CA1221610A - Process for forming a sealant web-pvdc-base film laminate - Google Patents
Process for forming a sealant web-pvdc-base film laminateInfo
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- CA1221610A CA1221610A CA000433854A CA433854A CA1221610A CA 1221610 A CA1221610 A CA 1221610A CA 000433854 A CA000433854 A CA 000433854A CA 433854 A CA433854 A CA 433854A CA 1221610 A CA1221610 A CA 1221610A
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Abstract
ABSTRACT OF THE DISCLOSURE
A film laminate comprising a base film and a first sealant web with a coating of polyvinylidene chloride (PVDC) sandwiched therebetween is disclosed. The first sealant web is selected from the group consisting of a) film made from a copolymer of ethylene and vinyl acetate, and b) a film made from a blend of i) a copolymer of ethylene and vinyl acetate with ii) a homopolymer of ethylene, or a copolymer of ethylene and one or more C4 to C10 .alpha.-olefins, said homo-polymer or copolymer having a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copoly-mer. The base film is selected from the group consisting of unmetallized or metallized oriented nylon film, oriented polyester film, oriented polypropylene film, cast nylon film, polyethylene film and a second sealant web, said second sealant web being selected from the same group as said first sealant web and having a slip coefficient of less than about 0.4. The PVDC coating consists of at least one layer, the layers being characterized by failing a Solvent Haze Test, and preferably having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the layer in contact with the base film being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C. If the base film is metal coated, then the PVDC is in direct contact with the metal. A process for forming the laminate is also disclosed. The process comprises bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll then said web which contacts the hot roll has a slip coefficient of less than about 0.4. The laminates may be used for packaging comestibles e.g. bacon, wieners and cheese.
A film laminate comprising a base film and a first sealant web with a coating of polyvinylidene chloride (PVDC) sandwiched therebetween is disclosed. The first sealant web is selected from the group consisting of a) film made from a copolymer of ethylene and vinyl acetate, and b) a film made from a blend of i) a copolymer of ethylene and vinyl acetate with ii) a homopolymer of ethylene, or a copolymer of ethylene and one or more C4 to C10 .alpha.-olefins, said homo-polymer or copolymer having a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copoly-mer. The base film is selected from the group consisting of unmetallized or metallized oriented nylon film, oriented polyester film, oriented polypropylene film, cast nylon film, polyethylene film and a second sealant web, said second sealant web being selected from the same group as said first sealant web and having a slip coefficient of less than about 0.4. The PVDC coating consists of at least one layer, the layers being characterized by failing a Solvent Haze Test, and preferably having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the layer in contact with the base film being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C. If the base film is metal coated, then the PVDC is in direct contact with the metal. A process for forming the laminate is also disclosed. The process comprises bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll then said web which contacts the hot roll has a slip coefficient of less than about 0.4. The laminates may be used for packaging comestibles e.g. bacon, wieners and cheese.
Description
PROCESS FOR FORMING A SEALANT WEB-PVDC-BASE FILM_LA~ltNATE
The present invention relates to heat lamination of a sealant web to a polyvinylidene chloride (PVDC)-coated base film.
Laminates of base films and a sealant web having a PVDC coating sandwiched therebetween are useful for packaging comestibles e.g. bacon, wieners and cheese. Examples of the base film are nylon, polyester and polypropylene films; an example of a sealant web is polyethylene. Usually such laminates are prepared by so-called adhesive lamination of the sealant web to the PVDC coating of the PVDC-coated base film. It is usual in such adhesive lamination processes to spread an adhesive, dissolved in a solvent, onto the PVDC
coating and to allow the solvent to evaporate until the adhesive is tacky. The sealant web is then pressure laminat-ed to the tacky adhesive-coated PVDC. The adhesive is usually a urethane adhesive. Such urethanes may be dissolved in volatile organic solvents e.g. acetone, ethyl acetate or toluene.
There are several drawbacks to adhesive lamination of sealant webs to PVDC coatings. One drawback relates to the use of the volatile organic solvents, which tend to be highly flammable, expensive and not easily recoverable. It is desirable, therefore, from a safety standpoint, to use aqueous adhesives or adhesive-less processes in order to remove or reduce the fire hazards. ~nother drawback relates to the type of PVDC that may be used. :tn order to prevent the PVDC from being attacked by the ~olvent used in an adhesive lamination process, cry~talline PVDC's mus~ be used.
However, crystalline PVDC's generally do not adhere well to the aEorementioned base films and it is usually necessary to bond the crystalline PVDC to the base film with a primer.
For example, an amorphous PVDC primer, as taught in Canadian patent application No. 391 235 of T.J. Lang, filed 19~1 December 01, may be used to adhere nylon film to a crystal-O
line PVDC.
Another technique for producing laminates of two plastic films with PV~C sandwiched therebetween is to coat one of the plastic films with a so-called PVDC barrier adhe-sive and then to heat-laminate the second plastic film to the barrier adhesive. Barrier adhesives are available for coating oriented polypropylene, medium density polyethylene (density of about 0.935 to 0.945 g/cm3), nitrocellulose-coated regenerated cellulose and nylon films. Such barrier adhesives allegedly may be heat laminated to low density polyethylene film. It has been found, however, that the bond strength with so-called slip-modified low density polyethyl-ene film i.e. a low density polyethylene film containing a slip additive, is only about 10-20 g/cm as measured on a Suter* tester. Commercially acceptable bond strengths are thought to be in excess of about 100 g/cm.
A laminate, and a process for forming the laminate, of a first sealant web and a base film, in which the base film is nylon film, oriented polypropylene film, oriented polyester film, or a second sealant web, which laminate has a PVDC layer between the first sealant web and the base film, which is made by a process which is not an adhesive lamina-tion process and which has comrnercially acceptable bond strengths has now been found.
Accordingly, the present invention provides a film laminate comprising a base film and a first sealant weh with a coating of PVDC sandwiched therebetween;
said first sealant weh bein~ sel.ected ;Erom the group consisting of a)a Eilm made from a copolymer of ethylene and vinyl acetate, and b)a film made from a blend of i)a copoly-mer oE ethylene and vinyl acetate with ii)a homopolymer of ethylene, or a copolymer of ethylene and one or more C4 to Clo ~-olefins, said homopolymer or copolymer havin~ a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copolymer, said base film being selected from *denotes trade mark.
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the group consisting of oriented nylon :Eilm, oriented poly-ester film, oriented polypropylene film, cast nylon film and a second sealant web, said second sealant web being selected from the same group as said first sealant web and having a slip coefficient of less than about 0.4;
said PVDC coating consisting of at least one layer, the layers being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film and polypropylene film, the layer in contact with the base film being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40~C.
The present invention also provides a process for forming the laminate of the present invention comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact wi~h the hot roll, then said sealant web that contacts the hot roll has a slip coe:Eficient of less than about 0.4.
In one embodiment the process comprises:
a) heating a PVDC-coated base film or a first sealant web to an extent sufficient to reduce the crystalli-nity index of the PVDC coating to less than about 1.05, b) passing the heated PVDC-coated base :EiLm or first sealant web over a hot roll, and c) when a PVDC-coated base :Eilm is used, bringing the first sealant web into contact with the PVDC
coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot ro].l, to form a laminate, and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to Eorm a laminate.
In other embodiments of the process, a PVDC-coated base film or first sealant web is taken and a further coating of PVDC is applied to the base film or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinhelow as Processes ~, B, C and D.
Process A comprises:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by ha~ing a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C;
b) coating the PVDC-coated base film with an aque-ous PVDC dispersion .o form a second PVDC coating, said second PVDC being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, c) drying and su~sequently heating the second PVDC
coating unt.il the temperature of t.he free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in con tact with said hot roll, said hot roll being at a temperature higher than about 70C, and e) brlnging the el.r~t seal.ant web lnto contact with the second .PVDC coating and nipping said :Eirst sealant web to the PVDC-coated base .Eilm, between a nlp roll and the hot roll to form a laminate.
Process ~ comprises:
a) heatlng the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-e~ ~y having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at ~0C.
b) coating the first sealant web having a surface tension of at least 42 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated sealant web, said PVDC coating on the first sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70C, and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
Process C comprises:
a) coating the PVDC-coated first sealant web with an aqueous PVDC clispersion to form a second PVDC coating, said second PVDC coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, iE the base :Eilm is selected from nylon film, polyester :Eilm or polypropylene Eilm, the second PVDC coating being Eurther characterized by having a crystallinity index of from 1.12 to 1.25 i.e dried and allowed to stand for 5 days at 40C, and said PVDC coating adjacent to the first sealant web being characterized by having a crystallinity index o:E less than 1.15 if dried and allowed to stand for 30 days at 20C, 16~
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70C, and d) bringing the base film into contact with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate.
Process D comprises:
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a la~inate.
In further embodiments of the process, a base film or Eirst sealant web is taken and a coating of PVDC is applied to the base film and/or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinbelow as Processes E, F and G.
Process E comprises:
a) coating the base film with a first PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days O
at 20DC and, if the base film is selected from nylon film, polyester film or polypropylene film, the first PVDC coating being further characterized by a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C;
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, to 0 form a second PVDC coating;
c) heating the said second coating until the temperature of the free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70C, and f) bring.ing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, toform a laminate.
Process F comprises:
a) coating a first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by having a crystallinity index ofless than 1.15 if dried and allowed to stand for 30 days at 20C, to form a first PVDC coating;
b) coating the PVDC-coated Eirst se~].ant weh formed in step a) with A second PVI)C, the secorld coating being characterized by having a cryst~llinity .index oE less than 1.15 i.f dried and allowed to stand :eor 30 days at 20C
and, if the hase film is nylon Eilm, polyester film or polypropylene film, the second RVDC coating being further characterized by a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, and a crystallinity index of from 1.12 to 1.25 if dried and allowed P~ Lo to stand for 5 days at 40C;
c) passing the base film over a hot roll, said base film being in contact with said hot holl, and said hot roll being at a temperature higher than about 70C, and d) bringing the PVDC-coated surace of the PVDC-coated first sealant web, formed duri.ng steps a) and d3, into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to :Eorm a laminate.
Process G comprises:
a) coating the base film with a :Eirst PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or polypropylene film, the first PVDC coating being further characterized by having a crystallinity index oE from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C, b) drying the first PVDC coating:
c) coating a f.irst sealant web, having a surface tension of at least 42 d~nes/cm with a second PVDC, the coat-ing being characterized by having a crystallinity index of less than 1.15 i:E dried and allowed to stand for 30 days at 20C; d) drying the second PVDC coating' e) passing the base film over a hot roll, said base ilm being in contact with said hot roll, and said hot roll being at a temperature higher than about 70C; and f) bringing the PVDC-coated s~lrfnce of the PVDC-coated :Eirst sealant weh into contact with khe PVDC-coated surface O:e the PVDC-coated base :Eilm and nipping the PVDC-coated .Eirst sealant web to the PVDC~coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred ernbodiment of the process of the present invention, the PVDC layers in contact with and furthest away from the base film are combined into a single layer, said PVDC layer being characteri.zed by having a crystallinity in~ex of less than 1.15 if dried and allowed to stand for 30 days at 20C and of from 1.12 to 1.25 if dried and allowe~ to stand for 5 days at ~0C.
In another embodiment, when the base film is a cast nylon film the PVDC coating which is furthest away from the base film i.e. the layer which contacts -the sealant web, is characterized by having a crystallinity index of less than 1.05 iE dried and allowed to stand for 30 days at 20C.
In particularly preEerred emboAiments the sealant web has a surface, adjacent to the PVDC coating, o~ a mate-rial selected from the group consisting of a) a copolymer of ethylene and vinyl acetate, b) a blend of a copolymer of ethylene and vinyl acetate and at least one of (i) a copolym-er of ethylene and at least one C4 - Clo ~-olefin having a density of from 0.915 to 0.955 g/cm3 and (ii) a homopolymer of ethylene having a density of from 0.915 to 0.955 g/cm3.
Preferred copolymers of ethylene and ~-olefins(s) are ethylene/butene-l, ethylene/ octene-l and ethylene/butene-l/-octene-l copolymers.
Preferably the vinyl acetate content of the copoly-mer of ethylene and vinyl acetate (EVA) is between about 1.0 and about 20 weight percent and the weight ratio of the EVA
to ethylene homopolymer, ethylene copolymer or blend of said copolymer and homopolymer is in the range of 2:98 to 50:50, especially in the range of 2:98 to 20:80.
In another embodiment the sealant web is an EVA co-polymer having a vinyl acetate content o~E hetw~en ahout 1.0 and about 15 weight percent and ~aid ~ealant web contains a slip additive. The slip coeEEicient oE the sealant web, as measured by ASTM Procedure D-1894 may be less than 0.4, especially less than 0.3.
In a further emhodiment the surface of the sealant web adjacent to the PVDC coating has been corona discharge-treated to a level between 38 and 45 dynes/cm prior to lamination.
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In another preferred embodiment, the base film is a nylon film, especially a film of nylon 6, nylon 66 or a condensation copolymer of -caprolactam and hexamethylene-diamine adipate (sometimes referred to as nylon 6/66).
In a further embodiment the base film has a metal-coated surface, said surface being between the base film and the PVDC coating. Said metal coating may be in the form of, for example, a vacuum deposited film. Preferably the metal is aluminum.
In another embodiment the sealant web is a copoly mer of ethylene and vinyl acetate, having a vinyl acetate content between 2 and 40 weight percent, bonded to a carrier web. Preferably the carrier web is made from an ionomer.
In a further embodiment the base film has an aluminum-coated surface, said surface being sandwiched between the base film and the PVDC coating.
In yet another embodiment a layer of PVDC is inter-posed between the first and second PVDC coatings, said inter-posed layer of PVDC being characterized by being capable of developing crystallinity to a level such that the interposed crystalline PVDC layer so formed resists attack by an organic solvent, as measured by the Solvent Haze Test described here-inbelow, said organic solvent being capable of dissolving PVDC coatings having a crystallinity index of less than 1.05.
An example of a PVDC dispersion suitable for forming the interposed layer is available under the trade mark Serfene 411.
In the Solvent Haze Test, the PVDC coating, when dry and after allowing crystallinity to develop, is sprayed with the organic solvent. If the PVDC coating has developed sufficient crystallinity, the PVDC coating will be unaffected by the solvent. If, however, the PVDC coating is insuffi-ciently crystalline the solvent will either turn the PVDC
coating turbid in appearance or will dissolve portions or all of thePVDC coating.
Crystallinity index, as defined in the present specification, is determined using infra-red spectroscopy by obtaining an attenuated total reflectance infra-red spectrum of the coated film. Crystallinity index may be measured 5 using a Perkin Elmer* 467 infra-red spectrophotometer and a Wilks* ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45. In the method, rectangles of film are placed on each side of the germanium crystal (i.e.
two rectangles of film are used~, with the PVDC-coated side of the film against the crystal. The reference heam attenuator is set at 85% at 1150 cm~l and the sample is scanned between 950 cm~l and 1150 cm~l. The absorbances A of the background, at 1115 cm~l, and at the peaks, at 1070 cm~
and 1042 cm~l, are measured. Crystallinity index is calcu-lated by dividing the difference between A1042 and Allls by the difference between A1070 and A1115 The following description of the invention is pri-marily directed to coating and laminating nylon base films.
Similar techniques to those used for nylon film, particularly to those used for oriented nylon film, may be used for the polyester and polypropylene base films. However, cast nylon films, particularly thin cast nylon films tend to require more stringent control when coating with PVDC and laminating the PVDC-coated nylon film to the sealant web because of the sensitivity of cast nylon film to moisture and heat. ~ase films made from a sealant web require a slip coeEficient o~
less than about 0.4 in order to prevent ~tickiny oE the film to the }lot roll.
The invention rnay he more fully understood by reference to the drawings in which Figure 1 shows in d.iagram-matic form a process of the present invention.
Referring to Figure 1, suitable apparatus comprises a first coating station 10, a first dryer 11, a second coat-ing station 12, a second dryer 13, and nip roll assembly 14.
Apparatus for supplying base film and sealant web and for *denotes trade mark.
- : :
,o ~ 12 -winding up the laminate are not shown.
First coating station 10 comprises a pan 34 ~or holding a PVDC dispersion, direct gravure roll 16 and nip roll 20, associated with gravure roll 16. Second coating station 12 is similar to first coating station 10 with pan 35, direct gravure roll 17 and nip roll 21. Direct gravure rolls 16 and 17 and associated nip rolls may be replaced by Meyer* rods, reverse gravure rolls or other coating apparatus if desired. It will be recognised by those skilled in the art that if apparatus which subjects the PVDC dispersion to relatively high shear is used, then the PVDC dispersion may have to be modified to minimize foaming e.g. with the addi-tion o~ iso-propyl alcohol.
Nip roll assembly 14 comprises a lamination roll 18, which has means for heating tnot shown), an associated nip roll 19, lay-on roll 36 which is adapted to guide PVDC-coated nylon film onto lamination roll 18, lay-on roll 37, which is adapted to guide sealant web into the nip between nip roll 19 and lamination roll 18, and take-of roll 38 which may be positioned to permit a laminate to remain in contact with lamination roll 18 a~ter passing through the nip between lamination roll 18 and nip roll 19.
There are various idler rollers (some are shown but not identi:Eied in the drawing) which are adapted, for example, to guide film through first dryer 11, after leaving first coating station 10 and before passing to second coating station 12.
In one embodiment oE the present invention, nylon film 30 is passed through th~ Eirst coating station 10 which may comprise a direct gravure roll 16 and associated nip roll 20. A first PVDC coating is applied at the first coating station. Typically 3.25 to 6.51 g/m2(2-4 lb/ream) PVDC coat-ing i.e. 6.50 to 13.02 g/m2 of 50% PVDC aqueous dispersion, is coated onto the nylon film if the nylon film is oriented, and 2.44 to 3.25 g/m2 of PVDC coating i.e. 4.88 to 6.51 g/m2 *denotes trade mark.
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of 50% PVDC aqueous dispersion, is coated onto the film if the nylon film is substantially unoriented e.g. is cast film.
The first PVDC coating is dried in first dryer 11 before being coated with the second PVDC coating in the second coating station 12. Typically 3.25 to 6.51 g/m2 of PVDC
coating is direct gravure coated onto the PVDC-coated film by means of direct gravure roll 17 and associated nip roll 21.
Even cast nylon film may, at this stage, be coated with up to 6.51 g/m2 of PVDC coating, or more, as the first PVDC
coating tends to prevent water in the PVDC dispersion from wrinkling or curling the nylon film. The second PVDC coating is dried in second dryer 13. The amount of heat applied to the PVDC-coated nylon film, in second dryer 13 is controlled to ensure that the second PVDC coating is dried sufficiently and has sufficient so-called "green tack", but is not heated to the extent that a relatively non-adherent skin forms on the PVDC coating.
The term "green tack", used in the art, may be a misnomer, as it is believed that the dried PVDC coating is not tacky in the normally accepted sense of the word. The term is believed to relate to a lack of crosslinking in the PVDC coating. In the present process, an indication of the sufficiency of the green tack may be ascertained by measuring the surface temperature of the PVDC coating just prior to the PVDC-coated film leaving the second dryer. At surface temperatures less than about 70C, the PVDC coating has sufficient green tack for subse~uent lamination. At ~urface temperatures above ahout 70C e.g. 85C, the PVDC coat.tng nlay have insufficient green tack Eor the PVDC coating to adh0re well to the sealant web. The PVDCcoated nylon film 31 which exits from second dryer 13 is wrapped around heated lamina-tion roll 18, the nylon film contacting roll 18. Sealant web 32 is fed onto PVDC-coated nylon film 31 so that the sealant web 32 contacts the PVDC coating. The PVDC-coated nylon film 31 and sealant web 32 are nipped together by the application .
o of nip roll 19 to the lamination roll 18. The laminate may then be passed further round heated lamination roll 18 or into a hot 20ne in order to strengthen the bond between the sealant weh and the PVDC coating. The laminate so formed, 33, is wound up on a roll, not shown.
In some embodiments of the present invention a sin-gle PVDC coating can be used which performs the functions of both layers of PVDC. The crystallinity index specifications for the single PVDC must meet the specifications of the two PVDC layers. The single PVDC may be applied in two steps as indicated hereinabove or in a single step. The single step process is particularly useful in the case of oriented nylon, polyester or polypropylene films, whereas the two step process may be desirable for cast nylon film, because of the tendency of the film to curl in the presence of moisture.
In the single step process wherein the PVDC coating is laid down in a single application, only one of the coating stations and associated dryer will be used. Furthermore, for a structure which has an interposed layer of crystalline PVDC
a third coating station and associated dryer (neither of which are shown in the drawing) will be required.
When dealing with cast i.e. substantially unorient-ed, nylon film it may be necessary to apply tension to the film in the transverse direction in order to prevent curl as the film passes through the dryer. This is particularly desirable in dryers which apply heat only to one side of the film e.g. a Faustel* dryer.
When dealing with oriented nylon, oriented poly-ester or oriented polypropylene ba~e films, it may be desir-able to pass the coated film through a dryer, under very lowlongitudinal tension. A so-called floater dryer is suitable.
Such a dryer avoids pulling the film under tension, which might otherwise induce wrinkling in the Eilm.
When the base film is a sealant web it is necessary that the film have a slip coeficient of less than about 0.4, preferably less than about 0.3, and especially about 0.2.
*denotes trade mark.
~2216;~0 Sealant webs having a slip coefficient of about 0.2 are some-times referred to by those skilled in the art as "high slip"
films.
The base film may also have a metal coating to make the final film structure substantially impermeable to oxygen.
The metal, e.g. aluminum, may be applied by known methods, for example by vacuum deposition. The amount of metal deposited on the base film depends on the required oxygen permeability of the final film structure. Typically, aluminum is deposited until an optical density of about 2.5 is attained. Optical density is defined as the logarithm of the quotient of, as dividend, the intensity of a 500 nm wave-length light beam prior to passage through the film structure and, as divisor, the intensity of the light beam after passage through the film structure. Optical density may be measured using a Cary* 210 UV-visible spectrophotometer. The aluminum-coated base film laminate is usually coated with a PVDC coating adjacent to the aluminum so that the mechanical integrity of the aluminum coating remains when the structure is used in packaging operations e.g. is not damaged by pin-holing or scratching, as it may be if on the outside of the package.
It is often desirable to apply coloured designs, and/or printed matter on the base film-PVDC coating-sealant web structure. In the context of the present invention such designs and/or printed matter may be placed on the structure using inks applied to the base film or the sealant web. The printing would therefore be between the base Eilm ancl the PVDC coating or between the PVDC coating and the sealan~ web.
Corona discharge treatment of the surface to be printed may be desirable. The extent of ink coverage depends in part on the bond strength between the ink and the base film and between the ink and the PVDC coating. It is desirahle to select an ink that bonds well to the PVDC coating and to the base film in order to ensure that the bond strengths between adjacent layers in the final structure are sufficient for the *denotes trade mark.
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anticipated end use.
In the event that PVDC-coated base film is avai]-able instead of uncoated film, the PVDC-coated base film may need to be heated in order to substantially destroy any crystallinity in the PVDC. For example, in the case where the PVDC coating of the pre-coated base film would have a crystallinity index o~ less than 1.15 when dry and iE allowed to stand for 30 days at 20C, and from 1.12 to 1.25 when dry and if allowed to stand for 5 days at 40C, the PVDC-coated base film may be directly heat laminated by passing the PVDC-coated base fllm through the nip roll assembly, provided the temperature of lamination roll 18 is sufficiently high e.g.
greater than about 85C, to substantially destroy any crys-tallinity which may have been developed in the PVDC coating.
The PVDC-coated base film should be heated to an extent sufficient to reduce or maintain the crystallinity index at less than about 1.05. It will be understood by those skilled in the art that such PVDC-coated base film, available on rolls, would have a slip sheet between the layers of film on the roll or the PVDC coating would contain an antiblock agent e.g. wax or talc.
The base film, pre-coated with a PVDC coating may also be heat laminated to a sealant web by PVDC coating at the s~cond coating station with a PVDC characterized by hav-ing a crystallinity index of less than 1.15 when dry and ifallowed to stand for 30 days at 20C, and subsequently drying and heat laminating as described hereinbefore.
It should be understood that, in the pre~ent speci-fication, when reEerring to films pre-coate~d with PVDC, the number of days, after which crystallinity index oE the PVDC
is determined, is measured from the time immediately after the applied PVDC dispersion has been dried. In the case where the film is coated by a person (the coater) other than the person who does the laminating (the laminator), it may not be apparent to the laminator how many days have lapsed since the film was coated and at what temperature the film ` 1221610 was ~tored. The laminator nay therefore nee~ to ma~e ~nquiry regar~ing the ch~racter~ation of the PVDC use~ as the co~t-ing f~r the baee film.
In the event th~t the base ~ilm i~ cast nylon film or a ~ealant web the lamination temperature should be kept as low ae pos6ible to minimi~e ehrinkage ~nd other effects associated with heat~ng the nylon film to too high a tempera-ture. In these ca~es it i6 advantageoue for the PVDC coating next to the eealant web to have ~ low heat sealing tempera-ture. Generally, such PVDC coating~ have a cryetallinityindex of less than about 1.05 when dry and if allowed to etand for 30 days at 20C. Three PVDC di~persions which are suitable in thie regard are Serfene*2011, Serfene 2012, Serfene 2015.
When the sealant web i8 not PVDC-coated, it i8 believed important that the crystallinity index of the PVDC
coating whic~ will conta~t the sealant web be less than about 1.05 immediately prior to lamination. The temperature of the PVDC-coated base film, upon leaving the fiecond dryer ~hould be less than about 75-C in order to sufficiently dry the PVDC
coating and to retain the so-called "green tack" of the dried PVDC coating. At temperaturee greater than about 75-C the "green tack" or adhe~ive nature of the dried PVDC coating may be insufficient. The temperature of the lamination roll should be at least about 70-C, preferably at least 85-C, in order to cause the PVDC coating to remain in or revert to a eubstantially amorphous etate. More preferably the tempera-ture of the lamination roll should be at least about ~S-C.
The temperature of the lamination roll ~hould be less than the melting temperature of the eealant web and preferably at least about 20-C less than the meltlng temperature of the sealant web. Although not wishing to be bound ky any theory, it is believed that the selection of temperature at which the lamination roll is operated depend~ to a certain e~tent on the eoftening point of the sealant web.
A~ indicated hereinbefore, the eealant webs may *denotes trade mark . ~
16~0 contain slip a~ditives.
PVDC coatings of the type uæeful for coating the base film and/or heat laminating to the sealant web generally have oxygen permeabilities of the order of 15.6 ml/m2/atmos./
day. This is believed sufficient for most applications. In the event that lower oxygen permeability is requiredl a more crystalline PVDC coating within the range of PVDC coatings of the present invention may be selected. Alternatively the base film may be coated with PVDC on both sides. As a further alternative, a crystalline PVDC coating e.g. one having a crystallinity of greater than about 1.30 when dry, may be sandwiched between the first and second PVDC coatings used in the present invention. As stated hereinbefore, an aluminum coating may be placed between the base film and the PVDC coating. Using vacuum deposited aluminum, oxygen perm-eabilities in the order of 0.75 ml/m2/ atmos./day are attainable.
Nylon copolymer e.g. nylon 6/66, films are prefer-red for applications where resistance to pinholing of the package is required. A preferred laminate for packaging cheese comprises a nylon base film and a sealant web of a film made from a blend of a linear copolymer of ethylene and a C4 - Cg ~-olefin and a copolymer of ethylene and vinyl acetate.
It may be seen from the foregoing that, for cast nylon film, one process comprises coating the film with two coatings of PVDC prior to heat laminating the PVDC-coated film to the sealant web. The Pirflt PV~C coating .is app].ied under conditions whlch mi~i1nize the chance of occurrence oE
curling or wrinkling, caused by high temperatures and/or the presence of excess quantities of moisture. This may be accomp]ished primarily by ensuring that as little as possible of the PVDC dispersion is applied to the nylon film, but it must be sufficient to provide complete coverage of the nylon film, with PVDC, after drying, so that there is little chance _ ~9 _ of absorption of water by the nylon film during the second application of PVDC dispersion. For these reasons the first layer of PVDC dispersion is usually applied at about 2.44 to 3.25 g/m2 ~dry basis). In addition it is desirable to control the transverse tension on the film as it passes through the dryer. The level of tension required will vary according to the type o~ nylon film, the quantity of PVDC
emulsion applied, the temperature of the dryer and the type o~ dryer e.g. one-side or two-side direction of the heat towards the film. Typically tension levels from ~ to 7 N/m width of film are desirable.
The second coating of PVDC may be applied at from
The present invention relates to heat lamination of a sealant web to a polyvinylidene chloride (PVDC)-coated base film.
Laminates of base films and a sealant web having a PVDC coating sandwiched therebetween are useful for packaging comestibles e.g. bacon, wieners and cheese. Examples of the base film are nylon, polyester and polypropylene films; an example of a sealant web is polyethylene. Usually such laminates are prepared by so-called adhesive lamination of the sealant web to the PVDC coating of the PVDC-coated base film. It is usual in such adhesive lamination processes to spread an adhesive, dissolved in a solvent, onto the PVDC
coating and to allow the solvent to evaporate until the adhesive is tacky. The sealant web is then pressure laminat-ed to the tacky adhesive-coated PVDC. The adhesive is usually a urethane adhesive. Such urethanes may be dissolved in volatile organic solvents e.g. acetone, ethyl acetate or toluene.
There are several drawbacks to adhesive lamination of sealant webs to PVDC coatings. One drawback relates to the use of the volatile organic solvents, which tend to be highly flammable, expensive and not easily recoverable. It is desirable, therefore, from a safety standpoint, to use aqueous adhesives or adhesive-less processes in order to remove or reduce the fire hazards. ~nother drawback relates to the type of PVDC that may be used. :tn order to prevent the PVDC from being attacked by the ~olvent used in an adhesive lamination process, cry~talline PVDC's mus~ be used.
However, crystalline PVDC's generally do not adhere well to the aEorementioned base films and it is usually necessary to bond the crystalline PVDC to the base film with a primer.
For example, an amorphous PVDC primer, as taught in Canadian patent application No. 391 235 of T.J. Lang, filed 19~1 December 01, may be used to adhere nylon film to a crystal-O
line PVDC.
Another technique for producing laminates of two plastic films with PV~C sandwiched therebetween is to coat one of the plastic films with a so-called PVDC barrier adhe-sive and then to heat-laminate the second plastic film to the barrier adhesive. Barrier adhesives are available for coating oriented polypropylene, medium density polyethylene (density of about 0.935 to 0.945 g/cm3), nitrocellulose-coated regenerated cellulose and nylon films. Such barrier adhesives allegedly may be heat laminated to low density polyethylene film. It has been found, however, that the bond strength with so-called slip-modified low density polyethyl-ene film i.e. a low density polyethylene film containing a slip additive, is only about 10-20 g/cm as measured on a Suter* tester. Commercially acceptable bond strengths are thought to be in excess of about 100 g/cm.
A laminate, and a process for forming the laminate, of a first sealant web and a base film, in which the base film is nylon film, oriented polypropylene film, oriented polyester film, or a second sealant web, which laminate has a PVDC layer between the first sealant web and the base film, which is made by a process which is not an adhesive lamina-tion process and which has comrnercially acceptable bond strengths has now been found.
Accordingly, the present invention provides a film laminate comprising a base film and a first sealant weh with a coating of PVDC sandwiched therebetween;
said first sealant weh bein~ sel.ected ;Erom the group consisting of a)a Eilm made from a copolymer of ethylene and vinyl acetate, and b)a film made from a blend of i)a copoly-mer oE ethylene and vinyl acetate with ii)a homopolymer of ethylene, or a copolymer of ethylene and one or more C4 to Clo ~-olefins, said homopolymer or copolymer havin~ a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copolymer, said base film being selected from *denotes trade mark.
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the group consisting of oriented nylon :Eilm, oriented poly-ester film, oriented polypropylene film, cast nylon film and a second sealant web, said second sealant web being selected from the same group as said first sealant web and having a slip coefficient of less than about 0.4;
said PVDC coating consisting of at least one layer, the layers being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film and polypropylene film, the layer in contact with the base film being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40~C.
The present invention also provides a process for forming the laminate of the present invention comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact wi~h the hot roll, then said sealant web that contacts the hot roll has a slip coe:Eficient of less than about 0.4.
In one embodiment the process comprises:
a) heating a PVDC-coated base film or a first sealant web to an extent sufficient to reduce the crystalli-nity index of the PVDC coating to less than about 1.05, b) passing the heated PVDC-coated base :EiLm or first sealant web over a hot roll, and c) when a PVDC-coated base :Eilm is used, bringing the first sealant web into contact with the PVDC
coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot ro].l, to form a laminate, and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to Eorm a laminate.
In other embodiments of the process, a PVDC-coated base film or first sealant web is taken and a further coating of PVDC is applied to the base film or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinhelow as Processes ~, B, C and D.
Process A comprises:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by ha~ing a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C;
b) coating the PVDC-coated base film with an aque-ous PVDC dispersion .o form a second PVDC coating, said second PVDC being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, c) drying and su~sequently heating the second PVDC
coating unt.il the temperature of t.he free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in con tact with said hot roll, said hot roll being at a temperature higher than about 70C, and e) brlnging the el.r~t seal.ant web lnto contact with the second .PVDC coating and nipping said :Eirst sealant web to the PVDC-coated base .Eilm, between a nlp roll and the hot roll to form a laminate.
Process ~ comprises:
a) heatlng the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-e~ ~y having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at ~0C.
b) coating the first sealant web having a surface tension of at least 42 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated sealant web, said PVDC coating on the first sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70C, and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
Process C comprises:
a) coating the PVDC-coated first sealant web with an aqueous PVDC clispersion to form a second PVDC coating, said second PVDC coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, iE the base :Eilm is selected from nylon film, polyester :Eilm or polypropylene Eilm, the second PVDC coating being Eurther characterized by having a crystallinity index of from 1.12 to 1.25 i.e dried and allowed to stand for 5 days at 40C, and said PVDC coating adjacent to the first sealant web being characterized by having a crystallinity index o:E less than 1.15 if dried and allowed to stand for 30 days at 20C, 16~
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70C, and d) bringing the base film into contact with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate.
Process D comprises:
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a la~inate.
In further embodiments of the process, a base film or Eirst sealant web is taken and a coating of PVDC is applied to the base film and/or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinbelow as Processes E, F and G.
Process E comprises:
a) coating the base film with a first PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days O
at 20DC and, if the base film is selected from nylon film, polyester film or polypropylene film, the first PVDC coating being further characterized by a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C;
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, to 0 form a second PVDC coating;
c) heating the said second coating until the temperature of the free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70C, and f) bring.ing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, toform a laminate.
Process F comprises:
a) coating a first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by having a crystallinity index ofless than 1.15 if dried and allowed to stand for 30 days at 20C, to form a first PVDC coating;
b) coating the PVDC-coated Eirst se~].ant weh formed in step a) with A second PVI)C, the secorld coating being characterized by having a cryst~llinity .index oE less than 1.15 i.f dried and allowed to stand :eor 30 days at 20C
and, if the hase film is nylon Eilm, polyester film or polypropylene film, the second RVDC coating being further characterized by a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, and a crystallinity index of from 1.12 to 1.25 if dried and allowed P~ Lo to stand for 5 days at 40C;
c) passing the base film over a hot roll, said base film being in contact with said hot holl, and said hot roll being at a temperature higher than about 70C, and d) bringing the PVDC-coated surace of the PVDC-coated first sealant web, formed duri.ng steps a) and d3, into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to :Eorm a laminate.
Process G comprises:
a) coating the base film with a :Eirst PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or polypropylene film, the first PVDC coating being further characterized by having a crystallinity index oE from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C, b) drying the first PVDC coating:
c) coating a f.irst sealant web, having a surface tension of at least 42 d~nes/cm with a second PVDC, the coat-ing being characterized by having a crystallinity index of less than 1.15 i:E dried and allowed to stand for 30 days at 20C; d) drying the second PVDC coating' e) passing the base film over a hot roll, said base ilm being in contact with said hot roll, and said hot roll being at a temperature higher than about 70C; and f) bringing the PVDC-coated s~lrfnce of the PVDC-coated :Eirst sealant weh into contact with khe PVDC-coated surface O:e the PVDC-coated base :Eilm and nipping the PVDC-coated .Eirst sealant web to the PVDC~coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred ernbodiment of the process of the present invention, the PVDC layers in contact with and furthest away from the base film are combined into a single layer, said PVDC layer being characteri.zed by having a crystallinity in~ex of less than 1.15 if dried and allowed to stand for 30 days at 20C and of from 1.12 to 1.25 if dried and allowe~ to stand for 5 days at ~0C.
In another embodiment, when the base film is a cast nylon film the PVDC coating which is furthest away from the base film i.e. the layer which contacts -the sealant web, is characterized by having a crystallinity index of less than 1.05 iE dried and allowed to stand for 30 days at 20C.
In particularly preEerred emboAiments the sealant web has a surface, adjacent to the PVDC coating, o~ a mate-rial selected from the group consisting of a) a copolymer of ethylene and vinyl acetate, b) a blend of a copolymer of ethylene and vinyl acetate and at least one of (i) a copolym-er of ethylene and at least one C4 - Clo ~-olefin having a density of from 0.915 to 0.955 g/cm3 and (ii) a homopolymer of ethylene having a density of from 0.915 to 0.955 g/cm3.
Preferred copolymers of ethylene and ~-olefins(s) are ethylene/butene-l, ethylene/ octene-l and ethylene/butene-l/-octene-l copolymers.
Preferably the vinyl acetate content of the copoly-mer of ethylene and vinyl acetate (EVA) is between about 1.0 and about 20 weight percent and the weight ratio of the EVA
to ethylene homopolymer, ethylene copolymer or blend of said copolymer and homopolymer is in the range of 2:98 to 50:50, especially in the range of 2:98 to 20:80.
In another embodiment the sealant web is an EVA co-polymer having a vinyl acetate content o~E hetw~en ahout 1.0 and about 15 weight percent and ~aid ~ealant web contains a slip additive. The slip coeEEicient oE the sealant web, as measured by ASTM Procedure D-1894 may be less than 0.4, especially less than 0.3.
In a further emhodiment the surface of the sealant web adjacent to the PVDC coating has been corona discharge-treated to a level between 38 and 45 dynes/cm prior to lamination.
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In another preferred embodiment, the base film is a nylon film, especially a film of nylon 6, nylon 66 or a condensation copolymer of -caprolactam and hexamethylene-diamine adipate (sometimes referred to as nylon 6/66).
In a further embodiment the base film has a metal-coated surface, said surface being between the base film and the PVDC coating. Said metal coating may be in the form of, for example, a vacuum deposited film. Preferably the metal is aluminum.
In another embodiment the sealant web is a copoly mer of ethylene and vinyl acetate, having a vinyl acetate content between 2 and 40 weight percent, bonded to a carrier web. Preferably the carrier web is made from an ionomer.
In a further embodiment the base film has an aluminum-coated surface, said surface being sandwiched between the base film and the PVDC coating.
In yet another embodiment a layer of PVDC is inter-posed between the first and second PVDC coatings, said inter-posed layer of PVDC being characterized by being capable of developing crystallinity to a level such that the interposed crystalline PVDC layer so formed resists attack by an organic solvent, as measured by the Solvent Haze Test described here-inbelow, said organic solvent being capable of dissolving PVDC coatings having a crystallinity index of less than 1.05.
An example of a PVDC dispersion suitable for forming the interposed layer is available under the trade mark Serfene 411.
In the Solvent Haze Test, the PVDC coating, when dry and after allowing crystallinity to develop, is sprayed with the organic solvent. If the PVDC coating has developed sufficient crystallinity, the PVDC coating will be unaffected by the solvent. If, however, the PVDC coating is insuffi-ciently crystalline the solvent will either turn the PVDC
coating turbid in appearance or will dissolve portions or all of thePVDC coating.
Crystallinity index, as defined in the present specification, is determined using infra-red spectroscopy by obtaining an attenuated total reflectance infra-red spectrum of the coated film. Crystallinity index may be measured 5 using a Perkin Elmer* 467 infra-red spectrophotometer and a Wilks* ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45. In the method, rectangles of film are placed on each side of the germanium crystal (i.e.
two rectangles of film are used~, with the PVDC-coated side of the film against the crystal. The reference heam attenuator is set at 85% at 1150 cm~l and the sample is scanned between 950 cm~l and 1150 cm~l. The absorbances A of the background, at 1115 cm~l, and at the peaks, at 1070 cm~
and 1042 cm~l, are measured. Crystallinity index is calcu-lated by dividing the difference between A1042 and Allls by the difference between A1070 and A1115 The following description of the invention is pri-marily directed to coating and laminating nylon base films.
Similar techniques to those used for nylon film, particularly to those used for oriented nylon film, may be used for the polyester and polypropylene base films. However, cast nylon films, particularly thin cast nylon films tend to require more stringent control when coating with PVDC and laminating the PVDC-coated nylon film to the sealant web because of the sensitivity of cast nylon film to moisture and heat. ~ase films made from a sealant web require a slip coeEficient o~
less than about 0.4 in order to prevent ~tickiny oE the film to the }lot roll.
The invention rnay he more fully understood by reference to the drawings in which Figure 1 shows in d.iagram-matic form a process of the present invention.
Referring to Figure 1, suitable apparatus comprises a first coating station 10, a first dryer 11, a second coat-ing station 12, a second dryer 13, and nip roll assembly 14.
Apparatus for supplying base film and sealant web and for *denotes trade mark.
- : :
,o ~ 12 -winding up the laminate are not shown.
First coating station 10 comprises a pan 34 ~or holding a PVDC dispersion, direct gravure roll 16 and nip roll 20, associated with gravure roll 16. Second coating station 12 is similar to first coating station 10 with pan 35, direct gravure roll 17 and nip roll 21. Direct gravure rolls 16 and 17 and associated nip rolls may be replaced by Meyer* rods, reverse gravure rolls or other coating apparatus if desired. It will be recognised by those skilled in the art that if apparatus which subjects the PVDC dispersion to relatively high shear is used, then the PVDC dispersion may have to be modified to minimize foaming e.g. with the addi-tion o~ iso-propyl alcohol.
Nip roll assembly 14 comprises a lamination roll 18, which has means for heating tnot shown), an associated nip roll 19, lay-on roll 36 which is adapted to guide PVDC-coated nylon film onto lamination roll 18, lay-on roll 37, which is adapted to guide sealant web into the nip between nip roll 19 and lamination roll 18, and take-of roll 38 which may be positioned to permit a laminate to remain in contact with lamination roll 18 a~ter passing through the nip between lamination roll 18 and nip roll 19.
There are various idler rollers (some are shown but not identi:Eied in the drawing) which are adapted, for example, to guide film through first dryer 11, after leaving first coating station 10 and before passing to second coating station 12.
In one embodiment oE the present invention, nylon film 30 is passed through th~ Eirst coating station 10 which may comprise a direct gravure roll 16 and associated nip roll 20. A first PVDC coating is applied at the first coating station. Typically 3.25 to 6.51 g/m2(2-4 lb/ream) PVDC coat-ing i.e. 6.50 to 13.02 g/m2 of 50% PVDC aqueous dispersion, is coated onto the nylon film if the nylon film is oriented, and 2.44 to 3.25 g/m2 of PVDC coating i.e. 4.88 to 6.51 g/m2 *denotes trade mark.
l;~hP~3LV
of 50% PVDC aqueous dispersion, is coated onto the film if the nylon film is substantially unoriented e.g. is cast film.
The first PVDC coating is dried in first dryer 11 before being coated with the second PVDC coating in the second coating station 12. Typically 3.25 to 6.51 g/m2 of PVDC
coating is direct gravure coated onto the PVDC-coated film by means of direct gravure roll 17 and associated nip roll 21.
Even cast nylon film may, at this stage, be coated with up to 6.51 g/m2 of PVDC coating, or more, as the first PVDC
coating tends to prevent water in the PVDC dispersion from wrinkling or curling the nylon film. The second PVDC coating is dried in second dryer 13. The amount of heat applied to the PVDC-coated nylon film, in second dryer 13 is controlled to ensure that the second PVDC coating is dried sufficiently and has sufficient so-called "green tack", but is not heated to the extent that a relatively non-adherent skin forms on the PVDC coating.
The term "green tack", used in the art, may be a misnomer, as it is believed that the dried PVDC coating is not tacky in the normally accepted sense of the word. The term is believed to relate to a lack of crosslinking in the PVDC coating. In the present process, an indication of the sufficiency of the green tack may be ascertained by measuring the surface temperature of the PVDC coating just prior to the PVDC-coated film leaving the second dryer. At surface temperatures less than about 70C, the PVDC coating has sufficient green tack for subse~uent lamination. At ~urface temperatures above ahout 70C e.g. 85C, the PVDC coat.tng nlay have insufficient green tack Eor the PVDC coating to adh0re well to the sealant web. The PVDCcoated nylon film 31 which exits from second dryer 13 is wrapped around heated lamina-tion roll 18, the nylon film contacting roll 18. Sealant web 32 is fed onto PVDC-coated nylon film 31 so that the sealant web 32 contacts the PVDC coating. The PVDC-coated nylon film 31 and sealant web 32 are nipped together by the application .
o of nip roll 19 to the lamination roll 18. The laminate may then be passed further round heated lamination roll 18 or into a hot 20ne in order to strengthen the bond between the sealant weh and the PVDC coating. The laminate so formed, 33, is wound up on a roll, not shown.
In some embodiments of the present invention a sin-gle PVDC coating can be used which performs the functions of both layers of PVDC. The crystallinity index specifications for the single PVDC must meet the specifications of the two PVDC layers. The single PVDC may be applied in two steps as indicated hereinabove or in a single step. The single step process is particularly useful in the case of oriented nylon, polyester or polypropylene films, whereas the two step process may be desirable for cast nylon film, because of the tendency of the film to curl in the presence of moisture.
In the single step process wherein the PVDC coating is laid down in a single application, only one of the coating stations and associated dryer will be used. Furthermore, for a structure which has an interposed layer of crystalline PVDC
a third coating station and associated dryer (neither of which are shown in the drawing) will be required.
When dealing with cast i.e. substantially unorient-ed, nylon film it may be necessary to apply tension to the film in the transverse direction in order to prevent curl as the film passes through the dryer. This is particularly desirable in dryers which apply heat only to one side of the film e.g. a Faustel* dryer.
When dealing with oriented nylon, oriented poly-ester or oriented polypropylene ba~e films, it may be desir-able to pass the coated film through a dryer, under very lowlongitudinal tension. A so-called floater dryer is suitable.
Such a dryer avoids pulling the film under tension, which might otherwise induce wrinkling in the Eilm.
When the base film is a sealant web it is necessary that the film have a slip coeficient of less than about 0.4, preferably less than about 0.3, and especially about 0.2.
*denotes trade mark.
~2216;~0 Sealant webs having a slip coefficient of about 0.2 are some-times referred to by those skilled in the art as "high slip"
films.
The base film may also have a metal coating to make the final film structure substantially impermeable to oxygen.
The metal, e.g. aluminum, may be applied by known methods, for example by vacuum deposition. The amount of metal deposited on the base film depends on the required oxygen permeability of the final film structure. Typically, aluminum is deposited until an optical density of about 2.5 is attained. Optical density is defined as the logarithm of the quotient of, as dividend, the intensity of a 500 nm wave-length light beam prior to passage through the film structure and, as divisor, the intensity of the light beam after passage through the film structure. Optical density may be measured using a Cary* 210 UV-visible spectrophotometer. The aluminum-coated base film laminate is usually coated with a PVDC coating adjacent to the aluminum so that the mechanical integrity of the aluminum coating remains when the structure is used in packaging operations e.g. is not damaged by pin-holing or scratching, as it may be if on the outside of the package.
It is often desirable to apply coloured designs, and/or printed matter on the base film-PVDC coating-sealant web structure. In the context of the present invention such designs and/or printed matter may be placed on the structure using inks applied to the base film or the sealant web. The printing would therefore be between the base Eilm ancl the PVDC coating or between the PVDC coating and the sealan~ web.
Corona discharge treatment of the surface to be printed may be desirable. The extent of ink coverage depends in part on the bond strength between the ink and the base film and between the ink and the PVDC coating. It is desirahle to select an ink that bonds well to the PVDC coating and to the base film in order to ensure that the bond strengths between adjacent layers in the final structure are sufficient for the *denotes trade mark.
- ~
:. :
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anticipated end use.
In the event that PVDC-coated base film is avai]-able instead of uncoated film, the PVDC-coated base film may need to be heated in order to substantially destroy any crystallinity in the PVDC. For example, in the case where the PVDC coating of the pre-coated base film would have a crystallinity index o~ less than 1.15 when dry and iE allowed to stand for 30 days at 20C, and from 1.12 to 1.25 when dry and if allowed to stand for 5 days at 40C, the PVDC-coated base film may be directly heat laminated by passing the PVDC-coated base fllm through the nip roll assembly, provided the temperature of lamination roll 18 is sufficiently high e.g.
greater than about 85C, to substantially destroy any crys-tallinity which may have been developed in the PVDC coating.
The PVDC-coated base film should be heated to an extent sufficient to reduce or maintain the crystallinity index at less than about 1.05. It will be understood by those skilled in the art that such PVDC-coated base film, available on rolls, would have a slip sheet between the layers of film on the roll or the PVDC coating would contain an antiblock agent e.g. wax or talc.
The base film, pre-coated with a PVDC coating may also be heat laminated to a sealant web by PVDC coating at the s~cond coating station with a PVDC characterized by hav-ing a crystallinity index of less than 1.15 when dry and ifallowed to stand for 30 days at 20C, and subsequently drying and heat laminating as described hereinbefore.
It should be understood that, in the pre~ent speci-fication, when reEerring to films pre-coate~d with PVDC, the number of days, after which crystallinity index oE the PVDC
is determined, is measured from the time immediately after the applied PVDC dispersion has been dried. In the case where the film is coated by a person (the coater) other than the person who does the laminating (the laminator), it may not be apparent to the laminator how many days have lapsed since the film was coated and at what temperature the film ` 1221610 was ~tored. The laminator nay therefore nee~ to ma~e ~nquiry regar~ing the ch~racter~ation of the PVDC use~ as the co~t-ing f~r the baee film.
In the event th~t the base ~ilm i~ cast nylon film or a ~ealant web the lamination temperature should be kept as low ae pos6ible to minimi~e ehrinkage ~nd other effects associated with heat~ng the nylon film to too high a tempera-ture. In these ca~es it i6 advantageoue for the PVDC coating next to the eealant web to have ~ low heat sealing tempera-ture. Generally, such PVDC coating~ have a cryetallinityindex of less than about 1.05 when dry and if allowed to etand for 30 days at 20C. Three PVDC di~persions which are suitable in thie regard are Serfene*2011, Serfene 2012, Serfene 2015.
When the sealant web i8 not PVDC-coated, it i8 believed important that the crystallinity index of the PVDC
coating whic~ will conta~t the sealant web be less than about 1.05 immediately prior to lamination. The temperature of the PVDC-coated base film, upon leaving the fiecond dryer ~hould be less than about 75-C in order to sufficiently dry the PVDC
coating and to retain the so-called "green tack" of the dried PVDC coating. At temperaturee greater than about 75-C the "green tack" or adhe~ive nature of the dried PVDC coating may be insufficient. The temperature of the lamination roll should be at least about 70-C, preferably at least 85-C, in order to cause the PVDC coating to remain in or revert to a eubstantially amorphous etate. More preferably the tempera-ture of the lamination roll should be at least about ~S-C.
The temperature of the lamination roll ~hould be less than the melting temperature of the eealant web and preferably at least about 20-C less than the meltlng temperature of the sealant web. Although not wishing to be bound ky any theory, it is believed that the selection of temperature at which the lamination roll is operated depend~ to a certain e~tent on the eoftening point of the sealant web.
A~ indicated hereinbefore, the eealant webs may *denotes trade mark . ~
16~0 contain slip a~ditives.
PVDC coatings of the type uæeful for coating the base film and/or heat laminating to the sealant web generally have oxygen permeabilities of the order of 15.6 ml/m2/atmos./
day. This is believed sufficient for most applications. In the event that lower oxygen permeability is requiredl a more crystalline PVDC coating within the range of PVDC coatings of the present invention may be selected. Alternatively the base film may be coated with PVDC on both sides. As a further alternative, a crystalline PVDC coating e.g. one having a crystallinity of greater than about 1.30 when dry, may be sandwiched between the first and second PVDC coatings used in the present invention. As stated hereinbefore, an aluminum coating may be placed between the base film and the PVDC coating. Using vacuum deposited aluminum, oxygen perm-eabilities in the order of 0.75 ml/m2/ atmos./day are attainable.
Nylon copolymer e.g. nylon 6/66, films are prefer-red for applications where resistance to pinholing of the package is required. A preferred laminate for packaging cheese comprises a nylon base film and a sealant web of a film made from a blend of a linear copolymer of ethylene and a C4 - Cg ~-olefin and a copolymer of ethylene and vinyl acetate.
It may be seen from the foregoing that, for cast nylon film, one process comprises coating the film with two coatings of PVDC prior to heat laminating the PVDC-coated film to the sealant web. The Pirflt PV~C coating .is app].ied under conditions whlch mi~i1nize the chance of occurrence oE
curling or wrinkling, caused by high temperatures and/or the presence of excess quantities of moisture. This may be accomp]ished primarily by ensuring that as little as possible of the PVDC dispersion is applied to the nylon film, but it must be sufficient to provide complete coverage of the nylon film, with PVDC, after drying, so that there is little chance _ ~9 _ of absorption of water by the nylon film during the second application of PVDC dispersion. For these reasons the first layer of PVDC dispersion is usually applied at about 2.44 to 3.25 g/m2 ~dry basis). In addition it is desirable to control the transverse tension on the film as it passes through the dryer. The level of tension required will vary according to the type o~ nylon film, the quantity of PVDC
emulsion applied, the temperature of the dryer and the type o~ dryer e.g. one-side or two-side direction of the heat towards the film. Typically tension levels from ~ to 7 N/m width of film are desirable.
The second coating of PVDC may be applied at from
2.44 to 6.51 g/m2 (dry hasis), although 2.44 to 3.25 g/m2 is usually sufficient to impart the required moisture and oxygen l~ permeability level to the final film laminate structure.
The thinner the cast nylon film, the more important it is to keep the rate of application of the first coating of PVDC at a low level e.g. from about 2.44 g/m2 to 2.85 g/m2, and to control the transverse tension of the coated film as it passes through the dryer.
For cast nylon, however, a preferred process is to coat the sealant web with PVDC, thus completely overcoming the problem of moisture sensitivity of the nylon. In addition to this advantage, there is a further advantage that a single coating of PVDC may be selected.
As cast nylon film is sensitive to wrinkling at elevated temperatures, the temperature of the laminatinc~ roll should be as low as possible, and/or the tirne c1llri.rl~ which the nylon ~il.m is in contact with the laminating roll should be kept to the minimum necessary to achieve the required bond strength of the laminate.
Oriented base films useful in the present invention are not as sensitive to temperature and moisture as cast nylon film. Accordingly the PVDC coating may be applied in two separate layers or as a single layer. Higher dryer tem-. .
~2~6~lO
peratures and lamina~ing temperatures may be used and trans-verse tensioning of the film as -the film passes through the dryer may not he required. With oriented base films a single application of PVDC dispersion is preferred.
When processes are used in which the sealant web is coated with PVDC it is essential that the surface of -the sealant web which is to be coated with PVDC has a surface tension of at least 38 dynes/cm. Treatment of the surface, with ozone or other oxidizing chemicals or with corona dis-charge, as is known in the art, is required in order to bring the surface tension to above the miniumum level re~uired.
Corona discharge treatment is preferred.
Where coating and laminating facilities are not owned by the same manufacturer, or when it is not convenient, for reasons of flexibility, to combine coating and laminating facilities in an in-line process, coating and laminating may be accomplished in two steps in a so-called out-of-line process. In such a process, the base film or sealant web is coated with one or more PVDC coatings and wound up on a roll.
To prevent blocking of the PVDC-coated film upon unwinding a slip sheet rnay be used or the last PVDC coating may be formu-lated to include slip ana anti-block agents e.g. wax, talc, silica. The wound roll may then be stored iIl preparation for lamination to the sealant web or base film, as appropriate.
The PVDC-coated film may then, at an appropriate time, be heat laminated to the other film according to the present invention.
In processes where an uncoated sealant web :is laminated to a PVDC-coated ~ase Eilm in or~er to en~lre that the PVDC coating will aflhere to the sealant web, it is believed necessary Eor the PVDC coating to have a crysta:Llin-ity index, at the time of lamination, of abo~lt l.OS or less.
This may be accomplished by heating the PVDC-coated film immediately prior to or at the time of lamination. Example 7, hereinafter, illustrates the out-of-line process.
The invention may be illustrated further by refer-12~6SO
ence to t~e following examples, of which ExaJnple 1 typifies the prior art.
In the Examples, melt index is measured according to the procedure o~ ~STM D-1238 (condition E).
Example 1 A 15 m thick film of an oriented nylon copolymer (a copolymer of 10 wt% -caprolactam and 90 wt~ hexamethyl-enediamine adipate) was direct gravure coated at 30.5 m/min with 6.175 g/m2 of Serfene 2011 PVDC dispersion to which 5~
by weight of isopropyl alcohol had been added. The PVDC of Serfene 2011 has a crystallinity index, when dry and after storing at 20C for 30 days, of 1.05, and after storing at 40C for 5 days, of 1.15. The coating was dried in a roll support arch dryer to a temperature of 70~C as measured by a non-contacting infrared radiation pyrometer. The PVDC-coated film was passed over a laminating roll held at 115C for a residence time of 0.33 seconds on the hot roll. A 51 ~m sealant web, comprising a blend of 85 wt~ of a linear ethylene/butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 and 15 wt~ of a high pressure poly-ethylene viz. a homopolymer of ethylene, having a density oF
0.g20 g/cm3 and a melt index of 0.8 dg/min, and 75 ppm by weight of the blend of erucamide (a slip additive), said sealant web having been corona discharge treated to a surface tension level of 38 dynes/cm, was laminated to the PVDC-coated nylon as described herein.
The resulting laminate was stored for 5 day~ at 20C. The laminate bond strength was then measured, using a Suter tester, and found to be between 11 and 2Q g/cln.
Other similar sealarlt webs containing hi~h pressure polyethylenes havin~ melt indices Erom 2 to 10 dg/min give similar results.
Example 2 Example 1 was repeated except that the sealant web cornprised a blend of 85 parts by weight of a linear ethylene/
butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75, 15 parts hy weight of a high pressure poly-ethylene having a density of 0.920 g/cm3 and a melt index of 0.8 dg/min, and 15 parts by weight of an ethylene/vinyl ace-tate copolymer having a vinyl acetate content of 12 wt~ of the copolymer and a melt index of 0.35 dg/min, available under the trade mark Elvax 3135X. The sealant web had a slip coefficient o~ about 0.2.
The laminate bond strength was tested after 5 days' storage at 20C and found to be 630 g/cm.
Example 3 Example 2 was repeated except that Serfene 2060 PVDC dispersion was used instead of the Serfene 2011 PVDC
j dispersion. The PVDC of Serfene 2060 has a crystallinity index, when dry and after storage at 20C for 30 days, of 1.10, and after storage at 40C for 5 days, of 1.19.
The laminate bond strength was tested after 5 days' storage at 20C and found to be 630 g/cm.
Example 4 Example 3 was repeated except that the oriented nylon copolymer film was replaced by a 25 m thick cast film made from a copolymer of 10 wt ~ -caprolactam and 90 wt hexamethylenediamine adipate.
The laminate bond strength was tested after 5 days storage at 20C and found to be 630 g/cm. However, the laminate was severely curled in both the machine and trans-verse directions, indicating that the quantity of moisture driven off in the dryer, and perhaps the temperature of the hot laminating roll, were too high for the laminat~on of ca~t film.
~ 5 q~he cast nylon film of Example 4 was coated with
The thinner the cast nylon film, the more important it is to keep the rate of application of the first coating of PVDC at a low level e.g. from about 2.44 g/m2 to 2.85 g/m2, and to control the transverse tension of the coated film as it passes through the dryer.
For cast nylon, however, a preferred process is to coat the sealant web with PVDC, thus completely overcoming the problem of moisture sensitivity of the nylon. In addition to this advantage, there is a further advantage that a single coating of PVDC may be selected.
As cast nylon film is sensitive to wrinkling at elevated temperatures, the temperature of the laminatinc~ roll should be as low as possible, and/or the tirne c1llri.rl~ which the nylon ~il.m is in contact with the laminating roll should be kept to the minimum necessary to achieve the required bond strength of the laminate.
Oriented base films useful in the present invention are not as sensitive to temperature and moisture as cast nylon film. Accordingly the PVDC coating may be applied in two separate layers or as a single layer. Higher dryer tem-. .
~2~6~lO
peratures and lamina~ing temperatures may be used and trans-verse tensioning of the film as -the film passes through the dryer may not he required. With oriented base films a single application of PVDC dispersion is preferred.
When processes are used in which the sealant web is coated with PVDC it is essential that the surface of -the sealant web which is to be coated with PVDC has a surface tension of at least 38 dynes/cm. Treatment of the surface, with ozone or other oxidizing chemicals or with corona dis-charge, as is known in the art, is required in order to bring the surface tension to above the miniumum level re~uired.
Corona discharge treatment is preferred.
Where coating and laminating facilities are not owned by the same manufacturer, or when it is not convenient, for reasons of flexibility, to combine coating and laminating facilities in an in-line process, coating and laminating may be accomplished in two steps in a so-called out-of-line process. In such a process, the base film or sealant web is coated with one or more PVDC coatings and wound up on a roll.
To prevent blocking of the PVDC-coated film upon unwinding a slip sheet rnay be used or the last PVDC coating may be formu-lated to include slip ana anti-block agents e.g. wax, talc, silica. The wound roll may then be stored iIl preparation for lamination to the sealant web or base film, as appropriate.
The PVDC-coated film may then, at an appropriate time, be heat laminated to the other film according to the present invention.
In processes where an uncoated sealant web :is laminated to a PVDC-coated ~ase Eilm in or~er to en~lre that the PVDC coating will aflhere to the sealant web, it is believed necessary Eor the PVDC coating to have a crysta:Llin-ity index, at the time of lamination, of abo~lt l.OS or less.
This may be accomplished by heating the PVDC-coated film immediately prior to or at the time of lamination. Example 7, hereinafter, illustrates the out-of-line process.
The invention may be illustrated further by refer-12~6SO
ence to t~e following examples, of which ExaJnple 1 typifies the prior art.
In the Examples, melt index is measured according to the procedure o~ ~STM D-1238 (condition E).
Example 1 A 15 m thick film of an oriented nylon copolymer (a copolymer of 10 wt% -caprolactam and 90 wt~ hexamethyl-enediamine adipate) was direct gravure coated at 30.5 m/min with 6.175 g/m2 of Serfene 2011 PVDC dispersion to which 5~
by weight of isopropyl alcohol had been added. The PVDC of Serfene 2011 has a crystallinity index, when dry and after storing at 20C for 30 days, of 1.05, and after storing at 40C for 5 days, of 1.15. The coating was dried in a roll support arch dryer to a temperature of 70~C as measured by a non-contacting infrared radiation pyrometer. The PVDC-coated film was passed over a laminating roll held at 115C for a residence time of 0.33 seconds on the hot roll. A 51 ~m sealant web, comprising a blend of 85 wt~ of a linear ethylene/butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 and 15 wt~ of a high pressure poly-ethylene viz. a homopolymer of ethylene, having a density oF
0.g20 g/cm3 and a melt index of 0.8 dg/min, and 75 ppm by weight of the blend of erucamide (a slip additive), said sealant web having been corona discharge treated to a surface tension level of 38 dynes/cm, was laminated to the PVDC-coated nylon as described herein.
The resulting laminate was stored for 5 day~ at 20C. The laminate bond strength was then measured, using a Suter tester, and found to be between 11 and 2Q g/cln.
Other similar sealarlt webs containing hi~h pressure polyethylenes havin~ melt indices Erom 2 to 10 dg/min give similar results.
Example 2 Example 1 was repeated except that the sealant web cornprised a blend of 85 parts by weight of a linear ethylene/
butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75, 15 parts hy weight of a high pressure poly-ethylene having a density of 0.920 g/cm3 and a melt index of 0.8 dg/min, and 15 parts by weight of an ethylene/vinyl ace-tate copolymer having a vinyl acetate content of 12 wt~ of the copolymer and a melt index of 0.35 dg/min, available under the trade mark Elvax 3135X. The sealant web had a slip coefficient o~ about 0.2.
The laminate bond strength was tested after 5 days' storage at 20C and found to be 630 g/cm.
Example 3 Example 2 was repeated except that Serfene 2060 PVDC dispersion was used instead of the Serfene 2011 PVDC
j dispersion. The PVDC of Serfene 2060 has a crystallinity index, when dry and after storage at 20C for 30 days, of 1.10, and after storage at 40C for 5 days, of 1.19.
The laminate bond strength was tested after 5 days' storage at 20C and found to be 630 g/cm.
Example 4 Example 3 was repeated except that the oriented nylon copolymer film was replaced by a 25 m thick cast film made from a copolymer of 10 wt ~ -caprolactam and 90 wt hexamethylenediamine adipate.
The laminate bond strength was tested after 5 days storage at 20C and found to be 630 g/cm. However, the laminate was severely curled in both the machine and trans-verse directions, indicating that the quantity of moisture driven off in the dryer, and perhaps the temperature of the hot laminating roll, were too high for the laminat~on of ca~t film.
~ 5 q~he cast nylon film of Example 4 was coated with
3.25 g/m2 of Serfene 2060 PVDC dispersion and dried. q'he coated film was then wound up with a high density polyethyl-ene 91ip sheet. A few hours later this coated nylon film was ~16~1) coated with 3.25 g/m2 Serfene 2015 PVDC dispersion, the slip sheet being removed and rewound on a secondary winder. The PVDC of Serfene 2015 has a crystallinity index, when dry and af-ter storage at 20C or 33 days, of 1.00, and after storage at 40C for 5 days, of 1.15. The Serfene 2015 PVDC coating was dried in a roll support arch drier to a temperature of 70C as measured by a non-contacting infrared radiation pyro-meter. The PVDC-coated film was passed over a laminating roll held at 90C *or a residence time of 0.33 seconds on the hot roll. A sealant web as described in Example 2 was lamin-ated to the PVDC-coated nylon film.
The resulting laminate was substantially curl-free and had a bond strength, after 5 days' storage at 20C, of at least 500 g/cm.
Example 6 . _ An 11 ~m thick oriented nylon copolymer film (10 wt~ -caprolactam and 90 wt% hexamethylene diamine adipate) was direct gravure coated with 7.8 g/m2 of Serfene 2060 PVDC
dispersion to which 5 wt% iso-propyl alcohol had been added.
The coated film was dried, in a roll support arch dryer, to a temperature of 70C. The coated film was passed over a laminating roll held at 115C for a residence time of 0.33 seconds on the hot roll, and was laminated to a sealant web made from a blend of 50 parts by weight of an ethylene/vinyl acetate copolymer having a density of 0.940 g/cm3, a melt index of 1.2 and a vinyl acetate content of 18 wt~ of the copolymer, available under the trade mark Ultrathene IJE-632, 42.5 parts of a linear ethylene/butene-l copolymer having a density of 0.919 g/cm3 an-l a melt Lndex Oe 0.75 and 7.5 parts by weight of a high pressure polyethylene havin~ a density oE
0.920 g/cm3 and a melt index of 0.8 dg/min, and 75 ppm by weight of the blend of erucamide.
The resultin~ laminate was stored for 5 days' at 20~C. The laminate bond strength was then tested and found to be at least 630 g/cm.
. ' :.
~2Zl~ilO
Example 7 A 15 ~m thick oriented nylon 66 film was coa-te<l with 4.06 g/m2 of a mixture of 97.7 parts by weight Serfene 2060 PVDC dispersion, 2 parts by weight of DL-96* wax emul-sion and 0.3 parts by weight of OX-50* silicon dioxide anti-block agent. The coated film was dried, wound up and stored for 6 months at room temperature. The PVDC coating was found to then have a crystallinity index of 1.31 + 0.02.
This coated film was then passed through a roll support arch dryer at 30.5 m/min for a residence time of 2.5 seconds. The temperature of the drier was 110C. The coated film was then passed over a laminating roll held at 115C.
The sealant web of Example 6 was laminated to the PVDC-coated nylon film.
The bond strength of the resulting laminate, after 5 days storage at 20C was at least 500 g/cm.
Example 8 Example 6 was repeated, except that the sealant web was made from an ethylene/vinyl acetate copolymer having a melt index of 1.5 and a vinyl acetate content of 6 wt %, available from C-I-L Inc. under the trade mark 1060.
The bond strength of the resulting laminate, after 5 days storage at 20C was at least 630 g/cm.
Example 9 A 15 ~m thick oriented nylon copolymer film, as in Example 1, was direct gravure coated with 4.06 g/m2 of Serfene 2060 PVDC dispersion with 5 wt~ isopropyl alcohol, and dried to a temperature of 70C prior to passing over a laminating roll held at 115C at a sp~ed of 30-35 m/min. ~'he residence time on the laminat:Ln~ roll wa~ 0.33 ~econds. The PVDC-coatecl nylon was lam.inated to an 18 ~m thick two-side acrylic-coated biaxially oriented polypropylene film. The resulting laminate was coated on the uncoated side of the nylon film with 4.06 g/m2 of Serfene 2060 PVDC dispersion containing 5 wt~ isopropyl alcohol. This latter PVDC coating *denotes trade mark.
~2Z~10 was laminated to ~he sealant web of Example 6.
The laminate was stored Eor 5 days at 20C before measuring bond strengths. The bond strength between the coated oriented polypropylene and the nylon film was found to be about 150 g/cm., and between the EVA-containing film and the nylon film was at least 630 g/cm.
Example 10 A 15 um thick nylon copolyrner film with Serfene 2060 PVDC coating was prepared and laminated to a one-side nitrocellulose-coated regenerated cellulose film, substan-tially in the manner described in Example 1. The resulting laminate was coated on the second side of the nylon and laminated to the EVA-containing film, as described in Example 9.
The bond strength between the nylon film and the cellulose film after 5 days storage at 20C was found to be 78 g/cm.
Exam~ 11 A 15 ~lm thick film oriented copolymer nylon was coated with Daran* 820 PVDC dispersion at 6.99 g/m2. The resulting coated film was dried ana laminated at 115C to the EVA-containing film of Example 6.
The bond strength, after 5 days storage at 20C, 25 was found to be 350 g/cm.
Example 12 A 51 ,um thick cast nylon 6 film was coated with 6.99 g/m2 Serfene 2060 dispersion with 5 wt% iso-propyl alcohol and passed through a dryer controlled at 120C, for a 30 residence time of ~ second~. The coatetl eilm leavin~ the dryer had a tem~)erature of 74C. The resultant film was laminated at the sealant web of Example 6.
The bond strength, after 5 days storage at 20C was found to be 275 g/cm. The Eilm was slightly curled, but was 35 successfully used in thermoforming operations on a Multivac*
8000 vacuum thermoformer.
*denotes trade mark.
~Z2~6~
Example 13 . .
A 76 ~m thick cast nylon 66 film was coated with 3 49 g/m2 SerEene PVDC 2060 dispersion with 5 wt~ iso-propyl alcohol. The coated film leaving the dryer had a surface temperature of 72C. The resultant film was laminated to 127 ~m thick sealant web made from a blend of 85 parts by weight of an ethylene/butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 dg/min and 15 parts by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 12 wt% of the copolymer and a melt index of 0.35 dg/min. The PVDC-coated film was passed over a laminating roll held at 112 C for a residence time of 0.7 seconds on the hot roll, 60% of that time being in contact with the sealant film.
The laminate bond strength was tested after 5 days storage at 20C and found to be 560 g/cm. The laminate was flat and thermoformable.
Example 14 A 11 ~m thick oriented polyester film i.e. poly-ethylene terephthalate film, corona discharge treated to a surface tension level oX 40 dynes/cm, was coated with 4.$3 g/m2 of Serfene 2060 PVDC dispersion with 5 wt% iso-propyl alcohol. The coated film was passed through a dryer main-tained at 138~C. The surface temperature of the coated film leaving the dryer was 70C. The film was passed over a laminating roll held at 113C for a residence time of 0.3 seconds. The coated film was laminated to the sealant web of Example 13.
The laminate bond ~trength was testerl ~fter 5 days' storage at 20C and Eound to be at least 630 g/cm.
xample 15 A sealant web made from 85 parts by weight of a linear ethylene/butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 dg/min and 15 parts by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate .
~2Zi~l~
content of 18% and a melt index of 0.7 dg/min was corona discharge treated to a level of about 42 dynes/cm. The sealant web had a slip coefficient higher than 0~5O
The sealant web was coated with 4.3 g/m2 of Serfene 2015 PVDC dispexsion containing 10% isopropyl alcohol. The coating was dried and then nipped to a 25 ~m thick nylon 66 film while the nylon film was in contact with a hot roll, heated to 92C.
The resulting laminate had a bond strength, measured after 5 days at 20~C of at least 600 g/cm and an measured oxygen permeability of less than 13.7 ml/m2/day/atm.
Exam ~
The sealant web of Example 2 was corona discharge treated to a level of about 42 dynes/cm and then coated with 4.8 g/m3 of Serfene 2011 PVDC dispersion, dried and wound up on a roll, with a slip sheet. Subsequently the PVDC-coated sealant web was unwound and coated with
The resulting laminate was substantially curl-free and had a bond strength, after 5 days' storage at 20C, of at least 500 g/cm.
Example 6 . _ An 11 ~m thick oriented nylon copolymer film (10 wt~ -caprolactam and 90 wt% hexamethylene diamine adipate) was direct gravure coated with 7.8 g/m2 of Serfene 2060 PVDC
dispersion to which 5 wt% iso-propyl alcohol had been added.
The coated film was dried, in a roll support arch dryer, to a temperature of 70C. The coated film was passed over a laminating roll held at 115C for a residence time of 0.33 seconds on the hot roll, and was laminated to a sealant web made from a blend of 50 parts by weight of an ethylene/vinyl acetate copolymer having a density of 0.940 g/cm3, a melt index of 1.2 and a vinyl acetate content of 18 wt~ of the copolymer, available under the trade mark Ultrathene IJE-632, 42.5 parts of a linear ethylene/butene-l copolymer having a density of 0.919 g/cm3 an-l a melt Lndex Oe 0.75 and 7.5 parts by weight of a high pressure polyethylene havin~ a density oE
0.920 g/cm3 and a melt index of 0.8 dg/min, and 75 ppm by weight of the blend of erucamide.
The resultin~ laminate was stored for 5 days' at 20~C. The laminate bond strength was then tested and found to be at least 630 g/cm.
. ' :.
~2Zl~ilO
Example 7 A 15 ~m thick oriented nylon 66 film was coa-te<l with 4.06 g/m2 of a mixture of 97.7 parts by weight Serfene 2060 PVDC dispersion, 2 parts by weight of DL-96* wax emul-sion and 0.3 parts by weight of OX-50* silicon dioxide anti-block agent. The coated film was dried, wound up and stored for 6 months at room temperature. The PVDC coating was found to then have a crystallinity index of 1.31 + 0.02.
This coated film was then passed through a roll support arch dryer at 30.5 m/min for a residence time of 2.5 seconds. The temperature of the drier was 110C. The coated film was then passed over a laminating roll held at 115C.
The sealant web of Example 6 was laminated to the PVDC-coated nylon film.
The bond strength of the resulting laminate, after 5 days storage at 20C was at least 500 g/cm.
Example 8 Example 6 was repeated, except that the sealant web was made from an ethylene/vinyl acetate copolymer having a melt index of 1.5 and a vinyl acetate content of 6 wt %, available from C-I-L Inc. under the trade mark 1060.
The bond strength of the resulting laminate, after 5 days storage at 20C was at least 630 g/cm.
Example 9 A 15 ~m thick oriented nylon copolymer film, as in Example 1, was direct gravure coated with 4.06 g/m2 of Serfene 2060 PVDC dispersion with 5 wt~ isopropyl alcohol, and dried to a temperature of 70C prior to passing over a laminating roll held at 115C at a sp~ed of 30-35 m/min. ~'he residence time on the laminat:Ln~ roll wa~ 0.33 ~econds. The PVDC-coatecl nylon was lam.inated to an 18 ~m thick two-side acrylic-coated biaxially oriented polypropylene film. The resulting laminate was coated on the uncoated side of the nylon film with 4.06 g/m2 of Serfene 2060 PVDC dispersion containing 5 wt~ isopropyl alcohol. This latter PVDC coating *denotes trade mark.
~2Z~10 was laminated to ~he sealant web of Example 6.
The laminate was stored Eor 5 days at 20C before measuring bond strengths. The bond strength between the coated oriented polypropylene and the nylon film was found to be about 150 g/cm., and between the EVA-containing film and the nylon film was at least 630 g/cm.
Example 10 A 15 um thick nylon copolyrner film with Serfene 2060 PVDC coating was prepared and laminated to a one-side nitrocellulose-coated regenerated cellulose film, substan-tially in the manner described in Example 1. The resulting laminate was coated on the second side of the nylon and laminated to the EVA-containing film, as described in Example 9.
The bond strength between the nylon film and the cellulose film after 5 days storage at 20C was found to be 78 g/cm.
Exam~ 11 A 15 ~lm thick film oriented copolymer nylon was coated with Daran* 820 PVDC dispersion at 6.99 g/m2. The resulting coated film was dried ana laminated at 115C to the EVA-containing film of Example 6.
The bond strength, after 5 days storage at 20C, 25 was found to be 350 g/cm.
Example 12 A 51 ,um thick cast nylon 6 film was coated with 6.99 g/m2 Serfene 2060 dispersion with 5 wt% iso-propyl alcohol and passed through a dryer controlled at 120C, for a 30 residence time of ~ second~. The coatetl eilm leavin~ the dryer had a tem~)erature of 74C. The resultant film was laminated at the sealant web of Example 6.
The bond strength, after 5 days storage at 20C was found to be 275 g/cm. The Eilm was slightly curled, but was 35 successfully used in thermoforming operations on a Multivac*
8000 vacuum thermoformer.
*denotes trade mark.
~Z2~6~
Example 13 . .
A 76 ~m thick cast nylon 66 film was coated with 3 49 g/m2 SerEene PVDC 2060 dispersion with 5 wt~ iso-propyl alcohol. The coated film leaving the dryer had a surface temperature of 72C. The resultant film was laminated to 127 ~m thick sealant web made from a blend of 85 parts by weight of an ethylene/butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 dg/min and 15 parts by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 12 wt% of the copolymer and a melt index of 0.35 dg/min. The PVDC-coated film was passed over a laminating roll held at 112 C for a residence time of 0.7 seconds on the hot roll, 60% of that time being in contact with the sealant film.
The laminate bond strength was tested after 5 days storage at 20C and found to be 560 g/cm. The laminate was flat and thermoformable.
Example 14 A 11 ~m thick oriented polyester film i.e. poly-ethylene terephthalate film, corona discharge treated to a surface tension level oX 40 dynes/cm, was coated with 4.$3 g/m2 of Serfene 2060 PVDC dispersion with 5 wt% iso-propyl alcohol. The coated film was passed through a dryer main-tained at 138~C. The surface temperature of the coated film leaving the dryer was 70C. The film was passed over a laminating roll held at 113C for a residence time of 0.3 seconds. The coated film was laminated to the sealant web of Example 13.
The laminate bond ~trength was testerl ~fter 5 days' storage at 20C and Eound to be at least 630 g/cm.
xample 15 A sealant web made from 85 parts by weight of a linear ethylene/butene-l copolymer having a density of 0.919 g/cm3 and a melt index of 0.75 dg/min and 15 parts by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate .
~2Zi~l~
content of 18% and a melt index of 0.7 dg/min was corona discharge treated to a level of about 42 dynes/cm. The sealant web had a slip coefficient higher than 0~5O
The sealant web was coated with 4.3 g/m2 of Serfene 2015 PVDC dispexsion containing 10% isopropyl alcohol. The coating was dried and then nipped to a 25 ~m thick nylon 66 film while the nylon film was in contact with a hot roll, heated to 92C.
The resulting laminate had a bond strength, measured after 5 days at 20~C of at least 600 g/cm and an measured oxygen permeability of less than 13.7 ml/m2/day/atm.
Exam ~
The sealant web of Example 2 was corona discharge treated to a level of about 42 dynes/cm and then coated with 4.8 g/m3 of Serfene 2011 PVDC dispersion, dried and wound up on a roll, with a slip sheet. Subsequently the PVDC-coated sealant web was unwound and coated with
4.8 g/m2 of Serfene 2015 PVDC dispersion, dried and nipped to a base film which was identical to the sealant web. The base film was in contact with the hot roll, which was heated to 8.2C.
The resulting laminate had a bond strength, measured after 5 days at 20C of at least 600 g/cm and an oxygen permeability of 7.8 ml/m2/day/atm.
.
~ ' :
' ` 3L~216~0 SUPPLEMENTARY DISCLOSURE_ _ It has now been found that the base film, useful in the present invention may be made from polyethylene. In addition it has also been found that the Solvent Haze Test is sufficient as an indicator of the crystallinity requirements of the PVDC coating. It is especially preferred that the polyethylene be coated with a metal, e.g. aluminum, for applications wherein superlative oxygen barrier properties are sought.
It has also been found that when the base film is metallized, there seems to be a synergistic effect, with respect to oxygen permeability, engendered by the direct contact of the PVDC and the metal.
The PVDC coating used in the present invention may be selected on the basis of results using the Solvent Haze Test. For the present purpose, acetone is the most preferxed solvent for this Test. When acetone is the solvent, the test may be referred to as the Acetone Haze Test. The PYDC is 20 selected by taking a sample of base film or first sealant web, coating such film or web with an aqueous dispersion of the PVDC with a sufficient quantity of dispersion to yield a PVDC coating of about 3.25 to 6.5 g/m3 of PVDC, drying the PVDC coated film or web and allowing the coated film to stand for 5 days at 4~C. The dried PVDC coated web or film is then either dipped in acetone or sprayed with acetone and the PVDC coating is observed to determine whether there has been any change in visual clarity of the PVDC. If the PVDC
coating becomes hazy or turbid in appearance, or if all or a portion of the PVnC coating dissolves, then the PVDC is suitable for use in the present invention. In the event of development of haziness, turbidness or in the event of dissolution of the PVDC coating, the PVDC is said to have failed the Solvent Haze Test.
If the PVDC coating passes the Solvent Haze Test, ~, .. .
~zz~o i.e. the PVDC coating remains unaffected by the solvent, the PVDC has developed too much crystallinity and is unsuitable as an essential component of ~he present invention. It is to be understood, however, that such a PVDC may be used as a centre layer, between two PVDC layers which fail the Solvent Haze Test, for applications where a better oxygen barrier film composite is ~esirable.
Accordingly, the present invention provides a film composite comprising a base film and a first sealant web with 0 a coating of PVDC sandwiched therebetween:
said first sealant web being selected from the group consisting of a)a fi]m made from a copolymer of ethylene and vinyl acetate, and b)a film made from a blend of i)a copolymer of ethylene and vinyl acetate with ii)a homopolymer 5 of ethylene, or a copolymer of ethylene and one or more C4 to C1o alpha-olefins, said homopolymer or copolymer having a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copolymer, said base film being selected from the group consisting of oriented nylon film, oriented polyester film, oriented polypropylene film, cast nylon film, polyethylene film, a second sealant web, metal-coated cast nylon film, metal-coated oriented nylon film, metal-coated oriented polyester film, metal-coated oriented polypropylene film, metal-coated polyethylene film and metal-coated second sealant web said second sealant web being selected from the same group as said first sealant web;
said PVDC coating consisting of at least one layer, said layers being characterized by failing the Acetone Haze Test; with the proviso that ;f the base film is metal-coated, then the PVDC is in direct contact with the metal coating.
In a preferred process,the second sealant web has a slip coefficient of less than about 0.4.
In another embodiment, the PVDC layers are characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, ~2 ~
if the base film is selected from nylon film, polyester film and polypropylene film, the layer in contact with the base film is further characterized by having a crystallinity index of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C.
In yet another embodiment, the metal coating is aluminum.
The present invention also provides a process for forming the composite of the present invention comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll, then said sealant web that contacts the hot roll has a slip coefficient of less than about 0.4.
In one embodiment the process comprises:
a) heating a PVDC-coated base film or a PVDC-coated sealant web to an extent su~fficient to reduce the crystallinity index of the PVDC coating to less than about 1.05;
b) passing the heated PVDC-coated base film or first PVDC-coated sealant web over a hot roll; and c) i) when a PVDC-coated-base film is used, bringing the first sealant web i.nto contact with the PVDC
coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate, or ii) when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate~
In other embodiments of the process, a PVDC-coated base film or first PVDC-coated sealant web is taken and a further coating of PVDC is applied to the base film or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinbelow as 6~0 Processes ~1, Bl, Cl and Dl.
Process Al comprises:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by failing the Acetone Haze Test;
b) coating the PVDC-coated base film with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by failing the Acetone Haze Test;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
In a preferred embodiment the PVDC adjacent to the base film is characterized by having a crystallinity index of less than 1.15 if dried an allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film and polypropylene film, the PVDC coating is further characterized by having a crystallinity index of from 1.12 to 1.25, especially if dried and allowed to stand for 5 days at 40C.
In another embodiment the PVDC coating applied in step b) is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C.
In yet another embodiment, the metal coating is aluminum.
In a further embodiment the hot roll is at a ~ .
~Z2~L6;10 temperature higher than about 70C.
Process Bl comprises:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC bein~ characteriz-ed by failing the Acetone Haze Test; and b) coating a first sealant web~ which has a surface tension of at least 38 dynes/cm, with an aqueous PVDC
dispersion to form a PVDC-coated sealant web, said PVDC
coating on the first sealant web being characterized by failing the Acetone Haze Test;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the - PVDC-coated base film and nipping said PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the P~DC adjacent to the base film is characterized by having a crystallinity index of less than 1.15 if dried an allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film and polypropylene film, the PVDC coating is further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C.
In another embodiment the PVDC coating applied in step b) is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C.
In yet another embodiment, the metal coating is aluminum.
Process Cl comprises:
~2Z~610 a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by failing the Acetone Haze Test and said PVDC coating adjacent to the first sealant web being characterized by failing the Acetone Haze Test;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the hot roll is at a temperature higher than about 70C.
In a preferred embodiment both PVDC coatings, of step a) are characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand to 30 days at 20C.
Process Dl comprises:
a) coating the base film with an aqueous PVDC
dispersion, the resultant coating being characterized by failing the Acetone ~aze Test;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60C:
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the first PVDC coating is characterized by having a crystallinity index of less than ~2Zlti~O
1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or polypropylene film, the first PVDC coating is further characterized by a crystallinity index of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C.
In another embodiment, the metal coating is aluminum.
In yet another embodiment the hot rollis at a temperature higher than about 70C~
In further embodiments of the process, a base film or first sealant web is taken and a coating of PVDC is 1.25 applied to the base film and/or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinbelow as Processes El, Fl and Gl.
Process El comprises: -a) coating the base film with a first PVDC, thecoating being characterized by failing the Acetone Haze Test;
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by failing the Acetone Haze Test, to form a second PVDC coating;
c) heating the said second coating until the temperature of the free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60C, and e) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the second PVDC coating ., -- ~:
161~
is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from the nylon film, polyester film and polypropylene film, the first PVDC coating is further characterized by a crystallinity index of from l.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C~
In another embodiment, the second PVDC coating is characterized by having a crystallinity index of less than 10 1.15 if dried and allowed to stand for 30 days at 20C.
In yet another embodiment, the metal coating is aluminum.
In another embodiment, the hot roll is at a temperature higher than about 70C.
lS Process Fl compri~es:
a) coating a first sealant web, which has a surface tension of at least 38 dynes/cm, with a first PVDC, the coating being characterized by failing the Acetone Haze Test, to form a first PVDC coating;
b) coating the PVDC-coated first sealant web formed in step a) with a second PVDC, the second coatin~
being characterized by failing the Acetone Haze Test;
c) passing the base film over a hot roll, said base film being in contact with said hot holl, and said hot roll being at a temperature higher than about 60C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the hot roll is at a temperature higher than about 70C.
Process Gl comprises:
a) coating the base film with a first PVDC, the coating being characterized by failing the Acetone Haze Test;
'~:
, ~2Z~
b) drying the first PVDC coating, c) coating a first sealant web, having a surface tension of at least 38 dynes/cm with a second PVDC, the coat-ing being characterized by failing the Acetone Baze Test:
e) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60C; and f) bringing the PVDC-coated surface of the PVDC-coated first sealant web into contact with the PVDC-coated-surface of the PVDC-coated base film and nipping the PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment, the first PVDC coating is characteri~ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C.
In another embodiment, the second PVDC coating is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is nylon film, polye-ster film or polypropylene film, the second PVDC coating is further characterized by a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, and a crystallinity index of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C.
In yet another embodiment the metal coating is aluminum.
In another embodiment, the hot roll is at a temperature higher than about 70C.
In a preferred embodiment of the process of the present invention, the PVDC layers in contact with and furthest away from the base film are combined into a single layer, said PVDC layer being characterized by failing the Acetone Haze Test.
In one embodiment, the PVDC layer is characterized by having a crystallinity index of less than 1.15 if dried l~Z~
and allowed to stand for 30 days at 20C and of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C. In another embodiment, the metal coating is aluminum.
In the Supplementary Disclosure and in all of the Examples crystallinity index is measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit. The method is described on page 11 of the present patent application.
The polyethylene base film may be made by a number of known process. A preferred process is the so-called blown film process disclosed in Canadian Patent 460 963 issued 1949 November 08 to E.D. Fuller. Film may also be made using an internal or external cooling mandrel with the blown film process, as disclosed for example in Canadian Patent 893 216 issued 1972 February 15 to M. Bunga and C.V. Thomas.
For food packaging applications, it is preferable that the polyethylene film have a density of from about 0.916 to 0.924 g/cm3. The polyethylene film preferably-is made from at least one linear ethylene/C4 - Clo alpha-olefin copolymer or blends thereof with so-called high pressure polyethylene. Preferred linear copolymers are ethylene/-butene-l, ethylene/hexene-l and ethylene/octene-l copolymers.
In the event that the end-use application for the film laminate requires the laminate to have very low oxygen permeability, placement of a metal coating adjacent the PVDC
is highly desirable. The most cost effective metal is aluminum. Coating is best accomplished by vacuum deposition, such a technique being known in the art. As used herein, the terrn "metal-coated base film" does not encompass base films with metal foils adhered thereto.
With respect to the strength of the bond between the metal coating and the base film, it should be noted that the bond strength is greater when the base film is a second ~2~1610 sealant web rather than when the base film is a polyethylene film.
It wil~ be clear to those skilled in the art that the film laminate may be made using sealant webs which form part of another structure, e.g. a coextrudate of the composition of the second sealant web, and polypropylene.
Examples of dispersions of PVDC which fail the Acetone Haze Test include Amsco-Res* P-546, Serfene 2011, Serfene 2012, Serfene 2015, Ser~fene 2060.
Further embodiments of the present invention are illustrated by the following examples.
Example 17 A 51 ~m thick metallized polyethylene film was direct gravure coated with 6.4 g/cm2 of Amsco-Res P-546 PVDC
dispersion. The polyethylene film was pigmented with a white pigment and was made from a blend of high pressure polyethylene and a linear ethylene/butene-l copolymer. The blend had a density of about 0.918 g/cm3. The PVDC of Amsco-Res P-546 has a crystallinity index, when dry and after storage at 20C for 30 days, of 1.05, and after storage at 40C for 5 days, of 1.35. It fails the Acetone Haze Test.
The coated film was dried, in a roll support arch dryer, to a temperature of 52C. The coated film was passed over a laminating roll held at 80C for a residence time of 0.33 seconds on the hot roll, and was laminated to a 51 ~m thick sealant web made from a blend of 85 parts by weight of linear ethylene/octene-l copolymer having a density 0.920 g/cm3 and and 15 parts by weight of an ethylene/vinyl acetate copolymer having a melt index of 0.35 dg/min and a vinyl acetate content of 12 wt % of the copolymer.
The resulting laminate had an oxygen permeability of 1.09 ml/m2/atmos./day. This compares with an oxygen permeability of 500 ml/m2/atmos./day for the plain metallized polyethylene film, and 10.9 ml/m2/atmos./day for a structure comprising the PVDC layer sandwiched between two * denotes trade mark .,~
-- :~2;~
films of the sealant web.
Example_18 Example 17 was repeated except that the base film was a metallized unpigmented polyethylene film. The laminate's oxygen permeability was 0.63 ml/m2/atmos./day.
For comparison purposes the metallized polyethylene film was adhesive laminated to a PVDC-coated sealant web, with Adcote* 503H adhesive. The sealant web was as in Example 17 and was direct gravure coated with 6.4 g/m2 of Amsco-Res P-546 PVDC dispersion, and then dried prior to adhesive lamination. The oxygen permeability of this laminate was between 10~3 and 11.9 ml/m2/atmos./day, which clearly demonstrates the superiority of the embodiment of the present invention wherein the aluminum and PVDC are in direct contact.
Example 19 Example 17 was repeated except that two layers of Amsco-Res P-546, each of 6.4 g/m2 PVDC, were coated onto the base film. The oxygen permeability of the laminate was 0.47 ml/m2/atmos./day.
Example 20 -Example 17 was repeated except that the base film was a 15 ~m thick metallized oriented polyester film and the PVDC dispersion was 5erfene 2011. The oxyyen permeability of the laminate was 0.31 ml/m2/atmos./day. This compares with an oxygen permeability of 2.19 to 2.97 ml/m2/atoms./day for the plain metallized polyester film and 1.09 ml/m2/atmos./day for a laminate structure comprisin~ the sealant web, adhesive laminated to the metallized surface of metallized polyester film, with the polyester film coated with Serfene 2015 PVDC and heat laminated to another layer of the sealant web.
* denotes trade mark .,;~, Example 21 Example 20 was repeated except that the base film was a metallized biaxially oriented polypropylene. The oxygen permeability of the laminate was 0.63 ml/m2/atmos./day.
Example 22 A 51~um thick metallized polythylene film was direct gravure coated with 6.4 g/cm2 of 76 Res* 701 PVDC
dispersion. The polyethylene film was made from a blend of high pressure polyethylene and a linear ethylenejbutene-l copolymer. The blend had a density of about 0.918 g/cm3.
The PVDC of 76 Res 701 fails the Acetone Haze Test and is completely amorphous~ e.g. has a crystallinity index, when dry and after storage at 40C for 5 days of 1Ø The coated film was dried, in a roll support arch dryer, to a ternperature of about 52C. The coated film was passed over a laminating roll held at 82C for a residence time of 0.33 seconds on the hot roll, and was laminated to 51 m thick sealant web made from a blend of 85 parts by weight of linear ethylene/butene-l copolymer having a density of about 0.916 g/cm3 and 15 parts by weight of an ethylene/vinyl acetate copolymer having a melt index of 0.35 dg/min and a vinyl acetate content of 12 wt. % of the copolymer.
The resulting laminate had an oxygen permeability of 3.7 cc/m2/atmos./day.
.
The resulting laminate had a bond strength, measured after 5 days at 20C of at least 600 g/cm and an oxygen permeability of 7.8 ml/m2/day/atm.
.
~ ' :
' ` 3L~216~0 SUPPLEMENTARY DISCLOSURE_ _ It has now been found that the base film, useful in the present invention may be made from polyethylene. In addition it has also been found that the Solvent Haze Test is sufficient as an indicator of the crystallinity requirements of the PVDC coating. It is especially preferred that the polyethylene be coated with a metal, e.g. aluminum, for applications wherein superlative oxygen barrier properties are sought.
It has also been found that when the base film is metallized, there seems to be a synergistic effect, with respect to oxygen permeability, engendered by the direct contact of the PVDC and the metal.
The PVDC coating used in the present invention may be selected on the basis of results using the Solvent Haze Test. For the present purpose, acetone is the most preferxed solvent for this Test. When acetone is the solvent, the test may be referred to as the Acetone Haze Test. The PYDC is 20 selected by taking a sample of base film or first sealant web, coating such film or web with an aqueous dispersion of the PVDC with a sufficient quantity of dispersion to yield a PVDC coating of about 3.25 to 6.5 g/m3 of PVDC, drying the PVDC coated film or web and allowing the coated film to stand for 5 days at 4~C. The dried PVDC coated web or film is then either dipped in acetone or sprayed with acetone and the PVDC coating is observed to determine whether there has been any change in visual clarity of the PVDC. If the PVDC
coating becomes hazy or turbid in appearance, or if all or a portion of the PVnC coating dissolves, then the PVDC is suitable for use in the present invention. In the event of development of haziness, turbidness or in the event of dissolution of the PVDC coating, the PVDC is said to have failed the Solvent Haze Test.
If the PVDC coating passes the Solvent Haze Test, ~, .. .
~zz~o i.e. the PVDC coating remains unaffected by the solvent, the PVDC has developed too much crystallinity and is unsuitable as an essential component of ~he present invention. It is to be understood, however, that such a PVDC may be used as a centre layer, between two PVDC layers which fail the Solvent Haze Test, for applications where a better oxygen barrier film composite is ~esirable.
Accordingly, the present invention provides a film composite comprising a base film and a first sealant web with 0 a coating of PVDC sandwiched therebetween:
said first sealant web being selected from the group consisting of a)a fi]m made from a copolymer of ethylene and vinyl acetate, and b)a film made from a blend of i)a copolymer of ethylene and vinyl acetate with ii)a homopolymer 5 of ethylene, or a copolymer of ethylene and one or more C4 to C1o alpha-olefins, said homopolymer or copolymer having a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copolymer, said base film being selected from the group consisting of oriented nylon film, oriented polyester film, oriented polypropylene film, cast nylon film, polyethylene film, a second sealant web, metal-coated cast nylon film, metal-coated oriented nylon film, metal-coated oriented polyester film, metal-coated oriented polypropylene film, metal-coated polyethylene film and metal-coated second sealant web said second sealant web being selected from the same group as said first sealant web;
said PVDC coating consisting of at least one layer, said layers being characterized by failing the Acetone Haze Test; with the proviso that ;f the base film is metal-coated, then the PVDC is in direct contact with the metal coating.
In a preferred process,the second sealant web has a slip coefficient of less than about 0.4.
In another embodiment, the PVDC layers are characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, ~2 ~
if the base film is selected from nylon film, polyester film and polypropylene film, the layer in contact with the base film is further characterized by having a crystallinity index of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C.
In yet another embodiment, the metal coating is aluminum.
The present invention also provides a process for forming the composite of the present invention comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll, then said sealant web that contacts the hot roll has a slip coefficient of less than about 0.4.
In one embodiment the process comprises:
a) heating a PVDC-coated base film or a PVDC-coated sealant web to an extent su~fficient to reduce the crystallinity index of the PVDC coating to less than about 1.05;
b) passing the heated PVDC-coated base film or first PVDC-coated sealant web over a hot roll; and c) i) when a PVDC-coated-base film is used, bringing the first sealant web i.nto contact with the PVDC
coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate, or ii) when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate~
In other embodiments of the process, a PVDC-coated base film or first PVDC-coated sealant web is taken and a further coating of PVDC is applied to the base film or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinbelow as 6~0 Processes ~1, Bl, Cl and Dl.
Process Al comprises:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by failing the Acetone Haze Test;
b) coating the PVDC-coated base film with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by failing the Acetone Haze Test;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
In a preferred embodiment the PVDC adjacent to the base film is characterized by having a crystallinity index of less than 1.15 if dried an allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film and polypropylene film, the PVDC coating is further characterized by having a crystallinity index of from 1.12 to 1.25, especially if dried and allowed to stand for 5 days at 40C.
In another embodiment the PVDC coating applied in step b) is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C.
In yet another embodiment, the metal coating is aluminum.
In a further embodiment the hot roll is at a ~ .
~Z2~L6;10 temperature higher than about 70C.
Process Bl comprises:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC bein~ characteriz-ed by failing the Acetone Haze Test; and b) coating a first sealant web~ which has a surface tension of at least 38 dynes/cm, with an aqueous PVDC
dispersion to form a PVDC-coated sealant web, said PVDC
coating on the first sealant web being characterized by failing the Acetone Haze Test;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the - PVDC-coated base film and nipping said PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the P~DC adjacent to the base film is characterized by having a crystallinity index of less than 1.15 if dried an allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film and polypropylene film, the PVDC coating is further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40C.
In another embodiment the PVDC coating applied in step b) is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C.
In yet another embodiment, the metal coating is aluminum.
Process Cl comprises:
~2Z~610 a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by failing the Acetone Haze Test and said PVDC coating adjacent to the first sealant web being characterized by failing the Acetone Haze Test;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the hot roll is at a temperature higher than about 70C.
In a preferred embodiment both PVDC coatings, of step a) are characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand to 30 days at 20C.
Process Dl comprises:
a) coating the base film with an aqueous PVDC
dispersion, the resultant coating being characterized by failing the Acetone ~aze Test;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60C:
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the first PVDC coating is characterized by having a crystallinity index of less than ~2Zlti~O
1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from nylon film, polyester film or polypropylene film, the first PVDC coating is further characterized by a crystallinity index of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C.
In another embodiment, the metal coating is aluminum.
In yet another embodiment the hot rollis at a temperature higher than about 70C~
In further embodiments of the process, a base film or first sealant web is taken and a coating of PVDC is 1.25 applied to the base film and/or the first sealant web prior to forming the laminate by heat lamination. Specific embodiments are shown hereinbelow as Processes El, Fl and Gl.
Process El comprises: -a) coating the base film with a first PVDC, thecoating being characterized by failing the Acetone Haze Test;
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by failing the Acetone Haze Test, to form a second PVDC coating;
c) heating the said second coating until the temperature of the free surface of said second coating is less than 75C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60C, and e) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the second PVDC coating ., -- ~:
161~
is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is selected from the nylon film, polyester film and polypropylene film, the first PVDC coating is further characterized by a crystallinity index of from l.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C~
In another embodiment, the second PVDC coating is characterized by having a crystallinity index of less than 10 1.15 if dried and allowed to stand for 30 days at 20C.
In yet another embodiment, the metal coating is aluminum.
In another embodiment, the hot roll is at a temperature higher than about 70C.
lS Process Fl compri~es:
a) coating a first sealant web, which has a surface tension of at least 38 dynes/cm, with a first PVDC, the coating being characterized by failing the Acetone Haze Test, to form a first PVDC coating;
b) coating the PVDC-coated first sealant web formed in step a) with a second PVDC, the second coatin~
being characterized by failing the Acetone Haze Test;
c) passing the base film over a hot roll, said base film being in contact with said hot holl, and said hot roll being at a temperature higher than about 60C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment the hot roll is at a temperature higher than about 70C.
Process Gl comprises:
a) coating the base film with a first PVDC, the coating being characterized by failing the Acetone Haze Test;
'~:
, ~2Z~
b) drying the first PVDC coating, c) coating a first sealant web, having a surface tension of at least 38 dynes/cm with a second PVDC, the coat-ing being characterized by failing the Acetone Baze Test:
e) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60C; and f) bringing the PVDC-coated surface of the PVDC-coated first sealant web into contact with the PVDC-coated-surface of the PVDC-coated base film and nipping the PVDC-coated first sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
In a preferred embodiment, the first PVDC coating is characteri~ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C.
In another embodiment, the second PVDC coating is characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C and, if the base film is nylon film, polye-ster film or polypropylene film, the second PVDC coating is further characterized by a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20C, and a crystallinity index of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C.
In yet another embodiment the metal coating is aluminum.
In another embodiment, the hot roll is at a temperature higher than about 70C.
In a preferred embodiment of the process of the present invention, the PVDC layers in contact with and furthest away from the base film are combined into a single layer, said PVDC layer being characterized by failing the Acetone Haze Test.
In one embodiment, the PVDC layer is characterized by having a crystallinity index of less than 1.15 if dried l~Z~
and allowed to stand for 30 days at 20C and of from 1.12 to 1.40, especially from 1.12 to 1.25, if dried and allowed to stand for 5 days at 40C. In another embodiment, the metal coating is aluminum.
In the Supplementary Disclosure and in all of the Examples crystallinity index is measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit. The method is described on page 11 of the present patent application.
The polyethylene base film may be made by a number of known process. A preferred process is the so-called blown film process disclosed in Canadian Patent 460 963 issued 1949 November 08 to E.D. Fuller. Film may also be made using an internal or external cooling mandrel with the blown film process, as disclosed for example in Canadian Patent 893 216 issued 1972 February 15 to M. Bunga and C.V. Thomas.
For food packaging applications, it is preferable that the polyethylene film have a density of from about 0.916 to 0.924 g/cm3. The polyethylene film preferably-is made from at least one linear ethylene/C4 - Clo alpha-olefin copolymer or blends thereof with so-called high pressure polyethylene. Preferred linear copolymers are ethylene/-butene-l, ethylene/hexene-l and ethylene/octene-l copolymers.
In the event that the end-use application for the film laminate requires the laminate to have very low oxygen permeability, placement of a metal coating adjacent the PVDC
is highly desirable. The most cost effective metal is aluminum. Coating is best accomplished by vacuum deposition, such a technique being known in the art. As used herein, the terrn "metal-coated base film" does not encompass base films with metal foils adhered thereto.
With respect to the strength of the bond between the metal coating and the base film, it should be noted that the bond strength is greater when the base film is a second ~2~1610 sealant web rather than when the base film is a polyethylene film.
It wil~ be clear to those skilled in the art that the film laminate may be made using sealant webs which form part of another structure, e.g. a coextrudate of the composition of the second sealant web, and polypropylene.
Examples of dispersions of PVDC which fail the Acetone Haze Test include Amsco-Res* P-546, Serfene 2011, Serfene 2012, Serfene 2015, Ser~fene 2060.
Further embodiments of the present invention are illustrated by the following examples.
Example 17 A 51 ~m thick metallized polyethylene film was direct gravure coated with 6.4 g/cm2 of Amsco-Res P-546 PVDC
dispersion. The polyethylene film was pigmented with a white pigment and was made from a blend of high pressure polyethylene and a linear ethylene/butene-l copolymer. The blend had a density of about 0.918 g/cm3. The PVDC of Amsco-Res P-546 has a crystallinity index, when dry and after storage at 20C for 30 days, of 1.05, and after storage at 40C for 5 days, of 1.35. It fails the Acetone Haze Test.
The coated film was dried, in a roll support arch dryer, to a temperature of 52C. The coated film was passed over a laminating roll held at 80C for a residence time of 0.33 seconds on the hot roll, and was laminated to a 51 ~m thick sealant web made from a blend of 85 parts by weight of linear ethylene/octene-l copolymer having a density 0.920 g/cm3 and and 15 parts by weight of an ethylene/vinyl acetate copolymer having a melt index of 0.35 dg/min and a vinyl acetate content of 12 wt % of the copolymer.
The resulting laminate had an oxygen permeability of 1.09 ml/m2/atmos./day. This compares with an oxygen permeability of 500 ml/m2/atmos./day for the plain metallized polyethylene film, and 10.9 ml/m2/atmos./day for a structure comprising the PVDC layer sandwiched between two * denotes trade mark .,~
-- :~2;~
films of the sealant web.
Example_18 Example 17 was repeated except that the base film was a metallized unpigmented polyethylene film. The laminate's oxygen permeability was 0.63 ml/m2/atmos./day.
For comparison purposes the metallized polyethylene film was adhesive laminated to a PVDC-coated sealant web, with Adcote* 503H adhesive. The sealant web was as in Example 17 and was direct gravure coated with 6.4 g/m2 of Amsco-Res P-546 PVDC dispersion, and then dried prior to adhesive lamination. The oxygen permeability of this laminate was between 10~3 and 11.9 ml/m2/atmos./day, which clearly demonstrates the superiority of the embodiment of the present invention wherein the aluminum and PVDC are in direct contact.
Example 19 Example 17 was repeated except that two layers of Amsco-Res P-546, each of 6.4 g/m2 PVDC, were coated onto the base film. The oxygen permeability of the laminate was 0.47 ml/m2/atmos./day.
Example 20 -Example 17 was repeated except that the base film was a 15 ~m thick metallized oriented polyester film and the PVDC dispersion was 5erfene 2011. The oxyyen permeability of the laminate was 0.31 ml/m2/atmos./day. This compares with an oxygen permeability of 2.19 to 2.97 ml/m2/atoms./day for the plain metallized polyester film and 1.09 ml/m2/atmos./day for a laminate structure comprisin~ the sealant web, adhesive laminated to the metallized surface of metallized polyester film, with the polyester film coated with Serfene 2015 PVDC and heat laminated to another layer of the sealant web.
* denotes trade mark .,;~, Example 21 Example 20 was repeated except that the base film was a metallized biaxially oriented polypropylene. The oxygen permeability of the laminate was 0.63 ml/m2/atmos./day.
Example 22 A 51~um thick metallized polythylene film was direct gravure coated with 6.4 g/cm2 of 76 Res* 701 PVDC
dispersion. The polyethylene film was made from a blend of high pressure polyethylene and a linear ethylenejbutene-l copolymer. The blend had a density of about 0.918 g/cm3.
The PVDC of 76 Res 701 fails the Acetone Haze Test and is completely amorphous~ e.g. has a crystallinity index, when dry and after storage at 40C for 5 days of 1Ø The coated film was dried, in a roll support arch dryer, to a ternperature of about 52C. The coated film was passed over a laminating roll held at 82C for a residence time of 0.33 seconds on the hot roll, and was laminated to 51 m thick sealant web made from a blend of 85 parts by weight of linear ethylene/butene-l copolymer having a density of about 0.916 g/cm3 and 15 parts by weight of an ethylene/vinyl acetate copolymer having a melt index of 0.35 dg/min and a vinyl acetate content of 12 wt. % of the copolymer.
The resulting laminate had an oxygen permeability of 3.7 cc/m2/atmos./day.
.
Claims (94)
1. A film laminate comprising a base film and a first sealant web with a coating of PVDC sandwiched therebetween, said first sealant web being selected from the group consisting of a) film made from a copolymer of ethylene and vinyl acetate, and b) a film made from a blend of i) a co-polymer of ethylene and vinyl acetate with ii) a homopolymer of ethylene, or a copolymer of ethylene and one or more C4 to C10 .alpha.-olefins, said homopolymer or copolymer having a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copolymer, said base film being selected from the group consisting of oriented nylon film, oriented polyester film, oriented polypropylene film, cast nylon film and a second sealant web, said second sealant web being selected from the same group as said first sealant web and having a slip coefficient of less than about 0.4, said PVDC coating consisting of at least one layer, the layers being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the layer in contact with the base film being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C, crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45°, the reference beam attenuator of said total reflectance unit having been set at 85% at 1150 cm-1.
2. A process for forming the laminate of Claim 1 comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll then said web which contacts the hot roll has a slip coefficient of less than about 0.4.
3. A process according to Claim 2 comprising:
a) heating a PVDC-coated base film or first seal-ant web to an extent sufficient to reduce the crystallinity index of the PVDC coating to less than about 1.05;
b) passing the heated PVDC-coated base film or first sealant web over a hot roll;
c) when a PVDC-coated base film is used, bringing the first sealant web into contact with the PVDC coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate;
and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate.
a) heating a PVDC-coated base film or first seal-ant web to an extent sufficient to reduce the crystallinity index of the PVDC coating to less than about 1.05;
b) passing the heated PVDC-coated base film or first sealant web over a hot roll;
c) when a PVDC-coated base film is used, bringing the first sealant web into contact with the PVDC coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate;
and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate.
4. A process according to Claim 2 comprising:
a) heating a PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) coating the PVDC-coated base film with an aque-ous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
a) heating a PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) coating the PVDC-coated base film with an aque-ous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
5. A process according to Claim 2 comprising:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C.
b) coating the first sealant web having a surface tension of at least 42 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated first sealant web, said PVDC coat-ing on the sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C.
b) coating the first sealant web having a surface tension of at least 42 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated first sealant web, said PVDC coat-ing on the sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
6. A process according to Claim 2 comprising:
a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the second PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C, and said PVDC coating adjacent to the first sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate;
a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the second PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C, and said PVDC coating adjacent to the first sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate;
7. A process according to Claim 2 comprising:
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystal-linity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70°C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystal-linity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70°C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
8. A process according to Claim 2 comprising:
a) coating the base film with a first PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C.
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a second PVDC coating;
c) heating said second coating until the tempera-ture of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70°C, and e) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) coating the base film with a first PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C.
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a second PVDC coating;
c) heating said second coating until the tempera-ture of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70°C, and e) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
9. A process according to Claim 2 comprising:
a) coating the first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a first PVDC coating;
b) coating the PVDC-coated first sealant web form-ed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
c) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70°C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
a) coating the first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a first PVDC coating;
b) coating the PVDC-coated first sealant web form-ed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
c) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 70°C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
10. A process according to Claim 2 wherein the first sealant web has a surface, adjacent to the PVDC
coating, of a material selected from the group consisting of a) a copolymer of ethylene and vinyl acetate, b) a blend of a copolymer of ethylene and vinyl acetate and at least one of (i) a copolymer of ethylene and a C4 - C10 ?-olefin having a density of from 0.915 to 0.955 g/cm3 (ii) a homopolymer of ethylene having a density of from 0.915 to 0.955 g/cm3.
coating, of a material selected from the group consisting of a) a copolymer of ethylene and vinyl acetate, b) a blend of a copolymer of ethylene and vinyl acetate and at least one of (i) a copolymer of ethylene and a C4 - C10 ?-olefin having a density of from 0.915 to 0.955 g/cm3 (ii) a homopolymer of ethylene having a density of from 0.915 to 0.955 g/cm3.
11. A process according to any one of Claim 2, Claim 3 and Claim 4 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
12. A process according to any one of Claim 5, Claim 6 and Claim 7 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
13. A process according to Claim 8 or Claim 9 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
14. A process according to any one of Claim 2, Claim 3 and Claim 4 wherein the base film is a nylon film.
15. A process according to any one of Claim 5, Claim 6 and Claim 7 wherein the base film is a nylon film.
16. A process according to Claim 8 or Claim 9 wherein the base film is a nylon film.
17. A process according to any one of Claim 2, Claim 3 and Claim 4 wherein the base film is a sealant web having a slip coefficient of less than 0.3.
18. A process according to any one of Claim 5, Claim 6 and Claim 7 wherein the base film is a sealant web having a slip coefficient of less than 0.3.
19. A process according to Claim 8 or Claim 9 wherein the base film is a sealant web having a slip coefficient of less than 0.3.
20. A process according to any one of Claim 2, Claim 3 and Claim 4 wherein the hot roll is at a temperature of from about 85°C to the melting temperature of the sealant web.
21. A process according to any one of Claim 5, Claim 6 and Claim 7 wherein the hot roll is at a temperature of from about 85°C to the molting temperature of the sealant web.
22. A process according to Claim 8 or Claim 9 wherein the hot roll is at a temperature of from about 85°C
to the melting temperature of the sealant web.
to the melting temperature of the sealant web.
23. A film laminate according to Claim 1 wherein a layer of vacuum deposited metal is interposed between the base film and the PVDC coating.
24. A film laminate according to Claim 23 wherein the metal is aluminum.
25. A film laminate according to Claim 23 wherein the base film is the second sealant web.
26. A film laminate according to Claim 24 wherein the base film is an aluminum-coated second sealant web.
27. A film laminate according to Claim 1 wherein the base film is an oriented nylon film, a cast nylon film, a metal-coated oriented nylon film or a metal-coated cast nylon film.
28. A film laminate according to Claim 27 wherein the base film is an aluminum coated film.
29. A film laminate according to Claim 1 wherein the base film is a second sealant web or a metal-coated second sealant web.
30. A film laminate according to Claim 29 wherein the base film is an aluminum-coated second sealant web.
31. A process according to Claim 2 wherein the base film has a vacuum deposited coating of aluminum thereon and the PVDC coating had been applied to the aluminum coating.
32. A process according to Claim 2 wherein the PVDC-coated base film is a PVDC-coated, metal coated base film wherein the metal coating is interposed between the base film and the PVDC coating.
33. A process according to Claim 32 wherein the metal coating is a vacuum deposited aluminum coating.
34. A process according to Claim 4 wherein the PVDC-coated base film is a PVDC-coated, metal coated base film wherein the metal coating is inteposed between the base film and the PVDC coating.
35. A process according to Claim 34 wherein the metal coating is a vacuum deposited aluminum coating.
36. A process according to Claim 5 wherein the PVDC-coated base film is a PVDC coated, metal coated base film wherein the metal coating is interposed between the base film and the PVDC coating.
37. A process according to Claim 36 wherein the metal coating is a vacuum deposited aluminum coating.
38. A process according to Claim 6 wherein the PVDC-coated base film is a PVDC-coated, metal coated base film wherein the metal coating is interposed between the base film and the PVDC coating.
39. A process according to Claim 38 wherein the metal coating is a vacuum deposited aluminum coating.
40. A process according to Claim 7 wherein the PVDC-coated base film is a PVDC-coated, metal coated base film wherein the metal coating is interposed between the base film and the PVDC coating.
41. A process according to Claim 40 wherein the metal coating is a vacuum deposited aluminum coating.
42. A process according to Claim 8 wherein the PVDC-coated base film is a PVDC-coated, metal coated base film wherein the metal coating is interposed bweteen the base film and the PVDC coating.
43. A process according to Claim 42 wherein the metal coating is a vacuum deposited aluminum coating.
44. A process according to Claim 9 wherein the PVDC-coated base film is a PVDC-coated, metal coated base film wherein the metal coating is interposed between the base film and the PVDC coating.
45. A process according to Claim 44 wherein the metal coating is a vacuum deposited aluminum coating.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
46. A film laminate comprising a base film and a first sealant web with a coating of PVDC sandwiched therebetween, said first sealant web being selected from the group consisting of a) film made from a copolymer of ethylene and vinyl acetate, and b) a film made from a blend of i) a co-polymer of ethylene and vinyl acetate with ii) a homopolymer of ethylene, or a copolymer of ethylene and one or more C4 to C10 alpha-olefins, said homopolymer or copolymer having a density of from about 0.915 to about 0.955 g/cm3, or blends of said homopolymer and copolymer, said base film being selected from the group consisting of oriented nylon film, oriented polyester film, oriented polypropylene film, cast nylon film, polyethylene film, a second sealant web, said second sealant web being selected from the same group as said first sealant web and having a slip coefficient of less than about 0.4, metal-coated oriented nylon film, metal-coated oriented polyester film, metal-coated oriented polypropylene film, metal-coated cast nylon film, metal-coated polyethylene film and metal-coated second sealant web, said PVDC coating consisting of at least one layer, the layers being characterized by failing the Acetone Haze Test;
with the proviso that if the base film is metal coated then the PVDC is in direct contact with the metal coating.
with the proviso that if the base film is metal coated then the PVDC is in direct contact with the metal coating.
47. A film laminate according to Claim 46 wherein said PVDC coating is additionally characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the layer in contact with the base film being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C, the crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45°C, the reference beam attenuator of said total reflectance unit having been set at 85% at 1150 cm-1.
48. A film laminate according to Claim 47 wherein the base film is nylon film.
49. A film laminate according to Claim 46 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
50. A film laminate according to Claim 49 wherein the polyethylene film has a density of from 0.916 to 0.924 g/cm3.
51. A film laminate according to Claim 50 wherein the polyethylene film is made from at least one linear ethylene/C4 - C10 alpha-olefin copolymer or blends thereof with high pressure polyethylene.
52. A film laminate according to Claim 49, 50 or 51 wherein the metal is aluminum.
53. A film laminate according to Claim 47 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
54. A film laminate according to Claim 53 wherein the polyethylene film has a density of 0.916 to 0.924 g/cm3.
55. A film laminate according to Claim 54 wherein the polyethylene film is made from at least one linear ethylene/C4 - C10 alpha-olefin copolymer or blends thereof with high pressure polyethylene.
56. A film laminate according to Claim 47, 48 or 49 wherein the metal is aluminum.
57. A process for forming the laminate of Claim 46 comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll then said web which contacts the hot roll has a slip coefficient of less than about 0.4.
58. A process according to Claim 51 comprising:
a) heating a PVDC-coated base film or first seal-ant web to an extent sufficient to reduce the crystallinity index of the PVDC coating to less than about 1.05, said crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut a t 45°C, the reference beam attenuator of said total reflectance unit having been set at 85% at 1150 cm-1;
b) passing the heated PVDC-coated base film or first sealant web over a hot roll;
c) when a PVDC-coated base film is used, bringing the first sealant web into contact with the PVDC coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate;
and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate.
a) heating a PVDC-coated base film or first seal-ant web to an extent sufficient to reduce the crystallinity index of the PVDC coating to less than about 1.05, said crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut a t 45°C, the reference beam attenuator of said total reflectance unit having been set at 85% at 1150 cm-1;
b) passing the heated PVDC-coated base film or first sealant web over a hot roll;
c) when a PVDC-coated base film is used, bringing the first sealant web into contact with the PVDC coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate;
and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate.
59. A process according to Claim 57 comprising:
a) heating a PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45°C, the reference beam attenuator of said total refectance unit having been set at 85% at 1150 cm-1;
b) coating the PVDC-coated base film with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by failing the Acetone Haze Test;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
a) heating a PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45°C, the reference beam attenuator of said total refectance unit having been set at 85% at 1150 cm-1;
b) coating the PVDC-coated base film with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by failing the Acetone Haze Test;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
60. A process according to Claim 57 comprising:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by failing the Acetone Haze Hest, said crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45°C, the reference beam attenuator of said total reflectance unit having been set at 85% at 1150 cm-1;
b) coating the first sealant web having a surface tension of at least 38 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated first sealant web, said PVDC coat-ing on the sealant web being characterized by failing the Acetone Haze Test;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by failing the Acetone Haze Hest, said crystallinity index having been measured using a Perkin Elmer 467 infra-red spectrophotometer and a Wilks ATR-9 attenuated total reflectance unit with a germanium crystal cut at 45°C, the reference beam attenuator of said total reflectance unit having been set at 85% at 1150 cm-1;
b) coating the first sealant web having a surface tension of at least 38 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated first sealant web, said PVDC coat-ing on the sealant web being characterized by failing the Acetone Haze Test;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 70°C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
61. A process according to Claim 51 comprising:
a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by failing the Acetone Haze Test;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate;
a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by failing the Acetone Haze Test;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate;
62. A process according to Claim 57 comprising:
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by failing the Acetone Haze Test;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by failing the Acetone Haze Test;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
63. A process according to Claim 57 comprising:
a) coating the base film with a first PVDC, the coating being characterized by failing the Acetone Haze Test;
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by failing the Acetone Haze Test;
c) heating said second coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C, and f) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) coating the base film with a first PVDC, the coating being characterized by failing the Acetone Haze Test;
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by failing the Acetone Haze Test;
c) heating said second coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C, and f) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
64. A process according to Claim 57 comprising:
a) coating the first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by failing the Acetone Haze Test;
b) coating the PVDC-coated first sealant web formed in step a) with a second PVDC, the second coating being characterized by failing the Acetone Haze Test;
c) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
a) coating the first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by failing the Acetone Haze Test;
b) coating the PVDC-coated first sealant web formed in step a) with a second PVDC, the second coating being characterized by failing the Acetone Haze Test;
c) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
65. A process according to any one of Claim 57, Claim 58 and Claim 59 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
66. A process according to any one of Claim 60, Claim 61 and Claim 62 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
67. A process according to Claim 63 or Claim 64 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
68. A process according to any one of Claim 57, Claim 58 and Claim 59 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
69. A process according to any one of Claim 60, Claim 61 and Claim 62 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
70. A process according to Claim 63 or Claim 64 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
71. A process according to any one of Claim 57, Claim 58 and Claim 59 wherein the base film is an aluminum-coated polyethylene film.
62. A process according to any one of Claim 60, Claim 61 and Claim 62 wherein the base film is an aluminum-coated polyethylene film.
73. A process according to Claim 63 or Claim 64 wherein the base film is an aluminum-coated polyethylene film.
74. A process according to any one of Claim 59, Claim 60 or Claim 61 wherein the hot rollis at a temperature higher than about 70°C.
75. A process according to any one of Claim 62, Claim 63 or Claim 64 wherein the hot roll is at a temperature higher than about 70°C.
76. A process for forming the laminate of Claim 47 comprising bringing the base film and the first sealant web together between a nip roll and a hot roll, said PVDC coating having been applied to at least the base film or the first sealant web, with the proviso that if the first or second sealant web is in contact with the hot roll then said web which contacts the hot roll has a slip coefficient of less than about 0.4.
77. A process according to Claim 76 comprising:
a) heating a PVDC-coated base film or first seal-ant web to an extent sufficient to reduce the crystallinity index of the PVDC coating to less than about 1.05;
b) passing the heated PVDC-coated base film or first sealant web over a hot roll;
c) when a PVDC-coated base film is used, bringing the first sealant web into contact with the PVDC coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate;
and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate.
a) heating a PVDC-coated base film or first seal-ant web to an extent sufficient to reduce the crystallinity index of the PVDC coating to less than about 1.05;
b) passing the heated PVDC-coated base film or first sealant web over a hot roll;
c) when a PVDC-coated base film is used, bringing the first sealant web into contact with the PVDC coating and nipping said first sealant web to the PVDC coated base film, between the nip roll and the hot roll, to form a laminate;
and when a PVDC-coated first sealant web is used, bringing the base film into contact with the PVDC-coated first sealant web, between the nip roll and the hot roll, to form a laminate.
78. A process according to Claim 76 comprising:
a) heating a PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) coating the PVDC-coated base film with an aque-ous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
a) heating a PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) coating the PVDC-coated base film with an aque-ous PVDC dispersion to form a second PVDC coating, said second PVDC being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying and subsequently heating the second PVDC
coating until the temperature of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and e) bringing the first sealant web into contact with the second PVDC coating and nipping said first sealant web to the PVDC-coated base film, between a nip roll and the hot roll to form a laminate.
79. A process according to Claim 76 comprising:
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.40 if dried and allowed to stand for 5 days at 40°C.
b) coating the first sealant web having a surface tension of at least 38 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated first sealant web, said PVDC coat-ing on the sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) heating the PVDC-coated base film to an extent sufficient to reduce the crystallinity index of the PVDC
coating to less than about 1.05, said PVDC being characteriz-ed by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, and if the base film is selected from nylon film, polyester film or poly-propylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.40 if dried and allowed to stand for 5 days at 40°C.
b) coating the first sealant web having a surface tension of at least 38 dynes/cm, with an aqueous PVDC disper-sion to form a PVDC-coated first sealant web, said PVDC coat-ing on the sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
c) drying the PVDC coating on the first sealant web;
d) passing the PVDC-coated base film over a roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C; and e) bringing the PVDC surface of the PVDC-coated first sealant web into contact with the PVDC surface of the PVDC-coated base film and nipping said PVDC-coated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
80. A process according to Claim 76 comprising:
a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the second PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C, and said PVDC coating adjacent to the first sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate;
a) coating the PVDC-coated first sealant web with an aqueous PVDC dispersion to form a second PVDC coating, said second PVDC coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the second PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C, and said PVDC coating adjacent to the first sealant web being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C;
b) drying the second PVDC coating;
c) passing a base film over a hot roll, said base film being in contact with said hot roll, said hot roll being at a temperature higher than about 60°C, and d) bringing the base film into content with the second PVDC coating and nipping said base film to the PVDC-coated first sealant web, between a nip roll and the hot roll, to form a laminate;
81. A process according to Claim 76 comprising:
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystal-linity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDCcoated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
a) coating the base film with an aqueous PVDC dis-persion, the resultant coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystal-linity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
b) drying the PVDC coating;
c) passing the PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C;
and d) bringing the PVDC-coated surface of a PVDC-coated first sealant web into contact with the PVDC-coated surface of the PVDC-coated base film and nipping the PVDCcoated sealant web to the PVDC-coated base film, between a nip roll and the hot roll, to form a laminate.
82. A process according to Claim 76 comprising:
a) coating the base film with a first PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C.
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a second PVDC coating;
c) heating said second coating until the tempera-ture of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C, and f) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC--coated base film, between a nip roll and the hot roll, to form a laminate.
a) coating the base film with a first PVDC, the coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C.
b) coating the PVDC-coated base film formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a second PVDC coating;
c) heating said second coating until the tempera-ture of the free surface of said second coating is less than 75°C;
d) passing the resulting PVDC-coated base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C, and f) bringing the sealant web into contact with the second PVDC coating and nipping said sealant web to the PVDC--coated base film, between a nip roll and the hot roll, to form a laminate.
83. A process according to Claim 76 comprising:
a) coating the first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a first PVDC coating;
b) coating the PVDC-coated first sealant web formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C
and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
c) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
a) coating the first sealant web, having a surface tension of at least 38 dynes/cm, with a first PVDC, the coat-ing being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C, to form a first PVDC coating;
b) coating the PVDC-coated first sealant web formed in step a) with a second PVDC, the second coating being characterized by having a crystallinity index of less than 1.15 if dried and allowed to stand for 30 days at 20°C
and, if the base film is selected from nylon film, polyester film or polypropylene film, the PVDC coating being further characterized by having a crystallinity index of from 1.12 to 1.25 if dried and allowed to stand for 5 days at 40°C;
c) passing the base film over a hot roll, said base film being in contact with said hot roll, and said hot roll being at a temperature higher than about 60°C; and d) bringing the PVDC-coated surface of the PVDC-coated first sealant web, formed during steps a) and d), into contact with the base film and nipping the PVDC-coated first sealant web to the base film, between a nip roll and the hot roll, to form a laminate.
84. A process according to any one of Claim 76, Claim 77 and Claim 78 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
85. A process according to any one of Claim 79, Claim 80 and Claim 81 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
86. A process according to Claim 82 or Claim 83 wherein the vinyl acetate content of the copolymer of ethylene and vinyl acetate is between about 1.0 and about 20 weight percent and the weight ratio of the copolymer of ethylene and vinyl acetate to the ethylene homopolymer, ethylene copolymer or blend thereof is in the range of 2:98 to 50:50.
87. A process according to any one of Claim 76, Claim 77 and Claim 78 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
88. A process according to any one of Claim 79, Claim 80 and Claim 81 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
89. A process according to Claim 82 or Claim 83 wherein the base film is a polyethylene film or a metal-coated polyethylene film.
90. A process according to any one of Claim 76, Claim 77 and Claim 78 wherein the base film is an aluminum-coated polyethylene film.
91. A process according to any one of Claim 79, Claim 80 and Claim 81 wherein the base film is an aluminum-coated polyethylene film.
92. A process according to Claim 82 or Claim 83 wherein the base film is an aluminum-coated polyethylene film.
93. A process according to any one of Claim 78, Claim 79 or Claim 80 wherein the hot roll is at a temperature higher than 70°C.
94. A process according to any one of Claim 81, Claim 82 or Claim 83 wherein the hot roll is at a temperature higher than 70°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8223259 | 1982-08-12 | ||
| GB82/023259 | 1982-08-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1221610A true CA1221610A (en) | 1987-05-12 |
Family
ID=10532272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000433854A Expired CA1221610A (en) | 1982-08-12 | 1983-08-04 | Process for forming a sealant web-pvdc-base film laminate |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5945150A (en) |
| AU (1) | AU566323B2 (en) |
| CA (1) | CA1221610A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP7482606B2 (en) * | 2019-05-31 | 2024-05-14 | 三井化学東セロ株式会社 | Manufacturing method of laminated film |
-
1983
- 1983-07-12 AU AU16740/83A patent/AU566323B2/en not_active Ceased
- 1983-08-04 JP JP14198783A patent/JPS5945150A/en active Granted
- 1983-08-04 CA CA000433854A patent/CA1221610A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU566323B2 (en) | 1987-10-15 |
| AU1674083A (en) | 1984-02-16 |
| JPH0336023B2 (en) | 1991-05-30 |
| JPS5945150A (en) | 1984-03-13 |
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| MKEX | Expiry |