THREAD, WOVEN FABRIC AND METHOD FOR PRODUCING THE SAME

Abstract

A thread made from extruded silicone rubber that is crosslinked after extrusion, wherein the thread includes a fluor rubber portion exclusively at a surface of the thread.

Claims

1. A thread made from extruded silicone rubber that is crosslinked after extrusion, wherein the thread includes a fluor rubber portion exclusively at a surface of the thread.

2. A fabric, comprising: warp threads or weft threads that are made from the thread according to claim 1.

3. The fabric according to claim 2, wherein the warp threads or weft threads are made from a stranded metal or stranded copper.

4. A hydraulic press, comprising a press pad made from the fabric according to claim 2.

5. A method for producing a thread, the method comprising the steps: continuously extruding the thread from silicone rubber; crosslinking the thread after the extruding; and producing fluor rubber in the thread exclusively by fluorizing a surface of the thread after the crosslinking, wherein the fluorizing is performed by a fluorizing gas.

6. A method for producing a fabric, the method comprising the steps: providing warp threads or weft threads with a coating made from silicone rubber; crosslinking the silicone rubber; and performing surface fluorization of the coating with a fluorization gas to produce fluor rubber in the coating.

7. The method for producing the fabric according to claim 6, wherein the warp threads or weft threads are initially coated by the silicone rubber and subsequently woven into the fabric.

8. The method according to claim 6, wherein the silicone rubber is crosslinked and fluorized before weaving.

9. The method according to claim 6, wherein the warp threads or weft threads are initially woven into the fabric and the fabric is coated with the silicon rubber thereafter.

10. The method according to one of the claim 5, wherein the fluorization gas is made from at least 0.5% by volume or at least 10% by volume fluoride gas or fluorization agent and from at least 50% volume % inert gas.

11. A hydraulic press, comprising a press pad made from the fabric according to claim 3.

12. The method according to claim 7, wherein the silicone rubber is crosslinked and fluorized before weaving.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention is now described based on an embodiment with reference to a drawing FIGURE.

DETAILED DESCRIPTION OF THE INVENTION

[0019] A thread 1 according to the invention is continuously extruded with 1.5 mm thickness from a non-crosslinked silicone rubber with a core thread made from stranded copper threads and crosslinked into a silicone elastomeric material in a heating zone that is downstream of the extruder. The drawing FIGURE illustrates an arrangement 2 for further processing a thread 1 after extrusion and crosslinking. The thread 1 runs through a first gate system 3 into a processing chamber 4. A roller system 5 with rising rollers and descending rollers 6 determines a processing time of the fluorization gas in the range of approximately two minutes based on a number of the rollers 6 and their distances.

[0020] The arrangement 2 is supplied with gas through a valve 7 that introduces inert gas, a valve 8 that introduces a fluor gas mix and a valve 9 that introduces air. A dosing measuring device 10 measures the introduced gas volumes. Another valve 8 controls the exhaust conduit 12, and a last valve 13 controls the exhaust gas to the absorber 14 for precipitating hydrogen fluoride and hydrogen fluoride mixes.

[0021] The fluoride thread 1 exits the arrangement 2 through a second gate system 15 and is then run to the winding station which is not illustrated. The gate systems 3, 15 prevent an exit of a non-illustrated fluorization gas from the processing chamber 4.

[0022] After exiting from the heating zone, the thread 1 has a temperature between 50 and 80 degrees C., which helps fluorization. In an alternative embodiment, the processing chamber 4 can be fitted with an additional heater.

[0023] The processing chamber 4 is initially flushed with inert gas (nitrogen argon neon, helium or another noble gas) at atmospheric pressure at room temperature and purged from air, thereafter the fluorization gas including 10 volume % fluor gas (F.sub.2) and 90 volume % nitrogen (N.sub.2) is introduced. In an alternative embodiment, the fluorization gas can be made from halogen or noble gas fluoride instead of molecular fluoride.

[0024] A dosing device 10 controls filling of the processing chamber 4 while the valve to the absorber is closed. Since the process is continuous, the process gas has to be continuously regulated.

[0025] The fluorization is a chemical reaction and not a coating. Therefore, a penetration depth of the fluoride atoms into the surface of the silicone elastomeric material is in the molecular range. The thread and the coating, therefore, have a fluorosilicone portion only in their surface. The main chain of silicone rubber is made from alternating silicone and oxygen atoms and attached hydrocarbon groups. The fluorization replaces hydrogen atoms with fluor atoms at a surface in the hydrocarbon groups. The hydrogen fluoride (HF) that is being generated is run over a calcium carbonate absorber and converted into calcium fluoride.

[0026] After fluorization the elastomeric threads are made from polymethylsiloxane and fluorosilicone rubber copolymers. Since a binding energy of carbon and fluor is higher than a binding energy of carbon and hydrogen, the fluorosilicone rubber that is being produced has much higher thermal and chemical resistance.

[0027] The high elasticity of the silicone elastomeric material is maintained. The fluorized surfaces furthermore have a blocking layer against non-polarized substances. Simultaneously, a permeation, diffusion and migration and an exit of volatile components from the silicone elastomeric material which can lead to odors is reduced. Overall, an extended service life of the press pads with constant material quality is achieved.

[0028] The coating of the thread 1 has a surface tension of 31 mN/m before fluorization and a surface tension 56 mN/m after fluorization. The static friction and dynamic friction is reduced by half from approximately 4.5 Newton to 2 Newton. The friction forces on glass are reduced from approximately 10 Newton to 0.8 Newton. The surface of the thread 1 according to the invention therefore does not have any tackiness after fluorization. Using release agent additives, in particular talcum powder, before the threads 1 are wound onto the coils is not required. Contaminations by deposits of the release additives at the machine components of the weaving arrangements do not occur anymore. The thread 1 runs perfectly without stopping, in particular in the weft direction, in the weaving plant. The static friction and the dynamic friction and tackiness is significantly reduced compared to the prior art or eliminated. Additionally, anaerobic aging is substantially prevented by depolymerization of the silicone elastomeric material.

[0029] The thread 1 according to the invention and the press pad made from the thread according to the invention have a high level of resistance against hot vapor, hot naphtha oil and aromatic oils, gasoline, olefatic and aromatic olefins, ketones, silicone oil, hydrogen fluorides, acids and bases, and good long-term resistance and good long-term stability at high temperatures greater than 130 degrees C. The thread 1 and the press pad have a high level of flexibility and good resetting properties.

REFERENCE NUMERALS AND DESIGNATIONS

[0030] 1. Thread [0031] 2. Arrangement [0032] 3. Gate system [0033] 4. Treatment chamber [0034] 5. Roller system [0035] 6. Roller [0036] 7. Valve for inert gas [0037] 8. Valve for fluor gas and fluor gas mix [0038] 9. Valve for air [0039] 10. Dosing measuring device [0040] 11. Exhaust air valve [0041] 12. Exhaust air conduit [0042] 13. Exhaust air valve [0043] 14. Absorber [0044] 15. Gate system