Method of anti-corrosion insulation of welded joints and pipeline repair

 

(57) Abstract:

The invention relates to the field of protection of underground pipelines from damage, as well as soil and atmospheric corrosion. The method is carried out by applying a heat-shrinkable multilayer adhesive tape containing a protective layer of plastic tape, electro-chemically modified to absorption dose of 25 to 50 Mrad and oriented in a shared direction for 25-75%, and the adhesive layer, in which the multilayer adhesive tape is applied epoxy composition and the adhesive layer is made of a composition containing two copolymers of ethylene with vinyl acetate (I and II), with the difference in the content of the vinyl acetate groups, equal to 5-20%, and further comprises a third copolymer of ethylene and vinyl acetate (III) with the content of 27-30% acetate groups and a melt flow index of 15-30 g/10 min, an inorganic filler, modifier - polyisocyanate. The technical result is an improvement of corrosion protection of welded joints and pipeline repair: adhesion to steel after exposure to salt water increases 1.7 times when the reduction in 2 times cathodic delamination. table 2.

The invention relates to protect the persons anticorrosive insulation of welded joints and pipeline repair with duct tape, paintings, obtained by applying on the basis of thermoplastics, in particular polyolefins, adhesive compositions, including, for example, resins, oils, agents sticky, bitumen and other special additives (see patent in Germany, No. 1504803, IPC C 09 J 7/02, 1976).

The disadvantage of this method is that it does not allow to obtain high adhesion to metal.

There is a method of anti-corrosion insulation of welded joints and pipeline repair using termousazhivaemoy material obtained three-layer coating of the adhesive composition on a polymer base, a first discrete (point, stripes), and then using special dowels connecting the adhesive layers in an inert basis (see UK patent No. 2023021, CL F 16 L 58/00, 1979).

The disadvantage of this method is insufficient adhesion to steel used in the method of heat-shrinkable material has a complex manufacturing technology.

There is also known a method of anti-corrosion insulation of welded joints and repair of the pipeline using termousazhivaemoy adhesive material obtained by coating on extruded and electron-chemically modified basis of thermoplastic adhesive sole (see the application of Norway No. 94/17324, CL F 16 L 58/10, 1994).

The disadvantage is that the method is practically not possible to get the same gel fraction in the layer basics termousazhivaemoy material, which ultimately leads to stratification of the polymer base.

There is a method of anti-corrosion insulation of welded joints and pipeline repair by applying anticorrosion tape containing protective layer of thermo - and light-stabilized polyethylene substrate and thermoplastic adhesive layer on the basis of a copolymer of ethylene with additives inorganic filler, modifier - alkylenediamines or indecomposable resin, and paraffin, in which the copolymer of ethylene used is a copolymer of ethylene with vinyl acetate content of 12-20% acetate groups, in the following ratio, wt.%:

a copolymer of ethylene with vinyl acetate 20-60

inorganic filler 30-70

modifier 2-15

paraffin 1-10

(see RU patent No. 2101183, the IPC 32 In 27/30, C 09 J 129/04, 1998). The disadvantage of this method is that the adhesive layer has poor adhesion to the metal.

The closest in technical essence is the way PR is mnogosloinoi adhesive tape, contains a protective layer of plastic tape, electro-chemically modified to absorption dose of 25 to 50 Mrad and oriented in a shared direction for 25-75%, and the adhesive layer, which is used as a composition including a copolymer of ethylene and vinyl acetate with a content of 8-25% acetate groups, modifier - diphenylmethanediisocyanate or gamma aminopropyltriethoxysilane, mineral filler, aluminum or zinc powder, antibacterial additive and stabilizer in the following ratio, wt.%:

a copolymer of ethylene with vinyl acetate 75-85

modifier - diphenylmethanediisocyanate, or gamma aminopropyltriethoxysilane 1,5-4,5

mineral filler 9-15

aluminum or zinc powder 2-3

bactericidal additive 1-2

the stabilizer 1-2

(see RU patent No. 2074875, IPC C 09 J 7/02, 32 27/32, 1997). The disadvantage of this method is that it does not allow to obtain high corrosion protection of welded joints and pipeline repair.

The objective of the invention is the improvement of corrosion protection of welded joints and pipeline repair.

The technical problem solved by way of counter who Inoi adhesive tape, contains a protective layer of plastic tape, electro-chemically modified to absorption dose of 25 to 50 Mrad and oriented in a shared direction for 25-75%, and the adhesive layer on the basis of a copolymer of ethylene with additives inorganic filler and modifier, in which the multilayer adhesive tape is applied epoxy composition, with the adhesive layer of the tape contains as a modifier of the polyisocyanate, and a copolymer of ethylene and a copolymer of ethylene with vinyl acetate (I) and a copolymer of ethylene with vinyl acetate (II), with the difference in the content of the vinyl acetate groups, equal to 5-20%, and further comprises a third copolymer of ethylene and vinyl acetate (III) with the content of 27-30% of vinyl acetate groups and a melt flow index of 15-30 g/10 min, in the following ratio, wt.%:

a copolymer of ethylene with vinyl acetate (I) 19-57

a copolymer of ethylene with vinyl acetate (II) (57-19

a copolymer of ethylene with vinyl acetate (III) 4-15

inorganic filler 8-17

modifier - the polyisocyanate 1-3

As a modifier in the composition of the adhesive layer of the tape, you can use:

the polyisocyanate brand “Desmodur Toueg (Germany);

the polyisocyanate B grade based on oligomeric derivatives of 2,4’- and 4,4’-diphenylmethanediisocyanate, 0.03% phenylisocyanate (TU 113-03-38-106-90) - low-viscosity liquid dark brown (=60 to 120 mPas). Mass fraction of isocyanate groups to 29.5%, hydrolyzable chlorine 0.23%, and the manufacture Dzerzhinsky plant chemicals;

the polyisocyanate brand "Tolonat" on the basis of dimer and trimer of 2,4-toluylene diisocyanate, with a mass content of isocyanate groups 29%, production concern "Rhone-Poulenc (France);

the polyisocyanate brand “Arison BP” on the basis of the trimer of 2,4-toluylene diisocyanate, blocked with phenol. Mass content of blocked isocyanate groups of 16%. Free of 0.1%. Melting point 90.

The filler used mineral filler:

- ground mica brand engineering-125, GOST 855-74;

- chalk, GOST 23683-89;

- talc, GOST 23683-89.

In the preparation of the composition are two of a copolymer of ethylene with vinyl acetate (I) and copolymer of ethylene with vinyl acetate (II), which have a difference in the content of vinyl acetate units, equal to 5-20%, and the third copolymer of ethylene and vinyl acetate (III) with the content of 27-30% of vinyl acetate groups and a melt flow index VA-2 may be of the following grades: 11306-075, 11104-030, 11507-375, 11708-1250, a copolymer of ethylene with vinyl acetate (III) can be brand 11808-1750.

For a better understanding of the invention examples of specific performance.

Example 1.

The tape from the high-pressure polyethylene cable brands produced by extrusion in a single - or twin-screw extruder with a slot die.

When using other grades of polyethylene in him also before the extrusion enter at least 2% of channel black brand DG-100 and not less than 1.5% of thermo stabilizer.

Extruded tape with thickness of 0.5-2 mm and a width of 550-1000 mm calendarbut on cooled three-roll calender to a temperature not exceeding 60C.

The cooled strip then enters the input window area sweep of the electron beam generated by an electron accelerator with energy of the electrons is not less than 0.7 MeV and power in the electron beam 10-30 kW. Electron accelerator must be provided with a device for uniform movement of the tape in the exposure zone.

From the output window area sweep of the electron beam tape guide in a tunnel furnace with 3-5 heating zones from 60 to S. A protective layer of plastic tape electro-chemically modify to absorption to alcami backup unit, where it is applied at 150-S layer previously prepared adhesive.

Take a copolymer of ethylene with vinyl acetate (I) brand 11104-030 with a content of acetate groups of 5% in the number of 19 wt.%, a copolymer of ethylene with vinyl acetate (II) brand 11306-075 with a content of acetate groups of 10% in the number of 57 wt.% with a difference of acetate groups 5%, a copolymer of ethylene with vinyl acetate (III) brand 11808-1750 with a content of acetate groups of 27% and a melt flow index of 15 g/10 min in the amount of 11 wt.%, filler - ground mica in an amount of 10 wt.% and modifying additive is a polyisocyanate with a content of NCO groups of 30% in the amount of 3 wt.%.

The adhesive will receive a pre-specified composition on Z-shaped heated mixer heavy type or twin-screw planetary extruder by mixing the components with subsequent granulation.

Dried pellets of adhesive (until the moisture content of 0.1%) is applied by extrusion through a heated slotted head at 150-S on a hot tape. Ready-to-tape passes through a system of cooling rolls, a device for edge trimming and winding into rolls.

The pipe surface before applying the tape clear of rust and inductional heating or ring gas burners. Further, the pipe wrapped with heat shrink tape, after which the surface is heated by the flame of a gas ring burner up to 160-S to fully shrink.

Reducible epoxy composition applied to protect pipes before winding heat-shrinkable tape:

- composition grade B-EP-0126 composition, wt.%:

epoxy resin ED-20 25,3

polyglycidol 14,5

strontium chronologicly 8,3

the zinc phosphate 10,2

the micro-talc 25,0

hardener YES-1 16,7

- composition grade B-EP-0147 composition, wt.%:

epoxy resin ED-20 32,9

polyglycidol 18,0

strontium chronologicly 9,5

the zinc phosphate 9,8

the micro-talc 11,1

hardener brand DTB-2 18,7

- hardener YES-1, representing a mixture of hardeners DTB-2 and AF-2: product of the interaction of Diethylenetriamine and butyl methacrylate in the presence of a catalyst solution of a complex of boron TRIFLUORIDE in diethylene glycol (brand DTB-2) (TU 6-05-241-224-79) and N-crazyechelonkiary (type AF-2) (TU 2494-511-0020333521-94) in the ratio 2:1;

- hardener brand DTB-2 - product interaction Diethylenetriamine and butyl methacrylate in the presence of cryogeny compositions compositions for the preparation of adhesive layer heat-shrinkable multilayer adhesive tape.

Table 2 shows the average values for saleimoa object in comparison with the prototype.

The inventive method of anti-corrosion insulation of welded joints and pipeline repair provides improved corrosion protection of welded joints and pipeline repair: adhesion to steel after exposure to salt water is increased in 2 times and reduce in 2 times cathodic delamination.

Method of anti-corrosion insulation of welded joints and pipeline repair by applying a heat-shrinkable multilayer adhesive tape containing a protective layer of plastic tape electro-chemically modified to absorption dose of 25 to 50 Mrad and oriented in a shared direction for 25-75%, and the adhesive layer on the basis of a copolymer of ethylene with additives inorganic filler and modifier, characterized in that before applying the multilayer adhesive tape is applied epoxy composition, with the adhesive layer of the tape contains as a modifier of the polyisocyanate, and a copolymer of ethylene and a copolymer of ethylene with vinyl acetate (I) and a copolymer of ethylene with vinyl acetate (II), with the -30% acetate groups and a melt flow index of 15-30 g/10 min, in the following ratio, wt.%:

A copolymer of ethylene with vinyl acetate (I) 19-57

A copolymer of ethylene with vinyl acetate (II) (57-19

A copolymer of ethylene with vinyl acetate (III) 4-15

Inorganic filler 8-17

Modifier - the polyisocyanate 1-3

 

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