CN1315891C - Method of preparing nano-polyethylene fiber using TiCl4/MCM-41 catalytic system extrusion polymerization - Google Patents

Abstract

The invention discloses a method for preparing nanometer polyethylene fibers by extruding and polymerizing a TiCl ₄ /MCM-41 catalytic system. Put carrier B in n-hexane, treat it with triethylaluminum at normal temperature, and then wash it with n-hexane; then add TiCl ₄ diluted with n-hexane to the n-hexane suspension treated with triethylaluminum, and Wash with n-hexane after the reaction under stirring; remove the n-hexane solvent by vacuum at room temperature to obtain a supported catalyst for polymerization, use triethylaluminum as a cocatalyst, and use the obtained loaded catalyst in the presence of β-cyclodextrin type catalyst for ethylene extrusion polymerization, and the diameter of the prepared nano polyethylene fiber is 30-80nm. The above-mentioned operation process is carried out under the protection of high-purity nitrogen. The production of the invention does not require specific production equipment, the process is simple, the cost is low, and the industrial production is easy.

Description

Method for preparing nano polyethylene fiber by extrusion polymerization with TiCl4/MCM-41 catalytic system

technical field

The invention relates to a method for preparing nano-polyethylene fibers through extrusion polymerization using a TiCl ₄ /MCM-41 catalytic system.

technical background

With the development of nanotechnology, nanomaterials are more and more widely used in practice. Nanofibers have become a research hotspot because of their large specific surface area and high strength. At present, the common preparation methods of nanofibers include gel spinning method, drawing method, electrospinning method, etc., but these preparation methods all require a series of specific processing equipment and complicated processing procedures.

Aida et al. reported a method of loading titanocene dichloride on mesoporous silica fibers, using MAO as a co-catalyst, and catalyzing ethylene polymerization at a high pressure of 1Mpa to prepare nano-polyethylene fibers, because the PE chains are stretched. Chain, so this fiber has higher strength, the discovery of this method has opened up a new way for preparing nanometer polyethylene fiber. ZhiBin Ye et al. used MCM-41 to load titanium dichloride to prepare nano-polyethylene fibers under a high pressure of 20 atmospheres.

These two methods require high polymerization pressure during the polymerization process, and relatively expensive metallocene catalysts are used, thus increasing the production cost.

Contents of the invention

The object of the present invention is to provide a kind of use TiCl ₄ /MCM-41 catalytic system to prepare nano polyethylene fiber through extrusion polymerization, it adopts mesoporous molecular sieve MCM-41 loading TiCl ₄ to prepare classical Ziegler-Natta catalyst, with the supported Type ZN catalysts were used to prepare nano-polyethylene fibers by extrusion polymerization under normal pressure.

The technical scheme that the present invention adopts is as follows:

First prepare loaded Ziegler-Natta catalyst, then use this catalyst to prepare the method for nano polyethylene fiber through extrusion polymerization, its step is as follows:

1. Supported Ziegler-Natta catalyst:

1) Material composition

Titanium compound A, A is TiCl ₄ ;

Carrier B, B is mesoporous molecular sieve MCM-41;

2) Preparation steps

Mix carrier B and n-hexane at a weight ratio of 1:25, treat with diluted triethylaluminum that is 5 times the weight of carrier B at room temperature for 1 to 3 hours, and then wash with n-hexane for 3 to 5 times; ₄ Add to the n-hexane suspension of carrier B treated with triethylaluminum, stir and react at room temperature for 1 to 3 hours, wash with n-hexane for 3 to 5 times; remove the remaining n-hexane solvent by vacuum, After drying, obtain a supported catalyst for polymerization;

2. Preparation of nano-polyethylene fibers through extrusion polymerization:

Under normal pressure, triethylaluminum is used as a cocatalyst, [Al]/[Ti] is 10-40, and in the presence of β-cyclodextrin with a weight of 15-40% of the supported catalyst, the obtained supported catalyst is used Carry out ethylene extrusion polymerization, the polymerization temperature of ethylene is 30-50°C, the polymerization time is 5-60 minutes, and the diameter of the prepared nano polyethylene fiber is 30-80nm;

The above-mentioned operation process is carried out under the protection of high-purity nitrogen.

The carrier B in the preparation process of the supported Ziegler-Natta catalyst is mesoporous molecular sieve MCM-41 with a pore size of 2.9 nm.

Compared with the background technology, the present invention has the beneficial effects of:

The invention adopts Z-N catalyst, has simple preparation process and low cost. Under normal pressure, the hydroxyl group of β-cyclodextrin is used to destroy the surface active center of MCM-41, and the nano-polyethylene fiber is prepared by extrusion polymerization. The production of such a nano-polyethylene fiber does not require specific production equipment, the process is simple, and the cost is low. , easy for industrial production.

Detailed ways

Example 1

Under nitrogen protection, 1 gram of MCM-41 (pore size: 2.9 nm) treated at 400°C was added to 40 ml of n-hexane, and 8 ml of triethylaluminum with a concentration of 0.955 mol/l was stirred at room temperature for 1 hour. Wash three times with normal hexane; add 5ml of TiCl ₄ normal hexane solution (0.91mol/l) and react at room temperature for 2 hours, then wash three times with normal hexane, remove the normal hexane solvent in vacuum, obtain the powdery solid catalyst, the loaded titanium of this catalyst The amount is 1.34 mmolTi/g.

Under normal pressure at 50°C, add 4.6mg of β-cyclodextrin and 16.5mg of TiCl ₄ /MCM-41 catalyst to 50ml of n-hexane, stir and react for 2 minutes, pass through ethylene gas to make it saturated, and then add 0.5ml of dilute Triethylaluminum ([Al]/[Ti]=20), the reaction is terminated with acidified ethanol after 30 minutes, and the product is filtered, washed and dried to obtain nano-polyethylene fibers with a diameter of 30-80 nm.

Example 2

Using the supported catalyst prepared in Example 1, carry out ethylene polymerization under normal pressure at 50°C, 3.8mg β-cyclodextrin and 23.9mg TiCl ₄ /MCM-41 catalyst, [Al]/[Ti]=20, reaction time After 30 minutes, the product is filtered, washed and dried to obtain nano polyethylene fibers with a diameter of 30-80 nm.

Example 3

Using the supported catalyst prepared in Example 1, carry out ethylene polymerization under normal pressure at 30°C, 4.3mg β-cyclodextrin and 18.8mg TiCl ₄ /MCM-41 catalyst, [Al]/[Ti]=20, reaction time After 30 minutes, the product is filtered, washed and dried to obtain nano polyethylene fibers with a diameter of 30-80 nm.

Example 4

Using the supported catalyst prepared in Example 1, carry out ethylene polymerization under normal pressure at 30°C, 9.3mg β-cyclodextrin and 25.1mg TiCl ₄ /MCM-41 catalyst, [Al]/[Ti]=20, reaction time After 30 minutes, the product is filtered, washed and dried to obtain nano polyethylene fibers with a diameter of 30-80 nm.

Claims (1)

1, uses TiCl ₄/ MCM-41 catalytic system extrusion polymerization is equipped with the method for nano-polyethylene fiber, it is characterized in that at first preparing the loading type Ziegler-Natta catalyst, prepares the method for nano-polyethylene fiber with this catalyzer through extruding polymerization then, and its step is as follows:

One, loading type Ziegler-Natta catalyst:

1) material is formed

Titanium compound A, A are TiCl ₄

Carrier B, B is mesopore molecular sieve MCM-41;

2) preparation process

Carrier B is mixed according to weight ratio with normal hexane at 1: 25, and normal temperature was handled 1～3 hour with the dilution triethyl aluminum of 5 times of carrier B weight down, washed 3～5 times with normal hexane then; TiCl with the normal hexane dilution ₄Join in the normal hexane suspension liquid of the carrier B that triethyl aluminum was handled, stirring reaction is 1～3 hour under the room temperature, washes 3～5 times with normal hexane; Adopt the method for vacuum to remove remaining normal hexane solvent, obtain the loaded catalyst that polymerization is used after the drying;

Two, the preparation for preparing nano-polyethylene fiber through extruding polymerization:

Under the normal pressure, with the triethyl aluminum is promotor, [Al]/[Ti] is 10～40, in the presence of the beta-cyclodextrin of loaded catalyst weight 15～40%, carry out the ethene extruding polymerization with the loaded catalyst that obtains, the polymerization temperature of ethene is 30～50 ℃, and polymerization time is 5～60 minutes, and the nano-polyethylene fiber diameter that makes is 30～80nm;

Above-mentioned operating process is all carried out under the protection of high purity nitrogen;

Carrier B in the described loading type Ziegler-Natta catalyst preparation process is mesopore molecular sieve MCM-41, and its aperture is 2.9nm.