Carbon nanotube modified polypropylene composite material and preparation method and application thereof

Abstract

The present application relates to the technical field of composite materials, and in particular to a carbon nanotube-modified polypropylene composite material, and its preparation method and application. The carbon nanotube-modified polypropylene composite material of the present application includes polypropylene, carbon nanotube masterbatch, filler, toughening agent, compatibilizer, and may also include antioxidant. The polypropylene includes three types of melt index polypropylene. By compounding and enhancing with carbon nanotube masterbatch and other components, the composite material of the present application has both strength and toughness, shock resistance and compression resistance, uniform conductivity, good electrostatic dissipation, high cleanliness, and good processing performance. The preparation method is to mix the components. The carbon nanotube-modified polypropylene composite material of the present application can be widely used in semiconductor packaging and electromagnetic wave shielding devices.

Description

Technical Field

[0001] The present application belongs to the technical field of composite materials, and in particular relates to a carbon nanotube-modified polypropylene composite material and a preparation method and application thereof. Background Art

[0002] Polypropylene, abbreviated as PP, is a thermoplastic lightweight general-purpose plastic. In the prior art, it can be compounded with conductive materials to obtain conductive plastics, which can be used in semiconductor device packaging, electromagnetic wave shielding and other fields. For example, the key dimensions of wafers or semiconductor chips are small, the patterns are dense, and the precision is high, so they cannot absorb dust and dirt during production and transportation to affect product quality; there are corresponding requirements for the mechanical properties of the packaging, such as shock resistance and pressure resistance; and in addition, wafers or semiconductor chips are electrostatically sensitive devices, which will generate friction with the plastic box during transportation and placement, and will generate charges during contact and separation. In order to avoid damage from static electricity and electromagnetic waves, polypropylene conductive plastics are often used to make anti-static packaging. The amount of charge generated during contact and separation is small, and it also has electrostatic dissipation characteristics, so that the generated charge is released in time, thereby protecting electrostatic sensitive devices.

[0003] Conductive agents used to modify polypropylene in the prior art include: conductive carbon black, carbon fiber, graphene, conductive graphite and carbon nanotubes, etc. The most widely used is the modified composite material of polypropylene plus carbon black, but such conductive composite materials will affect the physical properties of the material due to the high amount of carbon black added, and the cleanliness of the polypropylene composite material modified by the carbon black conductive agent is very poor. Although the use of carbon nanotubes as conductive agents can obtain highly clean conductive plastics, since carbon nanotubes are easy to agglomerate and have poor dispersibility, if the dispersion is uneven, the content of the conductive agent in the conductive plastic will be uneven, thereby affecting the uniformity of conductivity and the electrostatic dissipation characteristics.

[0004] However, further research found that the addition of carbon nanotubes during the preparation process would lead to poor fluidity and processing performance of the composite material. Especially when the carbon nanotubes are evenly dispersed, although they can improve the uniformity of conductivity and electrostatic dissipation properties, they also have negative effects, such as making the fluidity and processing performance of the composite material worse than when the carbon nanotubes are non-uniformly dispersed, thus affecting the application of the composite material. Summary of the invention

[0005] The purpose of the present application is to provide a carbon nanotube modified polypropylene composite material and its preparation method and application, aiming to solve the problem of poor processing performance of the composite material prepared by using carbon nanotube modified polypropylene in the prior art due to the uniform dispersion of carbon nanotubes.

[0006] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present application provides a carbon nanotube-modified polypropylene composite material, comprising the following components in parts by weight:

[0008]

[0009] The polypropylene includes a first polypropylene, a second polypropylene and a third polypropylene. The first polypropylene has a melt index of 1 to 5 g / 10 min, the second polypropylene has a melt index of 20 to 35 g / 10 min, and the third polypropylene has a melt index of 90 to 110 g / 10 min.

[0010] The carbon nanotube-modified polypropylene composite material of the present application is compounded with three polypropylenes with different melt indices and carbon nanotube masterbatches, and the components have a synergistic effect, so that the carbon nanotubes contained in the composite material can be evenly dispersed, giving the carbon nanotube-modified polypropylene composite material of the present application good conductive uniformity, electrostatic dissipation characteristics, strength and toughness, shock resistance and compression resistance, high cleanliness, and also has processing properties including good fluidity.

[0011] In a second aspect, the present application provides a method for preparing a carbon nanotube-modified polypropylene composite material, comprising the following steps:

[0012] The components contained in the carbon nanotube-modified polypropylene composite material of the above application are mixed and then subjected to a first kneading process.

[0013] The preparation method of carbon nanotube modified polypropylene composite material of the present application is to mix three kinds of polypropylene with different melt indexes with carbon nanotube masterbatch and other material components, and then perform a mixing process. On the basis of uniformly dispersing the carbon nanotubes, the raw material components can play a synergistic role under the action of the mixing process, and the prepared carbon nanotube modified polypropylene composite material has good uniform conductivity, good electrostatic dissipation, good strength and toughness, shock resistance and high cleanliness, and at the same time has processing properties including good fluidity. Moreover, the preparation method of carbon nanotube modified polypropylene composite material of the present application is process controllable, and the properties of the prepared composite material are stable.

[0014] In a third aspect, the present application provides applications of carbon nanotube-modified polypropylene composite materials in semiconductor packaging and electromagnetic wave shielding devices.

[0015] The carbon nanotube-modified polypropylene composite material of the present application is applied to semiconductor packaging, especially when it is made into packaging for precision semiconductor chips, such as wafer boxes. These packages have the characteristics of excellent strength and toughness, shock resistance and compression resistance, uniform conductivity, rapid static dissipation, high cleanliness, good processing performance, etc., and can protect semiconductor devices from impact, static electricity, dust, etc. during production, storage, and transportation. It can also be used as an absorbing material to make electromagnetic wave shielding devices, perform electromagnetic dissipation, and shield electromagnetic waves of certain bands. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0017] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0018] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0019] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0020] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0021] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass in the embodiment description of the present application can be μg, mg, g, kg and other mass units known in the chemical industry.

[0022] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0023] The first aspect of the embodiment of the present application provides a carbon nanotube-modified polypropylene composite material, comprising the following components in parts by weight:

[0024]

[0025]

[0026] The polypropylene includes a first polypropylene, a second polypropylene and a third polypropylene, the first polypropylene has a melt index of 1 to 5 g / 10 min, the second polypropylene has a melt index of 20 to 35 g / 10 min, and the third polypropylene has a melt index of 90 to 110 g / 10 min.

[0027] Melt index, also known as melt flow rate, is an indicator used to reflect the flow performance of the material in a molten state. The inventor has studied:

[0028] ① The carbon nanotube-modified polypropylene composite material (hereinafter referred to as the composite material) of the embodiment of the present application can effectively improve the fluidity and processing performance of the carbon nanotube-modified polypropylene composite material by compounding and enhancing the synergy of three polypropylenes with different melt indices, on the basis of ensuring that the composite material has excellent strength and toughness, sufficient shock and compression resistance, and sufficient dispersion of the carbon nanotube masterbatch. The three polypropylenes can have different melt indices due to different molecular weights, or different polymerization methods and different blocks. In the exemplary example, the melt index of the first polypropylene can include but is not limited to 1g / 10min, 3g / 10min, 5g / 10min; the melt index of the second polypropylene can include but is not limited to 20g / 10min, 30g / 10min, 35g / 10min; the melt index of the third polypropylene can include but is not limited to 90g / 10min, 100g / 10min, 110g / 10min.

[0029] ② In the embodiment of the present application, the conductive material is the carbon nanotube contained in the carbon nanotube masterbatch, which can improve the cleanliness of the composite material compared with conductive materials such as conductive carbon black. The carbon nanotube masterbatch is used as a component of the carbon nanotube-modified polypropylene composite material, unlike the prior art where only carbon nanotubes are compounded with other components, so that the carbon nanotube masterbatch has good dispersion in the carbon nanotube-modified polypropylene composite material, and improves the conductive uniformity and electrostatic dissipation effect of the material; in addition, it also avoids the high-strength carbon nanotubes contained in the carbon nanotube masterbatch from directly contacting and interacting with the polypropylene molecules over a large area, and improves the processing properties such as fluidity of the carbon nanotube-modified polypropylene composite material.

[0030] ③ The selection of different types of fillers can increase the strength or toughness of the composite material or reduce the cost; toughening agents can improve the toughness of the composite material; compatibilizers can improve the compatibility of organic and inorganic materials in the composite material, which is more conducive to uniform mixing, so as to enhance the synergistic effect of the mixed compounding of various materials; antioxidants enhance the antioxidant effect of the composite material, making the composite material suitable for long-term exposure in the air.

[0031] In some embodiments, the first polypropylene may include random copolymer polypropylene, which has low tensile yield strength and rigidity, fair impact strength and toughness, and relatively balanced comprehensive properties, and can be prepared into a low melt index as the first polypropylene.

[0032] In some embodiments, the second polypropylene may include block copolymer polypropylene. Block copolymer polypropylene has balanced rigidity and toughness and high impact strength, and can be used to prepare a moderate melt index as the second polypropylene, and fully balance various properties in the composite material.

[0033] In some embodiments, the third polypropylene may include the first homopolypropylene. Homopolypropylene has high rigidity, but poor impact strength and toughness. The melt index of homopolypropylene can be very high, and it can be used as the third polypropylene to fully improve fluidity and processing performance during processing.

[0034] In some embodiments, the mass ratio of the first polypropylene, the second polypropylene and the third polypropylene can be 1:2-3:5-8. After a thorough study of the properties of the three melt index polypropylenes, the inventors found that the three polypropylenes in these mass ratios were compounded to improve the processing performance of the carbon nanotube-modified polypropylene composite material in the embodiment of the present application, and the toughness, strength, shock resistance, compression resistance, electrical conductivity uniformity, and electrostatic dissipation of the material can achieve relatively good and balanced effects. In the exemplary examples, the mass ratio can include but is not limited to 1: (2 or 3): (5 or 6 or 7 or 8).

[0035] In an exemplary embodiment, the weight proportion of polypropylene contained in the carbon nanotube-modified polypropylene composite material of the embodiment of the present application may include but is not limited to 50 parts, 60 parts, and 70 parts.

[0036] In some embodiments, the carbon nanotube masterbatch may include carbon nanotubes, carboxymethyl cellulose, epoxy resin and a second homopolypropylene, and the weight ratio of the carbon nanotubes, carboxymethyl cellulose, epoxy resin and the second homopolypropylene may be (10-20): (1-3): (3-16): (10-40).

[0037] The inventors have studied that the carbon nanotube masterbatch containing carboxymethyl cellulose (hereinafter referred to as CMC), epoxy resin, carbon nanotubes and the second homopolypropylene can have better compatibility with the components of the carbon nanotube-modified polypropylene composite material of the embodiment of the present application, can be better dispersed in the composite material, make the conductivity uniform, and have good electrostatic dissipation, while reducing the influence of direct use of carbon nanotubes on the processing performance of the composite material. In the exemplary embodiment of the carbon nanotube masterbatch, the weight ratio of carbon nanotubes, carboxymethyl cellulose, epoxy resin and the second homopolypropylene can be (10 or 15 or 18 or 20): (1 or 2 or 3): (3 or 5 or 10 or 13 or 16): (10 or 20 or 30 or 40).

[0038] In some embodiments, the particle size of the carbon nanotube masterbatch can be 0.8-1.5 mm to better disperse and be compatible in the composite material. In the exemplary embodiment, the particle size can include but is not limited to 0.8 mm, 1.0 mm, 1.2 mm, and 1.5 mm. The smaller the particle size of the carbon nanotube masterbatch, the denser the mixture obtained, but the particles are more likely to adsorb and agglomerate with each other, which is not conducive to dispersion. The carbon nanotube masterbatch with the above particle size specifications has better processing and dispersion performance.

[0039] In some embodiments, the carbon nanotubes may include multi-walled carbon nanotubes. In some embodiments, the diameter of the carbon nanotubes may be 5 to 30 nm. In some embodiments, the length of the carbon nanotubes may be 1 to 100 μm. In some embodiments, the specific surface area of ​​the carbon nanotubes may be 150 to 400 m 2 / g. After research, the inventors selected the masterbatch made of these types and parameters of carbon nanotubes and applied it to the carbon nanotube-modified polypropylene composite material in the embodiment of the present application. It has better dispersibility and makes the conductivity of the composite material more uniform; and it has a corresponding improvement in the mechanical properties of the composite material while having little effect on the processing performance. In the exemplary embodiment, the diameter of the carbon nanotube can include but is not limited to 5nm, 15nm, 30nm; the tube length can include but is not limited to 1μm, 25μm, 50μm, 75μm, 100μm; the specific surface area can include but is not limited to 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g, 400m 2 / g.

[0040] In some embodiments, the second homopolypropylene may be in granular form, and the particle size may be 0.2 to 0.5 mm. When preparing the masterbatch, the second homopolypropylene and carbon nanotube particles of these particle sizes have similar volumes and masses, and can be better mixed with the carbon nanotubes to improve the dispersion of the carbon nanotubes in the masterbatch and the improvement of the properties of the composite material by the masterbatch. In the exemplary embodiment, the particle size of the second homopolypropylene may include but is not limited to 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm.

[0041] In an exemplary embodiment, the weight proportion of the carbon nanotube masterbatch contained in the carbon nanotube-modified polypropylene composite material of the embodiment of the present application may include but is not limited to 10 parts, 15 parts, and 20 parts.

[0042] In some embodiments, the fineness of the filler can be 50 to 10,000 mesh. The filler can include at least one of silicon dioxide, calcium carbonate, barium sulfate, talc, wollastonite, kaolin, mica powder, and montmorillonite. The selection of these fillers can improve the strength of the composite material and reduce the cost. At a certain fineness, it can be better mixed with the organic components in the composite material. In the exemplary embodiment, the fineness can include but is not limited to 50 mesh, 500 mesh, 1000 mesh, 5000 mesh, and 10,000 mesh. In the exemplary embodiment, the weight of the filler contained in the carbon nanotube-modified polypropylene composite material of the embodiment of the present application can include but is not limited to 10 parts, 15 parts, and 20 parts.

[0043] In some embodiments, the toughening agent includes at least one of vinyl elastomer, propylene elastomer, EPDM rubber, acrylonitrile-styrene-butadiene copolymer, and hydrogenated acrylonitrile-styrene-butadiene elastomer. The use of these toughening agents can further improve the toughness of the composite material, avoiding the low toughness of the composite material due to, for example, too high a content of the third polypropylene in the component. In the exemplary examples, the weight parts of the toughening agent contained in the carbon nanotube-modified polypropylene composite material of the embodiment of the present application can include but are not limited to 2 parts, 4 parts, 6 parts, and 8 parts.

[0044] In some embodiments, the compatibilizer includes at least one of a silane coupling agent, a titanate coupling agent, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene. The use of these compatibilizers can improve the compatibility of organic materials and inorganic materials in the composite material, and is more conducive to the uniform mixing of the components in the composite material. In the exemplary embodiment, the weight portion of the compatibilizer contained in the carbon nanotube-modified polypropylene composite material of the embodiment of the present application can include but is not limited to 0.5 parts, 1 part, and 2 parts.

[0045] In some embodiments, the antioxidant comprises at least one of 1010, 168, 1076, 1330, 1035, 3144, 1024, 126, B215, and B561. 1010 is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 168 is tris[2,4-di-tert-butylphenyl] phosphite, 1076 is β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1330 is 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and 1035 is 2,2'-thio Bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 3144 is 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, 1024 is N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, 126 is bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, B215 and B561 are antioxidants from BASF. In the exemplary embodiment, the antioxidant weight parts contained in the carbon nanotube-modified polypropylene composite material of the present application embodiment may include but are not limited to 0, 0.5 parts, and 1 part.

[0046] A second aspect of the present application provides a method for preparing a carbon nanotube-modified polypropylene composite material, comprising the following steps:

[0047] S01: mixing the components contained in the carbon nanotube-modified polypropylene composite materials of the above embodiments to obtain a mixture;

[0048] S02: subjecting the mixture to a first kneading process.

[0049] The preparation method of the embodiment of the present application is to mix three polypropylenes with different melt indexes with carbon nanotube masterbatch, filler, toughening agent and other material components, and then perform a mixing process. On the basis of uniformly dispersing the carbon nanotubes, the raw material components can play a synergistic role under the action of the mixing process, giving the prepared carbon nanotube-modified polypropylene composite material good uniformity of conductivity, good electrostatic dissipation, good strength and toughness, shock resistance and high cleanliness, and at the same time having processing properties including good fluidity, which greatly improves the production capacity under the same working conditions, and the prepared composite material is easier to be used in practice. Moreover, the preparation method of the carbon nanotube-modified polypropylene composite material of the present application is process-controllable, and the properties of the prepared composite material are stable.

[0050] Step S01:

[0051] The mixing process in step S01 can be to mix and stir the components. After research, the inventors found that the three types of polypropylenes can be mixed and set aside; after the toughening agent and the compatibilizer are mixed (for example, stirred at 200-400rpm for 5-10min), the filler is added thereto, and the mixture is continued to be mixed (for example, continued to be stirred at 200-400rpm for 10min) and set aside; the carbon nanotube masterbatch is mixed again with the first two mixed standby slurries, and an antioxidant can also be added as appropriate. The mixture obtained by this mixing method has a good dispersion effect, which is conducive to the compatibility of the components and the improvement of the various properties of the composite material.

[0052] In addition, the carbon nanotube masterbatch in step S01 can be commercially available, or can be prepared according to the following steps:

[0053] S011: oxidizing the carbon nanotubes;

[0054] S012: acidifying the oxidized carbon nanotubes;

[0055] S013: performing a first mixing treatment on the acidified carbon nanotubes and the CMC solution to obtain a first mixture;

[0056] S014: performing a second mixing process on the first mixture and the epoxy resin solution to obtain a second mixture;

[0057] S015: performing a third mixing process on the second mixture and the second homopolypropylene to obtain a third mixture;

[0058] S016: Drying the third mixture, and then performing a second kneading process.

[0059] Step S011: The oxidation treatment may be carried out under aerobic conditions at 500° C. for 20 minutes. Such treatment can remove impurities from the carbon nanotubes, especially other carbon materials remaining in the carbon nanotubes.

[0060] Step S012: Before the acidification treatment, the carbon nanotubes may be ultrasonically treated for 30 minutes to 1 hour to better disperse them. The acidification treatment may be carried out using a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1. The time may be 3 hours. This can further remove impurities, mainly to remove residual industrial catalysts in the carbon nanotubes, etc., and generate carboxyl and hydroxyl groups on the surface of the carbon nanotubes, which are easy to process later and compound with other components for synergy enhancement, thereby obtaining high-purity and high-cleanliness carbon nanotubes, and improving the dispersibility of the carbon nanotubes, so that the various properties and cleanliness of the finally obtained carbon nanotube-modified polypropylene composite material are further improved.

[0061] Step S013 to Step S014: The inventors have found through research that low-viscosity CMC solution and epoxy resin solution have good compatibility and have good wetting and dispersion effects on carbon nanotubes. They can be mixed together or divided into two steps for mixing and dispersion. In step S013, the viscosity of the CMC solution at 25°C is preferably 1000-1500 mPa·S, and then the impurity-removed carbon nanotubes are added. The first mixing treatment can be carried out in a high-speed disperser with a rotor speed of 800-1200 r / min, and high-speed shear dispersion is carried out for 15-30 minutes to obtain a first mixture, wherein the carbon nanotube content is preferably controlled at 10-20wt%; in step S014, the epoxy resin solution can be an ethanol solution of epoxy resin, and the volume ratio of epoxy resin to ethanol can be 1:5-10, and the viscosity of the epoxy resin solution at 25°C is preferably 1000-2000 mPa·S, and then the first mixture and the epoxy resin solution are subjected to a second mixing treatment, which can be carried out in a high-speed disperser with a rotor speed of 1500-2000 r / min, and high-speed shear dispersion is carried out for 20-30 minutes to obtain a second mixture. The volume ratio of the above CMC solution to the epoxy resin solution can be 1-3:1.

[0062] Step S015: The inventor has studied and found that a second homopolymer polypropylene powder with a particle size of 0.2 to 0.5 mm can be added to the slurry of the second mixture as a carrier. Since the volume and mass of the second homopolymer polypropylene are close to those of the carbon nanotubes in the slurry, no stratification will occur during mixing, thereby improving the mixing uniformity and dispersibility of the carbon nanotubes, making the carbon nanotube particles in the slurry and the carrier uniformly mixed, and improving the obtained carbon nanotube masterbatch to obtain excellent dispersibility in subsequent processing. The third mixing treatment can be carried out by mixing methods including stirring, ball milling, etc., and the slurry can be mixed uniformly. For example, a high-speed disperser can be used for mixing to obtain the third mixture.

[0063] Step S016: The drying treatment is mainly to remove the volatile solvent in the third mixture and increase the content of the effective component. The third mixture slurry can be concentrated to half of its weight and then dried at a temperature of 100-150°C for 8-12 hours. The second mixing treatment can be to melt-extrude the dried third mixture with a screw extruder at a melting temperature of 180-200°C and cut it into carbon nanotube masterbatch with a porous die.

[0064] Step S02: The first mixing process can mix the mixture obtained in step S01 into a conductive plastic that can be used in practice, which has both strength and toughness, is shockproof and pressure-resistant, has uniform conductivity, good static dissipation, high cleanliness, and good processing performance. The mixing process can be extrusion granulation through a twin-screw extruder. The screw combination in the twin-screw extruder can adopt a super-strong shear combination, the main engine speed can be 400-700rpm, and the mixing temperature can be 160-230℃. In the exemplary example, the temperature can include but is not limited to 160℃, 180℃, 200℃, and 230℃.

[0065] A third aspect of the embodiments of the present application provides applications of carbon nanotube-modified polypropylene composite materials in semiconductor packaging and electromagnetic wave shielding devices.

[0066] The carbon nanotube-modified polypropylene composite materials in the above embodiments are applied to semiconductor packaging, especially when made into packaging for precision semiconductor chips, such as wafer boxes. These packages have the characteristics of excellent strength and toughness, shock resistance and compression resistance, uniform conductivity, rapid static dissipation, high cleanliness, good processing performance, etc., and can protect semiconductor devices from impact, static electricity, dust, etc. during production, storage, and transportation. They can also be used as absorbing materials to make electromagnetic wave shielding devices, perform electromagnetic dissipation, and shield electromagnetic waves in some bands.

[0067] The following describes the invention in conjunction with specific embodiments.

[0068] Example 1

[0069] This embodiment provides a carbon nanotube-modified polypropylene composite material and a preparation method thereof. The carbon nanotube-modified polypropylene composite material of this embodiment includes the following components in parts by weight:

[0070]

[0071]

[0072] Wherein, polypropylene comprises the following components in parts by weight:

[0073] First polypropylene (melt index is 1-5g / 10min) 7 parts

[0074] Second polypropylene (melt index 20-35g / 10min) 21 parts

[0075] 42 parts of third polypropylene (melt index is 90-110 g / 10 min);

[0076] The carbon nanotube masterbatch comprises the following components in parts by weight:

[0077]

[0078] The preparation method of the carbon nanotube modified polypropylene composite material comprises the following steps:

[0079] S1. Preparation of carbon nanotube masterbatch:

[0080] Add carbon nanotubes to a CMC solution with a viscosity of 1200 mPa·S at 25°C, and disperse at high speed until uniform; then add an epoxy resin ethanol solution with a viscosity of 1500 mPa·S at 25°C, and disperse at high speed until uniform; then add homopolymer polypropylene, and disperse at high speed until uniform; concentrate the obtained slurry, and then dry it at 120°C for 10 hours; finally, extrude and granulate it at a melting temperature of 200°C using a screw extruder to obtain carbon nanotube masterbatch.

[0081] S2. Mixing the components of the composite material:

[0082] The three types of polypropylene are mixed and set aside; the toughening agent and the compatibilizer are mixed and stirred at 300 rpm for 10 minutes, and then the filler is added thereto, and the stirring is continued at 300 rpm for 10 minutes for set aside; the carbon nanotube masterbatch and the antioxidant are mixed and stirred with the first two mixed slurries to obtain a mixture.

[0083] S3. Mixing of the components of the composite material:

[0084] The mixture was extruded and granulated through a twin-screw extruder, the mixing temperature was set to 200° C., and the main engine speed was set to 500 rpm to obtain a carbon nanotube-modified polypropylene composite material.

[0085] Example 2

[0086] Carbon nanotube modified polypropylene composite material and preparation method thereof

[0087] This embodiment provides a carbon nanotube modified polypropylene composite material and a preparation method thereof. The difference between the carbon nanotube modified polypropylene composite material of this embodiment and that of embodiment 1 is that the weight of polypropylene is 65 parts, the weight of carbon nanotube masterbatch is 20 parts, the weight of three melt index polypropylenes contained in the polypropylene is adjusted in the same proportion, that is, the first polypropylene: the second polypropylene: the third polypropylene is 1:3:6; the weight of each component in the carbon nanotube masterbatch is also adjusted in the same proportion, that is, the carbon nanotube: CMC: epoxy resin: homopolymer polypropylene is 18:2:10:20. The preparation method is adjusted accordingly.

[0088] Example 3

[0089] Carbon nanotube modified polypropylene composite material and preparation method thereof

[0090] This embodiment provides a carbon nanotube modified polypropylene composite material and a preparation method thereof. The difference between the preparation method of this embodiment and that of embodiment 1 is that in step S1, the carbon nanotubes are pretreated, including oxidation treatment and acidification treatment. Specifically, the carbon nanotubes are oxidized at 500°C and in the presence of oxygen for 20 minutes; then ultrasonically treated for 30 minutes to 1 hour, and finally acidified for 3 hours with concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 to obtain high-purity and high-cleanliness carbon nanotubes for the preparation of carbon nanotube masterbatch.

[0091] Comparative Example 1

[0092] Polypropylene composite material and preparation method thereof

[0093] The difference between the polypropylene composite material provided in Comparative Example 1 and the carbon nanotube-modified polypropylene composite material provided in Example 1 is that 70 parts by weight of the polypropylene are all the second polypropylene, and the preparation method is adjusted accordingly.

[0094] Comparative Example 2

[0095] Polypropylene composite material and preparation method thereof

[0096] The polypropylene composite material provided in Comparative Example 2 differs from the carbon nanotube-modified polypropylene composite material provided in Example 1 in that 70 parts by weight of polypropylene are 28 parts of the first polypropylene and 42 parts of the third polypropylene, and the preparation method is adjusted accordingly.

[0097] Comparative Example 3

[0098] Polypropylene composite material and preparation method thereof

[0099] The polypropylene composite material provided in Comparative Example 3 differs from the carbon nanotube-modified polypropylene composite material provided in Example 1 in that 70 parts by weight of the polypropylene are 28 parts of the second polypropylene and 42 parts of the third polypropylene, and the preparation method is adjusted accordingly.

[0100] Comparative Example 4

[0101] Polypropylene composite material and preparation method thereof

[0102] The polypropylene composite material provided in Comparative Example 4 differs from the carbon nanotube-modified polypropylene composite material provided in Example 1 in that the carbon nanotube masterbatch is not included, but is replaced by 5.4 parts by weight of carbon nanotubes in the masterbatch, and the preparation method is adjusted accordingly.

[0103] Related performance tests and result analysis

[0104] 1. During the processing of the carbon nanotube-modified polypropylene composite materials in Examples 1 to 3, the processing performance of the carbon nanotube-modified polypropylene composite materials is relatively ideal, the processing stability is good, and the production capacity is stable at 180 to 300 kg / h; while the processing performance of Comparative Examples 1 to 4 is weaker than that of the composite materials of the embodiments, and the granulation efficiency is low under the same working conditions, less than 150 kg / h, especially the composite material of Comparative Example 4 is not stable enough in production, and the machine needs to be frequently debugged, and the granulation efficiency is low, less than 100 kg / h.

[0105] 2. The carbon nanotube-modified polypropylene composite materials of Examples 1 to 3 and the polypropylene composite materials prepared in Comparative Examples 1 to 4 were injection molded into standard parts for mechanical property testing:

[0106] The tensile properties are tested according to GB / T 1040-2018, injection molded specimens, and the tensile rate is 10 mm / min;

[0107] Bending properties were tested according to GB / T 9341-2008, injection molding, speed 2mm / min;

[0108] The notched cantilever beam impact strength is tested according to GB / T 1843-2008, with a pendulum energy of 2.75J.

[0109] Then the melt index and resistivity tests were carried out, and all the results were summarized as shown in Table 1:

[0110] Table 1

[0111]

[0112]

[0113] It can be seen from Table 1 that the mechanical properties of the carbon nanotube-modified polypropylene composite materials of Examples 1 to 3 are improved compared with those of the polypropylene composite materials of Comparative Examples 1 to 4, and the resistivity is also slightly better than that of the comparative examples, but the melt index test results are generally higher than those of the comparative examples. Combined with the processing process, it can be seen that the carbon nanotube-modified polypropylene composite materials of the embodiments of the present application have excellent strength and toughness, shock resistance and compression resistance, good electrical conductivity, rapid static dissipation, high cleanliness, and good processing performance.

[0114] 2. The particles of the carbon nanotube-modified polypropylene composite material of Example 3 were tested for the substances contained and the anion and cation contents thereof. The testing standard was in accordance with IPC-TM-650 2.3.28. The results are shown in Table 2 below.

[0115] Table 2

[0116] Test Items <![CDATA[Test results (μg / cm 2 )]]> <![CDATA[Detection limit (μg / cm 2 )]]> Li <![CDATA[2.4×10 -5 ]]> <![CDATA[5×10 -6 ]]> Na <![CDATA[1.203×10 -3 ]]> <![CDATA[5×10 -6 ]]> Mg <![CDATA[3.878×10 -3 ]]> <![CDATA[5×10 -6 ]]> K <![CDATA[1.37×10 -4 ]]> <![CDATA[5×10 -6 ]]> Ca <![CDATA[4.513×10 -3 ]]> <![CDATA[5×10 -6 ]]> <![CDATA[F - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[Ace - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[For - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[Cl - ]]> 0.534 <![CDATA[5×10 -4 ]]> <![CDATA[NO2 - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[ClO3 - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[Br - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[NO3 - ]]> <![CDATA[2.45×10 -3 ]]> <![CDATA[5×10 -4 ]]> <![CDATA[SO4 2- ]]> <![CDATA[1.65×10 -3 ]]> <![CDATA[5×10 -4 ]]> <![CDATA[I - ]]> N.D. <![CDATA[5×10 -4 ]]> <![CDATA[NH4 + ]]> N.D. <![CDATA[5×10 -4 ]]>

[0117] As can be seen from Table 2, the contents of each ion in Table 2 meet the application requirements, indicating that the carbon nanotubes are subjected to oxidation and acidification pretreatment, and the cleanliness of the carbon nanotube-modified polypropylene composite material is guaranteed, and can be applied to semiconductor chip packaging, etc.

[0118] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A carbon nanotube-modified polypropylene composite material, comprising the following components in parts by weight: The polypropylene includes a first polypropylene, a second polypropylene and a third polypropylene, the first polypropylene has a melt index of 1 to 5 g / 10 min, the second polypropylene has a melt index of 20 to 35 g / 10 min, and the third polypropylene has a melt index of 90 to 110 g / 10 min; The first polypropylene includes random copolymer polypropylene; The second polypropylene includes block copolymer polypropylene; The third polypropylene includes a first homopolypropylene; The mass ratio of the first polypropylene, the second polypropylene and the third polypropylene is 1:2-3:5-8; The carbon nanotube masterbatch comprises carbon nanotubes, carboxymethyl cellulose, epoxy resin and a second homopolypropylene, wherein the weight ratio of the carbon nanotubes, carboxymethyl cellulose, epoxy resin and the second homopolypropylene is (10-20): (1-3): (3-16): (10-40).

2. The carbon nanotube-modified polypropylene composite material according to claim 1, characterized in that: The filler has a fineness of 50 to 10000 mesh; and / or The filler comprises at least one of silicon dioxide, calcium carbonate, barium sulfate, talc, wollastonite, kaolin, mica powder, and montmorillonite; and / or The toughening agent comprises at least one of vinyl elastomer, propylene elastomer, EPDM rubber, acrylonitrile-styrene-butadiene copolymer, and hydrogenated acrylonitrile-styrene-butadiene elastomer; and / or The compatibilizer includes at least one of a silane coupling agent, a titanate coupling agent, maleic anhydride grafted polypropylene, and maleic anhydride grafted polyethylene; and / or The antioxidant includes at least one of 1010, 168, 1076, 1330, 1035, 3144, 1024, 126, B215, and B561.

3. The carbon nanotube-modified polypropylene composite material according to claim 1, characterized in that: The particle size of the carbon nanotube masterbatch is 0.8 to 1.5 mm; and / or The carbon nanotubes include multi-walled carbon nanotubes; and / or The diameter of the carbon nanotubes is 5 to 30 nm; and / or The carbon nanotubes have a tube length of 1 to 100 μm; and / or The specific surface area of ​​the carbon nanotubes is 150 to 400 m 2 / g; and / or The second homopolypropylene is in granular form, and the particle size is 0.2-0.5 mm.

4. A method for preparing a carbon nanotube-modified polypropylene composite material, comprising the following steps: The components contained in the carbon nanotube-modified polypropylene composite material according to any one of claims 1 to 3 are mixed and then subjected to a first kneading process.

5. The preparation method according to claim 4, characterized in that: The method for preparing the carbon nanotube masterbatch comprises the following steps: Performing a first mixing process on the carbon nanotubes and the carboxymethyl cellulose solution to obtain a first mixture; Performing a second mixing process on the first mixture and the epoxy resin solution to obtain a second mixture; performing a third mixing process on the second mixture and the second homopolypropylene to obtain a third mixture; The third mixture is dried and then subjected to a second kneading process.

6. The preparation method according to claim 5, characterized in that: Before the first mixing treatment, the method further includes the steps of subjecting the carbon nanotubes to oxidation treatment and acid treatment; and / or The viscosity of the carboxymethyl cellulose solution at 25° C. is 1000 to 1500 mPa·S; and / or The epoxy resin solution has a viscosity of 1000-2000 mPa·S at 25° C.; and / or The volume ratio of the carboxymethyl cellulose solution to the epoxy resin solution is 1 to 3:1; and / or The mass percentage of the carbon nanotubes in the first mixture is 10-20wt%; and / or The temperature for the second kneading treatment is 180-200°C.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The temperature for the first kneading treatment is 160-230°C.

8. Use of the carbon nanotube-modified polypropylene composite material according to any one of claims 1 to 3 in semiconductor packaging and electromagnetic wave shielding devices.

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