Note: Descriptions are shown in the official language in which they were submitted.
z~
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
-- 3 --
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
3~
-- 5 --
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.
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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
',~
-- 10 --
Gelbo Flex
(pinholes/100 in2
