JPS62282003A - Back sheet for disposable diaper and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a vapor-permeable and liquid-impermeable backsheet for disposable diapers that has particularly excellent flexibility and tensile/tear strength. and its manufacturing method.

(Conventional technique).

In recent years, disposable diapers, which are mainly composed of a liquid-permeable sheet, a liquid absorber, and a liquid-impermeable backsheet, have become extremely popular because they are convenient and easy to handle. As a backsheet for such disposable diapers, it is of course impermeable and vapor permeable. Ti
Functions such as moisture permeability, flexibility, and tensile/tear strength are required. Conventionally, for back sheets of disposable diapers, for example, a sheet made by melting a resin composition consisting of polyolefin and barium sulfate, forming a film, and then stretching it (Japanese Patent Application Laid-Open No. 1983-1999)
No. 185803), a film made by stretching a film of a composition consisting of a polyolefin, a filler, and a liquid or waxy hydrocarbon polymer to create micropores (1M No. 14930'5), or a film with a shape and physical properties. Identified sheet (% open/close No. 57-205505, Utsukai Showa 5
No. 9-69906) etc. have been proposed.

However, the backsheet of the disposable diaper proposed above does not satisfy all the required functions. A back sheet of a disposable diaper that has been given flexibility to a certain extent generally has a relatively weak tensile and tear strength, and therefore has the problem of breakage in practical use.

(Problems to be Solved by the Invention) Therefore, in view of the above problems, the object of the present invention is to improve physical properties such as liquid impermeability, vapor permeability, flexibility, strength, etc.
The object of the present invention is to provide a backsheet for disposable diapers, which is a porous sheet with excellent tear strength particularly in the width direction.

(Means for Solving Problem 151) As a result of intensive studies to solve the above problems, the present inventors found that a porous sheet obtained by biaxially stretching a sheet-like material of a specified polyolefin resin composition. It was discovered that the material has desired physical properties suitable for use as a backsheet for disposable diapers, and the present invention was proposed. That is, the present invention has an air permeability of 500 to 5000 seconds/1oocc and a moisture permeability of 100
0-600011/d・24 hr *Tensile strength 5O-
400Kf/d, tear strength 50-250#, flexibility 2
This is a backsheet for disposable diapers made of a biaxially stretched polyolefin sheet having a thickness of 0 to 60μ and a thickness of 20 to 80μ. Such a backsheet for disposable diapers of the present invention contains a composition consisting of 100 parts by weight of a polyolefin resin, 50 to 400 parts by weight of a filler, and 0.1 to 10 parts by weight of a silicone oil and/or a polyglycerol fatty acid ester surfactant. After forming into a sheet, it can be obtained by stretching in uniaxial and biaxial directions at a stretching ratio of 1.1 to 2.5 times, respectively.

The backsheet for disposable diapers of the present invention is described in detail in J.
Based on IS P8117 method (air permeability 500-5000)
sec/100cc, preferably 600-3000 sec/10
Based on the 0CC,'J'l8Z0208 method, the moisture permeability at a temperature of 40°C and a relative humidity of 90% is 1006 to 6.
oooy/rr?・2'4 hr, preferably 50
0'02500011'/m"24hr,'JIB F
Tensile strength based on 8115 method is 50~AOtJKI/a
11. Preferably 0-380Kg, JI8L
Tear strength based on 1085A-1 method is 5022509
．． Preferably 70-230#, flexibility based on JIB L1079 Clark method 20-60#, preferably 2
0-50μ and thickness 20-80μ, preferably 20
It is important that the thickness is ~60μ. That is, as a back sheet for disposable diapers, the air permeability of the sheet is 500.
Greater than 0 seconds/1oocc or moisture permeability is 100011
/nl・24 hr or less, the prevention of stuffiness when wearing disposable diapers is insufficient, and the air permeability is less than 500 seconds/1oocc or the moisture permeability is 60
If it is larger than 00II/-24hr, there is a fear of liquid leakage, and at the same time physical properties such as tear strength deteriorate, which is not preferable. In addition, if the tensile strength is less than 50 #/cd or the tear strength is less than 50I, it is easy to tear.
Conversely, it is desirable to have high tensile strength and tear strength, but the tensile strength is greater than 400-/- or the tear strength is bt25.
If it is thicker than 01, the moisture permeability will decrease.
When wearing it because it loses its flexibility? The fit to the skin is reduced. In particular, the backsheet for disposable diapers of the present invention has tensile strength and tear strength in uniaxial and biaxial directions of 50 Kf/- and 50g or more, respectively, in order to improve the releasability of the tape attached to the backsheet. suitable. In addition, if the sheet of the present invention has a flexibility lower than 201 m, the strength will be significantly reduced and defects such as easy tearing will occur, and if the flexibility is higher than 60, it will feel stiff. This is undesirable because the fit during installation deteriorates. Furthermore, if the sheet of the present invention is thinner than 20 μm, its strength will be poor, and if it is thicker than 80 μm, it will have poor flexibility, making it unsuitable as a back sheet for disposable diapers. Other physical properties include JIBL1092. Water pressure resistance according to the law is 500011
The backsheet for disposable diapers of the present invention having the above-mentioned physical properties is preferably made of a composition comprising a polyolefin resin, a filler, and a silicone oil and/or a polyglycerin fatty acid ester surfactant. It is suitably obtained by a method of forming into a shape and then biaxially stretching it.

As the polyolefin resin used in the present invention, homopolymers or copolymers of olefins such as ethylene, fluoropylene, and butene-1 can be used without particular limitation, but medium density polyethylene and linear low density polyethylene are particularly preferred. Density is 0.910-0.940.9/- and melt flow index (MFI) #to, 1-10j
Linear low density polyethylene of 1/10 min, preferably 0.1 to 5 Ii/10 min, is preferably used. Also, in one aspect of the present invention.

It is also possible to add or mix a small amount of one or more of, for example, high-density polyethylene, polypropylene, polybutene-1, etc. to the above-mentioned linear low-density polyethylene, and the thickness of the stretched sheet obtained by this addition and mixing can be adjusted. , especially tensile
Physical properties such as argument strength and flexibility can be adjusted as desired. .

The filler included in KJfl in the present invention is not particularly limited, but fillers usually mixed into rubber or plastics include calcium carbonate, gypsum, calcium sulfite, calcium phosphate, magnesium carbonate, basic magnesium carbonate, magnesium sulfate, and water. Japanese silicic acid, anhydrous silicic acid, powder ash, sodium chloride, barium sulfate, clay.

Various cements, volcanic ash, shirasu, titanium oxide.

Iron oxide, carbon black, various metal powders.

They are other inorganic substances or organic metal salts mainly composed of inorganic substances, and are generally used as powder or granules having an average particle diameter of 5 μm or less, varying from 0.1 to 3 μm. If a filler having an average particle diameter that is too large is used, the resulting stretched sheet will have poor pore density and poor water resistance. Furthermore, if a filler having an average particle diameter that is too small is used, a good porous sheet cannot be obtained if stretching unevenness occurs. The blending ratio of the filler is 50 to 100 parts by weight of the polyolefin resin.
400 parts by weight, preferably 60 to 300 parts by weight,
When the amount is less than 50 parts by weight, the number of communicating pores in the resulting porous sheet decreases, resulting in a decrease in moisture permeability.
If it exceeds 0.00 parts by weight, it becomes difficult to form and stretch a sheet-like product.

The silicone oil used in the present invention is generally not particularly limited as long as it has heat resistance to the extent that it does not volatilize at the melting temperature of the polyolefin resin;
50QOOO senna stroke (cat), preferably 500 to 100.000 cst, is suitable, and for example, polydimethylsiloxane, polymethylphenylsiloxane, etc. are preferably used. In addition, the polyglycerin fatty acid ester surfactant is an ester compound of polyglycerin and fatty acid obtained by dehydration of glycerin, and the degree of condensation of glycerin is usually 3 to 10, and higher fatty acids such as It refers to a compound that is partially or completely esterified with a carboxylic acid, and those with an HLB of 6 or less, preferably 3 or less and 4 are preferably used in order to obtain good volatility.

In the present invention, the silicone oil described above is used.

By blending at least one of the polyglycerin fatty acid ester surfactants with the resin 1-9 and the filler, a stretched sheet having a uniform predetermined thickness can be obtained satisfactorily, and the desired thickness can be obtained. A sheet having the following physical properties can be obtained.The blending amount of the silicone oil and/or polyglycerin fatty acid ester surfactant is the same as that of the polyolefin resin io.

Preferably, it is 0.1 to 10 parts by weight, and 1 to 5 parts by weight, and if it is less than 0.1 parts by weight, it will not uniformly whiten during uniaxial stretching, so-called stretching unevenness will occur. If the amount is more than 10 parts by weight, extrusion moldability becomes uneven, making it difficult to obtain a sheet with a uniform thickness.

In the present invention, the polyolefin resin composition is generally prepared using a high-speed stirring (mixing) machine such as a Henschel mixer, after adding and mixing silicone oil and/or polyglycerin fatty acid ester surfactant to the filler. Mix the mixture with polyolefin resin powder or pellets, or use the above mixer to add silicone oil and/or polyglycerin fatty acid ester surface active to the mixture of polyolefin resin powder or pellets and filler. After adding and mixing the ingredients, the mixture is kneaded using a mixing roll or screw extruder. In such preparations, a small amount of stabilizer.

Pigments or stearic acid and its metal salts for imparting fluidity can be mixed simultaneously or separately.

A method of biaxially stretching the above-mentioned polyolefin resin composition after forming it into a sheet is to form a sheet by, for example, an inflation molding method, an extrusion molding method using a tie die or an annular die, and then, for example, by a roll stretching method.
After axial stretching, there are no particular restrictions on methods such as subsequent biaxial stretching using a tenter stretching machine, air inflation method, mandrel stretching method, etc. After forming, the sheet is stretched in the uniaxial (longitudinal) direction by a roll stretching method, and then biaxially (lengthwise) by a mandrel stretching method.
(1) As a method for manufacturing unstretched raw sheets, the method for manufacturing cylindrical sheets using the inflation method is simpler and simpler than the T-die method, although the thickness accuracy is inferior to that of the T-die method. By rotating the die, a final product with a good shape can be obtained, and
There are also few Etziros.

(2) As a biaxial stretching method, the cylindrical stretching method has great economic advantages, such as lower equipment costs and less utility than the single tenter method.

These two points are more preferably adopted as percentages.

Uniaxial stretching is 1.1 to below the softening point of polyolefin resin.
Stretch 2.5 times, preferably 1.2 to 2 times. In the mandrel stretching method, the stretching temperature is 1.1 to 2.5 times, preferably 1.2 to 2 times, at a temperature below the softening point of the polyolefin resin.
Stretch twice.

The biaxially stretched sheet may be slit and wound as is, or the dimensional stability may be improved by heat treatment, and then the sheet may be slit and wound.

(Effect) The sheet thus obtained has an air permeability of 500 to 5000 seconds/100CC.
1000~60001/nl 24hr tensile strength 5
0 to 4/cIA~40 low/-Tear strength 509~2
501 Since the book has the property of flexibility 20■~60■, the thickness is 20~80μ,
Good breathability, moisture permeability, and water resistance, making it flexible and vertical (MD)
This sheet has excellent tensile strength and tear strength in both the transverse (TD) direction and is suitable as a backsheet for disposable diapers.

(Example) Examples and comparative examples will be shown below, and their physical properties were measured by the method shown below.

■ Tensile strength and elongation: Measured according to JIS P8113 (Tensile speed 200m/■) ■ Tear strength: JI
Measured according to SL1085 A-1 method ■ Moisture permeability: 40℃, relative humidity 90%, JIS Z
Measured according to 0208■ Water resistance; JIS L10
Measured according to 92B method (hydrostatic pressure method) ■ Air permeability: Measured according to JIS P8117 ■ Flexibility: Measured according to JIS L1079 method (Clark bending test method) ■ Tape removability: on the sheet 19m wide sellotape M
It was pasted on each of the D and TD directions, and the state of peeling when peeled off was evaluated based on the following criteria.

■ Diaper wearing test: The back sheet of an adult diaper (commercially available) was cut out as shown in Figure 1, and a sample sheet was welded to each of the traces to perform a stuffiness test.

(Evaluation) Three adults wore the sheets and evaluated whether they felt stuffiness using the non-perforated bank sheet as a standard as follows.

Example 1 and Comparative Example 1.2 Linear low-density polyethylene (manufactured by Sumitomo Chemical ■).

, xj car kyL FA201-0. MFI=2)1
00 parts by weight, 120 parts by weight of heavy calcium carbonate (manufactured by Shiraishi Calcium ■, Wheaton 5sB (red), particle size 1.2μ) and silicone oil (manufactured by Toshiba Silicon ■, T8F).
-451.

A composition consisting of 3 parts by weight (viscosity 10,000 cst) was mixed in a super mixer and then formed into pellets in a twin screw extruder. This bellet raskrieux diameter 50■φ, die diameter 1
A cylindrical sheet with a thickness of 50 μm and a folded diameter of 380% was molded using a 50 μΦ inflation extruder under the following conditions.

(Extrusion conditions) - Cylinder temperature: 160.170.175°C - Adapter I: 180°C - Die I: 180°C - Screw rotation speed: 60 rpm - Take-up speed: 10 m/m1n Next, the folded sheet is heated at 60° C. using a roll stretching machine. The film was uniaxially stretched to 1.4 times.

Further, this -axially stretched sheet was subjected to two-wheel stretching using a biaxial stretching machine having the following structure. In other words, 2CIPI) As an axial stretching device, a mandrel having a preheating section and a width expanding stretching section is suspended by a feeding roll, the mandrel is externally heated by an air ring, and a take-up roll takes up the stretched sheet. It is something.

Using this biaxial stretching apparatus, a uniaxially stretched sheet having a fold diameter of 350 square meters was stretched in the transverse direction at 80 DEG C. by a factor of 1.4, cooled, and wound up. The resulting sheet had a thickness of 40 microns, and the effective stretching ratio of the sheet was 1.4 x 1.3.

In addition, the thickness of the die lip was changed in Comparative Example 1.2, and blown raw sheets having a thickness of 20 μm in Comparative Example 1 and 120 μm in Comparative Example 2Vc were similarly stretched uniaxially and with two wheels. Table 1 shows the results of measuring the properties of the obtained sheet.

Comparative Examples 3 and 4 The same composition as in Example 1 was inflation extruded under the same conditions as in Example 1, then uniaxially stretched to 1.4 times and 2.6 times, respectively, and then biaxially stretched to 180 times and rolled. I took it. The obtained sheet width was 550 square meters in the case of 1.4 times, and 315 square meters in the case of 2.6 times. The properties of the obtained sheet are shown in Table 1.

Comparative Example 5.6 Table 1 shows the physical properties of commercially available breathable backsheets for disposable diapers and non-porous backsheets for disposable diapers.

From the results of Example 1 and Comparative Examples 1 to 6, Example 1 had superior tensile strength in the transverse direction and tear strength in the longitudinal direction compared to the commercially available breathable backsheet (Comparative Example 5), and a tape peel test was conducted. On the other hand, Comparative Example 5 was easily torn in the longitudinal direction in the tape peeling test, but in Example 1, the sheet was only stretched, but the tape and the sheet did not peel and tear. Also,
In comparison with Comparative Examples 6 and 3, Example 1 was clearly effective in preventing stuffiness in the diaper wearing test. Furthermore, in Comparative Example 1.2, when the thickness of the sheet was thin, a decrease in strength was observed, and when the sheet was thick, the flexibility was poor.

In Comparative Example 4, the tape releasability was poor due to the high stretching ratio.

Examples 2, 3.4 and comparative examples 7, 8 Linear low-density polyethylene (manufactured by Susumu Kagaku ■).

Sumikasen L-FA201-0. MFR=2')10
0 parts by weight of heavy calcium carbonate (manufactured by Shiraishi Calcium ■,
Whiten 5sB (red), particle size 1.2μ) was added to the book with varying amounts of silicone oil (Toshiba Silicone■ 1ll).
J, 'r8F-451, viscosity 6000 cst) were added to each, and after longitudinal stretching at 60°C in the same manner as in Example 1, stretching was carried out at 80°C along a mandrel.
．． It was laterally stretched 4 times.

The results obtained are shown in Table 2.

Examples 5.6.7 and Comparative Examples 9 and 10 Linear low-density polyethylene (manufactured by Sumitomo Chemical ■).

Sumikasen L, VFR=2) 90 parts by weight and high-density polyethylene (Showa Denko ■, Shorex N5008,
MFR=0.9) 100 parts by weight of a resin mixture containing 100 parts by weight of heavy calcium carbonate (manufactured by Shiraishi Calcium ■, Whiten 5SB (red) 1.2μ) and silicone oil (manufactured by Toshiba Silicone ■, T8F- 433, viscosity 450 cst) was granulated in the same manner as in Example 1, and after forming an extruded sheet, the uniaxial stretching ratio was varied, and the composition was further biaxially stretched in the same manner as in Example 1. The results obtained are shown in Table 3.

From the results obtained, the stretched sheet obtained in Comparative Example 9 had slightly inferior thickness accuracy and low moisture permeability. Example 5.6
．． No. 7 had good strength and moisture permeability. Comparative Example 10 had poor tear strength and tape releasability.

Example 8.9 and Comparative Example 11.12 After extrusion molding in the same manner as in Example 5, the uniaxial stretching was kept constant at 1.5 times at 60°C, and the diameter of the preheated part of the cylindrical mandrel was Transverse stretching was carried out under a constant pressure and with the ratio of the maximum wave part of the mandrel expansion part to 16 times, 2.2 times, and 5.4 times. The results are shown in Table-3. In Examples 8 and 9, stretched sheets with good properties were obtained, but in Comparative Example 12
Stretching was difficult with a mandrel that was 6.4 times larger than that of 6.4, and it broke immediately. Moreover, Comparative Example 11 was a sheet that was uniaxially stretched only, and this sheet had low air permeability and low moisture permeability.

Examples 10-14 and Comparative Examples 16-15 Linear low-density polyethylene (manufactured by Susumu Kagaku ■).

Sumikasen L, FA-201-0, MFR=2) 100
1 part by weight. , 120Ji parts of calcium carbonate (manufactured by Shiraishi Calcium ■, Whiten ssB, particle size 1.2μ) was added, and silicone oil (Toshiba Silicone ■lft) was added.
, TSF451i0000), Decaglyceryl Decaine Stearate (manufactured by Nikko Chemicals ■, Decaglin 1O)
Biaxial stretching was carried out in the same manner as in Example 1 while changing the amount of -Is) added. The results are shown in Table-4. Comparative example 13 is -
In the axial stretching, there was large stretching unevenness and a uniformly whitened sheet could not be obtained. Further, in Comparative Examples 14 and 15, the thickness accuracy was poor during extrusion, and breakage occurred at the biaxially stretched portion, resulting in failure to obtain a biaxially stretched sheet.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of the diaper used for the diaper wearing test.

Claims (1)

[Claims] 1) Air permeability 500-5000 seconds/100c. c. , moisture permeability 1000-6000g/m^2・24hr, tensile strength 50-400Kg/cm^2, tear strength 50-250g
, a back sheet for disposable diapers made of a biaxially stretched sheet made of polyolefin having a flexibility of 20 to 60 mm and a thickness of 20 to 80 μm 2) 100 parts by weight of polyolefin resin, 50 to 4 parts by weight of filler
After forming a composition consisting of 0.00 parts by weight and 0.1 to 10 parts by weight of silicone oil and/or polyglycerin fatty acid ester surfactant into a sheet shape, each stretch ratio was 1.1.
Method for producing a backsheet for disposable diapers, characterized by stretching in uniaxial and biaxial directions at ~2.5 times 3) After forming into a cylindrical sheet, the sheet is stretched in the longitudinal (length) direction by 1.1 times. The method for producing a backsheet for disposable diapers according to claim 2, which is stretched by a factor of 2.5 times and then 1.1 to 2.5 times in the transverse direction by a mandrel stretching method.