JP4633658B2 - Polyurethane elastic fiber - Google Patents

Description

  The present invention relates to a polyurethane elastic fiber. More specifically, the present invention relates to a polyurethane elastic fiber that is stabilized against color change caused by nitrogen oxide (NOx) or combustion gas in the air, and stabilized against discoloration or embrittlement caused by light, washing, sebum, or the like. .

Polyurethane elastic fibers are mixed with polyamide fibers, polyester fibers, cellulose fibers and the like due to their excellent stretch properties, and are widely used in leg clothing, inner clothing, sports clothing, and the like.
For products using polyurethane elastic fibers, sufficient stability against deterioration and coloring is required. Conventionally, various compounds such as hindered phenol antioxidants, hindered amine compounds, benzotriazole-based, benzophenone-based or salicylic acid-based UV absorbers, and acid hydrazide compounds are added for that purpose. It has also been proposed, but nothing was fully satisfactory.

A compound having a certain effect, for example, a phenolic compound having a high molecular weight (Patent Document 1) is described as having good compatibility with polyurethane, stable in dry cleaning, and excellent in deterioration resistance and coloring resistance. However, the coloring stability by NOx gas was not fully satisfactory. Although the combined use of this phenolic antioxidant and a urethane compound having an aliphatic tertiary amino group in the molecule is described, there is no description of the combination with a phosphorous acid type antioxidant.
In addition, regarding compounds having tertiary nitrogen and semicarbazide groups in the molecule (Patent Document 2), the molecular weight is high and the molecular weight distribution is narrow, thereby preventing scum formation and greatly improving light embrittlement resistance. However, it was not fully satisfactory. In this patent, a synergistic effect with a hindered phenolic antioxidant, a hindered amine antioxidant, and a benzotriazole ultraviolet absorber is also described, but the description about a phosphite antioxidant is described. Absent.

Moreover, although the synergistic effect of the substituted phenol compound and the phosphite ester system is described (Patent Document 3), the stabilizing effect against discoloration by ultraviolet rays or gas is not at a sufficiently satisfactory level. This patent does not describe a compound having a tertiary nitrogen and a semicarbazide group in the molecule.
Moreover, the polyurethane composition (patent document 4) which mix | blended the phenolic antioxidant, the phosphite-type antioxidant, and the hindered amine compound described that it was fully stabilized with respect to the discoloration degradation by NOx. However, these compositions have a problem that the chlorine resistance is lowered, and they are colored and embrittled by chlorine in the water when left for washing and exposed to tap water for a long time.
Japanese Patent Publication No. 5-24246 Japanese Patent Publication No. 2-34985 Japanese Examined Patent Publication No. 46-26873 JP 2000-239519 A

  In view of the problems of the prior art, the object of the present invention is to suppress discoloration due to NOx, combustion gas, etc., and discoloration and embrittlement due to light, and general consumption such as embrittlement and yellowing due to washing and sebum. It is to provide a polyurethane elastic fiber that does not cause problems in the situation.

As a result of intensive studies, the present inventor has come to make the present invention. That is, by using a combination of three specific types of compounds, it is possible to suppress discoloration due to NOx, combustion gas, etc., and discoloration and embrittlement due to light, as well as general embrittlement such as embrittlement and yellowing due to washing and sebum. The inventors have found that polyurethane elastic fibers that do not cause problems in the consumption situation can be obtained, and have reached the present invention. The present invention is as follows.
A polyurethane elastic fiber comprising a compound containing a plurality of tertiary nitrogen and semicarbazide groups in the molecule, a phosphite-based antioxidant, and a phenol-based antioxidant. A compound containing a plurality of tertiary nitrogens and semicarbazide groups therein is represented by the following general formula (1):

[However, in the above general formula, X represents the following formula (2);

Or the following formula (3);

Wherein at least three of Y ₁ , Y ₂ , Y ₃ and Y ₄ are represented by the general formula (4);

{However, in the formula, R ₁ and R ₂ are alkyl groups, and at least one of R ₁ and R ₂ is bonded to the nitrogen atom of the formula (4) by primary carbon, and R ₁ and R ₂ The total number of carbon atoms shall be 4 or more. Z represents the general formula (5);

(However, in the formula, R ₃ and R ₄ represent the same or different alkyl groups having 1 to 4 carbon atoms.)
It is group shown by these. However, it is assumed that at least three groups represented by the general formula (5) are present in the compound (1). }
In the case where another group is present, this group is a glycidyl derivative group. ]
A polyurethane elasticity characterized by containing a compound containing a plurality of tertiary nitrogen and semicarbazide groups in the molecule, a phosphite ester antioxidant, and a phenol antioxidant Fiber,
In addition, the phosphorous acid antioxidant is represented by the following general formula (6);

A polyurethane elastic fiber that is a hydrogenated bisphenol A-pentaerythritol phosphite polymer having a structure represented by:
In addition, the phenolic antioxidant is represented by the following general formula (7);

(In the formula, R1 is an alkyl group having 1 to 6 carbon atoms, R2 is an alkyl group having 4 to 9 carbon atoms, a cycloalkyl group or an aralkyl group, R3 and R4 are a hydrogen atom or a methyl group, n is the number of repeating units and represents a positive integer of 5 to 20.)
Is a polyurethane elastic fiber represented by
In addition, the content of the compound containing a plurality of tertiary nitrogen and semicarbazide groups in the molecule is 0.1 to 10% by weight, the content of the phosphite antioxidant is 0.1 to 5% by weight, phenol It is a polyurethane elastic fiber having a content of the system antioxidant of 0.1 to 5% by weight.

  The polyurethane elastic fiber according to the present invention has excellent discoloration resistance, and is often used in white and light colors, and the inner field where the discoloration resistance is required and the lace field where the polyurethane elastic fiber is easily visible from the surface. Especially suitable for such as.

The present invention will be specifically described below.
The present invention is characterized by containing a compound containing a plurality of tertiary nitrogens and semicarbazide groups in the molecule, a phosphite-based antioxidant, and a phenol-based antioxidant.
Examples of means for producing a compound containing a plurality of tertiary nitrogen and semicarbazide groups in the molecule include N, N, N ′, N′-tetraglycidylmetaxylylenediamine (hereinafter referred to as TGX) or 1, A compound obtained by reacting 3-bis (N, N-diglycidylaminomethyl) cyclohexane (hereinafter referred to as TGH) and its epoxy with an equivalent dialkylamine is obtained. Next, the isophorone diisocyanate corresponding to the equivalent and molar amount of the secondary alcohol group of this compound, that is, the more reactive isocyanate of the two isocyanate groups in isophorone diisocyanate, is reacted to give the following general formula (8 );

(Here, X, R1, and R2 represent the same groups as those described in Formulas (2), (3), and (4).)
To obtain a compound represented by: Next, the isocyanate group of the compound represented by the general formula (8) is reacted with an equivalent amount of N, N-dialkylhydrazine to obtain the compound of the present invention.

  The tetrafunctional epoxy compounds TGX and TGH used in the present invention are obtained by the reaction of metaxylylenediamine and epichlorohydrin, or 1,3-bis (aminomethyl) cyclohexane and epichlorohydrin, respectively. Other aliphatic diamines such as ethylene diamine, hexamethylene diamine, isophorone diamine, bis (3-aminopropyl) ether paraxylylene diamine, 1,4-bis (aminomethyl) cyclohexane and the like can be reacted with epichlorohydrin by reaction with epichlorohydrin. A functional epoxy compound can be obtained, and can be used as a tetrafunctional epoxy compound which is a raw material of the present invention in the same manner as TGX and TGH. Dialkylamines include diethylamine, di-n-propylamine, N-methyl-N-iso-butylamine, dimethacrylamine, di-n-butylamine, di (2-ethylhexyl) amine, dibenzylamine, N-methyl- Secondary amines such as N-laurylamine are exemplified.

  The diisocyanate needs to have a large difference in reactivity between the two types of isocyanate groups, and it is isophorone diisocyanate that is generally readily available as such. Examples of N, N-dialkylhydrazine include N, N-dimethylhydrazine, N, N-diethylhydrazine, N, N-diisopropylhydrazine, N-methyl-N-ethylhydrazine and the like, but the alkyl group has a carbon number. Is preferably 1 or more, an alkyl group having 4 or less carbon atoms is preferred. Particularly preferred is N, N-dimethylhydrazine. These N, N-dialkylhydrazines may be used as a mixture.

  Any known compound can be used as the phosphite antioxidant. An appropriate one can be selected in consideration of compatibility with polyurethane and the like. Phosphite compounds include tris (2,4-di-t-butylphenyl) phosphite, bis [2,4bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous Acid, tetrakis (2,4-di-t-butylphenyl) [1,1-biphenyl] -4,4′-diylbisphosphonite, bis (2,4-di-t-butylphenyl) pentaerythritol di Phosphite, distearyl pentaerythritol diphosphite, triphenyl phosphite, tetraphenyldipropylene glycol diphosphite, tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite, tetra (C12-C15 alkyl) -4,4'- Isopropylidenephenyl phosphite, bis (tridecyl ) Pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, 4,4′-butylidenebis (3-methyl-6-tert-butylphenyl-di-tridecyl phosphite), tristearyl phosphite, water Bisphenol A / pentaerythritol phosphite polymer, hydrogenated bisphenol A / phosphite polymer, trisnonylphenyl phosphite, tricresyl phosphite, triethyl phosphite, tris (2-ethylhexyl) phosphite, tridecyl phosphite, tri Lauryl phosphite, tris (tridecyl) phosphite, trioleyl phosphite, diphenyl mono (2-ethylhexyl) phosphite, diphenyl monodecyl phosphite Phosphite, diphenyl mono (tridecyl) phosphite, trilauryl trithiophosphite, diethyl hydrogenphosphite phosphite, dilauryl hydrogenphosphite phosphite, dioleyl hydrogenphosphite phosphite, and the like diphenyl hydrogenphosphite phosphite. Among these, hydrogenated bisphenol A / pentaerythritol phosphite polymer containing a structure represented by the formula (6) is preferable.

  Any known compound can be used as the phenolic antioxidant. An appropriate one can be selected in consideration of compatibility with polyurethane and the like. Examples of the phonol antioxidant include pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], Irganox 1010 (Ciba Specialty Chemicals), Knox 1076 (Ciba Specialty Chemicals), Irganox 565 (Ciba Specialty Chemicals), Irganox 1035 (Ciba Specialty Chemicals), Irganox 1330 (Ciba Specialty Chemicals), Smither GA-80 (Sumitomo Chemical), Syanox 2246 (Cytec) , Sianox 1790 (Cytech), Low Inox CPL (Gray Lake), Low Inox GP-45 (Great Lake), Low Inox HD-98 (Gray Tray) ), The following general formula (7);

(In the formula, R1 is an alkyl group having 1 to 6 carbon atoms, R2 is an alkyl group having 4 to 9 carbon atoms, a cycloalkyl group or an aralkyl group, R3 and R4 are a hydrogen atom or a methyl group, n represents the number of repeating units and represents a positive integer of 5 to 20.). Especially, the compound shown by the said General formula (7) is preferable. A general method for synthesizing this compound is disclosed in Japanese Patent Publication No. 5-24246.

  The amount of the stabilizer added to the polyurethane in the present invention may be an amount necessary for suppressing discoloration due to NOx, combustion gas, etc., and discoloration or embrittlement due to light, and the presence of more than necessary causes side effects. This is not preferable. The content of the compound containing a plurality of tertiary nitrogens and semicarbazide groups in the molecule is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight. The content of the phosphite antioxidant is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight. The content of the phenolic antioxidant is preferably 0.1 to 10% by weight, and more preferably 0.1 to 5% by weight.

  The polyurethane used in the present invention is, for example, a polymer intermediate having a number average molecular weight of 600 to 5000 and an organic diisocyanate are reacted to synthesize a urethane intermediate polymer that becomes a soft segment, and then a hard segment is polymerized with a chain extender. Known techniques can be used. When a low molecular weight diol is used as the chain extender, a polyurethane polymer whose hard segment is a urethane bond can be obtained, and when a bifunctional amine is used, a polyurethane urea polymer whose hard segment is a urea bond can be obtained. As the terminal terminator, any of monofunctional amines and monoalcohols can be used, which may be used in combination with a chain extender or may be used separately.

  Examples of the polymer glycol include homopolyether diols such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, and polyoxypentamethylene glycol, or two or more oxyalkylenes having 2 to 6 carbon atoms. Constituted copolymer polyether diol, adipic acid, sebacic acid, maleic acid, itaconic acid, azelaic acid, malonic acid and one or more dibasic acids and ethylene glycol, 1,2-propylene glycol, 1, 3-propylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, hexamethylene glycol, diethylene glycol, 1,10-decanediol, 1,3-di Methylolcyclo Polyester diol obtained from one or more of glycols such as xane and 1,4-dimethylolcyclohexane, or polyester amide diol, polyester ether diol, poly-ε-caprolactone diol, polyvalerolactone diol, etc. Examples include polylactone diol, polycarbonate diol, polyacryl diol, polythioether diol, polythioester diol, or a copolymer or a mixture of these diols.

  Examples of the organic diisocyanate include methylene-bis (4-phenylisocyanate), methylene-bis (3-methyl-4-phenylisocyanate), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m- and p-xylylene diisocyanate, α, α, α ′, α′-tetramethyl-xylylene diisocyanate, m- and p-phenylene diisocyanate, 4,4′-dimethyl-1,3-xylylene diisocyanate, 1-alkylphenylene -2,4 and 2,6-diisocyanate, 3- (α-isocyanatoethyl) phenyl isocyanate, 2,6-diethylphenylene-1,4-diisocyanate, diphenyl-dimethylmethane-4,4-diisocyanate, diphenyl ether-4, 4'-Diisocy Anate, naphthylene-1,5-diisocyanate, 1,6-hexamethylene diisocyanate, methylene-bis (4-cyclohexylisocyanate), 1,3- and 1,4-cyclohexylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, penta Examples include methylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like, or a mixture thereof.

  Examples of the chain extender having a polyfunctional active hydrogen atom include, for example, hydrazine, polyhydrazine, a linear or branched aliphatic, alicyclic, and aromatic amino group having 2 to 10 carbon atoms. Compounds having ethylenediamine, 1,2 propylenediamine, diamines such as diamines having a urea group described in JP-A-5-155841, hydroxylamine, water, etc., and low molecular weight glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, hexamethylene glycol, diethylene glycol, 1,10 -Decanediol, 1,3-dimethylolcyclohexane, 1,4-di It can be used Chi roll cyclohexane. Preferred are ethylene diamine and 1,2 propylene diamine.

Examples of the terminal terminator having a monofunctional active hydrogen atom include dialkylamines such as diethylamine and alkyl alcohols such as ethanol. These chain extenders and terminal terminators may be used alone or in combination of two or more.
In addition to the polyamide fine particles of the present invention, other compounds usually used for polyurethane elastic fibers, such as ultraviolet absorbers, light stabilizers, colorants, matting agents, fillers, and the like, may be added to the polyurethane.
The polyurethane thus obtained can be formed into a fiber shape by known dry spinning, wet spinning, melt spinning, etc. to produce polyurethane elastic fibers.

The compound for obtaining the fiber of the present invention can be added to the polyurethane at any stage of the production of the polyurethane, but it is mixed after the polyurethane polymerization is completed and before the defoaming and spinning process. preferable.
Polydimethylsiloxane, polyester-modified silicon, polyether-modified silicon, amino-modified silicon, mineral oil, mineral fine particles such as silica, colloidal alumina, talc, etc., higher fatty acid metal salt powder such as stearic acid Oils such as solid waxes at room temperature such as magnesium, calcium stearate, higher aliphatic carboxylic acids, higher aliphatic alcohols, paraffin, polyethylene, etc. may be applied alone or in any combination as required.

  The fabric containing the polyurethane elastic fiber of the present invention is suitably used for leg clothing, inner clothing, sports clothing, outer clothing, and the like. Leg clothing includes pantyhose, tights, knee stockings, high socks, short socks, etc.Inner clothing includes underwear, shorts, girdle, body fur, etc.Sport clothing includes swimwear, spats, leotards, etc. If it is used for fashionable purposes, such as stretch pants and jeans, it is stabilized against changes in color caused by nitrogen oxides (NOx) and combustion gases in the air, and is also resistant to discoloration and embrittlement due to light. On the other hand, it is possible to obtain a garment having a stabilized appearance quality and particularly preferred.

The present invention will be specifically described below. The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The measured values in Examples and the like are determined by the following measurement methods.
[Discoloration by NOx gas]
A skein of fiber boiled with water of Ph 4.2 for 30 minutes was used for a color change test with NOx gas. According to JIS L 0855-2005, a strong test of 3 units and 5 units was performed. The degree of coloration was visually discriminated in five ranks: first grade, brown, second grade, yellowish brown, third grade, yellow, fourth grade, pale yellow, fifth grade, uncolored. . However, when the hue is in the middle of each class, it is displayed by subtracting 0.5 class from the upper class.

[Discoloration by combustion gas]
A skein of fiber boiled with water of Ph 4.2 for 30 minutes was used for the discoloration test with combustion gas. The test was conducted according to AATCC-23. The degree of coloration was visually discriminated in five ranks: first grade, brown, second grade, yellowish brown, third grade, yellow, fourth grade, pale yellow, fifth grade, uncolored. . However, when the hue is in the middle of each class, it is displayed by subtracting 0.5 class from the upper class.

[Discoloration by light]
A skein of fiber boiled with water of Ph 4.2 for 30 minutes was used for the discoloration test by light. Ultraviolet rays were irradiated for 24 hours with a fade meter (U48AU-B type, manufactured by Suga Test Instruments). The degree of coloration was visually discriminated in five ranks: first grade, brown, second grade, yellowish brown, third grade, yellow, fourth grade, pale yellow, fifth grade, uncolored. . However, when the hue is in the middle of each class, it is displayed by subtracting 0.5 class from the upper class.

(Synthesis of compounds containing multiple tertiary nitrogens and semicarbazide groups in the molecule)
A compound containing a plurality of tertiary nitrogens and semicarbazide groups in the molecule was synthesized by the method described in JP-B-2-34985. N, N, N ′, N′-tetraglycidylmetaxylylenediamine was reacted with dibenzylamine corresponding to its epoxy equivalent. To this reaction product, the secondary alcohol equivalent produced in the reaction product and isophorone diisocyanate equivalent in molar amount were added and reacted. This compound was dissolved in NN-dimethylacetamide. Next, a 40% NN-dimethylacetamide solution of N, N-dimethylhydrazine was added and reacted with this compound solution to obtain a desired compound (No. A-6 described in JP-B-2-34985).

(Synthesis of phenolic antioxidants)
About the synthesis method of a phenolic antioxidant, it synthesize | combined by the method of Japanese Patent Publication No. 5-24246. 1.2 mol of paracresol is added to 1 mol of dicyclopentadiene, and BF _3. (C ₂ H ₅ ) ₂ O is added by 7 to 3% by weight of the total weight of dicyclopentadiene and paracresol. The mixture is heated in nitrogen gas with stirring and maintained at about 90 ° C. to about 150 ° C. for 5 hours and then dissolved in toluene at a concentration of 50%. Thereafter, asymmetric dimethylhydrazine is added to sufficiently remove BF _3, and then an acidic ion exchange resin is added. The mixture is heated to about 60 ° C. to 80 ° C. and isobutylene gas is added slowly until the isobutylene does not react. To this, NaF and diatomaceous earth are added and the acidic ion exchange resin is filtered off. Thereafter, the powder precipitates when the temperature of the reaction solution is gradually lowered. The phenolic compound No. 5 described in Japanese Patent Publication No. 5-24246 is obtained by filtering it and drying it. A-3 was obtained.

(Manufacture of polyurethane solution)
A polyurethane prepolymer having isocyanate groups at both ends is reacted with 1,500 g of polytetramethylene ether glycol having an average molecular weight of 1,800 and 312 g of 4,4′-diphenylmethane diisocyanate while stirring at 60 ° C. for 90 minutes in a nitrogen gas stream. A polymer was obtained. Next, after cooling to room temperature, 2,700 g of dimethylacetamide was added and dissolved to prepare a polyurethane prepolymer solution.
23.4 g of ethylenediamine and 3.7 g of diethylamine were dissolved in 1,570 g of dry dimethylacetamide and added to the prepolymer solution at room temperature to obtain a polyurethane solution having a viscosity of 2,200 poise (30 ° C.).

[Example 1]
A compound containing a plurality of tertiary nitrogens and semicarbazide groups in the molecule synthesized by the above method in the polyurethane solution produced by the above method, and a phenolic antioxidant synthesized by the above method, In addition, hydrogenated bisphenol A pentaerythritol phosphite polymer (JPH3800, manufactured by Johoku Chemical Co., Ltd.) is added as a phosphite ester antioxidant, and after stirring and mixing, vacuum defoaming is performed to remove bubbles in the solution. A polyurethane solution was obtained. Next, this solution was discharged from a hole orifice into an atmosphere of about 200 ° C., and spinning, drying, false twisting, and oiling were performed, and winding was performed at 500 m / min to obtain 44 dtex and 4-filament fibers. Five kinds of test fibers were made by changing the addition amount of the three kinds of compounds, and the performance was evaluated. The results are shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, four types of test fibers were produced and their performance was evaluated. The results are shown in Table 2.

[Comparative Example 2]
In the same manner as in Example 1, 1% by weight of the phenolic antioxidant synthesized by the above method and 2% by weight of hydrogenated bisphenol A pentaerythritol phosphite polymer (Johoku Chemical Co., Ltd., JPH3800), hindered amine stabilizer LOWILITE 62 (manufactured by Great Lakes) was added in an amount of 3% by weight to prepare test fibers in the same manner as described above. When the skein of fiber boiled with water of Ph 4.2 for 30 minutes was immersed in running tap water for 3 days, the discoloration and strength were clearly lowered, and fiber breakage was observed when squeezed by hand. There were no problems with the five test fibers of Example 1.

  The polyurethane elastic fiber of the present invention has excellent discoloration resistance and is often used in white and light colors, and the inner field where the discoloration resistance is required and the lace field where the polyurethane elastic fiber is easily visible from the surface. Especially suitable for such as.

Claims (4)

The following general formula (1);

[However, in the above general formula, X represents the following formula (2);

Or the following formula (3);

Wherein at least three of Y ₁ , Y ₂ , Y ₃ and Y ₄ are represented by the general formula (4);

{However, in the formula, R ₁ and R ₂ are alkyl groups, and at least one of R ₁ and R ₂ is bonded to the nitrogen atom of the formula (4) by primary carbon, and R ₁ and R ₂ The total number of carbon atoms shall be 4 or more. Z represents the general formula (5);

(However, in the formula, R ₃ and R ₄ represent the same or different alkyl groups having 1 to 4 carbon atoms.)
It is group shown by these. However, it is assumed that at least three groups represented by the general formula (5) are present in the compound (1). }
In the case where another group is present, this group is a glycidyl derivative group. And a compound containing a plurality of tertiary nitrogen and semicarbazide groups in the molecule, a phosphite-based antioxidant, and a phenol-based antioxidant. Elastic fiber. The phosphorous acid antioxidant is represented by the following general formula (6):

The polyurethane elastic fiber according to claim 1, which is a hydrogenated bisphenol A / pentaerythritol phosphite polymer having a structure represented by: The phenolic antioxidant is represented by the following general formula (7):

(In the formula, R1 is an alkyl group having 1 to 6 carbon atoms, R2 is an alkyl group having 4 to 9 carbon atoms, a cycloalkyl group or an aralkyl group, R3 and R4 are a hydrogen atom or a methyl group, n is the number of repeating units and represents a positive integer of 5 to 20.)
The polyurethane elastic fiber according to claim 1, wherein the polyurethane elastic fiber is represented by:   The content of the compound containing a plurality of tertiary nitrogen and semicarbazide groups in the molecule is 0.1 to 10% by weight, the content of the phosphite antioxidant is 0.1 to 10% by weight, phenolic The polyurethane elastic fiber according to any one of claims 1 to 3, wherein the content of the antioxidant is 0.1 to 10% by weight.