JPH093222A - Porous sheet, its production and absorbing material using the same - Google Patents

Abstract

PURPOSE: To obtain a porous sheet having sufficient mechanical strength and various physical properties such as flexibility, air permeability and moisture permeability required for a rear face material of an absorbing material such as a disposable diaper or a sanitary product and to readily and inexpensively produce the porous sheet. CONSTITUTION: This porous sheet is produced by molding a sheet from a mixture containing 50-90 pts.wt. of a crystalline polyolefin resin and 50-10 pts.wt. of an organic compound having miscibility with the crystalline polyolefin resin in a melted state of the crystalline polyolefin resin and phase-separating below a crystallization temperature of the crystalline polyolefin, guiding the sheet between a pair of embossing rolls, subjecting to a emboss processing and stretching the embossed sheet in at least one direction to 1.2-5 times.

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 a method for producing the same, and more particularly to a porous sheet having good moisture permeability, excellent mechanical properties and tear strength, and a method for producing the same. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a crystalline thermoplastic resin and a compound miscible with the crystalline thermoplastic resin have been melt-blended, and then the blended product is formed into a film and stretched to obtain a porous sheet. The method is known. For example, JP-A-59-64640 and JP-A-63-16103.
Japanese Patent Publication No. 5 describes a method of obtaining a breathable porous sheet by stretching a formed sheet. However, the porous sheet obtained by the method described in the above publication,
As a result of the progress of molecular orientation in the stretching direction by stretching in the machine direction, there is a drawback that the tensile strength and tear strength in the direction perpendicular to the stretching direction are low.

As a method for improving these mechanical properties, there are a method of stretching at a stretching ratio as low as possible and a method of biaxial stretching. However, the method of stretching at a low stretching ratio has drawbacks such that stretching unevenness occurs in the sheet, and practically sufficient moisture permeability cannot be obtained.
On the other hand, the method of performing biaxial stretching has the drawback that the stretching mechanism is complicated and the equipment cost is very high.

Other techniques for producing a moisture permeable sheet include those described in JP-A-62-68459 and JP-A-2-504. The above-mentioned publication describes a technique in which a film-formed sheet is stretched and subsequently embossed. However, the moisture-permeable sheet obtained by the method described in the above publication has its moisture permeability reduced by embossing, and therefore, it has been necessary to stretch the sheet to a considerable extent in order to obtain a practically sufficient moisture permeability.
As a result, the molecular orientation in the stretching direction is further advanced, and the tear strength in the direction perpendicular to the stretching direction is further reduced. Further, in the moisture permeable sheet, since the embossed portion is semi-transparent, when the moisture permeable sheet is used as a backing material of an absorbent article, the color of excrement is the moisture permeable sheet. It also had the drawback that it could be seen through.

Therefore, an object of the present invention is to have various mechanical properties such as flexibility, breathability, and moisture permeability required for a backing material of absorbent articles such as disposable diapers and sanitary products. It is to provide a porous sheet having good physical properties.
Another object of the present invention is to provide a method capable of easily and inexpensively producing the above-mentioned porous sheet.

[0006]

[Means for Solving the Problems] As a result of intensive studies by the present inventors in order to achieve the above object, as a result of subjecting a sheet formed from a specific composition to an embossing step and a subsequent stretching step, It has been found that the above various physical properties can be imparted to the sheet.

The present invention has been made based on the above findings, and is 50-90 parts by weight of the crystalline polyolefin resin and the crystalline polyolefin resin which is miscible with the crystalline polyolefin resin under melting. Organic compounds that undergo phase separation below the crystallization temperature of the polyolefin resin 50
Sheet is formed from a mixture containing 10 to 10 parts by weight, the sheet is interposed between a pair of embossing rolls to perform embossing, and then the embossed sheet is 1.2 times in at least one direction. The above object is achieved by providing a method for producing a porous sheet, which is characterized by stretching 5 times.

The present invention also provides a preferable porous sheet produced by the above method, which is compatible with 50 to 90 parts by weight of the crystalline polyolefin resin and the crystalline polyolefin resin under melting of the crystalline polyolefin resin. A sheet formed from a mixture containing 50 to 10 parts by weight of an organic compound that undergoes phase separation at a crystallization temperature of the crystalline polyolefin resin is embossed, and then stretched 1.2 to 5 times in at least one direction. The present invention provides a porous sheet obtained by

Furthermore, the present invention provides an absorbent article comprising a liquid-permeable surface material, a leak-proof backing material, and an absorber disposed between them, wherein the backing material is the above-mentioned material. It is intended to provide an absorbent article characterized by using a porous sheet.

The porous sheet obtained by the method of the present invention can be used in applications requiring waterproofness and moisture permeability, such as waterproof clothing, waterproof covers and packaging materials, but especially disposable diapers and menstruation. It is preferably used as a backing material for absorbent articles such as napkins.

The method of the present invention will be described in detail below.

The method of the present invention comprises: i) 50 to 90 parts by weight of a crystalline polyolefin resin and the crystalline polyolefin resin which is miscible with the crystalline polyolefin resin under melting and the crystallization temperature of the crystalline polyolefin resin. In the following, a first step of forming a sheet from a mixture containing 50 to 20 parts by weight of an organic compound that undergoes phase separation, ii) a second step of interposing the sheet between a pair of embossing rolls and performing embossing, and iii) It includes three steps of a third step of stretching the embossed sheet in at least one direction by 1.2 times to 5 times. Each of these steps will be described.

First, the first step will be described.
In the first step, first, 50 to 90 parts by weight of the crystalline polyolefin resin and the crystalline polyolefin resin which is miscible with the crystalline polyolefin resin under melting and is equal to or lower than the crystallization temperature of the crystalline polyolefin resin. A mixture containing 50 to 10 parts by weight of an organic compound that phase separates is prepared.

Explaining the crystalline polyolefin resin which is one component of the mixture, examples of the crystalline polyolefin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene and ethylene-vinyl acetate. Copolymer, ethylene-
Examples thereof include, but are not limited to, acrylic acid copolymer, polypropylene, ethylene-propylene copolymer, propylene-butene copolymer, ionomer resin and blends thereof. Among these, it is particularly preferable to use a polypropylene resin, a blend of a polypropylene resin and an ethylene-propylene copolymer resin, or a blend of a polypropylene resin and a polyethylene resin. The crystalline polyolefin may be blended with a polyester resin such as polyethylene terephthalate or polybutylene terephthalate as long as the intrinsic properties are not impaired.

The crystalline polyolefin resin preferably has a melt index of 3 g / 10 minutes or less, and more preferably 0.2 to 3 g / 10 minutes. By setting the melt index of the crystalline polyolefin resin to 3 g / 10 minutes or less, the melt tension required at the time of sheet formation can be obtained, and sheet formation can be performed more stably. The melt index is 0.2 g / 10.
If it is less than the minute, there is a case that a large amount of power is required for melt mixing of the crystalline polyolefin resin, and productivity may be lowered, so that it is preferably within the above range. In the present invention, the melt index means
2. According to ASTM D-1238, 230 ° C. in the case of polypropylene and polypropylene-based copolymer, 2.
The value measured under a load of 16 kgf, and in the case of polyethylene, the value measured under a load of 2.16 kgf at 190 ° C.

Explaining the organic compound which is another component of the mixture, the organic compound is miscible with the crystalline polyolefin resin under melting of the crystalline polyolefin resin and the crystalline polyolefin resin. At temperatures below the crystallization temperature of, the phases are separated.
Examples of the organic compound include liquid paraffin and α
-Olefin oligomers, mineral oils, synthetic lubricating oils, various hydrocarbons such as mineral spirits and paraffin wax, and aliphatic carboxylic acids such as dioctyl phthalate, diethyl phthalate, trimethylol propane laurate, distearyl adipate and tetraoctyl pyromellitate Examples thereof include various esters of polyhydric alcohol and polyhydric alcohol, but are not limited thereto. Of these,
It is preferable to use mineral oils, synthetic lubricating oils, paraffin waxes and esters of aliphatic carboxylic acids with polyhydric alcohols. When using the above mixture, a small amount of a water repellent such as silicone oil may be used in combination as long as the original properties are not impaired.

The mixing ratio of the crystalline polyolefin resin and the organic compound in the mixture is 50 to 90 parts by weight of the organic compound to 50 to 90 parts by weight of the crystalline polyolefin resin. If the compounding ratio of the organic compound is less than 10 parts by weight, a porous sheet having sufficient moisture permeability cannot be obtained, and if it exceeds 50 parts by weight, the mechanical strength of the obtained sheet becomes insufficient and the sheet is used for a long time. The organic compound bleeds out from the sheet during storage, which is not practical. The blending ratio is preferably 40 to 20 parts by weight of the organic compound with respect to 60 to 80 parts by weight of the crystalline polyolefin resin.

In addition to the crystalline polyolefin resin and the organic compound, other additives can be added to the mixture as needed. Particularly preferred as such additives are crystal nucleating agents. The use of such a crystal nucleating agent is preferable because it can improve the balance between moisture permeability and mechanical properties of the porous sheet. The crystal nucleus forming agent is preferably blended in an amount of 0.01 to 3 parts by weight, more preferably 0.05 to 1 part by weight. If the compounding amount of the above crystal nucleating agent is less than 0.01 part by weight, a sufficient crystal nucleating effect may not be obtained, and if it exceeds 3 parts by weight, the moisture permeability of the obtained porous sheet is insufficient. Therefore, it is preferable that the amount is within the above range.

The crystal nucleating agent is, for example, 1.
3,2,4-dibedylidene sorbitol, 1,3,2 ・
4-bis (p-methylbenzylidene) sorbitol, 1
3,2,4-bis (p-ethylbenzylidene) sorbitol, sodium bis (4-t-butylphenyl) phosphate, adipic acid, benzoic acid, sodium benzoate, talc, titanium oxide, kaolin and the like. However, the present invention is not limited to these.

When the above crystal nucleating agent is blended, it is preferably blended as a crystal nucleating agent masterbatch.

In addition to the crystal nucleating agent, additives that can be added to the mixture include, for example, inorganic fillers such as calcium carbonate, stabilizers such as antioxidants, antistatic agents, and the like.
Examples include organic pigments and dyes. These additives can be preferably blended in an amount of 0.01 to 10 parts by weight.

In the first step, a sheet is formed from the mixture. The sheet forming method is not particularly limited, and a conventionally known sheet forming method can be used. For example,
The mixture may be inflation-molded or extruded from a T-die to form a sheet, or the sheet may be formed by cast molding or calendar molding. For example, in the case of forming a sheet by inflation molding, the above-mentioned mixture containing the above-mentioned crystalline polyolefin and the above-mentioned organic compound and optional additives is fed from a hopper to a uniaxial or biaxial kneading machine and heated in the kneading machine. A melt-kneaded product is obtained by kneading. Such a melt-kneaded product is supplied to a single-screw extruder, extruded from a ring die connected to the tip, and the extruded melt-kneaded product is pulled upward to form a tube, and air is blown into the tube to form a sheet. Mold.

Further, by compounding the above mixture,
After the pellets are once produced, a sheet may be formed using the pellets as a raw material.

Next, the second step will be described. In the second step, the sheet obtained in the first step is interposed between a pair of embossing rolls for embossing. By performing such embossing,
During the subsequent stretching process, stress concentration is randomly dispersed throughout the sheet, and fine holes are uniformly generated in the sheet. That is, the moisture permeability of the obtained porous sheet is uniform.
Further, embossing also improves the mechanical strength of the sheet.

As the embossing roll, a pair of engraving rolls and a smooth roll are generally used.
As the engraving roll, for example, an iron roll having various patterns engraved on its surface can be used.
On the other hand, as the smooth roll, for example, a paper roll, a cotton roll, a rubber roll, an iron roll, or the like can be used.

In the embossing, the sheet before embossing can be preheated with a heating roll. It is also possible to heat the embossing roll itself and interpose the sheet between the heated rolls for embossing. At the time of heating, it is preferable to set the temperature of the embossing roll to a temperature lower by 10 ° C. or more than the melting point of the crystalline polyolefin resin.

The linear pressure at the time of embossing depends on the thickness of the sheet to be embossed, the heating temperature, and the running speed, but a general range is preferably 5 to 150 kg / cm.

Further, the area (emboss area ratio) of the portion embossed by the embossing is preferably 3 to 80% with respect to the area of the entire sheet, and 10 to 10.
It is more preferably 70%. If the above-mentioned embossed area ratio is less than 3%, stretching unevenness may occur or improvement in mechanical strength cannot be expected, and if it exceeds 80%, sufficient moisture permeability may not be obtained even if the sheet is stretched. Therefore, it is preferably within the above range.

The engraving roll of the embossing roll will be described in more detail. The depth of the unevenness of the engraving of the engraving roll is preferably 10 μm to 3 mm. If the depth is less than 10 μm, it approaches the depth of the unevenness due to the uneven thickness of a normal sheet, and the effect of embossing cannot be expected, and if the depth is 3 mm or more,
The mechanical strength of the sheet obtained as a result of embossing may be significantly reduced and the sheet may be broken in the subsequent stretching step, which makes it unsuitable for industrial production. Is preferred.

Explaining the embossed pattern on the engraving roll, various patterns can be used as the embossed pattern. However, the convex portion on the surface of the engraving roll is a continuous pattern. Is preferable from the viewpoint of improving mechanical strength. In particular, it is preferable to perform embossing of a continuous pattern such as a lattice pattern or a mesh pattern in which the convex portions are continuous, because the mechanical strength in the direction perpendicular to the stretching direction is improved. Further, the continuous pattern is a striped pattern consisting of a number of substantially straight lines,
It is also preferable that the striped pattern has an angle of 0 to 90 degrees with respect to the sheet forming direction from the viewpoint that the strength balance in the direction perpendicular to the stretching direction can be changed by the angle of the striped pattern. Another example of the embossed pattern is preferably one in which the convex portion on the surface of the engraving roll is a pattern pattern (for example, a dot pattern or a turtle shell pattern). By embossing such a pattern,
A porous sheet that has moisture permeability even at a low stretch ratio, can be stretched more uniformly, and has more uniform stretching can be obtained.

Next, the third step will be described. In the third step, the embossed sheet is stretched 1.2 times to 5 times (area ratio) in at least one direction. When the draw ratio is less than 1.2 times, the generation of fine pores is insufficient and sufficient moisture permeability cannot be obtained, and the draw ratio is 5
If it exceeds 2 times, it may be difficult to stably manufacture it because the sheet may be stretched or may be easily torn. The stretching ratio is more preferably 1.2 to 3 times, in order to obtain a better texture and sufficient moisture permeability.

In the stretching step, the sheet may be stretched in at least one direction. For example, in the case of uniaxial stretching, a uniaxial roll stretching machine can be used,
In the case of biaxial stretching, simultaneous biaxial stretching or sequential biaxial stretching can be performed using a tenter stretching machine or a mandrel stretching machine. At this time, the sheet to be stretched may be stretched while being heated.

The method for producing the porous sheet of the present invention has been described in detail above. However, in the method of the present invention, other steps may be carried out, if necessary, in addition to the above first to third steps. Good. For example, the stretched sheet is heat set to improve dimensional stability, and hydrocarbons such as normal hexane or 1,1,2,2-trichloro-1,2,2-trifluoroethane, trichlorofluoro The halogenated hydrocarbons such as methane and dichlorofluoromethane are used to extract the above organic compounds from the stretched sheet, or the stretched sheet is further embossed to reduce the frictional force of the sheet. It may be reduced or the appearance and texture may be improved.

Next, the preferable porous sheet produced by the above-mentioned method of the present invention will be explained. The above-mentioned porous sheet has fine pores from one surface to the other surface, and exhibits moisture permeability through the fine pores. The water vapor permeability of the porous sheet is preferably 480 to 9600 g / (m ² · day), more preferably 1200 to 6000 g / (m ² ), though it depends on its use.
・ Day). If the moisture permeability is less than 480 g / (m ² · day), it will be insufficient for use as a moisture-permeable sheet, and if it exceeds 9600 g / (m ² · day), the water pressure resistance and tear strength will be insufficient. In some cases, the above range is preferable.

The thickness of the porous sheet is preferably about 10 to 300 μm, more preferably 10 to 100 μm, although it depends on its application. If the thickness is less than 10 μm, sufficient strength cannot be obtained, and
If it exceeds 0 μm, the flexibility and texture will be poor, so it is preferable to set it within the above range.

Unlike the conventional porous sheet, the preferred porous sheet produced by the method of the present invention is subjected to an embossing process so that the tensile strength in the direction perpendicular to the stretching direction and the tear in the stretching direction are different from each other. It is characterized by improved strength. Specifically, the tensile strength in the direction perpendicular to the stretching direction is generally 350 to 100.
It is 0 kgf / cm ² . On the other hand, the tear strength in the stretching direction is generally 300 to 700 gf / mm.

The above-mentioned porous sheet has, as described at the beginning,
For example, although it can be used for applications requiring waterproofness and moisture permeability such as waterproof clothing, waterproof covers and packaging materials,
In particular, it is suitably used as a backing material for absorbent articles such as disposable diapers and sanitary napkins. Therefore, as a particularly preferable application of the porous sheet, an example in which the porous sheet is used as a backing material of an absorbent article will be described below with reference to the drawings. Here, FIG. 1 is a perspective view showing a disposable diaper as an example of the absorbent article, and FIG.
[Fig. 2] is a partially broken development view of the disposable diaper shown in Fig. 1.

The disposable diaper 1 shown in FIGS. 1 and 2 is
It comprises a liquid-permeable front surface material 2, a leakproof back surface material 3, and an absorber 4 arranged therebetween, and the porous sheet is used as the back surface material 3.

More specifically, the disposable diaper 1 is
As shown in FIG. 2, the front surface material 2, the back surface material 3, and the absorbent body 4, each of which is molded into an overflowing hourglass shape, include a back waist portion 5 ′, an abdominal waist portion 5, and
The leg portion 6 is formed. In addition, the elastic body 7 is provided between the front surface material 2 and the back surface material 3 in the abdominal waist portion 5, the back waist portion 5'and the leg portion 6, respectively.
Further, a pair of tape fasteners 10 are fixed to the left and right side edges of the back waist portion 5 ', thereby improving the function and performance as a diaper. Further, as shown in FIG. 2, the disposable diaper 1 is formed to be long in the vertical direction, and the surface material 2 and the back surface material 3 are formed to have substantially the same length and width. .

The surface material 2 generally has a basis weight of 15
Although a non-woven fabric of -40 g / m ² is used, a film or a net may be used as long as it is liquid permeable, and it is particularly preferable that the periphery is water repellent and the central portion is hydrophilic.

As the absorbent body 4, a cotton-like material obtained by crushing kraft pulp of softwood is generally covered with water-absorbent paper, and one containing particles of a superabsorbent polymer is particularly preferable. The weight of the cotton-like material is generally about 10 g-40
g. The superabsorbent polymer used in the absorbent may be located in any of the upper, middle and lower layers of the absorbent, or may be mixed with the pulp. Examples of the superabsorbent polymer include starch-based, cellulose-based, and synthetic polymer-based polymers, and examples thereof include starch-acrylic acid (salt) graft copolymers, saponified starch-acrylonitrile copolymers, and sodium carboxymethyl cellulose. Suitable are cross-linked products, acrylic acid (salt) polymers, and the like. The particles of such a high-absorbent polymer have a liquid-absorption retention force of 20 times or more of the own weight and have a gelling property.

Examples of the elastic body 7 include generally polyurethane, natural rubber or the like in the form of a string or ribbon, or a thread which exhibits elasticity when wetted with water. As described above, it is preferable that the number of the devices is approximately five. Further, the attachment length of the elastic body 7 is usually about 30 to about 60% of the length of the diaper, and the extension degree is preferably about 1.3 to about 2.0 times the free length.

Although the flat type disposable diaper has been described as an example of the absorbent article, the absorbent article is not limited to this, and other absorbent articles such as sanitary napkins and incontinence can be used. The porous sheet can be similarly applied to pads, pants-type diapers and the like.

[0044]

EXAMPLES Hereinafter, the method for producing a porous sheet of the present invention and the specific constitution of the porous sheet obtained thereby will be described by way of examples.

Example 1 56 parts by weight of homopolypropylene having a density of 0.91 g / cm ³ and a melt index of 0.4 g / 10 min and ethylene copolymer having a density of 0.91 g / cm ³ and a melt index of 0.5 g / 10 min. 14 parts by weight of polymerized block polypropylene (Chisso Petrochemical Co., Ltd.) and 30 parts by weight of mineral oil (PW-90, Idemitsu Petrochemical Co., Ltd.) were kneaded with a twin-screw type kneader to prepare pellets. The obtained pellets were supplied to an inflation molding machine to mold an inflation sheet having a thickness of 42 μm. The obtained molded sheet is obtained by engraving the convex portions of the engraving roll continuously, the groove depth of the irregularities is 1.6 mm, and the pitch between the convex portions is 2 m.
100 kg / line pressure between a pair of embossing rolls made of a combination of a metal engraving roll (heating temperature of 80 ° C.) with a grid-like mesh pattern and a silicon smoothing roll.
cm, running speed 5 m / min, embossing was performed. Then, it was uniaxially stretched 1.4 times at 50 ° C. using a roll stretching machine to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

[Example 2] 70 parts by weight of homopolypropylene (Chisso Petrochemical Co., Ltd.) having a density of 0.91 g / cm ³ and a melt index of 0.4 g / 10 min, a mineral oil (PW-
90, 30 parts by weight of Idemitsu Petrochemical Co., Ltd., and 0.1 parts by weight of a crystal nucleating agent (EC-1, EC Chemical Co., Ltd.) were kneaded with a twin screw type kneader to prepare pellets. The obtained pellets were supplied to an inflation molding machine to mold an inflation sheet having a thickness of 43 μm. The obtained formed sheet is a metal engraving roll with a vertical stripe pattern in which the convex portions of the engraving roll are continuous and the groove depth of the irregularities is 1 mm, and the pitch between the convex portions is 2 mm (heating temperature 80 ° C.) A linear pressure of 100 kg / cm and a running speed of 5 on a pair of embossing rolls consisting of a combination of paper and paper rolls.
Embossing was performed by passing through at m / min. Then, it was uniaxially stretched 1.4 times at 50 ° C. using a roll stretching machine to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

[Example 3] An inflation-molded sheet obtained by the same method as in Example 2 had continuous engraving roll projections with a groove depth of 1.8 mm and a pitch between projections and projections. A linear pressure of 100 kg applied to a pair of embossing rolls consisting of a horizontal striped metal engraving roll (heating temperature 80 ° C) and a paper roll configured to 2 mm.
/ Cm, the running speed was 5 m / min, and embossing was performed. Then, at 50 ° C. using a roll stretching machine, 1.4
It was uniaxially stretched to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

Example 4 An inflation-molded sheet obtained by the same method as in Example 2 was used as a metal engraving roll (heating temperature 80 ° C.) in which the engraving roll pattern was a dot pattern (dot diameter 0.9 mm) and silicon. A linear pressure of 100 kg /
cm and a running speed of 5 m / min for embossing. Then, it was uniaxially stretched 1.4 times at 50 ° C. using a roll stretching machine to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

Example 5 70 parts by weight of homopolypropylene (Chisso Petrochemical Co., Ltd.) having a density of 0.91 g / cm ³ and a melt index of 0.4 g / 10 min, 30 parts by weight of trimethylolpropane laurate, and crystals. 0.1 part by weight of a nucleating agent (aluminum benzoate) was kneaded with a twin-screw type kneader to prepare pellets. The obtained pellets are fed to an inflation molding machine and the thickness is 42μ.
m inflation sheet. The resulting molded sheet has engraved rolls with continuous projections and uneven grooves with a depth of 1
mm, a vertical striped metal engraving roll (heating temperature 100 ° C.) in which the pitch between the protrusions is 2 mm, and a pair of embossing rolls, which are a combination of a paper roll, a linear pressure of 100 kg / cm, and a running speed. It was passed at 5 m / min for embossing. Then, it was uniaxially stretched 1.5 times at 50 ° C. using a roll stretching machine to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

[Example 6] An inflation-molded sheet obtained by the same method as in Example 5 had continuous engraving roll protrusions with a groove depth of 1.8 mm and a pitch between protrusions and protrusions. A linear pressure of 100 kg applied to a pair of embossing rolls consisting of a horizontal striped metal engraving roll (heating temperature 80 ° C) and a paper roll configured to 2 mm.
/ Cm, the running speed was 5 m / min, and embossing was performed. Then, at 50 ° C. using a roll stretching machine, 1.5
It was uniaxially stretched to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

Example 7 An inflation-molded sheet obtained by the same method as in Example 5 was used as a metal engraving roll (heating temperature 80 ° C.) in which the engraving roll pattern was a dot pattern (dot diameter 0.9 mm) and silicon. A linear pressure of 100 kg /
cm, running speed 5 m / min, embossing was performed. Then, it was uniaxially stretched 1.4 times at 50 ° C. using a roll stretching machine to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

Comparative Example 1 The inflation-molded sheet obtained in Example 1 was uniaxially stretched 1.3 times at 50 ° C. using a roll stretching machine without embossing to obtain a porous sheet. . Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

Comparative Example 2 The inflation-molded sheet obtained in Example 1 was uniaxially stretched 1.6 times at 50 ° C. using a roll stretching machine without embossing to obtain a porous sheet. . Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

Comparative Example 3 The inflation-molded sheet obtained in Example 2 was uniaxially stretched 1.5 times at 50 ° C. using a roll stretching machine without embossing to obtain a porous sheet. . Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

[Comparative Example 4] Linear low density polyethylene 10
0 parts by weight (Ultox 2520F / Mitsui Petrochemical Industry, density 0.925, MFR 2.0), surface treated calcium carbonate (Ryton 22S / Shiraishi Industry: average particle size 1μ
m) 150 parts by weight, and polyester (trimethylolpropane / adipic acid / stearic acid molar ratio = 2/1
/ 4, SV = 240, AV = 1, OHV = 8) 5 parts by weight are mixed in a Henschel mixer, and then the mixture is extruded into strands using a twin-screw extruder with a screw diameter of 45 mm, and the strands are cut into pellets. did. The pellets thus obtained are fed to an inflation molding machine to obtain a thickness of 50
A μm inflation sheet was molded. The obtained formed sheet is a metal engraving roll with a grid-like mesh pattern in which the convex parts of the engraving roll are continuous, the groove depth of the concavo-convex groove is 1.6 mm, and the pitch between the convex part and the concave part is 2 mm. Temperature 6
(0 degree) and a pair of embossing rolls made of a combination of silicon rolls, linear pressure of 100 kg / cm, traveling speed of 5 m
/ Min, and embossed. Then, it was uniaxially stretched 2.0 times at 50 ° C. using a roll stretching machine to obtain a porous sheet. Then, using the obtained porous sheet as a backing material, a disposable diaper shown in FIGS. 1 and 2 was produced.

<Performance Evaluation> In order to evaluate the performance of the porous sheets obtained in Examples and Comparative Examples, their thickness, embossed area ratio, tensile strength, tear strength and moisture permeability were measured.
Table 1 shows the results. The tensile strength, tear strength and moisture permeability were measured by the following procedure.

<Tensile Strength> The tensile strength was measured by measuring the tensile strength in the direction perpendicular to the forming direction (longitudinal direction) of the porous sheet (lateral direction), and the breaking strength of the test sheet was taken as the tensile strength. . The dimensional width of the test sheet was set to 10 mm, and the tensile strength was measured using a Tensilon universal testing machine under tension conditions of a chuck distance of 50 mm, a pulling speed of 300 mm / min, and room temperature.

<Tear Strength> The tear strength is measured by measuring the tear strength in the molding direction (longitudinal direction) of the porous sheet, with the width of the test sheet being 30 mm and the length being 60 mm, and the center of the short side of the test piece. From inside to parallel to the long side about 30mm in length
Make a cut. Attach it to the tensile tester so that both sides of the cut side of the test piece are front and back, and pull speed 3
The tear average load was measured at 00 mm / min.

<Moisture Permeability> The moisture permeability is measured according to JIS Z-
0208, temperature 30 ℃, relative humidity 90 ± 2
It was measured under%.

[0060]

[Table 1]

As is clear from the above results, the porous sheets (Examples 1 to 7) obtained by the method of the present invention, in which the embossing is followed by the stretching, are high in moisture permeability, and the tensile strength and tear strength are high. It turns out that is high.
On the other hand, it can be seen that the tensile strength and tear strength in the transverse direction are low in the porous sheets (Comparative Examples 1 to 3) that were stretched without embossing. Further, it is understood that the tensile strength of the inorganic filler-based porous sheet (Comparative Example 4) is insufficient.

[0062]

As described above in detail, the porous sheet obtained by the method of the present invention has the mechanical strength, flexibility and transparency required for the backing material in absorbent articles such as disposable diapers and sanitary napkins. It becomes wet. Moreover, since the stretching step is performed after the embossing, the obtained porous sheet does not become translucent. Further, according to the method of the present invention, such a porous sheet can be mass-produced easily and inexpensively.

[Brief description of drawings]

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

FIG. 2 is a partially cutaway exploded view of the disposable diaper shown in FIG.

[Explanation of symbols]

 1 Disposable diaper 2 Liquid permeable surface material 3 Leakproof back surface material 4 Absorber 5 Abdominal waist portion 5'Back waist portion 6 Leg portion 7 Elastic body 10 Tape fastener

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B29K 105: 04 B29L 7:00 C08L 23:02 (72) Inventor Yoshihiro Sakai Kai Town, Haga-gun, Tochigi Prefecture 2606 Akabane Inside Kao Institute of Stock Companies (72) Inventor Kazuo Fujita 2606 Akabane Kaiga-cho, Haga-gun, Tochigi Prefecture Inside Kao Institute of Stock Companies

Claims (7)

[Claims] 1. An organic compound which is miscible with 50 to 90 parts by weight of a crystalline polyolefin resin and the crystalline polyolefin resin under melting, and phase-separates below the crystallization temperature of the crystalline polyolefin resin. A sheet is formed from a mixture containing 50 to 10 parts by weight of a compound, the sheet is interposed between a pair of embossing rolls for embossing, and then the embossed sheet is applied in at least one direction by 1.2. A method for producing a porous sheet, which comprises stretching the sheet 5 times to 5 times. 2. The method for producing a porous sheet according to claim 1, wherein the projections on the surface of the engraving roll of the embossing roll have a continuous pattern. 3. The porosity according to claim 2, wherein the continuous pattern is a striped pattern composed of a plurality of substantially parallel straight lines, and the striped pattern has an angle of 0 to 90 degrees with respect to a sheet forming direction. Of manufacturing a flexible sheet. 4. The method for producing a porous sheet according to claim 1, wherein the protrusions on the surface of the engraving roll of the embossing roll are patterned. 5. An organic compound which is miscible with the crystalline polyolefin resin in an amount of 50 to 90 parts by weight of the crystalline polyolefin resin and melts with the crystalline polyolefin resin, and phase-separates below the crystallization temperature of the crystalline polyolefin resin. A porous sheet obtained by subjecting a sheet formed from a mixture containing 50 to 10 parts by weight of a compound to embossing, and then stretching the sheet by 1.2 to 5 times in at least one direction. 6. The mixture further comprises a crystal nucleating agent,
The porous sheet according to claim 5. 7. An absorbent article comprising a liquid-permeable surface material, a leak-proof backing material, and an absorber arranged between them, wherein the backing material is the backing material. An absorbent article, characterized in that a porous sheet is used.