Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-06-07
2002-09-24
Neiland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C264S563000, C264S573000, C264S177140, C264S331160, C264S331130, C264S331160, C264S331180, C264S331190, C264S331210, C524S277000, C524S492000, C524S493000, C524S590000
Reexamination Certificate
active
06455618
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to mixtures of thermoplastic elastomers, readily soluble waxes and inorganic antiblocking agents (i.e., molding compositions), which have improved ease of passage through machines during extrusion processing.
BACKGROUND OF THE INVENTION
The ease of passage through machines of thermoplastic materials during extrusion processing can be affected by the constructional design of the mould used to work up the material. Optimisation is generally possible only with regard to certain raw materials characteristics of the material being processed. When processing different materials on one extrusion device, this can provide optimised ease of passage through the machine only in exceptional cases.
Thermoplastic resins are typically processed, for example, in screw-type tools. A review of their structures is given, for example, in: Wortberg, Mehleke and Effen in: Kunststoffe, 84 (1994), S. 1131-1138, Pearson in: Mechanics of Polymer Processing, Elsevier Publishers, New York 1985, Fa. Davis-Standard in: Paper, Film & Foil Converter 64 (1990), S. 84-90. Moulds for extruding the melts, for example to give tubular semi-finished products, are described inter alia, by: Michaeli in: Extrusionswerkzeuge, Hanser Verlag, Munich 1991.
Thermoplastic elastomers are a group of materials where the essential characteristics are thermoplastic processability combined with elastomer materials behaviour. The main members of the group of thermoplastic elastomers (TPE) are block copolymers. These, apart from thermoplastic polyurethanes (TPE-U), include but are not limited to thermoplastic styrene-based systems (TPE-S), thermoplastic polyetheresters (TPE-E) and thermoplastic polyether block amides (TPE-A).
As a result of the thermoplastic processability, these materials can be extruded in an extrusion process and then further processed with the aid of a die to give, for example, a profiled section, a cable sheath or a tubular semi-finished product. Films based on TPE-E are described, for example, in U.S. Pat. No. 5,859,083. Those based on TPE-A are described in EP-A 0 761 715. TPE-S materials suitable for extrusion and their uses are described, for example, in DE-A 19 628 834. Semi-finished products made of TPE-U, processes for preparing them and their use are known from the prior art, for example, from EP-A 0 308 683, EP-A 0 526 858, EP-A 0 571 868 or EP-A 0 603 680. The preparation of TPE-U semi-finished products using substantially incompatible polymers as matting agents in the TPE-U is also described, for example, in DE-A-41 26 499. A review of the group of thermoplastic elastomers is given, for example, in: Thermoplastic elastomers: a comprehensive review, ed. N. R. Legge, G. Holden and H. E. Schroeder, Carl Hanser Verlag, Munich, 1987 and Thermoplastische Elastomere—Herausforderung an die Elastomerverarbeiter, eds.: VDI-Gesellschaft Kunststofftechnik, VDI Verlag, Düsseldorf, 1997.
Auxiliary substances and additives may be used during the thermoplastic processing of TPE's. The following may be mentioned by way of example here: waxes which act as friction-reducing internal and external lubricants. In addition, waxes take on the task of a separating agent in order to prevent sticking of the material to the surrounding material (e.g. the die). They are also used as dispersants for other additives, e.g. pigments or colorants.
Waxes used in the plastics processing sector include, for example, fatty acid amides, e.g. stearyl amides and oleic acid amides, fatty acid esters, e.g. montanates and stearates, and also polyethylene waxes. A detailed review of this topic is available: Taschenbuch der Kunststoff-Additive, eds. R. Gächter, H. Müller, Hanser Verlag, Munich, Vienna, 1979, p. 229 et seq.
The specific processing and application temperatures of various thermoplastic materials and their different chemical reactivities typically leads to a situation in which not all waxes can be used in the same way. Substantially amide waxes, for example, are used for TPE-U. These exhibit a high tendency to migrate, which provides a very good separating effect. On the other hand, the lubricating effect of these waxes is expressed only weakly. Montanate waxes, for example, exhibit good lubricating properties in TPE-U (EP-A 0 308 683; EP-A 0 670 339). However, in this case the separating effect is inadequate, even at high concentrations. A reduction in internal and external friction during melt processing can also be produced with a TPE-U, for example, by the use of 0.2 to 5 wt. % of at least one polyolefin or polystyrene (U.S. Pat. No. 3,358,052).
The use of antiblocking agents as an additive is important when preparing flat semi-finished products. As a result of using these, for example, a surface topography is typically produced, which prevents the sticking together of flat plastics items during further processing, less so during melt-processing moulding (e.g. film preparation). Natural or synthetic silicas are used here for example. Additives consisting of incompatible materials such as e.g. polyolefins or also polystyrene are also known for use in TPE-U (DE-A-41 26 499).
SUMMARY OF THE INVENTION
There is the objective of improving ease of passage through machines during the extrusion processing of thermoplastic elastomers, no matter what the structural design of the extrusion device.
In accordance with the present invention, there is provided a thermoplastic molding composition comprising:
a) 0.05 to 1.5 wt. %, with respect to the entire molding composition, of a fatty acid amide ester wax;
b) 0.5 to 10 wt. %, with respect to the entire molding composition, of a silica selected from natural silica, synthetic silica and mixtures thereof;
c) 0 to 1 wt. %, with respect to the entire molding composition, of a montan wax; and
d) at least one thermoplastic elastomer.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, etc. used in the specification and claims are to be under stood as modified in all instance by the term “about.”
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly, the ease of passage through machines during the extrusion processing of a thermoplastic elastomer is clearly improved by the molding composition according to the invention. While not intending to be bound by any theory, it is believed based on the evidence at hand that this is due to improved flow characteristics of the melt coupled with a simultaneously increased mass throughput due to the reduced energy consumption of the extrusion device.
Fatty acid amide waxes which can be used according to the present invention include but are not limited to, for example, erucic amide ethyl erucate, oleic amide ethyl stearate, stearic amide butyl stearate, stearic amide ethyl oleate, cerotic amide ethyl cerotate.
“The molding composition of the present invention comprises a silica selected from natural silica, synthetic silica and mixtures thereof.
The molding composition of the present invention may optionally further comprise a montan wax as an additional component. The proportion of the montan wax, according to the invention, is typically between 0 and 1 wt. %, based on the weight of the molding composition. In a particularly preferred embodiment of the present invention, a portion of the montanic acid of the montan wax is esterified with butylene glycol, and the remainder of the montanic acid of the montan wax is saponified with calcium hydroxide. “The montan wax may contain, based on the total weight of the montan wax, from 0.1 % wt. to 1 % wt. of montan wax esterified with butylene glycol, and from 0.1 % wt. to 1 % wt. of montanic acid saponified with calcium hydroxide.”
According to the invention, the molding composition contains at least one thermoplastic elastomer. In a preferred embodiment of the present invention, the thermoplastic elastomer is a block copolymer such as, for example, copolyetheresters or polyether block amides.
In a particularly preferred embodiment, at least one thermoplastic polyurethane is used
Brandt Rainer
Funk Hans-Werner
Schledjewski Ralf
Schultze Dirk
Franks James R.
Gil Joseph C.
Neiland Patrick D.
Wolff Walsrode AG
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