CN110627958B

CN110627958B - Polyethylene composition, method for improving grafting efficiency of polyethylene and application of polyethylene composition

Info

Publication number: CN110627958B
Application number: CN201910984560.8A
Authority: CN
Inventors: 蒋波; 蔡飞鹏; 秦显忠; 王波; 姜桂林
Original assignee: Energy Research Institute of Shandong Academy of Sciences
Current assignee: Energy Research Institute of Shandong Academy of Sciences
Priority date: 2019-10-16
Filing date: 2019-10-16
Publication date: 2021-11-16
Anticipated expiration: 2039-10-16
Also published as: CN110627958A

Abstract

The invention relates to the technical field of polyethylene modification, in particular to a polyethylene composition and a method for improving the grafting efficiency of polyethylene and its application. The polyethylene composition comprises: 71.0-98.88 parts of polyethylene, 1-10.0 parts of polar monomers, 0.01-5.0 parts of initiators, 0.1-10.0 parts of mesoporous molecular sieves, and 0.01-4.0 parts of antioxidants. The method includes the following steps: 1) mixing an initiator, a mesoporous molecular sieve and a solvent, stirring to obtain a suspension, filtering the obtained solid product and drying the obtained solid product in a vacuum to obtain an initiator/mesoporous molecular sieve composite 2) The polyethylene, the polar monomer, the antioxidant and the compound obtained in step 1) are extruded after mixing, and the polyethylene is grafted and modified during the extrusion process. The invention utilizes the free radical controlled diffusion technology formed by the nano-channels of the mesoporous molecular sieve, and realizes the purpose of continuously generating a reasonable concentration of free radicals during the polyethylene extrusion process.

Description

Polyethylene composition, method for improving grafting efficiency of polyethylene and application of polyethylene composition

Technical Field

The invention relates to the technical field of polyethylene modification, in particular to a polyethylene composition, a method for improving the grafting efficiency of polyethylene and application thereof.

Background

The information disclosed in this background of the invention is only for enhancement of understanding of the general background of the invention and is not necessarily to be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Polyethylene is a kind of general plastic with the largest output, has excellent electrical insulation, hydrophobicity, chemical solvent corrosion resistance, low temperature property and ductility, and has low cost and good processability, and mainly comprises low-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene propylene copolymer, ethylene octene copolymer, ethylene propylene diene monomer and the like. However, polyethylene is a non-polar material, and has poor dyeing property and adhesion property, and poor compatibility with other polar polymers, so that the defects restrict the application of the polyethylene in many fields.

Polar groups (such as carboxyl, anhydride, hydroxyl, epoxy, ester and the like) are introduced into the polyethylene chain segment to modify the polyethylene chain segment, so that the cohesiveness and the compatibility with polar polymers can be remarkably improved, and the application range of the material is expanded. Among the modification methods, the free radical grafting modification is carried out by using a reactive extrusion method in an extruder, so that the method has the advantages of short reaction time, continuous production, easy realization of industrialization and the like, and becomes the most applied polyethylene modification method. For example, patent document CN 102241797a discloses a method for preparing acrylic acid grafted polypropylene by using peroxide as an initiator and adopting a reactive extrusion process.

Patent document CN 103059785a discloses a heat-resistant transparent polyolefin hot melt adhesive and a preparation method thereof, wherein an ethylene-octene copolymer, polyethylene, a peroxide initiator, and a polar monomer are uniformly mixed, and then reaction extrusion is carried out in a twin-screw extruder at the temperature of 160-.

Patent document CN 101781389a discloses an itaconic acid grafted ethylene- α -octene copolymer and a preparation method thereof, wherein an ethylene- α -octene copolymer, a peroxide initiator, and an itaconic acid polar monomer are uniformly mixed in a high-speed mixer, and then are subjected to reaction extrusion in an extruder at a temperature of 160-.

Patent document CN 102766239 a discloses a method for preparing itaconic acid grafted ethylene-octene block copolymer granules, wherein ethylene-octene block copolymer, dibenzoyl peroxide as a peroxide initiator, itaconic acid polar monomer and antioxidant are uniformly mixed and stirred, and then the mixture is extruded by a twin-screw extruder at the temperature of 150 ℃ and 170 ℃ to obtain the itaconic acid grafted ethylene-octene block copolymer, wherein the grafting efficiency of the copolymer is 1.35-1.65%.

Patent document CN 101831131B discloses an itaconic acid grafted polyolefin elastomer copolymer, which is prepared by mixing a polyolefin elastomer, a peroxide initiator dicumyl peroxide, an itaconic acid polar monomer, and polyethylene wax in an internal mixer, and then performing reaction extrusion in an extruder.

Further, there are domestic and foreign documents concerning polar monomer graft-modified polyethylene in an extruder: maleic anhydride-grafted linear low density polyethylene (ref 1), itaconic acid-grafted low density polyethylene (ref 2), maleic anhydride-grafted ethylene octene copolymer/polypropylene blend (ref 3), itaconic acid-grafted ethylene octene copolymer (ref 4), itaconic acid-grafted low density polyethylene (ref 5), and the like, which are prepared by uniformly mixing polyethylene with a peroxide initiator, a polar monomer, and then performing reactive extrusion, the graft efficiencies of the prepared graft copolymers are all less than 1.5%.

As can be seen from the above prior art: when the polyethylene polar monomer is grafted and modified in an extruder, the polyethylene, the polar monomer and an initiator are uniformly mixed, and then the mixture is subjected to reactive extrusion at a specific extrusion temperature and a screw rotation speed.

Documents of the prior art

Document 1: Saade-Caballero H., Mart i nez-Colunga J.G.reactive extraction process for the grafting of maleic anhydride on to linear low-density polyethylene with ultraviral radiation. journal of Applied Polymer Science, 2009, 113 (5): 3125-3129.

Document 2: pesetski S.S., Jurkowski B., Krivozu Y.M.free-radial writing of itaconic acid on to LDPE by reactive exclusion I.Effect of initiator solubility Polymer,2001,42(2):469-

Document 3: patent, POE/PE, extrusion grafted maleic anhydride, plastic additive, 2006, 3: 21-23.

Document 4: preparation of itaconic acid grafted ethylene-1-octene copolymer [ J ] according to Wangke, Achillea, King Xiaoli, science and engineering of high molecular materials, 2011,27(10):46-48.

Document 5: study on the reaction extrusion of Lonicera japonica, Japanese plum-Low Density polyethylene with grafting of itaconic acid [ J ] Plastic science 2007,35(2):40-43.

Disclosure of Invention

The inventor further researches and discovers that: since the initiator is easily decomposed at high temperature of the extruder, so that excessive free radicals generated by the decomposition of the initiator in the initial stage of the extrusion reaction are generated, and besides the main reaction that grafting points are formed on polyethylene chain segments to initiate polar monomer grafting, the excessive grafting points can cause the generation of cross-linking side reaction, which not only remarkably reduces the efficiency of initiating polar monomer grafting polyethylene by peroxide, but also reduces the flowability and processability of the graft product, the grafting efficiency of the graft copolymer in the prior art is not high (both less than 1.5%), and the melt flowability of the graft product is reduced. In view of the above problems, the present invention is directed to a polyethylene composition and a method for improving grafting efficiency of polyethylene and its application.

In order to achieve the purpose, the invention adopts the following technical means:

firstly, the invention discloses a polyethylene composition, which comprises the following raw materials in parts by weight: 71.0-98.88 parts of polyethylene, 1-10.0 parts of polar monomer, 0.01-5.0 parts of initiator, 0.1-10.0 parts of mesoporous molecular sieve and 0.01-4.0 parts of antioxidant.

Secondly, the invention discloses a method for improving the grafting efficiency of polyethylene, which comprises the following steps:

(1) mixing an initiator, a mesoporous molecular sieve and a solvent, stirring to obtain a suspension, filtering the suspension, and then drying the obtained solid product in vacuum to obtain an initiator/mesoporous molecular sieve compound;

(2) mixing polyethylene, a polar monomer, an antioxidant and the compound obtained in the step (1), extruding, and grafting and modifying the polyethylene in the extrusion process:

(3) and (3) the extrudate obtained in the step (2) is subjected to traction, cooling, drying and grain cutting to obtain the composite material.

The polyethylene composition and the method for improving the grafting efficiency of the polyethylene provided by the invention are characterized in that: by utilizing a large number of nano-level pore channels contained in the mesoporous molecular sieve (the mesoporous molecular sieve is an inorganic material with nano-scale pore diameter, huge surface area and ordered three-dimensional pore channel structure), initiator molecules are limited in the nano-pore channels by preparing an initiator/mesoporous molecular sieve compound, the free radical generated by the decomposition of the initiator can be subjected to polyethylene grafting reaction only by diffusing out of the pore canal of the mesoporous molecular sieve, and based on the free radical controlled diffusion technology, the concentration of the free radical in the polyethylene extrusion process can be reasonably controlled, not only ensures that enough free radicals are available for the reaction of polyethylene grafting polar monomers, but also prevents the occurrence of polyethylene crosslinking side reaction caused by the excessively high concentration of the free radicals, greatly improves the initiation efficiency and the polyethylene grafting efficiency of the initiator, and well inhibits the occurrence of polyethylene crosslinking side reaction.

Compared with the prior art, the invention has the following beneficial effects: the invention utilizes the free radical controlled diffusion technology formed by mesoporous molecular sieve nano-pore channels to realize the purpose of continuously generating free radicals with reasonable concentration in the polyethylene extrusion process, thereby ensuring that the polyethylene generates enough free radicals to initiate polar monomers for grafting, preventing the concentration of the free radicals from being too high to cause polyethylene crosslinking side reaction, greatly improving the initiation efficiency of an initiator and the polyethylene grafting efficiency, and simultaneously ensuring the processing performance of a grafted product. Through tests, compared with the traditional method of directly mixing polyethylene, polar monomer and initiator for grafting, the grafting rate and the melt index of the invention adopting the mesoporous molecular sieve are obviously improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of an initiator/mesoporous molecular sieve composite in an embodiment of the invention.

Fig. 2 is a schematic diagram of the diffusion of free radicals in the nanopores of the mesoporous molecular sieve in the embodiment of the invention.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

As described above, in some conventional methods, when polyethylene polar monomer is grafted and modified in an extruder, polyethylene, polar monomer and initiator are mixed uniformly, and then reaction extrusion is performed at a specific extrusion temperature and a specific screw rotation speed, which has the defects that a large amount of free radicals are decomposed at the initial stage of the extrusion reaction, excessive active sites of grafting free radicals are formed on a polyethylene chain segment, the occurrence probability of cross-linking side reactions is remarkably increased, the efficiency of grafting polyethylene with polar monomer is reduced, and the flowability of a grafted product is reduced. Accordingly, the present invention is directed to a polyethylene composition and method for increasing the grafting efficiency of polyethylene.

In some exemplary embodiments, the polyethylene comprises: low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Linear Low Density Polyethylene (LLDPE), ethylene propylene copolymer (EPR), ethylene octene copolymer (POE), and Ethylene Propylene Diene Monomer (EPDM).

In some exemplary embodiments, the polar monomer comprises: one or more of maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, crotonic anhydride, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate and glycidyl methacrylate.

In some exemplary embodiments, the initiator comprises: dibenzoyl peroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, 1, 4-bis (t-butylperoxyisopropyl) benzene, methyl ethyl ketone peroxide, 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2-di (t-butylperoxy) -5,5, 6-trimethylbicyclo [2.2.1] heptane, 2-bis (3-methyl-1-butynyl-3-ylperoxy) 5,5, 6-trimethylbicyclo [2.2.1] heptane, 2, 5-dimethyl-2-hydroxy-5-t-butylperoxy-3-hexyne, di-t-butyl peroxide, 2-di-t-butyl-5-diperoxide, one or more of 5, 6-trimethylbicyclo (2,2, l) heptane.

In some exemplary embodiments, the mesoporous molecular sieve comprises a silicon-based, non-silicon-based mesoporous molecular sieve, including a mixture of one or more of silicates, aluminosilicates, zeolites, silicophosphates, silicoaluminophosphates, transition metal oxides, phosphates, and sulfides.

Preferably, the mesoporous molecular sieve is any one of ZSM-5, MCM-41, KIT-6 and SBA-15, more preferably any one of MCM-41, KIT-6 and SBA-15, and the pore diameters of the three mesoporous molecular sieves are larger, so that the grafting rate of the polyethylene can be improved more effectively, and the reduction of the melt index of a graft is kept small.

In some exemplary embodiments, the antioxidant comprises: pentaerythritol [ tetrakis (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] (antioxidant 1010), octadecyl 3- (3, 5-di-tert-butyl-4-hydroxy) propene (antioxidant 1076), hexamethylenediamine N, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) (antioxidant 1098), 2, 6-di-tert-butyl-4-cresol (antioxidant 264), 2,4, 6-tri-tert-butylphenol (antioxidant 246), and triester phosphite 2, 4-di-tert-butylphenyl (antioxidant 168) or a mixture of more thereof.

In some exemplary embodiments, in step (1), the solvent is absolute ethanol, so as to remove the solvent in the subsequent drying.

In some typical embodiments, in the step (1), the stirring temperature is 45-50 ℃ and the stirring time is 1-1.5 h.

In some exemplary embodiments, in the step (1), the drying temperature is 35 to 45 ℃ and the time is 10 to 13 hours.

In some exemplary embodiments, in the step (1), the extrusion process parameters are: the extrusion temperature is 140-250 ℃, the rotating speed of the main screw is 30-200 r/min, and the rotating speed of the feeding screw is 10-60 r/min. Preferably, the extrusion temperature is between 160 and 180 ℃, the rotation speed of the main screw is 100-200 rpm, and the rotation speed of the feed screw is 50-60 rpm.

In some exemplary embodiments, the polyethylene compositions described above, as well as methods for increasing the grafting efficiency of polyethylene, are also used for the production of structurally specialized polyolefin products, industrial catalysis, product separation, and the like.

The invention will now be further described with reference to the drawings and detailed description.

Example 1

A method for improving grafting efficiency of polyethylene comprises the following steps:

(1) weighing 91.5 parts of low-density polyethylene (by weight, the same below), 6.0 parts of maleic anhydride, 0.5 part of dibenzoyl peroxide and 10102.0 parts of antioxidant, and mixing the raw materials in a high-speed mixer for 30 min;

(2) adding the mixture obtained in the step (1) into a hopper of an extruder, wherein the temperature of each zone of the extruder is 160-180 ℃, the rotating speed of a main screw is 100 revolutions per minute, the rotating speed of a feeding screw is 50 revolutions per minute, and an extrudate is subjected to traction, cooling, drying and grain cutting, wherein the traction speed is 5 m/minute, the cooling water temperature is 40 ℃, the air drying speed is 30/second, the speed of the grain cutting machine is 10Hz, and the monomer is grafted with modified polyethylene particles.

Example 2

(1) weighing 86.5 parts of low-density polyethylene (by weight, the same below), 6.0 parts of maleic anhydride, 0.5 part of dibenzoyl peroxide, 55 parts of mesoporous molecular sieve ZSM-55 parts and 10102.0 parts of antioxidant for later use;

(2) placing dibenzoyl peroxide and ZSM-5 in a round-bottom flask, adding 100ml of absolute ethyl alcohol, stirring at 50 ℃ for 1h, then filtering the suspension solution, and drying the obtained solid in a vacuum oven at 40 ℃ for 12h to obtain the initiator/mesoporous molecular sieve composite.

(3) Mixing low-density polyethylene, maleic anhydride, an antioxidant 1010 and the compound obtained in the step (2) in a high-speed mixer for 30min, adding the obtained mixture into a hopper of an extruder, controlling the temperature of each zone of the extruder to be 160-180 ℃, controlling the rotation speed of a main screw to be 100 rpm and controlling the rotation speed of a feeding screw to be 50 rpm, and carrying out traction, cooling, drying and grain cutting on an extruded product, wherein the traction speed is 5 m/min, the cooling water temperature is 40 ℃, the air drying speed is 30/sec and the grain cutting machine speed is 10Hz to obtain the polar monomer graft modified polyethylene particles.

Example 3

A method for improving the grafting efficiency of polyethylene, which is the same as example 2, except that: the mesoporous molecular sieve adopted is MCM-41.

Example 4

A method for improving the grafting efficiency of polyethylene, which is the same as example 2, except that: the adopted mesoporous molecular sieve is KIT-6.

Example 5

A method for improving the grafting efficiency of polyethylene, which is the same as example 2, except that: the mesoporous molecular sieve is SBA-15.

Example 6

A method for improving the grafting efficiency of polyethylene, which is the same as example 1, except that: the polyethylene used is linear low density polyethylene.

Example 7

A method for improving the grafting efficiency of polyethylene, which is the same as example 2, except that: the polyethylene used is linear low density polyethylene.

Example 8

A method for improving the grafting efficiency of polyethylene, which is the same as example 7 except that: the mesoporous molecular sieve adopted is MCM-41.

Example 9

A method for improving the grafting efficiency of polyethylene, which is the same as example 7 except that: the adopted mesoporous molecular sieve is KIT-6.

Example 10

A method for improving the grafting efficiency of polyethylene, which is the same as example 7 except that: the mesoporous molecular sieve is SBA-15.

Example 11

(1) weighing 71 parts (by weight, the same below) of ethylene octene copolymer, 10 parts of maleic anhydride, 5 parts of tert-butyl hydroperoxide, 1510 parts of mesoporous molecular sieve SBA and 10764 parts of antioxidant for later use;

(2) placing tert-butyl hydroperoxide and SBA-15 into a round-bottom flask, adding 120ml of absolute ethyl alcohol, stirring at 50 ℃ for 1h, then filtering the suspension solution, and drying the obtained solid in a vacuum oven at 45 ℃ for 10h to obtain the initiator/mesoporous molecular sieve composite.

(3) Mixing the ethylene-octene copolymer, maleic anhydride, an antioxidant 1076 and the compound obtained in the step (2) in a high-speed mixer for 30min, adding the obtained mixture into a hopper of an extruder, wherein the temperature of each zone of the extruder is 180-250 ℃, the rotating speed of a main screw is 30 r/min, the rotating speed of a feeding screw is 10 r/min, and the extrudate is subjected to traction, cooling, drying and grain cutting, wherein the traction speed is 5 m/min, the cooling water temperature is 40 ℃, the air drying speed is 30/s, and the grain cutting speed is 10Hz, so that the polar monomer graft modified polyethylene particles are obtained.

Example 12

(1) weighing 98.88 parts of ethylene-propylene copolymer (by weight, the same below), 1.0 part of maleic anhydride, 0.01 part of lauroyl peroxide, 60.1 parts of mesoporous molecular sieve KIT and 10980.01 parts of antioxidant for later use;

(2) placing lauroyl peroxide and KIT-6 in a round-bottom flask, adding 120ml of absolute ethyl alcohol, stirring at 45 ℃ for 1.5h, filtering the suspension solution, and drying the obtained solid in a vacuum oven at 35 ℃ for 13h to obtain the initiator/mesoporous molecular sieve composite.

(3) Mixing an ethylene-propylene copolymer, maleic anhydride, an antioxidant 1098 and the compound obtained in the step (2) in a high-speed mixer for 30min, adding the obtained mixture into a hopper of an extruder, controlling the temperature of each zone of the extruder to be between 140 and 160 ℃, controlling the rotation speed of a main screw to be 200 revolutions per minute and controlling the rotation speed of a feeding screw to be 60 revolutions per minute, and carrying out traction, cooling, drying and grain cutting on an extruded product, wherein the traction speed is 5 m/min, the cooling water temperature is 40 ℃, the air drying speed is 30/sec and the grain cutting speed is 10Hz to obtain the polar monomer graft modified polyethylene particles.

And (3) performance testing:

the performance test of the polyethylene grafts prepared in examples 1-5 is shown in Table 1, wherein example 1 is a control group, which does not use a mesoporous molecular sieve, but uses a conventional method, and the components are directly mixed and then extruded.

TABLE 1

Examples	Mesoporous molecular sieve type	Pore diameter of mesoporous molecular sieve	Grafting efficiency%	Melt index/g.10 min
					1	—	—	0.62	0.9
2	ZSM-5	1.5-1.7nm	1.21	2.3
					3	MCM-41	3-5nm	2.79	1.9
4	KIT-6	7-8nm	3.85	2.2
					5	SBA-15	6-11nm	2.68	1.6

The performance tests of the polyethylene grafts prepared in examples 6-12 are shown in Table 1, wherein example 6 is a control which does not use a mesoporous molecular sieve, but instead uses conventional methods to directly mix the components and extrude the mixture.

TABLE 1

Examples	Molecular sieve type	Pore size of molecular sieve	Grafting efficiency%	Melt index/g.10 min
					6	—	—	0.51	0.5
7	ZSM-5	1.5-1.7nm	1.14	2.0
					8	MCM-41	3-5nm	3.63	1.3
9	KIT-6	7-8nm	4.26	1.8
					10	SBA-15	6-11nm	2.47	1.1
11	SBA-15	6-11nm	2.73	1.4
					12	KIT-6	7-8nm	3.96	2.0

As can be seen from tables 1 and 2, the maleic anhydride grafted low density polyethylene prepared by the conventional method has a grafting ratio of only 0.51-0.62% and a melt index reduced to below 0.9 g.10 min (the melt index of the low density polyethylene raw material is 2.5 g.10 min, and the melt index of the linear low density polyethylene raw material is 2.1 g.10 min). The invention is based on the free radical controlled diffusion technology formed by mesoporous molecular sieve nano-pore channels, after mesoporous molecular sieves with different pore sizes are added in the polyethylene reaction extrusion process, the polyethylene grafting efficiency is obviously improved, and simultaneously, the reduction range of the melt index of the obtained graft is also obviously reduced.

In addition, it can be seen from tables 1 and 2 that when ZSM-5 is used, the grafting ratio is lower than that of other molecular sieves, because the pore size of the molecular sieve of ZSM-5 is too small, the initiator molecules are difficult to diffuse out of the pore channels of the molecular sieve, and the low density polyethylene grafting reaction cannot be effectively initiated. The polyethylene grafting rate is gradually improved along with the increase of the diameter of the molecular sieve pore channel, the embodiment taking KIT-6 as the mesoporous molecular sieve has the highest grafting efficiency, the melt index of the grafting product is reduced to the minimum, and then the diameter of the molecular sieve pore channel is increased, for example, the grafting efficiency of the embodiment taking SAB-15 as the mesoporous molecular sieve is reduced on the contrary, and the degree of reduction of the melt index of the grafting product is improved, which indicates that the overlarge pore channel diameter is not favorable for the grafting reaction of the low-density polyethylene in an extruder.

Through further research of the invention, the reason for this is found to be: referring to fig. 1 and 2, initiator molecules are heated to decompose to generate free radicals, the free radicals can initiate polyethylene to form free radical active sites only after diffusing out of nano-pores of the mesoporous molecular sieve, the number of the free radicals diffusing out of the mesoporous molecular sieve is remarkably reduced due to the limitation of the diffusion of the nano-pores of the mesoporous molecular sieve, a cross-linking side reaction caused by the large decomposition of the free radicals at the initial stage of a grafting reaction is inhibited, the efficiency of the polar monomer grafting reaction is improved, the free radicals which do not diffuse out of the nano-pores with the mesoporous molecular weight generate a coupling termination reaction in the nano-pores, the initiator is formed again, and the initiator can be decomposed again to form the free radicals along with the reaction. The free radical controlled diffusion technology based on mesoporous molecular sieve nanopores realizes the purpose of continuously generating free radicals with reasonable concentration in the polyethylene extrusion process, namely, the polyethylene is ensured to generate enough free radicals to initiate polar monomers for grafting, the concentration of the free radicals is not too high to cause polyethylene crosslinking side reaction, the initiation efficiency and the polyethylene grafting efficiency of an initiator are greatly improved, and the processability of a grafted product is ensured.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. a method for improving polyethylene grafting efficiency, is characterized in that, with polyethylene composition as raw material, comprises the steps:

(1) mixing initiator, mesoporous molecular sieve and solvent, stirring, to obtain suspension, after it is filtered, the obtained solid product is vacuum-dried to obtain initiator/mesoporous molecular sieve composite;

(2) the compound obtained by polyethylene, polar monomer, antioxidant and step (1) is extruded after mixing, and polyethylene graft modification is carried out in the extrusion process:

(3) the extrudate obtained in step (2) is pulled, cooled, dried and pelletized, to obtain final product;

Wherein, the polyethylene composition, in parts by weight, consists of raw materials: 71.0-98.88 parts of polyethylene, 1-10.0 parts of polar monomers, 0.01-5.0 parts of initiators, 0.1-10.0 parts of mesoporous molecular sieves, Antioxidant 0.01-4.0 parts.

2. The method for improving the grafting efficiency of polyethylene according to claim 1, wherein the polyethylene comprises: low density polyethylene, high density polyethylene, linear low density polyethylene, ethylene propylene copolymer, ethylene A mixture of one or several polyethylenes in octene copolymer and EPDM rubber.

3. the method for improving polyethylene grafting efficiency as claimed in claim 1, is characterized in that, described polar monomer comprises: maleic acid, fumaric acid, itaconic acid, citraconic acid, crotonic acid, horse One of leic anhydride, itaconic anhydride, citraconic anhydride, crotonic anhydride, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate or a mixture of several.

4. the method for improving polyethylene grafting efficiency as claimed in claim 1, is characterized in that, described initiator comprises: dibenzoyl peroxide, dicumyl peroxide, benzoyl peroxide, peroxide Dodecanoyl, di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl peroxybenzoate, 1,4-bis(tert-butyl isopropyl peroxide) benzene, methyl ethyl ketone peroxide, 2,5-Dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,2-bis(tert-butylperoxy)-5,5,6-trimethylbicyclo[ 2.2.1] Heptane, 2,2-bis(3-methyl-1-butynyl-3-yllperoxy)5,5,6-trimethylbicyclo[2.2.1]heptane, 2,5 -Dimethyl-2-hydroxy-5-tert-butylperoxy-3-hexyne, di-tert-butyl peroxide, 2,2-diperoxy-tert-butyl-5,5,6-trimethyl One or more mixtures of bicyclo(2,2,l)heptane.

5. The method for improving the grafting efficiency of polyethylene according to claim 1, wherein the antioxidant comprises: [tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] Pentaerythritol ester, 3-(3,5-di-tert-butyl-4-hydroxy) allyl octadecyl, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl) Propionyl)hexanediamine, 2,6-di-tert-butyl-4-cresol, 2,4,6-tri-tert-butylphenol, (2,4-di-tert-butylphenyl) phosphite triester one or a mixture of several.

6 . The method for improving the grafting efficiency of polyethylene according to claim 1 , wherein the mesoporous molecular sieve is a silicon-based or non-silicon-based mesoporous molecular sieve. 7 .

7. The method for improving the grafting efficiency of polyethylene according to claim 6, wherein the mesoporous molecular sieve is silicate, aluminosilicate, zeolite, silicophosphate, silicoaluminophosphate, transition metal One or a mixture of oxides, phosphates and sulfides.

8. The method for improving the grafting efficiency of polyethylene according to claim 6, wherein the mesoporous molecular sieve is any one of ZSM-5, MCM-41, KIT-6, and SBA-15.

9 . The method for improving the grafting efficiency of polyethylene according to claim 8 , wherein the mesoporous molecular sieve is any one of MCM-41, KIT-6 and SBA-15. 10 .

10. The method for improving the grafting efficiency of polyethylene according to claim 1, characterized in that, in the step (1), anhydrous ethanol is used as the solvent.

11. The method for improving the grafting efficiency of polyethylene according to claim 1, wherein in step (1), the stirring temperature is 45-50°C, and the time is 1-1.5h.

12 . The method for improving the grafting efficiency of polyethylene according to claim 1 , wherein, in step (1), the drying temperature is 35-45° C. and the time is 10-13 h. 13 .

13. The method for improving the grafting efficiency of polyethylene according to claim 1, wherein in step (2), the process parameters of the extrusion are: extrusion temperature 140°C-250°C, main screw rotation speed 30°C -200 rpm, feeding screw speed 10-60 rpm.

14. The method for improving the grafting efficiency of polyethylene according to claim 13, characterized in that, the extrusion temperature is between 160°C and 180°C, the rotational speed of the main screw is 100-200 rpm, and the rotational speed of the feeding screw is 50-60°C. rev/min.

15. The application of the polyethylene graft prepared by the method of any one of claims 1 to 14 in the preparation of polyolefin products, industrial catalysis, and product separation.