JPH1180414A - Double-structure continuous porous body and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a porous body having a specific surface area and a heightened permeability to liquids and gases by forming continuous pores having a specified smaller pore diameter in a porous polymer skeleton having continuous pores having a specified pore diameter. SOLUTION: A block copolymer comprising at least two monomers is mixed with a homopolymer, and the mixture is molten by heating or dissolved in a common solvent to establish a randomly mixed state, and the mixture in this state is subjected to temperature lowering or solvent evaporation to form a macrophase separation structure comprising a co-continuous structure comprising a copolymer phase and a homopolymer phase. This structure is subjected to further temperature lowering or solvent evaporation to form a microphase separation structure comprising a co- continuous structure and/or a cylinder structure in the copolymer phase. Next, the homopolymer is eluted from the macroseparation structure to form a porous body entirely consisting of the copolymer skeleton and having continuous pores having a pore diameter of several hundreds nm to several tens μm. Further, either phase of the copolymer is decomposed or the polymer is eluted from the phase to make the copolymer skeleton microporous to an extent that the pore diameter is in the range of several nm to several hundreds nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porous carrier having a novel structure suitable for use as a support such as metal fine particles for a catalyst, an adsorbent for gaseous or liquid substances, a separation membrane, and the like. It relates to the manufacturing method.

[0002]

2. Description of the Related Art Fine metal particles such as noble metals are widely used as catalysts, and it is known that the smaller the particle size, the greater the catalytic activity per unit weight. In this case, it is difficult to handle metal fine particles having a small particle size as they are,
For industrial use, it has been used by adsorbing and immobilizing it on some kind of support.

[0003] For this purpose, the form of the support is preferably a microporous body having a large specific surface area, and inorganic materials such as silica gel, activated carbon and alumina have been used for a long time.
However, since these inorganic materials are basically powders themselves, they are difficult in terms of moldability and workability, and a polymer-supporting film has been required for use as a film or film. .

With respect to a method for producing a microporous membrane using a polymer, the following typical examples are known. (1) JP-A-64-1739 A method for producing a porous body by subjecting a block polymer of a styrene derivative and a conjugated diene or acrylate derivative to microphase separation, and subjecting the conjugated diene or acrylate derivative to hydrolysis and treatment with oxygen-containing plasma.

(2) JP-A-2-279741 A mixture of a polymer having functional groups capable of ion bonding at both ends of a polymer and another polymer having functional groups capable of ion bonding to the functional groups at both ends is solution-cast. , One of the phases of the microphase-separated structure formed in the resulting film is cut with a base or an acid to cut the bond of the block copolymer,
One polymer is extracted with a solvent.

(3) Japanese Patent Laid-Open No. 5-287084 This invention relates to a method for producing a porous membrane having a pore diameter of several hundred nm which is considered to have a potential as a carrier for a catalyst or the like. Among the microphase-separated structures formed by various block copolymers, this is a method of decomposing or eluting one component, characterized by a bicontinuous structure, and the pore size distribution formed due to the bicontinuous structure is extremely low. It is characterized by being narrow.

However, these microporous materials have a small pore size and a relatively large specific surface area. However, since the pore size itself is small, for example, when a catalyst is actually supported and used, it is a reactant. Gas and liquid permeability is reduced. Therefore, when it is used as a membrane reactor, it has a disadvantage that the pressure applied to the membrane increases. Further, since the pore diameter is small, the gaseous or liquid substance to be applied has been limited to the one corresponding to the pore diameter.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, to provide a large specific surface area, a high liquid and gas permeability, and a wide application range. An object of the present invention is to provide a polymer porous body (microporous body) having a structure and a method for producing the same.

[0009]

According to the present invention, in order to solve the above-mentioned problems, a pore diameter of several hundred nm to several tens μm is required.
The porous body is characterized in that continuous pores having a pore diameter of several nm to several hundred nm are formed in a porous polymer skeleton having continuous pores of

Further, according to the present invention, there is provided a method for producing such a porous body, wherein a copolymer composed of two or more monomer units and a homopolymer are melted or dissolved by a solvent to form a random mixture. After forming the state, lowering the temperature or evaporating the solvent to form a macrophase-separated structure consisting of a bicontinuous structure of the copolymer phase and the homopolymer phase, followed by lowering the temperature or Evaporating the solvent to form a microphase-separated structure consisting of a bicontinuous structure and / or a cylinder structure in a phase of the copolymer; eluting the homopolymer from the macrophase-separated structure;
Forming a porous body consisting solely of a copolymer skeleton, and decomposing one phase of the copolymer and / or eluting a polymer contained in the phase from the microphase-separated structure to make the copolymer skeleton microporous A method for producing a porous body, comprising the step of: In a preferred embodiment of the production method of the present invention, a block copolymer in which two or more mutually incompatible block chains are bonded at each terminal is used. In another embodiment, a random copolymer in which two or more types of mutually incompatible monomer units are randomly copolymerized to partially form an aggregate of the same monomer unit is used as the copolymer.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the above-mentioned Japanese Patent Application Laid-Open No. 5-280.
Utilizing a micro phase separation structure of a copolymer as disclosed in 7804, and utilizing a macro phase separation of a homopolymer and a copolymer mixed into the system, a multi-structure (double layer) having two types of continuous pores having different pore diameters. The present invention has been completed by discovering that a polymer microporous material having the following structure is obtained.

Hereinafter, the features of the present invention will be described in detail along with each component and each manufacturing process of the porous body of the present invention. (1) Production method using a mixture of a block copolymer and a homopolymer: (i) Formation of a bicontinuous macrophase separation structure and a microphase separation structure In the present invention, a copolymer composed of two or more types of monomer units is preferably used. Are block copolymers in which two or more mutually incompatible block chains are linked at each end. That is, the polymer chain that finally forms the skeleton of the microporous material (called the skeletal polymer) and the polymer chain that finally forms the pores (the polymer that is called the pore-forming polymer) are chemically bonded at their ends. Prepare a block copolymer. A homopolymer incompatible with at least one block chain of the block copolymer is prepared, mixed with the block copolymer, and the “order-
By increasing the temperature above the "disorder transition temperature (T _ODT )" and melting, or dissolving in these common solvents,
All of the components form a mixed disordered state. At this time, the mixing ratio of the block copolymer and the homopolymer does not need to be particularly limited as long as a bicontinuous structure can be formed, but is preferably 70/30 to 30/70, more preferably 60/40 to 40/60 in volume ratio. . Further, for the control of the final microphase separation structure, another homopolymer may be mixed. By lowering the temperature to T _ODT or lower or evaporating the solvent and concentrating (casting), first, a macrophase is separated into a block copolymer phase and a homopolymer phase. Form the structure.

Subsequently, a microphase-separated structure composed of each block chain phase is formed in the block copolymer phase by lowering the temperature or evaporating the solvent.
In general, the microphase separation structure is preferably a bicontinuous structure, but a microphase separation structure in which a bicontinuous structure and a cylinder structure are mixed depending on the use of the porous body, or
A micro phase separation structure having a cylinder structure can also be used. The phase separation structure to be expressed is the volume fraction of the "skeleton polymer phase" and the volume fraction of the "pore forming polymer phase" in the block copolymer (when other homopolymers are mixed to control the micro phase separation structure) Can be controlled by the volume fraction to which the homopolymer is added). When a bicontinuous structure is obtained, as described later, one of the volume fractions φ is set to 0.33 as a standard, Further, the cylinder structure can be expressed with 0.18 <φ <0.32 as a guide.

(Ii) Pore formation of bicontinuous macrophase separation structure A polymer structure in which a microphase separation structure (particularly, bicontinuous structure) is formed in one phase of the bicontinuous macrophase separation structure is contained. The polymer is immersed in a solvent capable of selectively dissolving the homopolymer, whereby the homopolymer is eluted to obtain a porous body composed only of the block copolymer skeleton, that is, a polymer having continuous pores having a pore diameter of several hundred nm to several tens nm.

(Iii) Formation of pores in microphase-separated structure Since the obtained block copolymer skeleton is also a microphase-separated structure composed of phases of each block chain, one of these phases is decomposed or (and / or) By eluting the homopolymer contained in this phase, the polymer skeleton itself can be made microporous, and continuous pores having a pore size of several nm to several hundred nm are formed in the skeleton.

(Iv) Required properties for the block copolymer The properties required for the block copolymer for forming the skeleton are as follows. The number of block chains is not particularly limited as long as a bicontinuous structure can be formed when mixed with a homopolymer and subjected to macrophase separation, but an AB type diblock copolymer and an ABA type triblock copolymer are preferred. .

The pore-forming polymer chain constituting the block copolymer is preferably itself decomposable. For example, an ozonolytic conjugated diene polymer is most suitable, but a photodegradable polymer such as polymethyl vinyl ketone may be used.

The skeletal polymer to be used for forming the final matrix is not particularly limited as long as it is not compatible with the "polymer for forming pores" and does not decompose or elute during the pore forming operation. Temperature (T
_G ) is high). For example, polystyrene which is a general-purpose polymer having a glass transition temperature of about 100 ° C. is typical. If the polymer for forming the matrix has a crosslinkable functional group (for example, an amino group, an imino group, a carboxyl group, a hydroxyl group, a halogen, a dimethyl-propoxysilyl group, and the like), from the viewpoint of retaining formed pores. Is more preferred. Examples include poly (2-vinylpyridine) and poly (dimethyl-2-propoxysilylstyrene). In addition, when such a functional group is provided, a polymer chain having a _TG of room temperature or lower can be used.

Number average molecular weight M of polymer of each block chain
n may be 1,000 to 1,000,000, respectively, and its molecular weight can be designed according to the size of the micropore to be finally formed. However, there is a limit to the molecular weight ratio of each block chain, and when pore formation is performed only by decomposition of the pore-forming polymer to obtain a bicontinuous microphase-separated structure, the volume fraction of one block chain is 33% ± ( 10%)
It is necessary to control the molecular weight so that

If the polymer chain for forming pores is not decomposable, a homopolymer for elution as disclosed in JP-A-5-287084, that is, a homopolymer compatible with the polymer chain for forming pores is added. And eluted to form a microphase-separated structure. Further, a method of using a block copolymer which can be cleaved by an acid or base such as an ionic bond, an ester bond, or an amide bond, and cleaving the inter-polymer bond and eluting only one phase (Japanese Patent Laid-Open Publication No. 279741) can also be used.

(2) Production method using a mixture of a random copolymer and a homopolymer: It is difficult to form a desired microphase-separated structure of the porous body of the present invention with a completely random random copolymer. A random copolymer is an assembly where each monomer unit is partially bonded (generally consisting of several to several tens of monomer units)
Is formed. Therefore, instead of a block copolymer consisting of distinct block chains as described above, two or more monomer units are randomly copolymerized and partially
Even if a random copolymer that forms an aggregate of the same monomer unit is used, it is possible to form a similar multi-structure continuous porous body by forming a microphase-separated structure formed by these aggregates. is there.

[0022]

EXAMPLES The following examples are provided to further clarify the features of the present invention, but the present invention is not limited by these examples. Example A block copolymer P2VP-b-PI (Mn = 23) composed of poly (2-vinylpyridine) (P2VP) and polyisoprene (PI)
200-b-17100) and 100 mg of PI (Mn = 22000) were dissolved in chloroform, and a cast film was prepared at 40 ° C. for one day. In the process, first, macro phase separation occurs between a PI homopolymer-rich solution phase and a P2VP-b-PI-rich solution phase. At this time, in order to prevent large separation into two phases, when the polymer concentration exceeds 30%, the solution in which macro separation is largely performed is finely dispersed with an ultrasonic homogenizer so that both phases are finely dispersed with each other. A co-continuous structure of a copolymer phase and a homopolymer phase was formed. Thereafter, the solvent was evaporated to obtain a cast film in which a co-continuous structure composed of each block phase was formed in the block copolymer phase, and was dried under vacuum at room temperature for 24 hours.

The dried cast film was set in a vacuum vessel together with a small vessel containing 1,4-diiodobutane, and the whole vacuum vessel was cooled to -78 ° C. to reduce the pressure in the vessel. After that, the whole of the depressurized container is again heated to 40 °
To fill the vessel with 1,4-diiodobutane vapor. In this state, the P2VP block chain was cross-linked with 1,4-diiodobutane vapor by leaving the film to stand for 3 days, thereby fixing the phase separation structure in the cast film.

The cast film in which the P2VP phase is cross-linked and fixed is washed with hexane to elute the PI homopolymer forming one phase of the bicontinuous macrophase separation structure, and the P2VP-b-PI block copolymer alone is eluted. Was obtained. The pore size was about 2 μm.

Next, the network structure composed of only the P2VP-b-PI block copolymer was decomposed with ozone for 2 days to make the PI block chains in ethanol hollow. As a result, the matrix (skeleton) portion (A in FIG. 1) of the (0.5 to 2 μm) network structure shown in FIG. 1 is a finer (50 to 100 nm) network (FIG. 1). B)
A porous body having a double structure was obtained.

[0026]

According to the present invention, large continuous pores are formed using a macro phase separation structure of a homopolymer and a copolymer, and small continuous pores are formed using a micro phase separation structure of a block copolymer. Thus, a microporous body having a double structure can be obtained. At this time, since the macro phase separation structure is formed by the phase separation of the homopolymer and the copolymer, the size of the phase separation structure can be controlled by the speed of forming the ordered structure from the disordered state. On the other hand, the size of the microphase-separated structure does not depend on the structure formation speed, and in the case of a block copolymer, can be set by the molecular weight of each block chain and its volume fraction. As described above, according to the method of the present invention, the conditions for forming each phase separation structure can be independently controlled, and a plurality of types of free pore sizes (pore diameters) can be formed in a single porous body according to the purpose. Design becomes possible.

The porous body of the present invention has a large specific hole while maintaining a large specific surface area due to the small diameter continuous holes, and therefore has a high liquid or gas permeability since it has a large diameter continuous hole, so that it can be used as a membrane reactor. In some cases, the pressure applied to the membrane can be reduced. Further, in the porous body of the present invention, the number of kinds of liquid or gaseous substances to be applied, a plurality of types of pore diameters can be freely designed according to the size or properties of the molecule, etc. A porous body having a wide range of application to be used as a separation membrane or the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph showing a crystal structure of one example of a continuous porous body having a double structure of the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Jinnai, Inventor Koji Jinnai 7-36-8-1, Kodai, Seika-cho, Soraku-gun, Kyoto Prefecture Sun Mall Heights E101 (72) Inventor Seiji Tsutsumi 2 Nishitomigaoka, Nara City, Nara Prefecture -15-D-511

Claims (4)

[Claims] 1. A porous polymer skeleton having continuous pores having a pore diameter of several hundred nm to several tens of μm has a pore diameter of several nm to several hundred n.
A porous body, wherein m continuous holes are formed. 2. The method for producing a porous body according to claim 1, wherein a copolymer composed of two or more monomer units and a homopolymer are melted or dissolved by a solvent to form a disordered mixed state. Forming a macrophase-separated structure consisting of a co-continuous structure of a copolymer phase and a homopolymer phase by lowering the temperature or evaporating the solvent, followed by lowering the temperature or evaporating the solvent Forming a microphase-separated structure consisting of a co-continuous structure and / or a cylinder structure in a phase of a copolymer, eluting a homopolymer from the macrophase-separated structure to form a porous body consisting solely of a copolymer skeleton, And / or decompose one phase of the copolymer from the microphase-separated structure and / or A process for producing a porous body, comprising a step of eluting a mer to make the copolymer skeleton microporous. 3. The method for producing a porous body according to claim 2, wherein a block copolymer in which two or more types of mutually incompatible block chains are bonded at each terminal is used as the copolymer. 4. A random copolymer in which two or more types of mutually incompatible monomer units are randomly copolymerized to partially form an aggregate of the same monomer unit as the copolymer. Claim 2
A method for producing a porous body.