CN112430282A

CN112430282A - Polyolefin with low melting index and application thereof

Info

Publication number: CN112430282A
Application number: CN202011295689.7A
Authority: CN
Inventors: 王靖岱; 戴进成; 叶姝瑶; 历伟; 范小强; 陈毓明; 任聪静; 蒋斌波; 阳永荣; 廖祖维; 黄正梁; 孙婧元; 杨遥
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2020-11-18
Filing date: 2020-11-18
Publication date: 2021-03-02
Anticipated expiration: 2040-11-18
Also published as: CN112430282B

Abstract

本发明公开了一种低熔融指数的聚烯烃及其应用。所述低熔融指数的聚烯烃包括α‑烯烃的均聚物，重均分子量为800‑10000kg/mol，分子量分布指数为3‑10，在220℃、21.6kg压力下的熔体流动指数为0.01～60g/10min，可应用于耐冲击磨损零件、大型包装容器、聚烯烃管材、高分子纤维纺丝等领域。The invention discloses a low melt index polyolefin and its application. The low melt index polyolefin includes a homopolymer of α-olefin, the weight average molecular weight is 800-10000kg/mol, the molecular weight distribution index is 3-10, and the melt flow index at 220° C. and 21.6kg pressure is 0.01 ~60g/10min, can be used in impact-resistant wear parts, large packaging containers, polyolefin pipes, polymer fiber spinning and other fields.

Description

Polyolefin with low melting index and application thereof

Technical Field

The invention designs a polyolefin product, and particularly relates to a low-melt-index polyolefin and application thereof.

Background

Due to the ultra-long molecular chain and the ultra-high molecular weight, the ultra-high molecular weight polyolefin has excellent performance and can be used as a special high molecular material to be applied to important fields such as military and national defense, but the ultra-long molecular chain and a large number of chain entanglement structures cause poor segment mobility and slow diffusion rate of the molecular chain, so that the melt index is almost 0, and the processing and forming are difficult.

Disclosure of Invention

In order to solve the above technical problems, the present invention aims to provide a high molecular weight polyolefin material with a low melt index, which has good flowability and can solve the problem of difficult processing and molding of high molecular weight polyolefin in the prior art.

The invention also aims to provide application of the low-melt-index polyolefin in the fields of impact-resistant and wear-resistant parts, large packaging containers, polyolefin pipes and high-molecular fiber spinning.

According to an object of the present invention, there is provided a low melt index polyolefin comprising a homopolymer of α -olefin, having a weight average molecular weight of 800-10000kg/mol and a molecular weight distribution index of 3-10.

In the polyolefin with low melt index provided by the invention, the alpha-olefin is alpha-olefin with less than 12 carbon atoms, such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, etc., preferably ethylene and propylene.

According to one aspect of the invention, the polyolefin has a melting temperature of 125-.

In the low-entanglement polyolefin provided by the invention, the melt flow index of the polyolefin at 220 ℃ and 21.6kg is 0.01-60 g/10min, preferably 0.1-10g/10 min.

In one embodiment of the present invention, the polyolefin is prepared using a designed catalyst, the active component of which is TiCl₄During the synthesis of the catalyst, a proper amount of polysilsesquioxane [ (RSiO3/2) n ] is added]With MgCl₂The blend (Si/Ti molar ratio is between 40 and 5, Mg/Ti molar ratio is between 2 and 0.5) is used for increasing the distance between active centers, and is stirred for 3 to 10 hours at the temperature lower than 80 ℃, and the stirring speed is controlled below 150 rad/min. Therefore, in the reaction process, the molecular chains growing out of the active centers are isolated, and the molecular chains have larger movement diffusion space when the product is melted, so that the fluidity of the melt is enhanced.

In one embodiment of the invention, the polyolefin is prepared by intermittently introducing inert microbubbles during slurry polymerization. The aperture of the micro-bubble generator is controlled below 100 μm, the volume flow ratio of the inert gas and the reaction monomer is controlled between 0.1 and 3, the time of each aeration of the inert gas is controlled between 0.5 and 60s, and the interval time of the aeration of the inert gas is controlled between 0.05 and 60 s. During the period of introducing inert gas, the inert micro-bubbles wrap the growing polyethylene particles, the reaction monomers are inhibited from contacting the active center, the grown chain segments tend to be folded and arranged into a regular sequence, and when the product is melted, the degree of entanglement points formed by the diffusion and overlapping of the molecular chains is reduced, so that the flow property of the melt can be improved.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

The following methods were used to test the structure or properties of the polyolefins produced in the examples:

high temperature Gel Permeation Chromatography (GPC) is used to test the molecular weight of polyolefins and their distribution index.

The procedure for testing the melt index of the polyolefin was the same as GB/T3682-2000, wherein the test temperature was 220 ℃ and the test pressure was 21.6 kg.

Examples

Example 1

And (4) purging the reaction device by using high-purity nitrogen to remove air and water in the reaction device. Adding 0.1mmol TiCl₄Dissolved in 50mL hexane, 3. mu. mol polysilsesquioxane and 30. mu. mol MgCl were added₂The mixture of (1) was stirred for 3 hr. The polymerization reactor was adjusted to 60 ℃ and 350mL of heptane was added, 5mmol of triisobutylaluminum as a cocatalyst and 5mL of the above catalyst component solution were added, and stirred for 10min, after which ethylene (6bar) was introduced and polymerized for 30 min. The results of the relevant characterization and performance tests of the obtained product are shown in table 1.

Example 2

And (4) purging the reaction device by using high-purity nitrogen to remove air and water in the reaction device. Adding 0.1mmol TiCl₄Dissolved in 50mL hexane, 10. mu. mol polysilsesquioxane and 30. mu. mol MgCl were added₂The mixture of (1) was stirred for 3 hr. The polymerization reactor was adjusted to 60 ℃ and 350mL of heptane was added, 5mmol of triisobutylaluminum as a cocatalyst and 5mL of the above catalyst component solution were added, and stirred for 10min, after which ethylene (6bar) was introduced and polymerized for 30 min. The results of the relevant characterization and performance tests of the obtained product are shown in table 1.

Example 3

And (4) purging the reaction device by using high-purity nitrogen to remove air and water in the reaction device. Adding 0.1mmol TiCl₄Dissolved in 50mL hexane, 3. mu. mol polysilsesquioxane and 30. mu. mol MgCl were added₂Stirring the mixture for 3 hoursAnd r. The polymerization reactor was adjusted to 60 ℃ and 350mL of heptane was added, 5mmol of triisobutylaluminum as a cocatalyst and 5mL of the above catalyst component solution were added, and stirred for 10min, after which ethylene (3bar) was introduced and polymerized for 30 min. The results of the relevant characterization and performance tests of the obtained product are shown in table 1.

Example 4

TiCl supported with magnesium chloride₄As catalyst, triethyl aluminum is used as cocatalyst, and n-heptane is used as solvent. The microbubble generator feed gas is nitrogen, and the diameter of the micropores is 1 μm. The pressure of the pressure-controlled valve was set to 11 bar.

After replacing the fluidized bed reactor with nitrogen for several times at 60 ℃, the reactor was maintained in flow replacement with ethylene gas for 4 h. 5mg of catalyst and 5mmol of cocatalyst, triethylaluminium, were carried to the reactor by 400mL of feed solvent, n-heptane, after which ethylene reaction gas was passed (feed pressure 10 bar). Nitrogen (feed pressure 11.5bar) was intermittently passed through a microbubble generator (metal filter with pore size below 1 μm) into the reactor in the form of microbubbles with 3s duration per aeration and 0.5s interval between aerations. The ratio of the mass flow of the nitrogen to the mass flow of the ethylene is 1:2, and the product is obtained after 30min of polymerization. The results of the relevant characterization and performance tests of the obtained product are shown in table 1.

Example 5

After replacing the fluidized bed reactor with nitrogen for several times at 60 ℃, the reactor was maintained in flow replacement with ethylene gas for 4 h. 5mg of catalyst and 5mmol of cocatalyst, triethylaluminium, were carried to the reactor by 400mL of feed solvent, n-heptane, after which ethylene reaction gas was passed (feed pressure 10 bar). Nitrogen (feed pressure 11.5bar) was intermittently passed through a microbubble generator (metal filter with pore size below 1 μm) into the reactor in the form of microbubbles with 3s duration per aeration and 0.5s interval between aerations. The ratio of the mass flow of the nitrogen to the mass flow of the ethylene is 1:1, and the product is obtained after 30min of polymerization. The results of the relevant characterization and performance tests of the obtained product are shown in table 1.

Comparative example 1

And testing the polyolefin powder with the grade of Bile 350 of the Shanghai chemical research institute according to the characterization method. The results of the relevant characterization and performance tests of the obtained product are shown in table 1.

The results of the relevant property tests on the polyolefin products finally obtained in examples 1-2 and comparative example 1 are as follows:

as shown in the above table, the molecular weights of the products obtained in examples 1, 2, 4 and 5 were equivalent to those of the product obtained in comparative example 1, and the molecular weight distribution was narrower. Generally, the broader the molecular weight distribution, the higher the low molecular weight fraction of the product, which can improve the melt flow of the product. However, the products obtained in examples 1, 2, 4 and 5, which have a narrower molecular weight distribution, exhibit a higher melt index, indicating a better processability of the product. The lower weight average molecular weight of the product of example 3 demonstrates that the product disclosed herein also exhibits good melt flow at lower molecular weights. Therefore, when the product disclosed by the invention is processed into a large-scale packaging container and a polyethylene pipe, the melt is easier to flow and form, and less internal stress is remained in a forming member.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. a low melt index polyolefin, is characterized in that, it is the homopolymer of alpha-olefin, and weight average molecular weight is 800-10000kg/mol, and molecular weight distribution index is 3-10; The melting temperature of described polyolefin At 125-180°C; the melt flow index of the polyolefin at 220°C and 21.6 kg is 0.01-60 g/10min.

2. The low melt index polyolefin of claim 1, wherein the alpha-olefin is an alpha-olefin having less than 12 carbon atoms.

3 . The low melt index polyolefin according to claim 2 , wherein the α-olefin is ethylene, propylene, 1-butene, 1-hexene or 1-octene. 4 .

4 . The low melt index polyolefin according to claim 1 , wherein the melting temperature of the polyolefin is 135-145° C. 5 .

5 . The low melt index polyolefin according to claim 1 , wherein the melt flow index of the polyolefin under the conditions of 220° C. and 21.6 kg is 0.1-10 g/10 min. 6 .

6. The low melt index polyolefin according to any one of claims 1 to 3, wherein the polyolefin increases the distance and/or the distance between the active centers of polymerization by loading a blocker with a large steric hindrance on the catalyst. It is prepared by the method of intermittently dormant polymerization active center with inert gas.

7. The application of the low melt index polyolefin according to any one of claims 1 to 3 in the preparation of impact and wear-resistant parts, packaging containers, polyolefin pipes, and polymer fiber spinning.