Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
  • D01F2/24—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from cellulose derivatives
  • D01F2/28—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from cellulose derivatives from organic cellulose esters or ethers, e.g. cellulose acetate
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/10—Other agents for modifying properties

Definitions

• the present invention relates to a cellulose acetate fiber having biodegradability based on ISO14851 and a method for producing the same.
• Patent Document 1 Japanese Patent No. 6580348 discloses a cigarette filter tow including a cellulose acetate fiber in which cellulose acetate constituting the cellulose acetate fiber has an average degree of substitution of 1.4 to 1.85 and an average degree of polymerization of 50 to 180, and the cellulose acetate fiber has a single fiber denier of 2 to 15 denier.
• Patent Document 1 reports that, in an evaluation by a biodegradability test (MITI method) using an activated sludge, the cellulose acetate fiber having a low average degree of substitution has an enhanced biodegradability.
• MIMI method biodegradability test
• Patent Document 3 JP Laid-open Patent Publication No. 2003-82160 discloses a fiber produced by melt spinning a thermoplastic cellulose ester composition containing cellulose ester and polylactic acid as main components. According to Patent Document 3, the main focus is on melt-spinning of the thermoplastic cellulose ester composition, and biodegradability is not specifically evaluated.
• Patent Document 4 International Publication No. 2022/085119 discloses cellulose acetate in which a total degree of acetyl substitution is 1.75 or more and 2.55 or less, and at least one of a degree of acetyl substitution at 2-position and a degree of acetyl substitution at 3-position is 0.7 or less.
• Patent Document 4 indicates that the cellulose acetate has preferable marine biodegradability, and that the cellulose acetate has excellent melt-formability and is used as fibers for clothing.
• biodegradability of a plastic material is evaluated as biodegradability in a soil environment in many cases.
• An amount of enzyme produced in the soil environment by microorganisms which cause degradation is greater than that in a marine environment. Therefore, even in a case where biodegradability is demonstrated in the soil environment or by the MITI method (OECD TG 301C) in which the soil environment is simulated, the result thereof cannot be applied to biodegradability in a low enzyme state as it is.
• Patent Document 1 Although biodegradability is evaluated by the MITI method (OECD TG 301C), the effect is shown merely by the cellulose acetate fibers having a lower average degree of substitution is in a range of 1.4 to 1.85.
• Patent Document 2 although biodegradability is evaluated in soil, the biodegradability of the cellulose acetate fibers is considered to be reduced in an environment with a lower enzyme activity.
• Patent Document 3 The polylactic acid used in Patent Document 3 is degraded in a high temperature and high humidity environment in compost. However, it is known that polylactic acid is unlikely to be degraded in a normal soil environment or a normal water environment. Therefore, the thermoplastic cellulose ester fibers containing cellulose ester and polylactic acid as main components as obtained in Patent Document 3 are considered to have substantially insufficient biodegradability even in soil as in Patent Documents 1 and 2.
• An object of the present disclosure is to solve the above-mentioned problems and to provide a cellulose acetate fiber having good biodegradability based on ISO14851.
• the inventors have found that, where cellulose acetate is used in combination with a specific amount of an adipic acid ester-based compound, and furthermore, a degree of crystalline orientation of a cellulose acetate fiber containing the adipic acid ester-based compound is adjusted to a specific range, the obtained fiber can enhance biodegradability based on ISO14851, and have thus completed the present disclosure.
• the present disclosure may include the following aspects.
• Mw weight-average molecular weight
• the method for producing the cellulose acetate fiber according to aspect 5 in which the melt-spinning is performed at a spinning temperature of 250 to 290°C (preferably 255 to 280°C, and more preferably 260 to 270°C).
• X to Y as a range means “X or more and Y or less”.
• the adipic acid ester-based compound may exclude polyethylene adipate.
• the cellulose acetate fiber of the present disclosure contains a specific plasticizer and is controlled to have a degree of crystalline orientation in a specific range, so that it can enhance biodegradability based on ISO14851.
• Cellulose acetate which is a constituent component of a cellulose acetate fiber, is a semi-synthetic polymer in which at least one of three hydroxy groups (-OH) at 2-, 3-, and 6-positions in a glucose ring of cellulose, which is a natural polymer, is substituted with acetic ester (-OCOCH 3 ).
• a non-edible portion of a plant material can be used as a raw material.
• a degree of substitution indicates a degree to which hydroxy groups in one glucose ring are substituted with acetic ester, and is within a range of 1 to 3.
• An average degree of substitution is not particularly limited to a specific one as long as a fiber can be formed, and may be, for example, 2.0 to 2.6, preferably 2.1 to 2.5, and more preferably 2.3 to 2.5 from the viewpoint of improvement in melt spinnability.
• the average degree of substitution is a value measured by the method described in the Examples below.
• the cellulose acetate in which one of the degrees of substitution at 2- and 3-positions is 0.70 or less can be produced also by referring to the Journal of the Japan Wood Research Society, vol. 60, p. 144-168 (2014 ), and Biomacromolecules, 13, 2195-2201 (2012 ).
• a weight-average molecular weight (Mw) of the cellulose acetate may be, for example, 100000 to 1000000, preferably 100000 to 500000, and particularly preferably 100000 to 300000.
• the weight-average molecular weight is a value measured by the method described in the Examples below.
• the cellulose acetate can be produced by an acetylation reaction of dissolving pulp with an acylating agent such as acetic anhydride and glacial acetic acid in the presence of an acylation catalyst such as sulfuric acid.
• an acylating agent such as acetic anhydride and glacial acetic acid
• an acylation catalyst such as sulfuric acid.
• General cellulose acetate is marketed as, for example, the L series such as product names "L-20”, “L-30”, “L-50”, and “L-70” from Daicel Corporation.
• the cellulose acetate fiber contains an adipic acid ester-based compound as a constituent component.
• the adipic acid ester include an ester of adipic acid and at least one alcohol selected from the group consisting of an aromatic alcohol and an aliphatic alcohol. These types of the adipic acid ester may be used singly or in combination of two or more.
• ester of adipic acid and an aliphatic alcohol examples include dibutyl adipate, dioctyl adipate, dimethoxyethoxyethyl adipate, and dibutoxyethoxyethyl adipate.
• ester of adipic acid and an aromatic alcohol examples include diphenyl adipate, dibenzyl adipate, dicresyl adipate, and dixylyl adipate.
• a preferable mixed alcohol ester of adipic acid, and an aromatic alcohol and an aliphatic alcohol may be benzyl alkyl diglycol adipate.
• Benzyl alkyl diglycol adipate may be used singly, or a mixture containing benzyl alkyl diglycol adipate, and an ester of adipic acid and an aromatic alcohol, and/or an ester of adipic acid and an aliphatic alcohol may be used.
• a content of the benzyl alkyl diglycol adipate is preferably 35 wt% or more.
• An alkyl group of benzyl alkyl diglycol adipate may be linear or branched, and a linear alkyl group is preferably used.
• the number of carbon atoms in the alkyl group may be, for example, 1 to 20, preferably 1 to 8, and more preferably 1 to 4.
• benzyl alkyl diglycol adipate include benzyl methyl diglycol adipate, benzyl ethyl diglycol adipate, benzyl n-propyl diglycol adipate, and benzyl n-butyl diglycol adipate, which have linear C1 to C4 alkyl groups.
• a content of the adipic acid ester-based compound is 10 to 35 wt%, and may be preferably 12 to 25 wt%, and more preferably 13 to 20 wt% in the fiber from the viewpoint of fiber formability and biodegradability.
• the adipic acid ester-based compound is marketed as, for example, product name "DAIFATTY-101" from DAIHACHI CHEMICAL INDUSTRY CO., LTD.
• the cellulose acetate fiber can be produced by spinning a cellulose acetate resin composition containing 10 to 35 wt% of the adipic acid ester-based compound, at a predetermined draft ratio or draw ratio.
• the spinning is preferably melt-spinning from the viewpoint of reducing use of an organic solvent during fiber forming and reducing an environmental load.
• the cellulose acetate resin composition containing the adipic acid ester-based compound at a content of 10 to 35 wt%, preferably 12 to 25 wt%, and more preferably 13 to 20 wt% can be spun at a draft ratio (ratio of a take-up speed to a discharge speed) of 10 to 250 to produce the cellulose acetate fiber.
• the fiber obtained by the melt-spinning is advantageous in that the fiber can be produced as a fiber having a modified cross-section or a composite fiber.
• a resin composition containing the cellulose acetate and the adipic acid ester-based compound may be pelletized and fed to a melt-spinning machine.
• a melt-spinning machine a known melt-spinning machine can be used.
• the pellets may be melt-kneaded using a melt-extruder to obtain a molten material, and the molten material is fed to a spinning chimney.
• the molten material may be metered using a gear pump to discharge a predetermined amount from a spinneret at a predetermined spinning temperature, and the discharged fiber may be taken up (or wound up) at a predetermined draft ratio to produce a cellulose acetate fiber.
• the spinning temperature may be, for example, 250 to 290°C, preferably 255 to 280°C, and more preferably 260 to 270°C.
• the discharge speed from the spinneret can be suitably set depending on the spinning temperature, and the discharge speed may be, for example, 10 to 40 m/min, preferably 12 to 30 m/min, and more preferably 15 to 25 m/min.
• the take-up speed is adjusted depending on the discharge speed, and the draft ratio is preferably adjusted within a suitable range from the viewpoint of biodegradability and fiber tenacity.
• the discharged fiber is taken up such that the draft ratio is 10 to 250, preferably 10 to 200, more preferably 15 to 1500, and even more preferably 20 to 120, whereby the degree of crystalline orientation of the spun cellulose acetate fiber can be controlled.
• the cellulose acetate fiber may be a continuous fiber or a discontinuous fiber depending on the shape of the cellulose acetate fiber.
• the cellulose acetate fiber may be a crimped fiber or a non-crimped fiber. In a case where the cellulose acetate fiber is used for a nonwoven fabric, the cellulose acetate fiber is cut so as to have a suitable length depending on a type of the nonwoven fabric.
• the discontinuous fiber refers to a fiber having a fiber length of 100 mm or less.
• the continuous fiber refers to a fiber other than the discontinuous fibers.
• a cross-section of the fiber may have a round shape such as a circular shape, an elliptical shape, and a cocoon-like shape, and, in addition thereto, the cross-section of the fiber may have various modified cross-sectional shapes the examples of which include a polygonal shape such as a triangular shape, a quadrangular shape, a star shape, and an X shape, and a curved shape such as a clover-leave shape and an S shape.
• the cellulose acetate fiber may be a part of composite fiber such as core-sheath-type fiber, sea-island-type fiber, and side-by-side type fiber.
• the cellulose acetate fiber may be, for example, a composite fiber (for example, a core-sheath fiber, a sea-island fiber, a side-by-side fiber, a split-type fiber) obtained in combination with another polymer (for example, various biodegradable polymers) as long as biodegradability is not impaired.
• the cellulose acetate fiber is preferably non-composite fiber from the viewpoint of controlling the degree of crystalline orientation of the fiber.
• the other type of the lubricants is called an external lubricant, and is not dissolved well in the polymer and forms a lubricating layer between a metal surface and the resin to enhance fluidity of resin.
• each of the internal lubricant and the external lubricant can be contained in the cellulose acetate fiber. Some lubricants function as both. Even where the cellulose acetate has a high melt viscosity, fluidity can be adjusted by adding the lubricant so as to enhance lubricity with respect to a mold and a die.
• the lubricant include a low molecular weight compound which has two moieties having affinities to cellulose acetate molecules and a metal, respectively.
• Each of degrees of acetyl substitution at 2-, 3-, and 6-positions in a glucose ring of cellulose acetate can be measured by an NMR method according to method described in Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)). Specifically, free hydroxy groups in a cellulose acetate sample are propionylated with propionic anhydride in pyridine. The obtained sample is dissolved in deuterated chloroform, and 13 C-NMR spectrum is measured.
• a total degree of acetyl substitution is a sum of the degrees of acetyl substitution at the 2-, 3-, and 6-positions in the glucose ring of the cellulose acetate as obtained by the above-described measurement method.
• f represents a degree of crystalline orientation
• Ii represents a peak intensity at an azimuth angle of ⁇ i.
• ⁇ cos 2 ⁇ > represents an average of orientations of all molecules.
• An integration range i is azimuth angles of 0 to 90 degrees.
• fibers cut so as to have a length of 2 mm were added into 300 mL of a standard test culture solution containing, at a concentration of 100 mg/L, activated sludge in a sewage treatment plant in Kurashiki City, Okayama Prefecture such that a content of the fibers was 100 mg/L.
• the obtained product was cultured at 25 ⁇ 1°C, and an amount of oxygen consumed by biodegradation was measured using a BOD meter ("Oxitop" manufactured by WTW).
• a degree of biodegradation was obtained from a ratio between the measured value and a theoretical oxygen demand (ThOD), and the biodegradability was determined according to the following criteria.
• Hardwood prehydrolyzed kraft pulp containing 98.4 wt% of ⁇ -cellulose was ground into a cotton-like form using a disc refiner. Onto 100 parts by weight of the ground pulp (water content of 8%), 26.8 parts by weight of acetic acid was sprayed, and the resulting mixture was stirred well, and was then allowed to stand for 60 hours for activation as a pretreatment. The activated pulp was added to a mixture of 323 parts by weight of acetic acid, 245 parts by weight of acetic anhydride, and 13.1 parts by weight of sulfuric acid, and the resulting mixture was adjusted to have a maximum temperature of 5 to 40°C over 40 minutes, and acetylated for 90 minutes.
• a neutralizer (24% aqueous solution of magnesium acetate) was added over three minutes so as to adjust an amount of sulfuric acid (amount of ripening sulfuric acid) to 2.5 parts by weight.
• the temperature of the reaction bath was further increased to 75°C, and then water was added thereto such that the concentration of water (ripening water) in the reaction bath was adjusted to 52 mol%. Thereafter, ripening was performed at 85°C, and then the ripening was stopped by neutralizing sulfuric acid with magnesium acetate, to obtain a reaction mixture containing cellulose acetate.
• a diluted acetic acid aqueous solution was added to the obtained reaction mixture, and the cellulose acetate was separated, and then washed with water, dried, and stabilized by calcium hydroxide, to obtain cellulose acetate having a degree of acetyl substitution of 2.4 and a weight-average molecular weight of 180000.
• 80 wt% of the obtained cellulose acetate and 20 wt% of an adipic acid ester-based compound ("DAIFATTY-101" manufactured by DAIHACHI CHEMICAL INDUSTRY CO., LTD.) were added, and stirred and mixed so as to reach a temperature of 70°C or higher by frictional heat in the mixer. Thereafter, the resultant product was fed to a twin-screw extruder (cylinder temperature: 200°C, die temperature: 210°C), extruded, and pelletized.
• the obtained cellulose acetate composition in the form of pellets was discharged from a spinneret having round holes at a discharge speed of 400 m/min at a spinning temperature of 260°C using a melt-spinning machine, and then wound at a draft ratio of 31, to obtain multifilaments each having 500 dtex/24 filaments.
• the degree of biodegradation after three days of the obtained fibers was 11.3%.
• Cellulose acetate fibers were produced in the same manner as in Example 1 except that a spinning temperature was 270°C and a draft ratio was 118. The obtained cellulose acetate fibers were evaluated, and the evaluation results are shown in Table 1. The degree of biodegradation after three days of the obtained fibers was 9.0%.
• Cellulose acetate fibers were produced by subjecting the fibers obtained in Example 1 to dry heat drawing at 180°C such that a total draw ratio was 1.2. The obtained cellulose acetate fibers were evaluated, and the evaluation results are shown in Table 1. The degree of biodegradation after three days of the obtained fibers was 10.8%.
• Cellulose acetate fibers were produced in the same manner as in Example 2 except that a draft ratio was 247.
• the obtained cellulose acetate fibers were evaluated, and the evaluation results are shown in Table 1.
• the degree of biodegradation after three days of the obtained fibers was 4.8%.
• Cellulose acetate fibers were attempted to be produced in the same manner as in Example 1 except that an amount of the adipic acid ester-based compound was 3 wt% and a spinning temperature was 270°C. However, the cellulose acetate resin composition did not have fluidity at the spinning temperature, so that spinning was not able to be performed.
• Cellulose acetate fibers were attempted to be produced in the same manner as in Example 1 except that an amount of the adipic acid ester-based compound was 50 wt% and a spinning temperature was 204°C. However, the discharged fibers had a low tenacity, and thus, was not able to be wound.
• Cellulose acetate having a degree of acetyl substitution of 2.4 and a weight-average molecular weight of 180000 was added to DMSO, and stirred and dissolved at 90°C for 5 hours, to obtain a spinning dope in which a polymer concentration was 24 wt%.
• the spinning dope was subjected to dry-wet spinning in a coagulation bath using water as the coagulating liquid at 10°C through a spinneret having 80 holes each having a hole diameter of 0.12 mm ⁇ , and subjected to wet drawing at 1.5 times in a water bath at 20°C.
• DMSO in the fibers was extracted by water, a spinning oil was applied to the fibers, and the fibers was dried at 120°C. Thereafter, the obtained cellulose acetate fibers were subjected to dry heat drawing at 220°C such that a total draw ratio was 3.0.
• the degree of biodegradation after three days of the obtained fibers was 3.1%.
• Cellulose acetate fibers were attempted to be produced in the same manner as in Example 2 except that a draft ratio was 300. However, since the winding speed was excessively high, the discharged fibers were frequently broken while the fibers were wound, and fibers were not able to be obtained.
• Example 1 Cellulose acetate fibers were produced by subjecting the fibers obtained in Example 1 to dry heat drawing at 220°C such that a total draw ratio was 2.5. The obtained cellulose acetate fibers were evaluated, and the evaluation results are shown in Table 1.
• Table 1 Spinning method Draft ratio Total draw ratio Adipic acid ester-based compound Spinning temperature Average degree of substitution Weight-average molecular weight Tenacity Degree of crystalline orientation Biodegradability (times) (times) (wt%) (°C) (cN/dtex)
• Example 1 Melt-spinning 31 - 20 260 2.4 18 ⁇ 10 4 0.66 0.110 A
• Example 2 Melt-spinning 31 - 13 250 2.4 18 ⁇ 10 4 0.68 0.115 A
• Example 3 Melt-spinning 31 - 30 270 2.4 18 ⁇ 10 4 0.42 0.149 A
• Example 4 Melt-spinning 118 - 20 270 2.4 18 ⁇ 10 4 0.99 0.180 A
• Example 5 Melt-spinning 31 1.2 20
• Example 1 the degrees of crystalline orientation in Examples 1 to 6 were in a range of 0.010 to 0.260.
• biodegradability based on ISO14851 is good, and biodegradation quickly progresses in a short period of time in spite of a low-enzyme environment at or around 25°C.
• biodegradability at a low temperature (at or around 25°C) adopted for marine biodegradability can be evaluated. Therefore, in these Examples in which biodegradability is quickly demonstrated at a low temperature under a low-enzyme environment, biodegradability is expected to be excellent also in the marine environment.
• Example 2 and Example 6 in which the proportion between the cellulose acetate and the adipic acid ester-based compound is the same, it is found that fiber tenacity can be enhanced by increasing the draft ratio for spinning.
• melt spinnability differs depending on an amount of a plasticizer.
• an amount of the plasticizer was 3 wt%, the resin composition did not have fluidity even at a higher spinning temperature, so that the resin composition was not able to be melt-spun.
• Comparative Example 2 in which an amount of the plasticizer was 50 wt%, spinning was attempted, but discharged fibers were frequently broken due to low tenacity, and traveling fibers were not able to be wound.
• the cellulose acetate fiber of the present disclosure has excellent biodegradability, and can thus be suitably used in many applications such as agricultural materials, forestry materials, fishery materials, civil engineering materials, clothing fibers, daily materials, sanitary materials, and medical materials.

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• 2023
  • 2023-11-21 JP JP2024560154A patent/JPWO2024111569A1/ja active Pending
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