Cushioning material for forming press

Details Cushioning material for forming press Cushioning material for forming press

1997-07-10

2003-02-04

Cole, Elizabeth M. (Department: 1771)

Fabric (woven, knitted, or nonwoven textile or cloth, etc.)

Woven fabric

Including a foamed layer or component

C442S225000, C442S226000, C442S270000, C442S271000, C442S275000, C442S241000, C442S242000, C442S260000, C442S283000, C442S277000, C442S278000, C428S909000

Reexamination Certificate

active

06514888

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cushioning material for forming press used for pressing of decorative laminates, printed circuit boards, copper-clad laminates (CCL), flexible printed circuit material (FPC), electrical laminates and so on.
2. Description of the Background Art
Referring to
FIG. 1
, when a laminate is to be manufactured by hot press, generally, an object to be pressed is interposed between heating platens
1
and
2
, and a prescribed pressure and heat are applied thereto. At this time of pressing, as shown in the figure, metal mirror plates
4
and
5
are arranged at positions directly in contact with the object
3
to be pressed. Further, in order to apply uniform pressure and heat to the entire surface of the object to be pressed, a flat cushioning material
6
is positioned between heating platen
1
and metal mirror plate
4
, and a flat cushioning material
7
is positioned between heating platen
2
and metal mirror plate
5
.
A primary object of interposing cushioning materials
6
and
7
is to obtain a laminate having superior thickness precision and superior surface smoothness, by applying uniform pressure and uniform heat to the entire surface of the object
3
to be pressed. Therefore, cushioning property, thermal conductivity, heat resistance, durability, dimensional stability, surface releasing property and so on are necessary requirements of cushioning materials
6
and
7
.
Several sheets, for example about 5 to about 20 sheets of kraft paper superimposed on one another have been long used as the cushioning material for forming press. The cushioning material consisting of kraft paper is inexpensive, and it exhibits superior cushioning property at the initial stage of use. However, durability for repetitive use is rather poor, and its working life is only one to at most 5 times of use. Because of such disadvantage, cushioning material formed of kraft paper has gone out of use recently.
Cushioning materials having various structures have been proposed as having improved durability.
One example includes a reinforcing woven fabric embedded in a rubber sheet
8
, such as shown in FIG.
2
. This cushioning material is superior to the one formed of kraft paper in its durability for repetitive use. However, since there is not a space in rubber, when it receives compressive force, side portions which are open expand, causing elongation or permanent set. This change in dimension affects the quality of the laminate to be pressed. In order to suppress such change in dimension, reinforcing woven fabric
9
is embedded. However, by the provision of reinforcing woven fabric
9
, rubber elasticity is lost, and as a result, advantages of rubber sheet
8
such as good cushioning property and the effect of making uniform the pressure are lost. Further, since it does not have any space, thermal conductivity is so good that variation in temperature of heating platens is directly transmitted, causing variation in thermal conductivity.
FIG. 3
shows a cushioning material prepared by needle punching non-woven fabric layer
10
with reinforcing foundation fabrics
11
interposed therebetween. Reinforcing foundation fabric
11
embedded in non-woven fabric layer
10
may be one layer or two or more layers. This cushioning material has good cushioning property as non-woven fabric layer
10
includes spaces, and it also has good heat insulating effect. As for compressive force, unlike rubber, expansion in the direction of the side surfaces does not occur. In other words, dimensional stability with respect to compression is satisfactory.
Though the cushioning material formed of the needle punched non-woven fabric such as shown in
FIG. 3
has the above described advantages, it suffers from the following disadvantages. A non-woven fabric essentially includes ups and downs at its surface and has uneven area weight. Such ups and downs at the surface and the uneven area weight causes variation in thermal conductivity and variation in pressure. In addition, needle punching leads to further unevenness in area weight. The ratio of spaces in the non-woven fabric decreases with long time of use, and therefore thermal conductivity and cushioning property change with time. By contrast, rubber layer
8
shown in
FIG. 2
experiences less change with time, since it does not have any space.
A cushioning material shown in
FIG. 4
includes rubber layers
13
with a reinforcing woven fabric
12
interposed therebetween, and needle punched non-woven fabric layers
14
and
15
such as shown in
FIG. 3
on upper and lower surfaces of the rubber layers
13
. The cushioning material has superior cushioning property of non-woven fabric layers
14
and
15
as well as superior stability with time of rubber layer
13
. However, since non-woven fabric layers
14
and
15
are on the outermost surfaces, disadvantages of the non-woven fabric layer, that is, ups and downs of the surface and uneven area weight are directly reflected on the cushioning material.
A cushioning material shown in
FIG. 5
is prepared by superimposing needle punched non-woven fabric layers
16
and
17
with an adhesive material
18
, which is a glass cloth impregnated with epoxy resin, interposed. Since multiple layers of non-woven fabrics are superimposed in this manner, uneven area weight of each non-woven fabric layer can be offset to some extent. However, since non-woven fabric layers
16
and
17
still exist on the outermost surfaces, the aforementioned disadvantage inherent to the non-woven fabric layer cannot be thoroughly eliminated. Further, the adhesive material described above is hard, and therefore it cannot follow at all the change in shape of non-woven fabric layers
16
and
17
when compressive force is applied. Hence there is a possible problem of separation of the adhesive material caused by damage of glass cloth when the cushioning material is used for a long period of time.
A cushioning material
19
shown in
FIG. 6
is a paper-like material prepared by mixing aromatic polyamide fiber and rock wool. The cushioning material has superior heat resistance, experiences small change in dimension thanks to its material, and it also has the advantage of smaller variation of area weight. However, it has the following disadvantages. Namely, it has poor cushioning property, it has small ups and downs on its surface as it includes fiber material, and layers tend to separate from each other.
FIG. 7
shows a cushioning material for forming press disclosed in Japanese Patent Publication No. 47-46945. The cushioning material has rubber layers
21
and
22
on an upper surface and a lower surface of a needle punched non-woven fabric layer
20
. It is described that silicone rubber, nitrile rubber, butyl rubber or the like may be used for the rubber layer.
FIG. 8
is an enlargement of the cross section of FIG.
7
.
The cushioning material shown in
FIG. 7
has superior cushioning property of the needle punched non-woven fabric, as well as the effect of making uniform the pressure because of rubber elasticity of the surface rubber layers. Different from the cushioning materials shown in
FIGS. 3
to
5
, the cushioning material has rubber layers
21
and
22
positioned on the upper and lower surfaces of needle punched non-woven fabric layer
20
. Therefore, it is superior in that undesirable influences of ups and downs of the surface and uneven area weight of the needle punched non-woven fabric can be offset by the rubber layers
21
and
22
. This is because the unevenness of area weight and ups and downs of the surface can be absorbed by fluidized rubber entering irregular spaces of the fibers at the surface of non-woven fabric layer at the interface between non-woven fabric layer
20
and rubber layers
21
and
22
as shown in
FIG. 8
, when rubber layers
21
and
22
are vulcanized and bonded to non-woven fabric layer
20
during the steps of manufacturing the cushioning material.
However, the cushioning material for forming press disclosed in Japanese Pate

Affiliated with

Also associated with

Rating

Cushioning material for forming press does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Cushioning material for forming press, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cushioning material for forming press will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3150690