Natural fiber reinforced ABS material and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a natural fiber reinforced ABS (Acrylonitrile Butadiene Styrene) material and a preparation method thereof. The natural fiber reinforced ABS material is composed of a main material and an auxiliary material, the main material is prepared from the following raw materials in parts by weight: 75-90 parts of ABS, 5-25 parts of natural fiber and / or modified natural fiber, and 1-10 parts of hydroxyl-terminated polybutadiene, the modified natural fiber is natural fiber obtained by oxidizing primary alcohol hydroxyl at C6 position of a cellulose structure into carboxyl, and the auxiliary material is a natural fiber obtained by oxidizing primary alcohol hydroxyl at C6 position of a cellulose structure into carboxyl. The auxiliary material is prepared from 0.1 to 0.3 part of an antioxidant. According to the invention, active functional groups among the components are subjected to in-situ reaction under the processing condition by utilizing the characteristics of twin-screw extrusion so as to generate corresponding chemical action, so that the cost is reduced, the fiber reinforced material which is excellent in mechanical property, good in odor and not easy to burn can be obtained, and the fiber reinforced material has a wider application space in the fields of automobiles and household appliances.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a natural fiber reinforced ABS material and a preparation method thereof BACKGROUND

[0002] ABS is an amorphous copolymer, which is polymerized from styrene and acrylonitrile in the presence of polybutadiene. Due to its relatively low cost and good mechanical properties, dimensional stability, ABS materials are widely used in automobile parts, toys, office supplies, and refrigerator, washing machine, electric fan and television and other electrical equipment.

[0003] Natural fibers are a new generation of materials, which are widely concerned by scientific research and industry due to their unique chemical and physical properties. This kind of resource-rich and renewable material not only has the advantages of low density, high strength and flexibility, but also has chemical inertness and surface chemical modification ability, and has become an important product in the field of polymer industry.

[0004] At present, the research on using natural fibers to reinforce polypropylene (PP) or polyethylene (PE) materials is more, but the related research on natural fiber reinforced ABS material is less. Patent CN109735048A discloses a natural fiber reinforced ABS composite material and a preparation method thereof. By combining modified natural hemp fibers with alkynyl polybutadiene and antioxidants, using double screw extrusion processing technology, the compatibility and wrapping effect of the fibers and the matrix are improved, and a natural fiber reinforced ABS composite material with good mechanical properties is prepared. However, it is easy to burn due to the presence of azide functional group, and its application in the fields of automobiles, household appliances and the like is limited, and the natural fibers and hydroxyl-terminated polybutadiene need to be chemically modified. Not only does it increase the process flow and lead to cost increase, but also it will have certain influence on the structure and strength of the natural fibers. In addition, the materials used in the field of automobiles generally have requirements on odor, and the technical solution disclosed in the above patent does not effectively solve the odor problem.

[0005] Therefore, it is necessary to design a new interface reinforcing method which is cost-effective, more green and environmentally friendly. Not only can it improve the mechanical properties of the material, but also can reduce the production cost, and can take into account the odor and combustion characteristics of the material, so as to obtain better market application prospect. SUMMARY

[0006] In view of the problems existing in the prior art, the natural fiber reinforced material in the prior art and technology is chemically modified after the formula components, the cost is increased, and the fiber structure and strength are lost, and meanwhile, the combustion performance and odor of the material can be considered. The application utilizes the characteristics of double screw extrusion to make the active functional groups between the components react in situ under the processing conditions to produce corresponding chemical effects, thereby reducing the cost, better preserving the crystal structure of the fiber, and obtaining the fiber reinforced material with excellent mechanical properties, good odor and not easy to burn, so as to be applied more widely in the fields of automobiles and household appliances.

[0007] To achieve the above object, the technical scheme adopted by the application is as follows: a natural fiber reinforced ABS composite material, characterized in that the composite material is composed of main materials and auxiliary materials, the main materials are prepared from the following components by weight fraction:

[0008] acrylonitrile-butadiene-styrene copolymer 75-90 parts;

[0009] natural fiber and / or modified natural fiber 5-25 parts;

[0010] hydroxyl-terminated polybutadiene 1-10 parts;

[0011] The modified natural fiber is a natural fiber in which the primary alcohol hydroxyl group at the C6 position of the cellulose structure is oxidized into a carboxyl group;

[0012] The auxiliary materials are prepared from the following components by weight fraction, taking the total weight fraction of the main materials as 100 parts:

[0013] antioxidant 0.1-0.3 parts.

[0014] Preferably, the antioxidant is composed of beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propyl octadecyl ester and tri-(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:1.

[0015] Preferably, the butadiene content of the acrylonitrile-butadiene-styrene copolymer is 10-30%.

[0016] Preferably, the hydroxyl value of the hydroxyl-terminated polybutadiene is 0.47-0.70 mmol KOH / g, and the number average molecular weight is between 3000 and 4600.

[0017] Preferably, the preparation method of the modified natural fiber comprises the following steps:

[0018] (1) the dried natural fiber is prepared into a suspension with a mass fraction of 1-3% by using deionized water, and 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO) with a mass fraction of 1-2% and NaBr with a mass fraction of 8-13% are added (all the mass fractions are relative to the mass of the dried natural fiber) ;

[0019] (2) the NaClO solution is slowly added into the reaction system, and the reaction is stirred at room temperature for 3-5 hours; during the reaction, the pH value of the reaction system is adjusted to 10.0-10.5 by using NaOH and HCl solutions;

[0020] (3) when the reaction is completed, anhydrous ethanol is added to terminate the reaction, the pH value is adjusted to 7 by using an HCl solution, and the reaction solution is dialyzed in a dialysis bag (with a molecular weight cut-off of 3.5-4.0 kDa) for 3-4 days until the conductivity of the dialysis solution is similar to that of distilled water, and thus the modified natural fiber is obtained.

[0021] The application further provides a preparation method of a natural fiber reinforced ABS composite material, which comprises the following steps:

[0022] (1) the acrylonitrile-butadiene-styrene copolymer, the hydroxyl-terminated polybutadiene in the main material, and the antioxidant in the auxiliary material are uniformly mixed to obtain a mixture;

[0023] (2) the natural fiber and / or the modified natural fiber is added into another high-speed stirrer for homogenization;

[0024] (3) the mixed material in step (1) is added into a parallel double-screw extruder through a feeder, and the mixed material in step (2) is added into the parallel double-screw extruder laterally to perform melt extrusion and granulation, and the process parameters include: the temperature of the first zone is 160-180 DEG C, the temperature of the second zone is 170-190 DEG C, the temperature of the third zone is 185-205 DEG C, the temperature of the fourth zone is 195-215 DEG C, the temperature of the fifth zone is 190-210 DEG C, the temperature of the sixth zone is 210-230 DEG C, the temperature of the seventh zone is 210-230 DEG C, the temperature of the eighth zone is 210-230 DEG C, the temperature of the die head is 200-220 DEG C, and the screw rotation speed is 400-800 rpm.

[0025] Preferably, the screw shape of the parallel double-screw extruder is single thread; the ratio L / D of the screw length L and the screw diameter D of the parallel double-screw extruder is 35-55; the screw of the parallel double-screw extruder is provided with one or more than one meshing block zone and one or more than one reverse thread zone; and / or in step (1) and / or step (2), the stirrer is a high-speed stirrer, and the rotation speed is 350-1500 rpm.

[0026] The preparation method is simple, environmentally friendly, and efficient, and has good application prospects in the automotive and home appliance fields.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. This invention utilizes the inherent characteristics of twin-screw extrusion to enable in-situ reactions of active functional groups between components under processing conditions. While improving the compatibility between fibers and resin matrix, the twin-screw extrusion facilitates in-situ etherification and / or esterification reactions between natural fibers and / or modified natural fibers and butadiene with terminal hydroxyl groups. The generated H2O can be discharged under negative pressure and heating conditions, further carrying out small molecules in the material and achieving the effect of reducing odor.

[0029] 2. Unlike existing technologies that modify natural fibers through at least two steps, this invention obtains the target product in at most one step, selectively oxidizing the primary alcohol hydroxyl group at the C6 position of cellulose to a carboxyl group, thereby reducing costs while preserving the crystal structure and strength of cellulose.

[0030] 3. The composite material prepared by this invention can generate water vapor during combustion, which not only absorbs the heat of combustion, but also forms a barrier between the combustible material and the surrounding oxygen, thus delaying combustion and having a wide range of applications.

[0031] 4. The hydroxyl-terminated polybutadiene in the composite material prepared by the present invention can also form hydrogen bonds with the primary alcohol hydroxyl groups and / or carboxyl groups at the C6 position of natural fibers and / or oxidized natural fibers. This can improve compatibility and form a cross-linked network, hindering the volatilization of small molecules and improving odor.

[0032] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0033] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0034] Figure 1 These are TEM images of natural fibers, oxidized natural fibers, and azide-treated natural fibers, where (A) represents natural fibers, (B) represents oxidized natural fibers, and (C) represents azide-treated natural fibers.

[0035] Figure 2This is a schematic diagram of the reaction in which the primary alcohol hydroxyl group at the C6 position of the natural cellulose structure is oxidized to a carboxyl group.

[0036] Figure 3 This is a schematic diagram of the reaction between oxidized natural fibers and hydroxyl-terminated polybutadiene to form ester bonds.

[0037] Figure 4 This is a schematic diagram of the reaction between natural fibers and hydroxyl-terminated polybutadiene to form ether bonds. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art.

[0039] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, wholes, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or sets thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0040] This invention provides a technical solution: a natural fiber reinforced ABS composite material and its preparation method.

[0041] Examples 1-4 and Comparative Examples 1-4 were prepared according to the raw material components (in parts by weight) in Table 1, and following the steps below:

[0042] The steps in Examples 3-4 are as follows:

[0043] (1) Prepare a 2% (w / w) suspension of dried natural fiber with deionized water, and add 1.8% (w / w) of 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO) and 12% (w / w) of NaBr (w / w) (w / w) relative to the mass of dried natural fiber).

[0044] (2) Add 10 mmol / g NaClO solution dropwise to the reaction system and stir at room temperature for 4 h; during the reaction, adjust the pH of the reaction system to 10.2 with 0.1 mol / L NaOH and 0.1 mol / L HCl solution;

[0045] (3) When the reaction is complete, add anhydrous ethanol to terminate the reaction, then adjust the pH value to 7 with 0.1 mol / L HCl solution. Use a dialysis bag (molecular weight cutoff 3.7 kDa) to dialyze the reaction solution for 3 days until the conductivity of the dialysate is similar to that of distilled water, thus obtaining the modified natural fiber. The reaction diagram is shown below. Figure 2 As shown;

[0046] (4) The acrylonitrile-butadiene-styrene copolymer, hydroxyl-terminated polybutadiene and antioxidant in the main material are mixed evenly according to the raw material composition (in parts by weight) in Table 1 to obtain a mixture;

[0047] (5) Add the natural fiber and / or modified natural fiber to another high-speed mixer for homogenization according to the raw material composition (in parts by weight) in Table 1;

[0048] (6) The mixture prepared in step (4) is fed into the parallel twin-screw extruder via a feeder, and the mixture prepared in step (5) is added to the side of the parallel twin-screw extruder for melt extrusion and granulation. The process parameters include: zone 1 temperature is 170℃, zone 2 temperature is 180℃, zone 3 temperature is 195℃, zone 4 temperature is 205℃, zone 5 temperature is 200℃, zone 6 temperature is 220℃, zone 7 temperature is 220℃, zone 8 temperature is 220℃, die head temperature is 210℃, and screw speed is 500rpm.

[0049] Compared with Examples 3 and 4, Examples 1 and 2 omit steps (1) to (3) above, while the remaining steps are the same.

[0050] The resulting product is a natural hemp fiber reinforced ABS composite material, of which Comparative Example 2 and Comparative Example 4 are ABS materials and ABS composite materials without added natural fibers.

[0051] Different proportions of each component were selected in Examples 1-4, as detailed in Table 1.

[0052]

[0053] Comparative Example 1

[0054] Chinese invention patent, application number: 201811612098.0, publication announcement number: CN109735048A, discloses a natural fiber reinforced ABS composite material and its preparation method, which prepares azide-reinforced natural fibers and alkynylated polybutadiene by referring to the method described in the embodiments of its specification;

[0055] ① Place 3.0–5.0 parts by weight of natural hemp fiber into an aprotic polar solvent in a reactor, introduce nitrogen gas to create an inert environment inside the reactor, heat to 150°C and maintain for 1.5 hours, then lower the temperature to 100°C and add 8.0 parts by weight of anhydrous lithium chloride into the reactor and dissolve it. Then add 19 parts by weight of p-methylbenzenesulfonyl chloride at 8°C and react homogeneously to obtain an intermediate.

[0056] ② The intermediate is placed in a dimethyl sulfoxide solution containing 18 parts by weight of sodium azide, and after a substitution reaction, azide-functionalized natural fiber material is obtained.

[0057] ③ Add the hydroxyl-terminated polybutadiene solution to the potassium tert-butoxide solution, and under nitrogen protection, perform an ice bath and stirring. Then add the propyne bromine solution and react at 8°C for 30 hours to obtain the reaction solution.

[0058] ④The reaction solution was extracted to obtain alkynylated polybutadiene;

[0059] It should be noted that in step ①, the aprotic polar solvent is 150 parts by weight of N,N-dimethylacetamide, and the intermediate needs to be precipitated with an ethanol-water mixture and purified with deionized water, washed and vacuum dried before it can be obtained.

[0060] In step ②, the substitution reaction specifically involves reacting toluenesulfonate and sodium azide at 130°C for 10 hours; the azide-functionalized natural fiber material needs to be cooled, precipitated, purified, and vacuum dried before it can be obtained.

[0061] In step ③, the hydroxyl-terminated polybutadiene solution is prepared according to a mass-to-volume ratio of hydroxyl-terminated polybutadiene to tetrahydrofuran of 10 g: 20 mL.

[0062] The potassium tert-butoxide solution was prepared according to a mass-volume ratio of potassium tert-butoxide to tetrahydrofuran of 2g:20mL.

[0063] The propyne bromine solution was prepared with a volume ratio of propyne bromine to tetrahydrofuran of 2.0:60.

[0064] In step ④, the extraction process specifically involves adding brine to the reaction solution, separating the aqueous layer and retaining the tetrahydrofuran layer, then extracting the aqueous layer with ethyl acetate, collecting the organic layer, extracting the organic layer again with saturated brine, discarding the aqueous layer, and combining the obtained material with the aforementioned retained tetrahydrofuran layer to obtain the organic material; the organic material is dried with anhydrous MgSO4, filtered, and the solvent is evaporated to obtain alkynylated polybutadiene.

[0065] Compared with Examples 3-4, Comparative Examples 1-4 omit steps (1)-(3) above, while the remaining steps are the same.

[0066] Several basic performance tests were performed on the natural fiber reinforced ABS composite materials prepared in Examples 1-4 and Comparative Examples 1-4, and the average values ​​were taken. The test methods are as follows:

[0067] (1) Tensile strength, tested according to ISO 527 standard, with a tensile rate of 50 mm / min.

[0068] (2) Notched impact strength, tested according to ISO 180 standard.

[0069] (3) Burning rate, tested according to GB / T 2408-2021 standard, using the horizontal burning test to measure the burning rate of a 1.6 mm sample.

[0070] (4) Odor test: The odor was tested using the high-temperature bottle method according to the PV3900-2000 standard. The test conditions were 80±2℃ and 2h±10min. 20g of natural fiber reinforced ABS composite material particles were placed in a 1L special odor bottle. The container was placed in an oven at 80±2℃ and stored for 2 hours±10min. After the odor bottle was cooled to 60±5℃, the odor was evaluated. No odor -1; Odor present, but no interfering odor -2; Obvious odor present, but no interfering odor -3; Interfering odor present -4; Strong interfering odor present -5; Unbearable odor present -6.

[0071] The test results are shown in Table 2:

[0072] Table 2. Test results of basic properties of alloy materials

[0073]

[0074] pass Figure 1 It can be seen that, compared with the unmodified natural fibers, the modified natural fibers have slightly smaller fiber sizes and are more prone to aggregation in the transmission electron microscopy images. Among them, the morphology of the azide-modified natural fibers is significantly different from that of the unmodified natural fibers.

[0075] Comparing the test results of Examples 1-4 and Comparative Example 1, the mechanical properties, combustion (delayed combustion) performance, and odor of the natural fiber reinforced ABS material obtained in the embodiments of the present invention are significantly better than those of Comparative Example 1. This is because the present invention minimizes the steps of surface modification of natural fibers, and at most uses a one-step method to obtain the modified target product as needed. This not only reduces the process and lowers the cost, but also preserves the crystal structure and strength of cellulose to the greatest extent. Furthermore, the twin-screw extrusion process allows natural fibers and / or modified natural fibers to react in situ with hydroxyl-terminated polybutadiene to generate small molecule H2O. By heating and vacuuming, the volatile small molecules in the composite are carried out with the H2O gas flow, thereby achieving a low odor effect. In addition, the hydroxyl-terminated polybutadiene in the composite material prepared by the present invention can also form hydrogen bonds with the primary alcohol hydroxyl groups and / or carboxyl groups at the C6 position of natural fibers and / or oxidized natural fibers. This not only improves compatibility but also forms a cross-linked network, hindering the volatilization of small molecules and improving odor.

[0076] By comparing the test results of Examples 2-4 and Comparative Examples 1-2, it can be seen that the combustion rate of the examples is significantly lower. The present invention avoids the introduction of azide groups with energetic structures. The water vapor generated during combustion not only absorbs the heat of combustion, but also forms a barrier between the combustibles and the surrounding oxygen, thereby achieving the effect of delaying combustion.

[0077] Furthermore, by comparing the test results of Examples 2-4 and Comparative Examples 3-4, the mechanical properties, odor, and combustion (delayed combustion) performance of the examples were all better. By using the conditions of twin-screw extrusion processing to allow natural fibers and / or modified natural fibers to undergo an in-situ reaction with hydroxyl-terminated polybutadiene, not only was the compatibility between hydrophilic natural fibers and hydrophobic ABS improved through polybutadiene, thus obtaining good mechanical properties, but the prepared composite material also had the effects of low odor and delayed horizontal combustion rate.

[0078] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A natural fiber reinforced ABS composite material, characterized by: The composite material is composed of a main material and an auxiliary material, wherein the main material is prepared from the following components in parts by weight: acrylonitrile-butadiene-styrene copolymer 75-90 parts; natural fiber and / or modified natural fiber 5-25 parts; hydroxyl-terminated polybutadiene 1-10 parts; the modified natural fiber is a natural fiber with carboxyl groups obtained by oxidizing primary alcohol hydroxyl groups at C6 position of cellulose structure; the auxiliary material is prepared from the following components in parts by weight based on 100 parts of the total weight of the main material: antioxidant 0.1-0.3 parts.

2. The natural fiber reinforced ABS composite according to claim 1, characterized in that, the antioxidant is composed of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propyl octadecyl ester and tri-(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:

1.

3. The natural fiber reinforced ABS composite according to claim 1 or 2, characterized in that, the butadiene content of the acrylonitrile-butadiene-styrene copolymer is 10-30%.

4. The natural fiber reinforced ABS composite according to claim 1 or 2, characterized in that, the hydroxyl value of the hydroxyl-terminated polybutadiene is 0.47-0.70 mmol KOH / g, and the number average molecular weight is between 3000 and 4600.

5. The natural fiber reinforced ABS composite according to claim 1 or 2, characterized in that, the preparation method of the modified natural fiber comprises the following steps: (1) preparing a suspension of the dried natural fiber in deionized water with a mass fraction of 1-3%, and adding 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO) with a mass fraction of 1-2% and NaBr with a mass fraction of 8-13% (both relative to the mass of the dried natural fiber); (2) slowly adding NaClO solution to the reaction system, stirring at room temperature for 3-5 h; during the reaction, adjusting the pH value of the reaction system to 10.0-10.5 with NaOH and HCl solutions; (3) adding anhydrous ethanol to terminate the reaction at the end of the reaction, adjusting the pH value to 7 with an HCl solution, and dialyzing the reaction solution in a dialysis bag (molecular weight cut-off 3.5-4.0 kDa) for 3-4 days until the conductivity of the dialysate is similar to that of distilled water, thereby obtaining the modified natural fiber.

6. A process for the production of natural fiber reinforced ABS composites according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) mixing the acrylonitrile-butadiene-styrene copolymer, hydroxyl-terminated polybutadiene in the main material, and the antioxidant in the auxiliary material uniformly to obtain a mixture; (2) adding the natural fiber and / or modified natural fiber to another high-speed mixer for homogenization; (3) feeding the mixed material from step (1) into a parallel twin-screw extruder through a feeder, and adding the mixture from step (2) to the side of the parallel twin-screw extruder for melt extrusion and granulation, with the process parameters including: zone 1 temperature 160-180℃, zone 2 temperature 170-190℃, zone 3 temperature 185-205℃, zone 4 temperature 195-215℃, zone 5 temperature 190-210℃, zone 6 temperature 210-230℃, zone 7 temperature 210-230℃, zone 8 temperature 210-230℃, die temperature 200-220℃, and screw rotation speed 400-800 rpm.

7. The method of producing natural fiber reinforced ABS composites according to claim 6, characterized in that, The screw shape of the parallel twin-screw extruder is single thread; and / or, the ratio L / D of the screw length L and diameter D of the parallel twin-screw extruder is 35-55; the screw of the parallel twin-screw extruder is provided with one or more than one meshing block area and one or more than one reverse thread area; and / or, in step (1) and / or step (2), the mixer is a high-speed mixer, and the rotating speed is 350-1500 rpm.

Images