CN103816817B - Alkali-resistant cellulose membrane and preparation method thereof - Google Patents

Abstract

The invention relates to an alkali-resistant cellulose membrane and a preparation method thereof, characterized in that the alkali-resistant regenerated cellulose membrane includes an alkali-resistant regenerated cellulose ultrafiltration membrane and an alkali-resistant regenerated cellulose nanofiltration membrane, and also includes an alkali-resistant regenerated fiber Plain hollow fiber membranes and alkali-resistant regenerated cellulose flat membranes use NMMO containing 5-15wt% water as a solvent to directly dissolve cellulose pulp and additives, and then spin regenerated cellulose membranes by immersion gel phase inversion method. It is obtained after sodium hydroxide post-treatment, water washing and glycerin post-treatment. The pore diameter of the prepared alkali-resistant regenerated cellulose membrane is greater than 0.001 μm and less than 0.1 μm, and the molecular weight of the organic matter that can be intercepted is greater than 500 M _W . The present invention can be used for pressing waste water of viscose fiber, black liquor of alkaline papermaking, yarn cooking and mercerizing washing water in printing and dyeing industry, ash alkali dehairing waste water in tanning industry and waste water treatment in some production processes of petroleum and chemical industry, etc.

Description

A kind of alkali-resistant cellulose film and preparation method thereof

technical field

The invention relates to an alkali-resistant cellulose film and a preparation method thereof.

Background technique

Alkaline wastewater refers to wastewater containing certain alkalis and a pH value higher than 9, which can be divided into strong alkaline wastewater, weak alkaline wastewater, low concentration alkaline wastewater and high concentration alkaline wastewater. Alkaline wastewater usually contains a large amount of harmful substances such as organic matter and inorganic salts in addition to a certain concentration of alkali. Alkaline wastewater comes from a wide range of sources, mainly from viscose fiber pressing wastewater, black liquor from alkaline papermaking, yarn cooking and mercerizing washing water in the printing and dyeing industry, gray alkali dehairing wastewater in the leather industry, and wastewater from petroleum and chemical production processes. Wait. The treatment methods of alkaline wastewater include acid-base neutralization method, flocculation method, chemical precipitation method, combustion method, crystallization method, microbial method, electrodialysis method, etc. Membrane water treatment is expected to be widely used in the treatment of alkali-containing wastewater due to its advantages of high efficiency, practicality, adjustability, energy saving and simple process.

Cellulose has the advantages of wide sources, good biocompatibility, stable physical and chemical properties, acid and alkali resistance, etc., and is considered as an ideal membrane material. Usually, cellulose membranes are used in seawater desalination, hemodialysis, gas separation, oil-water separation, packaging films and other fields. The preparation methods of cellulose film include viscose method, copper ammonia method and solvent method. The performance of the membranes prepared by the solvent method and the copper ammonia method was compared in the application research of the solvent method cellulose hollow membrane by the Dalian Institute of Chemical Technology of the Chinese Academy of Sciences (China and Foreign Energy, 2006, 11 (4)). It shows good stability in higher concentrations of acidic or alkaline solutions, but the cellulose membrane prepared by the cuproammonia method has poor alkali resistance and will be dissolved in 18% NaOH solution, so it is necessary to develop a solvent Preparation of cellulose membrane for alkaline wastewater treatment.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a regenerated cellulose membrane. The method has simple membrane-making process, recyclable solvent and no pollution. The cellulose membrane has good alkali resistance and can be used for alkali-containing wastewater treatment.

In order to achieve the above object, the technical scheme adopted in the present invention is:

Alkali-resistant regenerated cellulose membranes include alkali-resistant regenerated cellulose ultrafiltration membranes and alkali-resistant regenerated cellulose nanofiltration membranes, as well as alkali-resistant regenerated cellulose hollow fiber membranes and alkali-resistant regenerated cellulose flat membranes. NMMO with % water is used as a solvent to directly dissolve cellulose pulp and additives, and then use the immersion gel phase inversion method to spin regenerated cellulose hollow fiber membranes or cast regenerated cellulose flat membranes, and then post-treat with sodium hydroxide, It is obtained by washing with water and post-treatment with glycerin.

The preparation method of the alkali-resistant regenerated cellulose film of the present invention comprises the following steps:

1) Preparation of casting solution: at 80-100°C, cellulose pulp with a weight percentage of 5-20:70-93.9:1-8:0.1-2, NMMO containing 5-15wt% water, Additives and antioxidants are uniformly mixed, stirred, dissolved, defoamed and filtered to prepare 5-20wt% cellulose casting solution;

2) Spun into a membrane by immersion gel phase inversion method: at 70°C, cast the casting solution prepared in step 1) on a glass plate to form a flat film, or mix the casting solution prepared in step 1) with The core liquid is extruded through the spinneret at the same time as the tubular film; the prepared flat film is placed in a gas environment for 0-120 seconds and then solidified in the coagulation bath for 3-5 minutes or the tubular film is solidified after passing through the gas environment of 0-20 cm solidify in the bath; then wash off the residual solvent in the film with deionized water;

3) Treat the cellulose membrane prepared in step 2) with 17-22 wt% sodium hydroxide aqueous solution for 45-100 min at 20-30°C;

4) The cellulose membrane prepared in step 3) is washed with water, soaked in 10-50 wt% glycerin aqueous solution for 3-24 hours, and then the membrane is taken out to dry at room temperature to obtain a regenerated cellulose membrane.

The cellulose pulp is one or a mixture of absorbent cotton, bamboo pulp, wood pulp, reed straw, wheat straw, rice straw, and sugarcane straw;

The degree of polymerization of the cellulose pulp is 500-1200, and the α-cellulose content is ≥ 90wt%;

Described antioxidant is propyl gallate;

The additive is a mixture of macromolecule pore-forming agent and small-molecule pore-forming agent;

The weight ratio of the polymer pore-forming agent to the small-molecule pore-forming agent is 1-5:1;

The polymer pore-forming agent is one or a mixture of polyvinylpyrrolidone and polyethylene glycol, the polyvinylpyrrolidone model is selected from K12, K17, K25, K30, K60, K90, and the molecular weight of polyethylene glycol is 200-20000;

The small molecule pore-forming agent is one of glycerin and formamide;

The core liquid is one of water and 1-20wt% glycerol aqueous solution;

The gas in the gas environment is one of air, nitrogen, and argon, the air gap temperature is 24°C, and the humidity is 30-90%RH;

The coagulation bath is one of water, NMMO containing 5-50wt% water, and 5-50wt% formamide aqueous solution, and the temperature is 10-50°C.

The alkali-resistant regenerated cellulose film of the present invention has the following advantages:

1) The film-making process of the present invention is simple, pollution-free, and the solvent NMMO is easy to recycle, which is a green process.

2) The cellulose pulp used in the present invention does not require high content of α-cellulose, which can reduce the production cost of cellulose pulp and expand the source range of raw materials.

3) Sodium hydroxide post-treatment can reduce the content of impurities such as hemicellulose and lignin in the cellulose film, and make the content of α-cellulose in the regenerated cellulose film as high as possible; this method can also change the content of the cellulose film. The pore structure provides a way to prepare porous cellulose membranes.

4) In the present invention, a polymer pore-forming agent and a small-molecule pore-forming agent are added to the regenerated cellulose casting solution, and through the compound combination of the polymer pore-forming agent and the small-molecule pore-forming agent, the The pore structure of the cellulose membrane makes the pore diameter of the regenerated cellulose membrane larger than 0.001 μm and smaller than 0.1 μm, and the molecular weight of the organic matter that can be intercepted is greater than 500 M _W .

5) The alkali-resistant regenerated cellulose film prepared by the present invention can be used for pressing wastewater of viscose fiber, black liquor of alkaline papermaking, yarn cooking and mercerizing washing water of printing and dyeing industry, ash-alkali depilation wastewater of leather industry and petroleum, chemical industry Wastewater treatment in some production processes, etc.

detailed description

Example 1

At 80 °C, 5 g of reed straw with a degree of polymerization of 1200 and an α-cellulose content of 90 wt%, 0.83 g of PVP-K90, 0.17 g of glycerol, 0.1 g of propyl gallate and 93.9 g of NMMO solvent containing 15 wt% of water were mixed , stir evenly to make it dissolve, it takes about 1 hour, after defoaming and filtering, a 5wt% cellulose casting solution is obtained; cast the casting solution on a glass plate at 70°C to form a flat film, and immediately put the film into Coagulate in deionized water for 5min; after washing, treat the membrane with 17wt% sodium hydroxide aqueous solution for 45min at 30°C, then soak the membrane in 30wt% glycerin aqueous solution for 3h after washing, and then dry the membrane in air at room temperature After drying, the regenerated cellulose flat ultrafiltration membrane can be obtained. The water flux of the membrane is 637L/m ² ·h, and the rejection rate of 1% bovine serum albumin is 98%.

Example 2

At 100°C, 20g of bamboo pulp with a degree of polymerization of 912 and an α-cellulose content of 93wt%, 4g of PEG8000, 4g of glycerin, 2g of propyl gallate and 70g of NMMO solvent containing 5wt% of water were mixed and stirred evenly to make It takes about 2 hours to dissolve, and after degassing and filtering, 20wt% cellulose casting solution is obtained; at 70°C, the casting solution and 20wt% glycerin aqueous solution are co-extruded into a tubular film through a spinneret, and the film is passed through 15cm at 24°C, 90%RH in an argon air gap and then solidified in a NMMO solvent containing 10wt% water at 50°C; after washing, the film was treated with 22wt% sodium hydroxide aqueous solution for 100min at 25°C, and then After washing with water, soak the membrane with 10wt% glycerol aqueous solution for 24 hours, and then dry the membrane in air at room temperature to prepare the regenerated cellulose hollow fiber nanofiltration membrane. The water flux of the membrane is 234L/m ² ·h, and the retention rate of impurities such as hemicellulose in viscose fiber pressing wastewater is as high as 98%.

Example 3

At 90 °C, 24 g of wood pulp with a degree of polymerization of 500 and an α-cellulose content of 92 wt%, 3.75 g of PVP-K30, 1.25 g of formamide, 2 g of propyl gallate and 169 g of NMMO solvent containing 10 wt% of water were mixed , stir evenly to dissolve it, it takes about 1.5h, after defoaming and filtering, a 12wt% cellulose casting solution is obtained; at 70°C, the casting solution and 1wt% glycerin aqueous solution are co-extruded into a tubular shape through a spinneret The membrane was immediately put into 30°C, 5wt% formamide aqueous solution to solidify; after washing, the membrane was treated with 20wt% sodium hydroxide aqueous solution for 60min at 20°C, and then soaked in 30wt% glycerin aqueous solution for 15h after washing with water. Then the membrane is dried in the air at room temperature to prepare the regenerated cellulose hollow fiber ultrafiltration membrane. The water flux of the membrane is 532L/m ² ·h, and the rejection rate of 1% bovine serum albumin is 99%.

Claims (7)

1. a kind of alkali resistant cellulose film is it is characterised in that this film includes alkali resistant cellulose hollow-fibre membrane and alkali resistant cellulose flat board Film, is directly to dissolve cellulose pulp and additive using the NMMO containing 5～15wt% water for solvent, then using the gel that soaks Phase inversion is spun into regenerated cellulose hollow fiber film or is cast into regenerated cellulose Flat Membrane, then locates after sodium hydroxide Reason, washing, glycerol post processing and be obtained,

The preparation method of described alkali resistant cellulose film, comprises the following steps：

1) preparation of casting solution：Under the conditions of 80～100 DEG C, percentage by weight is 5～20：70～93.9：1～8：0.1～2 Cellulose pulp, uniformly mix containing the NMMO of 5～15wt% water, additive and antioxidant, stir, dissolve, deaeration is filtered, The cellulose casting solution of 5～20wt% is obtained；

Described additive is macromolecular pore generators, the mixture of small molecule pore former；

Described small molecule pore former is one of glycerol, Methanamide；

2) the gel phase inversion that soaks is spun into film：Under the conditions of 70 DEG C, by step 1) be obtained casting solution flow on a glass Prolonging into Flat Membrane, or by step 1) casting solution and the core liquid that are obtained extrudes tubular film by spinneret simultaneously；Flat by be obtained Plate film one gaseous environment decentralization set to 0～120S after enter coagulating bath in solidification 3～5min or by tubular film through 0～20cm's Enter in coagulating bath after gaseous environment and solidify；Deionized water washes away the residual solvent in this film again；

Described core liquid is one of water, glycerine water solution of 1～20wt%；

Described coagulating bath is water, one of the NMMO containing 5～50wt% water, 5～50wt% formyl amine aqueous solution, and temperature is 10～50 DEG C；

3) under the conditions of 20～30 DEG C, with 17～22wt% sodium hydrate aqueous solution process step 2) cellulose membrane prepared 45～ 100min；

4) by step 3) it is immersed in 3～24h in the glycerine water solution of 10～50wt% after the washing of the cellulose membrane prepared, then will Film is taken out room temperature and is dried i.e. prepared alkali resistant cellulose film.

2. a kind of alkali resistant cellulose film described in a kind of claim 1 preparation method it is characterised in that the method include following Step：

1) preparation of casting solution：Under the conditions of 80～100 DEG C, percentage by weight is 5～20：70～93.9：1～8：0.1～2 Cellulose pulp, uniformly mix containing the NMMO of 5～15wt% water, additive and antioxidant, stir, dissolve, deaeration is filtered, The cellulose casting solution of 5～20wt% is obtained；

2) the gel phase inversion that soaks is spun into film：Under the conditions of 70 DEG C, by step 1) be obtained casting solution flow on a glass Prolonging into Flat Membrane, or by step 1) casting solution and the core liquid that are obtained extrudes tubular film by spinneret simultaneously；Flat by be obtained Plate film one gaseous environment decentralization set to 0～120S after enter coagulating bath in solidification 3～5min or by tubular film through 0～20cm's Enter in coagulating bath after gaseous environment and solidify；Deionized water washes away the residual solvent in this film again；

Described core liquid is one of water, glycerine water solution of 1～20wt%；

Described coagulating bath is water, one of the NMMO containing 5～50wt% water, 5～50wt% formyl amine aqueous solution, and temperature is 10～50 DEG C；

3) under the conditions of 20～30 DEG C, with 17～22wt% sodium hydrate aqueous solution process step 2) cellulose membrane prepared 45～ 100min；

4) by step 3) it is immersed in 3～24h in the glycerine water solution of 10～50wt% after the washing of the cellulose membrane prepared, then will Film is taken out room temperature and is dried i.e. prepared alkali resistant cellulose film.

3. a kind of alkali resistant cellulose film according to claim 1 it is characterised in that described cellulose pulp be absorbent cotton, The mixture of one of bamboo pulp, wood pulps, reed straw, wheat straw waste, rice straw, Caulis Sacchari sinensis straw or two kinds.

4. a kind of alkali resistant cellulose film according to claim 1 or 3 is it is characterised in that the described cellulose pulp degree of polymerization For 500～1200, alpha-cellulose content >=90wt%.

5. a kind of alkali resistant cellulose film according to claim 1 it is characterised in that described macromolecular pore generators with little point The weight of sub- pore former is than for 1～5：1.

6. according to claim 1 or 5 a kind of alkali resistant cellulose film it is characterised in that described macromolecular pore generators are poly- The mixture of one of vinylpyrrolidone, Polyethylene Glycol or two kinds, Polyvinylpyrrolidone model be selected from K12, K17, K25, K30, K60, K90, molecular weight polyethylene glycol is 200-20000.

7. a kind of alkali resistant cellulose film according to claim 1 is it is characterised in that step 2) described in gaseous environment in Gas is one of air, nitrogen, argon, and air gap temperature is 24 DEG C, and humidity is 30～90%RH.