Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
  • C10C3/00—Working-up pitch, asphalt, bitumen
  • C10C3/14—Solidifying, Disintegrating, e.g. granulating
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10C—WORKING-UP PITCH, ASPHALT, BITUMEN, TAR; PYROLIGNEOUS ACID
  • C10C3/00—Working-up pitch, asphalt, bitumen
  • C10C3/002—Working-up pitch, asphalt, bitumen by thermal means
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues

Definitions

• This invention relates to a process for producing a reformed pitch useful for various carbon materials by reacting a pitch in the presence of a Lewis acid and a co­solvent. Since the reformed pitch has a characteristic property that it has a high fixed carbon content in spite of its low softening point and low quinoline insoluble content and that it can be converted easily to mesophase by heat treatment, the reformed pitch can be used for various purposes, for example, an impregnant for high grade carbon materials such as carbon-carbon composite materials, artificial graphite electrodes, carbon graphite shaped articles, etc., a raw pitch for mesophase pitch based carbon fibers, and a mixing material for modifying various kinds of pitch.
• an impregnant for high grade carbon materials such as carbon-carbon composite materials, artificial graphite electrodes, carbon graphite shaped articles, etc.
• a raw pitch for mesophase pitch based carbon fibers such as carbon-carbon composite materials, artificial graphite electrodes, carbon graphite shaped articles
• This invention also relates to a process for produc­ing spherical meso-carbon microbeads which comprises sub­ jecting the reformed pitch to a heat treatment at a tem­perature of 200 ⁇ 380°C. Further, this invention relates to a process for producing meso-carbon microbeads having a uniform diameter in the range of 0.5 ⁇ 20 ⁇ m, at a high yield of about 60% or more.
• Meso-carbon microbeads are spherical carbon materials having a structure in which highly condensed polycyclic aromatic hydrocarbons are arranged in a definite direc­tion. Since meso-carbon microbeads have properties in­herent to carbon chemically, electrically and magnetically and have a good sintering property during carbonization, they are used for various industrial materials such as an electro conductive filler, a binderless isotropic high density carbon material, a catalyst carrier,a chromatogram filler, etc., in the form of meso-carbon microbeads as they are produced or after carbonization.
• High grade carbon materials such as carbon-carbon composite materials, artificial graphite electrodes, carbon-graphite shaped articles, etc. are generally produced by shaping, carbonizing and graphitizing a mix­ture of a basic material such as shaped cokes and a binder pitch.
• a basic material such as shaped cokes and a binder pitch.
• the impregnant is indispensable for producing a high grade carbon material, because the pitch impregnation of a carbonized material is effective to bind the basic materials with each other, to decrease a porosity and increase a density, strength, electric con­ductivity and a thermal conductivity of the produced carbon material.
• Pitch based impregnants are generally produced from petroleum or coal based pitch by heat-treating to cause a condensation polymerization reaction and to remove a low boiling point fraction.
• Pitch based impregnants are required to have properties as follows for various purposes.
• This polymerization reaction is carried out using a catalyst of a weak Lewis acid such as an anhydrous AlCl3 accompanied by a second component such as CuCl2 which has a function of reducing the activity of AlCl3.
• a catalyst of a weak Lewis acid such as an anhydrous AlCl3 accompanied by a second component such as CuCl2 which has a function of reducing the activity of AlCl3.
• orthodichlorobenzene, nitro benzene and trich­lorobenzene are preferable.
• the mesophase pitch which is obtained by subjecting a pitch, from which a catalyst has been removed, to heat treatment is preferable for spinning probably due to its slender molecule. Further, this mesophase pitch has a low soften­ing point and good shaping property at a low temperature.
• this mesophase pitch has a thin laminate layer of molecule compared with conventional mesophase pitches in spite of high completeness of crystal. Fur­ther, it is said that this mesophase pitch has charac­teristic properties different from the mesophase pitch produced by using a strong Lewis acid which is not accom­panied by the second component. According to this process, the control of the catalyst system is complicated and the growth of mesophase is restrained. there is no disclosure about the production of meso-carbon microbeads.
• the problem of this process is in the difficulty of production of meso-carbon microbeads having uniform diameter with a high yield. Even when good quality pitch containing no free carbon was used as a raw material, yield was 10 vol % or less.
• the present invention resides in a process for producing a reformed pitch useful for carbon materials which comprises mixing a pitch having an aromatic carbon ratio fa of more than 0.6, with a Lewis acid and a co­solvent so as to give a mol ratio of the said Lewis acid to the said pitch in the range of 0.3 ⁇ 5.0 and a mol ratio of the said co-solvent to the said pitch in the range of 2.5 ⁇ 50, reacting the mixture at a temperature of 100 ⁇ 300°C and removing the Lewis acid and the co-­solvent from the resulting reaction product.
• the pitch used in the process of the present inven­tion is selected from those having an aromatic carbon ratios fa (ratio of carbon forming aromatic rings to the total carbon) of more than 0.6 or more. It is preferable that the pitch is a petroleum or coal based high boiling point fraction, but the use of a low boiling point raw material is also allowable.
• a raw material having a boiling point e.g., in the extent of gas oil or kerosene.
• a raw material having a boiling point e.g., in the extent of gas oil or kerosene.
• a pure material having a high aromatic carbon ratio e.g. naphthalene, anthracene, phenanthrene, etc. is possible.
• the Lewis acid catalysts used in the present inven­tion are those such as BF3, or HF ⁇ BF3, anhydrous AlCl3, anhydrous CuCl2, anhydrous ZnCl2 or anhydrous SnCl2.
• an­hydrous AlCl3 is preferable, but in case where complete removal of a catalyst from a reaction product is neces­sary, a vaporizable catalyst is preferable.
• HF ⁇ BF3 is preferable since HF increases the function of the catalyst, and effectiveness as a solvent can be ex­pected and recovery and re-use are easy.
• the co-solvents used in the present invention are those compounds which have a boiling point preferably in the range of 100 ⁇ 350°C and most preferably in the range of 150 ⁇ 250°C and which do not cause a reaction as decom­position of Lewis acid and are easily separable from the reaction product.
• the co-solvents are preferably aromatic compounds having a neutral or an acidic substituent and most preferably, compounds in which one or more compounds selected from the group consisting of dichlorobenzene, nitrobenzene, trichlorobenzene are principal components. Even basic compounds such as pyridine, quinoline or the like, which react with the Lewis acid, but does not destroy the structure of the Lewis acid and does not form water by neutralization, are usable because they only weakens the catalytic effect.
• a pitch having a high softening point such as 250°C can be used as a raw material if the pitch dissolves in a co-solvent
• selection of a raw material can be varied flexibly depending upon the required quality of product.
• a raw material having a high softening point cannot be used because of limitative dis­solving power of HF.
• the amount of HF be­ comes greater, the reaction system turns to high pressure and separation and recovery of HF becomes difficult, but if a co-solvent is present, the amount of HF can be greatly reduced and reaction temperature can be lowered.
• a mixing ratio of a pitch, a Lewis acid and a co-­solvent is preferably in the range of 1:0.3 ⁇ 5:2.5 ⁇ 50.
• the amount of HF should be removed in the above mentioned ratio.
• Reaction temperature is in the range of 100 ⁇ 300°C, preferably 120 ⁇ 250°C.
• Reaction time is preferably in the range of 1 ⁇ 30 hours.
• 0.3 ⁇ 1.0 mol of BF3 and 1 ⁇ 5 mol of HF are present relative to 1 mol of pitch and reaction time is 1 ⁇ 5 hours, and even at a reaction temperature of 100°C a uniform reformed pitch can be obtained.
• Reduction of the ratio of Lewis acid to less than 0.3 is not preferable because reaction yield is reduced. If the ratio of Lewis acid is more than 5.0, the increase of reaction velocity becomes small and on the one hand the time necessary to remove Lewis acid from a reac­tion product becomes longer and this causes increase of cost and hence is not preferable. Reaction temperature lower than 100°C is not preferable because reaction yield from a pitch is extremely reduced.
• reaction temperature is elevated over 300°C, local rapid reactions tend to occur and the unifor­mity of the reformed pitch is lowered, and as for meso­carbon microbeads, optically anisotropic small sphericals become liable to coalesce and associate during the heat treatment and diameters of small spheres become non-­uniform.
• reaction time less than one hour provides generally low yield from a pitch.
• reaction yield from the pitch scarcely increases and the yield of optically anisotropic small spheres after heat treatment does not increase almost at all and no notable change occurs on the quality of meso-carbon microbeads and accordingly not ad­ vantageous in the point of cost.
• the co-solvent and the Lewis acid are removed from the reaction system.
• removal of the co-solvent is preferably carried out by vacuum distillation. It is preferable to carry out the operation in the inert gas atmosphere.
• the removal of the Lewis acid is preferably carried out by ex­traction with an aqueous solvent. Particularly, repeti­tion of washing with a dilute hydrochloric acid is effec­tive.
• purging by an inert gas or vacuum distillation is preferable to remove the co-solvent and the Lewis acid from the reaction sys­tem, followed by catching thereof. It is preferable to re-use the co-solvent or the Lewis acid.
• the properties of the produced reformed pitch fairly depend on the raw pitch. In the case of a pitch having a softening point of about 250°C, produced reformed pitch has a softening point of about 270°C, a quinoline in­soluble content of about 5 wt % and a fixed carbon content of about 90 wt%. In the case of a pitch having a soften­ing point of about 100°C, produced reformed pitch has a softening point of about 140°C, a quinoline insoluble con­tent of less than 1 wt% and a fixed carbon content of about 70 wt%, and the reformed pitch can be easily con­verted to 100% mesophase by a heat treatment in less than 2 hrs. This reformed pitch is very suitable for an im­pregnation pitch of carbon materials, because high den­sity, high strength carbon materials can be easily produced.
• the mesophase obtained by heat treatment of the reformed pitch of the present invention has a flow type structure and the increase of the softening point by the heat treatment is small.
• This mesophase is suitable for a spinning pitch to make a high performance carbon fiber, because 100% mesophase pitch having a softening point of less than 270°C can be produced.
• a reformed pitch produced by a vaporizable Lewis acid is preferable as raw pitch of the carbon fiber, because of no remaining of the catalyst.
• the reformed pitch of the present invention is also used to modify a conventional petroleum or coal based pitch.
• a mesophase containing pitch produced from a pitch having an aromatic carbon ratio fa of more than 0.6 is heat treated, the mesophase content can be increased, but at the same time the softening point is also raised to the extent which is unsuitable for spinning to make a carbon fiber.
• the resulting pitch has a low softening point and a high mesophase content and is useful for spinning to make a carbon fiber because the conversion rate to mesophase is increased the increase of the softening point is suppressed.
• the resulting pitch is a 100% mesophase pitch having a lowered softening point.
• meso-carbon microbeads having a uniform diameter in the range of 0.5 ⁇ 20 ⁇ m can be ob­tained at a high yield of about 60 wt% or more.
• the change of temperature at the time of heat treatment of the reformed pitch is most effective.
• the relation of the heat treatment temperature and mean diameter varies according to the conditions such as kind of a pitch, mol ratio of Lewis acid or the like.
• temperature of a heat treatment temperature of 250°C or lower is advantageous to the for­mation of a mean diameter less than 1 ⁇ m.
• a temperature of 250 ⁇ 300°C is advantages to the formation of a mean diameter of 1 ⁇ 5 ⁇ m and a temperature of 300 ⁇ 350°C, is advantageous to the formation of a mean diameter of 5 ⁇ 20 ⁇ m.
• HF ⁇ BF3 there is a tendency of requiring slightly higher temperature than that in case of AlCl3.
• quinoline As a solvent used to extract the optically anisotropic small spheres, quinoline has been used in most of the case. In case of the present invention, since solubilities of the resulting optically anisotropic small spheres and the isotropic component of matrix are both su­perior, if quinoline is used, yield of the small spheres becomes lower.
• a petroleum based pitch (having an initial distilla­tion fraction of 460°C and a final distillation fraction of 560°C) produced as a by-product of Fluid catalytic cracking (F.C.C.) of desulforized vacuum gas oil (DVGO) and having a softening point of 72°C (Mettler softening point measuring apparatus is used) and a number average molecular weight of 400 was taken in an amount of 200 g and put into glass round bottom flask, 90 g of anhydrous AlCl3 as a Lewis acid catalyst, 1000 ml of o-­dichlorobenzene as a solvent were added and reaction was carried out at a temperature of 180°C under reflux of a solvent for 26 hours. (Mol ratio of the pitch, Lewis acid and compatible co-solvent were 1 : 1.35 : 17.65).
• This pitch in an amount of 100 g was introduced into a stainless steel reaction vessel having an inner volume of 500 ml. While flowing nitrogen in a flow rate of 2N1/min. and with stirring at 300°C, heat treatment was carried out for 30 minutes to obtain a pitch product. Yield was 98 wt% relative to the raw reformed pitch.
• Example 1 The reformed pitch of Example 1 was subjected to heat treatment at a temperature of 330°C for 60 minutes, whereby yield of resulting pitch product was 95 wt%.
• a mean diameter of optical anisotropic small spheres bodies contained therein was 6.2 ⁇ m.
• the yield of resulting meso-carbon microbeads as an insoluble portion in trich­lorobenzene was 80 wt%.
• the heat treatment temperature of the reformed pitch of Example 1 was set to 250°C and heat-treatment time was set to 60 min., the yield of resulting pitch product was 98 wt% and an mean diameter of contained optically anisotropic small spheres was 0,7 ⁇ m and the yield of meso-carbon microbeads obtained as trichlorobenzene in­soluble portion was 65 wt%.
• a petroleum based pitch produced as a by-produce of F.C.C. of DVGO and having a softening point of 130°C and a number average molecular weight of 500 was reacted in the presence of anhydrous AlCl3 and o-dichlorobenzene (mole ratios were same as in Example 1) at 180°C under reflux of a solvent for 26 hours.
• Example 1 After completion of the reaction, anhydrous AlCl3 and o-dichlorobenzene were removed as in Example 1 and a reformed pitch having a softening point of 195°C was ob­tained at a yield of about 100%.
• This reformed pitch was heat treated at 250°C for 60 minutes to obtain a pitch product at a yield of 98 wt%.
• a mean diameter of contained optically anisotropic spheres was 4.6 ⁇ m and the yield of meso-carbon microbeads ob­tained as trichlorobenzene insoluble portion was 69 wt%.
• the raw material pitch of Example 1 was introduced immediately into a stainless steel reaction vessel without carrying out a reaction in which a Lewis acid catalyst is used. While flowing nitrogen at a flow rate of 2N1/min. and with stirring, heat treatment was carried out at 380°C for 12 hours whereby a pitch product was obtained. The yield was 92 wt% relative to the raw pitch.
• this pitch product was treated with trichlorobenzene as in Ex­ample 1, solubility of isotropic pitch was poor and isola­tion of meso-carbon microbeads was difficult.
• This pitch product was dissolved in quinoline in place of trich­lorobenzene and separation was carried out by filtration, meso-carbon microbeads was obtained as an insoluble por­tion with a yield of 16.3 wt%.
• Example 1 The reformed pitch of Example 1 which had been sub­jected to the treatment of and from which the Lewis acid had been removed by washing was subjected to heat treat­ment at 420°C for one hour, whereby a pitch of substan­tially 100% flow type mesophase was obtained.
• a coal based pitch having a softening point of 86.3°C (Mettler softening point measuring apparatus is used), toluene insoluble content of 20.9 wt%, quinoline insoluble content of 0.3 wt%, and a mean molecular weight of 450, was taken in an amount of 200 g and put into a glass, round bottom flask (capacity 2000 ml), 90 g of anhydrous AlCl3 as a Lewis acid catalyst, and 1000 ml of o-­dichlorobenzene as a co-solvent were added and reaction was carried out at 180°C under reflux of the solvent for 26 hours. (Mol ratio of the pitch, Lewis acid and co-­solvent was 1 : 1.52 : 20).
• This reformed pitch in an amount of 100 g was intro­duced into a 500 ml stainless steel reactor. While flow­ing nitrogen at a flow rate of 2N1/min. and with stirring, heat treatment was carried out at 340°C for 60 minutes to obtain a pitch product. Yield was 95 wt% relative to the raw reformed pitch.
• the pitch product When the pitch product was observed with a polariza­ tion microscope, it contained optically anisotropic small spheres having a mean diameter of 8.2 ⁇ m. When this pitch product was dissolved in trichlorobenzene and insoluble product was separated by filtration, meso-carbon microbeads was obtained with a yield of 73 wt%.
• a petroleum pitch (initial distillation fraction of 460°C to final distillation fraction of 560°C), produced as a by-product of fluid catalytic cracking process (F.C.C.) of desulfurized vacuum gas oil, having a soften­ing point of 72°C (Mettler softening point measuring ap­paratus was used) and an average molecular weight of 400, in an amount of 0.5 mols was introduced into a 500 ml stainless steel autoclave, 1.25 mols o-dichlorobenzene was added, after dissolving, the content was cooled till 5°C. Then, under cooled state 2.5 mols HF was introduced and after replacement of the inside with nitrogen, 0.5 mols BF3 was blown in.
• F.C.C. fluid catalytic cracking process
• the temperature was elevated at a heat­ing rate of 3°C/min. and reaction was carried out at 180°C for 2 hours. After completion of the reaction, cooling was carried out till room temperature. While purging with N2, temperature was elevated till 200°C, o-dichlorobenzene and HF ⁇ BF3 were removed to the outside of the system at the same time, and were caught. A reformed pitch was taken out after removal operation of o-dichlorobenzene and HF ⁇ BF3. The yield of the reformed pitch was 100%. The softening point of the reformed pitch was 114°C.
• Resulting reformed pitch in an amount of 50 g was in­troduced into a 350 ml stainless steel reactor. While flowing nitrogen at a flow rate of 2 N1/min. and with stirring, heat treatment was carried out at 350°C for one hour to obtain a pitch product. The yield was 97 wt% relative to the reformed pitch. The mean spheres con­tained therein was 7.6 ⁇ m.
• Lewis acid co-solvent reaction heat treatment product kind mol ratio kind mol ratio temperature °C time hr temperature °C time hr diameter m yield % 1 BF3 0.9 OCB 2.5 120 3 250 3 1 50 HF 5.0 2 BF3 0.9 OCB 2.5 160 3 330 1 2 60 HF 5.0 3 BF3 0.9 OCB 2.5 180 3 330 1 4 70 HF 5.0 4 BF3 0.5 OCB 4.0 180 3 370 1 18 70 HF 3.0 5 BF3 0.5 OCB 4.0 180 3 350 1 7 65 HF 3.0 (symbol) OCB: dichlorobenzene
• F.C.C. Fluid catalytic cracking process
• This reformed pitch was heat treated at 400°C for 2.5 hours.
• the resulting pitch was 100% mesophase having a softening point of 267°C.
• a carbon fiber was conven­tionally produced by spinning this resulting pitch at 285°C, infusiblizing and carbonizing at 2500°C.
• This carbon fiber had a tensile strength of 362 kgf/mm2 and a modulus of elasticity of 77 X 103 kgf/mm2.
• F.C.C. Fluid catalytic cracking process
• This reformed pitch was heat treated at 400°C for 2 hours.
• the resulting pitch was 100% mesophase having a softening point of 270°C.
• a carbon fiber was conven­tionally produced by spinning this resulting pitch at 288°C, infusiblizing and carbonizing at 2500°C.
• This carbon fiber had a tensile strength of 370 kgf/mm2 and a modulus of elasticity of 80 X 103 kgf/mm2.
• a petroleum based pitch as a by-product of F.C.C. of DVGO, having a softening point of 72°C, was heat treated in the nitrogen atmosphere to obtain Pitch A having a mesophase content of 10% and a softening point of 190°C.
• the heat treatment was further continued to obtain Pitch B having a mesophase content of 100% and a softening point of 278°C.
• Example 10 The reformed pitch of Example 10 (a softening point of 151°C) was blended to the Pitch A at a ratio of 20 wt% relative to Pitch A. The mixture was heat treated at 400°C for 2 hours, whereby the resulting pitch had a mesophase content of 90% and a softening point of 262°C
• Example 10 a softening point of 151°C was blended to the Pitch B at a ratio of 20 wt% relative to Pitch B.
• the mixture was heat treated at 380°C for 0.5 hours, whereby the resulting pitch had a mesophase content of 100% and a softening point of 270°C.
• This invention relates to a process for producing a reformed pitch useful for various carbon materials by reacting a pitch in the presence of a Lewis acid and a co-­solvent. Since the reformed pitch has a characteristic property that it has a high fixed carbon content in spite of its low softening point and low quinoline insoluble content and that it can be converted easily to mesophase by heat treatment, the reformed pitch can be used for various purposes, for example, an impregnant for high grade carbon materials such as carbon-carbon composite materials, artificial graphite electrodes, carbon-graphite shaped articles, etc., a raw pitch for mesophase pitch based carbon fibers, and a mixing material for modifying various kinds of pitch.
• an impregnant for high grade carbon materials such as carbon-carbon composite materials, artificial graphite electrodes, carbon-graphite shaped articles, etc.
• a raw pitch for mesophase pitch based carbon fibers such as carbon-carbon composite materials, artificial graphite electrodes, carbon-graphit
• the present invention relates to a process for producing meso-carbon microbeads having a uniform diameter, i.e. a mean diameter in the range of 0.5 ⁇ 20 ⁇ m from a petroleum based pitch or a coal based pitch or a mixture thereof with a high yield of about 60 wt% or more.
• Meso-carbon microbeads are spherical carbonaceous materials having a structure in which highly condensed polycyclic aromatic hydrocarbons are arranged in a definite direction.
• Meso-carbon microbeads have properties inherent to carbon chemically, electrically and magnetically. Since they have good sintering property during carbonization, they can be used for various in­dustrial materials such as an electrically conductive fil­ler, a binderless isotropical high density carbon material, a catalyst carrier, a chromatogram filler and the like. They are used in the form of meso-carbon microbeads as they are produced or after carbonization.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Civil Engineering (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Textile Engineering (AREA)
• Working-Up Tar And Pitch (AREA)
• Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Related Child Applications (1)

Publications (3)

Family

ID=14712933

Family Applications (2)

Family Applications After (1)

Country Status (3)

Cited By (1)

Families Citing this family (3)

Family Cites Families (5)

• 1989
  • 1989-05-12 DE DE1989608004 patent/DE68908004T2/de not_active Expired - Fee Related
  • 1989-05-12 DE DE1989617318 patent/DE68917318T2/de not_active Expired - Fee Related
  • 1989-05-12 EP EP19890108592 patent/EP0342542B1/de not_active Expired - Lifetime
  • 1989-05-12 JP JP1117468A patent/JP2630466B2/ja not_active Expired - Lifetime
  • 1989-05-12 EP EP91111551A patent/EP0456278B1/de not_active Expired - Lifetime

Also Published As

Similar Documents

Legal Events