JP5188117B2 - Elastic filament and elastic sheet using the same - Google Patents

Description

  The present invention relates to an elastic filament, an elastic sheet using the same, and an absorbent article.

  For example, in an absorbent article such as a disposable diaper, a stretchable member is used for preventing slipping off and improving fit, and as the stretchable member, an elastic fiber and a nonwoven fabric are combined. An elastic sheet is used. Since the stretchable sheet is excellent in texture and touch, it is particularly suitable for applications that require good touch feeling such as disposable diapers.

  As a conventional technique related to an elastic sheet, for example, Patent Document 1 discloses that a molten thermoplastic material (for example, elastomer-based polyester, polyurethane, polystyrene-polyisoprene-polystyrene, which has elasticity when cooled on one surface of a sheet made of nonwoven fabric or the like). There is described an elastic sheet-like composite material in which elastic strands made of polystyrene-polybutadiene-polystyrene or polystyrene-poly (ethylene-butylene) -polystyrene) are arranged so as to extend in one direction without crossing each other. Such a stretchable sheet in which a plurality of filaments are arranged so as to extend in one direction without crossing each other is melted from a plurality of spinning nozzles arranged at predetermined intervals in a direction perpendicular to the sheet conveying direction. Manufactured by extruding a filament and fusing it to the sheet.

  However, in the above-described method for producing an elastic sheet, the filament extruded in a molten state from the spinning nozzle may meander due to the influence of wind, static electricity, etc. before being fused to the sheet. As a result, filaments that should originally extend straight in one direction in the final product are joined on the sheet in a meandering state, and there is a problem that it is impossible to manufacture an elastic sheet in which a plurality of filaments are arranged at equal intervals. The meandering of the filament can be prevented by pulling the filament extruded from the spinning nozzle with a certain tension or more. However, if a tension that is effective for preventing meandering is applied to the melted filament, the filament breaks. In some cases, the filament could not be formed by spinning. In particular, when the filament diameter is small, yarn breakage often occurs due to take-up, and the productivity of the stretchable sheet is seriously lowered. On the other hand, the filament diameter tends to be desired to be thinner than the elastic yarn used for absorbent articles such as commercially available diapers from the viewpoint of improving the texture of the stretchable sheet.

Japanese National Patent Publication No. 10-501195

  Accordingly, an object of the present invention is to provide an elastic filament that is excellent in spinning moldability, does not cause yarn breakage when pulled from a spinning nozzle, and is difficult to meander, and an elastic sheet and an absorbent article using the elastic filament.

  The present invention comprises an A1-B-A2 type triblock copolymer comprising polymer blocks A1 and A2 mainly composed of vinyl aromatic polymer and polymer block B mainly composed of polyolefin. An elastic filament composed of a resin composition having a total weight average molecular weight of 14,000 to 20,000 as measured by gel permeation chromatography of each of the polymer blocks A1 and A2, and the polymer block B The object is achieved by providing an elastic filament having a weight average molecular weight of 40,000 to 80,000 as measured by gel permeation chromatography.

In addition, the present invention achieves the above object by providing an elastic sheet in which a large number of elastic filaments arranged so as to extend in one direction without crossing each other are joined to at least one surface of a stretchable nonwoven fabric. It is.
Moreover, this invention achieves the said objective by providing the absorbent article using the said elastic sheet.

The elastic filament of the present invention is excellent in spinning moldability, and even when the diameter is small, can be discharged from the spinning nozzle without causing yarn breakage and meandering, and high-speed production is possible.
In addition, since the elastic sheet of the present invention is configured to include the elastic filament, for example, various clothes including absorbent articles such as disposable diapers, and other articles formed on the human body. When applied as a material, it exhibits excellent fit by the action of the elastic filament and can effectively prevent the clothes from slipping off.
Moreover, since the absorbent article of this invention is comprised including the said expansion-contraction sheet | seat, it is excellent in the fitting property in mounting | wearing, and does not slip down easily.

[Elastic filament]
Hereinafter, the elastic filament of the present invention will be described.
The elastic filament of the present invention comprises an A1-B-A2 type triblock copolymer comprising polymer blocks A1 and A2 mainly composed of vinyl aromatic polymer and polymer block B mainly composed of polyolefin. It consists of the resin composition comprised by these.

Further, the total weight average molecular weight measured by the gel permeation chromatography (GPC) method of each of the polymer blocks A1 and A2 is 14,000 to 20000, preferably 14,000 to 18000, and the GPC of the polymer block B The weight average molecular weight measured by the method is 40,000 to 80,000, preferably 40,000 to 70,000.
In this specification, the weight average molecular weight measured by the GPC method is as follows: column: TSKgel G-2000H, column temperature: 40 ° C., mobile phase: tetrahydrofuran (THF), flow rate: 1.0 mL / min, sample concentration: 10 mg / 5 mL-THF, injection amount: 500 μL, measured under the conditions and converted by polystyrene. As a pretreatment, an analysis sample is prepared by dissolving 10 mg of a sample in 5 mL of tetrahydrofuran at room temperature for 10 minutes and then filtering with a sintered filter having a pore size of 0.45 μm.

When the resin composition contains two or more types of A1-B-A2 type triblock copolymers, for example, the “weight average molecular weight measured by GPC method of polymer block A1” is 2 It is calculated | required as a weight average value of the weight average molecular weight measured by GPC method of each polymer block A1 of A1-B-A2 type | mold triblock copolymer more than a kind.
That is, for example, when the resin composition is an A1-B-A2 type triblock copolymer, two types of (A1′-B′-A2 ′) and (A1 ″ -B ″ -A2 ″) are used. A content of (A1′-B′-A2 ′) [two or more kinds of A1-B-A2 type triblock copolymers contained in the resin composition, including an A1-B-A2 type triblock copolymer The content of A1′-B′-A2 ′ in the total amount] is 80% by weight, and the content of (A1 ″ -B ″ -A2 ″) is 20% by weight. The “weight average molecular weight measured by the GPC method of A1” is obtained by the following formula. (Weight average molecular weight measured by GPC method of polymer block A1 ′) × 0.8 + (Weight average molecular weight measured by GPC method of polymer block A1 ″) × 0.2
In the case where the resin composition contains two or more kinds of A1-B-A2 type triblock copolymers, the “weight average molecular weight of polymer block A2 measured by GPC method” and “polymer block” The “weight average molecular weight measured by the GPC method of B” is also determined in accordance with the above example for the polymer block A1.
In the case where the resin composition contains two or more types of A1-B-A2 type triblock copolymers, the “weight average molecular weights measured by the GPC method of each of the polymer blocks A1 and A2” “Total” is the sum of the weight average values of the weight average molecular weights of the polymer blocks A1 and A2 thus obtained.

  The elastic filament of the present invention is made of a resin composition containing an A1-B-A2 type triblock copolymer that satisfies the above physical properties. It is possible to perform discharge molding from the spinning nozzle without causing wrinkles and meandering. The elastic filament of the present invention is a long fiber having elasticity. Elasticity is the property of being able to stretch and contract when released from the stretched force.

  The polymer block A1 is mainly composed of a vinyl aromatic polymer. Examples of the vinyl aromatic constituting the vinyl aromatic polymer include styrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, α-methylstyrene, chloromethylstyrene, p-tert-butoxy. Styrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, vinyltoluene, 1-vinylnaphthalene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4- (phenylbutyl) Examples include styrene. A vinyl aromatic polymer may be comprised from 1 type of these vinyl aromatics, and may be comprised from 2 or more types. Of these vinyl aromatics, styrene is preferable from the viewpoint of ease of polymerization and versatility.

  The content of the vinyl aromatic polymer in the polymer block A1 is preferably 90 to 100% by weight, more preferably 95 to 100% by weight, based on all the structural units of the polymer block A1.

  The polymer block A1 may include a conjugated diene compound polymer in addition to the vinyl aromatic polymer. Examples of the conjugated diene compound constituting this conjugated diene compound polymer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 2-methyl-1,3. -Pentadiene, 1,3-hexadiene, phenylbutadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene and the like. The conjugated diene compound polymer may be composed of one of these conjugated diene compounds, or may be composed of two or more.

  The content of the conjugated diene compound polymer in the polymer block A1 is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, based on all structural units of the polymer block A1.

  The weight average molecular weight measured by GPC method of the polymer block A1 is preferably 7000 to 10000, more preferably 7000 to 9000.

As polymer block A2, the thing similar to polymer block A1 mentioned above can be used. For the points not specifically described for the polymer block A2, the description for the polymer block A1 is appropriately applied.
In the A1-B-A2 type triblock copolymer used in the present invention, the polymer block A1 and the polymer block A2 may have the same structure or different structures.

  In particular, it is preferable that the polymer blocks A1 and A2 are both polystyrene. That is, the elastic filament of the present invention preferably has a configuration containing only polystyrene as the polymer block A1 and only polystyrene as the polymer block A2.

  The total content of the polymer blocks A1 and A2 in the A1-B-A2 type triblock copolymer is preferably 15 to 40% by weight with respect to the total structural units of the A1-B-A2 type triblock copolymer. More preferably, it is 18 to 30% by weight.

  As described above, when both of the polymer blocks A1 and A2 are polystyrene, the ratio of the polymer block A1 and the polymer block A2 in the A1-B-A2 type triblock copolymer is a weight ratio, Preferably (A1 / A2) = 0.8 to 1.2, and more preferably (A1 / A2) = 0.9 to 1.1.

  The polymer block B is mainly composed of polyolefin. Examples of the olefin constituting the polyolefin include isoprene, butadiene, ethylene, propylene, butylene and the like. The olefin constituting the polymer block B may be composed of one of these olefins or may be composed of two or more. Among these olefins, ethylene and propylene are preferable from the viewpoint of weather resistance and stretchability.

  The content of the polyolefin in the polymer block B is preferably 90 to 100% by weight, more preferably 95 to 100% by weight, based on all the structural units of the polymer block B.

  In addition to the polyolefin, the polymer block B may be composed of another polymer derived from another polymerizable monomer and capable of polymerizing with the polyolefin. Examples of the other polymerizable monomer include styrene. The other polymer polymerizable with the polyolefin constituting the polymer block B may be composed of one of these other polymerizable monomers or may be composed of two or more.

  The content of the other polymer in the polymer block B is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, based on all structural units of the polymer block B.

  Specific examples of the polymer block B include polyisoprene, polybutadiene, poly (ethylene-propylene), poly (ethylene-butylene) and the like. Among these, poly (ethylene-propylene) is preferable because of weather resistance and stretchability.

  The content of the polymer block B in the A1-B-A2 type triblock copolymer is preferably 60 to 85% by weight, more preferably based on all structural units of the A1-B-A2 type triblock copolymer. Is 70 to 82% by weight.

  Specific examples of preferred A1-B-A2 type triblock copolymers include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and hydrogenated SBS. Styrene-ethylene-butylene-styrene block copolymer (SEBS), SIS hydrogenated styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer Examples include coalescence (SEEPS). Among these, SEBS, SEPS, and SEEPS are preferable because an elastic filament excellent in thermal stability and weather resistance can be obtained.

  A commercial item can also be used as an A1-B-A2 type | mold triblock copolymer. Examples of commercially available products of the A1-B-A2 type triblock copolymer preferably used in the present invention include, for example, trade name “Clayton” of Clayton Polymer Co., Ltd., trade names “Tuff Tech” and “Tufprene” of Asahi Kasei Chemicals Corporation, Kuraray Co., Ltd.'s brand names “Septon” and “Hibler” series are listed.

The A1-B-A2 type triblock copolymer can be synthesized, for example, in the following step.
First, a vinyl aromatic compound is added to a hydrocarbon solvent such as cyclohexane, and anionic polymerization is performed using an organolithium compound or metallic sodium as an initiator to obtain a polymer block A1.
Furthermore, an olefin monomer is added and polymerized to obtain a polymer block A1-B. When the olefin monomer is a conjugated diene, hydrogen is added to the double bond based on the conjugated diene of the copolymer to obtain the target polymer block A1-B. The hydrogenation rate of the double bond based on the conjugated diene is preferably 80% or more, particularly 90% or more from the viewpoint of heat resistance and weather resistance. The hydrogenation reaction can be performed using a noble metal catalyst such as platinum or palladium, an organic nickel compound, an organic cobalt compound, or a composite catalyst of these compounds and another organic metal compound. The hydrogenation rate is calculated by an iodine value measurement method.
Furthermore, a vinyl aromatic compound is added and polymerization is performed to obtain a polymer block A1-B-A2.

  The said resin composition which comprises the elastic filament of this invention may be comprised only including the A1-B-A2 type | mold triblock copolymer mentioned above, and in the range which does not impair the objective of this invention as needed. In addition to the A1-B-A2 type triblock copolymer, one or more other types of resins may be included. When the resin composition contains an A1-B-A2 type triblock copolymer and another resin, the content of the A1-B-A2 type triblock copolymer in the resin composition is preferably 90 to 100% by weight, more preferably 95 to 100% by weight. However, from the viewpoint of improving the spin moldability and stretchability to the maximum, the resin composition preferably includes only an A1-B-A2 type triblock copolymer.

  The resin composition may include one type of A1-B-A2 type triblock copolymer, and two or more types of A1-B-A2 type triblock copolymers having different structures. It may be comprised including.

  When the resin composition contains another resin in addition to the A1-B-A2 type triblock copolymer, examples of the other resin include rubber, polyolefin-based elastomer, polyester-based elastomer, and polyurethane-based resin. A thermoplastic elastomer such as an elastomer can be used. In addition, resins other than thermoplastic elastomers, for example, thermoplastic resins such as polyethylene and polypropylene can be used. These can also be used in combination of two or more.

  The resin composition is obtained by melt-mixing the A1-B-A2 type triblock copolymer or the A1-B-A2 type triblock copolymer and the other resin by various known methods. For example, the above components are simultaneously or sequentially charged into a Henschel mixer, a V-type blender, a tumbler mixer, a ribbon blender, etc. It is obtained by melt-kneading with a kneading apparatus.

  In addition to the resin component (A1-B-A2 type triblock copolymer, other resin), the resin composition may include a plasticizer (for example, paraffinic oil, paraffinic wax, naphthenic oil) as necessary. , Ethylene-α-olefin oligomer, low molecular weight polyethylene, etc.), weathering stabilizer, heat stabilizer, antistatic agent, lubricant, slip agent, nucleating agent, flame retardant, pigment, dye, inorganic or organic filler, etc. It can contain in the range which does not impair the objective of invention.

When the resin composition is heated and melted at 245 ° C., the discharge speed is 8.4 m / min. From a cylindrical nozzle hole having an inner diameter of 0.45 mm and a length of 4.5 mm. The maximum value of the melt tension when discharged at 0.06 to 0.20 cN, more preferably 0.07 to 0.15 cN. FIG. 5 shows a method for measuring the melt tension. The upward force applied to the load cell shown in FIG. 5 is measured, and this measured value is taken as the melt tension.
When the maximum value of the melt tension of the resin composition constituting the elastic filament of the present invention is in the above range, the spin moldability is further improved. The melt tension can be adjusted by adding, for example, a plasticizer (paraffin or the like), rubber, thermoplastic resin, or the like. The resin composition configured as described above has a melt tension in the above range.

  The elastic filament of the present invention can be produced using the above-described resin composition as a raw material and using a known spinning technique. For example, a melt blown method in which a molten resin composition is extruded from a nozzle hole, and the extruded molten resin composition is elongated with hot air to thin the fibers, or a semi-molten resin composition is cooled with cold air or mechanical It can be produced by a spunbond method in which stretching is performed according to a draw ratio. An elastic filament can also be produced by a spinning blow method, which is a type of melt spinning method.

  The elastic filament of the present invention is preferably obtained by drawing an undrawn yarn. By stretching, the polymer constituting the elastic filament is molecularly oriented in the length direction of the elastic filament, so that the value of the going / return ratio of the strength at 50% elongation increases, and the hysteresis loss at the time of expansion / contraction decreases. . Here, the going / returning ratio of the strength at 50% elongation is the load A (hereinafter also referred to as 50% return strength) when the elastic filament is stretched 100% along the extending direction of the elastic filament and 50% is restored from that state. And the ratio (A / B) to the load B (hereinafter also referred to as 50% strength) when the elastic filament 13 is extended by 50% along the extending direction. Further, a thin elastic filament can be obtained by stretching. From this viewpoint, the elastic filament of the present invention is preferably stretched 1.1 to 400 times, particularly 4 to 100 times. As specific operations for stretching, (a) a resin composition as a raw material for elastic filaments is melt-spun to obtain an unstretched yarn, and the elastic filament of the unstretched yarn is heated again to soften the temperature (hard segment). And (b) an operation of directly stretching a fiber in a molten state obtained by melt-spinning a resin composition that is a raw material of an elastic filament.

  The elastic filament of the present invention is a long fiber, specifically, has a fiber length of 50 mm or more, and includes continuous fibers. The elastic filaments of the present invention are preferably in the form of continuous fibers. This is because if the elastic filament is a continuous fiber, it is continuously stretched by hot air from the nozzle lip, so that not only the fiber diameter is reduced, but also the variation in the fiber diameter is reduced. Moreover, the same tendency is observed when stretching with cold air. As a result, when a nonwoven fabric is produced using the elastic filament of the present invention, the texture when viewed through the nonwoven fabric is improved, and the variation in stretch properties of the nonwoven fabric is reduced. The fact that a thin fiber diameter can be obtained can reduce the capacity of hot air and cold air, which is advantageous in terms of manufacturing cost.

  The diameter of the elastic filament of this invention is not specifically limited, According to the use of an elastic filament, it can adjust suitably. The diameter of the elastic filament of the present invention can be adjusted in the range of 30 to 300 μm. Conventionally, the diameter of the elastic filament used in absorbent articles such as disposable diapers is often in the range of 0.2 to 1 mm, but the diameter of the elastic filament is smaller from the viewpoint of improving the texture of the diaper. Things are desired. If the diameter of the elastic filament is reduced, the possibility of thread breakage at the time of spinning is increased, which may lead to a decrease in productivity. However, the elastic filament of the present invention may be designed to have a diameter as small as 30 μm. There is no risk of thread breakage.

[Elastic sheet]
Hereinafter, the stretchable sheet of the present invention will be described based on preferred embodiments with reference to the drawings.
The elastic sheet of the present invention is manufactured using the elastic filament of the present invention described above, and a plurality of elastic filaments arranged so as to extend in one direction without crossing each other are at least stretchable nonwoven fabrics. It is joined to one side.

  FIG. 1 shows a partially broken perspective view of an embodiment of the stretchable sheet of the present invention. The elastic sheet 10 of this embodiment is composed of a total of two nonwoven fabrics, a first nonwoven fabric 11 and a second nonwoven fabric 12, and a large number of elastic filaments 13 sandwiched between the nonwoven fabrics. Each elastic filament 13 is joined to the first and second nonwoven fabrics 11 and 12. The first nonwoven fabric 11 and the second nonwoven fabric 12 may be of the same type or different types. The same kind of non-woven fabric as used herein refers to non-woven fabrics in which the non-woven fabric manufacturing process, the type of constituent fibers of the non-woven fabric, the fiber diameter and length of the constituent fibers, the thickness and basis weight of the non-woven fabric are all the same. When at least one of these is different, it is said that it is a different kind of nonwoven fabric.

  Each of the nonwoven fabrics 11 and 12 can be extended. Each nonwoven fabric 11 and 12 can extend in the same direction as the direction in which the elastic filament 13 extends. Stretchable means (a) when the constituent fibers themselves of the nonwoven fabrics 11 and 12 are stretched, and (b) even if the constituent fibers themselves are not stretched, the fibers that are bonded at the intersection are separated, This includes a case where the three-dimensional structure formed by a plurality of fibers is structurally changed due to bonding or the like, or the constituent fibers are broken, and the whole nonwoven fabric is elongated.

  Each of the nonwoven fabrics 11 and 12 may be already stretchable in the state of the original fabric before being joined to the elastic filament 13. Alternatively, it is not stretchable in the state of the original fabric before being joined to the elastic filament 13, but is processed so as to be stretchable after being joined to the elastic filament 13, and becomes stretchable. Also good. Specific methods for making the nonwoven fabric stretchable include heat treatment, stretching between rolls, biting stretch using tooth gaps and gears, and tensile stretching using a tenter. In view of a preferable manufacturing method of the stretchable sheet 10 described later, the nonwoven fabrics 11 and 12 are the original ones because the transportability of the nonwoven fabrics 11 and 12 is improved when the elastic filaments 13 are fused to the nonwoven fabrics 11 and 12. In the opposite state, it is preferably not stretchable.

  Each nonwoven fabric 11, 12 is extensible and substantially inelastic. Elasticity is a property that can be stretched and contracts when released from the stretched force, but the nonwoven fabrics 11 and 12 do not have such a property. When each nonwoven fabric 11 and 12 has elasticity, a fiber containing an elastic resin is required as its constituent fiber, and the fiber containing the elastic resin tends to exhibit a sticky feeling that contributes to lowering the texture of the nonwoven fabric. . Therefore, in this embodiment, each nonwoven fabric 11 and 12 is made substantially inelastic, and the fall of the texture is prevented.

  Each elastic filament 13 is substantially continuous over the entire length of the stretchable sheet 10. The elastic filaments 13 are arranged so as to extend in one direction without crossing each other. Note that the elastic filaments 13 are allowed to cross unintentionally due to inevitable fluctuations in the manufacturing conditions of the stretchable sheet 10. Each elastic filament 13 may extend linearly as long as it does not cross each other, or may extend while meandering. Note that the elastic filament 13 is less likely to meander unintentionally due to unavoidable fluctuations in the manufacturing conditions of the stretchable sheet 10, as described in the section [Elastic Filament]. The direction in which the elastic filament 13 extends may coincide with the flow direction when the first and second nonwoven fabrics 11 and 12 are manufactured, or may be orthogonal to the flow direction when the nonwoven fabrics 11 and 12 are manufactured. . When the stretchable sheet 10 is manufactured according to a preferable manufacturing method described later, the extending direction of the elastic filament 13 coincides with the flow direction at the time of manufacturing the first and second nonwoven fabrics 11 and 12.

  The elastic filament 13 is bonded to the nonwoven fabrics 11 and 12 in a substantially non-stretched state. Since the elastic filaments 13 are not stretched, relaxation (creep) due to stretching does not occur, and the stretchability is reduced during raw material storage after the elastic filaments 13 are bonded to the nonwoven fabrics 11 and 12 or after processing such as stretching. There is an advantage that there is no. Further, there is no deformation due to the tightness of the wound-up raw material. Furthermore, for example, when the elastic filament 13 is stretched twice and bonded to the nonwoven fabrics 11 and 12, if it is temporarily returned to 1.3 times the initial value, it can be stretched only 1.7 times from this state. However, when bonding is performed in a non-stretched state, the initial origin when the stretchable sheet is stretched is different, so that the stretchable length of the nonwoven fabrics 11 and 12 or the maximum elongation of the elastic filament 13 is stretched. There is an advantage that becomes possible.

  The elastic filament 13 is preferably obtained by drawing an undrawn yarn, and is preferably drawn 1.1 to 400 times, particularly 4 to 100 times. The reason and the specific operation of stretching are as described in the section of [Elastic Filament].

  The elastic filament 13 obtained by stretching preferably has a diameter of 30 to 200 μm, particularly 50 to 130 μm. This range is determined in consideration of the texture of the stretchable sheet 10 and the productivity of the elastic filament 13. Specifically, if the diameter of the elastic filament 13 is too large, a step due to the elastic filament 13 is easily perceived when the elastic sheet 13 is touched. This step acts negatively on the texture of the stretchable sheet 10. From this point of view, it is preferable that the elastic filament 13 has a smaller diameter because only the texture of the nonwoven fabrics 11 and 12 is easily perceived. Moreover, the thinner one is preferable also in terms of concealing the elastic filament 13. Further, in the stretching by the tooth groove roll, which will be described later, the diameter of the elastic filament 13 is equal to or less than the tooth-to-tooth clearance between the tooth groove rolls (preferred clearance is to increase the endurance of the tooth and to increase the stretching ratio by the amount of biting. In this respect, the clearance becomes smaller and is 250 μm or less, and more preferably 200 μm or less. The elastic filament is less likely to be damaged (cracked or cut) during stretching. The ratio between the diameter of the elastic filament and the clearance is preferably 0.2 to 1, particularly 0.2 to 0.5. However, the smaller the elastic filament 13 is, the less easy it is to manufacture. Considering these, the diameter of the elastic filament 13 is preferably within the above-mentioned range.

  From the viewpoint of preventing the above-described step from being generated, the ratio of the diameter of the elastic filament 13 in the thickness direction of the elastic filament 13 to the thickness of the elastic sheet 10 is preferably 1 to 30%, particularly preferably 5 to 12%.

  The elastic filament 13 may have a circular cross section, but in some cases may have an elliptical cross section. For example, when the stretchable sheet 10 is manufactured according to the manufacturing method described later, the cross section of the elastic filament 13 tends to be elliptical. In this case, in the stretchable sheet 10, the elastic filament 13 has an elliptical long axis in the same direction as the plane direction of the stretchable sheet 10 and a short axis in the same direction as the thickness direction of the stretchable sheet 10. Preferably they are arranged.

  When the cross section of the elastic filament 13 is elliptical, the ratio of the long axis / short axis (average flatness) is 1.0 to 7.0, particularly 1.1 to 3.0. This is preferable from the viewpoint of increasing the bonding strength between the filament 13 and the constituent fibers of the nonwoven fabrics 11 and 12 and the concealability of the stretchable sheet 11. The elastic filaments 13 having an elliptical cross section are arranged so that the major axis direction thereof substantially coincides with the plane direction of the stretchable sheet 11. In addition, when the cross section of the elastic filament 13 is an ellipse, the diameter of the elastic filament 13 means what averaged the major axis diameter and the minor axis diameter.

  The elastic filament 13 is also preferably colored in a color different from the colors of the first and second nonwoven fabrics 11 and 12. Thereby, the elastic filament 13 can be seen through the first nonwoven fabric 11 and / or the second nonwoven fabric 12, and the design effect that the stretchable sheet 10 exhibits a striped pattern is exhibited. Such an effect becomes more remarkable especially when the thickness and basis weight of each nonwoven fabric are within the ranges described below.

  From the viewpoint of the stretchable sheet 10 exhibiting sufficient stretchability, from the viewpoint of developing a good cloth-like texture, and from the viewpoint of developing the above-described design effect as necessary, the pitch of the adjacent elastic filaments 13 (adjacent The distance between the centers of the elastic filaments) is preferably 0.1 to 5 mm, particularly preferably 0.3 to 1.8 mm, provided that the diameter of the elastic filament 13 is in the range described above.

  The elastic filament 13 is bonded to the nonwoven fabrics 11 and 12 over the entire length thereof. Here, “joining over the entire length” requires that all the fibers in contact with the elastic filament 13 (component fibers of the nonwoven fabrics 11 and 12) are joined to the elastic filament 13. In other words, it means that the elastic filament 13 and the constituent fibers of the nonwoven fabrics 11 and 12 are bonded to the elastic filament 13 in such a manner that there is no intentionally formed non-bonded portion. Since the elastic filament 13 is bonded to the nonwoven fabrics 11 and 12 over the entire length, the bonding force between the elastic filament 13 and the nonwoven fabrics 11 and 12 can be sufficiently increased. As a result, even if the elastic sheet 10 is stretched, the elastic filament 13 is difficult to peel from the nonwoven fabrics 11 and 12. If the elastic filament 13 peels from the nonwoven fabrics 11 and 12, in the natural state (relaxed state), floating occurs between the elastic filament 13 and the nonwoven fabrics 11 and 12, and wrinkles occur in the stretchable sheet 10. It becomes easy and lacks a sense of unity as the entire stretchable sheet 10.

  Examples of the bonding mode between the elastic filament 13 and the first and second non-woven fabrics 11 and 12 include fusion, bonding with an adhesive, and the like. When the elastic sheet 10 is manufactured according to a suitable manufacturing method described later, the elastic filament 13 is bonded to the nonwoven fabrics 11 and 12 by fusion bonding. According to this method, heat is not applied to the nonwoven fabrics 11 and 12, and the elastic filaments 13 are fused to the nonwoven fabrics before the elastic filaments 13 obtained by melt spinning are solidified. Since only the fibers present in the fiber are bonded to the elastic filaments 13 and the fibers located further away from the fibers maintain the texture of the nonwoven fabrics 11 and 12, the texture of the stretchable sheet 10 is kept good. There is an advantage of being. In this case, before bonding the nonwoven fabrics 11 and 12 and the elastic filaments 13, an adhesive can be applied as an auxiliary bonding means. Or after joining each nonwoven fabric 11 and 12 and the elastic filament 13, heat processing (steam jet, heat embossing), mechanical entanglement (needle punch, spunlace) etc. can also be performed as an auxiliary joining means. . However, these auxiliary joining means may damage the texture of the resulting stretchable sheet 10 or damage the elastic filament 13. Therefore, it is preferable to fuse the elastic filament 13 to the nonwoven fabrics 11 and 12 with the heat of fusion. However, when a heat treatment consisting of hot air blowing by an air-through method is used as an auxiliary joining means, the texture of the obtained stretchable sheet 10 is not impaired, and the nonwoven fabrics 11 and 12 having a high joining strength can be obtained. Is preferable.

  The stretchable sheet 10 is stretchable in the same direction as the direction in which the elastic filament 13 extends. The stretchability of the stretchable sheet 10 is expressed due to the elasticity of the elastic filament 13. When the stretchable sheet 10 is stretched in the same direction as the elastic filament 13 extends, the elastic filament 13 and the first and second nonwoven fabrics 11 and 12 extend. When the stretching of the stretchable sheet 10 is released, the elastic filament 13 contracts, and the first and second nonwoven fabrics 11 and 12 return to the state before stretching with the contraction.

  In the stretchable sheet 10 of the present embodiment, there is no other elastic filament bonded in a state orthogonal to the elastic filament 13. Therefore, when the stretchable sheet 10 is stretched in the same direction as the direction in which the elastic filament 13 extends, the stretchable sheet 10 stretches with little width shrinkage. That is, the stretchable sheet 10 has a substantially uniform width in the longitudinal direction in the stretched state. As a result, the handling property when the stretchable sheet 10 is conveyed in the extended state and processed is improved. Moreover, when the elastic sheet 10 is used, for example, as an outer wrapping material for a pants-type diaper, it is effectively prevented that the diaper is slipped or wrinkled while the diaper is worn. From this point of view, the stretchable sheet 10 preferably has a width shrinkage ratio of 90% to 99%, particularly 95% to 99% of the width before stretching when the stretchable sheet 10 is stretched 1.5 times. The width reduction can be obtained as a value obtained by dividing the width after expansion by the width before expansion. The measurement is performed by cutting out a sample having a length of 1 m and a width of 300 mm, and extending the sample by 1.5 times while maintaining the distance between both ends to be 300 mm in width. The measurement position of the width after extension is the center.

  2A and 2B are longitudinal sectional views along the extending direction of the elastic filament 13 in the stretchable sheet 10 of the present embodiment. Fig.2 (a) is a longitudinal cross-sectional view of the elastic sheet 10 in a natural state (relaxed state), and FIG.2 (b) is a longitudinal cross-sectional view of the elastic sheet 10 in an expansion | extension state. In the natural state, the stretchable sheet 10 has a corrugated shape in which top portions 14 ′ and valley portions 14 ″ are alternately arranged. The top portion 14 ′ and the valley portions 14 ″ are connected via a ridge line portion 15 ′. . The thickness of the ridge line portion 15 ′ is slightly smaller than the thickness of the top portion 14 ′ and the valley portion 14 ″, and light can be transmitted more easily than the top portion 14 ′ and the valley portion 14 ″. When the stretchable sheet 10 is viewed in plan, the top portion 14 ′, the ridge line portion 15 ′, and the valley portion 14 ″ extend in a direction orthogonal to the extending direction of the stretchable sheet 10. Therefore, the stretchable sheet 10 is in its natural state. Further, a horizontal stripe pattern caused by the ridge portion 15 ′ that easily transmits light and the top portion 14 ′ and the valley portion 14 ″ that hardly transmit light appears slightly. This horizontal stripe pattern becomes more prominent when the stretchable sheet 10 is extended.

  That is, as shown in FIG. 2B, in the stretchable stretchable sheet 10, the high basis weight portions 14 and the low basis weight portions 15 are alternately arranged along the extending direction of the elastic filaments 13. . Each of the portions 14 and 15 extends in a band shape in a direction orthogonal to the direction in which the elastic filament 13 extends. The high basis weight portions 14 and the low basis weight portions 15 are alternately arranged at a constant period. About the high basic weight part 14, what protrudes above the sheet | seat 10 and what protrudes below the sheet | seat 10 are arrange | positioned alternately. The high basis weight portion 14 protruding above the sheet 10 is derived from the top portion 14 ′ of the sheet 10 in the natural state shown in FIG. On the other hand, the high basis weight portion 14 projecting to the lower side of the sheet 10 is derived from the valley 14 ″ in the sheet 10 in the natural state shown in FIG. 2A. 2 (a) is derived from the ridge line portion 15 'in the natural sheet 10. In the high basis weight portion 14 and the low basis weight portion 15, the degree of light transmission due to the difference in basis weight. As a result, the stretchable sheet 10 has a horizontal stripe pattern extending in a direction orthogonal to the extending direction of the elastic filaments 13, and the design is improved. Since the elastic sheet 13 also exhibits a striped pattern, the stretchable sheet 10 also exhibits a lattice pattern in which the striped pattern is combined with the striped pattern derived from the high basis weight portion 14 and the low basis weight portion 15. And the design is even higher It made.

  The high basis weight portion 14 has a larger basis weight and a larger thickness than the low basis weight portion 15. As a result, the high basis weight portion 14 and the low basis weight portion 15 differ in the degree of light transmission, and a striped pattern is exhibited due to the difference. Each high basis weight portion 14 is substantially equal in width to each other, and similarly, each low basis weight portion 15 is also substantially equal in width to each other.

The thickness of the high basis weight portion 14 is preferably 0.3 to 10 mm, particularly preferably 0.5 to 1 mm. The thickness of the low basis weight portion 15 is preferably 0.1 to 3 mm, particularly preferably 0.2 to 0.6 mm from the viewpoints of stretchability and air permeability. The thickness is measured by the following method after the stretchable sheet 10 is left unloaded for 2 days or more in an environment of 20 ± 2 ° C. and 65 ± 5% RH. First, the stretchable sheet 10 is sandwiched between flat plates with a load of 0.5 cN / cm ^{2 in} a state where the stretchable sheet 10 is stretched 1.5 times. The cross section is observed with a microscope at a magnification of 50 to 200 times, and an average thickness is obtained in each field of view, and is obtained as an average value of the thicknesses of three fields of view. The high basic weight portion 14 and the low basic weight portion 15 are easily formed by manufacturing the stretchable sheet 10 according to the manufacturing method described later.

Next, the constituent material of the 1st and 2nd nonwoven fabrics 11 and 12 which comprise the elastic sheet 10 is demonstrated. Regarding the elastic filament 13, the description in the section of “elastic filament” is appropriately applied.
Examples of the fibers constituting each of the nonwoven fabrics 11 and 12 include fibers made of polyethylene (PE), polypropylene (PP), polyester (PET or PBT), polyamide, and the like. The fibers constituting each of the nonwoven fabrics 11 and 12 may be short fibers or long fibers, and may be hydrophilic or water repellent. Further, core-sheath type or side-by-side composite fibers, split fibers, irregularly shaped cross-section fibers, crimped fibers, heat-shrinkable fibers, and the like can also be used. These fibers can be used alone or in combination of two or more. Each non-woven fabric 11, 12 can be a continuous filament or short-fiber non-woven fabric. In particular, from the viewpoint of making the stretchable sheet 10 thick and bulky, the nonwoven fabrics 11 and 12 are preferably short-fiber nonwoven fabrics. When the stretchable sheet 10 is used as a member that comes into contact with the skin, a short fiber nonwoven fabric with good texture may be used on the skin contact side, and a high-strength continuous filament nonwoven fabric may be used on the opposite surface.

  Each of the nonwoven fabrics 11 and 12 preferably has two or more constituent fibers of a low melting point component and a high melting point component. In that case, the constituent fibers are bonded to each other at the fiber intersection by heat fusion of at least the low melting point component. As the core-sheath type composite fiber composed of two or more components of a low melting point component and a high melting point component, those having a core of high melting point PET, PP and a sheath of low melting point PET, PP, PE are preferable. In particular, the use of these composite fibers is preferable because the fusion with the elastic filaments 13 becomes strong and peeling between the two hardly occurs.

  It is preferable that the constituent fibers of the nonwoven fabrics 11 and 12 are of high elongation (for example, the maximum elongation of the fibers is 150 to 400%) in that the stretchable sheet 10 having high maximum strength can be obtained. The fiber elongation is in accordance with JIS L-1015 and is based on measurement under the conditions of measuring environment temperature and humidity 20 ± 2 ° C., 65 ± 5% RH, tensile tester gripping distance 20 mm, and tensile speed 20 mm / min. . In addition, when collecting fibers from an already manufactured non-woven fabric and measuring the elongation, when the gripping interval cannot be 20 mm, that is, when the length of the fiber to be measured is less than 20 mm, the gripping interval is set. Measure by setting to 10 mm or 5 mm.

The thickness of each nonwoven fabric 11 and 12 is preferably 0.05 to 5 mm, more preferably 0.1 to 1.0 mm, and still more preferably 0.15 to 0.5 mm. The thickness is measured by observing the cross section of the stretchable nonwoven fabric with a load of 0.5 cN / cm ² at a magnification of 50 to 200 times with a microscope, and obtaining the average thickness in each field of view. It can obtain | require as an average value of thickness. The thickness of the entire sheet can be obtained by measuring the distance between the flat plates. The basis weight of each of the nonwoven fabrics 11 and 12 is preferably ³ to 100 g / m ² , particularly 5 to 30 g / m ² from the viewpoints of texture, thickness, and design properties.

The basis weight of the elastic filament layer composed of a large number of elastic filaments 13 disposed between the two nonwoven fabrics 11 and 12 is 4 to 30 g / m ² , particularly 6 in terms of stretchability, texture, thickness, and cost. It is preferably ˜15 g / m ² .

  The elastic sheet 10 of this embodiment can be manufactured as follows, for example. In this manufacturing method, a large number of molten elastic filaments 13 spun from the spinning nozzle 16 are drawn and stretched at a predetermined speed, and the elastic filaments 13 do not cross each other before the elastic filaments 13 are solidified. The elastic filaments 13 are fused to the nonwoven fabrics 11 and 12 so as to be arranged in one direction, and then the nonwoven fabrics 11 and 12 to which the elastic filaments 13 are fused are stretched along the direction in which the elastic filaments 13 are stretched. It imparts extensibility to the nonwoven fabrics 11 and 12.

  As shown in FIG. 3, the spinning nozzle 16 is provided in the spinning head 17. The spinning head 17 is connected to an extruder. Resin can also be supplied to the spinning head 17 via a gear pump. The elastic resin melt-kneaded by the extruder is supplied to the spinning head 17. The spinning head 17 has a large number of spinning nozzles 16 arranged in a straight line. The spinning nozzle 16 is arranged along the width direction of the first and second nonwoven fabrics 11 and 12. The interval between the adjacent spinning nozzles 16 corresponds to the interval between the elastic filaments 13 in the target stretchable sheet 10. The spinning nozzle 16 is usually circular and has a cylindrical nozzle hole, and its diameter (inner diameter) affects the diameter and draw ratio of the elastic filament 13. From this viewpoint, the diameter (inner diameter) of the spinning nozzle 16 is preferably 0.1 to 2 mm, particularly preferably 0.2 to 0.6 mm.

  The melted elastic filaments 13 spun together with the first nonwoven fabric 11 and the second nonwoven fabric 12 fed from the original fabric at the same speed, and are sandwiched between the nonwoven fabrics 11 and 12 at a predetermined speed. Taken over. The take-up speed of the elastic filament 13 coincides with the feeding speed of both the nonwoven fabrics 11 and 12. The take-up speed of the elastic filament 13 affects the diameter and the draw ratio of the elastic filament 13. The tension generated in the elastic filament 13 by stretching prevents the elastic filament 13 from being disturbed due to wind or static electricity when the elastic filament 13 is bonded to the nonwoven fabrics 11 and 12. Thereby, the elastic filaments can be arranged in one direction without crossing each other. From these viewpoints, the drawing speed of the elastic filament 13 is 1.1 to 400 times, particularly 4 to 100 times, more preferably 10 to 80 times the resin discharge speed in the spinning nozzle hole. It is preferable to adjust.

  The elastic filament 13 merges with the first and second nonwoven fabrics 11 and 12 before solidification, that is, in a state capable of being fused. As a result, the elastic filament 13 is fused to the nonwoven fabrics 11 and 12 while being sandwiched between the first and second nonwoven fabrics 11 and 12. That is, the elastic filament 13 is pulled and stretched by fusing the elastic filament 13 before solidification to the nonwoven fabrics 11 and 12 to be conveyed. When the elastic filament 13 is fused, heat is not applied to the first and second nonwoven fabrics 11 and 12 from the outside. That is, the elastic filament 13 and the nonwoven fabrics 11 and 12 are fused only by the heat of fusion caused by the elastic filament 13 that can be fused. As a result, of the constituent fibers of both the nonwoven fabrics 11 and 12, only the fibers existing around the elastic filament 13 are fused to the elastic filament 13, and the fibers present at a position farther than that are not fused. As a result, since the heat applied to both the nonwoven fabrics 11 and 12 is kept to a minimum, the good texture inherent to the nonwoven fabric itself is maintained. Thereby, the texture of the stretchable sheet 10 obtained becomes favorable.

  Until the spun elastic filament 13 joins the first and second nonwoven fabrics 11 and 12, the elastic filament 13 is stretched and molecules are oriented in the stretching direction. Also, the diameter is reduced. Due to the molecular orientation, an elastic filament 13 having a large 50% stretch strength return / return ratio (A / B described above) can be obtained. From the viewpoint of sufficiently stretching the elastic filament 13 and from the viewpoint of preventing the elastic filament 13 from being broken, a wind (hot air or cold air) of a predetermined temperature is blown onto the spun elastic filament 13 to set the temperature of the elastic filament 13. You may adjust.

  The stretching of the elastic filament 13 may be not only stretching in a molten state (melt stretching) of the resin composition constituting the elastic filament 13 but also stretching in a softened state (softening stretching) in the cooling process. The molten state is a state in which the resin flows when an external force is applied. The melting temperature of the resin is measured as a peak temperature of Tan δ by viscoelasticity measurement (for example, measured by adding vibration strain in the rotational direction to a resin sandwiched between circular parallel plates). In order to prevent yarn breakage during stretching of the resin composition, it is preferable to secure a long stretching section. From this viewpoint, the melting temperature of the resin composition is preferably 130 to 300 ° C. Further, from the viewpoint of heat resistance (molding temperature) of the resin composition, the melting temperature is preferably 130 to 220 ° C. The softening temperature is measured as the temperature at the inflection point of the storage elastic modulus G ′ in the viscoelastic property of the measurement sample of the resin composition in sheet form. The range from the softening temperature to the melting temperature is called a softened state. The softening temperature is preferably 60 ° C. or higher, and more preferably 80 ° C. to 180 ° C., from the viewpoint of crystal growth of the resin composition during storage of the stretchable sheet 10 and a decrease in stretchability of the stretchable sheet 10 due to body temperature.

  The temperature of the elastic filament 13 when the elastic filament 13 and the nonwoven fabrics 11 and 12 are joined is preferably 100 ° C. or higher in order to ensure fiber fusion. Further, from the viewpoint of obtaining the stretchable sheet 10 having a good stretchability by maintaining the shape of the elastic filament 13, the temperature of the elastic filament is preferably 180 ° C. or lower. More preferably, it is the range of 120-160 degreeC. The bonding temperature is determined by using a film made of modified polyethylene or modified polypropylene having a melting point different from the melting point of the resin composition constituting the elastic filament 13 as a laminate base material to be bonded to the elastic filament 13. It can be measured by observing. At this time, if the elastic filament 13 and the laminate base material are fused, the joining temperature is equal to or higher than the melting point of the laminate base material.

  At the time of joining the elastic filament 13 and the nonwoven fabrics 11 and 12, the elastic filament 13 is substantially in a non-stretched state (a state in which it does not shrink when an external force is removed). In the bonding state between the two, at least a part of the fibers constituting the nonwoven fabrics 11 and 12 are fused to the elastic filament 13 or further, the elastic filament 13 and at least a part of the fibers constituting the nonwoven fabrics 11 and 12 More preferably, both are fused. This is because sufficient bonding strength can be obtained. The stretch properties of the resulting stretchable sheet 10 are affected by the density of the joint points between the elastic filament 13 and the nonwoven fabrics 11 and 12. In addition, the expansion / contraction characteristics can be adjusted by the joining temperature, the joining pressure, and the deviation of the joining point due to the stretching of the nonwoven fabrics 11 and 12 described later. By bonding the constituent fibers of the nonwoven fabrics 11 and 12 to the elastic filament 13, the bonding strength of each bonding point increases. Lowering the density of the joining points is preferable because the stretch inhibition by the nonwoven fabrics 11 and 12 is reduced and the stretch sheet 10 having sufficient joint strength is obtained.

  When the elastic filament 13 is merged with the first and second nonwoven fabrics 11 and 12, the elastic filaments 13 are arranged in one direction without crossing each other. Then, the elastic filament 13 is joined with the first and second nonwoven fabrics 11 and 12, and the elastic filament 13 is sandwiched between the nonwoven fabrics 11 and 12, and the three are sandwiched by a pair of nip rolls 18 and 18. Press. The condition of the clamping pressure affects the texture of the stretchable sheet 10 obtained. If the pinching pressure is too large, the elastic filament 13 is likely to bite into both the nonwoven fabrics 11 and 12, and the texture of the stretchable sheet 10 obtained due to this tends to be lowered. From this point of view, the clamping pressure by the nip rolls 18 and 18 is sufficient so that the elastic filament 13 contacts both the nonwoven fabrics 11 and 12, and an excessively high clamping pressure is not required.

  Another condition for the clamping pressure by the nip roll 18 is the temperature of the nip roll 18. As a result of the study by the present inventors, it is better not to heat the nip roll 18 in a heated state (that is, to leave it to the result), or to perform the pressing while cooling, a better texture. It was found that the elastic sheet 10 was obtained. When cooling the nip roll 18, it is preferable to use a coolant such as cooling water and adjust the temperature so that the surface setting temperature of the nip roll 18 is 10 to 50 ° C.

  In this way, a composite 19 in which the elastic filament 13 is sandwiched between the two nonwoven fabrics 11 and 12 is obtained. When the nonwoven fabrics 11 and 12 that are inherently extensible are used, the composite 19 becomes the stretchable sheet 10 itself. On the other hand, when the nonwoven fabrics 11 and 12 that do not inherently have extensibility are used, the composite 19 including the nonwoven fabrics 11 and 12 is subjected to stretching treatment. This stretching process is performed by an operation of stretching the composite 19 along the direction in which the elastic filament 13 extends to impart extensibility to the nonwoven fabrics 11 and 12.

  The said extending | stretching process can be performed using an extending | stretching apparatus as shown, for example in FIG. In FIG. 4, a stretching device having a pair of tooth gap rolls 20, 21 in which teeth and roots are alternately formed in the circumferential direction is used, and the composite 19 is conveyed in the direction, that is, the direction in which the elastic filament 13 extends. It is schematically shown that the composite 19 is stretched by being stretched along the line.

  The stretching apparatus shown in FIG. 4 has a known lifting mechanism (not shown) that vertically displaces the pivot portion of one or both of the tooth groove rolls 20 and 21, and the distance between the tooth groove rolls 20 and 21 is adjusted. It is possible. In this manufacturing method, each tooth gap roll 20 and 21 is inserted freely between the teeth of one tooth gap roll 21 and the tooth of the other tooth gap roll 21 is one tooth. It combines so that it may be loosely inserted between the teeth of the groove roll 20, and the composite body 19 is inserted between the both tooth groove rolls 20 and 21 of the state, and this is extended.

  In the stretching device, both of the pair of tooth groove rolls 20 and 21 may be driven by a driving source (co-rotating roll), and only one tooth groove roll 20 or 21 is driven by the driving source. In this manufacturing method, only the lower tooth gap roll 21 is driven by the drive source, and the upper tooth gap roll 20 is not connected to the drive source. The tooth gap roll 21 is driven (rotated) with rotation. The use of the accompanying roll is that the high basis weight portion 14 and the low basis weight portion 15 easily appear in a striped pattern in the stretchable sheet 10 after the stretching process, and the design property of the stretchable sheet 10 is improved. The basis weight portion 15 is preferable in that it has a lower basis weight and air permeability is improved. As the tooth profile of the tooth gap rolls 20 and 21, a general involute tooth profile and a cycloid tooth profile are used, and those having a narrowed tooth width are particularly preferable.

  As shown in FIG. 4, when the composite 19 passes between the tooth gap rolls 20 and 21, the composite 19 is in contact with the teeth 23 and 24 of the tooth gap rolls 20 and 21 (between P3-P2). , Between P1 and P4), it is hardly stretched. On the other hand, in the region (between P2 and P1) pressed toward the tooth surface of the tooth 23 of the tooth space roll 20 that is the driven roll by the tooth surface of the tooth 24 of the tooth space roller 21 that is the driving roll. The two teeth 20 and 21 are greatly stretched. Further, in the region (between P4 and P3) that is separated from the tooth 23 of the tooth space roll 20 by the tip of the tooth 24 of the tooth space roll 21, it is not as large as the region (between P2 and P1), but is greatly stretched. The

  The composite 19 is hardly stretched as described above in the region (between P3 and P2 and between P1 and P4) in contact with the tips of the teeth 23 and 24 of the tooth gap rolls 20 and 21, but the teeth 23 and 24 are as described above. Is pushed in the radial direction, that is, in the thickness direction of the composite 19, so that it becomes thinner in the thickness direction. However, because the region (between P3 and P2) and the region (between P1 and P4) are in the opposite direction, the thinning direction is the opposite direction.

  By the stretching process, the nonwoven fabrics 11 and 12 in the composite 19 can be efficiently stretched to impart extensibility while preventing the elastic filament 13 and the nonwoven fabrics 11 and 12 from being peeled off. And the area | region (between P2-P1 and between P4-P3) extended | stretched greatly becomes the low basic weight part 15, and the area | region (between P3-P2 and between P1-P4) hardly extended becomes the high basic weight part 14.

  The composite body 19 is stretched by the pair of tooth space rolls 20 and 21 to obtain the intended stretchable sheet 10. After the obtained elastic sheet 10 passes through the tooth gap rolls 20 and 21, the stretched state in the MD direction is quickly released by its own contraction restoring force. That is, the elongation is eased. As a result, the stretchable sheet 10 contracts in the transport direction. Thereby, in the extended state, the high basis weight portions 14 and the low basis weight portions 15 are alternately arranged in the extending direction of the elastic filaments 13. When the stretched state is released, the stretched state may be completely released, or the stretched state may be released in a state where a certain stretched state is maintained as long as stretchability is exhibited.

  By the stretching process, the thickness of the stretchable sheet 10 is preferably 1.1 times to 4 times, particularly 1.3 times to 3 times the thickness of the composite 19 before the stretching process. As a result, the constituent fibers of both nonwoven fabrics 11 and 12 are plastically deformed and stretched to make the fibers thinner. At the same time, both the nonwoven fabrics 11 and 12 become more bulky, have a good touch, and have good cushioning properties.

  The stretch sheet 10 obtained in this manner has a sufficient stretch property when the above-mentioned going / return ratio (A / B) at 50% stretch is 50% or more, particularly 65% or more. To preferred.

Moreover, although it is based also on a specific use, it is preferable that the elastic sheet 10 is 10-150 g / m < ² > of the whole basic weight, especially 25-50 g / m < ² >. Regarding the thickness of the stretchable sheet 10, it is preferably 0.05 to 5 mm, particularly preferably 0.5 to 2 mm. The thickness of the stretchable sheet 10 is measured by the same method as the measurement of the thickness of each of the nonwoven fabrics 11 and 12 described above.

The elastic sheet 10 of this embodiment is suitably used as an outer layer sheet of a pants-type disposable diaper. In this case, the stretchable sheet of the present invention can be used as an outer layer sheet, a non-stretchable sheet can be used as the inner layer sheet, and both sheets can be bonded together.
In addition to this use, it can be used for various uses such as surgical clothes and cleaning sheets by taking advantage of its good texture, fuzz prevention, stretchability, breathability and the like. In particular, it is preferably used as a constituent material of absorbent articles such as sanitary napkins and disposable diapers. As the constituent material, for example, a surface sheet that is a liquid-permeable sheet (including sublayers) located on the skin side of the absorbent body, a sheet that constitutes the outer surface of the disposable diaper, a waistline part and a waist part, Examples thereof include a sheet for imparting elastic stretchability to the leg periphery and the like. Moreover, it can be used as a sheet or the like for forming a stretchable wing of a napkin. Moreover, even if it is another site | part, it can be used for the site | part etc. which want to provide a stretching property. The basis weight and thickness of the stretchable sheet 10 can be appropriately adjusted according to the specific application. For example, when used as a constituent material of an absorbent article, it is desirable that the basis weight is about 20 to 60 g / m ² and the thickness is about 0.5 to 1.5 mm.

  The stretchable sheet of the present invention is not limited to the above embodiment. For example, in the expansion and contraction of the above-described embodiment, a large number of elastic filaments 13 are sandwiched between the two nonwoven fabrics 11 and 12, but instead, a large number of elastic filaments are formed on the surface of one nonwoven fabric. May be joined to form an elastic sheet.

  Moreover, in the said embodiment, since all the elastic filaments 13 were arrange | positioned with the same diameter and equal pitch, the elongation stress was the same even if it took any part of the elastic sheet 10. FIG. However, instead of this, the stretchable sheet may be configured to be composed of two or more regions having different extension stresses in the extension direction of the elastic filament. Two or more of the regions are arranged substantially in parallel with the extending direction. In this case, the pitches of the adjacent elastic filaments are different and / or the diameters of the elastic filaments are different between the regions having different elongation stresses. Thereby, the elongation stress can be made different between the regions.

  The elastic sheet 10 can be partially embossed, or the elastic filament 13 can be partially cut or partially heat sealed. These operations are performed for the purpose of forming a non-expandable portion in the stretchable sheet 10 or partially increasing the strength. Alternatively, it is performed for the purpose of bonding with other members or providing design.

  Regarding the stretching performed after the elastic filament 13 is joined to the nonwoven fabrics 11 and 12, the stretching direction is not limited to the flow direction of the nonwoven fabrics 11 and 12, but may be, for example, oblique. Furthermore, it is possible to combine two or more stretching methods, increase the stretching ratio stepwise, or perform partial stretching. The stretching direction may be not only one direction but also two orthogonal directions. A non-woven fabric that expands and contracts in one direction and a non-woven fabric that expands and contracts in a direction perpendicular to the non-woven fabric can be joined to give stretchability in all directions of the stretchable sheet.

  Moreover, in the manufacturing method of the said embodiment, although the extending | stretching apparatus provided with a pair of tooth space rolls 20 and 21 was used for the extending | stretching process of the composite body 19, it replaced with this and extended | stretched using the extending | stretching apparatus provided with the tenter May be performed.

  Furthermore, in this manufacturing method, as another method of joining the elastic filament 13 and the nonwoven fabrics 11 and 12, the elastic filament 13 can be directly extruded on one nonwoven fabric without being melt-drawn directly. The draw ratio of is 1. Moreover, before joining the elastic filament 13 and the nonwoven fabrics 11 and 12, an adhesive agent can be apply | coated to a nonwoven fabric or an elastic filament, and an elastic filament can be bonded together in the substantially unexpanded state after that. Furthermore, without applying an adhesive, the elastic filament 13 and the nonwoven fabrics 11 and 12 are overlapped, followed by heat treatment (hot air blowing by air-through method, steam jet, heat embossing), mechanical entanglement (needle punch, spunlace), etc. Can also be done. At this time, a fiber web can be used on one side or both sides instead of the nonwoven fabric.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Examples 2 and 3 to be described later are reference examples.

  The following eight types of A1-B-A2 type triblock copolymers (1) to (8) were prepared as elastic filament forming materials (resin compositions). Triblock copolymers (1) to (5) are within the scope of the present invention, and triblock copolymers (6) to (8) are outside the scope of the present invention.

  A1-B-A2 type triblock copolymer (1): A1′-B′-A2 ′ type triblock copolymer (SEPS triblock copolymer, styrene content 30% by weight, ethylene-propylene content 70 80% by weight, A1 ″ -B ″ -A2 ″ type triblock copolymer (SEPS triblock copolymer). Weight percent, A1 ′, A2 ′ weight average molecular weight 7500, B1 weight average molecular weight 35000) Styrene content 18 wt%, ethylene-propylene content 82 wt% A1 ″, A2 ″ weight average molecular weight 8100, B ″ weight average molecular weight 73800) 20 wt% mixed with a Henschel mixer, Used as the triblock copolymer (1). The maximum value of the melt tension of the triblock copolymer (1) (in a state heated and melted at 245 ° C., a discharge speed of 8.4 m / min from a cylindrical nozzle hole having an inner diameter of 0.45 mm and a length of 4.5 mm) ) Was 0.07 cN.

The weight average molecular weight of the polymer block A1 in the triblock copolymer (1) is [(weight average molecular weight of the polymer block A1 ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block A1 ″) × (two or more types of A1− contained in the resin composition) The content of the A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 7620.
The weight average molecular weight of the polymer block B in the triblock copolymer (1) is [(weight average molecular weight of the polymer block B ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block B ″) × (two or more kinds of A1− contained in the resin composition) The content of the A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 42760.
The weight average molecular weight of the polymer block A2 in the triblock copolymer (1) is [(weight average molecular weight of the polymer block A2 ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block A2 ″) × (two or more types of A1− contained in the resin composition) The content of the A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 7620.

  A1-B-A2 type triblock copolymer (2): A1-B-A2 type triblock copolymer (SEPS triblock copolymer, styrene content 18% by weight, ethylene-propylene content 82% by weight, The weight average molecular weight 8100 of A1 and A2 and the average molecular weight 73800 of B1) 100% by weight were used as the triblock copolymer (2). The maximum value of the melt tension of the triblock copolymer (2) was 0.13 cN.

  A1-B-A2 type triblock copolymer (3): A1-B-A2 type triblock copolymer (SEBS triblock copolymer, styrene content 20% by weight, ethylene-butylene content 80% by weight, A1 and A2 weight average molecular weight 9400, B1 average molecular weight 75200) 100% by weight was used as the triblock copolymer (3). The maximum value of the melt tension of the triblock copolymer (3) was 0.15 cN.

  A1-B-A2 type triblock copolymer (4): A1′-B′-A2 ′ type triblock copolymer (SEPS triblock copolymer, styrene content 30% by weight, ethylene-propylene content 70 60% by weight, A1 ″ -B ″ -A2 ″ type triblock copolymer (SEPS triblock copolymer, weight average molecular weight 7500 of B1, average molecular weight 35000 of B1), Styrene content 18 wt%, ethylene-propylene content 82 wt%, A1 ″, A2 ″ weight average molecular weight 8100, B ″ weight average molecular weight 73800) 40 wt% mixed with a Henschel mixer, Used as a triblock copolymer (4). The maximum value of the melt tension of the triblock copolymer (4) was 0.20 cN.

The weight average molecular weight of the polymer block A1 in the triblock copolymer (4) is [(weight average molecular weight of the polymer block A1 ′) × (two or more kinds of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block A1 ″) × (two or more types of A1− contained in the resin composition) The content of the A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 7740.
The weight average molecular weight of the polymer block B in the triblock copolymer (4) is [(weight average molecular weight of the polymer block B ′) × (two or more kinds of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block B ″) × (two or more kinds of A1− contained in the resin composition) The content of the A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 50520.
The weight average molecular weight of the polymer block A2 in the triblock copolymer (4) is [(weight average molecular weight of the polymer block A2 ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block A2 ″) × (two or more types of A1− contained in the resin composition) The content of the A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 7740.

  A1-B-A2 type triblock copolymer (5): A1′-B′-A2 ′ triblock type copolymer (SEPS triblock copolymer, styrene content 30% by weight, ethylene-propylene content 70 50% by weight, A1 ″ -B ″ -A2 ″ type triblock copolymer (SEPS triblock copolymer), weight average molecular weight of A1 ′, A2 ′, 7500, B1 average molecular weight of 35000) Styrene content 30% by weight, ethylene-propylene content 70% by weight, A1 ″, A2 ″ weight average molecular weight 10500, B ″ weight average molecular weight 49000) 50% by weight mixed with a Henschel mixer, Used as a triblock copolymer (5). The maximum value of the melt tension of the triblock copolymer (5) was 0.07 cN.

The weight average molecular weight of the polymer block A1 in the triblock copolymer (5) is [(weight average molecular weight of the polymer block A1 ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block A1 ″) × (two or more types of A1− contained in the resin composition) The content of A1 ″ -B ″ -A2 ″ in the total amount of B-A2 type triblock copolymer) =] 9000.
The weight average molecular weight of the polymer block B in the triblock copolymer (5) is [(weight average molecular weight of the polymer block B ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block B ″) × (two or more kinds of A1− contained in the resin composition) The content of A1 ″ -B ″ -A2 ″ in the total amount of the B-A2 type triblock copolymer) =] 42000.
The weight average molecular weight of the polymer block A2 in the triblock copolymer (5) is [(weight average molecular weight of the polymer block A2 ′) × (two or more types of A1-B-A2 type trimers contained in the resin composition]. Content of the A1′-B′-A2 ′ in the total amount of the block copolymer) + (weight average molecular weight of the polymer block A2 ″) × (two or more types of A1− contained in the resin composition) The content of A1 ″ -B ″ -A2 ″ in the total amount of B-A2 type triblock copolymer) =] 9000.

  A1-B-A2 type triblock copolymer (6): A1-B-A2 type triblock copolymer (SEPS triblock copolymer, styrene content 30% by weight, ethylene-propylene content 70% by weight, 100% by weight of A1 and A2 (weight average molecular weight 10500, B1 average molecular weight 49000) was used as the triblock copolymer (6). The maximum value of the melt tension of the triblock copolymer (6) was 0.08 cN.

  A1-B-A2 type triblock copolymer (7): A1-B-A2 type triblock copolymer (SEBS triblock copolymer, styrene content 20% by weight, ethylene-butylene content 80% by weight, A weight average molecular weight 4750 of A1 and A2 and an average molecular weight 38000 of B1) of 100% by weight were used as the triblock copolymer (7). The maximum value of the melt tension of the triblock copolymer (7) was 0.05 cN.

  A1-B-A2 type triblock copolymer (8): A1-B-A2 type triblock copolymer (SEBS triblock copolymer, styrene content 30% by weight, ethylene content 70% by weight, A1 The weight average molecular weight 22750 of A2, the average molecular weight 84500 of B1) 100% by weight was used as the triblock copolymer (8). Although the melt tension was measured as shown in FIG. 5, it could not be extruded due to the high viscosity and could not be measured.

[Example 1]
A composite 19 (a precursor of the stretchable sheet 10 as shown in FIGS. 1 and 2) was obtained using an apparatus as shown in FIG. 3, and this was used as a sample of Example 1. That is, an apparatus having a configuration in which a spinning head 17 including a spinning nozzle 16 in which 250 cylindrical nozzle holes having an inner diameter of 0.45 mm and a length of 4.5 mm are arranged in a straight line at intervals of 1 mm is attached to a single screw extruder. The triblock copolymer (1) as a resin composition is discharged from the spinning nozzle 16 at a melting temperature of 290 ° C. and a discharge rate of 0.3 kg / min, and the filament is a precursor of the elastic filament 13 At a position spaced 100 mm downward from the spinning nozzle 16 at 150 m / min. The air-through nonwoven fabrics 11 and 12 having a basis weight of 20 g / m ² , a thickness of 0.4 mm, and a fiber diameter of 3 dtex fed out at a speed of 5 mm are sandwiched and bonded, and the elastic filament 13 is sandwiched between the nonwoven fabric 11 and the nonwoven fabric 12. A composite 19 was obtained. The nonwoven fabrics 11 and 12 are not inherently extensible.

[Examples 2 to 5 and Comparative Examples 1 to 3]
In Example 1, the composite 19 was prepared in the same manner as in Example 1 except that each of the triblock copolymers (2) to (8) was used instead of the triblock copolymer (1) as the resin composition. These were used as samples of Examples 2 to 5 and Comparative Examples 1 to 3.

[Evaluation]
The properties of the composite 19 (elastic filament 13) obtained in the examples and comparative examples are shown in Table 1 and Table 2 below together with the composition of the resin composition (material for forming the elastic filament 13). The measuring method of each item in Table 1 and Table 2 is as follows.

<Spinning formability of elastic filament>
Cylindrical shape having an inner diameter of 0.45 mm and a length of 4.5 mm in a state where the resin composition [the triblock copolymers (1) to (8)] as an elastic filament forming material is heated and melted at 245 ° C. From the nozzle hole, a discharge speed of 8.4 m / min. Then, the filament is discharged as shown in FIG. 5, and the filament is collected on a stainless plate placed at a position of 100 mm downward from the nozzle hole. When the collected filaments are continuous without breaking, and when the filaments are observed by magnifying them 200 times with a microscope, the sides of the filaments are smooth. Is broken or discontinuous, or the filament is not uniform in thickness due to the die swell.

<Meandering state>
From the composites obtained in the examples and comparative examples, 30 cm was sampled in the machine flow direction (MD direction, the flow direction of the composite during manufacture of the composite), and the elastic filaments were covered with the elastic filaments. Observe visually through the nonwoven fabric. A case where no adjacent 250 elastic filaments cross or contact each other is indicated by ◯, and a case where even one elastic fiber crosses or contacts is indicated by x.

<Diaper diaperity>
The composites obtained in the examples and comparative examples were subjected to a stretching treatment using a stretching device provided with a pair of tooth gap rolls as shown in FIG. 4 to produce stretchable sheets as shown in FIGS. Using this as an outer layer sheet of a diaper, a pants-type disposable diaper having a waist circumference of 35 cm was produced. As shown in FIG. 6, this diaper was placed on an acrylic pipe having a circumference of 44 cm, the lower part of the diaper was fastened with a hook clip, the clip was placed on the upper side, and the acrylic pipe was placed on a jack. At this time, the position of the waist part of the diaper was marked on the acrylic pipe (the position at this time was set as the initial position A), and the jack was lowered by 50 mm while the clip was fixed. The distance between the position of the waist part after lowering the jack by 50 mm (the position at this time is set as the shift position) and the initial position A was measured, and this distance was defined as the shift amount of the diaper. When the amount of slippage is less than 10 mm, ◎ (very good for diaper slipping), when it is 10 mm or more but less than 20 mm, ○ (good for diaper slipping), or △ for 20 mm or more but less than 30 mm (a level that is practically acceptable) 30 mm or more was determined as x.

  As is clear from the results shown in Tables 1 and 2, Examples 1 to 5 all use the resin composition within the scope of the present invention. There is no meandering of the filament, and when an elastic sheet is used for the diaper, a diaper that is difficult to slip off is obtained. On the other hand, in Comparative Example 1, the thickness of the filament was not uniform due to the die swell, the filament was broken from the extremely thinned portion, and a continuous filament could not be obtained. In Comparative Example 2, the thickness was uniform, but the filament was broken because the melt tension was low, and a continuous filament could not be obtained. For this reason, in Comparative Examples 1 and 2, when the obtained stretchable sheet was used for a diaper, the slippage property deteriorated due to a decrease in stretchability due to filament breakage. In Comparative Example 3, the triblock copolymer (8) could not be spin-molded because of its high viscosity, and a filament could not be obtained.

FIG. 1 is a partially broken perspective view showing an embodiment of the stretchable sheet of the present invention. 2 (a) and 2 (b) are longitudinal sectional views in a natural state and an extended state, respectively, along the extending direction of the elastic filament in the stretchable sheet shown in FIG. FIG. 3 is a schematic view showing an apparatus suitably used for manufacturing the stretchable sheet shown in FIG. FIG. 4 is a schematic diagram showing a state in which the composite is stretched. FIG. 5 is an explanatory diagram of a method for measuring melt tension. FIG. 6 is an explanatory diagram of a method for evaluating diaper slippage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Elastic sheet 11 1st nonwoven fabric 12 2nd nonwoven fabric 13 Elastic filament 14 High basic weight area | region 14 'Top part 14 "Valley part 15 Low basic weight area | region 15' Ridge line part

Claims (3)

A resin composition comprising an A1-B-A2 type triblock copolymer comprising polymer blocks A1 and A2 mainly composed of vinyl aromatic polymer and polymer block B mainly composed of polyolefin. An elastic filament consisting of
The total weight average molecular weight measured by the gel permeation chromatography method for each of the polymer blocks A1 and A2 is 14,000 to 20000, and the weight average measured by the gel permeation chromatography method for the polymer block B Ri molecular weight of from 40,000 to 70,000 der,
When the resin composition is heated and melted at 245 ° C., the discharge speed is 8.4 m / min. From a cylindrical nozzle hole having an inner diameter of 0.45 mm and a length of 4.5 mm. An elastic filament having a maximum melt tension of 0.06 to 0.20 cN . Stretch sheet a number of claims 1 Symbol mounting elastic filaments arranged to extend in one direction without intersecting each other, formed by joined to at least one side of the extensible nonwoven fabric. An absorbent article using the stretchable sheet according to claim 2 .