JPH02153731A - Moisture absorbing sheet - Google Patents

Abstract

PURPOSE:To obtain a moisture absorbing sheet having an excellent water absorbing and water holding capacity at a low cost by laminating, and then integrating a water permeable fibrous sheet on at least one surface of a sheet-shaped water absorbing polymeric compound. CONSTITUTION:A fibrous base adhering and holding the water absorbing polymer of a water absorbing polymeric compound used herein is a fabric, knittwork or non- woven fabric such as tissue paper or cotton gauze made by molding fiber loosely. And, sponge-shaped base is a polymeric foaming body such as rubber sponge, polyethylene foam or the like, and it may preferably be a type having a continuous net-shaped porous structure, and water soluble ethylene unsaturated monomer may preferably be a type capable of being converted to water soluble polymer, and giving an excellent water absorbing ability after polymerizing and drying it. And, the monomer water solution is infiltrated or sprayed into a fibrous base or the like, and after the monomer dispersed uniformly on the fibrous base or sponge-shaped base is polymerized, a water permeable fibrous sheet is integrated on one side thereof by needle punching method, quilting method or the like. Consequently, a water absorbing sheet having a high water absorbing and water holding capacity can be obtained at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION Technical Field The present invention relates to moisture absorbing sheets. More specifically, the present invention comprises a water-absorbing polymer composite in which a water-absorbing resin is formed on a fibrous substrate, etc., and a water-permeable fibrous sheet that is laminated and integrated with the composite, and The present invention relates to a moisture-absorbing sheet that has little return of moisture and can be cut into any size or shape.

Conventional Technology During winter, especially in cold regions, water vapor inside a house condenses on low-temperature areas, such as window glass surfaces exposed to cold air.
condensation) may occur. Condensed moisture travels along the glass surface, collects at the bottom of the window frame, and eventually overflows from the window frame, often staining walls and the like. As a simple countermeasure, place a rag, paper towel, etc. at the bottom of the window frame.
This is used to absorb condensed water. However, these rags, vapor towels, and the like do not necessarily have sufficient water absorption ability, so to prevent staining, it is necessary to use them frequently, to replace them frequently, or to frequently squeeze out the water. However, it is not aesthetically pleasing to use rags, etc. (Also, even if you replace them or squeeze out the water, the moisture will not drip onto the floor etc. due to their insufficient water absorption ability. It's hard to avoid.

Improving water absorption and water retention capacity is an essential issue for moisture absorbing sheets, including such condensation water absorbing sheets.

[Summary of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a moisture-absorbing sheet with excellent water-absorbing and water-retaining abilities at an extremely low cost.

Therefore, the moisture-absorbing sheet according to the present invention is a sheet obtained by impregnating or coating a fibrous substrate or a sponge-like substrate with a water-soluble ethylenically unsaturated monomer, and then polymerizing the water-soluble ethylenically unsaturated monomer. A water-permeable fibrous sheet is laminated on at least one side of a water-absorbing polymer composite, and these are integrated.

Effects The moisture absorbing sheet according to the present invention has an excellent ability to absorb moisture and retain absorbed moisture due to the use of a super absorbent resin.

Furthermore, since the super absorbent resin is strongly fixed, the super absorbent resin or the water absorbing gel will not fall off.

Therefore, the moisture-absorbing sheet according to the present invention is particularly suitable for applications that require high water-absorbing and water-retaining abilities (for example, condensation water-absorbing sheets), and also for applications that require a certain degree of durability (for example, door mats). Available for use.

Furthermore, since the superabsorbent resin or water-absorbing gel does not fall off from the cut surface of the sheet, it is convenient to create a water-absorbing sheet of a desired shape and size by cutting a long sheet. Therefore, since productivity is high and manufacturing is possible at low cost, a disposable absorbent sheet can be provided.

Specific uses of the moisture absorbing sheet of the present invention include, in addition to the above-mentioned condensation water absorbing sheet, a mat for absorbing cleaning liquid during carpet cleaning, a mat for covering and absorbing water, a mat for absorbing water leakage, and a mat for absorbing rainwater. etc. Note that the moisture absorbing mat according to the present invention is not limited to these, as long as it can be used to quickly absorb and retain moisture.

[Detailed description of the invention]

Moisture-absorbing sheet The moisture-absorbing sheet according to the present invention is composed of a sheet-shaped water-absorbing polymer composite (details will be described later) and a water-permeable fibrous sheet. The water-permeable fibrous sheet is laminated and integrated.

Here, the term "composed of a sheet-shaped water-absorbing polymer composite and a water-permeable fibrous sheet" may include other purpose-oriented auxiliary sheets or auxiliary materials in addition to the above two essential materials. It shows good things.

(1) Water-absorbing polymer composite The water-absorbing polymer composite used in the water-absorbing sheet of the present invention is a water-soluble polymer that forms a super absorbent resin on a sheet-like fibrous base or sponge-like base. It is obtained by impregnating or coating an ethylenically unsaturated monomer and then polymerizing the water-soluble ethylenically unsaturated monomer.

1) Fibrous substrate or sponge-like substrate The fibrous substrate that holds the water-absorbing polymer in the bone canal is specifically formed by loosely molding fibers, such as a pad, carded or air-laid web, tissue vapor, or cotton. It can be a woven fabric like gauze, a knitted fabric, or a non-woven fabric.

Here, a "formed" fibrous substrate is one that is already in the form of a web, even though cutting, joining, shaping, etc. may be required to incorporate the fibrous substrate into an article.
Web forming operations are meant to require no further application. Further, the fibrous substrate may be a nonwoven fabric formed into a sheet by various methods such as spunbond dry method and wet method.

It is generally preferred to use a fibrous substrate based on absorbent fibrous materials such as wood bulbs, rayon, cotton and other cellulosic fibers and/or polyester fibers. However, other types of fibers, such as polyethylene, polypropylene, polystyrene, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile,
Fibers such as polyurea-based, polyurethane-based, polyfluoroethylene-based, polycyanide-based vinylidene, etc. may be included in the molded fibrous substrate.

The spongy substrate used in the present invention is a polymeric foam such as polyvinyl acetal sponge, rubber sponge, polyethylene foam, polypropylene foam, urethane foam, etc., and has a continuous mesh-like porous structure. Either is fine as long as it is.

The main role of these fibrous substrates or sponge-like substrates is to retain the produced water-absorbing polymer, but when this substrate is made of water-absorbing fibers as mentioned above, it can also be used as a water-retaining material like the water-absorbing polymer. It also functions as a.

2) Water-soluble ethylenically unsaturated monomer The water-soluble ethylenically unsaturated monomer to be impregnated or applied to the fibrous substrate or sponge-like substrate is one that can be converted into a water-absorbing polymer and provides good water-absorbing performance after polymerization and drying. Either is fine as long as it is.

Water-soluble monomers that provide such performance include water-soluble monomers having as functional groups carboxylic acids or (and) salts thereof, phosphoric acids or (and) salts thereof, and salts derived from sulfonic acids or (and) salts thereof. ethylenically unsaturated monomers. Specific examples include (meth)acrylic acid or its salts, vinylsulfonic acid or its salts, vinylphosphonic acid or its salts, and the like. Among these, (meth)acrylic acid or a salt thereof is particularly preferred.

The resulting polymer may be a homopolymer or copolymer of these monomers, or a graft polymer to starch or cellulose.

Furthermore, it is also possible to add crosslinking agents and additives to these monomers to improve absorption performance. As the crosslinking agent, water-soluble polyfunctional ethylenically unsaturated monomers such as methylene bisacrylamide, ethylene glycol di(meth)acrylate, and polyethylene fluoride di(meth)acrylate, ethylene glycol diglycidyl ether,
Polyglycidyl ethers such as polyethylene glycol diglycidyl ether, polyols such as glycerin and pentaerythritol, and polyamines such as ethylenediamine, which have two or more functional groups that can react with functional groups such as carboxylic acid, phosphoric acid, and sulfonic acid. Water-soluble compounds can be suitably used.

3) Polymerization of ethylenically unsaturated monomers In order to apply an aqueous solution of such monomers to a fibrous or sponge-like substrate, as long as the monomers remain uniformly dispersed on the fibrous substrate and can be polymerized, This can be done by any desired means or mode. One typical means for this purpose is to impregnate a fibrous substrate or the like with an aqueous solution of 7-summer or to spray the aqueous solution of 7-summer onto a fibrous substrate or the like.

Note that the monomer aqueous solution may contain a small amount of a water-soluble 6-solvent dissolved therein, if desired.

Further, the step of polymerizing the monomers uniformly dispersed on the fibrous substrate or the spongy substrate may be any suitable step. Typical of such methods is the action of a water-soluble radical polymerization initiator, specifically, adding the radical polymerization initiator to an aqueous monomer solution and decomposing it on the fibrous substrate. Alternatively, the radical polymerization initiator can be applied as a solution separate from the monomer evenly by spraying onto the fibrous substrate after the monomer aqueous solution has been applied, and the radical polymerization initiator can be decomposed on the fibrous substrate. A separate solution is applied to the fibrous substrate, and an aqueous solution of Hemotsuma is sprayed thereon.
It is applied uniformly by coating or the like. Another means of initiating polymerization is irradiation with high energy radiation.

The water-absorbing polymer composite thus obtained is usually dried by means such as hot air, microwaves, and infrared rays. If unreacted monomers, etc. remain in the composite, it is preferable to wash the composite with water or warm water prior to drying.

(n) Water-permeable fibrous sheet The water-permeable fibrous sheet is laminated on the water-absorbing polymer composite sheet to mainly protect or support the water-absorbing polymer composite or the superabsorbent polymer attached thereto. It plays the role of

As such a water-permeable fibrous sheet, for example, the same type of fibrous base material as that used in the above-mentioned water-absorbing polymer composite can be used, but in the present invention, a water-permeable and fibrous sheet can be used. If so, any one can be used as long as it does not contradict the purpose of the invention. In particular, in the present invention, it is preferable to include as a constituent a fiber such as polyester that is loosely formed by carding or the like, and among these, fibers with a high degree of freedom that can be easily processed by needle punching or the like described below are particularly preferred. Here, "water permeability" means that when it comes into contact with water, it is known for its property of rapidly passing water and transmitting it to the absorbent polymer complex located on the opposite side.

(m) Auxiliary Materials As described above, the moisture absorbing sheet according to the present invention may contain various materials that are more appropriate depending on the various uses.

Depending on the application, it may not be appropriate to treat these materials as mere auxiliary materials, but since they are not essential materials in the moisture absorbing sheet of the present invention, they will be treated as auxiliary materials for convenience.

A typical example of such an auxiliary material is a water-impermeable sheet. Note that even if the material is originally water-permeable or water-absorbing, it may be treated as a water-impermeable sheet in the present invention if it has been subjected to hydrophobic treatment, or if the water permeation rate is extremely slow due to its high density.

These auxiliary materials can be applied before or after integrating the water-absorbing polymer composite and the fibrous sheet.

When applying auxiliary materials before the integration process, use materials that will strengthen the integration between the water-absorbing polymer composite and the water-permeable fibrous sheet, or materials that will be integrated at the same time during the integration process. It is efficient to use a material (for example, a fibrous material when using the needle punch method).

(IV) Integration method The method for integrating the water-absorbing polymer composite and the water-permeable fibrous sheet must be such that sufficient bonding strength can be obtained and the water-absorbing capacity of the water-absorbing sheet can be maintained at a sufficient level. If so, it is optional. Preferred integration methods in the present invention include, for example, a needle punching method, a quilting method, a hot embossing method, and a dry laminating method. Among these, the needle punch method is particularly preferred.

The needle punch method is a process in which many needles with small barbs are moved up and down to push the fibers into the fibers.
This is a method that creates a dimensional intertwining of fibers and attempts to obtain cohesive strength through this intertwining of fibers.

When the needle punch method is employed in the present invention, the water-absorbing polymer composite, the water-permeable fibrous sheet, and other auxiliary sheets or materials as needed are superimposed and arranged in a planar manner. A keyed needle may be moved up and down and pierced to intertwine the fibers three-dimensionally between the two sheets and within each sheet. As a result, the superabsorbent resin generated and immobilized on the fibers of the water-absorbing polymer composite is further fixed three-dimensionally, so the holding power of the superabsorbent resin or water-absorbing gel is even stronger. become.

[Experiment example]

Example 1 A 70 mol 96 neutralized aqueous potassium acrylate solution with a solids content of 63% by weight was prepared. To this solution, 0.4ffi amount % of N-N' was added to the potassium acrylate monomer.
Methylenebisacrylamide and 0.3% by weight of potassium persulfate were dissolved, and then a polyester fiber nonwoven fabric with a basis weight of 40 g/rrr (Marix 90 manufactured by Unitika) was dissolved.
Sample A was obtained by uniformly impregnating this aqueous solution onto 403WS O) so that the polymer basis weight was 80 g/r+f.
was created. In addition, only the polymer basis weight is 50g/rr.
Sample B was produced in the same manner as above except that f was changed.

These seven-mer impregnated materials were placed in an oven purged with nitrogen for 1 hour to polymerize the monomers, and then dried under reduced pressure at 100°C to obtain a water-absorbing sheet made of a sheet-shaped water-absorbing polymer composite. . This water-absorbent sheet is made into a sheet by loosely carding polyester fibers (thickness 5m +
s, area weight 40 g/r+f) and sandwiched between thin polyester nonwoven fabrics, and laminated and integrated using a needle punch tester.

One of these sheets was prepared in a size of 10 x 10 (maximum), and after immersed in deionized water or 0.9% NaCl aqueous solution for 30 minutes, the water absorption amount of each sheet was determined by DI.

In the obtained absorbent sheet, the polymer was retained in the fiber base material even after water absorption, and the polymer did not fall off from the cut surface of the sheet. In addition, there was no leaching of the polymer onto the surface, and the product had a smooth feel.

[Brief explanation of the drawing]

FIG. 1 conceptually shows an enlarged view of a water-absorbing polymer composite that constitutes a water-absorbing sheet according to the present invention. FIG. 2 shows a cross-sectional view of the same water-absorbing polymer composite. FIG. 3 shows an example of processing a moisture absorbing sheet according to the present invention. 4 to 6 show preferred specific examples of the moisture absorbing sheet according to the present invention. 1... Fibrous base or sponge-like base, 2... Super water absorbent resin, 3... Water absorbent polymer composite, 4... Polyester nonwoven fabric (loosely carded), 5...
... Polyester non-woven fabric (thin), 6... Sheet for moisture absorption, 6a... Sheet for absorbing condensation, 6b... Sheet for covering water or absorbing water leakage, 6C... Mat for absorbing rainwater, 7... Window glass, 8... Condensation water, 9... Water covering or leakage, 10... Door.

Claims (1)

[Claims] After impregnating or coating a fibrous substrate or a sponge-like substrate with a water-soluble ethylenically unsaturated monomer, at least one side of a sheet-like water-absorbing polymer composite obtained by polymerizing the water-soluble ethylenically unsaturated monomer is applied. A moisture-absorbing sheet characterized by being made by laminating and integrating water-permeable fibrous sheets.