CA1181213A

CA1181213A - Nylon copolymer films

Info

Publication number: CA1181213A
Application number: CA000396847A
Authority: CA
Inventors: Alistair N. Mollison
Original assignee: DuPont Canada Inc
Current assignee: DuPont Canada Inc
Priority date: 1982-02-23
Filing date: 1982-02-23
Publication date: 1985-01-22

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention, useful for packing foods comprises an oriented nylon film made from a copolymerizate of hexamethylenediamine adipate and a comonomer selected from the group consisting of .epsilon.-caprolactam, aminononanoic acid, 11-aminoundecanoic acid, 12-aminoduodecanoic acid and hexa-methylenediamineduodecanate. The proportion of the hexa-methylenediamine adipate to the comonomer being in the range of 94:6 to 10:90, said copolymer having a relative viscosity of between about 40 and 100.

Description

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Nylon Copolymer Films The present invention relates to oriented nylon Eilm and more especially to -the l~mination of such nylon film to a sealant web.
The term "sealant web" as used herein refers to Eilms which may be heat-sealed to themselves. Films encom-passed by such term include films made from so-called high pressure polyethylene, so-called linear low densi-ty poly-ethylene, ethylene-vinyl aceta-te copolymers, ionomers, poly-vinyl chloride and blends thereof.
It is known that nylon or polyester Eilms are use-ful as part oE multilayer Eilm structures Eor packaging cer-tain foocls. ~riented nylon or polyester filrn, laminated to a sealant web e.g. polyethylene may be used Eor packaging meats, cheese, cof~ee and other comestibles. In applications where deterioration of foocl by oxidation is sought to be prevented or minimized, a layer of crystalline vinylidene chloride copolymer is usually sandwiched between the nylon or polyester film and the sealant web.
Oriented nylon 6 (poly ~-caprolactam~ film is often used instead of polyester film, in order to give better clarity, lower oxygen permeabili-ty and better resistance to pinholing of the film composite. Oriented nylon 66 (polyhexa-methylenediamirle adipate) film may be used instead of poly-ester or nylon 6 films because it is stiffer -than nylon 6 film and is clearer than polyester film. Stiffness is important where precision prin-ting is required. ~riented nylon 6 film suEfers in comparison to oriented nylon 66 or polyes-ter -films in that it is no-t as climensionally stable at temperatures above abou-t 130~C.
Canadian patent 897 885 issuecl 1972 ~pril 11 to F. ~I. Simons, refers to blends or copolymers of 0.2 - 5~
~-caprolactam with hexamethylenediamine aclipate, which may be used in making -textile Eibres, but which do not appear to be suitable Eor makincJ EiLms.
! U-S- patent 2 9~5 627 issued 1961 May 23 to Caldwell et al discloses copolymers formecl by condensation of an ali-phatic bifunctional omega - aminocarboxylic aclcl of 5-12 car-bon atoms and 20-50 mole percent of polyamide components derived from adipic acid and a bifunctional diamine selected from p-xylene~ diamine, trans-1,4-cyclohexane bis (methyl-amine) and cis-1,4 cyclohexane bis (methylamine).
Copolymers of ~-caprolactam and hexamethylenediamine adipate have been used to form cast ie. unoriented films use-ful for thermoforming applications, which films have a modulus, as measured by ASTM Procedure D-882-79, in the order of about 70 000 psia to 130 000 psia~
As indicated hereinbefore oriented polyester, nylon 66 and nylon 6 have been used in applications where clarity, pinhole resistance stiffness and dimensional stability are required. It appears that in order to overcome the deficien-cies of these materials, inventors have been led to more exotic polymers or to blends of nylon 6 and nylon 66 e.g. as disclosed in U.S. patent 3 995 084 issued 1976 November 30.
Applicant has now found that oriented films of certain copolymers of hexamethylenediamine adipate and certain nylon comonomers may be used to advantage.
Accordingly the present invention provides an ori-ented nylon film made from a copolymer of hexamethylenediamine adipate and a comonomer selected from the group consisting of aminononanoic acid, ~ -caprolactam, ll-aminoundecanoic acid, 12-aminoduodecanoic acid, and hexamethylenediamineduodecanate, the proportions of hexamethylenediamine adipate to the comono-mer being in the range of 94:6 to 10:90 by weight and said copolymer having a relative viscosity of between about 40 and 100 .
Relative viscosity (RV) of the polymer is measured by comparing the viscosity, at 25C, of a solution o~ 8.4~ by weight of the polymer in a solven-t consisting of 90~ by weight of formic acid and 10% by weight of water to the viscosity, at 25C, of the formic acid - water solvent.
In a preferred embodiment the proportions o hexa-methylenediamine adipate to the comonomer are be~ween about 94:6 and about 50:50, and especially between 92:8 and 75:25.
In another embodiment the relative viscosity of the copolymer is between 45 and 75.
~n a further embodiment the oriented film is a mono-axially machine-direction oriented film.
In one embodiment the film has been monoaxially oriented in the machine direction at a draw ratio of between about 1.1 and about 5.5. Preferably the draw ratio is between

2.6 and 4.8, especially from 3.0 to 4.2.
As used herein, the term "draw ratio" refers to ratio of the machine direction speed of the film after orien-tation -to the machine direction speed of the film prior to orientation.
The present invention further provides a multi-layer film comprising an oriented nylon film made from a copolymer of hexamethylenediamine adipate and a comonomer selected from the group consisting of ~-caprolactam, ll-amino-undecanoic acid, 12-aminoduodecanoic acid, aminononanoic acid and hexamethylenediamineduodecanate the proportions of hexa-methylenediamine adipate and the comonomer being in the range of 94:6 to 10:90, said copolymer having a relative viscosity of between about 40 and 100, and a sealant web.
In a preferred embodiment the proportion of hexa-methylenediamine adipate to the comonomer are between about 94:6 and 50:50, and especially between 92:8 and 75:25.
In a further embodiment the sealant web is selected from the group consisting of polyethylene, ethylene-vinyl acetate copolymers, ionomer, polyvinyl chloride and blends thereof, said sealant web being extrusion coated onto the oriented nylon film.
:[n another embodiment the polyethylene is selected ! 30 from the group consisting of polyethylene, ethylene-vinyl acetate copolymers, ionomer, polyvinyl chloride and blends thereof, said sealant web being laminated to the oriented nylon film using an adhesive. Preferably the adhesive is a polyurethane adhesive.
In yet another ernbodiment a layex oE crystalline vinylidene chloride copolymer is sandwiched between the `; 1 oriented nylon copolymer film and the sealant web.
In a further embodiment of the present invention the oriented copolymer film is between 10 and 38 ~m in thickness.
The copolymer useful in the present invention may be made by known batch or continuous polymerization processes in which an aqueous solution o-f the comonomer and an aqueous solution of the reaction product of hexamethylene diamine and adipic acid (herein referred to as hexamethylenediamine adipate) is heated to remove the water of solution and water of reaction resulting from the copolymerization of the comono-mer and hexamethylenediamine adipate.
The nylon copolymer used in the present invention may be extruded by known methods e.g. through a flat die.
When extruded through a flat die the copolymer film may be monoaxially oriented by a process similar to that disclosed in Canadian patent 1 011 520 issued 1977 June 07 to I.K.
MacGregor.
Preferably however the nylon copolymer may be orien-ted according to the process disclosed in copending patent application No. 396 859, filed 1982 February 23, to Hetherington et al.
In this process cast film is oriented between first and second counter rotating orientation rolls, the ratio of the peripheral speeds of the second roll to that of the first roll being between about 1.1 and about 5.5. Each orientation roll has a nip roll associated therewi-th, applying a substan-tially uniform force, across the width of the nip rolls, onto the associated orientation roll of between about 15 to ~5 newtons per centime-tre width of nip roll. The distance between the two orientation rolls is in the range of 100 to 2050 ~m. The temperature of the Eirst orientation roll is held at between 70 and l~0UC and tha-t of -the second orienta-tion roll is held at a temperature between the temperature oE
the first orientation roll and 20C below -the melting tempera-ture of -the copolymer. Preferably -the ratio of the peripheral speeds of the second and firs-t orientation rolls should be

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between 2.6 and 4.8 and especially from 3.0 to 4.2. It is further preferred that the oriented nylon copolymer film be heat set at a temperature between the orientation temperature and 20C below the melting temperature of the copolymer.
Preferably heat setting should be at a temperature between the orientation temperature and 30C below the melting temperature of the copolymer.
Film oriented accordingly has good film flatness, a property of particular importance where the oriented copolymer film is to be printed .
Alternatively the film of the copolymer may be biaxially oriented by known methods, e.g. tenter stretching.
The most preferred embodiment of the present inven-tion is an oriented nylon film made from a copolymer of ~-caprolactam and hexamethylenediamine adipate.
The oriented nylon copolymer film is advantageous-ly combined with a sealant web. The nylon film provides the required properties of printability, oxygen permeability, clarity, stiffness and dimensional stability, while the sealant web provides a heat sealable layer for heat sealing the edges of packages. This multilayer film may be formed in a number of ways.
One method of making the multilayer film is to ! extrusion coat the oriented nylon film with the sealant web by known extrusion coating methods. Sealant webs useful in this process include polyethylenes, ethylene-vinyl acetate copolymers, ionomers, polyvinyl chloride and blends thereof.
Another method of making the multilayer film is to laminate the sealant web Eilm to the oriented nylon film with a suitable adhesive. One such adhesive is a single component polyurethane adhesive. Such laminating processes are well known in the ar-t.
Pre~erred sealant webs are films made from linear low density polye-thylenes or blends of a linear low density polyethylene with a high pressure polyethylene or ethylene vinyl acetate copolymers. Preferred linear low density poly-ethylenes are homopolymers of ethylene or copolymers of ethyl-ene and C4 - qO ~olefins, having a density between 0.915 g/cm3 and 0.945 g/cm~. Part.icularly preferred are copolymers of ethylene and butene-l, and ethylene and octene-l.
If a multilayer film having a very low oxygen permeability is desired, a layer of crystalline vinylidene chloride copolymer may be placed between the nylon film and the sealant web. ~his may be accomplished in several ways e.g. using a polyurethane primer between the nylon film and the vinylidene chloride copolymer, similar to the method disclosed in Canadian patent 851 14~ issued 1970 September 08 to D.G. James, and then laminating e.g. with a polyurethane adhesive, the polyethylene film to the film of vinylidene chloride copolymer.
Alternatively the vinylidene chloride copolymer layer may be laid on the nylon film using an amorphous vinyli-dene chloride copolymer primer and a crystalline vinylidene chloride copolymer as disclosed in copending patent applica-tion No. 391 235, filed 1981 December 1, to Lang et al.
The following table shows the benefits of an orient ed nylon film of the present invention compared to oriented nylon 6, nylon 66 and polyester films.

,~'' Film Draw Modulus Gelbo Flex Haze Rati (psi) TD/Mr (pinholes/
TD MD 100 in2/
3000 cyclec Nylon 6 4.1 278 000 338 000 1.22 23 2.7 Nylon 66 3.7 502 000 405 000 0.81 77 2.0 Copolymer A 3.7 259 000284 000 1.10 9 1.1 Polyester 550 000 550 000 1.10 71 6.5 (biaxially oriented _ Copolymer A comprises 10 parts by weight of ~-caprolactam copolymerized with 90 by weight parts of hexamethylenediamine adipate, said copolymer having a relative viscosity oE 52.
Gelbo Flex, measured using a Gelbo Flex tester catalogue No.
TMT31-5, supplied by Testing Machines Inc. of ~mityville N.Y., is a measure of -~he pinhole resistance o~ the film being tested. Modulus is measured by ASTM procedure No.D-882-79.
Haze is measured by ASTM procedure No. D-1003.
The most preEerred embodiment oE the present inven-tion comprises an oriented film of a copolymer of 92 to 75 parts by weight of hexamethylenediamine adipate to 8 to 25 parts by weight oE ~-caproalactam, said copolymer having a relative viscosi-ty between about ~0 and 100. Preferably suc~
oriented Eilm is laminated to a polyethylene Eilm.
The examples Eollowing serve to illustrate the invention further. The test methods used were: ASTM procedure D-638-77a, sample Type IV Eor ultimate tensile strength (UTS);
~STM procedure D-~82-79 for moclulus; ASTM procedure D-100~ for Graves tear strength; ASTM procedure D-1922-67 Eor ElmendorE
tear streng-th; and 3000 cycles on a Gelbo Flex tester supplied by Testin~ Machines Inc. of Amityville, N.~. Eor Gelbo Flex.

Example 1 A copolymer comprising 10 parts by weight of ~-caprolactam copolymerized with 90 parts by weight of hexa-methylenediamine adipate, having a relative viscosity (RV) of 41, was ex-truded in-to Eilm at a rate of 550 kg/hr at 283~C, through a fla-t ~ilm die. The relative viscosity of the copolymer, a~ter extrusion was determined to be 53.
The film was chilled, annealed, pre-heated, oriented annealed and quenched by passing over a chill roll, first and seconcl orientation rolls, an annealing roll and a quenc~ roll held at 75C, 105C, 163C, 183C ana 40C respectively. The film t~ickness prior to orientation was 51 ~m and the film speed prior to orientation was 1.03 m/s. The draw ratio i.e.
the ratio of -the peripheral speeds of the second and *irst orientation rolls was 3.7 and the force on the nip rolls associated with each of the orientation rolls was 33 N/cm length of nip roll. The quench roll was run at a speed to allow about 1.5% shrinkage o the film. The oriented film was then wound up at a speed of about 3.75 m/s. The oriented film so produced was then tested to determine its ultimate tensile streng-th, modulus, Graves tear strength, Elmendorf ~ear strength and Gelbo flex. The results are shown in the Eollow-ing table, w~ich also shows comparative results for nylon 6 and nylon 66 similarly oriented.

Graves Elmendor~
UTS Modulus Tear Tear (psi) (psi) g/mil (g/mil) MD TD MD TD MD TD MD TD
Nylon 44 527 9105 259 000 284 000 1000 600 138 9 copolymer Nylon 66 ~9 164 6967 502 000 405 000 13~8104~ 175 132 Nylon 6 ~0 842 9532 278 000 338 000 1~621071 116 82 Gelbo flex (pinholes/100 in2t3000 cycles) Nylon copolymer 9 Nylon 66 77 Nylon 6 23 Examples 2 and 3 I'he copolymer nylon of Example 1 was extruded under similar conditions to Example 1 except that the chill roll and annealing roll were held at 60C and 80C respectively, and a 76 ~m film was produced at a line speed of 0.686 metres/sec.
The film was subsequently oriented with preheat and first orienting roll temperatures of 156C, second orienting roll temperature of 176C, a final quench roll tempera-ture of 40C, a draw ratio of 3.8, an orienting gap of 250 ~m, and nip rolls contacting the film to the orienting rolls with a orce of 33 N/cm length of nip roll. The film was subsequently wound up at a line speed of about 2.57 metres/sec.
Example 2, above, was repeated but with a draw ratio o~ 4.85.
The physical properties of the oriented films so produced were as follows:

Modulus Graves Tear Elmendorf Tear Draw UTS(psi) (psi) (g/mil) (g/mil) Ratio MD TD MD TD MD TD ~D TD
3.8 42000 7850 215 000 225 000 765 glO 320 185 ~.85 ~5000 7850 255 000 285 000 890 6~5 360 60 ',~

Gelbo Flex (pinholes/100 in2

Claims

CLAIMS:

1. A monoaxially oriented nylon film made from a copolymer of hexamethylenediamine adipate and a comonomer selected from the group consisting of .epsilon.-caprolactam, amino-nonanoic acid, 11-aminoundecanoic acid, 12-aminoduodecanoic acid and hexamethylenediamineduodecanate, the proportion of the hexamethylenediamine adipate to the comonomer being in the range of 94:6 to 10:90, said copolymer having a relative viscosity of between about 40 and 100.

2. A film according to Claim 1 which has been mono-axially oriented in the machine direction at a draw ratio of between about 1.1 and about 5.5.

3. A film according to Claim 2 wherein the draw ratio is between 2.6 and 4.8.

4. A film according to Claim 2 wherein the draw ratio is between 3.0 and 4.2.

5. A film of Claim 1, Claim 2 or Claim 4 wherein the proportion of hexamethylene adipate to the comonomer is between about 94:6 and 50:50.

6. A film of Claim 1 wherein the proportion of hexamethylene adipate to the comonomer is between 92:8 and 75:25.

7. A multilayer film comprising a film of Claim 1, Claim 4 or Claim 6 and a sealant web.

8. A multilayer film comprising an oriented nylon film of Claim 1, Claim 4 or Claim 6 and a sealant web selected from the group consisting of polyethylene, ethylene-vinyl acetate copolymers, ionomers, polyvinyl chloride and blends thereof, said sealant web being extrusion coated onto the oriented nylon film.

9. A multilayer film comprising an oriented nylon film of Claim 1, Claim 4 or Claim 6 and a sealant web selected from the group consisting of polyethylene, ethylene-vinyl acetate copolymers, ionomers, polyvinyl chloride and blends thereof, said sealant web being laminated to the oriented nylon film.

10. A multilayer film comprising an oriented nylon film of Claim 1, Claim 4, or Claim 6 and a sealant web select-ed from the group consisting of polyethylene, ethylene-vinyl acetate copolymers and blends thereof, said multilayer film having a layer of crystalline vinylidene chloride copolymer sandwiched between the nylon film and the sealant web.