POLYPROPYLENE COMPOSITION WITH IMPROVED SEALING CHARACTERISTICS Russian patent published in 2021 - IPC C08L23/12 C08L23/16 C08J5/18 C08K3/00 

FIELD: polymers.

SUBSTANCE: invention relates to a polypropylene composition for producing heat-sealable articles. The composition comprises (A) a mixture of polymers and (B) optionally one or more additives in a total amount of 0.0 to 5.0% wt. from the total weight of the polypropylene composition, selected from the group consisting of friction-reducing agents, anti-adhesion agents, UV-stabilisers, alpha and/or beta nucleating agents, antistatic agents, antioxidants. The mixture of polymers (A) therein includes: (A-1) from 55.0 to 75.0% wt. propylene polymer from the total weight of the polymer mixture containing two different comonomer units selected from ethylene and alpha-olefins with 4 to 12 carbon atoms randomly distributed in the chain of the propylene polymer containing (i) comonomer units obtained from ethylene, in the amount of 0.4 to 3.5% wt. from the total weight of the monomer units in the propylene polymer, and (ii) comonomer units obtained from alpha-olefins with 4 to 12 carbon atoms in the amount of 4.5 to 14.0% wt. from the total weight of the monomer units in the propylene polymer, wherein the propylene polymer has a melt flow rate MFR₂ within the range of 0.8 g/10 minutes to 15.0 g/10 minutes as defined according to ISO 1133, at a temperature of 230°C and a load of 2.16 kg and the content of the fraction soluble in cold xylene (XCS) less than 15.0% wt. as measured according to ISO 6427; and (A-2) 25.0 to 45.0% wt. from the total weight of the polymer mixture of an ethylene-based plastomer with a density of 0.850 g/cm³ to 0.915 g/cm³ as defined according to ISO 1183 and a melt flow rate MFR₂ within the range of 10.0 g/10 minutes to 45.0 g/10 minutes as defined according to ISO 1133, at a temperature of 190°C and a load of 2.16 kg. Also described are a method for producing a polypropylene composition, an article containing a polypropylene composition, and applications thereof.

EFFECT: provided are polypropylene composition with a satisfactory balance of low seal initiation temperature (SIT) combined with high strength of the welded joint in the hot state, improved optical properties and high melting point.

15 cl, 3 tbl, 3 ex