LYOCELL MATERIAL WITH CONTROLLED WHITENESS BY HYDROGEN PEROXIDE TREATMENT AND MANUFACTURING METHOD THEREOF

Abstract

 The present disclosure relates to a lyocell material with controlled whiteness by hydrogen peroxide treatment and a manufacturing method thereof, wherein the lyocell material has improved whiteness due to an aging effect through drying and packaging by a predetermined amount of hydrogen peroxide remaining in a tow, and may replace a CA cigarette filter to lower environmental pollution problems caused by discarded cigarette butts, and thus the lyocell material is suitable as a cigarette filter.

Description

Technical Field

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of Korean Patent Application Nos. 10-2021-0129847 filed on September 30, 2021, and 10-2022-0118768 filed on September 20, 2022 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.

[0002] The present disclosure relates to a lyocell material with controlled whiteness by hydrogen peroxide treatment and a method of manufacturing same.

Background Art

[0003] In general, cigarette filters include a cellulose acetate tow obtained by extracting cellulose from wood pulp and acetylating the cellulose.

[0004] Although a photocatalyst (TiO₂) has been added thereto to obtain whiteness of cellulose acetate (CA), it is impossible to use TiO₂ due to various problems of TiO₂. Because photocatalyst materials capable of replacing TiO₂ have not been developed until now, it is known that a photocatalyst will not be added to CA.

[0005] In addition, studies have recently been conducted to replace cellulose acetate tows with eco-friendly materials to protect the natural environment and reduce costs. For example, the development of tows using lyocell fibers obtained by fiberizing cellulose, unlike cellulose acetate, is in progress.

[0006] However, it is difficult to realize whiteness (white index of 80 or more and yellow index of 8 or less) desired by cigarette manufacturers by using tows formed of lyocell fibers developed to date.

Disclosure

Technical Problem

[0007] Provided are a lyocell material with controlled whiteness by hydrogen peroxide treatment suitable for a cigarette filter by realizing whiteness equivalent or superior to that of CA tows treated with a currently used photocatalyst, and a method of manufacturing the same.

[0008] Provided also are a lyocell material with controlled whiteness by hydrogen peroxide treatment capable of reducing environmental pollution factors caused by discarded CA cigarette butts, and a method of manufacturing the same.

Technical Solution

[0009] According to an aspect of the present disclosure, a method of manufacturing a lyocell material includes: (S1) spinning a lyocell spinning dope including cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution;

(S2) coagulating the lyocell spinning dope spun in the step (S1) to obtain lyocell multi-filaments;

(S3) water-washing the obtained lyocell multi-filaments;

(S4) treating the water-washed lyocell multi-filaments with oil and hydrogen peroxide;

(S5) crimping the lyocell multi-filaments treated with oil and hydrogen peroxide in the step (S4) to obtain a crimped tow; and

(S6) drying the crimped tow,

wherein (S4) includes

a process of treating the water-washed lyocell multi-filaments simultaneously with oil and hydrogen peroxide in a bath containing a mixed solution of the oil and hydrogen peroxide with a uniformly maintained concentration, or

a process of treating the water-washed lyocell multi-filaments sequentially in baths respectively containing a single solution of the hydrogen peroxide, and a single solution of oil.

[0010] According to an aspect of the present disclosure, a lyocell material includes a crimped tow formed of lyocell multi-filaments spun from a lyocell spinning dope comprising cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution, and treated with oil and bleached with hydrogen peroxide,
wherein the crimped tow includes a lyocell crimped tow including 1000 ppm or less of hydrogen peroxide and satisfying both a white index of 80 or more and a yellow index of 8 or less.

[0011] According to an aspect of the present disclosure, a cigarette filter includes the lyocell material.

[0012] Hereinafter, a lyocell material for a cigarette filter and a method of manufacturing the same according to embodiments of the present disclosure will be described in detail.

[0013] Before that, technical terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the present disclosure, unless they have clearly different meanings in the context.

[0014] Throughout the specification, an expression used in the singular encompasses the expression of the plural, unless otherwise indicated.

[0015] As used herein, the term 'include' specifies particular properties, regions, integers, processes, operations, elements, and/or components and are not intended to preclude the possibility that one or more other properties, regions, integers, processes, operations, elements, and/or components thereof may exist or may be added.

[0016] As used herein, the term 'at least one of' or "one or more", when preceding a list of elements, should be understood to include all possible combinations of the elements.

[0017] Hereinafter, the present disclosure will be described in detail.

Method of Manufacturing Lyocell Material

[0018] According to an embodiment of the present disclosure, a method of manufacturing a lyocell material includes: (S1) spinning a lyocell spinning dope including cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution;

(S2) coagulating the lyocell spinning dope spun in the step (S1) to obtain lyocell multi-filaments;

(S3) water-washing the obtained lyocell multi-filaments;

(S4) treating the water-washed lyocell multi-filaments with oil and hydrogen peroxide;

(S5) crimping the lyocell multi-filaments treated with oil and hydrogen peroxide in the step (S4) to obtain a crimped tow; and

(S6) drying the crimped tow,

wherein (S4) includes

a process of treating the water-washed lyocell multi-filaments simultaneously with oil and hydrogen peroxide in a bath containing a mixed solution of the oil and hydrogen peroxide with a uniformly maintained concentration, or

a process of treating the water-washed lyocell multi-filaments sequentially in separate baths respectively containing a single solution of hydrogen peroxide and a single solution of oil.

[0019] In the present disclosure, a lyocell fiber with controlled whiteness by hydrogen peroxide treatment and a method of manufacturing the same are provided.

[0020] The hydrogen peroxide, as a chemical compound used in a bleaching process of fabrics, is used to remove pigments and colored impurities in fabrics using oxidation by utilizing reactive oxygen species.

[0021] In view of these properties, the present disclosure provides a method of realizing whiteness equivalent or superior to that of currently used CA controlled by adding a bleaching process using hydrogen peroxide with a concentration in a certain range to a process of manufacturing a lyocell cigarette filter tow. That is, according to the present disclosure, whiteness of a tow may be improved in a short time by applying commonly used hydrogen peroxide to a continuous process of manufacturing a lyocell cigarette filter tow in a controlled concentration.

[0022] Specifically, the hydrogen peroxide may be used such that a content of hydrogen peroxide in a solution for treating lyocell multi-filaments is maintained in a concentration range of 2 wt% to 6 wt% or 3 wt% to 6 wt%.

[0023] In this regard, in the case of using hydrogen peroxide, the concentration should be controlled in the range of 2 wt% to 6 wt% or 3 wt% to 6 wt% to control a content of residual hydrogen peroxide in a final tow to be 1000 ppm or less and to improve whiteness. More specifically, the content of the hydrogen peroxide may be maintained in the range of 3 wt% to 6 wt% or 4 wt% to 6 wt% to optimize improvement of whiteness.

[0024] As the concentration of the hydrogen peroxide decreases, bleaching reaction of the lyocell multi-filaments is inactivated making it difficult to realize desired white index and yellow index. On the contrary, as the concentration of hydrogen peroxide increases, the content of hydrogen peroxide increases in the multi-filaments to be out of the optimal range in the final cigarette filter tow, and thus it is difficult to use the multi-filaments as a cigarette filter material.

[0025] That is, unless the concentration range of hydrogen peroxide of the present disclosure is satisfied, effects both on improving whiteness and physical properties cannot be obtained.

[0026] In addition, to realize desired whiteness of the lyocell tow for cigarette filter in the present disclosure, the filament tow may be treated with hydrogen peroxide simultaneously during a process of applying oil to the filament tow during the manufacturing process. Or, optionally, the filament tow may be treated sequentially with a single solution of hydrogen peroxide and a single solution of oil. In this case, a method of adding the hydrogen peroxide solution and the oil solution made-up in the concentration ranges disclosed herein may be used such that the concentrations are uniformly maintained. More specifically, a white index and a yellow index desired by the industry may be realized and controlled more effectively by treating the water-washed lyocell multi-filaments simultaneously with oil and hydrogen peroxide.

[0027] Thus, according to the present disclosure, a cigarette filter tow including a lyocell with excellent biodegradability may be manufactured, and whiteness desired by cigarette manufacturers may be realized by adding hydrogen peroxide during a tow manufacturing process without adding a photocatalyst (TiO₂). Therefore, according to the present disclosure, currently available CA cigarette butts (filter) may be manufactured by an eco-friendly method compared to conventional methods.

[0028] Hereinafter, each of the processes of the method of manufacturing a lyocell material with controlled whiteness by hydrogen peroxide treatment according to the present disclosure will be described in more detail.

(S1)

[0029] In the present disclosure, the step (S1) is a step of spinning the lyocell spinning dope including cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution. In this regard, the lyocell spinning dope may include 8 wt% to 13 wt% of the cellulose pulp; and 87 wt% to 92 wt% of the N-methylmorpholine-N-oxide aqueous solution, wherein the cellulose pulp may include 85 to 97 wt% of alpha-cellulose and have a degree of polymerization (DPw) of 600 to 1700.

[0030] If an amount of the cellulose pulp is less than 8 wt%, it is difficult to realize fibrous properties, and if the amount of the cellulose pulp exceeds 13 wt%, it may be difficult to dissolve the cellulose pulp in the aqueous solution. In addition, if an amount of the N-methylmorpholine-N-oxide aqueous solution is less than 87 wt%, dissolution viscosity significantly increases which is not desirable, and if the amount of the aqueous solution exceeds 92 wt%, spinning viscosity significantly decreases, making it difficult to manufacture uniform fibers in the spinning process.

[0031] In the N-methylmorpholine-N-oxide aqueous solution, a weight ratio of N-methylmorpholine-N-oxide to water may be from 93:7 to 85:15. If the weight ratio of the N-methylmorpholine-N-oxide to water exceeds 93:7, dissolution temperature increases causing degradation of cellulose during dissolution, and if the weight ratio is less than 85:15, solubility of a solvent decreases, making it difficult to dissolve cellulose.

[0032] The above-described spinning dope is discharged from a spinning nozzle of a flat or donut-shaped spinneret. In this case, the spinneret serves to discharge the spinning dope in the form of filaments into a coagulation solution contained in a coagulation bath through an air gap zone. The process of discharging the spinning dope from the spinneret may be performed at 100 °C to 120 °C.

(S2)

[0033] In the present disclosure, the step (S2) is a step of coagulating the lyocell spinning dope spun in the step (S1) above to obtain lyocell multi-filaments, and the coagulating in the step (S2) may include: primary coagulation performed by air quenching (Q/A) by coagulating the lyocell spinning dope spun in the step (S1) while supplying cooling air thereto; and secondary coagulation performed by immersing the primarily coagulated spun dope in a coagulation solution.

[0034] In the step (S1), after discharging the spinning dope through the flat or donut-shaped spinneret, the lyocell spinning dope spun in the step (S1) may pass through the air gap zone in a space between the above-described spinneret and the coagulation bath. In such an air gap zone, the cooling air may be supplied in a direction from one side to the opposite side of the spinneret in the case of the flat spinneret, and the cooling air may be supplied outwards from an air-cooling part located inside the spinneret in the case of the donut-shaped spinneret and a suction function may also be provided on the opposite side or the outside. The primary coagulation may be performed by air quenching in which the cooling air is supplied to the spinning dope.

[0035] In this regard, factors affecting physical properties of the lyocell multi-filaments obtained in the step (S2) are temperature and air flow rate of cooling air in the air gap zone, and the coagulation of the step (S2) may be performed by suppling cooling air at a temperature of 4 °C to 15 °C and with an airflow rate of 50 L/m³ to 250 L/m³.

[0036] If the temperature of the cooling air is below 4 °C during the primary coagulation, a surface temperature of the spinneret decreases to form a non-uniform cross-section of the lyocell multi-filaments and deteriorate spinning processibility, and if the temperature is above 15 °C, the primary coagulation by the cooling air does not proceed sufficiently, resulting in deterioration of spinning processibilty.

[0037] In addition, if the airflow rate of cooling air is less than 50 L/m³ during the primary coagulation, the primary coagulation by the cooling air does not proceed sufficiently to deteriorate spinning processibilty, thereby causing breakage of fibers in the tow, and if the airflow rate exceeds 250 L/m³, the spinning dope discharged from the spinneret is shaken by the air, resulting in deterioration of spinning processibility.

[0038] After the primary coagulation by air quenching, secondary coagulation may proceed by supplying the spun dope to a coagulation bath containing a coagulation solution. Meanwhile, for appropriate progress of the secondary coagulation, a temperature of the coagulation solution may be 30 °C or below. This is because the temperature for the secondary coagulation is maintained at a level not to be excessively higher than necessary, so that coagulation rate is appropriately maintained. In this regard, the coagulation solution is not particularly limited because it may be prepared and used in a composition commonly available in the art to which the present disclosure belongs.

(S3)

[0039] In the present disclosure, the step (S3) is a step of water-washing the lyocell multi-filaments obtained in the step (S2) described above. More specifically, the lyocell multi-filaments obtained in the step (S2) were fed into a draw roller and then into a water-washing bath to be washed with water.

[0040] In the process of washing the filaments with water, a water-washing solution at 0 to 100 °C may be used taking into consideration of recovery and reuse of the solvent after the water-washing process. Water may be used as the water-washing solution, and other additives may further be added thereto if required.

(S4)

[0041] In the present disclosure, the step (S4) is a step of treating the water-washed lyocell multi-filaments with oil and hydrogen peroxide.

[0042] The step (S4) may be a process of treating the lyocell multi-filaments washed with water in the step (S3) i) by using a mixed solution of the oil and hydrogen peroxide, or ii) by sequentially using a single solution of hydrogen peroxide and a single solution of the oil. By the above-described process, whiteness of the treated lyocell fibers may be controlled to realize a desired level of whiteness.

[0043] That is, the step (S4) is characterized by treating the lyocell multi-filaments washed with water in the step (S3) simultaneously with oil and hydrogen peroxide in the bath containing the mixed solution of the oil and hydrogen peroxide with uniformly controlled concentrations.

[0044] In addition, optionally, the step (S4) may include a process of treating the water-washed lyocell multi-filaments sequentially in separate baths respectively containing a single solution of the hydrogen peroxide and a single solution of the oil. In this method, the concentrations of the single solution of hydrogen peroxide and the single solution of the oil are uniformly maintained in each baths.

[0045] For the treatment with oil and hydrogen peroxide, a method of immersing the filament tow in the bath in which oil and hydrogen peroxide are made-up and releasing the filament tow may be used. Particularly, a method of simultaneously adding hydrogen peroxide at a constant concentration while the oil is made-up may be used.

[0046] Specifically, in the method, it is important to uniformly control the concentrations of both oil and hydrogen peroxide such that the oil and hydrogen peroxide are uniformly applied to the water-washed lyocell multi-filaments.

[0047] Therefore, in the present disclosure, a method of adding the two components made-up in constant concentrations may be used to uniformly maintain the concentrations of oil and hydrogen peroxide in the bath.

[0048] Thus, according to an embodiment of the present disclosure, the step (S4) process of treating the water-washed lyocell multi-filaments with oil and hydrogen peroxide may include a process of treating the filaments water-washed in the step (S3) simultaneously with oil and hydrogen peroxide by a method of immersing the filaments in a bath containing a mixed solution of oil and hydrogen peroxide with controlled concentrations and releasing the filaments. In this case, a bath containing the mixed solution of oil and hydrogen peroxide may be prepared and the bath may be connected to the water-washing bath. Also, a device for providing hydrogen peroxide and oil may be connected to the bath containing the mixed solution of the hydrogen peroxide and oil to uniformly maintain concentrations thereof.

[0049] In addition, according to another embodiment of the present disclosure, the step (S4) process of treating the water-washed lyocell multi-filaments with oil and hydrogen peroxide may include a process of treating the filaments water-washed in the step (S3) by a method of sequentially immersing the filaments in the bath containing the single solution of hydrogen peroxide with a controlled concentration and releasing the filaments, and then immersing the filaments in the bath containing the single solution of oil and releasing the filaments. In this case, the bath containing the single solution of hydrogen peroxide may be connected to the bath containing the single solution of oil and these baths may be connected to the water-washing bath. In addition, devices configured to provide hydrogen peroxide and oil may be connected to each of the baths to uniformly maintain the concentrations thereof.

[0050] Preferably, a higher white index and a lower yellow index may be more effectively obtained by treating the lyocell multi-filaments washed with water in the step (S3) simultaneously with oil and hydrogen peroxide using the mixed solution of oil and hydrogen peroxide with controlled concentrations in the step (S4).

[0051] In this regard, the hydrogen peroxide may be used such that the content of hydrogen peroxide in the solution for treating the lyocell multi-filaments is maintained in a concentration of 2 to 6 wt%. In addition, the hydrogen peroxide may be continuously added to the bath in a state of an aqueous solution to maintain the above-described concentration. In addition, the bath may be provided with a device configured to maintain concentrations of oil and hydrogen peroxide. For example, a device for measuring concentrations of oil and hydrogen peroxide may be provided, and a releasing device for circulating oil and hydrogen peroxide may be provided to maintain a level and standards of the mixed solution containing oil and hydrogen peroxide.

[0052] With a hydrogen peroxide concentration of 2 wt% or less, a desired white index cannot be obtained and hydrogen peroxide cannot uniformly permeate into the multi-filaments so that bleaching is not completely performed after a post-crimping process. With a hydrogen peroxide concentration of 6 wt% or more, the white index is not improved even by an increased content of hydrogen peroxide in the tow and hydrogen peroxide remains in large quantities after the post-crimping process so that physical properties may deteriorate.

[0053] The oil may be used such that a concentration of the oil in the solution for treating the lyocell multi-filaments is maintained in a range of 2 wt% to 8 wt% or 3 wt% to 7 wt% based on the lyocell multi-filaments. By maintaining of the amount of the oil within the ranges described above, friction generated while the lyocell multi-filaments are brought into contact with the machine may be reduced and formation of crimps between fibers may be facilitated during the crimping operation.

[0054] As such, in the case where the concentrations of hydrogen peroxide and oil are not maintained, it is difficult to uniformly bleaching the lyocell multi-filaments, the crimping process may not be effectively performed, or physical properties of the lyocell material may deteriorate, and thus effects on improving whiteness and physical properties cannot be obtained. Therefore, in the step (S4), it is important to control the concentrations of hydrogen peroxide and oil as described above.

[0055] By performing the step (S4), whiteness of the lyocell cigarette filter tow may be improved to a desired level compared to conventional tows, and deterioration in physical properties after the post process of forming crimps may be prevented.

[0056] In this case, the treatment with oil is performed in a state where the multi-filaments are completely immersed in the oil, and an amount of oil applied to the multi-filaments is uniformly maintained by squeezing rollers provided to an entry and release rollers of an oil treatment device.

[0057] In addition, the treatment with hydrogen peroxide may also be performed in a state where the lyocell multi-filaments are completely immersed in the bath in the same manner as in the treatment with oil. Also, after performing the step (S4) process, the step (S5) (crimping process) may be performed without drying the oil and hydrogen peroxide.

[0058] In addition, the oil used for application to the filaments, unlike oil used for common fibers, may be developed exclusively for lyocells. The oil is uniformly made-up because the oil does not react with hydrogen peroxide.

[0059] According to a preferred embodiment, the oil may provide a lubricating function capable of uniformly imparting physical properties of the cigarette filter tow, may optimize processibility of a filter manufacturing process by imparting an appropriate level of smoothness and cohesion, and may provide hydrophobicity, which delays penetration of smoker's saliva into the cigarette filter, to reduce a filter hardness decrease rate for minimizing a phenomenon in which hardness of a filter decreases as a result of deformation of the filter by smoker's saliva during smoking. In addition, the oil may be composed of components harmless to a smoker's body even when a certain amount of the oil remains in the cigarette filter.

[0060] However, the oil serves to decrease friction of the filaments upon contact with a drying roller and a guide and in the crimping process and also serves to effectively form crimps on fibers, and the oil is not particularly limited so long as the oil is commonly available for production of lyocell filaments.

[0061] As a preferred example, the oil may include at least one selected from the group consisting of a lubricating component, a cohesion component, a smoothness component, and a hydrophobic component.

(S5)

[0062] The step (S5) is a step of crimping the lyocell multi-filaments treated with oil and hydrogen peroxide in the step (S4) to obtain the crimped tow.

[0063] Specifically, this is a process of crimping the lyocell multi-filaments treated with oil and hydrogen peroxide by applying steam and pressure thereto, and a crimped tow may be obtained in the step (S5).

[0064] The term "crimping" used throughout the specification refers to providing wrinkles in filaments mainly to provide bulky texture to fibers. In the present disclosure, the crimping process may be performed by using a stuffer box provided with a press roller. The press roller may be a nip roller.

[0065] In this regard, a front end of the stuffer box is provided with a steam box for steam treatment of the filament tow, conditions therefore may be controlled to satisfy a pressure of steam of 0.1 to 3 kgf/cm² supplied to the steam box, a pressure of 1.5 to 4 kgf/cm² applied to a press roller, and an upper plate pressure of 0.1 to 3 kgf/cm². If the steam pressure is less than 0.1 kgf/cm², a modulus of the filaments cannot be lowered to a level appropriate for the process, failing to easily form crimps, and if an excessive amount of steam exceeding 3.0 kgf/cm² is supplied, the modulus of the filaments is minimized but the number of required crimps is not uniform due to a too high water content.

[0066] In addition, if the pressure applied by the press roller is less than 1.5 kgf/cm², the thickness of the fed filament may not be uniform, failing to uniformly form the crimps in a desired number, and if the pressure exceeds 4 kgf/cm², a too strong pressing force drastically decreases an amount of water or oil present in the tow so that the filament may not easily pass through the stuffer box. In this case, it is preferable to maintain a gap between the press rollers in a range of 0.01 to 3.0 mm. If the gap between the press rollers is less than 0.01 mm, a pressure applied to the filament by the roller increases, failing to form crimps or resulting in damage caused by surface friction of the filaments after formation of crimps, and if the gap exceeds 3.0 mm, a filament slipping phenomenon may occur between the press rollers, making it difficult to form uniform crimps.

[0067] In addition, if a pressure of the upper plate vertically moving to provide uniform crimps after the tow passes through the press roller is less than 0.1 kgf/cm², the upper plate cannot be fixed due to an internal pressure of the stuffer box, and thus the tow stays in the stuffer box for a long time failing to obtain continuity of the process or a desired number of crimps may not be obtained in the tow because an optimal stay time cannot be provided. If the pressure of the upper plate exceeds 3.0 kgf/cm², the tow cannot be released from the stuffer box resulting in a non-uniform shape of crimps.

[0068] Tows crimped under the above-described conditions may include and maintain 20 crimps or more per inch, or 20 to 40 crimps per inch, or 30 to 40 crimps per inch. Accordingly, because the lyocell crimped tow of the present disclosure is biodegraded and removed in a short period of time, and thus the lyocell crimped tow is not only eco-friendly but also more effectively satisfies physical properties required for cigarette filters, such as suction resistance, filter hardness, and filter removability, thereby maximizing the effects.

(S6)

[0069] The step (S6) is a step of drying the crimped tow obtained in the step (S5) at a constant temperature.

[0070] Specifically, the oil and hydrogen peroxide contained in the baths and uniformly applied to the filament tow immersed therein are picked up as levels capable of providing the uniform number of crimps in the crimping process.

[0071] Subsequently, by drying the crimped tow using a continuous drying device, a final lyocell crimped tow containing a uniform amount of hydrogen peroxide may be prepared.

[0072] The process of drying the crimped tow may be performed by using a continuous drying device at a temperature of 105 to 135 °C for 15 minutes to 45 minutes or at a temperature of 110 to 130 °C for 20 minutes to 40 minutes. Preferably, the drying of the crimped tow may be performed at a temperature of 110 to 130 °C for 20 minutes to 40 minutes to facilitate bleaching reaction contributing to providing products with excellent whiteness.

[0073] At a drying temperature of 105 °C or below, bleaching reaction does not easily occur and the tow is not completely dried failing to control a required moisture content. At a drying temperature of 135 °C or above, whiteness may be lowered due to a yellowing phenomenon. In addition, if a drying time is 15 minutes or less, bleaching reaction does not easily occur and there may be an irregularly dried portion. If the drying time is 45 minutes or more, the tow surface may be damaged due to the excessive drying time and whiteness may be lowered due to a yellowing phenomenon.

[0074] That is, for efficient bleaching reaction of hydrogen peroxide contained in the tow, conditions for the continuous drying device may be controlled within the ranges described above for the multi-filaments treated with oil and hydrogen peroxide.

[0075] In addition, the tow finally manufactured after the drying process may contain 1000 ppm or less of hydrogen peroxide and additional bleaching reaction may occur due to aging effect in a packed tow. Therefore, the present disclosure may provide a cigarette filter with excellent whiteness further improved by aging in accordance with packaging of the tow.

Lyocell Material

[0076] According to another embodiment, provided is a lyocell material including a lyocell crimped tow formed of lyocell multi-filaments obtained by spinning a lyocell spinning dope including cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution, treated with oil, and bleached with hydrogen peroxide, wherein the crimped tow includes 1000 ppm or less of hydrogen peroxide and satisfies a white index of 80 or more and a yellow index of 8 or less.

[0077] According to the above-described method, whiteness of the tow may be improved by remaining a certain amount of hydrogen peroxide in the tow by using hydrogen peroxide with a concentration controlled in a certain range together with oil in the process of treating the tow with oil, and whiteness may further be improved, particularly, by the aging effect in accordance with drying and packaging.

[0078] However, although the hydrogen peroxide content is 1000 ppm or less in the crimped tow, a desired level of whiteness required for cigarette filters cannot be obtained in the case of using a too low hydrogen peroxide content. Therefore, even in the case where the hydrogen peroxide content in the crimped tow satisfies 1000 ppm or less, the content may be higher than a certain level, specifically, a lower limit of 110 ppm.

[0079] Therefore, the crimped tow may be a lyocell tow including hydrogen peroxide in an amount of 110 ppm or more and 1000 ppm or less and satisfying a white index of 80 to 90 and a yellow index of 1 to 4.5. More specifically, the crimped tow may be a lyocell crimped tow including hydrogen peroxide in an amount of 400 ppm or more and 980 ppm or less and having excellent whiteness satisfying a white index of 80 to 90 and a yellow index of 1 to 4.

[0080] In addition, the lyocell material according to the present disclosure may realize a whiteness (white index of 80 or more and a yellow index of 8 or less) desired by cigarette manufacturers.

[0081] Furthermore, according to the present disclosure, environmental pollution problems caused by discarded cigarette butts may be reduced by replacing CA cigarette filters.

[0082] In this regard, the concentration of hydrogen peroxide used for bleaching treatment of the lyocell tow may be from 2 to 6 wt%.

[0083] The lyocell spinning dope may include 8 wt% to 13 wt% of the cellulose pulp; and 87 wt% to 92 wt% of the N-methylmorpholine-N-oxide aqueous solution.

[0084] The cellulose pulp may include 85 to 99 wt% of alpha-cellulose and may have a degree of polymerization (DPw) of 600 to 1700.

[0085] Meanwhile, according to another embodiment of the present disclosure, a cigarette filter including the lyocell material with controlled whiteness may be provided.

[0086] The composition of the cigarette filter is not limited except for the lyocell tow with improved whiteness.

[0087] For example, the cigarette filter may include a cylindrical lyocell tow including a plurality of lyocell fibers, a plasticizer, a curing agent, and the like.

[0088] The plurality of lyocell fibers are connected to each other by the curing agent to exhibit a mutually bonded structure in which surfaces of the fibers are in contact with the curing agent.

[0089] The curing agent may be any known material used to increase hardness of the filter. For example, the curing agent may include a cellulose derivative, a vinyl derivative, a vinyl emulsion derivative, a natural polymer including sodium alginate, and a polymer resin such as starch and a starch derivative.

Advantageous Effects

[0090] According to the present disclosure, by adding a chemical compound (hydrogen peroxide) for improving whiteness to a process of manufacturing a lyocell cigarette filter tow, a tow with excellent whiteness in which hydrogen peroxide remains therein in an amount of 1,000 ppm or less may be provided. In addition, according to the present disclosure, whiteness may further be improved by the drying process performed by bleaching reaction under a certain conditions and the aging effect in accordance with a process of packaging the dried material.

[0091] Therefore, whiteness (white index of 80 or more and a yellow index of 8 or less) desired by cigarette manufacturers may be realized by adding a bleaching process to a conventional tow manufacturing process.

[0092] In addition, because the lyocell tow is provided by using an eco-friendly method according to the present disclosure, environmental pollution factors caused by discarded cigarette butts may be reduced by replacing conventional CA cigarette filters.

Best Mode

[0093] Hereinafter, the present disclosure will be described in more detail with reference to the following examples. However, the following examples are merely presented to exemplify the present disclosure, and the scope of the present disclosure is not limited thereto.

Example 1

[0094] Cellulose pulp having a degree of polymerization (DPw) of 820 and including 93.9 % of alpha-cellulose was mixed with a NMMO/H₂O mixed solvent (weight ratio of 90/10) including 0.01 wt% of propyl gallate to prepare a spinning dope for preparing a tow for a cigarette filter with a concentration of 12 wt%. First, the spinning dope was maintained at a spinning temperature of 110 °C in a spinning nozzle and spun while adjusting a discharge amount and a spinning rate such that a single fiber fineness of filaments was adjusted to 2.4 De.

[0095] The spinning dope in the form of filaments discharged from the spinning nozzle was supplied to a coagulation solution contained in a coagulation bath through an air gap zone. In this case, the spinning dope was primarily coagulated in the air gap zone using cooling air at a temperature of 8 °C and an airflow rate of 100 L/m³. A coagulation solution including 75 wt% of water and 25 wt% of NMMO was used at 25 °C. In this case, a concentration of the coagulation solution was continuously monitored by using a sensor and a refractometer.

[0096] The coagulated filaments were washed by a water-wash solution sprayed by a water-washing device via a draw roller to remove NMMO remaining in the filaments.

[0097] Subsequently, the water-washed filaments were immersed in a bath containing a mixed solution of oil and hydrogen peroxide made-up in concentrations of 2 wt% of the oil and 5 wt% of the hydrogen peroxide. That is, a method of adding oil and hydrogen peroxide made-up in certain concentrations was used to continuously maintain uniform concentrations in the bath such that the oil content of 2 wt% and the hydrogen peroxide content of 5 wt% are maintained to uniformly apply oil and hydrogen peroxide to the filaments.

[0098] The oil treatment was performed by immersing the filaments in the bath and releasing the filaments, and simultaneously hydrogen peroxide treatment was performed.

[0099] Specifically, the filament tow immersed in the bath was treated at a pressure of 2 kgf/cm² by using a nip roller provided at the stuffer box of the front end of a Crimp M/C installed at a release portion of the bath to release the multi-filaments treated with oil and hydrogen peroxide in the bath. Then, the multi-filaments were fed into a Crimp M/C and crimped to prepare a lyocell crimped tow. The prepared tow was passed through a continuous drying device set to a temperature of 120 °C to obtain a dried tow product (drying treatment time: 25 min).

Example 2

[0100] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the concentration of hydrogen peroxide was changed to 3 wt%.

Example 3

[0101] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the concentration of hydrogen peroxide was changed to 2 wt%.

Example 4

[0102] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the concentration of hydrogen peroxide was changed to 6 wt%.

Example 5

[0103] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that a method of sequentially immersing the water-washed lyocell multi-filaments in a bath containing hydrogen peroxide made-up in a concentration of 5 wt% and in a bath containing oil made-up in a concentration of 2 wt% in the treatment of the water-washed lyocell multi-filaments with oil and hydrogen peroxide.

[0104] In addition, a method of adding oil and hydrogen peroxide made-up in certain concentrations was used to continuously maintain uniform concentrations in the baths such that the oil and hydrogen peroxide are uniformly applied to the filaments. By using the method, the oil content of 2 wt% and the hydrogen peroxide content of 5 wt% was maintained.

Comparative Example 1

[0105] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that only 2 wt% of an oil was used without adding hydrogen peroxide.

Comparative Example 2

[0106] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the concentration of hydrogen peroxide was changed to 1 wt%.

Comparative Example 3

[0107] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the concentration of hydrogen peroxide was changed to 7 wt%.

Comparative Example 4

[0108] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the concentration of hydrogen peroxide was changed to 10 wt%.

Comparative Example 5

[0109] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the drying treatment conditions were changed to 100 °C and 50 minutes in the continuous drying device.

Comparative Example 6

[0110] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the drying treatment conditions were changed to 100 °C and 10 minutes in the continuous drying device.

Comparative Example 7

[0111] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the drying treatment conditions were changed to 140 °C and 10 minutes in the continuous drying device.

Comparative Example 8

[0112] A lyocell tow for a cigarette filter was prepared in the same manner as in Example 1, except that the drying treatment conditions were changed to 140 °C and 50 minutes in the continuous drying device.

[Experimental Example]

[0113] Contents of hydrogen peroxide in the tows and whiteness of the tows of the examples and comparative examples described above were measured according to the following method, and the results are shown in Table 1.

Method of Measuring Physical Property

(1) Measurement of Content of Hydrogen Peroxide in Tow

[0114] Volumetric analysis was performed using a potassium permanganate solution (0.1 N) as a standard solution by applying the principle of redox titration.

[0115] Each of the tows prepared in the examples and comparative examples was allowed to stand for 24 hours under standard conditions for constant temperature and humidity. Then, the tow was immersed in ultrapure water in a weight ratio of 10 wt% to perform sonication for 30 minutes. After sonication, 10 ml of the ultrapure water was collected and 10 ml of distilled water and 2 ml of concentrated sulfuric acid were added thereto. Samples for titration prepared as described above were titrated by a Karl Fischer titrator using a standard solution and amounts of hydrogen peroxide contained in the tows were calculated by measuring endpoints.

[0116] In Equation 1, 0.0017 is a mass (g) of hydrogen peroxide equivalent to 1 m of the 0.1 N potassium permanganate solution, V is a titer (ml) of the 0.1 N potassium permanganate solution, F is a normality coefficient factor of the 0.1 N potassium permanganate solution, D is a dilution ratio of the hydrogen peroxide-containing solution extracted from the tow (=1), and S is a weight (g) of the sample.

[0117] Here, with regard to D, although the sample is diluted in the case where the concentration is high, D was 1 in the present disclosure because the extract was used as it is.

(2) Measurement of Whiteness of Tow

[0118] Whiteness was measured by using a CCM device (X-Rite ColorEye 7000A Spectrophotometer).

[0119] 3 strands of each of the tows prepared in the examples and comparative examples were prepared and fractured at the center in the same manner as in measurement of tensile strength. For measurement of whiteness, this experiment was repeated three times and fractured portions were overlapped and agglomerated. Then, the agglomerated sample was mounted on the CCM device to measure white index and yellow index and results were drawn.

[Table 1]

	Hydrogen peroxide concentration %	Bath Nip Roll pressure (kgf/cm2)	Contents of hydrogen peroxide in tow (ppm)	Whiteness
				W.I	Y.I
Example 1	5	2	900	82.1	3.3
Example 2	3	2	550	80.5	3.8
Example 3	2	2	400	80.1	4.0
Example 4	6	2	980	81.4	3.4
Example 5	5	2	300	80.0	4.4
Comparative Example 1	0	2	0	52.3	13.2
Comparative Example 2	1	2	100	74.0	5.3
Comparative Example 3	7	2	1350	74.7	5.7
Comparative Example 4	10	2	1500	71.8	6.8
Comparative Example 5	5	2	1200	78.2	4.6
Comparative Example 6	5	2	Partially not dried, not measurable
Comparative Example 7	5	2	Partially not dried, not measurable
Comparative Example 8	5	2	650	77.3	5.1

[0120] As a result of measuring physical properties, as shown in Table 1, it was confirmed that the level of whiteness required for cigarette filters was realized in Examples 1 to 5 compared to the comparative examples and the whiteness may be controlled to various levels (whiteness (W.I: 80 or more and Y.I: 8 or less). Specifically, according to Examples 1 to 5, lyocell crimped tows with excellent whiteness including 300 ppm to 980 ppm of hydrogen peroxide and satisfying both a white index of 80 to 90 and a yellow index of 1 to 5 may be provided.

[0121] Particularly, in the case of Examples 1 to 4 in which the concentration of hydrogen peroxide is maintained in the range of 5 to 6 wt%, the lyocell crimped tow satisfied a W.I of 81.4 to 82.1 and a Y.I of 3.3 to 3.4, and thus a cigarette filter with excellent whiteness may be provided.

[0122] In addition, in the case of Example 5 in which oil treatment was performed after treatment with hydrogen peroxide, the lyocell crimped tow satisfied a W.I of 80.0 and a Y.I of 4.4 indicating desired whiteness. In this regard, the whiteness of Example 5 was slightly inferior to those of the examples in which the tows were treated simultaneously with hydrogen peroxide and oil. It may be inferred that hydrogen peroxide contained in the tow is instantly detached by oil during the oil treatment process after the treatment with hydrogen peroxide. However, Example 5, like Examples 1 to 4, satisfied both the white index and yellow index desired by the industry with the hydrogen peroxide content of 1000 ppm or less in the tow compared to the comparative examples. Therefore, the tows of the embodiments of the present disclosure may be used as eco-friendly materials for cigarette filter more effectively compared to conventional materials.

[0123] On the contrary, in the case of Comparative Example 1, the tow was not treated with hydrogen peroxide, and it was confirmed that whiteness was inferior to the extent that results are visually distinguished.

[0124] In addition, although hydrogen peroxide is a factor affecting whiteness of the tows in Comparative Examples 2 to 4, the amount of hydrogen peroxide used for the treatment is out of the range of the present disclosure, and thus it was confirmed that distorted results in which whiteness was increased and decreased according to the residual concentration were obtained. Particularly, in the case of Comparative Example 2, although the hydrogen peroxide content in the tow was less than 1000 ppm, the level of whiteness required for cigarette filters was not satisfied because the content was too low. In addition, in the case of Comparative Examples 3 and 4, although the hydrogen peroxide contents in the tows were more than 1000 ppm, whiteness decreased failing to satisfy the level desired by the industry, showing an uneconomical effect compared to the amount of hydrogen peroxide used therefor.

[0125] In addition, in the case of Comparative Examples 5 to 8, although the tow was treated with hydrogen peroxide, the drying conditions are out of the ranges of the present disclosure, and thus desired whiteness was not able to be obtained due to insufficient bleaching reaction of hydrogen peroxide.

[0126] Therefore, according to the present disclosure, excellent whiteness desired by the cigarette manufacturers may be realized by treating the cigarette filter tow with hydrogen peroxide with a concentration controlled in a certain range. Furthermore, in the present disclosure, the W.I and the Y.I may be optimized by adjusting temperature conditions during bleaching reaction in addition to the treatment with hydrogen peroxide.

[0127] In addition, according to the present disclosure, environmental pollution caused by discarded CA cigarette buts may be reduced by replacing conventional CA cigarette filters treated with a photocatalyst.

Claims

1. A method of manufacturing a lyocell material, the method comprising:

(S1) spinning a lyocell spinning dope comprising cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution;

(S2) coagulating the lyocell spinning dope spun in the step (S1) to obtain lyocell multi-filaments;

(S3) water-washing the obtained lyocell multi-filaments;

(S4) treating the water-washed lyocell multi-filaments with oil and hydrogen peroxide;

(S5) crimping the lyocell multi-filaments treated with oil and hydrogen peroxide to obtain a crimped tow; and

(S6) drying the crimped tow,

wherein the step (S4) comprises

a process of treating the water-washed lyocell multi-filaments simultaneously with oil and hydrogen peroxide in a bath containing a mixed solution of the oil and hydrogen peroxide with a uniformly maintained concentration, or

a process of treating the water-washed lyocell multi-filaments sequentially in baths respectively containing a single solution of the hydrogen peroxide, and a single solution of oil.

2. The method of claim 1, wherein the hydrogen peroxide in the step (S4) is used to have a concentration maintained in a range of 2 wt% to 6 wt% in the solution for treating the lyocell multi-filaments.

3. The method of claim 1, wherein the oil in the step (S4) is used to have a concentration maintained in a range of 2 wt% to 8 wt% in the solution for treating the lyocell multi-filaments.

4. The method of claim 1, wherein the oil in the step (S4) comprises at least one selected from the group consisting of a lubricating component, a cohesion component, a smoothness component, and a hydrophobic component.

5. The method of claim 1, wherein the drying of the crimped tow in the step (S6) is performed by using a continuous drying device at a temperature of 105 °C to 135 °C for 15 minutes to 45 minutes.

6. The method of claim 1, wherein the coagulating in the step (S2) is performed by supplying cooling air to the spun dope at a temperature of 4 °C to 15 °C and at an airflow rate of 50 L/m³ to 250 L/m³.

7. The method of claim 1, wherein the lyocell spinning dope in the step (S1) comprises 8 wt% to 13 wt% of the cellulose pulp and 87 wt% to 92 wt% of the N-methylmorpholine-N-oxide aqueous solution.

8. The method of claim 1, wherein the cellulose pulp comprises 85 wt% to 99 wt% of alpha-cellulose and has a degree of polymerization (DPw) of 600 to 1700.

9. The method of claim 1, wherein the crimped tow is a lyocell crimped tow including hydrogen peroxide in an amount of 1000 ppm or less.

10. A lyocell material comprising:

a crimped tow formed of lyocell multi-filaments spun from a lyocell spinning dope comprising cellulose pulp and an N-methylmorpholine-N-oxide (NMMO) aqueous solution, and treated with oil and bleached with hydrogen peroxide,

wherein the crimped tow comprises a lyocell crimped tow including 1000 ppm or less of hydrogen peroxide and satisfying both a white index of 80 or more and a yellow index of 8 or less.

11. The lyocell material of claim 10, wherein the crimped tow is a lyocell crimped tow including hydrogen peroxide in an amount of 110 ppm or more and 1000 ppm or less and satisfying both a white index of 80 to 90 and a yellow index of 1 to 4.

12. The lyocell material of claim 10, wherein the hydrogen peroxide is used to have a concentration maintained in a range of 2 wt% to 6 wt% in the solution for treating the lyocell multi-filaments during the bleaching.

13. The lyocell material of claim 10, wherein the oil is used to have a concentration maintained in a range of 2 wt% to 8 wt% in the solution for treating the lyocell multi-filaments during the oil treatment.

14. The lyocell material of claim 10, wherein the lyocell spinning dope comprises 8 wt% to 13 wt% of the cellulose pulp and 87 wt% to 92 wt% of the NMMO aqueous solution.

15. The lyocell material of claim 14, wherein the cellulose pulp comprises 85 wt% to 99 wt% of alpha-cellulose and has a degree of polymerization (DPw) of 600 to 1700.

16. A cigarette filter comprising the lyocell material according to any one of claims 10 to 15.