GB2207634A - Thermodeformable coextruded multi-layer film with gas-proofing poperties - Google Patents

Thermodeformable coextruded multi-layer film with gas-proofing poperties Download PDF

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Publication number
GB2207634A
GB2207634A GB08718201A GB8718201A GB2207634A GB 2207634 A GB2207634 A GB 2207634A GB 08718201 A GB08718201 A GB 08718201A GB 8718201 A GB8718201 A GB 8718201A GB 2207634 A GB2207634 A GB 2207634A
Authority
GB
United Kingdom
Prior art keywords
layer
layer film
stabilizing agent
barrier layer
primer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB08718201A
Other versions
GB8718201D0 (en
Inventor
Dr Benedikt De Groof
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cobelplast
Original Assignee
Cobelplast
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cobelplast filed Critical Cobelplast
Publication of GB8718201D0 publication Critical patent/GB8718201D0/en
Publication of GB2207634A publication Critical patent/GB2207634A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/304—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/302—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B32B2250/242—All polymers belonging to those covered by group B32B27/32
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/306—Resistant to heat
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B32B2307/7242—Non-permeable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/738—Thermoformability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/04—Polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/10—Polypropylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2325/00—Polymers of vinyl-aromatic compounds, e.g. polystyrene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2327/00—Polyvinylhalogenides
    • B32B2327/06—PVC, i.e. polyvinylchloride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging

Landscapes

  • Laminated Bodies (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)

Abstract

Thermodeformable coextruded multi-layer films with gas-proofing properties, particularly for the production of food packaging, comprise an internal barrier layer of polyvinylidene chloride, primer layers on both sides of the barrier layer, and outer layers on the outside. These films are improved, in the sense that waste occurring during the production and the thermodeformation can be used for reprocessing, including the formation of new coextruded multi-layer films with a high sealing effect. For this purpose, the primer layers of the films are treated with a stabilizing agent increasing the heat resistance of the barrier layer of polyvinylidene chloride, preferably using tetrasodium-pyrophosphate.

Description

Thermodeformable coextruded multi-layer film with gas-proofing properties The invention relates to a thermodeformable coextruded multilayer foil with gas-proofing properties, particularly for food packaging, has an inner barrier layer of polyvinylidene chloride, primer layers on both sides of the barrier layer and covering the latter, and outer layers on the outside.
The above-mentioned multi-layer films are known for the production of hot or aseptically packaged foods, as well as for sterilized foods.
The polyvinylidene chloride barrier layer has very satisfactory blocking characteristics with respect to gas and humidity. Its use, however, presupposes a typical coextrusion processing technology.
Polyvinylidene chloride has, however, the disadvantage of relatively little heat resistance which becomes noticeable in an unfavourable manner primarily during the re-processing of the longitudinal edge cuttings produced and the waste resulting from the thermodeformable webs of film as reclaimed waste.
The above-mentioned disadvantages resulting from the low heat resistance of the polyvinylidene chloride are reduced when ethylene/vinylalcohol copolymers are used instead to form the barrier layer, but such copolymers have a high sensitivity to humidity which in turn leads to a reduction in the oxygen-proofing properties so that barrier layers of polyvinylidene chloride are still preferred for the multi-layer films described in the introduction.
In order to be able to process afresh the waste occurring during the production of multi-layer films with an internal barrier layer of polyvinylidene chloride, and the clippings occurring during the processing of the films, as reclaimed waste, it is known, during the conversion of the reclaimed waste, to add a stabilizing agent to this which increases the heat resistance of the polyvinylidene chloride. For example epoxides, magnesium oxide, tetra-sodiumpyrophosphate, metallic salts of the carboxylic fatty acids, organotin compounds, citrates, oxalates, phosphates and various amino complexing agents are known as such stabilizing agents. The addition of such a stabilizing agent - tetrasodium-pyrophosphate is used for preferance - can be effected in powder form, preferably finely ground, or be incorporated, in the form of a concentrate, in a basic material present in the reclaimed waste.Typical concentrations for the addition of tetrasodium-pyrophosphate for a satisfactory reprocessing of reclaimed polyv-inylidene chloride multi-layer films are of the order of magnitude of 0.5 to 10% by weight depending on the method of processing and thermal stressing. The addition of the stabilizing agent to the received waste during its preparation leads to a time delay because the stabilizing agent has to be intimately mixed with the reclaimed waste. Because of the separate addition of this agent, the reaction of the stabilizing agent with the polyvinylidene chloride material of the reclaimed multi-layer film is only slight so that relatively large amounts of the stabilizing agent are needed. Direct addition of the stabilizing agent to the polyvinylidene chloride of the barrier layer is unsuitable because it has an unfavourable effect on the blocking properties.
It is the object of the invention to develop a thermodeformable coextruded multi-layer film such that reprocessing of the waste occurring during the production and processing is feasible without problems.
Short-time incorporation of the stabilizing agent is achieved with simultaneous improvement in its effect by direct contact with the polyvinylidene chloride so that injection-moulded or blow-formed articles, or multilayer films with an internal barrier layer, can be produced from the reclaimed waste with little expenditure on stabilizing agents.
In order to solve the above problems, the invention provides a thermodeformable coextruded multi-layer film with gas-proofing properties, particularly for food packaging, has an inner barrier layer of polyvinylidene chloride, primer layers on both sides of the barrier layer and covering the latter, and outer layers on the outside, characterised in that the primer layers are treated with a stabilizing agent which increases the heat resistance of the barrier layer.
With the new construction of the multi-layer film, the stabilizing agent necessary for the later processing of the waste is already contained immediately adjacent to the barrier layer of polyvinylidene chloride so that there is a direct contact between the stabilizing agent and the said polyvinylidene chloride but without the stabilizing agent being incorporated in the barrier layer. As a result of the direct contact of the stabilizing agent with the polyvinylidene chloride the stabilizing agent acts rapidly and the heat stability is increased.During the preparation of the waste, the direct contact of the stabilizing agent with the polyvinylidene chloride is further improved or increased because the substances to be brought into contact are in the adjacent middle layers of the film so that during mechanical processing of the waste a greater mutual penetration of the middle layers takes place before the further thorough mixing with the substances of the covering layers occurs.
It is particularly favourable if tetrasodiumpyrophosphate is provided as a stabilizing agent, preferably added in a suitably finely pulverized form.
Combinations of various stabilizing agents often have a synergistic effect. Mixtures of tetrasodiumpyrophosphate and epoxides, and a mixture of tetrasodium-pyrophosphate and with magnesium oxide and/or metallic salts of the carboxylic fatty acids and/or organotin compounds and/or citrates and/or oxalates and/or phosphate and/or various amino complexing agents have proved satisfactory during experiments. It is important that, as a result of the addition of the stabilizing agent, any hydrochloric gas formed is absorbed and the discolouration of the resulting thermoplastic polymers is largely reduced.
The proportion of the stabilizing agent in the primer layer is appropriately 20 to 70% by weight, preferably below 50% in order to avoid adhesion problems.
During a renewed processing of the ground waste cuttings from a multi-layer film constructed according to the invention, it was found that an improved heat stability was achieved in comparison with processed waste produced from-multi-layer films according to the prior art and with which the same amount of stabilizing agent was added to the ground reclaimed waste.
The following experiments were carried out with a coextruded multi-layer film having an inner barrier layer of polyvinylidene chloride, the total thickness of the film being 1 mm.
Composition of film 1: Out-er covering layer of polystyrene - primer of copolymer of ethylene and vinyl acetate - barrier layer of polyvinylidene chloride - primer layer of copolymer of ethylene and vinyl acetate - outer covering layer of polystyrene.
For the covering layers, a high-impact polystyrene which is sold by the firm Dow Chemical under the trade mark "Styron" 485 was used.
For the primer layer a copolymer marketed under the trade mark "Elvax" 3175 and sold by Messrs. Dupont de Nemours was used.
The polyvinylidene chloride layer was the product of Messrs.Dow Chemical marketed under the trade mark "Saran" 5253.16.
The layer thicknesses were: Covering layers 350 and 550 um Primer layers each 30 um Polyvinylidene chloride layer 40 pm For film 2, an identical construction with the same layer thicknesses was used, but for the primer layers a combination of the copolymer already mentioned which is sold under the trade mark "Elvax" 3175 and ground tetrasodium-pyrophosphate with a grain size from 15 to 30 um, which was incorporated in the copolymer at 25% by weight.
The films 1 and 2 were thermoshaped into round containers, the waste occurring from the web was ground and re-used for the renewed extrusion into a threelayer film 1 mm thick under the same extrusion conditions.
The newly produced foil had the following construction: Two covering layers of high-impact polystyrene like films 1 and 2 but only in a thickness of 100 pm each and between the covering films, the reclaimed waste with a layer thickness of 800 pm.
After being ground, the waste from film 1 was treated with various additional concentrations of tetrasodiumpyrophosphate of 0,2,4 and 6% in the form of a polystyrene concentrate. When no stabilizer was used, a powerful development of gas (hydrogen chloride) was observed which became less with an increased addition of stabilizer. Only with an addition of 4% of tetrasodium-pyrophosphate was the formation of hydrochloric gas no longer visible.
During the preparation and renewed extrusion of the waste from film 2, no gas formation could be detected although the concentration of the added tetrasodiumpyrophosphate was only 1.5% by weight in relation to the total amount of film produced.
In further experiments with films according to the construction of film 2, with polypropylene covering layers, the same results were also observed as during the processing of the waste from the film 2.
Processing of the reclaimed waste from films in accordance with the invention can also be effected, as distinct from the experiments described, by applying primer layers to a barrier layer of polyvinylidene chloride, and an intermediate layer of the reclaimed waste is applied on one or both sides as well as the usual covering layers on the outside. The waste from the films produced using the reclaimed waste can also be further processed again, in the manner described above, to form multi-layer films or blow-formed or injection-moulded articles.

Claims (9)

Claims
1. A thermodeformable coextruded multi-layer film with gas-proofing properties, particularly for food packaging, has an inner barrier layer of polyvinylidene chloride, primer layers on both sides of the barrier layer and covering the latter, and outer layers on the outside, characterised in that the primer layers are treated with a stabilizing agent which increases the heat resistance of the barrier layer.
2. A multi-layer film as claimed in Claim 1, characterised in that the stabilizing agent is tetrasodium-pyrophosphate.
3. A multi-layer film as claimed in Claim 1, characterised in that the stabilizing agent is a mixture of tetrasodium-pyrophosphate and epoxides.
4. A multi-layer film as claimed in Claim 1, characterised in that the stabilizing agent is a mixture of tetrasodium-pyrophosphate with magnesium oxide and/or metallic salts of the carboxylic fatty acids and/or organotin compounds and/or citrates and/or oxalates and/or phosphates and/or various amino complexing agents.
5. A multi-layer film as claimed in one of the Claims i to 4, characterised in that the proportion of the stabilizing agent in the primer'layer is 20 to 70% by weight.
6. A multi-layer film as claimed in one of the Claims 1 to 4, characterised in that the proportion of the stabilizing agent in the primer layer is 20 to 50% by weight.
7. A multi-layer film as claimed in any preceding Claim where the primer layers are based on polystyrene copolymers, polyethylene copolymers or polypropylene copolymers, or mixtures thereof.
8. A multi-layer film as claimed in any preceding Claim wherein the outer layers are based on polystyrene, polyethylene, polypropylene, or polypropylene copolymers.
9. A multi-layer film substantially as herein described.
GB08718201A 1986-02-20 1987-07-31 Thermodeformable coextruded multi-layer film with gas-proofing poperties Withdrawn GB2207634A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19863605405 DE3605405A1 (en) 1986-02-20 1986-02-20 THERMOFORMABLE COEXTRUDED MULTILAYER FILM WITH GAS SEALING PROPERTIES

Publications (2)

Publication Number Publication Date
GB8718201D0 GB8718201D0 (en) 1987-09-09
GB2207634A true GB2207634A (en) 1989-02-08

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GB08718201A Withdrawn GB2207634A (en) 1986-02-20 1987-07-31 Thermodeformable coextruded multi-layer film with gas-proofing poperties

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GB (1) GB2207634A (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4965136A (en) * 1988-08-16 1990-10-23 W. R. Grace & Co.-Conn. Extruded vinylidene chloride copolymer flexible packaging film
US5030511A (en) * 1989-06-09 1991-07-09 W. R. Grace & Co.-Conn. Extruded vinylidene chloride copolymer flexible packaging film
US5147594A (en) * 1989-06-09 1992-09-15 W. R. Grace & Co.-Conn. Extruding vinylidene chloride copolymer flexible packaging film
US5202188A (en) * 1991-08-23 1993-04-13 W. R. Grace & Co.-Conn. Vinylidene chloride film
NZ244002A (en) * 1991-08-23 1996-03-26 Grace W R & Co Extrudable composition containing plasticiser, acrylate/styrene polymer and vinylidene chloride copolymer; multilayer polymeric films
CA2104625A1 (en) * 1992-12-17 1994-06-18 Cryovac, Inc. Extrudable vinylidene chloride polymeric film
US5538770A (en) * 1994-11-18 1996-07-23 W. R. Grace & Co. -Conn. Vinylidene chloride film with controlled gas permeability

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Publication number Publication date
DE3605405A1 (en) 1987-08-27
GB8718201D0 (en) 1987-09-09

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