Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ITE COVER SHEET MATERIAL CAPABLE
OF REFLECTING ULTRAVIOLET RAYS
FIELD OF THE INVENTION
The present invention relates to a white cover sheet
material capable of reflecting ultraviolet rays. More
particularly, the present invention relates to a white cover
sheet material which exhibits an excellent reflectivity to
ultraviolet rays, similar to that snow.
BACKGROUND OF THE INVBNTION
It is well-known that in order to conceal things and
persons, in an area covered with snow, from inspection with
the naked eye, they are covered with a white sheet material.
Also, it is well-known that in order to provide the white
cover sheet material, a conventional white pigment, for
instance, titanium dioxide, may be used. However, the
conventional white pigments have a property such that they
absorb most of the incidental ultraviolet rays and hardly
reflect the incidental ultraviolet rays, while snow reflects
70 to 90% of incidental ultraviolet rays. For this reason,
when the conventional white sheet material placed on snow is
scanned by using an ultraviolet ray-sensitive inspecting
means for instance, a special camera equipped with a filter
permieable for ultraviolet rays or another special device,
for example, a spectrophotometer, the conventional white
cover sheet ~aterial is easily and clearly distinguished
from the snow surface.
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Accordingly, when the ultraviolet ray inspection is
applied, the conventional white sheet cannot conceal
materials or people placed on snow.
SUMMARY OF THE I NVENTION
An object of the present invention is to provide a
white cover sheet material capable of reflecting ultraviolet
rays, and hardly distinguishable from the snow surface not
only by the naked eye, but also, by an inspection means in
which ultraviolet rays are applied.
The above object can be attained by using the white
cover sheet material capable of reflecting ultraviolet rays
of the present invention which comprises at least one outer
surface layer which comprises (A) a substantially colorless
matrix material comprising at least one thermoplastic
polymer material and, (B) a white ultraviolet ray-reflecting
agent dispersed in said matrix material and comprising at
least one member selected from the group consisting of
zirconium oxide ~ZrO2), barium sulfate (BaSO4), magnesium
oxide (MgO) and magnesium carbonate (MgCO3).
DETAILED DESCRIPTION OF THE INVENTION
In the white cover sheet material of the present
invention, it is essential that at least one outer surface
of the sheet material is capable of reflecting ultraviolet
rays. For this purpose, at least one outer surface layer of
the cover sheet material comprises:
(A) a substantially colorless matrix material and,
(B) a white ultraviolet ray-reflecting agent dispersed
in the matrix material.
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The matrix material comprises at least one substantially
colorless thermoplastic polymer material selected from, for
instance, natural rubber; synthetic rubbers, for example,
polybutadiene, butadiene-styrene compolymers, butadiene-
S acrylonitrile copolymers, polychloroprene, polyisoprene,polyisobutylene, isobutylene-isoprene copolymers, acrylic
ester copolymers, polyurethane rubbers and chlorosulfonated
polyethylene, and; thermoplastic synthetic resins, for
example, polyvinyl chloride, polyethylene, polypropylene,
ethylene-vinyl acetate copolymers, vinyl chloride-vinyl
acetate copolymers, and polyurethane. Polyvinyl chloride is
preferred as a matrix material. The matrix material may
contain any additives such as plasticizers, stabilizers, and
fillers unless the additives hinder the intended object of
the present invention.
The white ultraviolet ray-reflecting agent is selected
from the group consisting of zirconium oxide, barium
sulfate, magnesium oxide and magnesium carbonate.
In the outer surface layer, it is preferable that the
amount of the white ultraviolet ray-reflecting agent is in a
range of from 20 to 200~, based on the weight of the matrix
material. Preferably, the magnesium oxide is in a range of
from 20 to 70~, the magnesium carbonate is in a range of
from 20 to 100% and the barium sulfate is in a range of from
70 to 150~ based on the wei~ht of the matrix material.
When the amount of the white ultraviolet ray-reflecting
agent is less than 20%, sometimes, the resultant cover
sheet material exhibits an unsatisfactory reflectivity for
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ultraviolet rays and an insufficient shading effect for
visible light. Accordingly, it is difficult to conceal
materials and/or people by covering then with the sheet
material. When the amount of the white ultraviolet
ray-reflecting agent is more than 200%, the resultant outer
surface layer sometimes exhibits a poor flexibility and
becomes easily cracked at a low temperature. Also, in the
amount of the white ultraviolet ray-reflecting atent more
than 200%, the increase in its amount causes the reflectivity
of the resultant outer surface to the ultraviolet rays to
very slightly increase. Accordingly, usually, the ultra-
violet ray-reflecting agent is used in an amount of 20 to
200% based on the weight of the matrix material.
Also, it is preferable that the white ultraviolet ray-
reflecting agent is in the form of fine particles.
Furthermore, it is preferable that the fine particles have a
100 mesh size or smaller. That is, the preferable fine
particles can pass through a 100 mesh sieve, and more
preferably, a 350 mesh sieve.
The outer surface layer capable of reflecting ultra-
vilet rays, may be in the form of a film or a fiber fabric.
Also, the sheet material of the present invention may be
co~posed of the outer surface layer capable of reflecting
ultraviolet rays alone, or a substrate sheet layer and at
least one outer surface layer capable of reflecting ultra-
violet rays.
The fine particles of the white ultraviolet
ray-reflecting agent are uniformly dispered in the matrix
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material by using a conventional mixing apparatus, for
instance, calender mixer, Bumbury's mixer or screw extruder.
When the cover sheet material of the present invention
is composed of the outer surface layer containing the white
ultraviolet ray-reflecting agent, the mixture of the white
ultraviolet ray-reflecting agent with the matrix material is
formed into a sheet having desired dimensions by means of a
conventional sheet forming apparatus, for example, a
calender or extruder. The thickness of the sheet is not
limited to a special range of values. However, usually, the
thickness of the sheet is 0.05 mm or more, preferably,
0.1 mm or more.
In the case where the outer surface layer containing
the white ultraviolet ray-reflecting agent is formed on a
surface of a substrate sheet layer, the substrate sheet may
be selected from fiber fabrics, for example, woven, knitted
or non-woven fabric, and polymeric sheets or films.
The fiber fabric may be made from continuous filament
yarns, staple fiber spun yarns, split fiber yarns or tape
yarns. The fiber may be a natural organic fiber such as
cotton or wool; inorganic fiber such as glass fiber; organic
synthetic fiber such as polyester, polyamide, polyacronitrile
or water-insolubized or sparingly water-soluble modified
polyvinyl alcohol fiber; regenerated fiber such as viscose
or cupra fiber and; semi-synthetic fiber such as cellulose
acetate fiber. It is preferable that the substrate fiber
fabric is made o~ polyester, polyamide or modified polyvinyl
alcohol filaments or staple fibers. Especially, it is
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preferable that the substrate fiber fabric consists of the
water-isoluble or sparingly water-soluble polyvinyl alcohol
filaments or fibers. This type of fiber fabric exhibits an
excellent reflectivity of 60 to 70% to ultraviolet rays
having a wave length of from 300 to 400 millimicrons. When
this type of fiber fabric is employed as a substrate fiber
fabric, it becomes possible to reduce the amount of the
ultraviolet ray-reflecting agent to be contained in the white
outer surface layer. Also, since the reflectivity of the
modified polyvinyl alcohol substrate fiber fabric does not
decrease by being repeatedly washed or laundered, the ultra-
violet ray-reflecting effect of the substrate fiber fabric
can be maintained constant even if the cover sheet material
is subjected to repeated washing or laundering procedures.
In the case where the substrate sheet material is
composed of a polymeric sheet or film, the sheet or film may
be made of natural rubber; synthetic rubber, for example,
polybutadiene, butadiene-styrene copolymer, butadiene-
acrylonitrile copolymer, polychloroprene, polyisoprene,
polyisobutylene, isobutyleneisoprene copolymer, acrylic
ester copolymer, polyurethene rubber, or chlororulfonated
polyethylene, or; thermoplastic synthetic polymer, for
example, polyvinyl chloride, polyethylene, polypropylene,
ethylene-~inyl acetate copolymer, vinyl chloride-vinyl
acetate copolymer, or polyurethane.
The substrate sheet material preferably has a substan-
tially colorless surface on which the outer surface layer
having on which the outer surface layer having the
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ultraviolet ray-reflecting property is formed. The substrate
sheet material may comprise at least one substantially
colorless surface layer formed on at least one surface of a
supporting sheet material.
The substantially colorless surface layer may comprise
a substantially colorless matrix material comprising at
least one thermoplastic polymer material and titanium dioxide
dispersed in the matrix material. The amount of the titanium
dioxide is preferably in a range of from 2 to 50%, more
preferably, from 3 to 20%, based on the matrix material.
The titanium dioxide is in the form of fine particles
preferably having a size of 1.0 micron or less, more
preferably, from 0.2 to 0.6 microns. The titanium dioxide
may be either of a rutile type or of anatase. In regard to
whiteness and ultraviolet ray-reflecting properties, the
anatase type of titanium oxide is preferable for the present
invention.
The thermoplastic polymer matrix material in the
substrate sheet material may be selected from the polymer
materials usable for the outer surface layer containing the
ultraviolet ray-reflecting agent.
It is preferable that the substrate sheet material
exhibits such an excellent visible light-screening property
that an 8-point type cannot be seen through the substrate
sheet material in accordance with the method of JIS K-68 28,
4-10-2.
The substrate sheet material may contain one or more
metal foil, for example, aluminium foil, laminated with the
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polyme~ic sheet or film and/or the fiber fabric.
It is preferable that the surface of the substrate
sheet material exhibits a high degree of whiteness.
In order to provide a white outer surface layer capable
of reflecting ultraviolet rays, a film or sheet containing
the ultraviolet ray-reflecting agent in the matrix material
may be adhered to a surface of the white surface of the
substrate sheet material be using a colorless adhesive or by
a metl-bonding method. Otherwise, a solution or dispersion
of the mixture of the ultraviolet ray-reflecting agent and
the matrix material is a medium is applied to the white
surface of the substrate sheet material or impregnated by
the substrate sheet material and, then, the solution or
dispersion is solidified by removing the medium therefrom.
The thickness of the outer surface layer is preferably
in a range of from 0.05 to 0.5 mm, more preferably, from 0.1
to 0.3 mm.
The white cover sheet material of the present invention
exhibits not only an excellent whiteness but also an
excellent reflectivity of 70% or more, usually, from 80 to
85% to ultraviolet rays having a wave length of from 300 to
400 millimicrons. Therefore, when the white cover sheet
material of the present invention is placed on a snow
surface, it is difficult to distinguish it from the snow
surface not only with the naked eye, but also, with the
ultraviolet ray-inspecting device.
In the cover sheet material of the present invention,
the outer surface layer may contain, in addition to the
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white ultraviolet ray-reflccting agent, a white flame-
-retarding agent dispersed in the matrix material. The
white flame-retarding agent may be selected from conven-
tional white flame-retarding agents unless the purpose of
the present invention is hindered thereby. Usually, the
white flame-retarding agent comprises diantimony trioxide
which is effective for enhancing the flame-retarding
property of the sheet material without decreasing the
whiteness and the ultraviolet ray-reflecting property of the
outer surface layer. The flame-retarding agent may be
contained not only in the outer surface layer, but also, in
the substrate sheet material. The amount of the flame-
-retarding agent, for example, diantimony trioxide, is
preferably in a range of from 2 to 10%, more preferably,
from 4 to 7%, based on the weight of the matrix material.
The substrate sheet material may contain an electro-
-conductive substance which is capable of reflecting
electromagnetic waves usable for radar (radio direction-
-finding and ranging), unless the purpose of the present
invention is hindered thereby. The electric conductive
substance may be selected from fine wires of metals, for
example, stainless steel, copper and aluminium, carbon
fibers, graphite fibers, fine particles of metals, carbon
and graphite.
The cover sheet material of the present invention may
have various attachments, for example, threads, tapes, ropes
and the like. Needless to say, it is necessary that each of
the attachments has an outer surface layer containing the
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white ultraviolet ray-reflecting agent.
The following specific examples are presented for the
purpose of clarifying the present invention. However, it
should be understood that these are intended only to be
examples of the present invention and are not intended to
limit the present invention in any way.
In the examples, the reflectivities of sheet materials
to ultraviolet rays and visible light were measured at wave
lengths of 350 and 600 millimicrons, respectively, by using
a spectrophotometer (Type 607 made by Hitachi, Japan).
Examples 1 and 2
In each of the Examples 1 and 2, a mixture having a
composition as indicated in Table 1 was prepared. The
mixture was kneaded and formed into a sheet having a
thickness of 0.1 mm by using a calender. The resultant
sheet exhibited properties indicated in Table 1.
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T a b 1 e
Example No.
I t e m Example 1E~n~le 2
Composition (part by weight)
Polyvinyl chloride 100 100
D. O. P. 75 75
Zirccnium oxide 100 100
Diantim~ny trioxide 0 0
Zinc stearate 3 3
Reflectivity to ultraviolet rays 82 80
having a wave length of 350 m~ (%)
. __
Flame retardancy (class) 2-nd class l-st class
The flame retardancy was evaluated in accordance with
JIS-Z-2150-B, by heating for two minutes.
Comparative Example 1
The same procedures as those described in Example 1
were carried out, except that no zirconium oxide was used.
The resultant sheet was transparent and exhibited substan-
tially no reflectivity to ultraviolet rays having a wave
length of 350 millimicrons.
Comparateive Example 2
The same procedures as those described in ~xample 1
were carried out, except that the zirconium oxide was
replaced by titanium dioxide. The resultant sheet exhibited
an excellent whiteness. However, the sheet exhibited a very
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poor reflectivity of about 20% to ultraviolet rays having a
wave length of 350 millimicrons, and, therefore, was easily
distinguished from snow by means of ultraviolet ray
insepction.
Examples 3 and 4
In Example 3, the same white ultraviolet ray-reflecting
sheet as that described in Example 1 was heat-bonded to a
surface of a substrate woven fabric consisting of polyvinyl
alcohol continuous filament yarns which had been modified by
reacting with formaldehyde and which had the following
structure:
240 denier/single yarn x 240 denier/single yarn
29 yarns/25.4 mm x 2B yarns/25.4 mm
The resultant composite sheet had a thickness of 0.22 mm
and exhibited a reflectivity of 85% to ultraviolet rays
having a wave length of 350 millimicrons and a second class
flame retardancy.
In Example 4, the same procedures as those described in
Example 3, except that the same white ultraviolet ray-
reflectin~ sheet as that described in Example 2 was
heat-bonded to the substrate woven fabric. The resultant
composite sheet had a thickness of 0.2 mm and exhibited a
reflectivity of 83% to the ultraviolet rays having a wave
length of 350 millimicrons and a first class flame
retardancy.
Examples 5 through 12
In each of th~ Examples 5 through 12, a mixture having
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a composition indicated in Table 2 was kneaded and formed
into a sheet having a thickness of 0.1 mm by using a
calender.
Both surfaces of a woven fabric consisting of poly-
ethylene terephthalate fiber spun yarns and having a weight
of 159 g/m2 and the following structure:
20/l x 20/l
92 x 55
were heat coated with the above-prepared sheet. The
resultant composite sheet had a thickness of 0.58 mm and
exhibited properties indicated in Table 2.
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T a b 1 e 2
E x a m p 1 e N o.
I t e m
5 6 7 8 91.0 11 12
_ _ __ _
Canposition
Polyvinyl dlloride100 100100 100 100100 100 100
D. O. 2. 75 75 75 75 75 75 75 75
zinc stearate 3 3 3 3 3 3 3 3
BaSO4 150 - - 100 - 100 50 50
Mga~3 - 70 - - 70 50 50 50
MgO - - 30 - - - 10 10
Zr2 ~ ~ ~ 50 50 - _ _
Sb2O3 7 7 7 7 7 7 7
Reflectivity (%)to 83 80 76 84 80 82 80 78
ultraviolet rays ( )1
R~flectivity (%) to84 82 80 83 84 82 81 81
visible light ( ) 2
Li~ht-screenir~ good good go~d go~l goo:3 good good gocx~
~r~erty
Flame retardancy l-st l-st l-st l-st l-st l-st l-st 2-nd
(class)
Note: (*)1 ~- Wave length: 350 millimicrons
(*)2 --- ~ave len~th: 600 millimicrons
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Examples 13 through 22
Two types of white substrate sheets I and II were
prepared from compositions indicated in Table 3 by using a
calender.
T a b 1 e 3
Comp~sition (part by weight)
Ccmponent ite sheet I White sheet II
Polyvinyl chloride100 100
D. O. P. 75 75
Tit~um dioxide 8 8
Diant D ny trioxide 0 7
Zinc stearate 3 3
The resultant substrate sheets I and II had a thickness
of 0.1 mm.
Separately, eight types of white ultraviolet
ray-reflecting sheets A through H were prepared from
compositions indicated in Table 4 by using a calender.
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T a b 1 e 4
Ccmp~sition (part by weight)
_ _
S h e e t
A B C D E F G H
Polyvinyl 100 100 100 100 100 100 100 100
chloride
D. O. P.75 75 75 75 75 75 75 75
BaSO4 5 25 60 100 100 - - -
Mgo~3 S 25 40 - - 80
Zr2 10 - - - _ _ 80
MgO 5 - - - - - 30
Sb2O3 7 7 7 7 - 7 7 7
Zinc 3 3 3 3 3 3 3 3
stearate
In each of the Examples 13 through 22, a specific
substrate sheet indicated in Table 5 was heat-bonded with a
white ultraviolet ray-reflecting sheet as specified in Table
5, by using a calender.
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T a b l e 5
C ~ ination
. .
E~ple ~strateUltraviolet ray
Nb. sheet abso~ing sheet
13 II A
14 " B
n C
16 " D
17 n E
18 I D
19 I E
II F
21 II G
22 II H
The resultant composite sheets each had a thickness of
0. 2 mm, and exhibited properties, as indicated in Table 6 .
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Tab 1 e 6
Example Ref lectivitY to ReflectivitY to Flan~
No. ~lltraviolèt ray( )1 visible light -retardance
13 78 87 l-st class
14 80 85 "
82 85 "
16 82 85
17 82 85 "
18 82 85 "
19 82 85 2-r~ class
84 85 l-st class
21 85 88 n
22 78 80 "
Examp e ?3 through 29 and Comparison Example 3
In each of the Examples 23 through 29 and Comparison
Example 3, an aqueous suspension having a composition
indicated in Table 7 was prepared.
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Ta b l e 7
C~position (part by weight)
Example Example Ccmparison
No. 23 24 25 26 27 28 29 Exanple 3
(Canponent)
Zr2 50 - - - 30 40 30
BaSO4 ~ 50 ~ _ 20
MgO - - 50 - - lO
Mga)3 ~ ~ - 50 - - 20
2 ~ ~ ~ ~ ~ ~ - 50
Water 100 lO0 100 100 lO0 lO0 100 100
Primal HA-8( ) 50 50 50 50 50 50 50 50
Note (l): (*)l .... An emulsion of a polyacrylic ester
having a concentration of 40g6 by weight
Note (2): The viscosity of each suspension was adjusted to
2,500 c poises by using a snall amount of a a~nia
solution.
A plain weave fabric consisting of polyethylene
terephthalate spun yarns and having a weight of 195 g/m2 and
the following structure:
20/l x 20/1
92 x 55--
was scoured and bleached by an ordinary process and, then,
dried. The dried fabric was immersed in the above-mentioned
aqueous suspension, squeezed with a mangle in such a manner
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that the fabric is impregnated with a portion of the
suspension in an amount corresponding to about 70% of the
weight of the fabrlc, dried at a temperature of 100C and,
finally, heated at a temperature of 150C for two minutes to
5 heat-set the fabric and the polyacrlic ester emulsion on the
fabric.
The results are indicated in Table 8.
T a b 1 e 8
. .. ~
Exam leReflectivity (%) toReflectivity (%) to
NoPultraviolet rays visible light
(350 mll) (600 mlJ)
Example
23 82 87
24 80 84
.25 80 82
26 85 80
27 80 84
28 81 84
29 83 82
Ccmparison 10 90
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Example 30
The same procedures as those described in Example 26
were carried out, except that the aqueous suspension
contained, as an additive, 10 parts by weight of dianitimony
trioxide and the polyethylene terephthalate fabric was
replaced by a plain weave fabric consisting of polyvinyl
alcohol fiber spun yarns which had been water-insolubilized
by treating it with formaldehyde, and having the following
structure:
20/1 x 20/1
92 x 55
The resulting sheet exhibited a reflectivity of 87% to
ultraviolet rays (350 millimicrons), and a reflectivity of
80% to visible light (600 millimicrons), and the flame
retardancy of the sheet was first class.
The water-insolubilized polyvinyl alcohol fiber fabric
per se exhibited a reflectivity of about 60% to ultraviolet
rays (350 millimicrons).
Example 31
The same procedures as those described in Example 30
were carried out, except that the water-insolubilized
polyvinyl alcohol fiber fabric is replaced by nylon 6 fiber
fabric. The results were the same as those of Example 30.
