JP5346221B2 - Water-degradable nonwoven fabric - Google Patents

Description

  The present invention relates to a water-decomposable non-woven fabric that can be broken down into pieces when stirred in water.

  Water-degradable nonwoven fabrics that are capable of decomposing into strips when agitated in water are known. For example, Japanese Patent Laid-Open No. 9-78419 (Patent Document 1) describes this type of nonwoven fabric as a water-disintegrating nonwoven fabric. This non-woven fabric was made into a web by paper-making a mixture of regenerated cellulose fibers or synthetic fibers 70 to 97 wt% having a fiber length of 5 to 20 mm and fine pulp fibers 3 to 30 wt% having a water retention of 210 to 450%. Thereafter, a high-pressure jet water stream is jetted onto the web to mechanically interlace the fibers, and then dried. This non-woven fabric can be used as a raw material such as a wet tissue, a cleaning wipe, a diaper, a sanitary napkin, etc., and is easily disintegrated by a large amount of water flow.

JP-A-9-78419

  The non-woven fabric described in Patent Document 1 uses fine pulp fibers, and fine pulp fibers that have been finely beaten in a wet state and have a large surface area have fine hydrogen bonds generated when they are dried. There is a tendency to significantly increase the strength of the nonwoven fabric compared to the pulp fibers before being beaten, while making the nonwoven fabric hard, poor in flexibility, and poor in texture. In addition, this nonwoven fabric is manufactured through a papermaking process and a high-pressure jet water stream injection process, but the fine pulp fibers are easily removed from the web in these processes, and other web contained in the web. It may be difficult to interlace with the fiber, and it is difficult to say that the nonwoven fabric is easy to manufacture.

  Then, this invention makes it a subject to provide the water-decomposable nonwoven fabric which is easy to manufacture and has strength and flexibility.

  In order to solve the above-mentioned problems, the present invention is directed to a water-degradable nonwoven fabric that includes fibers that are mechanically entangled with each other and that can be separated from each other when stirred in water.

  In this water-decomposable nonwoven fabric, the present invention is characterized as follows. 10 to 50% by weight of the fibers are occupied by ultrafine thermoplastic synthetic fibers having a fineness of 0.01 to 0.5 dtex and a fiber length of 3 to 10 mm. 90-50% by weight of the fibers are occupied by at least one of chemical fibers having a fineness of 1-2 dtex and a fiber length of 5-20 mm and pulp fibers having a freeness of 600-770 cc. Yes.

  In one embodiment of the present invention, the ultrafine thermoplastic synthetic fiber is formed by dividing a divided fiber.

  In another embodiment of the present invention, the water-decomposable nonwoven fabric contains 3 to 10% by weight of a water-soluble binder.

  In another embodiment of the present invention, the water-decomposable nonwoven fabric is formed by mixing the ultrafine thermoplastic synthetic fiber and at least one of the chemical fiber and the pulp fiber with water. It was obtained by spraying a high pressure jet water stream onto the web obtained from the slurry and then drying the web.

  In another embodiment of the present invention, the slurry contains a water-soluble binder.

  The water-decomposable nonwoven fabric according to the present invention mechanically entangles the fibers contained in the water-decomposable nonwoven fabric using ultrafine thermoplastic synthetic fibers having a fineness of 0.01 to 0.5 dtex and a fiber length of 3 to 10 mm. Therefore, the water-decomposable nonwoven fabric is flexible and has high tensile strength in addition to easy manufacture.

The figure which shows an example of the manufacturing process of a water-decomposable nonwoven fabric.

The water-decomposable non-woven fabric according to the present invention can be used as a surface sheet for contact with skin or a back sheet for contact with clothes in body fluid treatment products such as disposable diapers, sanitary napkins, hemorrhoid pads, dry wipes and wet wipes. It is suitable for use as a liquid crystal and can be decomposed into a plurality of strips when it is poured into a large amount of water and stirred. Such a water-decomposable nonwoven fabric has a thickness of 0.15 to 0.4 mm and a basis weight of 25 to 60 g / m ² , and has a fineness of 0.01 to 0.5 dtex and a fiber of 3 to 10 mm. 10 to 50% by weight of ultrafine thermoplastic synthetic fiber having a long length. Moreover, 90 to 50% by weight of the nonwoven fabric is occupied by at least one of chemical fibers having a fineness of 1 to 2 dtex and a fiber length of 5 to 20 mm and pulp fibers having a freeness of 600 to 770 cc. . In addition, the thermoplastic synthetic fiber as used in this invention means the fiber currently formed with the thermoplastic synthetic resin which can be melt-spun using an extruder. The chemical fiber referred to in the present invention includes synthetic fibers including thermoplastic synthetic fibers, semi-synthetic fibers, and recycled fibers. An example of semi-synthetic fiber is acetate fiber, and an example of regenerated fiber is rayon. These fibers contained in the water-decomposable nonwoven fabric according to the present invention are mechanically entangled with each other under the action of the jetted high-pressure jet water flow. This water-decomposable non-woven fabric may also contain a water-soluble binder to reduce liquid permeability and improve tensile strength depending on its application, and on the contrary, it improves liquid permeability and liquid retention. In order to make it, it may contain a hydrophilic treatment agent.

  FIG. 1 is a diagram showing an example of a process for producing a water-decomposable nonwoven fabric according to the present invention. The process shown in FIG. 1 uses a well-known paper making process, and includes a first wire portion 11, a second wire portion 12, a third wire portion 13, a drying drum 14, and a winder 15. The first wire unit 11 is provided with a slurry supply unit 16 and a jet water injection unit 17. In the slurry supply part 16, the slurry 21 containing the fiber mixture for forming the water-decomposable nonwoven fabric 1 and water is supplied to the first wire part 11, and the web 22 is formed by the fiber mixture. The web 22 is sprayed with high-pressure jet water from a nozzle row 18 in which a plurality of nozzles are arranged in a crossing direction (also referred to as CD direction) with respect to the machine direction (also referred to as MD direction) in the spraying unit 17, and has an effect of required injection energy. The fibers contained in the web 22 are mechanically entangled. The injection unit 17 is provided with a suction box 19 for sucking high-pressure jet water after injection. The subsequent web 22 is carried by the second wire portion 12 and the third wire portion 13, placed on the peripheral surface of the drying drum 14, dried to become the water-decomposable nonwoven fabric 1, and taken up by the winder 15. .

  When the water-decomposable nonwoven fabric 1 thus obtained is poured into a large amount of water and stirred, the fibers are separated by mechanical entanglement, and the water-decomposable nonwoven fabric is divided into several pieces. Is possible.

  The slurry 21 in FIG. 1 is adjusted so that, for example, the amount of the fiber mixture is 0.5 to 1.5% by weight so that the fiber mixture for forming the water-decomposable nonwoven fabric 1 and water have an appropriate ratio. Has been. In the fiber mixture, a plurality of types of fibers are mixed at the same ratio as the constituent ratio of each fiber in the water-decomposable nonwoven fabric 1. That is, the fiber mixture in the water-decomposable nonwoven fabric 1 and the slurry 21 contains 10 to 50% by weight of ultrafine thermoplastic synthetic fiber having a fineness of 0.01 to 0.5 dtex and a fiber length of 3 to 10 mm. The fiber mixture in the water-disintegrable nonwoven fabric 1 and the slurry 21 also has (a) a chemical fiber having a fineness of 1 to 2 dtex and a fiber length of 5 to 20 mm, and (b) a freeness of 600 as a measure of the beating degree. It contains 90 to 50% by weight of at least one of pulp fibers that are ˜770 cc.

  As the ultrafine thermoplastic synthetic fiber contained in the hydrolyzable nonwoven fabric 1 and the slurry 21, for example, by dividing a commercially available composite fiber of polyester and nylon having a fineness of 3.3 dtex and capable of being divided into 11 parts What is obtained can be used. This composite fiber can be divided into 11 ultrafine thermoplastic synthetic fibers having about 0.3 dtex by mechanical treatment with a grinder or the like. Also, 16 ultrafine thermoplastic synthetic fibers having about 0.21 dtex obtained by dividing a commercially available composite fiber of polypropylene and polyester having a fineness of 3.3 dtex and capable of being divided into 16 parts are used. You can also In addition to these, an ultrafine thermoplastic synthetic fiber of about 0.21 dtex obtained by splitting a commercially available composite fiber of polyester and nylon having a fineness of 3.3 dtex and capable of being divided into 16 pieces, a fineness of 2. An ultra-thin thermoplastic synthetic fiber of about 0.13 dtex obtained by dividing a commercially available composite fiber of polypropylene and polyethylene having 0 dtex and capable of being divided into 16 parts, and having a fineness of 2.2 dtex and capable of being divided into 8 parts An ultrafine thermoplastic synthetic fiber of about 0.28 dtex obtained by dividing a commercially available composite fiber of polyester and polyethylene can be used for the water-decomposable nonwoven fabric 1. Furthermore, ultrafine thermoplastic synthetic fibers such as meltblown fibers having a fineness in the range of 0.01 to 0.51 dtex and a fiber length in the range of 3 to 10 mm can also be used.

  These ultrafine thermoplastic synthetic fibers having a fiber length in the range of 3 to 10 mm make the hydrolyzable nonwoven fabric 1 flexible with low rigidity and at the same time having high tensile strength when dry and when wet. Can do. In the present invention, the rigidity is a value measured by the bending / softening A method defined in JIS L 1096. A preferred water-decomposable nonwoven fabric 1 has a test piece whose length direction matches the direction parallel to the machine direction when manufacturing the non-woven fabric 1 and a test piece whose length direction matches the cross direction perpendicular to the machine direction. The average of the stiffness values for and is 80 mm or less. A nonwoven fabric having a stiffness value exceeding 80 mm is not preferred because it tends to be difficult to fit the skin when used as a sheet to be brought into contact with the skin in a body fluid treatment product. The tensile strength of the water-decomposable nonwoven fabric 1 means the breaking strength when a test piece having a width of 25 mm and a length of 150 mm is pulled by setting the distance between chucks of the tensile tester to 100 mm and setting the tensile speed to 100 mm / min. doing. Test specimens were prepared with the length direction matched with the machine direction and with the cross direction matched with each other. H. The strength after conditioning at 60% for 24 hours was defined as DRY strength, and the strength after spray impregnation with ion exchange water corresponding to 200% of the weight of each test piece was defined as WET strength. The preferred water-disintegrable nonwoven fabric 1 has a DRY strength of 3.0 N or more per 25 mm width in both the MD direction and the CD direction, and a WET strength of 2.0 N per 25 mm width in both the MD direction and the CD direction. That's it.

In this invention, the evaluation of the water decomposability of the water decomposable nonwoven fabric 1 is performed as follows. The evaluation method includes a visual observation method and a dispersion rate measurement method. In the visual observation method, a 100 × 100 mm test piece is dried at 100 ° C. for 2 hours to obtain a dry weight (W ₁ ). Then, this test piece and 800 ml of distilled water are put into a vertical separatory funnel shaker (SHKV-200 manufactured by IWKI) and shaken at a shaking speed of 240 rpm for 60 minutes, and then the inside of the separatory funnel is visually observed. The water-decomposable nonwoven fabric 1 according to the present invention is decomposed to such an extent that it does not retain its original shape after shaking, or has been decomposed to at least three strips. In the dispersion rate measurement method, the test piece in the separating funnel visually observed and the distilled water were vertically meshed with a metal mesh of 2 mesh (particle size 1.5 mm, mesh opening 11.2 mm, space ratio 77.8%). transferred to a cage width × height = 100 × 100 × 120 mm, the remaining specimens in the basket and dried 2 hours at 100 ° C., obtaining the dry weight _{(W 2).} The dispersion ratio is obtained from the dry weights W ₁ and W ₂ by the following equation.
{(W ₁ −W ₂ ) / W ₁ } × 100 = dispersion rate (%)

  The water-decomposable nonwoven fabric 1 according to the present invention has a dispersion rate of 50% or more.

  An ultrafine thermoplastic synthetic fiber having a fiber length in the range of 3 to 10 mm is also less likely to be regularly oriented in one direction when the web 22 is formed from the slurry 21 in the process of FIG. Since the fiber 22 is not entangled with the fibers in a complicated manner, the web 22 tends to be uniform with no uneven fiber distribution, and the water-decomposable nonwoven fabric 1 obtained from the web tends to be easily hydrolyzed. The ultrafine thermoplastic synthetic fiber having a fiber length exceeding 10 mm may interfere with obtaining a homogeneous web 22 or may obstruct obtaining a water-disintegratable nonwoven fabric 1 that can be easily hydrolyzed. On the other hand, the ultrathin thermoplastic synthetic fiber having a fiber length of less than 3 mm has the disadvantages that the fibers cannot be entangled with each other and that the first wire 11 is often dropped.

  The web 22 in the process of FIG. 1 when the amount of the ultrafine thermoplastic synthetic fiber in the water-decomposable nonwoven fabric 1 exceeds 50% by weight is poor in drainage, and the productivity of the water-degradable nonwoven fabric 1 is reduced. Become.

  The pulp fiber used in the present invention can be used to make the water-decomposable nonwoven fabric 1 liquid-absorbable or liquid-permeable, but makes the water-decomposable nonwoven fabric 1 as flexible as possible. Therefore, in order to prevent dropping from the first wire 11 when it is included in the web 22 in the step of FIG. 1, it is preferable that the beating is unbeaten or low beating. More specifically, as a measure of the beating degree, the freeness is measured using a Canadian standard freeness tester in accordance with JIS P2181, and the pulp fiber whose value is in the range of 600 to 770 cc is used. It is preferable to do. Even with such pulp fibers, the water-decomposable nonwoven fabric 1 using the same tends to have a high density and a high rigidity. The water-decomposable nonwoven fabric 1 including pulp fibers and having a relatively high rigidity is suitable for use as a wipe.

In the process of FIG. 1, by changing the composition of the fiber mixture contained in the slurry 21 and the injection conditions of the injection unit 17, the water-decomposable nonwoven fabric of the example having a basis weight of 35 g / m ² and the nonwoven fabric of the comparative example Got. The compositions, evaluation items, evaluation methods and evaluation results of the water-decomposable nonwoven fabric of the example and the nonwoven fabric of the comparative example are as shown in Table 1 and below.

（表１における組成）
１．ＮＢＫＰは、Ｎａｄｅｌｈｏｌｚ Ｂｌｅａｃｈｅｄ Ｋｒａｆｔ Ｐｕｌｐの略であり、針葉樹晒クラフトパルプを意味する。このパルプであって、カナディアンフリーネススタンダードフィルタを使用して測定したときの濾水度が７２０ｃｃのものを実施例において使用し、４００ｃｃのものを比較例において使用した。
２．ＰＥＴは、ポリエチレンテレフタレート繊維の略である。
３．分割繊維−１には、３．３ｄｔｅｘの繊度と５ｍｍの繊維長とを有し、１１分割可能に形成されたＰＥＴ／ナイロンの複合繊維を分割することによって得られた約０．３ｄｔｅｘの極細の繊維を使用した。
４．分割繊維−２には、３．３ｄｔｅｘの繊度と５ｍｍの繊維長とを有し、１６分割可能に形成されたポリプロピレン／ＰＥＴの複合繊維を分割することによって得られた約０．２１ｄｔｅｘの繊維を使用した。
５．水溶性バインダには、スルホポリエステル樹脂（Ｅａｓｔｍａｎ Ｃｈｅｍｉｃａｌ Ｃｏｍｐａｎｙ製ＡＱ５ＳＳ）を使用した。
（図１および表１の噴射処理条件）
１．図１の噴射部１７では、孔径９５μの噴射ノズルが交差方向へ０．５ｍｍのピッチで並ぶノズル列１８を機械方向に４列配置した。
２．各ノズル列１８の噴射処理条件は、次式によって求められる処理エネルギー量を変化させることによって調整した。その処理エネルギー量は、噴射圧力によって変化させた。
処理エネルギー量（ｋＷ／ｍ^２）
＝１．６３×噴射圧力（ｋｇ／ｃｍ^２）×噴射流量（ｍ^３／ｍｉｎ）／
処理速度（ｍ／ｍｉｎ）／６０
噴射流量（ｍ^３／ｍｉｎ）
＝７５０×オリフィス開孔総面積（ｍ^２）×噴射圧力（ｋｇ／ｃｍ^２）^{０．４９５}
噴射ノズル：孔径９５μ，ピッチ０．５ｍｍ
第１、第２、第３ワイヤ：日本フィルコン（株）製ＬＬ−７０Ｅ
（表１における評価項目）
１．坪量
３枚の１００×１００ｍｍの試験片について求めた坪量の平均値である。
２．厚さ
ダイアルシックネスゲージを使用し、３ｇ／ｃｍ^２の測定圧で測定した３枚の試験片の厚さの平均値である。
３．密度
坪量と厚さとから計算した値である。
４．ＤＲＹ強度
幅２５ｍｍ、長さ１５０ｍｍの試験片を２０℃、Ｒ．Ｈ．６０％で２４時間調湿し、その試験片についてチャック間隔１００ｍｍ、引張速度１００ｍｍ／ｍｉｎで引張ったときの破断強度を示す。試験片は、その長さ方向を機械方向（ＭＤ）と交差方向（ＣＤ）とに一致させたものを３本ずつ用意し、各方向について３本の試験片の引張強度の平均値を求めた。この発明に係る水解性不織布のＤＲＹ強度はＭＤ，ＣＤ両方向において、３ｋｇ以上であることが好ましい。
５．ＤＲＹ伸度
ＤＲＹ強度を測定したときの試験片の破断時における伸度の平均値を求めた。この発明に係る水解性不織布のＤＲＹ伸度は、ＭＤ，ＣＤ両方向において、１０％以上であることが好ましい。
６．ＷＥＴ強度
試験片にその重量の２００％に相当するイオン交換水をスプレーして含浸させた以外は、ＤＲＹ強度の測定条件と同じ条件で引張強度を求めた。この発明に係る水解性不織布のＷＥＴ強度は、ＭＤ，ＣＤ両方向において２ｋｇ以上であることが好ましい。
７．ＷＥＴ伸度
ＷＥＴ強度を測定したときの試験片の破断時における伸度の平均値を求めた。この発明に係る水解性不織布のＷＥＴ伸度は、ＭＤ，ＣＤ両方向において２０％以上であることが好ましい。
８．剛性
ＪＩＳ Ｌ １０９６のセクション８．１９．１に規定の剛軟性Ａ法（４５度カンチレバー法）に準拠して測定した。試験結果は、長さ方向をＭＤ方向に一致させた３枚の試験片の測定値と、長さ方向をＣＤ方向に一致させた３枚の試験片の測定値とを平均した値である。
９．水解性
（目視観察法）
１００×１００ｍｍの試験片１枚について、１００℃で２時間乾燥して乾燥重量（Ｗ_１）を求める。乾燥後の試験片と蒸留水８００ｍｌとを縦型分液ロート振盪機（ＩＷＫＩ製ＳＨＫＶ−２００）に入れて振盪速度２４０ｒｐｍで６０分間振盪する。その後に、分液ロート内を観察し、試験片がその原形をとどめない程度に分解しているときを高度水解性（○印）、試験片が少なくとも３つの細片に分解しているか、目視によっては本数を数えることができない程度の本数に繊維が分離しているときを中程度水解性（△印）、試験片の分解が中程度水解性にまで及ばないときを難水解性（×印）と判断した。この発明に係る水解性不織布は高度水解性または中程度水解性を有している。
（分散率測定法）
目視観察した後の分液ロート内の試験片と蒸留水とを２メッシュ（粒径１．５ｍｍ、目開き１１．２ｍｍ、空間率７７．８％）の金網でできた縦×横×高さ＝１００×１００×１２０ｍｍのかごに移し、かごの中に残った試験片を１００℃で２時間乾燥して、乾燥重量（Ｗ_２）を求める。この乾燥重量Ｗ_２と、目視観察するときに求めた乾燥重量Ｗ_１とから分散率を次式によって求める。
分散率（％）＝｛（Ｗ_１−Ｗ_２）／Ｗ_１｝×１００
１０．保液率
１００×１００ｍｍの大きさのＪＩＳ Ｐ ３８０１に規定のろ紙を５枚重ね、その上に１００×１００ｍｍの試験片（重量Ｗ_０）を載せる。試験片にはビュレットを使用して１０ｍｍの高さから、１ｃｃの生理用食塩水を１ｃｃ／２秒の速度で滴下する。滴下してから３０秒経過後の試験片の重量（Ｗ_１）を求め、次式によって保液率を算出する。
保液率（％）＝｛（Ｗ_１−Ｗ_０）／Ｗ_０｝×１００
この発明に係る水解性不織布１は、パルプ繊維および／またはレーヨン繊維を含むことによって保液率が高くなる。保液率が２０％よりも高い水解性不織布１は、ドライワイプスやウエットワイプスとして使用するのに好適なものである。
１１．吸液時間
保液率の測定時に、生理用食塩水の滴下終了後、試験片の表面から生理用食塩水の水滴が消失するまでの時間を測定する。表１において、測定時間が１秒とあるのは、水滴の消失する時間が１秒以下であったことを意味している。
この発明に係る水解性不織布１は、吸液時間が３秒以下であるときに透液性の水解性不織布として体液処理用品に使用することが可能であり、水溶性バインダを含むことによって吸液時間が６〜８秒になるものは、難透液性の水解性不織布として体液処理用品に使用することが可能である。
１２．拡散面積
保液率測定時に、生理用食塩水を滴下してから３０秒経過後に、試験片表面において生理用食塩水がＭＤ方向へ広がった寸法ＭＬ（ｍｍ）と、ＣＤ方向へ広がった寸法ＣＬ（ｍｍ）とを測定し、次式により拡散面積を求める。
拡散面積＝ＭＬ×ＣＬ
この発明に係る水解性不織布１は、親水性繊維であるレーヨンおよび／またはパルプ繊維を含むことによって、拡散面積が大きくなる傾向にある。拡散面積が２０００ｍｍ^２よりも大きな水解性不織布１は、ドライワイプスやウエットワイプスとして使用するのに好適なものである。拡散面積が１８００ｍｍ^２よりも小さい水解性不織布１は、スポット吸収に優れた体液処理用品を作るのに好適なものである。

(Composition in Table 1)
1. NBKP is an abbreviation for Nadelholz Bleached Kraft Pulp, and means softwood bleached kraft pulp. This pulp, having a freeness of 720 cc as measured using a Canadian Freeness Standard filter, was used in the examples, and a 400 cc was used in the comparative examples.
2. PET is an abbreviation for polyethylene terephthalate fiber.
3. The split fiber-1 has a fineness of 3.3 dtex and a fiber length of 5 mm, and an ultrafine fiber of about 0.3 dtex obtained by splitting a composite fiber of PET / nylon formed to be 11 splittable. Fiber was used.
4). Split fiber-2 has a fineness of 3.3 dtex and a fiber length of 5 mm, and a fiber of about 0.21 dtex obtained by splitting a composite fiber of polypropylene / PET formed so as to be capable of 16 splits. used.
5. A sulfopolyester resin (AQ5SS manufactured by Eastman Chemical Company) was used as the water-soluble binder.
(Injection treatment conditions in FIG. 1 and Table 1)
1. In the injection unit 17 in FIG. 1, four nozzle rows 18 in which jet nozzles having a hole diameter of 95 μ are arranged in a crossing direction at a pitch of 0.5 mm are arranged in the machine direction.
2. The injection processing conditions of each nozzle row 18 were adjusted by changing the processing energy amount obtained by the following equation. The amount of processing energy was changed depending on the injection pressure.
Processing energy (kW / m ² )
= 1.63 x injection pressure (kg / cm ² ) x injection flow rate (m ³ / min) /
Processing speed (m / min) / 60
Injection flow rate (m ³ / min)
= 750 × total orifice opening area (m ² ) × injection pressure (kg / cm ² ) ^0.495
Injection nozzle: hole diameter 95μ, pitch 0.5mm
1st, 2nd, 3rd wire: Nippon Filcon Co., Ltd. LL-70E
(Evaluation items in Table 1)
1. Basis weight This is the average value of the basis weight determined for three 100 × 100 mm test pieces.
2. Thickness An average value of the thicknesses of three test pieces measured using a dial thickness gauge at a measurement pressure of 3 g / cm ² .
3. Density Value calculated from basis weight and thickness.
4). DRY strength A test piece having a width of 25 mm and a length of 150 mm was measured at 20 ° C. H. The rupture strength when the humidity is adjusted at 60% for 24 hours and the test piece is pulled at a chuck interval of 100 mm and a tensile speed of 100 mm / min is shown. Three test pieces were prepared in which the length direction was matched with the machine direction (MD) and the cross direction (CD), and the average value of the tensile strength of the three test pieces was determined for each direction. . The DRY strength of the water-decomposable nonwoven fabric according to the present invention is preferably 3 kg or more in both the MD and CD directions.
5. DRY Elongation The average value of the elongation at break of the test piece when the DRY strength was measured was determined. The DRY elongation of the water-decomposable nonwoven fabric according to the present invention is preferably 10% or more in both the MD and CD directions.
6). WET strength Tensile strength was determined under the same conditions as the DRY strength measurement conditions, except that the test piece was impregnated with ion exchange water corresponding to 200% of its weight. The WET strength of the water-decomposable nonwoven fabric according to the present invention is preferably 2 kg or more in both the MD and CD directions.
7). WET elongation The average value of the elongation at break of the test piece when the WET strength was measured was determined. The WET elongation of the water-decomposable nonwoven fabric according to the present invention is preferably 20% or more in both MD and CD directions.
8). Rigidity Measured according to the pliability A method (45 degree cantilever method) defined in Section 8.19.1 of JIS L 1096. The test result is a value obtained by averaging the measured values of the three test pieces whose length direction is matched with the MD direction and the measured values of the three test pieces whose length direction is matched with the CD direction.
9. Water disintegration (visual observation method)
One test piece of 100 × 100 mm is dried at 100 ° C. for 2 hours to obtain a dry weight (W ₁ ). The test piece after drying and 800 ml of distilled water are placed in a vertical separatory funnel shaker (SHKV-200 manufactured by IWKI) and shaken at a shaking speed of 240 rpm for 60 minutes. Thereafter, the inside of the separatory funnel is observed, and when the test piece is decomposed to such an extent that it does not retain its original shape, it is highly water-degradable (marked with ○), and whether the test piece is decomposed into at least three pieces is visually Depending on the number of fibers, the number of fibers that cannot be counted is moderately water-degradable (△ mark), and when the test piece is not moderately degradable, poorly water-degradable (× mark). ). The water-decomposable nonwoven fabric according to the present invention has high water-degradability or moderate water-decomposability.
(Dispersion rate measurement method)
Vertical x horizontal x height made of wire mesh of 2 mesh (particle size 1.5 mm, mesh opening 11.2 mm, space ratio 77.8%) in the separating funnel after visual observation and distilled water = 100 × 100 × 120 mm The sample is transferred to a cage and the test piece remaining in the cage is dried at 100 ° C. for 2 hours to obtain the dry weight (W ₂ ). This dry weight W _2, obtains the dispersion rate from dry weight W ₁ Metropolitan determined when visually observed by the following equation.
Dispersion rate (%) = {(W ₁ −W ₂ ) / W ₁ } × 100
10. Liquid retention rate Five sheets of specified filter paper are stacked on JIS P 3801 having a size of 100 × 100 mm, and a test piece (weight W ₀ ) of 100 × 100 mm is placed thereon. Using a buret, 1 cc of physiological saline is dropped at a rate of 1 cc / 2 seconds from a height of 10 mm using a burette. The weight (W ₁ ) of the test piece after 30 seconds from dropping is determined, and the liquid retention rate is calculated by the following formula.
Liquid retention rate (%) = {(W ₁ −W ₀ ) / W ₀ } × 100
The water-decomposable nonwoven fabric 1 according to the present invention has a high liquid retention rate by including pulp fibers and / or rayon fibers. The water-degradable nonwoven fabric 1 having a liquid retention rate higher than 20% is suitable for use as dry wipes or wet wipes.
11. Liquid absorption time At the time of measuring the retention rate, the time from the end of dropping of the physiological saline to the disappearance of the physiological saline from the surface of the test piece is measured. In Table 1, the measurement time of 1 second means that the time for which the water droplets disappeared was 1 second or less.
The water-decomposable nonwoven fabric 1 according to the present invention can be used for a body fluid treatment article as a liquid-permeable water-decomposable nonwoven fabric when the liquid absorption time is 3 seconds or less. Those having a time of 6 to 8 seconds can be used for body fluid treatment articles as a hardly liquid-permeable water-decomposable nonwoven fabric.
12 Diffusion area Dimension ML (mm) in which sanitary saline spreads in the MD direction on the surface of the test piece and dimension CL spread in the CD direction 30 seconds after the sanitary saline was dropped at the time of measuring the liquid retention rate (Mm) is measured, and the diffusion area is determined by the following equation.
Diffusion area = ML x CL
The water-decomposable non-woven fabric 1 according to the present invention tends to have a large diffusion area by including rayon and / or pulp fibers which are hydrophilic fibers. The water-decomposable nonwoven fabric 1 having a diffusion area larger than 2000 mm ² is suitable for use as dry wipes or wet wipes. The water-decomposable non-woven fabric 1 having a diffusion area smaller than 1800 mm ² is suitable for making a body fluid treatment article excellent in spot absorption.

Example 1
As the fiber mixture in the slurry of the process of FIG. 1, a fiber mixture containing 20% by weight of split fiber-1 which is an ultrafine thermoplastic synthetic fiber and 80% by weight of rayon fiber which is a chemical fiber having a fineness of 1.1 dtex is used. Using four rows of nozzles having a jet energy of 0.0063 kW / m ² as the jet treatment conditions in FIG. 1, the same composition as this fiber mixture, having a basis weight of 35 g / m ² and a thickness of 0.24 mm A water-decomposable nonwoven fabric having The evaluation results of this water-decomposable nonwoven fabric were as shown in Table 1.

(Example 2) to (Example 8)
In Examples 2 to 8, the composition of the fiber mixture in the slurry and the composition of the fiber mixture as the water-decomposable non-woven fabric were changed to those shown in Table 1 in place of Example 1, and hydrolysis was conducted in the same manner as in Example 1. A non-woven fabric was obtained. The evaluation results of these water-decomposable nonwoven fabrics are as shown in Table 1. The water-decomposable nonwoven fabric of Example 2 and Example 5 has a relatively high density and rigidity, and is suitable for use as a liquid-absorbing wipe.

Example 9
A water-degradable nonwoven fabric having the same composition as the water-degradable nonwoven fabric of Example 1 was obtained except that a water-soluble binder was added to the slurry used in Example 1 and the water-degradable nonwoven fabric contained 8% by weight of the water-soluble binder. . The evaluation results of this water-decomposable nonwoven fabric are as shown in Table 1. Since the DRY strength and WET strength are high and the liquid absorption time is high, this water-decomposable nonwoven fabric is used as a water-decomposable back material in body fluid treatment products. It is suitable for.

(Comparative Example 1) to (Comparative Example 4)
The nonwoven fabrics of these comparative examples are different from the composition of the fiber mixture in Example 1 in the slurry in the process of FIG. 1, and the composition is made under the same conditions as in Example 1. Table 1 shows the evaluation results of the nonwoven fabrics of Comparative Examples 1 to 4.

(Comparative Example 5) to (Comparative Example 6)
The nonwoven fabrics of these comparative examples have different injection treatment conditions from those of Example 1, and are otherwise made under the same conditions as in Example 1. The evaluation results of the nonwoven fabrics of Comparative Examples 5 and 6 are as shown in Table 1.

1 Water-decomposable nonwoven fabric 21 Slurry 22 Web

Claims (5)

A water-degradable nonwoven fabric comprising fibers that are mechanically entangled with each other, wherein the entangled fibers can be separated from each other when stirred in water;
10 to 50% by weight of the fibers are occupied by ultrafine thermoplastic synthetic fibers having a fineness of 0.01 to 0.5 dtex and a fiber length of 3 to 10 mm;
90-50% by weight of the fibers are occupied by at least one of chemical fibers having a fineness of 1-2 dtex and a fiber length of 5-20 mm and pulp fibers having a freeness of 600-770 cc. The water-decomposable non-woven fabric described above.   The water-decomposable nonwoven fabric according to claim 1, wherein the ultrafine thermoplastic synthetic fiber is formed by dividing a divided fiber.   The water-decomposable nonwoven fabric according to claim 1 or 2, wherein the water-decomposable nonwoven fabric contains 3 to 10% by weight of a water-soluble binder.   A high-pressure jet water stream is jetted onto a web obtained from a slurry formed by mixing the ultrafine thermoplastic synthetic fiber and at least one of the chemical fiber and the pulp fiber with water, and then the web is The water-decomposable nonwoven fabric according to claim 1 or 2, which is obtained by drying.   The water-decomposable nonwoven fabric according to claim 4, wherein the slurry contains a water-soluble binder.

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