Foamable polypropylene material as well as preparation method and application thereof

Abstract

The invention discloses a foamable polypropylene material as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. Two kinds of expandable microspheres with different foaming property parameters are introduced into a polypropylene resin matrix, so that the dimensional stability of a product is improved; meanwhile, low-melting-point polypropylene resin and hyperbranched polyester are introduced into a polypropylene resin matrix for combined action, so that high dispersity and compatibility among the components are realized, sink marks on the surface of the product are avoided, the glossiness is low, the surface roughness is moderate, and the use requirements of decorative parts in an automobile are better met.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a foamable polypropylene material and a preparation method and application thereof. Background Art

[0002] In the field of automobile manufacturing, the process of preparing automobile decorative parts with polypropylene materials has become mature. However, due to the high crystallinity of polypropylene resin itself, the dimensional stability is not high when designed into thicker parts and products, and the shrinkage rate is large, resulting in shrinkage marks visible to the naked eye. Although the dimensional stability of some traditional chemical foamed polypropylene products has been improved, a large number of pores will appear inside the product after foaming, which may cause the problem of uneven surface and the same shrinkage phenomenon. At the same time, chemical foaming requires corresponding equipment for production, which is more cumbersome.

[0003] On the other hand, the existing polypropylene automotive decorative parts generally have a high glossiness, which is easy to cause light refraction in the cab, affecting the driver's driving. In addition, these products have a smooth surface and a low friction coefficient, so objects placed on the products are easy to slip during the driving of the car, resulting in a poor driving experience. For this reason, these decorative parts often need to be equipped with secondary parts such as blankets and anti-slip films, but this will affect the aesthetics of the car's interior. Summary of the invention

[0004] Based on the defects of the prior art, the purpose of the present invention is to provide a foamable polypropylene material, which improves the dimensional stability of the product by introducing two expandable microspheres with different foaming property parameters into a polypropylene resin matrix, and at the same time introduces a low-melting-point polypropylene resin and a hyperbranched polyester into the polypropylene resin matrix to work together to achieve high dispersibility and compatibility between components. The surface of the product will not have shrinkage marks, has low gloss and moderate surface roughness, making it more in line with the use requirements of decorative parts inside automobiles.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A foamable polypropylene material comprises the following components in parts by weight:

[0007] 100 parts of polypropylene composition, 0.1 to 8 parts of expandable microspheres and / or expandable masterbatch;

[0008] The polypropylene composition comprises 90-97 parts of polypropylene resin, 2-10 parts of low melting point polypropylene, and 0.1-0.5 parts of hyperbranched polyester;

[0009] The expandable microspheres include expandable microspheres A and expandable microspheres B; the initial foaming temperature of the expandable microspheres A is ≥190°C;

[0010] The initial foaming temperature of the expandable microspheres B is ≥125°C, and the peak foaming temperature is 195-205°C;

[0011] The initial foaming temperature of the expandable microsphere B is less than the initial foaming temperature of the expandable microsphere A;

[0012] The melting point of the low melting point polypropylene is ≤90°C.

[0013] In some embodiments, the initial foaming temperature and the peak foaming temperature of the expandable microsphere A and / or the expandable microsphere B are determined by referring to the method described in paragraph

[0047] of the specification of CN108912384B.

[0014] Preferably, the expandable microspheres include 0.5 to 5 parts of expandable microspheres A and 0.1 to 3 parts of expandable microspheres B;

[0015] Preferably, the expandable microsphere comprises an outer shell and an inner core, the outer shell comprises a thermoplastic polymer, and the inner core comprises an expandable substance.

[0016] Preferably, the initial foaming temperature of the expandable microsphere A is 200-250°C, and the peak foaming temperature is 230-265°C; the initial foaming temperature of the expandable microsphere B is 135-145°C.

[0017] In order to solve the comprehensive problems that the existing automotive interior parts made of polypropylene materials are difficult to maintain dimensional stability or high flatness after foaming in large and thick parts, resulting in shrinkage marks, high gloss, low roughness, and poor user experience, in the technical solution of the present invention, the inventors introduced two types of expandable microspheres with foaming starting and peak temperature gradient distributions into the polypropylene resin matrix. These two types of expandable microspheres will achieve different foaming ratios and foaming effects in the conventional 200-240°C injection molding temperature range during the same heating process. The expandable microsphere B with lower foaming temperature and peak temperature will achieve different foaming ratios and foaming effects after foaming. The size of expandable microspheres B is relatively large, which can provide a certain degree of roughness and deformation resistance for the product surface. However, due to the gaps between the expandable microspheres B, the surface after foaming is relatively rough, with obvious unevenness and poor flatness. For this reason, it is necessary to match it with expandable microspheres A, which have a smaller size after foaming. On the premise of achieving sufficient dimensional stability, the expandable microspheres A can be filled in the gaps of the expandable microspheres B, thereby improving the surface flatness of the product and avoiding shrinkage defects after foaming. On the other hand, if only expandable microspheres A are used alone, the product will also have shrinkage due to insufficient dimensional stability.

[0018] At the same time, in the system, in order to ensure the dispersibility and compatibility of the two expandable microspheres in the matrix resin, the product further introduces specific low-melting-point polypropylene and hyperbranched polyester as compounding ingredients to form a polypropylene composition, so as to avoid the inability to achieve the expected dimensional stability effect and surface roughness due to the compatibility and dispersion problems of the expandable microspheres. At the same time, these two components can also be dispersed on the surface during product injection molding, effectively regulating the surface gloss and roughness of the product to meet the use requirements of automotive interior parts. If the low-melting-point polypropylene or hyperbranched polyester is replaced with a dispersant or compatibilizer used in conventional polypropylene products, or other common hyperbranched polymer products such as hyperbranched polyamide, the same appearance and use effect may not be achieved, and the product surface may be too rough, and the use experience will also be poor.

[0019] Preferably, the thermoplastic polymer is a polymer obtained by reacting at least one of a nitrile monomer, an acrylate monomer, an amide monomer, and a carboxyl-containing reactive monomer having a polymerizable double bond.

[0020] Preferably, the nitrile monomer includes at least one of acrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaronitrile; the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, dicyclopentenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobornyl methacrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-phenoxypropyl acrylate; the carboxyl-containing active monomer having a polymerizable double bond includes at least one of an unsaturated monobasic acid and an unsaturated dibasic acid; the amide monomer includes at least one of acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, and N,N-dimethyl acrylamide;

[0021] More preferably, the unsaturated monoacid includes at least one of acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, and α-methylcinnamic acid; the unsaturated diacid includes at least one of maleic acid, itaconic acid, fumaric acid, and citraconic acid.

[0022] Preferably, the mass ratio of the nitrile monomer, the acrylate monomer, the amide monomer, and the carboxyl-containing reactive monomer having a polymerizable double bond is (50-100): (10-100): (1-50): (1-50).

[0023] Preferably, the expandable substance includes at least one of isobutane, isooctane, pentane and isopentane.

[0024] More preferably, the mass content of the expandable substance in the expandable microspheres is 10 to 45 wt %.

[0025] Further preferably, the expandable microspheres may be commercially available products, or may be prepared by themselves using the methods described in, for example, CN108912384B and CN113731310B. Those skilled in the art may make the selection according to actual needs.

[0026] Preferably, the expandable microsphere masterbatch comprises expandable microspheres A, expandable microspheres B and a matrix resin, the matrix resin comprises at least one of polypropylene resin and polyethylene resin, and the total mass content of expandable microspheres A and expandable microspheres B in the expandable microspheres is 40-60%.

[0027] More preferably, the base resin is polypropylene resin.

[0028] Further preferably, the expandable microspheres can be added in the form of masterbatch. Specifically, the expandable microsphere masterbatch is prepared according to the preparation method of polypropylene / expandable microsphere foaming masterbatch according to any one of claims 1 to 9 with reference to attachment CN117362893A, comprising the following steps:

[0029] Step S1: dissolving polypropylene in a solvent, and then adding an initiator and a silane coupling agent to prepare grafted polypropylene;

[0030] Step S2: adding expandable microspheres, nucleating agent, water generating agent, catalyst and surfactant to the solution in the above step S1, and stirring well;

[0031] Step S3: After the stirring of the solution in the above step S2 is completed, the flask is transferred to water at a certain temperature for quenching, and the stirring is continued to be uniform. The silane self-crosslinking PP / expandable microsphere composite is precipitated from the organic solution, filtered, and then washed with ethanol three times;

[0032] Step S4: Filter and wash the insoluble matter in the above step S3, place it in a 60°C to 80°C forced air oven and dry it for 2-4 hours to obtain polypropylene / expandable microsphere foaming masterbatch.

[0033] Those skilled in the art can also prepare expandable microsphere masterbatch according to other common masterbatch preparation methods, as long as the basic properties of the expandable microspheres in the masterbatch are not affected, which is not limited by the description of the present invention.

[0034] Preferably, the average particle size of the expandable microspheres A is 7 to 15 μm, and the average particle size of the expandable microspheres B is 10 to 25 μm.

[0035] More preferably, the average particle size of the expandable microspheres A is one of 7 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm or any two of the range values, and the average particle size of the expandable microspheres B is one of 10 μm, 12 μm, 14 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm or any two of the range values.

[0036] More preferably, the average particle size of the expandable microspheres A and the expandable microspheres B is directly confirmed by a two-dimensional microscope. At a magnification of 50 to 500 times, the expandable microspheres are distinguished as expandable microspheres A and expandable microspheres B according to their particle sizes under a microscope. Then, the magnification is 300 to 800 times according to the positioning. At a fixed magnification, mapping software is used to screen at least 100 expandable microspheres A and 100 expandable microspheres B in the same plane for particle size testing and finally the average value is statistically calculated, which is the average particle size of the two expandable microspheres.

[0037] Preferably, the weight proportion of the expandable microspheres A in the polypropylene composition is 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or any two of the range values; the weight proportion of the expandable microspheres B in the polypropylene composition is 0.1, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8 or 3 or any two of the range values.

[0038] More preferably, the mass ratio of the expandable microspheres A to the expandable microspheres B is (1-5):1.

[0039] The inventors have found through experiments that when the two expandable microspheres are compounded in the above ratio, the two can achieve better dispersion and filling after foaming and expansion. The product has moderate surface roughness and lower gloss without shrinkage.

[0040] Preferably, the polypropylene resin has a melting point of 150 to 170° C., and a melt flow rate of 10 to 35 g / 10 min at 230° C. and a load of 2.16 kg according to ISO 1133-2011.

[0041] Further preferably, the melt flow rate of the polypropylene resin at 230°C and 2.16 kg load is in the range of one or any two of 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 18 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, 32 g / 10 min, and 35 g / 10 min.

[0042] Preferably, the low melting point polypropylene has a melting point of 70 to 90° C., and a melt flow rate of 300 to 3000 g / 10 min at 230° C. and a load of 2.16 kg according to ISO 1133-2011.

[0043] Further preferably, the melt flow rate of the low melting point polypropylene at 230°C and a load of 2.16 kg is 300 g / 10min, 320 g / 10min, 350 g / 10min, 400 g / 10min, 800 g / 10min, 1000 g / 10min, 1200 g / 10min, 1500 g / 10min, 1800 g / 10min, 2000 g / 10min, 2200 g / 10min, 2400 g / 10min, 2600 g / 10min, 2800 g / 10min, 3000 g / 10min or any two of the range values.

[0044] Further preferably, the low melting point polypropylene has a melt flow rate of 340 to 2800 g / 10 min at 230° C. and a load of 2.16 kg.

[0045] Preferably, the melting points of the polypropylene resin and the low-melting-point polypropylene are tested by differential scanning calorimetry (DSC) according to Part 3 of GBT 19466.3-2004 Plastics Differential Scanning Calorimetry (DSC), with a heating rate of generally 10°C / min, a cooling rate of 10°C / min, a temperature range of 30 to 250°C, an N2 atmosphere, a flow rate of 50 mL / min, and the data of the second heating are taken.

[0046] The purpose of using low-melting-point polypropylene is not only to improve the dispersibility of expandable microspheres in polypropylene resin, thereby avoiding the problem of uneven surface of the product, but also the main purpose is that the introduction of this component can enhance the compatibility between the overall resin and the expandable microspheres, and will be distributed on the surface of the product after injection molding, effectively regulating the surface gloss and roughness of the product. If this component is not introduced, the product will not only have poor surface performance, but may even have problems with surface flatness, causing shrinkage marks.

[0047] More preferably, in the foamable polypropylene material, the total mass content of the polypropylene resin and the low-melting-point polypropylene is ≥ 80 wt%.

[0048] Preferably, the hyperbranched polyester comprises at least one of a carboxyl-terminated hyperbranched polyester and a hydroxyl-terminated hyperbranched polyester, and has a number average molecular weight of 800 to 6500 g / mol.

[0049] Preferably, the number average molecular weight of the hyperbranched polyester is 800 g / mol, 1200 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, 3500 g / mol, 4000 g / mol, 4500 g / mol, 5000 g / mol, 5500 g / mol, 6000 g / mol, 6500 g / mol or any two of the range values.

[0050] Preferably, the hyperbranched polyester has 5 to 25 carboxyl groups and / or hydroxyl groups per mole.

[0051] More preferably, the number of carboxyl groups and / or hydroxyl groups per unit mole of the hyperbranched polyester is in the range of 5, 8, 10, 12, 15, 18, 20, 22, 25 or any two of them.

[0052] More preferably, the hyperbranched polyester is a hydroxyl-terminated hyperbranched polyester.

[0053] Hyperbranched polyesters of different groups have a certain influence on the foaming effect of expandable microspheres, and also have a certain influence on the compatibility of the expandable microspheres after foaming in the resin system. When the hyperbranched polyester is preferably of the above type, the comprehensive performance of the product is better.

[0054] Preferably, the polypropylene composition further comprises 0.1 to 0.3 parts of a coupling agent.

[0055] More preferably, the coupling agent includes at least one of a vinyl silane coupling agent, an amino silane coupling agent, a methacryloxy silane coupling agent, a titanate coupling agent, and an aluminum-titanium composite silane coupling agent.

[0056] The foamable polypropylene material of the present invention can effectively improve the dimensional stability of the product by using expandable microspheres as solid fillers. On this basis, those skilled in the art can further add a certain amount of coupling agent into the polypropylene composition to improve the relative stability of the expandable microspheres and further inhibit the shrinkage creep of the polypropylene resin.

[0057] Preferably, the polypropylene composition, in addition to the coupling agent described above, may also include 0.1 to 1 part of other processing aids, including but not limited to at least one of an antioxidant, an antistatic agent, and a release agent.

[0058] Based on the actual needs of the product, technicians in this field can appropriately introduce some components commonly introduced into polypropylene products without affecting the product performance, such as antioxidants to improve the product's conventional oxidation resistance, release agents to improve the product's demolding performance, etc.

[0059] More preferably, the polypropylene composition comprises 0.1 to 0.2 parts of antioxidant.

[0060] More preferably, the antioxidant includes at least one of a hindered phenol antioxidant, a phosphite antioxidant, and a hindered amine antioxidant.

[0061] More preferably, the antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant, and the mass ratio of the two is 1:(0.8-1.2).

[0062] Another object of the present invention is to provide a method for preparing the foamable polypropylene material, comprising the following steps:

[0063] The raw material components of the polypropylene composition are added into a screw extruder for melt extrusion and granulation to obtain a polypropylene composition, and then the polypropylene composition is mixed with expandable microspheres and / or expandable microsphere masterbatch to obtain the foamable polypropylene material.

[0064] It should be noted that in the technical solution of the present invention, the polypropylene composition and the expandable microspheres and / or expandable microsphere masterbatch are mixed by physical mixing, such as but not limited to mixing with a mixer, mixing with a homogenizer, etc. As long as the normally expected mixing effect is achieved, the mixing method is not specifically limited.

[0065] Preferably, the heating temperature of the screw extruder is 100-220° C., and the screw speed is 350-450 rpm.

[0066] The preparation method of the foamable polypropylene mixture of the present invention is simple, has low requirements on equipment, and can realize industrial-scale production.

[0067] Another object of the present invention is to provide application of the foamable polypropylene material in the preparation of automotive interior parts.

[0068] More preferably, the automobile interior parts include an instrument panel and a sub-instrument panel.

[0069] Another object of the present invention is to provide a polypropylene product, which is obtained by injection molding a material including the foamable polypropylene material of the present invention.

[0070] Preferably, the injection molding is carried out using a single screw extruder, and the temperature zones of the single screw extruder are set as: feeding zone 40-60°C, zone one 200-210°C, zone two 200-210°C, zone three 230-240°C, zone four 230-240°C, zone five 235-240°C.

[0071] The foamable polypropylene material of the present invention is based on the mutual cooperation of three key components, namely, expandable microspheres, low-melting-point polypropylene and hyperbranched polyester. It not only has ideal dimensional stability after injection molding, but also has a good appearance without forming shrinkage marks, and has moderate surface roughness and low glossiness. The automotive interior parts prepared by the foamable polypropylene material not only have a good user experience, do not need to add additional accessories, and will not affect the driver's normal driving, but also have a good appearance, refined and beautiful appearance, and high comprehensive cost performance.

[0072] It should be noted that the foamable polypropylene material of the present invention can be packaged as a single component or as multiple components, such as two or three components. When it is packaged as multiple components, the polypropylene composition is packaged as one component, and the expandable microspheres A and expandable microspheres B are packaged as one or two components. There is no absolute restriction on the form and order of packaging and use.

[0073] The beneficial effect of the present invention is that the present invention provides a foamable polypropylene material, which improves the dimensional stability of the product by introducing two expandable microspheres with different foaming property parameters into a polypropylene resin matrix, and simultaneously introduces a low-melting-point polypropylene resin and a hyperbranched polyester into the polypropylene matrix resin to work together to achieve high dispersibility and compatibility between components. The product will not have a shrinkage phenomenon, has low gloss, and has a moderate surface roughness, so that it is more in line with the use requirements of decorative parts inside automobiles. DETAILED DESCRIPTION

[0074] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention, unless otherwise specified, are all commonly used common reagents and instruments.

[0075] Examples 1 to 14

[0076] The embodiments of the foamable polypropylene material and the preparation method and application thereof of the present invention, the components of the foamable polypropylene material are shown in Table 2.

[0077] The preparation method of the foamable polypropylene material comprises the following steps:

[0078] Add the raw material components of the polypropylene composition according to the formula in Table 1 into the main feeding system of the screw extruder for melt extrusion and granulation to obtain a polypropylene composition. When the components are melt extruded, the temperature zones of the screw extruder are set to 120° C. for zone 1, 220° C. for zone 2, 220° C. for zone 3, 210° C. for zone 4, 210° C. for zone 5, 210° C. for zone 6, 210° C. for zone 7, 210° C. for zone 8, 210° C. for zone 9, and 210° C. for zone 10, the screw speed is 400 rpm, and the screw aspect ratio is 40:1;

[0079] Then, the polypropylene composition and the expandable microspheres are mixed evenly by a mixer to obtain the foamable polypropylene material.

[0080] Comparative Examples 1 to 12

[0081] The difference between the comparative examples and the embodiments is only in the types and proportions of components, as shown in Tables 3-4.

[0082] Among the components described in each embodiment and comparative example,

[0083] Polypropylene resin 1 is PP HP500N produced by Daqing Refinery of PetroChina, with a melting point of 167.2°C and a melt flow rate of 12 g / 10 min at 230°C and a load of 2.16 kg;

[0084] Polypropylene resin 2 is PP EP548R produced by Shell, with a melting point of 165.3°C and a melt flow rate of 25 g / 10 min at 230°C and a load of 2.16 kg;

[0085] Expandable microsphere B1 is DU608M produced by Xineng Chemical Industry, with an average particle size of 22 μm, an initial foaming temperature of 135-145°C, and a foaming peak temperature of 195-205°C;

[0086] Expandable microsphere B2 is DU608S produced by Xineng Chemical Industry, with an average particle size of 12 μm, an initial foaming temperature of 135-145°C, and a foaming peak temperature of 195-205°C;

[0087] Expandable microsphere A1 is DU240 produced by Xineng Chemical, with an average particle size of 13 μm, an initial foaming temperature of 205-215°C, and a foaming peak temperature of 230-240°C;

[0088] The expandable microsphere A2 is DU260 produced by Xineng Chemical, with an average particle size of 8 μm, an initial foaming temperature of 200-250°C, and a foaming peak temperature of 255-265°C;

[0089] Expandable microsphere A3 is WU152-M produced by Xineng Chemical Industry, with an average particle size of 18 μm, an initial foaming temperature of 92-97°C, and a foaming peak temperature of 148-155°C;

[0090] Expandable microsphere B3 is DU180 produced by Xineng Chemical Industry, with an average particle size of 32 μm, an initial foaming temperature of 135-145°C, and a foaming peak temperature of 185-195°C;

[0091] Expandable microsphere B4 is DU175-M produced by Xineng Chemical Industry, with an average particle size of 22 μm, an initial foaming temperature of 132-142°C, and a foaming peak temperature of 180-190°C;

[0092] The low melting point polypropylene 1 is S400 produced by Idemitsu of Japan, with a melting point of 80°C and a melt flow rate of 2600 g / 10 min at 230°C and a load of 2.16 kg;

[0093] The low melting point polypropylene 2 is S600 produced by Idemitsu of Japan, with a melting point of 80°C and a melt flow rate of 390 g / 10 min at 230°C and a load of 2.16 kg;

[0094] Compatibilizer 1 is PC-1 produced by Foshan Bochen, maleic anhydride grafted polypropylene, with a grafting rate of 0.85%;

[0095] Compatibilizer 2 is MA8510 produced by Mitsui Chemicals, maleic anhydride grafted POE, with a grafting rate of 1%;

[0096] The lubricant is erucamide produced by Croda Xipu Chemical;

[0097] Hyperbranched polyester 1 is HyPer H202 produced by Wuhan Hyperbranching, a hydroxyl-terminated hyperbranched polyester with a number average molecular weight of 1200 g / mol and a hydroxyl number per unit mole of 11 / mol;

[0098] The hyperbranched polyester 2 is HyPer H302 produced by Wuhan Hyperbranching, a hydroxyl-terminated hyperbranched polyester with a number average molecular weight of 2500 g / mol;

[0099] The hyperbranched polyester 3 is HyPer C302 produced by Wuhan Hyperbranching, a carboxyl-terminated hyperbranched polyester with a number average molecular weight of 2800 g / mol;

[0100] The hyperbranched polyester 4 is HyPer C102 produced by Wuhan Hyperbranching, a carboxyl-terminated hyperbranched polyester with a number average molecular weight of 2600 g / mol;

[0101] The hyperbranched polyamide is HPN202 produced by Wuhan Hyperbranching, a hydroxyl-terminated hyperbranched polyamide with a number average molecular weight of 2700 g / mol;

[0102] Coupling agent 1 is JH-A110 produced by Hubei Jianghan New Materials, an aminosilane coupling agent;

[0103] Coupling agent 2 is SG-SI 172 produced by Nanjing Shuguang Silane Chemical, a vinyl silane coupling agent;

[0104] The antioxidant is a composite of a commercially available hindered phenol antioxidant and a commercially available phosphite antioxidant: antioxidant 168 and antioxidant 1010 mixed in a mass ratio of 1:1.

[0105] Unless otherwise specified, the components and raw materials used in the embodiments and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0106] Table 1

[0107]

[0108] Table 2

[0109]

[0110]

[0111] Table 3

[0112]

[0113] Table 4

[0114]

[0115] In order to verify the performance of the polypropylene composition of the present invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests, and the specific steps are as follows:

[0116] (1) Gloss test: The foamable polypropylene material was injection molded into a 60*100*2 mm square plate using a single screw extruder for testing, and then the 60° angle test data was tested and counted according to the standard GB / T 8807-1988;

[0117] (2) Surface roughness: The foamable polypropylene material was injection molded into a 60*100*2 mm square plate using a single screw extruder for testing. The profile was tested using a profilometer to calculate the average arithmetic deviation Ra of the profile.

[0118] (3) Appearance test: The foamable polypropylene material was injection molded into a 12.7×3.2×6 mm square plate using a single screw extruder. The surface of the square plate was then observed using a two-dimensional observation method to see if there was a sink mark. If so, the maximum length of the sink mark was measured and recorded.

[0119] The injection temperature of the single screw extruder is set as follows: feeding zone: 50°C, zone 1: 200°C, zone 2: 210°C, zone 3: 230°C, zone 4: 240°C, zone 5: 240°C.

[0120] The test results are shown in Tables 5 and 6.

[0121] Table 5

[0122]

[0123] Table 6

[0124]

[0125] It can be seen from Table 3 and Table 4 that the foamable polypropylene material of the present invention has good use effect and appearance decoration effect after injection molding, the glossiness of the product can be maintained below 72%, the roughness can be maintained above 0.55 μm and below 1 μm, and no shrinkage marks occur in the products. Compared with the unmodified comparative example 9 product, the glossiness is significantly reduced, the roughness is increased to a moderate range, and the use performance is greatly improved.

[0126] The reason why the product can achieve the above-mentioned ideal technical effect is mainly due to the combination of two expandable microspheres. If only one of the expandable microspheres is used, as shown in Comparative Examples 1 and 2, although due to the properties of a single microsphere, the dispersion of the overall component is higher than that of the embodiment, the surface roughness of the product is higher and the glossiness is lower, but due to the lack of the combination of two expandable microspheres, the dimensional stability and the surface flatness of the product after foaming cannot be taken into account, so the product has a shrinkage phenomenon. At the same time, the expandable microspheres in the product described in this scheme are distributed in a gradient distribution based on a specific interval of the foaming start and peak temperature, and have a special foaming ratio and foaming effect. If the foaming start and peak temperature are adjusted at will, as shown in Comparative Examples 3 and 4 and Comparative Example 12, the two choose to introduce the foaming start or peak temperature, which does not meet the requirements. The expandable microspheres are matched, regardless of whether the size is similar, although the product also has a gradient effect during foaming, but similar to Comparative Examples 1 and 2, the product still has obvious shrinkage phenomenon, indicating that it is not possible to achieve the effect of the embodiment product by any combination of expandable microspheres. In addition to expandable microspheres, the compatibility and dispersion of the compounded low-melting-point polypropylene and hyperbranched polyester are equally important. As shown in Comparative Examples 5 and 6 and Comparative Example 10, if low-melting-point polypropylene is not introduced, or conventional compatibilizers are used instead, the compatibility and dispersion of the components in the product cannot reach the expected state, and the product will still have shrinkage marks. In Comparative Examples 7 and 8 and Comparative Example 11, hyperbranched polyester is not introduced or conventional lubricants or hyperbranched polyamides with similar hyperbranched structures are used as substitutes. Although the surface of the obtained product does not show shrinkage marks, the roughness of the product reaches more than 1 μm. At this time, the surface roughness of the product increases sharply, and the driver's experience will be greatly reduced when used as a car interior.

[0127] According to the performance comparison of the products obtained in Examples 1 and 8 to 10, it can be seen that when the terminal hydroxyl hyperbranched polyester is selected as the compounding component, the obtained product has better performance in use; while the matching ratios of the two expandable microspheres in the products of Examples 1 and 11 to 14 are different, and the performance of the products is also different. When the mass ratio of the two is preferably in the range of (1 to 5): 1, the surface roughness of the obtained product is further improved within a moderate range and the glossiness is lower. However, it should be noted that in the technical solution of this application, the performance of the products obtained in Examples 11 to 14 is still significantly better than that of the comparative examples and existing products.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A foamable polypropylene material, characterized in that: The composition comprises the following components in parts by weight: 100 parts of polypropylene composition, 0.1 to 8 parts of expandable microspheres and / or expandable microsphere masterbatch; The polypropylene composition comprises 90-97 parts of polypropylene resin, 2-10 parts of low melting point polypropylene, and 0.1-0.5 parts of hyperbranched polyester; The expandable microspheres and / or expandable microsphere masterbatch include expandable microspheres A and expandable microspheres B; the initial foaming temperature of the expandable microspheres A is ≥190°C; The initial foaming temperature of the expandable microspheres B is ≥125°C, and the peak foaming temperature is 195-205°C; The initial foaming temperature of the expandable microsphere B is less than the initial foaming temperature of the expandable microsphere A; The melting point of the low melting point polypropylene is ≤90°C.

2. The foamable polypropylene material according to claim 1, characterized in that: The expandable microsphere masterbatch comprises expandable microspheres A, expandable microspheres B and a matrix resin, and the matrix resin comprises at least one of a polypropylene resin and a polyethylene resin.

3. The foamable polypropylene material according to claim 1, characterized in that: The expandable microspheres include an outer shell and an inner core, wherein the outer shell includes a thermoplastic polymer and the inner core includes an expandable substance.

4. The foamable polypropylene material according to claim 3, characterized in that: The thermoplastic polymer is a polymer obtained by reacting at least one of a nitrile monomer, an acrylate monomer, an amide monomer, and a carboxyl-containing active monomer having a polymerizable double bond; preferably, the initial foaming temperature of the expandable microsphere A is 200-250°C, and the peak foaming temperature is 230-265°C; the initial foaming temperature of the expandable microsphere B is 135-145°C.

5. The foamable polypropylene material according to claim 1, characterized in that: The melting point of the polypropylene resin is 150-170°C, and the melt flow rate at 230°C and 2.16kg load is 10-35g / 10min, and / or the melting point of the low-melting-point polypropylene is 70-90°C, and the melt flow rate at 230°C and 2.16kg load is 300-3000g / 10min.

6. The foamable polypropylene material according to claim 1, characterized in that: The hyperbranched polyester comprises at least one of a carboxyl-terminated hyperbranched polyester and a hydroxyl-terminated hyperbranched polyester, and has a number average molecular weight of 800 to 6500 g / mol.

7. The foamable polypropylene material according to claim 1, characterized in that: The polypropylene composition further includes 0.1 to 0.3 parts of a coupling agent; preferably, the coupling agent includes at least one of a vinyl silane coupling agent, an amino silane coupling agent, a methacryloxy silane coupling agent, a titanate coupling agent, and an aluminum-titanium composite silane coupling agent.

8. The method for preparing the foamable polypropylene material according to any one of claims 1 to 7, characterized in that: The following steps are involved: The raw material components of the polypropylene composition are added into a screw extruder for melt extrusion and granulation to obtain a polypropylene composition, and then the polypropylene composition is mixed with expandable microspheres and / or expandable microsphere masterbatch to obtain a foamable polypropylene material.

9. Use of the foamable polypropylene material according to any one of claims 1 to 7 in the preparation of automotive interior parts; preferably, the automotive interior parts include instrument panels and sub-instrument panels.

10. A polypropylene product, characterized in that: The foamable polypropylene material is obtained by injection molding.

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