DE1285650B - Production of coatings on parts of the chlor-alkali electrolysis machine at risk of corrosion - Google Patents

Description

The invention relates to the use of special, post-chlorinated PVC types for the production of coatings on parts of the chloralkali electrolysis apparatus that are at risk of corrosion.

It is known, pipes or sleeves for apparatus parts of the chlor-alkali electrolysis made of metallic Materials and to protect the surface with material that is exposed to the effects the aggressive liquids and gases of the electrolytic cell withstands, for example by rubber or Plastics. It is also known, pipes and sleeves made entirely of ceramic or the like Material, for example porcelain or glass are made to use. There are also versions of the above Apparatus parts partly made of solid plastics, both single-layer and multi-layer Plastics of various types with and without mechanical reinforcement by inorganic and organic Known fibers. The disadvantages of the listed materials are mainly that linings detach themselves from their base and often not enough to withstand chemical attack resist.

Ceramic material is generally chemical under chlor-alkali electrolysis conditions quite resistant, but the relatively low resistance to temperature changes and Breaking strength as a disadvantage. Furthermore, those previously used as a coating or also massively are subject to Plastics after long periods of use under the conditions mentioned changes the surfaces concern, so that, for example, a pipe movably guided in a sealing gland can no longer be moved, as well as those that gradually destroy the entire material to lead.

It has now been found that, while avoiding the disadvantages outlined above, post-chlorinated compounds in particular can be found PVC with a chlorine content of 65 to 70% j which the chlorine to 50 to 90%> preferably between 60 and 80% in 1,2-dichloroethylene units arranged contains, advantageous for the production of coatings on parts of the apparatus at risk of corrosion who can use chlor-alkali electrolysis.

Post-chlorinated PVC with a chlorine content of 65 to 70%, which the chlorine to 50 to 90%, preferably contains between 60 and 80%, arranged in 1,2-dichloroethylene units, for example according to a process which is described in Belgian patent specification 654,377.

The advantages of the use according to the invention of the post-chlorinated PVC types described lie both in the good thermal stability and breakage stability of such coatings, while at the same time being excellent Corrosion resistance. The covers mentioned can also be welded and glued. You can can continue to be machined, even afterwards.

The material described can be used, among other things, for pipes and protective sleeves that are at risk of corrosion for the power supply lines of the graphite anodes, cover covers, tub linings and the like Parts of chlor-alkali electrolysis systems are coated.

The coating material to be used according to the invention can contain the usual processing aids contain. The semifinished products that are used to produce the coatings can be made according to known methods Process of plastics processing are produced.

The use according to the invention of the post-chlorinated PVC types described is illustrated by the following Examples illustrated.

example 1

Use as protective sleeves

for power supply of the graphite anodes

a saline electrolysis

The power supply lines for the graphite anodes were made with pieces of plastic pipe with a wall thickness of 4 mm and 40 mm outer diameter coated and the influence of saline electrolysis in the specified Exposed to temperatures and times.

la to Ig: comparative examples;
lh to Ii: Use of post-chlorinated polyvinyl chloride types.

Tabel

material • Tem modification Findings after removal Ver running time temperature of the outside search- by- No. Polyethylene (Days) ( ⁰ Q knife Surface smooth, many individual bubbles, up to (unfilled) 60 83 (%) protruding by 3 mm la Polyethylene +1.5 Irregular surface, bumps up to 4 mm (soot stabilized) 143 85 about diameter Ib Polyethylene +2.4 Pitted surface, peeling of a layer (soot stabilized) 155 83 0.6 mm thick lc Polypropylene +9.4 Loss of substance through detachment thinner 155 83 Layers 0.1 mm thick ld Polypropylene -2.5 Loss of substance through detachment thinner 143 85 Layers 0.1 mm thick le Polyvinyl chloride -1.7 Even thickening over the entire 126 84 used external area. surface If +7.5 rough and brittle Polyvinyl chloride Even thickening over the entire 160 85 used external area. surface Ig +8.6 rough and brittle

Notes at the end of the table.

Continuation of the table

Ver
search-
No. material running time
(Days) Tem
temperature
( ⁰ C) modification
of the outside
by-
knife
C / o) Findings after removal lh
Ii Polyvinyl chloride
(post-chlorinatedX *)
Polyvinyl chloride
(post-chlorinatedX *) 155
143 83
85 +0.2
+0.2 Surface evenly smooth, unchanged
Surface evenly smooth, unchanged

*) A suspension PyC with a K value of 68 was brought to a chlorine content of 67.2% by post-chlorination. 69% of the chlorine is arranged in 1,2-dichloroethylene units (the 1,2-dichloroethylene unit content was determined by measuring the nuclear magnetic resonance spectrum). After adding 3 percent by weight of Ba-Cd laurate, 2 percent by weight of a lubricant, which is commercially available under the name E-wax, and 0.5 percent by weight of Ca stearate, the material was ^{extruded at 190 °} C. to give tubes of the specified thickness.

Example 2

Use as trough lining 2a and 2b: comparative tests; 2c: Use of a highly chlorinated type of polyvinyl chloride.

Tabel

Experimental

material

running time

(Days)

temperature

( ⁰ C)

Weight change finding

Fibercast (epoxy resin) -

plate
Polyethylene

(carbon black stabilized) plate

Polyvinyl chloride
(post-chlorinated) (*) plate

40

35

30th

83 78

75

*) A suspension PVC with a K value of 60 was used brought to a chlorine content of 65.8% by post-chlorination. 75.5% of the chlorine is in 1,2-dichloroethylene units appropriate (the determination of the 1,2-dichloroethylene unit content was again carried out by measuring the nuclear magnetic resonance -6.4

+4.2

+0.04

Loss of material, crumbly surface

Surface pitted, occasionally closed bubbles, bleached

Edges unchanged and smooth surface

spectrum). The material was kalanndriert after the addition of 3 percent by weight of Ba-Cd laurate, 1 percent by weight titanium dioxide and 0.5 percent by weight Ca stearate 0.5 mm thick sheet, and then pressed at 19O ⁰ C for 4 mm thick plates.

Claims (1)

Claim: Use of coating agents made from post-chlorinated PVC with a chlorine content of 65 to 70%, which the chlorine to 50 to 90%, preferably between 60 and 80%, in 1,2-dichloro Contains ethylene units arranged for the production of coatings on corrosion-prone Equipment parts of the chlor-alkali electrolysis.