Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2000-09-14
2001-05-15
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...
C528S272000, C528S308000, C528S308600, C528S503000, C526S065000
Reexamination Certificate
active
06232435
ABSTRACT:
The invention relates to an improved process for preparing polyalkylene arylates which have a high carboxyl end group content.
The invention also relates to the polyalkylene arylates obtainable by the novel process, and also to mixtures of these with polycarbonates and/or with polyamides, and to the use of molding compositions of this type for producing moldings, and the resultant moldings.
Processes for preparing polyesters are known, inter alia, from DE-A 25 14 116, EP-A 815 158 and GB-A 2 184 129. The starting materials, such as diols and acids and/or esters of these, are generally esterified or transesterified in the presence of catalysts, followed by one or more polycondensation steps under reduced or modified pressure. The polyesters obtained from most of the known processes have a low carboxyl end group content.
Polybutylene terephthalate, for example, has very low moisture absorption and high dimensional stability, together with good solvent resistance. A disadvantage, however, is its limited toughness, for example compared with polycarbonates or with polyamides.
Blends of these polymers with PBT have the combination of properties desired for a number of applications, where particular value is placed on good mechanical properties, such as, for example, high toughness.
In the prior art, high-molecular-weight polyester blends are prepared by a complicated compounding process, where the polyester is held above the melting point for long residence times and has to be mixed in this phase with the other component of the blend.
Adequate mixing of the blend components is a very important factor here. The formation of block copolymers, utilizing reactive groups on the polymer matrix, can improve phase compatibility.
When preparing a polyester blend of this type care must also be taken that the chemical properties of one polymer do not cause degradation of the other blend component.
In the prior art, polyester blends are prepared by mixing polymers using kneading machinery (single- or twin-shaft, co- or counter-rotating, intermeshing or non-intermeshing design). This additional process step causes thermal degradation of the polymer during melting and mixing.
For preparing a blend it would be desirable to use a polyester having a very high carboxyl end group content, thus promoting compatibilization via reactive coupling and very substantially preventing degradation of the other component of the blend.
It is an object of the present invention to provide a cost-effective process for obtaining polyalkylene arylates with a very high carboxyl end group content.
We have found that this object is achieved by means of a process for preparing polyalkylene arylates by esterifying or transesterifying an aromatic dicarboxylic acid or its esters or ester-forming derivatives with a molar excess of an aliphatic dihydroxy compound and polycondensing the resultant esterification or transesterification product, which comprises polycondensing the prepolymer with a viscosity number (VN) of <30 ml/g in the presence of an oxygen-containing gas.
Preferred embodiments are given in the subclaims.
We have also found that the polyalkylene arylates obtainable by the novel process, when combined with polycarbonates and/or with polyamides, give improved phase compatibility and therefore better mechanical properties. In addition, the molecular weight of the other component of the blend is very substantially unimpaired during the preparation.
Polyalkylene arylates are known per se and are described in the literature. Their main chain contains an aromatic ring which derives from the aromatic dicarboxylic acid. The aromatic ring may also be substituted, e.g. by halogen, such as chlorine and bromine, or by C
1
-C
4
-alkyl, such as methyl, ethyl, isopropyl, n-propyl, n-butyl, isobutyl or tert-butyl.
Preferred dicarboxylic acids which may be mentioned are 2,6-naphthalenedicarboxylic acid and terephthalic acid, and mixtures of these. Up to 30 mol %, preferably not more than 10 mol %, of the aromatic dicarboxylic acids may be replaced by aliphatic or cycloaliphatic dicarboxylic acids, such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and cyclohexanedicarboxylic acids.
Among the aliphatic dihydroxy compounds, preference is given to diols having from 2 to 6 carbon atoms, in particular 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 5-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and neopentylglycol, and mixtures of these.
Particularly preferred polyesters (A) which may be mentioned are polyalkylene terephthalates, which derive from alkanediols having from 2 to 10 carbon atoms, preferably from 2 to 6 carbon atoms. Among these, particular preference is given to polyethylene terephthlate and polybutylene terepthalate, and mixtures of these.
Other preferred polymers are polyethylene terephthalates and polybutylene terephthalates which contain, as other monomer units, up to 1% by weight, preferably up to 0.75% by weight, of 1,6-hexanediol and/or 5-methyl-1,5-pentanediol.
The preparation is preferably continuous and based on DE-A 44 01 055, by
a) in a first step, esterifying or transesterifying an aromatic dicarboxylic acid or its esters or ester-forming derivatives, with a molar excess of a dihydroxy compound,
b) in a second step, precondensing the transesterification or esterification product obtained in a), and
c) in a third step, polycondensing the product obtainable from b) to the desired viscosity number,
where steps a) and b) of the process are carried out in at least two temperature zones.
Step a) of the process is termed a transesterification or esterification reaction. This is carried out in at least two, and preferably at least three, temperature zones. The temperature here of each zone should be higher than that of the preceding zone by from 1 to 40° C., preferably from 2 to 30° C. and in particular from 5 to 10° C. The temperature range for the entire esterification reaction is generally (depending on the starting material) from 165 to 260° C., preferably from 170 to 250° C. and in particular from 180 to 240° C., and the pressure is generally from 1 to 10 bar, preferably from 1 to 4 bar and in particular from 1 to 2 bar.
Step a) of the process preferably operates in at least two temperature zones with very substantially identical pressure conditions in the individual zones. The technical requirements, such as apparatus (e.g. in the form of reactor cascades) for creating different temperature zones are known to the person skilled in the art, and therefore need not be described here in greater detail.
The starting materials, such as diols and acids, have already been described above.
The reaction is usually carried out with a molar excess of diol, in order to exert the desired influence on the ester equilibrium. The molar ratios of dicarboxylic acid and/or dicarboxylic ester to diol are usually from 1:1.1 to 1:3.5, preferably from 1:1.2 to 1:2.2. It is very particularly preferable for the molar ratios of dicarboxylic acid to diol to be from 1:1.5 to 1:2, and of diester to diol to be 1:1.25 to 1:1.5.
However, it is also possible to carry out the ester reaction with a small excess of diol in the first zone and correspondingly to add further amounts of diol in the other temperature zones. In the preferred embodiment of the novel process with three temperature zones, the entire amount of diol is divided over 3 zones in the following percentages: from 60 to 85 (1), from 10 to 25 (2) and from 5 to 15 (3), and preferably from 70 to 80 (1), from 10 to 20 (2), and from 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 in particular from 160 to 220 min, and the residence time for the first zone is from 100 to 190 min, preferably from 110 to 150 min, and for the second zone from 65 to 140 min, preferably from 65 to 110 min. For the preferred embodiment with three zones, the residence time in the 3rd zone is from 15 to 45 min, preferably from 15 to 30 min, with the residence times
Braune Peter
Heel Helmut
Heitz Thomas
Klatt Martin
Acquah Samuel A.
BASF - Aktiengesellschaft
Keil & Weinkauf
LandOfFree
Polyalkylene arylates containing a high proportion of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyalkylene arylates containing a high proportion of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyalkylene arylates containing a high proportion of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2452328