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Cling Enhancement and Control in Stretch Cling Films

IP.com Disclosure Number: IPCOM000223844D
Publication Date: 2012-Nov-30
Document File: 6 page(s) / 154K

Publishing Venue

The IP.com Prior Art Database

Abstract

Stretch cling films range from about 10 to 60 microns and are stretched from about 25% to over 300% in use. Cling is commonly accomplished by adding migratory liquids or low modulus resins to the cling skin layer of a coextruded film. Achieving adequate cling performance can be more difficult for thicker films, perhaps 30 to 60 microns; and is the topic of this work. Studies have shown that adding low levels of hydrocarbon resin(s) to common cling formulations such as propylene based elastomers allows higher and controllable cling performance that may not be achievable via other approaches.

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Cling Enhancement and Control in Stretch Cling Films

Paul German Jr.

Abstract:  Stretch cling films range from about 10 to 60 microns and are stretched from about 25% to over 300% in use.  Cling is commonly accomplished by adding migratory liquids or low modulus resins to the cling skin layer of a coextruded film.  Achieving adequate cling performance can be more difficult for thicker films, perhaps 30 to 60 microns; and is the topic of this work.  Studies have shown that adding low levels of hydrocarbon resin(s) to common cling formulations such as propylene based elastomers allows higher and controllable cling performance that may not be achievable via other approaches. 

Background:

Stretch cling films are commonly used to protect and unitize palletized loads.  They are also similarly used on other products such as large rolls including paper, textiles or silage.  Cling is required so that the film adheres to itself and stays secured on the wrapped load.  Cling is commonly accomplished by adding migratory liquids or low modulus resins to the cling skin layer(s) of a coextruded film.  Achieving adequate cling performance can be more difficult for thicker films, perhaps 30 to 60 microns; and is the topic of this work. 

Development:

Ethylene based plastomers and propylene elastomers and other materials are used to provide cling in stretch cling films.  These approaches have disadvantages of potential film roll blocking, especially when film rolls in warehouse storage/ transit conditions exceed 120F.   In some cases it is difficult or impossible to achieve adequate cling for thicker films, especially without concurrent disadvantages. 

Work has shown that adding low levels of selected hydrocarbon resins can enhance and tailor a film's cling performance without concurrent disadvantages.   These hydrocarbon resins typically have softening point greater than 100C, thereby mitigating sensitivity to films elevated temperature storage or use that may be seen with other cling agents.  Labs studies enclosed in Table 1 show that adding from 3% to 6% hydrocarbon resin to existing cling layer formulation of propylene elastomer dramatically improves cling, especially 100% stretched cling performance.   

Sample Data and Performance

Films were produced on the labs Black Clawson cast line targeting conditions as given in

 Table 1 below:

Table 1:  Escorez™ Cling Cast run -  Sample Number as listed below

15/20/30/20/15    ABBBC,  Make   1.25 mil at 500 fpm, Trim to 20" width, ~530 F melt

Target gauge within +/- 0.04 mil and 20 pt. gauge range of 0.10 mil max, 80F chill rolls

4 1/2 melt curtain length, normal vacuum box settings. 

Make 2 lab rolls and 1500 ft Highlight roll.   Calibrate gauge!

Film Tests: Tensiles, 1% Secant, Tear, Dart, Gauge, Haze, Gloss, Shrinkage, Puncture (B),

Lab Cling 0, 100, 200%,   HL ultimate.

Objectives:      Define processing/ cling/ properties for Escorez™ tackifying resin films

Develop lab kn...