Liquid crystal polymer composition, article, and manufacturing method

Abstract

Described herein are polymer compositions containing at least 20% by weight of a liquid crystal polymer ("LCP"), 10% to 40% by weight of flat glass fibers, and 15% to 50% by weight of boron nitride and / or zinc oxide. It has surprisingly been discovered that polymer compositions containing LCP in combination with flat glass fibers and boron nitride and / or zinc oxide have improved thermal conductivity and flexural properties relative to similar polymer compositions having round glass fibers instead of flat glass fibers.

Description

Technical Field

[0001] Related Applications This application claims priority to U.S. Patent No. 63 / 105,416, filed Oct. 26, 2020, and European Patent No. 21150658.9, filed Jan. 8, 2021, the entire contents of each of which are hereby incorporated by reference for all purposes.

[0002] A polymer composition is provided. The polymer composition has excellent thermal conductivity and comprises a liquid crystal polymer (“LCP”), flat glass fibers, and either or both of boron nitride and zinc oxide. Also provided are articles into which the polymer composition is introduced and methods of making the polymer composition and the articles.

Background Art

[0003] When the power density of an electrical component increases, the heat output of the electrical component also increases, at least in part due to the resistance of the current carriers. The result is a significantly increased heat accumulation in the electrical component. For example, with the increasing consumer demand for vehicles with higher capabilities, the demand for increasing the power density of electric motors for electric vehicles (e.g., automobiles, motorcycles, ships, and airplanes) has been continuously increasing. However, when the power density increases, the heat accumulation inside and around the electric motor also increases, which can significantly reduce the motor efficiency.

Summary of the Invention

[0004] In a first aspect, a polymer composition is provided that comprises a liquid crystal polymer (“LCP”) formed from the polycondensation of the following monomers: terephthalic acid, aromatic diol, a first aromatic dicarboxylic acid, and aromatic hydroxycarboxylic acid, 10 wt% to 40 wt% flat glass fibers, and boron nitride and / or zinc oxide, wherein the total concentration of boron nitride and zinc oxide is 15 wt% to 50 wt%. In some embodiments, the aromatic diol is 4,4'-biphenol, the aromatic hydroxycarboxylic acid is 4-hydroxybenzoic acid, and the first aromatic dicarboxylic acid is isophthalic acid.

[0005] In some embodiments, the polymer composition does not contain zinc oxide. In some embodiments, the polymer composition does not contain boron nitride. In some embodiments, the polymer composition contains boron nitride and zinc oxide. In such an embodiment, the relative concentration of boron nitride to zinc oxide is 0.5 to 2.

[0006] In some embodiments, the polymer composition has a through-plane thermal conductivity of 0.20 W / m-K to 0.9 W / m-K as measured according to ASTM E1461-13. In some embodiments, the polymer composition has a flexural strength of 100 MPa to 250 MPa according to ASTM D790. In some embodiments, the polymer composition has a flexural strain of 100 MPa to 190 MPa as measured according to ASTM D790. In some embodiments, the polymer composition has a shear rate of 100 s -1 a shear rate of 90 Pa·s to 300 Pa·s; 500 s -1 a shear rate of 35 Pa·s to 150 Pa·s, or 1000 s -1 a shear rate of 25 Pa·s to 100 Pa·s.

[0007] In some embodiments, the polymer composition does not contain circular glass fibers.

[0008] In another aspect, an article comprising a polymer composition, which is an electrical component, is provided. In some embodiments, the article is an electric motor component. In some embodiments, the article is a slot liner. In some embodiments, the article is selected from the group consisting of automotive parts, aerospace parts, and marine parts.

DETAILED DESCRIPTION OF THE INVENTION

[0009] A polymer composition is described herein that contains at least 20 weight percent liquid crystal polymer ("LCP"), 10 weight percent to 40 weight percent flat glass fibers, and 15 weight percent to 50 weight percent boron nitride and / or zinc oxide. The polymer composition containing LCP in combination with the combination of flat glass fibers and boron nitride and / or zinc oxide has surprisingly been found to have improved thermal conductivity and flexural properties compared to a similar polymer composition having circular glass fibers instead of flat glass fibers. As used herein, weight percent ("wt.%") is, unless otherwise specified, relative to the total weight of the polymer composition.

[0010] Even if any description is provided in relation to a specific embodiment, it applies to and is replaceable with other embodiments of the present disclosure. When an element or component is said to be included in and / or selected from a list of recited elements or components, in the relevant embodiments specifically contemplated in this application, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the specifically listed elements or components; any element or component listed in the list of elements or components can be omitted from such a list; any recitation in this specification of a numerical range by endpoints includes all numerical values within the recited range, as well as the endpoints of the range and equivalents. Unless specifically limited otherwise, the terms "alkyl" and derivative terms such as "alkoxy", "acyl", and "alkylthio", when used herein, include straight-chain, branched-chain, and cyclic moieties within their scope. Examples of alkyl groups are methyl, ethyl, 1-methylethyl, propyl, 1,1-dimethylethyl, and cyclopropyl.

[0011] Unless otherwise specifically described, each alkyl and aryl group may be unsubstituted or substituted with one or more substituents selected from, but not limited to, halogen, hydroxy, sulfo, C1-C6 alkoxy, C1-C6 alkylthio, C1-C6 acyl, formyl, cyano, C6-C15 aryloxy or C6-C15 aryl, provided that the substituents are sterically compatible and the rules of chemical bonding and strain energy are satisfied. The term "halogen" or "halo" includes fluorine, chlorine, bromine and iodine, with fluorine being preferred.

[0012] Similarly, unless otherwise specifically limited, the term "aryl" refers to a phenyl, indanyl or naphthyl group. An aryl group may contain one or more alkyl groups and in this case may be referred to as "alkylaryl"; for example, it may be composed of an aromatic group and two C1-C6 groups (e.g., methyl or ethyl). An aryl group may also contain one or more heteroatoms, such as N, O or S, and in this case may be referred to as a "heteroaryl" group; these heteroaromatic rings may be fused to other aromatic systems. Such heteroaromatic rings include, but are not limited to, furanyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, triazolyl, isoxazolyl, oxazolyl, thiazolyl, isothiazolyl, pyridyl, pyridazyl, pyrimidinyl, pyrazinyl and triazinyl ring structures. An aryl or heteroaryl substituent may be unsubstituted or substituted with one or more substituents selected from, but not limited to, halogen, hydroxy, C1-C6 alkoxy, sulfo, C1-C6 alkylthio, C1-C6 acyl, formyl, cyano, C6-C15 aryloxy or C6-C15 aryl, provided that the substituents are sterically compatible and the rules of chemical bonding and strain energy are satisfied.

[0013] Polymer composition The polymer composition contains LCP, 10 wt% to 40 wt% of flat glass fibers, and 15 wt% to 50 wt% of boron nitride and / or zinc oxide. The polymer composition containing LCP in combination with the combination of flat glass fibers and boron nitride and / or zinc oxide surprisingly has improved thermal conductivity and bending properties compared to a similar polymer composition having circular glass fibers instead of flat glass fibers. Further, in some embodiments, the polymer composition had a particularly desirable apparent viscosity for injection molding of thin-walled articles.

[0014] The polymer composition has surprisingly improved thermal conductivity. As described above, in high power density electrical component applications (such as electric motors for electric vehicles), there is a significantly increased heat output, which results in heat accumulation within and around the electrical components. Accordingly, there is a need to improve cooling. The polymer compositions described herein have significantly improved thermal conductivity to assist in conducting heat away from electric motor components. Of course, the same applies to any article (such as a power supply) that conducts a significant current or has high power density requirements. In some embodiments, the polymer composition has a through-plane thermal conductivity of at least 0.20 watts per meter kelvin (“W / m-K”), at least 0.25 W / m-K, at least 0.3 W / m-K, at least 0.35 W / m-K, at least 0.4 W / m-K, at least 0.45 W / m-K, at least 0.5 W / m-K, at least 0.55 W / m-K, or at least 0.6 W / m-K. In some embodiments, the polymer composition has a through-plane thermal conductivity of 0.9 W / m-K or less or 0.85 W / m-K or less. In some embodiments, the polymer composition has a through-plane thermal conductivity of 0.2 W / m-K to 0.9 W / m-K, 0.25 W / m-K to 0.9 W / m-K, 0.3 W / m-K to 0.9 W / m-K, 0.35 W / m-K to 0.9 W / m-K, 0.4 W / m-K to 0.9 W / m-K, 0.45 W / m-K to 0.9 W / m-K, 0.5 W / m-K to 0.9 W / m-K, 0.55 W / m-K to 0.9 W / m-K, or 0.6 W / m-K to 0.9 W / m-K. In some embodiments, the polymer composition has a through-plane thermal conductivity of 0.2 W / m-K to 0.85 W / m-K, 0.25 W / m-K to 0.85 W / m-K, 0.3 W / m-K to 0.85 W / m-K, 0.35 W / m-K to 0.85 W / m-K, 0.4 W / m-K to 0.85 W / m-K, 0.45 W / m-K to 0.85 W / m-K, 0.5 W / m-K to 0.85 W / m-K, 0.55 W / m-K to 0.85 W / m-K, or 0.6 W / m-K to 0.85 W / m-K. The through-plane thermal conductivity can be measured as described in the Examples section.

[0015] In addition, the polymer composition exhibited enhanced flexural properties. In some embodiments, the polymer composition has a tensile strength at break (referred to as "tensile strength") of 100 MPa to 250 MPa, 120 MPa to 250 MPa, 130 MPa to 250 MPa, 140 MPa to 250 MPa, or 150 MPa to 250 MPa. In some embodiments, the polymer composition has a tensile strength of 100 MPa to 250 MPa, 120 MPa to 220 MPa, 130 MPa to 220 MPa, 140 MPa to 220 MPa, or 150 MPa to 220 MPa. In some embodiments, the polymer composition has a tensile strength of 100 MPa to 200 MPa, 120 MPa to 200 MPa, 130 MPa to 200 MPa, 140 MPa to 200 MPa, or 150 MPa to 200 MPa. In some embodiments, the polymer composition has a tensile strength of 100 MPa to 190 MPa, 120 MPa to 190 MPa, 130 MPa to 190 MPa, 140 MPa to 190 MPa, or 150 MPa to 190 MPa. In some embodiments, the polymer composition has a tensile strain at break (referred to as "tensile strain") of 1% to 3%, 1.5% to 3%, or 1.8% to 3%. In some embodiments, the polymer composition has a tensile strain of 1% to 2.5%, 1.5% to 2.5%, or 1.8% to 2.5%. The tensile strength and tensile elongation can be measured as described in the Examples section.

[0016] In some embodiments, the polymer composition is 100 seconds -1 , (referred to as "s -1 ") and has an apparent viscosity (referred to as "η") of 90 Pa·s to 300 Pa·s, 120 Pa·s to 300 Pa·s, or 150 Pa·s to 300 Pa·s at a shear rate. In some embodiments, the polymer composition has an η of 90 Pa·s to 250 Pa·s, 120 Pa·s to 250 Pa·s, or 150 Pa·s to 250 Pa·s at a shear rate of 100 s -1 . In some embodiments, the polymer composition is 500 s -1It has an η of 35 Pa·s to 150 Pa·s, 70 Pa·s to 150 Pa·s, 35 Pa·s to 120 Pa·s, or 70 Pa·s to 120 Pa·s at a shear rate. In some embodiments, the polymer composition is 1000 s -1 It has an η of 25 Pa·s to 100 Pa·s, 50 Pa·s to 100 Pa·s, 25 Pa·s to 90 Pa·s, or 50 Pa·s to 90 Pa·s at a shear rate of -1 . η can be measured as described in the Examples section.

[0017] In some embodiments, the polymer composition has a melting temperature (“Tm”) of at least 300 °C, at least 320 °C, or at least 340 °C. In some embodiments, the polymer composition has a Tm of 430 °C or less, 410 °C or less, or 400 °C or less. In some embodiments, the polymer composition has a Tm of 300 °C to 430 °C, 320 °C to 410 °C, or 340 °C to 400 °C. Tm can be measured according to ASTM D3418.

[0018] Liquid crystal polymer The LCP is formed from the polycondensation of the following monomers: terephthalic acid, aromatic diol, a first aromatic dicarboxylic acid different from terephthalic acid, and aromatic hydroxycarboxylic acid. In some embodiments, at least one of the first aromatic dicarboxylic acid and the aromatic hydroxycarboxylic acid does not contain a naphthyl group.

[0019] In some embodiments, the aromatic diol is from the group of the following formulas: HO-Ar1-OH, and (1) HO-Ar2-T1-Ar3-OH, (2) (wherein Ar1 to Ar3 are independently selected from one or more substituents selected from the group consisting of halogen, C1 to C 15 alkyl, and C6 to C 15 aryl, and are optionally substituted with one or more substituents; T1 is selected from the group consisting of a bond, O, S, -SO2-, -C(=O)-, and C1 to C 30 alkyl) 15 (selected from the group consisting of). It is represented by a formula selected from. In some embodiments, the aromatic diol is 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 2,5-biphenyldiol, 4,4'-biphenol, 4,4'-(propane-2,2-diyl)diphenol, 4,4'-(ethane-1,2-diyl)diphenol, 4,4'-methylenediphenol, bis(4-hydroxyphenyl)methanone, 4,4'-oxydiphenol, 4,4'-sulfonyldiphenol, 4,4'-thiodiphenol, naphthalene-2,6-diol, and naphthalene-1,5-diol. Preferably, the aromatic diol is 4,4'-biphenol.

[0020] In some embodiments, the first aromatic dicarboxylic acid is from the group of the following formulas: HOOC-Ar1-COOH, and (3) HOOC-Ar2-T2-Ar3-COOH, (4) (wherein Ar1 to Ar3 are as given above and are independently selected; T2 is selected from a bond, O, and S) It is independently represented by a formula selected from. In some embodiments, the first aromatic dicarboxylic acid is isophthalic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-oxydibenzoic acid, 4,4'-(ethylenedioxy)dibenzoic acid, 4,4'-sulfanilyldibenzoic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, and naphthalene-2,3-dicarboxylic acid. Preferably, the first aromatic dicarboxylic acid is selected from the group consisting of isophthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, and naphthalene-2,3-dicarboxylic acid. Most preferably, the first aromatic dicarboxylic acid is isophthalic acid.

[0021] In some embodiments, the aromatic hydroxycarboxylic acid is HO-Ar1-COOH, and (5) HO-Ar2-Ar3-COOH, (6) (wherein, Ar1 to Ar3 are as defined above and are independently selected) It is represented by a formula selected from the group consisting of. In some embodiments, the aromatic hydroxycarboxylic acid is 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 6-hydroxy-1-naphthoic acid, 2-hydroxy-1-naphthoic acid, 3-hydroxy-2-naphthoic acid, 1-hydroxy-2-naphthoic acid, 5-hydroxy-1-naphthoic acid, and 4'-hydroxy-[1,1'-biphenyl]-4-carboxylic acid. Preferably, the aromatic hydroxycarboxylic acid is selected from the group consisting of 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 6-hydroxy-1-naphthoic acid, 2-hydroxy-1-naphthoic acid, 3-hydroxy-2-naphthoic acid, 1-hydroxy-2-naphthoic acid, and 5-hydroxy-1-naphthoic acid. Most preferably, the aromatic hydroxycarboxylic acid is 4-hydroxybenzoic acid.

[0022] In some embodiments, the LCP formed from the aforementioned monomers has repeating units R LCP1 ~R LCP4 having. The repeating unit R LCP1 is the following formula:

Chemical formula

[0023] In some embodiments, the total concentration of the repeating units R LCP1 ~R LCP4 is at least 50 mol%, at least 60 mol%, at least 70 mol%, at least 80 mol%, at least 90 mol%, at least 95 mol%, at least 99 mol%, or at least 99.9 mol%. In some embodiments, the concentration of terephthalic acid is 5 mol% to 30 mol%, preferably 10 mol% to 20 mol%. In some embodiments, the concentration of the aromatic diol is 10 mol% to 30 mol%, preferably 15 mol% to 25 mol%. In some embodiments, the concentration of the first aromatic dicarboxylic acid is 1 mol% to 20 mol%, preferably 1 mol% to 10 mol%. In some embodiments, the concentration of the aromatic hydroxycarboxylic acid is 35 mol% to 80 mol%, preferably 45 mol% to 75 mol%, most preferably 50 mol% to 17 mol%. In some embodiments, R LCP1 ~RLCP4 are derived from terephthalic acid, 4,4'-biphenol, isophthalic acid, and 4-hydroxybenzoic acid, respectively, where the concentration range for each repeating unit is within the range given above. As used herein, the mol% of each repeating unit is relative to the total number of moles of repeating units in the polymer, unless otherwise specified. For clarity, "derived from" refers to repeating units formed from the polycondensation of the listed monomers, as described above with respect to the relationship between Formulas 1-6 and 8-13.

[0024] In some embodiments, the LCP has a Tm of at least 310 °C, at least 320 °C, or at least 330 °C. In some embodiments, the LCP has a Tm of 390 °C or less, 380 °C or less, or 370 °C or less. In some embodiments, the LCP has a Tm of 310 °C to 390 °C, 320 °C to 380 °C, or 330 °C to 370 °C.

[0025] In some embodiments, the LCP has a number average molecular weight ("Mn") of at least 5,000 g / mol. In some embodiments, the LCP has an Mn of 20,000 g / mol or less. In some embodiments, the LCP has an Mn of 5,000 g / mol to 20,000 g / mol. The number average molecular weight Mn can be measured by gel permeation chromatography (GPC) according to ASTM D5296 and using a hexafluoropropanol solvent and a poly(methyl methacrylate) standard.

[0026] In some embodiments, the LCP concentration in the polymer composition is at least 20 wt%, at least 30 wt%, at least 35 wt%, or at least 40 wt%. In some embodiments, the LCP concentration in the polymer composition is 80 wt% or less, 75 wt% or less, or 70 wt% or less. In some embodiments, the LCP concentration in the polymer composition is from 30 wt% to 80 wt%, from 30 wt% to 75 wt%, or from 30 wt% to 70 wt%. In some embodiments, the LCP concentration in the polymer composition is from 35 wt% to 80 wt%, from 35 wt% to 75 wt%, or from 35 wt% to 70 wt%. In some embodiments, the LCP concentration in the polymer composition is from 40 wt% to 80 wt%, from 40 wt% to 75 wt%, or from 40 wt% to 70 wt%.

[0027] The LCPs described herein can be prepared by any conventional method adapted for the synthesis of LCPs.

[0028] boron nitride or zinc oxide The polymer composition includes boron nitride and / or zinc oxide. In some embodiments, the polymer composition includes either boron nitride or zinc oxide. In such an embodiment, the polymer composition includes boron nitride and does not include zinc oxide. In other embodiments, the polymer composition includes zinc oxide and does not include boron nitride. In some embodiments, the polymer composition includes both boron nitride and zinc oxide. As used herein and unless otherwise specified, the component “free of” means that the concentration of the component in the polymer composition is 1 wt% or less, 0.5 wt% or less, 0.1 wt% or less, or 0.05 wt% or less.

[0029] The total concentration of boron nitride and zinc oxide in the polymer composition is 15 wt% to 50 wt%. In some embodiments, the total concentration of boron nitride and zinc oxide is at least 20 wt%. In some embodiments, the total concentration of boron nitride and zinc oxide is 45 wt% or less or 40 wt% or less. In some embodiments, the total concentration of boron nitride and zinc oxide is 15 wt% to 45 wt% or 15 wt% to 40 wt%. In some embodiments, the total concentration of boron nitride and zinc oxide is 20 wt% to 50 wt%, 20 wt% to 45 wt% or 20 wt% to 40 wt%. In embodiments containing both boron nitride and zinc oxide, the relative concentration of boron nitride to zinc oxide (weight of boron nitride in the polymer composition / weight of zinc oxide in the polymer composition) is 0.5 to 2, 0.75 to 1.3, 0.80 to 1.2 or 0.90 to 1.1. In embodiments containing either boron nitride or zinc oxide, the boron nitride concentration or the zinc oxide concentration is, respectively, within the same ranges provided above with respect to the total concentration of boron nitride and zinc oxide.

[0030] Flat glass fiber The polymer composition further comprises flat glass fibers. The glass fibers are silica-based glass compounds containing several metal oxides that can be adjusted to yield various types of glass. The main oxide is silica in the form of quartz sand, and other oxides such as calcium, sodium and aluminum are incorporated to lower the melting temperature and prevent crystallization. The glass fibers can be added as continuous fibers or chopped glass fibers. All types of glass fibers (described in Chapter 5.2.3, pages 43-48 of Additives for Plastics Handbook, 2nd ed, John Murphy), such as A, C, D, E, M, S, R, T glass fibers, or any mixture thereof or mixtures thereof can be used. For example, R, S and T glass fibers are typically high modulus glass fibers having a modulus of elasticity of at least 76, preferably at least 78, more preferably at least 80, most preferably at least 82 GPa as measured according to ASTM D2343.

[0031] E, R, S, and T glass fibers are well known in the art. They are described, in particular, in Fiberglass and Glass Technology, Wallenberger, Frederick T.; Bingham, Paul A. (Eds.), 2010, XIV, chapter 5, pages 197 - 225. R, S, and T glass fibers are essentially composed of oxides of silicon, aluminum, and magnesium. In particular, those glass fibers typically contain 62 - 75 wt% SiO2, 16 - 28 wt% Al2O3, and 5 - 14 wt% MgO, based on the total weight of the glass fiber. In contrast to the normal E - glass fibers widely used in polymer compositions, R, S, and T glass fibers contain less than 10 wt% CaO.

[0032] Generally, glass fibers have an aspect ratio defined as the average ratio between the length and the largest of the width and thickness of at least 5, at least 10, at least 20, or at least 50. In some embodiments, the glass fibers have an average length of 3 mm to 50 mm. In some such embodiments, the glass fibers have an average length of 3 mm to 10 mm, 3 mm to 8 mm, 3 mm to 6 mm, or 3 mm to 5 mm. In alternative embodiments, the glass fibers have an average length of 10 mm to 50 mm, 10 mm to 45 mm, 10 mm to 35 mm, 10 mm to 30 mm, 10 mm to 25 mm, or 15 mm to 25 mm. The average length of the glass fibers can be considered as the average length of the glass fibers before being incorporated into the polymer composition or as the average length of the glass fibers in the polymer composition.

[0033] Flat glass fibers are glass fibers having a non - circular cross - section, such as an oval, elliptical, or rectangular cross - section.

[0034] In some embodiments, the glass fiber has a cross-sectional major axis length of at least 15 μm, preferably at least 20 μm, more preferably at least 22 μm, and even more preferably at least 25 μm. Further or alternatively, in some embodiments, the glass fiber has a cross-sectional major axis length of at most 40 μm, preferably at most 35 μm, more preferably at most 32 μm, and even more preferably at most 30 μm. In some embodiments, the glass fiber has a cross-sectional major axis length of 15 μm to 35 μm, preferably 20 μm to 30 μm, more preferably 25 μm to 29 μm. In some embodiments, the glass fiber has a cross-sectional minor axis length of at least 4 μm, preferably at least 5 μm, more preferably at least 6 μm, and even more preferably at least 7 μm. Further or alternatively, in some embodiments, the glass fiber has a cross-sectional minor axis length of at most 25 μm, preferably at most 20 μm, more preferably at most 17 μm, and even more preferably at most 15 μm. In some embodiments, the glass fiber has a cross-sectional minor axis length of 5 μm to 20 μm, preferably 5 μm to 15 μm, more preferably 7 μm to 11 μm. In some embodiments, the glass fiber has an aspect ratio of at least 2, preferably at least 2.2, more preferably at least 2.4, and even more preferably at least 3. The aspect ratio is defined as the ratio of the longest diameter to the shortest diameter in the cross-section of the glass fiber. In some embodiments, the glass fiber has an aspect ratio of at most 8, preferably at most 6, and more preferably at most 4. In some embodiments, the glass fiber has an aspect ratio of 2 to 6, preferably 2.2 to 4.

[0035] The shape of the cross-section of the glass fiber, its length, its cross-sectional diameter, and its aspect ratio can be easily determined using optical microscopy. For example, the aspect ratio of the fiber cross-section can be determined by measuring the longest (width) and smallest (height) dimensions of the fiber cross-section using a Euromex optical microscope and image analysis software (Image Focus 2.5) and dividing the first number by the second number.

[0036] In some embodiments, the glass fiber has an elastic modulus of at least 76 GPa, preferably at least 78, more preferably at least 80, even more preferably at least 82, and most preferably at least 84 GPa as measured according to ASTM C1557-03. In some embodiments, the glass fiber has a tensile strength of at least 3.5 GPa, preferably at least 3.6, more preferably at least 3.7, even more preferably at least 3.8, and most preferably at least 3.9 GPa as measured according to ASTM C1557-03. This level of elastic modulus and tensile strength is typically achieved when using a specific chemical composition of the glass used to manufacture the glass fiber. The glass is a silica-based glass compound containing several metal oxides that can be adjusted to produce different types of glass. The main oxide is silica in the form of silica sand, and other oxides such as calcium, sodium, and aluminum are introduced to lower the melting temperature and prevent crystallization. It is well known in the art that when using a glass with a high load of Al2O3, the glass fiber derived therefrom exhibits a high elastic modulus. In particular, those glass fibers typically contain 55-75 wt% SiO2, 16-28 wt% Al2O3, and 5-14 wt% MgO based on the total weight of the glass composition. Contrary to the ordinary E-glass fibers widely used in polymer compositions, the high modulus glass fibers contain less than 5 wt%, preferably less than 1 wt% B2O3 based on the total weight of the glass composition.

[0037] The flat glass fiber concentration in the polymer composition is 10 wt% to 40 wt%. In some embodiments, the flat glass fiber concentration in the polymer composition is 10 wt% to 35 wt%, 10 wt% to 30 wt%, 15 wt% to 40 wt%, 15 wt% to 35 wt%, or 15 wt% to 30 wt% based on the total weight of the polymer composition.

[0038] Additive In some embodiments, the polymer composition also includes an additive selected from the group consisting of additional reinforcing agents, strengthening agents, plasticizers, colorants, pigments, antistatic agents, dyes, lubricants, heat stabilizers, light stabilizers, flame retardants, nucleating agents, and antioxidants.

[0039] A wide variety of additional reinforcing agents can be added to the polymer composition. The additional reinforcing agents can be selected from fiber reinforcing agents and particulate reinforcing agents. A fiber reinforcing agent is herein considered to be a material having a length, width, and thickness such that the average length is significantly greater than both the width and the thickness. Generally, such materials have an aspect ratio defined as the average ratio between the length and the largest of the width and thickness of at least 5, at least 10, at least 20, or at least 50. In some embodiments, the fiber reinforcing agent has an average length of 3 mm to 50 mm. In some such embodiments, the fiber reinforcing agent has an average length of 3 mm to 10 mm, 3 mm to 8 mm, 3 mm to 6 mm, or 3 mm to 5 mm. In alternative embodiments, the fiber reinforcing agent has an average length of 10 mm to 50 mm, 10 mm to 45 mm, 10 mm to 35 mm, 10 mm to 30 mm, 10 mm to 25 mm, or 15 mm to 25 mm. The average length of the fiber reinforcing agent can be interpreted as the average length of the fiber reinforcing agent before incorporation into the polymer composition or as the average length of the fiber reinforcing agent in the polymer composition. Examples of fiber reinforcing agents include, but are not limited to, additional glass fibers (e.g., circular glass fibers), carbon fibers, synthetic polymer fibers, aramid fibers, aluminum fibers, titanium fibers, magnesium fibers, boron carbide fibers, rock wool fibers, and steel fibers. Circular glass fibers are glass fibers having a substantially circular cross-section (e.g., a cross-section having a vertical axis that varies by less than 5%, less than 1%, or less than 0.5% within the cross-section). Examples of particulate reinforcing agents include, but are not limited to, talc, mica, kaolin, calcium carbonate, calcium silicate, magnesium carbonate, and wollastonite.

[0040] In some embodiments, the concentration of the reinforcing agent in the polymer composition is at least 15 wt%, at least 20 wt%, at least 25 wt%, or at least 30 wt%. In some embodiments, the concentration of the reinforcing agent is 45 wt% or less. In some embodiments, the concentration of the reinforcing agent is from 20 wt% to 45 wt%, or from 30 wt% to 45 wt%.

[0041] In some embodiments, the polymer composition is free of a reinforcing agent. In some embodiments, the polymer composition is free of additional glass fibers. In some embodiments, the polymer composition is free of circular glass fibers. Being free of a reinforcing agent (e.g., additional glass fibers or circular glass fibers) means that the concentration of the reinforcing agent is less than 10 wt%, less than 5 wt%, less than 1 wt%, or less than 0.5 wt%.

[0042] The polymer composition may also include a toughening agent. The toughening agent is generally a low glass transition temperature (Tg) polymer, for example, having a Tg below room temperature, below 0 °C, or even below -25 °C. As a result of its low Tg, the toughening agent is typically elastomeric at room temperature. The toughening agent can be a functionalized polymer backbone.

[0043] The polymer backbone of the toughening agent can be selected from elastomeric backbones including polyethylene and its copolymers, such as ethylene-butene, ethylene-octene; polypropylene and its copolymers; polybutene; polyisoprene; ethylene-propylene rubber (EPR); ethylene-propylene-diene monomer rubber (EPDM); ethylene-acrylate rubber; butadiene-acrylonitrile rubber, ethylene-acrylic acid (EAA), ethylene-vinyl acetate (EVA); acrylonitrile-butadiene-styrene rubber (ABS), block copolymer styrene ethylene butadiene styrene (SEBS), block copolymer styrene butadiene styrene (SBS); methacrylate-butadiene-styrene (MBS) type core-shell elastomers, or mixtures of one or more of the above.

[0044] When the reinforcing agent is functionalized, the functionalization of the main chain can result from the copolymerization of monomers containing the functionalization or from the grafting of the polymer main chain with additional components.

[0045] Specific examples of functionalized reinforcing agents include, inter alia, terpolymers of ethylene, acrylate esters, and glycidyl methacrylate; copolymers of ethylene and butyl acrylate; copolymers of ethylene, butyl acrylate, and glycidyl methacrylate; ethylene - maleic anhydride copolymers; EPR grafted with maleic anhydride; styrene copolymers grafted with maleic anhydride; SEBS copolymers grafted with maleic anhydride; styrene - acrylonitrile copolymers grafted with maleic anhydride; and ABS copolymers grafted with maleic anhydride.

[0046] In some embodiments, the concentration of the reinforcing agent is at least 1 wt%, at least 2 wt% or at least 3 wt%. Further or alternatively, in some embodiments the concentration of the reinforcing agent is 30 wt% or less, 20 wt% or less, 15 wt% or less, or 10 wt% or less.

[0047] The polymer composition may also include other conventional additives commonly used in the art, such as plasticizers, colorants, pigments (e.g., black pigments such as carbon black and nigrosine), antistatic agents, dyes, lubricants (e.g., linear low - density polyethylene, calcium or magnesium stearate or sodium montanate), heat stabilizers, light stabilizers, flame retardants, nucleating agents, and antioxidants.

[0048] Preparation of the Polymer Composition The polymer composition can be prepared by melt - blending the LCP and the specific components (e.g., flat glass fibers and boron nitride or zinc oxide), as well as any other additives.

[0049] The polymer and non-polymer components may be mixed using any suitable melt blending method known in the art. For example, the polymer and non-polymer components can be fed into a melt mixer such as a single-screw or twin-screw extruder, a stirrer, a single-screw or twin-screw kneader, or a Banbury mixer, and the addition step can be a simultaneous addition of all components or a batchwise stepwise addition. When the polymer raw material and the non-polymer raw material are added gradually in a batchwise manner, a part of the polymer raw material and / or the non-polymer raw material is first added, and then it is melt-mixed with the remaining polymer raw material and non-polymer raw material that are added subsequently until a well-mixed composition is obtained. If the reinforcing agent exhibits a long physical shape (e.g., long glass fibers), stretch extrusion molding can be used to prepare the reinforced composition.

[0050] Articles and Uses The polymer composition can desirably be incorporated into an article. The article can be used, inter alia, in an application environment where a thin-walled article is formed (e.g., injection molded) from the polymer composition.

[0051] As used herein, a thin-walled article is an article having a portion (along a line perpendicular to the surface where the measurement is taken) with a maximum thickness of 1 mm or less, 0.9 mm or less, 0.8 mm or less, or 0.7 mm or less. Preferably, this portion is an area on the surface of an article that is at least 1 mm 2 at least 10 mm 2 at least 100 mm 2 or at least 1000 mm 2 in area.

[0052] In some embodiments, the article is an automotive part, an aerospace part, or a marine part (including but not limited to boats and jet skis). In some embodiments, including but not limited to the foregoing embodiments, the article is an electrical part (e.g., an electric vehicle part). In some embodiments, the electrical part is in contact with or includes an electric current carrier. In some embodiments, including but not limited to the foregoing embodiments, the article is an electric motor part (e.g., an electric vehicle motor part). In some embodiments, the article is a slot liner. The slot liner is incorporated into the stator or rotor of an electric motor (including a generator). The slot liner provides insulation between the stator core or motor core and the stator winding or rotor winding, respectively. As described above, the polymer compositions described herein are particularly desirable for high power density motor applications, at least because of the significantly improved through-plane thermal conductivity. For clarity, the articles described above can be thin or non-thin articles. Preferably the article is a thin article.

[0053] Melt extrusion involves the step of extruding a molten polymer or polymer composition through a die or orifice. The molten polymer can be formed during melt blending as described above, or it can be formed, for example, by melting a pre-formed polymer or polymer composition in the form of pellets. For injection molding applications, the molten polymer is pushed into a mold where it solidifies and is then removed (ejected from the mold). In some embodiments where the molten polymer is formed by melt blending (e.g., extrusion), the mold can be connected directly or indirectly to the melt blending apparatus (e.g., extruder) such that it is pushed into the mold before the polymer composition significantly cools. In other embodiments, solid pellets of the polymer or polymer composition can be melted and the melting apparatus can be connected directly or indirectly to the mold such that it can supply the molten polymer or polymer composition into the mold. The mold corresponds to the shape of the article to be formed. As noted above, the polymer composition has a melt viscosity that is highly desirable for injection molding applications, particularly for thin-walled articles formed by injection molding.

[0054] The article can be printed from a polymer composition, for example, by a process that includes the step of extruding the material in the form of filaments, or in this case, by a process that includes the step of laser sintering the material in the form of powder.

[0055] Also provided is a method of manufacturing a three-dimensional (3D) object using an additive manufacturing system, the method including the step of providing a part material including a polymer composition and the step of printing a layer of the 3D object from the part material.

[0056] The polymer composition can, therefore, be in the form of a thread or filament used in the process of 3D printing, for example, the fused filament fabrication method, also known as "FDM" (fused deposition modeling).

[0057] The polymer composition can also be in the form of a powder, for example a substantially spherical powder, for use in a 3D printing process such as selective laser sintering (SLS).

[0058] If the disclosure of any patent, patent application, and publication incorporated herein by reference conflicts with the description of this application to the extent that it obscures the terms, the description shall control.

Examples

[0059] The following examples demonstrate the film-forming ability as well as the dielectric and mechanical properties of the present polymer composition. The following raw materials were used in the examples: - LCP: A liquid crystal polymer formed from the following monomers: isophthalic acid; terephthalic acid; 4,4'-biphenol, p-hydroxybenzoic acid - Flat glass fiber (“FGF”): Commercially obtained from Nitto Boseki Co., LTD (CSG 3PA-830). - Round glass fiber (“RGF”): Commercially obtained from Saint-Gobain (910). - Lubricant: Commercially obtained from Solvay Specialty Polymers Italy, S.p.A. under the trade name Polymist® F5A. - Boron nitride: Commercially obtained from Momentive (CF600 Boron Nitride). - Zinc oxide: Commercially obtained from Dryteck (Pana-Tetra).

[0060] Example 1: Synthesis of LCP and Formation of Samples To synthesize the LCP, dicarboxylic acid monomers (terephthalic acid (167.0 g, Flint Hills Resources), isophthalic acid (55.7 g, Lotte Chemicals), p-hydroxybenzoic acid (555.5 g, Sanfu), 4,4'-biphenol (201.6 g, SI Group), and acetic anhydride (769.2 g, Aldrich)) were charged into a 2 L glass reactor. Potassium acetate (0.07 g, Aldrich) and magnesium acetate (0.2 g, Aldrich) were used as catalysts. The mixture was heated to 165 °C, and the acetylation reaction under reflux conditions was allowed to proceed for 1 hour. Then, while distilling off acetic acid from the reactor, heating was continued to 300 °C at a rate of 0.5 °C per minute. The prepolymer was discharged and cooled. The material was then ground into powder for solid-state polymerization. The resin was subjected to the following profile: 1 hour at 220 °C, 1 hour at 290 °C, and 12 hours at 310 °C under continuous nitrogen purging. The resulting high molecular weight resin had a melt viscosity of 60 - 140 Pa-s at 370 °C.

[0061] Samples were formed by melt blending the polymer composition in an extruder and cut into pellets. Samples for heat-cooling tests, mechanical tests, and physical tests were formed by injection molding. The sample parameters are shown in Table 1. All values in Table 1 are in units of weight %, based on the total weight of the polymer composition.

[0062]

Table 1

[0063] Example 2: Thermal properties, mechanical properties, and rheological properties This example demonstrates the thermal, mechanical, and rheological properties of the samples.

[0064] To demonstrate the thermal performance, the through-plane electrical conductivity was measured by the flash method using a Netzsch LFA467 HyperFlash instrument and in accordance with ASTM E1461-13, “Standard Test Method for Thermal Diffusivity by the Flash Method”. To demonstrate the mechanical performance, the flexural strength and flexural strain were measured in accordance with ASTM D790. To demonstrate the rheological performance, η (apparent viscosity) was measured in accordance with ASTM D3835. The results of the thermal, mechanical and rheological performances are shown in Table 2.

[0065]

Table 2

[0066] Samples having a combination of flat glass fibers and boron nitride had improved through-plane electrical conductivity, flexural strength at break, and flexural strain at break compared to samples having a combination of circular glass fibers and boron nitride. Referring to Table 2, the comparison of C1 and E4 demonstrates that the addition of boron nitride (E4) to the LCP composition with flat glass fibers results in a through-plane electrical conductivity of 0.38 W / m-K, showing an improvement of about 90% over a similar LCP composition without boron nitride (C1). The comparison of C2 and C3 demonstrates that the addition of boron nitride (C3) to the LCP composition with circular glass fibers results in only about 0.35 W / m-K of through-plane electrical conductivity, which is less than that of E4 and shows only about a 21% improvement over a similar LCP composition without boron nitride (C2). Furthermore, the addition of boron nitride in E4 compared to C1 and in C3 compared to C2 decreases the flexural strength at break and flexural strain at break, but E4 has improved flexural strength at break and flexural strain at break compared to C3.

[0067] Similarly, samples having a combination of flat glass fibers and zinc oxide had improved through-plane conductivity, breaking point flexural strength, and breaking point flexural strain compared to samples having a combination of circular glass fibers and zinc oxide. Referring to Table 2, the comparison between C1 and E5 demonstrated that the addition of zinc oxide (E5) to the LCP composition with flat glass fibers resulted in a through-plane conductivity of 0.25 W / m-K, showing an improvement of approximately 25% compared to a similar LCP composition (C1) without zinc oxide. The comparison between C2 and C4 demonstrated that the addition of zinc oxide (C4) to the LCP composition with circular glass fibers resulted in a through-plane conductivity of only about 0.24 W / m-K, which is slightly lower than that of E4, showing a decrease of approximately 17% compared to a similar LCP composition (C2) without zinc oxide.

[0068] Furthermore, the addition of zinc oxide in E5 relative to C1 and in C4 relative to C2 decreases the breaking point flexural strength and breaking point flexural strain, but E5 has improved breaking point flexural strength and breaking point flexural strain compared to C4. Furthermore, samples having a combination of flat glass fibers and both boron nitride and zinc oxide had improved flexural properties while maintaining excellent through-plane conductivity compared to samples having a combination of flat glass fibers and boron nitride only. Referring to Table 2, the comparison between E1 and E6 demonstrated that the former had a higher through-plane conductivity, while the latter had significantly improved breaking point flexural strength and improved breaking point flexural strain.

[0069] The above embodiments are intended to be illustrative and not limiting. Additional embodiments are within the concept of the present invention. In addition, while specific embodiments are described, those skilled in the art will recognize that changes in form and detail can be made without departing from the spirit and scope of the present invention. Any incorporation by reference of the above documents is limited so that no subject matter conflicting with the explicit disclosure herein is incorporated.

Claims

Claim 1 - A polymer composition comprising: at least 20% by weight of a liquid crystal polymer (LCP) formed from the polycondensation of the following monomers: terephthalic acid, 4,4'-biphenol, isophthalic acid, and 4-hydroxybenzoic acid, - 10% to 40% by weight of flat glass fibers, - boron nitride and zinc oxide, wherein the total concentration of boron nitride and zinc oxide is 15% to 50% by weight, - optionally, additives selected from the group consisting of reinforcing agents, plasticizers, colorants, pigments, antistatic agents, dyes, lubricants, heat stabilizers, light stabilizers, nucleating agents, and antioxidants wherein the relative concentration of boron nitride to zinc oxide, expressed as the weight of boron nitride in the polymer composition / the weight of zinc oxide in the polymer composition, is 0.5 to 2, and the polymer composition has a relative concentration of boron nitride to zinc oxide, expressed as the weight of boron nitride in the polymer composition / the weight of zinc oxide in the polymer composition, of 0.5 to 2. A polymer composition. Claim 2 The polymer composition according to claim 1, having a through-plane thermal conductivity of 0.20 W / m-K to 0.9 W / m-k, measured by laser flash according to ASTM E1461-13. Claim 3 The polymer composition according to claim 1 or 2, having a flexural strength of 100 MPa to 250 MPa according to ASTM D790. Claim 4 The polymer composition according to claim 1 or 2, having a flexural strain of 100 MPa to 190 MPa measured according to ASTM D790. Claim 5 a viscosity of 90 Pa·s to 300 Pa·s at a shear rate of 100 s, measured in accordance with ASTM D3835 －１ a viscosity of 35 Pa·s to 150 Pa·s at a shear rate of 500 s, －１ a viscosity of 25 Pa·s to 100 Pa·s at a shear rate of 1000 s, or －１ The polymer composition according to claim 1 or 2, having an apparent viscosity of Claim 6 The polymer composition according to claim 1 or 2, wherein the concentration of flat glass fibers is 10% to 30% by weight based on the total weight of the polymer composition. Claim 7 The polymer composition according to claim 1 or 2, wherein the glass fibers have an aspect ratio of at least 5, defined as the average ratio between the longest length and the largest of the width and thickness.

Images