A process for the preparation of a highly entangled, fatigue resistant polyolefin thermoplastic elastomer

Abstract

The application discloses a preparation method of a high entanglement and fatigue resistant polyolefin thermoplastic elastomer, and the material is prepared from the following raw materials: 100 parts of ETPO elastomer, 1-35 parts of ETPO-UHMWPE solution blending masterbatch, 1-10 parts of vinyl boron-containing crosslinking agent, 0.05-0.2 parts of antioxidant and 0.01-5 parts of initiator. First, the ETPO-UHMWPE solution blending masterbatch A is prepared by using hot dimethylbenzene; second, the vinyl boron-containing crosslinking agent B is prepared by using 1,4-benzene diboronic acid and 3-allyloxy-1,2 propanediol; then, the ETPO, the masterbatch A, the vinyl boron-containing crosslinking agent B, the antioxidant and the initiator are mixed in a mixer or an extruder; finally, the material is formed by secondary processing in a conventional polymer processing mode. The application creatively realizes the synergy of chain entanglement and vitrimer network, improves the tensile strength, fatigue resistance and use temperature, has the advantages of simple operation process, low production cost and repeatable processing, and adopts conventional polymer processing equipment, and has the industrial application potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high polymer materials, and particularly relates to a preparation method of a high-entanglement and fatigue-resistant polyolefin thermoplastic elastomer BACKGROUND

[0002] Thermoplastic elastomers are a kind of elastic materials with excellent elasticity and repeated processing capability, which have been developed significantly in recent years. Ethylene-octene multi-block copolymer OBC is a new type of polyolefin thermoplastic elastomer ETPO. The unique chain shuttling polymerization method obtains a multi-block structure with alternating crystalline hard segments and amorphous soft segments

Daniel J. Arriola, Edmund M. Carnahan, Phillip D. Hustad, Roger L. Kuhlman, Timothy T. Wenzel, Science, 2006, 312: 714-719.

[0003] For high polymer materials, the entanglement structure formed by long chains has an important influence on the mechanical properties. Taking ultra-high molecular weight polyethylene UHMWPE as an example, although the molecular chain structure is similar to that of high-density polyethylene, a large number of entanglement structures form a high-density physical crosslinking network, so that the ultra-high molecular weight polyethylene has excellent wear resistance and impact resistance, and even the ultra-high molecular weight polyethylene fiber can be used to manufacture bulletproof helmets, bulletproof clothes and the like. For elastomers or hydrogels, entanglement acts as a physical crosslinking point, which provides elasticity in a short time, viscosity in a long time, and sliding link effect under external force, so that the energy dissipation capacity is excellent

Jonsoo Kim, Guogao Zhang, Meixuanzi Shi, Zhigang Suo*, Science, 2021, 374: 212-216.

[0004] To solve the above problems, on the one hand, we use solution blending method to fully dissolve and dilute ultra-high molecular weight polyethylene in hot xylene, realize the chain disentanglement, and promote the molecular level mutual solubility of ETPO elastomer and ultra-high molecular weight polyethylene through continuous stirring, remove the xylene solvent to obtain ETPO / UHMWPE masterbatch, and then the modified elastomer with different UHMWPE addition amount can be easily obtained by melt mixing and dilution; on the other hand, the vitrimer dynamic covalent crosslinking network is introduced into the system, which can improve the heat resistance and also consider the repeated processing characteristics. Therefore, the present application develops a method for batch preparation of highly entangled polyolefin elastomer ETPO / UHMWPE vitrimer, which is simple to operate, and the dynamic chemical network of dynamic boron-oxygen bond is introduced while the entanglement density of ETPO elastomer is improved, so that the fatigue-resistant polyolefin elastomer with controllable entanglement density and wide use temperature can be realized, and the orientation self-reinforcement of the elastomer can be easily realized by melt shearing or stretching field. SUMMARY

[0005] In order to avoid the shortcomings of the prior art, the present application develops a method for batch preparation of ETPO / UHMWPE vitrimer elastomer, which is simple to operate, solves the problems of micro-agglomeration caused by difficult disentanglement of UHMWPE and macro-phase separation of blended elastomer due to thermodynamic tendency, and realizes the regulation of the entanglement density of polyolefin elastomer ETPO, the widening of the use temperature and the improvement of the self-reinforcement effect of the elastomer under the processing flow field.

[0006] In order to achieve the above purpose, the technical scheme is as follows:

[0007] Step one: weigh 100 parts of polyolefin thermoplastic elastomer ETPO, weigh 20-50 parts of ultra-high molecular weight polyethylene UHMWPE, take appropriate amount of xylene and add ETPO and UHMWPE in proportion into a three-necked flask, add 0.05 parts of antioxidant, heat at 120-140℃ and continuously stir until ETPO and UHMWPE are dissolved and form a transparent solution, then stir for 1-2h for sufficient mixing, and then remove the xylene by rotary evaporator to obtain ETPO-UHMWPE solution blending masterbatch A;

[0008] Step two: take 1,4-benzene diboronic acid and 3-allyloxy-1,2-propanediol as solvents, and add appropriate amount of molecular sieves or anhydrous magnesium sulfate, stir at room temperature for 24 hours, remove the molecular sieves or anhydrous magnesium sulfate by suction filtration, remove the solvent by rotary evaporator, and obtain the double bond end-capped boron-containing crosslinking agent B;

[0009] Step three: take 100 parts of ETPO, 1-35 parts of masterbatch A, 1-10 parts of boron-containing crosslinking agent B, 0.05-0.2 parts of antioxidant, 0.01-5 parts of initiator, and use a banbury mixer or an extruder, set the temperature to 125-220℃, and reactively mix for 5-20 minutes to obtain an ETPO / UHMWPE vitrimer elastomer.

[0010] Step four: take an appropriate amount of ETPO / UHMWPE vitrimer elastomer, and use a conventional polymer processing method with a melt temperature of 130-250℃ to obtain a sample bar after secondary processing for testing.

[0011] The ETPO of step one is any one or combination of ethylene-octene block copolymer OBC, ethylene-octene random copolymer POE, and ethylene-propylene-diene monomer EPDM.

[0012] The UHMWPE of step one has a molecular weight of 1,500,000-3,500,000.

[0013] The antioxidant of steps one and three is any one of hindered phenol and phosphite.

[0014] The initiator of step three is any one of dicumyl peroxide and vulcanizing agent bis-25.

[0015] The conventional polymer processing method of step four includes any one of mold pressing, injection molding machine, and extrusion-drawing machine.

[0016] The present application aims to solve the problems of poor fatigue resistance and low use temperature of polyolefin elastomers, and increases chain entanglement by processing ultra-high molecular weight polyethylene and prepares reversible covalent bonds by adding boron-containing crosslinking agents, thereby synergistically improving strength, fatigue resistance, and use temperature.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] 1. The present application synergistically improves the strength, fatigue resistance, and use temperature of polyolefin elastomers by increasing chain entanglement and constructing reversible covalent bonds, the room temperature tensile strength is up to 16.3MPa, which is 1.56 times higher, and the ETPO / UHMWPE vitrimer elastomer still has high elongation at 120 degrees, with an elongation at break of more than 500%.

[0019] 2. The high-entanglement polyolefin vitrimer elastomer prepared by the present application is easy to form an oriented crystalline structure due to entanglement, and will exhibit a significant self-reinforcing effect under processing external fields such as melt shear / tensile flow field.

[0020] 3、The application uses conventional equipment for polymer processing in addition to the preparation of the master batch, the operation process is simple, the production cost is low, continuous production is expected, and industrial application is suitable. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 . Comparison of compatibility of ETPO-UHMWPE master batch in different mixing methods, (a) solution blending master batch, (b) melt blending master batch.

[0022] Figure 2 . High temperature tensile property diagram of different samples, (a) tensile property at 80 degrees, (b) tensile property at 120 degrees.

[0023] Figure 3 . Flow field induced self-reinforcing effect of different samples, (a) mold secondary forming, (b) micro-injection secondary forming.

[0024] Figure 4 . Cycle fatigue property diagram of the sample of example 3.

[0025] Figure 5 . Thermoplastic repeated processing diagram of the sample of example 5 in the process of chopping-heat pressing. DETAILED DESCRIPTION

[0026] In order to further explain the technical scheme of the application, the following will be specifically described in combination with examples, but the protection scope of the application is not limited to these examples, and non-essential improvements and adjustments made by those skilled in the art to the application all belong to the protection scope of the application.

[0027] Example 1

[0028] Take 100 parts of EPTO and 50 parts of UHMWPE as the solvent, heat xylene, get transparent solution at high temperature (130℃) and mix and stir for 1h, then remove the solvent by rotary evaporator to get solution blending ETPO-UHMWPE master batch A; take 1,4-benzene diboronic acid and 3-allyloxy-1,2-propanediol according to the molar ratio of 1:1, continuously stir for 24h at room temperature in a proper amount of tetrahydrofuran solvent, remove the solvent by rotary evaporator to obtain vinyl boron-containing crosslinking agent B; take 100 parts of ETPO, 2 parts of ETPO-UHMWPE master batch A, 5 parts of vinyl boron-containing crosslinking agent B, 0.1 parts of antioxidant 1010, 0.3 parts of dicumyl peroxide, and reactive blend for 15 minutes by using banbury mixer to get ETPO / UHMWPE vitrimer 1; adopt mold forming or micro-injection forming secondary processing, set the temperature to 190℃, the fixed pressure is 20MPa during mold pressing, heat pressing for 10min, and use sample cutter to cut to get dumbbell-shaped sample, micro-injection forming directly prepares dumbbell-shaped sample for testing.

[0029] Example 2

[0030] Take 100 parts of EPTO and 50 parts of UHMWPE as solvents, get transparent solution at high temperature (130°C) and mix stirring for 1 h, then remove the solvent by rotary evaporator to get solution blending ETPO-UHMWPE masterbatch A; take 1,4-benzenediol and 3-allyloxy-1,2-propanediol according to the molar ratio of 1:1, continuously stirring for 24 h at room temperature in appropriate amount of tetrahydrofuran solvent, remove the solvent by rotary evaporator to obtain vinyl boron-containing crosslinking agent B; take 100 parts of ETPO, 5 parts of ETPO-UHMWPE masterbatch A, 5 parts of vinyl boron-containing crosslinking agent B, 0.1 parts of antioxidant 1010, 0.3 parts of dicumyl peroxide, reactive blending for 15 minutes by using internal mixer to get ETPO / UHMWPE vitrimer 2; adopt mold pressing or micro-injection molding secondary processing, set the temperature to 190°C, the fixed pressure is 20 MPa when mold pressing, hot pressing for 10 min, use sample cutter to cut to get dumbbell-shaped sample, micro-injection molding directly to prepare dumbbell-shaped sample for testing.

[0031] Example 3

[0032] Take 100 parts of EPTO and 50 parts of UHMWPE as solvents, get transparent solution at high temperature (130°C) and mix stirring for 1 h, then remove the solvent by rotary evaporator to get solution blending ETPO-UHMWPE masterbatch A; take 1,4-benzenediol and 3-allyloxy-1,2-propanediol according to the molar ratio of 1:1, continuously stirring for 24 h at room temperature in appropriate amount of tetrahydrofuran solvent, remove the solvent by rotary evaporator to obtain vinyl boron-containing crosslinking agent B; take 100 parts of ETPO, 12 parts of ETPO-UHMWPE masterbatch A, 5 parts of vinyl boron-containing crosslinking agent B, 0.1 parts of antioxidant 1010, 0.5 parts of dicumyl peroxide, reactive blending for 15 minutes by using internal mixer to get ETPO / UHMWPE vitrimer 3; adopt mold pressing or micro-injection molding secondary processing, set the temperature to 190°C, the fixed pressure is 20 MPa when mold pressing, hot pressing for 10 min, use sample cutter to cut to get dumbbell-shaped sample, micro-injection molding directly to prepare dumbbell-shaped sample for testing.

[0033] Example 4

[0034] Take 100 parts of EPTO and 50 parts of UHMWPE as the solvent, get transparent solution at high temperature (130℃) and mix stirring for 1h, then remove the solvent by rotary evaporator to get solution blending ETPO-UHMWPE masterbatch A; take 1,4-benzenediol and 3-allyloxy-1,2-propanediol according to the molar ratio of 1:1, continuously stirring for 24h at room temperature in appropriate amount of tetrahydrofuran solvent, remove the solvent by rotary evaporator to obtain vinyl boron-containing crosslinking agent B; take 100 parts of ETPO, 25 parts of ETPO-UHMWPE masterbatch A, 5 parts of vinyl boron-containing crosslinking agent B, 0.1 parts of antioxidant 1010, 0.5 parts of dicumyl peroxide, reactive blending for 15 minutes by using internal mixer to get ETPO / UHMWPE vitrimer 4; adopt mold pressing or micro-injection molding secondary processing, set the temperature to 190℃, the fixed pressure is 20MPa when mold pressing, hot pressing for 10min, use sample cutter to cut to get dumbbell-shaped sample, micro-injection molding directly to prepare dumbbell-shaped sample for testing.

[0035] Example 5

[0036] Take 100 parts of EPTO and 50 parts of UHMWPE as the solvent, get transparent solution at high temperature (130℃) and mix stirring for 1h, then remove the solvent by rotary evaporator to get solution blending ETPO-UHMWPE masterbatch A; take 1,4-benzenediol and 3-allyloxy-1,2-propanediol according to the molar ratio of 1:1, continuously stirring for 24h at room temperature in appropriate amount of tetrahydrofuran solvent, remove the solvent by rotary evaporator to obtain vinyl boron-containing crosslinking agent B; take 100 parts of ETPO, 12 parts of ETPO-UHMWPE masterbatch A, 9 parts of vinyl boron-containing crosslinking agent B, 0.1 parts of antioxidant 1010, 0.5 parts of dicumyl peroxide, reactive blending for 15 minutes by using internal mixer to get ETPO / UHMWPE vitrimer 5; adopt mold pressing or micro-injection molding secondary processing, set the temperature to 190℃, the fixed pressure is 20MPa when mold pressing, hot pressing for 10min, use sample cutter to cut to get dumbbell-shaped sample, micro-injection molding directly to prepare dumbbell-shaped sample for testing.

[0037] Comparative Example 1

[0038] Take 100 parts of ETPO, 0.1 parts of antioxidant 1010, 0.1 parts of dicumyl peroxide, high temperature mixing for 15 minutes by using internal mixer to get micro-crosslinked ETPO elastomer, adopt mold pressing or micro-injection molding secondary processing, set the temperature to 190℃, the fixed pressure is 20MPa when mold pressing, hot pressing for 10min, use sample cutter to cut to get dumbbell-shaped sample, micro-injection molding directly to prepare dumbbell-shaped sample for testing.

[0039] Comparative Example 2

[0040] Take 100 parts of ETPO, 5.4 parts of UHMWPE, 0.1 part of antioxidant 1010, and use an extruder to mix at high temperature for 15 minutes to obtain ETPO+UHMWPE mixed elastomer, and use mold forming or micro-injection forming secondary processing, set the temperature to 190℃, the fixed pressure is 20MPa during mold pressing, hot pressing for 10min, use sample cutter to cut to obtain dumbbell-shaped sample, micro-injection forming directly prepares dumbbell-shaped sample for testing.

[0041] Comparative Example 3

[0042] Take 100 parts of ETPO, 5 parts of ethylene-based boron-containing crosslinking agent B, 0.1 parts of antioxidant 1010, 0.5 parts of dicumyl peroxide, and use a banbury mixer to mix at high temperature for 15 minutes to obtain ETPO vitrimer, and use mold forming or micro-injection forming secondary processing, set the temperature to 190℃, the fixed pressure is 20MPa during mold pressing, hot pressing for 10min, use sample cutter to cut to obtain dumbbell-shaped sample, micro-injection forming directly prepares dumbbell-shaped sample for testing.

[0043] The formulation and dosage of each comparative example sample and example sample are shown in Table 1.

[0044] In order to investigate the compatibility of the solution blended master batch used in the examples, the morphology was characterized by polarized light microscope compared with melt blended master batch, the results showed that the solution blending method solved the problem of UHMWPE agglomeration and dispersion, and realized the molecular level mutual solubility with ETPO elastomer; further investigate the high temperature tensile properties of example samples in Table 1, the tensile properties of products with different secondary processing methods, cycle fatigue test and repeated processing experiment, the experimental results show that the ETPO / UHMWPE vitrimer elastomer of the application has the advantages of improved heat resistance, significant flow field induced self-reinforcing effect, excellent fatigue resistance, and repeatable processing.

[0045] Table 1 Raw materials and ratio of examples

[0046]

Claims

1. A method for preparing a highly entangled, fatigue-resistant polyolefin thermoplastic elastomer, characterized in that... Includes the following steps: Step 1: Weigh 100 parts of polyolefin thermoplastic elastomer ETPO, weigh 20-50 parts of ultra-high molecular weight polyethylene UHMWPE, weigh an appropriate amount of xylene and add it to a three-necked flask, then add ETPO and UHMWPE in proportion, add 0.05 parts of antioxidant, heat at a constant temperature of 120-140℃ and stir continuously until ETPO and UHMWPE dissolve and form a transparent solution, then stir for 1-2 hours to mix thoroughly, cool down and then use a rotary evaporator to remove xylene to obtain ETPO-UHMWPE solution blend masterbatch A; Step 2: Measure tetrahydrofuran as solvent, weigh 1,4-phenylenediboric acid and 3-allyloxy-1,2-propanediol, mix them according to the characteristic functional group molar ratio of 1:1, and add an appropriate amount of molecular sieve or anhydrous magnesium sulfate. Stir at room temperature for 24 hours, remove the molecular sieve or anhydrous magnesium sulfate by vacuum filtration, and remove the solvent by rotary evaporator to obtain double bond-terminated boron-containing crosslinking agent B. Step 3: Take 100 parts ETPO, 1-35 parts masterbatch A, 1-10 parts boron-containing crosslinking agent B, 0.05-0.2 parts antioxidant, and 0.01-5 parts initiator. Use a mixer or extruder, set the temperature to 125-220℃, and react for 5-20 minutes to obtain ETPO / UHMWPE vitrimer elastomer. The ETPO elastomer is any one or a combination of ethylene-octene block copolymer OBC, ethylene-octene random copolymer POE, and ethylene propylene diene monomer (EPDM) elastomer. Step 4: Take an appropriate amount of ETPO / UHMWPE vitrimer elastomer, process it using conventional polymer processing methods, with a melt temperature of 130-250℃, and obtain a sample for testing after secondary processing.

2. The method for preparing the highly entangled, fatigue-resistant polyolefin thermoplastic elastomer according to claim 1, characterized in that... The UHMWPE has a molecular weight of 1,500,000 to 3,500,000.

3. The method for preparing the highly entangled, fatigue-resistant polyolefin thermoplastic elastomer according to claim 1, characterized in that... The antioxidant is either hindered phenol or phosphite.

4. The method for preparing the highly entangled, fatigue-resistant polyolefin thermoplastic elastomer according to claim 1, characterized in that... The initiator is either dicumyl peroxide or bis-25, a sulfiding agent.

5. The method for preparing the highly entangled, fatigue-resistant polyolefin thermoplastic elastomer according to claim 1, characterized in that... The conventional polymer processing methods mentioned include any one of compression molding, injection molding, and extrusion traction machines.

Images