Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-09-07
2001-08-28
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S322000, C524S444000, C524S451000, C528S274000
Reexamination Certificate
active
06281283
ABSTRACT:
DESCRIPTION
The invention relates to an improved process for the continuous preparation of polyalkylene arylates containing lubricants and nucleating agents.
Polyalkylene arylates are characterized by low water absorption and good dimensional stability and also good resistance to solvents.
A disadvantageous property thereof is the low velocity of crystallization, which gives problems when processing high-molecular or very thin-walled injection mouldings.
By the addition of a nucleating agent—optionally in combination with other additives—the velocity of crystallization can be improved, as is disclosed in EP-A 255,735, U.S. Pat. No. 4,448,913, JP-A 62/275152 and JP-A 58/219255.
Nucleated polyesters are prepared in the prior art by incorporating the additives in an extruder for example. This additional processing step is cost-intensive and also causes thermal damage to the polymer. As regards their mechanical properties, particularly multiaxial toughness and colour fastness (yellowing) of the known molding materials are unsatisfactory.
It is thus an object of the present invention to provide an improved continuous process for the preparation of polyalkylene arylates containing lubricants and nucleating agents, which produces polyesters having improved properties in a more economical manner and with extremely little thermal damage to the polymer. In particular, it is desired to improve their mechanical properties such as multiaxial toughness and their color constancy, better processing being achieved due to fast crystallization.
Surprisingly, we have found that this object can be achieved by esterifying or transesterifying an aromatic dicarboxylic acid or esters or ester-forming derivatives thereof with a molar excess of an aliphatic dihydroxy compound and polycondensing the (trans)esterification product obtained, wherein, when the viscosity number has reached at least 80% of the desired value, there are added lubricants B) and nucleating agents C) to the polymer melt and condensation of the melt is optionally continued, the melt then being discharged, cooled and granulated.
Preferred embodiments are disclosed in the sub-claims.
The component A) present in the molding compositions produced by the process of the present invention comprises from 95 to 99.9 wt %, preferably from 96 to 99.8 wt % and more preferably from 98 to 99.5 wt % of a thermoplastic polyalkylene arylate.
Such polyalkylene arylates are obtained by esterifying or transesterifying an aromatic dicarboxylic acid or esters or ester-forming derivatives thereof with a molar excess of an aliphatic dihydroxy compound and polycondensing the (trans)esterification product obtained in known manner.
Preferred dicarboxylic acids are 2,6-naphthalenedioic acid and terephthalic acid or mixtures thereof. Up to 30 mol %, preferably not more as 10 mol %, of the aromatic dicarboxylic acids can be replaced by aliphatic or cycloaliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and cyclohexanedioic acids.
The preferred aliphatic dihydroxy compounds are diols having from 2 to 6 carbon atoms, particularly ethane-1,2-diol, propane-1,3-diol, butane-1,4-diol, hexane-1,6-diol, hexane-1,4-diol, 2-methylpentane-1,5-diol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol and neopentyl glycol or mixtures thereof.
Particularly preferred polyesters (A) are polyalkylene terephthalates derived from alkanediols containing from 2 to 10 carbon atom, preferably from 2 to 6 carbon atoms. Of these, polyethylene terephthalate and polybutylene terephthalate or mixtures thereof are particularly preferred.
Other preferred compounds are polyethylene terephthalates and polybutylene terephthalates containing up to 1 wt %, based on A), and preferably up to 0,75 wt %, of hexane-1,6-diol and/or 2-methylpentane-1,5-diol as additional monomer units.
Such polyalkylene terephthalates are known per se and are described in the literature. They contain an aromatic ring in the main chain, which comes from the aromatic dicarboxylic. The aromatic ring may also be substituted, eg by halogen such as chlorine and 45 bromine or by C
1
-C
4
alkyl such as methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl or tert-butyl.
In particular, preference is given to polyesters whose content of carboxylene end groups is up to 50 meq/kg, preferably up to 30 meq/kg and more preferably up to 27 meq/kg of polyester. Such polyesters can be prepared for example by the process of DE-A 4,401,055. The content of carboxylene end groups is usually determined by a titration method (eg potentiometry).
The preferred method of preparation is in accordance with DE-A 4,401,055 and is carried out continuously by
a) esterifying or transesterifying, in a first step, an aromatic dicarboxylic acid or esters or ester-forming derivatives thereof with a molar excess of a dihydroxy compound,
b) precondensing, in a second step, the (trans)esterification product obtained under a) and
c) polycondensing, in a third step, the product obtained in b) to the desired viscosity number, step a) and step b) of the process being carried out in at least two temperature zones.
Step a) of the process is referred to as the “(trans)esterification reaction”. This is carried out in at least two, preferably at least three temperature zones. The temperature in a succeeding zone should be 1-40° C., preferably 2-30° C. and more preferably 5-10° C. higher than the temperature of the preceding zone. The temperature range for the entire esterification reaction is generally (depending on the starting material) from 165° to 260° C., preferably from 1700 to 250° C. and more preferably from 1800 to 240° C., the pressure generally being from 1 to 10 bar, preferably from 1 to 4 bar and more preferably from 1 to 2 bar.
Preferably step a) of the process is carried out in at least two temperature zones under pressure conditions in the individual zones which are substantially identical. The industrial requirements in respect of for example equipment (eg in the form of cascades of boilers) for the creation of different temperature zones are known to the person skilled in the art, for which reason it is not necessary to mention further details here.
The starting materials, such as diols and acids, have already been described above (component A).
To effect conversion, use is usually made of a molar excess of diol in order to influence the ester balance to the desired degree. The molar ratios of dicarboxylic acid or alkyl dicarbonate to diol are usually from 1:1.1 to 1:3.5 and preferably from 1:1.2 to 1:2.2. Molar ratios of dicarboxylic acid to diol of from 1:1.5 to 1:2. or of diester to diol of from 1:1.2 to 1.5 are very much preferred.
Alternatively, the ester reaction can be carried out in the first zone using a lower excess of diol while further amounts of diol are fed to the other temperature zones. In the preferred embodiment of the process of the invention comprising three temperature zones the entire diol is distributed over 3 zones as follows (in percentages): 60 to 85 (1), 10 to 25 (2) and 5 to 15 (3), preferably 70 to 80 (1), 10 to 20 (2), 5 to 10 (3).
The residence times for the entire step a) are from 140 to 300 min, preferably from 150 to 260 min and more preferably from 160 to 220 min, the residence time in the first zone being from 100 to 190 min, preferably from 110 to 150 min and in the second zone from 65 to 140 min, preferably from 65 to 110 min. For the preferred embodiment comprising 3 zones the residence time in the third zone is from 15 to 45 min, preferably from 15 to 30 min, whilst the residence times in the second zone is reduced accordingly and in the first zone is retained as stated above.
In the preferred embodiment of the process of the invention the residence times decrease from the first zone to the third zone preferably in a ratio of 6:3:1.
In a particularly preferred embodiment of the process, there is added to the dihydroxy compound, prior to step a), first a catalyst and then an alkali metal compound or alkaline earth metal compound.
Preferred catalysts are titanium comp
Heitz Thomas
Klatt Martin
BASF - Aktiengesellschaft
Keil & Weinkauf
Yoon Tae H.
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