WO2005014253A1 - Process for granulating powders of thermoplastic polymers under improved economic conditions - Google Patents

Process for granulating powders of thermoplastic polymers under improved economic conditions Download PDF

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Publication number
WO2005014253A1
WO2005014253A1 PCT/EP2004/007760 EP2004007760W WO2005014253A1 WO 2005014253 A1 WO2005014253 A1 WO 2005014253A1 EP 2004007760 W EP2004007760 W EP 2004007760W WO 2005014253 A1 WO2005014253 A1 WO 2005014253A1
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WO
WIPO (PCT)
Prior art keywords
suspension medium
solvent
extruder
polymer powder
polymer
Prior art date
Application number
PCT/EP2004/007760
Other languages
French (fr)
Inventor
Reinhard KÜHL
Johannes-Friedrich Enderle
Michael Witt
Original Assignee
Basell Polyolefine Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE10334504A external-priority patent/DE10334504A1/en
Application filed by Basell Polyolefine Gmbh filed Critical Basell Polyolefine Gmbh
Priority to US10/566,392 priority Critical patent/US20060175725A1/en
Priority to JP2006521438A priority patent/JP2007500088A/en
Priority to EP04740980A priority patent/EP1648671A1/en
Publication of WO2005014253A1 publication Critical patent/WO2005014253A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29BPREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00Making granules
    • B29B9/02Making granules by dividing preformed material
    • B29B9/06Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00Processes of treating or compounding macromolecular substances
    • C08J3/12Powdering or granulating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04Polymers of ethylene
    • B29K2023/06PE, i.e. polyethylene
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/10Polymers of propylene
    • B29K2023/12PP, i.e. polypropylene
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment

Definitions

  • the present invention relates to a process for granulating powders of thermoplastic polymers, in particular thermoplastic polyolefins, preferably polyolefins having a multimodal molar mass distribution, in which the polymer powder prepared in the polymerization reactor or reactors is introduced into an Extruder, melted and homogenized in the extruder, then pressed through an extrusion die and subsequently comminuted and cooled.
  • thermoplastic polymers in particular thermoplastic polyolefins, preferably polyolefins having a multimodal molar mass distribution
  • thermoplastic polymers The granulation of thermoplastic polymers is known and serves to homogenize the polymer and incorporate any auxiliaries and additives such as stabilizers, colorants, agents for improving the mechanical properties, fillers and the like into the polymer.
  • auxiliaries and additives such as stabilizers, colorants, agents for improving the mechanical properties, fillers and the like into the polymer.
  • the handling of thermoplastic polymers during transport and further processing can be improved considerably by granulation compared to the handling of powders.
  • the introduction of polymer powders into the extruder at a temperature corresponding to ambient temperature is customary, particularly in compounding processes. This is due, in particular, to intermediate storage of the polymer powder in silos and the transport methods employing pneumatic conveying systems, where cooling of the powder to ambient temperature generally occurs.
  • polymer powder is generally fed to the extruder as bulk material at ambient temperature. After the feed zone, the powder has to be increasingly heated in the extruder by mechanical frictional forces and finally melted bit by bit.
  • the known granulation processes are still in need of improvement in respect of their throughput, the associated stressing of machines and the product quality of the granulated material.
  • solvent or suspension medium according to the invention is preferably effected by the polymer powder, which is prepared in suspension in the polymerization reactor, not being subjected to complete drying, but rather being dried only to such an extent that the desired amount of solvent or suspension medium is automatically established in the polymer powder.
  • the preferred amount of solvent or suspension medium is, according to the invention, in the range from 0.0015 to 15 % by weight, particularly preferably from 0.002 to 10 % by weight and very particularly preferably from 0.01 to 5 % by weight.
  • a further possible way of achieving the object using the invention is to take a previously dried polymer powder, mix this powder with an appropriate amount of organic solvent or suspension medium and then feed the mixture to the extruder for granulation.
  • organic solvent or suspension media used are saturated or alicyclic or polycyclic or aromatic hydrocarbons having from 3 to 18, preferably from 4 to 12, carbon atoms or a mixture thereof.
  • the enthalpy of fusion of the polymer powder is reduced and the homogenization in the extruder is improved at a given energy input, which is reflected in fewer specks being observed in the polymer.
  • Advantageous polymers which can be granulated particularly well by the process of the invention have been found to be, in particular, standard polymers such as polyolefins, polyesters or polyamides, preferably polyethylene or polypropylene.
  • the process of the invention is particularly useful when the polyethylene has a multimodal molar mass distribution, because additional swelling effects then occur in the case of this material and these lead to particularly favorable homogenization.
  • the process of the invention has, in particular, the advantage that the granulation can be carried out industrially under improved economic conditions.
  • the costs of drying polymer powders are significantly reduced because the particularly energy-intensive and costly drying step for removing the last 5% of suspension medium can be dispensed with.
  • the product quality is improved since fewer specks occur and the polymer is thermally and mechanically stressed to a lesser extent in the extruder.
  • the machine running times for the extruders are increased because less energy is required for a given throughput of polymer powder and the machine equipment is thus subjected to lower stresses and thus requires fewer repairs.
  • the throughput is increased when the machines are operated at the same energy input, which improves the profitability of the process in the industrial manufacture.
  • a bimodal polyethylene was prepared in suspension in hexane as suspension medium in the presence of a high-activity Ziegler catalyst in two reaction vessels connected in series.
  • the bimodal polyethylene had a proportion of 48 % by weight of low molecular weight homopolymer and a proportion of 52 % by weight of high molecular weight copolymer.
  • the density of the bimodal polyethylene was 0.955 g/cm 3 , while its MFI 5 was 0.35 dg/min.
  • the pulverulent polyethylene was subjected to the normal drying process after leaving the reaction vessel, however, the process was stopped at an early stage so that precisely 2.2 % by weight of hexane remained in the polymer powder.
  • the powder was introduced into an extruder and processed at a constant energy input to produce granules. Films having a thickness of 25 ⁇ m were subsequently produced from the granules in a blown film process, and these were examined for the presence of specks by visual examination under a microscope. The result is shown in the following table.
  • Example 2 The same polymer as in Example 1 was subjected to the normal drying process after leaving the reaction vessel, but the process was continued to completion, so that less than 0.001 % by weight of hexane remained in the polymer powder.
  • Example 1 The powder which had been dried in this way was introduced into the same extruder as in Example 1 and processed to produce granules under exactly the same conditions. Films having a thickness of 25 ⁇ m were produced from the granules on the blown film plant and these were subjected to the same examination as in Example 1.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

In a process for granulating thermoplastic polymers, in particular thermoplastic polyolefins, the polymer powder prepared in the polymerization reactor is introduced into an extruder, melted and homogenized in the extruder, then pressed through an extrusion die and granulated. According to the invention, an organic solvent or suspension medium is added to the polymer powder in an amount in the range from 0.001 to 20 % by weight, prior to introduction into the extruder. The invention is particularly useful for granulating polyethylene or polypropylene, thereby increasing the polymer throughput at constant energy consumption or decreasing the energy consumption at constant polymer throughput.

Description

Process for granulating powders of thermoplastic polymers under improved economic conditions.
The present invention relates to a process for granulating powders of thermoplastic polymers, in particular thermoplastic polyolefins, preferably polyolefins having a multimodal molar mass distribution, in which the polymer powder prepared in the polymerization reactor or reactors is introduced into an Extruder, melted and homogenized in the extruder, then pressed through an extrusion die and subsequently comminuted and cooled.
The granulation of thermoplastic polymers is known and serves to homogenize the polymer and incorporate any auxiliaries and additives such as stabilizers, colorants, agents for improving the mechanical properties, fillers and the like into the polymer. In addition, the handling of thermoplastic polymers during transport and further processing can be improved considerably by granulation compared to the handling of powders.
Apart from the direct coupling of polymerization and granulation, in which the polymer powder from the polymerization process is dried and then fed directly to the extruder, the introduction of polymer powders into the extruder at a temperature corresponding to ambient temperature is customary, particularly in compounding processes. This is due, in particular, to intermediate storage of the polymer powder in silos and the transport methods employing pneumatic conveying systems, where cooling of the powder to ambient temperature generally occurs.
Thus, in compounding, polymer powder is generally fed to the extruder as bulk material at ambient temperature. After the feed zone, the powder has to be increasingly heated in the extruder by mechanical frictional forces and finally melted bit by bit. However, the known granulation processes are still in need of improvement in respect of their throughput, the associated stressing of machines and the product quality of the granulated material.
It is an object of the present invention to provide a process for granulating thermoplastic polymers, in which the effectiveness of the homogenization during granulation is increased at a given throughput or in which the stress on the machines can be reduced, which would be reflected in a reduced energy consumption and a reduced need for repairs or reduced downtimes, or in which the product throughput of existing granulation plants can be increased, thereby maintaining the quality of homogenization and the energy consumption.
This object is achieved by a process of the generic type mentioned at the outset, in which an organic solvent or suspension medium is added to the polymer powder in an amount in the range of from 0.001 to 20 % by weight, based on the weight of polymer powder plus solvent or suspension medium, prior to the introduction into the extruder.
The addition of solvent or suspension medium according to the invention is preferably effected by the polymer powder, which is prepared in suspension in the polymerization reactor, not being subjected to complete drying, but rather being dried only to such an extent that the desired amount of solvent or suspension medium is automatically established in the polymer powder. The preferred amount of solvent or suspension medium is, according to the invention, in the range from 0.0015 to 15 % by weight, particularly preferably from 0.002 to 10 % by weight and very particularly preferably from 0.01 to 5 % by weight.
A further possible way of achieving the object using the invention is to take a previously dried polymer powder, mix this powder with an appropriate amount of organic solvent or suspension medium and then feed the mixture to the extruder for granulation.
According to the invention, organic solvent or suspension media used are saturated or alicyclic or polycyclic or aromatic hydrocarbons having from 3 to 18, preferably from 4 to 12, carbon atoms or a mixture thereof.
As a result of the presence of the amount according to the invention of solvent or suspension medium, the enthalpy of fusion of the polymer powder is reduced and the homogenization in the extruder is improved at a given energy input, which is reflected in fewer specks being observed in the polymer. Advantageous polymers which can be granulated particularly well by the process of the invention have been found to be, in particular, standard polymers such as polyolefins, polyesters or polyamides, preferably polyethylene or polypropylene. In the case of polyethylene, the process of the invention is particularly useful when the polyethylene has a multimodal molar mass distribution, because additional swelling effects then occur in the case of this material and these lead to particularly favorable homogenization.
The process of the invention has, in particular, the advantage that the granulation can be carried out industrially under improved economic conditions. The costs of drying polymer powders are significantly reduced because the particularly energy-intensive and costly drying step for removing the last 5% of suspension medium can be dispensed with. The product quality is improved since fewer specks occur and the polymer is thermally and mechanically stressed to a lesser extent in the extruder. The machine running times for the extruders are increased because less energy is required for a given throughput of polymer powder and the machine equipment is thus subjected to lower stresses and thus requires fewer repairs. Conversely, the throughput is increased when the machines are operated at the same energy input, which improves the profitability of the process in the industrial manufacture.
Example 1 (according to the invention)
A bimodal polyethylene was prepared in suspension in hexane as suspension medium in the presence of a high-activity Ziegler catalyst in two reaction vessels connected in series. The bimodal polyethylene had a proportion of 48 % by weight of low molecular weight homopolymer and a proportion of 52 % by weight of high molecular weight copolymer. The density of the bimodal polyethylene was 0.955 g/cm3, while its MFI5 was 0.35 dg/min.
The pulverulent polyethylene was subjected to the normal drying process after leaving the reaction vessel, however, the process was stopped at an early stage so that precisely 2.2 % by weight of hexane remained in the polymer powder.
The powder was introduced into an extruder and processed at a constant energy input to produce granules. Films having a thickness of 25 μm were subsequently produced from the granules in a blown film process, and these were examined for the presence of specks by visual examination under a microscope. The result is shown in the following table.
Example 2 (comparative example)
The same polymer as in Example 1 was subjected to the normal drying process after leaving the reaction vessel, but the process was continued to completion, so that less than 0.001 % by weight of hexane remained in the polymer powder.
The powder which had been dried in this way was introduced into the same extruder as in Example 1 and processed to produce granules under exactly the same conditions. Films having a thickness of 25 μm were produced from the granules on the blown film plant and these were subjected to the same examination as in Example 1.
Table
Figure imgf000005_0001

Claims

Claims:
1. A process for granulating powders of thermoplastic polymers, in which the polymer powder prepared in a polymerization reactor is introduced into an extruder, melted and homogenized in the extruder, then pressed through an extrusion die and granulated, wherein an organic solvent or suspension medium is added to the polymer powder in an amount in the range from 0.001 to 20 % by weight, based on the total weight of polymer powder plus solvent or suspension medium, prior to introduction into the extruder.
2. The process as claimed in claim 1 , wherein the thermoplastic polymers used are polyolefins.
3. The process as claimed in claim 1 or 2, wherein the polymers used are polyolefins having a multimodal molar mass distribution.
4. The process as claimed in any of claims 1 to 3, wherein the addition of solvent or suspension medium is effected by the polymer powder, which is prepared in suspension in the polymerization reactor, not being subjected to complete drying, but rather being partly dried only to such an extent that the desired amount of solvent or suspension medium is established in the range from 0.001 to 20 % by weight in the polymer powder.
5. The process as claimed in any of claims 1 to 3, wherein the addition of solvent or suspension medium is effected by addition to dry polymer powder so that the desired amount of solvent or suspension medium is established in the range from 0.001 to 20 % by weight in the polymer powder.
6. The process as claimed in any of claims 1 to 3, wherein the addition of solvent or suspension medium is effected by introduction into the extruder so that the desired amount of solvent or suspension medium is established in the range from 0.001 to 20 % by weight in the polymer powder.
7. The process as claimed in any of claims 1 to 6, wherein the amount of solvent or suspension medium in the powder of thermoplastic polymer is in the range from 0.0015 to 15 % by weight.
8. The process as claimed in any of claims 1 to 7, wherein the amount of solvent or suspension medium in the powder of thermoplastic polymer is in the range from 0.002 to 10 % by weight.
9. The process as claimed in any of claims 1 to 8, wherein the amount of solvent or suspension medium in the powder of thermoplastic polymer is in the range from 0.01 to 5 % by weight.
10. The process as claimed in any of claims 1 to 9, wherein the organic solvent or suspension medium used is a saturated or cyclic or polycyclic or aromatic hydrocarbon having from 3 to 18, preferably from 4 to 12, carbon atoms.
11. A Method for the increase of the throughput of thermoplastic polymer powder through an extruder during granualtion thereby maintaining the energy consumption, whereby an organic solvent or suspension medium is added to the polymer powder prior to its introduction into the extruder in an amount of from 0.01 to 5 % by weigt, based on the total weigt of the mix of polymer plus organic solvent or suspension medium.
12. A Method for the decrease of energy consumption of an extruder during granualtion of thermoplastic polymer powder thereby maintaining the throughput of polymer through the extruder, whereby an organic solvent or suspension medium is added to the polymer powder prior to its introduction into the extruder in an amount of from 0.01 to 5 % by weigt, based on the total weigt of the mix of polymer plus organic solvent or suspension medium.
PCT/EP2004/007760 2003-07-29 2004-07-14 Process for granulating powders of thermoplastic polymers under improved economic conditions WO2005014253A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US10/566,392 US20060175725A1 (en) 2003-07-29 2004-07-14 Process for granulating powders of thermoplastic polymers under improved economic conditions
JP2006521438A JP2007500088A (en) 2003-07-29 2004-07-14 Process for granulating thermoplastic polymer powders with improved economic conditions
EP04740980A EP1648671A1 (en) 2003-07-29 2004-07-14 Process for granulating powders of thermoplastic polymers under improved economic conditions

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE10334504.3 2003-07-29
DE10334504A DE10334504A1 (en) 2003-07-29 2003-07-29 Granulation of powders of thermoplastic polymer e.g. polyolefin, comprises adding preset amount of organic solvent or suspension medium to polymer powder and melting, homogenizing, pressing and granulating obtained mixture
US49815503P 2003-08-27 2003-08-27
US60/498,155 2003-08-27

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Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2573325C2 (en) * 2010-02-22 2016-01-20 Инеос Коммершиал Сервисиз Юк Лимитед Improved method of polyolefin production

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US3089194A (en) * 1955-10-10 1963-05-14 Phillips Petroleum Co Process and aparatus for treating plastic material
CH417088A (en) * 1957-11-05 1966-07-15 Bemberg Ag Process for the production of shaped structures from linear high polymers of unsaturated hydrocarbons
GB1394983A (en) * 1973-01-26 1975-05-21 Inventa Ag Process and apparatus for the isolation of aromatic polymers
US3902704A (en) * 1973-01-17 1975-09-02 Fujikura Ltd Equipment for preparation of foamed polyolefin insulated wires for telecommunication cables
US4332760A (en) * 1981-03-30 1982-06-01 Atlantic Richfield Company Direct production of elastomer compound from reactor solution
EP0393379A1 (en) * 1989-04-20 1990-10-24 Energy Research Corporation Method and apparatus for continuous formation of fibrillated polymer binder electrode component
EP0450924A2 (en) * 1990-04-02 1991-10-09 Nippon Shokubai Co., Ltd. Method for treating the surface of an absorbent resin
EP0634439A1 (en) * 1993-01-29 1995-01-18 Mitsui Petrochemical Industries, Ltd. Pellet of random cycloolefin copolymer and process for producing the same

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JP2671703B2 (en) * 1992-04-10 1997-10-29 松下電工株式会社 Blending method of high viscosity resin and low viscosity paraffin
JPH06228322A (en) * 1993-01-29 1994-08-16 Mitsui Petrochem Ind Ltd Production of pellet of cycloolefin random copolymer
US5409646A (en) * 1993-09-29 1995-04-25 Union Carbide Chemicals & Plastics Technology Corporation Method for compounding a polymerized alpha-olefin resin
JPH08245798A (en) * 1995-03-08 1996-09-24 Tonen Chem Corp Production of polyolefin solution
SE9603683L (en) * 1996-10-09 1998-02-09 Borealis Polymers Oy Methods for compounding a multimodal polymer composition

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3089194A (en) * 1955-10-10 1963-05-14 Phillips Petroleum Co Process and aparatus for treating plastic material
CH417088A (en) * 1957-11-05 1966-07-15 Bemberg Ag Process for the production of shaped structures from linear high polymers of unsaturated hydrocarbons
US3902704A (en) * 1973-01-17 1975-09-02 Fujikura Ltd Equipment for preparation of foamed polyolefin insulated wires for telecommunication cables
GB1394983A (en) * 1973-01-26 1975-05-21 Inventa Ag Process and apparatus for the isolation of aromatic polymers
US4332760A (en) * 1981-03-30 1982-06-01 Atlantic Richfield Company Direct production of elastomer compound from reactor solution
EP0393379A1 (en) * 1989-04-20 1990-10-24 Energy Research Corporation Method and apparatus for continuous formation of fibrillated polymer binder electrode component
EP0450924A2 (en) * 1990-04-02 1991-10-09 Nippon Shokubai Co., Ltd. Method for treating the surface of an absorbent resin
EP0634439A1 (en) * 1993-01-29 1995-01-18 Mitsui Petrochemical Industries, Ltd. Pellet of random cycloolefin copolymer and process for producing the same

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Publication number Publication date
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JP2007500088A (en) 2007-01-11

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