materials.

[0058] The one-component cationically polymerizable composition disclosed herein can be used in castings, potting compounds, encapsulants, coatings, composites, or laminates, and more particularly, can be used in electrical or electronic castings, electrical or electronic potting compounds, electrical or electronic encapsulants, electrical laminates, structural composites, or protective coatings. The compositions of the present invention can also be used in a variety of other end applications, including, for example, as adhesives in structural laminates, electrical laminates, coatings, castings, aerospace industry structures, printed circuit boards in the electronics industry, and in the formation of ski boards, ski poles, fishing rods, and other outdoor sports equipment. The compositions disclosed herein can also be used in electrical varnishes, sealants, semiconductors, filament-wound tubes, storage tanks, pump linings, and corrosion-resistant coatings, etc.

[0059] In yet another embodiment, there is also provided an article prepared by heat-curing the one-component cationically polymerizable composition of the present invention. The article can include, for example, castings, potting compounds, encapsulants, coatings, composites, or laminates. The article can also include, for example, printed circuit boards, electrical or electronic castings, electrical or electronic potting compounds, electrical or electronic encapsulants, electrical laminates, structural composites, or protective coatings. The curing reaction of the one-component cationically polymerizable composition can be carried out at a temperature generally of about 40 - 250 °C or about 100 - 220 °C or about 110 - 140 °C. The curing time can be a predetermined time interval, which can range from a few minutes to several hours, and generally the reaction time is greater than about 5 minutes and less than about 24 hours, preferably about 5 minutes to about 6 hours, and more preferably about 5 minutes to about 2 hours. In other embodiments, curing can be carried out at a first temperature and then at a second temperature or post-treated, and the post-treatment is generally carried out at a temperature higher than 100 °C or higher than 140 °C.

[0060] In one embodiment, when cured at at least one temperature between 110 - 120 °C, the gelling time of the one-component cationically polymerizable composition is not greater than about 800 seconds, preferably not greater than about 750 seconds, and more preferably not greater than about 720 seconds. For the purposes of the present invention, the gelling time is measured by a method using a gel timer device, in which a die made of aluminum or stainless steel is cycled up and down in a test tube filled with the composition to be tested. When the gel point is reached, the die pulls up the test tube, stops the timer, and the gelling time is read from the timer.

[0061] In another embodiment, when cured at at least one temperature between 120 - 145 °C, the surface gelling time of the one-component cationically polymerizable composition is not greater than about 75 minutes, or not greater than about 60 minutes, or not greater than about 45 minutes or not greater than about 30 minutes, which is measured by the following method: a sample of the composition to be tested is applied to a preheated hot plate at a temperature of 120 - 145 °C, and the time from the start of the experiment until the surface of the droplet exposed to the air becomes non-sticky is measured.

[0062] In a particular embodiment, there is provided the use of a one-component cationically polymerizable composition as an impregnating and coating composition for electric motors, transformers, and generators (such as the wound conductors of stators, rotors, generators, or transformers).

[0063] According to another embodiment, the one-component cationically polymerizable composition of the present invention can be applied to a substrate by trickle impregnation, dip impregnation, or vacuum impregnation. In some embodiments, the substrate can be one or more components of an electric motor or generator, such as coils or windings on conductors of a stator or rotor or transformer. In other embodiments, the substrate can include a primary insulation layer and the one-component cationically polymerizable composition can be applied to the primary insulation layer by trickle impregnation, dip impregnation, or vacuum impregnation.

[0064] Thus, in another embodiment, there is provided a method of forming an impregnated substrate, comprising the steps of: applying the one-component epoxy resin-based composition of the present invention to a substrate by dip impregnation, vacuum impregnation, or trickle impregnation to form an impregnated substrate, and curing the applied composition. In some embodiments, the substrate includes a primary insulation layer and the one-component epoxy resin-based composition is applied to the primary insulation layer. In another embodiment, there is provided a substrate impregnated with a one-component epoxy resin-based composition, such as a wound conductor of a stator, rotor, transformer, or generator.

[0065] The present invention is further described below with reference to the following non-limiting examples.

[0066] Embodiment

[0067] Example 1: One-Component Cationically Polymerizable Composition of the Present Invention

[0068] As shown in Table 1 below, different amounts of each component were added to a container and mixed to form a composition. Then the gel time and surface gel time of the composition were measured as described above, and the results are shown below.

[0069] Table 1

[0070]

[0071] a) Unless otherwise specified, all components were mixed under ambient conditions until a homogeneous solution was formed

[0072] b) Pre-dissolved in GY 250 at 50 °C

[0073] c) High exothermic curing

[0074] d) The test was stopped after 180 min

[0075] It was found that the addition of 10 parts by weight of an aliphatic epoxy reactive diluent (butanediol diglycidyl ether) significantly accelerated the gel time and the surface gel time (see Examples 1 and Comparative Example 1). In addition, it was observed that the combination of an epoxy reactive diluent with a carboxylic acid compound (maleic acid) could result in an increased transition temperature range between a long surface gel time and a highly exothermic cure (see Example 2). The same behavior was also seen when tert-butyl perbenzoate was applied to replace benzoin (see Examples 3-4 and Comparative Example 2).

[0076] Although the various embodiments of the present invention for its preparation and application have been described in detail above, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in a variety of specific contexts. The specific embodiments discussed herein only describe the specific ways of preparing and applying the present invention and do not limit the scope of the present invention.

Claims

1. A one-component cationically polymerizable composition, comprising: (a) an epoxy component containing at least 50 wt% of an aromatic epoxy resin and less than about 50 wt% of an epoxy-reactive diluent, wherein wt% is based on the total weight of the epoxy component; (b) a cationic polymerization initiator; and (c) a radical-forming compound selected from benzoin, peroxides, and azo compounds, wherein the epoxy reactive diluent is selected from glycidyl ethers of monofunctional C4-C 30 alcohols, glycidyl ethers of difunctional C2-C 15 alcohols, glycidyl ethers of trifunctional or polyfunctional alcohols, glycidyl ethers of phenolic compounds, glycidyl amines of aniline compounds or mono- or difunctional aliphatic or cycloaliphatic amines, and glycidyl esters of monocarboxylic or dicarboxylic acids.

2. The one-component cationically polymerizable composition of claim 1, wherein the aromatic epoxy resin is bisphenol A epoxy resin or bisphenol F epoxy resin.

3. The one-component cationically polymerizable composition of claim 1, wherein the aromatic epoxy resin is phenol novolac epoxy resin or cresol novolac epoxy resin.

4. The one-component cationically polymerizable composition according to any one of claims 1-3, wherein the cationic polymerization initiator is an aromatic iodonium salt-based cationic polymerization initiator, and preferably the aromatic iodonium salt-based cationic polymerization initiator is diphenyliodonium tetrakis(pentafluorophenyl)borate.

5. The one-component cationically polymerizable composition according to any one of claims 1-4, wherein the radical-forming compound is benzoin.

6. The one-component cationically polymerizable composition according to any one of claims 1-4, wherein the radical-forming compound is a peroxide.

7. The one-component cationically polymerizable composition according to any one of claims 1-6, wherein the composition further comprises a carboxylic acid, preferably present in an amount of about 0.01-5 wt%, wherein wt% is based on the total weight of the one-component cationically polymerizable composition.

8. The one-component cationically polymerizable composition according to any one of claims 1-7, further comprising one or more additives.

9. The one-component cationically polymerizable composition according to any one of claims 1-8, wherein (a) based on the total weight of the epoxy component, the aromatic epoxy resin is present in an amount of at least about 60 wt% to about 95 wt%, and the epoxy-reactive diluent is present in an amount of about 5 wt% to less than about 40 wt%; (b) based on the total weight of the one-component cationically polymerizable composition, the cationic polymerization initiator is present in an amount of about 0.01 wt% to about 5 wt%; and (c) based on the total weight of the one-component cationically polymerizable composition, the radical-forming compound is present in an amount of about 0.01 wt% to about 5 wt%.

10. A packaged product, comprising: a) a container having at least one outlet; and b) the one-component cationically polymerizable composition according to any one of claims 1-9.

11. The packaged product of claim 10, wherein the one-component cationically polymerizable composition according to any one of claims 1-9 has a storage stability of at least 6 months at 25 °C.

12. Use of the one-component cationically polymerizable composition according to any one of claims 1-9 for impregnating a protective coating or for adhesion to electrical or electronic castings, electrical or electronic potting compounds, electrical or electronic encapsulants, electrical laminates, or structural composites.

13. Use of the one-component cationically polymerizable composition according to any one of claims 1-9 as an impregnating or coating composition for electric motors, transformers, and generators.

14. A method of forming an impregnated substrate, comprising the steps of: applying a one-component cationically polymerizable composition according to any one of claims 1-9 to a substrate by immersion impregnation, vacuum impregnation or trickle impregnation to form an impregnated substrate, and curing the applied composition.

15. The method of claim 14, wherein the substrate comprises a main insulation layer and the one-component cationically polymerizable composition is applied to the main insulation layer, wherein the substrate is preferably a wound conductor of a rotor or a stator.

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