Polyurethane and preparation method thereof

Abstract

The invention discloses polyurethane, which is prepared from the following components in percentage by mole: 20 to 60 mol percent of polyether polyol (or polymercaptan: dimercapto polymercaptan, trimercapto polymercaptan and tetramercapto polymercaptan) unit, 30 to 70 mol percent of isocyanate and 5 to 20 mol percent of sulfur-containing chain extender. Meanwhile, based on the weight percentage of the polyurethane, the polyurethane also contains 1-5wt% of elemental selenium and 1-8wt% of selenium disulfide. According to the invention, through a specific polyether polyol chain segment and an isocyanate chain segment with a specific structure, a sulfur-containing chain extender containing a plurality of sulfur atoms is applied, elemental selenium and selenium disulfide are introduced before a chain extension reaction, and loop crosslinking is formed on a macromolecular chain segment by using various rings formed by non-polar covalent bonds with special electron balance of sulfur and selenium. Therefore, the polyurethane provided by the invention has tear resistance and temperature resistance.

Description

Technical Field

[0001] The invention relates to the field of high-resolution technology, in particular to polyurethane and a preparation method thereof. Background Art

[0002] Polyurethane elastomer is an important high-performance polymer material. It contains a large number of carbamate groups (NHCOO) in the molecular chain. It is a block polymer. Generally, the soft segment is composed of a long flexible chain of oligomer polyols, and the hard segment is composed of diisocyanate and chain extender. The hard segment and soft segment alternate to form a repeating structural unit. This unique chemical structure not only gives polyurethane materials the characteristics of high elasticity, but also enables them to have a variety of excellent properties such as wear resistance, tear resistance, chemical resistance and wide temperature compatibility. It occupies an important position in modern industry and is widely used in many high-end manufacturing fields, such as aerospace, high-end automobiles, precision machinery, electronic equipment and medical equipment.

[0003] With the advancement of science and technology and the continuous improvement of material performance requirements in the manufacturing industry, the high-performance design and preparation of polyurethane elastomers have become key factors in enhancing their application value. In high-end manufacturing, the performance requirements for materials are becoming more and more stringent. As a high-performance material, the design and application of polyurethane elastomers must meet specific technical standards.

[0004] The comprehensive performance of elastic polyurethane materials prepared by existing methods is not very good. For example, the hardness is sufficient, but the elasticity is not good, the tear resistance is not good, and the high temperature resistance in special occasions is not good. In order to further expand its application field, its performance needs to be further improved and enhanced. However, the common existing methods are to use different polyols or amines and other soft segments for improvement (CN202411292030), or to add coupling agents (cross-linking agents) to strengthen the interaction between polymer segments and increase the resistance to molecular movement, thereby improving the friction resistance and tear resistance of polyurethane materials (CN 118955865 A). Patent CN113583432A discloses that the Al2O3 modified by introducing silane coupling agent is prepared by reacting terminal hydroxyl polybutadiene with polyester polyol and diisocyanate. 2 O 3 , improve wear resistance. However, the olefin monomer used in this method has the phenomenon of heat aging cross-linking in this application scenario, and thermal stress concentration will occur during subsequent use, greatly reducing the service life and safety. These methods can enhance the mechanical properties of the material to a certain extent, but their control is not fine enough. They either increase the "soft" properties such as tearing resistance and wear resistance, while reducing the "hard" properties such as hardness to a certain extent, resulting in a loss of one thing while focusing on another, or fail to enhance the mechanical properties of the material as a whole. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical defects and provide a wear-resistant, tear-resistant and temperature-resistant material.

[0006] The present invention is achieved through the following technical solutions: A polyurethane, based on molar percentage, derived from 20-60 mol% of polyether polyol units, 30-70 mol% of isocyanate and 5-20 mol% of a sulfur-containing chain extender; Meanwhile, the polyurethane also contains 1-5wt% of selenium and 1-8wt% of selenium disulfide in terms of weight percentage of the polyurethane.

[0007] In the polyurethane of the present invention, a large amount of sulfur is contained in the resin matrix due to a specific sulfur-containing chain extender, and then selenium and selenium disulfide are added to form various rings to form a trap crosslinking of the polymer chain segments by utilizing the non-polar covalent bonds of the special electronic balance of sulfur and selenium.

[0008] Density Fourier Transformation Theory (DFT) calculations show that the ground state of selenium disulfide is 1 A 1 , whose structure belongs to the triatomic C 2V Configuration. Sulfur and selenium have similar electronegativity, 2.58 and 2.55 respectively, and they can form various rings through electron-balanced nonpolar covalent bonds. Formation includes six-membered rings (Se n S 6-n ), seven-membered ring (Se n S 7-n ), eight-membered ring (Se n S 8-n） and twelve-membered ring (Se n S 12-n ), so that it can be interlaced with the polyurethane chain segment, and secondly, the elemental selenium can bond with the sulfur on the chain segment, forming a trap cross-linking effect as a whole.

[0009] The polyether polyol is selected from at least one of polytetramethylene glycol, polybutylene adipate glycol, polycaprolactone glycol and glycerol polyether polyol, and has a molecular weight range of 2000-20000 g / mol.

[0010] The isocyanate is selected from at least one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0011] The sulfur-containing chain extender is selected from at least one of thiodiglycol mercaptan, dithiol polythiol, trithiol polythiol, and tetrathiol polythiol. Compared with conventional disulfide chain extenders, the sulfur-containing chain extender of the present invention contains more sulfur elements and can significantly increase the sulfur content in the resin matrix.

[0012] The average particle size of the selenium element is 50-130 nanometers.

[0013] Preferably, the polyurethane is derived from 30-50 mol% of polyether polyol units, 40-60 mol% of isocyanate and 8-14 mol% of sulfur-containing chain extender.

[0014] Preferably, the polyurethane further contains 2-4wt% of selenium and 3-6wt% of selenium disulfide, based on the weight percentage of the polyurethane.

[0015] The tensile strength of the polyurethane of the invention is greater than 58 MPa, the elongation at break is greater than 1500%, and the temperature at the maximum thermal weight loss rate is greater than 417°C.

[0016] The preparation method of polyurethane comprises the following steps: Step A: adding the dehydrated polyether polyol, isocyanate and catalyst into a reactor, reacting at 70-90° C. for 1-3 hours to obtain a prepolymer; the catalyst can be a common initiator such as triethylenediamine and stannous octoate, and the amount of the catalyst added is 0.01-5wt% (based on the total amount of polyether polyol, isocyanate and sulfur-containing chain extender).

[0017] Step B: adding a sulfur-containing chain extender, an organic solvent containing selenium disulfide, and selenium, and performing a chain extension reaction after the selenium disulfide is dissolved, the reaction temperature is 80-90° C., the reaction time is 10 minutes to 30 minutes, and then vacuum degassing is performed for 1-3 hours; Step C: subjecting the above materials to plate vulcanization and aging to obtain polyurethane.

[0018] The organic solvent is selected from carbon disulfide and the like.

[0019] The present invention has the following beneficial effects: The invention uses a specific polyether polyol chain segment and an isocyanate chain segment with a specific structure, applies a sulfur-containing chain extender containing multiple sulfur atoms, and introduces selenium and selenium disulfide before the chain extension reaction, and forms a trap crosslinking of the polymer chain segment by using various rings formed by non-polar covalent bonds with special electronic balance of sulfur and selenium, so that the polyurethane of the invention has tear resistance and temperature resistance. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0021] The raw materials used in the embodiments and comparative examples are derived from the following sources: Selenium disulfide: Sodium selenite is reduced with sodium sulfide at room temperature to obtain selenium disulfide precipitate.

[0022] Selenium: Slowly add vitamin C solution to a dispersion system containing sodium selenite at a temperature below 5°C to reduce the sodium selenite and freeze-dry to obtain red nano-element selenium with a particle size of less than 130 nm.

[0023] Polyether polyol A: polytetramethylene ether glycol, molecular weight 3000 g / mol, BASF, Germany; Polyether polyol B: polybutylene adipate diol, molecular weight 4000 g / mol, purchased from Jining Sunbright Biotechnology Co., Ltd.; Polyether polyol C: polycaprolactone diol, molecular weight 3000 g / mol, purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. Polyether polyol D: glycerol polyether polyol, molecular weight 2000 g / mol, purchased from Hai'an Petrochemical Plant, Jiangsu Province; Toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), thiodiglycol mercaptan, dithiopolymerthiol, trithiopolymerthiol, tetrathiopolymerthiol, 4,4'-diaminodiphenyl disulfide, 3,3'-dihydroxydiphenyl disulfide, and 2-hydroxyethyl disulfide were derived from commercially available products.

[0024] The preparation method of polyurethane in the embodiment and comparative example is as follows: dehydrated polyether polyol, isocyanate and stannous octoate (0.08wt%) are added into a reactor, and reacted at 70-90°C for 1-3 hours to obtain a prepolymer; a sulfur-containing chain extender, an organic solvent containing selenium disulfide and a selenium element are added, and a chain extension reaction is carried out after the selenium disulfide is dissolved, the reaction temperature is 80-90°C, the reaction time is 10 minutes to 30 minutes, and then vacuum degassing is carried out for 1-3 hours; the above materials are subjected to plate vulcanization and aging to obtain polyurethane.

[0025] Various test methods: (1) Tensile strength: refer to GB / T1040.1-2018.

[0026] (2) Elongation at break: refer to GB / T1040.1-2018.

[0027] (4) Temperature resistance: The polyurethane elastomer was placed in a thermogravimetric analyzer and tested for thermogravimetric properties in a nitrogen atmosphere. The temperature was raised from room temperature to 700°C at a heating rate of 10°C / min, and the temperature at which the maximum thermal weight loss rate occurred was measured.

[0028] Table 1: Polyurethane compositions and test results of Examples 1-6 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Polyether polyol selection A A A A B C Polyether polyol content, mol% 20 30 50 60 30 30 TDI, mol% 62 56 42 35 IPDI, mol% 56 MDI, mol% 56 Thiodiglycol mercaptan, mol% 18 14 8 5 Dithiol polythiol, mol% 14 Trithiopolythiol, mol% 14 Selenium, wt% 2 2 2 2 2 2 Selenium disulfide, wt% 3 3 3 3 3 3 Tensile strength, MPa 58.3 59.1 60.4 58.9 59.4 58.3 Elongation at break, % 1520 1658 1703 1683 1704 1790 Temperature resistance 419.3 420.3 423.5 417.5 419.5 420.1 It can be seen from Examples 1-4 that the preferred polyurethane repeating unit composition has better tensile strength, elongation at break and temperature resistance.

[0029] Table 2: Polyurethane compositions and test results of Examples 7-11 Example 7 Example 8 Example 9 Example 10 Embodiment 11 Polyether polyol selection D A A A A Polyether polyol content, mol% 30 30 30 30 30 TDI, mol% 56 56 56 56 HMDI, mol% 56 Thiodiglycol mercaptan, mol% 14 14 14 14 Tetrathiothiopolythiol, mol% 14 Selenium, wt% 2 1 4 5 4 Selenium disulfide, wt% 3 1 6 8 3 Tensile strength, MPa 61.8 58.7. 61.6 58.4 59.8 Elongation at break, % 1806 1606 1790 1640 1760 Temperature resistance 422.8 419.6 422.6 420.1 420.2 It can be seen from Examples 2 / 8-11 that the preferred content of selenium and selenium disulfide results in better performance.

[0030] Table 3: Comparative Examples 1-6 Polyurethane Composition and Test Results Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Polyether polyol selection A A A A A A Polyether polyol content, mol% 30 30 30 30 30 35 TDI, mol% 56 56 56 56 56 61 Thiodiglycol mercaptan, mol% 14 14 3 4,4'-Diaminodiphenyl disulfide, mol% 14 3,3'-Dihydroxydiphenyl disulfide, mol% 14 2-Hydroxyethyl disulfide, mol% 14 Selenium, wt% 2 2 2 0 2 2 Selenium disulfide, wt% 3 3 3 3 0 3 Tensile strength, MPa 46.3 47.1 51.2 52.4 53.1 51.6 Elongation at break, % 1203 1160 1430 1440 1208 1501 Temperature resistance 408.3 409.8 412.8 413.4 409.9 412.6 It can be seen from Comparative Examples 1-3 that other commonly used disulfide chain extenders in the art have relatively low performance.

[0031] It can be seen from comparative examples 4 / 5 that when no selenium or selenium disulfide is contained, various properties are poor.

[0032] It can be seen from Comparative Example 6 that when the content of the chain extender of the present invention is insufficient, the purpose of the present invention cannot be achieved.

Claims

1. A polyurethane, characterized in that In terms of molar percentage, it is derived from 20-60 mol% of polyether polyol units, 30-70 mol% of isocyanate and 5-20 mol% of sulfur-containing chain extender; Meanwhile, the polyurethane also contains 1-5wt% of selenium and 1-8wt% of selenium disulfide in terms of weight percentage of the polyurethane.

2. The polyurethane according to claim 1, characterized in that The polyether polyol is selected from at least one of polytetramethylene glycol, polybutylene adipate glycol, polycaprolactone glycol and glycerol polyether polyol, and has a molecular weight range of 2000-20000 g / mol.

3. The polyurethane according to claim 1, characterized in that The isocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate and lysine diisocyanate.

4. The polyurethane according to claim 1, characterized in that The sulfur-containing chain extender is selected from at least one of thiodiglycol mercaptan, dithiol polythiol, trithiol polythiol and tetrathiol polythiol.

5. The polyurethane according to claim 1, characterized in that The average particle size of the selenium element is 50-130 nanometers.

6. The polyurethane according to claim 1, characterized in that The polyurethane is derived from 30-50 mol% of polyether polyol units, 40-60 mol% of isocyanate and 8-14 mol% of sulfur-containing chain extender.

7. The polyurethane according to claim 1, characterized in that Calculated by weight percentage of the polyurethane, the polyurethane further contains 2-4wt% of selenium and 3-6wt% of selenium disulfide.

8. The polyurethane according to claim 1, characterized in that The tensile strength of the polyurethane is greater than 58MPa, the elongation at break is greater than 1500%, and the temperature at the maximum thermal weight loss rate is greater than 417°C.

9. The method for preparing the polyurethane according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step A: adding the dehydrated polyether polyol, isocyanate and catalyst into a reactor, reacting at 70-90° C. for 1-3 hours to obtain a prepolymer; Step B: adding a sulfur-containing chain extender, an organic solvent containing selenium disulfide, and selenium, and performing a chain extension reaction after the selenium disulfide is dissolved, the reaction temperature is 80-90° C., the reaction time is 10 minutes to 30 minutes, and then vacuum degassing is performed for 1-3 hours; Step C: subjecting the above materials to plate vulcanization and aging to obtain polyurethane.