RU2218980C2 - Method of manufacture of a gas-separating composite membrane - Google Patents

Abstract

FIELD: chemical, petrochemical, medical industries. SUBSTANCE: invention presents a method of manufacture the gas- separating composite membrane, that may find application in processes of gas-separation and concentration of the gases used in chemical, petrochemical, medical industries. The working solution of a block-copolymer is being prepared as the micellar system by a spontaneous dispersion of the block-polymer with its simultaneous mixing with dissolvent and nonsolvent, taken in the following ratio of mass shares: the block-polymer - 1, dissolvent - from 2 up to 40, nonsolvent - from 6 up to 35. The gas selecting layer shaping is exercised from this solution on the hydrophobic porous substrate made in the form of the ultra- or microfiltration membrane by a dry method using bonded fabric of the polypropylene or the polyester fibers, having the pores sizes chosen from the ratio: Ds = (0,05-0,9)Dm, where Ds is the pores size of the substrate, Dm is the size of micelles of the working solution of the block-copolymer - an equivalent diameter. The block- copolymer is chosen from the group - oligoarylate with oligodimethylsiloxane, oligocarbonate with α- oligobiscloreformatesiloxane, ω-bis(diethylamino)organosiloxane oligomer with phenylsylsesquioxane oligomer or oligosulphone with oligobutadiene. In the capacity of dissolvent they use methylene chloride or chloroform. In the capacity of non-solvent - hexane or petroleum ether. EFFECT: the invention ensures high efficiency and reliable operation alongside with high industrial reproducibility of the gas-separation properties in the systems of CO₂-O₂-N₂. gases. 2 cl, 3 tbl, 13 ex, 1 dwg

Description

FIELD OF TECHNOLOGY
The invention relates to a method for producing a gas separation composite membrane, which consists of a microporous hydrophobic substrate coated with a gas-selective block copolymer layer. Such a membrane has found application in gas separation and gas concentration processes in various industries and agricultural production, as well as in medical technology, in liquid-gas mass transfer processes, in particular in membrane oxygenators for enriching blood with oxygen.

 The use of such membranes in industry, agricultural and medicine determines such indicators of a gas separation composite membrane as selectivity, productivity, strength, reliability, and also the reproducibility of these properties in the technology of producing the membrane. In modern production of gas separation membranes based on organosilicon polymers, the reproducibility level of the operational properties of such membranes does not meet the growing requirements of these industries, in particular, the requirements of medical equipment.

BACKGROUND
There are various methods for producing gas separation composite membranes, among which the so-called "dry" molding method is also intensively developed for gas-selective membranes based on various polymers, including organosilicon ones (RF Patents 2065321 and 2074020).

Known from these inventions, the "dry" method for producing gas separation composite membranes includes four main stages:
1) obtaining a porous substrate in the form of an ultra- or microfilter,
2) obtaining a working polymer solution, including organosilicon (RF Patent 2074020),
3) applying a working solution to a porous substrate,
4) heat treatment of the system "porous substrate - deposited working solution" in the conditions of free evaporation of low-boiling components of the working solution.

Gas separation composite membranes obtained by the known "dry" method, are not intended for gas separation "CO ₂ -O ₂ -N ₂ ".

SUMMARY OF THE INVENTION
The basis of the invention is the creation of a method for producing a gas separation composite membrane based on polymers having high gas selective properties guaranteed to be reproducible under industrial conditions in CO ₂ -O ₂ -N ₂ gas systems with high performance and operational reliability.

The problem is solved by a number of proposed original techniques in the implementation of the "dry" method for producing such membranes, which (techniques) according to the invention include
a) the working solution of the block copolymer is prepared in the form of a micellar (colloidal, lyophilic) system,
b) receiving the micellar system is carried out the so-called "spontaneous dispersion" of the block copolymer simultaneously in its solvent and non-solvent,
c) the solvent, non-solvent and block copolymer for the preparation of the micellar system are taken in the ratio, parts by weight:
Polymer - 1
Solvent - 2 to 40
None Solvent - 6 to 35
g) the formation of the gas-selective layer is carried out from the micellar system of the block copolymer on a porous hydrophobic substrate,
d) as a porous hydrophobic substrate take an ultrafine or microfiltration hydrophobic membrane, the pore size of which is selected from the ratio
Dp = (0.05-0.9) DM
where Dp - pore size of the substrate membrane
Dm is the micelle size of the block copolymer working solution, equivalent diameter,
f) as a block copolymer, products from the group are selected: block copolymer of oligo arylate with oligodimethylsiloxane, block copolymer of oligocarbonate with α-oligobischloroformate siloxane, block copolymer of α-, ω-bis (dimethylamino) organosiloxane oligomesulfoxyl oligomes oloxomeroxyl oligomes oloxomeroxyl oligomes oloxomeroxyl oligomes oloxomeroxyl oligomers.

 According to the invention, it is preferable to use solvents selected from the class of chlorinated hydrocarbons (methylene chloride, chloroform), and as non-solvents selected from the class of aliphatic hydrocarbons or mixtures thereof with aromatic hydrocarbons (hexane or petroleum ether).

 To increase the gas-selective properties of the membrane, performance and operational reliability according to the invention, the gas-selective layer is formed in several completed stages (in the best case scenario 2 or 3), each of which uses the same micellar block copolymer system of the same composition.

 We have found that improving the technological and operational properties of a gas separation composite membrane based on certain block copolymers can be achieved on the way to the development of the so-called "spontaneous dispersion" (the general concept of this phenomenon is given in sufficient detail, in particular, in the book of S. S. Voyutsky, "The Course of Colloid Chemistry." - M .: Chemistry, 1975) with the formation of a micellar (colloid, lyophilic) system, which, as we found that it takes place when the studied block copolymers of the Silar type (block copolymer of oligo arylate with oligodimethylsiloxane), Carbosil (block copolymer of oligocarbonate with α-oligobischloroformatesiloxane), Lestosil (block copolymer of α-, ω-bisolenesilyl diethylamide oxane oligomer) or "Seragel" (block copolymer of oligosulfone and oligobutadiene) are mixed simultaneously with their solvent and non-solvent, taken in certain ratios, at normal temperature and pressure.

 Under the conditions for producing a micellar system of the said block copolymers found according to the invention, not only a thermodynamically stable colloidal system is formed, but also a system with a dispersion close to monodispersity. The latter, in turn, made it possible to use a porous substrate in the form of an ultra- or microfiltration membrane with a pore size associated with micelles of the colloidal system of the block copolymer with a ratio of Dp = (0.05-0.9) DM to obtain a gas separation composite membrane.

The proposed method for producing a gas separation composite membrane based on the described block copolymers can be implemented under industrial conditions using all of the above components produced on an industrial or pilot scale, as well as using the dry method for producing a gas separation membrane according to a continuous scheme (see drawing)
LIST OF DRAWINGS
The drawing shows a schematic flow diagram of obtaining a gas separation composite membrane by a continuous "dry" method, implemented according to the invention.

1 - Mernik for solvent (methylene chloride or chloroform),
2 - measuring device for a non-solvent (hexane or petroleum ether),
3 - reactor for the preparation of a micellar block copolymer system,
4 - pump for feeding the micellar system into the filter,
5 - filter
6 - deaerator,
7 - a chamber for receiving a gas separation membrane,
8 - take-up reel,
9 - reel for a porous membrane substrate (ultra- or microfiltration),
10 - bath with a working solution-micellar block copolymer system,
11 - calibrating roller,
12 - applying roller.

MODES FOR CARRYING OUT THE INVENTION
Proposed according to the invention, the method of producing a gas separation composite membrane was tested under experimental conditions on a continuous dry-forming machine (see drawing).

 The starting components in predetermined proportions (see Table 2) —the solvent from the measurer (1), the non-solvent from the measurer (2) and the block copolymer — are loaded into the reactor (3) to prepare the micellar system. The reactor (3) is equipped with a stirrer to accelerate the process of spontaneous dispersion of the block copolymer at normal temperature and pressure. The micellar system obtained in the reactor (3) is fed via a pump (4) to a filter (δ) and then to a deaerator (6). The working micellar system is controlled for mechanical inclusions and the absence of air bubbles and is loaded into the bath (10) of the molding chamber (7). In the chamber (7), a predetermined layer of the micellar system is applied to the ultrafine or microfiltration membrane wound from the bobbin (9) using rolls (12 and 11). The thickness of the applied layer of the micellar system is controlled by means of rolls (12 and 11), forming between them a corresponding gap (δ) and the difference in peripheral speeds of their rotation.

After applying the micellar system to the porous membrane substrate, it enters the upper drying zone of the chamber (7), in which an elevated temperature is maintained within the range of 50-90 ^° C to remove boiling components from the deposited layer of the micellar system and to fix it on the porous membrane substrate. The temperature of the micellar system in the bath (10) is maintained within 20 ± 7 ^o C.

 The finished gas separation membrane is wound on the take-up reel (8).

 To obtain the second (and subsequent) layer of the gas-selective layer, a bobbin (8) with a gas separation membrane wound on it is installed in place of the bobbin (9) and the process is repeated as many times as necessary.

 The performance of the gas separation composite membrane obtained according to the invention in the examples below, with statistical data on the reproducibility of the basic properties of this membrane are given in table 1.

 Tables 2 and 3 show the necessary initial data for the implementation of examples of obtaining the membrane according to the invention according to the flow diagram shown in figure 1.

Claims (2)

1. A method of obtaining a gas separation composite membrane by preparing a working solution of a block copolymer and forming from this solution a gas-selective layer on a hydrophobic porous substrate made in the form of an ultra- or microfiltration membrane by the dry method, characterized in that the working solution of a block copolymer selected from the group of oligo arylate with oligodimethylsiloxane oligocarbonate with α-oligobischloroformate siloxane, α, ω-bis (diethylamino) organosiloxane oligomer with phenylsilsesquioxane oligomer or olig sulfone oligobutadienom prepared as a micellar dispersion of the block copolymer spontaneous system when the simultaneous mixing with a solvent and nonsolvent in the ratio, mass parts .: Block copolymer 1 Solvent 2-40 Solvent 6-35 and forming the gas-selective layer is carried out from the micellar system of the polymer on a substrate of non-woven material made of polypropylene or polyester fibers having a pore size selected from the ratio Dp = (0.05-0.9) Dm, where Dp is the pore size of the substrate, Dm - the micelle size of the working solution of the block copolymer is the equivalent diameter. 2. A method of producing a gas separation composite membrane according to claim 1, characterized in that methylene chloride or chloroform is used as a solvent, and hexane or petroleum ether is used as a non-solvent.

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