Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-16
2001-06-26
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S538000
Reexamination Certificate
active
06251968
ABSTRACT:
This invention relates to a method of modifying products and/or semi-finished products made from multi-phase moulding compositions. The latter are preferably synthesised from mixtures of thermoplastics. The methods according to the invention are characterised by a modification of the specific gravity and/or surface structure by the selective biodegradation of one or more of the polymer resins which are used for the production thereof. The moulding compositions are obtained using mixtures comprising thermoplastic materials which exhibit good biodegradability and those which exhibit poor biodegradability or which do not exhibit biodegradability. The methods of modification according to the invention are superior to the methods which are known in the prior art for dissolving out defined components.
Methods are known in the prior art for the modification of polymers or polymer surfaces by the selective leaching-out of individual phases by solvents which exhibit a particular affinity for said individual phases. Surfaces to which a matt finish has been imparted can be produced by this mode of treatment, for example.
It is also known that certain phases can be dissolved out by suitable etching processes. In this method, for example, morphologies can be produced which have proved useful in electrochemical coating processes.
Moreover, in multi-phase plastics systems which contain phases of different elasticities it is known that a change in surface properties or in the properties of the matrix can be obtained by deliberate (over)stretching, optionally in a plurality of directions.
Modified matrix properties are advantageous, for example, if porous membrane structures are to be produced which in the optimum case possess a defined pore structure.
Modified surface properties are expected of colostomy aids, for example, which nowadays also have to exhibit biodegradability, at least in part. They also have to adapt to bodily movements in a flexible, elastic manner. Soft coverings of high flexibility which are kind to the skin are required for this purpose. They must exhibit a good feel, which is also termed “touch”. In particular, the coverings which are known from the prior art are obtained nowadays by the welding of preforms of anatomical shape, which can be produced by thermoforming. Thicker, thermoplastically deformable films are required for this purpose which do not exhibit the unpleasant feel of a comparatively smooth, glossy film which is typical of plastics.
The object of the present invention was thus to achieve an agreeable feel by means of modifications to the surface of the film. In particular, the object was to improve the matt character of plastics articles and was also to influence the properties of the matrix in a targeted manner.
It has surprisingly proved possible, using the method of the type described at the outset, to achieve modifications to the surface- or matrix properties of products or semi-finished products made from thermoplastic moulding compositions containing multi-phase plastics mixtures.
It was not obvious to the relevant person skilled in the art with previous experience in this field that articles and/or semi-finished products which are modified by the method according to the invention would have a pleasant feel whilst at the same time possessing an acceptable level of mechanical properties.
Methods according to the invention which are particularly suitable for modifying articles and/or semi-finished products made from polymer resin moulding compositions are characterised in that partial biodegradation occurs under uniform and defined ambient conditions with regard to temperature, pH and ambient medium.
The methods according to the invention are based on the degradation, at least in part, of at least one phase of plastics articles which are made from multi-phase plastics mixtures. Biodegradable thermoplastic resins have proved useful as a formulation component here.
Moulding compositions comprising mixtures of thermoplastic resins can be produced by methods which are known from the prior art.
Polymer mixtures, blends or cuts can be produced by the mechanical mixing of melts, latices or solutions of two separately produced polymer resins, or by the in-situ polymerisation of monomers in the presence of a polymer resin which has been formed previously.
This is advantageously effected by mixing two separately produced polymer resins in the molten state. For this purpose, polymer resins which usually exist in the form of compacted form, granules or powders are mixed in kneaders or in extruders. The thermoplastic polymer resins which are suitable according to the invention are heated above their glass transition or melting temperatures in the course of this procedure. Good mixing throughout is achieved at elevated temperatures and/or under high shearing stresses.
A procedure which is preferred according to the invention is the modification of products and/or semi-finished products made from polymer compounds which have been produced prior to the forming operation. For this purpose, the polymer resins which are used for the thermoforming operation are subjected beforehand to a premixing operation in a softened state in a compounding step. The compounding devices which are known in the art are suitable devices for a mixing step such as this. Devices which have proved useful are those which comprise a plurality of endless screws, particularly the twin endless screw kneaders which are favoured for compounding operations.
A procedure which has also proved to be advantageous is the production of products and/or semi-finished products by a method comprising the premixing, in an unsoftened state, of the raw materials for the moulding composition. Premixing here is effected before the thermal digestion of the moulding composition raw materials.
Customary thermal forming methods for the processing of plastics are particularly suitable for the production of products/semi-finished products which are suitable for modification according to the invention.
Appropriate methods of modifying plastics articles are particularly suitable according to the invention if said articles comprise a proportion of at least 30% by weight of a thermoplastic resin which exhibits good biodegradability and a proportion of at least 15% by weight of a thermoplastic resin which exhibits biodegradability which is less good.
Biodegradable plastics are particularly preferred as components of the thermoplastic formulation.
The biodegradability of biodegradable resins, resin mixtures or films is defined in accordance with DIN 54 900 (draft version of 1996).
Biodegradable resins which are particularly appropriate according to the invention for the formulation of suitable moulding compositions are those from the group comprising ester amide copolymer resins.
Suitable thermoplastic ester amide copolymers for the mixtures according to the invention are preferably formed from predominantly linear, thermoplastic ester amide copolymers which contain
A) an ester constituent formed from linear and/or cycloaliphatic bifunctional alcohols, for example from ethylene glycol, hexanediol or butanediol, preferably butanediol or cyclohexanedimethanol, and optionally from small amounts of alcohols of higher functionality in addition, for example 1,2,3-propanetriol or neopentyl glycol, and from linear and/or cycloaliphatic bifunctional acids, for example succinic acid, adipic acid or cyclohexanedicarboxylic acid, preferably adipic acid, and optionally small amounts of acids of higher functionality in addition, for example trimellitic acid, or
B) an ester constituent formed from acid- and alcohol-functionalised components. for example hydroxybutyric acid or hydroxyvaleric acid, or derivatives thereof, for example &egr;-caprolactone, or a mixture or a copolymer of A) and B) as an ester constituent, and
C) an amide constituent formed from linear and/or cycloaliphatic bifunctional amines and optionally from small amounts of amines of higher functionality in addition, for example tetramethylenediamine, hexamethylenediamine or
Koch Rainhard
Schledjewski Ralf
Schultze Dirk
Weber Gunter
Cain Edward J.
Franks James R.
Gil Joseph C.
Wolfe Walsrode AG
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