Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-09-11
2001-08-14
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
Reexamination Certificate
active
06274696
ABSTRACT:
The invention relates to a process for the continuous preparation of segmented elastomer polyester copolymers. Such processes are for example described in the Encyclopedia of Polymer Science and Technology, Vol. 12, pp. 84-85 (1986), and the references therein and they show a close correspondence to the continuous processes for producing polyethylene terephthalate and polybutylene teraphthalate, PET and PBT respectively. These processes essentially comprise a 2-step process, in which, in the first process step, the monomers, in this case the diols and the dicarboxylic acids or esters thereof, required for the formation of the hard and soft segments of the elastomer copolyester are mixed with optionally catalyst, additives, for example stabilisers, and optionally branching agents, for example a trifunctional carboxylic acid or alcohol or a precursor thereof, for example trimellitic acid anhydride, and heated to a temperature at which, through primarily a transesterification reaction or an esterification reaction, a low-molecular copolyester is formed, this prepolymerisation step being followed by a melt polycondensation, often referred to as a transesterification, in which the diol required for the formation of the hard segments, which is released in the polycondensation, is discharged at reduced pressure.
The first reaction is preferably carried out in a vertical polymerisation column, in which the pressure gradually decreases and the temperature increases, and the second reaction in a horizontal thin film finisher, a large area being created to enable the discharge of the alkylene glycol released. The continuous production method presents economic advantages in the case of the production of a single type of segmented copolyester. But in the case of the production of higher molecular types, the residence times required become too long and the advantage of the large scale cannot be exploited. In addition, switching to a different type of product is time-consuming owing to the size of the installations.
For various reasons it is advantageous if in the first reaction step use is made not of the monomers required for the hard and soft segments, but of an oligomer of the segments that already has approximately the desired length of the segment. In some cases, in particular in the case of segmented copolyesters, it is advisable to introduce the polymer yielding the hard segments into the transesterification reaction in a higher molecular weight. The soft segments are often already present in the form of a polyether polyol or a polyester polyol and are used as such.
But the preparation of the oligomers required for the hard segments demands an extra synthesis step, which further complicates the process and makes a continuous process even more inflexible and difficult to control. An example of such a process is given in R.W.M. van Berkel et al. in Developments in polyether-ester and polyester-ester segmented copolymers, Chapter. 7, of Developments in block copolymers, Vol. I, Ed. I.Goodman, Applied Science, London (1982), p. 266.
The inventors have now found a solution to the problem described above and have developed a continuous process that shows substantial flexibility with respect to the number of types of segmented copolyester and the production capacity thereof, in which an oligomer or polymer for the hard segments is added to the transesterification reaction.
The continuous process according to the invention for the production of segmented elastomer polyester copolymers composed of hard and soft segments, comprising a first reaction step in which, in a transesterification or esterification reaction, a segmented copolyester with a low molecular weight is formed from oligomer or polymer fed to the first reactor, and which consists of units corresponding to the units of which the hard segments are composed, and polymer glycols yielding the units for the soft segments, and the low-molecular segmented polyester copolymer obtained in the first reaction step is in a second reaction step condensed to a desired degree of polymerisation, characterised in that the oligomer or polymer compound yielding the hard segments that is fed to the first reaction step has been obtained as part of a product stream in the synthesis of a polyester consisting entirely of ester units that form the hard segments of the segmented elastomer polyester copolymer, the remaining part of the product stream of the polyester yielding the hard segments being further polymerised to a desired degree of polymerisation in at least one further process step.
REFERENCES:
patent: 4772652 (1988-09-01), Yoshifumi et al.
Bonte Geert I. V.
Hagen Rainer
Schulz Van Endert Eike
Boykin Terressa M.
DSM N.V.
Pillsbury & Winthrop LLP
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