CN111704734A

CN111704734A - Method for preparing cellulose film by recycling waste viscose film

Info

Publication number: CN111704734A
Application number: CN202010585020.5A
Authority: CN
Inventors: 朱坤坤; 余达山; 盛永新; 王友春; 徐卫林
Original assignee: Hubei Golden Ring Green Fiber Co ltd; Hubei Golden Ring New Materials Tech Ltd; Wuhan Textile University
Current assignee: Hubei Golden Ring Green Fiber Co ltd; Hubei Golden Ring New Materials Tech Ltd; Wuhan Textile University
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2020-09-25

Abstract

The invention provides a method for preparing a cellulose film by recycling a waste viscose film, which has simple process and is environment-friendly. Firstly, soaking a pretreated waste adhesive film in a sodium hydroxide aqueous solution at 4 ℃ for 1-24 hours to obtain a blend; then, shearing and violently stirring the blend at a high speed, crushing and dissolving, and defoaming to prepare a cellulose solution with the mass fraction of 2-6 wt%; and finally, carrying out the working procedures of film laying, regeneration, cleaning, drying and the like on the cellulose solution by a sol-gel conversion method to prepare the regenerated cellulose film. The film preparation method has the advantages of simple process, low cost, environmental friendliness and no pollution, and is a green production process for recycling the waste viscose films.

Description

Method for preparing cellulose film by recycling waste viscose film

Technical Field

The invention relates to the field of recycling of industrial wastes, in particular to a method for preparing a cellulose film by recycling a waste viscose film.

Background

The regenerated cellulose membrane as a packaging material has good flexibility and transparency like glass, so the regenerated cellulose membrane is called as glass paper, has excellent comprehensive performance and has the following main characteristics: 1) can be rapidly degraded by microorganisms and the like, does not cause secondary pollution, and has excellent environmental protection performance; 2) the composite material has excellent tensile strength and elasticity, does not generate static electricity and has excellent composite performance; 3) high temperature resistance, no deformation at 190 ℃; 4) after coating processing, the coating has the characteristics of moisture resistance, oil resistance, impermeability, air impermeability, heat sealability and the like, and has strong barrier property; 5) no toxicity, no smell and high transparency.

In recent years, recycling of scrap materials in industrial production has been receiving attention with the development of sustainable development concepts. Regenerated cellulose membranes are a common type of viscose membrane. The wood pulp or cotton pulp is made into solution by alkalization, squeezing, crushing, aging and yellowing, and then dissolved in NaOH solution, the solution is made into solution by ripening, impurity removal and defoaming, and then extruded into cellulose film regenerated by coagulating bath through long and narrow slit in a film drawing machine, and then the cellophane is made by drafting, water washing, desulfurization, bleaching, desalination, plasticization and drying. The drying process of the cellulose film after high-power drafting is easy to cause curling and thickening of two edges of the film, and the film at the two edges is generally cut off and discarded in order to ensure the quality of the product. The waste part cannot be recycled by a viscose dissolving method, so that the waste of the cellulose resource and the cost increase caused by waste treatment are caused.

The invention patent with application number CN201380059382.9 discloses a method for producing dissolving pulp, dissolving pulp and use of the method. The invention is based on the idea of using recycled or recycled paper or board containing cellulose, lignin and hemicellulose as a cellulosic raw material for producing dissolving pulp or similar fibrous products, subjecting the fibrous raw material to a cold alkaline extraction to reduce the hemicellulose content and a bleaching treatment with an oxidizing chemical agent to reduce the lignin content, whereby the obtained fibrous material is recovered as pulp. The process can be used to prepare pulps for the production of regenerated cellulose fibers, films and foams, impregnated fiber products and for the production of cellulose derivatives and for the production of nanocellulose products. However, the method has the disadvantages of complex treatment process, long time consumption and use of bleaching agent, and does not accord with the production concept of high efficiency, energy saving and environmental protection of modern enterprises.

The invention patent with application number CN201680008196.6 discloses a recovery of man-made cellulose fibers. The recycling method forms a cellulose solution by dissolving a cellulose raw material, extrudes the obtained cellulose solution to form a molded body, and coagulates and regenerates the cellulose to obtain a man-made cellulose molded body, wherein the recycled man-made cellulose raw material is mixed with the original cellulose raw material before forming the cellulose solution. However, the method has the defects of complex process and toxic chemical reagent CS₂And the like, and does not accord with the production concept of high efficiency, energy conservation and environmental protection of modern enterprises.

Therefore, the development of the method for preparing the cellulose film by recycling the waste viscose film with simple process and environmental friendliness has great significance for viscose manufacturing enterprises.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for preparing a regenerated cellulose film by recycling a waste viscose film, which has a simple process and is environment-friendly.

In order to realize the aim, the invention provides a method for preparing a cellulose film by recycling a waste viscose film, which comprises the following steps:

s1, preparing a sodium hydroxide solution with the mass fraction of 9 wt% as a solvent; dispersing and soaking the pretreated waste adhesive film into the solvent, standing for 1-24 hours at 4 ℃ to obtain a blend, wherein the mass fraction of the waste adhesive film in the blend is 2-6 wt%;

s2, vigorously stirring the blend prepared in the step S1 for 1-2 min, and defoaming to obtain a cellulose solution;

and S3, performing film laying, coagulating bath regeneration and post-treatment on the cellulose solution prepared in the step S2 to prepare a regenerated cellulose film.

Preferably, in step S1, the waste adhesive film is leftover bits or adhesive film waste generated in the process of preparing the cellophane by the adhesive method.

Preferably, in step S3, the film-laying and coagulation regeneration process is to scrape the cellulose solution on a flat support by a casting method, and then immerse the solution film in a coagulation bath to obtain a cellulose hydrogel film.

Preferably, in step S3, the film-laying and coagulation regeneration step is to extrude the cellulose solution into a coagulation bath through a slit to form a film, thereby obtaining a cellulose hydrogel film.

Preferably, in step S3, the coagulation bath is one of hydrochloric acid, sulfuric acid, oxalic acid, citric acid, formic acid, acetic acid, phytic acid, or a combination of at least two of the foregoing.

Preferably, the coagulation bath is a sulfuric acid solution.

Preferably, in step S3, the concentration of the acid in the coagulation bath is 15 wt%.

Preferably, in step S3, the post-treatment step is a washing and drying treatment to obtain a regenerated cellulose film.

Preferably, in step S2, the vigorous stirring is crushing and dissolving by a wall breaking machine with a wall breaking power of 600W.

Preferably, in step S1, the pretreatment process of the waste adhesive film includes shearing, drying and opening processes.

Preferably, the drying temperature of the drying treatment is 40-100 ℃, and the drying time is 0.1-24 h.

The invention has the beneficial effects that:

1. the method successfully dissolves the industrial waste viscose film, solves the problem that a viscose factory cannot dissolve the waste viscose film, simultaneously recycles the waste viscose film to prepare the cellulose film, achieves the aim of recycling the waste viscose film, is beneficial to the production enterprises to reasonably utilize resources and save production cost, and has great application value.

2. The invention has the advantages of simple process, low energy consumption, no pollution and the like. The waste viscose film is pretreated, soaked, sheared at high speed and dissolved to obtain cellulose solution, and compared with the existing viscose method, the method has the advantages of simple process flow and low energy consumption. Meanwhile, the adopted solvent NaOH is low in price, non-toxic and harmless and is widely applied to industrial production, so that the solvent recovery technology is mature, high in safety and free of pollution.

3. The film-making coagulation bath of the present invention is the same as the viscose method (both are sulfuric acid coagulation baths). Therefore, the technology can be directly applied to the existing cellophane production line of the viscose factory, which is beneficial to reducing the production cost of the viscose factory and quickening the application of the technology in industrial production.

Drawings

FIG. 1 is a process flow diagram of the method for preparing cellulose film by recycling waste adhesive film according to the present invention.

FIG. 2 is a stress-strain diagram of cellulose films obtained by regenerating 4 wt% of the used viscose film dissolving solution provided in examples 1 to 7 of the present invention in different acid coagulation baths.

FIG. 3 is a stress-strain graph of cellulose films obtained by regenerating waste viscose film dissolving solutions of different concentrations in 15 wt% phytic acid coagulation bath according to examples 7 to 9 of the present invention.

Detailed Description

The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

Referring to fig. 1, the present invention provides a method for preparing a cellulose film by recycling a waste adhesive film, comprising the following steps:

s1, preparing a sodium hydroxide solution with the mass fraction of 9 wt% as a solvent; pretreating a waste adhesive film (shown as a in figure 1), dispersing and soaking the waste adhesive film into the solvent, standing the mixture at 4 ℃ for 1-24 hours to obtain a blend, wherein the mass fraction of the waste adhesive film in the blend is 2-6 wt%;

s2, vigorously stirring the blend prepared in the step S1 for 1-2 min, and defoaming to obtain a cellulose solution (shown in a b in a figure 1);

s3, the cellulose solution prepared in step S2 is subjected to the steps of film laying, coagulation bath regeneration and post-treatment to prepare a regenerated cellulose film (shown in c in fig. 1).

Further, in step S1, the waste adhesive film is leftover material or adhesive film waste material generated in the process of preparing the cellophane by the adhesive method.

Further, in step S1, the waste adhesive film is leftover bits and pieces generated in the process of preparing the cellophane by the adhesive method or adhesive film waste.

Further, in step S3, the film-laying and coagulation regeneration process is to scrape the cellulose solution on a flat support by a casting method, and then immerse the solution film in a coagulation bath to obtain a cellulose hydrogel film.

Further, in step S3, the film laying and coagulation regeneration step is to extrude the cellulose solution into a coagulation bath through a slit to form a film, thereby obtaining a cellulose hydrogel film.

Further, in step S3, the coagulating bath is one of hydrochloric acid, sulfuric acid, oxalic acid, citric acid, formic acid, acetic acid, phytic acid, or a combination of at least two of the foregoing.

Further, the coagulation bath is a sulfuric acid solution.

Further, the concentration of the acid in the coagulation bath was 15 wt%.

Further, in step S3, the post-treatment process is a washing and drying process, and a regenerated cellulose film is obtained.

Further, in step S2, the vigorous stirring is a wall breaking machine with a power of 600W to crush and dissolve the powder.

Further, in step S1, the pretreatment process of the waste adhesive film includes cutting, drying and opening processes.

Further, the drying temperature of the drying treatment is 40-100 ℃, and the drying time is 0.1-24 h.

The method for preparing cellulose film by recycling the waste adhesive film provided by the present invention is further described in detail by the following specific examples.

Example 1

S1, preparing a sodium hydroxide solution with the mass fraction of 9 wt% at room temperature, and using the sodium hydroxide solution as a solvent; cutting the waste adhesive film, and drying in a drying oven at 60 ℃ for 5 h; then opening the dried waste viscose film fragments for 1min by a stirrer; dispersing and soaking the pretreated waste adhesive film into the solvent, standing for 12 hours at 4 ℃ to obtain a blend, wherein the mass fraction of the waste adhesive film in the blend is 4 wt%;

s2, placing the blend prepared in the step S1 into a wall breaking machine, shearing at a high speed, stirring vigorously for 2min, and defoaming to obtain a cellulose solution; wherein the wall breaking machine power is 600W;

and S3, scraping the cellulose solution prepared in the step S2 on a glass plate by a tape casting method, immersing the cellulose solution film obtained by film spreading and the glass plate into a hydrochloric acid solution coagulating bath with the mass fraction of 15 wt% for 10min, taking out the gel film, washing and airing to obtain the regenerated cellulose film with good mechanical property and uniform and compact structure.

In this example, the average tensile strength of the regenerated cellulose film was found to be 56.2MPa, and the elongation at break was found to be 4.7%.

Comparative example 1

The difference from example 1 is that: the pretreatment process (shearing, drying and opening pretreatment) of the waste adhesive film is not carried out, and the rest is the same as that of the embodiment 1, and the details are not repeated.

Compared with example 1, comparative example 1 has the problems that the waste adhesive film is immersed in the solvent to generate more air bubbles, the solvent is not fully contacted with the waste adhesive film, and the waste adhesive film cannot be completely dissolved after being immersed.

According to the invention, the waste adhesive film is subjected to shearing, drying and opening pretreatment, so that the effect that the waste adhesive film in a bundle is unfolded and the waste adhesive film is fully contacted with the solvent can be achieved. Therefore, the pretreatment process of the waste adhesive film effectively overcomes the defect of the prior art that the waste adhesive film can not be completely dissolved.

It should be noted that, in the drying pretreatment process of the waste adhesive film, the drying temperature and the drying time can be adjusted within the process parameter range of 40 to 100 ℃ of the drying temperature and 0.1 to 24 hours of the drying time according to actual conditions, and the good pretreatment effect on the waste adhesive film can be realized.

Example 2

The difference from example 1 is that: the type of the coagulation bath used was different, and example 2 used a 15 wt% sulfuric acid solution as the coagulation bath, and the rest was the same as example 1, and will not be described again.

Example 3

The difference from example 1 is that: the type of the coagulation bath used was different, and in example 3, a saturated oxalic acid solution at room temperature was used as the coagulation bath, and the rest was the same as in example 1, and thus, the description thereof is omitted.

Example 4

The difference from example 1 is that: the types of the coagulation baths adopted are different, and the citric acid solution with the mass fraction of 15 wt% is adopted as the coagulation bath in the example 4, and the rest is the same as the example 1, and the description is omitted.

Example 5

The difference from example 1 is that: the coagulation bath used was different in type, and example 5 used a formic acid solution with a mass fraction of 15 wt% as the coagulation bath, and the rest was the same as example 1, and will not be described again.

Example 6

The difference from example 1 is that: the kind of coagulation bath used was different, and example 6 used an acetic acid solution with a mass fraction of 15 wt% as the coagulation bath, and the rest was the same as example 1, and will not be described again.

Example 7

The difference from example 1 is that: the kind of coagulation bath used is different, and example 7 uses a phytic acid solution with a mass fraction of 15 wt% as the coagulation bath, and the rest is the same as example 1, and the description is omitted.

Comparative example 2

The difference from example 1 is that: pure water was used as the coagulation bath, and the rest was the same as in example 1, and thus, the description thereof is omitted.

The experimental result shows that in comparative example 2, pure water is used as the coagulating bath, the cellulose regeneration speed is slow, the strength of the regenerated hydrogel film is weak, and the cellulose film cannot be obtained by drying.

Table 1 shows the process parameter settings and performance parameters of examples 1-7 and comparative example 2

Examples 1-7 and comparative example 2 were analyzed in conjunction with table 1 and fig. 2:

in examples 1 to 7, when the cellulose solution film contacts the coagulant, sodium hydroxide in the solution immediately reacts with acid in the coagulation bath to neutralize, the stability of the cellulose solution is damaged, cellulose molecules are rapidly regenerated and bonded together through intramolecular hydrogen bonds to form a hydrogel film with a compact structure, and the hydrogel film is dried to obtain the cellulose film with the strength of 44 to 71 MPa.

In the pure water coagulation bath adopted in the comparative example 2, sodium hydroxide in the cellulose solution is freely diffused into the coagulation bath, the solution is diluted, cellulose molecules are far away from each other, the intermolecular hydrogen bond acting force is weakened, and the obtained hydrogel film has loose structure and weak strength, cannot be completely taken out of the pure water coagulation bath, so that a cellulose film cannot be obtained.

As shown in fig. 2, the cellulose film obtained by coagulation regeneration using formic acid, oxalic acid and sulfuric acid as coagulants has a high tensile strength, but has a low elongation at break. Compared with the coagulant, the phytic acid is adopted as the coagulant in the embodiment 7 of the invention, and the prepared regenerated cellulose film has higher tensile strength and elongation at break, which shows that the cellulose film obtained by coagulation and regeneration in the phytic acid coagulation bath has excellent comprehensive mechanical properties.

However, phytic acid is expensive and not suitable for industrial production. Sulfuric acid is a main coagulant for preparing regenerated cellulose fibers by a viscose method, the technology is mature in industrial application, the cost is low, and a sulfuric acid coagulation bath is used, and the technology can be directly applied to factory production without updating instruments and equipment, so that the sulfuric acid coagulation bath is optimal.

Example 8

S1, preparing a sodium hydroxide solution with the mass fraction of 9 wt% at room temperature, and using the sodium hydroxide solution as a solvent; cutting the waste adhesive film, and drying in a drying oven at 60 ℃ for 5 h; then opening the dried waste viscose film fragments for 1min by a stirrer; dispersing and soaking the pretreated waste adhesive film into the solvent, standing for 12 hours at 4 ℃ to obtain a blend, wherein the mass fraction of the waste adhesive film in the blend is 2 wt%;

s2, placing the blend prepared in the step S1 into a wall breaking machine, shearing at a high speed, stirring vigorously for 2min, and defoaming to obtain a cellulose solution;

s3, scraping the cellulose solution prepared in the step S2 on a glass plate by a tape casting method, immersing the cellulose solution film obtained by film laying and the glass plate into a phytic acid solution coagulating bath with the mass fraction of 15 wt% for 10min, taking out the gel film, washing and airing to obtain the regenerated cellulose film.

In this example, the regenerated cellulose film was found to have a tensile strength of 62.8MPa and an elongation at break of 11.8%.

Example 9

The difference from example 8 is that: the cellulose solution prepared from the waste viscose film has different concentrations, namely the cellulose concentration in example 9 is 6 wt%, and the rest is the same as that in example 8, and the details are not repeated.

Comparative example 3

The difference from example 8 is that: the cellulose solution prepared from the waste viscose film has different concentrations, the cellulose concentration in the comparative example 2 is 8 wt%, and the rest is the same as the example 8, and the details are not repeated.

The experimental result shows that in the comparative example 3, the waste viscose film dissolving solution with the concentration of 8 wt% has poor fluidity, is pasty, has poor centrifugal defoaming effect, and the obtained cellulose hydrogel film is whitish, has more bubbles, is seriously crushed in the drying process, and cannot obtain a complete cellulose film.

Table 2 shows the process parameter settings and performance parameters of examples 7 to 9 and comparative example 3

Examples 7-9 and comparative example 3 were analyzed in conjunction with table 2 and fig. 3:

as shown in fig. 3, as the concentration of the cellulose solution (concentration of the waste viscose film) increases, the more dense the structure of the prepared regenerated cellulose film is, the better the mechanical properties of the film are.

However, when the concentration of the cellulose solution is increased to 8 wt%, the cells remaining in the solution after centrifugation become defects in the cellulose hydrogel. In the drying process, the hydrogel film loses water and shrinks, and the film is cracked at the defect position due to stress concentration under the action of a shrinking force. Therefore, a high-concentration solution defoaming technology is required to further improve the mechanical properties of the cellulose film.

In summary, the present invention provides a method for preparing a regenerated cellulose film by using a waste adhesive film. Firstly, soaking a pretreated waste adhesive film in a sodium hydroxide aqueous solution at 4 ℃ for 1-24 hours to obtain a blend; then, shearing and violently stirring the blend at a high speed, crushing, dissolving and defoaming to obtain a cellulose solution with the mass fraction of 2-6 wt%; and finally, carrying out the procedures of film laying, regeneration, cleaning, drying and the like on the cellulose solution by a sol-gel conversion method to prepare the regenerated cellulose film with good tensile strength and elongation at break. The film preparation method has the advantages of simple process, low cost, environmental friendliness and no pollution, and is a green production process for recycling waste viscose films.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a cellulose film by recycling a waste viscose film is characterized by comprising the following steps: the method comprises the following steps:

2. The method for preparing the cellulose film by recycling the waste viscose film according to claim 1, wherein the method comprises the following steps: in step S1, the waste adhesive film is leftover material or adhesive film waste generated in the process of preparing the cellophane by the adhesive method.

3. The method for preparing the cellulose film by recycling the waste viscose film according to claim 1, wherein the method comprises the following steps: in step S3, the film-laying and coagulation bath regeneration process is to scrape the cellulose solution on a flat support by a casting method and then immerse the solution film in a coagulation bath to obtain a cellulose hydrogel film.

4. The method for preparing the cellulose film by recycling the waste viscose film according to claim 1, wherein the method comprises the following steps: in step S3, the step of laying a film and regenerating a coagulation bath includes extruding the cellulose solution through a slit into a coagulation bath to form a film, thereby obtaining a cellulose hydrogel film.

5. The method for preparing the cellulose film by recycling the waste adhesive film according to claim 3 or 4, wherein the method comprises the following steps: in step S3, the coagulating bath is one of hydrochloric acid, sulfuric acid, oxalic acid, citric acid, formic acid, acetic acid, phytic acid, or a combination of at least two of the foregoing.

6. The method for preparing cellulose film by recycling waste viscose film according to claims 5 and 6, wherein: the concentration of the coagulation bath was 15 wt%.

7. The method for preparing the cellulose film by recycling the waste viscose film according to claim 1, wherein the method comprises the following steps: in step S3, the post-treatment process is a washing and drying process to obtain a regenerated cellulose film.

8. The method for preparing the cellulose film by recycling the waste viscose film according to claim 1, wherein the method comprises the following steps: in step S2, the vigorous stirring is a wall breaking machine with a power of 600W to crush and dissolve the powder.

9. The method for preparing the cellulose film by recycling the waste viscose film according to claim 1, wherein the method comprises the following steps: in step S1, the pretreatment process of the waste adhesive film includes cutting, drying and opening processes.

10. The method for preparing the cellulose film by recycling the waste viscose film according to claim 9, wherein the method comprises the following steps: the drying temperature of the drying treatment is 40-100 ℃, and the drying time is 0.1-24 h.