Polypropylene-based composition, polypropylene foam thereof, and preparation method for polypropylene foam

Abstract

The present invention provides a polypropylene-based composition, comprising 100 parts by weight of a polypropylene matrix resin, 0.1-5 parts by weight of a polymer nucleating agent, and 0-50 parts by weight of an auxiliary agent. The polymer nucleating agent is incompatible with the polypropylene matrix resin, and the melting point of the polymer nucleating agent is greater than the melting point of the polypropylene matrix resin. The present invention also provides a polypropylene foam of the polypropylene-based composition and a preparation method for the polypropylene foam.

Description

Polypropylene-based compositions, polypropylene foam thereof, and methods for preparing polypropylene foam. Technical Field

[0001] This invention relates to the field of foaming materials technology, specifically to a polypropylene-based composition, a polypropylene foam thereof, and a method for preparing the polypropylene foam. In particular, the method for preparing the polypropylene foam of the polypropylene-based composition is simple, and the prepared polypropylene foam has high melt strength, good transport and flow during the molding of spherical foam particles, and is easier to fill into the molding die. It can be used for the molding and preparation of foamed precision structural parts. Background Technology

[0002] Polypropylene foam materials have promising applications in the automotive, packaging, toy, and building materials industries due to their excellent properties. Existing polypropylene foam materials typically use inorganic particles such as talc, mica, kaolin, montmorillonite, and graphene as heterogeneous nucleating agents to increase crystallization speed and improve the cell structure and mechanical properties of the foamed products. However, these inorganic nucleating agents often exhibit poor bonding with the polypropylene matrix resin during use, easily leading to agglomeration. This results in products with uneven cell structure and unstable mechanical properties, which is detrimental to the fabrication of precision components.

[0003] On the other hand, polypropylene matrix resins are typically modified with modifiers using a twin-screw extruder, followed by water-cooled granulation to obtain polypropylene microparticles. These microparticles are usually cylindrical with a diameter of 1 mm or more. After foaming, the resulting polypropylene foam generally has a particle size exceeding 2 mm. Because the particle size of polypropylene foam is prone to inconsistency and difficult to control precisely, it is unsuitable for molding and preparing precision components. Furthermore, modified polypropylene matrix resins with high viscosity and high melt strength are not suitable for use with granulation.

[0004] Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a polypropylene-based composition, a polypropylene foam of the same composition, and a method for preparing the same. This invention uses a polymer nucleating agent as a foaming nucleating agent, increasing melt strength while simultaneously achieving higher cell density in the foamed beads and better performance of the polypropylene foam. Furthermore, the modified granulation process employs underwater granulation, cutting the polypropylene matrix resin into granules while it is in a molten state, and then water-cooling and solidifying it into spherical particles. By controlling the diameter of the template pores, uniform and regular spherical particles with a particle size less than 0.5 mm can be prepared. The foamed polypropylene foam also exhibits small particle size and better flowability, making it suitable for the preparation of precision component molded bodies.

[0006] The technical solution adopted in this invention is as follows:

[0007] In one aspect, the present invention provides a polypropylene-based composition comprising 100 parts by weight of a polypropylene matrix resin, 0.1 to 5 parts by weight of a polymer nucleating agent, and 0 to 50 parts by weight of an additive; wherein the polymer nucleating agent is incompatible with the polypropylene matrix resin, and the melting point of the polymer nucleating agent is greater than the melting point of the polypropylene matrix resin.

[0008] In some specific embodiments, the polypropylene matrix resin is random copolymer polypropylene.

[0009] In some specific embodiments, the particle size of the polymer nucleating agent is less than 0.1 mm, and the polymer nucleating agent is at least one of polytetrafluoroethylene, polyethylene terephthalate, nylon 6, and nylon 66.

[0010] In some specific embodiments, the additive is at least one of the following: antioxidant, UV aging resistant agent, color masterbatch, flame retardant, and antistatic agent.

[0011] In some specific embodiments, the polymer nucleating agent is in the amount of about 0.1 to about 5 parts by weight, preferably, but not limited to, about 0.1, about 0.5, about 1.5, about 2, about 2.5, about 3, about 3.5, about 4, about 4.5, about 5, or any amount between about 0.1 and about 5 parts by weight, for example, about 0.69 parts by weight, about 2.81 parts by weight, or about 4.37 parts by weight.

[0012] In some specific embodiments, the additive is in the form of 0 to about 50 parts by weight, preferably, but not limited to, 0, about 0.1, about 0.5, about 1, about 1.5, about 2.5, about 5, about 7.5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, about 50, or any part by weight between 0 and about 50, for example, about 0.34 parts by weight, about 7.28 parts by weight, or about 31.96 parts by weight.

[0013] In some specific embodiments, the melting point of the polypropylene matrix resin is about 130°C to about 160°C, preferably, but not limited to, about 130°C, about 135°C, about 140°C, about 145°C, about 150°C, about 155°C, about 160°C, or any temperature between about 130°C and about 160°C, for example, about 139.51°C, about 142.38°C, or about 159.99°C.

[0014] In some specific embodiments, the melting point of the polymer nucleating agent is about 180°C to about 350°C, preferably, but not limited to, about 180°C, about 190°C, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C, about 250°C, about 260°C, about 270°C, about 280°C, about 290°C, about 300°C, about 310°C, about 320°C, about 330°C, about 340°C, about 350°C, or any temperature between about 180°C and about 350°C, for example, about 196.11°C, about 227.34°C, or about 318.73°C.

[0015] On the other hand, the present invention provides a method for preparing polypropylene foam, comprising the following steps:

[0016] The polypropylene-based composition described above is mixed and added to an extruder, and then pelletized underwater to obtain modified polypropylene microparticles.

[0017] The modified polypropylene microparticles were foamed in a single autoclave to obtain foamed beads.

[0018] The foamed beads are molded using steam to obtain the shaped polypropylene foam.

[0019] In some specific embodiments, the foaming agent for autoclaving is carbon dioxide.

[0020] In some specific embodiments, the foaming temperature of the autoclave foaming is ±2°C of the melting point of the polypropylene matrix resin.

[0021] In some specific embodiments, the foaming pressure of the autoclave foaming is about 2.0 MPa to about 5.0 MPa, preferably, but not limited to, about 2.0 MPa, about 2.5 MPa, about 3 MPa, about 3.5 MPa, about 4 MPa, about 4.5 MPa, about 5.0 MPa, or any pressure between about 2.0 MPa and about 5.0 MPa, for example, 2.36 MPa, 3.74 MPa, or 4.18 MPa.

[0022] In some specific embodiments, the modified polypropylene microparticle is a sphere having a diameter of about 0.3 mm to about 1.0 mm, preferably, but not limited to, about 0.3 mm, about 0.4 mm, about 0.5 mm, about 0.6 mm, about 0.7 mm, about 0.8 mm, about 0.9 mm, about 1.0 mm, or any diameter between about 0.3 mm and about 1.0 mm, such as 0.471 mm, 0.618 mm, or 0.829 mm.

[0023] In some specific embodiments, the density of the modified polypropylene microparticles is approximately 0.03 g / cm³. 3 ~ Approximately 0.09 g / cm³ 3Preferably, but not limited to, approximately 0.03 g / cm³. 3 0.04g / cm 3 0.05g / cm 3 0.06g / cm 3 0.07g / cm 3 0.08g / cm 3 0.09g / cm 3 or approximately 0.03 g / cm³ 3 ~ Approximately 0.09 g / cm³ 3 Any density between these values, for example, 0.0312 g / cm³. 3 0.0651 g / cm 3 or 0.0839 g / cm 3 .

[0024] On the other hand, the present invention provides a polypropylene foam obtained by the above-described method for preparing polypropylene foam.

[0025] In some specific embodiments, the polypropylene foam has the following characteristics: the average foam pore size is about 10 μm to about 120 μm, preferably, but not limited to, about 10 μm, about 20 μm, about 30 μm, about 40 μm, about 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, about 100 μm, about 110 μm, about 120 μm, or any size between about 10 μm and about 120 μm, for example, about 37.25 μm, about 96.53 μm, or about 104.69 μm.

[0026] In some specific embodiments, the polypropylene foam has the following characteristics: a foam pore density of approximately 10. 8 pcs / cm 3 ~ Approximately 10 13 pcs / cm 3 Preferably, but not limited to, about 10 8 pcs / cm 3 Approximately 10 9 pcs / cm 3 Approximately 10 10 pcs / cm 3 Approximately 10 11 pcs / cm 3 Approximately 10 12 pcs / cm 3 Approximately 10 13 pcs / cm 3 or about 10 8 ~ Approximately 10 13 pcs / cm 3 Any density between, for example, approximately 2.89 x 10⁻⁶. 9 pcs / cm 3Approximately 6.27 x 10 10 pcs / cm 3 or approximately 4.38 x 10 11 pcs / cm 3 .

[0027] In certain specific embodiments, the polypropylene foam has the following characteristics: a tensile strength of about 0.4 MPa to about 1.2 MPa, preferably, but not limited to, about 0.4 MPa, about 0.5 MPa, about 0.6 MPa, about 0.7 MPa, about 0.8 MPa, about 0.9 MPa, about 1.0 MPa, about 1.1 MPa, about 1.2 MPa, or any strength between about 0.4 MPa and about 1.2 MPa, such as about 0.689 MPa, about 0.876 MPa, or about 1.143 MPa. Attached Figure Description

[0028] Figure 1 is a scanning electron microscope image of a cross-section of polypropylene foam beads provided in Example 1 of the present invention.

[0029] Figure 2 is a scanning electron microscope image of a cross-section of polypropylene foam beads provided in Comparative Example 1 of the present invention. Detailed Implementation

[0030] Unless otherwise defined herein, scientific and technical terms used in connection with this document shall have the meanings commonly understood by one of ordinary skill in the art.

[0031] It should be noted that, as used herein, the singular terms “a,” “an,” and “the” include multiple indicators unless explicitly limited to one indicator.

[0032] As used herein, the terms “about,” “approximately,” or “approximately” essentially mean that the stated value or range is within 10%, therefore, about 1% refers to the range of 0.9% to 1.1%. The digitized quantities provided herein are approximate values, meaning they could be inferred even if the terms “about,” “approximately,” or “approximately” were not used.

[0033] The term "comprising" as used herein is open-ended, meaning that such embodiments may include additional elements. Conversely, the term "consisting of" is closed-ended, meaning that such embodiments do not include additional elements (except trace impurities). The term "substantially consisting of" is partially closed-ended, meaning that such embodiments may also include elements that do not substantially alter the essential characteristics of such embodiments.

[0034] When an invention or part thereof is defined using an open conjunction such as “comprising”, it should be readily understood (unless otherwise stated) that the specification should be interpreted as also using the conjunctions “substantially constitutes” or “consisting of” to describe the invention.

[0035] Other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the accompanying drawings.

[0036] Unless otherwise specified, the raw materials used in the embodiments of the present invention were all purchased through commercial channels. Unless otherwise specified, the testing methods were all conventional methods, and the instrument settings were all the settings recommended by the manufacturer.

[0037] Among them, polypropylene matrix resin 1 was purchased from Sinopec Shanghai Petrochemical Co, Ltd., model F800E, with a melting point of 149℃;

[0038] The polypropylene matrix resin 2 was purchased from Lotte Chemical Company (Seoul, South Korea), model number LOTTO750, with a melting point of 135℃.

[0039] Among them, the bulk density test is the mass of the foamed beads that naturally fall into a 1L graduated cylinder.

[0040] Density test: The density of polypropylene foamed board was measured using the water displacement method. The density analysis instrument was a density balance, model BT224S, from Beijing Sartorius Scientific Instruments Co., Ltd.

[0041] Cell structure analysis: The analysis was performed by scanning electron microscopy (SEM). The instrument used was a Hitachi TM1000 desktop scanning electron microscope from Japan. The analysis method was to analyze the cross-section of the prepared foamed sample.

[0042] Mechanical property testing: The tensile properties of the materials were tested using an Instron 5567 universal testing machine in accordance with GB1040-2006.

[0043] Example 1

[0044] S1: 100 parts by weight of polypropylene matrix resin 1 and 1 part by weight of polytetrafluoroethylene powder with an average particle size of 10 μm are mixed in a high-speed mixer and then added to a twin-screw extruder. The mixture is then processed through an underwater granulation system to produce polypropylene modified microparticles with a particle size of 0.5 mm. The melting point of the polypropylene matrix resin 1 is 149°C, and the melting point of the polytetrafluoroethylene powder is 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, or 350°C, preferably 327°C.

[0045] S2: Take 5 kg of the polypropylene modified microparticles prepared in S1 and put them into a high-pressure reactor. Introduce carbon dioxide at 2 MPa, heat to 151℃, depressurize, and dry to obtain foamed beads with a bulk density of 60 g / L, an average pore diameter of 50 μm, and a pore density of 2.4 × 10⁻⁶. 10 pcs / cm 3 ;

[0046] S3: The foamed beads are subjected to pressure and then molded with steam to obtain a polypropylene foam with a density of 0.06 g / cm³. 3 The tensile strength is 0.92 MPa.

[0047] Figure 1 is a scanning electron microscope image of a cross-section of the foamed beads prepared in Example 1. The filamentous structure in the figure represents the fibrous state of the polymer nucleating agent in the foam pores.

[0048] Example 2

[0049] S1: 100 parts by weight of polypropylene matrix resin 1, 5 parts by weight of polyethylene terephthalate powder with an average particle size of 5 μm, and 5 parts by weight of black masterbatch are mixed in a high-speed mixer and then added to a twin-screw extruder. The mixture is then processed through an underwater granulation system to prepare polypropylene modified microparticles with a particle size of 1 mm. The melting point of the polypropylene matrix resin 1 is 149℃, and the melting point of the polyethylene terephthalate powder is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, or 350℃, preferably 250℃ to 260℃.

[0050] S2: Take 5 kg of the polypropylene modified microparticles prepared in S1 and put them into a high-pressure reactor. Introduce carbon dioxide at 5 MPa, heat to 151.5℃, depressurize, and dry to obtain foamed beads with a bulk density of 30 g / L, an average pore diameter of 100 μm, and a pore density of 4.9 × 10⁻⁶. 8 pcs / cm 3 ;

[0051] S3: The foamed beads are subjected to pressure and then molded with steam to obtain a polypropylene foam with a density of 0.03 g / cm³. 3 The tensile strength is 0.48 MPa.

[0052] Example 3

[0053] S1: 100 parts by weight of polypropylene matrix resin 2 and 1 part by weight of polytetrafluoroethylene powder with an average particle size of 10 μm are mixed in a high-speed mixer and then added to a twin-screw extruder. The mixture is then processed through an underwater granulation system to prepare polypropylene modified microparticles with a particle size of 0.5 mm. The melting point of the polypropylene matrix resin 2 is 135℃, and the melting point of the polytetrafluoroethylene powder is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, preferably 327℃.

[0054] S2: Take 5 kg of the polypropylene modified microparticles prepared in S1 and put them into a high-pressure reactor. Purge with 2 MPa carbon dioxide, heat to 136℃, depressurize, and dry to obtain foamed beads with a bulk density of 50 g / L, an average pore diameter of 40 μm, and a pore density of 6.3 × 10⁻⁶. 10 pcs / cm 3 ;

[0055] S3: The foamed beads are subjected to pressure and then molded with steam to obtain a polypropylene foam with a density of 0.05 g / cm³. 3 The tensile strength is 0.73 MPa.

[0056] Example 4

[0057] S1: 100 parts by weight of polypropylene matrix resin 2 and 5 parts by weight of polytetrafluoroethylene powder with an average particle size of 10 μm are mixed in a high-speed mixer and then added to a twin-screw extruder. The mixture is then processed through an underwater granulation system to prepare polypropylene modified microparticles with a particle size of 0.3 mm. The melting point of the polypropylene matrix resin 2 is 135℃, and the melting point of the polytetrafluoroethylene powder is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, preferably 327℃.

[0058] S2: Take 5 kg of the polypropylene modified microparticles prepared in S1 and put them into a high-pressure reactor. Purge with 3 MPa carbon dioxide, heat to 137℃, depressurize, and dry to obtain foamed beads with a bulk density of 35 g / L, an average pore diameter of 90 μm, and a pore density of 6.3 × 10⁻⁶. 10 pcs / cm 3 ;

[0059] S3: The foamed beads are subjected to pressure and then molded with steam to obtain a polypropylene foam with a density of 0.035 g / cm³. 3 The tensile strength is 0.55 MPa.

[0060] Example 5

[0061] S1: 100 parts by weight of polypropylene matrix resin 1 and 0.1 parts by weight of nylon 66 powder with an average particle size of 10 μm are mixed in a high-speed mixer and then added to a twin-screw extruder. The mixture is then processed through an underwater granulation system to produce polypropylene modified microparticles with a particle size of 1 mm. The melting point of the polypropylene matrix resin 1 is 149℃, and the melting point of the nylon 66 powder is 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, preferably 252℃.

[0062] S2: Take 5 kg of the polypropylene modified microparticles prepared in S1 and put them into a high-pressure reactor. Purge with 2 MPa carbon dioxide, heat to 151℃, depressurize, and dry to obtain foamed beads with a bulk density of 60 g / L, an average pore diameter of 65 μm, and a pore density of 5.9 × 10⁻⁶. 9 pcs / cm 3 ;

[0063] S3: The foamed beads are subjected to pressure and then molded with steam to obtain a polypropylene foam with a density of 0.06 g / cm³. 3 The tensile strength is 0.90 MPa.

[0064] Comparative Example 1

[0065] S1: 100 parts by weight of polypropylene matrix resin and 1 part by weight of 1500 mesh talc powder are mixed in a high-speed mixer and then added to a twin-screw extruder. After traction and water cooling granulation, long strip particles with a diameter of 1 mm and a length of 1.5 mm are obtained.

[0066] S2: Take 5 kg of the microparticles prepared in S1 and put them into a high-pressure reactor. Purge with 2 MPa carbon dioxide, heat to 151℃, depressurize, and dry to obtain foamed beads with a bulk density of 60 g / L, an average pore diameter of 150 μm, and a pore density of 5.1 × 10⁻⁶. 7 pcs / cm 3 ;

[0067] S3: The foamed beads are subjected to pressure and then molded with steam to obtain a polypropylene foam with a density of 0.06 g / cm³. 3 The tensile strength is 0.87 MPa.

[0068] Figure 2 shows a scanning electron microscope image of the cross-section of the foamed beads prepared in Comparative Example 1. The uniformity of the pore size is poor, and the pore size distribution is 50-300 μm, which is widely distributed.

[0069] Comparative Example 2

[0070] S1: 100 parts by weight of polypropylene matrix resin 1 and 1 part by weight of polytetrafluoroethylene powder with an average particle size of 10μm are mixed in a high-speed mixer and then added to a twin-screw extruder. The mixture is granulated by water cooling during traction. Due to the excessive melt strength, the mixture is prone to breakage during traction, resulting in inconsistent particle size and making continuous production impossible, with a low yield.

[0071] In summary, the polypropylene matrix resin used in this invention is random copolymer polypropylene. The polymer nucleating agent is incompatible with the polypropylene matrix resin. The melting point of the polymer nucleating agent is higher than that of the polypropylene matrix resin. During the twin-screw extrusion process, the agent deforms and orients due to the heating and shearing action of the screw, forming a micron or nano-sized fiber structure with a high aspect ratio. This provides a large number of nucleation sites for the crystallization of the polymer matrix, which not only improves the crystallization ability of the polypropylene matrix resin, but also improves the melt strength of the matrix through the physical entanglement of the fibers. Ultimately, foamed products with smaller and more uniform cell size and stronger mechanical properties are obtained.

[0072] Compared with the prior art, the beneficial effects of the present invention are:

[0073] Polymer nucleating agents not only play a role in heterogeneous nucleation, but also appear in the polypropylene matrix resin in the form of micron or nanofiber structures, providing more heterogeneous nucleation sites for the polypropylene matrix resin, accelerating the crystallization rate of polypropylene, and making the cell structure more uniform and the cell density greater.

[0074] The fiber structure formed by the polymer nucleating agent becomes physically entangled with the polypropylene matrix resin, which can improve the melt strength of the polypropylene matrix resin and thus improve the mechanical properties of the foamed products.

[0075] Underwater granulation is employed to obtain modified microparticles with smaller, spherical structures. After foaming, the resulting foam beads exhibit improved flowability, making them suitable for the preparation of polypropylene foams with precise structures. The density of these spherical modified polypropylene microparticles ranges from 0.03 to 0.09 g / cm³. 3 The average cell size is 10–120 μm, and the cell density is 10. 8 ~10 13 pcs / cm 3 The tensile strength is 0.4–1.2 MPa.

[0076] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Details disclosed in some embodiments of the present invention are necessary for clarity in the specification, and those skilled in the art should understand that these details are not essential and should not be used to limit the present invention. Any equivalent changes or modifications made by those skilled in the art, after understanding the above-described technical features and embodiments of the present invention, without departing from the spirit and scope of the present invention, still fall within the scope of protection of the present invention, and the patent protection scope of the present invention shall be determined by the claims.

Claims

1. A polypropylene-based composition, characterized in that, include: 100 parts by weight of polypropylene matrix resin ； 0.1 to 5 parts by weight of a polymeric nucleating agent, wherein the polymeric nucleating agent is incompatible with the polypropylene matrix resin, and the melting point of the polymeric nucleating agent is higher than that of the polypropylene matrix resin; and 0 to 50 parts by weight of additives.

2. The polypropylene-based composition according to claim 1, characterized in that, The particle size of the polymer nucleating agent is less than 0.1 mm, and the polymer nucleating agent is at least one of polytetrafluoroethylene, polyethylene terephthalate, nylon 6 and nylon 66.

3. The polypropylene-based composition according to claim 1, characterized in that, The melting point of the polypropylene matrix resin is 130-160℃, and the melting point of the polymer nucleating agent is 180-350℃.

4. The polypropylene-based composition according to claim 1, characterized in that, The additive is at least one of the following: antioxidant, UV aging resistant agent, color masterbatch, flame retardant, and antistatic agent.

5. A method for preparing polypropylene foam, characterized in that, Includes the following steps: The polypropylene-based composition as described in claim 1 is mixed at high speed and then added to a twin-screw extruder, and then pelletized underwater to obtain modified polypropylene microparticles. The modified polypropylene microparticles were subjected to autoclaving to prepare foamed beads. The foamed beads were prepared into polypropylene foam by steam molding.

6. The preparation method according to claim 5, characterized in that, The foaming agent for this autoclave foaming process is carbon dioxide.

7. The preparation method according to claim 5, characterized in that, The foaming temperature of the autoclave foaming is ±2℃ of the melting point of the polypropylene matrix resin, and the foaming pressure of the autoclave foaming is 2.0~5.0MPa.

8. The preparation method according to claim 5, characterized in that, The modified polypropylene microparticles are spheres with a diameter of 0.3 to 1.0 mm.

9. The preparation method according to claim 5, characterized in that, The density of modified polypropylene microparticles is 0.03–0.09 g / cm³. 3 .

10. A polypropylene foam, characterized in that, The polypropylene foam prepared by the method described in claim 5 has the following characteristics: The average foam pore size is 10–120 μm; The foam pore density is 10 8 ~10 13 pcs / cm 3 ;as well as The tensile strength is 0.4–1.2 MPa.

Images