JPH0939147A - Water absorbing composite, manufacture thereof, and lubricating material for pulling out temporarily buried article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water absorbing composite having high mechanical strengths, a manufacturing method thereof, and a lubricating material for pulling out a temporarily buried article using the composite, by sewing together a part of a water absorbing sheet where a water absorbing polymer is directly fixed to a base material. SOLUTION: In a water absorbing sheet, a water absorbing polymer is directly fixed to a base material without a binder. The water absorbing polymer contains as main components, for example, an acrylic acid, an acrylic acid ester, an acrylic acid salt containing a sulfonic group or an acrylamide. A water absorbing composite is formed by sewing together at least one part of the water absorbing sheet. The water absorbing composite can be obtained, for example, by joining or superposing two sheets of the water absorbing sheet and sewing together their end parts by means of a sewing machine or manual sewing. Also, the water absorbing composite can be obtained by folding back the water absorbing sheet and sewing together the end parts by means of a sewing machine and the like.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a water absorbent composite and a method for producing the same. More specifically, it relates to a water-absorbent composite body in which at least a part of a water-absorbent sheet is sewn, and a method for producing the same.

[0002]

2. Description of the Related Art Heretofore, a water-absorbent composite material and a cold-insulating material obtained by processing a water-absorbent sheet having a water-absorbent polymer adhered to a base material into a bag have been known (Japanese Patent Laid-Open No. 30522/1993 and Japanese Patent Laid-Open No. 30522/1990). 182138, JP-A-6-337189).

These bag-like products were obtained by processing the water-absorbent sheet provided with the thermoplastic resin layer at the ends thereof by heat sealing to form a bag-like product.

[0004]

However, when a thermoplastic resin is provided and then the ends are heat-sealed to form a laminated bag, the bonded ends are deteriorated by heat-sealing and the ends are likely to tear. There was a problem.
Further, it is necessary to provide a thermoplastic resin layer on the water absorbent sheet in order to bond them by heat sealing. Therefore, such a method is not necessarily a highly productive manufacturing method. Further, in order to increase the adhesive strength, it is necessary to prolong the fusing time, which is not necessarily a high productivity method in continuous production.

The present invention is to solve the above problems, and an object thereof is to provide a water-absorbent composite having high mechanical strength, a method for producing the same, and a lubricant for extracting a temporary buried object using the composite. is there.

[0006]

The above-mentioned problems can be solved by a water-absorbent composite body in which at least a part of a water-absorbent sheet having a water-absorbent polymer directly adhered to a substrate is sewn.

Further, the above-mentioned problems can be solved by a method for producing a water-absorbent composite, which is characterized in that the ends of a water-absorbent sheet in which a water-absorbent polymer is directly adhered to a substrate are sewn together and joined together.

Further, the above-mentioned problems can be solved by a temporary buried object withdrawing lubricant in which at least a part of a water-absorbent sheet having a water-absorbent polymer directly adhered to a base material is formed into a bag shape or a tubular shape by stitching.

The present invention will be described in detail below.

In the water absorbent sheet of the present invention, the water absorbent polymer is directly adhered to the base material without interposing a binder or the like.

As the water-absorbent polymer in the present invention,
For example, it is obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing acrylic acid, an acrylic acid salt, an acrylic acid ester containing a sulfonic acid group or acrylamide as a main component, and optionally a cross-linking agent.
A water-absorbent polymer that absorbs 0 to 1000 times as much water and swells can be mentioned, and is preferably used.

Examples of water-absorbing polymers other than the above include, for example, cross-linked polyethylene oxide, cross-linked polyvinyl pyrrolidone, cross-linked sulfonated polystyrene, cross-linked polyvinyl pyridine, saponified starch-poly (meth) acrylonitrile graft copolymer, starch- Poly (meta)
Acrylic acid (and its salt) graft cross-linked copolymer, reaction product of polyvinyl alcohol and maleic anhydride (salt),
Examples thereof include crosslinked polyvinyl alcohol sulfonate, polyvinyl alcohol-acrylic acid graft copolymer, isobutylene-maleic anhydride copolymer crosslinked product, and carboxymethylcellulose crosslinked product.

In the water absorbent sheet of the present invention, the water absorbent polymer is directly adhered to the substrate without a binder.
Such a water-absorbent sheet is obtained by directly pressing a water-absorbent polymer softened with water onto the substrate A), and drying it if necessary. B) A method in which a water-soluble polymer obtained by polymerizing a monomer containing a water-soluble ethylenically unsaturated monomer that can be converted into a water-absorbing polymer by crosslinking is applied to a substrate, and then cross-linked. C) It can be obtained by, for example, a method of applying a monomer aqueous solution containing a water-soluble ethylenically unsaturated monomer capable of forming a water-absorbing polymer by polymerization to a substrate, and then polymerizing it in the presence of a crosslinking agent, if necessary. The method for obtaining the water-absorbent sheet of the present invention is not particularly limited as long as the water-absorbent polymer can be directly adhered to the substrate without a binder.

Among them, from the viewpoints of easiness of production, economy, durability of the water-absorbent sheet to be obtained, etc., after the monomer containing the water-soluble ethylenically unsaturated monomer is adhered to the substrate, the monomer is used as a base. A method of polymerizing and crosslinking on the material is preferable.

The water-soluble ethylenically unsaturated monomer that can be used is not particularly limited as long as it can be converted into a water-absorbing polymer by polymerizing it.
Specifically, acrylic acid, methacrylic acid, (meth) acryloylethanesulfonic acid, (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid and their alkali metal or ammonium salts, ( Examples thereof include (meth) acrylamide, methoxypolyethylene glycol (meth) acrylate, hydroxyalkyl (meth) acrylate, N, N′-dimethylaminoethyl acrylate and quaternary compounds thereof. Of these, one or more selected from acrylic acid, (meth) acryloylethanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, alkali metals thereof, and (meth) acrylamide are preferable.

Examples of the substrate used in the present invention include hydrophilic or hydrophobic woven fabrics, nonwoven fabrics, knitted fabrics, fibrous substrates such as paper, and porous materials such as sponges. Since the base material has voids in it, a swellable space for the water-absorbent polymer can be secured. Further, when used as a material for extracting a temporary embedding material such as H steel, cement water can effectively contact the water-absorbing polymer, which is preferable. As the material used for the substrate, when the substrate is a fibrous substrate, hydrophilic ones include wood pulp, cotton, wool, rayon, acetate, vinylon and other fibers, and hydrophobic ones Fibers of polyester, polyacrylonitrile, nylon, polypropylene, polyethylene, polyvinyl chloride, polyurethane, glass wool, rock wool can be mentioned. When the base material is sponge-like, polyacetal, polyurethane, cellulose, phenol resin and the like can be mentioned. Among them, from the viewpoints of workability, flexibility, and economical efficiency of the obtained lubricant for pulling out temporary embeddings, it is preferable to use a nonwoven fabric made of hydrophobic fibers such as polyester and polypropylene as a preferable base material. The thickness of the base material is not particularly limited, but is generally in the range of 0.01 to 10 mm. The basis weight is in the range of 10 to 500 g / m ² .

In the present invention, the weight ratio of the water-absorbent polymer to the substrate is 10 to 1000 parts by weight, preferably 80 to 50 parts by weight, based on 100 parts by weight of the substrate.
The range is 0 parts by weight. When the amount of the water-absorbent polymer is less than 10 parts by weight, the lubricating effect at the time of pulling out the temporary absorbent from the water-absorbent polymer is small, which is not preferable. On the other hand, when it exceeds 1000 parts by weight, the flexibility of the water-absorbent sheet obtained decreases, which is not preferable from the viewpoint of workability.

As a method of polymerizing the monomer containing the water-soluble ethylenically unsaturated monomer on the substrate after adhering the monomer to the substrate, for example, a method using heat, light, electron beam, ultraviolet ray, or the like is used. Can be adopted. If necessary, a water-soluble radical polymerization initiator such as a persulfate salt or a water-soluble amidino compound and other additives may be added to the above-mentioned aqueous solution of the monomer.

When the above-mentioned monomers are polymerized, divinylbenzene, tetraallyloxyethane, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di ( (Meth) acrylate, polyethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate
A polyfunctional water-soluble ethylenically unsaturated monomer represented by acrylate, pentaerythritol di (meth) acrylate, N, N-methylenebisacrylamide, triallyl isocyanurate, and trimethylolpropane diallyl ether can be added in advance. . By using the cross-linking agent, the durability and shape retention of the resulting water absorbent sheet can be improved. The amount of the cross-linking agent used can be appropriately selected depending on the type of the monomer and the polymerization conditions, but is generally 0.0
It is in the range of 01 to 10 mol% (relative to the monomer), and preferably in the range of 0.01 to 5 mol% (relative to the monomer).

In the water absorbent composite of the present invention, at least a part of the water absorbent sheet is sewn. This water-absorbent composite can be obtained, for example, by stacking or stacking the above-mentioned two water-absorbent sheets and stitching the ends by sewing or sewing. It can also be obtained by folding back the water absorbent sheet and stitching the end portions by a method such as sewing with a sewing machine or hand sewing.

The place to be sewn may be in the long side direction or the short side direction, or may be sewn in the long side direction and the short side direction. A tubular water-absorbent composite can be obtained by sewing only the long side direction or the short side direction. In addition, a bag-shaped water absorbent composite can be obtained by sewing the long side direction and the short side direction.

The shape of the water-absorbent composite of the present invention thus obtained is tubular or bag-like. Further, in the present invention, the ends of two or more water absorbent sheets may be sewn together to form a wide water absorbent composite. Alternatively, two or more water-absorbent sheets may be superposed and sewn together to form a water-absorbent composite body in which a plurality of water-absorbent sheets are laminated. Since the laminated body of the water absorbent sheet has a large water absorption amount per unit area, it can be suitably used for sanitary articles such as a water absorbent mat and a paper diaper.

Since the water-absorbent composite thus obtained has the ends thereof sewn together by a method such as sewing with a sewing machine, it has better mechanical strength as compared with the case where it is bonded by heat sealing or an adhesive. The suture does not impair the flexibility of the composite. Further, the productivity is high, and the production equipment is simpler as compared with the case where a heat seal or an adhesive is used, which is advantageous in cost. Further, it is advantageous in terms of raw material cost.

On the other hand, when they are attached by heat sealing, the seal portion may be deteriorated by heat, resulting in low mechanical strength. In addition, the sealed portion may become hard and impair flexibility. On the other hand, it is not preferable to use an adhesive, because when the bonded portion is cured, the adhesive becomes poor in flexibility. Further, it often takes time for the adhesive to harden, which is problematic in terms of productivity. In terms of environment, too, a solvent is often used, which is not preferable.
Further, there is a possibility that the water-absorbing performance may be deteriorated at a portion bonded by heat sealing or an adhesive.

In the present invention, the water absorbent sheet can be sewn as it is, but a base material such as cloth, non-woven fabric, paper or film can be laid on the sewn portion for reinforcement. In addition, a heat seal or an adhesive can be used together when stitching.

The water absorbent sheet may be provided with a thermoplastic resin layer or a metal foil such as an aluminum foil.

Examples of the thermoplastic resin layer include polyolefin such as polyethylene and polypropylene, nylon,
Examples thereof include polyester, polyvinyl chloride, polyvinylidene chloride and the like. These thermoplastic resins can be attached as they are to a water absorbent sheet as a film, or can be formed by applying a heat-melted resin to a water absorbent sheet. The thermoplastic resin layer can be provided on one side or both sides of the water absorbent sheet. Further, the thermoplastic resin layer may be provided on the entire one surface of the sheet, or may be provided partially such as streaks, lattices, or dots. When the thermoplastic resin layer is provided on both surfaces of the water absorbent sheet, it is necessary that at least one surface is partially or perforated. The thickness of the thermoplastic resin layer is not particularly limited, but is generally in the range of 1 to 2000 μm.
When the thickness is less than 1 μm, the thermoplastic resin layer has poor mechanical strength. On the other hand, when the thickness is more than 2000 μm, the water-absorbent composite has poor flexibility.

The water absorbent composite thus obtained has the following features.

1. Since the overlapped end portions of the water absorbent sheet are sewn together, the mechanical strength becomes better than that in the case where they are bonded by heat sealing.

2. Since the ends are bonded together by suturing, the water-absorbent composite has excellent flexibility as compared with the case of bonding with an adhesive or the like. 3. The water-absorbing performance deteriorates at a portion bonded by heat sealing or an adhesive, while the water-absorbing performance is maintained because the ends are sewn together. .

4. The strength is further improved by stacking base materials such as cloth, non-woven fabric, paper and film on the edges.

5. Since the water-absorbent polymer is directly adhered to the base material without interposing the binder, the water-absorbing property and the hygroscopic property of the polymer are not hindered by the binder, and the performance of the polymer is sufficiently exhibited. In particular, when the water-absorbent sheet is obtained by polymerization of a water-soluble ethylenically unsaturated monomer forming a water-absorbent polymer on a substrate, there is no dropout or migration of the polymer during water absorption or moisture absorption, and freshness is maintained. It can be suitably used as a material, a dew condensation preventing material, a sanitary article such as a diaper, a water absorbing mat, a cold insulating material, a lubricant for pulling out a temporary buried object such as H steel, and the like.

The method for producing the water-absorbent composite of the present invention has the following features.

Since the ends of the 1.2 water-absorbent sheets or the folded water-absorbent sheets are sewn by sewing with a sewing machine or the like, the productivity is high as compared with the case where heat sealing or bonding with an adhesive is used. In addition, the equipment is simple and good in terms of cost.

2. When pasting by heat sealing, it is necessary to provide a thermoplastic resin layer on the water-absorbent sheet, but since the end portions are sewn in the manufacturing method of the present invention, it is possible to perform the pasting without providing the thermoplastic resin layer, which is cost effective. Is advantageous to. 3. It takes time to cure when it is bonded with an adhesive, but such time is not necessary when the ends are sewn, and the productivity is high.

4. Adhering with an adhesive drains the organic solvent, which may require treatment and environmental problems, but when sewing the ends, such problems do not occur.

5. There is no need to use expensive adhesives or thermoplastic resins, which is advantageous in terms of cost.

[0038]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

-Production Example 1 of water-absorbent sheet-75% aqueous solution of partially neutralized sodium acrylate neutralized with sodium hydroxide (monomer concentration 40% by weight)
Methylenebisacrylamide 0.1 mol% (to sodium acrylate monomer), sodium persulfate 1 g / mol (to sodium acrylate monomer) and hydroxyethyl cellulose 1.5 parts by weight (to sodium acrylate monomer) are dissolved in the monomer. After preparing the aqueous solution,
Nitrogen gas was blown in to remove dissolved oxygen.

In this monomer aqueous solution, a width of 1 m and a basis weight of 25
After immersing a polypropylene nonwoven fabric of g / m ² in excess, remove excess monomer aqueous solution with a squeeze roll, continuously polymerize the monomer in a thermostatic chamber under a nitrogen atmosphere, then dry and wind it to fix the water-absorbing polymer to the nonwoven fabric. A water absorbent sheet (1) was obtained. Adhesion amount of water-absorbing polymer is 45g
/ M ² .

-Example 1-Water-absorbent sheet (1) obtained in Production Example 1
2 sheets were superposed and 1 cm from both ends were sewn with a nylon thread to obtain a cylindrical water-absorbent composite 1 having a width of 1 m.

The superposed portions of the side edges of the resulting water-absorbent composite 1 were cut out by 5 cm in the long direction and 5 cm in the short direction to obtain a sample having a length of 10 cm and a width of 5 cm. This was pulled longitudinally at a pulling speed of 200 mm / min, and the breaking strength was measured and found to be 2.6 kgf.

Example 2 Water Absorbent Sheet Polyethylene was melt-coated on one side of the water absorbent sheet (1) obtained in Production Example 1 to a thickness of 30 μm to obtain a water absorbent sheet (2). The two water-absorbent sheets (2) thus obtained were laminated so that the polyethylene layers face each other. Next, a 1-cm-wide tubular water-absorbing composite body 2 having a polyethylene layer provided inside was obtained by sewing with a nylon thread a portion 1 cm from both ends.

The superposed portions of the side edges of the resulting water-absorbent composite body 2 were cut out by 5 cm in the long direction and 5 cm in the short direction to obtain a sample having a length of 10 cm and a width of 5 cm. This was pulled in the longitudinal direction at a pulling speed of 200 mm / min and the breaking strength was measured and found to be 2.9 kgf.

-Comparative Example 1- Two water-absorbent sheets (1) obtained in Production Example 1 of water-absorbent sheet were superposed, and both end portions were pasted with a commercially available urethane adhesive. 1 until the bonded part is cured
After standing for a day, a comparative water absorbent composite 1 was obtained.

The bonded portion was stiff due to the cured adhesive. The breaking strength of the obtained comparative water-absorbent composite 1 was measured in the same manner as in Example 1 and found to be 1.8 kgf.

-Comparative Example 2-The two water-absorbent sheets (2) obtained in Example 2 were laminated so that the polyethylene layers face each other. Then, both end portions were heat-sealed to obtain a comparative water-absorbent composite 2 having a width of 1 m and provided with a polyethylene layer inside. The width of the heat seal was 2 mm.

The breaking strength of the obtained comparative water-absorbent composite 2 was measured in the same manner as in Example 1 and found to be 0.9 kgf.

Example 3 The water-absorbent composite body 2 obtained in Example 2 was cut to a length of 12 m, and one side of the opening was hooked with a sewing machine.

In this bag, H with a width of 30 cm and a length of 10 m
Diameter 60c filled with steel and filled with soil cement
It was constructed in the ground with a depth of 10 m and a depth of 10 m. The soil cement was prepared by mixing 12.8 parts by weight of cement, 52.6 parts by weight of water, 1.3 parts by weight of bentonite, and 33.9 parts by weight of clay.

After 30 days, H steel was extracted from the hardened cement, and the maximum extraction load was 2.2 t. Cement did not adhere around the drawn H steel, and the H steel was reusable. This is probably because the bag made from the water-absorbent composite of the present invention did not tear when embedded in cement.

Comparative Example 3 The comparative water-absorbent composite 2 obtained in Comparative Example 2 was cut to a length of 12 m, and one side of the opening was heat-sealed.

H steel was applied in the same manner as in Example 3 except that this bag was used, and the steel was pulled out after 30 days. The maximum withdrawal load was 1.5 t. Cement partially adhered around the drawn H steel. This is probably because the heat-sealed end of the bag was partially torn during construction.

Example 4-70 mol% acrylamide and sodium acrylate 3
0.1 mol% of methylenebisacrylamide (to the monomer), 1 g / mol of 2,2′-azobis (2-amidinopropane) dihydrochloride (to the monomer) and 0 mol% of the monomer aqueous solution (monomer concentration: 35% by weight) Hydroxyethyl cellulose (1.5% by weight (relative to monomer)) was added, and then dissolved oxygen was removed from the solution with nitrogen gas.

To this aqueous monomer solution, a width of 1 m and a basis weight of 60
A polyester non-woven fabric of g / m ² was dipped and impregnated with the aqueous solution, and then an excessive monomer aqueous solution was squeezed with a roller. This impregnated material is heated to perform radical polymerization, and 1
A water-absorbent polymer sheet (3) having 100 g / m ² of water-absorbent polymer directly adhered to the substrate was obtained.

Two sheets of this water-absorbent polymer sheet (3) were superposed on each other, and then a portion 1 cm from both ends was sewn with a nylon thread. This product was cut into a length of 12 m, and one opening side was hung on a sewing machine to obtain a bag-shaped water-absorbing complex 3. The breaking strength of this product was 5.1 kgf.

In this bag, H with a width of 30 cm and a length of 10 m
Diameter 60c filled with steel and filled with soil cement
It was constructed in the ground with a depth of 10 m and a depth of 10 m. The soil cement was prepared by mixing 12.8 parts by weight of cement, 52.6 parts by weight of water, 1.3 parts by weight of bentonite, and 33.9 parts by weight of clay.

After 30 days, H steel was pulled out from the hardened cement, and the maximum pulling load was 2.2 t. No cement adhered to the surface of the pulled H steel, and the H steel was reusable. Also, no rust was generated. This is probably because the bag made from the water-absorbent composite of the present invention did not tear when embedded in cement.

Example 5 The water-absorbent sheet (2) obtained in Example 2 was folded back along the lengthwise direction so that the outer side was a polyethylene layer, and the folded back end was sewn with a sewing machine. Cut this one into 1m,
One opening was hooked with a sewing machine to obtain a water absorbent composite 4 of the present invention.

60 kg in the bag-shaped water-absorbent composite 4
After putting in the rice bag, the remaining opening was hung on the sewing machine. When this product was put into the hold and transported, no mold was found due to the formation of dew condensation. On the other hand, when the rice bag was transported without being placed in the bag of the water-absorbent composite 4, the rice bag was wet due to the occurrence of dew condensation, and mold was generated on the rice.

[0061]

[Effect] The water-absorbent composite of the present invention is superior in mechanical strength such as breaking strength and maintains flexibility as compared with the composite obtained by using a heat seal or an adhesive. Therefore, it can be suitably used as a dew condensation preventing material, a freshness maintaining material and the like. Further, even when used as a lubricant for extracting a temporary buried object such as H steel, the pulling effect is not deteriorated due to the breakage of the end portion, and an excellent lubricating action is exhibited.

Further, the method for producing a water-absorbent composite of the present invention has good productivity and can inexpensively obtain a tubular or bag-shaped water-absorbent composite. Further, there is no environmental problem caused by the use of a solvent or the like.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location E02D 13/00 E02D 13/00 Z (72) Inventor Nobuyuki Harada 992, Okihama Nishioki, Aboshi-ku, Himeji-shi, Hyogo No. 1 within Nippon Shokubai Co., Ltd. (72) Inventor Naoyuki Shirane 4-1-1 Koraibashi, Chuo-ku, Osaka City, Osaka Prefecture Within Nihon Shokubai Co., Ltd.

Claims (9)

[Claims] 1. A water absorbent composite obtained by sewing at least a part of a water absorbent sheet having a water absorbent polymer directly adhered to a substrate. 2. The water-absorbing polymer is a polymer directly bonded to a substrate by polymerizing a water-soluble ethylenically unsaturated monomer capable of forming the polymer on the substrate.
The water-absorbing composite according to the above. 3. The water absorbent composite according to claim 1, wherein the shape of the water absorbent composite is a bag or a cylinder. 4. A method for producing a water-absorbent composite, which comprises stitching and joining together the ends of a water-absorbent sheet having a water-absorbent polymer directly adhered to a substrate. 5. The method for producing a water absorbent composite according to claim 4, wherein the water absorbent composite is sewn and connected so that the shape of the water absorbent composite becomes a tubular shape or a bag shape. 6. The method for producing a water absorbent composite according to claim 5, wherein the end portions of the two water absorbent sheets are sewn together. 7. The method for producing a water absorbent composite according to claim 5, wherein the water absorbent sheet is folded back and the end portions are sewn together. 8. A lubricant for extracting a temporary buried object, wherein at least a part of a water-absorbent sheet having a water-absorbent polymer directly adhered to a substrate is formed into a bag shape or a tubular shape by stitching. 9. The water-absorbing polymer is directly adhered to a substrate by polymerizing a water-soluble ethylenically unsaturated monomer capable of forming the polymer on the substrate.
Lubricant for pulling out the temporary buried object described.