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

Abstract

The invention provides a polypropylene-based composition which comprises 100 parts by weight of 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 that of the polypropylene matrix resin. The invention also provides a polypropylene foaming body of the polypropylene-based composition and a preparation method of the polypropylene foaming body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foaming materials, and relates to a polypropylene-based composition, a polypropylene foam of the polypropylene-based composition and a preparation method of the polypropylene foam. Specifically, the polypropylene foam of the polypropylene-based composition has a simple preparation method, high melt strength, good transport flowability in the process of forming spherical foaming particles, and is easier to fill into a forming mold, and can be used for the forming preparation of foamed precision structural product. BACKGROUND

[0002] Polypropylene foaming materials have good application prospects in the fields of automobiles, packaging, toys and building materials due to their excellent performance. Existing polypropylene foaming materials usually use talc, mica, kaolin, montmorillonite and graphene as inorganic particles as heterogeneous nucleating agents to improve the crystallization speed and improve the cell structure and mechanical properties of the foaming product. However, the inorganic nucleating agent is poorly combined with the polypropylene matrix resin during use, and is prone to agglomeration, which makes the product have uneven foaming holes and unstable mechanical properties, which is not conducive to the preparation of precision components.

[0003] On the other hand, the polypropylene matrix resin is usually processed by a double-screw modifier after being modified with a modifier, and then is granulated by water cooling to obtain polypropylene particles, which are usually cylindrical particles with a particle size of 1 mm or more. The particle size of the polypropylene foam produced after foaming is generally more than 2 mm. Since the particle size of the polypropylene foam is not uniform and is difficult to control accurately, it is not suitable for the forming preparation of precision components. On the other hand, the modified polypropylene matrix resin with high viscosity and high melt strength is not suitable for the use of the strand granulation. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a polypropylene-based composition, a polypropylene foam of the polypropylene-based composition and a preparation method thereof. The present application uses a polymer nucleating agent as a foaming nucleating agent to increase the melt strength and make the foaming beads have higher cell density and better polypropylene foam performance. Furthermore, the modified granulation process uses underwater granulation to cut the polypropylene matrix resin into granules when it is in a melt state, and solidifies into spherical particles through water cooling. By controlling the template hole diameter, uniform and regular spherical particles with a particle size of less than 0.5 mm can be prepared. The polypropylene foam after foaming also presents spherical particles with small particle size and better flowability, which is suitable for the preparation of precision component forming bodies.

[0005] The technical solutions adopted by the present application are as follows: In one aspect, the present application 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.

[0006] In some embodiments, the polypropylene matrix resin is a random copolymer polypropylene.

[0007] In some embodiments, the polymer nucleating agent has a particle size of less than 0.1 mm, and the polymer nucleating agent is at least one of polytetrafluoroethylene, polyethylene terephthalate, nylon 6, and nylon 66.

[0008] In some embodiments, the additive is at least one of an antioxidant, an ultraviolet light resistant aging agent, a color master, a flame retardant, and an antistatic agent.

[0009] In some embodiments, the parts by weight of the polymer nucleating agent is about 0.1 to about 5, 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 parts by weight between about 0.1 and about 5, for example, about 0.69 parts by weight, about 2.81 parts by weight, or about 4.37 parts by weight.

[0010] In some embodiments, the parts by weight of the additive is 0 to about 50, 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 parts 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.

[0011] In some 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.

[0012] In certain embodiments, the polymer nucleating agent has a melting point of 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 in between about 180 °C to about 350 °C, for example, about 196.11 °C, about 227.34 °C, or about 318.73 °C.

[0013] In another aspect, the present application provides a method for preparing a polypropylene foam, comprising the steps of: mixing the polypropylene-based composition as described above and feeding into an extruder, and underwater pelletizing to obtain a polypropylene modified particle; autoclave foaming the polypropylene modified particle to obtain a foamed bead; steam molding the foamed bead to obtain the molded polypropylene foam.

[0014] In certain embodiments, the foaming agent for the autoclave foaming is carbon dioxide.

[0015] In certain embodiments, the foaming temperature for the autoclave foaming is the melting point of the polypropylene matrix resin ± 2 °C.

[0016] In certain embodiments, the foaming pressure for 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 in between about 2.0 MPa to about 5.0 MPa, for example, 2.36 MPa, 3.74 MPa, or 4.18 MPa.

[0017] In certain embodiments, the polypropylene modified particle 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 in between about 0.3 mm to about 1.0 mm, for example, 0.471 mm, 0.618 mm, or 0.829 mm.

[0018] In certain embodiments, the polypropylene modified particle has a density of about 0.03 g / cm 3 ~ about 0.09 g / cm 3, preferably, but not limited to, about 0.03 g / cm 3 , 0.04 g / cm 3 , 0.05 g / cm 3 , 0.06 g / cm 3 , 0.07 g / cm 3 , 0.08g / cm 3 , 0.09 g / cm 3 , or about 0.03 g / cm 3 ~about 0.09 g / cm 3 Any density between, for example, 0.0312 g / cm 3 , 0.0651 g / cm 3 , or 0.0839 g / cm 3 .

[0019] In another aspect, the present invention provides a polypropylene foam prepared by the above-mentioned method for preparing a polypropylene foam.

[0020] In some embodiments, the polypropylene foam has the following characteristics: an average cell size of 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.

[0021] In some embodiments, the polypropylene foam has the following characteristics: a foam cell density of about 10 8 pieces / cm 3 ~about 10 13 pieces / cm 3 , preferably, but not limited to, about 10 8 pieces / cm 3 , about 10 9 pieces / cm 3 , about 10 10 pieces / cm 3 , about 10 11 pieces / cm 3 , about 10 12 pieces / cm 3 , about 10 13 pieces / cm 3 , or about 10 8 ~about 10 13 pieces / cm 3any density between about 2.89 x 10 9 3 about 6.27 x 10 10 3 about 4.38 x 10 11 3 .

[0022] In certain embodiments, the polypropylene foamed beads have 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 to about 1.2 MPa, for example, about 0.689 MPa, about 0.876 MPa, or about 1.143 MPa. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a scanning electron micrograph of a cross-section of a polypropylene foamed bead provided in Example 1 of the present invention.

[0024] Figure 2 is a scanning electron micrograph of a cross-section of a polypropylene foamed bead provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0025] Unless otherwise defined, scientific and technical terms used in connection with the present disclosure shall have the meanings that are commonly understood by those of ordinary skill in the art.

[0026] It must be noted that as used herein the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0027] The terms "about," "approximately," or "substantially" as used herein represent what is approximately or logically near the value or range being described, to within 10%, and thus, about 1% means a range of 0.9% to 1.1%. Numerical quantities given herein are approximate unless stated otherwise, meaning that the term "about" or "approximately" can be inferred when not expressly stated.

[0028] The word "comprising" is used herein to mean including, but not limited to, and the word "comprise" is used herein to mean including, but not limited to. The word "consisting" is used herein to mean including, and the word "consisting essentially of" is used herein to mean including and the ordinary meaning of "essentially," followed by a listing of the essential elements. Thus, a composition consisting essentially of the elements as ​​​

[0029] When using open-ended transitional phrases such as "comprising" in the definition of the invention or of a portion thereof, it is to be understood that the invention is not limited to the sum of the parts recited but also to other claimable aspects falling within the scope of the invention.

[0030] Other technical contents, features and effects of the present application will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings.

[0031] Unless otherwise specified, the raw materials in the embodiments of the present application are purchased through commercial channels, and unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all recommended settings of the manufacturers.

[0032] The polypropylene base resin 1 is purchased from Sinopec Shanghai Petrochemical Co, Ltd., model F800E, and the melting point is 149℃; The polypropylene base resin 2 is purchased from LOTTE Chemical Company, Seoul, South Korea, model lotto750, and the melting point is 135℃.

[0033] The bulk density test: the mass of the foamed beads naturally falling into a 1L measuring cylinder; Density test: the density of the polypropylene foamed board is measured by the drainage method, and the density analyzer is a density balance of BT224S of Beijing Sartorius Scientific Instrument Co., Ltd.; Cell structure analysis: analyzed by scanning electron microscopy (SEM) test, and the analysis instrument is a table type scanning electron microscope TM1000 of Japan Hitachi Company, and the analysis method is to analyze the cross section of the prepared foamed sample; Mechanical property test: according to GB1040-2006, the tensile properties of the material are tested by Instron5567 universal material testing machine. Example 1

[0034] S1: 100 parts by weight of polypropylene base resin 1 and 1 part by weight of polytetrafluoroethylene powder with an average particle size of 10μm are mixed by a high-speed mixer and then added into a twin-screw extruder, and a polypropylene modified microparticle with a particle size of 0.5mm is prepared by an underwater pelletizing system, the melting point of the polypropylene base resin 1 is 149℃, 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℃, and preferably 327℃; S2: 5 kg of modified polypropylene particles prepared in S1 were put into an autoclave, 2 MPa of carbon dioxide was introduced, and the mixture was heated to 151 ° C. After pressure relief and drying, foamed beads were obtained with a bulk density of 60 g / L, an average cell diameter of 50 μm, and a cell density of 2.4. 10 10 pieces / cm 3 ; S3: The foamed beads are subjected to pressure and then steam molded to obtain a polypropylene foam with a density of 0.06 g / cm 3 , the tensile strength is 0.92MPa.

[0035] in Figure 1 This is a scanning electron microscope image of the cross section of the foamed beads prepared in Example 1. The filamentous structure in the image is the fiber state of the polymer nucleating agent in the foaming pores. Example 2

[0036] S1: 100 parts by weight of a polypropylene matrix resin 1, 5 parts by weight of polyethylene terephthalate powder having an average particle size of 5 μm, and 5 parts by weight of a black masterbatch are mixed in a high-speed mixer and added to a twin-screw extruder. The mixture is pelletized in an underwater pelletizing system to prepare polypropylene modified particles having a particle size of 1 mm. The polypropylene matrix resin 1 has a melting point of 149° C., and the polyethylene terephthalate powder has a melting point of 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 250-260° C. S2: 5 kg of modified polypropylene particles prepared in S1 were put into an autoclave, 5 MPa of carbon dioxide was introduced, and the mixture was heated to 151.5 ° C. After pressure relief and drying, foamed beads were obtained with a bulk density of 30 g / L, an average cell diameter of 100 μm, and a cell density of 4.9. 10 8 pieces / cm 3 ; S3: The foamed beads are pressurized and then steam molded to obtain a polypropylene foam with a density of 0.03 g / cm 3 , the tensile strength is 0.48MPa. Example 3

[0037] S1: 100 parts by weight of polypropylene base resin 2 and 1 part by weight of polytetrafluoroethylene powder with an average particle size of 10 μm were mixed by a high-speed mixer and then fed into a twin-screw extruder, and a polypropylene modified particle with a particle size of 0.5 mm was prepared by an underwater pelletizing system; the melting point of the polypropylene base resin 2 was 135°C, and the melting point of the polytetrafluoroethylene powder was 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; S2: 5 kg of the polypropylene modified particle prepared in S1 was put into an autoclave, 2 MPa of carbon dioxide was introduced, heated to 136°C, depressurized, and dried to obtain foamed beads with a bulk density of 50 g / L, an average cell diameter of 40 μm, and a cell density of 6.3 10 10 / cm 3 ; S3: the foamed beads were molded by water vapor after being loaded with pressure to obtain a polypropylene foamed body with a density of 0.05 g / cm 3 and a tensile strength of 0.73 MPa. Example 4

[0038] S1: 100 parts by weight of polypropylene base resin 2 and 5 parts by weight of polytetrafluoroethylene powder with an average particle size of 10 μm were mixed by a high-speed mixer and then fed into a twin-screw extruder, and a polypropylene modified particle with a particle size of 0.3 mm was prepared by an underwater pelletizing system; the melting point of the polypropylene base resin 2 was 135°C, and the melting point of the polytetrafluoroethylene powder was 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; S2: 5 kg of the polypropylene modified particle prepared in S1 was put into an autoclave, 3 MPa of carbon dioxide was introduced, heated to 137°C, depressurized, and dried to obtain foamed beads with a bulk density of 35 g / L, an average cell diameter of 90 μm, and a cell density of 6.3 10 10 / cm 3 ; S3: the foamed beads were molded by water vapor after being loaded with pressure to obtain a polypropylene foamed body with a density of 0.035 g / cm 3 and a tensile strength of 0.55 MPa. Example 5

[0039] S1: 100 parts by weight of polypropylene base resin 1 and 0.1 parts by weight of nylon 66 powder with an average particle size of 10 μm were mixed by a high-speed mixer and then fed into a twin-screw extruder, and polypropylene modified microparticles with a particle size of 1 mm were prepared by an underwater pelletizing system; the melting point of the polypropylene base resin 1 was 149℃, and the melting point of the nylon 66 powder was 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, preferably 252℃; S2: 5 kg of the polypropylene modified microparticles prepared in S1 were put into an autoclave, 2 MPa of carbon dioxide was introduced, heated to 151℃, and then the pressure was released and dried to obtain foamed beads with a bulk density of 60 g / L, an average cell diameter of 65 μm and a cell density of 5.9 10 9 / cm 3 ; S3: the foamed beads were molded by water vapor after being loaded with pressure to obtain a polypropylene foamed body with a density of 0.06 g / cm 3 and a tensile strength of 0.90 MPa.

[0040] Comparative Example 1 S1: 100 parts by weight of polypropylene base resin and 1 part by weight of 1500 mesh talc powder were mixed by a high-speed mixer and then fed into a twin-screw extruder, and long strip microparticles with a diameter of 1 mm and a length of 1.5 mm were obtained by traction water cooling pelletizing; S2: 5 kg of the microparticles prepared in S1 were put into an autoclave, 2 MPa of carbon dioxide was introduced, heated to 151℃, and then the pressure was released and dried to obtain foamed beads with a bulk density of 60 g / L, an average cell diameter of 150 μm and a cell density of 5.1 10 7 / cm 3 ; S3: the foamed beads were molded by water vapor after being loaded with pressure to obtain a polypropylene foamed body with a density of 0.06 g / cm 3 and a tensile strength of 0.87 MPa.

[0041] Figure 2 It is a scanning electron microscope picture of the section of the foamed beads prepared in Comparative Example 1, and the cell size uniformity is poor, and the cell size distribution is 50-300 μm, which is widely distributed.

[0042] Comparative Example 2 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 microns are mixed by a high-speed mixer and then added into a twin-screw extruder, and then water-cooling granulation is performed by traction, but the melt strength is too large, the traction process is easy to break, the thickness is uneven, continuous production is not possible, and the yield is low.

[0043] In summary, the polypropylene matrix resin that can be used in the application is random copolymerized polypropylene, the polymer nucleating agent is an incompatible polymer with the polypropylene matrix resin, and the melting point of the polymer nucleating agent is higher than that of the polypropylene matrix resin. In the twin-screw extrusion process, deformation and orientation occur through the heating and shearing action of the screw, forming a micron or nanometer scale fiber structure with high aspect ratio, which provides a large number of nucleation sites for the crystallization of the polymer matrix. Not only does it improve the crystallization ability of the polypropylene matrix resin, but also the physical entanglement of the fibers can improve the melt strength of the matrix, ultimately obtaining a foamed product with smaller, more uniform cell size and stronger mechanical properties.

[0044] Compared with the prior art, the application has the following advantages: The polymer nucleating agent not only plays a role in heterogeneous nucleation, but also forms a micron or nanometer fiber structure in the polypropylene matrix resin, providing more heterogeneous nucleation sites for the crystallization of the polypropylene matrix resin, accelerating the crystallization speed of the polypropylene, and making the cell structure more uniform and the cell density larger.

[0045] The fiber structure formed by the polymer nucleating agent physically entangles with the polypropylene matrix resin, which can improve the melt strength of the polypropylene matrix resin and further improve the mechanical properties of the foamed product.

[0046] The underwater granulation processing method is used to obtain smaller, spherical structure modified particles, which have better flowability after foaming and are suitable for the preparation of polypropylene foams with precise structure. The density of the spherical polypropylene modified particles is 0.03-0.09 g / cm 3 , the average cell size is 10-120 microns, the cell density is 10 8 ~10 13 cm 3 , and the tensile strength is 0.4-1.2 MPa.

[0047] The above embodiments are only some preferred embodiments of the present application, and are not intended to limit the present application. In the embodiments of the present application, some details disclosed in the embodiments are necessary for the explicit disclosure of the specification, and those skilled in the art should understand that these details are not necessary and should not be used to limit the present application. Any equivalent changes or modifications made by those skilled in the art based on the technical features and embodiments of the present application without departing from the spirit and scope of the present application shall fall within the protection scope of the present application. The patent protection scope of the present application shall be subject to the definition of the claims.

Claims

1. A polypropylene-based composition, characterized in that, Comprising: 100 parts by weight of a polypropylene base resin; 0.1 to 5 parts by weight of a polymer nucleating agent, which is incompatible with the polypropylene base resin, and which has a melting point greater than that of the polypropylene base resin; and 0 to 50 parts by weight of an auxiliary agent. The polymer nucleating agent has a particle size of less than 0.1 mm, and is at least one of polytetrafluoroethylene, polyethylene terephthalate, nylon 6, and nylon 66.

2. The polypropylene-based composition according to claim 1, wherein The polypropylene base resin has a melting point of 130 to 160°C, and the polymer nucleating agent has a melting point of 180 to 350°C.

3. The polypropylene-based composition according to claim 1, wherein The auxiliary agent is at least one of an antioxidant, an ultraviolet light resistant aging agent, a color master, a flame retardant, and an antistatic agent.

4. The polypropylene-based composition according to claim 1, wherein Comprising the steps of:

5. A process for the production of a polypropylene foam, characterized in that, mixing the polypropylene base composition of claim 1 after high speed mixing, and adding it to a twin-screw extruder, and obtaining polypropylene modified particles by underwater pelletization; preparing foamed beads by autoclave foaming of the polypropylene modified particles; and preparing a polypropylene foam by water vapor molding of the foamed beads. The foaming agent for the autoclave foaming is carbon dioxide.

6. The production method according to claim 5, wherein The foaming temperature for the autoclave foaming is the melting point of the polypropylene base resin ± 2°C, and the foaming pressure for the autoclave foaming is 2.0 to 5.0 MPa.

7. The production method according to claim 5, wherein The polypropylene modified particles are a sphere having a diameter of 0.3 to 1.0 mm.

8. The production method according to claim 5, wherein Prepared by the preparation method of claim 5, and the polypropylene foam has the following characteristics:

9. The production method according to claim 5, wherein The density of the polypropylene modified microparticles is 0.03 to 0.09 g / cm 3 .

10. A polypropylene foam characterized by, an average foaming cell size of 10 to 120 μm; and a tensile strength of 0.4 to 1.2 MPa. The foamed hole density is 10 8 ~10 13 cm-1 3 ; and ​

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