GB2204043A - A method of treating extrudable polymers - Google Patents

Abstract

Extrudable polymer is treated with a migratory agent which acts to control the surface frictional characteristics in the polymer when extruded. The migratory agent may be an unsaturated long chain fatty acid amide such as oleamide or erucamide.

Description

A METHOD OF TREATING EXTRUDED POLYMERS This invention relates to a method of treating extruded polymers. The invention is particularly, but not exclusively, concerned with the treatment of polyolefin tape such as polypropylene. Such polypropylene tape is commonly woven into a fabric which is used for a variety of applications, e.g. as a carpet backing.

Polypropylene filament e.g. in the form of tape, is generally produced by extruding polypropylene in a plaatic state through either a spinnerette or by means of a slit film process. The tape thus formed is drawn and cooled and can subsequently be used in the formation of a woven fabric. Prior to extrusion it is known to include other constituents such as lubricants and additives and which constituents have a beneficial effect on the extruded product. For example, polyethylene can be incorporated as a softening agent for the finished filament and filler materials such as calcium carbonate can be incorporated.

During a weaving process, polypropylene tape is normally provided on spools and a number of such spools are utilised sequentially during this operation. When a changeover is made from the end of one spool to the beginning of a succeeding spool, circumstances can arise which are disadvantageous to the finished product due to frictional forces which become apparent during the weaving process, differing surface tensions in the tape from the two spools or variable shrinkage characteristics between the tape from the two spools. Such disadvantageous circumstances can result in creasing or puckering of the woven fabric which, in turn, can cause uneven surface effects or uneven acceptance of dye by a subsequent tufted carpet fabric which has been subjected to a form of hot, wet processing.

An object of the present invention is to obviate or mitigate the aforesaid disadvantages.

According to the present invention there is provided a method of treating an extrudable polymer comprising preparing a batch of said polymer, adding to said batch an amount of a migratory agent adapted to provide a substantially uniform controlled surface frictional characteristic in the polymer when extruded, and extruding the mixture.

Preferably the migratory agent is a higher alkyl unsaturated aliphatic carboxylic acid amide.

Preferably also, the acid amide is erucamide. or oleamide.

Preferably also, the acid amide is present in the extruded polymer in an amount of 0.1 to 0.5% by weight.

An embodiment of the present invention will now be described, by way of example Polypropylene tape was produced by extruding a melt comprising polypropylene homopolymer to form a continuous tape.

Prior to extrusion, the polypropylene homopolymer is modified by the addition of a composition consisting essentially of low density polyethylene containing a higher alkyl unsaturated aliphatic carboxylic acid amide.

The particular acid amide employed was erucamide or cis docosenoic acid amide having the chemical formula

The low density polyethylene added to the melt prior to extrusion contained 6% by weight of erucamide.

The resultant extruded tape had the following composition (by weight) Low density polyethylene 2.0% Calcium carbonate 1.1% Erucamide 0.1% the balance being polypropylene.

It was found that by the inclusion of erucamide in the melt prior to extrusion, the erucamide tended to migrate to the surface of the finished tape and acted to reduce the surface friction arising in the polypropylene tape manufacture and the weaving process, such friction being created by variable mechanical forces occurring during tape processing and weaving or by variable shrinkage characteristics between the tape from succeeding spools. For example, during the process of weaving tapes, a problem of consistency exists during the changeover of weft packages manifesting itself in width loss, typically 0.9 - 1% for a fabric comprising 34 tex warp and 89 tex weft in the absence of erucamide addition to the polypropylene.With the addition of 0.18 erucamide by weight on polymer to the polypropylene prior to extrusion, this width loss on weft package changeover is reduced to 0.2%.

In an alternative embodiment of the invention oleamide can merely be substituted for erucamide in the above described embodiment to give similar beneficial effects to those provided to extruded tape incorporating erucamide.

It is believed that the beneficial effect can be obtained by including in the mix prior to extrusion sufficient erucamide to produce 0.1 to 0.5% by weight of erucamide in the finished product. If desired, a deblocking or spacing agent such as a silicon-based product can be incorporated in the mix along with the erucamide. Although erucamide has the beneficial effects referred to above,-it is believed that other related amides may well be similarly beneficial, e.g. oleamide and also long chain fatty acid derivatives such as glycerol monostearate and stearic acid salts.

Claims (10)

1. A method of treating an extrudable polymer comprising preparing a batch of said polymer, adding to said batch an amount of a migratory agent adapted to provide a substantially uniform controlled surface frictional characteristic in the polymer when extruded, and extruding the mixture.

2. A method as claimed in claim 1, in which the migratory agent is a higher alkyl unsaturated aliphatic carboxylic acid amide.

3. A method as claimed in claim 2, in which the acid amide is included in a composition consisting essentially of the acid amide and low density polyethylene.

4. A method as claimed in claim 2, in which the acid amide is erucamide or oleamide.

5. A method as claimed in claim 2 or 3, in which the acid amide is present in the extruded polymer in an amount of from 0.1% to 0.5% by weight of the polymer.

6. A method as claimed in any preceding claim, in which the polymer is a polyolefin.

7. A method as claimed in claim 5, in which the polyolefin is polypropylene.

8. A method as claimed in claim 1, of treating an extrudable polymer substantially as hereinbefore described.

9. A tape when produced by the method as claimed in any preceding claim.

10. A woven fabric when produced from tape as claimed in claim 8.