CN112342635A

CN112342635A - Preparation method of high-performance polyethylene fiber

Info

Publication number: CN112342635A
Application number: CN202011343381.5A
Authority: CN
Inventors: 张淑文; 王颂杨; 陈国旺
Original assignee: Ningbo Lianzeng New Material Technology Co ltd
Current assignee: Ningbo Lianzeng New Material Technology Co ltd
Priority date: 2020-11-25
Filing date: 2020-11-25
Publication date: 2021-02-09
Anticipated expiration: 2040-11-25
Also published as: CN112342635B

Abstract

The invention discloses a preparation method of high-performance polyethylene fibers. Preparing polyethylene by using an inert solvent with a bubble point of more than 100 ℃ under standard pressure, polymerizing to obtain a mixed solution of the polyethylene and the inert solvent, directly using the mixed solution as a production raw material of polyethylene fibers, introducing the mixed solution into a screw extruder after preparing to obtain a spinning solution, spraying the spinning solution from a spinneret orifice after metering, quenching the spinning solution into gel fibers in a cold water bath, and then performing extraction drying and super-drawing to obtain the high-performance polyethylene fibers. The inert solvent adopted by the invention has high boiling point and high viscosity, the movement of the polyethylene chain generated in the polymerization process is limited, and the chains are difficult to form entanglement, so that a better nascent chain structure can be kept, and the problem of difficult dissolution of polyethylene particles in the gel spinning process is fundamentally solved.

Description

Preparation method of high-performance polyethylene fiber

Technical Field

The invention relates to the field of preparation of polyethylene fibers, in particular to a preparation method of a high-performance polyethylene fiber.

Background

Polyethylene fibers are the third generation of high performance fibers that emerged in the early 90 s of the 20 th century. The composite material has excellent mechanical properties, and also has the characteristics of small density, good weather resistance, chemical corrosion resistance, good low-temperature resistance, wear resistance, good bending resistance, good cutting resistance, high specific energy absorption, low conductivity, X-ray permeability, certain waterproofness and the like, and is widely applied to various fields of national defense and military equipment, aerospace, ocean engineering, transportation, sports equipment and the like.

The main production method of polyethylene fiber is gel spinning and super-drawing technology, which is firstly applied for patent by Dutch DSM company, and the main steps of the method are as follows: adding polyethylene particles into a proper solvent, stirring and dissolving to prepare a solution, extruding the solution by a screw extruder, forming through a spinneret orifice, cooling, extracting, drying and carrying out super-drawing to finally obtain the high-strength high-modulus polyethylene fiber. Among them, the preparation of polyethylene solution is critical.

High performance polyethylene fibers generally require polyethylene to have an extremely high molecular weight, whereas high molecular weight polyethylene has an ultra-long flexible chain structure with severe intermolecular and intramolecular entanglement. The dissolution process of polyethylene powder particles in a solvent is essentially a process in which the entanglement among macromolecules is gradually broken up and disentangled by solvent molecules, and the process can be divided into two stages: swelling and dissolution. In the swelling stage, the solvent is mainly permeated and diffused into the polyethylene, and the key point of the uniform dissolution and mixing is realized. However, the swelling process is slow, and insufficient swelling results in the formation of a highly viscous layer on the surface of the polyethylene particles, which prevents the solvent from continuously penetrating and diffusing further into the polymer and also prevents the diffusion of macromolecules into the solvent.

The larger the molecular weight of the polyethylene, the larger the maximum drawing factor that the gel yarn can bear, and the higher the strength of the finished fiber obtained. However, the molecular weight should not be too high. Too large molecular weight leads to increased intermolecular forces, severe chain entanglement within and between molecular chains, and is extremely disadvantageous for uniform dissolution. The form of polyethylene powder particles also influences the dissolving process, the swelling and dissolving degrees of powder materials with different particle sizes and bulk densities in a solvent are different, and the part which is not fully dissolved forms defects in the spinning process, so that the product performance is greatly influenced. In addition, the concentration of polyethylene in the solution is also limited by the dissolution process, and the dissolution is difficult when the concentration is too high, and the fluidity and the spinnability are poor; too low concentration, too few entanglement points among molecular chains, high cost and poor economical efficiency.

In the traditional process, polyethylene powder is directly put into spinning solution for swelling and dissolving, and the swelling process of 8 wt% polyethylene needs tens of minutes, so that the yield is greatly influenced, and economic production cannot be achieved. To solve this problem, prior patents propose various solutions.

Chinese patent CN 1160093a proposes a continuous preparation method of ultra-high molecular weight polyethylene fiber, which pre-swells the powdery ultra-high molecular weight polymer in a pre-swelling kettle equipped with a novel stirrer and a baffle to prepare a suspension solution. Chinese patent CN 20041009607615 proposes a continuous preparation and mixing method of ultra-high molecular weight polyethylene solution, and proposes that a static mixer and a screw with a short length-diameter ratio are adopted to continuously prepare and mix the ultra-high molecular weight polyethylene solution. Chinese patent CN 101608344a accelerated dissolution by adding high shear to the dissolution kettle to moderately unwind polyethylene.

Although the methods provided by the prior art can increase the swelling and dissolving speed to a certain extent, the production efficiency of high-performance polyethylene fibers cannot be fundamentally improved.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a preparation method of a high-performance polyethylene fiber. According to the preparation method of the high-performance polyethylene fiber, the inert solvent used for gel spinning is directly used as the solvent in the polymerization process, the mixture of the polyethylene and the solvent obtained by polymerization does not need to be completely separated, and the mixture is directly used as the production raw material of the polyethylene fiber, so that the process flow is greatly simplified. The inert solvent used for spinning is used as a polymerization solvent, and due to the fact that the boiling point is higher, the viscosity is higher, the movement of polyethylene chains generated in the polymerization process is limited, and entanglement is difficult to form between the chains, so that a good nascent state chain structure can be kept, the problem that polyethylene particles are difficult to dissolve in a gel spinning process can be fundamentally solved, and the time required for dissolving polyethylene in the solvent is greatly shortened. The preparation method provided by the invention can further improve the concentration of the polyethylene in the spinning solution, thereby improving the production efficiency. In addition, the initial entanglement degree of the nascent polyethylene generated in the polymerization process is lower, so that the polyethylene fiber prepared by the invention has better performance.

The preparation method of the high-performance polyethylene fiber provided by the invention comprises the following steps:

1) introducing ethylene, an inert solvent, a polymerization catalytic system and hydrogen into a polymerization reactor, and preparing a mixed solution of polyethylene and the inert solvent by slurry polymerization, wherein the mass concentration of the polyethylene in the mixed solution of polyethylene and inert solvent is less than or equal to 99 wt%.

2) Heating the mixed solution of polyethylene and an inert solvent to 100-300 ℃ under the protection of nitrogen, removing gasified components through nitrogen gas stripping, adding spinning solution and an antioxidant, stirring and dissolving to prepare uniform polyethylene spinning solution, introducing the uniform polyethylene spinning solution into a screw extruder, metering the polyethylene spinning solution by a metering pump, spraying the polyethylene spinning solution from a spinneret orifice, quenching the polyethylene spinning solution into gel fibers in a cold water bath, and performing extraction drying and super-drawing to obtain the polyethylene fibers. In the polyethylene spinning solution, the mass concentration of polyethylene is less than or equal to 99 wt%.

The preparation process can be carried out continuously or batchwise.

The polymerization catalyst system consists of a solid catalyst containing a transition metal component and a cocatalyst, wherein the transition metal component is a metal of IVB or VB group in the periodic table system.

The inert solvent has a bubble point at standard pressure of greater than 100 ℃ and is an alkane, cycloalkane, aromatic hydrocarbon, or a derivative of an alkane/cycloalkane/aromatic hydrocarbon, or a mixture of any of them; preferably, the bubble point is greater than 130 deg.C, more preferably greater than 150 deg.C.

The additional spinning dope is the inert solvent in step 1), is liquid at standard pressure and polyethylene dissolution temperature, and is alkane, cycloalkane, aromatic hydrocarbon, or a derivative of alkane/cycloalkane/aromatic hydrocarbon, or a mixture of any of them.

The supplementary antioxidant is one of antioxidant CA, antioxidant 1010, antioxidant 1076 and mixed antioxidant B225, or a mixture of any more of the above. The ratio of the mass of the added antioxidant to the mass of the polyethylene in the solution is greater than 0.005%.

The viscosity average molecular weight of the polyethylene and the polyethylene fiber is more than 1000000 g/mol.

The super-stretching is thermal stretching of more than 1 grade in a temperature range of more than 100 ℃, and the total stretching multiple is more than 10 times.

The invention also provides a polyethylene fiber product prepared according to the preparation method. Because the initial entanglement degree of the nascent polyethylene generated in the polymerization process is low, the polyethylene fiber prepared by the invention has the tensile strength of more than 4GPa and the tensile modulus of more than 150 GPa. The tensile strength and tensile modulus of polyethylene fibers are determined according to the national standard GB/T1040. The viscosity average molecular weight of the resulting polyethylene fibers is preferably greater than 3000000g/mol, more preferably greater than 6000000 g/mol.

Compared with the prior art, the invention has the following beneficial effects (advantages):

(1) the preparation method provided by the invention utilizes the inert solvent used for gel spinning as the solvent in the polymerization process, the polyethylene and the solvent mixture obtained by polymerization do not need to be completely separated, and the mixture is directly used as the production raw material of the polyethylene fiber, thereby greatly simplifying the process flow.

(2) The preparation method provided by the invention adopts the inert solvent used for the gel spinning as the polymerization solvent, and as the boiling point is higher, the viscosity is higher, the movement of the polyethylene chains generated in the polymerization process is limited, and the chains are difficult to be tangled, so that a better nascent chain structure can be maintained, the problem of difficult dissolution of polyethylene particles in the gel spinning process can be fundamentally solved, and the time for dissolving the polyethylene in the solvent is greatly shortened.

(3) The preparation method provided by the invention enables polyethylene chains in the spinning solution to be fully stretched, the stretching times in the hot stretching process are larger, and the prepared polyethylene fiber has the tensile strength of more than 4GPa and the tensile modulus of more than 150 GPa.

Detailed Description

The following examples are offered to those of ordinary skill in the art to make and evaluate the present invention, and are intended to be merely exemplary of the disclosure and not to limit the scope thereof. Although efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), some errors and deviations should be accounted for. Unless otherwise specified, temperature is in units of ° c or at ambient temperature, and pressure is at or near atmospheric pressure.

The preparation method of the high-performance polyethylene fiber comprises the following steps:

introducing ethylene, an inert solvent, a polymerization catalytic system and hydrogen into a polymerization reactor, and preparing a mixed solution of polyethylene and the inert solvent by adopting slurry polymerization.

The inert solvent has a bubble point greater than 100 ℃ at standard pressure and is an alkane, cycloalkane, aromatic hydrocarbon, or a derivative of an alkane/cycloalkane/aromatic hydrocarbon, or a mixture of any of them. Preferably, the bubble point is greater than 130 ℃, more preferably greater than 150 ℃, such as one of high boiling mineral oil, paraffin oil, kerosene, decalin.

The polymerization catalyst system used in the present invention is composed of a solid catalyst containing a transition metal component and a cocatalyst. The transition metal component includes a metal of group IVB or VB of the periodic Table system. Typical transition metal component-containing solid catalysts used for preparing high density polyethylene resins preferably use Ziegler-Natta catalysts. Particularly preferred transition metal components include titanium halides, alkoxyalkyl magnesium compounds, and alkyl aluminum dihalides supported on inorganic oxide supports. The cocatalyst is preferably an aluminum alkyl, especially a trialkylaluminum, for example trimethylaluminum, triethylaluminum and triisobutylaluminum. The ratio of the active solid catalyst component to the promoter aluminum alkyl component is 1:25 to 1:500 in terms of Ti/Al molar ratio.

Hydrogen is used to adjust the molecular weight and lower molecular weight polyethylene is obtained by increasing the hydrogen concentration in the slurry polymerization process.

Slurry polymerization can be divided into two process routes, a stirred tank slurry polymerization process and a loop slurry polymerization process, depending on the reactor. Both process routes are suitable for use in the present invention.

The slurry polymerization can be divided into a continuous slurry polymerization process and a batch slurry polymerization process according to whether the slurry polymerization process is intermittent or not. The present invention may be either a continuous slurry polymerization process or a batch slurry polymerization process.

If the slurry polymerization process is continuous, ethylene, inert solvent and a polymerization catalyst system are continuously added in the polymerization process, reaction products are continuously led out, the solid content of the outlet of the reactor needs to be monitored during the continuous polymerization process, and the molecular weight and the slurry concentration of polyethylene are controlled by the conditions of the volume of the reactor, the adding amount of the catalyst, the polymerization temperature and pressure, the hydrogen concentration and the like.

If the slurry polymerization process is intermittent, the inert solvent and the polymerization catalytic system are added at one time in the polymerization process, ethylene is continuously introduced in the reaction process to ensure that the reaction pressure is constant, and a reaction product is extracted at one time after the reaction is finished. The molecular weight of the polyethylene and the slurry concentration are controlled by the conditions of catalyst addition, polymerization temperature and pressure, polymerization time, hydrogen concentration and the like.

In the present invention, an inert solvent having a bubble point of more than 100 ℃ at a standard pressure is used as a slurry polymerization solvent, preferably one of high boiling point mineral oil, paraffin oil, kerosene, decalin, and the inert solvent used in the present invention has a higher molecular weight and a higher viscosity, resulting in a lower polymerization activity in slurry polymerization, compared to aliphatic alkane solvents such as isobutane, n-hexane, n-heptane, etc., used in conventional slurry polymerization. In order to improve the polymerization activity, reduce the production cost and improve the production benefit, the reaction temperature and the reaction pressure adopted by the invention can be improved on the basis of the conventional operation conditions.

In the present invention, the reaction temperature in the reactor needs to be high enough to achieve an acceptable activity of the catalyst. On the other hand, the temperature should not exceed the softening temperature of the polymer. Generally, the temperature is in the range of 40 to 100 ℃, preferably 50 to 90 ℃, and the pressure is in the range of 1 to 20bar, preferably 8 to 15 bar.

In the obtained mixed solution of polyethylene and inert solvent, the mass concentration of polyethylene is not more than 99 wt%, preferably not more than 80 wt%, more preferably not more than 50 wt%.

The viscosity average molecular weight of the polyethylene is greater than 1000000g/mol, preferably greater than 3000000g/mol, more preferably greater than 6000000 g/mol.

Viscosity average molecular weight

According to GB1841-1980, the intrinsic viscosity [ eta ] of polyethylene is measured]Then according to

K and alpha are constants, from which the viscosity average molecular weight is calculated

And then, heating the mixed solution of polyethylene and an inert solvent to a dissolving temperature under the protection of nitrogen, removing gasified components through nitrogen gas stripping, supplementing the spinning solution and an antioxidant, and stirring and dissolving to obtain a uniform polyethylene spinning solution. The dissolving temperature is 100-300 ℃, and the polyethylene can be prevented from being oxidized at high temperature under the protection of nitrogen.

The additional spinning solution is an inert solvent in slurry polymerization, is liquid at the polyethylene dissolution temperature, and can be alkane, cycloalkane, aromatic hydrocarbon, or alkane/cycloalkane/aromatic hydrocarbon derivative, or a mixture of any one of the above, preferably one of high boiling point mineral oil, paraffin oil, kerosene and decalin. In the polyethylene spinning solution, the mass concentration of polyethylene is less than or equal to 99 wt%, preferably less than or equal to 80 wt%, and more preferably less than or equal to 50 wt%.

Because the initial entanglement degree between the generated polyethylene chains is lower and the polyethylene chains are initially swelled in the reaction kettle, the dissolution time can be greatly reduced, and the polyethylene chains are fully stretched in the obtained polyethylene spinning solution, so that the dissolution effect is better.

Then the spinning solution is introduced into a screw extruder, is metered by a metering pump and then is sprayed out from a spinneret orifice, and then enters a cold water bath for quenching to form the gel fiber. The screw extruder can be any one of a single screw, a double screw, a triple screw, a quadruple screw and the like, and the working temperature of the screw extruder is kept within the range of 80-300 ℃. The temperature of the cold water bath is less than 5 ℃.

The gel fiber is extracted, dried and super-stretched to obtain the high-strength high-modulus polyethylene fiber. The super-stretching is more than 1-stage hot stretching in a range of more than 100, and the total stretching multiple is more than 10 times.

Because the initial entanglement degree of the nascent polyethylene generated in the polymerization process is low, the polyethylene fiber prepared by the invention has the tensile strength of more than 4GPa and the tensile modulus of more than 150 GPa. The tensile strength and tensile modulus of polyethylene fibers are determined according to the national standard GB/T1040. The viscosity average molecular weight of the polyethylene fibers is more than 1000000g/mol, preferably more than 3000000g/mol, more preferably more than 6000000 g/mol.

Example (b):

the test method comprises the following steps:

viscosity average molecular weight of polyethylene

The tensile strength and tensile modulus of polyethylene fibers are determined according to the national standard GB/T1040.

Example 1:

ethylene, an inert solvent, decalin (bubble point 191 ℃ at standard pressure), and a silica-supported titanium magnesium catalyst were introduced together with triethylaluminum in a 250L polymerization reactor in a continuous manner to produce polyethylene by slurry polymerization. The catalyst feed rate was 2g (Ti)/h and the molar ratio of aluminum in the cocatalyst to titanium in the solid component was 200. The reaction temperature is 60 ℃, the reaction pressure is 8bar, the residence time of the reactor is 2.5h, and the stirring speed is 500 r/m.

And continuously introducing the mixed solution of the polyethylene and the inert solvent obtained by the reaction into a dissolving kettle, further raising the dissolving temperature to 150 ℃ under the protection of nitrogen, adding decalin and 0.01 wt% of antioxidant 1010, and stirring and dissolving for 5 minutes to obtain the uniform polyethylene spinning solution. A portion of the sample was taken to measure the slurry concentration and polymer molecular weight. The mass concentration of the slurry was 20.2 wt%, and the viscosity-average molecular weight of the polymer was 630 ten thousand.

Introducing a polyethylene spinning solution into a double-screw extruder, wherein the working temperature is 260 ℃, the polyethylene spinning solution is metered by a metering pump and then is sprayed out from a circular spinneret orifice with the length-diameter ratio of 10 at the spraying speed of 5m/min, the polyethylene spinning solution enters a cold water bath at the temperature of-1-3 ℃ to be quenched into gel fibers, the gel fibers are remained for 1min and then are extracted, dried and stretched in an over-time mode, the stretching temperature is 130 ℃, the total stretching multiple is 40, the high-strength high-modulus polyethylene fibers are obtained, and the stretching strength and the stretching modulus are measured. The tensile strength was 4.2GPa and the tensile modulus was 201 GPa.

Example 2:

polyethylene was continuously produced by slurry polymerization by continuously introducing ethylene, an inert solvent mineral oil (bubble point at standard pressure 367 ℃ C.) and a silica-supported titanium magnesium catalyst together with triethylaluminum into a 250L polymerization reactor. The catalyst feed rate was 2g (Ti)/h and the molar ratio of aluminum in the cocatalyst to titanium in the solid component was 200. The reaction temperature is 60 ℃, the reaction pressure is 8bar, the residence time of the reactor is 2.5h, and the stirring speed is 500 r/m.

And continuously introducing the mixed solution of the polyethylene and the inert solvent obtained by the reaction into a dissolving kettle, further raising the dissolving temperature to 150 ℃ under the protection of nitrogen, adding the same mineral oil and 0.01 wt% of antioxidant 1010, stirring and dissolving for 5 minutes to obtain the uniform polyethylene spinning solution. A portion of the sample was taken to measure the slurry concentration and polymer molecular weight. The mass concentration of the slurry was 15.2 wt%, and the viscosity-average molecular weight of the polymer was 606 ten thousand.

Introducing a polyethylene spinning solution into a double-screw extruder, wherein the working temperature is 260 ℃, the polyethylene spinning solution is metered by a metering pump and then is sprayed out from a circular spinneret orifice with the length-diameter ratio of 10 at the spraying speed of 5m/min, the polyethylene spinning solution enters a cold water bath at the temperature of-1-3 ℃ to be quenched into gel fibers, the gel fibers are remained for 1min and then are extracted, dried and stretched in an over-time mode, the stretching temperature is 130 ℃, the total stretching multiple is 40, the high-strength high-modulus polyethylene fibers are obtained, and the stretching strength and the stretching modulus are measured. The tensile strength was 5.1GPa, and the tensile modulus was 241 GPa.

Example 3:

a mixed solution of ethylene, mineral oil as an inert solvent and n-heptane (n-heptane mass fraction 10 wt%, bubble point 151 ℃ at standard pressure) was continuously introduced into a polymerization reactor having a volume of 250L, and a silica-supported titanium magnesium catalyst was introduced together with triethylaluminum, and polyethylene was continuously produced by slurry polymerization. The catalyst feed rate was 2g (Ti)/h and the molar ratio of aluminum in the cocatalyst to titanium in the solid component was 200. The reaction temperature is 60 ℃, the reaction pressure is 8bar, the residence time of the reactor is 2.5h, and the stirring speed is 500 r/m.

And continuously introducing the mixed solution of the polyethylene and the inert solvent obtained by the reaction into a dissolving kettle, further raising the temperature to the dissolving temperature of 150 ℃ under the protection of nitrogen, removing a gasified component of n-heptane by nitrogen gas stripping, supplementing the same mineral oil and 0.01 wt% of antioxidant 1010, stirring and dissolving for 5 minutes to obtain the uniform polyethylene spinning solution. A portion of the sample was taken to measure the slurry concentration and polymer molecular weight. The mass concentration of the slurry was 17.7% by weight, and the viscosity-average molecular weight of the polymer was 669 ten thousand.

Introducing a polyethylene spinning solution into a double-screw extruder, wherein the working temperature is 260 ℃, the polyethylene spinning solution is metered by a metering pump and then is sprayed out from a circular spinneret orifice with the length-diameter ratio of 10 at the spraying speed of 5m/min, the polyethylene spinning solution enters a cold water bath at the temperature of-1-3 ℃ to be quenched into gel fibers, the gel fibers are remained for 1min and then are extracted, dried and stretched in an over-time mode, the stretching temperature is 130 ℃, the total stretching multiple is 40, the high-strength high-modulus polyethylene fibers are obtained, and the stretching strength and the stretching modulus are measured. The tensile strength was 4.8GPa and the tensile modulus was 224 GPa.

Example 4:

ethylene, an inert solvent paraffin oil (bubble point 225 ℃ at standard pressure), and a silica-supported titanium magnesium catalyst were introduced together with triethylaluminum in a 250L polymerization reactor in a continuous manner to prepare polyethylene by slurry polymerization. The catalyst feed rate was 2g (Ti)/h and the molar ratio of aluminum in the cocatalyst to titanium in the solid component was 200. The reaction temperature is 60 ℃, the reaction pressure is 8bar, the residence time of the reactor is 5h, and the stirring speed is 500 r/min.

And continuously introducing the mixed solution of the polyethylene and the inert solvent obtained by the reaction into a dissolving kettle, further raising the dissolving temperature to 150 ℃ under the protection of nitrogen, adding the same paraffin oil and 0.01 wt% of antioxidant 1010, stirring and dissolving for 5 minutes to obtain the uniform polyethylene spinning solution. A portion of the sample was taken to measure the slurry concentration and polymer molecular weight. The mass concentration of the slurry was 57.2 wt%, and the viscosity-average molecular weight of the polymer was 722 ten thousand.

Introducing a polyethylene spinning solution into a double-screw extruder, wherein the working temperature is 260 ℃, the polyethylene spinning solution is metered by a metering pump and then is sprayed out from a circular spinneret orifice with the length-diameter ratio of 10 at the spraying speed of 5m/min, the polyethylene spinning solution enters a cold water bath at the temperature of-1-3 ℃ to be quenched into gel fibers, the gel fibers are remained for 1min and then are extracted, dried and stretched in an over-time mode, the stretching temperature is 130 ℃, the total stretching multiple is 40, the high-strength high-modulus polyethylene fibers are obtained, and the stretching strength and the stretching modulus are measured. The tensile strength was 5.6GPa and the tensile modulus was 273 GPa.

Example 5:

inert solvent mineral oil (bubble 367 ℃ under standard pressure), silicon dioxide supported titanium magnesium catalyst and triethyl aluminum are added into a polymerization reactor with the volume of 250L at one time, the slurry polymerization is adopted to prepare polyethylene intermittently, and ethylene is continuously introduced in the reaction process to ensure that the reaction pressure is constant. The amount of the catalyst added was 5g, the molar ratio of aluminum in the co-catalyst to titanium in the solid component was 200, and the amount of the inert solvent added was 100L. The reaction temperature was 60 ℃, the reaction pressure was 8bar, and the stirring rate was 500 rpm.

And after the reaction is finished, leading out a reaction product at one time, then leading the reaction product into a dissolving kettle, further raising the temperature to the dissolving temperature of 150 ℃ under the protection of nitrogen, supplementing the same mineral oil and 0.01 wt% of antioxidant 1010, and stirring and dissolving for 5 minutes to prepare the uniform polyethylene spinning solution. A portion of the sample was taken to measure the slurry concentration and polymer molecular weight. The slurry had a mass concentration of 13.5% by weight and the polymer had a weight average molecular weight of 692 ten thousand.

Introducing a polyethylene spinning solution into a double-screw extruder, wherein the working temperature is 260 ℃, the polyethylene spinning solution is metered by a metering pump and then is sprayed out from a circular spinneret orifice with the length-diameter ratio of 10 at the spraying speed of 5m/min, the polyethylene spinning solution enters a cold water bath at the temperature of-1-3 ℃ to be quenched into gel fibers, the gel fibers are remained for 1min and then are extracted, dried and stretched in an over-time mode, the stretching temperature is 130 ℃, the total stretching multiple is 40, the high-strength high-modulus polyethylene fibers are obtained, and the stretching strength and the stretching modulus are measured. The tensile strength was 4.5GPa and the tensile modulus was 221 GPa.

Comparative example 1:

an inert solvent heptane (bubble point of 92 ℃ under standard pressure), a silicon dioxide supported titanium magnesium catalyst and triethyl aluminum are added into a polymerization reactor with the volume of 250L at one time, the slurry polymerization is adopted to prepare polyethylene intermittently, and ethylene is continuously introduced in the reaction process to ensure that the reaction pressure is constant. The amount of the catalyst added was 5g, the molar ratio of aluminum in the co-catalyst to titanium in the solid component was 200, and the amount of heptane, an inert solvent, was 100L. The reaction temperature was 60 ℃, the reaction pressure was 8bar, and the stirring rate was 500 rpm.

And after the reaction is finished, the reaction product is led out at one time, the polyethylene is separated from the heptane, and the polyethylene powder is obtained after the polyethylene is fully dried.

Adding polyethylene powder, spinning solution mineral oil and 0.01 wt% of antioxidant 1010 into a dissolving kettle, raising the dissolving temperature to 150 ℃ under the protection of nitrogen, and stirring for dissolving for 10 minutes to obtain a partially uniform polyethylene spinning solution. A portion of the sample was taken to measure the slurry concentration and polymer molecular weight. The mass concentration of the slurry was 8.5 wt%, and the viscosity-average molecular weight of the polymer was 701 ten thousand.

Introducing a polyethylene spinning solution into a double-screw extruder, wherein the working temperature is 260 ℃, the polyethylene spinning solution is metered by a metering pump and then is sprayed out from a circular spinneret orifice with the length-diameter ratio of 10 at the spraying speed of 5m/min, the polyethylene spinning solution enters a cold water bath at the temperature of-1-3 ℃ to be quenched into gel fibers, the gel fibers are remained for 1min and then are extracted, dried and stretched in an over-time mode, the stretching temperature is 130 ℃, the total stretching multiple is 40, the high-strength high-modulus polyethylene fibers are obtained, and the stretching strength and the stretching modulus are measured. The tensile strength was 3.5GPa and the tensile modulus was 180 GPa.

TABLE 1

The above examples and comparative examples show that the polyethylene fiber of the present invention can be prepared by using the inert solvent used in the gel spinning as the solvent in the polymerization process, such as decalin, mineral oil, paraffin oil, and the polymerized product can maintain a good nascent chain structure without separation and drying, and can be stirred, swelled and dissolved in the dissolution kettle for 5 minutes to obtain a uniform polyethylene spinning solution with a slurry concentration of up to 57.2 wt%.

In the conventional process shown in comparative example 1, polyethylene powder is obtained by polymerization preparation, separation and drying, and then the polyethylene powder is added into a dissolving kettle and stirred for dissolution. The results of comparative example 1 show that a polyethylene slurry having a concentration of 8.5 wt% still does not give a completely homogeneous polyethylene spinning solution when stirred at the same temperature for 10 minutes, and it can be seen that a part of polyethylene particles are not completely dissolved, and finally polyethylene fibers obtained by spinning and drawing have a tensile strength of 3.5GPa and a tensile modulus of 180 GPa. Therefore, the conventional process needs to provide dissolution temperature and stirring time in actual production, and also needs to sieve the polyethylene powder to use fine powder particles in the polyethylene powder for spinning and polyethylene fiber manufacturing.

Therefore, the method not only can greatly simplify the process and the operation flow, but also can obtain the high-performance polyethylene fiber, and has strong industrial application value.

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 method for preparing high performance polyethylene fibers, comprising the steps of:

1) introducing ethylene, an inert solvent, a polymerization catalyst system and hydrogen into a polymerization reactor, and preparing a mixed solution of polyethylene and the inert solvent by slurry polymerization, wherein the inert solvent has a bubble point of more than 100 ℃ at a standard pressure and is alkane, cycloalkane, aromatic hydrocarbon, or a derivative of alkane/cycloalkane/aromatic hydrocarbon, or a mixture of any more of the alkane, cycloalkane and aromatic hydrocarbon; in the mixed solution of the polyethylene and the inert solvent, the mass concentration of the polyethylene is less than or equal to 99 wt%.

2) Heating a mixed solution of polyethylene and an inert solvent to 100-300 ℃ under the protection of nitrogen, removing gasified components through nitrogen gas stripping, stirring and dissolving to obtain a uniform polyethylene spinning solution, introducing the uniform polyethylene spinning solution into a screw extruder, metering the polyethylene spinning solution by a metering pump, spraying the polyethylene spinning solution from a spinneret orifice, quenching the polyethylene spinning solution into a cold water bath to form gel fibers, and then performing extraction drying and super-drawing to obtain polyethylene fibers; in the polyethylene spinning solution, the mass concentration of polyethylene is less than or equal to 99 wt%.

2. The method of claim 1, further comprising a step of supplementing the spinning solution and the antioxidant between the step of stripping the vaporized components with nitrogen and the step of stirring and dissolving to obtain a uniform polyethylene spinning solution.

3. The production method according to claim 1, wherein the production method is carried out continuously or batchwise.

4. The process according to claim 1, wherein the polymerization catalyst system comprises a solid catalyst containing a transition metal component which is a metal of group IVB or VB of the periodic Table system and a cocatalyst.

5. The process of claim 2, wherein the additional dope is a liquid at the polyethylene dissolution temperature and the additional dope is an alkane, cycloalkane, aromatic hydrocarbon, or a derivative of alkane/cycloalkane/aromatic hydrocarbon, or a mixture of any of them.

6. The production method according to claim 5, wherein the additional spinning solution is the inert solvent in step 1).

7. The method of claim 2, wherein the additional antioxidant is one of antioxidant CA, antioxidant 1010, antioxidant 1076 and mixed antioxidant B225, or a mixture of any more of them; the ratio of the mass of the added antioxidant to the mass of the polyethylene in the solution is greater than 0.005%.

8. The method of claim 1 or 2, wherein the polyethylene and polyethylene fibers have a viscosity average molecular weight of greater than 1000000 g/mol.

9. The method of claim 1, wherein the super-drawing is a hot-drawing of more than 1 stage performed in a range of more than 100 ℃, and the total draw ratio is more than 10 times.

10. A polyethylene fiber product prepared according to the preparation method of claim 1.