CN104524995B - A kind of stable structure separation membrane and its preparation method - Google Patents

Abstract

The present invention relates to a separation membrane with a stable structure and a preparation method thereof, and belongs to the field of membrane separation technology. A separation membrane with a stable structure is obtained by treating a polymer membrane at 150-500°C for at least 0.1h under an oxidizing atmosphere, wherein the polymer is a thermoplastic polymer with a linear molecular structure. The present invention proposes a separation membrane with a thermally rigid stable structure, which has stable chemical properties and excellent gas separation performance, and will have broad application prospects in the field of gas and liquid separation.

Description

A kind of stable structure separation membrane and its preparation method

technical field

The invention relates to a separation membrane with a steady-state structure and a preparation method thereof, in particular to a polymer separation membrane with a thermally rigid steady-state structure and a preparation method thereof, belonging to the technical field of membrane separation.

Background technique

Membrane separation is based on the selective permeability of the membrane. The separation membrane is used as a spacer layer. Under the driving force of pressure difference, concentration difference or potential difference, the rate of each component in the fluid mixture permeating the membrane is different, so that it is separated from the membrane. The two sides are enriched separately to achieve the purpose of separation, purification, concentration and recycling. Membrane separation, as a new separation technology with high efficiency, energy saving and environmental friendliness, is one of the key technologies to solve the increasingly serious problems of energy, resources and environment. At present, membrane technology is widely used in seawater desalination, food concentration, oxygen-enriched air preparation, enrichment and recovery of carbon dioxide gas, gas and hydrocarbon separation, pure water and ultrapure water preparation, environmental protection and sewage treatment, etc.

So far, the gas separation membrane materials that have been commercially used are mainly polymer membrane materials. However, these polymer membrane materials either have high gas selectivity but low gas permeability, such as polysulfone, polyethersulfone, polyimide or polyetherimide membrane materials; Low resistance, such as silicone rubber membrane materials, especially polymer membranes have problems of poor heat resistance and solvent resistance. With the market's increasing performance requirements for gas separation membranes (high permeability and high selectivity, high temperature resistance, solvent resistance), these defects of polymer membranes have gradually emerged, making it difficult to meet the growing market requirements. How to improve the heat resistance and solvent resistance of polymer membranes has become a hot spot in the field of membrane technology.

Transforming polymers with linear structures into polymers with bulk structures through structural crosslinking is considered to be an effective method to improve the heat resistance and solvent resistance of polymer films. Chemical crosslinking is a commonly used method at present. In recent years, the thermal crosslinking method has attracted people's attention. Nurul Islam et al. (J.Membr.Sci., 2005,261:17-26) used sulfonated polyimide to prepare polymer membranes, and under nitrogen atmosphere Heating to 450°C for pyrolysis, the obtained low-temperature pyrolysis film maintains good flexibility of the polymer film, and improves its thermal stability and solvent resistance. Park et al. (Science, 2007, 318: 254-258) performed an irreversible thermal molecular rearrangement reaction on a polyimide polymer film containing -OH and -SH groups at a temperature of 350-450 ° C, and also Improved thermal stability of the polymer film. However, this thermal rearrangement reaction has certain limitations. It must be a polymer containing a thermally reactive group in the molecular structure to occur, and the thermal and chemical stability of this polymer is poor, and the rearrangement reaction is difficult. The conditions are more stringent. In addition, the synthesis process of polymers containing thermally reactive groups is relatively complicated, and the production cost is high, which is not conducive to its industrial application.

Contents of the invention

The present invention aims to provide a preparation method of a polymer separation membrane with a stable chemical structure, excellent separation performance, and a thermally rigid steady-state structure (referred to as a thermally rigid separation membrane), so as to solve and make up for the existing polymer separation membrane materials. Limited separation performance, poor temperature resistance, easy plasticization, unstable structure during use, and short service life. The invention adopts the polymer with the linear molecular structure as the precursor to prepare the polymer membrane, and undergoes heat-induced rigidity treatment in an oxidizing atmosphere, so that the obtained separation membrane material has a stable rigid molecular structure.

A separation membrane with a stable structure, which is obtained by treating a polymer membrane at 150-500°C for at least 0.1h in an oxidative atmosphere,

Wherein, the polymer is a thermoplastic polymer with a linear molecular structure.

The "polymer film" in the present invention refers to a film composed of a polymer, which is a thermoplastic polymer with a linear molecular structure, which can be purchased commercially or prepared according to methods disclosed in the prior art. In the present invention, the preferred polymer is polyacrylonitrile, polysulfone, polyethersulfone, polyetherimide, polyimide, polyethersulfoneketone, polyaryletherketone, polyethernitrileketone, polyarylethersulfone, One or more of phenolic resins, benzoxazine resins, and cyanate resin polymers.

The polymer membrane of the present invention is preferably made of polyacrylonitrile, polysulfone, polyethersulfone, polyetherimide, polyimide, polyethersulfoneketone, polyaryletherketone, polyarylethersulfone, polyethernitrile One or more of ketones, phenolic resins, benzoxazine resins, and cyanate resin-based polymers are the constituent polymer films.

In the present invention, it is preferable that the thickness of the polymer film is 10-100 μm.

The oxidizing atmosphere of the present invention is preferably provided by an oxygen-containing mixed gas, and the oxygen-containing mixed gas is composed of an oxidizing gas of 5% to 50% (V/V) and a balance carrier gas; the preferred oxidizing gas is oxygen, air Or one or more of ozone; preferably, the carrier gas is an inert gas, such as nitrogen, argon, etc.

In the present invention, preferably, the flow rate of the oxidizing gas is 5-500 mL/min.

In the present invention, preferably, the separation membrane with stable structure is obtained by treating the polymer membrane at 150-500° C. for 0.1-24 hours under an oxidative atmosphere, and the heating rate is 1-20° C./min.

Another object of the present invention is to provide a method for preparing the above-mentioned separation membrane.

A method for preparing the separation membrane, the polymer membrane is treated at 150-500°C for at least 0.1h in an oxidizing atmosphere

Wherein, the polymer is a thermoplastic polymer with a linear molecular structure.

In the present invention, the preferred polymer is polyacrylonitrile, polysulfone, polyethersulfone, polyetherimide, polyimide, polyethersulfoneketone, polyaryletherketone, polyarylethersulfone, polyethernitrileketone, One or more of phenolic resins, benzoxazine resins, and cyanate resin polymers.

In the present invention, it is preferable that the thickness of the polymer film is 10-100 μm.

The oxidizing atmosphere of the present invention is preferably provided by an oxygen-containing mixed gas, and the oxygen-containing mixed gas is composed of an oxidizing gas of 5% to 50% (V/V) and a balance carrier gas; the preferred oxidizing gas is oxygen, air Or one or more of ozone; preferably, the carrier gas is an inert gas, such as nitrogen, argon, etc.

In the present invention, preferably, the flow rate of the oxidizing gas is 5-500 mL/min.

In the present invention, the method for preparing the separation membrane preferably comprises the following steps: treating the polymer membrane at 150-500° C. for 0.1-24 hours in an oxidizing atmosphere, and the heating rate is 1-20° C./min.

The beneficial effects of the present invention are:

The invention proposes a method for preparing a separation membrane with a thermally rigid and stable structure. This method avoids the use of thermally rearranged polymers that are expensive and have poor thermal and chemical stability. The process is simple, low in cost, and applicable. The range is wide, the obtained material has stable chemical properties and excellent gas separation performance, and will have broad application prospects in the field of gas and liquid separation.

Description of drawings

Fig. 1 is the photo of the untreated polyacrylonitrile film of embodiment 1;

Fig. 2 is the photo of the heat-induced rigid separation membrane after the treatment of Example 1;

Figure 3 is a photo of the thermally rigid separation membrane after treatment in Example 1. It can be seen from Figure 3 that the prepared separation membrane with a stable structure not only has good rigidity, but also has good flexibility and mechanical strength.

detailed description

The following non-limiting examples can enable those skilled in the art to understand the present invention more fully, but do not limit the present invention in any way.

The test methods described in the following examples, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial sources.

The concentrations in the mixed gas involved in the following examples are volume concentration % (V/V).

Example 1

The polyacrylonitrile membrane was placed in an atmosphere furnace, and after repeated inflation/degassing 3 times, a mixed gas (composed of 5% ozone and 95% nitrogen) was introduced into the furnace at a flow rate of 500 mL/min, and the furnace temperature was set at 3 The temperature was raised to 350°C at a rate of °C/min and maintained at this temperature for 1 hour to obtain a thermally rigid separation membrane.

Example 2

According to the method described in Example 1, the polyacrylonitrile membrane was replaced by a polyimide membrane or a polysulfone membrane, and a mixed gas (composed of 15% ozone and 85% nitrogen) was introduced at a flow rate of 50 mL/min in an oven. The temperature was raised to 300°C at a rate of 5°C/min and maintained at this temperature for 0.1 hour to obtain a thermally rigid separation membrane.

Example 3

According to the method described in Example 1, the polyacrylonitrile membrane is replaced by a polyamic acid membrane, a polyether sulfone ketone membrane or a polyarylether ketone membrane, and a mixed gas (composed of 5% ozone and 95% nitrogen) is introduced, The flow rate is 250mL/min, the furnace temperature is raised to 150°C at a rate of 1°C/min, and maintained at this temperature for 24 hours to obtain a thermally rigid separation membrane.

Example 4

According to the method described in embodiment 1, feed mixed gas (composition of 5% oxygen and 95% argon), flow velocity is 50mL/min, furnace temperature is warming up to 450 ℃ with the speed of 10 ℃/min, and at this Maintain the temperature for 2 hours to obtain a thermally rigid separation membrane.

Example 5

According to the method described in Example 1, the polyacrylonitrile membrane is replaced by a polyamic acid membrane, a polyether sulfone ketone membrane or a polyarylether ketone membrane, and a mixed gas (composed of 50% oxygen and 50% argon) is introduced , the flow rate is 10mL/min, the furnace temperature is raised to 250°C at a rate of 2°C/min, and maintained at this temperature for 12 hours to obtain a thermally rigid separation membrane.

Example 6

According to the method described in Example 1, the polyacrylonitrile membrane was replaced by a polyimide membrane or a polysulfone membrane, and a mixed gas (consisting of 15% oxygen and 85% nitrogen) was introduced at a flow rate of 150 mL/min. The temperature was raised to 350°C at a rate of 3°C/min and maintained at this temperature for 6 hours to obtain a thermally rigid separation membrane.

Example 7

According to the method described in Example 1, feed the mixed gas (composed of 5% air and 95% argon), the flow rate is 250mL/min, the furnace temperature is heated up to 450°C at a speed of 10°C/min, and The temperature was maintained for 2 hours to obtain a thermally rigid separation membrane.

Example 8

According to the method described in Example 1, the polyacrylonitrile membrane is replaced by a polyamic acid membrane, a polyether sulfone ketone membrane or a polyarylether ketone membrane, and a mixed gas (composed of 50% air and 50% nitrogen) is introduced, The flow rate was 100mL/min, and the furnace temperature was raised to 500°C at a rate of 2°C/min, and maintained at this temperature for 18 hours to obtain a thermally rigid separation membrane.

Example 9

According to the method described in Example 1, the polyacrylonitrile membrane is replaced by a polyimide membrane or a polysulfone membrane, and a mixed gas (composed of 15% air and 85% nitrogen) is introduced, and the flow rate is 350mL/min. The temperature was raised to 450°C at a rate of 3°C/min and maintained at this temperature for 9 hours to obtain a thermally rigid separation membrane.

The thermally rigid separation membrane and the original membrane obtained in the above-mentioned Examples 1 to 9 were respectively placed in various organic solvents, and their solubility properties are shown in Table 1:

Table 1

The heat-induced rigid separation membrane and the original membrane obtained in the above-mentioned Examples 1 to 9 were respectively placed in dilute acid and dilute alkali for 24 hours, and its stability is shown in Table 2:

Table 2

The gas separation properties of the original polymer membranes listed in Examples 1 to 9 are as shown in Table 3:

table 3

1 Barrer＝1×10 ^-10 cm ³ (STP) cm/(cm ² s cm Hg)

The gas separation properties of the thermally induced rigid separation membranes obtained in Examples 1 to 9 are shown in Table 4:

Table 4

1 Barrer = 1×10 ⁻¹⁰ cm ³ (STP)·cm/(cm ² ·s·cm Hg).

Claims (5)

1. a Stable structure separation film, is by polymeric film in an oxidizing atmosphere, processes at least 0.1h in 150～500 DEG C Gained,

Wherein, described polymer is polyacrylonitrile, polysulfones, polyether sulfone, Polyetherimide, polyimides, polyethersulfone ketone, polyarylether One or more in ketone, polyether sulphone, polyethers nitrile ketone, phenolic resin piperazine resin, cyanate ester resin base polymer.

Separation film the most according to claim 1, it is characterised in that: oxidizing atmosphere is provided by containing oxygen gas mixture, described contains Oxygen gas mixture is made up of 5～the oxidizing gas of 50% (V/V) and surplus carrier gas.

Separation film the most according to claim 1, it is characterised in that: described oxidizing gas is oxygen, air or ozone.

Separation film the most according to claim 1, it is characterised in that: be by polymeric film in an oxidizing atmosphere, in 150～ 500 DEG C process 0.1～24h gained, heating rate 1～20 DEG C/min.

5. prepare the method separating film described in claim 1 for one kind, it is characterised in that: by polymeric film in an oxidizing atmosphere, At least 0.1h is processed in 150～500 DEG C,

Wherein, described polymer is polyacrylonitrile, polysulfones, polyether sulfone, Polyetherimide, polyimides, polyethersulfone ketone, polyarylether One or more in ketone, polyether sulphone, polyethers nitrile ketone, phenolic resin piperazine resin, cyanate ester resin base polymer.