JPH09206331A - Porous sheet and absorptive commodity using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous sheet with air permeability, moisture permeability, water resistance, good feeling, and high strength, by drawing a sheet formed with a melted kneaded mixture of a specific ratio of crystalline polyolefin resin and a specific ratio of a compound with specific volatilizing point and melting point in a specific drawing rate. SOLUTION: A sheet formed with a melted kneaded mixture containing 60-90wt.% of crystalline polyolefin resin and 40-10wt.% of a compound with a volatilizing point higher than or equal to 240 deg.C and a melting point lower than or equal to 100 deg.C is drawn in a drawing rate of 3-30% in the cross direction and 20-90% in the machine direction into a porous sheet. The polyolefin resin must be polypropylene resin, block copolymer of ethylene and propylene, or a mixture of block copolymer resin and/or polypropylene resin and polyethylene resin with a melt index lower than or equal to 3g/10min.

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, it has excellent tensile strength and molding productivity, good texture, moisture permeability and water pressure resistance. The present invention also relates to a porous sheet excellent in the like and an absorbent article using the same.

[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. Further, by further imparting flexibility to the excellent properties of such a porous sheet, it can be used as a backing material for absorbent articles such as disposable diapers, and thus the porous sheet can be provided with flexibility. In order to impart it, it has been proposed to use linear low density polyethylene as the olefin resin.

The commonly used disposable diapers 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, it has a stretching function that is provided to prevent wetting from the waist and legs, and a fastening function that consists of tape, etc. that fastens the dorsal and ventral waist when wearing a diaper. I have it. And this fastening tape is about 25 from the convenience.
Although the one with a width of mm is often used, it is formed by using the above-mentioned porous sheet to which flexibility is imparted when the fastening tape is to be peeled off due to a mistake in wearing a diaper or an inspection of urine while wearing. There is a problem that the backing material breaks due to lack of strength, and it has to be replaced with a new diaper. Therefore, in order to prevent this, a wide holding tape (commonly called landing tape) is previously attached to the back surface material around the abdominal region of the diaper, and a fastening tape (commonly known as fastening tape) is attached to the backing material. By attaching it on the top, the fastening tape can be repeatedly attached and removed.

However, the use of a landing tape has the drawback of increasing the number of diaper constituent members and the number of manufacturing processes, and the landing tape is the most expensive diaper material. Therefore, it is costly to use the tape widely (in large quantities). There is a drawback that the fastening tape may stick to the backing material other than the landing tape depending on the wearer's body shape even if the landing tape is used widely, and it may not be possible to remove 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 tapes such as disposable diapers cannot be omitted. Furthermore, since a radical generator is used, the melt flow characteristics of the molded product are different from that of the pre-molding composition, so it is difficult to recycle unnecessary parts such as edges that occur in a normal actual production process,
There is a problem of reduced productivity.

Further, Japanese Patent Publication No. 6-75001 discloses "100 parts by weight of polyolefin resin and 5 parts of inorganic filler.
A method for producing a porous film in which a film obtained from a mixture containing 0 to 500 parts by weight is embossed, then stretched in at least a uniaxial direction, and further heat embossed "
However, in Japanese Unexamined Patent Publication (Kokai) No. 6-84452, "A resin composition comprising 100 parts by weight of a polyolefin resin and 50 to 500 parts by weight of an inorganic filler is melt-cast into a film,
The film is transversely stretched 3 to 10 times, and further 1.1 to 5
A method for producing a porous film that is stretched in the longitudinal direction is proposed. In addition, Japanese Patent Publication No. 6-89163 and Japanese Patent Publication No.
JP-A-89164 discloses "a film obtained by subjecting a film surface obtained from a mixture containing 100 parts by weight of a polyolefin resin and 500 parts by weight or less of an inorganic filler as essential components to a specific embossing and stretching in a machine direction to obtain a sheet. , A method for producing a porous film which is embossed and stretched in a direction intersecting with the machine direction. However, in the above manufacturing method,
Although the tear strength in the MD direction is higher than that of a film of the same composition which is uniaxially stretched in the MD direction, the strength is not enough to omit the landing tape. Further, the stretched apertured film containing an inorganic filler inhibits the adhesiveness of the fastening tape, and since it is almost impossible to repeat the peeling and peeling, the landing tape cannot be omitted, and the inorganic filler When the content is reduced, the degree of tape adhesion inhibition is reduced, but there is a problem that the moisture permeability required for the absorbent article is not satisfied. Furthermore, 3 to 3
Ten times stretching requires production equipment such as a tenter system with heavy equipment, which is a problem in production.

Further, in Japanese Patent Publication No. 5-38011,
“A specific crystalline polymer and a specific compound (which is miscible with the polymer) are melt-blended, formed into a sheet, phase separation is caused in the cooling process, and the sheet is stretched to form a microporous sheet. A microporous sheet obtained by the "method for producing" has been proposed. The microporous sheet has a strength of 2 to 2 as compared with a porous sheet obtained by stretching a sheet formed by melting and kneading an ordinary olefin resin with an inorganic filler.
It can be tripled. However, this is still not strong enough to omit the landing tape. According to the study by the present inventors, the strength required is at least 4 times, preferably 5 times that of the porous sheet produced by the usual manufacturing method.

Further, in the fastening tape which must be repeatedly peeled off and peeled off, the yield point strength is important especially for the sheet strength when peeling off the tape, but the fastener having sufficient adhesive strength to hold the usage pattern of the diaper. The nin tape has a problem that when the fastening tape is peeled off, elongation of the sheet occurs, and the pressure-sensitive adhesive layer becomes thin so that the sheet easily peels off.Furthermore, such elongation of the sheet causes tearing of the sheet, and Since the starting point is made and the tape peeling is a human operation and the pulling speed becomes high, there is a problem that the tearing of the sheet progresses even if the tear strength of the sheet is strong.

Furthermore, 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 above microporous sheet has required strength and moisture permeability. A good texture cannot be obtained while holding. Further, in this publication, polypropylene, polyethylene, ethylene-propylene copolymer resin, etc. are disclosed as the above-mentioned specific crystalline polymer, but these only disclose usable resins, and the weight of ethylene and propylene. No ratio, copolymer form (random, block), etc. is disclosed.

Further, in the formulation of such a microporous sheet, since the volatilization temperature of the compound used is low, not only is there a risk of environmental pollution and ignition due to smoking during sheet formation,
Volatile substances often adhere to the die lip to cause a so-called "eye dent", and it is necessary to frequently disassemble and clean the product by interrupting molding, resulting in a markedly poor industrial productivity. There was a problem.

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

[0012]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a specific crystalline polyolefin resin and a compound having a specific volatilization temperature and melting point are melted in a specific amount. It was found that a kneaded material was formed into a sheet and a porous sheet stretched under specific stretching conditions could achieve the above object.

The present invention was made on the basis of the above-mentioned findings, and comprises 40 to 10 parts by weight of a crystalline polyolefin resin 60 to 90 parts by weight and a compound having a volatilization temperature at normal pressure of 240 ° C or higher and a melting point of 100 ° C or lower. A sheet formed from a melt-kneaded product of a resin composition containing 3 parts, and a stretching ratio in the CD direction of 3 to
The present invention provides a porous sheet characterized by being stretched at 30% and a stretching ratio in the MD direction of 20 to 90%.

The present invention also provides an absorbent article comprising a liquid-permeable front material, a leak-proof backing material, and an absorber disposed between these double-sided materials. An absorbent article characterized by using a porous sheet.

The porous sheet according to the present invention and the absorbent article using the same will be described in detail below. The porous sheet according to the present invention is a sheet obtained by molding a resin composition into a sheet shape and subjected to a stretching treatment under specific stretching conditions, and the resin composition has a specific blending ratio of a crystalline polyolefin resin and a specific compound. The composition contains a filler, a stabilizer, a colorant and the like, if necessary.

The crystalline polyolefin resin used in the resin composition in the present invention is a block copolymer resin of ethylene and propylene, or a mixture of the block copolymer resin and a polypropylene resin and / or a polyethylene resin. To be That is, examples of the crystalline polyolefin resin that can be used in the present invention include the following resins (1) to (3). The block copolymer resin. A mixture of the block copolymer resin and a polyethylene resin. A mixture of the block copolymer resin and a polyethylene resin. A mixture of the above block copolymer resin, polypropylene resin and polyethylene resin.

The melt index of each of the block copolymer resin, the propylene resin and the polyethylene resin used as the crystalline polyolefin resin is preferably 3 g / 10 min or less, and 0.2 to 3 g.
/ 10 minutes is more preferable, and 0.2 to 2 g / 10
Most preferred is minutes. If the melt index exceeds 3 g / 10 minutes, the tear strength and the tensile strength of the resulting porous sheet will decrease, and it will be 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. Further, in this case, the thickness of the porous sheet may be increased to obtain a desired strength, but the moisture permeability is lowered 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 in accordance with ASTM D-1238, and is 23 in the polypropylene resin and the block copolymer resin.
It is a value measured under conditions of 0 ° C. and 2.16 Kgf, and for polyethylene resin, under conditions of 190 ° C. and 2.16 Kgf.

Further, particularly the texture and the strength (tear strength,
When used as the backing material of the absorbent article from the viewpoint of (tensile yield point strength), the monomer-converted weight ratio of ethylene and propylene (wt% of ethylene / wt% of propylene) in the crystalline polyolefin resin is 4 / 96
It is preferably from 40/60 to 8/92 to 30/70.
Is more preferable. Further, two or more kinds of the above resins or copolymer resins (the above resins) may be mixed and used so that the weight ratio falls within the above range. If the monomer-equivalent weight ratio is less than 4/96, the tear strength becomes small and the texture becomes poor, and if it exceeds 40/60, the desired water vapor permeability cannot be obtained unless it is drawn at a high draw ratio. However, if the film is stretched at a stretching ratio such that such a desired water vapor transmission rate is obtained, the tear strength is reduced.

Further, even if the polymer in which the monomer-converted weight ratio of ethylene and propylene in the above-mentioned preferable range is within the above-mentioned preferable range, in the case of a random copolymer,
It is difficult for the desired moisture permeability to develop, and the tear strength and tensile strength are low.

In the present invention, the specific compound used in the resin composition has a volatilization temperature of 240 at normal pressure.
℃ or more, preferably 250 ℃ or more, more preferably 26
A compound having a melting point of 0 ° C. or higher and a melting point of 100 ° C. or lower, preferably 80 ° C. or lower, and more preferably 60 ° C. or lower (hereinafter simply referred to as “compound”). In the present invention,
The sheet molding temperature at the time of molding the melt-kneaded product of the resin composition is preferably 180 to 250 ° C., more preferably 190 ° C. to 240 ° C., and the volatilization temperature at atmospheric pressure of the compound is less than 240 ° C. In some cases, volatile fumes are more likely to be emitted during molding. The smoke emitted from volatiles during molding not only poses a risk of environmental pollution and fire, but also causes the volatiles to adhere to the die lip, commonly known as "eye stains."
This is the cause of burning. Therefore, when the smoke is generated, it is necessary to interrupt the sheet molding once and disassemble and clean the die lip frequently, which causes a problem that industrial productivity is significantly deteriorated. Further, the melting point of the above compound is limited to 100 ° C. or less because when the molded sheet is stretched, it is easier for the sheet to be microporous if the compound is softened or melted at the stretching temperature. This is because

The term "volatilization temperature" used in the present invention means that a thermobalance is used and the temperature rising rate is 10 in a nitrogen stream (30 ml / min).
The temperature at which the weight loss is 1% when the weight loss curve is drawn by measuring the volatilization weight loss at 10 ° C / min and 10 mg of the sample is meant.

Examples of the above compounds 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, and examples thereof include phthalic acid, trimellitic acid and pyromellitic acid. The aliphatic polybasic carboxylic acid is preferably an aliphatic dicarboxylic acid or an aliphatic tricarboxylic acid, and examples thereof include adipic acid, sebacic acid and citric acid. The alcohol is preferably a monohydric alkyl alcohol, and examples thereof include octyl alcohol, lauryl alcohol, stearyl alcohol, and oleyl alcohol.

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, and capric acid, lauric acid, palmitic acid, stearic acid or oleic acid. Preferred examples include ester compounds with an aliphatic monocarboxylic acid.

Further, a small amount of polycarboxylic acid such as adipic acid may be added as an ester component so that the resulting ester compound does not gel. Further, from the viewpoints of preventing environmental pollution and safety, polyester compounds of an aliphatic carboxylic acid and an aliphatic alcohol are preferable. Further, the compound having an ester bond in the molecule can be prepared from one or more kinds of the carboxylic acid and one or more kinds of the alcohol. The method for preparing the compound having an ester bond in the molecule is not particularly limited, and any conventionally known esterification method can be used. Further, in the compound having an ester bond in the molecule, all of the carboxyl groups in the carboxylic acid and the hydroxyl groups in the alcohol may not completely react, and the carboxyl group in the carboxylic acid and / or the alcohol group in the alcohol may not be completely reacted. It may also be a partially esterified compound in which some of the hydroxyl groups remain unreacted.

Specific examples of the above compounds include mineral lubricating oils such as mechanical lubricating oils sold by petroleum companies, process oils for rubber, liquid paraffin for fibers, and the like, and compounds having an ester bond in the molecule include , Distearyl phthalate, trioctyl trimellitate, tetraoctyl pyromellitate, distearyl adipate, distearyl sebacate, trimethylolpropane trilaurate, pentaerythritol tetracaprate, and the like. Further, these can be selected from combinations within the solubility parameter of the crystalline olefin resin and several units (the difference between the solubility parameter of the crystalline polyolefin and the solubility parameter of the compound is preferably 2 to 3).

The above specific blending ratio of the crystalline polyolefin resin and the compound in the resin composition used in the present invention is 60 to 90 crystalline polyolefin resins.
The amount is 40 to 10 parts by weight of the compound, preferably 35 to 20 parts by weight of the compound, relative to 65 to 80 parts by weight of the crystalline polyolefin resin. When the compounding ratio of the above compound exceeds 40 parts by weight, the sheet moldability of the resin composition is poor, and the strength of the porous sheet obtained by the stretching treatment is insufficient, and moreover, the porous sheet from Practicality is lacking because the compound bleeds out. Further, if the amount is less than 10 parts by weight, a porous sheet having a desired moisture permeability cannot be obtained by the stretching treatment.

A filler may 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, and a filler that is usually used for rubber or plastic, for example, calcium carbonate, gypsum, barium sulfate,
Examples thereof include talc, clay, silica, titanium oxide, 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. Further, the filler is preferably used as a powder or granular material having an average particle diameter of preferably 20 μm or less, more preferably 5 nm to 5 μm. The average particle size is 20
If it exceeds μm, the tear strength of the sheet will decrease and it will be 5 nm.
If it is less than 1, it does not substantially contribute to the stretch porosity, so it is preferable to have an average particle diameter within the above range. Also, the filler that melts at the molding temperature is difficult to control to the required particle size in the molded sheet. By adding the above filler,
The sheet can be opened at a lower draw ratio than when not added, and the desired moisture permeability can be obtained, so that the sheet strength, particularly the tear strength, can be further improved. It is effective in suppressing the decrease in moisture permeability when the content is increased. Moreover, the said filler can be preferably used 1 to 30 weight part with respect to 100 weight part of the said resin composition.

Furthermore, it is preferable to add a nucleating agent (crystal nucleating agent) to the above resin composition. A commercially available crystalline polyolefin resin that has a high rigidity and a high-cycle grade that contains a nucleating agent, or that does not have a nucleating agent but that has a substantial nucleating function. Some of the 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 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. 11 113
The nucleating agents described in the column “Functions and effects of plastic compounding agents = nucleating agents” on page 116 can be used. Specifically, metal salts of aromatic carboxylic acids [aluminum hydroxydipara-t- Butyl benzoate (Al-PTB
BA)] or the like, a high melting point polymer nucleating agent such as a sorbitol derivative, an organic phosphate [sodium 2,2-methylenebis (4,6-di-t-butylphenyl) phosphate (PTBPNa)], or an inorganic nucleus Examples thereof include talc as an agent.

However, depending on the composition of the "resin", the nucleating agent may not always be necessary. For example, the required strength / required moisture permeability can be obtained without adding a nucleating agent, probably because the crystallization rate of ethylene-propylene copolymer resin and the blended resin of polyethylene and polyethylene increases as the ethylene content increases. Can be done.

If desired, stabilizers, colorants and the like can be added to the above resin composition as additives. As the stabilizer and the colorant, known ones can be used without particular limitation. Further, if necessary, a small amount of an ordinary resin physical property improving agent such as an antistatic agent may be used as an additive as long as it does not adversely affect the basic physical properties of the porous sheet of the present invention. 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.

The porous sheet of the present invention is a porous sheet obtained by subjecting a sheet formed from the melt-kneaded product of the above resin composition to a stretching treatment under specific stretching conditions. here,
The above "molding" and the above "stretching treatment under specific stretching conditions"
This will be described in detail in the description of the “manufacturing method” below. The moisture permeability of the porous sheet of the present invention is preferably 0.5 to 4.0 g / 100 cm ² · Hr, and more preferably 1.0 to 2.5 g / 100 cm ² · H.
Hr. If the moisture permeability is less than 0.5 g / 100 cm ² · Hr, the effect of preventing stuffiness is poor when used as a backing material for absorbent articles, and conversely 4.0 g / 100 cm.
^If it exceeds ² · Hr, the water pressure resistance is lowered and the leakproof property is lowered. When the porous sheet is used as a backing material for absorbent articles such as disposable diapers, the porous sheet has a water pressure resistance of 1.5 mA.
It is preferably q or more, and particularly preferably 2.0 mAq or more. The tear strength of the porous sheet of the present invention is M
The 1% tensile strength in the D direction is 25 kgf / cm ² or more. The tensile yield point strength is preferably 110 kgf / cm ²
More preferably, it is 120 kgf / cm ² or more, most preferably 130 kgf / cm ² or more. In particular, C
The tensile yield point strength in the D direction is preferably 120 kg / 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. , Bandages, base materials for Hap materials such as clothing and medical use, freshness preservation, life preservation of small animals, seeds, etc., rot prevention packaging materials, fruit ripening materials, light shielding materials, filtration, diffusion prevention separation membranes, etc. It can be used as a material.

Next, the 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, and in actual production, the crystalline polyolefin resin is supplied from a hopper part. It is preferable to use a metering pump to press-in the compound from the kneading section (middle abdomen) of the extruder in which the resin is plasticized.
Further, when the melting point of the above compound is room temperature or higher, it is preferable to heat the compound to a temperature higher than the melting point to make it a liquid and inject.
In order to obtain a sheet by performing the above-mentioned molding, the melt-kneaded product is supplied to a die through a gear pump attached to the discharge part (tip) of the twin-screw kneading extruder, or a twin-screw kneading extruder and a single-screw extruder are used. In a tandem and then fed to the die through the single screw extruder.

A melt-kneaded product (compound) is once extruded into a filament shape by a twin-screw kneading extruder and then cut to obtain pellets. The obtained pellets are a single-screw extruder equipped with a die. It can also be molded in. Further, the above-mentioned molding may be performed using either a flat die or a circular die, but it is preferable to use the circular die from the viewpoint of the yield of the sheet.

Further, in order to obtain the porous sheet of the present invention, the cooling conditions in the above molding of the melt-kneaded product are important. That is, crystal formation of the crystalline polyolefin resin by cooling the molten resin composition (crystal size, preferably 2 to
8 μm) must be controlled, for example, the formation of maximum crystals by marked slow cooling and the formation of fine crystals by marked quenching hinders uniform stretching in the subsequent stretching treatment, resulting in poor strength of the porous sheet. Or, the moisture permeability may be lowered, which is not preferable. A preferable cooling condition is that the temperature of the melt-kneaded product of the resin composition is cooled from the temperature at the time of die discharge to the melting temperature of the crystalline polyolefin resin is 0.1 to 3 sec, and the melting temperature is further 1
It is desirable that the time for the temperature to drop by 00 ° C. be 2 to 20 seconds. For example, in the case of a resin composition using the block copolymer resin of ethylene and propylene having a melting point of 168 ° C. as the crystalline polyolefin resin, 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.

Next, the sheet is stretched under specific stretching conditions. The above-mentioned specific stretching conditions are such that the stretching ratio in the CD direction is 3 to 30%, preferably 7 to 30%, more preferably 10 to 25%, and the stretching ratio in the MD direction is 20 to 90%.
Preferably 30 to 70%, more preferably 40 to 60%
It is. Here, the "CD direction" means a direction orthogonal to the sheet forming direction, and the "MD direction" means a sheet forming direction. Further, for example, “stretching ratio of 3 to 30%” means stretching to 103 to 130 when the length before stretching is 100. Note that the stretching rate (%) is an actual stretching rate (%) including the stretching rate after annealing after stretching.

The reason why the stretching ratio in the CD direction is within the above range is to obtain a sufficient tensile yield point strength in the CD direction without impairing the softness of the obtained porous sheet, and in the MD direction. The reason why the stretching ratio is within the above range is to obtain the required moisture permeability without impairing the texture of the porous sheet obtained. That is, if the stretching ratio in the CD direction is less than 3%, the tensile yield strength becomes insufficient, and 3
If it exceeds 0%, the texture becomes poor in combination with the stretching in the MD direction. Further, if the stretching ratio in the MD direction is less than 20%, the water vapor permeability becomes low, and if it exceeds 90%, the texture becomes poor.

Further, in the ordinary non-perforated stretching, the elastic modulus increases with the stretching ratio, and in proportion thereto, the feeling of stiffness becomes stronger and the texture becomes worse. The higher the degree, the lower the apparent elastic modulus and the better the texture up to a stretching ratio of 70%. However, if the stretching ratio is higher than this, the apparent elastic modulus also becomes high and the texture becomes poor. In the present invention, the stretching ratio (the product of the stretching ratio in the MD direction and the stretching ratio in the CD direction) as a whole is 5
Since the softest feeling is best when the content is 0% to 100%, it is preferably within this range.

The stretching ratio in the CD direction is 20 to 90%.
Even if the stretching ratio in the MD direction is 3 to 30%, that is, even if the stretching ratio in the CD direction and the stretching ratio in the MD direction are respectively opposite to the stretching conditions of the present invention, the moisture permeability and the texture are obtained. However, the tensile yield point strength in the CD direction also increases, but under such conditions, heavy equipment such as a tenter stretching machine is required, which is extremely disadvantageous in terms of productivity, In addition, for example, when the obtained porous sheet is used as a backing material for an absorbent article, the porous sheet is supplied to the absorbent article manufacturing equipment in the MD direction, so under the above conditions, the MD direction at this time is used. When the tensile strength is low, the production becomes difficult due to the elongation caused by the conveyance tension and the displacement of the position.

Under the stretching conditions of the present invention, it is possible to perform stretching with simple equipment such as air inflation, a mandrel, and an embossing roll, and with simple control of only the sheet pulling force in the MD direction. Even when used as the backing material, the tensile yield strength that can withstand repeated peeling and removal of the fastening tape can be obtained without using a landing tape, and the MD direction can be freely selected by a roll drawing machine. Easy to control.

To carry out the above-mentioned stretching treatment, the stretching in the CD direction may be carried out by an air-inflation stretching machine, a mandrel stretching machine, etc.
In order to obtain a feel-sensitive sheet with high productivity, stretching in the CD direction with an embossing roll is preferable. The embossing pattern has a shape that is easily stretched in the CD direction, and a more uniform CD stretching can be obtained by the multi-step method of two steps (two passes) rather than the one-step method (one pass of emboss rose). However, CD partial stretching obtained by the one-step method also has an effect of preventing the propagation of tears, and is effective in preventing tears when peeling the tape. Also, MD
The stretching in the direction is most preferably performed by a roll stretching machine in terms of productivity. Further, the stretching temperature in the above stretching treatment,
Generally, it is preferably a temperature that is 20 ° C. or more lower than the melting point of the resin composition at room temperature or higher, and particularly 50 ° C. or more lower than the melting point.

After stretching, the stretching temperature is 5 ° C to 50 ° C.
It is preferable to perform the annealing treatment at a high temperature and at a temperature lower than the melting point of the resin composition by 10 ° C. or more.

The stretching treatment is carried out by stretching in the CD direction and then in the MD direction, or stretching in the MD direction and then in the CD.
It may be carried out by any one of the method of stretching in the machine direction, the method of simultaneously biaxially stretching, etc. However, since the above-mentioned sheet before stretching is already oriented in the MD direction, easiness of stretching control, simplification of equipment, etc. From the point of sex, MD is stretched in the CD direction
A method of stretching in the direction is preferred.

Next, regarding the absorbent article of the present invention, FIG.
This will be described in detail with reference to FIG. Although a disposable diaper will be described as an example here, it is also applicable to incontinence briefs, sanitary napkins, and the like. A disposable diaper 1 shown in FIG. 1 as an absorbent article of the present invention has a liquid-permeable front material 2, a leak-proof back material 3, and an absorbent body (not shown) arranged between these double-sided materials. ) And the above-mentioned back material 3
As the above, the porous sheet of the present invention is used. More specifically, the disposable diaper 1 includes an absorbent body that absorbs excrement such as urine, a surface material 2 that covers the surface of the absorbent body and is applied to the skin, and a back surface material that covers the absorbent body and prevents liquid leakage. Three
And these are bonded and integrated. Further, when the elastic member 7 and the diaper provided to prevent leakage from the waist portions 5, 5 ′ and the leg portions 6 are attached, the back side waist portion 5 ′ and the abdominal side waist portion 5 are fixed. A fastening tape 11 is provided. As a fastening tape, about 2 for convenience
The one with a width of 5 mm is often used.

Thus, the above-mentioned porous sheet of the present invention is used as the backing material 3. The thickness of the above backing material is usually the flexibility required for a diaper, the waist of the sheet required during the diaper assembly process, and the feeling of having a backing material, and the flexibility and cost required for the diaper. From the viewpoint, it is preferably 25 to 55 μm, more preferably 35 to 45 μm.
m.

In the disposable diaper 1 as the absorbent article of the present invention configured as described above, in the disposable diaper having the above-mentioned structure, the so-called landing tape is omitted and the fastening tape is directly attached to the backing material and peeled off. The strength of the backing material required for the above is 600 gf or more, preferably 700 gf or more, and particularly preferably 800 gf or more per 1 cm of sheet width in terms of tensile yield strength. Thus, for example, with a thickness of 55 μm, 6 per cm
To obtain 00 gf, the backing material must have a strength of 109 kgf / cm ² or more. Furthermore, in the continuous production facility for absorbent articles, the tension for conveying the porous sheet is 2 Kgf for a width of 30 cm. If the sheet elongation at this time is 0.5% or more, the position will be shifted successively and control will not be possible and production will not be possible. According to the study by the present inventors, it is necessary to evaluate the 1% tensile strength to 25 Kgf / cm ^{2 in} order to accommodate a 55 μm sheet with an elongation of 0.5% or less under the above conveying conditions.

On the other hand, the disposable diaper 1 is
The porous sheet of the present invention is used as the backing material 3, and the porous sheet has a tensile strength in the CD direction of 1
10 kgf / cm ² or more, since the MD direction 1 percent tensile strength is 25 kgf / cm ² or more, has sufficient strength. Since the tensile yield point strength is 110 kgf / cm ² or more, it has sufficient strength. Therefore, in the absorbent article of the present invention, since it is not necessary to use the landing tape, diaper mounting error does not occur,
Also, even if the fastening tape is peeled off for urination inspection while wearing, the back material is not broken. 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 the resin composition, but in this case, the tensile stress at 100% elongation is adopted as the yield point strength.

[0050]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Examples and Comparative Examples (Examples of Porous Sheet)] The following resins were used as the crystalline polyolefin resin:
A sheet was obtained by using the resin composition prepared by blending the following compound as a compound so that the crystalline polyolefin resin: compound = 7: 3 (weight ratio) according to a molding method described later.

Resin: Density 0.91 g / cm ³ , melt index 0.5 g / 10 minutes, melting point 168 ° C., ethylene content of 8% by weight block copolymer resin of ethylene and propylene [Chisso Petrochemical Co., Ltd. )] Compound: Esterification product of trimethylolpropane and lauric acid (acid value = 0.24, OH value = 3.8, abbreviation TTL). The volatilization temperature is 261 ° C. and the melting point is 15 to 20.
° C. Compound: Mineral oil [Chuo Kasei Co., Ltd., trade name "Flow Para 350S", flash point 220 ° C, aniline point 112 ° C, aroma / naphthene / paraffin type = 0/34/66;
Abbreviation 350S). The volatilization temperature is 220 ° C and the melting point is <0.
° C. In addition, the volatilization temperature is SSC manufactured by Seiko Denshi Kogyo Co., Ltd.
It was measured with 5000 TG / DTA200.

Sheet forming method A circular die (φ) with a gear pump sandwiched at the tip (discharge port) of a twin-screw kneading extruder (φ45 mm, L / D = 33.5)
200 mm) was connected. Then, using an air-cooled inflation molding facility having a distance from the die to the nip roll of 4 m, the above “resin” was supplied from the hopper at 270 cm ³ / min, and heated and liquefied in the middle part (kneading) part of the twin-screw kneading extruder. The "compound" was injected with a gear pump. The set temperature at this time is 190 ° C. for the cylinder C1 (hopper side) of the extruder, 210 ° C. for C2, and 2 for C3 to C8.
40 degreeC, the gear pump part was 230 degreeC, and the die was 230 degreeC. Further, while blowing air of 20 ° C. from the air ring onto the bubble and forcedly cooling it, 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.

Further, a sheet is prepared according to the above-mentioned molding method by using a compound instead of the above-mentioned compound, and the following (1) to () in molding the above-mentioned sheet when the above-mentioned compound is used and when the above-mentioned compound is used. The evaluation of 3) [smoke generation during molding, generation of eye blemishes and sheet moldability] was performed and compared with the compound. [Table 1]
Shown in (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 smoking. 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. X: Cannot be molded.

[0055]

[Table 1]

Then, the obtained sheet was stretched according to the following stretching treatment method to obtain porous sheets (E-0 to 24). Stretching method: An inflation stretching machine with a roll width of 1 m and a roll stretching machine with a width of 1 m (with an annealing device consisting of heating rolls / cooling rolls) were connected and used, and a sheet using the above compound was prepared at 50 ° C. [Table 2 ] The film was stretched under the stretching conditions [stretching rate (%)] shown below and then annealed.

The following tests were conducted on each of the obtained porous sheets. The results are shown in [Table 2].

(4) Tensile yield point strength in CD direction: A test sheet having a width of 10 mm was prepared in the CD direction, and tensile strength of the yield point was obtained by drawing a stress / strain curve in the CD direction with a Tensilon tensile tester at 300 mm / min in the CD direction. Was measured. (5) 1% tensile strength in MD direction; 10mm width test sheet was made in MD direction, pulled by 300mm / min in MD direction with Tensilon tensile tester, and drawn stress / strain curve at 1% strain (elongation) Was measured. (6) Water vapor transmission rate; measured in accordance with JIS Z0208. (7) Water pressure resistance; measured according to JIS L1093B method (8) Texture; The sheet obtained in the stretching treatment step was evaluated according to the following criteria by touch feeling with fingers. ◎: Flexible and very good texture ○: Flexible and good texture △: Slightly hard and slightly bad texture ×: Hard and poorly textured

[0059]

[Table 2]

[Examples and Comparative Examples (Examples and Comparative Examples of Disposable Diapers]] Sheet No. E-8, E-15, E
4 porous sheet and a conventional porous low density polyethylene and calcium carbonate porous sheet are used as the backing material, and the disposable diaper shown in FIG. 1 including the surface material, the absorber, the backing material and the fastening tape (however, , And no landing tape) were manufactured (referred to as Example 1, Example 2, Comparative Example 1 and Comparative Example 2 in that order). As a result, in Examples 1 and 2, the fastening tape was attached / detached better than the sheets of E-4 and the diapers using the conventional backing material (Comparative Examples 1 and 2). In particular, in the diaper of Comparative Example 5, the fastening tape was not peeled at all, and the backing material was broken. Moreover, in terms of texture, the diapers of Examples 1 and 2 were soft and exhibited an excellent feel.

[0061]

INDUSTRIAL APPLICABILITY The porous sheet of the present invention has air permeability, moisture permeability, and water resistance, and further 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. Further, since the absorbent article of the present invention uses the porous sheet of the present invention as a backing material, it is possible to attach and detach the fastening tape without using a landing tape, which is excellent in convenience. It is economically advantageous.

[Brief description of drawings]

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

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Claims (6)

[Claims] 1. A crystalline polyolefin resin of 60 to 90 parts by weight, a volatilization temperature at atmospheric pressure of 240 ° C. or higher, and a melting point of 1
A sheet formed from a melt-kneaded product of a resin composition containing 40 to 10 parts by weight of a compound at 00 ° C. or less is stretched at a stretching ratio of 3 to 30% in the CD direction and a stretching ratio of 20 to 90% in the MD direction. A porous sheet characterized by being formed. 2. The crystalline polyolefin resin is a polypropylene resin having a melt index of 3 g / 10 minutes or less, a block copolymer resin of ethylene and propylene,
Alternatively, the porous sheet according to claim 1, which is a mixture of the block copolymer resin and / or the polypropylene resin and the polyethylene resin. 3. The porous sheet according to claim 1, wherein the compound is mineral oil or a compound having an ester bond in the molecule. 4. The porous sheet according to claim 1, wherein the compound is an ester compound of an aliphatic monocarboxylic acid and a polyhydric alcohol. 5. The tensile yield strength in the CD direction is 120K.
g / cm ² or more, and water vapor transmission rate of 0.5 to 4.0 g / 10
It is 0 cm < ² > * Hr, The porous sheet of any one of Claims 1-4 characterized by the above-mentioned. 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, comprising the porous sheet according to any one of 1.