Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-04-09
1998-09-15
Short, Patricia A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525177, 525184, 525420, 525424, 525426, 525437, 525438, 525439, 525440, 525444, 525445, 525462, 525463, 525467, 525468, 521 48, 521 498, C08G 6380, C08G 6420, C08G 6906
Patent
active
058079327
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for increasing the molecular weight of polycondensates and to the polycondensates obtainable by the process.
Polycondensates, such as polyamides, polyesters and polycarbonates, are important engineering plastics with a wide variety of potential uses, for example in the form of films, bottles, fibres and injection mouldings. It is common to these polymers that they are prepared by polycondensation reactions. For technical or kinetic reasons, the synthesis of these polymers frequently does not give high molecular weights. Polymers having high molecular weights are therefore prepared by condensation in the solid phase.
Damage to such polycondensates during processing and use predominantly results, owing to chain cleavage, 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 polyamides, polyesters and polycarbonates and their production waste, for example from fibre production and injection moulding, is frequently only possible to a restricted extent without aftertreatment owing to the reduced molecular weight.
An improvement in the material properties of used or thermally or hydrolytically predamaged polycondensates is possible in principle. For Fakirov, Kunststoffe 74, 218 (1984) and R. E. Gruitzner et al., Kunststoffe 82, 284 (1992)!. However, this known method is protracted, and in addition is sensitive to impurities, as may be present in used material.
Furthermore, EP-0 410 230 has proposed carrying out the solid-phase condensation of polyamides using phosphoric acid, phosphorous acid or phosphonous acid as catalyst.
F. Mitterhofer has described studies using a diphosphonite as processing stabilizer in polymer recyclates (C.A. 91, 124534).
EP-A-0 090 915 describes a process for the condensation of poly(alkylene terephthalate) in the solid phase in the presence of esters of phosphorous acid, for example triphenyl phosphite, at from 25.degree. to 65.degree. C. below the melting point of the poly(alkylene terephthalate) while passing a stream of inert gas through the mixture.
The present invention therefore had the object of developing a process for post-condensation in the solid phase which allows an increase in the molecular weight of polycondensate, such as polyesters, polyamides and polycarbonates, and of corresponding copolymers and blends in a relatively short time and/or improves the properties of the polycondensate.
The invention thus relates to a process for increasing the molecular weight of polycondensates, which comprises heating a polycondensate in the temperature range below the melting point and above the glass transition temperature in the solid phase of the polymer with addition of at least one sterically hindered hydroxyphenylalkylphosphonic ester or monoester.
This increase in molecular weight results in an improvement in the properties of the polycondensates, which becomes evident, for example, in the injection-moulding sector, extrusion sector and in particular in recyclates. With the aid of the novel process, an increase in molecular weight can be achieved, in particular, in polycondensate recyclates from the collection of used industrial parts, for example from automobile and electrical applications. This allows recyclates to be re-used for high-quality applications, for example as high-performance fibres, injection mouldings, extrusion applications or foams. Such recyclates also originate, for example, from industrial or domestic collections of valuable materials, from production waste, for example from fibre production and trimmings, or return obligations, for example collections of PET drinks bottles.
The invention also relates to a process for increasing the molecular weight of polycondensates, which comprises heating a polycondensate in the temperature range below the melting point and above the glass transition temperature in the solid phase of the polymer with addition of at least one sterically hind
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patent: 4434276 (1984-02-01), Horlbeck
patent: 5250619 (1993-10-01), Heinz
patent: 5266659 (1993-11-01), Sivaram
patent: 5362783 (1994-11-01), Eiffler
patent: 5496920 (1996-03-01), Pfaendner
Herbst Heinz
Hoffmann Kurt
Pfaendner Rudolf
Ciba Specialty Chemicals Corporation
Crichton David R.
Hall Luther A. R.
Short Patricia A.
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