Hot melt adhesive

Abstract

To provide a hot melt adhesive which is excellent in holding force and flavor resistance and shows little adhesive residue and unpleasant odor.SOLUTION: A hot melt adhesive has (A) a thermoplastic block copolymer being a copolymer of vinyl-based aromatic hydrocarbon and a conjugated diene compound, where (A) the thermoplastic block copolymer contains (A1) an unhydrogenated product of a triblock type styrene isoprene block copolymer and (A2) an unhydrogenated product of a styrene butadiene block copolymer, and does not have an amount of 5 pts.wt. or more of (B) an α-methyl styrene-based resin with respect to 100 pts.wt. of the total weight of (A) and (B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hot melt adhesive. In particular, the present invention relates to a hot melt adhesive suitable for fixing absorbent articles such as sanitary napkins to clothing such as panties.

Background Art

[0002] An absorbent article is an article that is fixed to clothing such as underwear or a shirt, for example, in order to absorb body fluids generated from the body such as menstrual blood, vaginal discharge, urine, and sweat, and is used to prevent discomfort and unsanitary conditions caused by the adhesion of body fluids to clothing. Examples of absorbent articles include sanitary napkins, urine liners, postpartum shirts, breast pads, sweat pads, paper diapers, pet sheets, hospital gowns, and surgical gowns. Therefore, positioning adhesives for fixing such absorbent articles to the above-mentioned clothing so that their positions do not shift have also been developed.

[0003] Many absorbent articles generally have an absorbent body between a moisture-permeable topsheet that contacts the skin and a liquid-impermeable backsheet that contacts the underwear. The positioning adhesive is generally transferred to the backsheet after being coated on a release substrate. By bringing the transferred positioning adhesive into contact with the underwear, the absorbent article is held on the underwear.

[0004] If the performance of the positioning adhesive is insufficient, the absorbent article may not be held on the underwear, and body fluids may adhere to the clothing. Therefore, in recent years, further performance improvement of the positioning adhesive has been demanded.

[0005] For example, Patent Document 1 discloses a hot melt adhesive using a hydrogenated block copolymer such as styrene-ethylene / butylene-styrene block copolymer (SEBS) as an adhesive for positioning (see the claims, etc.). However, the hot melt adhesive of Patent Document 1 has insufficient holding power, and the absorbent article may shift from the adherend. To completely prevent the shift of the absorbent article, a relatively large amount of hot melt adhesive is used.

[0006] The hot melt adhesive of Patent Document 2 contains an unhydrogenated thermoplastic block copolymer and an α-methylstyrene resin, and is suitable for use in fixing absorbent articles such as sanitary napkins to underwear ([Claim 1]

[0001] [Table 1] to [Table 3]). The hot melt adhesive of this document can prevent the occurrence of glue residue, but has insufficient holding power, and although rare, the napkin may slightly shift from the adherend.

[0007] The hot melt adhesives of Patent Documents 1 and 2 have room for improvement in holding power, for example, the peel strength in a low-temperature (-10 to 10 °C) environment.

[0008] In recent years, for the purpose of reducing the odor of absorbent articles, fragrances such as limonene may be applied to the absorbent body. Since the fragrance is volatile, it penetrates into the hot melt adhesive applied to the backsheet, reducing the tack of the hot melt adhesive. When the tack of the hot melt adhesive decreases, the hot melt adhesive becomes too soft, and when peeling the absorbent article from the adherend, glue is likely to remain on the adherend.

[0009] In Patent Document 2, an α-methylstyrene resin is blended into the hot melt adhesive to improve the adhesion to the adherend. However, the α-methylstyrene resin contains volatile components, and its odor may be felt unpleasant.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention solves the above conventional problems, and an object thereof is to provide a hot melt adhesive having excellent holding power and fragrance resistance, and less glue residue and unpleasant odor.

Means for Solving the Problems

[0012] The present invention and preferred embodiments thereof are as follows.

[0013] 1. A hot melt adhesive having a thermoplastic block copolymer which is a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound, wherein (A) the thermoplastic block copolymer contains (A1) an unhydrogenated product of a triblock styrene-isoprene block copolymer and (A2) an unhydrogenated product of a styrene-butadiene block copolymer, and (B) does not contain an α-methylstyrene resin in an amount of 5 parts by weight or more based on 100 parts by weight of the total weight of (A) and (B).

[0014] 2. The hot melt adhesive according to 1, wherein the unhydrogenated product of (A1) the triblock styrene-isoprene block copolymer has a styrene content of 10 to 60% by weight.

[0015] 3. The hot melt adhesive according to 1 or 2, which contains 5 to 50 parts by weight of the unhydrogenated product of (A1) the triblock styrene-isoprene block copolymer based on 100 parts by weight of the total weight of (A) the thermoplastic block copolymer.

[0016] 4. Further, a hot melt adhesive according to any one of 1 to 3, which has (B) an α-methylstyrene resin, and the amount of (B) is 4.5 parts by weight or less based on 100 parts by weight of the total weight of (A) and (B).

[0017] 5. Further, a hot melt adhesive according to any one of 1 to 4, which has (C) a tackifier resin, and the (C) tackifier resin contains an unhydrogenated resin.

[0018] 6. A hot melt adhesive according to any one of 1 to 5, which is used for positioning an absorbent article.

[0019] 7. An absorbent article coated with a hot melt adhesive according to any one of 1 to 6.

Advantages of the Invention

[0020] The hot melt adhesive of the present invention can hold an absorbent article such as a sanitary napkin without shifting on clothing such as underwear, and when peeling off such an absorbent article from the clothing, no adhesive remains on the clothing, and further, there is no odor and the performance is not deteriorated by a fragrance such as limonene.

[0021] Therefore, the hot melt adhesive of the present application can improve the performance and usefulness of absorbent articles such as sanitary napkins.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0023] The hot melt adhesive of the present invention has (A) a thermoplastic block copolymer.

[0024] In the present invention, the “(A) thermoplastic block copolymer” is a copolymer obtained by block copolymerizing a vinyl aromatic hydrocarbon and a conjugated diene compound, and usually includes a resin composition having a vinyl aromatic hydrocarbon block and a conjugated diene compound block.

[0025] Here, the “vinyl aromatic hydrocarbon” means an aromatic hydrocarbon compound having a vinyl group. Specifically, for example, styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, etc. can be exemplified. Styrene is particularly preferred. These vinyl aromatic hydrocarbons can be used alone or in combination.

[0026] The “conjugated diene compound” means a diolefin compound having at least one pair of conjugated double bonds. Specific examples of the “conjugated diene compound” include 1,3-butadiene, 2-methyl-1,3-butadiene (or isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. 1,3-Butadiene and 2-methyl-1,3-butadiene are particularly preferred. These conjugated diene compounds can be used alone or in combination.

[0027] The (A) thermoplastic block copolymer of the present invention contains (A1) an unhydrogenated product of a triblock type styrene-isoprene block copolymer and (A2) an unhydrogenated product of a styrene-butadiene block copolymer.

[0028] (A1) The non-hydrogenated product of a triblock styrene-isoprene block copolymer is a triblock styrene-isoprene block copolymer in which the block based on the conjugated diene compound is not hydrogenated. Specifically, it is a styrene-isoprene-styrene polymer (hereinafter referred to as "SIS").

[0029] (A2) The non-hydrogenated product of a styrene-butadiene block copolymer is a styrene-butadiene block copolymer in which the block based on the conjugated diene compound is not hydrogenated. It may be a triblock copolymer or other types (radial block copolymer, linear block copolymer).

[0030] In this specification, whether the (A) thermoplastic block copolymer is hydrogenated or not is indicated by the "hydrogenation rate". If the hydrogenation rate is 0%, the (A) thermoplastic block copolymer is a non-hydrogenated product.

[0031] (A) The "hydrogenation rate" of a thermoplastic block copolymer refers to the ratio of the double bonds that have been hydrogenated and converted into saturated hydrocarbon bonds, based on all the aliphatic double bonds contained in the block based on the conjugated diene compound. This "hydrogenation rate" can be measured by an infrared spectrophotometer, a nuclear magnetic resonance apparatus, etc.

[0032] In this specification, a triblock styrene block copolymer refers to a styrene block copolymer having the block represented by the following formula (1) and not containing other blocks. This is clearly distinguished from the linear styrene block copolymer described later.

[0033] [Chemical Formula 1] S-E-S (1) [In the formula, S is a styrene block and E is a conjugated diene block.]

[0034] A linear styrene block copolymer refers to a styrene block copolymer having both the block represented by the following formula (1) and the block represented by the following formula (2).

[0035] [Chemical formula 2] S-E (2) [In the formula, S and E have the same meanings as described above.]

[0036] The styrene-conjugated diene block copolymer of formula (2) may be called a "diblock". The proportion of the styrene-conjugated diene compound block copolymer of formula (2) contained in the styrene block copolymer is referred to as the "diblock content".

[0037] That is, the triblock-type styrene block copolymer has a diblock content of 0% by weight, and is clearly distinguished from the linear-type styrene block copolymer by the diblock content.

[0038] In the present specification, (A1) SIS has an E (conjugated diene block) of formula (1) being an isoprene block, and (A2) has the structures of both formula (1) and formula (2), and the E (conjugated diene block) is a butadiene block.

[0039] The hot melt adhesive of the present invention contains (A1) SIS, so that the cohesive force is improved, the holding power is excellent, the fragrance resistance is also excellent, and when used in sanitary napkins, the occurrence of glue residue can be reduced.

[0040] (A1) SIS preferably has a styrene content of 10 to 60% by weight, more preferably 15 to 45% by weight, and particularly preferably 25 to 45% by weight. When the styrene content of (A1) is within the above range, the fragrance resistance of the hot melt adhesive of the present invention is further improved.

[0041] In the present invention, (A1) SIS is preferably contained in an amount of 15 to 50 parts by weight based on 100 parts by weight of the (A) thermoplastic block copolymer.

[0042] (A1) By containing SIS in the above ratio, the hot melt adhesive of the present invention maintains excellent holding power, suppresses the occurrence of glue residue, and is also excellent in fragrance resistance and coatability, making it particularly suitable as a positioning hot melt adhesive for sanitary napkins and the like.

[0043] (A1) Commercially available products of SIS include Vector4411A (trade name), Vector4211A (trade name), Vector4211N (trade name), Vector4114N (trade name) manufactured by Dexco, Kraton D1162PT manufactured by Clayton, and the like.

[0044] The hot melt adhesive of the present invention has an unhydrogenated product of (A2) a styrene-butadiene block copolymer, thereby improving the cohesive force and having excellent holding power.

[0045] (A2) The unhydrogenated product of the styrene-butadiene block copolymer may be a triblock type, a linear type, or a radial type.

[0046] The specific structure of the radial styrene block copolymer is shown in Formula (3).

[0047] [Chemical Formula 3] (S-B) n Y (3)

[0048] In Formula (3), n is an integer of 2 or more, S is a styrene block, B is a butadiene block, and Y is a coupling agent. n is preferably 3 or 4, and particularly preferably 3. The copolymer with n = 3 is called a three-branched type, and the copolymer with n = 4 is called a four-branched type.

[0049] The coupling agent is a polyfunctional compound that radially bonds linear styrene block copolymers. The type of the coupling agent is not particularly limited.

[0050] Examples of coupling agents include silane compounds such as halogenated silanes and alkoxysilanes, tin compounds such as tin halides, polycarboxylic acid esters, epoxy compounds such as epoxidized soybean oil, acrylic esters such as pentaerythritol tetraacrylate, divinyl compounds such as epoxy silane and divinylbenzene, and the like. Specific examples include trichlorosilane, tribromosilane, tetrachlorosilane, tetrabromosilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tin tetrachloride, diethyl adipate, and the like.

[0051] (A2) As the unhydrogenated product of styrene-butadiene block copolymer, JSR TR2000 (trade name) manufactured by JSR Corporation, JSR TR2003, Asaprene T420 (trade name) manufactured by Asahi Kasei Chemicals Corporation, Asaprene T438, Asaprene T439 (trade name), etc. are commercially available.

[0052] In the present invention, the (A) thermoplastic block copolymer may contain (A3) other styrene block copolymers that do not correspond to (A1) or (A2). Examples of (A3) other styrene block copolymers include "linear styrene-isoprene block copolymer", "radial styrene-isoprene block copolymer", and "hydrogenated styrene block copolymer".

[0053] Commercially available products of linear styrene-isoprene block copolymer include Quintac 3270 (trade name), Quintac 3421 (trade name), Quintac 3433N (trade name), Quintac 3520 (trade name), etc. manufactured by Nippon Zeon Co., Ltd.

[0054] Examples of radial styrene-isoprene block copolymer include Quintac 3460 (trade name), Quintac 3450 (trade name), etc. manufactured by Nippon Zeon Co., Ltd.

[0055] The hydrogenated styrene block copolymer refers to a block copolymer obtained by block copolymerizing a vinyl aromatic hydrocarbon and a conjugated diene compound, and in which all or part of the block based on the conjugated diene compound in the obtained block copolymer is hydrogenated.

[0056] Specific examples of the hydrogenated styrene-based triblock copolymer include SEPS triblock copolymer, SEBS triblock copolymer, SEEPS triblock copolymer, and SEEBS triblock copolymer.

[0057] The SEPS triblock copolymer is a block copolymer composed of a terminal block of a styrene polymer block and a central block in which an ethylene structure and a propylene structure are mixed, that is, a styrene-ethylene / propylene-styrene copolymer.

[0058] The SEBS triblock copolymer is a block copolymer composed of a terminal block of a styrene polymer block and a central block in which an ethylene structure and a butylene structure are mixed, that is, a styrene-ethylene / butylene-styrene copolymer.

[0059] SEEPS is a block copolymer of a styrene terminal block and a central block of hydrogenated isoprene / butadiene.

[0060] Commercially available products of SEPS include SEPTON 2006, 2007, 2063, 2104, 4033, and 4044 (trade names) manufactured by Kuraray Co., Ltd.

[0061] Commercially available products of SEEPS include SEPTON 4099, 4077, and 4055 (trade names) manufactured by Kuraray Co., Ltd.

[0062] Commercially available products of SEBS include Kraton G1657, G1650, G1654, and G1651 (trade names) manufactured by Kraton Polymers, and SEPTON 8007, 8076, and 8104 manufactured by Kuraray Co., Ltd.

[0063] In the hot melt adhesive of the present invention, (B) an α-methylstyrene resin may be blended with (A) a thermoplastic block copolymer. However, in a preferred embodiment, (B) the α-methylstyrene resin is not blended in an amount of 5 parts by weight or more with respect to 100 parts by weight of the total weight of (A) and (B). The blending amount of (B) the α-methylstyrene resin is preferably 4.5 parts by weight or less, and particularly preferably 4 parts by weight or less.

[0064] When the blending amount of (B) the α-methylstyrene resin is within the above range, the hot melt adhesive of the present invention is excellent in fragrance resistance and suppresses the generation of odors of volatile substances.

[0065] (B) As the α-methylstyrene resin, an α-methylstyrene polymer or a styrene-α-methylstyrene copolymer is used. As an aspect of the present invention, (B) the α-methylstyrene resin is more preferably a styrene-α-methylstyrene copolymer, and particularly preferably one having a softening point of 85 to 120 °C (measured by the ring and ball method defined in JIS K2207). Specifically, commercially available products such as Cristalex 3085 (trade name), Cristalex 3100 (trade name), Cristalex 1120 (trade name), Cristalex 5140 (trade name) manufactured by Eastman Chemical Company, and FTR-2120 (trade name) manufactured by Mitsui Chemicals, Inc. can be exemplified.

[0066] In addition, in this specification, it is assumed that the α-methylstyrene resin is not included in the (C) tackifying resin described later.

[0067] The hot melt adhesive of the present invention preferably has (C) a tackifying resin and (D) a plasticizer. The tackifying resin is one usually used in hot melt adhesives, and is not particularly limited as long as the hot melt adhesive aimed at by the present invention can be obtained.

[0068] In the present invention, the addition amount of (C) the tackifying resin is preferably 10 to 250 parts by weight with respect to 100 parts by weight of the total weight of (A) and (B).

[0069] (C) By the addition amount of the tackifier resin being within the above range, the hot melt adhesive of the present invention can reduce the addition amount of (B) the α-methylstyrene resin, resulting in a lower odor and further improved fragrance resistance.

[0070] Examples of the (C) tackifier resin include natural rosin, modified rosin, hydrogenated rosin, glycerol ester of natural rosin, glycerol ester of modified rosin, pentaerythritol ester of natural rosin, pentaerythritol ester of modified rosin, pentaerythritol ester of hydrogenated rosin, copolymer of natural terpene, three-dimensional polymer of natural terpene, hydrogenated derivative of copolymer of hydrogenated terpene, polyterpene resin, hydrogenated derivative of phenol-modified terpene resin, aliphatic petroleum hydrocarbon resin, hydrogenated derivative of aliphatic petroleum hydrocarbon resin, aromatic petroleum hydrocarbon resin, hydrogenated derivative of aromatic petroleum hydrocarbon resin, cycloaliphatic petroleum hydrocarbon resin, and hydrogenated derivative of cycloaliphatic petroleum hydrocarbon resin. These tackifier resins can be used alone or in combination. As long as the tackifier resin has a colorless to light yellow color tone, substantially no odor, and good thermal stability, a liquid type tackifier resin can also be used. Considering these characteristics comprehensively, an unhydrogenated tackifier resin is preferred as the tackifier resin.

[0071] (C) As the tackifier resin, commercially available products can be used. Examples of such commercially available products include ECR179EX (trade name) manufactured by Tonex Co., Ltd.; Maruclear H (trade name) manufactured by Maruzen Petrochemical Co., Ltd.; Alcon M100 (trade name) manufactured by Arakawa Chemical Industries, Ltd.; Imerb S100 (trade name) manufactured by Idemitsu Kosan Co., Ltd.; Clearon K100 (trade name), Clearon K4090 (trade name) and Clearon K4100 manufactured by Yasuhara Chemical Co., Ltd.; ECR179EX (trade name) and ECR231C (trade name) manufactured by Tonex Co., Ltd., Rigalite C6100L (trade name) and Rigalite C8010 (trade name) manufactured by Eastman Chemical Company; FTR2140 (trade name) manufactured by Mitsui Chemicals, Inc. and Quintone DX390N (trade name), Quintone DX395 (trade name) manufactured by Nippon Zeon Co., Ltd. These commercially available tackifier resins can be used alone or in combination.

[0072] In the present invention, when an unhydrogenated tackifier resin is used, a hot melt adhesive with less glue residue and excellent holding power can be obtained. When Quintone DX390N (trade name) and Quintone DX395 (trade name) are used as the unhydrogenated tackifier resin, a hot melt adhesive with an excellent balance between glue residue and holding power can be obtained.

[0073] In the present invention, based on 100 parts by weight of the total weight of components (A) and (B), the addition amount of (C) the tackifier resin is preferably 10 to 200 parts by weight, particularly preferably 130 to 200 parts by weight, more preferably 150 to 190 parts by weight, and most preferably 170 to 190 parts by weight. By the blending amount of (C) the tackifier resin being within the above range, the hot melt adhesive of the present invention can be imparted with tack and prevent the occurrence of glue residue.

[0074] (D) The plasticizer is formulated for the purpose of reducing the melt viscosity of the hot melt adhesive, imparting flexibility, and improving wetting to the adherend. It is not particularly limited as long as it is compatible with the block copolymer and can obtain the hot melt adhesive targeted by the present invention. Examples of (D) tackifying resins include paraffinic oil, naphthenic oil, and aromatic oil. Paraffinic oil, which is colorless and odorless, is particularly preferred.

[0075] (D) Commercially available products can be used as the plasticizer. For example, White Oil Broom350 (trade name) manufactured by Kukdong Oil&Chem, Diana Freshia S32 (trade name), Diana Process Oil PW-90 (trade name), DN Oil KP-68 (trade name), Enerper M1930 (trade name) manufactured by BP Chemicals, Kaydol (trade name) manufactured by Crompton, Primol 352 (trade name) manufactured by Esso, Process Oil NS100 manufactured by Idemitsu Kosan, KN4010 (trade name) manufactured by PetroChina Company, and Sun Pure N90 manufactured by Sun Oil can be exemplified. These (D) plasticizers can be used alone or in combination.

[0076] The hot melt adhesive of the present invention may further contain (E) a stabilizer. The "stabilizer" is formulated to prevent a decrease in molecular weight, gelation, coloring, odor generation, etc. of the hot melt adhesive due to heat, and improve the stability of the hot melt adhesive. It is not particularly limited as long as it can obtain the hot melt adhesive targeted by the present invention. Examples of the "stabilizer" include antioxidants and ultraviolet absorbers.

[0077] The "ultraviolet absorber" is used to improve the light resistance of the hot melt adhesive. The "antioxidant" is used to prevent oxidative degradation of the hot melt adhesive. Antioxidants and ultraviolet absorbers are generally used in disposable products, and can be used as long as they can obtain the target disposable product described later, and are not particularly limited.

[0078] Examples of the antioxidant include phenolic antioxidants, sulfur antioxidants, and phosphorus antioxidants. Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers and benzophenone-based ultraviolet absorbers. Furthermore, a lactone-based stabilizer can also be added. These can be used alone or in combination.

[0079] (E) As the stabilizer, commercially available products can be used. For example, Sumilizer GM (trade name), Sumilizer TPD (trade name), and Sumilizer TPS (trade name) manufactured by Sumitomo Chemical Co., Ltd., Irganox 1010 (trade name), Irganox HP2225FF (trade name), Irgafos 168 (trade name), and Irganox 1520 (trade name) manufactured by Ciba Specialty Chemicals, and JF77 (trade name) manufactured by Johoku Chemical Co., Ltd. can be exemplified. These can be used alone or in combination. The stabilizer is generally used for disposable products and can be used as long as it can obtain the target disposable product described later, and is not particularly limited.

[0080] The hot melt adhesive according to the present invention may contain additives other than the above, such as fine particle fillers, if necessary.

[0081] The hot melt adhesive of the present invention is produced by blending the above components in a predetermined ratio, further blending various additives as necessary, and heating, melting, and mixing them. Specifically, it is produced by charging the above components into a melt mixing kettle equipped with a stirrer and heating and mixing them.

[0082] The obtained hot melt adhesive preferably has a melt viscosity at 160 ° C of 5,000 mPa·s or less, particularly preferably 2,000 to 5,000 mPa·s, and most preferably 3,000 to 4,500 mPa·s.

[0083] As used herein, the "melt viscosity" refers to the viscosity of the melt of the hot melt adhesive, which is measured using a Brookfield RVT viscometer (spindle No. 27).

[0084] The hot melt adhesive according to the present invention has an excellent coating performance because the melt viscosity at 160°C is as low as 5,000 mPa·s or less.

[0085] The hot melt adhesive of the present invention can be supplied in a liquid or semi-liquid state. Since the hot melt adhesive can be stored in a heat-insulated container in a liquid or semi-liquid state and supplied as it is, it is very environmentally friendly. That is, when manufacturing the hot melt adhesive, the generation of waste materials can be reduced, and the power consumption can also be saved.

[0086] Furthermore, in the method for evaluating the holding force described in the examples, the hot melt adhesive according to the present invention preferably has a holding force at 40°C of 10 minutes or more, more preferably 30 minutes or more, and particularly preferably 50 minutes or more.

[0087] In addition, the hot melt adhesive according to the present invention preferably has a peel strength (at 10°C, 20°C, 40°C) of 1200 gf / inch (11.8 N / 3.05 cm) or more, more preferably 1400 gf / inch (13.7 N / 3.56 cm), according to the method for evaluating the peel strength described in the examples.

[0088] The hot melt adhesive according to the present invention can be produced by using a generally known method for producing a hot melt adhesive and blending (A) and (B), and various additives as required. For example, the above-mentioned components can be blended in a predetermined amount and heated and melted to produce it. As long as the target hot melt adhesive can be obtained, the order of adding each component, the heating method, etc. are not particularly limited.

[0089] In the present invention, using a dynamic viscoelasticity measuring device, each speed is fixed at 10 Rad / s, and in the temperature sweep mode, with a heating rate of 5 °C / min, a scan is performed from -25 °C to 150 °C, and the scan value at 50 °C is used to measure the storage elastic modulus G' of the present invention. The storage elastic modulus G' is a characteristic value corresponding to elasticity, but the loss elastic modulus G", which is a characteristic value corresponding to viscosity, is known. When measuring G' with a dynamic viscoelasticity device, G" is also measured simultaneously, so the loss tangent (tanδ) represented by the ratio (G" / G') of the loss elastic modulus G" to the storage elastic modulus G' can also be obtained simultaneously.

[0090] The hot melt adhesive according to the present invention preferably has a glass transition temperature (Tg) of 15 °C or lower, more preferably -10 °C to 13 °C, and most preferably 0 °C to 10 °C. Since the hot melt adhesive has a glass transition temperature (Tg) within the above range, it does not become too hard and can firmly hold the absorbent article to the underwear even in cold regions. If the Tg of the hot melt adhesive is higher than the use environment temperature of the absorbent article, the hot melt adhesive will be in a glass state, making it difficult to hold the absorbent article to the underwear with the hot melt adhesive. Considering the use of absorbent articles in cold regions, the Tg of the hot melt adhesive is preferably within the above range.

[0091] In this specification, the glass transition temperature (Tg) refers to the temperature indicating the peak top of the peak obtained by plotting the loss tangent (tanδ), which is measured simultaneously with the measurement of the storage elastic modulus G' performed by fixing the frequency at 10 Rad / s with the above-mentioned dynamic viscoelasticity measuring device, against temperature.

[0092] When applying a hot melt adhesive to a sanitary napkin whose backsheet is a polyolefin film, since the viscosity at 160 °C is 5000 mPa·s or less, the hot melt adhesive can be easily applied directly to the polyolefin film. Since the hot melt adhesive can be easily and uniformly applied to the film at 160 °C, there is no deterioration of the hot melt adhesive, the sanitary napkin is firmly held to the underwear, and there is no glue residue on the underwear when it is peeled off from the underwear.

[0093] The hot melt adhesive according to the present invention is widely used in paper processing, bookbinding, disposable products, etc., and is particularly effectively used in absorbent articles. The "absorbent article" is not particularly limited as long as it is a so-called sanitary material. Specifically, sanitary napkins, urine collection liners, postpartum shirts, breast pads, sweat pads, paper diapers, pet sheets, hospital gowns, surgical gowns, etc. can be exemplified.

[0094] The absorbent article is composed by applying the hot melt adhesive according to the present invention to at least one member selected from the group consisting of woven fabrics, non-woven fabrics, rubber, resin, papers, and polyolefin films. Incidentally, as the polyolefin film, a polyethylene film is preferable for reasons such as durability and cost.

[0095] The hot melt adhesive according to the present invention is suitable for sanitary napkins. Generally, a sanitary napkin has an absorber between, for example, a topsheet and a backsheet, the topsheet contacts the skin, and the backsheet contacts underwear or the like. The hot melt adhesive according to the present invention exhibits particularly effective effects when the backsheet, which is the non-skin contact surface of the sanitary napkin, is a polyolefin film.

[0096] By increasing the peel strength between the polyolefin coated with the hot melt adhesive and the underwear, the sanitary napkin does not shift from the underwear. In the present invention, by directly applying the hot melt adhesive to the polyolefin film or transferring the hot melt adhesive applied to the release film to the polyolefin film, it is possible not only to prevent the shift from the underwear but also to prevent the occurrence of glue residue on the underwear.

[0097] In the manufacturing line of absorbent articles, generally, the hot melt adhesive is applied to various members of disposable products (for example, release paper, tissue, cotton, non-woven fabric, polyolefin film, etc.). When applying, the hot melt adhesive may be ejected from various ejectors and used.

[0098] The method of applying the hot melt adhesive is not particularly limited as long as the target absorbent article can be obtained. Such application methods are roughly classified into contact coating and non-contact coating. "Contact coating" refers to a coating method in which an ejector is brought into contact with a member or film when applying the hot melt adhesive, and "non-contact coating" refers to a coating method in which the ejector is not brought into contact with the member or film when applying the hot melt adhesive. Examples of the contact coating method include slot coater coating and roll coater coating, etc. Examples of the non-contact coating method include spiral coating that can be applied in a spiral shape, omega coating or control seam coating that can be applied in a wave shape, slot spray coating or curtain spray coating that can be applied in a planar shape, dot coating that can be applied in a dot shape, etc.

[0099] The hot melt adhesive is applied by the above coating method to produce an absorbent article. Examples of the absorbent article include sanitary napkins, urine collection liners, maternity shorts, breast pads, sweat underarm pads, paper diapers, pet sheets, hospital gowns, surgical gowns, etc. In the present invention, a sanitary napkin with a backsheet made of a polyolefin film can exhibit the most effects.

Examples

[0100] Hereinafter, for the purpose of explaining the present invention in more detail and more specifically, the present invention will be described using examples. These examples are for explaining the present invention and do not limit the present invention in any way.

[0101] The components for formulating the hot melt adhesive are shown below.

[0102] (A) A thermoplastic block copolymer that is a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound (A1-1) An unhydrogenated product of a triblock styrene-isoprene block copolymer (Kraton D1162PT (trade name) manufactured by Kraton Polymers) (A1-2) Unhydrogenated triblock styrene-isoprene block copolymer (VECTOR 4211N (trade name) manufactured by DEXCO) (A1-3) Unhydrogenated triblock styrene-isoprene block copolymer (VECTOR 4114N (trade name) manufactured by DEXCO)

[0103] (A2) Unhydrogenated styrene-butadiene diblock copolymer (Asaprene T438 (trade name) manufactured by Asahi Kasei Corporation)

[0104] (A3-1) Unhydrogenated linear styrene-isoprene block copolymer (Quintac 3520N (trade name) manufactured by Nippon Zeon Co., Ltd.) (A3-2) Unhydrogenated linear styrene-isoprene block copolymer ((Quintac 3433N (trade name) manufactured by Nippon Zeon Co., Ltd.)

[0105] (B) α-Methylstyrene resin (B1) Styrene-α-methylstyrene copolymer (Kristalex 3100 (trade name) manufactured by Eastman Chemical Company)

[0106] (C) Tackifying resin (C1) Hydrogenated derivative of aromatic petroleum hydrocarbon resin (Quinton DX395 (trade name) manufactured by Nippon Zeon Co., Ltd.) (C2) Hydrogenated derivative of cyclic aliphatic petroleum hydrocarbon resin (Escorets HA103 (trade name) manufactured by ExxonMobil Corporation)

[0107] (D) Plasticizer (D1) Paraffinic oil (Diana Freshia S-32 (trade name) manufactured by Idemitsu Kosan Co., Ltd.)

[0108] (E) Stabilizer (E1) Hindered phenol antioxidant (Irganox 1010 (trade name) manufactured by Ciba Specialty Chemicals) (E2) Benzotriazole ultraviolet absorber (Tinosorb P (trade name) manufactured by Double Bond Chemical)

[0109] Tables 1 to 3 show the compounding ratios of components (A) to (E). Using a universal stirrer, each component was melt-mixed at about 140 °C for 2 hours to produce the hot-melt adhesives of Examples 1 to 13 and Comparative Examples 1 to 5. All numerical values regarding the composition (formulation) of the hot-melt adhesives shown in Tables 1 to 3 are in parts by weight.

[0110] For each of the hot-melt adhesives of the examples and comparative examples, the glass transition temperature was measured, and the fragrance resistance, holding power, glue residue, and odor were evaluated. The following is an explanation of the outline of each evaluation.

[0111] <Holding power (peel strength)> Each hot-melt adhesive was applied to a PET film with a thickness of 50 μm, and after forming an adhesive layer with a thickness of 50 μm on the PET film, it was formed into a width of 25 mm to obtain a test piece.

[0112] On the other hand, silk for the JIS dyeing fastness test (conforming to JIS L0803) was cut out into 30 × 70 mm in the fold direction and used as a bonding substrate.

[0113] After curing the test piece and the bonding substrate in an environment of 23 °C for 30 minutes or more, they were bonded together with a 2 kg roller. After bonding the two, immediately using a universal tensile tester, a 180° peel test was performed at a speed of 300 mm / min. For each hot-melt adhesive, at least 3 samples were measured, and the average value was obtained as the value of the peel strength.

[0114] The peel strength was evaluated according to the following criteria.

[0115] ◎······Exceeding 550 / 25 mm ○······400 - 550 / 25 mm △······200 - 400 / 25 mm ×······Less than 200 / 25 mm

[0116] <Glue residue> After measuring the peel strength, the peeled surface of the bonding substrate was immediately checked by finger touch to evaluate the presence or absence of adhesive residue. Since silk was the substrate for which adhesive residue could be significantly discriminated, silk was adopted as the evaluation substrate. The evaluation criteria for adhesive residue are shown below.

[0117] ◎ ······ No adhesive residue ○ ······ Slight adhesive residue △ ······ Some adhesive residue × ······ Obvious adhesive residue

[0118] <Fragrance resistance>

[0119] Each hot melt adhesive was formed into a cube shape (5 mm × 5 mm × 5 mm) to make a test piece. One side of the test piece was pasted onto a PET film and arranged at the bottom of a sealed container (a 710 ml metal tube). 0.4 ml of D-limonene (Yasuhara Chemical Co., Ltd.) was dropped into a glass bottle (15 ml). After fixing the test piece to the bottom of the sealed container, the lid was quickly closed and left to stand in an environment at 50°C for 3 days. Also, a test was carried out without dropping D-limonene as a blank (control sample), and it was similarly left to stand in an environment at 50°C for 3 days. After standing, the shape of the test piece was observed.

[0120] ◎ ······ Maintaining the shape without difference from the control sample (see Figure 1). ○ ······ Slightly different from the control sample but maintaining the shape (see Figure 2, the corners of the cube are slightly rounded). × ······ Different from the control sample and the shape is deformed (see Figure 3, the cube shape is deformed into a circular shape).

[0121] <Odor> 30 g of each hot melt adhesive was weighed into a glass bottle (70 ml), melted at 180°C in a dryer, and then cooled. After cooling, the sample was cured at 40°C for 30 minutes in a dryer to prepare a test piece. The odor of the test piece was evaluated by 10 subjects, and the odor level was artificially quantified.

[0122] The numerical values of the odor levels were based on the sensations of the subjects, and the following evaluation criteria were set.

[0123] Odor level (sensory evaluation) 1 ···· Do not feel any odor 2 ···· Slightly feel an odor 3 ···· Can determine the presence of an odor 4 ···· Feel an odor 5 ···· Feel a strong odor

[0124] For each hot melt adhesive, the average value of the odor levels of 10 subjects was calculated, and the odor of the hot melt adhesive was evaluated based on that average value. The evaluation criteria are as follows.

[0125] ◎ ···· Average value is less than 2.0 ○ ···· Average value is 2.0 - 3.0 △ ···· Average value is 3.0 - 3.5 × ···· Average value exceeds 3.5

[0126] <Glass transition temperature> Using a dynamic viscoelasticity measuring device (Rheometer AR-G2 (trade name) manufactured by TA Instruments Japan), the glass transition temperature was measured. The hot melt adhesive was heated with the jig of the device and formed into a disk shape with a diameter of 25 mmφ and a thickness of 15,000 μm.

[0127] The measurement of the glass transition temperature was carried out using a stainless steel parallel plate, fixed at an angular velocity of 10 rad / s, and the temperature was increased in a temperature sweep mode at a rate of 5 °C / min in the range of -25 °C to 150 °C.

[0128] In the temperature range below the softening point, the loss tangent Tanδ (G” / G’), which is represented by the ratio of the loss elastic modulus (G”) to the storage elastic modulus (G’), was measured. The loss tangent Tanδ was plotted against the temperature, and the temperature indicating the peak top of the obtained peak was read and taken as the glass transition temperature of the hot melt adhesive.

[0129]

Table 1

[0130]

Table 2

[0131]

Table 3

[0132] As shown in Tables 1 and 2, the hot-melt adhesive of the example contains both (A1) an unhydrogenated product of a triblock styrene-isoprene block copolymer and (A2) an unhydrogenated product of a styrene-butadiene block copolymer, and contains less than 5 parts by weight of (B) an α-methylstyrene resin. Therefore, it has no odor, its performance is not degraded by fragrances such as limonene, it has excellent peel strength, and there is almost no adhesive residue.

[0133] On the other hand, as shown in Table 3, the hot-melt adhesive of the comparative example either does not contain either component (A1) or (A2), or contains 5 parts by weight or more of component (B). Therefore, any of the performances is significantly inferior to the hot-melt adhesive of the example.

[0134] From these results, it was demonstrated that a hot-melt adhesive containing components (A1) and (A2) and optionally containing less than 5 parts by weight of component (B) has no odor, is excellent in fragrance resistance and holding power, and has little adhesive residue, and is thus particularly effective for positioning absorbent articles.

Industrial Applicability

[0135] The present invention can provide a hot-melt adhesive and an absorbent article coated with the hot-melt adhesive. The absorbent article according to the present invention is particularly effective as a sanitary napkin in which a backsheet, which is a non-skin contact surface, is a polyolefin film.

Claims

1. (A) A hot melt adhesive having a thermoplastic block copolymer which is a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound, (A) the thermoplastic block copolymer comprises (A1) an unhydrogenated triblock styrene-isoprene block copolymer and (A2) an unhydrogenated styrene-butadiene block copolymer, (B) A hot melt adhesive used for positioning absorbent articles having a fragrance, which does not contain an α-methylstyrene-based resin in an amount of 5 parts by weight or more per 100 parts by weight of the total weight of (A) and (B).

2. The hot melt adhesive according to claim 1, wherein the unhydrogenated triblock styrene-isoprene block copolymer (A1) has a styrene content of 10 to 60% by weight.

3. The hot melt adhesive according to claim 1 or 2, wherein the hot melt adhesive contains 15 to 50 parts by weight of an unhydrogenated triblock styrene-isoprene block copolymer (A1) relative to 100 parts by weight of the total weight of the thermoplastic block copolymer (A).

4. The hot melt adhesive according to any one of claims 1 to 3, further comprising (B) an α-methylstyrene-based resin, the amount of (B) being 4.5 parts by weight or less per 100 parts by weight of the total weight of (A) and (B).

5. An absorbent article to which the hot melt adhesive according to any one of claims 1 to 4 is applied.

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