RU2015901C1 - Method for production of fluoroplastic tape - Google Patents

Abstract

FIELD: manufacture of packing rings and spacers in mechanical engineering. SUBSTANCE: tablet is formed fully or partially by successive growing on of cylindrical layers with different amount and composition of filler or their fragments of uncompacted paste with pressing of each layer or its fragment separately to obtain multilayer tablet with functional layers. Tablet is extruded through discharge head and produced tube is cut along generating line, flatten and rolled by rolls. Produced tape is thermally stabilized by its winding on metal drum with fixation of tape free ends, heating and cooling. EFFECT: higher efficiency. 2 cl, 8 dwg

Description

 The invention relates to methods for processing polytetrafluoroethylene (PTFE 4D) and can be used in the manufacture of o-rings and gaskets in mechanical engineering and transport.

 There is a known method of manufacturing tubular products from fluoroplastic, which consists in preparing a homogeneous mixture of fluoroplastic powders, an inert filler and organic lubricant, from which a tube called an extrudate is produced by piston extrusion through a concentric slot and then subjected to drying, sintering and hardening operations.

 A known method of producing a multilayer film (tape) by applying additional layers to the base surface, in different ways (painting, spraying, etc.).

 However, a product with functional layers applied in this way due to low adhesion is characterized by limited durability.

 Known is the closest method of manufacturing a fluoroplastic tape, including the preparation of a homogeneous paste from a mixture of fluoropolymer powders with or without filler and organic lubricant, forming from the paste by pressing tablet blanks, obtaining a tube from the tablet blank by piston extrusion through ring nozzles, followed by drying sintering and hardening.

 This method does not allow to obtain tapes with layers that differ from each other in the concentration and composition of the filler and, accordingly, characteristics that are set by the functional purpose of the product during operation.

 The objective of the invention is to increase the operational life of sheet products by forming functional layers in a fluoroplastic tape.

 This goal is achieved in that the molding of the tablet preform is fully or partially carried out by sequentially building up cylindrical layers with different contents and composition of the filler or fragments thereof from the unconsolided paste, pressing each layer or its fragment separately to obtain a multilayer tablet preform with functional layers, which is extruded through nozzles, and the resulting tube is cut along the generatrix, deployed on a plane and rolled on rolls.

 In addition, the obtained tape is thermofixed by screwing it onto a calibration metal drum, fixing the free ends of the tape, heating and cooling.

 The implementation in the manufacturing process of a multilayer tape with functional layers that differ from each other in characteristics and, therefore, in properties, operations of cutting the tube along the generatrix, deploying it on a plane, followed by rolling on rolls, and heat setting allows you to get a multilayer fluoroplastic tape, which significantly expands the range of existing equipment and allows without significant alterations to increase the operational durability of sheet products. Introduction to the manufacturing process of cutting and deployment operations on the plane of the tube allows an equally well-established process for manufacturing a multilayer tube to obtain a multilayer tape.

 The introduction to the manufacturing process of the operation of rolling the tape on rolls with an adjustable clearance allows the calibration of the tape.

 The proposed method provides for obtaining a material that is uniform in its basic composition (fluoroplastic), which at the same time contains functional layers, i.e., a filler in the basic composition, which is not found in tape products sold by known manufacturing methods.

 Figure 1-8 shows the technological sequence of the implementation of the proposed method.

 The technological sequence of the implementation of the proposed method includes the following basic operations 1-8, presented respectively in Fig.1-8.

 Operation 1 - preparation of a homogeneous paste from a mixture of fluoroplastic powders, an inert filler (if necessary, and organic lubricant).

 Step 2 - tabletting, which consists in forming a tablet blank fully or partially by successively building up cylindrical layers (or fragments thereof) from uncompacted paste, accompanied by compaction of each layer (or its fragments) individually, mainly by isostatic or compression-isostatic pressing.

 Operation 3 - obtaining from a tablet blank tube by piston extrusion through a concentric gap.

 Step 4 - heat treatment of the extrudate (drying, sintering and hardening).

 Operation 5 - cutting the tube along the generatrix.

 Operation 6 - deployment of the cut tube on a plane.

 Operation 7 - rolling the tape on the rolls with an adjustable gap.

 Operation 8 - thermal fixation, which consists in wrapping the tape on a calibration drum, fixing the free ends of the tape and heating, followed by cooling.

 PRI me R. The manufacture of multilayer fluoroplastic tape with a thickness of 0.89 mm, a width of 12 mm, with a thickness of the outer layers of 0.3 mm, and the inner 0.29 mm.

 The method is implemented in the sequence depicted in figure 1 with the formation of the tablet blanks by compression-isostatic compaction of the layers of paste.

 Operation 1 (cooking pasta).

 To form the inner layer of the tablet blanks, a paste (with an inert filler-soot) of the following composition is used (composition a: fluoroplastic powder 4D grade SH, GOST 14906-77 (100 parts by weight), carbon black according to TU 14-7-24-73 (2 parts by weight) and organic lubricant - isooctane according to GOST 5394-70 (18 parts by weight). To form the outer layers of the tablet blanks, a paste (with a filler) of the following composition is used: fluoroplastic powder 4D grade Ш GOST 14906-77 (100 parts by weight), DM-2TU 48-19-133-85 molybdenum disulfide (5 parts by weight), coke according to GOST 25731-88 (15 parts by weight) and isooctane organic lubricant according to GOST 5394- 79 (18 parts by weight) (with becoming b).

 Operation 2 (tabletting).

Equipment - tablet press S-1387. In the cylinder of the press (diameter 112 mm), a pre-compacted layer made of a paste of composition a is placed by compression pressing in a tablet press under a pressure of 4 kgf / cm ² . The dimensions of the layer are dxDxh = = 50x92x300 mm. The inner and outer annular cavities are filled with a paste of composition b, after which an isostatic compaction of the inner and outer layers of the paste is performed by compressing layer a with a plunger. Pressing pressure 20 kgf / cm ² .

 Operation 3 (extrusion).

Equipment - extrusion press UESS-1. Obtained after operation 2, the tablet blank is placed in an extrusion press and extruded under a pressure of 150 kgf / cm ² .

 Operation 4 (heat treatment).

The obtained after operation extrudate is dried at 40-100 ^{° C,} sintering at 380-400 ^{° C,} followed by quenching with heating to 345-375 ^C and cooled in a water bath.

 Operation 5 (cutting). The equipment is knives.

 Received after operation 4, the tube is cut along the generatrix.

 Operation 6 (deployment).

 Obtained after operation 5, the cut tube is deployed on a plane.

 Operation 7 (rolling).

 Equipment - roller track with height-adjustable pinch roller. The limit position of the gap is set at the lower limit of the tolerance band on the thickness of the tape.

 Operation 8 (heat setting).

Equipment - oven. The obtained after Step 6 and 7, the tape 7 is wound on the drum calibration ⌀ 120 mm, fixed and free ends of the tape are subjected to heating at 200-250 ^C and cooled in a water bath.

 Multilayer fluoroplastic tapes made according to the above technology are used for the manufacture of gaskets, o-rings and clamps, which are then subjected to laboratory bench tests.

 According to the test results, it was found that the operational durability of the tape made by the proposed method exceeds the durability of similar tapes made by the known method more than 1.5 times.

 Using the proposed method of manufacturing a multilayer fluoroplastic tape provides, in comparison with known methods, increased durability of the tape, achieved by increasing the wear resistance of the tape to cracking and abrasion and the rational placement of functional layers in the manufactured tape.

Claims (2)

 1. METHOD FOR PRODUCING A PTFE TAPE, including the preparation of a homogeneous paste from a mixture of fluoropolymer powders with or without filler and organic lubricant, the formation of tablet blanks from a paste by pressing tablets, the production of a tube from a tablet blank by piston extrusion through ring nozzles, followed by drying, sintering and hardening, characterized in that the molding of the tablet blanks is fully or partially carried out by sequentially building up cylindrical layers with different contents and contents Avoiding the filler or fragments thereof from the unconsolidated paste with pressing each layer or its fragment separately to obtain a multilayer tablet blank with functional layers, which is extruded through nozzles, and the resulting tube is cut along the generatrix, deployed on a plane and rolled on rolls.  2. The method according to claim 1, characterized in that the obtained tape is thermofixed by screwing it onto a calibration metal drum with fixing the free ends of the tape, heating and cooling.

Images