JP2017002283A - Curable composition for electric machine and related method - Google Patents

Abstract

A curable composition for electrical machines and related methods is provided. The curable composition comprises (A) from about 10% to about 30% by weight of a polyfunctional cyanate ester and (B) from about 25% to about 60% by weight of a first difunctional. About 5 thermally conductive filler comprising cyanate ester or prepolymer thereof, (C) about 10 wt% to about 30 wt% of a second difunctional cyanate ester or prepolymer thereof, and (D) boron nitride. % To about 25% by weight. Related methods are also provided. [Selection] Figure 1

Description

  The present invention generally relates to a curable composition comprising a cyanate ester resin. Specifically, this invention relates to the cyanate ester resin composition for sealing the components of an electric machine.

  Thermosetting resins are commonly used as electrical insulating sealing (for example, potting) materials for electric machines. Thermosetting resins such as cyanate ester resins have the desired mechanical properties, thermal stability and chemical resistance. However, when used at high temperatures, the performance of these materials becomes inadequate and may cause significant thermal degradation even with short operating times. Conventional sealing materials can also crack and overheat at the operating temperature of the electrical machine. Therefore, it is desirable if the thermal conductivity and mechanical properties of the cyanate ester resin used for sealing the material can be improved. There is also a need for improved materials for dissipating the heat generated in electrical machines, particularly for generators used in aircraft and other aerospace applications.

  Therefore, an electrically insulating sealing material that can be used at high temperatures and is effective for heat dissipation from an electric machine is desired. Furthermore, an improved sealing method for electromechanical parts is also desired.

US Patent Application Publication No. 2014/0349089

Embodiments of the present invention include those that satisfy the above other needs. One embodiment is a curable composition for an electrical machine. The curable composition is
(A) from about 10% to about 30% by weight of a multifunctional cyanate ester of structure (I);

(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).

In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 25 wt% to about 60 wt% of the first difunctional cyanate ester of structure (II) or prepolymer thereof;

(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 10 wt% to about 30 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;

(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) about 5 wt% to about 25 wt% of a thermally conductive filler containing boron nitride.

One embodiment is a curable composition for sealing electrical machine components. The curable composition is
(A) about 14% to about 18% by weight of a multifunctional cyanate ester of structure (I);

(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).

In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 32 wt% to about 40 wt% of a first difunctional cyanate ester of structure (II) or a prepolymer thereof;

(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 18 wt% to about 22 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;

(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) about 18 wt% to about 22 wt% of a thermally conductive filler comprising boron nitride;
(E) about 5 wt.% To about 15 wt.

One embodiment is a method for sealing a component of an electrical machine, the method comprising contacting the component with a sealing material including the curable composition and curing the curable composition. Is
(A) from about 10% to about 30% by weight of a multifunctional cyanate ester of structure (I);

(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).

In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 25 wt% to about 60 wt% of the first difunctional cyanate ester of structure (II) or prepolymer thereof;

(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 10 wt% to about 30 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;

(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) about 5 wt% to about 25 wt% of a thermally conductive filler containing boron nitride.

  These and other features, aspects and advantages of the present invention may be better understood by reference to the following detailed description taken in conjunction with the drawings in which:

It is a figure which shows the stator containing the curable composition which concerns on one embodiment of this invention. It is a graph which shows the change of the thermal conductivity with the increase in the density | concentration of the boron nitride which concerns on one embodiment of this invention.

  As described in detail below, some of the embodiments of the present invention relate to compositions for sealing bonding of components or windings in an electric machine. More particularly, the present invention relates to a cyanate ester resin composition for sealing a component in an electric machine.

  Approximate expressions used in the specification and in the claims apply in modifying quantities and expressing quantities that can vary within an acceptable range that does not change the underlying function involved. Thus, values modified with terms such as “about” and “substantially” are not limited to the exact numerical values. In some cases, the approximate representation corresponds to the accuracy of the instrument that measures the value. The upper and lower limits of the ranges set forth in the specification and claims can be combined and / or interchanged with each other, and even if such ranges are specified, they are within the ranges unless otherwise apparent from the wording or context. All intermediate ranges belonging to are included.

  In the specification and in the claims, the singular forms also include a plurality of cases unless clear from the context. As used herein, the term “or” does not exclude the other, but means that there is one or more of the referenced components, and combinations of the referenced components unless the context clearly indicates otherwise. It also includes the case where exists.

As used herein, the term “aromatic group” refers to an atomic arrangement of one or more valences that includes one or more aromatic groups. The atomic arrangement of one or more valences containing one or more aromatic groups may contain heteroatoms such as nitrogen, sulfur, selenium, silicon and oxygen, or may consist of only carbon and hydrogen. The term “aromatic group” used in the present specification includes, but is not limited to, phenyl group, pyridyl group, furanyl group, thienyl group, naphthyl group, phenylene group and biphenyl group. As described above, the aromatic group includes one or more aromatic groups. The aromatic group is always a cyclic structure having 4n + 2 (where “n” is an integer of 1 or more) “delocalized” electrons, and includes a phenyl group (n = 1), a thienyl group (n = 1), furanyl group (n = 1), naphthyl group (n = 2), azulenyl group (n = 2), anthracenyl group (n = 3) and the like. The aromatic group may contain a non-aromatic component. For example, a benzyl group is an aromatic group that includes a phenyl ring (aromatic group) and a methylene group (non-aromatic component). Similarly, a tetrahydronaphthyl group is an aromatic group formed by condensing an aromatic group (C ₆ H ₃ ) with a non-aromatic component — (CH ₂ ) ₄ —. For convenience, the term “aromatic group” is used herein to refer to alkyl, alkenyl, alkynyl, haloalkyl, haloaromatic, conjugated dienyl, alcohol, ether, aldehyde, ketone, It is defined to include a wide range of functional groups such as acid groups, acyl groups (for example, carboxylic acid derivatives such as esters and amides), amine groups, and nitro groups. For example, the 4-methylphenyl radical is a C ₇ aromatic radical comprising a methyl group, the methyl group being a functional group which is an alkyl group. Similarly, the 2-nitrophenyl group is a C ₆ aromatic group containing a nitro group, and the nitro group is a functional group. Aromatic groups include 4-trifluoromethylphenyl, hexafluoroisopropylidenebis (4-phen-1-yloxy) (ie —OPhC (CF ₃ ) ₂ PhO—), 4-chloromethylphen-1-yl, trifluorovinyl-2-thienyl, 3-trichloromethylphen-1-yl _{(i.e., 3-CCl 3 Ph -)} , 4- (3- bromoprop-1-yl) phen-1-yl (i.e., 4 A halogenated aromatic group such as —BrCH ₂ CH ₂ CH ₂ Ph—). Other examples of aromatic groups include 4-allyloxyphen-1-oxy, 4-aminophen-1-yl (ie 4-H ₂ NPh-), 3-aminocarbonylphen-1-yl (ie , NH ₂ COPh -), 4-benzoyl 1-yl, dicyanomethylidene bis (4-phen-1-yloxy) _{(i.e., -OPhC (CN) 2 PhO -} ), 3- methyl-1-yl , methylenebis (4-phen-1-yloxy) (i.e., -OPhCH ₂ PhO -), 2- Echirufen-1-yl, phenylethenyl, 3-formyl-2-thienyl, 2-hexyl-5-furanyl, hexamethylene methylene-1,6-bis (4-phen-1-yloxy) _{(i.e., -OPh (CH 2) 6 PhO} -), 4- hydroxymethyl-1-yl (i.e., 4-HOCH ₂ h -), 4-mercaptomethyl-1-yl _{(i.e., 4-HSCH 2 Ph -)} , 4- methyl-thiophen-1-yl _{(i.e., 4-CH 3 SPh -)} , 3- methoxy-phen-1 Yl, 2-methoxycarbonylphen-1-yloxy (eg methyl salicyl), 2-nitromethylphen-1-yl (ie 2-NO ₂ CH ₂ Ph), 3-trimethylsilylphen-1-yl, 4- Examples include t-butyldimethylsilylphen-1-yl, 4-vinylphen-1-yl, vinylidenebis (phenyl), and the like. The term “C ₃ -C ₁₀ aromatic group” includes aromatic groups having 3 to 10 carbon atoms. The aromatic group 1-imidazolyl (C ₃ H ₂ N ₂ —) is a representative example of a C ₃ aromatic group. A benzyl group (C ₇ H ₈ —) is a representative example of a C ₇ aromatic group.

As used herein, the term “alicyclic group” refers to a group having a valence of at least one comprising an atomic arrangement that is cyclic but not aromatic. An “alicyclic group” as defined herein does not contain an aromatic group. An “alicyclic group” may contain one or more acyclic components. For example, a cyclohexylmethyl group (C ₆ H ₁₁ CH ₂ —) is an alicyclic group containing a cyclohexyl ring (a cyclic but non-aromatic atomic arrangement) and a methylene group (acyclic component). The alicyclic group may contain a heteroatom such as nitrogen, sulfur, selenium, silicon and oxygen, or may be composed only of carbon and hydrogen. For convenience, the term “alicyclic group” is used herein to refer to an alkyl group, alkenyl group, alkynyl group, haloalkyl group, conjugated dienyl group, alcohol group, ether group, aldehyde group, ketone group, carboxylic acid group, acyl group. Defined as containing a wide range of functional groups such as groups (eg carboxylic acid derivatives such as esters and amides), amine groups, nitro groups. For example, a 4-methylcyclopent-1-yl group is a C ₆ alicyclic group containing a methyl group, and the methyl group is a functional group that is an alkyl group. Similarly, the 2-nitrocyclobut-1-yl group is a C ₄ alicyclic group containing a nitro group, and the nitro group is a functional group. The alicyclic group may contain one or more halogen atoms that are the same or different. Halogen atoms include, for example, fluorine, chlorine, bromine and iodine. Alicyclic groups containing one or more halogen atoms include 2-trifluoromethylcyclohex-1-yl, 4-bromodifluoromethylcyclooct-1-yl, 2-chlorodifluoromethylcyclohex-1-yl, hexafluoro-2,2-bis (cyclohex-4-yl) _{(i.e., -C 6 H 10 C (CF} 3) 2 C 6 H 10 -), 2- chloromethyl-cyclohexadiene-1-yl, 3 -Difluoromethylenecyclohex-1-yl, 4-trichloromethylcyclohex-1-yloxy, 4-bromodichloromethylcyclohex-1-ylthio, 2-bromoethylcyclopent-1-yl, 2-bromopropylcyclohexa 1-yloxy _{(e.g., O- CH 3 CHBrCH 2 C 6} H 10) , and the like. Other examples of alicyclic groups include 4-allyloxycyclohex-1-yl, 4-aminocyclohex-1-yl (ie, H ₂ NC ₆ H ₁₀ —), 4-aminocarbonylcyclopenta- 1- yl _{(i.e., NH 2 COC 5 H 8 -} ), 4- acetyloxy-cyclohexadiene-1-yl, 2,2-dicyano isopropylidene bis (cyclohex-4-yloxy) (i.e., -OC ₆ H ₁₀ C _{(CN) 2 C 6 H 10} O -), 3- methylcyclohexanol 1-yl, methylenebis (cyclohex-4-yloxy) _{(i.e., -OC 6 H 10 CH 2 C} 6 H 10 O -), 1- Ethylcyclobut-1-yl, cyclopropylethenyl, 3-formyl-2-tetrahydrofuranyl, 2-hexyl-5-tetrahydrofuranyl, hexamethylene-1,6-bis (cyclohex-4- Yloxy) _{(i.e., -OC 6 H 10 (CH 2} ) 6 C 6 H 10 O -), 4- hydroxymethyl-cyclohexadiene-1-yl _{(i.e., 4-HOCH 2 C 6 H} 10 -), 4- mercapto methylcyclohexanol 1-yl _{(i.e., 4-HSCH 2 C 6 H} 10 -), 4- methylthiophenyl cyclohexadiene-1-yl _{(i.e., 4-CH 3 SC 6 H} 10 -), 4- methoxy cyclohexanol - 1-yl, 2-methoxycarbonyl-cyclohexadiene-1-yloxy _{(2-CH 3 OCOC 6 H} 10 O -), 4- nitro-methylcyclohexanol-1-yl _{(i.e., NO 2 CH 2 C 6 H} 10 -) 3-trimethylsilylcyclohex-1-yl, 2-t-butyldimethylsilylcyclopent-1-yl, 4-trimethoxysilylethylcyclohex-1-yl (for example, (CH ₃ O) ₃ SiCH ₂ CH ₂ C ₆ H ₁₀ -), 4- vinylcyclohexene-1-yl, and the like vinylidene bis (cyclohexyl). The term “C ₃ -C ₁₀ alicyclic group” includes alicyclic groups having 3 to 10 carbon atoms. The alicyclic group 2-tetrahydrofuranyl (C ₄ H ₇ O—) is a representative example of a C ₄ alicyclic group. Cyclohexylmethyl group (C ₆ H ₁₁ CH ₂ —) is C ₇ alicyclic As used herein, the term “aliphatic group” is an organic compound having a valence of 1 or more consisting of a linear or branched atom array that is not cyclic. Refers to the group. An aliphatic group is defined as containing one or more carbon atoms. The atomic arrangement forming the aliphatic group may include heteroatoms such as nitrogen, sulfur, silicon, selenium and oxygen, or may be composed of only carbon and hydrogen. For convenience, the term “aliphatic group” as used herein refers to an alkyl group, alkenyl group, alkynyl group, haloalkyl group, conjugated dienyl group, alcohol as part of a “non-cyclic linear or branched atom array”. It is defined to include a wide range of functional groups such as groups, ether groups, aldehyde groups, ketone groups, carboxylic acid groups, acyl groups (for example, carboxylic acid derivatives such as esters and amides), amine groups, and nitro groups. For example, a 4-methylpent-1-yl group is a C ₆ aliphatic group containing a methyl group, and the methyl group is a functional group that is an alkyl group. Similarly, the 4-nitrobut-1-yl group is a C ₄ aliphatic group containing a nitro group, and the nitro group is a functional group. The aliphatic group may be a haloalkyl group containing one or more halogen atoms that are the same or different. Halogen atoms include, for example, fluorine, chlorine, bromine and iodine. Aliphatic groups containing one or more halogen atoms include alkyl halides trifluoromethyl, bromodifluoromethyl, chlorodifluoromethyl, hexafluoroisopropylidene, chloromethyl, difluorovinylidene, trichloromethyl, bromodichloromethyl, bromoethyl, 2-bromotrimethylene (eg, —CH ₂ CHBrCH ₂ —) and the like. Other examples of aliphatic groups include allyl, aminocarbonyl (ie, —CONH ₂ ), carbonyl, 2,2-dicyanoisopropylidene (ie, —CH ₂ C (CN) ₂ CH ₂ —), methyl (ie, , —CH ₃ ), methylene (ie, —CH ₂ —), ethyl, ethylene, formyl (ie, —CHO), hexyl, hexamethylene, hydroxymethyl (ie, —CH ₂ OH), mercaptomethyl (ie, — CH ₂ SH), methylthio (i.e., -SCH _3), methylthiomethyl (i.e., -CH ₂ SCH _3), methoxy, methoxycarbonyl (i.e., CH ₃ OCO-), nitromethyl (i.e., -CH ₂ NO _2), Thiocarbonyl, trimethylsilyl (ie, (CH ₃ ) ₃ Si—), t-butyldimethylsilyl, 3-trimethoxysilylpropyl (ie, (CH ₃ O) ₃ SiCH ₂ CH ₂ CH ₂ —), vinyl, vinylidene and the like. As another example, the C ₁ -C ₁₀ aliphatic group has ₁ to ₁₀ carbon atoms. A methyl group (ie, CH ₃ —) is an example of a C ₁ aliphatic group. A decyl group (ie, CH ₃ (CH ₂ ) ₉ —) is an example of a C ₁₀ aliphatic group.

As described in detail below, certain embodiments of the present invention are directed to curable compositions for electrical machines. The curable composition is
(A) from about 10% to about 30% by weight of a multifunctional cyanate ester of structure (I);

(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).

In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 25 wt% to about 60 wt% of the first difunctional cyanate ester of structure (II) or prepolymer thereof;

(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 10 wt% to about 30 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;

(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) about 5 wt% to about 25 wt% of a thermally conductive filler containing boron nitride.

  As used herein, “polyfunctional cyanate ester” refers to a material containing three or more cyanate ester functional groups. As used herein, the term “bifunctional cyanate ester” refers to a material that contains two cyanate ester functional groups.

  Non-limiting examples of suitable multifunctional cyanate esters include phenol novolac cyanate esters, dicyclopentadiene novolac cyanate esters, 1,2,3-tris (4-cyanatephenyl) -propane, or combinations thereof. In certain embodiments, the multifunctional cyanate ester comprises a structure of formula (VII) or (VIII).

Non-limiting examples of suitable multifunctional cyanate esters include Primaset ™ PT30, Primaset ™ PT15 or combinations thereof commercially available from Lonza.

  In certain embodiments, the amount of multifunctional cyanate ester in the curable composition is from about 10% to about 30% by weight. In certain embodiments, the amount of multifunctional cyanate ester in the curable composition is from about 12% to about 22% by weight. In certain embodiments, the amount of multifunctional cyanate ester in the curable composition is from about 14% to about 18% by weight.

  In certain embodiments, the first bifunctional cyanate ester comprises a structure of formula (IV).

In the formula, Ar ³ is a C _{5 to} C ₃₀ aromatic group.

  In certain embodiments, the first bifunctional ester comprises a structure of formula (IX).

Non-limiting examples of suitable first bifunctional cyanate esters include Primaset ™ LECY, commercially available from Lonza.

  The amount of the first difunctional cyanate ester in the curable composition is from about 25% to about 60% by weight. In certain embodiments, the amount of the first difunctional cyanate ester in the curable composition is from about 30% to about 50% by weight. In certain embodiments, the amount of the first difunctional cyanate ester in the curable composition is from about 32% to about 40% by weight.

  In some embodiments, the second bifunctional cyanate ester comprises a prepolymer of a bifunctional cyanate ester having the formula (V).

In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁴ is a C _{3 to} C ₂₀ aliphatic group. As used herein, “prepolymer” refers to a product in which one or more monomers have reacted to an intermediate molecular weight state. This material can be further polymerized to a high molecular weight state by reactive groups. Thus, a mixture of reactive polymer and unreacted monomer can also be referred to as a prepolymer. The terms “prepolymer” and “polymer precursor” are sometimes used interchangeably.

  In some embodiments, the second bifunctional cyanate ester comprises a prepolymer of a bifunctional cyanate ester of formula (VI).

(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group.

  In certain embodiments, the second bifunctional cyanate ester comprises a prepolymer of a bifunctional cyanate ester of formula (X).

Non-limiting examples of suitable second bifunctional cyanate esters include Primaset ™ BA3000, commercially available from Lonza.

  In certain embodiments, the amount of the second difunctional cyanate ester in the curable composition is from about 10% to about 30% by weight. Further, the amount of the second difunctional cyanate ester in the curable composition is from about 15% to about 25% by weight. In certain embodiments, the amount of the second difunctional cyanate ester in the curable composition is from about 18% to about 22% by weight.

  The curable composition further includes a thermally conductive filler. The thermally conductive filler includes boron nitride. In certain embodiments, the thermally conductive filler is added at various compounding levels depending on some requirements of the cured composition (such as thermal conductivity, viscosity or toughness).

  In certain embodiments, the thermally conductive filler is present in the curable composition in an amount from about 5% to about 25% by weight. In certain embodiments, the thermally conductive filler is present in an amount from about 15% to about 25% by weight. In certain embodiments, the amount of thermally conductive filler in the curable composition is from about 18% to about 22% by weight.

  The curable composition may further include a toughening agent, which includes a reactive cyanate ester, a thermoplastic polymer, or a combination thereof. The toughening agent may be present in an amount from about 5% to about 15% by weight. As used herein, the term “reactive cyanate ester” refers to a cyanate ester moiety that can react with one or more of a multifunctional cyanate ester, a first difunctional cyanate ester, and a second difunctional cyanate ester. A material containing Non-limiting examples of suitable reactive cyanate esters include Primaset ™ HTL300, commercially available from Lonza.

  In certain embodiments, the thermoplastic polymer comprises polyimide. In certain embodiments, the polyimide comprises a structural unit of formula (XI).

In the formula, R ⁶ is a C _{3 to} C ₁₀ aliphatic group, a C _{5 to} C ₃₀ aromatic group, or a combination thereof. Non-limiting examples of suitable polyimides include P84 ™ commercially available from Evonik.

  The crosslinking reaction of the cyanate ester resin at elevated temperature can be controlled by the selection of a suitable catalyst. In certain embodiments, the curable composition may further comprise a suitable catalyst. Without being bound by theory, in the absence of a sufficient amount of catalyst, the curable composition reacts as soon as it is heated to a high temperature, and the reaction rate is correspondingly higher than the heat release rate, It is thought that local hot spots and thermal runaway may occur. In certain embodiments, the reaction temperature can be lowered and the reaction rate can be controlled by selecting an appropriate catalyst chemistry and controlling the amount of catalyst used.

  Non-limiting examples of suitable catalysts include transition metal carboxylates or chelates. In certain embodiments, non-limiting examples of suitable catalysts include acetylacetonate of zinc, copper, cobalt, manganese, iron, aluminum, or combinations thereof. In certain embodiments, the catalyst includes copper acetylacetonate, cobalt acetylacetonate, aluminum acetylacetonate, or combinations thereof. In some embodiments, a cocatalyst (eg, alkylphenol) that provides a source of active hydrogen may be used. In certain embodiments, the catalyst can be present in the range of about 25 ppm to about 150 ppm in the curable composition.

  In some embodiments, the curable composition may further include additional additives such as stabilizers, additional tougheners, and the like.

  The curable composition can be cured by an appropriate method. In certain embodiments, the curable composition can be cured by heating the composition. In certain embodiments, temperatures from about 18 ° C. to about 400 ° C. can be used for curing. In certain embodiments, a temperature of about 100 ° C. to about 300 ° C. can be used for curing. The time required for curing varies depending on the end use and depends on, for example, the thickness of the molded article or laminate. In certain embodiments, the time period sufficient for the composition to cure is from about 2 hours to about 12 hours. In embodiments where the curable composition is used as a molded article (such as made by resin transfer molding, compression molding or injection molding), a laminate, an adhesive part or a sealing material, it may be pressurized during the thermosetting process. Sometimes desirable. In other embodiments, microwaves, radio frequencies, ionizing radiation, electron beams, or combinations thereof may be used to perform the curing process.

  Without being bound by theory, it is believed that the polyfunctional cyanate ester after crosslinking provides the desired thermal stability and thermal properties. When the first bifunctional cyanate ester is blended with the polyfunctional cyanate ester, a heat stable resin is obtained, the resin having a glass transition temperature of greater than 280 ° C. Further, the first difunctional cyanate ester provides the desired viscosity for processing when blended with the multifunctional cyanate ester. However, the cured composition formed after crosslinking of the multifunctional cyanate ester and the first difunctional cyanate ester is typically rigid and prone to cracking during thermal cycling. In order to improve the mechanical properties of the composition while maintaining the viscosity and the desired thermal stability of the curable composition, a reinforcing material such as a second bifunctional cyanate ester is added. Such a reinforcing material reacts with the cyanate resin to form a homogeneous crosslinked structure with a long chain length, resulting in heat resistance and thermal stability. In certain embodiments, as described above, additional toughening agents may be further added to increase the toughness of the composition. Reinforcing agents include reactive cyanate esters, thermoplastic polymers, or combinations thereof.

  In order to provide a high temperature, thermal conductivity and mechanically tough potting composition for electrical machines, the thermal conductivity of the cured composition may be further increased. In some embodiments, boron nitride is added to increase the thermal conductivity of the cured composition. Without being bound by theory, it is believed that the boron nitride filler increases the thermal conductivity of the cured composition, but in some cases may reduce the toughness of the resulting composition. In such cases, an additional reinforcing agent (eg, a reactive cyanate ester or thermoplastic polymer) may be added to improve the toughness of the cured composition. Additional reinforcing agents can improve the fracture resistance. In one embodiment of the present invention, a multifunctional cyanate ester, a first bifunctional cyanate ester, a second bifunctional cyanate ester and a thermally conductive filler are used to produce a cured composition having desired properties. You may blend five main materials including (boron nitride etc.) and reinforcing materials (thermoplastic polymer or reactive cyanate ester etc.).

  Without being bound by theory, multifunctional cyanate ester, first difunctional cyanate ester, second difunctional cyanate ester, thermally conductive filler (such as boron nitride) and reinforcing material (thermoplastic) It is believed that by controlling the relative amount of polymer or reactive cyanate ester, etc., a combination of desired properties (thermal stability, thermal conductivity, flexural strength, fracture toughness, viscosity, etc.) can be obtained. . For example, as noted above, a minimum amount of multifunctional cyanate ester is desirable to achieve the desired thermal stability. Similarly, the amount of the first difunctional cyanate ester in the curable composition can be controlled so that the viscosity of the curable composition is low enough for processing. In certain embodiments, the curable composition may be substantially solvent-free, and the first bifunctional cyanate ester provides desirable viscosity characteristics. Further, the amount of the second difunctional cyanate ester in the curable composition can be controlled to provide the desired mechanical properties to the cured composition. As described above, an appropriate amount of a thermally conductive filler may be added to further increase the thermal conductivity of the composition. However, the addition of boron nitride may reduce the toughness of the composition, and the reduction can be recovered by the addition of an appropriate amount of a reinforcing material such as a thermoplastic polymer or a reactive cyanate ester.

  In certain embodiments, the curable composition is viscous and the cured composition has thermal and mechanical properties suitable for the end use (eg, potting material for generator stators). As used herein, the term “cured composition” encompasses both partially cured compositions and fully cured compositions.

  In certain embodiments, the curable composition has a viscosity of less than about 5000 centipoise (cP) at a temperature of about 100 ° C. In certain embodiments, the curable composition has a viscosity of less than about 4000 cP at a temperature of about 100 ° C. In certain embodiments, the curable composition has a viscosity of less than about 3000 cP at a temperature of about 100 ° C.

  In order to promote improved thermal stability, the cured composition desirably has a glass transition temperature of about 280 ° C. or higher in certain embodiments. In certain embodiments, the cured composition of the curable composition has a glass transition temperature of about 300 ° C. or higher.

  As described above, a thermally conductive filler material (such as boron nitride) is added to increase the thermal conductivity of the cured composition. In certain embodiments, the cured composition is about 0.75 W / m. K to about 1.2 W / m. K has a thermal conductivity of K. In other embodiments, the cured composition is 1.0 W / m. It has a thermal conductivity exceeding K.

The cured composition after thermal cycling is also characterized by bending strength and fracture toughness. In certain embodiments, the cured composition has a flexural strength of greater than 8000 psi. In certain embodiments, the cured composition has a flexural strength of about 8500 psi to about 11000 psi. In certain embodiments, the cured composition has a viscosity of about 1.2 MPa. m ^1/2 to about 1.6 MPa. It has a fracture toughness of m ^1/2 .

  Non-limiting specific examples of applications suitable for the curable composition include sealing, adhesion, insulation, lamination, or combinations thereof. In certain embodiments, the curable composition may be used to seal electrical machine components. Non-limiting examples of suitable components include stators, windings, core laminates, slot liners, slot wedges or combinations thereof. The electrical machine can be selected from the group consisting of a motor, a generator, a transformer, a toroid, an inductor, and combinations thereof. In some embodiments, the generator stator includes a curable composition of a curable composition. FIG. 1 shows a schematic view of a stator 100 impregnated with a curable composition 120. As shown in FIG. 1, the curable composition 120 and the resulting cured composition may fill all gaps and spaces that exist between the stator windings 110.

  In some embodiments, an electrically insulating encapsulant comprising a cured composition of the curable composition is also provided. In one example, the encapsulant material (1) maintains the desired thermal stability at temperatures above 250 ° C. and (2) viscosity by the use of a multifunctional cyanate ester and a thermally conductive filler (boron nitride). Therefore, the use of the first difunctional cyanate ester and the processability suitable for the impregnation treatment by the selection of a suitable catalyst for minimizing the exotherm resulting in thermal runaway are provided.

  Further, in some embodiments, the encapsulant is thermally stable and effective in dissipating heat from electrical machines that operate at high temperatures. High temperature stability and heat dissipation are useful, for example, in generator applications. Generators require heat dissipation while maximizing output, especially when used in aircraft and other aerospace applications. The sealing material is also suitable for use in motors and transformers. In that case, the sealing material provides the desired resistance to shock and vibration, as well as the elimination of moisture and corrosives under high speed vibration.

  A method of sealing an electrical machine component is also provided. The method includes contacting the part with a sealing material comprising the curable composition described above. As used herein, the term “contact” refers to impregnating one or more parts of an electrical machine with a curable composition using any suitable technique (eg, pressure impregnation or vacuum impregnation). For example, in certain embodiments, the method may include placing the stator in a mold. The stator cavity is impregnated with the sealing composition by applying pressure so that the sealing composition fills all the spaces and gaps present in the stator part (such as the gap between the stator windings). May be. The method further includes heating the part to cure the curable composition in the presence or absence of a vacuum.

  An example of such a method is the vacuum impregnation method, where the entire parts of the electromechanical assembly are placed in a pressure vessel under high vacuum that draws entrained air and other gases. The curable composition is introduced into a pressure vessel and the entire tank is pressurized (typically pressurized to 90 psi or more to penetrate the entire machine part). The assembly may be heated at an elevated temperature to cure the curable composition. In certain embodiments, the curable composition cures at a temperature of about 120 ° C to about 250 ° C.

Materials : BA3000, PT-30, LECY and Primaset HTL-300 were obtained from Lonza. Polyimide P84 NT2 was obtained from Evonik, and boron nitride PTX60P was obtained from Momentive. All resin mixing was done in a plastic cup (resin cup) designed for a high speed planetary centrifugal mixer equipped with a vacuum source. The boron nitride filler and thermoplastic toughening agent were dried in a vacuum oven at 150 ° C. for over 24 hours and removed from the oven before addition.

Preparation method of catalyst solution:
A copper acetylacetonate (II) solution was prepared by adding 0.300 g Cu (acac) ₂ to 10.0 g nonylphenol. The resulting copper acetylacetonate (II) solution was added to a large vial and sonicated at 50 ° C. for 60 minutes.

Details of the curing process:
Curing schedule: Various formulations in various molds and metal dishes were cured in a programmable oven according to the following protocol.
1) Heated from room temperature to 120 ° C, kept at 120 ° C for 3 hours,
2) Heat to 165 ° C. and keep warm for 2 hours.
3) Heat to 250 ° C. and keep warm for 4-6 hours.

  In another process, the first step was omitted and the sample was heated directly to 150-165 ° C. to fully gel the material and achieve most of the polymerization before final curing at high temperature.

The following ASTM method was used to measure the following characteristics. 1) Flexural strength (D790), 2) bending strain (D790), 3) fracture toughness (D5045), 4) a glass transition temperature The T _g DMA (E1640), 5) the thermal conductivity measured at 250 ° C. ( E1540).

Viscosity measurements were performed as follows :
The viscosity of the resin formulation was tested using a Brookfield DV-II + programmable viscometer with a Thermosel temperature controller. A disposable sample chamber (Model # HT-2DB) was charged with 17.5 g (± 0.5 g) of pre-warmed resin formulation (50 ° C.) and warmed to ensure homogeneity and then gently Mixed. An SC4 series Thermoset spindle was placed in the sample chamber that had been inserted into the Thermosel temperature controller. The viscosity was measured at a rotational speed of 6 rpm and a temperature of 100 ° C. After equilibrating for 15 minutes under these conditions, the viscosity was recorded.

Example 1: PT30, LECY, BA3000 and boron nitride (BN) blend BA3000 was placed in an oven at 75 ° C. for about 1 hour to facilitate transfer to a resin cup. A resin cup was charged with BA3000, LECY and PT-30 and heated in an oven for about 15-30 minutes. These ingredients were mixed for 4 minutes, then manually mixed to distribute undissolved BA3000 throughout the cup, and further mixed for 4 minutes. After cooling the resin mixture on the bench for 15-20 minutes, copper acetylacetonate in nonylphenol (50 ppm copper acetylacetonate relative to the resin) was added to the resin mixture and mixed for an additional 30 seconds. Dry boron nitride was added to the above resin and catalyst mixture and mixed for 30 seconds. Mixing was continued for an additional 3.5 minutes under vacuum to ensure thorough mixing and the homogeneous mixture was degassed. Immediately after mixing, the mixture was poured into Frekote pretreated molds and / or simple disposable dishes to prepare samples for thermal conductivity and mechanical testing. The remaining resin was stored at 4 ° C. until viscosity measurement and was reserved for additional testing. Table 1 shows the various blend samples and their compositions. In Table 1, Sample 1 is a comparative example containing neither PT30 nor a reinforcing agent. Table 2 shows comparison data for Samples 2-12 (blend with BN filler) and Comparative Sample 1 (blend without BN filler).

Example 3: PT30, LECY, BA3000, boron nitride and thermoplastic polyimide (P84) blend BA3000 was placed in an oven at 75 ° C. for about 1 hour to facilitate transfer to a resin cup. A resin cup was charged with BA3000, LECY and PT-30 and heated in an oven for 15-30 minutes. These ingredients were mixed for 4 minutes, then manually mixed to distribute undissolved BA3000 throughout the cup, and further mixed for 4 minutes. P84 thermoplastic was then added to the resin mixture and mixed for 30 seconds. After the resin mixture and toughening agent P84 were cooled on the bench for 15-20 minutes, copper acetylacetonate in nonylphenol (copper acetylacetonate 50 ppm with respect to the reactive resin) was added and mixed for another 30 seconds. Dry boron nitride was added to the mixture and mixed for 30 seconds. Mixing was continued for an additional 3.5 minutes under vacuum to ensure thorough mixing and the homogeneous mixture was degassed. Immediately after mixing, the mixture was poured into Frekote pretreated molds and / or simple disposable dishes to prepare samples for thermal conductivity and mechanical testing. The remaining resin was stored at 4 ° C. until viscosity measurement and was reserved for additional testing. Table 1 shows the various blend samples and their compositions. Table 2 shows comparison data for samples 4, 5, 7, 9, 11, and 12 (blend with P84 formulation) and comparative samples 2, 3, 6, 8, and 10 (blend without P84 reinforcement).

  Various blends with different BN concentrations including PT30, LECY, BA3000, P84 are contrasted in Table 2. In Table 1, Samples 11, 12, 7 and 9 show low to high (12.5, 15, 17.5 and 20 wt%) BN in blends with approximately the same amount of P84 toughener. When the BN concentration was increased from 12.5% by weight to 20% by weight, the concentrations of other components including P84 were decreased accordingly. The thermal conductivity (0.55, 0.62, 0.7, 0.82) and viscosity (450, 700, 1200, 2400 cP at 100 ° C.) of the blend increased with increasing BN concentration. The data is also shown in FIG. 2, and it can be seen that increasing the boron nitride concentration improves the thermal conductivity of the blend.

When a toughening agent such as thermoplastic polyimide is used in the blend (eg, blends of PT30, LECY, BA3000, BN and P84—Samples 4, 5, 7, 9, 11, and 12), a blend without a toughening agent (eg, PT30, LECY, BA3000 and BN blends-improved toughness compared to samples 2, 3, 6, 8 and 10). From the sample contrast it can be seen that the toughening agent P84 increases the mechanical strength of the material, in particular the fracture toughness (FT) (Table 2). Fracture toughness was increased from 1.07 (sample 8) to 1.27 Mps.s by increasing the P84 concentration of the sample from 0 to 8.2 wt% at 17.5 wt% BN. increased to m ^1/2 (sample 7). Similarly, for 20 wt% BN, the fracture toughness (FT) is increased from 1.23 (sample 10) to 1.43 (sample 9) Mps by increasing the P84 concentration of the sample from 0 to 8.0 wt%. . Increased to m ^1/2 .

Example 4: Blend BA3000 of PT30, LECY, BA3000, BN and Primaset HTL-300 was placed in an oven at 75 ° C for about 1 hour to facilitate transfer to a resin cup. A resin cup was charged with BA3000, LECY, PT-30 and HTL-300 (15 wt%) and heated in an oven for 15-30 minutes. These ingredients were mixed for 4 minutes, then manually mixed to distribute undissolved BA3000 throughout the cup, and further mixed for 4 minutes. After cooling on the bench for 15-20 minutes, copper acetylacetonate in nonylphenol (copper acetylacetonate 50 ppm relative to reactive resin) was added and mixed for another 30 seconds. Dry boron nitride was added and mixed for 30 seconds. The mixer was evacuated and mixing continued for an additional 3.5 minutes for thorough mixing to degas the homogeneous mixture. Immediately after mixing, samples for thermal conductivity and mechanical testing were prepared by pouring into Frekote pre-treated molds and / or simple disposable dishes. The remaining resin was stored at 4 ° C. until viscosity measurement and was reserved for additional testing.

  Table 3 shows the results of mechanical testing of blends with HTL-300. The formulation of HTL-300 increased the viscosity (1900 cP to 6500 cP at 100 ° C.) as shown in Table 3 (eg, in samples 13, 14, 15, 18, 16, and 17). If the level of HTL-300 is high enough, the viscosity will substantially increase in viscosity and improve various mechanical properties. Therefore, HTL-300 blends can be used for applications where low viscosity is not essential.

The above examples are merely illustrative to illustrate some of the features of the present invention. The following claims are intended to claim the invention to the fullest extent possible, and the examples set forth herein illustrate embodiments selected from a wide variety of embodiments. Accordingly, the scope of the appended claims should not be limited by the choice of examples used to illustrate features of the present invention. As used in the claims, the term “comprising” logically means, including, but not limited to, different terms with various definitions, such as “consisting essentially of” and “consisting of” . Ranges have been described where appropriate, but these ranges include subranges. Variations within these ranges will be apparent to those skilled in the art, and it should be understood that these variations are included in the appended claims if possible, even if not yet published. Scientific and technological advances are also expected to allow equivalents and alternatives that are not currently envisaged due to language inaccuracies. It should be understood that it is encompassed by the claims.

Claims (20)

A curable composition for an electric machine,
(A) from about 10% to about 30% by weight of a multifunctional cyanate ester of structure (I);
(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).
In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 25 wt% to about 60 wt% of the first difunctional cyanate ester of structure (II) or prepolymer thereof;
(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 10 wt% to about 30 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;
(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) A curable composition comprising about 5% to about 25% by weight of a thermally conductive filler comprising boron nitride.   The curable composition of claim 1, further comprising from about 5 wt% to about 15 wt% reinforcing agent comprising a thermoplastic polymer, a reactive cyanate ester, or a combination thereof.   The curable composition according to claim 2, wherein the thermoplastic polymer comprises polyimide. The curable composition of claim 2, wherein the toughening agent comprises a polyimide comprising a structural unit of formula (XI).
In the formula, R ⁶ is a C _{3 to} C ₁₀ aliphatic group, a C _{5 to} C ₃₀ aromatic group, or a combination thereof.   The curable composition of claim 1, wherein the multifunctional cyanate ester comprises a phenol novolac cyanate ester, dicyclopentadiene novolak cyanate ester, 1,2,3-tris (4-cyanatephenyl) -propane, or combinations thereof. . The curable composition of claim 1, wherein the first difunctional cyanate ester comprises a structure of formula (IV).
Where Ar ³ is a C ₅ -C ₃₀ aromatic group, The curable composition of claim 1, wherein the second bifunctional cyanate ester comprises a prepolymer of a bifunctional cyanate ester of formula (V).
In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁴ is a C _{3 to} C ₂₀ aliphatic group. The curable composition of claim 1, wherein the second bifunctional cyanate ester comprises a prepolymer of a bifunctional cyanate ester of formula (VI).
(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group.   The curable composition of claim 1, further comprising from about 25 ppm to about 150 ppm of catalyst.   The curable composition of claim 9, wherein the catalyst comprises copper acetylacetonate, cobalt acetylacetonate, aluminum acetylacetonate, or a combination thereof.   The curable composition of claim 1, wherein the curable composition has a viscosity of less than about 5000 cP at 100 ° C.   The curable composition has a cured composition of about 0.75 W / m. K to about 1.2 W / m. The curable composition of claim 1 having a thermal conductivity of K.   The curable composition of Claim 1 in which the curable composition of a curable composition has a glass transition temperature of 280 degreeC or more.   An electrical machine comprising a cured composition of the curable composition of claim 1, wherein the electrical machine is selected from the group consisting of a motor, a generator, a transformer, a toroid, an inductor, and combinations thereof.   An electrically insulating sealing material comprising the curable composition according to claim 1.   A generator stator (100) comprising a curable composition of the curable composition according to claim 1. A curable composition for sealing electrical machine parts,
(A) about 14% to about 18% by weight of a multifunctional cyanate ester of structure (I);
(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).
In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 32 wt% to about 40 wt% of a first difunctional cyanate ester of structure (II) or a prepolymer thereof;
(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 18 wt% to about 22 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;
(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) about 18 wt% to about 22 wt% of a thermally conductive filler comprising boron nitride;
(E) A curable composition comprising from about 5% to about 15% by weight of a toughening agent comprising a thermoplastic polymer, a reactive cyanate ester, or combinations thereof. A method of sealing an electromechanical component,
(A) from about 10% to about 30% by weight of a multifunctional cyanate ester of structure (I);
(In the formula, n is an integer of 1 or more, and Y is the structure (i) or (ii).
In the formula, Ar ¹ and Ar ² are each independently a C _{5 to} C ₃₀ aromatic group, and R ¹ and R ² are each independently a C _{1 to} C ₃ aliphatic group or a C _{3 to} C ₂₀ alicyclic group. And * represents a binding site. )
(B) about 25 wt% to about 60 wt% of the first difunctional cyanate ester of structure (II) or prepolymer thereof;
(In the formula, Ar ³ is a C ₅ -C ₃₀ aromatic group, and R ³ is a bond or a C ₁ -C ₂ aliphatic group.)
(C) about 10 wt% to about 30 wt% of a second difunctional cyanate ester of structure (III) or a prepolymer thereof;
(In the formula, Ar ⁴ is a C _{5 to} C ₃₀ aromatic group, and R ⁵ is a C _{3 to} C ₁₀ aliphatic group.)
(D) contacting the part with a sealing material comprising a curable composition comprising about 5 wt% to about 25 wt% of a thermally conductive filler comprising boron nitride;
Curing the curable composition.   The method of claim 18, wherein the cured composition further comprises from about 5 wt% to about 15 wt% toughening agent comprising a thermoplastic polymer, a reactive cyanate ester, or combinations thereof.   The method of claim 18, wherein the cured composition is cured at a temperature of about 120 ° C. to about 250 ° C.