阅读说明：本技术 一种清洁高效的纤维素丝（cf）及其制备方法 (Clean and efficient Cellulose Filament (CF) and preparation method thereof ) 是由 温洋兵 王春平 于 2021-01-15 设计创作，主要内容包括：本发明公开了的一种清洁高效的纤维素纤丝及其制备方法,其制备过程包括碱尿素溶液的配制及纸浆基材的制备和溶液浸泡及机械进一步加工。所述纤维素纤丝制备方法制备出的纤维素纤丝长径比高,结构均匀,利于改性应用,而且制备浓度高,本发明纤维素纤丝制备方法在实际操作过程中碱-尿素溶剂可循环使用。(The invention discloses a clean and efficient cellulose cellosilk and a preparation method thereof. The cellulose fibrils prepared by the cellulose fibril preparation method have high length-diameter ratio, uniform structure, benefit for modification application and high preparation concentration, and the alkali-urea solvent can be recycled in the actual operation process.)

1. A preparation method of clean and efficient cellulose filaments is characterized by comprising the following steps:

(1) carrying out low-temperature pretreatment on a paper pulp raw material by using an alkali-urea solution;

(2) then carrying out mechanical grinding;

(3) carrying out suction filtration to obtain uniform cellulose filaments;

(4) recovering the alkali-urea solution.

2. The method of claim 1, wherein the pulp material is selected from softwood pulp, hardwood pulp, and mixed pulp.

3. A method for preparing clean and highly efficient cellulose filaments according to claim 2, characterized in that the pulp concentration is controlled from 2% (w/v) to 20% (w/v), preferably from 5% (w/v) to 15% (w/v).

4. The method for preparing clean and efficient cellulose filaments according to claim 1, wherein the alkali-urea solution is obtained by mixing alkali with urea, wherein the alkali is an alkaline hydroxide substance, preferably sodium hydroxide, potassium hydroxide and lithium hydroxide.

5. The method for preparing clean and efficient cellulose filaments according to claim 4, wherein the mass concentration of the alkali is 2-30 wt%, and the mass concentration of the urea is 2-45 wt%.

6. The method of claim 5, wherein the sodium hydroxide is present in an amount of 5 to 10 wt.%, the potassium hydroxide is present in an amount of 2 to 20 wt.%, and the lithium hydroxide is present in an amount of 3 to 15 wt.%.

7. The method for preparing clean and efficient cellulose filaments according to claim 1, wherein the low-temperature pretreatment is to refrigerate the alkali-urea solution in a temperature-controlled refrigerating chamber for 1 hour, the temperature is controlled to be 0 ℃ to-30 ℃, then the pulp is put into the precooled solution, the stirring is carried out for 5min to 10min at room temperature, and finally the mixed solution is put into the refrigerating chamber for 1 hour to 4 hours.

8. The method for preparing clean and efficient cellulose filaments according to claim 1, wherein the mechanical grinding is one of a colloid mill, a high consistency disc mill, a medium consistency refiner or a double helix mill, and the number of grinding is 1-10.

9. The method for preparing clean and efficient cellulose filaments according to claim 1, wherein the recovered alkali-urea solution is obtained by suction filtering the mechanically ground fibers and recovering a filtrate.

10. A clean and efficient cellulose filament produced according to any one of claims 1-9.

Technical Field

The invention belongs to the technical field of cellulose silk preparation, relates to a cellulose silk and a preparation method thereof, and particularly relates to a clean and efficient preparation method of the cellulose silk.

Background

Cellulose filaments CF are fibers extracted from pulp, are a special novel fiber material, are filamentous fibers in appearance, have a length of between 100 mu m and 1mm and a diameter of between several hundred nanometers and 3 microns, have a large aspect ratio and excellent mechanical properties.

Various methods for preparing cellulose fibrils have been reported, mainly comprising: swelling the fibers by enzyme treatment, chemical pretreatment (TEMPO oxidation, cationization and the like), homogenizing by a high-pressure homogenizer and shearing by microjet to obtain the nano cellulose fibers. Due to the excellent physicochemical characteristics of the cellulose fiber, the cellulose fiber can be applied to a plurality of fields, so that a great amount of cellulose fiber preparation and application are reported in recent years at home and abroad, however, huge energy consumption and higher separation cost are still the primary problems restricting and disturbing the industrialization application of the cellulose fiber. At present, an enzyme-assisted mechanical method and a chemical pretreatment modification method are applied to the preparation of cellulose fibrils, but still have no major breakthrough in the aspects of preparation energy consumption and cost reduction, for example, although an enzyme in the preparation of the cellulose fibrils by a biological enzyme/mechanical method can promote devillicate fibrillation of fibers to a certain extent, hydrogen bonds among micro fibers in plant fibers cannot be combined to obtain swelling, the cellulose fibrils can be separated by depending on huge mechanical energy, the preparation concentration is low (less than 2%), and the fiber size is not uniform; the TEMPO/NaBr/NaCI0 oxidation system can selectively oxidize 6-position hydroxyl of cellulose, fully swell the fiber and obtain cellulose fibers with uniform size, but the cost is high, and the TEMPO oxidant has strong toxicity and corrosivity and strong irritation, so the TEMPO/NaBr/NaCI0 oxidation system cannot be an ideal and green preparation method of cellulose nano fibers.

Therefore, the exploration and research of a clean and efficient preparation method and process of the cellulose cellosilk have important significance for promoting the industrial production of the cellulose cellosilk.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a clean and efficient preparation method of cellulose fibrils. The method has simple process, easy implementation and operation, cleanness and high efficiency, and solves the defects in the prior art.

In order to realize the purpose of the invention, the adopted technical scheme is as follows:

a method for preparing clean and high-efficiency Cellulose Filaments (CF),

(1) carrying out low-temperature pretreatment on a paper pulp raw material by using an alkali-urea solution;

(2) then carrying out mechanical grinding;

(3) carrying out suction filtration to obtain uniform cellulose filaments;

(4) recovering the alkali-urea solution.

(5) Carrying out low-temperature pretreatment on a paper pulp raw material by using an alkali-urea solution;

(6) then carrying out mechanical grinding;

(7) carrying out suction filtration to obtain uniform cellulose filaments;

(8) recovering the alkali-urea solution.

Specifically, the method comprises the following steps:

the paper pulp raw material is one of softwood pulp, hardwood pulp or mixed pulp. Controlling the pulp concentration to be 2% (w/v) to 20% (w/v), wherein the concentration is preferably 5% (w/v) to 15% (w/v);

the alkali in the alkali-urea solution is alkaline hydroxide, preferably sodium hydroxide, potassium hydroxide or lithium hydroxide, and is mixed with urea. The mass percent of the alkali is 2-30 wt%, wherein the preferable concentration of the sodium hydroxide is 5-10 wt%, the preferable concentration of the potassium hydroxide is 2-20 wt%, the preferable concentration of the lithium hydroxide is 3-15 wt%, and the mass percent of the urea is 2-45 wt%;

the low-temperature pretreatment is to refrigerate the alkali-urea solution in a temperature-controllable refrigerating chamber for 1h, and the temperature is controlled to be 0 ℃ to-30 ℃. Then placing the paper pulp into the precooled solution, stirring for 5-10 min at room temperature, and finally placing the mixed solution into a refrigerating chamber for 1-4 h.

The mechanical grinding is one of a colloid mill, a high-consistency disc mill, a medium-consistency refiner and a double-helix grinder, and the mechanical force is utilized to slide or displace the fibers so as to separate the plant fibers into cellulose filaments. The number of grinding is 1 to 10

The recovery of the alkali-urea solution: and (4) carrying out suction filtration on the fiber after mechanical grinding, and recovering filtrate.

Compared with the preparation of cellulose fibers by using enzyme treatment and chemical pretreatment (TEMPO oxidation, cationization and the like), the preparation method of the clean and efficient cellulose fibers has the following advantages and beneficial effects:

1) the key factor of dissociation of the cellulose nanofiber is full swelling of the fiber, compared with the problems of high cost of a TEMPO/NaBr/NaCIO oxidation system, harm caused by toxicity of system chemicals, huge energy consumption input of enzyme-assisted treatment and the like, the alkali-urea swelling system is an ideal pretreatment method for dissociation of the cellulose nanofiber, has the characteristics of high efficiency, low cost and no pollution, and meets the current concept of green manufacturing;

2) and the hydrogen bond combination among the micro fibers in the plant fibers is destroyed by using an alkali-urea system swelling system, so that the fibers are fully swelled, the alkali-urea system swelling plant fiber chemical consumption is small, and the alkali-urea is easy to recycle.

3) The mechanical grinding treatment of the alkali-urea swelling system can effectively utilize the huge fiber friction force generated by high-concentration grinding pulp to replace a high-pressure homogenizer and other equipment, so that the dissociation concentration of the cellulose nanofiber can be improved, the input of energy consumption during the dissociation of the cellulose nanofiber is reduced, and the aim of reducing the production cost is finally achieved.

Drawings

FIG. 1 is a flow chart of CF production by high-consistency disc mill refining after potassium hydroxide/urea treatment;

FIG. 2 is a graph of the variation in width of fibers at partial KOH/urea concentration;

FIG. 3 is a diagram showing the morphology of fibers with different numbers of colloid milling;

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments are described in detail below with reference to the accompanying drawings. It should be noted that the following examples are not to be construed as limiting the scope of the invention, and that the invention is not to be limited thereto since modifications and variations of the invention described above are not essential to the skilled person.

Example 1

2000g of bleached kraft pulp of softwood was weighed out, pulp concentration selected to be 10% (w/v). Respectively putting 10% by mass of sodium hydroxide and 0%, 10%, 20%, 30%, 40% and 50% by mass of urea mixed solution into a 25L container with a stirrer, starting a stirring device, no crystal precipitation exists in the stirred solution, placing the alkali-urea solution in a refrigerating chamber with the temperature of-10 ℃ for precooling for 1h after stirring is finished, then respectively placing 2000g of softwood bleached sulfate pulp into the alkali-urea solution, stirring for 5min at room temperature, placing the container in the refrigerating chamber with the temperature of-10 ℃ for standing for 2h after stirring is finished, grinding the pulp for 5 times in a colloid mill grinding cycle, and filtering the pulp after grinding is finished. CF is obtained and the alkaline urea solution is recovered. Before colloid milling, the swelling effect of the alkali-urea treated fibers was significant, the fiber width was increased, and the fiber width was increased as shown in table 1, as compared to fibers not pretreated with alkali urea.

TABLE 1 Table of variation of fiber width with urea mass fraction

Example 2

20.0kg of hardwood pulp was weighed out with a pulp concentration of 10% (w/v) selected. Respectively putting 10% by mass of urea and 0%, 10%, 20%, 30%, 40% and 50% by mass of lithium hydroxide mixed liquor into a 200L container with a stirrer, starting a stirring device, no crystal precipitation exists in the stirred liquor, placing the alkali-urea liquor in a refrigerating chamber with the temperature of-10 ℃ for precooling for 1h after stirring is finished, then respectively putting 20.0kg of softwood bleached sulfate pulp into the alkali-urea liquor, stirring for 5min at room temperature, placing the container in the refrigerating chamber with the temperature of-10 ℃ for standing for 2h after stirring is finished, preparing the pulp into 25% concentration, grinding for 6 times by a high-concentration pulp grinder, and carrying out suction filtration on the pulp after grinding is finished. CF is obtained and the alkaline urea solution is recovered. Before high-concentration grinding, compared with the fiber which is not pretreated by the alkali urea, the fiber which is treated by the alkali-urea has obvious swelling effect and obviously increased fiber diameter.

Example 3

5.0kg of bleached kraft pulp of softwood was weighed out, with a pulp concentration of 8% (w/v). Respectively putting mixed liquid of 0-30% by mass of urea and 0-20% by mass of potassium hydroxide into a container with a stirrer, starting a stirring device, no crystal precipitation exists in the stirred liquid, placing alkali-urea liquid in a refrigerating chamber with the temperature of-10 ℃ for precooling for 1h after stirring is finished, then respectively putting 10.0kg of needle-leaved wood bleached sulfate pulp into the alkali-urea solution, stirring for 5min at room temperature, placing the container in the refrigerating chamber with the temperature of-10 ℃ for standing for 2h after stirring is finished, grinding the pulp for 6 times by a medium-concentration pulp grinder after standing is finished, wherein the pulp grinding concentration is 10%, and carrying out suction filtration on the pulp after grinding is finished. CF is obtained and the alkaline urea solution is recovered. Prior to grinding, the alkali-urea treated fibers had a significant swelling effect and a significant increase in fiber diameter compared to fibers not pretreated with alkali urea, as shown in fig. 2.

Example 4

5.0kg of bleached kraft pulp of softwood was weighed out, with a pulp concentration of 10% (w/v) selected. Respectively putting 10 percent by mass of potassium hydroxide and 25 percent by mass of urea into a 100L container with a stirrer, starting a stirring device, no crystal is separated out from the stirring liquid, placing the alkali-urea liquid in a refrigerating chamber for precooling for 1h at the temperature of 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃ and 30 ℃ after the stirring is finished, and then, 2000g of bleached kraft pulp of softwood is respectively put into an alkali-urea solution, stirring for 5min at room temperature, placing the container in a refrigerating chamber with the temperature of 0 ℃, 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃ and 30 ℃ for standing for 2h after stirring, grinding the slurry by a colloid mill for 5 times in a circulating manner after standing, and filtering the slurry after grinding. Through fiber morphology analysis, the swelling degrees of the alkali urea solutions with different precooling temperatures on the fibers are different, and the sizes and the uniformity of the CF prepared after grinding are also different.

Example 5

5.0g of bleached kraft pulp of softwood was weighed out, with a pulp concentration of 12% (w/v). Respectively putting mixed liquid of 10 percent by mass of potassium hydroxide and 16 percent by mass of urea into a 100L container with a stirrer, starting a stirring device, no crystal is separated out in the stirred liquid, placing the alkali-urea liquid in a refrigerating chamber with the temperature of minus 10 ℃ for precooling for 1h after stirring is finished, then respectively putting 5.0kg of needle-leaved wood bleached sulfate pulp into the alkali-urea solution, stirring for 5min at room temperature, placing the container in the refrigerating chamber with the temperature of minus 10 ℃ for standing for 2h after stirring is finished, grinding the pulp for 1 to 7 times in a colloid mill grinding cycle after standing is finished, and filtering the pulp after grinding is finished. CF is obtained and the alkaline urea solution is recovered. The results show that the mechanical force of the colloid mill can strip and disperse the fibers after swelling, and finally uniform CF is obtained. As shown in FIG. 3, in which a shows the fiber morphology after 1 time of colloid milling, and d shows the fiber morphology after 7 times of colloid milling.

The above embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be regarded as equivalent replacements within the protection scope of the present invention.