JPH0959408A - Porous sheet, its production and absorbent article made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous sheet having moisture permeability water pressure resistance and excellent sheet strength and can give e.g. an absorbent article having a good feeling of use by forming a crystalline polyolefin into a porous sheet of a specified structure. SOLUTION: This porous sheet is formed by melt-mixing 50-90 pts.wt. of a crystalline polyolefin with 50-10 pts.wt. of a compound (e.g. mineral oil) which is miscible with and soluble in the polyolefin at a temperature equal to or lower than the melting point of the polyolefin but forms a separate phase at a temperature lower than the melting point to form a molten resin composition, forming this melt into a sheet and at least uniaxially stretching this sheet to form micropores going from the surface of the sheet to its back and has a porous region having numerous micropores and a nonporous region freed from micropores. The porous sheet can be obtained by cooling a sheet-like melt or a formed sheet in such a manner that the cooling rate is varied according to the part to be cooled.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous sheet, a method for producing the same, and an absorbent article, and more specifically,
The present invention relates to a porous sheet having moisture permeability and water pressure resistance, excellent in sheet strength, and having a good feeling when used in an absorbent article and the like, a method for producing the same, and an absorbent article using the porous sheet.

[0002]

2. Description of the Related Art Conventionally, as a method for producing the above-mentioned porous sheet, a sheet is formed by melt-kneading 40 parts by weight or more of an inorganic filler in 100 parts by weight of an olefin resin such as polyethylene or polypropylene to form a sheet. Alternatively, a method of obtaining a porous sheet by stretching in a biaxial direction is known.

The porous sheet obtained by the above-mentioned production method is excellent in air permeability and moisture permeability and does not cause a dew condensation phenomenon, and therefore, it is suitably used as a wallpaper, a sheet for packaging or the like. Further, since the porous sheet to which flexibility is imparted to the above excellent properties can be suitably used as a material for forming an absorbent article such as a backing material of a disposable diaper, it can be used as the olefin resin. A porous sheet has been proposed in which linear flexibility is added to the above-mentioned excellent properties by using linear low-density polyethylene.

However, in the above-mentioned conventional porous sheet,
When used as a forming material for absorbent articles such as disposable diapers, there are the following problems.

For example, a commonly used disposable diaper is an absorbent body that absorbs excrement such as urine, a surface material that covers the surface of the absorbent body and that is applied to the skin, and a liquid that covers the absorbent body and prevents liquid leakage. It is composed of a back material and these are bonded and integrated. In addition, the disposable diaper further
Expansion and contraction function provided on the body circumference and leg circumference to prevent leakage from the body circumference and leg circumference, and a fastening function made of tape or the like provided to fix the diaper when worn by the user Is equipped with. Then, the porous sheet,
It is used as the back material. Here, the tape (commonly called fastening tape) provided as the fastening function is preferably used in a width of about 25 mm to 35 mm for convenience. Therefore, when trying to peel it off, the backing material to which flexibility has been imparted is broken due to insufficient strength, and it is unavoidable to replace it with a new diaper. For this purpose, a wide range of peelable tape (commonly called landing tape or target tape) is attached in advance to the back surface material of the abdominal region of the waist, and when the diaper is attached, the above fastening tape is repeatedly applied on the landing tape or the like. It is designed to be removable.

However, the use of the landing tape increases the number of diaper components and the number of manufacturing steps,
The landing tape and the like are expensive among diaper materials, and using a wide range (a large amount) of this will increase the cost. That is, there are many drawbacks such as the fact that it may be directly adhered to the back surface material, and the above-mentioned attachment / detachment may not be possible.

Therefore, in order to omit the landing tape, as a high-strength porous sheet, Japanese Patent Laid-Open No. 5-980 has been proposed.
In Japanese Patent Publication 57, "a porous sheet obtained by blending a specific polyolefin with a filler, a specific plasticizer, and a radical generator, inflation-molded, and further uniaxially stretched in the take-up direction" is proposed. . But,
Although the porous sheet in the above publication has a strength slightly more than twice as high as that of the porous sheet obtained by a conventional production method (forming an olefin resin by melting and kneading an inorganic filler into a sheet). However, the strength has not yet reached the level where the landing tape can be omitted. Further, in the above-mentioned porous sheet, a radical generator is used. However, by using the radical generator, the melt flow characteristics of the molded article are different from those of the composition before molding, and therefore, the usual There is also a problem that productivity is inferior because it is difficult to perform recycle molding of a portion that has not been used for the next processing such as an end portion that is actually produced.

For the same purpose, Japanese Patent Publication No. 5-3801
No. 1 discloses that "a specific crystalline polymer and a specific compound (which is miscible with the crystalline polymer) are melt-blended, formed into a sheet, and phase-separated in a cooling process to stretch the sheet. Has been proposed. However, the microporous sheet in the above publication has a strength improved by 2 to 3 times as compared with the porous sheet obtained by a conventional manufacturing method (forming an olefin resin by melt-kneading an inorganic filler and forming a sheet). However, the strength of the landing tape has not been reached yet (in the study by the present inventors, the strength is at least 4 times, preferably 5 times that of the porous sheet obtained by the conventional manufacturing method). is there).

Further, in the method for producing a microporous sheet in the above publication, as compared with the method for producing a porous sheet, there are problems such as contamination of the work environment due to scattering of the inorganic filler, abrasion of the screw and resin. There is also a problem that it causes the occurrence of burning, and the molding must be interrupted and the molding machine must be disassembled and cleaned frequently, so that the industrial productivity is significantly deteriorated. Further, in the method for producing 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 smoke during sheet molding, but the volatile matter is commonly known as sticking to the die lip. It also causes the occurrence of burns known as "eye stains." Therefore, there is a problem in that productivity is remarkably inferior industrially because disassembly and cleaning frequently occur after the molding is interrupted. Furthermore, a soft feel / texture is important for the backing material as a material for absorbent articles that come into contact with the skin, but the microporous sheet is good while maintaining the required strength and moisture permeability. I can't get a nice texture.

In short, the conventional porous sheet does not satisfy both the strength enough to omit the landing tape as a backing material of an absorbent article and the good usability, but satisfies both of them. At present, there is a demand for the development of a porous sheet that can be used.

Therefore, an object of the present invention is to have a soft and excellent texture, a lateral tensile strength that does not break when the fastening tape is peeled off, and breathability, moisture permeability, and water resistance. Therefore, it is an object of the present invention to provide a porous sheet which is industrially safe and can be continuously produced at high speed and has excellent productivity, a method for producing the same, and an absorbent article using the same.

[0012]

Means for Solving the Problems In order to solve the above problems, the present inventors have found that a porous sheet having a region having through holes and a region having no holes can achieve the above object. I found out.

The present invention has been made on the basis of the above findings and comprises 50 to 90 parts by weight of a crystalline polyolefin,
At a temperature above the melting point of the crystalline polyolefin, the compound is miscible and soluble in the crystalline polyolefin, but at a temperature below the melting point of the crystalline polyolefin, 50 to 10% by weight of a compound that causes phase separation with respect to the crystalline polyolefin. Part by melt mixing to obtain a melt of a resin composition comprising the crystalline polyolefin and the compound, forming a sheet from the melt, and then stretching the sheet in at least one direction. A porous sheet formed by forming fine pores penetrating from the front surface to the back surface of the porous sheet, wherein the porous sheet has a large number of porous areas having the fine pores and a non-porous area having no fine pores. The present invention provides a porous sheet comprising:

The present invention also comprises, as a preferred method for producing the porous sheet, a sheet forming step of forming a sheet from the melt and a sheet stretching step of stretching the obtained sheet in at least one direction. The manufacturing of a porous sheet, characterized in that the sheet forming step includes a cooling step of cooling the melt formed into a sheet or the formed sheet by partially providing a difference in cooling rate. It provides a method.

Further, the present invention provides an absorbent article comprising a liquid-permeable front surface material, a leakproof back surface material, and an absorber disposed between them, wherein the back surface material is the above-mentioned material. An absorbent article characterized by using a porous sheet.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION First, the porous sheet of the present invention will be described in detail below. The material for forming the porous sheet of the present invention is 50 to 90 parts by weight of crystalline polyolefin and is miscible with and melts at a temperature equal to or higher than the melting point of the crystalline polyolefin. A compound that causes phase separation with respect to the crystalline polyolefin at a temperature equal to or lower than the melting point (hereinafter, referred to as “compound A”).
50 to 10 parts by weight of the crystalline polyolefin and the compound A obtained by melt mixing.

The crystalline polyolefin used in the resin composition is one selected from the group consisting of isotactic polypropylene, polypropylene-α olefin copolymer, polypropylene-polyethylene block polymer, polyethylene-polypropylene random copolymer and polyethylene. Alternatively, two or more kinds may be used.

The melt index of the crystalline polyolefin is preferably 3 g / 10 minutes or less, more preferably 0.2 to 3 g / 10 minutes. Among them, the melt index generally used for extrusion molding is 0.2 to
A block copolymer resin of crystalline ethylene and propylene of 2 g / 10 min, and a blended product of the block copolymer resin and / or polypropylene resin are particularly preferably used. Here, when the crystalline polyolefin having a melt index of more than 3 g / 10 min is used for the porous sheet, the tear strength and the tensile strength of the porous sheet are lowered, and the necessary strength as a backing material such as disposable diapers is reduced. It is difficult to obtain, and it is conceivable to increase the thickness of the porous sheet in order to obtain the required strength. However, increasing the thickness lowers the moisture permeability of the porous sheet and increases the cost of the product. Invite. Further, when the crystalline polyolefin having a melt index of less than 0.2 g / 10 minutes is used for the porous sheet, there arises a problem that a large amount of power is required for extrusion molding when molding the porous sheet.

The melt index is ASTM
According to D-1238, polypropylene resin and polypropylene-based copolymer resin are 230 ° C. and 2.16 Kgf.
The polyethylene resin refers to a value measured at 190 ° C. and 2.16 Kgf.

The above compound A used in the above resin composition
Is compatible with the crystalline polyolefin at a temperature equal to or higher than the melting point of the crystalline polyolefin, and,
At a temperature below the melting point of the crystalline polyolefin, phase separation occurs with the crystalline polyolefin. Examples of the compound A include mineral oil and compounds having an ester bond in the molecule.

The above-mentioned mineral oils are hydrocarbons of aromatic / alicyclic / aliphatic which are collected from nature and whose low volatile content is removed, and alicyclic / aliphatic hydrocarbons of which aromatics are removed by hydrogenation or the like. Aliphatic hydrocarbons are used. Furthermore, ethylene / α-olefin oligomers called synthetic mineral oils are used.

The compound having an ester bond in the molecule may be an aliphatic or aromatic monobasic or polybasic carboxylic acid and an aliphatic, alicyclic or aromatic monohydric or polyhydric alcohol, respectively. Examples thereof include ester compounds (that is, mono- or polyester) obtained from a dehydration condensation reaction by a combination or a combination of compounds having both a hydroxyl group and a carboxyl group in the molecule. As the above-mentioned aliphatic and aromatic carboxylic acids, polybasic carboxylic acids are preferable, and among aromatic polybasic carboxylic acids, aromatic dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids are preferable, for example, phthalic acid, trimellitic acid and pyromellitic acid. Acid etc. are mentioned. As the aliphatic carboxylic acid, aliphatic dicarboxylic acid and tricarboxylic acid are preferable, and examples thereof include adipic acid, sebacic acid, citric acid and the like. The alcohol is preferably a monohydric alkyl alcohol or the like, for example,
Examples include octyl alcohol, lauryl alcohol, stearyl alcohol and oleyl alcohol.

As the compound having an ester bond in the molecule, an ester compound (that is, mono- or polyester) obtained from an aromatic polybasic carboxylic acid and a monovalent alkyl alcohol, or an aliphatic polybasic carboxylic acid is particularly preferable. An ester compound (that is, a mono- or polyester) obtained from a monohydric alkyl alcohol is preferable. Also, polyhydric alcohols (especially polyhydric alkyl alcohols)
Also preferred are ester compounds (that is, mono- or polyester) of carboxylic acid with monocarboxylic acid (particularly aliphatic monocarboxylic acid), and specific examples thereof include glycerin, diglycerin,
Preferred examples include ester compounds obtained from polyhydric alcohols such as trimethylolpropane, pentaerythritol, dipentaerythritol or sorbitan, and aliphatic monocarboxylic acids such as capric acid, lauric acid, palmitic acid, stearic acid or oleic acid. To be Also,
A small amount of polycarboxylic acid such as adipic acid may be added to the ester so that the obtained ester compound does not gel. Further, from the viewpoint of prevention of environmental pollution and safety, polyester obtained from an aliphatic carboxylic acid and an aliphatic alcohol is preferable.

The above-mentioned compound having an ester bond in the molecule can be prepared from one or more of the above-mentioned carboxylic acids and one or more of the above-mentioned alcohols, and the preparation method is not particularly limited and is conventionally known. Any of the above esterification methods can be used. Further, the compound having an ester bond in the molecule may not be an ester compound in which all of the carboxyl groups in the carboxylic acid and the hydroxyl groups in the alcohol are completely reacted, and the carboxyl group in the carboxylic acid and / or It may be a partial ester in which some of the hydroxyl groups in the alcohol are left unreacted.

The compound A has a volatilization temperature at atmospheric pressure of preferably 240 ° C. or higher, more preferably 250 ° C. or higher, and a melting point of preferably 100 ° C. or lower, more preferably 80 ° C. or lower. .

The sheet forming temperature of the melt of the resin composition in the present invention is preferably 180 to 250 ° C., more preferably 190 ° C. to 240 ° C., and the volatilization temperature of the compound A at atmospheric pressure is 240 ° C. If it is less than the above range, volatile fumes are likely to be generated during the sheet formation. The smoke of the volatiles not only poses a risk of environmental pollution and fire, but also causes the volatiles to adhere to the die lip and cause the occurrence of burns, which is commonly known as "eye stains". Therefore, the die lip must be disassembled and cleaned frequently, and the industrial productivity is extremely poor.

Further, it is preferable that the melting point of the compound A is 100 ° C. or lower. When the molded sheet is stretched, it is preferable that the compound A is softened or melted at the stretching temperature. This is because it is easily microporous. The "volatilization temperature" used in the present specification uses a thermobalance in a nitrogen stream (30 ml / min) at a temperature rising rate of 10 ° C / min.
Measurement with 10 mg sample, draw a heating weight loss curve, and mean the temperature at which the weight loss is 1%.

Specific preferred examples of the above compound A include:
Examples of the mineral oil include mechanical lubricating oils sold from petroleum companies, process oils for rubber, liquid paraffin for fibers, and the like.As the compound having an ester bond in the molecule, distearyl phthalate, trioctyl trimellitate, Tetraoctylpyromellitate, distearyl adipate, distearyl sebacate, trimethylolpropane trilaurate, pentaerythritol tetracaprate and the like can be mentioned. Further, these can be selected from the combination of the solubility parameter of the crystalline polyolefin and the unit within several units.

The above crystalline polyolefin and the above compound A
The blending ratio with the crystalline polyolefin is 50 to 90.
The amount of the compound A is 50 to 10 parts by weight, preferably the crystalline polyolefin 65 to 80, relative to parts by weight.
The amount is 35 to 20 parts by weight of the compound A with respect to parts by weight. When the blending ratio of the crystalline polyolefin is less than 50 parts by weight, the resin composition has poor sheet moldability, and the porous sheet obtained by the stretching treatment has insufficient strength, and the porous sheet is stored during long-term storage. The compound A lacks in practicality such as the compound A bleeding out from the sheet. Further, when the blending ratio of the crystalline polyolefin exceeds 90 parts by weight, it is not possible to obtain a porous sheet satisfying sufficient moisture permeability by stretching treatment.

If desired, additives such as fillers, stabilizers, colorants, antistatic agents, and other ordinary resin physical property improvers and nucleating agents (crystal nucleating agents) are added to the above resin composition. can do. The above-mentioned filler, which does not melt at the sheet forming temperature, can be used without particular limitation as long as it is a filler usually used for rubber, plastic, etc., for example, calcium carbonate, gypsum, barium sulfate, Talc, clay, silica, titanium oxide, metal powder and other inorganic or organic metal salts mainly composed of inorganic substances,
Examples thereof include granules and powders of thermosetting resin such as phenol resin, epoxy resin or sodium polyacrylate.
The above-mentioned filler is preferably used as a powder or granular material having an average particle size of preferably 20 μm or less, more preferably 5 nm to 5 μm. If the average particle size exceeds 20 μm, the tear strength of the obtained sheet may be reduced, which is not preferable. When it is less than 5 nm, it may not substantially contribute to the stretch openness. still,
When a filler that melts at the sheet forming temperature is used as the filler, it is difficult to control the particle size required in the molded sheet. Therefore, in the present invention, a filler that does not melt at the sheet forming temperature is used. To be

The porous sheet containing the above-mentioned filler is opened at a lower draw ratio than the porous sheet containing no filler to obtain the required moisture permeability, so that the sheet strength, especially the tear strength is improved. To do. In particular, in the block copolymer resin of ethylene and propylene, and in the blended product of the block copolymer resin and the polyethylene resin, the water vapor permeability decreases as the ethylene content increases, but by adding the above filler, The effects described above can be exhibited.

As the above-mentioned stabilizers and colorants, conventionally known ones can be used without particular limitation, and the above-mentioned resin physical property-improving agent does not adversely affect the basic physical properties of the porous sheet of the present invention. A small amount can be used.

Further, the function of the nucleating agent is important, and commercially available products of the above crystalline polyolefin have high rigidity,
The nucleating agent is blended to give a high cycle grade. Further, even if the nucleating agent is not blended, the nucleating agent need not be blended as long as it substantially has a nucleating agent function. Part of the above-mentioned "filler" also has the function of the nucleating agent. It is preferable to add the nucleating agent to the non-nucleating agent-added one and the nucleating agent-added one having a poor nucleating agent function, if necessary. As the above-mentioned nucleating agent, a known nucleating agent can be used without particular limitation. For example, Plastics (published by the Industrial Research Institute) Vol. 43 No. 11, 113-
On page 116, "Functions and effects of plastic compounding agents = Nucleating agents"
And the nucleating agent described in 1. Specific examples thereof include metal salts of aromatic carboxylic acids (Al-PTBBA, etc.), sorbitol derivatives, high melting point polymer nucleating agents such as organic phosphates (PTBNa), and talc as an inorganic nucleating agent.

The amount of the above-mentioned additive added is the same as that of the above resin composition 1.
The amount is preferably 0.01 to 21 parts by weight, more preferably 0.1 to 5 parts by weight, based on 00 parts by weight.

The porous sheet of the present invention is obtained by obtaining a melt of the above resin composition, forming a sheet from the melt, and then stretching the sheet in at least one direction to penetrate the sheet from the front surface to the back surface. The micropores are formed.

Thus, the porous sheet of the present invention is characterized by having a large number of porous regions having the fine pores and non-porous regions not having the fine pores.

The porous region has a large number of fine holes, that is, a region having a large number of fine holes penetrating from the front surface to the back surface of the sheet, and the fine holes penetrate in the thickness direction. Alternatively, it may penetrate without passing along the thickness direction (for example, in a direction such as a polygonal line or a curved line, in an oblique direction).

Since the porous region has a large number of the fine pores, it has moisture permeability, and the moisture permeability of the porous region is preferably 0.5 to 4.0 g / 100 cm ² ·. hr, more preferably 0.5 to 2.5 g / 100 cm ² ·
hr.

The water pressure resistance of the porous region is preferably 1.5 mAq or more, more preferably 2.0 mAq or more.

The tear strength of the porous region is preferably 180 gf / mm or more, more preferably 250 gf / mm.
gf / mm or more, and the tensile breaking strength is preferably 110 kgf / cm ² or more, more preferably 130 kgf / cm ²
That is all.

The planar shape of the porous region is arbitrary as long as desired moisture permeability and strength can be obtained.

The non-porous region is a region that does not have the fine pores and need not be continuous in the thickness direction of the sheet, and may be a partial region. In the present invention,
It is preferable that the non-porous regions are present in multiple rows at predetermined intervals in the longitudinal direction or the lateral direction of the sheet, and are continuously present in a mesh shape or continuously in the MD direction or the CD direction. preferable.

Here, "having no fine pores" means having almost no (or no) through-holes, and even if it has some holes from the front surface to the back surface, It suffices that the other portion has a portion that prevents penetration of the hole (a portion where the fine hole is not formed due to crystallization).

Since the non-porous region does not have the fine pores (has little (or no) penetrating holes) as described above, the moisture permeability of the non-porous region is preferably 0.5.
It is less than g / 100 cm ² · Hr. Therefore, in the non-porous region, for example, the moisture permeability to the extent that stuffiness of the absorbent article is prevented cannot be exhibited.

The water pressure resistance of the non-porous region is preferably 1.5 mAq or more, more preferably 2.0 mAq or more.

The non-porous region has a higher strength than the porous region, and the tear strength of the non-porous region is preferably 250 gf / mm or more, more preferably 330 g.
and at f / mm or more, tensile strength at break is preferably 130 kgf / cm ² or more, further preferably 150 kgf / cm ² or more.

The planar shape of the non-porous region is arbitrary as long as desired moisture permeability and strength can be obtained.

The water vapor permeability of the porous sheet of the present invention is preferably 0.5 to 4.0 g / 100 cm ² · Hr, more preferably 1.0 to 2.5 g / 100 cm ² · Hr. When the water vapor permeability is less than 0.5 g / 100 cm ² · Hr, the effect of preventing stuffiness as the backing material of the absorbent article is poor, and when it exceeds 4.0 g / 100 cm ² · Hr, It is not preferable because the water pressure tends to decrease and the leakproofness tends to decrease.

When the porous sheet of the present invention is used for absorbent articles such as disposable diapers, the water pressure resistance of the porous sheet is preferably 1.5 mAq or more, more preferably 2.0 mAq or more. is there.

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, and most preferably 330 gf / mm.
mm or more, and the tensile breaking strength is preferably 11
0 kgf / cm ² or more, more preferably 130 kgf / cm ² or more,
Most preferably, it is 150 kgf / cm ² or more.

As described above, the porous sheet of the present invention is
It has high strength and sufficient moisture permeability. Therefore, the porous sheet of the present invention is suitable as a backing material for absorbent articles such as sanitary napkins and disposable diapers, and can also be used for filters, medical materials, and clothing materials.

FIG. 1 shows the porous sheet of the present invention.
Further details will be described with reference to (a) to (c). FIG. 1 (a)
FIG. 4 is a schematic view of a porous sheet of the present invention manufactured using the plain weave net shown in FIG. 4 (a). Figure 1 (b) shows
1 is an enlarged view of the porous sheet shown in FIG.
(C) is an AA enlarged cross-sectional view of the porous sheet shown in FIG. 1 (a). The micropores shown in FIGS. 1B and 1C are schematic ones for explaining the present invention.

The porous sheet 1 of the present invention shown in FIGS. 1 (a) to 1 (c) has a large number of the fine pores 4 described above, and has a plurality of square-shaped pore regions 2 and the pores. It has a non-porous region 3 which is arranged in a grid pattern so as to divide the region 2 and which does not have the fine pores 4 which continuously exist in a mesh pattern. Also,
Each of the porous region 2 and the non-porous region 3 has a hole 5 that does not penetrate from the front surface to the back surface of the sheet.

The fine pores 4 are present in the porous region 2 as shown in FIG. 1 (b).
As shown in (c), the sheet penetrates from the front surface to the back surface. The average pore diameter and the density of the fine pores 4 are arbitrary as long as they satisfy the above-mentioned moisture permeability and strength.

In the porous sheet 1 of the present invention, the area ratio of the porous region 2 is 2 with respect to the entire sheet.
It is preferably from 0 to 80%, more preferably from 40 to 60%.

The thickness of the porous sheet 1 of the present invention is
The thickness is preferably 20 to 55 μm, more preferably 30 to 40 μm.

Another embodiment of the porous sheet of the present invention is shown in FIGS. 2 (a) and 2 (b). FIG. 2A is the same as FIG.
It is a schematic diagram of the porous sheet manufactured using the steel belt having the opening shown in (a), and FIG.
It is a schematic diagram of the porous sheet manufactured using the steel belt which has the opening part shown in FIG.5 (b).

The porous sheet of the present invention shown in FIG. 2 (a) has a large number of the fine pores 4 described above and separates a plurality of rectangular porous regions 2 from each other. It has a non-porous region 3 which does not have the fine pores 4 which are arranged in a chamfer and continuously exist. Further, the porous sheet of the present invention shown in FIG. 2 (b) has a large number of the fine pores 4 described above, and separates the plurality of hexagonal porous regions 2 from the porous regions 2. It has a non-porous region 3 which does not have the fine pores 4 which are arranged in a hexagonal lattice and continuously exist. The structure of the porous region 2 and the non-porous region 3 in the porous sheet of the present invention shown in FIGS. 2 (a) and 2 (b), the ratio of the area occupied by the porous region 2 and the porosity. The thickness and the like of the porous sheet are preferably the same as those in the porous sheet of the present invention shown in FIG.

Next, the method for producing the porous sheet of the present invention will be described in detail. The method for producing the porous sheet of the present invention,
A sheet forming step of forming a sheet from the melt is performed, and a sheet stretching step of stretching the obtained sheet in at least one direction is performed. In the sheet forming step, the sheet-shaped melt or formed sheet is formed. This can be carried out by performing a cooling step in which the sheet is partially cooled with different cooling rates.

In the cooling step, the difference in cooling rate is partially provided between the sheet-shaped melt and the formed sheet. Specifically, the melt or sheet is provided in a predetermined portion. Crystals of the crystalline polyolefin are grown to a certain size and gradually cooled until the melting point of the crystalline polyolefin is reached so that crystallization and phase separation of the crystalline polyolefin occur when the crystallization temperature is reached. In addition to providing a part, in the other part the melt or sheet is prevented from crystal growth of the crystalline polyolefin, fine crystals are formed, phase separation hardly occurs, and through holes do not form even when stretched. It means cooling by providing a portion for rapid cooling so that the strength becomes extremely high.

In the gradually cooling portion, the cooling rate is preferably 15 to 400 ° C./sec, more preferably 30 to 200 ° C./sec.

In the above rapidly cooling portion, the cooling rate is preferably 20 to 800 ° C./sec, more preferably 20 to 600 ° C./sec.

Specifically, the method for producing the porous sheet of the present invention is preferably carried out by the following methods (1) to (3).

The cooling step is performed by casting the melt on a plain or twill net or a steel belt or drum having openings. In the cooling step, the melt is cast on a casting roll having a quenching portion having a surface temperature of 10 to 90 ° C. and a slow cooling portion having a surface temperature higher than the quenching portion by 10 to 100 ° C. To do. The sheet forming step is performed by supplying the melt to an annular die to form a tubular sheet, and the cooling step cools the entire sheet arranged in the circumferential direction of the tubular sheet. A) using an air ring and a) using air nozzles arranged at predetermined intervals in the circumferential direction of the sheet to partially and rapidly cool the sheet, or b) in the circumferential direction of the sheet. The sheet is contacted with a cooling bar or a cooling roll that is partially and rapidly cooled and is placed at a predetermined interval. In this case, it is particularly preferable that the annular die be rotated in the circumferential direction thereof, and that the air ring and / or the air nozzle be rotated.

More specifically, with respect to the preferred method for producing the porous sheet of the present invention (methods 1 to 3), FIG.
4 (a) and (b), FIG. 5 (a) and (b), FIG.
This will be described with reference to FIGS. 7 and 8. FIG. 3 is a schematic view showing an example of a manufacturing apparatus used in the method for manufacturing a porous sheet of the present invention, and FIG. 4 (a) is an enlarged plan view of a plain weave net used in the manufacturing apparatus shown in FIG. FIG. 4 (b) is a BB cross-sectional view of the plain weave net shown in FIG. 4 (a), and FIGS. 5 (a) and 5 (b) show the openings used in the manufacturing apparatus shown in FIG. FIG. 7 is an enlarged view of a steel belt having the same, FIG. 6 is a schematic view showing another example of a manufacturing apparatus used in the method for manufacturing a porous sheet of the present invention, and FIG.
FIG. 8 is an enlarged perspective view of a casting roll used in the manufacturing apparatus shown in FIG. 6, and FIG. 8 is a schematic view showing still another example of the manufacturing apparatus used in the method for manufacturing the porous sheet of the present invention.

First, the above method will be specifically described. The manufacturing apparatus 100 used in the above method is
As shown in FIG. 3, a single-screw extruder 10 equipped with a T-die 11 for extruding a melt 1 ″ of the resin composition, and a cooling medium as a cooling medium for casting and cooling the extruded melt 1 ″ The plain weave net 20, the cooling roll 40 that cools the plain weave net 20, and the sheet 1 ′ that has passed through the cooling roll are M
MD direction stretching machine 60 that stretches in the D direction (direction along the flow of the sheet 1 ', longitudinal direction), and CD that stretches the sheet 1'in the CD direction (direction perpendicular to the flow of the sheet 1', transverse direction). It comprises a direction stretching machine 70, a winding machine 80 for winding the porous sheet 1 formed by stretching the sheet 1 ', and guide rollers 50, 51, 52.

Here, as shown in FIG. 4, the plain weave net 20 has a lattice pattern 21 and a large number of openings 22 formed by the lattice pattern 21, and each lattice pattern 21 is formed. A large number of wire rods 23 arranged in parallel and in multiple rows (toward the direction corresponding to the MD direction),
It is composed of a large number of wire rods 24 woven in the wire rod 23 in a plurality of rows (in the direction corresponding to the CD direction) so as to be orthogonal to the wire rod 23. In addition, the plain weave net 20
Is in the form of a belt conveyor so that the sheet 1'can be conveyed in the direction of the arrow. Wire 2 above
The line pitch and line width (line diameter) of 3 and 24 are arbitrary depending on the shapes of the porous region and the non-porous region of the desired porous sheet, and the line pitch and line width (line diameter) are appropriately set. By selecting, the moisture permeability and strength of the porous sheet of the present invention can be set to desired values. The material for forming the wire rods 23 and 24 is not particularly limited as long as it does not hinder the formation of the sheet 1'on which the melt is placed, but metal or the like is preferably used.

The sizes of the single-screw extruder 10 and the T-die 11 and the width and length of the plain weave net 20 are arbitrary depending on the desired size of the porous sheet.

Thus, the method for producing a porous sheet of the present invention comprises a step of forming a sheet 1'from the melt 1 "and a sheet for stretching the obtained sheet 1'in at least one direction. A stretching step, wherein the sheet forming step includes a cooling step of cooling the melt 1 ″ formed into a sheet or the formed sheet 1 ′ by partially providing a difference in cooling efficiency. Is.

To carry out the above manufacturing method, as shown in FIG. 3, in the sheet forming step, the resin composition is charged into the single-screw extruder 10 and the resin composition is melt-mixed to obtain a melt. 1 ″ is obtained, and the melt 1 ″ is extruded from the T die 11, cast on the plain weave net 20 cooled by the cooling roll 40, and cooled to form the sheet 1 ′. Further, in the sheet stretching step, the sheet 1 ′ can be stretched in the MD direction, the CD direction, or the MD direction and the CD direction.

Specifically, in the sheet forming step,
The set temperature of the T die 11 is preferably 190 to 300 ° C. And the extruded melt 1 "
Is rolled and conveyed in the direction of the arrow and formed into a sheet. At this time, the speed of the plain weave net 20 corresponds to the take-up speed of the sheet 1 ', and the take-up speed is preferably 5 to 200 m / min.

In the cooling step, the temperature of the cooling roll 40 for cooling the plain weave net 20 is 0.
The temperature is preferably ˜90 ° C., more preferably 15 to 40 ° C. Therefore, the temperature of the plain weave net 20 is set so that the cooling rates of the rapidly cooling portion and the gradually cooling portion fall within the above range.
The 24 parts are preferably 0 to 90 ° C., preferably 15 to 40
More preferably, the temperature is ° C.

Further, in the above sheet stretching step, the obtained sheet 1'is passed through the cooling roll 40, and then the MD direction stretching machine 60 and the CD through the guide roller 50.
It is supplied to the directional stretching machine 70. By operating only one of the MD direction stretching machine 60 and the CD direction stretching machine 70, the porous sheet 1 stretched in only one of the MD direction and the CD direction can be obtained. If both are operated, a porous sheet stretched in both directions can be obtained. Here, the above-mentioned stretching can be performed according to a usual stretching method, and the stretching ratio is MD direction, CD
It is preferable that the direction is 1 to 4 times. Then, the stretched porous sheet 1 can be supplied to the manufacturing process of various molded products by winding it with the winder 80 via the guide rollers 51 and 52.

As described above, the melt 1 ″ is extruded onto the plain weave net 20 and the melt 1 ″ is cooled by partially providing a difference in cooling efficiency, whereby the grid pattern 21 of the plain weave net 20 is obtained. The porous sheet 1 having the non-porous region corresponding to the above and the porous region corresponding to the opening 22 of the plain weave net 20 is obtained.

In the manufacturing apparatus 100, as the cooling medium, instead of the plain weave net 20, a steel belt 25 having a pleated structure shown in FIG. 5A or shown in FIG. 5B. A steel belt 25 'having a hexagonal honeycomb structure, a drum having a honeycomb structure on the surface, or the plain weave net 20 or the steel belts 25, 25' in the form of a drum may be used. It can be performed under the same conditions as when the plain weave net 20 is used. Here, as shown in FIG. 5A, the steel belt 25 has a large number of rod-shaped opening portions 26 and a steel portion 28 that is continuous in a humped shape so as to surround the opening portions 26. .
Further, the steel belt 25 'has a large number of hexagonal openings 27 and a steel portion 28' which is continuous in a worm-like shape so as to surround the openings 27, as shown in FIG. 5 (b). Is. The opening ratio of the opening portions 26 and 27 is arbitrary according to the shapes of the porous region and the non-porous region of the desired porous sheet, and by appropriately selecting the opening ratio,
The moisture permeability and strength of the porous sheet of the present invention can be set to desired values.

Further, the above-mentioned steel belts 25, 25 '
The temperature of the steel parts 28, 28 'is preferably 0 to 90 ° C so that the cooling rates of the rapidly cooling part and the gradually cooling part are in the above ranges,
It is more preferably 15 to 40 ° C. In this manner, the melt 1 ″ is extruded onto the steel belts 25, 25 ′ to partially provide a difference in cooling efficiency, and the melt 1 ″
By cooling the steel belt 25, 2
The porous sheet 1 having the non-porous regions corresponding to the steel parts 28, 28 'of 5'and the porous regions corresponding to the openings 26, 27 of the steel belts 25, 25'. Is obtained.

Next, the above method will be specifically described. The manufacturing apparatus 200 used in the above method is
As shown in FIG. 6, the apparatus is almost the same as the manufacturing apparatus 100 except that the plain weave net 20 is changed to the casting roll 30 and the circumference thereof is changed. That is, the manufacturing apparatus 200 includes a single-screw extruder 10 equipped with a T-die 11 for extruding a melt 1 ″ of the resin composition, and the single-screw extruder 1
The casting roll 30 as a cooling member for casting and cooling the melt 1 ″ extruded from 0, the pressing roll 41 for pressing the melt 1 ″ onto the casting roll 30, and the pressing roll 41 MD-direction stretching machine 60 for stretching the above-mentioned sheet 1'in the MD direction
A CD direction stretching machine 70 for stretching the sheet 1'in the CD direction, a winding machine 80 for winding the porous sheet 1 formed by stretching the sheet 1 ', and a guide roller 50,
It consists of 51 and 52.

In order to carry out the above manufacturing method, as shown in FIG. 6, in the sheet forming step, the resin composition is charged into the single-screw extruder 10 and the resin composition is melt-mixed to obtain a melted product. 1 ″ is obtained, and the melt 1 ″ is cast on the casting roll 30 and cooled to form the sheet 1 ′. Further, in the sheet stretching step, the sheet 1 ′ can be stretched in the MD direction, the CD direction, or the MD direction and the CD direction.

Specifically, the above casting roll 30
As shown in FIG. 7, it is a cylindrical roll, and on its circumferential surface, a quenching part 31 having a surface temperature of 10 to 90 ° C. and a surface temperature of 10 to 100 ° C. as compared with the quenching part 31. , Preferably 20 to 100 ° C., and more preferably 30 to 100 ° C. higher annealing part 32. When the difference in surface temperature between the quenching section 31 and the gradual cooling section 32 is less than 10 ° C, the porous sheet 1 having the porous region and the non-porous region cannot be obtained, and the temperature is 100 ° C. If the temperature exceeds the above range, the high temperature portion of the melt 1 ″ may be insufficiently cooled and the formation of the porous sheet 1 may not be stable. Further, the shape and area of the quenching portion 31 may be the desired non-pores of the porous sheet. The shape and area of the slow cooling part 32 are arbitrary depending on the shape of the quality region.
It is arbitrary depending on the shape of the porous region of the desired porous sheet. By appropriately selecting the shapes and areas of the rapid cooling part 31 and the slow cooling part 32, the moisture permeability and strength of the porous sheet of the present invention can be set to desired values.

The single screw extruder 10 and the T die 11 are also used.
The size, the width, and the length of the casting roll 30 are arbitrary depending on the size of the desired porous sheet.

The set temperature of the T die 11 is 19
The temperature is preferably 0 to 300 ° C. Then, the extruded melt 1 ″ is extruded from the T die 11 between the casting roll 30 and the pressing roll 41 to be supplied, and pressed by the pressing roll 41 to form the sheet 1 ′. The casting roll 30 is rotating in the direction of the arrow, and the pressing roll 41 is adapted to apply pressure in the direction of the arrow P. Further, the rotating speed of the casting roll 30 is the take-up of the sheet 1 '. It corresponds to the speed, and the take-up speed is preferably 5 to 200 m / min.

The temperature of the casting roll 30 is
The quenching part 31 is preferably 10 to 90 ° C., more preferably 30 to 50 ° C., and the slow cooling part 32 so that the cooling efficiency of the quenching part and the annealing part is in the above range. Is preferably 20 to 190 ° C., 80 to 1
More preferably, it is 20 ° C.

The sheet 1'obtained is the guide roller 5
MD direction stretching machine 60 and CD direction stretching machine 70
To supply. The sheet stretching step can be performed in the same manner as in the above method.

In this way, the casting roll 3
The melt 1 ″ is extruded on the surface of the casting roll 30 to partially cool the melt 1 ″ with a difference in cooling efficiency to form the non-porous region corresponding to the quenching portion 31 of the casting roll 30. Thus, the porous sheet 1 in which the porous region corresponding to the slow cooling part 32 of the casting roll 30 is formed is obtained.

Further, the above method will be specifically described. The manufacturing apparatus 300 used in the above method is
As shown in FIG. 8, a single screw extruder 10 having an annular die 12 for extruding a melt 1 ″ of the resin composition, and a melt 1 ″ extruded from the single screw extruder 10 are blown up to form an inflation. The air ring 42 for cooling the entire surface of the tubular sheet 1 ′, the air nozzle 43 for partially and rapidly cooling the sheet 1 ′, the air ring 42 and the tubular sheet cooled by the air nozzle 43 A guide plate 90 and a nip roll 91 for feeding and folding 1 ', and M for stretching the sheet 1'in the MD direction.
A D-direction stretching machine 60, a CD-direction stretching machine 70 for stretching the sheet 1'in the CD direction, a winding machine 80 for winding up the porous sheet 1 formed by stretching the sheet 1 ', and a guide roller. It consists of 50, 51 and 52.

To carry out the above manufacturing method, as shown in FIG. 8, in the sheet forming step, the resin composition is charged into a single-screw extruder 10 having an annular die 12, and the resin composition is melted. A melt 1 ″ is obtained by mixing, and the melt 1 ″ thus obtained is supplied to the annular die 12 and blown up, and the annular die 12 is rotated in the direction of the arrow to inflation-form the sheet 1 ′ to form a tube. And in the cooling step, the entire surface of the tubular sheet 1'is
After being cooled to some extent by the air ring 42 arranged in the circumferential direction of the sheet 1 ', the sheet 1'is further partially and rapidly cooled by the air nozzles 43 arranged at predetermined intervals in the circumferential direction. . Then, the cooled tube-shaped sheet 1 ′ is attached to the guide plate 90 and the nip roll 9
Supply 1 and fold. Then, in the sheet stretching step, the sheet 1'is treated in the MD direction, the CD direction, or the MD direction.
It can be performed by stretching in the machine direction and the CD direction.

At this time, in the sheet forming step, the sizes of the single screw extruder 10 and the annular die 12, and
The extrusion slit of the annular die 12, the depth of the groove, and the like are arbitrary depending on the desired size of the porous sheet. Also,
In the present invention, the annular die 12 preferably forms the sheet 1 ′ while rotating in the circumferential direction.

Further, the die set temperature in the above inflation formation is preferably 190 to 250 ° C., and the take-up speed is preferably 5 to 100 m / min.

In the cooling step, the types and sizes of the air ring 42 and the air nozzle 43 are arbitrary depending on the shapes of the porous region and the non-porous region of the desired porous sheet.

The cooling by the air ring 42 is preferably 0 to 50 ° C., more preferably 0 to 20 ° C. on the entire surface of the tubular sheet 1 ′ so that the cooling rate of the gradual cooling portion is in the above range. It can be performed by blowing air. At this time, the entire surface of the tubular sheet 1 ′ cooled by the air ring 42 is 100
The temperature is preferably -200 ° C, more preferably 110-150 ° C.

The cooling by the air nozzle 43 is
The tube-shaped sheet 1 ′ is preferably -20 to 50 ° C. so that the cooling rate of the quenching section is in the above range.
More preferably, it can be performed by blowing air at 0 to 20 ° C. partially and rapidly. At this time,
The quenching portion in the tubular sheet 1 ′ partially and rapidly cooled by the air nozzle 43 is
The temperature is preferably 160 ° C, more preferably 50 to 100 ° C.

The air ring 42 and the air nozzle 4
By setting the temperature of the air according to 3 in the above range, the moisture permeability and strength of the porous sheet of the present invention can be set to desired values.

In the cooling step, it is preferable to form the sheet 1'while rotating the air ring 42 and / or the air nozzle 43, whereby the sheet 1'having a predetermined angle with respect to the MD direction is formed. The non-porous portion can be formed, and the lateral strength (strength in the MD direction) of the porous sheet can be particularly improved. Also,
Even when the air nozzle 43 is replaced with the cooling roll or the cooling bar, it is preferable to form the sheet 1 ′ while rotating them.

The sheet stretching step can be performed in the same manner as in the above method.

As described above, by partially and rapidly cooling the tubular sheet 1'by the air nozzle 43, the non-porous region corresponding to the rapidly cooled portion formed by the air nozzle 43 is formed. The porous sheet 1 having the porous region corresponding to the portion other than the quenched portion can be obtained.

In the manufacturing apparatus 300, instead of the air nozzle 43 used in the above a), the cooling bar or cooling roll used in the above b) is used to partially cover the tubular sheet 1 '. Further, it can be cooled rapidly, and the cooling bar or the cooling roll can be performed by arranging the cooling bar or cooling roll in the circumferential direction of the tubular sheet 1 ′ and contacting the sheet 1 ′. Also in this case,
This can be performed under the same conditions as when the air nozzle 43 is used. The temperature of the cooling bar or the cooling roll when the cooling bar or the cooling roll is used is preferably −20 to 90 ° C., and 0 to 50 ° C. so that the cooling rate of the quenching section is in the above range. Is more preferable. Further, by setting the temperature of the cooling bar or the cooling roll within the above range, the strength of the porous sheet of the present invention can be set to a desired value.

Next, the absorbent article of the present invention will be described in detail. The absorbent article of the present invention comprises a liquid-permeable front material, a leak-proof back material, and an absorber arranged between them. Such a configuration and the material for forming the surface material and the absorber are the same as the conventionally known configuration and material. Thus, in the absorbent article of the present invention, the porous sheet of the present invention is used as the back material. Examples of the absorbent article of the present invention include disposable diapers, incontinence briefs, sanitary napkins, and the like, and the porous sheet is used in a desired shape depending on the application of the absorbent article.

When the absorbent article of the present invention is used as a disposable diaper, the disposable diaper includes an absorber that absorbs excrement such as urine, a surface material that covers the surface of the absorber and is applied to the skin, and It consists of a back material that covers the body and prevents liquid leakage, and these are bonded and integrated. The disposable diaper is a fastening tape that secures the back waist circumference and the abdominal waist circumference when the diaper is attached and the expansion / contraction function provided to prevent leakage from the waist circumference and leg circumference. It has a fastening function that consists of etc. The fastening tape is about 2 for convenience.
The one with a width of 5 mm is often used.

The thickness of the backing material used for the disposable diaper is usually 20 μm because of the flexibility required for the diaper, the waist of the sheet required when the diaper is assembled and processed, and the security of the backing material. As described above, it is particularly preferably 30 μm or more, while it is preferably 55 μm or less, particularly 40 μm or less from the viewpoint of flexibility and cost required for diapers. Therefore, the thickness of the back material used for the disposable diaper is preferably 20 to 55 μm, and 30
More preferably, it is ˜40 μm.

Further, the backing material used in the disposable diaper needs to have a strength for removing the so-called landing tape and directly attaching the fastening tape to the backing material and peeling it off. The tear strength of the backing material is preferably 10 gf or more, more preferably 14 gf or more, and most preferably 18 gf or more in terms of the sheet thickness used. Therefore, in order to withstand 10 gf at a thickness of 55 μm, the backing material must have a tear strength of 182 gf / mm. The tensile breaking strength of the backing material is preferably 500 gf or more, more preferably 600 gf or more, and most preferably 700 gf or more per 1 cm of sheet width. Therefore, in order to endure 500 gf per cm at a thickness of 35 μm, the backing material must have a strength of 143 kgf / cm ² or more.

As described above, the backing material used for the disposable diaper has a tensile breaking strength of 500 as described above.
When it is at least gf, it has sufficient strength. Therefore, since it is not necessary to use the landing tape, the diaper is not mistakenly attached, and the backing material is not broken even when the diaper is peeled off for urine inspection during wearing. Further, if the moisture permeability of the back surface material is within the moisture permeability range of the porous sheet of the present invention described above, stuffiness or the like does not occur and a comfortable wearing feeling can be maintained.

[0102]

EXAMPLES Hereinafter, the porous sheet of the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, "part" means "part by weight" unless otherwise specified.

Example 1 Using the composition shown in the following [Blending composition], melt kneading was carried out by the following [Biaxial kneading extruder] and extruded into filaments, which were cut into pellets, and then T-die. Attached. It was supplied to the following [single screw extruder], remelted, and formed into a sheet. At this time, "resin" and "granular material" are supplied from the hopper of the twin-screw kneading extruder, the resin is plasticized, and the middle part of the extruder in which the granular material is dispersed,
The "compound" was pressed in with a metering pump. As the manufacturing apparatus, the manufacturing apparatus 100 shown in FIG. 3 (a steel belt was used as a cooling medium) was used.

[Compounding composition] Homopolypropylene XF1932 (manufactured by Chisso Petrochemical Co., Ltd.); 44.2 parts ・ Block polypropylene WT6052 (manufactured by Chisso Petrochemical Co., Ltd.); 19.8 parts ・ Titanium oxide masterbatch (concentration) 60%) (manufactured by Toyo Ink Mfg. Co., Ltd.); 5 parts-Process Oil PW380 (manufactured by Idemitsu Kosan Co., Ltd.);
31 parts [biaxial kneading extruder]; PCM45 (φ43 mm, L / D
= 30) manufactured by Ikegai Co., Ltd. [Single-screw extruder]; YE50 (φ50 mm, L / D = 2)
8) Made by Yamaguchi Manufacturing Co., Ltd.

The above melt extruded from the T-die was cooled by casting on a steel belt having an opening at a temperature of 30 ° C., and further stretched 1.5 times in the MD direction so that a thickness of 35 μm was obtained. A porous sheet was obtained. As the steel belt, a steel belt 2 having a hexagonal honeycomb structure shown in FIG.
5'was used. The aperture ratio was 51%. And about the obtained porous sheet, the following 1) to 4)
Was evaluated. The results are shown in [Table 1] below.

[Evaluation and Evaluation Criteria] 1) Moisture Permeability: Measured in accordance with JIS ZO 208. 2) Water pressure resistance: Measured according to JIS L 1093B method. 3) Tensile strength: The obtained porous sheet was cut into 10 mm widths in the stretching direction and in a direction perpendicular to the stretching direction and subjected to a Tensilon tensile tester.
It was measured at 0 mm and a pulling speed of 300 mm / min. 4) Tear strength: 60 mm × 30 of the obtained porous sheet
A mm piece was cut out so that the long piece was equal to the stretching direction of the sheet, and further cut from the center of the above piece to one end of the short piece in parallel with the long side with a razor blade to obtain a sample. Then, using a Tensilon tensile tester, the two ends formed by cutting the sample were fixed to a chuck, the sample was T-shaped, and the tear measurement in the sheet stretching direction was performed at a tensile speed of 300 mm / min, The average load was determined from the obtained measurement chart and used as the tear strength.

Comparative Example 1 In the same manner as in Example 1, the melt extruded from the T-die was cast on a steel belt having no opening at a temperature of 30 ° C. for cooling, and further 1 in the MD direction. ．
A 35-micron-thick porous sheet was obtained by stretching 5 times. Regarding the obtained porous sheet, Example 1
The evaluation was performed in the same manner as described above. The results are shown in [Table 1].

Comparative Example 2 In the same manner as in Example 1, the above-mentioned melt extruded from the T die was cast on a steel belt having no opening at a temperature of 95 ° C. for cooling, and further 1 in the MD direction. ．
A 35-micron-thick porous sheet was obtained by stretching 5 times. Regarding the obtained porous sheet, Example 1
The evaluation was performed in the same manner as described above. The results are shown in [Table 1].

[0109]

[Table 1]

[0110]

INDUSTRIAL APPLICABILITY The porous sheet of the present invention has moisture permeability and water pressure resistance, is excellent in sheet strength, and has a good usability when used for absorbent articles and the like. Further, according to the method for producing a porous sheet of the present invention, the above-mentioned porous sheet can be easily produced. Further, since the absorbent article of the present invention uses the above-mentioned porous sheet as a backing material, even when there is no reinforcing tape in the tape fastening portion, even when it is adhesively fixed with a tape or the like during use, it is worn or removed. In addition, the sheet does not tear, and the tape can be attached and removed at any position, which is excellent in usability.

[Brief description of drawings]

1 (a) is a schematic view of a porous sheet of the present invention manufactured using the plain weave net shown in FIG. 4 (a), and FIG. 1 (b) is FIG. 1 (a). FIG. 1C is an enlarged plan view of the porous sheet shown in FIG. 1, and FIG. 1C is an AA enlarged cross-sectional view of the porous sheet shown in FIG.

2 (a) is a schematic view of the porous sheet of the present invention manufactured using the steel belt having the opening shown in FIG. 5 (a), and FIG. It is a schematic diagram of the porous sheet of this invention manufactured using the steel belt which has the opening part shown to 5 (b).

FIG. 3 is a schematic view showing an example of a manufacturing apparatus used in the method for manufacturing a porous sheet of the present invention.

4 (a) is an enlarged plan view of a plain weave net used in the manufacturing apparatus shown in FIG. 3, and FIG. 4 (b) is a cross section taken along the line BB of the plain weave net shown in FIG. 4 (a). It is a figure.

5 (a) and 5 (b) are enlarged plan views of a steel belt having an opening used in the manufacturing apparatus shown in FIG.

FIG. 6 is a schematic view showing another example of a manufacturing apparatus used in the method for manufacturing a porous sheet of the present invention.

FIG. 7 is an enlarged perspective view of a casting roll used in the manufacturing apparatus shown in FIG.

FIG. 8 is a schematic view showing still another example of the manufacturing apparatus used in the method for manufacturing a porous sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Porous sheet 1'Sheet 1 "Melt 2 Porous area 3 Non-porous area 4 Micropore 5 Hole 10 Single screw extruder 11 T die 12 Annular die 20 Plain weave net 21 Grid pattern 22 Open hole 23, 24 Wire rod 25 , 25 'Steel belt 26, 27 Opening part 28, 28' Steel part 30 Casting roll 31 Quenching part 32 Slow cooling part 40 Cooling roll 41 Pressing roll 42 Air ring 43 Air nozzle 50, 51, 52 Guide roller 60 MD direction stretching machine 70 CD direction stretching machine 80 Winding machine 90 Guide plate 91 Nip roller 100 Manufacturing apparatus used in the above method 200 Manufacturing apparatus used in the above method 300 Manufacturing apparatus used in the above method

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Odashima, 2606, Akao, Kaicho, Haga-gun, Tochigi Prefecture, Kao Institute of Stock Companies (72) Inventor, Haruo Sakahashi, 2606, Akabane, Kai-cho, Haga-gun, Tochigi Prefecture, Institute of Kao Corporation

Claims (10)

[Claims] 1. A crystalline polyolefin of 50 to 90 parts by weight and a temperature above the melting point of the crystalline polyolefin are miscible and soluble in the crystalline polyolefin, but at a temperature below the melting point of the crystalline polyolefin, Compounds 50 to 10 that cause phase separation with respect to the crystalline polyolefin
Parts by weight to obtain a melt of a resin composition comprising the crystalline polyolefin and the compound, form a sheet from the melt, and then stretch the sheet in at least one direction. A porous sheet formed by forming fine pores penetrating from the front surface to the back surface of the sheet, wherein the porous sheet has a porous region having a large number of the fine pores and a non-porous region having no fine pores. And a porous sheet. 2. The porous sheet according to claim 1, wherein the non-porous region is present continuously in a mesh shape or continuously in the MD direction or the CD direction. 3. The moisture permeability of the porous sheet is 0.
The porous sheet according to claim 1, which has a weight of 5 to 4.0 g / 100 cm ² · hr. 4. The method for producing a porous sheet according to claim 1, comprising a sheet forming step of forming a sheet from the melt, and a sheet stretching step of stretching the obtained sheet in at least one direction. The sheet forming step comprises a cooling step of cooling the melt formed into a sheet or the formed sheet by partially providing a difference in cooling rate. Production method. 5. The porous sheet according to claim 4, wherein the cooling step is performed by casting the melt on a plain weave or a twill net, or a steel belt or drum having openings. Manufacturing method. 6. The surface temperature of the cooling step is 10 to 90.
℃ quenching part and the surface temperature is 10-100 compared to the quenching part
The method for producing a porous sheet according to claim 4, which is performed by casting the melt on a casting roll having a slow cooling part having a high temperature of ℃. 7. The sheet forming step is performed by supplying the melt to an annular die to form a tubular sheet, and the cooling step is arranged in the circumferential direction of the tubular sheet. While using an air ring for cooling the entire surface of the sheet, a) using an air nozzle arranged at a predetermined interval in the circumferential direction of the sheet for partially and rapidly cooling the sheet, or the sheet 5. The production of a porous sheet according to claim 4, which is carried out by bringing a sheet into contact with a cooling bar or a cooling roll which is arranged at a predetermined interval in the circumferential direction and which partially and rapidly cools the sheet. Method. 8. The method for producing a porous sheet according to claim 7, wherein the annular die is rotated in the circumferential direction. 9. The method for producing a porous sheet according to claim 7, wherein the air ring and / or the air nozzle is rotated. 10. An absorbent article comprising a liquid-permeable front material, a leak-proof back material, and an absorber arranged between them, wherein the back material is any one of claims 1 to 3. An absorbent article comprising the porous sheet described above.