CN108560063B

CN108560063B - Dissolution and mixing process of UHMWPE (ultrahigh molecular weight polyethylene) fibers

Info

Publication number: CN108560063B
Application number: CN201810122742.XA
Authority: CN
Inventors: 姚湘江; 陈宏�
Original assignee: Zhejiang Qianxilong Special Fiber Co ltd
Current assignee: Zhejiang Qianxilong Special Fiber Co ltd
Priority date: 2018-02-07
Filing date: 2018-02-07
Publication date: 2020-12-08
Anticipated expiration: 2038-02-07
Also published as: CN108560063A

Abstract

The invention provides a dissolution and mixing process of UHMWPE (ultrahigh molecular weight polyethylene) fibers, which comprises the following steps of: step 1) feeding the spinning raw material into a single screw for melting-dissolving by a kettle type material mixing or weightless scale material mixing scheme, wherein the diameter of the single screw in a single screw extruder is 20-200mm, the length-diameter ratio of the single screw is 10-42, the rotating speed of the single screw is 90-150 rpm, the single screw extruder is heated in multiple sections, the temperature of a feeding section is 220-; and 2) extruding the extruded liquid by a single screw, and conveying the extruded liquid to a static mixer by a booster pump or directly by the single screw, wherein the temperature of the static mixer is 220-280 ℃, and the pressure of the melt in the static mixer is 2-8 MPa.

Description

Dissolution and mixing process of UHMWPE (ultrahigh molecular weight polyethylene) fibers

Technical Field

The invention belongs to the field of UHMWPE fiber production, and particularly relates to a dissolving and mixing process for UHMWPE fiber production.

Background

At present, in the production of UHMWPE fiber, almost completely one double screw is adopted to realize all processes of feeding, dissolving, mixing and the like, and the co-rotating double screws are realized at the process rotating speed: (1) the feeding amount of the feeding section meets the requirement of feeding in production, (2) the dissolution section realizes the rapid dissolution of UHMWPE, (3) the mixing section realizes the disentanglement of UHMWPE macromolecules under the strong shearing condition, the UHMWPE macromolecules are oriented along the shearing direction, and the requirement of gel spinning is met. The above method has the following drawbacks: (1) the degradation of UHMWPE is serious under the strong shearing condition, the degradation degree can reach more than 50 percent, for example, the molecular weight of UHMWPE powder with the molecular weight of 470 ten thousand, the molecular weight of jelly is only 180 plus 220 ten thousand, and is lower than 230 ten thousand; (2) the retention time of the materials in the twin-screw is short, the average retention time is 8-13min, the dissolution speed of the UHMWPE powder is slow, the larger the particle size is, the higher the molecular weight is, the longer the time required for complete dissolution is, the short retention time enables the twin-screw to be extremely sensitive to the particle size and the distribution of the UHMWPE powder, for example, under the same specific dissolution condition, the retention time required for the average particle size of 120 microns is 11.5min, and the retention time required for 160 microns is 14.8 min, in order to meet the spinning requirement.

Aiming at the phenomenon that the macromolecule degradation of finished fiber is serious and the performance of UHMWPE fiber is reduced due to the adoption of a single double-screw extrusion method at present; CN102277632B A method for preparing gel spinning of ultra-high molecular weight polyethylene fiber, comprising step A, conveying ultra-high molecular weight polyethylene powder with the mass fraction of 6% -12% and the viscosity average molecular weight of 150-1000 ten thousand and solvent to a batching emulsification kettle for fully mixing to obtain a mixture, feeding the mixture into a feeding kettle through a gear conveying pump, and feeding the mixture into a double-screw extruder for melting-dissolving to obtain an extruded liquid; namely, the prior CN102277632B can not avoid the pre-dissolution of practical double screws, so that the strong shearing action of the double screws can cause the degradation and degradation of UHMWPE in the dissolution spinning process, and meanwhile, the single screw is adopted to dissolve and spin UHMWPE fibers, so that the yield of UHMWPE fiber production by the method is extremely low due to the weak mixing capability and short retention time of the single screw, and the method has no prospect and significance of industrial application.

Disclosure of Invention

The invention provides a dissolution and mixing process of UHMWPE (ultrahigh molecular weight polyethylene) fibers, which comprises the following steps of: step 1) feeding the spinning raw material into a single screw for melting-dissolving by a kettle type material mixing and weightlessness scale material mixing scheme, wherein the diameter of the single screw in a single screw extruder is 20-200mm, the length-diameter ratio of the single screw is 10-42, the rotating speed of the single screw is 90-150 rpm, the single screw extruder is heated in multiple sections, the temperature of a feeding section is 220-; and 2) extruding the extruded liquid by a single screw, and conveying the extruded liquid to a static mixer by a booster pump or directly by the single screw, wherein the temperature of the static mixer is 220-280 ℃, and the pressure of the melt in the static mixer is 2-8 MPa.

Preferably, the static mixer consists of one or more groups of static mixing, which can be a coil pipe type or a tube type, and melt pipes forming the static mixer are arranged in series, the diameter of the melt pipes is 3-12mm, and the total length of the melt pipes is 5-56 m.

Preferably, the spinning raw material is obtained by the following preparation method: step a), conveying the ultrahigh molecular weight polyethylene powder with the mass fraction of 6-15 percent and the viscosity average molecular weight of 100-;

step b), conveying the ultrahigh molecular weight polyethylene powder with the mass portion of 0.5-1.5% and the viscosity average molecular weight of 100-;

mixing the swelling material and the dissolving material obtained in the step a) and the step b), and according to the method of the step 1 and the step 2 in the claim 1, sending the mixture into a mixing kettle to be uniformly mixed and stirred, wherein the mass fraction of the ultra-high molecular weight polyethylene powder in the mixed solution is 5-14.5%; the mixture enters a feeding kettle through a delivery pump, the mixture is sent into a single-screw extruder by the feeding kettle to be melted and dissolved, and the total retention time of the materials is more than 40 min.

Preferably, the process comprises the following steps: step A), preparing an UHMWPE solution with the concentration of 0.1-1%, and adding precisely metered polyolefin antioxidant, UHMWPE and white oil subjected to nitrogen filling and deoxidation into a reaction kettle, wherein the mass of the polyolefin antioxidant accounts for 0.5-5% of that of UHMWPE powder; gradually raising the temperature to 140-180 ℃ under stirring, wherein the stirring time is 0.5-2 h; adding a certain amount of cold white oil to reduce the temperature of UHMWPE/white oil to below 120 ℃ for standby;

b), placing the small materials into a strong shearing and bulk dispersing device with the stirring speed of 2000-10000 r/min, and shearing and dispersing the small materials to be uniform and stable at the temperature of 25-120 ℃;

step C), a weightlessness scale is used for realizing continuous and uniform feeding: three weight loss scales are arranged, wherein each weight loss scale comprises a plurality of UHMWPE powder scales, UHMWPE solution scales and small material scales which are respectively used for realizing the batching and metering of the powder, the UHMWPE dilute solution and the small material; (ii) a

Step D) feeding the UHMWPE solution in a and the small material in B above into a single screw according to the process of step 1 and step 2 of claim 1; realizing dissolution, homogenization and knot entanglement in a single screw, and feeding the mixture into a static mixer to balance the materials, wherein the retention time of the materials is more than 17 minutes.

Wherein the small material is selected from one or more of an antioxidant, a dispersing agent or nano-to micron-sized fine particles.

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

the invention adopts a method of matching a single screw and a static mixer for use, reduces the degradation effect of UHMWPE in the dissolving spinning process on an industrial level, the viscosity average molecular weight of the raw material is 300-.

Specifically, UHMWPE degradation rate < 35%; the consistency of the online viscosity of the melt is more than 99.95 percent; the super-drawing proportion of the fiber is improved by 3-10%, and the strength, modulus, wear resistance, thermal conductivity, creep resistance and the like of the fiber are improved. Compared with CN102277632B, the first: the degradation of UHMWPE is reduced to a greater extent; secondly, the method comprises the following steps: and simultaneously, the dissolution and spinning yield of the UHMWPE fiber is improved.

The strength of the product is more than 42g/d, and the modulus is more than 1650 g/d; CV can realize that the molecular weight of UHMWPE fiber is more than 500 ten thousand, and the UHMWPE fiber has higher strength, modulus, creep resistance, wear resistance, cutting resistance, heat conductivity coefficient and the like.

Detailed Description

Example 1

Step 1) conveying the ultrahigh molecular weight polyethylene powder with the mass fraction of 6-15% and the viscosity average molecular weight of 100-;

step 2) conveying the ultrahigh molecular weight polyethylene powder with the mass portion of 0.5-1.5% and the viscosity average molecular weight of 100-;

step 3) feeding the swelling material and the dissolving material into a mixing kettle according to the mass fraction requirement of the UHMWPE powder in the mixed solution in a certain proportion, uniformly mixing, and uniformly stirring, wherein the mass fraction of the ultrahigh molecular weight polyethylene powder in the mixed solution is 5-14.5%; the mixture enters a feeding kettle through a delivery pump, and the feeding kettle sends the mixture into a single-screw extruder for melting-dissolving; the single screw diameter of the single screw extruder is 20-200mm, the length-diameter ratio is 10-42, the rotating speed is 90-150 r/m, the single screw extruder is heated in multiple sections, the temperature of a feeding section is 160-;

step 4), extruding the extruded liquid by a single screw, and conveying the extruded liquid to a static mixer by a booster pump or directly by the single screw; the static mixer is composed of one or more groups of static mixing, can be a coil pipe type or a tube type, a melt pipeline forming the static mixer is arranged in series, the diameter is 3-12mm, the total length of the melt pipeline is 5-56m, the temperature of the static mixer is 220-280 ℃, and the pressure of the melt in the static mixer is 2-8 MPa; the total retention time of the materials is more than 40min, and the degradation rate is less than 38%.

And filtering the melt which passes through the static mixer in the steps, conveying the melt to a spinneret plate through a spinning metering pump, extruding the material by the spinneret plate, cooling the material in frozen water to obtain UHMWPE/white oil gel nascent fiber, and performing pre-stretching, extraction, drying and super-stretching on the nascent fiber to obtain the UHMWPE fiber. In the steps, the pre-stretching multiple is 2-8 times, the white oil content in the extracted fiber is less than 3%, and the total over-stretching multiple is 5-15 times.

Compared with the traditional double-screw mixing mode, the molecular weight of the obtained UHMWPE fiber reduces the degradation of UHMWPE macromolecules, obtains higher molecular weight, and improves the strength, modulus, wear resistance, thermal conductivity, creep resistance and the like of the fiber; the molecular weight of the raw material is as example, the molecular weight of the finished product is 525 thousands, the product strength is greater than 42g/d, and the modulus is greater than 1650 g/d.

Example 2

The feeding mode of the embodiment is the same as that of the embodiment 1, namely double screws are completely abandoned, single screw is adopted for feeding, the only difference is that the raw materials are mixed and the feeding mode is different, and the weight loss scale is adopted for feeding; the specific batching and feeding method comprises the following steps:

step 1) preparing a uniform solution of UHMWPE/white oil with the concentration of 0.1-1%; adding accurately metered polyolefin antioxidant, UHMWPE and white oil which is deoxidized by filling nitrogen into UHMWPE powder, polyolefin antioxidant and white oil, wherein the mass of the polyolefin antioxidant accounts for 0.1-3% of that of the UHMWPE powder;

gradually raising the temperature to 140 ℃ while stirring, stirring for 10-30 min, continuously raising the temperature to 160 ℃, stirring for 10-30 min, and continuously raising the temperature to 180 ℃. Obvious pole climbing effect can occur in the dissolution process of UHMWPE, and the stirring rotating speed can be properly reduced when the pole climbing effect occurs according to the production condition. Keeping the temperature and stirring for 30min after the temperature reaches 180 ℃. Adding a certain amount of cold white oil to reduce the temperature of UHMWPE/white oil to below 120 ℃ for standby. The UHMWPE/white oil dilute solution to be used.

The purpose of feeding with a dilute UHMWPE/white oil solution, rather than a pure white oil feed, is: (1) the screw has weak capacity of conveying low-viscosity liquid, the viscosity of the liquid inlet is improved, and the conveying capacity of the screw can be improved; (2) the UHMWPE/white oil homogeneous dilute solution is prepared, the output precision of the liquid weightlessness scale can be improved, the actual measurement result shows that the white oil is directly fed, the precision deviation of the scale is higher than 0.2 percent, the UHMWPE/white oil dilute solution is fed, and the output precision of the weightlessness scale can be reduced to be lower than 0.1 percent; (3) the UHMWPE concentration of 0.1-1% in the dilute solution is used for replacing pure white oil for production, and the total productivity can be improved by 2-10%.

2) A strong shearing small material batching device; stirring at 2000-10000 rpm, dispersing in bulk, adding antioxidant, dispersant and nanometer to micron level fine grains, and shearing at 25-120 deg.c to disperse homogeneously and stably; the strong shearing dispersion device is mature industrial equipment and is widely applied to the fields of paint, coating, cosmetics and the like, such as a shearing kettle, a shearing emulsifying machine, a shearing emulsifying pump and the like.

The antioxidant comprises a primary antioxidant, such as hindered phenol antioxidant, and a secondary antioxidant, such as phosphite ester/phosphate ester compound and thioether compound, and the compound effect is better, but the primary antioxidant and the secondary antioxidant can be used independently.

The dispersing agent can be one or more of polyoxyethylene, fatty alcohol polyoxyethylene ether methylsilane, oleic acid polyoxyethylene ester, sodium carboxymethylcellulose, sodium alkyl diphenyl ether sulfonate, alkylphenol polyoxyethylene ether phosphate, octadecyl amine, methylcellulose, tween-80, tween-60, sodium pyrophosphate, sodium hexametaphosphate and the like.

3) Setting three weightless scales, namely a plurality of UHMWPE powder scales, a liquid scale and a small material scale; feeding UHMWPE powder, the UHMWPE dilute solution in the step 1) and the small material obtained in the step 2) into a single screw rod respectively through an UHMWPE powder scale, a liquid scale and a small material scale, realizing dissolution, homogenization and knot entanglement in the single screw rod, setting the parameters of the single screw rod to be the same as those in the embodiment 1, feeding the single screw rod into a static mixer for balancing the materials, wherein the retention time of the materials is more than 17 minutes, and the degradation rate of the UHMWPE is less than 35 percent

Adding the UHMWPE/white oil dilute solution to be used into a weightlessness balance stock bin.

In a preferred embodiment of the invention, the mass fraction of the UHMWPE powder is 10-15% calculated by the sum of the mass of the UHMWPE powder, the UHMWPE/white oil homogeneous dilute solution and the small material; the mass fraction of the small materials is 1-15%; wherein UHMWPE powder is fed into the single screw at a certain speed, preferably at a speed of 42 kg/h-842 kg/h, and the feeding speed of the UHMWPE/white oil homogeneous dilute solution and the small material is set according to the mass ratio.

Feeding UHMWPE powder and an UHMWPE/white oil homogeneous dilute solution by adopting a hopper respectively, wherein in order to ensure smooth feeding, the powder hopper is provided with a bridge breaking device to prevent the UHMWPE powder from bridging; when the feeding material is UHMWPE solution, the oil weigher needs to be subjected to external heat preservation treatment, so that the working precision of the weightless weigher is prevented from being reduced due to temperature reduction and viscosity increase of the dilute solution. The bridge breaking device can be a bridge breaking oscillator, a bridge breaking stirrer, an airflow bridge breaking device and the like.

The ingredients enter an intermediate kettle with a stirring and constant temperature device, and the intermediate kettle supplements the ingredients for the small material scale, and the small material scale also needs to be provided with a stirring and external constant temperature device to avoid the separation or agglomeration of small material components.

Calculating the difference value between the actual feeding speed and the set value in the embodiment 2 by using the working curve of the weightlessness scale, and calculating the batching error; the results demonstrate dosing error < 0.1%.

By detecting the change of the on-line viscosity of the screw discharging, the change of the melt viscosity within a period of time is tested because the feeding deviation is in direct proportion to the change of the screw discharging viscosity, and the result proves that the batching precision is improved to 0.097% from 1.2%.

By adopting the batching method obtained in the embodiment 1, (1) the batching precision is higher, the unevenness is less than 0.1 percent, and the influence of the unevenness in batching on the product quality is reduced; (2) the product performance is improved by improving the consistency of the product; (3) various inorganic particles are added, so that different functions of the UHMWPE fiber are realized, wherein the functions are as shown in the table 1; (4) switching product specifications produces less waste than kettle-type compounding.

The strength of the obtained final ultra-high molecular weight polyethylene fiber product is more than 42g/d, and the modulus is more than 1650 g/d.

After a weightless scale type alternative kettle type batching mode is adopted, the batching precision is improved from 1.2% to 0.097%, under the same production condition, the titer CV value of the UHMWPE fiber is reduced from 3.1% to 0.52%, the achievable over-doubling tensile ratio of the fiber is improved by 3-10%, and the strength, the modulus, the wear resistance, the thermal conductivity, the creep resistance and the like of the fiber are improved.

Claims

1. A dissolution and mixing process of UHMWPE fibers is characterized in that: the process comprises the following steps:

step A), preparing a dilute UHMWPE solution with the concentration of 0.1-1%, and adding precisely metered polyolefin antioxidant, UHMWPE and white oil subjected to nitrogen filling and deoxidation into a reaction kettle, wherein the mass of the polyolefin antioxidant accounts for 0.1-3% of the mass of UHMWPE powder; gradually raising the temperature to 140-180 ℃ under stirring, wherein the stirring time is 0.5-2 h; adding a certain amount of cold white oil to reduce the temperature of UHMWPE/white oil to below 120 ℃ for standby;

step C), a weightlessness scale is used for realizing continuous and uniform feeding: three weightless scales are arranged, and each scale is provided with a plurality of scales: the UHMWPE powder scale, the UHMWPE dilute solution scale and the small material scale are respectively used for realizing the batching and metering of the powder, the UHMWPE dilute solution and the small material;

step D), feeding UHMWPE powder, the UHMWPE dilute solution in the step A) and the small material obtained in the step B) into a single-screw extruder for melting-dissolving through an UHMWPE powder scale, a liquid scale and a small material scale respectively, wherein the diameter of a single screw in the single-screw extruder is 20-200mm, the length-diameter ratio of the single screw is 10-42, the rotating speed of the single screw is 90-150 r/min, the single-screw extruder is heated in multiple sections, the temperature of a feeding section is 160-; extruding the extruded liquid by a single-screw extruder, and conveying the extruded liquid to a static mixer by a booster pump or directly through the single-screw extruder, wherein the temperature of the static mixer is 220-280 ℃, the pressure of the melt in the static mixer is 2-8Mpa, and the total retention time of the material in the static mixer is more than 17 minutes; the small materials are selected from one or more of antioxidants, dispersing agents or nano-to micron-sized fine particles.

2. The dissolution and mixing process of UHMWPE fibers according to claim 1, characterized in that: the static mixer is composed of one or more groups of static mixing, and can be a coil pipe type or a tube type, melt pipelines forming the static mixer are arranged in series, the diameter of the melt pipelines is 3-12mm, and the total length of the melt pipelines is 5-56 m.