Production of plastics based on metallocene catalysts

Transcription

1 Plasticheskie Massy, No. 4, 2001, pp Production of plastics based on metallocene catalysts V. T. Ponomareva and N. N. Likhacheva A. V. Topchiev Institute of Petrochemical Synthesis Selected from International Polymer Science and Technology, 28, No. 9, 2001, reference PM 01/04/08; transl. serial no Translation submitted by P. Curtis New polymerisation catalysts that have appeared in recent years, called metallocene catalysts, have made it possible to produce plastics with new physical properties. A fair number of catalysts of this kind are currently being investigated and employed, and therefore the term metallocene is often replaced with the broader term single-site, i.e. catalysts with a single polymerisation centre on the metal, in contrast to the catalysts traditionally used (Ziegler Natta, chromium, vanadium) which have several polymerisation centres. Here, the metal atom, which is a catalytically active centre, normally lies in a closed volume, and access to it for monomers is by a single path, which promotes the formation of polymers of homogeneous structure that are noted for increased strength, rigidity, transparency, and light weight. Furthermore, it is possible to produce plastics with prescribed properties, including constructional plastics, by using cheaper production technology. Metallocene catalysts generally have three components: an organometallic complex, a cocatalyst, and a support; the latter is absent in the case of solution polymerisation. The organometallic complex, including transition metals combined with different organic substituents, occupies 1 2 wt.% of the catalyst. By comparison, cocatalysts, called upon to intensify the action of transition metal systems, are often used in excess; aluminium oxides and fluorinated organoborate mixtures are normally used as cocatalysts. The activity of such catalysts is 2 5 times higher than the activity of typical Ziegler Natta catalysts. Their cost component in expenditure on polymer production is now estimated to be /lb ($10 13/t) of product. The polymer yield per unit catalyst can be changed substantially depending on the process conditions (ref. 1). The leaders in the area of the development, production, and use of metallocene catalysts are Chemical and, the first companies to produce batches of catalysts under the trade names Exxpol and Insite. Exxpol, patented by, is based on a dicyclopentadiene ring system, which is used in most metallocene technologies. In contrast to Exxpol, the Insite catalyst, developed by Dow, contains one organic ring (cyclopentadiene) and a second inorganic ring. By the end of the 1990s, a number of other, more ideal modifications of similar catalysts were developed, making it possible to broaden considerably the range of monomers used for polymerisation; in particular, it became possible to use polar monomers for these purposes. Furthermore, the new generation of catalysts is noted for resistance to ester and ketone impurities, which are poisons for the catalysts used earlier. Until 1995, only the and Dow companies produced plastics by using metallocene catalysts. Now, about 20 companies are using this technology to produce large-tonnage polymers (linear low-density polyethylene, high-density polyethylene, and polypropylene), including Phillips,, and Fina in the United States, BASF, Elenac, Borealis, BP Chemicals, and Targor in Western Europe, and Mitsui Chemicals, Sumimoto, Ube, and Asachi in. About 1 million t of metallocene polyethylene and t of polypropylene are now being produced; the polyethylene is used largely to produce film, while the polypropylene is used mainly to produce fibre (Figure 1). The capacities for the production of these plastics, amounting to ~1.5 million t/year, do not correspond to the potential market capacity; the demand for these products is roughly T/10 International Polymer Science and Technology, Vol. 29, No. 2, 2002

2 (a) (b) Figure 1 Directions of use of metallocene polyolefins in 1999: (a) polyethylene; (b) polypropylene double the current volume of production. By 2001, it is estimated that the worldwide demand for polypropylene will be at a level of t, and that the demand for polyethylene will be over 3 million t; this is largely for linear low-density polyethylene. The highest demand for polyethylene is anticipated to be in the United States, where it will amount to ~2 million t, including 1.7 million t of linear low-density polyethylene and 0.2 million t of high-density polyethylene (Figure 2). polyethylene based on metallocene catalysts has been edging out normal linear low-density polyethylene on the films market for the past 5 years, after Chemical produced the first commercial batch of film material, under the trade name Exceed, manufactured from metallocene polyethylene. In its properties, in particular its puncture resistance and tensile strength, it is significantly superior to film material manufactured from normal linear low-density polyethylene. Furthermore, metallocene films are noted for high gas permeability in relation to oxygen and carbon dioxide, which makes them ideally suited to the packing of foodstuffs, in particular vegetables. An important advantage is also their resistance to low temperatures, which makes it possible to use them in medicine, since many medical preparations are kept in dry ice, transported frozen, or mixed at low temperatures. According to an estimate by Chemical, by 2010, the worldwide use of linear low-density polyethylene based on metallocene catalysts will increase to 11 million t and will reach roughly half the total volume of consumption of plastics of this type (Figure 3). The anticipated consumption of metallocene polypropylene in this period, according to market estimates, will lie in the range 6 15 million t. About half the proposed increase in consumption will occur through polypropylene replacing more expensive constructional plastics used in the motor industry. Furthermore, according to market analysts, metallocene polypropylene with improved barrier properties and transparency may replace polyethylene terephthalate in the bottle container sector and polystyrene in some types of packaging (refs. 1, 3, 4, and 6). Figure 2 Worldwide demand for metallocene polyethylene in 2001, million t Figure 3 Consumption of linear low-density polyethylene in , in million t According to data of the consultants Chem Systems (London), the worldwide demand for metallocene linear low-density polyethylene will grow annually by 20 30%, whereas for standard linear low-density polyethylene this figure will not exceed 7%. This is due to the fact that As experts believe, in the near future the capacities for the production of metallocene polymers will increase significantly, both by expanding existing units and building new units and by converting a number of plants from traditional catalysts to metallocene catalysts. International Polymer Science and Technology, Vol. 29, No. 2, 2002 T/11

3 is doubling the production of linear low-density polyethylene at its plant in Mont Belvieu, Texas, after which its capacities for the production of this polymer using metallocene catalysts will reach 2 billion lb/year (~ t/year). This company is intending to start up by the end of the year 2000 a fourth line for the production of metallocene linear low-density polyethylene in Jorong Island (Singapore). is also continuing to increase its production of Achive polypropylene; in , a unit will be started up in North America, on which this product will be produced by using a new metallocene catalytic system. Certain progress in implementing Unipol polypropylene technology (using metallocene catalysts) has been made by the Union Carbide Corporation. In 1999 the company began to sell a new grade of highimpact polypropylene under the trade name IMPPAX, which has the best balance between rigidity and strength and also higher melt flow. By the same technology, together with the Tosco Corporation, Union Carbide is building a polypropylene unit of t/year capacity at the Bay Way Oil Refinery in Linden, New Jersey, on which several grades of polypropylene will be produced, including homopolymers and random and high-impact copolymers; start-up is proposed in Chevron Chemical has been licensed to produce polyethylene by technology including the Innovene gas-phase process of BP Amoco and Dow s Insite catalyst. It is proposed to start the production of metallocene plastic at the beginning of 2001 on plants in Cedar Bayou and Orange, Texas. In Belgium, Fina and Solvary are building two plants ( t/year) for the production of high-density polyethylene by licensed technology using metallocene catalysts. Equistar has announced its intention to start up in the near future a similar plant using the single-site catalyst Star at Clinton, Iowa (refs. 4, 6, and 9). The conversion of existing plants to single-site catalysts does not require great expenditure of time or financial resources, and therefore many plants earmarked in recent years for expansion are being oriented towards the production of metallocene polymers. In particular, in, companies are switching to the use of metallocene catalysts: Polyolefins is converting a plant for the production of linear low-density polyethylene ( t/year) in Kavasaki, and Polychem is converting one line for the production of polypropylene (Unipol technology) in Kashima; Mitsui is reprofiling the production of linear low-density polyethylene in Ichihara ( t/year) to the production of elastomers (ref. 4). Single-site catalysts are being used increasingly widely not only for the production of polyolefins but also for the production of a whole number of other products currently produced by many known companies (Table 1). Thus, Dow Plastics is producing an ethylene styrene copolymer under the trade name Index, which may replace block copolymers of ethyl vinyl acetate and flexible polyvinyl chloride (PVC). The new plastic has a controllable melt index and a narrow molecular weight distribution, is compatible with fillers, contains no plasticisers, is 40% lighter than PVC, and can be recycled. The process is carried out on a single-site catalyst with the use of an increased proportion of styrene (25 80%), which on the former catalyst was impossible, since no more than 10% styrene was permitted. Dow is producing this plastic on a pilot unit of 1 million lb/year (454 t/year) capacity, and before 2001 is planning to start up two industrial units of 50 and 400 million lb/year productivity. This company is producing, on a metallocene catalyst, the syndiotactic polystyrene Questra which is used in electronics, in the motor industry, and in the production of medical articles, edging out more expensive constructional plastics such as polyphenylene sulphide and mesomorphic polymers. This polymer is now being produced in Germany on an 80 million lb/year unit and in (11 million lb/year); the demand for it, estimated to be 120 million lb/year, may subsequently grow considerably (refs. 2 and 5). In Germany (Oberhausen), Hoechst AG and Mitsui Petrochemical have announced their intention to put into service in 2000 an industrial unit for the production of copolymers of cyclic olefins under the trade name Topaz. This colourless, transparent polymer is one of the lightest optical plastics currently available. It has a high heat resistance and is resistant to polar solvents (alcohols, ketones, solutions of acids and bases). It is assumed that the copolymers will be lower in price than those produced earlier ($ /kg, instead of $26 44/kg), which will make it possible to expand their use considerably, since, on account of the high cost, this type of product had a limited market until recently. They can be used as glass substitutes for the manufacture of medical articles and optical discs, competing with such transparent plastics as polycarbonates and acrylates (refs. 5 8). is producing, on its own metallocene catalyst Insite, elastomers under the name Engage which are used in the motor industry and for the production of wire and cable insulation. After the appearance of Engage on the market (in 1994), the demand for it has doubled annually. In the current year, the venture company Du Pont Dow Elastomers has announced the trebling of capacity for the production of this product by 2002 (up to 500 million lb/year) in Freport, Texas, and the construction of a 300 million lb/ year unit in Gulf Coast (refs. 3, 4, and 6). Investigators of Chemical and the Minnesota University recently reported on a new advantage of metallocene chemistry the possibility of producing composites from polyethylene and polypropylene. Owing to the presence of the crystal T/12 International Polymer Science and Technology, Vol. 29, No. 2, 2002

4 Table 1 Type Polymers produced using metallocene (single-site) catalysts of polymer Polyethylene Polypropylene Cycloolefinic Plastomers Elastomers Aliphatic Interpolymer Polystyrene polymers and copolymers polyketones Producer Borealis Total Elenac Phillips Ube Fina Polyolefins Industries Total Targor Chisso Fina Mitsui Chemicals BF Ticona Goodrich Du Pont Dow Elastomers CK Shell BP Witco Amoco-GE Plastics Idemitsu Petrochemical Product name Elite Exceed Borecene Finathene Luflexen Harmorex mpact Umerit Achieve Finapro Metocene Chisso Hspp Apel Appear Avatrel Duvcor Topas Affinity -P Exact Engage Nordel lp Trilene Royalene Carilon Ketonex Index Questra Zarec Ichi structure of the polyolefins produced using metallocene catalysts, a simple and effective path for the point bonding of polymer layers is ensured. As a result, highstrength compounds are formed which cannot be produced using polyolefins produced on normal Ziegler Natta catalysts (ref. 9). The development of the production and use of singlesite catalysts, associated with the need for a strong scientific provision, including highly qualified specialists, using special expensive equipment, requires considerable financial resources. The expenditure of large companies on carrying out scientific research is estimated to be $3 billion, and in future it will be necessary to invest at least $500 million annually. Furthermore, the existing strong competition on the large-tonnage plastics market makes it necessary to direct additional resources towards improving the service. For these purposes, in particular, use is made of the internet (E-commerce), which can ensure a reduction in marketing costs and a 10 20% reduction in product prices. In this context, many catalyst and polymer producers are creating special venture companies, associations, or licensing agreements oriented towards solving problems in the field of metallocene technology. Enterprises of this kind, having access to information and the research capacity of the companies that have founded them, promote an increase in the intellectural potential, a reduction in the catalyst development times, a reduction in production expenditure, and more rapid penetration of the market by new products. Thus, BASF and Hoechst have set up International Polymer Science and Technology, Vol. 29, No. 2, 2002 T/13

5 the venture company Targor for organising the production and realisation of metallocene polypropylene, and Mitsui and Sumitomo have set up the venture oriented towards metallocene polyethylene. Powerful associations are known, such as, which occupies leading positions in the development of the production of products based on metallocenes, or the association created by and Union Carbide under the name Univation Technologies, which is the largest patent holder (18%) in the area of single-site catalysts for polyolefins. To accelerate the process of creating catalysts, certain companies are using the combinatorial method, more familiar in the area of the development of new medicines. This essentially consists in the simultaneous use of several synthesis reactors, which makes it possible to investigate up to mixtures per week, instead of mixtures by the traditional method; sections of 48 polymerisation reactors that are now being manufactured by the company Symyx Technologies make it possible to study up to 100 trials per day (refs. 1, 3, and 4). REFERENCES 1. Chemical and Engineering News, 76, No. 27, 1998, pp ; No. 49, pp Chemical and Engineering News, 76, No. 40, 1998, pp ; No. 51, p European Plastics News, 25, No. 4, 1998, p. 14; 22, No. 6, 1995, pp. 24 and Chemical Week, 162, No. 6, 2000, pp. 16, 18, and 35 37; No. 12, p. 24; No. 24, p Modern Plastics International, 27, No. 7, 1997, pp ; 25, No. 12, 1995, p. 93; 26, No. 1, 1996, pp Chemical Week, 161, No. 21, 1999, pp ; No. 24, p. 40; No. 25, p. 32; No. 33, p. 5; 160, No. 26, 2000, pp European Plastics News, 25, No. 5, 1998, p. 51; No. 7, p. 21; No. 8, p Korinf, No. 28, 1997, p Chemical Week, 162, No. 20, 2000, p. 7; No. 25, p. 47; No. 32, p. 18 T/14 International Polymer Science and Technology, Vol. 29, No. 2, 2002