Melt-spun cellulosic fibers

Abstract

According to an exemplary aspect of the present invention, a method for melt spinning cellulosic fibers having controlled molar mass and different side lengths and continuous melt-spun cellulosic fibers thereof are provided.

Description

[Technical Field]

[0001] The present invention relates to melt-spun cellulosic fibers, in particular molar mass controlled cellulose (MMCC) esters and their use in the production of man-made continuous fibers by the melt-spinning process. [Background technology]

[0002] The market for biopolymers and bioplastics has enormous growth potential in the future. Estimates suggest that the production capacity of bio-based polymers will grow from 1.7 Mt in 2014 to 7.8 Mt in 2019 (a five-fold increase). Several well-known companies have announced their interest in replacing petroleum-based polymers with 100% renewable materials. Melt spinning is one of the most economical and convenient methods for producing continuous fibers in large quantities for the textile industry.

[0003] Currently, many of the man-made fibers used in clothing and furniture are derived from fossil oil. Burning products made from fossil oil increases atmospheric CO2 levels and accelerates the effects of climate change. Thermoplastic materials used to produce man-made fibers must have suitable properties from a processing perspective.

[0004] Only a few cellulosic melt-spun fibers have been previously reported using cellulose acetate butyrate (CAB) (Chen et al., 2010; Hooshmand et al., 2014b, a; Wang et al., 2018). However, all of these reported short-chain cellulose derivatives require a plasticizer (e.g., triethyl citrate).

[0005] WO2016 / 193542A1 discloses a general method for improving the reactivity and processability of cellulose, which provides a starting point for hydrolyzed and reactive molar mass controlled cellulose with thermoplastic properties.

[0006] JP 2005 / 248354 A discloses a method for producing cellulose fatty acid ester fibers with excellent mechanical properties, particularly strength and modulus, and excellent productivity. It also describes a melt spinning method for preparing continuous cellulosic fibers. However, it does not disclose how to control the molar mass and molar mass distribution of dissolving pulp raw materials by hydrolysis. Furthermore, the document discloses the use of 5 to 25 wt. % of a polyhydric alcohol-based plasticizer and a high melt spinning temperature of 260 to 340°C.

[0007] To increase the use of cellulosic materials in melt-spun fiber production, a means is needed to modify cellulosic fibers to have different thermoplastic properties, preferably by using lower melt-spinning temperatures without the addition of plasticizers. Summary of the Invention

[0008] The invention is defined by the features of the independent claims. Some particular embodiments are defined in the dependent claims.

[0009] According to one aspect of the present invention, a melt spinning process for preparing continuous cellulosic fibers is provided.

[0010] According to another aspect of the present invention, there is provided a melt spinning process for preparing continuous cellulosic fibers from fully bio-based, controlled molar mass cellulose esters and the melt spun fibers having suitable mechanical properties for various end uses, such as for textile industry purposes.

[0011] These and other aspects, together with the advantages thereof over known solutions, are accomplished by the present invention as hereinafter described and claimed.

[0012] The melt spinning method according to the present invention is mainly characterized by what is described in the characterizing part of claim 1.

[0013] The melt-spun fiber according to the invention is characterized by claim 10.

[0014] The present invention offers considerable advantages. The melt spinning process is one of the most convenient methods for producing polymer fibers on an industrial scale for the textile industry. Melt spinning is a simple process and offers many advantages over solvent or wet fiber spinning, including the absence of solvents, the absence of toxic by-products, and fast production rates. The MMCC grade used is a fully biobased thermoplastic material. Furthermore, the suitability of MMCC for fiber production is demonstrated herein without the addition of plasticizers.

[0015] The present technology will now be described in more detail with reference to specific embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016] This technology provides a melt-spinning process for thermoplastic cellulose esters. Molar mass-controlled cellulose esters with different side chain lengths and varying degrees of substitution (DS) were synthesized and their suitability for fiber production was evaluated. Capillary rheometer tests were performed to confirm differences in thermal behavior, and the optimal cellulose ester was selected based on the results and subjected to larger-scale melt-spinning tests. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a chart showing capillary rheometer testing of cellulose hexanate and cellulose octanate compared to a polypropylene standard. [Figure 2] 1 is an image showing melt-spun A) cellulose hexanate fiber (DS1.5) and B) cellulose octanate fiber (DS1.5). [Figure 3] SEM images of A) cross section and B) surface of melt-spun cellulose octanoate fibers at 300x magnification. Scale bar = 20 μm.

[0018] In this invention, several different grades of molar mass controlled cellulose (MMCC) with various side chain lengths (C6-C16) and degrees of substitution (DS) were tested. According to one embodiment of the present invention, it was found that molar mass controlled cellulose octanate (MMCC C8) with a degree of substitution of 1.4 provides one suitable starting point for increasing the use of cellulosic starting materials in melt-spun fiber production.

[0019] According to one embodiment of the present invention, the melt spinning method of the present invention comprises preparing a continuous cellulosic fiber: preparing a controlled-molecular-mass cellulose ester from a cellulose raw material, the cellulose ester having a side chain length of C2 to C18, a total degree of substitution of 0.7 to 3, and a molar mass distribution of 30 to 300 kDa; melt-spinning the controlled molar mass cellulose ester using a melt-spinning apparatus; recovering the melt-spun fibers; At least includes.

[0020] According to one embodiment, the method comprises controlling (i.e., reducing) the molar mass of a cellulose feedstock through hydrolysis, except for complete hydrolysis, and performing long-chain fatty acid modification, such as esterification or hydroxyalkylation, to obtain a molar mass-controlled cellulose.

[0021] According to a further embodiment of the present invention, the hydrolysis is controlled so that the average molecular weight of the cellulose is reduced by at least 60% and not more than 85% from the molecular weight of the starting material. It is preferable to control the hydrolysis so that after hydrolysis, the average molecular weight of the cellulose is 30 to 300 kDa, preferably 40 to 200 kDa. It should be noted that the molar mass of the cellulose is actually controlled so that the cellulose does not undergo complete hydrolysis.

[0022] According to one embodiment, the cellulose raw material is selected from natural softwood pulp, natural hardwood pulp, annual plant pulp such as bamboo pulp or straw pulp, softwood sulfite dissolving pulp, hardwood sulfite dissolving pulp, ozone-treated hydrolyzed pulp or enzyme-treated pulp.

[0023] According to a further embodiment, the cellulose is hydrolyzed and consequently activated by enzyme treatment, ozone treatment, hydrogen peroxide treatment, alkali treatment or other chemical treatment prior to long-chain fatty acid modification such as esterification or hydroxyalkylation.

[0024] The molar mass-controlled cellulose esters usable in this method can be prepared, for example, by homogeneous esterification of cellulose raw materials. In this method, a fatty acid chloride (C6, C8, C12, or C16, 3 or 4 equivalents per cellulose anhydroglucose unit; AGU) was added to the cellulose mixture using pyridine as a catalyst. The reaction temperature was 80°C and the reaction time was 16 hours. The product was precipitated with ethanol and washed with ethanol and acetone.

[0025] According to one embodiment of the present invention, the controlled molar mass cellulose ester preferably has a side length of C6 to C16, for example C8.

[0026] According to one embodiment of the present invention, the controlled molar mass cellulose ester preferably has a total degree of substitution of 0.9 to 2.0, for example 1.4.

[0027] According to one embodiment of the present invention, melt spinning is carried out at a temperature of 120 to 150°C, more preferably 125 to 140°C, using a melt spinning apparatus equipped with a single screw extruder, a melt pump, and a multi-strand filament die.

[0028] Therefore, one optimal method for carrying out the melt spinning process is to use a Fourne melt spinning machine (Fourne Polymertechnik GmbH, Germany) equipped with a 10 mm single-screw extruder (speed: 100 rpm), a melt pump (speed: 14 rpm), and a multi-strand filament die. In one example, a spinneret with eight holes (0.7 mm diameter) was used. Spinning was carried out at 130 °C. Before processing, the material was dried overnight under ambient vacuum. Melt-spun fibers were collected and oriented using a draw speed range of 0 to 200 m / min, with or without brightener.

[0029] Fully biobased, continuously melt-spun, molar mass-controlled cellulose fibers with good mechanical properties as shown in the preceding examples and figures are also within the scope of the present invention.

[0030] Throughout this specification, a reference to an embodiment means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment. Also, when a numerical value is referred to using terms such as "about" or "substantially," the exact numerical value is also disclosed.

[0031] While the foregoing examples illustrate the principles of the present invention in one or more particular applications, it will be apparent to those skilled in the art that numerous changes in form, application, and details of implementation can be made without the exercise of inventive faculty and without departing from the principles and concepts of the present invention. Accordingly, it is not intended that the present invention be limited except as by the claims that follow.

[0032] The verbs "comprise" and "contain" are used in this document as open limitations which neither exclude nor require the presence of unrecited features. Features recited in dependent claims may be freely combined with each other, unless expressly stated otherwise. Furthermore, it is to be understood that the use of "a" or "an", i.e., the singular, throughout this document does not exclude the plural. [Industrial Applicability]

[0033] Technical and hygiene nonwovens are the fastest growing textile materials and are typically derived from fossil synthetic polymers. Novel thermoplastic cellulose fatty acid esters have polyolefin-like properties, and the suitability of these cellulose esters for fiber production was evaluated herein. In this study, we demonstrated the melt spinning of textile fibers using thermoplastic controlled-molecular-mass cellulose. The melt spinning results indicate that the novel cellulosic fibers can provide a renewable and recyclable alternative to, for example, polypropylene, in some technical and hygiene textile applications. [Example]

[0034] (material) The cellulose material for esterification was commercially available softwood dissolving pulp manufactured by Domsjo Fabriker AB (Sweden). The pulp was pretreated with ozone according to the method described by Willberg-Keyrilainen et al. (2016). Polypropylene (PP) was used as the standard material, and commercially available Tallopol SLB (Bozzetto, Italy) was used as the brightener. All other reagents and solvents were purchased at the highest purity grade available from Sigma-Aldrich (Helsinki, Finland) and used as received.

[0035] (Preparation of Cellulose Ester) Homogeneous esterification of cellulose was carried out using the method proposed by Willberg-Keyrilainen et al. (2016, 2017a). In this method, pyridine was used as a catalyst, and a fatty acid chloride (C6, C8, C12, or C16, 3 or 4 equivalents per cellulose anhydroglucose unit; AGU) was added to the cellulose mixture. The reaction temperature was 80 °C, and the reaction time was 16 h. The product was precipitated with ethanol and washed with ethanol and acetone.

[0036] (Solid state nuclear magnetic resonance (ssNMR)) Cellulose ester is a solid 13 Analysis was performed using C CP / MAS NMR spectroscopy (ssNMR). Analysis was performed using an Agilent 600 MHz NMR spectrometer (Agilent Technologies, USA). All ssNMR experiments were performed at 22 °C using a 10 kHz MAS speed, 10,000 scans, and a 10 s recycle time.

[0037] (Capillary rheometer) The spinnability of the prepared cellulose esters was first evaluated with a Gottfert Rheograph 6000 capillary rheometer (Gottfert, Germany). Capillary rheometry was performed using a 1 / 30 mm die and a 30 s -1 ~1000 seconds -1 The shear rate range was used. Tests were carried out at 130°C with a preheat time of 3 minutes. The apparent values ​​were recorded and the spinnability was evaluated manually. Prior to the experiment, the material was dried overnight in a vacuum.

[0038] (melt spinning) Melt spinning was performed using a Fourne melt spinning machine (Fourne Polymertechnik GmbH, Germany) consisting of a 10 mm single-screw extruder (speed: 100 rpm), a melt pump (speed: 14 rpm), and a multi-strand filament die. An 8-hole spinneret (0.7 mm diameter) was used. Spinning was performed at 130 °C. The material was dried overnight under ambient vacuum before processing. Melt-spun fibers were collected and oriented using a draw speed range of 0 to 200 m / min, with or without brightener.

[0039] (Scanning Electron Microscope (SEM)) Scanning electron microscopy of the melt-spun fibers was performed using a field emission SEM (MERLIN FE-SEM, Carl Zeiss GmbH, Germany). An accelerating voltage of 3 kV was used. Prior to imaging, the fibers were sputter-coated with a thin layer of gold (Leica EM ACE200, Germany).

[0040] (Fiber tensile test) The mechanical properties of the melt-spun fibers were analyzed using a Favimat+ testing system (Textechno, Germany) equipped with a 210 cN load cell and a constant crosshead speed of 20 mm / min. Twenty replicate fibers were tested, and the fibers were stored at standard conditions (23 °C, 50% relative humidity) for one week before testing. Table 1 shows the properties of melt-spun cellulose octanate fibers as an example. [Table 1]

[0041] (List of citations) (Patent document) WO 2016 / 193542 A1 JP 2005 / 248354 A (Non-patent literature) 1. Chen B, Zhong L, Gu L (2010) Thermal properties and chemical changes in blend melt spinning of cellulose acetate butyrate and a novel cationic dyeable copolyester. J Appl Polym Sci 116:NA-NA. doi: 10.1002 / app.30984 2. Hooshmand S, Aitomaki Y, Skrifvars M, et al (2014a) All-cellulose nanocomposite fibers produced by melt spinning cellulose acetate butyrate and cellulose nanocrystals. Cellulose 21:2665-2678. doi: 10.1007 / s10570-014-0269-4 3. Hooshmand S, Cho S-W, Skrifvars M, et al (2014b) Melt spun cellulose nanocomposite fibres: comparison of two dispersion techniques. Plast Rubber Compos 43:15-24. doi: 10.1179 / 1743289813Y.0000000066 4. Wang X, Wang Y, Xia Y, et al (2018) Preparation, structure, and properties of melt spun cellulose acetate butyrate fibers. Text Res J 88:1491-1504. doi: 10.1177 / 0040517517703599 5. Willberg-Keyrilainen P, Talja R, Asikainen S, et al (2016) The effect of cellulose molar mass on the properties of palmitate esters. Carbohydr Polym 151:988-995. doi: 10.1016 / j.carbpol.2016.06.048 6. Willberg-Keyrilainen P, Vartiainen J, Harlin A, Ropponen J (2017a) The effect of side-chain length of cellulose fatty acid esters on their thermal, barrier and mechanical properties. Cellulose 24:505-517. doi: 10.1007 / s10570-016-1165-x

Claims

1. 1. A melt spinning process for preparing continuous cellulosic fibers, comprising: preparing a controlled molar mass cellulose ester from a cellulose feedstock having a side length of C6 to C18, a total degree of substitution of 0.7 to 3, and a molar mass of 30 to 300 kDa; melt-spinning the controlled molar mass cellulose ester using a melt-spinning apparatus; recovering the melt-spun fibers; The present invention is characterized by including at least The molar mass of the cellulose feedstock is controlled through hydrolysis, excluding complete hydrolysis; and The method, wherein the melt spinning is carried out at a temperature of 120 to 150°C.

2. 2. The method of claim 1, wherein the cellulose raw material is selected from natural softwood pulp, natural hardwood pulp, annual plant pulp, softwood sulfite dissolving pulp, hardwood sulfite dissolving pulp, ozone-treated hydrolyzed pulp, or enzyme-treated pulp.

3. The method described in claim 1 or 2, characterized in that hydrolysis is controlled so that the average molecular weight of the molar mass-controlled cellulose ester is reduced by 60% to 85% from the molecular weight of the cellulose raw material, whereby the molar mass of the molar mass-controlled cellulose ester after hydrolysis is in the range of 40 to 200 kDa.

4. 4. The method according to claim 1, wherein the cellulose raw material is hydrolyzed by enzyme treatment, ozone treatment, hydrogen peroxide treatment, alkali treatment or other chemical treatment.

5. The method according to any one of claims 1 to 4, characterized in that the controlled molar mass cellulose ester is prepared by adding a fatty acid chloride to a cellulose mixture using pyridine as a catalyst, and homogeneously esterifying the cellulose raw material at a reaction temperature of 80°C for a reaction time of 16 hours.

6. The method according to any one of claims 1 to 5, characterized in that the melt spinning is carried out using a melt spinning apparatus comprising a single screw extruder, a melt pump and a multi-strand filament die.

7. 7. The method of any one of claims 1 to 6, characterized in that the melt-spun fibers are recovered using a drawing speed of more than 0 m / min up to 200 m / min.

8. The method of any one of claims 1 to 7, wherein the controlled molar mass cellulose ester has a side length of C6 to C16.

9. The method according to any one of claims 1 to 8, characterized in that the controlled molar mass cellulose ester has a total degree of substitution of 0.9 to 2.0.

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