Polypropylene composite material as well as preparation method and application thereof

Abstract

The invention relates to a polypropylene composite material as well as a preparation method and application thereof. The polypropylene composite material comprises the following components in parts by weight: 79-91 parts of PP resin, 3-10 parts of multiwalled carbon nanotubes, 1-5 parts of black dye and 0-1 part of conductive carbon black. The polypropylene composite material disclosed by the invention has high blackness, good electromagnetic shielding performance and high laser welding strength.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a polypropylene composite material, its preparation method, and its application. Background Technology

[0002] PP resin is a propylene polymer that is widely used in household appliances, automobiles, medical devices, energy, construction and other fields.

[0003] PP resin, due to its lightweight and chemical corrosion resistance, is commonly used in the casings of electronic devices (such as mobile phones, computers, and 5G high-frequency equipment). With the increasing integration of integrated circuits within modern electronic devices, the requirements for electromagnetic shielding technology are becoming increasingly stringent. If the casing material lacks shielding capabilities, signals within the device will interfere with each other, leading to performance degradation or even failure. Furthermore, electromagnetic radiation from the external environment (such as high-voltage power lines and communication base stations) may penetrate the device casing and interfere with internal precision circuits.

[0004] Furthermore, many electronic devices and automotive parts require a dark color (such as black) to meet requirements such as aesthetics, stain resistance, or consistency with branding. Therefore, while achieving electromagnetic shielding and laser welding transparency, the material also needs to possess a good dark appearance.

[0005] In existing technologies, conductive carbon black filler is often dispersed in a PP resin matrix to achieve good electromagnetic shielding and to blacken the material to a certain extent. However, while carbon black achieves electromagnetic shielding by absorbing / reflecting electromagnetic waves through the conductive network it forms, it also strongly absorbs and scatters visible and near-infrared light, resulting in the material being almost opaque in the 900-980nm wavelength range. This fails to meet the light transmittance requirements of laser welding processes, making such materials difficult to laser weld.

[0006] Therefore, it is necessary to develop black polypropylene materials with good electromagnetic shielding properties and good laser-transmitting welding performance. Summary of the Invention

[0007] The primary objective of this invention is to overcome the problem that the black appearance, electromagnetic shielding performance, and light-transmitting welding performance of polypropylene materials in the prior art cannot be simultaneously achieved, and to provide a polypropylene composite material.

[0008] A further object of the present invention is to provide a method for preparing the above-mentioned polypropylene composite material.

[0009] A further object of the present invention is to provide the application of the above-mentioned polypropylene composite material in the preparation of household goods, electronic components, household appliances, gardening equipment, medical technology equipment, motor vehicle parts or body parts.

[0010] The above-mentioned objective of the present invention is achieved through the following technical solution: A polypropylene composite material comprising the following components in parts by weight: 79-91 parts of PP resin, 3-10 parts of multi-walled carbon nanotubes 1-5 parts black dye 0-1 part conductive carbon black; The surface of the multi-walled carbon nanotubes is modified with carboxyl groups; The black dye is at least one of quaternized aniline black or sulfonated aniline black.

[0011] This invention adds little or no conductive carbon black to avoid the negative impact of conductive carbon black on the laser welding strength of polypropylene composite materials.

[0012] However, the absence or minimal addition of carbon black results in insufficient blackness in polypropylene composites. The inventors of this invention have discovered that quaternized or sulfonated aniline black can impart a certain degree of blackness to polypropylene composites, with minimal impact on the material's light transmittance. Therefore, the laser welding strength of the polypropylene composite can be maintained while improving the material's blackness. If aniline black is not quaternized or sulfonated, its tendency to agglomerate leads to insufficient blackness in the polypropylene composite and affects laser transmittance, resulting in poor laser welding strength.

[0013] To impart electromagnetic shielding properties to polypropylene composites, this invention also incorporates multi-walled carbon nanotubes (MWCNTs). However, the improvement in electromagnetic shielding performance of polypropylene composites solely through the addition of MCCNTs is limited. The inventors of this invention discovered that by combining carboxyl-modified MCCNTs with a black dye, polypropylene composites can acquire excellent electromagnetic shielding properties. The principle is as follows: carboxyl-modified MCCNTs are less prone to aggregation and are effectively dispersed in different regions of the polypropylene composite. Meanwhile, quaternized or sulfonated aniline black possesses a certain degree of conductivity and good dispersibility, allowing it to fill areas inaccessible to the MCCNTs and co-construct a conductive network with them, thereby significantly improving the electromagnetic shielding performance of the polypropylene composite.

[0014] Furthermore, this invention also found that carboxylation of multi-walled carbon nanotubes is beneficial to improving the laser welding strength of polypropylene composites, possibly because the carboxyl-modified multi-walled carbon nanotubes have good dispersibility.

[0015] Preferably, the polypropylene composite material is a black polypropylene composite material.

[0016] More preferably, the L value of the polypropylene composite material is ≤21.5.

[0017] In this invention, the amount of PP resin can be 79, 80, 82, 85, 88, or 90 parts by weight, or any two of the above values ​​within a range; the amount of multi-walled carbon nanotubes can be 3, 4, 5, 6, 7, 8, 9, or 10 parts by weight, or any two of the above values ​​within a range; the amount of black dye can be 1, 2, 3, 4, or 5 parts by weight, or any two of the above values ​​within a range; and the amount of conductive carbon black can be 0, 0.2, 0.5, 0.8, or 1.0 parts by weight, or any two of the above values ​​within a range.

[0018] In this invention, PP resin is used as the main resin, accounting for at least 70 wt% of the polypropylene composite material.

[0019] Preferably, the melt flow rate of the PP resin measured at 230°C and 2.16 kg is 0.3~30 g / 10 min.

[0020] In this invention, the melt flow rate of PP resin can be measured according to GB / T 3682-2000.

[0021] Preferably, the PP resin is at least one of homopolymer PP resin or copolymer PP resin.

[0022] More preferably, the copolymer PP resin is at least one of random copolymer PP resin or block copolymer PP resin.

[0023] In this application, the multi-walled carbon nanotubes with carboxylic acid surface modification can be obtained commercially or introduced with carboxyl groups on the surface of multi-walled carbon nanotubes by conventional self-made methods in the art, such as introducing carboxyl groups by chemical oxidation.

[0024] Specifically, in one embodiment, oxidizing acid can be used to oxidize multi-walled carbon nanotubes to obtain multi-walled carbon nanotubes with carboxyl groups modified on the surface.

[0025] Preferably, the oxidation process is as follows: multi-walled carbon nanotubes are refluxed in an oxidizing acid at 60~120 °C for 2~6 h.

[0026] More preferably, the oxidizing acid includes, but is not limited to, concentrated nitric acid.

[0027] More preferably, the oxidizing acid has a mass fraction of 62-68%.

[0028] Preferably, the carboxyl content of the multi-walled carbon nanotubes is 0.5~1.5 mmol / g.

[0029] More preferably, the carboxyl content of the multi-walled carbon nanotubes is 0.52~0.80 mmol / g.

[0030] By adjusting the carboxyl content of multi-walled carbon nanotubes within this range, the polypropylene composite material exhibits better properties.

[0031] In this invention, the carboxyl content of multi-walled carbon nanotubes can be obtained by acid-base titration.

[0032] Preferably, the aspect ratio of the multi-walled carbon nanotube is 100 to 6000.

[0033] Preferably, the average diameter of the cross-section of the multi-walled carbon nanotube is 8~30 nm.

[0034] Preferably, the average length and average diameter of the cross-section of the multi-walled carbon nanotubes are measured according to GB / T24491-2009.

[0035] Preferably, the specific surface area of ​​the multi-walled carbon nanotubes is 250~400 m². 2 / g.

[0036] Preferably, the quaternized aniline black is alkyl-quaternized aniline black; more preferably, it is C 6~12 Alkyl quaternized aniline black.

[0037] Preferably, the alkyl-quaternized aniline black is obtained by reacting aniline black with a haloalkane; the haloalkane is C64-244-3 ... 6~12 Halogenated alkanes.

[0038] More preferably, the preparation process of the quaternized aniline black is as follows: first, aniline black is deprotonated, and then reacted with haloalkanes in the presence of an alkaline agent and a catalyst to obtain quaternized aniline black.

[0039] More preferably, the deprotonation process is as follows: aniline black is added to a sodium hydroxide solution (0.3~1 mol / L) and stirred for 1~4 hours.

[0040] More preferably, the mass ratio of aniline black to sodium hydroxide in the sodium hydroxide solution is 10:(3~6).

[0041] More preferably, the alkali is potassium carbonate and the catalyst is tetrabutylammonium bromide.

[0042] More preferably, the mass ratio of aniline black to the alkali agent is 10:(1~1.5).

[0043] More preferably, the mass ratio of aniline black to the catalyst is 10:(0.1~0.3).

[0044] More preferably, the mass ratio of aniline black to the haloalkane is 10:(1~2).

[0045] More preferably, the haloalkane is C 9~12 The quaternized alkane. Aniline black obtained by quaternizing this quaternized alkane can improve the properties of the resulting polypropylene composite material.

[0046] More preferably, the haloalkane is at least one of 1-bromododecane, 1-bromohexane, or 1-bromononane.

[0047] In this invention, the sulfonated aniline black can be obtained commercially, such as Acid Black 2 (CAS: 8005-03-6), or it can be obtained by a self-made method. In one embodiment, the preparation process of the sulfonated aniline black is as follows: aniline black is added to concentrated sulfuric acid, stirred at 30-40°C for 5-8 hours, precipitated, filtered, and dried to obtain the sulfonated aniline black.

[0048] Preferably, the mass ratio of the multi-walled carbon nanotubes to the black dye is 5~9:1~5; more preferably, it is 5~7:3~5. By adjusting the mass ratio within this range, the multi-walled carbon nanotubes and the black dye can construct a more complete conductive network, resulting in a polypropylene composite material with better electromagnetic shielding performance.

[0049] Preferably, the conductive carbon black accounts for no more than 1.3 wt% of the mass of the polypropylene composite material of the present invention.

[0050] Preferably, the conductive carbon black has an oil absorption value of 180~450ml / 100g and a specific surface area of ​​200~1200m². 2 / g.

[0051] In this invention, the oil absorption value of the conductive carbon black can be measured according to GB / T3780.2-2017, and the specific surface area can be measured according to GB / T 19587-2004.

[0052] Preferably, the polypropylene composite material further includes 0-2 parts of other additives.

[0053] More preferably, the other adjuvant is at least one of a coupling agent or an antioxidant.

[0054] Typically, the amount of the coupling agent is 0.1 to 1 part by weight, and the amount of the antioxidant is 0.1 to 1 part by weight.

[0055] More preferably, the coupling agent is at least one of γ-aminopropyltriethoxysilane or γ-(methacryloyloxy)propyltrimethoxysilane.

[0056] More preferably, the antioxidant is at least one of a primary antioxidant or a secondary antioxidant.

[0057] More preferably, the primary antioxidant is a hindered phenolic antioxidant.

[0058] More preferably, the hindered phenolic antioxidant is at least one of antioxidant 1010, antioxidant 1024, or antioxidant 1076.

[0059] More preferably, the auxiliary antioxidant is a phosphite antioxidant.

[0060] More preferably, the phosphite antioxidant is at least one of antioxidant Irgafos 126, antioxidant Ultranox 626, or antioxidant ADK STAB PEP24.

[0061] The preparation method of the above-mentioned polypropylene composite material includes the following steps: mixing the components, melt extruding, and granulating to obtain the polypropylene composite material.

[0062] Preferably, the screw speed of the melt extrusion extruder is 300~500 rpm, the length-to-diameter ratio is (36~48):1, and the temperature is 200~240℃.

[0063] The application of the above-mentioned polypropylene composite material in the preparation of laser-welded components or electromagnetic shielding components is also within the scope of protection of this invention.

[0064] A polypropylene component is made from the aforementioned polypropylene composite material.

[0065] Preferably, the component can be used in household goods, electronic components, household appliances, gardening equipment, medical technology equipment, motor vehicle parts or vehicle body parts.

[0066] Compared with the prior art, the beneficial effects of the present invention are: The polypropylene composite material of the present invention has high blackness, good electromagnetic shielding performance, and high laser welding strength. Detailed Implementation

[0067] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0068] The reagents used in the various embodiments and comparative examples of this invention are described below: PP resin #1: LyondellBasell, Moplen HP500H, melt index 12 g / 10min; PP resin #2: SABIC (Saudi Basic Industries Corporation), 575P, melt index 11 g / 10min; PP resin #3: Sinopec Yangzi Petrochemical, C180, melt index is 0.3 g / 10min; Multi-walled carbon nanotubes A#: Nanocyl, NC7000, with a specific surface area of ​​280 m² 2 / g, with an average cross-sectional diameter of 9.5 nm and an aspect ratio of 158; Multi-walled carbon nanotubes B#: Aladdin, CAS No.: 308068-56-6, specific surface area 350 m² 2 / g, with an average cross-sectional diameter of 15 nm and an aspect ratio of 5333; Multi-walled carbon nanotubes 1#: self-made, the preparation process is as follows: multi-walled carbon nanotubes A# are added to concentrated nitric acid with a mass fraction of 65% and refluxed at 80℃ for 3 h to obtain multi-walled carbon nanotubes 1#; the carboxyl content of multi-walled carbon nanotubes 1# is 0.52 mmol / g; Multi-walled carbon nanotubes 2#: self-made, the preparation process of which differs from that of multi-walled carbon nanotubes 1# is: reflux time of 4 h; carboxyl content of multi-walled carbon nanotubes 2# is 0.80 mmol / g; Multi-walled carbon nanotubes #3: self-made, the preparation process of which differs from that of multi-walled carbon nanotubes #1 is: reflux time of 6 h; carboxyl content of multi-walled carbon nanotubes #3 is 1.05 mmol / g; Multi-walled carbon nanotube 4#: self-made, the preparation process of which differs from that of multi-walled carbon nanotube 1# is that multi-walled carbon nanotube A# is replaced with multi-walled carbon nanotube B#; the carboxyl content of multi-walled carbon nanotube 4# is 1.10 mmol / g; Black dye A: Aniline black, CAS number 8005-02-5, Orientchemical, brand name NUBIAN BLACKTN-870; Black dye B: Aniline Black, CAS number 13007-86-8, BASF, grade L0080; Black dye #1: Dodecyl quaternized aniline black, homemade, process as follows: (1) Add 10 g of aniline black (black dye A) to 200 mL of 0.5 mol / L NaOH aqueous solution, stir vigorously at room temperature for 2 h to deprotonate and swell, filter, wash with water until neutral; dry under vacuum at 40℃ to obtain powder; (2) Under nitrogen protection, the powder was dispersed in N-methylpyrrolidone, potassium carbonate (1.2 g) and tetrabutylammonium bromide (0.2 g) were added, and the mixture was pre-stirred at 60 °C for 30 min. Then, 1-bromododecane (1.5 g) was added dropwise, and the mixture was heated to 90 °C and reacted for 8-12 h. After cooling, a large amount of ethanol was poured in to precipitate the mixture, and the mixture was filtered. The mixture was washed with ethanol and acetone alternately to remove unreacted raw materials, washed with water, and dried under vacuum at 40 °C to obtain dodecyl quaternized aniline black, which was designated as black dye No. 1. Black dye 2#: Hexyl quaternized aniline black, homemade, the process differs from that of black dye 1# in that: 1-bromododecane is replaced by 1-bromohexane in step (2); Black dye #3: Nonyl quaternary ammonium aniline black, homemade, the process is different from that of black dye #1 in that: 1-bromododecane in step (2) is replaced with 1-bromononane; Black dye #4: Homemade, the process is as follows: Slowly add 10g of aniline black (black dye A) to 100mL of concentrated sulfuric acid cooled to 3℃, and then stir at 40℃ for 6 hours; slowly pour the reaction solution into 500g of ice water, precipitate out, filter, wash thoroughly with water until the filtrate is neutral, and vacuum dry at 40℃ to obtain sulfonated aniline black; Black dye #5: Homemade, the process differs from that of black dye #1 in that black dye A is replaced with black dye B; Black dye #6: Sulfonated aniline black, Jiangxin Biotechnology, Acid Black 2, CAS number 8005-03-6; Conductive Carbon Black #1: Orion (Germany), Printex XE2B, oil absorption value 420 ml / 100g, specific surface area 1000 m² 2 / g; Conductive Carbon Black #2: Cabot (USA), Vulcan XC72R, oil absorption value 192 ml / 100g, specific surface area 254 m² 2 / g; Other auxiliary agent 1#: Coupling agent, γ-(methacryloyloxy)propyltrimethoxysilane, commercially available; Other additives #2: Antioxidant 1010, commercially available; Unless otherwise specified, all components used in the parallel examples and comparative examples (e.g., other additives 1#, other additives 2#) are the same commercially available products.

[0069] The performance of the polypropylene composite materials provided in the embodiments and comparative examples of this invention was determined according to the following test methods: 1. Blackness Evaluation: A colorimeter was used for testing, employing a D65 light source and a 10° viewing angle to measure the L, a, and b values ​​of a 2mm thick injection-molded sample surface. The L value (lightness) is used to evaluate blackness; the lower the L value, the darker the color.

[0070] 2. Electromagnetic shielding effectiveness test: The dual-cavity test equipment is used. The molded test piece (2mm thick, 50mm×50mm in area) is clamped in the waveguide cavity. The penetration loss of the 1GHz band is measured by a network analyzer (network vector instrument). Each group of samples is tested three times and the average is taken. The accuracy is ±1dB.

[0071] 3. Laser welding strength test: A 980nm near-infrared laser welding instrument was used with a welding power of 10W and a scanning speed of 200mm / s. After welding, the tensile strength at the weld fracture was determined using a universal tensile testing machine (tensile rate 5mm / min).

[0072] The polypropylene composite materials of the embodiments and comparative examples of the present invention were prepared by the following preparation method: According to the formula, each component is added to a high-speed mixer and mixed for 5 minutes at a speed of 500 rpm to obtain a mixture. The mixture is then melt-extruded and granulated using a twin-screw extruder to obtain a polypropylene composite material. The temperatures of the twin-screw extruder are as follows: Zone 1: 200℃; Zone 2: 200℃; Zone 3: 240℃; Zone 4: 240℃; Zone 5: 240℃; Zone 6: 240℃; Zone 7: 220℃; Zone 8: 220℃; Zone 9: 220℃; Zone 10: 240℃. The screw speed of the twin-screw extruder is 300 rpm, and the length-to-diameter ratio of the screw is 40:1.

[0073] Examples 1-16 Examples 1-16 provide a series of polypropylene composite materials, the formulations of which are shown in Tables 1 and 2.

[0074] Table 1. Formulations (parts by weight) for Examples 1-8

[0075] Table 2 Formulations (parts by weight) for Examples 9-16 .

[0076] Comparative Examples 1-5 Comparative Examples 1-5 provide a series of polypropylene composite materials, the formulations of which are shown in Table 2.

[0077] Table 2 Formulations (parts by weight) for Comparative Examples 1-5

[0078] The properties of the polypropylene composite materials of each embodiment and comparative example were determined according to the test methods mentioned above, and the test results are shown in Table 3.

[0079] Table 3. Performance test results of polypropylene composite materials in each example and comparative example. .

[0080] As can be seen from Table 3: The L-values ​​of the polypropylene composite materials in Examples 1-16 are all ≤21.5, the electromagnetic shielding effectiveness is ≥34dB, and the laser welding strength is ≥25.1MPa, indicating that the polypropylene composite materials of the present invention have high blackness, good electromagnetic shielding performance, and high laser welding strength.

[0081] In Comparative Example 1, the addition of unhydroxylated multi-walled carbon nanotubes resulted in poor electromagnetic shielding performance and low laser welding strength in the polypropylene composite material.

[0082] In Comparative Example 2, the addition of unmodified aniline black resulted in insufficient blackness, poor electromagnetic shielding performance, and poor laser welding strength in the polypropylene composite material.

[0083] Comparative Example 3 did not add quaternized aniline black or sulfonated aniline black, and obtained the required blackness and electromagnetic shielding effect by increasing the amount of conductive carbon black, but the laser welding strength of the polypropylene composite material was poor.

[0084] Comparative Example 4, without the addition of black dye, showed poor blackness and electromagnetic shielding performance in the polypropylene composite material.

[0085] Comparative Example 5, without the addition of multi-walled carbon nanotubes, showed poor electromagnetic shielding performance in its polypropylene composite material.

[0086] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A polypropylene composite, characterized in that, The polypropylene composite material comprises the following components in parts by weight: PP resin 79-91 parts, Multi-walled carbon nanotubes 3-10 parts, Black dye 1-5 parts, Conductive carbon black 0-1 part; The multi-walled carbon nanotubes are modified on the surface with carboxyl groups. The black dye is at least one of quaternized aniline black or sulfonated aniline black.

2. The polypropylene composite of claim 1, wherein, The PP resin has a melt flow rate of 0.3-30 g / 10 min measured at 230°C under a load of 2.16 kg.

3. The polypropylene composite of claim 1, wherein, The multi-walled carbon nanotubes have a carboxyl group content of 0.5-1.5 mmol / g.

4. The polypropylene composite of claim 1, wherein, The multi-walled carbon nanotubes have an aspect ratio of 100-6000.

5. The polypropylene composite of claim 1, wherein The quaternized aniline black is an alkyl quaternized aniline black; preferably C 6~12 alkyl quaternized aniline black; Preferably, the alkyl quaternized aniline black is obtained by reacting aniline black with a haloalkane; more preferably, the haloalkane is a haloalkane of the formula 6~12 .

6. The polypropylene composite of claim 1, wherein, The mass ratio of the multi-walled carbon nanotubes to the black dye is 5-9:1-5.

7. The polypropylene composite of claim 1, wherein The polypropylene composite material further comprises other auxiliary agents 0-5 parts.

8. A process for the production of the polypropylene composite according to any one of claims 1 to 7, characterized in that The polypropylene composite material is prepared by mixing the components, melt extruding, and granulating.

9. Use of the polypropylene composite material according to any one of claims 1-7 in the preparation of laser welding parts or electromagnetic shielding components.

10. A polypropylene article, characterized by, The polypropylene composite material is prepared according to any one of claims 1-7.

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