Highly branched polycondensates

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof

Reexamination Certificate

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C528S272000

Type

Reexamination Certificate

Status

active

Patent number

06528612

Description

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to highly branched polycondensates and to a process for producing them.
BACKGROUND OF THE INVENTION
Branched polycondensates have proven to be particularly suitable for certain applications. Thus, it is known that branched polycarbonates are distinguished by much higher pseudoplasticity than linear polycarbonates; this means that the apparent melt viscosity decreases as the shear rate increases. Polycarbonates with better pseudoplasticity or pronounced non-Newtonian flow behaviour have good processing properties during both extrusion and injection moulding.
Low-molecular branching agents are used for producing branched polycarbonates. These include, for example, phloroglucinol (DE 15 70 533 A), isatinbiscresol (DE 25 00 092 A), trimellitic acid (EP 140 341 A) and tris-1,1,1-(hydroxyphenyl)-ethane (EP 708 143 A). A drawback of the branched polycarbonates produced using low molecular branching agents is a relatively broad molecular weight distribution, i.e. a high degree of dispersion, and the fact that the molecular weight achieved is not sufficiently high or the branched polycarbonates tend to crosslink. This adversely affects the flow behaviour and therefore the processing properties of the polycarbonates. The transparency of the branched polycarbonates is also impaired by the formation of gel bodies.
For producing branched polycarbonates, it is basically known to use polymers as branching agents. However, this procedure is not usually recommended as the use of polymeric branching agents often leads to increased formation of gel bodies and the pseudoplasticity in the resultant polymer is relatively weakly pronounced because the polymeric branching agents have a high melt viscosity and are usually poorly soluble in other polymers. A further drawback of polymeric branching agents is that a large proportion of the chemical functionalities resides inside the statistical coil and can only be accessed for chemical reactions with difficulty or with a prolonged reaction time.
SUMMARY OF THE INVENTION
It is the object of the invention to prepare branched thermoplastic polycondensates with pronounced pseudoplasticity, which do not have the aforementioned drawbacks.
This object is achieved by highly branched polycondensates which can be obtained by polycondensation of monomers capable of polycondensation in the presence of branching agents, wherein the branching agents are polymers, oligomers consisting of 2 to 100 monomer units or dendritic polymers and are made up of monomers of the general formulae A—R—B
x
or A
x
—R—B, wherein
A represents a COX group and X is hydroxyl, halogen, preferably chlorine, alkoxy or aralkoxy, each having 1 to 30, preferably 1 to 20 or 1 to 8 carbon atoms and wherein
B represents an OY group and Y is hydrogen, trialkyl silyl, alkyl or acyl, each having 1 to 30, preferably 1 to 20 or 1 to 8 carbon atoms or wherein B is an amino group, an ammonium halide, preferably ammonium chloride, or an alkyl carbamate having 1 to 8 carbon atoms, preferably t-butylcarbamate,
R is an organic aromatic, aliphatic-aromatic or aliphatic radical containing 1 to 25 carbon atoms and x≧2.
These polycondensates are, for example, polycarbonates and copolycarbonates, polyesters, polyamides, polyesteramides and copolycondensates containing at least two of the aforementioned polymer units.
Polycarbonates and copolycarbonates according to the invention are highly transparent, have a very light inherent colour and are distinguished by excellent stability of the melt and pronounced pseudoplasticity. The polycarbonates according to the invention obtained by using dendritic macromolecular branching agents preferably contain less than 600 ppm of terminal OH groups. The highly branched polycarbonates have average molecular weights {overscore (M)}
w
of 8,000 to 80,000, preferably 12,000 to 40,000, which are determined by measuring the relative solution viscosity in dichloromethane or in mixtures of identical quantities by weight of phenol and o-dichlorobenzene, the measuring system being calibrated by light scattering.
Dendritic polymers in the sense of the invention include so-called highly branched polymers and so-called dendrimers. Both categories of polymer are known and described, for example, in A. Brenner “Hochverzweigte Strukturen auf der Basis von Polyestern und Polyamiden”, Herbert Utz-Verlag Wissenschaft, Munich (1996). The dendritic polymers are thermoplastics, for example polyesters or polyamides, and act as branching agents during polycondensation. The use of dendritic branching agents allows the production of polycondensates with interesting properties.
The use of dendritic branching agents and the polymeric products obtainable thereby are described hereinafter in the example of polycarbonates.
The highly branched polymers used as branching agents for producing the polycarbonates according to the invention are known and are generally distinguished by extremely low solution viscosity, extremely good solubility in comparison with their linear analogues, an approximately globular structure of the polymer molecules and a high number of functional groups on the surface of the polymeric spherulites. Owing to their particular properties, highly branched polymers can be used as branching agents for producing branched polycarbonate, without leading to the usual drawbacks of known polymeric branching agents.
DETAILED DESCRIPTION OF THE INVENTION
For example, the highly branched polyesters from U.S. Pat. No. 3,669,939 can be used as branching agents. U.S. Pat. No. 3,669,939 discloses highly branched polymers obtained by condensation of polyhydroxy monocarboxylic acids of formula (OH)
n
R—COOH, wherein n is an integer from 1 to 6 and R is a hydrocarbon radical having 1 to 22 carbon atoms and/or —CH
2
OH. For obtaining the highly branched polymer structure, it is essential that A-functionalities are able to react only with B-functionalities.
According to a particular embodiment of the invention, the branching agents used according to the invention can be obtained from monomers of formula
wherein X is hydroxyl, halogen, alkoxy or aralkoxy and Y is hydrogen, trialkyl silyl, alkyl or acyl and a is equal to 1 and b≧2 or a≧2 and b is equal to 1; or
wherein X, Y, a and b are as defined above and n and k, independently of one another, is an integer from 1 to 10; or
wherein X and Y are as defined above, R is hydrogen, alkyl or aralkyl and Z and Q, independently of one another, are optionally substituted alkyl, aryl or aralkyl.
Suitable monomers and their production are described, for example, in the above-mentioned document by A. Brenner “Hochverzweigte Strukturen auf der Basis von Polyestern und Polyamiden”, Herbert Utz-Verlag Wissenschaft, Munich 1996, pages 29to 32, 43 to 46 and 123 to 130.
Monomers of the following formulae (1) to (5) have proven particularly suitable for producing polyesters with highly branched polymer structure.
The highly branched polymers may be modified by addition of comonomers during the polycondensation reaction.
Dendrimeric polymers, in particular dendrimeric polyesters, as branching agents with a globular, perfectly branched macromolecular structure and hydroxyl functionalities on their surface may be obtained in accordance with WO 93/18079, reference being made to the disclosure thereof.
Pseudoplastic branched polycarbonates are produced by the so-called melt transesterification process in which bisphenols and carboxylic acid diesters are reacted in a known manner at temperatures of 80 to 400° C., preferably to 320° C., in the presence of a catalyst and a branching agent and the polycarbonate is obtained in a known manner, the above-mentioned polymers with a dendritic or highly branched polymer structure being used as branching agents.
For producing the branched polycarbonates, the branching agents to be used according to the invention are used in quantities of 0.05 to 2.0%, preferably 0.25 to 1.5% by mass, based on the mass of the bisphenol.
Bisphenols suitable for producing the branched polycarbonates acco

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