Hot melt adhesive

Abstract

The present application discloses a hot melt adhesive comprising: (A) a random copolymer of ethylene and an olefin having 3 to 20 carbon atoms; (B) a thermoplastic block copolymer; (C) a tackifying resin; and (D) a wax, in which the thermoplastic block copolymer (B) is contained in an amount of 1 part by mass or more and less than 5 parts by mass based on 100 parts by mass of the total amount of components (A) to (D), and in which (A) the random copolymer comprises (A1) a metallocene-based copolymer of ethylene and propylene.

Description

Technical Field

[0001] The present invention relates to a hot melt adhesive, and more particularly to a hot melt adhesive having excellent bonding properties to various substrates, especially to paper substrates such as cardboard, and suitable for assembling paper products using the paper substrates and the like. Background Art

[0002] Hot melt adhesives, which are solvent-free adhesives, are melted by heating, applied to an adherend by coating, and then cooled to solidify, thereby producing adhesive properties that enable instantaneous bonding and high-speed bonding. Therefore, hot melt adhesives are used in a wide range of fields, such as paper processing, wood processing, sanitary materials, and electronics.

[0003] As the base polymer for the hot melt adhesive described above, ethylene-based copolymers such as ethylene-vinyl acetate copolymer (hereinafter also referred to as "EVA") and ethylene-ethyl acrylate copolymer (hereinafter also referred to as "EEA"), olefin-based resins such as polyethylene, polypropylene and amorphous polyalphaolefin (hereinafter also referred to as "APAO"), synthetic rubbers such as styrene-based block copolymers (e.g., styrene-isoprene-styrene block copolymer (hereinafter also referred to as "SIS"), styrene-butadiene-styrene block copolymer (hereinafter also referred to as "SBS") and their hydrogenadditives, polyurethanes, etc. are widely used depending on the application.

[0004] Among these hot melt adhesives, hot melt adhesives containing a copolymer of ethylene and an α-olefin (for example, a copolymer of ethylene and propylene or a copolymer of ethylene and octene) as an olefin resin are often used in paper processing and disposable products.

[0005] PTL 1 teaches a hot melt adhesive for low temperature coating, which contains an olefin copolymer (see [Claim 1] in PTL 1). The detailed composition of the hot melt adhesive containing the olefin copolymer is disclosed as a sample in Table 1 (see

[0092] in PTL 1). Each sample contains an olefin random copolymer (Vistamaxx series, Engage series), an olefin block copolymer (Infuse series) or a styrene block copolymer (Kraton series) as a base polymer, and further contains a tackifying resin, wax and oil.

[0006] PTL 2 discloses a hot-melt adhesive containing an ethylene / α-olefin copolymer and a styrenic block copolymer (see [Claim 1] in PTL 2). As shown in Tables 1 to 4, the hot-melt adhesive contains: an olefin random copolymer and a styrenic block copolymer as base polymers, a tackifying resin, a wax, and an oil (see

[0080] to

[0086] in PTL 2).

[0007] PTL 3 discloses the hot-melt adhesive in Claim 1, which contains a hydrogenated thermoplastic block copolymer and a polyolefin. The composition of the hot-melt adhesive is disclosed as examples (see

[0061] to

[0063] and [Table 1] in PTL 3), indicating that the hot-melt adhesive contains an ethylene / α-olefin copolymer and a hydrogenated styrenic block copolymer.

[0008] The hot-melt adhesives of PTL 1 and PTL 3 are mainly used in disposable products (see

[0004] in PTL 1 and

[0005] in PTL 3). The hot-melt adhesive of PTL 2 is also used in paper products (see

[0064] to

[0065] in PTL 2).

[0009] In the case of applying a hot-melt adhesive to a paper substrate, a special coating machine called a hot-melt coater is often used. The hot-melt coater has a nozzle, which is a discharge outlet. The hot-melt adhesive is heated to about 120°C to 190°C, discharged from the end of the nozzle, and applied to the adherend. When applying the hot-melt adhesive, a filamentous material of the hot-melt adhesive may form between the end of the nozzle and the adherend. This filamentous material is caused by the stringing of the hot-melt adhesive and contaminates the nozzle, the manufacturing equipment around the nozzle, and the adherend. Therefore, the development of a low-stringy hot-melt adhesive is an important responsibility of adhesive manufacturers.

[0010] When applying the hot-melt adhesives of PTL 1 to PTL 3 to a substrate, the hot-melt adhesives may cause the formation of filamentous materials. In particular, in the case of using a hot-melt adhesive in the paper processing field, the hot-melt adhesive is required to have adhesive properties in a wide temperature range from low temperature to high temperature, and adhesive properties to a paper substrate coated with chemicals (a substrate with poor adhesion), while maintaining the property of reduced stringing.

[0011] In the case of high-speed coating of a hot-melt adhesive on a paper substrate, the hot-melt adhesive is required to have excellent initial cohesion and hot adhesion properties to improve the production efficiency of paper products.

[0012] In addition, in the case where a paper product (e.g., cardboard for packaging) bonded with a hot-melt adhesive is stored in a warehouse in summer, the bonding strength of the hot-melt adhesive decreases as the storage temperature rises, which may cause the cardboard box to crack. The hot-melt adhesive must have excellent creep resistance so that the paper substrate does not experience separation even at high temperatures (e.g., the cardboard box remains closed).

[0013] List of references

[0014] Patent documents

[0015] PTL 1: JP 2013-502493 A

[0016] PTL 2: JP 2020-521013 A

[0017] PTL 3: JP 2021-516265 A Summary of the invention

[0018] Technical problem

[0019] An object of the present invention is to provide a hot-melt adhesive that can reduce stringing and has excellent bonding characteristics in a wide temperature range from low to high temperatures and bonding characteristics to a paper substrate coated with chemicals, as well as excellent heat-resistant creep characteristics and hot-bonding characteristics.

[0020] Solution to the problem

[0021] As a result of in-depth research, the inventors of the present invention found that a hot-melt adhesive containing a specific random copolymer of ethylene and an olefin having 3 to 20 carbon atoms, a specific thermoplastic block copolymer, a tackifying resin, and a wax can solve the above problems, and thus such a hot-melt adhesive is suitable, especially in the field of paper processing. This led to the completion of the present invention.

[0022] In other words, the present disclosure encompasses the following embodiments.

[0023] 1. A hot-melt adhesive comprising: (A) a random copolymer of ethylene and an olefin having 3 to 20 carbon atoms; (B) a thermoplastic block copolymer; (C) a tackifying resin; and (D) a wax,

[0024] wherein, based on the total amount of 100 parts by mass of the components (A) to (D), the hot-melt adhesive contains 1 part by mass or more and less than 5 parts by mass of (B) the thermoplastic block copolymer, and

[0025] wherein (A) the random copolymer contains (A1) a metallocene-based copolymer of ethylene and propylene.

[0026] 2. The hot-melt adhesive according to 1, wherein based on the total amount of components (A) to (D) of 100 parts by mass, the hot-melt adhesive contains more than 25 parts by mass and less than 40 parts by mass of (A) the random copolymer and 10 parts by mass or more and 25 parts by mass or less of (D) the wax.

[0027] 3. The hot-melt adhesive according to 1 or 2, wherein (A) the random copolymer of ethylene and an olefin having 3 to 20 carbon atoms further contains at least one selected from the following: (A2) a metallocene-based copolymer of ethylene and octene, (A3) a metallocene-based copolymer of ethylene and hexene, and (A4) a metallocene-based copolymer of ethylene and butene.

[0028] 4. The hot-melt adhesive according to any one of 1 to 3, wherein based on the total amount of components (A) to (D) of 100 parts by mass, the hot-melt adhesive contains 2 parts by mass or more and 20 parts by mass or less of (A1) the metallocene-based copolymer of ethylene and propylene.

[0029] 5. The hot-melt adhesive according to any one of 1 to 4, wherein (B) the thermoplastic block copolymer contains at least one selected from the following: (B1) a block copolymer of ethylene and an olefin having 3 to 20 carbon atoms; and (B2) a styrene block copolymer.

[0030] 6. The hot-melt adhesive according to 5, wherein the component (B1) contains a block copolymer of ethylene and octene, and (B2) the styrene block copolymer contains a hydrogenated styrenic block copolymer.

[0031] 7. The hot-melt adhesive according to 6, wherein the hydrogenated styrenic block copolymer contains a styrene-ethylene-butene-styrene (SEBS) block copolymer.

[0032] 8. The hot-melt adhesive according to any one of 1 to 7, which further contains: (E) a copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond.

[0033] 9. The hot-melt adhesive according to 8, wherein based on the total amount of components (A) to (D) of 100 parts by mass, the hot-melt adhesive contains 0.5 parts by mass or more and 5.0 parts by mass or less of (E) the copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond.

[0034] 10. The hot-melt adhesive according to 8 or 9, wherein (E) the copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond comprises at least one selected from the group consisting of a copolymer of ethylene and vinyl acetate, a copolymer of ethylene and methyl methacrylate, and a copolymer of ethylene and butyl acrylate.

[0035] 11. A paper product comprising the hot-melt adhesive according to any one of 1 to 10.

[0036] Advantages of the present invention

[0037] The hot-melt adhesive in the embodiments of the present invention is excellent not only in the adhesion characteristics to substrates with poor adhesion, but also in reducing wire drawing and adhesion characteristics to paper in a wide temperature range, and further has excellent hot adhesion characteristics and heat-resistant creep characteristics.

[0038] When the hot-melt adhesive in the embodiments of the present invention is applied to an adherend (such as paper) via the nozzle of a coater, wire drawing is reduced, thereby preventing filamentous substances from contaminating the nozzle, the equipment around the nozzle, and the adherend.

[0039] Since the hot-melt adhesive in the embodiments of the present invention has excellent adhesion characteristics to substrates with poor adhesion, it is suitable for processed paper packaging containers to which a coating agent has been applied.

[0040] Since the hot-melt adhesive in the embodiments of the present invention has excellent hot adhesion characteristics, it can shorten the set time for adhesion and improve the production efficiency of processed paper products.

[0041] Since the hot-melt adhesive in the embodiments of the present invention has excellent heat-resistant creep characteristics, it prevents the paper substrate from being peeled off, and even when a cardboard box applied with the hot-melt adhesive is stored in a warehouse in summer, it can prevent the cardboard box from cracking due to temperature rise. Detailed embodiments

[0042] The hot-melt adhesive in the embodiments of the present invention comprises (A) a random copolymer of ethylene and an olefin having 3 to 20 carbon atoms (random copolymer of ethylene / olefin having 3 to 20 carbon atoms or ethylene-olefin having 3 to 20 carbon atoms random copolymer), (B) a thermoplastic block copolymer, (C) a tackifying resin, and (D) a wax as essential components.

[0043] As used herein, the term "hot-melt adhesive" refers to an adhesive that is solid at room temperature but has fluidity when melted by heating, for example, it can be applied by coating onto an object (such as a substrate or an adherend) and hardens and adheres when cooled.

[0044] "Copolymer" is a "polymer (or macromolecule)" obtained by polymerizing a plurality of monomers.

[0045] "Random copolymer" is a polymer composed of a plurality of different monomers, in which the arrangement of monomers (repeating units) in a polymer chain has no rule.

[0046] "Block copolymer" is a polymer composed of a plurality of different monomers, in which macromolecular chains each composed of the same kind of monomers are linked together in a single chain.

[0047] <Random copolymer of (A) ethylene and an olefin having 3 to 20 carbon atoms>

[0048] In an embodiment of the present invention, "random copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms" means a copolymer in which the arrangement of ethylene and an olefin having 3 to 20 carbon atoms has no rule. Copolymer (A) includes a metallocene-based copolymer of ethylene and propylene (metallocene-based ethylene-propylene copolymer) (A1).

[0049] Specific examples of "olefin having 3 to 20 carbon atoms" may include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, cis-2-butene, trans-2-butene, isobutene, cis-2-pentene, trans-2-pentene, 3-methyl-1-butene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene, etc. "Olefin having 3 to 20 carbon atoms" preferably includes olefins having 3 to 10 carbon atoms, more preferably at least one selected from propylene, butene, hexene, and octene, still more preferably at least one selected from propylene, butene, and octene, and particularly preferably octene.

[0050] The random copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms is preferably a copolymer polymerized by a metallocene catalyst. When the hot-melt adhesive in the embodiment of the present invention contains (A) a random copolymer polymerized by a metallocene catalyst (metallocene-based copolymer of ethylene and an olefin having 3 to 20 carbon atoms), its adhesion characteristics at high temperatures are excellent and it has improved heat-resistant creep characteristics.

[0051] Based on the total amount of components (A) to (D) of 100 parts by mass, the hot-melt adhesive in the embodiment of the present invention preferably contains 2 to 20 parts by mass, more preferably 5 to 15 parts by mass of the metallocene-based copolymer of ethylene and propylene (A1). When the content of component (A1) in the hot-melt adhesive in the embodiment of the present invention is within the above range, the hot-melt adhesive has more excellent adhesion characteristics in a wide range from low temperature to high temperature.

[0052] (A) Examples of the random copolymer of ethylene and an olefin having 3 to 20 carbon atoms include: copolymer of ethylene and octene (ethylene / octene copolymer or ethylene - octene copolymer), copolymer of ethylene, propylene and 1 - butene (ethylene / propylene / butene copolymer or ethylene - propylene - butene copolymer), copolymer of ethylene and propylene (ethylene / propylene copolymer or ethylene - propylene copolymer), and copolymer of ethylene and hexene (ethylene / hexene copolymer or ethylene - hexene copolymer), etc.

[0053] Examples of the metallocene - based random copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms include: (A1) copolymer of ethylene and propylene polymerized by a metallocene catalyst (metallocene - based ethylene / propylene copolymer or metallocene - based ethylene - propylene copolymer); (A2) copolymer of ethylene and octene polymerized by a metallocene catalyst (metallocene - based ethylene / octene copolymer or metallocene - based ethylene - octene copolymer); (A3) copolymer of ethylene and hexene polymerized by a metallocene catalyst (metallocene - based ethylene / hexene copolymer or metallocene - based ethylene - hexene copolymer); and (A4) copolymer of ethylene and butene polymerized by a metallocene catalyst (metallocene - based ethylene / butene copolymer or metallocene - based ethylene - butene copolymer).

[0054] Commercially available products can be used as the random copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms.

[0055] Examples of the metallocene - based copolymer (A1) of ethylene and propylene can include the Vistamaxx (trademark) (trade name) series manufactured by Exxon Mobil Corporation, etc.

[0056] Examples of the metallocene - based copolymer (A2) of ethylene and octene can include AFFINITY (trademark) GA1900 (trade name), AFFINITY (trademark) GA1950 (trade name), AFFINITY (trademark) GA1875 (trade name), AFFINITY (trademark) GA1000R (trade name), AFFINITY (trademark) GP1570 (trade name), AFFINITY (trademark) EG8185 (trade name), AFFINITY (trademark) EG8200 (trade name), ENGAGE (trademark) 8137 (trade name), ENGAGE (trademark) 8180 (trade name) and ENGAGE (trademark) 8400 (trade name) manufactured by The Dow Chemical Company, etc.

[0057] Examples of the metallocene-based copolymer of ethylene and hexene may include Kernel KJ604T (trade name) manufactured by Japan Polyethylene Corporation, Nipolon (registered trademark) Z HM510R manufactured by Tosoh Corporation, and EXCELLEN (registered trademark) FX402 manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED, etc.

[0058] Note that the random copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms may include a copolymer of ethylene and butene (ethylene-butene copolymer) polymerized by a metallocene catalyst (A4) or a polymer not polymerized by a metallocene catalyst.

[0059] Examples of the metallocene-based copolymer of ethylene and butene (A4) may include: TAFMER (trademark) A4085 (trade name) and TAFMER (trademark) DF7350 (trade name) manufactured by Mitsui Chemicals, Inc., and EXCELLEN (registered trademark) FX352 (trade name), EXCELLEN (registered trademark) FX555 (trade name), EXCELLEN (registered trademark) FX532 (trade name), and EXCELLEN (registered trademark) FX558 (trade name) manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED.

[0060] Specific examples of the polymer not polymerized by a metallocene catalyst may include: ethylene / propylene / 1-butene copolymers such as VESTOPLAST (registered trademark) 730 (trade name) and VESTOPLAST (registered trademark) 708 (trade name) manufactured by Evonik Degussa GmbH; and copolymers of ethylene and propylene such as Eastoflex (trademark) (trade name) E1016PL-1, Aerafin (trademark) 35 (trade name), and Aerafin (trademark) 17 (trade name) manufactured by Eastman Chemical Company, and REXenetac (registered trademark) 2304 (trade name) manufactured by REXtac LLC.

[0061] Such a copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms may be used alone or in combination.

[0062] The hot-melt adhesive in the embodiment of the present invention contains (A1) a metallocene-based copolymer of ethylene and propylene for improving heat resistance; the metallocene-based copolymer of ethylene and propylene improves the hot-melt characteristics of the hot-melt adhesive and the low-temperature adhesion characteristics to substrates with poor adhesion.

[0063] Preferably, the hot-melt adhesive in the embodiment of the present invention contains (A1) a metallocene-based copolymer of ethylene and propylene and (A2) a metallocene-based copolymer of ethylene and octene. When the hot-melt adhesive contains components (A1) and (A2), the hot-melt adhesive has significantly improved adhesion characteristics in the low-temperature range.

[0064] Preferably, the metallocene-based copolymer of (A2) ethylene and octene includes a product modified with a carboxylic acid and / or a carboxylic anhydride, especially for example "a metallocene-based copolymer of ethylene and octene modified with maleic anhydride by graft polymerization with maleic anhydride". When the hot-melt adhesive in the embodiment of the present invention contains "a metallocene-based copolymer of ethylene and octene modified with a carboxylic acid and / or a carboxylic anhydride", the adhesion characteristics of the hot-melt adhesive to substrates coated with chemicals and the low-temperature adhesion characteristics are more excellent.

[0065] Examples of commercially available products of "a metallocene-based copolymer of ethylene and octene modified with maleic anhydride" include AFFINITY (trademark) GA1000R (trade name) manufactured by The Dow Chemical Company.

[0066] <(B) Thermoplastic block copolymer>

[0067] Based on the total amount of components (A) to (D) of 100 parts by mass, the hot-melt adhesive in the embodiment of the present invention contains (B) a thermoplastic block copolymer in an amount of 1 part by mass or more and less than 5 parts by mass. The content of the (B) thermoplastic block copolymer is more preferably 1 part by mass or more and 4 parts by mass or less, and most preferably 1.5 parts by mass or more and 3.5 parts by mass or less.

[0068] Since the hot-melt adhesive contains the (B) thermoplastic block copolymer in the amount within the above range, the hot-melt adhesive in the embodiment of the present invention can maintain a more excellent balance between the hot-melt characteristics and the adhesion characteristics in the low-temperature range.

[0069] Examples of component (B) include: (B1) a block copolymer of ethylene and an olefin having 3 to 20 carbon atoms; and (B2) a styrene block copolymer.

[0070] The block copolymer (B1) of ethylene and an olefin having 3 to 20 carbon atoms preferably includes a block copolymer of ethylene and an olefin having 3 to 10 carbon atoms.

[0071] Examples of the block copolymer (B1) of ethylene and an olefin having 3 to 20 carbon atoms include a block copolymer of ethylene and octene, a block copolymer of ethylene and butene, and a block copolymer of ethylene and propylene. The block copolymer (B1) of ethylene and an olefin having 3 to 20 carbon atoms preferably contains at least one selected from a block copolymer of ethylene and octene, a block copolymer of ethylene and butene, and a block copolymer of ethylene and propylene, and more preferably a block copolymer of ethylene and octene.

[0072] When the hot melt adhesive in the embodiment of the present invention contains a block copolymer of ethylene and octene, the compatibility between components (A) and (B) is further improved, making it easier to maintain the balance between the hot tack property and the adhesion property in the low temperature range.

[0073] Commercially available products can be used as the block copolymer of ethylene and octene. Examples of such commercially available products include INFUSE (trademark) 9817 (trade name), INFUSE (trademark) 9807 (trade name), and INFUSE (trademark) 9900 (trade name) manufactured by Dow Global Technologies LLC.

[0074] Specific examples of the styrene block copolymer (B2) include styrene-isoprene block copolymer (also referred to as "SIS") and styrene-butadiene block copolymer (also referred to as "SBS").

[0075] Other examples of the styrene block copolymer (B2) may include hydrogenated products of the above-described "styrene block copolymer (B2)". Specific examples of such hydrogenated products may include hydrogenated styrene-isoprene block copolymer (also referred to as "SEPS") and hydrogenated styrene-butadiene block copolymer (also referred to as "SEBS").

[0076] In the embodiment of the present invention, it is preferred that component (B2) contains a hydrogenated styrene block copolymer. When the hot melt adhesive in the embodiment of the present invention contains a hydrogenated styrene block copolymer, the compatibility between component (B) and the tackifying resin (C) is further improved, resulting in further enhanced adhesion properties.

[0077] Examples of commercially available products of component (B2) may include: ASAPRENE (trademark) T439 (trade name), ASAPRENE (trademark) T436 (trade name), ASAPRENE (trademark) T432 (trade name), TUFTEC (trademark) H1052 (trade name) and TUFTEC (trademark) H1221 (trade name) manufactured by Asahi-Kasei Chemicals Corporation; TR2600 (trade name) manufactured by JSR Corporation;

[0078] STEREON (trademark) 857 (trade name) and STEREON (trademark) 841A (trade name) manufactured by Firestone Polymers, LLC; Kraton (trademark) D1162PT (trade name), Kraton (trademark) G1657 (trade name) and Kraton (trademark) G1652 (trade name) manufactured by Kraton Polymers LLC; SOL T166 (trade name) manufactured by EniChem; Quintac (registered trademark) 3433N (trade name) and Quintac (registered trademark) 3421 (trade name) manufactured by Zeon Corporation; and SEPTON (trademark) 2063 (trade name) and SEPTON (trademark) 4044 (trade name) manufactured by Kuraray Co., Ltd.

[0079] These products can be used alone or in combination.

[0080] <(C) Tackifying resin>

[0081] In an embodiment of the present invention, (C) the tackifying resin is not particularly limited as long as it is commonly used in hot melt adhesives and the desired hot melt adhesive of the present invention can be obtained using it.

[0082] When the hot melt adhesive in the embodiment of the present invention contains (C) the tackifying resin, the hot melt adhesive has significantly improved low temperature adhesion characteristics and more excellent hot adhesion characteristics.

[0083] Considering the desired hot melt adhesive of the present invention, it is preferred that the desired hot melt adhesive contains both a partially hydrogenated tackifying resin and a fully hydrogenated tackifying resin.

[0084] As used herein, a partially hydrogenated tackifying resin is a tackifying resin in which some of the double bonds are hydrogenated, and a fully hydrogenated tackifying resin is a tackifying resin in which all of the double bonds are hydrogenated.

[0085] The partially hydrogenated tackifying resin has good compatibility with the copolymer (E) of ethylene and a carboxylic acid derivative having an ethylenic double bond described later, and the fully hydrogenated tackifying resin has good compatibility with the random copolymer (A) of ethylene and an olefin having 3 to 20 carbon atoms. In other words, when the (C) tackifying resin contains both a partially hydrogenated tackifying resin and a fully hydrogenated tackifying resin, the compatibility of the hot melt adhesive in the embodiments of the present invention is completely improved, resulting in significantly improved wire drawing reduction characteristics and adhesion characteristics.

[0086] Examples of the (C) tackifying resin may include natural rosin, modified rosin, hydrogenated rosin, glycerol esters of natural rosin, glycerol esters of modified rosin, pentaerythritol esters of natural rosin, pentaerythritol esters of modified rosin, pentaerythritol esters of hydrogenated rosin, copolymers of natural terpenes, three-dimensional polymers of natural terpenes, hydrogenated derivatives of copolymers of hydrogenated terpenes, polyterpene resins, hydrogenated derivatives of phenol-modified terpene resins, aliphatic petroleum hydrocarbon resins, hydrogenated derivatives of aliphatic petroleum hydrocarbon resins, aromatic petroleum hydrocarbon resins, hydrogenated derivatives of aromatic petroleum hydrocarbon resins, alicyclic petroleum hydrocarbon resins, and hydrogenated derivatives of alicyclic petroleum hydrocarbon resins. These tackifying resins can be used alone or in combination. As the tackifying resin, a liquid-type tackifying resin can also be used as long as it has a color tone of colorless to light yellow, is substantially odorless, and has favorable thermal stability.

[0087] Preferably, the (C) tackifying resin contains both a hydrocarbon resin having a softening point of less than 120 °C and a hydrocarbon resin having a softening point of 120 °C or higher. When the hot melt adhesive in the embodiments of the present invention contains both a hydrocarbon resin having a softening point of less than 120 °C and a hydrocarbon resin having a softening point of 120 °C or higher, the adhesion characteristics in a wide temperature range can be improved, and wire drawing can be further reduced. The softening point of the (C) tackifying resin is measured according to JIS K2207.

[0088] Commercially available products can be used as the tackifying resin (C). Examples of such commercially available products can include: T-REZ HC103 (trade name), T-REZ HA103 (trade name), and T-REZ HA125 (trade name) manufactured by ENEOS Corporation; ECR5600 (trade name) manufactured by Exxon Mobil Corporation; Marcaclear H (trade name) manufactured by Maruzen Petrochemical; CLEARON K100 (trade name) manufactured by YASUHARA CHEMICAL CO., LTD.; Arcon M100 (trade name) manufactured by ARAKAWA CHEMICAL INDUSTRIES, LTD.; I-MARV (trademark) S100 (trade name), I-MARV (trademark) Y135 (trade name), and I-MARV (trademark) P125 (trade name) manufactured by Idemitsu Petrochemical CO., LTD.; CLEARON K4090 (trade name) and CLEARON K4100 (trade name) manufactured by YASUHARA CHEMICAL CO., LTD.; ECR231C (trade name) and ECR179EX (trade name) manufactured by Exxon Mobil Corporation; and Regalite (trademark) R7100 (trade name) manufactured by Eastman Chemical Company. These commercially available tackifying resins can be used alone or in combination.

[0089] Commercially available products can be used as the partially hydrogenated tackifying resin. Examples of such commercially available products are preferably T-REZ HC103 (trade name) manufactured by ENEOS Corporation and ARKON M100 (trade name) manufactured by ARAKAWA CHEMICAL INDUSTRIES, LTD. Examples of commercially available products of the fully hydrogenated tackifying resin are preferably T-REZ HA103 (trade name) and T-REZ HA125 (trade name) manufactured by ENEOS Corporation, and I-MARV (trademark) P125 (trade name) manufactured by Idemitsu Petrochemical Co., Ltd.

[0090] <(D) Wax>

[0091] In an embodiment of the present invention, the (D) wax refers to an organic substance having a weight average molecular weight of less than 10,000, which is solid at room temperature and becomes liquid when heated, and is generally referred to as "wax". The wax is not particularly limited as long as it has the characteristics of wax and the desired hot melt adhesive of the present invention can be obtained.

[0092] When the (D) wax is included, the hot melt adhesive in the embodiment of the present invention is more excellent in terms of adhesion characteristics, hot tack characteristics, and draw reduction characteristics in a high temperature range.

[0093] Examples of the (D) wax may include Fischer-Tropsch wax, paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, and the like. Commercially available products can be used as the wax. The wax can be used alone or in combination.

[0094] As used herein, preferably, the (D) wax contains Fischer-Tropsch wax. "Fischer-Tropsch wax" refers to wax synthesized by the Fischer-Tropsch process, and is generally referred to as Fischer-Tropsch wax. Fischer-Tropsch wax is obtained by fractionating wax having a relatively wide carbon number distribution of its component molecules so that the component molecules have a narrow carbon number distribution. Typical examples of Fischer-Tropsch wax may include: SARA WAX SX105 (trade name) and SARA WAX SX80 (trade name) manufactured by Shell plc, and Sasol (registered trademark) H1 (trade name), Sasol (registered trademark) C105 (trade name), and Sasol (registered trademark) C80 (trade name) manufactured by Sasol Wax. When the Fischer-Tropsch wax is included, the hot melt adhesive in the embodiment of the present invention is excellent in terms of thermal stability and adhesion characteristics in a high temperature range.

[0095] The melting point of the (D) wax can be, for example, 60 °C to 160 °C, such as 65 °C to 150 °C.

[0096] The melting point of Fischer-Tropsch wax is preferably 70 °C to 120 °C. The melting point of the wax refers to the value measured by differential scanning calorimetry (DSC). In particular, the temperature at the top of the melting peak obtained by weighing 10 mg of the sample in an aluminum container and measuring it at a heating rate of 10 °C / min using DSC6220 (trade name) manufactured by SII NanoTechnology Inc. is referred to as the melting point.

[0097] When the melting point of the (D) wax is within the above range, the hot melt adhesive in the embodiment of the present invention has a further excellent balance of adhesion characteristics, hot tack characteristics, and draw reduction characteristics in a high temperature range.

[0098] <Copolymer of (E) ethylene and a carboxylic acid derivative having an ethylenic double bond>

[0099] In an embodiment of the present invention, the “(E) copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond” (hereinafter also referred to as “(E) copolymer” or “component (E)”) refers to a copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond, and there is no particular limitation as long as the desired hot-melt adhesive of the present invention can be obtained.

[0100] As used herein, “a carboxylic acid derivative having an ethylenic double bond” refers to a carboxylic acid derivative (including carboxylic acids) having a double bond capable of addition polymerization with ethylene between carbon atoms. In particular, it is, for example, a “carboxylic acid having an ethylenic double bond”, “carboxylic anhydride having an ethylenic double bond”, or “carboxylic acid ester having an ethylenic double bond” as described herein.

[0101] “A carboxylic acid having an ethylenic double bond” refers to a compound having an ethylenic double bond and a carboxyl group, and there is no particular limitation as long as the desired hot-melt adhesive of the present invention can be obtained. Specific examples thereof may include oleic acid, linoleic acid, maleic acid, itaconic acid, acrylic acid, and methacrylic acid.

[0102] “A carboxylic anhydride having an ethylenic double bond” refers to a compound obtained by dehydration condensation of two carboxylic acid molecules or a compound obtained by dehydration of two carboxyl groups in one molecule, and there is no particular limitation as long as the hot-melt adhesive of the present invention can be obtained. Specific examples thereof may include maleic anhydride and fumaric anhydride.

[0103] Examples of “carboxylic acid esters having an ethylenic double bond” may include: (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; vinyl carboxylates such as vinyl acetate; and allyl carboxylates such as allyl acetate.

[0104] As used herein, (meth)acrylate means both acrylate and methacrylate.

[0105] In an embodiment of the present invention, “carboxylic acid esters having an ethylenic double bond” preferably include (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, or 2-ethylhexyl (meth)acrylate, more preferably methyl (meth)acrylate, ethyl (meth)acrylate, or butyl (meth)acrylate, and particularly preferably methyl methacrylate or ethyl acrylate.

[0106] Examples of the copolymer of (E) ethylene and a carboxylic acid derivative having an ethylenic double bond may include a copolymer of ethylene and a carboxylic acid having an ethylenic double bond (ethylene / carboxylic acid copolymer having an ethylenic double bond or ethylene - carboxylic acid copolymer having an ethylenic double bond), a copolymer of ethylene and a carboxylic anhydride having an ethylenic double bond (ethylene / carboxylic anhydride copolymer having an ethylenic double bond or ethylene - carboxylic anhydride copolymer having an ethylenic double bond), and a copolymer of ethylene and a carboxylic acid ester having an ethylenic double bond (ethylene / carboxylic acid ester copolymer having an ethylenic double bond or ethylene - carboxylic acid ester copolymer having an ethylenic double bond).

[0107] Examples of the copolymer of ethylene and a carboxylic acid having an ethylenic double bond may include a copolymer of ethylene and (meth)acrylic acid (ethylene / (meth)acrylic acid copolymer or ethylene - (meth)acrylic acid copolymer).

[0108] Examples of the copolymer of ethylene and a carboxylic acid ester having an ethylenic double bond may include: a copolymer of ethylene and (meth)acrylate (ethylene / (meth)acrylate copolymer or ethylene - (meth)acrylate copolymer); a copolymer of ethylene and vinyl carboxylate (ethylene / vinyl carboxylate copolymer or ethylene - vinyl carboxylate copolymer); and

[0109] a copolymer of ethylene and allyl carboxylate (ethylene / allyl carboxylate copolymer or ethylene - allyl carboxylate copolymer).

[0110] In an embodiment of the present invention, the copolymer of (E) ethylene and a carboxylic acid derivative having an ethylenic double bond preferably includes "a copolymer of ethylene and (meth)acrylic acid derivative". The "copolymer of ethylene and (meth)acrylic acid derivative" preferably contains at least one selected from ethylene / (meth)acrylate copolymer, ethylene / (meth)acrylic acid copolymer, and ethylene / (meth)acrylic anhydride copolymer, and most preferably ethylene / (meth)acrylate copolymer.

[0111] When component (E) contains "a copolymer of ethylene and (meth)acrylic acid derivative", the hot - melt adhesive in the embodiment of the present invention has further improved wire - drawing reduction characteristics.

[0112] The copolymer of ethylene and (meth)acrylic acid derivative preferably contains a copolymer of ethylene and (meth)acrylate (ethylene / (meth)acrylate copolymer), more preferably at least one selected from ethylene / (meth)methyl acrylate copolymer, ethylene / (meth)ethyl acrylate copolymer, ethylene / (meth)butyl acrylate copolymer, and ethylene / (meth)2 - ethylhexyl acrylate copolymer, still more preferably at least one selected from ethylene / (meth)methyl acrylate copolymer, ethylene / (meth)ethyl acrylate copolymer, and ethylene / (meth)butyl acrylate copolymer, and particularly preferably ethylene / methyl acrylate copolymer and / or ethylene / ethyl acrylate copolymer.

[0113] Component (E) contains a copolymer of ethylene and a (meth)acrylic acid derivative. The melt flow rate of component (E) can be 1 to 400 g / 10 min, for example 1 to 360 g / 10 min, preferably 1 to 200 g / 10 min, and most preferably 2 to 150 g / 10 min.

[0114] When the melt flow rate of component (E) is within the above range, the hot melt adhesive in the embodiments of the present invention can further reduce drawing and further improve thermal stability. As used herein, the melt flow rate is the value measured at 190 °C under a load of 2.16 kg, and it is measured according to JIS K7210.

[0115] In the case where component (E) contains an ethylene / (meth)acrylate copolymer, the hot melt adhesive in the embodiments of the present invention can further reduce drawing, has excellent adhesion characteristics to paper, and achieves a short setting time.

[0116] The content of the structural unit derived from (meth)acrylate in the ethylene / (meth)acrylate copolymer contained in component (E) is preferably 2% by mass to 24% by mass, particularly preferably 4% by mass to 24% by mass, further preferably 6% by mass to 24% by mass, and most preferably 7% by mass to 24% by mass.

[0117] When the content of the structural unit derived from (meth)acrylate in the ethylene / (meth)acrylate copolymer contained in component (E) is within the above range, the thermal stability of the hot melt adhesive in the embodiments of the present invention can be significantly improved.

[0118] As used herein, the content of the structural unit derived from (meth)acrylate in the ethylene / (meth)acrylate copolymer in (E) refers to the mass percentage (%) of the structural unit derived from (meth)acrylate based on the total amount of the ethylene / (meth)acrylate copolymer.

[0119] The ethylene / (meth)acrylate copolymer in (E) has a chemical structure derived from ethylene and a chemical structure derived from (meth)acrylate.

[0120] The "structural unit derived from (meth)acrylate" refers to the chemical structure derived from (meth)acrylate among the chemical structures of the ethylene / (meth)acrylate copolymer.

[0121] For example, an ethylene / methyl methacrylate copolymer with a methyl methacrylate content of 20% by mass means that the total amount of the chemical structure derived from methyl methacrylate is 20 mass parts in 100 mass parts of the total amount of the ethylene / methyl methacrylate copolymer.

[0122] The content of the structural unit derived from the ethylene / (meth)acrylate compound described in this text can be measured by infrared absorption spectroscopy using a pressed sheet of component (E).

[0123] For example, when the (meth)acrylate is methyl methacrylate, the content of the structural unit derived from methyl methacrylate in the ethylene / methyl methacrylate copolymer can be measured according to JIS K7192.

[0124] As the characteristic absorption of the infrared absorption spectrum, the peak attributed to the (meth)acrylate copolymer is used, and the comonomer content is determined by correcting the absorbance with the pressed sheet thickness. For example, when the (meth)acrylate is methyl methacrylate, the content of the methyl methacrylate unit in the ethylene / methyl methacrylate copolymer can be determined by producing a pressed sheet with a thickness of 0.3 mm and measuring it by infrared absorption spectroscopy using an infrared spectrometer. As the characteristic absorption of the infrared absorption spectrum, the peak at 3448 cm -1 attributed to methyl methacrylate is used, and the absorbance is corrected by thickness according to the following formula to determine the content.

[0125] MMA = 4.1×log(I0 / I) / t - 5.3

[0126] In the formula, MMA represents the content (mass%) of the methyl methacrylate unit, I represents the intensity of the transmitted light at the frequency of 3448 cm -1 and I0 represents the intensity of the incident light at the frequency of 3448 cm -1 , and t represents the thickness (cm) of the sample sheet to be measured.

[0127] The method for producing the copolymer (E) of ethylene and (meth)acrylic acid derivative is not particularly limited, and examples thereof include known liquid phase polymerization methods and high-pressure radical polymerization methods. Examples of the method for preparing component (E) by high-pressure radical polymerization include general methods of polymerizing ethylene and (meth)acrylic acid derivatives (e.g., (meth)acrylates) in the presence of a radical initiator using a tank reactor or a tubular reactor under the conditions of a polymerization pressure of 140 MPa or higher and 300 MPa or lower and a polymerization temperature of 100 °C or higher and 300 °C or lower.

[0128] In addition, hydrogen, hydrocarbons such as methane and ethane can be used as molecular weight regulators to control the melt flow rate.

[0129] Commercially available products can be used as the copolymer (E) of ethylene / (meth)acrylic acid derivative. Examples of such commercially available products include:

[0130] Acryft (registered trademark) WH401-F (trade name), Acryft (registered trademark) WH206-F (trade name), Acryft (registered trademark) WD301-F (trade name) and Acryft (registered trademark) WD203-1 (trade name) manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED;

[0131] LOTRYL (registered trademark) 17BA07N (trade name), LOTRYL (registered trademark) 24MA02N (trade name) and LOTADER (registered trademark) 4503 (trade name) manufactured by Arkema S.A.;

[0132] NUC-6220 (trade name) and DPDJ-9169 (trade name) manufactured by The Dow Chemical Company;

[0133] NUCREL (trademark) N1035 (trade name) manufactured by DOW-MITSUIPOLYCHEMICALS CO., LTD.; and

[0134] Escor (trademark) 5080 (trade name) manufactured by Exxon Mobil Corporation.

[0135] In the hot-melt adhesive in the embodiments of the present invention, based on the total amount of components (A) to (D) of 100 parts by mass, the content of component (A) is preferably more than 25 parts by mass and less than 40 parts by mass, particularly preferably 30 parts by mass or more and 40 parts by mass or less.

[0136] When the content of the (A) random copolymer in the hot-melt adhesive in the embodiments of the present invention is within the above range, the hot-melt adhesive is more excellent in terms of the balance of adhesion properties, hot adhesion properties and heat-resistant creep properties, and in particular, the adhesion properties and heat-resistant creep properties are further improved in a wide temperature range.

[0137] In the hot-melt adhesive in the embodiments of the present invention, based on the total amount of components (A) to (D) of 100 parts by mass, the content of the (C) tackifying resin is preferably 30 parts by mass or more and 60 parts by mass or less, more preferably 40 parts by mass or more and 60 parts by mass or less, and most preferably 45 parts by mass or more and 60 parts by mass or less.

[0138] When the content of the (C) tackifying resin in the hot-melt adhesive in the embodiments of the present invention is within the above range, the hot-melt adhesive has improved compatibility with other components, and thus is more excellent in terms of wire drawing reduction properties, adhesion properties and hot adhesion properties.

[0139] In the hot-melt adhesive of the invention of the present application, based on the total amount of components (A) to (D) of 100 parts by mass, the content of component (D) is preferably 10 to 25 parts by mass, particularly preferably 15 to 25 parts by mass.

[0140] When the content of (D) wax in the hot-melt adhesive in the embodiments of the invention of the present application is within the above range, the balance of the adhesion characteristics, hot tack characteristics, and wire drawing reduction characteristics of the hot-melt adhesive in the high-temperature range is more excellent.

[0141] Based on the total amount of components (A) to (D) of 100 parts by mass, in the hot-melt adhesive in the embodiments of the present invention, the content of component (E) is preferably 0.5 to 5.0 parts by mass, particularly preferably 0.5 to 3.0 parts by mass.

[0142] When the content of (E) copolymer in the hot-melt adhesive in the embodiments of the present invention is within the above range, the hot-melt adhesive can maintain the adhesion characteristics, hot tack characteristics, and heat-resistant creep characteristics at a high level while reducing wire drawing.

[0143] If necessary, the hot-melt adhesive in the embodiments of the present invention may further contain various additives. Examples of such various additives may include plasticizers, stabilizers (UV absorbers, antioxidants, etc.), fine particle fillers, and optical brighteners.

[0144] The compounded "plasticizer" is used to reduce the melt viscosity of the hot-melt adhesive, impart flexibility to the hot-melt adhesive, and improve the wettability to the adherend. It is not particularly limited as long as it is compatible with components (A) to (C) so that the desired hot-melt adhesive of the present invention can be obtained. Examples of the plasticizer may include paraffin oil, naphthenic oil, and aromatic oil. Colorless and odorless paraffin oil is particularly preferred.

[0145] Commercially available products can be used as the plasticizer. Examples thereof may include: White Oil Broom 350 (trade name) manufactured by Kukdong Oil&Chemicals Co., Ltd., Diana Fresia S32 (trade name), Diana Process Oil PW-90 (trade name), and DN Oil KP-68 (trade name) manufactured by Idemitsu Kosan Co., Ltd., Enerper M1930 (trade name) manufactured by BP Chemicals Limited, KAYDOL (registered trademark) (trade name) manufactured by Crompton Corporation, and Primol (trademark) 352 (trade name) manufactured by Esso. These plasticizers can be used alone or in combination.

[0146] Compound “stabilizer” to prevent the reduction of the molecular weight, gelation, coloring, odor generation, etc. of the hot-melt adhesive caused by heat, air or light, and to improve the stability of the hot-melt adhesive; and the stabilizer is not particularly limited as long as the desired hot-melt adhesive of the present invention can be obtained. Examples of the stabilizer may include antioxidants and UV absorbers.

[0147] “UV absorber” is used to improve the light resistance of the hot-melt adhesive. “Antioxidant” is used to prevent the oxidative deterioration of the hot-melt adhesive. The antioxidants and UV absorbers are not particularly limited as long as they are commonly used in hot-melt adhesives and the desired paper product described later can be obtained.

[0148] Examples of the “antioxidant” may include phenolic antioxidants, sulfur-based antioxidants and phosphorus-based antioxidants. Examples of the UV absorber may include benzotriazole-based UV absorbers and benzophenone-based UV absorbers. In addition, lactone-based stabilizers may also be added. These substances can be used alone or in combination.

[0149] Commercially available products can be used as stabilizers. Examples thereof may include: SUMILIZER (registered trademark) GM (trade name), SUMILIZER (registered trademark) TPD (trade name), and SUMILIZER (registered trademark) TPS (trade name) manufactured by Sumitomo Chemical Industry Company Limited, IRGANOX (registered trademark) 1010 (trade name), IRGANOX (registered trademark) HP2225FF (trade name), IRGAFOS (registered trademark) 168 (trade name) and IRGANOX (registered trademark) 1520 (trade name) manufactured by BASF SE, ADEKA STAB AO-60 (trade name) manufactured by ADEKA CORPORATION, and JF77 (trade name) and JP-650 (trade name) manufactured by JOHOKU CHEMICAL CO., LTD. These stabilizers can be used alone or in combination.

[0150] The hot-melt adhesive in the embodiment of the present invention may further contain fine particle fillers. The fine particle fillers are not particularly limited as long as the fine particle fillers can be the commonly used fine particle fillers and the desired hot-melt adhesive of the present invention can be obtained. Examples of the “fine particle filler” may include mica, calcium carbonate, kaolin, talc, titanium oxide, diatomaceous earth, urea-based resin, styrene beads, calcined clay and starch. Their shape is preferably spherical, and their size is not particularly limited (diameter in spherical form).

[0151] The hot-melt adhesive in the embodiments of the present invention may further contain a fluorescent brightening agent. There is no particular limitation on the fluorescent brightening agent as long as it can be a commonly used fluorescent brightening agent and the desired hot-melt adhesive of the present invention can be obtained. Commercially available products can be used as the fluorescent brightening agent. Examples of commercially available products of fluorescent brightening agents include TINOPAL (registered trademark) OB (trade name) manufactured by BASF SE.

[0152] The hot-melt adhesive in the embodiments of the present invention can be produced by compounding (or mixing) the following substances using a generally known hot-melt adhesive production method: (A) a random copolymer of ethylene and an olefin having 3 to 20 carbon atoms, (B) a thermoplastic block copolymer, (C) a tackifying resin, and (D) a wax, and if necessary, (E) a copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond and various additives.

[0153] For example, the hot-melt adhesive can be produced by mixing a predetermined amount of the above components and melting them by heating. The order of adding each component, the heating method, etc. are not particularly limited as long as the desired hot-melt adhesive can be obtained.

[0154] Various products can be produced by coating (applying) various substrates with the hot-melt adhesive in the embodiments of the present invention.

[0155] The method of coating with the hot-melt adhesive is not particularly limited as long as the desired product (such as a paper product) can be obtained; however, hot-melt coaters are widely used. Examples of hot-melt coaters can include ProBlue (registered trademark) P4 Melter (trade name) and ProBlue (registered trademark) P10 Melter (trade name) manufactured by Nordson Corporation.

[0156] Coating methods are roughly classified into, for example, contact coating and non-contact coating. "Contact coating" refers to a coating method in which the hot-melt adhesive is applied by bringing a member or film into contact with an injector. "Non-contact coating" refers to a coating method in which the injector does not come into contact with the member or film when coating with the hot-melt adhesive. Examples of contact coating methods can include slot coater coating and roll coater coating. Examples of non-contact coating methods can include spiral coating for spiral coating, Ω coating for wavy coating and controlled joint coating, slot spraying and curtain spraying for planar coating, dot coating for dot coating, and bead coating for linear coating.

[0157] In the case of coating the hot-melt adhesive in the embodiments of the present invention using a hot-melt coater (even in the case of coating the hot-melt adhesive by horizontally discharging the hot-melt adhesive with a hot-melt coater), it becomes more difficult to discharge the filamentous material of the hot-melt adhesive; preferably, it is substantially impossible to discharge it. Therefore, the adherend or the coater is less likely - preferably substantially not - to be contaminated by the filamentous material.

[0158] The hot-melt adhesives in the embodiments of the present invention can be widely used in fields such as electronic components, wood products, building materials, sanitary materials, and paper products. It can be suitably used for the production of paper products. Therefore, it can be used as a hot-melt adhesive for paper products.

[0159] The paper products in the embodiments of the present invention refer to paper products produced using the above-mentioned hot-melt adhesive. The type of the paper product is not particularly limited as long as it is produced using the above-mentioned hot-melt adhesive. Specific examples thereof include books (bookbinding), calendars, cardboard (including, for example, cardstock and paper boxes), and boxes and containers made of cardboard. Considering the characteristics of the hot-melt adhesive in the embodiments of the present invention, cardboard (including, for example, cardstock and paper boxes) and boxes and containers made of cardboard are particularly effective as paper products in the embodiments of the present invention.

[0160] Examples

[0161] Hereinafter, in order to more detailedly and specifically explain the object of the present invention, the present invention will be described using examples. These examples are intended to illustrate the present invention and are not intended to limit the present invention in any way. The components compounded in the hot-melt adhesive are shown below. (A) Random copolymer of ethylene and an olefin having 3 to 20 carbon atoms

[0162] (A1-1) Metallocene-based copolymer of ethylene and propylene (ethylene content: 6.0% by mass; melting point: 97 °C; melt viscosity at 190 °C: 1200 mPa·s; Vistamaxx (trademark) 8880 (trade name) manufactured by Exxon Mobil Corporation)

[0163] (A1-2) Metallocene-based copolymer of ethylene and propylene (ethylene content: 7.1% by weight; melting point: 112 °C; melt viscosity at 190 °C: 1850 mPa·s; Vistamaxx (trademark) A (prototype) manufactured by Exxon Mobil Corporation)

[0164] (A1-3) Metallocene-based copolymer of ethylene and propylene (melt viscosity at 177 °C: 12,500 mPa·s; AFFINITY (trademark) GP1570 (trade name) manufactured by The Dow Chemical Company)

[0165] (A2-1) Metallocene-based copolymer of ethylene and octene (1-octene content: 30 wt% to 40 wt%; melting point: 68 °C; melt flow rate: 660 g / 10 min; AFFINITY (trademark) GA1000R (trade name) manufactured by The Dow Chemical Company)

[0166] (A2-2) Metallocene-based copolymer of ethylene and octene (1-octene content: 35 mass% to 37 mass%; melt flow rate: 1000 g / 10 min; AFFINITY (trademark) GA1900 (trade name) manufactured by The Dow Chemical Company)

[0167] (A2-3) Metallocene-based copolymer of ethylene and octene (1-octene content: 35 mass% to 37 mass%; melt flow rate: 500 g / 10 min; AFFINITY (trademark) GA1950 (trade name) manufactured by The Dow Chemical Company)

[0168] (A2-4) Metallocene-based copolymer of ethylene and octene (1-octene content: 35 mass% to 37 mass%; melt flow rate: 1200 g / 10 min; AFFINITY (trademark) GA1875 (trade name) manufactured by The Dow Chemical Company)

[0169] (A2-5) Metallocene-based copolymer of ethylene and octene (weight-average molecular weight: 64,000; 1-octene content: 13 wt%; melt flow rate: 13 g / 10 min; ENGAGE 8137 (trade name) manufactured by The Dow Chemical Company)

[0170] (A3-1) Metallocene-based copolymer of ethylene and hexene (melt flow rate: 30 g / 10 min; melting point: 58 °C; Kernel KJ604T manufactured by Japan Polyethylene Corporation)

[0171] (A3-2) Metallocene-based copolymer of ethylene and hexene (Melt flow rate: 21 g / 10 min; Melting point: 110 °C; Nipolon (registered trademark) BL600K (trade name) manufactured by Tosoh Corporation)

[0172] (A4) Metallocene-based copolymer of ethylene and butene (Melt flow rate: 35 g / 10 min; Melting point: 55 °C; TAFMER (trademark) DF7350 (trade name) manufactured by Mitsui Chemicals, Inc.)

[0173] (B) Thermoplastic block copolymer

[0174] (B1-1) Block copolymer of ethylene and octene (INFUSE (trademark) 9807 (trade name) manufactured by The Dow Chemical Company)

[0175] (B1-2) Block copolymer of ethylene and octene (INFUSE (trademark) 9900 (trade name) manufactured by The Dow Chemical Company)

[0176] (B1-3) Block copolymer of ethylene and octene (INFUSE (trademark) 9817 (trade name) manufactured by The Dow Chemical Company)

[0177] (B2-1) Styrene-ethylene / butadiene-styrene block copolymer (SEBS block copolymer; Kraton (trademark) G1657 (trade name) manufactured by Kraton Polymers LLC)

[0178] (B2-2) Styrene-ethylene / butadiene-styrene block copolymer (SEBS block copolymer; Kraton (trademark) G1652 (trade name) manufactured by Kraton Polymers LLC)

[0179] (B2-3) Styrene-ethylene / butadiene-styrene block copolymer (SEBS block copolymer; TUFTEC (trademark) H1221 (trade name) manufactured by Asahi Kasei Corporation)

[0180] (B2-4) Styrene-ethylene / butadiene-styrene block copolymer (SEBS block copolymer; TUFTEC (trademark) H1052 (trade name) manufactured by Asahi Kasei Corporation)

[0181] (B2-5) Styrene-ethylene / propylene block copolymer (SEP block copolymer; SEPTON (trademark) 2063 (trade name))

[0182] (B2-6) Styrene-ethylene-ethylene / propylene-styrene block copolymer (SEEPS block copolymer; SEPTON (trademark) 4044 (trade name) manufactured by Kuraray Co., Ltd.)

[0183] (C) Tackifying resin

[0184] (C1) Partially hydrogenated tackifying resin (softening point: 103 °C; T-REZHC103 (trade name) manufactured by ENEOS Corporation)

[0185] (C2) Fully hydrogenated tackifying resin (softening point: 103 °C; T-REZHA103 (trade name) manufactured by ENEOS Corporation)

[0186] (C3) Fully hydrogenated tackifying resin (softening point: 125 °C; T-REZHA125 (trade name) manufactured by ENEOS Corporation)

[0187] (C4) Fully hydrogenated tackifying resin (softening point: 125 °C; I-MARV (trademark) P125 (trade name) manufactured by Idemitsu Petrochemical Co., Ltd.)

[0188] (C5) Partially hydrogenated tackifying resin (softening point: 100 °C; HA100 (trade name) manufactured by Henghe Materials&ScienceTechnology Co., Ltd.)

[0189] (C6) Fully hydrogenated tackifying resin (softening point: 100 °C; HM1000 (trade name) manufactured by Henghe Materials&ScienceTechnology Co., Ltd.)

[0190] (D) Wax

[0191] (D1) Fischer-Tropsch wax (melting point: 108 °C; penetration: 2; Sasol (registered trademark) H1 (trade name) manufactured by Sasol Ltd.)

[0192] (D2) Fischer-Tropsch wax (melting point: 112 °C; penetration: 2; Sasol (registered trademark) C105 (trade name) manufactured by Sasol Ltd.)

[0193] (D3) Fischer-Tropsch wax (Melting point: 80 °C; Penetration: 7; Sasol C80 (trade name) manufactured by Sasol Ltd.)

[0194] (D4) Paraffin wax (Melting point: 69 °C; Penetration: 12; Paraffin155F (trade name) manufactured by NIPPON SEIRO CO., LTD.)

[0195] (D5) Microcrystalline wax (Melting point: 84 °C; Penetration: 12; Hi-Mic-1080 (trade name) manufactured by NIPPON SEIRO CO., LTD.)

[0196] (D6) Polyethylene wax (Melting point: 118 °C; LC104N (trade name) manufactured by Lion Chemtech Co., LTD.)

[0197] (D7) Polypropylene wax (Melting point: 140 °C to 148 °C; Penetration: 1 or less; Hi-WAX (trademark) NP105 (trade name) manufactured by Mitsui Chemicals, Inc.)

[0198] (E) Copolymer of ethylene and a carboxylic acid derivative having an ethylenic double bond

[0199] (E1) Ethylene-methyl methacrylate copolymer (Methyl methacrylate content: 20% by mass; Melt flow rate: 20 g / 10 min; Acryft (registered trademark) WH401-F (trade name) manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED)

[0200] (E2) Ethylene-methyl methacrylate copolymer (Methyl methacrylate content: 20% by mass; Melt flow rate: 2 g / 10 min; Acryft (registered trademark) WH206-F (trade name) manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED)

[0201] (E3) Ethylene-methyl methacrylate copolymer (Methyl methacrylate content: 24% by mass; Melt flow rate: 2 g / 10 min; LOTRYL (registered trademark) 24MA02N (trade name) manufactured by Arkema S.A.)

[0202] (E4) Ethylene-ethyl acrylate copolymer (Ethyl acrylate content: 20% by mass; Melt flow rate: 20 g / 10 min; DPDJ-9169 (trade name) manufactured by The Dow Chemical Company)

[0203] (E5) Ethylene-acrylic acid copolymer (acrylic acid content: 10% by mass; melt flow rate: 30 g / 10 min; Escor (trademark) 5080 (product name) manufactured by Exxon Mobil Corporation)

[0204] (E6) Ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by mass; melt flow rate: 20 g / 10 min; Ultrasen 633 (product name) manufactured by Tosoh Corporation)

[0205] (E7) Ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by mass; melt flow rate: 160 g / 10 min; Ultrasen 680 (product name) manufactured by Tosoh Corporation)

[0206] (E8) Ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by mass; melt flow rate: 350 g / 10 min; Ultrasen 681 (product name) manufactured by Tosoh Corporation)

[0207] (F) Stabilizer

[0208] (F1) Phenolic antioxidant (ADEKA STAB AO-60 (product name) manufactured by ADEKA CORPORATION)

[0209] (F2) Phosphorus-based antioxidant (JP650 manufactured by JOHOKU CHEMICAL CO., LTD.)

[0210] The above components are melt-mixed at the ratios (parts by mass) shown in Tables 1 to 4. The components are melt-mixed using a general stirrer at about 145 °C for about 1 hour to produce the hot-melt adhesives of Examples 1 to 19 and Comparative Examples 1 to 7. The adhesion characteristics (to a standard substrate), adhesion characteristics to a substrate with poor adhesion, hot adhesion characteristics, and heat-resistant creep characteristics of the hot-melt adhesives of the Examples and Comparative Examples are evaluated using the following methods.

[0211] The adhesion characteristics (to a standard substrate) are evaluated by applying the hot-melt adhesive to a kraft liner cardboard and laminating it to another kraft liner cardboard to obtain a sample.

[0212] The adhesion characteristics to a substrate with poor adhesion are evaluated by applying the hot-melt adhesive to a cardboard coated with varnish and laminating it with another cardboard to obtain a sample.

[0213] The hot tack characteristics and heat-resistant creep characteristics were evaluated by performing a peel test after preparing samples by changing the pressing time.

[0214] The outline of each evaluation is described below.

[0215] <Adhesion characteristics to general cardboard (standard substrate)>

[0216] (Sample preparation)

[0217] A kraft linerboard sheet was coated with a hot-melt adhesive melted at 180°C at a coating amount of 2 g / m, and the kraft linerboard was laminated to another kraft linerboard sheet under the conditions of an open time of 3 seconds, a subsequent setting time (pressing time) of 10 seconds, and a pressing pressure of 1 kg / 25 cm 2 to prepare samples. At least three samples were prepared for each hot-melt adhesive.

[0218] (Evaluation method)

[0219] The prepared samples were cured in a thermostatic bath set at 60°C, 23°C, or -10°C for 24 hours. Thereafter, under the atmosphere, forced peeling was performed manually. The kraft linerboard destruction rate in the total adhesion area was defined as the material destruction rate (percentage of the material that was destroyed), and the state of the adhesion surface of the kraft linerboard was evaluated. The evaluation criteria are as follows.

[0220] Very good: The material destruction rate is greater than 80%.

[0221] Good: The material destruction rate is 60% or more and 80% or less.

[0222] Acceptable: The material destruction rate is 30% or more and less than 60%.

[0223] Unacceptable: The material destruction rate is less than 30%.

[0224] <Adhesion characteristics to cardboard coated with chemicals (substrate with poor adhesion)>

[0225] (Sample preparation)

[0226] A cardboard sheet having a surface coated with varnish (poor adhesion) was coated with a hot-melt adhesive melted at 180°C at a coating amount of 2 g / m, and the kraft linerboard was laminated to another cardboard sheet having a surface coated with varnish under the conditions of an open time of 3 seconds, a subsequent setting time (pressing time) of 10 seconds, and a pressing pressure of 1 kg / 25 cm 2 to prepare samples. At least three samples were prepared for each hot-melt adhesive.

[0227] (Evaluation method)

[0228] The prepared samples were cured in a thermostatic bath set at 60 °C, 23 °C, or -10 °C for 24 hours. Thereafter, under the atmosphere, forced peeling was carried out manually. The cardboard breakage rate of the varnish-coated area in the total adhesion area was defined as the material breakage rate (percentage of the damaged material), and the state of the adhesive surface of the varnish-coated cardboard was evaluated. The evaluation criteria are as follows.

[0229] Very good: The material breakage rate is greater than 80%.

[0230] Good: The material breakage rate is 60% or more and 80% or less.

[0231] Acceptable: The material breakage rate is 30% or more and 60% or less.

[0232] Unacceptable: The material breakage rate is less than 30%.

[0233] <Hot tack property>

[0234] (Sample preparation)

[0235] A kraft linerboard sheet was coated with a hot-melt adhesive melted at 180 °C at a coating amount of 2 g / m, and laminated to another kraft linerboard sheet under the conditions of an open time of 1 second, followed by different set times (pressing times) of 0.5 second, 1.0 second, 1.5 second, 2.0 second, or 2.5 seconds and a pressing pressure of 1 kg / 25 cm 2 to prepare samples. At least three samples were prepared for each hot-melt adhesive for each set time.

[0236] (Evaluation method)

[0237] After the pressing was completed, each prepared sample was immediately forced to peel vertically at a constant speed, and the set time (pressing time) until the material breakage of the kraft linerboard was completed was defined as the hot tack time. This time was measured.

[0238] Very good: The hot tack time is shorter than 1.5 seconds.

[0239] Good: The hot tack time is 1.5 seconds or longer and shorter than 2.0 seconds.

[0240] Acceptable: The hot tack time is 2.0 seconds or longer and shorter than 2.5 seconds.

[0241] Unacceptable: The hot tack time is 2.5 seconds or longer.

[0242] <Heat resistance to creep>

[0243] Coat a kraft linerboard sheet with a hot-melt adhesive melted at 180 °C at a coating amount of 2 g / m, and laminate the kraft linerboard to another kraft linerboard sheet under the conditions of an open time of 3 seconds, a subsequent setting time (pressing time) of 10 seconds, and a pressing pressure of 1 kg / 25 cm 2 to prepare samples. Prepare at least three samples for each hot-melt adhesive.

[0244] (Evaluation method)

[0245] Apply a load to the kraft linerboard on the sample side using a heavy object, and evaluate the heat-resistant creep characteristics at the temperature at which the heavy object falls from the sample. Specifically, in an atmosphere of 40 °C, suspend a 3 kg heavy object of each sample (5 cm long × 5 cm wide) vertically from the kraft linerboard on the sample side, and raise the temperature by 5 °C every 15 minutes. Confirm the temperature at which the heavy object falls. 2 Very good: The temperature at which the heavy object falls is 55 °C or higher.

[0246] Good: The temperature at which the heavy object falls is 50 °C or higher and lower than 55 °C.

[0247] Acceptable: The temperature at which the heavy object falls is 45 °C or higher and lower than 50 °C.

[0248] Unacceptable: The temperature at which the heavy object falls is lower than 45 °C.

[0249] <Drawing reduction characteristics>

[0250] Intermittently apply each hot-melt adhesive vertically to the adherend 20 cm away from the end (nozzle) of the hot-melt coater. Measure the mass percentage of the substance falling between the hot-melt gun and the adherend to evaluate drawing. The measurement conditions are as follows.

[0251] (Equipment)

[0252] ProBlue4 hot-melt coater manufactured by Nordson Corporation

[0253] (Measurement conditions)

[0254] Temperature setting: Each of the tank, hose, and nozzle is 180 °C

[0255] Nozzle diameter: 14 / 1000 inches (2.54 cm / inch)

[0256] Nozzle: Four-hole nozzle (Number of discharge outlets: 4)

[0257] Dispensing pressure: 0.3 MPa

[0258]

[0259] ​Number of allocated shots: For each of the four holes, 180 shots / 1 minute (measurement method)

[0260] Each hot melt adhesive is discharged from each nozzle (discharge outlet) of the hot melt coater onto the adherend at 180 shots per minute for 5 minutes. The filamentous adhesive that falls between the nozzle and the adherend is considered falling material, and the mass percentage (%) of the falling material is measured by the following formula to evaluate the draw reduction property.

[0261] Mass percentage (%) of falling material =

[0262] [Mass of the filamentous material (falling material) that falls between the nozzle and the adherend] × 100 / [Total mass of the hot melt adhesive discharged in 5 minutes]

[0263] The evaluation criteria are as follows.

[0264] Good: The mass percentage of the falling material is less than 0.18 mass%.

[0265] Acceptable: The mass percentage of the falling material is 0.18 mass% or more and less than 2.0 mass%.

[0266] Unacceptable: The mass percentage of the falling material is 2.0 mass% or more.

[0267] [Table 1-1]

[0268]

[0269]

[0270] [Table 1-2]

[0271]

[0272]

[0273] [Table 2]

[0274]

[0275]

[0276] [Table 3]

[0277]

[0278]

[0279] [Table 4]

[0280]

[0281]

[0282] As shown in Tables 1 to 3, the hot-melt adhesives of Examples 1 to 19 have an excellent balance of properties because their adhesion properties, adhesion properties to substrates with poor adhesion, hot adhesion properties, heat creep resistance properties, and draw reduction properties are not evaluated as "unacceptable".

[0283] Meanwhile, as shown in Table 4, the hot-melt adhesives of Comparative Examples 1 and 2 have reduced hot adhesion properties at 40°C because they do not contain component (A1). Since the hot-melt adhesives of Comparative Examples 3 to 5 differ from the present invention in the compounding amount of component (B), any one of the draw reduction property, hot adhesion property, and adhesion property to a substrate with relatively poor adhesion deteriorates, resulting in a lack of balance of properties as a paper processing adhesive. Since the hot-melt adhesive of Comparative Example 6 does not contain component (C), the draw reduction property and adhesion property decrease. Since the hot-melt adhesive of Comparative Example 7 does not contain component (D), not only do the draw reduction property and adhesion property deteriorate, but also the hot adhesion property and heat creep resistance property deteriorate.

[0284] Industrial Applicability

[0285] According to the present invention, a hot-melt adhesive and a paper product coated with the hot-melt adhesive can be provided. As the paper product in the embodiment of the present invention, for example, paper products made of paperboards (substrates) such as cardboard and paper boxes, and paper products made of packaging substrates with poor adhesion coated with chemicals are particularly effective.

[0286] Cross-Reference to Related Applications

[0287] This application claims priority under Article 4 of the Paris Convention based on Japanese Patent Application No. 2022-179769, filed in Japan on November 9, 2022. The entire content of the priority patent application is incorporated herein by reference.

Claims

1. A hot-melt adhesive, comprising: (A) a random copolymer of ethylene and an olefin having 3 to 20 carbon atoms; (B) a thermoplastic block copolymer; (C) a tackifying resin; and (D) a wax, wherein, based on the total amount of the components (A) to (D) of 100 parts by mass, the hot-melt adhesive contains 1 part by mass or more and less than 5 parts by mass of (B) the thermoplastic block copolymer, and wherein (A) the random copolymer contains (A1) a metallocene-based copolymer of ethylene and propylene.

2. The hot-melt adhesive according to claim 1, wherein, based on the total amount of the components (A) to (D) of 100 parts by mass, the hot-melt adhesive contains more than 25 parts by mass and less than 40 parts by mass of (A) the random copolymer and 10 parts by mass or more and 25 parts by mass or less of (D) the wax.

3. The hot-melt adhesive according to claim 1 or 2, wherein (A) the random copolymer of ethylene and an olefin having 3 to 20 carbon atoms further contains at least one selected from the following: (A2) a metallocene-based copolymer of ethylene and octene, (A3) a metallocene-based copolymer of ethylene and hexene, and (A4) a metallocene-based copolymer of ethylene and butene.

4. A paper product comprising the hot-melt adhesive according to claim 1.

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