KR101826447B1 - The preparation method of ultra-high molecular weight polyethylene - Google Patents

Abstract

The present invention relates to a magnesium supported titanium solid catalyst and a method for preparing ultrahigh molecular weight polyethylene using the same and, more specifically, to a method for preparing ultrahigh molecular weight polyethylene having uniform grain size and high apparent density using a catalyst manufactured by the following steps: (1) dissolving a magnesium dichloride compound using an alcohol, making the dissolved resultant with titanium tetrachloride and preparing a precursor; and (2) making the precursor prepared in the step (1) react with titanium tetrachloride and a carbonyl compound.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a preparation method of ultra high molecular weight polyethylene,

The present invention relates to a magnesium-supported titanium solid catalyst and a process for producing ultra-high molecular weight polyethylene using the same, wherein a solid catalyst containing titanium tetrachloride and a carbonyl compound is prepared and then subjected to a polymerization reaction to obtain a uniform particle size and a high apparent density ≪ / RTI > provides a method for preparing ultra high molecular weight polyethylene.

Ultrahigh molecular weight polyethylene means polyethylene having a molecular weight of at least 1000000 g / mol and has remarkably high molecular weight as compared with general purpose polyethylene, and thus has excellent properties such as rigidity, abrasion resistance, chemical resistance and electrical properties. Since ultra high molecular weight polyethylene has excellent mechanical properties and abrasion resistance among thermoplastic engineering plastics, it has been used not only in abrasion resistance of mechanical parts such as gears, bearings and cams but also in impact resistance and biocompatibility, It is also used as a material for joints.

Because ultrahigh molecular weight polyethylene has very high molecular weight and has little flowability in molten state, it can not be pelletized like general polyethylene. Therefore, particle size and distribution and apparent density of powder are very important because they are mostly produced and sold in powder form. Because ultrafine molecular weight polyethylene is difficult to melt process, it is dissolved and dissolved in a suitable solvent. However, since the powder having a large particle size may be deteriorated in dissolution characteristics, the particle size and apparent density of the powder may affect productivity It acts as an important factor.

The preparation of catalysts containing magnesium and titanium compounds and the production of ultrahigh molecular weight polyethylene using them have been reported in various patents. Korean Patent No. 0822616 discloses a process for preparing a catalyst comprising magnesium, titanium and a silane compound capable of producing an ultra-high molecular weight polyolefin polymer having high catalytic activity and uniform particle size distribution, but there is room for improvement in terms of apparent density , U.S. Patent No. 4,962,167 discloses a method for preparing ultra high molecular weight polyethylene catalyst by reacting a magnesium halide compound, a titanium alkoxide, an aluminum halide and a silicon alkoxide compound, but has a disadvantage in that the catalytic activity and the apparent density are relatively low.

U.S. Patent No. 5,587,440 discloses a method for producing ultra-high molecular weight polyethylene having a uniform particle size distribution and a high apparent density using a catalyst obtained by reacting a titanium compound with an organoaluminum, but has a disadvantage in that the polymerization activity of the catalyst is low.

Accordingly, the present invention provides a method for preparing a catalyst for ultrahigh molecular weight polyethylene which can provide a high polymerization activity while satisfying uniform particle size distribution and high apparent density, which are required characteristics of ultrahigh molecular weight polyethylene.

The present invention provides a method for preparing a catalyst capable of providing ultrahigh molecular weight polyethylene having excellent polymerization activity and uniform particle size and high apparent density.

A process for producing a catalyst capable of achieving the above object is characterized in that it is produced by the following steps.

(1) reacting magnesium dichloride (MgCl ₂ ) with an alcohol to prepare a magnesium compound solution;

(2) reacting the magnesium compound solution prepared in the step (1) with titanium tetrachloride to prepare a precursor;

(3) reacting the precursor with titanium tetrachloride and a carbonyl compound to prepare a catalyst

The magnesium solution used in the present invention can be prepared by using magnesium dichloride as a solvent in the presence of a hydrocarbon solvent. Examples of the hydrocarbon solvent usable herein include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane and kerosene, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane and methylcyclohexane, Aromatic hydrocarbons such as toluene, xylene, ethylbenzene, cumene and cymene, halogenated hydrocarbons such as dichloropropane, dichloroethylene, trichlorethylene, carbon tetrachloride, and chlorobenzene.

The alcohol used for preparing the magnesium compound solution in the step (1) is not particularly limited, but an alcohol having 4 to 20 carbon atoms is preferable.

The carbonyl compound used in the step (3) may be represented by the following general formula (I) or (II).

R ¹ (CO) R ² (I)

R ¹ (CO) OR ² (II)

Wherein R ¹ and R ² represent linear, cyclic and aromatic hydrocarbons having 1 to 10 carbon atoms.

The polymerization reaction of the present invention is carried out using the magnesium-supported titanium catalyst prepared by the above method and the Group II and Group III organometallic compounds of the Periodic Table.

The organometallic compounds useful in the present invention can be represented by the general formula of MRn wherein M is a Group II or Group IIIA metal element of the Periodic Table such as magnesium, calcium, zinc, boron, aluminum, gallium, and R is methyl, ethyl , Butyl, hexyl, octyl, decyl, and n represents the valence of the metal component. More preferred organometallic compounds are trialkylaluminums having alkyl groups with 1 to 6 carbon atoms, such as triethylaluminum and triisobutylaluminum, and mixtures thereof. In some cases, one or more halogen or hydride groups such as ethylaluminum dichloride, diethylaluminum chloride, ethylaluminum sesquichloride, diisobutylaluminum hydride and the like can be used.

The polymerization reaction can be carried out by liquid-phase slurry polymerization in the presence of an organic solvent in the presence of a gaseous or bulk polymerization or an organic solvent. These polymerization processes are carried out in the absence of oxygen, water, and other compounds that can act as catalyst poisons. Solvents include alkanes or cycloalkanes such as pentane, hexane, heptane, n-octane, isooctane, cyclohexane, methylcyclohexane; Alkylaromatics such as toluene, xylene, ethylbenzene, isopropylbenzene, ethyltoluene, n-propylbenzene, diethylbenzene; Halogenated aromatics such as chlorobenzene, chloronaphthalene, o-dichlorobenzene; And mixtures thereof.

The present invention provides a method for simply and efficiently producing a catalyst capable of providing ultrahigh molecular weight polyethylene having excellent polymerization activity and uniform particle size and high apparent density.

Hereinafter, the present invention will be described more specifically with reference to the following examples. These embodiments, however, are for illustrative purposes only.  The invention is not limited to these examples.

Example

Example  One

[Preparation of a solid catalyst for preparing ultrahigh molecular weight polyethylene]

(1) Step: Preparation of magnesium halide compound solution

25 g of magnesium dichloride (MgCl ₂ ), 300 ml of toluene and 100 ml of n-butanol were charged, the temperature was elevated to 65 ° C for 1 hour while stirring at 350 rpm, To obtain a uniform magnesium halide compound solution.

(2) Step: Preparation of solid complex titanium catalyst

After the temperature of the solution prepared in the step (1) was cooled to 40 ° C, 70 ml of TiCl ₄ was slowly injected for 1 hour. Upon completion of the injection, the temperature of the reactor was raised to 60 ° C for 1 hour and aged for an additional 1 hour. When all the process was completed, the reactor was allowed to stand to completely quench the solid component to remove the supernatant, and then the solid component in the reactor was washed with 200 ml of hexane. 200 ml of hexane, 60 ml of TiCl ₄ and 8 ml of ethyl benzoate were poured into the solid component, and the temperature of the reactor was raised to 70 ° C over 1 hour while stirring at 350 rpm, followed by aging for 2 hours. When all the procedures were completed, the reactor was allowed to stand to completely quench the solid components and remove the supernatant. The prepared solid catalyst was washed six times with 200 ml of hexane.

[Ultra High Molecular Weight Polyethylene Polymerization]

The 2-liter high-pressure reactor is dried in an oven and then assembled into a hot state, and nitrogen and vacuum are alternately operated three times to make the inside of the reactor nitrogen atmosphere. After injecting 1000 ml of hexane into the reactor, 1 mmol of triethylaluminum and 0.005 mmol of titanium catalyst based on the solid catalyst were injected. The temperature of the reactor was raised to 60 DEG C while stirring at 700 rpm, the ethylene pressure was adjusted to 130 psig, and polymerization was carried out for 3 hours. After the polymerization was completed, the temperature of the reactor was lowered to room temperature, and the resulting polymer was collected and dried in a vacuum oven at 50 ^° C. for at least 6 hours to obtain a white powder polymer.

The polymerization activity (kg-PE / g-catalyst) was calculated as the weight ratio of polymer produced per catalytic amount used. The particle size distribution of the polymer was measured using a laser particle analyzer (Mastersizer X, Malvern Instruments) and the result was an average particle size of D (v, 0.5) and a particle size distribution of D (v, 0.9) -D v, 0.1)) / D (v, 0.5). Where D (v, 0.9) and D (v, 0.5) represent the particle sizes represented by the samples at 90% and 10%, respectively. The smaller the number of distributions, the narrower the distribution. The intrinsic viscosity of the polymer can be calculated by dissolving the polymer by dissolving the polymer in decahydronaphthalene solvent according to ISO 1628 Part 3 and then extrapolating the relative viscosity to a value of zero concentration . From this, the average molecular weight (Mv) was calculated using Margolies's formula (Mv = 5.34 × 10 ⁴ × [η] ^1.49 , Mv = viscosity average molecular weight, η = intrinsic viscosity) well known in the art. The polymerization results are shown in Table 1 together with the apparent density (g / ml) of the polymer.

Example  2

The procedure of Example 1 was repeated except that 8 ml of 2,4-dimethyl-3-pentanone was used instead of ethyl benzoate in Example 1.

Example  3

The procedure of Example 1 was repeated except that 8 ml of benzophenone was used instead of ethyl benzoate in Example 1.

 

Comparative Example  One

The procedure of Example 1 was repeated except that 8 ml of diisobutyl phthalate was used instead of 8 ml of ethyl benzoate in Example 1.

Comparative Example  2

The procedure of Example 1 was repeated except that ethyl benzoate was not used in Example 1.

division Titanium content (wt%) in the catalyst activation
(kg-PE / g-catalyst) Apparent density (g / ml) Intrinsic viscosity
(dl / g) Viscosity average molecular weight
(10 ⁶ g / mol) Average particle size
(μm) Particle size distribution Example 1 2.1 40 0.42 27.8 7.6 132 0.5 Example 2 2.3 42 0.39 25.9 6.8 129 0.7 Example 3 2.2 33 0.41 29.3 8.2 134 0.6 Comparative Example 1 4.3 10 0.28 28.4 7.8 536 2.1 Comparative Example 2 7.1 36 0.33 22.4 5.5 234 1.2

As shown in Table 1, the catalysts prepared by the methods of Examples 1 to 3 can provide ultrahigh molecular weight polyethylene having excellent polymerization activity and uniform particle size and high apparent density.

Claims (3)

A process for preparing a catalyst for preparing ultra high molecular weight polyethylene, comprising the steps of:
(1) reacting magnesium dichloride (MgCl ₂ ) with an alcohol to prepare a magnesium compound solution;
(2) reacting the magnesium compound solution prepared in the step (1) with titanium tetrachloride to prepare a precursor;
(3) reacting the precursor with titanium tetrachloride and a carbonyl compound to prepare a catalyst. The process according to claim 1, wherein the alcohol is an alcohol having 4 to 20 carbon atoms. The process according to claim 1, wherein the carbonyl compound represented by the following general formula (I) or (II) is used:
R ¹ (CO) R ² (I)
R ¹ (CO) OR ² (II)
Wherein R ¹ and R ² represent linear, cyclic and aromatic hydrocarbons having 1 to 10 carbon atoms.