U.S. patent application number 10/704787 was filed with the patent office on 2004-05-20 for composite structure and production method thereof.
This patent application is currently assigned to Bridgestone Corporation. Invention is credited to Imai, Yasushi, Utsunomiya, Tadashi.
Application Number | 20040096677 10/704787 |
Document ID | / |
Family ID | 12227219 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040096677 |
Kind Code |
A1 |
Imai, Yasushi ; et
al. |
May 20, 2004 |
Composite structure and production method thereof
Abstract
A composite structure comprising a metallic sheet and two
thermoplastic material layers of a layer (A) and a layer (B) which
are placed in turn and integrated with each other, characterized in
that the layer (A) comprises a thermoplastic material capable of
being thermally fusedly adhered to the thermoplastic material in
the layer (B), the metallic sheet and the layer (A) are adhered to
each other, and the layers (A) and (B) are thermally fusedly
adhered to each other; and a process for producing a composite
structure which comprises installing, on a metallic sheet by
coating, a layer (A) comprising a thermoplastic material capable of
being thermally fusedly adhered to a thermoplastic material in a
layer (B) to be placed thereon, and further installing the layer
(B) on the layer (A) by thermally fusedly adhering a desirable
thermoplastic material on the (A).
Inventors: |
Imai, Yasushi;
(Kanagawa-ken, JP) ; Utsunomiya, Tadashi;
(Kanagawa-ken, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Bridgestone Corporation
Tokyo
JP
|
Family ID: |
12227219 |
Appl. No.: |
10/704787 |
Filed: |
November 12, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10704787 |
Nov 12, 2003 |
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09497200 |
Feb 3, 2000 |
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6673460 |
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Current U.S.
Class: |
428/461 |
Current CPC
Class: |
Y10T 428/31696 20150401;
B29K 2705/00 20130101; B32B 27/32 20130101; B29K 2715/006 20130101;
B32B 7/04 20130101; B32B 2037/243 20130101; B32B 2581/00 20130101;
Y10T 428/31678 20150401; B32B 27/08 20130101; B32B 27/302 20130101;
B29C 45/14811 20130101; B32B 2319/00 20130101; B32B 2325/00
20130101; Y10T 428/31692 20150401; B32B 2311/00 20130101; B32B
15/08 20130101 |
Class at
Publication: |
428/461 |
International
Class: |
B32B 015/08; B32B
027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 1999 |
JP |
11-027664 |
Claims
What is claimed is:
1. A composite structure comprising a metallic sheet and two
thermoplastic material layers of a layer (A) and a layer (B) which
are placed in turn and integrated with each other, characterized in
that said layer (A) comprises a thermoplastic material capable of
being thermally fusedly adhered to the thermoplastic material in
the layer (B), said metallic sheet and said layer (A) are adhered
to each other, and said layers (A) and (B) are thermally fusedly
adhered to each other.
2. The composite structure according to claim 1, wherein the layer
(A) comprises a modified polyolefinic resin, and the layer (B)
comprises a styrenic thermoplastic elastomer.
3. The composite structure according to claim 1, wherein the
metallic sheet is that subjected to non-electrolytic nickel
plating.
4. The composite structure according to claim 1, which is used as a
sealing member.
5. The composite structure according to claim 4, wherein the
sealing member is a gasket fitted to a cover for a hard disc
drive.
6. A process for producing a composite structure which comprises
installing, on a metallic sheet by coating, a layer (A) comprising
a thermoplastic material capable of being thermally fusedly adhered
to a thermoplastic material in a layer (B) to be placed thereon,
and further installing the layer (B) on said layer (A) by thermally
fusedly adhering a desirable thermoplastic material on said layer
(A).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a composite structure which
comprises a metallic sheet and thermoplastic materials and a
process for the production of said composite structure. More
particularly, the present invention is concerned with a composite
structure which is well suited for use in a gasketed cover and the
like to be used for housing electronic equipment, etc. and in which
an injection molded thermoplastic material is integrated with a
metallic sheet with favorable adhesivity by coating the metallic
sheet in advance, with an adhesive; and a process for readily and
efficiently producing said composite structure.
[0003] 2. Description of the Related Arts
[0004] The development of electronic equipment in recent years
really amazes the persons concerned. The aforesaid equipment, which
is subjected to printed circuit on a substrate by the use of
integrated circuits utilizing semiconductors, is directed to
compactified lightweight equipment, and is prone to be readily
damaged by moisture or dampness in particular. Accordingly, the
hermetically sealing properties of a case housing electronic
equipment is a factor of importance for the performance and
durability of the electronic equipment.
[0005] The case housing electronic equipment is constituted of a
box body and a cover body, which are integrated by interposing on
the jointing surface thereof, a gasket made of vulcanized rubber, a
urethane foam and a thermoplastic material or the like. The gasket
is usually in the form of a gasket which is fitted to a cover body
and thus fixed to the cover, but there is unavailable a favorable
method of adhesively bonding the gasket to the cover body.
Accordingly, the fixation is carried out by a (1) method comprising
fixing the gasket on the cover body by means of a double-coated
tape, a (2) method comprising making holes in the cover body and
fixing a gasket material from both sides of the cover body through
the holes or the like method. The gasketed cover body is fixed on a
box body by means of screws and accordingly, the fixing job is
markedly facilitated by the adhesion of the gasket to the cover
body.
[0006] As the above-mentioned (1) method comprising fixing the
gasket on the cover body by means of a double-coated tape, there is
usually adopted a method in which a sheet like gasket material to
which a double-coated tape is adhered, is punched into a shape of
gasket, and the resultant gasket is fixed to the cover body.
However, said method is involved in such problems that most of the
sheet-like gasket material after punching remains as waste material
and besides, the production process is made intricate or
troublesome, thus inevitably increasing the production cost, since
the gasket is fixed to the cover body after the gasket material has
been punched into a shape of gasket.
[0007] In addition, in the (2) method comprising making holes in
the cover body and fixing a gasket material through the holes,
since the gasket material is exposed on the upper side of the cover
body, the gasket material exposed thereon is sometimes upturned or
curled when the cover body is inserted into the space of an
electronic equipment main body, said space being narrowed
accompanying the recent compactified electronic equipment part
items. Thus, there is caused the problem that such upturning or
curling is responsible for defective sealing properties.
[0008] Moreover, in the case where the gasket which is fitted to a
cover body and which is produced by such a method, is used in a
hard disc unit, there is caused the problem that it is impossible
to suppress the vibration due to the rotation of the hard disc.
[0009] On the one hand, the adhesion between a thermoplastic
material and a metallic sheet as the cover body, is usually carried
out by a method in which the thermoplastic material is subjected to
adhesion treatment on the surface thereof by corona discharge or
the like, and thereafter is stuck to the metallic sheet by using an
epoxy-based or a urethane-based adhesive. Nevertheless, the job in
said method is intricate and troublesome, and is involved in gas
generation problem, whereby the method is inapplicable to a gasket
for use in electronic equipment.
[0010] In order to simplify and facilitate the aforesaid job,
consideration is given to a method comprising injection molding an
adhesive thermoplastic material for the purpose of direct adhesion.
However, such a thermoplastic material, even when being made rather
hard, is enlarged upon injection molding, thereby making it
impossible to employ the molded product as such as a gasket.
Therefore, said method has not been adopted to the production of a
gasket for a cover body in a hard disc.
SUMMARY OF THE INVENTION
[0011] Under such circumstances, it is a general object of the
present invention to provide a composite structure which comprises
a metallic sheet and a thermoplastic material that are integrated
in good adhesion by injection molding, and which is excellent in
such a performance as vibration-damping properties and is well
suited for usage in a gasket fitted to a cover body to be used for
housing electronic equipment and the like.
[0012] Other objects of the present invention will be obvious from
the text of the specification hereinafter disclosed.
[0013] In view of the foregoing, intensive extensive research and
investigation were accumulated by the present inventors in order to
develop the above-mentioned composite structure having favorable
properties. As a result, it has been found that the general object
can been achieved by the composite structure which is equipped, on
a metallic sheet by coating, with a layer comprising a
thermoplastic material capable of being thermally fusedly adhered
to a thermoplastic material to be placed thereon, and further
equipped on said layer with a layer comprising a desirable
thermoplastic material by means of thermal fusion adhesion. It
being so, the present invention has been accomplished on the basis
of the above-mentioned findings and information.
[0014] Specifically, the present invention provides a composite
structure comprising a metallic sheet and two thermoplastic
material layers of a layer (A) and a layer (B) which are placed in
turn and integrated with each other, characterized in that said
layer (A) comprises a thermoplastic material capable of being
thermally fusedly adhered to the thermoplastic material in the
layer (B), said metallic sheet and said layer (A) are adhered to
each other by coating, and said layers (A) and (B) are thermally
fusedly adhered to each other. The present invention further
provides a process or producing a composite structure which
comprises installing, on a metallic sheet by coating, a layer (A)
comprising a thermoplastic material capable of being thermally
fusedly adhered to a thermoplastic material in a layer (B) to be
placed thereon, and further installing the layer (B) on said layer
(A) by thermally fusedly adhering a desirable thermoplastic
material on said layer (A).
BRIEF DESCRIPTION OF THE DRAWING
[0015] FIG. 1 is a perspective illustration which shows one example
of a gasket fitted to a cover body according to the present
invention, wherein the symbols 1 and 2 denote gasket and cover
body, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The composite structure according to the present invention
comprises a metallic sheet and two thermoplastic material layers of
a layer (A) and a layer (B) which are placed in turn and integrated
with each other.
[0017] The above-mentioned metallic sheet is not specifically
limited, but can be properly selected for use according to the
purpose of use of the composite structure, from cold rolled steel
sheets, galvanized steel sheets, aluminum/zinc alloy plated steel
sheets, stainless steel sheets, aluminum sheets, aluminum alloy
sheets, magnesium sheets and magnesium alloy sheets, and the
like.
[0018] There is preferably usable a metallic sheet which is treated
with non-electrolytic nickel plating for its being inexpensive and
excellent in corrosion resistance. As a method for non-electrolytic
nickel plating, there is usable any of well known methods that have
heretofore been applied to metallic raw materials, for instance, a
method which comprises immersing a metallic sheet to be treated in
a non-electrolytic nickel plating bath comprising an aqueous
solution at a pH of approximately 4.0 to 5.0 and at a temperature
of approximately 85 to 95.degree. C. which contains nickel sulfate,
sodium hypochlolite, lactic acid, propionic acid and the like each
in a proper proportion.
[0019] The thickness of the metallic sheet to be employed in the
the present invention is properly selected for use according to the
purpose of use of the composite structure, and is in the range of
usually from 0.1 to 2 mm, preferably from 0.2 to 1 mm.
[0020] The layer (A) is a layer comprising a layer capable of being
thermally fusedly adhered to the thermoplastic material in the
layer (B) to be equipped thereon. The thermoplastic material in the
layer (A) is properly selected for use according to the type of the
thermoplastic material to be used in the layer (B), for instance,
from polyolefinic resin, polystyrenic resin, acrylic resin and the
like. In the case where a styrenic thermoplastic elastomer is used
in the layer (B), it is advantageous to use a modified polyolefinic
resin as a thermoplastic material in the layer (A). In this case,
the polyolefinic resin is exemplified by a homopolymer of an
.alpha.-olefin such as ethylene; propylene; butene-1;
3-methylpentene-1; and 4-methylpentene-1, a copolymer of at least
two in these, and a copolymer of any of these and an other
polymerizable unsaturated monomer. Typical examples thereof include
ethylenic polymer such as high density, intermediate density and
low density polyethylenes, straight-chain low density polyethylene,
ethylene/vinyl acetate copolymer and ethylene/ethyl acrylate
copolymer, propylenic polymer such as propylenic homopolymer,
propylene/ethylene block or random copolymer,
propylene/ethylene/diene compound copolymer, polybutene-1; and poly
4-methylpentene-1.
[0021] In order to enhance the adhesivity to the metal, there are
effectively usable the above-mentioned resins incorporated with an
acid anhydride, a functional group such as carboxyl group,
carboxylic acid ester group or chlorosulfonate group, or a
halogen.
[0022] The layer (A) in the present invention is installed onto the
metallic sheet in good adhesion by means of coating. In this case,
the coating is carried out usually at a temperature close to the
softening point or melting point of the thermoplastic material to
be used. The thickness of the layer (A) is selected in the range of
usually from 3 to 100 .mu.m, preferably from 5 to 30 .mu.m.
[0023] In the composite structure according to the present
invention, a thermoplastic material layer as the layer (B) is
formed on the layer (A) by means of thermal fusion adhesion. The
thermoplastic material which constitutes the layer (B) is not
specifically limited, but can be properly selected for use from
various materials according to the purpose of use of the composite
structure.
[0024] In the case where, for instance, the composite structure is
used as a sealing member, and the gasket portion is the layer (B),
the thermoplastic material which constitutes the layer (B) is
preferably a thermoplastic material having a low hardness of less
than 60 degrees in terms of JIS hardness A. Examples of said
thermoplastic material having a low hardness include thermoplastic
elastomers of styrenic base, olefinic base, urethane based and
acrylic base, respectively. In particular, with regard to a case
for housing electronic equipment, it is preferable to use such a
material that surely interrupts moisture and air and besides does
not generate a halogen base gas or an acidic gas. From the
viewpoint of adhesivity to the box body of a case and tackiness, it
is preferable to use a material having a JIS hardness being less
than 60 degrees, especially being in the range of 15 to 45 degrees.
The above-mentioned thermoplastic material is preferably a
thermoplastic elastomer of styrenic base, which is exemplified by
styrene/butadiene/styrene block copolymer (SBS), hydrogenated
styrene/butadiene/styrene block copolymer (SEBS), styrene/isoprene
block copolymer (SIR), styrene/isoprene/styrene block copolymer
(SIS) and hydrogenated styrene/isoprene/styrene block copolymer
(SEPS).
[0025] Specific examples of the foregoing styrenic thermoplastic
elastomer include "Rubberon" manufactured by Mitsubishi Chemical
Industries Co., Ltd., specifically exemplified by "Rubberon
MJ4300B" (trade name) having a JIS hardness A of 45 degrees and
"Rubberon T320C" (trade name) having a JIS hardness A of 15
degrees, "Septon" manufactured by Kuraray Co., Ltd., specifically
exemplified by "Septon 2063" (trade name) having a JIS hardness A
of 36 degrees, and "Elastomer AR" manufactured by Aron Kasei Co.,
Ltd. Different from EPDM and butyl rubber, the styrenic
thermoplastic elastomer need not vulcanization and can be recycled,
thereby greatly contributing to cost curtailment. Specific examples
of the olefinic thermoplastic elastomer include "Santprene"
manufactured by A. E. S. Japan Inc. (trade name) having a JIS
hardness A of 45 degrees.
[0026] The thermoplastic material which constitutes the layer (B)
may be used alone or in combination with at least one other.
[0027] With respect to the composite structure according to the
present invention, the thickness of the layer (B) to be placed on
the aforesaid layer (A) by means of thermal fusion adhesion is not
specifically limited, but can be properly selected for use in
accordance with the purpose of use of the composite structure, and
it is in the range of usually 0.1 to 5 mm, preferably 0.2 to 2
mm.
[0028] It is possible in the present invention that the
thermoplastic material layer as the layer (B) be incorporated, as
desired and to the extent that the objects of the present invention
are not impaired, with such additives as an antioxidants (age
resisters), ultraviolet absorbers, light stabilizers and a variety
of fillers specifically exemplified by carbon black, talc, barium
sulfite, calcium carbonate, magnesium carbonate, metal oxide, mica,
graphite, aluminum hydroxide, various metallic powders, wood
chipping, glass powder, ceramic powder, granular or powdery
polymer, glass fiber, metallic fiber, and organic fiber.
[0029] Particularly preferably usable composite structure in the
present invention, is that comprising a styrenic thermoplastic
elastomer as the layer (B) and a polyolefinic thermoplastic
elastomer as the layer (A).
[0030] The process for producing the composite structure according
to the present invention is not specifically limited, provided that
said process is capable of producing the composite structure
imparted with the above-mentioned properties. According to the
simplified process of the present invention as described hereunder,
it is made possible to efficiently produce a desirable composite
structure.
[0031] In the process according to the present invention, first of
all, the layer (A) is formed on a metallic sheet which has been
preferably subjected to non-electrolytic nickel plating by coating
the metallic sheet with a thermoplastic material (hereinafter
sometimes referred to as "thermoplastic material I") capable of
being thermally fusedly adhered to the thermoplastic material in
the layer (B) (hereinafter sometimes referred to as "thermoplastic
material II") to be placed on the layer (A). The metallic sheet or
the metallic sheet which has been subjected to non-electrolytic
nickel plating may be subjected at need, to a surface treatment
such as plasto-treatment, treatment by hair line, etching, crack
plating, oxidation, anodic oxidation, corona discharge, plasma or
primer coating.
[0032] The layer (A) may be formed by the use of an aqueous
emulsion of the thermoplastic material I from the standpoint of
environmental concern or suppression of gas generation.
Specifically in this case, the layer (A) may be formed by
pulverizing the thermoplastic material I such as polyolefinic resin
and emulsifying the resultant pulverized material with an
emulsifier according to a previously well known method to prepare
an aqueous emulsion containing the thermoplastic material I, and
applying coating of the resultant emulsion. In this case, an
adhesive component with good adhesivity of urethane base or epoxy
base may be added thereto as required, to the extent that the
objects of the present invention are not impaired thereby.
[0033] Subsequently, by applying the solution of the modified
adhesive polyolefinic resin onto the metallic sheet so that the
thickness of the resultant coating comes to be a desired value by a
well known method such as brush coating, padding coating, spray
coating, roller coating and flow coating, followed by drying, the
layer (A) is formed adhesively onto the metallic sheet.
[0034] It is preferable to apply the solution of the modified
adhesive polyolefinic resin only to the portion where the gasket
material is adhered by means of a dispenser, pat printing, screen
printing or the like from the viewpoint of preventing gas
generation and curtailing the manufacturing cost.
[0035] Subsequently, by thermally fusedly adhering a desired
thermoplastic material II, for instance, styrenic thermoplastic
elastomer or the like onto the layer (A) so as to form the layer
(B). In the formation of the layer (B), there is preferably used
injection insertion method, whereby for instance, a metallic sheet
equipped with the layer (A) is arranged in a mold, and the
thermoplastic material II is injectedly poured onto said layer (A)
so that the thermoplastic material II and the thermoplastic
material I are thermally fusedly adhered to each other to form the
layer (B) having a desired thickness on the layer (A).
Alternatively, there is usable a method in which the layer (B) is
formed onto the layer (A) by thermally fusedly adhering the layers
by means of pressing method.
[0036] The thermal fusion adhesion temperature is properly selected
according to the types of the thermoplastic material I and the
thermoplastic material II. In the case, for instance, where
polypropylene is used as the thermoplastic material I and SEBS or
SEPS, that is, styrenic thermoplastic elastomer is used as the
thermoplastic material II, said temperature is in the range of
approximately 170 to 200.degree. C.
[0037] In such a manner as described hereinbefore, there is
obtainable the composite structure according to the present
invention wherein the metallic sheet and the thermoplastic
materials are integrated with one another.
[0038] According to the process of the present invention, it is
made possible to readily integrate the thermoplastic material for a
gasket and the metallic sheet through injection molding only-by
applying in advance, the solution of an adhesive resin without
deteriorating the physical properties of the thermoplastic
material. Further, the composite structure according to the present
invention is excellent in vibration-damping properties, since the
metallic sheet is laminated with the thermoplastic material I, and
it is well suited for usage in the gasket fitted to a cover body to
be used in sealing members, particularly electronic equipment.
[0039] Moreover according to the present invention, it is made
possible to prevent the adhesion of dirt such as dust and the leak
of electromagnetic wave by mixing an electroconductive material in
the thermoplastic material I and/or the thermoplastic material II,
and besides to prevent heat accumulation in a hard disc by by
mixing a material having high heat releasabity in the thermoplastic
material I so as to enable to release internally generated heat to
the outside.
[0040] As described hereinbefore, the composite structure according
to the present invention, wherein the metallic sheet and
thermoplastic materials are integrated with one another in good
adhesivity by applying in advance the adhesive resin onto the
metallic sheet, and then injection molding the thermoplastic gasket
material, is excellent in vibration-damping properties, and is is
well suited for usage in the gasket fitted to a cover body to be
used in electronic equipment and the like.
[0041] Furthermore, the production process according to the present
invention enables to efficiently produce the composite structure,
dispensing with intricate or troublesome steps.
[0042] In what follows, the present invention will be described in
further detail with reference to comparative examples and working
examples, which however shall never limit the present invention
thereto.
EXAMPLE 1
[0043] An aluminum sheet which had a thickness of 0.5 mm and which
was equipped with non-electrolytic nickel-plated film of 5 .mu.m in
thickness was coated thereon with a solution of a modified adhesive
polyolefinic resin (maleic acid-modified copolymer of propylene,
ethylene and butene, manufactured by Mitsubishi Chemical Industries
Ltd. under the trade name "Unistol P-802"), and the resultant
coated sheet was heat treated at 50.degree. C. to prepare an
aluminum sheet having the coated film of 30 .mu.m in thickness.
[0044] Subsequently, onto the resultant adhesive polyolefinic resin
coat formed on the aluminum sheet, there was insertion molded a
styrenic thermoplastic elastomer having a JIS hardness A of 45
degrees (manufactured by Mitsubishi Chemical Industries Ltd. under
the trade name "Rubberon MJ 4300B") in a thickness of 0.5 mm by the
use of an injection molding machine under the temperature
conditions of the nozzle and cylinder at 180.degree. C. and the
insert aluminum sheet at room temperature to prepare a composite
structure.
[0045] The composite structure thus obtained was subjected to peel
test for styrenic thermoplastic elastomer in accordance with JIS Z
0237. As a result, there were found the destruction of the material
of the thermoplastic elastomer itself along with the delamination
on the interface between the aluminum sheet and the adhesive
polyolefinic resin coat. However, the peeling strength at the time
of delamination was at least 1.6 kg/25 mm, thus showing sufficient
adhesion strength for fixing the composite structure to the main
body by means of screws.
COMPARATIVE EXAMPLE 1
[0046] The procedure in Example 1 was repeated except that the
adhesive polyolefinic resin coat was not formed on the aluminum
sheet subjected to non-electrolytic nickel plating, namely the
styrenic thermoplastic elastomer was directly insertion molded onto
the aluminum sheet. As a result, because of failure in adhesion,
the elastomer was separated from the aluminum sheet at the time of
taking out thereof.
EXAMPLE 2
[0047] FIG.1 is a perspective illustration which shows a gasket
fitted to a cover to be used for a case housing a hard disc drive
unit as one embodiment of the composite structure according to the
present invention, and which is viewed from the sealing surface
side, wherein a gasket 1 is adhered to the surface of a metallic
cover body 2 as a cover for the case housing a hard disc drive
unit. Such equipment and machinery as a magnetic disc, a magnetic
head and an actuator are arranged in the box body side of the case
housing a hard disc drive unit, closed with said box body (not
illustrated on the drawing) and said gasket fitted to the cover,
and are housed in said case.
[0048] As the cover body 2, use was made of an aluminum sheet which
had a thickness of 0.5 mm and which was equipped with
non-electrolytic nickel-plated film of 5 .mu.m in thickness, was
coated thereon with a solution of a modified adhesive polyolefinic
resin (maleic acid-modified adhesive polypropylene, manufactured by
Mitsubishi Chemical Industries Ltd. under the trade name "Unistol
R-300"), and the resultant coated sheet was heat treated in the
same manner as in Example 1 to prepare an aluminum sheet with the
coated film of 30 .mu.m in thickness.
[0049] Subsequently, onto the resultant polypropylene coat formed
on the aluminum sheet, there was insertion molded a styrenic
thermoplastic elastomer in a thickness of 0.5 mm in the same manner
as in Example 1 to form the gasket 1 and prepare a gasket fitted to
a cover. As the result of peel test in accordance with JIS Z 0237,
the peeling strength at the time of delamination was at least 1.4
kg/25 mm, thus showing sufficient adhesion strength for fixing said
gasket to the main body by means of screws.
[0050] The gasket fitted to a cover thus prepared was used as the
cover of the case housing a hard disc drive unit for a period of 30
days so that the gasket portion faced the box body, and thereafter
visual observation was made of the gasket portion. As a result, the
dust preventive properties during the service was satisfactory
without observable sagging on the gasket portion. Further
observation was made of the vibration-damping performance of the
gasket fitted to a cover in the hard disc drive unit. As a result,
resonance due to the hard disc was not observed.
COMPARATIVE EXAMPLE 2
[0051] The procedure in Example 2 was repeated except that the
modified adhesive polyolefinic resin coat was not formed on the
aluminum sheet. Thus, there was prepared a gasket fitted to a cover
by injection molding a styrenic thermoplastic elastomer onto a
cover body having holes for fixing said elastomer. Then,
observation was made of the vibration-damping performance of the
gasket fitted to a cover in the hard disc drive unit. As a result,
resonance due to the hard disc was observed.
[0052] As is obvious from the foregoing results of evaluations, the
gasket fitted to a cover as one of the embodiments of the present
invention, can readily be produced, exhibits favorable dust
preventive properties owing to good adhesion between the gasket and
the cover body when used as a cover of a case housing a hard disc
drive unit, and besides is free from any deformation even after a
long time of service because of the gasket being constituted of a
material having a low hardness.
* * * * *