JPH05106190A - Swellable structure and its production - Google Patents

Abstract

PURPOSE:To obtain the title structure suitable for absorbing condensed water such as a sheet to be laid in a food container, by incorporating a fibrous carboxymethylcellulose salt dispersion with a cationic water-soluble polymer to produce a paper stock with part or the whole of the salt converted to polyelectrolyte complex followed by dehydration and molding of the paper stock. CONSTITUTION:(A) A fibrous carboxymethylcellulose salt dispersion is incorporated with (B) a cationic water-soluble polymer containing recurring units each having primary, secondary, tertiary and/or quaternary nitrogen atom and not containing any crosslinkable functional groups other than the above nitrogen atom to produce a paper stock with part or the whole of the salt converted to polyelectrolyte complex, and the paper stock is then dehydrated and molded, thus affording the objective swellable structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet to be laid in a food container to absorb juice and dew condensation from foods, and a packaging sheet to absorb dew condensation to maintain the freshness of fruits and vegetables. , A sheet that is attached to the ceiling, wall surface of a building or the inner wall of a container to absorb dew condensation water, and when water is heated in a microwave oven, absorbs water in advance and is used as a source of water vapor It can be used for various purposes such as wrapping after absorbing water for preserving meat and fish, and it is formed into a sheet that swells while absorbing the moisture and retains its original shape, and a shape other than the sheet. And a method for producing the same.

[0002]

2. Description of the Related Art Fresh food products are displayed in a film tray pack system that is placed on a tray made of a material such as expanded polystyrene and covered with a transparent film. However, the blood juice from meat and fish spoils the appearance, so the sheet form is used. It is practiced to lay a sheet that absorbs moisture while holding the tray between the tray and the food. In addition, a swelling sheet is used for dehumidifying cooked rice and preserving various foods, and for absorbing condensed water such as fruits and vegetables. Further, it is desired that the sheet attached to the ceiling or the wall in order to absorb the dew condensation water in the room is suitable for the interior. Conventionally known swellable sheets used for these applications include sheet-shaped water absorbents obtained by coating a water absorbent resin powder with a binder on a nonwoven fabric or a plastic sheet, and dry nonwoven fabrics containing superabsorbent fibers. However, in the former, the swollen gel particles are likely to fall off and the coating amount cannot be increased, or the swelling property is hindered by the binder, so that the water absorption amount cannot be increased, and the latter has a cloth-like appearance, and therefore has a use purpose. limited.

As a proposed absorbent sheet for food packaging, a laminated material of a breathable foamed molded product of polyethylene and a sheet of cellulose fiber (Jitsuko 54-534).
No. 9) has a small amount of absorbed water and also has a small holding power for the absorbed liquid. A sheet having a breathable liquid-permeable layer such as paper, cloth, and a porous sheet on one or both sides, and a water-absorbent resin laminated as an intermediate layer (Actual No. Sho 58-49779) requires holding and bonding with an adhesive. Difficult to manufacture,
Further, an absorbent sheet (Actual Kaihei No. 1-163123) in which protective sheets are integrated on both sides of a water absorbent non-woven sheet is a porous protective sheet on both sides of a water absorbent nonwoven fabric made of acrylonitrile-acrylate copolymer or the like. It is necessary to laminate a film made of a thermoplastic resin or a non-woven fabric made of fibers of a thermoplastic resin as a protective sheet by using an adhesive or by thermocompression bonding.

[0004]

The above conventional swellable sheet has insufficient swelling performance, avoids contact with foods, protects the water-absorbent resin of the water-absorbent layer and the water-absorbent nonwoven fabric, and protects the surface. It requires a surface layer to prevent sliming and is generally limited to sheet form.

When a polyfunctional agent such as epichlorohydrin is added to a water-soluble salt of fibrous carboxymethyl cellulose (hereinafter, abbreviated as "fibrous CMC" as needed) to form cross-links, It is known that water-solubility is lost and a swollen gel body is formed, and a water-absorbent fibrous structure based on this phenomenon has been proposed (JP-A-54-5).
2189). However, this product has a weak strength of the swollen sheet and cannot be used for the above-mentioned applications as it is. Further, by cross-linking the fibrous CMC with a polyfunctional resin such as a polyamide polyamine epichlorohydrin-based resin, paper-making and alkali-treating the fibrous CMC to obtain a water-soluble salt of the fibrous CMC, which has a certain degree of wet strength. Although it can be applied, since the pH of the paper surface becomes alkaline because it is finally coated with alkali, it is not suitable without a protective layer for direct contact with food or the human body.
Further, since the absorbed water is mainly taken into the swollen gel of the water-soluble salt of fibrous CMC, sliming of the surface is unavoidable, and a surface layer is also required to prevent slimming.

The present invention is a neutral swellable structure having excellent liquid absorbency and wet strength, which does not require a surface layer,
It is intended to provide a structure that can be used as a single layer of a swollen body and can be molded into various shapes, not limited to the sheet shape.

[0007]

The present invention relates to a swellable structure comprising a salt of fibrous carboxymethyl cellulose, and at least selected from primary nitrogen atom, secondary nitrogen atom, tertiary nitrogen atom and quaternary nitrogen atom. A cationic water-soluble polymer containing a repeating unit having one kind and having substantially no functional group forming a cross-linking bond other than these nitrogen atoms can be incorporated into at least a part of the salt of the fibrous carboxymethyl cellulose. The present invention relates to a swellable structure characterized by being formed with a molecular electrolyte complex.

Here, the primary nitrogen atom is a nitrogen atom having a bond to one carbon atom and two hydrogen atoms, and is called an amino group or conventionally a primary amino group. .. The compound containing a primary nitrogen atom is a primary amine. The secondary nitrogen atom is a nitrogen atom having a bond bonded to two carbon atoms and one hydrogen atom, and may be conventionally referred to as a secondary amino group. The compound containing a secondary nitrogen atom is a secondary amine. The tertiary nitrogen atom is a nitrogen atom having a bond to three carbon atoms, and may be conventionally referred to as a tertiary amino group. The compound containing a tertiary nitrogen atom is a tertiary amine. The quaternary nitrogen atom is a nitrogen atom having a bond with four carbon atoms and forms a quaternary ammonium salt by ionic bond with an anion.

In the present invention, a polyamine resin, a polyethyleneimine, an ionene polymer, a polyfunctional resin or a polyfunctional resin which does not crosslink a salt of fibrous CMC is used.
It is characterized in that a polyelectrolyte complex is formed in at least a part of the salt of the fibrous CMC by using another cationic polymer.

The cation type water-soluble polymer is a polymer compound having a basic group in the molecule, and has at least one selected from primary, secondary, tertiary and quaternary nitrogen atoms. It is a water-soluble polymer composed of units. An example of such a cation-type water-soluble polymer is a natural polymer compound chitosan, and synthetic polymers include a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or a tertiary nitrogen atom in the side chain of the polymer. Four
There are a polymer (1) having a primary nitrogen atom and a polymer (2) having a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or a quaternary nitrogen atom in the main chain of the polymer.

One example of the polymer (1) having a primary, secondary, tertiary or quaternary nitrogen atom in the side chain of the polymer is (1-a) primary, secondary, tertiary or quaternary. It is a homopolymer of a monomer having a primary nitrogen atom and a polymerizable group such as a vinyl group in addition thereto, that is, a homopolymer of the following monomers. N, N-dialkylvinylamine, vinyltrialkylammonium, N-alkylaminoalkyl acrylate, N-alkylaminoalkyl methacrylate, N
-Alkylaminoalkylacrylamide, N-alkylaminoalkylmethacrylamide, N, N-dialkylaminoalkyl acrylate, N, N-dialkylaminoalkylmethacrylate, N, N-dialkylaminoalkylacrylamide, N, N-dialkylaminoalkylmeth Acrylamide, acryloyloxyalkyltrialkylammonium, methacryloyloxyalkyltrialkylammonium, acrylamidoalkyltrialkylammonium, methacrylamidoalkyltrialkylammonium, vinyloxyalkylamine, N-alkylvinyloxyalkylamine, N, N-dialkylvinyloxyalkyl Amine,
Monomers such as N, N, N-trialkylvinyloxyalkylammonium. In these monomers, the alkyl group has 1 to 4 carbon atoms, and an alkanol group may be introduced instead of the alkyl group.
An alkoxycarbonylalkylene group may be introduced instead of one alkyl group bonded to the nitrogen atom of the ammonium salt. A specific example of a homopolymer of the above monomers is poly (methacryloyloxyethyltrimethylammonium chloride).

Another example of the polymer (1) having a primary, secondary, tertiary or quaternary nitrogen atom in the side chain of the polymer is (1-b) primary, secondary, tertiary or quaternary. It is a copolymer of a monomer having a primary nitrogen atom and another polymerizable group, and another monomer, that is, a copolymer of the monomer described in (1-a) above and another monomer. Other monomers include acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, alkyl acrylate, alkyl methacrylate, vinyl acetate, styrene,
Examples include α-methylstyrene, 4-vinylpyridine, 2-vinylpyridine and the like. A specific example of the copolymer is poly (3-acrylamido-3-methylbutyltrimethylammonium chloride-CO-acrylamide).

As another example of the polymer (1) having a primary, secondary, tertiary or quaternary nitrogen atom in the side chain of the polymer, (1-c) a homopolymer such as polyacrylamide is modified with Mannich. Alternatively, it is cationized by a Hoffmann decomposition reaction.

The polymer (2) having a primary, secondary, tertiary or quaternary nitrogen atom in the main chain of the polymer is (2)
There are (a) ionene polymers, (2-b) polyethyleneimines, (2-c) polyamine resins in a narrow sense, and (2-d) other condensation polymers.

The (2-a) ionene polymer is a polymer having an ionic amino group, especially a quaternary ammonium group in its main chain, and most of the nitrogen atoms are quaternized. 2-a-i) Polyaddition product of a dihalo compound having a halogen atom at both ends of the molecule and a ditertiary amine having a tertiary nitrogen atom at both ends of the molecule (general formula (I))

[0016]

[Chemical 1]

(In the above general formula (I), R has a carbon number of 1 to 4 even when it has a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group (provided that the carbon number of the substituent is not included. ) Represents an alkyl group, and Y has a carbon number of 1 to 10 (including the number of carbon atoms of the substituent, including a case where it has a substituent such as a hydroxyl group, a hydroxymethyl group, and an alkyl group having a carbon number of 1 to 3). ) Alkylene group, arylene alkylene group (eg: ethylenephenethylene group, etc.)
Represents. X represents a halogen atom. A is a methylene group,
Or hydroxyl group, hydroxymethyl group, carbon number 1
~ 3 represents a methylene group having a substituent such as an alkyl group, and k and f are integers of 1-10. B is the next 2
It is one of the valence groups.

[0018]

[Chemical 2]

Further, m is a positive integer. ),

(2-a-ii) A polymerizable precursor (a tertiary amine having chlorine groups at both ends of the molecule) formed by ring-opening addition of 2 mol of epichlorohydrin to 1 mol of the primary amine, and both ends of the molecule With a di-tertiary amine having a tertiary nitrogen atom at the end (general formula (II))

[0021]

[Chemical 3]

(In the general formula (II), R ¹ has a carbon number of 1 to 20 even when it has a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group (provided that the carbon number of the substituent is included. No)) and R ² is
It represents an alkyl group having 1 to 6 carbon atoms (provided that it does not include the carbon number of the substituent) including a case where it has a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group.
Y is a hydroxyl group, a hydroxymethyl group, a carbon number of 1
It represents an alkylene group having 1 to 10 carbon atoms (provided that it does not include the carbon number of the substituent) and an arylene alkylene group (eg, ethylene phenethylene group, etc.), which may include a substituent such as an alkyl group of 3 to 3. m is a positive integer. ),

(2-a-iii) A chlorine atom is formed on one molecular end and a tertiary nitrogen atom is formed on the other molecular end, which is formed by ring-opening addition of 1 mol of epichlorohydrin to 1 mol of a secondary amine. A polymer obtained by polyaddition of a compound having the general formula (II
I))

[0024]

[Chemical 4]

(In the above general formula (III), R ¹ and R ² have a carbon number of 1 to 10 (provided that the carbon atoms of the substituents are carbon atoms including a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group). (Including no number), an aralkyl group (eg, a phenethyl group, etc.), R ¹ and R ² may be the same or different, and m is a positive integer.

(2-b) Polyethyleneimine is a polymer produced by ring-opening polymerization of ethyleneimine,
The main chain branched from the main chain has primary, secondary and tertiary nitrogen atoms.

The academic definition of the (2-c) polyamine resin has not been established, but in a narrow sense, for example, primary, secondary, and tertiary.
Containing quaternary and quaternary nitrogen atoms is defined as having less than half of the total number of nitrogen atoms in the quaternized nitrogen atom, and is distinguished from the ionene polymer in that the number of quaternized nitrogen atoms is small.

As an example, (2-ci) primary amine 1
A polyamine (general formula (IV)), which is a polymer obtained by polycondensing a compound in which 1 mol of epichlorohydrin is subjected to ring-opening addition per mol by suppressing generation of a quaternary nitrogen atom, is a hydrochloride (general formula: It becomes formula (V)).

[0029]

[Chemical 5]

(In the above general formulas (IV) and (V), R is a carbon number of 1 to 20 (provided that the carbon atoms of the substituents are the same as those having a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group). (Not including the number) represents an alkyl group,
m is a positive integer. )

Polyamine resin which is a polycondensation product of (2-c-ii) alkylenediamine and epichlorohydrin

[0032]

[Chemical 6]

(In the general formula (VI), Y has a carbon number of 1 to 10 even when it has a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group (however, the carbon number of the substituent is not included. ) Represents an alkylene group, and m is a positive integer.),

Polyamine resin which is a polycondensation product of (2-c-iii) alkylenediamine and alkylenedihalide.

[0035]

[Chemical 7]

(In the general formula (VII), Y and Y'each have a carbon number of 1 to 10 including a substituent such as a hydroxyl group, a hydroxymethyl group and a hydroxyethyl group (however, the carbon number of the substituent is Is not included), and m is a positive integer.

(2-d) Other condensation polymers include (2-d-i) polyamine polyamides which are polycondensates of alkylene polyamines and dicarboxylic acids, for example, polycondensates of diethylenetriamine and adipic acid, (2- d
-Ii) When epichlorohydrin and dimethylamine are further added to this polyamine polyamide, the chlorine group of epichlorohydrin is added to the amide group of polyamine polyamide to be quaternized, and epichlorohydrin is opened to dimethylamine. Cycloaddition results in a polymer having secondary, tertiary and quaternary nitrogen atoms in the main chain and tertiary nitrogen atoms in the side chains.

Further, in the above chitosan, homopolymers, copolymers, modified products, etc., polymers obtained by quaternizing primary, secondary or tertiary nitrogen atoms with a quaternizing agent are also cationic type water-soluble polymers. Is. The quaternizing agent is capable of introducing an alkyl group or an alkoxycarbonylalkylene group into a primary, secondary or tertiary nitrogen atom, and is a halogenated alkyl such as methyl chloride, ethyl chloride or methyl bromide, dimethylsulfate or chloro. Such as methyl acetate. The quaternization reaction may be carried out after the repeating unit is a monomer, and then polymerized, or after the polymerization, the repeating unit in the polymer may be quaternized by a polymer reaction.

The cationic water-soluble polymer used in the present invention is a functional group having a high reactivity other than a primary, secondary, tertiary or quaternary nitrogen atom, which forms a cross-linking bond, such as a glycidyl group or an aldehyde group. Carboxyl group, vinyl group, allyl group, N-methylol group, thiol group, isocyanate,
It is necessary that it is substantially free of isothiocyanate and the like. This is because the cationic water-soluble polymer is a fibrous CM
This is to prevent the formation of covalent crosslinks, etc., other than forming a polymer electrolyte complex in C. By "substantially free" is meant that covalent crosslinks are not included to the extent that they inhibit or reduce the formation of polyelectrolyte complexes and, as a result, cause the water-swellable swellable structure to become slimy.

The cationic water-soluble polymer used in the present invention has a cation equivalent of 0.1 to 20 meq / g, preferably 1 to 15 meq / g, and more preferably 2 in the range of pH 3 to 9. 10 to 10 meq / g, and the (number) average molecular weight is 5,000 to 100,000, preferably 5,000 to 70,000, and more preferably 5,000.
~ 20,000.

The fibrous CMC salt is a lithium salt, sodium salt, potassium salt, calcium salt, magnesium salt, ammonium salt, or amine salt such as methylamine or ethanolamine. The degree of etherification of the fibrous CMC is 0.1 to 1.0, preferably 0.3 to 0.8, more preferably 0.4 to 0.6, and the degree of base saturation of the salt of the fibrous CMC ( The proportion of the carboxyl group which has become a salt) is 50 to 100%, preferably 80 to 100%,
More preferably, it is 90 to 95%.

The amount of the cation-type water-soluble polymer added to the salt of the fibrous CMC is within the range corresponding to the cation equivalent of 0.1 to 100% of the anion equivalent of the fibrous CMC. An appropriate amount is selected according to the type of polymer. The addition of the cationic water-soluble polymer forms a polyelectrolyte complex in the salt of fibrous CMC. The polyelectrolyte complex is a complex that is considered to be formed mainly between the salt of the fibrous CMC having an opposite charge and the cationic polymer through Coulomb force. Although the details of the structure are not clear, cation-type water-soluble polymer is ionically crosslinked between the molecules of fibrous CMC, or fibrous CM
A structure in which a cation-type water-soluble polymer is close to the molecular chain of C may be considered.

The swellable structure according to the present invention contains at least one selected from a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom and a quaternary nitrogen atom in a dispersion liquid of a salt of fibrous carboxymethyl cellulose. A cationic water-soluble polymer containing a repeating unit having, and having substantially no functional groups forming a cross-link other than these nitrogen atoms is added, and the polymer is added to at least a part of the salt of the fibrous carboxymethyl cellulose. It can be produced by preparing a stock having an electrolyte complex formed, and dehydrating and molding the stock.

Here, dehydration and molding are not limited to the case where paper is formed and dried to form a sheet by a usual papermaking technique, and a convex wire net for molding is immersed in the raw material dispersion liquid, Including the case where the inside of the wire net is decompressed, fibers are deposited on the wire net, and after pressing, drying, the mold is removed, so-called mold forming method and the like are formed into various shapes.

In the production of the swellable structure of the present invention,
In addition to the above raw materials, wood pulp, non-wood pulp, dissolving pulp, semi-synthetic fiber for papermaking, synthetic fiber for papermaking, inorganic fiber for papermaking, etc. are added to reduce cost and improve papermaking property.
You may mix | blend in the range of weight% or less, desirably 25 weight% or less. A small amount of a wet paper strength imparting agent may be added.

[0046]

In the swellable structure according to the present invention, the first grade,
At least a part of the salt of fibrous CMC forms a polyelectrolyte complex by a cationic water-soluble polymer that does not substantially contain a functional group that forms a cross-linking bond other than the secondary, tertiary or quaternary nitrogen atom. The swollen structure has high wet strength. It is considered that this is because the fibrous CMCs are bound to each other via the cationic water-soluble polymer, and the type of the binding is the quaternization of the COO ⁻ group of the fibrous CMC and the cationic water-soluble polymer. Ionic bond with nitrogen atom, COO ^- group and 1
Amides formed by dehydration of primary or secondary nitrogen atoms (primary or secondary amino groups) in the drying process, and COOH groups remaining in the fibrous CMC after formation of the polyelectrolyte complex Examples thereof include acid anhydrides formed by dehydration in the drying process.

It is considered that the fibrous CMC salt swells and gels while retaining the fiber form, and retains water in many voids between the fibers. When crosslinking is performed with a cationic polymer containing a highly reactive functional group such as a glycidyl group, a covalent cross-linking bond is formed between fibrous CMC molecules, and the formation of a polymer electrolyte complex is suppressed. Therefore, the absorbed water is mainly absorbed in the swollen gel of the salt of fibrous CMC, whereas in the swellable structure according to the present invention, the water is absorbed in the swollen gel of the salt of fibrous CMC. Besides, it is retained inside the void structure of the fiber. The water absorbed in the swollen gel of the salt of fibrous CMC is not discharged even when an external force is applied, and when the absorbed amount is large, it causes sliminess, but the water retained in the voids of the fiber is As it were, so to speak, taken into the pores of the sponge structure, even if a large amount is held, the structure surface does not feel slimy and is discharged by an external force. Therefore, the swellable structure according to the present invention does not cause slimy on the surface of the swelled body, although it has an absorption amount of 7 to 15 times its own weight. Therefore, the swellable structure of the present invention,
It does not require a surface layer for preventing slimming, can be used as a single layer, and can be molded into various structures other than sheets. Furthermore, since the absorbed water is discharged by an external force, repeated use is possible depending on the application.
Also, since no alkali coating is applied at the end of the manufacturing process,
It has a neutral pH and can be used in a state where it comes into direct contact with food or the human body.

Further, in addition to producing a single-layer sheet by papermaking, a plurality of wet paper webs are produced from the same raw material by a paper machine having two or more paper making machines, and the resulting papers are combined to produce a sheet having a large basis weight. It is also possible to make sheets of different kinds of raw materials, and it is also possible to produce various laminated structures by laminating with sheets of synthetic resin.

[0049]

EXAMPLES Examples of the swellable structure according to the present invention will be shown below. In each example, the water absorption amount of the swellable structure,
Wet tensile strength, degree of slime in wet state, paper surface p
H was evaluated as follows.

<Water Absorption> A test piece of 10 cm × 12 cm was dipped in 1000 ml of tap water for 30 minutes and then pulled up, and one end was hung up for 1 minute to drop excess water, and then the weight of the test piece was measured. The amount of water absorption was calculated by the following formula. Water absorption (g / g) = {(weight of test piece after removal of excess water g)
-(Test piece air dry weight g)} ÷ {Test piece air dry weight g}

<Wet tensile strength> Width 15 mm, length 2
A 00 mm test piece was immersed in tap water at 20 ° C. for 30 minutes, then excess water was wiped with a filter paper, and the tensile strength was measured with a Shopper-type tensile tester.

<Wet sliminess> 10 cm × 12 c
The test piece of m was immersed in 1000 ml of tap water for 3 minutes and then pulled up, and the feel of the surface of the test piece was sensory evaluated.

<Paper pH> A pH indicator solution was applied to a test piece, and the color was observed by comparing with a standard plate.

Example 1 A dispersion of a fibrous CMC Na salt (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.43, degree of base saturation 90%) was dispersed in water to a concentration of 1.5%. I prepared. Polyamine resin (Sumitomo Chemical Co., Ltd., trade name Sumirez Resin FR-2P, number average molecular weight 10000, cation equivalent 5.8 meq / g at pH 6, quaternized nitrogen atom and tertiary nitrogen atom) Inclusion: Throughout the examples, "FR
-2P ") is added at a ratio of 2.0% by weight to the Na salt of the fibrous CMC and stirred to prepare a paper stock, and the stock is prepared using a cylinder-type paper machine. 70g /
to produce a sheet of m ^2.

With respect to the obtained swellable sheet, the water absorption,
Wet tensile strength and wet sliminess were evaluated, and the results are shown in Table 1. For comparison, the evaluation results of the tissue paper are also shown in Table 1 as a comparative product. Table 1
As can be seen from the above, the product of the present invention based on Example 1 absorbed 12 times as much tap water as its own weight and had a high wet strength even after absorbing water, so that it could retain the sheet form. Since the fibrous CMC in the sheet that absorbed water had a high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

Next, two disposable lunch boxes made of Styrofoam, consisting of a container and a lid, are prepared, and a hot-melt pressure-sensitive adhesive (made by Toyo Peterlite Co., Ltd., trade name Topco P618A) is provided inside one of the lids. Was applied, the above swellable sheet was attached. Immediately after cooking rice, 300 g of cooked rice was placed in two lunch boxes, and a lid with a swellable sheet and a lid without a swelling sheet were placed on each of the lunch boxes. When the lid was opened after 4 hours and the state of the cooked rice was observed, it was found that when the swellable sheet was attached to the lid, the water content of the cooked rice did not increase because the steam of the condensed rice was absorbed in the swellable sheet. The cooked rice did not become watery. On the other hand, when the swelling sheet is not attached to the lid, the cooked rice absorbs the condensed water and becomes watery, and the commercial value as a food is significantly reduced.

From these results, the swellable sheet according to the present invention can prevent the dew condensation water from adhering to foods such as cooked rice by absorbing the dew condensation water of steam, and can be used for packaging containers for various foods. It turns out to be effective.

Example 2 A dispersion of 1.5% concentration was prepared by dispersing Na salt of fibrous CMC (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.43, degree of base saturation 100%) in water. did. Polyethyleneimine resin (Nippon Shokubai Kagaku Kogyo KK, trade name Epomin SP200, number average molecular weight 20000, branched structure, containing primary, secondary and tertiary nitrogen atoms) was added to this fibrous CMC.
-A 1 wt% ratio to Na salt was added and stirred to prepare a paper stock. Using this paper stock, a handsheet having a basis weight of 60 g / m ² was prepared according to JIS P8209.

With respect to the obtained swellable sheet, the water absorption,
Wet tensile strength and wet sliminess were evaluated, and the results are shown in Table 1. As can be seen in Table 1, the product of the present invention based on Example 2 absorbs 13 times as much tap water as its own weight and has a high wet strength even after absorbing water, and therefore can retain the sheet form. It was Fibrous CM in a sheet that has absorbed water
Since C has a high gel strength, almost no sliminess was felt. The pH on the paper surface was in the range of 6 to 8, and the same swelling sheet as in Example 1 was obtained.

Example 3 A Na salt of fibrous CMC (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.43, degree of base saturation 95%) was dispersed in water to obtain a dispersion liquid having a concentration of 1.5%. Na of this fibrous CMC
2% by weight of salt of polyamine resin (FR-2P)
Was added and mixed with 80 parts by weight of the stirred dispersion, 20 parts by weight of the dispersible pulp (manufactured by Sanyo Kokusaku Pulp Co., Ltd.) to a concentration of 1.5% to prepare a papermaking raw material, A sheet having a basis weight of 30 g / m ² was manufactured by a paper machine.

The resulting swellable sheet was evaluated for water absorption, wet tensile strength, and wet sliminess. The results are shown in Table 1. As can be seen from Table 1, the product of the present invention based on Example 3 absorbs 10 times as much tap water as its own weight and has a high wet strength even after absorbing water, and thus can retain the sheet form. It was Fibrous CMC in a sheet that has absorbed water
Since the gel had high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. PH on paper is 6
At ~ 7, it was in the neutral range.

On this swelling sheet, a highly water-absorbent resin (manufactured by Sumitomo Seika Co., Ltd., trade name AQUAKEEP 10SH) was applied.
After spraying g / m ² , the same sheets are overlaid and embossed to form a swellable sheet / super absorbent polymer / swellable sheet.
A laminate consisting of layers was produced. This three-layer structure has an absorption rate of tap water dropped on the laminated body as compared with the laminated body composed of tissue paper / super absorbent resin / tissue paper (tissue paper basis weight 18 g / m ^{2 for} each). It was fast. Further, the water droplets dropped on the swellable sheet constituting the three-layer laminate are rapidly diffused and absorbed by the swellable sheet, and then the water in the voids of the swellable sheet is absorbed by the superabsorbent resin and swells. Since the permeable sheet is brought close to a dry state, it has a feature that it can be quickly absorbed even if water droplets are dropped again on the swellable sheet.

Therefore, a three-layer laminate using this swellable sheet is used in conventional sanitary products for women, disposable diapers and the like, and is a conventional fluff pulp (defibrated cotton-like pulp) and tissue paper / super absorbent resin / tissue. It can be suitably used in place of the combination of paper laminates, and since bulky fluff pulp is not used, the overall size and thickness can be reduced.

Example 4 A two-layer laminated paper comprising a water absorbing layer and a heat sealing layer was prepared as follows.

Fibrous CMC Na salt (Nichirin Chemical Co., Ltd., degree of etherification 0.43, degree of base saturation 90%)
Was dispersed in water to a concentration of 1.5%, and 2% by weight of polyamine resin (FR-2P) was added to the Na salt of the fibrous CMC. Part, a core-sheath type heat-fusible composite fiber (manufactured by Daiwa Boshoku Co., Ltd., trade name NBF-E: hereinafter abbreviated as "NBF") was disaggregated to a concentration of 1.5%, and 20 parts by weight of a dispersion liquid was prepared. Was prepared as the first papermaking raw material for forming the water absorbing layer. Here, NBF was blended for joining with the heat seal layer and for reinforcing the wet strength of the water absorbing layer.

On the other hand, softwood bleached wood pulp (hereinafter referred to as "NB
(KP) is 550 ml CSF with Canadian freeness.
After beating up to 0.3% by weight of NBKP absolute dry weight, a wet strength imparting agent for papermaking (Dick Hercules Co., Ltd., trade name Kaimen 557H) was added, and then NBF was added to NBKP. : NBF = 40: 60 (weight ratio) to prepare a second papermaking raw material for forming the heat seal layer.

Into each cylinder cylinder of a cylinder type paper machine equipped with two cylinder cylinders, the above two kinds of papermaking raw materials were introduced, and a first wet paper web formed from the first papermaking raw material, Second
The second wet paper made from the papermaking raw material of
A two-ply laminated paper having a basis weight of 70 g / m ² and one side having water absorbency and the other side having heat sealability was prepared. First
The water-absorbent layer formed from the wet paper of 50 g has a basis weight of 50 g / m ² , and the heat-seal layer formed of the second wet paper has a basis weight of 20 g.
/ M ² .

With respect to the obtained swellable two-layer laminated sheet, the water absorption, the wet tensile strength and the sliminess in the wet state were evaluated, and the results are shown in Table 1. As shown in Table 1, the laminate including the layer formed of the swellable structure according to the present invention absorbs 8 times as much tap water as its own weight and has high wet strength even after absorbing water. The shape could be retained. Since the fibrous CMC in the sheet that has absorbed water has a high gel strength, it does not feel slimy at all, and the paper surface pH is 6 to 7
And it was in the neutral range.

The heat-sealing surfaces of the swellable two-layer laminated sheet were combined together at 160 ° C., 2 kg / cm ² (0.
Heat sealing under the condition of (196 MPa) for 2 seconds,
The heat-sealing strength of a 15 mm wide test piece measured by a T-shaped peeling tester was 500 g / 15 mm (327 N /
m), and had practically sufficient strength. From the above, it is clear that a sheet having heat sealability on one side and water swelling on the other side can be obtained, and the swellable structure according to the present invention is a composite film with another material such as a synthetic film. And bag making can be performed very easily.

Example 5 A dispersion of fibrous CMC Na salt (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.35, base saturation 95%) was dispersed in water to a concentration of 1.5%. Na of this fibrous CMC
3% by weight of salt of polyamine resin (FR-2P)
Was added and the dispersion liquid stirred was used as a mold raw material.

Length × width × depth = 20 cm × 20 cm × 10
A convex mold for molding for molding a cm tray was prepared. The molding die is made of a porous metal plate having a wire mesh of 150 mesh at the portion in contact with the side and bottom of the tray, and is equipped with a suction pipe capable of depressurizing the inside. Immersion was performed to reduce the pressure inside the molding die to deposit fibers on the surface of the wire mesh to a thickness of 2 to 3 mm, press dehydration, and then drying to take out a molded product from the molding die.

The water absorption amount and sliminess in a wet state of the obtained molded product were evaluated. The molded product absorbed 10 times as much tap water as its own weight, and could retain the shape of the molded product even after absorbing water. Since the fibrous CMC in the water-absorbed molded product has high gel strength and elasticity, the entire molded product also has elasticity, no sliminess is felt at all, and the paper surface pH
Was in the range of 6-7.

Example 6 A dispersion liquid was prepared in which a Na salt of fibrous CMC (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.43, degree of base saturation 95%) was dispersed in water to a concentration of 1%. A cation type polyacrylamide resin (manufactured by Meisei Chemical Industry Co., Ltd., trade name AG Fix M15, cation equivalent 4.5 meq / g, quaternized nitrogen atom-containing) was added to the fibrous CMC Na.
Two types of paper stocks were prepared by adding 2.0 wt% or 4.0 wt% to the salt and stirring. Using these paper materials, two types of basis weight 60 based on JIS P8209
A handsheet of g / m ² was prepared.

With respect to the obtained swellable sheet, the water absorption,
Wet tensile strength and wet sliminess were evaluated, and the results are shown in Table 2. For comparison, Table 2 also shows the evaluation results of a cellulosic dry type nonwoven fabric having a basis weight of 68 g / m ² . As seen in Table 2, the product of the present invention based on Example 6 absorbs 10 to 11 times as much tap water as its own weight, and 90 to 120 g / 15 mm (59 to 78) even after absorbing water.
Since it has a wet tensile strength of N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength, almost no sliminess was felt in the entire sheet. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 7 A dispersion of 1% concentration was prepared by dispersing Na salt of fibrous CMC (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.43, degree of base saturation 95%) in water. Concentration of chitosan 2.
A chitosan solution (produced by Katakura Chikkarin Co., Ltd., containing primary and secondary nitrogen atoms and having a cation equivalent of 4.2 meq / g) dissolved in a 5% lactic acid aqueous solution with respect to the Na salt of the fibrous CMC was prepared. Then, 2.5% by weight or 10% by weight was added and stirred to prepare two types of paper materials. Using these paper materials, two types of basis weight 60 based on JIS P8209
A handsheet of g / m ² was prepared.

With respect to the obtained swellable sheet, the water absorption,
Wet tensile strength and wet sliminess were evaluated in the same manner as in Example 6, and the results are shown in Table 2. As can be seen in Table 2, the product of the present invention based on Example 7 absorbs 7 to 9 times as much tap water as its own weight, and 210 to 450 g / 15 mm even after absorbing water.
Since it has a wet tensile strength of (137 to 294 N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength, almost no sliminess was felt in the entire sheet as in Example 6. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 8 50% by weight of methacryloyloxyethyltrimethylammonium chloride and 50% by weight of acrylamide were dissolved in water to a concentration of 10% by weight, and ammonium persulfate was used as an initiator and heated at 70 to 75 ° C. for polymerization. After that, it was purified by fractional precipitation in a water-methanol system to prepare a copolymer. This copolymer had quaternized nitrogen atoms and had a cation equivalent of 3.2 meq / g at pH 6. Next, Na salt of fibrous CMC (Nichirin Chemical Co., Ltd., degree of etherification 0.43, degree of base saturation 95%)
Was dispersed in water to prepare a dispersion having a concentration of 1%. 4.0% by weight of the above copolymer with respect to the Na salt of fibrous CMC was separated and dissolved in water to a concentration of 1%, and then added to the Na salt of the fibrous CMC and stirred to paper. As a material, a handsheet having a basis weight of 60 g / m ² was prepared from this paper material according to JIS P8209.

With respect to the obtained swellable sheet, the water absorption,
As a result of evaluating the wet tensile strength and the slimyness in the wet state, as shown in Table 2, the product of the present invention based on Example 8 absorbs 10 times as much tap water as its own weight, and 100% even after absorbing water.
Since it had a wet tensile strength of g / 15 mm (65 N / m), the sheet form could be retained and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 9 45 g of dimethylamine liquefied by cooling to -20 ° C
(66 ml, 1 mol) of epichlorohydrin 9 at 15 ° C
2 g (1 mol) was added dropwise over 2 hours, left at 15 ° C. for 4 hours, 20 ml of pure water was added, and the mixture was heated at 70 ° C. for 24 hours to polymerize to give a secondary amine / epichlorohydrin polyaddition polymer. Prepared. The reaction solution was poured into acetone and the precipitate was dried to obtain the above polymer as a solid. The cation equivalent of this solid was 6.2 meq / g at pH 6, and the average molecular weight (converted to styrene) determined by gel permeation chromatography was 8900. next,
A Na salt of fibrous CMC (manufactured by Nichirin Kagaku Co., Ltd., degree of etherification 0.43, degree of base saturation 90%) was dispersed in water to prepare a dispersion liquid having a concentration of 1%. Fibrous CMC Na
2.0% by weight of the solid matter with respect to the salt was collected, dissolved in water to a concentration of 1%, added to the Na salt of the fibrous CMC, and stirred to prepare a paper stock. From paper fee to JIS P
A handsheet having a basis weight of 70 g / m ² was prepared based on 8209.

With respect to the obtained swellable sheet, the water absorption,
As a result of evaluating wet tensile strength and sliminess in a wet state, as shown in Table 2, the product of the present invention based on Example 9 absorbs 12 times as much tap water as its own weight, and even after absorbing water, 110
Since it had a wet tensile strength of g / 15 mm (72 N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 10 62 g (1 mol) of a 50 wt% aqueous solution of monomethylamine was mixed with 175 g of methanol, and 184 g (2 mol) of epichlorohydrin was added to the mixture at a reaction temperature of 30-.
Dropwise at a rate such that the temperature was maintained in the range of 40 ° C., and held at 40 ° C. for 12 hours to obtain 51% by weight of partially polymerized bis (3-chloro-2-hydroxypropyl) methylamine.
A containing methanol solution was prepared. The above methanol solution 2
79 g {bis (3-chloro-2-hydroxypropyl)
0.5 mol as methylamine}, 67 g (0.6 mol) of N, N, N ′, N′-tetramethyl-1,2-diaminoethane and 100 g of pure water were mixed, and the mixture was heated at 80 to 90 ° C. for 20 minutes.
After holding for a period of time, 400 g of pure water was added and cooled, concentrated sulfuric acid was added to adjust the pH after the reaction to 4, and the primary amine-epichlorohydrin-di-tertiary amine represented by the following formula: An addition polymer was obtained.

[0082]

[Chemical 8]

The cation equivalent of this polymer was 4.5 meq / g at pH 6, and the viscosity of a 25% strength by weight aqueous solution was 1200 centipoise. Next, fibrous C
An Na salt of MC (manufactured by Nichirin Kagaku Co., Ltd., etherification degree 0.43, base saturation 90%) was dispersed in water to prepare a dispersion liquid having a concentration of 1%. An aqueous solution of the above polymer, in terms of solid content, was taken out in an amount of 2.0% by weight based on the Na salt of the fibrous CMC, added to the Na salt of the fibrous CMC and stirred to prepare a paper stock. A handsheet having a basis weight of 70 g / m ² was prepared from a paper material according to JIS P8209.

With respect to the obtained swellable sheet, the water absorption,
As a result of evaluating the wet tensile strength and the slimyness in the wet state, as shown in Table 2, the product of the present invention based on Example 10 absorbs 11 times as much tap water as its own weight, and after absorbing 90,
Since it had a wet tensile strength of g / 15 mm (59 N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 11 N, N, N ', N'-tetramethylethylenediamine 116
g (1 mol), dichloroethyl ether 142 g (1 mol) and pure water 150 g were mixed, and the mixture was mixed at 80 to 100 ° C. for 16 minutes.
An aqueous solution of a dihalo compound / di-tertiary amine polyaddition polymer represented by the following formula and having a concentration of 63% by weight was prepared by heating for an hour.

[0086]

[Chemical 9]

This polymer has almost all nitrogen atoms of 4
It was graded and had a cation equivalent of 7.0 meq / g at pH 6. Next, Na salt of fibrous CMC (Nichirin Chemical Co., Ltd., degree of etherification 0.43, degree of base saturation 9
0%) was dispersed in water to prepare a dispersion having a concentration of 1%. An aqueous solution of the above-mentioned polymer is converted into fibrous C in terms of solid content
An amount of 2.0% by weight based on Na salt of MC was added to the Na salt of fibrous CMC and stirred to prepare a paper stock. Based on JIS P8209, a paper weight of 70 g / m ^{2 was obtained.}
A handmade sheet was prepared.

With respect to the obtained swellable sheet, the water absorption,
As a result of evaluating the wet tensile strength and the slimyness in the wet state, as shown in Table 2, the product of the present invention based on Example 11 absorbs 10 times as much tap water as its own weight, and even after absorbing water, 15
Since it has a wet tensile strength of 0 g / 15 mm (98 N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 12 208 g (1.1 mol) of tetraethylenepentamine was dissolved in 50 g of pure water, and ethylene dichloride 109 was dissolved in this solution.
g (1.1 mol) was gradually added dropwise, 50 g of pure water was added,
The temperature was adjusted so that a slight reflux occurred, and the mixture was heated for 3 hours. 90 g (2.2 mol) of sodium hydroxide was dissolved in 100 g of pure water and gradually added to the produced polyethylene polyamine hydrochloride for neutralization, and sodium chloride produced as a by-product was removed to obtain polyethylene polyamine which is a polyamine resin. Of 4
An aqueous solution with a concentration of 6% by weight was obtained. Next, N of fibrous CMC
a salt (manufactured by Nichirin Chemical Co., Ltd., degree of etherification 0.43,
A base saturation 90%) was dispersed in water to prepare a dispersion having a concentration of 1%. An aqueous solution of the above-mentioned polyethylene polyamine resin, in terms of solid content, was taken out in an amount of 2.0% by weight with respect to the Na salt of the fibrous CMC, added to the Na salt of the fibrous CMC, and stirred to prepare a stock material. From this paper fee to JIS P82
09, a handsheet having a basis weight of 70 g / m ² was prepared.

With respect to the obtained swellable sheet, the water absorption,
As a result of evaluating the wet tensile strength and the slimyness in the wet state, as shown in Table 2, the product of the present invention based on Example 12 absorbs 10 times as much tap water as its own weight, and 95% even after absorbing water.
Since it had a wet tensile strength of g / 15 mm (62 N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

Example 13 116 g (1.0 mol) of hexamethylenediamine was dissolved in 108 g of pure water, and 92 g of epichlorohydrin was added thereto.
(1.0 mol) is gradually added dropwise at 20 ° C at 45 ° C to 50 ° C.
After heating for an hour, acetic acid was added to adjust the pH to 5 to obtain a polyamine resin diamine-epichlorohydrin polycondensate. Next, Na salt of fibrous CMC (Nichirin Chemical Co., Ltd., degree of etherification 0.43, degree of base saturation 90%)
Was dispersed in water to prepare a dispersion having a concentration of 1%. An aqueous solution of the above polyamine resin is converted into a fibrous C in terms of solid content.
An amount of 2.0% by weight based on Na salt of MC was added to the Na salt of fibrous CMC and stirred to prepare a paper stock. Based on JIS P8209, a paper weight of 70 g / m ² was prepared.
A handmade sheet was prepared.

With respect to the obtained swellable sheet, the water absorption,
As a result of evaluating the wet tensile strength and the sliminess in the wet state, as shown in Table 2, the product of the present invention based on Example 13 absorbs 10 times as much tap water as its own weight, and even after absorbing 90
Since it had a wet tensile strength of g / 15 mm (59 N / m), the sheet form could be retained. Since the fibrous CMC in the sheet that absorbed water had a high gel strength and elasticity, the entire sheet also had elasticity and no sliminess was felt at all. The pH on the paper surface was 6 to 7, which was in the neutral range.

[0093]

[Table 1]

[0094]

[Table 2]

[0095]

According to the present invention, a swellable structure having a high wet strength, capable of absorbing a sufficient amount of liquid, and retaining its original shape such as a sheet even if it swells and prevents slimming. It does not require a surface layer for the purpose of obtaining a liquid having a high liquid absorption rate, and can be used in many applications as a liquid-absorptive structure of various forms. In addition, since it is neutral, it can be used without a surface layer for the purpose of directly contacting foods.

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Claims (6)

[Claims] 1. A swellable structure comprising a salt of fibrous carboxymethyl cellulose, containing a repeating unit having at least one selected from a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom and a quaternary nitrogen atom. , A polyelectrolyte complex is formed in at least a part of the salt of the fibrous carboxymethyl cellulose by a cationic water-soluble polymer that does not substantially contain a functional group that forms a cross-linking bond other than these nitrogen atoms. A swellable structure characterized by the above. 2. The swellable structure according to claim 1, wherein
The cationic water-soluble polymer is chitosan, a polymer having a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or a quaternary nitrogen atom in the side chain of the polymer, and a primary nitrogen atom in the main chain of the polymer, A swellable structure comprising at least one selected from polymers having a secondary nitrogen atom, a tertiary nitrogen atom or a quaternary nitrogen atom. 3. The swellable structure according to claim 2, wherein
A swellable structure in which the polymer having a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or a quaternary nitrogen atom in the main chain of the polymer is an ionene polymer, polyethyleneimine, a polyamine resin or a polyamine polyamide. 4. A dispersion liquid of a salt of fibrous carboxymethyl cellulose contains a repeating unit having at least one selected from a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom and a quaternary nitrogen atom. A paper stock in which a polyelectrolyte complex is formed in at least a part of the salt of the fibrous carboxymethyl cellulose by adding a cationic water-soluble polymer that does not substantially contain a functional group that forms a cross-linkage other than a nitrogen atom. Is prepared, and the paper material is dehydrated and molded, and a method for producing a swellable structure. 5. The method for producing a swellable structure according to claim 4, wherein the cationic water-soluble polymer is chitosan, a side chain of the polymer has a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or Swelling characterized by being a polymer having a quaternary nitrogen atom and at least one selected from polymers having a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or a quaternary nitrogen atom in the main chain of the polymer. Of manufacturing a flexible structure. 6. The method for producing a swellable structure according to claim 5, wherein the polymer having a primary nitrogen atom, a secondary nitrogen atom, a tertiary nitrogen atom or a quaternary nitrogen atom in the main chain of the polymer is an io A method for producing a swellable structure which is a Nene polymer, polyethyleneimine, polyamine resin or polyamine polyamide.