CS211480B1 - Polyamide packing material of the rotation seals - Google Patents

Description

It is known to use polyamide in rotary seals, either as gaskets or segments of pure polyamide, or polyamide filled with graphite, or with a sulfide of anolybdenum, glass fiber, sawdust and the like.

Said fillers are used to improve some of the polyamide properties, especially water absorption, thermal expansion, friction coefficient, hardness, friction wear, chemical resistance and the like.

When using a one-component filler, only certain properties are improved over other properties.

Pure polyamide has a high coefficient of friction, water absorption up to 12%, and a coefficient of thermal expansion of 11.105 K @ -1. By using 40% of the graphite additive, the coefficient of friction is reduced by about 25%, the water absorptivity decreases to 6% _f , its coefficient of thermal expansion is reduced to 36.10 ^ K ^-1 , the hardness decreases to 30 HS and the wear increases more than double. By using 30% glass fibers, the tensile strength increases by more than 50% _t but, on the other hand, the friction coefficient increases, the wear increases by three times compared to the unfilled polyamide. Polyamide filled with 10% molybdenum silica has a 50% lower friction coefficient but water absorption, the coefficient of thermal expansion remains at the level of unfilled polyamide and its tensile strength decreases by about 20%.

The use of metal-filled polyamide will increase the thermal conductivity,

211480 ..2 which is important for heat dissipation of spawning surfaces, but at the same time the friction coefficient will increase by up to 30 JS depending on the content and the second metal component.

SUMMARY OF THE INVENTION The present invention provides a filler composition of polyamide sealants comprising 5 to 12% graphite of a grain size finer than 0.01 mm, 2 to 8% of microazbestos less finer than 0.7 mm, 5 to 7% molybdenum granules of finer than 0.01 and ground pitched or petroleum calcined coke of a grain finer than 0,04 mm.

The filler content of the polyamide sealants is 40 to 75%.

By using said filler in polyamide sealing elements, optimum properties are achieved, which are characterized by lower wear, higher mechanical resistance and compared to the materials used hitherto, e.g. from graphodure or from Teflon up to 30 times lower production costs for their production, which represents a significant saving of material, working time, energy and other overhead costs.

As an example of the application of our invention is the production of the sealing ring of the flexible rotary shaft seal and the production of the sealing segment of the radial shaft.

Filling preparation:

Into the heated boom mixer, the following raw materials are weighed.

grain finer than (mm) composition (#) Graphite netol powder 0.01 12 Mikroazbest 0.7 8 Molybdenum disulphide 0.01 5 Ground petroleum coke 0.04 75

The mixture is stirred at 110-120 ° C for 1 hour to allow complete homogenization and evaporation of any moisture. It is then sieved through a sieve with a mesh size of 0.7 mm to break up the agglomerates and remove any impurities.

EXAMPLE

Production of sealing ring in series over 1000 pcs

60 parts by weight of polyamide 6, a granulate with 0.5 parts by weight of petroleum jelly, are homogenized in a cold mixer. After homogenization, 0.5 part by weight of calcium stearate is added and after mixing 40 parts by weight of the filler are added and thoroughly mixed. The thus prepared mixture is sprayed on a die extruder at a temperature of about 260 ° C to a granulate, which is injected into a die at a pressure of 13 MPa. The compact is deburred or glued to the functional surface.

In this way, the polyamide material achieves the following properties:

Compressive strength 45 MPa

Elongation 8%

Heat resistance according to Vicata 197 ° C

Porosity 0.2%

Hardness HS 61

Example 2

Production of sealing segment

75 parts by weight of the filler composition as described above are homogenized in a cold mixer; 25 parts by weight of powdered polyamide with a grain size of less than 0.06 mm and the mixture is passed through a 0.7 mm mesh sieve to remove any clumps. The mixture thus prepared is weighed in the necessary amount into a pressing tool and pressed under a pressure of 25 MPa. Under the press, the tool is wedged, inserted into a sintering space heated to a temperature of 190 to 260 ° C, then pressed with a pressure of 30 MPa, cooled and the molded part removed from the press tool, deburred or the functional area glued. In this way, a polyamide material having the following properties is obtained:

Compressive strength elongation

Heat resistance under Vicata

porosity

Hardness HS

MPa 2%

198 ° C 0.8% 52

The filler composition of the polyamide sealing material can be used, inter alia, for the production of toothed and worm gears for which self-lubricating is required, e.g. in car windscreen wiper transmissions.

Claims (1)

OBJECT OF THE INVENTION Polyamide sealant of rotary seals having a filler content of 40 to 75% molded or hot sprayed, characterized in that the filler contains 5 to 12% graphite of grain size less than 0.7 mm, 5 to 7% of molybdenum disulphide grain size less than 0 And about 73-88% of ground pitched or petroleum calcined coke of finer finer than 0.04 mm.