JP2007146083A - Method for continuous production of polyethylene - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for the continuous production of a polyethylene having a broad or bimodal molecular weight distribution (MWD), containing a low-molecular weight component, a high-molecular weight component and a small amount of ultrahigh-molecular weight component at the same time, suitable for the production of a hollow molded article by blow molding and a pipe material by extrusion molding and having excellent ESCR property, etc. <P>SOLUTION: The continuous production method uses four reactors connected in series. At least one reactor in the reactors is supplied with ethylene, an α-olefin, a solid catalyst and an organic aluminum compound and subjected to multi-stage polymerization reaction and mixing. The intrinsic viscosity of the ethylene polymer produced in the first reactor is 0.1-4.0, that in the second reactor is 1.0-7.0, that in the third reactor is 1.0-7.0, and that in the fourth reactor is 2.0-11.5, and the final ethylene resin composition has intrinsic viscosity of 1.1-8.0 and a density of 0.935-0.965 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multistage continuous production method for polyethylene, and more particularly to a multistage polymerization method for a polyethylene resin composition having a broad or two-peak molecular weight distribution.

  In recent years, with the emergence of new technologies and new products on the market, processor and consumer market demands for high performance polyethylene resins are increasing day by day. Therefore, the development, modification research and efficient production of high performance polyethylene has always been the focus of competition that can not be neglected by those skilled in the art. However, along with this, requirements for polyethylene processing performance, such as material strength, environmental stress crack resistance (ESCR), impact resistance, and rigidity, have become increasingly severe. It is known that these performances can be improved by increasing the molecular weight, for example, by producing high molecular weight high density polyethylene (HMW-HDPE) having a relative molecular weight of 250,000 or more. However, when the molecular weight of polyethylene is increased, the processing performance of extrusion molding, compression molding, blow molding, thermoforming or rotary molding becomes worse. However, polyethylene having a relatively wide width or two-peak molecular weight distribution (MWD) can overcome these disadvantages quite effectively. This is believed to be due to the long chains present in the polymer providing mechanical strength and the short chains providing the lubricating effect. Furthermore, it is very important to control the distribution of the comonomer. In other words, the copolymer itself must have good connectivity to the relative high molecular weight chain, but the opposite is true for the relatively low molecular weight chain. In short, molecular weight distribution is one of the important factors affecting environmental stress crack resistance. This is because the molecular weight distribution directly reflects the contents of the large and small molecules of the polymer. If the content of the large molecule is large, the number of linked molecules between the cores is increased, and the ESCR performance is improved. On the other hand, the effects of density and crystallinity on ESCR are more complex. That is, the higher the density, the higher the crystallinity and the number of linked molecules between the cores, leading to a decrease in ESCR performance. When the density of polyethylene is low or has a relatively high intrinsic viscosity, the polymer has a relatively good ESCR performance, but it is known that the lower the density of the polymer, the lower the mechanical strength and rigidity of the resin composition. It has been. If the intrinsic viscosity or molecular weight of polyethylene is too high, the fluidity of the resin is deteriorated, resulting in a problem that hinders the molding process. Therefore, improving the ESCR performance of the polyethylene resin and improving the rigidity under the condition in which the density of the polyethylene is controlled are problems that restrain each other, and a balance between the two must be appropriately taken.

  As is well known, the slurry process is one of the methods for producing a broad molecular weight distribution polyethylene by blow molding. In this direction, various methods for producing polyethylene having a wide molecular weight distribution by a Ziegler method using a catalyst have been proposed. For example, Non-Patent Documents 1 and 2 disclose techniques relating to the production of polyethylene having a two-peak molecular weight distribution by a two-stage polymerization reaction. Generally speaking, it is known that the polyethylene resin composition obtained by the two-stage polymerization method can provide better ESCR performance and overall rigidity performance than the polyethylene obtained by the one-stage polymerization method. Patent Documents 1, 2 and 3 propose methods for adjusting or controlling the rigidity of polyethylene by copolymerization of α-olefin. It is also disclosed that the overall performance of ESCR and stiffness can be significantly improved by mixing the α-olefin with the polymer. According to this method, it is easily understood that the amount of α-olefin contained in the polymer of the high molecular weight section is larger than the amount of α-olefin contained in the polymer of the low molecular weight section. However, a blow molded product blow molded using a polymer obtained by such a two-stage polymerization method has a weak pinch-off weld strength, a low expansion ratio (die swell), and a sufficient amount of extrusion. There are unsatisfactory issues.

  In order to solve the above problems, Patent Documents 4 to 12 propose a method for producing polyethylene modified by a three-stage polymerization method, and disclose a technique for continuously producing polyethylene copolymers having three different molecular weights. However, as described in Patent Documents 5 and 6, although the expansion ratio of polyethylene is improved, the improvement in which the overall performance of rigidity and ESCR meets expectations is not obtained. In addition, the conventional three-stage polymerization method usually produces low molecular weight and high molecular weight components by a general two-stage polymerization method, and also produces a small amount of ultra-high molecular weight polymer components. This ultra-high molecular weight component causes the generation of fish eyes or gels that greatly affect the product surface and quality, which is disadvantageous for the molding process.

Low density polyethylene resins (LLDPE and LDPE) have been used for blow molding processes, taking advantage of the excellent tearing properties that low density properties give to films. For example, Patent Document 12 proposes a method for producing high molecular weight medium density polyethylene by a three-stage polymerization method. In this method, a low molecular weight component having a density in the range of 0.904 to 0.970 g / cm ³ is produced in the first stage polymerization step, and after degassing and releasing the pressure, the density is reduced. 0.900~0.940g / cm in the range of ³ to introduce mixed into the second-stage polymerization step by polymerizing adjusting the composition fraction of high molecular weight, finally, the density of 0.930~0.944g / cm ³ A high-molecular-weight medium density polyethylene (HMW-MDPE) is obtained. In order to obtain a higher molecular weight component, it has also been proposed to perform granulation under conditions where the oxygen concentration is 5% and the temperature of the extruder is 200 to 300 ° C.

  Patent Document 13 proposes a method for producing a polyethylene resin blend by a three-stage polymerization method. In this method, polymers (A, B, and C) having three types of non-ultra high molecular weight components are produced, respectively, and further, the intrinsic viscosity of each polymer (for example, B, C) (the molecular weight is increased). By limiting the compatibility (miscibility) of each component of the polymer, and as a result, the quality of the resulting resin blend is very uniform and the gel or fish eye He states that he has found that it rarely occurs. Furthermore, in the examples of this document, in the production of such an admixture, steps (a), (b), (c) are used in order to bring the amounts and molecular weights of the respective polymers obtained in the second and third stages closer. Alternatively, continuous production (polymerization) is preferably performed in the order of steps (b), (a), and (c), and the concentration of hydrogen in the subsequent stage is lower than the concentration of hydrogen in the previous stage. A purge of hydrogen gas is required. In short, according to this manufacturing method, in order to prevent the difference in intrinsic viscosity between the composition (A) and the composition (B) from becoming too large regardless of the order of steps described above, It is necessary to perform a pressure release by an air tank (flash tank) and a process of once lowering the temperature and then increasing again, and in order to include a large amount of α-olefin in the composition of step (c), step (c ) -Α-olefin should be added more than the α-olefin added in step (a) and step (b). Therefore, there is a problem in that it is inconvenient for industrialized production and costs are increased, which is disadvantageous for continuous production.

Macromolecular. Symp. , 163, 135-143 (2001). Plastics, Rubber and Composites Processing and Applications, 25 (8), 368-372 (1996) Japanese Patent Laid-Open No. 2-155906 JP-A 64-1709 JP-A 64-79204 JP 58-138719 A Japanese Examined Patent Publication No. 59-227913 JP 61-207404 A Japanese Examined Patent Publication No. 62-61057 JP-A 64-79204 Japanese Patent Publication No. 3-29805 Japanese Patent Publication No. 4-14686 JP-A-62-25105 Chinese Patent Application No. CN1449414A Chinese Patent Application No. CN1405224A

However, in the three-stage polymerization method of Patent Documents 4 to 11, a high molecular weight and a low molecular weight component, as well as a small amount of ultra high molecular weight polymer components are produced, which causes fish eye or gel generation, and particularly high speed. This has a detrimental effect on the recent development of blow molding technology that aims to make the system more precise, more precise, more complex, and larger.
Moreover, in patent document 12, since the compatibility of the resin composition obtained by the blend of the high density and the low density polyethylene is deteriorated, and further, a cross-linking reaction is performed at a high temperature with oxygen gas, the molecular weight rapidly increases, Although excellent tearability and optical properties can be obtained, there is a problem in that the uniformity of the mixture is impaired and sharkskin, gel, fish eyes, etc. are generated, and the appearance of the hollow molded article is adversely affected. In addition, since the density is relatively low, a hollow molded product obtained by blow molding with such HMW-MDPE has a softer and better texture than a general HDPE hollow molded product, but has a high extrusion rate blow. In the production of molded articles or films, the stability of the film bubbles tends to deteriorate, resulting in a disadvantage for speeding up and increasing the production of the processor.
Moreover, in patent document 13, even if it employ | adopts any of the order of step (a, b, c) in manufacture, the difference of the intrinsic viscosity of the said component (A) and a component (B) does not become so large. Therefore, in each step, it is necessary to release the pressure in the deaeration tank (flash tank) and lower the temperature once, and then increase the temperature again, and in addition, a large amount of the composition in step (c) In order to include the α-olefin, the amount of α-olefin added in step (c) needs to be larger than the amount of α-olefin added in steps (a) and (b). There are disadvantages in terms of process inconvenience and high cost, and there is a problem in that it is disadvantageous for continuous and consistent industrial production.

  The present invention has been made in view of such problems, the molecular weight and molecular weight distribution of the ethylene resin composition can be arbitrarily adjusted, the dissolution fluidity is good, and the composition has a low molecular weight. In addition to the composition and the high molecular weight component, there is an even smaller amount of a particularly high molecular weight component, the molecular weight of which is between the high molecular weight and the ultra high molecular weight (hereinafter referred to as “special high molecular weight composition”). Having a broad width to two-peak molecular weight distribution (MWD) characteristics, excellent environmental stress crack resistance (ESCR), rigidity and strength, and the fish eye or gel is difficult to form, and Provided a multi-stage continuous production method of polyethylene that is suitable for blow molding of large hollow molded products such as containers of chemicals, solvents, etc. or drums, and extrusion molding of pipe materials, which have good processability It is an object of Rukoto.

In order to achieve the above object, the invention described in claim 1 is directed to continuously producing polyethylene by introducing a monomer as a raw material into four reactors arranged in series and performing a multistage polymerization reaction and mixing. In this method, the at least one reactor includes, in addition to the raw material monomer, at least (a) a solid catalyst containing at least components of titanium, magnesium and a halide, and a solid catalyst containing a metallocene compound and an aluminoxane. A mixture of a catalyst and (b) an organoaluminum compound is introduced, and a multistage continuous polymerization reaction and mixing are performed by the reactor and another reactor into which the same raw material monomer is introduced in series with the reactor, and the final resin The intrinsic viscosity [η] (dl / g) of the mixture is in the range of 1.1 to 8.0, and the density is 0.935 to 0.965. / Cm A method for producing polyethylene in the range of ^3, the four respectively reactor carried out polymerization step a, b, c, control conditions of the d is, step a: at a temperature 70 to 100 ° C. An ethylene polymer having an intrinsic viscosity [η1] (dl / g) in the range of 0.1 to 4.0, and step b: at a temperature of 60 to 90 ° C., the intrinsic viscosity [η2] (dl / g) is An ethylene polymer in the range of 1.0 to 7.0 is produced, and step c: ethylene weight having an intrinsic viscosity [η3] (dl / g) in the range of 1.0 to 7.0 at a temperature of 60 to 90 ° C. Step d: producing an ethylene polymer having an intrinsic viscosity [η4] (dl / g) in the range of 2.0 to 11.5 at a temperature of 40 to 70 ° C., and (1) Step a, The content of the ethylene polymer produced by steps b and c is respectively It accounts for 20 to 50 wt% with respect to the total weight of the polymerization composition, and (2) the content of the ethylene polymer produced by step d is 0.5 to 10 wt% with respect to the total weight of the polymerization composition (3) (amount of polymer composition according to step b + amount of polymer composition according to step c): (amount of polymer composition according to step a) = 6/7 to 5/1 And (4) using hydrogen or alcohols as molecular weight regulators in step d.

  According to the first aspect of the present invention, the molecular weight distribution (MWD) has a wide width or two peaks, and includes a low molecular weight component, a high molecular weight component, and a small amount of a special high molecular weight component at the same time. The fluidity is good and the molecular weight and molecular weight distribution can be arbitrarily adjusted to meet the desired conditions, as well as high environmental stress crack resistance (ESCR), impact strength and rigidity. Further, it is possible to produce polyethylene which is difficult to form a gel and has high molding process stability, particularly used for molding hollow molded articles such as polyethylene drums and pipes and films.

According to a second aspect of the present invention, in the method according to the first aspect, the steps a, b, c and d are arranged under the control conditions, the arrangement of the reactors is unchanged, and the arrangement of the steps The polymerization reaction can be carried out by arbitrarily changing the order.
According to the second aspect of the present invention, the order of the steps can be arbitrarily changed without changing the arrangement of the reactors.

The invention according to claim 3 is the method according to claim 1 or 2, wherein the ethylene polymer is an ethylene homopolymer or an ethylene copolymer.
According to invention of Claim 3, an ethylene homopolymer and / or an ethylene copolymer can be obtained.

The invention according to claim 4 is the method according to claim 3, wherein the ethylene copolymer is an ethylene copolymer having an α-olefin content of 10 wt% or less.
According to invention of Claim 4, the molecular weight of the ethylene resin composition of a final product can be adjusted suitably.

  According to the method for producing polyethylene of the present invention, the molecular weight and molecular weight distribution state of the ethylene resin composition can be arbitrarily adjusted, the solution fluidity is good, and the composition has a low molecular weight component and A polyethylene having a high molecular weight component and a small amount of a special high molecular weight component and having a broad to two-peak molecular weight distribution is obtained. Polyethylene produced by this method has good moldability, and is particularly suitable for blow molding of large hollow molded products such as containers for chemicals and solvents or drums, and extrusion molding of pipe materials. A molded product having ESCR, impact strength, or short-term static hydraulic strength and hardly generating fish eye or gel can be obtained.

  FIG. 1 is a block diagram showing a method for continuously producing polyethylene according to the present invention. In the figure, the continuous production method of polyethylene of the present invention is a method by four-stage polymerization. An apparatus for carrying out this method is arranged in series to produce ethylene homopolymers having different intrinsic viscosities or ethylene copolymers having an α-olefin content within a predetermined range under different temperature conditions. It is composed of reactors (1, 2, 3, 4). The reactor (1, 2, 3, 4) preferably uses a high-pressure kettle equipped with a stirrer inside. In addition to the ethylene monomer (10), the α-olefin monomer (20) and the solvent (30), the raw material further contains a catalyst (40) and an organoaluminum compound (50). These raw materials are supplied to the reactor (1, 2, 3, 4) by a conventional method, and a polymerization reaction is caused to occur under control of preset conditions, and polyethylenes having different intrinsic viscosities [η] are stepped. And finally a polyethylene resin blended with these can be obtained. The polyethylene resin thus obtained may be an ethylene homopolymer or an ethylene copolymer. The steps performed in each reactor (1, 2, 3, 4) are defined as steps (a, b, c, d) in the order of the reactors (1, 2, 3, 4). Steps a to d are arranged in series and are continuous continuous operations that flow from upstream to downstream, so that the polymer polymerized in step a is fed into step b and mixed with the polymer polymerized in step b After reacting and mixing with the polymer of step c in step c, the final product polyethylene resin (60) is produced by mixing with the polymer of step d in step d.

  As shown in FIG. 1, the catalyst (40) and the organoaluminum compound (50) are usually supplied only to the first reactor (1), that is, step (a). However, if necessary, it can be supplied to one or more of the second reactor (2), the third reactor (3), and the fourth reactor (4). . As the catalyst (40), a solid Ziegler catalyst mainly containing titanium, magnesium and halide components, or a solid catalyst containing a metallocene compound and an aluminoxane is used. In any case, commercially available products or home-made products may be used.

Specifically, in the present invention, in the four-stage continuous production method of polyethylene, at least one reactor (1) is provided with ethylene (10) and / or α-olefin monomer (20) as a raw material and solvent (30). ), At least one of (A) a solid catalyst containing titanium, magnesium and halide components, and a solid catalyst containing a metallocene compound and an aluminoxane, and (B) an organoaluminum compound. (50) and a multistage continuous polymerization reaction and mixing by the reactor (1) and the other reactors (2, 3, 4) to which only the raw material monomer and the solvent are supplied. the intrinsic viscosity of the resin mixture [η] (dl / g) in the range of 1.1 to 8.0, a density in the range of 0.935~0.965g / cm ³ The continuous production of polyethylene resin (60) that.

In addition, the order of the operations of steps a, b, c, and d in each reactor can be arbitrarily changed, and the operations are performed under the following control conditions.
Step a: Ethylene homopolymer having an intrinsic viscosity [η1] (dl / g) in the range of 0.1 to 4.0 at a temperature of 70 to 100 ° C. or an ethylene copolymer having an α-olefin content of 10 wt% or less Manufacture and
Step b: Ethylene homopolymer having an intrinsic viscosity [η2] (dl / g) in the range of 1.0 to 7.0 at a temperature of 60 to 90 ° C. or an ethylene copolymer having an α-olefin content of 10 wt% or less Manufacture and
Step c: an ethylene homopolymer having an intrinsic viscosity [η3] (dl / g) in the range of 1.0 to 7.0 at a temperature of 60 to 90 ° C. or an ethylene copolymer having an α-olefin content of 10 wt% or less Manufacture and
Step d: An ethylene homopolymer having an intrinsic viscosity [η4] (dl / g) in the range of 2.0 to 11.5 or an ethylene copolymer having an α-olefin content of 4.5 wt% or less at a temperature of 40 to 70 ° C. A polymer is produced.

The content of the ethylene homopolymer or the copolymer produced by the above steps a, b and c by performing multistage continuous polymerization using the solid catalyst (40) and the organoaluminum compound (50). Each containing 20 to 50 wt%, preferably 25 to 45 wt%, based on the total weight of the polymerization composition, and containing the ethylene homopolymer or copolymer thereof produced by step d The amount is controlled to occupy 0.5-10 wt%, preferably 2.0-6.0 wt%, based on the total weight of the polymerization composition, and further (the amount of polymerization composition according to step b + Amount of polymerization composition according to step c): (amount of polymerization composition according to step a) = 6/7 to 5/1, preferably adjusted to be within a range of 1/1 to 3/1. The intrinsic viscosity [η] is 1. 8.0, the resin composition of the molecular weight distribution of greater width to 2 peaks in the range density of 0.935~0.965g / cm ³ is obtained. The total weight of the polymer obtained in each process can be freely adjusted or polymer designed according to the characteristics of the product and the user's request, it is adaptable and the lag time of the polymerization reaction is increased. There are advantages that the activity of the catalyst is greatly improved, the production rate is increased, and the cost is reduced.

  In the present invention, it is preferable to use α-olefin as a copolymerization simple substance in addition to ethylene simple substance as a raw material simple substance. In this case, the α-olefin is preferably an α-olefin containing 3 to 20 carbons such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1 One or more selected from -dodecene and 1-eicosene are selected and used. Among them, 1-butene, 4-methyl-1-pentene, 1-hexene or 1-octene can be preferably used. Solvents used in the slurry polymerization include aliphatic propane, butane, pentane, hexane, heptane, octane, dodecane, cyclopentane, methylcyclohexane, and aromatic benzene or xylene. Among them, hexane and heptane are included. Is optimal.

  The order of the flows of steps a, b, c and d for producing a polyethylene resin mixture by the multistage continuous polymerization of the present invention can be arbitrarily changed as necessary. The polymerization reaction of the monomer in the step a is performed under temperature control of 70 to 100 ° C, preferably 75 to 95 ° C, more preferably 75 to 85 ° C. When the polymerization temperature exceeds 100 ° C., a part of the polymer is dissolved and a nodule is easily formed, which causes a hindrance to subsequent continuous operation. However, when the polymerization temperature is lower than 70 ° C., the polymerization reaction becomes dull, the catalyst activity is lowered, the efficiency is lowered, and the cost is increased. In this step a, an ethylene homopolymer having an intrinsic viscosity [η1] in the range of 0.1 to 4.0 or an ethylene copolymer having an α-olefin content of 10 wt% or less is preferably produced. Produces an ethylene homopolymer having an intrinsic viscosity in the range of 0.2 to 2.5 or an ethylene copolymer having an α-olefin content of 0.1 to 2.5 wt%. When the α-olefin content exceeds 10 wt%, it is necessary to lower the temperature of the polymerization reaction, the production rate decreases, the fluidity of the resin composition deteriorates, the ESCR and rigidity decrease, The solvent-soluble component of the polymer is increased. If the intrinsic viscosity is less than 0.1, the welding strength at the pinch-off portion of the blow molded product may be insufficient. However, if the intrinsic viscosity exceeds 4.0, the ESCR and rigidity of the resin composition tend to deteriorate again.

  Next, in the step b, the polymerization reaction is performed at a temperature of 60 to 90 ° C, preferably 65 to 85 ° C, more preferably 70 to 80 ° C. When the polymerization temperature exceeds 90 ° C., a part of the polymer is dissolved and a nodule is easily formed, which causes a hindrance to subsequent continuous operation. However, when the temperature is lower than 60 ° C., the polymerization reaction becomes dull, the activity of the catalyst is lowered, the efficiency is reduced, and the cost is increased. In this step b, an ethylene homopolymer having an intrinsic viscosity [η2] in the range of 1.0 to 7.0 or an ethylene copolymer having an α-olefin content of 10 wt% or less is preferably produced. Produces an ethylene homopolymer having an intrinsic viscosity in the range of 1.5 to 5.6 or an ethylene copolymer having an α-olefin content of 0.1 to 1.5 wt%. When the α-olefin content exceeds 10 wt%, it is necessary to lower the temperature of the polymerization reaction, the production rate decreases, the fluidity of the resin composition deteriorates, the ESCR and rigidity decrease, The solvent-soluble component of the polymer is increased. When the intrinsic viscosity is less than 1.0, the impact strength of the resin composition is lowered, and when the intrinsic viscosity exceeds 7.0, the fluidity of the resin composition is deteriorated, and a hollow molded article by blow molding or Fish eyes and gels are likely to occur in a molded product by extrusion molding.

  Further, step c is entered, where the polymerization reaction is carried out at a temperature of 60 to 90 ° C., preferably 65 to 85 ° C., more preferably 70 to 80 ° C. When the polymerization temperature exceeds 90 ° C., a part of the polymer is dissolved and a nodule is easily formed, the subsequent continuous operation is hindered, the production rate is deteriorated, and the control of the intrinsic viscosity becomes difficult. However, when the temperature is less than 60 ° C., the polymerization reaction becomes dull, the activity of the catalyst is remarkably lowered, the efficiency is reduced, and the cost is increased. In this step c, an ethylene homopolymer having an intrinsic viscosity [η3] in the range of 1.0 to 7.0 or an ethylene copolymer having an α-olefin content of 10 wt% or less is preferably produced. An ethylene homopolymer having an intrinsic viscosity in the range of 1.5 to 5.6 or an ethylene copolymer having an α-olefin content of 0.1 to 1.5 wt% is produced. When the content of α-olefin exceeds 10 wt%, it is necessary to lower the temperature of the polymerization reaction, the production rate is lowered, the fluidity of the resin composition is deteriorated, the ESCR and the rigidity are also lowered, and the copolymer The solvent-soluble component increases. When the intrinsic viscosity is less than 1.0, the impact strength of the resin composition is lowered, and when the intrinsic viscosity is more than 7.0, the fluidity of the resin composition is deteriorated, and a hollow molded product or extrusion by blow molding is caused. Fish eyes and gels are likely to be generated in extruded products by molding.

  Finally, step d is entered, where the polymerization reaction is carried out at a temperature of 40 to 70 ° C, preferably 45 to 65 ° C, more preferably 45 to 55 ° C. When the polymerization temperature exceeds 70 ° C., a part of the polymer is dissolved to easily form a nodule, hindering the subsequent continuous operation, the production rate is deteriorated, and the control of the intrinsic viscosity becomes difficult. However, when the temperature is lower than 40 ° C., the polymerization reaction becomes dull, the catalyst activity is remarkably lowered, the efficiency is reduced, and the cost is increased. In this step d, an ethylene homopolymer having an intrinsic viscosity [η4] in the range of 2.0 to 11.5 or an ethylene copolymer having an α-olefin content of 4.5 wt% or less is preferable. Produces an ethylene homopolymer having an intrinsic viscosity in the range of 4.5 to 9.5 or an ethylene copolymer having an α-olefin content of 0.5 wt% or less. When the α-olefin content exceeds 4.5 wt%, it is necessary to lower the temperature of the polymerization reaction, the production rate is lowered, the fluidity of the resin composition is deteriorated, and the ESCR and rigidity are also lowered. When the intrinsic viscosity is less than 2.0, the impact strength of the resin composition is lowered. When the intrinsic viscosity is more than 11.5, the fluidity of the resin composition is deteriorated. Fish eyes and gels are likely to be generated in extruded products by molding.

  The content of the ethylene homopolymer or ethylene copolymer produced by step a, step b and step c is 20 to 50 wt%, preferably 25 to 45 wt%, respectively, based on the total weight of the polymerization composition. And the content of the ethylene homopolymer or ethylene copolymer obtained by step d is 0.5 to 10 wt%, preferably 2.0%, based on the total weight of the polymerization composition. ˜6.0 wt%, and further, (amount of polymerization composition according to step b + amount of polymerization composition according to step c): (amount of polymerization composition according to step a) = 6/7 to 5 / 1, preferably within a range of 1/1 to 3/1. When the amount of the polymerization composition in step a is less than 20 wt%, the fluidity of the resin composition is deteriorated, and the moldability during blow molding or extrusion molding is deteriorated. However, when the amount of the polymerization composition exceeds 50 wt%, the generation of fish eyes and gels increases. Moreover, when the polymerization amount of the process b and / or the process c is less than 20 wt%, the ESCR of the resin composition is lowered, and when it exceeds 50 wt%, the rigidity of the resin composition is deteriorated. In addition, when the amount of the polymerization composition in step d is less than 0.5 wt%, the impact strength of the resin composition is deteriorated, and when it exceeds 10 wt%, the generation of fish eyes and gels increases.

  In this invention, from the limiting range of the intrinsic viscosity in each step, a low molecular weight component is produced in step a, a high molecular weight component is produced in steps b and c, and a special high molecular weight component is produced in step d. It can be seen that the molecular weight of the special high molecular weight composition of d is between the molecular weight of the high molecular weight composition of Steps b and c and the general ultrahigh molecular weight. Step d is to produce a very small amount of special high molecular weight component compared to the amount of low molecular weight and high molecular weight, but as described above, the presence of the special high molecular weight component causes fish eye or gel generation. There is a risk of causing it. However, the present invention has found a method capable of suppressing the generation of such fish eye or gel. Specifically, in the step d, the above problem was solved by using a trace amount of hydrogen gas or a trace amount of alcohol as a molecular weight modifier. When a trace amount of hydrogen is added, the molar ratio of the gas phase composition of hydrogen and ethylene can be adjusted very low. When a small amount of alcohol is added, it is preferable that the concentration of the alcohol in the solvent does not exceed 10 ppm (weight). As the alcohol used in the present invention, ethyl alcohol or isopropyl alcohol is preferably used.

In the production process of the present invention, the order of the steps can be arbitrarily changed without changing the arrangement position of the reactors (1, 2, 3, 4). In other words, it is possible to replace only the steps performed inside the reactor without changing the arrangement of the reactor. The order of the steps is preferably the order of steps a → b → c → d, but steps a → c → b → d, steps b → a → c → d, steps b → c → a → d, steps c → b → a → Any of the order of d may be used. Therefore, the manufacturing process is flexible or adaptable, and adjustment and polymer design can be performed according to the characteristics of a predetermined product and the user's request. In addition, the delay time of the polymerization reaction is prolonged, and the activity of the catalyst is greatly improved, so that the production rate is increased and the cost is reduced. When the ethylene resin composition obtained by the production method of the present invention is used for blow molding or extrusion molding, a high-quality molded product can be produced.
In order to continuously produce the ethylene copolymer which is the resin composition of the present invention, a polymer having a high molecular weight composition is obtained by using α-olefin as a monomer for copolymerization. It is essential to promote the reaction action and capacity and / or to carry out the copolymerization reaction under favorable polymerization conditions. As the catalyst used for this purpose, a solid high activity Ziegler catalyst mainly containing titanium, magnesium and halide components may be used. Examples of the highly active Ziegler catalyst include, for example, Japanese Patent Publication No. 50-32270, Japanese Patent Publication No. 52-13232, Japanese Patent Publication No. 52-36790, Japanese Patent Publication No. 52-36915, Japanese Patent Publication No. 53-6019, Japanese Patent Publication No. 54-25517. JP-B 56-5403, JP-B 62-54326, JP 50-31835, JP 50-95384, JP 53-40696, JP 54-161091, JP No. 54-41985, JP-A-55-729, JP-A-55-149307, JP-A-57-12006, etc., U.S. Pat. No. 4,071,674, Taiwanese Patent No. There is a manufacturing method and it can be used suitably. A solid catalyst containing a metallocene compound and an aluminoxane can also be used. In this case, for example, a catalyst produced by a catalyst production method proposed in JP-A-8-208717, JP-A-10-255194, JP-A-10-296535, or the like can be suitably used.

  Hereinafter, preferred embodiments of the present invention will be described. The following examples are described so that the actual state of the production method of the present invention can be easily understood, and do not limit the present invention. All polymerization reaction operations were carried out under a nitrogen atmosphere unless otherwise specified.

The test or measurement method of the physical property parameters related to the resin composition of the present invention is in accordance with the following essential points.
1) Intrinsic viscosity [η] (dl / g): measured in a naphthalene solution at 135 ° C.
2) Density (g / cm ³ ): Measured based on the method of ASTM D1505.
3) ESCR (hr): Measured based on the method of ASTM D1693.
4) Izod impact strength (kg-cm / cm notch): Measured based on the method of ASTM D256. As a result, the state of no breaking (No breaking) is represented by “NB”.
5) Short-term static hydraulic strength (MPa) of pipe material: Measured based on the measurement method of ASTM D1599.
6) Blow bottle inner wall and appearance: Fisheye with processing temperature of hollow product blow molding machine set to the following setting conditions C1 / C2 / C3 / C4 / AD / D = 180/180/180/180/180/180 ° C. And the state of the gel is judged by visual observation.
7) Extrusion method of polyethylene pipe material:
a. Extruder: Extruder manufactured by Battenfeld, Germany.
b. Screw diameter: 45mm
c. Pipe material diameter and wall thickness: 40 mm diameter x 5.8 mm wall thickness
d. Extruder temperature: 190/195/200/200 ° C
e. Mold temperature: 200/200/200/200/210/210/210/215/215 ° C.

[Example 1]
First, a catalyst produced by the method proposed in Japanese Patent Publication No. 62-54326 was used. As the reactor (1, 2, 3, 4), an autoclave with a stirrer having a capacity of 800 liters purged with nitrogen gas and replaced with ethylene gas was used. Into the first reactor, 245 liters of hexane, 247 mM of triethylaluminum (TEAL) and 6.24 g of the catalyst were introduced in this order, and ethylene, 1-butene and hydrogen gas were continuously introduced while maintaining the polymerization temperature at 80 ° C. Then, the total pressure is maintained at 0.95 Meb (megabar) (surface pressure), and the molar ratio of hydrogen and ethylene gas phase composition is controlled to 1.5 while the polymerization reaction time is set to 4 hours. Then, the polymerization reaction of step a was performed. Next, it transferred to the 2nd reactor and the polymerization reaction of the process b was performed. Here, the molar ratio of the gas phase composition of hydrogen and ethylene becomes 0.31 under the polymerization temperature of 75 ° C., the total pressure of 0.61 Meb (surface pressure), and the polymerization reaction time of 2.5 hours. The polymerization reaction was carried out under such control. Then, it transferred to the 3rd reactor and performed the polymerization reaction of the process c. Here, the molar ratio of the gas phase composition of hydrogen and ethylene becomes 0.06 under a polymerization temperature of 75 ° C., a total pressure of 0.52 Meb (surface pressure), and a polymerization reaction time of 1.5 hours. The polymerization reaction was carried out under such control. Then, after purging ethylene, hydrogen, and 1-butene with nitrogen gas, the temperature was lowered to 55 ° C. and finally transferred to the fourth reactor to carry out the polymerization reaction of step d. Here, in a state where the temperature inside the kettle is maintained at 50 ° C. and the total pressure is 0.2 Meb (surface pressure), ethylene, 1-butene and a small amount of hydrogen as a molecular weight regulator are supplied by liquid phase continuous supply, and the polymerization time After 0.5 hour, the final polymerization reaction was carried out by controlling the molar ratio of the gas phase composition of hydrogen and ethylene to 0.015. By adding a small amount of hydrogen, it was possible to obtain a special high molecular weight composition and to suppress the generation of an ultrahigh molecular weight composition. The molecular weight of the special high molecular weight composition was between the high molecular weight and the ultrahigh molecular weight composition (see Table 1).
After completion of the polymerization reaction, the pressure was released, and after substitution, cooling, and drying, a powdered ethylene copolymer resin composition was obtained. Table 2 shows the results of analyzing and measuring the polymerization activity and molecular weight of the resin composition. Further, the powdered resin composition was blended with a stabilizer, granulated with a two-screw extruder, and this was subjected to a hollow bottle molding process test using a blow molding machine. Thereafter, the molecular weight, density, ESCR, and Izod impact strength of the resin composition were measured, and the occurrence of gel and fish eye was visually inspected and judged. The hollow bottle molded with this resin composition has no fisheye or gel on the inner wall and appearance, and has excellent ESCR, impact strength and rigidity. Therefore, the ethylene resin composition produced in the present invention can be suitably used for molding large containers such as chemical drums having a capacity of 200 liters or more. The results are as shown in Table 2.

[Example 2]
A resin composition of ethylene copolymer was produced in exactly the same procedure as in Example 1, and after granulation, a hollow bottle was formed. The difference from Example 1 is that, as shown in Table 1, the amount of polymerization in each step was simply changed, and in Example 1, 1-butene was introduced as α-olefin in steps a and c. In the example, 1-butene is only introduced into the process d in addition to the process a and the process c.

[Example 3]
A resin composition of ethylene copolymer was produced in exactly the same procedure as in Example 1, and after granulation, a hollow bottle was formed. The difference from Example 1 is that, as shown in Table 1, only the amount of polymerization in each step was changed and 1-butene was introduced into steps b and d.

[Example 4]
In Example 2, while maintaining the polymerization reaction in step d at a polymerization temperature of 50 ° C. and a total pressure of 0.2 Meb (surface pressure), ethylene and a trace amount of 1-butene were supplied in a liquid phase continuous supply system. Furthermore, a trace amount of isopropyl alcohol having a concentration of 8 ppm was added as a molecular weight modifier, and a resin composition having a special high molecular weight composition similar to that of Example 2 was obtained after a polymerization time of 0.5 hours. This special high molecular weight component effectively suppressed the generation of ultra high molecular weight components. Its molecular weight was between high and ultra high molecular weight.
After completion of the polymerization reaction, the pressure was released, and after substitution, cooling, and drying, a powdered ethylene copolymer resin composition was obtained. This resin composition was analyzed and measured for polymerization activity and molecular weight. Further, the powdered resin composition was granulated with a two-screw extruder, and this was subjected to a blow bottle molding process test. Thereafter, the molecular weight, density, ESCR, and Izod impact strength of the resin composition were measured, and the gel generation state was examined. The hollow bottle molded with this resin composition was in a uniform state, and no gel was observed. The results are as shown in Table 2.

[Example 5]
As in Example 1, an autoclave with a stirrer having a capacity of 800 liters purged with nitrogen gas and replaced with ethylene gas was used. In step a, 260 liters of hexane, 262 mM of triethylaluminum (TEAL) and 7.41 g of the catalyst were introduced in this order, and while maintaining the polymerization temperature at 80 ° C., 1-butene was removed and ethylene and hydrogen gas were removed. Continuously introduced, the total pressure is maintained at 0.87 Meb (megabar) (surface pressure), the molar ratio of hydrogen and ethylene gas phase composition is controlled to 3.5, and the polymerization time is 3.7 hours. Then, a polymerization reaction was performed. Next, the polymerization reaction was performed by entering step b. Here, ethylene, 1-butene and hydrogen gas were continuously introduced again, and after a polymerization temperature of 75 ° C., a total pressure of 0.61 Meb (surface pressure) and a polymerization reaction time of 2.2 hours, the gas phase composition of hydrogen and ethylene was obtained. The polymerization reaction was carried out while controlling the molar ratio to be 0.16. Then, it entered into the process c and performed the polymerization reaction. Here, under a polymerization temperature of 75 ° C., a total pressure of 0.52 Meb (surface pressure), and a polymerization reaction time of 1.7 hours, the molar ratio of the gas phase composition of hydrogen and ethylene was controlled to be 0.058. The polymerization reaction was carried out. Then, after purging ethylene, hydrogen, and 1-butene with nitrogen gas, the temperature was lowered to 55 ° C., and finally the polymerization reaction of step d was performed. Here, in a state where the polymerization temperature is maintained at 50 ° C. and the total pressure is 0.2 Meb (surface pressure), ethylene, 1-butene and a trace amount of hydrogen as a molecular weight regulator are supplied by continuous supply, and the polymerization time is 0.4 hours. Then, the final polymerization reaction was performed by controlling the molar ratio of the gas phase composition of hydrogen and ethylene to be 0.044 (see Table 1).
After completion of the polymerization reaction, the pressure was released, and after substitution, cooling, and drying, a powdered ethylene copolymer resin composition was obtained. Table 2 shows the results of analyzing and measuring the polymerization activity and molecular weight of the resin composition. Further, the powdered resin composition was blended with a stabilizer, granulated with a two-screw extruder, and this was subjected to a hollow bottle molding process test using a blow molding machine. Thereafter, the molecular weight, density, ESCR, and Izod impact strength of the resin composition were measured, and the occurrence of gel and fish eye was visually inspected and judged. The hollow bottle molded with this resin composition did not show fish eyes or gel on the inner wall and appearance, and also had excellent ESCR and impact strength (Izod impact strength 35).
In order to confirm the possibility of applying to a polyethylene pipe material, a polyethylene pipe having a diameter of 63 mm and a wall thickness of 5.8 mm was manufactured by extrusion molding, and a burst test was performed by a hydraulic test. As a result, it has been found that the pipe exhibits unique fish-like ductile fracture characteristics and has excellent short-term static hydraulic strength. The results are as shown in Table 2.

[Example 6]
The polymerization reaction was carried out under the same method and conditions as in Example 5. However, 1-hexene was used instead of 1-butene. Tables 1 and 2 show the physical properties of the resin composition and the molded product thus obtained. Clearly very high ESCR and short-term static hydraulic strength were obtained.

[Comparative Example 1]
In Example 1, the two-stage polymerization reaction of only step a and step b was performed. In step a, the polymerization temperature is maintained at 80 ° C., and in step b, the polymerization temperature is maintained at 75 ° C., and the molar ratio of the gas phase composition of hydrogen and ethylene and butene and ethylene in step b is obtained as a high molecular weight composition. So that the molecular weight and density of the resin composition of the final product were approximately the same as those of the resin composition obtained in Example 1 (see Table 3). As shown in Table 4, the ESRC and impact strength of the resin composition thus obtained are clearly very low as compared with the results of Examples 1 to 3. Moreover, there are also a few gels and the polymerization activity is also low compared with Examples 1-3.

[Comparative Example 2]
In Example 1, the three-stage polymerization reaction of only step a, step b, and step d was performed. In step d, an ultrahigh molecular weight component was produced instead of the special high molecular weight component. Specifically, in Comparative Example 2, an autoclave with a stirrer having a capacity of 800 liters purged with nitrogen gas and replaced with ethylene gas was used as a reactor used in each step. In the reactor of step a, 245 liters of hexane, 247 mM of triethylaluminum (TEAL), and 6.24 g of the catalyst obtained by the above-described method were sequentially introduced, and while maintaining the polymerization temperature at 80 ° C., ethylene, 1-butene and Polymerization of step a by continuously introducing hydrogen gas, maintaining the total pressure at 0.85 Meb (megabar) (surface pressure), and controlling the molar ratio of the gas phase composition of hydrogen and ethylene to 1.48 The reaction was carried out for 3 hours. Next, the raw material was transferred to the reactor of step b to conduct a polymerization reaction. Here, under a polymerization temperature of 75 ° C., a total pressure of 0.4 Meb (surface pressure) and a polymerization time of 2.5 hours, the molar ratio of the gas phase composition of hydrogen and ethylene was controlled to be 0.16. A polymerization reaction was performed. Subsequently, after purging ethylene, hydrogen, and 1-butene with nitrogen gas, the temperature was lowered to 55 ° C., and finally the polymerization reaction of step d was performed. Here, in a state where the polymerization temperature is maintained at 50 ° C. and the total pressure is 0.2 Meb (surface pressure), ethylene and hydrogen are supplied, and after a polymerization time of 0.5 hours, the molar ratio of the gas phase composition of hydrogen and ethylene Was controlled to be 0.005 to carry out the final polymerization reaction (see Table 3).
After completion of the polymerization reaction, the pressure was released, and after substitution, cooling, and drying, a powdered ethylene copolymer resin composition was obtained. This resin composition was analyzed and measured for polymerization activity and molecular weight. Further, the powdered resin composition was granulated with a two-screw extruder, and this was subjected to a blow bottle molding process test. Thereafter, the molecular weight, density, ESCR, and Izod impact strength of the resin composition were measured, and the occurrence state of gel and fish eye was examined. The hollow bottle molded with this resin composition is not in a uniform state, a large number of small gels are generated on the inner and outer walls, and its ESCR is very low compared to Examples 1-3 (see Table 4). .

[Comparative Example 3]
The polymerization reaction was performed in exactly the same manner and under the same conditions as in Example 1, but no hydrogen as a molecular weight modifier was added in Step d (see Table 3). The hollow bottle molded with the resin composition thus obtained was non-uniform and a large number of small gels were generated. Table 4 shows the results.

[Comparative Example 4]
In Example 5, the two-stage polymerization reaction of only the process a and the process b was performed. In step a, the polymerization temperature is maintained at 80 ° C. and the polymerization time is 3 hours, in step b, the polymerization temperature is maintained at 75 ° C. and the polymerization time is 2 hours. Was controlled so that a high molecular weight composition was obtained, so that the molecular weight and density of the resin composition of the final product were almost similar to those of the resin composition obtained in Example 5 (see Table 3). The resin composition thus obtained was granulated, and a polyethylene pipe having a diameter of 63 mm and a wall thickness of 5.8 mm was produced with an extrusion molding machine, and a burst test was performed by a hydraulic test. As a result, it can be seen that the pipe exhibits the characteristics of non-fish-like ductile fracture and the short-term static hydraulic strength is considerably inferior to that of Example 5. The results are as shown in Table 4.

It is a flowchart of the continuous manufacturing method of the polyethylene of this invention.

Explanation of symbols

1, 2, 3, 4 Reactor 10 Ethylene 20 α-Olefin 30 Solvent 40 Solid catalyst 50 Organoaluminum compound 60 Polyethylene resin

Claims (4)

In the method of continuously producing polyethylene by introducing the monomer as a raw material into four reactors arranged in series and performing a multistage polymerization reaction and mixing, at least one reactor contains a raw material monomer in addition to the raw material monomer. A mixture of at least (a) a solid catalyst containing components of titanium, magnesium and halide, and a solid catalyst containing a metallocene compound and an aluminoxane, and (b) an organoaluminum compound, A multistage continuous polymerization reaction and mixing are performed by the reactor and another reactor into which the same raw material monomer is introduced in series, and the ultimate viscosity [η] (dl / g) of the final resin mixture is 1.1 to 8.0 range, in a way that density producing polyethylene in the range of 0.935~0.965g / cm ³ , The four respectively reactor carried out polymerization step a, b, c, control conditions of the d is,
Step a: producing an ethylene polymer having an intrinsic viscosity [η1] (dl / g) in the range of 0.1 to 4.0 at a temperature of 70 to 100 ° C .;
Step b: producing an ethylene polymer having an intrinsic viscosity [η2] (dl / g) in the range of 1.0 to 7.0 at a temperature of 60 to 90 ° C.,
Step c: producing an ethylene polymer having an intrinsic viscosity [η3] (dl / g) in the range of 1.0 to 7.0 at a temperature of 60 to 90 ° C .;
Step d: producing an ethylene polymer having an intrinsic viscosity [η4] (dl / g) in the range of 2.0 to 11.5 at a temperature of 40 to 70 ° C .;
(1) The content of the ethylene polymer produced by the steps a, b and c occupies 20 to 50 wt% with respect to the total weight of the polymerization composition,
(2) The content of the ethylene polymer produced by step d accounts for 0.5 to 10 wt% with respect to the total weight of the polymerization composition;
(3) (Amount of polymer composition according to step b + Amount of polymer composition according to step c): (Amount of polymer composition according to step a) = adjusted to be in the range of 6/7 to 5/1, And,
(4) A method for continuously producing polyethylene, wherein hydrogen or alcohols are used as molecular weight regulators in step d.   The process a, the process b, the process c, and the process d can perform the polymerization reaction by arbitrarily changing the arrangement order of the processes without changing the arrangement of the reactors under the control conditions. A method for continuously producing polyethylene as described in 1. above.   The method for continuously producing polyethylene according to claim 1 or 2, wherein the ethylene polymer is an ethylene homopolymer or an ethylene copolymer.   The method for continuously producing polyethylene according to claim 3, wherein the ethylene copolymer is an ethylene copolymer having an α-olefin content of 10 wt% or less.

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