Polyester as well as preparation method and application thereof

Abstract

The invention provides polyester as well as a preparation method and application thereof, the polyester comprises a structural unit derived from an imide monomer and a connecting structural unit derived from a connecting structural unit monomer, and the polyester is obtained by mixing and reacting a reaction raw material of the imide monomer and the connecting structural unit monomer; reaction raw materials of the imide monomer comprise acid anhydride and an amino compound, and the imide monomer comprises terminal hydroxyl or carboxyl. The polyester provided by the invention does not need to add extra solvents during preparation, is environment-friendly and low in preparation cost, and is beneficial to reducing the viscosity of the polyester and improving the heat resistance of the impregnating varnish.

Description

Technical Field

[0001] The present invention relates to the field of organic materials, and in particular to polyester and a preparation method and application thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, the demand for automotive motors has surged. In order to extend the service life of automotive motors, impregnation varnish is usually used to form a protective layer of paint on the surface of automotive motors. Due to its low price, low viscosity and high mechanical strength, polyester resin is an ideal raw material for impregnation varnish. In the related art, the heat resistance of the impregnation varnish can be improved by modifying polyester with imide, but this method requires the preparation of imide first, which is a cumbersome step. A large amount of solvents are used in the preparation and purification of imide, which will produce harmful waste liquid and cause great pollution to the environment. Therefore, there is a need for a polyester that does not require the addition of additional solvents, is environmentally friendly, and can improve the heat resistance of the impregnation varnish. Summary of the invention

[0003] In view of this, the present application provides a polyester and a preparation method and application thereof. The preparation of the polyester does not require the addition of additional solvents, is environmentally friendly, and the prepared polyester has low viscosity, which is beneficial to improving the heat resistance of the impregnating varnish.

[0004] In a first aspect, the present application provides a polyester, which includes a structural unit derived from an imide monomer and a connecting structural unit derived from a connecting structural unit monomer, and the polyester is obtained by mixing the reaction raw materials of the imide monomer and the connecting structural unit monomer and reacting them; the reaction raw materials of the imide monomer include anhydride and an amino compound, and the imide monomer includes a terminal hydroxyl group or a carboxyl group.

[0005] Optionally, the imide monomer includes At least one of .

[0006] Optional, R 1 , R 3 and R 5 are independently selected from substituted or unsubstituted trivalent alkyl, substituted or unsubstituted trivalent aryl, or substituted or unsubstituted trivalent alicyclic group, R 2 , R 4 , R 6 , R 8 , R 9 , R 10 and R 11 are independently selected from substituted or unsubstituted divalent alkyl groups, substituted or unsubstituted divalent aromatic groups, or substituted or unsubstituted divalent alicyclic groups, R 7 is selected from a carbon atom, a substituted or unsubstituted tetravalent aromatic group, or a substituted or unsubstituted tetravalent alicyclic group.

[0007] Optionally, X1, X2, Y1, Y2 and Z1 are independently selected from hydroxyl, carboxyl, halogen, nitro, amine, thiol, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, substituted or unsubstituted aryloxy, and at least one of X1 and Y1 is hydroxyl or carboxyl, and at least one of X2, Y2 and Z1 is hydroxyl or carboxyl.

[0008] Optionally, the substituents in the substituted alkyl, the substituted alkenyl, the substituted alkynyl, the substituted alkoxy, the substituted aryl, the substituted aryloxy, the substituted divalent alkyl, the substituted divalent aryl, the substituted divalent alicyclic group, the substituted trivalent alkyl, the substituted trivalent aryl, the substituted trivalent alicyclic group, the substituted tetravalent aryl, and the substituted tetravalent alicyclic group include at least one of halogen atoms, hydroxyl groups, nitro groups, amine groups, thiol groups, cyano groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted aryl groups, and substituted or unsubstituted aryloxy groups.

[0009] Optionally, the imide monomer has an asymmetric structure.

[0010] Optionally, the amino compound includes at least one of monoethanolamine, aminopropionic acid, propylenediamine, hexamethylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, m-phenylenediamine, diethylenetriamine, triaminotriethylamine and 2,2'-oxybis(ethylamine).

[0011] Optionally, the acid anhydride includes at least one of a hydroxyl-containing acid anhydride compound, a carboxyl-containing acid anhydride compound and a polyanhydride compound.

[0012] Optionally, the linking structure unit monomer includes at least one of a hydroxyl-containing compound, a carboxyl-containing compound and anhydride-containing compound.

[0013] Optionally, the hydroxyl-containing compound includes at least one of hydrogenated bisphenol A, ethylene glycol, propylene glycol, glycerol, propylene alcohol, diethylene glycol, neopentyl glycol, trimethylolpropane, benzyl alcohol, polyether polyol, 1,2-propylene glycol, 1,3-butylene glycol and dipropylene glycol.

[0014] Optionally, the carboxyl-containing compound includes at least one of isophthalic acid, terephthalic acid, maleic acid, fumaric acid and adipic acid.

[0015] Optionally, the anhydride-containing compound includes at least one of phthalic anhydride, chlorendic anhydride, maleic anhydride and fumaric anhydride.

[0016] Optionally, the weight average molecular weight of the polyester is 500-10000.

[0017] The polyester provided in the present application does not produce harmful liquids during the preparation process, is environmentally friendly, and can improve the heat resistance of the dipping varnish.

[0018] In a second aspect, the present application provides a method for preparing polyester, comprising: mixing an acid anhydride, an amino compound and a connecting structural unit monomer together to obtain a mixed liquid, and obtaining polyester after reaction.

[0019] Optionally, the reaction temperature is 20°C-250°C, and the reaction time is 6h-36h.

[0020] The preparation method of the polyester provided in the present application is novel, the preparation process is simple, no additional solvent is required, and environmental friendliness is improved. The prepared polyester has low viscosity, which is beneficial to improving the heat resistance of the impregnating varnish.

[0021] In a third aspect, the present application provides the use of the polyester described in the first aspect or the polyester prepared by the preparation method described in the second aspect in the fields of plastics, artificial stones, fibers or paints.

[0022] The polyester provided in this application has a wide range of application scenarios, which is conducive to its industrial application.

[0023] In a fourth aspect, the present application provides an impregnation varnish, wherein the impregnation varnish comprises the polyester described in the first aspect or the polyester prepared by the preparation method described in the second aspect.

[0024] Optionally, the impregnation varnish further comprises at least one of a reactive diluent, an initiator and an inhibitor.

[0025] Optionally, the reactive diluent includes a liquid compound containing an olefin double bond, and the liquid compound containing an olefin double bond includes at least one of styrene, vinyl toluene, 1,4-butanediol dimethacrylate, methyl methacrylate, diallyl phthalate and cyanuric acid triacrylate. Optionally, the inhibitor includes at least one of a phenolic hydroxyl-containing compound, a benzoquinone-containing compound and a free radical scavenger, and the phenolic hydroxyl-containing compound includes at least one of hydroquinone, 2-tert-butylhydroquinone, p-hydroxyanisole and 2,5-di-tert-butylhydroquinone, the benzoquinone-containing compound includes at least one of p-benzoquinone and methylhydroquinone, and the free radical scavenger includes 2,2,6,6-tetramethylpiperidin-1-oxyl free radical.

[0026] Optionally, the initiator includes at least one of a peroxide bond-containing compound and an azo compound, the peroxide bond-containing compound includes at least one of benzoyl peroxide, tert-butyl hydroperoxide, diisopropyl peroxide, tert-butyl perbenzoate and diisopropyl peroxydicarbonate, and the azo compound includes azobisisobutyronitrile.

[0027] Optionally, in the impregnating varnish, the mass percentage of the polyester is 30%-80%, the mass percentage of the inhibitor is less than or equal to 1%, and the mass percentage of the initiator is 0.01%-5%.

[0028] The impregnating varnish provided by the present application has good heat resistance and excellent comprehensive performance.

[0029] In a fifth aspect, the present application provides a motor, comprising a motor body and a paint layer provided on the motor body, wherein the paint layer is formed by the impregnation paint described in the fourth aspect.

[0030] The motor provided by the present application has good insulation performance, good heat resistance and high mechanical strength, which is beneficial to extending the service life of the motor.

[0031] In a sixth aspect, the present application provides a vehicle, comprising the motor described in the fifth aspect.

[0032] The vehicle provided by this application has excellent comprehensive performance, greatly improved safety performance, and strong product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the prior art description. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0034] Figure 1 A reaction flow chart of a polyester provided in one embodiment of the present application;

[0035] Figure 2 This is an infrared spectrum test chart of the dipping varnish provided in Example 1 of the present application;

[0036] Figure 3 This is an infrared spectrum test chart of the dipping varnish provided in Example 2 of the present application;

[0037] Figure 4 This is an infrared spectrum test chart of the dipping varnish provided in Example 3 of the present application;

[0038] Figure 5 This is an infrared spectrum test chart of the dipping varnish provided in Example 4 of the present application;

[0039] Figure 6This is an infrared spectrum test chart of the dipping varnish provided in Example 5 of the present application;

[0040] Figure 7 This is an infrared spectrum test chart of the dipping paint provided in Comparative Example 1 of the present application;

[0041] Figure 8 This is an infrared spectrum test chart of the dipping paint provided in Comparative Example 2 of the present application;

[0042] Fig. 9 This is an infrared spectrum test chart of the dipping paint provided in Comparative Example 3 of the present application;

[0043] Fig.10 This is an infrared spectrum test chart of the dipping paint provided in Comparative Example 4 of the present application;

[0044] Fig.11 Thermogravimetric analysis diagrams of the dipping varnishes provided for Examples 1-5 and Comparative Examples 1-4 of the present application. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0046] The present application provides a polyester, including a structural unit derived from an imide monomer and a connecting structural unit derived from a connecting structural unit monomer, wherein the polyester is obtained by mixing and reacting the reaction raw materials of the imide monomer and the connecting structural unit monomer; the reaction raw materials of the imide monomer include anhydride and an amino compound, and the imide monomer includes a terminal hydroxyl group or a carboxyl group. The polyester provided by the present application is obtained by mixing and reacting the reaction raw materials of the imide monomer and the connecting structural unit monomer, that is, the anhydride, the amino compound and the connecting structural unit monomer are mixed to prepare the polyester; the amino compound and the acid anhydride react to prepare the imide monomer, which is then reacted with the connecting structural unit monomer to form the polyester, and no additional solvent is required in the reaction process, no harmful solution is produced, and the polyester is environmentally friendly; the imide monomer includes a terminal hydroxyl group or a carboxyl group, which is easy to undergo an esterification reaction with the connecting structural unit monomer, so that the imide monomer can be embedded in the molecular main chain of the polyester, thereby improving the degree of modification of the polyester, and when applied to the polyester, it is beneficial to improve the heat resistance of the impregnating varnish. The polyester provided by the present application does not require additional solvent to be added during the preparation process, is environmentally friendly, and can improve the heat resistance of the impregnating varnish.

[0047] In one embodiment of the present application, the imide monomer includes At least one of. Exemplary, the imide monomer may include but is not limited to

[0048]

[0049] In one embodiment of the present application, the imide monomer may be The imide monomer has an asymmetric structure.

[0050] The imide monomer is a large conjugated rigid structural unit that is easy to form molecular forces such as π-π and / or CH-π, which improves the crystallinity of the polyester and increases the viscosity of the polyester. When the area ratio and volume ratio of the rigid groups in the imide monomer are similar, the asymmetric imide monomer has a twisted molecular chain structure and large molecular stacking steric hindrance, which reduces the formation of intermolecular forces and is not easy to stack. It can reduce the crystallinity of the polyester, which is beneficial for the polyester to obtain a relatively low viscosity, improve the comprehensive performance of the polyester, and further help to improve the heat resistance and mechanical properties of the impregnating varnish. In another embodiment of the present application, the imide monomer can be

[0051] In some embodiments, the structural formula of the imide monomer is The imide monomer has an asymmetric structure. In some other embodiments, the structural formula of the imide monomer is R 3 and R 5 When X1 and Y1 are different groups and / or X1 and Y1 are different groups, the imide monomer has an asymmetric structure. In other embodiments, the structural formula of the imide monomer is R 6 and R 8 When X1 and Y1 are different groups and / or X1 and Y1 are different groups, the imide monomer has an asymmetric structure. In other embodiments, the structural formula of the imide monomer is R 9 and R 10 When X2 and Y2 are different groups and / or X2 and Y2 are different groups, the imide monomer has an asymmetric structure.

[0052] In one embodiment of the present application, R 1 , R 3 and R 5 are independently selected from substituted or unsubstituted trivalent alkyl, substituted or unsubstituted trivalent aryl, or substituted or unsubstituted trivalent alicyclic group, R 2 , R 4 , R 6 , R 8 , R 9 , R 10 and R 11are independently selected from substituted or unsubstituted divalent alkyl groups, substituted or unsubstituted divalent aromatic groups, or substituted or unsubstituted divalent alicyclic groups, R 7 R is selected from a carbon atom, a substituted or unsubstituted tetravalent aromatic group, or a substituted or unsubstituted tetravalent alicyclic group. 1 , R 3 and R 5 It can be the same group or different groups. 2 , R 4 , R 6 , R 8 , R 9 , R 10 and R 11 They may be the same group or different groups.

[0053] In one embodiment of the present application, X1, X2, Y1, Y2 and Z1 are independently selected from hydroxyl (-OH), carboxyl (-COOH), halogen atoms (-Cl, -Br, -F, etc.), nitro (-NO2), amine (-NH x , x is 0, 1 or 2, etc.), mercapto (-SH), cyano (-CN), substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, or substituted or unsubstituted aryloxy, and at least one of X1 and Y1 is a hydroxyl group or a carboxyl group, which can promote the imide monomer to form the molecular main chain of the polyester. That is to say, X1 and Y1 can be the same group, in which case both X1 and Y1 are hydroxyl or carboxyl groups, which can further improve the synthesis of polyester and promote the formation of the polyester main chain; X1 and Y1 can also be different groups, in which case at least one of X1 and Y1 is a hydroxyl or carboxyl group. For example, when X1 is a hydroxyl or carboxyl group, Y1 can be selected from any one of a hydroxyl group, a carboxyl group, a halogen atom, a nitro group, an amine group, a thiol group, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted aryloxy group.

[0054] In one embodiment of the present application, at least one of X2, Y2 and Z1 is a hydroxyl group or a carboxyl group. That is, X2, Y2 and Z1 can be the same group, in which case X2, Y2 and Z1 are all hydroxyl groups or carboxyl groups, which can further improve the synthesis of polyester and promote the formation of the polyester backbone; X2, Y2 and Z1 can also be different groups, in which case at least one of X2, Y2 and Z1 is a hydroxyl group or a carboxyl group, for example, when X2 is a hydroxyl group or a carboxyl group, Y2 and Z1 can be independently selected from any one of a hydroxyl group, a carboxyl group, a halogen atom, a nitro group, an amine group, a thiol group, a cyano group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aryloxy group.

[0055] In one embodiment of the present application, when the imide monomer includes multiple hydroxyl groups or multiple carboxyl groups, the imide monomer can react with multiple linking structural unit monomers to form polyester. In another embodiment of the present application, when the imide monomer includes one hydroxyl group or one carboxyl group, the imide monomer can serve as an end-capping group of the polyester.

[0056] Alkyl is an alkane molecule with one hydrogen atom removed, including straight-chain alkyl and branched alkyl. In one embodiment of the present application, the number of carbon atoms of the alkyl is 1-8. Specifically, the number of carbon atoms of the alkyl may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7 or 8, etc. Exemplarily, the alkyl may include, but is not limited to, at least one of methyl, ethyl, n-propyl, n-butyl, isobutyl, n-pentyl, 2-methylbutyl, 2,2-dimethylpropyl, n-hexyl, heptyl, 2-methylhexyl, 5-methylpentyl, 2-ethylbutyl, 3-ethylbutyl, nonyl and decyl. In one embodiment of the present application, the alkyl may be methyl. In another embodiment of the present application, the alkyl may be ethyl.

[0057] The alkoxy group is composed of an alkyl group and an oxygen atom. In one embodiment of the present application, the number of carbon atoms of the alkoxy group may be, but is not limited to, 2, 3, 4, 5, 6, 7 or 8, etc. Exemplarily, the alkoxy group may include, but is not limited to, at least one of a methoxy group, an ethoxy group and a propoxy group. In one embodiment of the present application, the alkoxy group may be an ethoxy group.

[0058] Alkenyl is a divalent unsaturated hydrocarbon chain containing at least one double bond, and may include straight chain alkenyl and branched chain alkenyl. In one embodiment of the present application, specifically, the carbon number of the alkenyl may be, but is not limited to, 2, 3, 4, 5, 6, 7 or 8, etc. Exemplarily, the alkenyl may include, but is not limited to, at least one of vinyl, propenyl, butadienyl, pentenyl, hexadienyl, heptenyl, octenyl, nonenyl and decenyl. In one embodiment of the present application, the alkenyl may be butadienyl.

[0059] Alkynyl is a divalent unsaturated hydrocarbon chain containing at least one triple bond, and may include straight chain alkynyl and branched chain alkynyl. In one embodiment of the present application, specifically, the carbon number of the alkynyl may be, but is not limited to, 2, 3, 4, 5, 6, 7 or 8, etc. Exemplarily, the alkynyl may include, but is not limited to, at least one of ethynyl, propynyl, butynyl, pentynyl and hexynyl. In one embodiment of the present application, the alkynyl may be a propynyl.

[0060] Aryl is an aromatic group. In one embodiment of the present application, the number of carbon atoms of the aryl group is 6-30. Specifically, the number of carbon atoms of the aryl group may be, but is not limited to, 6, 10, 12, 14, 18, 22, 24, 26 or 30, etc. Specifically, the aryl group may include, but is not limited to, at least one of phenyl, naphthyl, anthracenyl, naphthyl, pentacene and tetrahydronaphthyl.

[0061] A divalent alkyl group is a divalent group in which two hydrogen atoms are removed from an alkane molecule. In one embodiment of the present application, the number of carbon atoms of the divalent alkyl group is 1-18, and may include a straight-chain divalent alkyl group and a branched divalent alkyl group. Specifically, the number of carbon atoms of the divalent alkyl group may be, but is not limited to, 1, 4, 6, 8, 10, 12, 14, 16 or 18, etc.; illustratively, the divalent alkyl group may include, but is not limited to, at least one of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2- and -CH2CH2CH2CH2CH2CH2-. In one embodiment of the present application, the divalent alkyl group may be -CH2CH2CH2CH2-. In another embodiment of the present application, the alkyl group may be -CH2CH2-.

[0062] A divalent aromatic group is a general term for the divalent group remaining after two hydrogen atoms are removed from the aromatic carbon of the aromatic hydrocarbon molecule. In one embodiment of the present application, the number of carbon atoms of the divalent aromatic group is 6-30. Specifically, the number of carbon atoms of the divalent aromatic group may be, but is not limited to, 6, 10, 12, 14, 18, 22, 24, 26 or 30, etc.; illustratively, the divalent aromatic group may include, but is not limited to, at least one of a divalent phenyl group, a divalent naphthyl group, a divalent anthracene group, a divalent tetraphenyl group, a divalent pentacene group and a divalent tetrahydronaphthyl group. In one embodiment of the present application, the divalent aromatic group may be a divalent anthracene group. In another embodiment of the present application, the divalent aromatic group may be a divalent phenyl group.

[0063] The divalent alicyclic group may be a divalent cycloalkyl group. In one embodiment of the present application, the number of carbon atoms of the divalent alicyclic group is 3-30. Specifically, the number of carbon atoms of the divalent alicyclic group may be, but is not limited to, 3, 5, 9, 10, 13, 15, 18, 23, 26 or 30, etc. For example, the divalent alicyclic group may include, but is not limited to, at least one of a divalent cyclopropane group, a divalent cyclobutane group, a divalent cyclopentane group, a divalent cyclohexane group and a divalent cyclopentane group. In one embodiment of the present application, the divalent alicyclic group may be a divalent cyclopropane group. In another embodiment of the present application, the divalent alicyclic group may be a divalent cyclopentane group.

[0064] A trivalent alkyl group is a trivalent group in which three hydrogen atoms are removed from an alkane molecule. In one embodiment of the present application, the trivalent alkyl group has 1 to 18 carbon atoms, and may include a straight-chain trivalent alkyl group or a branched trivalent alkyl group. Specifically, the trivalent alkyl group may have, but is not limited to, 1, 4, 6, 8, 10, 12, 14, 16, or 18 carbon atoms, etc.; illustratively, the trivalent alkyl group may include, but is not limited to, In one embodiment of the present application, the trivalent alkyl group may be

[0065] A trivalent aryl is a general term for the remaining trivalent groups after three hydrogen atoms are removed from the aromatic carbon nucleus of an aromatic hydrocarbon molecule. In one embodiment of the present application, the number of carbon atoms of the trivalent aryl is 6-30. Specifically, the number of carbon atoms of the trivalent aryl may be, but is not limited to, 6, 10, 12, 14, 18, 22, 24, 26 or 30, etc.; the trivalent aryl may include, but is not limited to, at least one of a trivalent phenyl, a trivalent naphthyl, a trivalent anthracene, a trivalent tetraphenyl, a trivalent pentacene and a trivalent tetrahydronaphthyl. In one embodiment of the present application, the trivalent aryl may be a trivalent anthracene. In another embodiment of the present application, the trivalent aryl may be a trivalent phenyl.

[0066] The trivalent alicyclic group may be a trivalent cycloalkyl group. In one embodiment of the present application, the trivalent alicyclic group has a carbon number of 3-30. Specifically, the trivalent alicyclic group may have a carbon number of, but not limited to, 3, 5, 9, 10, 13, 15, 18, 23, 26 or 30, etc. For example, the trivalent alicyclic group may include, but not limited to, at least one of a trivalent cyclopropane group, a trivalent cyclobutane group, a trivalent cyclopentane group, a trivalent cyclohexane group and a trivalent cyclopentane group. In one embodiment of the present application, the trivalent alicyclic group may be a trivalent cyclopropane group. In another embodiment of the present application, the trivalent alicyclic group may be a trivalent cyclopentane group.

[0067] A tetravalent aromatic group is a general term for the remaining tetravalent groups after four hydrogen atoms are removed from the aromatic carbon nucleus of an aromatic hydrocarbon molecule. In one embodiment of the present application, the number of carbon atoms of the tetravalent aromatic group is 6-30. Specifically, the number of carbon atoms of the tetravalent aromatic group may be, but is not limited to, 6, 10, 12, 14, 18, 22, 24, 26 or 30, etc.; the tetravalent aromatic group may include, but is not limited to, at least one of a tetravalent phenyl group, a tetravalent naphthyl group, a tetravalent anthracene group, a tetravalent tetraphenyl group, a tetravalent pentacene group and a tetravalent tetrahydronaphthyl group. In one embodiment of the present application, the tetravalent aromatic group may be a tetravalent anthracene group. In another embodiment of the present application, the tetravalent aromatic group may be a tetravalent phenyl group.

[0068] The tetravalent alicyclic group may be a tetravalent cycloalkyl group. In one embodiment of the present application, the number of carbon atoms of the tetravalent alicyclic group is 3-30. Specifically, the number of carbon atoms of the tetravalent alicyclic group may be, but is not limited to, 3, 5, 9, 10, 13, 15, 18, 23, 26 or 30, etc. Exemplarily, the tetravalent alicyclic group may include, but is not limited to, at least one of a tetravalent cyclopropane group, a tetravalent cyclobutane group, a tetravalent cyclopentane group, a tetravalent cyclohexane group and a tetravalent cyclopentane group. In one embodiment of the present application, the tetravalent alicyclic group may be a tetravalent cyclopropane group. In another embodiment of the present application, the tetravalent alicyclic group may be a tetravalent cyclopentane group.

[0069] In one embodiment of the present application, the substituents in the substituted alkyl, substituted alkenyl, substituted alkynyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted divalent alkyl, substituted divalent aryl, substituted divalent alicyclic group, substituted trivalent alkyl, substituted trivalent aryl, substituted trivalent alicyclic group, substituted tetravalent aryl, and substituted tetravalent alicyclic group include at least one of halogen atoms, hydroxyl, nitro, amine, thiol, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, and substituted or unsubstituted aryloxy.

[0070] In one embodiment of the present application, the amino compound may be a compound containing an amino group. Specifically, the amino compound may be, but is not limited to, at least one of monoethanolamine, aminopropionic acid, propylenediamine, hexamethylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, m-phenylenediamine, diethylenetriamine, triaminotriethylamine, and 2,2'-oxybis(ethylamine); illustratively, the amino compound may include, but is not limited to,

[0071] In one embodiment of the present application, the amino compound may have a structural formula of trimethylhexamethylenediamine. The asymmetric amino compound may increase the asymmetry of the imide monomer, aggravate the degree of distortion of the molecular structure, increase the molecular stacking steric hindrance, and reduce the intermolecular force, which is conducive to obtaining a polyester with relatively low crystallinity and viscosity, and improving the heat resistance and mechanical properties of the dipping varnish.

[0072] In one embodiment of the present application, the acid anhydride includes at least one of a hydroxyl-containing acid anhydride compound, a carboxyl-containing acid anhydride compound and a polyanhydride compound. Specifically, the acid anhydride may be, but is not limited to, at least one of trimellitic anhydride, pyromellitic anhydride, diphenyl ether tetracarboxylic anhydride, cyclobutane tetracarboxylic anhydride, methyltetrahydrophthalic anhydride, diacid anhydride, polyazelaic anhydride, dodecyl succinic anhydride, nadic anhydride, chlorendic anhydride and 2,3,3',4'-biphenyltetracarboxylic anhydride; illustratively, the acid anhydride may include, but is not limited to,

[0073] In one embodiment of the present application, the structural formula of the anhydride can be The asymmetric anhydride structure can improve the asymmetry of polyester, intensify the distortion of the molecular structure, increase the molecular stacking steric hindrance, and reduce the intermolecular force, which is beneficial to reduce the crystallinity and viscosity of polyester and improve the mechanical properties of polyester.

[0074] In one embodiment of the present application, the polyester further includes a connecting structural unit derived from a connecting structural unit monomer, and the connecting structural unit is connected to a structural unit derived from an imide monomer. The connecting structural unit monomer includes at least one of a hydroxyl-containing compound, a carboxyl-containing compound, and an anhydride-containing compound. Specifically, the hydroxyl-containing compound may include, but is not limited to, at least one of a monohydric alcohol and a polyhydric alcohol. For example, the hydroxyl-containing compound may include, but is not limited to, at least one of hydrogenated bisphenol A, ethylene glycol, propylene glycol, glycerol, propylene alcohol, diethylene glycol, neopentyl glycol, trimethylolpropane, benzyl alcohol, polyether polyol, 1,2-propylene glycol, 1,3-butylene glycol, and dipropylene glycol. In one embodiment of the present application, the hydroxyl-containing compound may be a monohydric alcohol, in which case the monohydric alcohol may be used as an end-capping group of the polyester. In another embodiment of the present application, the hydroxyl-containing compound may be 1,2-propylene glycol, and the polyhydric alcohol has a low melting point, which can promote the dissolution of anhydrides and amino compounds, and evenly disperse them, which is beneficial to improving the synthesis efficiency of the imide monomer. In some embodiments, the linking structural unit monomer includes an unsaturated hydroxyl-containing compound, and the polyester obtained is an unsaturated polyester.

[0075] In one embodiment of the present application, the carboxyl-containing compound may include but is not limited to at least one of isophthalic acid, terephthalic acid, maleic acid, fumaric acid and adipic acid. In one embodiment of the present application, the carboxyl-containing compound may be terephthalic acid. In another embodiment of the present application, the carboxyl-containing compound may be maleic acid, in which case the carboxyl-containing compound contains an unsaturated bond, and the polyester obtained is an unsaturated polyester.

[0076] In one embodiment of the present application, the compound containing anhydride may include, but is not limited to, at least one of phthalic anhydride, chlorendic anhydride, maleic anhydride, fumaric anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride. In one embodiment of the present application, the compound containing anhydride may be maleic anhydride, in which case the compound containing anhydride contains an unsaturated bond, and the polyester obtained is an unsaturated polyester.

[0077] In one embodiment of the present application, the end-capping group of the polyester is derived from at least one of a monohydric alcohol, a monoacid and a monofunctional amide monomer. Specifically, the end-capping group may include but is not limited to at least one of oleic acid, N-(2-hydroxyethyl)phthalimide and benzyl alcohol. In one embodiment of the present application, the end-capping group may be N-(2-hydroxyethyl)tetrahydrophthalimide.

[0078] In one embodiment of the present application, except for the end-capping group, the remaining structural units derived from the imide monomer and the connecting structural units are connected to form a repeating unit, and the repetition number n may be greater than or equal to 1. Specifically, the repetition number may be, but is not limited to, 1, 20, 40, 60, 80 or 100, etc. In one embodiment of the present application, the repetition number may be 1-20. In another embodiment of the present application, the repetition number may be 5-40.

[0079] In one embodiment of the present application, the molecular weight of the polyester is 500-10000. Suitable molecular weight can improve the bonding ability and storage period of the polyester, which is conducive to improving the coating ability of the dipping paint. Specifically, the molecular weight of the polyester can be, but is not limited to, 500, 1000, 1500, 3000, 5000, 7000, 8000, 9000 or 100000, etc. In one embodiment of the present application, the molecular weight of the polyester can be 500-3000, which can further improve the comprehensive performance of the dipping paint. In another embodiment of the present application, the molecular weight of the polyester can be 2000-10000.

[0080] The present application also provides a method for preparing polyester, comprising: mixing anhydride, amino compound and connecting structural unit monomer together to obtain a mixed liquid, and then obtaining polyester. In the present application, the amino compound and the acid anhydride have high reaction activity and are easy to react, and can synthesize an imide monomer, and the subsequently generated imide monomer undergoes a second esterification reaction with the connecting structural unit monomer to form polyester. The preparation method provided in the present application does not require the preparation and purification of the imide monomer separately, and does not require the addition of additional solvents. The polyester can be prepared in one pot. The polyester includes structural units derived from the imide monomer, which improves the heat resistance of the polyester, reduces the polyester preparation process, reduces the preparation cost of the polyester, does not require waste liquid treatment, and is environmentally friendly. The polyester described in any of the above embodiments can be prepared by this method.

[0081] In one embodiment of the present application, the reaction includes a first stage and a second stage. The first stage is the reaction of anhydride and amino compound to obtain imide monomer, and the reaction can be completed at a relatively low temperature to obtain imide monomer; the second stage is the reaction of imide monomer and connecting structure unit monomer to obtain polyester.

[0082] In one embodiment of the present application, the temperature of the first stage is 20°C-180°C, which can promote the dissolution of the amino compound and the anhydride in the solvent and promote the occurrence of the first stage. Specifically, the temperature of the first stage can be, but is not limited to, 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 170°C or 180°C, etc. In one embodiment of the present application, the temperature of the first stage can be 20°C-100°C. In another embodiment of the present application, the temperature of the first stage can be 90°C-180°C. In some embodiments, the amino compound is mixed with a solvent, and the amino compound is completely dissolved in the solvent at 50°C, and then the anhydride is added in batches, and the temperature of the solution in the first stage is controlled to be less than 100°C. After the addition is completed, stir for 30 minutes, and the temperature of the first stage is raised to 160°C to promote the occurrence of the first stage.

[0083] In one embodiment of the present application, the time of the first stage is 1h-6h, and the appropriate time of the first stage can promote the synthesis of the imide monomer. Specifically, the time of the first stage can be, but is not limited to, 1h, 2h, 3h, 4h, 5h or 6h, etc. In one embodiment of the present application, the time of the first stage can be 1h-4h. In another embodiment of the present application, the time of the first stage can be 3h-6h.

[0084] In one embodiment of the present application, after the first stage, when the acid value of the mixed solution is close to or equal to the theoretical value after the imide monomer is completely converted, the amino compound and the amide are completely reacted to form the imide monomer. The calculation formula of the theoretical value is: Among them, AV x％ is the theoretical acid value when the imide monomer is converted to x%, in mgKOH / g, 56.1 is the amount of KOH, in g / mol, n 酐 It is the amount of all anhydride groups in the feed, in mol, n NH2 It is the amount of all amino groups in the feed, in mol; n COOH It is the amount of all carboxyl groups in the feed, in mol, m 总 is the total mass of all materials put in, in g, m 水 It is the mass of water discharged from the reactor when sampling, in grams. This formula can be used to calculate the theoretical acid value AV corresponding to a certain degree of reaction. x％ The reaction degree x% can also be inferred from the measured acid value. In some embodiments, when the reaction degree x% is greater than 90% or the acid value decreases very slowly, the next step can be performed.

[0085] In one embodiment of the present application, a variety of different acid anhydrides can be added to obtain imide monomers with various structures. In some embodiments, after the first amino compound and the first acid anhydride react to form the first imide monomer, a different second amino compound and / or second acid anhydride can be added to form a second imide monomer.

[0086] In one embodiment of the present application, the first stage also includes multiple sub-stages. In the first stage, when the acid anhydride and the amino compound react to form an imide monomer, the acid anhydride and other connecting structural unit monomers may also react to form an ester compound, but the ester structure is unstable. In the presence of the amino compound, the ester group will still be converted into an imide group to form an imide monomer.

[0087] In one embodiment of the present application, after the first stage, the formed imide monomer and the connecting structural unit monomer undergo a second stage to form a polyester. Specifically, the connecting structural unit monomer may include but is not limited to at least one of a hydroxyl-containing compound, a carboxyl-containing compound, and an anhydride-containing compound. In one embodiment of the present application, the connecting structural unit monomer may be a hydroxyl-containing compound and a carboxyl-containing compound. In another embodiment of the present application, the connecting structural unit monomer may be an anhydride-containing compound and a hydroxyl-containing compound.

[0088] In one embodiment of the present application, the connecting structural unit monomer includes a hydroxyl-containing compound. At this time, the hydroxyl-containing compound also serves as a solvent in the first stage, which can promote the uniform dispersion of amino compounds and acid anhydrides in the solvent to form a uniform solution, promote the rapid occurrence of the first stage, and is conducive to the synthesis of imide monomers. The acid anhydride or amino compound has good solubility in the hydroxyl-containing compound and can form a uniform solution, which is conducive to the first stage occurring at a lower temperature. Specifically, the hydroxyl-containing compound can be, but is not limited to, at least one of: ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, 1,2-propylene glycol, 1,3-butylene glycol, dipropylene glycol, benzyl alcohol and polyether polyols. In one embodiment of the present application, the hydroxyl-containing compound can be 1,2-propylene glycol, and the low melting point is conducive to the dissolution of the acid anhydride or amino compound at low temperature.

[0089] In one embodiment of the present application, anhydride and solvent (hydroxyl compound) can be mixed first, and then mixed with amino compound to form a mixed solution, which can further improve the uniformity of the solution in the first stage and promote the progress of the first stage. In some embodiments, the amino compound can be slowly added in batches to control the heat release rate, avoid the temperature of the mixed solution from being too high, and promote the rapid synthesis of imide monomers by the amino compound. In another embodiment of the present application, the amino compound can also be mixed with the solvent (hydroxyl compound), and then anhydride is added to carry out the first stage, which can also improve the uniformity of the solution in the first stage and promote the progress of the first stage. That is to say, the order of adding anhydride and amino compound is not limited.

[0090] In one embodiment of the present application, in the first stage, the hydroxyl-containing compound does not participate in the reaction and acts as a reaction medium, but in the second stage, the hydroxyl-containing compound acts as a connecting structural unit monomer and participates in the second stage to synthesize polyester.

[0091] In one embodiment of the present application, after the first stage is over, a connecting structure unit monomer can be added to the mixed solution multiple times to promote the formation of polyester and regulate the structure of polyester. In one embodiment of the present application, after the first stage is over, a connecting structure unit monomer containing an unsaturated bond can be added to the mixed solution to obtain an unsaturated polyester. In another embodiment of the present application, after the first stage is over, a connecting structure unit monomer with poor solubility can be added to the mixed solution to avoid affecting the synthesis of the imide monomer in the first stage and to obtain a polyester with an ideal structure. In some embodiments, the acid value of the mixed solution is used to determine whether the imide monomer and the connecting structure unit monomer are completely reacted.

[0092] In one embodiment of the present application, the temperature of the second stage is 170°C-250°C, which can promote the formation of polyester. Specifically, the temperature of the second stage can be, but not limited to, 170°C, 175°C, 180°C, 190°C, 200°C, 220°C or 250°C. In one embodiment of the present application, the temperature of the second stage can be, but not limited to, 170°C-190°C. In another embodiment of the present application, the temperature of the second stage can be, but not limited to, 185°C-250°C.

[0093] In one embodiment of the present application, the second stage lasts for 5 hours to 30 hours, which can promote the reaction of the imide monomer and the connecting structural unit monomer, and is conducive to the formation of polyester. Specifically, the second stage lasts for, but is not limited to, 5 hours, 8 hours, 10 hours, 20 hours, 25 hours or 30 hours. In one embodiment of the present application, the second stage lasts for 5 hours to 15 hours. In another embodiment of the present application, the second stage lasts for 8 hours to 30 hours.

[0094] See also Figure 1, which is a reaction flow chart of a polyester provided in one embodiment of the present application, comprising: mixing trimellitic anhydride and ethylene glycol to obtain a clear solution, adding monoethanolamine to the clear solution; monoethanolamine reacting with trimellitic anhydride (1) to obtain an amide monomer, which then reacts (5) to dehydrate to obtain an imide monomer; a small amount of trimellitic anhydride and ethylene glycol react (2) to form an ester-containing compound, the amino compound reacts with the ester group (3) to obtain an amide monomer, which then reacts (5) to dehydrate to obtain an imide monomer; the generated amide monomer has a carboxyl group, the carboxyl group reacts with ethylene glycol (4) to form an ester-containing compound, the ester-containing compound can remove ethylene glycol to react (6) to obtain an imide monomer; then a linking unit monomer is added to the imide monomer to react (7) to form a polyester. The preparation process can prepare polyester in one pot, does not require additional solvents, does not require separation and purification of the imide monomer, shortens the reaction time, and reduces the reaction cost.

[0095] In one embodiment of the present application, both the first stage and the second stage are carried out under an inert atmosphere to avoid oxidation contamination in the first stage and the second stage, thereby improving the purity of the polyester. Specifically, the inert atmosphere may be, but is not limited to, at least one of nitrogen, argon and carbon dioxide. In one embodiment of the present application, the inert atmosphere may be nitrogen.

[0096] The present application also provides the application of polyester in the field of plastics, artificial stones, fibers or paints, which can improve the bonding ability, mechanical properties, heat resistance and / or oil resistance of plastics, artificial stones, fibers or paints.

[0097] The present application also provides an impregnating varnish, which includes the polyester described in any one of the above embodiments, thereby reducing the preparation cost of the polyester and shortening the preparation process of the impregnating varnish.

[0098] In one embodiment of the present application, the impregnation varnish further comprises at least one of a reactive diluent, an initiator and an inhibitor. The reactive diluent can reduce the viscosity of the impregnation varnish and improve the coating ability of the impregnation varnish; the initiator can promote the curing reaction of the impregnation varnish and increase the curing rate of the impregnation varnish; the inhibitor can prevent large-scale agglomeration in the impregnation varnish and increase the storage time of the impregnation varnish.

[0099] In one embodiment of the present application, the mass percentage of polyester in the dipping varnish is 30%-80%. Specifically, the mass percentage of polyester can be, but is not limited to, 30%, 40%, 50%, 60%, 70% or 80%. In one embodiment of the present application, the mass percentage of polyester in the dipping varnish can be 30%-60%. In another embodiment of the present application, the mass percentage of polyester in the dipping varnish can be 50%-80%.

[0100] In one embodiment of the present application, the reactive diluent can reduce the viscosity of the impregnating varnish, improve the coating ability of the impregnating varnish, and help improve the use effect of the impregnating varnish. Specifically, the reactive diluent may include, but is not limited to, a liquid compound containing an olefin double bond. For example, the liquid compound containing an olefin double bond may include, but is not limited to, at least one of styrene, vinyl toluene, methyl methacrylate, 1,4-butanediol dimethacrylate, diallyl phthalate, and cyanuric acid triacrylate. In one embodiment of the present application, the reactive diluent may be vinyl toluene. In another embodiment of the present application, the reactive diluent may be cyanuric acid triacrylate.

[0101] In one embodiment of the present application, the mass percentage of the active diluent in the impregnation varnish is 10%-70%. Specifically, the mass percentage of the active diluent may be, but is not limited to, 10%, 30%, 40%, 50%, 60%, 65% or 70%, etc. In one embodiment of the present application, the mass percentage of the active diluent in the impregnation varnish may be 10%-60%. In another embodiment of the present application, the mass percentage of the active diluent in the impregnation varnish may be 50%-70%.

[0102] In one embodiment of the present application, the initiator can promote the curing reaction of the impregnating varnish and increase the curing rate of the impregnating varnish. Specifically, the initiator may include, but is not limited to, at least one of a peroxide-containing compound and an azo compound. Exemplarily, the peroxide-containing compound includes at least one of benzoyl peroxide, tert-butyl hydroperoxide, diisopropyl peroxide, tert-butyl perbenzoate, and diisopropyl peroxydicarbonate, and the azo compound includes azobisisobutyronitrile, etc. In one embodiment of the present application, the initiator may be diisopropyl hydroperoxide. In another embodiment of the present application, the initiator may be azobisisobutyronitrile.

[0103] In one embodiment of the present application, the mass percentage of the initiator in the impregnating varnish is 0.01%-5%, and an appropriate amount of the initiator can promote the curing reaction of the impregnating varnish. Specifically, the mass percentage of the initiator can be, but is not limited to, 0.01%, 1%, 2%, 3%, 4% or 5%. In one embodiment of the present application, the mass percentage of the active diluent in the impregnating varnish can be 0.01%-4%. In another embodiment of the present application, the mass percentage of the active diluent in the impregnating varnish can be 2%-5%.

[0104] In one embodiment of the present application, the inhibitor can prevent large-scale agglomeration in the impregnation varnish and increase the storage time of the impregnation varnish. Specifically, the inhibitor may include but is not limited to at least one of a phenolic hydroxyl compound, a benzoquinone compound and a free radical scavenger. For example, the phenolic hydroxyl compound may include but is not limited to at least one of hydroquinone, 2-tert-butylhydroquinone, p-hydroxyanisole and 2,5-di-tert-butylhydroquinone; the benzoquinone compound may include but is not limited to at least one of p-benzoquinone and methylhydroquinone, and the free radical scavenger includes 2,2,6,6-tetramethylpiperidin-1-oxyl free radical, etc. In one embodiment of the present application, the inhibitor may be hydroquinone. In another embodiment of the present application, the inhibitor may be p-hydroxyanisole.

[0105] In one embodiment of the present application, in the dipping varnish, the mass percentage of the inhibitor is less than or equal to 0.1%, and an appropriate amount of the inhibitor can improve the storage capacity of the dipping varnish. Specifically, the mass percentage of the inhibitor can be, but is not limited to, less than or equal to 0.1%, less than or equal to 0.08%, less than or equal to 0.06%, less than or equal to 0.05%, less than or equal to 0.03%, or less than or equal to 0.01%, etc. In one embodiment of the present application, in the dipping varnish, the mass percentage of the inhibitor can be less than or equal to 0.07%. In another embodiment of the present application, in the dipping varnish, the mass percentage of the inhibitor can be less than or equal to 0.05%.

[0106] In one embodiment of the present application, the impregnation varnish further includes a defoamer, which can reduce the surface tension and promote the discharge of bubbles in the impregnation varnish, which is beneficial to improving the coating ability of the impregnation varnish. Specifically, the impregnation varnish can be, but is not limited to, at least one of BYK-A-550, BYK-057, Euka 130S, Deqian AU318D, EFKA-2720 and Troysol307. In one embodiment of the present application, the impregnation varnish can be BYK-A-550.

[0107] In one embodiment of the present application, an auxiliary agent may be added to the dipping varnish to increase the total energy of the dipping varnish to meet different industrial requirements. The auxiliary agent may include but is not limited to at least one of a leveling agent, a pigment, a flame retardant and a light stabilizer.

[0108] In one embodiment of the present application, the preparation method of the impregnation varnish includes: mixing polyester, reactive diluent, initiator and inhibitor to obtain the impregnation varnish. Specific process: after the second stage, adding reactive diluent and inhibitor, stirring at 60℃-100℃ for 1h-3h, cooling to 20℃-50℃, adding initiator, stirring for 1h-3h, filtering, and obtaining the impregnation varnish.

[0109] The present application provides a motor, comprising a motor body and a paint layer provided on the motor body, wherein the paint layer is formed by the impregnation paint described in any of the above embodiments. The motor provided by the present application has good mechanical properties, strong bonding ability, excellent heat resistance and oil resistance, improves the insulation performance, heat resistance and mechanical strength of the motor, and is conducive to extending the service life of the motor. In one embodiment of the present application, the paint layer can be provided by immersion, vacuum impregnation, dripping, spraying or coating. In one embodiment of the present application, the paint layer is formed on the motor body by immersing the motor in the impregnation paint and curing it.

[0110] The present application provides a vehicle, which includes a motor provided by any one of the above-mentioned embodiments. The motor has good insulation performance, good heat resistance, high mechanical strength, and a long service life, which is beneficial to improving the safety performance and service life of the vehicle.

[0111] The effect of the technical solution of the present application is further illustrated below through specific examples.

[0112] Example 1

[0113] Weigh the connecting structural unit monomer (135.6g of 1,3-butanediol and 156.2g of neopentyl glycol) and 60.3g of symmetrical amino compound (1,6-hexanediamine) and add them to the reactor. Stir at 50℃ under nitrogen until it becomes a clear liquid. Weigh 192.8g of asymmetrical acid anhydride (trimellitic anhydride) and slowly add it to the reactor in batches. Control the feeding speed so that the material temperature does not exceed 100℃. Stir for 30min. The material temperature no longer rises spontaneously. Gradually heat it to 160℃, increase the nitrogen flow rate to about 0.2L / min appropriately, so that the water vapor is quickly discharged, and keep the steam temperature of the distillation head below 90℃. Keep the reaction for about 3h. When the acid value is lower than 100mgKOH / g, add 314g of connecting structural unit monomer (maleic anhydride), gradually heat it to 190℃, and keep the reaction for about 4h. When the acid value is lower than 160mgKOH / g, add 194.6g of connecting structural unit monomer (benzyl alcohol). The reaction was continued at the temperature for about 4 hours. When the acid value was lower than 20 mgKOH / g, the reaction was terminated to obtain polyester, which included structural units derived from imide monomers and connecting structural units derived from connecting structural unit monomers, wherein the structural formula of the imide monomer is

[0114]

[0115] Cool to 90°C, add 500g of active diluent (100g of vinyltoluene and 400g of 1,4-butanediol dimethacrylate) and 0.15g of inhibitor (hydroquinone), stir at 70°C for 1h to mix evenly, cool to below 40°C, add 32g of initiator (tert-butyl perbenzoate), continue stirring for 1h, filter the material to obtain the impregnation paint, and store it in a sealed container away from light.

[0116] Example 2

[0117] The difference from Example 1 is that the connecting structure unit monomer (76g of propylene glycol and 253g of neopentyl glycol) and the symmetrical amino compound (29.6g of 1,2-propylenediamine) are weighed into the reactor, heated to 100°C under nitrogen conditions to melt and dissolve into a clear liquid, first added and stirred evenly, and then the asymmetric acid anhydride (152.1g of trimellitic anhydride) is added in batches, and the feeding rate is controlled so that the material temperature does not exceed 120°C. After the addition is completed, stirring is continued for 30 minutes, the material temperature no longer rises spontaneously, and the temperature is gradually raised to 170°C, and the nitrogen flow rate is appropriately increased to about 0.2L / min to quickly discharge water vapor, while keeping the steam temperature of the distillation head below 90°C, and the reaction is kept warm for about 2h. When the acid value is lower than 85 mgKOH / g, cool to 120°C, add anhydride (274 g of tetrahydrophthalic anhydride) and stir evenly, then add amino compound (136 g of isopropanolamine) in batches, control the feeding speed so that the material temperature does not exceed 150°C, and after the feeding is completed, continue stirring for 30 minutes, the material temperature no longer rises spontaneously, and the temperature is raised to 170°C, and the reaction is kept warm for about 2 hours. When the acid value is lower than 50 mgKOH / g, add connecting structural unit monomers (314 g of maleic anhydride and 73 g of adipic acid), gradually heat to 200°C, and keep warm for about 8 hours. When the acid value is lower than 50 mgKOH / g, close the nitrogen valve, evacuate to about -0.09 MPa, and keep warm for about 2 hours. When the acid value is lower than 20 mgKOH / g, the reaction is terminated to obtain polyester, which includes structural units derived from imide monomers and connecting structural units derived from connecting structural unit monomers, wherein the structural formula of the imide monomer is

[0118] Cool down to 90°C, add 750g of active diluent (150g of vinyl toluene and 600g of 1,4-butanediol dimethacrylate) and 0.35g of inhibitor (hydroquinone), stir at 70°C for 1h to mix evenly. Cool down to below 40°C, add 45g of initiator (tert-butyl perbenzoate), continue stirring for 1h, filter the material, obtain the impregnation paint, and seal it to avoid light.

[0119] Example 3

[0120] The difference from Example 1 is that the connecting structure unit monomer (76g of propylene glycol and 253g of neopentyl glycol) and the symmetrical amino compound (29.6g of 1,3-propylenediamine) are weighed into the reactor, heated to 100°C under nitrogen conditions to melt and dissolve into a clear liquid, first added and stirred evenly, and then the asymmetric acid anhydride (152.1g of trimellitic anhydride) is added in batches, and the feeding rate is controlled so that the material temperature does not exceed 120°C. After the addition is completed, stirring is continued for 30 minutes, the material temperature no longer rises spontaneously, and the temperature is gradually raised to 170°C, and the nitrogen flow rate is appropriately increased to about 0.2L / min to quickly discharge water vapor, while keeping the steam temperature of the distillation head below 90°C, and the reaction is kept warm for about 2h. When the acid value is lower than 85 mgKOH / g, cool to 120°C, add anhydride (274 g of tetrahydrophthalic anhydride) and stir evenly, then add amino compound (110 g of monoethanolamine) in batches and control the feeding speed so that the material temperature does not exceed 150°C. After the feeding is completed, continue stirring for 30 minutes, the material temperature no longer rises spontaneously, and the temperature is raised to 170°C, and the reaction is kept warm for about 2 hours. When the acid value is lower than 50 mgKOH / g, add connecting structural unit monomers (314 g of maleic anhydride and 73 g of adipic acid), gradually heat to 200°C, and keep warm for about 8 hours. When the acid value is lower than 50 mgKOH / g, close the nitrogen valve, evacuate to about -0.09 MPa, and keep warm for about 2 hours. When the acid value is lower than 20 mgKOH / g, the reaction is terminated to obtain polyester, which includes structural units derived from imide monomers and connecting structural units derived from connecting structural unit monomers, wherein the structural formula of the imide monomer is

[0121] Cool down to 90°C, add 750g of active diluent (150g of vinyl toluene and 600g of 1,4-butanediol dimethacrylate) and 0.35g of inhibitor (hydroquinone), stir at 70°C for 1h to mix evenly. Cool down to below 40°C, add 45g of initiator (tert-butyl perbenzoate), continue stirring for 1h, filter the material, obtain the impregnation paint, and seal it to avoid light.

[0122] Example 4

[0123] The difference from Example 1 is that 82.1 g of an asymmetric amino compound (trimethylhexamethylenediamine) is added, wherein the imide monomer structure is

[0124] Example 5

[0125] The difference from Example 1 is that the asymmetric acid anhydride (trimellitic anhydride) is replaced by 109g of the symmetric acid anhydride (pyromellitic dianhydride), wherein the obtained imide structural formula is:

[0126]

[0127] Comparative Example 1

[0128] The difference from Example 1 is that 135.6g of 1,3-butanediol, 156.2g of neopentyl glycol, 166g of isophthalic acid and 59.2g of hexanediol are weighed and added to the reactor, and stirred at 100°C under nitrogen conditions until a clear liquid is formed. Gradually heat to 180°C, appropriately increase the nitrogen flow rate to about 0.2L / min, so that the water vapor is quickly discharged, while keeping the steam temperature of the distillation head below 90°C, and keep the reaction warm for about 3h. When the acid value is lower than 100mgKOH / g, 314g of the connecting structural unit monomer (maleic anhydride) is added, and the temperature is gradually increased to 190°C, and the reaction is kept warm for about 4h. When the acid value is lower than 160mgKOH / g, 194.6g of the connecting structural unit monomer (benzyl alcohol) is added. Continue to keep the reaction warm for about 4h. When the acid value is lower than 20mgKOH / g, the reaction ends to obtain a polyester free of imide groups, wherein the polyester does not include imide groups.

[0129] Comparative Example 2

[0130] The difference from Example 1 is that, first, 1,6-hexanediamine and trimellitic anhydride are used to synthesize an imide monomer, the structural formula of which is

[0131] Secondly, weigh 23.22g of the obtained imide monomer and the connecting structural unit monomer (135.6g of 1,3-butanediol and 156.2g of neopentyl glycol) and add them to the reactor for reaction. Stir at 100°C under nitrogen until it becomes a clear liquid. Gradually heat to 180°C, appropriately increase the nitrogen flow rate to about 0.2L / min, so that the water vapor is quickly discharged, while keeping the steam temperature of the distillation head below 90°C, and keep the reaction warm for about 3h. When the acid value is lower than 100mgKOH / g, add 314g of maleic anhydride, gradually heat to 190°C, and keep the reaction warm for about 4h. When the acid value is lower than 160mgKOH / g, add 194.6g of benzyl alcohol. Continue to keep the reaction warm for about 4h. When the acid value is lower than 20mgKOH / g, the reaction is completed to obtain polyester.

[0132] Comparative Example 3

[0133] The difference from Example 2 is that first, 1,2-propylenediamine and trimellitic anhydride are used to synthesize the first imide monomer separately. The structural formula of the first imide monomer is Then, tetrahydrophthalic anhydride and isopropanolamine are used to synthesize the second imide monomer separately. The structural formula of the second imide monomer is Subsequent reaction with linking structural unit monomers gives polyester.

[0134] Comparative Example 4

[0135] The difference from Example 3 is that first, 1,3-propylenediamine and trimellitic anhydride are used to synthesize the first imide monomer separately. The structural formula of the first imide monomer is Then, tetrahydrophthalic anhydride and monoethanolamine are used to synthesize the second imide monomer separately; and then reacted with the connecting structural unit monomer. The structural formula of the second imide monomer is Polyester is obtained.

[0136] Performance Testing

[0137] The dipping varnishes prepared in the above Examples 1-5 and Comparative Examples 1-4 were subjected to viscosity tests at room temperature according to GB / T 24148.4-2009. The test results are shown in Table 1.

[0138] The dipping varnishes prepared in the above Examples 1-5 and Comparative Examples 1-4 were subjected to a gel time test according to GB / T 15022.2-2017. The test results are shown in Table 1.

[0139] The impregnating varnishes prepared in the above Examples 1-5 and Comparative Examples 1-4 were tested for bonding strength using a twisted coil method according to GB / T11028-1999. The test results are shown in Table 1.

[0140] The dipping varnishes prepared in the above Examples 1-5 and Comparative Examples 1-4 were subjected to a tensile strength test according to GB / T 2567-2008. The test results are shown in Table 1.

[0141] The impregnating varnishes prepared in the above Examples 1-5 and Comparative Examples 1-4 were subjected to a thermogravimetric analysis test according to GB / T 13464-2008. The test process was as follows: the cured impregnating varnish was ground into powder, filtered through a 100-mesh filter, and dried at 200°C for 16 hours. 8±2 mg of the sample was taken and heated to 600°C at 5°C / min in an oxygen atmosphere to test the temperature at which the weight loss was 10wt%. The test results are shown in Table 1.

[0142] The impregnating varnishes prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to infrared spectroscopy test according to GB / T 6040-2019. The test results are as follows: Figure 2-Figure 10 shown. Figure 2 This is the infrared spectrum test chart of the dipping varnish provided in Example 1 of the present application, Figure 3 This is the infrared spectrum test chart of the dipping varnish provided in Example 2 of the present application, Figure 4 This is the infrared spectrum test chart of the dipping varnish provided in Example 3 of the present application, Figure 5 This is the infrared spectrum test chart of the dipping varnish provided in Example 4 of the present application, Figure 6 This is the infrared spectrum test chart of the dipping varnish provided in Example 5 of the present application, Figure 7The infrared spectrum test chart of the dipping varnish provided in Comparative Example 1 of the present application is as follows: Figure 8 The infrared spectrum test chart of the impregnation varnish provided in Comparative Example 2 of the present application is as follows: Fig. 9 This is the infrared spectrum test diagram of the dipping paint provided in Comparative Example 3 of the present application, Fig.10 This is the infrared spectrum test diagram of the impregnated paint provided in Comparative Example 4 of the present application. It can be seen that Examples 1-5 are respectively at 1394.02 cm -1 、1391.54cm -1 、1390.76cm -1 、1394.11cm -1 and 1393.80cm -1 The characteristic peak of the imide group appeared at 1393.80 cm-1, while no characteristic peak of the imide group was observed in Comparative Example 1. The characteristic peak of the imide group was observed in Comparative Examples 2, 3, and 4 at 1393.80 cm-1. -1 、1391.24cm -1 、1390.23cm -1 Similar characteristic peaks of imide groups appear. The preparation method of polyester provided in the present application can embed imide groups into polyester. Fig.11 Thermogravimetric analysis diagrams of the dipping varnishes provided for Examples 1-5 and Comparative Examples 1-4 of the present application.

[0143] Table 1 Performance test results

[0144]

[0145]

[0146] It can be seen from Examples 1-5 and Comparative Examples 1-4 that the impregnation varnish provided by the present application has high heat resistance and good thermal stability, does not require the addition of solvents during the preparation process, and is environmentally friendly. It can be seen from Example 1 and Comparative Example 1 that the imide monomer can improve the heat resistance and mechanical strength of polyester. It can be seen from Examples 1-5 that a suitable imide content can improve the heat resistance of the impregnation varnish and increase its thermal weight loss temperature. It can be seen from Examples 1 and 2-5 that during the preparation process, the use of an asymmetric amino compound and / or an asymmetric acid anhydride can reduce the crystallinity of the polyester, increase the degree of distortion of the molecular chain, make it less prone to entanglement and accumulation, reduce the viscosity of the polyester, and improve its solubility. Therefore, within a certain viscosity requirement range, the use of an asymmetric imide monomer can introduce more imide groups, thereby making the impregnation varnish have higher mechanical strength and heat resistance. It can be seen from Example 1, Examples 3-4 and Comparative Examples 2-4 that the preparation method provided in the present application can produce polyester with the same structure as the traditional method, and its heat resistance and mechanical properties are comparable to those of the polyester produced by the traditional method. However, the preparation method of the present application is simple, does not require the addition of additional solvents, is environmentally friendly, and can produce polyester with excellent heat resistance and good mechanical properties in one pot.

[0147] The above is a preferred embodiment of the present application, but it should not be understood as limiting the scope of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application, and these improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A polyester, characterized in that The polyester includes a structural unit derived from an imide monomer and a connecting structural unit derived from a connecting structural unit monomer, and the polyester is obtained by mixing the reaction raw materials of the imide monomer and the connecting structural unit monomer and reacting them; the reaction raw materials of the imide monomer include anhydride and an amino compound, and the imide monomer includes a terminal hydroxyl group or a carboxyl group.

2. The polyester according to claim 1, characterized in that The imide monomer includes At least one of; wherein R 1 , R 3 and R 5 are independently selected from substituted or unsubstituted trivalent alkyl, substituted or unsubstituted trivalent aryl, or substituted or unsubstituted trivalent alicyclic group, R 2 , R 4 , R 6 , R 8 , R 9 , R 10 and R 11 are independently selected from substituted or unsubstituted divalent alkyl groups, substituted or unsubstituted divalent aromatic groups, or substituted or unsubstituted divalent alicyclic groups, R 7 is selected from a carbon atom, a substituted or unsubstituted tetravalent aromatic group, or a substituted or unsubstituted tetravalent alicyclic group; X1, X2, Y1, Y2 and Z1 are independently selected from hydroxyl, carboxyl, halogen, nitro, amine, thiol, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, or substituted or unsubstituted aryloxy, and at least one of X1 and Y1 is a hydroxyl or carboxyl group, and at least one of X2, Y2 and Z1 is a hydroxyl or carboxyl group.

3. The polyester according to claim 2, characterized in that The substituents in the substituted alkyl, substituted alkenyl, substituted alkynyl, substituted alkoxy, substituted aryl, substituted aryloxy, substituted divalent alkyl, substituted divalent aryl, substituted divalent alicyclic group, substituted trivalent alkyl, substituted trivalent aryl, substituted trivalent alicyclic group, substituted tetravalent aryl, and substituted tetravalent alicyclic group include at least one of halogen atoms, hydroxyl, nitro, amine, thiol, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, and substituted or unsubstituted aryloxy.

4. The polyester according to claim 1, characterized in that The imide monomer has an asymmetric structure.

5. The polyester according to claim 1, characterized in that The amino compound includes at least one of monoethanolamine, aminopropionic acid, propylenediamine, hexamethylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, m-phenylenediamine, diethylenetriamine, triaminotriethylamine and 2,2'-oxybis(ethylamine).

6. The polyester according to claim 1, characterized in that The acid anhydride includes at least one of a hydroxyl-containing acid anhydride compound, a carboxyl-containing acid anhydride compound, and a polyanhydride compound.

7. The polyester according to claim 1, characterized in that The connecting structural unit monomer includes at least one of a hydroxyl-containing compound, a carboxyl-containing compound and an anhydride-containing compound; The hydroxyl-containing compound comprises at least one of hydrogenated bisphenol A, ethylene glycol, propylene glycol, glycerol, propylene alcohol, diethylene glycol, neopentyl glycol, trimethylolpropane, benzyl alcohol, polyether polyol, 1,2-propylene glycol, 1,3-butylene glycol and dipropylene glycol; The carboxyl-containing compound comprises at least one of isophthalic acid, terephthalic acid, maleic acid, fumaric acid and adipic acid; The acid anhydride-containing compound includes at least one of phthalic anhydride, chlorendic anhydride, maleic anhydride, fumaric anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride and methylhexahydrophthalic anhydride.

8. The polyester according to claim 1, characterized in that The weight average molecular weight of the polyester is 500-10000.

9. A method for preparing the polyester according to any one of claims 1 to 8, characterized in that: include: Acid anhydride, amino compound and connecting structural unit monomer are mixed together to obtain a mixed solution, and polyester is obtained after reaction.

10. The preparation method according to claim 9, characterized in that: The reaction temperature is 20°C-250°C, and the reaction time is 6h-36h.

11. Use of the polyester according to any one of claims 1 to 8 or the polyester prepared by the preparation method according to any one of claims 9 to 10 in the fields of plastics, artificial stones, fibers or paints.

12. A dipping varnish, characterized in that: The impregnating varnish comprises the polyester described in any one of claims 1 to 8 or the polyester prepared by the preparation method described in any one of claims 9 to 10.

13. The impregnation varnish according to claim 12, characterized in that The impregnation varnish further comprises at least one of a reactive diluent, an initiator and an inhibitor; The reactive diluent comprises a liquid compound containing olefin double bonds, and the liquid compound containing olefin double bonds comprises at least one of styrene, vinyl toluene, 1,4-butanediol dimethacrylate, methyl methacrylate, diallyl phthalate and cyanuric acid triacrylate; The inhibitor includes at least one of a phenolic hydroxyl-containing compound, a benzoquinone-containing compound and a free radical scavenger, the phenolic hydroxyl-containing compound includes at least one of hydroquinone, 2-tert-butylhydroquinone, p-hydroxyanisole and 2,5-di-tert-butylhydroquinone, the benzoquinone-containing compound includes at least one of p-benzoquinone and methylhydroquinone, and the free radical scavenger includes 2,2,6,6-tetramethylpiperidin-1-oxyl free radical; The initiator includes at least one of a peroxide bond-containing compound and an azo compound, the peroxide bond-containing compound includes at least one of benzoyl peroxide, tert-butyl hydroperoxide, diisopropyl peroxide, tert-butyl perbenzoate and diisopropyl peroxydicarbonate, and the azo compound includes azobisisobutyronitrile.

14. The impregnation varnish according to claim 13, characterized in that In the impregnating varnish, the mass percentage of the polyester is 30%-80%, the mass percentage of the inhibitor is less than or equal to 1%, and the mass percentage of the initiator is 0.01%-5%.

15. A motor, characterized in that: The motor comprises a motor body and a paint layer arranged on the motor body, and the paint layer is formed by the impregnation paint according to any one of claims 12-14.

16. A vehicle, characterized in that: The vehicle comprises the electric machine of claim 15 .

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