EP4615925A1

EP4615925A1 - Hot melt adhesive

Info

Publication number: EP4615925A1
Application number: EP23813089.2A
Authority: EP
Inventors: Ai Takamori
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2022-11-09
Filing date: 2023-11-08
Publication date: 2025-09-17
Also published as: WO2024101397A1; JP2024069015A; KR20250102031A; CN120202274A

Abstract

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

Description

HOT MELT ADHESIVE

The present invention relates to a hot melt adhesive and more specifically relates to a hot melt adhesive that has excellent adhesive property to various substrates, especially to paper substrates such as cardboard, and is suitable for assembling paper products using paper substrates and the like.

Hot melt adhesives, as solventless adhesives, are melted by heating, applied to an adherend by coating, and then cooled to be solidified, thereby developing adhesive property, which allows instant adhesion and high-speed adhesion. Therefore, the hot melt adhesives are used in a wide range of fields, such as paper processing, woodworking, sanitary materials, and electronic fields.

As the base polymers for hot melt adhesives described above, ethylenic copolymers such as ethylene-vinyl acetate copolymer (hereinafter also referred to as "EVA") and ethylene-ethyl acrylate copolymer (hereinafter also referred to as "EEA"), olefinic resins such as polyethylene, polypropylene, and amorphous polyalphaolefin (hereinafter also referred to as "APAO"), synthetic rubbers such as styrenic block copolymer (e.g., styrene-isoprene-styrenic block copolymer (hereinafter also referred to as "SIS"), styrene-butadiene-styrenic block copolymer (hereinafter also referred to as "SBS"), and hydrogen additives thereof, polyurethane, and the like are widely used depending on the applications.

Among these hot melt adhesives, a hot melt adhesive comprising a copolymer of ethylene with α olefin(e.g., copolymer of ethylene with propylene or copolymer of ethylene with octene) as a copolymer of olefin resin is often used for in paper processing and disposable products.

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 an olefin copolymer is disclosed in Table 1 as a sample (see [0092] in PTL 1). Each sample comprises an olefinic random copolymer (Vistamaxx series, Engage series), an olefinic block copolymer (Infuse series), or a styrenic block copolymer (Kraton series) as a base polymer, and further comprises a tackifying resin, wax, and oil.

PTL 2 discloses a hot melt adhesive comprising an ethylene/α olefin copolymer and a styrenic block copolymer (see [Claim 1] in PTL 2). As shown in Tables 1 to 4, a hot melt adhesive comprises an olefinic 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).

PTL 3 discloses a hot melt adhesive in claim 1, which comprises a hydrogenated thermoplastic block copolymer and a polyolefin. The composition of the hot melt adhesive is disclosed as an example (see [0061] to [0063] and [Table 1] in PTL 3), showing that the hot melt adhesive comprises an ethylene/α olefin copolymer and a hydrogenated styrenic block copolymer.

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).

In a case of applying a hot melt adhesive to a paper substrate, a dedicated applicator called a hot melt applicator is often used. The hot melt applicator has a nozzle, which is a discharge outlet. A hot melt adhesive is heated to about 120°C to 190°C, discharged from the tip of the nozzle, and applied to an adherend. When a hot melt adhesive is applied, filamentous matter of the hot melt adhesive may be formed between the tip of the nozzle and the adherend. This filamentous matter is caused by stringing of the hot melt adhesive and stains the nozzle, the manufacturing equipment around the nozzle, and the adherend. Therefore, the development of low-stringy hot melt adhesives is an important responsibility of adhesive manufacturers.

The hot melt adhesives of PTL 1 to PTL 3 may cause filamentous matter to be formed when applying the hot melt adhesives to substrates. In particular, in the case of utilizing a hot melt adhesive in the field of paper processing, the hot melt adhesive is required to have adhesive property in a wide temperature range from low to high temperature and adhesive property to a paper substrate coated with a chemical (poorly adherent substrates) while keeping the stringing reduction property.

In a 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 tack property to increase the production efficiency of the paper product.
In addition, in a case in which a paper product bonded with a hot melt adhesive (e.g., cardboard for packaging) is stored in a warehouse in summer, the bonding strength of the hot melt adhesive decreases along with a storage temperature increase, which may cause a cardboard box to be opened. Hot melt adhesives must have excellent creep resistance such that paper substrates do not experience detachment even at high temperatures (e.g., a cardboard box is kept closed).

JP 2013-502493 A JP 2020-521013 A JP 2021-516265 A

An object of the present invention is to provide a hot melt adhesive, which can reduce stringing and has excellent adhesive property in a wide temperature range from low to high temperature and adhesive property to a paper substrate coated with a chemical, as well as excellent heat-resistant creep property and hot tack property.

As a result of intensive studies, the present inventors found that a hot melt adhesive comprising a specific random copolymer of ethylene with an olefin having 3 to 20 carbon atoms, a specific thermoplastic block copolymer, a tackifying resin, and wax can solve the above problem, and thus such a hot melt adhesive is suitable, especially in the field of paper processing. This has led to the completion of the present invention.
In other words, the present disclosure encompasses the following embodiments.
1. A hot melt adhesive comprising: (A) a random copolymer of ethylene with an olefin having 3 to 20 carbon atoms; (B) a thermoplastic block copolymer; (C) a tackifying resin; and (D) a wax,
wherein the hot melt adhesive comprises (B) the thermoplastic block copolymer in an amount of 1 part by mass or more and less than 5 parts by mass on the basis of 100 parts by mass of the total of the components of (A) to (D), and
wherein (A) the random copolymer comprises (A1) a metallocene-based copolymer of ethylene with propylene.
2. The hot melt adhesive according to 1, wherein the hot melt adhesive comprises (A) the random copolymer in an amount of more than 25 parts by mass and less than 40 parts by mass and (D) the wax in an amount of 10 parts by mass or more and 25 parts by mass or less on the basis of 100 parts by mass of the total of the components of (A) to (D).
3. The hot melt adhesive according to 1 or 2, wherein (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms further comprises at least one selected from (A2) a metallocene-based copolymer of ethylene with octene, (A3) a metallocene-based copolymer of ethylene with hexene, and (A4) a metallocene-based copolymer of ethylene with butene.
4. The hot melt adhesive according to any one of 1 to 3, wherein the hot melt adhesive comprises (A1) the metallocene-based copolymer of ethylene with propylene in an amount of 2 parts by mass or more and 20 parts by mass or less on the basis of 100 parts by mass of the total of the components of (A) to (D).
5. The hot melt adhesive according to any one of 1 to 4, wherein (B) the thermoplastic block copolymer comprises at least one selected from: (B1) a block copolymer of ethylene with an olefin having 3 to 20 carbon atoms; and (B2) a styrene block copolymer.
6. The hot melt adhesive according to 5, wherein the component (B1) comprises a block copolymer of ethylene with octene and (B2) the styrene block copolymer comprises a hydrogenated styrenic block copolymer.
7. The hot melt adhesive according to 6, wherein the hydrogenated styrenic block copolymer comprises a styrene-ethylene-butylene-styrene (SEBS) block copolymer.
8. The hot melt adhesive according to any one of 1 to 7, which further comprises: (E) a copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond.
9. The hot melt adhesive according to 8, wherein the hot melt adhesive comprises (E) the copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond in an amount of 0.5 parts by mass or more and 5.0 parts by mass or less on the basis of 100 parts by mass of the total of the components of (A) to (D).
10. The hot melt adhesive according to 8 or 9, wherein (E) the copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond comprises at least one selected from a copolymer of ethylene with vinyl acetate, a copolymer of ethylene with methyl methacrylate, and a copolymer of ethylene with butyl acrylate.
11. A paper product comprising the hot melt adhesive according to any one of 1 to 10.

The hot melt adhesive in the embodiments of the present invention is excellent in stringing reduction and adhesive property to paper in a wide temperature range in addition to adhesive property to a poorly adherent substrate and further has excellent hot tack property and heat-resistant creep property.
Stringing is reduced when applying the hot melt adhesive in the embodiments of the present invention to an adherend such as paper via a nozzle of an applicator, preventing filamentous matter from staining the nozzle, the equipment around the nozzle, and the adherend.
Since the hot melt adhesive in the embodiments of the present invention is excellent in adhesive property to a poorly adherent substrate, it is suitable for a processing paper packaging container to which a coating agent has been applied.
Since the hot melt adhesive in the embodiments of the present invention has excellent hot tack property, it can shorten the set time for bonding and improve the production efficiency of processed paper products.
Since the hot melt adhesive in the embodiments of the present invention has excellent heat-resistant creep property, it prevents a paper substrate from being peeled off, and even when a cardboard box, to which the hot melt adhesive has been applied, is stored in a warehouse in summer, the cardboard box can be prevented from being opened due to a temperature increase.

The hot melt adhesive in the embodiments of the present invention comprises, as essential components, (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms (random copolymer of ethylene/an olefin having 3 to 20 carbon atoms or random copolymer of ethylene-an olefin having 3 to 20 carbon atoms), (B) the thermoplastic block copolymer, (C) the tackifying resin, and (D) the wax.
As used herein, the term "hot melt adhesive" refers to an adhesive that is a solid at room temperature but has fluidity when melted by heating, for example, being capable of being applied by coating to a subject such as a substrate or adherend and hardening and adhering when cooled.

A "copolymer" is a "polymer (or macromolecule)" obtained by polymerizing a plurality of kinds of monomers.
A "random copolymer" is a polymer consisting of a plurality of different monomers in which there is no order in the arrangement of the monomers (repeating units) in one polymer chain.
A "block copolymer" is a polymer consisting of a plurality of different monomers in which macromolecular chains, each consisting of monomers of the same kind, are linked together in a single chain.

<(A) Random Copolymer of Ethylene with Olefin Having 3 to 20 Carbon Atoms>
In the embodiments of the present invention, the "random copolymer of ethylene with an olefin having 3 to 20 carbon atoms (A)” refers to a copolymer in which there is no order in the arrangement of ethylene with an olefin having 3 to 20 carbon atoms. The copolymer (A) comprises the metallocene-based copolymer of ethylene with propylene (metallocene-based ethylene-propylene copolymer) (A1).

Specific examples of the "olefin having 3 to 20 carbon atoms” can comprise propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonen, 1-decene, cis-2-butene, trans-2-butene, isobutylene, cis-2-pentene, trans-2-pentene, 3-methyl-1-butene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene and the like. The "olefin having 3 to 20 carbon atoms” comprises preferably olefin having 3 to 10 carbon atoms, and is more preferably at least one selected from propylene, butene, hexene, and octene, still more preferably at least one selected from propylene, butene, and octene, particularly preferably octene.

The random copolymer of ethylene with an olefin having 3 to 20 carbon atoms (A) is preferably a copolymer polymerized by a metallocene catalyst. When the hot melt adhesive in the embodiments of the present invention comprises (A) the random copolymer (metallocene-based copolymer of ethylene with olefin having 3 to 20 carbon atoms) polymerized by a metallocene catalyst, it is excellent in adhesive property at high temperatures with improved heat-resistant creep property.

The hot melt adhesive in the embodiments of the present invention comprises preferably 2 to 20 parts by mass, more preferably 5 to 15 parts by mass, of the metallocene-based copolymer of ethylene with propylene (A1) on the basis of 100 parts by mass of the total of the components of (A) to (D). When the content of the component (A1) in the hot melt adhesive in the embodiments of the present invention is in the above-described range, the hot melt adhesive is more excellent in adhesive property in a wide range of low to high temperatures.

Examples of (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms comprise a copolymer of ethylene with octene (ethylene/octene copolymer or ethylene-octene copolymer), a copolymer of ethylene, propylene, and 1-butene (ethylene/propylene/butene copolymer or ethylene-propylene-butene copolymer), a copolymer of ethylene with propylene (ethylene/propylene copolymer or ethylene-propylene copolymer), and a copolymer of ethylene with hexene (ethylene/hexene copolymer or ethylene-hexene copolymer) and the like.

Examples of the metallocene-based random copolymer of ethylene with an olefin having 3 to 20 carbon atoms (A) comprise: (A1) the copolymer of ethylene with propylene polymerized by a metallocene catalyst (metallocene-based ethylene/propylene copolymer or metallocene-based ethylene-propylene copolymer); (A2) the copolymer of ethylene with octene polymerized by a metallocene catalyst (metallocene-based ethylene/octene copolymer or metallocene-based ethylene-octene copolymer); (A3) the copolymer of ethylene with hexene polymerized by a metallocene catalyst (metallocene-based ethylene/hexene copolymer or metallocene-based ethylene-hexene copolymer); and (A4) the copolymer of ethylene with butene polymerized by a metallocene catalyst (metallocene-based ethylene/butene copolymer or metallocene-based ethylene-butene copolymer).
Commercially available products can be used as (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms.

Examples of the metallocene-based copolymer of ethylene with propylene (A1) can comprise Vistamaxx (trademark) (trade name) series manufactured by Exxon Mobil Corporation and the like.
Examples of (A2) the metallocene-based copolymer of ethylene with octene can comprise 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 and the like.

Examples of (A3) the metallocene-based copolymer of ethylene with hexene can comprise 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 and the like.
Note that (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms may comprise (A4) the copolymer of ethylene with butene polymerized by a metallocene catalyst (copolymer of ethylene with butene) or a polymer that is not polymerized by a metallocene catalyst.
Examples of (A4) the metallocene-based copolymer of ethylene with butene can comprise 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.

Specific examples of the polymer that is not polymerized by a metallocene catalyst can comprise: 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 with 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.
Such copolymer of ethylene with an olefin having 3 to 20 carbon atoms (A) can be used singly or in combination.

The hot melt adhesive in the embodiments of the present invention comprises (A1) the metallocene-based copolymer of ethylene with propylene for improving heat resistance; (A1) the metallocene-based copolymer of ethylene with propylene improves the hot tack property and low-temperature adhesive property to a poorly adherent substrate of the hot melt adhesive.
It is preferable that the hot melt adhesive in the embodiments of the present invention comprises (A1) the metallocene-based copolymer of ethylene with propylene and (A2) the metallocene-based copolymer of ethylene with octen. When the hot melt adhesive comprises the components (A1) and (A2), the hot melt adhesive has significantly improved adhesive property in a low-temperature range.

It is preferable that (A2) the metallocene-based copolymer of ethylene with octene comprises a product modified with carboxylic acid and/or carboxylic acid anhydride, which is specifically, for example, a "metallocene-based copolymer of ethylene with octene modified with maleic anhydride via graft polymerization with maleic anhydride." In a case in which the hot melt adhesive in the embodiments of the present invention comprises a "metallocene-based copolymer of ethylene with octene modified with carboxylic and/or carboxylic anhydride," the hot melt adhesive is more excellent in adhesive property to a substrate coated with a chemical and low-temperature adhesive property.
Examples of commercially available products of the "metallocene-based copolymer of ethylene with octene modified with maleic anhydride" comprise AFFINITY (trademark) GA1000R (trade name) manufactured by The Dow Chemical Company.

<(B) Thermoplastic Block Copolymer>
The hot melt adhesive in the embodiments of the present invention comprises (B) the thermoplastic block copolymer in an amount of 1 part by mass or more and less than 5 parts by mass on the basis of 100 parts by mass of the total of the components of (A) to (D). The content of (B) the thermoplastic block copolymer is more preferably 1 part by mass or more and 4 parts by mass or less, most preferably 1.5 parts by mass or more and 3.5 parts by mass or less.
Since the hot melt adhesive comprises (B) the thermoplastic block copolymer in an amount within the above-described range, the hot melt adhesive in the embodiments of the present invention can maintain a more excellent balance between the hot tack property and adhesive property in a low-temperature range.

Examples of the component (B) comprise: (B1) the block copolymer of ethylene with an olefin having 3 to 20 carbon atoms; and (B2) the styrene block copolymer.
The block copolymer of ethylene with an olefin having 3 to 20 carbon atoms (B1) comprises preferably a block copolymer of ethylene with an olefin having 3 to 10 carbon atoms.

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

In a case in which the hot melt adhesive in the embodiments of the present invention comprises a block copolymer of ethylene with octene, the compatibility between the components (A) and (B) is further improved, making it easier to maintain the balance between the hot tack property and adhesive property in a low-temperature range.
Commercially available products can be used as the block copolymer of ethylene with octene. Examples of such commercially available products comprise INFUSE (trademark) 9817 (trade name), INFUSE (trademark) 9807 (trade name), and INFUSE (trademark) 9900 (trade name) manufactured by Dow Global Technologies LLC.

Specific examples of (B2) the styrene block copolymer comprise a styrene-isoprene block copolymer (also referred to as "SIS") and a styrene-butadiene block copolymer (also referred to as "SBS").
Other examples of (B2) the styrene block copolymer can comprise hydrogenated products of "(B2) the styrene block copolymer" described above. Specific examples of such hydrogenated products comprise can comprise a hydrogenated styrene-isoprene block copolymer (also referred to as "SEPS") and a hydrogenated styrene-butadiene block copolymer (also referred to as "SEBS").

In the embodiments of the present invention, it is preferable that the component (B2) comprises a hydrogenated styrene block copolymer. In a case in which the hot melt adhesive in the embodiments of the present invention comprises a hydrogenated styrene block copolymer, the compatibility of the component (B) with (C) the tackifying resin is further improved, resulting in further enhanced adhesive property.

Examples of commercially available products of the component (B2) can comprise: 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;
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.
These may be used singly or in combination.

<(C) Tackifying Resin>
In the embodiments of the present invention, (C) the tackifying resin is not particularly limited as long as it is usually used in hot melt adhesives, and the desired hot melt adhesive of the present invention can be obtained with it.
In a case in which the hot melt adhesive in the embodiments of the present invention comprises (C) the tackifying resin, the hot melt adhesive has significantly improved low-temperature adhesive property and more excellent hot tack property.

In consideration of the desired hot melt adhesive of the present invention, it is preferable that the desired hot melt adhesive comprises both a partially hydrogenated tackifying resin and a fully hydrogenated tackifying resin.
As used herein, the partially hydrogenated tackifying resin is a tackifying resin in which some of the double bonds are hydrogenated, and the fully hydrogenated tackifying resin is a tackifying resin in which all of the double bonds are hydrogenated.
The partially hydrogenated tackifying resin is well-compatible with (E) the copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond described later, and the fully hydrogenated tackifying resin is well-compatible with (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms. In other words, when (C) the tackifying resin comprises 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 entirely improved, resulting in significantly enhanced stringing reduction property and adhesive property.

Examples of (C) the tackifying resin can comprise natural rosin, modified rosin, hydrogenated rosin, glycerol ester of natural rosin, glycerol ester of modified rosin, pentaerythritol ester of natural rosin, pentaerythritol ester of modified rosin, pentaerythritol ester of hydrogenated rosin, a copolymer of natural terpene, a three-dimensional polymer of natural terpene, a hydrogenated derivative of a copolymer of hydrogenated terpene, polyterpene resin, a hydrogenated derivative of phenolic modified terpene resin, aliphatic petroleum hydrocarbon resin, a hydrogenated derivative of aliphatic petroleum hydrocarbon resin, aromatic petroleum hydrocarbon resin, a hydrogenated derivative of aromatic petroleum hydrocarbon resin, cycloaliphatic petroleum hydrocarbon resin, and a hydrogenated derivative of cycloaliphatic petroleum hydrocarbon resin. These tackifying resins may be used singly or in combination. As the tackifying resin, a liquid type tackifying resin can also be used as long as it is colorless to pale yellow in color tone, has substantially no odor, and has favorable thermal stability.

It is preferable that (C) the tackifying resin comprises 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 more. In a case in which the hot melt adhesive in the embodiments of the present invention comprises 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 more, the adhesive property can be improved in a wide temperature range, and stringing can be further reduced. The softening point of (C) the tackifying resin is measured in accordance with JIS K2207.

Commercially available products can be used as (C) the tackifying resin. Examples of such commercially available products can comprise 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 may be used singly or in combination.

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.

<(D) Wax>
In the embodiments of the present invention, (D) the wax refers to an organic substance having a weight average molecular weight of less than 10,000 that is solid at room temperature and becomes liquid when heated, and is generally known as "wax." The wax is not particularly limited as long as it has the properties of wax and the desired hot melt adhesive of the present invention can be obtained.
The hot melt adhesive in the embodiments of the present invention is more excellent in adhesive property in a high-temperature range, hot tack property, and stringing reduction property when comprising (D) the wax.

Examples of (D) the wax can comprise Fischer-Tropsch wax, paraffin wax, microcrystalline wax, polyethylene wax, and polypropylene wax and the like. Commercially available products can be used as waxes. Waxes can be used singly or in combination.

As used herein, it is preferable that (D) the wax comprises Fischer-Tropsch wax. "Fischer-Tropsch wax" means a wax synthesized by the Fischer-Tropsch method and is generally referred to as Fischer-Tropsch wax. Fischer-Tropsch wax is obtained by fractionating a wax whose component molecules have a relatively wide carbon number distribution such that the component molecules will have a narrow carbon number distribution. Typical examples of Fischer-Tropsch wax can comprise 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. The hot melt adhesive in the embodiments of the present invention is excellent in thermal stability and adhesive property in a high-temperature range when comprising Fischer-Tropsch wax.

The melting point of (D) the wax may be, for example, 60°C to 160°C such as 65°C to 150°C.
The melting point of Fischer-Tropsch wax is preferably 70°C to 120°C. The melting point of wax means a value measured by differential scanning calorimetry (DSC). Specifically, the temperature at the top of the melting peak obtained by weighing 10 mg of a sample in an aluminum container and performing a measurement at a heating rate of 10°C/min using DSC6220 (trade name) manufactured by SII NanoTechnology Inc. is referred to as the melting point.
When the melting point of (D) the wax is within the above-described range, the hot melt adhesive in the embodiments of the present invention has a further excellent balance of adhesive property in a high-temperature range, hot tack property, and stringing reduction property.

<(E) Copolymer of Ethylene with Carboxylic Acid Derivative Having Ethylenic Double Bond>
In the embodiments of the present invention, "(E) the copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond" (hereinafter also referred to as "(E) the copolymer" or "the component (E)") means a copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond, and is not particularly limited, as long as the desired hot melt adhesive of the present invention can be obtained.

As used herein, the "carboxylic acid derivative having an ethylenic double bond" means a carboxylic acid derivative (comprising carboxylic acid) having a double bond between carbon atoms capable of undergoing addition polymerization with ethylene. Specifically, it is, for example, "carboxylic acid having an ethylenic double bond," "carboxylic anhydride having an ethylenic double bond," "carboxylic acid ester having an ethylenic double bond," or the like as described herein.

The "carboxylic acid having an ethylenic double bond" means a compound having an ethylenic double bond and a carboxyl group and is not particularly limited as long as the desired hot melt adhesive of the present invention can be obtained. Specific examples thereof can comprise oleic acid, linoleic acid, maleic acid, itaconic acid, acrylic acid, and methacrylic acid and the like.

The "carboxylic anhydride having an ethylenic double bond" means a compound obtained by dehydration condensation of two carboxylic acid molecules or a compound obtained by dehydrating two carboxyl groups in one molecule and is not particularly limited as long as the hot melt adhesive of the present invention can be obtained. Specific examples thereof can comprise fumaric anhydride and maleic anhydride and the like.

Examples of the "carboxylic acid ester having an ethylenic double bond" can comprise: (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and (meth)acrylic acid 2-ethylhexyl; carboxylic acid vinyl esters such as vinyl acetate; and carboxylic acid allyl esters such as allyl acetate and the like.
As used herein, (meth)acrylic acid ester represents both acrylic acid ester and methacrylic acid ester.

In the embodiments of the present invention, the "carboxylic acid ester having an ethylenic double bond" comprises preferably (meth)acrylic acid ester such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, or (meth)acrylic acid 2-ethylhexyl, more preferably methyl (meth)acrylate, ethyl (meth)acrylate, or butyl (meth)acrylate, particularly desirably methyl methacrylate or ethyl acrylate.

Examples of "(E) the copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond" can comprise a copolymer of ethylene with a carboxylic acid having an ethylenic double bond (copolymer of ethylene/a carboxylic acid having an ethylenic double bond or copolymer of ethylene-a carboxylic acid having an ethylenic double bond), a copolymer of ethylene with a carboxylic anhydride having an ethylenic double bond (copolymer of ethylene/a carboxylic anhydride having an ethylenic double bond or copolymer of ethylene-a carboxylic anhydride having an ethylenic double bond), and a copolymer of ethylene with a carboxylic acid ester having an ethylenic double bond (copolymer of ethylene/a carboxylic acid ester having an ethylenic double bond or copolymer of ethylene-a carboxylic acid ester having an ethylenic double bond).

Examples of the copolymer of ethylene with a carboxylic acid having an ethylenic double bond can comprise a copolymer of ethylene with (meth)acrylic acid (ethylene/(meth)acrylic acid copolymer or ethylene-(meth)acrylic acid copolymer).
Examples of the copolymer of ethylene with a carboxylic acid ester having an ethylenic double bond can comprise: a copolymer of ethylene with (meth)acrylic acid ester (ethylene/(meth)acrylic acid ester copolymer or ethylene-(meth)acrylic acid ester copolymer); a copolymer of ethylene with vinyl carboxylate (ethylene/vinyl carboxylate copolymer or ethylene-vinyl carboxylate copolymer); and
a copolymer of ethylene with allyl carboxylate (ethylene/allyl carboxylate copolymer or ethylene-allyl carboxylate copolymer).

In the embodiments of the present invention, (E) the copolymer of ethylene with a carboxylic acid derivative having an ethylenic double bond comprises preferably a "copolymer of ethylene with a (meth)acrylic acid derivative." The "copolymer of ethylene with a (meth)acrylic acid derivative" comprises preferably at least one selected from an ethylene/(meth)acrylic acid ester copolymer, an ethylene/(meth)acrylic acid copolymer, and an ethylene/(meth)acrylic acid anhydride copolymer, most preferably an ethylene/(meth)acrylic acid ester copolymer.
When the component (E) comprises the "copolymer of ethylene with a (meth)acrylic acid derivative," the hot melt adhesive in the embodiments of the present invention has further improved stringing reduction property.

The copolymer of ethylene with a (meth)acrylic acid derivative comprises preferably a copolymer of ethylene with (meth)acrylic acid ester (ethylene/(meth)acrylic acid ester copolymer), more preferably at least one selected from an ethylene/methyl (meth)acrylate copolymer, an ethylene/ethyl (meth)acrylate copolymer, an ethylene/butyl (meth)acrylate copolymer, and an ethylene/(meth)acrylic acid 2-ethylhexyl copolymer, still more preferably at least one selected from an ethylene/methyl (meth)acrylate copolymer, an ethylene/ethyl (meth)acrylate copolymer, and an ethylene/butyl (meth)acrylate copolymer, particularly preferably an ethylene/methyl methacrylate copolymer and/or an ethylene/ethyl acrylate copolymer.

The component (E) comprises a copolymer of ethylene with a (meth)acrylic acid derivative. The melt flow rate of the component (E) may be 1 to 400 g/10 min such as 1 to 360 g/10 min and is preferably 1 to 200 g/10 min, most preferably 2 to 150 g/10 min.
When the melt flow rate of the component (E) is in the above-described range, the hot melt adhesive in the embodiments of the present invention can further reduce stringing and further improve thermal stability. As used herein, the melt flow rate is a value measured at 190°C under a load of 2.16 kg, which is measured in accordance with JIS K7210.

In a case in which the component (E) comprises an ethylene/(meth)acrylic acid ester copolymer, the hot melt adhesive in the embodiments of the present invention can further reduce stringing, be excellent in adhesive property to paper, and achieve short set time.
The content of constitutional units derived from (meth)acrylic acid ester of the ethylene/(meth)acrylic acid ester copolymer comprised in the component (E) is preferably 2% to 24% by mass, particularly preferably 4% to 24% by mass, further preferably 6% to 24% by mass, and most preferably 7% to 24% by mass.
In a case in which the content of constitutional units derived from (meth)acrylic acid ester of the ethylene/(meth)acrylic acid ester copolymer comprised in the component (E) is in the above-described range, thermal stability of the hot melt adhesive in the embodiments of the present invention can be significantly improved.

As used herein, the content of constitutional units derived from (meth)acrylic acid ester of ethylene/(meth)acrylic acid ester copolymer in (E) means a percentage (%) by mass of constitutional units derived from (meth)acrylic acid ester on the basis of the total of the ethylene/(meth)acrylic acid ester copolymer.
The ethylene/(meth)acrylic acid ester copolymer in (E) has a chemical structure derived from ethylene and a chemical structure derived from (meth)acrylic acid ester.
The "constitutional units derived from (meth)acrylic acid ester" refer to chemical structures derived from (meth)acrylic acid ester among chemical structures of the ethylene/(meth)acrylic acid ester copolymer.

For example, an ethylene/methyl methacrylate copolymer having a methyl methacrylate content of 20% by mass means that the total of the methyl methacrylate-derived chemical structure is 20 parts by mass in 100 parts by mass of the total of the ethylene/methyl methacrylate copolymer.

The content of constitutional units derived from an ethylene/(meth)acrylic acid ester compound described herein can be measured by infrared absorption spectroscopy using a press sheet of the component (E).
For instance, in a case in which (meth)acrylic acid ester is methyl methacrylate, the content of constitutional units derived from methyl methacrylate in the ethylene/methyl methacrylate copolymer can be measured according to JIS K7192.
As the characteristic absorption of the infrared absorption spectrum, the peak attributed to the (meth)acrylic acid ester copolymer is used, and the comonomer content is determined by correcting the absorbance with the press sheet thickness. For example, in a case in which (meth)acrylic acid ester is methyl methacrylate, the content of methyl methacrylate units in the ethylene/methyl methacrylate copolymer can be determined by creating a 0.3 mm thick press sheet and performing a measurement 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 the thickness according to the following formula to determine the content.

MMA = 4.1 × log(I0/I)/t-5.3
In the formula, MMA represents the content of methyl methacrylate units (% by mass), I represents the intensity of transmitted light at a frequency of 3448 cm^-1, I0 represents the intensity of incident light at a frequency of 3448 cm^-1, and t represents the thickness (cm) of the sample sheet to be measured.

A method for producing the copolymer of ethylene with a (meth)acrylic acid derivative (E) is not particularly limited, and examples thereof comprise known liquid phase polymerization methods and high-pressure radical polymerization methods. Examples of a method for producing the component (E) by high-pressure radical polymerization comprise a general method of polymerizing ethylene and a (meth)acrylic acid derivative (e.g., (meth)acrylic acid ester) in the presence of a radical generator using a tank reactor or tubular reactor under conditions of polymerization pressure of 140 MPa or more and 300 MPa or less and polymerization temperature of 100°C or more and 300°C or less.
In addition, hydrogen, hydrocarbons such as methane, and ethane can be used as molecular weight modifiers to control the melt flow rate.

Commercially available products can be used as the copolymer of ethylene/a (meth)acrylic acid derivative (E). Examples of such commercially available products comprise:
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;
LOTRYL (registered trademark) 17BA07N (trade name), LOTRYL (registered trademark) 24MA02N (trade name), and LOTADER (registered trademark) 4503 (trade name) manufactured by Arkema S.A.;
NUC-6220 (trade name) and DPDJ-9169(trade name) manufactured by The Dow Chemical Company;
NUCREL (trademark) N1035 (trade name) manufactured by DOW-MITSUI POLYCHEMICALS CO., LTD.; and
Escor (trademark) 5080 (trade name) manufactured by Exxon Mobil Corporation.

In the hot melt adhesive in the embodiments of the present invention, the content of the 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 on the basis of 100 parts by mass of the total of the components of (A) to (D).
When the content of (A) the random copolymer in the hot melt adhesive in the embodiments of the present invention is in the above-described range, the hot melt adhesive is more excellent in balance of adhesive property, hot tack property and heat-resistant creep property, and particularly in a wide temperature range the adhesive property and heat-resistant creep property are further improved.

In the hot melt adhesive in the embodiments of the present invention, the content of (C) the 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, most preferably 45 parts by mass or more and 60 parts by mass or less on the basis of 100 parts by mass of the total of the components of (A) to (D).
When the content of (C) the tackifying resin in the hot melt adhesive in the embodiments of the present invention is in the above-described range, the hot melt adhesive has improved compatibility with other components and thus is more excellent in stringing reduction property, adhesive property, and hot tack property.

In the hot melt adhesive of the invention of the present application, the content of the component (D) is preferably 10 to 25 parts by mass, particularly preferably 15 to 25 parts by mass on the basis of 100 parts by mass of the total of the components of (A) to (D).
When the content of (D) the wax in the hot melt adhesive in the embodiments of the invention of the present application is in the above-described range, the hot melt adhesive is more excellent in balance of adhesive property in a high-temperature range, hot tack property, and stringing reduction property.

The content of the component (E) in the hot melt adhesive in the embodiments of the present invention is preferably 0.5 to 5.0 parts by mass, particularly preferably 0.5 to 3.0 parts by mass on the basis of 100 parts by mass of the total of the components of (A) to (D).
When the content of (E) the copolymer in the hot melt adhesive in the embodiments of the present invention is within the above-described range, the hot melt adhesive can maintain the adhesive property, hot tack property, and heat-resistant creep property at higher levels while reducing stringing.

The hot melt adhesive in the embodiments of the present invention may further comprise various additives, if necessary. Examples of such various additives can comprise a plasticizer, a stabilizer (UV absorber, antioxidant, or the like), a fine particle filler, and an optical brightener.

The "plasticizer" is compounded for reducing the melt viscosity of the hot melt adhesive, imparting flexibility to hot melt adhesive, and improving wettability to the adherend. It is not particularly limited as long as it is compatible with the components (A) to (C), making it possible to obtain the desired hot melt adhesive of the present invention. Examples of the plasticizer can comprise paraffinic oils, naphthenic oils, and aromatic oils. Paraffinic oils, which are colorless and odorless, are particularly preferable.

Commercially available products can be used as the plasticizer. Examples thereof can comprise 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 may be used singly or in combination.

The "stabilizer" is compounded so as to prevent molecular weight reduction, gelling, coloration, odor generation and the like of the hot melt adhesive due to heat, air, light or the like, 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 can comprise an antioxidant and a UV absorber.

The "UV absorber" is used for improving the light resistance of the hot melt adhesive. The "antioxidant" is used for preventing oxidative deterioration of the hot melt adhesive. The antioxidant and the UV absorber are not particularly limited as long as they are generally used in hot melt adhesives and the desired paper product described later can be obtained.

Examples of the "antioxidant” can comprise a phenolic antioxidant, a sulfur-based antioxidant, and a phosphorus-based antioxidant. Examples of the UV absorber can comprise a benzotriazole-based UV absorber and a benzophenone-based UV absorber. In addition, a lactone-based stabilizer can also be added. These may be used singly or in combination.

Commercially available products can be used as the stabilizer. Examples thereof can comprise SUMILIZER (registered trademark) GM (trade name), SUMILIZER (registered trademark) TPD (trade name), and SUMILIZER (registered trademark) TPS (trade name) 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 may be used singly or in combination.

The hot melt adhesive in the embodiments of the present invention may further comprise a fine particle filler. The fine particle filler is not particularly limited as long as the fine particle filler may be one generally used and the desired hot melt adhesive of the present invention can be obtained. Examples of the "fine particle filler” can comprise mica, calcium carbonate, kaolin, talc, titanium oxide, diatomaceous earth, urea-based resin, styrene beads, calcined clay, and starch. Their shapes are preferably spherical, and their dimensions have no particular limitations (diameter in the spherical form).

The hot melt adhesive in the embodiments of the present invention may further comprise an optical brightener. The optical brightener is not particularly limited as long as the optical brightener may be one generally used and the desired hot melt adhesive of the present invention can be obtained. Commercially available products can be used as the optical brightener. Examples of commercially available products of the optical brightener comprise TINOPAL (registered trademark) OB (trade name) manufactured by BASF SE.

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

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

Various products can be produced by coating various substrates with the hot melt adhesive in the embodiments of the present invention (application).
The method for coating with the hot melt adhesive is not particularly limited as long as the desired product (e.g., paper product) can be obtained; however, hot melt applicators are widely used. Examples of hot melt applicators can comprise ProBlue (registered trademark) P4 Melter (trade name) and ProBlue (registered trademark) P10 Melter (trade name) manufactured by Nordson Corporation.

Coating methods are broadly classified into, for example, contact coating and non-contact coating. "Contact coating" refers to a coating method in which a hot melt adhesive is applied by contacting a member or a film with an ejector. "Non-contact coating" refers to a coating method in which an ejector does not come into contact with a member or film when coating with a hot-melt adhesive. Examples of contact coating methods can comprise slot coater coating and roll coater coating. Examples of non-contact coating methods can comprise spiral coating for helical coating, omega coating and control seam coating for wavy coating, slot spray coating and curtain spray coating for planar coating, dot coating for point-like coating, and bead coating for linear coating.

In a case of coating with the hot melt adhesive in the embodiments of the present invention using a hot melt applicator (even in a case of coating with the hot melt adhesive using a hot melt applicator by discharging the hot melt adhesive horizontally with the ground), It becomes more difficult to discharge filamentous matter of the hot melt adhesive; preferably, it is substantially impossible to discharge it. Therefore, the adherend or applicator is less prone to, preferably substantially free from, fouling by filamentous matter.

The hot melt adhesive in the embodiments of the present invention can be widely used in the fields of, for example, electronic components, woodwork, building materials, sanitary materials, and paper products and the like. It can be suitably used for producing paper products. Thus, it is useful as a hot melt adhesive for paper products.

The paper product in the embodiments of the present invention refers to a paper product produced using the above-described hot melt adhesive. The type of paper product is not particularly limited as long as it is produced using the above-described hot melt adhesive. Specific examples thereof comprise books (bookbinding), calendars, paperboard (comprising, for example, cardboard and cartons), and boxes and containers made of paperboard. In consideration of the properties of the hot melt adhesive in the embodiments of the present invention, paperboard (comprising, for example, cardboard and cartons) and boxes and containers made of paperboard are particularly effective as the paper products in the embodiments of the present invention.

Hereinafter, the present invention will be described using examples for the purpose of explaining the present invention in more detail and more specifically. These examples are intended to illustrate the present invention and are not intended to limit the present invention in any way. The components to be compounded in the hot melt adhesive are shown below.

(A) Random Copolymer of Ethylene with Olefin Having 3 to 20 Carbon Atoms
(A1-1) Metallocene-based copolymer of ethylene with propylene (ethylene content: 6.0% by mass; melting point: 97°C; 190°C melt viscosity: 1200 mPa.s; Vistamaxx (trademark) 8880 (trade name) manufactured by Exxon Mobil Corporation)
(A1-2) Metallocene-based copolymer of ethylene with propylene (ethylene content: 7.1% by weight; melting point: 112°C; 190°C melt viscosity: 1850 mPa.s; Vistamaxx (trademark) A (prototype) manufactured by Exxon Mobil Corporation)
(A1-3) Metallocene-based copolymer of ethylene with propylene (177°C melt viscosity: 12500 mPa.s; AFFINITY (trademark) GP1570 (trade name) manufactured by The Dow Chemical Company)
(A2-1) Metallocene-based copolymer of ethylene with octene (1-octene content: 30% to 40% by weight; melting point: 68°C; melt flow rate: 660 g/10 min; AFFINITY (trademark) GA1000R (trade name) manufactured by The Dow Chemical Company)
(A2-2) Metallocene-based copolymer of ethylene with octene (1-octene content: 35% to 37% by mass; melt flow rate: 1000 g/10 min; AFFINITY (trademark) GA1900 (trade name) manufactured by The Dow Chemical Company)
(A2-3) Metallocene-based copolymer of ethylene with octene (1-octene content: 35% to 37% by mass; melt flow rate: 500 g/10 min; AFFINITY (trademark) GA1950 (trade name) manufactured by The Dow Chemical Company)
(A2-4) Metallocene-based copolymer of ethylene with octene (1-octene content: 35% to 37% by mass; melt flow rate: 1200 g/10 min; AFFINITY (trademark) GA1875 (trade name) manufactured by The Dow Chemical Company)
(A2-5) Metallocene-based copolymer of ethylene with octene (weight average molecular weight: 64000; 1-octene content: 13% by weight; melt flow rate: 13 g/10 min; ENGAGE 8137 (trade name) manufactured by The Dow Chemical Company)
(A3-1) Metallocene-based copolymer of ethylene with hexene (melt flow rate: 30 g/10 min; melting point: 58°C; Kernel KJ604T manufactured by Japan Polyethylene Corporation)
(A3-2) Metallocene-based copolymer of ethylene with hexene (melt flow rate: 21 g/10 min; melting point: 110°C; Nipolon (registered trademark) BL600K (trade name) manufactured by Tosoh Corporation)
(A4) Metallocene-based copolymer of ethylene with butene (melt flow rate: 35 g/10 min; melting point: 55°C; TAFMER (trademark) DF7350 (trade name) manufactured by Mitsui Chemicals, Inc.)

(B) Thermoplastic Block Copolymer
(B1-1) Block copolymer of ethylene with octene (INFUSE (trademark) 9807 (trade name) manufactured by The Dow Chemical Company)
(B1-2) Block copolymer of ethylene with octene (INFUSE (trademark) 9900 (trade name) manufactured by The Dow Chemical Company)
(B1-3) Block copolymer of ethylene with octene (INFUSE (trademark) 9817 (trade name) manufactured by The Dow Chemical Company)
(B2-1) Styrene-ethylene/butadiene-styrene block copolymer (SEBS block copolymer; Kraton (trademark) G1657 (trade name) manufactured by Kraton Polymers LLC)
(B2-2) Styrene-ethylene/butadiene-styrene block copolymer (SEBS block copolymer; Kraton (trademark) G1652 (trade name) manufactured by Kraton Polymers LLC)
(B2-3) Styrene-ethylene/butadiene-styrene block copolymer (SEBS block copolymer; TUFTEC (trademark) H1221 (trade name) manufactured by Asahi Kasei Corporation)
(B2-4) Styrene-ethylene/butadiene-styrene block copolymer (SEBS block copolymer; TUFTEC (trademark) H1052 (trade name) manufactured by Asahi Kasei Corporation)
(B2-5) Styrene-ethylene/propylene block copolymer (SEP block copolymer; SEPTON (trademark) 2063 (trade name))
(B2-6) Styrene-ethylene-ethylene/propylene-styrene block copolymer (SEEPS block copolymer; SEPTON (trademark) 4044 (trade name) manufactured by Kuraray Co., Ltd.)

(C) Tackifying Resin
(C1) Partially hydrogenated tackifying resin (softening point: 103°C; T-REZ HC103 (trade name) manufactured by ENEOS Corporation)
(C2) Fully hydrogenated tackifying resin (softening point: 103°C; T-REZ HA103 (trade name) manufactured by ENEOS Corporation)
(C3) Fully hydrogenated tackifying resin (softening point: 125°C; T-REZ HA125 (trade name) manufactured by ENEOS Corporation)
(C4) Fully hydrogenated tackifying resin (softening point: 125°C; I-MARV (trademark) P125 (trade name) manufactured by Idemitsu Petrochemical Co., Ltd.)
(C5) Partially hydrogenated tackifying resin (softening point: 100°C; HA100 (trade name) manufactured by Henghe Materials & Science Technology Co., Ltd.)
(C6) Fully hydrogenated tackifying resin (softening point:100°C; HM1000 (trade name) manufactured by Henghe Materials & Science Technology Co., Ltd.)

(D) Wax
(D1) Fischer-Tropsch wax (melting point: 108°C; degree of penetration: 2; Sasol (registered trademark) H1 (trade name) manufactured by Sasol Ltd.)
(D2) Fischer-Tropsch wax (melting point: 112°C; degree of penetration: 2; Sasol (registered trademark) C105 (trade name) manufactured by Sasol Ltd.)
(D3) Fischer-Tropsch wax (melting point: 80°C; degree of penetration: 7; Sasol (registered trademark) C80 (trade name) manufactured by Sasol Ltd.)
(D4) Paraffin wax (melting point: 69°C; degree of penetration: 12; Paraffin 155F (trade name) manufactured by NIPPON SEIRO CO., LTD.)
(D5) Microcrystalline wax (melting point: 84°C; degree of penetration: 12; Hi-Mic-1080 (trade name) manufactured by NIPPON SEIRO CO., LTD.)
(D6) Polyethylene wax (melting point: 118°C; LC104N (trade name) manufactured by Lion Chemtech Co., LTD.)
(D7) Polypropylene wax (melting point: 140°C to 148°C; degree of penetration: 1 or less; Hi-WAX (trademark) NP105 (trade name) manufactured by Mitsui Chemicals, Inc.)

(E) Copolymer of Ethylene with Carboxylic Acid Derivative Having Ethylenic Double Bond
(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)
(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)
(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.)
(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)
(E5) Ethylene-acrylic acid copolymer (acrylic acid content: 10% by mass; melt flow rate: 30 g/10 min; Escor (trademark) 5080 (trade name) manufactured by Exxon Mobil Corporation)
(E6) Ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by mass; melt flow rate: 20 g/10 min; Ultrasen 633 (trade name) manufactured by Tosoh Corporation)
(E7) Ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by mass; melt flow rate: 160 g/10 min; Ultrasen 680 (trade name) manufactured by Tosoh Corporation)
(E8) Ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by mass; melt flow rate: 350 g/10 min; Ultrasen 681 (trade name) manufactured by Tosoh Corporation)

(F) Stabilizer
(F1) Phenolic antioxidant (ADEKA STAB AO-60 (trade name) manufactured by ADEKA CORPORATION)
(F2) Phosphorus-based antioxidant (JP650 manufactured by JOHOKU CHEMICAL CO., LTD.)

The above-described components were melt-mixed at the ratios (parts by mass) shown in Tables 1 to 4. The components were melt-mixed using a universal stirrer at about 145°C for about 1 hour, thereby producing hot melt adhesives of Examples 1 to 19 and Comparative Examples 1 to 7. The hot melt adhesives of the Examples and Comparative Examples were evaluated for adhesive property (to standard substrates), adhesive property to poorly adherent substrates, hot tack property, and heat-resistant creep property using the following methods.
The adhesive property (to standard substrates) was evaluated by applying a hot melt adhesive to K-liner cardboard and laminating it to another K-liner cardboard, thereby obtaining a sample.
The adhesive property to poorly adherent substrates was evaluated by applying a hot melt adhesive to varnish-coated cardboard and laminating it with another cardboard, thereby obtaining a sample.
The hot tack property and heat-resistant creep property were evaluated by performing a peeling test after preparing samples by changing the pressurization time.
The outline of each evaluation is described below.

<Adhesive property to General Cardboard (standard substrate)>
(Sample Preparation)
A sheet of K-liner cardboard was coated with a hot melt adhesive melted at 180°C at a coating amount of 2 g/m, and the K-liner cardboard was laminated to another sheet of K-liner cardboard under conditions of 3 seconds of open time followed by 10 seconds of set time (pressurization time) at 1 kg/25 cm² of press pressure, thereby preparing a sample. At least three samples were prepared for each hot melt adhesive.
(Evaluation Method)
The prepared samples were cured for 24 hours in a constant temperature bath set at 60°C, 23°C, or -10°C. Thereafter, under the atmosphere, forced peeling was performed by manual peeling. The K-liner cardboard destruction rate in the total bonded area was defined as the rate of material destruction (percentage of material destroyed), and the state of the bonded surface of the K-liner cardboard was evaluated. The evaluation criteria are as follows.
Very good: The rate of material destruction is more than 80%.
Good: The rate of material destruction is 60% or more and 80% or less.
Acceptable: The rate of material destruction is 30% or more and less than 60%.
Not acceptable: The rate of material destruction is less than 30%.

<Adhesive property to Chemical-Coated Cardboard (poorly adherent substrate)>
(Sample Preparation)
A sheet of (poorly adherent) cardboard having a surface coated with varnish was coated with a hot melt adhesive melted at 180°C at a coating amount of 2 g/m, and the K-liner cardboard was laminated to another sheet of cardboard having a surface coated with varnish under conditions of 3 seconds of open time followed by 10 seconds of set time (pressurization time) at 1 kg/25 cm² of press pressure, thereby preparing a sample. At least three samples were prepared for each hot melt adhesive.
(Evaluation Method)
The prepared samples were cured for 24 hours in a constant temperature bath set at 60°C, 23°C, or -10°C. Thereafter, under the atmosphere, forced peeling was performed by manual peeling. The varnish-coated cardboard destruction rate in the total bonded area was defined as the rate of material destruction (percentage of material destroyed), and the state of the bonded surface of the varnish-coated cardboard was evaluated. The evaluation criteria are as follows.
Very good: The rate of material destruction is more than 80%.
Good: The rate of material destruction is 60% or more and 80% or less.
Acceptable: The rate of material destruction is 30% or more and 60% or less.
Not acceptable: The rate of material destruction is less than 30%.

<Hot Tack Property>
(Sample Preparation)
A sheet of K-liner cardboard was coated with a hot melt adhesive melted at 180°C at a coating amount of 2 g/m, and the K-liner cardboard was laminated to another sheet of K-liner cardboard under conditions of 1 second of open time followed by a different set time (pressurization time) of 0.5 seconds, 1.0 seconds, 1.5 seconds, 2.0 seconds, or 2.5 seconds at 1 kg/25 cm² of press pressure, thereby preparing a sample. At least three samples were prepared for each hot melt adhesive for each set time.
(Evaluation Method)
Immediately after pressurization was completed, each prepared sample was forcibly peeled vertically at a constant speed, and the set time (pressurization time) until the completion of material destruction of the K-liner cardboard was defined as hot tack time. The time was measured.
Very good: The hot tack time is less than 1.5 seconds.
Good: The hot tack time is 1.5 seconds or more and less than 2.0 seconds.
Acceptable: The hot tack time is 2.0 seconds or more and less than 2.5 seconds.
Not acceptable: The hot tack time is 2.5 seconds or more.

<Heat Creep Resistance>
A sheet of K-liner cardboard was coated with a hot melt adhesive melted at 180°C at a coating amount of 2 g/m, and the K-liner cardboard was laminated to another sheet of K-liner cardboard under conditions of 3 seconds of open time followed by 10 seconds of set time (pressurization time) at 1 kg/25 cm² of press pressure, thereby preparing a sample. At least three samples were prepared for each hot melt adhesive.
(Evaluation Method)
A load was applied to the K-liner cardboard on one side of the sample with a weight, and the heat-resistant creep property was evaluated at the temperature at which the weight dropped from the sample. Specifically, a weight of 3 kg per 25 cm² (5 cm in length × 5 cm in width) of the sample was suspended vertically from the K-liner cardboard on one side of the sample in an atmosphere of 40°C, and the temperature was raised by 5°C every 15 minutes. The temperature at which the weight dropped was confirmed.
Very good: The temperature of the dropping of the weight is 55°C or more.
Good: The temperature of the dropping of the weight is 50°C or more and less than 55°C.
Acceptable: The temperature of the dropping of the weight is 45°C or more and less than 50°C.
Not acceptable: The temperature of the dropping of the weight is less than 45°C.

<Stringing Reduction Property>
Each hot melt adhesive was vertically intermittently applied to an adherend 20 cm away from a tip (nozzle) of a hot melt applicator. The percentage by mass of fallen matter between the hot melt gun and the adherend was measured, thereby evaluating stringing. The measurement conditions are as follows.
(Device)
Hot melt applicator ProBlue 4 manufactured by Nordson Corporation
(Measurement Conditions)
Temperature setting: 180°C for each of the tank, hose, and nozzle
Nozzle diameter: 14/1000 inch (2.54 cm per inch)
Nozzle: Four-orifice nozzle (Number of discharge outlets: 4)
Dispensing pressure: 0.3 MPa
Number of dispensed shots: 180 shots/1 minute for each of four orifices
(Measurement Method)
Each hot melt adhesive was discharged at 180 shots per minute onto the adherend from each nozzle (discharge outlet) of the hot melt applicator for 5 minutes. The filamentous adhesive that fell between the nozzle and the adherend was regarded as fallen matter, and the percentage by mass of the fallen matter (%) was measured by the following formula, thereby evaluating the stringing reduction property.
Percentage by mass of fallen matter (%) =
[Mass of filamentous matter (fallen matter) that fell between the nozzle and the adherend] × 100 / [Total mass of the hot melt adhesive discharged for 5 minutes]
The evaluation criteria are as follows.
Good: The percentage by mass of fallen matter is less than 0.18% by mass.
Acceptable: The percentage by mass of fallen matter is 0.18% by mass or more and less than 2.0% by mass.
Not acceptable: The percentage by mass of fallen matter is 2.0% by mass or more.

As shown in Tables 1 to 3, the hot melt adhesives of Examples 1 to 19 have an excellent balance of properties because they were not evaluated as "Not acceptable” for the adhesive property, adhesive property to poorly adherent substrates, hot tack property, heat-resistant creep property, and stringing reduction property.
Meanwhile, as shown in Table 4, the hot melt adhesives of Comparative Examples 1 and 2 have decreased hot tack properties at 40°C because they do not comprise the component (A1). Since the hot melt adhesives of Comparative Examples 3 to 5 differ from the present invention in the compounded amount of the component (B), any of the stringing reduction property, hot tack property, and adhesive property to poorly adherent substrates deteriorates, resulting in a lack of the balance of properties as paper-processing adhesives. Since the hot melt adhesive of the Comparative Example 6 does not comprise the component (C), the stringing reduction property and adhesive property declined. Since the hot melt adhesive of Comparative Example 7 does not comprise the component (D), not only the stringing reduction property and adhesive property but also the hot tack property and heat-resistant creep property deteriorated.

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 embodiments of the present invention, for example, paper products manufactured from paperboard (substrate) such as cardboard and cartons, and paper products manufactured from poorly adherent packaging substrate coated with a chemical are particularly effective.

Cross-Reference to Related Application

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

Claims

A hot melt adhesive comprising: (A) a random copolymer of ethylene with an olefin having 3 to 20 carbon atoms; (B) a thermoplastic block copolymer; (C) a tackifying resin; and (D) a wax,
wherein the hot melt adhesive comprises (B) the thermoplastic block copolymer in an amount of 1 part by mass or more and less than 5 parts by mass on the basis of 100 parts by mass of the total of the components of (A) to (D), and
wherein (A) the random copolymer comprises (A1) a metallocene-based copolymer of ethylene with propylene.
The hot melt adhesive according to claim 1, wherein the hot melt adhesive comprises (A) the random copolymer in an amount of more than 25 parts by mass and less than 40 parts by mass and (D) the wax in an amount of 10 parts by mass or more and 25 parts by mass or less on the basis of 100 parts by mass of the total of the components of (A) to (D).
The hot melt adhesive according to claim 1 or 2, wherein (A) the random copolymer of ethylene with an olefin having 3 to 20 carbon atoms further comprises at least one selected from (A2) a metallocene-based copolymer of ethylene with octene, (A3) a metallocene-based copolymer of ethylene with hexene, and (A4) a metallocene-based copolymer of ethylene with butene.
A paper product comprising the hot melt adhesive according to claim 1.