JP2006291404A - Moisture absorbing nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture absorbing nonwoven fabric that shows redused powder dropout, high flexibility and can be applied in a variety of usage. <P>SOLUTION: On the backing sheet made of nonwoven fabric that includes more than 60 wt.% of a thermally bonding fiber having a fineness of 1 to 4 dtex, fibers are bonded by thermal treatment and has the unit weight of 10 to 100 g/m<SP>2</SP>, is formed by the air-laid method, a web layer that comprises polyolefin pulp and moisture-absorbing powder at a weight ratio of 90/10 to 10/90 and has the unit weight of 20 to 1,500 g/m<SP>2</SP>to produce the moisture absorbing nonwoven fabric. Further, an upper layer sheet made of the same nonwoven fabric as the backing sheet may be laminated on the web layer, additionally adhesive nonwoven fabric may be intervened between the backing material sheet layer and the web layer and/or between the web layer and the upper layer sheet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nonwoven fabric having high hygroscopicity. The hygroscopic nonwoven fabric of the present invention has functions of humidity control and dew condensation prevention, and does not fall off hygroscopic powder, and is also flexible, so various building materials, sanitary materials, daily life materials, pharmaceuticals and foods It can be applied to a wide range of applications such as industrial members, electrical and electronic parts, and wire materials.

Conventionally, nonwoven fabrics have been widely used in civil engineering materials and sanitary materials, and nonwoven fabric composites combining nonwoven fabrics and inorganic fillers have been proposed.
For example, Patent Document 1 (Japanese Patent Laid-Open No. 62-104956) discloses a sheet made of dry paper making (Air Lay) of synthetic pulp, natural pulp, and inorganic fillers such as silica, alumina, diatomaceous earth and the like. ing. However, this application relates to a sheet used for hot press molding of automobile interior materials and the like, and is completely different from the hygroscopic sheet intended by the present invention, and is also a hygroscopic property that is the object of the present invention. There is no mention or suggestion about the composite of the nonwoven fabric forming the front and back layers, which is an important component for the sheet.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-113580) discloses a method for obtaining a highly hygroscopic nonwoven fabric composite that is webbed by blowing air current on a net in a state where hygroscopic fine particles and short fibers are mixed. In order to fix the inorganic fine particles to the fiber, there is a description that the non-woven fabric can contain a heat-sealing fiber, or a protective layer such as a fiber sheet can be provided on one side or both sides. In Example 2 of the patent document, porous silica fine particles and heat-fusible core-sheath polyester short fibers are mixed on a polyester spunbonded nonwoven fabric having a basis weight of 60 g / m ² and a thickness of 0.3 mm to produce an air current. An example of spraying, laminating and hot pressing is disclosed. However, the average value of the fiber diameter constituting the nonwoven fabric is preferably only 0.1 to 1,000 μm, and the synthetic pulp having a multi-branched fiber structure, which is an important constituent element of the present invention, is mixed with the powder. There is no mention of a technique for preventing the powder from falling off and improving the uniform dispersion of the powder.

  Furthermore, the invention described in Patent Document 3 (Japanese Patent Laid-Open No. 2003-340231) forms a hygroscopic sheet by ejecting a mixture of hygroscopic powder and ultrafine short fibers onto a porous support. It is also disclosed that a non-woven fabric is laminated on one side or both sides. And in patent document 3, when it is in the state in which the said ultra-fine short fiber was entangled, it will become difficult to disperse | distribute an ultra-fine short fiber to each ultra-fine short fiber by the effect | action of compressed gas, and to disperse | distribute uniformly (Paragraph “0047” of the same patent document), combining a hygroscopic powder and a polyolefin-based synthetic pulp having a multi-branch fiber structure obtained by the flash spinning method, reduces the amount of powder falling off and is flexible. A concept that is not compatible with the technical idea of the present invention that a hygroscopic sheet that is rich in properties and can be applied to various uses is shown.

JP 62-104956 A JP 2003-113580 A JP 2003-340231 A

  The present invention provides a hygroscopic sheet that combines a polyolefin synthetic pulp and a hygroscopic powder and uses the airlaid method to reduce powder fall-off, have high flexibility, and can be applied to various applications. The purpose is to provide.

The present invention provides a polyolefin-based synthetic pulp on a base sheet made of a nonwoven fabric containing 60% by weight or more of heat-adhesive fibers having a fineness of 1 to 4 dtex and having a basis weight of 10 to 100 g / m ² bonded between fibers by heat treatment. And a hygroscopic powder are mixed in a ratio of 90/10 to 10/90% by weight, and a web layer having a basis weight of 20 to 1,500 g / m ² is formed by the airlaid method and laminated and integrated. This relates to a hygroscopic nonwoven fabric.
In the present invention, on the web layer composed of the polyolefin synthetic pulp and the hygroscopic powder, the basis weight further includes 60% by weight or more of heat-adhesive fibers having a fineness of 1 to 4 dtex and are bonded between fibers by heat treatment. You may laminate | stack the upper layer sheet | seat which consists of 10-100 g / m < ² > nonwoven fabric.
Moreover, you may interpose the nonwoven fabric which consists of thermoadhesive conjugate fiber further between the said base material sheet and a web layer, and / or between a web layer and an upper layer sheet.
The hygroscopic nonwoven fabric of the present invention is preferably heat treated.

In the present invention, when the web is formed from the polyolefin synthetic pulp and the hygroscopic powder, the airlaid method is employed, so that the polyolefin synthetic pulp and the hygroscopic powder are entangled in the air stream, Hygroscopic powder is entangled in the pulp, so that the hygroscopic powder does not fall off from the formed web. In addition, a base sheet (carrier sheet) is used in advance, and an olefin type is formed thereon by the airlaid method. Since webs made of synthetic pulp and hygroscopic powder are laminated, even if the hygroscopic powder falls off the generated web, it is not collected by this base sheet and dropped out of the system. Moreover, the hygroscopic nonwoven fabric obtained is rich in flexibility and excellent in hygroscopicity.
Moreover, the hygroscopic nonwoven fabric laminated with the upper layer does not drop the hygroscopic powder on both the front and back sides.
Furthermore, when a non-woven fabric made of a heat-adhesive conjugate fiber is further interposed between the base sheet layer and the web layer and / or the web layer and the upper layer, delamination of the resulting hygroscopic non-woven fabric and removal of the hygroscopic powder Can be further suppressed.
In addition, the hygroscopic nonwoven fabric of the present invention can further suppress delamination and hygroscopic powder dropping by heat treatment such as hot air treatment or calendering with a hot roll.

Base sheet:
The base sheet used in the present invention is composed of a non-woven fabric having a basis weight of 10 to 100 g / m ² containing 60% by weight or more of heat-adhesive fibers having a fineness of 1 to 4 dtex and bonded between fibers by heat treatment. The base sheet may not be bonded between fibers by heat treatment in advance. For example, in the final stage of the hygroscopic nonwoven fabric manufacturing process of the present invention, the base sheet is heat treated together with the web layer or the upper layer sheet and bonded between fibers. It may be.
The base sheet may be prepared by any of the card method, the spun bond method, the melt blow method, the air laid method, or the wet papermaking method, but is preferably the air laid method.

  As the heat-adhesive fiber used for the base sheet, a heat-adhesive conjugate fiber is suitable. For example, a core-sheath type in which a low melting point component is a sheath component and a high melting point component is a core component, a side-by-side type in which one is a low melting point and the other is a high melting point component. Examples of the combination of both components of these composite fibers include PP [polypropylene] / PE (polyethylene), PET (polyethylene terephthalate) / PE, PP / low-melting copolymer PP, PET / low-melting copolymer polyester, and the like. . Here, examples of the low-melting point copolyester include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, etc. as a basic skeleton, aromatic dicarboxylic acids such as isophthalic acid and 5-metal sulfoisophthalic acid, adipic acid, and sebacic acid. And a modified copolymer with an aliphatic polycarboxylic acid such as diethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol and the like.

  The melting point of the thermal adhesive component, which is a low melting point component, is usually 110 to 160 ° C., preferably 120 to 155 ° C. When the temperature is less than 110 ° C., the heat resistance of the nonwoven fabric is low, so that it is not practical. On the other hand, when the temperature exceeds 160 ° C., it is necessary to increase the heat treatment temperature in the nonwoven fabric production process, the productivity is lowered, and it is not practical, and the adhesive effect in the hot-pressure integration with the airlaid fiber layer described later cannot be expected. .

The fineness of the heat-adhesive fiber is 1 to 4 dtex, preferably 1.1 to 3 dtex. If it is less than 1 dtex, thin fibers tend to be entangled with each other and mixing with other fibers becomes difficult, increasing the risk of uneven texture and occurrence of bulk defects. On the other hand, in the case of a thick fiber exceeding 4 dtex, the number of fibers decreases even at the same mixing rate, and thus the effects of preventing hygroscopic powder from falling off, imparting strength, and imparting heat sealability are reduced.
In addition, when the manufacturing method of a base material sheet is an airlaid method, it is preferable that the fiber length is 2-15 mm, More preferably, it is 3-10 mm. When the fiber length is less than 2 mm, the effect of increasing the strength is not sufficient. On the other hand, when the fiber length exceeds 15 mm, the fibers tend to be entangled with each other, leading to deterioration in processability and texture.

  The heat-adhesive fiber may be crimped or not, and may be a strand chop. When crimped, both zigzag-type two-dimensional crimped fibers and spiral-type and ohmic-type three-dimensional (three-dimensional) crimped fibers can be used.

  Examples of fibers other than these heat-adhesive fibers include PP fibers, PET fibers, PBT fibers, nylon 6 fibers, nylon 6,6 fibers, aromatic polyamide fibers, acrylic fibers, synthetic pulp (for example, Mitsui Chemicals ( Multi-branched fibrillar fibers made of PE or PP, such as SWP manufactured by Co., Ltd.), wood pulp, hemp, rayon, viscose fibers, etc. are mixed within a range not impairing the gist and effect of the present invention. Also good. In this case, the proportion of other fibers is preferably kept below 50% by weight. If it is 50% by weight or more, not only the strength of the nonwoven fabric and the heat sealability will be affected, but fibers without thermal adhesiveness will easily fall off during actual use.

The basis weight of the base sheet is 10 to 100 g / m ² , preferably 12 to 80 g / m ² . When the amount is less than 10 g / m ^2, the hygroscopic powder present in the web layer falls off without being captured by the base sheet, and the strength of the nonwoven fabric is lowered, so troubles such as breakage are likely to occur during actual use. On the other hand, if it exceeds 100 g / m ² , not only will the requirement of air permeability of 2 seconds or less necessary as a base material for the airlaid method be apt to occur, but the moisture absorption intended by the present invention is due to low air permeability. Adversely affected.
The air permeability of the base sheet is preferably 2 seconds or less. The airlaid method is a method in which a fiber layer is formed on a breathable material by ejecting a mixture of fibers and air from the top of the breathable material and drawing air from the bottom by suction. Air permeability is an important requirement. When the air permeability exceeding 2 seconds is poor, the air-laid fiber layer is likely to be non-uniform and the productivity is also deteriorated. The air permeability is preferably 0.5 to 2 seconds.

  The base sheet may be formed at the same time as the lamination with the web layer. For example, the use of a base sheet that has been prepared and heat-treated in advance by the airlaid method can simplify the manufacturing process by the airlaid method. Is preferable.

Formation and lamination integration of web layer by airlaid nonwoven manufacturing method:
Next, a web layer made of polyolefin synthetic pulp and hygroscopic powder is formed on the base sheet by the airlaid method. That is, a mixture of polyolefin synthetic pulp and hygroscopic powder is ejected from a single unit or a large number of ejection units located on a porous net conveyor and sucked by an air suction unit arranged on the lower surface of the net conveyor. A web layer is formed on a conveyor. At this time, a laminated body can be obtained at once by placing a base material sheet as the base material on a net conveyor in advance. Thereafter, hot air treatment and / or hot-pressure calender treatment is applied to the laminate to form an airlaid layer-to-fiber bond and a thermal bond with the substrate to be integrated as a nonwoven sheet.
Furthermore, you may mix the heat bondable fiber together with the web layer. In this case, it is possible to expect effects such as fixing of powder, prevention of dropping, and improvement of delamination strength. When a heat-adhesive fiber is used in combination with the web layer, it is particularly effective for preventing powder from falling off from the end face of the sheet of the present invention. As the heat-adhesive fiber, the above-mentioned heat-adhesive conjugate fiber is particularly suitable. The mixing ratio is preferably 60% by weight or less of the entire web layer. When it exceeds 60% by weight, not only the flexibility of the sheet after heat treatment is lost, but also the surroundings of the hygroscopic powder are covered with many heat-adhesive fibers, which adversely affects the hygroscopicity.
Necessary characteristics can be controlled by adjusting the fiber amount, ejection conditions, air suction conditions, heat treatment conditions, and the like.

Here, the polyolefin synthetic pulp is, for example, a high temperature, high pressure state polyolefin, a polymer solvent selected from a fatty acid hydrocarbon and an alicyclic hydrocarbon having a boiling point lower than the boiling point of water, and a dispersion comprising water. A dispersion at a temperature at which substantially all of the solvent evaporates and does not cause substantial evaporation of water when rapidly released into the vacuum zone, is released through the precipitation nozzle into the vacuum zone. The polyolefin is recovered as a fibrous material dispersed in water, and the fibrous material dispersed in water is obtained by beating or refining the surfactant immediately at an initial temperature of 50 ° C. or higher. It is done. The method for producing the polyolefin-based synthetic pulp is described in detail in, for example, the claims in the first column of JP-B-52-47049, column 3, line 5 to column 19, line 25. The gist of the present invention, that is, a method for producing a polyolefin-based synthetic pulp composed of fibrillar fibers having a trapping action for hygroscopic powder, is not necessarily limited to these.
As the polyolefin synthetic pulp, those having an average fiber length of 0.5 to 3 mm and an average fiber diameter of 1 to 100 μm can be suitably used.
Moreover, as a commercial item of this polyolefin synthetic pulp, SWP E790, E400, EST-8, E620, UL410, NL490, AU690, Y600, ESS-5, ESS-2, E380, E780 manufactured by Mitsui Chemicals, Inc. , E90, UL415, and the like.

  Since these polyolefin-based synthetic pulps have a multi-branched fiber structure (fibrillated, multi-branched and have a high specific surface area), they have a feature of excellent hygroscopic powder capturing properties. Further, when the substrate sheet is sprayed by the airlaid method, the web layer in which the polyolefin synthetic pulp and the hygroscopic powder are integrated in an air current is uniformly placed on the sheet.

On the other hand, the other hygroscopic powder forming the web layer may be any hygroscopic powder, preferably zeolite, silica-based particles, alumina gel, alumina-based particles, silica-alumina-based dry Agents, diatomaceous earth, charcoal, bamboo charcoal, activated carbon, molecular sieves, poly (meth) acrylic acid or polyvinylpyrrolidone, or alkali metal salts thereof.
The average particle diameter of these hygroscopic powders is usually 0.01 to 2 mm, preferably 0.1 to 1 mm.

  The mixing ratio of the polyolefin-based synthetic pulp forming the web layer and the hygroscopic powder is 90/10 to 10/90% by weight, preferably 80/20 to 20/80% by weight, and more preferably 70/30 to 20%. / 80% by weight. When the polyolefin-based synthetic pulp is less than 10% by weight, the function of capturing the hygroscopic powder is not sufficient, and the powder easily falls off. On the other hand, if the hygroscopic powder is less than 10% by weight, the hygroscopic nonwoven fabric obtained has poor hygroscopicity, which is not intended by the present invention.

The web layer formed by the airlaid method usually has a basis weight of 20 to 1,500 g / m ² , preferably 40 to 1,000 g / m ² . When it is less than 20 g / m ² , the hygroscopic property, the nonwoven fabric strength, and the heat seal strength are low, which is not suitable for practical use. On the other hand, if it exceeds 1,500 g / m ² , it is not preferable because it is too thick and the flexibility becomes poor, and it becomes difficult to form a uniform web by the airlaid method.
The airlaid method for producing the web layer of the present invention is extremely easy to use because of the short length of fibers that can be easily defibrated to a single fiber by air flow, compared to existing dry nonwoven fabric manufacturing methods such as the card method. A great feature is that a non-woven fabric having good texture, that is, good uniformity can be obtained. In hygroscopic applications, uniformity is an important requirement for the performance of low powder leakage and good hygroscopicity, and is difficult to obtain with existing card method nonwoven fabrics, spunbond nonwoven fabrics, and melt blown nonwoven fabrics. Moreover, according to this manufacturing method, there is also a merit that the vertical / horizontal strength ratio is close to 1/1.

Upper sheet:
The hygroscopic non-woven fabric of the present invention is made of this polyolefin synthetic pulp and hygroscopic powder in order to further prevent the hygroscopic powder present in the web layer from falling off and to enhance functions such as surface abrasion resistance. An upper sheet made of a non-woven fabric further comprising 60% by weight or more of heat-adhesive fibers having a fineness of 1 to 4 dtex and having a basis weight of 10 to 100 g / m ² bonded between fibers by heat treatment. It is preferable to laminate.
Examples of the upper layer sheet include the same sheet as the base sheet.

Adhesive nonwoven fabric made of heat-adhesive conjugate fiber:
The hygroscopic nonwoven fabric of the present invention comprises a heat-adhesive conjugate fiber between the base sheet and the web layer or between the web layer and the upper layer sheet in order to ensure the bonding. It is preferable to interpose an adhesive nonwoven fabric.
In order to interpose the adhesive nonwoven fabric, the adhesive nonwoven fabric layer is formed by the airlaid method on the substrate sheet as the substrate and / or the web layer. That is, an air suction unit in which a heat-adhesive conjugate fiber having a melting point of 110 to 160 ° C. of an adhesive component is ejected together with an air flow from a single unit or a plurality of ejection units located on a porous net conveyor, and arranged on the lower surface of the net conveyor. The fiber layer is formed on the net conveyor while sucking at the part. At this time, the base material sheet layer, or the base material sheet layer and the web layer are laid in advance on the net conveyor to obtain a laminated body at once. Thereafter, hot air treatment and hot-pressure calender treatment are applied to the laminate to form an airlaid layer-to-fiber bond and a thermal bond with the base sheet layer to be integrated as a nonwoven sheet.
Necessary characteristics can be controlled by adjusting the fiber amount, ejection conditions, air suction conditions, heat treatment conditions, and the like.

As the heat-adhesive conjugate fiber used for the adhesive nonwoven fabric, those similar to the heat-adhesive conjugate fiber used for the base sheet are used.
Basis weight of the adhesive nonwoven fabric, usually, 2 to 50 g / ^{m 2,} preferably 4~30g / ^{m 2,} is less than 2 g / ^{m 2,} the base sheet and the web layer, or the web layer and the upper layer sheet Adhesion is insufficient. On the other hand, if it exceeds 50 g / m ² , it is too thick and tends to adversely affect the hygroscopic performance.

Heat treatment:
As for the hygroscopic nonwoven fabric of this invention, it is preferable to heat-process the nonwoven fabric laminated body obtained as mentioned above. Examples of the heat treatment include hot air treatment and / or hot pressure treatment.
Among these, the hot air treatment for forming the fiber-to-fiber bond requires a temperature equal to or higher than the melting point of the low-melting component of the heat-adhesive conjugate fiber. However, if the melting point is 30 ° C. or higher than the melting point of the low melting point component, or the melting point of the high melting point component (the core component of the core-sheath type composite fiber or the high melting point component of the side-by-side type composite fiber), the heat shrinkage of the fiber. Is liable to be large, which leads to deterioration of the texture, and in extreme cases, it causes deterioration of the fibers, which is not preferable.
The hot air treatment temperature is usually 110 to 190 ° C, preferably 120 to 175 ° C.

  Further, after the hot air treatment, a hot pressure treatment, specifically, a hot pressure calendar treatment may be added. As a roller used for the calendering treatment, it is preferable to use a pair of metal rollers having a smooth surface or a combination of a metal roller and an elastic roller in order to apply a uniform heat pressure to the whole, but a multi-stage roller may also be used. In addition, an embossing roller with an uneven surface may be used as long as the gist of the present invention is not impaired.

In the case of calendering, the pressure may be applied at any temperature from room temperature (non-heated) to high temperature if it is simply for thickness adjustment. The pressure can be appropriately selected to achieve a desired thickness. The temperature of the roller surface is higher than the melting point of the low-melting component of the heat-adhesive conjugate fiber so as to reinforce the thermal bond between the fibers with a hot-pressure calender and improve strength, surface abrasion resistance, delamination prevention, etc. Temperature is required. However, if the melting point is 30 ° C. or higher than the melting point of the low melting point component, or the melting point of the high melting point component (the core component of the core-sheath type composite fiber or the high melting point component of the side-by-side type composite fiber), the heat shrinkage of the fiber. Not only tends to be large, but also sticks to the roller surface and lacks processability. When the temperature is lower than the melting point, it is a matter of course that the reinforcement between the fibers is not sufficient.
The heat treatment temperature for reinforcing the fiber-to-fiber bond is usually 110 to 190 ° C, preferably 120 to 175 ° C.

  Moreover, if the linear pressure of the calendar process is set so as to be a uniform contact pressure in the width direction, an arbitrary pressure can be selected. In the case of high pressure, the density, non-woven fabric strength and interlayer strength increase, and the thickness decreases. In the case of low pressure, of course, an adverse effect occurs. If importance is attached to the strength of the nonwoven fabric, a high pressure is preferred as much as possible. If flexibility is important, low pressure is preferable. The linear pressure of the calendar process can usually be arbitrarily selected in the range of 10 to 100 kgf / cm.

In addition, although the thickness of the hygroscopic nonwoven fabric of this invention obtained is 0.3-30 mm normally, Preferably it is 0.5-20 mm, but according to the fabric weight (20-1,500 g / m < ² >) of a web layer. And can be set according to the application.
The total weight of the hygroscopic nonwoven fabric of the present invention is usually 40 to 1,800 g / m ² , preferably 50 to 1,500 g / m ² .

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples.

Example 1
First, a PET (polyethylene terephthalate) / PE (polyethylene) based composite fiber 2.2 dt × 5 mm (Teijin Fibers Ltd., F6) was used as a raw material fiber to form a sheet by an airlaid method. The basis weight was adjusted to 12 g / m ² and heat-treated at a hot oven temperature of 136 ° C. The air permeability of this sheet was 0.8 seconds. Next, this sheet is used as a base sheet (carrier sheet), on which polyethylene synthetic pulp (Mitsui Chemicals Co., Ltd., SWP · E795) 20% by weight and crushed B-type silica gel (Shinetsu Chemical Industries Co., Ltd.) , GB (W) 30 mesh pass) was formed as a web layer by the airlaid method so as to be 180 g / m ² . Further, the sheet of 12 g / m ² is placed on the upper part as an upper layer sheet, and the multi-layer sheets are stacked and subjected to hot air treatment in a 136 ° C. hot oven, followed by a pair of metal rollers having a flat surface. Hot pressing was performed at 10 ° C. and 10 kgf / cm. The resulting laminated integrated nonwoven fabric with a basis weight of 204 g / m ² is flexible and free of powder leakage, has practically strong strength, surface wear resistance, etc., has excellent hygroscopicity, and has low moisture after being absorbed once. It exhibited the property of releasing moisture under the environment, and was useful as a moisture absorbing / releasing nonwoven fabric.

Comparative Example 1
All web layers were made of polyethylene synthetic pulp, and the others were the same as in Example 1. The obtained laminated integrated nonwoven fabric lacked hygroscopicity.

Comparative Example 2
The same procedure as in Example 1 was conducted except that the polyethylene synthetic pulp was replaced with PET / PE composite fiber 2.2 dt × 5 mm (Teijin Fibers Ltd., F6) during the composition of the web layer. Although the obtained laminated integrated nonwoven fabric had hygroscopicity, powder leakage was severe and lacked practicality.

Example 2
First, PP (polypropylene) / PE-based composite fiber 2.2 dt × 51 mm (Chisso Corporation, ESC) is used as a raw material fiber, and a web having a basis weight of 16 g / m ² is obtained by a card method. Heat-treated into a sheet. The air permeability of this sheet was 0.9 seconds. Next, using this sheet as a base sheet, 15% by weight of polyethylene-based synthetic pulp (Mitsui Chemicals Co., Ltd., SWP · E795) and crushed B-type silica gel (Shinetsu Kasei Co., Ltd. GB (W)) (30 mesh pass) A 70% by weight and further 15% by weight PP / PE composite fiber 1.7 dt × 3 mm (Chisso Corporation, Intac) mixture was formed as a web layer by the airlaid method to 100 g / m ² . . Further, on the upper part, the above-mentioned 16 g / m ² air-through non-woven sheet is placed as an upper layer sheet. After these multilayer sheets are stacked, hot air treatment is performed in a 136 ° C. hot oven, and then a pair of metal rollers with a flat surface is used. Hot pressing was performed at 100 ° C. and 20 kgf / cm. The obtained laminated integrated nonwoven fabric having a basis weight of 132 g / m ² was flexible and free from powder leakage, had practical strength, surface wear resistance, etc., and was useful as a hygroscopic nonwoven fabric.

Example 3
Using PP spunbond (Mitsui Chemicals, Syntex) with a basis weight of 30 g / m ² and an air permeability of 1.4 seconds as a base sheet, first, PP / PE composite fiber 1.7 dt × 3 (Chisso) A web was formed by an airlaid method so as to be 10 g / m ² as an adhesive nonwoven fabric layer. Next, on top of this, polyethylene synthetic pulp (Mitsui Chemicals Co., Ltd., SWP · E795) 10% by weight and crushed B-type silica gel (Shinetsu Kasei Co., Ltd., GB (W) 30 mesh pass) 80% by weight % And a PP / PE composite fiber 1.7 dt × 3 mm (Chisso Corporation, Intac) 10 wt% mixture was formed as a web layer by the airlaid method so as to be 320 g / m ² . Furthermore, a web was formed on the upper portion of the PP / PE composite fiber 1.7 dt × 3 (Chisso Corporation, Intac) by an airlaid method so as to be 10 g / m ² , thereby forming an adhesive nonwoven fabric layer. Further, the above-mentioned 30 g / m ² PP spunbond is placed on the upper part as an upper layer sheet, and these multi-layer sheets are stacked and heated in a hot oven at 138 ° C., and then a pair of metal rollers with a flat surface is used. Calendar treatment was performed at 60 ° C. and 10 kgf / cm. The obtained laminated integrated nonwoven fabric with a basis weight of 400 g / m ² was flexible and free from powder leakage, had practical strength, surface wear resistance, etc., and was useful as a hygroscopic nonwoven fabric.

<Note>
(1) Air permeability: Expressed in terms of air permeability (seconds) using a JIS P8117 Gurley tester.
(2) Thickness: According to a load of 40 g / cm ² .
(3) Moisture absorption test; specimen 10 cm x 10 cm. After pre-drying 90 ° C. × 24 h, it is allowed to cool at room temperature in a desiccator for 2 h, and then left in a desiccator with a predetermined temperature and humidity for 24 hours. The change in weight was measured and converted to g / m ² .
(4) Moisture release test; after absorbing moisture under the conditions of high humidity RH90% × 24h, letting it stand in a desiccator with low humidity RH20% for 24 hours to measure moisture release and change in weight to determine the residual moisture absorption g / m Converted to ² .
(5) Powder leakage: A 10 cm × 10 cm specimen was placed in a plastic bag, shaken vigorously for 10 seconds, and then the powder in the bag was observed. “Very trace amount” means 1% by weight or less, and “very high” means more than 10% by weight.

The hygroscopic nonwoven fabric of the present invention has functions of humidity control and dew condensation prevention, and does not drop hygroscopic powder, and is also flexible.For example, an oxygen scavenger, desiccant, exothermic agent, hygroscopic agent, deodorant, etc. It can be applied to products such as packages containing insecticides, insect repellents, dehumidifiers and fragrances. Furthermore, it can be applied to a wide range of uses such as various building materials, hygiene materials, daily life materials, pharmaceutical / food materials, electrical and electronic parts, and electric wire materials.
Specific examples of building material applications include interior materials, wallpaper, roofing materials, roof covering materials, exterior materials, flooring materials, carpet parts, closet sheets, curtains, roll curtains, partition materials, etc. As diaper parts for infants, adults, sanitary products, medical gowns, surgical supplies, care sheets, medical materials, care products, etc. Examples of the dehumidifying agent for pharmaceutical packaging and the food member include a dehumidifying agent inside a package such as sweets.
In addition to packaging of electrical and electronic parts that dislike humidity, it can also be mounted inside electrical and electronic equipment such as copying machines and video equipment to exhibit moisture absorption and humidity control functions.

Claims (7)

Polyolefin synthetic pulp and hygroscopic powder on a base sheet made of a nonwoven fabric containing 60% by weight or more of heat-adhesive fibers having a fineness of 1 to 4 dtex and bonded to each other by heat treatment and having a basis weight of 10 to 100 g / m ² A hygroscopic nonwoven fabric comprising a web layer having a body of 90/10 to 10/90% by weight and a basis weight of 20 to 1,500 g / m ² formed by an airlaid method and laminated and integrated.   The hygroscopic nonwoven fabric according to claim 1, wherein the nonwoven fabric constituting the substrate sheet is obtained by a card method, a spunbond method, a melt blow method, an airlaid method, or a wet papermaking method.   The hygroscopic nonwoven fabric according to claim 1 or 2, wherein the polyolefin synthetic pulp is a polyolefin synthetic pulp having a multi-branched fiber structure obtained by a flash method.   Hygroscopic powder is zeolite, silica-based particles, alumina gel, alumina-based particles, silica-alumina-based desiccant, diatomaceous earth, charcoal, bamboo charcoal, activated carbon, molecular sieves, poly (meth) acrylic acid or polyvinylpyrrolidone, and these The hygroscopic nonwoven fabric according to claim 1, which is at least one selected from the group of alkali metal salts. On the web layer composed of the polyolefin synthetic pulp and the hygroscopic powder, further, 60 wt% or more of heat-adhesive fibers having a fineness of 1 to 4 dtex, and a basis weight 10 to 100 g / m hygroscopic nonwoven fabric according to any one claims 1 to 4 formed by laminating a top-layer sheet consisting of the nonwoven fabric m ^2.   The adhesive nonwoven fabric which consists of a thermoadhesive conjugate fiber is further interposed between a base material sheet and a web layer, and / or between a web layer and an upper layer sheet. Hygroscopic nonwoven fabric. The hygroscopic nonwoven fabric according to any one of claims 1 to 6, which is heat-treated.