POLYMER COMPOSITION FOR CROSS-LINKED PIPES Russian patent published in 2014 - IPC C08L23/08 C08L23/04 F16L9/12 

FIELD: chemistry.

SUBSTANCE: invention relates to method of obtaining cross-linked pipe and to cross-linked pipe, which contains cross-linked polymer composition, containing cross-linked ethylene polymer. method of manufacturing cross-linked pipe includes: (i) polymerisation of ethylene non-obligatorily with one or several comonomers (comonomer) in presence of Ziegler-Natta catalyst with obtaining ethylene polymer, which contains carbon-carbon double bonds; ethylene polymer has: (A) linkability, expressed through the level of gel content, equal, at least, 50 wt %, according to the measurement of disc-shaped sample of cross-linked ethylene polymer (ASTMD 2765-01, Method A, extraction in decalin); or/and (B) content of carbon-carbon double bonds in a number higher than 0.2 carbon-carbon double bond/1000 carbon atoms, according to the measurement by FTIR method; and (ii) obtaining polymer composition, including, at least, 50% wt % of ethylene polymer; (iii) formation of pipe from composition, obtained at stage (ii); (iv) cross-linking pipe, obtained at stage (iii). Ethylene polymer represents ethylene homopolymer or ethylene copolymer with one or several comonomers, and is selected from elastomers (POE), plastomers (OPO) or very low density ethylene copolymers of (VLDPE), which cover the density range from 855 to 909 kg/m³, linear low density ethylene copolymers (LLDPE), which have density in the range from 910 to 930 kg/m³ (ISO 1183), medium density ethylene copolymers (MDPE), which have density in the range from 931 to 945 kg/m³, or high density polyethylenes (HDPE), which are selected from homo- or copolymers of ethylene, and which have density higher than 946 kg/m³. Cross-linked pipe consists of cross-linked polymer composition. Polymer composition before cross-linking includes, at least, 50 wt % of ethylene polymer, where ethylene polymer is obtained by polymerisation of ethylene optionally together with one or several comonomers (comonomer) in presence of Ziegler-Natta catalyst, where ethylene polymer contains carbon-carbon double bonds in a number higher than 0.4 carbon-carbon double bond/1000 carbon atoms, according to the measurement by FTIR method, where ethylene polymer has linkability, expressed through the level of gel content, equal, at least, 50 wt %, according to the measurement for disc-shaped sample of cross-linked ethylene polymer (ASTMD 2765-01, Method A, extraction in decalin) and has MFR₂ from 0.01 to 5.0 g/10 min, Mn/Mw from 0.1 to 20.0 g/10 min, and where ethylene polymer represents ethylene homopolymer or ethylene copolymer with one or several copolymers, and is selected from linear low density ethylene copolymers (LLDPE), which have density in the range from 910 to 930 kg/m³ (ISO 1183), medium density ethylene copolymers (MDPE), which have density in the range from 931 to 945 kg/m³, or high density polyethylenes (HDPE), which are selected from ethylene homo- or copolymers and which have density higher than 946 kg/m³.

EFFECT: improvement of material properties.

18 cl, 5 tbl