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CN-116888208-B - Polyethylene composition for film applications with improved toughness and stiffness

CN116888208BCN 116888208 BCN116888208 BCN 116888208BCN-116888208-B

Abstract

The present invention relates to a polyethylene composition comprising a multimodal linear low density ethylene copolymer, wherein the linear low density ethylene copolymer comprises fractions having different platelet thickness and the ratio of the amount of fractions having a platelet thickness of not more than 11.8nm to not more than 21.7 is in the range of 1.30 to 1.60, an article, such as a film, comprising said polyethylene composition, and the use of said polyethylene composition for the production of blown films for greenhouse film applications, heavy duty shipping bag applications, laminate film applications, joint shrink film applications, stand up bag applications or pool liner applications.

Inventors

  • Ash Kumar
  • Sentil Kumar Kariapan
  • Sadikali Cherutazekat
  • Lakshe Pandia

Assignees

  • 阿布扎比聚合物有限公司博禄
  • 博里利斯股份公司

Dates

Publication Date
20260505
Application Date
20211222
Priority Date
20201228

Claims (15)

  1. 1. A polyethylene composition comprising a multimodal linear low density ethylene copolymer, wherein the multimodal linear low density ethylene copolymer comprises fractions having different platelet thicknesses and the ratio of the amount of fractions having a platelet thickness of no more than 11.8nm to the amount of fractions having a platelet thickness of from more than 11.8nm to no more than 21.7nm is in the range of from 1.30 to 1.60.
  2. 2. The polyethylene composition according to claim 1, wherein the amount of fraction having a platelet thickness of more than 11.8nm to not more than 21.7nm is from 35.0 to 60.0 mole% of the total amount of the multimodal linear low density ethylene copolymer.
  3. 3. The polyethylene composition according to claim 1, wherein the amount of fraction having a platelet thickness of not more than 5.0nm is 17.0 to 30.0 mole% of the total amount of the multimodal linear low density ethylene copolymer.
  4. 4. The polyethylene composition according to claim 1, wherein the amount of fraction having a platelet thickness of not more than 4.2nm is at least 8.5 mole% of the total amount of the multimodal linear low density ethylene copolymer.
  5. 5. The polyethylene composition according to claim 1, wherein the ratio of the amount of fraction having a platelet thickness of not more than 4.2nm to the amount of fraction having a platelet thickness of from more than 11.8nm to not more than 21.7nm is in the range of from 0.20 to 0.30.
  6. 6. The polyethylene composition according to claim 1, wherein the ratio of the amount of fraction having a platelet thickness of not more than 4.2nm to the amount of fraction having a platelet thickness of from more than 5.0nm to not more than 6.1nm is in the range of from 0.85 to 1.15.
  7. 7. The polyethylene composition according to claim 1, wherein the multimodal linear low density ethylene copolymer is a copolymer of ethylene and 1-butene.
  8. 8. The polyethylene composition according to claim 1, wherein the multimodal linear low density ethylene copolymer has a density of 915.0 to 925.0kg/m 3 .
  9. 9. The polyethylene composition according to claim 1, wherein the multimodal linear low density ethylene copolymer comprises two ethylene copolymer fractions having different molecular weights, wherein the weight ratio of the low molecular weight ethylene copolymer fraction and the high molecular weight ethylene copolymer fraction in the multimodal linear low density ethylene copolymer is from 25.0:75.0 to 44.0:56.0.
  10. 10. The polyethylene composition according to claim 9, wherein the ratio of short chain branching number per 1000 carbon atoms (SCB/1000C) in the polymer chains of the high molecular weight ethylene copolymer fraction is in the range of 15.0 to 35.0%.
  11. 11. The polyethylene composition according to claim 1, wherein the polyethylene composition has a melt flow rate MFR 5 measured at 190 ℃ under a load of 5kg of from 0.40 to 0.85g/10 min.
  12. 12. An article comprising the polyethylene composition according to any one of claims 1 to 11.
  13. 13. The article of claim 12, wherein the article is a film having a dart impact strength DDI of at least 250g when measured on a 40 μιη blown film according to ISO 7765-1.
  14. 14. The article of claim 12, wherein the article is a film having a 1% secant transverse tensile modulus of at least 275MPa when measured on a 40 μιη blown film according to ISO 527-3.
  15. 15. Use of the polyethylene composition according to any one of claims 1 to 11 for producing a blown film for greenhouse film applications, heavy duty shipping bag applications, laminate film applications, co-shrink film applications, stand-up bag applications or pool liner applications.

Description

Polyethylene composition for film applications with improved toughness and stiffness Technical Field The present invention relates to a polyethylene composition comprising a multimodal linear low density ethylene copolymer having a specific pattern of the amount of fractions of varying platelet thickness, an article, such as a film, comprising said polyethylene composition, and the use of said polyethylene composition for producing blown films in several heavy applications. Background Polyethylene compositions comprising in particular linear low density ethylene copolymers (LLDPE) are particularly suitable for film applications, such as films for packaging or greenhouse applications. The industry trend for packaging is thinning. In order to obtain packaging materials with reduced material thickness but identical material properties, innovative resins with improved property balances are needed, in particular in terms of stiffness and toughness. The improved balance of stiffness and toughness contributes to the thinning of the film structure and contributes to the overall sustainability goals of the industry. To increase toughness, it is desirable to reduce the density of the packaging material, but lower densities result in lower stiffness, so higher density MDPE and HDPE products are increasingly used in packaging applications. Another approach to improving the balance of stiffness and toughness is to use higher alpha-olefin comonomers (such as 1-hexene and 1-octene) as comonomers in the polyethylene resin. In greenhouse applications, in addition to the improved balance of stiffness and toughness, another property that has shown great benefit is haze. High haze results in better light diffraction, which has been shown to improve crop yield performance. Typically, for greenhouse applications, LLDPE products and highly branched high pressure Low Density Polyethylene (LDPE) products are used. LLDPE films with high haze and improved stiffness-toughness property balance using 1-butene comonomer as an economical efficient alternative to using higher alpha-olefin comonomer are not readily available on the market. Up to now, the use of 1-butene comonomers has not achieved the desired toughness properties of films designed for certain applications, such as high dart impact strength (DDI). WO 2004/000902 A1 discloses a polyethylene composition comprising a bimodal LLDPE with 1-butene comonomer which shows sufficient stiffness properties but poor toughness. Accordingly, there is a need in the art for polyethylene compositions comprising linear low density polyethylene that can be produced economically and efficiently and have an improved balance of properties in terms of high stiffness, high toughness and high haze. Surprisingly, it has been found that when the molecular design of a multimodal linear low density ethylene copolymer is carefully tuned such that the copolymer has a specific platelet thickness distribution, polyethylene compositions can be obtained which show an improved balance of properties, such as high stiffness as shown in good tensile properties, high toughness as shown in high puncture resistance, in particular high dart impact strength and high haze. In addition, the polyethylene composition of the invention exhibits good processability, as demonstrated by high melt flow rate and rheological properties. Disclosure of Invention The present invention relates to a polyethylene composition comprising a multimodal linear low density ethylene copolymer, wherein the linear low density ethylene copolymer comprises fractions having different platelet thicknesses and the ratio of the amount of fractions having a platelet thickness of not more than 11.8nm to the amount of fractions having a platelet thickness of more than 11.8nm to not more than 21.7nm is in the range of 1.30 to 1.60, more preferably in the range of 1.35 to 1.55 and most preferably in the range of 1.40 to 1.50. Furthermore, the present invention relates to an article, preferably a mulch film, more preferably a multilayer film, still more preferably a multilayer blown film, comprising a polyethylene composition as described above or below. Still further, the present invention relates to the use of a polyethylene composition as described above or below for producing a blown film for greenhouse film applications, heavy duty shipping bag applications, laminate film applications, co-shrink film applications, stand-up bag applications or pool liner applications. Definition of the definition The polyethylene composition according to the invention refers to a polymer derived from more than 50 mole% of ethylene monomer units and optionally additional comonomer units. The term "copolymer" refers to a polymer derived from ethylene monomer units and additional comonomer units in an amount exceeding 0.05 mole percent. A polyethylene composition or base resin comprising more than one fraction differing from each other in at least one property, such as wei