JPH11152667A - Water-disintegrable nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-disintegrable nonwoven fabric that can retain the strength withstanding the operation such as washing and the like in the dried or moisturized state and disintegrates the fibers constituting the woven fabric from each other in a large amount of water flow. SOLUTION: The first web formed by subjecting a mixed fiber comprising 20-80 wt.% of the first regenerated cellulose fibers and 80-20 wt.% of wood pulp fibers to the wet type paper-making process and the second web layer formed by subjecting a mixed fiber comprising 20-80 wt.% of the second regenerated cellulose fibers and 80-20 wt.% of wood pulp fibers to the wet type paper- making process are laminated on the perforated and conveyable supporter and the laminated webs are treated with the high pressure columnar water flow from one face or from both faces to entangle the fibers into the integrated nonwoven fabric. In the resultant nonwoven fabric, the ratio (L/D) of the fiber lengths of the first and the second regenerated cellulosic fibers L1 and L2 in mm to the fiber diameters of the first and the second regenerated cellulosic fibers D1 and D2 in mm range from 135 to 1,750 and these L/D values satisfy the following formula: (L1 /D1 )>(L2 /D2 ).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-disintegratable nonwoven fabric which has a strength which can withstand operations such as cleaning in a dry state and a wet state, and which can disintegrate fibers constituting the nonwoven fabric in a large amount of water flow. About. More specifically, strength enough to withstand practical use when dry or when wetted with water or chemicals for use as a wet tissue, cloth, or cleaning wiper, or when used as a top sheet for disposable diapers or sanitary napkins And a water-disintegratable nonwoven fabric which can be easily disaggregated in a large amount of water flow in a toilet or the like.

[0002]

2. Description of the Related Art In general, wet products such as wet tissues, wipes, and wipers for cleaning, and many hygiene products such as disposable diapers and sanitary napkins are discarded as garbage after use. For example, considering the use of wet wipes, treatment with a wet wiper is superior to stool wiping compared to treatment with toilet paper,
It has excellent performance such as low skin irritation. However, it has a drawback that it cannot be flushed to a flush toilet after use, and disposal treatment tends to be unsanitary.

[0003] For this reason, generally used wipes are used only for very limited uses such as baby wipes and nursing wipes for nursing care. Not in. As a method of improving the wiping property and skin irritation of the toilet paper, a method of impregnating the toilet paper with a humectant or the like has been proposed, but has not yet reached a performance comparable to the case where a wet wiper is used.

[0004] Examples of the water-disintegrable non-woven fabric usable as a top sheet for wet tissues and sanitary articles include, for example, JP-A-47-9486, JP-A-1-168999, JP-A-2-149237, and JP-A-3-149. 277
No. 335, Japanese Patent Application Laid-Open No. 4-370300, Japanese Patent Application No. 8-142825, Japanese Patent Application No. 9-48870, and the like have been proposed.

In Japanese Patent Application Laid-Open No. 47-9486, polyvinyl alcohol and borax react by spraying a binder solution containing polyvinyl alcohol and borax onto a sheet and then heating and drying the sheet. It is described that this hydrolyzed paper is useful as an absorbent pad for napkins, diapers and the like. However, this water-disintegrated paper does not have a strength enough to withstand a mechanically-cleaning operation such as that used for wiping a butt or a cleaning sheet for a toilet or the like when impregnated with water.

JP-A-1-168999 proposes using a calcium salt of water-insoluble carboxymethylated pulp as a base paper. However, in the water-disintegrated paper proposed in the publication, the upper limit of the water content in the cleaning liquid is 60%, and it is necessary to add at least 30% of an organic solvent such as alcohol. The use in which the liquid can be used is limited, and it is particularly difficult to use it for uses such as wiping the ass. Also, by adding an organic solvent, it is necessary to add a large amount of fragrance to eliminate the smell of the organic solvent, and the strength may be reduced during cleaning work due to an increase in the percentage of water due to volatilization of the organic solvent. There is a disadvantage that. Furthermore, the adverse effect on the human body due to the high concentration of the organic solvent cannot be ignored.

[0007] Japanese Patent Application Laid-Open No. 2-149237 discloses that a hydrolyzed paper containing a specific water-soluble binder is impregnated with an aqueous solution containing a specific metal ion and an organic solvent.
We propose to obtain a water-disintegratable cleaning article that has sufficient strength to perform cleaning work in a state of being impregnated with a water-containing cleaning agent, and has a water-disintegrating performance that can be easily washed away in a toilet or the like. I have. However, this cleaning article needs to contain specific metal ions and an organic solvent in the impregnating liquid to be impregnated into the hydrolyzed paper, and its use is extremely limited because the impregnating liquid cannot be freely selected according to the purpose. It was done. Further, using a water-soluble binder having a carboxyl group as a specific water-soluble binder, such as water-soluble binder carboxymethyl cellulose, carboxyethyl cellulose, polysaccharide derivatives such as alkali metal salts such as carboxymethylated starch, synthetic polymers, natural polymers However, the blending of these binders has the disadvantage that the texture of the sheet becomes hard.

In Japanese Patent Application Laid-Open No. 3-277335, water-soluble carboxymethylcellulose calcium is used as a paper-strength enhancer for a base paper, and calcium ions coexist in the washing liquid, whereby sufficient washing can be achieved even in a washing liquid having a high water content. A wiping material that exhibits strength and easily disperses in water at 100% water has been proposed. Calcium chloride or calcium acetate is used as a calcium ion source, but it is likely to cause rough hands when used as a wiping material, and is difficult to use for cleaning the skin such as wiping the ass. The upper limit of the water content during the impregnation is also about 85%. However, from the viewpoint of diversification of uses, a base material that can be used even if the water content in the impregnating liquid is even higher is desired.

Japanese Patent Application Laid-Open No. Hei 4-370300 has a multilayer structure having at least two layers, and one outermost layer has 10 layers.
~ 60% paper strength agent, the other outermost layer is 5% by weight
Hydrolysis papers containing the following paper-strengthening agents have been proposed. As the paper strength enhancer used in the outermost layer of the hydrolyzed paper, carboxymethylated pulp salt, water-soluble polyvinyl alcohol, water-soluble polyvinyl alcohol fiber, or a mixture thereof is used. This water-disintegrated paper is intended to improve the productivity by reducing the deterioration of the releasability of the dryer part during papermaking due to the addition of a paper strength enhancer. However, when there is much moisture in the chemical solution to be impregnated, it is difficult to have sufficient wet strength for use, and the texture is hard because a large amount of paper strength enhancer is compounded in the outermost layer on one side of the hydrolyzed paper. It will be something.

In view of these drawbacks of the hydrolyzed paper, the present inventors have proposed a water-disintegratable nonwoven fabric which has no binder and has sufficient strength and water-disintegrability for use, and a method for producing the same. That is, in Japanese Patent Application No. 8-142825, a high-pressure water column flow is applied to a wet paper-made web obtained by mixing 40 to 85% by weight of regenerated cellulose fiber having a specific fiber length and 60 to 15% of pulp fiber having a specific freeness. By applying the composition, fiber entanglement is imparted, and a water-disintegratable nonwoven fabric having both wet strength and water-disintegration is obtained. However, since the water-disintegratable nonwoven fabric has a high content of rayon fibers of 40 to 80% by weight, the cost is high. Therefore, a water-disintegratable nonwoven fabric which can be produced at lower cost is desired.

In Japanese Patent Application No. 9-48870, 55 to 15% by weight of a regenerated cellulose fiber having a specific fineness and L / D is mixed with 45 to 85% by weight of a wood pulp fiber having a specific Runkel ratio. It has been proposed to apply a high-pressure water column flow treatment to the obtained web under conditions of a specific additional specific energy to impart fiber entanglement, and to obtain a water-disintegratable nonwoven fabric having both wet strength and water-disintegrability. Although the water-disintegratable nonwoven fabric according to this proposal has a certain level of performance, it is desired to achieve both wet strength and water-disintegration at a higher level when considering more applications.

[0012]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fiber which has a strength which can withstand operations such as cleaning in a dry state and a wet state, and which constitutes a nonwoven fabric in a large amount of water flow. To provide a water-disintegratable nonwoven fabric that can be disintegrated.

[0013]

In view of such circumstances, the present inventors have developed a water-disintegratable nonwoven fabric which has strength enough to withstand use even in a wet state and is easily disintegrated into a fibrous form in a large amount of water. The inventor has studied diligently about the manufacturing method.

As a result, the present inventors have determined that the fiber length L (mm)
The first regenerated cellulose fiber and the wood pulp fiber having a relatively large ratio (L / D) between the first regenerated cellulose fiber and the wood pulp fiber are formed into a web by wet papermaking, and the L / D is relatively large. The second regenerated cellulose fiber and the wood pulp fiber are laminated with a second web layer formed by web-forming by a wet papermaking method, and then placed on a transportable perforated support made of a wire net or a plastic net. A nonwoven fabric obtained by placing the laminated web and subjecting it to a high-pressure water column flow treatment from one or both sides of the laminated web, wherein the L / D values of the first regenerated cellulose fibers and the second regenerated cellulose fibers to be used are within a specific range. The present inventors have found that it is possible to achieve both wet strength that can withstand use even in a state where wood pulp fibers are blended at a high rate and water dissolvability in a large amount of water, and have completed the present invention.

According to the present invention, the first regenerated cellulose fibers 20 to
A first web layer in which 80% by weight and 80 to 20% by weight of wood pulp fiber are formed into a web by a wet papermaking method, a second regenerated cellulose fiber of 20 to 80% by weight and a wood pulp fiber of 80 to 2%
0 wt% and a second web layer formed into a web by a wet papermaking method are laminated on a perforated support capable of being transported, and a high-pressure water column flow treatment is performed from one or both sides of the laminated web, and each layer is subjected to A nonwoven fabric obtained by entanglement and integration of fibers to be formed, wherein a ratio (L / D value) of a fiber length L (mm) to a fiber diameter D (mm) is 135 to 1750.
Wherein the L / D value of the first regenerated cellulose fiber and the second regenerated cellulose fiber satisfies the following formula (1). (L1 / D1)> (L2 / D2) (1) where L1: fiber length (mm) of the first regenerated cellulose fiber D1: fiber diameter (mm) of the first regenerated cellulose fiber L2: length of the second regenerated cellulose fiber Fiber length (mm) D2: Fiber diameter (mm) of second regenerated cellulose fiber

[0016]

The important point in the present invention is that the obtained water-disintegratable nonwoven fabric has a fiber length L (mm) and a fiber diameter D (m).
m), the first regenerated cellulose fiber having a relatively large ratio (L / D value), the second regenerated cellulose fiber having a relatively small L / D, and the wood pulp fiber. (1) There are many regenerated cellulose fibers and wood pulp fibers, and on the other surface, there are many second regenerated cellulose fibers and wood pulp fibers.

That is, fibers having a large L / D value generally have high flexibility, so that when fibers are entangled by a high-pressure water column flow or the like, strong fibers are entangled. For this reason, when only the fiber having a large L / D value is used, a sheet having a high strength is obtained. However, even in a large amount of water flow, the entanglement of the fiber entanglement does not proceed so much, and the sheet tends to be poor in water disintegration. Conversely, since fibers having a small L / D value have low flexibility, they do not show very strong inter-fiber entanglement even if the entanglement action by a high-pressure water column flow or the like works. For this reason, if only a fiber having a small L / D value is used, a high-strength sheet cannot be obtained, but the fiber entanglement in a large amount of water flow is rapidly disintegrated, and the sheet tends to be excellent in water dissolvability. To satisfy these, L /
It is necessary to select so that the range of the D value is 135 to 1750. L of the first regenerated cellulose fiber of the formula (1)
An essential condition is the magnitude relationship between 1 / D1 and L2 / D2 of the second regenerated cellulose fiber.

Therefore, when the first regenerated cellulose fiber having a large L / D value and the second regenerated cellulose fiber having a small L / D value are simultaneously used and entangled by a high-pressure water column flow to form a sheet, The wet strength of the obtained nonwoven fabric is maintained by the entanglement strength of the first regenerated cellulose fiber having a large L / D value, and the second regenerated cellulose fiber having a small L / D value is disintegrated at an early stage in a large amount of water flow. ,
Since the fibers fall off from the nonwoven fabric, a gap is formed in the fiber entangled structure, and the first regenerated cellulose fibers that have exhibited strong inter-fiber entanglement are easily disintegrated, and the water dissolvability of the obtained nonwoven fabric can be maintained.

In the case of the water-disintegrable non-woven fabric obtained in the present invention, the non-woven fabric contains a large amount of first regenerated cellulose fiber and wood pulp fiber having a large L / D value on one surface, and has an L / D value on the other surface. A large amount of the second regenerated cellulose fiber and the wood pulp fiber, and a large amount of entanglement of these two regenerated cellulose fibers is present in the middle layer area of the nonwoven fabric. L /
It can be obtained by strong fiber entanglement of the first regenerated cellulose fibers having a large D value, and the water-disintegration of the nonwoven fabric is such that the second regenerated cellulose fibers having a small L / D value are quick in a large amount of water as described above. Since the disintegration starts at the stage, first, the surface containing a large amount of the second regenerated cellulose fibers loses the shape of the sheet and hydrolyzes, and at the same time, the entanglement point is formed in the middle layer area of the nonwoven fabric or the surface containing a large amount of the first regenerated cellulose fibers. Since the formed second regenerated cellulose fibers are also deflocculated, a gap is also formed in the middle layer area or the fiber entangled portion on the surface containing a large amount of the first regenerated cellulose fiber, and the surrounding fiber entangled portion is easily loosened. Eventually this situation spread in a chain to the surrounding area,
In addition to the mechanical action of the water flow, the surface containing a large amount of the first regenerated cellulose fibers can also be obtained by losing the sheet shape and hydrolyzing.

In particular, in the present invention, in order to effectively exhibit the above-mentioned phenomenon, the L / D value ratio between the fiber length L (mm) and the fiber diameter D (mm) of both regenerated cellulose fibers is represented by the following formula (2). It is advantageous to use two types of regenerated cellulose fibers satisfying the above conditions. (L1 / D1) / (L2 / D2) = 1.2 to 5.0 (2) where L1: fiber length (mm) of the first regenerated cellulose fiber D1: fiber diameter (mm) of the first regenerated cellulose fiber L2: Fiber length (mm) of second regenerated cellulose fiber D2: Fiber diameter (mm) of second regenerated cellulose fiber

In the above equation, the ratio of L / D values is 1.2
If it is less than 10, the difference between the properties of the two types of regenerated cellulose fibers used is small, and it is difficult to simultaneously impart sufficient wet strength and water disintegration to the resulting water-disintegratable nonwoven fabric even if these are used. There is. On the other hand, when the ratio of L / D exceeds 5.0, the regenerated cellulose fibers are not preferable because the difference in the added specific energy required for obtaining appropriate entanglement occurs. That is, if the ratio of the L / D value is too large, the second specific gravity having the relatively small L / D value will be generated at the additional specific energy at which the first regenerated cellulose fiber having the relatively large L / D value is appropriately entangled. Since the regenerated cellulose fibers can hardly be entangled, the fibers are liable to come off, and the wet strength of the obtained water-disintegratable nonwoven fabric tends to decrease.
At an additional specific energy of such an extent that the regenerated cellulose fibers are appropriately entangled, the entanglement strength of the first regenerated cellulose fibers having a relatively large L / D value becomes too strong, so that the water-disintegrable properties of the obtained water-disintegratable nonwoven fabric tend to be inferior. This is not preferred.

The fineness of the two types of regenerated cellulose fibers used in the present invention is preferably 1.0 to 5.0 denier. When the fineness of the regenerated cellulose fiber is less than 1.0 denier, it is difficult to disperse during wet paper making, and it is difficult to obtain a wet paper web with good formation. The fineness is 1.0
Regenerated cellulose fibers having less than denier are difficult to produce stably and are difficult to obtain at low cost. On the other hand, if the regenerated cellulose fiber has a fineness of more than 5.0 denier, the resulting water-disintegratable nonwoven fabric tends to have a hard feel and a poor touch, which is not preferable.

Further, the fiber length of the two types of regenerated cellulose fibers used in the present invention is preferably 3 to 15 mm. When the fiber length of the regenerated cellulose fiber is less than 3 mm, insufficiently entangled fibers are liable to be generated, and when the obtained water-disintegratable nonwoven fabric is used, the fibers are liable to fall off and become a cause of paper powder and the like. Since the entanglement strength of the fibers is also weak, the wet strength of the obtained water-disintegratable nonwoven fabric is undesirably reduced. Conversely, if the fiber length of the regenerated cellulose fiber exceeds 15 mm, it is difficult to disperse during wet papermaking, it is difficult to obtain a wet paper web with good formation, and it also causes filter clogging, making continuous production difficult. It is not preferable.

The two types of regenerated cellulose fibers used in the present invention are made of viscose rayon obtained by resolving cellulose from wood pulp or cotton linter in the form of viscose and then regenerating and spinning the cellulose in an acid. After dissolving the cellulose in the copper ammonia solution, the cellulose is dissolved in a non-aqueous cellulose solvent such as copper ammonia rayon regenerated and spun in an acid, N-methylmorpholine-N-oxide, and then spun. The obtained regenerated cellulose fibers can be mentioned.

The wood pulp fibers used in the present invention are not particularly limited, and unbleached pulp obtained by digesting softwood and hardwood wood by a kraft method, a sulfite method, a soda method, a polysulfite method, or the like. Fiber or bleached pulp fiber, or mechanical pulp such as ground pulp fiber or thermomechanical pulp fiber from the above-mentioned coniferous wood can be used alone or in combination as necessary.

These wood pulp fibers are JIS P 8
It is desirable to use a filter having a Canadian standard freeness of 550 ml or more as indicated by 121. Freeness is 550ml
Wood pulp fibers having a density of less than 100% are not preferable because they have a high density when formed into a sheet and become a hard sheet. Further, the bonding force between the wood pulp fibers is too strong, and the water-disintegrable property of the obtained water-disintegratable nonwoven fabric is inferior. In addition, the amount of waste materials during high-pressure water column flow treatment increases, which is not economical. The freeness is the highest value when wood pulp is used without being beaten, and generally the freeness of unbeaten wood pulp is 750 to 750.
It is about 650 ml.

The water-disintegrable nonwoven fabric obtained in the present invention is
First regenerated cellulose fiber 10 having a relatively large L / D value
10 to 45% by weight of a second regenerated cellulose fiber having a relatively small L / D value of 45 to 45% by weight and wood pulp fiber 45.
Advantageously it is composed of up to 80% by weight. The first
If the blending ratio of the regenerated cellulose fiber is less than 10% by weight, the entanglement point of the first regenerated cellulose fiber having a strong entanglement strength becomes insufficient, and it becomes impossible to provide sufficient wet strength to the obtained water-disintegratable nonwoven fabric, which is not preferable. Further, when the blending ratio of the second regenerated cellulose fiber is less than 10% by weight, the fibers constituting the obtained water-disintegratable nonwoven fabric do not progress because the number of fibers that begin to disintegrate early in a large amount of water flow is reduced.
It is not preferable because water disintegration becomes inferior.

On the other hand, if the total compounding ratio of the two regenerated cellulose fibers exceeds 55% by weight, the proportion of the regenerated cellulose fibers, which are more expensive than the wood pulp fibers, becomes too large, so that the water-disintegrable nonwoven fabric according to the present invention is used. It is not preferable because it cannot be manufactured at low cost. Therefore, the upper limit of the mixing ratio of the regenerated cellulose fiber is 45% by weight when the mixing ratio of the other regenerated cellulose fiber is set to the lower limit of 10% by weight.
Becomes In addition, the compounding ratio of the wood pulp fiber is 80 to 45% by weight because the total compounding ratio of the regenerated cellulose fiber is 20 to 55% by weight as described above.

In the present invention, the obtained water-disintegratable nonwoven fabric has a large amount of first regenerated cellulose fiber and wood pulp fiber having a relatively large L / D value on one surface and a relatively large amount on the other surface. In order to adopt a configuration in which a large amount of the second regenerated cellulose fiber and the wood pulp fiber having a small L / D value are present,
In order to obtain the water-disintegrable nonwoven fabric, the first regenerated cellulose fiber and the wood pulp fiber are mixed, and then the first wet papermaking web made by a conventionally known method, the second regenerated cellulose fiber and the wood pulp fiber are mixed. Therefore, a second wet papermaking web formed by a conventionally known method is required.

The two wet papermaking webs used in the present invention are composed of 20 to 80% by weight of regenerated cellulose and 80 to 20% by weight of wood pulp fibers. When the blending ratio of the regenerated cellulose fiber is less than 20% by weight, the surface strength of the obtained water-disintegratable nonwoven fabric is low because the amount of wood pulp fibers increases, and fluffing or falling off of wood pulp fibers is observed during use. In addition, the feel is hard and the texture is inferior, which is not preferable. The compounding ratio is 2
If the content is significantly lower than 0% by weight, it is difficult to satisfy the minimum compounding ratio in the obtained water-disintegrable nonwoven fabric, which is not preferable.

On the other hand, when the blending ratio of the regenerated cellulose fiber is 8
If the content exceeds 0% by weight, the entanglement between the regenerated cellulose fibers is increased on the surface side where the regenerated cellulose fibers are present in a large amount. Although the wet strength of the obtained water-disintegratable nonwoven fabric is improved because the number of entanglement points of the cellulose fibers increases, the water-disintegration property of the first wet-type papermaking web side is deteriorated because these entanglement points are difficult to disintegrate, and thus the obtained water-disintegrability The non-woven fabric also has poor water-disintegrability, and when the second regenerated cellulose fiber is large, the number of entangled points of the second regenerated cellulose fibers that are easily defibrated increases, so that the water-disintegrability of the obtained non-woven fabric improves. On the other hand, these entangled points are not so strong in entanglement strength, so that the wet strength of the second wet papermaking web side is reduced, and the wet strength of the resulting hydrolyzable nonwoven fabric is inferior. Runode is not preferable it is difficult to achieve both wet strength and decomposability in water in the resulting water-decomposable non-woven fabric.

In the present invention, the sum of the basis weights of the above two wet papermaking webs measured by a method according to JIS P 8124, that is, the basis weight of the obtained water-disintegratable nonwoven fabric is 30 to 8
The range is 0 g / m ² . When the grammage is less than 30 g / m ² , the strength tends to be insufficient when the obtained water-disintegratable nonwoven fabric is used for an application such as a wiper, and the water-disintegratable nonwoven fabric is more likely to break during use and become unusable. Conversely, the grammage is 80 g / m
^When it exceeds ² , the rigidity of the obtained water-disintegrable nonwoven fabric increases and it becomes difficult to use it, and the water-disintegratable nonwoven fabric tends to have poor water-disintegrability when poured into a water stream, which is not preferable. The basis weight of each of the first and second wet papermaking webs is arbitrary, and may be determined based on the blending ratio (amount) of the regenerated cellulose fibers and wood pulp fibers to be used.

In the present invention, the high-pressure water column flow treatment performed to integrate the two wet papermaking webs can be performed by a conventionally known method. That is, a wet papermaking web is placed on a porous support such as a wire mesh, and the pore size is from 0.08 to 0.
High-pressure water is sprayed at a water pressure of 15 to 150 kg / cm ² through a nozzle having a large number of pores of about 30 mm arranged therein, and the fibers constituting the web are entangled with each other. The energy imparted to the wet papermaking web by the high-pressure water column flow treatment is represented by the additional specific energy of the following formula (3), but in the present invention, 0.07 to 0.30 kWh / kg per high-pressure water column flow treatment. It is. E = (A × (2 / ρ) ^1/2 × (g × P) ^3/2 ) / (M × 60 × S) (3) where E: additional specific energy (kWh / kg) ρ: water Density (kg / cm ³ ) g: gravity acceleration (m / s ² ) P: water pressure at the nozzle (Pa) S: web passing speed (m / min) M: web mass (g / m ² )

If the added specific energy per one high pressure water column flow treatment is less than 0.07 kWh / kg, the entanglement of the fibers constituting each layer and the entanglement of the fibers between the two web layers become insufficient, and the resulting water-disintegratable nonwoven fabric is obtained. And the fibers constituting the obtained water-disintegratable nonwoven fabric are not easily arranged in the thickness direction of the sheet, and the texture becomes paper-like, which is not preferable. Conversely, if the added specific energy exceeds 0.30 kWh / kg, the inter-fiber entanglement becomes too strong, and the water-disintegrable properties of the resulting water-disintegratable nonwoven fabric are undesirably low.

The high pressure water column flow treatment is performed immediately after two wet papermaking web layers are combined using a conventionally known papermaking machine such as a round papermaking machine, a short netting papermaking machine, an inclined wire papermaking machine, a fourdrinier papermaking machine, or the like. May be performed on-line, or once the combined web is dried, and then may be performed on-line or off-line.
After making the layers separately and drying each once,
The lamination may be performed online or offline.

The nonwoven fabric subjected to the high-pressure water column flow treatment by the above-described method and entangled between the fibers is dried by a dryer such as an air-through drier and then wound up.
The water-disintegratable nonwoven fabric thus obtained has a water-disintegrability of 60
~ 300 seconds. The water-disintegration property is as follows: a water-disintegratable nonwoven fabric having a size of 5 cm square is put into 100 ml of pure water, shaken at a shaking speed of 300 cycles / minute, and the water-disintegratable nonwoven fabric is disintegrated in water. It was expressed as the time required for defibration to about 1 cm ² . This water disintegration is 300
If the time is longer than seconds, the dissolution of the nonwoven fabric in the water stream is slow, and it is likely to cause pipe clogging when flushed into a toilet or the like, which is not preferable. Therefore, the shorter the water disintegration is, the more preferable it is. However, the value of the water disintegration achieved while maintaining the strength of the nonwoven fabric is naturally limited, and is about 60 seconds at the shortest.

The required wet strength of the water-disintegratable nonwoven fabric varies depending on the application, but wet products such as wet tissues, baby wipes, and wipers for cleaning which are one of the main applications of the water-disintegrable nonwoven fabric according to the present invention. When it is used, the wet tensile strength measured according to JIS P 8135 is 200 gf / 25 m in the longitudinal wet tensile strength.
m or more, and preferably 50 gf / 25 mm or more in terms of wet tensile strength in the transverse direction, and more preferably 200 gf / 25 mm or more as the geometric average value represented by the formula (4). Average of wet tensile strength = (XY) ^1/2 (4) where X is the wet tensile strength (g) in the longitudinal direction of the water-disintegratable nonwoven fabric.
f: 25 mm) Y: Wet tensile strength in the transverse direction of the water-disintegratable nonwoven fabric (gf / 25)
mm)

When a water-disintegratable nonwoven fabric is used as a wet product, it is easy to process into a wet product (suitability for processing: difficult to cause trouble due to paper cutting, etc.), and hard to break when taken out of the container after processing (removal). Aptitude) and the likelihood of tearing during actual use (usability). Processing suitability and takeout suitability can be used as long as the wettability of the water-disintegratable nonwoven fabric in the longitudinal direction is 200 gf / 25 mm or more. The suitability for use is 50 in the longitudinal and transverse directions of the water-disintegratable nonwoven fabric.
There is almost no problem if the wet strength is not less than gf / 25 mm. The geometric mean value of the wet tensile strength is 200 gf /
If it is 25 mm or more, it can be used without practical problems even in applications that wipe with very strong force such as some cleaning wipers,
More preferred. However, when the water-disintegratable nonwoven fabric is manufactured by the method according to the present invention, the value of the wet strength in the vertical direction when the water-disintegrability is set to a value of 300 seconds or less is about 1000 gf /
The upper limit is about 25 mm.

In order to use the water-disintegratable nonwoven fabric of the present invention as a wet product such as a wet tissue, a wiping wipe, a wiper, etc., if necessary, water and a wetting agent such as propylene glycol, alcohols and parabenzoic esters, etc. Various agents such as antibacterial, fungicide, fragrance, and components having a specific medicinal effect can be impregnated alone or in combination. Further, when the water-disintegratable nonwoven fabric according to the present invention is used as a surface material such as a sanitary material, it can be used as it is, but the nonwoven fabric may be subjected to a treatment for enhancing hydrophilicity and water repellency as desired.

As described above, the water-disintegratable nonwoven fabric according to the present invention has a strength that can withstand operations such as cleaning in a dry state and a wet state, and forms the nonwoven fabric in a large amount of water flow. The fiber can be disintegrated and can be used as a wet product such as a wet tissue, a cloth, a cleaning wiper, or a top sheet of a disposable diaper or a sanitary napkin.After use, it is easily disintegrated by a large amount of water flow in a toilet or the like. It can be.

[0041]

The present invention will be described in more detail with reference to the following examples, which, of course, are not intended to limit the present invention. In Examples and Comparative Examples, “%” means “% by weight” unless otherwise specified. The density of rayon fibers used in Examples and Comparative Examples is 1.53 g / cm ³ unless otherwise specified.

Example 1 40% of first rayon fiber (L / D = 593) having a fineness of 1.5 denier and a fiber length of 7 mm and 60% of unbeaten softwood bleached kraft pulp (Canada standard type freeness: 720 ml) As a raw material, a wet papermaking web was formed using an inclined wire paper machine and then dried to obtain a first paper having a basis weight of 25 g / m ² .
A rayon / pulp mixed web layer was obtained.

Similarly, 40% of a second rayon fiber (L / D = 420) having a fineness of 3.0 denier and a fiber length of 7 mm and an unbeaten softwood bleached kraft pulp (Canadian standard freeness:
720 ml) 60% as a raw material and a basis weight of 25 g / m ²
A second rayon / pulp mixed web layer was obtained. The L / D of the first rayon fiber and the second rayon fiber at this time was
Was 1.41.

Next, the first web layer is laminated on the upper side and the second web layer is laminated on the lower side and placed on a transfer support net formed of a 50-mesh wire net.
Injecting a high-pressure water column flow from the first web layer side at a water pressure of 80 kg / cm ² using a high-pressure water column flow treatment device in which nozzle holes having a hole diameter of 0.15 mm are arranged at 1.0 mm intervals while transferring at a speed of in. Then, after applying a high-pressure water column flow treatment, the resultant was dried to obtain a water-disintegratable nonwoven fabric having a basis weight of 50 g / m ² . The added specific energy imparted to the laminated web by this high-pressure water column flow treatment was 0.12 kWh / kg. The final blending ratio of each fiber was as follows: first rayon fiber / second rayon fiber / pulp fiber = 20% / 20% / 60%.

The quality of the obtained water-disintegratable nonwoven fabric was evaluated by the following evaluation method. 1. Wet tensile strength (gf / 25 mm) With the width of a test piece set to 25 mm, the strength in the vertical and horizontal directions was measured according to JIS P 8135, and the following formula (5)
, The geometric average of the wet strength was determined. Average of wet tensile strength = (XY) ^1/2 (5) where X: wet tensile strength (g) in the longitudinal direction of the water-disintegratable nonwoven fabric
f: 25 mm) Y: Wet tensile strength in the transverse direction of the water-disintegratable nonwoven fabric (gf / 25)
mm)

2. Water-disintegrable (second) A water-disintegratable nonwoven fabric having a size of 5 cm × 5 cm square is prepared.
Put 100 ml of pure water into a 150 ml Erlenmeyer flask,
The water disintegratable nonwoven fabric is put into a flask and shaken at a speed of 3
Shake at 00 cycles / minute, stop shaking every 30 seconds, observe the disintegration state of the water-disintegratable nonwoven fabric, and repeat shaking. The largest piece of water-disintegratable non-woven fabric is about 1cm ²
The time required for deflocculation until the water disintegration rate was defined as the water disintegration value (second), and represented by the average value of n = 5. Water disintegration is 30
If it is 0 second or less, it can be said that the water dissolving property is excellent.

3. Texture (point) The texture was determined by a tactile test by 20 monitors.
In the test method, the water-disintegratable nonwoven fabric was gripped by hand, and expressed as a total score (a maximum of 100 points) of the results of a rating of 5 points per monitor based on the following evaluation criteria. If the total score is 75 points or more, it can be said that the texture is good. 5 points: Very good feel 4 points: Excellent feel 3 points: Normal feel 2 points: Somewhat poor feel 1 point: Poor feel 0 points: Very poor feel

4. Formation (point) The formation was determined by visual evaluation by 20 monitors. The evaluation was performed based on the following evaluation criteria, with a maximum of 5 points per monitor, and the result was represented by an average score (a maximum of 5 points). If the average score is 3.5 or more, it can be said that the formation is good. 5 points: very uniform formation 4 points: uniform formation 3 points: slight formation unevenness 2 points: formation formation unevenness and uneven formation 1 point: Extremely uneven formation with severe uneven formation

Example 2 As raw materials, 40% of a first rayon fiber (L / D = 849) having a denier of 1.5 denier and a fiber length of 10 mm and 60% of softwood bleached kraft pulp (Canadian standard type freeness: 600 ml) were used as raw materials. Then, a wet papermaking web was formed using an inclined wire paper machine, and then dried to obtain a first rayon / pulp mixed web layer having a basis weight of 25 g / m ² .

Similarly, 40% of a second rayon fiber (L / D = 424) having a fineness of 1.5 denier and a fiber length of 5 mm and bleached softwood kraft pulp (Canadian standard freeness: 600
ml) 60% as a raw material and a second material having a basis weight of 25 g / m ² .
A rayon / pulp mixed web layer was obtained. At this time, the ratio of L / D of the first rayon fiber to the second rayon fiber was 2.00.
Met. Hereinafter, a water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1.

Example 3 The first rayon fiber had a fineness of 0.5 denier and a fiber length of 7 m.
m, L / D = 1029 rayon fiber, second rayon fiber with fineness of 3.0 denier, fiber length 7 mm, L / D = 42
0 rayon fiber, and the L / D ratio at this time was 2.4.
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the value was set to 5.

Example 4 The first rayon fiber had a fineness of 1.5 denier and a fiber length of 7 m.
m, L / D = 593 rayon fiber, second rayon fiber with fineness of 8.0 denier, fiber length 7 mm, L / D = 257
Rayon fiber, and the L / D ratio at this time was 2.31.
A water-disintegrable non-woven fabric was obtained and evaluated in the same manner as in Example 1 except for the above.

Example 5 The first rayon fiber had a fineness of 1.5 denier and a fiber length of 20 m.
m, L / D = 1698 rayon fiber, 2nd rayon fiber with 1.5 denier, 7 mm fiber length, L / D = 59
3 rayon fiber, and the L / D ratio at this time was 2.8.
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the sample was set to 6.

Example 6 The first rayon fiber had a fineness of 1.5 denier and a fiber length of 7 m.
m, L / D = 593 rayon fiber, second rayon fiber with fineness 1.5 denier, fiber length 2 mm, L / D = 170
Rayon fiber, and the L / D ratio at this time was 3.49.
A water-disintegrable non-woven fabric was obtained and evaluated in the same manner as in Example 1 except for the above.

Example 7 The ratio of the first rayon fibers in the first rayon / pulp blended web layer was 60%, and the ratio of the unbeaten softwood bleached kraft pulp was 40%.
Rayon fiber / second rayon fiber / pulp fiber = 30%
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the ratio was / 20% / 50%.

Example 8 The basis weight of the first rayon / pulp blended web layer was 15 g / m
^2. The basis weight of the second rayon / pulp mixed web layer is 35 g
/ M ² , the final blending ratio of each fiber is 1st rayon fiber / 2nd rayon fiber / pulp fiber = 12% / 28% / 6
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the content was set to 0%.

Example 9 The first rayon fiber had a fineness of 3.0 denier and a fiber length of 10 m.
m, L / D = 600 rayon fiber, second rayon fiber with fineness 1.5 denier, fiber length 7 mm, L / D = 594
Rayon fiber, and the L / D ratio at this time is 1.01
A water-disintegrable non-woven fabric was obtained and evaluated in the same manner as in Example 1 except for the above.

Example 10 The first rayon fiber had a fineness of 1.0 denier and a fiber length of 12 m.
m, L / D = 1248 rayon fiber, second rayon fiber with fineness of 3.0 denier, fiber length 4 mm, L / D = 24
0 rayon fiber, and the L / D ratio at this time was 5.2.
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the value was set to 0.

COMPARATIVE EXAMPLE 1 The first rayon / pulp mixed web was made such that the blending ratio of the first rayon fibers in the first rayon / pulp mixed web layer was 90%, the pulp fiber was 10%, the basis weight was 10 g / m ^2, and the second rayon / pulp mixed web Except that the basis weight of the layer was 40 g / m ² and the final blending ratio of each fiber was 1st rayon fiber / second rayon fiber / pulp fiber = 18% / 32% / 50%, all were the same as in Example 1. To obtain a water-disintegrable nonwoven fabric and evaluated.

[0060] 15% blend ratio of the first rayon fiber in Comparative Example 2 first rayon / pulp混抄web layer, the compounding ratio of unrefined bleached softwood kraft pulp 85%, the basis weight and 40 g / m ^2, a second The blending ratio of the second rayon fiber in the rayon / pulp blended web layer is 50%, the blending ratio of the unbeaten softwood bleached kraft pulp is 50%, and the basis weight is 10 g / m ² , and the final blending ratio of each fiber is the first rayon. A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the ratio of fiber / second rayon fiber / pulp fiber was 12% / 10% / 78%.

Table 1 shows the quality of the water-disintegrable nonwoven fabric according to the examples and comparative examples.

[Table 1]

As can be seen from Table 1, the water-disintegratable nonwoven fabric according to the present invention has an excellent balance between wet tensile strength and water-disintegration, and has a good feel. On the other hand, if the ratio of the L / D values of the two regenerated cellulose fibers constituting the water-disintegratable nonwoven fabric is too small, there is no difference in the fiber properties between the two, so that the performance is biased to one of the performances and both wet strength and water-disintegration are achieved. This is somewhat difficult (Example 9). Conversely, if the ratio of the L / D values is too large, the fibers having a small L / D value will not be sufficiently entangled with an additional specific energy at which the fibers having a large L / D value are appropriately entangled. And it is somewhat difficult to achieve both wet strength and water disintegration (Example 10).

If the blending ratio of the regenerated cellulose fibers in the web before the high-pressure water column flow treatment is too large, the entanglement between the regenerated cellulose fibers becomes too large, and the water dissolvability of the surface containing a large amount of the regenerated cellulose fibers deteriorates. However, it was not possible to achieve both wet strength and water dissolvability (Comparative Example 1). Conversely, if the blending ratio of the regenerated cellulose fiber was too small, the texture on the side where the regenerated cellulose fiber was blended was hard and the feel was inferior (Comparative Example 2).

[0064]

As described above, according to the present invention, the mixing ratio of the regenerated cellulose fiber and the wood pulp fiber in each web layer is set in a specific range, and the first regenerated cellulose fiber having a relatively large L / D value and the wood are used. A first web layer in which pulp fibers are formed into a web by a wet papermaking method, and a second web layer in which second regenerated cellulose fibers having relatively small L / D values and wood pulp fibers are formed into a web by a wet papermaking method And a nonwoven fabric obtained by subjecting one or both sides of the laminated web to high-pressure water column flow treatment, wherein the L / D value ratio between the first regenerated cellulose fiber and the second regenerated cellulose fiber to be used is a specific value. By setting it within the range, it is possible to provide a water-disintegratable nonwoven fabric that can provide both wet strength that can withstand use even in a state where wood pulp fibers are blended at a high rate and water-disintegration in a large amount of water flow.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // A61F 13/54 D21H 5/14 A

Claims (2)

[Claims] 1. A first web layer formed by web-forming a first regenerated cellulose fiber of 20 to 80% by weight and a wood pulp fiber of 80 to 20% by weight, and a second regenerated cellulose fiber of 20 to 80% by weight. And wood pulp fiber 80-20% by weight
And a second web layer formed into a web by a wet papermaking method, are laminated on a perforated support capable of being transferred, and subjected to a high-pressure water column flow treatment from one or both sides of the laminated web to form fibers forming each layer. A nonwoven fabric obtained by entanglement and integration with each other, wherein the ratio (L / D value) of the fiber length L (mm) to the fiber diameter D (mm) of both regenerated cellulose fibers is 135 to 1750. Wherein the L / D value of the first regenerated cellulose fiber and the second regenerated cellulose fiber satisfies the following expression: (L1 / D1)> (L2 / D2) where L1: fiber length (mm) of first regenerated cellulose fiber D1: fiber diameter (mm) of first regenerated cellulose fiber L2: fiber length of second regenerated cellulose fiber ( mm) D2: Fiber diameter (mm) of second regenerated cellulose fiber 2. The water-disintegratable nonwoven fabric according to claim 1, wherein the L / D value ratio of the first regenerated cellulose fiber and the second regenerated cellulose fiber satisfies the following expression. (L1 / D1) / (L2 / D2) = 1.2 to 5.0