IT8121883A1 - New laminated, printed and metallized films and the process for their preparation - Google Patents

Description

.J JUIUKI Hdiiaiid nusillB ?.?,?, ?.?,?.

DESCRIPTION of the patent for industrial invention from title:

'Laminated, printed, and metallized films and their preparation procedures'

on behalf of: Societ? Italiana Resine S.I.R. S.p.A. with registered office in Milan, V1a Grazioli 33, of Italian nationality.

Designated inventors: Pierpaolo Buzio, Lucio Edefonti and Giaji luigi Argel?.

21 MAS, 198|

Deposited on

SUMMARY

A printed, metallized, coupled film with heat-resistant characteristics is described, consisting of the union of:

1) a printed and metallized film formed by an oriented polyolefin film, carrying on both surfaces a layer of "primer", applied by means of an aqueous or hydroalcoholic solution, one of said "primer" layers being lacquered by means of a vinyl, vinyldene or acrylic polymer or copolymer, the other "primer" layer being metallized by means of a layer of aluminum; 2) a film formed by a non-oriented film, of a polyolefin nature, having heat-sealable characteristics; the coupling occurs by joining one surface of the film 2) with the metallized surface of the film 1).

Scrofa Italiana Resino S.I.R, S.p.A. According to one embodiment, the film 1) carries the - 2 - print on the unlacquered "primer" layer, said print being applied in a phase preceding the metallization phase.

According to another form of implementation the film 1) po?

ta the print on the lacquered layer, said print being

applied to the said film 1) before or after its application?

pleasure with film 2).

DESCRIPTION

The present invention relates to a new film?

printed and metallized pair, with heat-sealing characteristics, useful in the packaging sector, especially for food products. The invention concerns

also the procedure for preparing this film.

In the packaging sector, especially for food products, the use of

coupled which make it possible to create films having the desired final characteristics, by joining films with different characteristics, such as

appropriately combining the properties of the individual

films.

The fundamental characteristics which they must satisfy_

to make such composite materials are those relating to the

termosaidabi1it? , waterproofness, printability?

and the mechanical resistance of the packaging.

j ?ma nanaiia nesma ?.F.fl. 5.D.A.

A type of laminate, known in the art, is formed - 3 - by the union of a biaxially oriented crystalline polypropylene film with a film formed by a non-oriented film (sealing layer).

Another type of coupled d1, known in the art, is obtained by joining a non-oriented film (welding layer) with a film consisting of a biaxially oriented crystalline polypropylene film, carrying a lacquer layer on both surfaces.

The coupling of these films generally occurs by passing the films themselves between a pair of clamping cylinders, after interposing a layer of adhesive.

When a greater barrier effect is desired (impermeability to oxygen, gases and vapors in general, and light), special structures are used that include an aluminum layer, applied through a high-vacuum metallization process. Films known in the art are formed from a biaxially stretched crystalline polypropylene film, carrying a lacquer layer on both surfaces, one of the lacquer layers being metallized by applying an aluminum layer. The metallized films of the prior art generally present disadvantages in the high-vacuum metallization step, which is carried out with

usuici tiuiiana ticillS ?,?,?, ?.?,?, produced on a double-coated polypropylene film and, as such, with a high residual solvent content.

Generally these metallized films are then coupled with a further oriented polypropylene film.

biaxially, applied by adhesive on the metal layer, having a protective action for the metal and the eveji

your press.

The welding characteristics of the said metallized laminates are poor since this function is delegated

to the outer layer of lacquer only.

In conclusion, the improvement of the barrier effect

of the metallized laminates of the known art, has led to a net loss of heat-sealability characteristics.

It is therefore an object of the present invention

It is a coupled, printed and metallized film, which has a high barrier effect, together with optimal heat-insulating characteristics.

It is another object of this Invention

a process for preparing said film.

Further objects of the invention will become apparent from the following description, considered in conjunction with the experimental examples.

In particular the coupled, printed, metallized and heat-resistant film,

?uwuia italiana ?asina 5,?.?, 5.p.A, the present invention is formed by the union of: - 5 -1) a printed and metallized film formed by a

oriented polyolefin film, bearing on both sides

surfaces a layer of "primer" applied by means of an aqueous or hydroalcoholic solution, one of said layers of

"primer" being lacquered by a polymer or copoly_

vinyl, vinylidene or acrylic, the other layer

of primer being metallized by applying a

aluminum layer;

2) a film formed by a non-oriented film, of a polyolefin nature, having thermo-debilitating characteristics;

the mating occurs after the interposition of adhesions

I go, by joining a surface of the film 2) with the metallized surface of the film 1);

to film 1) the print being also applied on the unlacquered "primer" layer d1, in a previous phase

to that of metallization of said layer, or on the

lacquer layer, at a stage before or after

that of the coupling of film 1) with film 2).

Polymers of polyolefin nature, suitable for pe11J_

cola 2), are preferably chosen from: polyethylene, polypropylene, polypropylene-ethylene copolymers, ethylene-vinyl acetate copolymers, ionomeric polymers and blends

?cc-?eia uauana HBSIIIB ?J.H. ?.p.A, lative. In the preferred embodiment the film 2) - 6 - is treated on one surface with electrical discharges

at high frequency and the surface thus treated is p?

comes into contact with the metallized surface of film 1) in the coupling phase.

The process for preparing the said coupled product

It essentially consists of spreading an adhesive on the

metallized surface of the film 1), in drying the adhesive thus spread and in coupling the two films

between a pair of clamping cylinders, operating in an am

temperature range from 50 to 80?C, better in the order of 60

-70?C .

For coupling, two-component solvent-based adhesives, of the polyurethane type, suitable for lamination with metal, can be successfully used and the resulting coupling is free from those random phenomena.

of "whitening" that afflicted the couples of the

known technique.

The coupled films of the present invention present

They have excellent printability characteristics. In particular, printing can be applied on the "primer" layer d1

of the film 1), in a phase preceding the metallization of said layer. In this case, good adhesion characteristics of the metal on the surface are achieved.

perfide of "primer" printed. According to another form of

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implementation the print is applied on the lacquered surface of the film 1) in a phase preceding or following that of its coupling with the film 2).

The laminated films of the present invention exhibit high barrier properties against oxygen, gases and vapors in general, and light, as the metallization of the primer layer allows the thickness of the aluminum layer to be adjusted to controlled and constant values. Said laminated films are also easily heat-sealed, with good heat retention of the weld and good resistance to delamination, and are characterized by a low residual solvent content due to the presence of only one layer of lacquer, which facilitates the metallization of the film 1).

Film 1)

Polyolefin films suitable for use in film 1) are those with a thickness of 10 to 100 microns, obtained by miniature and orientation of alpha-olefin polymers or copolymers. The preferred polyolefin films are those obtained from a crystalline propylene polymer having melt-index values of the order of 1.5-4 g/10'. In the most preferred form, these are polypropylene films, with the crystallinity and melt-index characteristics indicated above, which have been stretched mono-axially or bi-axially, up to a final thickness of the order of

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20-40 microns. - 8 -These polyolefin films are subjected to a surface treatment with electric discharges, with a flame or with oxidizing solutions, up to wettability values of the order of 38-40 dynes/cm (ASTM 0-2578).

A "primer" layer is deposited on both surfaces of the film thus treated, one of these layers being subsequently destined to receive the 1st layer, while the other constitutes the surface that is subjected to metallization following possible printing.

As regards this last "primer" layer, special measures must be taken to obtain a smooth and uniform surface, with slippery characteristics and the absence of "blocking" in the reel (for storage before subsequent treatments), as well as characteristics of receptivity for any printing and the metal layer.

More specifically, this "primer" layer consists of polyethyleneimine; condensation products of urea or melamine with formaldehyde, especially etherified ones; polyhydroxylated alkoxy1ky1 melamines; or mixtures of these compounds.

The application of the said "primer" to the polyolefin film is conveniently done using an aqueous or hydroalcoholic solution. Furthermore, in the case of application of the polyolefin imine alone, the quantity applied is kept within a certain range.

range of values from 5 to 50 mg/m. In the case of application of a mixture of polyethylenimine with one or more of the other compounds indicated, the ratio between said polyethylenimine and the other compounds is conveniently maintained within a range of values from 1/1 to 5/1 on a weight basis. Furthermore, the quantity of mixture applied as a "primer" on the surface of the polyolefin film may vary in a

2

range of values from 10 to 100 mgr/m. This range of values is also adopted in the case of application as a "primer" of only polyhydroxylated alkoxymethylenes.

After applying the "primer", it is dried by thermally treating it at temperatures of around 70-90°C, especially in the presence of a gaseous flow capable of removing the vaporised solvent.

In the preferred form, this "primer" layer is also subjected to washing with water at room temperature, or at values close to room temperature, before and/or after the drying phase.

The purpose of this washing is essentially to remove any excess primer applied and to make its distribution more uniform on the polyolefin film. It has in fact been found that a uniform distribution of the primer on the surface of the polyolefin film, careful drying of the layer thus deposited and washing of said layer with water, give

uuuiuifl Iiauaiia nysiilfl ?,?.?, J.|i, '

the latter features slipperiness and absense 1 0

blocking capacity in the reel, as well as excellent print and metal reception characteristics.

The "primer" intended to receive the lacquer layer presents less critical aspects with regards to its composition, the quantity applied per unit surface and its distribution on said surface.

However, to simplify operations, it is advisable to apply the two layers of "primer" simultaneously or successively starting from the same aqueous or hydroalcoholic solution and dry the two layers thus applied simultaneously. Washing with water, however, can be reserved for only the "primer" layer intended for printing and metallization.

In preparing film 1), a layer of a lacquer is applied consisting of polymers or copolymers of acrylic or methacrylic esters, preferably methyl methacrylate polymers with a molecular weight of around 20,000-100,000. Alternatively, mixtures of said methyl methacrylate polymers with polymers or copolymers of vinyl chloride, vinyl acetate, and acrylonitrile can be used to advantage. The lacquer is conveniently applied as a solution in an organic solvent, especially a ketone or ester, with a concentration of 20-40% by dry weight. This solution can be used with

?',???? ????????? IICCIIIO ?,?,?. ?.?.?-contain other ingredients such as slip agents, plasti_ - 11 agents, antistatics and adhesion promoters known in the art?

Is the application of the lacquer done using the usual techniques?

2 li, with a deposition of a quantity of lacquer from 1 to 3 gr/m

2

and preferably 1.5-2 g/m, calculated on a dry basis. Finally, the solvent is evaporated by heating to temperatures of around 90-100°C, preferably without a gas flow, for example in a tunnel traversed by hot gas.

According to one embodiment of the present invention, the uncoated primer layer of film 1) is subjected to a printing treatment. This treatment is carried out using inks with low solvent retention characteristics.

According to another embodiment, the print is applied to the lacquer layer of film 1), before or after its coupling with film 2). In this case, any inks known in the art, suitable for lacquered surfaces, can be used. In any case, the "primer" layer of film 1), whether printed or not, is subjected to high-vacuum metallization with the deposition of an aluminum layer with a thickness of approximately 200 to 600 Angstroms.

Devices are generally used for this purpose^

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multi-chamber type machines, in which the metallization area is separated from the material unwinding and winding chamber by film passage ducts and an intermediate suction chamber. In these machines, the film enters the high vacuum chamber (approximately 10-4-10-5 torr) only at the time of metallization.

The metal, usually aluminium, is heated to around 1300-1400°C in evaporation pans made of metallic or refractory material and the vapours thus released are condensed on the film which passes over the pans in close contact with a process cylinder equipped with a suitable cooling system.

These devices can be equipped with cryogenic panels, both in the metallization chamber and in the degassing chamber, which have the function of reducing vacuum formation times and operating pressures.

The thickness of the metal thus deposited is measured by optical and/or electrical detection.

Film 2)

Film 2), useful for the purposes of the present invention, can be any film of olefin nature, unstretched and suitable to act as a sealing layer of the laminate. Generally these films are prepared

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made from polymers such as: polyethylene, polypropylene, propylene-ethylene copolymers, ethylene-vinyl acetate copolymers, ionomeric polymers and their mixtures.

Specific, non-limiting examples of polymers useful for film formation 2) are the following:

- low density polyethylene having the following general characteristics: density 0.918-0.934 g/ml, "melt-index" (190°C) 1-6 g/101, VICAT softening point 90-100°C; - physical mixtures of isotactic polypropylene and atactic polypropylene, the latter in quantities of 15 to 30% by weight in the mixture;

- isotactic polypropylene with an atactic fraction content of 15 to 30% by weight, obtained directly from propylene polymerization processes;

- "random" propylene-ethylene copolymers, with low ethylene content and generally less than about 5% by weight; - blends of isotactic polypropylene, atactic polypropylene and propylene-ethylene copolymer;

- blends of isotactic polypropylene and low density polyethylene.

These polymers, or polymer blends, are extruded in the form of films with thicknesses of the order of 10-10(1 microns, preferably 20-50 microns.

Before extrusion, antioxidant agents (especially phenolics), slip agents (usually

Societ? italiana ?esine ?.i.n. s.p. A te chosen among the amides of higher fatty acids) and ? 14 antistatic agents. The film thus obtained is usually treated on a surface with electric discharges emitted by a high-frequency generator.

Coupling of films 1) and 2)

The coupling occurs by joining the treated surface of the non-oriented film 2) with the metallized layer of the film 1), generally through the lamination technique with the adhesive placed between the two films.

The adhesive is usually spread on the metallized surface of the film 1), in a total quantity of 2

of 1.5-3.0 g (as dry) for each m of surface.

The adhesive used is usually a thermosetting, solvent-based adhesive consisting of two components that are mixed shortly before application, as is known in the field of laminated film technology. Advantageously, polyurethane adhesives dissolved in solvents such as methyl ethyl ketone or ethyl acetate can be used, usually in concentrations of 15-40% by weight. The solvent is removed from the film on which the adhesive solution has been spread, generally by passing through a hot gas tunnel.

The coupling of the films finally takes place between a pair of clamping cylinders heated to a temperature

? w'!0ia irensna nesine ?.I.K. ?.p.A,

temperature which can generally vary from 50 to 80?C and preferably from 60 to 70?C.

The invention is now illustrated by the following experimental examples, which are illustrative and not limitative of the invention.

In these examples, parts and percentages are to be understood as weight.

Example 1

Film preparation 1)

A biaxially stretched ?sotactic polypropylene film, 25 microns thick, rot-2 2 load is used

longitudinal strength 10 kg/mm and transverse strength 25 kg/mm, longitudinal elongation at break 160% and transverse strength 40%, these determinations being carried out according to the ASTM D-882 method (Procedure A). The polypropylene film is treated on the two surfaces with electric discharges up to a wettability value of the treated film equal to 40 dlne/cm, according to the ASTM D-2578 method. Polyethylene imine (commercial product POLYMIN P from the BASF company) in a 0.75% hydroalcoholic solution is applied to the surfaces of the film thus treated, in a quantity equal to 30 mg (as dry) for each m of surface.

The application is done using the "gravure" roller technique with successive passes on the two surfaces of the polypropylene film.

Selcia Italiana Resina S.I.R, S.pA The drying process is then carried out by heating in tujn - 16 - in the path of heated air at 80?C and washing with

water at room temperature (about 20?C) of one of the

two layers of "primer".

The composition for lacquering is prepared separately, consisting of:

- Vinyl chloride-vinyl acetate copolymers, with a

vinyl chloride content of 87% and with a weight of mo_

lecular 15,000 (commercial product VYHD of the UNION CARBIDE Company). 42

- Methyl polymethyl methacrylate with molecular weight 70,000

(commercial product PLEX 8664 of ROHM Company). 33

- Anchor (commercial product PACR0SIR SP0183 of the

(Italian Resins Company S.I.R.). 20

- Diphenyl 1octyl phosphate (commercial product SANTICIZER)

141 of the MONSANTO Company). 5

- Polyethylene wax (commercial product HIN 3 of the

SPICA Society). 1

- Emulsifier (commercial product SPAN 65 from the ATLAS Company). 1

- Slippery (commercial product SYL0ID 166 from the GRACE Company). 0.15

This composition is dissolved in 2-butanone until

at a concentration of 25% and the resulting solution

is applied to the unwashed "primer" layer, in

?irii;' Milana fissfnn SJ.R. s.p *

2

quantity equal to 1.5 g (as dry) for each m of surface area, using the "gravure" roller coating technique. S1 then proceeds to drying in a tunnel traversed by air heated to 100°C.

The polyolefin film thus obtained is then subjected to metallization, in a multi-chamber metallization apparatus, on the surface bearing the washed "primer" layer, operating under the following conditions:

- speed: 6 * 6.5 m/sec.

- pre-vacuum time: 25-30 min.

- vacuum level: from 1 to 2*10-5 torr.

- vacuum variation: < 20%

The thickness of the deposited aluminium layer is approximately 450 A, with a surface resistivity of d12-2.2 Jl (ASTM D-257).

Film 1) thus prepared is receptive to all inks used for lacquered surfaces and the printability characteristics of this surface are optimal. Film preparation 2)

A non-oriented film is prepared from low density polyethylene pellets, having the following characteristics: density 0.924 g/ml, "melt-index" 2 g 10' (190°C), VICAT softening point 98°C. Before extrusion, an antioxidant and a slip agent are added to the polymer.

or ".itila ????????? embroider ?,?.?. ?,?,?,

and an antistatic agent and the unstretched film thus obtained, with a thickness of approximately 25 microns, is treated on the surface with electric discharges.

Coupling of films 1) and 2)

A two-component adhesive, AOCOTE 575 CATA-LYST F (from MORT0N), in a ratio of 85/15, in the form of a 25% solution in ethyl acetate, is spread over the metallized surface of film 1). Application is done using the "gravure" roller technique, depositing 2 g of adhesive (as dry) per m2 of surface. The film 1) thus treated is then passed through a tunnel traversed by hot air to remove the solvent from the adhesive.

The coupling between the adhesive-coated surface of film 1) and the electrically discharged surface of film 2) occurs by passing the two films between two clamping cylinders heated to 65°C. The metallized and coupled film thus obtained has the characteristics summarized in Table 1).

Example 2

The procedure is similar to that of example 1 above, with the only difference being that the washed "primer" layer of film 1) is printed, before being metallised, with five colours and with an opacity greater than approximately 50%.

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The metallized and coupled film finally obtained presents characteristics completely similar to those of the metallized and coupled film of example 1).

Example 3

We proceed as in example 1 using as film 2) a film obtained from polypropylene commercially known as NOVOLEN 1320L, produced by BASF, having the following characteristics: atactic fraction content approximately 20%, density 0.892 g/ml, "melt-index" 6 g/10' (230°C), melting range 167-172°C. This polymer, after adding the usual antioxidant, slip and antistatic agents, is transformed into an unstretched film with a thickness of approximately 25 microns and one of the surfaces of this film is treated with electric discharges. We then proceed by coupling film 1) of example 1) with film 2) indicated above, operating under the conditions of example 1), and a metallized and coupled film is obtained with the characteristics reported in table 1). These characteristics do not undergo significant variations when in the film 1) the washed "primer" layer is printed, before its metallization, with five colors and with a coverage greater than approximately 50%.

Example 4

We proceed as in example 1 using which skins

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cola 2) a non-oriented film, obtained from a "random" propylene-ethylene copolymer, having the following characteristics: ethylene content 2%, "melt-Index" 7 g/10' (230°C), melting point 150°C (determined by polarizing microscope), density 0.901 g/ml. The polymer, after the addition of the usual oxidizing, slipping and antistatic agents, is transformed into an unstretched film, with a thickness of 25 microns, and one of the surfaces of said film is treated with electric discharges.

We then proceed by coupling film 1) of example 1) with film 2) indicated above, operating under the conditions of said example 1 and we obtain a metallised and coupled film with the characteristics reported in table 1).

These characteristics do not undergo significant variations when the "primer" layer on the film 1) is printed, before its metallization, with five colors and with an opacity greater than approximately 50%. Example 5

We proceed as in example 1) using as pe11 cola 2) a non-oriented film prepared from a polymer mixture containing 50% of NOVOLEN 1320L (commercial product of the BASF company - polypropylene with an atactic fraction content of approximately 20%, density 0.892

TABLE

Ex. Thickness Density Permeability to Oxygen Permeability to Water Vapor Resistance Range (microns) Weldability Soldering

3 2

(cm /m2*24 hours*atm) (gr/m ?24 hours) (?C) (gr/cm)

1 53 2,5 10 1 115-135 650

3 53 2.5 5 0.7 140-160 800

4 53 2.5 6 0.7 135-155 800

5 53 2.5 6 0.7 138-160 800

Optical density: log.^ (where T = Transparency measured spectrophotometrically)

Oxygen Permeability: ASTM D 1434 at 25°C

Water vapor permeability: ASTM E 96 procedure A CO Tz et? Weld strength: ASTM F 88.

ST

to the

I co ro -30 co

Claims (9)

1. Laminated, printed, metallized and heat-sealable film formed by the union of: 1) a printed and metallized film made of an oriented polyolefin film, bearing on both surfaces a layer of "primer" applied using an aqueous or hydroalcoholic solution, one of said "primer" layers being lacquered using a vinyl, vinylidene or acrylic polymer or copolymer, Società Italiana Resino S.I.R. S.p.A, the other "primer" layer being metallized including the addition of a layer of aluminum; 2)*a film made of a non-oriented film,?of polyolefinic nature, having ter characteristics. mosa1dabi1it?; the coupling occurs, after the interposition of adhesive, by joining one surface of the film 2) with the metallized surface of the film 1); to the film 1) the print is also applied on the unlacquered "primer" layer, in a phase prior to the metallization of said layer, or on the lacquer layer, in a previous stage or subsequent to that of film coupling 1) with the film 2). 2. Laminated film according to claim 1 carat terized by the fact that the polyolefin film of the film 1) is a film with a thickness of 10-100 microns and preferably a film with a thickness of 20-40 microns, obtained by filming and orienting crystalline polypropylene with a "melt-index" of 1.5-4 qr/10'. 3. Laminated film according to claim 1 dear? characterized by the fact that the "primer" applied to the surfaces of the polyolefin film of film 1) is polyethyleneimine in quantities from 5 to 50 mgr/m , or polyhydroxyalkoxyalkylamines in quantities from 10 iocieia l?aliaua RE 'ne SJ.R, $p A 2 at 100 mgr/m , or a mixture of polyethylenimine 24 with the condensation products of urea or melamine with formaldehyde, especially etherified ones, and/or with alcohols polyhydroxylated sialkylmelamines, with a ratio weight between said polyethyleneimine and said others 2 composed of 1/1 to 5/1, in quantities from 10 to 100 mgr/m of the surface of the olefin film. 4. Laminated film according to claim 1 characterised in that the lacquer of the film 1) ? consists of methyl methacrylate polymers with molecular weights of 20,000-100,000, or mixtures of these with polymers or copolymers of vinyl chloride, aceta^ 2 vinyl and acrylic, in quantities from 1 to 3 g/m 2 and preferably 1.5 to 2 gr/m . 5. Laminated film according to claim 1 carat^ caused by the fact that the aluminum layer of the film 1) has a thickness of 200-600 Angstroms. 6. Laminated film according to claim 1, characterized in that the polyolefin polymers of the film 2) are selected from: polyethylene, polypropylene, propylene-ethylene copolymers, ethylene-vinyl acetate copolymers, ionomeric polymers and blends relative. 7. Laminated film according to claim 1 characterized in that the thickness of the film 2) ? 10-100 microns and preferably 20-50 microns. 25 8. Process for preparing the coupled film according to claims 1 to 7, characterised by connecting the metallised surface of the film 1) with one of the surfaces of the film 2) by interposing an adhesive and passing it through a pair of clamping cylinders heated to a temperature of 50 to 80°C and preferably 60 to 70°C. 9. Process according to claim 8, characterised in that the surface of the film 2), to be coupled to the metallised surface of the film 1), is treated by high frequency electric discharges before coupling.