Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-12-19
2004-08-31
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S135000
Reexamination Certificate
active
06784233
ABSTRACT:
The invention relates to thermoplastic molding compositions comprising
A) from 1 to 97.85% by weight of at least one thermoplastic polyester,
B) from 1 to 97.85% by weight of at least one polycarbonate,
C) from 1 to 50% by weight of an elastomeric polymer,
D) from 0.1 to 5% by weight of a phosphorus-containing stabilizer,
E) from 0.05 to 2% by weight of an organic acid, and
F) from 0 to 60% by weight of other additives,
where the percentages by weight of components A) to F) give 100%.
The invention further relates to the use of the novel molding compositions for producing fibers, films or moldings, and also to the resultant moldings of any type.
Industry is increasingly interested in polymer mixtures, since they provide tailored combinations of properties. Of particular interest here are polymer mixtures made from incompatible polymers which have unusual combinations of properties.
Polymer mixtures based on polyesters and polycarbonates are known (U.S. Pat. Nos. 4,522,797, 4,764,556, 4,897,448, EP-A 180 648, DE-A 3302124). Industrially significant products also have impact modifiers present to improve toughness, in particular at low temperatures, and preferred modifiers here are MBS modifier, acrylate graft rubbers and also ethylene copolymers with polar comonomers.
J. Devaux, P. Godard, J. P. Mercier, Polym. Eng. Sci., 22, 229 (1982) has disclosed that catalyst residues present in the polyester cause transesterification during melt compounding with polycarbonate. This gives copolymers, which improve the mechanical properties of the resultant blends. However, at high processing temperatures the transesterification is so rapid that there is substantial impairment of the mechanical and thermal properties of the resultant moldings. In addition, molding compositions prepared at high processing temperatures have poor surface quality (streaks and discoloration).
A wide variety of experiments has also been undertaken to improve the processing stability of polyester/polycarbonate blends. For example, EP-A 114 288 describes polyester/polycarbonate blends in which the MBS rubber added is premixed with a stabilizer in a prior step. This measure improves the mechanical properties of the molding compositions. However, the stability of the molding compositions at relatively high processing temperatures is unsatisfactory.
EP-A 634 435 describes a catalyst mixture composed of a Ti compound and a phosphorus compound which can be used to prepare polyesters. Polyesters prepared in this way have a slightly reduced tendency to transesterify in blends with polycarbonate.
U.S. Pat. No. 4,452,932 proposes, for example, ortho-substituted aromatic hydroxyl compounds to protect polycarbonate/polybutylene terephthalate blends from transesterification.
DE-A 19900891 proposes a process for premixing phosphonites with polyesters to improve processing stability.
EP-A 256 461 describes molding compositions based on polycarbonate and polyesters, which comprise small amounts of sulfonic acids. Although the products have improved toughness, processing stability is inadequate.
In particular when large-surface-area parts are produced, the long flow paths continue to cause processing problems since the blends known hitherto do not have sufficient stabilization.
It is an object of the present invention to provide polyester-polycarbonate blends which have improved processing stability and mechanical properties. In particular, heat resistance and melt stability for long cycle times should be improved.
We have found that this object is achieved by means of the thermoplastic molding compositions defined at the outset. Preferred embodiments are given in the subclaims.
The novel molding compositions comprise, as component (A), from 5 to 97.85% by weight, preferably from 10 to 92.7% and in particular from 12.5 to 89.85% by weight, of a thermoplastic polyester.
Use is generally made of polyesters A) based on aromatic dicarboxylic acids and on an aliphatic or aromatic dihydroxy compound.
A first group of preferred polyesters is that of polyalkylene terephthalates whose alcohol moiety has from 2 to 10 carbon atoms.
Polyalkylene terephthalates of this type are known per se and are described in the literature. Their main chain contains an aromatic ring which derives from the aromatic dicarboxylic acid. There may also be substitution of the aromatic ring, e.g. by halogen, such as chlorine or bromine, or by C
1
-C
4
-alkyl, such as methyl, ethyl, iso- or n-propyl, or n-, iso- or tert-butyl.
These polyalkylene terephthalates may be prepared by reacting aromatic dicarboxylic acids, or their esters or other ester-forming derivatives, with aliphatic dihydroxy compounds in a manner known per se.
Preferred dicarboxylic acids are 2,6-naphthalenedicarboxylic acid, terephthalic acid and isophthalic 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.
Preferred aliphatic dihydroxy compounds are 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, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and neopentyl glycol, and mixtures of these.
Particularly preferred polyesters (A) are polyalkylene terephthalates derived from alkanediols having from 2 to 6 carbon atoms. Among these, particular preference is given to polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate, and mixtures of these. Preference is also given to PET and/or PBT which comprise, as other monomer units, up to 1% by weight, preferably up to 0.75% by weight, of 1,6-hexanediol and/or 2-methyl-1,5-pentanediol.
The viscosity number of the polyesters (A) is generally in the range from 50 to 220, preferably from 80 to 160 (measured in a 0.5% strength by weight solution in a phenol/o-dichlorobenzene mixture in a weight ratio of 1:1 at 25° C. in accordance with ISO 1628.
Particular preference is given to polyesters whose carboxyl end group content is up to 100 mval/kg of polyester, preferably up to 50 mval/kg of polyester and in particular up to 40 mval/kg of polyester. Polyesters of this type may be prepared, for example, by the process of DE-A 44 01 055. The carboxyl end group content is usually determined by titration methods (e.g. potentiometry).
Particularly preferred molding compositions comprise, as component A), a mixture of polyesters which are different from PBT, for example polyethylene terephthalate (PET). The proportion e.g. of the polyethylene terephthalate in the mixture is preferably up to 50% by weight, in particular from 10 to 30% by weight, based on 100% by weight of A).
It is also advantageous to use recycled PET materials (also termed scrap PET), if desired in a mixture with polyalkylene terephthalates, such as PBT.
Recycled materials are generally:
1) those known as post-industrial recycled materials: these are production wastes during polycondensation or during processing, e.g. sprues from injection molding, start-up material from injection molding or extrusion, or edge trims from extruded sheets or films.
2) post-consumer recycled materials: these are plastic items which are collected and treated after utilization by the end consumer. Blow-molded PET bottles for mineral water, soft drinks and juices are easily the predominant items in terms of quantity.
Both types of recycled material may be used either as ground material or in the form of pellets. In the latter case, the crude recycled materials are isolated and purified and then melted and pelletized using an extruder. This usually facilitates handling and free flow, and metering for further steps in processing.
The recycled materials used may either be pelletized or in the form of regrind. The edge length should not be more than 6 mm, preferably less than 5 mm.
Because polyesters undergo hydrolytic cleavage during processing (due to traces of moisture) it is advisable
Hennig Ingolf
Weber Martin
BASF - Aktiengesellschaft
Keil & Weinkauf
Szekely Peter
LandOfFree
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