WO2019151370A1 - Method for producing stretchable laminate - Google Patents

Abstract

A method for producing a stretchable laminate is provided by which a stretchable laminate having a good touch and being excellent in terms of stress during elongation can be obtained and in which a stretch member can be coated using an ordinary hot-melt adhesive applicator. The method, which is for producing a stretchable laminate, is characterized by comprising: step 1, in which a molten hot-melt composition is applied to obtain a hot-melt composition layer; step 2, in which first nonwoven fabric, the hot-melt composition layer in a stretched state, and second nonwoven fabric are stacked in this order; and step 3, in which the hot-melt composition layer in the stretched state is bonded to the first nonwoven fabric and the second nonwoven fabric by hot-melt adhesive bonding and/or ultrasonic fusion bonding. The production method is further characterized in that the hot-melt composition comprises a hydrogenated styrene-based block copolymer (A) and a plasticizer (B), that the hydrogenated styrene-based block copolymer (A) and the plasticizer (B) are contained in amounts of 55-70 mass% and 5-25 mass%, respectively, per 100 mass% the hot-melt composition, that the hydrogenated styrene-based block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and/or a styrene-ethylene-butylene/styrene-styrene copolymer, and that the hot-melt composition has a melt viscosity at 180°C of 10,000-30,000 mPa∙s.

Description

Method for producing stretch laminate

The present invention relates to a method for producing a stretchable laminate.

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

A stretchable film containing a thermoplastic elastomer has been proposed as a stretchable member of a stretchable laminate provided in a sanitary material 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 excellent in moisture permeability and flexibility and suitable for sanitary materials such as sanitary products is provided.

Also, a hot-melt stretchable adhesive composition has been proposed as a stretchable material that can be used in a hot-melt adhesive application device (see, for example, Patent Document 2). Patent Document 2 discloses a block copolymer comprising an elastic polymer segment and a polystyrene polymer segment, which is a hydrogenated polymer of a butadiene polymer or an isoprene polymer, or one or more polymers selected from ethylene propylene polymers. A hot melt stretchable adhesive composition is disclosed. 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. By laminating, a hot melt adhesive that can easily form a gathered portion is provided.

Japanese Unexamined Patent Publication No. 2015-86367 Japanese Patent No. 2919385

However, if the rubber thread as described above is used, a linear pressure is applied to the human body, which may cause a feeling of pressure or a rash when worn. Further, since a plurality of thin thread rubbers are used for the sanitary material, the thread rubber is easily cut during the manufacture of the sanitary material, which often makes it difficult to manufacture the sanitary material.

Further, with respect to the stretchable film as described in Patent Document 1, since the stretchable film has a high viscosity, an extrusion device is required, and it cannot be used with a commonly used hot melt adhesive coating device. There is a problem from the viewpoint.

Furthermore, in the stretchable laminate using the stretchable adhesive composition of Patent Document 2, since the stress at the time of elongation is not sufficient, the sanitary material may fall off when worn. Moreover, 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 obtain a stretchable laminate having a good touch and excellent stress at the time of elongation, and a normal hot melt adhesive application device. An object of the present invention is to provide a method for producing a stretchable laminate, which can be coated with a stretchable member.

As a result of intensive studies to achieve the above object, the present inventors can obtain a stretchable laminate having a good touch and excellent stress during elongation by using a predetermined hot melt composition. In addition, the present inventors have found that a stretchable member can be applied using a normal hot melt adhesive application device. The present inventors have further studied based on such knowledge and have completed the present invention.

That is, the present invention provides the following method for producing a stretchable laminate.
Item 1.
A method for producing an elastic laminate,
Step 1 of applying a melted 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, and
Step 3 of joining the stretched hot melt composition layer to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive joining and / or ultrasonic fusion,
The hot melt composition is:
Comprising a hydrogenated styrenic block copolymer (A) and a plasticizer (B),
In 100% by mass of the hot melt composition, 55 to 70% by mass of the hydrogenated styrenic block copolymer (A) and 5 to 25% by mass of the plasticizer (B) are included.
The hydrogenated styrene block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and / or a styrene-ethylene-butylene / styrene-styrene copolymer,
A manufacturing method, wherein the melt viscosity at 180 ° C. is 10,000 to 30,000 mPa · s.
Item 2.
At a temperature at which the value of loss tangent tan δ (= loss elastic modulus G ″ / storage elastic modulus G ′) is maximum between −60 ° C. and −20 ° C., the value of tan δ is 1. Item 2. The production method according to Item 1, which 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).
Item 4.
Item 4. The method according to any one of Items 1 to 3, wherein the first nonwoven fabric and the second nonwoven fabric are at least one selected from a spunbonded nonwoven fabric, a spunlace nonwoven fabric, an airlaid nonwoven fabric, and an air-through nonwoven fabric.

According to the method for producing a stretchable laminate according to the present invention, it is possible to obtain a stretchable laminate having a good touch and excellent stress during elongation, and using a normal hot melt adhesive application apparatus. Thus, it is possible to provide a method for producing a stretchable laminate that can be coated with a stretchable member.

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

The present invention is a method for producing a stretch laminate,
Step 1 of applying a melted 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, and
Step 3 of joining the stretched hot melt composition layer to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive joining and / or ultrasonic fusion,
The hot melt composition is:
Comprising a hydrogenated styrenic block copolymer (A) and a plasticizer (B),
In 100% by mass of the hot melt composition, 55 to 70% by mass of the hydrogenated styrenic block copolymer (A) and 5 to 25% by mass of the plasticizer (B) are included.
The hydrogenated styrene block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and / or a styrene-ethylene-butylene / styrene-styrene copolymer,
The melt viscosity at 180 ° C. is 10,000 to 30,000 mPa · s.

Generally, as a member used for the stretchable laminate, natural rubber and / or thread rubber obtained by forming a synthetic polymer into a thread form is known. The elastic member used for the gathered part of the conventional sanitary material is formed by joining a base material such as a nonwoven fabric and a plurality of thread rubbers. Since the stretchable member formed in this manner has good stretchability, when used for absorbent articles, it is difficult for the wearer to shift during wearing, giving the wearer a sense of security. However, the stretchable laminate formed as described above may feel a strong tightening feeling because the linear pressure applied by the linear thread rubber is applied to the wearer's waist.

Since the pressure applied to the wearer is dispersed by using an elastic member using an elastic film that tightens the waistline with surface pressure, a good feeling of tightening can be achieved. However, since the stretchable film has a high viscosity and is not a hot-melt type, it cannot be applied using a commonly used hot-melt coating apparatus, and the hygiene material manufacturing process becomes complicated.

By using the hot-melt stretchable adhesive composition as a stretchable member, a stretchable laminate that can be tightened with a surface pressure using a normal hotmelt coating apparatus can be created. However, since the conventional hot-melt stretchable adhesive composition has a low stress when stretched, a sufficient tightening feeling cannot be obtained at the time of wearing, and the sanitary material may fall off.

On the other hand, according to the method for producing a stretchable laminate of the present invention, by using a predetermined hot melt composition, it is possible to obtain a stretchable laminate having a good texture and excellent stress during elongation. And the manufacturing method of the elastic laminated body which can apply an elastic member using a normal hot-melt-adhesive coating device can be provided.

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

1. Process 1
In step 1, the melted hot melt composition is applied to obtain a hot melt composition layer. In the present specification, “hot melt” means fluidity when heated (for example, 180 ° C.), and then 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). Further, it may contain an ethylene-vinyl acetate copolymer (C) and / or other additives.

(Hydrogenated styrene block copolymer (A))
The hydrogenated styrene block copolymer is obtained by block copolymerization of a vinyl aromatic hydrocarbon and a conjugated diene compound, and all or a part of the blocks based on the conjugated diene compound in the obtained block copolymer is hydrogen. It refers to the added block copolymer.

“Vinyl aromatic hydrocarbon” refers to an aromatic hydrocarbon compound having a vinyl group. Specifically, for example, styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1 , 3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene and the like, and styrene is 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 the conjugated diene compound 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, and 1,3-butadiene and 2-methyl-1,3-butadiene are preferred. A conjugated diene compound may be used independently or 2 or more types may be used together.

The ratio of hydrogenation in the hydrogenated styrene 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. The ratio of ethylenically unsaturated double bonds converted to hydrocarbon bonds. The hydrogenation rate can be measured with an infrared spectrophotometer or a nuclear magnetic resonance apparatus.

The hydrogenated styrene 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 stretchability of the hot melt composition layer becomes excellent, and the stress during elongation is also improved. As a result, the stretchability of the resulting stretchable laminate and the stress at elongation are also excellent. Among them, any one of styrene-ethylene-butylene-styrene copolymers and styrene-ethylene-butylene / styrene-styrene copolymers from the viewpoint of further improving the stretchability of the stretchable laminate and the stress during elongation. Or it is especially preferable to contain both.

The styrene-ethylene-butylene-styrene copolymer is a copolymer in which the terminal styrene unit is an end block phase and the ethylene-butylene unit is a mid block phase. By using a copolymer in which the midblock phase is a hydrogenated ethylene-butylene unit, the polarity difference from the styrene unit in the endblock phase becomes significant. In comparison, the styrene unit of the end block phase becomes stronger. As a result, the stress at the time of expansion | extension of a hot-melt composition layer can be improved.

The styrene content of the styrene-ethylene-butylene-styrene copolymer is preferably 15-30% by mass, more preferably 17-25% by mass, with the styrene-ethylene-butylene-styrene copolymer being 100% by mass. 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 becomes easier to apply (coating unevenness is reduced).

In the present specification, the “styrene content” of the styrenic block copolymer refers to the content ratio (% by mass) of the styrene block in the styrenic block copolymer.

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

As the styrene-ethylene-butylene-styrene copolymer, a commercially available product can be used. Commercially available products include Asahi Kasei's Tuftec H1041 and Kraton Polymer's MD1648.

The styrene-ethylene-butylene-styrene copolymer may be used alone or in combination of two or more. For example, a styrene-ethylene-butylene-styrene copolymer having a high styrene content and a styrene-ethylene-butylene-styrene copolymer having a low styrene content may be mixed and used. What is necessary is just to calculate the styrene content of the whole styrene-ethylene-butylene-styrene copolymer when mixing 2 or more types by the average value based on a weight.

The styrene-ethylene-butylene / styrene-styrene copolymer is a styrene-ethylene-butylene-styrene copolymer in which the terminal styrene unit is the end block phase and the ethylene-butylene unit is the mid block phase. Is a copolymer in which styrene is dispersed. By using a copolymer in which styrene is dispersed in the midblock 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 extensibility. Therefore, a hot melt composition containing a styrene-ethylene-butylene / styrene-styrene copolymer can achieve both good extensibility and improvement of stress during elongation. Furthermore, since a styrene-ethylene-butylene / styrene-styrene copolymer in which styrene is dispersed in the midblock phase is used in the hot melt composition, an increase in melt viscosity at low temperature is suppressed, so the hot melt composition The coating suitability of can be further improved.

The method for preparing the styrene-ethylene-butylene / styrene-styrene copolymer is not particularly limited, and examples thereof include 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, and 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 the coating suitability is improved.

As the styrene-ethylene-butylene / styrene-styrene copolymer, commercially available products can be used. As a commercial item, Kraton Polymer Co., Ltd. MD6951 etc. are mentioned.

The styrene-ethylene-butylene / styrene-styrene copolymer may be used alone 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. What is necessary is just to calculate the styrene content of the whole styrene-ethylene-butylene / styrene-styrene copolymer at the time of using 2 or more types mixedly by the average value based on a weight.

The content of the hydrogenated styrenic block copolymer (A) in the hot melt composition used in the method for producing a stretchable laminate of the present invention is 55 to 70, based on 100% by mass of the hot melt composition. % By mass, more preferably 58 to 65% by mass. When the content of the styrenic block copolymer (A) is less than 55% by mass or more than 70% by mass, the stretchable laminate finally obtained has insufficient stretchability and stress during elongation. turn into.

The melt viscosity at 180 ° C. of the hot melt composition is 10,000 to 30,000 mPa · s, more preferably 13,000 to 25,000 mPa · s, and more preferably 15,000 to 20,000 mPa · s. More preferably. When the melt viscosity at 180 ° C. of the hot melt composition is less than 10,000 mPa · s, the stress at the time of elongation of the stretchable laminate finally obtained becomes insufficient. On the other hand, when the melt viscosity at 180 ° C. exceeds 30,000 mPa · s, coating unevenness due to excessive viscosity is applied when forming a hot composition layer by coating with a normal hot melt adhesive coating apparatus. Will occur.

In this specification, “melt viscosity” is defined as the viscosity of a hot melt adhesive that has been heated and melted at a certain temperature. Although it does not specifically limit as a measuring method, For example, a hot-melt composition is heat-melted and the viscosity of the molten state in 180 degreeC can be measured using a Brookfield RVT type | mold viscosity meter (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 the present specification, “liquid” means a state showing fluidity. 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. Of these, paraffinic process oil, naphthenic process oil, liquid paraffin, and hydrocarbon synthetic oil are preferable from the viewpoint of excellent heat stability, and hydrocarbon synthetic oil is more preferable from the viewpoint of excellent stretchability.

Commercially available products can be used as the paraffinic process oil. Examples of commercially available products include Idemitsu Kosan PW-32, Idemitsu Kosan PS-32, Idemitsu Kosan PS-90, and the like.

Commercial products can be used as naphthenic process oil. Examples of commercially available products include Diana Fresia N28 manufactured by Idemitsu Kosan Co., Ltd., Diana Fresia U46 manufactured by Idemitsu Kosan Co., Ltd., Nyflex 222B manufactured by Nynas, and the like.

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

Commercial products can be used as the hydrocarbon synthetic oil. Examples of 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 alone or in combination of two or more.

The content of the plasticizer (B) in the hot melt composition is 5 to 25% by mass, more preferably 10 to 20% by mass, based on 100% by mass of the hot melt composition. When the content of the plasticizer (B) is less than 5% by mass, the melt viscosity of the hot melt composition becomes high, and the hot melt composition cannot be applied with a normal hot melt adhesive coating apparatus. On the other hand, when the content of the plasticizer (B) exceeds 25% by mass, the hot melt composition layer becomes too soft, and the stress at the time of elongation of the stretchable laminate finally obtained becomes insufficient.

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

Commercially available products can be used as the ethylene-vinyl acetate copolymer. Examples of commercially available products include AC-400 manufactured by Honeywell and AC-430 manufactured by Honeywell.

The 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 to 35% by mass, more preferably 15 to 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 stretchable laminate is improved. When the content of the ethylene-vinyl acetate copolymer (C) is 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 a stretchable laminate of the present invention may contain other additives as long as the object of the present invention is not essentially hindered. Examples of the other additives include antioxidants and ultraviolet absorbers.

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-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,4-bis (octylthiomethyl) -o-cresol, 2 -T-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 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] hindered phenolic antioxidants such as methane; dilauryl thiodipropionate, lauryl stearyl thiodipropionate, pentaerythritol tetrakis (3-lauryl) Sulfur antioxidants such as thiopropionate); phosphorus antioxidants such as tris (nonylphenyl) phosphite and tris (2,4-di-t-butylphenyl) phosphite. An antioxidant may be used individually by 1 type, and 2 or more types may be mixed and used for it.

The content of the antioxidant in the hot melt composition is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, based on 100% by mass of the hot melt composition. 1 to 1% by mass is more preferable. By making the content of the antioxidant 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 stretchable laminate using the hot melt composition is also reduced.

Examples of the ultraviolet absorber 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 ultraviolet absorbers; 2-hydroxy-4-methoxybenzophenone and other benzophenone ultraviolet absorbers; salicylic acid ester Examples include ultraviolet absorbers; cyanoacrylate ultraviolet absorbers; hindered amine light stabilizers. An ultraviolet absorber may be used individually by 1 type, and 2 or more types may be mixed and used for it.

The content of the ultraviolet absorber is preferably 0.01 to 2% by mass, more preferably 0.05 to 1.5% by mass, and more preferably 0.1 to 1% by mass, based on 100% by mass of the hot melt composition. Further preferred. By making the content of the ultraviolet absorber 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 the odor of the stretchable laminate using the hot melt composition is also reduced.

The hot melt composition used in the method for producing a stretchable laminate of the present invention has a loss tangent tan δ between −60 ° C. and −20 ° C. measured in the course of temperature rise at a frequency of 1 Hz by dynamic viscoelasticity measurement. = Loss elastic modulus G ″ / Storage elastic modulus G ′) At a temperature at which the value of tan δ is maximized, the value of tan δ is preferably 1.0 or less.

Dynamic viscoelasticity measurement is performed in the rotational shear mode with the frequency fixed at 1 Hz. Specifically, the dynamic viscoelasticity measurement is performed in the following manner. The hot melt composition is heated and melted at 180 ° C., and then placed on a release-treated PET film. Thereafter, another PET film that has been subjected to a release treatment is superimposed on the stretchable hot melt composition so that the release surface is in contact with the hot melt composition. Thereafter, the film is compressed by 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 using a dynamic viscoelasticity measuring device and raising the temperature from -80 to 130 ° C at 5 ° C / min in a rotational shear mode at a frequency of 1 Hz. The loss tangent tan δ (= loss elastic modulus G ″ / storage elastic modulus G ′) is calculated from the storage elastic modulus G ′ and loss elastic modulus G ″ measured at this time. Examples of the dynamic viscoelasticity measuring apparatus include a rotational rheometer (trade name “AR-G2”) commercially available from TA Instruments.

The hot melt composition has a loss tangent tan δ (= loss elastic modulus G) between −60 ° C. and −20 ° C. when measured at a frequency of 1 Hz from a temperature of −80 ° C. to 130 ° C. by dynamic viscoelasticity measurement. It is preferable to have a temperature at which ″ / storage elastic modulus G ′) is maximized. When the temperature of the hot melt composition is increased from −80 ° C., the glass state changes to the rubber 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 a stretchable laminate of the present invention has a loss tangent tan δ (= loss elastic modulus G ″ / storage elastic modulus) measured in a temperature rising process at a frequency of 1 Hz by dynamic viscoelasticity measurement. In G ′), at a temperature at which the value of tan δ between −60 ° C. and −20 ° C. is maximum, the value of tan δ is preferably 1.0 or less, and more preferably 0.9 or less. By setting the value of tan δ to 1.0 or less, the viscosity property of the hot melt composition is lowered, so that the adhesiveness is lowered and hardened, so that the stress during elongation of the hot melt composition is improved. . As a result, the stress at the time of expansion | extension of the elastic laminated body which uses this hot-melt composition also improves.

The hot melt composition is manufactured by a known method. For example, it is manufactured by charging a hydrogenated styrene block copolymer, a plasticizer, various additives, etc. into a double-arm kneader heated to 150 ° C., and melt-kneading while heating.

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

Further, the coated surface on which the melted hot melt composition is coated is not particularly limited as long as the hot melt composition in a molten state can be cooled. The material of the coated surface is not particularly limited. For example, a so-called chill roll that circulates a cooling fluid inside a roll made of stainless steel can be used. There is no particular limitation on the shape of the surface to be coated, and various shapes such as a flat plate shape can be mentioned. In consideration of productivity, it is also preferable to use a cylindrical shape.

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

The method for applying the hot melt composition to the surface to be coated is not particularly limited, and a general method can be used. For example, the hot melt composition is charged into a hot melt tank heated to 180 ° C., sufficiently melted, and then discharged from a discharge nozzle heated to 180 ° C. The discharge pattern is not particularly limited, and examples thereof include slot coating, slit coating with slits in the 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, known nonwoven fabrics can be widely used. Specifically, it is preferable to use one or more selected from a spunbond nonwoven fabric, a spunlace nonwoven fabric, an airlaid nonwoven fabric, and an air-through nonwoven fabric. Moreover, the 1st nonwoven fabric and the 2nd nonwoven fabric may use a mutually different kind, and may use the same kind.

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 touch of the finally obtained laminate, the basis weight of the nonwoven fabric is preferably 30 g / m ² or less, more preferably 15 g / m ² or less.

Further, the nonwoven fabric used is preferably a nonwoven fabric that does not have extensibility in at least one direction. By adopting such a configuration, it is possible to obtain an advantage that, when a nonwoven fabric is conveyed, even if a tensile stress in the conveying direction acts, it does not substantially expand.

As described above, as the first nonwoven fabric and the second nonwoven fabric, when using a nonwoven fabric that does not have extensibility in at least one direction, the direction in which the first nonwoven fabric in the laminated state does not have extensibility; It is preferable to laminate in the same direction in which the nonwoven fabric has no extensibility.

In the present specification, “nonwoven fabric not having extensibility in at least one direction” means that when a nonwoven fabric is transported, it does not substantially stretch even if a tensile stress in the transport direction acts. More specifically, the extension rate during conveyance is less than 30%.

When laminating, the hot melt composition layer is in a stretched state. As a stretching method, a known method can be widely adopted, and there is no particular limitation. Here, stretching refers to stretching in the transport direction from a state in which no stretching stress is applied to the hot melt composition in order to cause stretchability by the hot melt composition, and the upstream transport speed in the transport direction. The hot melt composition can be stretched by increasing the downstream conveying speed. The stretching ratio is preferably about 200% to 500% (2 to 5 times) of the natural length where no elongation stress acts. By having such a configuration, it is possible to obtain a stretchable laminate having excellent stress during elongation.

The stretched state of the hot-melt composition layer in the stretched state in Step 2 is maintained until it is joined in Step 3 to be described later.

3. Process 3
In step 3, the stretched hot melt layer is joined to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive joining and / or ultrasonic fusion.

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

There is no particular limitation on the specific mode of ultrasonic fusion, and widely known methods can be employed.

Next, an example of a method for producing a stretchable laminate according to the present invention will be described with reference to FIG. In addition, this invention is not limited to this example, Of course, it can implement with a various form in the range which does not deviate from the summary of this invention.

In the figure, reference numeral 1 denotes a hot melt applicator, which discharges a hot melt composition melted by heating from a discharge 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 above-described discharge pattern, whereby 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 conveyance speed of the nip rolls 5 and 5 is faster than the conveyance speed of the nip rolls 4 and 4, so that the stretchable member 3 is stretched and the stretchability of the stretchable member is expressed.

Further, between the nip rolls 5 and 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 an elastic material. The non-woven fabric 6 and the non-woven fabric 7 are preliminarily coated with a hot-melt adhesive by hot melt applicators 8 and 8 on the surface facing the elastic member 3, whereby the non-woven fabric 6, the non-woven fabric 7 and the elastic member 3 are joined. 9 is formed.

The stretchable laminate 9 derived from the nip rolls 5 and 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 stretchable member 3 are ultrasonically welded.

The non-woven fabric 6, the non-woven fabric 7 and the elastic member 3 may be joined only by a hot melt adhesive or by ultrasonic welding. In the case of only the hot melt adhesive, the equipment is inexpensive, and in the case of only the ultrasonic welding, the stretchable laminate 9 that is flexible and has a good touch is obtained. The stretch laminate 9 produced in this way has a high stress when stretched, and can be used for sanitary materials such as disposable diapers, thereby preventing slippage during wearing.

The use of the stretch laminate is not particularly limited, and can be suitably used for so-called sanitary materials such as paper diapers and sanitary napkins.

The embodiments of the present invention have been described above. However, the present invention is not limited to these examples, and it is needless to say that the present invention can be implemented in various forms without departing from the gist of the present invention.

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

(Manufacture of hot melt composition)
The following raw materials were put into a stirring kneader equipped with a heating device in respective compounding amounts. Kneading while heating at 150 ° C. for 90 minutes produced stretchable hot melt compositions 1 to 4.

(Hot melt composition 1)
・ Hydrogenated styrenic block copolymer MD6951 by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
-Hydrogenated styrenic block copolymer MD1648 manufactured by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
・ Plasticizer Lucant HC-10 manufactured by Mitsui Chemicals (blending amount: 4.5% by mass)
-Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (mixing amount: 35% by mass)
Antioxidant BASF IRGANOX1010 (blending amount: 0.5% by mass)

(Hot melt composition 2)
・ Hydrogenated styrenic block copolymer MD6951 by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
-Hydrogenated styrenic block copolymer MD1648 manufactured by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
-Plasticizer Lucant HC-10 (Mixed amount: 14.5% by mass) manufactured by Mitsui Chemicals, Inc.
・ Ethylene-vinyl acetate copolymer Honeywell AC-400 (blending amount: 25% by mass)
Antioxidant BASF IRGANOX1010 (blending amount: 0.5% by mass)

(Hot melt composition 3)
・ Hydrogenated styrenic block copolymer MD6951 by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
-Hydrogenated styrenic block copolymer MD1648 manufactured by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
-Plasticizer Lucant HC-10 manufactured by Mitsui Chemicals (mixing amount: 24.5% by mass)
-Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (mixing amount: 15% by mass)
Antioxidant BASF IRGANOX1010 (blending amount: 0.5% by mass)

(Hot melt composition 4)
・ Hydrogenated styrenic block copolymer MD6951 by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
-Hydrogenated styrenic block copolymer MD1648 manufactured by Kraton Polymer Co., Ltd. (blending amount: 30% by mass)
・ Plasticizer Lucant HC-10 (Mixed amount: 0.5% by mass) manufactured by Mitsui Chemicals
-Ethylene-vinyl acetate copolymer AC-400 manufactured by Honeywell (mixing amount: 39% by mass)
Antioxidant BASF IRGANOX1010 (blending amount: 0.5% by mass)

(Example 1)
A stretchable laminate was produced by the process shown in FIG. The hot melt composition 1 was put into a hot melt 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 . Thereafter, the stretchable hot melt composition is sandwiched between ^two spunbonded nonwoven fabrics (basis weight: 18 g / mm ² ) while being stretched to about 350% (3.5 times) the natural length at which no extension stress acts. The nonwoven fabric and the hot melt composition were joined by a fusion apparatus to obtain a stretchable laminate. At this time, the line speed was 70 m / min.

(Example 2)
A stretchable laminate was obtained in the same process as in Example 1 except that the hot melt composition 2 was used.

Example 3
A stretchable laminate was obtained in the same process as in Example 1 except that the hot melt composition 3 was used.

Example 4
The hot melt composition 2 was put into a hot melt 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 . Thereafter, the stretchable hot melt composition is sandwiched between ^two spunbonded nonwoven fabrics (basis weight: 18 g / mm ² ) while being stretched so as to be about 350% (3.5 times) the natural length at which no elongation stress acts. I made it. At this time, a hot melt adhesive is spray-applied to the ^two spunbond nonwoven fabrics at a coating amount of 3.5 g / m ² , and the hotmelt composition is joined to the spunbond nonwoven fabric by the hotmelt adhesive agent, thereby being stretchable. A laminate was obtained. As the hot melt adhesive used for joining the hot melt composition and the spunbond nonwoven fabric, a rubber-based hot melt adhesive was used.

(Comparative Example 1)
A stretchable laminate was obtained in the same process as Example 1 except that the hot melt composition 4 was used.

The characteristics of the obtained hot melt composition were evaluated under the following measurement conditions.

(Melt viscosity)
The hot melt adhesive was heated and melted, and the viscosity in a 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. Subsequently, separation and discoloration of the hot melt adhesive were visually observed at room temperature, and evaluated according to the following evaluation criteria. In addition, if evaluation is more than (triangle | delta), it can be evaluated that there is no problem in actual use.
○: No separation of the hot melt composition is observed, and there is no discoloration.
(Triangle | delta): Although isolation | separation of a hot-melt composition is not seen, the degree of discoloration is slight.
X: Separation of the hot melt composition is observed, and the degree of discoloration is deep.

(Tan δ maximum)
The dynamic viscoelasticity measurement is performed in the rotational shear mode with the frequency fixed at 1 Hz. Specifically, the dynamic viscoelasticity measurement is performed in the following manner. The hot melt composition is heated and melted at 180 ° C., and then placed on a release-treated PET film. Thereafter, another PET film subjected to the release treatment is overlaid on the hot melt composition so that the release surface is in contact with the hot melt composition. Thereafter, the film is compressed by 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 using a dynamic viscoelasticity measuring device and raising the temperature from -80 to 130 ° C at 5 ° C / min in a rotational shear mode at a frequency of 1 Hz. The loss tangent tan δ (= loss elastic modulus G ″ / storage elastic modulus G ′) is calculated from the storage elastic modulus G ′ and loss elastic modulus G ″ measured at this time. The value of tan δ at a temperature at which tan δ between −60 ° C. and −20 ° C. was maximized was recorded and taken as the tan δ maximum value.

(Coating property)
When the hot melt composition is discharged from the nozzle, the 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 is visually confirmed. (Dischargeability) was evaluated. If the evaluation is Δ or more, it can be evaluated that there is no problem.
○: Coating is possible without uneven coating. Δ: Uneven coating is observed but there is no problem in use. ×: Uneven coating is noticeable or a predetermined amount of hot melt composition is not discharged.

(2 times elongation stress)
The stretchable laminate was cut into strips of 100 mm in the hot melt composition coating direction (MD direction) and 50 mm in the direction perpendicular to the coating direction (CD direction) to prepare test pieces. . Thereafter, the test piece was fixed to a tensile tester set to a jig width of 50 mm so as to hold the long side of the test piece, and the test piece was pulled at a pulling speed of 500 mm / min. The stress when the test piece was extended twice from the initial length of the long side was defined as the stress at the time of double extension.

(touch)
The stretch laminate was touched by 10 people to evaluate the degree of touch of the stretch laminate. The touch evaluation results of the stretchable laminates were classified according to the following criteria, and entered in the column “Table 1”. In addition, if evaluation is more than (triangle | delta), it can be evaluated that there is no problem in actual use.
○: 8 out of 10 people answered “feel good” Δ: 5-7 out of 10 people said “feel good” ×: 1-4 people out of 10 “feel good” Replied

The results are shown in Table 1.

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 Stretchable laminate 10 Ultrasonic horn 11 Anvil roll

Claims (4)

A method for producing an elastic laminate,
Step 1 of applying a melted 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, and
Step 3 of joining the stretched hot melt composition layer to the first nonwoven fabric and the second nonwoven fabric by hot melt adhesive joining and / or ultrasonic fusion,
The hot melt composition is:
Comprising a hydrogenated styrenic block copolymer (A) and a plasticizer (B),
In 100% by mass of the hot melt composition, 55 to 70% by mass of the hydrogenated styrenic block copolymer (A) and 5 to 25% by mass of the plasticizer (B) are included.
The hydrogenated styrene block copolymer (A) is a styrene-ethylene-butylene-styrene copolymer and / or a styrene-ethylene-butylene / styrene-styrene copolymer,
A manufacturing method, wherein the melt viscosity at 180 ° C. is 10,000 to 30,000 mPa · s. At a temperature at which the value of loss tangent tan δ (= loss elastic modulus G ″ / storage elastic modulus G ′) is maximum between −60 ° C. and −20 ° C., the value of tan δ is 1. The manufacturing method of 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 an 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 at least one selected from a spunbond nonwoven fabric, a spunlace nonwoven fabric, an airlaid nonwoven fabric, and an air-through nonwoven fabric. Method.

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