JPH0565523B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ultra-high molecular weight ethylene polymer powder suitable for powder processing and molding such as compression molding, powder molding, and fluidized dipping. Ultra-high molecular weight polyolefins, represented by ultra-high molecular weight polyethylene, have traditionally been used as resins that are lightweight, have excellent wear resistance, impact resistance, chemical resistance, and self-lubricating properties, and are used in mechanical parts, sliding materials, lining materials, and sports. It is used for many purposes such as supplies. However, because ultra-high molecular weight polyolefins have poor fluidity when melted, melt molding processes such as injection molding or extrusion molding are difficult. Due to unevenness, it may not exhibit sufficient strength. Molding methods using powder, such as rotational molding, powder molding, and compression molding, have been developed as methods for molding ultra-high molecular weight polyolefins in place of such melt molding methods. Among these methods, especially compression molding, the ultra-high molecular weight polyolefin powder conventionally used has disadvantages in handling, such as the powder easily scattering during the molding process, and it also causes roughness and roughness on the surface of the molded product. It also had drawbacks such as easy whitening caused by air bubbles. In view of the above-mentioned situation with the conventional ultra-high molecular weight polyethylene powder used in compression molding, the present inventors have found that when used in compression molding, the powder is difficult to scatter and is easy to handle. and
As a result of extensive research into a method for producing ultra-high molecular weight ethylene polymer powder that has improved the problems such as roughening of the surface appearance of molded products and whitening due to air bubbles, we found that The inventors have discovered that the above object can be achieved by using a powder of a high molecular weight ethylene polymer, and have arrived at the present invention. That is, the method for producing an ultra-high molecular weight ethylene polymer powder according to the present invention includes forming the ultra-high molecular weight ethylene polymer powder from a solid titanium catalyst component and an organoaluminum compound catalyst component, which are prepared into granules through a magnesium compound in a melt or solution state. The intrinsic viscosity [η] measured in decalin at 135°C is 5 dl/g or more, and the particle size is
10% or less of the total powder is 840μ or more, 90% or more of the total has a particle size in the range of 44 to less than 840μ, and the average particle size is in the range of 200 to 700μ, and the bulk density is 0.30g/cm It is characterized by producing ethylene polymers in the range of ³ or more. Hereinafter, the method for producing the ultra-high molecular weight ethylene polymer powder according to the present invention will be specifically explained. The ultra-high molecular weight ethylene polymer powder of the present invention can be obtained by homopolymerizing ethylene as a raw material in the presence of a specific Ziegler type catalyst as described below, or by homopolymerizing ethylene as a main component and α other than ethylene.
- Can be directly produced by copolymerizing with olefin. α-olefins other than ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene,
Examples include 4-methyl-1-pentene and 3-methyl-1-pentene. Such α-olefins may be used alone or in combination of two or more. When producing ultra-high molecular weight ethylene polymer powder using the above-mentioned ethylene raw material monomers, a solid titanium catalyst component prepared into granules via a magnesium compound in a melt or solution state and an organic A catalyst formed from an aluminum compound catalyst component (Ziegler type catalyst) is used. The solid titanium catalyst component used in the polymerization reaction preferably has an average particle size in the range of 5 to 40μ, particularly preferably 7 to 30μ,
The particle size distribution is narrow. The solid titanium catalyst component is a magnesium compound-supported catalyst prepared into granules by using a magnesium compound in a melt or solution state, for example, the method for preparing a solid titanium catalyst component disclosed in JP-A-56-811. It can be produced by strictly adjusting the precipitation conditions when a liquid magnesium compound and a liquid titanium compound are brought into contact with each other to precipitate a solid product. For example, in the method disclosed in the publication, a hydrocarbon solution in which magnesium chloride and a higher alcohol are dissolved and titanium tetrachloride are mixed at a low temperature, and then the temperature is raised to about 50 to 100°C to precipitate a solid product. In this process, a trace amount of monocarboxylic acid ester of about 0.01 to 0.2 mol is present per 1 mol of magnesium chloride, and the precipitation is carried out under strong stirring conditions.
Further, if necessary, it may be washed with titanium tetrachloride. In this way, a solid catalyst component having satisfactory activity and particle properties can be obtained. Such catalyst components contain, for example, about 1 to about 6% by weight of titanium, with a halogen/titanium (atomic ratio) of about 5 to about 90 and a magnesium/titanium (atomic ratio) of about 4 to 50. The ultra-high molecular weight ethylene polymer of the present invention comprises the above-mentioned highly active finely powdered titanium catalyst component and organoaluminum compound catalyst component, such as trialkylaluminum such as triethylaluminum and triisobutylaluminum, diethylaluminum chloride, diisobutylaluminum chloride. dialkylaluminum chlorides such as ethylaluminum sesquichloride, alkylaluminum sesquichlorides such as ethylaluminum sesquichloride, or mixtures thereof, optionally with an electron donor, in a hydrocarbon medium such as pentane, hexane, heptane, kerosene. It can be produced by slurry polymerization of ethylene-based raw material monomers under temperature conditions such as , 50 to 90°C. At this time, the concentration of the titanium catalyst component should be about 0.001 to 1.0 mg atoms/liter in terms of titanium raw material, and each catalyst component should be adjusted so that the organoaluminum compound catalyst component has an Al/Ti (atomic ratio) of about 5 to 500. is used, and the slurry concentration of ethylene polymer is 50 to 400.
It suffices if the operation is carried out so that the amount is about g/liter. In order to produce an ultra-high molecular weight ethylene polymer with a desired intrinsic viscosity, it is necessary to adjust the polymerization temperature or the amount of
Just adjust the amount of _H2 . The ultra-high molecular weight ethylene polymer obtained in this way is non-deashing, has a low catalyst residue such as Ti content of 10 ppm or less and chlorine content of 100 ppm or less, and is free from rust during molding and product quality. There is little negative impact on The ultra-high molecular weight ethylene polymer obtained by the present invention is polyethylene, which is an ethylene homopolymer, or a copolymer containing ethylene as a main component. Examples of copolymers containing ethylene as a main component include copolymers of ethylene and α-olefin. Such α-olefins include, for example, propylene, 1-butene, 1-pentene, 1
-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1pentene, 3-methyl-
Examples include 1-pentene. Such a copolymer of ethylene and α-olefin is the above-mentioned α-olefin.
- It may be a copolymer consisting of two or more components of olefins and ethylene. Further, such ultra-high molecular weight ethylene polymer is in powder form. 135℃ of these ultra-high molecular weight ethylene polymers
The intrinsic viscosity [η] measured in decalin is 5 dl/
g or more, preferably 7 to 50 dl/g, particularly preferably 10 to 30 dl/g.
It is within the range of g. Intrinsic viscosity [η] is 5
Ultra-high molecular weight ethylene polymers with a molecular weight of less than dl/g have good normal melt molding processability, and are not included in the ultra-high molecular weight ethylene polymers of the present invention. The ultra-high molecular weight ethylene polymer powder obtained by the present invention has a specific average particle size and particle size distribution. That is, the average particle size of the ultra-high molecular weight ethylene polymer powder needs to be in the range of 200 to 700μ, and more preferably in the range of 250 to 700μ.
600μ, particularly preferably in the range of 250 to 500μ. When the average particle size is smaller than 200μ,
During compression molding, the scattering of powder becomes large, and the surface of the molded product becomes rough and white due to air bubbles.If it is larger than 700μ, the surface roughness and whitening due to air bubbles become large. In addition, the particle size distribution of the ultra-high molecular weight ethylene polymer is such that powder with a particle size of 840μ or more, measured by the method of JIS K0069, accounts for 10% or less of the total, and the particle size is 44 or more.
It is necessary that powder with a particle size of less than 840μ accounts for 90% or more of the total, and furthermore, powder with a particle size of 840μ or more accounts for 5% or less of the total, and powder with a particle size of 44 to less than 840μ accounts for 95% or more of the total. It is preferable that there be. If the ultra-high molecular weight ethylene polymer powder with a particle size of 840μ or more exceeds 10% of the total, the surface of the molded product will become rough and white due to bubbles, so it must be within the above range. be. The bulk density of the ultra-high molecular weight ethylene polymer powder obtained by the present invention must be in the range of 0.30 g/cm ³ or more, and more preferably 0.32 to 0.50 g/cm 3 .
It is preferably in the range of g/cm ³ . The bulk density of the ultra-high molecular weight ethylene polymer powder is 0.30 g/cm ³
If it is less than that, the workability will be lowered and the moldability of details will also be lowered. Further, the angle of repose of the ultra-high molecular weight ethylene polymer powder is in the range of 25 to 40°, preferably 26 to 35°. The ultra-high molecular weight ethylene polymer powder of the present invention can be suitably used in compression molding, but it can also be used in any other field of powder processing such as powder molding, fluidized dipping, and fluidized baking. I can do it. The ultra-high molecular weight ethylene polymer powder may contain various heat stabilizers, weather stabilizers, antioxidants, antistatic agents,
A nucleating agent, a lubricant, etc. can be blended, and their blending ratio is appropriate. Next, the method for producing the ultra-high molecular weight ethylene polymer powder of the present invention will be specifically explained with reference to Examples. The various properties that define the powder of the present invention were measured by the following methods. [η]: ASTM O 1601-78 Bulk density: ASTM D 1238 Particle size distribution: JIS K 0069 Angle of repose: Measured by injection method. [Solid Catalyst Preparation] Solid catalysts used in Examples and Comparative Examples described later were synthesized as follows. (1) Solid catalyst component A: 4.76 g (50 mmol) of anhydrous magnesium chloride,
25ml decane and 2-ethylhexyl alcohol
After heating and reacting 23.4 ml (150 mmol) at 135°C for 2 hours to make a homogeneous solution, 1.11 g (7.5 mmol) of phthalic anhydride was added to this solution, and the mixture was stirred and mixed at 130°C for an additional 1 hour. , phthalic anhydride is dissolved in the homogeneous solution. After the homogeneous solution thus obtained was cooled to room temperature, the entire amount was dropped over 1 hour into 200 ml (1.8 mol) of titanium tetrachloride maintained at -20°C. After charging, the temperature of this mixed liquid was raised to 110℃ over the above period, and when it reached 110℃, 2.68ml of diisobutyl phthalate was added.
(1.25 mmol) was added thereto, and the mixture was kept under stirring at the same temperature for 2 hours. After 2 hours of reaction, collect the solid part by hot filtration, and add 200 ml of this solid part.
After resuspending in _TiCl4 , again at 110℃ for 2 hours.
Perform a heating reaction. After the reaction was completed, the solid part was collected again by hot filtration, and then diluted with decane and hexane at 110°C.
Wash thoroughly with purified hexane until no free titanium compound is detected in the washing solution. Obtained solid 2
triethylaluminum in hexane suspension of
After adding 1.1 ml and 0.23 ml of trimethylmethoxysilane and stirring at 20°C for 1 hour, the solid portion collected by filtration was washed with hexane to obtain solid catalyst A. The average particle size of the granular catalyst thus obtained is
It was 14μ. (2) Solid catalyst B: 4.76 g (50 mmol) of anhydrous magnesium chloride,
25ml decane and 2-ethylhexyl alcohol
After heating 23.2 ml (150 mmol) at 120°C for 2 hours to make a homogeneous solution, 1.4 ml of ethyl benzoate was added.
ml (10 mmol). After the homogeneous solution thus obtained was cooled to room temperature, the entire amount was dropped over 1 hour into 200 ml (1.8 mmol) of titanium tetrachloride maintained at -20°C. After charging, the temperature of this mixture was raised to 80℃, and ethyl benzoate was added.
Add 1.4 ml (10 mmol). After carrying out a heating reaction at 80°C for 2 hours, collect the solid part by hot filtration, resuspending this solid part in 200ml of TiCl ₄ , and then carrying out a heating reaction again at 90°C for 2 hours. . After completion of the reaction, the solid portion is again collected by hot filtration and thoroughly washed with purified hexane at 90°C with decane and hexane until no free titanium compound is detected in the washing liquid. 0.7 ml of triethylaluminum and 0.4 ml of tetraethoxysilane were added to a hexane suspension of 2 g of the obtained solid, and after stirring at 20°C for 1 hour, the solid part collected by filtration was washed with hexane to obtain solid catalyst B. Ta. The average particle size of the granular catalyst thus obtained was 15μ. (3) Solid Catalyst C Solid Catalyst C was obtained in the same manner as in the preparation of Solid Catalyst B, except that the amount of ethyl benzoate initially added was 1.0 ml (7 mmol). The average particle size of the obtained catalyst was 10μ. (4) Solid Catalyst D Solid Catalyst D was obtained in the same manner as in the preparation of Solid Catalyst B, except that the amount of ethyl benzoate initially added was changed to 0.7 ml (5 mmol). The average particle size of the obtained catalyst was 4μ. (5) Solid Catalyst E 1 mol of commercially available anhydrous magnesium chloride was suspended in 4 liters of kerosene, and 6 liters of ethanol was added thereto at room temperature, followed by stirring for 1 hour. Next, 2.9 mol of diethylaluminium chloride was added dropwise at room temperature and stirred for 1 hour. After adding 500 c.c. of titanium tetrachloride, the system was heated to 100°C and the reaction was carried out with stirring for 3 hours. After the reaction was completed, the supernatant was thoroughly washed with fresh kerosene by decanting. The obtained catalyst was amorphous. (6) Solid catalyst F: 4.76 g (50 mmol) of anhydrous magnesium chloride,
6.7 g (50 mmol) of ethanol, 100 ml of decane,
200 mg of sorbitan distearate was charged under a nitrogen atmosphere, the temperature was raised to 130°C, and the mixture was stirred for 3 hours.
The content liquid was allowed to protrude from the bottom outlet through a well-insulated discharge line and an emulsification pipe with an inner diameter of 1 mm and a length of 1 meter at the tip of the discharge line. This liquid was introduced into the gas phase of a 1 liter stirring vessel equipped with a cooling jacket containing 250 ml of decane.
It was rapidly cooled to ℃. A decane slurry containing spherical solid supports with a particle size range of 5 to 400 microns was thus obtained. 200ml
Put 25 g of the above spherical carrier in titanium tetrachloride,
The temperature was raised to 120°C and stirred for 2 hours. The solid portion was collected by filtration and thoroughly washed with hexane to obtain solid catalyst F. [Preparation of polymerized powder] Ethylene polymer powder was prepared by the methods of Examples and Comparative Examples described below. The properties of the obtained powder are shown in Table 1. Example 1 One liter of purified decane was charged into an autoclave having an internal volume of 2 liters, and the temperature was raised to 50°C. Next, 1.0 mmol of triethylaluminum and 0.01 mmol of the solid catalyst A above in terms of Ti atoms were added in a nitrogen atmosphere, and ethylene was added to increase the gauge pressure.
The weight was 8.0Kg/ ^cm2 . 75 for 5 hours while continuously supplying ethylene to maintain the total pressure at 8 kg/cm ² -G.
Polymerization was carried out by keeping at ℃. A powder of ultra-high molecular weight polyethylene was obtained from the polymerization mixture after the completion of the polymerization reaction.
Its properties are shown in Table 1. Example 2 Polymerization was carried out in the same manner as in Example 1, except that the temperature was kept at 85° C. for 4 hours while continuously supplying ethylene, to obtain a powder of ultra-high molecular weight polyethylene. Its properties are shown in Table 1. Example 3 Polymerization was carried out in the same manner as in Example 1 except that solid catalyst B was used to obtain ultra-high molecular weight polyethylene powder. Its properties are shown in Table 1. Example 4 Polymerization was carried out in the same manner as in Example 2 except that solid catalyst C was used to obtain ultra-high molecular weight polyethylene powder. Its properties are shown in Table 1. Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that solid catalyst D was used to obtain ultra-high molecular weight polyethylene powder. Its properties are shown in Table 1. Comparative Example 2 Among the ultra-high molecular weight polyethylene powders obtained in Example 3, only powders with a particle size of 840μ or more were fractionated, and their properties are shown in Table 1. Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that solid catalyst E was used, and the ultra-high molecular weight polyethylene powder is shown in Table 1. Comparative Example 4 Polymerization was carried out in the same manner as in Example 1 except that solid catalyst F was used to obtain ultra-high molecular weight polyethylene powder. Its properties are shown in Table 1. Comparative Example 5 1 Preparation of Catalyst Component 150 ml of thoroughly degassed and purified n-heptane was placed in a 1-liter flask purged with nitrogen, and then anhydrous MgCl ₂ (pulverized for 24 hours in a ball mill) was added.
0.1 mol of Ti(O-nC ₄ H 9 ) 4 and 0.03 mol of Ti(O-nC 4 H ₉ ) ₄ were introduced, the temperature was raised to 70° C., and the mixture was stirred for 1 hour. 0.08 mol of n-butanol was introduced and stirred for 1 hour, then 0.02 mol of AlCl ₃ was introduced and stirred for 1 hour, and 0.02 mol of TiCl ₄ and 0.15 mol of methylhydrodiene polysiloxane were each introduced. The mixture was stirred at ℃ for 2 hours. After the reaction is complete,
When a portion of the solid component was taken and the Ti content in the solid component was measured, it was found to be 5.9% by weight, Mg = 13% by weight, and Cl = 50% by weight. 2. Polymerization of ethylene Into a stainless steel autoclave with an internal volume of 1.5 liters equipped with a stirring and temperature control device, after repeating vacuum-ethylene displacement several times, 800 ml of sufficiently dehydrated and deoxygenated n-heptane was introduced.
Subsequently, 50 mg of triethyl aluminum, 150 mg of diethyl aluminum ethoxide, and 5.0 mg of the catalyst component synthesized above were introduced [OR ³ / (R ¹ + R ² ) =
0.32]. Furthermore, ethylene is introduced and the total pressure is 6
Kg/ ^cm2 . The temperature was raised to 70°C and polymerization was carried out for 2 hours. These reaction conditions were kept the same during the polymerization.
However, the pressure that decreases as the polymerization progresses is
A constant pressure was maintained by introducing only ethylene. After the polymerization was completed, ethylene was purged, the contents were taken out from the autoclave, the polymer slurry was filtered, and it was dried in a vacuum dryer overnight. 316 g of polymer (PE) were obtained. 3 Properties of Polymer The properties of the obtained polymer are shown in Table 1. [Performance evaluation of ultra-high molecular weight polyethylene powder] The moldability of the ethylene polymer powder was evaluated by the method described below. The results are shown in Table 1. <Molding conditions> Mold...0.5mm thick plate mold (300mm x 150mm), area weight
23g Heating: 200℃, 40Kg/cm ² -G 12 minutes Cooling: Water cooling, 40Kg/cm ² -G 8 minutes <Evaluation conditions> Air bubbles...Evaluation of ease of fusion of powder A: No air bubbles left at all . B: Some small bubbles remain. C: Large and small air bubbles remain on the entire surface of the molded product. Powder blow-up...Workability during molding A: No blow-up at all. B: There is some swelling. C: There is considerable upwelling. Skin: Smoothness of the surface of the molded product A: The entire surface is smooth. B: The surface is slightly rough. C: The surface is rough. 【table】

Claims (1)

[Claims] 1 Intrinsic viscosity [η ] is 5 dl/g or more, and the particle size
10% or less of the total powder is 840μ or more, 90% or more of the total has a particle size in the range of 44 to less than 840μ, and the average particle size is in the range of 200 to 700μ, and the bulk density is 0.30g/cm A method for producing an ultra-high molecular weight ethylene polymer powder, the method comprising producing an ethylene polymer having a molecular weight of ³ or more.