Abstract: An asymmetric hollow-fiber gas separation membrane is made of a soluble aromatic polyimide that is composed of a specific repeating unit. The tetracarboxylic acid component of the unit has a diphenylhexafluoropropane structure and a biphenyl structure. The diamine component of the unit essentially contains diaminobenzoic acids and any of diaminodibenzothiophenes, diaminodibenzothiophene=5,5-dioxides, diaminothioxanthene-10,10-diones, and diaminothioxanthene-9,10,10-triones.

Abstract: A hydrogen separation membrane and its associated method of fabrication. The hydrogen separation membrane has a first material layer that is permeable to atomic hydrogen. The first material has a first catalytic ability to disassociate molecular hydrogen into atomic hydrogen. Complex particles are applied to the first material layer, either to produce a second layer or to act as a barrier between the first layer and a subsequent layer. The complex particles are hollow bucky structure, filled bucky structures or core particles coated with a hydrogen permeable metal. The complex particles prevent material from opposite sides of the hydrogen separation membrane from interdiffusing over time. Consequently, palladium based materials and Group V based materials can be used on opposite sides of the hydrogen separation membrane. This produces a hydrogen separation membrane that is more permeable to hydrogen in one direction than it is in the opposite direction.

Abstract: Disclosed herein are processes for producing a CO2-depleted product gas stream. The processes involve feeding a natural gas feed stream comprising greater than about 10 vol % CO2 to at least one membrane unit comprising a plurality of polymer membranes to provide a CO2-rich permeate comprising at least 95 vol % CO2 and a CO2-depleted product gas stream. The polymer membranes comprise a crosslinked polyimide polymer having covalent ester crosslinks and have a CO2 permeance of at least 20 GPU and a CO2/CH4 selectivity of greater than 20, at 35 degrees C. and a feed pressure of 100 psia. Also disclosed herein is an apparatus incorporating the crosslinked polyimide polymer for producing a CO2-depleted product gas stream from a natural gas feed stream.

Abstract: A device for removal of at least a portion of carbon dioxide from an aqueous fluid includes at least one membrane through which carbon dioxide can pass to be removed from the fluid and immobilized carbonic anhydrase on or in the vicinity of a first surface of the membrane to be contacted with the fluid such that the immobilized carbonic anhydrase comes into contact with the fluid. The first surface exhibits carbonic anhydrase activity of at least 20% of maximum theoretical activity of the first surface of the membrane based on monolayer surface coverage of carbonic anhydrase in the case that the carbonic anhydrase is immobilize on the first surface.

Abstract: A gas-separation membrane assembly, and a gas-separation process using the assembly. The assembly incorporates multiple gas-separation membranes in an array within a single vessel or housing, and is equipped with two permeate ports, enabling permeate gas to be withdrawn from both ends of the membrane module permeate pipes.

Abstract: A process and apparatus for dehumidifying a gas stream is provided. The apparatus includes a single semi-permeable osmotic membrane, at least one gas stream compartment formed in part by the osmotic membrane, and at least one osmotic fluid compartment formed in part by the osmotic membrane. The semi-permeable osmotic membrane has randomly arranged pores disposed across a thickness extending between a first side and a second side, and wherein some of the pores are small enough to permit capillary condensation within the membrane, leading to condensate travel across the thickness of the single membrane without requiring a separate capillary condenser, and which single membrane restricts transport of the osmotic fluid across the thickness of the membrane. The first side of the osmotic membrane is exposed to the gas stream compartment, and the second side of the osmotic membrane is exposed to the osmotic fluid compartment.

Abstract: A gas separation membrane and a method of manufacturing such gas separation membrane that comprises a porous substrate treated with a layer of metal-coated inorganic oxide particles and with the layer of such metal-coated inorganic oxide particles being coated with an overlayer of a gas-selective material.

Abstract: This invention relates to a stack comprising a continuous solid-phase matrix and tubular fuel cells embedded in the matrix. Each fuel cell comprises an inner electrode layer, an outer electrode layer, and an electrolyte layer sandwiched between the inner and outer electrode layers. The matrix is sufficiently porous to allow a first reactant to flow through the matrix and to the outer electrode of each fuel cell, and have sufficient mechanical strength to support the fuel cells in the stack. The fuel cells are embedded such that a second reactant may be flowed through the inside of each tubular fuel cell and to the inner electrode thereof. Alternatively, a stack of tubular separation membranes or a stack of tubular membrane reactors may be embedded in the matrix. The matrix material may comprise solid state foam, metal filament, or metal, cermet, or ceramic wool.

Abstract: The membrane air dryer includes a housing with an air inlet adjacent a first end of the housing, an air outlet adjacent a second end of the housing, a sweep air inlet and a sweep air outlet. A membrane separator has surfaces extending between and connected to the air inlet and the air outlet. A first sweep air passage in the housing extends between the first and second ends of the membrane along and including surfaces of the membrane. The first sweep air passage has an inlet adjacent the air outlet and an outlet adjacent the air inlet and connected to the sweep air outlet. The sweep air inlet and outlet is adjacent the air inlet. A second sweep air passage in the housing extends between the first and second ends of the membrane. The second sweep air passage has an inlet that is connected to the sweep air inlet and is adjacent the air inlet and has an outlet that is adjacent the air outlet and in fluid communication with the inlet of the first sweep air passage.

Abstract: An air separation module comprising a bundle of hollow elongated membranes, and a pressure vessel enclosing the bundle. The pressure vessel includes an outer tube, end caps at opposite ends of the tube, and an inner tube located within the fiber bundle. The inner tube is fixedly mechanically connected at opposite ends to the end caps to form a structural spine of the pressure vessel, whereby loads acting on the air separation module are transferred between the end caps primarily by the center tube.

Abstract: A process of producing an asymmetric membrane of multicomponent polyimide. The process includes the steps of (1) preparing a multicomponent polyimide blend solution by mixing a polyimide component A having a number-averaged polymerization index NA and a polyimide component B having a number-averaged polymerization index NB, wherein NA and NB satisfies equation 1: 2.35×NA?2.09<NB<450×NA?1.12??1 (2) subjecting the multicomponent polyimide blend solution to further polymerization and imidation reaction, and (3) causing a phase inversion in the resulting multicomponent polyimide blend solution to form an asymmetric membrane. The polyimide component A is raw materials of polyimide A containing a fluorine atom in the chemical structure thereof and/or a polymerization and imidation reaction product of the raw materials. The polyimide component B is raw materials of polyimide B and/or a polymerization and imidation reaction product of the raw materials.

Abstract: A carbon dioxide separation system for a fuel cell system having a small volume and weight of a separation device and of a membrane, at simultaneous increase of the separated volume of carbon dioxide, comprises a separation device for containing a fluid phase, a carbon dioxide phase, and a two phase fluid including fluid and carbon dioxide. The separation device comprises a two phase fluid inlet, a fluid outlet, a carbon dioxide outlet, a carbon dioxide separation membrane, and a flow restrictor creating a backpressure which presses separated carbon dioxide through the carbon dioxide separation membrane. The flow restrictor comprises at least one narrow aperture, and is mounted downstream of the separation device. The carbon dioxide separation membrane is positioned in the separation device in such a manner that at least a part of the total membrane area is arranged above a two phase fluid level and is in touch with carbon dioxide contained in the separation device above the two phase fluid level.

Abstract: An elongated flow-through degassing apparatus includes an elongated gas and liquid impermeable outer member and a gas-permeable, liquid-impermeable inner barrier extending within the outer member and at least partially along a first chamber defined within the outer member. The apparatus also includes inlet and outlet connection structures operably coupled to respective portions of the outer member and a second chamber defined by the inner barrier to further enable a sealed engagement between the outer member and the inner barrier, and to provide for connection devices to operably couple the degassing apparatus of the present invention to respective spaced apart components. The degassing apparatus may be sufficiently flexible so as to be readily manipulatable into desired configurations.

Abstract: The present invention relates to methods and apparatuses for water filtration comprising contacting a water stream with a membrane comprising a polysulfone having structural units of Formula I wherein X is OH, NR1R2, or OR3; R1 and R2 are independently at each occurrence hydrogen, a C1-C5000 aliphatic radical, a C3-C12 cycloaliphatic radical, a C3-C12 aromatic radical, a polypeptide, a combination thereof, or R1 and R2 taken together form a 5- or 6-membered aliphatic ring or a 5-membered aromatic ring; R3 is a C1-C20 aliphatic radical, C3-C12 cycloaliphatic radical, C3-C12 aromatic radical, or a combination thereof; B? and C? are independently at each occurrence a nitro group, C1-C20 aliphatic radical, C3-C12 cycloaliphatic radical, C3-C12 aromatic radical, or a combination thereof; and q and r are independently at each occurrence 0 to 4.

Abstract: A degassing apparatus is provided that accomplishes the connecting of a degassing element and a connecting member and/or the joining of a vacuum (reduced-pressure) chamber and the connecting member without using a fastening structure screwed together with the connecting member. A degassing apparatus includes: a reduced-pressure chamber having a through port for flowing a degassing target liquid therethrough; a degassing element, accommodated in the chamber, for passing the liquid therethrough; and a tubular connecting member joined to the chamber at the through port. The degassing element includes a gas-permeable tube, for passing the liquid therethrough, being covered with a joint piece at an end portion of the gas-permeable tube. The degassing element is fixed to the chamber by heat sealing the connecting member and the joint piece together.

Abstract: A gas permeable, carbon based, nanocomposite membrane comprises a nanoporous carbon matrix comprising a pyrolyzed polymer, and a plurality of nanoparticles of carbon or an inorganic compound disposed in the matrix. The matrix is prepared by pyrolyzing a polymer, and nanoparticles of the particulate material are disposed in the polymer prior to pyrolysis. The particles may be disposed in a precursor of the polymer, which precursor is subsequently polymerized, or in the polymer itself.

Abstract: A hydrogen gas separator fixing structure includes a gas separator having a support and a membrane provided on at least one surface of the support, which membrane contains a first metal capable of separating hydrogen gas from a hydrogen-containing gas, a metal flange connected to at least one open end of the gas separator, a bonding layer containing a second metal, provided at the portion at which the gas separator and the metal flange are connected to each other and on the surface of the gas separation membrane side of the portion, a packing provided on the bonding layer, and a ring-shaped metal member capable of fixing the packing by pressing, provided so that at least part thereof is in contact with the bonding layer, wherein the bonding layer is provided by a heat treatment conducted at a temperature lower than the melting point of the second metal.

Abstract: Ozone resistant O2/N2 gas separation membranes comprise a polymer membrane and an ozone reacting component, such as an antioxidant. The antioxidant may be included in the support layer of a composite membrane or included in the entire structure of an asymmetric membrane. The antioxidants in the separation membrane reduce oxidation and deterioration of the actual separation layer of the membrane.

Abstract: A filtering medium is comprised of a non-woven fabric containing mainly an organic fiber, in which single fibers are fixed, wherein the non-woven fabric is constructed of a plurality of single fibers having different Young's moduli and finenesses, a non-crimped single fiber having a Young's modulus of 150 cN/dtex or more, and a fineness of 7 dtex or more is contained at a ratio of 20% or more of a total fiber mass, and single fibers are fixed with a resin having a glass transition temperature of 30° C. or more.

Abstract: A degasifier is provided in which the deterioration in sealing property (deterioration in airtightness) is prevented while sealing members to be placed between a container and covers that compose a decompression chamber can be omitted. A degasifier includes a decompression chamber provided with a container and covers, and a gas-permeable tube. The container is a tubular body extending along the central axis. The covers seal the openings of the ends of the tubular body. The gas-permeable tube is contained in the decompression chamber in such a manner that a liquid to be degassed that has entered from the outside of the decompression chamber flows therethrough and the liquid to be degassed that has flowed therethrough flows out of the decompression chamber.

Abstract: A membrane air dryer includes a proportioning valve for providing sweep air to the dryer. The valve may be located in an easily accessible location and may be oriented so that the movable valve element extends transverse to the length of the shell. The valve may be configured to allow air to flow back from the delivery port to the fibers during a compressor unload cycle to maintain pressure on the fibers, while blocking flow of air from the delivery port to the sweep chamber.

Abstract: A thin film composite membrane comprises a core layer and a sheath UV-crosslinked polymer layer. The thin film composite membrane is produced by the co-extrusion of two polymer solutions. The core layer and the sheath layer can be separately optimized. The sheath layer may be UV-crosslinked to provide stability and selectivity at the desired operating temperature of the composite membrane.

Abstract: A gas exchange membrane is for use in an artificial lung. The membrane consists of a foamed, closed-cell material, in particular of silicone rubber. The membrane is produced by extruding a basic material which contains a foaming agent. The extrudate is then foamed. The result is a gas exchange membrane which has an increased gas exchange performance compared to known material due to the high permeability of the surface.

Abstract: Microtanks are formed in capped holey fibers. Holey fiber is composed of a shell, a porous layer and a hollow core. Compressed gas can be stored in plurality of microtanks at elevated pressure. A method of storing and releasing hydrogen gas in or out of a plurality of microtanks is also disclosed.

Abstract: A suspension of inorganic particles, a copolymer comprising soft segments and hard segments, and a solvent may be extruded through a spinnerette to produce inorganic/organic composite hollow precursor fibers. The precursor fibers may be sintered. The fibers may be utilized in a gas separation module for separation of a gas mixture or production of syngas. The fibers may be installed in the gas separation module after sintering or they may be sintered after installation.

Abstract: A membrane air dryer includes a housing with an air inlet, an air outlet, a sweep air inlet and a sweep air outlet; and a membrane separator having surfaces extending between and having an inlet and an outlet respectively connected to the air inlet and the air outlet. A sweep air passage in the housing extends between first and second ends of the membrane along and includes surfaces of the membrane. The sweep air passage has an inlet adjacent the air outlet and has an outlet adjacent the air inlet and connected to the sweep air outlet. A volume is concentric to the membrane separator, has an inlet connected to the outlet of the membrane separator and has an outlet connected to the sweep air inlet. The filter may be mounted in a reservoir with the membrane separator extending into the reservoir.

Abstract: An apparatus for producing hydrogen gas wherein the apparatus includes a reactor. In one embodiment, the reactor includes at least two conversion-removal portions. Each conversion-removal portion comprises a catalyst section configured to convert CO in the stream to CO2 and a membrane section located downstream of and in flow communication with the catalyst section. The membrane section is configured to selectively remove the CO2 from the stream and to be in flow communication with a sweep gas.

Abstract: An H2-permeable membrane system (117) comprises an electroless-deposited plating (115) of Pd or Pd alloy on a porous support (110, 110?). The Pd plating comprises face-centered cubic crystals cumulatively having a morphology of hexagonal platelets. The permeability to H2 of the membrane plating (115) on the porous support is significantly enhanced, being at least greater than about 1.3×10?8 mol·m?1·s?·Pa?0.5 at 350° C., and even greater than about 3.4×10?8 mol·m?1·s?1·Pa?0.5. The porous support (110, 110?) may be stainless steel (1100 and include a thin ceramic interlayer (110?) on which the Pd is plated. The method of providing the electroless-deposited plating includes preheating a Pd electroless plating solution to near a plating temperature substantially greater than room temperature, e.g. 60° C., prior to plating.

Abstract: A membrane contactor includes a housing, a stack of membrane mats, and a cap. The housing has a closed end and an open end. The closed end includes an outlet port. The cap is united to the open end and includes an inlet port. A stack of membrane mats is within the housing stacked substantially perpendicular to the longitudinal axis of the housing. Each membrane mat has a plurality of hollow fiber members. A potting material bonds the membrane mats to each other and simultaneously bonds one end of the stack to the closed end and bonds the other end of the stack to the cap. The potting material forms an internal chamber and at least one external chamber within the housing. The hollow fiber members extend through the potting material from the internal chamber into the external chambers. The inlet port and the outlet port are in communication with the internal chamber. At least one side port is in communication with the external chambers.

Abstract: A dry compressed air module is provided for attachment to the frame of commercial vehicle. The dry compressed air module includes a shell, an air compressor, an air dryer, and a reservoir. The air compressor, the air dryer, and the reservoir are disposed on the shell, and can be collectively attached to the frame using the shell. The air dryer is provided with compressed air from the air compressor, and the reservoir is provided with dry compressed air from the air dryer. The reservoir capable of storing and supplying the dry compressed air to the vehicle.

Abstract: The instant invention is a hollow fiber membrane contactor. The hollow fiber membrane contactor includes a cartridge, a shell, a first end cap, and a second end cap. The shell, which is adapted for enclosing the cartridge, has two ends and an opening. The cartridge further includes a perforated center tube, a hollow fiber fabric, a first tube sheet, a second tube sheet, and a plug. The perforated center tube has a first end and a second end, and the hollow fiber fabric surrounds the center tube. The hollow fiber fabric includes hollow fiber membranes, and each hollow fiber membrane has a lumen. A first tube sheet and a second tube sheet affixes said fabric to said center tube at each end of the center tube, and the plug is located at the first tube sheet. Hollow fiber lumens are open at the first tube sheet and hollow fiber lumens are closed at the second tube sheet. The first end cap and the first tube sheet define a first headspace therebetween.

Abstract: The present invention provides a hollow fiber membrane submodule comprising a hollow fiber membrane element, permeated fluid collectors, and snaps for securing the permeated fluid collectors to the hollow fiber membrane element, wherein the permeated fluid collectors are closely attached to the hollow fiber membrane element with the snaps in engagement therebetween and being arranged non-continuously around the outer periphery of each permeated fluid collector, and the permeated fluid collectors can be removed from and installed in the hollow fiber membrane element. With the hollow fiber membrane submodule of the present invention, when replacing the membranes, the hollow fiber membrane element is replaced with a new hollow fiber membrane element, and then the permeated fluid collectors can be reattached to the replaced element and reused.

Abstract: A fuel stabilization unit includes an electrochemical device for promoting the formation of water utilizing oxygen from a fuel stream for generating an oxygen partial pressure differential across an oxygen permeable membrane.

Abstract: A hollow fiber cartridge includes a stack of hollow fiber mats. The stack has a major axis and two end faces. Each mat is substantially perpendicular to the axis. An end cap is united to each end face.

Abstract: Disclosed is a hollow fiber that includes a hollow positioned at the center of the hollow fiber, macropores positioned at adjacent to the hollow, and mesopores and picopores positioned at adjacent to macropores, and the picopores are three dimensionally connected to each other to form a three dimensional network structure. The hollow fiber includes a polymer derived from polyimide, and the polyimide includes a repeating unit obtained from aromatic diamine including at least one ortho-positioned functional group with respect to an amine group and dianhydride.

Abstract: Carbon dioxide is separated from a gas stream using a supported carrier liquid membrane having a selected concentration of carrier species, the method being especially suitable for use in anaesthesia under conditions of periodic flow.

Abstract: Disclosed is a hollow fiber that includes a hollow positioned at the center of the hollow fiber, macropores positioned at adjacent to the hollow, and mesopores and picopores positioned at adjacent to macropores, and the picopores are three dimensionally connected to each other to form a three dimensional network structure. The hollow fiber includes a polymer derived from polyamic acid, and the polyamic acid includes a repeating unit obtained from aromatic diamine including at least one ortho-positioned functional group with respect to an amine group and dianhydride.

Abstract: It is an object of the present invention to provide a separation membrane in which a film-forming solution can be prevented from reaching a rear surface of a porous support in a step of forming a film, the adhesion between a functional film for separation and the porous support is high, and the thickness can be reduced. In the present invention, the separation membrane includes a porous support having a rough rear surface and a functional film for separation, and the functional film is disposed on a front surface of the porous support and extends into the porous support.

Abstract: The membrane module according to the invention is characterized in that it has concrete flanges. This membrane module is made by first sealing a bundle of ceramic fiber membranes at one end using a viscous sealant and then pressing it into a fluid mass of concrete in a mould. After the mass of concrete has hardened the process is repeated with the other end of the bundle. Finally the ends of the fiber membranes are opened by sawing off a slice of the flanges.

Abstract: A membrane module comprising an outer casing having an interior region, a seal disposed within the outer case, thereby dividing the interior region into a first chamber and a second chamber, and a plurality of hollow fiber membranes extending through the first chamber and the second chamber, where at least a portion of the plurality of hollow fiber membranes have first segments located within the first chamber and second segments located within the second chamber, the first segments being configured to allow vapor transmission therethrough, and the second segments being configured to substantially prevent vapor transmission therethrough, and further configured to allow transmission of thermal energy therethrough.

Abstract: Device for exchange of moisture, between at least two counter-current gas flows (A, B), comprising a generally closed chamber (1, 101) having an inlet (7, 107) and an outlet (8, 108) for a first gas flow (B), such that the first gas flow flows in a first direction from the inlet to the outlet inside the chamber; and at least one duct (2, 102), which extends inside the chamber, generally in parallel with the first direction, which duct (2, 102) is arranged to conduct a second fluid flow (A) in an opposite direction to the first direction and which duct (2, 102) comprises a duct wall material with high permeability to water.

Abstract: A process for removing carbon dioxide or nitrogen from gas, especially natural gas. The process uses three membrane separation stages without compression between the second and third stages.

Abstract: The invention relates to a method for reducing the carbon dioxide concentration in air of a closed or partially closed unit of space. The inventive method may comprise the steps of removing an air flow from the unit of space, guiding the air flow in a membrane system that may contain at least one membrane module having a CO2/O2 selectivity of greater than 2, removing the carbon dioxide permeated through the membrane, and returning the air flow that has been depleted of carbon dioxide in the membrane system to the unit of space. The inventive method may be optionally combined with an oxygen enrichment method. The invention also relates to corresponding devices for carrying out the inventive method.

Abstract: A method of removing carbon monoxide from an oxygen carrier including setting a carbon monoxide bonded oxygen carrier solution across a separation membrane from an oxygen-dissolved solution; and exposing the setting part to the light and a method of removing carbon monoxide from an oxygen carrier including setting a carbon monoxide oxygen carrier solution across a hollow fiber separation membrane from an oxygen-dissolved solution; and exposing the setting part to light.

Abstract: A fuel system for a gas turbine engine removes oxygen from fuel with a fuel stabilization unit (FSU). The FSU includes a first vacuum stage, where vacuum pressure is created by an ejector and a second vacuum stage where vacuum pressure is created by the ejector and a vacuum pump. The vacuum stream from the first vacuum stage and the second vacuum stage flow through the ejector. The vacuum stream from the second vacuum stage is all that passes through the vacuum pump.

Abstract: The invention relates to gas separation, in particular to separation of CO2 from CO2-rich liquids, particularly from CO2 absorption liquids used in the removal of CO2 from off-gases or product flows, such as natural gas or synthesis gas. According to the invention, CO2 is separated from a CO2-rich liquid by a method comprising a step wherein, under elevated pressure, said liquid is contacted with a membrane based on polyacetylene substituted with trimethylsilyl groups such that the pressure across the membrane is at least 1 bar and that at least a part of the CO2 is transported from the liquid through the membrane.

Abstract: The present invention provides methods for making a microporous ceramic material using a metal silicon powder and including a reaction sintering process of the silicon. A material for forming a microporous ceramic material used in these methods includes a metal silicon powder, a silicon nitride powder and/or a silicon carbide powder, and if desired, a yttrium oxide powder and/or an aluminum oxide powder. These methods can make a microporous ceramic material that can be used preferably as a gas or liquid filter, a catalyst carrier or a support of a gas separation membrane.

Abstract: A mixed ionic and electronic conducting membrane includes a two-phase solid state ceramic composite, wherein the first phase comprises an oxygen ion conductor and the second phase comprises an n-type electronically conductive oxide, wherein the electronically conductive oxide is stable at an oxygen partial pressure as low as 10?20 atm and has an electronic conductivity of at least 1 S/cm. A hydrogen separation system and related methods using the mixed ionic and electronic conducting membrane are described.

Abstract: Thin layers of a mixed composition are deposited on a porous substrate by chemical vapor deposition in an inert atmosphere at high temperature. The resulting membrane has excellent stability to water vapor at high temperatures. An exemplary membrane comprises an amorphous mixed-element surface layer comprising silica and at least one oxide of additional element, an optional porous substrate on which said surface layer is deposited, and a porous support on which said substrate or mixed-element surface layer is deposited, wherein the permeance of the membrane is higher than 1×10?7 mol m?2 s?1 Pa?1 and the selectivity of H2 over CO, CO2, and CH4 is larger than 100, and wherein the H2 permeance of the membrane after exposure to a stream containing 60 mol % water vapor at 673 K for 120 h is at least 50% of its initial H2 permeance.

Abstract: A ceramic filter is provided, including a base body having partition walls made of a ceramic porous body and defining cells, filter membranes provided on the partition walls which are made of a ceramic porous body having an average pore diameter smaller than that of the surface of each partition wall, and a glass seal provided to cover at least the end face of the base body. The glass seal includes an alkali-free glass containing silica (SiO2) in an amount of 55 to 65 mol %, zirconia (ZrO2) in an amount of 1 to 10 mol % and at least one kind of alkaline earth metal oxide selected from calcia, baria and strontia, but which does not substantially contain zinc oxide.