JPH093224A - Porous sheet and absorbing material using the same - Google Patents

Abstract

PURPOSE: To obtain a porous sheet having air permeability, moisture permeability and resistance to water and excellent feeling and high strength (high tear strength and tensile yield point strength) and capable of industrially safely and continuously producing at a high rate and to obtain an absorbing material using the sheet. CONSTITUTION: A sheet molded from a melted blended material of a resin composition composed of (a) 50-90 pts.wt. of a crystalline polyolefin resin and (b) 50-10 pts.wt. of a compound having miscibility with the crystalline polyolefin resin (a) at a temperature higher than the melting point of the crystalline polyolefin resin (a) and generating phase separation to the crystalline polyolefin resin (a) at a temperature below the melting point of the crystalline polyolefin resin (a) and has >=100cSt kinematic viscosity at 40 deg.C and <=1000cSt kinematic viscosity at 100 deg.C is stretch in at least one direction to obtain the objective porous sheet.

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 waterproofness. 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 formed by melting and kneading an inorganic filler with an ordinary olefin resin, it is possible to omit a landing tape such as a disposable diaper. Absent. 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 is required to have a required strength,
It retains moisture permeability but does not have a good texture.

Therefore, an object of the present invention is to have air permeability, moisture permeability, and water resistance, and also to have good texture and high strength (high tear strength and tensile breaking strength), and to be industrially used. 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.

[0009]

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

The present invention has been made based on 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). At a temperature that is miscible with (a) and is lower than the melting point of the crystalline polyolefin resin (a), phase separation occurs with the crystalline polyolefin resin (a), and the kinematic viscosity at 40 ° C. is 100 cSt.
A sheet formed from a melt-kneaded product of a resin composition consisting of 50 to 10 parts by weight of the compound (b) having a kinematic viscosity of 1000 cSt or less at 100 ° C. and stretched in at least one direction. To provide a porous sheet.

Further, the present invention provides an absorbent article comprising a liquid-permeable front surface material, a leakproof back surface material, and an absorber disposed between these double side materials, wherein the back surface material is 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 subjecting a sheet formed from a melt-kneaded product of a resin composition to a stretching treatment, and the resin composition comprises a specific crystalline polyolefin resin (a) and a specific compound. A composition containing (b) in a specific blending ratio and, if necessary, a stabilizer, a colorant, an antistatic agent, and the like.

The crystalline polyolefin resin (a) used in the present invention is preferably a polypropylene resin mainly, and in addition, a copolymer containing ethylene or another vinyl monomer or the like to the extent that propylene and crystallinity are not impaired. Resin may be used. Specific examples thereof include polypropylene resin, propylene-ethylene block copolymer resin, propylene-ethylene random copolymer resin, and copolymer resin of propylene and other α-olefin. In the present invention, it is also possible to use the above resin alone,
Alternatively, two or more kinds can be used as a mixture. Furthermore, for the purpose of improving physical properties such as feeling and strength, polyethylene resin, a copolymer resin of ethylene and another vinyl monomer, a polystyrene resin, a polyester resin may be added to the above resin within a range that does not impair the original properties. Resins such as polyamide resin, polycarbonate resin, polyacrylic resin, and polymethacrylic resin can be blended.

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. As the crystalline polypropylene resin (a), a crystalline ethylene-propylene block polymer having a melt index of 0.2 to 2 g / 10 min and a blend system of the resin and crystalline isotactic polypropylene can be preferably used. .

In the present invention, the specific compound (b) used in the resin composition has miscibility with the crystalline polyolefin resin (a) at a temperature higher than the melting point of the crystalline polyolefin resin (a). It 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 below the melting point of the crystalline polyolefin resin (a), the crystalline polyolefin resin ( It must be a compound that causes phase separation with a). The compound (b) has a kinematic viscosity at 40 ° C. of 100 cSt or more, preferably 200 cSt or more, more preferably 30 cSt or more.
The kinematic viscosity at 0 ° CSt or more and 100 ° C is 1000
The compound is cSt or less, preferably 500 cSt or less, more preferably 300 cSt or less.

The kinematic viscosity of a compound is an index showing the viscosity of the compound, and values at 40 ° C. and 100 ° C. are widely used at present. Kinematic viscosity is JIS-K-2283
Can be easily measured by. On the other hand, the temperature of the compound used for forming the porous sheet is preferably from room temperature to 100 ° C. from the viewpoint of economy and operability, and it is generally known that the kinematic viscosity decreases as the temperature rises. Therefore, the values of 40 ° C. and 100 ° C. can be used as a representative value of the value of kinematic viscosity. Thus,
The kinematic viscosity of a compound is determined by the composition, chemical structure and molecular weight of the compound. This kinematic viscosity has a high correlation with various physical properties such as melting point, boiling point, flash point, and second-order transition point for substances having almost the same chemical structure.

When the porous sheet is manufactured in the present invention, the kinematic viscosity of the compound (b) has a great influence on the moldability during film formation. When the viscosity of the compound (b) is too low, smoke is generated and stable molding cannot be performed. Further, if the viscosity of the compound (b) is too high, a pressure loss in the pipe may occur when the compound (b) is injected into the extruder using a gear pump in the production of the porous sheet in the present invention. The production efficiency is lowered without significantly increasing the transportation efficiency. The above problem can be solved by keeping the compound (b) at a high temperature and decreasing the viscosity of the compound (b). However, when the compound (b) is heated to a high temperature, it is in a tank, a pipe or a gear pump. Not only is it costly to heat and retain the compound, but the compound (b) may be thermally deteriorated. If the viscosity of the compound (b) is too high, the miscibility of the crystalline polyolefin (a) and the compound (b) will decrease when a porous sheet is produced using a resin composition containing the compound (b). Not only does the molded sheet become uneven and the stability at the time of molding deteriorates, but also the physical properties of the sheet such as texture, moisture permeability and tensile strength are significantly reduced.

In addition to that, the viscosity of such a compound has a great influence on the physical properties of the porous sheet. The tensile strength when a porous sheet is formed using a compound having a somewhat high viscosity to exhibit preferable moisture permeability is significantly better than when a porous sheet is formed using a low viscosity compound. This is when using high viscosity compounds,
This is because moisture permeability can be exhibited and the compounding ratio of the resin can be increased with a relatively small addition amount. Furthermore, when a compound having a high viscosity to some extent is used, moisture permeability can be obtained at a low draw ratio. In the case of uniaxial stretching, the lower the stretching ratio, the smaller the strength ratio in the stretching direction and the non-stretching direction. Therefore, it is possible to obtain a sheet having an excellent balance of longitudinal and lateral strengths and a high tear strength. This property is particularly preferable for attaching and removing the tape on the sheet.

Further, when such a sheet is used as a leak preventer for an absorbent article, since the sheet contains a liquid compound, the water pressure resistance of the sheet decreases over time, and the sheet has a high water resistance. There is a problem that the absorbed liquid leaks out through the leak preventer. At this time, the sheet becomes transparent and the concealing power is significantly reduced. This is because the compound is a liquid. Therefore, by controlling the mobility of the compound in the sheet by using a compound having a somewhat high viscosity, this problem can be solved. From the above, the kinematic viscosity at 40 ° C. and the kinematic viscosity at 100 ° C. of the compound (b) are within the above range.

Examples of the compound (b) include mineral oil, synthetic lubricating oil, liquid paraffin, and compounds having an ester bond in the molecule. As the mineral oil, an aromatic /
Examples include alicyclic / aliphatic hydrocarbons, and alicyclic / aliphatic hydrocarbons obtained by hydrogenating these to remove aromatics, and ethylene / synthetic mineral oils
An α-olefin oligomer and the like are also included.

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 liquid paraffin, commercially available Diana process oil (manufactured by Idemitsu Kosan Co., Ltd.), Lubuflex, Shelf Rex, Dutrex (manufactured by Shell Chemical Co., Ltd.), Moresco White (Matsumura Oil Research Institute) (Manufactured by Co., Ltd.) and the like.

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 obtained 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 above compound (b) include mechanical lubricating oils sold by petroleum companies, process oils for rubber, liquid paraffin for fibers, etc. as mineral oils, 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 liquid paraffin, or the compound having an ester bond in the molecule may be used alone or in combination of two or more kinds.

Further, the compound used in the porous sheet of the present invention is preferably colorless and transparent. Mineral oils and lubricating oils are generally colored brown or brown in many cases. When such a compound is used in the present invention, the porous sheet is discolored, which is not preferable in appearance. Further, when the compound is poor in thermal stability, the compound is modified during molding and coloring occurs on the sheet. Therefore, the compound preferably has a thermal decomposition temperature of at least the molding temperature, more preferably 250 ° C.
That is all. The color of the compound according to ASTM is preferably 3 or less, particularly preferably 1 or less, further preferably 0.5.
It is the following.

The crystalline polyolefin resin (a) and the compound (b) in the resin composition used in the present invention.
The compounding ratio of the compound (b) is 50 to 90 parts by weight with respect to the crystalline polyolefin resin (a).
10 to 10 parts by weight, preferably 60 to 80 parts by weight of the crystalline polyolefin resin (a), and the compound 4
0 to 20 parts by weight. When the compounding ratio of the compound (b) is more than 50 parts by weight, the resin composition has poor sheet moldability, and the porous sheet obtained by the stretching treatment has insufficient strength, and further, the porous sheet obtained from the sheet during long term storage is The compound (b) bleeds out, so that it is not practical. 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.

If necessary, a nucleating agent can be added to the above resin composition. By adding an appropriate amount of the nucleating agent to the resin composition, the tensile strength and tear strength can be further improved without impairing the moisture permeability of the manufactured porous sheet. However, when added in excess, the moisture permeability is impaired. The type of nucleating agent is not particularly limited, but an inorganic filler such as titanium oxide or calcium oxide,
Aluminum benzoate or the like can be used. The amount of the nucleating agent added varies depending on the type of the nucleating agent used, but is preferably 0.01 to 10%, more preferably 0.
1 to 5%. In addition, a stabilizer, a colorant and the like can be added to the above resin composition, if necessary. Known stabilizers, colorants and the like can be used without particular limitation. Furthermore, if necessary, a small amount of an ordinary resin physical property improving agent such as an antistatic agent may be added as an additive so long as the basic physical properties of the porous sheet of the present invention are not adversely affected. These additives can be added preferably in an amount of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, based on the total amount of the resin composition.

Thus, the porous sheet of the present invention is a porous sheet obtained by stretching a sheet formed from a 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 favorable.
More preferably 0.2-4.0g / 100cm^Two・ In Hr
More preferably 0.5 to 2.5 g / 100 cm^Two・
Hr. Water vapor transmission rate is 0.2g / 100cm^Two・ Hr not
If it is full, it will not work when used as a backing material for absorbent articles.
Inferior in anti-removal effect, and conversely 4.0g / 100cm
^Two・ If Hr is exceeded, the water pressure resistance will decrease and the leakproof property will decrease.
You. In addition, the porous sheet is used for absorbing disposable diapers and the like.
When used as a backing material for articles,
Water pressure is preferably 1.5 m or more, more preferably 2.0
It is m or more.

The tensile strength of the porous sheet of the present invention is preferably 10 in the direction of lowest 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, etc. for clothing and medical use, freshness preservation, life preservation of small animals, seeds, decay spun packaging material, ripening material of fruit, light shielding 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) and optionally the nucleating agent and the additives used as needed are supplied from a hopper using a quantitative feeder, and the kneading section of an extruder in which the resin is plasticized. From the (middle abdomen), the method of press-fitting the compound (b) with a metering pump 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 nucleating agent or an additive is added, it may be charged from the hopper together with the resin as described above, or the compound (b) previously mixed with the compound (b) may be added. ) And press fit.

In order to obtain the sheet by carrying out 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, once the melt-kneaded material (compound) was extruded into a filament shape by a biaxial kneading extruder, it 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 a block copolymer resin of ethylene and polypropylene having a melting point of 168 ° C., the melt-kneading temperature is 22.
0 to 240 ° C., melting temperature is 158 to 160 ° C., cooling time to melting temperature is 0.8 to 2.0 s
ec, and the time for further lowering by 100 ° C. is preferably 5 to 20 seconds.

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
3 times, that is, 1.1 to 4 times in the longitudinal direction in the case of uniaxial stretching, and 1.1 to 4 times in the longitudinal direction and in the transverse direction in the case of biaxial stretching, the mechanical balance and strength retention, excellent moisture permeability and It is preferable for developing 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.

[0048]

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 3 and Comparative Examples 1 to 3 (Examples of Porous Sheet)] As the crystalline polyolefin resin (a), the crystalline polyolefin resin 1 and the crystalline polyolefin resin 2 shown below are prepared in a ratio of 7: 3. A blended in proportion was used. Crystalline polyolefin resin 1; density 0.91 g / cm ² melt index 0.5 g / 10 minutes, melting point 169 ° C. crystalline polypropylene (manufactured by Chisso Petrochemical Co., Ltd., grade WT 6048) crystalline polyolefin resin 2: density 0. 91 g / cm ² melt index 0.5 g / 10 min, melting point 168 ° C., 8% by weight of ethylene component, crystalline block copolymer polypropylene (Chisso Petrochemical Co., Ltd., grade WT605
2)

As the compound (b), the compounds shown in Table 1 were used. In addition, in Table 1, each compound (b)
And the kinematic viscosity at 40 ° C and 100 ° C. All of the compounds (b) shown in Table 1 are miscible with the crystalline polyolefin resin at a temperature equal to or higher than the melting points of the crystalline polyolefin resins 1 and 2, but at a temperature lower than the melting point, the crystalline It is a compound that causes phase separation with a polyolefin resin. Further, as an additive, titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., TAIPAKE CR-60, average particle size 209n)
m) was added. The mixing ratio of the crystalline polyolefin resin (a), the compound (b) and titanium oxide was 66: 31: 3 (parts by weight).

[0050]

[Table 1]

Molding was performed according to the method described below. Kneading method Using a twin-screw kneading extruder (φ45 mm, L / D = 30),
The crystalline polyolefin resin (a) and titanium oxide 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), if necessary, the compound (b) may
It was heated to a temperature of 0 ° C. or lower and supplied. 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 was 20 kg / hr. The set temperature at this time is the cylinder C1 of the extruder.
(Hopper side) part is 150 ° C, C2 / C3 part is 220
℃, C4 is 200 ℃, C5-C7 parts and head part 18
It was set to 0 ° 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 is 190 ° C at C1 (hopper side),
220 ° C for C2 / C3 part, 200 ° C for C4 part and die part
And Then, air was blown from the air ring at 20 ° C. to the bubbles to perform forced air cooling, and a film was formed at a take-up speed of 6 m 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 Using a roll stretching machine having a width of 1 m, the above sheet was stretched in the molding direction at 50 ° C to a ratio shown in Table 2, and then 120 ° C.
Annealed in. The thickness of all the obtained sheets was 35 to 40 μm.

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

Evaluation criteria of porous sheet (1) Moldability ⊚: Stable molding is possible for a long time. ○: Pulsation of motor load and extrusion amount is observed during biaxial kneading, or smoke, eyes and the like are observed during inflation molding, but molding is possible. X: Pulsation of motor load and extrusion amount was observed during biaxial kneading, or smoke, eyes and the like were markedly difficult during inflation molding. (2) Urine oozing property; surfactant 10 on porous sheet
A 0 ppm solution was dropped and the state after 4 hours was observed. ⊚: No bleeding at all. ○: The sheet is transparent, but there is no noticeable bleeding. X: The surfactant solution is oozing out.

(3) Tear strength: A piece of 60 mm × 30 mm was cut out so that its long side was equal to the stretching direction of the sheet, and further parallel to the long side with a razor blade from the center of the above section to one end of the short side. The sample was cut so that Then, using a Tensilon tensile tester, the two ends formed by cutting the sample were fixed to a chuck, the sample was made into a T shape, and the tear measurement in the sheet stretching direction was performed at 300 mm / min to obtain the The average load was calculated from the measured charts and used as the tear strength. (4) Tensile breaking strength / elongation; 10 in the direction perpendicular to the stretching direction
Using a Tensilon tensile tester, a sheet cut out in mm width has a chuck distance of 50 mm and a pulling speed of 300 mm /
It was determined by measuring at min. (5) Water vapor transmission rate; measured according to JIS Z0208. (6) Water pressure resistance: Measured according to JIS L1093B method.

Example 4 Crystalline polyolefin (a)
A porous sheet was obtained in exactly the same manner as in Example 1 except that the ratio of the compound (b) to the compound (b) was 68:32 and the resin composition containing no titanium oxide was used. The evaluation results of the obtained porous sheet are shown in [Table 2].

Example 5 The crystalline polyolefin (a), compound (b) and titanium oxide were mixed at a ratio of 72: 2.
A porous sheet was obtained in the same manner as in Example 1 except that the ratio was 5: 3. The evaluation results of the obtained porous sheet are shown in [Table 2].

[Comparative Example 4] The ratio of the crystalline polyolefin (a), the compound (b) and the titanium oxide was 72: 2.
A porous sheet was obtained in the same manner as in Comparative Example 1 except that the ratio was 5: 3. The evaluation results of the obtained porous sheet are shown in [Table 2].

[0060]

[Table 2]

As is clear from the above [Table 2], all the porous sheets of Examples 1 to 5 were excellent in moldability, did not exude urine, and had sufficient moisture permeability despite a low stretch ratio. It was something that had. Further, it had a tensile strength and a tear strength capable of withstanding the attachment and detachment of the tape.
In the porous sheet of Comparative Example 2, the compound (b) used had a very high viscosity, and the compound (b) was not uniformly dispersed in the sheet during the molding process. However, the appearance was very poor, and at the same time, it did not have excellent moisture permeability. The porous sheets of Comparative Example 1 and Comparative Example 3 were stretched at the same ratio as in Examples 1 to 1.
It was inferior to the porous sheet of No. 4 in moisture permeability and was more likely to exude urine. Further, the porous sheet of Comparative Example 4 was inferior in moisture permeability. The porous sheet of Comparative Example 3 generated severe smoke and eye blemishes during molding.

[Examples 6 to 10 and Comparative Examples 5 to 7 (Examples of Absorbent Articles)] Examples 1 to 4, Comparative Example 1, and Comparative Example 3
And using the porous sheet obtained in Comparative Example 4 as the backing material,
A disposable diaper (without a landing tape) as an absorbent article shown in FIG. 1 including a surface material, an absorbent body, a back surface material, and a fastening tape was manufactured (Example 6 in order).
10 and Comparative Examples 5 to 7).

The disposable diapers of Examples 6 to 10 and Comparative Examples 5 to 7 were subjected to a use test with 10 monitors. The disposable diapers of Examples 6 to 10 were good in the feel of the backing material (feeling softness, flexibility and dryness) and the fastening tape was easily removed, and were resistant to stuffiness and rash. In addition, no urine exuded from the back material during use. In terms of feeling, the diaper of Example 6 obtained particularly high evaluation. On the other hand, in the disposable diaper of Comparative Example 5, the backing material was torn due to the attachment and removal of the fastening tape, and the urine exuded from the backing material in use with a probability of 30%. In addition, the disposable diaper of Comparative Example 7 was inferior in moisture permeability, and therefore, was easily stuffy and rash. Further, oozing of urine from the backing material during use occurred with a probability of 40% in the disposable diaper of Comparative Example 6 and with a probability of 10% in the disposable diaper of Comparative Example 7.

[0064]

Industrial Applicability The porous sheet of the present invention has air permeability, moisture permeability, and water resistance, and has a good texture and high strength (tear strength and tensile breaking strength). It is excellent in productivity and can be continuously produced at high speed safely. 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) Inventor Katsushi Maeda 2606 Akabane Kai, Choi, Haga-gun, Tochigi Prefecture Kao Stock Company Research Institute (72) Haruo Sakahashi 2606 Akabane Kai, Choi, Haga-gun, Tochigi Research Center, Kao Corporation

Claims (2)

[Claims] 1. A crystalline polyolefin resin (a) 50-
90 parts by weight and at a temperature above the melting point of the crystalline polyolefin resin (a) are miscible with the crystalline polyolefin resin (a), and at a temperature below the melting point of the crystalline polyolefin resin (a), Phase separation occurs with the crystalline polyolefin resin (a), and the kinematic viscosity at 40 ° C is 1
A kinematic viscosity of 100 cC or more and 100 c or more
A sheet formed from a melt-kneaded product of a resin composition comprising 50 to 10 parts by weight of a compound (b) having a concentration of 0 cSt or less,
A porous sheet which is stretched in at least one direction. 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.