High melt-strength polypropylene composite

Abstract

The present invention relates to a high melt strength polypropylene composition comprising a high melt strength polypropylene, the high melt strength polypropylene composition having a length of 20 mm, a width of 2 mm, an initiation velocity v of 9.8 mm / s, and an acceleration of 6 mm / s 2 The melt strength is at least 65 cN when measured at 200°C in accordance with ISO 16790:2005 using a cylindrical capillary tube.

Description

[Technical Field]

[0001] The present invention relates to a high melt strength polypropylene composition, a foam containing a high melt strength polypropylene composition, an article containing a foam, a process for manufacturing a foam, and the use of a high melt strength polypropylene composition in the manufacture of a foam. [Background technology]

[0002] Polymer foams are used in a wide range of applications, including building and construction, automotive, household applications such as food and protective packaging, and consumer applications. Foams are very popular due to their excellent mechanical rigidity, insulation, and shock absorption properties. In addition, the use of foams significantly contributes to reducing the use of raw materials. Furthermore, using foams enables lightweight solutions, which is advantageous not only from a cost perspective but also from a transportation perspective, as it requires less energy to transport lighter materials.

[0003] Polypropylene foam is superior to other polymer foams due to its excellent mechanical properties, particularly its rigidity (hardness), ease of recycling (compared to polystyrene, which requires further steps in the waste separation process), and excellent chemical resistance (oil and acid resistance), heat resistance, and non-absorbent properties.

[0004] Long-chain branched polypropylene is commonly used to foam polypropylene. One example of such long-chain branched polypropylene is Dploy, which is commercially available from Borealis. M It's WB140HMS.

[0005] However, there is a continuing demand for improvements to long-chain branched polypropylene. For example, it is desirable to improve the processability, recyclability, and / or properties of foams produced using long-chain branched polypropylene. Furthermore, there is pressure to reduce the environmental impact of polypropylene foams, for example, by further reducing weight and / or improving recyclability. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a high melt strength polypropylene composition that can achieve the production of foamed sheets with higher bending rigidity without increasing the environmental impact (i.e., without increasing the amount of raw materials required). [Means for solving the problem]

[0007] The objective is a length of 20 mm, a width of 2 mm, and a starting speed of 9.8 mm / s. 2 This is achieved by a high melt strength polypropylene composition containing high melt strength polypropylene having a melt strength of 65 cN or more, measured at 200°C in accordance with ISO 16790:2005 using a cylindrical capillary tube.

[0008] It has been found that using the high melt-strength polypropylene composition of the present invention can increase the overall bending stiffness of sheets manufactured therefrom. Therefore, the high melt-strength polypropylene composition of the present invention, with a melt strength of 65 cN or higher, can be suitably used in applications requiring higher overall bending stiffness. In applications requiring the same overall bending stiffness, the amount of the high melt-strength polypropylene composition of the present invention used can be reduced to obtain the same overall bending stiffness, i.e., thinner foamed sheets and / or sheets with lower foam density can be manufactured. Such so-called down-gauge reduction is advantageous from both an environmental perspective (reduced carbon footprint, reduced transportation costs and energy) and an economic (cost) perspective.

[0009] The sheet defined here has a shape in which the length is greater than the width and the width is greater than the thickness. The thickness of this sheet is not important in principle, but it may be, for example, between 5 μm and 100 cm.

[0010] In the context of the present invention, "foamed" or "foamed material" means that, due to the presence of bubbles (e.g., air), its shape has a lower density compared to the density of the same material in which bubbles are not present.

[0011] High melt-strength polypropylene composite High melt strength polypropylene compositions having a melt strength of 65 cN or higher can be obtained, for example, by the process disclosed in International Publication No. 2009 / 003930. International Publication No. 2009 / 003930 discloses an irradiated polymer composition comprising at least one polyolefin resin and at least one non-phenolic stabilizer, which is produced by a process comprising mixing the polyolefin resin and the non-phenolic stabilizer and irradiating the mixture under a reduced oxygen environment. In addition, high melt strength polypropylene with a melt strength of 65 cN or higher is available from SABIC as SABIC® PP UMS561P as of February 18, 2021.

[0012] Preferably, the high melt strength polypropylene composition is Step a) involves irradiating a long-chain branched polypropylene with at least one non-phenolic stabilizer selected from the group consisting of at least one non-phenolic stabilizer, preferably a hindered amine, for a time sufficient to obtain the long-chain branched polypropylene, wherein the irradiation is performed by irradiating with an electron beam of 2.0 megalards or more and 20 megalards or less in a reduced oxygen environment, and the amount of reactive oxygen species is 15% by volume or less of the total volume of the reduced oxygen environment, It is produced by step b) deactivating the freezicals in the long-chain branched polypropylene to form a high melt strength polypropylene composition.

[0013] Methods for inactivating free radicals are known in the art, for example, by heating as described in WO 2009 / 003930.

[0014] Examples of non - phenolic stabilizers are known in the art and are disclosed on pages 37 - 60 of WO 2009 / 003930, which is incorporated herein by reference. Preferably, the non - phenolic stabilizer is selected from the group of hindered amines. More preferably, the non - phenolic stabilizer is at least one hindered amine selected from the group consisting of Chimassorb® 944, Tinuvin® 622, Chimassorb® 2020, Chimassorb® 119, Tinuvin® 770, and mixtures thereof, and / or at least one hydroxylamine, nitrone, amine oxide, or benzofuranone selected from N,N - di(hydrogenated tallow)amine (Irgastab® FS - 042), N,N - di(alkyl)hydroxylamine produced by direct oxidation of N,N - di(hydrogenated tallow)amine (Irgastab® FS - 042), N - octadecyl - α - heptadecyl nitrone, Genox® EP, di(C16 - C18)alkylmethylamine oxide, 3 - (3,4 - dimethylphenyl)-5,7 - di - tert - butyl - benzofuran - 2 - one, Irganox® HP - 136 (BFl), and mixtures thereof, and / or at least one organic phosphite or phosphonite selected from tris(2,4 - di - tert - butylphenyl)phosphite (Irgafos® 168). Even more preferably, the non - phenolic stabilizer of the present subject matter can include those described in U.S. Patent Nos. 6,664,317 and 6,872,764, which are incorporated herein in their entirety by reference.

[0015] The melt strength of the high melt strength polypropylene composition is preferably 100 cN or less, for example 95 cN or less, for example 90 cN or less, for example 87 cN or less.

[0016] The melt strength of the high melt strength polypropylene composition is measured at 200 °C using a cylindrical capillary with a length of 20 mm, a width of 2 mm, an initial velocity v0 of 9.8 mm / s, and an acceleration of 6 mm / s2 in accordance with ISO 16790:2005.

[0017] The polypropylene used herein is a propylene homopolymer, a copolymer of propylene and an α-olefin, or a heterophasic propylene copolymer.

[0018] Preferably, the high melt strength polypropylene composition contains 95% by weight or more, more preferably 96% by weight or more, still more preferably 97% by weight or more, still more preferably 98% by weight or more, for example 99% by weight or more, for example 99.6% by weight or more, for example 99.8% by weight or more, for example 99.9% by weight or more of the high melt strength polypropylene composition, based on the high melt strength polypropylene composition.

[0019] Preferably, the high melt strength polypropylene is a polypropylene selected from the group consisting of a propylene homopolymer and a propylene copolymer containing a portion derived from one or more comonomers selected from the group consisting of propylene and one or more α-olefins having 4 to 12 carbon atoms.

[0020] Preferably, the propylene copolymer is 13When measured using 13C NMR, the propylene copolymer contains a portion derived from one or more comonomers selected from the group consisting of ethylene and α-olefins having 4 to 12 carbon atoms in an amount of 10% by weight or less, for example, 1.0% to 7.0% by weight. For example, the propylene copolymer contains a portion derived from one or more comonomers selected from the group consisting of ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, and 1-dodecene, preferably a portion derived from ethylene.

[0021] The synthesis processes for polypropylene and polypropylene are known. Propylene homopolymers are obtained by polymerizing propylene under suitable polymerization conditions. Propylene copolymers are obtained by copolymerizing propylene with one or more other comonomers, such as ethylene, under suitable polymerization conditions. The production of propylene homopolymers and copolymers is described, for example, in Moore, EP (1996) Polypropylene Handbook, Polymerization, Characterization, Properties, Processing, Applications, Hanser Press: New York.

[0022] Propylene homopolymers, propylene copolymers, and heterophase propylene copolymers can be produced by any known polymerization technique and any known polymerization catalyst system. Regarding techniques, slurry polymerization, solution polymerization, or gas-phase polymerization can be referred to. Regarding catalyst systems, examples include Ziegler-Natta, metallocene, or single-site catalyst systems. All of these are known in the art.

[0023] It is preferable that the VOC value measured according to VDA278(2011-10) is 250 μg / g or less, preferably 50 μg / g or less, and / or the FOG value measured according to VDA278(2011-10) is 500 μg / g or less, preferably 100 μg / g or less.

[0024] Preferably, the high melt strength polypropylene composition has a melt flow rate measured in accordance with ASTM D1238 (2013) at a temperature of 230°C and a load of 2.16 kg, which is 0.50 g / 10 min or more and 8.0 g / 10 min or less, more preferably 0.70 g / 10 min or more and 5.0 g / 10 min or less, and most preferably 1.0 g / 10 min or more and 4.0 g / 10 min or less.

[0025] In another embodiment, the present invention relates to a foam containing the high melt strength polypropylene composition of the present invention. Preferably, the high melt strength polypropylene composition is present in the foam at a concentration of 10% by weight or more. For example, the high melt strength polypropylene composition is present in an amount of 15% by weight or more and 99.9% by weight or less, for example, 20% by weight or more and 99.5% by weight or less, for example, 25% by weight or more and 99% by weight or less, for example, 30% by weight or more and 98% by weight or less, for example, 40% by weight or more and 97% by weight or less, for example, 50% by weight or more and 96% by weight or less, preferably 60% by weight or more and 99.9% by weight or less. Preferably, the high melt strength polypropylene composition is present in the foam at a concentration of 30% by weight or more and 99.9% by weight or less.

[0026] The high melt strength polypropylene composition may further contain additives such as flame retardants, pigments, lubricants, slip agents, flow promoters, antistatic agents, processing stabilizers, long-term stabilizers, and / or UV stabilizers. The additives may be present in any required amount as measured by those skilled in the art, but are preferably present in an amount of 0.001% to 5.0% by weight, more preferably 0.01% to 4.0% by weight, and even more preferably 0.01% to 3.0% by weight relative to the high melt strength polypropylene composition.

[0027] In one embodiment, the foam preferably further comprises 10% to 90% by weight of additional polypropylene relative to the foam, for example, 10% to 40% by weight, or 50% to 90% by weight. The additional polypropylene may be a propylene homopolymer, a propylene copolymer, for example, a copolymer of propylene and α-olefin as described herein, or a heterogeneous propylene copolymer as described herein.

[0028] The foam may further contain a nucleating agent. A nucleating agent may be necessary to increase the bubble density and alter the dynamics of bubble formation and growth (Gendron, Thermoplastic Foam Processing, 2005, p. 209). The amount of nucleating agent relative to the foam may be, for example, 0.10% to 5.0% by weight, for example, 0.20% to 4.0% by weight, for example, 0.30% to 3.0% by weight, preferably 0.40% to 2.5% by weight, more preferably 0.50% to 1.5% by weight, and most preferably 0.50% to 1.2% by weight.

[0029] Suitable nucleating agents include, but are not limited to, a mixture of talc, silica, sodium bicarbonate, and citrate. Other suitable nucleating agents include amides, saturated or unsaturated aliphatic (C) compounds such as azodicarboxamides. 10 ~C 34 )Includes amines and / or esters of carboxylic acids. Examples of suitable amides include fatty acid (bis)amides, such as stearamide, caproamide, caprylamide, undecylamide, lauramide, myristamide, palmitamide, behenamide and arachidamide, hydroxystearamide and alkylenediyl-bis-alkaneamide, preferably (C2~C 32 )Alkyl-bis-(C2-C 32 ) Alkanamides, such as ethylenebisstearate (EBS), butylenebisstearamide, hexamethylenebisstearamide, ethylenebisbehenamide and mixtures thereof. Suitable amines include, for example, ethylenebishexamide and hexamethylenebishexamide (C2-C18 ) It contains an alkylene diamine. A saturated or unsaturated aliphatic (C 10 -C 34 ) ester of a carboxylic acid is preferably an ester of an aliphatic (C 16 -C 24 ) carboxylic acid. Preferably, the nucleating agent is selected from the group consisting of talc, sodium hydrogen carbonate, citric acid, azodicarbonamide and mixtures thereof, and more preferably, it is talc.

[0030] In order to produce a foam, it may be necessary to use a foam stabilizer. The foam stabilizer is a permeability modifier that delays the diffusion of hydrocarbons such as isobutylene to produce a dimensionally stable foam. Preferred foam stabilizers include, but are not limited to, glyceryl monostearate (GMS), glyceryl monopalmitate (GMP), palmitic acid esters and / or amides (Gendron et al., Thermoplastic Foam Processing, 2005, pages 31 and 149). Suitable amides are, for example, stearoyl stearamide, palmitide and / or stearamide. Suitable mixtures include, for example, mixtures containing GMS and GMP, or mixtures containing stearamide and palmitoamide. Preferably, when using a foam stabilizer, it is glyceryl monostearate or stearamide. The amount of the foam stabilizer added depends on the desired cell size and the composition for producing the foam. Generally, the addition amount of the foam stabilizer may be 0.10% by weight or more and 3.0% by weight or less based on the foam.

[0031] Preferably, the density of the foam is such that the density measured in accordance with ISO 845 (2006) is 750 kg / m 3 or less and 15 kg / m 3 or more, preferably 500 kg / m 3 or less and 25 kg / m 3 or more.

[0032] Preferably, the foam has an open-cell content of 15.0% or less, preferably 12.0% or less, more preferably 10.0% or less, even more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, and even more preferably 2.0% or less, as measured according to ASTM D6226-10.

[0033] The manufacturing processes for polypropylene foams and foamed sheets are within the scope of knowledge of those skilled in the art. In this process, a molten high-melt-strength polypropylene composition mixed with a gaseous or liquid blowing agent rapidly expands due to a pressure drop. In addition to continuous foaming processes, discontinuous processes are also applicable. In continuous foaming processes, the polypropylene composition is melted and gas-filled in an extruder, usually under a pressure of over 20 bar, before it is extruded through a die into which the foam is formed by the pressure drop. For example, the mechanism by which polypropylene foams in this foaming extrusion process is described in HENaguib, CBPark, and N.Reichelt, "Basic Foaming Mechanisms Controlling Volume Expansion of Extruded Polypropylene Foams," Journal of Applied Polymer Science, 91, 2661-2668 (2004). The foaming process is outlined in STLee, "Foam Extrusion," Technical Press (2000). In discontinuous foaming processes, the polypropylene composition (micro) particles are pressurized with a blowing agent and heated below the melting temperature before the pressure in the autoclave is rapidly released. The dissolved foaming agent forms bubbles, creating a foamed structure.

[0034] Accordingly, the present invention also relates to a foam produced by a foam extrusion process, an autoclave process, an injection molding process, a blow molding process, or a rotational molding process.

[0035] When the foam of the present invention is a foamed sheet, the foamed sheet is preferably manufactured by a foaming extrusion process.

[0036] In another aspect, the present invention relates to a process for manufacturing the foam of the present invention. In particular, the present invention also relates to a process for manufacturing the foam, a) The step of providing a high melt strength polypropylene composition of the present invention, b) A step of adding a blowing agent to a high melt strength polypropylene composition, and optionally adding a nucleating agent and / or additional polypropylene, wherein, for example, the amount of blowing agent added is 0.10% by weight or more and 20% by weight or less relative to the high melt strength polypropylene composition, optional nucleating agent and optional additional polypropylene, c) A manufacturing method comprising the steps of sequentially subjecting a mixture of a high melt strength polypropylene composition, a blowing agent, an optional nucleating agent, and an optional additional polypropylene to a foaming process to produce a foam.

[0037] For example, the amount of foaming agent depends on the desired density and the polymer composition used. The amount of foaming agent used may be, for example, 0.10% to 20% by weight relative to the polymer composition.

[0038] Suitable physical blowing agents include, but are not limited to, isobutane, CO2, pentane, butane, nitrogen, and / or fluorohydrocarbons. Preferably, the physical blowing agent is isobutane and / or CO2, most preferably isobutane.

[0039] Examples of suitable chemical blowing agents include, but are not limited to, citric acid or citric acid-based materials (e.g., mixtures of citric acid and sodium bicarbonate) and azodicarbonamides. Such chemical blowing agents include, for example, Hydrocerol from Clariant. TM CF-40E TM or Hydrocerol TM CF-05E TM It can be sold commercially as such.

[0040] The foamed sheet produced in this manner can itself be stretched uniaxially or biaxially using known methods.

[0041] Therefore, the present invention also, a) The step of providing a high melt strength polypropylene composition of the present invention, b) Adding a blowing agent to a high melt strength polypropylene composition, and adding additional polypropylene, a nucleating agent and / or a foam stabilizer as needed, c) A step of subjecting a mixture of a high melt strength polypropylene composition, a blowing agent and an optional nucleating agent, as well as any additional polypropylene and an optional foam stabilizer, to a foaming process, preferably a foaming extrusion process, for forming a foamed sheet. The present invention relates to a manufacturing process that sequentially includes the steps of stretching a foamed sheet in at least one direction.

[0042] The present invention also relates to a foamed sheet manufactured from the high melt-strength polypropylene composition of the present invention, which is stretched in at least one direction. For example, the present invention relates to a foamed sheet of the present invention which is stretched uniaxially (e.g., longitudinally) or biaxially stretched, for example, longitudinally (MD) and transversely (MD). As is known to those skilled in the art, stretching in MD and TD may be carried out simultaneously or in successive steps.

[0043] For example, the stretching ratio in MD may be between 1.1 and 7.0, for example between 1.1 and 3.0. The stretching ratio in the lateral direction may be between 1.1 and 7.0, for example between 1.1 and 3.0.

[0044] In another aspect, the present invention relates to the use of the high melt strength polypropylene composition of the present invention in the production of foams.

[0045] The foam of the present invention can be suitably used in building and construction, automotive applications, household applications such as food packaging and protective packaging, and consumer applications. For example, the foam can be used to manufacture cups, trays, containers, bottles, seals, and reusable cartridges.

[0046] Other applications of the foam of the present invention include sandwich panels, pipe insulation, concrete jointing material, residential insulation, aquarium insulation, and floor insulation (underlayment). The excellent cushioning properties of the foam of the present invention provide safety and comfort to the user. This foam is suitable for a variety of applications requiring anti-slip properties, such as footwear, protective guards, sports floor mats, and foam rollers.

[0047] Therefore, in another aspect, the present invention relates to articles comprising the foam of the present invention, for example, articles that are sheets, films, profiles, rods or tubes. In yet another aspect, the present invention relates to the use of the foam of the present invention in building and construction, automotive applications, household applications such as food packaging and protective packaging, consumer applications, and the like.

[0048] The present invention also relates to the use of the foam in the manufacture of articles, for example, articles such as cups, trays, containers, bottles, seals, reusable boxes, sandwich panels, pipe insulation, concrete jointing material, residential insulation, aquarium insulation or floor insulation (underlayment), footwear, protective guards, sports floor mats or foam rollers.

[0049] The foam of the present invention can be used as an alternative to polystyrene foam, which is typically used in applications such as disposable food containers.

[0050] Furthermore, the present invention relates to subject matter as defined in the independent claims, or any possible combination of the features described herein, particularly preferably subject matter combined with the features present in the claims. Therefore, it is understood that all combinations of features relating to the compositions according to the present invention are possible. All combinations of features relating to the processes according to the present invention, and all combinations of features relating to the compositions according to the present invention and features relating to the processes according to the present invention are described herein.

[0051] Furthermore, the term "contains" does not exclude the presence of other elements. However, it should be understood that a description of a product / composition containing certain components also discloses products / compositions consisting of those components. Products / compositions consisting of these components may be advantageous because they provide a simpler and more economical process for manufacturing the product / composition. Similarly, a description of a process that includes certain steps should be understood as disclosing processes consisting of those steps. Processes consisting of these steps may be advantageous because they provide a simpler and more economical process.

[0052] The present invention will be described by the following embodiments, but is not limited thereto. [Modes for carrying out the invention]

[0053] Examples How to use Meltflow rate The polymer melt flow rate is 230°C (MFR) according to ASTM D1238 (2013). 230 ), measured with a load of 2.16 kg.

[0054] Melt strength Melt strength is measured according to ISO standard 16790:2005. Melt strength is defined as the maximum (pull-down) force (in cN) that the molten strand can withstand before fracture, for example, during rheotens measurement. The measurement was performed on a Goettfert Rheograph 6000 at 200°C using the setup shown in Figure 1 of ISO standard 16790:2005. The rheometer is equipped with a 12 mm diameter oven. A capillary tube 20 mm long and 2 mm wide was used. The inlet angle of the capillary tube was 180° (flat). The rheometer piston was moved at a speed of 0.272 mm / s to obtain an outlet velocity v0 of 9.8 mm / s. After filling the rheometer, the molten material was held in the rheometer for 5 minutes to stabilize the temperature and completely melt the polymer. The strand, separated from the capillary tube, was measured at 6 mm / s using Goettfert Rheotens II. 2 The tube was pulled out until it broke under the given acceleration. The distance between the capillary tube exit and the Rheotens II intake wheel (=extension length) was set to 100 mm. The pressure required to push the molten polymer into the capillary tube, the maximum stretching force (=melt strength), and the maximum stretch ratio at fracture were recorded.

[0055] Flexural modulus The flexural modulus of the foam sheet samples was measured by a three-point bending test in accordance with ISO 1209-2, using a test speed of 20 mm / min, to measure the bending properties of rigid foam plastics. Samples with a span of 60 mm and a width of 20 mm were cut from the foam sheet. The samples were cut in the longitudinal direction (MD, extrusion direction) and transverse direction (TD, direction perpendicular to the extrusion direction and direction perpendicular to the thickness direction) so as to maintain the thickness of the foam sheet (Table 2). As used herein, the thickness direction is the dimension of the foam sheet with the minimum dimensions.

[0056] The average bending modulus is the average of the bending modulus MD and the bending modulus TD.

[0057] foam density Foam density (kg / m³) 3This is the apparent total density measured in accordance with ISO 845:2006.

[0058] Thickness and width The thickness and width of the foam sheet are measured without applying pressure to the foam sheet.

[0059] Open cell content The open-cell content was measured using a Quantachrome Pentapyc 5200e gas hydrometer according to the method based on ASTM D6226-10. The sample was immersed in water, and its volume was determined from its external shape using Archimedes' principle. It was assumed that the absorption of the sample into water was negligible. After drying the adhering water from the sample, the volume was measured under various pressures using a hydrometer according to ASTM D6226-10 (V SPEC The sample volume was measured according to the following procedure.

[0060] To minimize compression of the foam, the applied pressure is always less than 0.1 bar. Here,

number

[0061] The sample volume of the foam was plotted at applied pressures (0.090 bar; 0.075 bar, 0.060 bar, 0.045 bar, 0.035 bar, 0.020 bar, 0.010 bar). Linear regression was used to fit a line segment passing through the measurement points. The intercept of the linear regression line with the Y-axis at p=0 bar represents the volume (V) used in the following equation. 規格0 )

[0062] Open cell content V 連続 (%) is calculated using the following formula: Here,

number

[0063] Materials used PP-UMS1 is a melt flow rate MFR that can be purchased from SABIC on February 18, 2021, under the SABIC® PPUMS 561P label without confidentiality restrictions. 230 It is a long-chain branched propylene homopolymer with a melt strength of 71 cN and a melt strength of 2.5 g / 10 min. SABIC® PPUMS 561P had a VOC value of 10.9 g / g after 7 days post-manufacturing, according to VDA278 (2011-10). SABIC® PPUMS 561P had a FOG value of 56.4 g / g after 7 days post-manufacturing, according to VDA278 (2011-10).

[0064] PP-HMS is deployed from Borealis. TM This is a long-chain branched propylene homopolymer commercially available as WB140HMS. Its melt flow rate (MFR) is also known as MFR. 230 The concentration was 2.2 g / 10 min, and the melt strength was 42 cN.

[0065] The talc is TALCOLIN PP70+, a propylene homopolymer masterbatch with a talc content of 70% by weight (d50 is 9 μm), available from JM Polymers.

[0066] The foaming agent is isobutane.

[0067] Manufacturing of foam sheets The foamed sheets were manufactured on a Theysohn 30mm twin-screw foaming extruder with an aspect ratio (l / d) of 40. The extruder consisted of nine electrically heated zones with water cooling, followed by a cooling section, a static mixer, and dies. Isobutane was added as a physical foaming agent at a concentration of 2.5 wt% based on the composition shown in Table 1, and the polymer molten material was introduced into the eighth zone of the extruder. A thickness-adjustable slit die was used for the production of the foamed sheets. The die pressure was adjusted by adjusting the thickness of the slit die so that the pressure at the die was 50 bar. A 35mm wide slit die was used.

[0068] Next, the foamed sheet was stretched longitudinally using a double-belt stretching device at the stretching ratios shown in Table 2. Afterward, the resulting sheet was cooled in a water-cooled calibration unit to fix the dimensions of the manufactured foamed sheet. The stretching ratio was adjusted by adjusting the speed of the double-belt unit to match the outlet velocity of the foam when it is freely expanding. When the stretching ratio is 1, the outlet velocity of the foam during free expansion (v 出力 ) is the speed (v) of the double belt unit. 線速度 ) is equal to ). Table 1 shows the high melt strength polypropylene composition, foaming extrusion conditions, and results.

[0069] Table 1. Compositions used, foaming conditions, and results [Table 1]

[0070] conclusion As shown in Table 1, according to the present invention, when a foamed sheet is produced from a high melt strength polypropylene composition with a melt strength of 45 cN or more, a higher average flexural modulus (Comparative Examples E1~E4~CE1~CE4) is obtained than that of a foamed sheet produced from a high melt strength polypropylene composition with a melt strength of less than 45 cN. The average value of the flexural modulus is a matrix of the overall bending stiffness.

[0071] Therefore, the high melt-strength polypropylene composition of the present invention can be suitably used in applications requiring higher overall bending stiffness. In applications requiring the same overall bending stiffness, the amount of the high melt-strength polypropylene composition of the present invention used can be reduced to obtain the same overall bending stiffness, i.e., thinner foamed sheets and / or sheets with lower foam density can be produced. Such so-called weight reduction is advantageous from both an environmental perspective (reduced carbon footprint, reduced transportation costs and energy) and an economic (cost) perspective.

Claims

1. A foam comprising a high melt-strength polypropylene composition containing polypropylene, The aforementioned high melt strength polypropylene composition has a length of 20 mm, a width of 2 mm, and an initiation speed v ０ 9.8mm / s, acceleration 6mm / s ２ Using a cylindrical capillary tube, a melt strength of 65 cN or more is measured at 200°C in accordance with ISO 16790:2005. The high melt strength polypropylene composition is present in an amount of 10% by weight or more relative to the foam. The foam density, as measured in accordance with ISO 845 (2006), is between 750 kg / m³ and 15.0 kg / m³, and / or the open-cell content of the foam, as measured in accordance with ASTM D6226-10, is 15.0% or less. A foam characterized by the following features.

2. The foam according to claim 1, wherein the melt strength is 95 cN or less.

3. The foam according to claim 1 or 2, wherein the polypropylene is selected from the group consisting of a propylene homopolymer and a propylene copolymer comprising a portion derived from propylene and one or more comonomers selected from ethylene and α-olefins having 4 to 12 carbon atoms, and / or the high melt strength polypropylene composition contains 95% by weight or more of the polypropylene with respect to the high melt strength polypropylene composition.

4. The foam according to any one of claims 1 to 3, comprising 0.001% by weight or more and 5.0% by weight or less of an additive to the high melt strength polypropylene composition.

5. The foam according to any one of claims 1 to 4, wherein the high melt strength polypropylene composition has a melt flow rate of 0.50 g / 10 min or more and 8.0 g / 10 min or less, as measured in accordance with ASTM D1238 (2013) at a temperature of 230°C and a load of 2.16 kg.

6. The foam according to any one of claims 1 to 5, wherein the foam further comprises a nucleating agent, the nucleating agent present in an amount of 0.10% by weight or more and 5.0% by weight or less relative to the foam, and / or the nucleating agent is selected from the group consisting of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof.

7. An article comprising the foam described in any one of claims 1 to 6.

8. A foam manufacturing process, a) A step of providing a high melt strength polypropylene composition comprising polypropylene, wherein the high melt strength polypropylene composition has a melt strength of 65 cN or more, as measured at 200°C in accordance with ISO 16790:2005 using a cylindrical capillary tube with a length of 20 mm, a width of 2 mm, an initial velocity v0 of 9.8 mm / s, and an acceleration of 6 mm / s². b) A step of adding a blowing agent to the high melt strength polypropylene composition, and optionally adding a nucleating agent and / or additional polypropylene, wherein the blowing agent is added in an amount of 0.10% by weight or more and 20% by weight or less relative to the high melt strength polypropylene composition, the optional nucleating agent and the optional additional polypropylene, c) A step of sequentially subjecting a mixture of the high melt strength polypropylene composition, the blowing agent, the optional nucleating agent, and the optional additional polypropylene to a foaming process to produce a foam, The high melt strength polypropylene composition is present in an amount of 10% by weight or more relative to the foam. The foam density, as measured in accordance with ISO 845 (2006), is between 750 kg / m³ and 15.0 kg / m³, and / or the open-cell content of the foam, as measured in accordance with ASTM D6226-10, is 15.0% or less. A process characterized by the following features.

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