Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2000-10-19
2001-07-24
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S488000, C528S503000, C524S123000, C264S211210, C264S211230
Reexamination Certificate
active
06265533
ABSTRACT:
The present invention relates to a process for increasing the molecular weight of polyesters and to the polyesters obtainable by said process.
Polyesters are important engineering plastics having a wide range of possible uses, for example in the form of films, sheets, bottles, fibres and injection moulded articles. They are produced by polycondensation reactions. For technical, thermodynamic or kinetic reasons, the high molecular weights necessary for some applications are frequently not available during synthesis.
Because of chain cleavages, the thermal and photochemical damage through processing and use results mainly in polymer fragments containing functional terminal groups. Since the mechanical and physical properties are crucially dependent on the molecular weight of the polymer, high quality recycling of used polyesters from production wastes, e.g. from fibre production and from the injection moulding sector, is often only possible to a limited extent owing to the reduced molecular weight.
It is, in principle, known to enhance the material properties of used polycondensates or of polycondensates predamaged by heat or hydrolysis. These polycondensates can, for example, be subjected to postcondensation in the solid state [S. Fakirov, Kunststoffe 74, 218 (1984) and R. E. Grüitzner et al., Kunststoffe 82, 284 (1992)]. However, this known method is lengthy and is, moreover, highly sensitive to impurities such as may be present in waste material.
EP-A-0090915 describes a process for condensing poly(alkylene terephthalate) in the solid phase, processing being carried out in the presence of, for example, triphenylphosphite, at a temperature from 25 to 65° C. below the melting point of the poly(alkylene terephthalate) and while passing through an inert gas stream.
WO 94/24188 and WO 95/23176 disclose that the molecular weight of polyesters can be increased by heating a hydroxyphenylalkylphosphonic acid ester or half-ester and a diepoxide or a tetracarboxylic anhydride together with the polyester to above the melting point. It is thus necessary to add at least two components to the polymer in order to achieve the desired effect.
Surprisingly, it has been found that the application of certain processing/extrusion conditions makes it possible to increase the molecular weight of polyesters within a relatively short time without predrying, directly in the processing apparatus in the melt and solely by addition of specific phosphonates. Polyesters having a higher molecular weight are obtained in simple manner.
This increase in molecular weight effects an enhancement of the properties of the poly-esters, for example in the injection moulding and extrusion sectors and, in particular, in the case of recyclates. Using the process of this invention, the molecular weight can be increased in particular in the case of polyester recyclates collected from used technical parts, such as from automotive and electrical applications and from used bottle collections. Recyclates can thus be recycled in high-quality, e.g. in the form of high performance fibre, injection moulded articles, extrusion applications or foams. Such recyclates originate also, for example, from industrial or domestic useful material collections, from production wastes, such as from fibre production, from trimmings or from obligatory returnables, such as collections of PET drinks bottles.
This invention relates to a process for increasing the molecular weight of polyesters, copolyesters or polyester blends by adding one or more than one phosphonate to the processing apparatus and fusing the mixture to above the melting point, in which process the processing apparatus is a single-screw extruder, twin-screw extruder, planetary-gear extruder, ring extruder or Ko-kneader having at least one vent zone to which underpressure is applied.
In the case of copolyesters, the process can be carried out independently of the statistics of the comonomer composition.
The polyesters, copolyesters or their recyclates can be processed without any predrying.
A preferred process is that which comprises applying an underpressure of less than 250 mbar, particularly preferably of less than 100 mbar and, very particularly preferably, of less than 50 mbar to the vent zone.
Another preferred process is that wherein the processing apparatus is a closely intermeshing twin-screw extruder or a ring extruder with screws rotating in the same direction and with a feed section, a transition section, at least one vent zone and a metering zone, the vent zone being separated from the transition section or from a further vent zone by a fusing plug.
This separation via a fusing plug can be effected, for example, by a combination of a kneading and a return screw element.
The processing apparatus preferably has 1-4 vent zones, particularly preferably 1-3.
The processing stretch is preferably 1 to 60 screw diameters, particularly preferably 35 to 48 screw diameters.
The screw revolution rate is preferably from 25 to 1200, particularly preferably from 50 to 250 revolutions per minute.
The maximum throughput is the result of screw diameter, screw speed and drive power. The process of this invention can also be carried out at a throughput lower than the maximum by varying these parameters and/or by adding metering units.
Suitable extruders and kneaders are described, inter alia, in Handbuch der Kunststoffextrusion, Vol. I, editors F. Hensen, W. Knappe and H. Potente, 1989, pages 3-7.
The maximum melt temperature is preferably in the range from 1800 to 320° C., particularly preferably from 220 to 300° C. This temperature depends on the polyesters, copolyesters or polyester blends used. In the case of, for example, polyethylene therephthalate (PET) it is in the range from 250 to 300° C., in the case of polybutylene therephthalate (PBT) in the range from 220 to 2700 C, in the case of polyethylene naphthylate (PEN) in the range from 260 to 300° C. and in the case of polytrimethylene terephthalate (PTT) in the range from 220 to 270° C.
Polyester, copolyester or polyester blend recyclates are preferred.
The polyester, i.e. virgin polyester as well as polyester recyclate, can be homo- or copolyesters which are composed of aliphatic, cycloaliphatic or aromatic dicarboxylic acids and diols or hydroxycarboxylic acids.
The polyesters can be prepared both by direct esterification (PTA process) and by transesterification (DMT process). Any known catalyst systems can be used for the preparation.
The aliphatic dicarboxylic acids can contain 2 to 40 carbon atoms, the cycloaliphatic dicarboxylic acids 6 to 10 carbon atoms, the aromatic dicarboxylic acids 8 to 14 carbon atoms, the aliphatic hydroxycarboxylic acids 2 to 12 carbon atoms and the aromatic and cycloaliphatic hydroxycarboxylic acids 7 to 14 carbon atoms.
The aliphatic diols can contain 2 to 12 carbon atoms, the cycloaliphatic diols 5 to 8 carbon atoms and the aromatic diols 6 to 16 carbon atoms.
Polyoxyalkylene glycols having a molecular weight from 150 to 40000 can also be used.
Aromatic diols are those, wherein two hydroxyl groups are bound to one or to different aromatic hydrocarboxylic radicals.
It is also possible that the polyesters are branched with small amounts, e.g. 0.1 to 3 mol %, based on the dicarboxylic acids present, of more than difunctional monomers (e.g. pentaerythritol, trimellitic acid, 1,3,5-tri(hydroxyphenyl)benzene, 2,4-dihydroxybenzoic acid or 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)propane).
Suitable dicarboxylic acids are linear and branched saturated aliphatic dicarboxylic acids, aromatic dicarboxylic acids and cycloaliphatic dicarboxylic acids.
Suitable aliphatic dicarboxylic acids are those containing 2 to 40 carbon atoms, for example oxalic acid, malonic acid, dimethylmalonic acid, succinic acid, pimelic acid, adipic acid, trimethyladipic acid, sebacic acid, azelaic acid and dimeric acids (dimerisation products of unsaturated aliphatic carboxylic acids such as oleic acid), alkylated malonic and succinic acids, such as octadecylsuccinic acid.
Suitable cycloaliphatic dicarboxylic acids are:
Andernach Roland
Herbst Heinz
Hoffmann Kurt
Pfaendner Rudolf
Regel Karin
Acquah Samuel A.
Ciba Specialty Chemicals Corporation
Stevenson Tyler A.
LandOfFree
Increasing the molecular weight of polyesters does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Increasing the molecular weight of polyesters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Increasing the molecular weight of polyesters will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2485866