A method for manufacturing flexible materials using textiles.

Abstract

[Problem] The present invention aims to provide a method for producing a flexible material using a woven fabric through a heat-pressure polymer infiltration process. [Solution] The present invention first uses an alkaline ionic liquid aqueous solution to activate and dissolve the cellulose contained in the fabric, thereby obtaining a cellulose polymer ionic liquid solution similar to an "adhesive." Subsequently, the undissolved fibers are bonded together by a hot-press process, and the material after hot-pressing is further softened by a polymer impregnation treatment, ultimately obtaining a high-strength flexible material made from waste textile products. The present invention does not use pure ionic liquids and does not require the complete dissolution of cellulose, resulting in a short processing time and a simple process. Furthermore, it can partially retain the inherent strength of natural fibers and significantly improve the breaking stress and breaking elongation of the flexible material. The maximum breaking stress reaches 60 MPa or more, and the maximum breaking elongation reaches 50% or more.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling waste fiber products, and particularly relates to a method for manufacturing a flexible and biodegradable material using fabrics.

[0002] [Claiming Priority] The present invention claims the priority of a Chinese invention patent application with application number 202310412795.6 and title "Method for Manufacturing a Flexible Material Using Fabrics", which was filed with the State Intellectual Property Office of the People's Republic of China on April 18, 2023.

Background Art

[0003] In recent years, with the improvement of people's living standards, the renewal rate of clothing has accelerated, generating a large amount of waste fiber products. Among these fiber products, cotton fabrics account for a large proportion.

[0004] Currently, as a method for recycling waste fabrics or cellulose-based materials, mainly a method of completely dissolving cellulose and then recycling the completely dissolved cellulose is used.

[0005] However, although the main component of waste fabrics is cellulose, recycling after complete dissolution is still difficult. The reasons are as follows: First, cellulose is a polyhydroxy compound, which increases the crystallinity of cellulose fibers and makes complete dissolution difficult.

[0006] In the conventional viscose method, first, an alkali treatment is performed, and then cellulose is esterified with carbon disulfide to obtain cellulose xanthate. The xanthate is dissolved in a dilute alkali solution to produce regenerated cellulose. However, this manufacturing process has problems such as high energy consumption, heavy pollution, and complex processes.

[0007] The new NMMO (N-methylmorpholine-N-oxide) method is technically challenging, and because NMMO is highly explosive, industrialization is difficult unless the recovery rate exceeds 95%.

[0008] Furthermore, the ionic liquid method requires the dissolution and processing of cellulose using a completely anhydrous, pure ionic liquid, and since pure ionic liquids have high viscosity, production costs are extremely high.

[0009] Furthermore, because textiles always contain a variety of colors, decolorizing these discarded textiles when they are mixed together is extremely difficult and requires a multi-stage bleaching process. This further exacerbates environmental pollution.

[0010] Furthermore, textiles contain a certain percentage of blended fibers, which are extremely difficult to remove, making the dissolution of cellulose even more challenging. Therefore, reusing cellulose textiles through strategies to completely dissolve cellulose has been difficult to industrialize until now.

[0011] Existing cellulose complete dissolution technologies are often used for known substances with high cellulose content found in nature, such as pulp and cotton, and the products obtained after processing are mainly regenerated fibers and regenerated cellulose films. Furthermore, complete dissolution requires high temperatures and long periods of time, which reduces the degree of polymerization of cellulose, resulting in problems such as lower strength and toughness of the regenerated material.

[0012] On the other hand, the rapid development of online shopping has led to an increase in the consumption of packaging materials and the amount of logistics waste. Currently, film materials used for home delivery packaging include polyethylene, polypropylene, cellulose, nylon, and aluminum foil.

[0013] Of these, most plastics (e.g., polyethylene, polystyrene, and polyvinyl chloride) have stable, long-chain polymer structures and do not decompose for hundreds or thousands of years. Therefore, if a portion of waste textiles containing cellulose can be processed into flexible film materials, it would not only solve the recycling problem of waste textile products but also address the problem of the difficulty of decomposing packaging materials due to the large amount of cellulose contained in the textiles. [Overview of the project]

[0014] The present invention aims to produce a flexible material by utilizing cellulose present in textiles containing cellulose fibers, first activating the cellulose with an alkaline aqueous solution of an ionic liquid, and then using a method of thermal pressure bonding and polymer impregnation modification. This aims to solve the problems of the conventional technology, which involves a complex process of completely dissolving and recycling cellulose when processing waste textiles, as well as the low flexibility of the resulting cellulose material.

[0015] To solve the above problems, the present invention discloses a method for producing a flexible material using a woven fabric, the method of first activating and pre-treating the woven fabric with an ionic liquid aqueous solution, then performing hot-press bonding, and finally treating it with a polymer impregnation step to obtain a flexible material.

[0016] The textiles used in this invention include woven fabrics, knitted fabrics, nonwoven fabrics, braided cords, and the like.

[0017] In one embodiment of the present invention, the ionic liquid aqueous solution is an alkaline ionic liquid aqueous solution obtained by adding deionized water to an ionic liquid and adjusting the pH of the solution using an alkaline substance such as imidazole.

[0018] In one embodiment of the present invention, the textile includes waste textiles. Waste textiles refer to cellulose-containing fabrics that have been used, deteriorated, or discarded by households, businesses, or individuals, and include clothing, sheets, comforters, etc. The ionic liquid includes at least one of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, and 1-ethyl-3-methylimidazolium diethyl phosphate.

[0019] In one embodiment of the present invention, the fabric is a pure spun or blended fabric having a cellulose fiber content of 30 to 100%, the pure spun fabric includes any of cotton fabric, linen fabric, rayon fabric, paper yarn fabric, or copper ammonia fabric, and the blended fabric is a fabric containing at least two of cotton, linen, rayon, paper yarn, and copper ammonia.

[0020] In one embodiment of the present invention, the mass fraction of the ionic liquid in the ionic liquid aqueous solution system is 70 to 95%, the mass fraction of the alkaline substance in the ionic liquid aqueous solution is 1 to 5%, and the remainder is deionized water. The alkaline substance includes at least one of imidazole, sodium hydroxide, and choline.

[0021] The objective of this invention is to produce a flexible material in which partially dissolved cellulose forms the bonding area and undissolved fibers form the backbone. This invention employs a method of immersing a fabric in an aqueous solution of an ionic liquid and controlling the solubility by evaporation of water. If there is too little water, the fibers in the fabric will dissolve excessively, reducing the backbone portion in the product and adversely affecting its mechanical properties and flexibility. On the other hand, if there is too much water, the dissolution of the fibers in the fabric will be insufficient, resulting in a lack of bonding areas and making it difficult to obtain a uniform film-like material. The addition of an alkaline substance is done to promote the swelling of the fibers in the fabric, to ensure better mixing of the ionic liquid and cellulose, and to improve the uniformity of the product. Here, "uniform" means that the thin film material is a single continuous material and that there are no macroscopic pores or defects that affect product performance throughout its entire width, but it does not mean that all parts of the thin film are completely identical.

[0022] In one embodiment of the present invention, the activation pretreatment includes an immersion step and a dissolution step. The immersion step is a step of immersing the fabric in an aqueous solution of ionic liquid, and the dissolution step is a step of heat-activating the fabric after wringing.

[0023] The temperature in the aforementioned heat activation treatment is 45 to 200°C, preferably 90 to 200°C, more preferably 45 to 125°C, and the duration is 5 to 120 minutes.

[0024] Optionally, a squeezing step may be included between the immersion step and the dissolution step. The squeezing step is a step of removing excess ionic liquid aqueous solution from the fabric after immersion.

[0025] In one embodiment of the present invention, the temperature during hot pressing is 80 to 200°C, preferably 120 to 200°C, the pressure is 0.05 to 15 MPa, preferably 0.05 to 1.5 MPa, and the hot pressing time is 0.5 to 300 seconds, preferably 0.5 to 60 seconds.

[0026] The hot pressing process is to reach the dissolution temperature of the ionic liquid in the fabric after the activation pretreatment and reach a predetermined solubility of the fibers in the fabric, so as to form a flexible material with partially dissolved cellulose as the joint and undissolved fibers as the skeleton. Therefore, the range of the hot pressing temperature should be set within the range where the fibers can be dissolved. The hot pressing time should not be too long or too short. If the time is too long, there will be many joints in the obtained thin film, the fiber skeleton will be less, and the mechanical properties and flexibility of the film will decrease. If the time is too short, it will be difficult to form a uniform film-like material.

[0027] In one embodiment of the present invention, the polymer penetration step includes a step of subjecting the fabric after hot pressing adhesion to penetration treatment in a liquid containing a polymer. The polymer includes at least one of polyethylene glycol, polyvinyl alcohol, citrate-based polymer, sorbitol ester-based polymer, the polymer concentration in the liquid containing the polymer is 1 to 50%, and the penetration treatment time is 0.1 to 24 hours.

[0028] By performing the penetration treatment in a liquid containing a polymer, the polymer enters into the cellulose, weakens the interaction between cellulose molecular chains, and increases the mobility of the molecular chains. Thereby, the plasticity and flexibility of the thin film material are improved. Compared with the case where the fabric is only penetrated with an aqueous solution of water or a solvent, the flexibility of the obtained thin film material can be significantly improved.

[0029] The present invention also discloses a flexible material manufactured by the above method.

[0030] In one embodiment of the present invention, the flexible material includes a cellulose-based thin film material.

[0031] One of the objects of the present invention is also to provide for the use of the above flexible material in the fields of fibers, pharmaceutical and food packaging, adhesive tapes, cables, insulating substrates, flexible electronic devices, etc.

Advantages of the Invention

[0032] (1) The present invention produces a flexible material by activating and dissolving cellulose with an alkaline ionic liquid aqueous solution, followed by a hot-pressure bonding-polymer infiltration method. Partial activation and dissolution of the fiber surface generates an ionic liquid solution of cellulose polymer, which acts as an "adhesive," and then a hot-pressure process bonds the remaining undissolved fibers together to obtain a flexible material in which "partially dissolved cellulose forms the bonding area and undissolved fibers form the backbone." In order to achieve partial dissolution rather than complete dissolution, the present invention employs an alkaline aqueous solution system of ionic liquid and controls the degree of dissolution by evaporation of water. In order to increase the toughness of the material, the present invention employs a polymer infiltration strategy, in which an alcohol-based or ester-based polymer with similar hydrogen bonding ability penetrates between cellulose molecular chains to enhance the flexibility of the material, ultimately obtaining a biodegradable cellulose-based flexible material.

[0033] (2) Because the present invention does not require the complete dissolution of cellulose, it retains the inherent strength of natural fibers and significantly improves the tensile strength (breaking stress) of cellulose-based flexible materials. The maximum breaking stress can reach 60 MPa or more.

[0034] (3) The cellulose-based flexible material obtained by the method of the present invention has high elongation at break. After polymer impregnation treatment, the toughness of the flexible material is greatly improved, and the maximum elongation at break can reach 50% or more.

[0035] (4) By reusing waste textiles using the method of the present invention, processing time is significantly reduced, resulting in high efficiency and energy savings. Conventional cellulose film formation processes require film formation by casting after complete dissolution, which involves high dissolution temperatures and often takes several hours. In the present invention, it is not necessary to completely dissolve the cellulose in the textile; a slight surface dissolution of a few minutes is required to obtain an ionic liquid solution of cellulose, after which hot and pressure operations can be performed immediately, resulting in reduced processing time and a reduction in energy and resources. [Modes for carrying out the invention]

[0036] To further clarify the object, technical means, and advantages of the present invention, the technical solutions will be clearly and completely described below based on embodiments of the present invention. Clearly, the embodiments described are only some embodiments of the present invention and do not constitute all embodiments. All other embodiments that a person skilled in the art can obtain without creative work based on embodiments of the present invention are within the scope of the protection of the present invention.

[0037] The raw materials used in Examples 1-8 and Control Examples 1-2 of the present invention are cotton fiber spunlace nonwoven fabrics (hereinafter abbreviated as "nonwoven fabric"). The raw material used in Example 9 is a discarded rayon fabric, and the basis weight (basic weight) of the rayon fabric is 200 g / m². 2 The raw material used in Example 10 was a paper yarn fabric, which was a blended fabric of 76% paper yarn and 24% polyester, with a basis weight of 20 g / m². 2 That is the case.

[0038] The ionic liquid used in Examples 1-8 and Control Examples 1-2 of the present invention is 1-butyl-3-methylimidazolium chloride, and the ionic liquid used in Example 9 is 1-ethyl-3-methylimidazolium chloride.

[0039] In measuring the liquid content (liquid content), the weight of the fabric before and after immersion is weighed as W0 and W1, respectively, and the liquid content is calculated using the following formula.

[0040] P = [(W1 - W0) / W0] × 100% The liquid content can be adjusted by controlling the calendering (rolling) time and pressure.

[0041] Tensile performance test: The test was conducted in accordance with gB / T13022-1991 "Test method for tensile performance of plastic films".

[0042] Biodegradation Test Method: The test was conducted using the natural biodegradation method in accordance with JIS K6950-94. Specifically, a predetermined weight of flexible film material was taken, and the weight obtained after oven drying was defined as M0. This material was then buried at a depth of 10 cm in natural soil, retrieved at predetermined time intervals, and the remaining weight M1 was weighed. The decomposition rate was then calculated using the following formula: Br(%) = [(M0-M1) / M0] × 100%

[0043] Example 1 A method for producing a flexible material using waste textiles, comprising the following steps:

[0044] (1) Preparation of alkaline ionic liquid aqueous solution: Take 70 g of 1-butyl-3-methylimidazolium ionic liquid, add 1 g of imidazole and 29 g of pure water, and stir to form a homogeneous mixed solvent.

[0045] (2) Activation pretreatment: The cotton spunlace nonwoven fabric is immersed in the above ionic alkaline aqueous solution at room temperature, and the liquid content after squeezing is maintained at 100%. Then, the nonwoven fabric is placed in an oven at 90°C and treated for 180 minutes to obtain an activated pre-treated nonwoven fabric sample.

[0046] (3) Hot-press bonding: The pre-treated nonwoven fabric sample obtained in step (2) is placed on a hot-press stage, and a hot-press treatment is performed at a hot-press temperature of 120°C, a pressure of 1.5 MPa, and a hot-press time of 60 s to obtain the film material after hot-pressing.

[0047] (4) Penetration treatment: The hot-pressed film material obtained in step (3) is penetrated in a 1% polyethylene glycol (Mn=20000) solution at room temperature for 24 hours, then removed and air-dried to obtain a translucent flexible film material.

[0048] The test results showed that the obtained translucent flexible film material had a tensile breaking stress of 25.6 MPa, a breaking elongation of 32.93%, and a 90-day biodegradation rate of 93.43%.

[0049] Example 2 Example 2 is similar to Example 1, except that the polymer used in the penetration treatment process is different. Specifically, while Example 1 used polyethylene glycol with a number average molecular weight of 20,000 as the penetration polymer, Example 2 used polyvinyl alcohol (PVA1788) and sorbitan ester as the penetration treatment polymers, respectively.

[0050] Table 1. Effects of different polymer penetrations on the mechanical properties of the film. JPEG2026511701000001.jpg52149

[0051] As is clear from Table 1, by using an aqueous solution of the above polymer as a coagulation bath and performing a penetration treatment, the resulting recycled film materials all clearly exceeded 10% in terms of elongation at break, and all exhibited remarkable flexibility in their mechanical properties.

[0052] Example 3 Example 3 is similar to Example 1 except that the polymer used in the penetration treatment process is different. Specifically, while the penetration polymer selected in Example 1 was polyethylene glycol with a number average molecular weight of 20,000, in Example 3, polyethylene glycol (PEG) was selected as the penetration polymer, and PEG with molecular weights of 600 and 4,000 were used as the penetration treatment polymers, respectively.

[0053] Table 2 Effect of PEG molecular weight on the mechanical properties of the film As is clear from Table 2, when polyethylene glycol (PEG) solutions of different molecular weights were used as a coagulation bath for the penetration treatment, the resulting recycled film materials all clearly exceeded 10% in terms of elongation at break, and their mechanical behavior all showed remarkable flexibility.

[0054] Among these, the use of PEG20000 yielded superior overall mechanical performance.

[0055] Example 4 Example 4 is similar to Example 1, except that the process parameters during hot-press bonding are different.

[0056] Specifically, in Example 1, hot pressing was performed for 60 seconds under conditions of 120°C and 1.5 MPa, whereas in Example 4, the hot pressing process parameters used and the various performance characteristics of the resulting film are shown in Table 3.

[0057] Table 3: Effects of thermal pressure process parameters on film performance JPEG2026511701000003.jpg70152

[0058] As is clear from Table 3, all of the recycled film materials obtained using the above-described hot-pressure process parameters exhibited good fracture stress and elongation at fracture, and their mechanical behavior showed excellent flexibility.

[0059] Example 5 Example 5 is similar to Example 1 except that the temperature during the activation pretreatment is different.

[0060] Specifically, in Example 1, the oven temperature in the activation pretreatment step was 90°C, whereas in Example 5, the activation pretreatment temperature used and the various performance characteristics of the resulting film are shown in Table 4.

[0061] Table 4. Effect of activation pretreatment temperature on film performance JPEG2026511701000004.jpg59136

[0062] As is clear from Table 4, the recycled film materials obtained at the above activation pretreatment temperatures all exhibited good fracture stress and elongation at fracture, and their mechanical behavior all showed excellent flexibility.

[0063] Example 6 Example 6 is similar to Example 1, except that the concentration of the ionic liquid used is different.

[0064] In other words, while the concentration of the ionic liquid aqueous solution in Example 1 was 70%, Table 5 shows the concentration of the ionic liquid used in Example 6 and the various performance characteristics of the resulting film.

[0065] Table 5: Effect of ionic liquid concentration on film performance JPEG2026511701000005.jpg48136

[0066] As is clear from Table 5, compared to pure ionic liquids, the recycled film materials obtained by activation pretreatment using aqueous solutions of ionic liquids exhibited superior mechanical performance and flexibility.

[0067] Example 7 Example 7 is similar to Example 1, except that the alkali content in the ionic liquid solution used is different.

[0068] In other words, while the alkali content of the ionic liquid solution in Example 1 was 1%, Table 6 shows the alkali content of the ionic liquid solution used in Example 7 and the various performance characteristics of the resulting film. Table 6: Effect of alkali content on film performance JPEG2026511701000006.jpg47165

[0069] As is clear from Table 6, the recycled film materials obtained by activation pretreatment with the above-mentioned alkali-containing ionic liquid aqueous solution all clearly showed a break elongation exceeding 10%, and their mechanical behavior all exhibited remarkable flexibility.

[0070] Example 8 Example 8 is similar to Example 1, except that the type of alkali used in the ionic liquid solution is different.

[0071] In other words, while the alkali added in Example 1 was imidazole, Table 7 shows the different types of alkali used in Example 8 and the various performance characteristics of the resulting films. Table 7: Effect of alkali type on film performance JPEG2026511701000007.jpg47152

[0072] As is clear from Table 7, the recycled film materials obtained by activation pretreatment with ionic liquid aqueous solutions using the various alkalis described above all had a break elongation clearly exceeding 10%, and their mechanical behavior all showed remarkable flexibility.

[0073] Comparative Example 1 Comparative Example 1 differs from Example 1 in that no polymer impregnation treatment is performed on the nonwoven fabric after heat pressing.

[0074] Table 8 shows the various performance characteristics of the obtained films.

[0075] Table 8: Effect of polymer impregnation treatment on film performance JPEG2026511701000008.jpg35170

[0076] As is clear from Table 8, the recycled film material treated with polymer impregnation showed a significant increase in elongation at break and a remarkable improvement in material flexibility.

[0077] Comparative Example 2 Comparative Example 2 differs from Example 1 in that the order of polymer treatment is different.

[0078] In Comparative Example 2, the same concentration of PEG was directly added to the fabric before heat pressing, and no polymer impregnation treatment was performed after heat pressing.

[0079] On the other hand, in Example 1, the fabric is subjected to a penetration treatment after heat and pressure.

[0080] Table 9 shows the various performance characteristics of the obtained films.

[0081] Table 9: Effect of polymer addition order on film performance JPEG2026511701000009.jpg36159

[0082] As is clear from Table 9, by performing a penetration treatment on the fabric after heat pressing, the mechanical properties and flexibility of the resulting film can be significantly improved compared to when the polymer is added before heat pressing.

[0083] Example 9 Example 9 is similar to Example 1 in that it uses different raw materials.

[0084] In Example 1, a nonwoven fabric made of cotton fibers was used as the raw material, whereas in Example 9, a rayon fabric was used as the raw material.

[0085] The test results showed that the resulting flexible film material had a tensile breaking stress of 33.4 MPa and a breaking elongation of 34.27%.

[0086] Example 10 Example 10 is similar to Example 1 in that it uses different raw materials.

[0087] In Example 1, cotton nonwoven fabric was used as the raw material, whereas in Example 10, paper yarn fabric was used as the raw material.

[0088] The test results showed that the resulting flexible film material had a tensile breaking stress of 28 MPa and a breaking elongation of 18%.

Claims

1. A method for manufacturing flexible materials using textiles, The method for producing a flexible material is characterized by first activating and pre-treating a fabric with an ionic liquid aqueous solution, then performing hot-press bonding, and finally treating it with a polymer impregnation step to obtain a flexible material.

2. The method for producing a flexible material according to claim 1, characterized in that the ionic liquid aqueous solution is an alkaline ionic liquid aqueous solution obtained by adding deionized water to an ionic liquid and adjusting the pH of the solution using an alkaline substance.

3. The aforementioned ionic liquid is 1-allyl-3-methylimidazolium chloride, 1-Butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-Butyl-3-methylimidazolium acetate, 1-Ethyl-3-methylimidazolium diethyl phosphate A method for producing a flexible material according to claim 1 or 2, characterized by comprising at least one of the following.

4. The aforementioned fabric is a pure spun fabric or a blended fabric having a cellulose fiber content of 30 to 100%. The aforementioned pure spun fabric is one of the following: cotton fabric, linen fabric, rayon fabric, paper yarn fabric, or copper ammonia fabric. The method for producing a flexible material according to claim 1 or 2, characterized in that the blended fabric is a fabric containing at least two of the following: cotton, linen, rayon, paper yarn, and copper ammonia.

5. In the aforementioned ionic liquid aqueous solution system, the mass fraction of the ionic liquid is 70-95%, the mass fraction of the alkaline substance is 1-5%, and the remainder is deionized water. The method for producing a flexible material according to claim 1 or 2, characterized in that the alkaline substance comprises at least one of imidazole, sodium hydroxide, and choline.

6. The activation pretreatment includes an immersion step and a dissolution step, The aforementioned immersion step is a step of immersing the fabric in an aqueous solution of ionic liquid, The aforementioned dissolution step is a step of heat-activating the fabric after squeezing, A method for producing a flexible material according to claim 1 or 2, characterized in that the temperature of the heat activation treatment is 90 to 200°C and the treatment time is 5 to 120 minutes.

7. A method for producing a flexible material according to claim 1 or 2, characterized in that the temperature during the hot-press bonding is 100 to 200°C, the pressure is 0.05 to 1.5 MPa, and the hot-press bonding time is 0.5 to 60 seconds.

8. The aforementioned polymer impregnation treatment step is a process of impregnating the fabric after heat-press bonding in a liquid containing a polymer. The polymer comprises at least one of polyethylene glycol, polyvinyl alcohol, citrate ester polymer, and sorbitan ester polymer. A method for producing a flexible material according to claim 1 or 2, characterized in that the polymer concentration in the liquid containing the polymer is 1 to 50%, and the penetration treatment time is 0.1 to 24 hours.

9. A flexible material manufactured by the method described in any one of claims 1 to 8.

10. The use of the flexible material according to claim 9, The use is characterized by the flexible material being used in the fields of textiles, pharmaceutical and food packaging, adhesive tapes, cables, insulating substrates, and flexible electronic devices.

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