JP2020056116A - Polyurethane elastic fiber - Google Patents

Abstract

To provide a polyurethane elastic fiber that can suppress occurrence of yarn breakage by excellent running property and heat resistance thereof, and that make it possible to obtain sanitary products and medical products with excellent design without impairing appearance of colors, patterns, characters, etc. applied to a base material such as a non-woven fabric by high light transmittance thereof, when bonded to a substrate such as the non-woven fabric by an adhesive such as a hot melt adhesive.SOLUTION: The polyurethane elastic fiber comprises 0.005-0.5 wt.% titanium oxide, wherein the polyurethane elastic fiber has a dynamic friction coefficient (μd) of 0.2 to 1.5 measured under predetermined conditions, and a film formed from the polyurethane elastic fiber has a L value of reflected light of 50 or less measured under a predetermined condition.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a polyurethane elastic fiber that can be suitably used for elastic members of sanitary products, medical products, and the like.

BACKGROUND ART Absorbent articles represented by disposable diapers have been known in which a pattern such as an animal or a character is displayed on the surface of the diaper in order to enhance the taste and design effect for infants and parents.
In addition, disposable diapers are required to have excellent fit and follow the active movement of the wearer in order to suppress the diaper from shifting and prevent excrement from leaking. For this reason, in a state where the polyurethane elastic fiber is stretched around the waist of the disposable diaper or the like, it is adhered to a nonwoven fabric with a hot melt adhesive or the like to form a gather portion.
Therefore, since the polyurethane elastic fiber is adhered onto the non-woven fabric on which the design is displayed, if the transparency of the yarn is low, the design is partially concealed, and there is a problem that the design is significantly impaired.

  Normally, titanium oxide is added to polyurethane elastic fibers in order to prevent yarn breakage in the diaper manufacturing process. This is because the addition of titanium oxide reduces the coefficient of friction between the yarn and various guides that pass through in the diaper manufacturing process, thereby reducing yarn breakability in the process. However, when the amount of titanium oxide exceeds a certain range, the coefficient of friction with the guide decreases, but the heat resistance decreases, so that the polyurethane elastic fiber is adhered to a base material such as a nonwoven fabric via an adhesive such as hot melt. When heat is applied, the physical properties decrease due to heat and yarn breakage occurs. Further, by using the polyurethane elastic fiber to which titanium oxide is added for a long period of time, the yarn path in the diaper manufacturing process, that is, various guides and rollers to which the polyurethane elastic fiber is in contact is damaged, and the cut portion causes the yarn breakage. Sometimes. Further, there is a problem that the transparency of the yarn is reduced and the design of the diaper is impaired. On the other hand, if the amount of titanium oxide is too small, the transparency of the yarn is increased, so that the design of the diaper is not impaired, but the coefficient of friction between the yarn and the guide is increased, and the occurrence of yarn breakage during diaper production is increased.

  Originally, titanium oxide has heretofore been used as a matting agent for polyurethane elastic fibers. As described in Patent Literature 1 or 2 below, titanium oxide is generally classified, dried, and pulverized in a final production step to produce a product. When drying, aggregated particles are formed, and such coarse molecules remain. Therefore, there is a problem that the dispersibility in a dispersion medium is deteriorated, and thus, an attempt has been made to coat titanium oxide with a water-soluble coating agent. Since such a technique is to add titanium oxide as a matting agent, it is premised on addition of a predetermined amount or more of titanium oxide, and from the viewpoint of increasing the transparency of the yarn and improving the design of the diaper, from the viewpoint of improving the design of the diaper. The content, particle size, specific surface area and the like have not been studied.

Patent Literature 3 or 4 below discloses a polyetherester fiber containing 0.01 to 3% by weight of titanium oxide having an average particle size of 0.01 to 2 µm. Since heat resistance is inferior to polyurethane elastic fiber and the recovery rate upon elongation is also inferior, it is not suitable for diaper applications in the first place. Further, the specific surface area with respect to the average particle diameter is not clear. When the specific surface area is larger than the particle size, there is a problem that titanium oxide is aggregated in the spinning step, and yarn breakage occurs in the spinning step.
As described above, the conventional polyurethane elastic fiber has not been able to suppress yarn breakage in the diaper manufacturing process and to improve the design of the diaper.

JP-A-2002-363825 JP 2004-204393 A JP 2009-91445 A JP 2009-167541 A

  The present invention has been made in view of the above problems of the prior art, and as a polyurethane elastic fiber used for gather members such as sanitary products and medical products represented by disposable diapers, sanitary products, medical products, etc. In the manufacturing process, when the elastic fiber is adhered to a base material such as a nonwoven fabric with an adhesive such as hot melt, the occurrence of thread breakage is suppressed due to excellent running properties and heat resistance, and the light transmittance is high. Therefore, in a product, there is provided a polyurethane elastic fiber capable of obtaining a hygienic product, a medical product, and the like excellent in design without impairing the appearance of colors, patterns, letters, etc. applied to a substrate such as a nonwoven fabric. That is.

  The inventors of the present application have conducted intensive studies and repeated experiments to solve the above problems, and as a result, determined the content, particle size, and specific surface area of titanium oxide used for polyurethane elastic fibers constituting elastic members of disposable diapers. Thus, the present inventors have found that the above-mentioned problems can be solved, and have completed the present invention.

That is, the present invention is as follows.
[1] A polyurethane elastic fiber containing 0.005 to 0.5% by weight of titanium oxide,
Measured when a ceramic hook guide is inserted at a friction angle of 90 ° into the running path of the yarn of the polyurethane elastic fiber when the yarn of the polyurethane elastic fiber is running at a feeding speed of 50 m / min and a winding speed of 150 m / min from the package. The input-side thread tension (T ₁ ) and the output-side thread tension (T ₂ ) are calculated by the following equation (1):
Dynamic friction coefficient (μd) = ln (T ₂ / T ₁ ) /0.5π
And the dynamic friction coefficient (μd) of the polyurethane elastic fiber is 0.2 to 1.5, and
90 g of dimethylacetamide was added to 10 g of a short fiber aggregate obtained by cutting the polyurethane elastic fiber into a length of 3 mm, and the mixture was stirred at room temperature to prepare a uniform 10% polyurethane solution. Pour into a rectangular parallelepiped container, leave it to have a uniform thickness, leave it in a 50 ° C incubator until the dimethylacetamide is completely evaporated, and place the formed 100 μm thick film on a blackboard. With a commercially available spectrophotometer, the light source is D65 / 2 ° C., and the L value of the measured reflected light is 50 or less.
The polyurethane elastic fiber as described above.
[2] The polyurethane elastic fiber according to [1], further comprising a step of spinning a polyurethane polymer containing titanium oxide having a particle size of 0.015 to 0.5 μm and a specific surface area of 5 to 110 m ² / g. Production method.

  The polyurethane elastic fiber according to the present invention has a running property and heat resistance when bonded to a base material such as a nonwoven fabric by an adhesive such as hot melt by specifying the content, particle size, and specific surface area of titanium oxide. Hygiene products with excellent design, which suppresses the occurrence of thread breaks, and have high light transmittance, so that they do not impair the appearance of colors, patterns, letters, etc. applied to substrates such as non-woven fabrics, and are excellent in design. And medical products.

It is the schematic of the apparatus used for the evaluation method of the yarn sway test.

Hereinafter, embodiments of the present invention will be described in detail.
The polyurethane elastic fiber of the present embodiment is a polyurethane elastic fiber containing 0.005 to 0.5% by weight of titanium oxide,
Measured when a ceramic hook guide is inserted at a friction angle of 90 ° into the running path of the yarn of the polyurethane elastic fiber when the yarn of the polyurethane elastic fiber is running at a feeding speed of 50 m / min and a winding speed of 150 m / min from the package. The input-side thread tension (T ₁ ) and the output-side thread tension (T ₂ ) are calculated by the following equation (1):
Dynamic friction coefficient (μd) = ln (T ₂ / T ₁ ) /0.5π
And the dynamic friction coefficient (μd) of the polyurethane elastic fiber is 0.2 to 1.5, and
90 g of dimethylacetamide was added to 10 g of a short fiber aggregate obtained by cutting the polyurethane elastic fiber into a length of 3 mm, and the mixture was stirred at room temperature to prepare a uniform 10% polyurethane solution. Pour into a rectangular parallelepiped container, leave it to have a uniform thickness, leave it in a 50 ° C incubator until the dimethylacetamide is completely evaporated, and place the formed 100 μm thick film on a blackboard. It is characterized in that the L value of the measured reflected light is 50 or less using a commercially available spectrophotometer with the light source set to D65 / 2 ° C.
The particle size of the titanium oxide present in the polyurethane polymer before spinning of the polyurethane elastic fiber is preferably 0.015 to 0.5 μm, and the specific surface area is preferably 5 to 110 m ² / g. .

The polyurethane elastic fiber in the present embodiment includes a soft segment portion made of polyether diol and organic diisocyanate, and a hard segment portion made of organic diisocyanate and diamine or diol.
As the polyalkylene ether diol in the polyurethane elastic fiber used in the present embodiment, for example, an alkylene group having 2 to 6 carbon atoms such as polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol is linear. Or a linear one having 2 to 6 carbon atoms such as ethylene, propylene, tetramethylene or hexamethylene, 1,2-propylene, 3-methyltetramethylene, or the like. A copolymerized polyalkylene ether diol having a methyl group in a side chain, in which two or more kinds of branched alkylene groups having 2 to 10 carbon atoms such as -methylpentamethylene and 2,2-dimethylpropylene are ether-bonded. May be used.

  As the organic diisocyanate compound in the polyurethane elastic fiber used in the present embodiment, for example, among the aliphatic, alicyclic, and aromatic diisocyanates, all that show a solution or a liquid under the reaction conditions can be applied. . For example, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, methylene-bis (3-methyl-4-phenyl isocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m- And p-xylylene diisocyanate, α, α, α ′, α′-tetramethyl-p-xylylene diisocyanate, m- and p-phenylene diisocyanate, 4,4′-dimethyl-1,3-xylylene diisocyanate, -Alkylphenylene-2,4 and 2,6-diisocyanate, 3- (α-isocyanatoethyl) phenylisocyanate, 2,6-diethylphenylene-1,4-diisocyanate, diphenyl-dimethylmethane-4,4-diisocyanate, diphenylether -4 4,4'-diisocyanate, naphthylene-1,5-diisocyanate, 1,6-hexamethylene diisocyanate, methylene-bis (4-cyclohexyl isocyanate), 1,3- and 1,4-cyclohexylene diisocyanate, trimethylene diisocyanate, tetramethylene Examples include methylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. These diisocyanates may be used alone or in combination of two or more. 4,4'-diphenylmethane diisocyanate is preferred from the viewpoint of reactivity and stress during elongation.

  Examples of the polyfunctional active hydrogen atom-containing compound that is a chain extender that reacts with an isocyanate group in the polyurethane elastic fiber used in the present embodiment include, for example, hydrazine, polyhydrazine, a linear or branched compound having 2 to 10 carbon atoms. Compounds having an amino group or hydroxyl group having an aliphatic, alicyclic or aromatic active hydrogen, for example, ethylenediamine, 1,3-propylenediamine, 1,5-diaminopentane, 1,6-diaminohexane, N- Methylethylenediamine, N, N'-dimethylethylenediamine, N-ethylethylenediamine, N, N'-diethylethylenediamine, N-isopropylethylenediamine, 1,2-diaminopropane, 2-methyl-1,3-propanediamine, 3-methyl -1,5-pentanediamine, 1,3-bis ( (Minomethyl) cyclohexane, phenylenediamine, xylylenediamine, 4,4'-diaminodiphenylmethane, piperazine, diamines such as diamines having a urea group described in JP-A-5-155841, hydroxylamine, water, low molecular weight Glycols, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, hexa Methylene glycol, diethylene glycol, 1,10-decanediol, 1,3-dimethylolcyclohexane, 1,4-dimethylolcyclohexane and the like can be used. Ethylenediamine or 1,2-propylenediamine is preferred.

As the monofunctional active hydrogen atom which is a terminal terminator that reacts with the isocyanate group in the polyurethane elastic fiber used in the present embodiment, for example, a dialkylamine such as diethylamine or an alkyl alcohol such as ethanol is used. These chain extenders and terminal terminators may be used alone or in combination of two or more.
Regarding the reaction operation for converting the polyurethane elastic fiber into a polyurethane, a solvent such as no solvent or a solvent such as dimethylformamide, dimethylsulfoxide, or dimethylacetamide may be used.

The polyurethane polymer of the polyurethane elastic fiber according to the present embodiment is obtained by reacting a polyalkylene ether diol with a molar excess of organic diisocyanate to synthesize a urethane intermediate polymer serving as a soft segment, and then polymerizing the hard segment with a chain extender. However, it can be produced using a known technique such as terminal blocking with a terminal terminator.
The number average molecular weight of the soft segment portion in the polyurethane elastic fiber is preferably 4500 or more and 6500 or less. If the number average molecular weight is less than 4500, the proportion of the hard segment portion in the entire polyurethane increases, causing a decrease in the viscosity stability of the polyurethane polymer and further causing breakage in the spinning step. The proportion occupied by the hard segment portion in the whole decreases, the heat resistance of the polyurethane elastic fiber decreases, and further, the elastic performance of the polyurethane elastic fiber greatly decreases.

  The number average molecular weight of the hard segment portion of the polyurethane is preferably 650 or more and 820 or less. If the number average molecular weight is less than 650, the stress at the time of recovery and heat resistance of the polyurethane elastic fiber are not satisfactory. On the other hand, if it is more than 820, sufficient elongation at break of the polyurethane elastic fiber cannot be obtained, and the yarn breakage in the diaper manufacturing process. Occurs.

  The amount of titanium oxide to be added to the polyurethane polymer composition is preferably from 0.005 to 0.5% by weight, more preferably from 0.001 to 0.35% by weight, even more preferably from polyurethane elastic fibers. 0.003 to 0.25% by weight. If the amount of titanium oxide is less than 0.005% by weight, the coefficient of friction of the polyurethane elastic fiber increases, and the occurrence of thread breakage in the diaper manufacturing process increases. On the other hand, if the amount exceeds 0.5% by weight, It is not preferable because the transmittance of the yarn becomes low and the design of the diaper is impaired.

The particle size of titanium oxide added to the polyurethane polymer composition is preferably 0.015 to 0.5 μm, more preferably 0.05 to 0.4 μm, and still more preferably 0.1 to 0.3 μm. is there. When the particle size of titanium oxide is smaller than 0.015 μm, aggregation of titanium oxide occurs during the spinning process of polyurethane elastic fibers, and spinning stability is impaired. On the other hand, when the particle size exceeds 0.5 μm, heat resistance becomes poor. This is not preferable because the rate of yarn breakage in the diaper manufacturing process increases.
It is preferable that the specific surface area of titanium oxide particles added to the polyurethane polymer composition is 5~110m ² / g, more preferably 6~40m ² / g, even more preferably at 7~25m ² / g . If the specific surface area of the titanium oxide is smaller than 5 m ² / g, the cost for classification of the titanium oxide is increased, which is not preferable. On the other hand, if it exceeds 110 m ² / g, the aggregation of the titanium oxide during the spinning process of the polyurethane elastic fiber is performed. And spinning stability is impaired, which is not preferable.

  Any method can be adopted as a method for adding titanium oxide to the polyurethane solution. When the titanium oxide is added to the polyurethane solution, it can be used in the form of powder, slurry, or paste. The timing of addition is the method of adding at the time of polyurethane polymerization, the method of preparing a masterbatch containing titanium oxide in advance and blending the masterbatch with the base polymer solution at the time of spinning, or the method of preparing a liquid material containing titanium oxide and spinning at the time of spinning. Titanium oxide can be added by a general method such as a blending method. As a typical method of mixing, various methods such as a method using a static mixer, a method using stirring, a method using a homomixer, and a method using a twin screw extruder can be adopted. Here, the titanium oxide to be added is preferably added as a master batch of the solution from the viewpoint of performing uniform addition to the polyurethane solution.

The polyurethane polymer composition may contain various stabilizers and pigments in addition to titanium oxide. For example, light stabilizers, hindered phenolic agents and benzotriazoles, benzophenones, phosphorus and various hindered amine antioxidants, iron oxide, zinc oxide, cerium oxide, inorganic substances such as magnesium oxide, carbon black and various pigments, Antibacterial agents, deodorants, antistatic agents, nitric oxide scavengers, thermal oxidation stabilizers, light stabilizers and the like containing silver, zinc or these compounds may be added in combination.
The polyurethane polymer thus obtained can be formed into a fibrous shape by a known dry spinning, melt spinning, wet spinning, or the like to obtain a polyurethane elastic fiber. Further, a polyurethane polymer polymerized using different raw materials may be mixed and spun at a stage prior to spinning.

The number of single yarns of the polyurethane elastic fiber is not limited, and may be either monofilament or multifilament. From the viewpoint of adhesiveness, single yarn fineness is 5 to 35 dT (decitex), preferably 6 to 25 dT, more preferably 8 to 17 dT. Is preferred. If the single yarn fineness is less than 5 dT, yarn breakage occurs during spinning, which is not preferable. If it exceeds 35 dT, there is a risk of solvent remaining in the yarn, and excessive production such as lowering the spinning speed due to solvent removal. It is not preferable because it requires cost.
The total fineness of the elastic fibers is preferably 10 to 3000 dt, preferably 40 to 1800 dT, and more preferably 100 to 1300 dT. If the total fineness is less than 10 dT, the fit when used in a diaper or the like is not sufficient, and if it exceeds 3000 dT, a large amount of hot melt adhesive is required to increase the diameter of the yarn, and the texture becomes hard. Alternatively, disadvantages such as an increase in cost occur, which is not preferable.
The obtained polyurethane elastic fiber is usually provided with a treatment agent by a known method such as roll oiling, guide oiling, spray oiling or the like before or after winding into a paper tube package, but is wound without applying the treatment agent. You may.

  The treatment agent used is not particularly limited, but polydimethylsiloxane, polyester-modified silicon, polyether-modified silicon, amino-modified silicon, mineral oil, mineral fine particles, for example, silica, colloidal alumina, talc, etc., higher fatty acid metal salt powder, For example, magnesium stearate, calcium stearate, etc., higher aliphatic carboxylic acids, higher aliphatic alcohols, paraffins, oils such as solid waxes at room temperature such as polyethylene, etc. may be applied alone or in any combination as needed. Good. Further, for the purpose of improving the adhesiveness to a nonwoven fabric via a hot melt, the unwinding property from a wound body, and the frictional property during a diaper manufacturing process, a homo- or copolymerized polyalkylene ether diol and carbon having an OH group at the terminal are used. A treating agent obtained by adding mineral oil, dimethyl silicon, or a mixture of mineral oil and dimethyl silicon to a mixture of higher alcohols having a number of 8 to 25 may be used.

The dynamic friction coefficient (μd) of the polyurethane elastic fiber thus obtained is preferably from 0.2 to 1.5, more preferably from 0.2 to 1.3, and still more preferably from 0.2 to 1.0. is there. When the coefficient of kinetic friction is less than 0.2, the polyurethane elastic fiber may break off from the wound body, causing thread breakage in the diaper manufacturing process. And the coefficient of friction with the various guides arranged at the same time increases, and the yarn breakage rate of the polyurethane elastic fiber increases.
The reflected light L value of a 100 μm-thick film produced by dissolving polyurethane elastic fibers in a solvent is preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less. If the L value, which is reflected light, exceeds 50, when used in the gather portion of a disposable diaper, the design displayed on the nonwoven fabric is partially concealed and the design property is significantly impaired, which is not preferable.

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.
(1) Method of Measuring Dynamic Friction Coefficient The dynamic friction coefficient (μd) is obtained from the ratio of the yarn tension of the yarn running through the ceramic guide before and after the ceramic guide. That is, when the yarn is traveling at a feeding speed of 50 m / min and a winding speed of 150 m / min from the package, and the ceramic hook guide is inserted into the traveling path of the yarn at a friction angle of 90 °, the input side of the The yarn tension (T ₁ ) and the output-side yarn tension (T ₂ ) are measured. The dynamic friction coefficient (μd) is calculated by the following equation (1):
Dynamic friction coefficient (μd) = ln (T ₂ / T ₁ ) /0.5π
Is calculated by Incidentally, various guides, rotating rolls and the like having low frictional resistance may be used in the yarn path in order to secure a friction angle of 90 °. The smaller the μd, the better the friction with the ceramic hook guide.

(2) Particle Size Measurement Method of Titanium Oxide The average particle diameter of the primary particles of the titanium oxide raw material was obtained by measuring the particle diameter of 100 primary particles in an image using a transmission electron microscope and taking the average value. (Electron microscopy).

(3) Measurement method of specific surface area of titanium oxide particles The specific surface area of titanium oxide particles was measured by a BET one-point method by nitrogen adsorption. The apparatus used was Monosorb manufactured by Yuasa Ionics or Monosorb Model No. MS-22 manufactured by Quantachrome Instruments.

(4) Evaluation method of yarn breakage in diaper manufacturing process The wound body 1 of the elastic fiber obtained by spinning is set on the apparatus shown in FIG. 1, and the elastic fiber delivery roll 2 is wound around the elastic fiber three times at a speed of 50 m / min. The pre-draft roll 3 was run at a speed of 80 m / min, and the take-up roll 4 was run at a speed of 85 m / min. The behavior of the elastic fiber at the observation site 5 was visually observed for 3 minutes and evaluated according to the following evaluation criteria:
◎◎: Yarn swing width of 0 mm to less than 2 mm ◎: Yarn swing width of 2 mm to less than 4 mm ○: Yarn swing width of 4 mm to less than 6 mm △: Yarn swing width of 6 mm or more ×: Yarn breakage

(5) Production method of film The polyurethane elastic fiber is cut into a length of 3 mm to produce an aggregate of short fibers of the polyurethane elastic fiber. 90 g of dimethylacetamide was added to 10 g of the obtained aggregate of short fibers, and the mixture was stirred at room temperature to prepare a uniform 10% polyurethane solution. 1 g of a 10% polyurethane solution was poured into a rectangular parallelepiped metal container having a bottom of 10 cm square, adjusted to have a uniform thickness, and allowed to stand still in a 50 ° C. thermostat until dimethylacetamide was completely evaporated. A 100 μm film was formed.

(6) Method of measuring L value Using Spectro Color Meter SQ2000 manufactured by Nippon Denshoku Industries Co., Ltd., setting the light source to D65 / 2 ° C, placing the film on a previously formed 100 μm thick film blackboard, and setting the L value of the reflected light Was measured.

(7) Method of evaluating design of gather portion Henkel Japan where three elastic fibers were arranged in parallel at 5 mm intervals, stretched so as to be three times the original length of the elastic fibers, and melted at 160 ° C. It is applied to an elastic fiber obtained by stretching Dispomelt 5434 (manufacturer) with a comb gun manufactured by Suntool (manufacturer) so that the fiber becomes 0.03 g / m per fiber, and has a width of 5 cm and a basis weight of 17 g / m ² . A nonwoven fabric made by Asahi Kasei Senryo Co., Ltd. and Eltasgard (registered trademark) were sandwiched between the two sheets, and then pressed with a roller from above to produce a gather member.

The gather member prepared by the above method is stretched and fixed on the waterproof sheet on which the animal pattern is printed in advance, and at this time, the animal pattern from the gather member does not impair the design and clean Visibility was determined for 10 subjects according to the following criteria:
◎: 8 to 10 persons who judged that the design was not impaired and the animal's pattern looked beautiful ○: 6 to 7 persons who judged that the design was not impaired and the animal's pattern looked beautiful Δ: 4 to 5 people judged that the design was not impaired and the animal's pattern looked beautiful ×: 3 or less people judged that the design was not impaired and the animal's pattern looked beautiful

[Example 1]
400 parts of polytetramethylene glycol (hereinafter abbreviated as PTMG) having a number average molecular weight (Mn) of 1800 and 91.7 parts of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI) were placed in a dry nitrogen atmosphere. The mixture was reacted at 80 ° C. for 3 hours under stirring to obtain a polyurethane prepolymer capped with isocyanate at the end. After cooling to room temperature, 720 parts of dimethylacetamide was added and dissolved to prepare a polyurethane prepolymer solution. Next, a solution was prepared by dissolving 5.41 parts of ethylenediamine and 0.80 part of diethylamine in 390 parts of dimethylacetamide, and this solution was added to the above polyurethane prepolymer solution at room temperature to give a viscosity of 4500 poise (30 ° C.). , 31% by weight of polyurethane solution A.
Next, commercially available titanium oxide (average primary particle diameter: 0.3 nm, specific surface area: 12 m ² / g) and DMAc were added to the polyurethane solution A to prepare a master batch dispersion of titanium oxide. This was designated as Dispersion B (titanium oxide 10% by weight, solid content of polyurethane 21% by weight, total 31% by weight).

The polyurethane solution A and the dispersion B were added so that the weight of titanium oxide was 0.005% by weight based on the solid content of the polyurethane, and they were mixed uniformly to obtain a spinning dope.
Using a spinneret, this spinning stock solution is discharged under an atmosphere of a heated nitrogen gas temperature of 270 ° C. immediately below the spinneret, and the winding speed is adjusted under a condition of a draft 1.15 between the Goded roller and the winding bobbin. After applying an oil agent containing dimethyl silicon as a main component at 400 m / min, it was wound around a bobbin to obtain a polyurethane elastic fiber of 620 dtex (72 filaments). Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Example 2]
The procedure was performed in the same manner as in Example 1 except that the weight of titanium oxide was added to be 0.01% by weight based on the polyurethane solid content. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Example 3]
The same operation as in Example 1 was performed, except that the weight of titanium oxide was added to be 0.25% by weight based on the solid content of the polyurethane. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Example 4]
The procedure was performed in the same manner as in Example 1, except that the weight of titanium oxide was added to be 0.5% by weight based on the solid content of the polyurethane. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Example 5]
Except that the average primary particle diameter of the titanium oxide used was 0.35 nm, the specific surface area was 6.5 m ² / g, and the weight of the titanium oxide was 0.25% by weight based on the polyurethane solid content. And carried out in the same manner as in Example 1. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Example 6]
Except that the average primary particle diameter of the titanium oxide used was 0.08 nm, the specific surface area was 30 m ² / g, and the weight of the titanium oxide was 0.25% by weight based on the polyurethane solid content, It carried out similarly to Example 1. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Comparative Example 1]
The procedure was performed in the same manner as in Example 1, except that the weight of titanium oxide was 0.8% by weight based on the solid content of the polyurethane. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Comparative Example 2]
The procedure was performed in the same manner as in Example 1, except that the weight of titanium oxide was added to be 0.003% by weight based on the solid content of the polyurethane. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Comparative Example 3]
Except that the average primary particle diameter of the titanium oxide used was 0.7 nm, the specific surface area was 5.2 m ² / g, and the weight of the titanium oxide was 0.6% by weight based on the solid content of the polyurethane. And carried out in the same manner as in Example 1. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

[Comparative Example 4]
Except that the average primary particle diameter of the titanium oxide used was 0.01 nm, the specific surface area was 150 m ² / g, and the weight of the titanium oxide was 0.25% by weight with respect to the polyurethane solid content, It carried out similarly to Example 1. Various evaluation test results of the obtained polyurethane elastic fibers are shown in Table 1 below.

  The polyurethane elastic fiber of the present invention suppresses the occurrence of thread breakage during the manufacturing process of sanitary products, medical products, etc., and also does not impair the appearance of colors, patterns, letters, etc. applied to a substrate such as a nonwoven fabric. It improves the design of sanitary products and medical products.

DESCRIPTION OF SYMBOLS 1 Winding body of elastic fiber 2 Sending roll 3 Pre-draft roll 4 Winding roll 5 Observation site 6 Ceramic hook guide 7 Bearing free roller

Claims (2)

A polyurethane elastic fiber containing 0.005 to 0.5% by weight of titanium oxide,
Measured when a ceramic hook guide is inserted at a friction angle of 90 ° into the running path of the yarn of the polyurethane elastic fiber when the yarn of the polyurethane elastic fiber is running at a feeding speed of 50 m / min and a winding speed of 150 m / min from the package. The input-side thread tension (T ₁ ) and the output-side thread tension (T ₂ ) are calculated by the following equation (1):
Dynamic friction coefficient (μd) = ln (T ₂ / T ₁ ) /0.5π
And the dynamic friction coefficient (μd) of the polyurethane elastic fiber is 0.2 to 1.5, and
90 g of dimethylacetamide was added to 10 g of a short fiber aggregate obtained by cutting the polyurethane elastic fiber into a length of 3 mm, and the mixture was stirred at room temperature to prepare a uniform 10% polyurethane solution. Pour into a rectangular parallelepiped container, leave it to have a uniform thickness, leave it in a 50 ° C incubator until the dimethylacetamide is completely evaporated, and place the formed 100 μm thick film on a blackboard. With a commercially available spectrophotometer, the light source is D65 / 2 ° C., and the L value of the measured reflected light is 50 or less.
The polyurethane elastic fiber as described above. The method for producing a polyurethane elastic fiber according to claim 1, comprising a step of spinning a polyurethane polymer containing titanium oxide having a particle size of 0.015 to 0.5 µm and a specific surface area of 5 to 110 m ² / g.

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