WO2023087617A1 - High-flux polyethylene water treatment membrane and preparation method therefor - Google Patents

Abstract

A high-flux polyethylene water treatment membrane and a preparation method therefor. Using a polymer sodium salt as a porogen, uniformly mixing the porogen with polyethylene powder, an antioxidant and a diluent, then defoaming and dispersing the mixture to obtain a suspension; extruding the suspension to form a membrane; stretching and extracting the film, and removing the polymer sodium salt to obtain the high-flux water treatment membrane.

Description

A kind of high flux polyethylene water treatment membrane and preparation method thereof

Cross References to Related Applications

This disclosure claims the priority of the Chinese patent application with the application number "CN202111351665.3" and the title "a high-flux polyethylene water treatment membrane and its preparation method" submitted to the China Patent Office on November 16, 2021. The entire contents are incorporated by reference in this disclosure.

technical field

The disclosure belongs to the technical field of membrane separation, and in particular relates to a high-flux polyethylene water treatment membrane and a preparation method thereof.

Background technique

Membrane separation technology has the characteristics of high efficiency, energy saving and environmental protection, and has been widely used in many fields such as water treatment and chemical separation. In the market, the MBR membranes used for sewage filtration are mainly microfiltration membranes and ultrafiltration membranes; the membrane materials are generally polyvinylidene fluoride (PVDF), and their forms are mostly hollow fibers, and the cost of raw materials is relatively high. High (more than 100,000 yuan/ton).

For microfiltration membranes and ultrafiltration membranes, the flux of the membrane is a very important performance index, and the flux of the membrane is related to the pore size and porosity. The average pore diameter of polyethylene microporous membranes currently on the market ranges from 30 to 55 nm, and the pore diameter of PVDF hollow fiber commercial membranes is 0.1 to 0.4 μm. The pore diameter characteristics of polyethylene membranes make them long-term used as battery separators, and have not been widely used in the field of water treatment membranes. application.

In the technical exploration field of preparing polyethylene microporous membranes with larger pore size and higher porosity, the general method is to add various porogens, such as inorganic powders, or some polymers that are insoluble in water and solvents, etc., but these additions During the preparation process, the substances have poor compatibility with polyethylene or poor dispersion uniformity, which will lead to poor uniformity of the internal structure of the membrane, and most of these substances remain in the membrane, which has a greater effect on the improvement of pore size and porosity. big impact. Therefore, preparing a polyethylene water treatment membrane with large pore size and high porosity is still a problem that we need to solve at present.

Contents of the invention

The disclosure provides a method for preparing a high-flux polyethylene water treatment membrane, the preparation process at least including the following steps:

1) Suspension preparation: First, add polyethylene powder, polymer sodium salt powder and antioxidant powder to an appropriate amount of diluent and mix evenly; then, the uniform mixture is degassed and dispersed to obtain a suspension liquid;

2) Cast sheet: the suspension is added to the extruder to extrude the diaphragm;

3) Stretching: Stretching the membrane under a certain temperature condition to obtain a film with uniform thickness;

4) Extraction: put the stretched film into the extractant for extraction, and dry it;

5) Template removal: soak the film in a wetting agent. After soaking, the film is transferred to a H ₂ O ₂ solution with a certain temperature and pH for soaking, then transferred to distilled water with a certain temperature for cleaning, and finally the film is dried.

In some embodiments, the composition ratio of polyethylene, high molecular sodium salt, antioxidant, and diluent during preparation is: 10% to 50% polyethylene, 1% to 20% high molecular sodium salt additive, and 0.1 %~5% antioxidant, diluent accounts for 60%~90%; the polyethylene is two-component polyethylene, including ultra-high molecular weight polyethylene and high-density polyethylene, ultra-high molecular weight polyethylene, weight average molecular weight 6×10 ⁵ ～2×10 ⁶ , the auxiliary material is high-density polyethylene, the density is between 0.950g/cm ³ and 0.974g/cm ³ , the weight average molecular weight is 3×10 ⁵ ～6×10 ⁵ , high The density polyethylene content accounts for 20% to 70% of the total polyethylene mass; the high molecular sodium salt additive is any one or more of sodium alginate, sodium lignosulfonate, and sodium carboxymethyl cellulose, which The weight average molecular weight is 3×10 ⁴ to 2.5×10 ⁵ ; the antioxidant is any one or more of antioxidant 1010, antioxidant 1076 and antioxidant 168; the diluent is white oil .

In some embodiments, the temperature range of each zone of the screw during casting is 180°C-200°C, the temperature of the die head is 185°C-200°C, the thickness of the extruded film is 0.4mm-1mm, and the temperature of the cooling roll is 25°C-200°C. 60°C, the screw speed is 30r/min～60r/min.

In some embodiments, in the stretching step, the stretching temperature is 110° C. to 130° C., the stretching ratio is 5×5 to 10×10, and the stretching rate is 10 mm/s to 50 mm/s.

In some embodiments, the extractant is any one or more of dichloromethane or ethanol, and the extraction time is 5 minutes.

In some embodiments, in the template removal step, the wetting agent is any one or more of ethanol, DMAC, sodium dodecylbenzenesulfonate, etc., and the soaking time is 3 minutes to 10 minutes; The above-mentioned certain pH range is 2-13, the substance for adjusting pH is any one of HCl and NaOH, the temperature of the solution is 30°C-70°C, and the temperature of distilled water is 30°C-70°C.

The present disclosure also provides a high-flux polyethylene water treatment membrane, which is prepared by the above method.

In some embodiments, the polyethylene water treatment membrane has a porosity of 60% to 80%, an average pore diameter of 0.06 μm to 0.2 μm, and a pure water flux of 1000 L/(m ^2. h)/bar to 2000L/(m ^2. h)/bar.

The present disclosure also provides the use of the high-flux polyethylene water treatment membrane in water treatment and chemical separation.

Detailed ways

In order to further understand the present disclosure, preferred solutions of the present disclosure are described below in conjunction with specific embodiments, so as to facilitate those skilled in the art to understand the present disclosure.

Some embodiments of the present disclosure provide a polyethylene water treatment membrane with large pore size, high porosity, and high water flow and a preparation method thereof. The present disclosure uses high molecular sodium salt as a porogen, and polyethylene powder, antioxidant The solvent and the diluent are mixed to obtain a suspension, and then co-extruded to obtain a film, and then the high-flux polyethylene water treatment membrane can be obtained after the high-molecular sodium salt in the film is completely removed.

Some embodiments of the present disclosure provide a method for preparing a high-flux polyethylene water treatment membrane, the preparation process at least including the following steps:

1) Suspension preparation: First, add polyethylene powder, polymer sodium salt powder and antioxidant powder to an appropriate amount of diluent and mix evenly; then, the uniform mixture is degassed and dispersed to obtain a suspension liquid;

2) Cast sheet: the suspension is added to the extruder to extrude the diaphragm;

3) Stretching: Stretching the membrane under a certain temperature condition to obtain a film with uniform thickness;

4) Extraction: put the stretched film into the extractant for extraction, and dry it;

5) Template removal: soak the film in a wetting agent. After soaking, the film is transferred to a H ₂ O ₂ solution with a certain temperature and pH for soaking, then transferred to distilled water with a certain temperature for cleaning, and finally the film is dried.

In some embodiments, the composition ratio of polyethylene, polymer sodium salt, antioxidant, and diluent during preparation is: 10% to 50% (such as 15% to 45%, 20% to 40% or 30% ～35%) polyethylene, 1%～20% (such as 5%～15%, 8%～12% or 9%～11%) polymer sodium salt additive, and 0.1%～5% (such as 0.5%～4.5 %, 1.5%-4% or 2%-3%) antioxidant, diluent accounts for 60%-90%, such as 65%-85%, 70%-80% or 72%-78%. In one or more embodiments, the polyethylene is a two-component polyethylene, including ultra-high molecular weight polyethylene and high-density polyethylene. In one or more embodiments, the ultra-high molecular weight polyethylene has a weight average molecular weight of 6×10 ⁵ to 2×10 ⁶ , such as 8×10 ⁵ to 1.8×10 ⁶ , 8.5×10 ⁵ to 1.5×10 ⁶ Or 9.5×10 ⁵ to 1×10 ⁶ . In one or more embodiments, the auxiliary material is high-density polyethylene, with a density between 0.950g/cm ³ and 0.974g/cm ³ such as 0.955g/cm ³ and 0.970g/cm ³ , 0.960g/cm 3 ³ to 0.965g/cm ³ or 0.961g/cm ³ to 0.964g/cm ³ , with a weight average molecular weight of 3×10 ⁵ to 6×10 ⁵ such as 3.5×10 ⁵ to 5.5×10 ⁵ , 4×10 ⁵ ~5×10 ⁵ or 4.2×10 ⁵ ~4.8×10 ⁵ . In one or more embodiments, the high-density polyethylene accounts for 20%-70% of the total mass of polyethylene, such as 25%-65%, 35%-55%, or 40%-50%. In one or more embodiments, the polymer sodium salt additive is any one or more of sodium alginate, sodium lignosulfonate, and sodium carboxymethylcellulose. In one or more embodiments, the weight average molecular weight of the polymer sodium salt additive is 3×10 ⁴ to 2.5×10 ⁵ such as 6×10 ⁴ to 2×10 ⁵ , 8×10 ⁴ to 1.5×10 ⁵ Or 9×10 ⁴ to 1×10 ⁵ . In one or more embodiments, the antioxidant is any one or more of the antioxidant 1010, the antioxidant 1076 and the antioxidant 168. In one or more embodiments, the diluent is white oil.

In some embodiments, the temperature range of each zone of the screw during casting is 180°C to 200°C. In one or more embodiments, the temperature of the die head during casting is 185°C-200°C. In one or more embodiments, the thickness of the extruded film is 0.4 mm to 1 mm during casting. In one or more embodiments, the temperature of the cooling roll during casting is 25°C to 60°C. In one or more embodiments, the rotational speed of the screw during casting is 30r/min-60r/min.

In some embodiments, in the stretching step, the stretching temperature is 110°C to 130°C. In one or more embodiments, the stretch ratio is 5×5˜10×10. In one or more embodiments, the stretching rate is between 10 mm/s and 50 mm/s.

In some embodiments, the extractant is any one or more of dichloromethane or ethanol. In one or more embodiments, the extraction time is 5 minutes.

In some embodiments, in the template removal step, the wetting agent is any one or more of ethanol, DMAC, sodium dodecylbenzenesulfonate, and the like. In one or more embodiments, the infiltration time is 3 min to 10 min, such as 4 min to 9 min, 5 min to 8 min, or 6 min to 7 min. In one or more embodiments, the certain pH range is 2-13, such as 3-11, 4-8 or 6-7, and the substance for adjusting the pH is any one of HCl and NaOH. In one or more embodiments, the temperature of the solution is 30°C-70°C, such as 40°C-60°C, 45°C-55°C or 48°C-50°C. In one or more embodiments, the temperature of the distilled water is 30°C-70°C, such as 40°C-60°C, 45°C-55°C or 48°C-50°C.

The present disclosure also provides a high-flux polyethylene water treatment membrane prepared by the above method.

In some embodiments, the polyethylene water treatment membrane has a porosity of 60% to 80%, such as 64% to 78%, 66% to 76%, or 68% to 72%, with an average pore size of 0.06 μm to 0.2 μm Between, such as 0.08μm～0.18μm, 0.10μm～0.15μm or 0.12μm～0.14μm, the pure water flux is 1000L/(m ^2. h)/bar～2000L/(m ^2. h)/bar , such as 1200L/(m ^2. h)/bar～1800L/(m ^2. h)/bar, 1400L/(m ^2. h)/bar～1600L/(m ^2. h)/bar or 1500L/(m ^2. h)/bar～1550L/(m ^2. h)/bar.

Some embodiments of the present disclosure also provide applications of the high-flux polyethylene water treatment membrane in water treatment and chemical separation.

This disclosure selects the high molecular sodium salt as the porogen. The high molecular sodium salt has certain compatibility with polyethylene. The porogen is evenly distributed in the film after being extruded into the film. Uniform; the polymer form of the polymer sodium salt has a prominent effect on increasing the average pore size of the water treatment membrane and increasing the porosity of the water treatment membrane; and the polymer sodium salt is sensitive to the pH change of the solution, and can be adjusted at a certain temperature The pH value of the solution reduces the molecular weight of the high-molecular sodium salt in the polyethylene membrane, thereby realizing the complete removal of the high-molecular sodium salt. Therefore, the finished membrane has a larger pore size, higher porosity, better uniformity, and the water flux has also been significantly improved. improvement.

Example

The concrete method that carries out film performance test and characterization in following embodiment and comparative example is as follows:

Thickness measurement: According to GB/T6672-2001 plastic film and sheet thickness measurement method, the German Marr film thickness gauge C1216 is used for measurement, the same sample is tested at different positions, and the average value is taken as the thickness.

Flux measurement equipment: measured by self-made flat membrane measurement equipment.

Flux test method: Under the pressure of 0.02MPa, use deionized water as the feed liquid to pre-press the membrane for 1 hour to stabilize it; then conduct the flux test under the negative pressure of 0.02MPa. The effective membrane area of the test device is 192cm ² . The calculation formula is as follows:

Wherein, Q is the volume (L) of the permeated pure water, Δt is the permeation time (h), and A is the effective area of the permeable membrane (m ² ).

Example 1

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium alginate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and dispersing to obtain Suspension. The weight average molecular weight of polyethylene is 300,000 and 1 million respectively and the corresponding ratio is 2:1, polyethylene powder accounts for 25%; sodium alginate accounts for 5%, the weight average molecular weight is 5×10 ⁴ , antioxidant 1010 accounted for 0.5%, white oil accounted for 69.5%, and the speed of the vacuum defoaming disperser was 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, then soak in 70°C H ₂ O ₂ aqueous solution with pH=11 for 5 minutes, then wash in 70°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Example 2

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium alginate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and dispersing to obtain Suspension. The weight average molecular weight of polyethylene is 300,000 and 1 million respectively and the corresponding proportion is 7:3, polyethylene powder accounts for 20%, sodium alginate accounts for 15%, the weight average molecular weight is 5×10 ⁴ , antioxidant 1010 accounts for 0.5%, white oil accounts for 64.5%, and the speed of the vacuum defoaming disperser is 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, then soak in 70°C H ₂ O ₂ aqueous solution with pH = 11 for 5 minutes, then wash in 70°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Example 3

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium alginate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for degassing and dispersing to obtain Suspension. The weight-average molecular weight of polyethylene is 300,000 and 1 million respectively, and the corresponding ratio is 1:2. Polyethylene powder accounts for 25%, sodium alginate accounts for 5%, and the weight-average molecular weight is 5×10 ⁴ . Antioxidant 1010 accounted for 0.5%, white oil accounted for 69.5%, and the speed of the vacuum defoaming disperser was 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feed section, the temperature in the compression section is 185°C, the temperature in the homogenization section is 190°C, the temperature of the die head is 195°C, the thickness of the extruded film is 0.73mm, and the temperature of the cooling roll is 28°C;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, then soak in 70°C H ₂ O ₂ aqueous solution with pH = 11 for 5 minutes, then wash in 70°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Example 4

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium carboxymethyl cellulose and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and Disperse to obtain a suspension. The weight-average molecular weight of polyethylene is 300,000 and 1 million respectively, and the corresponding proportion is 1:4, polyethylene powder accounts for 25%, sodium carboxymethyl cellulose accounts for 5%, and the weight-average molecular weight is 5×10 ⁴ , Antioxidant 1010 accounted for 0.5%, white oil 69.5%, and the speed of the vacuum defoaming disperser was 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, and then soak in 30°C H ₂ O ₂ aqueous solution with pH=5 for 5 minutes, then wash in 30°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Example 5

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium alginate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and dispersing to obtain Suspension. The weight-average molecular weight of polyethylene is 300,000 and 1 million respectively, and the corresponding proportion is 2:1, polyethylene powder accounts for 25%; sodium alginate accounts for 5%, the weight-average molecular weight is 2.5×10 ⁵ , antioxidant 1010 accounted for 0.5%, white oil accounted for 69.5%, and the speed of the vacuum defoaming disperser was 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 125°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, then soak in 70°C H ₂ O ₂ aqueous solution with pH = 11 for 5 minutes, then wash in 70°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Example 6

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium lignin sulfonate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and dispersing , to obtain a suspension. The weight-average molecular weight of polyethylene is 300,000 and 1 million respectively, and the corresponding ratio is 2:1. Polyethylene powder accounts for 25%; sodium lignosulfonate accounts for 5%, and the weight-average molecular weight is 5×10 ⁴ . Oxygen agent 1010 accounts for 0.5%, white oil accounts for 69.5%, and the speed of the vacuum defoaming disperser is 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, then soak in 70°C H ₂ O ₂ aqueous solution with pH = 11 for 5 minutes, then wash in 70°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Example 7

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium alginate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and dispersing to obtain Suspension. The weight average molecular weight of polyethylene is 300,000 and 1 million respectively and the corresponding ratio is 2:1, polyethylene powder accounts for 25%; sodium alginate accounts for 5%, the weight average molecular weight is 5×10 ⁴ , antioxidant 1010 accounted for 0.5%, white oil accounted for 69.5%, and the speed of the vacuum defoaming disperser was 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 9×9 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 9 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Template removal: soak the film in 75% ethanol aqueous solution for 5 minutes, then soak in 70°C H ₂ O ₂ aqueous solution with pH = 11 for 5 minutes, then wash in 70°C distilled water for 5 minutes, and finally The film was dried in an oven at 70°C.

Comparative example 1

1) Suspension preparation: Add polyethylene powders of different molecular weights and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for deaeration and dispersion to obtain a suspension. The weight-average molecular weight of polyethylene is 300,000 and 1 million respectively, and the corresponding proportion is 2:1, polyethylene powder accounts for 25%, antioxidant 1010 accounts for 0.5%, white oil 74.5%, and vacuum defoaming disperser The speed is 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller;

The temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, 45°C in the cooling roll, and 30r// min;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Cleaning and drying: the extracted film was wetted with ethanol, washed in water at 70°C for 5 minutes, and finally dried in an oven at 70°C.

Comparative example 2

1) Suspension preparation: Add polyethylene powders of different molecular weights, sodium alginate and antioxidant 1010 into white oil, and stir evenly; pour the uniform mixture into a vacuum defoaming disperser for defoaming and dispersing to obtain Suspension. The weight average molecular weight of polyethylene is 300,000 and 1 million respectively and the corresponding ratio is 2:1, polyethylene powder accounts for 25%; sodium alginate accounts for 5%, the weight average molecular weight is 5×10 ⁴ , antioxidant 1010 accounted for 0.5%, white oil accounted for 69.5%, and the speed of the vacuum defoaming disperser was 900r/min;

2) Cast sheet: Add the suspension into the twin-screw extruder at a constant speed through the peristaltic pump, extrude the diaphragm, and then cool it through the cooling roller. Among them, the temperature of each zone of the screw is 185°C in the feeding section, 185°C in the compression section, 190°C in the homogenization section, 195°C in the die head, 0.73mm in thickness of the extruded film, and 45°C in the cooling roll;

3) Stretching by a biaxial stretching film testing machine: the film is biaxially stretched by a biaxial stretching film testing machine under the conditions of a stretching temperature of 115°C, a stretching ratio of 6×6 and a stretching rate of 5 mm/s. Obtain a uniform film with a thickness of 20 μm;

4) Extraction: put the stretched film into dichloromethane for extraction for 5 minutes, and dry it at 40°C;

5) Cleaning and drying: the extracted film was wetted with ethanol, washed in water at 70°C for 5 minutes, and finally dried in an oven at 70°C.

See Table 1 for the comparison of the average pore diameter, porosity and negative pressure (0.02Mpa) of the pure water flux data of the comparative example and the embodiment

Table 1.

As can be seen from the above table, the high molecular sodium salt is used as the porogen in the application of this case, which has a prominent effect on increasing the average pore size of the water treatment membrane and improving the porosity of the water treatment membrane; at the same time, the complete removal of the porogen in this application In addition to the exploration, in the _H2O2 solution with a certain pH value and temperature, the molecular weight of the high-molecular sodium salt is first reduced, and then the high-molecular sodium salt is removed, so that the removal rate of the high _- molecular sodium salt is higher, and the finished polyethylene The water treatment membrane has a larger pore size and higher porosity, which significantly improves the pure water flux of the water treatment membrane, and has a good application prospect in the field of water treatment membranes.

The above are only optional implementations of the present disclosure. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the concept of the present disclosure. These improvements and modifications are also should be considered within the scope of this disclosure.

Industrial Applicability

The high-flux polyethylene water treatment membrane provided by the present disclosure has more uniform membrane pores, and at the same time, the finished membrane has a larger pore size, higher porosity, and better uniformity, and the water flux has also been significantly improved. It has excellent industrial performance. Application performance and broad market prospects.

Claims (9)

1. A method for preparing a high-flux polyethylene water treatment membrane, characterized in that the preparation process at least includes the following steps:

   1) Suspension preparation: First, add polyethylene powder, polymer sodium salt powder and antioxidant powder to an appropriate amount of diluent and mix evenly; then, the uniform mixture is degassed and dispersed to obtain a suspension liquid;

   2) Cast sheet: the suspension is added to the extruder to extrude the diaphragm;

   3) Stretching: Stretching the membrane under a certain temperature condition to obtain a film with uniform thickness;

   4) Extraction: put the stretched film into the extractant for extraction, and dry it;

   5) Template removal: soak the film in a wetting agent. After soaking, the film is transferred to a H ₂ O ₂ solution with a certain temperature and pH for soaking, then transferred to distilled water with a certain temperature for cleaning, and finally the film is dried.
2. The preparation method of a kind of high flux polyethylene water treatment membrane as claimed in claim 1, is characterized in that, the composition ratio of described polyethylene, high molecular sodium salt, antioxidant, diluent during preparation is: 10% ～50% polyethylene, 1%～20% polymer sodium salt additive, and 0.1%～5% antioxidant, the diluent accounts for 60%～90%; the polyethylene is two-component polyethylene, including super High-molecular-weight polyethylene and high-density polyethylene, ultra-high-molecular-weight polyethylene, with a weight-average molecular weight of 6×10 ⁵ to 2×10 ⁶ , and high-density polyethylene as an auxiliary material, with a density between 0.950g/cm ³ and 0.974g/cm ³ , the weight-average molecular weight is 3×10 ⁵ to 6×10 ⁵ , and the content of high-density polyethylene accounts for 20% to 70% of the total mass of polyethylene; the high-molecular sodium salt additives are sodium alginate, lignosulfonate Any one or more of sodium carboxymethyl cellulose and sodium carboxymethyl cellulose, the weight average molecular weight of which is 3×10 ⁴ to 2.5×10 ⁵ ; the antioxidants are antioxidant 1010, antioxidant 1076 and antioxidant Any one or more of oxygen agents 168; the diluent is white oil.
3. The method for preparing a high-flux polyethylene water treatment membrane according to claim 1, wherein the temperature range of each zone of the screw is 180°C to 200°C during casting, and the temperature of the die head is 185°C to 200°C , the thickness of the extruded film is 0.4mm-1mm, the temperature of the cooling roll is 25°C-60°C, and the screw speed is 30r/min-60r/min.
4. The method for preparing a high-flux polyethylene water treatment membrane according to claim 1, wherein in the stretching step, the stretching temperature is 110°C-130°C, and the stretching ratio is 5×5- 10×10, the stretching rate is 10mm/s～50mm/s.
5. The method for preparing a high-flux polyethylene water treatment membrane according to claim 1, wherein the extraction agent is any one or more of dichloromethane or ethanol, and the extraction time is 5 minutes.
6. The preparation method of a kind of high flux polyethylene water treatment membrane as claimed in claim 1, is characterized in that, in described template removal step, described wetting agent is ethanol, DMAC, dodecylbenzenesulfonic acid Any one or more of sodium, etc., the soaking time is 3min-10min; the certain pH range is 2-13, the substance to adjust the pH is any one of HCl and NaOH, and the solution temperature is 30°C-70°C , Distilled water temperature is 30 ℃ ~ 70 ℃.
7. A high-flux polyethylene water treatment membrane prepared according to the method described in any one of claims 1-6.
8. A high-flux polyethylene water treatment membrane as claimed in claim 7, wherein the polyethylene water treatment membrane has a porosity of 60% to 80%, an average pore diameter of 0.06 μm to 0.2 μm, The flux of pure water is 1000L/(m ² ·h)/bar～2000L/(m ² ·h)/bar.
9. Use of the high-flux polyethylene water treatment membrane as claimed in claim 7 in water treatment and chemical separation.