JP2024124293A - Laminate - Google Patents

Abstract

To provide a laminate of a hot melt adhesive and a non-woven fabric including a specific cellulose-based fiber, which has excellent adhesiveness and strength over time and is used for bonding non-woven fabrics including a cellulose-based fiber and for bonding a non-woven fabric including a cellulose-based fiber and other non-woven fabrics.SOLUTION: There is provided a laminate which has a non-woven fabric layer (I) constituted by a non-woven fabric α including a cellulose-based fiber and a non-woven fabric layer (II) constituted by an optional non-woven fabric in this order, wherein the non-woven fabric layer (I) and the non-woven fabric layer (II) are bonded via a hot melt adhesive β, a mean deviation (SMD) of surface roughness of a surface on a side in contact with the non-woven fabric (II) via the hot-melt adhesive β in the non-woven fabric α is 2.3 or less or 3.0 or more, the hot melt adhesive β includes a component (A), a thermoplastic elastomer and a component (B), a tackifier and the hot melt adhesive β has a loss tangent of 0.21 or more at a temperature of 50°C, a frequency of 0.05 Hz and a strain of 0.05% and a loss tangent of 0.35 or more at a temperature of 50°C, a frequency of 1.00 Hz and a strain of 0.05%.SELECTED DRAWING: None

Description

The present invention relates to a laminate.

Currently, single-use plastics are the main materials used in sanitary products such as diapers and napkins. However, in the future, these materials are expected to be replaced by more environmentally friendly materials.

Currently, the materials used for these sanitary products are mainly petroleum-based nonwoven fabrics, but in the future, this is expected to be replaced by nonwoven fabrics made from natural materials.

The surface condition of a nonwoven fabric made from a petroleum-based material is different from that of a nonwoven fabric made from a natural material.
For this reason, when adhesives used in the manufacture of conventional sanitary products are used in the process of bonding nonwoven fabrics made from natural substrates, suitable adhesive properties cannot be obtained.

When nonwoven fabrics used in such sanitary products are laminated with an adhesive, it is necessary that the nonwoven fabrics not only adhere well to each other in situ, but also that the adhesiveness is maintained even over a long period of time (hereinafter, in this specification, this property will be referred to as "strength over time").
To achieve this, in addition to the surface characteristics of the nonwoven fabric, the selection of the adhesive to be combined with it is also important.

Patent Document 1 discloses a hot melt adhesive that is said to have good adhesion even to uneven substrates such as those used in sanitary products.

Furthermore, Patent Document 2 discloses a hot melt adhesive that is said to have good adhesion to hydrophilic substrates such as cellulose-based substrates and cotton-based substrates.

International Publication No. WO 2021/039118 JP 2007-169531 A

However, it is unclear whether the hot melt adhesive disclosed in Patent Document 1 exhibits good adhesive properties for nonwoven fabrics made from natural base materials, and it is also unclear whether consideration has been given to the strength over time when nonwoven fabrics made from natural base materials are adhered to the adhesive.

In addition, the hot melt adhesive disclosed in Patent Document 2 is also described in the examples.
Although the adhesive strength between the film and cotton cloth has been confirmed, it is unclear as to the adhesive strength between natural base material nonwoven fabrics, or between natural base material nonwoven fabrics and other nonwoven fabrics. It is also unclear whether the design has been designed with consideration given to strength over time.

In view of the above circumstances, an object of the present invention is to find a laminate of a hot melt adhesive and a nonwoven fabric containing specific cellulose fibers, which has excellent adhesive properties and strength over time and can be used for bonding nonwoven fabrics containing cellulose fibers to each other, or between a nonwoven fabric containing cellulose fibers and another nonwoven fabric.

As a result of intensive research conducted by the inventors in order to solve the above problems, it was found that excellent adhesive properties and strength over time can be obtained by adopting a combination of a nonwoven fabric containing cellulose fibers and having a specified surface roughness, and a hot melt adhesive having a specified composition. Based on this finding, the inventors conducted further research and have completed the present invention.

That is, the present invention provides the following laminate.
Item 1.
The present invention has a nonwoven fabric layer (I) made of a nonwoven fabric α containing cellulosic fibers and a nonwoven fabric layer (II) made of any nonwoven fabric in this order, and the nonwoven fabric layer (I) and the nonwoven fabric layer (
II) is bonded via a hot melt adhesive β,
The surface roughness mean deviation (SMD) of the surface of the nonwoven fabric α that contacts the nonwoven fabric layer (II) via the hot melt adhesive β is 2.3 or less or 3.0 or more,
The hot melt adhesive β contains a component (A) a thermoplastic elastomer and a component (B) a tackifier,
The hot melt adhesive β has a loss tangent of 0.21 or more at a temperature of 50° C., a frequency of 0.05 Hz, and a strain of 0.05%, and also has a loss tangent of 0.21 or more at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.
05% loss tangent of 0.35 or more.
Item 2.
Item 2. The laminate according to item 1, wherein the hot melt adhesive β has a loss modulus of 10,000 Pa or more at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.05%.
Item 3.
The hot melt adhesive β is
Loss modulus at temperature 23°C, frequency 1.00Hz, and strain 0.05% is 200,000
Pa or more, and
Item 3. The laminate according to item 1 or 2, having a loss tangent of 1.40 or more at a temperature of 23° C., a frequency of 1.00 Hz, and a strain of 0.05%.
Item 4.
Item 2. The laminate according to item 1, wherein the nonwoven fabric α has a basis weight of 15 to 40 g/ ^m2 .
Item 5.
Item 1 or 4, wherein the cellulosic fiber contained in the nonwoven fabric α is cotton or rayon.
The laminate according to claim 1.
Item 6.
Item 5. The laminate according to item 1 or 4, wherein the hot melt adhesive β is a hot melt adhesive for absorbent articles.

The laminate according to the present invention thus obtained also has excellent adhesion and strength over time.

FIG. 2 is an explanatory diagram of the production of laminates in Examples and Comparative Examples.

In this specification, "containing" means "comprise" or "consists essentially of"
In addition, in this specification, when a numerical range is indicated as "A to B," it means A or more and B or less.

(1. Laminate)
The laminate of the present invention comprises a nonwoven fabric layer (I) composed of a nonwoven fabric α containing cellulosic fibers.
and a nonwoven fabric layer (II) made of any nonwoven fabric in this order,
and the nonwoven fabric layer (II) is bonded to the nonwoven fabric layer (II) via a hot melt adhesive β, the surface of the nonwoven fabric α that contacts the nonwoven fabric layer (II) via the hot melt adhesive β has a surface roughness mean deviation (SMD) of 2.3 or less or 3.0 or more, the hot melt adhesive β contains a component (A) a thermoplastic elastomer and a component (B) a tackifier, and the hot melt adhesive β has a loss tangent of 0.21 or more at a temperature of 50° C., a frequency of 0.05 Hz, and a strain of 0.05%, and a loss tangent of 0.40 or more at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.05%.

It is also a preferred embodiment to laminate one or more additional nonwoven fabrics (which may be the same nonwoven fabric as nonwoven fabric α) to the laminate of the present invention by bonding them to the laminate using a separate hot melt adhesive (which may be the same hot melt adhesive as hot melt adhesive β).

A method in which the nonwoven fabric constituting the laminate of the present invention is subjected to processing such as embossing or perforation before or after the step of bonding the nonwoven fabric constituting the laminate via a hot melt adhesive is also a preferred embodiment.

(2. Nonwoven fabric layer (I))
The nonwoven fabric layer (I) is composed of a nonwoven fabric α containing cellulosic fibers. The content of cellulosic fibers in the nonwoven fabric α is preferably 5% by mass or more, and more preferably 20% by mass or more, based on 100% by mass of the nonwoven fabric α. The content of the cellulose-based fiber is preferably 100% by mass or more, and more preferably 50% by mass or more, based on 100% by mass of the nonwoven fabric α.
It is preferable that the nonwoven fabric α is composed only of cellulosic fibers.

Such cellulosic fibers can be widely used from known sources, including, but not limited to, cotton, rayon, and lyocell.

The basis weight of the nonwoven fabric α is preferably 15 g/m ² or more, and more preferably 25 g/m ² or more. By having the basis weight of the nonwoven fabric α be 15 g/m ² or more, it is possible to impart a good water retention effect. In addition, the basis weight of the nonwoven fabric α is preferably 40 g/m ² or less, and more preferably 35 g/m ² or less. By having the basis weight of the nonwoven fabric α be 40 g/m ² or less, it is possible to impart good breathability.

The surface roughness mean deviation (SMD) of the surface of the nonwoven fabric α constituting the nonwoven fabric layer (I) that contacts the nonwoven fabric layer (II) via the hot melt adhesive β is 2.3 or less or 3.0 or more. If the value is greater than 2.3, the anchoring effect of the adhesive on the nonwoven fabric substrate cannot be expected, resulting in a decrease in adhesive strength. If the value is less than 3.0, the contact area between the nonwoven fabric substrate and the adhesive decreases, resulting in a decrease in adhesive strength.

In this specification, the surface roughness mean deviation (SMD) of the nonwoven fabric surface is specifically defined as being measured and calculated as follows.

A surface tester (e.g., KES-FB4-A manufactured by Kato Tech Co., Ltd.) is used as the measuring device, and the measurement conditions are an environment of temperature 23°C, humidity 50%, a 0.5 mm roughness sensor is used as a sensor for thickness change, and a test piece (20 cm x 20 cm) of the nonwoven fabric to be tested is used.
The SPEED is 1.0 mm/sec, the roughness static load is 10.0 gf, and a tension is applied to the nonwoven fabric using a 100 g paperweight, and the measurement is performed in the MD direction of the nonwoven fabric.

The test procedure is as follows: the test piece is set so that the MD direction of the nonwoven fabric is the same as the moving direction of the sensor, and a tension of 100 g is applied in the MD direction of the nonwoven fabric to measure the surface roughness. The measurement is carried out at 12 randomly selected points on the nonwoven fabric, and the average value is taken as the SMD.

The surface roughness mean deviation (SMD) of the surface of the nonwoven fabric α constituting the nonwoven fabric layer (I) that contacts the nonwoven fabric layer (II) via the hot melt adhesive β is preferably 2.3 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. The SMD is preferably 0 or more, and more preferably 1.0 or more.

On the other hand, the surface roughness mean deviation (SMD) of the surface of the nonwoven fabric α constituting the nonwoven fabric layer (I) that contacts the nonwoven fabric layer (II) via the hot melt adhesive β is preferably 3.0 or more, more preferably 3.2 or more, and even more preferably 3.5 or more. The SMD is preferably 7.0 or less, and more preferably 6.5 or less.

(3. Nonwoven fabric layer (II))
The nonwoven fabric layer (II) is composed of any nonwoven fabric. As such a nonwoven fabric, a wide variety of known nonwoven fabrics can be used, including nonwoven fabrics containing cellulosic fibers or nonwoven fabrics composed only of cellulosic fibers. Of course, the nonwoven fabric may be the same as the nonwoven fabric α described above.

In addition, nonwoven fabrics made of petroleum-based materials, such as those conventionally used in sanitary products, may also be used.

(4. Hot melt adhesive β)
The hot melt adhesive β contains a component (A) a thermoplastic elastomer and a component (B) a tackifier.

(4.1. Component (A) Thermoplastic Elastomer)
The thermoplastic elastomer of component (A) is not particularly limited, and examples thereof include styrene-based block copolymers, olefin-based block copolymers, polyurethane-based block copolymers, polyester-based block copolymers, etc. Among these, styrene-based block copolymers are preferred from the viewpoint of further improving the peel strength of the hot melt adhesive.

The styrene-based block copolymer is a block copolymer obtained by block copolymerizing a vinyl aromatic hydrocarbon with a conjugated diene compound.

Vinyl aromatic hydrocarbons are aromatic hydrocarbon compounds having a vinyl group. Specific examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, etc., and among these, styrene is preferred. The vinyl aromatic hydrocarbons can be used alone or in combination of two or more.

The conjugated diene compound is 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
1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc., among which 1,3-butadiene, 2
-methyl-1,3-butadiene (isoprene) is preferred. The conjugated diene compounds may be used alone or in combination of two or more.

The styrene block copolymer is preferred because it can exhibit better peel strength.
It is preferable that the copolymer is an unhydrogenated styrene-based block copolymer. As the unhydrogenated styrene-based block copolymer, for example, a styrene-butadiene block copolymer (
Examples of suitable styrene block copolymers include styrene-butadiene-styrene block copolymers (SB), styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), and styrene-butadiene-styrene-butadiene block copolymers (SBSB). These styrene block copolymers can be used alone or in combination of two or more. Among these styrene block copolymers, styrene-butadiene-styrene block copolymers (SBS) are preferred because they can exhibit even better peel strength.

The content of the styrene skeleton in the styrene block copolymer is preferably 10 to 70% by mass of the styrene block copolymer, since this allows the copolymer to exhibit better peel strength.
% by mass is preferred, and 30 to 60% by mass is more preferred.

In this specification, the styrene skeleton content in the styrene block copolymer refers to the content (mass%) of the styrene block in the styrene block copolymer. The styrene skeleton content in the styrene block copolymer can be calculated, for example, according to JIS K6
Examples of the method include a method using proton nuclear magnetic resonance spectroscopy in accordance with 239 and infrared spectroscopy.

In the present invention, from the viewpoint of achieving better peel strength, it is preferable that the thermoplastic elastomer (A) is a styrene-based block copolymer, and that the styrene-based block copolymer contains a styrene-butadiene-styrene block copolymer (SBS).

In the present invention, the styrene block copolymer is heated at a high temperature for a long time (for example, 160
From the viewpoint of further improving the heat stability when the composition is heated at 40° C. for 72 hours, it is preferable that the composition does not contain an asymmetric styrene-isoprene-styrene block copolymer.

In the present invention, it is preferred that the thermoplastic elastomer (A) is a styrene-based block copolymer, and that the styrene-based block copolymer does not contain an asymmetric styrene-isoprene-styrene block copolymer.

In the present invention, it is more preferable that the styrene-based block copolymer contains a styrene-butadiene-styrene block copolymer (SBS) and does not contain an asymmetric styrene-isoprene-styrene block copolymer.

In this specification, the term "asymmetric" in the asymmetric styrene-isoprene-styrene block copolymer means that the styrene skeleton content is different in the styrene phases at both ends.

As the styrene-based block copolymer, known commercially available products can be widely used. Examples of commercially available products include Asahi Kasei Corporation's product name "Asaprene T-439" (styrene skeleton content: 45% by mass), Asahi Kasei Corporation's product name "Asaprene T-438" (styrene skeleton content: 35% by mass), Asahi Kasei Corporation's product name "Asaprene T-436" (styrene skeleton content: 30% by mass), Kraton Polymer Corporation's product name "DX-405" (styrene skeleton content: 24% by mass), Kraton Polymer Corporation's product name "D-1155" (styrene skeleton content: 40% by mass), Kraton Polymer Corporation's product name "D-1118" (styrene skeleton content: 30% by mass), and CHIMEI Corporation's "PB5502" (styrene skeleton content: 32% by mass). These commercially available products can be used alone or in combination of two or more types.

The content of the thermoplastic elastomer (A) in 100% by mass of the hot melt adhesive of the present invention is preferably 10 to 35% by mass, from the viewpoint of exhibiting better peel strength.
It is more preferably 15 to 30% by mass, and even more preferably 18 to 25% by mass.

The content ratio of the styrene-based block copolymer in 100% by mass of the hot melt adhesive of the present invention is preferably 10 to 35% by mass, more preferably 15 to 30% by mass, and even more preferably 18 to 25% by mass, from the viewpoint of exhibiting even better peel strength.

(4.2. Component (B) Tackifier)
The tackifier component (B) preferably contains the components (B1) and (B2). The tackifier component (B) may be formed of only the components (B1) and (B2).

Component (B1) is a terpene-based tackifier, a rosin-based tackifier, or a fully hydrogenated hydrocarbon-based tackifier.

Examples of the terpene tackifier include terpene resins (monoterpene, diterpene, triterpene, polyperene, etc.), terpene phenol resins, aromatic modified terpene resins, etc. These terpene tackifiers can be used alone or in combination of two or more.

As the terpene-based tackifier, a wide variety of known commercially available products having an acid value of 15 mgKOH/g or less can be used, such as "YS Resin TO-105" (acid value: 0 mgKOH/g) manufactured by Yasuhara Chemical Co., Ltd. and "SYLVARES TRM1115" (acid value: 0 mgKOH/g) manufactured by Kraton.

As the rosin-based tackifier, from the viewpoint of exhibiting better adhesiveness (tack),
It is preferable to use at least one of natural rosin and an esterified product of the natural rosin (rosin ester resin), and it is more preferable to use a rosin ester resin.

Examples of the natural rosin include tall rosin, gum rosin, wood rosin, etc. These natural rosins may be used alone or in combination of two or more kinds.

Examples of the rosin ester resin include rosin glycerin ester, rosin pentaerythritol ester, rosin methyl ester, rosin ethyl ester, rosin butyl ester, rosin ethylene glycol ester, etc. These rosin ester resins can be used alone or in combination of two or more.

As the rosin-based tackifier, a wide variety of known commercially available products having an acid value of 15 mgKOH/g or less can be used. Examples of such commercially available products include "
Super Ester A100 (acid value: 5 mgKOH/g), a product name of Arakawa Chemical Industries, Ltd.
Examples include Pine Crystal KE-100 (acid value: 6 mg KOH/g), Kraton's product name "SYLVALITE 9100" (acid value: 7 mg KOH/g), and Arakawa Chemical Industries' product name "Super Ester A75" (acid value: 5 mg KOH/g). These commercially available products can be used alone or in combination of two or more.

Examples of the fully hydrogenated hydrocarbon tackifier include fully hydrogenated petroleum resins obtained by adding hydrogen to petroleum resins such as C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, and dicyclopentadiene petroleum resins. Note that the C5 petroleum resin is a petroleum resin made from a C5 fraction of petroleum, the C9 petroleum resin is a petroleum resin made from a C9 fraction of petroleum, and the C5C9 petroleum resin is a petroleum resin made from a C5 fraction and a C9 fraction of petroleum. Examples of the C5 fraction include cyclopentadiene, isoprene, and pentane.
The 9th fraction includes styrene, vinyltoluene, indene, and the like.

Component (B2) is an unhydrogenated hydrocarbon-based tackifier or a partially hydrogenated hydrocarbon-based tackifier.

Specific examples of the tackifier of component (B2) include unhydrogenated or partially hydrogenated hydrocarbon tackifiers of petroleum resins such as the above-mentioned C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, and dicyclopentadiene petroleum resins.

In this specification, the ring and ball softening point of the tackifier (B) refers to the temperature measured in accordance with JIS K 6863.

The content of the tackifier (B) in 100% by mass of the hot melt adhesive β is preferably 30 to 65% by mass, more preferably 35 to 65% by mass, in order to further improve the peel strength.
0% by mass, and more preferably 40 to 55% by mass.

The content of the tackifier (B) is preferably 0.1 to 0.5% by weight, more preferably 0.5 to 0.5% by weight, and most preferably 0.5 to 0.5% by weight.
The amount is preferably 150 to 350 parts by mass, more preferably 200 to 300 parts by mass, based on 100 parts by mass of the thermoplastic elastomer.

In the present invention, when the parts by mass of the thermoplastic elastomer (A) are A and the parts by mass of the tackifier (B) are B, the ratio represented by B/A is preferably 1.5 to 3.5.
, and more preferably 2.0 to 3.0.

Furthermore, in order to obtain good adhesion, the amount of component (B1) in the total amount of components (B1) and (B2) being 100% by mass is preferably 50% by mass or less, and more preferably 40% by mass or less.

On the other hand, the amount of component (B1) in the total amount of components (B1) and (B2) is 100% by mass, and preferably 5% by mass or more, and more preferably 10% by mass or more. By using a component (B1) amount of 5% by mass or more, excellent strength over time can be obtained.

(4.3. Various Additives)
The hot melt adhesive β may contain various additives as necessary within a range that does not essentially impede the object of the present invention. The various additives include plasticizers, antioxidants, ultraviolet absorbers,
Examples include liquid rubbers, waxes, and particulate fillers.

Examples of the plasticizer include naphthenic process oil, paraffinic process oil, etc., and naphthenic process oil is preferred from the viewpoint of further improving the heat stability and peel strength. These plasticizers can be used alone or in combination of two or more kinds.

A wide range of commercially available plasticizers can be used.

As a commercially available naphthenic process oil, for example, the product name "
KN4010, Idemitsu Kosan's product name "Diana Fresia N28", Idemitsu Kosan's product name "Diana Fresia U46", Nynas's product name "Nyflex 222B", etc.

Commercially available paraffin-based process oils include, for example, "Diana Process Oil PW32", "Diana Process Oil PW90", "Diana Process Oil PS32", and "Diana Process Oil PS90" manufactured by Idemitsu Kosan Co., Ltd.; and "Kaydol" manufactured by Witco Corporation.

When the hot melt adhesive β contains a plasticizer, the upper limit of the content of the plasticizer in 100% by mass of the hot melt adhesive is preferably 40% by mass, more preferably 30% by mass, and even more preferably 25% by mass.

When the hot melt adhesive β contains a plasticizer, the lower limit of the content of the plasticizer (C) in 100% by mass of the hot melt adhesive is preferably 1% by mass, and more preferably 5% by mass.

As the antioxidant, a wide variety of known antioxidants can be used, including, for example, 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-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,
Examples of the antioxidant include phenol-based antioxidants such as dilauryl thiodipropionate, lauryl stearyl thiodipropionate, pentaerythritol tetrakis(3-lauryl thiopropionate), and phosphorus-based antioxidants such as tris(nonylphenyl)phosphite and tris(2,4-di-t-butylphenyl)phosphite. These antioxidants may be used alone or in combination of two or more. Among these antioxidants, phenol-based antioxidants are preferred from the viewpoint of further improving heat stability.

As the antioxidant, a wide variety of commercially available products can be used. Commercially available phenolic antioxidants include, for example, "
"Evernox 10" etc.

When the hot melt adhesive β contains an antioxidant, the hot melt adhesive 100% by mass
The upper limit of the content of the antioxidant in the composition is preferably 5% by mass, more preferably 4% by mass,
More preferably, it is 3% by mass.

When the hot melt adhesive β contains an antioxidant, the hot melt adhesive 100% by mass
The lower limit of the content of the antioxidant in the composition is preferably 0.1 mass%, more preferably 0.5
% by mass, and more preferably 1% by mass.

As the ultraviolet absorbing agent, a wide variety of known ultraviolet absorbing agents can be used, for example, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'
,5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5
benzotriazole-based ultraviolet absorbers such as 2-hydroxy-4-methoxybenzophenone; salicylic acid ester-based ultraviolet absorbers; cyanoacrylate-based ultraviolet absorbers;
hindered amine light stabilizers. These ultraviolet absorbers can be used alone as follows:
Or two or more of them can be used in combination.

As the liquid rubber, a wide variety of known liquid rubbers can be used, including, for example, liquid polybutene, liquid polybutadiene, liquid polyisoprene, and hydrogenated resins thereof. These liquid rubbers can be used alone or in combination of two or more.

As the particulate filler, a wide variety of known particulate fillers can be used, including, for example, calcium carbonate, kaolin, talc, titanium oxide, mica, styrene beads, etc. These particulate fillers can be used alone or in combination of two or more kinds.

When the hot melt adhesive β contains the various additives, the content of the various additives in 100% by mass of the hot melt adhesive is preferably 5% by mass or less.

The nonwoven fabric used in the laminate of the present invention can be manufactured by standard methods.

The hot melt adhesive β may also be produced by a standard method, and there is no particular limitation on the method of production thereof. For example, the components (A) and (B) and, if necessary, the various additives described above are placed in a stirring kneader equipped with a heating device and kneaded while heating.

The heating temperature during kneading is not particularly limited, and is preferably 100 to 200° C., and more preferably 120 to 180° C. The kneading time is not particularly limited, and is preferably 40 to 140 minutes, and more preferably 60 to 120 minutes.

When obtaining a laminate, the hot melt adhesive β can be applied by a wide variety of known coating methods, such as spiral spray coating, slot coater coating, curtain spray coating, roll coater coating, omega coating, dot coating, bead coating, and the like.

As a coating device for coating the hot melt adhesive β on the bonding portion, a wide variety of known coating devices can be used, for example, a hot melt applicator. As a hot melt applicator, for example, a product name "REKA Hand Gun TR8" manufactured by Suntool Co., Ltd. can be used.
0LCD (spray)" etc.

The hot melt adhesive β can exhibit excellent adhesive properties to porous substrates made of natural materials such as cellulose-based materials and cotton-based materials; hydrophilic nonwoven fabrics, etc., and is therefore suitably used to bond adherends together in the manufacture of absorbent articles.
It is preferable that the adhesive layer 10 is made of a hot melt adhesive β.

Water-absorbent articles are intended to absorb bodily fluids such as blood, urine, sweat, pus, gastric juice, saliva, nasal mucus, etc. Examples of water-absorbent articles include disposable diapers, sanitary napkins, panty liners, incontinence pads, portable toilets, portable waste disposal bags, animal waste disposal sheets, hospital gowns, surgical lab coats, wound dressings, first aid bandages, freshness-preserving materials for meat, fish, etc. Among these, the hot melt adhesive of the present invention is suitable for use in disposable diapers, sanitary napkins,
It is suitable for use as a panty liner.

A paper diaper is basically composed of a liquid-impermeable back sheet made of a polyolefin resin film or the like, a liquid-permeable top sheet made of a nonwoven fabric or the like, a liquid-diffusion sheet that diffuses the liquid that has permeated through the top sheet, and an absorbent disposed between the liquid-diffusion sheet and the liquid-impermeable back sheet. In order to prevent the absorbent from becoming sticky after absorbing urine or the like, the absorbent is used with its surface covered with absorbent paper such as tissue. In addition, absorbent articles are structured so that elastic members such as rubber are attached in a stretchable manner to fit around the legs and waist of the wearer and prevent excrement from leaking out.

Hot melt adhesive β is suitably used in the manufacture of such paper diapers, for example, to bond cellulose-based porous substrates together, and to bond cellulose-based porous substrates to other porous substrates such as nonwoven fabrics.

The method of bonding the nonwoven fabric layers (I) and (II) to form a laminate with the hot melt adhesive β is not particularly limited, and any known method can be used. For example, a method is used in which the hot melt adhesive β that has been heated and melted is applied to the nonwoven fabric layer (I) or (II), and then the other nonwoven fabric layer is superimposed on the applied hot melt adhesive, and then they are pressure-bonded.

(4.4. Dynamic viscoelasticity of hot melt adhesive β)
The dynamic viscoelasticity of the hot melt adhesive β used in the present invention is such that the loss tangent calculated when viscoelasticity measurements are performed under conditions of a specified temperature and a specified strain and the frequency (frequency at which strain is applied) applied to the hot melt adhesive β is changed falls within a specified range.

The hot melt adhesive β has a predetermined measured value in a dynamic viscoelasticity measurement test carried out at a temperature of 50° C. Specifically,
The loss tangent at 5% strain is 0.21 or more, and the loss tangent at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.05% is 0.35 or more.

The dynamic viscoelasticity measurement test carried out at the above temperature of 50 ° C is carried out as follows. The hot melt adhesive β is heated and melted at 150 ° C, and dropped onto the release layer side of a release-treated polyethylene terephthalate film so that no air bubbles are trapped. Then, another release-treated polyethylene terephthalate film is laminated onto the hot melt adhesive so that the release layer side is in contact with the hot melt adhesive. Furthermore, the obtained laminate is compressed by a heat press to obtain a laminate with substantially no air bubbles, in which the thickness of the hot melt adhesive is adjusted to 3 mm. The laminate is sandwiched between polyethylene terephthalate films and left to stand at 23 ° C for 24 hours, and then a test piece is cut to a length of 10 mm and a width of 10 mm to prepare a sample for dynamic viscoelasticity measurement.

The prepared sample is attached to a dynamic viscoelasticity measuring device (a rotational rheometer manufactured by TA Instruments, product name "DHR-10"), and dynamic viscoelasticity measurement is performed under the following measurement conditions to obtain the loss tangent tan δ at a temperature of 50°C, the storage modulus G' (Pa) at a temperature of 50°C, and the loss modulus G'' (Pa) at a temperature of 50°C.
<Measurement conditions for dynamic viscoelasticity measurement at 50°C>
・Frequency range: 0.01Hz to 10.00Hz
Measurement temperature: 50°C
Strain: 0.05%
Lower plate: 25mm diameter parallel plate Upper plate: 8mm diameter crosshatch plate

The loss tangent of the hot melt adhesive β at a temperature of 50° C., a frequency of 0.05 Hz, and a strain of 0.05% is 0.21 or more, preferably 0.22 or more, and more preferably 0.23 or more. If the value is less than 0.21, the laminate cannot obtain sufficient adhesion over time.
The loss tangent at a strain of 0.05% is preferably 0.60 or less, and more preferably 0.48 or less.

In addition, the hot melt adhesive β is subjected to the following tests: temperature 50° C., frequency 1.00 Hz, and strain 0.05%.
The loss tangent at a temperature of 50° C. and a frequency of 1.0 is 0.35 or more, preferably 0.40 or more, and more preferably 0.50 or more. If the value is less than 0.35, the laminate cannot obtain sufficient adhesion over time.
The loss tangent at 0 Hz and strain of 0.05% is preferably 2.50 or less, and more preferably 0.65
The following is more preferred:

The loss modulus of the hot melt adhesive β at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.05% is preferably 10,000 Pa or more, more preferably 12,000 Pa or more, and even more preferably 15,000 Pa or more.
When the elastic modulus is 10,000 Pa or more, the laminate can have sufficient adhesiveness over time.

The hot melt adhesive β preferably has a predetermined measured value in a dynamic viscoelasticity measurement test carried out at a temperature of 23° C. The hot melt adhesive β is heated and melted at 150° C., and dropped onto the release layer side of a release-treated polyethylene terephthalate film.
Next, another release-treated polyethylene terephthalate film is laminated on the hot melt adhesive so that the surface of the release layer is in contact with the hot melt adhesive. The resulting laminate is then compressed by a heat press to obtain a laminate in which the thickness of the hot melt adhesive is adjusted to 3 mm. The laminate is sandwiched between polyethylene terephthalate films and left to stand at 23° C. for 24 hours, and then a test piece is cut to a length of 10 mm and a width of 10 mm to prepare a sample for dynamic viscoelasticity measurement.

The prepared sample is attached to a dynamic viscoelasticity measuring device (a rotational rheometer manufactured by TA Instruments, product name "DHR-10"), and dynamic viscoelasticity measurement is performed under the following measurement conditions to obtain the loss tangent tan δ at a temperature of 23°C, the storage modulus G' (Pa) at a temperature of 23°C, and the loss modulus G'' (Pa) at a temperature of 23°C.
<Measurement conditions for dynamic viscoelasticity measurement at 23°C>
- Measurement temperature range: -20℃ to 130℃
Frequency: 1.00Hz
Heating rate: 5°C/min. Strain: 0.05%
Lower plate: 25mm diameter parallel plate Upper plate: 8mm diameter crosshatch plate

The loss modulus of the hot melt adhesive β at a temperature of 23° C., a frequency of 1.00 Hz, and a strain of 0.05% is preferably 200,000 Pa or more, more preferably 300,000 Pa or more, and even more preferably 400,000 Pa or more. By having this value of 200,000 Pa or more, sufficient adhesiveness over time of the laminate can be obtained.

The loss tangent of the hot melt adhesive β at a temperature of 23° C., a frequency of 1.00 Hz, and a strain of 0.05% is preferably 1.40 or more, and more preferably 1.50 or more.
It is more preferable that the value is 1.40 or more. When the value is 1.40 or more, sufficient adhesiveness over time of the laminate can be obtained.
The loss tangent at 3° C., a frequency of 1.00 Hz, and a strain of 0.05% is preferably 6.00 or less, and more preferably 4.50 or less.

Although the embodiment of the present invention has been described above, the present invention is not limited to these examples, and it is needless to say that the present invention can be embodied in various forms without departing from the gist of the present invention.

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

Preparation of Hot Melt Adhesive β Thermoplastic elastomers, tackifiers, plasticizers, antioxidants, and various additives as shown in Tables 1 and 2 below were charged into a stirring kneader equipped with a heating device, heated to 145°C, and kneaded for 90 minutes to obtain Hot Melt Adhesive Preparation Examples 1 to 11.

Preparation of nonwoven fabrics Cotton nonwoven fabrics I to III, rayon nonwoven fabric, and air-through nonwoven fabric made of polyethylene and polypropylene fibers were prepared. The average deviation of surface roughness (SM
Regarding D), measurements were performed using a surface tester (e.g., KES-FB4-A manufactured by Kato Tech Co., Ltd.). The results were: Cotton nonwoven fabric I: 1.623; Cotton nonwoven fabric II: 3.179;
Cotton nonwoven fabric III is 6.931, rayon nonwoven fabric is 4.857, and air-through nonwoven fabric is 2.
It was measured at .676.

Preparation of Laminate As shown in FIG. 1, the above nonwoven fabrics I to III and the rayon nonwoven fabric were laminated by 70 mm in the MD and 70 mm in the CD.
A 50 mm size was cut out in the direction (substrate A), the release paper of each of the above-mentioned adhesive sheets was peeled off, and the laminate was attached to the surface of the nonwoven fabric on which the SMD measurement was performed, and a 500 g roll was placed on top of it and moved back and forth at a speed of 5 mm/sec. Furthermore, the release film of the adhesive sheet was peeled off, and another nonwoven fabric (substrate B) prepared was attached to the exposed adhesive surface on the surface on which the SMD measurement was performed. In both Examples and Comparative Examples, the two nonwoven fabrics sandwiching the adhesive sheet were a combination of nonwoven fabrics of the same material. A 100 g roll was placed on the obtained laminate, and 5
The needle was moved back and forth at a speed of 1 mm/sec.

Dynamic Viscoelasticity Measurement Test Based on the above-mentioned method, the dynamic viscoelasticity was measured for the hot melt adhesives of the above Production Examples 1 to 11. The obtained values are shown in Table 3 below.

As shown in FIG. 1, a tensile tester (Shimadzu Corporation, AGS-X) was used to test the nonwoven fabric in each of the examples and comparative examples in a laminate, with the base material B fixed and the base material A fixed in the MD direction to a tensile strength of 100.
A T-peel test was performed at 100 mm/min to measure the maximum convex test force. The measurement was performed three times, and the average value was adopted as the test result of the maximum convex test force. The measurement was performed at two points after each Example and Comparative Example was manufactured, after leaving it for 24 hours in an environment with a temperature of 23° C. and a humidity of 50%, and after leaving it for two weeks in an environment of 50° C. Note that, in the present specification, the measurement result after leaving it for 24 hours will be referred to as "initial strength", and the measurement result after leaving it for two weeks will be referred to as "2W strength". In addition, as the evaluation criteria, the average value obtained by performing the maximum convex test force measurement three times was evaluated according to the following criteria. It was determined that sufficient adhesion was obtained when it was evaluated as ◯ or ◎ according to the following evaluation criteria.
<Evaluation criteria>
Less than 2.00N ×
2.00N or more and less than 2.50N △
2.50N or more but less than 3.00N 〇 3.00N or more ◎

As shown in the following Tables 4 to 18, the laminates of Examples 1 to 40 were confirmed to have excellent adhesion even after two weeks, whereas the laminates of Comparative Examples 1 to 15 were not confirmed to have such excellent adhesion.

Claims (6)

The present invention has a nonwoven fabric layer (I) made of a nonwoven fabric α containing cellulosic fibers and a nonwoven fabric layer (II) made of any nonwoven fabric in this order, and the nonwoven fabric layer (I) and the nonwoven fabric layer (
II) is bonded via a hot melt adhesive β,
The surface roughness mean deviation (SMD) of the surface of the nonwoven fabric α that contacts the nonwoven fabric layer (II) via the hot melt adhesive β is 2.3 or less or 3.0 or more,
The hot melt adhesive β contains a component (A) a thermoplastic elastomer and a component (B) a tackifier,
The hot melt adhesive β has a loss tangent of 0.21 or more at a temperature of 50° C., a frequency of 0.05 Hz, and a strain of 0.05%, and also has a loss tangent of 0.21 or more at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.
05% loss tangent of 0.35 or more. The laminate according to claim 1 , wherein the hot melt adhesive β has a loss modulus of 10,000 Pa or more at a temperature of 50° C., a frequency of 1.00 Hz, and a strain of 0.05%. The hot melt adhesive β is
Loss modulus at temperature 23°C, frequency 1.00Hz, and strain 0.05% is 200,000
Pa or more, and
3. The laminate according to claim 1 or 2, which has a loss tangent of 1.40 or more at a temperature of 23° C., a frequency of 1.00 Hz, and a strain of 0.05%. The laminate according to claim 1, wherein the nonwoven fabric α has a basis weight of 15 to 40 g/ ^m2 . The laminate according to claim 1 or 4, wherein the cellulosic fibers contained in the nonwoven fabric α are cotton or rayon. The hot melt adhesive β is a hot melt adhesive for absorbent articles according to claim 1 or 4.
The laminate according to claim 1.

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