A thermoplastic polyurethane elastomer with low dielectric properties, preparation method and application thereof

Abstract

The present invention discloses a thermoplastic polyurethane elastomer with low dielectric properties, a preparation method and its application, and belongs to the technical field of high molecular polymer materials. The thermoplastic polyurethane elastomer is mainly prepared from the following raw materials: (1) 33% to 72% of polyol; (2) 3% to 20% of chain extender; (3) 18% to 56% of diisocyanate; (4) 0.3%-1.0% of auxiliary agent. The TPU of the present invention can be prepared by a one-step method, and it has very excellent low dielectric properties, good mechanical strength, transparency and processing performance. Compared with ordinary thermoplastic polyurethane, its dielectric constant can be reduced by about 5%-30%. The TPU of the present invention is suitable for 5G consumer electronics applications such as mobile phones, computers, and wireless home appliances.

Description

Technical Field

[0001] The invention relates to the technical field of thermoplastic polyurethane elastomers, and in particular to a thermoplastic polyurethane elastomer with low dielectric properties, a preparation method thereof and application thereof. Background Art

[0002] Thermoplastic polyurethane elastomer (TPU) is a multi-block polymer containing soft segments and hard segments. The soft segments are provided by polyol segments, and the hard segments are provided by isocyanate and chain extender segments. The molecular structure of the combination of soft and hard segments gives TPU excellent elasticity and high mechanical strength, making it widely used in protective cases for electronic products such as mobile phones and tablets.

[0003] Organic functional groups such as methylene in the molecular structure of TPU have general dielectric properties. With the advent of the 5G signal era, 5G signal transmission requires high frequency and high efficiency. The dielectric properties of ordinary TPU can no longer meet the requirements. It is necessary to further reduce the dielectric constant of TPU and reduce signal transmission loss through special molecular structure formula design. At present, the methods for reducing the dielectric properties of polyurethane elastomers can be summarized into two categories: one is that most of them introduce inorganic groups with low molar polarizability of silicon and fluorine to reduce the polarity of the molecule and thus reduce the dielectric constant. For example, patent CN111635503A discloses a fluorosilicone modified epoxy resin, its preparation method and application. By introducing -CF3 and -O-Si-O- structures, the characteristics of the weak dipole polarization ability of CF bonds and Si-O bonds, as well as the large steric hindrance effect, can effectively reduce the dielectric constant of the material and improve the dielectric loss of the material. Patent CN105885386A discloses a low dielectric constant POSS polyurethane composite film and a preparation method thereof, and CN114316182A discloses a compression-resistant low dielectric rigid polyurethane foam plastic and a preparation method thereof, both of which are prepared by introducing silicon elements, such as cage-like silsesquioxane POSS or needle-like wollastonite (aspect ratio 22-26, mesh number 1250) or hollow glass microspheres, with the purpose of utilizing the weak dipole moment of the Si-O bond to reduce the dielectric constant of the main organic material, while maintaining good mechanical properties. The second is to avoid introducing or generating organic functional groups / molecules with high molar polarizability in the material (-OH groups, carboxyl groups, amide bonds and other groups have very high dielectric constants). For example, patent CN103627091B discloses a low dielectric constant dynamically vulcanized thermoplastic elastomer and a preparation method thereof. A low dielectric constant dynamically vulcanized thermoplastic elastomer is prepared by selecting a special cross-linking agent that can reduce the dielectric constant. The special cross-linking agent is triisopropyl cyanurate. The purpose is to utilize triisopropyl cyanurate to not decompose alcohol -OH groups during the cross-linking process, while traditional cross-linking agents will produce alcohols and ketones during the decomposition process. Therefore, the elastomer prepared using the special cross-linking agent of triisopropyl cyanurate has a lower dielectric constant. CN107207852B discloses a low dielectric resin composition, which is prepared by mixing conventional polycarbonate polyurethane resin, epoxy resin, and organic filler (selected from organic phosphorus compounds, phosphazene compounds, and melamine), and then used for FPC film, which has low dielectric properties, flexibility and electrical insulation reliability. Its purpose is to utilize the large steric hindrance groups in the organic filler to reduce the dielectric properties of the material.

[0004] However, the above method of reducing the dielectric constant has the disadvantages of complex and difficult production process, the introduction of fillers or other inorganic materials will affect the transparency of the material and is incompatible with TPU elastomers. The above method cannot widely meet the application of low dielectric performance TPU elastomers in 5G electronic products such as mobile phones, tablets, and watches. Summary of the invention

[0005] The object of the present invention is to provide a thermoplastic polyurethane elastomer with low dielectric properties and excellent transparency, mechanical properties, processing properties and resilience. The present invention adopts a unique organic molecular structure design to reduce the dielectric constant, introduces more methylene groups with low molar polarization, reduces the ester group density and the ether group density, and introduces a highly sterically hindered aromatic ring molecular structure design, so as to prepare a polycarbonate TPU elastomer with a special structure, which can well solve the problem that ordinary TPU is difficult to achieve a low dielectric constant.

[0006] Another object of the present invention is to provide a method for preparing the low dielectric property TPU elastomer.

[0007] Another object of the present invention is to provide applications of such low dielectric performance TPU.

[0008] To achieve the above purpose, the technical solution of the present invention is as follows:

[0009] A thermoplastic polyurethane elastomer with low dielectric properties, wherein the thermoplastic polyurethane elastomer is prepared from raw materials comprising the following components:

[0010] (1) 33% to 72% polyol;

[0011] (2) 3% to 20% chain extender;

[0012] (3) 18% to 56% diisocyanate;

[0013] (4) 0.3%-1.0% additives.

[0014] Wherein, the polyol is selected from at least one of polycarbonate polyol and optional polyester polyol, polyether polyol, and polycaprolactone polyol; preferably, the polycarbonate polyol is prepared by ester exchange reaction between saturated diol and / or diol containing aromatic ring / ester ring and dimethyl carbonate.

[0015] In a specific embodiment, the polyester polyol is selected from any one of aliphatic polyester polyols, aromatic polyester polyols, and bio-based polyester polyols; preferably, the number average molecular weight of the polycarbonate polyol is 500-5000 g / mol, preferably 2000-3000 g / mol.

[0016] In a specific embodiment, the diol containing an aromatic ring / ester ring is selected from at least one of 1,4-cyclohexanedimethanol (CHDM), hydroquinone-bis(β-hydroxyethyl) ether (HQEE) series, resorcinol-bis(β-hydroxyethyl) ether (HER) series, 4-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HQEE-L) series, 3-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HER-L) series, 9H-fluorene-2,7-diol series, and ethylene oxide-terminated bisphenol A, wherein n is a natural number of 1 to 10; the general structural formula of the saturated diol is HO-C a H 2a -OH, wherein a=a natural number of 1 to 10; preferably, the diol containing an aromatic ring / ester ring is selected from at least any one of CHDM, 9H-fluorene-2,7-dimethanol, HQEE, and bisphenol A terminated with ethylene oxide; the saturated diol is selected from butanediol with a=4 or hexanediol with a=6.

[0017]

[0018] In a specific embodiment, the diol required for synthesizing the polycarbonate polyol is a mixed diol, wherein the ratio of the mixed diol is any ratio; preferably, the diol containing aromatic rings / ester rings accounts for 0.1 mol% to 50 mol% of the total amount of the mixed diol.

[0019] In a specific embodiment, the chain extender is a diol containing an aromatic ring / ester ring and / or a saturated diol; preferably, the diol containing an aromatic ring / ester ring is selected from at least one of hydroquinone-bis(β-hydroxyethyl) ether (HQEE), resorcinol-bis(β-hydroxyethyl) ether (HER), 4-hydroxyethyloxyethyl-1-hydroxyethyl benzene diether (HQEE-L), 3-hydroxyethyloxyethyl-1-hydroxyethyl benzene diether (HER-L), 1,4-cyclohexanedimethanol (CHDM), preferably CHDM; the saturated diol has a general formula of HO-C a H 2a -OH, wherein a=a natural number from 1 to 10, preferably butanediol wherein a=4.

[0020] In a specific embodiment, the diisocyanate is selected from one or more of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates, preferably aromatic diisocyanates or aliphatic diisocyanates, and more preferably diphenylmethane diisocyanate MDI and hexamethylene diisocyanate (HDI).

[0021] In a specific embodiment, the raw material of the thermoplastic polyurethane elastomer has an isocyanate index of 0.80 to 1.30, preferably 0.90 to 1.20.

[0022] In a specific embodiment, the auxiliary agent is an antioxidant auxiliary agent and / or a processing demolding auxiliary agent; preferably, the antioxidant auxiliary agent is selected from one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis(4-hydroxy-3,5-tert-butylphenylpropionate), 3,5-di-tert-butyl-4-hydroxyphenylpropionate octadecyl, and triphenyl phosphite, and the processing demolding auxiliary agent is selected from one or more of amide demolding auxiliary agents and silicon-containing demolding auxiliary agents.

[0023] On the other hand, the method for preparing the aforementioned thermoplastic polyurethane elastomer comprises the following steps:

[0024] 1) Mix polyol, chain extender and optional auxiliary agent at 50-110° C. and stir evenly;

[0025] 2) adding diisocyanate to the mixture obtained in step 1), stirring rapidly until the temperature rises to 90 to 150° C., preferably 110 to 130° C., and stopping stirring to obtain a gel;

[0026] 3) The gel obtained in step 2) is quickly poured into a mold, aged, crushed, and injection molded to obtain a thermoplastic polyurethane elastomer product.

[0027] On the other hand, the application of the aforementioned thermoplastic polyurethane elastomer or the thermoplastic polyurethane elastomer prepared by the aforementioned method in the field of consumer electronics is preferably applied in the field of 5G consumer electronics such as mobile phones, computers, and wireless home appliances.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention adopts a unique organic molecular structure design to reduce the dielectric constant. By introducing more methylene groups with low molar polarization, reducing the density of ester groups and ether groups, and introducing a highly sterically hindered aromatic ring molecular structure design, the special structure polycarbonate TPU elastomer prepared in this way can well solve the problem that ordinary TPU is difficult to achieve a low dielectric constant. This is completely different from the patent content of reducing dielectric properties disclosed in the background technology. In the present invention, other substances are not blended, but a special organic molecular structure design combined with chemical bonds is adopted. The functional group that reduces the dielectric properties is introduced into the thermoplastic polyurethane elastomer by a synthetic method, thereby achieving the thermoplastic polyurethane elastomer with low dielectric properties. Compared with ordinary TPU, the low dielectric thermoplastic polyurethane elastomer of the present invention can reduce the dielectric constant of the low dielectric performance TPU elastomer by about 5%-30%.

[0030] In the present invention, a cyclic diol molecular structure (such as 9H-fluorene-2,7-dimethanol, CHDM, HQEE, etc.) is innovatively introduced directly into the polycarbonate polyol. Since the ester exchange reaction temperature in the process of synthesizing the polycarbonate polyol is sufficient to melt the diol containing the cyclic molecular structure and then react, a polycarbonate polyol with a low melting point and partially containing a cyclic molecular structure is finally synthesized, thereby avoiding the problem of high melting point and difficult operation encountered when using the diol containing the cyclic molecule for chain extension synthesis of TPU.

[0031] The positive effect of the present invention is that the dielectric constant / dielectric loss of TPU is reduced, so that it has very excellent low dielectric properties, while maintaining comparable transparency, mechanical strength, and processing resilience to ordinary TPU, making it widely used in 5G electronic products such as mobile phones, tablets, and watches. DETAILED DESCRIPTION

[0032] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0033] A thermoplastic polyurethane elastomer (TPU) with low dielectric properties that is easy to process is prepared from the following raw materials:

[0034] (1) 33% to 72% polyol, such as 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.;

[0035] (2) 3% to 20% of chain extender, such as 5%, 10%, 15%, 20%, etc.;

[0036] (3) 18% to 56% diisocyanate, such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, etc.;

[0037] (4) 0.3%-1.0% of an auxiliary agent, such as 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, etc.

[0038] In the present invention, the polyol is selected from polycarbonate polyol and at least one of polyester polyol, polyether polyol and polycaprolactone polyol; that is, the polyol includes at least polycarbonate polyol, which can be a single polycarbonate polyol or a mixture of polycarbonate polyol and at least one of polyester polyol, polyether polyol and polycaprolactone polyol, such as a mixed polyol of polycarbonate polyol and polycaprolactone polyol, but not limited thereto. The polyester polyol includes aliphatic polyester polyol, aromatic polyester polyol, bio-based polyester polyol and the like.

[0039] Wherein, the polycarbonate polyol is prepared by ester exchange reaction between saturated diol and / or diol containing aromatic ring / ester ring or mixed diol and dimethyl carbonate. That is, the polycarbonate polyol can be prepared by reaction between saturated diol and dimethyl carbonate, or by reaction between diol containing aromatic ring and / or ester ring and dimethyl carbonate, or by reaction between mixed diol composed of saturated diol and diol containing aromatic ring and / or ester ring and dimethyl carbonate.

[0040] Wherein, the diol containing aromatic ring / ester ring is 1,4-cyclohexanedimethanol (CHDM) and at least one of the following series of aromatic ring-containing molecular structural formulas, n is a natural number of 1 to 10, for example, n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; the general formula of the saturated diol is HO-C a H 2a -OH, wherein a=a natural number of 1 to 10, for example, n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Preferably, the diol containing an aromatic ring / ester ring is selected from CHDM, 9H-fluorene-2,7-dimethanol, HQEE; and the saturated diol is selected from butanediol.

[0041]

[0042] In a preferred embodiment, the polycarbonate polyol is prepared by transesterification of diols containing aromatic rings / ester rings and saturated diols with dimethyl carbonate. The mixed diols required for synthesizing the polycarbonate polyols described above have any ratio of different diols, for example, 0.1 mol% to 50 mol%.

[0043] The significance of the above-mentioned special molecular structure polycarbonate polyol containing cyclic molecules or long-chain methylene groups is that the cyclic molecular structure has a high steric effect, which can effectively prevent the molecule from being polarized; the long-chain methylene group has a low molar dipole moment, and the longer the long-chain methylene group, the more effectively it can reduce the density of the ester group, which is more beneficial to low dielectric properties. The TPU elastomer prepared with polycarbonate diol containing these two types of functional groups has the advantages of low dielectric constant, high transparency, high mechanical strength, and easy processing.

[0044] Calculated based on the total amount of mixed diols required to synthesize the polycarbonate polyol with special molecular structure, the diol containing a cyclic molecular structure accounts for 0.1 mol% to 50 mol% of the total amount of the mixed diols, such as but not limited to 0.5 mol%, 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%. The molar ratio of the mixed diol to dimethyl carbonate is 30:1 to 1:15, such as but not limited to 25:1, 20:1, 15:1, 10:1, 5:1, 1:1, 1:5, 1:10, 1:15; the terminal group of the polycarbonate polyol with special molecular structure finally formed is a hydroxyl group, and the average functionality is 1.9 to 2.2, and the preferred functionality is 2.0.

[0045] The diol containing a cyclic molecular structure is preferably selected from one or more of 1,4-cyclohexanedimethanol (CHDM), 9H-fluorene-2,7-dimethanol, HQEE, and bisphenol A terminated with ethylene oxide.

[0046]

[0047] The ester exchange reaction method for preparing the above polycarbonate polyol can refer to the existing technology, for example, the following steps are adopted: it is carried out in two steps, first, the calculated amount of the above diol and dimethyl carbonate are mixed at a molar ratio of 30:1 to 1:15 at room temperature, and the first stage reaction is carried out at a temperature of 70-280°C under normal pressure or reduced pressure, and the generated methanol and dimethyl carbonate mixture is removed at the same time, and a low molecular weight polycarbonate diol can be obtained. Then, the second stage reaction is carried out, and the vacuum is continued and the temperature is gradually increased, and the heating reaction is controlled at 150-350°C, and the unreacted diol and dimethyl carbonate are continuously removed, and the low molecular weight polycarbonate diol is condensed, so that a polycarbonate polyol of a specified molecular weight can be obtained.

[0048] The number average molecular weight of the polycarbonate polyol of the present invention is 500-5000 g / mol, including but not limited to 500 g / mol, 1000 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, preferably 2000-3000 g / mol.

[0049] In the present invention, the chain extender is a diol containing an aromatic ring / ester ring and / or a saturated diol, that is, it can be a single diol containing an aromatic ring / ester ring, or it can be a mixed diol of a diol containing an aromatic ring / ester ring and a saturated diol. Among them, the diol containing an aromatic ring / ester ring is selected from at least one of hydroquinone-bis(β-hydroxyethyl) ether (HQEE), resorcinol-bis(β-hydroxyethyl) ether (HER), 4-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HQEE-L), 3-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HER-L), 1,4-cyclohexanedimethanol (CHDM), preferably CHDM; the saturated diol has a general formula of HO-C a H 2a -OH, wherein a=a natural number of 1 to 10, for example, n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; preferably, butanediol with a=4; more preferably, the chain extender is a mixed diol of butanediol and CHDM.

[0050] In the present invention, the diisocyanate is selected from one or more of aromatic diisocyanate, aliphatic diisocyanate and alicyclic diisocyanate, preferably aromatic diisocyanate and aliphatic diisocyanate, such as diphenylmethane diisocyanate MDI and hexamethylene diisocyanate (HDI). When the diisocyanate is a mixture, the usage ratio of each diisocyanate is not particularly limited, such as 0-100%, that is, the two diisocyanates can be in any ratio.

[0051] The raw material of the thermoplastic polyurethane elastomer has an isocyanate index of 0.80 to 1.30, preferably 0.90 to 1.20, wherein the isocyanate index is the molar ratio of NCO of isocyanate in the raw material to OH in polyol or diol.

[0052] The raw materials for preparing the thermoplastic polyurethane elastomer also contain additives, which are antioxidant additives and processing demolding aids. The antioxidant additive is selected from one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis(4-hydroxy-3,5-tert-butylphenylpropionate), octadecyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate, and triphenyl phosphite. The processing demolding aid is selected from one or more of amide demolding aids, silicon-containing demolding aids, and the like.

[0053] On the other hand, a method for preparing the above thermoplastic polyurethane elastomer is prepared by a one-step reaction method. The one-step reaction method is to use manual or machine casting one-step reaction molding, and the steps are as follows:

[0054] 1) Mix polyol, chain extender and optional auxiliary agent at 50-110° C. and stir evenly;

[0055] 2) adding isocyanate to the mixture obtained in step 1), stirring rapidly until the temperature rises to 90-150° C., preferably 110-130° C., stopping stirring to obtain a gel, and the reaction gel time is 1-5 minutes, preferably 1-2 minutes;

[0056] 3) The gel obtained in step 2) is quickly poured into a mold, matured, crushed, and injection molded into a product. The said mature temperature is 90-130° C., and the mature time is 4-20 hours.

[0057] In the present invention, the above-mentioned thermoplastic polyurethane elastomer is prepared. Based on the total mass of the thermoplastic polyurethane elastomer, 0-150ppm of catalyst needs to be added to adjust the reaction rate between the isocyanate and the compound containing active hydrogen. When the reaction rate time is greater than 180 seconds, a catalyst that promotes the reaction is used. When the reaction rate time is less than 30 seconds, a catalyst that inhibits the reaction is used. The catalyst is any catalyst commonly used in the art and literature. The catalyst that can promote the reaction is selected from organic acid salts, inorganic acid salts and organometallic derivatives of tin, bismuth, cobalt, zinc, nickel, molybdenum, zirconium, copper, aluminum and iron. Preferably, an organotin catalyst is used, and more preferably, one or more of stannous octoate, dibutyltin dilaurate and dibutyltin dioctoate. The catalyst that can inhibit the reaction is a catalyst containing free active H + The protonic acid is selected from one or more of phosphoric acid, dilute sulfuric acid, and sulfonic acid, preferably phosphoric acid. This is well known to those skilled in the art.

[0058] When performing performance testing on the above products, test pieces of different shapes need to be injection molded. The test pieces obtained by injection molding are placed in an oven for annealing at a temperature of 70 to 120°C for 8 to 24 hours. The test pieces are then taken out and placed in a standard constant temperature and humidity laboratory (23°C, 50% humidity) for 12 to 30 hours. Samples of different shapes are cut for testing and evaluation.

[0059] The present invention is further described below in conjunction with embodiments. The following examples are only used as illustrations of the present invention and are not intended to limit the scope of the present invention.

[0060] Analytical methods:

[0061] The dielectric performance test is based on IEC 60250-1969, the Shore hardness test is based on ASTM D2240, the tensile test is based on ASTM D412, the tear strength test is based on ASTM D624, and the transparency test is based on ASTM D1003.

[0062] Analytical instruments:

[0063]

[0064]

[0065] The main raw materials used are as follows:

[0066]

[0067]

[0068] Preparation process of special structure polycarbonate polyol:

[0069] The transesterification reaction method for preparing the polycarbonate polyol is as follows: it is carried out in two steps, firstly, the calculated amount of mixed diol and dimethyl carbonate are mixed and added at room temperature according to the molar ratio or weight ratio of Table 1, and a metal catalyst is added at the same time, and the first stage reaction is carried out at normal pressure or reduced pressure, nitrogen atmosphere protection, and the reaction temperature is controlled to be 150°C, and the generated methanol and dimethyl carbonate mixture is removed at the same time, and a low molecular weight polycarbonate diol can be obtained. Then, the second stage reaction is carried out, and the vacuum is continued to be evacuated and the temperature is gradually increased under a vacuum of 400 mbar, and the heating reaction is controlled at 280°C, and the unreacted diol and dimethyl carbonate are continuously removed, and the low molecular weight polycarbonate diol is condensed at the same time, so that a special structure polycarbonate polyol with a specified molecular weight can be obtained for use.

[0070] The weights of diols and dimethyl carbonate used in preparing polycarbonate polyols with special structures are listed in Table 1:

[0071] Table 1: Raw materials used in the preparation of polyester polyols

[0072]

[0073]

[0074] Comparative Example 1

[0075] In Comparative Example 1, a thermoplastic polyurethane elastomer was synthesized using a material dosage formula with an isocyanate index R=1.005. 550 g of polyester polyol PBA2000, 100.4 g of BDO chain extender, 5 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid octadecyl ester, 6 g of monocarbodiimide auxiliary and a small amount of catalyst were stirred and mixed uniformly at 55° C., 349.6 g of MDI isocyanate was added, and the mixture was stirred rapidly until the temperature rose to 95° C., stirring was stopped, and gelation was performed for 2.5 minutes. The mixture was quickly poured into a mold, aged at 100° C. for 8 hours, and then broken. Test pieces of different shapes were injection molded at a molding temperature of 205° C. The test pieces obtained by injection molding were placed in an oven at 90° C. for annealing for 12 hours, and then taken out and placed in a standard constant temperature and humidity laboratory (23° C., 50% humidity) for 24 hours, and then strips of different shapes were cut for testing and evaluation.

[0076] Example 1

[0077] In Example 1, a thermoplastic polyurethane elastomer is synthesized using a material dosage formula with an isocyanate index R=1.20: 400g of polycarbonate polyol A, 200g of polyester polyol PBA2000, 71.5g of butanediol chain extender, 2g of 2,6-di-tert-butyl-4-methylphenol, 8g of monocarbodiimide auxiliary agent, and a catalyst are stirred and mixed uniformly at 70°C, 328.5g of MDI isocyanate is added, and the mixture is stirred rapidly until the temperature rises to 115°C. Stirring is stopped, and the mixture is gelled for 1.5 minutes. The mixture is quickly poured into a mold, aged at 110°C for 10 hours, and then broken and injection-molded test pieces of different shapes. The test pieces obtained by injection molding are annealed in an oven at 100°C for 12 hours, and then taken out and placed in a standard constant temperature and humidity laboratory (23°C, 50% humidity) for 24 hours, and then strips of different shapes are cut for testing and evaluation.

[0078] Example 2

[0079] In Example 2, a material dosage formula with an isocyanate index R=1.05 was used to synthesize a thermoplastic polyurethane elastomer. 300g of polycarbonate polyol B, 300g of polycaprolactone polyol PCL1000, 117.7g of hexanediol chain extender, 15g of tetrakis(4-hydroxy 3,5-tert-butylphenyl propionic acid) pentaerythritol ester, 1g of polycarbodiimide auxiliary agent, and a catalyst were stirred and mixed uniformly at 75°C, 282.2g of HDI isocyanate was added, and the mixture was rapidly stirred until the temperature rose to 100°C. Stirring was stopped and the mixture was gelled for 1.0min. The mixture was rapidly poured into a mold and aged at 90°C for 16h. The mixture was then broken and injection molded into test pieces of different shapes. The injection molding temperature was 220°C. The test pieces obtained by injection molding were annealed in an oven at 80°C for 12h, then taken out and placed in a standard constant temperature and humidity laboratory (23°C, 50% humidity) for 24h, and then strips of different shapes were cut for testing and evaluation.

[0080] Example 3

[0081] In Example 3, a material dosage formula with an isocyanate index R=0.95 was used to synthesize a thermoplastic polyurethane elastomer. 600g of polycarbonate polyol C, 140g of CHDM chain extender, 5g of 2,6-di-tert-butyl-4-methylphenol, 6g of polycarbodiimide auxiliary agent, and a catalyst were stirred and mixed uniformly at 65°C, 260g of MDI isocyanate was added, and the mixture was rapidly stirred until the temperature rose to 100°C. Stirring was stopped and the mixture was gelled for 1.5 minutes. The mixture was rapidly poured into a mold and aged at 100°C for 12 hours. The mixture was then broken and injection molded into test pieces of different shapes at an injection molding temperature of 210°C. The test pieces obtained by injection molding were annealed in an oven at 90°C for 12 hours, then taken out and placed in a standard constant temperature and humidity laboratory (23°C, 50% humidity) for 24 hours, and then strips of different shapes were cut for testing and evaluation.

[0082] Example 4

[0083] In Example 4, a thermoplastic polyurethane elastomer was synthesized using a material dosage formula with an isocyanate index R=0.85. 600 g of polycarbonate polyol D, 148 g of BDO chain extender, 10 g of 2,6-di-tert-butyl-4-methylphenol, 5 g of polycarbodiimide additive, and a catalyst were stirred and mixed uniformly at 65° C., 252 g of HDI isocyanate was added, and the mixture was rapidly stirred until the temperature rose to 100° C. The stirring was stopped, and the mixture was gelled for 1.5 minutes. The mixture was rapidly poured into a mold, aged at 100° C. for 12 hours, and then broken. Test pieces of different shapes were injection molded at a molding temperature of 210° C. The test pieces obtained by injection molding were placed in an oven at 90° C. for annealing for 12 hours, and then taken out and placed in a standard constant temperature and humidity laboratory (23° C., 50% humidity) for 24 hours, and then strips of different shapes were cut for testing and evaluation.

[0084] The products made of thermoplastic polyurethane elastomers in Examples 1-4 have low dielectric constants and dielectric losses, which are about 8% lower than the dielectric constants and dielectric losses of conventional thermoplastic polyurethane elastomers in Comparative Example 1. The products in Examples 1-4 also maintain the same mechanical properties, appearance properties, and processing properties as the product in Comparative Example 1.

[0085] Example 5

[0086] In Example 5, a thermoplastic polyurethane elastomer was synthesized using a material dosage formula with an isocyanate index R=1.005. 550 g of polycarbonate polyol E, 100.4 g of BDO chain extender, 5 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid octadecyl ester, 6 g of monocarbodiimide auxiliary and a small amount of catalyst were stirred and mixed uniformly at 55° C., 349.6 g of MDI isocyanate was added, and the mixture was rapidly stirred until the temperature rose to 95° C. The stirring was stopped, and the mixture was gelled for 2.5 minutes. The mixture was rapidly poured into a mold, aged at 100° C. for 8 hours, and then broken. Test pieces of different shapes were injection molded at a molding temperature of 205° C. The test pieces obtained by injection molding were annealed in an oven at 90° C. for 12 hours, and then taken out and placed in a standard constant temperature and humidity laboratory (23° C., 50% humidity) for 24 hours, and then strips of different shapes were cut for testing and evaluation.

[0087] Embodiment 6-7

[0088] In Examples 6 and 7, the thermoplastic polyurethane elastomer was synthesized using a material dosage formula with an isocyanate index of R = 0.990, and the calculated amounts of Example 6 (600 g polycarbonate polyol F, 115.9 g HQEE-L chain extender), Example 7 (600 g polycarbonate polyol G, 111.6 g HER chain extender), 11 g 2,6-di-tert-butyl-4-methylphenol, 4g polycarbodiimide auxiliary agent and catalyst were stirred and mixed at 90°C, 284.1g (Example 6) and 288.4g (Example 7) of MDI isocyanate were added respectively, and the mixture was stirred rapidly until the temperature rose to 120°C. Stirring was stopped, and the mixture was gelled for 1.5min. The mixture was quickly poured into a mold, and aged at 100°C for 12h. The mixture was then broken, injection molded into test pieces of different shapes, and annealed in an oven at 100°C for 12h. The mixture was then taken out and placed in a standard constant temperature and humidity laboratory (23°C, 50% humidity) for 24h, and then strips of different shapes were cut for testing and evaluation.

[0089] The product made of the thermoplastic polyurethane elastomer of Example 5 has a lower dielectric constant and dielectric loss and better performance. The dielectric constant and dielectric loss of the conventional thermoplastic polyurethane elastomer of Comparative Example 1 are reduced by about 20%, and the mechanical properties are improved by about 10%, while maintaining the same processing performance as the product of Comparative Example 1.

[0090] The specific performance results of the comparative examples and embodiments are listed in Table 2:

[0091] Table 2: Comparative Examples and Example Product Performance Test Results

[0092]

[0093]

[0094] From the comparison in Table 2, it can be seen that the polycarbonate products of Examples 1-4 have lower dielectric constants and significantly lower dielectric loss than the common thermoplastic polyurethane product of Comparative Example 1, which is reduced by about 8%, and have good mechanical properties and high and low temperature resistance. The polycarbonate products of the special structure containing aromatic ring groups introduced in Examples 5-7 have lower dielectric constants and dielectric loss, which are reduced by about 20%, and have higher mechanical properties and heat resistance due to the introduction of rigid groups.

[0095] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A thermoplastic polyurethane elastomer with low dielectric properties, characterized in that: The thermoplastic polyurethane elastomer is prepared from raw materials comprising the following components: (1) 33% to 72% polyol; (2) 3% to 20% chain extender; (3) 18% to 56% diisocyanate; (4) 0.3%-1.0% additives; Wherein, the polyol is selected from polycarbonate polyol; the polycarbonate polyol is prepared by saturated diol and diol containing aromatic ring, or diol containing aromatic ring and dimethyl carbonate through ester exchange reaction.

2. The thermoplastic polyurethane elastomer according to claim 1, characterized in that The number average molecular weight of the polycarbonate polyol is 500-5000 g / mol.

3. The thermoplastic polyurethane elastomer according to claim 2, characterized in that: The number average molecular weight of the polycarbonate polyol is 2000-3000 g / mol.

4. The thermoplastic polyurethane elastomer according to claim 1, characterized in that The aromatic ring-containing diol is selected from at least one of hydroquinone-bis(β-hydroxyethyl) ether (HQEE), resorcinol-bis(β-hydroxyethyl) ether (HER), 4-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HQEE-L), 3-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HER-L), 9H-fluorene-2,7-diol, and bisphenol A terminated with ethylene oxide, wherein n is a natural number of 1 to 10; the general structural formula of the saturated diol is HO-C a H 2a -OH, wherein a=a natural number from 1 to 10.

5. The thermoplastic polyurethane elastomer according to claim 4, characterized in that: The aromatic ring-containing diol is selected from at least any one of 9H-fluorene-2,7-dimethanol, HQEE, and bisphenol A terminated with ethylene oxide; the saturated diol is selected from butanediol with a=4 or hexanediol with a=6.

6. The thermoplastic polyurethane elastomer according to any one of claims 1 to 5, characterized in that: The diols required for synthesizing the polycarbonate polyol are mixed diols, wherein the diols containing aromatic rings account for 0.1 mol% to 50 mol% of the total amount of the mixed diols.

7. The thermoplastic polyurethane elastomer according to any one of claims 1 to 4, characterized in that: The chain extender is a diol containing an aromatic ring or an aliphatic ring and / or a saturated diol.

8. The thermoplastic polyurethane elastomer according to claim 7, characterized in that The aromatic / alicyclic diol is selected from at least one of hydroquinone-bis(β-hydroxyethyl) ether (HQEE), resorcinol-bis(β-hydroxyethyl) ether (HER), 4-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HQEE-L), 3-hydroxyethyloxyethyl-1-hydroxyethylbenzene diether (HER-L), and 1,4-cyclohexanedimethanol (CHDM); the saturated diol is of the general formula HO-C a H 2a -OH, wherein a=a natural number from 1 to 10.

9. The thermoplastic polyurethane elastomer according to claim 8, characterized in that: The diol containing aromatic rings / alicyclic rings is CHDM; the saturated diol is butanediol with a=4.

10. The thermoplastic polyurethane elastomer according to any one of claims 1 to 5, characterized in that: The diisocyanate is selected from one or more of aromatic diisocyanate, aliphatic diisocyanate and alicyclic diisocyanate.

11. The thermoplastic polyurethane elastomer according to claim 10, characterized in that: The diisocyanate is an aromatic diisocyanate or an aliphatic diisocyanate.

12. The thermoplastic polyurethane elastomer according to claim 11, characterized in that The diisocyanate is diphenylmethane diisocyanate MDI or hexamethylene diisocyanate HDI.

13. The thermoplastic polyurethane elastomer according to any one of claims 1 to 5, characterized in that: The raw material of the thermoplastic polyurethane elastomer has an isocyanate index of 0.80 to 1.

30.

14. The thermoplastic polyurethane elastomer according to claim 13, characterized in that The raw material of the thermoplastic polyurethane elastomer has an isocyanate index of 0.90 to 1.

20.

15. The thermoplastic polyurethane elastomer according to any one of claims 1 to 5, characterized in that The auxiliary agent is an antioxidant auxiliary agent and / or a processing demoulding auxiliary agent.

16. The thermoplastic polyurethane elastomer according to claim 15, characterized in that The antioxidant aid is selected from one or more of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis(4-hydroxy-3,5-tert-butylphenylpropionate), octadecyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate, and triphenyl phosphite, and the processing demolding aid is selected from one or more of amide demolding aids and silicon-containing demolding aids.

17. The method for preparing a thermoplastic polyurethane elastomer according to any one of claims 1 to 16, characterized in that: The following steps are involved: 1) Mix the polyol, chain extender and additive at 50-110°C and stir evenly; 2) adding diisocyanate to the mixture obtained in step 1), stirring rapidly until the temperature rises to 90-150° C., and stopping stirring to obtain a gel; 3) The gel obtained in step 2) is quickly poured into a mold, aged, crushed, and injection molded to obtain a thermoplastic polyurethane elastomer product.

18. The preparation method according to claim 17, characterized in that: In step 2), the temperature rises to 110-130° C., and stirring is stopped to obtain a gel.

19. Use of the thermoplastic polyurethane elastomer according to any one of claims 1 to 16 or the thermoplastic polyurethane elastomer prepared by the method according to any one of claims 17 to 18 in the field of consumer electronics.

20. The use according to claim 19, characterized in that Application in 5G consumer electronics field of mobile phones, computers, and wireless home appliances.

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