JPH0348214B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a propylene polymer having good moldability. More specifically, it maintains the excellent rigidity, impact resistance, transparency, heat resistance, etc. inherent to crystalline propylene polymers, while producing good molded products in blow molding, extrusion molding, vacuum/pressure molding, etc. The present invention also relates to a method for producing a propylene polymer that eliminates the problem of fish eye formation. Due to its favorable properties, polypropylene is used in a wide range of applications such as detergent containers, blow molded products, extrusion molded products such as films and sheets, and vacuum and pressure molded products such as food containers and trays. In order to increase productivity and efficiency, polypropylene with even higher speed moldability is desired. Normally, when blow molding or extrusion molding is carried out at high speeds, the surface of the molded product becomes noticeably rough, making it impossible to obtain a molded product with good surface properties. The occurrence of rough skin can be avoided by lowering the average molecular weight of polypropylene or increasing the molding temperature, but on the other hand, due to the lower melt viscosity, parisons sag due to their own weight in blow molding, and in vacuum/pressure molding. Unfavorable effects such as sagging of the molten sheet due to its own weight appear. Skin roughness during high-speed molding is controlled by the melt viscosity in the high shear rate range, while sagging of the parison or sheet due to its own weight is controlled by the melt viscosity in the low shear rate range. resolved,
In addition, in order to prevent parisons and sheets from sagging due to their own weight, it is necessary to lower the melt viscosity in the high shear rate region and increase the melt viscosity in the low shear rate region without changing the average molecular weight. The purpose is to make the viscous behavior more pronounced. Various methods have been proposed in the past for the purpose of improving the moldability of propylene polymers. For example, JP-A-54-38389 and JP-A-54-144448 propose a multi-stage polymerization method in which the content of high molecular weight propylene polymer is 0.05 to 15% by weight or 5 to 30% by weight. However, according to studies by the present inventors, this method improves the molding processability to some extent, but it is not sufficient, and even if an attempt is made to improve it sufficiently, the molded product will often suffer from fish eyes. If frequent occurrence of fish eyes is prevented, the improvement in moldability is insufficient. Further, JP-A-54-74844 proposes a composition in which the content of a high molecular weight propylene polymer is 60 to 95% by weight. However, according to studies conducted by the present inventors, although this method can prevent the occurrence of fish eyes, it has not been sufficient to improve moldability. The inventors of the present invention have conducted intensive studies with the aim of producing a propylene polymer with improved moldability and the problem of fish eye generation, and as a result, by adopting certain specific polymerization conditions, The inventors have discovered that the above objects can be achieved while maintaining the excellent steel properties, impact resistance, transparency, heat resistance, etc. inherent to crystalline propylene polymers, and have thus arrived at the present invention. The gist of the present invention is to produce propylene homopolymer or propylene-α-olefin copolymer by polymerizing propylene or propylene and α-olefin using a catalyst system mainly consisting of a titanium-containing solid catalyst component and an organoaluminum compound. 40% by weight of a propylene homopolymer or a propylene-α-olefin copolymer having an intrinsic viscosity [η] (measured at 135°C in tetralin) of 0.6 to 2.5 dl/g. 54% by weight or less, and the intrinsic viscosity [η] is 2.5 to 10 dl/g.
and a step of producing a propylene homopolymer or a propylene-α-olefin copolymer in which [η] is at least twice that of the former, from 46% to less than 60% by weight, and the total weight is The present invention relates to a method for producing a propylene homopolymer or a propylene-α-olefin copolymer, characterized in that the intrinsic viscosity [η] of the polymer is 2 to 4 dl/g. Further, to explain the present invention in detail, the catalyst system used in the present invention includes a titanium-containing solid catalyst component and an organoaluminum compound. The titanium-containing solid catalyst component is a known carrier-supported catalyst component obtained by contacting a solid magnesium compound, titanium tetrahalide, and an electron-donating compound, titanium trichloride, or a known catalyst containing titanium trichloride as a main component. Selected from ingredients. Further, a highly active catalyst system in which 1 kg or more of polymer can be obtained per 1 g of catalyst is particularly preferred since the step of removing the Ti component can be omitted. The organoaluminum compound of the cocatalyst has the general formula AlRnX _3-o (wherein R has 1 to 20 carbon atoms)
represents a hydrocarbon group, X represents a halogen,
n represents a number of 3≧n>1.5).
If the titanium-containing solid catalyst component is a carrier-supported catalyst component containing a solid magnesium compound,
It is preferable to use AlR ₃ or a mixture of AlR ₃ and AlR ₂
Preference is given to using _AlR2X . The ratio of each catalyst component used is usually 1:1 to 1:1 molar ratio of Ti:AlRnX _3-o in the titanium-containing solid catalyst component.
100, preferably from the range of 1:2 to 40. Furthermore, in the method of the present invention, a known electron-donating compound may be used as a third component in addition to the catalyst and cocatalyst components described above. When using a third component, the titanium-containing solid catalyst component is usually
The molar ratio of Ti:third component is selected from the range of 1:0.01 to 10, preferably 1:0.05 to 2. In the method of the present invention, the polymerization is carried out in two stages in the method for producing a propylene polymer or a copolymer of propylene and α-olefin using the catalyst system described above. Either the step of obtaining a polymer with a high molecular weight or the step of obtaining a high molecular weight polymer may be performed first. The polymerization method may be carried out batchwise or continuously using two or more reaction vessels. The polymerization may be carried out in an inert hydrocarbon diluent such as propane, butane, hexane, hebutane or in liquefied propylene, or by so-called gas phase polymerization. Polymerization temperature is usually 40-100℃, preferably 50-80℃
selected from the range. α copolymerized with propylene
-Olefins include ethylene, butene-1, hexene-1, 4-methylpentene-1, octene-1
Selected from etc. Hydrogen, dialkylzinc, etc. are used to adjust the molecular weight, and hydrogen is preferred. To explain the step of obtaining a low molecular weight polymer, the intrinsic viscosity [η], which represents the size of the molecular weight, is
The polymerization temperature and the amount of hydrogen as a molecular weight regulator are selected so that the amount is 0.6 to 2.5 dl/g, preferably 0.7 to 2.0 dl/g. Usually, the hydrogen concentration in the gas phase (the ratio of hydrogen to propylene or the sum of propylene and α-olefin) is 1 to 50 mol%. This low molecular weight polymer can be a propylene homopolymer,
Random copolymerization of propylene and α-olefin may also be used. In this case, the content of α-olefin in the copolymer is 10% by weight or less. The stereoregularity (hereinafter sometimes abbreviated) of the polymer is 80% or more, preferably 90% or more. Intrinsic viscosity [η] (dl/g) (hereinafter sometimes abbreviated as [η])
are determined in tetralin solution at 135 DEG C. and stereoregularity (%) is the amount remaining after extraction with boiling n-heptane for 6 hours in a modified Soxhlet extractor. Further, the polymerization time is selected so that the amount of the low molecular weight polymer is more than 40% by weight and less than 54% by weight of the total amount of polymer produced. Next, to explain the step of obtaining a high molecular weight polymer, the polymerization temperature and the amount of hydrogen as a molecular weight regulator are adjusted so that the intrinsic viscosity [η] is 2.5 to 10 dl/g, preferably 3 to 8 dl/g. Choose. Usually, the hydrogen concentration in the gas phase is 0.01 to 1 mol%.
If [η] is less than 2.5 dl/g, the effect of improving non-Newtonian viscosity behavior will be small, which is not preferable. Also, [η]
If it exceeds 10 dl/g, the molded product obtained from the final polymer will suffer from fish eyes, which is undesirable. This high molecular weight polymer may of course be a propylene homopolymer, but when emphasis is placed on physical properties such as impact resistance of the molded article, it is more preferable to use a random copolymer of propylene and α-olefin. In this case, the content of α-olefin in the copolymer is 10
% by weight or less. The stereoregularity of the polymer is 80%
or more, preferably 90% or more. In addition, the amount of high molecular weight polymer should be 46% by weight or more of the total amount of polymer produced60
The polymerization time is selected so that the polymerization time is less than % by weight. If the amount of the high molecular weight polymer is less than 30% by weight, especially less than 10% by weight, the non-Newtonian viscosity behavior will not be sufficiently improved, and therefore the effect of improving moldability will be small and satisfactory results will not be obtained. In cases where a significant improvement in non-Newtonian viscous behavior was observed, the appearance of fish eyes was observed in the molded products. Also, 60% by weight
If the amount exceeds 80% by weight, the effect of improving moldability will not be sufficient and satisfactory results will not be obtained. The ratio of [η] of the high molecular weight polymer to [η] of the low molecular weight polymer is 2 or more, particularly preferably 2.5 or more, but if this ratio is less than 1.5, particularly 1.2 or less, the effect of improving non-Newtonian viscosity behavior will not be sufficient. Therefore, the effect of improving moldability is not sufficient. The intrinsic viscosity [η] of all produced polymers is 2 to 4 dl/g
shall be. Note that a small amount of a third component having a different molecular weight may be mixed in by polymerization as long as it does not impair the purpose of the present invention. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, in the examples, evaluation methods for various physical properties of the polymer are as follows. Outflow ratio: Melt/as per ASTM D1238-70
at 230°C using a flow index measuring device.
Throughput at shear stress 5 × 10 ⁵ dynes/cm ² and 5 × 10 ⁴
The ratio of throughput in dynes/cm ² was determined. The larger the flow rate ratio, the more pronounced the non-Newtonian viscosity behavior, that is, the higher the viscosity in the low shear rate region and the lower the viscosity in the high shear rate region, which is a desirable property. Melt drooping property; using a screw type extruder, the outer diameter
By measuring the change in the falling speed of parisons extruded at 230°C from a circular die of 12.0 mm and inner diameter of 10.0 mm, the parisons were ranked as follows.

[Table] Rough skin, flaky skin; Rough skin (so-called shark skin) and flaky skin on the surface of a parison extruded at 210°C from a circular die with an outer diameter of 11.0 mm and an inner diameter of 10.0 mm using a screw extruder.
The eyes were observed and ranked as follows.

[Table] First yield point strength: Determined in accordance with ASTM D638-72 by a tensile test of a dumbbell piece punched from a press sheet. Unless otherwise specified, values are measured at 20°C. Izot impact strength: Measured in accordance with ASTM D256 using a notched strip cut out from a press sheet. Tensile impact strength: Measured on dumbbell pieces punched out from press sheets in accordance with ASTM D-1822. These are all measured values at 20°C. Note that the ratio of the first-stage and second-stage polymers was calculated from the catalyst (Ti) content in the first-stage and all produced polymers determined by fluorescent X-ray method. Further, the second stage [η] was calculated according to a conventional method from the first stage [η], [η] of the total polymer, and the polymerization ratio of the first stage and the second stage. The ethylene content in the polymer was determined by a conventional method using infrared absorption spectroscopy. Catalyst production example 1 (A) Production of solid titanium trichloride catalyst component 5.0% n-hexane and 3.0% titanium tetrachloride were placed in a container 10 autoclave which was sufficiently purged with nitrogen.
2.7 moles of di-n-octyl ether were added. While stirring and maintaining the temperature at 25°C, a solution of 1.0 mol of diethylaluminum monochloride dissolved in 0.5 mol of n-hexane was gradually added dropwise, resulting in a homogeneous solution of titanium trichloride in n-hexane with a greenish black color. Obtained. Then, when the homogeneous solution of titanium trichloride was heated to 95°C, a purple precipitate of titanium trichloride was observed to form during the temperature rise. After stirring at 95° C. for 2 hours, the precipitate was separated and washed repeatedly with n-hexane to obtain a finely granular purple solid titanium trichloride catalyst component. Elemental analysis of this material revealed that it had a composition of the formula TiCl ₃ .(AlCl ₃ ) _0.003 .[(n-C ₈ H ₁₇ ) ₂ O] _0.11 . (B) Pretreatment with propylene Charge 12.5 liters of n-hexane into an autoclave with a capacity of 20, which has been fully purged with nitrogen, and heat it with stirring.
1.6 mol of n-propyl aluminum monochloride and the solid titanium trichloride catalyst component obtained in (A) above were charged so that the amount of TiCl ₃ was 250 g.
Then, the internal temperature was adjusted to 30°C, and blowing of propylene gas was started while stirring, and the blowing of propylene gas was continued at the same temperature until the polymerized propylene amounted to 1250 g. The solid is then separated and n
- Washing with hexane was repeated to obtain a polypropylene-containing titanium trichloride catalyst component. Example 1 Liquefied propylene in an autoclave with a capacity of 5 g
3.3, hydrogen, 3.0 mmole of di-n-propylaluminum monochloride and 0.04 m of phenyl acetate
I prepared a mole. After raising the temperature to 65℃, catalyst production example 1
The amount of TiCl ₃ in the titanium trichloride catalyst component obtained in (B) is
Subsequently, a small amount of ethylene was charged so that the total amount was 55 mg, and the first stage polymerization was started. During polymerization, the hydrogen concentration in the gas phase (ratio of hydrogen to propylene) is
The ethylene concentration in the gas phase (ratio of ethylene to propylene) was kept at 0.8 mole%. After 3.0 hours, the liquefied propylene phase in the autoclave was purged to complete the first stage polymerization. 1
Catalyst (Ti) content of polymer in stage, [η]
After sampling a small amount of polymer to measure the following, liquefied propylene 2.2 and hydrogen were immediately charged, the autoclave was adjusted to 70°C, and the second stage polymerization was started. During the polymerization, the hydrogen concentration in the gas phase was kept at 16.7 mole%. After 2.0 hours, the liquefied propylene phase in the autoclave was purged to complete the second stage polymerization, yielding 951 g of total polymer powder, and proceeding to the next step without removing the catalyst Ti component. That is, in the thus obtained polymer powder,
0.1% BHT (2,6-di-t-butyl-p-cresol), 0.1% Irganox 1010 (Geigy Stabilizer, Trademark), 0.2% dilaurylthiodipropionate, 0.2% calcium stearate.
After pelletizing using a single screw extruder with an inner diameter of 40 mm, various physical properties were measured. The results are shown in Table 1, and the outflow ratio was large, so non-Newtonian viscosity behavior was significant. In addition, the dissolution and sagging properties of the parison were good, and evaluations of rough skin and burning eyes were also good. Furthermore, it had high Izot impact strength and tensile impact strength, and had an excellent balance between steel properties and impact resistance. Comparative Examples 1-2 In Example 1, only the first stage polymerization was performed. However, the hydrogen concentration, ethylene concentration, polymerization temperature, and polymerization time in the gas phase were changed as shown in Table 1. The results are shown in Table 1. In Comparative Example 1, the overall intrinsic viscosity [η] was made almost the same as in Example 1, but the sagging of the parison was somewhat large, so the melt sagging property was not fully satisfactory, and even higher speed extrusion was required. This caused rough skin on the outer surface of the parison. In Comparative Example 2, [η] was lowered, and although the skin roughness was good, the melting and drooping properties of the parison were further deteriorated.

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Table: Examples 2-7 Example 1 was repeated. However, the hydrogen concentration, ethylene concentration, polymerization temperature, and polymerization time in the gas phase were changed as shown in Table 2. The results are shown in Table 2, and the outflow ratio was improved in all Examples, especially Examples 2 to 5 and 7.
This is remarkable. Roughness on the outer surface of the parison, melt sagging properties, and even burning eyes were good. In terms of impact resistance, the Izot impact strength and tensile impact strength were high, and the balance with steel properties was also excellent. Comparative Examples 3-10 Example 1 was repeated. However, the hydrogen concentration, ethylene concentration, polymerization temperature, and polymerization time in the gas phase were changed as shown in Table 3. The results are shown in Table 3. In Comparative Example 3, the [η] of the high molecular weight polymer was increased, and the flow rate ratio was large and the melt drooping property was good. However, due to the extremely poor dispersion of the high molecular weight polymer, fish eyes frequently occurred, and roughness on the outer surface of the parison was also extremely poor. Furthermore, impact resistance is also poor. In Comparative Examples 4 and 5, the proportion of the high molecular weight polymer was increased, but the parison was not sufficiently rough in terms of rough skin and melt sagging properties. In Comparative Examples 6 to 8 and 10, on the other hand, the proportion of high molecular weight polymer was reduced. In Comparative Example 6, the effect of improving the flow rate ratio was small, and the melt drooping property was not sufficient. On the other hand, in Comparative Examples 7 and 8, especially Comparative Example 8, the outflow ratio was greatly improved. Although an improvement effect is observed in terms of rough skin and melt sagging properties, a large number of fissure eyes are observed on the surface of the parison, which is undesirable as it significantly impairs the commercial value. In addition, the impact resistance is low and not sufficient. Comparative Example 10 shows some improvement in rough skin, melt drooping properties, and hard eyes, but the improvement effect is insufficient compared to the examples. Comparative Example 9 is a case where the ratio of [η] between the high molecular weight polymer and the low molecular weight polymer is made small, but the outflow ratio is small and the parison sag is somewhat large, so the melt sagging property is not sufficient. .

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Claims (1)

[Claims] 1. Propylene homopolymer or propylene-α by polymerizing propylene or propylene and α-olefin using a catalyst system mainly consisting of a titanium-containing solid catalyst component and an organoaluminum compound.
- A method for producing an olefin copolymer,
The step of producing a propylene homopolymer or propylene-α-olefin copolymer having an intrinsic viscosity [η] of more than 40% by weight and less than 54% by weight, and having an intrinsic viscosity [η] of 0.6 to 2.5 dl/g. ] is 2.5~10dl/
g and the step of producing 46% or more and less than 60% by weight of a propylene homopolymer or propylene-α-olefin copolymer in which [η] is at least twice that of the former, and the total A method for producing a propylene homopolymer or a propylene-α-olefin copolymer, characterized in that the intrinsic viscosity [η] of the polymer is 2 to 4 dl/g.