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Light stabilized polyolefin films, tapes and monofilaments

IP.com Disclosure Number: IPCOM000246055D
Publication Date: 2016-Apr-29

Publishing Venue

The IP.com Prior Art Database

Abstract

A process for reducing water carry-over of a light stabilized polyolefin film, tape or filament which contains component (A) as light stabilizer and which is passed through a water bath during production, characterized in that the polyolefin film, tape or monofilament additionally comprises component (B) as light stabilizer. Components (A) and (B) are selected from the group of sterically hindered amines.

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Light stabilized polyolefin films, tapes and monofilaments

The present invention relates to a process for the reduction of water carry-over of a light stabilized polyolefin film, tape or monofilament which is passed through a water bath during production, to the polyolefin film, tape or monofilament made in accordance

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to that process and to the use of specific light stabilizers to reduce the water carry-over of a light stabilized polyolefin film, tape or monofilament.

A widespread method for producing polyolefin films, tapes or monofilaments consists in extruding the polymer melt through a suitable apparatus and, in the form of a film, tape

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or monofilament, into a water bath, where the film, tape or monofilament is cooled and solidified. The film, tape or monofilament may then in turn be passed out of the water bath and subjected to further steps of processing. On emerging from the water bath the film, tape or monofilament can entrain water, which interferes with subsequent steps of processing. This effect, the entrainment of water from the water bath, is often termed

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"water carry-over" in the technical literature, and this can be abbreviated to WCO.

Stretching of the film at a suitable temperature results in orientation and further crystal- lization of the polymer, resulting in the specific properties. This second step of pro- cessing may take place directly on the film, but the primary film is often split into tapes

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prior to the stretching process. Since the desired properties are obtained during the stretching process, precise adherence to all process parameters is essential here. Even traces of moisture on the film or on the tapes prior to the stretching process alter the subsequent stretching and orientation so as to produce very severe variations in the quality of the product obtained. The effects of this go beyond merely the corre- 25

sponding major variations in the quality of the resultant final product. Even during pro- duction or processing, the poor quality can cause break-offs of the tapes, for example, and thus stop production. A source of water which can lead to the problems mentioned is the cooling bath into which the primary film is extruded. Although most plastics, in particular the polyolefins, such as polyethylene (PE) or polypropylene (PP) are very

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hydrophobic and therefore have little tendency to absorb water, it is frequently found that at relatively high production speeds water droplets or a thin film of water adhere to the film when this is drawn over the water bath. In addition, various additives such as light stabilizers have to be added to the polymer to ensure that the final product has good functionality. Some of these additives contribute to increased entrainment of wa- 35

ter from the water bath. The additives, and also a maximum processing speed, are


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essential if suitable products are to be produced at low cost. A reduction in processing speed leads to uneconomic pro...