RU2269418C1 - Method of lining of a concave surface with a fluoroplastic - Google Patents

Abstract

FIELD: chemical engineering; methods of lining of concave surfaces with fluoroplastics.

SUBSTANCE: the invention is pertaining to the field of chemical engineering, in particular, to the methods of lining of apparatuses with the corrosion resistant polymeric compounds - fluoroplastics. The method provides for a placing of a fluoroplastic billet on the subjected to lining product, its heating, pressing down by the air to the subjected to lining surface with following cooling. At that depending on the fluoroplastic grade a heating of the billet is conducted up to the temperature within the limits of 155-390°C. Pressing of the billet to the subjected to lining surface is exercised by air at the atmospheric pressure. For this purpose they vacuumize the space between the subjected to lining surface and the billet at the speed of 0.05 - 0.15 kg/cm²·h. In the capacity of a billet use a plane billet made out of polytetrafluoroethylene grade: fluoroplastic-4, fluoroplastic-4 modified, fluoroplastic -4D, fluoroplastic-4MB, fluoroplastic-3, fluoroplastic-2М, fluoroplastic-50. On the subjected to lining surface before laying the billet first superimpose an underlayer of fluoroplastic-4МБ or another hot melt fluorocopolymer. The invention allows to increase quality of the lining, to eliminate fissuring of the fluoroplastic.

EFFECT: the invention allows to improve quality of the lining and to prevent fissuring of the fluoroplastic.

3 cl

Description

The invention relates to the field of chemical engineering, specifically to methods for lining apparatus with corrosion-resistant fluoropolymers.

A known method of lining the surface with polytetrafluoroethylene sheets using glue. To improve adhesion, heat-resistant inorganic material in the form of fibers or grains is applied to the sheets and pressed into the sheet at high temperature and pressure. On this side, the sheet is glued to the surface with glue. The joint is filled with a TFE-HFP copolymer, another sheet is put and crimped under heating and pressure (Pat. Jap. No. 51-47472, 1976, ref. In RZhKhim, 1977, 24T249p). The disadvantage of this method is the need to use glue, which, as a rule, is less heat-resistant than polytetrafluoroethylene, which limits the temperature range of use of equipment coated with the described method.

The closest set of essential features and the achieved result to the proposed invention is a method of lining a metal surface with fluoroplastic. The known method is used for lining the inner surface of metal pipes with fluoroplastic resins - fluoroplastics. For this, a fluoroplastic pipe is inserted inside a metal pipe, clogged and injected air, or hot air is supplied under pressure (Pat. Jap. No. 4581, 1960, ref. In RZhKhim, 1960, No. 19, p. .

The disadvantage of this method is that when lining large surfaces of chemical apparatuses using air under pressure, fluoroplastic cracking occurs, which leads to impaired tightness of the lining.

The technical problem solved by the claimed method is to improve the quality of the lining, the elimination of cracking of fluorine plastic.

The stated technical problem is solved by the fact that in the method of lining a concave surface, including applying a fluoroplastic preform, heating, if necessary, inflating the preform with air, pressing it with air to the lined surface, according to the invention, the pressing is carried out with air at atmospheric pressure, for which the space between the lined surface is evacuated and harvesting.

As a fluoroplastic preform, a flat preform of polytetrafluoroethylene of the fluoroplast-4 brand, fluoroplast-4 modified, fluoroplast-4D, fluoroplast-4MB, fluoroplast-3, fluoroplast-2M or fluoroplast-50 is used, heating is carried out to a temperature of 155 ÷ 390 ° V depending on the brand of fluoroplastic and vacuum with a speed of 0.05 ÷ 0.15 kg / cm ² · h

In addition, it is possible to apply a sublayer of fluoroplast-4MB or other hot-melt fluoropolymer before applying the fluoroplastic preform to the lined surface.

Example 1

The lining of a metal bottom of a spherical shape with a circumferential diameter of 900 mm and a radius of curvature of about 335 mm is as follows.

Pre-thermostabilized at a temperature of 250 ° C for 5 hours, a sheet of modified PTFE-4 modified is placed on top of the metal surface of the lid flange to be protected from corrosion, and pressed with a metal ring to the lid flange. Then the sheet is heated to a temperature of 355 ÷ 375 ° C and the sheet is preliminarily blown with air at a pressure of 0.05 ÷ 0.15 kgf / cm ² (g) to the size of the cover. After holding under pressure for 10 ÷ 20 min, vacuum at a rate of 0.05 ÷ 0.15 kgf / cm ² · h. After stopping the growth of vacuum (the fluoroplastic preform fits snugly on the surface of the lid), turn off the heating and begin forced blowing of the fluoroplastic preform with cold air to a temperature of 30 ÷ 40 ° C, after which the fluoroplastic preform is trimmed along the edge flange.

After exposure to vacuum and cooling, the lining has no cracks and tears over the entire surface.

Example 2

The lining of a metal elliptical bottom with a circle diameter of 430 mm and a radius of curvature of approximately 110 mm is carried out similarly to that described in example 1.

After exposure to vacuum and cooling, the lining has no cracks and tears over the entire surface.

Example 3

The bottom described in Example 2 is lined. A fluoroplastic-2M sheet is used as a fluoroplastic preform, which is placed on top of the metal surface of the lid flange to be protected from corrosion and pressed with a metal ring to the lid flange. The sheet is heated to a temperature of 155-175 ° C and vacuumized at a speed of 0.05 ÷ 0.15 kgf / cm ² · h. After stopping the growth of vacuum (the fluoroplastic preform fits snugly on the surface of the lid), turn off the heating and begin forced blowing of the fluoroplastic preform with cold air to a temperature of 30 ÷ 40 ° C, after which the fluoroplastic preform is cut along the flank of the lid.

After exposure to vacuum and cooling, the lining has no cracks and tears over the entire surface.

From the presented data it can be seen that the inventive method provides an increase in the quality of the lining, eliminates the cracking of fluoroplastic.

Claims (3)

1. A method of lining a concave surface with a fluoroplastic material, comprising applying a fluoroplastic preform to a lined product, heating it, pressing air against the lined surface, preform cooling, characterized in that the preform is heated to a temperature in the range of 155-390 ° C. depending on the fluoroplastic grade , the pressing is carried out with air at atmospheric pressure, for which the space between the lined surface and the workpiece is vacuumized at a speed of 0.05-0.15 kg / cm ² · h. 2. The method according to claim 1, characterized in that a flat preform of polytetrafluoroethylene of the brand: fluoroplast-4, fluoroplast-4 modified, fluoroplast-4D, fluoroplast-4MB, fluoroplast-3, fluoroplast-2M, fluoroplast-50 is used as a preform . 3. The method according to claim 1 or 2, characterized in that a fluoroplastic-4MB sublayer or other hot-melt fluoropolymer is preliminarily applied to the lined surface before applying the preform.