CN116078185A

CN116078185A - Method for preparing membrane filaments of hollow fiber deamination membrane

Info

Publication number: CN116078185A
Application number: CN202310088981.9A
Authority: CN
Inventors: 祝国亮; 李汉克
Original assignee: Hubei Meichen Environmental Protection Co ltd
Current assignee: Hubei Meichen Environmental Protection Co ltd
Priority date: 2023-02-09
Filing date: 2023-02-09
Publication date: 2023-05-09

Abstract

The invention discloses a preparation method of membrane filaments of a hollow fiber deamination membrane, and belongs to the technical field of polymer membranes. The method comprises the following steps: s101: 15-25 parts by weight of polypropylene, 3-8 parts by weight of polyethylene, 3-8 parts by weight of plasticizer, 50-60 parts by weight of filling powder, 0.5-2 parts by weight of coupling agent, 2-5 parts by weight of lubricant and 0.5-3 parts by weight of ammonia adsorbent are mixed at a high speed at a temperature of 5-25 ℃ to prepare mixed powder; s102: extruding the mixed powder in an extruder at 120-160 ℃ to form particles, and simultaneously injecting 12-17 parts by weight of plasticizer from an oil filling hole of the extruder; s103: melting and extruding the particles prepared in the step S102 at 130-165 ℃ to obtain hollow fiber filaments; s104: and (3) stretching the hollow fiber yarn obtained in the step (S103), carrying out enzymolysis or acid washing, and finally carrying out water washing and air drying to obtain the deaminated hollow fiber membrane yarn.

Description

Method for preparing membrane filaments of hollow fiber deamination membrane

Technical Field

The invention belongs to the technical field of polymer membranes, and particularly relates to a preparation method of membrane filaments of a hollow fiber deamination membrane.

Background

The high ammonia nitrogen wastewater generally generates malodor, causes the deterioration of natural water environment such as river channels and the like, and needs to be effectively treated for discharge. Currently, the methods for treating ammonia nitrogen include biochemical method, adsorption method, break point chlorination method, chemical precipitation method, stripping method and the like. The biochemical method is generally applicable to domestic sewage with low ammonia nitrogen and enough carbon source and low-concentration industrial wastewater; the adsorption method is generally applied to occasions with low ammonia nitrogen content; the break point chlorination method and the chemical precipitation method are generally used on special water bodies and have limited removal efficiency; the stripping method is applied to wastewater with higher ammonia nitrogen content, but the stripping method needs heating or a large amount of air stripping during operation, carbon dioxide in the air can react with calcium and magnesium ions to generate precipitate, so that the operation cost is high, the removal efficiency is low, the treatment efficiency is greatly affected by temperature, the treatment effect is difficult to meet the requirement when the temperature is low, ammonia is easy to leak in the treatment process, and secondary pollution can be caused.

Along with the progress of the membrane technology level, the application advantages of the membrane technology in the environmental field are increasingly revealed, and the ammonia nitrogen wastewater membrane deamination technology is also a hot spot for research and application. Membrane deamination systems employing the principle of membrane contact reactions are gaining increasing attention and use.

Compared with the stripping method, the method has the characteristics of low operation energy consumption and high deamination efficiency. Common membrane deamination techniques are vacuum membrane deamination, membrane absorption deamination, membrane bioreactor deamination, etc. Wherein, the membrane bioreactor is a branch of biological deamination and has limited application in the field of deamination in high-concentration nondegradable industrial wastewater. The vacuum membrane deamination and the membrane absorption deamination are both that a microporous membrane is adopted to separate liquid and gas phases or liquid and liquid phases, deamination membrane holes provide a liquid and gas phase or liquid-liquid phase mass transfer interface, mass transfer driving force is ammonia partial pressure difference at two sides of a membrane interface, and the vacuum membrane deamination is that membrane interface transmembrane ammonia molecules are quickly brought out by utilizing a vacuum technology to form an interface ammonia partial pressure difference; the membrane absorption deamination uses acid solution as absorbent, and the rapid chemical reaction leads the interfacial ammonia partial pressure difference to be obviously increased, thus having higher deamination efficiency. The membrane deamination technology provides a larger contact area, and is a brand new and more effective contact mass transfer. The membrane deamination method has the characteristics of low investment, low energy consumption, high efficiency, convenient use, simple operation and the like, has the advantage of large mass transfer area, does not have the phenomena of entrainment, flooding, channeling, bubbling and the like, and has obvious technical advantages.

At present, a selective deamination membrane has not been studied and produced, and membrane deamination is realized by taking a hydrophobic membrane as an interface and increasing the partial pressure difference of ammonia by acid absorption. Hydrophobic membrane materials commonly used in polytetrafluoroethylene, polyvinylidene fluoride or polypropylene. Wherein, polytetrafluoroethylene is a material with high price and difficult processing, polyvinylidene fluoride is made into a hydrophobic film with poor hydrophobic performance, which is easy to cause pollution and blockage, and the polymethyl acetamide solvent used in the hydrophobic film production process is not easy to be biochemically treated, which can cause great pollution to the environment. Polypropylene is a high-crystallization nonpolar polymer, has the characteristics of good chemical stability, acid and alkali resistance and low price, and is widely studied at home and abroad. However, polypropylene is stretched into a film, and particularly, the transverse strength of the hollow fiber membrane is extremely poor, so that the film yarn has insufficient elasticity, and the film yarn is easy to flatten in the process of manufacturing a film assembly and practical application. It is therefore necessary to increase the transverse strength of polypropylene films. The polypropylene fiber membrane produced at present is mostly prepared by using white oil, dioctyl ester or soybean oil and the like as solvents, soaking the polypropylene fiber membrane in alcohol or seventh gasoline to extract the organic solvents, and recycling the alcohol or the gasoline, thereby greatly increasing the production investment cost and the raw material consumption. In addition, alcohol and No. seven gasoline belong to inflammable and explosive products, and have a certain risk in the production process.

In addition, although the use of a hydrophobic membrane as an effective means for membrane deamination, the hydrophobic membrane has no selective permeability, so the deamination rate is relatively low, and the deamination rate is only 83-86% under the same conditions.

Disclosure of Invention

In order to solve the problems, the invention provides a preparation method of membrane filaments of a hollow fiber deamination membrane, which takes polypropylene, polyethylene, filling powder, a coupling agent, a plasticizer, a lubricant and an ammonia adsorbent as raw materials, and adopts high mixing, granulating by a double-screw extruder, spinning by a conical double-screw extruder, stretching the membrane filaments, carrying out enzymolysis or acid washing, washing with water and airing to prepare the hollow fiber deamination membrane. The membrane yarn produced by the method has the advantages of simple production process, low price, environmental friendliness, adjustable membrane pore diameter, high deamination rate and the like. The technical scheme is as follows:

the invention provides a preparation method of membrane filaments of a hollow fiber deamination membrane, which comprises the following steps:

s101: 15-25 parts by weight of polypropylene, 3-8 parts by weight of polyethylene, 3-8 parts by weight of plasticizer, 50-60 parts by weight of filling powder, 0.5-2 parts by weight of coupling agent, 2-5 parts by weight of lubricant and 0.5-3 parts by weight of ammonia adsorbent are mixed at a high speed at a temperature of 5-25 ℃ to prepare mixed powder. In the step, when the materials are mixed at a high speed, the temperature of the materials can be increased, and more plasticizer is added; if the temperature is higher, the materials are sticky, and the materials are not fed well during extrusion granulation.

In addition, in the patent, the rigidity of the membrane wire and the transverse tension of the membrane wire can be greatly improved by adding a certain proportion of polyethylene into polypropylene.

S102: extruding the mixed powder in an extruder at 120-160 ℃ to form particles, and simultaneously injecting 12-17 parts by weight of plasticizer into the extruder from an oil filling hole of the extruder.

In this patent, the plasticizer is added at step S101 and step S102, respectively, because: the polypropylene oil absorption value is very low, and the addition of all plasticizers can form very sticky dough in the high mixing process, and feeding cannot be performed during extrusion granulation, so that an oil injection hole is required to be formed in the second heating section of the double-screw extruder, and the peristaltic pump is used for injecting the plasticizers into the extruder for mixing granulation. The more plasticizer is added, the higher the porosity is, so as to improve the deamination rate of the film wire.

S103: and (3) melting and extruding the particles prepared in the step (S102) at 130-165 ℃ to obtain the hollow fiber yarn.

S104: and (3) stretching the hollow fiber yarn obtained in the step (S103), carrying out enzymolysis or acid washing, and finally carrying out water washing and air drying to obtain the deaminated hollow fiber membrane yarn.

Wherein the plasticizer is selected from triethyl citrate or glycerol.

Wherein the filling powder is selected from corn starch, water-soluble starch, maltodextrin or nano calcium carbonate.

Wherein the lubricant is selected from white oil No. 20, triethyl citrate, dioctyl phthalate or Fischer-Tropsch wax, etc.; preferably 20 white oil, wherein the 20 white oil plays roles of internal lubrication and external lubrication at the same time, and the effect is particularly obvious when corn starch is used as filling powder.

Wherein the coupling agent is selected from titanate coupling agent or aluminate coupling agent, preferably liquid titanate coupling agent, and can modify the filling powder at low temperature.

Wherein the ammonia adsorbent is selected from sulfo-modified silica aerosol, fluorosilane-modified silica aerosol and the like.

Wherein, the triethyl citrate is a plasticizer of polypropylene and polyethylene, and can also lubricate the starch.

When the filling powder is selected from corn starch, water-soluble starch or maltodextrin, the plasticizer is glycerin, and in step S104, the treatment process after stretching is enzymolysis. Because the polypropylene and the polyethylene have very low oil absorption values, and the corn starch has very high oil absorption values, more soluble glycerin can be added into a film forming system, so that the hollow fiber film has higher void ratio, and the pore size of the film can be controlled by adjusting the proportion between the glycerin and the starch. In addition, when corn starch, water-soluble starch or maltodextrin is used as filling powder, if glycerol is used as a plasticizer, the glycerol reacts with the corn starch, the water-soluble starch or the maltodextrin at high temperature to prepare thermoplastic starch, and the thermoplastic starch has good compatibility with polypropylene, so that high-strength film yarns can be prepared; and meanwhile, the specific surface area of the starch is larger, so that the porosity of the deamination film can be greatly improved.

When the filler powder is nano calcium carbonate, the plasticizer is triethyl citrate, and in step S104, the treatment process after stretching is acid washing. The triethyl citrate is a biodegradable and slightly water-soluble organic matter, and can be extracted from membrane filaments in the processes of pickling and water washing, so that alcohol or No. seven gasoline is not needed to be extracted, and the investment cost and the inflammable and explosive risks in production are greatly reduced.

In step S101, polypropylene, polyethylene, filler powder, ammonia adsorbent and lubricant are mixed in a high-speed mixer at high speed for 1-2 minutes (specifically, 2 minutes), coupling agent is further added, mixing is continued for 4-6 minutes (specifically, 5 minutes), plasticizer is finally added, and mixing is performed at low speed for 8-12 minutes (specifically, 10 minutes).

Specifically, in step S102, the plasticizer is added from the oil filler point of the second heating section of the extruder.

Preferably, in step S102, the pellets are pelletized by a twin screw extruder, specifically, a phi 45 twin screw extruder having an aspect ratio of 44 may be employed. In step S103, the fiber is melted in a conical twin screw and extruded through a twin hole annular spinneret to form a hollow fiber membrane filament. The conical double-screw extruder has higher feeding ratio, can improve the compactness of the membrane wire, increase the rigidity of the membrane wire, and can easily prepare a uniform net structure when stretching the membrane wire, thereby improving the porosity of the membrane wire. The spinning speed and the caliber of the spinneret plate can be adjusted to produce products with different specifications. Specifically, in step S103, hollow fiber filaments having an inner/outer diameter of 1.0/1.3mm are produced; in step S104, deaminated hollow fiber membrane filaments having an inner/outer diameter of 0.7/1.0 mm were produced. In this patent, the pore size of the membrane is mainly controlled by the particle size of the filler powder, the draw ratio, and the ratio between the lubricant and plasticizer.

Specifically, in step S104, the enzyme treatment process is: the treatment is performed by a solution containing a low temperature amylase and a saccharifying enzyme. Specifically, the low-temperature amylase is used for hydrolyzing corn starch, water-soluble starch or maltodextrin into short-chain starch, and the saccharifying enzyme is used for hydrolyzing the short-chain starch into glucose so as to be beneficial to washing the starch from the film yarns. In particular, hydrochloric acid may be used for the acidic process.

Specifically, in step S104, the stretching process is: stretching by four co-rotating five-roller tractors, wherein the stretching ratio is 3.0-5.5; the hollow fiber membrane filaments are led out from a first tractor, heated by a first heating channel, led into the second heating channel at a speed higher than that of the first tractor by a second tractor, led into a third heating channel by a third tractor with the same speed as the second tractor, and led out from a fourth tractor for winding at 85-90% of the speed of the third tractor; wherein the length of the first heating channel is 5-7 m (specifically, 6 m), the temperature is 60-80 ℃, the lengths of the second heating channel and the third heating channel are 8-12 m (specifically, 10 m), and the temperatures are 100-110 ℃. The conventional heat setting of the polypropylene deamination film is that after the film yarn is stretched, the film yarn is kept stand for 24 hours under a certain temperature condition, and the invention can continuously heat and set, thereby greatly improving the production efficiency.

Wherein, the particle size of the nano calcium carbonate in the embodiment of the invention is 100-200 nanometers.

Preferably, when the filling powder in the embodiment of the present invention is selected from corn starch, water-soluble starch or maltodextrin, the lubricant is 20 white oil.

Preferably, the polyethylene in the embodiments of the present invention is a high density polyethylene of either the drawn or hollow grade. The polyethylene of the grade is easier to form and is not easy to break.

In the patent, the price of the polyethylene polypropylene used is tens times lower than that of polyvinylidene fluoride and polytetrafluoroethylene, and the price of the filling powder such as calcium carbonate, starch and the like used for replacing organic solvent for pore-forming is relatively low; the large amount of lubricants such as triethyl citrate, glycerol and the like added in the method can be biodegraded and can be directly discharged to a sewage plant for biochemical treatment; the membrane yarn prepared by the invention has the characteristics of low price and good environment.

Detailed Description

The present invention will be described in further detail below in order to make the objects, technical solutions and advantages of the present invention more apparent.

The film forming system is prepared according to the following steps:

(1) The polypropylene, the polyethylene, the filling powder, the ammonia adsorbent and the lubricant are mixed in a high-speed mixer for 2 minutes at high speed, then are injected into the coupling line, are mixed for 5 minutes continuously, and finally are mixed for 10 minutes at low speed.

(2) And (3) melting and granulating the mixture obtained in the step (1) at 140-160 ℃ by using a phi 45 double-screw extruder with the length-diameter ratio of 44. While the remaining plasticizer is injected proportionally from the second heating section of the extruder.

(3) The obtained particles are added into a conical double screw to be subjected to hollow fiber spinning, the water temperature of a spinning cooling water tank is controlled below 25 ℃, and the water inlet distance is controlled to be about 3cm, so that the freshly spun membrane yarn has a quenching process to obtain the membrane yarn with high strength and high aperture ratio.

Stretching and heat setting:

stretching by four co-rotating five-roller tractors, wherein the stretching ratio is 3.0-5.5; the hollow fiber membrane filaments are led out from a first tractor, heated by a first heating channel, led into the second heating channel at a speed higher than that of the first tractor by a second tractor, led into a third heating channel by a third tractor with the same speed as the second tractor, and led out from a fourth tractor for winding at 85-90% of the speed of the third tractor; wherein the length of the first heating channel is 6 m, the temperature is 60-80 ℃, the lengths of the second heating channel and the third heating channel are 10 m, and the temperatures are 100-110 ℃.

Enzymolysis or acid washing process:

bundling the stretched membrane filaments into bundles, soaking the bundles in a hydrochloric acid solution or a solution containing amylase and saccharifying enzyme for 4 hours, repeating the steps for 3 times to extract filling powder, soaking the bundles in water for 1 time, and repeatedly washing the bundles for 6 times. And (5) airing the washed membrane filaments to obtain the hollow fiber deamination membrane.

Example 1

An embodiment provides a method for preparing membrane filaments of a hollow fiber deamination membrane, which comprises the following steps: blending and granulating 2.5 kg of polypropylene, 0.50 kg of high-density polyethylene, 0.1 kg of titanate coupling agent, 4.6 kg of corn starch, 0.5 kg of white oil, 0.2 kg of sulfo-modified silicon dioxide and 1.6 kg of glycerin, melt spinning, and soaking with amylase and saccharifying enzyme to remove corn starch in the hollow fiber membrane to obtain the hollow fiber membrane yarn. The outer diameter of the hollow fiber membrane wire is 1.0mm, the inner diameter is 0.7mm, the membrane pore diameter is 0.2um, the porosity of the membrane wire is 65%, and the deamination rate is 92%.

Example two

Embodiment II provides a method for preparing membrane filaments of a hollow fiber deamination membrane, which comprises the following steps: blending and granulating 2.4 kg of polypropylene, 0.4 kg of high-density polyethylene, 0.1 kg of titanate coupling agent, 4.6 kg of corn starch, 0.7 kg of triethyl citrate, 0.2 kg of sulfo-modified silicon dioxide and 1.6 kg of glycerin, melt spinning, soaking with amylase and saccharifying enzyme to remove corn starch in the hollow fiber membrane, and washing with water to remove the triethyl citrate to obtain the hollow fiber membrane yarn. The outer diameter of the hollow fiber membrane wire is 1.0mm, the inner diameter is 0.7mm, the membrane pore diameter is 0.2um, the porosity of the membrane wire is 65%, and the deamination rate is 95%.

Example III

Embodiment three provides a method for preparing membrane filaments of a hollow fiber deamination membrane, which comprises the following steps: 2.5 kg of polypropylene, 0.6 kg of high-density polyethylene, 0.1 kg of titanate coupling agent, 4.6 kg of water-soluble starch, 0.4 kg of dewaxing, 0.2 kg of sulfo-modified silicon dioxide and 1.6 kg of glycerin are mixed, granulated, melt-spun, soaked by amylase and saccharifying enzyme to remove the water-soluble starch in the hollow fiber membrane, and washed with water to obtain the hollow fiber membrane yarn. The outer diameter of the hollow fiber membrane wire is 1.0mm, the inner diameter is 0.7mm, the membrane pore diameter is 0.2um, the porosity of the membrane wire is 60%, and the deamination rate is 93%.

Example IV

An embodiment IV provides a method for preparing membrane filaments of a hollow fiber deamination membrane, comprising the following steps: blending and granulating 2.4 kg of polypropylene, 0.4 kg of high-density polyethylene, 0.1 kg of titanate coupling agent, 4.6 kg of corn starch, 0.7 kg of triethyl citrate, 0.1 kg of sulfo-modified silicon dioxide, 0.1 kg of fluorosilane-modified silicon dioxide and 1.6 kg of glycerin, melt spinning, soaking with amylase and saccharifying enzyme to remove corn starch in the hollow fiber membrane, and washing with water to remove the triethyl citrate to obtain the hollow fiber membrane yarn; the outer diameter of the hollow fiber membrane wire is 1.0mm, the inner diameter is 0.7mm, the membrane pore diameter is 0.2um, the porosity of the membrane wire is 68%, and the deamination rate is 98%.

Example five

The fifth embodiment provides a method for preparing membrane filaments of a hollow fiber deamination membrane, which comprises the following steps: blending and granulating 2.1 kg of polypropylene, 0.3 kg of high-density polyethylene, 0.1 kg of titanate coupling agent, 5.3 kg of nano calcium carbonate, 0.5 kg of dioctyl phthalate, 0.2 kg of sulfo-modified silicon dioxide and 1.5 kg of triethyl citrate, melt spinning, soaking with hydrochloric acid to remove nano calcium carbonate in the hollow fiber membrane, and washing with water to remove the triethyl citrate to obtain the hollow fiber membrane yarn; the outer diameter of the hollow fiber membrane wire is 1.0mm, the inner diameter is 0.7mm, the membrane pore diameter is 0.5um, the porosity of the membrane wire is 63%, and the deamination rate is 95%.

The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

1. The preparation method of the membrane yarn of the hollow fiber deamination membrane is characterized by comprising the following steps:

s101: 15-25 parts by weight of polypropylene, 3-8 parts by weight of polyethylene, 3-8 parts by weight of plasticizer, 50-60 parts by weight of filling powder, 0.5-2 parts by weight of coupling agent, 2-5 parts by weight of lubricant and 0.5-3 parts by weight of ammonia adsorbent are mixed at a high speed at a temperature of 5-25 ℃ to prepare mixed powder;

s102: extruding the mixed powder in an extruder at 120-160 ℃ to form particles, and simultaneously injecting 12-17 parts by weight of plasticizer into the extruder from an oil filling hole of the extruder;

s103: melting and extruding the particles prepared in the step S102 at 130-165 ℃ to obtain hollow fiber filaments;

s104: stretching the hollow fiber yarn obtained in the step S103, carrying out enzymolysis or acid washing, and finally carrying out water washing and air drying to obtain deaminated hollow fiber membrane yarn;

the plasticizer is selected from triethyl citrate or glycerol;

the filling powder is selected from corn starch, water-soluble starch, maltodextrin or nano calcium carbonate;

the lubricant is selected from white oil No. 20, triethyl citrate, dioctyl phthalate or Fischer-Tropsch wax;

the coupling agent is selected from titanate coupling agent or aluminate coupling agent;

the ammonia adsorbent is selected from sulfo-modified silica aerosol or fluorosilane-modified silica aerosol;

wherein, when the filling powder is selected from corn starch, water-soluble starch or maltodextrin, the plasticizer is glycerin, and in step S104, the treatment procedure after stretching is enzymolysis;

when the filler powder is nano calcium carbonate, the plasticizer is triethyl citrate, and in step S104, the stretched treatment process is acid washing.

2. The method for preparing membrane filaments of a hollow fiber deamination membrane according to claim 1, wherein in step S101, polypropylene, polyethylene, filler powder, ammonia adsorbent and lubricant are mixed in a high speed mixer for 1-2 minutes according to a ratio, then coupling agent is added, mixing is continued for 4-6 minutes, finally plasticizer is added, and mixing is performed for 8-12 minutes at a low speed.

3. The method for producing a membrane wire of a hollow fiber deamination membrane according to claim 1, wherein in step S102, a plasticizer is added from an oil filler hole of a second heating section of the extruder.

4. The method for producing membrane filaments of a hollow fiber deamination membrane according to claim 1, wherein in step S102, granulation is performed by a twin screw extruder; in step S103, the fiber is melted in a conical twin screw and extruded through a twin hole annular spinneret to form a hollow fiber membrane filament.

5. The method for producing membrane filaments of a hollow fiber deamination membrane according to claim 1, wherein in step S104, the enzyme treatment process is: the treatment is performed by a solution containing a low temperature amylase and a saccharifying enzyme.

6. The method for producing a membrane yarn of a hollow fiber deamination membrane according to claim 1, wherein in step S104, the stretching process is: stretching by four co-rotating five-roller tractors, wherein the stretching ratio is 3.0-5.5; the hollow fiber membrane filaments are led out from a first tractor, heated by a first heating channel, led into the second heating channel at a speed higher than that of the first tractor by a second tractor, led into a third heating channel by a third tractor with the same speed as the second tractor, and led out from a fourth tractor for winding at 85-90% of the speed of the third tractor; wherein the length of the first heating channel is 5-7 m, the temperature is 60-80 ℃, the lengths of the second heating channel and the third heating channel are 8-12 m, and the temperatures are 100-110 ℃.

7. The method for producing membrane filaments of a hollow fiber deamination membrane according to claim 1, wherein the nano calcium carbonate has a particle size of 100 to 200 nm.

8. The method for producing membrane filaments of a hollow fiber deamination membrane according to claim 1, wherein the lubricant is 20 white oil when the filler powder is selected from corn starch, water-soluble starch or maltodextrin.

9. The method for producing membrane filaments of a hollow fiber deamination membrane according to claim 1, wherein the polyethylene is a high density polyethylene of a drawing grade or a hollow grade.