Patent Description:
Antennas are widely used in telecom communication for example in base stations. Base stations are built with certain distance in-between to ensure the coverage of electromagnetic signal and antennas are mounted on the top of the station. For this type of antennas to be used in exterior and exposed to open air, antenna housing can be used to provide physical protection again environment. Plastic housings for telecom communication antennas are known. There are several severe requirements to which the polymer compositions have to comply in order to be suitable for use in antenna housing, such as a high temperature resistance, good ultraviolet absorption resistance, good ageing resistance, good crazing resistance, good corrosion resistance, and high mechanical and dimensional strength. These antenna housings may be located in a severe environment e.g. located in high altitude and exposed to extreme weather like hailstorm and therefore it should have excellent low temperature falling weight impact resistance.

Preferably a polymer composition with non-crack percentage at -<NUM> of at least <NUM> % in a falling weight impact test is used for the preparation of an antenna housing.

The falling weight impact test according to the present invention may be performed on a customized machine comprising a weight release mechanism and a plaque support,.

<CIT> discloses a light-weight antenna housing comprising a resin matrix, glass fiber, hollow glass microsphere, toughening modifying agent, weather resistant agent, lubricant and antioxidant. However, it did not disclose falling weight impact resistance. Similarly, <CIT> and <CIT> disclose antenna housings comprising a polymer composition made of a thermoplastic polymer, glass fiber and an inorganic filler.

It is an object of the present invention to provide an antenna housing with improved falling weight impact resistance.

In a preferred embodiment, it is an object of the present invention to provide an antenna housing with improved falling weight impact resistance at low temperature, e.g. -<NUM>.

The present invention further relates to a process for the preparation of an antenna housing with improved resistance to falling weight impact resistance and the use of a polymer composition for the preparation of an antenna housing.

The present invention further relates to the use of a polymer composition for the preparation of an article preferably an antenna housing with non-crack percentage of at least <NUM>% at -<NUM> in a falling weight impact test.

One or more of these objects are achieved by an antenna housing according to the invention comprising a polymer composition, wherein the polymer composition comprises a thermoplastic polymer, glass fiber and an inorganic filler.

It was surprisingly found that this antenna housing according to the present invention has improved resistance against falling weight impact.

A thermoplastic is a polymer that becomes pliable or mouldable above a specific temperature and solidifies upon cooling. Suitable examples of thermoplastic polymers include but are not limited to polyamide, such as polyamide <NUM>, polyamide, <NUM> or polyamide <NUM>; polyolefins, for example polypropylenes and polyethylenes; polyesters, such as polyethylene terephthalate, polybutylene terephthalate; polycarbonates; polyphenylene sulphide; polyurethanes and and mixtures thereof.

The thermoplastic polymer is preferably a polyolefin, more preferably a polyolefin chosen from the group of polypropylenes or elastomers of ethylene and α-olefin comonomer having <NUM> to <NUM> carbon atoms, and any mixtures thereof.

In an embodiment of the present invention, the thermoplastic polymer is polypropylene. The polypropylene may for example be a propylene homopolymer or a random propylene-α-olefin copolymer or a heterophasic propylene copolymer.

The α-olefin in the random propylene-α-olefin copolymer is for example an α-olefin chosen from the group of α-olefin having <NUM> or <NUM> to <NUM> carbon atoms, preferably ethylene, <NUM>-butene, <NUM>-hexene or any mixtures thereof. The amount of α-olefin is preferably at most <NUM> wt% based on the propylene-α-olefin copolymer, for example in the range from <NUM>-7wt% based on the propylene-α-olefin copolymer.

A heterophasic propylene copolymer consists of a propylene-based matrix and a dispersed ethylene-α-olefin copolymer. The matrix of a heterophasic propylene copolymer can be a propylene homopolymer or a random propylene-α-olefin copolymer, preferably the matrix of the heterophasic propylene copolymer is a propylene homopolymer; the α-olefin in the ethylene-α-olefin copolymer contains <NUM>-<NUM> carbon atoms, preferably propylene, <NUM>-butene, <NUM>-hexene or any mixtures thereof, more preferably the ethylene-α-olefin copolymer is a ethylene-propylene copolymer.

Polypropylenes can be made by any known polymerization technique as well as with any known polymerization catalyst system. Regarding the techniques, reference can be given to slurry, solution or gas phase polymerizations; regarding the catalyst system reference can be given to Ziegler-Natta, metallocene or single-site catalyst systems. All are, in themselves, known in the art.

In the present invention, the polypropylene is a heterophasic propylene copolymer consisting of a propylene-based matrix and a dispersed ethylene-α-olefin copolymer.

In an preferred embodiment of the present invention, the heterophasic propylene copolymer has a melt flow rate from <NUM> to <NUM>/<NUM> as determined in accordance with ISO <NUM>:<NUM>-<NUM> (<NUM>, <NUM>). In the present invention, the heterophasic propylene copolymer comprises between <NUM> and <NUM> wt % of said matrix and between <NUM> and <NUM> wt % of said dispersed phase.

In a preferred embodiment of the present invention, the amount of heterophasic propylene copolymer is at least <NUM> wt%, for example at least <NUM> wt%, for example at least <NUM> wt% and/or at most <NUM> wt%, for example at most <NUM> wt%, for example at most <NUM> wt%, for example at most 50wt% based on the total weight 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 fiber 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 fiber, e.g. diameter, length.

Both long glass fiber (length from <NUM> to <NUM>) and short glass fiber (length shorter than <NUM>) can be used in the present invention.

In an embodiment of the present invention, the average diameter of the glass fiber ranges from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>.

Inorganic fillers are known to be used in polymer composition to achieve improvement on properties e.g. optical, electrical and especially mechanical properties.

In the present invention, the inorganic filler is present in an amount of <NUM> to <NUM> wt%, preferably <NUM> to 15wt%, more preferably <NUM> to 12wt%, most preferably <NUM> to <NUM> wt% of the total polymer composition.

In the present invention, the total amount of glass fiber and the inorganic filler is from <NUM> to <NUM> wt%, preferably from <NUM> to <NUM> wt%, more preferably from <NUM> to <NUM> wt%, most preferably from <NUM> to 35wt% based on the total polymer composition.

In the present invention, the ratio between the amount of glass fiber and the amount of inorganic filler is in from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>.

Suitable examples of inorganic include but are not limits to talc, calcium carbonate, wollastonite, barium sulfate, kaolin, glass flakes, laminar silicates (bentonite, montmorillonite, smectite) and mica.

In a preferred embodiment of the present inventor, the inorganic filler is for example talc, for example calcium carbonate, for example wollastonite, for example mica, or a mixture thereof.

In an embodiment of the present invention, the inorganic filler is talc. The average size of talc (D50) of talc is preferably in the range from <NUM> to <NUM> micron, preferably from <NUM> to <NUM> micron, more preferably from <NUM> to <NUM> micron, even more preferably from <NUM> to <NUM> micron according to sedimentation analysis, Stockes' law (ISO <NUM>-<NUM>:<NUM>).

In an embodiment of the present invention, the polymer composition further comprises a stabilizing additive mixture, wherein said stabilizing additive mixture comprises:.

A "substituted amine group" as used in the present description means a group comprising a nitrogen atom that is substituted with other atoms than hydrogen. In other words, no - N(-H)- group. In an embodiment, the substituted amine group is an -N(-OR)- group or an - N(-R)- group wherein R is not a hydrogen.

In an embodiment, Q<NUM> and Q<NUM> are each -CH<NUM>CH<NUM>-; R<NUM> and R<NUM> each -C<NUM>H<NUM>. This is a dialkyl ester of thiodipropionic acid, with <NPL>, and it is commercially available for instance under the name Irganox PS <NUM> FL from BASF.

In an embodiment, the substituted amine group in the HALS is a -N(R)- group; wherein R is a hydrocarbyl group. In a specific embodiment, the HALS is according to Formula Ila or IIb
<CHM>
wherein:.

In a further embodiment, in Formula Ila or IIb, R<NUM>=R<NUM>=R<NUM>=R<NUM>= methyl. In a further embodiment, in in Formula Ila or IIb, R<NUM> is a branched alcohol group.

In a preferred embodiment, the HALS is a NOR-type hindered amine light stabilizer with the following structure:
<CHM>.

NOR-type HALS is commercially available, for instance, Tinuvin® XT <NUM> FF from BASF.

In an embodiment, the inorganic acid scavenger is a hydrotalcite. In a preferred embodiment, this hydrotalcite is of the chemical family of aluminium-magnesium-carbonate-hydroxide (hydrate), with the following formula: Mg<NUM>. 3Al<NUM>(OH)<NUM>. 6CO<NUM>-mH<NUM>O. This compound has <NPL>, and is commercially available for instance as Hycite <NUM> of Clariant.

In an embodiment of the present invention, the antenna housing comprises a polymer composition further comprising a polyolefin based elastomer.

In a preferred embodiment of the invention, the polyolefin based elastomer is an elastomer of ethylene and α-olefin comonomer having <NUM> to <NUM> carbon atoms.

The elastomer for example has a density in the range from <NUM> to <NUM>/cm<NUM>. The elastomer may also sometimes be referred as a plastomer.

The α-olefin comonomer in the elastomer is preferably an acyclic monoolefin such as <NUM>-butene, <NUM>-pentene, <NUM>-hexene, <NUM>-octene, or <NUM>-methylpentene.

Accordingly, the elastomer is preferably selected from the 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.

In a preferred embodiment, the elastomer is an ethylene-<NUM>-octene copolymer.

In a preferred embodiment, the density of the elastomer is at least <NUM>/cm<NUM> and/or at most <NUM>/cm<NUM>. For example, the density of the elastomer is at least <NUM>/cm<NUM>, for example at least <NUM>/cm<NUM>, and/or for example at most <NUM>/cm<NUM>, for example at most <NUM>/cm<NUM>, for example at most <NUM>/cm<NUM>, for example at most <NUM>/cm<NUM>, for example at most <NUM>/cm<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 Nexlene™ from SK Chemicals.

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.

In a preferred embodiment, the elastomer has a melt flow index of <NUM> to <NUM> dg/min (ISO1133, <NUM>, <NUM>), for example at least <NUM> dg/min and/or at most <NUM> dg/min. More preferably, the elastomer has a melt flow index of at least <NUM> dg/min, for example of at least <NUM> dg/min, for example of at least <NUM> dg/min, for example of at least <NUM> dg/min, and/or preferably at most <NUM> dg/min, more preferably at most <NUM> dg/min, more preferably at most <NUM> dg/min measured in accordance with ISO <NUM> using a <NUM> weight and at a temperature of <NUM>ºC.

In a preferred embodiment, the amount of ethylene used to prepare the elastomer is at least <NUM> wt%. More preferably, the amount of ethylene used to prepare the elastomer is at least <NUM> wt%, for example at least <NUM> wt%, at least <NUM> wt%. The amount of ethylene used to prepare the elastomer may typically be at most <NUM> wt%, for example at most <NUM> wt%, for example at most <NUM> wt% or at most <NUM> wt%.

The polymer composition may further comprise additives, for example nucleating agents and clarifiers, stabilizers, release agents, fillers, peroxides, plasticizers, anti-oxidants, lubricants, antistatics, cross linking agents, scratch resistance agents, high performance fillers, pigments and/or colorants, impact modifiers, flame retardants, blowing agents, acid scavengers, recycling additives, coupling agents, anti-microbials, anti-fogging additives, slip additives, anti-blocking 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.

The amount of polymer composition is at least <NUM> wt%, for example at least <NUM> wt%, for example at least <NUM> wt%, for example at least <NUM> wt%, for example at least <NUM> wt% based on the weight of the antenna housing.

The present invention further relates to the process for the preparation of an antenna housing. The process for the preparation of an antenna housing comprises steps of providing a polymer composition, for example by extrusion or dry blending. The process for the preparation of an antenna housing further comprises steps of converting the polymer composition into an antenna housing, for example by injection molding or extrusion molding.

The present invention further relates to the use of said polymer composition for the preparation of an antenna housing.

The present invention further relates to the use of said polymer composition for the preparation of an article preferably an antenna housing with non-crack percentage of at least <NUM>% at -<NUM> in a falling weight impact test.

One or more of the objects of the invention are achieved by the appended claims.

The present invention is further elucidated based on the Examples below which are illustrative only and not considered limiting to the present invention.

The composition in prepared by compounding in a twin screw extruder as pellets, then testing sample preparation is done by single screw extrusion using the prepared pellets.

Strain at break is obtained by tensile test according to ISO527-<NUM>:<NUM> at <NUM> by ZWICK ZOOS. Testing specimen were conditioned for 72hr at <NUM>±<NUM> and at relative humidity of <NUM>±<NUM>% before testing.

Samples were moulded into plaques with dimension: <NUM>*<NUM>*<NUM>. 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 comprises two square-shape metallic clamps with open space in the centre, the shape of the open space is also square. The outside dimensions of the clamps is <NUM>*<NUM> and inside dimension of the clamps is <NUM>*<NUM>. The horizontal geometric centre of the outer square superposes with that of the inner square. When a plaque is installed on the plaque support, it is fixed horizontally by compression between the clamps and the horizontal geometric centre of the plaque superposes with that of the clamps.

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.

The composition of all examples and their properties are indicated in t Table <NUM>.

Claim 1:
An antenna housing comprising a polymer composition, wherein the polymer composition comprises a thermoplastic polymer, glass fiber and an inorganic filler, wherein the thermoplastic polymer is a heterophasic propylene copolymer consisting of a propylene-based matrix and a dispersed ethylene-α-olefin copolymer, wherein the heterophasic copolymer comprises between <NUM> and <NUM> wt % of said matrix and between <NUM> and <NUM> wt % of said dispersed phase,
wherein the inorganic filler is present in an amount of <NUM> to <NUM> wt% of the total polymer composition, the total amount of glass fiber and the inorganic filler is from <NUM> to <NUM> wt%, and
wherein the ratio between the amount of glass fiber and the amount of inorganic filler is from <NUM> to <NUM>.