Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-09-17
2004-05-18
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S409000, C524S413000, C524S426000, C524S427000
Reexamination Certificate
active
06737454
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to thermoplastic molding compositions and more particularly to impact-resistant poly(ester)carbonate compositions.
SUMMARY OF THE INVENTION
Impact-resistant poly(ester)carbonate composition containing at least one oxalate compound is disclosed. The oxalate is selected from the group consisting of metal oxalates, metal hydroxy oxalates, oxalic acid esters and metal salts of oxalic acid esters. The resulting composition is flame resistant and exhibits an advantageous combination of notched impact strength, stress-cracking resistance under the action of chemicals, heat resistance and weld line strength and good processing behavior.
BACKGROUND OF THE INVENTION
Impact-resistant modified polycarbonate compositions that have been rendered flameproof are known. As flame retardants there may be used, beyond halogen-containing substances, in particular phosphorus-containing compounds, and on a large industrial scale in particular aromatic phosphoric acid esters. Such compositions are described for example in EP-A 0 363 608 and EP-A 0 640 655.
Silicate materials such as talcum may be added to such impact-resistant modified polycarbonate compositions that have been rendered flameproof with phosphoric acid esters (see for example JP-A 11199768, WO 00/46298, EP-A 1 026 205) in order to improve the flameproofing properties. Nanoscale inorganic powders such as basic aluminium oxides may also be added for the same purpose (see for example U.S. Pat. No. 5,849,827). The compositions that are thus obtained are characterized by an insufficient weld line strength however.
The use of mineral flame retardants such as aluminium trihydroxide, magnesium dihydroxide or antimony trioxide in polymers is summarised for example in M. Weber, “Mineral Flame Retardants”, Industrial Minerals, February 2000, pp.19 to 27. Such flame retardants are typically not used in polycarbonate and its blends. The most widely used mineral flame retardant, aluminium trihydroxide, has a comparatively low decomposition temperature of about 200° C. and is therefore unsuitable for polymers such as polycarbonate and polycarbonate blends that are produced or processed at a processing temperature of >200° C. For polymers with processing temperatures of >200° C. magnesium dihydroxide is therefore frequently used, which has a decomposition temperature of about 340° C. Magnesium dihydroxide has the disadvantage however that it is much more expensive than aluminium hydroxide and when used in polycarbonate and its blends leads, on account of its basic character, to the breakdown of the polymer.
An oxalate-modified aluminium hydroxide with a decomposition temperature of >330° C. and its use as a flame retardant in various polymer compositions is described in J. Stinson, W. Horn, “
Flame Retardant Performance of a Modified Aluminium Trihydroxide with Increased Thermal Stability
”, Journal of Vinyl & Additive Technology, June 1995, Issue 1, No. 2, pp. 94-97. The described oxalate-modified aluminium hydroxide exhibits in concentrations of 50% to 60% in various polymers such as high-density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET) etc., a good flameproofing action as evaluated by the UL-94 V test. Only in polycarbonate (PC) did the addition of oxalate-modified aluminium hydroxide fail to provide the desired improvement of the flameproofing in terms of UL-94 V.
The production and characterization of aluminium hydroxide-lithium oxalate compounds is furthermore known from U.S. Pat. No. 5,075,472.
In this specification it is mentioned that such compounds can be useful for rendering polymers flameproof.
WO 01/58999 describes polymer blends containing a phosphorus compound and oxalate salts, the oxalate salts being added in a quantity of up to 30 parts by weight. In the examples, polycarbonate/ABS compositions are described which contain 10 parts by weight of aluminium oxalate.
It has been found that oxalate compounds in quantities according to the present invention do not or hardly have any negative effects on the impact strength properties of the test specimens but have positive effects on the weld line strength and the ESC properties (stress-cracking behaviour on exposure to chemicals). For the purposes of a particularly balanced property profile with regard to impact strength, weld line strength and ESC behavior, the most preferred concentration range for the oxalate compound is 0.3 to 3.0% by weight, based on the total composition.
Particularly in the case of thin wall thicknesses (≦1.2 mm) the molding compositions have excellent flame resistance according to UL-94 V and excellent processability, i.e. in particular, good melt flowability.
DETAILED DESCRIPTION OF THE INVENTION
This object is achieved by an impact-resistant modified polycarbonate composition that contains at least one oxalate compound selected from the group comprising metal oxalates, basic metal oxalates (metal hydroxy oxalates), oxalic acid esters and metal salts of oxalic acid esters in quantities of 0.1 to 5 parts by weight (based on 100 parts by weight of the total composition).
A characteristic feature of the impact-resistant modified compositions according to the invention is that they contain at least one oxalate compound. Oxalate compounds according to the invention are for example metal oxalates, basic metal oxalates, all metal salts of oxalic acid as well as esters of oxalic acid and metal salts of such esters. The metal salts of oxalic acid and oxalic acid esters may be single, double, mixed and complex salts with one or more identical or different, ionic, covalently or complexly bound metals. The metal oxalates, basic metal oxalates and metal salts of oxalic acid esters used according to the invention may contain any suitable metals. Particularly suitable are metals of the 1
st
, 2
nd
and 3
rd
main groups of the Periodic Table. Most particularly preferred are aluminium, magnesium and/or lithium salts as well as mixed forms of these salts. Such metal oxalates and basic metal oxalates are generally known and are described in the literature, for example in “Ullmans Enzyklopädie der Technischen Chemie” 4
th
Edition, Vol. 17, Verlag Chemie, Weinheim, 1979, p. 480 ff.
Metal oxalate compounds that may preferably be used according to the invention are described hereinafter under component D.
According to a preferred embodiment of the invention an impact-resistant modified polycarbonate composition is provided that contains, in addition to the metal oxalate compound, a phosphorus-containing flame retardant, for example an oligophosphate, as further flame retardant. A particularly good property profile of the polycarbonate composition is obtained by the combination of the two flame retardants.
The impact-resistant modified polycarbonate compositions according to the invention may contain in addition to metal oxalate compounds further thermoplastic polymers, in particular polyester carbonates, polyesters, graft copolymers and vinyl (co)polymers.
These constituents and further components that may be used in these compositions according to the invention are described by way of example hereinafter.
Component A
The composition according to the invention contains polycarbonate and/or polyester carbonate (referred to below as poly(ester)carbonate), preferably aromatic poly(ester)carbonate. Suitable aromatic polycarbonates and/or aromatic polyester carbonates of Component A according to the invention are known in the literature or may be produced by processes known in the literature such as interface polymerization or melt polymerization processes (for the production of aromatic polycarbonates see for example Schnell “Chemistry and Physics of Polycarbonates”, Interscience Publishers, 1964 as well as DE-AS 1 495 626, DE-A 2 232 877, DE-A 2 703 376, DE-A 2 714 544, DE-A 3 000 610, DE-A 3 832 396; for the production of aromatic polyester carbonates see for example DE-A 3 077 934).
The production of aromatic polycarbonates may be carried out for example by reacting diphe
Eckel Thomas
Seidel Andreas
Wittmann Dieter
Bayer Aktiengesellschaft
Gil Joseph C.
Matz Gary F.
Preis Aron
Sanders Kriellion A.
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