Method for removing cellulose from mechanic mixture of cellulose and at least one synthetic fibrous polymer

Abstract

The invention relates to a method for removing cellulose from a mechanic mixture of cellulose and at least one synthetic fibrous polymer in which the mechanic mixture of cellulose and at least one synthetic fibrous polymer is exposed to hydrogen chloride (HCI) at a temperature of 50 to 90 °C, for a period of 40 to 120 minutes, with a weight ratio of hydrogen chloride to cellulose of between 1 :10 and 1 :15. This either results in hydrolysis or decomposition of cellulose. The products of this reaction are then removed from the mixture by washing with water or mechanically.

Description

[0001] Method for removing cellulose from mechanic mixture of cellulose and at least one synthetic fibrous polymer

[0002] Technical field

[0003] The invention relates to a method for removing cellulose from a mechanic mixture of cellulose and at least one synthetic fibrous polymer, e.g., from a blended textile, etc.

[0004] Background art

[0005] Numerous technical materials and products are currently produced by mechanical mixing of different polymers. The blending of polymers is advantageous with regard to the resulting properties of the blends and also with regard to the price that can be regulated by the proportion of the individual components (with different prices) in the blend. A special case is fibre blends, which are used in large volumes for the production of textile structures. Generally speaking, blending significantly complicates subsequent recycling, because the individual components of the mechanical blend must first be separated and then recycled separately.

[0006] The blending of fibres of different polymers is a common and widely used textile technology in the production of clothing textiles. Cellulosic fibres (cotton, linen, viscose, etc.) are blended with synthetic fibres (aliphatic and aromatic polyesters, polyamides, etc.) in order to improve the comfort properties of the resulting textiles. Fibrous polymers differ significantly from standard polymers of the same chemical composition, especially by the length of molecular chains, partially oriented crystallinity, orientation of the amorphous phase and special fibrillar supramolecular structure. This leads to up to a hundred times higher values of tensile modulus and other mechanical characteristics. A typical blended textile is one that contains in its structure cotton fibres and polyester fibres (e.g., polyethylene terephthalate - PET).

[0007] Since cellulose is a polymer with high resistance to chemical agents and since it does not melt and dissolves only in special solvents, the existing processes for separating cellulose from a mixture with other fibrous polymer / polymers are complicated and costly. Currently known processes use environmentally unsuitable agents to remove cellulose, such as carbon disulphide (CS2), sulphuric acid (H2SO4), N-Methylmorpholine-N-oxide (NMMO) and ionic liquids, and these processes are usually carried out under elevated pressure.

[0008] The object of the invention is to provide a method for removing cellulose from a mechanic mixture of cellulose and at least one synthetic fibrous polymer that would eliminate the disadvantages of the existing technologies.

[0009] Summary of invention

[0010] In the method for removing cellulose from a mechanic mixture of cellulose and at least one synthetic fibrous polymer according to the invention, the mechanic mixture of cellulose and at least one synthetic fibrous polymer, e.g. in the form of a blended textile, is exposed to hydrogen chloride (HCI) at an elevated temperature. The exposure to hydrogen chloride takes place at a temperature of 50 to 90 °C, for a period of 40 to 120 minutes, the weight ratio of hydrogen chloride to cellulose being 1 : 10 to 1 : 15.

[0011] If the process takes place at a temperature lower than 60 °C, the action of hydrogen chloride leads to hydrolysis (depolymerization) of cellulose, in which cellulose is broken down into shorter chains, whereas synthetic fibrous polymers are not disrupted. The product of cellulose hydrolysis is a mixture of carbohydrates and polysaccharides, which is soluble in water, and also nanocellulose, i.e., cellulose in the form of nanofragments or nanofibrils. After completion of hydrolysis, the decomposition products of the reaction and possibly residual hydrogen chloride are removed from the treated structure, preferably, e.g., by washing in a water bath. The resulting structure, which retains its original shape, is thus composed only of synthetic fibrous polymer / polymers.

[0012] The decomposition products of hydrolysis can then be extracted and further utilized - for example, the mixture of carbohydrates and polysaccharides can be utilized as a raw material for biotechnological applications; nanocellulose as a material for technical applications. If the process takes place at a temperature higher than 60 °C, the action of hydrogen chloride causes the decomposition of cellulose, but not of the synthetic fibrous polymer / polymers. During the decomposition, the cellulose turns brown to black and becomes brittle; however, it remains mechanically integrated in the treated structure. After this process is completed, the decomposition products of cellulose and possibly hydrogen chloride residues are removed mechanically from the treated structure, e.g., in a water bath with the support of ultrasound at a frequency of 20 to 30 kHz for at least 25 minutes, preferably for 30 to 50 minutes. The resulting structure, which retains its original shape, is then composed only of synthetic fibrous polymer / polymers. If necessary, ultrasound can be applied already during the cellulose decomposition.

[0013] The cellulose decomposition products can be subsequently extracted and further used, for example as a starting material for the preparation of functional carbon structures by their carbonization and / or graphitization, etc.

[0014] Brief description of drawings

[0015] In the enclosed drawing, Fig. 1 shows SEM images of cellulose particles after their removal from a mechanical mixture of cellulose with polyester fibres by the method according to the invention at a magnification of 500 times, and Fig. 2 shows an SEM image of these particles at a magnification of 2,500 times.

[0016] Examples of embodiment

[0017] Below are five specific examples of the method according to the invention for illustration purposes.

[0018] Example 1

[0019] A 10 g sample of a blended textile (fabric) with a basis weight of 200 g / m2consisting of 50 % cotton (cellulose) fibres and 50 % polyester (PE) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 50 °C. In the process, hydrochloric acid released hydrogen chloride (HCI) which hydrolyzed (depolymerized) the cellulose in the blended textile sample, but not the polyester. The product of hydrolysis was a mixture of carbohydrates and polysaccharides and also nanocellulose. The reaction took place for a period of 120 minutes. After it was completed and the container was cooled, the blended textile sample was immersed in a water bath, where the decomposition products of the reaction and hydrogen chloride residues were spontaneously washed out of it. The resulting structure was composed only of pure polyester fibres.

[0020] Example 2

[0021] A 10 g sample of a blended textile (fabric) with a basis weight of 200 g / m2consisting of 50 % cotton (cellulose) fibres and 50 % polyester (PE) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 57 °C. In the process, hydrochloric acid released hydrogen chloride (HCI) which hydrolyzed (depolymerized) the cellulose in the blended textile sample, but not the polyester. The hydrolysis product was a mixture of carbohydrates and polysaccharides and also nanocellulose. The reaction took place for a period of 90 minutes. After it was completed and the container was cooled, the blended textile sample was immersed in a water bath, where the decomposition products of the reaction and hydrogen chloride residues were spontaneously washed out of it. The resulting structure was composed only of pure polyester fibres.

[0022] Example 3

[0023] A 10 g sample of a blended textile (woven fabric) with a basis weight of 260 g / m2consisting of 50 % cotton (cellulose) fibres and 50 % polyester (PE) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 75 °C. In the process, hydrochloric acid released hydrogen chloride (HCI), which degraded cellulose in the blended textile sample; but not the polyester. As a result of the decomposition, the cellulose darkened and became brittle; however, it remained mechanically integrated in the structure of the treated fabric. The reaction took place for a period of 60 minutes. After its completion, the blended textile sample was immersed in a water bath, where the hydrogen chloride residues were washed out. The resulting structure was composed of polyester fibres with cellulose decomposition products. To separate them, the textile sample was exposed to ultrasound in an aqueous environment - exposure time being 30 minutes and frequency being 20 kHz. The resulting structure was composed only of pure polyester fibres.

[0024] Example 4

[0025] A 10 g sample of a blended textile (fabric) with a basis weight of 260 g / m2consisting of 50 % cotton (cellulose) fibres and 50 % polyester (PE) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 90 °C. In the process, hydrochloric acid released hydrogen chloride (HCI) which degraded the cellulose in the blended textile sample, but not the polyester. As a result of the decomposition, the cellulose darkened and became brittle; however, it remained mechanically integrated in the structure of the treated fabric. The reaction took place for a period of 40 minutes. After its completion, the blended textile sample was immersed in a water bath, where the hydrogen chloride residues were washed out of it. The resulting structure was composed of polyester fibres with cellulose decomposition products. To separate them, the textile sample was exposed to ultrasound in an aqueous environment - exposure time being 25 minutes and frequency being 30 kHz. The resulting structure was composed only of pure polyester fibres.

[0026] Subsequently, the cellulose decomposition products were pyrolyzed in molten inorganic salts (Na2CO3-K2CO3) at a temperature of 850 °C for a period of 70 minutes, thereby obtaining carbon particles with high porosity. Example 5

[0027] A 10 g sample of a blended textile (fabric) with a basis weight of 260 g / m2consisting of 50 % cotton (cellulose) fibres and 50 % polypropylene (PP) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 70 °C. In the process, hydrochloric acid released hydrogen chloride (HCI) which degraded the cellulose in the blended textile sample, but not the polypropylene. As a result of the decomposition, the cellulose darkened and became brittle; however, it remained mechanically integrated in the structure of the treated fabric. The reaction took place for a period of 45 minutes. After its completion, the blended textile sample was immersed in a water bath, where the hydrogen chloride residues were washed out of it. The resulting structure was made up of polypropylene fibres with cellulose decomposition products. To separate them, the textile sample was exposed to ultrasound in an aqueous environment - exposure time being 30 minutes and frequency being 25 kHz. The resulting structure was composed of only pure polypropylene fibres.

[0028] Example 6

[0029] A 10 g sample of a blended textile (fabric) with a basis weight of 260 g / m2consisting of 50 % cotton (cellulose) fibres and 50 % polypropylene (PP) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 .5 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 75 °C. In the process, hydrochloric acid released hydrogen chloride (HCI) which degraded the cellulose in the blended textile sample; but not the polypropylene. As a result of the decomposition, the cellulose darkened and became brittle; however, it remained mechanically integrated in the structure of the treated fabric. The reaction took place for a period of 45 minutes. After its completion, the blended textile sample was immersed in a water bath, where the hydrogen chloride residues were washed out of it. The resulting structure was made up of polypropylene fibres with cellulose decomposition products. To separate them, the textile sample was exposed to ultrasound in an aqueous environment - exposure time being 30 minutes and frequency being 25 kHz. The resulting structure was composed of only pure polypropylene fibres.

[0030] Example 7

[0031] A 10 g sample of a blended textile (fabric) with a basis weight of 200 g / m2consisting of 50 % cotton (cellulose) and 50 % polyester (PE) fibres was placed in a 100 ml container, the inner space of which was divided into two superimposed parts by a separating porous ceramic membrane. In the lower part, 1 g of 35% hydrochloric acid (HCI) was placed. The container was heated to a temperature of 80 °C. In the process, hydrochloric acid released hydrogen chloride (HCI) which degraded the cellulose in the blended textile sample, but not the polyester. As a result of the decomposition, the cellulose darkened and became brittle; however, it remained mechanically integrated in the structure of the treated fabric. The reaction was carried out for a period of 120 minutes. After the reaction was completed, the textile sample was immersed in a water bath, where the hydrogen chloride residues were washed out of it. The resulting structure consisted of polyester fibres with cellulose decomposition products. In order to separate them, the textile sample was exposed to ultrasound in an aqueous environment for a period of 30 minutes at a frequency of 25 kHz. The resulting structure consisted only of pure polyester fibres. In the enclosed drawing, Figs. 1 and 2 are SEM images of the removed cellulose particles at 500x magnification (Fig. 1 ) and 2,500x magnification (Fig. 2).

Claims

PATENT CLAIMS1. A method for removing cellulose from a mechanic mixture of cellulose and at least one synthetic fibrous polymer, characterized in that the mechanic mixture of cellulose and at least one synthetic fibrous polymer is exposed to hydrogen chloride (HCI) at a temperature of 50 to 90 °C, for a period of 40 to 120 minutes, the weight ratio of hydrogen chloride to cellulose being between 1 :10 and 1 :15, whereby: a) at a temperature lower than 60 °C, hydrogen chloride hydrolyzes cellulose to form carbohydrates and polysaccharides and nanocellulose, which are subsequently removed from the mixture with at least one synthetic fibrous polymer by washing out with water, or b) at a temperature higher than 60 °C, hydrogen chloride degrades cellulose, which becomes brittle as a result, wherein the brittle cellulose is subsequently removed mechanically from the mixture with at least one synthetic fibrous polymer.

2. The method for removing cellulose from a mechanic mixture of cellulose and at least one synthetic fibrous polymer according to claim 1 , characterized in that the embrittled cellulose is removed from the mixture with at least one synthetic fibrous polymer in a water bath by ultrasonication at a frequency of 20 to 30 kHz for at least 25 minutes.

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