Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Woven fabric – Strand material is composed of two or more polymeric...
Reexamination Certificate
2001-03-16
2004-05-18
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Woven fabric
Strand material is composed of two or more polymeric...
C442S228000, C442S229000, C442S238000
Reexamination Certificate
active
06737370
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a press pad for use in single daylight or multi-daylight, i.e. single layer or multi-layer, hot presses. The press pad comprises a woven fabric containing elastomer material.
BACKGROUND INFORMATION
It is conventionally known to use press pads of the above mentioned general type in various types of high pressure and low pressure presses, for example short cycle presses and multi-daylight or multi-layer presses for pressing and laminating melamine sheets or the like onto wood fiberboard or plywood or the like, or high pressure presses for manufacturing high pressure laminates, and various other types of presses for many different uses in many different fields. Since the sheet work-pieces to be pressed or laminated, as well as the components of the above mentioned presses themselves generally have tolerances of their dimensions and the like, the press pads serve the purpose of compensating these tolerances and transmitting the pressing forces uniformly over the entire surface of the sheet goods workpiece that is to be pressed. Simultaneously, the press pads serve to uniformly distribute and transmit the heat from the hot press platen to the sheet goods workpiece.
Typical press pads are conventionally constructed in the form of a single layer or multi-layer arrangement of woven fabric, web or mesh. In view of the above described requirements and functions of the press pad, namely achieving a uniform temperature distribution and pressing force distribution while compensating any tolerances, the woven fabric of the press pad generally comprises or consists of materials that are suitable for use at temperatures up to above 200° C., while possessing the largest possible thermal conductivity together with the greatest possible elastic resilience and spring-back or recovery under intermittent pressure loading.
A conventional press pad of the above described type is known from German Utility Model DE 90 17 587 U1 for example. That conventional press pad comprises a flexible press pad woven fabric made of a yarn of aromatic polyamides, which may be mixed with other yarn materials as required. Furthermore, the woven textile fabric of the press pad shall contain metal threads in an amount between 0 and 70 wt. % relative to the total weight of the press pad, in order to adjust the thermal conductivity of the press pad to the required value.
European Patent Publication EP 0,713,762 A2 discloses another conventional press pad for high pressure and lower pressure presses, whereby the press pad is made of the following components.
Group 1:
1.1 yarn made of aromatic polyamide, which may be mixed with other yarn materials as required and contains metal threads in any desired proportions,
1.2 metal yarn.
Group 2:
2.1 heat resistant filament made of rubber or a rubber mixture,
2.2 heat resistant filament made of silicone or a silicone mixture,
2.3 heat resistant elastic synthetic plastic filament,
2.4 material of the groups 2.1, 2.2 and/or 2.3 with a metal core, whereby this metal core does not have to be fixedly connected with the material that surrounds it,
2.5 material of at least one of the groups 2.1 to 2.4, surrounded by metal threads,
2.6 yarn of the group 1.1, but without metal threads.
A further conventional press pad is known from the published European Patent Specification EP 0,735,949 B1, in which the press pad comprises a woven textile web or fabric with weft threads and warp threads, whereby the warp threads and/or the weft threads comprise a silicone elastomer. For example, the silicone elastomer may be woven into the fabric in the form of solid threads, or in the form of metal wires that are respectively encased or sheathed with silicone elastomer.
In the pressing art, there is a constant trend toward achieving shorter pressing times, which necessarily involve the use of higher press platen temperatures of the pressing equipment. For this reason, the demands placed on the press pads used in such presses have recently been increasing steadily. In this context it has been found that the conventionally known press pads suffer limitations and inadequacies in view of the shorter pressing cycles and higher pressing temperatures. For example, one disadvantage of the previously known press pads is that they have an inadequate chemical resistance, for example with respect to hydraulic oil. Thus, in the event of any hydraulic oil leaking out of a hydraulic press into the woven web of the press pad, the press pad suffers a rapid breakdown or degradation, with a consequent loss of its mechanical properties. Particularly, the above mentioned silicone elastomers or polyamides used in the conventional press pads have an inadequate or non-existent chemical resistance with respect to hot oils, gasoline and other petroleum products, aliphatic and aromatic olefins, chlorinated hydrocarbons, and acids, for example.
Moreover, further problems arise due to the high pressing temperatures and reactions during the pressing process. For example, in connection with the polycondensation of aminoplast resins in the pressing equipment, chemical fission products are generated and penetrate into the woven web of the press pads. These chemical fission byproducts can chemically attack or degrade the material of conventional press pads. Moreover, the conventional press pads subjected to a relatively high continuous duty temperature of 100 to 250° C. become embrittled rather quickly, or become oxidized or hydrolized, whereby the press pads lose their mechanical properties and no longer provide the required pad characteristics.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide a press pad that will better meet the requirements and demands in present day technical innovations in various pressing applications. Particularly, the invention aims to provide a press pad that has a high temperature resistance for constant duty use at temperatures over 250° C., and a chemical resistance against hot oils, gasoline and other petroleum products, aliphatic and aromatic olefins, chlorinated hydrocarbons, and acids. Furthermore, the inventive press pad shall provide a high flexibility and resilient elastic recovery characteristic of the woven web material. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a press pad comprising a woven fabric that contains a substantial proportion of an elastomer selected from the group consisting of fluoroelastomers, fluorosilicone elastomers, blend elastomers prepared by crosslinking a mixture of a raw crude silicone rubber and a raw crude fluorosilicone rubber, and blend elastomers prepared by crosslinking a mixture of a raw crude silicone rubber and a raw crude fluorinated rubber.
Throughout this specification, the term “woven fabric” refers to any woven material such as a woven textile, web, mesh, screen, etc. The weave may be a two-dimensional weave or a three-dimensional weave among several woven layers. The term “elastomer” refers to a solid polymer material that is at least partially crosslinked or vulcanized and that exhibits rubbery elastic extensibility and restoring characteristics, while the term “raw crude rubber” refers to a viscous liquid or semisolid starting material that has little defined resiliency and practically no defined strength, but that forms an elastomer when crosslinked. Generally, the raw crude rubber is the starting material, which is crosslinked to form an elastomer. This starting material of raw crude rubber has also been known in connection with the terms “caoutchouc”, “gum resin”, and the like.
Elastomers significant in this application are also to be distinguished from non-elastomeric thermoplastic polymers or compounds. In this regard, thermoplastics are linear or branched, non-crosslinked polymers that may be repeatedly melted, flowed and reformed (e.g. by various molding techniques) upon being
Fasse W. F.
Fasse W. G.
Juska Cheryl A.
Rheinische Filztuchfabrik GmbH
Salvatore Lynda
LandOfFree
Press pad containing fluoroelastomer or fluorosilicone... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Press pad containing fluoroelastomer or fluorosilicone..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Press pad containing fluoroelastomer or fluorosilicone... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3251769