JPH0810284A - Production of cellulosic fiber and absorbent structure - Google Patents

Abstract

PURPOSE:To provide a process for producing cellulosic fibers which have a low water holding degree, have excellent liquid absorbability and releasability and are adequately usable for absorbent members, such as paper diapers, sanitary napkins and pads for incontinent persons, etc., and an absorbent structure formed by using these cellulose fibers. CONSTITUTION:Hydrophobing chemicals are added to the cellulosic fibers having in the state of moistening the fibers with water and shearing force is applied to the fibers by subjecting the fibers to a mechanical agitation treatment; thereafter, the fibers are subjected to drying and fluxing in a non-restraining state at 105 to 170 deg.C. These hydrophobing chemicals are selected from anionic, cationic or nonionic surfactants, wax water repellents and sizing agents. The absorbent structure is composed by using the cellulosic fibers which have the water holding degree of 2 to 28% and are produced by this process for production.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cellulosic fiber having low water retention and high liquid absorbency, and an absorbent structure using the same. More specifically, the present invention is used for absorbent members such as paper diapers, sanitary napkins, pads for incontinence, etc., a method for producing a cellulosic fiber having excellent liquid permeability and release properties, and the fiber. It relates to the absorbent structure used.

[0002]

BACKGROUND OF THE INVENTION Absorbent articles such as disposable diapers, sanitary napkins, adult incontinence pads and the like are generally absorbent members, ie, fibrous webs of entangled fiber masses, for receiving and retaining body fluids. It has a structure. In order for such an absorbent article to function efficiently, after the body fluid is rapidly absorbed from the application point of the absorbent article to the absorbent member, it is further distributed over the entire absorbent member to maximize the body fluid. It must be contained within the absorbent member.

At present, cellulosic fibers typified by wood cellulosic fibers are widely used as absorbent members such as disposable diapers and sanitary napkins because of their excellent liquid absorbency. Taking a disposable diaper as an example, the main body of the disposable diaper is usually composed of a liquid-permeable topsheet, a liquid-impermeable backsheet, and an absorbent member arranged between the topsheet and the backsheet. Various structures and materials have been studied as the absorbent member, and the technology thereof has been disclosed. Examples of the absorbent material used here include absorbent paper, bleached pulp and / or fluffed pulp, and super absorbent polymer (hereinafter abbreviated as SAP). However, since SAP has a large liquid absorption capacity but a low absorption rate, even if it is brought into contact with a large amount of urinary fluid at one time, SAP alone cannot completely absorb the entire amount. Therefore, it is necessary to once absorb such a liquid in the cellulosic fiber and take it in, and then gradually to gradually absorb the taken-in liquid into the SAP again with the passage of time.

As the absorbent member, (1) a cellulosic material typified by wood pulp fibers is made into a fine fiber to have high voids and low density, and has high water absorption capacity in the voids. Particles of an absorbent gelling substance (a substance that forms a hydrogel when in contact with a liquid) are dispersed (JP-A-2-5945, JP-A-2-60645, etc.), and (2) a cellulosic fiber It has a three-layer structure (Japanese Patent Laid-Open No. 5-49658) in which a web is formed, the web layer is used as an upper layer and a lower layer, and SAP is used as an intermediate layer. Using flexible and perforated stamped pulp board (Japanese Patent Laid-Open No. 5-1233)
No. 56) is known.

On the other hand, as the cellulosic fiber, it is well known that a known softwood bleached pulp and a fluffed pulp thereof, which have not been chemically modified, have been used as an absorbent. Generally, an absorbent member made of such a softwood pulp is an attractive material that is widely used as a liquid absorbent substance because it absorbs liquid very easily. Taking a paper diaper as an example,
Originally, only softwood bleached pulp was used as the absorbent material for paper diapers, but this pulp is used from the surface of human skin.
Immediately, the liquid was wiped off and absorbed, and at the same time, the absorbed liquid was confined inside the pulp layer.

However, the softwood bleached pulp is
Since it has a small liquid absorption capacity and can hold only a certain amount of water or body fluid, it cannot absorb more than that amount, and it also easily releases the absorbed water and body fluid, causing a problem that the liquid may easily return. It was SAP has come to be used with softwood pulp as one of the solutions to these problems. That is, as an intermediate layer between the upper and lower layers of a fluffed softwood bleached pulp web
A paper diaper has been introduced which is provided with particles and has an absorbent member structured such that the pulp web sandwiches the SAP layer.

Thus, the mechanism of body fluid absorption of the absorbent member began to be conscious of, and the division of roles between softwood bleached pulp and SAP began to be recognized. Now softwood bleached pulp wipes away body fluid from the surface of the human body and SAP
And SAP is designed to absorb and retain the liquid. However, when using normal softwood bleached pulp, the liquid enters into the lumen of the pulp fiber due to the capillary phenomenon, so after the fiber absorbs the liquid, it is difficult to release the liquid, and on the other hand pulp fiber Since the surface is hydrophilic, it is very difficult to transfer the liquid absorbed between the web layers of pulp fibers to SAP. Furthermore, in the case of an absorbent structure using such fibers, the volume of the fiber layer is large before absorbing body fluid, but once it absorbs body fluid, the volume becomes small, and absorption of body fluid after the next time There is also the problem that the speed drops sharply.

In order to solve the problems of such softwood pulp fibers, for example, Japanese Patent Publication No. 5-71702 discloses C2-C8 dialdehyde and C having an acid functionality.
Using various cross-linking agents as chemical stiffening substances such as 2-C8 monoaldehyde, it reacts with at least two hydroxyl groups on the cellulose chain of the cellulosic fiber to crosslink the inside of the cellulosic fiber, thereby creating an absorbent structure. It is possible to give the cellulosic fibers the rigidity that is indispensable for the expansion of the material, and the water retention value (relative centrifugal force 1500 to 1700 G, 19 to
A method for producing a cellulosic cross-linked fiber having a water retention value such that the fiber is centrifugally dehydrated in 21 minutes and then dried to have a reduced water retention ratio (weight ratio of absorbed water to dry weight of fiber) of 28 to 50%. It is disclosed. In addition, JP-A-3-20617
No. 4, JP-A-3-206175, and JP-A-3-206175.
No. 206176 discloses a method for producing a crosslinked fiber having a water retention value of 28 to 60% by internally crosslinking a cellulosic fiber with a C2 to C9 polycarboxylic acid.
However, when the fibers obtained by these methods of cross-linking have a structure such as a pad, the release performance of the absorbed liquid is improved as compared with that of untreated cellulosic fibers. In terms of sex, it has not yet reached a satisfactory level of performance.

[0009]

In view of the above situation, the present inventors have earnestly studied a method for producing a cellulosic fiber that quickly absorbs a liquid and easily releases the liquid. By adding a hydrophobizing agent to a certain cellulosic fiber and subjecting the cellulosic fiber to a relatively simple physical and chemical treatment, the cellulosic fiber is modified by immobilizing the fiber morphology and hydrophobizing the fiber surface. It was found that a cellulosic fiber capable of exhibiting excellent performance in absorbing and releasing liquid can be obtained, and the present invention has been completed.

The object of the present invention is that it has a low water retention and an excellent performance in absorbing and releasing liquids, and can be suitably used for absorbent members such as disposable diapers, sanitary napkins and incontinent pads. It is intended to provide a method for producing a cellulosic fiber and an absorbent structure using the cellulosic fiber.

[0011]

The first method for producing a cellulosic fiber of the present invention is to subject a cellulosic fiber in a water-wet state to mechanical shearing treatment in the presence of a hydrophobizing chemical to apply a shearing force. After that, drying in an unrestrained state at a temperature of 105 to 170 ° C. and fluffing are performed.

In the second method for producing cellulosic fibers of the present invention, in the first method, the hydrophobizing agent is one selected from anionic, cationic or nonionic surfactants. A third cellulose-based fiber production method of the present invention is characterized in that, in the first production method, the hydrophobizing agent is a wax-based water repellent, and further the fourth cellulose of the present invention. The method for producing a system fiber is characterized in that, in the first production method, the hydrophobizing chemical is a sizing agent. The absorbent structure of the present invention,
It is characterized in that it is constituted by using a cellulosic fiber having a water retention of 2 to 28% obtained by the first to fourth cellulosic fiber production methods.

That is, in the method for producing a cellulosic fiber of the present invention, the bleached cellulosic fiber is chemically treated with a hydrophobizing chemical, and the cellulosic fiber is chemically treated with the hydrophobizing chemical. Before or after the treatment, or at the same time, in a water-wet state, a shearing force due to mechanical agitation imparts a deformation such as curl or twist, and then the cellulosic fiber subjected to such deformation is unconstrained. It consists of fixing the deformation of the fibers and fluffing by drying at.

The cellulosic fibers used in the present invention are
Known kraft pulping method, sulfite pulping method,
Obtained by a chemical pulping method such as an alkali pulping method,
It is a pulp having a Hunter whiteness of 80 to 95% which has been bleached by a known multi-stage bleaching method, or a pulp obtained by chemically treating such a pulp by a known crosslinking reaction or mercerization reaction. Examples of raw materials used in the pulping method include pine, cedar, cypress and other softwood materials, beech, shii, eucalyptus and other hardwood materials, flax, kenaf and other non-wood fibers, but are particularly limited. Not a thing.

The water-wet state of the cellulosic fiber in the present invention means a solid content concentration of the fiber of 2 to 60%, but it is easily curled or twisted when subjected to mechanical agitation. ˜50% is preferred, and 15-40% is more preferred. The hydrophobizing agents for cellulosic fibers for the present invention include fatty acid soaps, carboxylates such as alkyl ether carboxylates, sulfonates such as alkylbenzene sulfonates, dialkylsulfosuccinate ester salts, and higher alcohol sulfates. Anionic surfactants composed of ester salt, sulfate ester salt such as alkyl ether sulfate ester salt, alkyl ether phosphate ester salt, phosphate ester salt such as alkyl phosphate ester salt,
Cationic consisting of aromatic amine quaternary salt, aliphatic quaternary ammonium salt, aromatic quaternary ammonium salt such as benzalkonium salt, heterocyclic quaternary ammonium salt such as benzalkonium salt, pyridinium salt, imidazolinium salt Ether type such as surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether,
From ether ester type such as polyoxyethylene glycerin fatty acid ester and polyoxyethylene sorbitan fatty acid ester, ester type such as polyethylene glycol fatty acid ester and polyglycerin fatty acid ester, nitrogen-containing type such as polyoxyethylene fatty acid amide and polyoxyethylene alkylamine Nonionic (nonionic) surfactants, wax-based water repellents, rosin-based sizing agents, alkenyl succinic anhydride-based, alkyl ketene dimer-based, silicone-based, wax-based, petroleum resin-based synthetic sizing agents, etc. The paper sizing agent and the like used in the papermaking can be mentioned, and one kind or at least one kind is appropriately selected from these.

The amount of these hydrophobizing chemicals added varies depending on the nature of the chemicals and the adhesion and reactivity to the cellulosic fibers, and cannot be specified unconditionally, but in the case of anionic, cationic or nonionic surfactants, The solid content is 0.1 to 20%, preferably 1 to 10% based on the weight of the bone-dry fiber.
If the amount added is out of the range of 0.1 to 20% and is too small or too large, the desired effect cannot be obtained. In the case of wax type water repellent, the addition amount is 0.00 in terms of solid content based on the weight of the bone dry fiber.
It is 1 to 5%, preferably 0.01 to 1%. If the amount added is less than 0.001%, the desired effect will not be exhibited, and if it exceeds 5%, the fibers will repel the liquid, which is not suitable. In the case of a sizing agent, the amount added is 0.1 to 10%, preferably 1 to 5% in terms of solid content based on the weight of bone-dry fiber. As in the case of the water repellent, too little or too much is not suitable.

The method of adding the hydrophobizing chemical to the fiber is as follows:
(1) Method of adding to cellulosic fiber suspension before mechanical treatment, (2) Method of adding mechanical treatment at the same time, (3) Mechanical treatment and before drying treatment (4) A method in which the fibers are mechanically treated and then spray-added during the fiber drying treatment, (5)
Examples of the method include spraying with a spray after the completion of drying and re-drying. Considering the treatment equipment, operation efficiency, easiness, and effects obtained, before the fiber is subjected to the drying treatment, in particular (1) or (2 It is preferable to add it by the method of (1).

The drying temperature of the fiber is 105 to 17
It is 0 ° C, preferably 120 to 160 ° C. Temperature is 10
If the temperature is lower than 5 ° C, it takes too long to dry, and conversely, if the temperature exceeds 170 ° C and becomes too high, the cellulosic fibers are colored, which is not suitable. The heat treatment time may be a time required for the moisture content of the fiber according to JIS P 8127 to reach 4% by weight or less, preferably 2% by weight or less. There is no change in the performance of. To impart a deformation such as curl or twist to the cellulosic fiber, before drying the fiber, to the cellulosic fiber in a water-wet state, or simultaneously with the drying of the fiber, refiner,
It is essential to apply a shearing force with mechanical stirring by a known fluffing device such as a kneader or a disperser.

In the case of the present invention, in order to obtain a good absorbent structure, the deformed fiber morphology is sufficiently fixed, and it is not deformed even in a water wet condition, or a compressive force is applied. It is desirable that the material has the ability to return to its original shape when deformed, that is, has excellent wet resilience. In other words, the liquid absorbing ability when the cellulosic fiber is made into an absorbent structure such as a pad has a low density, especially while the cellulosic fiber is fixed in a state where it has deformation such as curl or twist. In this sense, Japanese Patent Publication No. 5-71702 and Japanese Patent Laid-Open No. 3-2
As disclosed in JP-A-06174, JP-A-3-206175, JP-A-3-206176, etc., a cellulosic fiber whose fiber shape is fixed by a crosslinking reaction is used in the present invention to further make it hydrophobic. When the fibers are subjected to shearing force by treatment and mechanical agitation to be fluffed, the cellulosic fibers can be provided with further excellent performance.

According to the present invention, the water retention of the cellulosic fiber (centrifugal force 1500 G, 20 minutes, ratio of absorbed liquid weight to absolute dry fiber weight) is in the range of 2 to 28%,
The lower the water retention, and the higher the curl factor that indicates the degree of deformation such as curling and twisting of the fiber, the higher the liquid absorption rate when the absorbent structure is made, and the lower the liquid retention of the fiber. , Therefore, do not make the human body feel wet. However, the lower the water retention, the better the liquid absorption performance can be imparted to the fiber,
In order to reduce the water retention of the fiber to less than 2%, the hydrophobic treatment must be performed in multiple stages or repeated multiple times, and a large amount of hydrophobic chemicals must be used, which complicates the process and increases efficiency. It is not suitable as it will impair the balance of performance. On the other hand, if the water retention is higher than 28%, the hydrophobicity of the fibers becomes insufficient, so that the liquid absorption rate cannot be increased in the absorbent structure, and the fibers themselves retain the liquid. Therefore, it is inferior as a liquid-absorbent structure because it gives a wet feeling on the surface that comes into contact with the skin of the human body.

The water retention value produced by the method of the present invention is 2 to 2.
When making an absorbent structure from 8% cellulosic fibers, it is necessary to sufficiently loosen the cellulosic fibers, and for that purpose, a machine usually used for pulp fluffing as a method for disaggregating cellulosic fibers. A device selected from known devices such as a fluffer, a refiner, a blender, and a flash dryer capable of simultaneously performing drying and fluffing is preferably used.

The cellulosic fiber obtained by the present invention has a water retention of 2 to 28% as described above, and a liquid absorbent structure such as a pad formed by using the cellulosic fiber has a water retention property. It exhibits superior liquid absorption rates and increased wet and dry resilience as compared to absorbent structures made with high density cellulosic fibers. In the present invention, the term “resilience” means a swelling force that tends to return to its original state when a compressive force is applied to a structure such as a pad from the outside and then the compressive force is released. Thus, dry resilience is the ability of an absorbent structure to expand and restore its original shape when the compressive force applied when the structure of cellulosic fibers is substantially dry is released. Means Similarly, the wet resilience is the property of the absorbent structure that expands when releasing the compressive force applied when the fibers used in the structure are in a wet state and restores its original shape. Means ability.

In the present invention, the cellulosic fibers are chemically treated with a hydrophobizing agent to an extent that the water retention is 2 to 28%, and the fibers are further subjected to shearing force by mechanical stirring. After that, or while applying a shearing force by stirring, the fiber is subjected to a drying treatment in an unconstrained state, so that the fiber shape is fixed with the deformation such as curl and twist imparted to the fiber. In this case, the drying treatment of the cellulosic fibers in an unrestrained state is, for example, a method in which the fibers are formed into a sheet by a wet process, and not a method of drying in a state in which tension is applied in the longitudinal direction or the transverse direction, and It refers to a method of drying without forming a sheet, that is, without applying any tension to the fiber. If the fibers are formed into a sheet and dried by applying tension, the deformation such as curl and twist imparted by the mechanical treatment is destroyed, which is not suitable.

That is, the shape of the cellulosic fiber, such as curl and twist, produced by drying the fiber to which the mechanical shearing force is applied in an unconstrained state is preserved as it is, and the inside of the swollen fiber wall is preserved. The removal of water by drying from the water removes water involved in hydrogen bonding within the fiber walls or between fibers, and hydrogen bonding between celluloses is strengthened. At the same time, since the fiber surface is hydrophobized by a chemical treatment with a hydrophobizing chemical, even if such a fiber comes into contact with water again, water is difficult to be reabsorbed in the fiber. In this way, the water retention of the fiber itself is reduced, and when the preformed deformation is fixed as a structure such as a pad and the liquid absorbent member is a combination of polymer absorbent materials, the fiber pad is bulky. Since it has a low density, it has excellent liquid absorbency (absorption rate and absorption amount), and the liquid absorbed by the fiber pad in such a structure is not absorbed by the fibers themselves but is absorbed by the adjacent polymer. Since it easily migrates to the material with time, it is considered that the fiber pad does not give a wet feeling even if the human body touches it.

As described above, the cellulosic fibers are subjected to a hydrophobizing treatment with a hydrophobizing agent so as to have a water retention of 2 to 28%, and the cellulosic fibers in a water-wet state are subjected to a mechanical stirring treatment so that the shear force is increased. After adding
The cellulosic fiber according to the present invention, which is dried and fluffed in an unrestrained state at the temperature of, is a cellulosic fiber that exhibits excellent liquid absorption and release properties when used as a liquid absorbent structure. Therefore, it is possible to obtain a cellulosic fiber which is excellent as a liquid absorbing member such as a disposable diaper, a sanitary napkin, and a pad for an incontinent person.

[0026]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto. Further, in the examples and comparative examples,% means% by weight.

Example 1 As a cellulosic fiber, 30 g of coniferous bleached kraft pulp which has been completely dried is a double-arm kneader (model: S
1-1, manufactured by Moriyama Seisakusho Co., Ltd., and as a hydrophobizing agent, an alkyl ketene dimer type synthetic sizing agent (trademark: SP)
K-902, solid content concentration 15%, manufactured by Arakawa Chemical Industry Co., Ltd.) is added at a solid content of 0.5% per absolute dry pulp weight, and then water is added to adjust the solid content concentration of the pulp to 20%, and then at room temperature. The two arms were rotated at 60 rpm and 100 rpm, respectively, and stirred for 20 minutes. Then, the pulp was taken out from the kneader, and the pulp was well loosened by hand, then placed in a blower dryer at a temperature of 160 ° C., and dried in an unconstrained state for 2 hours. The dried pulp was taken out of the drier and cooled, and then the pulp lumps were disaggregated and fluffed by a laboratory Warburg blender. The water retention and the curl factor of the obtained pulp were measured and evaluated by the following test methods.

Further, an absorbent structure (pad) is produced using the obtained pulp by the method shown in the following test method,
The water absorption rate, dry resilience and wet resilience of artificial urine were measured. In addition, an absorbent structure was prepared using this pulp and a polymer absorbent (trade name: Aralip S-151, manufactured by Arakawa Chemical Industry Co., Ltd.), and the amount of reversion of water was measured and evaluated by the following test method. .

Test Method (1) Moisture Retention of Pulp 0.5 g of pulp that had been defibrated and fluffed to dryness was collected, placed in a container with a stopper containing 100 ml of distilled water, and immersed at room temperature for 24 hours. . The soaked pulp was collected on a filter, and then put into a centrifuge tube of a centrifugal separator (model: H-103N, manufactured by Kokusan Centrifuge Co., Ltd.) having a G2 glass filter, and centrifugally dehydrated for 20 minutes at a centrifugal force of 1500G. . The centrifugally dehydrated pulp was taken out from the centrifuge tube, weighed in a wet state, and then dried in a drier at 105 ° C. until a constant weight was obtained, and the dry weight was measured. The water retention was calculated by the formula (1). Water retention (%) = {(WD) / D} × 100 (1) However, W in the formula (1) is the wet weight (g) of the pulp after centrifugal dehydration, and D is the pulp. It is a dry weight (g).

(2) 100 fibers of curl factor fluffed dry pulp are placed on a microscope slide glass, and an actual length LA of fibers and a maximum projected length (enclosing the fibers are surrounded by an image analyzer). LB (equal to the length of the longest side of the rectangle) was measured, the curl factor was calculated from the equation (2), and the average value thereof was used. Curl factor = LA / LB-1 (2)

(3) Dry resilience of the absorbent structure,
Wet resilience and absorption rate of liquid (body fluid) 4 g of fluffed dry pulp was collected, and the pulp was introduced into a plastic pipe having a diameter of 54 mm with a 40 mesh wire mesh stretched inside, and a small cleaner was applied from the opposite side. Using a certain degree of vacuum, draw a density of 0.0 on the wire mesh.
4 g / cm ³ of absorbent structure was formed. The structure was then transferred into another same diameter pipe into a transparent pipe with a 40 mesh wire mesh at the bottom. afterwards,
A load equivalent to a pressure of 2.5 KPa was uniformly applied on the absorbent structure, and the height h1 of the structure at this time was taken as the dry resilience. Further, in the loaded state, artificial urine (1.9% urea, 0.8% sodium chloride, calcium chloride 0. 1%, magnesium sulfate 0.1%, liquid composed of pure water 97.1%) and the time t required for artificial urine to penetrate to the upper end of the absorbent structure in the transparent pipe. The measurement was performed, and the absorption rate of the liquid (artificial urine) of the absorbent structure was obtained from the formula (3). Liquid absorption rate of absorbent structure (cm / sec) = h1 / t (3) where h1 is the thickness of the fiber layer when a load is applied before the liquid is absorbed by the dry resilience ( cm) and t indicate the time (seconds) required for the liquid (artificial urine) to reach the upper end of the fiber layer. Further, in the above method, the height of the absorbent structure after absorbing the liquid and removing the load is h2
(Cm) and used as wet resilience.

(4) Amount of reversion of water 5 cm × 1 using 4 g of fluffed dry pulp
Two 5 cm fluff pulp sheets were prepared and used as the upper and lower layers, and a polymer absorbent (trademark: Araleep S-
151, manufactured by Arakawa Chemical Industry Co., Ltd.) to prepare an absorbent structure having 4 g as a middle layer. 100 ml of pure water was poured from the top of this structure to absorb the liquid (water) into the structure, and after 30 minutes, 5 filter papers were stacked on this structure and a weight of 5 kg was placed, and after 1 minute. The filter paper was removed, and the weight of the liquid absorbed by the filter paper was measured. The weight of the liquid absorbed by the filter paper was defined as the amount of water reversion.

EXAMPLE 2 A wax emulsion type water repellent (trademark: Size Pine W-1) was used as a hydrophobizing agent with a pulp solid content concentration of 40%.
09, Arakawa Chemical Industry Co., Ltd.) 0.1
%, And the pulp after being treated with a kneader is heated to 150 ° C
Fluffed pulp was obtained in the same manner as in Example 1 except that the pulp was dried for 3 hours, and the quality and the quality of the absorbent structure using this pulp were evaluated.

Example 3 30 g of linter pulp was used as a cellulosic fiber, water was added to prepare a solid content concentration of 15%, and this was prepared as a 12-inch single refiner equipped with a fine blade (model: 18034-N). (Model: DR30-300HB, manufactured by Kumagai Riki Kogyo Co., Ltd.), treated once, and the obtained linter pulp was well loosened by hand, and then placed in a blast dryer at a temperature of 150 ° C. for drying for 3 hours. A spray gun of a cationic surfactant (trademark: Sofnon SSK-15, Amide imidazoline type, manufactured by Toho Chemical Industry Co., Ltd.) as a hydrophobizing agent prepared to a solid content concentration of 0.3% while stirring the dried linter. Was sprayed and added at a solid content of 0.3% based on the weight of absolutely dry linter pulp, and the linter pulp was again dried at 150 ° C. for 30 minutes in a blow dryer. The obtained linter pulp was deflocculated by using a Warburg blender for fluffing, and its quality and the quality of the absorbent structure using this pulp were evaluated in the same manner as in Example 1.

Example 4 As a cellulosic fiber, a double-arm kneader (model S
1-1, manufactured by Moriyama Seisakusho), and a non-formaldehyde-based cross-linking agent (trademark: Sumitex NF-500K, Sumitomo Chemical Co., Ltd.) and its cross-linking aid (trademark: Sumitex ACC).
(ELERATOR MX, manufactured by Sumitomo Chemical Co., Ltd.) was added at 0.5% and 0.25%, respectively, based on the weight of the absolutely dry pulp, and then water was added to adjust the solid content concentration to 20%, and then the double arms were respectively allowed to be heated at room temperature. Rotate at 60 rpm and 100 rpm,
It was stirred for 20 minutes. Then, without removing the pulp from the kneader, a cationic surfactant (trademark: Sofnon SSK-15, manufactured by Toho Kagaku Kogyo Co., Ltd.) was added as a hydrophobizing agent in an amount of 0.3% in terms of solid content based on the weight of absolutely dry pulp to produce a pulp. After adjusting the solid content concentration to 15%, stirring treatment was performed at room temperature for 20 minutes. Then, the pulp is taken out from the kneader, and the pulp is thoroughly loosened by hand, and then the temperature is set to 150.
It was placed in a blast dryer at 0 ° C. and dried for 2 hours in an unconstrained state. The dried pulp was taken out of the drier and cooled, and then the pulp lump was disaggregated into a fluff by a laboratory Warburg blender. The quality of the obtained pulp and the quality of the absorbent structure using this pulp were evaluated in the same manner as in Example 1.

Example 5 To 476 g of a 16.0% aqueous solution of caustic soda, 30 g of an absolutely dried softwood bleached kraft pulp as a cellulosic fiber was added with stirring (pulp concentration 7.0%), and the alkali concentration was maintained at 16% with stirring. The mercerization reaction was performed at 0.0% for 20 minutes. After the reaction was completed, the pulp was thoroughly washed with water to completely remove the alkali to obtain a mercerized softwood bleached pulp. To this pulp, 0.1% of a wax emulsion-type water repellent (trade name: Size Pine W-109, manufactured by Arakawa Chemical Industry Co., Ltd.) was added to the dry pulp weight to prepare a pulp solid content concentration of 40%. Put in a 1-liter dual-arm kneader (Moriyama Seisakusho), rotate the dual-arm at 60 rpm and 100 rpm respectively at room temperature, and
A stirring process was performed for 0 minutes. Then, remove the pulp from the kneader, loosen the pulp by hand, and heat it to a temperature of 1
It was put in a blast dryer at 50 ° C. and dried for 3 hours in an unconstrained state. The dried pulp was taken out of the drier and cooled, and then the pulp lump was disaggregated into a fluff by a laboratory Warburg blender. The quality of the obtained pulp and the quality of the absorbent structure using this pulp were evaluated in the same manner as in Example 1.

Comparative Example 1 Fluffed dry pulp was produced in the same manner as in Example 1 except that the softwood bleached kraft pulp was not subjected to mechanical treatment and no sizing agent was added as a hydrophobizing chemical, and its quality and The quality of the absorbent structure using this pulp was evaluated in the same manner as in Example 1.

Comparative Example 2 A fluffed pulp was produced in the same manner as in Example 2 except that a wax emulsion type water repellent as a hydrophobizing chemical was not added, and its quality and an absorbent structure using this pulp. The quality was evaluated in the same manner as in Example 1.

Comparative Example 3 A fluffed pulp was produced in the same manner as in Example 4 except that a cationic surfactant as a hydrophobizing chemical was not added, and its quality and the quality of an absorbent structure using this pulp. Was evaluated in the same manner as in Example 1.

The results obtained in Examples and Comparative Examples are shown in Table 1.

[0041]

[Table 1]

As is apparent from the table, the cellulosic fiber according to the present invention has a low water retention and a high curl factor, and the absorbent structure produced by using the fiber has a high liquid absorption rate and reversion of water. Absorbing member having a low amount (that is, the absorbed liquid is not absorbed by the fibers, so that the fibers have excellent liquid-releasing properties), and also has excellent dry and wet resilience, and has excellent liquid absorption suitability. (Examples 1 to 5). On the other hand, when no hydrophobizing chemical is used, the water retention is high at 28% or more, and the dry and wet resilience is somewhat low, but the liquid absorption rate is low and the water reversion amount is large, so Not suitable as a member. When the solid content concentration is low in a water-wet state when a mechanical shearing force is applied to the fiber without using a hydrophobizing agent (Comparative Example 1), the curl factor becomes low,
Along with that, the wet resilience becomes particularly low. On the other hand, when the solid content concentration is high (Comparative Example 2), the above problem is slightly improved, but the suitability as an absorbing member is still insufficient. Even if the cellulosic fiber is treated with a treatment chemical such as a crosslinking agent (Comparative Example 3), the water retention is high (2
8% or more), the suitability as an absorbing member is insufficient in terms of the liquid absorption rate and the amount of water reversion (liquid releasing property of fibers).

[0043]

INDUSTRIAL APPLICABILITY The present invention is capable of imparting a low water retention property and a high curl factor to cellulosic fibers, and is a method for producing cellulosic fibers suitable for absorbent members such as disposable diapers, sanitary napkins and incontinence pads. And an effect of providing a liquid-absorbent structure.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C09K 3/18 101 // D04H 1/40 A D21D 1/20

Claims (5)

[Claims] 1. A hydrophobic chemical is added to a cellulosic fiber in a water-wet state, a mechanical stirring process is performed to apply a shearing force, and then drying is performed at a temperature of 105 to 170 ° C. in an unconstrained state, and A method for producing a cellulosic fiber, which comprises fluffing. 2. The method for producing a cellulosic fiber according to claim 1, wherein the hydrophobizing agent is one kind selected from anionic, cationic and nonionic surfactants. 3. The method for producing a cellulosic fiber according to claim 1, wherein the hydrophobizing agent is a wax-based water repellent. 4. The method for producing a cellulosic fiber according to claim 1, wherein the hydrophobizing agent is a sizing agent. 5. An absorptive structure comprising cellulosic fibers having a water retention of 2 to 28% obtained by the production method according to any one of claims 1 to 4.