JPH0315645B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an ultra-high molecular weight polyethylene resin with improved moldability. More specifically, polypropylene or polybutene-1 is polymerized in two or more stages in the presence of a Ziegler type catalyst.
The present invention relates to a method for producing an ultra-high molecular weight polyethylene resin containing the following components. Ultra-high molecular weight polyethylene has a molecular weight of 1 million to 7 million, so it has excellent properties such as wear resistance, impact resistance, self-lubricating properties, and solvent resistance, and is attracting attention as a special high-performance resin. However, as mentioned above, since its molecular weight is too large, it cannot be molded using normal methods, and a special molding process is required, resulting in high prices for molded products and a limited scope of use. Conventionally, the molding processability of ultra-high molecular weight polyethylene has been improved mainly through its molding process.
Publication No. 2) is a typical example. On the other hand, methods for improving the moldability itself include adding lubricating oil, wax, etc. to ultra-high molecular weight polyethylene (Japanese Patent Publication No. 41-217863), and mixing acrylic polymer, polypropylene, etc. Publication No. 24649, Polish Patent No.
No. 86534) is proposed. However, if polypropylene is simply added to ultra-high molecular weight polyethylene in powder form or in an extruder and kneaded, the two will not be dispersed uniformly and a composition with no elongation will be obtained. The impact resistance at low temperatures, which is one of the typical physical properties of steel, also deteriorates significantly. The present inventors used a so-called Ziegler type catalyst to polymerize polypropylene or polybutene-1 with good melt fluidity in the first step, and then polymerized ultra-high molecular weight polyethylene in the second step on the same catalyst. Although polymers have excellent physical properties such as wear resistance, impact resistance, and low coefficient of friction,
Surprisingly, it was found that it had sufficient melt fluidity to be molded using a normal molding machine.Based on this, further intensive studies were conducted, and as a result, the present invention as described below was arrived at. That is, the present invention uses a Ziegler type catalyst consisting of a solid catalyst component containing a transition metal component and an organometallic component, and polymerizes monomers in two or more stages with different monomer compositions and hydrogen concentrations to produce an ultra-high molecular weight polyethylene resin. During production, propylene or a monomer mainly composed of propylene or a monomer mainly composed of butene-1 or butene-1 is polymerized in the presence of hydrogen at any stage of the production to produce 2 to 60% by weight of the total polymer. of polypropylene or polybutene-1, and in one or more remaining steps, ethylene or ethylene-based monomers are polymerized in the substantial absence of hydrogen to produce more than 98 to 40% by weight of the total polymer. The present invention relates to a method for producing an ultra-high molecular weight polyethylene resin with improved moldability, characterized by producing a high molecular weight polyethylene component. The so-called Ziegler type catalyst, which is composed of a solid catalyst component containing a transition metal component and an organometallic component, used in the present invention is a known catalyst system that gives isotactic polypropylene or polybutene-1, and the solid catalyst component is a halogen. atoms and Ti, V,
A compound containing at least one atom of Zr or Cr, and preferable examples include a titanium compound whose main component is a trivalent and/or tetravalent titanium compound, a titanium compound composite modified with an organic compound and/or an inorganic compound, etc. TiC
₄ and those treated with organic aluminum components ~
Examples include those prepolymerized with ethylene or propylene. Examples of organometallic components include trialkylaluminum such as triethylaluminum and triisobutylaluminum, alkylaluminum halides such as diethylaluminum chloride, diisobutyl monobromide, and ethylaluminum dichloride, but if necessary, an electron-donating compound may also be used at the same time. use Particularly suitable is a catalyst system in which a solid catalyst containing Mg, Ti, a halogen atom, and an electron-donating compound is combined with an organoaluminum compound whose main component is trialkylaluminum or the like. Polypropylene polymerized at any stage is a propylene homopolymer or propylene and α
- Refers to a copolymer with olefin. Examples of α-olefin include ethylene, butene-1, hexene-1,4-methylpentene-1, octene-1,
1, decene-1, etc., and one or more of these are copolymerized. The propylene content in the copolymer is 80% by weight or more, preferably 90% by weight or more. The MFI (230°C, 2.16Kg load) of this polymer is preferably 0.1 to 3000g/10 minutes, more preferably 2 to 3000g/10 minutes.
2000g/10 minutes. The monomer composition and hydrogen concentration at this time vary depending on the catalyst system used, the comonomer to be copolymerized, the intended MFI, the polymerization temperature, etc., and are determined in advance by conducting the polymerization only at this stage. Polybutene-1 which is also polymerized at any stage
refers to a butene-1 homopolymer or a copolymer of butene-1 and α-olefin. Examples of α-olefin include ethylene, propylene, hexene-1,4-methylpentene-1, octene-1,
1, decene-1, etc., and one or more of these are copolymerized. Butene in copolymer
1 content is 80% by weight or more, preferably 90% by weight or more. The MI of this polymer (190℃, 2.16Kg load) is preferably 0.1 to 3000g/10 minutes, and more preferably 2 to 3000g/10 minutes.
2000g/10 minutes. The monomer composition and hydrogen concentration at this time vary depending on the catalyst system used, the comonomer to be copolymerized, the intended MFI, the polymerization temperature, etc., and are determined in advance by conducting the polymerization only at this stage. The remaining ultra-high molecular weight polyethylene that is polymerized in at least one step is one that is polymerized substantially in the absence of hydrogen and is an ethylene homopolymer or a copolymer of ethylene and α-olefin. α−
Examples of olefins include propylene, butene-
Copolymerizing one or more of 1,hexene-1,4-methylpentene-1, octene-1, decene-1, etc. The ethylene content in the copolymer is at least 60% by weight, preferably at least 80% by weight. At this time, 3% or less of a diene compound may be copolymerized. The molecular weight of ultra-high molecular weight polyethylene is 500,000 or more, preferably 1,000,000 or more, but this will vary depending on the polymerization temperature, comonomer content, and trace amount of hydrogen at this stage, so polymerization at this stage must be carried out separately in advance to achieve the desired molecular weight. Set conditions so that The content of the ultra-high molecular weight polyethylene part in the total polymer consisting of the polypropylene or polybutene-1 part and the ultra-high molecular weight polyethylene part is 40 to 98% by weight, preferably 50 to 97% by weight, more preferably 60 to 95% by weight.
Weight%. When the content of the ultra-high molecular weight polyethylene portion is small, moldability improves, but abrasion resistance and impact resistance decrease. If this content is too large, the above physical properties will be excellent, but the effect of improving moldability will be poor. On the other hand, the content of the polypropylene or polybutene-1 portion is 2 to 60% by weight, preferably 3 to 50% by weight, and more preferably 5 to 40% by weight. Polymerization is carried out in two or more stages; one of the stages produces polypropylene or polybutene-1, and the remaining at least one stage produces ultra-high molecular weight polyethylene. At each stage, polymerization may be carried out in two or more tanks as long as the composition and molecular weight are within the above-mentioned ranges. In addition to these steps, a polymer having an intermediate molecular weight or an intermediate composition in the two steps described above may be polymerized in an amount of 30% by weight or less. The step of producing polypropylene or polybutene-1, which is an essential component, and the step of producing ultra-high molecular weight polyethylene can be carried out in any order, but from the viewpoint of homogeneity of dispersion of the final polymer, it is preferable to polymerize the polypropylene or polybutene-1 component. It is preferred that the ultra-high molecular weight polyethylene component is subsequently polymerized. Melt flow index of final polymer (190
℃, 2.16 kg load) is 0.2 g/10 minutes or less, preferably 0.1 g/10 minutes, more preferably 0.05 g/10 minutes or less. As the melt flow index increases, the moldability is further improved, but the abrasion resistance and cold impact resistance, which are characteristics of ultra-high molecular weight polyethylene, decrease. One of the features of the present invention is that the load dependence and shear rate dependence of the fluidity during melting of the polymer are improved by more than 10 times. ) and the value (MI) at a load of 2.16 kg (HLMI/MI) is 300 or more, usually 600 or more.
For ordinary polyethylene, it is 30 to 100. 2.16Kg
If the melt index (MI) of the load is too small to be measured, the value at 10 kg load (MLMI)
It can be evaluated by the ratio HLMI/MLMI, but this value is
It is 10 or more, and it is 3 to 6 for ordinary polyethylene, and a large improvement in load dependence (that is, shear rate dependence) is recognized. Therefore, in ordinary molding machines such as injection molding, blow molding, and sheet molding, which require higher shear rates, this surprisingly large shear rate dependence is even more advantageous. For example, the melt viscosity at 1×10 ³ sec ^-1, which is a typical shear rate for actual molding, is that of the polymer of the present invention with an MI of 0.002 g/10 min.
General-purpose polyethylene with an MI of 0.6g/10 minutes shows almost the same value. The effect of the present invention is that even if the practical molding processability is greatly improved as described above, the characteristic physical properties of ultra-high molecular weight polyethylene, such as abrasion resistance and cold impact resistance, are hardly deteriorated. Regarding the amount of wear under the same conditions, the amount of wear for the above-mentioned polymer of the present invention at MI of 0.002g/10 minutes is approximately 0.6%.
In contrast, it is about 3.5% for commercially available polyethylene with an MI of 0.6 g/10 min, which exhibits the same melt viscosity at a shear rate of 1×10 ³ sec ⁻¹ . Under the same conditions, ordinary ultra-high molecular weight polyethylene had a content of about 0.5%. The IZod impact strength (notched) value of the above three polymers at an extremely low temperature of -40°C is 3 kg-cm/cm for commercially available polyethylene, whereas the ultra-high molecular weight polyethylene and the polymer of the present invention do not crack. Yes, there is no practical difference between the first two. Polymerization may be carried out either continuously or batchwise, and there are no particular limitations on the form of the polymerization reactor. There is no particular restriction on the polymerization temperature, as long as it is a temperature at which propylene or butene-1 and ethylene can be polymerized, but since the molecular weight of the ultra-high molecular weight polyethylene portion decreases as the polymerization temperature increases and wear resistance deteriorates, it should be 30 to 120. °C is preferred. More specifically, the production of the polypropylene component is carried out at 40 to 90 °C in a hydrocarbon solvent or in a monomer solvent, and the production of the ultra-high molecular weight polyethylene component is carried out at 30 to 100 °C in a hydrocarbon solvent.
Particular preference is given to carrying out at .degree. Known antioxidants, ultraviolet absorbers, lubricants, antistatic agents, pigments, etc. can be optionally added to the polymer of the present invention. As mentioned above, the polymer of the present invention has excellent physical properties such as wear resistance, cold resistance, self-lubrication, solvent resistance, and chemical resistance, so it can be used for injection molded products such as automobile parts and home appliance parts. It can be used in a wide range of applications, including blow molded products and extrusion molded products such as pipes and sheets. The present invention will be explained below with reference to Examples and Comparative Examples, and the methods for measuring various physical properties in the Examples are as follows. Amount of wear...The sample of the molding material to be tested is fixed to the stirring shaft and heated at 1900 rpm for 7 hours.
Rotate it in a water mixture and measure the subsequent weight loss (%) MFI…conforms to JIS K6760 MI, HLMI…conforms to JIS K6758 Stress at yield point (σ _y )…conforms to ASTMD 638 Elongation at break (E)…ASTMD Compliant with 638 Izot impact strength (with notch)…ASTMD
Based on 250 Average molecular weight of polyethylene (viscosity method)...
Compliant with ASTMD 1505 Melt viscosity...190℃, D=0.7696φ, L/D=
Measurement at 33.089 Example 1 TiC prepared separately by co-pulverizing 100 parts by weight of magnesium chloride and 30 parts by weight of benzoyl chloride.
₄ /dimethyldimethoxysilane complex (molar ratio 2:
Add to the toluene solution of 1), mix at 65℃ for 2 hours, wash with toluene, and dry to obtain 1.44 g of solid components, 23 g of triethylaluminum, and 4.5 g of ethyl benzoate.
100 stainless steel autoclave, followed by propylene monomer 30Kg, hydrogen pressure 5
Kg/cm ² , polymerization was carried out at 65°C for 20 minutes. Now completely purge the propylene and H ₂ and add new isoptan.
60 was added, ethylene was introduced, and the ultra-high molecular weight polyethylene component was polymerized at an ethylene pressure of 5 kg/cm ² at 50° C. for 2 hours, and the polymerization was stopped by purging ethylene and isoptan from the system. After the first stage was completed, a small amount of polypropylene powder was collected and the polypropylene component was measured.
The MFI (230°C, 2.16 kg load) was 76 g/10 minutes, and the fraction of heptane extraction residue was 93.4%. The obtained polymer weighed 14.3 kg, and the propylene content was 26.5 wt% as determined by infrared absorption spectrum. This polymer has BHT (2.6-di-tert-butyl-p-
Cresol) 0.1% and calcium stearate (CaST) 0.1Wt% were added and pelletized at 230℃ using a 40mmφ extraction machine.
HLMI (190℃21.6Kg load) is 3.6g/10 minutes, MLMI
(190℃ 10Kg load) is 0.07g and HLMI/MLMI is
It was 51.4. This pellet was press-molded and subjected to physical property measurements. The results are shown in Table 1. Comparative Example 1 Ultra-high molecular weight polyethylene was polymerized in exactly the same manner as in Example 1, except that no polypropylene component was produced and without H ₂ . The obtained polymer could not be pelletized using an extruder, so it was press-molded as a powder and subjected to physical property measurements.
The results are shown in Table 1. Comparative Example 2 The polymerization of the propylene component in Example 1 and the polymerization of the ultra-high molecular weight polyethylene component were carried out separately, and the resulting powders were blended in the same ratio as in Example 1 and pelletized. The strands from the extruder were non-uniform and were broken one after another, making it impossible to form them into pellets.
The mixed powder was similarly press-molded and subjected to physical property measurements. The results are shown in Table 1. Examples 2-9 Example 1 was repeated by changing the composition, MFI and content of the polypropylene component produced in the first stage.
The results are shown in Table 1. Examples 10-13 Example 1 was repeated by changing the composition and molecular weight of the ultra-high molecular weight polyethylene produced in the second stage. The results are shown in Table 1.

【table】

[Table] Example 14 Butene was used instead of propylene monomer in the first stage.
Example 1 was repeated except that the polymerization was carried out at 20° C. for 50 minutes using 30 kg of each monomer and a hydrogen pressure of 10 kg/cm ² . The results are shown in Table 1. Example 15 The procedure was the same as in Example 1 except that the ultra-high molecular weight polyethylene component was polymerized in the first stage and the polypropylene component was polymerized in the second stage. The results are shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1. When producing ultra-high molecular weight polyethylene resin by polymerizing monomers in two or more stages with different monomer compositions and hydrogen concentrations using a Ziegler type catalyst consisting of a solid catalyst component containing a transition metal component and an organometallic component, At any stage, propylene or a propylene-based monomer or butene-1 or a butene-1-based monomer is polymerized in the presence of hydrogen to produce polypropylene or polybutene-1 in an amount of 2 to 60% by weight of the total polymer. Manufacture one ingredient,
In the remaining one or more steps, ethylene or an ethylene-based monomer is polymerized in substantially the absence of hydrogen to produce an ultra-high molecular weight polyethylene component of 98 to 40% by weight of the total polymer. A method for producing ultra-high molecular weight polyethylene resin with improved moldability.