JPH04257441A - Water-absorptive sheet - Google Patents

Abstract

PURPOSE:To increase water absorption and prevent a peeling phenomenon of a water-absorptive coating layer from a base sheet at the time of water absorption by forming the water-absorptive coating layer including a specific resin binder and water-insoluble, water-absorptive resin powder on the base sheet. CONSTITUTION:A resin binder has a main component in which acrylic ester or ester methacrylate and an alpha,beta-unsaturated carboxylic acid are copolymerized with each other, and is composed of the mixture of a copolymer obtained by the neutralizing treatment of a part of its carboxyl groups with a chlorinated ethylene-vinyl acetate copolymer and/or chlorinated polypropylene. The former copolymer includes hydrophilic groups and moreover has water-solubility due to the neutralizing treatment of a part of the carbo xyl groups. Accordingly, a water-absorptive coating layer 2 has high wettability and, on the other hand, the peel of the coating layer from a base sheet 1 at the time of water absorption is prevented by the chlorinated ethylenevinyl acetate copolymer and the like having hydrophilic properties.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a water-absorbing sheet that absorbs water or an aqueous solution when it comes into contact with water or an aqueous solution such as a salt, swells, and prevents the movement of water, and particularly improves its water-absorbing ability. This invention relates to improvements in water absorbent sheets.

0002

2. Description of the Related Art As shown in FIG. 2, this type of water-absorbing sheet includes a base sheet a and a water-absorbing paint layer b provided on the base sheet a and containing a resin binder and water-insoluble water-absorbing resin powder. It is widely used in products that require relatively high water absorption capacity, such as sanitary products, diapers, disposable wipes, paper towels, and medical gauze, and in recent years, Some applications have also been put into practical use for waterproof cables (optical fiber cables, power cables, etc.) that require higher water absorption capacity.

[0003] To explain an optical fiber cable as an example of a waterproof cable to which the water-absorbing sheet is applied, this optical fiber cable has a central tensile strength member c made of steel wire or fiber-reinforced plastic, as shown in FIG. , a plurality of optical fiber core wires e to e twisted together with an intervening buffer layer d of polypropylene yarn around this, and a water-absorbing tape f wound around the outer periphery of these fibers and provided with the water-absorbing paint layer on the inside thereof. , a wrap layer g (Laminated
Aluminum Polyethylene (laminated body of aluminum tape and polyethylene) and a sheath layer h made of polyethylene or the like provided on the outer periphery of the aluminum polyethylene (aluminum polyethylene) are the main parts. In the event of damage, rainwater, seawater, etc. that enter through the damaged area will be absorbed by the water-absorbing paint layer of the water-absorbing tape f, and this water-absorbing paint layer will swell and block the damaged area. It prevents water from entering the interior and also allows optical fiber cables to be installed.
It was also possible to prevent water from entering (water running) in the length direction.

0004

[Problems to be Solved by the Invention] By the way, most of the water-insoluble water-absorbing resins such as starch-sodium acrylate graft copolymers that constitute the main part of the water-absorbing paint layer are powders with low adhesion and are not based on Since it is difficult to directly apply the water-insoluble water-absorbing resin powder to a base sheet, the conventional method has been to use a resin binder and adhere the water-insoluble water-absorbing resin powder to a base sheet via the resin binder, as described above.

[0005] As this resin binder, for example, chlorinated ethylene-vinyl acetate copolymer resin or chlorinated polypropylene resin is used, taking into consideration adhesiveness to the base sheet and affinity with the water-insoluble water-absorbing resin. (Tokuko Showa 63-1
9545), or polyamide resin,
Linear thermoplastic polyester resins, vinyl chloride-vinyl acetate copolymer resins, cyclized rubber, chlorinated rubber, urethane resins, etc. are used (see Japanese Patent Publication No. 63-40665 and Japanese Patent Publication No. 63-63376). .

However, these resin binders are hydrophobic resins, and the water-absorbing paint layer, the main part of which is composed of these hydrophobic resins and water-insoluble water-absorbing resin powder, is also hydrophobic, so its wettability is However, when this water-absorbing paint layer comes into contact with water or an aqueous solution such as a salt, there is a problem that the water-absorbing property cannot always be fully exhibited.

That is, due to the incompatibility of the resin binder with respect to moisture, contact between the water-insoluble water-absorbing resin powder in the water-absorbing paint layer and moisture is likely to be inhibited, and the water-insoluble resin in the water-absorbing paint layer used for water absorption is likely to be inhibited. Because the water-absorbing resin powder is limited to those that exist in areas where it easily comes into contact with moisture,
There is a problem that the water absorption rate is slow at the initial stage of contact with water, and since the saturation state is reached with a small amount of water absorption, there is a problem that the subsequent water absorption capacity is extremely reduced due to the initial water absorption.

[0008] Therefore, when this water-absorbing sheet is applied to optical fiber cables etc. that require high water-absorbing ability, the initial water-absorbing speed is slow and the water-absorbing performance decreases with a small amount of water absorption, as described above. Therefore, water running etc. easily occur, and there are problems in that even optical fiber cables where there are no cracks etc. are damaged and become unusable, and equipment connected to this optical fiber cable also deteriorates. If the optical fiber core wire in the optical fiber cable is immersed in seawater etc. for a long time, the strength will decrease, and in the worst case, the optical fiber core wire will break due to the tension applied to the optical fiber core wire. there were.

The present invention was made in view of the above-mentioned problems, and its object is to provide a water-absorbing sheet that can withstand applications such as waterproof cables that require high water-absorbing capacity. Our goal is to provide the following.

0010

[Means for Solving the Problem] That is, the invention according to claim 1 is based on a water-absorbing sheet comprising a water-absorbing paint layer containing a resin binder and a water-insoluble water-absorbing resin powder provided on a base sheet, The main components of the resin binder are a copolymer obtained by copolymerizing an acrylic ester or a methacrylic ester and an α,β unsaturated carboxylic acid and neutralizing at least a part of the carboxyl groups, and a chlorine On the other hand, the invention according to claim 2 is characterized in that it is composed of a mixture of chlorinated ethylene-vinyl acetate copolymer and/or chlorinated polypropylene. Assuming a water-absorbing sheet consisting of a water-absorbing paint layer containing powder on a base sheet,
The main component of the resin binder is a copolymer obtained by copolymerizing an acrylic ester or a methacrylic ester, an α, β unsaturated carboxylic acid, and a styrene monomer, and neutralizing at least a portion of the carboxyl groups. Combination and
It is characterized by being composed of a mixture of chlorinated ethylene-vinyl acetate copolymer and/or chlorinated polypropylene.

[0011] In such technical means, the acrylic ester as a component of the above copolymer includes methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-acrylate. -amyl, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate,
N-octyl acrylate, n-lauryl acrylate, etc. can be applied, and examples of methacrylate esters include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and methacrylate. It is possible to apply n-amyl, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-lauryl methacrylate, and the like.

[0012] As the α,β unsaturated carboxylic acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc. can be used. Since the copolymer of these monomers and the above acrylic ester or methacrylic ester has a hydrophilic carboxyl group as an α,β unsaturated carboxylic acid component, this copolymer can be used as one component. The water-absorbing paint layer containing the resin binder and the water-insoluble water-absorbing resin powder becomes wettable.

On the other hand, alkylamines such as trimethylamine and triethylamine, alkali metal compounds, and the like can be used as the basic material that neutralizes at least a portion of the carboxyl groups. This neutralization treatment makes some of the side chain groups of the copolymer water-soluble and increases the hydrophilicity of the copolymer, which has the effect of further improving the wettability of the water-absorbing paint layer. Note that the degree of neutralization treatment is appropriately set in consideration of the degree of hydrophilicity of the synthesized copolymer before this treatment.

Furthermore, the above styrene monomers include:
Vinyl toluene such as styrene, 2-methylstyrene, chlorostyrene, etc. can be used, and there is an advantage that the cohesiveness of the resin binder can be improved by blending these styrenic polymers.

[0015] When selecting the type of acrylic ester or methacrylic ester, α, β unsaturated carboxylic acid, etc., it is important to ensure that the copolymer to be synthesized has hydrophilicity and physical properties such as viscosity. It is desirable to set an appropriate combination in consideration of the molecular weight, glass transition temperature, etc. of each component so that it is easy to handle.

On the other hand, in this technical means, a chlorinated ethylene-vinyl acetate copolymer and/or a chlorinated polypropylene resin is added as the other component of the resin binder. Incidentally, as described above, these resins are hydrophobic resins and inherently have a negative effect on increasing the water absorption ability of the water-absorbing paint layer. However, if the copolymer obtained by copolymerizing the above-mentioned acrylic ester or methacrylic ester and α, β unsaturated carboxylic acid and partially neutralizing the carboxyl groups becomes more water-soluble, due to contact with moisture, There is a risk that the water-absorbing paint layer will be dissolved and peeled off from the base sheet, resulting in a decrease in its water-absorbing ability. This is the reason for adding the above-mentioned chlorinated ethylene-vinyl acetate copolymer, etc. By adding these resins, it is possible to prevent the peeling phenomenon of the hydrophilic copolymer. Therefore, taking this point into consideration, the above-mentioned copolymer of acrylic ester or methacrylic ester and α,β unsaturated carboxylic acid and chlorinated ethylene-vinyl acetate copolymer and/or chlorinated polypropylene resin are combined. The mixing ratio is set, and preferably the mixing ratio of the copolymer of acrylic ester or methacrylic ester and α, β unsaturated carboxylic acid is 2 based on the total weight of the resin binder.
It is good to set it to 5 weight% - 75 weight%.

Next, as the water-insoluble water-absorbing resin powder that constitutes the water-absorbing paint layer together with the resin binder containing the above-mentioned mixture as a main component, starch-sodium acrylate graft polymers and hydrated starch-acrylonitrile graft polymers are used. Decomposition product, partially crosslinked starch-polyacrylic acid copolymer, partially crosslinked starch-polymethacrylic acid copolymer, partially crosslinked starch-polymethyl methacrylate hydrolyzate, and the above substances starch, salt etc.
Graft polymerization type, or crosslinked synthetic resin type such as partially crosslinked polyacrylate, polyisobutylene-maleic anhydride copolymer, hydrolyzate of methyl methacrylate-vinyl acetate copolymer, etc. Basically, water-soluble polymers are partially cross-linked to make them insolubilized, and when this polymer comes in contact with water or an aqueous solution such as a salt, it quickly absorbs water or an aqueous solution and swells. It is not particularly limited as long as it has the property of retaining.

[0018] Furthermore, the particle size of the water-insoluble water-absorbing resin powder to be applied is usually 100 mesh or less for the following reasons.
Preferably, the range is 35 mesh or less and 5 μm or more. In other words, if the particle size is coarser than 35 mesh, there will be problems with stability, fluidity, and coating workability when used as a water-absorbing paint.Furthermore, the coated surface will lack smoothness and uniformity, and after coating, it will not work as a base. This has the disadvantage that the material falls off from the sheet. On the other hand, fine powders with a particle diameter of less than 5 μm have the disadvantage that their water absorption capacity per gram decreases and they tend to aggregate, making them difficult to handle. Furthermore, when applied to a base sheet, this water-insoluble water-absorbing resin powder is buried in the resin binder film, resulting in a significant drop in water-absorbing performance. Note that the water-insoluble water-absorbing resin powder has excellent water-absorbing performance and workability when the shape is closer to a spherical shape, but it is not limited to this shape.

Next, regarding the blending ratio of the resin binder and the water-insoluble water-absorbing resin powder, the resin binder 10
The water-insoluble water-absorbing resin powder is set at 140 parts by weight or more and 1000 parts by weight or less relative to 0 parts by weight. That is, if the blending ratio of the water-insoluble water-absorbing resin powder is less than 140 parts by weight, when the water-absorbing paint layer is applied to the base sheet to form a water-absorbing sheet, the blending ratio is too small and the water-absorbing ability is not sufficient. Even when it comes into contact with water, it takes time for it to start absorbing water and swelling, making it difficult to effectively develop the water absorbing effect. On the other hand, if the blending ratio of the water-insoluble water-absorbent resin powder exceeds 1000 parts by weight, the surface area becomes too large even if the water-insoluble water-absorbent resin powder is made into coarse particles, resulting in an insufficient amount of resin binder added and It becomes difficult to securely hold the Therefore, 1 part by weight of water-insoluble water-absorbing resin powder is added to 100 parts by weight of resin binder.
It is desirable to set the amount to be 40 parts by weight or more and 1000 parts by weight or less.

[0020] In addition, when obtaining a water-absorbing paint by suitably blending the resin binder and water-insoluble water-absorbing resin powder, examples of solvents include alcohols such as methanol and ethanol, and acetate esters such as ethyl acetate and butyl acetate. , ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and hydrocarbon solvents such as n-hexane and toluene. The water-absorbing paint mentioned above is applied as a dispersion-like paint in which a large amount of water-insoluble water-absorbing resin powder is dispersed in a large amount of solvent in which a resin binder is dissolved. In order to improve workability, etc., it is desirable to add non-aqueous additives such as dispersants, viscosity modifiers, colorants, etc. in an amount of 2% by weight or less based on the total solid content. Furthermore, depending on the use of the water-absorbing sheet, preservatives, bactericidal agents, fragrances, deodorizing agents, etc. may also be added.

[0021]Although stirring with a disper may be used as a mixing means when blending the resin binder and the water-insoluble water-absorbing resin powder, a mixing method with higher energy such as an attritor or a ball mill may be used. This is desirable.

Furthermore, as a means of applying these water-absorbing paints to the base sheet, the usual coating method used for solvent-based paints can be applied as is, but if the water-absorbing paints contain a large amount of highly drying solvent. In the case of a dispersion paint, a gravure method, a roll coating method, a flow coating method, a dipping method, etc. are preferred. Incidentally, it is also possible to apply a spray method by appropriately adjusting the viscosity of the water-absorbing paint, the nozzle shape, etc.

Next, polyethylene terephthalate, polyvinyl chloride, metal, etc. can be used as the base sheet on which the water-absorbing paint layer is formed, and these are used in the form of a sheet or nonwoven fabric.

[0024] Furthermore, the scope of application of the water-absorbing sheet according to the inventions of claims 1 and 2 is similar to the conventional products, such as sanitary products, diapers, disposable rags, paper towels, medical gauze, etc., which require high water-absorbing ability. In addition, it can also be applied to waterproof cables such as optical fiber cables.

When applied as a water-absorbing tape for optical fiber cables, etc., the above-mentioned water-absorbing sheet is cut into strips, and this water-absorbing tape is wound spirally around the outer peripheral surface of a plurality of optical fiber core wires twisted together with an intervening buffer layer. It is what you use.

[0026]

[Function] According to the invention according to claim 1, the main component of the resin binder in the water-absorbing paint layer is a copolymer of acrylic ester or methacrylic ester and α,β unsaturated carboxylic acid, and at least one of the carboxyl groups thereof is copolymerized. It is composed of a mixture of a copolymer obtained by neutralizing the copolymer and a chlorinated ethylene-vinyl acetate copolymer and/or a chlorinated polypropylene, and the former copolymer contains α and β. It has a hydrophilic carboxyl group as an unsaturated carboxylic acid component, and at least a portion of it has been neutralized and is water-soluble, so the water-absorbing paint layer containing this component has strong wettability. The phenomenon of peeling from the base sheet due to dissolution during water absorption is suppressed by the action of the latter chlorinated ethylene-vinyl acetate copolymer and/or chlorinated polypropylene component having hydrophobic properties.

Therefore, the ratio of the water-insoluble water-absorbing resin powder used for the initial water absorption and subsequent water absorption action is dramatically increased compared to the conventional method, which improves the initial water absorption rate and the amount of water absorbed by the entire water-absorbing paint layer. It becomes possible to increase the amount of paint, and also to prevent the peeling phenomenon of the water-absorbing paint layer from the base sheet during water absorption.

On the other hand, according to the invention according to claim 2, the main component of the resin binder in the water-absorbing paint layer is a copolymer of acrylic ester or methacrylic ester, α, β unsaturated carboxylic acid, and styrene monomer. A copolymer obtained by neutralizing at least a portion of the carboxyl groups, a chlorinated ethylene-vinyl acetate copolymer and/or
or a mixture with chlorinated polypropylene, and the former copolymer has a hydrophilic carboxyl group as an α,β unsaturated carboxylic acid component, and at least a part of it is neutralized. Since it is water-soluble, the water-absorbing paint layer containing this component has strong wettability.
In addition, the presence of the styrene monomer component improves the cohesiveness of the water-absorbing paint layer, while the latter chlorinated ethylene-vinyl acetate copolymer has hydrophobic properties that cause it to peel off from the base sheet as it dissolves during water absorption. and/or suppressed by the action of the chlorinated polypropylene component.

Therefore, the ratio of the water-insoluble water-absorbing resin powder used for the initial water absorption and subsequent water absorption action is dramatically increased compared to the conventional method, which improves the initial water absorption rate and the water absorption amount of the entire water-absorbent paint layer. It becomes possible to increase the amount of paint, and also to prevent the peeling phenomenon of the water-absorbing paint layer from the base sheet during water absorption.

[0030]

[Examples] Examples of the present invention will be described in detail below.

[Example 1] As shown in Table 1 below, 83% by weight of n-butyl acrylate (BA), 5% by weight of methyl methacrylate (MMA) and 9% by weight of acrylic acid (AA)
These were copolymerized at a blending ratio of 3% by weight, and the carboxyl groups of this copolymer were neutralized with 3% by weight of trimethylamine.The resin agent was then dissolved in a mixed solvent of ethyl acetate and methanol to form acetic acid with a resin concentration of 50%. An ethyl methanol solution was obtained.

Next, 105 parts by weight of a 20% toluene solution of chlorinated ethylene-vinyl acetate copolymer (chlorinated EVA...manufactured by Sanyo Kokusaku Pulp Co., Ltd., trade name Super Chron B) and chlorinated polypropylene (chlorinated PP...Sanyo Kokusaku Pulp Co., Ltd., trade name Super Chron B) were added. 45 parts by weight of a 20% toluene solution of Super Chron 803MW (manufactured by Co., Ltd., trade name) was mixed with 140 parts by weight of the ethyl acetate/methanol solution having a resin concentration of 50%, resulting in a mixture of hydrophilic resin and hydrophobic resin. A resin binder solution was obtained.

Further, 250 parts by weight of a crosslinked product of sodium polyacrylate (fine water-insoluble water-absorbing resin powder) was added to this mixed resin binder solution, and these were stirred and mixed to obtain a water-absorbing paint.

[0034] Then, this water-absorbing paint was applied onto a polyethylene terephthalate film with a thickness of 80 μm using a solid gravure plate, and this was dried to form a water-absorbing paint layer with a thickness of 200 μm. A water-absorbing tape composed of a base tape 1 and a water-absorbing paint layer 2 as shown in FIG. 1 was obtained by cutting.

[Example 2] As shown in Table 1 below, the above resin concentration of 50% ethyl acetate/methanol solution was
The parts by weight are substantially the same as in Example 1, except that the 20% toluene solution of chlorinated EVA is 175 parts by weight, and the 20% toluene solution of chlorinated PP is 75 parts by weight.

[Example 3] As shown in Table 1 below, 79% by weight of n-butyl acrylate (BA) and styrene (St
) and 2% by weight of acrylic acid (AA), and the carboxyl groups of this copolymer were neutralized with 1% by weight of trimethylamine.The resin agent was then mixed with ethyl acetate and methanol. Dissolved in a solvent to a resin concentration of 5
Obtain a 0% ethyl acetate/methanol solution and add this solution 1
40 parts by weight of 20% toluene solution of chlorinated EVA 105
This example is substantially the same as Example 1 except that a mixed resin binder solution containing 45 parts by weight of a 20% toluene solution of chlorinated PP and chlorinated PP is applied.

[Example 4] As shown in Table 2 below, the above resin concentration of 50% ethyl acetate/methanol solution was 100%
The parts by weight are substantially the same as in Example 3, except that the 20% toluene solution of chlorinated EVA is 175 parts by weight, and the 20% toluene solution of chlorinated PP is 75 parts by weight.

[Example 5] As shown in Table 2 below, 87% by weight of n-lauryl methacrylate (LMA) and 9% by weight of acrylic acid (AA) were copolymerized. A resin agent whose combined carboxyl group has been neutralized with 3% by weight of trimethylamine is dissolved in a mixed solvent of ethyl acetate and methanol to obtain an ethyl acetate/methanol solution with a resin concentration of 50%, and 140 parts by weight of this solution is added with chlorinated EV.
105 parts by weight of 20% toluene solution of A and 2 parts of chlorinated PP
This is substantially the same as Example 1 except that a mixed resin binder solution containing 45 parts by weight of 0% toluene solution is used.

Comparative Example Next, the following comparative example (to which a conventional hydrophobic resin binder was applied) was conducted to confirm the characteristics of the water-absorbing tapes according to Examples 1 to 5.

(Comparative Example 1) As shown in Table 2 below, 350 parts by weight of a 20% toluene solution of chlorinated EVA and chlorinated P
This example is substantially the same as Example 1 except that a resin binder composed of 150 parts by weight of a 20% toluene solution of P is used.

(Comparative Example 2) As shown in Table 2 below, 10
This example is substantially the same as Example 1 except that a resin binder composed of 0 parts by weight of polyester resin (Vylon #200) is used.

``Confirmation Test'' Next, in order to check the characteristics of these water-absorbing tapes, a confirmation test was conducted regarding the following items, and the results shown in Table 3 below were obtained.

(1) Water absorption amount: 5 pieces of each water-absorbing tape cut into 100×100 m/m pieces.
Place it in a bag made of polyester non-woven fabric with a density of less than μm and immerse it in seawater.After 2 minutes, take out a part and sandwich it between blotting papers.After draining for 1 minute in this state, its water absorption amount was measured and used as water absorption data after 2 minutes. The amount of water absorbed was determined as the difference between the weight of the water-absorbing tape after draining and the weight of the water-absorbing tape itself that had not been immersed in seawater.

[0044] Further, another water-absorbing tape that had been soaked for 30 minutes was taken out and sandwiched between absorbent papers, and the same process was repeated for 30 minutes.
The water absorption amount data was calculated after 1 minute.

(2) Coating properties Workability and coating unevenness were checked when applying water-absorbing paints of each composition onto polyethylene terephthalate film, and
The evaluation was rated as × if the adhesiveness was poor and the workability was poor or the coating was uneven, ○ if there was no such problem, and △ if there was no such problem.

(3) Adhesion The water-absorbing paint layer of each water-absorbing tape was scratched with a fingernail, and the peeling state was visually confirmed. The evaluation was rated as × if it was easy to peel off, ○ if it was difficult to peel off, and △ in the middle.

(4) Blocking property Prepare multiple layers of water-absorbing tape, and apply 500 g/cm2 of water to it under the conditions of 40° C. and 20% RH.
Apply pressure to check whether the upper and lower water absorbent tapes are adhered or not. If there is no adhesion, mark ○, if there is, mark ×.
, and the middle was evaluated as △.

(5) Check whether the water-absorbing paint layer of the flexible water-absorbing tape has flexibility by wrapping each water-absorbing tape around an optical fiber cable. Cases where it was difficult to do so were evaluated as ×, and cases in between were evaluated as △.

[Evaluation] As is clear from the results shown in Table 3 below, the water absorption amount of the water absorption tapes according to Examples 1 to 5 after 2 minutes was significantly higher than that of the water absorption tape according to the comparative example. It can be confirmed that the initial water absorption rate increases.

Moreover, the amount of water absorbed after 30 minutes also increased, and it was confirmed that the amount of water absorbed did not reach the saturated state during the initial water absorption.

Therefore, even if the water-absorbing tapes according to these embodiments are applied to waterproof cables that require high water-absorbing ability, they will absorb a sufficient amount of water at the initial stage of water immersion, and the water-absorbing ability of the water-absorbing paint layer will be reduced. It was confirmed that water running etc. could be sufficiently prevented regardless of subsequent flooding, as the water did not reach a saturated state.

[0052] In addition, the water-absorbing tape according to each example uses a mixed resin binder, which is a mixture of a hydrophilic resin and a hydrophobic resin, in place of the conventional hydrophobic resin binder. It was also confirmed that the characteristics conditions were satisfied in all respects such as coatability, adhesion of the water-absorbing paint layer to the base tape, blocking property, and flexibility of the water-absorbing paint layer.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

Effects of the Invention According to the invention according to claim 1, the ratio of the water-insoluble water-absorbing resin powder used for initial water absorption and subsequent water absorption action is dramatically improved, so that the initial water absorption rate is improved and the water absorption property is improved. It is possible to increase the amount of water absorbed by the entire paint layer, and it is also possible to prevent the water-absorbing paint layer from peeling off from the base sheet when water is absorbed.

[0057] Therefore, a large amount of water is absorbed in the initial water absorption, and the amount of water absorption does not reach a saturated state, and the peeling phenomenon of the water-absorbing paint layer from the base sheet does not easily occur, resulting in a high water absorption capacity. It has sufficient durability even when applied to waterproof cables, etc. that require

On the other hand, according to the invention according to claim 2, the ratio of the water-insoluble water-absorbing resin powder used for the initial water absorption and the subsequent water absorption action is dramatically improved, so that the initial water absorption rate is improved and the water absorption property is improved. It is possible to increase the amount of water absorbed by the entire paint layer, and it is also possible to prevent the water-absorbing paint layer from peeling off from the base sheet when water is absorbed.

[0059] Therefore, a large amount of water is absorbed in the initial water absorption, and the amount of water absorption does not reach a saturated state, and the phenomenon of peeling of the water-absorbing paint layer from the base sheet does not easily occur, resulting in a high water absorption capacity. It has the effect of being able to withstand more fully even when applied to waterproof cables etc. that require

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a water-absorbing tape according to an embodiment of the present invention.

FIG. 2 is a perspective view of a conventional water absorbent sheet.

FIG. 3 is a cross-sectional view of an optical fiber cable to which a conventional water-absorbing tape is applied.

[Explanation of symbols]

1 Base tape 2 Water-absorbing paint layer

Claims (2)

[Claims] 1. A water-absorbing sheet comprising a water-absorbing paint layer containing a resin binder and water-insoluble water-absorbing resin powder on a base sheet, wherein the main component of the resin binder is:
Acrylic acid ester or methacrylic acid ester and α, β
A mixture of a copolymer obtained by copolymerizing an unsaturated carboxylic acid and neutralizing at least a portion of its carboxyl groups, and a chlorinated ethylene-vinyl acetate copolymer and/or a chlorinated polypropylene. A water-absorbing sheet characterized by the following: 2. A water-absorbing sheet comprising a water-absorbing paint layer containing a resin binder and a water-insoluble water-absorbing resin powder provided on a base sheet, wherein the main component of the resin binder is:
Acrylic acid ester or methacrylic acid ester and α, β
A copolymer obtained by copolymerizing an unsaturated carboxylic acid and a styrene monomer and neutralizing at least a portion of its carboxyl groups, and a chlorinated ethylene-vinyl acetate copolymer and/or a chlorinated polypropylene. A water absorbent sheet comprising a mixture of.