CA2122283A1

CA2122283A1 - Deep-drawable, sealable recycled film in at least three layers, based on polyamide and polyolefins and with a high content of recycled material

Info

Publication number: CA2122283A1
Application number: CA 2122283
Authority: CA
Inventors: Andreas S. Gasse; Rudi Klein; Ulrich Reiners
Original assignee: Wolff Walsrode AG
Current assignee: Dow Produktions und Vertriebs GmbH and Co oHG
Priority date: 1993-04-30
Filing date: 1994-04-27
Publication date: 1994-10-31
Also published as: FI941966A; EP0622183A2; KR100292214B1; JPH071689A; HUT68598A; FI941966A0; HU9401239D0; GR3032265T3; DK0622183T3; EP0622183A3; DE59408829D1; ATE185742T1; CZ105294A3; ES2137280T3; DE4314212A1; EP0622183B1; PT622183E; HU212047B; PL174131B1

Abstract

Deep-drawable, sealable recycled film in at least three layers, based on polyamide and polyolefins and with a high content of recycled material.

Abstract The invention relates to a multilayer sealable recycled film comprising at least one scrap layer, one sealing layer and one accompanying layer disposed either between the scrap layer and the sealing layer or externally on the side remote from the sealing layer, wherein - the film is deep-drawable, - the scrap layer consists of recycled polyamide/polyolefin and a primer, the proportion of recycled material in the scrap layer being 60 to 98%
by weight and the proportion of primer being 2 to 40%
by weight, - the recycled material contains 3 to 45% by weight of polyamide, - the sealing layer has one or more layers and consists of polyolefinic polymer or copolymer, the layers optionally being the same or different, and - the accompanying layer is of polyamide, polyolefin, EVOH and/or a primer or primer mixture.

Description

The invention relates to recycled film ba~ed on polyamide and polyolefin waste occurring e.g. in the production of laminated films. The invention relates to use of waste material occurring in the manufacturing process and is therefore of high ecological and economic importance. The deep-drawable film is usable on modern deep-drawing automatic machines for packaging industrial medical equipment, semi-finished products and finished parts and for packaging of food. The invention can be completely recycled.

In the prior art, there are various known composite film structures containing scrap material based on polyamide and polyolefins. The term "scrap material" here means waste ~ ~
20 film occurring e.g. in the production of laminated film, ---e.g. edge trimmings, starting rolls or cutting waste, which is subsequently agglomerated and optionally regranulated.
Most films made from scrap material are single-layer films ~e.g. JP 04-1119809 or JP 03-237143), and will not be further considered here.

In the multilayer film sector, incorporation of scrap material originated from the fact that edge trimmings, which inevitably occur in the production process, were returned to the process whenever possible. This is called "recycling of edge trimmings". The aim is to incorporate the scrap material substantially without affecting the properties of the film ~e.g. mechanical and optical properties or transparency). The result is that only small quantities of scrap material can be incorporated in this manner. The scrap material is either added in small quantities to a layer - usually internal - of the film, or forms a single layer between existing layers. Layers of 5382- Forei gn countri es 21222~3 polyamide and polyolefin scrap are morphologically unhomogeneous and cannot be deep-drawn by themselves in the prior art. As a result of the incompatibility of the phases formed, micro-cracks occur even when not under tension, and result in premature fracture under tensile loads (Braun, D.: Chemische Prozesse bei der Herstellung und Verarbeitung von Polymerblends: [D. Braun: "Chemical processes during the manufacture and processing of polymer blend"] in "Aufbereiten von Polymerblends, VDI Verlag, Dusseldorf (1989), pages 129 ff).

AU 88-26-473 discloses a laminate containing an intermediate layer which can comprise scrap material - -originating from the same film (e.g. edge trimmings). In this case, obviously, the total composite material can be made heat-deformable only if the unhomogeneous, easily-torn -scrap layer is supported on both sides. Machinery for encapsulating scra~ layers is described in GB 2075-914.

US-PS 4 668 571 describes a three-layer structure having an internal layer which can incorporate scrap material from the same film. To obtain the desired properties in this case, pure material from the adjacent layers must be mixed with the scrap layer.
US-PS 4 647 509 describes a polystyrene-containing multilayer structure having a first and a second layer designed so that scrap material from the two layers can be recycled by returning to the second layer.
All these films have the disadvantage that only scrap material originating from the same film can be returned thereto, and no foreign material can be incorporated in the scrap. There is no existing sealable film comprising a scrap layer which can contain large quantities of either `~ 21222~3 .
the same or foreign scrap material, based on polyamide and polyolefins, and which is deep-drawable.

The problem therefore is to produce a multilayer film which is deep-drawable and ~ealable and contains large quantities of recycled material based on polyamide and polyolefins.

To this end, the recycled material can contain any unsorted polyamide/polyolefin waste film, e.g. produced during the manufacture of polyamide/polyolefin films. The film structure according to the invention, therefore, in addition to being completely recyclable, must therefore include a scrap layer capable of incorporating waste film from other polyamide-polyolefin film structures.
The film must be deep-drawable and sealable and consequently of use in modern deep-drawing automatic machines, either as a cover film or a blister film for packaging. The film therefore must also have good lubricating properties.
. :
The film must have an optically homogeneous appearance, both in the deep-drawn state and in the state before shaping.
Surprisingly, this has been achieved by means of a ~ -sealable, multi-layer recycled film comprising one scrap layer, one sealing layer and one accompanying layer disposed either between the scrap layer and the sealing layer or externally on the side remote from the sealing layer, characterised in that - the film is deep-drawable, - the scrap layer consists of recycled polyamide/
polyolefin and a primer, the proportion of recycled -:
~L~2 3 --~

''--" 2122 ~J 5 3 material in the scrap layer being 60 to 98% by weight and the proportion of primer being 2 to 40% by weight, - the recycled material contains 15 to 45% by weight of polyamide, - the sealing layer has one or more layers and consists of polyolefinic polymer or copolymer, the layers optionally being the same or different, and - the accompanying layer is of polyamide, polyolefin EVOH and/or a primer or primer mixture.

The polyamide/polyolefin recycled material can be regenerated ~granulated with admixtures after remelting), or regranulated (granulated without admixtures after remelting) or agglomerated (without admixtures), prepared from waste film~ The proportion of polyamide in the recycled material is 3 to 45% by weight. The polyamide is either an aliphatic polyamide such as PA 6, PA 11, PA 12, PA 66, PA 6.66, PA 6.8, PA 6.9, PA 6.10, PA 6.11 or PA 6.12, or a copolymer of the monomer units therein or a mixture of the aforementioned aliphatic polyamides. The polyolefinic component consists of polymers such as high-density, medium- density, low-density or linear low-density polyethylene, polypropylene or polypropylene copolymers, ethylene/~inyl acetate copolymers, ethylene/vinyl alcohol copolymers, ethylene acrylic acetate copolymers, ethylene/methylacrylic acetate copolymers, ionomers or adhesive residues from laminated composite films.

The primer is an anhydride-modified polyolefin or an anhydride-modified ethylene/vinyl acetate copolymer.

~ 212~ ,~3 Preferably it is an ethylene, propylene or ethylene/vinyl acetate based polymer grafted with maleic acid anhydride.

The sealing layer is made of conventional sealing material.
This can be a polyethylene, polypropylene, polypropylene copolymer, ethylene/vinyl acetate copolymer, ethylene acrylic acid copolymer, ethylene/methylene acrylic acid copolymer or ionomer, or a blend of the aforementioned polymers.
The accompanying layer, which is disposed between the sealing and the scrap layer or on the side remote from the sealing layer, is used for varying the properties of the film (e.g. the appearance and barrier properties). The accompanying layer can be of polyamide (disposed externally to give a brilliant appearance), or polyolefin (to obtain excellent water-vapour barriers) or a polyamide/polyolefin mixture enriched with primer (to obtain variable adjustable properties) or a polyamide/EVOH/polyamide structure -20 (excellent oxygen barrier). --. , Surprisingly, as a result of the structure of the film according to the invention, the special requirements regarding deep-drawing and sealing have been met. It could not be expected that a mixture of incompatible polymers, processed in a layer with small quantities of primer and with an adjacent accompanying layer, could be deep-drawn in a multilayer composite structure. It is also surprising that the scrap layer can contain recycled material based on polyamide and polyolefins but not originating from the same film. Unexpectedly, the optical appearance of the film is homogeneous and comparable in both the original and in the deep-drawn state.

Advantageously the claimed film is produced by co-extrusion. If co-extrusion is impossible, the individual .~ -2 1 % ~ ~J ~ 3 layers are manufactured singly and subsequently joined by adhesive lamination. A combination of the processes i~
also possible. Known machinery conventional in the prior art can be used.
An important feature for evaluating the invention is the deep-drawing capacity. In order to determine the deep-drawing capacity, previously-manufactured film samples were tested on modern automatic deep-drawing machines ~e.g.
Tiromat or Multivac) used in the packaging industry. To this end, webs of films tensioned in the machine were heated in portions over a heating plate. The heat can be applied either from the sealing side or from the side remote therefrom. After being preheated by plates at temperatures of 100 - 110C, the films were drawn by negative pressure into a cavity having the frame dimensions 185 x 115 mm. The depth of the cavity was varied between 20 and 70 mm.

The result of deep drawing was marked as follows:

1. Unsatisfactory - every attempt to form a cavity results in tears in the film:
Marked "--"

2. Defective - an unacceptable number of attempts to form a cavity result in cracks in the film:
Marked "-"

3. Good - no cracks occur and the shape of the cavity is good: ~-Marked "+"
: -21222~3 The elongation at tear to DIN 53 455 was determined at thesame time as the deep-drawing capacity was experimentally evaluated. The "elongation at tear" means the alteration in length of the test-piece in mm at the tearing force, S relative to the original measured length in mm (see definition in DIN 53 455). To this end, ten~ile tests were made to the aforementioned DIN. Test-pieces 15 mm wide were investigated at 23C and 50$ relative air humidity.
The test speed was 100 mm/min.
A. Example 1:

Multilayer film having the structure:

PA-PO-HV/~cr~p/EV~
lS / lOS / S0 ~m The film was produced by co-extrusion. PA-PO-HV is a polyamide/polyolefin/primer mixture consisting of 35% by weight of polyamide 6, 10% by weight of primer in the form of LLDPE-based polymer grafted with maleic acid anhydride, and 55% by weight of low-density polyethylene (density 923 kg/m3). The scrap layer contained 20% by weight of primer and 80% by weight of recycled material. The primer was the same as in the PA-PO-HV layer. The proportion of polyamide in the recycled material was 33% by weight. EVA is an ethylene/vinyl acetate copolymer containing 5% by weight of -~
vinyl acetate.

B. Example 2:
:~
Multilayer film having the structure: :~

Scrap / mr / PA / ~ / PE / ~VA
100 / 10 / 20 / - / 20 / 40 ~m : ::

The scrap/HV/PA structure was produced by flat film co-extrusion and the PE-EVA structure was produced by blown film co-extrusion. Next, the aforementioned ~tructures were bonded together by adhesive lamination. The scrap layer contained 20% by weight of primer and 80% by weight of recycled material. The primer was an LLDPE-based polymer grafted with maleic acid anhydride. The content of polyamide in the recycled material was 33% by weight. HV
is a primer and the same polymer as the primer in the scrap layer. The polyamide ~PA) was a polyamide 6. The adhesive system (K) was a solvent-containing aromatic two-component polyurethane adhesive system. PE is a commercial low-density polyethylene and EVA is an ethylene/vinyl acetate copolymer containing 5% by weight of vinyl acetate.
C. Example 3:

Multilayer film having the structure:

PA ~ ~V / Scrap ~ X / PE / EV~
20 / 10 / 100 / - / 20 / 40 ~m The scrap/HV/PA structure was produced by flat film co-extrusion and the PE-EVA structure was produced by blown film co-extrusion. Next, the aforementioned structures were bonded together by adhesive lamination. The scrap ~ -layer contained 20% by weight of primer and 80% by weight of recycled material. The primer was an LLDPE-based copolymer grafted with maleic acid anhydride. The content of polyamide in the recycled material was 33% by weight.
HV is a primer and the same polymer as the primer in the scrap layer. The polyamide (PA) was a polyamide 6. The adhesive system (K) was a solvent-containing aromatic two-component polyurethane adhesive system. PE is a commercial low-density polyethylene and EVA is an ethylene/vinyl acetate copolymer containing 5% by weight of vinyl acetate.
~.

D. Comparative Example 1:

Single-layer film having the structure:

Scs~p 70 ,um The film was extruded in a single layer. The scrap layer --contained 1S% by weight of primer and 85% by weight of recycled material. The primer was an LLDPE-based polymer grafted with maleic acid anhydride. The content of polyamide in the recycled material was 33% by weight.

E. Comparative Example 2.
Single-layer film having the structure:

Scr~p 70 ,um The film was extruded in a single layer. The scrap layer contained 15% by weight of primer and 85% by weight of recycled material. The primer was an LLDPE-based polymer -grafted with maleic acid anhydride. The content of 25 polyamide in the recycled material was 33% by weight. ~

The elongation at tear of the aforementioned films A, B, C, - -D and E was determined to DIN 53 455 and the deep-drawing properties were evaluated as previously described.
The result is shown in Table 1:

21~22~3 Table 1: Comparison between the film structures A, B, C, D
and E

Elongation Deep-drawing Proportion of at tear t%) properties primer in the scrap A. Example 1 485 + 19 ~ 20% by weight B. Example 2 464 + 9 + 20% by weight C. Example 3 396 + 26 + 20% by weight . . _ . . . _ 15 D. Comparison 1 336 + 37 - 15% by weight E. Comparison 2 36 + 24 -- < 1% by weight The single-layer film E, which was produced substantially without a primer, was clearly not deep-drawable. Film D
shows that the primer does not result in adequate deep-drawing properties when used alone. Films A, B and Cproduced according to the invention were surprisingly deep-drawable. The measured elongation at tear emphasises the measured deep-drawing properties. The deep-drawable films A, B and C had much higher elongation at tear than films D
and E, which were not deep-drawable.

--.. . .. .. .... . . . .

Claims

1. A multilayer sealable recycled film comprising at least one scrap layer, one sealing layer and one accompanying layer disposed either between the scrap layer and the sealing layer or externally on the side remote from the sealing layer, characterised in that - the film is deep-drawable, - the scrap layer consists of recycled polyamide/
polyolefin and a primer, the proportion of recycled material in the scrap layer being 60 to 98% by weight and the proportion of primer being

2 to 40% by weight, - the recycled material contains 3 to 45% by weight of polyamide, - the sealing layer is in one or two layers and consists of polyolefinic polymer or copolymer, the layers optionally being the same or different, and - the accompanying layer is of polyamide, polyolefin, EVOH and/or a primer or primer mixture.

2. A film according to claim 1, characterised in that the film is produced by adhesive lamination, extrusion, co-extrusion, extrusion lamination and/or extrusion coating, the film optionally containing additional intermediate layers of primer.

3. A film according to claims 1 and 2, characterised in that the polyolefinic polymer or copolymer in the sealing layer is a polyethylene, polypropylene, polypropylene copolymer, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/
methylene acrylic acid copolymer or ionomer or a blend of the aforementioned polymers.

4. A film according to claims 1 to 3, characterised in that the recycled material is regenerated, regranulated or agglomerated on the basis of polyamide/polyolefin film waste or is a mixture of two or three of the aforementioned recycled materials.

5. A film according to claims 1 to 4, characterised in that a polyamide/polyolefin/primer mixture comprises 10 to 60%, preferably 20 to 40% by weight of polyamide, 40 to 80%, preferably 50 to 70% by weight of polyolefin, and 5 to 30%, preferably 5 to 15% by weight of primer.

6. A film according to claims 1 to 5, characterised in that the polyamide consists of aliphatic polyamides such as PA 6, PA 11, PA 12, PA 66, PA 6.66, PA 6.8, PA
6.9, PA 6.10, PA 6.11 or PA 6.12, or a copolymer of the monomer units therein or a mixture of the aforementioned aliphatic polyamides.

7. A film according to claims 1 to 6, characterised in that the primer is an anhydride-modified polyolefin or an anhydride-modified ethylene/vinyl acetate copolymer.

8. A film according to claims 1 to 7, characterised in that the scrap layer makes up 20 to 80%, preferably 40 to 60% of the thickness of the film, and the sealing layer makes up 10 to 50%, preferably 20 to 40% and the accompanying layer makes up 0 to 50%, preferably 10 to 30%.

9. A film according to claims 1 to 8, characterised in that the film has a total thickness of 0.050 to 0.500 mm, preferably 0.080 to 0.4 mm.

10. A film according to claims 1 to 9, characterised in that it is composed of a support layer / a sandwich layer / polyolefin / an intermediate layer /
polyolefin, either the sandwich layer or the intermediate layer or both being a scrap layer and the support layer being composed of polyamide / primer /
polyamide / primer or polyamide / primer or polyamide / EVOH / polyamide or consisting of one or more polyamide layers, a primer or adhesive being optionally used to bond the polyamide and the sandwich layer.

11. A film according to claim 10, characterised in that either the intermediate layer or the sandwich layer are omitted.

12. A film according to claims 1 to 11, characterised in that at least one layer is coloured and/or printed.

13. Use of the film according to any of claims 1 to 12, characterised in that the film is used as packaging for industrial medical equipment, semi-finished products and finished products or for packaging of food.