AU2005201962A1 - Process for producing micron-size, modified palygorskite as a Ziegler-Natta catalyst for production of polyethylene - Google Patents

Description

tf) TITLE OF THE INVENTION C Process for producing micron-size, modified palygorskite as a Ziegler-Natta catalyst for production of polyethylene FIELD OF THE INVENTION This invention relates to processes for producing micron-size, modified palygorskite as a Ziegler-Natta catalyst for synthesizing polyethylene. Naturally occurring palygorskite, also Sknown as attapulgite, will be sized, purified and then in-situ coordinated with TiC14 on its O surfaces and structural channels. Magnesium atoms required for the catalytic process will be supplied from the Mg atoms within the palygorskite structure, their numbers can be boosted 0 using the chemical replacement method during the purification process.

BACKGROUND OF THE INVENTION Traditionally chemical compounds containing magnesium and titanium are used as Ziegler-Natta catalysts for synthesizing polyethylene. Early inventions, such as British patent Nos. GB1111493, GB1115845, GB1066605, GB1099092, GB1030770 and GB1031232 and Chinese patent No. CN1451669 all have the catalytic compounds in liquid form. The trend is to use a solid carrier for the catalytic compounds. Most of the inventions either have silica as the carrier, such as in British patent No. GB1122157, Chinese patent Nos. CN1195668 and CN1232043, Japanese patent Nos. JP10279617 and JP55016030, US patent No. US4952649. The others use aluminum compounds as carriers, such as in Belgian patent No. BE776301, British patent Nos. GB1091664 and GB1115730, German patent No. DE4235405, Japanese patent Nos. JP54058787, JP3143906, JP2020510, JP1090204, JP63135407, JP61276803, JP61209204, JP59142209, JP58127710, JP57128707, JP57000104, JP56151708, JP55016030 and JP55013723, Korean patent Nos. KR7900675 and KR8202052, Spanish patent Nos. ES8603915, European patent No. EP0518604 and US patent No. US4103078 etc. There is only one invention, i.e. Chinese patent No. CN1330101, utilizes a naturally occurring clay mineral, montmorillonite as the Ziegler-Natta catalyst carrier.

To improve the mechanical properties of a polymer, clay minerals are usually used as fillers. It was reported in the invention of World patent No. WOO 198397 that the mechanical properties of a polymer have been greatly enhanced by adding palygorskite as filler during the manufacturing process.

Palygorskite, also known as attapulgite, is a naturally occurring clay mineral with a typical chemical formula of (Mg,AI) 2 Si 4 0 1 0(OH)-4H 2 0. In its natural state, it may take a variety of macroscopic forms from massive to papyraceous to fibrous. It is fibrous on a microscopic scale, of 0.5-5ptm in length and 30-100nm in diameter. Therefore, from the If) point of view of single crystals, it is a typical one-dimensional nano-sized natural mineral.

SThe crystal structures of palygorskite contains continuous planes of tetrahedron layers of Si-O Cl with Mg-O(OH) octahedron layers locate between them. They form a basis of the structure.

>These bases arrange alternatively and form parallel tunnels. These parallel tunnels have a cross-section of 0.37 x 0.64nm which gives palygorskite a very large specific surface area and potential for adsorbing various atoms* radicals and molecules and thus is a very favourable candidate for using as the carrier for catalysts.

Since Ziegler-Natta catalysts usually consist of titanium chloride (TiCI 4 with Mg present kLO and palygorskite has Mg atoms in its structure, therefore it is possible for palygorskite to adsorb TiC14 on its surfaces and within its tunnels and also to utilize its structural Mg atoms to Sform a Ziegler-Natta catalyst. The fibrous properties of palygorskite will further enhance Smechanical properties of polyethylene synthesized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The objective of this invention is to provide methods of producing modified palygorskite as a Ziegler-Natta catalyst for synthesizing polyethylene. Mg atoms required for the catalytic process will be supplied from the Mg atoms within the palygorskite structure, their numbers can be boosted using the chemical replacement method during the purification process. The other component for the Ziegler-Natta catalyst is TiC14 which will be in-situ coordinated with TiCI 4 on surfaces and also in structural channels ofpalygorskite.

Palygorskite, also known as attapulgite, is a naturally occurring clay mineral. It is fibrous on a microscopic scale, of 0.5-5im in length and 30-100nm in diameter. It is a typical one-dimensional nano-sized natural mineral. In its raw state just after mining, palygorskite is usually mixed with other impurities and is in massive lumps. Untreated, raw palygorskite usually does not possess the physical or chemical characteristics of nano-sized particles.

The ideal chemical formula for palygorskite is Mg 2 Si 4 01(OH)-4H 2 0. In its crystal structure, there is an Mg-O(OH) octahedron layer located between two tetrahedron layers of Si-O. They form the basis of the structure. These structural units are arranged alternately and form parallel tunnels. These tunnels have a cross-section of 0.37 x 0.64nm, which gives palygorskite a very large specific surface area and potential for adsorbing various atoms* radicals and molecules and thus makes palygorskite a very favourable candidate for using as the carrier for catalysts.

For naturally occurring palygorskite, there are not only Mg 2 cations at the central position of the octahedrons, but also other cations such as Al3 e3+ 2 Ni 2 Ga 2 and Na etc. The existence of those impurities will reduce the number of coupling bonds between Mg 2 and TiCI 4 As a result, it will then reduce the catalytic capacity of the catalyst.

iLc The core processes for this invention are firstly to physically purify the natural Spalygorskite to obtain high purity- micron-size palygorskite; secondly all the impurities at the (N Mg 2 site at the centre of the octahedrons will be replaced by Mg 2 through the selective >dissolution and ion exchange processes; finally TiC1 4 will be coupled with Mg2+ in the structure. Therefore, palygorskite in the final product has become not only the carrier of the catalyst but is also actually involved in the catalytic reaction. Advantages of this invention are: palygorskite is a naturally occurring abundant mineral which is cheaper than synthetic carriers for catalysts; Mg 2 cations in the crystal lattices are involved in the catalytic process, which increases the catalytic activity of the product; the catalytic compound is chemically bonded with the carrier and the fibrous micron-size palygorskite is distributed homogeneously in the synthesized polyethylene which will have higher density and strength Scompared with products synthesized with other catalysts.

(I

SDetails of these processes are described as follows: 1i. Palygorskite is pulverized down to 300 mesh and then washed with mineral acids. The mineral acids can be hydrochloric acid, nitric acid, sulphuric acid or combinations of them. With regard to the environmental and economic concerns, hydrochloric acid is the preferable acid. Some of the mineral impurities associated with palygorskite, such as carbonates, certain clay minerals, oxides of iron family elements etc. can be dissolved and removed by the acid. The dissolution of those mineral impurities, especially the carbonates, will cause loss of the aggregation of other minerals in the sample and allow them to be easily separated. During the actual process, concentrations and the amount of acids used are adjusted according to the amount of carbonates in the sample. The more carbonates contained, the larger amount or more concentrated the acids should be.

During the acid treatment, certain impurities, i.e. cations other than Mg 2 and Si 4 in the crystal lattice of palygorskite can be preferentially dissolved, Lattice positions of those impurities will be replaced by This preferential dissolution by acids can increase the chemical activity of crystal lattices in minerals. After treatment by acids, the sample should be washed with clean water several times to remove any remaining acid.

2. The second stage of the processes is ion-exchange and purification. Treating the acid-cleaned palygorskite with MgC12 or Mg(N0 3 2 can replace those lattice positions which were occupied by H with Mg 2 thus the crystal lattices of palygorskite will be purified. In order to further break up the aggregation within the sample, so as to avoid the conglomeration of small particles and to preserve the original fibrous structure of palygorskite, dispersants are added while the sample is emulsified into a slurry with a high shearing disperse mill. The emulsified slurry is then transferred into a tall container which is approximately 100cm in height, 40-80cm in diameter and a tap is located about 3-5cm from the bottom. The desired particle size of palygorskite can be separated by sedimentation and calculated by the Stoke's law. At room temperature, the actual time and height required for particle sizes <20am can be calculated from the following equation: t 0.124X+ 0.017 l) here X is the depth of the solution (in cm) and t is the time (in hr). At the calculated Stime, the tap is opened and slurry from the tap upward will be drawn out. The Cl remaining slurry can be fed back to the disperse mill and then the sedimentation process can be repeated. The collected palygorskite slurry should be de-watered by either filtration or centrifuging and then washed by water to remove the remaining salts.

These cleaning processes should be repeated several times. The cleaned palygorskite is then mixed with a suitable amount of water and then spray-dried. The product from the spray-dry process contains loosely bonded small palygorskite spheres. There is no conglomeration among palygorskite fibers and thus the characteristic surface activities of 0 nano-particles are still maintained.

0 3. The final stage of the processes is in-situ coordinated the palygorskite with TiC14. TiC14 tt can easily lose its catalytic ability after reaction with water: C- TiCl 4

H

2 0 -*TiO 2

HCI

The product from spray-drying should be calcined to remove all the contained water.

Palygorskite contains 3 types of water in its structure. Those free water molecules located within the tunnels of palygorskite structure are removed after palygorskite has heated to 110-160°C. Those water molecules structurally bonded with Mg+ ions by molecular bonds within the tunnels are half removed after heating at 300-340 0 C, the other half will be removed at 400-700C. Those water molecules which form chemical bonds with Si 4 and Mg 2 as hydroxyls are removed after heating at 830-850°C. Crystal structure of palygorskite will collapse and chemical activity of palygorskite will disappear after heating at such temperatures. Therefore, the calcine temperatures should be kept below 700 0 C. Calcined palygorskite is hydroscopic and should be kept away from moisture and stored in sealed containers.

In order to further remove moisture in palygorskite, it is then treated with trimethyl aluminium (AI(CH 3 3 or trisobutyl aluminium (TIBAL) (Al[(CH 3 2

CH-CH

2 3 solution: 2AI(CH 3 3 3H20 A1 2 0 3 6CH 4 2AI[(CH 3 2

CH-CH

2 3 6H20 A1 2 0 3 6 (CH 3 2

CH-CH

3 Once the organic solvent dissolved TiCl 4 is added into the above treated palygorskite, TiCI 4 will in-situ coordinated with Mg 2 in the palygorskite: Mg(+ +TiCl 4 Mg(c)Ti( c After being dried, the product is a Ziegler-Natta catalyst for synthesizing polyethylene with micron-size palygorskite as the carrier. The organic solvent can be recovered with distillation and recycled. Temperatures for the above reaction and drying process should be maintained below 90°C. The product is hydroscopic and can absorb moisture from the air and lose its catalytic capability, therefore it should be stored in sealed containers and protected with dried nitrogen.

tI EXAMPLES Cl Examples of the process of this invention in the laboratory are described as follows: EXAMPLE 1: 1. 10Kg of palygorskite was firstly pulverized to <300mesh and mixed well with 30Kg of concentration of added hydrochloric acid. The slurry was occasionally stirred during the reaction. After 30min, water from the slurry was removed by filtration.

The filter cake was washed with clean water, followed by filtration 5 times to remove all CO the remaining acid.

2. The cleaned filter cake was mixed well with 30Kg of 3mol of MgC12 solution, then 5g of 0 sodium tripolyphosphate (NasP 3 00o) was added into the mixture. This was fed into a Shigh shearing disperse mill and made into a slurry. The emulsified slurry was 0 transferred into a tall container of 100cm in height and 50cm in diameter with a tap ^l located at 5cm from the bottom. Water was added into the container so that the water level reached to the 100cm mark. Thoroughly mix the slurry and then left it for settling.

The top part of the slurry was carefully drawn out by opening the tap at 12hr. Water was added into the remaining slurry to the marker and mixed well. The slurry was allowed to settle and the top part of slurry was drawn out again at 12hr. These sedimentation processes were repeated 5 times. All the collected slurries were combined together, then washed with clean water and de-watered by centrifuging 3 times.

3. The cleaned filter cake was mixed with 30Kg of water and the slurry was spray-dried.

The dried power is the micron-size palygorskite with crystal lattice purified.

4. Calcined the above powder at 500C for 6 hr then cooled it to room temperature under the dried nitrogen atmosphere.

Dissolved 30g of trimethyl aluminium (AI(CH 3 3 in 1Kg of furanidine ((CH 2 4 while under the protection of dried nitrogen, mixed into 1Kg of the above calcined powder.

While continuously stirring, slowly added furanidine with 50g of TiC14 dissolved.

6. Dried the solid by distillation and protected the solid under dried nitrogen atmosphere. The final product is a TiCl 4 contained Ziegler-Natta catalyst with micron-size palygorskite as the carrier EXAMPLE 2: 1. 10Kg of palygorskite was firstly pulverized to <300mesh and mixed well with 80Kg of Imol concentration of added nitric acid. The slurry was occasionally stirred during the reaction. After 24hr, water from the slurry was removed by filtration. The filter cake was washed with clean water 3 times to remove all the remaining acid.

2. The cleaned filter cake was mixed well with 80Kg of Imol Mg(N0 3 2 solution, then of tetrasodium pyrophosphate (Na 4

P

2 07) was added into the mixture. This was fed into a high shearing disperse mill and made into a slurry. The emulsified slurry was transferred into a tall container of 100cm in height and 50cm in diameter with a tap located at 5cm from the bottom. Water was added into the container so that the water level reached to the 100cm mark. Thoroughly mix the slurry and then left it for settling.

ttf) The top part of the slurry was carefully drawn out by opening the tap at 12hr. Water was Sadded into the remaining slurry to the marker and mixed well. The slurry was allowed C to settle and the top part of slurry was drawn out again at 12hr. These sedimentation processes were repeated 5 times. All the collected slurries were combined together, then washed with clean water and de-watered by centrifuging 3 times.

3. The cleaned filter cake was mixed with 30Kg of water and the slurry was spray-dried.

SThe dried power is the micron-size palygorskite with crystal lattice purified.

4. Calcined the above powder at 700C for 3 hr then cooled it to room temperature under the dried nitrogen atmosphere.

LNO 5. Dissolved 100g of TIBAL (Al[(CH 3 2

CH'CH

2 3 in 2Kg of hexene (C 6

H

1 4 while under Sthe dried nitrogen protection, mixed into 1Kg of the above calcined powder. After 0 continuously stirring for 30min, slowly added hexene with 100g of TiCl 4 dissolved.

Cl 6. Dried the solid by distillation and protected the solid under dried nitrogen atmosphere. The Sfinal product is a TiCl4 contained Ziegler-Natta catalyst with micron-size palygorskite as the C( carrier EXAMPLE 3: 1. 10Kg of palygorskite was firstly pulverized to <300mesh and mixed well with 30Kg of 3mol concentration of added sulphuric acid. The slurry was occasionally stirred during the reaction. After 12hr, water from the slurry was removed by centrifuging. The filter cake was washed with clean water 5 times to remove all the remaining acid.

2. The cleaned filter cake was mixed well with 50Kg of Imol Mg(N0 3 2 solution, then of sodium lignosulfonate was added into the mixture. This was fed into a high shearing disperse mill and made into a slurry. The emulsified slurry was transferred into a tall container of 100cm in height and 50cm in diameter with a tap located at 5cm from the bottom. Water was added into the container so that the water level reached to the 100cm mark. Thoroughly mix the slurry and then left it for settling. The top part of the slurry was carefully drawn out by opening the tap at 12hr. Water was added into the remaining slurry to the marker and mixed well. The slurry was allowed to settle and the top part of slurry was drawn out again at 12hr. These sedimentation processes were repeated times. All the collected slurries were combined together, then washed with clean water and de-watered by centrifuging 3 times.

3. The cleaned filter cake was mixed with 30Kg of water and the slurry was spray-dried.

The dried power is the micron-sized palygorskite with crystal lattice purified.

4. Calcined the above powder at 600 0 C for 4 hr then cooled it to room temperature under the dried nitrogen atmosphere.

Dissolved 30g of trimethyl aluminium (AI(CH 3 3 in 3Kg of hexane, while under the nitrogen protection, mixed into 1Kg of the above calcined powder. After continuously stirring for 20min, slowly added heptane (C 7

H

1 6 with 50g of TiCl 4 dissolved.

6. Dried the solid by distillation and protected the solid under dried nitrogen atmosphere. The final product is a TiCl 4 contained Ziegler-Natta catalyst with micron-size palygorskite as the carrier.

VI EXAMPLE 4: 1. 10Kg of palygorskite was firstly pulverized to <300mesh and mixed well with 50Kg of C 3mol concentration of added hydrochloric acid. The slurry was occasionally stirred Sduring the reaction. After 30min, water from the slurry was removed by filtration. The filter cake was washed with clean water 5 times to remove all the remaining acid.

2. The cleaned filter cake was mixed well with 30Kg of 2mol MgCI 2 solution, then 10g of sodium tripolyphosphate was added into the mixture. This was fed into a high shearing disperse mill and made into a slurry. The emulsified slurry was transferred into a tall container of 100cm in height and 50cm in diameter with a tap located at 5cm from the bottom. Water was added into the container so that the water level reached to the 100cm mark. Thoroughly mix the slurry and then left it for settling. The top part of the slurry O was carefully drawn out by opening the tap at 12hr. Water was added into the remaining p slurry to the marker and mixed well. The slurry was allowed to settle and the top part of 0 slurry was drawn out again at 12hr. These sedimentation processes were repeated CI times. All the collected slurries were combined together, then washed with clean water and de-watered by centrifuging 3 times.

3. The cleaned filter cake was mixed with 30Kg of water and the slurry was spray-dried.

The dried power is the micron-sized palygorskite with crystal lattice purified.

4. Calcined the above powder at 600°C for 5hr then cooled it to room temperature under the dried nitrogen atmosphere.

Dissolved 50g of trimethyl aluminium (AI(CH 3 3 in 2Kg of hexane, while under the nitrogen protection, mixed into 1Kg of the above calcined powder and continuously stirred for 10min. While stirring, slowly added octane (CsH 1 8 with 80g of TiC14 dissolved.

6. Dried the solid by distillation and protected the solid under dried nitrogen atmosphere. The final product is a TiCl4 contained Ziegler-Natta catalyst with micron-size palygorskite as the carrier.

Claims (2)

1. 3-6hr then cooled down to room temperature under the dried nitrogen atmosphere, the calcined palygorskite is mixed with trimethyl aluminium (Al(CH 3 3 or trisobutyl aluminium (TIBAL) (Al[(CH3) 2 CH-CH 2 3 which is 0.3-1.0% of palygorskite's weight and dissolved in organic solvents which are 1-2 times of palygorskite's weight, the mixture is reacted for
2. 10-30min under the protection of dried nitrogen atmosphere with occasional stirring, the organic solvent dissolved TiC14 which is 0.5-1.0% of the palygorskite by weight is slowly added into the mixture, the slurry is dried by distillation and the final product is a Ziegler-Natta catalyst for synthesizing polyethylene with micron-size palygorskite as the carrier which is kept under a dried nitrogen atmosphere. CLAIM 4: A method of producing micron-size, modified palygorskite as a Ziegler-Natta catalyst for synthesizing polyethylene as claimed in CLAIM 3, where the mineral acids are 3-5mol of either hydrochloric acid, or nitric acid or sulphuric acid or their combination. CLAIM A method of producing micron-size, modified palygorskite as a Ziegler-Natta catalyst for synthesizing polyethylene as claimed in CLAIM 3, where the dispersants added for emulsifying are either sodium tripolyphosphate (Na 5 P 3 0 1 0 or tetrasodium pyrophosphate (Na 4 P20 7 or sodium lignosulfonate or their combination CLAIM 6: A method of producing micron-size, modified palygorskite as a Ziegler-Natta catalyst for synthesizing polyethylene as claimed in CLAIM 3, where the organic solvents used are furanidine ((CH 2 4 or hexane (C 6 H 14 or heptane(C 7 H 1 6 or octane(CsH 18 or their combination. Names of Applicants Ying Ye Xuegang Chen Daidai WU Wei-Jui Chang Dated this 10th of May, 2005