Antimicrobial acrylic fiber and method for producing the same

Abstract

To provide an antimicrobial acrylic fiber that exhibits high antimicrobial activity and excellent retention capability.SOLUTION: The present invention provides an antimicrobial acrylic fiber wherein an antimicrobial agent component is distributed in a region of length L from the outer periphery of a fiber cross-section, and wherein a fiber cross-sectional radius R and the length L from the outer periphery of the fiber cross-section satisfy a relationship of formula (1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antibacterial acrylic fiber having high and sustained antibacterial properties and a method for producing the same. [Background technology]

[0002] Compared to other synthetic fibers, acrylic fibers have a soft texture that is most similar to wool, and are used in a wide range of fields, including clothing and interior goods. In particular, for clothing products such as underwear and socks, antibacterial fiber products that have been imparted with antibacterial properties are widely available, with the aim of inhibiting the growth of bacteria caused by human sweat and preventing the generation of unpleasant odors. One of the characteristics required for these antibacterial products is that the antibacterial component is able to maintain its antibacterial properties without leaching or falling off from the fiber.

[0003] To meet such demands, various technologies have been proposed. For example, the method proposed in Patent Document 1 strengthens the binding of antibacterial agents to acrylic fibers, suppressing the decline in antibacterial activity and providing high durability. However, even this proposed method faces the problem of a decline in antibacterial activity due to post-processing such as dyeing, bleaching, and softening of the fibers, as well as treatments the textile product undergoes in the usage environment, such as washing. Similarly, the method of supporting chitosan particles proposed in Patent Document 2 also faces the problem of dissolution or mechanical detachment during spinning and post-processing, resulting in a loss of satisfactory antibacterial activity. Therefore, there has been a demand for acrylic fibers that combine high antibacterial activity itself with the ability to retain that activity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-65327 [Patent Document 2] Japanese Patent Application Publication No. 10-140418 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the background of the prior art, the present invention aims to provide an antibacterial acrylic fiber having a long-lasting high antibacterial activity and an industrially stable method for producing the same. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention has the following configuration.

[0007] That is, the antibacterial acrylic fiber of the present invention and its production method are as follows.

[0008] (1) An antibacterial acrylic fiber characterized in that an antibacterial agent component is distributed in a region of length L from the periphery of the fiber cross section, and the radius R of the fiber cross section and the length L from the periphery of the fiber cross section satisfy the relationship of the following formula (1).

[0009]

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[0010] (2) An antibacterial acrylic fiber according to claim 1, characterized in that the antibacterial agent is a quaternary ammonium salt.

[0011] (3) A method for producing antibacterial acrylic fibers by wet spinning an acrylic polymer and then adding an antibacterial agent, the diffusion coefficient of which in water is 4 × 10 cm 2 3. The method for producing antibacterial acrylic fibers according to claim 1, wherein the spinning is carried out using an organic solvent at a rate of 1 / sec or more.

[0012] (4) A spun yarn containing at least 20 wt % of the antibacterial acrylic fiber according to claim 1 or 2. [Effects of the Invention]

[0013] The antibacterial acrylic fiber and the method for producing the same of the present invention can provide an antibacterial acrylic fiber that can be used to obtain textile products that exhibit long-lasting, high antibacterial performance. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view illustrating the cross-sectional radius R and the length L from the outer periphery of the cross-sectional surface of the fiber of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] First, the method for producing the antibacterial acrylic fiber of the present invention will be described. The acrylic polymer constituting the acrylic fiber of the present invention is not particularly limited as long as it can be formed into fibers, but an acrylonitrile polymer containing 80% by mass or more, preferably 90% by mass or more, of acrylonitrile is preferably used, and in addition to a polymer consisting of acrylonitrile alone, it can optionally contain a copolymerization component. The copolymerization component can be acrylic acid, methacrylic acid or their esters, acrylamide, methacrylamide, vinyl acetate, vinyl chloride, vinylidene chloride, or other olefin-based monomers, or unsaturated sulfonic acids or their salts, such as allyl sulfonic acid, vinyl sulfonic acid, acryl sulfonic acid, methallyl sulfonic acid, and p-styrene sulfonic acid, with methyl acrylate and sodium methallyl sulfonate being particularly preferred.

[0016] The acrylic polymer that can be used in the present invention is as described above, but the polymerization method is not particularly limited, and a general polymerization method such as suspension polymerization, emulsion polymerization, interfacial polymerization, or solution polymerization can be used.

[0017] Although dry spinning, wet spinning, and dry-wet spinning are mainly used for acrylic fibers, wet spinning is the preferred spinning method for the acrylic fibers of the present invention because voids are easily formed in the fiber during the coagulation process. The formation of these voids makes it easier for the antibacterial agent to penetrate deeper into the fiber than the surface during the antibacterial agent application process described below, resulting in fibers with excellent washing durability.

[0018] The solvent used to dissolve the polymer preferably has a large diffusion coefficient relative to the poor solvent used in the spinning bath. The larger the diffusion coefficient, the faster the coagulation of the extruded filaments proceeds in the coagulation step, and the more likely voids are to form in the fibers. When water is used as the poor solvent for the spinning bath, the solvent that dissolves the polymer generally includes dimethyl sulfoxide (hereinafter referred to as DMSO), dimethyl formamide (hereinafter referred to as DMF), dimethylacetamide, an aqueous solution of rhodanate, an aqueous solution of nitric acid, etc., but in the present invention, from the viewpoint of the likelihood of void formation, a solvent with a diffusion coefficient relative to water of 4×10-5 cm is used. 2 DMSO with a % CO₂ concentration of 1 / sec or more is preferred.

[0019] The state (quantity and size) of voids can be controlled by the diffusion coefficient of the organic solvent, as well as the concentration and temperature of the organic solvent in the coagulation bath. The lower the concentration and the higher the temperature, the more rapid the solvent exchange occurs, causing the spinning solution to coagulate and voids to form. The organic solvent concentration is preferably 43 to 70 wt%, and the coagulation bath temperature is preferably 30 to 45°C.

[0020] The proportion of the acrylonitrile polymer in the spinning dope is 20 to 25% by mass, and the proportion of the organic solvent must be 75 to 80% by mass. Preferably, the proportion of the acrylonitrile polymer is 21 to 24% by mass, and the proportion of the organic solvent is 76 to 79% by mass. If the proportion of the acrylonitrile polymer in the spinning dope is less than 20% by mass, the resulting fibers may become devitrified, losing their luster and decreasing their color development. On the other hand, if the proportion of the acrylonitrile polymer exceeds 25% by mass, spinnability will be significantly deteriorated. The spinning dope prepared in this manner is spun using a conventional wet spinning device.

[0021] When the spinning dope is spun into the DMSO aqueous solution in the coagulation bath, the spinning dope temperature is set to 60 to 80°C, preferably 65 to 75°C. If the spinning dope temperature is lower than 60°C, not only will the spinnability of the spinning dope be insufficient, but the high viscosity will cause equipment damage such as an increase in nozzle pressure. If the spinning dope temperature is higher than 80°C, the spinning dope will often undergo denaturation such as gelation, making stable spinning impossible.

[0022] After the spinning process, the fiber is produced through a typical acrylic fiber production process, including drawing, washing, and drying / densification. The draw ratio in the drawing process is preferably 4 to 7 times, more preferably 4.5 to 5.5 times, and is preferably the minimum draw ratio necessary to achieve sufficient strength for use as a fiber. The fiber is produced under tension, minimizing shrinkage after final drawing. After drying / densification, the fiber is crimped, then heat-treated with wet or dry heat, and cut to the desired fiber length to obtain short fibers. While known mechanical crimping methods can be used to impart crimp, a press-type crimper is particularly preferred due to its ability to impart uniform and stable crimp. By appropriately setting the conditions for various crimping methods, the required number of crimps and crimp percentage for the acrylic fiber of the present invention can be achieved. For example, in a method using a push-in crimper, the temperature of the tow entering the push-in crimper is preferably 60°C or higher and 75°C or lower, more preferably 65°C or higher and 70°C or lower. A temperature of 60°C or higher imparts flexibility to the tow, improving its ability to impart crimp. Known methods for raising the temperature of the tow include wet heat treatment with steam, as well as dry heat treatment with hot rollers or hot air. The wet heat treatment temperature after crimping is preferably 100 to 125°C. If the temperature is lower than 100°C, single fiber shrinkage occurs during dyeing, changing the single fiber fineness. Furthermore, if the temperature exceeds 125°C, the balance between dry strength and elongation is disrupted, resulting in low dry strength and high dry elongation, and poor spinning processability.

[0023] Regarding the method of applying the antibacterial agent, by applying it to the fiber in a gel state with voids before drying and densifying, the antibacterial agent adheres from the surface to the inside, resulting in an antibacterial fiber with excellent antibacterial agent drop-off prevention properties. A specific method is the DIP method, in which the fiber bundle before drying and densifying is immersed in an aqueous solution (antibacterial liquid) in which the antibacterial agent has been dissolved. In addition to the antibacterial agent, process oils and other additives can be added to the antibacterial liquid to improve processability.

[0024] The concentration of the antibacterial agent in the antibacterial solution is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, to achieve the desired antibacterial properties, while it is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, to prevent the antibacterial agent from falling off in subsequent processes.

[0025] Next, the antibacterial acrylic fiber of the present invention produced as described above will be described. The antibacterial acrylic fiber of the present invention is characterized in that the antibacterial agent component is distributed in a region of length L from the periphery of the fiber cross section, and the fiber cross-sectional radius R and the length L from the periphery of the fiber cross section satisfy the relationship of the following formula (1):

[0026]

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[0027] More preferably, the relationship of the following formula (2) is satisfied.

[0028]

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[0029] In the antibacterial acrylic fiber of the present invention, the relationship between the length L from the outer periphery of the fiber cross section and the radius R of the fiber cross section is

[0030]

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[0031] If the length L from the periphery of the fiber cross section and the radius R of the fiber cross section are within this range, the antibacterial agent component falls off, causing a decrease in antibacterial performance, and the durability of the antibacterial effect is also reduced.

[0032]

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[0033] By satisfying these requirements, high antibacterial performance is exhibited and antibacterial properties are well retained. Figure 1 shows a schematic diagram of a single fiber cross section of the antibacterial acrylic fiber of the present invention. As shown in Figure 1, by adding an antibacterial agent before drying and densification, the antibacterial agent is distributed not only on the outer surface of the fiber cross section but also to a certain depth, i.e., in a region (layered region) with a certain width. The length of this antibacterial agent-distributed region from the outer periphery to the center (center of gravity) of the fiber cross section is defined as L, and the radius of the fiber cross section is defined as R. For fibers with cross sections other than circular, L and R are calculated based on the cross-sectional area converted to a circular cross section. That is, R is the radius of a perfect circle of the same area, and L is similarly calculated as the distance from the periphery to the layered region of the same area as the presence region of the perfect circle. "Antibacterial agent distribution" refers to the detection of an antibacterial agent peak by TOF-SIMS, i.e., the presence of the antibacterial agent regardless of concentration. Regarding the detection of the antibacterial agent ion peak, a maximum ion count per pixel of the ion image of 4 or more is considered to be present. The antibacterial agent is preferably distributed in a concentration gradient from high to low from the periphery to the center of the fiber, as this concentration gradient allows the antibacterial effect to be exerted more efficiently.

[0034] The antibacterial agent used in the present invention can be selected from those used in fibers, but in terms of excellent antibacterial activity, quaternary ammonium salts having a long-chain alkyl group, such as benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetylpyridinium chloride, cetrimonium bromide, didecyldimethylammonium chloride, and domiphen bromide, are preferably used.

[0035] According to the present invention, by optimizing the production conditions and maximizing the synergistic effect thereof, it is possible to stably and efficiently obtain fibers that have high antibacterial activity and excellent antibacterial retention, are versatile, and have high commercial value.

[0036] The antibacterial acrylic fiber of the present invention is preferably cut into staple fibers, spun, and used as a spun yarn. The spun yarn may be composed of 100 wt% of the antibacterial acrylic fiber of the present invention, or may be blended with other fibers, such as synthetic or chemical fibers such as polyester, nylon, or rayon, or natural fibers such as cotton, wool, or silk, at a ratio of 20 wt% or more to produce a spun yarn that exhibits high antibacterial performance. If the blending ratio of the antibacterial acrylic fiber is less than 20 wt%, the effect of the antibacterial acrylic fiber in the spun yarn is small, making it difficult to achieve its characteristics when made into a textile product. The single fiber fineness of the fiber constituting the spun yarn is preferably 0.4 dtex or more; if it is less than 0.4 dtex, frequent neps occur during the carding process, making spinning difficult. The tensile strength is 2.0 cN / dtex or more and 3.5 cN / dtex or less, preferably 2.5 cN / dtex or more and 3.3 cN / dtex or less. A tensile strength of 2.0 cN / dtex or more can prevent fly formation during spinning even with fine fibers, and can maintain good passability through the spinning process. [Example]

[0037] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0038] [Antibacterial activity value (antibacterial performance)] The antibacterial performance was evaluated using the quantitative test method (bacterial liquid absorption method) of JIS L 1902 (2015) (antibacterial test method and antibacterial effect of textile products), which is part of the certification standards for antibacterial and deodorizing textile products from the Textile Evaluation Technology Council, and the antibacterial activity value was calculated. The same method was used to evaluate antibacterial properties after washing, and the washing method followed the "SEK Mark Textile Product Washing Manual" established by the Council. In addition, the number of washes was determined to be 10 or 100 times, depending on the specified number of times, and the calculated antibacterial activity value was judged on the following three levels, with excellent (S) and good (A) being considered valid. <Acrylic fiber (raw cotton)> Excellent (S): Antibacterial activity value ≥ 5.0 Good (A): Antibacterial activity value = 2.2 to 4.9 · Poor (B): Antibacterial activity value < 2.2. <Knitted fabric> Excellent (S): Antibacterial activity value ≥ 3.0. Good (A): Antibacterial activity value = 2.2 to 2.9 · Poor (B): Antibacterial activity value < 2.2.

[0039] [Washing durability evaluation] The washing durability was evaluated by taking the difference in antibacterial activity values ​​before and after 10 and 100 washes in the above antibacterial performance measurement and judging them on the following three levels, with excellent (S) and good (A) being considered effective. Excellent (S): Difference in antibacterial activity before and after each wash is less than 0.4 Good (A): Difference in antibacterial activity before and after each wash = 0.4 ~ 0.8 Poor (B): The difference in antibacterial activity before and after each wash was > 0.8.

[0040] [TOF-SIMS] (principle) Pulsed ions (primary ions) are irradiated onto a sample surface placed in an ultra-high vacuum. The ions emitted from the sample surface (secondary ions) acquire a certain kinetic energy and are guided to a time-of-flight mass spectrometer. Each secondary ion, accelerated with the same energy, passes through the spectrometer at a speed dependent on its mass. However, because the distance to the detector is constant, the time it takes to reach the detector (time of flight) is a function of mass. By precisely measuring the distribution of these time-of-flights, the mass distribution of the secondary ions, or mass spectrum, can be obtained. Analysis of the mass spectrum allows identification of organic and inorganic substances present on the sample surface, and their peak intensities provide insight into their abundance. Furthermore, focusing the primary ion beam to less than 1 m enables analysis of minute areas and high-spatial-resolution imaging measurements (distribution observation). This analytical technique allows detection to a depth of less than a few nanometers.

[0041] (Measurement conditions) Device: M6 (IONTOF) Primary ion: Bi3 ++ Primary ion accelerating voltage: 30 kV Bunching: None Secondary ion polarity: positive Raster size: 30 μm Charge neutralization: Yes The main peaks observed are shown in Table 1.

[0042] [Table 1]

[0043] [Distribution of antimicrobial agents, L and R] After preparing the fiber cross-section observation sample, the distribution of the antibacterial agent in the fiber was confirmed by positive ion mapping using TOF-SIMS (time-of-flight secondary ion mass spectrometry). The center of the fiber was set to zero, and the distance (maximum R) to each point where benzalkonium chloride was detected was plotted on a box-and-whisker plot. The difference between R and the first quartile was calculated, and the average value for 50 fibers was taken as L. The fiber cross-sectional radius R was also calculated from the fiber cross-sectional photograph.

[0044] [comprehensive evaluation] Excellent (S): Antibacterial activity and washing durability after 10 washes are both rated S, and antibacterial activity and washing durability after 100 washes are both rated A or higher. Good (A): Both the antibacterial activity value after 10 washes and the washing durability are rated A or higher, and both the antibacterial activity value after 100 washes and the washing durability are rated A or higher. · Poor (B): Grade B for either the antibacterial activity value or washing durability after 10 washes or 100 washes.

[0045] [Example 1] 92% by mass of acrylonitrile, 7% by mass of methyl acrylate, and 1% by mass of sodium methallylsulfonate were copolymerized in DMSO to a spinning dope concentration of 22% by mass. The spinning dope was adjusted to a temperature of 68°C and spun into a coagulation bath containing 48% by mass of DMSO and 52% by mass of water adjusted to a temperature of 40°C. The fibers were then stretched 4.0 times in hot water and washed with water. The fiber bundle was then immersed in an antibacterial bath containing 0.25% by mass of an antibacterial agent (benzalkonium chloride) and squeezed with nip rollers. The fibers were then dried and densified using a hot air dryer at 167°C and a relaxation rate of 5% to impart crimping, followed by a wet heat treatment at 102°C to obtain antibacterial acrylic fibers with a cut length of 38 mm and a single fiber fineness of 1.1 dtex. The results are shown in Table 2.

[0046] The obtained antibacterial acrylic fiber was spun into a 1 / 52 count yarn by a conventional method, blended with rayon fiber having a single fiber fineness of 1.4 dtex and a cut length of 38 mm in a ratio of 60:40. The spun yarn was knitted into a jersey knit fabric on an automatic changeover cylindrical knitting machine with a basis weight of 90 g / m. 2 The antibacterial performance of the prepared acrylic fiber, the dyed acrylic fiber, and the knitted fabric was measured, and the results of the antibacterial performance evaluation are shown in Table 3.

[0047] [Examples 2 to 3 and Comparative Examples 1 to 3] The acrylonitrile polymer, the polymer ratio in the spinning dope, the organic solvent for the coagulation bath, the conditions for the coagulation bath, the antibacterial agent, and the antibacterial agent application process in Example 1 were changed as shown in Table 2, and the fibers obtained were spun to prepare knitted fabrics. The results of evaluating the antibacterial performance of these fabrics are shown in Table 3 (raw cotton) and Table 4 (knitted fabrics).

[0048] [Table 2]

[0049] [Table 3]

[0050] [Table 4]

[0051] As is clear from the results in Tables 1 and 2, the antibacterial acrylic fibers produced under conditions that satisfy the process requirements of the present invention not only have excellent antibacterial activity and antimicrobial retention by themselves, but also maintain good antibacterial activity and antimicrobial retention even after being blended with other fibers. [Explanation of symbols]

[0052] L: Length of the area where the antibacterial agent is distributed from the outer periphery of the fiber cross section R: Radial length of fiber cross section 1: Fiber cross section 2: Outer circumference 3: Antibacterial agent distribution area (layered area) 4: Center (center of gravity)

Claims

1. An antibacterial acrylic fiber characterized in that an antibacterial agent is distributed in a region of length L from the outer periphery of the fiber cross section, and the radius R of the fiber cross section and the length L from the outer periphery of the fiber cross section satisfy the relationship of the following formula (1). [Equation 1]

2. 2. The antibacterial acrylic fiber according to claim 1, wherein the antibacterial agent is a quaternary ammonium salt.

3. A method for producing antibacterial acrylic fibers by wet spinning an acrylic polymer and then adding an antibacterial agent, the antibacterial agent having a diffusion coefficient in water of 4×10 －５ cm ２ 3. The method for producing antibacterial acrylic fiber according to claim 1, wherein the spinning is carried out using an organic solvent for 1 / sec or more.

4. A spun yarn containing at least 20 wt % of the antibacterial acrylic fiber according to claim 1 or 2.

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