Polymer composition with improved flowability and resistance to falling weight impact at low temperatures

Abstract

The present invention relates to a polymer composition comprising polypropylene, an ethylene-based elastomer, grafted polypropylene, and glass fibers. The polymer composition according to the present invention has improved flowability and resistance to falling weight impact at low temperatures.

Description

[0001] The present invention relates to a polymer composition comprising polypropylene, an ethylene-based elastomer, grafted polypropylene and glass fiber. The present invention also relates to a method for preparing the polymer composition and an article comprising the polymer composition, and the present invention also relates to the use of the polymer composition in an article.

[0002] Antenna housings are used in antenna stations to provide protection for the antenna from environmental influences. Therefore, it is desirable that the antenna housing is made of a polymer composition having sufficient rigidity and high low-temperature impact resistance to withstand extreme weather, such as high winds or hail. Another common requirement for polymer compositions used for antenna housings is excellent fluidity, because antenna housing pieces are typically large and are prepared by injection molding, and during the injection molding process, excellent fluidity is essential for allowing the polymer composition to completely fill the mold. Methods for measuring fluidity are known in the art, for example, melt flow index (MFI) measurements and spiral flow measurements. In the context of the present invention, excellent fluidity refers to excellent results in spiral flow measurements, because under injection molding conditions, spiral flow measurements are more representative of fluidity than MFI measurements.

[0003] Antenna housings based on polymer compositions comprising polypropylene are known in the art, for example:

[0004] EP 1852938 B1 discloses an antenna housing comprising an electromagnetic window portion through which electromagnetic signals pass in use, wherein a wall layer of the electromagnetic window is formed of self-reinforced polypropylene.

[0005] US 20170190884 A1 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 the radar while protecting the radar from the surrounding environment.

[0006] There remains a need to provide polymer compositions having excellent spiral flow properties and drop weight impact resistance at low temperatures.

[0007] This need is met in the present invention by a polymer composition comprising polypropylene, an ethylene-based elastomer, a grafted polypropylene and glass fibers, wherein the polypropylene has a melt flow index (MFI) of 17 to 68 dg / min, measured at 230°C / 2.16 kg, according to ISO 1133-1:2011, wherein the amount of the ethylene-based elastomer is 15.5 to 28.3 wt.-%, based on the total polymer composition, wherein the MFI of the ethylene-based elastomer is 0.8 to 36 dg / min, measured at 190°C / 2.16 kg, according to ISO 1133-1:2011, and wherein the amount of the grafted polypropylene is 1.2 to 2.9 wt.-%, based on the total polymer composition.

[0008] The inventors of the present invention surprisingly found that the composition according to the present invention has excellent spiral flow properties and drop weight impact resistance at low temperatures.

[0009] Polypropylene

[0010] The polypropylene according to this invention is preferably a heterophasic propylene copolymer, wherein the heterophasic propylene copolymer is producible in one or more reactors by polymerizing propylene and optionally subsequently an ethylene-α-olefin mixture in the presence of a catalyst.

[0011] The polypropylene according to the present invention can be produced using any conventional technology known to the skilled person, for example a multistage process polymerization, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or any combination thereof. Any conventional catalyst system can be used, for example Ziegler-Natta or metallocene. Such technology and catalysts are described, for example, in WO 06 / 010414; Servan der Ven's Polypropylene and other Polyolefins, Studies in Polymer Science 7, Elsevier 1990; WO 06 / 010414, US 4399054 and US 4472524. Preferably, the polypropylene is made using a Ziegler-Natta catalyst.

[0012] Preferably, the polypropylene according to this invention comprises a propylene based matrix and a dispersed ethylene-α-olefin copolymer.

[0013] Preferably, the amount of propylene-based matrix is ​​60-99 wt%, such as 65-95 wt%, such as 70-90 wt%, such as 75-85 wt%, such as 72-87 wt%, based on the total amount of polypropylene.

[0014] Preferably, the amount of dispersed ethylene-α-olefin copolymer is 40 to 1 wt%, such as 35 to 5 wt%, such as 30 to 10 wt%, such as 28 to 13 wt%, based on the total amount of polypropylene.

[0015] The total amount of the propylene-based matrix and the dispersed ethylene-α-olefin copolymer is preferably 100 wt %. The ratio of the amount of the propylene-based matrix and the dispersed ethylene-α-olefin copolymer is preferably 95:5 to 65:35, preferably 90:10 to 70:30, preferably 87:13 to 72:28.

[0016] The amount of propylene-based matrix and dispersed ethylene-α-olefin copolymer can be determined by NMR, which is well known in the art.

[0017] The propylene-based matrix may consist of a propylene homopolymer and / or a propylene-α-olefin copolymer consisting of at least 70 wt% propylene and up to 30 wt% ethylene and / or an α-olefin having 4 to 10 carbon atoms, based on the total amount of the propylene-based matrix, e.g., a propylene-α-olefin copolymer consisting of at least 80 wt% propylene and up to 20 wt% ethylene and / or an α-olefin having 4 to 10 carbon atoms, based on the total amount of the propylene-based matrix, e.g., a propylene-α-olefin copolymer consisting of at least 90 wt% propylene and up to 10 wt% ethylene and / or an α-olefin having 4 to 10 carbon atoms, based on the total amount of the propylene-based matrix.

[0018] The α-olefin in the propylene-α-olefin copolymer can be selected from ethylene and α-olefins having 4 to 10 carbon atoms, such as 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and mixtures thereof. Preferably, the α-olefin in the propylene-α-olefin copolymer is ethylene.

[0019] Preferably, the propylene based matrix is ​​a propylene homopolymer.

[0020] The propylene-based matrix is ​​preferably semi-crystalline, i.e. it is neither 100% amorphous nor 100% crystalline. For example, the propylene-based matrix is ​​at least 40% crystalline, such as at least 50%, such as at least 60% crystalline and / or such as at most 80% crystalline, such as at most 70% crystalline. For example, the propylene-based matrix has a crystallinity of 60-70%. For the purposes of the present invention, the crystallinity of the propylene-based matrix is ​​determined according to ISO 11357-1 and ISO 11357-3, 1997, using differential scanning calorimetry (DSC), using a scan rate of 10°C / min, a sample of 5 mg, and a second heating curve using 207.1 J / g as a theoretical standard for 100% crystalline material.

[0021] The amount of ethylene in the ethylene-α-olefin copolymer is preferably 20 to 80 wt %, more preferably 30 to 70 wt %, more preferably 40 to 65 wt %, more preferably 50 to 65 wt %, even more preferably 55 to 65 wt %, based on the ethylene-α-olefin copolymer.

[0022] Preferably, the α-olefin in the ethylene-α-olefin copolymer is propylene.

[0023] The MFI of the polypropylene is 17 to 68 dg / min, preferably 23 to 59 dg / min, more preferably 32 to 47 dg / min, determined according to ISO 1133 (2.16 kg / 230°C).

[0024] The amount of polypropylene is preferably 26-76 wt%, preferably 33-62 wt%, more preferably 39-53 wt%, based on the total polymer composition.

[0025] Fiberglass

[0026] Generally speaking, glass fiber is a glassy cylindrical substance in which its length is significantly longer than the diameter of its cross section. It is well known that the addition of glass fiber can improve the mechanical properties (e.g., strength and rigidity) of polymer resins. The degree of performance improvement depends largely on the properties of the glass fiber, for example, the diameter, length, and surface properties of the glass fiber.

[0027] For the purposes of the present invention, the diameter of the glass fibers is preferably from 5 to 50 microns, preferably from 10 to 30 microns, more preferably from 15 to 25 microns.

[0028] It is also known that long glass fibers (length of 0.5 to 50 mm) can provide superior property improvements to the composition than short glass fibers (length shorter than 0.5 mm). The length of the glass fibers in the present invention depends largely on the method used to prepare the composition. Preferably, the glass fibers in the polymer composition according to the present invention are long glass fibers.

[0029] In the present invention, the amount of glass fiber is preferably 16-42 wt%, preferably 25-34 wt%, based on the total amount of the polymer composition.

[0030] Ethylene-based elastomers

[0031] The polymer composition of the present invention further comprises an ethylene-based elastomer.

[0032] The ethylene-based elastomer is preferably selected from the group consisting of ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers and mixtures thereof, and preferably the polyolefin-based elastomer is an ethylene-octene copolymer.

[0033] Preferably, the density of the ethylene-based elastomer is preferably 0.845 to 0.883 g / cm 3 , preferably 0.848 to 0.865 g / cm 3 , more preferably 0.853 to 0.860 g / cm 3 .

[0034] The MFI of the ethylene-based elastomer is 0.8 to 36 dg / min, preferably 0.9 to 23 dg / min, more preferably 0.9 to 13 dg / min, even more preferably 0.9 to 4.8 dg / min, measured at 190°C / 2.16 kg according to ISO 1133-1:2011.

[0035] The Shore A hardness of the ethylene-based elastomer is preferably from 35 to 90, preferably from 42 to 69, more preferably from 47 to 60, most preferably from 50 to 57, as determined according to ASTM D2240-15, 1s.

[0036] Ethylene-based elastomers suitable for use in the present invention are commercially available, for example, under the trademark EXACT TM Available from Exxon Chemical Company of Houston, Texas, or under the trademark ENGAGE TM The polymers (a series of metallocene-catalyzed plastomers) are available from The Dow Chemical Company of Midland, Michigan, or under the trademark TAFMER TM Available from MITSUI Chemicals Group of Minato Tokyo at the Port of Tokyo or under the trademark Fortify TM and Cohere TM From SABIC.

[0037] Ethylene-based elastomers can be prepared using methods known in the art, such as by using a single-site catalyst, i.e., a catalyst whose transition metal component is an organometallic compound and whose at least one ligand has a cyclopentadienyl anionic structure through which such ligand is bonded and coordinated to the transition metal cation. This type of catalyst is also known as a "metallocene" catalyst. Metallocene catalysts are described, for example, in U.S. Patent Nos. 5,017,714 and 5,324,820. Elastomers can also be prepared using conventional types of heterogeneous, multisite Ziegler-Natta catalysts.

[0038] Preferably, the amount of ethylene introduced into the polyolefin-based elastomer is at least 40 wt%. More preferably, the amount of ethylene introduced into the polyolefin-based elastomer is at least 42 wt%, such as at least 44 wt%. The amount of ethylene introduced into the polyolefin-based elastomer may typically be at most 95 wt%, such as at most 85 wt%, such as at most 75 wt%, such as at most 65 wt%, such as at most 60 wt%, such as at most 58 wt%.

[0039] The amount of ethylene-based elastomer is 15.5 to 28.3 wt%, more preferably 18.2 to 23.6 wt%, based on the total polymer composition.

[0040] Grafted Polypropylene

[0041] When at least part of the hydrogen atoms on the main chain of polypropylene are replaced by functional groups, the polypropylene becomes a grafted polypropylene.

[0042] The grafted polypropylene in the present application is preferably maleic anhydride grafted polypropylene. Preferably, the grafted polypropylene comprises 0.1 to 3.0 wt% of maleic anhydride functional groups based on the total amount of grafted polypropylene.

[0043] Maleic anhydride grafted polypropylene is known in the art and is marketed, for example, under the trade name Exxelor TM PO1015 and Exxelor TM PO1020 is available from ExxonMobil.

[0044] Preferably the grafted polypropylene is (semi)crystalline.

[0045] The MFI of the grafted polypropylene is preferably 150 to 600 dg / min, more preferably 290 to 460 dg / min, measured according to ISO 1133-1:2011 at 230°C / 2.16kg.

[0046] The amount of grafted polypropylene is 1.2 to 2.9 wt % based on the total polymer composition. The inventors of the present application surprisingly found that this amount of grafted polypropylene leads to improved drop weight resistance at low temperatures.

[0047] Optional additives

[0048] The polymer composition may contain conventional additives, such as nucleating and clarifying agents, stabilizers, mold release agents, peroxides, plasticizers, antioxidants, lubricants, antistatic agents, crosslinking agents, anti-scratch agents, flame retardants, foaming agents, acid scavengers, recycling additives, biocides, anti-fog additives, slip additives, anti-blocking additives, polymer processing aids, etc. Such additives are well known in the art. The technician knows how to select the type and amount of additives so that they do not adversely affect the target properties.

[0049] The invention also relates to a process for preparing the polymer composition.

[0050] The polymer composition according to the invention can be prepared by methods known in the art for preparing fiber reinforced compositions, such as: pultrusion methods, wire coating methods as described in EP 0921919 B1 and EP 0994978 B1, or compounding.

[0051] The polymer composition produced in this process is in the form of pellets.

[0052] The present invention also relates to an antenna housing comprising the polymer composition according to the invention in an amount of at least 95 wt %, preferably at least 98 wt %, more preferably 100 wt % of the total antenna housing.

[0053] The present invention also relates to a method for preparing an antenna housing, comprising the following steps in order:

[0054] - Providing the polymer composition according to the invention in the form of pellets.

[0055] - Injection molding the polymer composition in the previous step into an antenna housing.

[0056] The invention also relates to the use of the polymer composition according to the invention in an antenna housing.

[0057] experiment

[0058] Material

[0059] Polypropylene

[0060] The heterophasic propylene copolymer 1 (HECO 1) used to prepare the samples is commercially available from Sinopec. HECO 1 has an MFI of 35 dg / min measured at 230°C / 2.16kg according to ISO 1133-1:2011. HECO 1 consists of a propylene homopolymer as a matrix and an ethylene-propylene copolymer as a dispersed phase, the amount of the dispersed phase in HECO 1 being 16% by weight based on the total amount of HECO 1, and the amount of the structural part derived from ethylene being 8% by weight based on the total amount of HECO 1.

[0061] The heterophasic propylene copolymer 2 (HECO 2) used to prepare the samples is commercially available from SABIC. HECO 2 has an MFI of 70 dg / min measured at 230°C / 2.16 kg according to ISO 1133-1:2011. HECO 2 consists of a propylene homopolymer as a matrix and an ethylene-propylene copolymer as a dispersed phase, the amount of the dispersed phase in HECO 2 being 17.2 wt% based on the total amount of HECO 2, and the amount of the structural part derived from ethylene being 7.8 wt% based on the total amount of HECO 2.

[0062] Exxelor PO1020 (PO1020) is a maleic anhydride grafted polypropylene commercially available from ExxonMobil. It has an MFI of 430 dg / min measured at 230°C / 2.16 kg according to ISO 1133-1:2011.

[0063] Several ethylene-based elastomers were used in the examples, their commercial names, suppliers and properties can be found in the table below.

[0064] Table 1. POE information

[0065]

[0066] Stabilizers and impregnants:

[0067] The stabilizer used in the example is 3.1 wt %. The impregnating agent used in the example is the same as that used in WO2009 / 080281A1, and the amount of the impregnating agent is 2.65 wt %. The amount of the additive and the impregnating agent is based on the total amount of the composition.

[0068] Glass Fiber (GF):

[0069] The glass fiber used was standard Type 30 roving SE4220, supplied in roving packages by 3B, having a filament diameter of 19 microns and containing a sizing composition containing aminosilane.

[0070] method:

[0071] The samples were prepared in the following order:

[0072] In the first step, HECO is melt mixed with POE and a stabilizer to prepare a thermoplastic resin in the form of pellets.

[0073] In the second step, the thermoplastic resin, glass fiber and impregnating agent obtained in the first step are used to prepare a polymer composition by the wire coating method described in the examples of WO2009 / 080281A1. The composition details of the polymer composition are given in Table 2.

[0074] In the third step, the pellets of the polymer composition are injection molded into plaques. The dimensions of the plaques are suitable for the measurements.

[0075] Measurement method:

[0076] Spiral flow: The spiral flow measurement was performed on FANUC UH1000. The pellets obtained in the second step of the method were injected into a spiral mold at an injection speed of 30 mm / s, and when the injection pressure reached 700 kgf / cm 2 The injection process ends when the melt cools down and is removed from the mold and its length is measured. The channel of the spiral mold has a rectangular cross section with a height of 2 mm and a width of 15 mm.

[0077] Drop weight impact test:

[0078] The plate used in this measurement had dimensions: 830*400*3 mm.

[0079] Drop weight impact testing was performed on a custom-built machine consisting of two parts: a weight release mechanism and a plate holder.

[0080] The weight release mechanism can release a metal ball with a weight of 500g and a diameter of 50mm from a height of 2m or 1.3m, and the metal ball generates a drop weight impact on the test panel as a free-falling object with an initial velocity of 0.

[0081] The plate support has a square shape with a space in the center. The outer dimensions of the support are 830*400mm and the inner dimensions are 810*380mm. The horizontal geometric center of the outer square coincides with the horizontal geometric center of the inner square. The plate is placed horizontally on the plate support, and the horizontal geometric center of the plate coincides with the horizontal geometric center of the support.

[0082] The weight release mechanism and the plate support are arranged in such a way that the drop weight impact is produced vertically on the plate surface. The horizontal geometric center of the plate coincides with the horizontal geometric center of the impact point.

[0083] The plates were conditioned in a -40°C freezer for at least 4 hours before being mounted on the plate holder. The plates were removed from the freezer and the entire drop weight impact procedure was completed within 30 seconds.

[0084] After the drop weight impact, the plate was visually inspected for the presence of cracks on its surface. Five plates were tested for each formulation and the crack-free (pass) percentage was calculated.

[0085] Table 2. Formulation and properties of polymer compositions

[0086]

[0087] According to IE1 and EX1 of Table 2, POE amounts above 15.5 wt% lead to significantly higher pass rates of the drop weight impact test. Comparing IE2 and EX4, HECO with an MFI of 17 to 68 dg / min measured at 230°C / 2.16 kg according to ISO1133-1:2011 leads to a higher pass rate of the drop weight impact test. Comparison between IE2, EX2 and EX3 shows that POE1 with an MFI of 0.8 to 36 dg / min measured at 190°C / 2.16 kg according to ISO1133-1:2011 leads to improved spiral flow and drop weight impact resistance at low temperatures. Comparison between IE2 and EX5 shows that PO1020 in an amount of 1.2-2.9 wt% leads to improved drop weight impact resistance at low temperatures.

Claims

1. A polymer composition comprising polypropylene, an ethylene-based elastomer, grafted polypropylene, and glass fibers, wherein the polypropylene is a heterophasic propylene copolymer and has a melt flow index of 17 to 59 dg / min as measured at 230 °C / 2.16 kg according to ISO 1133-1:2011, wherein the amount of the ethylene-based elastomer is 15.5 to 28.3% by weight based on the total amount of the polymer composition, wherein the melt flow index of the ethylene-based elastomer measured at 190 °C / 2.16 kg according to ISO 1133-1:2011 is 0.8 to 4.8 dg / min, and wherein the density of the ethylene-based elastomer is 0.848 to 0.865 g / cm measured according to ASTM D792-13 3 , wherein the amount of the grafted polypropylene is 1.2 to 2.9% by weight based on the total amount of the polymer composition, and wherein the melt flow index of the grafted polypropylene is 150 to 600 dg / min as measured at 230 °C / 2.16 kg according to ISO 1133-1:2011.

2. The polymer composition according to claim 1, wherein the melt flow index of the polypropylene is 23 to 59 dg / min as measured at 230 °C / 2.16 kg according to ISO 1133-1:2011.

3. The polymer composition according to claim 1, wherein the melt flow index of the polypropylene is 32 to 47 dg / min as measured at 230 °C / 2.16 kg according to ISO 1133-1:2011.

4. The polymer composition according to any one of claims 1-3, wherein the polypropylene comprises an ethylene-α-olefin copolymer, and the amount of the ethylene-α-olefin copolymer is 13 to 28% by weight based on the total amount of the polypropylene.

5. The polymer composition according to any one of claims 1-3, wherein the ethylene-based elastomer is selected from ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, and mixtures thereof.

6. The polymer composition according to any one of claims 1-3, wherein the Shore A hardness of the ethylene-based elastomer is 35 to 90 as measured according to ASTM D2240-15, 1 s.

7. The polymer composition according to any one of claims 1-3, wherein the Shore A hardness of the ethylene-based elastomer is 42 to 69 as measured according to ASTM D2240-15, 1 s.

8. The polymer composition according to any one of claims 1-3, wherein the Shore A hardness of the ethylene-based elastomer is 47 to 60 as measured according to ASTM D2240-15, 1 s.

9. The polymer composition according to any one of claims 1-3, wherein the Shore A hardness of the ethylene-based elastomer is 50 to 57 as measured according to ASTM D2240-15, 1 s.

10. The polymer composition according to any one of claims 1-3, wherein the grafted polypropylene is maleic anhydride-grafted polypropylene.

11. The polymer composition according to any one of claims 1-3, wherein the diameter of the glass fibers is 5 to 50 microns.

12. The polymer composition according to any one of claims 1-3, wherein the diameter of the glass fibers is 10 to 30 microns.

13. The polymer composition according to any one of claims 1-3, wherein the diameter of the glass fibers is 15 to 25 microns.

14. The polymer composition according to any one of claims 1 - 3, wherein the amount of the glass fiber is 16 to 42% by weight based on the total amount of the polymer composition.

15. The polymer composition according to any one of claims 1 - 3, wherein the amount of the glass fiber is 25 to 34% by weight based on the total amount of the polymer composition.

16. The polymer composition according to any one of claims 1 - 3, wherein the amount of the polypropylene is 26 - 76% by weight based on the total amount of the polymer composition.

17. The polymer composition according to any one of claims 1 - 3, wherein the amount of the polypropylene is 33 - 62% by weight based on the total amount of the polymer composition.

18. The polymer composition according to any one of claims 1 - 3, wherein the amount of the polypropylene is 39 - 53% by weight based on the total amount of the polymer composition.

19. The polymer composition according to any one of claims 1-3, wherein the density of the ethylene-based elastomer is from 0.853 to 0.860 g / cm as determined according to ASTM D792-13 3 .

20. The polymer composition according to any one of claims 1 - 3, wherein the melt flow index of the ethylene - based elastomer is 0.9 to 4.8 dg / min as measured according to ISO1133 - 1:2011 at 190 °C / 2.16 kg.

21. The polymer composition according to any one of claims 1 - 3, wherein the melt flow index of the grafted polypropylene is 290 to 460 dg / min as measured according to ISO1133 - 1:2011 at 230 °C / 2.16 kg.

22. An antenna housing comprising the polymer composition according to any one of claims 1 - 21, wherein the amount of the polymer composition is at least 95% by weight of the total amount of the antenna housing.

23. The antenna housing according to claim 22, wherein the amount of the polymer composition is at least 98% by weight of the total amount of the antenna housing.

24. The antenna housing according to claim 22, wherein the amount of the polymer composition is 100% by weight of the total amount of the antenna housing.

25. A method for preparing an antenna housing, comprising the steps in the following order: providing the polymer composition according to any one of claims 1 to 21 in the form of pellets; injection - molding the polymer composition in the previous step into an antenna housing.

26. Use of the polymer composition according to any one of claims 1 to 21 in an antenna housing.

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