RU2228944C1 - Heat-shrinkage layered adhesive tape - Google Patents

Abstract

FIELD: insulation materials. SUBSTANCE: invention provides two-layer material with polyethylene substrate and thermoplastic adhesive layer, which can be used for insulating underground pipelines. Object of invention is to widen reserve of heat- shrinkage layered adhesive tapes, to create the one based on cross-linked polyethylene and having adhesive layer based on ethylene copolymer, which would have high adhesiveness for metal. Tape according to invention comprises protective and adhesive layers, the former being polyethylene tape electronically and chemically modified to absorption of dose 25-50 MRad and oriented in lengthwise direction by 25-75% and the latter containing composition based on ethylene copolymer completed by polyisocyanate modifier and mineral filler. In particular, ethylene copolymer is composed of two ethylene/vinyl acetate copolymers differed by content of vinyl acetate groups by 5 to 20% and additionally contains third ethylene/vinyl acetate copolymer with 27-30% vinyl acetate groups and melt flowability index 15-30 g/10 min. All components are taken in specified proportions. EFFECT: widened reserve of anticorrosive tapes with elevated adhesive strength for metal. 2 tbl

Description

The invention relates to a two-layer material with a polyethylene base and an adhesive thermoplastic layer and can be used to isolate underground pipelines.

Known electrical insulating sealing film containing thermally and light-stabilized polyethylene base - a protective layer and an adhesive thermoplastic layer based on a copolymer of ethylene with vinyl acetate, containing 8-12% vinyl acetate groups with additives of paraffin and inorganic filler, in the following ratio, wt.%:

Ethylene Vinyl Acetate Copolymer

with a content of 8-12% of vinyl acetate groups 95.0-99.3

Paraffin 0.2-2.0

Aerosil 0.5-5.0

(see SU Copyright Certificate 954256, IPC B 32 V 27/30, 27/32, 1982).

However, this film has a low adhesion to metal (0.3-3.2 kgf / cm2) and low water resistance.

Known anti-corrosion tape containing a protective layer of thermo- and light-stabilized polyethylene base and an adhesive thermoplastic layer based on an ethylene copolymer with paraffin and inorganic filler additives, in which it contains an ethylene-vinyl acetate copolymer containing 12-20% vinyl acetate groups, and additionally contains alkylphenolamine or indencumarone resin in the following ratio, wt.%:

Ethylene Vinyl Acetate Copolymer

with a content of 12-20% vinyl acetate groups 20-60

Inorganic filler 30-70

Alkylphenolamine or indencumarone resin 2-15

Paraffin 1-10,

(see RU Patent 2101183, IPC B 32 V 27/30, C 09 J 129/04, 1998).

The disadvantages of the anti-corrosion tape is that it has insufficient strength of the adhesive layer to the metal.

The closest in technical essence is a heat-shrinkable multilayer adhesive tape containing a protective and adhesive layers, which as a protective layer contains a polyethylene tape electronically chemically modified to absorb a dose of 25-50 Mrad and oriented in the direction of 25-75%, and as the adhesive layer, it contains a composition based on an ethylene copolymer with a content of 8-25% vinyl acetate groups, including, wt.%:

Ethylene vinyl acetate copolymer 75–85

Diphenylmethanediisocyanate

or gamma-aminopropyltriethoxysilane 1.5-4.5

Mineral filler 9-15

Aluminum or zinc powder 2-3

Bactericidal additive 1-2

Stabilizer 1-2

(see RU Patent 2074875, IPC C 09 J 7/02, 32 V 27/32, 1997).

The disadvantage of this anti-corrosion tape is that it has insufficient strength of the adhesive layer to the metal.

The objective of the invention is to provide a heat-shrinkable multilayer adhesive tape based on cross-linked polyethylene and with an adhesive layer based on an ethylene copolymer having high adhesive properties to the metal.

The technical problem is solved in that a heat-shrinkable multilayer adhesive tape containing a protective and adhesive layers, as a protective layer contains a polyethylene tape, electron-chemically modified to absorb a dose of 25-50 Mrad and oriented in a fractional direction by 25-75%, and as the adhesive layer it contains a composition based on a copolymer of ethylene with vinyl acetate, a modifier-polyisocyanate and a mineral filler, in which the adhesive layer contains two copolymers of eth ylene with vinyl acetate (I) and (II) having a difference in the content of vinyl acetate groups of 5-20%, and further comprises a third copolymer of ethylene with vinyl acetate (III) with a content of 27-30% vinyl acetate groups and a melt flow rate of 15-30 g / 10 min, in the following ratio of components, wt%:

Ethylene Vinyl Acetate Copolymer (I) 19-57

Ethylene Vinyl Acetate (II) Copolymer 57-19

Copolymer of ethylene with vinyl acetate (III) 4-15

Modifier – Polyisocyanate 1-3

Mineral filler 8-17

The solution to the technical problem allows you to expand the arsenal of anti-corrosion tapes with high adhesive strength to metal.

The composition of the adhesive layer as a modifier may contain a polyisocyanate:

- Grade B polyisocyanate based on oligomeric derivatives of 2,4'-and 4,4'-diphenylmethanediisocyanate, 0.03% phenylisocyanate (TU 113-03-38-106-90) - a low-viscosity liquid of a dark brown color (η = 60- 120 MPa s). Mass fraction of isocyanate groups 29.5%, hydrolyzable chlorine 0.23%. Production of the Dzerzhinsky Chemical Reagents Plant.

- Tolonat brand polyisocyanate with a mass content of 29% isocyanate groups based on a dimer and trimer of 2,4-toluene diisocyanate, manufactured by Ron-Poulenc concern (France)

- Polyisocyanate brand "Desmodur TT" based on a dimer of 2,4-toluene diisocyanate, the mass content of isocyanate groups 24%, manufactured by Wauer (Germany).

- Polyisocyanate brand “Surizon BP” based on trimer 2,4 toluene diisocyanate blocked by phenol. The mass content of blocked isococyanate groups is 16%. Free 0.1%. Melting point 90 ° C.

The composition of the adhesive layer as a filler may contain a mineral filler:

- ground mica grade SMF-125, GOST 855-74;

- chalk, GOST 23683-89;

- talc, GOST 23683-89.

In preparing the composition, a copolymer of ethylene with vinyl acetate (I) and a copolymer of ethylene with vinyl acetate (II) are used, which have a difference in the content of vinyl acetate units equal to 5-20%, and a third copolymer of ethylene with vinyl acetate (III) containing 27-30% vinyl acetate groups and melt flow rate of 15-30 g / 10 min.

The ethylene vinyl acetate copolymer - SEVA (I) and the ethylene vinyl acetate copolymer - SEVA (II) can be of the following grades: 11306-075, 11104-030, 11507-375, 11708-1250, the ethylene vinyl acetate copolymer - SEVA (III) of the brand 11808-1750.

For a better understanding of the invention, we give examples of specific performance.

Example 1

Cable grades are made of high pressure polyethylene by extrusion on a single or twin screw slotted head extruder.

When using other grades of polyethylene, at least 2% of channel soot DG-100 and at least 1.5% of the heat stabilizer are additionally introduced into it before extrusion.

An extruded tape with a thickness of 0.5-2 mm and a width of 550-1000 mm is calendared on a three-roll cooled calender to a temperature of not more than 60 ° C.

The cooled tape then goes to the input window of the scanning zone of the electron beam generated by the electron accelerator with an electron energy of at least 0.7 MeV and an electron beam power of 10-30 kW. The electron accelerator should be equipped with a device for uniform movement of the tape in the irradiation zone.

From the exit window of the scanning zone of the electron beam, the tape is sent to a tunnel furnace with 3-5 heating zones from 60 to 170 ° C, in which the tape is oriented and thermofixed, modified to absorb a dose of 25-50 Mrad and oriented in a fractional direction to 25-75 % Next, the tape is captured by the receiving rolls of the backup unit, where a layer of pre-prepared adhesive is applied to it at 150-170 ° C.

- Take a copolymer of ethylene with vinyl acetate (I) grade 11104-030 with a content of vinyl acetate groups of 5% in an amount of 19 wt.%, A copolymer of ethylene with vinyl acetate (II) grade 11306-075 with a content of vinyl acetate groups of 10% in an amount of 57 wt.% S the difference between vinyl acetate groups is 5%, a copolymer of ethylene with vinyl acetate (III) of grade 11808-1750 with a content of vinyl acetate groups of 27% and a melt flow rate of 15 g / 10 min., in the amount of 11 wt.%, the filler is ground mica in the amount of 10 wt. % and modifier-polyisocyanate brand "Tolonat" with a mass content of isocyanate groups of 29% newer than the dimer and trimer of 2,4-toluene diisocyanate, production of Ron-Poulenc concern (France) in an amount of 3 wt.%.

The adhesive is preliminarily obtained from the composition on a heavy-type Z-shaped heated mixer or on a twin-screw planetary extruder by mixing the components and then granulating it.

Dried adhesive granules (to a moisture content of 0.1%) are applied by extrusion through a heated slit head at 150-170 ° C on a hot tape. The finished tape passes through a system of cooling rolls, a device for trimming the edges and winding into rolls.

Table 2 shows the properties of the tape, averaged for all compositions shown in table 1.

The surface of the pipeline before applying the tape should be cleaned of rust and other deposits by a sandblasting unit, heating to 120-130 ° C using an induction heating unit or ring gas burners. Next, the pipeline is wrapped with a heat-shrinkable tape, after which its surface is again heated by the flame of a gas ring burner to 120-130 ° C until full heat shrink.

Table 1 shows the composition of the compositions to obtain an adhesive layer of heat-shrink tape.

Table 2 shows the properties of the tape, averaged for all compositions shown in table 1.

The proposed heat-shrinkable multilayer adhesive tape can be used to create reliable insulating anti-corrosion coatings of underground pipelines due to high properties, in particular, its resistance to long-term exposure to salt water and cathodic peeling, while the adhesion to steel after exposure in salt water increases by 1.4 times with a decrease in cathodic exfoliation of 1.5 times.

Claims (1)

Heat-shrinkable multilayer adhesive tape containing a protective and adhesive layer, which contains a polyethylene tape as a protective layer, electronically chemically modified to absorb a dose of 25-50 Mrad and oriented in the fractional direction by 25-75%, and as an adhesive layer it contains a composition based on a copolymer of ethylene with vinyl acetate, a modifier-polyisocyanate and a mineral filler, characterized in that the adhesive layer contains two copolymers of ethylene with vinyl acetate as an ethylene copolymer atom (I) and (II) having a difference in the content of vinyl acetate groups equal to 5-20%, and additionally contains a third copolymer of ethylene with vinyl acetate (III) with a content of 27-30% vinyl acetate groups and a melt flow index of 15-30 g / 10 min in the following ratio of components, wt.%: Ethylene Vinyl Acetate Copolymer (I) 19-57 Ethylene Vinyl Acetate (II) Copolymer 57-19 Copolymer of ethylene with vinyl acetate (III) 4-15 Modifier-polyisocyanate 1-3 Filler 8-17