CN108085766B - Cellulose nano fibril reinforced acrylic fiber and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of polymer molding, and discloses a cellulose nanofiber reinforced acrylic fiber and a preparation method and application thereof. The preparation method of the cellulose nanofibril reinforced acrylic fiber is divided into two steps: in the first step, polyacrylonitrile is pretreated and then dissolved in a solvent as an acrylic fiber stock solution, and then cellulose nanofibrils are added to the acrylic fiber stock solution. , and the spinning solution is obtained after uniform dispersion. In the second step, the spinning solution is spun on a spinning machine, and after coagulation bath, it is drawn according to a certain drawing ratio, and finally it is crimped and packaged. The cellulose nanofibril reinforced acrylic fiber not only has good tensile strength, but also has greatly improved dyeing properties compared with traditional acrylic fibers, and can be used to make fabrics such as blankets and carpets, and can also be used as outdoor fabrics. Such as ski jackets, sails, military canvas, tents, etc.

Description

A kind of cellulose nanofibril reinforced acrylic fiber and its preparation method and application

technical field

The invention belongs to the technical field of polymer molding, and in particular relates to a cellulose nanofiber reinforced acrylic fiber and a preparation method and application thereof.

Background technique

Nanofibers have become widely studied and applied one-dimensional nanomaterials due to their unique physicochemical properties and properties. Nanofibers can be further divided into cellulose nanowhiskers and cellulose nanofibrils. Cellulose nanowhiskers are generally prepared by acid hydrolysis. They have a highly oriented structure, but are small in size (2-20nm in diameter, 100-600nm in length, and 10-100 in aspect ratio). The preparation process requires strong acid treatment. The preparation process is complicated and the cost is high. Cellulose nanofibrils are the products of cellulose raw materials treated by enzymatic hydrolysis or mechanical methods to fibrillate cellulose, and have a high aspect ratio (diameter 10-40nm, length greater than 1μm, aspect ratio greater than 100) ( Siro, I., & Plackett, D. (2010). Microfibrillated cellulose and new nanocomposite materials: review. Cellulose, 17(3), 459-494.). Compared with cellulose nanowhiskers, the preparation method of cellulose nanofibrils is simple and lower in cost, and it is easier to realize the application in industrialization.

Acrylic fiber, also known as polyacrylonitrile fiber, is known as "synthetic wool". Although compared with wool, there is still a certain distance in terms of hygroscopicity, hand feel, milled type and elasticity, but acrylic fiber also has many advantages. Such excellent characteristics as warmth retention, mildew resistance, moth resistance, and bulkiness are widely studied on its application. At the same time, it has the remarkable characteristics of sun resistance and chemical resistance. fiber. However, the dyeability and hygroscopicity of acrylic fibers are not good, resulting in poor wearing performance, and it is not easy to be made into high-end acrylic fibers. Most of them are products with low added value. The strength of traditional polyacrylonitrile fibers is not high, and the wear resistance and fatigue resistance are also poor. Some researchers have blended acrylic fibers with cellulose fibers, but the fibers of single-dyed fabrics are unevenly mixed, and the acrylic fibers are scratched. The rubbing damage causes the problem of crosspieces such as hairiness deterioration, which further restricts the improvement of the quality of acrylic fibers.

Most of the published patents related to acrylic fibers focus on the functionalization of acrylic fibers, such as flame retardancy (Chinese Patent Application No. 2015101883251), anti-pilling (Chinese Patent Application No. 2012103590942), antibacterial properties (Chinese Patent Application No. 2016104843744) ), UV resistance (Chinese Patent Application No. 2015104585036), and electrical conductivity (Chinese Patent Application No. 2008100742254); however, there are few patent reports on cellulose nanofibrils directly reinforcing acrylic fibers. The Chinese patent application with application number 201610425121X discloses a calcium titanate nanofiber and acrylic fiber pulp reinforced thermal insulation mortar and a preparation method thereof. The method adopts calcium titanate nanomaterials to enhance and improve the thermal insulation and corrosion resistance of acrylic fiber pulp As a building insulation material, there is no disclosure of the application of acrylic fibers. The Chinese patent application with the application number of 2013101658127 discloses a preparation method of high-strength viscose fiber. The purpose of reinforcing the viscose fiber is realized by adding nano-whiskers in the viscose liquid, but the size of the nano-whiskers used is small and industrialized. The preparation cost is relatively high, which is not conducive to large-scale industrial application.

SUMMARY OF THE INVENTION

In order to solve the shortcomings and deficiencies of the prior art and obtain acrylic fibers with high tensile strength, moisture absorption performance, dyeing performance and wearability, the primary purpose of the present invention is to provide a preparation of cellulose nanofibrils reinforced acrylic fibers method. The invention improves the traditional preparation process of acrylic fibers, introduces cellulose nanofibrils as a reinforcing phase, obtains acrylic fibers with good tensile strength, moisture absorption performance, dyeing performance and wearability, and expands the application range of cellulose nanofibrils. The surface of cellulose nanofibrils is rich in hydroxyl groups, has a high Young's modulus and has an extremely high specific surface area, making it the material of choice for many advanced applications. On the other hand, cellulose nanofibrils have the characteristics of natural fibers that are easy to absorb moisture and regain moisture, and can also be used in the improvement of material functionalization.

Another object of the present invention is to provide a cellulose nanofibril reinforced acrylic fiber.

Another object of the present invention is to provide the application of the above-mentioned cellulose nanofibril reinforced acrylic fiber.

For realizing the above-mentioned purpose of the invention, the present invention adopts following technical scheme:

A preparation method of cellulose nanofibril reinforced acrylic fiber, comprising the following steps:

(1) Dissolve polyacrylonitrile (PAN) in the dissolving solution after pretreatment to prepare a certain mass fraction of acrylic fiber stock solution;

(2) adding cellulose nanofibrils (CNF) into the acrylic fiber stock solution, so that the CNF/PAN reaches a suitable ratio, and preparing the acrylic fiber spinning solution; deaerating the acrylic fiber spinning solution under vacuum;

(3) The defoamed acrylic spinning solution is spun on a spinning machine, and after passing through a coagulation bath, the draw ratio is adjusted, and the cellulose nanofibril-reinforced acrylic fibers are collected after washing and drying.

Preferably, the pretreatment in step (1) is alkaline pretreatment, and the specific conditions are: in an aqueous solution with a mass fraction of sodium hydroxide of 1-20% and a mass fraction of ethanol of 75-95%, at 60-100° C. Treatment 30 ~ 150min.

Preferably, the dissolving solution in step (1) can be one of dimethylformamide, dimethyl sulfoxide, sodium thiocyanate, zinc chloride, etc., preferably dimethylformamide;

Preferably, the mass fraction of the PAN in the dissolving solution in step (1) is 1-50% (that is, the mass fraction of the acrylic fiber stock solution is 1-50%).

Preferably, the CNF/PAN described in step (2) is a mass ratio of 1:(1～100);

Preferably, the cellulose nanofibrils described in step (2) have a diameter of 10-100 nm, a length greater than 1 μm, and an aspect ratio greater than 100. The surface chemical groups, specific surface area and reactivity of cellulose nanofibrils with different aspect ratios are different, so the length and diameter of cellulose nanofibrils affect properties such as tensile strength, elongation at break and elastic modulus.

More preferably, the cellulose nanofibrils described in step (2) have a diameter of 10-100 nm and a length of 2-10 μm.

Preferably, the vacuum defoaming conditions in step (2) are that the vacuum degree is -0.1MPa, and the defoaming time is 1-10h.

Preferably, the coagulation bath described in step (3) is an aqueous solution of sodium sulfate, zinc sulfate and sulfuric acid; the mass concentrations of sodium sulfate, zinc sulfate and sulfuric acid are respectively 1-20%, 1-20% and 1-20%.

Preferably, the drafting multiple in step (3) is 1 to 20 times;

Preferably, the drying conditions in step (3) are drying at 40-150° C. for 1-24 hours.

The above-mentioned cellulose nanofibril reinforced acrylic fiber can be widely used in the textile field, and can be used to make fabrics such as blankets and carpets, and can also be used as outdoor fabrics, such as ski jackets, sails, military canvas, tents, and the like.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The method for preparing a cellulose nanofibril reinforced acrylic fiber according to the present invention firstly conducts partial hydrolysis of polyacrylonitrile under alkaline conditions, so that cyano group (-C≡N) and ^OH- undergo nucleophilic addition The reaction finally generates carboxyl and amide groups. On the one hand, CNF contains a large amount of -OH, which has a strong hydrogen bond effect with the N atom, carboxyl group and amide group in the modified polyacrylonitrile structure during the drying process, which increases the strength of the acrylic fiber. On the other hand, taking advantage of the high crystallinity and small size of CNF, by mixing CNF and PAN spinning solution and spinning, and drawing the yarn with the help of external force, the close arrangement of CNF in the radial direction can be achieved to enhance the strength of acrylic fiber. Purpose. On the other hand, cellulose nanofibrils retain the characteristics of natural fibers that are easy to absorb moisture and regain moisture, which can improve the moisture absorption performance of acrylic fibers to a certain extent.

Description of drawings

FIG. 1 is a schematic diagram of the preparation process of a cellulose nanofibril reinforced acrylic fiber of the present invention.

FIG. 2 is a topography diagram of the cellulose nanofibril reinforced acrylic fiber prepared by the present invention.

Fig. 3 is the tensile strength diagram of acrylic fiber.

Figure 4 is a graph of the elongation of acrylic fibers.

Detailed ways

The present invention will be described in further detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

Each starting material in the preparation method of the present invention can be purchased from the market.

D的纤维素酶)，在40～50℃下震荡18～24h，得到纤维素悬浮液，过滤洗涤后，滤液在80～90℃高温灭活。将上述处理后的纤维素在压力为1000～1500 Bar下微纤化磨浆，得到浆液浓度为15wt％的微纳米纤维素浆液，然后用高压微射流均质机在20000～30000Bar压力下处理3～10次，即可制得直径为10～100nm，长度为2～10μm的纤维素纳米纤丝。The preparation method of the cellulose nanofibrils used in the examples refers to our previous related reports (Chen Kefu, Zeng Jinsong, Wang Bin, Li Jinpeng. A preparation method of micro-nano cellulose [P]. 2016. CN106367455A), The control of the diameter and length of cellulose nanofibrils (ie micro-nanocellulose described in patent CN106367455A) can be achieved according to different homogenization treatment conditions. The specific method is as follows: mix the plant fiber raw material with the citric acid-sodium citrate buffer solution of pH=(5～8) in a liquid ratio of 1:(25～35) g/ml, and add the plant fiber raw material in a ratio of 20～40IU /g of cellulase (Novozymes model is

D cellulase), shake at 40-50°C for 18-24h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 80-90°C. Microfibrillating and refining the cellulose after the above treatment at a pressure of 1000-1500 Bar to obtain a micro-nano cellulose slurry with a slurry concentration of 15 wt%, and then using a high-pressure micro-jet homogenizer to process 3 under a pressure of 20,000-30,000 Bar. 10 times, the cellulose nanofibrils with a diameter of 10-100 nm and a length of 2-10 μm can be prepared.

Comparative ratio

The preparation method of the cellulose nanofibrils of this comparative example is as follows:

D的纤维素酶)，在40℃下震荡24h，得到纤维素悬浮液，过滤洗涤后，滤液在85℃高温灭活。将上述处理后的纤维素在压力为1000Bar下微纤化磨浆，得到浆液浓度为5wt％的微纳米纤维素浆液，然后用高压微射流均质机在 20000Bar压力下处理10次，得到直径为5nm、长度为1.5μm的纤维素纳米纤丝。The plant fiber raw material is mixed with the citric acid-sodium citrate buffer solution of pH=6 according to the liquid ratio of 1:20g/ml, and the cellulase (Novozymes company model is 30IU/g) is added to the plant fiber raw material.

D cellulase), shake at 40°C for 24h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 85°C. The cellulose after the above treatment is microfibrillated and refined under a pressure of 1000Bar to obtain a micro-nanocellulose slurry with a slurry concentration of 5wt%, and then treated with a high-pressure microjet homogenizer for 10 times under a pressure of 20000Bar to obtain a diameter of Cellulose nanofibrils of 5 nm and 1.5 μm in length.

The comparative example of cellulose nanofibril reinforced acrylic fiber, the specific preparation method is as follows:

(1) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 100 °C for 90 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in sodium thiocyanate to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 20%.

(2) Add cellulose nanofibrils (CNF) with a diameter of 5 nm and a length of 1.5 μm into the acrylic fiber stock solution, so that the mass ratio of CNF to PAN reaches 1.5:1, and after mixing, it is configured into an acrylic fiber spinning solution. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 36h.

(3) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with a mass fraction of sodium sulfate, zinc sulfate and sulfuric acid of 8%, 12%, and 20%, respectively. The stretching ratio was 1 times, and the cellulose nanofibril-reinforced acrylic fibers were collected after washing and drying.

The mechanical properties of the prepared fibers were tested by a monofilament fiber tensile tester. The test method was GB T 14337-2008. The experimental results showed that the tensile strength and elongation at break of the fibers in this comparative example were 1.93 cN/Tex and 7.56%, respectively. .

Example 1

The preparation method of the additive-free acrylic fiber is as follows:

(1) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 85 °C for 30 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethylformamide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 10%. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 10h.

(2) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with the mass fractions of sodium sulfate, zinc sulfate and sulfuric acid of 20%, 5%, and 10%, respectively. The stretching ratio is 5 times, and the acrylic fibers are collected after washing and drying.

Example 2

Inorganic nano-silicon carbide whiskers reinforced acrylic fiber, the preparation method is as follows:

(1) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 85 °C for 30 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethylformamide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 10%.

(2) Inorganic nano-silicon carbide with a diameter of 20 nm and a length of 800 nm was added to the acrylic fiber stock solution, so that the mass ratio of inorganic nano-silicon carbide and PAN reached 1:100, and the acrylic fiber spinning solution was prepared after stirring. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 10h.

(3) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with a mass fraction of sodium sulfate, zinc sulfate and sulfuric acid of 10%, 20%, and 1%, respectively. The elongation factor is 2 times, and the acrylic fiber reinforced by inorganic nano-silicon carbide whiskers is collected after washing and drying.

Example 3

Nano cellulose whisker reinforced acrylic fiber, its preparation method is as follows:

(1) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 85 °C for 30 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethylformamide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 15%.

(2) Nanocellulose whiskers (NCC) with a diameter of 5 nm and a length of 200 nm were added to the acrylic fiber stock solution, so that the mass ratio of NCC and PAN reached 1:100, and the acrylic fiber spinning solution was prepared after mixing. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 10h.

(3) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with a mass fraction of sodium sulfate, zinc sulfate and sulfuric acid of 10%, 20%, and 1%, respectively. The elongation factor was 20 times, and the nanocellulose whisker-reinforced acrylic fibers were collected after washing and drying.

Example 4

A preparation method of cellulose nanofibril reinforced acrylic fiber, the steps are as follows:

D的纤维素酶)，在40℃下震荡18h，得到纤维素悬浮液，过滤洗涤后，滤液在80℃高温灭活。将上述处理后的纤维素在压力为1000Bar下微纤化磨浆，得到浆液浓度为8wt％的微纳米纤维素浆液，然后用高压微射流均质机在25000Bar压力下处理4次，得到直径为10nm、长度为5μm的纤维素纳米纤丝。(1) Preparation of cellulose nanofibrils: Mix the plant fiber raw material with the citric acid-sodium citrate buffer solution of pH=8 in a liquid ratio of 1:40 g/ml, and add fibers with a ratio of 35 IU/g to the plant fiber raw material. Vegetase (Novozymes model is

D cellulase), shake at 40 °C for 18 h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 80 °C. The cellulose after the above treatment was microfibrillated and refined under a pressure of 1000Bar to obtain a micro-nanocellulose slurry with a slurry concentration of 8wt%, and then treated with a high-pressure micro-jet homogenizer for 4 times under a pressure of 25000Bar to obtain a diameter of Cellulose nanofibrils of 10 nm and 5 μm in length.

(2) Polyacrylonitrile (PAN) was treated in an aqueous solution with a mass fraction of 1% sodium hydroxide and a mass fraction of 95% ethanol at 85 °C for 30 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethylformamide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 50%.

(3) Add cellulose nanofibrils (CNF) with a diameter of 10 nm and a length of 5 μm into the acrylic fiber stock solution, so that the mass ratio of CNF to PAN reaches 1:100, and after mixing, it is prepared into an acrylic fiber spinning solution. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 10h.

(4) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with sodium sulfate, zinc sulfate and sulfuric acid with mass fractions of 10%, 20%, and 1%, respectively. The draw ratio was 20 times, and the cellulose nanofibril reinforced acrylic fibers were collected after washing and drying.

Example 5

A preparation method of cellulose nanofibril reinforced acrylic fiber, the steps are as follows:

(1) Preparation of cellulose nanofibrils: mix the plant fiber raw material with a citric acid-sodium citrate buffer solution of pH=7 in a liquid ratio of 1:30 g/ml, add fibers with a ratio of 20 IU/g to the plant fiber raw material Vegetase (Novozymes model is D cellulase), shake at 45°C for 20h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 90°C. The cellulose after the above treatment was microfibrillated and refined at a pressure of 1300Bar to obtain a micro-nanocellulose slurry with a slurry concentration of 1wt%, and then treated with a high-pressure microjet homogenizer for 3 times under a pressure of 28000Bar to obtain a diameter of 1 wt %. Cellulose nanofibrils of 50 nm and 10 μm in length.

(2) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 60 °C for 60 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethyl sulfoxide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 10%.

(3) Add cellulose nanofibrils (CNF) with a diameter of 50 nm and a length of 10 μm into the acrylic fiber stock solution, so that the mass ratio of CNF to PAN reaches 1:80, and mixes evenly to prepare an acrylic fiber spinning solution. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 5h.

(4) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with sodium sulfate, zinc sulfate and sulfuric acid whose mass fractions are 20%, 1%, and 10%, respectively. The stretching ratio was 10 times, and the cellulose nanofibril-reinforced acrylic fibers were collected after washing and drying.

Example 6

A preparation method of cellulose nanofibril reinforced acrylic fiber, the steps are as follows:

(1) Preparation of cellulose nanofibrils:

D的纤维素酶)，在50℃下震荡20h，得到纤维素悬浮液，过滤洗涤后，滤液在90℃高温灭活。将上述处理后的纤维素在压力为1000Bar下微纤化磨浆，得到浆液浓度为5wt％的微纳米纤维素浆液，然后用高压微射流均质机在 30000Bar压力下处理5次，得到直径为50nm、长度为5μm的纤维素纳米纤丝。The plant fiber raw material is mixed with the citric acid-sodium citrate buffer solution of pH=7.5 according to the liquid ratio of 1:25g/ml, and the cellulase (Novozymes company model is 25IU/g) is added with the plant fiber raw material ratio.

D cellulase), shake at 50 °C for 20 h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 90 °C. The cellulose after the above treatment is microfibrillated and refined under a pressure of 1000Bar to obtain a micro-nanocellulose slurry with a slurry concentration of 5wt%, and then treated with a high-pressure microjet homogenizer for 5 times under a pressure of 30000Bar to obtain a diameter of 5 wt%. Cellulose nanofibrils of 50 nm and 5 μm in length.

(2) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 100 °C for 90 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in sodium thiocyanate to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 1%.

(3) Add cellulose nanofibrils (CNF) with a diameter of 20 nm and a length of 2.5 μm into the acrylic fiber stock solution, so that the mass ratio of CNF to PAN reaches 1:50, and mixes evenly to prepare an acrylic fiber spinning solution. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 1h.

(4) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with a mass fraction of sodium sulfate, zinc sulfate and sulfuric acid of 8%, 12%, and 20%, respectively. The draw ratio was 20 times, and the cellulose nanofibril reinforced acrylic fibers were collected after washing and drying.

Example 7

A preparation method of cellulose nanofibril reinforced acrylic fiber, the steps are as follows:

(1) Preparation of cellulose nanofibrils: Mix the plant fiber raw material with a citric acid-sodium citrate buffer solution of pH=6 in a liquid ratio of 1:35 g/ml, and add fibers with a ratio of 30 IU/g to the plant fiber raw material. Vegetase (Novozymes model is D cellulase), shake at 50°C for 18h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 90°C. The cellulose after the above treatment was microfibrillated and refined at a pressure of 1500Bar to obtain a micro-nanocellulose slurry with a slurry concentration of 1wt%, and then processed 6 times with a high-pressure microjet homogenizer under a pressure of 25000Bar to obtain a diameter of 1 wt %. Cellulose nanofibrils of 30 nm and 5 μm in length.

(2) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 85 °C for 150 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethylformamide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 50%.

(3) Add cellulose nanofibrils (CNF) with a diameter of 30 nm and a length of 5 μm into the acrylic fiber stock solution, so that the mass ratio of CNF to PAN reaches 1:1, and after mixing, it is prepared into an acrylic fiber spinning solution. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 10h.

(4) The acrylic fiber spinning solution after defoaming is spun on a spinning machine, and then coagulated into a coagulation bath with the mass fractions of sodium sulfate, zinc sulfate and sulfuric acid of 1%, 12%, and 5%, respectively. The stretching ratio was 1 times, and the cellulose nanofibril-reinforced acrylic fibers were collected after washing and drying.

Example 8

A preparation method of cellulose nanofibril reinforced acrylic fiber, the steps are as follows:

D的纤维素酶)，在40℃下震荡24h，得到纤维素悬浮液，过滤洗涤后，滤液在80℃高温灭活。将上述处理后的纤维素在压力为1000Bar下微纤化磨浆，得到浆液浓度为0.5wt％的微纳米纤维素浆液，然后用高压微射流均质机在30000Bar压力下处理10次，得到直径为10nm、长度为2μm的纤维素纳米纤丝。(1) Preparation of cellulose nanofibrils: Mix the plant fiber raw material with a citric acid-sodium citrate buffer solution of pH=8 in a liquid ratio of 1:35 g/ml, and add fibers with a ratio of 35 IU/g to the plant fiber raw material. Vegetase (Novozymes model is

D cellulase), shake at 40°C for 24h to obtain a cellulose suspension, filter and wash, and inactivate the filtrate at a high temperature of 80°C. Microfibrillating and refining the cellulose after the above treatment at a pressure of 1000Bar to obtain a micro-nanocellulose slurry with a slurry concentration of 0.5wt%, and then using a high-pressure microjet homogenizer for 10 times under a pressure of 30000Bar to obtain a diameter of Cellulose nanofibrils of 10 nm and 2 μm in length.

(2) Polyacrylonitrile (PAN) was placed in an aqueous solution with a mass fraction of sodium hydroxide of 1% and a mass fraction of ethanol of 95%, treated at 85 °C for 30 min, washed with water until neutral, and dried at 105 °C for 5 h. The pretreated polyacrylonitrile was dissolved in dimethylformamide to prepare an acrylic fiber stock solution with a mass fraction of polyacrylonitrile of 15%.

(3) Add cellulose nanofibrils (CNF) with a diameter of 10 nm and a length of 2 μm into the acrylic fiber stock solution, so that the mass ratio of CNF to PAN reaches 1:20, and after mixing, it is prepared into an acrylic fiber spinning solution. The acrylic fiber spinning solution was vacuum defoamed at -0.1MPa for 8h.

(4) The degassed acrylic fiber spinning solution is spun on a spinning machine, and then coagulated into a coagulation bath with sodium sulfate, zinc sulfate and sulfuric acid whose mass fractions are 10%, 12%, and 5%, respectively. The stretching ratio was 5 times, and the cellulose nanofibril-reinforced acrylic fibers were collected after washing and drying.

The tensile strength and elongation of the acrylic fibers prepared in Examples 1-8 were tested, and the test method was GB T14337-2008. The test results are shown in Figures 3 and 4.

Figure 2 shows the appearance and morphology of the acrylic fibers prepared in Examples 1 to 5. It can be seen that the appearance of the acrylic fibers does not change much after the addition of cellulose nanofibrils. As can be seen from Figure 3 and Figure 4, compared with the control experiment (Examples 1-3), both nanowhiskers (inorganic carbon nanotubes and nanocellulose whiskers, etc.) and cellulose nanofibrils can play a role in acrylic fibers. However, the effect of cellulose nanofibrils on the mechanical properties of acrylic fibers is better. When the mass ratio of cellulose nanofibrils and polyacrylonitrile was 1:90, the tensile strength of the prepared acrylic fibers increased significantly. With the increase of the concentration of cellulose nanofibrils in the acrylic fiber, the tensile strength first increases and then decreases. It may be that excessive addition of cellulose nanofibrils leads to uneven dispersion and flocculation in polyacrylonitrile, which eventually leads to the strength reduce.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (8)

1. A preparation method of cellulose nanofibril reinforced acrylic fiber is characterized by comprising the following steps:

(1) pretreating polyacrylonitrile, and dissolving in a dissolving solution to prepare an acrylic fiber stock solution with a certain mass fraction; the dissolving solution can be one of dimethylformamide, dimethyl sulfoxide, sodium thiocyanate and zinc chloride;

(2) adding the cellulose nano-fibrils into the acrylic fiber stock solution to enable the cellulose nano-fibrils/polyacrylonitrile to reach a proper proportion, and preparing acrylic fiber spinning solution; defoaming the acrylic fiber spinning solution in vacuum; the diameter of the cellulose nano-fibril is 10-100 nm, the length is more than 1 mu m, and the length-diameter ratio is more than 100; the mass ratio of the cellulose nano-fibril to the polyacrylonitrile is 1 (1-100);

(3) spinning the defoamed acrylic spinning solution on a spinning machine, adjusting the draft multiple after coagulating bath, washing and drying, and collecting the cellulose nanofibril reinforced acrylic fibers; the drafting multiple is 1-20 times.

2. The method for preparing cellulose nanofibril reinforced acrylic fiber according to claim 1, wherein the pretreatment in the step (1) is alkaline pretreatment, and the specific conditions are as follows: treating the mixture for 30-150 min at 60-100 ℃ in an aqueous solution with 1-20% by mass of sodium hydroxide and 75-95% by mass of ethanol;

the dissolving solution in the step (1) can be one of dimethylformamide, dimethyl sulfoxide, sodium thiocyanate and zinc chloride; in the step (1), the mass fraction of the polyacrylonitrile in the dissolving solution is 1-50%.

3. The method for preparing cellulose nanofibril reinforced acrylic fiber according to claim 1, wherein the vacuum defoaming condition in the step (2) is-0.1 MPa of vacuum degree and 1-10 h of defoaming time.

4. The method for preparing cellulose nanofibril reinforced acrylic fiber according to claim 1, wherein the coagulating bath in step (3) is an aqueous solution of sodium sulfate, zinc sulfate and sulfuric acid; the mass concentrations of the sodium sulfate, the zinc sulfate and the sulfuric acid are respectively 1-20%, 1-20% and 1-20%.

5. The method for preparing cellulose nanofibril reinforced acrylic fiber according to claim 1, wherein the drying condition in the step (3) is 40-150 ℃ for 1-24 hours.

6. A cellulose nanofibril reinforced acrylic fiber characterized in that it is produced by the method for producing a cellulose nanofibril reinforced acrylic fiber according to any one of claims 1 to 5.

7. The use of the cellulose nanofibril reinforced acrylic fiber according to claim 6 in the textile field.

8. The use according to claim 7, wherein the cellulose nanofibril reinforced acrylic fibres are used for making carpets, ski coats, sails, military canvases or tents.

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