WO2023082144A1

WO2023082144A1 - Epdm-containing polyolefin composition with improved surface properties in injection moulding

Info

Publication number: WO2023082144A1
Application number: PCT/CN2021/130066
Authority: WO
Inventors: Ning Sun; Shengquan ZHU; Feild SHEN
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2021-11-11
Filing date: 2021-11-11
Publication date: 2023-05-19

Abstract

A polyolefin composition (PC) comprising: i) from 50.0 to 70.0 wt. -%of a first polypropylene (PP1) having an MFR 2 of 5.0 to 120 g/10 min; ii) from 5.0 to 20.0 wt. -%of a first elastomeric ethylene copolymer (EC1) having an MFR 2 of 0.2 to 15 g/10 min; iii) from 5.0 to 15.0 wt. -%of an ethylene-propylene-diene monomer rubber masterbatch composition (MB); iv) from 5.0 to 25.0 wt. -%of a filler (F); and v) optionally from 0.1 to 5.0 wt. -%of additives (A), wherein the ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises: a) from 40.0 to 60.0 wt. -%of ethylene-propylene-diene monomer rubber (EPDM); b) from 15.0 to 50.0 wt. -%of a second polypropylene (PP2) having an MFR 2 of 0.2 to 50 g/10 min; and c) from 2.0 to 29.0 wt. -%of a second elastomeric ethylene copolymer (EC2) having an MFR 2 of 0.2 to 20 g/10 min.

Description

AN EPDM-CONTAINING POLYOLEFIN COMPOSITION WITH IMPROVED SURFACE PROPERTIES IN INJECTION MOULDING

FIELD

The present invention relates to a polyolefin composition (PC) comprising a specific ethylene-propylene diene monomer rubber masterbatch composition (MB) , a process for producing said polyolefin composition (PC) , and injection-moulded articles comprising said polyolefin composition (PC) .

BACKGROUND

Achieving a balance of mechanical properties remains one of the key aims in the provision of propylene polymer compositions, either through the provision of new polymers, or through the compounding of two or more different polymers. In particular, the balance between the stiffness (e.g. flexural Modulus and/or tensile modulus) and the impact strength (e.g. Charpy NIS or Izod NIS) , is of vital significance in most polymer-containing items, since the factors that tend to improve the stiffness often lead to a reduced impact strength and vice versa.

A well-known strategy for achieving a beneficial balance of properties is through the addition of so-called impact modifiers to polypropylene compositions already having good stiffness properties. These impact modifiers, often elastomeric ethylene copolymers, improve the impact strength without degrading the stiffness to an unacceptable level. Whilst this strategy has been employed over a number of decades, there are a number of drawbacks. Prominent amongst these drawbacks is the tendency for compositions containing more than 5 wt. -%of elastomeric ethylene copolymers to exhibit surface defects when undergoing injection moulding, especially for large moulded articles. One manifestation of these surface defects is in the appearance of so-called “tiger stripes” (or “flow marks” ) , wherein alternating flossy and dull bands are observed on the polymer surface. Hypothesised to be a result either of a slip-stick phenomenon or of an unstable flow front during the filling of the mould, these defects give a negative impression of the quality of the article.

Another major manifestation of surface defects is the appearance of so-called pinhole defects, typically formed as a result of micro bubbles and/or gel micro particles, which may be the result of elastomer and/or filler in the compositions.

Polypropylene-containing injection-moulded articles with a spray-free and metal-like surface are highly desired in the automotive market, but requirements for surface quality thereof are very strict, especially with regard visible defects, including tiger-stripes and pinholes, on glossy-finished surface of the moulded articles, which should be kept to as low a level as possible. The glossy-finished surface of injection-moulded articles results from a mould having an inner cavity with a glossy-finished inner surface.

Some of surface defects with a particle size ≥ 200μm, such as micro-bubbles and gel micro-particles, can typically be eliminated by optimizing procedure parameters in the compounding process. Some surface defects with a particle size ≤ 80 μm, are not visible, and do not impact surface quality. Surface defects with a particle size of 80-200 μm, such as so-called pinholes, are visible and affect surface quality. These should be controlled and limited to an acceptable range. For example, the count of visual defects (pinholes) on an area of 150 mm (L) ×100 mm (W) on the glossy-finished surface of an injection-moulded plaque is required to be less than 10.

Therefore, it is desired in the market to provide polyolefin compositions having a better surface quality, e.g. reduced incidence of tiger-stripes and reduced incidence of pinhole defects, in particular in glossy-surface injection-moulded articles. In particular, a pinhole count of no greater than 10 for a 150 mm × 100 mm area is considered to be acceptable.

SUMMARY

The present invention is based on the finding that the addition of a masterbatch comprising an elastomeric ethylene copolymer and an EPDM rubber and a polypropylene matrix into PP compounds results in the avoidance of tiger stripe formation on the surface of the PP compounds, which is suppressed by the presence of the EPDM. Furthermore, polyolefin compositions thus obtained have low pinhole counts, which can be reduced even further by careful tailoring of the relative viscosities of the individual components.

The masterbatch improves EPDM dispersion within polypropylene compositions to which the masterbatch has been added, and facilitates the performance of EPDM in the composition.

Therefore, in a first aspect, the present invention is directed to a polyolefin composition (PC) comprising:

i) a first polypropylene (PP1) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, in the range from 5.0 to 120 g/10 min;

ii) a first elastomeric ethylene copolymer (EC1) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, in the range from 0.2 to 15 g/10 min;

iii) an ethylene-propylene-diene monomer rubber masterbatch composition (MB) ;

iv) of a filler (F) ; and

v) optionally additives (A) ,

wherein the ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises:

a) from 40.0 to 60.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of ethylene-propylene-diene monomer rubber (EPDM) ;

b) from 15.0 to 50.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of a second polypropylene (PP2) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, in the range from 0.2 to 50 g/10 min; and

c) from 2.0 to 29.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of a second elastomeric ethylene copolymer (EC2) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, in the range from 0.2 to 20 g/10 min, wherein the individual contents of the ethylene-propylene-diene monomer rubber (EPDM) , the second polypropylene (PP2) , and the second elastomeric ethylene copolymer (EC2) add up to at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%, most preferably 100 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) .

In another aspect, the present invention is directed to a process for producing a polyolefin composition (PC) according to the first aspect, comprising the steps of:

a) providing the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer masterbatch composition (MB) , the filler (F) , and optional additives (A) ;

b) blending and extruding the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer masterbatch composition (MB) , the filler (F) and optional additives (A) at a temperature in the range from 120 to 250 ℃ in an extruder, preferably a twin-screw extruder, thereby generating the polyolefin composition, preferably in pellet form.

In a final aspect, the present invention is directed to an injection-moulded article comprising at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%of the polyolefin composition (PC) of the first aspect, more preferably a glossy-surface injection-moulded article.

Definitions

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although, any methods and materials similar or equivalent to those described herein can be used in practice for testing of the present invention, the preferred materials and methods are described herein. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below.

Unless clearly indicated otherwise, use of the terms “a, ” “an, ” and the like refers to one or more.

In the following, amounts are given in %by weight (wt. -%) unless it is stated otherwise.

A propylene homopolymer is a polymer that essentially consists of propylene monomer units. Due to impurities especially during commercial polymerization processes, a propylene homopolymer can comprise up to 0.1 mol%comonomer units, preferably up to 0.05 mol%comonomer units and most preferably up to 0.01 mol%comonomer units.

A propylene copolymer is a copolymer of propylene monomer units and comonomer units, preferably selected from ethylene and C ₄-C ₈ alpha-olefins. A propylene random copolymer is a propylene copolymer wherein the comonomer units are randomly distributed along the polymer chain, whilst a propylene block copolymer comprises blocks of propylene monomer units and blocks of comonomer units. Propylene random copolymers can comprise comonomer units from one or more comonomers different in their amounts of carbon atoms.

The heterophasic propylene copolymers typically comprise:

a) a crystalline propylene homopolymer or copolymer matrix (M) ; and

b) an elastomeric rubber, preferably a propylene-ethylene copolymer (E) ;

The present invention will now be described in more detail.

DETAILED DESCRIPTION

First polypropylene (PP1)

The main component of the polyolefin composition (PC) is the first polypropylene (PP1) .

The first polypropylene (PP1) of the polyolefin composition (PC) may be a first propylene homopolymer, or a first propylene copolymer, more preferably a first propylene copolymer. The first propylene copolymer is preferably a first propylene-ethylene copolymer. The first propylene copolymer may be a first propylene random copolymer or a first propylene block copolymer, more preferably a first propylene block copolymer.

In one preferred embodiment, the first propylene block copolymer is a first heterophasic propylene copolymer (HECO1) , even more preferably a first heterophasic propylene-ethylene copolymer.

The first heterophasic propylene copolymer (HECO1) , more preferably the first heterophasic propylene-ethylene copolymer, comprises:

c) a crystalline propylene homopolymer matrix (M) ; and

d) an elastomeric propylene-ethylene copolymer (E) ;

The first propylene copolymer, preferably the first propylene block copolymer, more preferably the first heterophasic propylene copolymer (HECO1) of the polyolefin composition (PC) comprises comonomer (s) selected from the group consisting of ethylene and alpha olefins containing 4 to 12 carbon atoms, more preferably from the group consisting of ethylene, butene, hexene and octene, yet more preferably selected from ethylene or butene, most preferably ethylene. It is particularly preferred that the only comonomer present is ethylene.

The first polypropylene (PP1) , more preferably the propylene copolymer, yet more preferably the first propylene block copolymer, still more preferably the first heterophasic propylene copolymer (HECO1) , even more preferably the first heterophasic propylene-ethylene copolymer, has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 230 ℃ and 2.16 kg, in the range from 5.0 to 120 g/10 min, more preferably in the range from 8.0 to 115 g/10 min, most preferably in the range from 10.0 to 100 g/10 min.

If the first polypropylene (PP1) is a first propylene copolymer, the comonomer content, more preferably the ethylene (C2) content, is preferably in the range from 2.0 to 30.0 wt. -%, more preferably in the range from 3.0 to 25.0 wt. -%, most preferably in the range from 5.0 to 20.0 wt. -%, relative to the total weight of the first propylene copolymer.

It is preferred that the first heterophasic propylene copolymer (HECO1) , more preferably the first heterophasic propylene-ethylene copolymer, has a xylene cold solubles (XCS) content in the range from 5 to 50 wt. -%, preferably in the range from 10 to 45 wt. -%, most preferably in the range from 12 to 40 wt. -%.

It is preferred that the first heterophasic propylene copolymer (HECO1) , more preferably the first heterophasic propylene-ethylene copolymer, has a total comonomer content, more preferably a total ethylene (C2) content, in the range from 2.0 to 30.0 wt. -%, preferably in the range from 3.0 to 25.0 wt. -%, most preferably in the range from 5.0 to 20.0 wt. -%.

It is preferred that the first heterophasic propylene copolymer (HECO1) , more preferably the first heterophasic propylene-ethylene copolymer, has a comonomer content of the xylene cold soluble fraction, more preferably an ethylene content of the xylene cold soluble fraction (C2 (XCS) ) , in the range from 10 to 50 wt. -%, preferably in the range from 20 to 45 wt. -%, most preferably in the range from 30 to 40 wt. -%.

It is preferred that the first heterophasic propylene copolymer (HECO1) , more preferably the first heterophasic propylene-ethylene copolymer, has an intrinsic viscosity of the xylene cold soluble fraction (IV (XCS) ) in the range from 1.0 to 4.0 dl/g, preferably in the range from 1.5 to 3.5 dl/g, most preferably in the range from 2.0 to 3.0 dl/g.

It is preferred that the crystalline propylene homopolymer matrix (M) of the first heterophasic propylene copolymer (HECO1) , more preferably of the first heterophasic propylene-ethylene copolymer, has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 230℃ and 2.16 kg, in the range from 10 to 220 g/10 min, more preferably in the range from 20 to 210 g/10 min, most preferably in the range from 30 to 200 g/10 min.

The first polypropylene (PP1) , more preferably the first propylene copolymer, yet more preferably the first propylene block copolymer, still more preferably the first heterophasic propylene copolymer (HECO1) , even more preferably the first heterophasic propylene-ethylene copolymer, preferably comprises a polymeric nucleating agent.

A preferred example of such a polymeric nucleating agent is a vinyl polymer, such as a vinyl polymer derived from monomers of the formula

H ₂C = CH-CHR ¹R ²

wherein R ¹ and R ², together with the carbon atom they are attached to, form an optionally substituted saturated or unsaturated or aromatic ring or a fused ring system, wherein the ring or fused ring moiety contains four to 20 carbon atoms, preferably 5 to 12 membered saturated or unsaturated or aromatic ring or a fused ring system or independently represent a linear or branched C4-C30 alkane, C4-C20 cycloalkane or C4-C20 aromatic ring. Preferably R ¹ and R ², together with the C-atom wherein they are attached to, form a five-or six-membered saturated or unsaturated or aromatic ring or independently represent a lower alkyl group comprising from 1 to 4 carbon atoms. Preferred vinyl compounds for the preparation of a polymeric nucleating agent to be used in accordance with the present invention are in particular vinyl cycloalkanes, in particular vinyl cyclohexane (VCH) , vinyl cyclopentane, and vinyl-2-methyl cyclohexane, 3-methyl-1-butene, 3-ethyl-1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene or mixtures thereof. It is particularly preferred that the vinyl polymer is a vinyl cycloalkane polymer, preferably selected from vinyl cyclohexane (VCH) , vinyl cyclopentane and vinyl-2-methyl cyclohexane, with vinyl cyclohexane polymer being a particularly preferred embodiment.

It is further preferred that the vinyl polymer of the polymeric nucleating agent is a homopolymer, most preferably a vinyl cyclohexane homopolymer.

The first polypropylene (PP1) , more preferably the first propylene copolymer, yet more preferably the first propylene block copolymer, still more preferably the first heterophasic propylene copolymer (HECO1) , even more preferably the first heterophasic propylene-ethylene copolymer, of the present invention may either be synthesized or selected from commercially available polypropylenes.

The first polypropylene (PP1) , more preferably the first propylene copolymer, yet more preferably the first propylene block copolymer, still more preferably the first heterophasic propylene copolymer (HECO1) , even more preferably the first heterophasic propylene-ethylene copolymer, of the present invention is preferably produced in a sequential multistage polymerization process in the presence of a Ziegler-Natta catalyst.

A preferred multistage process is a “loop-gas phase” -process, such as developed by Borealis A/S, Denmark (known as

technology) described e.g. in patent literature, such as in EP 0 887 379, WO 92/12182, WO 2004/000899, WO 2004/111095, WO 99/24478, WO 99/24479 or in WO 00/68315.

A further suitable slurry-gas phase process is the

process of Basell described e.g. in figure 20 of the paper by Galli and Vecello, Prog. Polym. Sci. 26 (2001) 1287-1336.

First elastomeric ethylene copolymer (EC1)

Another essential component of the polyolefin composition (PC) is the first elastomeric ethylene copolymer (EC1) .

The first elastomeric ethylene copolymer (EC1) has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 190℃ and 2.16 kg, in the range from 0.2 to 15 g/10 min, more preferably in the range from 0.3 to 10 g/10 min, most preferably in the range from 0.5 to 7.0 g/10 min.

It is preferred that the first elastomeric ethylene copolymer (EC1) has a density, measured according to ISO 1183-187, in the range from 860 to 880 g/cm ³, preferably in the range from 865 to 875 g/cm ³, most preferably in the range from 867 to 871 g/cm ³.

It is preferred that the first elastomeric ethylene copolymer (EC1) has a melting temperature, measured according to ISO 11357, is in the range from 30 to 120 ℃, more preferably in the range from 50 to 100 ℃, most preferably in the range from 60 to 80 ℃.

It is preferred that the first elastomeric ethylene copolymer (EC1) is a copolymer of ethylene and one or more comonomers selected from C5 to C12 alpha olefins, more preferably selected from C6 to C10 alpha olefins, most preferably the first elastomeric ethylene copolymer (EC1) is an ethylene-octene copolymer or an ethylene-hexene copolymer.

The comonomer content of the first elastomeric ethylene copolymer (EC1) is preferably in the range from 10 to 65 wt. -%, more preferably from 20 to 60 wt. -%, most preferably from 30 to 50 wt. -%, based on the total weight of the first elastomeric ethylene copolymer (EC1) .

Ethylene-propylene-diene monomer rubber masterbatch composition (MB)

Another essential component of the polyolefin composition (PC) is the ethylene-propylene-diene monomer rubber masterbatch composition (MB) .

The ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises ethylene-propylene-diene monomer rubber (EPDM) , a second polypropylene (PP2) and a second elastomeric ethylene copolymer (EC2) , the properties of which are discussed below.

The ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises, more preferably consists of:

b) from 15.0 to 50.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of the second polypropylene (PP2) ;

c) from 2.0 to 29.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of the second elastomeric ethylene copolymer (EC2) ; and

d) optionally, from 0.1 to 5.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of additives.

In a preferred embodiment, the ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises, more preferably consists of:

a) from 42.0 to 58.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of ethylene-propylene-diene monomer rubber (EPDM) ;

b) from 18.0 to 40.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of the second polypropylene (PP2) ;

c) from 10.0 to 28.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of the second elastomeric ethylene copolymer (EC2) ; and

d) optionally, from 0.1 to 2.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of additives.

In a further preferred embodiment, the ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises, more preferably consists of:

a) from 45.0 to 55.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of ethylene-propylene-diene monomer rubber (EPDM) ;

b) from 20.0 to 30.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of the second polypropylene (PP2) ;

c) from 20.0 to 27.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of the second elastomeric ethylene copolymer (EC2) ; and

d) optionally, from 0.1 to 1.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of additives.

The individual contents of the ethylene-propylene-diene monomer rubber (EPDM) , the second polypropylene (PP2) , and the second elastomeric ethylene copolymer (EC2) add up to at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%, most preferably 100 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) .

The additives, if present, are preferably selected from pigments, antioxidants, UV-stabilisers, anti-scratch agents, mould release agents, acid scavengers, lubricants, anti-static agents, and mixtures thereof.

It is preferred that the ratio of ethylene-propylene-diene monomer rubber (EPDM) to the second elastomeric ethylene copolymer (EC2) in the ethylene-propylene-diene monomer masterbatch composition (MB) is in the range from 1.0: 1 to 5.0: 1, more preferably in the range from 1.3: 1 to 4.0: 1, most preferably in the range from 1.5: 1 to 3.0: 1

It is preferred that the ethylene-propylene-diene monomer rubber masterbatch composition (MB) has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 230 ℃ and 2.16 kg, in the range from 0.05 to 5.0 g/10 min, more preferably in the range from 0.10 to 3.0 g/10 min, most preferably in the range from 0.15 to 1.0 g/10 min.

It is preferred that the ethylene-propylene-diene monomer rubber masterbatch composition (MB) is obtainable by, more preferably obtained by a process comprising the steps of:

a) providing the second polypropylene (PP2) , the second elastomeric ethylene copolymer (EC2) , and the ethylene-propylene-diene monomer rubber (EPDM) ;

b) blending and extruding second polypropylene (PP2) , the second elastomeric ethylene copolymer (EC2) , and the ethylene-propylene-diene monomer rubber (EPDM) at a temperature in the range from 120 to 250 ℃ in an extruder, preferably a twin-screw extruder, thereby generating the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , preferably in pellet form.

In particular, it is preferred to use a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin-screw extruder. More preferably, mixing is accomplished in a co-rotating twin-screw extruder. The polymer materials recovered from the extruder are usually in the form of pellets. These pellets may then be used as an EPDM masterbatch for the introduction of EPDM into other polypropylene compositions, in particular polypropylene compositions for forming moulded articles.

Ethylene-propylene-diene monomer rubber (EPDM)

The major component of the masterbatch composition is the ethylene-propylene-diene monomer rubber (EPDM) .

It is preferred that the ethylene-propylene-diene monomer rubber (EPDM) is a terpolymer of ethylene, propylene and ethylidene norbornene (ENB) .

It is preferred that the ethylene-propylene-diene monomer rubber (EPDM) , more preferably the terpolymer of ethylene, propylene and ethylidene norbornene (ENB) , has a Mooney viscosity M _L (1+4) , measured according to ASTM D1646 at 125 ℃, in the range from 40 to 100 MU, preferably in the range from 60 to 95 MU, most preferably in the range from 75 to 90 MU.

It is preferred that the ethylene-propylene-diene monomer rubber (EPDM) , more preferably the terpolymer of ethylene, propylene and ethylidene norbornene (ENB) , has an ethylene content (C2) in the range from 50 to 90 wt. -%, preferably in the range from 55 to 85 wt. -%most preferably in the range from 60 to 80 wt. -%.

It is preferred that the ethylene-propylene-diene monomer rubber (EPDM) , more preferably the terpolymer of ethylene, propylene and ethylidene norbornene (ENB) , has a diene content, more preferably an ethylidene norbornene content (ENB) , in the range from 1.0 to 10.0 %, preferably in the range from 2.0 to 8.0 %, most preferably in the range from 3.0 to 7.0 %.

It is preferred that the ethylene-propylene-diene monomer rubber (EPDM) , more preferably the terpolymer of ethylene, propylene and ethylidene norbornene (ENB) , has a density, measured according to ISO 1183-187, in the range from 0.80 to 0.96 g/cm ³, preferably in the range from 0.83 to 0.93 g/cm ³, most preferably in the range from 0.86 to 0.90 g/cm ³.

The ethylene-propylene-diene monomer rubber (EPDM) , more preferably the terpolymer of ethylene, propylene and ethylidene norbornene (ENB) , of the present invention may either be synthesized or selected from commercially available EPDM rubbers, such as Nordel ^TM IP 4785HM commercially available from Dow Chemical Company (Shanghai, China) .

Second polypropylene (PP2)

Another essential component of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) is the second polypropylene (PP2) .

The second polypropylene (PP2) of the polyolefin composition (PC) may be a second propylene homopolymer, or a second propylene copolymer, more preferably a second propylene copolymer. The second propylene copolymer is preferably a second propylene-ethylene copolymer. The second propylene copolymer may be a second propylene random copolymer or a second propylene block copolymer, more preferably a second propylene block copolymer, most preferably a second heterophasic propylene copolymer (HECO2) .

With the exception of the following ranges for the melt flow rate (MFR ₂) of the second polypropylene (PP2) , the other properties, including the comonomer choice, the comonomer/ethylene content, the xylene cold solubles (XCS) content, the comonomer/ethylene content of the XCS fraction, the intrinsic viscosity of the XCS fraction, matrix melt flow rate (MFR ₂) of the second polypropylene (PP2) or the second heterophasic propylene copolymer as well as all properties regarding the optional polymeric nucleating agent and preparation methods are the same as those described above for the first polypropylene (PP1) or the first heterophasic propylene copolymer.

The second heterophasic propylene copolymer (HECO2) , more preferably the second heterophasic propylene-ethylene copolymer, comprises:

a) a crystalline propylene homopolymer matrix (M) ; and

b) an elastomeric propylene-ethylene copolymer (E) ;

The second polypropylene (PP2) , more preferably the propylene copolymer, yet more preferably the second propylene block copolymer, still more preferably the second heterophasic propylene copolymer (HECO2) , even more preferably the second heterophasic propylene-ethylene copolymer, has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 230 ℃ and 2.16 kg, in the range from 0.2 to 50 g/10 min, more preferably in the range from 0.3 to 35 g/10 min, most preferably in the range from 0.5 to 30 g/10 min.

In the polyolefin composition (PC) , the second polypropylene (PP2) may be same as the first polypropylene (PP1) , or the second polypropylene (PP2) may be different from the first polypropylene (PP1) . Preferably, the second polypropylene (PP2) has a lower MFR than the first polypropylene (PP1) .

Second elastomeric ethylene copolymer (EC2)

Another essential component of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) is the second elastomeric ethylene copolymer (EC2) .

The definitions of the second elastomeric ethylene copolymer (EC2) with regard the density, melting temperature, comonomer choice and comonomer content are the same as those of the first elastomeric ethylene copolymer (EC1) as described above.

The second elastomeric ethylene copolymer (EC2) has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 190℃ and 2.16 kg, in the range from 0.2 to 20 g/10 min, more preferably in the range from 0.3 to 15 g/10 min, most preferably in the range from 0.5 to 10 g/10 min.

In the polyolefin composition (PC) , the second elastomeric ethylene copolymer (EC2) may be same as the first elastomeric ethylene copolymer (EC1) , or the second elastomeric ethylene copolymer (EC2) may be different from the first elastomeric ethylene copolymer (EC1) . Preferably, the second elastomeric ethylene copolymer (EC2) has a higher MFR ₂ than the first elastomeric ethylene copolymer (EC1) .

Filler (F)

Another essential component of the polyolefin composition (PC) is the filler (F) .

It is preferred that the filler is an inorganic filler, more preferably is selected from the group containing talc, calcium carbonate, barium sulfate, mica, and mixtures thereof.

Most preferably, the inorganic filler (F) is talc.

Additives (A)

The polyolefin composition (PC) of the present invention may contain additives (A) in an amount of from 0.1 to 5.0 wt. -%. The skilled practitioner would be able to select suitable additives that are well known in the art.

The additives (A) are preferably selected from pigments, antioxidants, UV-stabilisers, anti-scratch agents, mould release agents, acid scavengers, lubricants, anti-static agents, and mixtures thereof.

It is understood that the content of additives (A) , given with respect to the total weight of the polyolefin composition (PC) , includes any carrier polymers used to introduce the additives to said polyolefin composition (PC) , i.e. masterbatch carrier polymers. An example of such a carrier polymer would be a polypropylene homopolymer in the form of powder.

Polyolefin composition (PC)

The polyolefin composition (PC) of the present invention comprises the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , the filler (F) and optionally additives (A) .

The individual contents of the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , the filler (F) and the optional additives (A) preferably add up to at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%, most preferably 100 wt. -%, relative to the total weight of the polyolefin composition (PC) .

The polyolefin composition (PC) preferably comprises, more preferably consists of:

i) from 50.0 to 70.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first polypropylene (PP1) ;

ii) from 5.0 to 20.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first elastomeric ethylene copolymer (EC1) ;

iii) from 5.0 to 15.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) ;

iv) from 5.0 to 25.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the filler (F) ; and

v) optionally from 1.0 to 5.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of additives (A) .

In a preferred embodiment, the polyolefin composition (PC) comprises, more preferably consists of:

i) from 55.0 to 67.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first polypropylene (PP1) ;

ii) from 7.0 to 17.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first elastomeric ethylene copolymer (EC1) ;

iii) from 7.0 to 13.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) ;

iv) from 7.0 to 20.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the filler (F) ; and

In each of these embodiments, the individual contents of the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , the filler (F) and the optional additives (A) preferably add up to at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%, most preferably 100 wt. -%, relative to the total weight of the polyolefin composition (PC) .

In a further preferred embodiment, the polyolefin composition (PC) comprises, more preferably consists of:

i) from 60.0 to 65.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first polypropylene (PP1) ;

ii) from 9.0 to 14.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first elastomeric ethylene copolymer (EC1) ;

iii) from 8.0 to 12.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) ;

iv) from 10.0 to 15.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the filler (F) ; and

It is preferred that the melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, of the first polypropylene (PP1) is higher than the melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, of the second polypropylene (PP2) .

Furthermore, it is preferred that the melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, of the first elastomeric ethylene copolymer (EC1) is lower than the melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, of the second elastomeric ethylene copolymer (EC2) .

It is furthermore preferred that the ratio between the viscosity of the ethylene-propylene-diene monomer rubber masterbatch composition, η (MB) , to the viscosity of the first polypropylene, η(PP1) , [η (MB) /η (PP1) ] is in the range from 1.00 to 5.00, more preferably in the range from 1.20 to 4.75, most preferably in the range from 1.50 to 4.50, wherein the viscosity is determined according to ISO 11443 at a temperature of 250 ℃ and a shear rate of 640 s ^-1, which match respectively typical temperature and shear rate in compounding process in a two-screw extruder for polyolefine..

It is also preferred that the ratio between the viscosity of the ethylene-propylene-diene monomer rubber masterbatch composition, η (MB) , to the viscosity of the first elastomeric ethylene copolymer, η (EC1) , [η (MB) /η (EC1) ] is in the range from 0.10 to 1.50, more preferably in the range from 0.30 to 1.45, most preferably in the range from 0.50 to 1.25, wherein the viscosity is determined according to ISO 11443 at a temperature of 250 ℃ and a shear rate of 640 s ^-1.

It is a particular finding of the present invention that when either of the viscosity ratios given above are fulfilled, then the surface quality of injection-moulded articles is further improved, such as pinholes, with excellent results.

It is preferred that the the ratio between the viscosity of the ethylene-propylene-diene monomer rubber masterbatch composition, η (MB) , to the viscosity of the first polypropylene, η (PP1) , [η (MB) /η (PP1) ] is in the range from 1.00 to 5.00, more preferably in the range from 1.20 to 4.85, most preferably in the range from 1.50 to 4.75, for all values of the viscosity determined according to ISO 11443 at temperatures in the range from 200 and 300 ℃ and shear rates in the range from 80 and 1280 s ^-1, which match respectively the ranges of shear rate and temperature in compounding process in a two-screw or single-screw extruder or an injection-moulding machine for polyolefins.

It is likewise preferred that the ratio between the viscosity of the ethylene-propylene-diene monomer rubber masterbatch composition, η (MB) , to the viscosity of the first elastomeric ethylene copolymer, η (EC1) , [η (MB) /η (EC1) ] is in the range from 0.10 to 1.50, more preferably in the range from 0.3 to 1.45, most preferably in the range from 0.50 to 1.25, for all values of the viscosity determined according to ISO 11443 at temperatures in the range from 200 and 300 ℃ and shear rates in the range from 80 and 1280 s ^-1.

It is a particular finding of the present invention that when either of the viscosity ratios given above (over the temperature range of 200-300 ℃ and the shear rate range of 80-1280 s ^-1) are fulfilled, then the surface quality of injection-moulded articles, such as pinholes, is further improved with excellent results.

The polyolefin composition (PC) preferably has a melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, in the range from 5.0 to 100 g/10 min, more preferably in the range from 7.0 to 80 g/10 min, most preferably in the range from 10.0 to 60 g/10 min.

In the EPDM masterbatch, the choice of second elastomeric ethylene copolymer (EC2) and second polypropylene (PP2) improves EPDM dispersion within the masterbatch, whilst the masterbatch in turn aids the dispersion of EPDM within polypropylene compositions to which the masterbatch has been added. Therefore, the final polypropylene compositions have not only a homogeneous phase dispersion, but also a better surface quality as a result of the incorporated EPDM.

In addition, the polypropylene compositions of present invention can be compounded at a lower specific energy input (≤0.20 kw h/kg) than the usual specific energy input for polypropylene compositions (0.25 kw h/kg or more) in compounding procedures, even though EPDM has been incorporated.

Furthermore, the final polypropylene compositions have good mechanical properties, including flexural modulus, impact, etc., acceptable to end user, in addition to the improved surface quality.

The polyolefin composition (PC) is obtainable, more preferably obtained by the process described below.

Process for producing the polyolefin composition (PC)

a) providing the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , the filler (F) , and optional additives (A) ;

b) blending and extruding the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , the filler (F) and optional additives (A) at a temperature in the range from 120 to 250 ℃ in an extruder, preferably a twin-screw extruder, thereby generating the polyolefin composition (PC) , preferably in pellet form.

In particular, it is preferred to use a conventional compounding or blending apparatus, e.g. a Banbury mixer, a 2-roll rubber mill, Buss-co-kneader or a twin-screw extruder. More preferably, mixing is accomplished in a co-rotating twin-screw extruder. The polymer materials recovered from the extruder are usually in the form of pellets.

It is particularly preferred that the polyolefin composition (PC) of the present invention is used for the production of injection-moulded articles. It is thus preferred that the process further comprises, after step b) the step of:

c) injection moulding the polyolefin composition (PC) produced in step b) to form an injection-moulded article,

wherein the injection moulding is preferably glossy-surface injection moulding.

The person skilled in the art would understand that glossy-surface injection moulding involves the use of highly specialised, so-called Grade A, moulds having a high gloss finish, thus generating very smooth injection-moulded articles. Suitable injection moulds are commercially available and well known in the art.

Articles

The present invention is further directed to injection-moulded articles comprising the polyolefin composition (PC) of the invention.

Preferably, the injection-moulded article is a glossy-surface injection-moulded article.

The injection-moulded article, more preferably the glossy-surface injection-moulded article, comprises at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%of the polyolefin composition (PC) .

In one particularly preferred embodiment, the injection-moulded article, more preferably the glossy-surface injection-moulded article, consists of the polyolefin composition (PC) .

It is particular preferred that the injection-moulded article, more preferably the glossy-surface injection-moulded article, is obtainable, more preferably obtained, via the process having steps a) through c) as described above.

Preferably, the article is a part of automotive articles, especially of car exteriors, like bumper, or interiors, like instrumental carriers, dashboards, interior trims and the like.

EXAMPES

1. Definitions/Measuring Methods

The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

Density is measured according to ISO 1183-187. Sample preparation is done by compression moulding in accordance with ISO 1872-2: 2007.

MFR ₂: The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g/10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR ₂ of polypropylene is determined at a temperature of 230 ℃ and a load of 2.16 kg. The MFR ₂ of elastomeric ethylene copolymers is determined at a temperature of 190℃ and a load of 2.16 kg.

Melting temperature Tm: The melting temperature is measured according to ISO 11357-3.

Quantification of propylene copolymer microstructure by NMR spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the propylene polymers.

Quantitative ¹³C { ¹H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for ¹H and ¹³C respectively. All spectra were recorded using a ¹³C optimised 10 mm extended temperature probehead at 125 ℃ using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1, 2-tetrachloroethane-d ₂ (TCE-d ₂) along with chromium- (III) -acetylacetonate (Cr (acac) ₃) resulting in a 65 mM solution of relaxation agent in solvent as described in G. Singh, A. Kothari, V. Gupta, Polymer Testing 2009, 28 (5) , 475.

To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme as described in Z. Zhou, R. Kuemmerle, X. Qiu, D. Redwine, R. Cong, A. Taha, D. Baugh, B. Winniford, J. Mag. Reson. 187 (2007) 225 and V. Busico, P. Carbonniere, R. Cipullo, C. Pellecchia, J. Severn, G. Talarico, Macromol. Rapid Commun. 2007, 28, 1128. A total of 6144 (6k) transients were acquired per spectra. Quantitative ¹³C { ¹H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present.

With characteristic signals corresponding to 2, 1 erythro regio-defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4) , 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio-defects on determined properties was required. Characteristic signals corresponding to other types of regio-defects were not observed.

Characteristic signals corresponding to the incorporation of ethylene were observed (as described in Cheng, H. N., Macromolecules 1984, 17, 1950) and the comonomer fraction calculated as the fraction of ethylene in the polymer with respect to all monomer in the polymer.

The comonomer fraction was quantified using the method of W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157, through integration of multiple signals across the whole spectral region in the ¹³C { ¹H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

The mole percent comonomer incorporation was calculated from the mole fraction.

The weight percent comonomer incorporation was calculated from the weight fraction.

Comonomer content in the elastomeric ethylene copolymer (EC) and the ethylene-propylene-diene monomer rubbers (EPDM) were measured in a known manner based on Fourier transform infrared spectroscopy (FTIR) calibrated with ¹³C-NMR, using Nicolet Magna 550 IR spectrometer together with Nicolet Omnic FTIR software. Films having a thickness of about 250 μm were compression moulded from the samples. Similar films were made from calibration samples having a known content of the comonomer. The comonomer content was determined from the spectrum from the wave number range of from 1430 to 1100 cm ^-1. The absorbance is measured as the height of the peak by selecting the so-called short or long base line or both. The short base line is drawn in about 1410 -1320 cm ^-1 through the minimum points and the long base line about between 1410 and 1220 cm ^-1. Calibrations need to be done specifically for each base line type. Also, the comonomer content of the unknown sample needs to be within the range of the comonomer contents of the calibration samples.

The xylene soluble fraction (XCS) at room temperature (XCS, wt. -%) : The amount of the polymer soluble in xylene is determined at 25 ℃ according to ISO 16152; first edition; 2005-07-01. The remaining part is the xylene cold insoluble (XCU) fraction.

The intrinsic viscosity (IV) is measured according to ISO 1628-1 (at 135 ℃ in decalin) .

Mooney viscosity is measured according to ASTM D1646 at 125 ℃.

Charpy impact test: The Charpy notched impact strength (NIS) was measured according to ISO 179-1 eA at +23 ℃ and -20 ℃, using injection-moulded bar test specimens of 80x10x4 mm3 prepared in accordance with ISO 1873-2: 2007.

Flexural Modulus: The flexural modulus was determined in 3-point-bending at 23℃according to ISO 178 on 80x10x4 mm ³ test bars injection-moulded in line with EN ISO 1873-2.

Viscosity: The viscosity was determined according to ISO 11443: 2021 using a Goettfert Capillary Rheometer “RG25” , having a capillary die with a size of d = 1 mm and L = 10 mm.

Surface quality: Pinholes and tiger stripes

150 mm × 100 mm × 3 mm injection-moulded plaques were prepared according to ISO 19069-2, using an injection moulding machine “Engel 120” of ENGEL AUSTRIA GmbH with a mould having a glossy-finished inner surface of the inner cavity.

The injection-moulded plaques were examined for tiger-stripes and pinhole defects with a particle size of 80-200 μm by the naked eye, which were counted on the area of 150 mm × 100 mm on the surface of the plaque.

2. Examples

2.1. Synthesis of heterophasic propylene-ethylene copolymers (HECOs)

The catalyst used in each of the polymerizations was a Ziegler-Natta catalyst from Borealis having Ti-content of 1.9 wt. -% (as described in EP 591 224) . Before the polymerization, the catalyst was prepolymerized with vinyl-cyclohexane (VCH) as described in EP 1 028 984 and EP 1 183 307. The ratio of VCH to catalyst of 1: 1 was used in the preparation, thus the final poly-VCH content was less than 100 ppm.

In the first stage the catalyst described above was fed into prepolymerization reactor together with propylene and small amount of hydrogen (2.5 g/h) and ethylene (330 g/h) . Triethylaluminium as a cocatalyst and dicyclopentyldimethoxysilane as a donor was used. The aluminium to donor ratio was 7.5 mol/mol and aluminium to titanium ratio was 300 mol/mol. Reactor was operated at a temperature of 30 ℃ and a pressure of 55 barg.

The subsequent polymerization has been effected under the following conditions.

Table 1: Polymerization conditions for the HECOs

In addition, the following commercially available polymer grades were used in the following examples:

EPDM ethylene-propylene-ethylidene norbornene terpolymer with a trade name of NORDEL ^TM IP4785HM, commercially available from Dow Chemicals Inc. (USA) , having an MFR ₂ (190℃) ＜＜ 0.2 g/10 min, a Mooney Viscosity (ML 1+4, 125℃) of 85 MU, an ethylene content of 68 wt. -%, an ethylidene norbornene content of 4.9 wt. -%, a propylene content of 27.1%, and a density of 0.88 g/cm ³.

EC1 elastomeric ethylene-octene copolymer with a trade name of Fortify C5070D, commercially available from Sabic (Shanghai) Trading Co. Ltd (China) , having an MFR ₂ (190 ℃) of 5.0 g/10 min, a Mooney Viscosity (ML 1+4, 125℃) of 8 MU and a density of 0.868 g/cm ³.

EC2 elastomeric ethylene-octene copolymer with a trade name of Engage XLT 8677, commercially available from Dow Chemicals Inc. (USA) , having an MFR ₂ (190 ℃) of 0.5 g/10 min, a Mooney Viscosity (ML 1+4, 125℃) of 45 MU, and a density of 0.870 g/cm ³.

EC3 elastomeric ethylene-octene copolymer with a trade name of Engage 8100, commercially available from Dow Chemicals Inc. (USA) , having an MFR ₂ (190 ℃) of 1.0 g/10 min, a Mooney Viscosity (ML 1+4, 125℃) of 24 MU, and a density of 0.870 g/cm ³.

F Talc with a trade name of HTP Ultra 5L, commercially available from IMI Fabi (Italy) .

CMB A colour masterbatch with a trade name KMB-L5305HW, available from Kestro Polychem, Inc. (China) .

Additives an additive masterbatch, consisting of 0.8 wt. -%of a carrier propylene homopolymer with a trade name of PP-H 225, available from Hongji petrochemical (China) , having an MFR ₂ (230 ℃, 2.16 kg) of 27 g/10 min, 0.15 wt. -%of an antioxidant with a trade name of Irganox 1076 (CAS-no. 2082-79-3) , available from BASF SE (Germany) , 0.15 wt. -%of an antioxidant with a trade name of Irgafos 168 (CAS-no. 31570-04-4) , available from BASF SE (Germany) , 0.15 wt. -% of a glycerol monostearate (CAS-no. 91052-47-0) with a trade name of Rikemal AS-005, available from Riken Vitamin Co., Ltd. (Japan) , 0.30 wt. -%of a UV stabiliser with a trade name of Cyasorb V703, available from Solvay (China) , 0.30 wt. -%of a slip agent with a trade name of Crodamide VRX, available from Croda (UK) , and 0.15 wt. -%of calcium stearate (CAS-no. 1592-23-0) , available from FACI Chemicals (Zhangjiagang) Co., Ltd (China) , based on 100%of total weight of the polyolefin composition.

2.2. Compounding preparation of masterbatch composition

The masterbatch composition (MB) was prepared from 25 wt. -%of HECO1, 25 wt. -%of EC1 and 50 wt. -%of EPDM, by compounding in a co-rotating twin-screw extruder “STS35” commercially available from Coperion, with a barrel temperature of 210 ℃, a die temperature of 212℃, a screw speed of 507 rpm, throughput of 40.5 kg/h, torque of 47 %, die pressure of 3.3 bar, and a specific energy input (SEI) of 0.392 kW·h/kg.

2.3. Compounding preparation of inventive and comparative examples

The inventive and comparative examples were prepared based on the recipes indicated in Table 2 by compounding in a co-rotating twin-screw extruder “STS35” from Coperion under the conditions described in Table 3.

Table 2: Recipes for Inventive and Comparative examples

Table 3: Compounding conditions for comparative and inventive examples in twin-screw extruder

2.4. Viscosity properties of components and compositions

The MFR ₂ (Table 4) and viscosity (η) (Table 5) of each of the polymeric components and the inventive and comparative compositions were determined and the viscosity ratio calculated (Table 6) . The viscosity was measured at temperatures ranging from 200 to 300 ℃ and at shear rates ranging from 80 to 1280 s ^-1, which reflect the conditions within a typical polyolefin compounding in an extruder or within a typical polyolefin compounding in an injection-moulding machine.

Table 4 Measured melt flow rates (MFR ₂) at 230 and 190℃

Table 5a: Measured viscosities (in Pa. s) at shear rates of 80 to 1280 s ^-1 and temperatures of 200 to 300 ℃

Table 5b: Measured viscosities (in Pa. s) at shear rates of 80 to 1280 s ^-1 and temperatures of 200 to 300 ℃

Table 6a: Ratio of viscosities between EPDM masterbatch and HECOs

Table 6b: Ratio of viscosities between EPDM masterbatch and ECs

2.5. Injection-moulded articles

150 mm × 100 mm × 3 mm injection-moulded plaques were prepared from the inventive and comparative polyolefin compositions according to the injection moulding method described in the determination methods (under surface quality) .

The injection-moulded plaques were examined for pinhole defects, which were counted on the 150 mm × 100 mm face of the plaque. The results are summarised in Table 7.

80 mm × 10 mm × 4 mm injection-moulded test bars were prepared from the inventive and comparative polyolefin compositions according to the injection moulding method described in the determination methods (under Charpy impact strength and flexural modulus tests) and the mechanical properties evaluated. The results are summarised in Table 7.

Table 7 Surface properties of injection-moulded plaques

As can be seen from Table 7, the inventive compositions have much lower pinhole counts than the comparative example, whilst all inventive compositions and comparative composition have no tiger-stripes on the surface due to the presence of EPDM.

Furthermore, it may be seen that the examples having a viscosity ratio [η (MB) /η (PP1) ] of more than 5.0 and a viscosity ratio [η (MB) /η (EC1) ] of at least 1.50, i.e. IE1 to IE3, have pinhole counts of more than 10 (on a surface of 150 mm × 100 mm) . Whilst this is considerably better than the comparative example, it is of course desirable to achieve as low a pinhole content as possible. In particular, as discussed above, a threshold of 10 is often deemed to be the acceptable threshold for glossy-finished surfaces of injection-moulded articles.

IE4 and IE5 have a viscosity ratio of [η (MB) /η (PP1) ] of less than 5.00. Although the other viscosity ratio [η (MB) /η (EC1) ] is still at least 1.50, the pinhole count now falls below the threshold of 10 (on a surface of 150 mm × 100 mm) .

IE6 and IE7 have a viscosity ratio of [η (MB) /η (EC1) ] of less than 1.50. Although the other viscosity ratio [η (MB) /η (PP1) ] is still more than 5.00, the pinhole count now falls below the threshold of 10 (on a surface of 150 mm × 100 mm) .

In addition, as shown in Table 7, mechanical properties of present inventive compositions are good and acceptable for injection-moulded articles.

Claims

A polyolefin composition (PC) comprising:

i) a first polypropylene (PP1) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, in the range from 5.0 to 120 g/10 min;

ii) a first elastomeric ethylene copolymer (EC1) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, in the range from 0.2 to 15 g/10 min;

iii) an ethylene-propylene-diene monomer rubber masterbatch composition (MB) ;

iv) a filler (F) ; and

v) optionally additives (A) ,

wherein the ethylene-propylene-diene monomer rubber masterbatch composition (MB) comprises:

a) from 40.0 to 60.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of ethylene-propylene-diene monomer rubber (EPDM) ;

b) from 15.0 to 50.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of a second polypropylene (PP2) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, in the range from 0.2 to 50 g/10 min; and

c) from 2.0 to 29.0 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , of a second elastomeric ethylene copolymer (EC2) having a melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, in the range from 0.2 to 20 g/10 min,

wherein the individual contents of the ethylene-propylene-diene monomer rubber (EPDM) , the second polypropylene (PP2) , and the second elastomeric ethylene copolymer (EC2) add up to at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%, most preferably 100 wt. -%, relative to the total weight of the ethylene-propylene-diene monomer rubber masterbatch composition (MB) .
The polyolefin composition (PC) according to claim 1, wherein the melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, of the first polypropylene (PP1) is higher than the melt flow rate (MFR ₂) , determined according to ISO 1133 at 230 ℃ at a load of 2.16 kg, of the second polypropylene (PP2) , and/or

the melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, of the first elastomeric ethylene copolymer (EC1) is lower than the melt flow rate (MFR ₂) , determined according to ISO 1133 at 190 ℃ at a load of 2.16 kg, of the second elastomeric ethylene copolymer (EC2) .
The polyolefin composition (PC) according to either claim 1 or claim 2, wherein the ratio between the viscosity of the ethylene-propylene-diene monomer rubber masterbatch composition, η (MB) , to the viscosity of the first polypropylene, η (PP1) , [η (MB) /η (PP1) ] is in the range from 1.00 to 5.00, more preferably in the range from 1.20 to 4.75, most preferably in the range from 1.50 to 4.50; and/or

wherein the ratio between the viscosity of the ethylene-propylene-diene monomer rubber masterbatch composition, η (MB) , to the viscosity of the first elastomeric ethylene copolymer, η (EC1) , [η (MB) /η (EC1) ] is in the range from 0.10 to 1.50, more preferably in the range from 0.30 to 1.45, most preferably in the range from 0.50 to 1.25,

wherein each viscosity is determined according to ISO 11443 at a temperature of 250 ℃and a shear rate of 640 s ^-1.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the polyolefin composition (PC) comprises:

i) from 50.0 to 70.0 wt. -%, preferably 55.0 to 67.0 wt. -%, more preferably 60.0 to 65.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first polypropylene (PP1) ;

ii) from 5.0 to 20.0 wt. -%, preferably 7.0 to 17.0 wt. -%, more preferably 9.0 to 14.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the first elastomeric ethylene copolymer (EC1) ;

iii) from 5.0 to 15.0 wt. -%, preferably 7.0 to 13.0 wt. -%, more preferably 8.0 to 12.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of an ethylene-propylene-diene monomer rubber masterbatch composition (MB) ;

iv) from 5.0 to 25.0 wt. -%, preferably 7.0 to 20.0 wt. -%, more preferably 10.0 to 15.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of the filler (F); and

v) optionally from 0.1 to 5.0 wt. -%, relative to the total weight of the polyolefin composition (PC) , of additives (A) ,

wherein the individual contents of the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer rubber masterbatch composition (MB) , the filler (F) and the optional additives (A) add up to at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%, most preferably 100 wt. -%, relative to the total weight of the polyolefin composition (PC) .
The polyolefin composition (PC) according to any one of the preceding claims, wherein the first polypropylene (PP1) is a first propylene copolymer , more preferably a first propylene-ethylene copolymer having an ethylene content in the range from 2.0 to 30.0 wt. -%,

wherein the first propylene copolymer, more preferably the first propylene-ethylene copolymer, preferably has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 230 ℃ and 2.16 kg, in the range from 8.0 to 115 g/10 min, most preferably in the range from 10.0 to 100 g/10 min.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the first elastomeric ethylene copolymer (EC1) is a copolymer of ethylene and one or more comonomers selected from C5 to C12 alpha olefins, preferably wherein the first elastomeric ethylene copolymer (EC1) , has one or both, preferably both, of the following properties:

a) a melt flow rate (MFR ₂) , measured according to ISO 1133 at 190 ℃ and 2.16 kg, in the range from 0.3 to 10 g/10 min, more preferably in the range from 0.5 to 7.0 g/10 min; and

b) a density, measured according to ISO 1183-187, in the range from 860 to 880 g/cm ³, preferably in the range from 865 to 875 g/cm ³, most preferably in the range from 867 to 871 g/cm ³.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the second polypropylene (PP2) is a second propylene copolymer, more preferably a second propylene-ethylene copolymer having an ethylene content in the range from 2.0 to 30.0 wt. -%,

wherein the second propylene copolymer, more preferably the second propylene-ethylene copolymer, preferably has a melt flow rate (MFR ₂) , measured according to ISO 1133 at 230 ℃ and 2.16 kg, in the range from 0.3 to 35 g/10 min, most preferably in the range from 0.5 to 30 g/10 min.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the second elastomeric ethylene copolymer (EC2) is a copolymer of ethylene and one or more comonomers selected from C5 to C12 alpha olefins, preferably wherein the second elastomeric ethylene copolymer (EC2) , has one or both, preferably both, of the following properties:

a) a melt flow rate (MFR ₂) , measured according to ISO 1133 at 190 ℃ and 2.16 kg, in the range from 0.3 to 15 g/10 min, more preferably in the range from 0.5 to 10 g/10 min; and

b) a density, measured according to ISO 1183-187, in the range from 860 to 880 g/cm ³, preferably in the range from 865 to 875 g/cm ³, most preferably in the range from 867 to 871 g/cm ³.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the ethylene-propylene-diene monomer rubber (EPDM) is a terpolymer of ethylene, propylene and ethylidene norbornene (ENB) , preferably having one or more of, preferably all of, the following properties:

i) a Mooney viscosity M _L (1+4) , measured according to ASTM D1646 at 125 ℃, in the range from 40 to 100 MU, preferably in the range from 60 to 95 MU, most preferably in the range from 75 to 90 MU;

ii) an ethylene content (C2) in the range from 50 to 90 wt. -%, preferably in the range from 55 to 85 wt. -%, most preferably in the range from 60 to 80 wt. -%;

iii) an ethylidene norbornene content (ENB) in the range from 1.0 to 10.0 %, preferably in the range from 2.0 to 8.0 %, most preferably in the range from 3.0 to 7.0 %; and

iv) a density, measured according to ISO 1183-187, in the range from 0.80 to 0.96 g/cm ³, preferably in the range from 0.83 to 0.93 g/cm ³, most preferably in the range from 0.86 to 0.90 g/cm ³.
The polyolefin composition (PC) according to any one of the preceding claims, wherein the filler (F) is an inorganic filler, more preferably selected from the group containing talc, calcium carbonate, barium sulfate, mica, and mixtures thereof, most preferably the inorganic filler (F) is talc.
A process for producing a polyolefin composition (PC) according to any one of the preceding claims, comprising the steps of:

a) providing a first polypropylene (PP1) , according to any one of claims 1, 2, 3, or 5, a first elastomeric ethylene copolymer (EC1) according to any one of claims 1, 2, 3, or 6, an ethylene-propylene-diene monomer rubber masterbatch composition (MB) according to any one of claims 1, 2, 3, 7, 8, or 9, a filler (F) according to claim 1 or 10, and optional additives (A) ; and

b) blending and extruding the first polypropylene (PP1) , the first elastomeric ethylene copolymer (EC1) , the ethylene-propylene-diene monomer masterbatch composition (MB) , the filler (F) and optional additives (A) at a temperature in the range from 120 to 250 ℃ in an extruder, preferably a twin-screw extruder, thereby generating the polyolefin composition (PC) , preferably in pellet form.
The polyolefin composition (PC) according to any one of claims 1 to 10, wherein the polyolefin composition (PC) is obtainable, more preferably obtained, via the process according to claim 11.
The process according to claim 11, further comprising, after step b) , the step of:

c) injection moulding the polyolefin composition (PC) produced in step b) to form an injection-moulded article,

wherein the injection moulding is preferably glossy-surface injection moulding.
An injection-moulded article comprising at least 90 wt. -%, more preferably at least 95 wt. -%, yet more preferably at least 98 wt. -%of the polyolefin composition (PC) according to any one of claims 1 to 10 or claim 12, more preferably a glossy-surface injection-moulded article.
The injection-moulded article according to claim 14, being obtainable via, more preferably obtained via, the process according to claim 13.
The injection-moulded article according to claim 14 or 15, being a gloss-surface injection-moulded article having no more than 10 pinhole defects per 150 mm × 100 mm surface area.