Packaging material and its manufacturing method

Abstract

The present invention relates to an environmentally friendly paper-based packaging material that is an alternative to plastic packaging, which is recyclable and reusable, but also provides the oxygen, moisture, aroma, and grease barrier characteristics necessary to maintain food freshness for extended periods, such as in packaging made from fossil sources or to replace those made from fossil sources.

Description

[Technical field]

[0001] The present invention relates to paper-based packaging materials primarily intended for food packaging, and more particularly to high gas, water vapor, aroma and grease barrier paper-based packaging.

[0002] Nowadays, increasing environmental awareness has raised many concerns regarding the pollution of nature and therefore it has become more important than ever to limit the use of plastic materials.

[0003] Therefore, the demand for food and non-food packaging made from environmentally friendly materials is rapidly increasing to replace the traditional ones made from synthetic based polymers such as polypropylene, polyethylene, polyethylene terephthalate, polyamides, or combinations thereof with each other, and other polymers, all made from petroleum derived materials.

[0004] The objective of the present invention is to provide an environmentally friendly alternative to plastic packaging by producing a paper-based packaging material that is recyclable and reusable but also provides the levels of oxygen, moisture and grease barrier required to maintain food freshness for extended periods of time, such as in the case of packaging made from fossil sources or to replace those made from fossil sources. [Background technology]

[0005] Packaging used in the confectionery, biscuit and snacks categories typically consists of one or more plastic substrate(s).

[0006] In the current state of the art, the majority of food packaging is made of plastic films and their combinations, but there are also packaging in which plastic packaging films and paper are used together to give consumers a more natural appearance. However, such packaging with different structures is not favorable from the viewpoint of complete recyclability and reusability, since they are composed of different materials coming from natural and non-natural sources.

[0007] For example, state-of-the-art WO 2020 / 261170 refers to gas barrier films based on microfibrillated cellulose that have good and stable oxygen transmission rates at relatively high humidity levels. This state-of-the-art document further relates to paper and paperboard-based packaging materials comprising such barrier films.

[0008] In the prior art, there are many metallized paper-based packages where different metallization techniques are used mainly for decorative purposes to give paper or cardboard a shinier and more sophisticated appearance. For example, labels and packages of luxury products such as fragrances, spirits, etc. have partially or fully metallized surfaces to attract the consumer's attention.

[0009] Metallization is also used to make paper and cardboard resistant to water, moisture, grease, and mineral oil.

[0010] For all of these packaging applications, there are some methods by which the metallization can be performed on the base material.

[0011] The most widely used metallization technique is the lamination of paper with thick aluminum foil, usually with a thickness of more than 5 microns. Here, the metal foil is attached to the paper or paperboard by adhesive or extruded hot polymer melt. This technique has been used for many years in the production of industrial bags, sacks, and pouches for various food products, such as cereals, coffee, powder products, medical packaging, tobacco packaging, etc.

[0012] Another metallization technique is the conventional vacuum deposition technique, where a metal (usually aluminum) is melted in a vacuum chamber, vaporized, and the vaporized metal molecules are deposited on a web passing around a cooled roll, thus giving the final product a metallic finish. The thickness of the metal layer is usually kept in the range of 500-900 angstroms.

[0013] For many labelling applications, food packaging, and tobacco packaging, this technology has been used for decorative purposes, or to provide a moisture barrier to protect the contents from ambient humidity or to retain moisture in the contents inside the pack to maintain their freshness for an extended period of time.

[0014] Another technique for metallization is based on physical vacuum deposition (PVD) or chemical vacuum deposition (CVD) methods, using AlO x (For example, Al 2 O 3 ), SiO x (For example, Si0 2 ) and combinations thereof are coated either in a mixed form or in separate layers overlying one another to form very thin, transparent inorganic films.

[0015] This technology has been used for many years in packaging moisture- and oxygen-sensitive foods and is used primarily on polyester films and less frequently on paper-based packaging. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] International Publication No. 2020 / 261170 Summary of the Invention

[0017] The packaging material realized to achieve the object of the present invention as detailed in the first claim and each of its claims comprises a main substrate which is paper, a thin metal layer, preferably from aluminum, coated on the base by transfer metallization method, and an adhesive between the main substrate and the metal layer. In a preferred embodiment, the packaging material further comprises at least one functional coating further added under or on top of this transfer metallization surface to reach a target barrier level for keeping the contents in the package fresh.

[0018] The use of transfer metallization methods results in the formation of a primarily paper-based substrate with high oxygen, water vapor barrier, which also provides a grease, fragrance, and mineral oil barrier.

[0019] The transfer metallization method used in the present invention comprises: - coating the main substrate with a metal layer on a carrier film, the coating being achieved by an adhesive, which is preferably acrylic; - peeling off the carrier film, leaving the metal layer on the main substrate; Includes.

[0020] The result is a roll of paper or cardboard with a thin metal layer by transferring the metal, preferably aluminum, from the polymer film.

[0021] In a preferred embodiment of the invention, the carrier film is preferably at least 350 Angstroms thick.

[0022] In a preferred embodiment of the present invention, the peeled transparent carrier is subsequently recycled in the PET stream, which is another environmentally friendly aspect of the present invention.

[0023] In alternative embodiments of the present invention, the roll of packaging material may be further processed in a slitting step or may be used as a roll for subsequent converting processes.

[0024] Following an appropriate converting process which may include application of artwork printing, brand logo etc. or labelling, the metallised paper / cardboard is fed into dedicated packaging lines and given a form to safely encase, protect and transport the contents.

[0025] In a final step the pack is sealed by application of heat, with hot or cold adhesives or ultrasonic sealing, or is ready for transport and display to the consumer at the point of sale.

[0026] Generally, metallized substrates are preferred to provide a moisture barrier for food packaging.

[0027] The primary objective of the present invention is to produce high oxygen, aroma, and water vapor barrier packaging substrates that include a transferred metallized layer by combining the transferred metallized layer with various functional coatings.

[0028] The drawings are not meant to limit the scope of protection specified in the claims, nor should they be referred to alone to interpret the scope specified in the claims without relying on the technical disclosure in the description of the present invention. [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic diagram of a packaging material of the present invention. [Diagram 2] FIG. 1 is a schematic diagram of a transfer metallization process. [Explanation of symbols]

[0030] The following designations are assigned to the different layers of the packaging shown in the drawings and referenced in this detailed description of the invention. M1: Outer metal layer P: Main base material G: Adhesive M: Metal layer C1: Precoat layer C2: Barrier layer C3: Protective layer F: Carrier film DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The packaging material comprises a textile-based main substrate (P), preferably paper or cardboard, with a metal layer (M), preferably an aluminum layer, which is transferred to the inside of the main substrate (P) by peeling it off from a carrier film (F) of polymeric origin.

[0032] In one embodiment of the present invention, the metal layer (M) of the packaging material is fixed onto the main substrate (P) with an adhesive (G) to ensure adhesion.

[0033] The primary substrate (P) acts as a receiving medium for all further chemicals and coatings applied to one or both sides of the substrate.

[0034] The main substrate (P) can be any type of paper. In a preferred embodiment of the present invention, the main substrate (P) comprises at least ·Minimum 40gr / m 2 Grammage, Minimum thickness of 40 microns, Moisture content up to 5% A blank sheet of paper having At least one surface is calendered and / or chemically pretreated. In a preferred embodiment, such pretreatment is a clay coating applied in a mill to maximize closure of micropores and cracks that may otherwise adversely affect barrier properties during subsequent coating processes and at later stages such as conversion.

[0035] The primary substrate (P) is free of fluorochemicals, PVDC, or hazardous and ozone depleting chemicals.

[0036] The adhesive (G) bonds the metal layer (M) to the primary substrate (P). The adhesive (G) can be any type of solventless, solvent-based, water-based, or UV-curable adhesive that has strong adhesion to the metal layer (M) and the primary substrate (P).

[0037] The chemical adhesive (G) is selected from the families of urethanes, latexes, polyesters, vinyl acetates, modified ethylene copolymers of vinyl alcohol, acrylics or sugars, for example: Mixture of 5-chloro-2-methyl-4-isothiazolin-3-one [EC No 247-500-7] and 2-methyl-4-isothiazolin-3-one [EC No 220-239-6] (3:1); ·Copolymers of styrene and butadiene latex; · EVA (ethylene vinyl acetate) copolymers and terpolymers, preferably water soluble, although solvent-based carriers can also be used; · Copolymers of ethylene with unsaturated carboxylic acids or their ester compounds; EAA (ethylene acrylic acid copolymer), EMAA (ethylene methacrylic acid copolymer), EMA (ethylene methyl acrylate copolymer), EEA (ethylene ethyl acrylate copolymer), EMMA (ethyl methyl methacrylate copolymer) (these also help to improve the barrier against grease, oil and moisture); Based on cellulose, starch, glycogen, or chitin (C 6 H 10 O 5 )n.

[0038] The adhesive (G) can be applied to the metal layer (M) by several coating methods such as rod, reverse roll, air knife, flexographic printing, or rotogravure.

[0039] The metal layer (M), preferably made of aluminum, transferred from the polymeric carrier film (F) onto the main substrate (P), is in a preferred embodiment - at least 99,9% purity, a thickness of at least 100 Angstroms, Optical density (average) 2~3 It has the following characteristics.

[0040] In a preferred embodiment of the invention, the main function of the metal layer (M) is to provide a moisture barrier which is important for maintaining the freshness and crispness of many dry foods.

[0041] In one embodiment of the present invention, the transferred metal layer (M) is made of a thin, opaque aluminum oxide coating, preferably vacuum deposited.

[0042] Furthermore, the metal layer (M) is made of aluminum, silicone, or SiO 2 , Al 2 O 3 Alternatively, metal oxides of magnesium, zinc, or copper can also be used to improve the aforementioned barrier properties.

[0043] The precoat layer (C1) is water-resistant and is preferably selected, for example, from the family of EVA (ethylene vinyl acetate) copolymers and terpolymers, EAA (ethylene acrylic acid) polymers, styrene acrylates and PEI (polyethyleneimine), for example EVA (ethylene vinyl acetate) copolymers and terpolymers, preferably water soluble but also capable of using solvent based carriers; Copolymers of ethylene with unsaturated carboxylic acids or their ester compounds; EAA (ethylene acrylic acid copolymer), EMAA (ethylene methacrylic acid copolymer), EMA (ethylene methyl acrylate copolymer), EEA (ethylene ethyl acrylate copolymer), EMMA (ethyl methyl methacrylate copolymer) (these also help to improve the barrier against grease, oil and moisture), Dispersions of styrene acrylate in water, -PEI (polyethyleneimine).

[0044] In one embodiment of the invention, the packaging material further comprises an oxygen barrier layer (C2) which acts as a barrier against oxygen.

[0045] In this embodiment, the oxygen barrier layer (C2) is coated on the precoat layer (C1), which enhances the bonding of the oxygen barrier layer (C2) onto the metal layer (M).

[0046] The oxygen barrier layer (C2) also protects the metal layer (M) from scratches and micro-pitting.

[0047] In one embodiment, the oxygen barrier layer (C2) is an ethylene modified vinyl alcohol (PVOH) copolymer, more specifically, a water-soluble EVOH, which is a non-ionic water-soluble polymer that provides excellent barrier properties against oxygen, grease, fragrances, oils, and mineral oils. PVOH has been selected as a sustainable material that can be easily processed together with paper-based waste because it is both recyclable and repulpable.

[0048] In its water-soluble form, the oxygen barrier layer (C2) of this embodiment also provides strong anchoring with paper-based metallized and non-metallized substrates, in addition to providing very good, glossy and uniform film formation on the surface of properly pretreated paper and transferred metal coatings, and also exhibits good printability properties.

[0049] During the coating test, the PVOH uncoated metallized paper was subjected to 10 cc.m under ambient conditions, i.e., 23C, 50% RH. 2 It has been shown to provide oxygen transmission rates of over 1000 times per day (measurements taken from the metal side).

[0050] On the other hand, when a properly selected paper is metallized and then coated with 10-15% (w / w) PVOH aqueous solution as an oxygen barrier layer (C2), this structure exhibits an oxygen barrier strength of 1.0 cc.m at 23 C and 65% RH if the coating thickness is kept at about 5.0 mics. 2It was found that the coating thickness provided oxygen barrier levels of less than 100 / day. Higher coating thicknesses obviously resulted in lower oxygen transmission rates.

[0051] More specifically, 12% modified PVOH dissolved in water has a viscosity of 12.5 gr / m 2 Wet coating weight (this gives 1.5gr / m 2 is approximately 1.5 mics thick (equals dry weight) at 0.1 cc.m 2 It has been demonstrated that PVOH-coated paper packaging materials have significantly improved oxygen barrier over their uncoated versions, providing oxygen barrier levels as low as 100 / day (at 23° C. and 50% RH).

[0052] In another embodiment of the present invention, the oxygen barrier layer (C2) used to improve the oxygen barrier level is a water-based solution of sugars that can be coated onto the metal layer.

[0053] 30% solids and about 4-5gr / m on metallized paper 2 A water-based emulsion of sugar with a dry weight coating of 0.4 cc / m under ambient conditions 2 Oxygen barrier levels as low as .d were achieved.

[0054] In another embodiment, the packaging material may only have an oxygen barrier layer (C2) and no precoat layer (C1). In this embodiment, the metal layer (M) is fixed to at least one surface of the main substrate by a transfer metallization process and directly coated without a precoat layer (C1).

[0055] In another version of this embodiment, the oxygen barrier layer (C2) is made of polysaccharides, more specifically starch or cellulose or both, to provide a gas, aroma, oil and grease barrier to the packaging material.

[0056] In another embodiment of the present invention, the packaging material further comprises a protective layer (C3) coated on top of the barrier layer (C2) on the main substrate (P) to prevent the barrier layer (C2) from being affected by ambient moisture that may deteriorate its oxygen barrier, but at the same time can also exhibit heat sealability characteristics depending on the final packaging application.

[0057] In a preferred embodiment of the invention, the protective layer (C3) is a water-soluble, preferably a compostable water-soluble emulsion or dispersion, and is therefore water-resistant.

[0058] In one embodiment of the present invention, the protective layer (C3) is capable of low temperature seal adhesion and acts as a receptive layer for a latex-based low temperature seal adhesive. In one embodiment of the present invention, the protective layer (C3) can be water-based, solvent-free or solvent-based, and can be non-sealing or sealable.

[0059] The protective layer (C3) may be selected from any type of acrylic polymer, preferably EVA (ethylene acetate), EAA (ethylene acrylic acid) polymers, vinyl polymers, polyesters, and ionomers.

[0060] In a different embodiment of the invention, the protective layer (C3) EVA (ethylene vinyl acetate) copolymers and terpolymers, preferably water soluble but also capable of using solvent based carriers; Copolymers of ethylene with unsaturated carboxylic acids or their ester compounds; EAA (ethylene acrylic acid copolymer), EMAA (ethylene methacrylic acid copolymer), EMA (ethylene methyl acrylate copolymer), EEA (ethylene ethyl acrylate copolymer), EMMA (ethyl methyl methacrylate copolymer) (these also help to improve the barrier against grease, oil and moisture), Styrene acrylate dispersion in water It is based on.

[0061] In another embodiment of the present invention, the packaging material also comprises an outer metal layer (M1) on the other side of the main substrate (P), preferably formed by a transfer metallization process, mainly for aesthetics and metallic appearance.

[0062] In this embodiment, the same transfer metallization process that is applied to the inside of the main substrate (P) is also applied to the outer metal layer (M1) side.

[0063] The outer metallic layer (M1) can be printed directly or after priming, partially or completely, depending on the brand owner's artwork.

[0064] The carrier film (F) for the metal layers (M) and (M1) can be any polymer film, either in oriented or unoriented form, preferably where the backbone polymer is from the family of polyolefins, polyethylene terephthalate, or polyamide.

[0065] This provides an environmentally friendly alternative to packaging materials made from synthetic polymers such as polypropylene, polyethylene, polyethylene terephthalate, polyamides, etc., which are derived from petroleum-based sources. Furthermore, effective moisture and oxygen barriers are achieved, providing both food protection and an environmentally friendly alternative to plastic-based packaging.

[0066] The metal layer (M) is fixed to at least one surface of the main substrate and mainly improves the MVTR (water vapor transmission rate) and provides the following values ​​for both MVTR and OTR (oxygen transmission rate): MVTR:<2.0g / m 2 .d(23℃, 85%RH) MVTR:<1.0g / m 2 .d(23℃, 50%RH) MVTR:<10.0g / m 2 .d(38℃, 90%RH) OTR:<50ccm / m 2 .d(23℃, 50%RH)

[0067] A preferred embodiment of the packaging material, which is a metallized paper, after being coated with a layer (C2) made of either PVOH or sugar, exhibits the following barrier properties: MVTR:<1,6g / m 2 .d(23℃, 85%RH) MVTR:<1.0g / m 2 .d(23℃, 50%RH) OTR:<0.5ccm / m 2 .d(23℃, 50%RH)

[0068] The method for producing the packaging material of the present invention comprises the steps of: A coating step (101) of the main substrate (P) with a metal layer (M) lying on a carrier film (F), the coating being achieved by means of an adhesive (G), preferably acrylic; A step (102) of peeling off the carrier film (F) to leave the metal layer (M) on the main substrate (P); Includes.

[0069] In one embodiment of the invention, the manufacturing method comprises the further step of processing the packaging material after step (102) in a slitting step (103a).

[0070] In another embodiment of the invention, the manufacturing method comprises after step (102) a further winding step (103b) of the packaging material.

[0071] In one embodiment of the present invention, the manufacturing method comprises, after step (103a or 103b), a further step of transforming the packaging material with the application of artwork printing, brand logos etc. or labelling.

Claims

1. a fiber-based main substrate (P), preferably paper or cardboard; a metal layer (M) which is transferred to the inside of said main substrate (P) by peeling it off from a carrier film (F) of polymeric origin; an adhesive (G) between the main substrate (P) and the metal layer (M) to ensure adhesion; Including packaging materials.

2. The packaging material according to claim 1 , wherein the metal layer (M) is fixed onto the main substrate (P) by an adhesive (G).

3. The main substrate (P) is at least ・Minimum 40gr / m ２ Grammage, - minimum thickness of 40 microns, - Maximum moisture content of 5% A blank sheet of paper having 3. The packaging material according to claim 1 or 2, wherein at least one surface is calendered and / or chemically pretreated.

4. 4. The packaging material of claim 3, wherein one surface is pretreated with a clay coating in a mill.

5. 5. The packaging material according to any one of claims 1 to 4, wherein the main substrate (P) is free of fluorochemicals and PVDC.

6. 6. Packaging material according to any one of claims 1 to 5, wherein the metal layer (M) consists of aluminium having a thickness of at least 100 Angstroms.

7. 6. Packaging material according to any one of claims 2 to 5, wherein the adhesive (G) is selected from the family of urethanes, latexes, polyesters, vinyl acetates, modified ethylene copolymers of vinyl alcohol, acrylics, or sugars.

8. The metal layer (M) - purity of at least 99.9%; - a thickness of at least 100 Angstroms; Optical density (average) of 2-3 The packaging material according to claim 1 , having

9. 9. Packaging material according to any one of claims 1 to 8, wherein the metal layer (M) is made of magnesium or copper.

10. The metal layer (M) is formed of aluminum, silicon, or SiO by either physical vapor decomposition (PVD) or chemical vapor decomposition (CVD) methods. ２ , Al ２ O ３ 9. The packaging material according to claim 1, made with an inorganic transparent coating of an oxide thereof such as tungsten, tin, tantalum or a mixture thereof.

11. 11. The packaging material according to any one of claims 1 to 10, further comprising a barrier layer (C2) that acts as a barrier against oxygen, aromas, grease and mineral oil, and a precoat layer (C1) that strengthens the bonding of the oxygen barrier layer (C2) onto the metal layer (M).

12. 12. The packaging material according to claim 11, wherein the precoat layer (C1) is water-resistant and is selected from the family of EVA (ethylene vinyl acetate) copolymers and terpolymers, EAA (ethylene acrylic acid) polymers, styrene acrylates, and PEI (polyethyleneimine).

13. 13. The packaging material according to claim 11 or 12, wherein the oxygen barrier layer (C2) is a non-ionic water-soluble polymer, ethylene vinyl alcohol (PVOH) copolymer.

14. 13. Packaging material according to claim 11 or 12, wherein said oxygen barrier layer (C2) is made of a polysaccharide, more particularly a polysaccharide based on starch or cellulose, or both.

15. 15. The packaging material according to any one of claims 1 to 14, comprising a protective layer (C3) coated on top of the barrier layer (C2) on the main substrate (P) to prevent the barrier layer (C2) from being affected by ambient moisture.

16. 16. The packaging material according to claim 15, wherein said protective layer (C3) is a water-soluble, preferably a compostable water-soluble emulsion or dispersion.

17. 17. Packaging material according to claim 15 or 16, wherein said protective layer (C3) is selected from any type of acrylic polymer, preferably EVA (ethylene acetate), EAA (ethylene acrylic acid) polymers, vinyl polymers, polyesters and ionomers.

18. 18. The packaging material according to any one of claims 15 to 17, wherein the protective layer (C3) is low-temperature sealable and acts as a receiving layer for a latex-based low-temperature seal adhesive.

19. 19. The packaging material according to any one of the preceding claims, wherein on the other face of the main substrate (P) there is also an outer metal layer (M1), preferably formed by a transfer metallization process.

20. A method for producing a packaging material according to any one of claims 1 to 19, comprising the steps of: a coating step (101) of coating said main substrate with a metal layer (M) on a carrier film (F), said coating being achieved by means of an adhesive (G) that is preferably of acrylic nature; - peeling off the carrier film (F) leaving the metal layer on the main substrate (P) (102); A manufacturing method comprising:

21. 21. A method for producing a packaging material according to claim 20, comprising the further step of processing said packaging material after said step (102) in a slitting step (103a).

22. A method for producing a packaging material according to claim 20 or 21, comprising after said step (102) a further winding step (103b) of said packaging material.

23. 23. A method for producing a packaging material according to any one of claims 20 to 22, comprising after said step (103a or 103b) a further step of transforming said packaging material with the application of artwork printing, brand logos etc. or labelling.

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