CN108624983B

CN108624983B - Preparation method of cellulose casein composite fiber

Info

Publication number: CN108624983B
Application number: CN201711494817.9A
Authority: CN
Inventors: 俞啸华; 郭建雄
Original assignee: Longsi Shanghai New Material Technology Co ltd
Current assignee: Longsi Shanghai New Material Technology Co ltd
Priority date: 2017-12-31
Filing date: 2017-12-31
Publication date: 2020-12-08
Anticipated expiration: 2037-12-31
Also published as: CN108624983A

Abstract

The invention discloses a preparation method of cellulose casein composite fiber, which comprises the following steps: a) dissolving casein and cellulose in an ionic liquid aqueous solution to prepare a homogeneous mixed spinning solution; b) filtering, spinning, solidifying, stretching, washing, bleaching, oiling and drying the obtained spinning stock solution to obtain the cellulose casein composite fiber; the ionic liquid is prepared by mixing 90-110 parts by mass of 1-butyl-3-methylimidazole chloride salt, 5-15 parts by mass of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and 5-15 parts by mass of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt. The invention realizes the industrial production of composite fiber prepared by the cosolution symbiosis of casein and cellulose, and has strong practical value.

Description

Preparation method of cellulose casein composite fiber

Technical Field

The invention relates to a preparation method of composite fiber, in particular to a preparation method of cellulose casein composite fiber.

Background

Cellulose is a polysaccharide which is widely distributed and has the largest content in the nature, accounts for more than 50 percent of the carbon content in the plant, and is one of the most abundant natural organic matters in the nature. The cellulose is mainly derived from plants, such as cotton, wood, cotton linter, wheat straw, reed, hemp, mulberry bark and the like, wherein the cellulose content of the cotton is close to 100 percent and is the natural purest cellulose source, and the cellulose accounts for 40 to 50 percent, 10 to 30 percent of hemicellulose and 20 to 30 percent of lignin in the common wood. As a degradable green biomaterial, natural fiber gradually plays an increasingly important role due to its superior properties of light weight, degradability, low price, high modulus, high strength and the like. Therefore, natural cellulose obtained from plants is dissolved to prepare regenerated fibers, so that the regeneration and functionalization of the cellulose are realized, and the method is an important way for effectively utilizing the cellulose.

The protein is a peptide chain combined with amino acid, has a plurality of amino acids required by human body, has good biocompatibility and skin care and health care functions, and the composite fiber prepared by combining the protein and the cellulose can ensure that the cellulose fiber has a comfortable health care function, thereby obtaining the textile fabric with high added value. The traditional composite fiber is mainly prepared by a method for blending cellulose fiber and protein fiber, the composite fiber prepared by the method only blends two fibers, the performance of the cellulose and protein is not improved actually, the performance of the prepared composite fiber is improved to a limited extent, the protein addition amount in the blended fiber is limited, the firmness is low, the protein content is reduced quickly after a plurality of times of water washing, and the skin care and health care function is basically not realized. Therefore, the development of the cellulose and protein composite fiber in the true sense is of great significance.

Casein is one of the proteins, which is the major protein in mammalian including cow, sheep and human milk, and there are few reports on cellulose-casein complex fiber at present. Casein is binding protein containing calcium phosphate, is sensitive to acid, can precipitate when the pH value is lower, has hydrophobicity and is not easy to dissolve in water; meanwhile, due to the characteristics of self aggregation state structures, namely, a large number of hydrogen bonds exist in molecules and among molecules, and the cellulose has higher crystallinity, so that the cellulose is difficult to dissolve in conventional solvents (such as water and most organic solvents); and because both cellulose and casein belong to natural polymer substances, and natural polymer polar groups contained in the cellulose and casein have strong interaction, the cellulose and casein are difficult to be directly dissolved in a conventional solvent, and the co-dissolution symbiosis of the cellulose and casein can not be realized, so that the conventional cellulose and casein composite fiber usually adopts the solvent to dissolve casein to prepare casein stock solution, then the casein stock solution and viscose are mixed, and then the composite fiber is prepared by wet spinning, or adopts the solvent to dissolve the casein and the cellulose respectively, and then the composite fiber is prepared by wet spinning. In the process of preparing the composite fiber by the blending method, strong alkali, N-dimethylacetamide/lithium chloride (DMAc/LiCl), N-dimethylformamide/dinitrogen tetroxide (DMF/N) are generally used₂O₄) N-methyl-N-oxomorpholine (NMMO), dimethyl sulfoxide/tetrabutylammonium fluoride (DMSO/TBAF) and also molten salt hydrates (e.g. LiClO)₄·3H₂O、LiSCN·2H₂O), and the like, for example: zhang Shuai, et al (Zhang Shuai, Donghua university college of textile (China), Li Fang school, Shu Jiang Yong, Dong)The Huazhou modern textile research institute (China); regenerated cellulose-casein blended biological fiber; international textile declaration 2011, 4 th, pages 10-12) uses lithium hydroxide/urea/thiourea aqueous solution as a cosolvent to dissolve casein and cellulose, and prepare casein-cellulose blend fiber, wherein the mass ratio of casein to cellulose is 10:90, and compared with cellulose fiber, the crystalline structure and mechanical properties of the blend fiber are improved. However, the solvent system used by the blended fiber has the defects of strong toxicity, high cost, difficult recycling of the solvent, instability in the using process and the like, and is not suitable for industrial production.

The ionic liquid is a salt existing in a liquid state at room temperature or near room temperature, has the liquidity of the liquid and the chemical activity of the salt, and has a plurality of unique properties, such as designable structure, wide liquid range, vapor pressure close to zero, non-flammability, high thermal stability and chemical stability, and the like. At present, ionic liquid has made many advances in the aspects of separation process, catalysis, organic synthesis, electrochemistry and the like, and is considered to be a novel environment-friendly green medium with wide application prospect in green synthesis and clean production.

It has been found that ionic liquids can directly dissolve cellulose and proteins, for example: chinese patent CN200510077288.3 discloses a method for preparing bioprotein wool fiber by mixing and dissolving animal hair and cellulose raw materials by taking ionic liquid as a solvent; chinese patent CN200810033113.6 discloses a method for preparing cellulose fibroin composite fiber by mixing and dissolving cellulose and fibroin by taking ionic liquid as a solvent; chinese patent CN201510313099.5 discloses a method for preparing keratin composite fibers by dissolving keratin and cellulose with ionic liquid as a solvent; chinese patent CN201610058920.8 discloses a method for preparing composite fiber by dissolving silk fibroin and cellulose with ionic liquid as solvent; the method also provides a new method for preparing cellulose and casein composite fibers, Chinese patent CN200710043567.7 discloses a method for preparing protein modified cellulose fibers by mixing dissolved protein and cellulose by taking ionic liquid as a solvent, and in example 5 and example 12, respectively discloses a method for preparing composite fibers by using milk casein and straw pulp, and milk casein and hemp pulp; although the method realizes the co-dissolution symbiosis of protein including casein and cellulose, when the ionic liquid (alkyl quaternary ammonium salt, alkyl imidazolium salt, alkyl pyrrolate salt and the like) is used for dissolving the protein and the cellulose in the patent, the pure ionic liquid is used for dissolving the protein and the cellulose, so that the prepared spinning solution has high viscosity and poor spinnability, has great influence on the pressure resistance and the drafting of a spinneret plate in the subsequent spinning process, and is not beneficial to the subsequent spinning; furthermore, the above-mentioned methods inevitably result in loss of fibrous properties of the raw material, and the resulting composite fibers have poor properties, such as: the filament or the staple of the protein modified cellulose fiber prepared in CN200710043567.7 has a filament number of 1.5-5.0 dtex and a strength of 2.0-6.2 cN/dtex, wherein the filament number of the composite fiber prepared from the casein modified rice straw pulp of milk in example 5 is 2.0dtex and the strength is 4.6 cN/dtex; the filament number of the composite fiber prepared by the milk casein modified hemp pulp in the example 12 is 2.8dtex, and the strength is 4.2 cN/dtex; under the circumstances, at present, although the cosolution symbiosis of protein including casein and fiber can be realized, the cosolution symbiosis still remains in a laboratory stage, the industrialization scale cannot be realized, and the application and the development of the composite fiber are severely limited. In addition, in the method, when the ionic liquid is used for dissolving protein (including casein) and cellulose, the dissolving time is long, generally 2-48 hours, even up to 120 hours, and the industrial production is also severely limited; the dissolving temperature is high, generally about 100 ℃, even up to 150 ℃, the energy consumption is high, the industrial production is not easy, and the casein cannot resist high temperature due to the special performance of the casein, so that the co-dissolving symbiosis of the casein and cellulose needs to be realized at a lower temperature, and the high temperature is obviously not beneficial to the co-dissolving preparation of the composite fiber by the casein and the cellulose.

In addition, although the composite fiber prepared by compounding casein with other fibers can modify the physical and chemical properties of the fibers, the higher the content of the casein in the composite fiber is, for example, Nippon dragon and the like (Nippon dragon, Shujiangyong, Gaojing, the properties of casein modified acrylonitrile fibers with different feeding ratios; reported in textile science; 6 month in 2009, 30 th volume, 6 th period, 19 th to 23 th page) modify acrylonitrile fibers by adopting casein to prepare casein modified acrylonitrile fibers, and the introduction of casein with proper mass fraction is mentioned in the article to improve the strength of the fibers, greatly improve the moisture absorption performance, and simultaneously have good friction performance and better serviceability; meanwhile, the composite fiber is also mentioned that the total casein content is less than the feeding content, and the larger the feeding ratio is, the larger the casein loss quality is, because the polymerization process has partial hydrolysis, the spinning process has free casein loss, the impurity content in the fiber is also improved along with the increase of the casein content, probably because the casein has larger polarity and is easy to adsorb impurities such as oil solution and the like, thereby influencing the fiber composition; in fact, although no experiment proves that the content of casein in the cellulose-casein composite fiber cannot be high, the mass fraction of the milk casein is 4% when the milk casein is compounded with the rice straw pulp in the example 5 of the Chinese patent CN200710043567.7, and the mass fraction of the milk casein is 5% when the milk casein is compounded with the hemp pulp in the example 12, while the content of the casein in the cellulose-casein composite fiber sold in the market at present is only 8% at most, which also proves that the content of the casein in the composite fiber is kept low from the side.

In summary, although casein and cellulose present a good development situation in terms of co-solvent symbiosis, many disadvantages still exist, and the content of casein in the composite fiber is low, and the modification of the performance of the composite fiber is limited, so that there is a need to develop a new preparation method of cellulose-casein composite fiber to promote the industrial production of cellulose-protein composite fiber.

Disclosure of Invention

In view of the above problems in the prior art, the present invention aims to provide a method for preparing cellulose-casein composite fibers, so as to promote the industrial production of cellulose-protein composite fibers.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of cellulose casein composite fiber comprises the following steps:

a) dissolving casein and cellulose in an ionic liquid aqueous solution to prepare a homogeneous mixed spinning solution;

b) filtering, spinning, solidifying, stretching, washing, bleaching, oiling and drying the obtained spinning stock solution to obtain the cellulose casein composite fiber;

wherein the ionic liquid is prepared from the following components:

1-butyl-3-methylimidazolium chloride salt: 90-110 parts by mass;

bis 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt: 5-15 parts by mass;

bis 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride: 5-15 parts by mass;

mixing to obtain; wherein:

the chemical structural formula of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt is as follows:

the chemical structural formula of the bi-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride is as follows:

preferably, the dissolving temperature in the step a) is 50-100 ℃ (preferably 60-80 ℃), and the dissolving time is 5-30 minutes (preferably 10-25 minutes).

Preferably, the mass fraction of the ionic liquid aqueous solution is 20-98%, and more preferably 50-98%.

Preferably, the preparation of the ionic liquid comprises the following steps:

firstly, 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride perchlorate are uniformly mixed according to the proportion, and then the mixture is stirred and reacted for 5 to 15 hours at the temperature of 110 to 130 ℃.

Preferably, the preparation of the bis 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt comprises the following steps: dropwise adding N-methylimidazole into 1, 4-dichlorobutane at the temperature of 65-85 ℃ under the protection of inert gas, and then carrying out reflux reaction for 12-72 hours.

More preferably, the molar ratio of 1, 4-dichlorobutane to N-methylimidazole is 1:1 to 1: 1.5.

As a further preferable mode, the inert gas is nitrogen or argon.

Preferably, the preparation of the bis 1, 4-bis [1- (3-methylimidazole) ] butyl diperchlor comprises the following steps:

firstly, dissolving the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and the lithium perchlorate in water, then stirring and reacting for 12-48 hours at the temperature of 75-85 ℃, then cooling to room temperature, and continuing stirring for 5-15 hours at room temperature.

In a further preferred embodiment, the molar ratio of the bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt to the lithium perchlorate is 1:1 to 1: 1.5.

Preferably, the casein comprises cow milk casein and sheep milk casein, and the protein content is more than or equal to 90 wt%.

Preferably, the cellulose is selected from any one of wood pulp, cotton pulp, bamboo pulp, mulberry bark pulp, rice pulp, reed pulp, bagasse pulp or hemp pulp, the cellulose content is more than or equal to 90 wt%, and the polymerization degree is more than or equal to 500.

Preferably, the content of the casein accounts for 1-55 wt% of the total amount of the cellulose and the casein.

Preferably, the mass ratio of the total amount of the cellulose and the casein to the ionic liquid aqueous solution is 1: 3-1: 20.

Preferably, in the step b), a dry-jet wet spinning process is adopted for spinning, the temperature of a spinning solution is 50-100 ℃ (preferably 60-80 ℃), and the spinning speed is 60-150 m/min.

The dry-jet wet spinning process is characterized in that spinning solution is extruded through a spinneret to form spinning trickle, and the spinning trickle is preliminarily formed in wet cold air. The wet cold air is air with the temperature of 5-25 ℃ and the relative humidity of 60-95%.

Preferably, in the step b), the coagulation bath adopted in coagulation consists of ionic liquid and water, the temperature is 0-20 ℃ (preferably 5-15 ℃), and the mass percentage of the ionic liquid is 1-20%.

Compared with the prior art, the invention has the following remarkable beneficial effects:

the invention prepares a novel ionic liquid by compounding 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt, the aqueous solution of the ionic liquid can realize the co-dissolution of casein and cellulose under the conditions that the dissolution temperature is 50-100 ℃ and the dissolution time is 5-30 minutes, thereby not only saving the cost and improving the production efficiency, but also realizing the low-temperature dissolution of casein, avoiding the damage to the performance of casein, simultaneously, the prepared spinning solution has lower viscosity, is beneficial to spinning, can not cause the loss of the fibrous characteristic of the raw material in the subsequent process, and can lead the breaking strength to reach 3.2cN/dtex when the monofilament titer of the prepared composite fiber is 1.67dtex, the spinning solution has excellent mechanical properties, is beneficial to large-scale spinning, and the number of spinneret holes is increased to 14000-30000 holes from 60-100 holes in the traditional laboratory stage during spinning, so that industrial production is realized; particularly, the content of casein in the prepared composite fiber is increased to 55 percent, and the modification of the casein on the performance of the composite fiber is greatly improved; in addition, the preparation process can prepare the composite fiber without a defoaming step, is economical and practical, has simple preparation process, low cost, no need of using any organic solvent, environmental friendliness, no pollution, no need of special equipment and harsh conditions, easy realization of industrial production and high practical value.

Detailed Description

The technical scheme of the invention is further detailed and completely explained by combining the embodiment, the application example and the comparative example.

Example 1

Preparation of mono-bis 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt:

under the protection of nitrogen and at the temperature of 80 ℃, 1.2mol of N-methylimidazole is slowly dripped into 1mol of 1, 4-dichlorobutane, after the dripping is finished, the reflux reaction is carried out for 72 hours, the reaction is finished, the reaction liquid is cooled to the room temperature, the obtained product is washed by diethyl ether to remove the unreacted raw materials, and a white solid substance, namely the bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt (the HPLC purity is 98.8%, and the yield is 88%) is obtained.

Preparation of di, di 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloride:

dissolving 1mol of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride and 1.2mol of lithium perchlorate in 1L of water, stirring and reacting at 80 ℃ for 36 hours, cooling to room temperature, continuing stirring at room temperature for 12 hours, dispersing the reaction solution into chloroform with the same volume, separating, washing a chloroform phase with water until the water phase has no chloride ions, and concentrating the chloroform phase under reduced pressure to obtain a colorless transparent liquid, namely bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride (the HPLC purity is 98.9%, and the yield is 78%).

Thirdly, preparing the ionic liquid:

uniformly mixing 100g of 1-butyl-3-methylimidazole chlorine salt, 10g of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and 10g of bis-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt, stirring and reacting at 120 ℃ for 12 hours, finishing the reaction, and cooling to room temperature to obtain the ionic liquid.

Fourthly, preparing the composite fiber:

a) dissolving the ionic liquid in deionized water to prepare an 80 wt% ionic liquid aqueous solution for later use; uniformly mixing 0.5 part by mass of milk casein (with the protein content of 92%) and 9.5 parts by mass of cotton pulp (with the cellulose content of 99% and the polymerization degree of 600), adding the mixture into 100 parts by mass and 80 wt% of ionic liquid aqueous solution, and stirring the mixture for 25 minutes at 70 ℃ to obtain stable and uniform spinning stock solution;

b) filtering the obtained spinning solution (the spinning solution can be spun only by filtering and defoaming in the traditional preparation method, the process steps are complex), spinning by using a porous spinneret plate (the number of holes of the spinneret plate is 20000, the temperature of the spinning solution is 70 ℃, the spinning speed is 100 m/min), immersing the spinning solution into a coagulating bath containing 10 wt% of ionic liquid for coagulation, the temperature of the coagulating bath is 15 ℃, stretching by 3.5 times, washing, bleaching, oiling and drying to obtain the cellulose casein composite fiber.

According to the test, the breaking strength of the cellulose casein composite fiber prepared in the embodiment is about 2.2cN/dtex under the condition that the filament number is 1.67 dtex. And the experiment shows that: under the same conditions, when single ionic liquid aqueous solution of 80 wt% of 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt or 1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt is adopted to dissolve casein and cotton pulp, stable and uniform spinning solution can be obtained only by stirring for 3-5 hours at 110-130 ℃, and the breaking strength of the prepared comparative composite fiber is only about 1.3cN/dtex under the condition that the filament number is the same as 1.67dtex, which indicates that the preparation process of the embodiment is adopted, so that the co-dissolution symbiosis of cellulose and casein is realized, and the prepared composite fiber has better mechanical property;

in addition, the present example realizes that the ionic liquid aqueous solution is used to dissolve casein and cellulose by using the ionic liquid, but both casein and cellulose are not easily dissolved in water, and the added water is not beneficial to the dissolution of cellulose and casein (which is also the reason that organic solvent, such as DMSO, is added in the traditional ionic liquid to promote the dissolution of cellulose); in addition, the water is added into the dissolving system, so that the viscosity of the spinning solution can be reduced, and high-hole spinning is facilitated; in addition, the dissolving temperature is obviously reduced, and the dissolving time is obviously shortened.

The composite fiber prepared by the embodiment has good mechanical property and low viscosity of the spinning solution, so that the number of holes of a spinneret plate can reach 20000 holes during spinning, the spinning speed can be 100 m/min, and industrial production is realized.

In the step a) of this embodiment, the mass fraction of the ionic liquid aqueous solution may be 20 to 98%, and the rest conditions are unchanged.

In the step a) of the present embodiment, the dissolving temperature may be 50 to 100 ℃, the dissolving time may be 5 to 30 minutes, and the other conditions are not changed.

The cotton pulp used in step a) of this example may be wood pulp, bamboo pulp, mulberry bark pulp, rice straw pulp, reed pulp, bagasse pulp or hemp pulp, with the remainder being unchanged.

In the step b) of the embodiment, the number of the spinning holes can be 14000-30000, the rest conditions are unchanged, the temperature of the spinning solution can be 50-100 ℃, the spinning speed can be 60-150 m/min, and the rest conditions are unchanged.

In the step b) of this embodiment, the coagulation bath may be a 1-20 wt% ionic liquid aqueous solution, the temperature of the coagulation bath may be 0-20 ℃, and the rest conditions are unchanged.

In the step b) of this embodiment, the stretching may be 1.5 to 4 times of stretching, and the rest conditions are unchanged.

Example 2

This embodiment differs from embodiment 1 only in that: 1 part by mass of milk casein (protein content 92%) and 9 parts by mass of cotton pulp (cellulose content 99%, polymerization degree 600) were mixed uniformly, and the rest was the same as described in example 1.

According to the test, the breaking strength of the cellulose and casein composite fiber prepared in the embodiment is about 2.8cN/dtex under the condition that the filament number is 1.67 dtex. And the experiment shows that: under the same conditions, when casein and cotton pulp are dissolved by adopting a single ionic liquid aqueous solution of 80 wt% of 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt or 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloridate, stable and uniform spinning solution can be obtained only by stirring for 3-5 hours at 110-130 ℃, and the breaking strength of the prepared comparative composite fiber is only about 1.4cN/dtex under the condition that the filament number is the same as 1.67 dtex.

Example 3

This embodiment differs from embodiment 1 only in that: 2 parts by mass of milk casein (protein content 92%) and 8 parts by mass of cotton pulp (cellulose content 99%, degree of polymerization 600) were mixed uniformly, and the rest was the same as described in example 1.

According to the test, the breaking strength of the cellulose and casein composite fiber prepared in the embodiment is about 3.2cN/dtex under the condition that the filament number is 1.67 dtex. And the experiment shows that: under the same conditions, when casein and cotton pulp are dissolved by adopting a single ionic liquid aqueous solution of 80 wt% of 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt or 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloridate, stable and uniform spinning solution can be obtained only by stirring for 3-5 hours at 110-130 ℃, and the breaking strength of the prepared comparative composite fiber is only about 1.5cN/dtex under the condition that the filament number is the same as 1.67 dtex.

Example 4

This embodiment differs from embodiment 1 only in that: 4 parts by mass of milk casein (protein content 92%) and 6 parts by mass of cotton pulp (cellulose content 99%, degree of polymerization 600) were mixed uniformly, and the rest was the same as described in example 1.

According to the test, the breaking strength of the cellulose and casein composite fiber prepared in the embodiment is about 2.7cN/dtex under the condition that the filament number is 1.67 dtex. And the experiment shows that: under the same conditions, when casein and cotton pulp are dissolved by adopting a single ionic liquid aqueous solution of 80 wt% of 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt or 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloridate, stable and uniform spinning solution can be obtained only by stirring for 3-5 hours at 110-130 ℃, and the breaking strength of the prepared comparative composite fiber is only about 1.2cN/dtex under the condition that the filament number is the same as 1.67 dtex.

Example 5

This embodiment differs from embodiment 1 only in that: 5.5 parts by mass of milk casein (protein content: 92%) and 4.5 parts by mass of cotton pulp (cellulose content: 99%, degree of polymerization: 600) were uniformly mixed, and the rest was the same as described in example 1.

According to the test, the breaking strength of the cellulose and casein composite fiber prepared in the embodiment is about 2.2cN/dtex under the condition that the filament number is 1.67 dtex. And the experiment shows that: under the same conditions, when casein and cotton pulp are dissolved by adopting a single ionic liquid aqueous solution of 80 wt% of 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt or 1, 4-bis [1- (3-methylimidazole) ] butyl diperchichloridate, stable and uniform spinning solution can be obtained only by stirring for 3-5 hours at 110-130 ℃, and the breaking strength of the prepared comparative composite fiber is only about 1.0cN/dtex under the condition that the filament number is the same as 1.67 dtex.

As can be seen from examples 1 to 5, the breaking strength of the composite fiber prepared by the composite ionic liquid of the present invention is about twice of the breaking strength of the comparative composite fiber when the composite fiber prepared by the preparation process of the present invention, especially the composite ionic liquid of the present invention is used for dissolving cellulose and casein, under the same single fiber fineness, which means that the preparation process of the present invention not only realizes the co-dissolution symbiosis of cellulose and casein, but also the mechanical properties of the prepared composite fiber are better, especially, the casein content in the composite fiber prepared by the present invention can be increased to 55%, although the casein content is 20%, the performance of the prepared composite fiber is the best, and the composite fiber performance is reduced when 55% is added, even if 55% is added, the composite fiber has the same single fiber fineness of 1.67dtex, the breaking strength of the composite fiber can also reach 2.2N/dtex, and is still superior to the breaking strength of 1.4-1.5 which can be achieved when the optimal addition amount of the composite fiber is compared, so that the defect that the content of casein in the conventional composite fiber cannot be too high is overcome.

In summary, the following steps: the invention prepares a novel ionic liquid by compounding 1-butyl-3-methylimidazole chlorine salt, bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt and bi-1, 4-bis [1- (3-methylimidazole) ] butyl dichloride salt, the obtained ionic liquid can realize the co-dissolution symbiosis of casein and cellulose and can be used for preparing cellulose and casein composite fiber, the prepared cellulose and casein composite fiber has excellent mechanical property, and in the preparation process of the composite fiber, the co-dissolution of casein and cellulose can be realized without using pure ionic liquid, the dissolution temperature is obviously reduced, the dissolution time is shortened (and the dissolution time is also shortened along with the increase of the addition amount of casein under the same dissolution temperature), the dissolving efficiency is improved, the production cost is reduced, the production efficiency is improved, and compared with pure ionic liquid, the viscosity of the obtained spinning stock solution is lower when the ionic liquid aqueous solution is used, the concentration of the ionic liquid aqueous solution can be adjusted as required, and the viscosity of the spinning stock solution is further flexibly adjusted, so that the spinning stock solution is easy to spin, the number of spinning holes can reach 14000-30000 holes during spinning, the spinning speed can be 60-150 m/min, and industrial production is realized; in addition, the preparation process can prepare the composite fiber without a defoaming step, has the advantages of simple process steps, economy, practicability, simple preparation process, low cost, no use of any organic solvent, environmental friendliness, no pollution, no need of special equipment and harsh conditions, easy realization of industrial production, and extremely high practical value, and obtains remarkable progress and unexpected effect compared with the prior art.

Finally, it should be pointed out here that: the above is only a part of the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention, and the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above description are intended to be covered by the present invention.

Claims

1. A preparation method of cellulose casein composite fiber comprises the following steps:

a) dissolving casein and cellulose in an ionic liquid aqueous solution with the mass fraction of 80-98% to prepare a homogeneous mixed spinning solution;

the ionic liquid is characterized by comprising the following components:

1-butyl-3-methylimidazolium chloride salt: 90-110 parts by mass;

mixing to obtain; wherein:

2. the method of claim 1, wherein: the dissolving temperature in the step a) is 50-100 ℃, and the dissolving time is 5-30 minutes.

3. The method of claim 1, wherein the ionic liquid is prepared by the steps of:

4. The method according to claim 3, wherein the bis-1, 4-bis [1- (3-methylimidazole) ] butyldichloride salt is prepared by the steps of: dropwise adding N-methylimidazole into 1, 4-dichlorobutane at the temperature of 65-85 ℃ under the protection of inert gas, and then carrying out reflux reaction for 12-72 hours.

5. The method according to claim 3, wherein the bis-1, 4-bis [1- (3-methylimidazole) ] butyl diperchichlorate is prepared by the steps of:

6. The method of claim 1, wherein: the cellulose is selected from any one of wood pulp, cotton pulp, bamboo pulp, mulberry bark pulp, rice straw pulp, reed pulp, cane bagasse pulp or hemp pulp, the cellulose content is more than or equal to 90 wt%, and the polymerization degree is more than or equal to 500.

7. The method of claim 1, wherein: the content of the casein accounts for 1-55 wt% of the total amount of the cellulose and the casein.

8. The method of claim 1, wherein: the mass ratio of the total amount of the cellulose and the casein to the ionic liquid aqueous solution is as follows: 1:3 to 1: 20.

9. The method of claim 1, wherein: in the step b), spinning is carried out by adopting a dry jet wet spinning process, wherein the temperature of a spinning solution is 50-100 ℃, and the spinning speed is 60-150 m/min.