JPH093225A - Porous sheet and absorbing material using the same - Google Patents

Abstract

PURPOSE: To obtain a porous sheet having excellent air permeability and moisture permeability and useful for an absorbing material, etc., by drawing a sheet molded of a melted and blended material of a resin composition composed of a specific ratio of respectively specific crystalline polyolefin resin, an organic compound and a propylene-based resin. CONSTITUTION: This porous sheet is obtained by stretching a sheet molded of a melted and blended material of a resin composition composed (A) 50-90 pts.wt. of a crystalline polyolefin resin such as a PP resin or a propylene- ethylene copolymer resin, (B) 50-100 pts.wt. of an organic compound having miscibility to the component A at a temperature higher than the melting point of the component A and generating phase separation with the component A at a temperature below the melting point of the component A such as a mineral oil or a synthetic lubricating oil and (C) 0.5-20 pts.wt. (to 100 pts.wt. of the component A) of a propylene-based resin having a long chain branch in more than one directions. Preferably, an absorbing material is produced from a liquid- permeable surface material, a leak-proof rear face material using the porous sheet and an absorbing material placed between these both face materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous sheet and an absorbent article using the same, and more specifically to a porous sheet having excellent tensile strength and molding productivity as well as excellent moisture permeability and water resistance. The present invention relates to a sheet and an absorbent article using the sheet.

[0002]

2. Description of the Related Art
As a method for producing a porous sheet, a method is known in which 40 parts by weight or more of an inorganic filler is melt-kneaded in an olefin resin such as polyethylene or polypropylene to form a sheet, and then stretched in a uniaxial or biaxial direction. ing. The porous sheet thus obtained is excellent in breathability and moisture permeability and does not cause a dew condensation phenomenon, and thus is suitably used for wallpaper, wrapping paper, and the like. In addition, by imparting flexibility to the excellent properties of such a porous sheet, it can be used as a backing material of an absorbent article such as a disposable diaper. It has been proposed to use a linear low-density polyethylene as the olefin-based resin in order to provide the resin.

[0003] Disposable diapers that are commonly used are:
An absorber that absorbs excretions such as urine, a surface material that covers the surface of the absorber and is applied to the skin, and a back material that covers the absorber and prevents liquid leakage, are bonded and integrated. ing. In addition, there is a telescopic function provided to prevent leakage from the waist circumference and leg circumference, and a fastening function consisting of tape etc. to fasten the back waist circumference and the abdominal waist circumference when the diaper is attached. Have. And this fastening tape is about 25 from the convenience.
mm width is preferred and often used, but when trying to peel off the fastening tape for diaper mounting mistakes or urination inspection while wearing, etc., it was formed using the above porous sheet with flexibility. There is a problem that the back material is torn due to insufficient strength and must be replaced with a new diaper. Therefore, in order to prevent this, a wide holding tape (commonly called landing tape) is pasted on the back material around the ventral torso of the disposable diaper, and a fastening tape (commonly called fastening tape) is attached at the time of mounting. By sticking on it, the fastening tape can be repeatedly attached and detached.

However, the use of a landing tape is disadvantageous in that the number of diaper components and manufacturing steps is increased. Since the landing tape is the most expensive of diaper materials, it is costly to use the tape widely (in large quantities). Even if the landing tape is wide, the fastening tape may stick to the backing material other than the landing tape depending on the body type of the wearer even if the landing tape is wide, and it may not be possible to peel off the fastening tape. is there.

Therefore, as a high-strength porous sheet, in JP-A-5-98057, a specific polyolefin is mixed with a filler, a specific plasticizer, and a radical generator, and inflation molding is performed. A porous sheet obtained by a uniaxially stretching method has been proposed. However, although the porous sheet has improved strength as compared with a porous sheet obtained by stretching a sheet obtained by melt-kneading an inorganic filler with an ordinary olefin resin, at such strength, landing tape for disposable diapers and the like. Can not be omitted. Furthermore, since a radical generator is used, the melt flow characteristics of the molded product are different from those of the pre-molding composition, making it difficult to recycle unnecessary parts such as edges that occur in the normal actual production process, thus improving productivity. Is inferior.

In Japanese Patent Publication No. 5-38011, a specific crystalline polymer is melt-blended with a specific compound (miscible with the polymer) to form a sheet, and phase separation occurs in the cooling process. And a microporous sheet produced by stretching the sheet is disclosed. However, this is still not strong enough to omit the landing tape.

Further, the back surface material is required to have a soft feel / feel as a material of an absorbent article which comes into contact with the skin, but the microporous sheet retains required strength and moisture permeability. However, it does not have a good texture.

Further, in order to obtain a porous sheet having excellent molding stability and high tensile strength and moisture permeability, it is indispensable to use a nucleating agent in the raw material composition. The nucleating agent prevents the formation of maximal spherulites of the crystalline polyolefin resin in the sheet formation of the melt-kneaded product, and enables uniform stretching in the stretching treatment. However, since the above-mentioned effect can be obtained only by containing a small amount of the nucleating agent in the kneaded product, it is necessary to control the addition amount with considerable accuracy. Further, when the nucleating agent is added, there are many problems such as poor dispersion of the nucleating agent, occurrence of burning, and blurring of the addition, and there is a problem that productivity is remarkably deteriorated.

Therefore, an object of the present invention is to have air permeability, moisture permeability, and water resistance, and also to have a good texture and high strength (high tear strength and tensile rupture strength). It is an object of the present invention to provide a porous sheet that can be continuously produced safely and at high speed, and an absorbent article using the porous sheet.

[0010]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to solve the above problems, and as a result, have found that a specific crystalline polyolefin resin, a specific organic compound, and a polypropylene having a specific long-chain branch. It was found that a porous sheet obtained by melting and kneading a specific amount of a resin achieves the above object.

The present invention has been made on the basis of the above findings, and is 50 to 90 parts by weight of the crystalline polyolefin resin (a), and the crystalline polyolefin resin (at a temperature above the melting point of the crystalline polyolefin resin (a) ( 50 to 10 parts by weight of an organic compound (b) which is miscible with a) and causes phase separation with the crystalline polyolefin resin (a) at a temperature lower than the melting point of the crystalline polyolefin resin (a), and propylene. A porous sheet obtained by stretching a sheet formed from a melt-kneaded product of a resin composition comprising a resin (c) in at least one direction, wherein the crystalline polyolefin resin (a) is a polypropylene resin or propylene. −
Ethylene copolymer resin, a mixture of polypropylene resin and propylene-ethylene copolymer resin, a mixture of polypropylene resin and polyethylene resin, or a mixture of propylene-ethylene copolymer resin and polyethylene resin,
The propylene-based resin (c) is a propylene-based resin having a long chain branch and is contained in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the crystalline polyolefin resin (a). Is provided.

Further, the present invention provides an absorbent article comprising a liquid-permeable front surface material, a leak-proof back surface material, and an absorber arranged between these double-sided materials. The present invention provides an absorbent article characterized by using the porous sheet of.

First, the porous sheet of the present invention will be described in detail below. The porous sheet of the present invention is a porous sheet obtained by stretching a sheet formed from a melt-kneaded product of a resin composition, and the resin composition comprises a specific crystalline polyolefin resin (a) and a specific organic compound. A composition containing (b) and a specific propylene-based resin (c) in a specific blending ratio and, if necessary, a stabilizer, a colorant and the like.

The specific crystalline polyolefin resin (a) used in the composition in the present invention is mainly a polypropylene resin, and other ethylene or other vinyl monomer contained in an amount not to impair the crystallinity with propylene. It may be a copolymer resin containing the above. Specifically, polypropylene resin, propylene-ethylene copolymer resin (propylene-ethylene block copolymer resin and propylene-ethylene random copolymer resin), polypropylene resin and propylene-ethylene copolymer resin (propylene-ethylene block copolymer resin and Propylene-ethylene random copolymer resin), a mixture of polypropylene resin and polyethylene resin, or propylene-ethylene copolymer resin (propylene-ethylene block copolymer resin and propylene-ethylene random copolymer resin) and polyethylene resin Examples of the propylene-based resin (c), which is a mixture, include a propylene-based resin having a long chain branch. In the present invention, the above resins may be used alone or in combination of two or more. For the purpose of improving physical properties such as feeling and strength, polyethylene is preferably blended within a range that does not impair the original properties, and / or a copolymer resin of ethylene and another vinyl monomer, a polystyrene resin. Resins such as polyester resin, polyamide resin, polycarbonate resin, and poly (meth) acrylic resin can be blended.

When the crystalline polyolefin resin (a) contains the copolymer resin or the polyethylene resin, the monomer-to-monomer weight ratio of ethylene and propylene (wt% ethylene / wt% propylene) is 4%. /
It is preferably 96 to 40/60, and 8/92 to 3
It is more preferably 0/70. Since the monomer-converted weight ratio is within the above range, the porous sheet of the present invention is particularly useful as a backing material for absorbent articles such as disposable diapers from the viewpoint of texture and strength (tear strength and tensile yield point strength). The sheet is suitable for use.

The crystalline polyolefin resin (a) is
The melt index is preferably 3 g / 10 minutes or less, and more preferably 0.2 to 3 g / 10 minutes. When the melt index exceeds 3 g / 10 minutes, the tear strength and the tensile strength of the resulting porous sheet are lowered, and it is difficult to obtain the necessary strength as a backing material for absorbent articles such as disposable diapers. So
It is preferable to be within the above range. In this case, the thickness of the porous sheet may be increased in order to obtain a desired strength. However, when the thickness of the porous sheet is increased, the moisture permeability is reduced and the cost of the product is increased. Further, if the melt index is less than 0.2 g / 10 min, the disadvantage that a large amount of power is required for extrusion molding at the time of sheet molding occurs and the productivity falls, so it is preferably within the above range.

In the present invention, the melt index is a value measured according to ASTM D-1238. The crystalline polyolefin resin (a) is preferably a crystalline polypropylene resin having a melt index of 0.2 to 2 g / 10 minutes, a crystalline ethylene-propylene copolymer resin, or a mixture of these resins and a polyethylene resin. Can be used.

In the present invention, the specific organic compound (b) used in the resin composition is miscible with the crystalline polyolefin resin (a) at a temperature higher than the melting point of the crystalline polyolefin resin (a). And is a compound that causes phase separation with the crystalline polyolefin resin (a) at a temperature lower than the melting point of the crystalline polyolefin resin (a). In the compound (b), an internal structure capable of imparting moisture permeability to the sheet by stretching is formed by phase separation accompanying crystallization of the crystalline polyolefin (a),
At a temperature equal to or higher than the melting point of the crystalline polyolefin resin (a), it is miscible with the crystalline polyolefin resin (a), and at a temperature lower than the melting point of the crystalline polyolefin resin (a), the crystalline polyolefin resin ( It must be a compound that causes phase separation with a).

Examples of the compound (b) include mineral oil, synthetic lubricating oil, paraffin wax, and compounds having an ester bond in the molecule. Examples of the mineral oil include aromatic / alicyclic / aliphatic hydrocarbons obtained from nature and having low volatile content removed, and alicyclics obtained by hydrogenating these to remove aromatics / Examples of the hydrocarbon include aliphatic hydrocarbons, and also include an ethylene / α-olefin oligomer called synthetic mineral oil.

As the above synthetic lubricating oil, ethylene / α-
Olefin oligomers (Lucant, manufactured by Mitsui Petrochemical Industry Co., Ltd.), polybutenes (Nisseki polybutene, manufactured by Nippon Petrochemical Co., Ltd.) and the like.

As the above-mentioned paraffin wax, commercially available dyna process oil (Idemitsu Kosan Co., Ltd.)
, Manufactured by RUBFLEX, Shelf Rex, Dutrex (manufactured by Shell Chemical Co., Ltd.), and Moresco White (manufactured by Matsumura Oil Research Institute Co., Ltd.).

As the compound having an ester bond in the molecule, an aliphatic or aromatic monobasic or polybasic carboxylic acid and an aliphatic, alicyclic or aromatic monohydric or polyhydric alcohol are dehydrated. Examples thereof include an ester compound obtained by condensation; or an ester compound (that is, a mono- or polyester compound) obtained by a dehydration condensation reaction of a compound having both a hydroxyl group and a carboxyl group in the molecule.

As the above-mentioned aliphatic carboxylic acid and aromatic carboxylic acid, polybasic carboxylic acids are preferable. As the aromatic polybasic carboxylic acid, aromatic dicarboxylic acids, aromatic tricarboxylic acids and aromatic tetracarboxylic acids are preferable,
Examples thereof include phthalic acid, trimellitic acid and pyromellitic acid. The aliphatic polybasic carboxylic acid is preferably an aliphatic dicarboxylic acid and an aliphatic tricarboxylic acid,
Examples thereof include adipic acid, sebacic acid, citric acid and the like. The alcohol is preferably a monovalent alkyl alcohol or the like, for example, octyl alcohol,
Examples include lauryl alcohol, stearyl alcohol, oleyl alcohol and the like.

In particular, as the compound having an ester bond in the molecule, an ester compound of an aromatic polybasic carboxylic acid and a monovalent alkyl alcohol (that is, a mono- or polyester compound), an aliphatic polybasic carboxylic acid Ester compound of monohydric alkyl alcohol with monohydric alkyl alcohol (that is, mono- or polyester compound), or ester of polyhydric alcohol (particularly preferably polyhydric alkyl alcohol) and monocarboxylic acid (particularly preferably aliphatic monocarboxylic acid) A compound (that is, a mono- or polyester compound) is preferably used. Specifically, for example, polyhydric alcohols such as glycerin, diglycerin, trimethylolpropane, pentaerythritol, dipentaerythritol or sorbitan, capric acid, lauric acid,
Preferable examples include ester compounds with an aliphatic monocarboxylic acid such as palmitic acid, stearic acid or oleic acid.

Further, a small amount of polycarboxylic acid such as adipic acid may be added as an ester component so that the resulting ester compound does not gel. Furthermore, environmental pollution prevention,
From the viewpoint of safety, a polyester compound obtained from an aliphatic carboxylic acid and an aliphatic alcohol is most preferable.

The compound having an ester bond in the molecule can be prepared from at least one of the carboxylic acid and at least one of the alcohol. Further, the method for producing the compound having an ester bond in the molecule is not particularly limited, and any conventionally known esterification method can be used. The compound having an ester bond in the molecule is not only a compound in which all of the carboxyl groups in the carboxylic acid and the hydroxyl groups in the alcohol are completely reacted, but also the carboxyl group in the carboxylic acid and / or the hydroxyl group in the alcohol. It may also be a partially esterified compound in which some of the groups remain unreacted.

The compound having an ester bond in the molecule is not limited to a synthetic product, but a natural product such as
It may be an esterified compound collected and purified from coconut, soybean or the like.

Specific examples of the compound (b) include mineral lubricating oils such as mechanical lubricating oils, process oils for rubber, and liquid paraffin for fibers, which are sold by petroleum companies, and which have an ester bond in the molecule. As the compound, distearyl phthalate, trioctyl trimellitate,
Tetraoctylpyromellitate, distearyl adipate, distearyl sebacate, trimethylolpropane trilaurate, pentaerythritol tetracaprate and the like can be mentioned. Further, these are selected from combinations within the solubility parameter of the crystalline polyolefin resin (a) and several units (the difference between the solubility parameter of the crystalline polyolefin resin (a) and the solubility parameter of the compound is preferably 2 to 3). be able to. In the present invention, the mineral oil, the synthetic lubricating oil, the paraffin wax, or the compound having an ester bond in the molecule may be used alone or in combination of two or more kinds.

In the present invention, the resin composition contains the crystalline polyolefin resin (a) and the organic compound (b) together with the specific propylene resin (c). By adding the propylene-based resin, it becomes unnecessary to add a nucleating agent, which was conventionally required to be added to the composition for producing a porous sheet, and the tensile strength and the molding productivity are excellent. A porous sheet is obtained. The propylene-based resin (c) is a propylene-based resin having a long chain branch, and is mainly a propylene-based resin having a propylene unit branch. Examples of general production methods include radiation (high energy) irradiation, peroxide crosslinking, copolymerization, and the like.
It can also be produced by the method described in JP-A-121704, JP-A-2-298536 or JP-A-6-80729.

Generally, commercially available crystalline polyolefin resins are linear, and the polymer molecule is a chain of propylene units and has no branch of propylene units. The reason is that with Ziegler-Natta catalysis, the secondary radical reaction that occurs in the radical polymerization of ethylene is extremely unlikely to occur. The crystalline polypropylene resin as the above-mentioned crystalline polyolefin resin (a) is mainly produced by radical polymerization and is formed by a straight chain without a branch of a propylene unit and does not contain a branch.

The propylene resin (c) preferably has a melt tension and a melt flow index (MFR) satisfying the following relational expressions. log (melt tension)>-1.16 x log (MFR) +
0.92 However, MFR is preferably 0.01 to 100 g / 10.
Min, more preferably 0.05 to 10 g / 10 min, most preferably 0.1 to 5 g / 10 min. In the present invention, the melt tension is a value measured using a melt tension tester manufactured by Toyo Seiki Co., Ltd. with an orifice inner diameter of 2 mm. In addition, MFR is based on JIS-K-7210 and uses the melt tension tester, and the orifice length is 8 mm, the resin temperature is 230 ° C., and the take-up speed is 6.
It is a value measured at 5 m / min and an extrusion speed of 15 mm / min. The branching of the propylene unit of the polyolefin resin (c) is determined by a general analysis method such as intrinsic viscosity and NMR.
You can verify its existence.

The specific blending ratio of the crystalline polyolefin resin (a) and the organic compound (b) in the resin composition used in the present invention is 50 to 90 parts by weight of the crystalline polyolefin resin (a). On the other hand, it is 50 to 10 parts by weight of the organic compound (b), preferably 40 to 20 parts by weight of the organic compound (b) with respect to 60 to 80 parts by weight of the crystalline polyolefin resin (a). When the compounding ratio of the organic compound (b) exceeds 50 parts by weight, the sheet formability of the resin composition is poor, and the strength of the porous sheet obtained by the stretching treatment is insufficient, and the sheet is hardly stored for a long time. Therefore, the organic compound (b) bleeds out, and thus lacks practicality. If the amount is less than 10 parts by weight, a porous sheet satisfying a desired moisture permeability cannot be obtained by the stretching treatment.

The specific blending ratio of the crystalline polyolefin resin (a) and the propylene resin (c) in the resin composition used in the present invention is 100 parts by weight of the crystalline polyolefin resin (a). The propylene resin (c) is 0.5 to 20 parts by weight, and preferably 1 to 5 parts by weight with respect to 100 parts by weight of the crystalline polyolefin resin (a). If the blending ratio of the propylene resin (c) exceeds 20 parts by weight, the moisture permeability and tensile strength of the porous sheet obtained by the stretching treatment will decrease. If the amount is less than 0.5 part by weight, the stretchability of the resin composition will be poor.

If desired, stabilizers, colorants and the like can be added to the above resin composition as additives.
Well-known stabilizers and colorants are used without particular limitation. Further, if necessary, a small amount of a usual resin physical property improving agent such as an antistatic agent may be used as an additive so long as the basic physical properties of the porous sheet of the present invention are not adversely affected. These additives are preferably 0.01 to 10% by weight, more preferably 0.1 to 10% by weight based on the total amount of the resin composition.
~ 5 wt% can be added.

The porous sheet of the present invention is a porous sheet obtained by stretching a sheet formed from the melt-kneaded product of the above resin composition in at least one direction. The above “forming” and “stretching” will be described in detail in the description of the “production method” described later.

The moisture permeability of the porous sheet of the present invention is preferably 0.2 to 4.0 g / 100 cm ² · H.
r, more preferably 0.5 to 2.5 g / 100c
m ² · Hr. Moisture vapor transmission rate is 0.2g / 100cm ^2.
If it is less than Hr, the effect of preventing stuffiness is poor when used as a backing material for absorbent articles, and 4.0 g / 100.
If it exceeds cm ² · Hr, the water pressure resistance is reduced and the leakproofness is reduced. When the porous sheet is used as a backing material for absorbent articles such as disposable diapers, the water pressure resistance of the porous sheet is preferably 1.5 m or more, and particularly preferably 2.0 m or more.

The tensile strength of the porous sheet of the present invention is preferably 10 in the direction of lowest tensile strength (generally at right angles to the direction of stretching in the case of uniaxial stretching).
0 kgf / cm ² or more, more preferably 130 k
gf / cm ² or more, most preferably 160 kgf
/ Cm ² or more (breaking elongation is preferably 200% or more, more preferably 300% or more, most preferably 40% or more).
0% or more). The tear strength is preferably 2
00 gf / mm or more, more preferably 300 gf
/ Mm or more.

The porous sheet of the present invention is suitable as a backing material for absorbent articles such as disposable diapers, and is also laminated with woven cloth, non-woven cloth, paper, etc. for waterproofing, cold protection, germ proofing, tents and bedding. , Wrapping bag, base material of Hap material for clothing and medical use, freshness preservation, life preservation of small animals and seeds, packaging material for decay prevention, ripening material for fruits, shading material, filtration, separation membrane for diffusion prevention, etc. It can be used as a material.

Next, a preferred method for producing the porous sheet of the present invention will be described. To manufacture the porous sheet of the present invention, first, a melt-kneaded product of the above resin composition is molded into a sheet. Here, the melt-kneaded product is preferably obtained by kneading the resin composition by a kneading method using a commonly used twin-screw kneading extruder. At the time of actual production, the crystalline polyolefin resin (a), the propylene resin (c), and optionally the stabilizer and the colorant which are optionally used are supplied from a hopper using a quantitative feeder, and the resin is plasticized. A method of press-fitting the organic compound (b) with a metering pump from the kneading part (middle abdomen) of the extruder that has been changed is preferable. When the melting point of the compound (b) is higher than room temperature, it is preferable that the compound is heated to a temperature equal to or higher than the melting point to be in a liquid state and injected. When a stabilizer or a colorant is added, it may be added from the hopper together with the resin as described above, or the premixed with the organic compound (b) may be added to the organic compound ( Press-fitting may be performed together with b).

In order to obtain a sheet by performing the above-mentioned molding, the melt-kneaded product is obtained by a method in which a twin-screw kneading extruder and a single-screw extruder are combined in tandem, and the mixture is fed to a die through the single-screw extruder. it can.

Further, the melt-kneaded product (compound) was once extruded into a filament shape by a biaxial kneading extruder, and this was cut to obtain pellets, and the obtained pellets were uniaxially attached with a die. It is also possible to form a sheet with an extruder. Further, the above-mentioned molding may be performed using either a flat die or a circular die, but it is preferable to perform the molding using a circular die from the viewpoint of the yield of the sheet.

Further, in order to obtain the porous sheet of the present invention with a good yield, the cooling conditions in the above molding of the melt-kneaded product are important. That is, it is necessary to control the crystal formation (crystal size, preferably 2 to 8 μm) of the crystalline polyolefin resin by cooling the molten resin composition. The generation of fine crystals is not preferable because it may hinder the uniform stretching in the subsequent stretching treatment, and the resulting porous sheet may have low strength or low moisture permeability. A preferable cooling condition is such that the time for cooling the melt-kneaded product of the resin composition from the temperature at the time of die discharge to the melting temperature of the crystalline polyolefin resin (a) is 0.1 to 3 sec. It is desirable that the time for the temperature to drop by 100 ° C. be 2 to 20 seconds. For example, when the crystalline polyolefin resin (a) is crystalline polypropylene having a melting point of 175 ° C., the melt-kneading temperature is 220 to 240 ° C., the melting temperature is 158 to 160 ° C., and it is cooled to the melting temperature. It is preferable that the time is 0.8 to 2.0 sec, and the time to lower the temperature by 100 ° C. is 5 to 20 sec.

Then, the sheet is stretched. For the stretching, a uniaxial stretching method in which the film is stretched in the machine direction (MD), a uniaxial stretching method in which the film is stretched in the transverse direction (TD) by a tenter stretching machine, an air inflation stretching machine or a mandrel stretching machine after stretching in the longitudinal direction. There is an axial stretching method or a simultaneous biaxial stretching method in which stretching is performed simultaneously in the machine direction and the transverse direction. In these cases, the stretching temperature is generally preferably at least room temperature and at least 10 ° C. lower than the melting point of the resin composition, and more preferably at least 30 ° C. lower. The stretching ratio is at least 1.1 times in the uniaxial direction (the original length is 1.0 and the length after stretching is 1.1).
Above, preferably 1.2 to 4, more preferably 1.3 to
4 times, that is, in the case of uniaxial stretching, in the longitudinal direction, and in the case of biaxial stretching, it is 1.1 to 4 times in the machine direction and the transverse direction, respectively, to maintain mechanical balance and strength, to provide excellent moisture permeability and It is preferable to exhibit water resistance.

Next, regarding the absorbent article of the present invention, FIG.
This will be described in detail with reference to FIG. Here, a disposable diaper will be described as an example, but the present invention can also be applied to incontinence briefs, sanitary napkins, and the like. A disposable diaper 1 shown in FIG. 1 as an absorbent article according to the present invention includes a liquid-permeable surface material 2, a leak-proof back material 3, and an absorber (not shown) disposed between these two materials. ), And the above-described porous sheet of the present invention is used as the back surface member 3.

More specifically, the disposable diaper 1 is
An absorbent body that absorbs excretions such as urine, a surface material 2 that covers the surface of the absorbent body and is applied to the skin, and a back material 3 that covers the absorbent body and prevents liquid leakage, are bonded and integrated. Has been Further, when the elastic member 7 and the diaper provided to prevent leakage from the torso peripheral portions 5 and 5 'and the leg peripheral portion 6 are attached, the back torso peripheral portion 5' and the abdominal torso peripheral portion 5 are fixed. A fastening tape 11 is provided. As the fastening tape, a tape having a width of about 25 mm is preferably and frequently used for convenience.

The above-mentioned porous sheet of the present invention is used as the backing material 3. The thickness of the backing material is usually the flexibility required for disposable diapers, the point of giving a sense of security that there is a sheet waist and backing material required during assembling processing of disposable diapers, and the flexibility required for disposable diapers. From the viewpoints of properties and cost, the thickness is preferably 25 to 55 μm, and more preferably 30 to 45 μm.

In the above-mentioned disposable diaper 1 as the absorbent article of the present invention constructed as described above, the strength of the backing material necessary for removing the so-called landing tape and directly attaching the fastening tape to the backing material for peeling is ,
8gf or more in the sheet thickness used in tear strength,
It is preferably 10 gf or more, and most preferably 12 gf or more. Therefore, for example, 8g for a backing material with a thickness of 35μm
A tear strength of 228 gf / mm is required to obtain a tear strength of f. Further, in the tensile breaking strength, 350 gf or more, preferably 450 gf or more, and most preferably 550 gf per 1 cm of the sheet width in the direction of the lowest strength.
gf or more. Therefore, for example, if the thickness is 35 μm, 1c
100 k to obtain a tensile breaking strength of 350 gf per m
The backing material is required to have a strength of gf / cm ² or more.

The above disposable diaper as the absorbent article of the present invention uses the porous sheet of the present invention as the backing material, and the tear strength of the porous sheet is 230.
gf / mm or more, tensile breaking strength is 100 kgf / cm ²
Since it is above, it will have sufficient strength. Therefore, in the absorbent article of the present invention, since it is not necessary to use a landing tape, a mistake in wearing the diaper does not occur, and even if the fastening tape is peeled off for urination inspection during wearing, the backing material Will not be torn. Further, if the moisture permeability of the back surface material is within the above range, stuffiness does not occur and a comfortable wearing feeling can be maintained.

[0049]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

[Examples 1 to 4 and Comparative Examples 1 to 4 (Examples of Porous Sheet)] As the crystalline polyolefin resin (a), the following crystalline polyolefins (a)-and (a)-
, The following organic compound as the organic compound (b) and the following propylene resin (c) -as the propylene resin (c):
Sheets were obtained by using the resin compositions having the compositions shown in Table 1 and (c)-, respectively, according to the molding method described below. In Comparative Examples 3 and 4, the following low density polyethylene was used instead of the propylene resin (c).

Crystalline polyolefin resin (a)-; density 0.91 g / cm ³ , melt index 0.5 g /
Crystalline homopolypropylene resin (WT6048, manufactured by Chisso Petrochemical Co., Ltd.) having a melting point of 169 ° C. for 10 minutes. Crystalline polyolefin resin (a)-; density 0.91 g
/ Cm ³ , melt index 0.5 g / 10 minutes, melting point 168 ° C. crystalline block polypropylene resin (WT6052, manufactured by Chisso Petrochemical Co., Ltd.). Organic compound (b); mineral oil (manufactured by Idemitsu Kosan Co., Ltd., Diana Process Oil PW-90, flash point = 272 ° C, Anrin point = 127 ° C, aroma-based / naphthene-based / paraffin-based = 0/29/71. The organic compound is miscible with the crystalline polyolefin resin at a temperature equal to or higher than the melting points of the crystalline polyolefin resins (a)-and (a)-, but at a temperature lower than the melting point, the crystalline polyolefin resin. A propylene-based resin (c)-; a density of 0.9 g / cm ³ ,
Long chain branched homopolypropylene with a melt index of 3.0 g / 10 min (Showa Denko KK, Himont PF-8
14). Propylene resin (c)-; Density 0.91 g / c
m ^3, a melt index 2.4 g / 10 min of long chain branching random polypropylene (Showa Denko KK, Himont SD-632). Low density polyethylene resin; density 0.925 g / cm ³ ,
Low-density polyethylene having a melt index of 2 g / 10 minutes and a melting point of 122 ° C. (Ultzex 2520F manufactured by Mitsui Petrochemical Industry Co., Ltd.).

[0052]

[Table 1]

Molding was performed according to the following method. Kneading method Using a twin-screw kneading extruder (φ45 mm, L / D = 30),
The crystalline polyolefin resin (a) and the long-chain branched polypropylene were supplied from the hopper, and the compound (b) was injected from the middle part of the twin-screw kneading extruder with a gear pump and melt-kneaded. Depending on the viscosity of the compound (b), the compound (b) was heated and supplied at a temperature of 100 ° C. or lower as needed. The kneaded product was extruded in a strand form from a discharge port, solidified by water cooling, and then pelletized. The discharge rate at this time is 20k
g / hr. In addition, the set temperature at this time is 150 ° C and C2 ・ C3 at the cylinder C1 (hopper side) of the extruder.
Part was 220 ° C., C4 part was 200 ° C., C5-C7 part and head part were 180 ° C.

The obtained pellets were formed into a sheet according to the following film forming method.・ Film forming method A circular die (φ200 mm) is connected to the tip (discharge port) of a single-screw extruder (φ40 mm, L / D = 28), and air-cooled inflation molding equipment with a distance from the die to the nip roll of 5 m is obtained. The pellet was formed into a film. At this time, the set temperature was 190 ° C. in the C1 (hopper side)
2. C3 part was 220 ° C., C4 part and die part were 200 ° C. Then, a film was formed at a take-up speed of 6 m while blowing air at 20 ° C. from the air ring onto the bubble and forcibly air-cooling to obtain a sheet having a sheet folding width of 60 cm and a thickness of 40 to 45 μm.

Then, the obtained sheet was stretched according to the following stretching treatment method to obtain a porous sheet. -Stretching method The sheet was stretched 1.4 times in the forming direction at 50 ° C using a roll stretching machine having a width of 1 m, and subsequently annealed at 120 ° C. The thickness of the obtained sheet is 35-4
It was 0 μm.

Each of the obtained porous sheets was evaluated according to the following evaluation criteria. The results are shown in [Table 2].

Evaluation criteria for porous sheet (1) Tear strength: A 60 mm × 30 mm section was cut out so that its long sides were equal to the stretching direction of the sheet, and a razor was cut from the center of the section to one end of the short side. A sample was cut with a blade of No. 2 so as to be parallel to the long side to obtain a sample. Then, using a Tensilon tensile tester, the two ends formed by the notch of the sample were fixed to a chuck,
Tear was measured in the sheet stretching direction at 300 mm / min using the sample as a T-shape, and the average load was determined from the obtained measurement chart to obtain the tear strength.

(2) Tensile rupture strength / elongation: A sheet cut out in a width of 10 mm in a direction perpendicular to the stretching was used with a Tensilon tensile tester, a chuck distance was 50 mm, and a pulling speed was 30.
It was determined by measuring at 0 mm / min. (3) Water vapor transmission rate; measured in accordance with JIS Z0208. (4) Water pressure resistance; measured according to JIS L1093B.

[0059]

[Table 2]

As is clear from the above [Table 2], the porous sheet of Comparative Example 1 was produced from a resin composition containing no long-chain branched polypropylene resin, and the porous sheet was very brittle and stretched. When the film was stretched, it broke before reaching the necessary stretching ratio for obtaining moisture permeability.

In addition, the porous sheets of Examples 1 to 3 are
The porous sheet was produced from a resin composition containing 3 to 3% by weight of long-chain branched polypropylene. The stretchability of the sheet was greatly improved, and the balance between moisture permeability and mechanical properties was excellent.

The porous sheets of Comparative Examples 2 and 3 are porous sheets produced from resin compositions obtained by replacing the long-chain branched polypropylene in the resin compositions of Examples 1 to 3 with low density polyethylene. Although the porous sheet of Comparative Example 2 was stretchable, it was inferior to the porous sheets of Examples 1 to 3 in breaking strength and elongation, and the porous sheet of Comparative Example 3 had no great effect on the improvement of strength. Nevertheless, the water vapor permeability was reduced.

The porous sheets of Example 4 and Comparative Example 4 were produced from a resin composition obtained by adding block polypropylene to a part of polypropylene. Although the porous sheet of Comparative Example 4 had improved stretchability as compared with the porous sheet of Comparative Example 1, its strength was not satisfactory. In addition, the porous sheet of Example 4 has highly balanced physical properties due to the addition of long-chain branched polypropylene, and the texture (softness, softness, and low noise) due to the incorporation of block propylene. It was also an excellent porous sheet.

[Examples 5 to 8 and Comparative Examples 5 to 7 (Examples of Absorbent Articles)] The porous sheets obtained in Examples 1 to 4 and Comparative Examples 2 to 4 were used as backing materials, and surface materials were used. Disposable diaper as an absorbent article shown in FIG. 1, which is composed of an absorbent body, a backing material, and a fastening tape (without using a landing tape).
Were manufactured (Examples 5 to 8 and Comparative Examples 5 to 7 in that order).
And).

The disposable diapers of Examples 5 to 8 and Comparative Examples 5 to 7 were subjected to a use test with 10 monitors. The disposable diapers of Examples 5 to 8 were good in the feel of the backing material (touch, softness, and dry sound) and the fastening tape was easily removed, and were resistant to stuffiness and rash. Above all, the disposable diaper of Example 8 was particularly highly evaluated in terms of texture. In contrast,
In the disposable diapers of Comparative Examples 5 and 6, the backing material was ruptured by peeling off the fastening tape. Comparative Example 7
Since the disposable diaper of 1 was inferior in moisture permeability, it was easy to get stuffy and had a rash.

[0066]

INDUSTRIAL APPLICABILITY The porous sheet of the present invention has air permeability, moisture permeability, and water resistance, and also has good texture and high strength (tear strength and tensile yield point strength). It is an industrially safe and excellent product that can be continuously produced at high speed. In addition, the absorbent article of the present invention is excellent in convenience and economically advantageous because the fastening tape can be attached and removed without using a landing tape.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a disposable diaper as an absorbent article of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaya Nishio, 2606, Akao, Kai, Cho, Haga-gun, Tochigi Prefecture, Kao Institute of Stock Companies (72) Yoshihiro Sakai, 2606, Akabane, Kai-cho, Haga, Tochigi, Institute of Kao Corporation

Claims (2)

[Claims] 1. A crystalline polyolefin resin (a) 50-
90 parts by weight, at a temperature above the melting point of the crystalline polyolefin resin (a), it is miscible with the crystalline polyolefin resin (a), and at a temperature below the melting point of the crystalline polyolefin resin (a), the crystal Compounds (b) 50 to 10 that cause phase separation with the organic polyolefin resin (a)
A porous sheet obtained by stretching in at least one direction a sheet formed from a melt-kneaded product of a resin composition comprising parts by weight and a propylene-based resin (c), wherein the crystalline polyolefin resin (a) is A polypropylene resin, a propylene-ethylene copolymer resin, a mixture of a polypropylene resin and a propylene-ethylene copolymer resin, a mixture of a polypropylene resin and a polyethylene resin, or a mixture of a propylene-ethylene copolymer resin and a polyethylene resin, and Propylene resin (c)
Is a propylene-based resin having a long-chain branch and is contained in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the crystalline polyolefin resin (a). 2. An absorbent article comprising a liquid-permeable surface material, a leak-proof backing material, and an absorber arranged between these double-sided materials, wherein the backing material is the backing material according to claim 1. An absorbent article comprising a porous sheet.