GB2444761A

GB2444761A - Polymeric films

Info

Publication number: GB2444761A
Application number: GB0524039A
Authority: GB
Inventors: Daniel Boulton
Original assignee: Amcor Flexibles Winterbourne Ltd
Current assignee: Amcor Flexibles Winterbourne Ltd
Priority date: 2005-11-25
Filing date: 2005-11-25
Publication date: 2008-06-18
Also published as: GB0524039D0

Abstract

A cast polyolefin film has a first outer layer consisting of a propylene (propene) based copolymer with a minor portion of butylene (butene) units, and a second layer comprising at least mostly propylene units, wherein the first layer contains a non-migratory antistatic agent and the second layer contains an anti-static agent. In the preferred embodiment comprising three layers: (A) the first outer layer comprising propylene-co-butylene (20% by weight butylene) nylon and anti-static agent polyetheresteramide, (B) the core layer comprises propylene-co-butylene (20% by weight butylene), propylene homopolymers, titanium dioxide, glycerol monostearate, bis-methoxylated amine and polyethylene, (C) a third layer comprising the material of layer (B) and silica.

Description

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S 0 * S S S.. S *. * S Polymeric Films This invention concerns polymeric films and more particularly polyolefin films, for example for use as in-mold labels.

In-mold labelling is a technique in which a pre-formed polymeric label is incorporated into a polymeric article in a mold containing a label, the individual labels usually being removed from a stack before being introduced into the mold.

Pjthough satisfactory results can be achieved using such a technique, problems can occur when individual labels stick to each other. This tends to occur as a result of electrostatic forces between individual labels.

According to the present invention there is provided a cast polyolefin film comprising a first outer layer comprising a polymer including a major proportion of units derived from propylene and a minor proportion of units derived from butene-l, and a second outer layer comprising a polymer including a major proportion of units derived from propylene, the first outer * S S S S ItS * . S S SI IS * S I S I * S S S II * S S S * I S S * S S S I S S S *, * ** *i, e S layer containing a non-migratory antistatic agent, and the second outer layer containing a migratory or a non-migratory antistatic agent.

Films in accordance with the present invention have shown good and reliable destackability when formed into labels for in-mold labelling. They have also shown good sealing efficiency when used as in-mold labels.

By the term cast polyolefin films we mean films which have been produced by casting melts of the respective layers without substantial stretching of the resulting film The first outer layer of films of the present invention is formed from a polymer containing a major proportion of units derived from propylene and a minor proportion of units derived from butene-l.

The amount of units derived from butylene-l in the polymer forming the first outer layer is preferably from 2 to 12, more preferably from 8 to 12, and especially about 10% by weight of units derived from butene-1 based on the weight of the polymer.

The non-migratory antistatic agent is preferably a polyether ester amide, a particularly preferred non-migratory antistatic agent being sold under the Trade Mark Irgastat P18. The first outer layer preferably contains from 5 to 10% by weight of a non-migratory antistatic agent.

The second outer layer of films of the present invention is preferably formed from a polymer containing a major proportion of units derived from propylene and a minor proportion of units derived from one or more of ethylene and butene-1. Copolymers of propylene and butene-1 are preferred, and particularly preferred are copolymers of propylene and butene-1 which contain from 2 to 12, more preferably from 8 to 12, and especially about 10% by weight of units derived from butene-1.

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* * I I I S S S I.. B 115 III S S -3--4 The second outer layer preferably contains an antistatic agent which can be migratory or non-migratory. Known migratory antistatic agents which can be used for the purpose include bis-methoxylated amines. When a non-migratory antistatic agent is used it is preferably a polyether ester amide, a particularly preferred non-migratory antistatic agent being sold under the Trade Mark Irgastat P18. The first outer layer preferably contains from 0.1 to 2.0% by weight of an antistatic agent.

Preferred amounts of migratory slip agents for the second outer layer are from 0.1 to 2.0% by weight based on the weight of the layer.

The second outer layer preferably contains a slip agent, for example glycerol monostearate, particularly when the antistatic agent is migratory.

It is generally preferred to include an antiblock agent, for example silica, in the second outer layer of films of the present invention.

In use, the second outer layer will in general form part of the outer surface of a blow molded article formed by blowing a parison in a mold, with the first outer layer of the film contacting the blown parison. The polymer used to form the first outer layer of the films of the present invention preferably has a melting temperature in the range of from 138 to 144 C.

The second outer layer will usually be printed prior to being incorporated into a blown article, and it is preferbly treated to increase its surface energy, for example by flame or corona discharge treatment.

Films in accordance with the present invention can include one or more further layers between the first and second outer layers. Such layers are preferably formed from olefin polymers containing a major amount of units derived from propylene with optionally minor amounts of units derived from other olefins, * * S * S *S.

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* I S I * * I I I S * S S S S SI* p 55. *a* * S for example ethylene or butene-1. Preferred copolymers contain a major amount of units derived from propylene and a minor amount of units derived from butene-1, for example from 2 to 12, preferably from B to 12, and more preferably about 10% by weight of butene-l based on the weight of the polymer.

When said further layers are present they can contain migratory slip and antistatic agents, for example as described herein for the second outer layer.

One or more of the layers of films of the present invention can include one or more pigments. However, it is generally preferred that the said first outer layer be substantially free of pigment.

Films of the present invention will generally have a thickness of from 50 to 200pm, a preferred range of thicknesses being from to 120pm.

The individual thicknesses of the various layers of films of the present invention can in general be selected as desired.

However, the outer layers are preferably at least 1pm thick, with substantially thicker layers being preferred, for example 5pm or more. The thickness of the first outer layer containing the non-migratory antistatic agent is preferably not more that 10pm thick due to the cost of such agents. If the second outer layer also contains a non-migratory antistatic agent, it preferably has a thickness of not more than 10pm.

When a further layer or layers are present between the first and second outer layers, they will make up the balance of the overall thickness of films.

Films in accordance with the present invention can be made by known methods, for example by coextruding layers of the respective polymers and additives through a slot die, allowing the resultant cast film to cool, and then winding it up.

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* , * a * a I a *, * a.. laS * * The following Example is given by way of illustration only.

Example

A three layer film was coextruded through a slot die, the first layer being formed from a mixture of a propylene/butylene-1 random copolymer (10% by weight of units derived from butylene-l) and 18.0% by weight of a masterbatch containing 18% by weight of a masterbatch containing 50% by weight of a polyetheresteramjde (Irgastat P18) in nylon, a core layer consisting of a mixture of the random propylene/butene-l copolymer used for the first layer, 5% by weight of a masterbatch of titanium dioxide (65%, mean particle size <1pm) in polypropylene hornopolyrner, and 1.5% by weight of a masterbatch consisting of a mixture of glycerol monostearate and bis-methoxylated amine (50:50 weight ratio) in polyethylene, and a third layer consisting of the mixture used for the core layer but additionall containing 4.0% by weight of a masterbatch of an antiblock (silica, 65% by weight) dispersed in a propylene homopolymer.

The cast coextrudate was cooled and the resulting film had an overall thickness of 82pm, the first layer being 5pm thick, the second outer layer being 34pm thick, and the core layer being 43pm thick.

Labels were then cut from the film and formed into a stack.

Individual labels destacked satisfactorily from the stack, and they molded satisfactorily to blown parisons in a conventional in-mold labelling process. S *t.

Claims

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S I.. 1*5 S I Claims 1. A cast polyolefin film comprising a first outer layer comprising a polymer including a major proportion of units derived from propylene and a minor proportion of units derived from butene-l, and a second outer layer comprising a polymer including a major proportion of units derived from propylene, the first outer layer containing a non-migratory antistatic agent, and the second outer layer containing a migratory or a non-migratory antistatic agent.
2. A film according to claim 1, wherein the polymer forming the first outer layer has a butene-l content of from 2 to 12% by weight based on the weight of the polymer.
3. A film according to claim 2, wherein the polymer forming the first outer layer has a butene-l content of from B to 12% by weight based on the weight of the polymer.
4. A film according to claim 3, wherein the polymer forming the first outer layer has a butene-l content of about 10% by weight based on the weight of the polymer.
5. A film according to any of the preceding claims, wherein the non-migratory antistatic agent in the first layer comprises a polyether ester amide.
6. A film according to any of the preceding claims, wherein the first outer layer contains from 5 to 10% by weight of a non-migratory antistatic agent.
7. A film according to any of the preceding claims, wherein the second outer layer comprises a copolymer containing a major amount of units derived from propylene and a minor amount of units derived from butene-1.
8. A film according to claim 7, wherein the copolymer contains from 2 to 12% by weight of units derived from butene-1.

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9. A film according to claim 8, wherein the copolymer contains from 8 to 12% by weight of units derived from butene-1.
10. A film according to claim 9, wherein the copolymer contains about 10% by weight of units derived from butene-l.
11. A film according to any of the preceding claims, wherein the second outer layer contains a slip agent.
12. A film according to any of the preceding claims, wherein the second outer layer contains an antiblock agent.
13. A film according to any of the preceding claims, including at least one further polymeric layer between the first and second layers.
14. A film according to claim 13, wherein the further layer or layers comprise copolymers containing major amounts of units derived from propylene and minor amounts of units derived from butene-1.
15. A film according to any of the preceding claims, wherein at least one of the layers thereof contains a pigment.
16. A film according to any of the preceding claims, wherein second outer layer has been flame or corona discharge treated.