RU2772703C2 - Products obtained by injection molding containing polyethylene resin obtained by polymerization catalyzed by metallocene - Google Patents

Abstract

FIELD: material engineering.

SUBSTANCE: invention relates to products obtained by injection molding containing polyethylene resin obtained by polymerization catalyzed by metallocene, and to the manufacture of such a product. In particular, the present invention relates to fuel tanks containing polyethylene and to the manufacture of such tanks. The product obtained by injection molding contains at least one polyethylene resin obtained by metallocene-catalyzed polymerization, containing at least two polyethylene fractions A and B obtained by metallocene-catalyzed polymerization, and at least one polyethylene resin obtained by metallocene-catalyzed polymerization contains at least 40 wt. %, to no more than 50 wt. %, of polyethylene fraction A based on the total mass of at least one polyethylene resin, obtained by metallocene-catalyzed polymerization, wherein fraction A is characterized by a melt flow rate of MI2 of at least 100.0 g/10 min, determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg; and moreover, at least one polyethylene resin obtained by metallocene-catalyzed polymerization is characterized by a density ranging from at least 0.940 g/cm³ to no more than 0.950 g/cm³, measured for granules in accordance with ISO 1183 at 23°C; melt flow index MI2, ranging from at least 1.4 g/10 min to no more than 2.5 g/10 min, measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg. The method for obtaining the specified product obtained by injection molding provides for the stages: a) providing at least one polyethylene resin obtained by metallocene-catalyzed polymerization described in this document; and b) injection molding of the specified polyethylene resin into the product.

EFFECT: invention provides products characterized by improved mechanical properties and improved machinability.

15 cl, 2 ex, 3 tbl, 3 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to injection molded articles containing a polyethylene resin obtained by metallocene catalyzed polymerization and to the manufacture of such an article. In particular, the present invention relates to fuel tanks containing polyethylene and to the manufacture of such tanks.

BACKGROUND OF THE INVENTION

Automotive fuel tanks containing high-density polyethylene are known. Such fuel tanks are typically produced by blow molding. Plastic automotive fuel tanks must demonstrate high safety performance, particularly in terms of fire and impact resistance. Such fuel tanks must meet minimum industry performance requirements for both creep resistance when the tank is subjected to fire tests and impact resistance when the tank is subjected to impact. An automotive fuel tank for use in Europe must be flame retardant and impact resistant to the relevant requirements of the standards defined in ECE34.

In order to meet these standards, automotive manufacturers require known blow molded automotive fuel tanks to have a minimum wall thickness of at least 3 mm in order to provide sufficient toughness and creep resistance for the entire fuel tank. An automotive fuel tank comprised of polyethylene typically has a volume of no more than about 100 liters or even more.

The requirement for such volumes, combined with the need for gradually decreasing wall thicknesses, places high demands on the physical properties of the tank walls, both after manufacture and during end use. Thus, the walls of the fuel reservoir must not deform or shrink after they are manufactured, and must have a well-defined shape and stiffness during use.

The use of an injection molding process would make it possible to obtain much more complex geometries than those obtained by conventional blow molding methods. However, it is believed that the physical properties discussed above would not be suitable for an injection molded fuel reservoir. Current common polyethylene grades for injection molding do not meet the high mechanical properties required for automotive fuel tanks (Environmental Crack Resistance (ESCR), cold impact resistance, etc.)

Thus, there is a continuing need to develop injection molded products that exhibit resistance to cracking or tearing. Hydrocarbon containers and fuel containers for non-automotive applications also often require improved physical performance and may be subject to various legal and/or industry requirements. Accordingly, there is a need for hydrocarbon and fuel containers exhibiting good environmental stress crack resistance, creep resistance, and impact resistance.

Thus, it is an object of the present invention to provide injection molded articles containing polyethylene resin having improved mechanical properties and improved machinability.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides an injection molded article comprising at least one metallocene catalyzed polymerization polyethylene resin comprising at least two metallocene catalyzed polymerization polyethylene fractions A and B, wherein at least one polyethylene resin obtained by metallocene catalyzed polymerization contains

from at least 40 wt. % up to not more than 50 wt. % of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where fraction A has a melt flow index MI2 of at least 100.0 g/10 min., determined in accordance with ISO 1133 , condition D, at 190°C and under a load of 2.16 kg; and

where at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a density of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C; a melt flow index MI2 of at least 1.4 g/10 min. to no more than 2.5 g/10 min., measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

The present invention also relates to a method for producing an injection molded article according to the first aspect of the present invention, comprising the steps of a) providing at least one polyethylene resin obtained by the metallocene catalyzed polymerization described herein; and b) injection molding said polyethylene resin into an article.

The present inventors have demonstrated that the injection molded articles of the present invention, such as hydrocarbon and fuel containers, have improved creep resistance and stability while maintaining adequate strength, stress cracking resistance, impact resistance, low distortion and shrinkage. .

The independent and dependent claims set forth specific and preferred features of the present invention. Features from dependent claims may be combined with features from independent or other dependent claims, as appropriate.

Hereinafter, the present invention will be described in more detail. In the following parts, various aspects of the present invention are defined in more detail. Each aspect thus defined may be combined with any other aspect or aspects, unless expressly stated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graph of rheometric dynamic analysis ("RDA") results showing viscosity versus shear rate for two polyethylene products according to embodiments of the present invention and two comparative examples.

Figure 2 is a graph showing spiral flow length (SFL) vs. injection molding pressure increase for a polyethylene product according to embodiments of the present invention and two comparative examples.

Figure 3 is a graph showing the % shrinkage of cast squares containing either polyethylene resins according to embodiments of the present invention or comparative resins.

DETAILED DESCRIPTION OF THE INVENTION

When describing the present invention, the terms used are to be construed in accordance with the following definitions, unless the context requires otherwise.

As used herein, the singular forms include both the singular and the plural unless the context clearly dictates otherwise. By way of example, "resin" means one resin or more than one resin.

The terms "comprising", "comprises", and "consisting of" as used herein are synonymous with "comprising", "comprises" or "comprising", "comprises", and are inclusive or subject to change, and do not exclude additional, not listed members, elements or steps of the method. It is understood that the terms "comprising", "comprises" and "consisting of" as used herein include the terms "consisting of", "consists of", and "consists of".

The listing of numerical ranges by endpoints includes all integers and, if appropriate, fractions referred to this range (for example, from 1 to 5 can include 1, 2, 3, 4, when it comes to, for example, the number of elements, and may also include 1.5, 2, 2.75 and 3.80 when referring to measurements, for example). The endpoint enumeration also includes the endpoint values themselves (for example, 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range listed herein is intended to include all subranges included therein.

All references cited in this specification are hereby incorporated by reference in their entirety. In particular, the ideas of all references specifically mentioned in this document are incorporated by reference.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, occurrences of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment, but may. In addition, specific features, structures, or characteristics may be combined in any suitable manner, as will be apparent to those skilled in the art from this disclosure, in one or more embodiments. In addition, while some of the embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments should be within the scope of the invention and form different embodiments, as will be appreciated by those skilled in the art. the field of technology.

Preferred claims (features) and embodiments of the articles, resins, and uses of this invention are given below. Each statement and embodiment of the present invention thus defined may be combined with any other statement and/or embodiment, unless otherwise indicated. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features or claims indicated as being preferred or advantageous. While the present invention, in particular, is covered by any one or any combination of one or more of the following aspects and embodiments 1-29 with any other statement and/or embodiments.

1. An injection molded article comprising at least one polyethylene resin obtained by a metallocene catalyzed polymerization, said at least one resin containing at least two polyethylene fractions A and B obtained by a metallocene catalyzed polymerization, wherein at least one polyethylene resin obtained by metallocene catalyzed polymerization contains

from at least 40 wt. % up to not more than 50 wt. % of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where fraction A has a melt flow index MI2 of at least 100.0 g/10 min., determined in accordance with ISO 1133 , condition D, at 190°C and under a load of 2.16 kg, and/or fraction A has a melt flow index MI105 of at least 13.0 g/10 min., determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg, using a head characterized by a diameter of 1.05 mm and a height of 4 mm; and

where at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a density of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C; a melt flow index MI2 of at least 1.4 g/10 min. to no more than 2.5 g/10 min., measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

2. An injection molded article comprising at least one polyethylene resin obtained by a metallocene catalyzed polymerization, said at least one resin containing at least two polyethylene fractions A and B obtained by a metallocene catalyzed polymerization, wherein at least one polyethylene resin obtained by metallocene catalyzed polymerization contains

from at least 40 wt. % up to not more than 50 wt. % of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where fraction A has a melt flow index MI2 of at least 100.0 g/10 min., determined in accordance with ISO 1133 , condition D, at 190°C and under a load of 2.16 kg; and

where at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a density of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C; a melt flow index MI2 of at least 1.4 g/10 min. to no more than 2.5 g/10 min., measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

3. An injection molded article comprising at least one polyethylene resin obtained by a metallocene catalyzed polymerization, said at least one resin containing at least two polyethylene fractions A and B obtained by a metallocene catalyzed polymerization, wherein at least one polyethylene resin obtained by metallocene catalyzed polymerization contains

from at least 40 wt. % up to not more than 50 wt. % of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where fraction A has a melt flow index MI105 of at least 13.0 g/10 min., determined in accordance with ISO 1133 , condition D, at 190° C. and under a load of 2.16 kg, using a head having a diameter of 1.05 mm and a height of 4 mm; and

where at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a density of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C; a melt flow index MI2 of at least 1.4 g/10 min. to no more than 2.5 g/10 min., measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

4. An injection molded article according to any one of Claims 1-3, wherein at least one polyethylene resin obtained by metallocene catalyzed polymerization has a density of at least 0.941 g/cm ³ , preferably at least 0.942 g/cm ³ , preferably at least 0.943 g/cm ³ , preferably at least 0.944 g/cm ³ , measured for granules according to ISO 1183 at 23°C.

5. An injection molded article according to any one of Claims 1-4, wherein at least one polyethylene resin produced by metallocene catalyzed polymerization has a density of at least 0.941 g/cm3 to at most ^0.950 g/cm ³ , preferably from at least 0.942 g/cm ³ to at most 0.950 g/cm ³ , preferably from at least 0.943 g/cm ³ to at most 0.950 g/cm ³ , preferably from at least 0.944 g /cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C.

6. An injection molded article according to any one of Claims 1-5, wherein at least one polyethylene resin produced by metallocene catalyzed polymerization has a melt flow index MI2 of at least 1.5 g/10 min. to no more than 2.5 g/10 min., measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

7. An injection molded article according to any one of Claims 1-6, wherein at least one polyethylene resin produced by metallocene-catalyzed polymerization has a molecular weight distribution M _w /M _n of at least 4, 0 to not more than 6.0, while M _w is the weight average molecular weight, and M _n is the number average molecular weight, determined using gel permeation chromatography, while preferably at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a distribution of molecular weight M _w /M _n constituting from at least 4.1 to not more than 5.5, for example, from at least 4.2 to not more than 5.5, preferably from at least 4, 3 to not more than 5.4, preferably from at least 4.4 to not more than 5.4, preferably from at least 4.4 to not more than 5.3, preferably from at least 4 .4 up to no more than 5.2.

8. An injection molded article according to any one of Claims 1-7, wherein at least one polyethylene resin produced by metallocene catalyzed polymerization has an HLMI of at least 50.0 g/10 min, preferably at least 60.0 g/10 min., preferably at least 65.0 g/10 min., preferably at least 70.0 g/10 min., measured in accordance with ISO 1133:1997, condition G, at 190°C and under a load of 21.6 kg.

9. An injection molded article according to any one of Claims 1-8, wherein Fraction A of at least one polyethylene resin produced by metallocene catalyzed polymerization has a flake density that is at least 0.005 g /cm ³ greater than the density of at least one polyethylene resin obtained by metallocene-catalyzed polymerization; preferably characterized by a density that is at least 0.010 g/cm ³ greater than the density of at least one polyethylene resin obtained by metallocene catalyzed polymerization, which is preferably at least 0.015 g/cm ³ greater, preferably at least 0.020 g/cm ³ greater than the density of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where the density is measured in accordance with ISO 1183 at 23°C.

10. The product obtained by injection molding, in accordance with any of the statements 1-9, where the fraction A of at least one polyethylene resin obtained by metallocene catalyzed polymerization is characterized by a density measured for flaky particles of at least 0.960 g / cm ³ , preferably at least 0.965 g/cm ³ , preferably at least 0.970 g/cm ³ , determined according to ISO 1183 at 23°C.

11. An injection molded article according to any one of claims 1-10, wherein the polyethylene fraction A of at least one polyethylene resin obtained by metallocene catalyzed polymerization has a melt flow index MI2, measured for flake particles, of at least at least 100.0 g/10 min., preferably at least 110.0 g/10 min., preferably at least 120.0 g/10 min., preferably at least 130.0 g/10 min., preferably at least 140.0 g/10 min., preferably at least 150.0 g/10 min., preferably at least 155.0 g/10 min., determined in accordance with ISO 1133, condition D, at 190 °C and under load 2.16 kg.

12. An injection molded article according to any one of claims 1-11, wherein the polyethylene fraction A of at least one polyethylene resin obtained by metallocene catalyzed polymerization has a melt flow index MI105, measured for flake particles, of at least at least 13.0 g/10 min., preferably at least 14.0 g/10 min., preferably at least 15.0 g/10 min., preferably at least 18.0 g/10 min., preferably at least 20.0 g/10 min., preferably at least 23.0 g/10 min., determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg, using a head , characterized by a diameter of 1.05 mm and a height of 4 mm.

13. The product obtained by injection molding, in accordance with any of the statements 1-12, where at least one polyethylene resin obtained by metallocene-catalyzed polymerization contains from 41 wt. % up to not more than 50 wt. % polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene-catalyzed polymerization, for example, from 42.0 wt. % up to not more than 50.0 wt. %, for example, from 42.0 wt. % up to not more than 49.0 wt. %, preferably from 42.0 wt. % up to not more than 48.0 wt. %, for example, from 43.0 wt. % up to not more than 50.0 wt. %, for example, from 43.0 wt. % up to not more than 49.0 wt. %, for example, from 43.0 wt. % up to not more than 48.0 wt. %.

14. An injection molded article according to any one of claims 1-13, wherein at least one polyethylene resin obtained by metallocene-catalyzed polymerization has a multimodal molecular weight distribution, and preferably said at least one polyethylene resin , obtained by metallocene-catalyzed polymerization, is characterized by a bimodal molecular weight distribution.

15. The product obtained by injection molding, in accordance with any of the statements 1-14, where each fraction of the specified at least one polyethylene resin obtained by metallocene catalyzed polymerization obtained in different reactors from at least two reactors connected in series, preferably at least two loop reactors connected in series, preferably at least two slurry loop reactors connected in series.

16. An injection molded article according to any one of claims 1-15, wherein at least one polyethylene resin obtained by metallocene-catalyzed polymerization is obtained using a method comprising the steps of:

(a) supplying ethylene monomer, diluent, at least one metallocene catalyst, optionally hydrogen, and optionally one or more olefin comonomers to at least one first slurry loop reactor; carrying out the polymerization of ethylene monomer and optionally one or more olefin comonomers in the presence of a metallocene catalyst and optionally hydrogen in said first slurry loop reactor to obtain a first polyethylene fraction A and

(b) supplying the first polyethylene fraction A to a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and optionally one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining polyethylene resin obtained by metallocene catalyzed polymerization.

17. An injection molded article according to any one of Claims 1-16, wherein said at least one polyethylene resin obtained by metallocene-catalyzed polymerization is obtained using a method comprising the steps of:

(a) supplying ethylene monomer, diluent, at least one metallocene catalyst, optionally hydrogen, and optionally one or more olefin comonomers to at least one first slurry loop reactor; carrying out the polymerization of ethylene monomer in the presence of a metallocene catalyst and optionally hydrogen in the specified first slurry loop reactor to obtain the first polyethylene fraction A and

(b) feeding the first polyethylene fraction A into a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining a polyethylene resin obtained by metallocene catalyzed polymerization.

18. An injection molded article according to any one of Claims 1-17, wherein fraction A of said at least one polyethylene resin obtained by metallocene catalyzed polymerization is an ethylene homopolymer and fraction B of said at least one polyethylene resin obtained by metallocene catalyzed polymerization is an ethylene copolymer.

19. An injection-molded article according to any one of claims 1-18, wherein the article is a tank, drum, container, tank, vat, canister, cylinder, tank, fuel damper, connector, plug, or lid, or any other cast component.

20. An injection molded article according to any one of Claims 1-19, wherein the article is an automotive fuel tank.

21. An injection molded article according to any one of Claims 1-20, wherein the article is a Selective Catalytic Reduction (SCR) tank or an AdBlue® tank.

22. A method for producing an injection molded article according to any one of claims 1-21, comprising the steps of a) providing at least one polyethylene resin obtained by a metallocene-catalyzed polymerization described in any one of claims 1-18; and b) injection molding said polyethylene resin into an article.

23. A tank for a car containing at least one polyethylene resin obtained by metallocene catalyzed polymerization, while said at least one resin contains at least two polyethylene fractions A and B obtained by metallocene catalyzed polymerization, where at least one polyethylene resin obtained by metallocene-catalyzed polymerization contains from at least 40 wt. % up to not more than 50 wt. % of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where fraction A has a melt flow index MI2 of at least 100.0 g/10 min., determined in accordance with ISO 1133 , condition D, at 190°C and under a load of 2.16 kg, and/or fraction A has a melt flow index MI105 of at least 13.0 g/10 min, determined in accordance with ISO 1133, condition D, at 190° C. and under a load of 2.16 kg, using a head characterized by a diameter of 1.05 mm and a height of 4 mm; and

where at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a density of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C; a melt flow index MI2 of at least 1.4 g/10 min. to no more than 2.5 g/10 min., measured for granules in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

24. An automobile reservoir according to claim 23, comprising at least one polyethylene resin obtained by the metallocene catalyzed polymerization described in any one of claims 1-18.

25. An automobile tank according to any of claims 23-24, comprising at least two parts that have been joined together to form said tank having a wall defining a chamber, at least one of the parts being injection molded from at least one polyethylene resin obtained by the catalyzed metallocene polymerization described in any of statements 1-18.

26. A tank for an automobile in accordance with any of the statements 23-25, which contains two injection molded parts that have been connected together.

27. A tank for an automobile according to any of the statements 23-26, where the two parts were connected together by welding.

28. A tank for an automobile in accordance with any of the statements 23-27, which is a tank for automotive fuel.

29. An automobile tank according to any of statements 23-28, which is a selective catalytic reduction (SCR) tank or an AdBlue® tank.

The present invention relates to a product obtained by injection molding, obtained using a composition containing at least one polyethylene resin obtained by catalyzed metallocene polymerization, described in this document, containing from at least 40 wt. % up to not more than 50 wt. % of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, where fraction A has a melt flow index MI2 of at least 100.0 g/10 min., determined in accordance with ISO 1133 , condition D, at 190°C and under a load of 2.16 kg, and/or fraction A has a melt flow index MI105 of at least 13.0 g/10 min., determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg, using a head characterized by a diameter of 1.05 mm and a height of 4 mm; and wherein at least one polyethylene resin obtained by metallocene-catalyzed polymerization has a density measured for granules of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ determined in accordance with ISO 1183 at 23 °C; a melt flow index MI2, measured for pellets, of at least 1.4 g/10 min. to no more than 2.5 g/10 min., determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

By "comprising" it is preferably meant that said product obtained by injection molding contains from 50 wt. % up to 100 wt. % of at least one polyethylene resin obtained by metallocene-catalyzed polymerization.

As used herein, the term "polyethylene resin" refers to polyethylene flake particles or powder that are extruded and/or melted and granulated and can be obtained by mixing and homogenizing the polyethylene resin as described herein, for example, using a mixing and /or extruder equipment. The measurements of density and melt flow index of the polyethylene resin obtained by metallocene catalyzed polymerization given in the claims are carried out for the granular form. Under normal manufacturing conditions in a manufacturing plant, the melt flow rate MI2 is expected to be higher for flake particles compared to resin (pellets).

As used herein, the terms "flake particles" or "powder" refer to a polyethylene material with a wear-resistant catalyst particle at the core of each grain and is defined as the material after exiting the polymerization reactor (or the final polymerization reactor in the case of several reactors connected in series) , but not granulated, extruded and/or melted. Density and melt flow rate measurements of fraction A of the polyethylene resin obtained by metallocene-catalyzed polymerization given in the claims are made for flake particles.

In some embodiments, fraction A has a density measured for the polymeric material after it leaves the polymerization reactor (flake particles) that is at least 0.008 g/cm ³ greater than the density of the polyethylene resin, preferably at least 0.013 g/cm ³ more, preferably at least 0.018 g/cm ³ more, preferably at least 0.023 g/cm ³ more than the density of at least one polyethylene resin obtained by metallocene-catalyzed polymerization according to ISO 1183 at 23°C. In some embodiments, Fraction A has a density, measured for the polymeric material after it leaves the polymerization reactor, of at least 0.963 g/cm ³ ; preferably at least 0.967 g/cm ³ , preferably at least 0.970 g/cm ³ according to ISO 1183 at 23°C.

In a preferred embodiment, at least one polyethylene resin obtained by metallocene catalyzed polymerization suitable for use in an injection molded article has a multimodal molecular weight distribution. In some embodiments, the polyethylene resin produced by metallocene catalyzed polymerization has a bimodal molecular weight distribution.

As used herein, the term "monomodal polyethylene" or "polyethylene with a monomodal molecular weight distribution" refers to a polyethylene having a single peak in its molecular weight distribution curve, which is also defined as a unimodal distribution curve. As used herein, the term "bimodal molecular weight distribution polyethylene" or "bimodal polyethylene" means that the polyethylene has a distribution curve that is the sum of two unimodal molecular weight distribution curves and refers to a polyethylene based product having two different but possibly overlapping populations of polyethylene macromolecules, each of which is characterized by different weight average molecular weights. The term "polyethylenes with multimodal molecular weight distribution" or "multimodal polyethylenes" means polyethylenes with a distribution curve that is the sum of at least two, preferably more than two unimodal distribution curves, and refers to a polyethylene-based product containing two or more different, but possibly overlapping populations of polyethylene macromolecules, each with a different weight average molecular weight. A multimodal polyethylene resin may have an "apparently monomodal" molecular weight distribution, which is a molecular weight distribution curve with a single peak and no shoulder. However, a polyethylene resin will still be multimodal if it contains two different populations of polyethylene macromolecules, each with different weight average molecular weights as defined above, for example, if the two different populations were produced in different reactors and/or in different conditions.

In some embodiment, at least one polyethylene resin obtained by metallocene catalyzed polymerization for use in an injection molded article has a multimodal, preferably bimodal, molecular weight distribution. At least one polyethylene resin obtained by metallocene catalyzed polymerization suitable for use in an injection molded article can be obtained by polymerizing ethylene and one or more optional comonomers, optionally hydrogen, in the presence of a metallocene-based catalyst system.

As used herein, the term "catalyst" refers to a substance that causes a change in the rate of a polymerization reaction. In the present invention, the term is particularly applicable to catalysts suitable for the polymerization of ethylene to polyethylene. The present invention especially relates to polyethylene obtained in the presence of a metallocene catalyst. As used herein, the terms "polyethylene resin produced by metallocene catalyzed polymerization" and "polyethylene produced by metallocene catalyzed polymerization" are synonymous and used interchangeably and refer to polyethylene produced in the presence of a metallocene catalyst.

The term "metallocene catalyst" is used herein to describe any transition metal complexes containing metal atoms associated with one or more ligands. Metallocene catalysts are compounds of transition metals of group IV of the Periodic Table of elements such as titanium, zirconium, hafnium, etc., and have a coordination structure with a metal-containing compound and ligands consisting of one or two groups of cyclopentadienyl, indenyl, fluorenyl, or their derivatives . The structure and geometry of the metallocene can be modified to adapt to the specific needs of the manufacturer, depending on the desired polymer. Metallocenes contain a single metal site, which allows for better control of the branching and molecular weight distribution of the polymer. Monomers are inserted between the metal and the growing polymer chain.

In one embodiment of the present invention, the metallocene catalyst is a compound of formula (I) or (II),

where the metallocenes according to formula (I) are non-bridged metallocenes, and the metallocenes according to formula (II) are bridged metallocenes;

where the specified metallocene in accordance with the formula (I) or (II) contains two Ar associated with M, which may be the same or different from each other;

where Ar is an aromatic ring, group or fragment, and each Ar is independently selected from the group consisting of cyclopentadienyl, indenyl (IND), tetrahydroindenyl (THI) and fluorenyl, where each of these groups may be optionally substituted with one or more substituents , each independently selected from the group consisting of halogen, a hydrosilyl group, SiR ₃ , where R is a hydrocarbyl containing 1 to 20 carbon atoms and a hydrocarbyl containing 1 to 20 carbon atoms, and said hydrocarbyl is optionally contains one or more atoms selected from the group consisting of B, Si, S, O, F, Cl and P;

where M is a transition metal selected from the group consisting of titanium, zirconium, hafnium and vanadium; and preferably is zirconium;

where each Q is independently selected from the group consisting of halogen; a hydrocarboxy group containing from 1 to 20 carbon atoms; and hydrocarbyl containing from 1 to 20 carbon atoms, and while the specified hydrocarbyl optionally contains one or more atoms selected from the group consisting of B, Si, S, O, F, Cl and P; and

where R'' is a divalent group or moiety bridging two Ar groups and selected from the group consisting of C ₁ -C ₂₀ alkylene, germanium, silicon, siloxane, alkylphosphine and amine, and said R'' is optionally substituted with one or more substituents each independently selected from the group consisting of halogen, a hydrosilyl group, SiR ₃ , where R is a hydrocarbyl of 1 to 20 carbon atoms and a hydrocarbyl of 1 to 20 carbon atoms, and wherein said hydrocarbyl optionally contains one or more atoms selected from the group consisting of B, Si, S, O, F, Cl and P.

Preferably, the metallocene contains a bridged bis-indenyl and/or bridged bis-tetrahydrogenated indenyl component. In some embodiments, the metallocene may be selected from one of the following formulas (IIIa) or (IIIb):

where each R in formula (IIIa) or (IIIb) is the same or different and is independently selected from hydrogen or XR' _v , in which X is selected from the elements of group 14 of the Periodic Table of the Elements (preferably carbon), oxygen or nitrogen, and each R' is the same or different and is selected from hydrogen or C 1 -C 20 hydrocarbyl, where v+1 is a valence of X, preferably R is hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl group; R'' is a structural bridge between two indenyls or tetrahydrogenated indenyls, which contains a C ₁ -C ₄ alkylene radical, dialkylgermanium, silicon or siloxane, or an alkylphosphine or amine radical; Q is a hydrocarbyl radical containing from 1 to 20 carbon atoms, or halogen, preferably Q is F, Cl or Br; and M is a Group 4 transition metal of the Periodic Table of the Elements or vanadium.

Each indenyl or tetrahydroindenyl component may be substituted with R in the same manner or in a different manner from each other at one or more positions of any of the articulated rings. Each substitute is selected independently.

If the cyclopentadienyl ring is substituted, then its substituents should not be so bulky as to interfere with the coordination of the olefin monomer to the metal M. Any XR' _v substituents on the cyclopentadienyl ring are preferably methyl. More preferably, at least one and most preferably both of the cyclopentadienyl rings are unsubstituted.

In a particularly preferred embodiment, the metallocene contains a bridged unsubstituted bis-indenyl and/or bis-tetrahydrogenated indenyl, i. e. all R are hydrogen atoms. More preferably, the metallocene contains a bridged unsubstituted bis-tetrahydrogenated indenyl.

Illustrative examples of metallocene catalysts include, without limitation, bis(cyclopentadienyl)zirconium dichloride (Cp ₂ ZrCl ₂ ), bis(cyclopentadienyl)titanium dichloride (Cp2TiCl ₂ ), bis(cyclopentadienyl)hafnium dichloride (Cp ₂ HfCl ₂ ); bis(tetrahydroindenyl)zirconium dichloride, bis(indenyl)zirconium dichloride and bis(n-butylcyclopentadienyl)zirconium dichloride; ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, ethylenebis(1-indenyl)zirconium dichloride, dimethylsilylene-bis(2-methyl-4-phenylinden-1-yl)zirconium dichloride, diphenylmethylene(cyclopentadienyl) )(fluoren-9-yl)zirconium dichloride and dimethylmethylene[1-(4-tert-butyl-2-methylcyclopentadienyl)](fluoren-9-yl)zirconium dichloride. The most preferred metallocene is ethylene-bis(tetrahydroindenyl)zirconium dichloride or ethylene-bis(tetrahydroindenyl)zirconium difluoride.

Used in this document, the term "hydrocarbyl containing from 1 to 20 carbon atoms" refers to a fragment selected from the group consisting of linear or branched C ₁ -C ₂₀ alkyl; C ₃ -C ₂₀ cycloalkyl; C ₆ -C ₂₀ aryl; C ₇ -C ₂₀ alkylaryl and C ₇ -C ₂₀ arylalkyl, or any combination thereof. Illustrative hydrocarbyl groups are methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2-ethylhexyl, and phenyl.

As used herein, the term "hydrocarboxy group containing from 1 to 20 carbon atoms" refers to a fragment with the formula hydrocarbyl-O-, where the hydrocarbyl contains from 1 to 20 carbon atoms, as described in this document. Preferred hydrocarboxy groups are selected from the group consisting of alkyloxy, alkenyloxy, cycloalkyloxy or aralkoxy groups.

As used herein, the term "alkyl", by itself or as part of another substituent, refers to a straight or branched saturated hydrocarbon group linked by carbon-carbon single bonds containing 1 or more carbon atoms, for example, from 1 to 12 carbon atoms, eg 1 to 6 carbon atoms, eg 1 to 4 carbon atoms. Where a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, C _1-2 alkyl means alkyl with 1-12 carbon atoms. Examples of alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, pentyl and its chain isomers, hexyl and its chain isomers, heptyl and its chain isomers, octyl and its chain isomers chains, nonyl and its chain isomers, decyl and its chain isomers, undecyl and its chain isomers, dodecyl and its chain isomers. Alkyl groups are characterized by the general formula C _n H _2n+1 .

As used herein, the term "cycloalkyl", by itself or as part of another substituent, refers to a saturated or partially saturated cyclic alkyl radical. Cycloalkyl groups are characterized by the general formula C _n H _2n-1 . Where a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, examples of C _3-6 cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.

As used herein, the term "aryl", by itself or as part of another substituent, refers to a radical derived from an aromatic ring such as phenyl, naphthyl, indanyl, or 1,2,3,4-tetrahydronaphthyl. Where a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain.

As used herein, the term "alkylaryl", by itself or as part of another substituent, refers to an aryl group as defined herein, where the hydrogen atom is replaced by an alkyl as defined herein. Where a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the named group or subgroup may contain.

As used herein, the term "arylalkyl", by itself or as part of another substituent, refers to an alkyl group, as defined herein, where the hydrogen atom is replaced by aryl, as defined herein. Where a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Examples of C _6-10 aryl-C _1-6 alkyl radicals include benzyl, phenethyl, dibenzylmethyl, methylphenylmethyl, 3-(2-naphthyl)butyl and the like.

As used herein, the term "alkylene", by itself or as part of another substituent, refers to alkyl groups that are divalent, i. with two single bonds to join two other groups. Alkylene groups may be linear or branched and may be substituted as described herein. Non-limiting examples of alkylene groups include methylene (-CH ₂ -), ethylene (-CH ₂ -CH ₂ -), methylmethylene (-CH(CH ₃ )-), 1-methylethylene (-CH(CH ₃ )-CH ₂ -) , n-propylene (-CH ₂ -CH ₂ -CH ₂ -), 2-methylpropylene (-CH ₂ -CH (CH ₃ ) -CH ₂ -), 3-methylpropylene (-CH ₂ -CH ₂ -CH (CH ₃ )-), n-butylene (-CH ₂ -CH ₂ -CH ₂ -CH ₂ -), 2-methylbutylene (-CH ₂ -CH (CH ₃ ) -CH ₂ -CH ₂ -), 4-methylbutylene ( -CH ₂ -CH ₂ -CH ₂ -CH(CH ₃ )-), pentylene and its chain isomers, hexylene and its chain isomers, heptylene and its chain isomers, octylene and its chain isomers, nonylene and its chain isomers, decylene and its chain isomers, undecylene and its chain isomers, dodecylene and its chain isomers. Where a subscript is used herein after a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. For example, C ₁ -C ₂₀ alkylene refers to alkylene containing from 1 to 20 carbon atoms.

Exemplary halogen atoms include chlorine, bromine, fluorine, and iodine, where fluorine and chlorine are preferred.

The metallocene catalysts used herein are preferably supported on a solid support. The support may be an inert organic or inorganic solid that does not chemically react with any of the components of a conventional metallocene catalyst. Suitable support materials for the supported catalyst include solid inorganic oxides such as silica, alumina, magnesium oxide, titanium oxide, thorium oxide, as well as mixed oxides of silica and one or more Group 2 or 13 metal oxides, such as mixed silica-magnesium oxides and silica-alumina oxides. Silica, alumina, and mixed oxides of silica and one or more Group 2 or 13 metal oxides are preferred substrate materials. Preferred examples of such mixed oxides are silica-alumina. Most preferred is a silica compound. Preferably, the metallocene catalyst is supported on a solid support, preferably a solid silica support. The silica may be in granular, agglomerated, colloidal or other form.

и предпочтительно от 75 до 220

.In some embodiments, the metallocene catalyst support is a porous support, and preferably a porous silica support, having a surface area of 200 ^m2 /g to 900 ^m2 /g. In another embodiment, the polymerization catalyst support is a porous support, and preferably a porous a silica support having an average pore volume of 0.5 ml/g to 4 ml/g. In yet another embodiment, the polymerization catalyst support is a porous support, and preferably a porous silica support, having an average pore diameter of 50 to 300

and preferably from 75 to 220

.

Preferably, the supported metallocene catalyst is activated. The cocatalyst that activates the metallocene catalyst component can be any cocatalyst known for this purpose, such as an aluminium-containing cocatalyst, a boron-containing cocatalyst, or a fluorinated catalyst. The aluminum-containing cocatalyst may contain an aluminoxane, an aluminum alkyl, a Lewis acid, and/or a fluorinated catalyst support.

In some embodiments, an alumoxane is used as an activating agent for a metallocene catalyst. Alumoxane can be used in combination with a catalyst to improve the activity of the catalyst during the polymerization reaction.

As used herein, the terms "alumoxane" and "aluminoxane" are used interchangeably and refer to a substance that is capable of activating a metallocene catalyst. In some embodiments, alumoxanes include oligomeric linear and/or cyclic alkylalumoxanes. In a further embodiment, the alumoxane is characterized by formula (IV) or (V):

where x is 1-40 and preferably 10-20;

where y is 3-40 and preferably 3-20; and

where each R ^a is independently selected from C ₁ -C ₈ alkyl, and preferably each R ^a is methyl. In a preferred embodiment, the alumoxane is methylalumoxane (MAO).

In a preferred embodiment, the metallocene catalyst is a supported metallocene-alumoxane catalyst containing a metallocene and an alumoxane that are bonded to a porous silica support. Preferably, the metallocene catalyst is a bridged bis-indenyl catalyst and/or a bridged bis-tetrahydrogenated indenyl catalyst.

One or more aluminum alkyls represented by the formula AlR ^b _x can be used as an additional cocatalyst, where each R ^b is the same or different and is selected from halogen atoms or from alkoxy groups or alkyl groups containing from 1 to 12 carbon atoms, and x is from 1 to 3. Non-limiting examples are triethylaluminum (TEAL), triisobutylaluminum (TIBAL), trimethylaluminum (TMA), and methylmethylethylaluminum (MMEAL). Particularly suitable are trialkylaluminum compounds, most preferred being triisobutylaluminum (TIBAL) and triethylaluminum (TEAL).

Suitable polymerization of ethylene includes, without limitation, homopolymerization of ethylene or copolymerization of ethylene and a higher 1-olefin comonomer.

As used herein, the term "comonomer" refers to olefin comonomers that are suitable for polymerization with an alpha-olefin monomer. The comonomers may contain, without limitation, aliphatic C ₃ -C ₂₀ alpha-olefins. Examples of suitable aliphatic C ₃ -C ₂₀ alpha olefins include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. In some embodiments of the present invention, said comonomer is 1-hexene.

In a preferred embodiment, Fraction A of at least one polyethylene resin produced by metallocene catalyzed polymerization for use in said injection molded article is an ethylene homopolymer. In a preferred embodiment, fraction B of at least one polyethylene resin obtained by metallocene catalyzed polymerization for use in said injection molded article is an ethylene copolymer. As used herein, the term "ethylene copolymer" is intended to cover polymers that are essentially composed of repeating units derived from ethylene and at least one other C ₃ -C ₂₀ alpha-olefin comonomer, preferably the comonomer is 1-hexene. As used herein, the term "ethylene homopolymer" is intended to encompass polymers that essentially consist of repeating units derived from ethylene. For example, homopolymers may contain at least 99.8%, preferably 99.9 wt. % of repeating units that are derivatives of ethylene.

Preferably, at least one polyethylene resin obtained by metallocene catalyzed polymerization for use in said injection molded article is produced in two or more reactors connected in series. In some embodiments, at least one polyethylene resin obtained by metallocene catalyzed polymerization contains two polyethylene fractions A and B obtained by metallocene catalyzed polymerization, where each fraction is produced in different reactors from two reactors connected in series.

The polyethylene resin obtained by metallocene-catalyzed polymerization is preferably obtained by using at least two reactors under different polymerization conditions.

The polyethylene resin obtained by metallocene-catalyzed polymerization can be obtained in gas phase, solution or suspension. Slurry polymerization is preferably used to produce a polyethylene resin composition, preferably in a slurry loop or continuously stirred reactor.

Preferably, the polyethylene resin produced by the metallocene catalyzed polymerization is produced in two or more reactors connected in series, comprising at least one first and at least one second reactor, preferably loop reactors, more preferably slurry loop reactors, most preferably full liquid liquid loop reactors. loop filling in the presence of the same or different metallocene catalysts. The most preferred polymerization process is carried out in two slurry loop reactors connected in series, preferably liquid loop reactors with full loop filling, i.e. in a two-loop reactor.

As used herein, the terms "loop reactor" and "slurry loop reactor" may be used interchangeably herein.

The catalyst is preferably added to the loop reactor as a catalyst slurry. As used herein, the term "catalyst slurry" refers to a composition containing catalyst solids and a diluent. The solid particles may be suspended in the diluent either spontaneously or by homogenization techniques such as mixing. Solid particles can be unevenly distributed in the diluent and form a precipitate or deposit.

As used herein, the term "diluent" refers to any organic diluent that does not dissolve the synthesized polyolefin. As used herein, the term "diluent" refers to diluents in liquid state, liquid at room temperature, and preferably liquid under loop reactor pressure conditions. Suitable diluents include, without limitation, hydrocarbon-based diluents such as aliphatic, cycloaliphatic, and aromatic hydrocarbon solvents, or halogenated versions of such solvents. Preferred solvents are saturated C ₁₂ hydrocarbons or lower straight or branched chain hydrocarbons, saturated alicyclic or aromatic C ₅ -C ₉ hydrocarbons, or halogenated C ₂ -C ₆ hydrocarbons. Non-limiting illustrative examples of solvents are butane, isobutane, pentane, hexane, heptane, cyclopentane, cyclohexane, cycloheptane, methylcyclopentane, methylcyclohexane, isooctane, benzene, toluene, xylene, chloroform, chlorobenzenes, tetrachloroethylene, dichloroethane and trichloroethane, preferably isobutane.

In certain embodiments, each loop reactor may include interconnected pipes defining a path through the reactor. In certain embodiments, each loop reactor may comprise at least two risers, at least one upper reactor conduit segment, at least one lower reactor conduit segment connected to each other by connections to form a complete loop, one or more supply lines, one or more outlets, one or more cooling jackets per pipe and one pump, thus defining a continuous flow path for the polymer slurry. The vertical sections of the pipe segments are preferably provided with cooling jackets. The heat of the polymerization reaction can be recovered by the cooling water circulating in these reactor jackets. The loop reactor preferably operates in an all liquid mode.

In certain embodiments, the first and second loop reactors may be connected by means such as a transfer line or one or more settling tanks. In some embodiments, the first polyethylene fraction may be transferred from the first loop reactor to the second loop reactor via a transfer line. In some embodiments, the first polyethylene fraction may be discharged in batches, sequentially or continuously from the first loop reactor through one or more settling tanks and transferred to the second loop reactor via a transfer line.

In some embodiments, at least one polyethylene resin obtained by metallocene catalyzed polymerization for use in an injection molded article is obtained using a method comprising the steps of:

(a) supplying ethylene monomer, diluent, at least one metallocene catalyst, optionally hydrogen, and optionally one or more olefin comonomers to at least one first slurry loop reactor; carrying out the polymerization of ethylene monomer and optionally one or more olefin comonomers in the presence of a metallocene catalyst and optionally hydrogen in said first slurry loop reactor to obtain a first polyethylene fraction and

(b) feeding the first polyethylene fraction into a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and optionally one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining a polyethylene resin obtained by metallocene catalyzed polymerization.

In some preferred embodiments, at least one polyethylene resin obtained by metallocene catalyzed polymerization for use in an injection molded article is obtained using a method comprising the steps of:

(a) supplying ethylene monomer, diluent, at least one metallocene catalyst, optionally one or more olefin comonomers, and optionally hydrogen, to at least one first slurry loop reactor; polymerizing the ethylene monomer in the presence of a metallocene catalyst and optionally hydrogen in said first slurry loop reactor to produce a first polyethylene fraction, and

(b) feeding the first polyethylene fraction into a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining a polyethylene resin obtained by metallocene-catalyzed polymerization.

In some alternative embodiments, at least one polyethylene resin obtained by metallocene catalyzed polymerization for use in an injection molded article is obtained using a method comprising the steps of:

(a) feeding ethylene monomer, diluent, one or more olefin comonomers, at least one metallocene catalyst, optionally hydrogen, to at least one first slurry loop reactor; carrying out the polymerization of ethylene monomer and one or more olefin comonomers in the presence of a metallocene catalyst and optionally hydrogen in said first slurry loop reactor to obtain a first polyethylene fraction and

(b) feeding the first polyethylene fraction into a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and optionally one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining a polyethylene resin obtained by metallocene catalyzed polymerization.

The polymerization steps can be carried out over a wide range of temperatures. In certain embodiments, the polymerization steps can be carried out at a temperature of 20°C to 125°C, preferably 60°C to 110°C, more preferably 75°C to 100°C, and most preferably 78°C to 98°C. FROM. Preferably, the temperature range may include the range from 75°C to 100°C and most preferably from 78°C to 98°C.

In certain embodiments, the polymerization steps can be carried out at a pressure of from about 20 bar to about 100 bar, preferably from about 30 bar to about 50 bar, and more preferably from about 37 bar to about 45 bar.

In some embodiments, the reactants include an ethylene monomer, isobutane as a hydrocarbon based diluent, a supported metallocene catalyst, and optionally use at least one comonomer such as 1-hexene.

In some embodiments, the injection molded article comprises at least one polyethylene resin obtained by metallocene catalyzed polymerization, said at least one resin comprising at least two polyethylene fractions A and B obtained by metallocene catalyzed polymerization, where at least one polyethylene resin obtained by metallocene-catalyzed polymerization contains from at least 42.0 wt. % up to not more than 49.0 wt. % polyethylene fraction A, based on the total weight of the polyethylene resin; and wherein at least one polyethylene resin obtained by metallocene-catalyzed polymerization has a density of at least 0.942 to at most 0.950 g/cm ³ measured according to ISO 1183 at 23°C; and a melt flow index MI2 of at least 1.5 g/10 min. to no more than 2.5 g/10 min., determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

In a preferred embodiment, the injection molded article comprises at least one polyethylene resin obtained by metallocene catalyzed polymerization containing two polyethylene fractions A and B, wherein fraction B has a higher molecular weight and lower density than fraction A , and each fraction is obtained in different reactors from two slurry loop reactors connected in series. The molecular weight of the fractions obtained in each of the reactors can be controlled using known techniques, such as changing the amount of hydrogen used. The density of the fractions obtained in each of the reactors can be adjusted using known techniques such as changing the amount of comonomer used.

In some embodiments, the polyethylene resin obtained by metallocene catalyzed polymerization has a melt flow index MI2 measured for pellets of at least 1.4 g/10 min. up to not more than 2.5 g/10 min., preferably the polyethylene resin has a melt flow index MI2 of at least 1.4 g/10 min. up to not more than 2.4 g/10 min., preferably from at least 1.4 g/10 min. to no more than 2.2 g/10 min., determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg.

In some embodiments, the polyethylene resin made by metallocene catalyzed polymerization has an HLMI of at least 53.0 g/10 min, measured on beads according to ISO 1133:1997, condition G, at 190° C. and under load. 21.6 kg. Preferably, the polyethylene resin has an HLMI of at least 58.0 g/10 min, preferably of at least 63.0 g/10 min, preferably of at least 68.0 g/10 min, preferably of at least at least 73.0 g/10 min, preferably at least 75.0 g/10 min.

As used herein, the molecular weight (M _n (number average molecular weight), M _w (weight average molecular weight) and M _z (average molecular weight z)) and molecular weight distributions D (M _w /M _n ), and D' (M _z /M _w ) was determined using size exclusion chromatography (SEC) and, in particular, using gel permeation chromatography (GPC).

For a polyethylene resin obtained by a metallocene-catalyzed polymerization containing two fractions A and B, where fraction B is obtained in the second reactor, the density of fraction B is related to the density of fraction A by the following expression:

where d is the density of the final polyethylene flake particles, W _A is the mass fraction of fraction A, d _A is the density of fraction A, d _B is the density of fraction B, and the sum of both fractions A and B by weight ( _WA + W _B ) is equal to 1. A similar formula can be presented for any polyethylene resin containing more than two fractions.

For a polyethylene resin produced by a metallocene-catalyzed polymerization containing two fractions A and B, the HLMI of fraction B is related to the HLMI of fraction A by the following expression:

LogHLMI ^final \u003d W _A × LogHLMI _A + W _B × LogHLMI _B ,

where LogHLMI ^final is the LogHLMI of the final polyethylene flocculent particles, W _A is the mass fraction of fraction A, LogHLMI _A is the Log HLMI of fraction A, LogHLMI _B is the LogHLMI of fraction B, and where the sum of both fractions A and B by weight (W _A +W _B ) equals 1. A similar formula can be presented for any polyethylene resin containing more than two fractions.

For a polyethylene resin obtained by a metallocene-catalyzed polymerization containing two fractions A and B, the MI2 of fraction B is related to the MI2 of fraction A by the following expression:

LogMI2 ^final =W _A ×LogMI2 _A +W _B ×LogMI2 _B ,

where LogMI2 ^final is the LogMI2 of the final polyethylene flocculent particles, W _A is the mass fraction of fraction A, LogMI2 _A is the Log MI2 of fraction A, LogMI2 _B is the LogMI2 of fraction B, and where the sum of both fractions A and B by weight (W _A +W _B ) equals 1. A similar formula can be presented for any multimodal polyethylene resin containing more than two fractions.

The polyethylene resin can be mixed with one or more additives, in particular additives such as processing aids, mold release agents, anti-slip agents, primary and secondary antioxidants, light stabilizers, anti-UV agents, acid scavengers. , flame retardant additives, fillers, nanocomposites, lubricants, antistatic agents, nucleating/brightening agents, antibacterial agents, plasticizers, colorants/pigments/dyes, sealing resins, and mixtures thereof. Illustrative pigments or colorants include titanium dioxide and carbon black. Specific examples of additives include lubricants and mold release agents such as calcium stearate, zinc stearate, SHT, antioxidants such as Irgafos®168, Irganox®1010 and Irganox®1076, anti-slip agents such as erucamide, light stabilizers such as such as Tinuvin®622, Tinuvin®326 and Cyasorb TNT®4611, ionomers and nucleating agents such as Milliken HPN20E™, conductive carbon black and carbon nanotubes.

The present invention also encompasses an injection molding method for producing an injection molded article according to the present invention comprising the steps of a) providing at least one polyethylene resin obtained by the metallocene catalyzed polymerization described herein; and b) injection molding said polyethylene resin into an article.

The resin can be processed with traditional injection molding machines. The finish of the resulting castings is uniform and can be further improved by increasing the casting speed or by raising the mold temperature.

The products obtained by the injection molding process according to the present invention show little warping, little sagging and little deformation. They also benefit from improved stability and rigidity; as well as good tensile properties.

In the case where the product is obtained by sealing two injection-molded shell halves, the very low curvature of the resin is particularly advantageous since said shell halves are easily sealed due to their good flatness.

Injection molded products include tanks, drums, containers, vats, vats, canisters, cylinders, tanks, hoppers, and other components such as connectors, plugs or lids, or any other molded component, etc.

In a preferred embodiment, said injection molded article may be a container, in particular a tank such as automotive fuel tanks, SCR (Selective Catalytic Reduction) or AdBlue® tanks.

Such an injection molded article may also be the interior of a reservoir, such as a fuel damper, connector, rack, or the like.

Further, the present invention will be illustrated by the following non-limiting illustrative examples of specific embodiments of the invention.

EXAMPLES

Testing Methods

Density was measured according to the ISO 1183:2 method at 23°C.

Melt flow index MI2 was measured according to the method of ISO 1133:1997, condition D, at 190° C. and under a load of 2.16 kg.

Melt flow index MI105 was measured according to the method of ISO 1133:1997, condition D, at 190°C and under a load of 2.16 kg, and using a head with the following parameters: diameter 1.05 mm and height 4 mm.

High shear melt flow index HLMI was measured according to the method of ISO 1133:1997, state G, at 190° C. and under a load of 21.6 kg.

Melt flow index MI5 was measured according to the method of ISO 1133:1997, condition T, at 190° C. and under a load of 5 kg.

Molecular weight (M _n (number average molecular weight), M _w (weight average molecular weight) and M _z (average molecular weight z)) and molecular weight distributions D (Mw/Mn) and D' (Mz/Mw) were determined using size exclusion chromatography (SEC) and, in particular, using gel permeation chromatography (GPC). Briefly, GPC-IR5 from Polymer Char was used: 10 mg of a polyethylene sample was dissolved at 160° C. in 10 ml of trichlorobenzene for 1 hour. Injection volume: Approximately 400 µl, automatic sample acquisition and injection temperature of 160°C. Column temperature: 145°C. Detector temperature: 160°C. Two Shodex AT-806MS columns (Showa Denko) and one Styragel HT6E (Waters) were used with a flow rate of 1 ml/min. Detector: infrared detector (2800-3000 cm ^-1 ). Calibration: narrow molecular weight (PS) polystyrene standards (commercially available). The calculation of the molecular weight Mi of each fraction and the eluted polyethylene is based on the Mark-Huvink equation (log ₁₀ (M _PE )=0.965909×log ₁₀ (M _PS ) - 0.28264) (cutoff at the low molecular weight end at M _PE = 1000).

The average molecular weights used in establishing the molecular weight/property ratios are number average (M _n ), weight average (M _w ), and z-average (M _z ) molecular weights. These averages are determined by the following equations and are determined from the calculated M _i :

In this case, N _i and W _i represent, respectively, the number and mass of molecules characterized by the molecular weight M _i . The third representation in each case (far right) determines how to obtain these averages from the SEC chromatograms. h _i is the height (from baseline) of the SEC curve for the i-th elution fraction, and M _i is the molecular weight of the particles eluted at a given increment.

The rheological long chain branching index g _{rheo was} measured according to the formula described in WO 2008/113680:

where Mw (SEC) is the weight average molecular weight obtained by size exclusion chromatography, expressed in kDa;

and while Mw (η ₀ , MWD, SCB) is determined in accordance with the following equation, also expressed in kDa:

where the zero shear viscosity in Pa.s is obtained from a swept frequency experiment combined with a creep experiment to extend the frequency range down to 10 ^-4 s ^-1 or lower, and assuming the usual assumption of corner frequency equivalence (rad/s) and shear rate; where the zero shear viscosity η ₀ is estimated by fitting the Carro-Yasuda (η-W) flow curve at 190° C. obtained by oscillating shear rheological measurement on ARES-G2 equipment (manufactured by TA Instruments) in the range of linear viscoelasticity ; where the circular frequency (W to rad/s) varies from 0.05-0.1 rad/s to 250-500 rad/s, typically 0.1 to 250 rad/s, and the shear strain is typically is 10%. In practice, the creep experiment is carried out at a temperature of 190°C in a nitrogen atmosphere with such a stress level that after 1200 s the total deformation is less than 20%; where the apparatus used is an AR-G2 manufactured by TA instruments.

Dynamic rheometry (RDA) analyzes were performed on an ARES rheometer from TA Instruments (Waters SA) measured on parallel 25 mm diameter plates. The temperature was 190° C., the strain was 10%, and the scan rate was 0.1 to 300 rad/s.

Bell's ESCR was measured according to ASTM D 1693 B at 50°C using 10% or 100% Igepal CO-630 as the chemical agent (wherein Igepal CO-630 (CAS number 68412-54-4) is commercially available from Rhodia ).

FNCT: Resistance to slow crack growth was tested using the Full Notch Creep Test (FNCT) according to ISO DIS 16770-3, in which the fracture time was recorded for a sample with circumferential notches (depth 1600 µm) having a cross section of 10 mm × 10 mm, taken from compressed plates (compression from the melt at a cooling rate of 15°C/min.). In one experiment, samples were placed in a surfactant solution containing 2 wt. % (in water) Arkopal N100, at a temperature of 80°C for a long period of time and subjected to a tensile stress of 4 MPa. In another experiment, the samples were placed in a solution of a surfactant containing 2 wt. % (in water) Arkopal N100, at a temperature of 50°C for a long period of time and subjected to a tensile stress of 6 MPa.

The flexural modulus was measured according to the ISO 178 three-point bending test at 23°C.

Tensile modulus was measured according to ISO 527-2 at 23°C.

Charpy impact strength was measured according to ISO 179 at 23°C, -15°C and -30°C.

Determination of shrinkage on injection molded squares: squares with a nominal length of 61 mm (mould size) were cast using a 60 tonne Netstal injection molding machine. The actual dimensions were measured after cooling in each direction, and the shrinkage was calculated depending on the cast material in %.

Example 1 Receiving resins.

Polyethylene resins: five resins (resins 1, 2, 3, 4 and 5) having a bimodal molecular weight distribution were prepared in two slurry loop reactors connected in series (double loop reactor) under the conditions shown in Table 1 below. Polyethylene resins (resins 1 , 2, 3, 4 and 5) was obtained using a supported catalyst based on dichlorinated ethylene, bis(tetrahydroindenyl)zirconium, methylalumoxane (MAO). The silica substrate was supplied by PQ Corporation under the name ES70W. It had the following characteristics: specific surface area = 291 m ² /g; D50 = 40 µm; porous volume = 1.6 ml/g. The supported metallocene catalyst contained 30 wt. % MAO (supplied by Albemarle) and 2 wt. % metallocene. In the first reactor, hexene was not used, degassing was not carried out. Granulation was carried out on a ZSK58 twin screw extruder.

Example 2 Moldable Grades for SCR/AdBlue Tank Application: Lumicene M5220 vs Examples According to the Invention

Applicable material

Lumicene® M5220, commercially available from TOTAL Refining & Chemicals, is a metallocene-derived high-density polyethylene having a density of 0.952 g/cm ³ (ISO 1183), a melt flow index (190°C/2.16 kg) of 2.0 g /10 min. (ISO 1133-D), HLMI (ISO 1183) 66.8 g/10 min. and Mw/Mn 4.6.

The properties of resins 1-5 used are shown in Table 1 of Example 1.

ESCR and FNCT analyzes were performed and compared with results obtained using a commercially available high density bimodal polyethylene resin made by metallocene catalyzed polymerization, Lumicene® mPE M5220 castable grade from Total Refining & Chemicals, characterized by MI2 (ISO 1133/D 2.16 kg - 190°C), 2.0 g/10 min. and a density of 0.952 g/cm ³ (ISO 1183). The results of ESCR and FNCT are shown in Table 2.

Conducted analyzes of impact strength and modulus of elasticity. The results are shown in Table 3.

RDA analyzes were performed. The RDA results are shown in Figure 1, which plots the viscosity (Pa.s) for each resin against shear rate (rad/s).

Conducted tests on the ability to cast. Non-isothermal tests that simulated the injection molding process were used to evaluate resin workability in injection molding processes. The spiral flow test involved measuring the length of the spiral flow before solidifying the molten injection molded polymer into a standard mold under standard filling conditions. Conducted a standard test for formability. The molten polymer was poured into a standard mold having a simple helical geometry allowing for a long flow path. The moldability index was defined as the length of the flow, i.e. the length of the mold filled to cure under standard filling conditions. The spiral flow length (SFL) was measured at a temperature of 240° C. and, respectively, at casting pressures of 500, 800 and 1100 bar. Spiral flow was determined on a 60 tonne Netstal injection molding machine with a 32 mm screw and an L/D ratio of 25. The injection pressure was varied. Spiral flow lengths (SFL) were provided for several resins versus cast pressure build-up at 240° C. and are shown in Figure 2, which plots spiral flow length (SFL) vs cast pressure build-up.

The shrinkage of the cast squares was evaluated following the method described herein above. The results are shown in figure 3.

Claims (23)

1. An injection molded article comprising at least one polyethylene resin obtained by metallocene catalyzed polymerization, comprising at least two polyethylene fractions A and B obtained by metallocene catalyzed polymerization, wherein at least one polyethylene resin obtained by metallocene catalyzed polymerization , contains from 42.0 wt.% to not more than 48.0 wt.% of polyethylene fraction A, based on the total weight of at least one polyethylene resin obtained by metallocene catalyzed polymerization, and fraction A has a melt flow index MI2 of at least 100 .0 g/10 min, determined in accordance with ISO 1133, condition D, at 190°C and under a load of 2.16 kg; and and at least one polyethylene resin obtained by metallocene catalyzed polymerization, characterized by a density of at least 0.940 g/cm ³ to not more than 0.950 g/cm ³ measured for granules in accordance with ISO 1183 at 23°C; melt flow index MI2 of at least 1.4 g/10 min to not more than 2.5 g/10 min, measured on pellets in accordance with ISO 1133, condition D, at 190°C and under load 2.16 kg. 2. The injection molded article of claim 1, wherein the at least one metallocene catalyzed polymerization polyethylene resin has a molecular weight distribution M _w /M _n of at least 4.0 to at most 6 ,0, wherein M _w is the weight average molecular weight and M _n is the number average molecular weight. 3. The product obtained by injection molding, according to any one of paragraphs. 1, 2, in which at least one polyethylene resin obtained by metallocene catalyzed polymerization has an HLMI of at least 50.0 g/10 min, preferably of at least 55.0 g/10 min, preferably of at least at least 60.0 g/10 min, preferably at least 65.0 g/10 min, preferably at least 70.0 g/10 min, measured on granules according to ISO 1133:1997, condition G, at 190°C and under load 21.6 kg. 4. The product obtained by injection molding, according to any one of paragraphs. 1-3, in which fraction A of at least one polyethylene resin obtained by metallocene catalyzed polymerization has a density that is at least 0.005 g/cm ³ greater than the density of at least one polyethylene resin obtained by metallocene catalyzed polymerization. 5. The product obtained by injection molding, according to any one of paragraphs. 1-4, in which fraction A of at least one polyethylene resin obtained by metallocene catalyzed polymerization has a density measured for flaky particles of at least 0.960 g/cm ³ , preferably of at least 0.965 g/cm ³ , preferably component of at least 0.970 g/cm ³ measured in accordance with ISO 1183 at 23°C. 6. The product obtained by injection molding, according to any one of paragraphs. 1-5, wherein at least one polyethylene resin produced by metallocene catalyzed polymerization has a multimodal molecular weight distribution, and preferably wherein said at least one polyethylene resin produced by metallocene catalyzed polymerization has a bimodal molecular weight distribution. 7. The product obtained by injection molding, according to any one of paragraphs. 1-6, in which each fraction of said at least one polyethylene resin obtained by metallocene catalyzed polymerization is obtained in different reactors from at least two reactors connected in series, preferably at least two loop reactors connected in series, preferably at least two slurry loop reactors connected in series. 8. The product obtained by injection molding, according to any one of paragraphs. 1-7, in which at least one polyethylene resin obtained by metallocene catalyzed polymerization is obtained using a method comprising the steps of: (a) supplying ethylene monomer, diluent, at least one metallocene catalyst, optionally hydrogen, and optionally one or more olefin comonomers to at least one first slurry loop reactor; carrying out the polymerization of ethylene monomer and optionally one or more olefin comonomers in the presence of a metallocene catalyst and optionally hydrogen in said first slurry loop reactor to obtain a first polyethylene fraction A and (b) supplying the first polyethylene fraction A to a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and optionally one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining polyethylene resin obtained by metallocene catalyzed polymerization. 9. The product obtained by injection molding, according to any one of paragraphs. 1-8, in which the specified at least one polyethylene resin obtained by metallocene catalyzed polymerization, obtained using a method comprising the steps: (a) supplying ethylene monomer, diluent, at least one metallocene catalyst, optionally hydrogen, and optionally one or more olefin comonomers to at least one first slurry loop reactor; carrying out the polymerization of ethylene monomer in the presence of a metallocene catalyst and optionally hydrogen in the specified first slurry loop reactor to obtain the first polyethylene fraction A and (b) feeding the first polyethylene fraction A into a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining a polyethylene resin obtained by metallocene catalyzed polymerization. 10. The product obtained by injection molding, according to any one of paragraphs. 1-9, wherein fraction A of said at least one metallocene catalyzed polymerization polyethylene resin is an ethylene homopolymer and fraction B of said at least one metallocene catalyzed polymerization polyethylene resin is an ethylene copolymer. 11. The product obtained by injection molding, according to any one of paragraphs. 1-8, in which the specified at least one polyethylene resin obtained by metallocene catalyzed polymerization, obtained using a method comprising the steps: (a) supplying ethylene monomer, a diluent, at least one metallocene catalyst, one or more olefin comonomers, and optionally hydrogen, to at least one first slurry loop reactor; carrying out polymerization of ethylene monomer in the presence of a metallocene catalyst and optionally hydrogen in said first slurry loop reactor to obtain a first polyethylene fraction, and (b) feeding the first polyethylene fraction into a second slurry loop reactor connected in series with the first slurry loop reactor, and in the second slurry loop reactor, carrying out the polymerization of ethylene and optionally one or more olefin comonomers in the presence of the first polyethylene fraction and optionally hydrogen, thereby obtaining a polyethylene resin obtained by metallocene catalyzed polymerization. 12. The product obtained by injection molding, according to any one of paragraphs. 1-11, and the product is a tank, drum, container, tank, vat, canister, cylinder, tank or fuel damper, rack, connector, or plug, or cover. 13. The product obtained by injection molding, according to any one of paragraphs. 1-12, wherein the article is an automotive fuel tank. 14. The product obtained by injection molding, according to any one of paragraphs. 1-12, wherein the product is a selective catalytic reduction (SCR) tank or an AdBlue® tank. 15. The method of obtaining products obtained by injection molding, according to any one of paragraphs. 1-14, comprising steps a) providing at least one polyethylene resin obtained by metallocene-catalyzed polymerization, as described in any of paragraphs. 1-11; and b) injection molding said polyethylene resin into an article.

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