JP3750753B2 - Underwear elastic knitted fabric - Google Patents

Description

【０００７】
さらに本発明のポリウレタン系繊維糸条は、１４０℃×１分、１００％伸長状態での乾熱処理での熱セット率が７５％以上であることが必要である。熱セット率が７５％より低い場合には、染色前のプレセット工程で幅不良等の寸法安定性に問題を生じやすい。
ここで言う乾熱セット性とは以下の方法で測定した値を言う。ポリウレタン系弾性繊維のデニール当り１ｍｇの荷重を掛けＬ０を試料長とする。次いで、試料を２倍に伸長し伸長状態のまま乾熱処理（１４０℃×１分）を行い、１時間常温にて弛緩後、１ｍｇ／ｄの荷重下で長さＬ１を測定し、下記式で算出する。
熱セット率（％）＝（Ｌ1 −Ｌ0 ）／Ｌ0 ×１００
【０００８】
非伸縮性糸条は、アクリル繊維の極細デニールを５〜４０％、セルロース繊維を９５〜６０％含む混紡糸であることが必要である。極細デニールの範囲は０．３〜０．９デニール望ましくは０．５〜０．８デニールである。０．３デニール未満の極細糸は生産操業性が低くコスト高にもなる。また後加工での工程通過性も悪い。０．９デニールより太いと本発明の目的である生地のソフト感の付与に合わず特徴が得られない。
該極細繊維の混率が５％未満ではソフト感の付与とならず、逆に４０％より多いと生地の風合が柔らかくなりすぎ、たらたら感が強く特に洗濯回数の増加とともにその傾向が増してしまう。
該アクリル極細繊維と混用する素材は吸湿性のあるセルロース繊維がよい。その中でも肌着用によく使われている綿が好ましい。綿の混率はソフト感の要望によって決まるアクリル極細繊維の混率によって設定される。
【０００９】
該アクリル極細繊維とセルロース繊維を通常の方法で混綿し混紡糸を得る。肌着用糸条としてはその肌触り、吸湿性等の要求性能が高いので毛羽のある紡績糸タイプが適する。
【００１０】
前述の非伸縮性糸条と伸縮性糸条を、丸編機を用いて同一給糸部に伸縮性糸条が生地表裏に露出しないように給糸し、編成する。この場合伸縮性糸条は積極給糸装置を用い、１６０〜２００％の伸長を与えながら給糸すること、また伸縮性糸条を生地表裏に露出しないようにするため、同一給糸部で伸縮性糸条を非伸縮性糸条より若干後部から給糸することが必要である。
【００１１】
このような条件で編成される編地において、非伸縮性糸条の太さは伸縮性糸条の太さに対して２．５倍以上、更には３〜６倍太いことが好ましい。これは伸縮性糸条の主組成物であるポリウレタンが他の素材に比べて耐光性に劣る性質を持つため、伸縮性糸条を極力生地内部に偏在させ非伸縮性糸条で覆い直接光に晒させない目的と、ポリウレタンの持つゴム状のぬめり風合を生地表面に出さない目的もある。
また該編地において、伸縮性糸条の混率は要求性能による伸縮力の強さによって設定されるが、５〜２０％の範囲にあるのがよい。５％未満では伸縮力が弱すぎて効果を出せない。また２０％より多くなると生地のドレープ性が低下するとともにコスト面でも高くなってしまうので好ましくない。
【００１２】
得られた編地は、通常の工程であるリラックス、精練を実施した後、プレセット工程で最終目標の性量に合わせて乾熱温度１３０〜１５０℃の範囲で３０秒〜２分の時間内で熱セットし寸法を安定化させる。該工程で乾熱温度が１３０℃より低い場合には、該編地の寸法安定性、収縮特性に劣り、１５０℃より高い場合には、アクリル繊維の熱黄変や伸縮性糸条の物性変化等が生じ易く好ましくない。プレセットをした後、カチオン染料あるいは酸性染料を用いて染色する。その後、仕上げ工程で再度熱セットをするが、乾熱温度は１２０〜１３０℃の範囲で３０秒〜２分の時間内で行う。最も重要なことはプレセット工程での熱セット条件よりやや緩い条件を採用することである。
【００１３】
本発明によれば、低温での熱セット性のよいポリウレタン系弾性繊維を使用し、細デニールのアクリル系繊維を混用することにより、仕上げ生地の伸縮性を保持しつつ、寸法安定性もよく、また従来の綿肌着の特徴を生かしながらさらにソフト感を付加し、かつ加工工程での生産効率を良い肌着用緯編地を得ることができる。
【００１４】
以下、実施例により本発明を説明する。ただし本発明はこの実施例に拘束されるものではない。なお実施例における％は重量％を示す。
【実施例】
アクリロニトリル９０％、メチルアクリレート９．８％およびメタアリルスルフォン酸ソーダ０．２％を重合した重合体をロダンソーダ水溶液中に溶解して得られた紡糸原液を、凝固浴中に湿式紡糸し、常法に従って水洗、延伸し熱処理等施して得られたステープル繊維（単糸デニール０．８ｄ）を１０％、エジプト綿を９０％の比率で混綿し綿番手で５０／１s の紡績糸を紡出した。これを非伸縮性糸条として用いる。
一方、高分子ジオールにポリブチレンアジペート、有機ジイソシアネートに４，４’−ジフェニルメタンジイソシアネート、低分子ジオールに１，４−ブタンジオールを用いて重合したポリウレタンエラストマーを紡糸し、２０デニールのモノフィラメントを作製した。ウレタン基濃度は１６００であった。これを伸縮性糸条として用いる。
【００１５】
該非伸縮性糸条と伸縮性糸条を３０インチ口径、２０ゲージの丸編機に仕掛け、編組織を２：１のリブ編として編成した。この時伸縮性糸条のドラフト伸長率（伸長率）は２．５倍とした。伸縮性糸条の生地全体に占める混率は７％であった。
【００１６】
得られた編地を、リラックス処理し続いて精練剤マーポンＴ １ｇ／ｌ、ソーダ灰 ０．５ｇ／ｌの浴中で精練処理を行った後、丸セッターで１３５℃の温度で３０秒の時間で乾熱セットした。常法により過酸化水素水を用いた漂白を行ない、その後染色工程としてカチオン染料、カチオン緩染剤、均染剤を用い９８℃×９０分間染色、仕上げ工程として、プレセット工程と同様にして１３０℃×３０秒間セットして肌着用伸縮性編地を得た。
使用した伸縮性糸条の熱セット率、仕上げ生地の性量、熱黄変性、洗濯収縮率等を表１に示す。
【００１７】
（比較例１）
伸縮性弾性糸条として、ポリテトラメチレングリコール、４，４−ジフェニルメタンジイソシアネート、エチレンジアミンより乾式紡糸した２０デニール２フィラメントのポリウレタン弾性繊維を用いたこと以外は実施例と同一方法、同一条件にて加工し、肌着用伸縮性編地を得た。
使用した伸縮性糸条の熱セット率、仕上げ生地の性量、熱黄変性、洗濯収縮率等を表１に示す。
【００１８】
（比較例２）
伸縮性弾性糸条として、ポリテトラメチレングリコール、４，４−ジフェニルメタンジイソシアネート、エチレンジアミンより乾式紡糸した２０デニール２フィラメントのポリウレタン弾性繊維を用い、プレセット工程として１９０℃の温度で６０秒の時間で乾熱処理したこと以外は実施例と同一方法、同一条件にて加工し、肌着用伸縮性編地を得た。
使用した伸縮性糸条の熱セット率、仕上げ生地の性量、熱黄変性、洗濯収縮率等を表１に示す。
【００１９】
（比較例３）
非伸縮性糸条として、アクリル繊維とエジプト綿の混率を４５％、５５％とした綿番手で５０／１s の紡績糸を用いた以外は実施例と同一方法、同一条件にて加工し、肌着用伸縮性編地を得た。
使用した伸縮性糸条の熱セット率、仕上げ生地の性量、熱黄変性、洗濯収縮率等を表１に示す。
【００２０】
比較例１は、熱セット性が低いため、洗濯収縮率が大きく寸法安定性に極めて劣る。
比較例２は、洗濯収縮率、伸長特性は良好だが、高温セットしているため、アルリル繊維の熱黄変、硬化の影響がみられる。
比較例３は、伸縮糸条の熱セット率も高く洗濯収縮率、伸長特性は良好だが、アクリル繊維の混率が高いため、やや黄変がみられる。特に欠点として、風合面で柔らか過ぎ“たらたら感”が強い。
【００２１】
以下、本発明の詳細な説明、実施例等で用いた測定法の中で説明しなかった項目について記す。
（１）熱黄変性
精練、プレセット上がりの生地の黄変度をＣＥＩ−Ｌａｂ* 測色計［東京電色（株）製］によりｂ* 値を測定した。
（２）洗濯収縮率
ＪＩＳ−Ｌ１０１８法に準拠し、試験片タテ２５ｃｍ、ヨコ２５ｃｍを用い、タテおよびヨコ方向の洗濯収縮率を測定した。
（３）伸長率、伸長回復率
ＪＩＳ−Ｌ１０１８法の定荷重時伸び率（荷重１ｋｇ）測定法を用い、伸長率を測定した。
ＪＩＳ−Ｌ１０１８法の伸長弾性率Ａ法（定伸長法）を用い、伸長回復率とした。
一定伸長率はタテ方向５０％、ヨコ方向１００％とした。
【００２２】
【表１】

【００２３】
【発明の効果】
本発明によれば、従来技術の課題を改善し、仕上げ生地の伸縮性を保持しつつ、加工工程での生産効率を良くすることができる。また従来の綿肌着の特徴を生かしながら、さらにソフト感を付加したソフトフィットタイプの新しい肌着用生地を作ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a weft knitted fabric used for underwear and the like, and more specifically, improves the soft feel while maintaining the characteristics of conventional cotton underwear, and uses stretch yarns in combination with the fabric of the weft knitted fabric. A method for efficiently producing a soft-fit type skin-wearing knitted fabric having good dimensional stability and stretchability by using the elastic yarn. The purpose is to provide.
[0002]
[Prior art]
Conventionally, acrylic fibers have been used extensively as inner materials taking advantage of their unique feel and heat retention, but due to thermal yellowing, which is a drawback of acrylic fibers, there are limitations on the materials used for mixing. . In particular, when general polyurethane elastic fibers are used as the material for blending in order to give the fabric elasticity, the polyurethane elastic fibers have poor heat setability (dimensional stability) at low temperatures, and the pass rate of the finished fabric is low. Low. On the other hand, if the temperature is set to improve the dimensional stability, the acrylic fiber is yellowed, so that the efficient production is impossible.
Furthermore, in order to give softness and softness, which are one of the important required characteristics of underwear, the knitted fabric using fine denier of acrylic fiber is too soft after washing and has the disadvantage that it feels loose and dyeing. There was also a problem with dimensional stability in the processing process.
[0003]
[Problems to be solved by the invention]
The present invention is to attempt to improve the problems of the prior art, while maintaining the elasticity of the finished fabric, to improve the production efficiency of the machining process, heat setting properties at low temperatures (dimensional stability) C., also seeks to provide an undergarment for stretchable transverse knitted fabric can further be added a sense of soft while taking advantage of the conventional cotton underwear.
[0004]
[Means for Solving the Problems]
The present invention uses a polyurethane-based elastic fiber yarn having good heat setability (dimensional stability) at low temperatures, and uses fine denier acrylic fiber to add a soft feeling while taking advantage of the characteristics of conventional cotton underwear. It is characterized by mixing.
That is, in the weft knitted fabric in which the ground texture is formed by the non-stretchable yarn and the polyurethane elastic fiber yarn, the non-stretchable yarn is 0.3. Thermoplastic polyurethane having a urethane group concentration of 1,500 or more, and a polyurethane elastic fiber yarn comprising a high molecular diol, an organic diisocyanate, and a low molecular diol. A skin-wearable elastic flat knitted fabric characterized by being an elastomer filament and having a heat setting rate of 75% or more after a dry heat treatment at 140 ° C. for 1 minute in a 100% stretched state.
The polyurethane elastic fiber having good heat setability (dimensional stability) at low temperature used in the present invention has a urethane group concentration of 1500 or more obtained by spinning a polyurethane elastomer comprising a high molecular diol, an organic diisocyanate, and a low molecular diol. Polyurethane filament yarn. Examples of the polymer diol used in the present invention include polytetramethylene glycol, polyε-caprolactone, or polybutylene adipate. Examples of organic diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 2,4 -Naphthalene diisocyanate, m-xylene diisocyanate, 4,4'-diisocyanate dicyclohexane, 4,4'-diisocyanate dicyclohexylmethane, isophorone diisocyanate and the like. These may be used alone or in combination of two or more. Low molecular diols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol. 1,8-6 nandiol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, 1,4-bis (β-hydroxyethoxybenzene) and the like. These can be used alone or in a mixture of two or more.
[0005]
In producing the polyurethane elastomer which is the raw material of the polyurethane elastic fiber in the present invention, a known method is used. For example, one-shot method in which polymer diol, low molecular diol, and organic diisocyanate are reacted together in a solvent or without solvent, or a prepolymer is prepared by previously reacting polymer diol and organic diisocyanate, and then low molecular diol is solvent For example, a prepolymer method in which the reaction is performed under or without a solvent.
In view of cost, a melt polymerization method in which the production is performed without a solvent is desirable.
[0006]
The urethane group concentration of the thermoplastic polyurethane elastomer in the present invention needs to be 1500 or more. When the urethane group concentration is less than 1500, the stretch function of the obtained yarn is not sufficiently exhibited.
In addition, the urethane group density | concentration said here is represented by following Formula, when 4,4'- diphenylmethane diisocyanate (it abbreviates as MDI) is used as organic diisocyanate, for example.

[0007]
Furthermore, the polyurethane fiber yarn of the present invention is required to have a heat set rate of 75% or more in a dry heat treatment at 140 ° C. × 1 minute and 100% elongation. When the heat setting rate is lower than 75%, a problem is likely to occur in dimensional stability such as defective width in the pre-setting process before dyeing.
The dry heat setting property mentioned here means a value measured by the following method. A load of 1 mg per denier of polyurethane elastic fiber is applied and L0 is taken as the sample length. Next, the sample was stretched twice and subjected to a dry heat treatment (140 ° C. × 1 minute) in the stretched state. After relaxation at room temperature for 1 hour, the length L1 was measured under a load of 1 mg / d. calculate.
Heat set rate (%) = (L1-L0) / L0 × 100
[0008]
The non-stretchable yarn needs to be a blended yarn containing 5 to 40% of ultrafine denier of acrylic fiber and 95 to 60% of cellulose fiber. The range of ultra fine denier is 0.3 to 0.9 denier, preferably 0.5 to 0.8 denier. Extra fine yarn of less than 0.3 denier has low production operability and high cost. Moreover, the process passability in post-processing is also bad. If it is thicker than 0.9 denier, the softness of the dough, which is the object of the present invention, is not imparted and characteristics cannot be obtained.
When the mixing ratio of the ultrafine fibers is less than 5%, soft feeling is not imparted. Conversely, when the mixing ratio is more than 40%, the texture of the fabric becomes too soft. .
The material mixed with the acrylic ultrafine fiber is preferably a hygroscopic cellulose fiber. Of these, cotton often used for skin wear is preferred. The mixing ratio of cotton is set by the mixing ratio of acrylic extra fine fibers determined by the desire for soft feeling.
[0009]
The acrylic ultrafine fiber and the cellulose fiber are blended by a usual method to obtain a blended yarn. As the skin-wearing yarn, a spun yarn type with fluff is suitable because its required performance such as touch and moisture absorption is high.
[0010]
The aforementioned non-stretchable yarn and stretchable yarn are fed and knitted using a circular knitting machine so that the stretchable yarn is not exposed on the front and back sides of the fabric. In this case, the elastic yarn is supplied with a positive yarn feeding device and is supplied while giving 160 to 200% elongation, and the elastic yarn is expanded and contracted at the same yarn supply part so as not to be exposed on the front and back of the fabric. It is necessary to feed the sexual yarn slightly from the rear of the non-stretchable yarn.
[0011]
In the knitted fabric knitted under such conditions, the thickness of the non-stretchable yarn is preferably 2.5 times or more, more preferably 3 to 6 times thicker than the thickness of the stretchable yarn. This is because polyurethane, which is the main composition of stretch yarns, has inferior light resistance compared to other materials, so that the stretch yarns are unevenly distributed inside the fabric as much as possible and covered with non-stretch yarns for direct light. There is also a purpose not to expose, and a purpose to prevent the rubber-like slime texture of polyurethane from appearing on the fabric surface.
Further, in the knitted fabric, the mixing ratio of the elastic yarn is set by the strength of the elastic force depending on the required performance, but is preferably in the range of 5 to 20%. If it is less than 5%, the stretching force is too weak to produce an effect. On the other hand, if it exceeds 20%, the drapeability of the fabric is lowered and the cost is increased, which is not preferable.
[0012]
The obtained knitted fabric is subjected to relaxation and scouring, which are normal processes, and within a time range of 30 seconds to 2 minutes within a dry heat temperature range of 130 to 150 ° C. according to the final target amount of sex in the presetting process. Set the heat to stabilize the dimensions. If the dry heat temperature is lower than 130 ° C in this step, the knitted fabric is inferior in dimensional stability and shrinkage properties. If it is higher than 150 ° C, the acrylic fiber is thermally yellowed and the physical properties of the elastic yarn are changed. Etc. are likely to occur and are not preferable. After pre-setting, dye with a cationic dye or acid dye. Thereafter, heat setting is performed again in the finishing process, but the dry heat temperature is in the range of 120 to 130 ° C. within a period of 30 seconds to 2 minutes. The most important thing is to adopt a slightly looser condition than the heat setting condition in the presetting process.
[0013]
According to the present invention, by using a polyurethane-based elastic fiber having a good heat setting property at a low temperature and mixing acrylic fibers of fine denier, while maintaining the stretchability of the finished fabric, the dimensional stability is also good, Further, it is possible to obtain a weft knitted fabric for skin wearing that gives a soft feeling while taking advantage of the characteristics of conventional cotton underwear and has good production efficiency in the processing step.
[0014]
Hereinafter, the present invention will be described by way of examples. However, the present invention is not limited to this embodiment. In addition,% in an Example shows weight%.
【Example】
A spinning stock solution obtained by dissolving a polymer obtained by polymerizing 90% of acrylonitrile, 9.8% of methyl acrylate and 0.2% of sodium methallylsulfonate in an aqueous rhodium soda solution was wet-spun into a coagulation bath, and the usual method In accordance with the above, staple fibers (single yarn denier 0.8d) obtained by washing with water, drawing and heat treatment were blended at a ratio of 10% and Egyptian cotton at a ratio of 90%, and a spun yarn of 50/1 s was spun with a cotton count. This is used as a non-stretchable yarn.
On the other hand, a polyurethane elastomer polymerized using polybutylene adipate as the polymer diol, 4,4′-diphenylmethane diisocyanate as the organic diisocyanate, and 1,4-butanediol as the low molecular diol was spun to produce a 20 denier monofilament. The urethane group concentration was 1600. This is used as an elastic yarn.
[0015]
The non-stretch yarn and the stretch yarn were set on a 30 inch diameter, 20 gauge circular knitting machine, and the knitted structure was knitted as a 2: 1 rib knitting. At this time, the draft elongation rate (elongation rate) of the elastic yarn was 2.5 times. The mixing ratio of the stretchable yarn to the entire fabric was 7%.
[0016]
The obtained knitted fabric was subjected to a relaxation treatment, followed by a scouring treatment in a bath of a scouring agent Marpon T 1 g / l and soda ash 0.5 g / l, followed by a round setter at a temperature of 135 ° C. for 30 seconds. Set with dry heat. Bleaching using hydrogen peroxide is performed in a conventional manner, and then dyeing process is performed by using a cationic dye, a cation dyeing agent, and a leveling agent at 98 ° C. for 90 minutes, and a finishing process is performed in the same manner as in the presetting process. C. set for 30 seconds to obtain an elastic knitted fabric for skin wear.
Table 1 shows the heat setting rate of the stretch yarn used, the amount of finished fabric, the heat yellowing property, the shrinkage rate of washing, and the like.
[0017]
(Comparative Example 1)
The elastic elastic yarn was processed in the same manner and under the same conditions as in the Examples except that 20-denier 2-filament polyurethane elastic fiber spun from polytetramethylene glycol, 4,4-diphenylmethane diisocyanate and ethylenediamine was used. The skin-wearing elastic knitted fabric was obtained.
Table 1 shows the heat setting rate of the stretch yarn used, the amount of finished fabric, the heat yellowing property, the shrinkage rate of washing, and the like.
[0018]
(Comparative Example 2)
As the elastic elastic yarn, 20 denier 2-filament polyurethane elastic fiber spin-spun from polytetramethylene glycol, 4,4-diphenylmethane diisocyanate, and ethylenediamine was used, and dried at a temperature of 190 ° C. for 60 seconds as a presetting process. Except that it was heat-treated, it was processed in the same manner and under the same conditions as in the examples, and a skin-wearing stretch knitted fabric was obtained.
Table 1 shows the heat setting rate of the stretch yarn used, the amount of finished fabric, the heat yellowing property, the shrinkage rate of washing, and the like.
[0019]
(Comparative Example 3)
The non-stretch yarn is processed in the same manner and under the same conditions as in the examples except that 50/1 s spun yarn is used with a cotton count of acrylic fiber and Egyptian cotton of 45% and 55%. Elastic knitted fabric was obtained.
Table 1 shows the heat setting rate of the stretch yarn used, the amount of finished fabric, the heat yellowing property, the shrinkage rate of washing, and the like.
[0020]
Since Comparative Example 1 has a low heat setting property, the shrinkage rate of washing is large and the dimensional stability is extremely inferior.
Comparative Example 2 has good washing shrinkage ratio and elongation characteristics, but is set at a high temperature, so the effects of thermal yellowing and curing of the allyl fiber are observed.
In Comparative Example 3, the heat set rate of the stretchable yarn is high and the washing shrinkage rate and elongation characteristics are good. However, since the mixing ratio of the acrylic fibers is high, a slight yellowing is observed. As a particular disadvantage, it is too soft on the surface and has a strong “feeling when you feel”.
[0021]
Hereinafter, items not described in the detailed description of the present invention and the measurement methods used in Examples and the like will be described.
(1) The b * value was measured with a CEI-Lab * colorimeter [manufactured by Tokyo Denshoku Co., Ltd.] for the yellowing degree of the dough after heat yellowing scouring and pre-setting.
(2) Laundry shrinkage rate In accordance with the JIS-L1018 method, the test shrinkage in the vertical and horizontal directions was measured using a test piece length of 25 cm and a width of 25 cm.
(3) Elongation rate and elongation recovery rate Elongation rate was measured using the JIS-L1018 method for measuring elongation at constant load (load 1 kg).
The elongation recovery rate was determined by using the elongation modulus A method (constant elongation method) of JIS-L1018 method.
The constant elongation was 50% in the vertical direction and 100% in the horizontal direction.
[0022]
[Table 1]

[0023]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the subject of a prior art can be improved and the production efficiency in a process can be improved, maintaining the stretchability of finished fabric. In addition, it is possible to create a new soft-fit type underwear fabric that adds a soft feeling while taking advantage of the characteristics of conventional cotton underwear.

Claims (3)

In a weft knitted fabric in which a non-stretch yarn and polyurethane elastic fiber yarn form a ground structure, the non-stretch yarn contains 0.3 to 0.9 denier acrylic fiber in a range of 5 to 40%. The polyurethane elastic fiber yarn is a thermoplastic polyurethane elastomer filament having a urethane group concentration of 1500 or more composed of high molecular diol, organic diisocyanate, and low molecular diol, and dried at 140 ° C. for 1 minute in a 100% stretched state. underwear for stretchable weft knitting fabric, wherein the heat setting rate after heat treatment is 75% or.   The stretchable flat knitted fabric for underwear according to claim 1, wherein the non-stretchable yarn is a spun yarn composed of cellulosic fibers and acrylic fibers of 0.3 to 0.9 denier. In a flat knitted fabric that forms a ground structure with non-stretchable yarn and polyurethane elastic fiber yarn, the thickness of the non-stretchable yarn is 2.5 times or more than the thickness of the polyurethane elastic fiber yarn. The stretchable flat knitted fabric for skin wear according to claim 1, wherein the mixing ratio of the elastic yarn is in the range of 5 to 20%.