JPH01131257A - Production of microcellular molded body of high polymer - Google Patents

Abstract

PURPOSE:To obtain the title molded body, having many regular pores and suitable for selective separation membranes for substances, etc., by freezing a molded body of a solution consisting of a liquid crystal high polymer substance and solvent while keeping the above-mentioned high polymer substance in an oriented state and removing a solvent from the afore-mentioned frozen molded body. CONSTITUTION:A solution consisting of a liquid crystal high polymer substance selected from polyglutamic acid derivatives (e.g., poly-gamma-benzyl glutamate) and a solvent (A) (e.g., 1,4-dioxane) is molded to orient the high polymer in the resultant molded body. The molded body is then frozen while keeping the high polymer in an oriented state to replace the solvent (A) with a solvent (B) (e.g., methanol), capable of dissolving the solvent (A) and having a lower freezing point than that of the solvent (A) without dissolving the high polymer substance and the solvent (B) is then removed from the molded body by a critical point drying method or the solvent (A) is removed from the afore-mentioned molded body by a freeze-drying method under a vacuum.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to the production of a microporous polymer molded body made of a liquid crystalline polymer substance and having a large number of fine and regular pores inside and on the surface. It is about the method. More specifically, the present invention provides microporous polymer moldings made of liquid crystalline polymer materials and useful for applications such as selective separation membranes for substances, active ion transport membranes, antithrombotic materials, and electronic components. The present invention relates to a method of manufacturing a body.

[Conventional technology]

A liquid crystalline polymer (sometimes referred to as liquid crystal polymer, liquid crystalline polymer, or LCP) refers to a polymer that becomes liquid crystalline when melted by heat or dissolved in a solvent. The former,
The latter are called thermotropic (melting type) liquid crystalline polymer substances, and the latter are called lyotropic (solution type) liquid crystalline polymer substances. Such polymeric substances either have a rigid mesogen (a chemical structure that causes liquid crystallinity) in their main chain or side chain, or have α
- It is characterized by the ability to take a rigid conformation such as a helical structure.

Even in the molten state or solution state, such polymeric substances do not assume a random coil state like normal polymers, but maintain their rigidity, so the molecules are very easy to orient. It has characteristics. An example of a thermotropic liquid crystalline polymer material is a copolyester of polyethylene terephthalate and hydroxybenzoic acid. Known examples of lyotropic liquid crystalline polymer substances include aromatic polyamides, polypeptides, and cellulose derivatives. In the solution obtained by dissolving these lyotropic liquid crystalline polymer substances in a solvent,
The expression of the liquid crystal state, the peace jSi state, etc. are affected by the chemical structure and degree of polymerization of the polymeric substance that is the solute, the type of solvent, and the concentration and temperature of the solution. Specifically, the present invention relates to lyotropic liquid crystalline polymer materials.

In liquid crystalline polymer substances, whether they are lyotropic or thermotropic, spontaneous molecular alignment occurs under suitable conditions, and this alignment phenomenon is similar to that of low-molecular liquid crystal substances. In most liquid crystalline polymers, the state of orientation is expressed by external stimuli such as shear force, electric field, magnetic field, and influence from interfaces, and therefore, its orientation state cannot be controlled by external stimuli. Yes (orientation treatment). Methods for applying shear force to a liquid crystal material sample include placing the sample between two plates and shifting the plates, and extruding the sample through a thin die.
In this case, the molecules are usually oriented with their long axes in the direction of the shear force. One method of applying an electric field to a liquid crystal material sample is to sandwich the sample between electrode plates made of indium, tin, or oxide-deposited glass, and apply a voltage to the sample. In this case, the molecules usually have their long axes Orient towards the direction of the electric field. To apply a magnetic field to a liquid crystal material sample, there are methods such as placing the sample in a container and placing it between magnetic poles. In this case, the molecules are usually oriented with their long axes in the direction of the magnetic field. There are various methods for orienting a liquid crystal material sample by the influence of the interface, but well-known methods include rubbing the glass surface in contact with the sample solution in a certain direction with cotton (rubbing method); There are methods such as applying a silane coupling agent to the glass surface and coating the glass surface with polyimide resin. When orientation is caused by the influence of an interface in this way, the orientation behavior of molecules is complicated.

In many solvents, liquid crystalline solutions of polyglutamic acid derivatives have an orientation structure (cholesteric state) in which the molecules are oriented in layers and the orientation direction of the molecules changes at a constant angle between adjacent layers. Take. However, when methylene bromide is used as a solvent, or when an equimolar solution of one derivative and four derivatives is used, the cholesteric state as described above is not obtained. Furthermore, it is known that a liquid crystalline solution of polyglutamic acid is oriented in response to an electric field or a magnetic field very well. In this case, the molecules in the oriented state are said to associate with each other and take a layered or fibrillar higher-order structure of about 1100n to 1p (Koubunshi, Vol. 21, No. 246, pp. 463-470) , 1972).

In recent years, liquid crystalline polymer substances have attracted attention for their industrial use, and the main reason for this is that, as mentioned above, by taking advantage of the property that molecules can be easily aligned, that cannot be obtained in any other way,
This is because materials with highly oriented molecules can be created. Polymer materials in which molecules are highly oriented have extremely high strength and elastic modulus in the direction of their orientation axes, and have performance comparable to metals and inorganic materials while retaining the characteristics unique to organic materials.

A method for producing a molecularly oriented molded article from a thermoplastic liquid crystalline polymer is similar to a conventional molding method for thermoplastic polymers, and has been industrialized in several fields. However, in order to obtain a solution-type liquid crystalline polymer molded product, the object to be molded is a liquid and contains a solvent, so it is necessary to solidify it. This is one of the reasons why industrialization of molded bodies of polymeric substances is restricted. Note that the term "forming" used in this specification includes a membrane forming (film forming) operation and a fiber forming (spinning) operation.

Methods for obtaining molded bodies from liquid crystalline polymer solutions that have been announced so far include the following.

In the case of aromatic polyamide, it is dissolved in pure sulfuric acid to form a liquid crystalline solution at a certain concentration or higher. As a method for producing a fibrous molded article from this solution, a method for obtaining high-strength fibers by wet spinning a sulfuric acid solution of aromatic polyamide (US Pat. No. 3,671,542, etc.) is known.

Also, when a cellulose derivative is dissolved in an organic solvent,
At a concentration above a certain level, a liquid crystalline solution is formed, and methods have been published in which high-strength fibers are obtained by spinning this solution by a wet or dry method (such as JP-A-52-96230).

In addition, as a method for obtaining a three-dimensional molded body that maintains an oriented structure from a liquid crystalline polymer solution, polyglutamic acid is dissolved in n,n'-dimethylacrylamide to form a liquid crystalline solution (cholesterically linked state). and polymerizing n,n'-dimethylacrylamide in this solution to obtain a molded article (Journal of Polymer Science, Polymer Letters Edition, Vol. 15, 47
5-479, 1977).

The molded product thus obtained is said to have optical properties specific to a cholesteric structure.

With the conventional methods of obtaining molded bodies from solutions of liquid crystalline polymer substances as mentioned above, it is possible to obtain materials with high strength and materials with unique optical properties, but the removal of the solvent During this process, the initial liquid crystal structure is destroyed, or the solvent is directly polymerized, resulting in a liquid crystalline polymer in which polymers are distributed in a regular structure in the solvent. It is difficult to obtain a microporous molded body having the original structure of a molecular solution. if,
If only the solvent could be removed from the molded body while maintaining the oriented structure of such a liquid crystalline polymer substance solution, it would be possible to use selective separation membranes for substances, active ion transport membranes, antithrombotic materials, and It is believed that a microporous material useful as electronic components etc. can be obtained.

[Problem that the invention seeks to solve]

The present invention aims to provide a method for manufacturing a novel microporous liquid crystalline polymer material having a fine and regular structure that cannot be obtained by conventional liquid crystalline polymer solution molding methods. It is.

[Means and effects for solving the problem] Regarding the conventional technology, as mentioned above, the present inventors have made earnest efforts in order to effectively utilize the characteristics of liquid crystalline polymer substance solutions industrially. As a result of repeated efforts, we found and completed a new labor union as shown below. That is, the method for producing a microporous polymeric material molded article of the present invention involves molding a solution consisting of a liquid crystalline polymeric material and a solvent A, orienting the liquid crystalline polymeric material in the solution molded material, and Freezing the solution molded body while maintaining the orientation state of the liquid crystalline polymer substance,
This method is characterized in that the solvent A is removed from a shaped frozen body of the solution.

In the method of the present invention, a preferred method for removing the solvent (solvent A, which may be a mixed solvent consisting of a plurality of solvent substances) constituting the solution of the liquid crystalline polymer substance is to dissolve the solvent A in a frozen state. However, the extraction solvent (solvent B), which cannot dissolve the polymeric substance and has a freezing point lower than that of the solvent, is heated at a temperature lower than the freezing point of solvent A and higher than the freezing point of solvent B. In this method, a frozen molded body is immersed in a solution of a liquid crystalline polymer substance, thereby replacing the solvent A in the frozen shaped body with solvent B, and then removing the solvent B from the solvent-substituted molded body. .

When the extraction and substitution of solvent A is completed, the liquid crystalline polymer substance becomes
The molded product is solidified, and the solvent B can be removed from the molded product by methods such as air drying, freeze drying, and critical point drying. When the solvent B is removed, a solid polymeric molded product having a layered or fibrillar structure and easy to remove is obtained. As a method for removing solvent B, it is preferable to use a critical point drying method. The critical point drying method uses a substance that is compatible with the solvent to be removed and has a critical point near room temperature.
This is a method in which the solvent is replaced and the substance is evaporated and removed while maintaining it at a critical point. According to this method, deformation of the sample due to the surface tension of the liquid during evaporation of the replacement substance can be prevented. When methanol is used as solvent B, carbon dioxide is preferably used as the critical point drying substance.

Other preferred methods for removing the solvent A from the frozen liquid crystalline polymer solution molded product include, in addition to the above-mentioned method, a method in which the frozen liquid crystalline polymer solution molded product is placed in a vacuum and freeze-dried. be. When using this method, there is no need to replace solvent A in advance.

For example, in the case of poly-γ-benzyl glutamate, the molded product prepared in this way has a regular microporous structure with a pore diameter of several hundred nm to several lines, and its Jlm can be confirmed with a scanning electron microscope. I can do it.

The liquid crystalline polymer substance used in the method of the present invention may be any lyotropic liquid crystalline polymer substance that assumes a liquid crystal state in a solution state and can be oriented in molecular orientation. Generally, materials suitable for the method of the invention are polyglutamic acid derivatives such as poly-γ-benzylglutamate and poly-γ-ethylglutamate. Polyglutamic acid derivatives may be used singly in the method of the present invention, either one or six thereof, but an equimolar mixture of the β and six polyglutamic acid derivatives (for example, polyglutamic acid derivatives) may be used in the method of the present invention. - an equimolar mixture of benzylene-1-glutamate and poly-γ-benzyle-d-glutamate), the structure of the resulting molded article is particularly excellent.

In addition, the types of substituents of this polyglutamic acid derivative are as follows:
It has a great influence on the structure of the completed molded product. In other words, the size of the microporous structure formed in the molded product can be controlled by selecting the type of substituents in the homopolymer or by introducing multiple different types of substituents onto the same main chain to form a copolymer. be able to.

To introduce different types of substituents onto the same main chain, a normal transesterification method or the like can be used. The degree of polymerization of the polymer material suitable for the method of the present invention is generally preferably 100 or more, and those having a degree of polymerization of 200 to 600 are particularly preferred.

Any solvent may be used as the solvent constituting the solution of the liquid crystalline polymer substance as long as it can dissolve the liquid crystalline polymer substance without decomposing it. When selected from polyglutamic acid derivatives, solvent A is preferably selected from meta-cresol, methylene chloride, methylene bromide, chloroform, 1,4-dioxane, or mixtures thereof. Among these, a particularly suitable solvent A is 1,4-dioxane.

The concentration and temperature of the solution to be molded have a large effect on the structure of the completed molded article. That is, by appropriately selecting the concentration and temperature of the solution, the distance between the eyebrows in the layered structure of the molded article can be controlled to a desired value.

-Finally, the higher the temperature of the solution and the lower the concentration, the greater the distance between the eyebrows. In the method of the present invention, the concentration of the liquid crystalline polymer substance is not particularly limited as long as the solution can exhibit anisotropy. However, for example, in the case of poly-gamma-benzyl glutamate, a range of 10 to 30 volume percent is particularly suitable. The temperature of the solution is not particularly limited as long as the solution can exhibit anisotropy; however, if the temperature is too low, the viscosity of the solution will increase, the time required for molecules to become oriented will increase, and However, if the temperature is too high, the orientation state may be disturbed or the solvent may evaporate and bubbles may be generated.

As the temperature rises further, the solution loses its liquid crystallinity and becomes completely isotropic. The temperature at which this solution becomes completely isotropic is determined depending on the type of polymer substance used, degree of polymerization, type of solvent, solution concentration, etc. For example, polyγ
For a 13 volume percent solution of -benzyl glutamate in 1,4-dioxane, the preferred temperature range for use in the process of the invention is from 20<0>C to 35<0>C.

Methods for aligning a liquid crystalline polymer substance in its solution include placing a solution molded body in a direct current electric field, placing it in a static magnetic field, and applying an alignment treatment to the solid interface that comes into contact with the solution, as described above. There are various methods, and all of these methods are suitable for the method of the present invention.

Methods for applying alignment treatment to the solid interface include, for example, when glass is used as the interface in contact with the solution, a method of cleaning the glass surface with hot concentrated sulfuric acid, a method of applying a silane-based alignment treatment agent (for example, n, n Suitable methods include a method of applying ``-dimethyl-n-octadecyl-3-aminopropyltrimethoxysilyl chloride), a method of forming a film of polyimide resin, a method of vapor depositing silicon dioxide, and a method of rubbing.

In the method of the present invention, any method may be used to freeze the solution molded product of the liquid crystalline polymer substance, as long as the solution molded product can be quickly frozen and the frozen sample is not contaminated. However, for example, a method of immersing the solution molded body in liquid nitrogen is particularly suitable.

Furthermore, in the method of the present invention, the solvent B used for replacing and removing the solvent A does not substantially dissolve the polymeric substance;
Any solvent may be used as long as it can dissolve the frozen solvent A and has a freezing point lower than that of the solvent A, and there is no particular limitation on its type, but for example, when using a polyglutamic acid derivative as the polymer substance, It is particularly suitable to use lower alcohols as solvent B. For example, 1,4-dioxane (freezing point = 11.80°C) as solvent A
When using methanol (freezing point = -
It is preferable to use temperatures such as 97.78°C).

When replacing and removing the solvent, it is necessary to use a sufficient amount of solvent B and to maintain its temperature above the freezing point of solvent B itself and below the freezing point of solvent A. The frozen liquid crystalline polymer substance solution molded article immersed in the solvent B is immersed in the solvent B solution maintained at the above temperature for a sufficient time to extract the solvent A. When the molded body sample is a film-like body sandwiched between glass plates, it is necessary to give the solvent B sufficient time to penetrate into the molded body sample from between the spacer and the glass plate and come into contact with the molded body sample. be. enough solvent A
After the extraction of 1 and the coagulation of the polymer substance have sufficiently progressed, the temperature of the entire solvent B solution is raised to room temperature and the extraction operation is continued again. After extraction has proceeded sufficiently at room temperature, the molded body sample is immersed in a new solvent B solution to extract solvent A again.

Any method may be used to remove the solvent B from the molded body thus obtained as long as it does not cause deformation of the molded body sample during the drying process, but the critical point drying method is It is particularly suitable in this respect. To perform critical point drying of a molded body containing solvent B, remove the polymeric substance molded body from which solvent A has been removed from the solvent B solution, and if solvent B is not ethanol, immerse the molded body sample in ethanol. Then replace the medium B therein with ethanol. After the replacement with ethanol is completed, the molded sample is placed in the sample chamber of the critical point drying device, and after replacing the ethanol with carbon dioxide, the carbon dioxide is vaporized and removed at the critical point (approximately 100 kg/cd, 45 ° C.). Dry the sample. When the solvent B consists of ethanol, the above-mentioned ethanol substitution step is not necessary, and the molded body sample may be directly subjected to the above-mentioned critical point drying.

〔Example〕

The invention is further illustrated by the following examples.

2.0 grams of methylene bromide was added to 0.5 grams of poly-γ-benzyl-l-glutamate (average molecular weight 1,160,000) and the mixture was stirred slowly from time to time.
The mixture was dissolved over two weeks at room temperature under a tightly capped condition. A 250 micron thick fluororesin spacer is sandwiched between two cover glasses coated with polyimide resin, and the above solution is poured into the gap space so that the polyimide resin coated surface is in contact with the solution. and injected. This molded body sample was allowed to stand for 24 hours, then placed in liquid nitrogen and frozen with the solution molded body. The frozen molded body sample was placed in methanol at -70°C together with a cover glass, and left to stand still at -70°C day and night. Thereafter, the temperature of methanol was raised to room temperature over 24 hours, the cover glass and spacer were removed, and the solidified film-like molded product sample was taken out.

This film-like molded product was dried by a critical point drying method using carbon dioxide, and its cross section and film surface were examined using a scanning electron microscope.
I observed it in the mirror. In the sample cross section, a layered structure perpendicular to the membrane surface was regularly formed, and slit-like openings were observed on the membrane surface, and cross-sectional observation revealed that the pores penetrated the membrane. .

The width of the slit and the spacing between the layers of the layered structure was 800 nanometers.

Run 1 0.5 grams of poly-γ-benzyru! - Add 3.0 grams of 1,4-dioxane to a mixture of glutamate (average molecular weight 170,000) and 0.5 grams of poly-gamma-benzyl-d-glutamate (average molecular weight 170,000) and stir this mixture from time to time. The mixture was dissolved over a period of 2 weeks at room temperature under a tightly closed cap while stirring slowly. The resulting solution exhibited optical anisotropy. A 250 micron thick fluororesin spacer is sandwiched between two electrode glass plates on which an indium tin oxide (ITO) film has been deposited, and the above solution is applied to the space between the glass plates, where the ITO is deposited. was injected so that it was in contact with the solution. A DC voltage of 2.3 cm was applied between these two electrodes using a dry battery, and in this state
It was left standing for a minute. After 20 minutes, the voltage was removed and the molded body was
It was placed in liquid nitrogen together with a glass electrode and frozen. The frozen molded body was placed in methanol at -20°C together with a glass electrode, and left as it was at -20°C day and night. Thereafter, the temperature of methanol was raised to room temperature over 24 hours, the glass electrode and spacer were removed, and the solidified film-like molded product was taken out. This film-like molded product was dried by a critical point drying method using carbon dioxide, and its cross section and film surface were observed using a scanning electron microscope.

The results are shown in FIGS. 1 and 2.

FIG. 1 (magnification: 500) shows the cross-sectional formation of the film-like molded body. In FIG. 1, the polymeric material is regularly oriented perpendicular to the membrane surface to form a layered structure, in which a large number of slit-like micropores are formed. Such a microporous structure was uniformly distributed throughout the film-like molded body. Moreover, the slit-like micropores extended so parallel to the surface of the film-like molded body.

FIG. 2 (magnification: 8000) is an enlarged photograph of a part of the surface of the film-like molded product shown in FIG.
It shows that slit-like micropores with uniform y dimensions are regularly formed in parallel in a layered or striped manner between them. The width of the slit-like micropores and the interlayer spacing of the layered portions were about 1 mm.

Lieutenant 11: Add poly-r-ethyl-1-glutamate (average molecular weight i 160,000) to a 1.0 gram separable plastic bottle and add 5.6
grams of paratoluenesulfonic acid and an additional 25-1
, 1,2,2-tetrachloroethane, and the mixture was stirred and dissolved at room temperature for 30 minutes. 8.0 mZ of benzyl alcohol was added to this solution, and the resulting solution was heated to 70° C. in an oil bath and stirred for 50 minutes.

After 50 minutes had elapsed, the pressure inside the system was reduced to 1,100 millimeters of mercury, and the mixture was stirred for 6 hours. After cooling the solution to room temperature, 200 rn! was slowly added to methanol with stirring. The precipitated resin was filtered using a glass filter, and the filtered resin was dissolved in chloroform 50
Dissolve in milliliter and from this solution again 200rn!
The resin was precipitated using methanol.

After repeating this operation three times, the resulting resin was vacuum dried at 40°C. As a result of quantitative determination of substituents by proton NMR, the produced resin contained 30% ethyl groups,
It was determined that the copolymer had 70 percent benzyl groups.

3.0 grams of 1,4-dioxane was added to 0.5 grams of the polymer prepared above and dissolved over a period of two weeks at room temperature under a sealed stopper with occasional slow stirring. The resulting solution exhibited optical anisotropy. This solution was placed between two heat-treated cover glasses coated with n,n'-dimethyl-n-octadecyl-3-aminopropyltrimethoxysilyl chloride, and a 100 micron thick fluororesin spacer was placed between them. The solution was injected into the gap between the glass plates thus formed so that the resin surface was in contact with the solution. The obtained molded body sample was
After being allowed to stand at room temperature for two weeks, it was frozen in liquid nitrogen. The frozen molded sample was placed under vacuum and freeze-dried.1.
4-dioxane was removed. The cross section and membrane surface of the obtained membrane-like molded body were observed with a scanning electron microscope. In the cross section of the membrane-like molded body, a layered structure perpendicular to the membrane surface is regularly formed, and slit-like openings can be seen on the membrane surface, and the pores penetrate the membrane from the cross-sectional observation.・I found out. The width of the slit and the distance between the eyebrows of the layered structure are 6
00 nanometers.

〔Effect of the invention〕

The present invention has the following unique effects.

(1) A microporous solid molded body can be easily produced while maintaining the liquid crystal orientation structure of the liquid crystal polymer substance solution.

(2) A molded body having a uniform orientation structure even inside can be manufactured.

(3) The size and shape of the microporous structure can be controlled as desired.

[Brief explanation of the drawing]

FIG. 1 is a scanning electron micrograph (X
500), and FIG. 2 is an enlarged photograph (x 8000) of the surface of the film-like molded product shown in FIG. 1 taken with a scanning electron microscope.

Claims (1)

[Claims] 1. Molding a solution consisting of a liquid crystalline polymer substance and solvent A, and orienting the liquid crystalline polymer substance in the solution molded body,
A method for producing a microporous polymeric substance molded article, comprising freezing the solution molded article while maintaining the liquid crystalline polymeric substance in an oriented state, and removing the solvent A from the shaped frozen body of the solution. . 2. In removing the solvent A, the solvent A can be dissolved from the liquid crystalline polymeric substance solution-molded frozen body in its frozen state, but the polymeric substance may not be substantially dissolved. The solution-formed frozen body is immersed in a solvent B which is not capable of forming a liquid and has a freezing point lower than that of the solvent A at a temperature lower than the freezing point of the solvent A and higher than the freezing point of the solvent B, thereby , replacing the solvent A in the solution-molded frozen body with the solvent B,
2. The method according to claim 1, wherein the solvent B is then removed from the molded article in which the solvent has been replaced. 3. The method according to claim 2, wherein the solvent B is removed from the solvent-substituted molded article by a critical point drying method. 4. The method according to claim 1, wherein the solvent A is removed from the liquid crystalline polymer solution-molded frozen body by freeze-drying under vacuum. 5. The method according to claim 1, wherein the polymeric substance is selected from polyglutamic acid derivatives. 6. The method according to claim 1, wherein the polymeric substance is poly-γ-benzylglutamate. 7. The method according to claim 1, wherein the polymeric substance is a mixture of equal amounts of l-form and d-form of a polyglutamic acid derivative. 8. The method according to claim 1, wherein the solvent A is 1,4-dioxane. 9. The method according to claim 2, wherein the solvent B is methanol.