Two-component core / shell structured foamed polypropylene beads and processing method thereof

Abstract

The present invention generally relates to the field of expanded polypropylene. Specifically, the present invention relates to novel bicomponent core / shell expanded polypropylene beads and methods for processing the same. The bicomponent core / shell expanded polypropylene comprises 5% to 95% by weight of a core component and 95% to 5% by weight of a shell component, based on the total weight of the bicomponent core / shell expanded polypropylene, wherein the core component comprises a first polypropylene comprising homopolypropylene, ICP, RCP, Ter PP, or a combination thereof; and 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.

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 physically foamed products widely used in industrial packaging and automotive applications. Foamed polypropylene (EPP) is often used to replace cartons in the packaging industry or as a backseat component to reduce vehicle weight. Expanded polystyrene (EPS) is often used to protect items in packaging during transport. EPP generally has better mechanical properties than EPS, and EPP can be recycled and reused, making it more sustainable than EPS. Consequently, there is a trend in 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 from random copolymer / terpolymer pellets to form foamed beads and then steam-formed. Due to the high melting point (Tm) of random copolymer / terpolymer, this molding 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 achieve the temperature required to mold EPP beads, the steam energy cost can be as much as half of the total cost of the final product. In addition, the insufficient bonding strength between beads produced based on this method can lead to reduced product durability.

[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, which increases energy costs and accounts 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] Traditional technologies for expanding polypropylene foam include single-screw / twin-screw extrusion to produce single-component polypropylene (PP) microparticles. This involves melting the PP raw material under high temperature and pressure. The molten PP is then extruded through a single-screw / twin-screw extruder to form continuous PP filaments, which are then cut into PP microparticles using a pelletizer.

[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] An underwater pelletizer is a device that cools molten polymer materials (such as polypropylene and polyethylene) into pellets. 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 then fall directly into water to cool, forming spherical pellets. However, this process has several significant disadvantages: large equipment investment, high water consumption, high maintenance costs, difficulty in controlling pellet size, and environmental pollution.

[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 continuous strands that are then cooled and cut into pellets.

[0012] Bicomponent (Bico) fibers are single fibers made 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 noteworthy that a special type of bicomponent fiber, core / shell structured fibers, has found application in textile materials science, particularly in the nonwovens industry. This fiber achieves precise control of fiber properties by meticulously controlling the composition, ratio, and distribution of the core and shell. The core / shell structure not only enhances the fiber's internal bonding but also imparts a more complex surface morphology and functional properties, thereby enhancing the overall performance and usability of nonwovens. While bicomponent core / shell fibers have found application in the nonwovens industry, they have yet to be applied in the expanded polypropylene (PP) industry.

[0014] However, in the traditional non-woven 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 drawing industry products cannot achieve good foaming of the core and shell structures, and may 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 enable both core / shell structures to be well foamed, reduce steam molding temperature to save energy and reduce costs, and improve 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 shortcomings and deficiencies of the above-mentioned prior art.

[0017] The first aspect of the present invention relates to a bicomponent 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 bicomponent core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, the first polypropylene comprising homopolypropylene, ICP, RCP, Ter PP or a combination thereof; the shell component comprises an alpha olefin plastomer and / or elastomer, and optionally polypropylene (PP) or polyethylene (PE), or a combination thereof; wherein the bicomponent core / shell structure foamed polypropylene is prepared according to the second aspect of the present invention as described below, and the core structure and shell structure of the prepared bicomponent core / shell structure foamed polypropylene are both well foamed.

[0018] The second aspect of the present invention relates to a method for preparing the bicomponent core / shell structured 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 passed through two different hoppers to extrude into bicomponent filaments of a core / shell structure, wherein after the core component and the shell component are extruded from the extruder die, the speed difference of subsequent stretching rollers on the production line is adjusted to obtain filaments with different stretch ratios, wherein the stretch 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 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 bicomponent core / shell structured foamed polypropylene in packaging, construction or automotive industries.

[0023] Surprisingly, the above technical solution 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 particular description of the invention, briefly summarized above, may be obtained by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only typical embodiments of the invention and are not therefore to be considered limiting of its scope, as the invention may admit to other equally effective embodiments. It is emphasized that the drawings are not necessarily to scale, and that certain features and certain views of the drawings may be shown exaggerated in scale or in schematic form 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 This 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 This is a picture of bicomponent core / shell structured expanded 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 This is a picture of core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) after foaming in a foaming kettle at a temperature of 110°C, a CO2 pressure of 15 MPa, and a time of 60 minutes.

[0035] Figure 4C This is a picture of core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) after foaming in a foaming kettle at a temperature of 115°C, a CO2 pressure of 15 MPa, and a time of 60 minutes.

[0036] Figure 4D This is a picture of core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) after foaming in a foaming kettle at a temperature of 115°C, a CO2 pressure of 15 MPa, and a time of 90 minutes.

[0037] Figure 4E This is a picture of core-shell structured particles with a stretching ratio of 8:1 (corresponding to sample 5 (core / shell (C / S) ratio of 6:4)) after foaming in a foaming kettle at a temperature of 115°C, a CO2 pressure of 20 MPa, and a time of 90 minutes.

[0038] Figure 5 This is a picture of the overall appearance of 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 : 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 Graph showing the relationship between storage modulus G' (Pa) and temperature (°C) for sample 7 (containing only RCP, comparative sample) and sample 9 (using DMTA).

[0041] Figure 8 Sample 7 (containing only RCP, comparative sample) and sample Vistamaxx TM A plot of the storage modulus G' (Pa) and temperature (°C) for 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 can adopt various alternative changes and step sequences. In addition, except in any operating examples or as otherwise noted, all numerical values ​​representing the amount of the composition used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters listed in the following specification and the appended claims are approximate values, which can vary according to the desired properties to be obtained according to 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 significant figures reported and by applying common 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] Furthermore, it should be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of "1 to 10" is intended to include all subranges between (and including) 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. The following description of exemplary embodiments simplifies 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 in itself define the relationship between the various embodiments and / or configurations. Finally, without departing from the scope of the present disclosure, the embodiments given below can be combined in any combination, i.e., any element from one embodiment can 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 more than 5%, and in any case does not include any other component at a level greater than 3% by 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 be less likely to cause pore collapse or deformation during subsequent processing or use.

[0050] When used in conjunction with core / shell polypropylene, the term "well-foamed" means that both the core and shell remain intact, foaming uniformly. During the foaming process, a uniform, dense, and stable cell structure is formed, with no core or shell breakage. The core / shell structure of the foamed polypropylene maintains cell stability, making cell collapse or deformation less likely during subsequent processing or use. The core / shell polypropylene obtained according to the method of the present invention is well-foamed.

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

[0052] As used herein, when the term "about" or its synonyms (e.g., "approximately," "substantially," "essentially," 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 "ppm by weight" 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 a substance of any 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 wt% to 30 wt%, it is understood that the repeating units / monomer units, or simply units, in the copolymer are derived from propylene in the polymerization reaction, and that the derived units are present at 10 wt% to 30 wt% 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 front cover of F. Albert Cotton et al., Advanced Inorganic Chemistry, 6th edition (John Wiley & Sons, Inc., 1999).

[0059] As used herein, the term "Phr" is used to represent the number of parts of an additive per 100 parts (by weight) of rubber or resin. This unit is primarily 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 the monomer used to form a polymer, such as the unreacted compound in its form prior to polymerization, and can also refer to the 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. Its structure is characterized by the presence of multiple branches, which are usually introduced by the comonomers, 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, where elasticity is the ability of a material that has been deformed by a force (e.g., by stretching) to at least partially return to its original dimensions once the force has been removed.

[0063] As used herein, the term "plastomer" refers to a material that, upon removal of an external force, retains or partially retains its original shape, rather than returning completely to its original state. A plastomer possesses the property of plasticity, meaning it can deform under the action of an external force. However, this deformation is irreversible; in other words, it cannot fully return to its original shape and volume after the external force is removed.

[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 comprise the copolymer of homopolypropylene, isotactic polypropylene, height isotactic polypropylene, syndiotactic polypropylene and propylene or their mixture.Comprise the product of one or more propylene monomers polymerized with one or more additional monomers and 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 and comprising propylene individually or comprising propylene together with any polymer of one or more comonomers, wherein propylene is main component (for example, greater than 50 % by weight propylene).

[0066] "Polypropylene impact copolymers," or simply "impact copolymers" (ICPs), are combinations of crystalline and amorphous polymers, such as iPP (isotactic polypropylene) and rubber, typically heterophasic, which provide the ICP with stiffness and toughness greater than that of the amorphous polymer(s) and toughness greater than that of the crystalline polymer(s). The ICPs may typically 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 copolymers may have an MFR in the range of from 10, or 15, or 20, or 26 g / 10 min to 30, or 36, or 40, or 50 g / 10 min 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 / 10 min to an upper limit of about 10, 15, 20, or 30 g / 10 min. 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 copolymer comprises 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 can have an MFR in the range of from 3, 5, 8 or 12 g / 10 min to 20, 30, 40 or 50 g / 10 min. Most preferably, the propylene copolymer can be an ethylene-propylene copolymer.

[0069] As used herein, the term "random polypropylene" broadly means a single-phase copolymer of propylene with up to 9 wt%, preferably 2 wt% to 8 wt%, of an α-olefin comonomer. Preferred α-olefin comonomers have 2 carbon atoms, or 4 to 12 carbon atoms. Preferably, the α-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 to 0.970g / cm 3 Ethylene homopolymers and ethylene copolymers with 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 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 to 0.940g / cm 3 LLDPE can be produced using 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 in solution reactors using any of the disclosed catalysts.

[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 deemed to include equivalents to the various elements or limitations specified in the claims. Depending on the context, all references to the "invention" may in some cases refer only to certain specific embodiments. In other cases, it will be understood that references to the "invention" will refer to the subject matter recited in one or more, but not necessarily all, of the claims. Each invention will now be described in more detail below, including specific embodiments, variants, and examples, but the invention is not limited to these embodiments, variants, or examples, which, when combined with publicly available information and technology, are included to enable those of ordinary skill in the art to implement and use the invention.

[0075] An embodiment of the present invention relates to a bicomponent 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 total weight of the bicomponent core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, the first polypropylene comprising homopolypropylene, ICP, RCP, Ter PP or a combination thereof; the shell component comprises an alpha olefin plastomer and / or elastomer, and optionally polypropylene (PP) or polyethylene (PE), or a combination thereof; wherein the bicomponent core / shell structure foamed polypropylene is prepared by another embodiment of the present invention as described below, and the core structure and shell structure of the prepared bicomponent core / shell structure foamed polypropylene are both well foamed.

[0076] Another embodiment of the present invention relates to a method for preparing the bicomponent core / shell structured 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 passed through two different hoppers to extrude into a core / shell structured bicomponent filament;

[0078] 2. Cutting the core / shell 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 microparticles: a pressure range of 8-25 MPa, preferably 10-20 MPa; a temperature range of 95-140°C, preferably 100-130°C; and / or a time range of 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 testers 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 head, it falls into water for cooling, passes through a steam-heated trough after exiting the water trough, passes through different stretching rollers, and achieves different stretching ratios 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 rotational 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, 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 repeat 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 0.862 g / cm 3The composite material 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) 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 (190°C / 2.16 kg) of 1.0 g / 10 min (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 RCP in the core component and the shell component has a C2 content of 1%-8%, preferably 2%-6%, more preferably 3%-4%, and a C3 content of 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 structured 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 with a specially designed extruder and die head according to the present invention (the internal design involves dual flow channels).

[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 length of the microparticles ranges from 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 screw zone 1 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 metering pump temperature is 190-310°C, preferably 220-280°C, more preferably 240-260°C, the connecting block temperature 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 shell screw processing parameters are as follows: the temperature of screw zone 1 is 150-270°C, preferably 180-240°C, more preferably 200-220°C, the temperature of zone 2 is 160-280°C, preferably 190-250°C, more preferably 210-230°C, the temperature of zone 3 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 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 allow the microparticles to foam and form beads.

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

[0112] In the present invention, filament production and pelletization can be performed by processes including batch, semi-continuous or continuous systems.

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

[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 bicomponent 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 bicomponent core / shell structure foamed polypropylene, wherein the core component comprises a first polypropylene, the first polypropylene comprising 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.

[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 structured foamed polypropylene according to aspect 1 or 2, characterized in that the shell component contains 1 to 100 wt% of a C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer.

[0120] 5. The bicomponent core / shell structure foamed polypropylene according to aspect 1 or 2, characterized in that the bicomponent 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.

[0121] 6. The two-component core / shell structured 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 structured foamed polypropylene according to aspect 6, characterized in that the RCP further comprises 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 structured foamed polypropylene according to aspect 1 or 2, which is in the form of beads.

[0125] 10. A method for preparing the bicomponent core / shell structured 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 passed through two different hoppers to extrude into bicomponent filaments with a core / shell structure, wherein after the core component and the shell component are extruded from the extruder die, the speed difference of subsequent stretching rollers on the production line is adjusted to obtain filaments with different stretch ratios, wherein the stretch ratio is less than or equal to 2.5:1;

[0127] 2. Cutting the core / shell 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 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

[0130] The shell screw processing parameters are: screw zone 1 temperature is 180-240℃, zone 2 temperature is 190-250℃, zone 3 temperature is 200-260℃, metering pump temperature is 200-260℃, connecting block temperature is 215-275℃, and die temperature 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 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 foam the microparticles into beads,

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

[0133] Steam molding includes the following steps: 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 bicomponent core / shell structured foamed polypropylene according to any one of aspects 1 to 9 in the 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 talc, such as HTPul tra5L talc; 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 talc, such as HTPul tra5L talc; 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 + 0.8 phr 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 talc, such as HTPul tra5L talc; 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 talc, such as HTPul tra5L talc; 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 + 0.8 phr of 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 talc, such as HTPultra5L talc; wherein the core structure and 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 + 0.8 phr 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 talc, such as HTPultra5L talc; wherein the core structure and shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

[0144] 23. A method for preparing the bicomponent core / shell structured 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 dual flow channel), the core component and the shell component described in any one of Aspects 17 to 22 are passed through two different hoppers to extrude into bicomponent filaments with core / shell structures having different draw ratios;

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

[0147] 2. Cut 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 table below;

[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: placing the particles cut in step 2 above into a foaming kettle, introducing carbon dioxide under corresponding foaming conditions, and releasing the pressure after a certain period of time to allow the particles to foam 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: 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 can be further described using the following examples.While the following examples relate to specific embodiments, they are not to be construed as limiting in any specific respect.

[0157] 1. Formulation design

[0158] Several sets of bicomponent filament formulations (sample numbers 1 to 6) were designed based on the core-shell compositions and their corresponding ratios as shown in Table 1. The nucleating agent used was HTPul tra5L talc purchased from Imifabi, the RCP was PP9513 (MFR 7-8 g / 10 min, C2 content 3%-4%, the remainder being C3) purchased from ExxonMobil, and Vistamaxx was used. TM 3588FL (C3-C2 copolymer, i.e. elastomer made by copolymerization of 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 from propylene and ethylene monomers) were purchased from ExxonMobil. The processability and foamability of the samples were also verified using relevant methods. 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 (the 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 passed through two different hoppers to extrude into bicomponent filaments with core / shell structures having different draw ratios. The draw ratio for Samples 1 to 6 was 1:1, and a sample with a draw 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. By adjusting the speed of the stretching rollers, different stretching ratios can be achieved.

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

[0166] 2. Cutting the core / shell bicomponent filaments 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 foaming and steam molding the two-component microparticles.

[0170] The physical foaming process includes the following steps: placing the cut particles from step 2 above into a foaming kettle, introducing carbon dioxide under appropriate foaming conditions, and then releasing the pressure after a certain period of time to allow the particles to foam and form beads. The physical foaming process is performed at a pressure of 15 MPa, a temperature of 120°C, and a duration of 60 minutes.

[0171] Steam molding includes the following steps: 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 bicomponent filaments obtained in step 1 have a diameter of about 1 mm, and the cut microparticles obtained in step 2 have a length of about 0.5-3.0 mm.

[0174] Attachment 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 core shift problems.

[0175] Foaming tests were performed on the bicomponent filaments of Sample 5 obtained in Step 1 above (stretch ratios of 1:1 and 8:1, respectively). For the 1:1 stretch ratio sample, the sample was cut into microparticles using the method described in Step 2 above for foaming. For the 8:1 stretch ratio sample, 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 evenly and there is no 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 particle sample 5 with a stretching ratio of 8:1 was first foamed in a foaming kettle at a temperature of 110°C, a CO2 pressure of 15 MPa, and a time of 60 min. Figure 4B It is clearly seen in the figure that the surfaces of the core-shell structured particles adhere 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 foaming was attempted in a foaming kettle under the conditions of CO2 pressure of 15MPa and time of 60min. 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 The time was extended to 90 min under the basic conditions, and foaming was attempted in a foaming kettle at a temperature of 115 ° C and a CO2 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 the basic conditions, the CO2 pressure was increased to 20MPa, and foaming was attempted in a foaming kettle at a temperature of 115℃ and a time of 90min. 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 key elements of foaming. Generally, extending the time, increasing the temperature, and increasing the pressure help the material foam, but only if the particles / filaments do not stick together. However, in the aforementioned experiments, after trying all three of these factors, we found that the particles / filaments all stuck together, and foaming failed. Therefore, increasing the temperature, pressure, and time could not solve the foaming problem.

[0182] As can be seen from the above figures, 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 shows that, compared to Comparative Sample 7, which does not contain Vistamaxx, formulations containing varying amounts of Vistamaxx significantly improve seal force at both 130°C and 140°C, i.e., significantly improve adhesive strength. Surprisingly, Samples 8, 9, 11, and 13 in particular show a seal force improvement of more than 10 times that of Comparative Sample 7 at 130°C; the other samples also show a significant improvement in seal force at 130°C. Samples 8, 10, 12, and 13 show a seal force improvement of nearly 50% at 140°C relative to the Comparative Sample; the other samples also show a significant improvement in seal force at 140°C.

[0189] Further, 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 for VMX 3588FL ends before 120°C. This is because VMX 3588FL exhibits a viscous flow state around 120°C, which is inconsistent with the material's actual use environment. Materials are generally used before exhibiting a viscous flow state. Storage modulus is almost non-existent at temperatures near 120°C.

[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 various modifications may be made to the details of the invention 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 contains 50 wt% to 80 wt% of a core component and 20 wt% to 50 wt% of a shell component, based on the overall weight of the bicomponent core / shell structure foamed polypropylene. in The core component comprises a first polypropylene, wherein the first polypropylene is 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 an RCP; wherein the MFR of the RCP is 7-8 g / 10min and the C2 content is 2 wt%-4 wt%; The two-component core / shell structured foamed polypropylene is prepared by the following method, which comprises the following steps in sequence: (1) using a twin-screw extruder to pass a core component and a shell component through two different hoppers to extrude a core / shell structured bicomponent filament, wherein after the core component and the shell component are extruded from a 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 1.5:1; (2) cutting the core / shell 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; the length of the microparticles is in the range of 0.5-3 mm; The core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both 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 includes 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 including 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 consists of a C3-C2, C2-C8 or C2-C4 plastomer and / or elastomer, optionally RCP, a nucleating agent and optionally additives.

5. 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.

6. The two-component core / shell structure foamed polypropylene according to claim 1 or 2, characterized in that The shell component comprises 30 to 100 wt% of a C3-C2 propylene-based elastomer.

7. The two-component core / shell structure foamed polypropylene according to claim 1, characterized in that The core component consists of a first polypropylene, a nucleating agent and optional additives.

8. The two-component core / shell structure foamed polypropylene according to claim 1, characterized in that The RCP further comprises C3.

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

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

11. A method for preparing a two-component core / shell structured foamed polypropylene according to any one of claims 1 to 10, characterized in that It includes the following steps in sequence: (1) using a twin-screw extruder to extrude the core component and the shell component described in any one of claims 1 to 10 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 extruder die, 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 1.5:1; (2) cutting the core / shell 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.

12. The method according to claim 11, characterized in that The core layer screw processing parameters in step 1 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 shell screw processing parameters are: screw zone 1 temperature is 180-240℃, zone 2 temperature is 190-250℃, zone 3 temperature is 200-260℃, metering pump temperature is 200-260℃, connecting block temperature is 215-275℃, and die temperature is 215-275℃.

13. The method according to claim 11, 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 into 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 of 8-25 MPa; temperature range of 95-140°C; and / or time range of 30-120 min. Steam molding includes the following steps: 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.

14. Use of the two-component core / shell structured foamed polypropylene according to any one of claims 1 to 10 in packaging, construction or automotive industries.

15. The two-component core / shell structure foamed polypropylene according to claim 1, 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 talc; wherein the core structure and the shell structure of the two-component core / shell structure foamed polypropylene are both well foamed.

16. The two-component core / shell structure foamed polypropylene according to claim 15, characterized in that The talc powder is HTPultra5L talc powder.

17. A method for preparing the two-component core / shell structure foamed polypropylene according to claim 15, characterized in that It includes the following steps in sequence: (1) using a twin-screw extruder with a specially designed extruder and die head to pass the core component and the shell component described in claim 15 through two different hoppers to extrude into core / shell 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 passes through different stretching rollers. By adjusting the speed of the stretching rollers, different stretching ratios are achieved, and finally a core / shell structure bicomponent filament sample with the following stretching ratio is obtained: 1±0.05:1; (2) Cutting the core / shell structured bicomponent filaments produced in step 1 into microparticles, wherein: The processing temperature of the core layer is: screw zone 1 temperature is 230℃, zone 2 temperature is 240℃, zone 3 temperature is 250℃, metering pump temperature is 250℃, connecting block temperature is 245℃, and die temperature is 245℃; The processing temperature of the shell layer is: the temperature of the screw zone 1 is 210℃, the temperature of the second zone is 220℃, the temperature of the third zone is 230℃, the temperature of the metering pump is 230℃, the temperature of the connecting block is 245℃, and the temperature of the die is 245℃; (3) physically foaming and steam molding the microparticles obtained in step 2, The physical foaming molding comprises the following steps: placing the microparticles cut in step 2 above into a foaming kettle, introducing carbon dioxide under appropriate foaming conditions, and releasing the pressure after a certain period of time to allow the microparticles to foam into beads, wherein the pressure during the physical foaming of the microparticles is 15 MPa, the temperature is 120° C., and the time is 60 minutes; Steam molding includes the following steps: 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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