Hot-melt adhesive

Abstract

To provide a hot-melt adhesive which is excellent in coating property, adhesiveness and creep resistance, and can bond and hold a stretchable material to a material containing biodegradable plastic, and a disposal product obtained using the hot-melt adhesive.SOLUTION: A hot-melt adhesive contains (A) a thermoplastic block copolymer that is a copolymer of vinyl-based aromatic hydrocarbon and a conjugated diene compound, and (B) a tackifier resin, wherein (A) the thermoplastic block copolymer contains (A1) a styrene block copolymer having a styrene percentage content of 35-50 mass%, and (A2) a styrene block copolymer having a styrene percentage content of more than 10 mass% and less than 35 mass%, (B) the tackifier resin contains (B1) a natural resin, and 20 pts.mass or more of the component (B1) is contained in 100 pts.mass of the component (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt adhesive, and more particularly to a hot melt adhesive used in the field of disposable products such as paper diapers and napkins. [Background technology]

[0002] Hot melt adhesives are used in disposable products such as disposable diapers and napkins. The hot melt adhesive is applied to substrates such as nonwoven fabrics, tissues, and polyethylene films, and disposable products are manufactured by combining these substrates.

[0003] Examples of hot melt adhesives include synthetic rubber-based hot melt adhesives whose main component is a thermoplastic block copolymer, and olefin-based hot melt adhesives such as ethylene / propylene / butene copolymers. Considering coatability and cohesive strength, synthetic rubber-based hot melt adhesives are sometimes used in preference to olefin-based adhesives.

[0004] Generally, hot melt adhesives contain a base polymer and a plasticizer. By reducing the amount of base polymer and increasing the amount of plasticizer, it is possible to lower the viscosity of the hot melt adhesive and improve its applicability.

[0005] However, hot melt adhesives containing a large amount of plasticizer have a poor balance between cohesive strength and tack, which results in a problem of reduced adhesiveness to disposable diaper materials (for example, polyethylene film).

[0006] One type of disposable diaper incorporates elastic thread. Hot melt adhesive is used to bond the stretched elastic thread to the disposable diaper body. Because the disposable diaper body is made of a non-elastic material, the disposable diaper body with the elastic thread attached is folded by the contraction force of the elastic thread when it contracts. As a result, the elastic force of the elastic thread is imparted to the disposable diaper body, allowing the disposable diaper to fit the body.

[0007] Hot melt adhesives used to bond elastic materials, such as rubber thread, to a disposable diaper body must have excellent creep resistance. If a hot melt adhesive with insufficient creep resistance is used to bond an elastic material to a disposable diaper body, the hot melt adhesive will be stretched by the contractile force of the elastic material and will no longer be able to hold the elastic material in place on the disposable diaper body. As a result, the elastic material will shrink without the disposable diaper body. This shrinkage of the elastic material will prevent the disposable diaper body from folding, resulting in an unfitted disposable diaper. Therefore, hot melt adhesives must have excellent creep resistance.

[0008] Patent Documents 1 to 3 disclose synthetic rubber hot melt adhesives based on styrene block copolymers.

[0009] Patent Document 1 discloses a hot melt composition containing a styrene-based block copolymer and a plasticizer (Claim 1). The styrene-based block copolymer contains a high molecular weight component and a low molecular weight component in a predetermined ratio. The hot melt adhesive of Patent Document 1 has excellent stretchability and stretch recovery after stretching, and is intended for use as a stretchable material in stretchable laminates for hygienic materials. The hot melt composition of Patent Document 1 is shown to have excellent elongation at break and permanent set, referring to the property evaluation results of the examples (Table 1 in

[0093] ).

[0010] On the other hand, Patent Document 1 does not mention the adhesiveness of the hot melt composition. The hot melt compositions in Table 1 do not contain a tackifying resin, so they have low tack and are thought to have insufficient adhesion to an article such as a diaper body.

[0011] Patent Document 2 describes (abstract) a low application temperature hot melt adhesive composition containing a specific amount of a styrene block copolymer having a diblock content of about 10% by weight or less. The hot melt adhesive composition of Patent Document 2 has low viscosity while maintaining mechanical properties (e.g., peel strength and creep) equivalent to those of hot melt adhesives with higher viscosity, and is used in applications such as structural and positioning purposes in disposable articles.

[0012] On the other hand, with reference to the compositions of the examples (Tables 1 to 4 in

[0094] to

[0097] ), the hot melt adhesive composition of Patent Document 2 contains a large amount of tackifying resin and oil, and therefore has low creep resistance. For example, in applications where rubber threads are incorporated into disposable products, it is thought that the performance of adhering and holding the rubber threads to the adherend is insufficient.

[0013] Patent Document 3 discloses a hot melt adhesive containing a radial styrene block copolymer and a linear styrene block copolymer, for fixing rubber thread to a disposable product ([Claim 1] [Claim 3]). As shown in the examples, the hot melt adhesive of Patent Document 3 has excellent creep resistance, and is able to adhere and hold rubber thread to an adherend when incorporating the rubber thread into a disposable product (

[0096] to

[0100] ). [Prior art documents] [Patent documents]

[0014] [Patent Document 1] International Publication No. 2020 / 110921 [Patent Document 2] Special Publication No. 2018-514604 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-44289 Summary of the Invention [Problem to be solved by the invention]

[0015] In recent years, biodegradable plastics have been used as materials for disposable products in order to reduce the burden on the environment. Examples of such materials include polylactic acid-based nonwoven fabrics. However, conventional hot melt adhesives have insufficient adhesive properties for materials containing biodegradable plastics, making it difficult to adhere stretchable materials such as rubber threads to materials containing biodegradable plastics.

[0016] The present invention aims to provide a hot melt adhesive that has excellent coatability, adhesive properties, and creep resistance and is capable of adhering and holding stretchable materials to materials including biodegradable plastics, and a disposable product obtained using the hot melt adhesive. [Means for solving the problem]

[0017] The present invention and preferred embodiments thereof are as follows. 1. A hot melt adhesive comprising (A) a thermoplastic block copolymer which is a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound, and (B) a tackifying resin, (A) a thermoplastic block copolymer, (A1) a styrene block copolymer having a styrene content of 35 to 50% by mass; and (A2) a styrene block copolymer having a styrene content of more than 10% by mass and less than 35% by mass; Including, (B) a tackifying resin, (B1) natural resin; Including, The hot melt adhesive contains 20 parts by mass or more of component (B1) per 100 parts by mass of component (B).

[0018] 2. The hot melt adhesive according to 1, wherein component (B1) is contained in an amount of 50 to 90 parts by mass per 100 parts by mass of component (B).

[0019] 3. A hot melt adhesive according to 1 or 2, wherein the (B1) natural resin comprises a rosin ester.

[0020] 4. The hot melt adhesive according to any one of 1 to 3, wherein (B) the tackifier resin further contains (B2) a petroleum resin.

[0021] 5. The hot melt adhesive according to 4, wherein (B2) the petroleum resin comprises a hydrogenated petroleum resin having a softening point of 100°C or higher.

[0022] 6. The hot melt adhesive according to any one of 1 to 5, wherein component (A1) is contained in an amount of 60 to 90 parts by mass per 100 parts by mass of the total of components (A1) and (A2).

[0023] 7. The hot melt adhesive according to any one of 1 to 6, wherein component (A1) is a linear styrene block copolymer.

[0024] 8. The hot melt adhesive according to any one of 1 to 7, wherein component (A) is contained in an amount of 30 to 80 parts by mass per 100 parts by mass of component (B).

[0025] 9. The hot melt adhesive according to any one of 1 to 8, which is used to fix a stretchable material to a disposable product body.

[0026] 10. A disposable product coated with the hot melt adhesive according to any one of 1 to 9. [Effects of the Invention]

[0027] The hot melt adhesive of the present invention has excellent coatability, adhesion, and creep resistance, and is capable of adhering and holding stretchable materials to materials containing biodegradable plastics. By using the hot melt adhesive of the present invention, stretchable materials can be adhered and held to materials containing biodegradable plastics, making it possible to produce disposable products that have a low environmental impact. DETAILED DESCRIPTION OF THE INVENTION

[0028] The hot melt adhesive of the present invention contains (A) a thermoplastic block copolymer and (B) a tackifying resin.

[0029] <(A) Thermoplastic block copolymer> In the hot melt adhesive of the present invention, the thermoplastic block copolymer (A) is a copolymer obtained by block copolymerization of a vinyl aromatic hydrocarbon and a conjugated diene compound. The thermoplastic block copolymer (A) is usually a resin composition containing a copolymer having a vinyl aromatic hydrocarbon block and a conjugated diene compound block.

[0030] Here, "vinyl aromatic hydrocarbon" refers to an aromatic hydrocarbon compound having a vinyl group, and specific examples thereof include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene. Among these, styrene is preferred. These vinyl aromatic hydrocarbons can be used alone or in combination.

[0031] The term "conjugated diene compound" refers to 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. Among these, 1,3-butadiene and 2-methyl-1,3-butadiene are preferred. These conjugated diene compounds can be used alone or in combination.

[0032] The thermoplastic block copolymer (A) according to the present invention may be either an unhydrogenated product or a hydrogenated product.

[0033] Specific examples of the "unhydrogenated thermoplastic block copolymer (A)" include those in which the blocks based on a conjugated diene compound are not hydrogenated. Specific examples of the "hydrogenated thermoplastic block copolymer (A)" include block copolymers in which all or part of the blocks based on a conjugated diene compound are hydrogenated.

[0034] The hydrogenation rate of the "hydrogenated thermoplastic block copolymer (A)" can be expressed as the "hydrogenation rate." The "hydrogenation rate" of the "hydrogenated thermoplastic block copolymer (A)" refers to the rate of double bonds that have been hydrogenated and converted to saturated hydrocarbon bonds, based on the total aliphatic double bonds contained in the block based on the conjugated diene compound. This "hydrogenation rate" can be measured using an infrared spectrophotometer, a nuclear magnetic resonance spectrometer, or the like.

[0035] Specific examples of the "unhydrogenated thermoplastic block copolymer (A)" include styrene-isoprene block copolymer (also referred to as "SIS") and styrene-butadiene block copolymer (also referred to as "SBS"). Specific examples of the "hydrogenated thermoplastic block copolymer (A)" include hydrogenated styrene-isoprene block copolymer (also referred to as "SEPS") and hydrogenated styrene-butadiene block copolymer (also referred to as "SEBS").

[0036] As long as the object of the present invention is achieved, the structure of the thermoplastic block copolymer (A) may be either a linear type or a radial type.

[0037] In this specification, the term "linear type" refers to a linear structure. A linear type styrene block copolymer is a linear copolymer in which a styrene block and a conjugated diene block are bonded together.

[0038] The radial styrene block copolymer is a branched styrene block copolymer having a structure in which a plurality of linear styrene block copolymers protrude radially from a coupling agent at the center.

[0039] The specific structure of the radial styrene block copolymer is shown below.

[0040] [C1] (SE) n Y (1)

[0041] In the formula, n is an integer of 2 or more, S is a styrene block, E is a conjugated diene compound block, and Y is a coupling agent. n is preferably 3 or 4, and particularly preferably 3. The conjugated diene compound is preferably butadiene or isoprene.

[0042] The styrene block copolymer is a resin composition, which contains a certain proportion of a styrene-conjugated diene block copolymer represented by formula (2).

[0043] [C2] SE (2)

[0044] In the formula, S and E are as defined above. The styrene-conjugated diene block copolymer of formula (2) is sometimes called a "diblock".

[0045] The coupling agent is a polyfunctional compound that radially bonds the linear styrene block copolymers. The type of coupling agent is not particularly limited.

[0046] 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, epoxy silanes, divinyl compounds such as divinylbenzene, etc. Specific examples include trichlorosilane, tribromosilane, tetrachlorosilane, tetrabromosilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrachlorotin, diethyl adipate, etc.

[0047] The thermoplastic block copolymer (A) includes (A1) a styrene block copolymer having a styrene content of 35 to 50% by mass, and (A2) a styrene block copolymer having a styrene content of more than 10% by mass but less than 35% by mass.

[0048] In this specification, the term "styrene content" refers to the proportion of styrene blocks contained in component (A).

[0049] In the hot melt adhesive of the present invention, by ensuring that the styrene content of component (A1) and component (A2) is within the above range, a good balance between cohesive strength and tackiness is achieved, resulting in improved adhesiveness.

[0050] By ensuring that the styrene content of component (A1) is within the above range, the hot melt adhesive has high holding power (cohesion), excellent creep resistance, and can adhere and hold stretchable materials with high elongation to the body of the disposable product.By ensuring that the styrene content of component (A2) is within the above range, the hot melt adhesive maintains a balance between tack and cohesion, improving adhesion.

[0051] The thermoplastic block copolymer (A) of the present invention preferably has a diblock content of 0 to 90% by mass, more preferably 15 to 85% by mass.

[0052] The term "diblock content" refers to the proportion of the styrene-conjugated diene compound block copolymer of formula (2) contained in component (A).

[0053] The diblock content of component (A1) is preferably 0 to 80% by mass, more preferably 0 to 65% by mass, and the diblock content of component (A2) is preferably 0 to 70% by mass, more preferably 0 to 65% by mass.

[0054] When the diblock content of component (A1) and component (A2) is within the above range, the hot melt adhesive of the present invention has a good balance between cohesive strength and tackiness, resulting in excellent adhesive properties.

[0055] Component (A1) is preferably a linear styrene block copolymer. Due to the linear structure of component (A1), the hot melt adhesive of the present invention can more strongly bond and hold stretchable materials to materials containing biodegradable plastics.

[0056] As component (A1), commercially available products can be used, such as Quintac 3390 (trade name) manufactured by Zeon Corporation, LCY5562 (trade name) and LCY3545 (trade name) manufactured by LCY GRIT Corporation, Taipol 4270 manufactured by TSRC Corporation, and N308 (trade name) manufactured by Asahi Kasei Corporation.

[0057] Component (A2) preferably contains at least one selected from a styrene-butadiene block copolymer and a styrene-isoprene block copolymer, and more preferably contains a styrene-isoprene block copolymer. By including a styrene-isoprene block copolymer as component (A2), the hot melt adhesive of the present invention has an improved balance between tack and cohesive strength, resulting in excellent adhesive properties.

[0058] Commercially available products can be used as component (A2), such as Asaprene T432 (trade name) and Asaprene T436 (trade name) manufactured by Asahi Kasei Corporation, Kraton D1161 (trade name) manufactured by Kraton Corporation, VECTOR 4213NS (trade name) manufactured by TSRC Corporation, JH8291 (trade name) manufactured by Jinhai Chemical Corporation, and Quintac 3270 (trade name) manufactured by Zeon Corporation.

[0059] In the hot melt adhesive of the present invention, component (A1) is preferably contained in an amount of 60 to 90 parts by mass per 100 parts by mass of the total of components (A1) and (A2). When the content of component (A1) is 60 parts by mass or more, the creep resistance of the hot melt adhesive is further improved, and when it is 90 parts by mass or less, a decrease in adhesiveness is prevented. When the content of component (A1) is within the above range, the hot melt adhesive of the present invention has higher cohesive strength, making it easier to adhere and hold stretchable materials to disposable products. The content of component (A1) per 100 parts by mass of the total of components (A1) and (A2) is preferably 67 to 86 parts by mass, more preferably 70 to 80 parts by mass.

[0060] <(B) Tackifying resin> In the hot melt adhesive of the present invention, the tackifier resin (B) contains a natural resin (B1). The natural resin (B1) is contained in an amount such that the amount of the natural resin (B1) is 20 parts by mass or more per 100 parts by mass of the tackifier resin (B). The amount of the natural resin (B1) in the tackifier resin (B) is preferably 25 to 90 parts by mass, more preferably 50 to 90 parts by mass, even more preferably 56 to 85 parts by mass, and most preferably 73 to 83 parts by mass.

[0061] The (B1) natural resin imparts appropriate tack to the hot melt adhesive while maintaining cohesive strength, improving the adhesiveness of the hot melt adhesive to materials containing biodegradable plastics. As a result, the hot melt adhesive of the present invention, which contains the (B1) natural resin in the above-mentioned proportion, is able to adhere and hold a stretchable material to materials containing biodegradable plastics.

[0062] In this specification, "natural resin" refers to a resinous substance secreted by an animal or plant due to physiological or pathological action or extracted from their tissues, or a denatured product of the extracted resinous substance. (B1) Natural resins are broadly classified into rosin-based and terpene-based resins.

[0063] Examples of rosin-based resins include rosin and rosin derivatives (hydrogenated rosin, rosin ester, disproportionated rosin, polymerized rosin, maleated rosin, maleic acid-modified rosin resin, and rosin-modified phenolic resin).

[0064] Examples of terpene resins include terpene resins, terpene-modified phenolic resins, aromatic-modified terpene resins, and hydrogenated terpene resins.

[0065] The (B1) natural resin preferably has a biomass content of 50% or more, more preferably 65% ​​or more, and most preferably 80% or more.

[0066] When the biomass degree of component (B1) is within the above range, the hot melt adhesive of the present invention has a high biomass degree and exhibits excellent adhesion to materials including biodegradable plastics.

[0067] In this specification, "biomass content" refers to the carbon C contained only in biological materials. 14 It is a value calculated by measuring the content of C, and is measured using an accelerator mass spectrometer (AMS). 14 is not contained in fossil resources such as petroleum and coal. 14 By calculating the content, the biomass degree of component (B1) can be calculated, and the biomass degree of the entire hot melt adhesive can be calculated from the biomass degree of component (B1).

[0068] Commercially available natural resins (B1) include SYLVALITE 9100 (trade name), SYLVALITE 6100 (trade name), and SYLVARES TRM1115 (trade name) manufactured by Kraton Corporation, KE100L (trade name) manufactured by Guangdong KOMO Corporation, Pine Crystal KR612 (trade name) and Pine Crystal KE100 (trade name) manufactured by Arakawa Chemical Industries, Ltd., and YS Polystar U115 (trade name), YS Polystar T130 (trade name), and YS Polystar S145 (trade name) manufactured by Yasuhara Chemical Co., Ltd.

[0069] In the present invention, the natural resin (B1) preferably contains a rosin ester. By containing the rosin ester, the hot melt adhesive of the present invention has improved adhesion to materials containing biodegradable plastics, and can more strongly adhere and hold stretchable materials to materials containing biodegradable plastics.

[0070] The tackifying resin (B) preferably contains a petroleum resin (B2) together with a natural resin (B1). The petroleum resin (B2) has the effect of increasing the creep resistance of the hot melt adhesive.

[0071] The hot melt adhesive of the present invention contains both component (B1) and component (B2), which improves both adhesion to materials containing biodegradable plastics and creep resistance, making it possible to more strongly adhere and hold stretchable materials to materials containing biodegradable plastics.

[0072] In this specification, "petroleum resin" refers to a synthetic resin produced by polymerizing unsaturated petroleum fractions, and is obtained by polymerizing the raw material, mainly the highly unsaturated C5 fraction produced as a by-product in naphtha cracking, using this raw material in the presence of a Friedel-Crafts catalyst.

[0073] (B2) Petroleum resins are broadly classified into aliphatic, aromatic, copolymer, and hydrogenated types. Aliphatic petroleum resins are resins made from the C5 fraction of naphtha cracked oil. Aromatic petroleum resins are resins made from the C9 fraction of naphtha cracked oil. Copolymer petroleum resins are made from C5-C9 fraction copolymer resins that combine the properties of both aliphatic and aromatic petroleum resins. Hydrogenated petroleum resins are obtained by hydrogenating aromatic petroleum resins or dicyclopentadiene polymer resins.

[0074] Commercially available petroleum resins (B2) include T-Rez HA103 (trade name), T-Rez HB125 (trade name), and T-Rez HC103 (trade name) manufactured by Eneos Corporation, HD1120 (trade name) and HD1100 (trade name) manufactured by Zibo Luhua Hongjin New Material Corporation, ECR5600 (trade name) manufactured by ExxonMobil Corporation, Eastac H130 (trade name) and Plastolyn 290LV (trade name) manufactured by Eastman Co., Ltd., SUKOREZ SU420 (trade name) and SUKOREZ SU400 (trade name) manufactured by Colon Co., Ltd., Imarv S100 (trade name) and Imarv P125 (trade name) manufactured by Idemitsu Kosan Co., Ltd., and Alcon M100 (trade name) and Alcon P115 (trade name) manufactured by Arakawa Chemical Industries, Ltd.

[0075] In the present invention, the softening temperature of the (B2) petroleum resin is preferably 100° C. or higher, more preferably 120° C. or higher. When the softening point of component (B2) is within the above range, the hot melt adhesive of the present invention exhibits excellent heat resistance and also excellent coatability at temperatures of about 140° C. to 160° C.

[0076] The hot melt adhesive contains 30 to 80 parts by mass of the (A) thermoplastic block copolymer per 100 parts by mass of the (B) tackifier resin. The content of the (A) thermoplastic block copolymer is preferably 35 to 65 parts by mass, more preferably 40 to 55 parts by mass. By including the (B) tackifier resin so that the content of the (A) thermoplastic block copolymer falls within the above range, the hot melt adhesive of the present invention has improved performance in adhering and holding stretchable materials to materials containing biodegradable plastics.

[0077] <(C) Plasticizer> The hot melt adhesive of the present invention preferably contains a plasticizer (C) in addition to components (A) and (B). The plasticizer is blended to reduce the melt viscosity of the hot melt adhesive, impart flexibility, and improve wetting to the adherend, thereby improving the coatability of the hot melt adhesive. Examples of the plasticizer (C) include paraffinic oil, naphthenic oil, and aromatic oil. The amount of the plasticizer (C) contained in the hot melt adhesive is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, per 100 parts by mass of the tackifying resin (B).

[0078] Commercially available plasticizers can be used. Examples include White Oil Broom 350 (trade name) manufactured by Kukdong Oil & Chem Co., Ltd., Diana Fresia S32 (trade name), Diana Process Oil PW-90 (trade name), DN Oil KP-68 (trade name) manufactured by Idemitsu Kosan Co., Ltd., Enerper M1930 (trade name) manufactured by BP Chemicals Co., Ltd., Kaydol (trade name) manufactured by Crompton, Primol 352 (trade name) manufactured by Esso Corporation, Process Oil NS100 manufactured by Idemitsu Kosan Co., Ltd., and KN4010 (trade name) manufactured by PetroChina Company. These plasticizers can be used alone or in combination.

[0079] The hot melt adhesive according to the present invention may further contain various additives as needed, such as stabilizers and fine particle fillers.

[0080] The stabilizer is added to improve the stability of the hot melt adhesive by preventing the hot melt adhesive from being thermally degraded, gelling, discoloration, odor generation, etc., and is not particularly limited as long as it can provide the hot melt adhesive that is the objective of the present invention. Examples of "stabilizers" include antioxidants and ultraviolet absorbers.

[0081] 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 produce the desired disposable product described below, and are not particularly limited.

[0082] Examples of antioxidants include phenol-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers and benzophenone-based ultraviolet absorbers. Lactone-based stabilizers can also be added. These can be used alone or in combination.

[0083] Commercially available stabilizers can be used. Examples include 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. These stabilizers can be used alone or in combination.

[0084] 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 to melt and mix them. Specifically, the above components are charged into a melt mixing vessel equipped with a stirrer, and heated and mixed.

[0085] The resulting hot melt adhesive preferably has a melt viscosity at 160°C of 50,000 mPa·s or less, more preferably 2,000 to 8,000 mPa·s. "Melt viscosity" refers to the viscosity of a molten hot melt adhesive. It is measured using a Brookfield RVT viscometer (spindle No. 27).

[0086] Furthermore, the hot melt adhesive of the present invention preferably exhibits a retention rate of 80% or more, more preferably more than 90%, when evaluated for retention of applied length (creep resistance) of rubber threads as described in the Examples. When the hot melt adhesive exhibits a retention rate of 80% or more, it is possible to stretch non-elastic materials by adhering and holding stretched rubber threads, making it suitable for use in disposable products.

[0087] The hot melt adhesive according to the present invention is widely used in paper processing, bookbinding, disposable products, etc., but is mainly used for disposable products. The "disposable product" is not particularly limited as long as it is, for example, a so-called sanitary material. Specific examples of sanitary materials include disposable diapers, sanitary napkins, pet sheets, hospital gowns, and surgical gowns.

[0088] The hot melt adhesive of the present invention is preferably used to adhere stretched elastic material to the main body of the product when producing the above-mentioned disposable products incorporating elastic material.

[0089] In another aspect of the present invention, there is provided a disposable product obtained by applying the above-mentioned hot melt adhesive. The disposable product is constructed by bonding at least one member selected from the group consisting of woven fabric, nonwoven fabric, rubber, resin, and paper to a polyolefin film using the hot melt adhesive of the present invention. For reasons of durability, cost, etc., the polyolefin film is preferably a polyethylene film.

[0090] Considering the burden on the environment, materials containing biodegradable plastics are preferred for the components of the disposable products.

[0091] A specific example of a material containing biodegradable plastic is a biodegradable plastic nonwoven fabric. A biodegradable plastic nonwoven fabric is a sheet material having a nonwoven web layer containing long fibers of biodegradable plastic. Specific examples of biodegradable plastics include polylactic acid, poly-ε-caprolactone (PCL), polyglycolic acid, cellulose, chitin, viscose rayon, and collagen.

[0092] In a manufacturing line for disposable products, a hot melt adhesive is generally applied to at least one of various components of the disposable product (e.g., nonwoven fabric) and a polyolefin film, and the film and the component are pressure-bonded to produce the disposable product. When applying the hot melt adhesive, the adhesive may be sprayed from various sprayers.

[0093] In the present invention, the coating may be either contact coating or non-contact coating.

[0094] "Contact application" refers to a coating method in which the sprayer comes into contact with the component or film when applying hot melt adhesive. Specifically, V-slit coating is one example.

[0095] "Non-contact application" refers to a coating method in which the sprayer does not come into contact with the member or film when applying the hot melt adhesive. Specific examples of non-contact application methods include spiral coating, which allows for spiral application, omega coating and control seam coating, which allow for wave-like application, slot spray coating and curtain spray coating, which allow for planar application, and dot coating, which allows for spot-like application.

[0096] The present invention will be specifically and in detail explained below with reference to Examples and Comparative Examples, but these Examples are merely one embodiment of the present invention, and the present invention is not limited by these Examples. In the description of the Examples, unless otherwise specified, parts by mass and % by mass are based on the parts not taking into account the solvent. [Example]

[0097] The components used in this example are listed below. (A) Thermoplastic block copolymer (A1) A styrene block copolymer having a styrene content of 35 to 50% by mass (A1-1) Linear styrene-isoprene block copolymer (Quintac 3390 (trade name), styrene content 48% by mass, diblock content 0% by mass (triblock content 100% by mass), manufactured by Zeon Corporation) (A1-2) Linear styrene-isoprene block copolymer (LCY5562 (trade name), styrene content 45% by mass, diblock content 0% by mass (triblock content 100% by mass), manufactured by LCY GRIT Corporation) (A1-3) Linear styrene-butadiene block copolymer (LCY3545 (trade name), styrene content 43% by mass, diblock 60% by mass, manufactured by LCY GRIT Corporation) (A1-4) Linear styrene-butadiene block copolymer (Taipol 4270 (trade name), styrene content 37% by mass, diblock content 70% by mass, manufactured by TSRC Corporation) (A1-5) Radial styrene-butadiene block copolymer (N308 (trade name), styrene content 40% by mass, diblock content 75% by mass, manufactured by Asahi Kasei Chemical Corporation)

[0098] (A2) Styrene block copolymer having a styrene content of more than 10% by mass and less than 35% by mass (A2-1) Linear styrene-isoprene block copolymer (Kraton D1161 (trade name), styrene content 15% by mass, diblock content 19% by mass, manufactured by Kraton) (A2-2) Linear styrene-isoprene block copolymer (Vector 4213NS (trade name), styrene content 25% by mass, diblock content 25% by mass, manufactured by TSRC Corporation) (A2-3) Linear styrene-isoprene block copolymer (Quintac 3270 (trade name), styrene content 24% by mass, diblock content 67% by mass, manufactured by Zeon Corporation) (A2-4) Linear styrene-isoprene block copolymer (JH8291 (trade name), styrene content 30% by mass, diblock content 0% by mass (triblock content 100% by mass), manufactured by Jinhai Chemical Corporation) (A2-5) Linear styrene-butadiene block copolymer (Asaprene T432 (trade name), styrene content 30% by mass, diblock content 0% by mass (triblock content 100% by mass), manufactured by Asahi Kasei Chemical Corporation) (A2-6) Linear styrene-butadiene block copolymer (Asaprene T436 (trade name), styrene content 32% by mass, diblock content 50% by mass, manufactured by Asahi Kasei Chemical Corporation)

[0099] (B) Tackifying resin (B1) Natural resin (B1-1) Rosin ester (SYLVALITE 9100 (trade name), biomass content 93%, manufactured by Kraton) (B1-2) Rosin ester (KEL100 (trade name), biomass content 85%, manufactured by Guangdong KOMO Corporation) (B1-3) Styrene-modified terpene (SYLVARES 6100 (trade name), biomass content 69%, manufactured by Kraton) (B1-4) Terpene polymer (SYLVARES TRM1115 (trade name), 100% biomass, manufactured by Kraton)

[0100] (B2) Petroleum resin (B2-1) Hydrogenated dicyclopentadiene / C9 copolymer resin (T-Rez HB125 (trade name), softening point 125°C, manufactured by Eneos Corporation) (B2-2) Hydrogenated dicyclopentadiene resin (HD1120 (trade name), softening point 120°C, manufactured by Zibo Luhua Hongjin New Material Corporation) (B2-3) Hydrogenated C5 resin (Eastman Tack H130 (trade name), softening point 130°C, manufactured by Eastman Tack) (B2-4) Hydrogenated C5 / C9 copolymer resin (SUKOREZ SU420 (product name), softening point 120℃, manufactured by Colon) (B2-5) α-methylstyrene resin (Plastolyn 290LV (trade name), softening point 140°C, manufactured by Eastman Tack) (B2-6) Hydrogenated dicyclopentadiene resin (T-Rez HC103 (trade name), softening point 103°C, manufactured by Eneos Corporation) (B2-7) Hydrogenated dicyclopentadiene resin (HD1100 (trade name), softening point 100°C, manufactured by Zibo Luhua Hongjin New Material Corporation) (B2-8) Hydrogenated dicyclopentadiene resin (ECR5600 (trade name), softening point 103°C, manufactured by ExxonMobil Corporation) (B2-9) Hydrogenated dicyclopentadiene resin (Imarv S100 (trade name), softening point 100°C, manufactured by Idemitsu Kosan Co., Ltd.) (B2-10) Hydrogenated C9 resin (Arcon M100 (trade name), softening point 100°C, manufactured by Arakawa Chemical Industries, Ltd.)

[0101] (C) Plasticizer (C1) Naphthenic oil ("KN4010" (trade name), manufactured by PetroChina Corporation) (C2) Paraffin oil (Diana Fresia S32 (trade name), manufactured by Idemitsu Kosan Co., Ltd.)

[0102] (D) Stabilizer (D1) Phenolic antioxidant (Sumilizer GM (Sumitomo Chemical Co., Ltd.)) (D2) Phenolic antioxidant (Irganox 1010 (BASF)) (D3) Sulfur-based antioxidant (Sumilizer TPD (Sumitomo Chemical Co., Ltd.))

[0103] [Preparation of hot melt adhesives of examples and comparative examples] The above-mentioned components (A) to (D) were blended in the proportions shown in Table 1, and melt-mixed using a universal mixer at approximately 150°C for 2 hours to prepare the hot melt adhesives of the Examples and Comparative Examples. All values ​​relating to the composition (blending) of the hot melt adhesives shown in the table are in parts by mass.

[0104] [Table 1]

[0105] [Table 2]

[0106] The hot melt adhesives of the Examples and Comparative Examples thus obtained were examined for melt viscosity, coatability, and retention of the applied length of rubber threads. The evaluation results are shown in Table 1. The above properties were evaluated by the following methods.

[0107] [Melt viscosity] The hot melt adhesive was heated to melt, and the viscosity in the molten state was measured at 140°C, 160°C and 180°C using a Brookfield RVT type viscometer (spindle No. 27).

[0108] [Coatability] The hot melt adhesive was applied to rubber thread using a V-slit coating method, and the rubber thread was stretched and bonded to nonwoven fabric to prepare a coated sample. The coating temperature was 160°C. The open time of the coating device was 0.4 seconds, and the coating amount was 0.04 g / m (discharge rate 12 g / min).

[0109] The rubber threads and nonwoven fabrics used were the following commercially available products. Thread rubber: Toray Operentex "Lycra" (registered trademark), 620 detex urethane thread Nonwoven fabric: FITESA polylactic acid nonwoven fabric with 100% polylactic acid content by mass The stretching ratio of the rubber thread was set to 3.0. The evaluation criteria were as follows:

[0110] A (Good): The hot melt adhesive does not splatter or drip, and can be applied evenly to rubber threads (melt viscosity at 160°C is 2000-8000 mPa.s). B (Acceptable): The hot melt adhesive has a high viscosity, making it difficult to apply evenly to the rubber thread (melt viscosity at 160°C is 8000-50000 mPa.s). C (Not acceptable): The hot melt adhesive has low viscosity, so it bleeds out when applied to rubber threads (melt viscosity at 160°C is less than 2000 mPa.s). D (Poor): The viscosity of the hot melt adhesive is too high, making it difficult to dispense from the nozzle and impossible to apply (melt viscosity at 160°C exceeds 50,000 mPa.s).

[0111] [Peel strength (adhesion) to polyethylene film] A hot melt adhesive was applied to a 50 μm thick polyethylene terephthalate (PET) film to create a 50 μm thick adhesive layer. This was then molded into a 25 mm wide specimen, which served as the test specimen. This specimen was then bonded to a 100 μm thick polyethylene film at 20°C. During bonding, a 2 kg roller was brought into contact with the PET film at a speed of 5 mm / sec. The specimen was left at 20°C for one day. After leaving the specimen at 40°C, a peel test was conducted at a tensile speed of 300 mm / min, and the strength of the specimen when peeled from the polyethylene (PE) film was measured. The evaluation criteria were as follows:

[0112] A (Good): Peel strength exceeds 1000 (g / 25 mm) B (Acceptable): Peel strength is 800 (g / 25mm) or more and 1000 (g / 25mm) or less C (unacceptable): Peel strength is 400 (g / 25 mm) or more and less than 800 (g / 25 mm) D (bad): Peel strength is less than 400 (g / 25 mm)

[0113] [Evaluation of the retention of the applied length of rubber threads made from polylactic acid-based nonwoven fabric (creep resistance)] The rubber thread was bonded to a polylactic acid (PLA) nonwoven fabric to prepare a sample, which was then cut to a length of 250-300 mm and attached to a cardboard board in a fully stretched state. Two marks were then made with an oil-based pen at any two points on the bonded specimen so that the rubber length was 200 mm. The rubber was then cut at these marks and left at 40°C for four hours.

[0114] After 4 hours, the length of the stretched and attached rubber thread was measured, and the attachment length retention rate of the rubber thread was calculated. The formula for calculating the retention rate is shown below. The evaluation criteria are as follows:

[0115] [Number 1] Retention rate (%) = Rubber length after 4 hours (mm) x 100 / 200

[0116] A (Good): Retention of adhesive length after 4 hours exceeds 90% B (Acceptable): Retention of adhesive length after 4 hours is 85% or more and 90% or less C (Not acceptable): The retention of the adhesive length after 4 hours is 80% or more but less than 85% D (bad): The retention of the adhesive length after 4 hours is less than 80%.

[0117] [Table 3]

[0118] [Table 4]

[0119] As shown in Tables 3 and 4, the hot melt adhesives of Examples 1 to 8 have a good balance of coatability, adhesion (peel strength), and thread rubber application length retention (creep resistance), while the hot melt adhesives of Comparative Examples 1 to 6 were rated C or D for either coatability, adhesion (peel strength), or thread rubber application length retention (creep resistance).

[0120] It has been proven that when a hot melt adhesive contains component (A1), component (A2), and component (B1) and the blending amount of component (B1) is high, the balance of the coatability, adhesiveness, and retention of the applied length of the thread rubber of the hot melt adhesive is improved. [Industrial Applicability]

[0121] The present invention provides a hot melt adhesive and a disposable product obtained by applying the hot melt adhesive. The hot melt adhesive according to the present invention is suitable for manufacturing disposable products, and is particularly capable of retaining stretchable materials in materials including biodegradable plastics. Disposable product bodies comprising polylactic acid-based nonwoven fabric, a type of biodegradable plastic, are easy to dispose of and have a low environmental impact.

Claims

1. A hot melt adhesive comprising (A) a thermoplastic block copolymer which is a copolymer of a vinyl aromatic hydrocarbon and a conjugated diene compound, and (B) a tackifier resin, (A) the thermoplastic block copolymer, (A1) a styrene block copolymer having a styrene content of 35 to 50% by mass; and (A2) a styrene block copolymer having a styrene content of more than 10% by mass and less than 35% by mass; Including, (B) the tackifying resin, (B1) natural resin; Including, A hot melt adhesive containing 20 parts by mass or more of component (B1) per 100 parts by mass of component (B).

2. 2. The hot melt adhesive of claim 1, wherein the (B1) natural resin comprises a rosin ester.

3. 3. The hot melt adhesive according to claim 1 or 2, wherein the tackifier resin (B) further comprises a petroleum resin (B2).

4. The hot melt adhesive according to claim 3, wherein the petroleum resin (B2) comprises a hydrogenated petroleum resin having a softening point of 100°C or higher.

5. The hot melt adhesive according to any one of claims 1 to 4, which is used to fix a stretchable material to a disposable product body.

6. A disposable product coated with the hot melt adhesive according to any one of claims 1 to 5.

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