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Thermoplastic polyolefins with high flowability and excellent surface quality produced by a multistage process

a multi-stage process and polyolefin technology, applied in the field of thermoplastic polyolefins, can solve the problems of tigerstripes or flow marks, common surface quality problems, and inability to completely prevent marks

Inactive Publication Date: 2011-04-14
BOREALIS AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The invention relates to a process for producing reactor grade thermoplastic polyolefins (RTPO) with high flowability and excellent surface quality, especially for automotive applications. The process involves using a special Ziegler-Natta procatalyst containing a trans-esterification product of a lower alcohol and a phthalic ester in combination with a special external donor. The resulting RTPO exhibits minimal flow marks, which are common surface defects in plastic industry. The invention also provides a method for producing RTPO with high MFR values, which are important for injection molding large articles."

Problems solved by technology

Unfortunately the problem of optical irregularity arises during injection molding of such large articles due to the necessary long flow paths of the resin.
Such surface defects, which are also known as “Tigerstripes” or flow marks, are a common problem for surface quality respectively appearance in plastic industry.
It has however been found, that either the occurrence of flow marks could not be entirely prevented, or the physical properties of the polymer compositions were unsatisfactory.
Due to such a degrading step peroxide residues remain in the end polymer leading to a decrease of purity and increase in odour causing components.

Method used

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  • Thermoplastic polyolefins with high flowability and excellent surface quality produced by a multistage process
  • Thermoplastic polyolefins with high flowability and excellent surface quality produced by a multistage process
  • Thermoplastic polyolefins with high flowability and excellent surface quality produced by a multistage process

Examples

Experimental program
Comparison scheme
Effect test

example 1

Preparation of Base Resin According to the Invention

The base resin was produced in a plant having a prepolymerization reactor, a loop reactor and two fluid bed gas-reactors connected in series. The catalyst used in the polymerization was prepared according to WO 92 / 19653 with DOP as dialkylphthalat of the formula (I) and ethanol as alcohol, the cocatalyst was Triethylaluminium (TEA) and as an external donor (D) diethylamino triethoxy silane was used.

After a first pre-polymerisation step the catalyst system was fed to the slurry reactor, where the polymerisation of the polypropylene homopolymer matrix phase was performed. The slurry phase loop reactor was then followed by a first gas phase reactor in series, in which a first elastomeric rubber disperse phase was produced by copolymerisation of propylene with ethylene comonomer. The polymerisation temperature in the slurry phase loop reactor was 62° C., whereas the temperature in the first gas phase reactor was 80° C. After transfer t...

example 2

In order to show the advantageousness of the catalyst system used according to inventive Example 1 in comparison to the catalyst system used according to EP 1 600 480 (ZN104 (commercially available from LyondellBasell), triethylaluminium as cocatalyst and dicyclopentyldimethoxysilane as external donor) regarding fines produced during production of the polypropylene matrix, several polypropylene matrices with different MFR were produced in the above described plant set up and the amount of fines produced in the loop reactor were determined by sieving the polymer powder obtained from the loop reactor.

The powder passing a 0.180 mm screen was considered as fines.

TABLE 1wt % of finesMFRpp-matrixCat. of Example 1 / [g / 10 min]ZN104 / DCDMSDEATES502.5 wt %0.9 wt %1005.4 wt %1.2 wt %250n.a.1.4 wt %DCDMS dicyclopentyl dimethoxy silaneDEATES diethylamino triethoxy silanen.a. not applicable

With the combination of ZN104 / DCDMS it was not possible to produce a polypropylene matrix with an MFR of above...

example 3

Testing of the Base Resin

The base resin (RTPO) was initially obtained in powder form.

The resin together with 10 wt % Tital15 (talc from Ankerport) and 0.1% NA11 as well as 10 wt % of EG8200 (elastomer Engage®8200 from DuPont Dow Elastomers) were pelletized by feeding the blend to a Prism 24twin-screw extruder (Prism Ltd., Staffordshire, UK). The polymer was extruded through a strand die, cooled and chopped to form pellets.

TABLE 2Properties of compounded RTPOMFR 230° C. / 2.16 kg[g / 10′]29.2Flexural Modulus [MPa]1281Tensile Modulus [MPa]1229Impact - Charpy NIS(23° C.) [kJ / m2]17.5Impact - Charpy NIS(0° C.) [kJ / m2]8.2Impact - Charpy NIS(−20° C.) [kJ / m2]5.5Shrinkage longitudinal [%]0.58Shrinkage lateral [%]0.9

Surface Quality (Tigerskin)

Plaques of a dimension of 210×189×3 mm3, grained with VW grain K50, were produced under following conditions:

Melt temperature: 240° C.

Mold temperature: 30° C.

Dynamic pressure: 10 bar hydraulic

The filmgate over the whole width had a thickness of 1.4 mm.

With t...

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Abstract

Reactor grade thermoplastic polyolefins with high flowability and excellent surface quality comprising (A) 40-90 wt % of a propylene homo- or copolymer matrix with an MFR in accordance with ISO 1 133 (230° C., 2.16 kg load) of >200 g / 10 min and (B) 2-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of ≦2.8 dl / g and an ethylene content of >50 to 80 wt % and (C) 8-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 3.0-6.5 dl / g and an propylene content of 50 to 80 wt %, the reactor grade thermoplastic polyolefins being obtainable by a multistage polymerization process with at least 3 polymerization steps in the presence of a catalyst system comprising (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester and (ii) an organometallic cocatalyst and (iii) external donor represented by formula (I) Si(OCH2CH3)3(NR1R2) wherein R1 and R2 can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms, as well as the use of these reactor grade thermoplastic polyolefins and molded articles produced from them.

Description

This invention is in the field of thermoplastic polyolefins and more specifically reactor grade thermoplastic polyolefins (RTPO).The invention is further directed to RTPOs having high flowability and excellent surface quality, when molded into articles of manufacture, especially for automotive applications, a process for producing them and their use.Furthermore the invention is related to the use of a special Ziegler-Natta procatalyst, which contains a trans-esterification product of a lower alcohol and a phthalic ester in combination with a special external donor for the production of RTPOs with high flowability and excellent surface quality.STATE OF THE ART Thermoplastic polyolefins (TPOs), which typically comprise polypropylene and an elastomer, have many desirable properties, e.g. lightweight, durability, low costs, etc., that make them an attractive material for the construction of many interior and exterior automotive parts. There are two types of TPOs which essentially differ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C08L23/16B01J31/12
CPCC08F110/02C08F210/06C08F210/16C08F297/08C08F297/083C08L23/10C08L2205/02C08L23/16C08L23/12C08F2/001C08F4/6465C08L2666/06C08L2666/02C08F2500/12C08F2500/17C08F2500/21Y02P20/52
Inventor GREIN, CHRISTELLEBERNREITNER, KLAUS
Owner BOREALIS AG
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