JP2012132119A - Water-dispersible laminated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-dispersible laminated paper that has rapid water-dispersibility and is capable of preventing drops in water-dispersibility over time.SOLUTION: The water-dispersible laminated paper has a substrate composed of wood pulp and/or non-wood pulp and a polyvinyl alcohol resin laminate layer on at least one surface of the substrate. The water-dispersible laminated paper has rapid water-dispersibility and prevents drops in water-dispersibility over time by using a refined pulp having an α-cellulose content of 88% or more in an amount of 15-95 wt.% of the pulp constituting the substrate.

Description

  The present invention relates to a water-dispersible laminated paper that is rapidly dispersed by water.

In agriculture, fertilizers and pesticides are used from the viewpoint of promoting the growth of crops and protecting them from pests. In fisheries (especially farms), baits and antibiotics containing various vitamins are used from the viewpoint of promoting the growth of fish and protecting them from infectious diseases.
However, when powdered fertilizer or pesticide is sprayed, the powder is scattered, so it is necessary to spray more than necessary, and the surrounding environment may be adversely affected. In addition, when food or antibiotics containing various vitamins in a powder form are sown in a farm, there is a bias in the range to be sown. For this reason, there was a problem that it was not possible to spread food and antibiotics uniformly throughout the farm. Therefore, powdery fertilizers and pesticides can be put in a bag to prevent the powder from being scattered and not to be sprayed more than necessary. In addition, the powdery fertilizer and agricultural chemicals put in the bag are eluted by rain and the effect is exhibited. In addition, powdered bait and antibiotics can be put in a bag, so that it can be spread over a wide range of farms. In addition, the powdered bait, antibiotics, etc. which were put in the bag are eluted with seawater, and the effect is expressed. However, after the fertilizers, pesticides, foods and antibiotics in the bags were eluted, there was a problem that the bags became garbage. Therefore, the heat described in Patent Document 1, in which papermaking fibers and fibrous carboxymethylcellulose are mixed, water-soluble paper added with an alkali metal compound is used as a base material, and water-soluble PVA resin is laminated on one side of the base material. Using a packaging material having sealing properties, fertilizers, pesticides, baits, and antibiotics in bags are made, and the problem that the bags are melted and lost by rainwater or seawater is eliminated.

JP-B 43-001214

However, a packaging material obtained by mixing paper-making fibers and fibrous carboxymethyl cellulose, laminating a water-soluble polyvinyl alcohol resin on a water-soluble paper base material to which an alkali metal compound has been added, depends on the alkali contained in the water-soluble paper. The laminated polyvinyl alcohol is saponified, and there is a problem that the bag is not dissolved by rainwater or seawater over time.
Then, an object of this invention is to provide the water dispersible laminated paper which prevented the rapid water dispersibility and the water dispersibility fall with time.

  In a laminated paper having a polyvinyl alcohol resin laminate layer on at least one surface of a base material made of wood pulp and / or non-wood pulp, 15 to 95% by weight of the pulp constituting the base material has an α cellulose content of 88% or more. It has been found that a water-dispersible laminated paper having rapid water dispersibility and preventing deterioration of water dispersibility over time can be obtained by using purified pulp, and the present invention has been completed.

  ADVANTAGE OF THE INVENTION According to this invention, the water dispersible laminated paper which prevented the rapid water dispersibility and the water dispersibility fall with time can be obtained. Moreover, since sufficient intensity | strength is expressed, it can endure use for uses, such as a bag.

  The water-dispersible laminated paper of the present invention is a laminated paper having a polyvinyl alcohol resin (hereinafter sometimes referred to as “PVA resin”) laminate layer on at least one surface of a base material made of wood pulp and / or non-wood pulp. The water-dispersible laminated paper is characterized in that 15 to 95% by weight of the pulp constituting the substrate is a purified pulp having an α-cellulose content of 88% or more.

(Base material)
The refined pulp used for the base material of the present invention is strengthened cooking conditions during pulp production, such as mercerized pulp or dissolving pulp made from non-wood such as softwood, hardwood, flax, linter, etc., A pulp obtained by removing hemicellulose and the like by chemical treatment before cooking or after cooking to increase cellulose purity.

  The mercerized pulp is a pulp obtained by immersing kraft pulp or sulfite pulp in a strong alkali solution and then washing with water to remove the alkali.

  Dissolving pulp is pulp with high cellulose purity obtained by sulfite cooking or prehydrolysis kraft cooking, and pulps with various cellulose purity can be obtained by combining bleaching and selective processing after cooking.

  In the base material of the water dispersible laminated paper of the present invention, the reason why excellent dispersibility is obtained when 15 to 95% by weight of the pulp is a refined pulp having an α cellulose content of 88% or more is presumed as follows. The Refined pulp has very little hemicellulose content that contributes to fiber swelling and adhesion between fibers, and thus forms a sheet having low strength, high bulk and high water dispersibility in an unbeaten state. In addition, when refined pulp is beaten, the hemicellulose content is small, so the swelling and fibrillation of the fiber due to the beating action is suppressed, the water retention does not increase so much, the fiber is rigid and easily cut, and the short fiber content is reduced. Increase. As a result, the sheet formed from the refined pulp that has been beaten increases in strength and slightly impairs the bulk compared to unbeaten, but the water dispersibility is not significantly impaired because the amount of short fibers that contribute to the improvement of water dispersibility increases. I can't.

The α cellulose content is used as an index of cellulose purity of the refined pulp used for the base material in the present invention. The α cellulose content of the refined pulp needs to be 88% or more, preferably 92% or more, and more preferably 95% or more. When the α cellulose of the refined pulp is less than 88%, it becomes difficult to disperse into a single fiber, so that the dispersibility in water decreases.
In addition, in this invention, alpha cellulose content is the value measured by alpha cellulose prescribed | regulated to TAPPI standard T203om-83 (JIS P8101-1994 (currently abolished)).

  In the present invention, the water retention of refined pulp having an α-cellulose content of 88% or more (hereinafter sometimes simply referred to as “refined pulp”) is the Canadian standard freeness (hereinafter referred to as “freeness”). In the refined pulp beaten to 450 ml CSF, 140% or less, preferably 120% or less is preferable from the viewpoint of water dispersibility.

  In the refined pulp having a water retention in this range, the fibers are difficult to swell and fibrillate, so that the ratio of beating energy used for cutting the fibers increases. As a result, the refined pulp that has been beaten has a low and short interfiber bonding ability, and a sheet with high water dispersibility is formed. On the other hand, when the refined pulp having a water retention of 140% in a freeness of 450 ml CSF is beaten, the fiber swells and fibrillates to increase the bond between fibers, making it difficult to obtain a sheet dispersed in a single fiber form. . In addition, water retention is the value of JAPAN TAPPI No. 26 is an index of the degree of swelling of the pulp specified in No. 26, and indicates the ratio of the moisture taken in and retained in the swollen fibers to the weight of the whole pulp.

  In the present invention, the average fiber length of the refined pulp is 0.1 to 5 mm, preferably 0.5 to 3 mm, and more preferably 0.8 to 2 mm.

  The base material of the water-dispersible laminated paper of the present invention is sometimes referred to as refined pulp having different characteristics and wood pulp other than refined pulp having an α cellulose content of 88% or more and / or non-wood pulp (hereinafter simply referred to as “pulp”). ) And has excellent water dispersibility, and can be provided with strength sufficient for use as a bag.

  Wood pulp and / or non-wood pulp other than refined pulp having an α-cellulose content of 88% or more used for the base material of the water-dispersible laminated paper of the present invention includes wood pulp fibers such as conifers and hardwoods, flax and linters. Non-wood pulp fibers such as kenaf, bagasse, and Manila hemp. Wood pulp and / or non-wood pulp other than the above-described refined pulp is inherently water-dispersible because paper is made after disaggregation in water. Use after adjusting the degree of beating so that water dispersibility is not impaired even after the sheet is formed.

  The base material of the water-dispersible laminated paper of the present invention requires that the purified pulp having an α cellulose content of 88% or more in the total pulp amount constituting the base material is 15 to 95% by weight, preferably It is 20 to 80% by weight, more preferably 20 to 60% by weight. When the blending ratio of the refined pulp is less than 15% by weight, the fiber-to-fiber bond between the fibers forming the sheet becomes too strong, so that sufficient water dispersibility cannot be obtained. On the other hand, when the blending ratio of the refined pulp exceeds 95% by weight, the strength of the sheet is extremely lowered, and the handleability in practical use is lowered.

  In the base material of the water-dispersible laminated paper of the present invention, the refined pulp and pulp can be used after being beaten separately (hereinafter referred to as “single beat”), or after being blended ( Hereinafter, it can be used as a mixed beating.

  In the base material of the water dispersible laminated paper of the present invention, the degree of beating of the stock containing the refined pulp and the pulp is 450 to 700 ml CSF in terms of freeness in both cases of single beating and mixed beating, preferably 550-650 ml CSF. When the freeness is lower than 450 ml CSF, the fiber-to-fiber bond becomes strong, and good water dispersibility is lowered. On the other hand, when the freeness is 700 ml CSF or more, the fiber-to-fiber bond is reduced and the sheet strength is lowered.

  In the base material of the water-dispersible laminated paper of the present invention, when the refined pulp and pulp are mixed and beaten to the above freeness, it is preferable to use a refined pulp having a water retention of 140% or less in 450 ml CSF. When using refined pulp with a water retention of 140% or less in 450 ml CSF, beating energy is consumed for cutting the refined pulp, resulting in the formation of short fibers with less swelling and fibrillation from the refined pulp, and excessive pulp beating Therefore, excellent water dispersibility is exhibited. On the other hand, refined pulp with a water retention of 140% in a freeness of 450 ml CSF has a water dispersibility because when it is singly or mixed and beaten, the fiber swells and fibrillates and the interfiber bond increases. Decrease significantly. In addition, when used without beating, the pulp fibers easily fall off from the sheet, resulting in a disadvantage that paper dust increases.

  The base material of the water-dispersible laminated paper of the present invention can be produced from a refined pulp and a stock made of pulp by a known papermaking technique. The paper machine may be any of a circular net type paper machine, a slanted short net type paper machine, a long net type paper machine, a twin wire type paper machine, and the like, and can be properly used according to required strength and water dispersibility. For example, when a circular net type paper machine is used, since the strength anisotropy is large and the strength in the horizontal direction is weaker than that in the vertical direction, a base paper that can be easily shredded in water in the horizontal direction can be manufactured. .

  The base paper can be made as a single-layer sheet, or a sheet with a large basis weight can be manufactured by making multiple wet papers and making them together using a paper machine with two or more nets from the same paper stock. It is also possible to combine with sheets of different kinds of paper.

  It is preferable to adjust the paper surface pH of the substrate of the water-dispersible laminated paper of the present invention to 6 to 8 (neutral region), preferably 6.2 to 7.2. By adjusting the paper surface pH within this range, the effects on plants and animals can be eliminated.

  In the base material of the water-dispersible laminated paper of the present invention, the method for adjusting the paper surface pH is not particularly limited, and is a method for producing water-dispersed paper based on a material in a neutral region, alkaline or acidic. There is a production method that neutralizes water-dispersed paper with an acidic substance or alkaline substance, but the production of water-dispersed paper with the neutral region as the main component has an effect on soil and sea, and prevents insolubilization of the PVA resin laminate layer. From the point of view, it is preferable.

  In order to improve the water dispersibility (particularly fibrous dispersion time) and dry strength of the water dispersible laminated paper of the present invention, it is preferable to impregnate or apply a water-soluble polymer to a substrate. By impregnating or coating a water-soluble polymer described later on a base material made of wood pulp and / or non-wood pulp containing 15 to 95% by weight of refined pulp having an α-cellulose content of 88% or more, a water-soluble polymer is obtained. As the inter-fiber gaps of the base paper are filled, the drying strength of the water-dispersed paper is increased, and the water-soluble polymer present in the inter-fiber gaps swells when contacted with water and spreads between the fibers. Is easily separated.

  In the present invention, the water-soluble polymer preferably has a dry film that is easily re-dissolved in water. Carboxyalkyl cellulose salt, alginate, pectate, polyacrylate, polymethacrylate, carboxyalkylated starch , Phosphate esterified starch, anionic polyelectrolyte salts such as anionic polyacrylamide, methyl cellulose, hydroxyalkyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, polyalkylene oxide, polyvinyl ethyl ether, hydroxyethylated starch, oxidized starch, pregelatinized Polymer electrolytes such as starch, water-soluble polysaccharides such as guar gum, tant gum, xanthan gum, gum arabic, carrageenan, galactomannan, pullulan, dextran, dextrin, water such as gelatin, casein Can be exemplified a gender proteins, it can be used in combination one kind or two kinds or more. Of these, the use of a carboxymethyl cellulose salt is preferable from the viewpoint of improving water dispersibility and improving strength.

  In the present invention, it is preferable from the viewpoint of improving water dispersibility that the water-soluble polymer uniformly penetrates into the interfiber spaces of the base paper. For this reason, the water-soluble polymer impregnated or coated on the base paper is preferably one having a viscosity of 2 to 20% aqueous solution at 20 ° C. by 1 to 20 mPa · s.

  In the present invention, the addition amount (dry weight) by impregnation or coating of the water-soluble polymer is 2 to 14% by weight, preferably 3 to 12% by weight, more preferably 6 to 10% by weight, based on the base paper. It is. When the amount of the water-soluble polymer added is less than 2% by weight based on the base paper, a sufficient effect on water dispersibility and strength cannot be expected. Moreover, when there are more addition amounts than 14 weight%, the further improvement effect of water dispersibility or intensity | strength is not seen.

  The water-soluble polymer can be added to the substrate by impregnation with mangle, size press, etc., surface coating with gate roll coater, blade coater, bar coater, gravure coater, die coater, curtain coater, spray coater, etc. Can be appropriately selected and used.

  In order to improve the water dispersibility and dry strength of the water-dispersible laminated paper of the present invention, when impregnating or coating the substrate with a water-soluble polymer, to impart strength to the substrate to impregnate or coat. In addition, it is preferable that the base material contains a water-soluble polymer electrolyte salt.

  In the water-dispersible laminated paper of the present invention, the water-soluble polyelectrolyte salt is applied to the base material by adding it as an aqueous solution to the stock (refined pulp and pulp) slurry before paper making, or on wet paper after paper making There are methods such as squeezing and drying after adding with a roll coater, curtain coater, spray coating device or the like.

  In the present invention, the water-soluble polyelectrolyte salt to be contained in the substrate needs to have an adhesive force that enhances interfiber bonding and water solubility that easily dissolves and separates fibers when the sheet is wetted. Any anionic or amphoteric polyelectrolyte salt can be used as long as it meets this requirement. Carboxyalkylcellulose salts such as carboxymethylcellulose salts, alginates, carboxymethylated starches, polyacrylates, polymethacrylates Salts, anionic polyacrylamides, amphoteric polyacrylamides and the like are listed, and preferred are carboxymethylcellulose sodium salt and carboxymethylated starch. Two or more of these water-soluble polymer electrolyte salts may be added.

  In the present invention, since the refined pulp and the pulp are anionic, it is preferable to use a cationic fixing agent in combination in order to improve the fixing rate of the water-soluble polymer electrolyte salt.

  This cationic fixing agent needs to have an action of fixing a water-soluble polymer electrolyte salt to a base paper fiber without impairing water dispersibility, and a polyamine resin represented by the following general formula (1) is used as the cationic fixing agent. It is preferable.

（上記一般式(１)中、Ｒ_１は、ヒドロキシル基、ヒドロキシメチル基、ヒドロキシエチル基などの置換基を有する場合も含む炭素数１〜１０（但し、置換基の炭素数を含まない）のアルキル基を表し、Ｒ_２は、水素原子またはヒドロキシル基、ヒドロキシメチル基、ヒドロキシエチル基などの置換基を有する場合も含む炭素数１〜１０（但し、置換基の炭素数を含まない）のアルキル基であり、ｎは正の整数である。）
カチオン性定着剤として用いるポリアミン樹脂は、カチオン当量がｐＨ３〜９の範囲において０．１〜２０ミリ当量／ｇ、好ましくは１〜１５ミリ当量／ｇ、更に好ましくは２〜１０ミリ当量／ｇであり、数平均分子量は５０００〜１０００００、好ましくは５０００〜７００００、更に好ましくは５０００〜２００００である。

(In the above general formula (1), R ₁ is a carbon number of 1 to 10 (not including the carbon number of the substituent), including those having a substituent such as a hydroxyl group, a hydroxymethyl group, and a hydroxyethyl group. Represents an alkyl group, and R ₂ is an alkyl having 1 to 10 carbon atoms (not including the carbon number of the substituent) including a hydrogen atom or a substituent such as a hydroxyl group, a hydroxymethyl group, or a hydroxyethyl group. And n is a positive integer.)
The polyamine resin used as the cationic fixing agent has a cation equivalent of 0.1 to 20 meq / g, preferably 1 to 15 meq / g, more preferably 2 to 10 meq / g in the range of pH 3-9. The number average molecular weight is 5,000 to 100,000, preferably 5,000 to 70,000, and more preferably 5,000 to 20,000.

  In the present invention, the content of the water-soluble polymer electrolyte salt and the cationic fixing agent in the base material is not particularly limited as it is appropriately adjusted according to the required quality. It is preferable to adjust the addition amount of the water-soluble polymer electrolyte salt and the cation fixing agent in the following range when added to the slurry (refined pulp and pulp) as an aqueous solution.

  When the water-soluble polymer electrolyte salt and the cationic fixing agent are used in combination, the amount of water-soluble polymer electrolyte salt added (in terms of solid content) is 0.5 to 10% by weight based on the total amount of refined pulp and pulp. Preferably, it is 2 to 6% by weight. When the addition amount of the water-soluble polymer electrolyte salt is less than 0.5% by weight, the strength improvement is small and there is no effect of addition. When the addition amount of the water-soluble polymer electrolyte salt is more than 10% by weight, further improvement effect of strength and water dispersibility cannot be expected.

  The addition amount of the cationic fixing agent is preferably 0.2 to 4.0% by weight, more preferably 0.5 to 2.0% by weight, based on the total amount of refined pulp and pulp. When the addition amount of the cationic fixing agent is 0.2% by weight or less, the fixing rate of the water-soluble polymer electrolyte salt is lowered, and the strength required for the subsequent processing cannot be obtained. If the addition amount of the cationic fixing agent is 4.0% by weight or more, the bond between fibers of the base paper becomes too strong, and the water dispersibility (particularly, the fiber dispersion time) is impaired.

It is preferable that the cationic fixing agent is added to the paper or wet paper before the water-soluble polymer electrolyte salt, and the water-soluble polymer electrolyte salt is added after imparting cationicity to the fiber.
(Laminate layer)
In the present invention, the PVA resin laminate layer is a layer provided by laminating a PVA resin on a substrate.

  As the PVA resin in the present invention, those described in Japanese Patent No. 2920925 and JP-A-9-277465 are preferably used. Specifically, the saponification degree of the PVA resin is preferably in the range of 20 to 98 mol%, more preferably. Is in the range of 40 to 80 mol%, and the viscosity average polymerization degree of the PVA resin is preferably 50 or more and 4000 or less, particularly preferably 100 or more and 2000 or less. The method for forming the PVA resin laminate layer is not particularly limited, and a method such as a resin laminate method described in Japanese Patent No. 2920925 can be used, and a general processing machine such as an extrusion molding machine can be used. Can be used. When the resin laminating method is used, a polyvinyl alcohol-based resin is charged into an extruder having a T die and extruded as a film from the T die at a resin temperature of 100 to 300 ° C., more preferably 150 to 250 ° C., and between the nip roll and the cooling roll. A good resin laminate layer can be formed by pressure bonding with water dispersible paper and cooling at the same time.

  In the present invention, the thickness of the PVA resin laminate layer is 8 to 80 μm, preferably 12 to 35 μm. If it is less than 8 μm, the sealing strength at the time of heat sealing decreases. On the other hand, if it is 80 μm or more, it is not preferable from the viewpoint of water solubility and economy.

  In the present invention, water dispersibility can be evaluated by the flock-like water dispersion time and the fibrous water dispersion time. The flock-like water dispersion time is a time in which 300 ml of deionized water is put in a 300 ml beaker, a 3 cm square test piece is put into a 300 ml beaker while stirring at 650 rpm, and the test piece is cut into two or more pieces. Within seconds, more preferably within 20 seconds, and even more preferably within 10 seconds. If this flock-shaped water dispersion time is prolonged, when water-dispersed paper is flowed, it may cause clogging of the drain port or piping.

  On the other hand, the fiber dispersion time is the time when 300 ml of deionized water is put into a 300 ml beaker, and a 3 cm square test piece is added while stirring at 650 rpm with a stirrer, so that the test piece is completely loosened into individual fibers. Within 80 seconds, more preferably within 40 seconds, and even more preferably within 20 seconds. If this fibrous dispersion time is long, when water-dispersed paper is poured, it will cause clogging of the waste receptacle at the drain outlet.

  The water-dispersible laminated paper of the present invention can be subjected to calendering using a general papermaking calendar such as a machine calendar, a super calendar, a soft nip calender, etc. in order to improve smoothness and provide for printing applications. .

  In addition, in order to impart printability and printability to the non-laminated surface, a clear coat layer mainly composed of a water-soluble polymer, a pigment coat layer mainly composed of a pigment and a water-soluble polymer, and It is also possible to provide a heat-sensitive recording layer containing colorants and dyes as main components and an ink jet recording layer containing a cationic compound.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Moreover, the evaluation method used in the Example is shown below. This was commonly used in each example.

1) Water dispersion time Five test pieces of 3 cm square were prepared. Next, 300 ml of deionized water was placed in a 300 ml beaker, and one test piece was added while stirring at 650 rpm with a stirrer. Use a stopwatch to determine how long the base paper part of the test piece is torn into two or more pieces and how long the test piece is completely unraveled into individual fibers. It was set as water dispersion time, and the time until the PVA resin laminate layer was cut into two or more and the time until complete dissolution were taken as the film fusing time and the film dissolving time, respectively.
Further, the test piece was treated in an environment of 60 ° C. and 80% RH (1 day, 4 days, 8 days), and the floc water dispersion time, the fibrous water dispersion time, the film fusing time, and the film dissolution time were evaluated. .

2) Tensile strength Measured according to JIS P8113.

3) Paper surface pH
The measurement of the pH on the paper surface was conducted using JAPAN TAPPI No. In accordance with No. 49-1, distilled water was used as the wetting liquid, the wet surface of the paper onto which distilled water was dropped was brought into contact with the electrode, and the pH value after 2 minutes was read.

4) Heat seal strength Using a heat sealer (heat seal tester TP-701, manufactured by Tester Sangyo Co., Ltd.), the PVA laminate layer surfaces were heat sealed under the following conditions, and the heat seal strength was measured.
Condition 1: 120 ° C. × ² Kgf / cm ² × 1 second Condition 2: 160 ° C. × ² Kgf / cm ² × 1 second Heat seal strength was measured according to the heat seal strength test method described in JIS Z0238.

5) Delamination resistance A test piece having a width of 15.0 ± 0.1 mm and a length of 150 mm was taken so that the longitudinal direction was the paper making direction (laminating direction). The laminate resin is peeled off at the boundary surface with the base paper over a length of about 20 mm from one end of the test piece, and is added to each gripping tool of a constant speed extension type tensile tester (manufactured by Tensilon Toyo Seiki Co., Ltd.). The maximum load when the laminate resin and the base paper were peeled off was defined as the delamination resistance. In addition, the humidity control and measurement of the sample were performed in a temperature-controlled room with an air temperature of 23 ° C. and a relative humidity of 50%.

Example 1
Containing 60% by weight of softwood bleached kraft pulp (hereinafter referred to as NBKP; alpha cellulose content 85.6%) and 40% by weight of softwood mercerized pulp (alpha cellulose content 97.5%, water retention 138% in 450 ml CSF) In addition, polyamine resin (trade name Alcofix 159, product of Ciba Specialty Chemicals Co., Ltd.) as a cationic fixing agent is added to the raw material for papermaking mixed and beaten to a freeness of 641 ml CSF in an amount of 0.9% by weight based on the raw material. Further, an aqueous solution of carboxymethyl cellulose sodium salt (hereinafter referred to as CMC, trade name: Sunrose, Nippon Paper Chemicals Co., Ltd.) as a water-soluble polymer electrolyte salt was added at 2.0% by weight in terms of solid content, and then a basis weight of 60 g / Hand-drawn m ² base paper. On the obtained base paper, a 4% by weight solution of CMC (trade name Sunrose, a product of Nippon Paper Chemicals, the viscosity of a 2% by weight aqueous solution at 20 ° C. is 5 mPa · s) as a water-soluble polymer is applied to the base paper by a size press method. A neutral water-dispersible base paper (basis weight: 59.7 g / m ² , thickness: 89) coated with 9.3 wt% (5.6 g / m ² ) and having a paper surface pH of 6.8. .2 μm).
On the obtained base paper, a PVA resin (trade name: CP-1220T10, manufactured by Kuraray Co., Ltd.) melted at 185 ° C. was extruded and laminated so as to have a film thickness of 15 μm. (Basis weight: 83.4 g / m ² , thickness: 105.8 μm).
Table 1 shows the measurement results of water dispersion time, tensile strength, paper surface pH (non-laminated surface), and heat seal strength of this water-dispersible laminated paper.

  The water-dispersible laminated paper immediately after lamination was in water, and the base paper and the PVA laminated layer were melted at the same time in 2.6 seconds. Further, after 12.2 seconds, the base paper was dispersed in a fiber shape, and at this point, the PVA laminate layer was completely dissolved. In addition, after lamination, the water dispersible laminated paper in which the test piece was exposed to an environment of 60 ° C. and 80% RH for 8 days, the base paper and the PVA laminated layer were simultaneously melted in 2.7 seconds. Further, after 13.7 seconds, the base paper was dispersed in a fiber shape, and at this point, the PVA laminate layer was completely dissolved.

(Comparative Example 1)
A water-dispersible laminated paper was obtained in the same manner as in Example 1 except that a commercially available water-soluble paper (trade name: 60MDP, manufactured by Nippon Paper Papillia Co., Ltd.) having a paper surface pH of 9.8 and exhibiting alkalinity was used as the base paper.

  In the water-dispersible laminated paper immediately after lamination, the base paper and the PVA laminate layer were simultaneously melted in water in 2.8 seconds. Further, after 12.5 seconds, the base paper was dispersed in a fiber form, and at this point, the PVA laminate layer was completely dissolved. On the other hand, the water dispersible laminated paper in which the test piece was exposed for 8 days in an environment of 60 ° C. and 80% RH after lamination had a time of 4.0 seconds until the base paper was dispersed in a flock shape. The time until the PVA laminate layer was melted was 109.4 seconds. Further, the time until the base paper is dispersed in a fiber form is 34.3 seconds, and the time until the PVA laminate layer is completely dissolved is 300 seconds or more. The fiber dispersibility of the base paper and the PVA laminate layer The solubility was significantly reduced.

Claims (1)

  In a laminated paper having a polyvinyl alcohol resin laminate layer on at least one surface of a base material made of wood pulp and / or non-wood pulp, 15 to 95% by weight of the pulp constituting the base material has an α cellulose content of 88% or more. A water-dispersible laminated paper, which is a refined pulp.