Polycarbonate polyol composition and preparation method thereof, low-colloid polyurethane elastomer and application thereof

Abstract

The invention relates to a polycarbonate polyol composition, which comprises 30 to 100 ppm of cyclic carbonate, and the structure of the cyclic carbonate is as follows: in the formula, R is a C2-C12 alkylene group, such as a C2-C12 alkylene group. The invention further relates to a low-colloid polyurethane elastomer, the colloid content increment of the polyurethane elastomer prepared from the polycarbonate polyol is lower than 10mg / 100mL, and the polyurethane elastomer is excellent in oil resistance and can be applied to oil storage, oil transportation and the like, such as a crusty pancake, an oil bag, an oil pipe and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyurethane, in particular to a polycarbonate polyol composition and a preparation method thereof, a low gum polyurethane elastomer and application and a preparation method thereof. BACKGROUND

[0002] Polycarbonate polyols are polymers with repeating carbonate groups (-O-C=O-O-) in the main chain and hydroxyl groups (-OH) at the chain ends. According to the difference in the main chain, they can be divided into aliphatic, aromatic and mixed types, among which aliphatic polycarbonate polyols are the most widely used. Polycarbonate polyurethane has high mechanical strength, excellent hydrolysis resistance and heat resistance, and can be used in the fields of leather, PUD, elastomer, UV, etc. The small molecule diol and carbonate polycondensation method is a common preparation process for polycarbonate polyols. The high polycondensation temperature, insufficient deoxygenation of the reaction kettle, and oxidation caused by the contact of high-temperature liquid with air during the packaging process of the finished product often result in high color number of the finished product. Moreover, when polycarbonate polyols are used to prepare polyurethane products, part of the impurities may migrate and precipitate, affecting the quality of the polyurethane products. When used in storage containers for military diesel oil, aviation fuel, etc., long-term immersion in oil and fuel can accelerate the release of impurities, resulting in an increase in the gum content in such chemicals and pollution of the chemicals.

[0003] Cyclic carbonate is an unavoidable by-product in the preparation process of polycarbonate polyols. Because its molecular weight is relatively low compared with that of polycarbonate polyols, it is generally considered to be the main impurity causing migration and precipitation. Therefore, to improve the migration and precipitation of impurities and improve the quality of polyurethane products, the content of cyclic polycarbonate is usually controlled at a low level. However, too low a content of cyclic polycarbonate requires high process operation, increasing the process cost. SUMMARY

[0004] The purpose of the present application is to provide a polycarbonate polyol composition and a preparation method thereof, a low gum polyurethane elastomer and application thereof, by controlling the content of cyclic carbonate and the proportion of cyclic carbonate with 8 or more members in the polycarbonate polyol, a low-color polycarbonate polyol can be prepared. By using the polycarbonate polyol of the present application to prepare a polyurethane elastomer, a polyurethane elastomer with good flowability for extrusion processing and low gum content can be obtained, which can be used for oil storage and oil transportation and other applications.

[0005] A polycarbonate polyol composition, comprising 30-100 ppm of cyclic carbonate, the structure of the cyclic carbonate is:

[0006] wherein R is a C2-C12 hydrocarbylene group, such as a C2-C12 alkylene group.

[0007] The alkylene group in the present application can be linear or branched.

[0008] Preferably, the mass content of the cyclic carbonate in which R is a C6-C12 alkylene group is more than 80%, preferably more than 85%, for example, 85%-99% of the total mass of the cyclic carbonate.

[0009] Preferably, the mass content of the cyclic carbonate in which R is a C6-C12 alkylene group is more than 80%, preferably more than 85%, for example, 85%-99% of the total mass of the cyclic carbonate.

[0010] Preferably, the mass content of the polycarbonate polyol in the polycarbonate polyol composition is more than 98%, preferably more than 99%.

[0011] A preparation method of a polycarbonate polyol, prepared by the following steps:

[0012] Under nitrogen protection, the small molecule diol, the carbonate, and the catalyst are mixed and added to a reaction kettle, the reaction kettle is gradually heated to 150-180℃, and reacted for 3-6h, then heated to 190-200℃, and continued to react for 10-12h, while distilling to remove the carbonate and the byproduct small molecule alcohol. Continue to react at 190-200℃ for 15-20h, vacuumize to a pressure <200Pa, heat to 200-210℃, and keep for 30min-1h, vacuumize to a pressure <100Pa, and discharge after cooling to 100-150℃ under nitrogen atmosphere protection;

[0013] The hydroxyl group termination rate of the polycarbonate polyol is >99.6%.

[0014] In the present application, the small molecule diol is a C2-C12 diol, including one or more of ethylene glycol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol, preferably one or more of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol.

[0015] In the present application, the carbonate is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, diphenyl carbonate, and ethylene carbonate.

[0016] In the present application, the catalyst is one or more of tetraethyl titanate, tetra-n-butyl titanate, tetraisopropyl titanate, dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin octoate, di-n-butyl tin oxide, stannous octoate.

[0017] In the present application, the raw material for preparing the polycarbonate polyol can further include polyether diol and / or lactone. The polyether diol is one or more of polytetrahydrofuran diol, poly-1,2-propanediol, poly-1,3-propanediol, polyethylene glycol, and copolyether diol, which is a copolymer diol obtained by copolymerization of two or more of ethylene oxide, propylene oxide, and tetrahydrofuran. The lactone is one or more of caprolactone, valerolactone, butyrolactone, and lactide.

[0018] Preferably, the total molar amount of the added small molecule diol and polyether diol is in a molar ratio of 0.8-0.96 to the carbonate. Preferably, the added amount of the lactone is 0-5 times the total molar amount of the small molecule diol and the polyether diol.

[0019] Preferably, the added amount of the catalyst is 10-50 ppm of all raw materials. In the present application, the content of the cyclic carbonate can be controlled by adjusting the reaction conditions such as reaction temperature, secondary vacuum devolatilization under high temperature, and the like, or the proportion and content of the cyclic carbonate can be obtained by adding the cyclic carbonate or post-treatment, and the like.

[0020] The present application further provides a polyurethane elastomer prepared by reacting the above polycarbonate polyol, diisocyanate, and chain extender.

[0021] The polyurethane elastomer of the present application has an increase in gum content of less than 10 mg / 100 mL according to the GJB 3986A standard test.

[0022] In the present application, the diisocyanate is one or more of aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate; preferably one or more of 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, 1,4-phenylene diisocyanate, m-xylylene diisocyanate, diphenylmethane-3,3'-dimethoxy-4,4'-diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate, 2,4-dicyclohexylmethane diisocyanate, isophorone diisocyanate, lysine diisocyanate, L-lysine diisocyanate, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, more preferably 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate and 4,4'-dicyclohexylmethane diisocyanate.

[0023] In the present application, the chain extender is aliphatic diol and / or alicyclic diol with a molecular weight of 60-200 g / mol; preferably, the aliphatic diol is one or more of ethylene glycol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, preferably 1,4-butanediol, 1,6-hexanediol; the alicyclic diol is one or more of 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, preferably 1,4-cyclohexanedimethanol.

[0024] The polyurethane elastomer has the following mass ratio of each component based on the total weight of raw materials:

[0025] Polycarbonate polyol 30%-80%, preferably 40-75%;

[0026] Chain extender 5%-30%, preferably 7-20%;

[0027] Diisocyanate 15-60%, preferably 20-50%.

[0028] The polyurethane elastomer in the present application can be prepared by methods known in the art, which are not limited in the present application.

[0029] The present application also provides the use of the polyurethane elastomer, which can be used in oil storage and oil transportation, such as oil pads, oil bags, oil pipes, etc.

[0030] Advantages of the present application:

[0031] The present application provides a polycarbonate polyol with a cyclic carbonate byproduct content of 30-100 ppm, wherein the proportion of 8-membered or more cyclic carbonates is 80% or more. Because low-membered ring molecules have low molecular weight and low melting point, they are easily migrated, and controlling the proportion to be less than 20% can greatly reduce precipitation, while 8-membered or more cyclic carbonates have high melting points and are resistant to precipitation, which is beneficial to improving the flowability of polyurethane during extrusion processing, and high-quality polyurethane products can be prepared. The present application reduces the discharge temperature to 100-150℃, and discharges under the protection of a nitrogen atmosphere, thereby improving the oxidation yellowing during high-temperature discharge, and the color number is ≤10.

[0032] The present application solves the defects of the above prior art and provides a polycarbonate polyol with a specific cyclic carbonate impurity content. The polyurethane elastomer prepared using the polycarbonate polyol of the present application has low gum content and is suitable for the storage of high-end oil products. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below in conjunction with specific examples, but the scope of the present application is not limited to these examples. Various substitutions or changes made according to ordinary technical knowledge and conventional means in the art without departing from the method idea of the present application should be included in the scope of the present application.

[0034] Main raw material sources:

[0035] Dimethyl carbonate, 1,4-butanediol, 4,4'-diphenyl methane diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, Wanhua Chemical Group Co., Ltd., industrial grade. 1,6-hexanediol, Yuanli Chemical Group Co., Ltd., industrial grade. Polytetrahydrofuran diol (molecular weight 650), BASF, industrial grade.

[0036] Main test methods:

[0037] Cyclic carbonate test method: accounting for the proportion after GPC separation and purification.

[0038] Tensile strength test equipment: Shimadzu tensile testing machine, test standard ASTM D412.

[0039] Gum content increment test standard: GJB 3986A, test pipe material: polyurethane particle extruded pull pipe, nominal diameter 80 mm, inner diameter 76 mm.

[0040] Color number (Pt-Co) test standard: GB / T 3143-1982.

[0041] The raw materials used in the examples or comparative examples are obtained from commercial channels if not specified.

[0042] Example 1 Preparation of polycarbonate polyol A

[0043] Under nitrogen protection, 1.8 kg of 1,4-butanediol, 9.5 kg of 1,6-hexanediol, 9.6 kg of dimethyl carbonate, and 0.4 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 160°C, reacted for 4 h, heated to 195°C, and continued to react for 10 h while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, reacted for 20 h, vacuumized to a pressure < 200 Pa, continued to heat to 210°C, kept for 30 min, vacuumized to a pressure < 100 Pa, the hydroxyl value was 56.16 mgKOH / g, and the temperature was lowered to 100°C, discharged under nitrogen atmosphere protection. Color number (Pt-Co) = 10 Hazen.

[0044] Example 2 Preparation of polycarbonate polyol B

[0045] Under nitrogen protection, 2.7 kg of 1,4-butanediol, 7.3 kg of 1,5-pentanediol, 9.6 kg of dimethyl carbonate, and 0.4 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 170°C, reacted for 3 h, heated to 195°C, and continued to react for 12 h while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, reacted for 18 h, vacuumized to a pressure < 200 Pa, continued to heat to 210°C, kept for 1 h, vacuumized to a pressure < 100 Pa, the hydroxyl value was 56.16 mgKOH / g, and the temperature was lowered to 120°C, discharged under nitrogen atmosphere protection. Color number (Pt-Co) = 10 Hazen.

[0046] Example 3 Preparation of polycarbonate polyol C

[0047] Under nitrogen protection, 1.2 kg of ethylene glycol, 9.5 kg of 1,6-hexanediol, 9.7 kg of dimethyl carbonate, and 0.5 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 170°C, reacted for 3 h, heated to 195°C, and continued to react for 12 h while distilling off the carbonate and byproduct small molecule alcohol. The temperature was continued to be raised to 195°C, reacted for 18 h, vacuumized to a pressure < 200 Pa, continued to heat to 210°C, kept for 30 min, vacuumized to a pressure < 100 Pa, the hydroxyl value was 56.18 mgKOH / g, and the temperature was lowered to 110°C, discharged under nitrogen atmosphere protection. Color number (Pt-Co) = 5 Hazen.

[0048] Example 4 Preparation of polycarbonate polyol D

[0049] Under nitrogen protection, 0.6 kg of ethylene glycol, 9.4 kg of 1,5-pentanediol, 9.6 kg of dimethyl carbonate, and 0.5 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 165°C, reacted for 3 h, heated to 195°C, and continued to react for 12 h, while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, and the reaction was continued for 19 h. The pressure was reduced to <200 Pa, and the temperature was increased to 210°C for 30 min. The pressure was reduced to <100 Pa, the hydroxyl value was 56.12 mgKOH / g, the temperature was reduced to 150°C, and the product was discharged under nitrogen protection. Color number (Pt-Co) = 10 Hazen.

[0050] Preparation of polycarbonate polyol E

[0051] Under nitrogen protection, 1.8 kg of 1,4-butanediol, 9.5 kg of 1,6-hexanediol, 9.6 kg of dimethyl carbonate, and 0.4 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 160°C, reacted for 4 h, heated to 195°C, and continued to react for 10 h, while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, and the reaction was continued for 20 h. The hydroxyl value was 56.14 mgKOH / g, and the product was discharged. Color number (Pt-Co) = 30 Hazen.

[0052] Preparation of polycarbonate polyol F

[0053] Under nitrogen protection, 2.7 kg of 1,4-butanediol, 7.3 kg of 1,5-pentanediol, 9.6 kg of dimethyl carbonate, and 0.4 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 170°C, reacted for 3 h, heated to 195°C, and continued to react for 12 h, while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, and the reaction was continued for 18 h. The hydroxyl value was 56.13 mgKOH / g, and the product was discharged. Color number (Pt-Co) = 35 Hazen.

[0054] Preparation of polycarbonate polyol G

[0055] Under nitrogen protection, 5.6 kg of ethylene glycol, 1.0 kg of 1,5-pentanediol, 9.6 kg of dimethyl carbonate, and 0.4 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 170°C, reacted for 3 h, heated to 195°C, and continued to react for 12 h, while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, and the reaction was continued for 18 h. The hydroxyl value was 56.14 mgKOH / g, and the product was discharged. Color number (Pt-Co) = 35 Hazen.

[0056] Preparation of polycarbonate polyol H

[0057] Under nitrogen protection, 5.9 kg of ethylene glycol, 0.6 kg of 1,6-hexanediol, 9.6 kg of dimethyl carbonate, and 0.4 g of tetrabutyl titanate were mixed and added to a reaction kettle, the reaction kettle was gradually heated to 170°C, reacted for 3 h, heated to 195°C, and continued to react for 12 h, while distilling off the carbonate and byproduct small molecule alcohol. The temperature was raised to 200°C, and reacted for 18 h, and then vacuumed to 1000 Pa, the hydroxyl value was 56.14 mgKOH / g, and the product was discharged. Color number (Pt-Co) = 35 Hazen.

[0058] Table 1 Polycarbonate polyol parameters

[0059] Test item Hydroxyl end capping rate Cyclic carbonate impurity content 8-membered ring or more ratio Color number Unit ％ ppm ％ Hazen Example 1 99.7 94 85 10 Example 2 99.8 87 86 10 Example 3 99.7 65 82 5 Example 4 99.6 48 90 15 Comparative Example 1 99.4 468 34 30 Comparative Example 2 99.3 523 38 35 Comparative Example 3 99.2 626 15 35 Comparative Example 4 99.2 116 32 30

[0060] Preparation of polyurethane 1

[0061] After 60 parts of polycarbonate polyol A, 8.6 parts of 1,4-butanediol, 31.39 parts of 4,4'-diphenyl methane diisocyanate, and 0.01 parts of stannous octoate were mixed by stirring, they were continuously poured into a twin-screw extruder, and the temperature of each temperature zone was 120-220°C. After sufficient reaction, a thermoplastic polyurethane elastomer was prepared by underwater pelletization. After sufficient drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding processing.

[0062] Preparation of polyurethane 2

[0063] After 55 parts of polycarbonate polyol B, 10.09 parts of 1,4-butanediol, 34.9 parts of 4,4'-diphenyl methane diisocyanate, and 0.01 parts of stannous octoate were mixed by stirring, they were poured into a twin-screw extruder, and the temperature of each temperature zone was 120-220°C. After sufficient reaction, a thermoplastic polyurethane elastomer was prepared by underwater pelletization. After sufficient drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding processing.

[0064] Preparation of polyurethane 3

[0065] After 70 parts of polycarbonate polyol C, 8.41 parts of 1,4-butanediol, 21.58 parts of 1,6-hexamethylene diisocyanate, and 0.01 parts of dibutyl tin dilaurate were mixed by stirring, they were poured into a twin-screw extruder, and the temperature of each temperature zone was 120-220°C. After sufficient reaction, a thermoplastic polyurethane elastomer was prepared by underwater pelletization. After sufficient drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding processing.

[0066] Preparation of polyurethane 4

[0067] A thermoplastic polyurethane elastomer was prepared by pouring 50 parts of polycarbonate polyol D, 11.11 parts of 1,4-butanediol, 38.88 parts of 4,4'-dicyclohexylmethane diisocyanate and 0.01 part of dibutyl tin dilaurate into a twin-screw extruder after stirring and mixing, and fully reacting at 120-220°C in each temperature zone, and then cutting under water. After drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding.

[0068] Preparation of polyurethane 5

[0069] A thermoplastic polyurethane elastomer was prepared by pouring 60 parts of polycarbonate polyol E, 8.6 parts of 1,4-butanediol, 31.39 parts of 4,4'-diphenylmethane diisocyanate and 0.01 part of stannous octoate into a twin-screw extruder after stirring and mixing, and fully reacting at 120-220°C in each temperature zone, and then cutting under water. After drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding.

[0070] Preparation of polyurethane 6

[0071] A thermoplastic polyurethane elastomer was prepared by pouring 55 parts of polycarbonate polyol F, 10.09 parts of 1,4-butanediol, 34.9 parts of 4,4'-diphenylmethane diisocyanate and 0.01 part of stannous octoate into a twin-screw extruder after stirring and mixing, and fully reacting at 120-220°C in each temperature zone, and then cutting under water. After drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding.

[0072] Preparation of polyurethane 7

[0073] A thermoplastic polyurethane elastomer was prepared by pouring 70 parts of polycarbonate polyol G, 8.41 parts of 1,4-butanediol, 21.58 parts of 1,6-hexamethylene diisocyanate and 0.01 part of dibutyl tin dilaurate into a twin-screw extruder after stirring and mixing, and fully reacting at 120-220°C in each temperature zone, and then cutting under water. After drying at 100°C, a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm was prepared by extrusion processing, and a 2 mm test piece was prepared by injection molding.

[0074] Preparation of polyurethane 8

[0075] A thermoplastic polyurethane elastomer was prepared by mixing 50 parts of polycarbonate polyol H, 11.11 parts of 1,4-butanediol, 38.88 parts of 4,4'-dicyclohexylmethane diisocyanate and 0.01 parts of dibutyl tin dilaurate, pouring into a twin-screw extruder, and fully reacting at 120-220°C in each temperature zone. After the reaction, the product was cut into pellets under water. After drying at 100°C, the pellets were extruded into a pipe with a nominal diameter of 80 mm and an inner diameter of 76 mm, and injection-molded into 2 mm test pieces.

[0076] The data for the examples and comparative examples of the polyurethane elastomer are shown in Table 2.

[0077] Table 2 Properties of the polyurethane elastomer

[0078] Test item Tensile strength Tear strength Gum content increment Unit MPa KN / m mg / 100 mL Example 5 36 101 8 Example 6 41 121 7 Example 7 31 94 9 Example 8 30 98 8 Comparative Example 5 34 98 76 Comparative Example 6 39 118 68 Comparative Example 7 30 92 83 Comparative Example 8 29 95 43

[0079] According to the test results in Table 2, the gum content of the thermoplastic polyurethane elastomer of the examples was 7-9 g / 100 mL, which was significantly lower than the 43-83 g / 100 mL of the comparative examples.

Claims

1. A polycarbonate polyol composition characterized in that, comprises 30-100 ppm of a cyclic carbonate having a structure of: wherein R is a C2-C12 hydrocarbylene group, such as a C2-C12 alkylene group.

2. The composition of claim 1, wherein, In the cyclic carbonate, the mass fraction of the cyclic carbonate in which R is a C5-C12 hydrocarbylene group is 80% or more, preferably 85% or more, and more preferably 85%-99% of the total mass of the cyclic carbonate. Preferably, in the cyclic carbonate, the mass fraction of the cyclic carbonate in which R is a C6-C12 hydrocarbylene group is 80% or more, preferably 85% or more, and more preferably 85%-99% of the total mass of the cyclic carbonate.

3. The composition according to claim 1 or 2, characterized in that, The mass content of the polycarbonate polyol in the polycarbonate polyol composition is 98% or more, and preferably 99% or more.

4. A process for the preparation of a polycarbonate polyol, characterized in that, Prepared by the following steps: Under nitrogen protection, the small molecule diol, carbonate and catalyst are mixed and added to a reaction kettle, the reaction kettle is gradually heated to 150-180°C, and reacted for 3-6h, then heated to 190-200°C, and continued to react for 10-12h, while distilling off the carbonate and byproduct small molecule alcohol. Continue to react at 190-200°C for 15-20h, vacuum to a pressure <200Pa, heat to 200-210°C, and keep for 30min-1h, vacuum to a pressure <100Pa, and when the hydroxyl value is qualified, cool to 100-150°C, and discharge under nitrogen atmosphere protection; Preferably, the hydroxyl end-capping rate of the polycarbonate polyol is >99.6%.

5. The preparation method according to claim 4, characterized in that, The small molecule diol is a C2-C12 diol, including one or more of ethylene glycol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol, preferably one or more of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 3-methyl-1,5-pentanediol; and / or, the carbonate is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, diphenyl carbonate, and ethylene carbonate; and / or, the catalyst is one or more of tetraethyl titanate, tetra-n-butyl titanate, tetraisopropyl titanate, dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin octoate, di-n-butyl tin oxide, and stannous octoate; and / or, the raw materials for preparing the polycarbonate polyol further include a polyether diol and / or a lactone; the polyether diol is one or more of polytetrahydrofuran diol, poly-1,2-propanediol, poly-1,3-propanediol, polyethylene glycol, and a copolyether diol obtained by copolymerization of two or more of ethylene oxide, propylene oxide, and tetrahydrofuran; and the lactone is one or more of capro-lactone, valerolactone, butyrolactone, and lactide; and / or, the total molar amount of the small molecule diol and the polyether diol added is 0.8-0.96 times the molar amount of the carbonate; and / or, the amount of the lactone added is 0-5 times the total molar amount of the small molecule diol and the polyether diol.

6. A polyurethane elastomer prepared by reacting the polycarbonate polyol, diisocyanate and chain extender according to any one of claims 1-3.

7. The polyurethane elastomer according to claim 6, characterized in that, The polyurethane elastomer has a gum content increment of less than 10 mg / 100 mL according to the GJB3986A standard.

8. The polyurethane elastomer according to claim 6, wherein, The diisocyanate is one or more of aromatic polyisocyanate, aliphatic polyisocyanate and alicyclic polyisocyanate; preferably one or more of 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, 1,4-phenylene diisocyanate, m-xylylene diisocyanate, diphenylmethane-3,3'-dimethoxy-4,4'-diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 2,4-hexahydrotoluene diisocyanate, 2,6-hexahydrotoluene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate, 2,4-dicyclohexylmethane diisocyanate, isophorone diisocyanate, lysine diisocyanate, L-lysine diisocyanate, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, more preferably 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate and 4,4'-dicyclohexylmethane diisocyanate. The chain extender is aliphatic diol and / or alicyclic diol with a molecular weight of 60-200 g / mol; preferably the aliphatic diol is one or more of ethylene glycol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, preferably 1,4-butanediol and 1,6-hexanediol; the alicyclic diol is one or more of 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol and 1,4-cyclohexanedimethanol, preferably 1,4-cyclohexanedimethanol.

9. The polyurethane elastomer according to any of claims 6 to 8, characterized in that The polyurethane elastomer has the following mass ratio of each component based on the total weight of raw materials: polycarbonate polyol 30%-80%, preferably 40-75%; chain extender 5%-30%, preferably 7-20%; diisocyanate 15-60%, preferably 20-50%.

10. Use of the polyurethane elastomer according to any one of claims 6-9 for oil storage and oil transportation, preferably oil tank, oil bag and oil pipe.

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