U.S. patent application number 11/603152 was filed with the patent office on 2007-05-31 for method for producing resin film and layered article.
This patent application is currently assigned to SUMITOMO CHEMICAL COMPANY, LIMITED. Invention is credited to Jinsho Nambu, Nobuhiro Oosaki, Taiichi Sakaya.
Application Number | 20070122557 11/603152 |
Document ID | / |
Family ID | 38087867 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070122557 |
Kind Code |
A1 |
Oosaki; Nobuhiro ; et
al. |
May 31, 2007 |
Method for producing resin film and layered article
Abstract
Methods for producing a resin film or a layered article which
are excellent in gas barrier properties under high humidity
conditions are disclosed. In the methods, a precursor film of a
resin composition composed of alkali metal ions and a resin
component having both hydroxyl groups and carboxyl groups is
subjected to treatments including (i) dry heating treatment of
holding the precursor film under an atmosphere characterized by a
temperature not lower than 100.degree. C. and a water vapor
concentration less than 50 g/m.sup.3, (ii) wet heating treatment of
holding the precursor film resulting from the dry heating treatment
under an atmosphere characterized by a temperature not lower than
100.degree. C. and a water vapor concentration more than 290
g/m.sup.3 or in water at a temperature not lower than 80.degree.
C., and (iii) drying the precursor film resulting from the wet
heating treatment.
Inventors: |
Oosaki; Nobuhiro;
(Sodegaura-shi, JP) ; Nambu; Jinsho;
(Kamakura-shi, JP) ; Sakaya; Taiichi; (Chiba-shi,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
SUMITOMO CHEMICAL COMPANY,
LIMITED
|
Family ID: |
38087867 |
Appl. No.: |
11/603152 |
Filed: |
November 22, 2006 |
Current U.S.
Class: |
427/379 ;
427/384 |
Current CPC
Class: |
C08J 5/18 20130101; C08L
2205/03 20130101; C08L 33/02 20130101; C08L 29/04 20130101; C08J
2329/04 20130101; C08L 29/06 20130101; C08L 29/04 20130101; C08L
2666/04 20130101; C08L 29/06 20130101; C08L 2666/02 20130101 |
Class at
Publication: |
427/379 ;
427/384 |
International
Class: |
B05D 3/02 20060101
B05D003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2005 |
JP |
2005-345218 |
Claims
1. A method for producing a resin film, comprising subjecting a
precursor film (D) made of a resin composition (C) which comprises
a resin component (A) with hydroxyl groups and carboxyl groups and
alkali metal ions (B) and satisfies conditions (1) and (2) given
below to the following treatments: dry heating treatment comprising
holding the precursor film under an atmosphere characterized by a
temperature not lower than 100.degree. C. and a water vapor
concentration less than 50 g/m.sup.3, wet heating treatment
comprising holding the precursor film resulting from the dry
heating treatment under an atmosphere characterized by a
temperature not lower than 100.degree. C. and a water vapor
concentration more than 290 g/m.sup.3 or in water at a temperature
not lower than 80.degree. C., and drying the precursor film
resulting from the wet heating treatment: condition (1): the ratio
of the number of the hydroxyl groups to the number of the carboxyl
groups in the resin component (A) is from 30:70 to 95:5 (hydroxyl
groups: carboxyl groups), condition (2): the weight of the alkali
metal ions (B) contained in the resin composition (C) is from 0.2%
to 5% of the weight of the resin component (A).
2. The method according to claim 1, wherein the combined weight of
the hydroxyl groups and the carboxyl groups in the resin component
(A) is from 30% to 60% of the weight of the resin component
(A).
3. The method according to claim 1, wherein the resin component (A)
is a resin component (A1) having both hydroxyl groups and carboxyl
groups in one molecule.
4. The method according to claim 1, wherein the resin component (A)
comprises a resin component (A2) having hydroxyl groups and a resin
component (A3) having carboxyl groups.
5. The method according to claim 3, wherein the resin component
(A1) is a vinyl alcohol-acrylic acid copolymer or a vinyl
alcohol-methacrylic acid copolymer.
6. The method according to claim 4, wherein the resin component
(A2) is a polyvinyl alcohol.
7. The method according to claim 4, wherein the resin component
(A3) comprises at least one species selected from polyacrylic acid,
polymethacrylic acid, partially neutralized polyacrylic acid and
partially neutralized polymethacrylic acid.
8. The method according to claim 1, wherein the alkali metal ions
(B) are sodium ions.
9. A method for producing a layered structure comprising a resin
film and a substrate having thereon the resin film, comprising:
applying a liquid to a substrate, the liquid having been prepared
by dispersing a resin composition (C) which comprises a resin
component (A) with hydroxyl groups and carboxyl groups and alkali
metal ions (B) and satisfies conditions (1) and (2) given below in
a solvent, removing the solvent from the applied liquid to form a
precursor film (D') on the substrate, and subjecting the precursor
film (D') to the following treatments together with the substrate:
dry heating treatment comprising holding the precursor film under
an atmosphere characterized by a temperature not lower than
100.degree. C. and a water vapor concentration less than 50
g/m.sup.3, wet heating treatment comprising holding the precursor
film resulting from the dry heating treatment under an atmosphere
characterized by a temperature not lower than 100.degree. C. and a
water vapor concentration more than 290 g/m.sup.3 or in water at a
temperature not lower than 80.degree. C., and drying the precursor
film resulting from the wet heating treatment: condition (1): the
ratio of the number of the hydroxyl groups to the number of the
carboxyl groups in the resin component (A) is from 30:70 to 95:5
(hydroxyl groups: carboxyl groups), condition (2): the weight of
the alkali metal ions (B) contained in the resin composition (C) is
from 0.2% to 5% of the weight of the resin component (A).
10. The method according to claim 9, wherein the combined weight of
the hydroxyl groups and the carboxyl groups in the resin component
(A) is from 30% to 60% of the weight of the resin component
(A).
11. The method according to claim 9, wherein the resin component
(A) is a resin component (A1) having both hydroxyl groups and
carboxyl groups in one molecule.
12. The method according to claim 9, wherein the resin component
(A) comprises a resin component (A2) having hydroxyl groups and a
resin component (A3) having carboxyl groups.
13. The method according to claim 11, wherein the resin component
(A1) is a vinyl alcohol-acrylic acid copolymer or a vinyl
alcohol-methacrylic acid copolymer.
14. The method according to claim 12, wherein the resin component
(A2) is a polyvinyl alcohol.
15. The method according to claim 12, wherein the resin component
(A3) comprises at least one species selected from polyacrylic acid,
polymethacrylic acid, partially neutralized polyacrylic acid and
partially neutralized polymethacrylic acid.
16. The method according to claim 9, wherein the alkali metal ions
(B) are sodium ions.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to methods for producing resin
films or layered articles which exhibit excellent gas barrier
properties under high humidity conditions.
[0003] 2. Description of the Related Art
[0004] Films made of polyvinyl alcohol are known to have good gas
barrier properties and are used widely in wrapping material
applications and the like. Unfortunately, the gas barrier
properties of such films of polyvinyl alcohol depend on humidity so
greatly that gas barrier properties of such films will deteriorate
under high humidity conditions. As a solution of such a problem,
U.S. Pat. No. 5,552,479 discloses a method for producing a gas
barrier film by heat treating, under specific conditions, a film
formed from a mixture of polyvinyl alcohol and poly(meth)acrylic
acid.
[0005] Films produced by the above-mentioned method have somewhat
improved gas barrier properties under high humidity conditions in
comparison to films before heat treatment, but their performances
are not satisfactory yet.
SUMMARY OF THE INVENTION
[0006] The object of the present invention is to offer a method for
producing a resin film having good gas barrier properties under
high humidity conditions and a method for producing a layered
article including such a resin film and a substrate.
[0007] Namely, the present invention is, in a first aspect, a
method for producing a resin film, comprising subjecting a
precursor film (D) made of a resin composition (C) which comprises
a resin component (A) with hydroxyl groups and carboxyl groups and
alkali metal ions (B) and satisfies conditions (1) and (2) given
below to the following treatments:
[0008] dry heating treatment comprising holding the precursor film
under an atmosphere characterized by a temperature not lower than
100.degree. C. and a water vapor concentration less than 50
g/m.sup.3,
[0009] wet heating treatment comprising holding the precursor film
resulting from the dry heating treatment under an atmosphere
characterized by a temperature not lower than 100.degree. C. and a
water vapor concentration more than 290 g/m.sup.3 or in water at a
temperature not lower than 80.degree. C., and
[0010] drying the precursor film resulting from the wet heating
treatment:
[0011] condition (1): the ratio of the number of the hydroxyl
groups to the number of the carboxyl groups in the resin component
(A) is from 30:70 to 95:5 (hydroxyl groups: carboxyl groups),
[0012] condition (2): the weight of the alkali metal ions (B)
contained in the resin composition (C) is from 0.2% to 5% of the
weight of the resin component (A).
[0013] Further, the present invention is, in a second aspect, a
method for producing a layered structure comprising a resin film
and a substrate having thereon the resin film, comprising:
[0014] applying a liquid to a substrate, the liquid having been
prepared by dispersing a resin composition (C) which comprises a
resin component (A) with hydroxyl groups and carboxyl groups and
alkali metal ions (B) and satisfies conditions (1) and (2) given
below in a solvent,
[0015] removing the solvent from the applied liquid to form a
precursor film (D') on the substrate, and subjecting the precursor
film (D') to the following treatments together with the
substrate:
[0016] dry heating treatment comprising holding the precursor film
under an atmosphere characterized by a temperature not lower than
100.degree. C. and a water vapor concentration less than 50
g/m.sup.3,
[0017] wet heating treatment comprising holding the film resulting
from the dry heating treatment under an atmosphere characterized by
a temperature not lower than 100.degree. C. and a water vapor
concentration more than 290 g/m.sup.3 or in water at a temperature
not lower than 80.degree. C., and
[0018] drying the film resulting from the wet heating
treatment:
[0019] condition (1): the ratio of the number of the hydroxyl
groups to the number of the carboxyl groups in the resin component
(A) is from 30:70 to 95:5 (hydroxyl groups: carboxyl groups),
[0020] condition (2): the weight of the alkali metal ions (B)
contained in the resin composition (C) is from 0.2% to 5% of the
weight of the resin component (A).
[0021] Since the method of the second aspect is an application of
the method of the first aspect, desirable conditions for the method
of the first aspect are preferably applied also to the method of
the second aspect.
[0022] By use of the method for producing of a resin film of the
present invention, it is possible to obtain a resin film which is
excellent in gas barrier properties under high humidity conditions.
Further, by use of the method for producing of a layered article of
the present invention, it is possible to obtain a layered article
which is excellent in gas barrier properties under high humidity
conditions.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The resin composition (C) contains alkali metal ions (B) and
a resin component (A) having hydroxyl groups and carboxyl groups
and the resin composition satisfies the following conditions (1)
and (2):
[0024] condition (1): the ratio of the number of the hydroxyl
groups to the number of the carboxyl groups in the resin component
(A) is from 30:70 to 95/5 (hydroxyl groups:carboxyl groups),
[0025] condition (2): the weight of the alkali metal ions (B)
contained in the resin composition (C) is from 0.2% to 5% (i.e.
from 2,000 ppm to 50,000 ppm) of the weight of the resin component
(A).
[0026] The resin component (A) having hydroxyl groups and carboxyl
groups may be a resin component (A1) having both hydroxyl groups
and carboxyl groups in one molecule or alternatively may be a resin
component including a resin component (A2) having hydroxyl groups
and a resin component (A3) having carboxyl groups. Here, the term
"hydroxyl group" means a so-called "alcoholic hydroxyl group" and
does not include a hydroxyl group in a carboxyl group. Examples of
the resin component (A1) include vinyl alcohol-acrylic acid
copolymers and vinyl alcohol-methacrylic acid copolymers. Examples
of the resin component (A2) having hydroxyl groups include
polyvinyl alcohols, partially saponified polyvinyl alcohols and
polysaccharides. Examples of the resin component (A3) having
carboxyl groups include polyacrylic acids, polymethacrylic acids,
partially neutralized polyacrylic acids and partially neutralized
polymethacrylic acids.
[0027] As the resin component (A2) having hydroxyl groups,
polyvinyl alcohols are most preferable due to their satisfactory
solubilities in aqueous solvents, easiness of handling and gas
barrier properties of resulting resin films. The "polyvinyl
alcohol" refers to a polymer predominantly comprising monomer units
of vinyl alcohol. Examples of such "polyvinyl alcohol" include
polymers obtained by subjecting acetic acid portions of vinyl
acetate polymers to hydrolysis, and polymers obtained by
hydrolyzing a polymer such as vinyl trifluoroacetate polymer, vinyl
formate polymer, vinyl pivalate polymer, tert-butyl vinyl ether
polymer and trimethylsilyl vinyl ether polymer. As to the details
of the "polyvinyl alcohol", a book entitled "PVA No Sekai (World of
PVA)" edited by POVAL-KAI (POVAL Society), (1992), published by
KOBUNSHI KANKO-KAI (Polymer Publishing Society) K.K.; and a book
entitled "Poval" written by Nagano et al. (1981), published by
KOBUNSHI KANKO-KAI may be referred to. The degree of saponification
of the ester portions of a polymer is preferably not less than 70
mol %, more preferably not less than 85 mol % and even more
preferably not less than 98 mol %. A polymer having a degree of
saponification of 98 mol % or more is called a "perfectly
saponified polymer." The degree of polymerization of a polyvinyl
alcohol for use in the present invention is preferably from 100 to
5,000, and more preferably from 200 to 3,000.
[0028] The polyvinyl alcohol may have functional groups other than
hydroxyl groups. Examples of such functional groups include amino
group, thiol group, carboxyl group, sulfone group, phosphate group,
carboxylate group, sulfonic acid ion group, phosphate ion group,
ammonium group, phosphonium group, silyl group, siloxane group,
alkyl group, allyl group, fluoroalkyl group, alkoxy group, carbonyl
group and halogen group.
[0029] The resin component (A3) having carboxyl groups preferably
comprises at least one species selected from polyacrylic acids,
polymethacrylic acids, partially neutralized polyacrylic acids and
partially neutralized polymethacrylic acids. Copolymers of acrylic
acid and methacrylic acid may also be used. The weight-average
molecular weight of the resin component (A3) having carboxyl groups
preferably falls within the range of from 2,000 to 1,000,000, and
more preferably within the range of from 100,000 to 1,000,000.
[0030] The aforementioned partially neutralized polyacrylic acids
or partially neutralized polymethacrylic acids can be obtained
through addition of an alkali to an aqueous solution of polyacrylic
acid or polymethacrylic acid. It is possible to obtain a desired
degree of neutralization by adjusting the ratio of the amount of
polyacrylic acid or polymethacrylic acid to the amount of alkali.
Here, the degree of neutralization of a polyacrylic acid or
polymethacrylic acid is defined by the formula provided below. From
the viewpoint of gas barrier properties and transparency of a
resulting resin film, the partially neutralized polyacrylic acids
and partially neutralized polymethacrylic acids preferably have
degrees of neutralization of from 0.1% to 20%. Degree of
neutralization=(A/B).times.100
[0031] A: The molar number of neutralized carboxyl groups contained
in a one-gram portion of polyacrylic acid or polymethacrylic
acid.
[0032] B: The molar number of carboxyl groups contained in a
one-gram portion of polyacrylic acid or polymethacrylic acid before
neutralization.
[0033] The ratio of the number of the hydroxyl groups to the number
of the carboxyl groups in the resin component (A) is from 30:70 to
95:5, and preferably from 70:30 to 95:5. From the viewpoint of gas
barrier properties under high humidity conditions of a resulting
resin film, the combined weight of the hydroxyl groups and the
carboxyl groups in the resin component (A) is preferably from 30 to
60%, more preferably from 35 to 55%, of the weight of the resin
component (A).
[0034] The ratio of the number of the hydroxyl groups to the number
of the carboxyl groups in the resin component (A) can be determined
by an NMR method, an IR method, or the like. For example, in the IR
method, a working curve is produced by using samples each having a
known ratio of the number of hydroxyl groups to the number of
carboxyl groups. The ratio of the number of hydroxyl groups to the
number of carboxyl groups of an unknown sample can be calculated by
using the working curve. In the case of using a vinyl alcohol
homopolymer and an acrylic acid homopolymer and/or a methacrylic
acid homopolymer, the ratio of the number of hydroxyl groups to the
number of carboxyl groups in the combined portion of the polymers
can be calculated from the molar numbers of hydroxyl groups and
carboxyl groups in each polymer determined in advance on the basis
of the weight of each polymer. Like the ratio of the number of
hydroxyl groups to the number of carboxyl groups, the combined
weight of hydroxyl groups and carboxyl groups in the resin
component (A) can be determined by an NMR method, an IR method or
the like. For example, in the IR method, working curves are
produced by using polyol polymers each having a known number of
polyol units and polycarboxylic acids each having a known number of
polycarboxylic acid units. The combined weight of hydroxyl groups
to carboxyl groups in an unknown sample can be calculated by using
the working curves. In the case of using a vinyl alcohol
homopolymer and an acrylic acid homopolymer and/or a methacrylic
acid homopolymer, the combined weight of hydroxyl groups and
carboxyl groups in the combined portion of the polymers can be
calculated from the weights of hydroxyl groups and carboxyl groups
in each polymer determined in advance on the basis of the weight of
each polymer.
[0035] Examples of the kind of alkali metal ions (B) contained in
the resin composition (C) include sodium ion, lithium ion and
potassium ion. The weight of the alkali metal ions (B) contained in
the resin composition (C) is from 0.2% to 5% (namely, from 2,000
ppm to 50,000 ppm), preferably, from 0.2% to 2% (namely, 2,000 ppm
to 20,000 ppm), of the weight of the resin component (A).
[0036] The alkali metal ions (B) usually originate in alkali metal
ion-donating compounds. Therefore, the resin composition (C)
usually contains alkali metal ion-donating compounds. Examples of
such alkali metal ion-donating compounds include sodium hydroxide,
sodium hypophosphite, lithium hydroxide, potassium hydroxide and
clay minerals containing alkali metal ion. Two or more kinds of
alkali metal ion-donating compounds may be used together.
[0037] Clay minerals are typically laminar compounds. From the
viewpoint of gas barrier properties of a resulting resin film, it
is desirable to use clay mineral as the alkali metal ion-donating
compounds. Examples of such clay mineral include montmorillonite,
beidellite, nontronite, saponite, sauconite, stevensite, hectorite,
tetrasilylic mica, sodium taeniolite, muscovite and phlogopite.
So-called "organically modified clay minerals" obtained by
subjecting clay minerals such as those mentioned above to treatment
like ion exchange with an organic substance also may be used as the
alkali metal ion-donating compounds. "Organically modified clay
minerals" are explained in detail in Masahiro MAENO, "Nendo No
Kagaku (Science of Clay)" pp. 174-181, 1993, The Nikkan Kogyo
Shimbun, Ltd. As the organic substance for treating clay minerals,
quaternary ammonium salts such as dimethyldistearyl ammonium salt
and trimethylstearyl ammonium salt, phosphonium salts, imidazolium
salts, etc. may be used.
[0038] From the viewpoint of gas barrier properties of a resulting
resin film under high humidity conditions, the alkali metal ions
are preferably sodium ions and a sodium ion donating compound which
donates a sodium ion is preferably a sodium ion-containing clay
mineral. Particularly, montmorillonite is preferably used.
[0039] The clay mineral to be used as an alkali metal ion-donating
compound preferably has an aspect ratio falling within the range of
from 200 to 3,000. When the aspect ratio is too small, gas barrier
properties tend to become insufficient. When the aspect ratio is
too large, it becomes difficult to swell and cleave the clay
mineral with a solvent, resulting in insufficient gas barrier
properties. The clay mineral to be used preferably has an average
particle diameter up to 5 .mu.m. When the average particle diameter
is too large, the gas barrier properties and transparency of a
resulting film and the film forming property of a resulting resin
composition tend to become poor. Particularly in the production of
products to be used in applications where high transparency is
required, the average particle diameter of the clay mineral is
preferably up to 1 .mu.M.
[0040] In the present invention, the aspect ratio (Z) of a clay
mineral is defined by the formula: Z=L/a. In the formula, "L" is an
average particle diameter of the clay mineral and "a" indicates the
unit thickness of the clay mineral, i.e., the thickness of a unit
crystal layer of the clay mineral. The thickness can be determined
by the powder X-ray diffraction method (see a book entitled
"Kiki-Bunseki No Tebiki (Handbook on Instrumental Analysis) (a)",
page 69, (1985), editorially supervised by Jiro SHIOKAWA, published
by Kagakku Dojin Publishing Co.).
[0041] The clay mineral to be used in the present invention
preferably has a swell value, determined by a swellability test
described below, of 5 or more, more preferably 20 or more. Further,
the clay mineral preferably has a cleavage value, determined by a
cleavability test described below, of 5 or more, more preferably 20
or more.
<Swellability Test>
[0042] In a 100-ml graduated cylinder, 100 ml of liquid medium is
charged, and 2 g of clay mineral is added thereto. Through keeping
of the mixture at rest at 23.degree. C. for 24 hours, the mixture
separates into a clay mineral dispersion layer and a supernatant
layer. Then, the volume in milliliter of the clay mineral
dispersion layer in the graduated cylinder is read from the
graduation at the interface between the clay mineral dispersion
layer and the supernatant liquid. The larger the value (swell
value), the higher the swellability.
<Cleavability Test>
[0043] Thirty grams of clay mineral is added slowly to 1,500 ml of
a solvent and is dispersed by means of a dispersing instrument
(DESPA MH-L manufactured by Asada Iron Works Co., Ltd.; vane
diameter of 52 mm; rotation speed: 3,100 rpm; container capacity: 3
liters; clearance between the bottom of the container and the vane:
28 mm) with a peripheral speed of 8.5 m/sec at 23.degree. C. for 90
minutes. Thereafter, a 100-ml portion of the resulting dispersion
is poured into a graduated cylinder and is kept at rest for 60
minutes. Thus, the dispersion separates into a clay mineral
dispersion layer and a supernatant layer. Then, the volume of the
clay mineral dispersion layer is read from the graduation at the
interface between the clay mineral dispersion layer and the
supernatant layer. The larger the value (cleavage value), the
higher the cleavability.
[0044] In the case where the clay mineral is a hydrophilic
swellable clay mineral, examples of the solvent to be used for
swelling and cleaving clay mineral include water, alcohols (e.g.
methanol, ethanol, propanol, isopropanol, ethylene glycol,
diethylene glycol, etc.), dimethylformamide, dimethylsulfoxide and
acetone. Water, alcohols and mixtures of water and alcohol are
preferred.
[0045] In the case where the clay mineral is an organically
modified clay mineral, liquid medium may be used, for example,
aromatic hydrocarbons such as benzene, toluene and xylene, ethers
such as ethyl ether and tetrahydrofuran, ketone such as acetone,
methyl ethyl ketone and methyl isobutyl ketone, aliphatic
hydrocarbons such as n-pentane, n-hexane and n-octane, halogenated
hydrocarbons such as chlorobenzene, carbon tetrachloride,
chloroform, dichloromethane, 1,2-dichloroethane and
perchloroethylene, ethyl acetate, methyl methacrylate, dioctyl
phthalate, dimethylformamide, dimethylsulfoxide, methylcellosolve
and silicone oil.
[0046] The resin composition (C) may contain various types of
additives such as UV absorbers, colorants and antioxidants in
addition to the resin component (A) and the alkali metal ions
(B).
[0047] Examples of a method for preparing the resin composition (C)
include a method comprising melt-kneading a resin component (A) and
an alkali metal ion-donating compound, a method comprising
dissolving or dispersing a resin component (A) and an alkali metal
ion-donating compound individually in separated portions of
solvent, followed by combining the resulting solutions or
dispersions to form a dispersion of a resin composition, and a
method comprising dissolving or dispersing a resin component (A)
and an alkali metal ion-donating compound in the same portion of
solvent to form a dispersion of a resin composition. When the resin
component (A) is a mixture of a resin component (A2) having
hydroxyl groups and a resin component (A3) having carboxyl groups,
the resin component (A2) and the resin component (A3) may be
dissolved or dispersed individually in separated portions of
solvent or, alternatively, in the same portion of solvent.
[0048] When a dispersion of a resin composition is prepared by
using clay mineral as the alkali metal ion-donating compound, it is
desirable to disperse the clay mineral by a high-pressure
dispersion process in order to swell and cleave the clay mineral
fully in the solvent. The high-pressure dispersion treatment used
herein is a treatment method comprising forcing a liquid mixture
composed of clay mineral and a solvent to pass through capillary
tubes at high speed and then combining the flows of the liquid
mixture, thereby causing the flows to collide with each other or
against the inner walls of the capillary tubes to apply high shear
and/or high pressure to the liquid mixture. In the high-pressure
dispersion treatment, it is desirable to cause the liquid mixture
to pass through capillary tubes with a diameter of from about 1
.mu.m to about 1000 .mu.m so that a maximum pressure of 100
kgf/cm.sup.2 or more is applied to the liquid mixture. The maximum
pressure is more preferably 500 kgf/cm.sup.2 or more, particularly
preferably 1000 kgf/cm.sup.2 or more. The maximum speed of the
liquid mixture at which the liquid mixture arrives during it passes
through capillary tubes is preferably not less than 100 m/s and the
rate of heat transfer due to pressure loss is preferably not less
than 100 kcal/hr. The high-pressure dispersion treatment can be
conducted by use of a high-pressure dispersing apparatus, such as
an ultrahigh-pressure homogeniser manufactured by Microfluidics
Corporation (commercial name: MICROFLUIDIZER), NANOMIZER
manufactured by Nanomizer Inc., a Manton Gaulin type high-pressure
dispersing device, and Homogenizer manufactured by Izumi Food
Machinery Co., Ltd. The liquid which is subjected to the
high-pressure dispersion treatment may contain the resin component
(A).
[0049] It is desirable to add a surfactant to the dispersion liquid
of the resin composition. By forming a precursor film (D) through
application of a dispersion liquid of a resin composition
containing a surfactant to a substrate, it is possible to improve
the adhesion between the precursor film (D) and the substrate. The
content of the surfactant is typically from 0.001 to 5% based on
100% by weight of the dispersion liquid of the resin composition.
Addition of too a small amount of surfactant will result in an
insufficient effect of improving the adhesion. On the other hand,
addition of too a large amount of surfactant will cause
deterioration in gas barrier properties.
[0050] As the surfactant, conventional surfactants such as anionic
surfactants, cationic surfactants, amphoteric surfactants and
nonionic surfactants may be used. In particular, it is desirable,
from the viewpoint of improvement in adhesion, to use alkali metal
salts of carboxylic acids with an alkyl chain having from 6 to 24
carbon atoms, ether type nonionic surfactants (silicone-based
nonionic surfactants) such as polydimethylsiloxane-polyoxyethylene
copolymers, or fluorine type nonionic surfactants
(fluorine-containing nonionic surfactants) such as perfluoroalkyl
ethylene oxide compounds.
[0051] The precursor film (D) used in the method of the first
aspect of the present invention can be produced by a method which
includes melt-kneading a resin component (A) and an alkali metal
ion-donating compound to yield a resin composition (C) and
converting the resin composition (C) into a film by extrusion,
injection molding, compression molding, etc. It is also possible to
form a precursor film (D) by a method in which a resin composition
dispersion liquid prepared through dispersion of a resin
composition (C) containing a resin component (A) and alkali metal
ions (B) into a solvent is applied to a substrate and then the
solvent is removed to form the precursor film (D) on the substrate.
The latter method is preferred because it is easy to produce a
precursor film (D) which is thin and uniform in thickness.
[0052] The second aspect of the present invention is directed to a
method for producing a layered structure including a resin film and
a substrate having thereon the resin film, including:
[0053] applying a liquid to a substrate, the liquid having been
prepared by dispersing a resin composition (C) which includes
alkali metal ions (B) and a resin component (A) with hydroxyl
groups and carboxyl groups and satisfies conditions (1) and (2)
given below in a solvent,
[0054] removing the solvent from the liquid applied to form a
precursor film (D') on the substrate, and
[0055] subjecting the precursor film (D') to the following
treatments together with the substrate:
[0056] dry heating treatment comprising holding the precursor film
under an atmosphere characterized by a temperature not lower than
100.degree. C. and a water vapor concentration less than 50
g/m.sup.3,
[0057] wet heating treatment comprising holding the precursor film
resulting from the dry heating treatment under an atmosphere
characterized by a temperature not lower than 100.degree. C. and a
water vapor concentration more than 290 g/m.sup.3 or in water at a
temperature not lower than 80.degree. C., and
[0058] drying the precursor film resulting from the wet heating
treatment to form a resin film on the substrate:
[0059] condition (1): the ratio of the number of the hydroxyl
groups to the number of the carboxyl groups in the resin component
(A) is from 30:70 to 95/5 (hydroxyl groups:carboxyl groups),
[0060] condition (2): the weight of the alkali metal ions (B)
contained in the resin composition (C) is from 0.2% to 5% (from
2,000 ppm to 50,000 ppm) of the weight of the resin component
(A).
[0061] The material which forms the substrate may be, but is not
particularly limited to, metal, resin, wood, ceramic and glass. The
form of the substrate may be, but is not particularly limited to,
paper, woven fabric, nonwoven fabric and film. Either thermoplastic
resin or thermosetting resin can be used as the resin. In the
production of a layered article for use in packaging application,
it is desirable to use a substrate made of thermoplastic resin.
Examples of the thermoplastic resin include polyolefin such as low
density polyethylene, high density polyethylene, linear low density
polyethylene, ethylene-propylene copolymers, ethylene-butene
copolymers, ethylene-hexene copolymers, ethylene-octene copolymers,
polypropylene (PP), ethylene-vinyl acetate copolymers,
ethylene-methyl methacrylate copolymers and polyolefin-based
ionomer resins; polyester resins such as polyethylene
terephthalate, polybutylene terephthalate and polyethylene
naphthalate; amide resins such as Nylon-6 (Ny-6), Nylon-6,6,
m-xylenediamine-adipic acid polycondensates, polymethyl
methacrylimide and polymetaxylylene adipamide (MXD6-Ny); acrylic
resins such as polymethyl methacrylate; styrene homopolymers,
acrylonitrile homopolymers, styrene-acrylonitrile copolymers,
styrene-acrylonitrile-butadiene copolymers; hydrophobicized
cellulose resins such as cellulose triacetate and cellulose
diacetate; halogen-containing resins such as polyvinyl chloride,
polyvinylidene chloride and polyvinylidene fluoride; hydrogen
boning resins having a hydroxyl group weight fraction of from 20 to
60% such as polyvinyl alcohol, ethylene-vinyl alcohol copolymers
(EVOH) and cellulose derivatives; and polycarbonate resins,
polysulfone resins, polyethersulfone resins, polyether ether ketone
resins, polyphenylene oxide resins and polymethylene oxide resins.
Examples of the aforesaid thermosetting resin include phenol resin,
melamine resin and urea resin. In the production of a layered film,
the substrate may be any one selected from non-oriented film,
uniaxially oriented film and biaxially oriented film. However,
preferred are biaxially oriented films made of polypropylene,
polyester resin or amide-based resin, or layered articles made of
two or more kinds of biaxially oriented films laminated to each
other. The substrate may be a multilayer film such as
Ny-6/MXD6-Ny/Ny-6 film and PP/EVOH/PP film. Further, films with
aluminum, alumina or silica or the like deposited thereon may also
be used.
[0062] One example of preferable substrate is a substrate having,
on at least one side thereof, a heat-seal layer made of resin.
Specific examples of the resin constituting the heat-seal layer
include polyolefin resins such as low density polyethylene, high
density polyethylene, linear low density polyethylene,
ethylene-propylene copolymers, ethylene-butene copolymers,
ethylene-hexene copolymers, ethylene-4-methyl-1-pentene copolymers,
ethylene-octene copolymers, polypropylene, ethylene-vinyl acetate
copolymers, ethylene-methyl methacrylate copolymers,
ethylene-methyl acrylate copolymers, ethylene-acrylic acid
copolymers and polyolefin-based ionomer resins, polyacrylonitrile
resins, and polyester resins. By using such a substrate and
constituting a layered article so as to form one surface from a
heat-seal layer and the other surface from a resin film of a resin
composition (C), it is possible to obtain a layered article
resistant to oxidization even under exposure to high temperatures
in the presence of oxygen.
[0063] A substrate with a heat-seal layer can be produced, for
example, by a method comprising coextrusion of a resin for forming
the heat-seal layer and a resin for forming the substrate, a method
comprising applying, to the substrate, a solution prepared by
dissolving a resin for forming the heat-seal layer in a solvent,
followed by removal of the solvent to form the heat-seal layer on
the substrate, a method comprising extrusion-lamination of a resin
for forming the heat-seal layer onto the substrate, and a method
comprising dry-lamination of a heat-sealable resin film or sheet
with the substrate. The substrate's surface on which the heat-seal
layer is to be disposed may have been subjected to various types of
pre-treatment such as corona treatment, ozone treatment, electron
beam treatment and application of an anchor coating agent. Examples
of such an anchor coating agent include ethyleneimine-based anchor
coating agents and two-component curable urethane-based anchor
coating agents.
[0064] When an anchor coat layer or a precursor film (D') is formed
by application of liquid, gravure methods such as the direct
gravure method and the reverse gravure method, roll coating methods
such as the two-roll beat coating method and the bottom-feed
three-roll reverse coating method, the doctor knife method, the die
coating method, the bar coating method, the dipping method and the
spray coating method may be used. In order to form a layer uniform
in thickness, it is desirable to use the gravure method.
[0065] From the viewpoints of gas barrier properties of a resulting
resin layer and cost, the thickness of the precursor film (D') is
typically from 0.01 .mu.m to 100 .mu.m, and preferably from 0.01
.mu.m to 5 .mu.m.
[0066] By the method for producing a layered article of the present
invention, it is also possible to produce a layered article in
which a clay mineral layer is formed adjacent to the resin layer
formed on the substrate. The clay mineral layer is a layer which is
composed substantially only of clay mineral. As the clay mineral
for forming the clay mineral layer, clay minerals provided
previously as examples of the alkali metal ion-donating compound
contained in the resin composition (C) may be used. The clay
mineral layer can be formed by applying a dispersion liquid
prepared by dispersing clay mineral in a solvent on the precursor
film (D') formed on the substrate, then removing the solvent, and
further conducting dry heating treatment, wet heating treatment and
drying treatment for treating the precursor film (D').
Alternatively, the clay mineral layer can also be formed by
applying a dispersion liquid prepared by dispersing clay mineral in
a solvent to a resin film formed by subjecting the precursor film
(D') to dry heating treatment, wet heating treatment and
drying-treatment, followed by removal of the solvent. From the
viewpoint of gas barrier properties of a resulting layered article,
it is preferable to form, on the clay mineral layer formed on the
resin film, an additional resin layer. The resin layer may be
formed on one side or both sides of the substrate and may be formed
so as to cover the substrate partly or entirely.
[0067] In the present invention, a precursor film (D) or (D')
formed of a resin composition (C) including a resin component (A)
and alkali metal ions (B) is subjected to dry heating treatment in
which the precursor film is held under an atmosphere characterized
by a temperature not lower than 100.degree. C. and a water vapor
concentration less than 50 g/m.sup.3. The dry heating treatment
temperature is preferably from 120.degree. C. to 200.degree. C. The
dry heating treatment time is typically from one second to one
hour. The water vapor concentration in the atmosphere during the
dry heating treatment is preferably from 0 to 40 g/m.sup.3.
[0068] The resin film which has experienced the dry heating
treatment is then subjected to wet heating treatment in which the
resin film is held under an atmosphere characterized by a
temperature not lower than 100.degree. C. and a water vapor
concentration more than 290 g/m.sup.3 or in water at a temperature
not lower than 80.degree. C. The wet heating treatment time is
typically from one second to one hour. In the treatment under an
atmosphere characterized by a temperature not lower than
100.degree. C. and a water vapor concentration more than 290
g/m.sup.3, the temperature is preferably within the range from
120.degree. C. to 200.degree. C. and the water vapor concentration
is preferably within the range from 500 to 20,000 g/m.sup.3. Before
the wet heating treatment, the resin film resulting from.the dry
heating treatment may be subjected to aging, for example, at
23.degree. C. and 50% RH.
[0069] The drying treatment after the wet heating treatment is
performed in order to remove the moisture given to the resin film
through the wet heating treatment. Typically, the resin film is
held under conditions characterized by a humidity up to 50% RH and
a temperature from 20.degree. C. to 100.degree. C. for a period of
time of from one second to 24 hours.
[0070] By the methods of the present invention, it is possible to
produce a resin film and a layered article which are excellent in
gas barrier properties under high humidity conditions. Layered
articles produced by the method of the present invention are
suitably used as packaging materials for boiling or retorting due
to their excellent whitening resistance at boiling or
retorting.
EXAMPLES
[0071] The invention is described in detail below with reference to
Examples.
[0072] First, methods for measuring physical properties and the
like are described.
<Thickness Measurement>
[0073] Thicknesses of not less than 0.5 .mu.m were measured by
means of a commercially available digital thickness measuring
device (contact-type thickness measuring device, trade name:
Ultra-High Precision Deci-Micro Head MH-15M, manufactured by Nihon
Kogaku K. K.). Thicknesses less than 0.5 .mu.m were determined
through cross-sectional observation with a transmission electron
microscope (TEM).
<Particle Diameter Measurement>
[0074] The particle diameter was measured using a laser
diffraction/scattering particle size distribution analyzer (LA910,
manufactured by HORIBA, Ltd.). The average particle diameter of
clay mineral in a resin composition dispersion liquid (1) mentioned
later was measuredbythe paste cell method at an optical path length
of 50 .mu.m. Further, the average particle diameter of the clay
mineral in a diluted liquid of the dispersion liquid (1) was
measured by the flow cell method at an optical path length of 4 mm.
In both the measurements, the average particle diameters determined
were the same. This fact made certain that the clay mineral in the
dispersion liquid was fully swollen and cleaved. The value obtained
was considered as the average particle diameter of the clay mineral
in a resin film.
<Measurement of the Ratio of the Number of Hydroxyl Groups to
the Number of Carboxyl Groups in Resin Component (A)>
[0075] A polyvinyl alcohol (perfectly saponified product) and a
polyacrylic acid were used as the resin component (A2) having
hydroxyl groups and the resin component (A3) having carboxyl
groups, respectively. The number of hydroxyl groups in the
polyvinyl alcohol and the number of carboxyl groups in the
polyacrylic acid were calculated from the formulas given below and
then their ratio was calculated.
[0076] The number of hydroxyl groups=(Amount of resin component
(A2) added)/(molecular weight per monomer unit constituting resin
component (A2))
[0077] The number of carboxyl groups=(Amount of resin component
(A3) added)/(molecular weight per monomer unit constituting resin
component (A3))
<Measurement of the Combined Weight of Hydroxyl Groups and
Carboxyl Groups in Resin Component (A)>
[0078] A polyvinyl alcohol (perfectly saponified product) and a
polyacrylic acid were used as the resin. component (A2) having
hydroxyl groups and the resin component (A3) having carboxyl
groups, respectively. The weight of hydroxyl groups and the weight
of carboxyl groups were calculated by the formulas given below and
they were summed.
[0079] The weight of hydroxyl groups=(17/(molecular weight per
monomer unit constituting resin component (A2)).times.(weight of
resin component (A2) added/weight of resin component (A) added)
[0080] The weight of carboxyl groups=(45/(molecular weight per
monomer unit constituting resin component (A3)).times.(weight of
resin component (A3) added/weight of resin component (A) added)
<Measurement of Alkali Metal Ion Concentration>
[0081] The sodium ion concentration of the entire layered article
was measured using an inductively coupled plasma emission
spectroscopy (Optima 3000, manufactured by Perkin Elmer). Then, the
sodium ion concentration in the resin film was calculated by
subtracting the sodium ion concentration in the layer or layers
other than the resin layer from the sodium ion concentration of the
entire layered article. A sample was prepared by the following
procedure. One-gram portions were sampled from the layered article
and the substrate, respectively. To each sample, 1 ml of 96%
sulfuric acid was added, followed by ashing in an electric furnace.
The residue was dissolved in 10 ml of 5% hydrochloric acid. The
resulting solution was placed in the inductively coupled plasma
emission spectroscopy. Thus, the sodium ion concentrations of the
samples were measured and then their difference was calculated.
<Aspect Ratio Calculation>
[0082] The diffraction measurement of a clay mineral was conducted
by the powder method using an X-ray diffraction analyzer (XD-5A,
manufactured by Shimadzu Corp.). Thus, the unit thickness "a" of
the clay mineral was determined. Using an average particle diameter
"L" measured by the method described above, the aspect ratio "Z" of
the clay mineral was calculated from an equation Z=L/a. An X-ray
diffraction measurement conducted for a material obtained by drying
the resin composition dispersion liquid (1) revealed that the
interplanar spacing of the clay mineral was enlarged.
<Dry Heating Treatment>
[0083] A layered article sized 210 mm by 300 mm was heat treated in
an oven conditioned at a temperature of 150.degree. C. and a water
vapor concentration of 5 g/m.sup.3.
<Wet Heating Treatment>
[0084] Using a compact retorting autoclave (RK-3030, manufactured
by ALP Corp.), a layered article sized 210 mm by 300 mm was
subjected to wet heating treatment under a water vapor atmosphere
at 120.degree. C. for a predetermined period of time. The water
vapor concentration was 1,113 g/m.sup.3.
<Drying treatment>
[0085] A layered article sized 210 mm by 300 mm was kept at rest
for 24 hours under an atmosphere at 23.degree. C. and 50% RH.
<Oxygen Permeability Measurement>
[0086] The oxygen permeability was measured in accordance with JIS
K7126 at 23.degree. C. and 90% RH by use of a supersensitive oxygen
permeability analyzer (OX-TRAN ML, manufactured by MOCON).
<Preparation of Resin Composition Dispersion Liquid>
(1) Preparation of Resin Composition Dispersion Liquid (1)
[0087] In a dispersion pot (trade name: DESPA MH-L, manufactured by
ASADA Iron Works, Co., Ltd.), 1300 g of ion exchange water
(specific conductivity: 0.7 second/cm or less) and 130 g of
polyvinyl alcohol (PVA 117H, manufactured by Kuraray Co., Ltd.,
degree of saponification: 99.6%, degree of polymerization: 1,700)
were mixed together and heated up to 95.degree. C. under slow
stirring (1,500 rpm, peripheral speed: 4.1 m/min). After stirring
the mixture at that temperature for 30 minutes to dissolve the
polyvinyl alcohol, the mixture was cooled to 60.degree. C. to yield
an aqueous polyvinyl alcohol solution. While the aqueous polyvinyl
alcohol solution (60.degree. C.) was stirred under conditions the
same those mentioned above, an aqueous alcohol solution prepared by
mixing 122 g of 1-butanol, 122 g of isopropyl alcohol and 520 g of
ion exchange water was dropped over 5 minutes. After the dropping,
the stirring mode was switched to high-speed stirring (3,000 rpm,
peripheral speed: 8.2 m/min) and then 82 g of high purity
montmorillonite (trade name: Kunipia G, manufactured by Kunimine
Industries Co., Ltd.) was added slowly. After the addition,
stirring was continued at 60.degree. C. for 60 minutes. Then, 243 g
of isopropanol was further added over 15 minutes, followed by
cooling of the mixture to room temperature. Thus, a liquid (1)
containing clay mineral was obtained. To the liquid (1) containing
clay mineral, 0.1% by weight, based on the weight of the dispersion
liquid, of a nonionic surfactant
(polydimethylsiloxane-polyoxyethylene copolymer, trade name:
SH3746, manufactured by Dow Corning Toray Co., Ltd.) was added
under slow-speed stirring (1,500 rpm, peripheral speed: 4.1 m/min).
Then, the mixture was conditioned to pH6 by means of ion exchange
resin. Thus, a clay mineral dispersion liquid (1) was prepared.
[0088] In another dispersion pot (trade name: DESPA MH-L,
manufactured by ASADA Iron Works, Co., Ltd.), 1,067 g of ion
exchange water (specific conductivity: 0.7 second/cm or less) and
33 g of polyacrylic acid (manufactured by Wako Pure Chemical
Industries, Ltd., average molecular weight: 1,000,000) were mixed
together and stirred at low speed (1,500 rpm, peripheral speed: 4.1
m/min) at room temperature. Thus, a solution of resin component
(A3) was produced.
[0089] A liquid mixture was prepared by mixing 2,519 g of the clay
mineral dispersion liquid (1) and 1,100 g of the solution of resin
composition (A3) slowly under low-speed stirring (1,500 rpm,
peripheral speed: 4.1 m/min). The liquid mixture was treated under
a pressure of 1,100 kgf/cm.sup.2 using a high-pressure dispersion
instrument (trade name: Ultrahigh-Pressure Homogenizer M110-E/H,
manufactured by Microfluidics Corp.). Thus, a resin composition
dispersion liquid (1) was obtained. The montmorillonite cleaved in
the resin composition dispersion liquid (1) had an average particle
diameter "L" of 560 nm, a unit thickness "a", determined by powder
X-ray diffraction, of 1.2156 nm, and an aspect ratio "Z" of
460.
(2) Preparation of Resin Composition Dispersion Liquid (2)
[0090] A resin composition dispersion liquid (2) was prepared in a
manner the same as that in the preparation of the resin composition
dispersion liquid (1) except for adjusting the pH of the clay
mineral dispersion liquid (1) to 4.
(3) Preparation of Resin Composition Dispersion Liquid (3)
[0091] A resin composition dispersion liquid (3) was prepared in a
manner the same as that in the preparation of the resin composition
dispersion liquid (1) except for adjusting the pH of the clay
mineral dispersion liquid (1) to 2.2.
(4) Preparation of Resin Composition Dispersion Liquid (4)
[0092] A resin composition dispersion liquid (4) was prepared by
further adding 0.32 g of sodium hypophosphite to a 100-gram portion
of the resin composition dispersion liquid (3).
Example 1
[0093] A 15-.mu.m thick biaxially oriented Nylon (ONy) film (trade
name: ON-U, manufactured by Unitika Ltd.), one surface of which had
been corona-treated, was used as a substrate. To the corona-treated
surface of the substrate, the resin composition dispersion liquid
(1) was gravure coated by the microgravure coating method (the
number of gravure lines: 150) at a coating speed of 3 m/min by
means of a test coater (manufactured by Yasui Seiki Co.). Drying of
the coated substrate at 100.degree. C. resulted in a layered
article (1') composed of the substrate and a resin film disposed
thereon. The thickness of this resin film was 0.4 .mu.m and the Na
content in the resin film was 0.7% (7,000 ppm). The resulting
layered article (1') was subjected to dry heating treatment,
followed by aging for 24 hours under an atmosphere at 23.degree.
C., 50% RH. Subsequently, the layered article was subjected to wet
heating treatment for 60 minutes, followed by drying treatment.
Thus, a layered article (1) was produced. Then, the oxygen
permeability of the layered article (1) was measured. The results
are shown in Table 1.
Example 2
[0094] A layered article (2') was produced in a manner the same as
that in Example 1, except for using the resin composition
dispersion liquid (2) instead of the resin composition dispersion
liquid (1) in Example 1. The thickness of this resin film was 0.4
.mu.m and the Na content in the resin film was 0.4% (4,000 ppm).
The resulting layered article (2') was subjected to dry heating
treatment, followed by aging for 24 hours under an atmosphere at
23.degree. C., 50% RH. Subsequently, the layered article was
subjected to wet heating treatment for 60 minutes, followed by
drying treatment. Thus, a layered article (2) was produced. Then,
the oxygen permeability of the layered article (2) was measured.
The results are shown in Table 1.
Example 3
[0095] A layered article (3') was produced in a manner the same as
that in Example 1, except for using the resin composition
dispersion liquid (4) instead of the resin composition dispersion
liquid (1) in Example 1. The thickness of this resin film was 0.4
.mu.m and the Na content in the resin film was 1.3% (13,000 ppm).
The resulting layered article (3') was subjected to dry heating
treatment, followed by aging for 24 hours under an atmosphere at
23.degree. C., 50% RH. Subsequently, the layered article was
subjected to wet heating treatment for 60 minutes, followed by
drying treatment. Thus, a layered article (3) was produced. Then,
the oxygen permeability of the layered article (3) was measured.
The results are shown in Table 1.
Example 4
[0096] The layered article (1') obtained in Example 1 was subjected
to dry heating treatment, followed by aging for 24 hours under an
atmosphere at 23.degree. C., 50% RH. Subsequently, the layered
article was subjected to wet heating treatment for one minute,
followed by drying treatment. Thus, a layered article (4) was
produced. Then, the oxygen permeability of the layered article (4)
was measured. The results are shown in Table 1.
Comparative Example 1
[0097] The layered article (1') obtained in Example 1, the article
being composed of the substrate and a resin film disposed thereon,
was subjected to dry heating treatment, followed by aging for 24
hours under an atmosphere at 23.degree. C., 50% RH. The oxygen
permeability of this layered article was measured and the result is
shown in Table 1.
Comparative Example 2
[0098] The layered article (1') obtained in Example 1, the article
being composed of the substrate and a resin film disposed thereon,
was subjected to-wet heating treatment, followed by aging for 24
hours under an atmosphere at 23.degree. C., 50% RH. The oxygen
permeability of this layered article was measured and the result is
shown in Table 1.
Comparative Example 3
[0099] A layered article composed of a substrate and a resin layer
disposed thereon was produced in a manner the same as that in
Example 1, except for using the resin composition dispersion liquid
(3) instead of the resin composition dispersion liquid (1) in
Example 1. The thickness of this resin film was 0.4 .mu.m and the
Na content in the resin film was 0.15% (1,500 ppm). The resulting
layered article was subjected to dry heating treatment, followed by
aging for 24 hours under an atmosphere at 23.degree. C., 50% RH.
Subsequently, the layered article was subjected to wet heating
treatment, followed by dry heating treatment. Thus, a layered
article was produced. Then, the oxygen permeability of the layered
article was measured. The results are shown in Table 1.
Comparative Example 4
[0100] The layered article (1') obtained in Example 1, the article
being composed of the substrate and a resin film disposed thereon,
was subjected first to wet heating treatment, followed by aging for
24 hours under an atmosphere at 23.degree. C., 50% RH and further
dry heating treatment. Then, the oxygen permeability of the layered
article was measured. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Combined amount of Number ratio of hydroxyl
groups and Na hydroxyl groups to carboxyl groups in Treatment
Oxygen content carboxyl groups in resin component (A) Dry Wet
permeability (ppm) resin component (A) (% by weight) heating
heating Drying (cc/m.sup.2 day atm) Remarks Example 1 7000 86/14
43.4 Yes Yes Yes 1.2 Wet heating for 60 min. Example 2 4000 86/14
43.4 Yes Yes Yes 2.3 Wet heating for 60 min. Example 3 13000 86/14
43.4 Yes Yes Yes 3.0 Wet heating for 60 min. Example 4 7000 86/14
43.4 Yes Yes Yes 1.3 Wet heating for 1 min. Comparative 7000 86/14
43.4 Yes No Yes 5.2 Example 1 Comparative 7000 86/14 43.4 No Yes
Yes >10 Example 2 Comparative 1500 86/14 43.4 Yes Yes Yes >10
Example 3 Comparative 7000 86/14 43.4 Yes Yes Yes >10 Wet
heating Example 4 was followed by drying and then dry heating
<Retort Evaluation>
[0101] A 70-.mu.m thick non-oriented polypropylene (CPP) film
(trade name: PYLEN FILM-CT P1146; manufactured by Toyobo Co., Ltd.,
oxygen permeability: about 1,400 cc/M.sup.2dayatm) as a heat seal
layer was dry-laminated onto the substrate of the layered product
(4) obtained in Example 4. Thus, a laminated layered article (1)
was obtained. The oxygen permeability of the laminated layered
article (1) was measured to be 0.9 cc/m.sup.2dayatm. Subsequently,
using a compact retorting autoclave (RK-3030, manufactured by ALP
Corp.), the laminated layered article (1) was retort-treated under
a water vapor atmosphere at 120.degree. C. for 60 minutes. The
appearance of the laminated layered article (1) after the treatment
was good and was the same as that before the retorting.
[0102] For comparison, a laminated layered article (2) was produced
by dry lamination of a heat-seal layer onto the surface of the
layered article (4) obtained in Example 4 opposite with the
substrate. The laminated layered article was then subjected to
retort-treatment and further drying treatment. The laminated
layered article (2) after the treatment was whitened in comparison
to that before being retorted.
* * * * *