Double-component core / shell structure foamed polypropylene bead and processing method thereof

Abstract

The present invention relates generally to the field of foamed polypropylene. Specifically, the invention relates to a novel double-component core / shell structure foamed polypropylene bead and a processing method thereof. The two-component core / shell structure foamed polypropylene comprises 5-95 wt% of a core component and 95-5 wt% of a shell component, based on the overall weight of the two-component core / shell structure foamed polypropylene, the core component comprises a first polypropylene, the first polypropylene comprises homo-polypropylene, ICP, RCP, Ter PP or a combination thereof, and the shell component comprises a second polypropylene, based on the overall weight of the two-component core / shell structure foamed polypropylene, based on the overall weight of the two-component core / shell structure foamed polypropylene, based on the overall weight of the two-component core / shell structure foamed polypropylene, the shell component comprises a C3-C2, C2-C8, or C2-C4 plastomer and / or elastomer, and optionally a polypropylene (PP) or a polyethylene (PE), or a combination thereof.

Description

Technical Field

[0001] The present invention generally relates to the field of foamed polypropylene. Specifically, the present invention relates to novel bicomponent core / shell structured foamed polypropylene beads and a processing method thereof. Background Art

[0002] Foamed beads are physical foam products that are widely used in industrial packaging or the automotive field. Usually foamed polypropylene (EPP) is used to replace cartons in the packaging industry or as part of the back seat to reduce the weight of the car. Foamed polystyrene (EPS) is generally used to protect the items in the package during transportation. EPP generally has better mechanical properties than EPS, and EPP can be recycled and reused, which is more sustainable than EPS. Therefore, there is a trend in the industry to replace EPS and other forms of packaging with more EPP.

[0003] Expanded polypropylene is a material with many excellent properties and is widely used in packaging, construction, automobiles and other fields. Currently, RCP (random copolymer) or terpolymer is used as the raw material for the production of EPP. Expanded polypropylene is usually made of random copolymer / terpolymer pellets to make foamed beads and then steam-formed. Due to the high melting point (Tm) of random copolymer / terpolymer, this method requires high steam temperature and consumes a lot of energy. In addition, due to the high Vicat softening point or melting temperature of EPP, the steam pressure requirement is usually 2-4kg / cm 2 To provide the temperature required for molding EPP beads. The energy cost of steam can be as much as half of the total cost of the final product. In addition, due to the insufficient bonding strength between the beads made based on this method, the durability of the product is reduced.

[0004] Therefore, the above method has the following disadvantages:

[0005] High energy consumption: The high melting point of random copolymers / terpolymers requires high steam temperatures, resulting in high energy consumption.

[0006] High cost: To achieve the required molding temperature, high steam pressure is required, increasing energy costs, which can account for up to 50% of the final product cost.

[0007] Insufficient strength: The beads made based on this method have insufficient bonding strength, resulting in reduced product durability.

[0008] The main technology of traditional foamed polypropylene includes single-screw / twin-screw extrusion to produce single-component polypropylene (PP) micro-particles. Single-screw / twin-screw extrusion is to melt the polypropylene (PP) raw material under high temperature and pressure, and push the molten PP out of the die through a single-screw / twin-screw extruder to form continuous PP filaments, which are then cut into PP micro-particles by a pelletizing device.

[0009] This technology mainly covers the following two granulation methods: underwater granulation using an underwater granulator (forming spherical granules) and strip granulation (forming cylindrical granules).

[0010] Underwater pelletizer is a kind of equipment that cools molten polymer materials (such as polypropylene, polyethylene, etc.) into granules. Its main feature is that the molten polymer is extruded through an extruder, and cut into spherical particles directly at the die head with a cutter. The cut particles fall directly into the water to cool and form spherical pellets. However, it has the following disadvantages that cannot be ignored: large equipment investment, large water resource consumption, high maintenance cost, difficulty in controlling pellet size, environmental pollution, etc.

[0011] Strand pelletizing, also known as strand granulation, is a widely used technology for producing polymer pellets. It involves forcing the molten polymer through an extruder to form a continuous strand that is then cooled and cut into pellets.

[0012] Bicomponent (Bico) fibers are single fibers composed of two different raw material components. The growing demand for nonwovens is one of the growth drivers of the global bicomponent fiber industry.

[0013] It is worth noting that a special type of core / shell structure fiber among bicomponent fibers has been used to a certain extent in the field of textile material science, especially in the non-woven fabric industry. This fiber achieves precise regulation of fiber properties by finely controlling the composition, proportion and distribution of the core and shell. The core / shell structure not only enhances the internal bonding force of the fiber, but also gives the fiber a more complex surface morphology and functional properties, thereby improving the overall performance and use value of the non-woven fabric. Although bicomponent core / shell structure fibers have been used to a certain extent in the non-woven fabric industry, they have not yet been used in the foamed polypropylene industry.

[0014] However, in the traditional nonwoven fabric industry, the yarns produced using a two-component core / shell structure have a large stretch ratio, and the large stretch ratio caused by the conventional method of producing ordinary wire drawing industry products cannot achieve good foaming of the core and shell structures, and even cause mutual adhesion, resulting in failure to foam.

[0015] Therefore, there is an urgent need for a novel method for preparing foamed polypropylene that can avoid the above-mentioned shortcomings of the prior art, which can make the core / shell structure well foamed, reduce the steam molding temperature to save energy and reduce costs, and improve the bead bonding strength to increase product durability. Summary of the invention

[0016] The present invention extends the two-component processing technology to produce well-foamed polypropylene with a core / shell (C / S) structure, thereby overcoming the above-mentioned shortcomings and deficiencies in the prior art.

[0017] The first aspect of the present invention relates to a two-component core / shell structure foamed polypropylene, which comprises 5 wt % to 95 wt % of a core component and 95 wt % to 5 wt % of a shell component, based on the overall weight of the two-component core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, the first polypropylene comprises homopolymer polypropylene, ICP, RCP, Ter PP or a combination thereof; the shell component comprises an alpha olefin plastomer and / or an elastomer, and optionally polypropylene (PP) or polyethylene (PE), or a combination thereof; wherein the two-component core / shell structure foamed polypropylene is prepared by the second aspect of the present invention as described below, and the core structure and the shell structure of the prepared two-component core / shell structure foamed polypropylene are both well foamed.

[0018] The second aspect of the present invention relates to a method for preparing the two-component core / shell structure foamed polypropylene according to the first aspect of the present invention, which comprises the following steps in sequence:

[0019] 1. Using a twin-screw extruder, the core component and the shell component according to the first aspect of the present invention are respectively extruded through two different hoppers to form a core / shell structured bicomponent filament, wherein after the core component and the shell component are extruded from the die of the extruder, the speed difference of the subsequent stretching rollers on the production line is adjusted to obtain filaments with different stretching ratios, wherein the stretching ratio is less than or equal to 2.5:1, preferably less than or equal to 2:1, more preferably less than or equal to 1.5:1, and most preferably about 1:1;

[0020] 2. Cutting the core / shell structured bicomponent filaments obtained in step 1 into microparticles;

[0021] 3. Physically foaming and steam molding the microparticles obtained in step 2.

[0022] The third aspect of the present invention relates to the use of the two-component core / shell structured foamed polypropylene in packaging, construction or automobile industries.

[0023] Unexpectedly, the above technical scheme of the present invention can overcome the shortcomings of the above-mentioned prior art, so that the core / shell structure of the foamed polypropylene is well foamed, the steam molding temperature is reduced to save energy and reduce costs, and the bead bonding strength is improved to increase product durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order that the manner in which the above-described features of the present invention may be understood in detail, a more specific description of the invention briefly outlined above may be obtained by reference to embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof, as the present invention may admit of other equally effective embodiments. It is emphasized that the drawings are not necessarily to scale, and certain features and certain views of the drawings may be shown exaggerated in scale or in schematic diagrams for the sake of clarity and / or simplicity.

[0025] Figure 1 It is a schematic diagram of the overall appearance of a core / shell structured bicomponent polypropylene filament.

[0026] Figure 2 It is a schematic diagram of the overall appearance of core / shell structured two-component polypropylene particles.

[0027] Figure 3A This is a cross-sectional view of Sample 1 (core / shell (C / S) ratio of 1:1) described in Table 1 below (photographed using a Zeiss Axio Imager Z2 optical microscope, scale bar 100 μm).

[0028] Figure 3B This is a cross-sectional view of Sample 2 (core / shell (C / S) ratio of 6:4) described in Table 1 below (photographed using a Zeiss Axio Imager Z2 optical microscope, scale bar 100 μm).

[0029] Figure 3C This is a cross-sectional view of Sample 3 (core / shell (C / S) ratio of 7:3) described in Table 1 below (photographed using a Zeiss Axio Imager Z2 optical microscope, scale bar: 100 μm).

[0030] Figure 3D This is a cross-sectional view of sample 4 (core / shell (C / S) ratio of 8:2) described in Table 1 below (photographed using a Zeiss Axio Imager Z2 optical microscope, scale bar: 100 μm).

[0031] Figure 3E This is a cross-sectional view of sample 5 (core / shell (C / S) ratio of 6:4) described in Table 1 below (photographed using a Zeiss Axio Imager Z2 optical microscope, scale bar: 100 μm).

[0032] Figure 3F This is a cross-sectional view of Sample 6 (core / shell (C / S) ratio of 7:3) described in Table 1 below (photographed using a Zeiss Axio Imager Z2 optical microscope, scale bar: 100 μm).

[0033] Figure 4A It is a picture of bicomponent core / shell structured foamed polypropylene beads prepared from filaments with a draw ratio of 1:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)).

[0034] Figure 4B The core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) were heated to 110°C and CO 2 The picture after foaming attempt in the foaming kettle under the conditions of pressure of 15MPa and time of 60min.

[0035] Figure 4C The core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) were heated to 115°C and CO 2 The picture after foaming attempt in the foaming kettle under the conditions of pressure of 15MPa and time of 60min.

[0036] Figure 4D The core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) were heated to 115°C and CO 2 The picture after foaming attempt in the foaming kettle under the conditions of pressure of 15MPa and time of 90min.

[0037] Figure 4E The core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) were heated to 115°C and CO 2 The picture after foaming attempt in the foaming kettle under the conditions of pressure of 20MPa and time of 90min.

[0038] Figure 5 This is a picture of the overall appearance of the steam-formed two-component core / shell structured foamed polypropylene beads (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)).

[0039] Figure 6 It is a bar graph of the sealing force (N) of sample 7 (containing only RCP, comparative sample) and samples 8-13 at 130°C and 140°C.

[0040] Figure 7 It is a graph showing the relationship between the storage modulus G' (Pa) and temperature (°C) of sample 7 (containing only RCP, comparative sample) and sample 9) (using DMTA).

[0041] Figure 8 Sample 7 (RCP only, comparison sample) and sample Vistamaxx TM Storage modulus G' (Pa) and temperature (°C) of 3588FL (using DMTA). DETAILED DESCRIPTION

[0042] For the purpose of the following detailed description, it should be understood that, unless explicitly indicated otherwise, the present invention may adopt various alternative changes and step sequences. In addition, except in any operating examples or otherwise specified, all numerical values ​​representing the amount of the components used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise specified, the numerical parameters listed in the following specification and the attached claims are approximate values, which can vary according to the desired properties to be obtained by the present invention. At least, it is not intended to limit the scope of the application of the doctrine of equivalents to the claims, and each numerical parameter should at least be interpreted according to the numerical value of the reported significant figures and by applying ordinary rounding techniques.

[0043] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0044] In addition, it should be understood that any numerical range recited herein is intended to include all sub-ranges included therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including the endpoints) the recited minimum value of 1 and the recited maximum value of 10, i.e., having a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0045] As used in the specification and the appended claims, the articles "a," "an," and "the" include plural referents unless expressly and unequivocally limited to one referent.

[0046] It should be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures or functions of the present invention. Exemplary embodiments are described below to simplify the present disclosure; however, these exemplary embodiments are provided only as examples and are not intended to limit the scope of the present invention. In addition, the present disclosure may repeat figure numerals and / or letters in various embodiments and in the drawings provided herein. This repetition is for the purpose of simplicity and clarity and does not itself specify the relationship between various embodiments and / or configurations. Finally, without departing from the scope of the present disclosure, the embodiments given below may be combined in any combination, i.e., any element from one embodiment may be used in any other embodiment.

[0047] In the following discussion and in the claims, the terms "comprising" and "including" are used in an open-ended manner, and thus should be interpreted to mean "including but not limited to." The phrase "consisting essentially of means that the described / claimed composition does not include any other component that would materially alter its property by any greater than 5%, and in any case does not include any other component at a level greater than 3 mass%.

[0048] Definition of terms

[0049] As used in the present invention, the term "good foaming" when used in connection with polypropylene microparticles / granules / beads, etc., means that through an appropriate foaming process, the polypropylene microparticles / granules / beads, etc. form a uniform, fine and stable pore structure during the foaming process, while maintaining or improving the original excellent properties of the material, such as heat resistance, chemical corrosion resistance, cushioning performance, etc.; the foamed polypropylene microparticles / granules / beads should be able to maintain the stability of the pore structure, and it is not easy for the pores to collapse or deform during subsequent processing or use.

[0050] When used in connection with core / shell structured polypropylene, the term "good foaming" means that the core and shell remain intact, foaming uniformly, forming a uniform, dense and stable cell structure during the foaming process, without core rupture and shell rupture. The core / shell structure of the polypropylene after foaming can maintain the stability of the cell structure, and it is not easy to cause cell collapse or deformation during subsequent processing or use. The core / shell structured polypropylene obtained according to the method of the present invention can foam well.

[0051] As used in the present invention, the expression "about 1:1" refers to the range of 1±0.05:1, and may be 1.01:1, 1.03:1, 1.05:1 or 1:1.

[0052] As used in the present invention, when the term "about" or its synonyms (for example, "approximately", "substantially", "substantially", etc.) is used in conjunction with a specified amount, value or condition, it can be understood as an amount, value or condition that deviates from the specified amount, value or condition by 5% or less, 1% or less, 0.1% or less or 0.01% or less.

[0053] The term "or" is intended to include both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless the context clearly dictates otherwise. The indefinite articles "a" and "an" refer to both the singular (i.e., "an") and the plural (i.e., one or more) unless the context clearly dictates otherwise. For example, embodiments using "an olefin" include embodiments using one, two, or more olefins, unless specified to the contrary or the context clearly indicates that only one olefin is used.

[0054] The term "wt%" means percent by weight, "vol%" means percent by volume, "mol%" means percent by mole, "ppm" means parts per million and "wt ppm" and "wppm" are used interchangeably and mean parts per million on a weight basis. All concentrations herein are expressed based on the total amount of the composition in question unless otherwise indicated.

[0055] The term "polymer" refers to any substance of two or more identical or different repeating units / monomer units. The term "homopolymer" refers to a polymer having identical units. The term "copolymer" refers to a polymer having two or more units that are different from each other, and includes terpolymers, etc. The term "terpolymer" refers to a polymer having three units that are different from each other. When referring to units, the term "different" indicates that the units differ from each other by at least one atom or are isomerically different. Likewise, as used herein, the definition of polymer includes homopolymers, copolymers, etc. By way of example, when a copolymer is said to have a "propylene" content of 10% to 30% by weight, it is understood that the repeating units / monomer units or simply referred to as units in the copolymer are derived from propylene in the polymerization reaction, and the derived units are present at 10% to 30% by weight based on the weight of the copolymer.

[0056] As used herein, the term "polymer" also includes impact, block, graft, random and alternating copolymers. Unless otherwise specifically stated, the term "polymer" shall also include all possible geometric configurations. Such configurations may include isotactic, syndiotactic and random symmetries.

[0057] The term "α-olefin" refers to any linear or branched compound of carbon and hydrogen having at least one double bond between an α carbon atom and a β carbon atom. For purposes of this specification and the appended claims, when a polymer or copolymer is referred to as comprising an α-olefin, such as a polyα-olefin, the α-olefin present in such a polymer or copolymer is the polymerized form of the α-olefin.

[0058] The nomenclature of elements and their groups used herein is based on the periodic table used by the International Union of Pure and Applied Chemistry after 1988. An example of a periodic table is shown on the inside cover of Advanced Inorganic Chemistry, 6th edition, by F. Albert Cotton et al. (John Wiley & Sons, Inc., 1999).

[0059] As used herein, the term "Phr" is used to represent the number of parts of additives per 100 parts (by weight) of rubber or resin. This unit is mainly used to describe the amount of additives, fillers or other ingredients that need to be added in a certain proportion during the processing of rubber or resin.

[0060] As used herein, the term "monomer" or "comonomer" can refer to a monomer used to form a polymer, such as the unreacted compound in its form prior to polymerization, and can also refer to a monomer after it has been incorporated into a polymer.

[0061] As used herein, the term "terpolymer polypropylene" or "Ter PP" refers to a terpolymer polypropylene, which is a polymer synthesized from propylene monomer and at least two other comonomers (such as ethylene and 1-butene) through multiple active centers in polymerization kinetics theory. Its structural feature is that it contains multiple branches, which are usually introduced by comonomers, thereby giving it unique physical and chemical properties.

[0062] As used herein, the term "elastomer" shall refer to any polymer that exhibits a degree of elasticity, wherein elasticity is the ability of a material that has been deformed by a force (eg, by stretching) to at least partially return to its original dimensions once the force has been removed.

[0063] As used herein, the term "plastic body" shall refer to a material that, after the external force is removed, the object subjected to the force cannot completely return to its original state but maintains or partially maintains its current shape. A plastic body has the property of plasticity, that is, it can be deformed under the action of an external force, but this deformation is irreversible, that is, when the external force is removed, the plastic body cannot completely return to its original shape and volume.

[0064] As used herein, the terms "polypropylene", "propylene polymer" and "propylene-based polymer" refer to a polymer or copolymer comprising at least 50 mol% propylene units, preferably at least 70 mol% propylene units, more preferably at least 80 mol% propylene units, even more preferably at least 90 mol% propylene units, even more preferably at least 95 mol% propylene units or 100 mol% propylene units in the case of a homopolymer.

[0065] Polypropylene can be or can include homopolypropylene, isotactic polypropylene, highly isotactic polypropylene, syndiotactic polypropylene and copolymer of propylene or their mixture. The product including one or more propylene monomers polymerized with one or more additional monomers can be more generally referred to as random copolymer (RCP) or impact copolymer (ICP). Impact copolymer can also be referred to as heterophasic copolymer in the art. As used herein, "propylene-based" means containing any polymer comprising propylene alone or comprising propylene together with one or more comonomers, wherein propylene is the main component (e.g., greater than 50 weight % propylene).

[0066] "Polypropylene impact copolymer" or simply "impact copolymer" (ICP) is a combination of crystalline and amorphous polymers, such as iPP (isotactic polypropylene) and rubber, usually heterophasic, which provides the ICP with a stiffness and toughness greater than that of one or more amorphous polymers and a toughness greater than that of one or more crystalline polymers. The ICP may generally have a morphology such that the matrix phase comprises a relatively high proportion of the crystalline polymer, and the rubber is present in a relatively high proportion in a dispersed or co-continuous phase, for example a blend comprising 60 to 95 wt% of a matrix of iPP and 5 to 40 wt% of ethylene, propylene or other polymer having a Tg of 30°C or less.

[0067] Suitable ICPs include a polypropylene homopolymer and from 10, 15, 20, 22, or 24 wt % to 26, 28, 30, 35, 40, or 45 wt % of a propylene copolymer, based on the total weight of the ICP, wherein the copolymer comprises from about 7, or 10, or 15, or 20, or 25, or 30, or 35 wt % to 40, or 45, or 50, or 55, or 60 wt % ethylene, 1-butene, 1-hexene and / or 1-octene derived units and 80-40 wt % propylene-derived units, based on the weight of the propylene copolymer. The propylene-based impact copolymer may have an MFR in the range of from 10, or 15, or 20, or 26 g / 10min to 30, or 36, or 40, or 50 g / 10min and an elongation at break of greater than 60, or 70, or 80, or 90, or 100% (or in the range of from 60 or 80% to 120, or 150, or 300, or 400%). The MFR may also range from a lower limit of about 2.5, 3.5, or 4 g / 10min to an upper limit of about 10, 15, 20, or 30 g / 10min. Such ICPs tend to have improved toughness (T-ICP) compared to other ICPs described in detail herein. The propylene copolymer may be an ethylene-propylene copolymer.

[0068] Suitable ICPs also include polypropylene homopolymers and from 6, or 8, or 10 wt % to 14, or 16, or 20 wt % propylene copolymers, based on the weight of the ICP, wherein the propylene copolymers comprise from 20, or 25, or 30, or 35 wt % to 40, or 45, or 50, or 55, or 60 wt % ethylene, 1-butene, 1-hexene and / or 1-octene derived units and from 80, 75, 70, or 65 wt % to 60, 55, 50, 45, or 40 wt % propylene-derived units, based on the weight of the propylene copolymer. The ICP may have an MFR in the range of from 3, 5, 8 or 12 g / 10min to 20, 30, 40 or 50 g / 10min. Most preferably, the propylene copolymer may be an ethylene-propylene copolymer.

[0069] The term "random polypropylene" as used herein broadly means a single phase copolymer of propylene with up to 9 wt%, preferably 2 wt% to 8 wt% of an alpha-olefin comonomer. Preferred alpha-olefin comonomers have 2 carbon atoms, or 4-12 carbon atoms. Preferably, the alpha-olefin comonomer is ethylene.

[0070] The term RCP as used herein is specifically defined as a copolymer of propylene and 1 to 10 wt% of an olefin selected from ethylene and C4-C8 alpha-olefins.

[0071] As used herein, "HDPE" or "high density polyethylene" means a polyethylene produced in a gas phase and / or slurry phase polymerization and having a density of 0.940 g / cm 3 Up to 0.970g / cm 3 Ethylene homopolymers and ethylene copolymers having a range of densities.

[0072] As used herein, "LDPE" or "low density polyethylene" means a polyethylene produced in high pressure free radical polymerization and having a density of 0.910 g / cm 3 Up to 0.940g / cm 3 Ethylene homopolymers and / or ethylene copolymers having a density within a certain range.

[0073] As used herein, "LLDPE" or "linear low density polyethylene" means a polyethylene produced in a suspension, solution, slurry or gas phase polymerization process and having an average molecular weight of 0.910 g / cm 3 Up to 0.940g / cm 3 The LLDPE can be produced with conventional Ziegler-Natta catalysts, vanadium catalysts, metallocene catalysts, and / or other suitable catalysts for polymerizing ethylene and comonomers in gas phase reactors, high pressure tubular reactors and / or slurry reactors and / or with any of the disclosed catalysts in solution reactors.

[0074] A detailed description of the two-component core / shell structured foamed polypropylene beads will now be provided. Each of the separate inventions defined in the appended claims is considered to include the equivalents of the various elements or limitations specified in the claims. Depending on the context, all references to the "invention" may refer only to certain specific embodiments in some cases. In other cases, it will be appreciated that references to the "invention" will refer to the subject matter recorded in one or more but not necessarily all claims. Each invention will now be described in more detail below, including specific embodiments, variants and examples, but the present invention is not limited to these embodiments, variants or examples, and when the information in this disclosure is combined with publicly available information and technology, these embodiments, variants or examples are included to enable those of ordinary skill in the art to implement and use the present invention.

[0075] An embodiment of the present invention relates to a two-component core / shell structure foamed polypropylene, which comprises 5 wt % to 95 wt % of a core component and 95 wt % to 5 wt % of a shell component, based on the overall weight of the two-component core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, the first polypropylene comprises homopolymerized polypropylene, ICP, RCP, Ter PP or a combination thereof; the shell component comprises an alpha olefin plastomer and / or an elastomer, and optionally polypropylene (PP) or polyethylene (PE), or a combination thereof; wherein the two-component core / shell structure foamed polypropylene is prepared by another embodiment of the present invention as described below, and the core structure and the shell structure of the prepared two-component core / shell structure foamed polypropylene are both well foamed.

[0076] Another embodiment of the present invention relates to a method for preparing the two-component core / shell structure foamed polypropylene described in the above embodiment, which comprises the following steps in sequence:

[0077] 1. Using a twin-screw extruder, the core component and the shell component described in the above embodiment of the present invention are respectively passed through two different hoppers to extrude into a core / shell structured bicomponent filament;

[0078] 2. Cutting the core / shell structured bicomponent filaments obtained in step 1 into microparticles;

[0079] 3. Physically foaming and steam molding the microparticles obtained in step 2.

[0080] In certain embodiments of the present invention, the physical foaming process of the microparticles comprises the following steps: placing the microparticles obtained based on the above step 2 into a foaming kettle, introducing a physical foaming agent under foaming conditions, and releasing the pressure after a certain period of time to allow the microparticles to foam into beads.

[0081] In certain preferred embodiments of the present invention, the following process parameters are used during the physical foaming of particles: pressure range is 8-25 MPa, preferably 10-20 MPa; temperature range is 95-140°C, preferably 100-130°C; and / or time range is 30-120 min, preferably 60-90 min.

[0082] In certain embodiments of the present invention, the steam molding comprises the following steps: passing the physically foamed beads into a corresponding mold, then passing steam for a period of time to melt the surface of the beads and bond them together, and then cooling, demolding, and shaping to obtain the final product.

[0083] In certain embodiments of the present invention, in step 1 of the above-mentioned preparation method, after the core component and the shell component are extruded from the extruder die, filaments with different stretching ratios are obtained by adjusting the speed difference of subsequent stretching rollers on the production line, wherein the stretching ratio is less than or equal to 2.5:1, preferably less than or equal to 2:1, more preferably less than or equal to 1.5:1, and most preferably about 1:1, wherein a conventional roller speed meter is used to measure the stretching ratio.

[0084] Conventional roller speed measuring instruments may include, but are not limited to, commercially available rubber roller testers, double roller testers, or pressure roller testers.

[0085] In certain preferred embodiments of the present invention, in step 1 of the above-mentioned preparation method, after the core / shell structure monofilament is extruded from the die, it falls into water for cooling, passes through a steam-heated trough after exiting the water trough, passes through different stretching rollers, and different stretching ratios are achieved by adjusting the different rotation speeds of the stretching rollers.

[0086] In certain preferred embodiments of the present invention, in step 1 of the above-mentioned preparation method, the rotation speed ratio of the front roller and the rear roller in the stretching roller is less than or equal to 2.5:1, preferably less than or equal to 2:1, more preferably less than or equal to 1.5:1, and most preferably about 1:1.

[0087] In certain embodiments of the present invention, the core component and / or the shell component further comprises a nucleating agent.

[0088] In certain embodiments of the present invention, the nucleating agent comprises talc, zinc borate, nano calcium carbonate or a combination thereof, preferably talc.

[0089] In certain embodiments of the present invention, the content of the nucleating agent in the core component or the shell component is preferably 0.1-5 phr, more preferably 0.2-2 phr, even more preferably 0.5-1 phr.

[0090] In certain embodiments of the present invention, the bicomponent core / shell structure foamed polypropylene preferably comprises 10 wt % to 90 wt %, 20 wt % to 80 wt %, or 30 wt % to 70 wt % of a core component and 90 wt % to 10 wt %, 80 wt % to 20 wt %, or 70 wt % to 30 wt % of a shell component, based on the overall weight of the bicomponent core / shell structure foamed polypropylene.

[0091] In certain preferred embodiments of the present invention, the core component comprises, preferably consists of, a first polypropylene and 0.1-5 phr, more preferably 0.2-2 phr, even more preferably 0.5-1 phr of a nucleating agent.

[0092] In certain preferred embodiments of the present invention, the first polypropylene comprises, preferably consists of, RCP.

[0093] In certain preferred embodiments of the present invention, the shell component comprises an alpha olefin (preferably linear) including a C3-C2, C2-C8 or C2-C4 elastomer, preferably a C3-C2 elastomer, wherein C3-C2 refers to a copolymer of propylene and ethylene, C2-C8 refers to a copolymer of ethylene and octene, and C2-C4 refers to a copolymer of ethylene and butene.

[0094] In certain preferred embodiments of the present invention, the shell component comprises 1 to 100 wt%, preferably 30 to 100 wt%, more preferably 50 to 100 wt% of a C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer, and preferred elastomers include propylene-based elastomers.

[0095] Suitable elastomers are propylene-based elastomers which are available under the trade name VISTAMAXX TM (available from ExxonMobil Chemical Company) (e.g. VISTAMAXX TM 3000, VISTAMAXX TM 3588FL、VISTAMAXX TM 6102、VISTAMAXX TM 8880),VERSIFY TM (available from The Dow Chemical Company), certain grades of TAFMER TM XM or NOTIO TM (available from Mitsui Company), and certain brands of SOFTEL TM (available from Basel Polyolefins) are commercially available. The specific grade(s) of commercially available propylene-based elastomer suitable for use in the present invention can be readily determined using methods well known in the art.

[0096] Vis tamaxx TM (abbreviated as VMX) 6102 is a polymer with isotactic propylene repeating units and random ethylene distribution, which is produced using ExxonMobil's proprietary metallocene catalyst technology.

[0097] Specifically, "Vistamaxx TM 6102" is a propylene-based elastomer containing 16 wt% ethylene-derived units and has a thermal conductivity of 0.862 g / cm 3The composite has a density of 1.0 g / 10 min (ASTM D1505), a melt index of 1.4 g / 10 min (190°C; 2.16 kg) (ASTM D1238), a melt mass flow rate (MFR) of 3 g / 10 min (230°C; 2.16 kg) (ASTM D1238), a Shore A durometer hardness of 66 (ASTM D2240) and a Vicat softening temperature of 52.2°C (ASTM D1525).

[0098] Vis tamaxx TM 3000、Vistamaxx TM 3020 / 3020FL、Vistamaxx TM 3588, and Vistamaxx TM 3980, and Vistamaxx TM 6102 / 6102FL、Vistamaxx TM 6502 is preferred, all of which are commercially available from ExxonMobile Chemical Company in Houston, Texas.

[0099] Examples of elastomers / plastomers include for example those sold under the trademark Exact TM (ExxonMobil Chemical Company, Houston, Texas) For example, Exact TM 5171 Plastic body for sale.

[0100] ExxonMobil TM Exact TM 5171 is an ethylene 1-octene copolymer available from ExxonMobile Chemical Company. TM 5171 has the following properties: (1) 0.868 g / cm 3 (2) a melt index of 1.0 g / 10 min (190° C. / 2.16 kg) (ASTM D1238); and (3) a melt mass flow rate (MFR) of 2.3 g / 10 min (230° C.; 2.16 kg) (ASTM D1238).

[0101] In certain preferred embodiments of the present invention, the MFR of the RCP in the core component and the shell component is 3-15 g / 10 min, preferably 5-10 g / 10 min, more preferably 7-8 g / 10 min (230° C.; 2.16 kg) (ASTM D1238).

[0102] In certain preferred embodiments of the present invention, the C2 content of the RCP in the core component and the shell component is 1%-8%, preferably 2%-6%, more preferably 3%-4%, and the C3 content is 99%-2%, preferably 98%-4%, more preferably 97%-96%, preferably consisting of C2 and C3.

[0103] In certain preferred embodiments of the present invention, the shell component further comprises other components, and the other components include RCP, Ter PP, HDPE, LDPE, LLDPE or a combination thereof.

[0104] In certain preferred embodiments of the present invention, the two-component core / shell structure foamed polypropylene is obtained by foaming with a physical foaming agent, and the physical foaming agent includes carbon dioxide, nitrogen or a combination thereof.

[0105] In the present invention, the foamed composition can also be made by single-screw compounding, twin-screw compounding, kneader / internal mixer mixing or similar technology, preferably a twin-screw extruder (internal design involves dual flow channels) with a specially designed extruder and die according to the present invention.

[0106] According to embodiments provided herein, foamed products are lighter in weight and lower in density than mechanically equivalent products made from expanded polypropylene, polystyrene or RCP and are particularly useful in footwear such as slippers or midsoles; packaging, yoga mats, and other consumer products.

[0107] In certain preferred embodiments of the present invention, the diameter of the core / shell structured bicomponent filaments ranges from 0.3-3.0 mm, preferably 0.5-2.0 mm, more preferably 0.7-1.5 mm; the particle length is 0.3-5 mm, preferably 0.5-3 mm, more preferably 1.5-2.5 mm.

[0108] In certain preferred embodiments of the present invention, the core layer screw processing parameters in step 2 are: the temperature of the first zone of the screw is 170-290°C, preferably 200-260°C, more preferably 220-240°C, the temperature of the second zone is 180-300°C, preferably 210-270°C, more preferably 230-250°C, the temperature of the third zone is 190-310°C, preferably 220-280°C, more preferably 240-260°C, the temperature of the metering pump is 190-310°C, preferably 220-280°C, more preferably 240-260°C, the temperature of the connecting block is 185-305°C, preferably 215-275°C, more preferably 235-255°C, the die temperature is 185-305°C, preferably 215-275°C, more preferably 235-255°C; and / or

[0109] The processing parameters of the shell screw are as follows: the temperature of the first zone of the screw is 150-270°C, preferably 180-240°C, more preferably 200-220°C, the temperature of the second zone is 160-280°C, preferably 190-250°C, more preferably 210-230°C, the temperature of the third zone is 170-290°C, preferably 200-260°C, more preferably 220-240°C, the temperature of the metering pump is 170-290°C, preferably 200-260°C, more preferably 220-240°C, the temperature of the connecting block is 185-305°C, preferably 215-275°C, more preferably 235-255°C, and the die temperature is 185-305°C, preferably 215-275°C, more preferably 235-255°C.

[0110] In certain preferred embodiments of the present invention, the foaming process in step 3 comprises the following steps: placing the microparticles obtained based on step 2 into a foaming kettle, introducing a physical foaming agent under foaming conditions, and releasing the pressure after a certain period of time to allow the microparticles to foam into beads.

[0111] In some preferred embodiments of the present invention, one or more additives may be optionally incorporated into the core / shell component. The example of additive may include, but is not limited to, stabilizer, antioxidant, filler, colorant, nucleator, dispersant, mold release agent, slip agent, flame retardant, plasticizer, pigment, vulcanization or curing agent, vulcanization or curing accelerator, curing retarder, processing aid, tackifying resin, etc., and any combination thereof. Other additives may include filler and / or reinforcing material, such as carbon black, clay, talcum, calcium carbonate, mica, silicon dioxide, silicate, etc., and any combination thereof.

[0112] In the present invention, filament production and pelletization may be performed by including a batch, semi-continuous or continuous system.

[0113] In the present invention, dynamic mechanical thermal analysis (DMTA) was measured at a frequency of 1 Hertz (Hz) and a strain of 0.1% using an RSA rheometer (TA INSTRUMENTS, Delaware, USA) according to ASTM E1867-18 (2018).

[0114] Unless otherwise stated, any features of the above-described embodiments of the present invention can be combined with each other.

[0115] The present invention is further described by the following aspects.

[0116] 1. A two-component core / shell structure foamed polypropylene, characterized in that it comprises 5 wt % to 95 wt % of a core component and 95 wt % to 5 wt % of a shell component, based on the overall weight of the two-component core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, the first polypropylene comprising homopolymer polypropylene, ICP, RCP, Ter PP or a combination thereof; the shell component comprises a C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer, and optionally polypropylene (PP) or polyethylene (PE), or a combination thereof; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0117] 2. The two-component core / shell structure foamed polypropylene according to aspect 1 is characterized in that the core component and / or the shell component further comprises a nucleating agent, the nucleating agent comprises talc, zinc borate, nano-calcium carbonate or a combination thereof, wherein the content of the nucleating agent in the core component or the shell component is 0.1-5 phr.

[0118] 3. The two-component core / shell structure foamed polypropylene according to aspect 1 or 2, characterized in that the shell component further comprises other components, and the other components include RCP, Ter PP, HDPE, LDPE, LLDPE or a combination thereof.

[0119] 4. The two-component core / shell structure foamed polypropylene according to aspect 1 or 2, characterized in that the shell component contains 1 to 100 weight % of C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer.

[0120] 5. The two-component core / shell structure foamed polypropylene according to aspect 1 or 2, characterized in that the two-component core / shell structure foamed polypropylene contains 10 wt% to 90 wt% of a core component and / or 90 wt% to 10 wt% of a shell component.

[0121] 6. The two-component core / shell structure foamed polypropylene according to aspect 1, characterized in that the MFR of the RCP is 7-8 g / 10 min and the C2 content is 3 wt%-4 wt%.

[0122] 7. The two-component core / shell structure foamed polypropylene according to aspect 6, characterized in that the RCP also contains C3.

[0123] 8. The two-component core / shell structure foamed polypropylene according to aspect 1 or 2, characterized in that the two-component core / shell structure foamed polypropylene is obtained by foaming with a physical foaming agent, and the physical foaming agent includes carbon dioxide, nitrogen or a combination thereof.

[0124] 9. The two-component core / shell structure foamed polypropylene according to aspect 1 or 2, which is in the form of beads.

[0125] 10. A method for preparing a two-component core / shell structure foamed polypropylene according to any one of aspects 1 to 9, characterized in that it comprises the following steps in sequence:

[0126] 1. Using a twin-screw extruder, the core component and the shell component described in any one of aspects 1 to 9 are respectively extruded through two different hoppers to form a core / shell structured bicomponent filament, wherein after the core component and the shell component are extruded from the die of the extruder, the speed difference of subsequent stretching rollers on the production line is adjusted to obtain filaments with different stretching ratios, wherein the stretching ratio is less than or equal to 2.5:1;

[0127] 2. Cutting the core / shell structured bicomponent filaments obtained in step 1 into microparticles;

[0128] 3. Physically foaming and steam molding the microparticles obtained in step 2.

[0129] 11. The method according to aspect 10, characterized in that the core layer screw processing parameters in step 2 are: screw zone 1 temperature is 200-260°C, zone 2 temperature is 210-270°C, zone 3 temperature is 220-280°C, metering pump temperature is 220-280°C, connecting block temperature is 215-275°C, and die temperature is 215-275°C; and / or

[0130] The processing parameters of the shell screw are: the temperature of the first zone of the screw is 180-240℃, the temperature of the second zone is 190-250℃, the temperature of the third zone is 200-260℃, the temperature of the metering pump is 200-260℃, the temperature of the connecting block is 215-275℃, and the temperature of the die is 215-275℃.

[0131] 12. The method according to aspect 10, characterized in that the foaming process in step 3 comprises the following steps: placing the microparticles obtained in step 2 into a foaming kettle, introducing a physical foaming agent under foaming conditions, and releasing the pressure after a certain period of time to foam the microparticles to form beads,

[0132] The following process parameters are used during the foaming process: pressure range is 8-25 MPa; temperature range is 95-140°C; and / or time range is 30-120 min.

[0133] Steam molding includes the following steps: the physically foamed beads are passed into the corresponding mold, and then steam is passed for a period of time to melt the surface of the beads and bond them together, and then cooled, demolded, and shaped to obtain the final product.

[0134] 13. The method according to any one of aspects 10 to 12, characterized in that the physical blowing agent comprises carbon dioxide, nitrogen or a combination thereof.

[0135] 14. The method according to any one of aspects 10 to 12, characterized in that the diameter of the core / shell structured bicomponent filaments ranges from 0.5 to 2.0 mm; and the length of the microparticles ranges from 0.5 to 3 mm.

[0136] 15. The method according to any one of aspects 10 to 12, characterized in that the stretching ratio is less than or equal to 1.5:1.

[0137] 16. Use of the two-component core / shell structure foamed polypropylene according to any one of aspects 1 to 9 in packaging, construction or automotive industries.

[0138] 17. A two-component core / shell structured foamed polypropylene, characterized in that it comprises 50 wt% of RCP+0.8 phr of nucleating agent as a core component and 50 wt% of Vistamaxx as a shell component TM 3588FL+0.8phr nucleating agent; wherein the nucleating agent is talcum powder, such as HTPul tra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0139] 18. A two-component core / shell structured foamed polypropylene, characterized in that it comprises 60 wt% of RCP+0.8 phr of nucleating agent as a core component and 40 wt% of Vistamaxx as a shell component TM 3588FL+0.8phr nucleating agent; wherein the nucleating agent is talcum powder, such as HTPul tra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0140] 19. A two-component core / shell structured foamed polypropylene, characterized in that it comprises 70 wt% of RCP+0.8phr of nucleating agent as a core component and 30 wt% of Vistamaxx as a shell component TM 3588FL+0.8phr nucleating agent; wherein the nucleating agent is talcum powder, such as HTPul tra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0141] 20. A two-component core / shell structured foamed polypropylene, characterized in that it comprises 80 wt% of RCP+0.8 phr of nucleating agent as a core component and 20 wt% of Vistamaxx as a shell component. TM 3588FL+0.8phr nucleating agent; wherein the nucleating agent is talcum powder, such as HTPul tra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0142] 21. A two-component core / shell structured foamed polypropylene, characterized in that it comprises 60 wt% of RCP+0.8phr nucleating agent as a core component and 40 wt% of Vistamaxx as a shell component. TM 6102FL+RCP+nucleating agent, including Vistamaxx TM 6102FL:RCP:nucleating agent=50:50:0.5phr; wherein the nucleating agent is talcum powder, such as HTPultra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0143] 22. A two-component core / shell structured foamed polypropylene, characterized in that it comprises 70 wt% of RCP+0.8phr of nucleating agent as a core component and 30 wt% of Vistamaxx as a shell component. TM 6102FL+RCP+nucleating agent, including Vistamaxx TM 6102FL:RCP:nucleating agent=50:50:0.5phr; wherein the nucleating agent is talcum powder, such as HTPultra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0144] 23. A method for preparing a two-component core / shell structure foamed polypropylene according to any one of aspects 17 to 22, characterized in that it comprises the following steps in sequence:

[0145] 1. Using a twin-screw extruder with a specially designed extruder and die head (the internal design involves a double flow channel), the core component and the shell component described in any one of Aspects 17 to 22 are respectively passed through two different hoppers to extrude into bicomponent filaments of core / shell structure with different draw ratios;

[0146] The core / shell structure monofilament is extruded from the die head and then falls into water for cooling. After exiting the water tank, it passes through a steam-heated tank and different stretching rollers. By adjusting the different speeds of the stretching rollers, different stretching ratios are achieved. Finally, core / shell structure bicomponent filament samples with the following stretching ratios are obtained: about 1:1, 1.1:1, 1.2:1, and 2:1.

[0147] 2. Cutting the core / shell bicomponent filament produced in step 1 into microparticles, wherein the processing temperatures of the core layer and the shell layer are listed in the following table;

[0148] Processing temperature of core and shell

[0149]

[0150]

[0151] 3. Physically foaming and steam molding the microparticles obtained in step 2,

[0152] The physical foaming molding comprises the following steps: putting the particles cut in step 2 into a foaming kettle, introducing carbon dioxide under corresponding foaming conditions, and releasing the pressure after a certain period of time to foam the particles into beads.

[0153] The pressure during the physical foaming of the microparticles is about 15 MPa; the temperature is about 120° C.; and the time is about 60 min.

[0154] Steam molding includes the following steps: the physically foamed beads are passed into the corresponding mold, and then steam is passed for a period of time to melt the surface of the beads and bond them together, and then cooled, demolded, and shaped to obtain the final product.

[0155] Example

[0156] The embodiments discussed and described herein may be further described using the following examples.While the following examples are directed to specific embodiments, they are not to be construed as limiting in any specific respect.

[0157] 1. Formulation design

[0158] Several groups of bicomponent filament formulations (sample numbers 1 to 6) were designed based on the core-shell composition and its corresponding proportions as shown in Table 1. The nucleating agent used was HTPul tra5L talc purchased from Imifabi, RCP was PP9513 (MFR 7-8g / 10min, C2 content 3%-4%, the rest was C3) purchased from ExxonMobil, Vistamaxx TM 3588FL (C3-C2 copolymer, i.e., elastomer copolymerized from propylene and ethylene monomers), Vistamaxx TM 3980FL (also a C3-C2 copolymer, i.e. an elastomer made by copolymerization of propylene and ethylene monomers) and Vistamaxx TM 6102FL (also a C3-C2 copolymer, i.e. an elastomer made of propylene and ethylene monomers) were purchased from ExxonMobil. The processability and foamability of the samples were also verified by relevant methods. From 1% to 100% of Vistamaxx in the shell TM Than are applicable to this process.

[0159] Table 1. Bicomponent filament formulation design (% by weight)

[0160]

[0161]

[0162] 2. Preparation method of two-component core-shell beads

[0163] 1. Using a twin-screw extruder with a specially designed extruder and die head (internal design involves dual flow channels), the core layer materials and shell layer materials of samples 1 to 6 shown in Table 1 above were respectively passed through two different hoppers to extrude into bicomponent filaments with core / shell structures having different stretch ratios, wherein the stretch ratio for samples 1 to 6 was 1:1, and a sample with a stretch ratio of 8:1 was additionally prepared for sample 5;

[0164] Specifically, the core / shell structure monofilament is extruded from the die head and then falls into water for cooling. After exiting the water tank, it passes through a steam-heated tank and different stretching rollers. Different stretching ratios are achieved by adjusting the rotation speeds of the stretching rollers.

[0165] The stretch ratio is measured using a conventional roll speed tester.

[0166] 2. Cutting the bicomponent filaments of the core / shell structure produced in the previous steps into microparticles, wherein the processing temperatures of the core layer and the shell layer are listed in Table 2 below;

[0167] Table 2: Processing temperatures of core and shell layers

[0168]

[0169] 3. Physically foam and steam mold the two-component microparticles.

[0170] The physical foaming molding comprises the following steps: putting the particles cut in step 2 into a foaming kettle, introducing carbon dioxide under corresponding foaming conditions, and releasing the pressure after a certain period of time to make the particles foam to form beads. The pressure during the physical foaming of the particles is 15 MPa, the temperature is 120°C, and the time is 60 minutes.

[0171] Steam molding includes the following steps: the physically foamed beads are passed into the corresponding mold, and then steam is passed for a period of time to melt the surface of the beads and bond them together, and then cooled, demolded, and shaped to obtain the final product.

[0172] 3. Processing and sample test results

[0173] The diameter of the bicomponent filaments obtained in step 1 is about 1 mm. The length of the cut microparticles obtained in step 2 is about 0.5-3.0 mm.

[0174] Attached Figures 3A to 3F The cross-sectional images of the bicomponent filaments shown in Figure 2 all show good structures at different C / S ratios, without obvious nuclear shift problems.

[0175] The bicomponent filaments (stretching ratios of 1:1 and 8:1, respectively) of sample 5 obtained in step 1 were subjected to a foaming test. For the sample with a stretching ratio of 1:1, the sample was cut into microparticles using the method in step 2 above for foaming; for the sample with a stretching ratio of 8:1, the sample was manually cut into shorter filaments or microparticles for foaming.

[0176] Figure 4A The picture of the foamed beads shows that the micro beads are foamed uniformly without any rupture between the core and the shell. The black color is the core and the light color is the shell, achieving good foaming of the core / shell structure. Figure 4A It can be clearly seen that the sample with a stretching ratio of 1:1 can be well formed into beads.

[0177] Figure 4B The core-shell structure microparticle sample 5 with a stretching ratio of 8:1 was firstly tested at a temperature of 110°C and CO 2 The foaming was carried out in a foaming kettle under the conditions of 15 MPa pressure and 60 min. Figure 4B It can be clearly seen in the figure that the surfaces of the core-shell structured particles are adhered to each other and therefore cannot be successfully foamed.

[0178] For the core-shell structure particle sample 5 with a stretching ratio of 8:1, Figure 4B Under the basic conditions, the temperature was raised to 115℃, and CO 2 The foaming was attempted in a foaming kettle under the conditions of 15 MPa pressure and 60 min. Figure 4C It can be clearly seen in the figure that the surfaces of the core-shell structured particles are also adhered to each other, so they cannot be successfully foamed.

[0179] For the core-shell structure particle sample 5 with a stretching ratio of 8:1, Figure 4C Under the basic conditions, the time was extended to 90 min, and the temperature was 115 ° C, CO 2 The foaming was attempted in a foaming kettle at a pressure of 15 MPa. Figure 4D It can be clearly seen in the figure that the surfaces of the core-shell structured particles are also adhered to each other, so they cannot be successfully foamed.

[0180] For the core-shell structure particle sample 5 with a stretching ratio of 8:1, Figure 4D Under basic conditions, CO 2 The pressure was increased to 20 MPa, and foaming was attempted in a foaming kettle at a temperature of 115°C for 90 min. Figure 4E It can be clearly seen in the figure that the surfaces of the core-shell structured particles are also adhered to each other, so they cannot be successfully foamed.

[0181] In summary, time, temperature and pressure are the three elements of foaming. Generally, extending the time, increasing the temperature and pressure will help the material foam, but the premise is that the particles / filaments cannot stick together. However, in the above experiment, after trying the above three elements, it was found that the particles / filaments all stuck together and failed to foam successfully. Therefore, it is no longer possible to increase the temperature, pressure and extend the time to solve the foaming problem.

[0182] It can be seen from the above figures that a stretching ratio of 1:1 achieves good foaming of the core / shell structure at the same time; a stretching ratio of 8:1 cannot even achieve foaming under various conditions.

[0183] Table 3. Film formulations used for sealing force testing

[0184]

[0185] Table 4. Sealing force test results of each sample

[0186]

[0187] Films were made using pure Vistamaxx and Vistamaxx blended RCP as shown in Table 3, and then the sealing force (heat seal strength) of the films was tested.

[0188] Table 4 above shows that, compared with the comparative sample 7 without Vistamaxx, the formulations containing different amounts of Vistamaxx significantly improve the sealing force at 130°C and 140°C, that is, significantly improve the adhesive strength. Unexpectedly, the sealing force of samples 8, 9, 11 and 13 at 130°C is improved by more than 10 times relative to the comparative sample 7; the sealing force of the other samples is also greatly improved at 130°C; the sealing force of samples 8, 10, 12 and 13 at 140°C is improved by nearly 50% relative to the comparative sample; the sealing force of the other samples is also greatly improved at 140°C.

[0189] Furthermore, if Figure 7 and 8 As shown, formulations containing Vistamaxx can help reduce the molding temperature (DMTA). Lower storage modulus means lower softness.

[0190] about Figure 8 , the curve of VMX 3588FL ends before 120℃, because VMX 3588FL will show a viscous flow state at around 120℃, which is inconsistent with the actual use environment of the material. The material is generally used before showing a viscous flow state. There is almost no storage modulus when the temperature is close to 120℃.

[0191] Compared with pure RCP without Vistamaxx, Figure 7 and 8 It shows that the storage modulus of the formulation containing Vistamaxx is lower at the same temperature, which means that Vistamaxx helps to reduce the molding temperature.

[0192] While specific embodiments of the present invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous modifications of the details of the invention may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A two-component core / shell structure foamed polypropylene, characterized in that It comprises 5 wt % to 95 wt % of a core component and 95 wt % to 5 wt % of a shell component, based on the overall weight of a bicomponent core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, which comprises homopolypropylene, ICP, RCP, Ter PP or a combination thereof; the shell component comprises a C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer, and optionally polypropylene (PP) or polyethylene (PE), or a combination thereof; wherein both the core structure and the shell structure of the bicomponent core / shell structure foamed polypropylene are well foamed.

2. The two-component core / shell structure foamed polypropylene according to claim 1, characterized in that The core component and / or the shell component further comprises a nucleating agent, which comprises talc, zinc borate, nano calcium carbonate or a combination thereof, wherein the content of the nucleating agent in the core component or the shell component is 0.1-5 phr.

3. The two-component core / shell structure foamed polypropylene according to claim 1 or 2, characterized in that The shell component further comprises other components, and the other components include RCP, Ter PP, HDPE, LDPE, LLDPE or a combination thereof.

4. The two-component core / shell structure foamed polypropylene according to claim 1 or 2, characterized in that The shell component comprises 1 to 100 wt % of a C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer.

5. The two-component core / shell structure foamed polypropylene according to claim 1 or 2, characterized in that The two-component core / shell structure foamed polypropylene comprises 10 wt % to 90 wt % of a core component and / or 90 wt % to 10 wt % of a shell component.

6. The two-component core / shell structure foamed polypropylene according to claim 1, characterized in that The MFR of the RCP is 7-8 g / 10 min, and the C2 content is 3 wt%-4 wt%.

7. The two-component core / shell structure foamed polypropylene according to claim 6, characterized in that The RCP further comprises C3.

8. The two-component core / shell structure foamed polypropylene according to claim 1 or 2, characterized in that The two-component core / shell structure foamed polypropylene is obtained by foaming with a physical foaming agent, wherein the physical foaming agent includes carbon dioxide, nitrogen or a combination thereof.

9. The two-component core / shell structure foamed polypropylene according to claim 1 or 2, which is in the form of beads.

10. A method for preparing a two-component core / shell structured foamed polypropylene according to any one of claims 1 to 9, characterized in that It includes the following steps in sequence:

1. Using a twin-screw extruder, the core component and the shell component described in any one of claims 1 to 9 are respectively passed through two different hoppers to extrude into a core / shell structured bicomponent filament, wherein after the core component and the shell component are extruded from the extruder die, the speed difference of the subsequent stretching rollers on the production line is adjusted to obtain filaments with different stretching ratios, wherein the stretching ratio is less than or equal to 1.5:1; 2. Cutting the core / shell structured bicomponent filaments obtained in step 1 into microparticles; 3. Physically foaming and steam molding the microparticles obtained in step 2, The diameter of the core / shell structured bicomponent filaments is in the range of 0.5-2.0 mm; and the length of the microparticles is in the range of 0.5-3 mm.

11. The method according to claim 10, characterized in that In step 2, the core layer screw processing parameters are: screw zone 1 temperature is 200-260°C, zone 2 temperature is 210-270°C, zone 3 temperature is 220-280°C, metering pump temperature is 220-280°C, connecting block temperature is 215-275°C, and die temperature is 215-275°C; and / or The processing parameters of the shell screw are: the temperature of the first zone of the screw is 180-240℃, the temperature of the second zone is 190-250℃, the temperature of the third zone is 200-260℃, the temperature of the metering pump is 200-260℃, the temperature of the connecting block is 215-275℃, and the temperature of the die is 215-275℃.

12. The method according to claim 10, characterized in that The foaming process in step 3 comprises the following steps: placing the microparticles obtained in step 2 into a foaming kettle, introducing a physical foaming agent under foaming conditions, and releasing the pressure after a certain period of time to foam the microparticles to form beads, wherein the physical foaming agent comprises carbon dioxide, nitrogen or a combination thereof; The following process parameters are used during the foaming process: pressure range is 8-25 MPa; temperature range is 95-140°C; and / or time range is 30-120 min. Steam molding includes the following steps: the physically foamed beads are passed into the corresponding mold, and then steam is passed for a period of time to melt the surface of the beads and bond them together, and then cooled, demolded, and shaped to obtain the final product.

13. Use of the two-component core / shell structure foamed polypropylene according to any one of claims 1 to 9 in packaging, construction or automobile industry.

14. A two-component core / shell structure foamed polypropylene, characterized in that It contains 60 wt% RCP + 0.8 phr nucleating agent as core component and 40 wt% Vistamaxx as shell component. TM 6102FL+RCP+nucleating agent, including Vistamaxx TM 6102FL:RCP:nucleating agent=50:50:0.5phr; wherein the nucleating agent is talcum powder, such as HTPultra5L talcum powder; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

15. A method for preparing the two-component core / shell structure foamed polypropylene according to claim 14, characterized in that It includes the following steps in sequence:

1. Using a twin-screw extruder with a specially designed extruder and die head, the core component and the shell component described in claim 14 are respectively passed through two different hoppers to extrude into core / shell structured bicomponent filaments with different draw ratios; The core / shell structure monofilament is extruded from the die head and then falls into water for cooling. After exiting the water tank, it passes through a steam-heated tank and different stretching rollers. By adjusting the different speeds of the stretching rollers, different stretching ratios are achieved. Finally, a core / shell structure bicomponent filament sample with the following stretching ratio is obtained: about 1:1; 2. Cutting the core / shell bicomponent filament produced in step 1 into microparticles, wherein the processing temperatures of the core layer and the shell layer are listed in the following table; Processing temperature of core and shell 3. Physically foaming and steam molding the microparticles obtained in step 2, The physical foaming molding comprises the following steps: putting the particles cut in the above step 2 into a foaming kettle, introducing carbon dioxide under corresponding foaming conditions, and releasing the pressure after a certain period of time to make the particles foam to form beads, wherein the pressure during the physical foaming of the particles is about 15 MPa; the temperature is about 120° C.; and the time is about 60 minutes; Steam molding includes the following steps: the physically foamed beads are passed into the corresponding mold, and then steam is passed for a period of time to melt the surface of the beads and bond them together, and then cooled, demolded, and shaped to obtain the final product.

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