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Tie Layers for Film Compositions Containing Polyvinylidene Chloride Copolymers

IP.com Disclosure Number: IPCOM000012147D
Publication Date: 2003-Apr-11
Document File: 2 page(s) / 23K

Publishing Venue

The IP.com Prior Art Database

Abstract

Hot fill (~ 90 - 100 C) and retort (~ 100-135 C) are two food sterilization techniques that are particularly well-suited to co-extruded films containing Polyvinylidene Chloride Copolymers (PVDC) as barrier layers. The oxygen barrier properties of PVDC are not adversely affected by the high moisture exposure associated with these two methods. One area identified for improved performance is interlayer adhesion at higher temperatures. Ethylene Vinyl Acetate (EVA) copolymers adhere PVDC well to polyolefin skins at room temperature, but the adhesion tends to drop off at higher temperatures due to the relatively low melting point of the EVA.

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Tie Layers for Film Compositions Containing

� Polyvinylidene Chloride Copolymers

Improved Tie Layer Adhesion at Higher Temperatures

Hot fill (~ 90 - 100 °C) and retort (~ 100-135 °C) are two food sterilization techniques that are particularly well-suited to co-extruded films containing Polyvinylidene Chloride Copolymers (PVDC) as barrier layers.� The oxygen barrier properties of PVDC are not adversely affected by the high moisture exposure associated with these two methods.� One area identified for improved performance is interlayer adhesion at higher temperatures.� Ethylene Vinyl Acetate (EVA) copolymers adhere PVDC well to polyolefin skins at room temperature, but the adhesion tends to drop off at higher temperatures due to the relatively low melting point of the EVA.�

One way to improve higher temperature adhesion performance is to blend in some higher melting point polyolefin material into the EVA.� Data is shown below for one such example compared to an EVA control.� The skin resins were 2 I2 LDPE, and the films were 6 mil total thickness.� The layer compositions, by volume, were approximately 37% skin/ 8% tie / 10% PVDC/ 8% tie / 37% skin.� �

Tie Resin

Adhesion at 23 °C

lb./in.

Adhesion at 90 °C

lb./in.

EVA (25% VA, 2 I2)

3.3

0.16

EVA/ PE Blend*

3.8

0.33

The polyolefin blended into the EVA can be chosen from a wide range of resins including LDPE, heterogeneous or homogeneous PE (HDPE, LLDPE, ULDPE, , etc.).� It can even be a higher melting point polyolefin copolymer, such as an EVA resin with a relatively low level of vinyl acetate (6-12% VA).� The amount of polyolefin blended into the EVA typically can range between 20-40% by weight.�

The same principle also can be applied by substituting other polar ethylene copolymers, such as ethylene-acrylate copolymers, in place of the EVA, as the main component of the blend.

For adhesion to polypropylene skins, a similar concept can be used, blending in various types and amounts of PP homopolymer or cop...