JPH01239102A - Disposable diaper - Google Patents

Abstract

PURPOSE:To obtain the subject product capable of absorbing a large amount of urine by the longitudinally extending wrinkles to prevent the leakage of the urine, by using a rectangular absorbing material containing longitudinally oriented fiber base material and settling the absorbing material in such a manner as to direct the oriented direction of the fiber material parallel to both side lines of the diaper. CONSTITUTION:A solution of an acrylic monomer for a highly absorptive resin is applied to a fiber web containing fiber base material 9 oriented in a definite direction and the monomer is polymerized to fix the highly absorptive resin 7 to the fiber base material 9 and obtain a rectangular absorbing material 8 containing longitudinally oriented fiber base material 9. The objective product is produced by using said absorbing material 8 in such a manner as to direct the orientation direction of the fiber base material 9 of the absorbing material 8 parallel to both side lines of the diaper. The crimp of the base fiber is preferably formed by a two-dimensional straight-chain mechanical crimping to obtain a fiber web containing a fiber base material oriented in definite direction.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a disposable diaper that contains a superabsorbent resin, can absorb a large amount of urine, and does not leak. More specifically, it efficiently draws out the latent absorption capacity of superabsorbent resin, can absorb a large amount of urine in a short time, and has good structural stability after swelling after repeatedly absorbing urine 4.5 times. The present invention relates to a disposable diaper that has excellent properties such as not becoming squishy, trapping absorbed urine and preventing wet back.

"Prior Art" Recently, the market for so-called disposable sanitary materials such as disposable diapers has rapidly expanded due to the popularity of superabsorbent resins. As shown in FIG. 17, disposable diapers usually consist of a water-permeable top layer 1 that comes into contact with the skin of infants, sick people, and the elderly, a liquid absorbing and retaining layer 2 located in the middle, and an outer water-impermeable packing layer 3. However, conventionally, the liquid absorption and retention layer 2 has been made of a mixture of pulverized wood pulp fibers and fine particulate superabsorbent resin, or a layered absorbent layer has been used. When the wood absorbs a large amount of urine, the wet wood pulp fibers and swollen granular superabsorbent resin mix together, forming a mushy slurry that collects in the crotch of the user, such as an infant, and is then excreted. It has the disadvantage that urine leaks through the diaper.As a way to improve the form stability of this absorbent material, a sorted absorbent material made by adhering superabsorbent resin to fibers has been proposed. (Japanese Unexamined Patent Publication No. 59-135
Publication No. 149).

``Problem to be Solved by the Invention'' By the way, when a notebook-shaped absorbent material formed by fixing the above-mentioned superabsorbent resin to a fiber base material is used in a diaper, it will cause a large area expansion when a large amount of urine is absorbed. This causes problems such as the formation of irregular irregularities inside the diaper, resulting in loss of adhesion to the user's skin, and subsequent leakage of urine and urine.

The object of the present invention is to eliminate the drawbacks of conventional disposable diapers, and to provide a disposable diaper that can absorb urine in a large amount and does not cause leakage.

In order to prevent disposable diapers from being worn tightly between the user's crotch from the front to the back, the absorbent material 4 is shaped like a long and narrow rectangle, as shown in FIG. 18(a). It is a notebook-shaped device placed inside a disposable diaper, but if it absorbs a large amount of urine,
As shown in Figure 18 (0), urine spreads and spreads (5)
, both edges in the middle direction cause diaper leakage (6), especially when the absorbent material 4 expands significantly due to swelling and forms irregular wrinkles in the limited space inside the disposable diaper. If the adhesive loses its adhesion to the user's skin, leakage becomes noticeable.

The disposable diaper of the present invention uses a sorted absorption method that selectively causes swelling and elongation in only one direction, and the direction of swelling and elongation is perpendicular to the direction from front to back through the crotch of the user of the disposable diaper. As a result, the absorbent material forms uneven wrinkles that extend along the length of the disposable diaper, and urine that is subsequently excreted spreads along the grooves formed by these depressions and is used with the protrusions. It prevents leakage from 11 directions by making close contact with the person's skin.

In other words, the disposable diaper according to the present invention is made by applying an acrylic acid-based superabsorbent resin monomer solution to a fiber web in which the fiber base material is oriented in a certain direction, and polymerizing the solution to form a superabsorbent resin. The absorbent material is made of a rectangular absorbent material that is fixed to the fiber base material and whose longitudinal direction is the orientation direction of the fiber base material. vertical direction in use)
Shino is characterized by its placement along the

Hereinafter, the present invention will be explained in more detail using figures. 1st
The figure shows a schematic diagram of a square absorbent material used in the present invention. Here, the superabsorbent resin 7 is fixed to the fiber base material 9 in an elongated stripe shape along the longitudinal direction of the absorbent material 8 . FIG. 2 schematically shows the deformation and shape of the absorbent material 8 shown in FIG. 1 when it absorbs urine and swells and expands freely. Here, the broken line shows the size after swelling, and the solid line shows the size after swelling.

The absorption swelling ratio (L/Lox 100%) in the fiber base material orientation direction of Absorbent O8 used in the present invention is 15% or less, and the absorption swelling ratio in the I+ force direction (W/WoX 100%) is 30 to 80%. is desirable. Absorption swelling rate in the orientation direction is 15%
If the absorbent material 8 absorbs urine and stretches in the longitudinal direction, the sagging absorbent material 8 will form irregular wrinkles on the user's abdomen or back, making it easy for urine to leak sideways from the diaper. In addition, when the absorption swelling rate in the width direction exceeds 80%, the absorbent material 8, which absorbs urine and stretches and sag, becomes irregularly uneven vertical wrinkles and bends, and is unable to fit in the crotch, resulting in poor adhesion. A certain feeling of wearing will be lost. The absorption swelling rate in the width direction is
If it is less than 30%, the ability to absorb urine is insufficient.

The orientation direction of the fiber base material of the absorbent material used in the present invention and the force direction absorption swelling rate perpendicular to this orientation direction are determined by vacuum drying at 80°C for 2 hours and temperature control at 25°C in an atmosphere of 160fl I (%). Measurement is performed using a prototype piece prepared by cutting a sample into pieces of 10 cm on each side (the directions of the sides match the orientation direction and the +17 direction, respectively).

As shown in FIGS. 3(a) and 3(b), the test piece IO was placed on the second part of the wire mesh 11 of the IO mesh, and the test solution prepared in advance (physiological saline solution 20.9% by weight) 12
to avoid absorbing the test liquid. After being immersed for 1 hour, the test piece IO is gently pulled up while still being placed on the wire mesh 11, and the lengths of the sides in the fiber base material orientation direction and in the middle direction are measured, and the absorption swelling ratio in each direction is determined.

When the absorbent material used in the present invention absorbs urine and swells, it swells in a certain direction (the web conveyance direction of the web manufacturing device).
It is characterized by being selectively stretched in the width direction without being stretched very much. To obtain such an absorbent material, an acrylic acid-based superabsorbent tree monomer solution is applied to a production web in which the fiber groups are oriented in the flow (machine) direction of the production web.
Then, it may be polymerized. Then, the superabsorbent resin becomes 1
A book or several fiber base materials are bundled together and wrapped in a sheath at the same time. (It is fixed in a striped manner intermittently in the same direction as the A base material.If this absorbent material is used in a diaper with the fiber base orientation direction along the side of the diaper,
The superabsorbent resin that has absorbed urine is difficult to stretch vertically along the axial direction, and swells in the rlj direction, i.e., to increase the circumference. (2) Since the fibrous web has a large stretching stress in the machine direction, it is difficult to swell and stretch in this direction, but the stretching stress is small in the middle direction, so it swells and stretches very easily. Such an absorbent material that selectively swells only in the width direction exhibits various characteristics when used as an absorbent material for disposable diapers. The absorbent material of disposable diapers is generally shaped into an elongated rectangular notebook that is placed between the crotch of the user, such as an infant, and is carried from the abdomen to the back.

In the absorbent material 8, as described above, the superabsorbent resin is intermittently continuous in long and narrow stripes along the orientation direction (machine direction) of the fiber base material within the fiber web, as shown in FIG. When the longitudinal direction of the absorbent material 8 used in the diaper matches the direction of the resin stripes, the absorbed urine wets and spreads in an elongated oval shape in the longitudinal direction of the absorbent material 8, as shown in FIG. This prevents leakage from the sides of the diaper. Conversely, as shown in FIG. 6, if the width direction of the absorbent material 8 is made to match the direction of the resin streaks, urine in the diaper will form an elongated oval shape in the width direction of the absorbent material 8, as shown in FIG. As it gets wet and spreads, it can easily leak from the sides. In addition, in the arrangement of the absorbent material 8 as shown in FIG. 4, the swelling and expansion of the absorbent material 8 occurs selectively in the rt] direction, and almost no expansion occurs in the longitudinal direction, and the expansion in the width direction occurs in the longitudinal direction. Since it stretches and bends smoothly, it maintains close contact with the user's skin, and as a result, urine does not leak from the sides even after continued use.

In addition, absorption (E8) is flexible and easy to bend in the width direction when it gets wet and swells, so the elongation that occurs in the middle direction becomes unevenness extending in the longitudinal direction and helps it bend.

A fibrous web in which the fiber base material is oriented in the machine direction is produced by uniformly blending bulky base fibers and heat-sealable binder fibers, forming a web by carding, and then dry heat-treating and heat-sealing the fibers. It can be easily formed by carrying out this process, and it can be controlled by the strength of the orientation of the fiber base material, the crimping form of the fibers, the use of special cards, and combinations thereof. In other words, when the crimp form of the base fiber is a latent crimp type three-dimensional crimp, each fiber base material is curled into three-dimensional form and the orientation is randomized, so the crimp form of 1 is a two-dimensional linear chain. Preferably, it is mechanically crimped.

In addition, fiber webs for nonwoven fabrics with a small basis weight are usually heated by 5 to 60% of the surface speed of the dofufer immediately after the dofufu of the card opening machine in order to bring the strength balance in the machine direction and the width direction closer, or to emphasize the bulk. A slow condensing roll (compression roll) is provided to three-dimensionally take out the fiber base material arranged in the -dimension direction, but the fiber web used in the present invention requires the fiber base material to be oriented. It is preferable to take out the web as it is from -.

FIGS. 8 and 9 illustrate cards for producing a fibrous web in which the fibrous base material is oriented in the machine direction.

FIG. 8 is an example of a roller card. In the figure, reference numeral 14 is a cylinder, and 15 is a walker, whose surface speed is slower than that of the cylinder 14, and whose function is to scrape off the second layer of the cylinder 111''. 16 is a stripper whose surface speed is faster than the walker I5 or slower than the cylinder 14, and moves by scraping the fibers on the surface of the walker 15 without transferring them to the cylinder 14.

In FIG. 9 showing an example of a flat card, reference numeral 1
Reference numeral 7 denotes a top clothing, whose surface speed is slightly moving or stationary, and serves to align the thick fiber waste on the cylinder 14. In the figure, reference numeral 18 indicates a foot roll, 19 indicates a nose plate, 20 indicates a take-in roll, 2I indicates a doffer roll, and 22 indicates a clearer roll.

If a known method for obtaining a dry nonwoven fabric is used to obtain the fibrous web used in the present invention, it is possible to form a fibrous L web with large voids and high compressive elasticity, which can improve the safety and health of drugs on the skin. No problem.

Hess fibers constituting the zigzag fiber web used in the present invention; (C
The fineness is 2 to 20 denier and the fiber length is 32 to 128 m.
Preferably, the range is m. If the fineness is less than 2 denier, large pores with good air permeability and high compressive elasticity required by the present invention cannot be obtained, and if it exceeds 20 denier, it becomes difficult to sufficiently increase the amount of monomer solution deposited. If the fiber length is less than 32n+m, the intertwining between the fibers is weak and the web will break before heat treatment, while if it exceeds 128mm, the intertwining will be too strong and opening and carding at high speed will become difficult.

In addition, fiber-forming polymers include polyester, polyamide,
One or more thermoplastic polymers may be selected from among polypropylene, polyethylene, etc., and polyester fibers are particularly preferred since they have excellent fiber performance. A bulky and highly elastic base fiber can be easily obtained by making the cross section of the fiber hollow.

In addition, the binder fibers can be made into fibers by heat treatment. If the entire fiber web is fused, the morphology of the fiber web cannot be stabilized, so a core-sheath type composite that combines a low melting point polymer component that melts and softens with heat treatment at 80°C to 180°C and a polymer component that does not melt and soften. It is better to use spun fibers. The melting point of the low melting point polymer component disposed in the sheath is not particularly limited as long as it is at least 30°C lower than the melting point of the polymer component disposed in the core. Examples of such thermoplastic polymer combinations include, for example, a low melting point polyester polymer and polyethylene terephthalate, polyethylene and polyethylene terephthalate, polyethylene and polyamide, polyethylene and polypropylene, polypropylene and polyethylene terephthalate, polypropylene and polyamide, and many others. Combinations are possible, but of course they are not limited to these. Furthermore, binder fibers may be constructed by selecting two or more types of fibers from a combination of -1. For example, can you name a combination of a composite spun fiber made of a low melting point polyester polymer and polyethylene terephthalate, and a composite yarn fiber f(t) made of polyethylene and polyethylene terephthalate?If polyester fiber is used as the base fiber, When a core-sheath type binder fiber <M is used, a composite spun fiber in which a low-melting point polyester polymer is arranged in the sheath part and polyethylene terephthalate in the core part is used, the polyester polymer of the base fiber and binder fibers is formed by heat treatment. Since they are compatible with each other, a fibrous web with extremely good shape stability can be obtained.

Such a low melting point polyester polymer is not particularly limited as long as it has good fiber forming properties and melts and softens at 80 to 180°C. In terms of ease of fiber production and fiber properties, it is preferable to use a copolymer of terephthalic acid, isophthalic acid and ethylene glycol as the low melting point polyester polymer.

The ratio of the low melting point polymer component disposed in the sheath and the polymer disposed in the core may be 10:90 to 90:10. 10:
If the ratio is less than 90, core-sheath type composite spinning will be fine, but if it exceeds 90:10, the fiber performance will deteriorate.

The binder fibers preferably have a fineness of 1.5 to 6 deniers and a fiber length of 32 to 128+n11+. Decreasing the fineness of the binder fibers increases the number of fibers and increases the number of intertwined bonding points, improving the morphological stability of the fiber web and increasing the amount of monomer solution attached, but conversely, the porosity decreases. This results in poor ventilation.

Conversely, when the fineness is increased, the number of fibers decreases and the number of intertwined bonding points decreases, impairing the morphological stability of the fibrous web.

Furthermore, if the fiber length is less than 321 nWI, the web will break into sheets on the heat-treated surface, and if it exceeds 128 mm, the opening carding properties will be reduced. The blending ratio of binder fibers in the fibrous web is preferably 5 to 50% by weight.

If it is less than 5% by weight, the fibrous web will lack morphological stability,
If the weight exceeds 50 weight, the texture of the fibrous web becomes thin and hard, making it impossible to obtain a bulky fibrous web with good air permeability.

The fibrous web used in the present invention, which is composed of base fibers such as woven fabric and binder fibers, has a basis weight of 10 to 100.
g/m' is preferred. log/m", it is difficult to attach the 1.1 superabsorbent resin monomer required as an absorbent material for disposable diapers.
If it exceeds "g/m", the air permeability becomes unmanageable and it becomes economically disadvantageous.

In addition, the bulkiness of this fiber web is preferably 08 to 6 x l O'' (cc/g) in terms of fiber XB web volume (cc) per 1 g of fiber base material, that is, specific volume (cc/g). If it is less than 0°8 X l O”cc/g, the monomer solution will form a film between the fiber base materials and adhere to it.
．． If it exceeds 6 x 10'cc/g, the thickness of the obtained absorbent material will become too large, making it difficult to handle in subsequent steps.

Second, the compression recovery rate of this fiber web is 60 to 90%.
is preferred. If it is less than 60%, the wet back will increase when urine is absorbed. Regeneration of bulk, that is, recovery of specific volume, is not sufficient, and although the higher the compression recovery rate, the better, it is actually difficult to exceed 90%.

Furthermore, the air permeability of this fiber web is 10cc/5ea
(IOOmmHto) or more is preferable, and l
If Occ/5ec (100mm1-120) is not sufficient, the rapid polymerization heat generated during polymerization is not dissipated, so the monomer temperature rises rapidly and an abnormal self-crosslinking reaction occurs, resulting in poor absorption performance. Resin will be formed.

In the fibrous web used in the present invention, hydrophilic fibers K(t
When the fiber surface of the base material is provided with at least one or more concave portions that are continuous along the fiber axis to give an irregular cross section, the adhesion of the monomer solution to the fiber surface is improved and the adhering resin becomes streaky. That is, the monomer solution applied to the fiber surface quickly diffuses along the four parts (grooves) of the fiber, so that the monomer adheres along the fiber axis. Further, when the fibers have irregular cross-sections, the surface area increases and the retention of the monomer solution improves, so it becomes possible to prevent the monomer solution from slipping along the fiber axis.

When the fibrous web used in the present invention is composed of a fibrous base material coated with a water-soluble agent on the fiber surface, the state of adhesion of the acrylic acid monomer solution can be further improved. Examples of such hydrophilicity imparting agents include the following known surfactants.

(a) Nonionic surfactants such as polyoquinoedylene alkyl ether, borioquinoedylene alkylphenol ether, polyoquinoedylene propylene block polymer, and the like.

(b) Anionic surfactants such as fatty acid salts, alkylnaphthalene sulfonates, alkyl sulfate ester salts, and higher alcohol sulfate ester salts.

(C) Cationic surfactants such as alkylamine salts and alkyl quaternary ammonium salts.

Among the above surfactants, H L selected from the anionic surfactant group seems to be a nonionic surfactant group.
It is desirable to use one or more surfactants in which B is 10 or more or to use a combination of two or more surfactants selected from both groups.

Generally, in thermoplastic synthetic fibers, anionic or cationic surfactants are used as antistatic agents to avoid problems caused by static electricity. Of course, it is also possible to select an antistatic agent from among them and have both the antistatic effect and the wetting effect. Furthermore, if a fiber base material in which a parent wood group-containing oligomer is applied to the fiber surface instead of a surfactant with a large wetting effect is used, durable hydrophilicity can be imparted to the fiber web.

Here, in the hydrophilic fiber base material, for example, both the base fiber and the binder fiber may be made hydrophilic, or either one of them may be made hydrophilic. Furthermore, a portion of each of the base fibers and binder fibers may be made into a hydrophilic fiber base material.

The hydrophilic fibrous substrate has at least 20%
It is preferable that the amount is greater than or equal to the weight. Here, a hydrophilic fiber base material is defined as one whose sedimentation speed in water is 30 seconds or less, as determined by measuring the sedimentation rate in water of a cotton mass obtained by card-opening a fiber base material.
That is, when a sample is dropped into water, it reaches the water surface and completely sinks within 30 seconds.

In the present invention, the fibrous base material from which the fibrous web is made is oriented in a certain direction (machine direction) as a whole, as described above, so the monomer solution applied by the coding roll has a hydrophilic effect on the fiber surface. Envelops one or several fiber base materials due to its wettability with the monomer solution, capillary action between closely parallel fibers, or liquid cohesive force derived from the surface tension of the monomer solution. While being bundled, it is attached in a long, thin and intermittently continuous line in the same direction as the fiber base material. And the monomer solution is
A polymerization initiator is sprayed, and a redox type polymerization reaction forms a streak-like superabsorbent resin oriented in the same direction as the fiber base material.

The absorbent material, which is made of superabsorbent resin that is intermittently long and thin and dispersed in the same direction as the fiber base material, selectively swells and stretches in the width direction when wet with urine, and also becomes flexible in the width direction. It comes to show that.

As described above, the orientation of the fiber':(t group R influences the form of attachment of the superabsorbent resin to the fibrous web, and in turn has a large effect on the performance of the absorbent material.

The orientation of the fiber base material can of course be determined by visual observation, but for example, the strength ratio of the machine direction tensile strength (Sb) MD and width direction tensile strength C5b) CD of other fiber webs is 1
:sb) MD/C3b1 CDte can be expressed quantitatively. In the present invention, [Sb) MD of the fiber web
/ (S b) CD is preferably in the range of 2 to IO. C9b) When MD/(Sb:l CD is less than 2), the monomer solution applied to the fiber base material merely forms dots, but does not change the orientation of the fiber base material. It does not form continuous streaks. On the other hand, if it exceeds 10, the fiber base material will be too aligned in one direction, and the fibers W and base material will be bundled excessively by the liquid aggregation horns of the applied monomer solution, resulting in noticeable width shrinkage of the fiber web. It begins to occur.

Next, the absorbent material used in the present invention will be described in its manufacturing method (10th
This will be explained in more detail, focusing on Figure).

The fibrous web 24 is coated with a monomer solution 30 containing one of the redox type polymerization initiators and a crosslinking monomer using a nip type coating roll 29.
is applied, followed by spraying with the other initiator solution 31, and then led to a polymerization tank 32 maintained at 60-100°C. The polymerization initiator added to the monomer solution contacts the other sprayed initiator to initiate a radical polymerization reaction, and the monomer solution on the fiber base material of the fiber fat web 24 forms droplets without generating heat. Polymerizes from the surface and finishes the reaction in a few seconds. Super absorbent resin 33 obtained in this way
is a hydrated polymer containing approximately 10 to 30% water and contains a large amount of unreacted residual acid monomer, so it is then irradiated with electron beams and/or ultraviolet rays by electron beam irradiation device 34 and ultraviolet ray irradiation device 35, respectively. to complete the polymerization. When irradiating electron beams and ultraviolet rays, adjusting the moisture content to 15 to 25% in advance can effectively reduce unreacted residual acid monomers. The humidity is controlled by spraying water using a suitable means such as a rotating brush 36.

Thereafter, as shown in FIG. 11, a solution of a crosslinking agent having two or more functional groups capable of reacting with carboxylic acid groups in its molecule is sprayed onto the hydrous polymer using a suitable means such as a rotating brush 37. Then, the resin is introduced into a heating device 38 to form crosslinks on the resin surface at 100 to 200°C, thereby improving absorption performance. Note that the reference numeral 25 in the figure indicates a blower 126 that is a heater.

Next, the acrylic acid-based superabsorbent resin monomer solution used in the present invention will be explained. This monomer solution is preferably an aqueous solution of acrylic acid or a mixture of acrylic acid and methacrylic acid, in which 20 to 95% of the total carfoquinol groups are
is preferably partially neutralized with an alkali metal salt or ammonium salt.

If the degree of partial neutralization is too high, it will be difficult to increase the concentration of the aqueous solution, and therefore the crosslinking reaction will be suppressed and the proportion of the water-soluble resin portion will increase, resulting in the formation of an occlusive gel film on the resin surface. Furthermore, if the degree of partial neutralization is too high, the swollen gel will exhibit weak alkalinity, which is unfavorable in terms of safety and hygiene. On the other hand, if the partial neutralization is too low, the absorption capacity of the resin will decrease. Alkali metal hydroxides, bicarbonates, ammonium salts, etc. can be used to neutralize the acrylic acid monomer;
Sodium hydroxide or potassium hydroxide is preferred from the viewpoint of cost and safety, and potassium hydroxide is particularly preferred because it allows the concentration of the aqueous solution of the acrylic acid monomer to be varied at a high level. The concentration of these acrylic acid monomer solutions is
It is preferable that it is at least 35 rM in%, and the higher it is, the larger the resin polymerization density is, and the amount of monomer attached to the fiber web can be increased.
Unless there are other problems, it is preferable to use a concentration slightly lower than the saturation concentration at the operating temperature.

The monomer solution preferably has a viscosity in the range of 2 to 200 cps, and if the viscosity is less than 2 cps, the monomer solution once attached to the fiber base material immediately slides down along the fiber axis, causing the fiber base material to form a sheath. A narrow, enveloping film is not formed. On the other hand, if it exceeds 200 cps, the monomer solution applied to the fiber web will form a film, which is not preferable.

The absorbent material used in the present invention has a basis weight of 10~! 00g/m2
Effective urine absorption ff1 (0,5psi
The absorbent material normally used in disposable diapers is a rectangular sort of approximately 11] 15 cm and a length of 40 cm (area: 0.06 m'). ), and about 50
In order to avoid absorbing and retaining the urine of a cc baby 4 to 5 times, the amount of the superabsorbent resin needs to be at least twice the weight of the fiber web itself.

In the present invention, as a crosslinking agent, a crosslinking monomer having two or more double bonds copolymerizable with an acrylic acid monomer in its molecule is added to the acrylic acid monomer in an amount of 0. O1~1
．． By adding 0% by weight to form intermolecular crosslinks, the morphology of the swollen gel can be stabilized.

In the present invention, the absorption performance of the superabsorbent resin may be improved by adding a high molecular weight polysaccharide to the acrylic acid monomer solution and performing graft polymerization using this polysaccharide as a backbone polymer.

In addition, in the present invention, viscosity modifiers such as water-soluble polymers such as sodium polyacrylate and polyvinyl alcohol, high molecular weight polysaccharides such as hydroquine ethyl cellulose, and colloidal adhesive agents such as thixotrophic agents can be added to the monomer solution. Particulate inorganic compounds selected from at least I
It is possible to improve the adhesion of the monomer solution to the fiber weir by using the following compound.

In the present invention, the acrylic acid-based superabsorbent resin monomer is converted into a resin by a so-called oxidation-reduction type (redox type) polymerization method in which radicals are generated by a combination of a peroxide substance and a reducing substance to initiate polymerization. This polymerization method requires less radical generation activation energy than the thermal decomposition type radical polymerization method, and it is possible to perform explosive polymerization at a relatively low temperature. It is extremely suitable for manufacturing absorbent materials by applying a solution and completing polymerization in an extremely short period of time (several seconds).

The peroxide substance is at least one compound selected from hydroperoxide compounds such as t-butyl hydroperoxide, azo compounds such as azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, etc. Is it good to compose from

The reducing substance is a sulfite compound such as sodium hydrogen sulfite, a reducing organic acid compound such as L-ascorbic acid,
It is preferable to use at least one compound selected from salt compounds such as ferrous sulfate, but the present invention is not limited thereto.

These polymerization initiators are preferably large, water-soluble polymers, and the amount used varies depending on the combination of initiators and polymerization temperature, but is generally in the range of 0.01 to 2.0% by weight based on the monomer. It is good to use it. If it is less than 0.01% by weight, the polymerization reaction will not proceed sufficiently, and if it exceeds 2.0% by weight, the effect will not be obtained even if the amount of initiator is increased.

By the way, the application of the acrylic acid monomer solution to the fiber web is carried out by kiss coating using a coating roll,
Furthermore, by scattering using a rotating plano, fiber webs running at high speed can be efficiently coated, and the amount of coating can be easily controlled. Among these, a nip-type coating roll is most preferred.

As described above, after the monomer solution is applied to the fibrous web, an initiator is added over the monomer solution to initiate polymerization. At this time, it is preferable to add the aqueous solution of the initiator to the surface of the monomer solution in the form of fine particles using a spray device.

The higher the concentration of the opening agent, the better, but in order to avoid clogging of the injection nozzle, it is preferable to keep the concentration lower than the saturation concentration at a predetermined temperature. Further, in order to uniformly spray the entire fiber web, it is preferable to provide a large number of spray nozzles.

The amount of initiator added is 0. 1 to 2.0% by weight of O is sufficient. The monomer solution applied to the fibrous web is then led to a polymerization tank maintained at 60 to 100°C, where a polymerization reaction takes place.

There are no particular restrictions on the shape of the reaction tank used, but if polymerization is to be completed in a short time while the fiber web is running continuously, the fiber web can be moved from top to bottom or from top to bottom as shown in Figure 2. It is preferable to carry out the reaction in a polymerization tank in which the temperature is maintained at 60 to 100° C. and the humidity is 80% or more using hot air saturated with moisture while traveling from the bottom to the bottom.

If the temperature of the reaction tank is less than 60°C, the basic molecular weight of the resin obtained will increase, and although the absorption performance of the resin will improve, it will take a long time to complete the polymerization reaction, so a temperature of 60°C or higher is desirable. Furthermore, if the temperature exceeds 100°C, a self-crosslinking type polymerization reaction occurs, which is not preferable because the absorption performance of the resin decreases.

Normally, in the polymerization of acrylic acid monomers, large reaction heat is generated as the reaction progresses, and it is not uncommon for local rapid temperature increases to occur, resulting in abnormal reactions. Since a bulky and breathable fiber web is used, the water in the monomer solution efficiently evaporates outside the system during polymerization, and the reaction heat is cooled by the latent heat of vaporization, resulting in a uniform temperature distribution. This can prevent troubles such as localized temperature rise causing self-crosslinking to progress to a high degree in that area, resulting in a decrease in absorption performance. In the present invention, the polymerization reaction, which is accompanied by rapid heat generation, is completed homogeneously within an extremely short period of time. It becomes possible for the first time.

The polymerization reaction of the monomers is usually completed in a few seconds (3 to 15 seconds), and about 90 to 95% by weight of the acid monomer is converted into a superabsorbent resin. The tree substance obtained in this way is a hydrous polymer containing water in the shape of a 20-fold lance, and has 50% water content inside.
~IO wt% unreacted residual acid monomer. Residual acrylic acid or a mixture monomer of acrylic acid and methacrylic acid not only reduces the absorption performance of the superabsorbent resin, but also irritates the baby's skin and causes rashes and sores, which is undesirable from a health and safety standpoint. . Therefore, it is necessary to reduce these residual monomers to a safe value by well-known electron beam and/or ultraviolet irradiation.

In the present invention, by increasing the crosslinking density in the surface layer of the superabsorbent resin, it is possible to prevent so-called gel block, where a pasty gel is formed on the surface layer, thereby allowing urine to quickly reach the inside of the resin. Seem to penetrate? This allows the absorption performance to be further improved. Examples of such crosslinking agents include polydanyl ethers such as ethylene glycol nogundyl ether, which have two or more functional groups that react with carboxylic acid in the molecule, polyols such as ethylene glycol, and polyamines such as ethylene amine. can be mentioned. When these crosslinking agents are added to a water-containing polymer and heated, it is possible to form extremely uniform intermolecular crosslinks on the surface layer of the water-containing polymer, and it is also possible to reduce the size of the mesh structure formed by crosslinking. It can be controlled to some extent.

In addition, the bulkiness (cc/g) of the fiber web used in the present invention,
Compressive modulus (%) is measured as follows.

The bulk height (cc/g) was determined by cutting four test pieces obtained by cutting the fiber web into squares with each side of 10 cm (the directions of the sides coincided with the machine direction and the width direction, respectively). Laminated in alternating directions, methyl methacrylate resin plates and weights are placed on top of them, and the weight is 0.5 g/c.
A load of m2 is applied for 10 minutes, the volume V, (cc) of the fiber web layer at that time is measured, and this Vl is divided by the weight of the fiber web layer weighed in advance.

On the other hand, the compressive elastic modulus (%) is determined by applying a load of 35 g/m2 to the fiber web layer whose bulkiness V, (cc) was measured, and measuring the volume V2 (cc) when the layer is left for 10 minutes.

(2) Determine the compressive elastic modulus (%) according to the formula below.

Compression recovery rate (%) - V 2 / V + Measurement is performed using a test piece cut to match Using a "Tennron", hold both ends of the test piece between the ends of the test piece and adjust the test length to 10 cm. Next, the sample is stretched at a stretching rate of 100%/min to obtain a relationship curve between the response angle and elongation. From this relationship curve, read the tensile strength (g/25 mm) and strength (%) when the test piece breaks.

Further, the tensile strength and elongation of the fibrous web are determined in each of the machine direction and the medium direction.

In addition, the absorption performance of the absorbent material obtained by the present invention, that is, the absorption capacity and water retention capacity, was determined by vacuum drying at 80°C for 2 hours.
C60R) (% humidity) for 8 hours in an atmosphere of 1
Measurement is performed using a test piece cut into a square with sides of 10 cm (the directions of the sides match the machine direction and the width direction, respectively). First, the weight [a] (g) of the test piece is weighed, and then, as shown in FIG. The sample is immersed in a shallow container 46 containing a previously prepared test solution (physiological saline = 0.9% NacC) 45 to absorb the test solution. After being immersed for one hour, the test piece 43 was taken out along with the nylon cloth bag 44, and as shown in FIG. Drain the water under a pressure of 35 g/cm'' for 15 minutes. Then, take out the test piece 43 and weigh the weight ffi[b] (g).

Return the test piece 43 to the nylon cloth bag 44 again, place it together with the nylon cloth bag 44 on the side wall of the rotating tank of the centrifugal dehydrator, and
After performing centrifugal dehydration for 90 seconds with a centrifugal force of 50 G, the test piece 43 was taken out from the nylon cloth bag 44) and
](g).

” Calculate the absorption capacity and water retention capacity from the two pairs [al, [b], and [c] according to the following formula.

"Function" When the absorbent material disposed therein absorbs urine, the disposable diaper of the present invention exhibits a specific swelling behavior and selectively stretches in one direction. In other words, when placed perpendicular to the direction from front to back through the crotch of a user such as a baby, uneven wrinkles are created along the longitudinal direction of the disposable diaper due to expansion and expansion, promoting rapid diffusion and absorption of urine. (Prevents diaper leakage from yellow.

"Example" Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example-1) Relative viscosity obtained by polycondensation after esterifying a nocarboxylic acid component of 60 mol% of terephthalic acid and 10 mol% of isophthalic acid with ethylene glycol The solvent is a mixture of equal weights of
A polyester copolymer with a relative viscosity of 1.55 and a melt softening point of 260 °C is known. , using a well-known core-sheath type composite spinning nozzle device,
Polyester copolymer and polyethylene terephthalate were melt-spun at a discharge ratio of 1=1, cooled in a conventional manner, applied with an oil agent, taken off at 680 m/min, bundled, and poured into a can. The undrawn yarn of the core-sheath type composite spun fiber thus obtained has a fiber cross-sectional shape in which the sheath portion 50 has a polyester copolymer and the core portion 51 has polyethylene terephthalate. was. This undrawn yarn tow was drawn 3.5 times at 50 m/min using a horizontal drawing machine, and then mechanically crimped using a crimper formed by a crimper roll and crimper hooks. , heat treated in an autoclave at 100°C for 10 minutes, and then carded into short fibers.

(Example-2) Polyethylene terephthalate fibers (hardness (1,57) 70% by weight as heath fibers and 30% by weight of the core-sheath composite spun fibers obtained in Example-1 as binder fibers were used as opener fibers. - After uniformly spreading the kombu and opening the cotton using a
Carding is carried out at a speed of 1/2 minute, two thin webs are taken from each cart, and these are laminated to form a single web.
A homogeneous card web was formed.

Here, the polyethylene terephthalate fiber has a hollow cross-sectional shape, has a two-dimensional linear fiber sheath shrinkage, has a fineness of 6 denier, has a fiber Q< of 51 mm in length, has 10 crimps/inch, and has a crimp degree. A short fiber Ka of 83 was used.

The nq-marked card web is then guided to a flat belt type air-through type heat treatment equipment, and 16
Hot air at 0° C. was passed through for 10 seconds to melt the binder fibers and weld the fibers together to form a fibrous web with good shape stability.

Table 1 shows the performance of the fibrous web thus obtained.

(Example-3) While running the fiber web obtained in Example-2 at 50 m/min, hydrogen peroxide was added at 167% by weight based on the monomer using a nip-type coating roller, and the mixture was heated to 40°C. The monomer solution with a monomer weight 1 of 200 g/m”
After coating the fibrous web so as to have the following properties, a 5% by weight aqueous solution of L-ascorbic acid was sprayed onto the monomer solution at a concentration of 0.34% by weight based on the monomer, and immediately the atmosphere was set at 80°C and humidity was 80% or more. The polymer was introduced into a polymerization tank maintained at a constant temperature.

Here, the monomer solution is a partially neutralized acrylic acid monomer aqueous solution with a concentration of 65% by weight, in which 60% of the total alkoxyl groups of acrylic acid are neutralized with potassium hydroxide, and NN'-methylbisacrylamide is added as a crosslinking monomer. 0.085% of the total amount was added.

The polymerization reaction started immediately after the monomer solution was applied to the fiber substrate, and the reaction was completed in about 8 seconds without generating heat. The residual monomer in the superabsorbent resin obtained by this polymerization reaction, that is, the partial potassium salt of polyacrylic acid, was measured and found to be 5000 ppm.

Next, as shown in FIG. 1O, electron beams of 2 megarats (M rad) each for a total of 4 megarats are irradiated on both sides of the fiber web using accelerated electron beam irradiation devices 34 and 34 facing each other alternately. , the remaining monomers were polymerized to effect crosslinking. Further, water is sprayed onto this resin-coated web to adjust the water content to 20% by weight based on the resin, and then the fiber web is coated using ultraviolet irradiation devices 36 and 36 facing each other alternately as shown in FIG. Both sides were irradiated with ultraviolet rays of 100 millijoules/cfflffi to polymerize substantially all of the remaining monomers.

The performance of the absorbent material thus obtained is shown in Table 2.

(Example-4) The absorbent material obtained in Example-3 was cut into a rectangular shape with the long side in the machine direction of the fiber web, and after placing it in a disposable diaper as shown in Figure 18, a doll test was carried out. 50c per time using the device
When the 09% saline solution of c was drained 5 times every hour,
There was no leakage from the sides, and as shown in FIG. 15, unevenness was formed along the long side direction of the absorbent material 60.

(Comparative Example-1) In Example-4, instead of cutting the absorbent material obtained in Example-3 into a rectangular shape with the long side in the machine direction of the fiber web, [
Example - except that it was cut into a rectangle with the long side in the IJ force direction.
The same operation as in 4 was performed. As a result of the doll test of the obtained diaper, leakage occurred after the first discharge of 50 cc of 0.9% saline solution, and after the fifth discharge, as shown in Fig. 16.
Large unevenness occurred along the short side direction of the absorbent material 60a.

(Margins below) Table 1 Table 2 "Effects of the Invention" As explained above, the disposable diaper of the present invention quickly absorbs multiple urine and does not leak, making it comfortable to wear and sanitary. It is.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the absorber (4) used in the present invention;
The figure shows the deformed state when the absorbent material absorbs urine and swells and expands. Figures 3(a) and 3(b) are explanatory diagrams of the method for measuring the swelling rate of the absorbent material, and Figure 4 shows the method of measuring the swelling rate of the absorbent material. Fig. 5 is a diagram showing the form of the absorbent material used, and Fig. 5 is a diagram showing the wet state when the absorbent material shown in Fig. 4 absorbs urine. Figure 7 is a diagram showing the wet state when the absorbent material in Figure 6 absorbs urine, Figure 8 is a diagram showing the configuration of the roller card used in the present invention, and Figure 9 is the configuration of the flat card used in the present invention. Fig. 10 is a block diagram of the manufacturing apparatus for the filter absorbent used in the present invention, Fig. 11 is a block diagram of the crosslinking agent solution spraying and heat treatment apparatus used in the present invention, and Figs. 12 and 13 are FIG. 14 is a cross-sectional diagram of the core-sheath type composite spun fibers of the fiber web constituting the absorbent used in the present invention.
Fig. 15 is a state diagram of the absorbent material after the urine absorption test in Example 4, Fig. 16 is a state diagram of the absorbent material after the urine absorption test in Comparative Example 1, and Fig. 17 is a cross-sectional configuration diagram of a conventional disposable diaper. 18(a) is a plan configuration diagram of a conventional disposable diaper, and FIG. 18(b) is a state diagram when the diaper shown in FIG. 18(a) is wet with urine. l...Top sort, 2...Liquid absorption and retention layer, 3...Packing sort, 4...Absorbent material, 5...Urine wet part , 6... Side leakage part, 7... Highly absorbent resin, 8...
Absorbent material, 9...Fiber base material, 10...Absorbent material, 11...Wire mesh, I2...Test liquid, 1
3... Container, 14... Roller roll, 15... Worker roll, 16...
・Stripper roll, 17...Top clothing, 18
...Feedrow, I9...Nose plate, 20...Tekine roll, 2I...
... Dotsfer roll, 22 ... Clearer roll, 24 ... Fiber web, 25 ... Blower, 26 ... Heater, 27 ... Hot air, 28. Heald, 29... Nip type coding roll, 30... Monomer solution, 31...
Initiator solution, 32... Polymerization tank, 33... Super absorbent resin, 34... Electron beam irradiation device, 35... Ultraviolet irradiation device, 36... Rotary plan water spraying device, 37...
Rotating plano crosslinking agent solution spraying device, 38... Heating device, 43 Sample, 44... Nylon mesh bag, 45
...Test liquid, 46 ... Container, 47 ... Wire mesh,
48...acrylic wood board, 49...weight,
50... Sheath part, 51... Core part, 60.60a.
...Absorbent material. Applicant: Mitsubishi Rayon Co., Ltd. Co., Ltd. Showa Year, Month, Day 1. Display of the case 1986 Patent Application No. 65378 2, Name of the invention Disposable diaper 3, Relation with the amended Sekiji ('[13th edition Applicant (603) Mitsubishi Rayon Co., Ltd. 1 (1) Specification "Claims" and "Detailed Description of the Invention" columns. 6. Contents of amendment (1) The claims are corrected as shown in the attached sheet. (2) On page 6, line 11 of the specification. "Temperature control" should be replaced with "
Corrected to "humidity control". <3) In the second line of page 11 of Akira I11iJ, the word "nose plate" is corrected to "datesh plate." (4) In the 6th line of page 19 of the specification, "coating roll" is corrected to "coating roll." (5) On page 19, line 15 of the specification, "polymerization reaction" is corrected to "polymerization initiation reaction." (6) In the fourth line of page 21 of the specification, the phrase "60-100°C" is corrected to "temperature 60-100°C, humidity 80% or more." (7) The statement "15-25%" on page 21, line 17 of the specification is corrected to "20-30%." (8) In the 12th and 13th lines of page 25 of the specification, the words "polymerization method" are corrected to "polymerization initiation method." (9) Ming 11! On page 27, line 9, the word "opening agent" is corrected to "initiator." (10) On page 27, line 16 of the specification, “60 to 100°C
” is replaced by “Temperature 60 to 100℃, 80% or more of m degrees”
Correct to. (11) On page 30, line 6 of the specification, "ethylene glycol diglycidyl" is corrected to "ethylene glycol diglycidyl." (12) On page 30, line 7 of the specification, "polyglycidyl ether" is corrected to "polyglycidyl ether." (13) The following sentence from line 6 to 10t'r on page 31 of the specification: ``On the other hand, the compressive modulus (%) is 359/m for the fiber wear layer whose bulkiness V+ (CC) was measured. Apply a load of 10
Measure the volume V2 (CC) when left for minutes, and
The compressive elastic modulus (%) is determined from l and V2 according to the formula below. Compression recovery rate (%) = Vz / Vl x 100J
Delete. (14> Add the following sentence between lines 5 and 6 on page 31 of the specification. “On the other hand, the compression recovery rate (%) is the l! The volume V2 (CC) was measured when a load of 50? Measure the volume V3 (CC) and find the compression recovery rate (%) according to the following formula: Compression recovery rate (%) = 100X (V3 - V2) / (Vl - V2)
J(15) On page 31, line 11 of the specification, the phrase "extension strength" is corrected to "extension strength and elongation." (16) In the 7th line of page 30 of the specification, [absorption capacity (g/g) = [0]” - [a] [a]
" is changed to [absorption capacity (g/9) - [b] - [a] [a] " by n pressure. (17) In the 8th line of page 33 of the specification, "Water retention ratio, /,) - [b] - [a] [a]" is replaced with [Water retention ratio (g/g) = [C] - [ a] [a]
Correct to J. (18) On page 34, line 8 of the specification, [Titanium chloride J is corrected to read "carbon tetrachloride." (19) On page 35, line 20 of the specification, the words "textured sheath" are corrected to "fiber length." (20) Page 37 of the specification, lines 2 to 3 [Corrected to all alkoxyls. (21) On page 37, line 16 and line 17 of the specification, the words "F Megarat" are corrected to "Megarad." (22) "20" on page 34, line 19 of the specification is corrected to "30". (23) In the left column of Table 2, page 40 of the Memorandum of Understanding, "water retention ratio" is corrected to "absorption ratio" and "absorption ratio" to "water retention ratio J." An acrylic acid-based superabsorbent resin top solution is applied to a fiber web in which a range fiber H base material is oriented in a certain direction, and this is polymerized to fix the superabsorbent resin onto the fiber base material, A disposable diaper made of a rectangular absorbent material with the orientation direction of the VA miscellaneous materials as the longitudinal direction, and the absorbent material is arranged so that the orientation direction of the IJt1 base material matches the both sides of the diaper. Disposable diapers.

Claims (1)

[Scope of Claims] An acrylic acid-based superabsorbent resin monomer solution is applied to a fibrous web in which a threaded base material is blended in a certain direction, and this is polymerized to fix the superabsorbent resin onto the fibrous base material. Then,
A disposable diaper made of a rectangular absorbent material with the orientation direction of the fiber base material being the longitudinal direction, wherein the absorbent material is arranged so that the orientation direction of the fiber base material is along both sides of the diaper. Disposable diapers with special features.