U.S. patent application number 09/210895 was filed with the patent office on 2001-07-19 for vacuum thermal insulator.
Invention is credited to KURODA, TOSHIYA, SAKAYA, TAIICHI.
Application Number | 20010008671 09/210895 |
Document ID | / |
Family ID | 27523458 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008671 |
Kind Code |
A1 |
KURODA, TOSHIYA ; et
al. |
July 19, 2001 |
VACUUM THERMAL INSULATOR
Abstract
A vacuum thermal insulator which is excellent in thermal
insulation property and maintainability in that property is
disclosed. The vacuum thermal insulator comprises a shell which
defines a vacuum space inside and comprises at least one layer (GB
layer) comprising a thermoplastic resin and satisfying the formula
(1): W.times..lambda..times.P<1.times.10.sup.-6 (1) wherein W is
a thickness (m) of the GB layer, .lambda. is a thermal conductivity
(W/m.cndot.K) of the GB layer and P is an oxygen permeability
(cc/m.sup.2.cndot.day.cndot.atm) of the GB layer at 23.degree. C.
in a humidity of 50% RH.
Inventors: |
KURODA, TOSHIYA;
(TAKATSUKI-SHI, JP) ; SAKAYA, TAIICHI;
(TAKATSUKI-SHI, JP) |
Correspondence
Address: |
PILLSBURY MADISON AND SUTRO
INTELLECTUAL PROPERTY GROUP
1100 NEW YORK AVENUE NW
NINTH FLOOR EAST TOWER
WASHINGTON
DC
200053918
|
Family ID: |
27523458 |
Appl. No.: |
09/210895 |
Filed: |
December 16, 1998 |
Current U.S.
Class: |
428/69 |
Current CPC
Class: |
Y10T 428/239 20150115;
F16L 59/065 20130101; Y10T 428/231 20150115 |
Class at
Publication: |
428/69 |
International
Class: |
B32B 001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 1997 |
JP |
09-346200 |
Dec 16, 1997 |
JP |
09-346201 |
Mar 10, 1998 |
JP |
10-058667 |
Mar 10, 1998 |
JP |
10-058672 |
Mar 10, 1998 |
JP |
10-058673 |
Claims
What is claimed is:
1. A vacuum thermal insulator comprising a shell which defines a
vacuum space inside and comprises at least one layer (GB layer)
comprising a thermoplastic resin and satisfying the formula
(1):W.times..lambda..times- .P<1.times.10.sup.-6 (1)wherein W is
a thickness (m) of the GB layer, .lambda. is a thermal conductivity
(W/m.cndot.K) of the GB layer and P is an oxygen permeability
(cc/m.sup.2.cndot.day.cndot.atm) of the GB layer at 23.degree. C.
in a humidity of 50% RH.
2. The vacuum thermal insulator according to claim 1, wherein at
least one GB layer comprises a thermoplastic resin and an inorganic
laminar compound.
3. The vacuum thermal insulator according to claim 1 further
comprising a core material inside the shell.
4. The vacuum thermal insulator according to claim 1 further
comprising a hollow structural body inside the shell.
5. The vacuum thermal insulator according to claim 4 further
comprising a core material inside the hollow structural body.
6. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, wherein one GB layer satisfies the formula
(2):1.times.10.sup.2<V/(- P.times.S)<5.times.10.sup.3 (2)
wherein S is a area (cm.sup.2) of the inner surface of the GB
layer, V is an actual volume (cm.sup.3) of the vacuum space and P
is an oxygen permeability (cc/m.sup.2.cndot.day.cndot.- atm) of the
GB layer at 23.degree. C. in a humidity of 50% RH.
7. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, wherein the shell comprises at least one GB layer and a
sealant layer constituting the inner circumference layer of the
shell.
8. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, wherein at least one GB layer has an oxygen
permeability of 0.5 cc/m.sup.2.cndot.day.cndot.atm or less at
23.degree. C. in a humidity of 50% RH.
9. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, further comprising a getter inside the shell.
10. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, which has, inside the shell, a getter previously
dehydrated.
11. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, which has, inside the shell, a getter comprising iron
powder.
12. The vacuum thermal insulator according to any one claims 1, 2,
3 and 4, which has, inside the shell, a getter formed of a
composition comprising iron powder and resin.
13. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, which has, inside the shell, a synthetic zeolite having
pores.
14. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, which has, inside the shell, a synthetic zeolite having
pores, wherein an average diameter of the pores ranges from 8 .ANG.
to 12 .ANG..
15. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, which has an alloy getter inside the shell.
16. The vacuum thermal insulator according to any one of claims 1,
2, 3 and 4, wherein the shell is constructed from at least one
multi-layered film comprising at least one GB layer and at least
one sealant layer constituting at least one surface of the
multi-layered film with at least a part of the sealant layer being
sealed with another part of the sealant layer or with at least a
part of another sealant layer wherein the part of the sealant layer
sealed satisfies the formula (3):H/d>20 (3)wherein H and d,
respectively, indicate a width (mm) and a thickness (mm) of the
sealant layer in the sealed part.
17. Use of a vacuum thermal insulator according to any one of
claims 1-16 as thermal insulation parts of a refrigerator or a
freezing chamber.
18. Use of the vacuum thermal insulator according to any one of
claims 1-17 as construction materials.
Description
BACKGROUND OF THE INVENTION 1. Field of the Invention
[0001] The present invention relates to vacuum thermal insulators,
and particularly to vacuum thermal insulation vacuum thermal
insulators having good thermal insulation property which is
maintained for a long time. 2. Description of Related Art
[0002] Vacuum thermal insulators that have a structural body which
is sealed by a container or a wrapping material composed of a gas
barrier material and which has a substantially vacuum space inside
has been known. Also, a vacuum thermal insulator which has core
materials filled in the structural body in order to improve its
thermal insulation property and maintain its shape also has been
known. Such vacuum thermal insulators can attain high thermal
insulation property by maintaining the inside of the structural
body at a high vacuum degree to minimize heat transmission caused
by gas. In order to maintain such high thermal insulation property
for a long time, it is important to form the structural body of a
material which has excellent gas barrier property.
[0003] Resin, particularly thermoplastic resin, is a preferable
material for the structural body in view of its good moldability.
However, even PVDC (polvinylidene chloride) and EVOH (a saponified
ethylene/vinyl acetate copolymer), which are representative resins
of high gas barrier property, are not satisfactory to be used for
vacuum thermal insulators and they can not maintain the high
thermal insulation property for a long time.
[0004] For example, Japanese unexamined patent publications Nos.
Shou 63-279083 and Shou 63-233284 disclose that a laminate in which
aluminium foil is laminated on a thermoplastic resin film can
produce a structural body having good gas barrier property. A
vacuum thermal insulator composed of such a laminate can maintain a
high vacuum degree for a long time. However, metals such as
aluminium have relatively high heat conductivity comparing to resin
and air. For example, although heat conductivity of polypropylene
resin and air, respectively, are about 0.23 W/m.cndot.K and about
0.02 W/m.cndot.K, that of aluminium is about 200 W/m.cndot.K.
Accordingly, a vacuum thermal insulator composed of a metal
laminate causes "heat bridging" which is a phenomenon that heat is
transmitted in the metal layer and the thermal insulation property
drastically deteriorates. The attempt to suppress the heat bridging
by thinning the metal layer has resulted in many pinholes opening
in the metal layer and has caused deterioration in the gas barrier
property and maintainability of the property for a long time.
SUMMARY OF THE INVENTION
[0005] The present inventors have studied to develop thermal
insulators having good thermal insulation property which is
maintained for a long time, and have accomplished the present
invention.
[0006] The present invention provides a vacuum thermal insulator
comprising a shell which has a vacuum space inside and has at least
one layer (hereinafter referred to as a "GB layer") which contains
a resin and satisfies the formula (1):
W.cndot..lambda.P<1.times.10.sup.-6 (1)
[0007] wherein W is the thickness (m) of the GB layer, .lambda. is
the heat conductivity (W/m.cndot.K) of the GB layer and P is the
oxygen permeability (cc/m.sup.2.cndot.day.cndot.atm) of the GB
layer at 23.degree. C. in a humidity of 50% RH.
BRIEF DESCRIPTION OF DRAWINGS
[0008] In the drawings:
[0009] FIG. 1 is a graph schematically showing a relationship
between an X-ray diffraction peak of an inorganic laminar compound
and a "unit thickness a" of the compound;
[0010] FIG. 2 is a graph schematically showing a relationship
between an X-ray diffraction peak of a resin composition containing
an inorganic laminar compound and a "lattice spacing (or distance
between lattice planes) d" of the composition;
[0011] FIG. 3 is a graph schematically showing a relationship
between an X-ray diffraction peak of a resin composition and a
"lattice spacing d" of the composition, in a case where the peak
corresponding to the lattice spacing d is superposed on halo (or
background) and is difficult to detected. In this Figure, the area
obtained by subtracting a "base line" portion from the peak area in
the lower angle side below 2.cndot..theta..sub.d is treated as the
peak corresponding to the "lattice spacing d";
[0012] FIG. 4 is a schematic section of one example of a laminate
which has a GB layer;
[0013] FIG. 5 is a schematic section of another example of a
laminate which has a GB layer;
[0014] FIG. 6 is a schematic section of one example of a vacuum
thermal insulator of the present invention; and
[0015] FIG. 7 is a schematic section of another example of a vacuum
thermal insulator of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The vacuum thermal insulator of the present invention has a
shell which has a vacuum space inside. The shell is not limited in
its hardness so long as it can be used for a vacuum thermal
insulator. That is, both one which is hard enough to maintain a
desired shape by itself and one which is soft and can not maintain
the desired shape by itself are referred to as the shell.
[0017] The GB layer in the shell is a layer which contains a resin,
and a product of whose thickness W (m), thermal conductivity
.lambda. (W/m.cndot.K) and oxygen permeability at 23.degree. C. in
a humidity of 50% RH P (cc/m.sup.2.cndot.day.cndot.atm) satisfies
the formula (1):
W.cndot..tau.P<1.times.10.sup.-6 (1)
[0018] When a layer containing a resin satisfies the formula (1),
deterioration of the thermal insulation property due to the heat
bridging and deterioration in the thermal insulation property in
the course of time can be efficiently suppressed. It is preferable
that the product, W.cndot..lambda..cndot.P, is as small as
possible. Specifically, the product is preferably less than
2.times.10.sup.-7, and more preferably less than 1.times.10.sup.-7.
When the vacuum thermal insulator is used for a use which requires
extremely high thermal insulation property, the product is
preferably less than 1.times.10.sup.-8, more preferably less than
1.times.10.sup.-9, and most preferably 1.times.10.sup.-10.
[0019] Values of W, .lambda. and P can be determined by the
measuring techniques mentioned below. When the GB layer is too thin
and it is difficult to determine the values of .lambda. and P of
the GB layer directly, they can be calculated by using the heat
conductivity and the oxygen permeability of the whole shell and
those of the layer(s) other than the GB layer contained in the
shell.
[0020] Individual values of W, .lambda. and P are not particularly
limited so long as the product of them is less than
1.times.10.sup.-6. In view of suppressing the heat bridging, W is
preferably 10 mm or less, more preferably 1 mm or less, and most
preferably 100 .mu.m. Also, W is preferably 1 mm or more. .lambda.
is preferably 100 W/m.cndot.K, more preferably 10 W/m.cndot.K or
less, and most preferably 1 W/m.cndot.K or less. Also, .lambda. is
0.001 W/m.cndot.K or more.
[0021] In view of maintainability in thermal insulation property
for a long time, the oxygen permeability of the GB layer at
23.degree. C. in a humidity of 50% RH is preferably not more than
0.5 cc/m.sup.2.cndot.day.cndot.atm, more preferably not more than
0.1 cc/m.sup.2.cndot.day.cndot.atm, and still more preferably not
more than 0.01 cc/m.sup.2.cndot.day.cndot.atm. Also, P is
preferably 1.times.10.sup.-5 cc/m.sup.2.cndot.day.cndot.atm or
more. When the oxygen permeability of the GB layer at 23.degree. C.
is relatively small, it can be determined from extrapolation of an
arrhenius' plot which has been made on the basis of oxygen
permeability data detected in a high temperature range.
[0022] The resin contained in the GB layer is preferably a resin
which has excellent gas barrier property in view of the
maintainability of the thermal insulation property. For example,
liquid crystal-type polymers such as liquid polyester resin,
hydrophobic resins such as aramid resin, resins having 20-60% by
weight of hydrogen bonding group or ionic group (hereinafter
referred to as "highly hydrogen bonding resins"), thermosetting
resins such as aromatic epoxy resin and phenol resin can be listed.
Among the high hydrogen bonding resins, ones having 30-50% by
weight of hydrogen bonding group or ionic group are preferred.
Here, the high hydrogen bonding group is a group that has at least
one hydrogen atom which is directly attached to a hetero atom other
than a carbon atom. The ionic group is a group that has positive or
negative charges polarizing to the extent that it can hydrate in
water.
[0023] Examples of the hydrogen bonding group contained in the
highly hydrogen bonding resin are a hydroxyl group, amino group,
imino group, thiol group, carboxyl group, sulfonic acid group and
phosphoric acid group. The hydroxyl group, amino group, carboxyl
group and sulfonic acid group are preferred. Examples of the ionic
group are carboxylate group, sulfonate ion group, phosphate ion
group, ammonium ion group and phosphonium ion group. The
carboxylate group, sulfonic ion group and ammonium group are
preferred.
[0024] Specific examples of the highly hydrogen bonding resins to
be used in the present invention include polyvinyl alcohol,
ethylene/vinyl alcohol copolymers having a viniy alcohol unit
fraction of at least 41 mole %, polysaccharides such as
hydroxymethylcellulose, hydroxyethylcellulose,
carboxymethylcellulose, amylose, amylopectin, pullulan, cardran,
xanthan, chitin, chitosan and cellulose, polyacrylic acid, sodium
polyacrylate, polybenzenesulfonic acid, sodium
polybenzenesulfonate, polyethyleneimine, polyallylamine and
ammonium salt thereof, polyvinylthiol and polyglycerol.
Particularly preferable highly hydrogen bonding resin are polyvinyl
alcohol and polysaccharides.
[0025] Polyvinyl alcohol is a polymer prepared by hydrolyzing
(saponifying) ester bonds in polyvinyl acetate. It has a structure
of a copolymer of vinyl alcohol and ethyl acetate. The
saponification degree of polyvinyl alcohol is preferably at least
70%, and more preferably at least 85%, based on the total number of
ester bonds and bonds derived therefrom. The polymerization degree
of polyvinyl alcohol is preferably 100 or more and 5,000 or
less.
[0026] The polysaccharides are biopolymers which are synthesized by
polycondensation of various monosaccharides in organisms. In the
present invention, the polysaccharides may include not only ones
synthesized in organisms but also ones obtained by chemically
modifying them.
[0027] The GB layer may be either a layer of the above-mentioned
resin or a layer of a resin composition containing a resin and a
material which can impart gas barrier property to the resin such as
a metal oxide, a metal hydroxide and an inorganic laminar compound.
Particularly, a resin composition comprising the resin and the
inorganic laminar compound is preferred. When the GB layer is
composed of such a resin composition, it is preferred that the
resin forms a continuous phase in view of mechanical strength.
[0028] The inorganic laminar compound is an inorganic compound
wherein unit crystal layers are mutually stacked to form a layer
structure. The "layer structure" is a structure wherein planes,
each of which comprises atoms strongly bonded to each other on the
basis of covalent bonds, etc., so as to form close packing, are
stacked substantially parallel to each other on the basis of weak
bonding power such as van der Waals' force.
[0029] Specific examples of the inorganic laminar compound may
include graphite, phosphoric acid salt-type derivative compounds
(such as zirconium phosphate-type compounds), chalcogen-type
compounds, clay minerals, etc. The "chalcogen-type compound" used
herein refers to a di-chalcogen type compound which comprises an
element of Group IV (Ti, Zr, Hf), Group V (V, Nb, Ta), and Group VI
(Mo, W), and is represented by a formula of MX.sub.2. Here, M is an
atom selected from Groups IV, V and VI and X is a chalcogen (S, Se,
Te).
[0030] The clay minerals may be classified into two types, i.e.,
one type having a two-layer structure, that comprises a silica
tetrahedral layer and an octahedral layer which is disposed thereon
and comprises a central metal such as aluminum and magnesium; and
another type having a three-layer structure, that comprises an
octahedral layer comprising a central metal such as aluminum and
magnesium, and a silica tetrahedral layer disposed on both sides of
the octahedral layer so as to sandwich the octahedral layer.
[0031] Specific examples of the former two-layer type include
kaolinite series, antigorite series, etc. Specific examples of the
latter three-layer type include smectite series, vermiculite
series, mica series, etc.
[0032] Examples of clay minerals to be used in the present
invention include kaolinite, dickite, nacrite, halloysite,
antigorite, chrysotile, pyrophyllite, montmorillonite, hectorite,
tetrasilylic mica, sodium taeniolite, muscovite, margarite, talc,
vermiculite, phlogopite, xanthophyllite, chlorite, etc.
[0033] In the resin composition constituting the GB layer, a weight
ratio of the inorganic laminar compound to the resin is preferably
in the range of 5/95-90/10, and more preferably in the range of
5/95-50/50, in view of thermal insulating efficiency and
moldability.
[0034] In the preparation for a GB layer composed of a resin
composition comprising a resin and an inorganic laminar compound, a
resin, a solvent to which the resin is soluble and an inorganic
laminar compound which can be moderately swollen or cleft with the
solvent are preferably used in combination.
[0035] In view of economical efficiency, easiness of obtaining and
gas barrier property of the GB layer, the aspect ratio (Z) of the
inorganic laminar compound is preferably not less than 50 and not
more than 5,000, and more preferably not less than 200 and not more
than 3,000. In view of moldability, the particle size of the
inorganic laminar compound is preferably 5 .mu.m or less, and more
preferably 3 .mu.m or less.
[0036] The above-mentioned aspect ratio (Z) of the inorganic
laminar compound is represented by the formula: Z=L/a, in which L
is a particle size of the inorganic laminar compound determined by
a dynamic light-scattering method by dispersing the inorganic
laminar compound in a solvent and a is a unit thickness of the
inorganic laminar compound which is determined by a powder X-ray
diffraction analysis of powder which is obtained by swelling or
cleaving an inorganic laminar compound in a solvent completely and
then removing the solvent. More specifically, as schematically
shown in the graph of FIG. 1 wherein the abscissa denotes 2.theta.,
and the ordinate denotes the intensity of X-ray diffraction peaks,
the "unit thickness a" is a spacing obtained from the Bragg's
equation (n.cndot..lambda.=2D.cndot.sin .theta., n=1, 2, 3 . . . ),
wherein .theta. denotes the angle corresponding to the peak having
the lowermost angle among those of the observed diffraction peaks.
With respect to the details of the powder X-ray diffraction method,
the book entitled "Kiki-Bunseki no Tebiki (Handbook on Instrumental
Analysis) (a)", page 69, (1985), editorially supervised by Jiro
SHIOKAWA, published by KAGAKU DOJIN K. K. may be referred to.
[0037] A powder X-ray diffraction analysis of a resin composition
containing an inorganic laminar compound can provide a lattice
spacing, d, of the inorganic laminar compound in the resin
composition. Specifically, as schematically shown in the graph of
FIG. 2 wherein the abscissa denotes 2.theta., and the ordinate
denotes the intensity of X-ray diffraction peaks, the "lattice
spacing d" (a<d is a spacing corresponding to the peak having
the lowermost angle among the observed diffraction peaks appearing
on the lower angle (larger spacing) side as compared to the
position of the diffraction peak corresponding to the
above-mentioned "unit thickness a". In a case where the above peak
corresponding to the "lattice spacing d" is superposed on a halo
(or background) as schematically shown in the graph of FIG. 3 so
that it is difficult to detect such a peak, the area of a portion
obtained by subtracting the base line portion from a portion
corresponding to an angle lower than 2 .theta..sub.d, is treated as
a peak corresponding to the "lattice spacing d". The
".theta..sub.d" used herein is an angle of diffraction
corresponding to "(unit thickness a)+(width of one resin chain)".
With respect to the details of a method of determining the "lattice
spacing d", the book entitled "Nendo no Jiten (Encyclopedia of
Clay)", page 35 et seq. and page 271 et seq., (1985), edited by
Shuichi IWAO et al., published by ASAKURA SHOTEN K. K. may be
referred to.
[0038] The integrated intensity of the diffraction peak
(corresponding to the "lattice spacing d") observed in the powder
X-ray diffraction of a resin composition preferably has a relative
ratio of at least 2 (more preferably, at least 10), with respect to
the integrated intensity of the diffraction peak as a standard
(corresponding to the "unit thickness a". In general, the
difference between the above lattice spacing d and the "unit
thickness a", namely, the value of k=(d-a) (when converted into
"length") may be equal to, or larger than the width of one resin
chain constituting the resin composition (k=d-a).gtoreq.(width of
one resin chain)). The "width of one resin chain" may be determined
by simulation calculation, etc., as described in, e.g., the book
entitled "KOBUNSHI KAGAKU JORON (Introduction to Polymer
Chemistry)", pages 103-110 (1981), published by KAGAKU DOJIN K. K..
In the case of polyvinyl alcohol, the width is 4-5 .ANG., and in
the case of water molecules, the width is 2-3 .ANG..
[0039] In a case where there is a relationship of a<d between
the lattice spacing d determined by the powder X-ray diffraction
method for the resin composition and the "unit thickness a"
determined by the powder X-ray diffraction method for the inorganic
laminar compound alone; and the value of (d-a) is not smaller than
the width of one resin chain in the resin composition, it is
assumed that the resin is inserted between layers of the inorganic
laminar compound.
[0040] For example, in the manufacture of a vacuum thermal
insulator having a shell comprising a substrate layer and a GB
layer, which is a representative embodiment of the present
invention, the GB layer is often formed by applying a dispersion
liquid containing an inorganic laminar compound and a resin to a
substrate and then removing the dispersion medium therefrom. A
solvent to which the resin is soluble is usually used as the
dispersion medium. When a dispersion liquid in which the inorganic
laminar compound is swollen or cleft with the dispersion medium is
used, a GB layer which has particularly excellent gas barrier
property can be formed. It is, therefore, preferable to use an
inorganic laminar compound having such property that it can be
swollen or cleft with the solvent to which the resin for the GB
layer is soluble. The degree of swelling and that of cleavage of
the inorganic laminar compound may be evaluated by the following
"swelling property test" and "cleavage property test",
respectively. The inorganic laminar compound may preferably have a
swelling property of at least about 5 (more preferably, at least
about 20) determined by the following swelling property test. On
the other hand, the inorganic laminar compound may preferably have
a cleavage property of at least about 5 (more preferably, at least
about 20) determined by the following cleavage property test. When
the inorganic laminar compound is a swellable natural clay mineral,
it is preferable to use water as the solvent.
[0041] Swelling property test
[0042] Two grams of an inorganic laminar compound is added to 100
ml of a solvent and mixed, while 100-ml graduated cylinder is used
as a container. The resultant mixture is left standing for about
one day, and thereafter the volume of the former (the dispersion
layer of the inorganic laminar compound) is read from the
graduations corresponding to the interface between the dispersion
layer of the inorganic laminar compound and the supernatant. The
larger the resultant value is, the higher the swelling property in
the solvent is.
[0043] Cleavage property test
[0044] Thirty grams of an inorganic laminar compound is slowly
added to 1500 ml of a solvent, and is dispersed by means of a
dispersion machine at 23.degree. C. Thereafter, 100 ml of the
resultant dispersion liquid is taken out and then is left standing
for 60 minutes. Then, the volume of the dispersion layer of the
inorganic laminar compound is read from the graduation
corresponding to the interface between the dispersion layer of the
inorganic laminar compound and the supernatant. The larger the
volume is, the higher the cleaving property in the solvent is.
[0045] Although the solvent (dispersion medium) can be suitably
chosen depending upon the types of the resin and the inorganic
laminar compound to be used, examples of the solvent include water,
alcohol such as methanol, dimethylformamide, dimethylsulfoxide and
acetone. Among them, water and alcohol are often preferably
used.
[0046] A method for preparing the resin composition comprising the
above-mentioned inorganic laminar compound and a resin is not
particularly limited. In view of dispersibility of the inorganic
laminar compound in the resin and easiness in handling, it is
possible to adopt, e.g., a method (first method) wherein a solution
obtained by dissolving a resin in a solvent, and a dispersion
obtained by previously swelling or cleaving, an inorganic laminar
compound with the solvent, and mixed with each other, and
thereafter the solvent is removed; a method (second method) wherein
a dispersion obtained by swelling or cleaving an inorganic laminar
compound with a solvent is added to a resin, and thereafter the
solvent is removed; a method (third method) wherein an inorganic
laminar compound is added to a solution obtained by dissolving a
resin in a solvent to obtain a dispersion in which the inorganic
laminar compound is swollen or cleft, and thereafter the solvent is
removed; and a method (fourth method) wherein an inorganic laminar
compound and a resin are kneaded under heating using a solvent.
Lowering of the aspect ratio of the inorganic laminar compound in
the manufacture of the resin composition can be efficiently
suppressed by the former three methods. In the former three
methods, the use of a high-pressure dispersing machine is
preferable from the viewpoint of dispersion efficiency of the
inorganic laminar compound.
[0047] Examples of the high-pressure dispersing machine include a
superhigh-pressure homoginizer manufactured by Mcrofluidics
Corporation (trade name: Microfluidizer), Nanomizer manufactured by
Nanomizer K. K. and Mantongorin-type high-pressure dispersing
machines such as Homogenizer manufactured by Izumifoodmachinary K.
K.
[0048] Additionally, also in the GB layer in the vacuum thermal
insulator, the inorganic laminar compound preferably has aspect
ratios of 50-5,000, more preferably 200-3000, wherein the aspect
ratio is defined as a ratio of the particle size to the unit
thickness of the inorganic laminar compound in the resin
composition.
[0049] The vacuum thermal insulator of the present invention has a
shell having at least one GB layer and can attain high thermal
insulation property by having a substantially vacuum space inside.
When a plurality of GB layers contained in the shell, compositions
of each GB layer may be either identical or different. Two or more
GB layers may adjoin. Alternatively, one or more layers other than
the GB layers may intervene between the GB layers.
[0050] Although one preferred example of the vacuum thermal
insulator of the present invention is a vacuum thermal insulator
having a shell containing at least one continuous GB layer without
having any splits or holes, every GB layer in the shell may have a
slit, gap and hole. However, in such a case, it is preferable that
the defective part of the GB layer is covered with a material of
high gas barrier property in view of thermal insulation property
and maintainability in the property.
[0051] The vacuum thermal insulator of the present invention may
have, inside the shell, a core material or a hollow structural body
set forth below. Furthermore, the hollow structural body may have
the core material inside.
[0052] The vacuum thermal insulator of the present invention
preferably has the core material inside the shell. The core
material is a material which is used for maintaining a desired size
of the vacuum thermal insulator. The core material is not
particularly limited in type unless it has a bad influence upon
thermal insulation property. Ones having a heat conductivity
measured by a procedure according to JIS R2618 of less than 0.1
W/m.cndot.K are preferred. The use of the core material which has
spaces finely divided results in excellent thermal insulation
property. Specific examples of the core material include perlite
powder, silica powder, precipitated silica powder, glass wool, rock
wool, foamed resin body having open cells and a honeycomb
structural body of resin or metal.
[0053] If necessary, getters may be employed together with the core
material. The getter also may be used as the core material.
[0054] The getter is a material which can absorb a gas such as
carbon dioxide, oxygen, nitrogen and water vapor. Examples thereof
include iron powder, resin molded article in the form of pellet or
sheet containing iron powder, synthetic zeolite represented by
molecular sieves, alloy getter such as zirconium-containing alloy
and barium-lithium alloy. COMBOGETTER manufactured by Saes getter
Co., Ltd. is one specific example of the alloy getter. With respect
to zeolite-type getters, ones which have previously dehydrated by,
for example, heating are preferred in view of the absorbing power.
Synthetic zeolites having pores whose diameter is 8-13 .ANG. are
preferred.
[0055] The vacuum thermal insulator of the present invention may
have a hollow structural body inside the shell. The hollow
structural body is composed of a continuous wall which defines a
substantially closed space. The configuration of the hollow
structural body can be selected depending upon the desired
configuration of the vacuum thermal insulator and is not
particularly limited. The thickness of the wall is preferably 10 mm
or less, more preferably 5 mm or less, and most preferably 1 mm or
less. Although the material of the hollow structural body is not
particularly limited, resins are preferred in view of thermal
insulation property. The pressure of the space lying inside the
hollow structural body is preferably 1 Torr or less, more
preferably 0.1 Torr or less and most preferably 0.01 Torr or
less.
[0056] The hollow structural body may have the above-mentioned core
material and/or getter inside.
[0057] Examples of the resins which composes the hollow structural
body include polyolefin resins such as low- or high-density
polyethylene, ethylene/propylene copolymer, ethylene/butene
copolymer, ethylene/hexene copolymer, ethylene/octene copolymer,
polypropylene, ethylene/vinyl acetate copolymer, ethylene/methyl
methacrylate copolymer and ionomer resins; polyester resins such as
polyethylene terephthalate, polybutylene terephthalate and
polyethylene naphthalate; amide resins such as Nylon-6, Nylon-6,6,
m-xylenediamine/adipic acid polycondensate and polymethyl
methacrylimide; acrylic resins such as polymethyl methacrylate;
styrene or acrylonitrile base resins such as polystyrene,
styrene/acrylonitrile copolymer, styrene/acrylonitrile/butadiene
copolymer and polyacrylonitrile; hydrophobicized cellulose resins
such as cellulose triacetate and cellulose diacetate;
halogen-containing resins such as polyvinyl chloride,
polyvinylidene chloride, polyvinylidene fluoride and Teflon;
hydrogen bonding resins such as polyvinyl alcohol, ethylene/vinyl
alcohol copolymer and cellulose derivatives; liquid crystal
polymers such as liquid crystal polyester resin; and engineering
plastics such as polycarbonate resins, polysulfone resins,
polyethersulfone resins, polyether ether ketone resins,
polyphenylene oxide resins, polymethylene oxide resins and aramid
resins.
[0058] A structure of the shell is not particularly limited so long
as at least one GB layer is contained therein. The shell may be,
for example, a laminate which comprises a GB layer and a sealant
layer as illustrated in FIG. 4 and a laminate which comprises a
sealant layer, a substrate layer and a GB layer as illustrated in
FIG. 5. In view of strength, the shell preferably has the substrate
layer in addition to the GB layer.
[0059] The vacuum thermal insulator of the present invention may be
one which is manufactured by preparing a bag which is composed of a
laminate comprising a GB layer and a sealant layer, putting a core
material and/or a hollow structural body into the bag, evacuating
the bag and sealing the sealant layer together as shown in FIG. 6.
The vacuum thermal insulator also may be a hollow molded body
having a GB layer wherein the inside of the hollow molded body is
filled with a core material and evacuated as shown in FIG. 7.
[0060] The way of evacuation is not particularly limited and may be
carried out by evacuating through a vacuum suction opening provided
to a hollow molded body as shown in FIG. 7 and then sealing the
opening.
[0061] The pressure of the space lying inside the shell is
preferably 1 Torr or less in usual, more preferably 0.1 Tort or
less, and most preferably 0.001 Torr or less in view of the
suppression of lowering thermal insulation property due to a
convection of gas inside the vacuum thermal insulator.
[0062] The shell preferably has at least one GB layer which
satisfies the following formula (2):
1.times.10.sup.2<V/(P.times.S)<5.times.10.sup.3 (3)
[0063] wherein S (cm.sup.2) is the area of the outside surface of
the GB layer, V (cm.sup.3) is the space volume inside the shell and
P has the same meaning as that in the formula (1).
[0064] The space volume inside the shell is a volume of the space
lying inside the shell after the evacuation. If the vacuum thermal
insulator has a core material inside the shell, V is a value which
is calculated by subtracting the true volume occupied by the core
material from the unobstructed capacity of the shell. The true
volume occupied by the core material can be determined from the
true specific gravity of the core material and the total weight of
the core material used. If the vacuum thermal insulator has a
hollow structural body inside the shell, V is a value which is
calculated by subtracting the total volume of the wall forming the
hollow structural body from the unobstructed capacity of the shell.
If the hollow structural body has the core material and the like
inside, V is a value which is calculated by subtracting the total
volume of the wall forming the hollow structural body and the true
volume occupied by core material and the like from the unobstructed
capacity of the shell. S can be determined by using the weight,
apparent specific cavity and thickness of the GB layer.
[0065] In a case where the shell has a substrate layer, a material
of the substrate layer preferably has a heat conductivity as low as
possible in view of suppression of heat bridging. Considering the
moldability, resins are preferably used. Examples of resins for the
substrate layer include polyolefin resins such as low- or
high-density polyethylene, ethylene/propylene copolymer,
ethylene/butene copolymer, ethylene/hexene copolymer,
ethylene/octene copolymer, polypropylene, ethylene/vinyl acetate
copolymer, ethylene/methyl methacrylate copolymer and ionomer
resins; polyester resins such as polyethylene terephthalate,
polybutylene terephthalate and polyethylene naphthalate; amide
resins such as Nylon-6, Nylon-6,6, m-xylenediamine/adipic acid
polycondensate and polymethyl methacrylimide; acrylic resins such
as polymethyl methacrylate; styrene or acrylonitrile base resins
such as polystyrene, styrene/acrylonitrile copolymer,
styrene/acrylonitrile/butadiene copolymer and polyacrylonitrile;
hydrophobicized cellulose resins such as cellulose triacetate and
cellulose diacetate; halogen-containing resins such as polyvinyl
chloride, polyvinylidene chloride, polyvinylidene fluoride and
Teflon; hydrogen bonding resins such as polyvinyl alcohol,
ethylene/vinyl alcohol copolymer and cellulose derivatives; and
engineering plastics such as polycarbonate resins, polysulfone
resins, polyethersulfone resins, polyether ether ketone resins,
polyphenylene oxide resins, polymethylene oxide resins, liquid
crystal polyester resins and aramid resins. Among these resins,
liquid crystal polyester resins, aramid resins, biaxially oriented
polypropylene, biaxially oriented polyethylene terephthalate, and
biaxially oriented Nylon are preferred. In addition, films obtained
by coating the above-mentioned biaxially oriented resins with
polyvinylidene chloride and deposited films of the biaxially
oriented resins such as an aluminium-, alumina- or silica-
deposited film are preferably used.
[0066] When the shell has a sealant layer, the sealant layer is
usually composed of resin. Such resin is not particularly limited,
and examples thereof include polyolefin resins, e.g., low- or
high-density polyethylene, ethylene/polyvinyl alcohol copolymer,
ethylene/propylene copolymer, ethylene/butene copolymer,
ethylene/hexene copolymer, ethylene/4-methyl- 1-pentene copolymer,
ethylene/octene copolymer, polypropylene, ethylene/vinyl acetate
copolymer,. ethylene/methyl methacrylate copolymer, ethylene/methyl
acrylate copolymer, ethylene/acrylic acid copolymer and ionomer
resins; polyamide resins such as Nylon-6 and Nylon-6,6;
styrene/acrylonitrile/butadiene copolymer; styrene/acrylonitrile
copolymer; polyacrylonitrile and polyacrylates such as
polymethylmethacrylate.
[0067] The above-mentioned laminates can be manufactured by
conventional lamination method such as a dry-lamination method and
a coating method. For example, in order to form a GB layer of a
resin composition comprising an inorganic laminar compound and
polyvinyl alcohol on a substrate layer, a dispersion liquid
obtained by dispersing the inorganic laminar compound in aqueous
polyvinyl alcohol may be applied to the substrate layer, followed
by drying it.
[0068] In order to attain satisfactory adhesion strength between
layers contained in the laminate, each layer may be subjected to
treatments such as corona treatment, ozone treatment, electron beam
treatment and anchor coating.
[0069] The above-mentioned GB layer, substrate layer and sealant
layer may be incorporated with various additives which are
conventionally incorporated to resins such as ultraviolet
absorbers, colorants and antioxidants, unless the effect of the
present invention is damaged.
[0070] In view of thermal insulation property, such a vacuum
thermal insulator that its heat conductivity is 0.005
kcal/m.cndot.hr.cndot..degr- ee. C. or less when the pressure in
the space lying inside the shell is particularly preferred.
[0071] The vacuum thermal insulator of the present invention may
have a detector for measuring the degree of vacuum. The detector
may be a soft urethane foam having a high impact resilience
modulus, and so on.
[0072] The vacuum thermal insulator of the present invention can be
manufactured, for example, by using a multi-layered film having at
least one GB layer and at least one sealant layer. For example, the
vacuum thermal insulator can be manufactured by folding a
multi-layered film into two so that the sealant layers face each
other, supplying a core material between the sealant layers,
sealing the sealant layers along the periphery of the core
material, and evacuating. Another type of vacuum thermal insulator
can be produced by supplying a core material between two
multi-layered which are placed so that their sealant layers face
each other, sealing the sealant layers along the periphery of the
core material and evacuating. Still another type of vacuum thermal
insulator can be produced by supplying a core material into a
tubular inflation film whose innermost layer is a sealant layer,
sealing the both open end of the tube and evacuating. In the
above-mentioned processes, a hollow structural body may be used in
place of or together with the core material.
[0073] The way of sealing is not particularly limited and
conventional sealing methods such as welding by radiofrequency
heating, sealing with pressure, heat sealing (sealing with pressure
and heat) and adhering with adhesives. Among these ways, heat
sealing is preferred in view of sealing strength and so on.
[0074] A sealed portion in the vacuum thermal insulator preferably
satisfies the relationship of H/d>20 wherein a (mm) is the
thickness of the sealant layer and H (mm) is the width of the
sealed portion. When the value of H/d is more than 20, the
permeation of gas along the sealed surface can be efficiently
prevented. It is so desirable that the value of H/d is large in
view of gas barrier property. The value of H/d is preferably
1.times.10.sup.2 or more and more preferably 1.times.10.sup.3.
[0075] Although the values of H and d may be set so that the above
formula is satisfied, d is preferably 0.2 mm or less, more
preferably 0.05 mm or less and most preferably 0.04 mm or less. H
is preferably 10 mm or more and more preferably 20 mm or more.
[0076] The vacuum thermal insulator of the present invention which
has good thermal insulation property and can maintain the property
for a long time can be utilized as a thermal insulator which is
incorporated into walls of a refrigerator, freezing chamber and the
like. The vacuum thermal insulator also can be used as construction
materials for a ceiling, wall, floor and the like.
[0077] Furthermore, the vacuum thermal insulator of the present
invention can be employed for various uses which require thermal
insulation such as for keeping cold or for keeping warm. Specific
examples of uses of the vacuum thermal insulator include a
refrigerator, a freezing chamber, a cold reserving car, a ceiling
of a vehicle, a battery, a refrigerated ship, a freezing ship, a
heat retaining container, a freezing showcase, a cold reserving
showcase, a portable cold-reserving box, a heat retaining showcase
for cooking, a vending machine, a solar water heater, a floor
heating device, construction materials for an attic, plant
equipment such as hot- or cold-water pipes and cold fluid transfer
pipes, clothes and bedclothes.
[0078] The present invention will be explained in detail by the
following examples which should not be construed to limit the scope
of the invention.
[0079] Methods for measuring physical properties are as follows
[0080] Heat conductivity
[0081] Heat conductivity of a GB layer was measured according to
JIS R 2618. When the GB layer was thin, the GB layer having a
thickness of W (m) was laminated on an adequate substrate layer
having a thickness of L.sub.B (m) and a heat conductivity of
.lambda..sub.B to form a laminate. The laminate was measured its
thickness, L.sub.t (m), and heat conductivity, .lambda..sub.t.
Using the values of W, L.sub.B, .lambda..sub.B, L.sub.t, and
.lambda..sub.t, the heat conductivity of the GB layer was
calculated according to the following formula:
L.sub.t/.lambda..sub.t=W/.lambda.+L.sub.B/.lambda..sub.B
[0082] Heat conductivity of the vacuum thermal insulator was
measured according to JIS A 1412.
[0083] Oxygen permeability
[0084] Oxygen permeability was measured by using an oxygen
permeability measuring apparatus (trade name: OX-TRAN 100;
manufactured by MOCON Co.) at 23.degree. C. in a humidity of 50%
RH.
[0085] Thickness
[0086] A thickness of at least 0.5 .mu.m was measured by a
commercially available digital-type thickness measuring device
(contact-type thickness measuring device; trade name: Ultra-High
Precision Deci-Micro Head MH-15M; manufactured by Nihon Kogaku
Co.).
[0087] On the other hand, a thickness of less than 0.5 .mu.m was
determined by a gravimetric analysis method wherein the weight of a
film having a predetermined area was measured, the resultant weight
was divided by the area, and further divided by the specific
gravity of the composition; or, in the case of a laminate
comprising a gas barrier resin composition layer and a substrate
layer, an elemental analysis method wherein the ratio between the
thickness of the resin composition layer and that of the substrate
layer was determined from the ratio between the analytical value of
a predetermined inorganic element (originating from the
composition) of the laminate and the fraction of the inorganic
laminar compound alone.
[0088] Particle size
[0089] A particle size was measured by using a ultrafine particle
size analyzing apparatus (trade name: BI-90; manufactured by
Brookheaven Co.) at a temperature of 25.degree. C. in a water
solvent. The particle size, L, was determined as a central particle
diameter measured by a photon correlation method based on a dynamic
light-scattering method.
[0090] Aspect ratio
[0091] X-ray diffraction patterns were obtained by the powder
method using an X-ray diffraction meter (trade name: XD-5A;
manufactured by Shimadzu Corporation) with the inorganic laminar
compound alone and the resin composition containing the inorganic
laminar compound. The lattice spacing (unit thickness) "a" of the
inorganic laminar compound was calculated from the X-ray
diffraction pattern. It was confirmed from the X-ray diffraction
pattern for the resin composition that the lattice spacing of the
inorganic laminar compound was widened in some parts. By using the
particle size, L, obtained by the above-mentioned method, the
aspect ratio, Z, was calculated by using a formula of Z=L/a.
[0092] Heat sealing condition
[0093] Unless otherwise stated, he at sealing was carried out under
conditions of: a temperature of 208.degree. C., for 0.5 seconds,
and with a heat-sealing width of 10 mm, by using a heat sealer
(trade name: FUJI IMPULSE T230; manufactured by FUJI IMPULSE CO.,
LTD.).
[0094] Preparation of coating liquid No. 1
[0095] Into a dispersion vessel (trade name: DESPA MH-L;
manufactured by ASADA Iron Works Co.), 980 g of ion-exchange water
(electric conductivity: 0.7 .mu.S/cm or less) and 20 g of polyvinyl
alcohol (trade name: PVA 103; manufactured by Kuraray Co., Ltd.;
saponification degree: 98.5%; polymerization degree: 300) were
placed and heated to 95.degree. C. with stirring at a low speed
(1500 rpm; circumferential speed: 4.10 m/min). The resultant
mixture was stirred at that temperature for one hour to provide the
resin solution (A). Separately, powder of synthetic smectite (trade
name: Smectone SA; manufactured by Kunimine Industries Co., Ltd.)
was added to a mixture of 980 g of ion-exchange water and 20 g of
polyvinyl alcohol in the dispersion vessel, and the resultant
mixture was stirred at a high speed (3100 rpm; circumferential
speed: 8.47 m/min) for 90 minutes to produce the solution (B)
having a solid content of 2% by weight. The solutions (A) and (B)
were mixed in a weight ratio of (A) to (B) of 1/2 and stirred to
produce the mixed resin composition liquid (C) having a total solid
content of 2% by weight.
[0096] To the liquid (C), a silicone-type surfactant (trade name:
SH3746; manufactured by Dow Corning Toray Silicone Co., Ltd.) was
added in an amount of 0.01% by weight based on the total weight of
the liquid (C) to provide the coating liquid No. 1.
EXAMPLE 1
[0097] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 12 .mu.m thick
biaxially oriented PET manufactured by Toray Industries, Inc.,
which was a substrate film, by a microgravure-coat method using a
test coater manufactured by Yasui Seiki (coating speed: 3 m/min;
drying temperature: 80.degree. C). The thickness of the resultant
anchor coating layer after dry was 0.15 .mu.m. A biaxially oriented
PET film having a resin-containing gas barrier layer (GB layer) was
produced by gravure-coating the coating liquid No. 1 on the anchor
coating layer by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The GB layer had a heat conductivity
of 0.24 W/m.cndot.K and a thickness after dry of 0.4 .mu.m.
[0098] On the GB layer in the resultant biaxially oriented PET
film, a surface-corona-treated linear polyethylene (LLDPE)
(manufactured by Kan Fil Co.; thickness: 40 .mu.m) was
dry-laminated using a urethane-based adhesive (trade name: Unoflex
J3; manufactured by Sanyo Chemical Industries, Ltd.) to produce a
laminate film. An oxygen permeability of the GB layer in the
laminated film was measured. The result is given in Table 1.
Referential Example 1
[0099] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the
laminated film produced in Example 1 together at their three sides.
The bag is filled with perlite, which is a core material,
manufactured by MITSUI MINING & SMELTING CO., LTD. and
evacuated to 0.01 Torr. The bag is then sealed at its unsealed side
to produce a vacuum thermal insulator. The thus obtained vacuum
thermal insulator has extremely low heat conductivity and can
exhibit good thermal insulation property. The thermal insulation
property hardly deteriorates dung aging.
Comparative Example 1
[0100] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 12 .mu.m thick
biaxially oriented PET manufactured by Toray Industries, Inc.,
which was a substrate film, by a microgravure-coat method using a
test coater manufactured by Yasui Seiki (coating speed: 3 m/min;
drying temperature; 80.degree. C). The thickness of the resultant
anchor coating layer after dry was 0.15 .mu.m. A biaxially oriented
PET film having a resin-containing layer was produced by
gravure-coating a polyvinylidene chloride emulsion (trade name:
Kureharon D888; manufactured by Kureha Chemical Industry Co., Ltd.)
on the anchor coating layer by a microgravure-coat method using a
test coater manufactured by Yasui Seiki (coating speed: 6 m/min;
drying temperature: 100.degree. C.). The resin-containing layer in
the film had a heat conductivity of 0.24 W/m.cndot.K and a
thickness after dry of 3 .mu.m.
[0101] On the resin-containing layer in the resultant biaxially
oriented PET film, a surface-corona-treated linear polyethylene
(LLDPE) (manufactured by Kan Fil Co.; thickness: 40 .mu.m) was
dry-laminated using a urethane-based adhesive (trade name: Unoflex
J3; manufactured by Sanyo Chemical Industries, Ltd.) to produce a
laminate film. An oxygen permeability of the resin-containing layer
in the laminated film was measured. The result is given in Table
1.
Comparatative Referential Example 1
[0102] A vacuum thermal insulator can be obtained in the same way
as disclosed in Referential Example 1 using two films obtained from
the laminated film produced in Comparative example 1. Thermal
insulation property of the resultant vacuum thermal insulator
deteriorates during aging.
1 TABLE 1 Oxygen permeability (cc/atm .multidot. m.sup.2 .multidot.
day) (at 23.degree. C., 50% RH) W .multidot. .lambda. .multidot. P
Example 1 0.1 or less 9 .times. 10.sup.-9 or less Comparative
Example 1 8.0 5.5 .times. 10.sup.-6
[0103] Preparation of coating liquid No. 2
[0104] Into a dispersion vessel (trade name: DESPA MH-L;
manufactured by ASADA Iron Works Co.), 2800 g of ion-exchange water
(electric conductivity: 0.7 S/cm or less) and 200 g of polyvinyl
alcohol (trade name: PVA 117H; manufactured by Kuraray Co., Ltd.;
saponification degree: 99.6%; polymerization degree: 1700) were
placed and heated to 95.degree. C. with stirring at a low speed
(1500 rpm; circumferential speed: 4.10 m/min) so that polyvinyl
alcohol was dissolved. The resultant mixture was cooled to
40.degree. C. while stirring and 188 g of 1-butanol and 563 g of
isopropylalcohol were added thereto, followed by stirring
sufficiently. The resultant mixture was then heated to 60.degree.
C. under stirring and 100 g of powdery natural montmorillonite
(trade name: Kunipia G; manufactured by Kunimine Industries Co.,
Ltd.) was added to the mixture. After making sure that the
montmorillonite has thoroughly precipitated in the liquid, the
mixture was stirred at a high speed (3100 rpm; circumferential
speed: 8.47 m/min) for 90 minutes to produce the solution (D)
having a total solid content of 8% by weight. The liquid (D) was
passed through a high-pressure dispersing machine (trade name:
Superhigh Pressure Homogenizer M100-E/H; manufactured by
Microfluidics Corporation) and treated once at 1750 kgf/cm.sup.2 to
produce a uniform dispersion liquid (F) containing polyvinyl
alcohol (PVA) and montmorillonite. The liquid (F) was casted to
form a film and subjected to an X-ray analysis. The basal spacing
of the montmorillonite was determined to be 41.2 .ANG. from a peak
observed and the montmorillonite was sufficiently cleft. The
particle size of the montmorillonite (Kunipia G) determined by a
dynamic light-scattering method was 560 nm. The unit thickness "a"
determined by a powder X-ray diffraction was 1.2156 nm. The aspect
ratio (Z) was 461.
[0105] To the liquid (F), 0.38 g of silicone-type surfactant (trade
name: SH3746; manufactured by Dow Corning Toray Silicone Co., Ltd.)
was added to provide the coating liquid No. 2.
EXAMPLE 2
[0106] An anchor coating agent (E) (a mixture of ADCOAT AD)335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 12 .mu.m thick
biaxially oriented polypropylene (OPP) film (trade name: Pylene
P2102; manufactured by TOYOBO CO., LTD.), which had been subjected
to a surface-corona treatment, by a microgravure-coat method using
a test coater manufactured by Yasui Seiki (coating speed: 3 m/min;
drying temperature: 80.degree. C). The thickness of the resultant
anchor coating layer after dry was 0.15 .mu.m. A coated film was
produced by gravure-coating the coating liquid No. 2 on the anchor
coating layer by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0107] On the coating layer in the coated film obtained above, a
surface-corona-treated linear polyethylene (LLDPE) (manufactured by
Kan Fil Co.; thickness: 40, .mu.m) was dry-laminated using a
urethane-based adhesive (trade name. Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) to produce a laminate film. An
oxygen permeability of the laminated film was measured. The result
is given in Table 2.
Referential Example 2
[0108] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the
laminated film produced in Example 2 together at their three sides.
The bag is filled with perlite, which is a core material,
manufactured by MITSUI MINING & SMELTING GO., LTD. and
evacuated to 0.01 Torr. After that, the bag is sealed by welding at
its unsealed side to produce a vacuum thermal insulator. The thus
obtained vacuum thermal insulator has extremely low heat
conductivity and can exhibit good thermal insulation property. The
thermal insulation property hardly deteriorates during aging.
Comparative Example 2
[0109] Carrying out dry-lamination of a gas barrier layer of EVOH-F
(manufactured by Kuraray Co., Ltd.; thickness: 15 .mu.m) onto one
side of a biaxially oriented PET (a substrate film) using a
urethane-based adhesive (trade name: Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) and dry-lamination of a
surface-corona-treated LLDPE (manufactured by Kan Fil Co.;
thickness: 40 .mu.m) (inner layer) onto the other side of the
biaxially oriented PET gave a laminated film. An oxygen
permeability of the laminated film was measured. The result is
given in Table 2.
[0110] Comparative referential example 2
[0111] A vacuum thermal insulator can be obtained in the same way
as disclosed in Referential Example 2 using two films obtained from
the laminated film produced in Comparative Example 2. The thermal
insulation property of the vacuum thermal insulator drastically
deteriorates during aging.
2 TABLE 2 Oxygen permeability (cc/atm .multidot. m.sup.2 .multidot.
day) (50% RH) 23.degree. C. 55.degree. C. 80.degree. C. Example 2
0.1 or less 0.1 or less 0.1 or less Comparative Example 2 0.3 12
31
[0112] Preparation of coating liquid No. 3
[0113] Into a dispersion vessel (trade name: DESPA DM-L;
manufactured by ASADA Iron Works Co.), 3551 g of ion-exchange water
(electric conductivity: 0.7 .mu.S/cm or less) and 200 g of
polyvinyl alcohol (trade name: PVA 117H; manufactured by Kuraray
Co., Ltd.; saponification degree: 99.6%; polymerization degree:
1700) were placed and heated to 95.degree. C. with stirring at a
low speed (1500 rpm; circumferential speed: 4.10 m/min) so that
polyvinyl alcohol was dissolved. The resultant mixture was then
heated to 60.degree. C. under stirring and 100 g of powdery natural
montmorillonite (trade name: Kunipia G; manufactured by Kunimine
Industries Co., Ltd.) was added to the mixture. After making sure
that the montmorillonite has thoroughly precipitated in the liquid,
the mixture was stirred at a high speed (3100 rpm; circumferential
speed: 8.47 m/min) for 90 minutes to produce the solution (G)
having a total solid content of 8% by weight.
[0114] The liquid (G) was casted to form a film and subjected to an
X-ray analysis. The basal spacing of the montmorillonite was
determined to be 41.2 .ANG. from a peak observed and the
montmorillonite was sufficiently cleft. The particle size of the
montmorillonite (Kunipia G) determined by a dynamic
light-scattering method was 560 nm. The unit thickness "a"
determined by a powder X-ray diffraction was 1.2156 nm. The aspect
ratio (Z) was 461.
[0115] To the liquid (G), 0.38 g of silicone-type surfactant (trade
name: SH3746; manufactured by Dow Corning Toray Silicone Co., Ltd.)
was added to provide the coating liquid No. 3.
EXAMPLE 3
[0116] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 20 .mu.m in thick
biaxially oriented polypropylene (trade name: Pylene P2102;
manufactured by TOYOBO CO. LTD.), which had been subjected to a
surface-corona treatment, by a microgravure-coat method using a
test coater manufactured by Yasui Seiki (coating speed: 3 m/min;
drying temperature: 80.degree. C). The thickness of the resultant
anchor coating layer after dry was 0.15 .mu.m. A coated film was
produced by gravure-coating the coating liquid No. 3 on the anchor
coating layer by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0117] On the coating layer in the coated film obtained above, a
surface-corona-treated LLDPE (trade name: KF101; manufactured by
Kan Fil Co.; thickness: 40 .mu.m) was dry-laminated using a
urethane-based adhesive (trade name; Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) to produce a laminate film.
Referential Example 3
[0118] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 3 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
EXAMPLE 4
[0119] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a miff ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 12 .mu.m thick
biaxially oriented polyethylene terephthalate (trade name; Lumilar
Q27; manufactured by Toray Industries Inc.), which had been
subjected to a surface-corona treatment, by a microgravure-coat
method using a test coater manufactured by Yasui Seiki (coating
speed: 3 m/min; drying temperature: 80.degree. C.). The thickness
of the resultant anchor coating layer after dry was 0.15 .mu.m. A
coated film was produced by gravure-coating the coating liquid No.
3 on the anchor coating layer by a microgravure-coat method using a
test coater manufactured by Yasui Seiki (coating speed: 6 m/min;
drying temperature: 100.degree. C.). The coating layer had a
thickness after dry of 0.5 .mu.m.
[0120] On the coating layer in the coated film obtained above, a
surface-corona-treated LLDPE (trade name: KF101; manufactured by
Kan Fil Co.; thickness: 80 .mu.m) was dry-laminated using a
urethane-based adhesive (trade name: Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) to produce a laminated film.
Referential Example 4
[0121] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 4 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
EXAMPLE 5
[0122] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on an alumina-deposited
surface of a 12 .mu.m thick aluminium-deposited biaxially oriented
polyethylene terephthalate (trade name: VM-PET, E7075; manufactured
by TOYOBO CO., LTD.) by a microgravure-coat method using a test
coater manufactured by Yasui Seiki (coating speed: 3 m/min; drying
temperature: 80.degree. C.). The thickness of the resultant anchor
coating layer after dry was 0.15 .mu.m. A coated film was produced
by gravure-coating the coating liquid No. 3 on the anchor coating
layer by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0123] On the coating layer in the coated film obtained above, a
surface-corona-treated LLDPE (trade name: KF101; manufactured by
Kan Fil Co.; thickness: 80 .mu.m) was dry-laminated using a
urethane-based adhesive (trade name: Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) to produce a laminated film.
[0124] Referential Example 5
[0125] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 5 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
EXAMPLE 6
[0126] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a silica-deposited
surface of a 12 .mu.m thick silica-deposited biaxially oriented
polyethylene terephthalate (trade name: Techbarrier S; manufactured
by Mitsubishi Chemical Corporation) by a microgravure-coat method
using a test coater manufactured by Yasui Seiki (coating speed: 3
m/min; drying temperature: 80.degree. C.). The thickness of the
resultant anchor coating layer after dry was 0.15 .mu.m. A coated
film was produced by gravure-coating the coating liquid No. 3 on
the anchor coating layer by a microgravure-coat method using a test
coater manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0127] On the coating layer in the coated film obtained above, a
surface-corona-treated LLDPE (trade name: KF10; manufactured by Kan
Fil Co.; thickness: 80 .mu.m) was dry-laminated using a
urethane-based adhesive (trade name: Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) to produce a laminate film.
Referential Example 6
[0128] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 6 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
EXAMPLE 7
[0129] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a corona-treated
surface of a 12 t m thick biaxially oriented polyethylene
terephthalate (trade name: Lumilar Q27; manufactured by Toray
Industries Inc.) by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 3 m/min; drying
temperature: 80 .degree. C.). The thickness of the resultant anchor
coating layer after dry was 0.15 .mu.m. A coated film was produced
by gravure-coating the coating liquid No. 3 on the anchor coating
layer by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0130] On the coating layer in the coated film obtained above, a
deposited CPP (trade name: VM-CPP, FKB; manufactured by Meiwa Packs
Co.; thickness: 60 .mu.m) was dry-laminated using a urethane-based
adhesive (trade name: Unoflex J3; manufactured by Sanyo Chemical
Industries, Ltd.) to produce a laminate film.
Referential Example 7
[0131] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 7 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
EXAMPLE 8
[0132] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a silica-deposited
surface of a 12 .mu.m thick silica-deposited biaxially oriented
polyethylene terephthalate (trade name: Techbarrier S; manufactured
by Mitsubishi Chemical Corporation) by a microgravure-coat method
using a test coater manufactured by Yasui Seiki (coating speed: 3
m/min; drying temperature: 80.degree. C.). The thickness of the
resultant anchor coating layer after dry was 0.15 .mu.m. A coated
film was produced by gravure-coating the coating liquid No. 3 on
the anchor coating layer by a microgravure-coat method using a test
coater manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0133] On the coating layer in the coated film obtained above, a
deposited CPP (trade name: VM-CPP, FKB; manufactured by Meiwa Packs
Co.; thickness: 60 .mu.m) was dry-laminated using a urethane-based
adhesive (trade name: Unoflex J3; manufactured by Sanyo Chemical
Industries, Ltd.) to produce a laminated film.
Referential Example 8
[0134] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 8 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
EXAMPLE 9
[0135] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a silica-deposited
surface of a 12 .mu.m thick silica-deposited biaxially oriented
polyethylene terephthalate (trade name: Techbarrier S; manufactured
by Mitsubishi Chemical Corporation) by a microgravure-coat method
using a test coater manufactured by Yasui Seiki (coating speed: 3
m/min; drying temperature: 80.degree. C.). The thickness of the
resultant anchor coating layer after dry was 0.15 .mu.m. A coated
film was produced by gravure-coating the coating liquid No. 3 on
the anchor coating layer by a microgravure-coat method using a test
coater manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C). The coating layer had a thickness
after dry of 0.5 .mu.m.
[0136] On the coating layer in the coated film obtained above, an
aluminium foil (manufactured by SHOWA ALUMINUM CORPORATION;
thickness: 60 .mu.m) was dry-laminated using a urethane-based
adhesive (trade name: Unoflex J3; manufactured by Sanyo Chemical
Industries, Ltd.) so as not to cover a heat sealing portion, and
subsequently, a surface-corona-treated LLDPE (trade name: KF101;
manufactured by Kan Fil Co.; thickness: 80 .mu.m) was laminated on
the coating layer to produce a laminate film.
Referential Example 9
[0137] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 9 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
using a vacuum sealer (manufactured by NPC Co.) so that the inner
pressure becomes 0.01 Torr to produce a vacuum thermal insulator.
The thus obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
Comparative Example 3
[0138] Carrying out dry-lamination of a gas barrier layer composed
of a polyvinylidene chloride film (trade name: Saran UB;
manufactured by Asahi Chemical Industry Co., Ltd.; thickness: 15
.mu.m) onto one side of a substrate film composed of a biaxially
oriented OPP (20 .mu.m) using a urethane-based adhesive (trade
name: Unoflex J3; manufactured by Sanyo Chemical Industries, Ltd.)
and dry-lamination of a surface-corona-treated LLDPE (trade name:
KF101; manufactured by Kan Fil Co.; thickness: 40 .mu.m) as an
inner layer onto the other side of the biaxially oriented OPP gave
a laminated film.
Comparative referential example 3
[0139] A vacuum thermal insulator can be obtained in the same way
as disclosed in Referential Example 9 using two films obtained from
the laminated film produced in Comparative Example 3. The thermal
insulation property of the vacuum thermal insulator drastically
deteriorates during aging.
EXAMPLE 10
[0140] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 20 .mu.m thick
biaxially oriented OPP (trade name: Pylene P2102; manufactured by
TOYOBO CO. LTD.) by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 3 m/min; drying
temperature: 80.degree. C.). The thickness of the resultant anchor
coating layer after dry was 0.15 .mu.m. A biaxially oriented PET
film having a gas barrier resin-containing layer (GB layer) thereon
was produced by gravure-coating the coating liquid No. 1 on the
anchor coating layer by a microgravure-coat method using a test
coater manufactured by Yasui Seiki (coating speed: 6 m/min; drying
temperature: 100.degree. C.). The coating layer had the GB layer
had a heat conductivity of 0.24 W/m.cndot.K and a thickness after
dry of 0.5 .mu.m.
[0141] On the GB layer in the biaxially oriented PET film obtained
above, a surface-corona-treated linear polyethylene (LLDPE) (trade
name: KF101; manufactured by Kan Fil Co.; thickness: 40 .mu.m) was
dry-laminated using a urethane-based adhesive (trade name: Unoflex
J3; manufactured by Sanyo Chemical Industries, Ltd.) to produce a
laminate film. An oxygen permeability of the GB layer in the
laminated film was measured. The result is given in Table 3.
Referential Example 10
[0142] A bag 250 mm long and 250 mm wide was prepared by sealing
LLDPE layers (inner layers) of two films obtained from the laminate
film produced in Example 10 together at their three sides. The bag
is filled with 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
and a getter (trade name: COMBOGETTER; manufactured by Saes getter
Co., Ltd.), and the bag is sealed by welding at its unsealed side
(sealed width: 10 mm) using a vacuum sealer (manufactured by NPC
Co.) so that the inner pressure becomes 0.01 Torr to produce a
vacuum thermal insulator. The value of H/d is 250. The thus
obtained vacuum thermal insulator has extremely low heat
conductivity and the thermal insulation property hardly
deteriorates during aging.
Comparative Example 4
[0143] An anchor coating agent (E) (a mixture of ADCOAT AD335 and
CAT10 having a mixing ratio of 15/1 (weight ratio); manufactured by
TOYO MORTON Co. Ltd.) was gravure-coated on a 20 .mu.m thick
biaxially oriented OPP (trade name: Pylene P2102; manufactured by
TOYOBO CO. LTD.) by a microgravure-coat method using a test coater
manufactured by Yasui Seiki (coating speed: 3 m/min; drying
temperature: 80.degree. C.). The thickness of the resultant anchor
coating layer after dry was 0.15 .mu.m. A biaxially oriented OPP
film having a resin-containing layer was produced by
gravure-coating a polyvinylidene chloride emulsion (trade name:
Kureharon DO888S; manufactured by Kureha Chemical Industry Co.,
Ltd. on the anchor coating layer by a microgravure-coat method
using a test coater manufactured by Yasui Seiki (coating speed: 6
m/min; drying temperature: 100.degree. C.). The resin-containing
layer in the film had a heat conductivity of 0.24 W/m.cndot.K and a
thickness after dry of 3 .mu.m.
[0144] On the resin-containing layer in the resultant biaxially
oriented OPP film, a surface-corona-treated linear polyethylene
(LLDPE) (manufactured by Kan Fil Co.; thickness: 150 .mu.m) was
dry-laminated using a urethane-based adhesive (trade name: Unoflex
J3; manufactured by Sanyo Chemical Industries, Ltd.) to produce a
laminate film. An oxygen permeability of the resin-containing layer
in the laminated film was measured. The result is given in Table
3.
Comparative referential example 4
[0145] A vacuum thermal insulator can be obtained in the same way
as disclosed in Referential Example 10 using two films obtained
from the film produced in Comparative Example 4. The value of H/d
is 67. The thermal insulation property of the vacuum thermal
insulator drastically deteriorates during aging.
3 TABLE 3 Oxygen permeability Thermal (cc/atm .multidot. m.sup.2
.multidot. day) insulation (at 23.degree. C., 50% RH) H/d property
W .multidot. .lambda. .multidot. P Example 10 0.1 at less 250 Good
9 .times. 10.sup.-9 or less Comparative 8.0 67 Poor 5.8 .times.
10.sup.-6 Example 4
Referential Example 11
[0146] Using two films obtained from the laminated film produced in
the same way disclosed in Example 3, a vacuum thermal insulator can
be produced in the same way as disclosed in Referential Example 3
except that the 100% open urethane foam having an average cell
diameter of 75 .mu.m (a core material; manufactured by KURABO
INDUSTRIES LTD.) which has been heated at 120.degree. C. for 1 hour
is packed alone. The value of H/d becomes 250. The thus obtained
vacuum thermal insulator has extremely low heat conductivity and
the thermal insulation property hardly deteriorates during
aging.
Comparative Example 5
[0147] Carrying out dry-lamination of a gas barrier layer of EVOH-F
(manufactured by Kuraray Co., Ltd.; thickness: 15 .mu.m) onto one
side of a biaxially oriented PET (a substrate film) using a
urethane-based adhesive (trade name: Unoflex J3; manufactured by
Sanyo Chemical Industries, Ltd.) and dry-lamination of a
surface-corona-treated LLDPE (manufactured by Kan Fil Co.;
thickness; 150 .mu.m) (inner layer) onto the other side of the
biaxially oriented PET gave a laminated film.
Comparative referential example 5
[0148] A vacuum thermal insulator can be obtained in the same way
as disclosed in Referential Example 11 using two films obtained
from the laminated film produced in Comparative Example 5. The
value of H/d is 67. The thermal insulation property of the vacuum
insulator drastically deteriorates during aging.
* * * * *