Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1992-12-28
1994-08-16
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
528486, 528503, 528302, 528481, 528483, 26421111, 26421117, 26421121, C08F 2000
Patent
active
053388089
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of high molecular weight polyester resins from resins having lower molecular weight using a new polyaddition process in the solid state.
Particularly, the invention relates to a process in which the polyester resin is blended in molten state with a new upgrading additive capable of addition reactions with the terminal groups of the polyester resin which is then granulated, and the granulate subjected to crystallization and upgrading reaction in the solid state.
In Applicant's previous pending European patent application EP No. 89119049.8 a solid state upgrading process is described in which the polyester resin is upgraded in the presence of a dianhydride of an aromatic tetracarboxylic acid.
The solid state upgrading process according to the invention comprises the steps of blending the resin with the new upgrading additive, pelletizing the resin, subjecting the granules to crystallization and then to upgrading at temperatures in the range from 100.degree. to 230.degree. C.
The process is preferably carried out in continuous way using continuous crystallizers and reactors where the chips are fed counter currently with a stream of heated gas such as air, nitrogen, carbon dioxide.
The well known solid state polycondensation reactions mainly consist of post-transesterification and esterification reactions, the by-products of which are ethylene glycol and water.
The diffusion of these by-products of the granules is the factor controlling the kinetic of the upgrading process.
In the solid state polyaddition process of the invention in which the polymer chain extension is obtained by addition reactions of the particular additive used, there is no formation of by-products which adversely affect the upgrading process. The process therefore can be carried out at temperatures lower than those up to now used or, then the same upgrading temperature is used, the increase of IV can be obtained with much shorter residence times, for instance, residence time of only 2-5 hours can be used instead of the 15-38 hours needed with the known upgrading processes. The shorter residence times result in an increased productivity of the plant.
The possibility of using lower upgrading temperatures allows to upgrade polyester resins such as the copolyethylenterephthalates containing 10-20% of units deriving from isophthalic acid (COPETs) which have low melting points (lower than 220.degree. C.) and which cannot be upgraded in the solid state using the known solid state polycondensation processes, due to the sticking of the COPETs on the walls of the reactor.
In the case of COPETs the upgrading process can be carried out at temperatures from about 100.degree. C. to 180.degree. C.
The upgrading additive used in the process of the invention is a compound different from a dianhydride of an aromatic tetracarboxylic acid, containing at least two groups capable of addition reactions with the terminal OH and COOH groups of the polyester resin.
By addition reactions it is intended the addition reactions between the terminal groups of the polyester resin and the upgrading additive leading to a linear extension of the polymer chain length.
By upgrading process it is meant the process or the conditions which lead to an increase of the intrinsic viscosity of the polyester resin.
Groups capable of addition reaction under the upgrading conditions comprise the anhydride group, the isocyanate group, the imino group.
A criterion for determining the capability of a substance to give addition reactions with the terminal groups of the polyester resin is the increase of the viscous modulus of at least 20% with respect to the polyester without additive, determined by rheometric measurement at 270.degree. C.
Representative upgrading additives are the dianhydrides of aliphatic and cycloaliphatic tetracarboxylic acids, and of tetrahydrofuran acids. Aromatic or aliphatic diisocyanates or polyisocyanates are also suitable.
The preferred dianhydrides are selected from the group consisting of 1,2,3,4-cyc
REFERENCES:
patent: 3553157 (1971-01-01), Dijkstra et al.
patent: 4176101 (1979-11-01), Leslie et al.
patent: 4234708 (1980-11-01), Edelman et al.
patent: 4880860 (1989-11-01), Blocker
World Patents Index, Derwent Publications Ltd., London, GB, Class A23-G2, AN 41720R & JP B,70 14671 (Tokyo Shibaura Electric Co. Ltd.) Jun. 8, 1970.
Acquah Samuel A.
Kolomayets Andrew G.
M. & G. Ricerche S.p.A.
Manzo Edward D.
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