JPS6397666A - Low-temperature soluble type stock solution and production thereof - Google Patents

Abstract

PURPOSE:To produce a stock soln. which is of a low-temperature soluble type which causes phase separation on a high-temperature side, allows a temp. effect during solidification to be easily utilized and can be stably stored at low temp., by adding a specified additive to a soln. obtd. by mixing a hydrophobic high-molecular material with a hydrophilic high-molecular material. CONSTITUTION:An additive (A) which is a non-solvent for the component B and a wetting agent (e.g., water, 1,4-butanediol, etc.) is added to a soln. obtd. by mixing a hydrophobic high-molecular material (B) (e.g., polysulfone) as a principal ingredient with a hydrophilic high-molecular material (C) (e.g., polyvinylpyrrolidone) and mixing them (e.g., a dimethylacetamide soln.) to produce a low-temperature soluble type stock soln. which causes phase separation on a high-temperature side. The stock soln. can be easily stored at low temp. and advantageously used in the production of semipermeable membranes having large pores in particular. Further, the stock soln. contains the hydrophilic high-molecular material so that dry membranes can be easily prepd. If the hydrophilic high-molecular material is crosslinkable, it can be used in the fields of articles requiring resistance to water and dissolution, even when the crosslinkable material is water-soluble.

Description

[Detailed description of the invention] (Industrial application field) TECHNICAL FIELD The present invention relates to a method for producing a low-temperature solution and a stock solution.

[Conventional technology]

Conventionally, many polymeric compounds such as cellulose acetate, polyacrylonitrile, polymethyl methacrylate, polyamide, polyolefin, polyimide, polycarbonate, polyarylate, polysulfone, and polyester have been used as membranes and coating agents. especially,
A large number of membranes are available that are made mainly of hydrophobic polymers such as polyacrylonitrile, polymethyl methacrylate, polyolefin, polyimide, polycarbonate, polyarylene, polysulfone, and polyester. In particular, the following methods have been proposed for forming porous membranes for materials with strong intermolecular cohesion, such as polysulfone resins.

■ A method that utilizes microphase separation between different types of polymers.

(Japanese Patent Publication No. 48-176, Japanese Unexamined Patent Publication No. 14445/1972)
Publication No. 6, Publication No. 57-50506, Publication No. 57-505
(No. 07, No. 57-50501) (2) A method that includes extraction and elution operations after film formation. (Unexamined Japanese Patent Publication No. 5
(No. 4-26283, No. 57-35906, No. 58-91822) (2) A method of forming a film in a metastable liquid dispersion state of a film forming stock solution. (JP-A-56-154051, JP-A No. 59-58041, JP-A No. 59-18376)
(Japanese Patent Application Laid-Open No. 59-2280)
(No. 16 Publication) However, method (2) only utilizes the difference in coagulation rate between polymers, and has not yet achieved large pores with a molecular weight cut-off of 100,000 or more. Moreover, since a large amount is blended, the original good performance of the polysulfone resin is likely to be lost.

In addition, the method (2) is broadly classified into two methods: extraction of the blend polymer and elution of the la-free granules. In the former, polyethylene glycol and polyvinylpyrrolidone are the main polymers, but it is difficult to obtain a sufficient pore size and to perform extraction operations.

In the latter example, in the above-mentioned Japanese Patent Application Laid-Open No. 58-91822,
After mixing silica powder and forming a film, it was eluted using an alkali and was successful in creating large pores of 0.05 μm or more, but it is noted that it has a drawback in water wettability.

Method (2) involves mixing a large amount of a polysulfone resin non-solvent or swelling agent with a film-forming stock solution, and forming a film just before the film-forming stock solution undergoes phase separation.

With such a method, only a film having defects in water wettability can be obtained.

Method ① involves blowing high-humidity air during film formation.
Although the pore size expansion on the surface is achieved, this method is effective only on one side, and in particular, in the case of hollow fiber membranes, only a small range of fractionated molecules can be obtained.

All of these conventional rIjA stock solutions are characterized by phase separation at low temperatures. For this reason, even if the temperature of the coagulation bath is increased in an attempt to increase the exchange rate between the non-solvent, etc. in the coagulation bath and the good solvent in the membrane during membrane formation, the membrane-forming stock solution will move toward a homogeneous system, resulting in It has the property of forming a dense layer and is difficult to store at low temperatures. Additionally, due to its hydrophobic nature, it has the disadvantage that once it has been dried, it is difficult to recover its wettability without special treatment. did not exist.

[Problem that the invention seeks to solve]

The present inventors analyzed the above-mentioned drawbacks, and as a result of intensive study, they arrived at the present invention. In particular, the purpose is to provide a stock solution that is a low-temperature melting type that undergoes phase separation on the high-temperature side, is easy to utilize the temperature effect during solidification, and is stable even when stored at low temperatures.

[Means for solving problems]

The present invention has the following configuration. That is, (1) a low-temperature dissolving stock solution characterized by phase separation on the high-temperature side;

(2) A low-temperature dissolution type characterized by adding an additive such as a non-solvent or a swelling agent for the main hydrophobic polymer to a solution in which the main hydrophobic polymer and the hydrophilic polymer are mixed and dissolved. This is a method for producing a stock solution.

The method for preparing the low-temperature solution stock solution of the present invention will be specifically explained below.

In the present invention, the main hydrophobic polymer (I>) is a polymer such as polyacrylonitrile, polymethyl methacrylate, polyolefin, polyimide, polycarbonate, polyarylate, polysulfone, or polyester.

Among these, polysulfone resin will be explained as an example, but it is not limited to this resin.

The low-temperature solution stock solution of the present invention is basically composed of a four-component system consisting of a polysulfone resin (■), a hydrophilic polymer (■), a solvent (I [I)], and an additive (IV). The polysulfone resin (I> mentioned here is usually represented by the formula (1),
Alternatively, it is composed of a repeating unit of formula (2) H3, but is not particularly limited, even if it contains a functional group or is an alkyl type unit.

The hydrophilic polymer (n) is a polymer that is compatible with polysulfone resin (I>) and has hydrophilic properties. Polyvinylpyrrolidone is the most desirable, but other examples include modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone, Examples include, but are not limited to, polyethylene glycol, polyvinyl acetate, etc. It is necessary to make an appropriate judgment depending on the compatibility with the main hydrophobic polymer.

The solution W (nl) is a solvent that dissolves both the polysulfone resin (I) and the hydrophilic polymer (II).

Various solvents can be used, such as dimethyl sulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, and dioxane, but dimethylacetamide, dimethylsulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone are particularly preferred.

The additive (IV) can be anything as long as it is compatible with the solvent (III), serves as a good solvent for the hydrophilic polymer (II>), and serves as a non-solvent or swelling agent for the polysulfone resin (1). For example, water, methanol, ethanol, isopropanol, beki-1-non'ol, 1,4-butanediol, etc.Water is most preferable in terms of production cost.Additive (IV) is polysulfone resin. (It may be selected after considering the coagulability against I>.

Each of these combinations J is arbitrary, and it is easy for those skilled in the art to think of combinations having the above properties. In addition, the solvent (I[[) and additive (IV) are 2
A mixed system of different types of compounds may also be used.

Surprisingly, this membrane-forming stock solution undergoes phase separation on the high temperature side, contrary to the normal phase separation behavior in which phase separation occurs on the low temperature side. This principle will be explained below.

◇, it is assumed that this film-forming stock solution is homogeneous at a certain temperature T.

In this case, the additive (IV) is shielded from the polysulfone resin (I>) by the hydrophilic polymer (If), and does not directly interact with the polysulfone resin (1). In systems where the hydrophilic polymer (II) is not mixed, the system resin (I> will naturally coagulate and the additive (IV) will be added to a concentration such that phase separation occurs.
This means that even after adding , the system remains homogeneous without phase separation. Here, when the temperature is raised, the mobility of molecules increases, especially for hydrophilic polymers (II>) and additives (
The bond with the polysulfone resin (IV) becomes weaker, the hydrogen bond is broken, and the apparent concentration of the additive (IV) that is not bonded to the hydrophilic polymer (n) increases from that at temperature T. The interaction between I> and the additive (IV) ultimately causes coagulation and phase separation of the polysulfone resin (I).In other words, the membrane forming stock solution undergoes phase separation on the high temperature side. Roughly speaking, if the amount of additive (IV) in this system is increased, even at the temperature T, in this stock solution system, the additive (1v) at the temperature T of the hydrophilic polymer (II) is no longer ), the membrane forming stock solution undergoes phase separation due to the addition of the additive (IV) at the highest concentration.

However, if the temperature is lowered too much, the molecular mobility of the hydrophilic polymer (n) decreases, the number of bonding ports with the additive (IV) increases, and the apparent concentration of the additive (IV) decreases. The system becomes a homogeneous system again. When the temperature is raised again, the system becomes non-uniform, but when the hydrophilic polymer (n) is added this time, the number of bonds between the hydrophilic polymer (n) and the additive (IV) increases, and the system becomes heterogeneous again. It becomes uniform.

As described above, the phase separation behavior of this membrane-forming stock solution is the opposite of normal, and the phase transition is reversible.

As for the composition of the film-forming stock solution, the main cocoon-water polymer (I>) may be in a moisture content range of 5 to 50% by weight, as long as it can be formed into a film and has properties as a film.

In order to obtain high water permeability and a large molecular weight, the polymer concentration should be low, preferably from 5 to 20% by weight. If the amount is less than 5% by weight, sufficient viscosity of the film-forming stock solution cannot be obtained and a film cannot be formed. Also, 50
If the amount exceeds %, it becomes difficult to form through holes. Hydrophilic polymers (n), especially in the case of polyvinylpyrrolidone, are commercially available with molecular weights of 360,000, 160,000, 40,000, and 10,000, and it is convenient to use these, but of course there are other Those with molecule O may be used. However, one of the reasons for adding the hydrophilic polymer (II>) is to consider the thickening effect, so the more the polymer layer is used, the better the addition port is, and the temperature dependence of the phase separation phenomenon. The reversal of polyvinylpyrrolidone is also significant, so it is important to obtain a membrane with high water permeability.The added weight of polyvinylpyrrolidone is preferably 1 to 20% by weight, especially 3 to 10mG%, but depending on the amount of polyvinylpyrrolidone used, It depends on the molecular weight.In general, if the amount added is too small or the molecular weight is too low, the phase separation reversal phenomenon will occur.
If the polymer concentration is high and the polymer molecular weight is too large, cleaning after film formation becomes difficult. Therefore, one method is to mix substances with different molecular weights and use them in different roles.

The polymers (1) and (II) above are mixed and dissolved in the solvent (III). Additive (IV) is added here, and especially in the case of water, since the polysulfone resin of formula (1) has high coagulability, it is preferably 7 wt % or less, particularly 1 to 5 wt %. In the case of the resin of formula (2), it is necessary to add 15% by weight or less, particularly 3 to 13% by weight. Also, in the case of polyacrylonitrile, it is necessary to add 5 to 20% by weight.

It is easily assumed that when an additive with low coagulability is used, the amount of m to be added increases. Adjustment of these coagulant additives is also related to the equilibrium moisture content of the hydrophobic polymer. As the concentration of additive (IV) increases, the phase separation temperature of the membrane forming stock solution decreases. The phase separation humidity needs to be set in consideration of the desired opening radius of the membrane, etc.

〔Example〕

The invention will be explained in further detail by the following examples.

Note that the phase separation temperature here refers to the temperature at which a stock solution maintained at a constant temperature becomes cloudy from a homogeneous state when viewed with the naked eye.

Example 1 15 parts of polysulfone (Needel P-3500), 8 parts of polyvinylpyrrolidone (K2O), and 7 parts of 1,4-butanediol were added to 70 parts of dimethylacetamide and dissolved by heating at 80°C. This four-component stock solution is a low-temperature solution,
And phase separation occurred at 65°C.

Example 2 15 parts of polysulfone, polyvinylpyrrolidone (K2O)
8 parts and 2.4 parts of water to 75 parts of dimethylacetamide.
The mixture was heated and dissolved at °C. This four-component stock solution was a low-temperature solution, and phase separation occurred at 65°C.

Comparative Example 1 12 parts of polysulfone and 6 parts of polyvinylpyrrolidone were mixed with N-
It was added to 82 parts of methylpyrrolidone and dissolved by heating with ao'c. This three-component stock solution was a high-temperature solution that became more uniform as the temperature increased.

Example 3 Polyether sulfone (Pictrex 300p) 15
parts, polyvinylpyrrolidone (K-90>8 parts, and 8 parts of water) were added to 75 parts of dimethylacetamide and dissolved by heating at 100°C.
Phase separation occurred at 0°C.

Example 4 13.5 parts of polyacrylonitrile (molecular weight approximately 10,000), polyvinylpyrrolidone (K-90>7 parts), and 5 parts of water were added to 75 parts of dimethyl sulfoxide and dissolved by heating at 110'C.This four-component stock solution was Low temperature melting type and 100%
Phase separation occurred at °C.

Example 5 15 parts of polysulfone (Needel P-3500), 8 parts of polyvinylpyrrolidone (K2O), and 3 parts of water were mixed with N-methyl-
The mixture was added to 74 parts of 2-pyrrolidone and dissolved by heating at 85°C. This four-component stock solution was a low-temperature dissolution type, and phase separation occurred at 25°C.

〔Effect of the invention〕

The low-temperature solution stock solution of the present invention can be easily stored at low temperatures and can be very advantageously used for producing semipermeable membranes, especially those having large pores. Furthermore, since it contains a hydrophilic polymer, a dry film can be easily produced. Furthermore, as long as the hydrophilic polymer is crosslinkable, even water-soluble polymers can be used in applications requiring water resistance and elution resistance.

Furthermore, due to the porosity and hydrophilicity of the film formed when used as a coating agent, moisture can be efficiently dispersed.
It can be used to form a film that can be used to remove heat, and the heat of vaporization at that time can also be used to manufacture highly efficient heat sinks.

Claims (2)

[Claims] (1) A low-temperature solution stock solution characterized by phase separation on the high-temperature side. (2) Low-temperature dissolution characterized by adding an additive such as a non-solvent or a swelling agent for the main hydrophobic polymer to a solution in which the main hydrophobic polymer and the hydrophilic polymer are mixed and dissolved. Manufacturing method of mold stock solution.