Block copolymer as well as preparation method and application thereof

Abstract

The invention relates to a block copolymer as well as a preparation method and application thereof. The preparation raw materials of the block copolymer comprise a cycloolefin monomer and a polymer of which the main chain contains double bonds, wherein the polymer of which the main chain contains double bonds is selected from at least one of polybutadiene, polyisoprene, butadiene styrene rubber, polycyclopentene, polycyclooctene and polycyclooctadiene. The block copolymer can be used as a compatibilizer for polyethylene and polypropylene kneaded products. Physical entanglement or'emulsification 'is generated at an interface through chain segments, similar to polyethylene and polypropylene, in molecules of the block copolymer, so that interphase bonding is enhanced, the structural stability of a blend is improved, two phases can better bear external stress together, and therefore, the mechanical properties (such as strength and toughness) and processability of the blend material are improved.

Description

Technical Field

[0001] This invention relates to the field of compatibilizer technology, and in particular to a block copolymer, its preparation method, and its application. Background Technology

[0002] Polypropylene (PP) is polymerized from propylene monomers through an addition polymerization reaction. It contains methyl side chains in its molecular chain and has a high degree of molecular chain regularity, making it a semi-crystalline polymer.

[0003] Polyethylene (PE) is polymerized from ethylene monomers. Based on different polymerization methods and molecular structures, it can be divided into low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE).

[0004] PE and PP are widely popular due to their excellent chemical stability and low price, and are used to manufacture various products. However, because of their high stability, they are difficult to degrade naturally, leading to serious white pollution problems once they enter the environment. Since PE and PP have similar densities and appearances, they are difficult to separate effectively during recycling, and mixing them further complicates sorting. To solve the white pollution problem caused by PE and PP, recycling has become the most feasible solution. However, simple blending often leads to a significant decrease in mechanical properties, with elongation at break typically only around 15%. This is mainly because PE and PP are generally incompatible; to achieve effective material compounding and recycling, these materials must undergo compatibilization treatment.

[0005] Diblock or multiblock copolymers are the most widely used compatibilizers, extensively studied in PMMA (polymethyl methacrylate) / PS (polystyrene) systems, but less so in PE / iPP (isomeric polypropylene) systems. Geoffrey W. Coates' group used pyridineamine hafnium catalysts to prepare PE-b-iPP diblock and multiblock copolymers, which were then used for compatibilization of PE / iPP, showing significant compatibilization and reinforcement effects. Dow Chemical's multiblock OBC (polyolefin copolymer) prepared using chain shuttle technology can also effectively compatibilize and reinforce PE / iPP two-phase blends. Random copolymers ethylene propylene rubber (EPR) and ethylene propylene diene monomer (EPDM) are also commonly used additives for PE / iPP compatibilization and compounding.

[0006] Among existing technologies, DOW Chemicals' technology is the most mature, and its polyolefin copolymer (OBC) products have been commercialized. However, the preparation method is limited by the catalyst. Although the copolymerization method uses a wide range of catalysts, it is difficult to control the structure of the resulting graft copolymer, resulting in unreacted branched homopolymers, and excessively long branches lead to low copolymerization efficiency. EPDM is the most widely studied compatibilizer for PE and iPP composites, but the amount added is too large, and the mechanical properties are poor. Summary of the Invention

[0007] The purpose of this invention is to disclose a block copolymer, its preparation method and application, in order to solve one or more technical problems existing in the prior art and provide at least one beneficial option or create conditions.

[0008] A first aspect of the present invention is to provide a block copolymer.

[0009] A second aspect of the present invention is to provide a method for preparing the block copolymer described in the first aspect of the present invention.

[0010] A third aspect of the present invention is to provide the use of the block copolymer described in the first aspect of the present invention.

[0011] The raw materials for preparing the block copolymer according to the first aspect of the present invention include cyclic olefin monomers and polymers containing double bonds in the main chain, wherein the polymers containing double bonds in the main chain are selected from at least one of polybutadiene (PB), polyisoprene (PI), styrene-butadiene rubber (SBR), polycyclopentene (PolyCPE), polycyclooctene (PCOE), and polycyclooctadiene (PCOD).

[0012] In a further application embodiment, the cyclic olefin monomer is selected from at least one of norbornene (NB), ethylene norbornene (ENB), dicyclopentadiene (DCPD), cyclopentene (CPE), and cyclooctene (COE).

[0013] In a further application embodiment, the molar percentage of the cyclic olefin monomer is 20-90%, and the molar percentage of the polymer containing double bonds in the main chain is 10-80%. The molar percentage of the cyclic olefin monomer is preferably 30-60%, more preferably 45-50%. The molar percentage of the polymer containing double bonds in the main chain is preferably 40-70%, more preferably 50-55%.

[0014] The block copolymers described in this invention use cyclic olefin monomers and polymers containing double bonds in the main chain as starting substrates, and generate high molecular weight multiblock copolymers through olefin metathesis, followed by hydrogenation.

[0015] The preparation method according to the second aspect of the present invention includes the following steps: 1) Dissolve cyclic olefin monomers and polymers containing double bonds in a solvent, and add an olefin metathesis catalyst; 2) After polymerization is complete, a terminator is added, and the intermediate product is obtained after purification; 3) The intermediate product is hydrogenated to obtain the block copolymer.

[0016] The preparation method is based on olefin metathesis, which includes ring-opening metathesis polymerization (ROMP) of cyclic olefin monomers and cross metathesis (CM) between ring-opening cyclic olefins and polymers with double bonds in the main chain.

[0017] In a further application embodiment, the molar ratio of the cyclic olefin monomer to the polymer containing double bonds in the main chain is (0.1~9):1.

[0018] In a further application implementation, the molar ratio of the double bond in the reaction substrate to the olefin metathesis catalyst is (1000~200000):1.

[0019] In a further application embodiment, the olefin metathesis catalyst includes a Grubbs I catalyst or a Grubbs II catalyst.

[0020] In a further application embodiment, the terminator is a vinyl ether or allyl alcohol. Preferably, the molar ratio of the terminator to the olefin metathesis catalyst is 2000:1.

[0021] In a further application embodiment, the vinyl ether is selected from vinyl ethyl ether, n-butyl vinyl ether, or isobutyl vinyl ether.

[0022] In a further application embodiment, the allyl alcohol is selected from methyl allyl alcohol, cinnamyl alcohol, or 2-buten-1-ol.

[0023] In a further application embodiment, the purification refers to filtering off the olefin metathesis catalyst through a silica gel column, then adding ethanol and retaining the precipitate.

[0024] In a further application embodiment, the hydrogenation treatment involves dissolving the intermediate product in xylene, adding tri-n-propylamine and p-methylbenzenesulfonyl hydrazine, heating under a nitrogen atmosphere under reflux, cooling, adding ethanol, and retaining the precipitate.

[0025] In a further application implementation, the heating reflux refers to heating to 135±1℃ and refluxing for 5~10 hours.

[0026] In a further application embodiment, the solvent is tetrahydrofuran (THF).

[0027] Taking the synthesis of NB and PB as an example, the rapid chain growth of NB promotes the formation of long-chain norbornene (PNB) blocks. This is attributed to the near-complete suppression of intra- and inter-chain secondary metathesis in PNB. During NB polymerization, the active centers of the olefin metathesis catalyst transfer to the PB chain, leading to the formation of PB block structures. Subsequently, NB continues chain growth at the new active sites, forming new PNB blocks. Furthermore, the presence of NB monomers inhibits intra-chain metathesis in PB or PNB through ring-chain equilibrium, reducing the likelihood of polymer chain degradation into cyclic oligomers. The polymerization process, with active sites shuttling between PB chains, ultimately produces a high-molecular-weight multi-block copolymer (PNB-PB). This block copolymer is subsequently hydrogenated and, after hydrogenation, can be used as a compatibilizer for PE / iPP blends.

[0028] The application described in the third aspect of the present invention refers to the use of the block copolymer as a compatibilizer in the compounding process of polyethylene and polypropylene.

[0029] In a further application embodiment, the amount of the block copolymer added is 0.1~10%.

[0030] In a further application implementation, the mass ratio of polyethylene to polypropylene is 1:(0.05~20).

[0031] In a further application embodiment, the polyethylene includes at least one of HDPE, LDPE, LLDPE and polyethylene fiber.

[0032] In a further application embodiment, the polypropylene includes at least one of isomeric polypropylene (iPP), atactic polypropylene (aPP), and syndiotactic polypropylene (sPP).

[0033] In a further application embodiment, the temperature of the mixing process is 170~190℃.

[0034] In a further application implementation, the mixing process takes 1 to 10 minutes.

[0035] The technical solution provided by this invention has the following advantages or beneficial effects: The block copolymer, as a compatibilizer for PE and PP, enables the reuse of recycled polyolefin plastics. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the reaction principle in Example 1; Figure 2 This is a melting point diagram of the block copolymer obtained in Example 1; Figure 3 Melting point diagram of the block copolymer obtained in Example 2 Figure 4 The graph shows the tensile test results of different addition amounts of block copolymer No. 1 in Example 3; Figure 5 The image shows the tensile test results of different amounts of the No. 2 block copolymer in Example 3. Detailed Implementation

[0037] In the description of this invention, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0038] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0039] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present invention.

[0041] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0042] Example 1, Preparation of Block Copolymer No. 1 The block copolymer was prepared using NB and PB as starting substrates. Experimental conditions included: Initial NB concentration: [NB]0 = 0.5 mol / L; The ratio of the initial molar concentration of NB to the molar concentration of the catalyst: [NB]0 / [Cat.]=2500; The ratio of the initial concentration of NB to the initial molar concentration of butadiene in the PB chain: [NB]0 / [B]0 = 50 / 50; Mass of NB: m(NB) = 4 g; The molecular weight of PB was determined by gel permeation chromatography. M w (PB) = 510 kg / mol; PB Dispersion D̵ =2.53; Mass of PB: m(PB) = 2.25 g; Volume of tetrahydrofuran in the polymerization solution: V(THF) = 85 mL; Catalyst Cat. mass: 14 mg; The aggregation time is 60 minutes.

[0043] The molecular weight of the metathesis block copolymer (PNB-b-PB) was determined by gel permeation chromatography: M w (NB) = 240 kg / mol; PNB-b-PB dispersion: D̵ =1.94; Experimental principle as follows Figure 1 As shown, the specific preparation steps include: S1. In a glove box, NB and purified PB are first dissolved in THF solution, then Grubbs I catalyst is added for polymerization. After polymerization is complete, 2 mL of vinyl ether is added to terminate the polymerization. S2. Remove the reaction flask from the glove box, then puff in air for 30 minutes, then add 100 mL of dichloromethane to dilute, remove the catalyst by passing through a silica gel column, and then precipitate in ethanol to obtain the intermediate product; S3. Dissolve the obtained intermediate product in xylene, add 48 g of tri-n-propylamine and 62 g of p-methylbenzenesulfonylhydrazine, purge with nitrogen for 10 minutes, heat to 135°C, reflux for 8 hours, and then precipitate in ethanol to obtain the block copolymer.

[0044] After drying, the melting point of block copolymer No. 1 was measured using a differential scanning calorimeter as follows: Figure 2 As shown, the melting points are 122℃ for polyethylene segments and 139.4℃ for hydrogenated polynorbornene, respectively.

[0045] Example 2, Preparation of Block Copolymer No. 2 The block copolymer was synthesized using Grubbs II catalyst instead of Grubbs I catalyst in Example 1. The specific preparation steps included: S1. In a glove box, NB and purified PB are first dissolved in THF solution, then Grubbs II catalyst is added for polymerization. After polymerization is complete, 2 mL of vinyl ether is added to terminate the polymerization. S2. Remove the reaction flask from the glove box, then puff in air for 30 minutes, then add 100 mL of dichloromethane to dilute, remove the catalyst by passing through a silica gel column, and then precipitate in ethanol to obtain the intermediate product; S3. Dissolve the obtained intermediate product in xylene, add 48 g of tri-n-propylamine and 62 g of p-methylbenzenesulfonylhydrazine, purge with nitrogen for 10 minutes, heat to 135°C, reflux for 8 hours, and then precipitate in ethanol to obtain the block copolymer.

[0046] After drying, the melting point of block copolymer No. 2 was measured using a differential scanning calorimeter as follows: Figure 3 As shown, the melting point of polyethylene segment is 120℃ and the melting point of hydrogenated polynorbornene is 137.0℃, respectively.

[0047] Example 3: Application of block copolymers as compatibilizers To test the compatibilizing effect of the aforementioned front-end copolymer on PE / PP, samples with different amounts of block copolymer were designed and prepared for testing.

[0048] The compounded samples consisted of components A, B, and C. Component A was HDPE, component B was iPP, and component C was a mixture of block copolymer (No. 1 or No. 2) and antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]). The total mass of components A, B, and C in all compounded samples was 14 g. The antioxidant in component C was 70 mg, while the addition amounts of block copolymer were 3%, 1%, 0.2%, and 0% of the total mass, respectively, which are 0.42 g, 0.14 g, 0.028 g, and none; the remainder consisted of components A and B in a mass ratio of 7:3.

[0049] Preparation method: Mix all components at 180℃ and 90 rpm for 5 minutes in a mixer (model RM-200C, Harbin Hap Electric Technology Co., Ltd.). Remove the mixed sample and press it on a flat vulcanizing machine at 180℃ for 5 minutes, then cool and cut it into test strips.

[0050] The tensile curve of the sample without the block copolymer is as follows: Figure 4 As shown, the elongation at break is only about 15%.

[0051] The tensile curve of the sample prepared using block copolymer No. 1 is as follows: Figure 4As shown, the sample with an addition of 0.2% achieved an elongation at break of 40%; when the addition of the block copolymer reached 1%, the elongation at break of the compounded sample was as high as 850%, while the maximum tensile strength reached nearly 25 MPa; the sample with an addition of 3% of the block copolymer, although its maximum tensile strength exceeded 25 MPa, its elongation at break was actually reduced to only about 600%.

[0052] The tensile curve of the sample prepared using block copolymer No. 2 is as follows: Figure 5 As shown, the sample with an addition of 0.2% exhibited an elongation at break of 360%; when the addition of the block copolymer reached 1%, the elongation at break of the compounded sample reached 580%; and the sample with an addition of 3% of the block copolymer achieved an elongation at break as high as 860%. The maximum tensile strength of the samples with 1% and 3% addition of block copolymer No. 2 both exceeded 25 MPa.

[0053] Experimental results show that the block copolymer, when added in appropriate amounts, has excellent compatibilizing and reinforcing effects in polyethylene and polypropylene blends. It has advantages such as low addition amount and simple preparation method, and can help with the recycling and reuse of polyolefin plastics.

[0054] Comparative Example 1 HDPE / iPP compound control samples were prepared using EPDM compatibilizer to evaluate the mechanical property improvement brought about by the block copolymer of the present invention as a compatibilizer.

[0055] The preparation method of the compounded control sample is as follows: (I) HDPE, iPP, EPDM (DOW 4820P), and antioxidant 1010 are mixed in a mixer for a mixing time t1 of 10 minutes. The mass of compatibilizer EPDM is 5% of the total mass of polyethylene and polypropylene, and the mass of antioxidant is 0.5% of the total mass of polyethylene and polypropylene. The mixing temperature is 180~200℃. The mass ratio of HDPE to iPP is 7:3.

[0056] (II) Vulcanization: Add a vulcanizing agent (sulfur and ZnO in a molar ratio of 1:1) to the product obtained in step (I). The amount of vulcanizing agent added is 0.5% of the total mass of HDPE and iPP. Mix for a period of time, t2 is 5 minutes.

[0057] Then, injection molding and tableting are performed to obtain the composite material. The tableting temperature is 190°C.

[0058] The tensile strength of the obtained compound control sample was 22.5 MPa, and the elongation at break was 680%.

[0059] The results are shown in Table 1, comparing the compounded sample with a block copolymer addition of 1% as described in Example 2.

[0060] Table 1. Comparison of compounded samples with block copolymer compatibilizer and EPDM compatibilizer

[0061] It is evident that the compounded sample prepared from the block copolymer is of superior quality.

[0062] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A block copolymer, characterized in that, The raw materials for its preparation include cyclic olefin monomers and polymers containing double bonds in the main chain, wherein the polymers containing double bonds in the main chain are selected from at least one of polybutadiene, polyisoprene, styrene-butadiene rubber, polycyclopentene, polycyclooctene, and polycyclooctadiene.

2. The block copolymer according to claim 1, characterized in that, The cyclic olefin monomer is selected from at least one of norbornene, ethylidene norbornene, dicyclopentadiene, cyclopentene, and cyclooctene.

3. The block copolymer according to claim 1 or 2, characterized in that, In the raw materials for preparing the block copolymer, the molar percentage of cyclic olefin monomers is 20-90%, and the molar percentage of polymers containing double bonds in the main chain is 10-80%.

4. A method for preparing the block copolymer according to any one of claims 1 to 3, characterized in that, Including the following steps: 1) Dissolve the cyclic olefin monomer and the polymer containing double bonds in the main chain in a solvent, and add an olefin metathesis catalyst; 2) After polymerization is complete, a terminator is added, and the intermediate product is obtained after purification; 3) The intermediate product is hydrogenated to obtain the block copolymer.

5. The preparation method according to claim 4, characterized in that, The terminating agent is a vinyl ether or allyl alcohol; preferably, the vinyl ether is selected from vinyl ethyl ether, n-butyl vinyl ether or isobutyl vinyl ether; preferably, the allyl alcohol is selected from methyl allyl alcohol, cinnamyl alcohol or 2-buten-1-ol.

6. The preparation method according to claim 4, characterized in that, The purification process involves filtering the catalyst off through a silica gel column, adding ethanol, and retaining the precipitate.

7. The preparation method according to claim 4, characterized in that, The hydrogenation process involves dissolving the intermediate product in xylene, adding tri-n-propylamine and p-methylbenzenesulfonyl hydrazine, heating under a nitrogen atmosphere under reflux, cooling, adding ethanol, and retaining the precipitate.

8. The preparation method according to claim 7, characterized in that, The heating and reflux refers to heating to 135±1℃ and refluxing for 5~10 hours.

9. The use of the block copolymer according to any one of claims 1 to 3 as a compatibilizer in the compounding of polyethylene and polypropylene.

10. The application according to claim 9, characterized in that, The amount of the block copolymer added is 0.1-10% of the total mass.

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