JP6399998B2 - Water-decomposable nonwoven fabric and method for producing the same - Google Patents

Description

  The present invention relates to a water-decomposable nonwoven fabric and a method for producing the same.

  Conventionally, it has been proposed to use a water-decomposable non-woven fabric as a top sheet for wiping products such as wet tissues and cleaning wipers, and sanitary products such as paper diapers and sanitary napkins. The water-decomposable non-woven fabric used in such applications needs to satisfy both a predetermined wet strength that can withstand use and a predetermined water-decomposability so that it can be washed away after use.

  For example, Patent Document 1 describes a water-disintegrating nonwoven fabric that has sufficient strength in a wet state and that disintegrates when contacted with a large amount of water. The water-disintegrating nonwoven fabric described in Patent Document 1 is composed of regenerated cellulose fibers having a fiber length of 4 to 20 mm and pulp, and the fibers are entangled with each other by high-pressure water jet flow treatment, and is measured by JIS P 8135: 1998. The tensile strength is 100 to 800 gf / 25 mm. The water-disintegrating non-woven fabric described in Patent Document 1 has a high-pressure water jet flow specified on one side or both sides of the obtained web after forming the web with a wet paper machine in order to express high wet tensile strength. It is produced by strongly entangled the regenerated cellulose fibers by spraying at a range of additional specific energy, that is, 0.1 to 0.6 kWh / kg per side. However, the water-disintegrating non-woven fabric described in Patent Document 1 may be clogged due to the regenerated cellulose fibers that are strongly entangled, depending on the thickness of the piping such as a toilet piping. It was not enough. Furthermore, the water-decomposable nonwoven fabric used in wiping products and sanitary products has a good texture and texture in addition to having sufficient wet tensile strength and good ease of loosening in a water stream as described above. Is desired.

JP-A-9-228214

  The present invention solves the above-mentioned problems of the prior art, and has sufficient wet tensile strength to withstand the load applied during use such as cleaning work and wiping work in a state wet with a small amount of moisture, It has good ease of loosening when it is washed away in a flush toilet after use, and also has a texture and texture (ie, feel of texture, feel of softness when touched by people) An object of the present invention is to provide a water-decomposable nonwoven fabric with improved water resistance and a method for producing the same.

This inventor consists of 15-30 mass% of regenerated cellulose fibers having a fiber length of 3-4 mm and a fineness of 0.3 dtex or less, and 70-85 mass% of pulp, and has a basis weight of 35-50 g / m ^2. The present inventors have found that the above-described problems can be solved by using a nonwoven fabric having the present invention and have completed the present invention.

That is, in one embodiment, the present invention comprises 15 to 30% by mass of regenerated cellulose fiber having a fiber length of 3 to 4 mm and a fineness of 0.3 dtex or less and 70 to 85% by mass of pulp, and 35 to 50 g / m. It is a water-degradable nonwoven fabric having a basis weight of ² and having a wet tensile strength of 1.2 N / 25 mm or more, having a looseness within 100 seconds in a looseness test of JIS P 4501: 1993.

  The water-decomposable nonwoven fabric of the present invention requires a binder and a paper strength enhancer even though the regenerated cellulose fiber has a relatively short fiber length of 3 to 4 mm and a relatively small fineness of 0.3 dtex or less. In addition, it exhibits sufficient wet tensile strength during use in a state wet with a small amount of water, and also exhibits sufficient water decomposability after use. Furthermore, as described above, the water-decomposable nonwoven fabric of the present invention has high density by including regenerated cellulose fibers having an ultrafine and short fiber length in the above-mentioned specific blending amount, and therefore, good texture and good texture. Have When the water-decomposable nonwoven fabric of the present invention has a good texture, for example, it is possible to reduce the psychological anxiety that dirt wiped off using the nonwoven fabric permeates the nonwoven fabric and adheres to the user's hand.

In another embodiment, the present invention is a method for producing the water-decomposable nonwoven fabric,
(A) A slurry containing a regenerated cellulose fiber having a fiber length of 3 to 4 mm and a fineness of 0.3 dtex or less and pulp in a mass ratio of 15:85 to 30:70 at a fiber basis weight of 35 to 50 g / m ^2. Forming a web by wet papermaking,
(B) A step of hydroentangling the web obtained in step (A) with an energy of 0.05 kWh / kg to 0.1 kWh / kg to entangle the fibers, and (C) a hydroentangled web. Drying step,
It is a method including.

  The water-decomposable nonwoven fabric of the present invention has sufficient wet tensile strength to withstand the load applied during use in a wet state, and exhibits good ease of loosening when thrown away into water after use, and is also good. It has a good texture and a good texture.

Drawing 1 is a figure showing typically one embodiment of the nonwoven fabric manufacturing device used for the manufacturing method of the water-decomposable nonwoven fabric of the present invention. FIG. 2 is a perspective view showing an example in which water is jetted from the jet nozzle 13 onto the web 20. FIG. 3 is a diagram illustrating an example of the nozzle hole of the injection nozzle. FIG. 4 is a diagram for explaining the principle that fibers in a web are entangled by a water flow jetted from a nozzle. FIG. 5 is a schematic cross-sectional view in the width direction of the web on which the water flow is jetted.

Some of the embodiments of the invention related to the present invention are shown below.
[Aspect 1]
It consists of 15 to 30% by mass of regenerated cellulose fiber having a fiber length of 3 to 4 mm and a fineness of 0.3 dtex or less, and 70 to 85% by mass of pulp, and has a basis weight of 35 to 50 g / m ² , JIS P 4501 : A water-degradable nonwoven fabric having a looseness of 100 seconds or less in a 1993 ease of looseness test and a wet tensile strength of 1.2 N / 25 mm or more.
According to the aspect 1, it has sufficient wet tensile strength to withstand the load applied during use in a wet state, and exhibits good ease of loosening when it is poured into water after use and discarded.

[Aspect 2]
The water-decomposable nonwoven fabric according to aspect 1, wherein the regenerated cellulose fiber has a fineness of 0.1 to 0.3 dtex.
According to aspect 2, it is difficult to produce regenerated cellulose fibers having a fineness of less than 0.1 dtex with good productivity, and when the fineness of the regenerated cellulose fibers exceeds 0.3 dtex, the water disintegration property of the nonwoven fabric Results in an inferior nonwoven fabric.

[Aspect 3]
A method for producing the water-decomposable nonwoven fabric according to aspect 1,
(A) A slurry containing a regenerated cellulose fiber having a fiber length of 3 to 4 mm and a fineness of 0.3 dtex or less and pulp in a mass ratio of 15:85 to 30:70 at a fiber basis weight of 35 to 50 g / m ^2. Forming a web by wet papermaking,
(B) A step of hydroentangling the web obtained in step (A) with an energy of 0.05 kWh / kg to 0.1 kWh / kg to entangle the fibers, and (C) a hydroentangled web. Drying step,
Including methods.
According to the aspect 3, there is provided a water-decomposable nonwoven fabric that has a wet tensile strength sufficient to withstand a load applied during use in a wet state and exhibits good ease of loosening when poured into water after use and discarded. The

The water-decomposable nonwoven fabric of the present invention has a basis weight of 35 to 50 g / m ² and is 15 to 30% by mass, preferably 15 to 20% by mass of 3 to 4 mm fiber based on the total mass of the nonwoven fabric. It consists of regenerated cellulose fibers having a length and fineness of 0.3 dtex or less, and 70 to 85 mass%, preferably 80 to 85 mass% pulp. When the water-decomposable nonwoven fabric of the present invention is brought into contact with a large amount of water, the pulp swells and the pulp is detached from the nonwoven fabric, so that the entangled regenerated cellulose fibers are easily unraveled. When the nonwoven fabric contains regenerated cellulose fibers in an amount of more than 30% by mass, the number of entanglement points between the regenerated cellulose fibers is excessively large, and thus the entangled regenerated cellulose fibers are difficult to loosen. Depending on the thickness of the piping such as piping, the piping may be clogged, and the ease of loosening is not sufficient. Moreover, when the number of entanglement between regenerated cellulose fibers becomes too large, the touch of the nonwoven fabric is impaired. Furthermore, when the basis weight of the nonwoven fabric is 35 g / m ² , it is difficult to achieve sufficient wet tensile strength. When the basis weight exceeds 50 g / m ² , the number of entangled points between the regenerated cellulose fibers is excessively large, and thus the entangled regenerated cellulose fibers are difficult to be loosened. Depending on the size, there is a risk of clogging the piping, and the ease of loosening is not sufficient.

  In the water-decomposable nonwoven fabric of the present invention, the regenerated cellulose fiber has a fiber length of 3 to 4 mm. When the fiber length of the regenerated cellulose fiber is less than 3 mm, it is difficult to sufficiently entangle the regenerated cellulose fibers with each other. Therefore, it is sufficient to withstand the load during use such as cleaning work and wiping work. Achieving wet tensile strength is difficult. Since the regenerated cellulose fiber having a fiber length exceeding 4 mm has low dispersibility, a nonwoven fabric having uneven texture and wet tensile strength is produced. In addition, due to the low dispersibility of the regenerated cellulose fiber having a fiber length exceeding 4 mm, it is difficult for the obtained nonwoven fabric to pass the flammability test of JIS P 4501: 1993. The water-decomposable non-woven fabric of the present invention includes an extremely fine regenerated cellulose fiber having a fiber length of 3 to 4 mm, so that, for example, when used as a wiping product such as a wet tissue or a cleaning wiper, Can remove dirt to details. In addition, the water-decomposable nonwoven fabric of the present invention has an excellent feature that it is easy to scrape large dirt by having a concavo-convex structure having fine ridges and grooves on the surface by the hydroentanglement process described later.

  In the water-decomposable nonwoven fabric of the present invention, the regenerated cellulose fiber has a fineness of 0.3 dtex or less, preferably 0.1 to 0.3 dtex. It is difficult to produce regenerated cellulose fibers having a fineness of less than 0.1 dtex with good productivity. When the fineness of the regenerated cellulose fiber exceeds 0.3 dtex, a nonwoven fabric inferior in water disintegrability of the nonwoven fabric is brought about. Since the regenerated cellulose fiber is an ultrafine fiber having a fineness of 0.3 dtex or less, preferably 0.1 to 0.3 dtex, it results in a water-degradable nonwoven fabric having a smooth surface. In general, at the same mass% and the same fiber length, the smaller the fineness, the greater the number of fibers per unit area of the nonwoven fabric. Therefore, the above-mentioned fineness of the regenerated cellulose fiber has a good texture. Bring a nonwoven. On the other hand, at the same mass% and the same fiber length, the greater the fineness, the smaller the number of fibers per unit area of the nonwoven fabric, and hence the number of entanglement points between the regenerated cellulose fibers. Therefore, when the fiber length of the regenerated cellulose fiber exceeds 4 mm and the fineness exceeds 0.3 dtex, a nonwoven fabric having a wet tensile strength of 1.2 N / 25 mm or more cannot be produced.

  The water-decomposable nonwoven fabric of the present invention has an ease of loosening within 100 seconds, preferably within 90 seconds, more preferably within 80 seconds, and even more preferably 70 seconds, in the ease of loosening test of JIS P 4501: 1993. Has ease of loosening within. If the ease of loosening exceeds 100 seconds, the pipe may be clogged depending on the thickness of the toilet pipe or the like. There is no particular lower limit to the ease of loosening. Note that JIS P 4501: 1993, “1. Quality” of toilet paper, Table 1 describes that toilet paper should satisfy the standard of ease of loosening within 100 seconds. The nonwoven fabric has the same ease of loosening as toilet paper.

With respect to the water-decomposable nonwoven fabric of the present invention, the wet tensile strength is measured according to “7.1 General Method” of “Paper and Paperboard—Wet Tensile Strength Test Method” of JIS P 8135: 1998, except for the following differences. The
Difference: A test piece having a width of 25 mm and a length of 150 mm is cut out from the produced nonwoven fabric. A test piece is immersed in 250 mass% distilled water by mass ratio, and then the test piece is allowed to stand on a wire mesh for 1 minute. Next, under the conditions of a temperature of 20 ° C. and a relative humidity of 65%, the test piece was set on a Tensilon type tensile tester with a chuck interval of 100 mm, the test piece was pulled at a pulling speed of 100 mm / min, and the tensile strength at break of the test piece was Measure (N).

  The regenerated cellulose fiber constituting the water-decomposable nonwoven fabric of the present invention is not particularly limited as long as it has a fiber length and fineness within the above ranges. Examples of the regenerated cellulose fiber include viscose rayon, copper ammonia rayon, lyocell (registered trademark), and tencel (registered trademark). The water-decomposable nonwoven fabric of the present invention can contain one type or two or more types of regenerated cellulose fibers.

  The kind of pulp constituting the water-decomposable nonwoven fabric of the present invention is not particularly limited, and examples of the pulp include wood pulp such as softwood pulp and hardwood pulp, non-wood pulp such as walla pulp, bagasse pulp, reed pulp, kenaf pulp , Mulberry pulp, bamboo pulp, hemp pulp, cotton pulp (for example, cotton linter) and the like. The pulp can be non-beaten pulp, beaten pulp, or a combination thereof. Softwood pulp is preferred in terms of water decomposability.

  The non-beaten pulp preferably has a Canadian Standard Freeness (CSF) of 700 mL or more. The Canadian standard freeness is measured in accordance with JIS P 811-2: 2012 "Pulp-Freeness test method-Part 2: Canadian standard freeness method". The average fiber length of the non-beaten pulp is not particularly limited, but generally 2 to 4 mm is preferable from the viewpoint of economy and productivity. The beaten pulp is a pulp obtained by beating non-beaten pulp by a method such as free beating and viscous beating, and has a main body portion and a microfiber portion extending from the main body portion. When the wet tissue contains beaten pulp, the wet strength and dry strength of the wet tissue are improved. The beaten pulp preferably has a Canadian standard freeness of 500 to 680 mL, and more preferably has a Canadian standard freeness of 550 to 650 mL. If the Canadian standard freeness is less than the above lower limit value, it is not preferable because a stiff nonwoven fabric with poor feel and softness is produced. When the Canadian standard freeness exceeds the upper limit, a water-decomposable nonwoven fabric having sufficient wet tensile strength cannot be obtained.

The water-decomposable non-woven fabric of the present invention has a basis weight of 35~50g / ^{m 2.} If the basis weight of the nonwoven fabric is less than 35 g / m ² , it will not provide sufficient wet tensile strength to withstand the load during use. When the basis weight exceeds 50 g / m ² , a stiff nonwoven fabric inferior in feel and softness is brought about. The water-decomposable nonwoven fabric of the present invention preferably has a basis weight of 35 to 45 g / m ^{2 in} terms of water-decomposability.

The water-decomposable nonwoven fabric of the present invention is
(A) A slurry containing a regenerated cellulose fiber having a fiber length of 3 to 4 mm and a fineness of 0.3 dtex or less and pulp in a mass ratio of 15:85 to 30:70 at a fiber basis weight of 35 to 50 g / m ^2. Forming a web by wet papermaking,
(B) A step of hydroentangling the web obtained in step (A) with an energy of 0.05 kWh / kg to 0.1 kWh / kg to entangle the fibers, and (C) a hydroentangled web. Drying step,
It can manufacture by the method containing.

Hereinafter, the manufacturing method of the water-decomposable nonwoven fabric of the present invention will be described in more detail with reference to the drawings.
The method for producing a water-decomposable nonwoven fabric of the present invention can be carried out using a nonwoven fabric manufacturing apparatus 1 schematically shown in FIG. In addition, FIG. 1 is the figure which showed typically one Embodiment of the nonwoven fabric manufacturing apparatus which can be used in order to manufacture the water-decomposable nonwoven fabric of this invention, and a nonwoven fabric manufacturing apparatus is not limited to the aspect shown in FIG.

  In producing the water-decomposable nonwoven fabric of the present invention, first, a slurry containing the regenerated cellulose fiber having the above fiber length and fineness and pulp at a mass ratio of 15:85 to 30:70 is prepared. The obtained slurry is supplied from the raw material supply head 10 of the nonwoven fabric manufacturing apparatus 1 onto the support 11 of the web forming conveyor and is deposited on the support 11. The support body 11 can be comprised from a wire mesh, a blanket, etc., for example. The slurry deposited on the support 11 is appropriately dehydrated by the two suction boxes 12 to form a web 20 containing moisture. Next, the web 20 is passed between the two nozzles 13 disposed on the support 11 and the two suction boxes 13 disposed on the opposite side of the nozzle 13 with the support 11 interposed therebetween. , Hydroentangle the web. In the present invention, the water flow injected from the nozzle 13 has specific energy as described above.

  FIG. 2 is a perspective view showing an example in which water is jetted from the nozzle 13 to the web 20. The nozzle 13 injects a plurality of water streams 31 arranged in the width direction (CD) of the web 20 toward the web 20 on the support 11. As a result, a plurality of grooves 22 extending in the longitudinal direction or the machine direction (MD) are formed on the upper surface of the web 20 along the width direction of the web 20. Moreover, when a water flow hits the web 20, the groove part 22 will be formed in the web 20 as mentioned above, and the fibers of the web 20, especially the regenerated cellulose fibers will be entangled, and the wet strength of the web 20 will become high.

  FIG. 3 schematically shows an example of nozzle holes provided in the nozzle 13. For example, the nozzle holes 121 of the nozzle 13 are arranged in a line in the width direction (CD) of the web 20. The hole diameter of the nozzle 13 is preferably 90 to 150 μm. When the hole diameter of the nozzle 13 is smaller than 90 μm, there may be a problem that the nozzle is easily clogged. Further, when the hole diameter of the nozzle 13 is larger than 150 μm, there may be a problem that the processing efficiency is deteriorated. The hole pitch of the nozzle 13 (distance between the centers of adjacent holes) is preferably 0.5 to 1.0 mm. When the hole pitch of the nozzles 13 is smaller than 0.5 mm, there is a case where the pressure resistance of the nozzles is reduced and the nozzles are broken. Moreover, when the hole pitch of the nozzle 13 is larger than 1.0 mm, the problem that the entanglement between fibers may become inadequate may arise. The distance between the tip of the nozzle 13 and the upper surface of the web 20 is preferably 10 to 20 mm. If the distance between the tip of the nozzle 13 and the upper surface of the web 20 is less than 10 mm, the fibers that bounce back to the tip of the nozzle are likely to adhere, and a problem of entanglement failure may occur. Further, if the distance between the tip of the nozzle 13 and the upper surface of the web 20 is greater than 20 mm, the water flow energy may be reduced, and the water flow may not penetrate the fiber web, resulting in a problem of entanglement failure.

  The energy of the water stream 31 ejected from the nozzle toward the web 20 is preferably 0.05 to 0.1 kWh / kg. This energy is a value converted into the amount per 1 kg of the dry mass of the web treated by the water flow. A person skilled in the art can determine the energy of the water flow based on the injection pressure at the tip of the nozzle, the injection flow rate of the nozzle, the web processing speed, the web width, the basis weight and the like.

  When the energy of the water flow is less than 0.05 kWh / kg, it is difficult to obtain a water-decomposable nonwoven fabric having sufficient wet tensile strength at the time of use. If the energy of the water flow exceeds 0.1 kWh / kg, the nonwoven fabric becomes too stiff, and it becomes difficult for the nonwoven fabric to pass the flammability test of JIS P 4501: 1993, and also in terms of feel and softness. Inferior.

  With reference to FIG. 4, the principle of entanglement of fibers in the web 21 and the principle of forming an uneven structure having fine ridges and grooves on the upper surface of the web 20 will be described. It is not limited. As shown in FIG. 4, when the nozzle 13 ejects the water flow 31, the water flow 31 passes through the support 11. As a result, the fibers of the web 20 are drawn around the portion 42 where the water flow 31 passes through the support 11. As a result, the fibers of the web 20 gather toward the portion 32 where the water flow 31 passes through the support 11, and the fibers are entangled. Since the strength of the web 20 is increased when the fibers of the web 20 are entangled with each other, the wet strength can be increased without adding a binder or a paper strength enhancer to the slurry. Moreover, the uneven structure which has a fine collar part and a groove part is formed in the upper surface of the web 20 with a water flow. The concavo-convex structure having fine ridges and grooves is retained even after the web 20 is dried, and a nonwoven fabric having a fine concavo-convex structure on the surface is obtained.

  In the concavo-convex structure, the pitch of the ridges (or grooves) can be arbitrarily adjusted based on the pitch of the nozzles 13 of the nonwoven fabric manufacturing apparatus. In consideration of ease of formation, wet tissue wiping, and the like, the pitch of the ridges (or grooves) is preferably 0.5 to 1.0 mm. In the above concavo-convex structure, the height of the top of the ridge and the height of the bottom of the groove can be arbitrarily adjusted by the pressure of water sprayed from the nozzle, etc. The difference between the height of the top and the height of the bottom of the groove is preferably 0.10 mm or more, and more preferably 0.15 to 0.40 mm. The height of the top of the flange and the height of the bottom of the groove are measured by a laser displacement meter. Examples of the laser displacement system include a high-precision two-dimensional laser displacement meter LJ-G series (model: LJ-G030) manufactured by Keyence Corporation.

  FIG. 5 shows a cross-section in the width direction of the web 20 at a position after passing between the two nozzles 13 and the two suction boxes 13 (position 21 in FIG. 1). An uneven structure having fine ridges and grooves is formed on the upper surface of the web 20 by the water flow.

  The web processed by the water flow is then transferred to the first conveyor 15 by the suction pickup 14 as shown in FIG. The web 20 is then transferred to the second conveyor 16 and transferred to the heated cylindrical surface of the dryer 17. The dryer 17 can be, for example, a Yankee dryer. The web 20 is dried to a predetermined moisture content by the dryer 17. The heating temperature can be, for example, about 120 ° C to about 160 ° C. The dried web 20 is then wound by a winder 18 as a nonwoven fabric. In production, the fiber composition, basis weight, and the like of the nonwoven fabric can be adjusted by adjusting the composition of the raw material and the supply amount of the raw material.

  By cutting the nonwoven fabric manufactured as described above into a predetermined size according to the application, the nonwoven fabric is wiped with wet tissue, wipes for cleaning, hygiene products such as disposable diapers, sanitary napkins, etc. It can be suitably used as a sheet. When the water-decomposable nonwoven fabric of the present invention is used as, for example, a wet tissue, the nonwoven fabric is cut into a desired size, the cut sheet is folded, and the wet tissue is completed by impregnating with a chemical solution. The water-decomposable nonwoven fabric of the present invention can be thrown away into water after use in a flush toilet or the like.

  The above description is merely an example of the present invention, and the present invention is not limited to the above embodiment.

  Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to these examples.

In Examples and Comparative Examples, basis weight, wet tensile strength and water disintegration property were determined by the following methods.
[Basis weight]
The basis weight is calculated by cutting 10 test pieces having a size of 10 cm × 10 cm from the manufactured nonwoven fabric raw material, measuring the mass of each test piece, and dividing the mass of the test piece by the area. The average value was obtained, and the average value was taken as the basis weight.

[Wet tensile strength]
The wet tensile strength is measured according to “7.1 General Method” of “Paper and Paperboard—Wet Tensile Strength Test Method” of JIS P 8135: 1998, except for the following differences.
Difference: From a manufactured nonwoven fabric, a test piece having a width of 25 mm × length of 150 mm whose longitudinal direction is the machine direction of the original fabric and a width of 25 mm × length of 150 mm where the longitudinal direction is the width direction of the original fabric Cut a test specimen of size. A test piece is immersed in 250 mass% distilled water by mass ratio, and then the test piece is allowed to stand on a wire mesh for 1 minute. Next, under the conditions of a temperature of 20 ° C. and a relative humidity of 65%, the test piece was set on a Tensilon type tensile tester with a chuck interval of 100 mm, the test piece was pulled at a pulling speed of 100 mm / min, and the tensile strength at break of the test piece was Measure (N). The average value of the tensile strength of each of the three test pieces in the machine direction and the width direction was taken as the wet tensile strength in the machine direction and the width direction.
In addition, the wet tensile strength was measured using the autograph and AGS-1kNG by Shimadzu Corporation as a tensile tester.

[Hydrolysis]
According to JIS P 4501: 1993 “Toilet paper”, the ease of loosening was evaluated. That is, the test piece was produced by cutting out a test piece having a size of 114 mm × 114 mm from the manufactured nonwoven fabric original fabric. The test conditions were a temperature of 20 ° C. and a relative humidity of 65%. A 300 mL beaker containing 300 mL of water (water temperature 20 ° C.) is placed on a magnetic stirrer (stirrer TTP for paper loosening test manufactured by AS ONE Co., Ltd.), and the rotation speed of the rotor is 600 rpm. After adjusting, the test piece was put into water and a stopwatch was pushed. After the rotor speed has fallen once due to the resistance of the test piece, it rises as the test piece loosens, and when the speed has recovered to 540 revolutions, the stopwatch is stopped and the time is measured in units of 1 second. . The results of ease of loosening were expressed as an average value of five tests. A shorter measurement time means that the nonwoven fabric is more easily loosened. When the rotation speed did not recover to 540 even after 300 seconds, the measurement was interrupted and the result was expressed as “300>”.

  Hereafter, the preparation methods of the nonwoven fabric of an Example and a comparative example are demonstrated.

<Example 1>
The nonwoven fabric of Example 1 was produced using the nonwoven fabric manufacturing apparatus 1 according to one embodiment shown in FIG. Raw material slurry containing 80% by weight unbeaten softwood bleached kraft pulp (NBKP, CSF: 770 mL) and 20% by weight of rayon fibers (fiber length 3 mm, fineness 0.3 dtex, Daiwabo Rayon Co., Ltd. corona) Was prepared. The slurry was supplied onto the web forming belt (Nippon Filcon Co., Ltd. OS80) using the raw material head, and the slurry deposited on the web forming belt was dehydrated with a suction box to form a web. The moisture content of the web at this time was 80%. Thereafter, a stream of equal energy was sprayed from two nozzles onto the web. The nozzle hole diameter of each nozzle was 92 μm, the nozzle hole pitch was 0.5 mm, the spray pressure at the nozzle tip was 30 kg / cm ² , and the distance between the nozzle tip and the upper surface of the web was 20 mm. The passing speed (paper making speed) of the web was 80 m / min. Next, the web is transferred to the first conveyor by suction pickup, transferred from the first conveyor to the second conveyor, and then transferred to the cylindrical surface of the Yankee dryer heated to 120 ° C. The web was dried. The dried web was wound as a nonwoven fabric by a winder.
For the nozzles used in Example 1 and Examples 2 to 9 and Comparative Examples 1 to 3 described later, the energy E (kWh / kg) of the water flow injected from one nozzle is calculated according to the following formula (1), The calculated energy is shown in Table 1 below as the water entangling treatment energy per time. Regarding the nonwoven fabrics of Examples 2 to 9 and Comparative Examples 1 to 3 below, the hydroentanglement energy was obtained in the same manner as in Example 1 and listed in Table 1.

<Example 2>
A nonwoven fabric was produced in the same manner as in Example 1 except that the fiber length of the rayon fiber was 4 mm.

<Example 3>
A nonwoven fabric was produced in the same manner as in Example 1 except that the amount of rayon fiber was 15% by mass based on the total amount of pulp and rayon fiber.

<Example 4>
A nonwoven fabric was produced in the same manner as in Example 1 except that the amount of rayon fiber was 30% by mass based on the total amount of pulp and rayon fiber.

<Example 5>
The nonwoven fabric of Example 5 is a nonwoven fabric produced in the same manner as in Example 1 except that the basis weight of the nonwoven fabric was 35 g / m ² .

<Example 6>
The nonwoven fabric of Example 6 is a nonwoven fabric produced in the same manner as in Example 1 except that the basis weight of the nonwoven fabric was 50 g / m ² .

<Example 7>
Example 1 except that a blend of unbeaten softwood bleached kraft pulp (NBKP, CSF: 770 mL) and beaten softwood bleached kraft pulp (NBKP, CSF: 600 mL) with a mass ratio of 50:50 was used as the pulp. A nonwoven fabric was prepared in the same manner as described above.

<Example 8>
A nonwoven fabric was produced in the same manner as in Example 1 except that the water entangling treatment energy per time was 0.05254 kWh / kg.

<Example 9>
A nonwoven fabric was produced in the same manner as in Example 1 except that the water entangling treatment energy per one time was 0.09397 kWh / kg.

<Comparative Example 1>
A nonwoven fabric was produced according to Example 1 described in Japanese Patent No. 3129192. That is, in a laboratory hand-drawing machine at a concentration of 0.2% using a mixture of 70% by weight of rayon fiber having a fiber length of 7 mm and a fineness of 1.5 denier and 30% of CSF 200 ml of beef conifer bleached kraft pulp fiber. Papermaking was performed to prepare a web having a basis weight of 50 g / m ² of 25 cm × 25 cm and dried to a moisture content of 4%. This web is placed on a transfer conveyor made of a 25 mesh plain woven wire mesh, and while transferring the web at a speed of 15 m / min, nozzle holes with a hole diameter of 0.1 mm are arranged in a staggered pattern at intervals of 0.64 mm. Using three rows of water jet injection devices, a high pressure water jet was injected at a water pressure of 35 kg / cm ² so that the water jet penetrated from the front surface to the back surface of the web. Then, it dried with the hot air dryer of the temperature of 150 degreeC, and the water disintegrating nonwoven fabric was obtained.

<Comparative Example 2>
A nonwoven fabric was produced in the same manner as in Example 1 except that the fiber length of the rayon fiber was 4 mm and the fineness was 0.7 dtex.

<Comparative Example 3>
A nonwoven fabric was produced in the same manner as in Comparative Example 2 except that the water entangling treatment energy per one time was 0.18793 kWh / kg.

  From Table 1, the nonwoven fabrics of Examples 1 to 9 have a tensile strength in the transport direction and orthogonal direction of the wet tissue of 1.2 N / 25 mm or more, and the ease of loosening is within 100 seconds. It can be seen that both water solubility and water solubility are compatible. Moreover, the nonwoven fabric manufactured by Examples 1-9 had the uneven structure which has a ridge and a groove | channel on one side, and was excellent in wiping property. Comparative Example 1 according to Example 1 described in Japanese Patent No. 3129192 has a higher wet tensile strength than Example 1, but its water disintegrability is “300>” and is not easily loosened. In Comparative Example 2, the water disintegration property was equivalent to that of Example 7, but the wet tensile strength was insufficient. Similar to Comparative Example 1, Comparative Example 3 had a higher wet tensile strength than Example 1, but had a water disintegrability of “300>” and was not easily loosened.

  The water-decomposable non-woven fabric of the present invention has sufficient wet tensile strength at the time of use, and can be poured into water after use, so that it can be thrown away into water, wet tissue, wipes such as cleaning wipers, paper diapers, sanitary napkins, etc. It can be suitably used as a top sheet for sanitary products.

DESCRIPTION OF SYMBOLS 1 Nonwoven fabric manufacturing apparatus 10 Raw material supply head 11 Support body 12 Suction box 13 Nozzle 14 Suction pickup 15 First transport conveyor 16 Second transport conveyor 17 Dryer 18 Winder 20 Web

Claims (9)

It consists of 15 to 30% by mass of regenerated cellulose fiber having a fiber length of 3 to 4 mm and a fineness of 0.3 dtex or less, and 70 to 85% by mass of pulp, and has a basis weight of 35 to 50 g / m ² , JIS P 4501 : A water-decomposable nonwoven fabric having a wet tensile strength of 1.2 N / 25 mm or more, having a concavo-convex structure on one side, and having a concavo-convex structure on the other side. Has a concavo-convex structure and is a water-degradable nonwoven fabric . The water-decomposable nonwoven fabric according to claim 1, wherein the regenerated cellulose fiber has a fineness of 0.1 to 0.3 dtex. The water-decomposable nonwoven fabric according to claim 1 or 2, wherein the concavo-convex structure has a plurality of ridges and a plurality of grooves alternately arranged in parallel to each other. The water-decomposable nonwoven fabric according to claim 3, wherein a difference between the height of the top of the ridge and the height of the bottom of the groove in the concavo-convex structure is 0.15 to 0.40 mm. The water-decomposable nonwoven fabric according to claim 3 or 4, wherein a pitch of the plurality of ridges is 0.5 to 1.0 mm. It is a manufacturing method of the water-decomposable nonwoven fabric according to claim 1,
(A) 35-50 g / m of a slurry containing a regenerated cellulose fiber having a fiber length of 3-4 mm and a fineness of 0.3 dtex or less and pulp in a mass ratio of 15: 85-30: 70 ² Forming a web by wet papermaking with a fiber basis weight of
(B) A flow of water from a nozzle having a plurality of nozzle holes arranged in a line in the width direction of the web in the web obtained in step (A) is 0.05 kWh / kg to 0.1 kWh / kg. A step of hydroentangling the web to entangle the fibers by spraying with the energy of, and
(C) drying the hydroentangled web,
Including
In the step (B), the distance between the tip of the nozzle and the upper surface of the web is 10 to 20 mm,
A method in which an uneven structure is formed on one side of the web by the hydroentanglement process. The method according to claim 6, wherein a hole pitch of the nozzle is 0.5 to 1.0 mm. The method according to claim 6 or 7, wherein the concavo-convex structure has a plurality of ridges and a plurality of grooves alternately arranged in parallel to each other. The method according to claim 8, wherein a difference between a height of a top portion of the flange portion and a height of a bottom portion of the groove portion in the uneven structure is 0.15 to 0.40 mm.

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