PC (polycarbonate) composition as well as preparation method and application thereof

Abstract

The invention discloses a PC (polycarbonate) composition as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials, the PC composition comprises the following components in parts by weight: 70-99 parts of PC resin, 5-22 parts of cellulose nanocrystals and 0.5-12 parts of a flame retardant; the composition has a V-0-level flame retardant effect, meanwhile, due to the fact that the cellulose nanocrystals are introduced into the components and the length-diameter ratio of the cellulose nanocrystals and the melt flow rate of PC resin in a product are cooperatively regulated and controlled, a good long-term low-temperature toughness effect can be achieved, and when the obtained PC composition is used as a shell part, the flame retardance of the PC composition is improved. The paint has a beautiful structural color effect and self-cleaning performance, and is excellent in comprehensive performance.

Description

Technical Field

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

[0002] PC (polycarbonate) has good processing performance and mechanical strength, and good heat resistance. After the introduction of flame retardant ingredients to prepare flame retardant PC materials, its application scenarios are very wide, including automobiles, electronics, aerospace, construction and other fields.

[0003] However, when used for housing parts such as automobile lamp housings or power supply housings, flame-retardant PC materials have major defects: (1) Although the material has good heat resistance and basic mechanical properties, in low-temperature environments, especially long-term low-temperature environments, the mechanical properties of the product, especially the toughness, are low, making it difficult to withstand external stress; (2) The material composition is complex, and the surface appearance cannot achieve the beautiful structural color effect that people expect; (3) The material is easy to accumulate dirt after continuous use and requires frequent cleaning. Summary of the Invention

[0004] Based on the defects of the prior art, the purpose of the present invention is to provide a PC composition that has V-0 flame retardant performance. At the same time, due to the introduction of cellulose nanocrystals into the components and the coordinated regulation of the aspect ratio of the cellulose nanocrystals and the melt flow rate of the PC resin in the product, good long-term low-temperature toughness can be achieved. When the resulting PC composition is used as a shell component, it has a beautiful structural color effect and self-cleaning properties, and has excellent comprehensive performance.

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

[0006] A PC composition comprising the following components in parts by weight:

[0007] 70-99 parts of PC resin, 5-22 parts of cellulose nanocrystals, and 0.5-12 parts of flame retardant;

[0008] The PC resin has a melt flow rate of 5 to 30 g / 10 min at 300° C. and a load of 1.2 kg according to ISO 1133-2-2011, and the cellulose nanocrystals have a retained aspect ratio of 12 to 30 in the PC composition.

[0009] Cellulose nanocrystals (CNC) are a special material that will gradually spontaneously assemble to form a cholesteric liquid crystal state with a left-handed helical nanostructure. Its polymer monomer is glucose. When the wavelength of the external reflected light is in the visible light range, it refracts and reflects light and finally presents a more beautiful structural color. The structural color will vary based on the actual distribution characteristics. This component has a wide range of sources and can be easily prepared by conventional industrial means. In the scheme of the present invention, the inventors introduced cellulose nanocrystals into PC resin containing flame retardant components as a key component, and at the same time synchronously regulated the retained aspect ratio of cellulose nanocrystals in the product and the melt flow rate of PC resin. On the one hand, as mentioned above, the self-assembly effect of cellulose nanocrystals is related to the distribution characteristics, and these materials are not fixed after being prepared into products, but have a certain degree of creeping. The degree of creeping is related to the fluidity of the matrix resin, and the fluidity of PC resin itself is also related to the low-temperature toughness performance of the product. On the other hand, the aspect ratio of cellulose nanocrystals and their relative contact area in the product and even the surface of the product are closely related. Roughness and chemical composition are related. When the fluidity of the product is appropriate, cellulose nanocrystals will more easily form an ordered and relatively hydrophobic film layer on the surface of the material, which reduces the wettability of the product surface to liquids such as water, increases the contact angle to 90° and above, and has a stronger tendency to form water droplets after contacting the surface. When the water droplets roll, they can easily carry away dust, stains, etc., achieving self-cleaning. In addition, under appropriate fluidity, the aspect ratio of cellulose nanocrystals increases, which can form a role similar to "bridge" and "reinforcement ribs" in the product, inhibiting the shrinkage and brittleness of the resin in low-temperature environments, and improving the toughness of the product in long-term low-temperature environments. Finally, as mentioned above, changes in the aspect ratio of cellulose nanocrystals will lead to differences in their microscopic arrangement, which in turn will lead to differences in the red-blue shift of the optical wavelength reflected by themselves, which will ultimately lead to differences in the structural color of the product. When the ratio of the retained aspect ratio of the cellulose nanocrystals in the product to the melt fluidity of the PC resin is adjusted to the above range, the product can not only achieve the expected flame retardant effect, but also has excellent low-temperature toughness, the reflection wavelength in the vertical surface direction of the product is appropriate, the product after injection molding can achieve beautiful structural color (reflection wavelength is in the range of 600 to 780 nm), and also has excellent self-cleaning properties and good overall performance.

[0010] Preferably, the melt flow rate of the PC resin at 300° C. and a load of 1.2 kg is within the range of one or any two of 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, and 30 g / 10 min, and the retained aspect ratio of the cellulose nanocrystals is within the range of one or any two of 12, 15, 16, 18, 20, 22, 24, 25, 28, 29, and 30.

[0011] More preferably, the PC resin has a melt flow rate of 6 to 20 g / 10 min at 300° C. and a load of 1.2 kg, and the cellulose nanocrystals have a retained aspect ratio of 15 to 30.

[0012] When the PC composition satisfies the above further preferred range, the cellulose nanocrystals have better dispersibility in the matrix resin, have less tendency to disperse agglomerate or creep agglomerate, and have higher uniformity when subjected to external force impact, and the low-temperature toughness performance of the product can be further improved.

[0013] Preferably, in the PC composition, the weight proportion of the PC resin is in the range of one or any two of 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, and 99 parts; the weight proportion of the cellulose nanocrystals is in the range of one or any two of 5, 8, 10, 12, 14, 16, 18, 20, and 22 parts; and the weight proportion of the flame retardant is in the range of one or any two of 0.5, 1, 2, 5, 8, 10, and 12 parts.

[0014] More preferably, the PC composition comprises the following components in parts by weight:

[0015] 73-90 parts of PC resin, 8-20 parts of cellulose nanocrystals, and 1-10 parts of flame retardant;

[0016] Preferably, in the PC composition, the mass percentage of PC resin is ≥60wt%.

[0017] The PC composition of the present invention is not particularly limited in the type of PC resin in its components. When preparing the product, a conventional bisphenol A-type copolymerized PC resin can be selected, or a copolymerized PC resin prepared by a phosgene method or copolymerization method can be selected. A silicon copolymerized PC resin with better corrosion resistance and hydrolysis resistance known to those skilled in the art can also be used. Various different PC resins can also be blended for use. As long as the melt flow rate of the PC composition prepared from the PC resin and the retained average aspect ratio of the cellulose nanocrystals can be controlled within a specified range, the PC composition is not limited.

[0018] Preferably, the PC resin includes at least one of a silicon copolymerized PC resin and a bisphenol A copolymerized PC resin.

[0019] More preferably, the mass content of siloxane in the silicone copolymer PC resin is 2 to 20 wt%.

[0020] Specifically, the mass content of siloxane in the silicon copolymer PC resin can be tested by inductively coupled plasma optical emission spectrometry combined with nuclear magnetic resonance. Specifically, inductively coupled plasma optical emission spectrometry is used to confirm the mass content of silicon in the sample in advance, and then nuclear magnetic resonance waves are used to determine the type and molecular weight of siloxane in the sample. Finally, the mass content of siloxane in the sample is calculated based on the mass content of silicon.

[0021] Preferably, the cellulose nanocrystals are chiral cellulose nanocrystals.

[0022] Cellulose materials are abundant in nature, and the cost of mining and processing is low and the operation is simple. Cellulose nanocrystals are one of the products. They can be prepared by a variety of simple and easy-to-operate methods including enzymatic hydrolysis, acid hydrolysis, and ultrasonic method, and have basically been industrialized. Technicians in this field can purchase them according to actual conditions, or prepare them using conventional methods.

[0023] The technical solution of this application does not limit the source of the cellulose nanocrystals of the PC composition. Specifically, the cellulose nanocrystals can be prepared by acid hydrolysis, and the preparation method comprises the following steps:

[0024] The precursor material is soaked in a dilute sulfuric acid solution, the obtained mixed solution is diluted and allowed to stand, the supernatant is removed, and then centrifuged, trapped, purified, concentrated, dried and cultured to obtain the cellulose nanocrystals.

[0025] More preferably, the precursor material includes at least one of absorbent cotton, pine wood, bamboo, and flax.

[0026] More preferably, the average degree of polymerization of the precursor material is 50-200.

[0027] The average polymer of the precursor material can be measured using an Ubbelohde viscometer at a temperature of 25°C. A copper ethylenediamine solution is used to preheat and mix the precursor material until it is completely dissolved. The viscometer is then used to measure the mixture and calculate the viscosity n. Finally, the degree of polymerization of the sample is calculated. For specific operations, please refer to "Determination of the Degree of Polymerization of Cotton Fibers" - Xing Daqun, Beijing Guanghua Dyeing and Weaving Factory.

[0028] More preferably, the concentration of the dilute sulfuric acid solution is 60-70 wt%.

[0029] More preferably, the soaking temperature is 40-50° C., and the soaking time is 60-120 min.

[0030] More preferably, the ratio of the mass of the precursor material to the volume of the sulfuric acid solution is 1 g: (5-15) mL.

[0031] Furthermore, the average molecular weight of the cellulose nanocrystals is 15,500 to 17,000 g / mol.

[0032] The average molecular weight of the cellulose nanocrystals described in the present application can be confirmed in the following manner: since the basic repeating unit of nanocrystalline cellulose is glucose, the molecular weight of the repeating unit is 162 g / mol. According to the average degree of polymerization D of the precursor material, the average molecular weight of the cellulose nanocrystals can be calculated as 162 g / mol × D. At the same time, the molar amount of the cellulose nanocrystals is the mass of the cellulose nanocrystals / the average molecular weight of the cellulose nanocrystals.

[0033] It is well known to those skilled in the art that in the process of separating and hydrolyzing the cellulose in the precursor material by acid hydrolysis, parameters such as the concentration of the acid solution, reaction temperature, reaction time and liquid-solid ratio will affect the degree of hydrolysis of its amorphous region, thereby resulting in the length and diameter of the cellulose nanocrystals finally obtained. Specifically, as the concentration of the acid solution increases, the hydrolysis reaction rate accelerates, and the acid solution can more effectively remove the amorphous region of cellulose, thereby resulting in a decrease in the length and diameter of the obtained cellulose nanocrystals. Increasing the temperature also has a similar effect. Properly increasing the temperature is conducive to the hydrolysis of the amorphous region, increasing the length of the cellulose nanocrystals, thereby increasing the aspect ratio. However, if the temperature continues to increase, resulting in a further increase in the reaction activity, the cellulose nanocrystals will cause the aspect ratio to decrease due to structural changes. Based on actual conditions, those skilled in the art can choose to adjust the parameters of the preparation process when obtaining cellulose nanocrystals in a homemade manner, and there is no special restriction on this.

[0034] Preferably, the rotation speed during the centrifugation is 4000-6000 rpm, and the time for a single centrifugation is 4-6 minutes.

[0035] Preferably, the molecular weight cut-off of the dialysis device used for the interception is 8000 to 14000.

[0036] Preferably, the temperature during the dry culture is 20-30° C., and the time is 40-60 h.

[0037] More preferably, in the PC composition, the retained average aspect ratio of the cellulose nanocrystals is 15-30.

[0038] As mentioned above, when the cellulose nanocrystals are evenly dispersed, they can serve as the "bridge" and "reinforcement rib" of the product, thereby preferably improving the low-temperature toughness of the product. When the retained aspect ratio is preferably within the above range, the dispersion effect and creeping dispersion effect of the cellulose nanocrystals in the product are better, the reinforcing effect of the product is better, the low-temperature toughness is better, and the self-cleaning performance of the product surface meets the standards.

[0039] It should be noted that the retained aspect ratio of the cellulose nanocrystals of the present invention is not the same as the original aspect ratio of the cellulose nanocrystals. During the processing of the PC composition, based on procedures such as material stirring or mixing processing, the retained aspect ratio of the cellulose nanocrystals in the product is different from its original aspect ratio. In order to ensure the performance of the product during use, the present invention is based on its retained aspect ratio. As described above, those skilled in the art can adjust the final retained aspect ratio by regulating the original aspect ratio of the cellulose nanocrystals through the preparation process. At the same time, those skilled in the art can also select cellulose nanocrystals with a fixed original aspect ratio and, when processing the PC composition, use different feeding methods, such as delivering cellulose nanocrystals through the main feeding port and the side feeding port, and setting different mixing screw speeds to regulate the retained aspect ratio of the cellulose nanocrystals.

[0040] More preferably, in the PC composition, the retained average length of the cellulose nanocrystals is 100 to 400 nm, and the retained average diameter is 5 to 15 nm.

[0041] Furthermore, in the PC composition, the average retained length of the cellulose nanocrystals is 120 to 370 nm, and the average retained diameter is 8 to 13 nm.

[0042] More preferably, the test method for the retained average length, retained average diameter and retained average aspect ratio of the cellulose nanocrystals in the PC composition is:

[0043] The PC composition was cut into thin slices with a thickness of about 100 nm, and then placed under a transmission electron microscope and observed at a magnification of 20k. At the magnification, 200 cellulose nanocrystals were identified and selected, and their length and diameter were tested using measurement software (when testing the diameter, the diameters of the head, tail, and middle of the cellulose nanocrystal were tested and the average value was taken). The data of the 200 samples were averaged to obtain the retained average length and retained average diameter of the cellulose nanocrystals in the product, and then the aspect ratio was calculated to obtain the retained average aspect ratio.

[0044] Preferably, the flame retardant includes at least one of a nitrogen-based flame retardant and a phosphorus-based flame retardant.

[0045] In the PC composition of the present invention, there is no particular limitation on the type of flame retardant, as long as the expected flame retardant effect can be achieved in the system and the product meets the flame retardancy standards.

[0046] Specifically, the nitrogen-based flame retardant includes at least one of melamine cyanurate, melamine phosphate, dicyandiamide, and ammonium polyphosphate; the phosphorus-based flame retardant includes at least one of phosphate ester, phosphite, phosphonate, organic phosphorus salt, and phosphorus heterocyclic compound.

[0047] It should be noted that the components of the product of the present invention also include 0.01 to 3 parts of processing aids. More preferably, the processing aids include lubricants, antioxidants, etc. Those skilled in the art can add them according to actual needs as long as they do not affect the expected technical effects of the product of the present invention.

[0048] Preferably, the cellulose nanocrystals are polyetheramine grafted modified cellulose nanocrystals.

[0049] After further grafting polyetheramine on the surface of cellulose nanocrystals, the component can form a certain flexible polyetheramine layer on the surface. In addition to improving the affinity of the component with other components, this protective layer can also effectively inhibit the influence of cellulose nanocrystals on the toughness and strength of the product in a low-temperature environment, further improving the product's stress resistance in a low-temperature environment, and effectively improving the low-temperature impact strength of the product.

[0050] More preferably, the modification grafting rate of the polyetheramine grafted modified cellulose nanocrystals is 15 to 45 wt %.

[0051] More preferably, the modification grafting rate of the polyetheramine grafted modified cellulose nanocrystals is 25 to 35 wt%.

[0052] At a lower modification grafting rate, the flexible layer on the surface of the modified cellulose nanocrystal is relatively sparsely dispersed, and the degree of improvement in the low-temperature toughness strength of the product is low. As the grafting rate increases, the continuity of the flexible layer improves, and the degree of modification also increases accordingly. When the grafting rate is preferably within the above range, the polyetheramine is more uniform, and the performance of the product, especially the low-temperature toughness, can reach the optimal level.

[0053] It should be noted that the modification grafting rate of the polyetheramine grafted modified cellulose nanocrystals of the present invention is confirmed by thermogravimetric analysis: the polyetheramine grafted modified cellulose nanocrystals and unmodified cellulose nanocrystals are respectively placed in a thermogravimetric analyzer, and the temperature is raised from 30°C to 700°C at 20K (Fahrenheit) / min under a nitrogen atmosphere. The thermal weight loss of the grafted polyetheramine in the polyetheramine grafted modified cellulose nanocrystals is confirmed by comparing the thermal weight loss curve and thermal decomposition peak of the unmodified cellulose nanocrystals. The modification grafting rate of the polyetheramine grafted modified cellulose nanocrystals is calculated as 100%×thermal weight loss / initial weight of the polyetheramine grafted modified cellulose nanocrystals.

[0054] More preferably, the polyetheramine grafted modified cellulose nanocrystals are obtained by introducing epoxy groups into cellulose nanocrystals through a ring-opening reaction with 3-glycidoxypropyltrimethoxysilane, and then reacting with amino-terminated polyether for a nucleophilic addition reaction.

[0055] More preferably, the polyetheramine is an amine-terminated polyether.

[0056] More preferably, the polyetheramine grafted modified cellulose nanocrystals can be prepared by, but not limited to, the following method:

[0057] Cellulose nanocrystals and 3-glycidyloxypropyltrimethoxysilane are placed in an organic solvent for a ring-opening reaction, and then an amino-terminated polyether is introduced for a nucleophilic addition reaction. The obtained product is washed with ethanol, dried, and ground to obtain the polyetheramine-grafted modified cellulose nanocrystals.

[0058] More preferably, the temperature of the ring-opening reaction is 50-120° C., and the reaction time is 1-12 h.

[0059] More preferably, the temperature of the nucleophilic addition reaction is 40-80° C., and the reaction time is 4-8 hours.

[0060] More preferably, the molar ratio of the cellulose nanocrystals to 3-glycidoxypropyltrimethoxysilane is 1:(0.5-1.2).

[0061] More preferably, the mass ratio of the cellulose nanocrystals to the amino-terminated polyether is 5:(0.08-0.2).

[0062] More preferably, the mass ratio of the cellulose nanocrystals to the amino-terminated polyether is (3-8):1.

[0063] In the technical solution of the present invention, those skilled in the art can prepare the components by the above process, by adjusting the addition molar ratio of cellulose nanocrystals and 3-glycidoxypropyltrimethoxysilane, the reaction temperature and the reaction time during the ring-opening reaction, and adding the amount of the amino-terminated polyether, thereby regulating the grafting rate of the final polyetheramine. Other reaction conditions can also be used for regulation, which is not limited here.

[0064] Preferably, the amino-terminated polyether can be selected from various commercially available products, including but not limited to one or more of D2000, D230, D400, T5000, ED2003, and ED9.

[0065] More preferably, the amine value of the amine-terminated polyether is 0.95 to 1.05 mmol / g.

[0066] Another object of the present invention is to provide a method for preparing the PC composition, comprising the following steps:

[0067] After the components are uniformly mixed, they are melt-extruded and granulated in a screw extruder to obtain the PC composition.

[0068] The preparation method of the conductive PC alloy of the present invention has simple operation steps and can realize industrial-scale production.

[0069] Preferably, the temperature range of the screw extruder is set to: 240-280°C, the screw speed is 400-600r / min, and the screw length-diameter ratio is (45-50):1.

[0070] Another object of the present invention is to provide an application of the PC composition in preparing shell packaging materials.

[0071] Preferably, the housing packaging materials include automobile housing parts and electronic and electrical appliance housing parts.

[0072] More preferably, the automobile housing components include instrument panels and automobile lamp housings, and the electronic and electrical housing components include power supply housings, junction boxes, and socket housings.

[0073] Another object of the present invention is to provide a shell packaging material comprising the PC composition of the present invention.

[0074] The PC composition of the present invention has ideal comprehensive properties. It not only has the expected flame retardant properties, but also can maintain sufficient impact resistance in low-temperature environments. The contact angle of the product surface is ≥90°, it has self-cleaning properties, and the appearance has a beautiful structural color, thus meeting the appearance and practicality requirements of the outer shell packaging material.

[0075] The beneficial effects of the present invention are that the present invention provides a PC composition having V-0 flame retardant performance. At the same time, due to the introduction of cellulose nanocrystals into the components and the coordinated regulation of the aspect ratio of the cellulose nanocrystals and the melt flow rate of the PC resin, good long-term low-temperature toughness can be achieved. Moreover, when the obtained PC composition is used as a shell component, it has a beautiful structural color effect and self-cleaning properties, and has excellent comprehensive performance. DETAILED DESCRIPTION

[0076] 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. Its purpose 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 all fall within the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all conventional common reagents and instruments unless otherwise specified.

[0077] Examples 1 to 15

[0078] The PC composition of the present invention and its preparation method and application examples are shown in Table 1.

[0079] The preparation method of the product comprises the following steps:

[0080] The components are mixed evenly, and then placed into a screw extruder for melt extrusion and granulation to obtain the PC composition.

[0081] The temperature zones of the screw extruder are set to: zone 1: 240°C, zone 2: 250°C, zone 3: 255°C, zone 4: 260°C, zone 5: 265°C, zone 6: 265°C, zone 7: 270°C, zone 8: 275°C, zone 9: 280°C, zone 10: 270°C, the screw speed is 500r / min, and the aspect ratio is 48:1; a double vacuum mode is set during the processing, and the vacuum degree is -0.07 to 0.08MPa.

[0082] Comparative Examples 1 to 6

[0083] The difference between the comparative examples and the examples is only in the types and proportions of the components, as shown in Table 2.

[0084] Among the components described in each embodiment and comparative example,

[0085] PC resin 1 is PC 7030PJ produced by Mitsubishi Engineering-Plastics Corporation, with a melt flow rate of 3 g / 10 min at 300°C and 1.2 kg;

[0086] PC resin 2 is PC 7027R produced by Mitsubishi Engineering-Plastics Corporation, with a melt flow rate of 6 g / 10 min at 300°C and 1.2 kg;

[0087] PC resin 3 is PC 2070 produced by Wanhua Chemical, with a melt flow rate of 7 g / 10 min at 300°C and 1.2 kg;

[0088] PC resin 4 is PC S-2000VR produced by Mitsubishi Engineering-Plastics Corporation, with a melt flow rate of 10 g / 10 min at 300°C and 1.2 kg;

[0089] PC resin 5 is PC MX 2021 produced by Mitsubishi Engineering-Plastics Corporation, with a melt flow rate of 16 g / 10 min at 300°C and 1.2 kg;

[0090] PC resin 6 is PC 2350 produced by Wanhua Chemical, with a melt flow rate of 35 g / 10 min at 300°C and 1.2 kg;

[0091] PC resin 7 is PC CH9115LT produced by Cangzhou Dahua, a silicone copolymer PC with a siloxane content of 6 wt % and a melt flow rate of 12 g / 10 min at 300 ° C and 1.2 kg;

[0092] Cellulose nanocrystals 1 to 6 are all homemade products. The specific method is as follows:

[0093] Commercially available absorbent cotton (average degree of polymerization = 100) was broken into small pieces of 1 × 1 cm, and then 20 g was weighed and placed in 200 mL of 64-70 wt% dilute sulfuric acid aqueous solution, and mechanically stirred at 600 rpm at 45-50 ° C for 90 min, and then 1800 mL of deionized water was added for dilution. The mixture was allowed to stand for 12 h, and the supernatant was removed. The remaining milky white suspension was centrifuged at 5000 rpm for 5 min, the supernatant was removed, 200 mL of deionized water was added and shaken, and the centrifugation was repeated. The obtained white suspension was dialyzed and purified in deionized water using a dialysis bag with a molecular weight cutoff of 8000 to 14000 until the pH of the deionized water in the outer layer of the dialysis bag was 6. The obtained substance was concentrated to a solid content of 4 wt % using a rotary evaporator. Subsequently, 2.2 g of the concentrate was dispersed in a 35 mm culture dish and the water was evaporated at 25° C. and 50% RH for 48 h to obtain cellulose nanocrystals having an average molecular weight of 16200 g / mol.

[0094] The cellulose nanocrystals are directly dispersed in ethanol to prepare a sample, which is then placed under a transmission electron microscope and observed at a magnification of 20k. At the magnification, 200 cellulose nanocrystals are confirmed and selected, and their lengths and diameters are tested using measurement software (when testing the diameter, the diameters of the head, tail, and middle of the cellulose nanocrystal are tested and the average value is taken). The data of the 200 samples are averaged to obtain the average length and average diameter of the cellulose nanocrystals in the product.

[0095] Specifically, the concentration of the dilute sulfuric acid aqueous solution used for soaking the cellulose nanocrystals 1 was 70 wt % and the temperature was 50° C. The average length of the obtained product was 95 nm and the average diameter was 8.2 nm.

[0096] The concentration of the dilute sulfuric acid aqueous solution used for soaking the cellulose nanocrystals 2 was 68 wt % and the temperature was 50° C. The average length of the obtained product was 136 nm and the average diameter was 8.8 nm.

[0097] The dilute sulfuric acid aqueous solution used for soaking cellulose nanocrystals 3 had a concentration of 68 wt % and a temperature of 48° C. The average length of the obtained product was 245 nm and the average diameter was 10.3 nm.

[0098] The concentration of the dilute sulfuric acid aqueous solution used for soaking the cellulose nanocrystals 4 was 66 wt % and the temperature was 45° C. The average length of the obtained product was 316 nm and the average diameter was 11.5 nm.

[0099] The concentration of the dilute sulfuric acid aqueous solution used for soaking cellulose nanocrystals 5 was 64 wt % and the temperature was 42° C. The average length of the obtained product was 360 nm and the average diameter was 12.3 nm.

[0100] The concentration of the dilute sulfuric acid aqueous solution used for soaking cellulose nanocrystals 6 was 64 wt % and the temperature was 45° C. The average length of the obtained product was 386 nm and the average diameter was 12.6 nm.

[0101] Modified cellulose nanocrystals 1 were prepared in-house by the following method:

[0102] 5 g of cellulose nanocrystals 4 and 3-glycidyloxypropyltrimethoxysilane were mixed in DMF at a molar ratio of 1:1 and heated to 75 °C for a ring-opening reaction for 4 h. Subsequently, 0.150 g of amino-terminated polyether was added and subjected to a nucleophilic addition reaction at 60 °C for 6 h to obtain the grafting product with a grafting rate of 35 wt%;

[0103] Modified cellulose nanocrystals 2 were homemade and prepared as follows:

[0104] 5 g of cellulose nanocrystals 4 and 3-glycidyloxypropyltrimethoxysilane were mixed in DMF at a molar ratio of 1:0.7 and heated to 75 °C for a ring-opening reaction for 3.5 h. Subsequently, 0.140 g of amino-terminated polyether was added and subjected to a nucleophilic addition reaction at 60 °C for 6 h to obtain the grafting product with a grafting rate of 25 wt%;

[0105] Modified cellulose nanocrystals 3 were homemade and prepared by the following method:

[0106] 5 g of cellulose nanocrystals 4 and 3-glycidyloxypropyltrimethoxysilane were mixed in DMF at a molar ratio of 1:0.5 and heated to 70 °C for a ring-opening reaction for 2 h. Subsequently, 0.085 g of amino-terminated polyether was added and subjected to a nucleophilic addition reaction at 60 °C for 6 h to obtain the grafting product with a grafting rate of 18 wt%;

[0107] Modified cellulose nanocrystals 4 were homemade and prepared by the following method:

[0108] 5 g of cellulose nanocrystals 4 and 3-glycidyloxypropyltrimethoxysilane were mixed in DMF at a molar ratio of 1:1.2 and heated to 80 °C for a ring-opening reaction for 4 h. Subsequently, 0.195 g of amino-terminated polyether was added and subjected to a nucleophilic addition reaction at 60 °C for 6 h to obtain the grafting product with a grafting rate of 41 wt%;

[0109] The 3-glycidyloxypropyltrimethoxysilane is a product produced by Aladdin, CAS 2530-83-8;

[0110] The amino-terminated polyether is D2000 produced by Shandong Shenmao, with an amine value of 1 mmol / g;

[0111] Microcrystalline cellulose 1 and 2 were produced by McLean, CAS: 9004-34-6, with average lengths of 25 μm and 65 μm, respectively, and average diameters of 1 μm;

[0112] Flame retardant 1 is a phosphorus-based flame retardant FP-600 produced by Aidi, a phosphate ester, 4,4'-(isopropylidene diphenyl)bis(diphenyl phosphate);

[0113] Flame retardant 2 is a phosphorus-based flame retardant PX-200 produced by Wansheng, a phosphate ester, 1,3-phenylene tetrakis(2,6-xylyl)phosphate;

[0114] Flame retardant 3 is nitrogen-based flame retardant XS-MC-15 produced by Zhejiang Xusen, melamine cyanurate;

[0115] Unless otherwise specified, the components and raw materials used in the examples 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.

[0116] Table 1

[0117]

[0118] Table 2

[0119] Component weight parts Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 PC resin 1 85 PC resin 3 85 85 85 85 PC resin 6 85 Cellulose nanocrystals 1 15 Cellulose nanocrystals 4 15 15 Cellulose nanocrystals 6 15 Microcrystalline cellulose 1 15 Microcrystalline cellulose 2 15 Flame retardant 1 1 1 1 1 1 1 Average retention length of cellulose nanocrystals (nm) 313.7 312.4 92 384.5 / / Average diameter of cellulose nanocrystals retained (nm) 11.3 11.2 8.0 12.3 / / Cellulose nanocrystals retain the average aspect ratio 27.8 27.9 11.5 31.2 / /

[0120] Effect Example 1

[0121] In order to verify the performance of the products of the present invention, the products of each embodiment and comparative example were subjected to the following performance tests, and the specific steps are as follows:

[0122] (1) Low-temperature notched impact strength test: After each product was injection molded into a 3.2 mm thick test specimen, it was first placed in a -23°C freezer for 48 h, then quickly taken out and subjected to a notched impact strength test according to ASTM D256-10, type A notch, impact energy 2.75 J;

[0123] (2) Contact angle test: According to GB / T 30693-2014, the sample was fixed on the sample stage of the contact angle tester, and a suitable droplet was formed on its surface using a microinjector. The droplet image was obtained by the instrument imaging system, and the contact angle was measured using analysis software.

[0124] (3) Vertical combustion test: According to the UL94 standard, a 0.8 mm thick injection molded product specimen is fixed vertically on the test device. A standard flame spray gun is ignited so that it contacts the bottom edge of the specimen. The burning phenomenon and time after the material is ignited are observed and recorded.

[0125] (4) Vertical Surface Reflection Wavelength Test: Place a product molded into a size of 3×100×100 mm flat on the sample stage of an Ocean Optics UV-Visible-NIR SR6 spectrometer. The instrument emits light of a specific wavelength range vertically to the surface of the plastic plate. The detector receives the vertical reflected light and analyzes the spectral characteristics of the reflected light to determine the reflection wavelength data. If the reflected wavelength is not within the visible light region (400-780 nm), it will not be counted and recorded with a “ / ”.

[0126] The test results are shown in Tables 3 and 4.

[0127] Table 3

[0128]

[0129]

[0130] Table 4

[0131] Component weight parts Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Low temperature notched impact strength (J / m) 735 685 705 685 556 578 Is the contact angle ≥90°? no no no yes no no Vertical burning level (0.8mm) V-0 V-0 V-0 V-0 V-0 V-0 Reflection wavelength perpendicular to the surface (nm) 766 763 583 780 / /

[0132] As can be seen from Tables 3 and 4, the PC composition of the present invention incorporates cellulose nanocrystals of a specific aspect ratio, selected based on their melt flow rate, as a key component in the resin. While achieving a V-0 flame retardant rating at a 0.8 mm thin layer, it not only achieves high low-temperature toughness, but also achieves a notched impact strength of 700 J / m at low temperatures. The surface wetting contact angles of the products all reach over 90°, enabling self-cleaning properties. Furthermore, the products can achieve a good, beautiful structural color with a reflection wavelength in the range of 600-780 nm. In contrast, the products of Comparative Examples 1-4, due to the mismatch between the retained aspect ratio of the nanocrystalline cellulose and the melt flow rate of the PC resin, not only exhibit poor dispersibility, potentially failing to achieve an effective hydrophobic surface layer, but also struggle to form bridges or reinforcements, resulting in poor low-temperature toughness. Comparative Examples 5-6, in which microcrystalline cellulose of varying sizes is used as a substitute for the cellulose nanocrystals, fail to achieve a structural color effect (no apparent color) compared to Example 1, and the resulting products exhibit poor surface wettability and lack self-cleaning properties. Examples 3 and 11-14 show that when the cellulose nanocrystals in the product are grafted with polyetheramine, the product's low-temperature toughness can be further improved without significantly affecting the product's structural color and appearance, resulting in superior overall performance. Furthermore, when the grafting ratio of this component is further optimized within the range of 25-35%, the product's dispersion uniformity is improved, and its low-temperature toughness is further enhanced.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A PC composition, characterized in that The composition comprises the following components in parts by weight: 70-99 parts of PC resin, 5-22 parts of cellulose nanocrystals, and 0.5-12 parts of flame retardant; The PC resin has a melt flow rate of 5 to 30 g / 10 min at 300° C. and a load of 1.2 kg, and the cellulose nanocrystals have a retained aspect ratio of 12 to 30 in the PC composition.

2. The PC composition according to claim 1, wherein The PC resin has a melt flow rate of 6-20 g / 10 min at 300° C. and a load of 1.2 kg, and the retained aspect ratio of the cellulose nanocrystals is 15-30.

3. The PC composition according to claim 1, wherein The PC resin includes at least one of a silicon copolymerized PC resin and a bisphenol A type PC resin.

4. The PC composition according to claim 1, wherein In the PC composition, the average retained length of the cellulose nanocrystals is 100 to 400 nm, and the average retained diameter is 5 to 15 nm.

5. The PC composition according to claim 1, wherein The cellulose nanocrystals are polyetheramine grafted modified cellulose nanocrystals.

6. The PC composition according to claim 5, wherein The modified grafting rate of the cellulose nanocrystals is 15 to 45 wt%.

7. The PC composition according to claim 1, wherein The flame retardant includes at least one of a nitrogen-based flame retardant and a phosphorus-based flame retardant.

8. The method for preparing the PC composition according to any one of claims 1 to 8, wherein: The following steps are involved: After the components are uniformly mixed, they are melt-extruded and granulated in a screw extruder to obtain the PC composition.

9. Use of the PC composition according to any one of claims 1 to 8 in preparing shell packaging materials.

10. A shell packaging material, characterized in that: The PC composition comprises the PC composition according to any one of claims 1 to 8.

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