JP7389023B2 - hot melt composition - Google Patents

Description

The present invention relates to hot melt compositions.

In recent years, absorbent articles including sanitary materials such as disposable diapers and sanitary napkins have been widely used. These absorbent articles use stretchable laminates made of stretchable members to prevent them from slipping off when worn.

Rubber threads made of natural rubber or synthetic polymers in the form of threads are known as stretchable members used in stretchable laminates. Since rubber thread exhibits good stress when stretched, it is effective in preventing absorbent articles from slipping off when worn.

Furthermore, a stretchable film containing a thermoplastic elastomer has been proposed as a stretchable member of a stretchable laminate provided in an absorbent article (for example, see 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 having excellent moisture permeability and flexibility and suitable for absorbent articles such as sanitary products is provided.

Further, a hot melt stretchable adhesive composition has been proposed as a stretchable material that can be used in a hot melt adhesive application device (for example, see Patent Document 2). Patent Document 2 describes a block copolymer comprising an elastic polymer segment and a polystyrene polymer segment, which are one or more polymers selected from a hydrogenated polymer of a butadiene polymer or an isoprene polymer, or an ethylene propylene polymer. A hot melt stretchable adhesive composition comprising coalescence is disclosed. According to the hot melt stretchable adhesive composition, it can be applied using a normal hot melt applicator, and since it itself has both adhesiveness and stretchability, it is compatible with base materials such as nonwoven fabrics. A hot melt adhesive that can easily form a gather portion by laminating is provided.

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

However, when the above-mentioned rubber thread is used as a stretchable member used in a stretchable laminate, there is a problem in that linear pressure is applied to the human body, causing a feeling of pressure and irritation when worn. Furthermore, since a plurality of thin rubber threads are used in absorbent articles such as sanitary materials, the rubber threads tend to break during the manufacture of the absorbent articles, which often makes it difficult to manufacture the absorbent articles.

According to the stretchable film of Patent Document 1, the above-mentioned problem when using thread rubber is solved because surface pressure is applied to the human body, but the stretchable film is made by extruding resin using an extrusion device. Since it is manufactured by molding, it cannot be coated with a normal hot melt coating device, and there is a problem that the coatability (shape processability) is not sufficient.

Further, according to the hot melt stretchable adhesive composition of Patent Document 2, since a normal hot melt coating device can be used, the coatability as a stretchable member is improved, but the stretchability is reduced. Not sufficiently considered. When a sanitary material such as a paper diaper is worn, the expandable member used in the sanitary material is kept in a stretched state at a temperature close to body temperature for a long period of time. Therefore, the elastic member is required to suppress a decrease in elastic recovery even if it is heated and held in an expanded state.

In view of the above circumstances, the present invention suppresses the deterioration of elastic recovery and breakage even after being heated and held in an elongated state, and can be coated with a normal hot melt coating device. The purpose of the present invention is to provide a hot melt composition with excellent coating properties.

As a result of extensive studies to achieve the above object, the inventors of the present invention have developed a hot melt composition containing a thermoplastic resin (A) and a plasticizer (B), whose dynamic viscoelasticity was measured under specific conditions. In the master curve obtained by setting the reference temperature to 40°C, (1) calculate the log at the point where log(G'') is maximum in the range of -6.0<log(f)<-1.0. When the value of (f) is -2.5 or less and the value of (2) log(f) is -4, the logarithm (log( The inventors have discovered that the above object can be achieved by using a hot melt composition having a tan δ) value of 0 or less, and have completed the present invention.

That is, the present invention relates to the following hot melt composition.
1. A hot melt composition comprising a thermoplastic resin (A) and a plasticizer (B),
Dynamic viscoelasticity measurements were performed under the conditions of temperature -20 to 120°C and frequency (f) -0.2 to 2.0Hz, and the measured storage The logarithm (log(G')) of the elastic modulus (G') and the logarithm (log(G'')) of the measured loss modulus (G'') are plotted, and the reference temperature is set to 40°C. In the master curve,
(1) The value of log(f) at the point where log(G'') is maximum in the range of -6.0<log(f)<-1.0 is -2.5 or less, and
(2) When the value of log(f) is -4, the value of the logarithm of tanδ (log(tanδ)) calculated by (G''/G') is 0 or less,
A hot melt composition characterized by:
2. The hot melt composition according to item 1, having a melt viscosity at 180° C. of 5,000 mPa·s or more and 45,000 mPa·s or less.
3. Item 3. The hot melt composition according to Item 1 or 2, wherein the content of the thermoplastic resin (A) is 40 to 75% by mass based on 100% by mass of the hot melt composition.
4. Item 4. The hot melt composition according to any one of Items 1 to 3, wherein the thermoplastic resin (A) is a styrenic block copolymer.
5. Item 5. The hot melt composition according to Item 4, wherein the styrenic block copolymer is a hydrogenated styrenic block copolymer.
6. Item 6. A stretchable laminate, characterized in that a nonwoven fabric is bonded to at least one side of a film formed from the hot melt composition according to any one of Items 1 to 5.

The hot melt composition of the present invention suppresses deterioration in stretch recovery and breakage even after being heated and held in a stretched state, and can be coated with a normal hot melt coating device. It can be coated easily and has excellent coating properties.

1. Hot melt composition The hot melt composition of the present invention is a hot melt composition containing a thermoplastic elastomer (A) and a plasticizer (B),
Dynamic viscoelasticity measurements were performed under the conditions of temperature -20 to 120°C and frequency (f) -0.2 to 2.0Hz, and the measured storage The logarithm (log(G')) of the elastic modulus (G') and the logarithm (log(G'')) of the measured loss modulus (G'') are plotted, and the reference temperature is set to 40°C. In the master curve,
(1) The value of log(f) at the point where log(G'') is maximum in the range of -6.0<log(f)<-1.0 is -2.5 or less, and
(2) When the value of log(f) is -4, the value of the logarithm of tan δ (log(tan δ)) calculated by (G''/G') is 0 or less. By having the configurations (1) and (2) above, the hot melt composition of the present invention suppresses a decrease in elastic recovery even after being heated and held in an elongated state. It exhibits excellent stretch recovery properties and is also suppressed from breaking.

The above-mentioned hot melt composition of the present invention can be suitably used as a stretchable member forming a stretchable laminate used for absorbent articles such as sanitary materials.

In this specification, "warming" refers to raising the temperature to about the same as human body temperature, and is approximately 35 to 42 degrees Celsius, preferably approximately 35.5 to 41.5 degrees Celsius, more preferably 36 to 41 degrees Celsius. It means the temperature of the degree.

The above master curve can be obtained by the following method. That is, the hot melt composition is heated and melted at 180° C., and then dropped onto the release layer side surface of the release-treated PET film. Next, another release-treated PET film is laminated on the hot melt composition so that the surface on the release layer side is in contact with the hot melt composition. Next, the hot melt composition is compressed using a hot press heated to 120° C., and the thickness of the hot melt composition is adjusted to about 2 mm. After the hot melt composition is sandwiched between PET films and allowed to stand at 23° C. for 24 hours, the release film is removed to prepare a sample for dynamic viscoelasticity measurement.

Using the sample, dynamic viscoelasticity is measured in the rotating shear mode of the dynamic viscoelasticity measuring device under measurement conditions of temperature from -20°C to 120°C and frequency of 0.2 to 2.0Hz. Specifically, the storage modulus G' and the loss modulus G'' are measured under a constant temperature condition of -20° C. in a rotating shear mode with a frequency of 0.2 to 2.0 Hz. Similar measurements are made every 10°C up to 120°C. The logarithms of the measured storage modulus G' and loss modulus G'' are taken and plotted against the logarithm of frequency (log(f)). Next, the reference temperature is set to 40°C, and shift factors are set for log(G'), log(G''), and log(tanδ) (=log(G''/G')), and the X-axis is Master curves of log(G'), log(G''), and log(tan δ) are created by overlapping each other while translating in parallel in the direction.

In the master curve of log(G'') obtained, the value of log(f) at the point where log(G'') in the range of -6.0<log(f)<-1.0 is maximum. Read and record. In addition, in the above master curve, if there is no point where log(G'') is maximum in the range of -6.0<log(f)<-1.0, log(G'') in the above range is Read and record the value at the maximum point. In addition, in the master curve of log(tanδ) obtained, the value of log(tanδ) when log(f) is -4.0, and the value of log(tanδ) when log(f) is -4.0. ) and record the value.

In addition, in the master curve, the following relational expression holds between the frequency f (Hz) and the time s (seconds).
f=1/2πs
Further, log(f)=-4.0 and log(f)=-3.0 correspond to 30 minutes and 3 minutes, respectively.
Note that the dynamic viscoelasticity measuring device is not particularly limited, and examples thereof include a rotational rheometer manufactured by TA Instruments (trade name "AR-G2") and the like.

In the hot melt composition of the present invention, in the master curve obtained by the above method, the log(G'') at the point where the maximum in the range of -6.0<log(f)<-1.0 The value of (f) is -2.5 or less. If the value of log(f) exceeds -2.5, the elastic recovery property of the hot melt composition after being kept at a temperature decreases. The value of log(f) is preferably -2.7 or less, more preferably -2.9 or less. Further, the lower limit of the log(f) value is not particularly limited, and is preferably -6.0 or more, more preferably -5.8 or more, from the standpoint of further improving the coating properties of the hot melt composition.

In order to adjust the value of log(f) at the point where log(G'') is maximum in the range of -6.0<log(f)<-1.0 to a smaller value, use an end block of thermoplastic resin. All you have to do is make the phase stronger. Specifically, the value of log(f) can be increased by using a thermoplastic resin with a high styrene content, reinforcing the styrenic end block phase with an end block resin, or bonding the end block phases together. It can be adjusted smaller. Furthermore, the value of log(f) can be adjusted to a smaller value by using a thermoplastic resin with a high weight average molecular weight or by increasing the content of the thermoplastic resin in the hot melt composition. .

In addition, in the above master curve, if there is no point where log(G'') is maximum in the range of -6.0<log(f)<-1.0, log(G'') in the above range is It is sufficient that the value of log(f) at the maximum point is within the above range.

In the hot melt composition of the present invention, in the master curve obtained by the above method, when the value of log(f) is −4, the logarithm (log( The value of tan δ) is 0 or less. When the value of (log(tan δ)) exceeds 0, the elasticity recovery property of the hot melt composition after being kept at a temperature decreases. The value of (log(tan δ)) is preferably -0.05 or less, more preferably -0.1 or less. Further, the lower limit of the value of (log(tan δ)) is not particularly limited, and is preferably -1.0 or more, and more preferably -0.9 or more, in terms of further improving the coating properties of the hot melt composition. preferable.

When the value of log(f) is -4, in order to adjust the value of the logarithm of tanδ (log(tanδ)) calculated by (G''/G') to a smaller value, use an end block of thermoplastic resin. All you have to do is make the phase stronger. Specifically, the logarithm of tan δ (log(tan δ )) can be adjusted to a smaller value. Furthermore, the value of the logarithm of tan δ (log(tan δ)) can be further reduced by methods such as using a thermoplastic resin with a high weight average molecular weight or increasing the content of the thermoplastic resin in the hot melt composition. Can be adjusted.

In the hot melt composition of the present invention, the difference between the value of log(tan δ) when log(f) is -4 and the value of log(tan δ) when log(f) is -3 is 0. It is preferably 0.05 or more, and more preferably 0.1 or more. When the above-mentioned difference is within the above-mentioned range, the stretch recovery property of the hot-melt composition after being held at a temperature is further improved, and breakage is further suppressed. Further, the upper limit of the above-mentioned difference is not particularly limited, and is preferably 0.6 or less, more preferably 0.5 or less, from the viewpoint of further improving the reduction in stretch recovery properties and the suppression of breakage of the hot melt composition.

(Thermoplastic resin (A))
The thermoplastic resin (A) is not particularly limited as long as the hot melt composition can satisfy the conditions (1) and (2) above, and a thermoplastic elastomer is preferred since it has even better elasticity. Moreover, a reactive thermoplastic resin can be used as the thermoplastic resin (A). Examples of thermoplastic resins having such reactivity include thermoplastic resins containing a styrenic block copolymer having a reactive polystyrene hard block in the molecule of the thermoplastic resin. By using such a thermoplastic resin and further containing a photopolymerization initiator, the hot melt composition is irradiated with light such as ultraviolet rays to react with the reactive polystyrene hard blocks and crosslink molecules. Accordingly, properties such as dynamic viscoelasticity of the hot melt composition can be adjusted.

Examples of the thermoplastic elastomer include styrene block copolymers, olefin block copolymers, olefin random copolymers, urethane block copolymers, and polyester block copolymers. Among these, styrenic block copolymers are preferred, and those containing hydrogenated styrenic block copolymers, which are hydrogenated products of styrenic block copolymers, are particularly preferred. A hydrogenated product of a styrenic block copolymer is a block copolymer of 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 A hydrogenated block copolymer.

A vinyl aromatic hydrocarbon is an aromatic hydrocarbon compound 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, and vinylanthracene. Among these, styrene is preferred. Vinyl aromatic hydrocarbons may be used alone or in combination of two or more.

A conjugated diene compound is a diolefin compound having at least one pair of conjugated double bonds. Specifically, the conjugated diene compound includes 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1 , 3-hexadiene, etc. Among these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferred. The conjugated diene compounds may be used alone or in combination of two or more.

In this specification, the hydrogenated ratio in a hydrogenated thermoplastic block copolymer, such as a hydrogenated product of a styrenic block copolymer, is indicated as a "hydrogenation rate." The "hydrogenation rate" of a hydrogenated thermoplastic block copolymer is based on all the ethylenically unsaturated double bonds contained in the block based on a conjugated diene compound, and among them, the hydrogenated and saturated hydrocarbon Refers to the percentage of ethylenically unsaturated double bonds converted to bonds. The hydrogenation rate can be measured using an infrared spectrophotometer, a nuclear magnetic resonance device, or the like.

As the hydrogenated product of the styrenic block copolymer, partially hydrogenated and fully hydrogenated hydrogenated products can be used. Among these, fully hydrogenated hydrogenated products are preferred. When the hydrogenated styrenic block copolymer is completely hydrogenated, the heating stability of the hot melt composition is further improved. The hydrogenation rate of the hydrogenated styrenic block copolymer is preferably about 100%.

Hydrogenated substances for styrenic block copolymers are not particularly limited, and include styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butylene-butadiene-styrene copolymer (SBBS), styrene-ethylene-butylene /Styrene-styrene copolymer (SEB/S-S), styrene-ethylene-propylene-styrene copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS), styrene-ethylene-butylene -Olefin crystal copolymer (SEBC) and the like. By using the above-mentioned thermoplastic elastomer as the thermoplastic resin (A), the hot-melt composition of the present invention can reduce elastic recovery even after being heated and held in an elongated state. Breakage is further suppressed. Among these, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-butylene/ Styrene-styrene copolymers are preferred.

The above-mentioned hydrogenated styrenic block copolymer may be used alone or in combination of two or more.

The styrene-ethylene-butylene-styrene copolymer (SEBS) is a copolymer in which the terminal styrene units form an end block phase and the ethylene-butylene units form a mid-block phase. By using a copolymer in which the mid-block phase is hydrogenated ethylene-butylene units, the polarity difference from the styrene units in the end-block phase becomes more pronounced, and the copolymer in the non-hydrogenated mid-block phase Compared to this, the styrene units in the end block phase are stronger. As a result, the stretch recovery properties of the hot melt composition can be further improved. Furthermore, since the mid-block phase is hydrogenated, it is possible to provide a hot melt composition with even better heating stability.

The above-mentioned styrene-ethylene-butylene-styrene copolymer contains a styrene-based block copolymer having a reactive polystyrene-based hard block in the molecule of the thermoplastic resin. Polymers may also be used. By using a reactive styrene-ethylene-butylene-styrene copolymer and further containing a photopolymerization initiator, the hot melt composition is irradiated with light such as ultraviolet rays to react with the reactive polystyrene hard block. The properties of the hot melt composition, such as dynamic viscoelasticity, can be adjusted by crosslinking the molecules. As the styrene-ethylene-butylene-styrene copolymer having such reactivity, commercially available products can be used, and examples of commercially available products include Septon V9827 manufactured by Kuraray Co., Ltd.

The styrene content of the styrene-ethylene-butylene-styrene copolymer is preferably 15-45% by mass, and more preferably 20-40% by mass, based on 100% by mass of the styrene-ethylene-butylene-styrene copolymer. When the lower limit of the styrene content is within the above range, the stretch recovery properties of the hot melt composition after stretching are further improved. When the upper limit of the styrene content is within the above range, the hot melt composition becomes softer and can exhibit even better extensibility.

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

In addition, the method for calculating the styrene content in the styrenic block copolymer in this specification is not particularly limited, and examples thereof include methods using proton nuclear magnetic resonance method or infrared spectroscopy according to JIS K6239. .

As the styrene-ethylene-butylene-styrene copolymer, commercially available products can be used. Commercially available products include G1650 manufactured by Kraton Polymer, MD1648 manufactured by Kraton Polymer, and Tuftec H1041 manufactured by Asahi Kasei.

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 used in combination. The styrene content of the entire styrene-ethylene-butylene-styrene copolymer when two or more types are used as a mixture may be calculated from an average value based on weight.

The above styrene-ethylene-butylene/styrene-styrene copolymer (SEB/S-S) is a styrene-ethylene-butylene-styrene copolymer in which the terminal styrene units form an end block phase and the ethylene-butylene units form a mid-block phase. It is a copolymer in which styrene is also dispersed in the mid-block phase. By using a copolymer in which styrene is dispersed in the mid-block phase, the styrene block copolymer does not become too hard even if the total styrene content of the styrene block copolymer increases, resulting in good extensibility. 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 in a hot melt composition, the increase in melt viscosity at low temperatures is suppressed. coating properties can be further improved.

The method for 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 60% by mass, and 25 to 55% by mass, based on 100% by mass of the styrene-ethylene-butylene/styrene-styrene copolymer. More preferred. When the lower limit of the styrene content is within the above range, the stretch recovery properties of the hot melt composition after stretching are further improved. When the upper limit of the styrene content is within the above range, the hot melt composition becomes softer and can exhibit even better extensibility.

As the styrene-ethylene-butylene/styrene-styrene copolymer, commercially available products can be used. Commercially available products include MD6951 manufactured by Kraton Polymer, A1536 manufactured by Kraton Polymer, and the like.

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

The styrene-ethylene-butylene-olefin crystal copolymer (SEBC) is a block polymer of styrene-ethylene-butylene-olefin crystals. By using the styrene-ethylene-butylene-olefin crystal copolymer, the hot-melt composition has even better elasticity recovery properties after being kept at temperature, further improves coating properties, and has improved tensile strength and transparency. will further improve.

The method for producing the styrene-ethylene-butylene-olefin crystal copolymer is not particularly limited, and it can be produced by the following production method. That is, first, 1,3-butadiene is polymerized using an organolithium initiator, and then 1,3-butadiene is polymerized so that the 1,2-vinyl bond content is 30 to 70%. Block polybutadiene with different vinyl bond content is produced. Next, a vinyl aromatic compound containing 90% by mass or more of styrene is added to polybutadiene and polymerized to produce a block copolymer before hydrogenation. Next, a styrene-ethylene-butylene-olefin crystalline copolymer can be produced by hydrogenating the block copolymer before hydrogenation by a known method.

Examples of vinyl aromatic compounds include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylstyrene, N,N-diethyl-p-aminoethylstyrene, and vinyl Examples include pyridine. Among these, styrene and α-methylstyrene are preferred.

Examples of organolithium compounds used as organolithium initiators include n-butyllithium, sec-butyllithium, tert-butyllithium, propyllithium, amyllithium, and butyllithium/barium nonyl phenoxide/trialkylaluminum/dialkylamino. Examples include ethanol.

The styrene content of the styrene-ethylene-butylene-olefin crystalline copolymer is preferably 10 to 30% by mass, more preferably 15 to 25% by mass, based on 100% by mass of the styrene-ethylene-butylene-olefin crystalline copolymer. . When the lower limit of the styrene content is within the above range, the stretch recovery properties of the hot melt composition after stretching are further improved. When the upper limit of the styrene content is within the above range, the hot melt composition becomes softer and can exhibit even better extensibility.

As the styrene-ethylene-butylene-olefin crystal copolymer, commercially available products can be used. Commercially available products include DYNARON 4600P manufactured by JSR.

The styrene-ethylene-butylene-olefin crystal copolymer may be used alone or in combination of two or more. For example, a styrene-ethylene-butylene-olefin crystal copolymer having a high styrene content and a styrene-ethylene-butylene-olefin crystal copolymer having a low styrene content may be used in combination. The styrene content of the styrene-ethylene-butylene-olefin crystal copolymer when two or more types are used as a mixture may be calculated from an average value based on weight.

The content of the thermoplastic resin (A) in the hot melt composition of the present invention is preferably 40 to 75% by mass, preferably 50 to 70% by mass, and 55 to 65% by mass, based on 100% by mass of the hot melt composition. % is more preferable. When the content of the thermoplastic resin (A) is within the above range, the hot melt composition of the present invention has even more excellent elasticity recovery properties after being kept at temperature, and also has excellent coatability.

The styrene content of the thermoplastic resin (A) in the hot melt composition of the present invention is preferably 10 to 35% by mass, more preferably 12 to 25% by mass, based on 100% by mass of the thermoplastic resin (A). . When the lower limit of the styrene content is within the above range, the stretch recovery properties of the hot melt composition after being kept at temperature are further improved. When the upper limit of the styrene content is within the above range, the hot melt composition becomes even softer and can exhibit even better extensibility.

The weight average molecular weight (Mw) of the thermoplastic resin (A) in the hot melt composition of the present invention is preferably 30,000 to 200,000, more preferably 40,000 to 150,000, and more preferably 45,000 to 125 ,000 is more preferable. When the lower limit of the weight average molecular weight is within the above range, the stretch recovery property of the hot melt composition after being kept at temperature is further improved. When the upper limit of the weight average molecular weight is within the above range, the hot melt composition becomes even softer and can exhibit even better extensibility.

Note that the weight average molecular weight (Mw) of the thermoplastic resin is a measured value obtained by conversion using standard polystyrene using a gel permeation chromatography measuring device.

The weight average molecular weight (Mw) in this specification can be measured, for example, using the following measuring device and measurement conditions.
Measuring device: Manufactured by Waters, product name “ACQUITY APC”
Measurement conditions: Column - ACQUITY APCXT45 1.7 μm x 1 - ACQUITY APCXT125 2.5 μm x 1 - ACQUITY APCXT450 2.5 μm x 1 Mobile phase: Tetrahydrofuran 0.8 mL/min Sample concentration: 0.2 mass%
Detector: Differential refractive index (RI) detector Standard material: Polystyrene (manufactured by Waters, molecular weight: 266-1,800,000) Column temperature: 40°C
RI detector temperature: 40℃

(Plasticizer (B))
The hot melt composition of the present invention contains a plasticizer (B). The plasticizer (B) is preferably liquid at 23°C. Note that in this specification, "liquid" refers to a state exhibiting fluidity. The pour point of such a plasticizer (B) is preferably 23°C or lower, more preferably 10°C or lower.

In this specification, pour point is a value measured by a measuring method based on JIS K2269.

The plasticizer (B) is not particularly limited, and includes, for example, paraffinic process oil, naphthenic process oil, aromatic process oil, liquid paraffin oil, hydrocarbon synthetic oil, and the like. Among these, paraffin-based process oils, naphthenic process oils, liquid paraffin oils, and hydrocarbon-based synthetic oils are preferred from the viewpoint of excellent heating stability, and the expansion and contraction recovery properties of the hot melt composition after heating and holding are further improved. From the viewpoint of improving performance, hydrocarbon-based synthetic oil is more preferred.

As the paraffinic process oil, commercially available products can be used. Commercially available products include, for example, PW-32 manufactured by Idemitsu Kosan Co., Ltd. and PS-32 manufactured by Idemitsu Kosan Co., Ltd.

As the naphthenic process oil, commercially available products can be used. Examples of commercially available products include Diana Flexia N28 manufactured by Idemitsu Kosan, Diana Flexia U46 manufactured by Idemitsu Kosan, and Nyflex 222B manufactured by Nynas.

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

As the hydrocarbon synthetic oil, commercially available products can be used. 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 of the present invention is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and 12 to 45% by mass, based on 100% by mass of the hot melt composition. % is more preferable. When the upper limit of the content of the plasticizer (B) is within the above range, the stretch recovery property of the hot melt composition after being kept at a temperature is further improved. When the lower limit of the content of the plasticizer (B) is within the above range, the melt viscosity of the hot melt composition is further reduced, and the coatability of the hot melt composition is further improved.

(Wax (C))
The hot melt composition of the present invention may contain a wax (C) having in its molecule at least one group selected from the group consisting of a carbonyl group, a carboxyl group, and a carboxylic acid anhydride group. The wax (C) is preferably solid at 23°C. Note that in this specification, "solid" refers to a state that does not exhibit fluidity. The softening point of such wax (C) is preferably 23°C or higher, more preferably 30°C or higher, and even more preferably 40°C or higher.

In this specification, the softening point is a value measured by a measuring method based on ASTM D-3954.

A wax having at least one group selected from the group consisting of a carbonyl group, a carboxyl group, and a carboxylic acid anhydride group in its molecule has high polarity, so it has good compatibility with the styrenic block copolymer. Good dispersion within the composition is achieved. Therefore, the heat stability of the hot melt composition can be further improved compared to a wax that does not have a carbonyl group, a carboxyl group, or a carboxylic acid anhydride group in its molecule. The wax (C) having in its molecule at least one group selected from the group consisting of a carbonyl group, a carboxyl group, and a carboxylic acid anhydride group is not particularly limited, and includes, for example, vinyl acetate wax, acrylic acid wax, Examples include maleic anhydride-modified wax. Among them, vinyl acetate wax is preferred from the viewpoint of better heating stability.

As the vinyl acetate wax, commercially available products can be used. Commercially available products include, for example, AC-400 manufactured by Honeywell, AC-430 manufactured by Honeywell, and the like.

As the acrylic acid wax, commercially available products can be used. Commercially available products include, for example, AC-540 manufactured by Honeywell and AC-580 manufactured by Honeywell.

As the maleic anhydride modified wax, commercially available products can be used. Commercially available products include, for example, AC-573P manufactured by Honeywell, AC-577P manufactured by Honeywell, and MAW-0300 manufactured by Nippon Seirosha.

The waxes having at least one group selected from the group consisting of carbonyl groups, carboxyl groups, and carboxylic acid anhydride groups in the molecule may be used alone or in combination of two or more. May be used.

The content of wax (C) in the hot melt composition of the present invention is preferably 5 to 40 mass %, more preferably 5 to 35 mass %, and 10 to 30 mass %, based on 100 mass % of the hot melt composition. More preferred. When the lower limit of the content of wax (C) is within the above range, the stress at the time of double elongation of the hot melt composition is further improved. When the upper limit of the content of wax (C) is within the above range, the stretch recovery property of the hot melt composition after being kept at a temperature is further improved.

(Other additives)
The hot melt composition of the present invention may contain other additives as long as they do not essentially impede the object of the present invention. Examples of the other additives include antioxidants, ultraviolet absorbers, tackifier resins, photopolymerization initiators, liquid rubbers, fine particle fillers, and the like.

As antioxidants, 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]phenylacrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)]acrylate, tetrakis[methylene-3-(3, Hindered phenolic antioxidants such as 5-di-t-butyl-4-hydroxyphenyl)propionate] methane; dilaurylthiodipropionate, laurylstearylthiodipropionate, pentaerythritol tetrakis (3-laurylthiopropionate) Examples include sulfur-based antioxidants such as tris(nonylphenyl) phosphite and tris(2,4-di-t-butylphenyl) phosphite. The antioxidants may be used alone or in combination of two or more.

The content of the antioxidant in the hot melt composition of the present invention 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. , 0.1 to 1% by mass is more preferable. When the content of the antioxidant is 0.01% by mass or more, the thermal stability of the hot melt composition is further improved. When the content of the antioxidant is 2% by mass or less, the odor of the hot melt composition is reduced.

As ultraviolet absorbers, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-t-butylphenyl)benzotriazole, 2-(2' Benzotriazole UV absorbers such as -hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole; Benzophenone UV absorbers such as 2-hydroxy-4-methoxybenzophenone; Salicylic acid esters Examples include ultraviolet absorbers; cyanoacrylate ultraviolet absorbers; and hindered amine light stabilizers. The ultraviolet absorbers may be used alone or in combination of two or more.

The content of the ultraviolet absorber in the hot melt composition of the present invention 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. , 0.1 to 1% by mass is more preferable. When the content of the ultraviolet absorber is 0.01% by mass or more, the weather resistance of the hot melt composition is improved. When the content of the ultraviolet absorber is 2% by mass or less, the odor of the hot melt composition is reduced.

Tackifying resins include natural rosin, modified rosin, glycerol ester of natural rosin, glycerol ester of modified rosin, pentaerythritol ester of natural rosin, pentaerythritol ester of modified rosin, copolymer of natural terpene, three-dimensional polymer of natural terpene, Hydrogenated derivatives of copolymers of natural terpenes, terpene resins, hydrogenated derivatives of phenolic modified terpene resins; petroleum resins such as C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, dicyclopentadiene petroleum resins, Partially hydrogenated petroleum resins, fully hydrogenated petroleum resins, etc., which are obtained by adding hydrogen to these petroleum resins, can be mentioned. As the tackifying resin, petroleum resins, partially hydrogenated petroleum resins, and fully hydrogenated petroleum resins are preferable in terms of the odor and thermal stability of the hot melt composition. Added petroleum resin is more preferred. These tackifier resins may be used alone or in combination of two or more.

The ring and ball softening point temperature of the tackifying resin is preferably 80° C. or higher, more preferably 90° C. or higher, since the hot melt composition has even better elasticity and thermal stability. Further, the ring and ball softening point temperature of the tackifier resin is preferably 125°C or lower, more preferably 120°C or lower, from the viewpoint of making the hot melt composition more flexible and further suppressing brittleness. . In this specification, the ring and ball softening point temperature of the tackifying resin is a value measured in accordance with JIS K2207.

The content of the tackifying resin in the hot melt composition of the present invention is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the hot melt composition. When the content of the tackifier resin is 30% by mass or less, the hot melt composition does not become too hard, and the elastic recovery after elongation is further improved.

Examples of the photopolymerization initiator include ultraviolet polymerization initiators. When the hot melt composition of the present invention contains a styrenic block copolymer having a reactive polystyrene hard block in the molecule as the thermoplastic resin (A), it may further contain a photopolymerization initiator, Properties such as dynamic viscoelasticity of the hot melt composition can be adjusted by irradiating the hot melt composition with light such as ultraviolet rays to cause the reactive polystyrene hard blocks to react and crosslink molecules. When irradiating the hot melt composition with ultraviolet rays, the irradiation intensity of the ultraviolet rays is preferably about 50 to 1,000 mW/cm ² , and the cumulative light amount is preferably about 1,000 to 15,000 mJ/cm ² to achieve desired properties. It may be adjusted as appropriate to achieve this. The photopolymerization initiators may be used alone or in combination of two or more.

Examples of the liquid rubber include liquid polybutene, liquid polybutadiene, liquid polyisoprene, and hydrogenated resins thereof. One type of liquid rubber may be used alone, or two or more types may be used in combination.

The content of liquid rubber in the hot melt composition of the present invention is preferably 1 to 20% by weight, more preferably 2 to 15% by weight, and even more preferably 3 to 10% by weight, based on 100% by weight of the hot melt composition. When the content of liquid rubber is 1% by mass or more, the melt viscosity of the hot melt composition is reduced, and the coating suitability is further improved. When the content of liquid rubber is 20% by mass or less, the hot melt composition does not become too soft, and the stretch recovery properties are further improved.

The particulate filler is not particularly limited, and examples thereof include calcium carbonate, kaolin, talc, titanium oxide, mica, and styrene beads. The fine particle fillers may be used alone or in combination of two or more.

The hot melt composition of the present invention preferably has a melt viscosity at 180° C. of 45,000 mPa·s or less, more preferably 28,000 mPa·s or less, and even more preferably 22,000 mPa·s or less. When the upper limit of the melt viscosity is within the above range, the coatability of the hot melt composition is further improved. Further, the lower limit of the melt viscosity at 180° C. of the hot melt composition is not particularly limited, and may be about 5,000 mPa·s.

As used herein, "melt viscosity" refers to the viscosity of a hot melt composition heated to a molten state at a certain temperature. As a method for measuring the melt viscosity at 180°C, for example, a method of heating and melting a hot melt composition and measuring the viscosity of the melted state at 180°C using a Brookfield RVT type viscometer (spindle No. 29) is used. can be mentioned.

The hot melt composition of the present invention is manufactured by a known method. For example, thermoplastic resin (A), plasticizer (B), wax if necessary, various additives, etc. are put into a double-arm kneader heated to 150°C, and the mixture is melted and kneaded while heating. Ru.

The hot melt composition of the present invention is usually solid in the temperature range of 0 to 60°C, particularly at room temperature of 23°C, and exhibits stretchability, so it can be used as a stretchable hotmelt composition for various purposes.

Applications of the hot melt composition of the present invention are not particularly limited, and include, for example, absorbent articles including sanitary materials, hospital gowns, masks, and the like. Specific examples of the sanitary materials include paper diapers, sanitary napkins, and the like.

The hot melt composition of the present invention is suitably used as a stretchable member of a stretchable laminate including a stretchable film and a stretchable member. Examples of such a stretchable laminate include a stretchable laminate in which a nonwoven fabric is bonded to at least one side of a film formed from the hot melt composition. Such a stretchable laminate is also part of the present invention.

The use of the stretchable laminate is not particularly limited, and includes, for example, absorbent articles including sanitary materials, hospital gowns, masks, and the like. Specific examples of the sanitary materials include paper diapers, sanitary napkins, and the like.

Examples of the present invention will be described below. The invention is not limited to the examples below.

The raw materials used in the Examples and Comparative Examples are as follows.

Styrenic block copolymer (A1) :
・Styrene-ethylene-butylene/styrene-styrene (SEB/S-S) copolymer manufactured by Kraton Polymer Co., Ltd. MD6951 (styrene content 34% by mass, Mw = 100,000)
Styrenic block copolymer (A2) :
・Styrene-ethylene-butylene-styrene (SEBS) copolymer manufactured by Kraton Polymer Co., Ltd. MD1648 (styrene content 20% by mass, Mw = 54,000)
Styrenic block copolymer (A3) :
・Styrene-ethylene-butylene-olefin crystal copolymer (SEBC) DYNARON 4600P manufactured by JSR (styrene content 20% by mass)
Styrenic block copolymer (A4) :
・Styrene-ethylene-butylene-styrene (SEBS) copolymer Tuftec H1041 manufactured by Asahi Kasei Corporation (styrene content 30% by mass, Mw = 61,000)
Styrenic block copolymer (A5) :
・Styrene-ethylene-butylene-styrene (SEBS) copolymer manufactured by Kuraray Co., Ltd. Septon V9827 (styrene content 30% by mass, contains reactive polystyrene hard blocks in the molecule)

Plasticizer (B) :
・Hydrocarbon-based synthetic oil (B1) Lucant HC-10 manufactured by Mitsui Chemicals (pour point -32.5°C)
・Liquid paraffin oil (B2) Kaydol manufactured by Sonneborn (pour point -21°C)

Tackifier :
・End block resin manufactured by Mitsui Chemicals FTR-0120

Photopolymerization initiator /alkylphenone photopolymerization initiator manufactured by BASF IRGACURE184

Antioxidant :
・Phenolic antioxidant IRGANOX1010 manufactured by BASF

(Example and comparative example)
The above-mentioned raw materials were put into a stirring kneader equipped with a heating device in the amounts shown in Table 1. A hot melt composition was prepared by kneading while heating at 150° C. for 90 minutes. In addition, Example 5 and Comparative Example 2 have the same composition, but in Example 5, the hot melt composition was irradiated with ultraviolet rays to react the reactive polystyrene hard block of the styrenic block copolymer, The molecules were crosslinked to adjust the properties of the hot melt composition. The irradiation intensity of ultraviolet rays in Example 5 was 500 mW/cm ² , and the cumulative amount of light was 1000 mJ/cm ² .

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

(180℃ melt viscosity)
The hot melt composition was heated and melted, and the viscosity of the melted state at 180° C. was measured using a Brookfield RVT viscometer (spindle No. 29).

(Coatability)
The hot melt composition was put into a melting tank heated to 180 to 190°C, and discharged from a slot nozzle heated to 180 to 190°C, and contact-coated onto a release-treated PET film. In Example 5, after contact coating, the hot melt composition was irradiated with ultraviolet rays under the above conditions to crosslink molecules to adjust the properties of the hot melt composition. The coatability of the hot melt composition at this time was visually observed and evaluated according to the following evaluation criteria.
◎: Can be coated evenly at a coating temperature of 180°C.
○: Can be coated without uneven coating at a coating temperature of 190°C.
Δ: Slight coating unevenness was observed at a coating temperature of 190° C., but it was not a problem in use.
×: Significant coating unevenness is observed, or a predetermined amount of hot melt composition is not discharged.

(return rate)
Preparation of test pieces
The hot melt composition was applied at a coating temperature of 180 to 190° C. to the release layer side of the release-treated PET film in a coating weight of 50 g/m ² . The coating width was 80 mm. Next, one side was laminated with release paper that had been subjected to release treatment to produce a laminate. The obtained laminate was cut into a length of 85 mm in the MD direction. The PET film and release paper of the laminate were peeled off to prepare a test piece of the hot melt composition with a length of 85 mm and a width of 80 mm.

Measurement of return rate A test box was prepared whose top surface was completely open. The length of the opening was 170 mm. The test piece prepared as described above was stretched in the length direction (MD direction) to a length of 170 mm, both ends were fixed to the opening of the test box, and the test piece was held in the stretched state. . The test box with the test piece fixed at both ends was placed in a constant temperature bath at 40° C. and allowed to stand for 1 hour. Next, the test piece was removed from the test box, and the length of the test piece after the test was measured. The return rate was calculated using the following formula.
Return rate (%) = Length of test piece after test (mm) / Length of test piece before test (85 mm) x 100

(Viscoelastic master curve)
The hot melt composition was heated and melted at 180° C. and dropped onto the release layer side surface of the release-treated PET film. Next, another release-treated PET film was laminated on the hot melt composition so that the surface on the release layer side was in contact with the hot melt composition. Next, the hot melt composition was compressed using a hot press heated to 120° C., and the thickness of the hot melt composition was adjusted to about 2 mm. After the hot melt composition was sandwiched between PET films and allowed to stand at 23° C. for 24 hours, the release film was removed to prepare a sample for dynamic viscoelasticity measurement.

Using the sample, dynamic viscoelasticity was measured in the rotary shear mode of the dynamic viscoelasticity measuring device under measurement conditions of temperature from -20°C to 120°C and frequency of 0.2 to 2.0Hz. Specifically, the storage modulus G' and the loss modulus G'' were measured under a constant temperature condition of -20° C. in a rotating shear mode with a frequency of 0.2 to 2.0 Hz. Similar measurements were carried out every 10°C up to 120°C. The logarithm of the measured storage modulus G' and loss modulus G'' was taken and plotted against the logarithm of frequency (log(f)). Next, the reference temperature is set to 40°C, and shift factors are set for log(G'), log(G''), and log(tanδ) (=log(G''/G')), and the X-axis is Master curves of log (G'), log (G''), and log (tan δ) were created by overlapping each other while moving parallel to the direction.

In the master curve of log(G'') obtained, the value of log(f) at the point where log(G'') in the range of -6.0<log(f)<-1.0 is maximum. was read and recorded. In addition, in the master curve of log(tanδ) obtained, the value of log(tanδ) when log(f) is -4.0, and the value of log(tanδ) when log(f) is -4.0. ) values were read and recorded.

In addition, in the master curve, the following relational expression holds between the frequency f (Hz) and the time s (seconds).
f=1/2πs
Further, log(f)=-4.0 and log(f)=-3.0 correspond to 30 minutes and 3 minutes, respectively.
As a dynamic viscoelasticity measuring device, a rotational rheometer manufactured by TA Instruments (trade name "AR-G2") was used.

The results are shown in Table 1.

Claims (4)

A hot melt composition comprising a thermoplastic resin (A) and a plasticizer (B),
The thermoplastic resin (A) is selected from the group consisting of styrene-ethylene-butylene/styrene-styrene copolymer (SEB/S-S) and styrene-ethylene-butylene-olefin crystal copolymer (SEBC). at least one type of
The styrene content of the styrene-ethylene-butylene/styrene-styrene copolymer (SEB/S-S) is 20% by mass when the styrene-ethylene-butylene/styrene-styrene copolymer (SEB/S-S) is 100% by mass. ~60% by mass,
The styrene content of the styrene-ethylene-butylene-olefin crystalline copolymer (SEBC) is 10 to 30% by mass based on 100% by mass of the styrene-ethylene-butylene-olefin crystalline copolymer (SEBC),
The plasticizer (B) is at least one selected from the group consisting of paraffinic process oil, naphthenic process oil, aromatic process oil, liquid paraffin oil, and hydrocarbon synthetic oil,
The content of the thermoplastic resin (A) is 40 to 75% by mass, with the hot melt composition being 100% by mass,
The content of the plasticizer (B) is 5 to 60% by mass based on 100% by mass of the hot melt composition,
Dynamic viscoelasticity measurements were performed under the conditions of temperature -20 to 120°C and frequency (f) -0.2 to 2.0Hz, and the measured storage The logarithm (log(G')) of the elastic modulus (G') and the logarithm (log(G'')) of the measured loss modulus (G'') are plotted, and the reference temperature is set to 40°C. In the master curve,
(1) The value of log(f) at the point where log(G'') is maximum in the range of -6.0<log(f)<-1.0 is -2.5 or less, and
(2) When the value of log(f) is -4, the value of the logarithm of tanδ (log(tanδ)) calculated by (G''/G') is 0 or less,
A hot melt composition characterized by: The hot melt composition according to claim 1, having a melt viscosity at 180° C. of 5,000 mPa·s or more and 45,000 mPa·s or less. According to claim 1 or 2, the total content of the thermoplastic resin (A) and the content of the plasticizer (B) is 45 to 99.5% by mass, based on 100% by mass of the hot melt composition. Hot melt compositions as described. A stretchable laminate, characterized in that a nonwoven fabric is bonded to at least one side of a film formed from the hot melt composition according to any one of claims 1 to 3.