Heat-shielding acrylic fiber

Abstract

To provide an acrylic fiber which has an excellent ultraviolet shielding property, and excellent thread-making and spinning properties by setting an appropriate particle size and addition amount of an inorganic particle.SOLUTION: There is provided a heat-shielding acrylic fiber that is characterized by containing 0.2 to 2.5 mass% of inorganic particles having an average particle size of 0.5 μm or more and 1.5 μm or less. The acrylic fiber preferably has a single fiber fineness of 0.5 to 2.2 dtex and a tensile strength of 2.0 cN / dtex or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat-shielding acrylic fiber. [Background technology]

[0002] Traditionally, acrylic fibers have been used in clothing such as sweaters and socks because they have a texture similar to sheep's wool, or as pile materials for animal-hair-like pile products, taking advantage of their animal-hair-like texture and luster.

[0003] On the other hand, clothing products for spring and summer are required to have UV-shielding properties and anti-transparency properties to prevent sunburn. As one means for imparting UV-shielding properties and anti-transparency properties to fibers, Patent Document 1 discloses that excellent UV-shielding properties are imparted to acrylic fibers by incorporating titanium oxide particles with an average particle size of 0.1 to 0.18 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-112056 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, adding titanium oxide of a specific particle size to acrylic fibers succeeded in efficiently blocking ultraviolet rays. Meanwhile, acrylic fibers are also required to have heat-shielding properties by blocking near-infrared rays to prevent the temperature inside clothing from rising due to direct sunlight. In order to block near-infrared rays, it is necessary to add fine particles with a particle size larger than usual, which causes problems such as thread breakage at the spinneret surface and a decrease in thread strength, and therefore there is a need to develop heat-shielding acrylic fibers. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides an acrylic fiber with excellent heat-shielding properties. That is, the present invention is a heat-shielding acrylic fiber containing 0.2 to 2.5 mass% of inorganic particles having an average particle size of 0.5 to 1.5 μm. In the present invention, it is preferable that the single fiber fineness is 0.5 to 2.2 dtex, the tensile strength is 2.0 cN / dtex or more, and the inorganic particles are contained in an amount of 0.3 to 1.0%. [Effects of the Invention]

[0007] The acrylic fiber of the present invention is produced by uniformly dispersing inorganic particles in a polyacrylonitrile polymer and then spinning the resulting polymer into a heat-shielding acrylic fiber that efficiently blocks near-infrared rays in the range of 1000 nm to 3000 nm with a small amount of additive, thereby solving problems with spinnability. DETAILED DESCRIPTION OF THE INVENTION

[0008] The heat-shielding acrylic fiber of the present invention will now be described.

[0009] 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 it may be a polymer or copolymer of acrylonitrile (hereinafter collectively referred to as acrylonitrile (co)polymer), preferably containing 50% by mass or more of acrylonitrile units, more preferably 85% by mass or more. By setting the copolymerization ratio of acrylonitrile to 85% by mass or more, a spun yarn with good strength and good processability in the spinning process can be obtained, with an upper limit of 100% by mass of acrylonitrile. In other words, a homopolymer may be used, but a copolymer is preferred in terms of stretchability in the spinning process.

[0010] Preferred copolymerization components other than acrylonitrile when preparing an acrylonitrile copolymer include vinyl monomers other than acrylonitrile that are copolymerizable with acrylonitrile, such as acrylic acid, methacrylic acid, or alkyl esters, vinyl acetate, vinyl chloride, maleic acid, fumaric acid, itaconic acid, styrene, vinylidene chloride, sodium allylsulfonate, sodium methallylsulfonate, sodium vinylsulfonate, and other vinyl monomers having a sulfonic acid group, and these are used alone or in combination of two or more. Among these, it is preferred to copolymerize a vinyl monomer having a sulfonic acid group with other vinyl monomers in combination.

[0011] When these acrylonitrile copolymers are prepared, the content of copolymer components other than acrylonitrile is preferably 50% by mass or less, more preferably 15% by mass or less, and from the viewpoint of stretchability in the spinning process, preferably 3% by mass or more.

[0012] In particular, when a vinyl monomer having a sulfonic acid group and other vinyl monomers are used in combination as copolymerization components copolymerizable with acrylonitrile, it is preferable to copolymerize 0.5 to 5 mass% of the vinyl monomer having a sulfonic acid group and 2 to 15 mass% of the other vinyl monomer, and it is even more preferable to copolymerize 1 to 3 mass% of the vinyl monomer having a sulfonic acid group and 3 to 7 mass% of the other vinyl monomer. In the present invention, the copolymerization ratio means the mass ratio of each copolymerization component when the mass of the entire acrylonitrile-based copolymer is 100 mass%.

[0013] The acrylonitrile (co)polymer used in the present invention is usually polymerized in a solution, and in this case, a polymerization initiator, a pH adjuster, a molecular weight adjuster, etc. can be added to the polymerization reaction solution as needed.

[0014] Examples of inorganic particles as a near-infrared shielding material in the present invention include Fe2O3, rutile-type TiO2, anatase-type TiO2, CeO2, ZnS, PbCl2, CdO, Sb2O3, WO3, SiC, In2O3, PbO, Ta2O3, ZnO, ZrO2, MgO, CeF3, AlF3, and Al2O3, but metal oxides are preferred, and among them, TiO2, ZnO, and PbO are preferred, with TiO2 being most preferred. It is also possible to use a combination of two or more of these inorganic particles.

[0015] The inorganic particles in the present invention have an average particle size of 0.5 μm or more and 1.5 μm or less when dispersed in a fiber. Preferably, inorganic particles having an average particle size of 0.7 μm or more and 1.2 μm or less are used. If the average secondary particle size is less than 0.5 μm, near-infrared rays cannot be efficiently blocked. If the average particle size is greater than 1.5 μm, thread breakage occurs at the spinneret surface during wet spinning. The average particle size in the present invention refers to an average particle size (Dave-10) calculated by measuring the maximum length (Dmax) and minimum length (Dmin) of particles observed on a fiber cross section using a scanning electron microscope (SEM), calculating the average value (Dave-5) by averaging the average values ​​(Dave) for five particles per fiber, and then averaging the average values ​​(Dave-5) for ten fibers.

[0016] The knitted fabric using the acrylic fiber of the present invention preferably has a heat shielding rate of 35% or more. A heat shielding rate of 35% or more indicates heat shielding properties, more preferably 45% or more, and even more preferably 55% or more.

[0017] The content of inorganic particles in the fiber of the present invention must be 0.2 to 2.5% by mass in order to efficiently shield near-infrared rays. Preferably, it is 0.3 to 1.0% by mass. If it is less than 0.2% by mass, the near-infrared shielding properties will be insufficient. If it is more than 2.5% by mass, the occurrence of yarn breakage during spinning will increase. In the present invention, the content of inorganic particles refers to the mass ratio of inorganic particles when the mass of the entire acrylic fiber is taken as 100% by mass.

[0018] The method for adding inorganic particles to acrylic fibers is not particularly limited, but a preferred example is a method in which inorganic particles are added to an organic solvent used in the spinning dope or a solution in which the same acrylonitrile copolymer as used in the spinning dope is dissolved at a concentration of 5 to 15 mass %, and the resulting dispersion is dispersed to prepare a dispersion, which is then mixed with the spinning dope midway through the spinning dope line.

[0019] The shape of the acrylic fiber of the present invention is not particularly limited, and the cross section may be any shape such as round, C-shaped, triangular, flat, dog-bone, or multi-lobed.

[0020] The acrylic fiber of the present invention preferably has a single fiber fineness of 0.5 to 2.2 dtex. If the single fiber fineness is less than 0.5 dtex, the amount of cotton that sinks into the cylinder during the carding process in spinning processing may increase, or poor transfer to the doffer may occur, resulting in a significant decrease in spinnability. If the single fiber fineness exceeds 2.2 dtex, the texture of the resulting clothing product may become stiff, making it unsuitable for use in clothing products.

[0021] The acrylic fiber of the present invention preferably has a tensile strength of 2.0 cN / dtex or more. If the tensile strength is lower than 2.0 cN / dtex, problems such as fly and nep formation and roller winding may occur during the carding process when the fiber is processed into a spun yarn, resulting in a significant decrease in productivity. The tensile strength can be increased, for example, by increasing the polymerization ratio of acrylonitrile, reducing the content of inorganic particles, increasing the draw ratio, or setting the drying and densification conditions to a higher temperature and for a longer period of time.

[0022] The fiber length of the short fibers is preferably 10 mm or more and 120 mm or less. If it is less than 10 mm, the entanglement between the fibers may be poor, and if it exceeds 120 mm, the openability and processability may be poor.

[0023] The acrylic modified cross-section fiber of the present invention is preferably cut into short fibers, then spun into spun yarn. The spun yarn may be composed of 100 wt% of the acrylic modified cross-section fiber of the present invention, or may be blended with other fibers, such as synthetic or chemical fibers such as polyester fibers, nylon fibers, or rayon fibers, or natural fibers such as cotton, wool, or silk, at a ratio of 20 wt% or more to produce a spun yarn, which improves the firmness and texture of the textile product. If the blending ratio of the acrylic modified cross-section fiber is less than 20 wt%, the effect of the acrylic modified cross-section fiber in the spun yarn is small, and the textile product made into a heat-shielding material is unlikely to exhibit heat-shielding properties.

[0024] Next, the method for producing the heat-shielding acrylic fiber of the present invention will be described.

[0025] <Polymerization> The polymerization method for the acrylonitrile (co)polymer used in the present invention may be any polymerization method such as suspension polymerization, emulsion polymerization, solution polymerization, etc. Examples of organic solvents used in polymerization include dimethyl sulfoxide (hereinafter sometimes referred to as DMSO), dimethylacetamide, dimethylformamide, etc. Among them, since the acrylic (co)polymer used in the present invention has excellent spinnability in DMSO-based wet spinning, the polymerization method and polymerization solvent are preferably solution polymerization using DMSO.

[0026] <Spinning> The ratio of the acrylonitrile (co)polymer to the entire spinning dope is preferably 20 to 25% by mass, and in this case, the ratio of the organic solvent is preferably 75 to 80% by mass. The ratio of the acrylonitrile (co)polymer to the entire spinning dope is more preferably 21 to 24% by mass, and the ratio of the organic solvent is more preferably 76 to 79% by mass.

[0027] When the ratio of the acrylonitrile-based (co)polymer in the spinning solution is 20% by mass or more, the obtained fiber is less likely to devitrify and lose its luster, and the dyeing unevenness and color development are likely to be improved. On the other hand, when the ratio of the acrylonitrile-based (co)polymer is 25% by mass or less, the spinning property is likely to be improved.

[0028] The spinning dope thus prepared can be spun using a conventional spinning device. Examples of organic solvents used as a coagulation bath in wet spinning include DMSO, dimethylformamide, and dimethylacetamide. Among these, an aqueous DMSO solution is preferred, as it has a high solvent diffusion coefficient and provides excellent spinnability when wet-spinning an acrylonitrile-based (co)polymer.

[0029] Although there are no particular limitations on the method for adding inorganic particles to acrylic fibers, a preferred example is a method in which inorganic particles are added to the organic solvent used in the spinning dope or a solution in which the same acrylonitrile copolymer used in the spinning dope is dissolved at a concentration of 5 to 15 mass %, and then dispersed to form a dispersion (inorganic particle-dispersed spinning dope), which is then mixed with the spinning dope midway through the spinning dope line. By using this method, inorganic particles with an average particle size of 0.5 to 1.5 μm can be uniformly dispersed in the acrylic fibers.

[0030] The acrylic fiber of the present invention may have a composite structure of an acrylonitrile (based) polymer containing inorganic particles and another acrylonitrile (co)polymer. Examples of the composite structure include a core-sheath structure, a side-by-side structure, and a multilayer structure. In this case, the acrylic fiber having the composite structure is evaluated so that it satisfies the range specified in the present invention. The acrylic fiber of the present invention may be uniform in the length direction or may have thickness variations.

[0031] The acrylic fiber of the present invention can be produced, for example, by the following method. Spinning methods for obtaining the acrylic fiber of the present invention include dry spinning, in which an acrylonitrile copolymer containing inorganic particles is extruded from a spinneret hole into air or an inert atmosphere and then coagulated by vaporizing the solvent with heat; wet spinning, in which a spinning dope (a mixture of the spinning dope and the inorganic particle-dispersed spinning dope) is directly extruded from a spinneret hole into a coagulation bath; and dry-wet spinning, in which a spinning dope (a mixture of the spinning dope and the inorganic particle-dispersed spinning dope) is extruded from a spinneret hole into air or an inert atmosphere and then introduced into a coagulation bath. After spinning by any of these spinning methods, the acrylic fiber of the present invention can be obtained by hot drawing, washing with water, drying and densifying, adding an oil, crimping, and heat-relaxing. The obtained acrylic fiber is cut to a desired fiber length to form short fibers, which are then spun to obtain spun yarns. [Example]

[0032] The present invention will be described in more detail below with reference to examples, but is not limited to these examples. In the examples, the average particle size of the inorganic particles, tensile strength, spinnability, heat shielding rate, and knitted fabric texture were evaluated by the following methods.

[0033] (1) Average particle size of inorganic particles The average particle size of inorganic particles was determined by observing the cross sections of 10 random single fibers at 10,000x magnification using a Keyence VE-9800 scanning electron microscope. Five secondary particles were observed per fiber, and the maximum length (Dmax) and minimum length (Dmin) of each particle were measured to calculate the average value (Dave). The average values ​​(Dave) for the five particles were averaged to calculate the average value (Dave-5), and the average values ​​(Dave-5) for the 10 particles were averaged to calculate the average value (Dave-10). This average value (Dave-10) was defined as the average particle size of the inorganic particles.

[0034] (2) Single fiber fineness and tensile strength Measurements were made in accordance with JIS L1015:2021 chemical fiber staple test method.

[0035] (3) Evaluation of spinnability Regarding spinnability, a fiber with no breakage on the spinneret surface or no winding around the stretching roller was rated as "A" and was deemed to pass spinnability. A fiber with some breakage on the spinneret surface or winding around the roller was rated as "B", and a fiber with frequent breakage was rated as "C" and was deemed to fail spinnability.

[0036] (4) Evaluation of spinning properties Regarding spinnability, if there was no wrapping around the cylinder at the carding stage and minimal dropout of inorganic particles at each stage, the spinning performance was deemed acceptable, with a grade of "A." If there was some wrapping around the cylinder at the carding stage or dropout of inorganic particles, the spinning performance was deemed acceptable, with a grade of "B." If there was frequent wrapping around the cylinder at the carding stage or dropout of inorganic particles, the spinning performance was deemed unacceptable, with a grade of "C."

[0037] (5) Evaluation of heat shielding rate The knitted fabrics were measured in accordance with JIS L1951:2019, which defines the heat shielding index used to objectively evaluate the effectiveness of clothing in preventing temperature increases due to sunlight. The heat shielding rate (%) was calculated using the formula: [(ΔTb - ΔTs) / ΔTb] x 100. (ΔTb: average temperature rise of the blank (°C), ΔTs: average temperature rise of the sample (°C).) A heat shielding rate of 65% or more was rated "SS," 55% or more was rated "S," 45% or more was rated "A," 35% or more was rated "B," and 34% or less was rated "C." "SS," "S," and "A" were considered pass marks, while "B" and "C" were considered fail marks. The knitted fabrics used in the above measurements were prepared as follows:

[0038] That is, the acrylic fibers obtained in the examples and comparative examples were each cut to 38 mm and spun into Ac100, 2 / 53 count yarns using a staple spinning method. The spun yarns were then spun into yarns with a basis weight of 145 g / m using an automatic changeover cylindrical knitting machine. 2 A cylindrical knit was produced.

[0039] (6) Evaluation of knitted fabric texture The evaluation method for the knitted fabric texture was that five judges evaluated the knitted fabrics produced in (5) above by touch, and those judged to have sufficient softness were given an "A", and those judged to lack softness or have a crisp feel were given a "C". If all five judges gave an A, the evaluation result was AA, and if three or more judges gave an A, the evaluation result was A, with "AA, A" being considered a pass for the texture, and if three or more judges gave a C, the evaluation result was C, with "C" being considered a fail for the texture.

[0040] [Example 1] An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning solution with an acrylonitrile-based copolymer concentration of 22.4% by weight) was obtained by solution polymerization using DMSO as the solvent. This acrylonitrile-based copolymer solution was mixed with anatase-type titanium dioxide (TiO2) with an average particle size of 1.4 μm to obtain a titanium dioxide content of 0.3% by weight based on the acrylic fiber mass, to prepare a titanium dioxide-dispersed spinning solution. The spinning solution and the dispersed spinning solution were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.050 mm round-hole spinneret. The fiber was then stretched six times in hot water at 95°C, washed with water, and dried and densified for one minute in hot air at 160°C to obtain acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.5 cN / dtex.

[0041] [Example 2] An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning dope with an acrylonitrile-based copolymer concentration of 22.4% by weight) was prepared by solution polymerization using DMSO as the solvent. Titanium dioxide (titanium dioxide) with an average particle size of 1.3 μm was added to this acrylonitrile-based copolymer solution to obtain a 0.5% by weight titanium dioxide content relative to the acrylic fiber mass, creating an anatase-type titanium dioxide-dispersed spinning dope. The spinning dope and the dispersed spinning dope were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.05 mm round-hole spinneret. The resulting fiber was stretched 6 times in hot water at 95°C, washed with water, and dried and densified with hot air at 160°C for 1 minute, yielding an acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.3 cN / dtex.

[0042] [Example 3] An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning solution with an acrylonitrile-based copolymer concentration of 22.4% by weight) was prepared by solution polymerization using DMSO as the solvent. This acrylonitrile-based copolymer solution was mixed with titanium dioxide (titanium dioxide) with an average particle size of 1.2 μm to obtain a titanium dioxide-dispersed spinning solution, with the titanium dioxide content at 2% by weight relative to the acrylic fiber mass. The spinning solution and the dispersed spinning solution were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.05 mm round-hole spinneret. The mixture was then stretched 6 times in hot water at 95°C, washed with water, and dried and densified with hot air at 160°C for 1 minute, yielding an acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.4 cN / dtex.

[0043] [Comparative Example 1] An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning solution with an acrylonitrile-based copolymer concentration of 22.4% by weight) was prepared by solution polymerization using DMSO as the solvent. Titanium dioxide (titanium dioxide) with an average particle size of 0.42 μm was added to this acrylonitrile-based copolymer solution to obtain a titanium dioxide-dispersed spinning solution, with the titanium dioxide content at 1.0% by weight relative to the acrylic fiber mass. The spinning solution and the dispersed spinning solution were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.05 mm round-hole spinneret. The mixture was then stretched 6 times in hot water at 95°C, washed with water, and dried and densified with hot air at 160°C for 1 minute, yielding an acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.5 cN / dtex.

[0044] Comparative Example 2 An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning solution with an acrylonitrile-based copolymer concentration of 22.4% by weight) was prepared by solution polymerization using DMSO as the solvent. This acrylonitrile-based copolymer solution was mixed with titanium dioxide (titanium dioxide) with an average particle size of 2.5 μm to obtain a titanium dioxide-dispersed spinning solution, with the titanium dioxide content at 1.0% by weight relative to the acrylic fiber mass. The spinning solution and the dispersed spinning solution were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.05 mm round-hole spinneret. The mixture was then stretched 6 times in hot water at 95°C, washed with water, and dried and densified with hot air at 160°C for 1 minute, yielding an acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.4 cN / dtex.

[0045] Comparative Example 3 An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning dope with an acrylonitrile-based copolymer concentration of 22.4% by weight) was prepared by solution polymerization using DMSO as the solvent. This acrylonitrile-based copolymer solution was mixed with titanium dioxide (titanium dioxide) with an average particle size of 1.3 μm to obtain a titanium dioxide content of 0.1% by weight relative to the acrylic fiber mass, to prepare an anatase-type titanium dioxide-dispersed spinning dope. The spinning dope and the dispersed spinning dope were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.05 mm round-hole spinneret. The resulting fiber was stretched 6 times in hot water at 95°C, washed with water, and dried and densified with hot air at 160°C for 1 minute, yielding an acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.6 cN / dtex.

[0046] Comparative Example 4 An acrylonitrile-based copolymer solution containing 91.4% by weight of acrylonitrile-derived units, 7.2% by weight of methyl acrylate-derived units, and 1.4% by weight of sodium methallylsulfonate-derived units (spinning solution with an acrylonitrile-based copolymer concentration of 22.4% by weight) was prepared by solution polymerization using DMSO as the solvent. Titanium dioxide (titanium dioxide) with an average particle size of 1.4 μm was added to this acrylonitrile-based copolymer solution to obtain a titanium dioxide-dispersed spinning solution, with the titanium dioxide content at 3.0% by weight relative to the acrylic fiber mass. The spinning solution and the dispersed spinning solution were stirred in a mixer for 2 hours and then wet-spun into a 60% by weight DMSO aqueous solution using a 0.05 mm round-hole spinneret. The mixture was then stretched 6 times in hot water at 95°C, washed with water, and dried and densified with hot air at 160°C for 1 minute, yielding an acrylic fiber with a single fiber fineness of 1.7 dtex and a tensile strength of 2.2 cN / dtex.

[0047] [Table 1]

[0048] The heat-shielding acrylic fibers produced in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated for the above-mentioned (3) spinnability, (4) spinnability, (5) heat-shielding rate, and (6) knitted fabric texture, and the results are shown in Table 1. As a result, it was clear that the acrylic fibers of the present invention have excellent knitted fabric texture and heat-shielding properties, as well as excellent spinnability and spinnability.

Claims

1. A heat-shielding acrylic fiber containing 0.2 to 2.5 mass % of inorganic particles having an average particle size of 0.5 to 1.5 μm.

2. 2. The heat-shielding acrylic fiber according to claim 1, which has a single fiber fineness of 0.5 to 2.2 dtex and a tensile strength of 2.0 cN / dtex or more.

Images