Method of removing catalyst from ethylene-alpha-olefin copolymer

Abstract: After a copolymer of ethylene and an alpha-olefin of at least 3 carbon atoms (e.g. propylene) and optionally also a non-conjugated diene has been prepared with the use of a vanadium catalyst and an organoaluminum (e.g. alkyl) compound, the residual catalyst is removed from the polymerisation reaction mixture in a hydrocarbon solvent (eg.hexane)by,a halogenated ester compound being optional, oxidising the reaction mixture with an oxidising agent (preferably O 2 ), e.g. to convert the vanadium to pentavalent V, in an aqueous solution of an alkaline compound (e.g. hydroxide of Li, Na or K) in an amount to give an aqueous phase pH of at least 10. The organic phase is then separated and washed with water and the polymer is recovered therefrom. The catalyst residue is thus reduced to very low levels, so that the copolymer is not affected thereby.

Description: This invention relates to a method for purifying ethylene-α-olefin copolymers by removing therefrom catalytic ingredients. In the preparation of an ethylene-α-olefin copolymer in a hydrocarbon solvent in the presence of a catalyst comprising a vanadium compound and an organo-aluminum compound, or a catalyst comprising a vanadium compound, an organoaluminum compound, and a halogenated ester compound, if the catalytic ingredients remain or are incorporated in the copolymer as a final product, problems such as discoloration of the copolymer and deterioration in weather resistance and heat resistance of the copolymer occur. Hence, the catalytic ingredients remaining in the copolymer obtained by the polymerization reaction must be completely removed from the copolymer. Conventional methods for removing the catalytic ingredients from the ethylene-α-olefin copolymer prepared in the presence of a vanadium-based catalyst include a method wherein a large amount of water is added to a polymer solution, the mixture is mixed in a mixer, the catalyst is extracted into an aqueous phase, the aqueous phase is separated from an organic phase, and the polymer containing a reduced amount of the catalytic ingredients is recovered from the organic phase; and a method wherein water or an alcohol is added to a slurry obtained by a copolymerization reaction in a solvent which does not dissolve therein the polymer, to reduce the amount of catalytic residue in the polymer [see, Yasuharu Saeki, Polymer Production Process, published by Kogyo Chosakai (1971)]. However, these methods have some disadvantages described below. In the method wherein a polymer solution is treated with a large amount of water, it is considered that the catalytic ingredients which are solubilized in water by bringing them into contact with water are extracted with water. However, when one expects that the catalytic ingredients are more completely removed, the mixing of the polymer solution with water must be thoroughly made, and a large-size, heavy-duty mixer must be used at a high speed (at high revolution number). Hence, the costs of equipment and power are high and, therefore, the method is not industrially advantageous. In the method using an alcohol, the alcohol must be purified and reused and, hence, not only is the process complicated, but the energy consumption is increased. Thus, the method also is not industrially advantageous. As other methods, JP-A-63-275605 ("JP-A" means an unexamined published Japanese patent application) discloses a method wherein copolymers prepared in the presence of a titanium-based catalyst are washed with water containing an alkaline compound; and JP-B-43-6471 ("JP-B" means an examined Japanese patent publication) discloses a method wherein copolymers prepared in the presence of a vanadium-based catalyst are oxidized and then washed with water containing an alkaline compound. In recent years, since ethylene-α-olefin rubbery copolymers are mixed with other polymers such as polypropylene and are widely used for automobile parts and packaging materials, the requirements for weather resistance and non-discoloration of the rubbery copolymers have become more stringent. In order to meet the requirements, it is highly desirable to further reduce the amount of the catalytic ingredients remaining in the rubbery copolymer. For example, it is required that the amount of the vanadium compound in the copolymer is reduced to not higher than 1 ppm in terms of V 2 O 5 . Further, there is a problem that in addition to the metallic catalytic ingredients, halogenated ester compounds (used as activating agents for the polymerization reaction) remain in the copolymer; and this causes problems such as lowering in the quality of the copolymer so that corrosion of processing machines and coloration of the copolymers occur, and the copolymers are no longer useful as vessels and packaging materials for foods and medicines. Therefore, the conventional purification techniques described in the aforesaid patent specifications are not yet satisfactory. FR-A-1551506 (GB-A-1141783) describes a process for purification from polymerization catalyst residues of an olefin polymer specifically in the presence of a polymerizable monomer. BE-A-683637 (GB-A-1092022) relates to a process for removing coloured vanadium constituents in catalyst residues contained in a polymer of a polymerized olefinic compound where the compound to be purified is first treated with an oxidising agent having a pH between 4 to 9. BE-A-655084 (GB-A-1008832) describes a process for purifying polyolefins comprising washing the polymer with an alkaline alcoholic solution. BE-A-676500 (GB-A-1070634) relates to a process for the production of polyolefins where the polymer after polymerization is simultaneously treated with an aqueous alkali solution and gaseous oxygen or hydrogen peroxide but the polymer is recovered from the resulting mixture without prior removal of the aqueous phase. An object of the present invention is thus to provide a method capable of removing catalytic ingredients, to a level which could not be achieved by conventional methods, in purifying a polymerization reaction mixture containing an ethylene-α-olefin copolymer obtained by polymerizing ethylene with an α-olefin having at least 3 carbon atoms, or ethylene with an α-olefin having at least 3 carbon atoms and a non-conjugated diene compound, in a hydrocarbon solvent in the presence of a catalyst comprising a vanadium compound and an organoaluminum compound, or a catalyst comprising a vanadium compound, an organoaluminum compound, possibly a halogenated ester compound. According to the present invention therefore there is provided a method of purifying an ethylene-α-olefin copolymer described in Claim 1. The present invention provides a method of purifying an ethylene-α-olefin copolymer obtained by polymerizing ethylene with an α-olefin having at least 3 carbon atoms, or ethylene with an α-olefin having at least 3 carbon atoms and a non-conjugated diene compound, in a hydrocarbon solvent in the presence of a catalyst comprising a vanadium compound and an organoaluminum compound, the method including treating a polymerization reaction mixture obtained by the polymerization reaction with an oxidizing agent in an aqueous alkaline solution in such an amount as to give an aqueous phase having a pH of not lower than 10.0 after oxidation. In the said polymerization reaction mixtures to be purified, any solvent or medium in which the copolymer is soluble or insoluble can be used as the hydrocarbon solvent or dispersant. Examples of solvents which can be suitably used include aromatic compounds such as benzene and toluene; aliphatic hydrocarbon compounds such as pentane, hexane and heptane; alicyclic hydrocarbon compounds such as cyclopentane, methylcyclopentane and cyclohexane; α-olefins such as liquefied propylene, liquefied 1-butene and 4-methylpentene-1; and mixtures thereof. Examples of the vanadium compound which can be used in the present invention include VCl 3 , VCl 4 , VOCl 3 and VO(OR) 3-m Cl m (wherein R is a straight chain or branched alkyl group, a cycloalkyl group or an aryl group, each having 1 to 10 carbon atoms; and 3 ≧ m ≧ 0), such as VO(OCH 3 )Cl 2 , VO(OCH 3 ) 2 Cl, VO(OCH 3 ) 3 , VO(OC 2 H 5 )Cl 2 , VO(OC 2 H 5 )Cl, VO(OC 2 H 5 ) 3 , VO(OC 3 H 7 )Cl 2 , VO(OC 3 H 7 ) 2 Cl, VO(OC 3 H 7 ) 3 , VO(OisoC 3 H 7 )Cl 2 , VO(OisoC 3 H 7 ) 2 Cl, VO(OisoC 3 H 7 ) 3 , V(OCH 3 ) 3 and V(OCH 2 COOCH 3 ) 3 . Examples of the organoaluminum compound which can be used include AlR' n Cl 3-n and AlR' n (OR') 3 (wherein R' is a straight chain or branched alkyl group having 1 to 8 carbon atoms; and 3 ≧ n ≧ 0), such as (C 2 H 5 ) 2 AlCl, (C 4 H 9 ) 2 AlCl, (C 6 H 13 ) 2 AlCl, (C 2 H 5 ) 1.5 AlCl 1.5 , (C 4 H 9 ) 1.5 AlCl 1.5 , (C 6 H 13 ) 1.5 AlCl 1.5 , C 2 H 5 AlCl 2 , C 4 H 9 AlCl 2 and C 6 H 13 AlCl 2 . A halogenated ester compound which can be effectively used is a compound represented by the following formula: wherein R" represents an organic group having 1 to 20 carbon atoms, which is partially or wholly substituted by a halogen atom; and R''' represents a hydrocarbon group having 1 to 20 carbon atoms. Compounds wherein R''' is wholly substituted by chlorine atoms and compounds having a phenyl group and a chlorine-substituted alkyl group are preferred. More preferred are perchlorocrotonic acid esters, perchloro-3-butenoic acid esters, and phenyldichloroacetic acid esters. Specific examples of the halogenated ester compound include ethyl dichloroacetate, methyl trichloroacetate, ethyl trichloroacetate, methyl dichlorophenylacetate, ethyl dichlorophenylacetate, methyl perchlorocrotonate, ethyl perchlorocrotonate, propyl perchlorocrotonate, isopropyl perchlorocrotonate, butyl perchlorocrotonate, cyclopropyl perchlorocrotonate, phenyl perchlorocrotonate, methyl perchloro-3-butenoate, ethyl perchloro-3-butenoate, propyl perchloro-3-butenoate and butyl perchloro-3-butenoate. In addition to these catalytic ingredients, hydrogen, etc. as a molecular weight modifier may be used in the present invention. Examples of an α-olefin having at least 3 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methylpentene-1, 1-octene and 1-decene. Examples of the non-conjugated diene compound include dicyclopentadiene, tricyclopentadiene, 5-methyl-2,5-norbornadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5-isopropylidene-2-norbornene, 5-isopropenyl-2-norbornene, 5-(1'-butenyl)-2-norbornene, 5-(2'-butenyl)-2-norbornene, 1,4-hexadiene, 1,6-octadiene and 6-methyl-1,5-heptadiene. There is no particular limitation with regard to other polymerization conditions than tbose described above. The polymerization reaction mixtures to be purified in the present invention can be obtained in the manner mentioned above. The purification methods of the present invention are now described. The present invention is a method of purifying an ethylene-α-olefin copolymer, the method including an oxidation treatment of the above-described polymerization reaction mixture in an aqueous alkaline solution in such an amount as to give an aqueous phase having a pH of not lower than 10.0 after the oxidation treatment. This method preferably comprises the following first and second steps. First step: the polymerization reaction mixture is oxidized with an aqueous solution consisting essentially of an oxidizing agent in at least five times of a stoichiometric amount required for oxidizing vanadium present in the polymerization reaction mixture to a pentavalent state and an alkaline compound in such an amount that an aqueous phase separated in the subsequent second stage has a pH of not lower than 10.0. Second step: the mixture obtained in the first step is separated into an aqueous phase and an organic phase, and the organic phase is washed with neutral water. An embodiment of the present method can comprise the following three steps: First step: the polymerization reaction mixture obtained by the polymerization reaction is mixed and stirred in an aqueous solution containing an alkaline compound in such an amount that an aqueous phase formed in the subsequent second stage has a pH of not lower than 10.0. Second step: 1/5 to 10 parts by volume of water containing an oxidizing agent in at least five times of a stoichiometric amount required for oxidizing vanadium in the polymerization reaction mixture to a pentavalent state is added to one part by volume of the mixture obtained in the first step. Third step: the mixture obtained in the second step is separated into an aqueous phase and an organic phase, and the organic phase is washed with neutral water. Examples of the alkaline compound which can be used in the embodiment include lithium hydroxide, sodium hydroxide, potassium hydroxide, concentrated ammonia and ammonium hydroxide. Among then, lithium hydroxide, potassium hydroxide and sodium hydroxide are particularly preferred. The alkaline compound must be used in an amount sufficient to give an aqueous phase having a pH of not lower than 10, and preferably not lower than 11, the aqueous phase being separated from the organic phase after the oxidation treatment. When the amount of the alkaline compound is insufficient, the removal of the catalytic ingredients is insufficient. A preferred way for adding the alkaline compound in the embodiment is that an aqueous alkaline solution having a pH of not lower than 12, and preferably not lower than 13, is used, and 1/1000 to 10 parts by volume of the aqueous alkaline solution is added to and mixed with one part by volume of the polymerization reaction mixture. Examples of the oxidizing agent which can be used in the embodiment include alkali metal nitrites, persulfates, peroxides, hypochlorites, oxygen, ozone and air, such as sodium nitrite, potassium nitrite, hydrogen peroxide or hydroxylamine hydrochloride. Among them, air or oxygen is particularly preferred as the oxidizing agent because not only is air or oxygen easy to handle, but there is no risk that any air or oxygen remains in the copolymer. The oxidizing agent is used in at least a stoichiometric amount required for oxidizing all of the vanadium present in the polymerization reaction mixture to a pentavalent state. When the amount of the oxidizing agent is insufficient, the removal of the catalytic ingredients can be insufficient, and the desired effect of the present invention is not obtained. When the oxidizing agent is used in an amount of twice or more the stoichiometric amount, the valence of all the vanadium can be brought to a pentavalent oxidation state; pentavalent vanadium is colorless and transparent and, hence, the final product copolymer can be completely prevented from being colored. However, when an oxidizing agent other than oxygen is excessively used, the oxidizing agent remains in the final product copolymer. Hence, it is desirable that oxidizing agents other than oxygen are used in an amount of 10 times or less the stoichiometric amount. There is no fear that oxygen remains in the copolymer, even when oxygen is excessively used. Eowever, when a large excess amount of oxygen is used in the continuous polymerization process (including a solvent recycling process), oxygen is accumulated in the solvents, and the copolymer is oxidized and deteriorated. Eence, it is desirable that oxygen is used in an amount of 50 times or less the stoichiometric amount. Eowever, when an oxidizing agent-removing process is provided in an after-stage, such consideration is not required. In the oxidation treatment, water is used in an amount sufficient to effectively extract therewith ashes mainly formed from the catalytic ingredients and to separate the organic phase and the aqueous phase. Specifically, water is used in an amount of preferably 1/5 to 10 parts by volume, and more preferably 1/4 to 5 parts by volume per part by volume of the polymerization reaction mixture. It is preferred that water to be used has an iron content as low as possible. When iron components exist in water, the desired copolymer is apt to be colored. Preferably, the concentration of the iron components is not more than 0.1 ppm. The mixing and stirring or treatment of the polymerization reaction mixture with an aqueous alkaline solution or an aqueous alkaline solution containing an oxidizing agent may be carried out by using any method, so long as the catalytic ingredients can be efficiently brought into contact wtih these solutions so as to extract the catalytic ingredients into the aqueous phase. For example, a method using a line mixer can be used. As a method for separating the aqueous phase and the organic phase, a method using a stationary separating drum can for example be used. A step of mixing and stirring or treating the polymerization reaction mixture with the aqueous alkaline solution or the aqueous alkaline solution containing an oxidizing agent and the step of separating the aqueous and organic phases are carried out at a temperature of generally 20 to 160°C, and preferably 50 to 100°C under a pressure of 98.07 to 1961.4 kPaG (1 to 20 kg/cm 2 G), and preferably 196.114 to 980.7 kPaG (2 to 10 kg/cm 2 G). Preferably after the phase separation is carried out, water washing is carried out several times. The thus obtained organic phase containing the desired copolymer is subjected to a conventional after-treatment stage. For example, the hydrocarbon solvent is distilled off by evaporation upon heating, and the residue is dried to obtain the desired ethylene-α-olefin copolymer. The important characteristic feature resides in the oxidation treatment in an aqueous alkaline solution. The significance thereof is as follows. When the polymerization reaction mixture is treated with an aqueous alkaline solution, a water-insoluble low-valent vanadium compound remains in the organic phase. When the vanadium compound is oxidized with an oxidizing agent to a pentavalent state, since a hydroxide of pentavalent vanadium has good solubility in water, the hydroxide of pentavalent vanadium migrates into the aqueous phase and is removed from the organic phase. On the contrary, when the polymerization reaction mixture is subjected to the oxidation treatment under neutral or acidic conditions, an oxide of vanadium is formed; this compound has poor solubility in water even under alkaline conditions and migrates with difficulty into the aqueous phase and, hence it is difficult to remove the compound. As a result, the vanadium compound remains in the desired copolymer. The organoaluminum compound and the halogenated ester compound as a polymerization activator can be decomposed and extracted into the aqueous phase when treated with an aqueous alkaline solution. The oxidation treatment does not interfere with the extraction of the vanadium compound but rather has an effect of accelerating the extraction of the vanadium compound into the aqueous phase. The present invention in now illustrated in greater detail by reference to the Examples 1 to 6. The examples show the removal of the catalytic ingredients to low levels not hitherto obtainable. EXAMPLE 1 Ethylene and propylene were copolymerized in the presence of a catalyst comprising vanadium oxytrichloride, ethylaluminum sesquichloride, and BPCC (manufactured by Marine Crott, U.S.A., n-butyl perchlorocrotonate according to a catalog of said company) by a conventional method (e.g., the method described in JP-B-44-9390) to prepare a hexane solution containing an ethylene-propylene copolymer. This uniform hexane solution (containing about 8 wt% of the copolymer) of the ethylene-propylene copolymer (ethylene content: 73 wt%) contained 47 ppm of V 2 O 5 , 560 ppm of Al 2 O 3 , 700 ppm of Cl, and about 110 ppm of BPCC, calculated as the copolymer. To 2000 ml of the hexane solution of the copolymer prepared as above was added an aqueous alkaline solution (NaOH content: 1.25 mol/ℓ, pH: at least 14) formed by dissolving 10 g of sodium hydroxide in 200 ml of pure water (saturated with air and having air dissolved therein under atmospheric pressure; iron content: 0.1 ppm or less). The mixture was mixed with stirring in a nitrogen atmosphere at 60°C under a pressure of 0kPaG (0kg/cm 2 G) in a mixer (12000 rpm) for 5 minutes. After stirring, 500 ml of pure water (saturated with air and having air dissolved therein under atmospheric pressure) was further added, and the mixture was mixed with stirring in a mixer (12000 rpm) for an additional 5 minutes. After the mixture was left to stand for about 10 minutes to separate an aqueous phase, the pH of the aqueous phase was measured and found to be 13.4. To the separated oily phase was added 500 ml of neutral pure water, and the mixture was mixed with stirring in a mixer (12000 rpm) for 5 minutes to carry out washing. Hexane was distilled off from the oily phase by heating to isolate the copolymer. The content of ashes in the copolymer was determined by means of X-ray fluorometry. The coloration of the copolymer was visually evaluated. The results are shown in Table 1. EXAMPLES 2 AND 3 The procedures of Example 1 were essentially repeated except that the concentration of the aqueous alkaline solution and the amount thereof to be added were changed. The results together with conditions are shown in Table 1. COMPARATIVE EXAMPLE 1 The procedures of Example 1 were essentially repeated except that the aqueous alkaline solution was omitted. The results are shown in Table 1. EXAMPLE 4 Into a 50 liter-volume polymerizer were continuously introduced 913 g/hr of ethylene, 1630 g/hr of propylene, 4.08 ℓ/hr of hexane, 0.32 mmol/hr of vanadium oxytrichloride, 6.8 mmol/hr of ethylaluminum sesquichloride and 0.28 g/h of BPCC (manufactured by Marine Crott, U.S.A.) as a polymerization activator. While 7.2 ℓ/hr of hydrogen as a molecular weight modifier was fed to the mixture, a polymerization reaction was carried out at a temperature of 50°C under a pressure of 13 kg/cm 2 G. The reaction mixture in the polymerizer was continuously drawn out so that the volume of the reaction mixture in the polymerizer was controlled to 25 liters. The drawn-out reaction mixture was led to a flash drum where the reaction mixture was flashed at a temperature of 60°C under a pressure of 78.456 kPaG (0.8 kg/cm 2 G) to thereby remove the monomer gases. In order to maintain the temperature of the flashed solution, heated hexane was added. To 11.6 kg/hr (about 18 ℓ/hr) of the thus obtained polymerization mixture was added an aqueous sodium hydroxide solution (concentration: 0.16 mol/ℓ, pH: 13.2) at a rate of 200 ml/hr. The mixture was mixed in a mixer. Subsequently, 5 ℓ/hr of water saturated with air (deaerated pure water was saturated with air at a temperature of 20°C under a pressure of 1 kg/cm 2 G, iron content: 0.1 ppm or less) was added to the mixture. The mixture was mixed in a mixer, and an organic phase was separated from an aqueous phase in a stationary separation drum. The organic phase was washed with water to obtain the final organic phase. Hexane was then distilled off from the final organic phase by flash distillation. The residue was dried to obtain an ethylene-propylene copolymer. The contents of Cl, Al 2 O 3 and V 2 O 5 in the copolymer were determined by X-ray fluorometry. The coloration of the copolymer was visually evaluated. The results are shown in Table 2. EXAMPLE 5 The procedures of Example 1 were essentially repeated except that the polymerization activator was omitted. The results are shown in Table 2. EXAMPLE 6 The procedures of Example 1 were essentially repeated except that 1-butene as the α-olefin was used in place of propylene that and a deaerated aqueous alkaline solution was used. The results shown in Table 2. COMPARATIVE EXAMPLES 2 AND 3 The procedures of Example 1 or 2 was essentially repeated except that deaerated pure water containing no air was used in place of air-saturated water used in Example 4 or 5 The results are shown in Table 2.

Claims: A method of purifying an ethylene-α-olefin copolymer obtained by polymerizing ethylene with an α-olefin having at least 3 carbon atoms, optionally with a non-conjugated diene compound, in a hydrocarbon solvent in the presence of a catalyst comprising a vanadium compound and an organo-aluminum compound and optionally a halogenated ester compound, said method comprising an oxidation treatment of the polymerization reaction mixture obtained by the polymerization reaction in an aqueous alkaline solution in such an amount that an aqueous phase obtained after the oxidation treatment has a pH of not lower than 10.0, wherein said oxidation treatment comprises: a first step wherein the oxidation treatment of the polymerization reaction mixture obtained by the polymerization reaction is carried out in an aqueous solution consisting essentially of (i) an oxidizing agent in at least five times of a stoichiometric amount required for oxidizing vanadium present in said mixture to a pentavalent state and (ii) an alkaline compound in such an amount that an aqueous phase separated in the subsequent second stage has a pH of not lower than 10.0; and a second step wherein the mixture obtained in the first step is separated into an aqueous phase and an organic phase, and the organic phase is washed with neutral water; and wherein the first and the second step are carried out at a temperature of 20 to 160°C. A method as claimed in Claim 1, wherein said aqueous alkaline solution is an aqueous alkaline solution having a pH of 12 or more. A method as claimed in Claim 1, wherein said oxidation treatment comprises: a first step wherein the oxidation treatment of the polymerization reaction mixture obtained by the polymerization reaction is carried out in an aqueous solution containing (i) an alkaline compound in such an amount that an aqueous phase formed in the subsequent second step has a pH of not lower than 10.0; a second step wherein 1/5 to 10 parts by volume of water containing (ii) an oxidizing agent in at least five times of a stoichiometric amount required for oxidizing vanadium present in said mixture to a pentavalent state is added to one part by volume of water obtained in the first step; and a third step wherein the mixture obtained in the second step is separated into an aqueous phase and an organic phase, and the organic phase is washed with neutral water. A method as claimed in Claim 1, 2 or 3, wherein said oxidizing agent is oxygen. A method as claimed in any preceding claim, wherein said vanadium compound is selected from VCl 3 , VCl 4 , VOCl 3 , and VO(OR) 3-m Cl m , wherein R is a straight or branched alkyl group, a cycloalkyl group, or an aryl group, each having 1 to 10 carbon atoms; and 3≥m≥0. A method as claimed in any preceding claim, wherein said organoaluminum compound is selected from AlR' n Cl 3-n and AlR' n (OR') 3 , wherein R' is a straight chain or branched alkyl group having 1 to 8 carbon atoms; and 3≥m≥0. A method as claimed in any preceding claim, wherein said halogenated ester compound is represented by the formula: wherein R" represents an organic group having 1 to 20 carbon atoms, which is partially or wholly substituted by a halogen atom; and R" ' represents a hydrocarbon group having 1 to 20 carbon atoms.

Inventors: INAGAKI KATSUNARI, SABA HAYATO, SUGIMORI KIYOYUKI, WAKATSUKI KIZUKU, YAMAMOTO KEISAKU, INAGAKI, KATSUNARI, SABA, HAYATO, SUGIMORI, KIYOYUKI, WAKATSUKI, KIZUKU, YAMAMOTO, KEISAKU, Wakatsuki, Kizuku, Sumitomo Kagaku Shiizu-Ryo
Applicants: SUMITOMO CHEMICAL CO, SUMITOMO CHEMICAL COMPANY LIMITED
Application year: 1991
Main classification: C08F6
IPC codes: C08F6