Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-07-18
2004-04-27
Nolan, Sandra M. (Department: 1772)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C428S035700, C525S444000
Reexamination Certificate
active
06727324
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to moldable resin compositions and molded articles obtained therefrom.
The invention relates in particular to blow moldable resin compositions based on polyether ester elastomers or block copolymers in which rubber like polyether soft segments and plastic like hard segments are alternately linked to one another.
2. Description of the Related Art
The blow molding of polyesters in particular polyether ester elastomers is known, but remains problematic especially for the blow molding of very long parts which requires specific rheological properties, in particular a closely controlled high melt strength to avoid unwanted sagging.
U.S. Pat. No. 4,010,222 reports that the addition of a copolymer containing polymerized ethylene units and polymerized carboxylic acid units to a copolyester elastomer improves its processing by blow molding.
U.S. Pat. No. 4,912,167 describes a blow moldable composition of a polyester such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET) or a PBT/PET blend, an epoxide polymer and a source of catalytic ions.
U.S. Pat. No. 5,128,404 describes a blow moldable composition containing polybutylene terephthalate, an ethylene copolymer containing epoxide groups and an ionomer obtained by partially neutralizing with Na
+
of K
+
the carboxyl groups of an ethylene copolymer containing (meth)acrylic acid.
U.S. Pat. No. 5,523,135 describes the problems of blow molding thermoplastic polyester resins, and reports an improvement for a combination of a thermoplastic polyester resin, typically, PBT, with a styrenic copolymer. In Comparative Example 12 it reports that blow molding was impossible when the PBT was replaced with a PBT-containing polyester ether elastomer.
EP-A-0,577,508 aimed to improve the blow moldability of polyether ester elastomers (block copolymers) which hitherto were not considered suitable for blow molding, by mixing them with an epoxy compound and a phenol alkali metal salt.
Canadian Patent Application 2,039,132 proposed a general improvement in polyether ester elastomers (block copolymers) by mixing them with an aromatic thermoplastic polyester, like PBT, PET or blends thereof, a rubbery interpolymer and optionally a mineral filler.
Whereas certain polyether ester elastomer formulations have been successfully used for blow molding, it still remains problematic to provide a blow moldable resin composition based on polyether ester resin that has a high parison stability, with little tendency to sag, for the blow molding of very long parts, especially for sequential co-extrusion or 3-D parison manipulation techniques.
SUMMARY OF THE INVENTION
According to the invention a moldable resin composition with improved properties for blow molding comprises the following components (A)-(F).
(A) A blend of two polyether ester elastomers (A1) and (A2), (A1) with a hardness in the range 45-72 Shore D, in an amount 70-95 wt. % of the blend, and (A2) with a hardness in the range 25-40 Shore D, in an amount 5-30 wt. % of the blend.
(B) A copolymer comprising from 94 to 50 wt. % of ethylene, from 5 to 35 wt. % of at least one alkyl or cycloalkyl acrylate or methacrylate, in which the alkyl or cycloalkyl group has from 2 to 10 carbon atoms, and from 1 to 15 wt. % of at least one unsaturated epoxide.
At least one of (C) and (D), where (C) is a copolymer comprising from 88 to 60 wt. % of ethylene, from 11.5 to 40 wt. % of at least one alkyl or cycloalkyl acrylate or methacrylate, in which the alkyl or cycloalkyl group has from 2 to 10 carbon atoms, and from 0.5 to 6 wt. % of at least one anhydride of an unsaturated dicarboxylic acid; and (D) is at least one rubbery polymer that can be finely dispersed into the composition by extrusion.
(E) A calcium compound capable of reacting with acid end-groups of the polyether ester resins of blend (A).
(F) One or more optional additives.
In the composition according to the invention: the resin blend (A) is present in an amount of 60-90 wt. % of the composition. Copolymer (B) is present in an amount of 6-15 wt. % of the resin blend A. Copolymer (C) when present is in an amount up to 20 wt. % of the composition, and the rubbery polymer (D) when present is in an amount up to 20 wt. % of the composition, providing the sum of (C) and (D) is at least 2 wt. % of the composition. The calcium compound (E) is in an amount such as to provide up to 2 wt. % elemental calcium in the composition. Lastly, the optional additive(s) (F) when present is/are in an amount up to 20 wt. % of the composition.
The composition according to the invention provides a high parison stability, with little tendency to sag, enabling the successful blow molding of very long parts, which could not be achieved with prior polyether ester elastomer formulations, at the same time combining a good surface aspect of the molded part. This composition is especially advantageous for sequential co-extrusion and for 3-D parison manipulation techniques.
The copolyester elastomers (A) are advantageously copolyetheresters consisting essentially of a multiplicity of recurring long chain ester units and short chain ester units joined head-to-tail through ester linkages. The long chain ester units are represented by the formula
and the short chain ester units are represented by the formula
where G is a divalent radical remaining after removal of terminal hydroxyl groups from a poly(alkylene oxide) glycol having a molecular weight of about 400-6000 and a carbon-to-oxygen ratio of about 2.0-4.3; R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight less than about 300 and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less than about 250; provided said short chain ester units amount to about 15-95% by weight of the copolyetherester.
Alternatively, the copolyester elastomer is a copolyester ester.
Copolyetherester elastomers and copolyester ester elastomers are described for example in U.S. Pat. Nos. 4,981,908, 5,824,421 and 5,731,380, the descriptions whereof are incorporated herein by way of reference.
Polyetherester block copolymers and their preparation are also described in Encyclopedia of Polymer Science and Engineering, Volume 12, pages 76-177 (1985) and the references reported therein.
Various polyetherester block copolymers are commercially available from a number of companies under various tradenames, for example HYTREL of E. I. du Pont de Nemours, RITEFLEX of Ticona and ARNITEL of DSM.
Varying the ratio hard/soft segment and using different alkylene oxides and molar weights of the soft segments makes it possible to obtain block copolyesters having different hardnesses, for example between Shore D 25 and 80. The invention employs a blend of two polyether ester elastomers, one with a hardness in the range 45-72 Shore D, and the other with a hardness in the range 25-40 Shore D.
The employment of a blend of copolyester elastomers of high and low hardnesses is critical for the invention and gives benefit for the parison aspect (less melt fracture). Moreover, the blend used in the invention has been found to improve the surface aspect of the parison when coming out of the die, leading to less surface defects in the molded part.
Using a blend of copolyester elastomers of high and low hardnesses is not equivalent to using a single copolyester elastomer of median properties. This is because the length of the soft blocks in the copolyester elastomer tends to be longer for the softer grades, hence the presence of even a small fraction of long soft blocks can influence the crystallisation speed and density of entanglement retained when the material solidifies from the molten state.
Preferably the soft segments in the soft copolyester elastomer is polytetramethyleneglycol (PTMEG) with a molecular weight of the order of 2000, whereas the soft segment in the hard copolyester elastomer is PTMEG with a molecular weight of the order of 1000.
The relative amounts of
Fortmann Kathy Lynn
Kirchner Olaf Norbert
Philippoz Jean-Michel
E. I. du Pont de Nemours and Company
Nolan Sandra M.
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