JPH093223A - Porous sheet and absorbing material using the same - Google Patents

Abstract

PURPOSE: To obtain a porous sheet having air permeability, moisture permeability and waterproof property and excellent feeling and high strength (tear strength and tensile yield point strength) and having excellent producibility 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) 55-90 pts.wt. of a crystalline polyolefin resin, (b) 45-10 pts.wt. of a compound having >=240 deg.C volatile temperature under atmospheric pressure and <=45 deg.C melting point and (c) 0.01-15 pts.wt. of a compound is stretched in at least one direction to obtain the objective porous sheet. The compound (c) is a compound suitably compatible with the compound (b) and has >=220 deg.C volatile temperature under atmospheric pressure and <=25 dyne/cm surface tension, and total amount of the compound (b) and the compound (c) is 45-10 pts.wt. to 55-90 pts.wt. of the crystalline polyolefin resin (a).

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, the strength of the porous sheet is slightly more than twice the strength of a porous sheet obtained by stretching a sheet formed by melt-kneading an inorganic filler with an ordinary olefin resin, but at this level of strength. Landing tape for disposable diapers cannot 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 normal actual production processes,
There is a problem of poor productivity.

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. The microporous sheet can have a strength two to three times that of a porous sheet obtained by stretching a molded sheet obtained by melt-kneading an ordinary olefin resin with an inorganic filler. However, this is still not strong enough to omit the landing tape. According to the study by the present inventors, in order to omit the landing tape, it is necessary that the strength is at least 4 times, preferably 5 times as high as that of the porous sheet produced by the usual manufacturing method.

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. Further, in this publication, polypropylene, polyethylene, ethylene-propylene copolymer resin and the like are disclosed as the above-mentioned specific crystalline polymer, but these disclose only usable resins, and the weight ratio of ethylene and propylene is only disclosed. No copolymerization form (random, block), etc. is disclosed. Furthermore, the most important drawback of the microporous sheet is that it is inferior in waterproofness. That is, the waterproofness required for absorbent articles such as disposable diapers is at least 1 hour, but such microporous sheets will leak water within 30 minutes even if the water pressure resistance is zero.

Further, the above-mentioned microporous sheet is a conventional polyester.
Tylene resin and filler (mainly CaCO _Three) And
Obtained by stretching a sheet formed from the composition
It is more hydrophobic than the porous sheet
As described above, it is inferior in waterproofness and is a liquid as a blend compound.
In particular, when using a compound like
is there. The feel (softness) required for absorbent articles such as disposable diapers.
Liquid compounds are preferable to obtain (softness), but
Since the Karusu sheet is inferior in waterproofness, it does not absorb disposable diapers.
It cannot be used as a profitable article. Furthermore, such a microporous sheet
In the formulation, since the compound used has a low volatilization temperature,
There is a risk of environmental pollution and ignition due to smoke during sheet forming.
Not only that, but also known as volatiles attached to the die lip
Burns often called "eye stains" occur,
It is necessary to frequently perform disassembly and cleaning after interrupting molding.
There was a problem that it was extremely inferior in commercial productivity.

Further, in JP-A-7-500623, a specific crystalline polymer, a specific compound (miscible with the polymer) and a specific fluorochemical oxazolidinone compound are melt-blended to form a sheet. ,
A microporous sheet produced by causing phase separation in the cooling process and stretching the sheet has been proposed. Such a microporous sheet has improved water repellency and oil repellency as compared with the microporous sheet disclosed in Japanese Patent Publication No. 5-38011. However, since it is inferior in miscibility with resin and melt fluidity due to the oil repellency peculiar to fluorine compounds,
It has a drawback that it is inferior in melt moldability and actual productivity. Further, there is a problem that the oil repellency remarkably lowers the tape adhesiveness, and it is not sufficient for the back material of absorbent articles such as disposable diapers to be attached with a fastening tape.

Further, in Japanese Patent Publication No. 5-83099, a silane-based dispersant or a fluorosurfactant is uniformly dispersed in a specific polypropylene, and a composition in which a large amount of a filler and a plasticizer are mixed is molded. There has been proposed a microporous film in which the sheet thus obtained is stretched for molecular orientation, and a method for producing the same. The water pressure resistance of the microporous film is 10 to 50 m, but here, the silane compound and the fluorine-based surfactant assist the dispersion of the filler, and the micropores (0.005 to 0.6 μm) have a high porosity ( 30-90
%) And is suitable for applications that do not require much strength, such as battery separators,
It is difficult to use for absorbent articles such as disposable diapers that need to have a soft feel and excellent tensile strength.

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

[0012]

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, melt-knead a specific amount of a specific crystalline polyolefin resin and two specific compounds. It was found that the obtained porous sheet can achieve the above object.

The present invention has been made on the basis of the above findings, and is 55 to 90 parts by weight of a crystalline polyolefin resin (a), the volatilization temperature at atmospheric pressure is 240 ° C. or higher, and the melting point is 45.
A sheet formed from a melt-kneaded product of a resin composition consisting of 45 to 10 parts by weight of a compound (b) and 0.01 to 15 parts by weight of a compound (c) at a temperature of 0 ° C. or less is stretched in at least one direction. A porous sheet, wherein the compound (c) is moderately compatible with the compound (b), has a volatilization temperature of 220 ° C. or higher at normal pressure, and a surface tension of 25 dyne /
The total amount of the compound (b) and the compound (c) is 45 to 10 parts by weight with respect to 55 to 90 parts by weight of the crystalline polyolefin resin (a). 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 arranged between these double sided materials, wherein the back surface material is the above-mentioned back material. 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 contains the specific crystalline polyolefin resin (a) and a specific crystalline polyolefin resin (a). It is a composition which contains the compounds of the species ((b) and (c)) in a specific blending ratio and, if necessary, a filler, a stabilizer, a colorant and the like.

The specific crystalline polyolefin resin (a) used in the resin composition in the present invention is a crystalline polypropylene resin, a crystalline ethylene / propylene block copolymer resin, or the block copolymer resin and crystals. It is a mixture with a crystalline polyethylene resin and / or a crystalline polypropylene resin. That is, the crystalline polyolefin resin (a) that can be used in the present invention is a resin of the following (1) to (3). Crystalline polypropylene resin. The block copolymer resin. A mixture of the block copolymer resin and a crystalline polyethylene resin. A mixture of the block copolymer resin and a crystalline polypropylene resin. A mixture of the above block copolymer resin, crystalline polyethylene resin and crystalline polypropylene resin. As the crystalline polyolefin resin (a), it is preferable to use the block copolymer resin or resin mixture described in the above items 1 to 3.

When the crystalline polyolefin resin (a) is the block copolymer resin or the mixture (cases 1 to 3), the weight ratio of ethylene and propylene in terms of monomer (% by weight of ethylene / propylene). (Wt%) is preferably 4/96 to 40/60, more preferably 8/92 to 30/70.
When 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 (tearing strength and tensile yield point strength). The sheet is suitable for use. In the case where the crystalline polyolefin resin (a) is the block copolymer resin or the mixture (cases 1 to 3), if the monomer-converted weight ratio is within the above range, the above resin or copolymer resin. Two or more of (the above resins) may be mixed and used. When the crystalline polyolefin resin (a) is the block copolymer resin or the mixture (cases 1 to 3) and the ethylene weight ratio is less than 4 (wt%), the porous sheet obtained by stretching is The tear strength becomes smaller and the texture becomes worse. Also, when the ethylene weight ratio exceeds 40 (wt%), the desired moisture permeability cannot be obtained unless stretching is performed at a high stretch ratio. If the film is stretched at a stretching ratio that can obtain the above-mentioned value, the tear strength may decrease, so it is preferable to set it within the above range.

When the crystalline polyolefin resin (a) is the block copolymer resin or the mixture (cases 1 to 3), even if the monomer-converted weight ratio is within the above range, a random copolymer weight is obtained. In case of coalescence,
Since it is difficult for the porous sheet to exhibit the desired moisture permeability, and the tear strength and the tensile strength are low, it is necessary to use a block copolymer.

The propylene resin, the block copolymer resin, and the polyethylene resin used as the crystalline polyolefin resin (a) preferably have a melt index of 3 g / 10 minutes or less, and 0.2.
More preferably, it is ˜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. Therefore, it is preferably 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 230 ° C. and 2.16 Kgf in the crystalline polypropylene resin and the block copolymer resin according to ASTM D-1238, and the crystalline polyethylene is 190 ° C, 2.16 Kgf for resin
It is the value measured in.

In the present invention, the specific compound (b) used in the resin composition has a volatilization temperature at atmospheric pressure of 240 ° C. or higher, preferably 250 ° C. or higher, and a melting point of 45 ° C. or lower, A compound having a temperature of 35 ° C. or lower is preferable. In the present invention, the sheet molding temperature at the time of molding the melt-kneaded product of the resin composition is preferably 180.
Since the compound (b) has a volatilization temperature under atmospheric pressure of less than 240 ° C, the volatile matter is likely to be fumed during sheet formation. And, the smoke of volatile matter at the time of molding as described above is not only a cause of environmental pollution and ignition, but also a cause of burning which is commonly referred to as "eye stain" because the volatile matter adheres to the die lip. Become. Therefore, when the smoke is generated,
Sheet molding must be interrupted once to disassemble and clean the die lip frequently, which causes a problem that the industrial productivity is significantly deteriorated. In addition, the melting point of the compound (b) is 45.
The reason why the temperature is limited to not higher than 0 ° C is that when the melting point of the above compound is not higher than 45 ° C, the produced sheet has high flexibility.

The "volatilization temperature" in the present invention means a heating raw material curve obtained by measuring a volatile raw material in a nitrogen stream (30 ml / min) at a temperature rising rate of 10 ° C./min and a sample of 10 mg using a thermobalance. It means the temperature at which the weight loss when drawn is 1%.

Examples of the compound (b) include mineral oil 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 include aliphatic hydrocarbons, and also include ethylene / α-olefin oligomers called synthetic mineral oils.

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. 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 or the compound having an ester bond in the molecule may be used alone, or two or more kinds may be mixed and used.

In the present invention, the resin composition contains the crystalline polyolefin resin (a) and the compound (b) together with the specific compound (c). The present inventors have found that the addition of the compound (c) makes it possible to obtain a porous sheet having high waterproofness and excellent feel / feel as compared with the case where the compound (c) is not added. Found out in a study. This is a synergistic effect of the compound (b) and the compound (c) to obtain a porous sheet suitable for use as a backing material sheet of an absorbent article such as a disposable diaper that comes into contact with the skin. . Further, since the compound (c) has excellent heat resistance stability and miscibility with a resin and has appropriate lubricity, when added to a resin composition, it is easily melt-molded to obtain a porous sheet having excellent actual productivity. Is something that can be done.

The compound (c) is appropriately compatible with the compound (b), has a volatilization temperature at atmospheric pressure of 220 ° C. or higher, preferably 240 ° C. or higher, and more preferably 250 ° C. or higher, and has a surface. The compound has a tension of 25 dyne / cm or less, preferably 23 dyne / cm or less. In the present invention, “comparably compatible” means that two compounds are vigorously stirred and mixed at room temperature and then allowed to stand, and the time until the two compounds are phase separated is measured. The above is the case within 2 days. If the compound (c) is not properly compatible with the compound (b), the sheet moldability of the resin composition will be poor, and the waterproof property of the porous sheet obtained by stretching will not be improved. Further, when the compound (c) is completely compatible with the compound (b), the improvement in waterproofness of the porous sheet obtained by stretching is very slight. When the volatilization temperature of the compound (c) at atmospheric pressure is lower than 220 ° C., the compound (c) volatilizes during molding of the melt-kneading sheet to reduce the residual amount of the compound (c) in the sheet,
It is difficult to improve the waterproof property of the porous sheet obtained by stretching,
In addition, long-time moldability (productivity) is poor due to die stains during molding. The surface tension of the compound (c) is 25 dyn.
When it exceeds e / cm, the waterproof property of the porous sheet obtained by stretching is not improved.

As the above-mentioned compound (c), a compound containing a silicone compound as a main component is preferably used, and examples of the silicone compound include silicone oligomers. As the silicone-based oligomer,
For example, “Oligomer Handbook, March 3, 1977.
1 day, published by Kagaku Kogyo Nippo Co., Ltd. can be used, and examples thereof include chain polydimethylsiloxane and polydimethylphenylsiloxane. In the present invention, it is preferable to use polydimethylsiloxane from the viewpoints of compatibility, heat resistance stability, and safety. Further, a silicone-based oligomer in which one of the methyl groups of the above polydimethylsiloxane is substituted with a long-chain alkyl group, a phenyl group or the like, and a silicone-based oligomer in which one of the methyl groups is a hydrogen group can also be preferably used. Specific examples of the compound (c) include silicone oils sold by silicone manufacturers. For example, Toray Silicone SH200 oil and Toray Silicone SH510 oil sold by Toray Silicone Co., Ltd. Can be used.

The crystalline polyolefin resin (a) and the compound (b) in the resin composition used in the present invention.
The above specific blending ratio of the compound (b) with the crystalline polyolefin resin (a) is 55 to 90 parts by weight.
45 to 10 parts by weight, preferably 35 to 15 parts by weight of the compound (b) with respect to 65 to 85 parts by weight of the crystalline polyolefin resin (a). When the compounding ratio of the compound (b) exceeds 45 parts by weight, the resin composition is inferior in sheet moldability, and the porous sheet obtained by the stretching treatment has insufficient strength, and moreover, 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.

The crystalline polyolefin resin (a) and the compound (c) in the resin composition used in the present invention.
The above specific blending ratio of the compound (c) with respect to the crystalline polyolefin resin (a) 55 to 90 parts by weight.
0.01 to 15 parts by weight, preferably 0.1 to 10
Parts by weight. When the compounding ratio of the compound (c) exceeds 15 parts by weight, the sheet moldability of the resin composition is poor, and when it is less than 0.01 part by weight, the waterproof property of the porous sheet obtained by stretching is reduced. Does not improve.

The total amount of the compound (b) and the compound (c) in the resin composition used in the present invention is 45 to 10 with respect to 55 to 90 parts by weight of the crystalline polyolefin resin (a). Parts by weight, preferably 35
１５15 parts by weight. When the total amount of the compound (b) and the compound (c) exceeds 45 parts by weight, the above-mentioned sheet formability is poor, and the strength of the porous sheet obtained by the stretching treatment is insufficient, and the tape The stability of the adhesive property over time decreases. Further, if the amount is less than 10 parts by weight, it is impossible to obtain a porous sheet satisfying the desired moisture permeability by the stretching treatment.

Further, a filler can be added to the above resin composition, if necessary. The filler that can be used at this time is preferably a granular material that does not melt at the sheet forming temperature, fillers that are usually used for rubber and plastics, for example, calcium carbonate, gypsum, barium sulfate, talc, clay, silica, titanium oxide, Examples include metal powder and other inorganic substances or organic metal salts mainly composed of inorganic substances. Further, a granular material or a powder material of a thermosetting resin such as a phenol resin, an epoxy resin or sodium polyacrylate can also be used. These fillers are preferably 5 nm to 20 μm.
m, more preferably 5 nm to 5 μm, and it is desirable to use it as a granular material having an average particle diameter. If the average particle size of the filler exceeds 20 μm, the tear strength of the sheet decreases, and if it is less than 5 nm, it does not substantially contribute to the stretch opening property, so a filler having an average particle size within the above range is used. Preferably. In addition, since it is difficult to control the filler that melts at the molding temperature to the required particle size in the molded sheet, it is preferable to use a granular material that does not melt at the sheet molding temperature as the filler.

By adding the above-mentioned filler, it is possible to open the sheet at a low draw ratio as compared with the case where it is not added, and the desired moisture permeability can be obtained, so that the sheet strength, especially the tear strength, is further improved. In the case where the crystalline polyolefin resin (a) is a block copolymer or a mixture, it is effective in suppressing a decrease in moisture permeability when the ethylene content is increased. Moreover, the said filler can be preferably used 1 to 30 weight part with respect to the total amount of the said compound (b) and the said compound (c).

If necessary, stabilizers, colorants and the like can be added to the 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.

Furthermore, a nucleating agent (crystal nucleating agent) can be added to the above resin composition. The crystalline polyolefin resin that is already on the market is blended with a high-rigidity, high-cycle grade nucleating agent, or with a nucleating agent function even if it is not blended as a nucleating agent. Some fillers and pigments also have this function. It is preferable to add a nucleating agent to the grade to which these nucleating agents or those having a nucleating agent function are not added and the grade to which these nucleating agents have been added but the effect of the nucleating agent is inferior, if necessary. At this time, the nucleating agent to be used is not particularly limited, and a nucleating agent known in the art can be used. For example, Plastics (published by the Industrial Research Institute) Vol. 43 No. 1
The nucleating agents described in the column “Functions and effects of plastic compounding agents = nucleating agents” on pages 1, 113 to 116 can be used. Specifically, metal salts of aromatic carboxylic acids [aluminum hydroxydipara -T-butyl benzoate (Al
-PTBBA), etc.], sorbitol derivatives, organic phosphates [2,2-methylenebis (4,6-di-t-phosphate phosphate]
Butylphenyl) sodium (PTBNa)] and other high melting point polymer nucleating agents, and talc as an inorganic nucleating agent.

However, the nucleating agent is not always necessary depending on the type of resin used in the resin composition. For example, when the crystalline polyolefin resin (a) is a mixture of a block copolymer resin of ethylene and propylene and a crystalline polyethylene resin and / or a crystalline propylene resin, the crystallization rate increases as the ethylene content increases. Because of the difference, the desired strength and moisture permeability can be obtained in the resulting porous sheet without adding a nucleating agent.

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 0.5 to 4.0 g / 100 cm ² · H.
r, more preferably 1.0 to 2.5 g / 100c
m ² · Hr. Water vapor transmission rate is 0.5g / 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.
When it exceeds cm ² · Hr, waterproofing time is shortened and leakproof property is deteriorated. Also,
When the porous sheet is used as a backing material for absorbent articles such as disposable diapers, the waterproofing time of the porous sheet is preferably 1 hour or longer, more preferably 2 hours or longer, and most preferably 3 hours or longer. is there. In the present invention, the waterproof time means volatilization of artificial urine by placing a porous sheet horizontally, placing 1 cc of artificial urine on the porous sheet, and laying the porous sheet down with a petri dish having a diameter of 10 cm and a height of 1 cm. It means the time until the bleeding of artificial urine on the underside of the seat is felt with the touch of a finger while preventing.

The tear strength of the porous sheet of the present invention is preferably 180 gf / mm or more, more preferably 250 gf / mm or more, most preferably 330 gf / mm or more.
gf / mm or more. The tensile yield point strength is preferably 110 kgf / cm ² or more, more preferably 12
0 kgf / cm ² or more, most preferably 130 kgf /
cm ² 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) and the above-mentioned fillers and additives that are used as needed are supplied from a hopper using a quantitative feeder, and the kneading part ( From the middle abdomen), a method is preferred in which the compound (b) and the compound (c), which have been premixed, or the compound (b) and the compound (c), respectively, are press-fitted with a metering pump. When the melting point of the compound (b) and / or the compound (c) is higher than room temperature,
It is preferable to inject the compound in a liquid state by heating it to a temperature equal to or higher than the melting point. Also, when adding fillers and additives,
It may be charged from the hopper together with the resin as described above, or the above compound (b) and / or the above compound (c).
What was pre-mixed with may be press-fitted with the compound (b) and / or the compound (c).

In order to perform the above-mentioned molding and obtain a sheet, the melt-kneaded product is fed to a die through a gear pump attached to the discharge portion (tip) of the twin-screw kneading extruder, or a twin-screw kneading extruder and a single screw. It can be obtained by a method in which the extruder is combined in tandem, and the mixture is fed to a die through the single screw extruder.

Further, once the melt-kneaded product (compound) was extruded into a filament shape by a biaxial kneading extruder, 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. When the melt-kneaded product is formed into pellets in this manner, the cooled filaments are stretched about 1.2 to 1.5 times, as compared with the case where the molten resin composition extruded in the usual filament form is cooled and cut as it is. It is desirable to cut afterwards. By carrying out this treatment, part of the compound does not bleed on the surface of the filament, the bite into the next single-screw extruder can be made good, and the sheet formability can be improved. 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).
Or more, preferably 1.2 to 4 times, more preferably 1.3
To 3 times, that is, 1.1 to 4 times in the machine direction in the case of uniaxial stretching and 1.1 to 4 times in the machine direction and the transverse direction in the case of biaxial stretching, respectively, to maintain the mechanical balance, strength and excellent moisture permeability. And is preferable for developing waterproofness.

Next, regarding the absorbent article of the present invention, FIG.
This will be described in detail with reference to FIG. Here, the disposable diaper of the present invention using the porous sheet of the present invention as a backing material will be described as an example, but in addition to this, it can be applied to an incontinence brief, a sanitary napkin, 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.

Thus, the above-mentioned porous sheet of the present invention is used for the back surface material 3. The thickness of the backing material is usually the flexibility required for a disposable diaper, the waist of the sheet required during the assembly and processing of the disposable diaper, and the feeling of having a backing material, and the flexibility required for the disposable diaper. From the viewpoint of productivity and cost, the thickness is preferably 25 to 55 μm, more preferably 35 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 ,
10gf in sheet thickness used for tear strength
Or more, preferably 14 gf or more, most preferably 18 g
f or more. Therefore, for example, in order to obtain a tear strength of 10 gf with a backing material having a thickness of 55 μm, 182 gf /
A tear strength of mm is required. Further, the tensile yield strength is 600 gf or more, preferably 700 gf or more, and most preferably 800 gf or more per 1 cm of the sheet width. Thus, for example, with a thickness of 55 μm, 60 per cm
109 kgf / cm to obtain 0 gf tensile yield strength
² or more strength is required for the backing material.

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 1.
80 gf / mm or more, tensile yield strength is 110 kgf /
Since it is cm ² or more, it has 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. The tensile yield point of the porous sheet may not be apparent depending on its resin composition. In this case, the tensile stress at 100% elongation is adopted as the yield point strength.

[0056]

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 5 and Comparative Examples 1 to 3 (Examples of Porous Sheet)] The following crystalline polyolefin resin as the crystalline polyolefin resin (a) and the following compound (b) -as the compound (b): To (b)-, and the following compounds (c)-and (c)-as the compound (c) are used as resin compositions shown in [Table 1].
A sheet was obtained by molding according to the molding method described below. still,
Compound (b)-to (b)-as well as compound (c)-
The volatilization temperature and melting point of (c)-are shown in [Table 2].
The volatilization temperature is SSC500 manufactured by Seiko Instruments Inc.
GT / DTA200 of.

Crystalline polyolefin resin; density 0.9
1 g / cm ³ , melt index 0.4 g / 10 minutes,
Homopolypropylene resin having a melting point of 169 ° C. (manufactured by Chisso Petrochemical Co., Ltd.). Crystalline polyolefin resin; Density 0.91 g / c
m ³ , melt index 0.5 g / 10 minutes, melting point 16
A block copolymer resin of ethylene and propylene (manufactured by Chisso Petrochemical Co., Ltd.) having an ethylene content of 8% by weight at 8 ° C. Compound (b)-; Esterified product of trimethylolpropane and lauric acid (acid value = 0.24, OH value = 3.
8 ,; Abbreviation TTL Compound (b)-; Mineral oil (manufactured by Idemitsu Kosan Co., Ltd., trade name “Diana Process Oil PW-90, flash point = 272
° C, aniline point = 127.7 ° C, aroma type / naphthene type / paraffin type = 0/29/71; abbreviation PW-90) Compound (b)-; Mineral oil (Chuo Kasei Co., Ltd., trade name "Ryu" Para 350S ", flash point = 220 ° C, aniline point =
112 ° C, aroma type / naphthene type / paraffin type = 0 /
34/66; abbreviation 350S) compound (c)-; polydimethyl silicone (Toray
Product name "SH-200 Oil 10" manufactured by Silicone Co., Ltd.
00cs ", surface tension 21.2 dyne / cm, flash point = 350 ° C or higher, abbreviation SH200-1000) compound (c)-; polydimethylphenyl silicone (manufactured by Toray Silicone Co., Ltd., trade name" SH510 oil 100cs ", Surface tension 24.1 dyne / cm,
Flash point = 275 ° C or higher, abbreviated as SH510-100) It should be noted that any of the compounds (c)-to (c)-is appropriately compatible with the compounds (b)-and (b)-.

[0059]

[Table 1]

[0060]

[Table 2]

Molding Method A circular die (φ220 mm) was connected to the tip (discharge port) of a twin-screw kneading extruder (φ45 mm, L / D = 33.5) with a gear pump interposed. Then, using an air-cooled inflation molding facility with a distance between the die and the nip roll of 4 m, the hopper to the crystalline polyolefin resin (a)
And the heated liquefied compound (b) and compound (c) were injected into the middle (kneading) part of the twin-screw kneading extruder with a gear pump. The supply rate of the resin composition at this time was 270 cm ³ / min. The setting temperature is 190 ° C for the cylinder C1 part (hopper side) of the extruder and 2 for C2 part.
10 ℃, C3 ~ C8 part 240 ℃, gear pump part 23
The temperature was 0 ° C and the die was 230 ° C. Then, while blowing air of 20 ° C. from the air ring onto the bubbles to force air cooling,
A sheet having a thickness of 38 to 40 μm was obtained at a sheet folding width of 60 cm and a take-up speed of 8 m / min.

Then, the obtained sheet was stretched according to the stretching treatment method described below to obtain a porous sheet. -Stretching method: Using a roll stretching machine with a width of 1 m, the sheet was stretched 1.5 times in the molding direction at 50 ° C, and then annealed to 1.4 times (1.4 times before stretching). . The thickness of all the obtained sheets was 35 to 37 μm. However, Example 5 was stretched 1.8 times and annealed to 1.7.
Doubled.

Each of the obtained porous sheets was evaluated according to the following evaluation criteria. The results are shown in [Table 3].

Evaluation Criteria for Porous Sheet (1) Smoke emission during molding: The smoke emission state of the volatile matter during the sheet molding was visually evaluated according to the following criteria. ◎: No smoke was emitted. ○: A little smoke. Δ: A lot of smoke is emitted. X: Very much smoke is emitted. (2) Occurrence time (accumulation) of eye blemishes: The time until occurrence of a die line, which can be visually observed on the sheet surface in the above-mentioned sheet molding, was measured.

(3) Sheet formability: The sheet was visually evaluated according to the following criteria. ◎; valve stable, no die line. ◯: Valve is stable and has a die line. Δ: Valve fluctuation. ×: Cannot be molded. (4) Stretchability: The sheet was visually evaluated in the above stretching process according to the following criteria. ⊚: No cutting, uniform whitening. (Note that the present inventors have confirmed that there is a correlation between whitening and stretching). ◯: No cutting, slight whitening unevenness. Δ: No cutting, many uneven whitenings. X: cutting.

(5) Tear strength: A 30 mm cut is made in equilibrium from the center of the short piece at one end in the longitudinal direction of a sample piece having a width of 30 mm and a length of 60 mm in the stretching direction (MD direction) toward the inside. Then, the cut piece of the test piece is attached to a tensile tester so that both sides of the cut piece are on the front and back sides, and the test piece is torn at a pulling speed of 300 mm / min to determine the average stress. (6) Tensile yield point strength: A test sheet having a width of 10 mm was prepared, and the tensile strength was measured by a Tensilon tensile tester in a direction perpendicular to the stretching direction.
The yield point was measured from the stress / strain curve by pulling at 00 mm / min. (7) Water vapor transmission rate: measured according to JIS Z0208. (8) Waterproofness: A porous sheet was placed horizontally, and 1 cc of artificial urine was placed on it (surface). The artificial urine used was urea 1.94%, sodium chloride 0.795%, magnesium sulfate 0.110%, calcium chloride 0.062%, potassium sulfate 0.197%, Red No. 2 (dye) 0.010.
%, Water 96.88%, polyoxyethylene nonylphenyl ether (about 0.00035%), surface tension 50
It was adjusted to ± 1 dyne / cm. Then, the porous sheet was placed on a petri dish having a diameter of 10 cm and a height of 1 cm to prevent volatilization of the artificial urine, and the time until the bleeding of the artificial urine on the lower surface of the sheet was felt by a finger was measured. However, the measurement was not performed for 3 hours or more.

(9) Texture: The sheet obtained in the stretching treatment step was evaluated by touch feeling according to the following criteria. ◎: Soft and very good texture. ○: Soft and good texture. Δ: Slightly hard and slightly bad in texture. X: Hard and bad texture.

[0068]

[Table 3]

[Comparative Example 4] As a resin composition, 100 parts by weight of linear low-density polyethylene (manufactured by Mitsui Petrochemical Industry Co., Ltd., trade name "Ultzex 2520F") and surface-treated calcium carbonate (average particle size 1 0.1 μm), and 5 parts by weight of polyester (trimethylolpropane / adipic acid / stearic acid = 2 mol / 1 mol / 4 mol SV = 241, AV = 0.8, OHV = 7). 180 parts of the C1 part of the twin-screw extruder
A sheet was molded in exactly the same manner as in Example 1 except that the temperature, C2 and C3 parts were 190 ° C., and the die was 190 ° C. to obtain a sheet having a thickness of 48 to 50 μm. Then, using the same roll stretching machine as in Example 1, the stretching was performed at a stretching roll temperature of 50 ° C by 2.2 times, and at an annealing temperature of 70 ° C by 2.0 times. The thickness of the obtained sheet was 35 to 37 μm. The evaluation results of the obtained porous sheet are shown in [Table 3].

[Examples 6 to 7 and Comparative Examples 5 to 6 (Examples of Absorbent Articles)] The porous sheets obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 4 were used as backing materials. The disposable diaper (without using the landing tape) as the absorbent article shown in FIG. 1, which is composed of a surface material, an absorbent body, a back surface material, and a fastening tape, was manufactured (Example 6, Example 7, comparison in order). Example 5 and Comparative Example 6).

Ten disposable diapers of Examples 6 and 7 and Comparative Examples 5 and 6 were worn on 10 babies for 5 hours. The disposable diapers of Examples 6 and 7 showed no leakage and the fastening tape was peeled off. Was good. On the other hand, in the disposable diaper of Comparative Example 6, the backing material was broken without peeling the fastening tape at all. Regarding the texture, the disposable diaper of Example 6 was soft and exhibited the best feel, but the disposable diapers of Comparative Examples 5 and 6 were inferior in texture. Example 6
Also, the disposable diaper of Example 7 did not leak urine even after being worn for 5 hours, but the disposable diaper of Comparative Example 5 was worn 1
Urine leaked from 80% at the time. Moreover, in the disposable diaper of Comparative Example 6, urine did not leak in 1 hour after wearing, but urine leaked from 40% at 5 hours. Furthermore, the disposable diaper of Comparative Example 6 could not be peeled off with the fastening tape and was torn when forcedly peeled off.

EFFECT OF THE INVENTION The porous sheet of the present invention has air permeability, moisture permeability, and waterproofness, 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.

Claims (6)

[Claims] 1. A crystalline polyolefin resin (a) 55-
90 parts by weight, 45 to 10 parts by weight of the compound (b) having a volatilization temperature at normal pressure of 240 ° C. or higher and a melting point of 45 ° C. or lower,
And at least 1 sheet formed from a melt-kneaded product of a resin composition comprising 0.01 to 15 parts by weight of the compound (c).
A porous sheet formed by stretching in one direction, wherein the compound (c) is appropriately compatible with the compound (b), the volatilization temperature at atmospheric pressure is 220 ° C. or higher, and the surface tension is 2.
The compound is 5 dyne / cm or less, and the total amount of the compound (b) and the compound (c) is 55 to 90 parts by weight of the crystalline polyolefin resin (a).
A porous sheet comprising 45 to 10 parts by weight. 2. The crystalline polyolefin resin (a)
Is a crystalline polypropylene resin, a crystalline block copolymer resin of ethylene and propylene, a mixture of the block copolymer resin and a crystalline polyethylene resin and / or a crystalline polypropylene resin, and the crystalline polyolefin resin (a ) Is the above block copolymer resin or the above mixture, the monomer-to-monomer weight ratio of ethylene and propylene (wt% ethylene / wt% propylene) is 4/96.
The porous sheet according to claim 1, which is -40/60. 3. The porous sheet according to claim 1, wherein the compound (b) is a mineral oil and / or a compound having an ester bond in the molecule. 4. The porous sheet according to claim 1, wherein the compound (c) is a compound containing polydimethylsiloxane as a main component. 5. A moisture vapor transmission rate of 0.5 to 4.0 g / 100 cm.
^2. Hr and waterproof time is 1 hour or more.
4. The porous sheet according to any one of 4 above. 6. An absorbent article comprising a liquid-permeable front surface material, a leakproof back surface material, and an absorber disposed between these double sided materials, wherein the back surface material is any one of claims 1 to 5. An absorbent article using the porous sheet according to any one of 1.