Anti-corrosive covering sheet

Claim 2

An anti-corrosive covering sheet for wrapping aroung a metal pipe comprising a three layer laminate consisting essentially of an outer heat-shrinkagle plastic sheet, an intermediate adhesive layer and an outer anti-corrosive layer said adhesive layer comprising a hot-melt adhesive material having a melting temperature of not lower than 50° C. and containing 30-80% by weight of an adhesive olefin copolymer; and said anti-corrosive layer has a thickness in the range of 1-10 microns, and contains an anti-corrosive agent selected from the group consisting of organic anti-corrosive agents and inorganic anti-corrosive agents dispersed in the same hot-melt adhesive material which comprises said adhesive layer in an amount of 0.01-1 mg/cm 2 .

Claim 3

The anti-corrosive covering sheet as claimed in claim 1, in which a thickness of the anti-corrosive layer ranges from 1.5 to 7 microns.

Claim 4

The anti-corrosive covering sheet as claimed in claim 1, in which the anti-corrosive agent is in particulate solid form.

Claim 5

The anti-corrosive covering sheet as claimed in claim 3, in which the anti-corrosive agent is selected from the group consisting of a metal salt of chromic acid, a metal salt of phosphoric acid, and a mixture thereof.

Claim 6

The anti-corrosive covering sheet as claimed in claim 2, in which the anti-corrosive agent is in a particulate solid form.

Claim 7

The anti-corrosive covering sheet as claimed in claim 5, in which the anti-corrosive agent is selected from the group consisting of a metal salt of chromic acid, a metal salt of phosphoric acid, and a mixture thereof.

Claim 8

The anti-corrosive covering sheet as claimed in claim 5, in which the anti-corrosive agent is a metal chromate and is present in said anti-corrosive layer in an amount of 0.05-0.5 mg/cm 2 .

Claim 9

The anti-corrosive covering sheet as claimed in claim 7, in which the anti-corrosive agent is zinc chromate.

Claim 10

The anti-corrosive covering sheet as claimed in claim 8, wherein said hot-melt adhesive layer comprises ethylene-propylene copolymer elastomer and ethylene-vinyl acetate copolymer.

Claim 11

The anti-corrosive covering sheet as claimed in claim 9, in which said hot-melt adhesive material further comprises styrene-butydiene-styrene block copolymer, cumarone resin, terpene-phenol copolymer and hydrogenated rosin ester.

Claim 12

The anti-corrosive covering sheet as claimed in claim 5, in which the anti-corrosive agent is a metal phosphate and is present in said anti-corrosive layer in an amount of 0.05-0.5 mg/cm 2 .

Claim 13

The anti-corrosive covering sheet as claimed in claim 7, in which the anti-corrosive agent is zinc phosphate.

Claim 14

The anti-corrosive covering sheet as claimed in claim 12, wherein said hot-melt adhesive layer comprises ethylene-propylene copolymer elastomer and ethylene-vinyl acetate copolymer.

Claim 15

The anti-corrosive covering sheet as claimed in claim 13, in which said hot-melt adhesive material further comprises styrene-butydiene-styrene block copolymer, cumarone resin, terpene-phenol copolymer and hydrogenated rosin ester.

Claim 16

The anti-corrosive covering sheet as claimed in claim 2, wherein said hot-melt adhesive layer comprises ethylene-propylene copolymer elastomer and ethylene-vinyl acetate copolymer.

Claim 17

The anti-corrosive covering sheet as claimed in claim 15, in which said hot-melt adhesive material further comprises styrene-butydiene-styrene block copolymer, cumarone resin, terpene-phenol copolymer and hydrogenated rosin ester.

Claim 18

The anti-corrosive covering sheet as claimed in claim 8, wherein said hot-melt adhesive composition comprises 17 parts of ethylene-propylene copolymer elastomer, 20 parts of ethylene-vinyl acetate copolymer, 17 parts of styrene-butydiene-styrene block copolymer, 17 parts of cumarone resin, 20 parts of terpene-phenol copolymer and 9 parts of hydrogenated rosin ester.

Claim 19

The anti-corrosive covering sheet as claimed in claim 12, wherein said hot-melt adhesive composition comprises 17 parts of ethylene-propylene copolymer elastomer, 20 parts of ethylene-vinyl acetate copolymer, 17 parts of styrene-butydiene-styrene block copolymer, 17 parts of cumarone resin, 20 parts of terpene-phenol copolymer and 9 parts of hydrogenated rosin ester.

Claim 20

A process for the preparation of an anti-corrosive covering sheet for wrapping aground a metal pipe comprising a three layer laminate consisting essentially of an outer heat-shrinkable palstic sheet, an intermediate adhesive layer and an outer anti-corrosive layer, which comprises: forming a layer of a dispersion or solution containing an anti-corrosive agent selected from the group consisting of organic anti-corrosive agents and inorganic anti-corrosive agents on the surface of an adhesive layer coating a heat-shrinkable plastic sheet, in which the adhesive layer comprises a hot-melt adhesive material having a melting temperature of not lower than 50° C. and containing 30-80% by weight of an adhesive olefin copolymer; and drying the dispersion or solution layer to prepare an anti-corrosive layer having a thickness in the range of 1-10 microns.

Claim 21

A process for the preparation of an anti-corrosive covering sheet for wrapping aground a metal pipe comprising a three layer laminate consisting essentially of an outer heat-shrinkable palstic sheet, an intermediate adhesive layer and an outer anti-corrosive layer, which comprises: forming a layer of a dispersion or solution containing an anti-corrosive agent selected from the group consisting of organic anti-corrosive agents and inorganic anti-corrosive agents on the surface of an adhesive layer coating a heat-shrinkable plastic sheet, in which the adhesive layer comprises a hot-melt adhesive material having a melting temperature of not lower than 50° C. and containing 30-80% by weight of an adhesive olefin copolymer; and drying the dispersion or solution layer to prepare an anti-corrosive layer having a thickness in the range of 1-10 microns.

Claim 22

A process for the preparation of an anti-corrosive covering sheet for wrapping around a metal pipe comprising a three layer laminate consisting essentially of an outer heat-shrinkable plastic sheet, and intermediate adhesive layer and an outer anti-corrosive layer, which comprises: forming a layer of a dispersion or solution containing an anti-corrosive agent selected from the group consisting of organic anti-corrosive agents and inorganic anti-corrosive agents on a first surface of an adhesive film which comprises a hot-melt adhesive material having a melting temperature of not lower than 50° C. and containing 30-80% of weight of an adhesive olefin copolymer; drying the dispersion or solution layer to prepare an anti-corrosive layer having a thickness in the range of 1-10 microns; and laminating a heat-shrinkable plastic sheet onto the second surface of the adhesive film having the anti-corrosive layer on said first surface thereof.

Claim 23

A process for the preparation of an anti-corrosive covering sheet for wrapping around a metal pipe comprising a three layer laminate consisting essentially of an outer heat-shrinkable plastic sheet, and intermediate adhesive layer and an outer anti-corrosive layer, which comprises: forming a layer of a dispersion or solution containing an anti-corrosive agent selected from the group consisting of organic anti-corrosive agents and inorganic anti-corrosive agents on a first surface of an adhesive film which comprises a hot-melt adhesive material having a melting temperature of not lower than 50° C. and containing 30-80% of weight of an adhesive olefin copolymer; drying the dispersion or solution layer to prepare an anti-corrosive layer having a thickness in the range of 1-10 microns; and laminating a heat-shrinkable plastic sheet onto the second surface of the adhesive film having the anti-corrosive layer on said first surface thereof.