Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-09-21
2003-03-11
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
Reexamination Certificate
active
06531569
ABSTRACT:
FIELD OF TECHNOLOGY
This invention relates to resin materials for gas separation base and a process for producing the same and, particularly to resin materials for gas separation base consisting of polymers in which hydrogen atoms in the side-chain benzyl and/or allyl position are replaced by halogen atoms, resin materials for gas separation base consisting of cardo polymers in which hydrogen atoms in the side-chain benzyl and/or allyl position are replaced by specified functional groups, halogen- or functional group-modified polymers of a cardo polyimide structure in which hydrogen atoms in the side-chain benzyl and/or allyl position are replaced by halogen atoms or functional groups, a process for producing the aforementioned polymers, and gas separation membranes based on the aforementioned resin materials for gas separation base. Resin materials of this invention are useful in a variety of areas such as recovery of carbon dioxide from exhaust gas, separation of methane/carbon dioxide from natural gas, dehumidification of gases, and manufacture of oxygen and nitrogen from air and are also applicable as functional resin materials to a variety of areas.
BACKGROUND TECHNOLOGY
In recent years, numerous attempts have been made to separate and purify a mixture of gases by means of resin or polymer materials, in particular, polymer gas separation membranes. For example, an attempt is being made to prepare oxygen-enriched air by passing air through a polymer gas separation membrane thereby selectively permeating oxygen and utilize it in medical care, combustion system, and the like.
Gas separation membranes to be used in the aforementioned applications are required to exhibit excellent permeability and selectivity toward the gas to be separated. Moreover, depending upon the environment in which they are used, there is also a demand for additional property requirements such as stability, heat resistance, chemical resistance, and high strength. Moreover, another important requirement is ease of their processibility into hollow fibers that provide a configuration suitable for highly efficient gas separation. A large number of polymer separation membranes have been tested for a variety of gases to see whether they satisfy the aforementioned requirements or not.
An indicator of gas permeability of a polymer membrane or permeability coefficient is expressed by the product of solubility coefficient that is an indicator of the solubility of gas in the polymer membrane and diffusion coefficient that is an indicator of the diffusibility of gas in the polymer membrane. Moreover, separation factor that is an indicator of selectivity is expressed by the ratio of the permeability of the gas to be separated to that of the gas not to be separated. Therefore, in order to improve selectively the permeability of the gas to be separated relative to that of the gas not to be separated, it becomes necessary to improve selectively the solubility coefficient and/or diffusion coefficient of the gas to be separated relative to that of the gas not to be separated.
A means that is considered to be effective for selectively improving the solubility coefficient is to provide the membrane with an affinity to the gas to be separated and various studies are being made on polymers containing a structure (a functional group) exhibiting a physical or chemical affinity to the gas to be separated.
Regarding separation membranes for CO
2
, for example, Japan Kokai Tokkyo Koho Hei 08-332,362 (1996) utilizes an idea of the existence of an affinity between CO
2
and ester and reports on a polyimide-type gas separation membrane synthesized from a cardo monomer containing an ester group. Although this gas separation membrane is capable of improving the separation factor, it still leaves the permeability coefficient at a low level.
Yoshikawa et al., holding an idea of the existence of an affinity between CO
2
and amine, report on polymers prepared from a monomer containing a tertiary amino group in Chemistry Letters, p. 243 (1994). In this case, however, they face the same problem as in the aforementioned cardo monomer containing an ester group, that is, the separation factor improves but the permeability coefficient remains low.
In the case of polymers that are synthesized from monomers containing a functional group exhibiting an affinity to gas as described in the aforementioned examples, such monomers become difficult to polymerize if the functional group in the monomer is chemically reactive or spatially bulky; monomers of this type are not suitable for the synthesis of polymers for gas separation membranes that require a high degree of polymerization.
On the other hand, separately from the aforementioned methods, studies are being made on an approach that introduces a functional group exhibiting an affinity to gas to polymers after formation of the polymer backbone. In numerous examples reported, the starting materials for this type of polymer reaction are polymers in which aromatic rings containing side chains are halogenated in the benzyl position, that is, polymers containing a halogenated carbon atom in the benzyl position as an active site in the reaction. Halogenated polymers containing halogenated carbon atoms in the benzyl position are generally easy to synthesize and show good storage stability. These halogenated polymers exhibit high reactivity with nucleophilic reagents and the reaction can be controlled with ease.
Such being the case, Okamoto et al. have proposed in Chemistry Letters, p.613 (1996) and in the specification of Japan Kokai Tokkyo Koho Hei 09-173,801 (1997) to subject aromatic polyimides containing methyl groups as substituents to bromination at the side chain, convert the brominated polymers into film, treat the film with an amine to give amine-modified polyimides, and use the resulting film as a gas separation membrane. Regarding this gas separation membrane, however, it is essential that the gas to be separated accompanies water vapor and the examples disclose only those membranes which are used in the configuration of film and none in the configuration of hollow fiber that is suitable for a gas separation membrane. Moreover, there is the possibility of the amino groups in the polyimide polymer in question being oxidized in air, but no description is given on the durability of the polymer. What is more, aromatic polyimides show low solvent solubility in general and it is often the case that solvents useful for chemical modification such as bromination are limited. Therefore, a reaction in a homogeneous system, that is, a reaction to be carried out with the reactants dissolved in a solvent may be applicable to one kind of aromatic polyimide, but it is not necessarily applicable to another kind of aromatic polyimide. Rather, a reaction in a homogeneous system is often difficult to apply to aromatic polyimides.
On the other hand, there is a thought that providing the polymer backbone with planarity and rigidity is effective for selectively improving the diffusion coefficient and studies have been made on polymers containing a bulky structure in the polymer backbone. For example, Japan Tokkyo Koho Sho 55-41,802 (1980) describes polyimide-type gas separation membranes containing a rigid polyimide skeleton to which a substituent is introduced and states that restriction of free rotation around the polymer backbone is an effective means for enhancing the gas permeability and gas selectivity of polymer gas separation membranes.
Aside from the applications as gas separation membranes, a number of reports have been made on modification of polymer backbone in order to provide polymers with a variety of functions.
For example, Ohkawara et al. reported in 1966 on the reaction of chlorinated poly(chloromethylstyrene) (PCMS) with various nucleophilic reagents and Nishikubo et al. reported on exceptional acceleration of this reaction by adding to the reaction system a quaternary ammonium salt or the so-called phase-transfer catalyst. Reference should be made to Tadaomi Nishikubo et al., Journal of the Chemi
Haraya Kenji
Mano Hiroshi
Tachiki Akira
Boykin Terressa M.
National Institute of Advanced Industrial Science and Technology
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