WO2020118566A1

WO2020118566A1 - Heterophasic polypropylene composition providing high surface gloss

Info

Publication number: WO2020118566A1
Application number: PCT/CN2018/120643
Authority: WO
Inventors: Ben Chen; Henry ZHOU
Original assignee: Borouge Compounding Shanghai Co., Ltd.
Priority date: 2018-12-12
Filing date: 2018-12-12
Publication date: 2020-06-18
Also published as: CN113166503A; CN113166503B

Abstract

A heterophasic polypropylene composition providing high surface gloss, a process for producing such a heterophasic polypropylene composition and an article obtained from such a heterophasic polypropylene composition by molding are provided. The heterophasic polypropylene composition comprises a blend of a nucleated heterophasic polypropylene having a melt flow rate MFR 2 at 230 ℃ and 2.16 kg load of 10.0 to 150 g/10 min, a polystyrene having a melt flow rate MFR 5 at 200 ℃ and 5 kg load of 3.0 to 30.0 g/10 min, and a compatibilizer.

Description

Heterophasic Polypropylene Composition Providing High Surface Gloss

The present invention is directed to a heterophasic polypropylene composition providing high surface gloss. The present invention is further directed to a process for producing such a heterophasic polypropylene composition and to an article obtained from such a heterophasic polypropylene composition by molding, like a trim for use in interior applications in automotive, wherein the article has high surface gloss.

Heterophasic polypropylene compositions are known in the art. They are composed of a continuous propylene homopolymer and/or propylene random copolymer phase acting as matrix in which an elastomeric phase, e.g. an ethylene-propylene rubber (EPR) , is dispersed. Depending on the particular design of the heterophasic polypropylene composition various property profiles can be established. Factors of influence are the constitution of the matrix phase, the constitution of the dispersed phase, and the relative amounts thereof. As indicated already above, the matrix can be a propylene homopolymer and/or a propylene random copolymer. For the dispersed phase there are several options considering e.g. the type of monomer/comonomer, the amount of comonomer, and the molecular weight.

Heterophasic polypropylene compositions were designed to provide improved impact properties if compared to propylene homopolymers and propylene random copolymers. The improved impact strength of heterophasic polypropylene compositions is attributed to the presence of the dispersed phase.

It is, however, a difficult task to provide a polypropylene composition with sufficient impact properties and good optical properties since light scattering occurs at the interface between the continuous matrix phase (crystalline region) and the dispersed elastomeric phase (amorphous region) . Accordingly, heterophasic polypropylene compositions appear somewhat opaque.

Heterophasic polypropylene compositions and articles made thereof are widely used for automotive exterior parts such as bumper and exterior trim. Most of the automotive exterior parts use paint on the polypropylene surface to have a high gloss effect.

However, an environmental and cost driven development has recently promoted a trend to replace painting for providing sufficient surface finish by unpainted articles such as internal trims of automative. Doing so, from an environmental point of view, paint in general and in particular volatile organic compounds (VOC) are reduced. Furthermore, if no paint is used, also costs can be saved.

The disadvantage of this approach is that heterophasic polypropylene is a semi-crystalline polymer with a partly crystalline matrix phase and an amorphous dispersed phase and accordingly –as indicated already above –light scattering occurs at the phase boundaries between the matrix phase and the dispersed phase. This optical behavior does not allow providing articles for internal trims of automotive with high gloss.

Hence, these materials are still not sufficient for preparation of articles with high gloss as required for unpainted internal trims of automotive.

It is therefore an object of the present invention to provide a polypropylene composition with improved optical properties, in particular gloss, for unpainted internal trims of automotive.

The present invention is based on the finding that the object can be solved by provision of a heterophasic polypropylene composition comprising a blend of a nucleated heterophasic polypropylene (HecoPP) , a polystyrene (PS) , and a compatibilizer.

The present invention is accordingly in a first aspect directed to a heterophasic polypropylene composition comprising a blend of

(A) a nucleated heterophasic polypropylene having a melt flow rate MFR ₂ at 230 ℃ and 2.16 kg load of 10.0 to 150 g/10 min,

(B) a polystyrene having a melt flow rate MFR ₅ at 200 ℃ and 5 kg load of 3.0 to 30.0 g/10 min, and

(C) a compatibilizer.

The heterophasic polypropylene composition according to the present invention provides improved gloss compared to a conventional heterophasic polypropylene.

Nucleated Heterophasic Polypropylene (A)

As indicated already above, the heterophasic polypropylene composition according to the present invention comprises a nucleated heterophasic polypropylene (A) , preferably in an amount of 40.0–70.0 wt%based on the weight of the entire heterophasic polypropylene composition according to the present invention. This amount is more preferably 45.0–65.0 wt%, still more preferably 47.5–62.5 wt%.

As indicated already above, the nucleated heterophasic polypropylene (A) has a melt flow rate MFR ₂ at 230 ℃ and 2.16 kg load of 10.0 to 150 g/10 min. The MFR ₂ is preferably 30.0 to 130 g/10 min, more preferably 50.0 to 110 g/10 min.

The heterophasic polypropylene comprises a matrix phase and an elastomeric phase dispersed therein. The matrix phase is based on a propylene homopolymer or a propylene random copolymer like a propylene ethylene random copolymer. The dispersed phase is based on an elastomeric polymer, preferably an ethylene-propylene rubber (EPR) . The heterophasic polypropylene further comprises a nucleating agent, preferably a polymeric nucleating agent.

The heterophasic polypropylene is preferably produced by sequential polymerization wherein in at least one step the matrix phase is produced, and in at least one subsequent step the dispersed phase is produced in the presence of the matrix phase. Accordingly, the dispersed phase is usually not present as a separate fraction. Since in a heterophasic polypropylene the matrix phase and the dispersed phase usually cannot exactly be divided from each other, one cannot directly measure amount and properties of the dispersed phase, or the elastomeric phase, respectively.

In order to characterize the matrix phase and the elastomeric phase of a heterophasic polypropylene composition several methods are known. One method is the extraction of a xylene cold solubles (XCS) fraction, thus separating a xylene cold solubles (XCS) fraction from a xylene cold insoluble (XCI) fraction. It is known that the xylene cold solubles (XCS) fraction of a heterophasic polypropylene largely corresponds to the elastomeric phase. It may, however, contain small parts of the matrix phase, e.g. around 1.0 wt%. The xylene extraction is especially suitable for heterophasic polypropylene compositions with a highly crystalline matrix phase such as a propylene homopolymer matrix phase.

Another method is the separation of a crystalline fraction and a soluble fraction with the CRYSTEX QC method using 1, 2, 4-trichlorobenzene (TCB) as solvent. This method is described below in the measurement methods section. In this method, a crystalline fraction (CF) and a soluble fraction (SF) are separated from each other. The crystalline fraction (CF) largely corresponds to the matrix phase and contains only a small part of the elastomeric phase, while the soluble fraction (SF) largely corresponds to the elastomeric phase and contains only a small part of the matrix phase.

Due to the differences in the separation methods using extraction by xylene and by 1, 2, 4-trichlorobenzene, the properties of XCS/XCI fractions on the one hand and soluble/crystalline (SF/CF) fractions on the other hand are not exactly the same, but are similar.

The nucleated heterophasic polypropylene (A) according to the present invention is preferably characterized by a soluble fraction (SF) determined in 1, 2, 4-trichlorobenzene at 40 ℃ in the range of 5.0 to 20.0 wt%, based on the total weight of the nucleated heterophasic polypropylene (A) , and the soluble fraction (SF) has an ethylene content C2 (SF) in the range of preferably 30.0 to 50.0 wt%, more preferably 35.0 to 45.0 wt%, like 37.0 to 41.0 wt%.

The nucleated heterophasic polypropylene (A) according to the present invention is preferably also characterized by a xylene cold solubles (XCS) fraction in the range of 5.0 to 20.0 wt%, based on the total weight of the nucleated heterophasic polypropylene (A) .

The nucleated heterophasic polypropylene (A) according to the present invention is preferably also characterized by an ethylene content of the xylene cold solubles (XCS) fraction C2 (XCS) in the range of 30.0 to 50.0 wt%, more preferably 35.0 to 45.0 wt%, like 37.0 to 41.0 wt%.

The nucleated heterophasic polypropylene (A) according to the present invention is preferably also characterized by an ethylene content of 3.0 to 10.0 wt%, more preferably 5.0 to 8.0 wt%, like 5.5 to 7.5 wt%.

The nucleated heterophasic polypropylene (A) according to the present invention is preferably characterized by an MFR ₂ of the matrix phase of 100 to 280 g/10 min (230 ℃/2.16 kg) , more preferably 130 to 250 g/10 min, like 160 to 220 g/10 min.

The nucleated heterophasic polypropylene (A) according to the present invention is preferably characterized by an intrinsic viscosity of the elastomeric phase of 1.5 to 3.5 dl/g, more preferably 1.8 to 3.0 dl/g, like 2.1 to 2.5 dl/g.

The nucleated heterophasic polypropylene (A) comprises at least one nucleating agent, preferably at least one polymeric nucleating agent.

Preferred polymeric nucleating agents are polymerized vinyl compounds. The vinyl compound is selected from the group consisting of vinyl cycloalkanes, in particular vinyl cyclohexane (VCH) , vinyl cyclopentane, vinyl-2-methylcyclohexane, and vinyl norbornane, 3-methyl-l-butene, 3-ethyl-1-hexene, or mixtures thereof.

The amount of the at least one polymeric nucleating agent is preferably 0.0001 to 1.0 wt%, based on the weight of the nucleated heterophasic polypropylene (A) . The polymeric nucleating agent is preferably a polyvinylcyclohexane (PVCH) .

The at least one polymeric nucleating agent may be introduced either as a master batch by a compounding step subsequently to polymerization of the matrix phase and the dispersed phase, or via a pre-polymerization step prior to the first polymerization step wherein the polymeric nucleating agent is produced and a mixture of the catalyst and the polymeric nucleating agent is obtained. The polymerization of the matrix phase and of the dispersed phase is then conducted in the presence of this mixture of the catalyst and the polymeric nucleating agent.

As indicated already above, the heterophasic polypropylene is preferably produced by sequential polymerization wherein in at least one step the matrix phase is produced, and in at least one subsequent step, the dispersed phase is produced in the presence of the matrix phase.

A particular preferred process comprises polymerizing propylene in at least three polymerization steps in the presence of a suitable catalyst, i.e. a Ziegler-Natta catalyst or a single site catalyst, wherein

a) in the first polymerization reactor (R1) propylene is polymerized to obtain a first propylene homopolymer fraction (H-PP1) , said first propylene homopolymer fraction (H-PP1) is transferred to a second polymerization reactor (R2) ,

b) in the second polymerization reactor (R2) a second propylene homopolymer fraction (H-PP2) is produced, forming together with the first propylene homopolymer fraction (H-PP1) the propylene homopolymer (H-PP) ,

c) in the third polymerization reactor (R3) the elastomeric ethylene propylene rubber fraction (EPR) is produced in the presence of the propylene homopolymer (H-PP) which is produced in reaction steps a) and b) , and

d) the polymeric nucleating agent is introduced either

- as a master batch by a compounding step subsequently to polymerization step c) ,

or

- via a pre-polymerization step prior to the first polymerization step a) in a pre-polymerization reactor (PR) wherein the polymeric nucleating agent is produced and a mixture of the catalyst and the polymeric nucleating agent is obtained, and, subsequent to the pre-polymerization, the mixture of the catalyst and the polymeric nucleating agent produced in the pre-polymerization reactor (PR) is transferred to the first reactor (R1) .

In this particular preferred process it is further preferred that the first polymerization reactor (R1) is a slurry loop reactor and that the second polymerization reactor (R2) is a gas phase reactor and that the third polymerization reactor (R3) is a gas phase reactor.

Such processes are known as

technology, as disclosed in EP 0 887 379 A1.

Polystyrene (B)

As indicated already above, the heterophasic polypropylene composition according to the present invention comprises a polystyrene (B) , preferably in an amount of 20.0–50.0 wt%based on the weight of the entire heterophasic polypropylene composition according to the present invention. This amount is more preferably 25.0–45.0 wt%, still more preferably 27.5–42.5 wt%.

As indicated already above, the polystyrene (B) has a melt flow rate MFR ₅ at 200 ℃ and 5 kg load of 3.0 to 30.0 g/10 min. The MFR ₂ is preferably 5.0 to 20.0 g/10 min, more preferably 5.0 to 15.0 g/10 min.

Polystyrene is known to the skilled person and can be produced by polymerizing styrene.

Compatibilizer (C)

As indicated already above, the heterophasic polypropylene composition according to the present invention comprises a compatibilizer (C) , preferably in an amount of 2.0–10.0 wt%based on the weight of the entire heterophasic polypropylene composition according to the present invention. This amount is more preferably 3.0–8.0 wt%, still more preferably 3.5–6.5 wt%.

Preferably, the compatibilizer (C) comprises a styrene ethylene butylene styrene block copolymer. More preferably, the styrene ethylene butylene styrene block copolymer makes up at least 90.0 wt%of the compatibilizer (C) . Even more preferably, the compatibilizer (C) consists of the styrene ethylene butylene styrene block copolymer.

Preferably, the styrene ethylene butylene styrene block copolymer, in the following SEBS, has a melt flow rate MFR ₂ at 230 ℃ and 2.16 kg load of 1.0 to 15.0 g/10 min. The MFR ₂ is preferably 1.0 to 10.0 g/10 min, more preferably 1.0 to 8.0 g/10 min.

SEBS is known to the skilled person. It can be obtained by hydrogenation of a butadiene styrene block copolymer, also known as poly (styrene-butadiene-styrene) or SBS rubber. SBS rubber can be obtained by living anionic polymerization. The backbone chain of SBS rubber is made up of three segments. The first segment is a long chain of polystyrene, the middle segment is a long chain of polybutadiene, and the last segment is another long chain of polystyrene. After hydrogenation, polybutadiene of the middle segment becomes a copolymer of ethylene and butylene.

SEBS according to the present invention has preferably a styrene content, i.e. the content of units derived from styrene, of 10 to 20 wt%, and a content of ethylene/butylene copolymer of 80 to 90 wt%.

SEBS is used as a compatibilizer between the nucleated heterophasic polypropylene (A) and polystyrene (B) in the heterophasic polypropylene composition according to the present invention.

Heterophasic Polypropylene Composition

As indicated already above, the heterophasic polypropylene composition according to the present invention comprises a blend of a nucleated heterophasic polypropylene (A) , a polystyrene (B) , and a compatibilizer (C) .

The amounts of these three essential ingredients of the blend are according to the present invention preferably

40.0–70.0 wt%of the nucleated heterophasic polypropylene (A) ,

20.0–50.0 wt%of the polystyrene (B) , and

2.0–10.0 wt%of the compatibilizer (C) ,

wherein the values are based on the weight of the entire heterophasic polypropylene composition according to the present invention.

45.0–65.0 wt%of the nucleated heterophasic polypropylene (A) ,

25.0–45.0 wt%of the polystyrene (B) , and

3.0–8.0 wt%of the compatibilizer (C) ,

The heterophasic polypropylene composition according to the present invention may optionally comprise in addition usual additives and polypropylene. The polypropylene is usually in the form of powder and used as carrier for the additives.

Hence, the heterophasic polypropylene composition according to the present invention may optionally comprise one or more of usual additives in a total amount of up to 3.0 wt%based on the weight of the entire heterophasic polypropylene composition according to the present invention.

Such usual additives are coupling agents, antioxidants, mold release agents, and acid-scavengers.

In case additives are present, the heterophasic polypropylene composition according to the present invention preferably also contains polypropylene in an amount of 0.5–2.0 wt%based on the weight of the entire heterophasic polypropylene composition according to the present invention, wherein this polypropylene is usually applied as powder and acts as carrier for the additives. This polypropylene is different from the nucleated heterophasic polypropylene (A) .

The heterophasic polypropylene composition according to the present invention may optionally comprise in addition a color master batch in an amount of up to 5.0 wt%based on the weight of the entire heterophasic polypropylene composition according to the present invention.

The heterophasic polypropylene composition according to the present invention may comprise an antioxidant, such as sterically hindered phenol, phosphorus-based antioxidant, sulphur-based antioxidant, nitrogen-based antioxidant, or mixtures thereof.

The heterophasic polypropylene composition according to the present invention may further comprise an antistatic agent, or an acid scavenger, such as calcium stearate, sodium stearate or zinc stearate.

The heterophasic polypropylene composition according to the present invention may further comprise an additional compatibilizer, e.g. besides SEBS, such as polypropylene grafted with maleic anhydride group.

Process

The present invention is in a second aspect directed to a process for producing a heterophasic polypropylene composition according to the present invention as described above, including all its preferred embodiments.

In case the polypropylene composition according to the present invention comprises usual additives and/or a color master batch as described above, the process of the present invention comprises as first step preparing and feeding an additive mixture. In such a first step polypropylene powder is pre-mixed with all additives like coupling agents, antioxidants, mold release agents, and acid-scavengers, and with a color master batch thereby obtaining a pre-mixture. This pre-mixture is subsequently fed into an extruder, preferably a twin-screw extruder, more preferably into feeder 2 of a twin-screw extruder, wherein feeder 2 is a side feeder.

A nucleated heterophasic polypropylene (A) , a polystyrene (B) , and a compatibilizer (C) as defined above are fed into an extruder, preferably a twin-screw extruder, more preferably into feeder 1 of a twin-screw extruder, wherein feeder 1 is a main feeder, thereby obtaining a mixture.

All fed materials, i.e. the mixture and optionally the pre-mixture, are heated and mixed homogeneously in the extruder at a temperature of 100 to 250 ℃ and the final mixture thus formed is extruded from the extruder.

The present invention is in a third aspect directed to a heterophasic polypropylene composition obtained by the process of the second aspect of the present invention, including all its preferred embodiments.

Article

The present invention is in a fourth aspect directed to an article obtained from a heterophasic polypropylene composition according to the present invention as described above, i.e. according to the first aspect or the third aspect, respectively, including all its preferred embodiments, by molding, preferably by injection molding. Such an article is preferably a trim for use in interior applications in automotive. The article according to the present invention has high surface gloss. The value of surface gloss is preferably higher than 65 gloss unit, measured according to ISO2813.

In the following, the present invention is further illustrated by means of examples.

EXAMPLES

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.

Ethylene Content

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 probe head 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 {8} . 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 {3, 4} . 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 using proprietary computer programs. 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. Characteristic signals corresponding to the incorporation of ethylene were observed {7} .

The comonomer fraction was quantified using the method of Wang et. al. {6} 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 regiodefects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents. For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

E = 0.5 (Sββ + Sβγ + Sβδ + 0.5 (Sαβ + Sαγ) )

Through the use of this set of sites the corresponding integral equation becomes:

E = 0.5 (I _H +I _G + 0.5 (I _C + I _D) )

using the same notation used in the article of Wang et al. {6} . Equations used for absolute propylene content were not modified.

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

E [mol%] = 100 *fE

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

E [wt%] = 100 * (fE *28.06 ) / ( (fE *28.06) + ( (1-fE) *42.08) )

Bibliographic references:

1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.

2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251.

3) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225.

4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128.

5) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

6) Wang, W-J., Zhu, S., Macromolecules 33 (2000) , 1157.

7) Cheng, H.N., Macromolecules 17 (1984) , 1950.

8) Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009) , 475.

9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150.

10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.

11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

Melt Flow Rate

Melt flow rate MFR ₂ of polypropylene and of styrene ethylene butylene styrene block copolymer is determined according to ISO 1133 at 230 ℃ under a load of 2.16 kg. Melt flow rate MFR ₅ of polystyrene is determined according to ISO 1133 at 200 ℃ under a load of 5 kg.

Soluble and Crystalline Fraction (SF, CF)

The soluble fraction (SF) and the crystalline fraction (CF) of the composition as well as ethylene content and intrinsic viscosity of the respective fractions were analyzed by the CRYSTEX QC, Polymer Char (Valencia, Spain) .

The crystalline and soluble fractions are separated through temperature cycles of dissolution at 160 ℃, crystallization at 40 ℃ and re-dissolution in 1, 2, 4-trichlorobenzene (1, 2, 4-TCB) at 160 ℃. Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an infrared detector (IR4) and an online 2-capillary viscometer which is used for the determination of the intrinsic viscosity (IV) .

The IR4 detector is a multiple wavelength detector detecting IR absorbance at two different bands (CH3 and CH2) for the determination of the concentration and the ethylene content in ethylene-propylene copolymers. IR4 detector is calibrated with series of 8 ethylene-propylene copolymers with known ethylene content in the range of 2 wt%to 69 wt% (determined by ¹³C-NMR) and various concentration between 2 and 13 mg/ml for each used ethylene-propylene copolymer used for calibration.

The amounts of the soluble fraction (SF) and the crystalline fraction (CF) are correlated through the XS calibration to the “xylene cold soluble” (XCS) quantity and respectively xylene cold insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration is achieved by testing various ethylene-propylene copolymers with XS content in the range 2–31 wt%.

The intrinsic viscosity (IV) of the parent ethylene-propylene copolymer and its soluble and crystalline fractions are determined with a use of an online 2-capillary viscometer and is correlated to corresponding IV’s determined by standard method in decalin according to ISO 1628. Calibration is achieved with various ethylene-propylene copolymers with IV = 2–4 dl/g.

A sample of the composition to be analyzed is weighed out in concentrations of 10 mg/ml to 20 mg/ml. After automated filling of the vial with 1, 2, 4-TCB containing 250 mg/l 2, 6-tert-butyl-4-methylphenol (BHT) as antioxidant, the sample is dissolved at 160 ℃ until complete dissolution is achieved, usually for 60 min, with constant stirring of 800 rpm.

A defined volume of the sample solution is injected into the TREF column filled with inert support (column filled with inert material e.g. glass beads) where the crystallization of the sample and separation of the soluble fraction from the crystalline part is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the IV [dl/g] and the C2 [wt%] of the composition. During the second injection the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt%SF, wt%C2, IV) .

(see Del Hierro, P.; Ortin, A.; Monrabal, B.; ‘Soluble Fraction Analysis in polypropylene, The Column Advanstar Publications, February 2014. Pages 18–23) .

Xylene Cold Solubles (XCS)

The xylene cold solubles content is measured at 25 ℃ according to ISO 16152, first edition; 2005-07-01. The part which remains insoluble is the xylene cold insoluble (XCI) fraction.

Charpy Notched Impact Strength

Charpy notched impact strength is determined according to ISO 179 /1eA at 23 ℃ and at -20 ℃ by using injection moulded test specimens as described in EN ISO 1873-2 (80 × 10 × 4 mm ³) .

Flexural Modulus

Flexural modulus is determined according to ISO 178: 2010 /Amd. 1: 2013 on injection molded specimens of prepared in accordance with ISO 294-1: 1996 (80 × 10 × 4 mm ³) .

Gloss

Gloss was determined according to ISO 2813 at 60 ℃.

2. Examples

The following materials are used for compounding and forming the compositions of inventive Examples 1–3 (IE1–IE3) and of Reference Example (RE) :

HECO-PP Heterophasic propylene copolymer having an MFR ₂ of 110 g/10 min (230 ℃, 2.16 kg, ASTM D1238) , a total ethylene content of 6.5 wt%, an ethylene content of the xylene cold soluble fraction of 39 wt%, and a density of 0.90 g/cm ³ (ASTM D792) , commercially available as Moplen EP540V from LyondellBasell.

N-HECO-PP Nucleated heterophasic propylene copolymer having an MFR ₂ of 95 g/10 min (230 ℃, 2.16 kg, ISO 1133) , a total ethylene content of 7.6 wt%, an ethylene content of the xylene cold soluble fraction of 39 wt%, and a density of 906 kg/m ³ (ISO 1183) .

PS Polystyrene having an MFR ₅ of 8 g/10 min (200 ℃, 5 kg) , a surface gloss of 90, commercially available as PG-33 from Chi Mei Corporation, Taiwan.

SEBS Hydrogenated styrene-butadiene thermoplastic elastomer block copolymer having an MFR ₂ of 4.5 g/10 min (230 ℃, 2.16 kg, ISO 1133) , a density of 0.89 g/cm ³ (ISO 1183) , a styrene content of 15 wt%, and an ethylene/butylene content of 85 wt%, commercially available as Tuftec H1062 from Asahi Kasei Chemicals Corporation, Japan.

CA Compatibilizer based on polypropylene functionalized with maleic anhydride, commercially available as

TPPP 8112 FA from Byk (Altana Group) .

PP Polypropylene powder, as a carrier of additives.

AO1 Antioxidant, pentaerythrityl-tetrakis (3- (3’, 5’-di-tert. butyl-4-hydroxyphenyl) -propionate, CAS-no. 6683-19-8, commercially available as Irganox 1010 from BASF SE.

AO2 Antioxidant, tris (2, 4-di-t-butylphenyl) phosphite, CAS-no. 31570-04-4, commercially available as Irgafos 168 from BASF SE.

AS-105 Mold release agent, distilled monoglycerides, commercially available as Rikemal AS-105 from Rikevita.

AS Acid scavenger, calcium stearate.

P-MB MBB206, commercially available from Teknor Apex Asia Pacific Pte, SingaSingapore

Preparation of N-HECO-PP

The nucleated heterophasic propylene copolymer (N-HECO-PP) used for inventive examples IE1–IE3 was prepared with one slurry loop reactor and two gas phase reactors by the known

technology, as disclosed in EP 0 887 379 A1.

The catalyst used in the polymerization process for the preparation of the nucleated heterophasic propylene copolymer (N-HECO-PP) (inventive examples IE1–IE3) has been produced as follows:

First, 0.1 mol of MgCl ₂ x 3 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of –15 ℃ and 300 ml of cold TiCl ₄ was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20 ℃. At this temperature, 0.02 mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135 ℃ during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCl ₄ was added and the temperature was kept at 135 ℃ for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80 ℃. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described in general e.g. in patent publications EP 491 566, EP 591 224 and EP 586 390. As co-catalyst triethyl-aluminium (TEAL) and as donor dicyclopentyldimethoxysilane [ (C ₅H ₉) ₂Si (OCH ₃) ₂] was used. The aluminium to donor ratio and process parameters are indicated in Table 1 below.

Preparation of the heterophasic polypropylene composition

The materials as listed above are mixed according to the recipes as indicated in Table 2 below, following the compounding steps as described below, and forming the compositions. Properties of the compositions are also indicated in Table 2 below.

Table 1 Preparation and Properties of N-HECO-PP

Table 2: Recipes for Compounding and Properties of Compositions

As first step an additive mixture is prepared. The polypropylene powder is pre-mixed with all additives and with a color master batch thereby obtaining a pre-mixture. This pre-mixture is subsequently fed into feeder 2 of a twin-screw extruder, wherein feeder 2 is a side feeder.

(Nucleated) heterophasic propylene copolymer, polystyrene, and hydrogenated styrene butadiene thermoplastic elastomer (SEBS) are fed into into feeder 1 of the twin-screw extruder, wherein feeder 1 is a main feeder, thereby obtaining a mixture.

All fed materials, i.e. the mixture and the pre-mixture, are heated and mixed homogeneously in the extruder at a temperature of 100 to 220 ℃ as shown below in Table 3 and the final mixture thus formed is extruded from the extruder.

Table 3: Compounding Process in Extruder

It can be clearly seen that the surface gloss of the polypropylene compositions of inventive examples IE1, IE2, and IE3 is considerably higher than that of the polypropylene compositions of the reference example RE. Gloss of HECO-PP or RE is 42, gloss of N-HECO-PP is 55 (not indicated above) , but gloss of IE1 to IE3 is between 70 and 82. Mechanical properties of the polypropylene compositions of inventive examples IE1, IE2, and IE3 are acceptable for interior trim of automotive.

Claims

A heterophasic polypropylene composition comprising a blend of

(A) a nucleated heterophasic polypropylene having a melt flow rate MFR ₂ at 230 ℃ and 2.16 kg load of 10.0 to 150 g/10 min,

(B) a polystyrene having a melt flow rate MFR ₅ at 200 ℃ and 5 kg load of 3.0 to 30.0 g/10 min, and

(C) a compatibilizer.
The heterophasic polypropylene composition according to claim 1, wherein the blend comprises

- 40.0–70.0 wt%of the nucleated heterophasic polypropylene (A) ,

- 20.0–50.0 wt%of the polystyrene (B) , and

- 2.0–10.0 wt%of the compatibilizer (C) ,

wherein the values are based on the weight of the entire heterophasic polypropylene composition.
The heterophasic polypropylene composition according to claim 2, wherein the blend comprises

- 45.0–65.0 wt%of the nucleated heterophasic polypropylene (A) ,

- 25.0–45.0 wt%of the polystyrene (B) , and

- 3.0–8.0 wt%of the compatibilizer (C) .
The heterophasic polypropylene composition according to any one of claims 1 to 3, wherein the nucleated heterophasic polypropylene (A) has an MFR ₂ of 30.0 to 130 g/10 min.
The heterophasic polypropylene composition according to any one of claims 1 to 4, wherein the polystyrene (B) has an MFR ₅ of 5.0 to 20.0 g/10 min.
The heterophasic polypropylene composition according to any one of claims 1 to 5, wherein the compatibilizer (C) comprises a styrene ethylene butylene styrene block copolymer having a melt flow rate MFR ₂ at 230 ℃ and 2.16 kg load of 1.0 to 15.0 g/10 min.
The heterophasic polypropylene composition according to claim 6, wherein the styrene content of the styrene ethylene butylene styrene block copolymer is 10 to 20 wt%.
The heterophasic polypropylene composition according to any one of claims 1 to 7, wherein the nucleated heterophasic polypropylene (A) has a xylene cold solubles fraction in the range of 5.0 to 20.0 wt%, based on the total weight of the nucleated heterophasic polypropylene (A) .
The heterophasic polypropylene composition according to any one of claims 1 to 8, wherein the ethylene content of the xylene cold solubles fraction of the nucleated heterophasic polypropylene (A) is in the range of 30.0 to 50.0 wt%.
The heterophasic polypropylene composition according to any one of claims 1 to 9, wherein the nucleated heterophasic polypropylene (A) has an ethylene content of 3.0 to 10.0 wt%
The heterophasic polypropylene composition according to any one of claims 1 to 10, wherein the nucleated heterophasic polypropylene (A) comprises at least one polymeric nucleating agent.
The heterophasic polypropylene composition according to claim 11, wherein the amount of the at least one polymeric nucleating agent is 0.0001 to 1.0 wt%, based on the weight of the nucleated heterophasic polypropylene (A) .
The heterophasic polypropylene composition according to any one of claims 11 or 12, wherein the at least one polymeric nucleating agent is a polyvinylcyclohexane.
A process for preparing a heterophasic polypropylene composition according to any one of claims 1 or 13, the process comprising the following steps:

a) optionally pre-mixing polypropylene powder with additives and a color master batch thereby obtaining a pre-mixture of additives and feeding the pre-mixture into an extruder;

b) feeding the nucleated heterophasic polypropylene (A) , the polystyrene (B), and the compatibilizer (C) into an extruder thereby obtaining a mixture;

c) heating and homogeneously mixing the mixture and optionally the pre-mixture in the extruder at a temperature of 100 to 250 ℃ thereby forming a final mixture; and

d) extruding the final mixture from the extruder.
An article obtained by molding of a heterophasic polypropylene composition according to any one of claims 1 to 13.