Patent Description:
Polymer compositions comprising polypropylene and glass fiber are known in the art. Depending on the application, color pigments may be used in the polymer composition. To achieve a light color, a pigment with a pure color is often compounded with a white pigment. For instance, to achieve a light blue color, a pure blue pigment can be compounded with a white pigment. Typically, white pigments leads to a substantial degradation of the impact performance, especially the low temperature impact resistance of the polymer composition.

Antenna housings are used in antenna stations to provide protection on antennas from the environment. Therefore, it is desirable that the antenna housings are made of polymer compositions with sufficient stiffness and a high low temperature impact resistance to withstand extreme weathers, e.g. gales or hail. Another common requirement on the polymer compositions to be used in antenna housing is light color for an aesthetic reason - as antennas are often installed in high places, a light color better matches the color of the sky. Antenna housings based polymer compositions comprising polypropylene are known in the art, for instance:
<CIT> discloses an antenna housing comprising an electromagnetic window portion through which electromagnetic signals are passed in use, wherein a layer of a wall of the electromagnetic window is formed from self reinforced polypropylene.

<CIT> discloses a resin composition for a radar cover. The resin composition includes carbon nanotubes and a polymer resin. The resin composition does not interfere with the transmission of signals from a radar while protecting the radar from the surroundings.

White or light color of the polymer composition can be achieved by adding white color pigment in the polymer composition, but this often leads to an inferior impact performance, yet there is still a need to provide a polymer composition with a white or light color and superior preservation of impact resistance.

This need is satisfied in the present invention by a polymer composition comprising polypropylene, glass fiber and a pigment comprising an inorganic zinc salt and an inorganic barium salt; wherein the MFI of the polypropylene is in the range from <NUM> to <NUM> dg/min, as measured according to ISO1133 at <NUM>/<NUM>, wherein the xylene soluble part of the polypropylene is in the range from <NUM> to <NUM> wt% as measured according to by ISO16152:<NUM>, wherein the amount of the polypropylene is in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition, wherein the amount of the glass fiber is in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition.

The inventors of the present invention surprisingly found that the composition according to the invention has a white or light color and superior preservation of impact resistance.

In the context of the present invention, "white or light color" is meant that the L value of the polymer composition is at least <NUM> wherein L value is measured according to ISO <NUM>-<NUM>:<NUM>; In the context of the present invention, with "superior preservation of impact resistance" is meant that the ratio between the impact resistance of a composition comprising <NUM> wt% white pigment and a composition wherein the <NUM> wt% white pigment is substituted by <NUM> wt% of the polypropylene according to the invention is at least <NUM>, wherein the impact resistance is measured according to ISO180:<NUM> at <NUM>.

Preferably, the invention relates to a polymer composition comprising polypropylene, glass fiber, a pigment comprising an inorganic zinc salt and an inorganic barium salt, and a polyolefin based elastomer, wherein the MFI of the polypropylene is in the range from <NUM> to <NUM> dg/min, as measured according to ISO1133 at <NUM>/<NUM>, wherein the xylene soluble part of the polypropylene is in the range from <NUM> to <NUM> wt% as measured according to by ISO16152:<NUM>, wherein the amount of the polypropylene is in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition, wherein the amount of the glass fiber is in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition, wherein the density of the polyolefin based elastomer is in the range from <NUM> to <NUM>/cm3 as measured according to ASTM D792-<NUM>, wherein the MFI of the polyolefin based elastomer is in the range from <NUM> to <NUM> dg/min as measured according to ASTM D1238-<NUM>,<NUM>, <NUM>. Such polymer composition may have a superior low temperature falling weight impact resistance.

The polypropylene according to the invention is preferably a heterophasic propylene copolymer, wherein the heterophasic propylene copolymer may be prepared in one or more reactors, by polymerization of propylene in the presence of a catalyst and optionally subsequent polymerization of an ethylene-α-olefin mixture.

The polypropylene according to present invention can be produced using any conventional technique known to the skilled person, for example multistage process polymerization, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or any combinations thereof. Any conventional catalyst systems, for example, Ziegler-Natta or metallocene may be used. Such techniques and catalysts are described, for example, in <CIT>; <NPL>; <CIT>, <CIT> and <CIT>. Preferably, the polypropylene is made using Ziegler-Natta catalyst.

Preferably the polypropylene according to the invention consists of a propylene-based matrix and a dispersed ethylene-α-olefin copolymer.

Preferably the amount of the propylene-based matrix is from <NUM> to 99wt%, for example from <NUM> to <NUM> wt%, for example from <NUM> to 90wt%, for example from <NUM> to 85wt%, for example from <NUM> to 85wt% based on the total amount of the polypropylene.

Preferably the amount of the dispersed ethylene-α-olefin copolymer is from <NUM> to <NUM> wt%, for example from <NUM> to <NUM> wt%, for example from <NUM> to <NUM> wt%, for example from <NUM> to <NUM> wt%, based on the total amount of the polypropylene.

The total amount of the propylene-based matrix and the dispersed ethylene-α-olefin copolymer is preferably <NUM> wt%. The amountt ratio between the propylene-based matrix and the dispersed ethylene-α-olefin copolymer is preferably in the range from <NUM>:<NUM> to <NUM>:<NUM>, preferably from <NUM>:<NUM> to <NUM>:<NUM>, preferably from <NUM>:<NUM> to <NUM>:<NUM>.

The amounts of the propylene-based matrix and the dispersed ethylene-α-olefin copolymer may be determined by NMR, as well known in the art.

The propylene-based matrix may consists of a propylene homopolymer and/or a propylene- α-olefin copolymer consisting of at least <NUM> wt% of propylene and up to <NUM> wt% of ethylene and/or an α-olefin having <NUM> to <NUM> carbon atoms, for example a propylene- α-olefin copolymer consisting of at least <NUM> wt% of propylene and up to <NUM> wt% of ethylene and/or an α-olefin having <NUM> to <NUM> carbon atoms, for example consisting of at least <NUM> wt% of propylene and up to <NUM> wt% of ethylene and/or an α-olefin having <NUM> to <NUM> carbon atoms, based on the total amount of the propylene-based matrix.

The α-olefin in the propylene- α-olefin copolymer may be selected from the group ethylene and α-olefins having <NUM>-<NUM> carbon atoms, for example <NUM>-butene, <NUM>-pentene, <NUM>-methyl-<NUM>-pentene, <NUM>-hexen, <NUM>-heptene, <NUM>-octene and mixtures thereof, preferably the α-olefin in the propylene- α-olefin copolymer is ethylene.

Preferably, the propylene-based matrix is a propylene homopolymer.

Preferably the melt flow index (MFI) of the propylene-based matrix MFIPP is at least <NUM> dg/min and at most <NUM> dg/min, measured according to ISO1133 (<NUM>/<NUM>). MFIPP may be for example at least <NUM> dg/min, at least <NUM> dg/min, at least <NUM> dg/min, at least <NUM> dg/min or at least <NUM> dg/min, and/or for example at most <NUM> dg/min, at most <NUM> dg/min, at most <NUM> dg/min or at most <NUM> dg/min, measured according to ISO1133 (<NUM>/<NUM>).

The propylene-based matrix is preferably semi-crystalline, that is it is not <NUM>% amorphous, nor is it <NUM>% crystalline. For example, the propylene-based matrix is at least <NUM>% crystalline, for example at least <NUM>%, for example at least <NUM>% crystalline and/or for example at most <NUM>% crystalline, for example at most <NUM>% crystalline. For example, the propylene-based matrix has a crystallinity of <NUM> to <NUM>%. For purpose of the invention, the degree of crystallinity of the propylene-based matrix is measured using differential scanning calorimetry (DSC) according to ISO11357-<NUM> and ISO11357-<NUM> of <NUM>, using a scan rate of <NUM>/min, a sample of <NUM> and the second heating curve using as a theoretical standard for a <NUM>% crystalline material <NUM> J/g.

The MFI of the dispersed ethylene-α-olefin copolymer ( MFIEPR) may be for example at least <NUM> dg/min, at least <NUM> dg/min, at least <NUM> dg/min, at least <NUM> dg/min, at least <NUM> dg/min, at least <NUM> dg/min, and/or for example at most <NUM> dg/min, at most <NUM> dg/min, at most <NUM> dg/min, at most <NUM> dg/min, at most <NUM> dg/min, at most <NUM> dg/min as measured according to ISO1133 (<NUM>/<NUM>).

The amount of ethylene in the ethylene-α-olefin copolymer is preferably in the range from <NUM> to 80wt% based on the ethylene-α-olefin copolymer, more preferably, the amount of ethylene in the ethylene-α-olefin copolymer is from <NUM> to <NUM> wt%, more preferably from <NUM> to <NUM> wt%, more preferably from <NUM> to <NUM> wt%, even more preferably from <NUM> to 65wt%.

Preferably, the α-olefin in the ethylene-α-olefin copolymer is propylene.

The MFI of the polypropylene is in the range from <NUM> to <NUM> dg/min, preferably in the range from <NUM> to <NUM> dg/min, more preferably in the range from <NUM> to <NUM> dg/min, even more preferably in the range from <NUM> to <NUM> dg/min as measured according to ISO1133 (<NUM>/<NUM>).

The xylene soluble part of the polypropylene according to the invention is in the range from <NUM> to <NUM> wt%, preferably in the range from <NUM> to <NUM> wt%, more preferably in the range from <NUM> to <NUM> wt% as measured according to by ISO16152:<NUM>. The intrinsic viscosity of the xylene soluble part of the polypropylene is preferably in the range from <NUM> to <NUM> dl/g, preferably in the range from <NUM> to <NUM> dl/g, even more preferably in the range from <NUM> to <NUM> dl/g as measured according to ISO1628-<NUM>:<NUM> in decalin at <NUM>.

The amount of the polypropylene is in the range from <NUM> to <NUM> wt%, preferably from <NUM> to <NUM> wt% based on the total amount of the polymer composition.

In general, glass fiber is a glassy cylindrical substance where its length is significantly longer than the diameter of its cross section. It is known that adding glass fibers is able to improve the mechanical performance (e.g. strength and stiffness) of polymeric resin. The level of performance improvement depends heavily on the properties of the glass fibers, e.g. diameter, length and surface property of the glass fiber.

For the purpose of the present invention, the diameter of the glass fibers is preferably in the range from <NUM> to <NUM> microns, preferable from <NUM> to <NUM> microns, more preferable from <NUM> to <NUM> microns.

It is also know that long glass fiber (length from <NUM> to <NUM>) is able to provide superior property improvement than short glass fiber (length shorter than <NUM>) to the composition. The length of glass fibers in the present invention depends heavily on the process used to prepare the said composition. Preferably the glass fiber in the polymer composition according to the invention are long glass fibers.

In the present invention, the amount of glass fibers is from <NUM> to <NUM> wt%, more preferably from <NUM> to <NUM> wt% based on the total amount of the polymer composition.

The total amount of the polypropylene and glass fiber is preferably at least <NUM> wt%, more preferably at least <NUM> wt%, more preferably at least <NUM> wt% based on the total amount of the polymer composition.

The pigment comprises, preferably consists of an inorganic zinc salt and an inorganic barium salt. Preferably the pigment is a white pigment. A pigment is able to change the color of reflected or transmitted light as the result of wavelength-selective absorption. A pigment is a finely-divided solid which is essentially insoluble in its polymeric application medium. Pigments are incorporated by a dispersion process into the plastic while it is in a molten phase and, after the plastic solidifies, the dispersed pigment particles are retained physically within the solid polymer matrix.

In the present invention, "salt" is defined as "<NPL>. Following this definition, a metal salt can be considered as a metal compound, e.g. an inorganic zinc salt is an inorganic zinc compound, an inorganic barium salt is an inorganic barium compound.

The molar ratio between the inorganic zinc salt and the inorganic barium salt is preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, even more preferably in the range from <NUM> to <NUM>.

The total amount of the inorganic zinc salt and the inorganic barium salt is preferably in the range from <NUM> to <NUM> wt%, more preferably in the range from <NUM> to <NUM> wt%, even more preferably in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition.

The inorganic zinc salt according to the invention is selected from a group consisting of zinc sulfide, zinc oxide and a mixture thereof, preferably the inorganic zinc salt is zinc sulfide.

The inorganic barium salt according to the invention is selected from a group consisting of barium carbonate, barium sulfate, barium chloride and a mixture thereof, preferably the inorganic barium salt is barium sulfate.

Preferably the inorganic zinc salt according to the invention is zinc sulfide and the inorganic barium salt according to the invention is barium sulfate.

The polymer composition in the present invention preferably further comprises a polyolefin based elastomer.

The polyolefin based elastomer is preferably selected from a group consisting of ethylene-<NUM>-butene copolymer, ethylene-<NUM>-hexene copolymer, ethylene-<NUM>-octene copolymer and mixtures thereof, more preferably wherein the elastomer is selected from ethylene-<NUM>-octene copolymer. Most preferably, the elastomer is an ethylene-<NUM>-octene copolymer.

Preferably the density of the polyolefin based elastomer is preferably in the range from <NUM> to <NUM>/cm3, preferably in the range from <NUM> to <NUM>/cm3, more preferably in the range from <NUM> to <NUM>/cm3 as measured according to ASTM D792-<NUM>.

Preferably the MFI of the polyolefin based elastomer is in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM> dg/min as measured according to ASTM D1238-<NUM>,<NUM>, <NUM>.

The shore A hardness of the polyolefin based elastomer is preferably in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM> as measured according to ASTM D2240-<NUM>, <NUM>.

The inventors of the present invention surprisingly found that the polymer composition according to the invention comprising a polyolefin based elastomer having an MFI in the range from <NUM> to <NUM> dg/min as measured according to ASTM D1238-<NUM>,<NUM>, <NUM> and a density in the range from <NUM> to <NUM>/cm3 as measured according to ASTM D792-<NUM> has an excellent falling weight impact resistance at -<NUM>.

Elastomers which are suitable for use in the current invention are commercially available for example under the trademark EXACT™ available from Exxon Chemical Company of Houston, Texas or under the trademark ENGAGE™ polymers, a line of metallocene catalyzed plastomers available from Dow Chemical Company of Midland, Michigan or under the trademark TAFMER™ available from MITSUI Chemicals Group of Minato Tokyo or under the trademark Fortify™ and Cohere™ from SABIC.

The elastomers may be prepared using methods known in the art, for example by using a single site catalyst, i.e., a catalyst the transition metal components of which is an organometallic compound and at least one ligand of which has a cyclopentadienyl anion structure through which such ligand bondingly coordinates to the transition metal cation. This type of catalyst is also known as "metallocene" catalyst. Metallocene catalysts are for example described in <CIT> and <CIT>. The elastomer s may also be prepared using traditional types of heterogeneous multi-sited Ziegler-Natta catalysts.

Preferably, the amount of ethylene incorporated into the polyolefin based elastomer is at least <NUM> wt%. More preferably, the amount of ethylene incorporated into the polyolefin based elastomer is at least <NUM> wt%, for example at least <NUM> wt%. The amount of ethylene incorporated into the polyolefin based elastomer may typically be at most <NUM> wt%, for example at most <NUM> wt%, for example at most <NUM> wt%, for example at most <NUM> wt%, for example at most <NUM> wt%, for example at most <NUM> wt%.

The amount of the polyolefin based elastomer is preferably in the range from <NUM> to <NUM> wt%, more preferably in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition.

The thermoplastic polymer composition may further contain the usual additives, for instance nucleating agents and clarifiers, stabilizers, release agents, fillers, peroxides, plasticizers, antioxidants, lubricants, antistatics, cross linking agents, scratch resistance agents, high performance fillers, impact modifiers, flame retardants, blowing agents, acid scavengers, recycling additives, coupling agents, anti-microbials, anti-fogging additives, slip additives, antiblocking additives, polymer processing aids and the like. Such additives are well known in the art. The skilled person will know how to choose the type and amount of additives such that they do not detrimentally influence the aimed properties.

Pigments other than the inorganic zinc salt and the inorganic barium salt may be added to the polymer composition, however such pigments should not deteriorate the white or light color and the impact performance of the polymer composition, wherein composition preferably does not contain a pigment that deteriorates the L value of the polymer composition to a value lower than <NUM>, preferably the composition does not contain a pigment that deteriorates the L value of the polymer composition to a value lower than <NUM>, more preferably the composition does not contain a pigment that deteriorates the L value of the polymer composition to a value lower than <NUM> wherein L value is measured according to ISO <NUM>-<NUM>:<NUM>, wherein the composition preferably does not contain a pigment that deteriorates the preservation of impact resistance of the polymer composition to a value lower than <NUM>, preferably the composition does not contain a pigment that deteriorates the preservation of impact resistance of the polymer composition to a value lower than <NUM>, more preferably the composition does not contain a pigment that deteriorates the preservation of impact resistance of the polymer composition to a value lower than <NUM> wherein the impact resistance is measured according to ISO180:<NUM> at <NUM> wherein the reservation of impact resistance is calculated as the ratio between the impact resistance at of a composition comprising <NUM> wt% pigment and a composition wherein the <NUM> wt% pigment is substituted by <NUM> wt% of PP, wherein the impact resistance is measured according to ISO180:<NUM> at <NUM>.

The present invention further relates to a process for the preparation of the polymer composition.

The polymer composition according to the invention can be prepared by a process known in the art for the preparation of a fiber reinforced composition, for instance: a pultrusion process, a wire-coating process as described in <CIT> and <CIT>, or compounding. The polymer composition prepared in such process is in pellet form.

The present invention further relates to an article comprising the polymer composition according to the invention, wherein the article comprises preferably at least <NUM> wt%, preferably at least <NUM> wt%, more preferably at least <NUM> wt% of the polymer composition according to the invention based on the total amount of the article. Preferably the article is an antenna housing.

The present invention further relates to a process for the preparation of the article comprising the following sequential steps:.

The present invention further relates to the use of the polymer composition according to the invention in an article, preferably the article is an antenna housing.

Polypropylene (PP) used for the preparation of samples is commercially available from SABIC. The PP has an MFI of <NUM> dg/min as measured according to ISO1133 at <NUM>/<NUM>. The PP has an xylene soluble part of <NUM> wt% as measured according to ISO16152:<NUM>, the intrinsic viscosity of the xylene soluble part is <NUM> dl/g as measured according to ISO1628-<NUM>:<NUM> in decalin at <NUM>.

The glass fibres used were standard Type <NUM> roving SE4220, supplied by 3B as a roving package, have filament diameter of <NUM> microns and contain aminosilane-containing sizing composition.

The pigments used in the examples include titanic dioxide TiO<NUM> (KRONOS® <NUM>), zinc sulfide ZnS (SACHTOLITH HD from Sachtleben Chemie GmbH), and lithopone ZnS· BaSO<NUM> (B311 from Union Titanium Enterprise (Shanghai)co.

Several grades of ethylene-octene copolymer commercially available from SABIC under the trade mark Fortify were used. Their characteristics are summarized in Table <NUM>:.

The additives used in the examples consists of <NUM> wt% of compatibilizer and <NUM> wt% of stabilizer. The impregnating agent used in the examples is the same as the one used in <CIT>, the amount of the impregnating agent is <NUM> wt%. The amounts of additives and the impregnating agent are based on the total amount of the composition.

Specimens are prepared in the following sequential steps:
In a first step, PP was melt-mixed with POE, white pigment and additives to prepare a thermoplastic resin in pellet form.

In a second step, polymer compositions were prepared by wire-coating process as described in the examples of <CIT> using the thermoplastic resin obtained in the first step, glass fibers and impregnating agent. The compositional detail of the polymer compositions is given in Table <NUM>.

In a third step, the pellets of the polymer compositions were injection molded into plaques. The dimensions of the plaques are suitable for the measurements.

The color (L. b) of specimens with different pigments is tested according to ISO/CIE <NUM>-<NUM>:<NUM>. L value of the specimens are shown in Table <NUM>.

The stiffness was determined by measuring the flexural modulus according to ISO178:<NUM>.

Impact resistance of the examples was measured by two methods: Izod test and falling weight test.

The falling weight impact test was performed on a customized machine. The customized machine comprises two parts: A weight release mechanism and a plaque support.

The weight release mechanism is able to release a metallic ball with <NUM> gram weight and <NUM> diameter from <NUM> height with <NUM> initial velocity as a free falling object to create falling weight impact on the test plaque.

The plaque support has a square shape with one space in the centre, the outside dimension of the support is <NUM>*<NUM> and inside dimension of the dimension is <NUM>*<NUM>. The horizontal geometric centre of the outer square superposes with that of the inner square. A plaque was placed horizontally on the plaque support, the horizontal geometric centre of the plaque superposed with that of the support.

The weight release mechanism and the plaque support are positioned in a way that the falling weight impact is created perpendicularly on the plaque surface. The horizontal geometric centre of the plaque superposes with that of the impact point.

The plaque was conditioned in a freezer at -<NUM> for at least <NUM> hours before installation on the plaque support. The whole falling impact operation is completed within <NUM> secs starting from taking the plaque out of the freezer.

After the falling impact, the plaque was checked visually whether a crack is present on its surface. <NUM> plaques were tested for each formulation and a non-crack percentage is calculated.

According to Table <NUM> CE1-CE3 and IE1, TiO<NUM>, ZnS and ZnS· BaSO<NUM> provide similar level of whiteness when comparing to reference CE2 but these white pigments lead to different level of preservation of impact resistance, wherein IE <NUM> comprising ZnS· BaSO<NUM> has the highest preservation values which are higher than <NUM> at both <NUM> and -<NUM>.

Claim 1:
A polymer composition comprising polypropylene, glass fiber and a pigment comprising an inorganic zinc salt and an inorganic barium salt, wherein the MFI of the polypropylene is in the range from <NUM> to <NUM> dg/min, as measured according to ISO1133 at <NUM>/<NUM>, wherein the xylene soluble part of the polypropylene is in the range from <NUM> to <NUM> wt% as measured according to by ISO16152:<NUM>, wherein the amount of the polypropylene is in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition, wherein the amount of the glass fiber is in the range from <NUM> to <NUM> wt% based on the total amount of the polymer composition.