JP7235251B2 - Method for manufacturing elastic laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an elastic laminate.

In recent years, in the manufacture of sanitary materials such as disposable diapers and sanitary napkins, thread rubber made of natural rubber and/or synthetic polymer is used to prevent slippage during wear. Since the rubber thread exhibits good stress when stretched, the use of the rubber thread in the sanitary material is effective in preventing the sanitary material from slipping down when worn.

A stretchable film containing a thermoplastic elastomer has been proposed as a stretchable member of a stretchable laminate provided in sanitary materials other than thread rubber (see, for example, Patent Document 1). Patent Document 1 discloses a stretchable film containing a thermoplastic elastomer and a hydrophilic resin. According to the stretchable film, a stretchable film that is excellent in moisture permeability and flexibility and suitable for sanitary materials such as sanitary products is provided.

A hot-melt stretchable adhesive composition has also been proposed as a stretchable material that can be used in a hot-melt adhesive applicator (see, for example, Patent Document 2). Patent Document 2 describes a block copolymer containing an elastic polymer segment and a polystyrene polymer segment, which are hydrogenated polymers of butadiene polymers or isoprene polymers, or one or more polymers selected from ethylene propylene polymers. A hot melt stretchable adhesive composition is disclosed comprising: According to the hot-melt stretchable adhesive composition, it can be applied using a normal hot-melt applicator, and itself has both adhesiveness and stretchability, so it can be used with a substrate such as a nonwoven fabric. A hot-melt adhesive that can be easily formed into a gather portion by lamination is provided.

Japanese Patent Application Laid-Open No. 2015-86367 Japanese Patent No. 2919385

However, if the rubber thread as described above is used, linear pressure is applied to the human body, which may cause a feeling of oppression or a rash when worn. In addition, since a plurality of thin rubber threads are used in the sanitary material, the thread rubber is easily cut during the production of the sanitary material, which often makes the production of the sanitary material difficult.

In addition, regarding the stretchable film as in Patent Document 1, since the stretchable film has high viscosity, it requires an extrusion device and cannot be used with a hot-melt adhesive coating device that is usually used. There is a problem from the viewpoint of

Furthermore, in the elastic laminate using the elastic adhesive composition of Patent Document 2, the stress during elongation is not sufficient, so the sanitary material may slip off when worn. In addition, it cannot be said that it is sufficient in terms of touch when worn.

In view of the circumstances as described above, an object of the present invention is to provide a stretchable laminate which is pleasant to the touch and excellent in stress when stretched, and which uses a conventional hot-melt adhesive applicator. To provide a method for manufacturing a stretchable laminate that can be coated with a stretchable member using

The present inventors have made intensive studies to achieve the above object, and as a result, it is possible to obtain a stretchable laminate that is comfortable to the touch and has excellent stress during elongation by using a predetermined hot-melt composition. In addition, it was found that the elastic member can be coated using a normal hot-melt adhesive coating device. The inventors of the present invention conducted further studies based on such knowledge, and completed the present invention.

That is, the present invention provides the following method for producing a stretchable laminate.
Section 1.
A method for manufacturing an elastic laminate,
Step 1 of applying a molten hot-melt composition to obtain a hot-melt composition layer;
Step 2 of laminating the first nonwoven fabric, the stretched hot-melt composition layer, and the second nonwoven fabric in this order;
A step 3 of joining the stretched hot melt composition layer to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive bonding and / or ultrasonic fusion,
The hot melt composition is
Containing a hydrogenated styrenic block copolymer (A) and a plasticizer (B),
55 to 70% by mass of the hydrogenated styrenic block copolymer (A) and 5 to 25% by mass of the plasticizer (B) in 100% by mass of the hot melt composition,
The hydrogenated styrenic block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and/or a styrene-ethylene-butylene/styrene-styrene copolymer,
A production method characterized in that the melt viscosity at 180° C. is 10,000 to 30,000 mPa·s.
Section 2.
The hot-melt composition has a loss tangent tan δ (= loss elastic modulus G″/storage elastic modulus G′) at a temperature between −60° C. and −20° C. at which the tan δ value is 1.0° C. Item 1. The manufacturing method according to Item 1, wherein the ratio is 0 or less.
Item 3.
Item 3. The production method according to Item 1 or 2, wherein the hot melt composition contains 10 to 35% by mass of the ethylene-vinyl acetate copolymer (C).
Section 4.
Item 4. The manufacturing method according to any one of Items 1 to 3, wherein the first nonwoven fabric and the second nonwoven fabric are one or more selected from spunbond nonwoven fabrics, spunlace nonwoven fabrics, air-laid nonwoven fabrics, and air-through nonwoven fabrics.

According to the method for producing a stretchable laminate according to the present invention, it is possible to obtain a stretchable laminate that is comfortable to the touch and has excellent stress during elongation. It is possible to provide a method for manufacturing a stretchable laminate, which can be coated with a stretchable member by using a method.

Explanatory drawing of an example which uses a conveyance roll in the manufacturing method of this invention.

The present invention is a method for manufacturing an elastic laminate,
Step 1 of applying a molten hot-melt composition to obtain a hot-melt composition layer;
Step 2 of laminating the first nonwoven fabric, the stretched hot-melt composition layer, and the second nonwoven fabric in this order;
A step 3 of joining the stretched hot melt composition layer to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive bonding and / or ultrasonic fusion,
The hot melt composition is
Containing a hydrogenated styrenic block copolymer (A) and a plasticizer (B),
55 to 70% by mass of the hydrogenated styrenic block copolymer (A) and 5 to 25% by mass of the plasticizer (B) in 100% by mass of the hot melt composition,
The hydrogenated styrenic block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and/or a styrene-ethylene-butylene/styrene-styrene copolymer,
It is characterized by having a melt viscosity of 10,000 to 30,000 mPa·s at 180°C.

In general, thread rubber is known as a member used in a stretchable laminate, which is a thread of natural rubber and/or synthetic polymer. A stretchable member used in a gather part of a conventional sanitary material is formed by joining a base material such as a nonwoven fabric and a plurality of rubber threads. Since the stretchable member formed in this way has good stretchability, when it is used in an absorbent article, it is difficult for the stretchable member to slip when worn, and the wearer can be given a sense of security. However, in the stretchable laminate formed as described above, since linear pressure is applied to the waist of the wearer by the linear rubber thread, the wearer may feel a strong tightness.

By using a stretchable member using a stretchable film that tightens the waist with surface pressure, the pressure applied to the wearer is dispersed, so that a good tightening feeling can be achieved. However, since the elastic film has a high viscosity and is not of the hot-melt type, it cannot be applied using a commonly used hot-melt applicator, which complicates the manufacturing process of sanitary materials.

By using the hot-melt stretchable adhesive composition as the stretchable member, a stretchable laminate that can be tightened by surface pressure can be produced using a normal hot-melt applicator. However, since conventional hot-melt stretchable adhesive compositions have low stress when stretched, they do not provide a sufficient feeling of tightness when worn, and there is a risk that the sanitary material will slip off.

In contrast, according to the method for producing a stretchable laminate of the present invention, it is possible to obtain a stretchable laminate that is comfortable to the touch and has excellent stress during elongation by using a predetermined hot-melt composition. Furthermore, it is possible to provide a method for manufacturing a stretchable laminate, which allows the stretchable member to be coated using a normal hot-melt adhesive applicator.

Hereinafter, the method for producing the elastic laminate of the present invention will be described in detail.

1. Process 1
In step 1, a molten hot melt composition is applied to obtain a hot melt composition layer. In this specification, the term "hot melt" means that it exhibits fluidity when heated (for example, 180°C), and then loses its fluidity and solidifies when cooled to room temperature (23°C). .

(Hot melt composition)
The hot melt composition contains a hydrogenated styrenic block copolymer (A) and a plasticizer (B). Furthermore, it may contain an ethylene-vinyl acetate copolymer (C) and/or other additives.

(Hydrogenated styrenic block copolymer (A))
A hydrogenated styrenic block copolymer is obtained by block copolymerizing a vinyl aromatic hydrocarbon and a conjugated diene compound, and all or part of the blocks based on the conjugated diene compound in the obtained block copolymer are hydrogen. Refers to the added block copolymer.

The term "vinyl-based aromatic hydrocarbon" refers to an aromatic hydrocarbon compound having a vinyl group, and specifically includes, for example, styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1 , 3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene and the like, with styrene being preferred. The vinyl aromatic hydrocarbons may be used alone or in combination of two or more.

"Conjugated diene compound" means a diolefin compound having at least one pair of conjugated double bonds. Specific examples of conjugated diene compounds include 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. , 1,3-hexadiene and the like, with 1,3-butadiene and 2-methyl-1,3-butadiene being preferred. The conjugated diene compounds may be used alone or in combination of two or more.

The ratio of hydrogenation in the hydrogenated styrenic block copolymer is indicated by "hydrogenation rate". The "hydrogenation rate" of a hydrogenated thermoplastic block copolymer is based on the total ethylenically unsaturated double bonds contained in the block based on the conjugated diene compound, among which hydrogenated saturated Refers to the ratio of ethylenically unsaturated double bonds converted to hydrocarbon bonds. The hydrogenation rate can be measured by an infrared spectrophotometer, a nuclear magnetic resonance apparatus, or the like.

The hydrogenated styrenic block copolymer is not particularly limited, but styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), styrene-ethylene-butylene. / styrene-styrene copolymer (SEB/SS), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), styrene-ethylene-butylene - It is preferably at least one selected from olefin crystal copolymers (SEBC). By adopting such a configuration, the hot-melt composition layer has excellent stretchability, and the stress during elongation is also improved. As a result, the obtained stretchable laminate has excellent stretchability and excellent stress during elongation. Among them, from the viewpoint of further improving the stretchability and stress during elongation of the stretchable laminate, either a styrene-ethylene-butylene-styrene copolymer or a styrene-ethylene-butylene/styrene-styrene copolymer. or both are particularly preferred.

A styrene-ethylene-butylene-styrene copolymer is a copolymer in which terminal styrene units form an endblock phase and ethylene-butylene units form a midblock phase. By using a copolymer in which the mid-block phase is hydrogenated ethylene-butylene units, the polarity difference with the styrene units in the end-block phase becomes significant, and the copolymer with the unhydrogenated mid-block phase By comparison, the styrene units in the endblock phase are stronger. As a result, the stress during elongation of the hot-melt composition layer can be improved.

The styrene content of the styrene-ethylene-butylene-styrene copolymer is preferably 15 to 30% by mass, more preferably 17 to 25% by mass, based on 100% by mass of the styrene-ethylene-butylene-styrene copolymer. When the styrene content is 15% by mass or more, the stress during elongation is further improved. When the styrene content is 30% by mass or less, the hot-melt composition becomes softer and the hot-melt composition is easier to apply (coating unevenness is reduced).

In addition, in this specification, the "styrene content" of a styrenic block copolymer means the content ratio (% by mass) of the styrene block in the styrenic block copolymer.

The method for calculating the styrene content in the styrenic block copolymer is not particularly limited, but examples thereof include a method using proton nuclear magnetic resonance or infrared spectroscopy according to JIS K6239.

A commercially available product can be used as the styrene-ethylene-butylene-styrene copolymer. Commercially available products include Tuftec H1041 manufactured by Asahi Kasei Corporation and MD1648 manufactured by Kraton Polymer.

The styrene-ethylene-butylene-styrene copolymer may be used singly or in combination of two or more. For example, a styrene-ethylene-butylene-styrene copolymer with a high styrene content and a styrene-ethylene-butylene-styrene copolymer with a low styrene content may be mixed and used. The styrene content of the entire styrene-ethylene-butylene-styrene copolymer when two or more types are mixed and used may be calculated from the average value based on the weight.

Styrene-ethylene-butylene/styrene-styrene copolymers are styrene-ethylene-butylene-styrene copolymers in which terminal styrene units form the end-block phase and ethylene-butylene units form the mid-block phase. is also a copolymer in which styrene is dispersed. By using a copolymer in which styrene is dispersed in the mid-block phase, even if the total styrene content of the styrene block copolymer increases, the styrene block copolymer does not become too hard and has good elongation. Therefore, a hot melt composition containing a styrene-ethylene-butylene/styrene-styrene copolymer can achieve both good extensibility and improved stress during elongation. Furthermore, by using a styrene-ethylene-butylene/styrene-styrene copolymer in which styrene is dispersed in the mid-block phase, an increase in melt viscosity at low temperatures is suppressed, so that the hot-melt composition can be improved. The coating suitability of can be further improved.

The method of preparing the styrene-ethylene-butylene/styrene-styrene copolymer is not particularly limited and includes, for example, the method described in US Pat. No. 7,169,848.

The styrene content of the styrene-ethylene-butylene/styrene-styrene copolymer is preferably 20 to 40% by mass, preferably 25 to 35% by mass, based on 100% by mass of the styrene-ethylene-butylene/styrene-styrene copolymer. more preferred. When the styrene content is 20% by mass or more, the stress during elongation is further improved, and the stretchability of the stretchable laminate is excellent. When the styrene content is 40% by mass or less, the hot-melt composition becomes softer and has good coatability.

Commercially available products can be used as the styrene-ethylene-butylene/styrene-styrene copolymer. Commercially available products include MD6951 manufactured by Kraton Polymer Co., Ltd., and the like.

The styrene-ethylene-butylene/styrene-styrene copolymer may be used singly or in combination of two or more. For example, a styrene-ethylene-butylene/styrene-styrene copolymer having a high styrene content and a styrene-ethylene-butylene/styrene-styrene copolymer having a low styrene content may be mixed and used. The styrene content of the entire styrene-ethylene-butylene/styrene-styrene copolymer when two or more types are mixed and used may be calculated from the average value based on the weight.

The content of the hydrogenated styrenic block copolymer (A) in the hot-melt composition used in the method for producing the elastic laminate of the present invention is 55 to 70, with the hot-melt composition being 100% by mass. % by mass, more preferably 58 to 65% by mass. If the content of the styrenic block copolymer (A) is less than 55% by mass or more than 70% by mass, the stretchability and stress during elongation of the finally obtained elastic laminate will be insufficient. turn into.

The melt viscosity of the hot melt composition at 180° C. is 10,000 to 30,000 mPa s, more preferably 13,000 to 25,000 mPa s, and 15,000 to 20,000 mPa s. is more preferred. If the melt viscosity of the hot-melt composition at 180° C. is less than 10,000 mPa·s, the stress during elongation of the finally obtained elastic laminate will be insufficient. On the other hand, if the melt viscosity at 180° C. exceeds 30,000 mPa s, when forming a hot composition layer by coating with a normal hot melt adhesive coating device, uneven coating due to excessive viscosity occurs.

As used herein, "melt viscosity" is defined as the viscosity of a hot-melt adhesive that is heated and melted at a certain temperature. Although the method of measurement is not particularly limited, for example, the hot-melt composition can be heated and melted, and the viscosity in the molten state at 180° C. can be measured using a Brookfield RVT viscometer (spindle No. 29).

(Plasticizer (B))
As the plasticizer (B), it is preferable to use a plasticizer that is liquid at 23°C in order to improve the stretchability of the hot-melt composition at 23°C. In this specification, the term "liquid" refers to a fluid state. The plasticizer (B) is not particularly limited, and examples thereof include paraffinic process oil, naphthenic process oil, aromatic process oil, liquid paraffin, and hydrocarbon synthetic oil. Among them, paraffin-based process oil, naphthenic process oil, liquid paraffin, and hydrocarbon-based synthetic oil are preferable from the viewpoint of excellent heat stability, and hydrocarbon-based synthetic oil is more preferable from the viewpoint of excellent stretchability.

A commercially available product can be used as the paraffinic process oil. Examples of commercially available products include PW-32 manufactured by Idemitsu Kosan Co., Ltd., PS-32 manufactured by Idemitsu Kosan Co., Ltd., PS-90 manufactured by Idemitsu Kosan Co., Ltd., and the like.

A commercially available product can be used as the naphthenic process oil. Examples of commercially available products include Dianafrecia N28 manufactured by Idemitsu Kosan Co., Ltd., Dianafrecia U46 manufactured by Idemitsu Kosan Co., Ltd., and Nyflex222B manufactured by Nynas.

Commercially available liquid paraffin can be used. Commercially available products include P-100 manufactured by MORESCO, Kaydol manufactured by Sonneborn, and the like.

A commercially available product can be used as the hydrocarbon synthetic oil. Commercially available products include Lucant HC-10 manufactured by Mitsui Chemicals, Lucant HC-20 manufactured by Mitsui Chemicals, and the like.

The above plasticizers may be used singly or in combination of two or more.

The content of the plasticizer (B) in the hot-melt composition is 5-25% by mass, more preferably 10-20% by mass, based on 100% by mass of the hot-melt composition. If the content of the plasticizer (B) is less than 5% by mass, the melt viscosity of the hot-melt composition increases, making it impossible to coat the hot-melt composition with a normal hot-melt adhesive coating device. On the other hand, if the content of the plasticizer (B) exceeds 25% by mass, the hot-melt composition layer becomes too soft, and the stress during elongation of the finally obtained elastic laminate becomes insufficient.

(Ethylene-vinyl acetate copolymer (C))
The hot melt composition may contain an ethylene-vinyl acetate copolymer.

A commercially available product can be used as the ethylene-vinyl acetate copolymer. Commercially available products include AC-400 manufactured by Honeywell, AC-430 manufactured by Honeywell, and the like.

The above ethylene-vinyl acetate copolymer may be used alone or in combination of two or more.

The content of the ethylene-vinyl acetate copolymer (C) in the hot-melt composition is preferably 10-35% by mass, more preferably 15-30% by mass, based on 100% by mass of the hot-melt composition. By setting the content of the ethylene-vinyl acetate copolymer (C) to 10% by mass or more, the stress during elongation of the elastic laminate is improved. By setting the content of the ethylene-vinyl acetate copolymer (C) to 35% by mass or less, the heat stability of the hot-melt composition is improved.

(other additives)
The hot-melt composition used in the method for producing the elastic laminate of the present invention may contain other additives as long as the objects of the present invention are not essentially hindered. Examples of the other additives include antioxidants, ultraviolet absorbers, and the like.

Antioxidants include 2,6-di-t-butyl-4-methylphenol, n-octadecyl-3-(4′-hydroxy-3′,5′-di-t-butylphenyl)propionate, 2, 2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,4-bis(octylthiomethyl)-o-cresol, 2 -t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 2,4-di-t-amyl-6-[1-(3,5 -di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate, tetrakis[methylene-3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionate]methane; hindered phenolic antioxidants such as dilaurylthiodipropionate, laurylstearylthiodipropionate, pentaerythritol tetrakis(3-laurylthiopropionate sulfur-based antioxidants such as tris (nonylphenyl) phosphite and tris (2,4-di-t-butylphenyl) phosphite; An antioxidant may be used individually by 1 type, and may be used in mixture of 2 or more types.

The content of the antioxidant in the hot melt composition is preferably 0.01 to 2 mass %, more preferably 0.05 to 1.5 mass %, more preferably 0.05 to 1.5 mass %, based on 100 mass % of the hot melt composition. 1 to 1% by mass is more preferable. By setting the content of the antioxidant to 0.01% by mass or more, the thermal stability of the hot-melt composition is improved. By setting the content of the antioxidant to 2% by mass or less, the odor of the hot-melt composition is reduced, so that the odor of the elastic laminate using the composition is also reduced.

UV absorbers include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-t-butylphenyl)benzotriazole, 2-(2' -Hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole and other benzotriazole UV absorbers; 2-hydroxy-4-methoxybenzophenone and other benzophenone UV absorbers; salicylate esters UV absorbers; cyanoacrylate UV absorbers; hindered amine light stabilizers. Ultraviolet absorbers may be used singly or in combination of two or more.

The content of the ultraviolet absorber is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, and 0.1 to 1% by mass, based on 100% by mass of the hot melt composition. More preferred. By setting the content of the ultraviolet absorber to 0.01% by mass or more, the weather resistance of the hot-melt composition is improved. By setting the content of the ultraviolet absorber to 2% by mass or less, the odor of the hot-melt composition is reduced, so that the odor of the stretchable laminate using the hot-melt composition is also reduced.

The hot melt composition used in the method for producing the elastic laminate of the present invention has a loss tangent tan δ ( = Loss modulus G''/storage modulus G') is preferably 1.0 or less at the temperature at which the value of tan δ is maximized.

Dynamic viscoelasticity measurements are taken in rotational shear mode with a fixed frequency of 1 Hz. Specifically, the dynamic viscoelasticity measurement is performed in the following manner. After the hot-melt composition is heated and melted at 180° C., it is poured onto a release-treated PET film. After that, another PET film that has been subjected to a release treatment is superposed on the stretchable hot-melt composition so that the release surface is in contact with the hot-melt composition. Then, it is compressed with a hot press heated to 120° C., and the thickness of the hot-melt composition is adjusted to about 1 to 2 mm.

After leaving the hot-melt composition sandwiched between release films at 23° C. for 24 hours, the release film is removed to prepare a sample for dynamic viscoelasticity measurement. This sample is subjected to dynamic viscoelasticity measurement (heating process) by increasing the temperature from −80 to 130° C. at a rate of 5° C./min in a rotational shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device. A loss tangent tan δ (=loss elastic modulus G″/storage elastic modulus G′) is calculated from the storage elastic modulus G′ and the loss elastic modulus G″ measured at this time. The dynamic viscoelasticity measuring device includes, for example, a rotational rheometer (trade name “AR-G2”) available from TA Instruments.

The hot-melt composition has a loss tangent tan δ (= loss elastic modulus G ''/storage modulus G') preferably has a maximum temperature. When the hot-melt composition is heated from -80°C, it transitions from a glassy state to a rubbery state with an increase in molecular motion. At this time, the value of tan δ takes a maximum value, and the temperature at that time is evaluated as the glass transition temperature.

The hot-melt composition used in the method for producing the elastic laminate of the present invention has a loss tangent tan δ (= loss elastic modulus G''/storage elastic modulus measured in the process of heating at a frequency of 1 Hz by dynamic viscoelasticity measurement. In G′), the value of tan δ is preferably 1.0 or less, more preferably 0.9 or less, at the temperature between −60° C. and −20° C. where the value of tan δ is maximum. By setting the tan δ value to 1.0 or less, the viscous properties of the hot-melt composition are lowered, so that the adhesiveness is lowered and the hot-melt composition is hardened, so that the stress during elongation of the hot-melt composition is improved. . As a result, the stress during elongation of the elastic laminate using such a hot-melt composition is also improved.

Hot-melt compositions are manufactured by known methods. For example, a hydrogenated styrenic block copolymer, a plasticizer, various additives, and the like are put into a double-arm kneader heated to 150° C. and melt-kneaded while being heated.

(Hot melt composition layer)
The hot-melt composition layer can be obtained by coating the hot-melt composition that has been melted. The melting temperature at this time is not particularly limited, and is preferably 160 to 200° C., for example.

The surface to be coated with the molten hot-melt composition is not particularly limited as long as it can cool the molten hot-melt composition. The material of the surface to be coated is not particularly limited, and for example, a so-called chill roll, in which a cooling fluid is circulated inside a roll made of stainless steel, can be used. The shape of the surface to be coated is not particularly limited, and various shapes such as a flat plate shape can be mentioned, but it is also preferable to use a cylindrical shape in consideration of productivity.

The basis weight of the hot-melt composition layer is preferably 1 g/m ² or more, more preferably 5 g/m ² or more, in order to obtain the desired adhesive strength. On the other hand, considering the texture of the resulting laminate, the basis weight of the hot-melt composition layer is preferably 30 g/m ² or less, more preferably 10 g/m ² or less.

The method of applying the hot-melt composition to the surface to be coated is not particularly limited, and general methods can be used. For example, the hot-melt composition is put into a hot-melt tank heated to 180°C, and after sufficiently heat-melted, the hot-melt composition is discharged from a discharge nozzle heated to 180°C. The ejection pattern is not particularly limited, and examples thereof include slot coating, slit coating in which slits are formed in a slot shape, spray coating such as spiral coating and curtain coating, and bead coating.

2. Process 2
In step 2, the first nonwoven fabric, the stretched hot-melt composition layer, and the second nonwoven fabric are laminated in this order.

(First nonwoven fabric and second nonwoven fabric)
As the nonwoven fabric, a wide range of known nonwoven fabrics can be used. Specifically, it is preferable to use one or more selected from spunbond nonwoven fabrics, spunlaced nonwoven fabrics, air-laid nonwoven fabrics, and air-through nonwoven fabrics. Also, the first nonwoven fabric and the second nonwoven fabric may be of different types, or may be of the same type.

The basis weight of the nonwoven fabric is preferably 10 g/m ² or more, more preferably 13 g/m ² or more, from the viewpoint of securing tensile strength. On the other hand, considering the texture of the finally obtained laminate, the fabric weight of the nonwoven fabric is preferably 30 g/m ² or less, more preferably 15 g/m ² or less.

Moreover, the nonwoven fabric to be used is preferably a nonwoven fabric that does not have stretchability in at least one direction. By adopting such a configuration, it is possible to obtain the advantage that the nonwoven fabric is not substantially elongated even if a tensile stress acts in the transport direction when the nonwoven fabric is transported.

As described above, when nonwoven fabrics having no stretchability in at least one direction are used as the first nonwoven fabric and the second nonwoven fabric, It is preferable that the direction of non-stretchability of the non-woven fabric is the same for lamination.

In this specification, the term "non-woven fabric having no stretchability in at least one direction" means that the non-woven fabric does not substantially stretch even if a tensile stress acts in the transport direction when the non-woven fabric is transported. More specifically, it means that the elongation rate during transportation is less than 30%.

During lamination, the hot-melt composition layer is in a stretched state. A wide range of known methods can be used as the stretching method, and there is no particular limitation. Here, stretching means stretching in the conveying direction from a state in which no elongation stress is applied to the hot-melt composition in order to make the hot-melt composition stretchable. The hot-melt composition can be stretched by increasing the conveying speed on the downstream side. As for the draw ratio, it is preferable to draw the film to about 200% to 500% (2 times to 5 times) of the natural length at which the elongation stress does not act. By having such a configuration, it is possible to obtain a stretchable laminate that is excellent in stress during elongation.

The hot-melt composition layer stretched in step 2 is maintained in the stretched state until it is joined in step 3, which will be described later.

3. Step 3
In step 3, the stretched hot melt layer is bonded to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive bonding and/or ultrasonic fusion.

The hot-melt adhesive used for hot-melt adhesive bonding is not particularly limited, and known hot-melt adhesives can be used. The hot melt adhesive contains a thermoplastic elastomer. The thermoplastic elastomer is not particularly limited, and examples thereof include styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, and styrene-ethylene-propylene. - styrene block copolymers, styrene-ethylene-ethylene-propylene-styrene copolymers, styrene-butylene-butadiene-styrene block copolymers, polyethylene copolymers, polypropylene copolymers, polyethylene-polypropylene copolymers, polyethylene - Vinyl acetate copolymers and the like. These thermoplastic elastomers may be used singly or in combination of two or more. More specifically, for example, a hot melt adhesive containing a styrenic block copolymer as disclosed in Japanese Patent Application Laid-Open No. 2008-239931 can be used.

A specific mode of ultrasonic fusion is not particularly limited, and a wide range of known methods can be employed.

Next, an example of a method for manufacturing an elastic laminate according to the present invention will be described with reference to FIG. The present invention is not limited to such an example, and can of course be embodied in various forms without departing from the gist of the present invention.

Reference numeral 1 in the figure denotes a hot melt applicator, which is designed to eject a hot melt composition melted by heating from an ejection nozzle (not shown). The hot-melt composition discharged from the discharge nozzle is cooled by being applied onto the surface of the cooling roll 2 in the discharge pattern described above, and the stretchable member 3 is formed.

The stretchable member 3 passes between the nip rolls 4 and 4 and is conveyed between the nip rolls 5 and 5 on the downstream side. Here, the conveying speed of the nip rolls 5, 5 is higher than the conveying speed of the nip rolls 4, 4, so that the stretchable member 3 is stretched and the stretchability of the stretchable member is exhibited.

Further, between the nip rolls 5, 5, a nonwoven fabric 6 as a first base material and a nonwoven fabric 7 as a second base material are introduced so as to sandwich the elastic material. A hot-melt adhesive is applied in advance to the surfaces of the nonwoven fabric 6 and the nonwoven fabric 7 facing the elastic member 3 by hot melt applicators 8, 8, whereby the nonwoven fabric 6, the nonwoven fabric 7 and the elastic member 3 are joined to form an elastic laminate. 9 is formed.

The elastic laminate 9 led out from the nip rolls 5, 5 is further supplied between the ultrasonic horn 10 and the anvil roll 11, and the nonwoven fabric 6, the nonwoven fabric 7 and the elastic member 3 are ultrasonically welded.

The nonwoven fabric 6, the nonwoven fabric 7 and the elastic member 3 may be joined only by a hot-melt adhesive or only by ultrasonic welding. In the case of using only hot-melt adhesive, equipment is inexpensive, and in the case of using only ultrasonic welding, a stretchable laminate 9 that is flexible and pleasant to the touch can be obtained. The stretchable laminate 9 produced in this way has a high stress when stretched, and can be used as a sanitary material such as a paper diaper to prevent slipping down when worn.

The application of the elastic laminate is not particularly limited, and for example, it can be suitably used for so-called sanitary materials such as disposable diapers and sanitary napkins.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to such examples, and can of course be embodied in various forms without departing from the gist of the present invention.

EXAMPLES Hereinafter, embodiments of the present invention will be described more specifically based on Examples, but the present invention is not limited to these.

(Production of hot-melt composition)
The following raw materials were put into a stirring and kneading machine equipped with a heating device at respective blending amounts. The elastic hot-melt compositions 1 to 4 were produced by kneading while heating at 150° C. for 90 minutes.

(Hot melt composition 1)
・ Hydrogenated styrene-based block copolymer MD6951 manufactured by Kraton Polymer (blended amount: 30% by mass)
・ Hydrogenated styrene-based block copolymer MD1648 manufactured by Kraton Polymer (compound amount: 30% by mass)
・Plasticizer Lucanto HC-10 manufactured by Mitsui Chemicals (mixing amount: 4.5% by mass)
・Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (blended amount: 35% by mass)
Antioxidant IRGANOX1010 manufactured by BASF (blended amount: 0.5% by mass)

(Hot melt composition 2)
・ Hydrogenated styrene-based block copolymer MD6951 manufactured by Kraton Polymer (blended amount: 30% by mass)
・ Hydrogenated styrene-based block copolymer MD1648 manufactured by Kraton Polymer (compound amount: 30% by mass)
・Plasticizer Lucanto HC-10 manufactured by Mitsui Chemicals (mixing amount: 14.5% by mass)
・Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (blended amount: 25% by mass)
Antioxidant IRGANOX1010 manufactured by BASF (blended amount: 0.5% by mass)

(Hot melt composition 3)
・ Hydrogenated styrene-based block copolymer MD6951 manufactured by Kraton Polymer (blended amount: 30% by mass)
・ Hydrogenated styrene-based block copolymer MD1648 manufactured by Kraton Polymer (compound amount: 30% by mass)
・Plasticizer Lucanto HC-10 manufactured by Mitsui Chemicals (mixing amount: 24.5% by mass)
・ Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (blended amount: 15% by mass)
Antioxidant IRGANOX1010 manufactured by BASF (blended amount: 0.5% by mass)

(Hot melt composition 4)
・ Hydrogenated styrene-based block copolymer MD6951 manufactured by Kraton Polymer (blended amount: 30% by mass)
・ Hydrogenated styrene-based block copolymer MD1648 manufactured by Kraton Polymer (compound amount: 30% by mass)
・Plasticizer Lucanto HC-10 manufactured by Mitsui Chemicals, Inc. (mixing amount: 0.5% by mass)
・ Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (blended amount: 39% by mass)
Antioxidant IRGANOX1010 manufactured by BASF (blended amount: 0.5% by mass)

(Example 1)
An elastic laminate was manufactured by the steps shown in FIG. The hot-melt composition 1 was put into a hot melting tank heated to 190°C, and discharged from a discharge nozzle heated to 190°C so that the coating width was 70 mm and the coating amount was 60 g/m ² . After that, the stretchable hot-melt composition was stretched to about 350% (3.5 times) of the natural length at which extension stress does not act, and sandwiched between two spunbond nonwoven fabrics (basis weight: 18 g/mm ² ). The nonwoven fabric and the hot-melt composition were joined by a fusion device to obtain an elastic laminate. At this time, the line speed was 70 m/min.

(Example 2)
An elastic laminate was obtained in the same process as in Example 1, except that the hot-melt composition 2 was used.

(Example 3)
An elastic laminate was obtained in the same process as in Example 1, except that hot-melt composition 3 was used.

(Example 4)
The hot-melt composition 2 was put into a hot melting tank heated to 190°C, and discharged from a discharge nozzle heated to 190°C so that the coating width was 70 mm and the coating amount was 60 g/m ² . After that, the stretchable hot-melt composition is stretched to about 350% (3.5 times) of the natural length at which the stretching stress does not act, and sandwiched between two spunbond nonwoven fabrics (basis weight 18 g/mm ² ). made it At this time, a hot-melt adhesive was spray-coated to the two spunbonded nonwoven fabrics at a coating amount of 3.5 g/m ² , and the hot-melt composition was bonded to the spunbonded nonwoven fabrics with the hot-melt adhesive, resulting in a stretchability. A laminate was obtained. A rubber-based hot-melt adhesive was used as the hot-melt adhesive used for bonding the hot-melt composition and the spunbond nonwoven fabric.

(Comparative example 1)
An elastic laminate was obtained in the same process as in Example 1, except that hot melt composition 4 was used.

The properties of the resulting hot-melt composition were evaluated under the following measurement conditions.

(melt viscosity)
The hot-melt adhesive was heated and melted, and the viscosity of the molten state at 80° C. was measured using a Brookfield RVT viscometer (spindle No. 29).

(heating stability)
20 g of the hot melt composition was placed in a 70 ml glass bottle and allowed to stand at 180° C. for 3 days. Next, separation and discoloration of the hot-melt adhesive were visually observed under room temperature conditions and evaluated according to the following evaluation criteria. If the evaluation is Δ or higher, it can be evaluated that there is no problem in actual use.
◯: No separation of the hot-melt composition was observed, and no discoloration was observed.
Δ: No separation of the hot-melt composition was observed, but the degree of discoloration was slight.
x: Separation of the hot-melt composition was observed, and the degree of discoloration was large.

(tan δ maximum value)
Dynamic viscoelasticity measurements are taken in rotational shear mode with a fixed frequency of 1 Hz. Specifically, the dynamic viscoelasticity measurement is performed in the following manner. After the hot-melt composition is heated and melted at 180° C., it is poured onto a release-treated PET film. After that, another PET film that has been subjected to a release treatment is overlaid on the hot-melt composition so that the release surface is in contact with the hot-melt composition. Then, it is compressed with a hot press heated to 120° C., and the thickness of the hot-melt composition is adjusted to about 1 to 2 mm.

After leaving the hot-melt composition sandwiched between release films at 23° C. for 24 hours, the release film is removed to prepare a sample for dynamic viscoelasticity measurement. This sample is subjected to dynamic viscoelasticity measurement (heating process) by increasing the temperature from −80 to 130° C. at a rate of 5° C./min in a rotational shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device. A loss tangent tan δ (=loss elastic modulus G″/storage elastic modulus G′) is calculated from the storage elastic modulus G′ and the loss elastic modulus G″ measured at this time. The value of tan δ at the temperature between −60° C. and −20° C. at which tan δ is maximum was recorded and taken as the tan δ maximum value.

(Coatability)
When the hot-melt composition is discharged from the nozzle, visually confirm coating unevenness under the conditions of a line speed of 70 m / min, a coating width of 70 mm, and a coating amount of 60 g / m ^2. Coatability ( Ejectability) was evaluated. If the evaluation is Δ or higher, it can be evaluated as having no problem.
○: Can be applied without uneven coating △: Some uneven coating is observed, but there is no problem in use ×: Remarkable uneven coating is observed, or a predetermined amount of hot melt composition is not discharged

(Stress at double elongation)
The elastic laminate was cut into strips of 100 mm in the coating direction (MD direction) of the hot-melt composition and 50 mm in the direction perpendicular to the coating direction (CD direction) to prepare test pieces. . Then, the test piece was fixed to a tensile tester set to a jig width of 50 mm so as to press the long side of the test piece, and the test piece was pulled at a tensile speed of 500 mm/min. The stress when the long side of the test piece was elongated twice from the initial length was defined as the stress at double elongation.

(touch)
The elastic laminate was touched with fingers by 10 people to evaluate the degree of feel of the elastic laminate. The results of evaluating the feel of the elastic laminate were classified according to the following criteria, and entered in the column of "feel" in Table 1. If the evaluation is Δ or higher, it can be evaluated that there is no problem in actual use.
○: 8 or more out of 10 people answered that it feels good on the skin △: 5 to 7 out of 10 people answered that it feels good on the skin ×: 1 to 4 out of 10 people said it feels good on the skin answered

Table 1 shows the results.

REFERENCE SIGNS LIST 1 hot melt applicator 2 cooling roll 3 elastic member 4 nip roll 5 nip roll (downstream side)
6 nonwoven fabric 7 nonwoven fabric 8 hot melt applicator 9 elastic laminate 10 ultrasonic horn 11 anvil roll

Claims (4)

A method for manufacturing an elastic laminate,
Step 1 of applying a molten hot-melt composition to obtain a hot-melt composition layer;
Step 2 of laminating the first nonwoven fabric, the stretched hot-melt composition layer, and the second nonwoven fabric in this order;
A step 3 of joining the stretched hot melt composition layer to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive bonding and / or ultrasonic fusion,
The hot melt composition is
Containing a hydrogenated styrenic block copolymer (A) and a plasticizer (B),
55 to 70% by mass of the hydrogenated styrenic block copolymer (A) and 5 to 25% by mass of the plasticizer (B) in 100% by mass of the hot melt composition,
The hydrogenated styrenic block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and/or a styrene-ethylene-butylene/styrene-styrene copolymer,
A production method characterized in that the melt viscosity at 180° C. is 10,000 to 30,000 mPa·s. The hot-melt composition has a loss tangent tan δ (= loss elastic modulus G″/storage elastic modulus G′) at a temperature between −60° C. and −20° C. at which the tan δ value is 1.0° C. 2. The production method according to claim 1, which is 0 or less. The production method according to claim 1 or 2, wherein the hot melt composition contains 10 to 35% by mass of the ethylene-vinyl acetate copolymer (C). The production according to any one of claims 1 to 3, wherein the first nonwoven fabric and the second nonwoven fabric are one or more selected from spunbond nonwoven fabrics, spunlace nonwoven fabrics, air-laid nonwoven fabrics, and air-through nonwoven fabrics. Method.

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