DESCRIPTION

Title of Invention

HOT MELT ADHESIVE

Technical Field

[0001]

The present invention relates to a hot melt adhesive and more specifically to a hot melt adhesive which has excellent adhesion to various substrates and is particularly suitable for assembling paper substrates such as corrugated cardboards.

Background Art

[0002]

A hot melt adhesive is a solvent-less adhesive, which is heat-melted, applied to an adherend, and then solidified by cooling to exhibit adhesion, and thus a hot melt adhesive enables instantaneous adhesion and rapid adhesion, and is applicable in wide variety fields such as paper processing, woodworking, hygienic materials, and electronics.

[0003]

As a base polymer for the hot melt adhesive, for example, an ethylene- based copolymer such as an ethylene -vinyl acetate copolymer (hereinafter also referred to as "EVA") and an ethylene-ethylacrylate copolymer (hereinafter also referred to as "EEA"), an olefin-based resin such as polyethylene, polypropylene, amorphous polyalphaolefin (hereinafter also referred to as "APAO"), a styrene- based block copolymer (e.g., styrene-isoprene-styrene-based block copolymer (hereinafter also referred to as "SIS") and styrene-butadiene-styrene-based block copolymer (hereinafter also referred to as "SBS")) and a synthetic rubber of hydrogenated product thereof, and polyurethane are widely used, depending on intended use of the hot melt adhesive.

[0004]

Among these hot melt adhesives, a hot melt adhesive including an ethylene -based copolymer as base polymer is often used in a paper processing field such as book binding and packaging, and a woodworking field.

[0005] For application of a hot melt adhesive, a dedicated coating device called hot melt applicator is often used. The hot melt applicator has a nozzle, i.e., a discharge opening. The hot melt adhesive heated to about 120 to 190°C is discharged from the tip of the nozzle for application to an adherend.

[0006]

In application of the hot melt adhesive, a hot melt adhesive string may sometimes occur between the tip of nozzle and the adherend. The occurrence of string is due to the stringing properties of a hot melt adhesive, soiling the nozzle and the adherend. Accordingly, adhesive manufacturers have important responsibility for developing a hot melt adhesive having less stringing.

[0007]

In Patent Literature 1 and Patent Literature 2, ethylene (polyolefin) -based hot melt adhesives with the purpose of reducing stringing are described. The Patent Literature 1 discloses a hot melt adhesive including ethylene/C3 ^_ C2o or olefin copolymer as base polymer, for use in packaging, book binding,

woodworking and the like (refer to claim 1 and "0013"). The Patent Literature 2 discloses an olefin hot melt adhesive which includes a "stringing reducing agent" which is formed by modifying an olefin with unsaturated polycarboxylic acid, or acid anhydride or ester thereof (refer to claim 1 and "0024" Table l), for use in packaging and book binding (refer to "0001" and "0028").

[0008]

Reducing stringing of a hot melt adhesive has been more severely required year by year. Particularly, users of thick paper such as corrugated cardboards and cartons earnestly require the reduction in stringing. Although the hot melt adhesives of Patent Literatures 1 and 2 have reduced stringing properties, it cannot be said that the performance severely required by the users is sufficiently satisfied with the adhesives.

[0009]

Furthermore, the users of a hot melt adhesive such as paper product manufacturers and film manufacturers have recently tended to use

environmentally-friendly substrates. Accordingly, a hot melt adhesive is also required to have excellent biodegradability and to be a carbon- neutral material.

[0010]

A hot melt adhesive including poly lactic acid is known as an

environmentally-friendly hot melt adhesive for paper. In Patent Literature 3 and Patent Literature 4, polylactic acid-based hot melt adhesives for use as paper adhesive are disclosed. In the hot melt adhesives including a polylactic acid- based resin, however, compatibihty with other components such as a tackifier resin is not sufficient. Therefore, the adhesion, the thermal stability, and the like are liable to be extremely poor compared to ethylene-based hot melt adhesives and "stringing properties" is not reduced. Furthermore, polylactic acid has poor compatibility with an "ethylene-based copolymer" as stringing reducing agent, having poor thermal stability.

Citation List

Patent Literature

[0011]

Patent Literature 1 Japanese Patent Laid pen No. 2008-527067

Patent Literature 2 Japanese Patent Laid pen No. 2008-214539

Patent Literature 3 Japanese Patent LaidOpen No. 2010-155951

Patent Literature 4 Japanese Patent Laid pen No. 2004-256642

Summary of Invention

Technical Problem

[0012]

An object of the present invention is to provide a hot melt adhesive in excellent harmony with environment, having less stringing and excellent adhesion to corrugated cardboards and carton paper.

Solution to Problem

[0013]

The present invention and preferred embodiments of the present invention are as follows.

[0014]

1. A hot melt adhesive comprising ^' -

(A) a polar functional group-modified polymer,

(B) an aliphatic polyester-based resin,

(C) an olefin-based polymer,

(D) a tackifier resin, and (E) a wax.

[0015]

2. The hot melt adhesive according to the item 1, wherein the wax (E) comprises Fischer-Tropsch wax.

[0016]

3. The hot melt adhesive according to the item 1 or 2, wherein the polar functional group-modified polymer (A) comprises at least one selected from a polar functional group -modified conjugated diene-based polymer and a polar functional group -modified olefin-based polymer.

[0017]

4. The hot melt adhesive according to any one of the items 1 to 3, wherein the polar functional group is at least one functional group selected from an acid anhydride group, a maleic acid group, a carboxyl group, an amino group, an imino group, an alkoxysilyl group, a silanol group, a silyl ether group, a hydroxy 1 group and an epoxy group.

[0018]

5. The hot melt adhesive according to any one of the items 1 to 4, wherein the aliphatic polyester-based resin (B) is at least one selected from a polylactic acid- based resin, a polyO utylene succinate) and a poly(hydroxybutyrate).

[0019]

6. The hot melt adhesive according to any one of the items 1 to 5, wherein the olefin-based polymer (C) comprises ethylene "based copolymer.

[0020]

7. The hot melt adhesive according to the item 6, wherein the ethylene-based copolymer comprises a copolymer of ethylene and an a-olefin having 3 to 20 carbon atoms.

[0021]

8. The hot melt adhesive according to the item 7, wherein the copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms comprises a copolymer of ethylene, propylene and butene.

[0022]

9. A paper product produced by applying the hot melt adhesive according to any one of the items 1 to 8.

Advantageous Effects of Invention [0023]

In the present invention, a polar functional group -modified polymer is blended into a hot melt adhesive, so that compatibility of an aliphatic polyester- based resin such as polylactic acid-based resin with other components is improved. Consequently, an environmentally-friendly hot melt adhesive having reduced stringing, and improved adhesion, thermal stability and the like can be provided. The present invention provides a hot melt adhesive suitable for application to paper substrate to be bonded, particularly to corrugated cardboards and carton paper to be bonded.

Description of Embodiments

[0024]

The hot melt adhesive of the present invention comprises at least (A) a polar functional group-modified polymer, (B) an ahphatic polyester-based resin, (C) an olefin-based polymer, (D) a tackifier resin and (E) a wax. Hereinafter, these may be described below as a "(A) component," a "(B) component," a "(C) component", a "(D) component" and "(E) component" respectively. A "modified polymer" means to include both (i) one in which a functional group is provided after a polymer is obtained and (ii) one in which a functional group is introduced in the process of polymerization.

[0025]

<(A) Polar Functional Group-Modified Polymer>

In the hot melt adhesive of the present invention, the use of the polar functional group-modified polymer (A) ((A) component) increases the compatibihty between the ahphatic polyester-based resin (B) and other components, such as the olefin-based polymer (C) and tackifier resin (D), and improves the pressure - sensitive adhesiveness, adhesion, thermal stability and the like.

[0026]

The polar functional group -modified polymer (A) used in the present invention refers to a polymer having at least one polar functional group. The position at which the polar functional group is introduced is not particularly limited, and may be at an end of the polymer or at inside of the polymer other than the ends of the polymer. The polar functional group may be provided to an obtained polymer, or introduced in the process of polymerizing a monomer.

[0027] Examples of the "polar functional group" include acid anhydride groups, such as a maleic anhydride group, a carboxyl group, a maleic acid group, an amino group, an imino group, an alkoxysilyl group, a silanol group, a silyl ether group, a hydroxyl group and an epoxy group. Among these, a maleic anhydride group, a maleic acid group, an amino group and an epoxy group are preferred.

[0028]

The polar functional group-modified polymer (A) is not particularly limited, and preferably comprises at least one selected from a polar functional group - modified conjugated diene-based polymer (Al) and a polar functional group - modified olefin-based polymer (A2). Two or more of these may be used in combination. These will be described in detail below.

[0029]

(Al) Polar Functional Group -Modified Conjugated Diene-Based Polymer

A "conjugated diene-based polymer" refers to a polymer having a structural unit based on a conjugated diene compound (conjugated diene unit).

[0030]

Here, the "conjugated diene compound" means a diolefin compound having at least a pair of conjugated double bonds. Specific examples of the "conjugated diene compound" include 1,3-butadiene, 2-methyM,3-butadiene (or isoprene), 2,3- dimethyl-l,3-butadiene, 1,3-pentadiene and 1,3-hexadiene. 1,3-Butadiene and 2- methyl- 1,3-butadiene are particularly preferred. These conjugated diene compounds may be used alone or in combination.

[0031]

In the present invention, the conjugated diene-based polymer may have, in addition to the conjugated diene unit, structural units based on other monomers. Examples of other monomers include vinyl-based aromatic hydrocarbons, vinyl nitrile and unsaturated carboxylate esters.

[0032]

In the present invention, the "conjugated diene-based polymer" is not particularly limited as long as the hot melt adhesive targeted by the present invention can be obtained. For example, a copolymer in which a vinyl-based aromatic hydrocarbon and a conjugated diene compound are blockxopolymerized, that is, one having a vinyl-based aromatic hydrocarbon block and a conjugated diene compound block, is preferred.

[0033] The "vinyl-based aromatic hydrocarbon" means an aromatic hydrocarbon compound having a vinyl group. Specific examples thereof include styrene, o- methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, cc methylstyrene, vinylnaphthalene and vinylanthracene. Particularly, styrene is preferred. These vinyl-based aromatic hydrocarbons may be used alone or in combination.

[0034]

In the present invention, the conjugated diene-based polymer constituting the polar functional group -modified conjugated diene-based polymer contained as the (A) component may be a non-hydrogenated conjugated diene-based polymer or a hydrogenated conjugated diene-based polymer, and a hydrogenated conjugated diene-based polymer is more preferred.

[0035]

Examples of the "non-hydrogenated conjugated diene-based polymer" include a styrene-isoprene-styrene block copolymer (also referred to as "SIS") and a styrene-butadiene-styrene block copolymer (also referred to as "SBS").

[0036]

Examples of the "hydrogenated conjugated diene-based polymer" can include a hydrogenated styrene-isoprene-styrene block copolymer (that is, also referred to as the styrene-ethylene/propylene-styrene block copolymer "SEPS") , a

hydrogenated styrene-butadiene-styrene block copolymer (that is, also referred to as the styrene-ethylene butylene-styrene block copolymer "SEBS") and a hydrogenated styrene-butadiene-crystalline ethylene block copolymer (that is, also referred to as the styrene-ethylene/butylene-crystalline ethylene block copolymer "SEBC").

[0037]

Among these, SEBS and/or SEBC are (is) preferred, and SEBS and/or SEBC having a styrene content of 3 to 40% by weight is more preferred for the

conjugated diene-based polymer constituting the polar functional group-modified conjugated diene-based polymer contained as the (A) component.

[0038]

Examples of the "polar functional group" of the "polar functional group- modified conjugated diene-based polymer" include acid anhydride groups, such as a maleic anhydride group, a carboxyl group, a maleic acid group, an amino group, an imino group, an alkoxysilyl group, a silanol group, a silyl ether group, a hydroxyl group and an epoxy group. Among these, a maleic acid group and an amino group are more preferred.

[0039]

As a method for producing the polar functional grou -modified conjugated diene-based polymer, the polar functional group -modified conjugated diene-based polymer may be produced by synthesizing a conjugated diene-based polymer first, and introducing a polar functional group later, or by performing a

copolymerization reaction using a monomer containing a polar functional group.

[0040]

Examples of the "polar functional group -modified conjugated diene-based polymer" include amino group -modified SEBS, maleic acid group -modified SEBS and amino group -modified SEBC. In a polar functional group-modified conjugated diene-based copolymer, the position at which a polar group, such as an amino group or a maleic acid group, is introduced is not particularly limited. For example, the polar group is preferably introduced into at least one end of the conjugated diene-based copolymer.

[0041]

As the polar functional group-modified conjugated diene-based copolymer, commercial products may be used. Examples thereof include Tuftec MP10 manufactured by Asahi Kasei Chemicals Corporation, DYNARON 8630P and DYNARON 4630P manufactured by JSR and Tuftec M1913 manufactured by Asahi Kasei Chemicals Corporation.

[0042]

(A2) Polar Functional Group -Modified olefin-Based Polymer

In the present invention, an "olefin-based polymer" means a polymer having a structural unit based on an olefin, and may be an olefin homopolymer or a copolymer obtained by copolymerizing a compound copolymerizable with an olefin. In the present invention, preference is given to a polyolefin-based copolymer containing an olefin in an amount of 50% by weight or more, preferably 80% by weight or more, and containing a compound copolymerizable with an olefin in an amount of less than 50% by weight, preferably less than 20% by weight. Compounds corresponding to the above "polar functional group -modified conjugated diene-based polymer" herein are not included in the "polar functional group -modified olefin-based polymer".

[0043] As the olefin, ethylene or an a- olefin having 3 to 20 carbon atoms is preferred. Examples of the orolefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl- 1-butene, 3- methyl- 1-pentene, 3-ethyl- 1-pentene, 4-methyl- 1-pentene, 4-methyl- 1-hexene, 4,4- dimethyl- 1-hexene, 4,4'dimethyl- 1-pentene, 4-ethyl- 1-hexene, 3-ethyl- 1-hexene, 9- methyl- 1-decene, ll-methyM-dodecene, 12 -ethyl- 1-tetradecene and combinations thereof. While these may be used alone or in combination of two or more of these, ethylene is preferably contained as the olefin.

[0044]

In the present invention, the olefin-based polymer may contain a structural unit based on a compound copolymerizable with an olefin to the extent that the object of the present invention is not impaired. Examples of the compound copolymerizable with an olefin include unsaturated carboxylic acids or derivatives thereof and vinyl carboxylates, specifically, unsaturated carboxylic acids or derivatives thereof including acrylic acid, methacrylic acid and (meth)acrylates (for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl

methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, t-butyl acrylate, t-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, acrylates or methacrylates of polyethylene glycol and polypropylene glycol, trimethoxysilylpropyl acrylate, trimethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl acrylate, methyldimethoxysilylpropyl methacrylate, methyl orhydroxymethylacrylate, dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate); and vinyl carboxylates including

monofunctional aliphatic vinyl carboxylates (for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, isopropenyl acetate, 1-butenyl acetate, vinyl pivalate, vinyl 2-ethylhexanoate and vinyl cyclohexanecarboxylate), aromatic vinyl carboxylates (for example, vinyl benzoate and vinyl cinnamate), and polyfunctional vinyl carboxylates (for example, vinyl monochloroacetate, divinyl adipate, vinyl methacrylate, vinyl crotonate and vinyl sorbate). Among these, methyl acrylate, ethyl acrylate and methacrylic acid are preferred. These may be used alone or in combination of two or more of these.

[0045]

Examples of the "polar functional group" of the "polar functional group - modified olefin-based polymer" include acid anhydride groups, such as a maleic anhydride group, a carboxyl group, a maleic acid group, an amino group, an imino group, an alkoxysilyl group, a silanol group, a silyl ether group, a hydroxyl group and an epoxy group. Among these, a maleic anhydride group, an epoxy group, a maleic acid group and a carboxyl group are more preferred.

[0046]

As a method for producing the polar functional group -modified olefin-based polymer, the polar functional group -modified olefin-based polymer may be produced by synthesizing an olefin-based polymer, and introducing a polar functional group later, or by performing a copolymerization reaction using a monomer containing a polar functional group. As the monomer containing a polar functional group, for example, glycidyl methacrylate is preferred.

[0047]

Examples of the "polar functional group-modified olefin-based polymer" include an ethylene/methyl acrylate/glycidyl methacrylate copolymerized resin, an ethylene -glycidyl methacrylate -styrene copolymer, a maleic anhydride-modified polyethylene copolymer, ethylene/1 -octene maleic acid copolymer and

ethylene/ethyl acrylate maleic acid copolymer. In the polar functional group - modified olefin-based polymer, the position at which a polar functional group, such as an epoxy group or a maleic anhydride group, is introduced is not particularly limited. The polar functional group may be introduced into an end of the polymer or into the structural unit at inside of the polymer other than the ends of the polymer.

[0048]

As the polar functional grou -modified olefin-based polymer, commercial products may be used. Examples thereof include BOND FAST 7M manufactured by Sumitomo Chemical Co., Ltd., MODIPER A4100 manufactured by NOF CORPORATION, AFFINITY GA1000R manufactured by Dow Chemical

Company, BONDINE HX8210 manufactured by Arkema K.K. and Fusabond N525 manufactured by DuPont. [0049]

In the present invention, a polymer having an aliphatic polyester structure as a moiety (in particular, a polymer having an aliphatic polyester moiety as main constituent) is classified into a component (B), which is different from a

component (A).

[0050]

In the present invention, the (A) component preferably comprises a polar functional group-modified polymer having a weight average molecular weight (Mw) of 1.0 x 10 ⁴ to 3.0 x 10 ⁵ , and particularly preferably of 2.0 ^χ 10 ⁴ to 2.0 x 10 ⁵ .

[0051]

The weight average molecular weight is measured by gel permeation chromatography (GPC) using a cahbration curve using monodisperse molecular weight polystyrene as a standard substance to convert molecular weight.

[0052]

In the hot melt adhesive of the present invention, the (A) component is blended in an amount of preferably 1 to 20 weight parts, more preferably 1 to 15 weight parts, relative to 100 weight parts of the total of (A) to (E) components.

[0053]

<(B) Aliphatic Polyester-Based Resin>

In the hot melt adhesive of the present invention, the use of the aliphatic polyester-based resin (B) ((B) component) is effective to reduce the content of a material made from petroleum and the like, and therefore the environmental load can be reduced.

[0054]

As the aliphatic polyester-based resin (B), known resins can be used.

Examples thereof include polylactic acid-based resins, poly(butylene succinate), poly(butylene succinate-adipate), poly(butylene succinate-terephthalate), poly(ethylene succinate), poly(butylene succinate-carbonate), polyglycolic acid, polycaprolactone, polyhydroxybutyric acid, polyhydroxyvaleric acid and a hydroxybutyric acid-hydroxyvaleric acid copolymer. Among these, polylactic acid-based resins, poly(butylene succinate) and polyhydroxybutyric acid are preferred, and polylactic acid and/or poly(butylene succinate) are more preferred. These may be used alone or in combinations of two or more.

[0055] The above polylactic acid-based resin is a polymer comprising L-lactic acid and/or D -lactic acid as main constituents, and may comprise other

copolymerization components other than lactic acid. Examples of such other copolymerization component units include polyvalent carboxylic acids, polyhydric alcohols, hydroxycarboxylic acids and lactones. Specific examples are units produced from polyvalent carboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedionic acid, fumaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, anthracenedicarboxylic acid, 5-sodium sulfoisophthalic acid and 5-tetrabutylphosphonium sulfoisophthalic acid; polyhydric alcohols, such as ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4- cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, aromatic polyhydric alcohols obtained by the addition reaction of bisphenol A or bisphenol with ethylene oxide, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; hydroxycarboxylic acids, such as glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and hydroxybenzoic acid; and lactones, such as glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone and δ-valerolactone, and the like. The content of such other copolymerization units other than lactic acid is generally preferably 0 to 30 mol %, preferably 0 to 10 mol %, based on 100 mol % of total monomer units.

[0056]

In the hot melt adhesive of the present invention, (B) component is blended in an amount of preferably 20 to 50 parts by weight, and more preferably 20 to 40 parts by weight, based on 100 parts by weight of the total amount of the (A) to (E) components.

[0057]

<(C) Olefin-based polymer>

By comprising an olefin-based polymer (C), the hot melt adhesive of the present invention has improved adhesion to a polyolefin substrate, while

maintaining the adhesion to a paper substrate. Having improved adhesion to a polyolefin substrate, the hot melt adhesive of the present invention may be used not only for processing paper but also for manufacturing vehicle interior material and hygienic material which are formed of polyolefin.

[0058]

The olefin-based polymer (C) herein is not modified with a polar functional group. (In other words, a polymer simply described as "olefin-based polymer" means an olefin-based polymer which is not modified with a polar functional group.) Accordingly, the olefin-based polymer (C) is clearly distinguished from a polar functional group-modified olefin-based polymer (A2).

[0059]

The same explanation and the specific examples of "olefin" described in "(A2) Polar functional group -modified olefin-based polymer" can also apply to the "olefin" of the olefin-based polymer (C).

[0060]

In the present invention, the olefin-based polymer (C) may be either a homopolymer or a copolymer, preferably including an ethylene -based copolymer. An "ethylene-based copolymer" herein means a copolymer of ethylene and other polymerizable monomer(s).

[0061]

The "other polymerizable monomer" means a monomer having a double bond between carbon atoms which enables addition polymerization with ethylene.

[0062]

Specific examples of the "other polymerizable monomer" include an "olefin- based hydrocarbon except for ethylene" and a "carboxylate ester having an ethylenic double bond".

[0063]

Examples of the "olefin-based hydrocarbon except for ethylene" include cr olefin having 3 to 20 carbon atoms, and specifically include propylene, 1 -butene, 1- pentene, 1-hexene, 1-heptene, 1-octen, 1-nonene, 1-decene, cis-2-butene, trans-2- butene, isobutylene, cis-2-pentene, trans-2-pentene, 3-methyl-l-butene, 2-methyl- 2-butene, and 2,3"dimethyl-2-butene.

[0064]

Examples of the "carboxylate ester having an ethylenic double bond" include (meth)acrylate ester such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and vinyl carboxylate and allyl ester such as vinyl acetate and allyl acetate. [0065]

The "other polymerizable monomer" may be used singly or in combination of two or more.

[0066]

In the present invention, the ethylene-based copolymer preferably includes a "copolymer of ethylene and an olefin except for ethylene" in view of the adhesion to a paper substrate. Accordingly, the "other polymerizable monomer" is preferably an "olefnrbased hydrocarbon except for ethylene", particularly a-olefin having 3 to 20 carbon atoms, more preferably propylene, butene, and octene.

[0067]

Examples of the "copolymer of ethylene and an olefin except for ethylene" preferably include a copolymer of ethylene and an a-olefin having 3 to 20 carbon atoms, and specifically a copolymer of ethylene and octene, a copolymer of ethylene, propylene and 1-butene, a copolymer of ethylene and propylene, and a copolymer of ethylene and butene, more preferably a copolymer of ethylene and octene, and a copolymer of ethylene, propylene and 1-butene, and particularly preferably a copolymer of ethylene, propylene and 1-butene. The copolymers of ethylene and an olefin may be used singly or in combination. A commercialized product may be used as the copolymer of ethylene and an olefin.

[0068]

Examples of the "copolymer of ethylene, propylene and 1-butene" include VESTO PLAST 703 (trade name) and VESTO PLAST 708 (trade name) made by Evonik Degussa Co., Ltd.

[0069]

Examples of the "copolymer of ethylene and octene" include AFFINITY GA1900 (trade name), AFFINITY GA1950 (trade name), AFFINITY EG8185 (trade name), AFFINITY EG8200 (trade name), ENGAGE 8137 (trade name), ENGAGE 8180 (trade name), and ENGAGE 8400 (trade name) made by Dow Chemical Company.

[0070]

Examples of the "copolymer of ethylene and propylene" include

EASTOFLEX E1016PL-1 made by Eastman Chemical Company.

[0071]

In the present invention, the ethylene-based copolymer may include a copolymer of ethylene and at least one selected from the "carboxylate ester having an ethylenic double bond", which may be a commercialized product, and may be used singly or in combination of two or more kinds.

[0072]

Examples of the "copolymer of ethylene and a carboxylate ester having an ethylenic double bond" include an ethylene -vinyl acetate copolymer, an ethylene - methyl methacrylate copolymer, an ethylene-2-ethylhexyl acrylate copolymer, an ethylene-butyl acrylate copolymer, and an ethylene-butyl methacrylate copolymer. Among them, an ethylene-vinyl acetate copolymer and ethylene -methyl

methacrylate copolymer are more preferred, and an ethylene-vinyl acetate copolymer is particularly preferred.

[0073]

In the hot melt adhesive of the present invention, a homopolymer such as polyethylene and polypropylene may be used as the (C) component.

[0074]

In the hot melt adhesive of the present invention, the (C) component is blended in an amount of preferably 3 to 30 weight parts, more preferably 5 to 25 weight parts, relative to 100 weight parts of the total of components (A) to (E).

[0075]

<(D) Tackifier Resin>

In the hot melt adhesive of the present invention, the use of the tackifier resin (D) ((D) component) improves the pressure-sensitive adhesiveness. The "tackifier resin" is not particularly limited as long as it is generally used in hot melt adhesives and provides the hot melt adhesive targeted by the present invention.

[0076]

Examples of the tackifier resin can include natural rosins, modified rosins, hydrogenated rosins, glycerol esters of natural rosins, glycerol esters of modified rosins, pentaerythritol esters of natural rosins, pentaerythritol esters of modified rosins, pentaerythritol esters of hydrogenated rosins, copolymers of natural terpenes, three-dimensional polymers of natural terpenes, hydrogenated

derivatives of copolymers of hydrogenated terpenes, polyterpene resins,

hydrogenated derivatives of phenol-based 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, cyclic aliphatic petroleum hydrocarbon resins and hydrogenated derivatives of cyclic aliphatic petroleum hydrocarbon resins. These tackifier resins may be used alone or in combination. For the tackifier resin, liquid type tackifier resins can also be used as long as they are colorless to pale yellow in color tone, have substantially no odor, and have good thermal stability. Considering these properties comprehensively,

hydrogenated derivatives of resins and the like are preferred as the tackifier resin.

[0077]

As the tackifier resin, commercial products may be used. Examples of such commercial products include MARUKACLEAR H (trade name)

manufactured by Maruzen Petrochemical Co., Ltd., Clearon K100 (trade name) manufactured by YASUHARA CHEMICAL Co., Ltd., ARKON M100 (trade name) manufactured by Arakawa Chemical Industries, Ltd., TMARV S100 (trade name), I-MARV P100 (trade name) manufactured by Idemitsu Kosan Co., Ltd., Clearon K4090 (trade name) and Clearon K4100 manufactured by YASUHARA

CHEMICAL Co., Ltd., ECR5380 (trade name), ECR179EX (trade name),

ECR5400 (trade name) and ECR5600 (trade name) manufactured by Exxon Mobil Corporation, Regalite R7100 (trade name) and Easttack H-100W (trade name) manufactured by Eastman Chemical Company, ECR179X (trade name)

manufactured by Exxon, ARKON P100 (trade name) manufactured by Arakawa Chemical Industries, Ltd., Lmarv S110 (trade name) and Lmarv Y135 (trade name) manufactured by Idemitsu Kosan Co., Ltd., Easttack CIOO-R (trade name) manufactured by Easttack and KR-85 (trade name) manufactured by Arakawa Chemical Industries, Ltd. These commercial tackifier resins may be used singly or in combination.

[0078]

In the hot melt adhesive of the present invention, the blending ratio of the (D) component is preferably 5 to 70 parts by weight, more preferably 10 to 60 parts by weight, based on 100 parts by weight of the total amount of the (A) to (E) components.

[0079]

<(E) Wax>

By comprising a wax (E), the hot melt adhesive of the present invention has improved workability with reduced viscosity, adjusted open time, improved heat resistance, and reduced stringing properties.

[0080] The "wax" herein means an organic substance generally called "wax", which is solid at normal temperature and forms liquid when heated, and is not specifically limited as long as having wax-like properties for obtaining the hot melt adhesive of the present invention. The wax generally has a weight- average molecular weight less than 10,000.

[0081]

The wax (E) may be a wax commonly used for a hot melt adhesive which may be denatured with a polar functional group or the like, as long as the intended hot melt adhesive of the present invention can be obtained. Specific examples of the wax (E) include a synthetic wax such as a Fischer-Tropsch wax, a polyolefin wax (e.g. polyethylene wax and polypropylene wax), a petroleum wax such as paraffin wax and microcrystalline wax, and a natural wax such as castor wax.

[0082]

In the present invention, the wax (E) preferably includes a Fischer-Tropsch wax. A Fischer-Tropsch wax means the wax synthesized by Fischer-Tropsch method and generally defined as a Fischer-Tropsch wax (including an acid- modified product). The Fischer-Tropsch wax is a wax fractionated from a wax including component molecules with a relatively wide distribution of the number of carbon atoms so as to include component molecules with a narrow distribution of the number of carbon atoms. Examples of the typical Fischer-Tropsch wax include SASOL HI (trade name), SASOL H8 (trade name), SASOL H 105 (trade name), and SASOL C80 (trade name), which are all available from Sasol Wax Limited.

[0083]

Examples of the commercialized paraffin wax include PARAFFIN WAX- 150 made by Nippon Seiro Co., Ltd.

[0084]

By comprising the wax, the hot melt adhesive of the present invention has excellent stringing properties, thermal stability, and adhesion strength in a high temperature region. The melting point of wax is preferably 50 to 120°C. The melting point of wax is a measured value by differential scanning calorimetry (DSC). More specifically, the melting point is the melting peak temperature measured with DSC6220 (trade name) made by SII Nanotechnology Inc., for 10 mg of a sample weighed in an aluminum container, at a temperature increase rate of 10°C/min.

[0085]

In the hot melt adhesive of the present invention, the (E) component is blended in an amount of preferably 10 to 70 weight parts, more preferably 15 to 60 weight parts, relative to 100 weight parts of the total of components (A) to (E).

[0086]

The hot melt adhesive of the present invention preferably comprises a stabilizing agent (F) (hereinafter also referred to as "component (F)") in addition to the components (A) to (E).

[0087]

The "stabilizer" is blended to prevent reduction of molecular weight by heating, gelation, coloration, generation of an odor and the like in the hot melt adhesive to improve the stability of the hot melt adhesive. The "stabilizer" is not particularly limited as long as the hot melt adhesive targeted by the present invention can be obtained. Examples of the "stabilizer" include an antioxidant and an ultraviolet absorbing agent.

[0088]

The "ultraviolet absorbing agent" is used to improve the light resistance of the hot melt adhesive. The "antioxidant" is used to prevent the oxidative degradation of the hot melt adhesive. The antioxidant and the ultraviolet absorbing agent are not particularly limited, and can be used as long as they are generally used in disposable products, and the targeted disposable product described later can be obtained.

[0089]

Examples of the antioxidant include phenol -based antioxidants, sulfur- based antioxidants and phosphorus-based antioxidants. Examples of the ultraviolet absorbing agent include benzotriazole-based ultraviolet absorbing agents and benzophenone-based ultraviolet absorbing agents. Further, a lactone-based stabilizer may also be added. These may be used alone or in combination. As commercial products of antioxidants, the following products may be used.

[0090]

Specific examples thereof include SUMILIZER GM (trade name),

SUMILIZER TPD (trade name) and SUMILIZER TPS (trade name) manufactured by Sumitomo Chemical Co., Ltd., IRGANOX 1010 (trade name), IRGANOX HP2225FF (trade name), IRGAFOS 168 (trade name), IRGANOX 1520 (trade name) and TINUVIN P manufactured by Ciba Specialty Chemicals, JF77 (trade name) manufactured by Johoku Chemical Co., Ltd., TOMINOX TT (trade name) manufactured by API Corporation and AO-412S (trade name) manufactured by ADEKA CORPORATION. These stabilizers may be used alone or in combination.

[0091]

The hot melt adhesive of the present invention may further comprise a fine particle filler. The fine particle filler may be a generally used one, and is not particularly limited as long as the hot melt adhesive targeted by the present invention can be obtained. Examples of the "fine particle filler" include mica, calcium carbonate, kaolin, talc, titanium oxide, diatomaceous earth, urea-based resins, styrene beads, fired clay and starch. The shape of these is preferably a spherical shape, and their sizes (diameter in the case of a spherical shape) are not particularly limited.

[0092]

The hot melt adhesive according to the present invention may be produced by blending the (A) component, the (B) component, the (C) component and the (D) component and preferably the (E) component and further various additives as required, using a generally known method for producing a hot melt adhesive. For example, the hot melt adhesive according to the present invention may be produced by blending predetermined amounts of the above-described components, and heating and melting them. The order of adding the components, the heating method and the like are not particularly limited as long as the targeted hot melt adhesive is obtained.

[0093]

As a further preferred mode of the present invention, the hot melt adhesive preferably has a viscosity (or melt viscosity) at 180°C of 5000 mPa-s or less, particularly preferably 3000 mPa-s or less, most preferably 2000 mPa-s or less.

[0094]

The viscosity allowing application of uniform coating with the hot melt adhesive is 5000 mPa-s or less, and the viscosity allowing easy application of uniform coating is less than 2000 mPa-s. With the viscosity at 180°C in the above range, the hot melt adhesive is much more suitable for coating. The viscosity (or melt viscosity) at 180°C herein means a value measured by a

Brookfield viscometer using a No. 27 rotor.

[0095]

The hot melt adhesive of the present invention may be manufactured by a known manufacturing method of a hot melt adhesive, including blending the components (A) to (E), and the stabilizing agent (F) and various kinds of additives as needed. For example, the manufacturing method includes blending predetermined amounts of the components mentioned above, and heating and melting the blended components. The order of adding the components, the heating method and the like are not particularly limited as long as the targeted hot melt adhesive is obtained.

[0096]

The hot melt adhesive of the present invention may be in various shapes, generally in a block shape or a film (sheet) shape at normal temperature. The block shape may be obtained by directly cooling and solidifying a product obtained by the manufacturing method, while the film (sheet) shape may be obtained by further forming the product obtained by the manufacturing method into a film shape.

[0097]

The hot melt adhesive of the present invention may be applied to an adherend for use. No organic solvent is required to be blended in the hot melt adhesive when applied, resulting in an environmentally preferable adhesive.

[0098]

The method for applying the hot melt adhesive is not particularly limited and generally known method for applying (or coating with) a hot melt adhesive may be used. Such application methods may be broadly divided into contact application and noncontact application. The "contact application" refers to an application method in which an ejection machine is brought into contact with a member or a film when the hot melt adhesive is applied. The "noncontact application" refers to an application method in which an ejection machine is not brought into contact with a member or a film when the hot melt adhesive is applied. Examples of the contact application method include slot coater coating and roll coater coating. Examples of the noncontact application method can include spiral coating which allows coatings in the form of a spiral, omega coating and control seam coating which allows coatings in the form of a wave, slot spray coating and curtain spray coating which allows coatings in the form of a plane, and dot coating which allows coatings in the form of dots, bead coating which allows coating in the form of a line.

[0099]

By the application method, the hot melt adhesive of the present invention is applied to various substrates at about 180°C.

[0100]

The hot melt adhesive of the present invention is widely applicable in, for example, electronic components, woodworking, construction materials, hygienic materials, and paper products. The hot melt adhesive of the present invention can be suitably used in manufacturing paper products, and is particularly useful as hot melt adhesive for paper products.

[0101]

The paper product of the present invention is a paper product which is manufactured using the hot melt adhesive. The types of the paper products are not specifically limited as long as the hot melt adhesive is used in manufacturing, specifically including, for example, book binding, calendars, corrugated

cardboards, and cartons.

[0102]

One preferred embodiment of paper products of the present invention is a carton whose surface is coated with an agent for imparting high-grade feeling to a packaging of products.

Examples

[0103]

For the purpose of describing the present invention in more details and more specifically, the present invention will be described below using Examples. These Examples are for describing the present invention, and do not limit the present invention in any way.

[0104]

Components blended in hot melt adhesives are shown below.

[0105]

<(A) Polar functional group-modified copolymers>

(Al) Polar functional group -modified conjugated die ne -based copolymers (Al-1) amino group-modified SEBS ("DYNARON 8630P" manufactured by

JSR)

(Al-2) amino group-modified SEBC ("DYNARON 4630P" manufactured by

JSR)

[0106]

(A2) Polar functional group -modified ole fin-based polymers

(A2-1) Ethylene/methyl acrylate/glycidyl methacrylate copolymerized resin ("BONDFAST 7M" (trade name) manufactured by Sumitomo Chemical Co., Ltd.)

(A2-2) Ethylene/l-octene maleic acid copolymer ("AFFINITY GA1000R" made by Dow Chemical Company)

(A2-3) Ethylene/ethyl acrylate maleic acid copolymer ("BONDINE HX8210" made by Arkema K.K.)

[0107]

<(B) Aliphatic polyester-based resins>

(Bl) Poly LD -lactic acid resin ("4060D" (trade name) manufactured by Nature Works LLC)

(B2) Poly(butylene succinate) resin ("AD92W" (trade name) manufactured by Mitsubishi Chemical Corporation)

[0108]

<(C) Olefin-based polymer>

(CI) Propylene/ethylene/l-butene copolymer ("VESTO PLAST 703" made by Evonik Degussa Co., Ltd.)

(C2) Propylene/ethylene/l-butene copolymer ("VESTO PLAST 708" made by Evonik Degussa Co., Ltd.)

(C3) Ethylene/octene copolymer ("AFFINITY GA1950" made by Dow

Chemical Company)

(C4) Ethylene/vinyl acetate copolymer ("ULTRASEN 722" made by Tosoh Corporation)

(C5) Ethylene/methyl methacrylate polymer ("ACRYFT CM5022" made by Sumitomo Chemical Co., Ltd.)

(C6) Polypropylene ("L-MODU S400" made by Idemitsu Kosan Co., Ltd.) (C7) Polyethylene ("PETROSEN 249" made by Tosoh Corporation)

[0109]

<(D) Tackifier resins> (Dl) a hydrogenated aromatic petroleum resin ("I-marv P100" (trade name) manufactured by Idemitsu Kosan Co., Ltd.)

(D2) C5-based petroleum resin ("EAST TACK H-100W" made by Eastman Chemical Company)

[0110]

<(E) Wax>

(El) Fischer-Tropsch wax (SASOL H8 made by Sasol Wax Limited)

(E2) Maleic acid modified Fischer-Tropsch wax (SASOL H105 made by Sasol Wax Limited)

(E3) Paraffin wax (PARAFFIN WAX- 150 made by Nippon Seiro Co., Ltd.)

[0111]

<(F) Antioxidants>

(Fl) Antioxidant (AO-60 manufactured by ADEKA CORPORATION)

[0112]

These components were blended in blending proportions shown in Table 1 and Table 2, and melted and mixed at about 160°C over about 3 hours using a universal stirrer to produce the hot melt adhesives of Examples 1 to 12 and Comparative Examples 1 to 6. The numerical values regarding the composition (blend) of the hot melt adhesives shown in Tables 1 and 2 are all parts by weight.

[0113]

The thermal stability and the adhesion to various kinds of substrates were evaluated for each of the hot melt adhesives in Examples and Comparative Examples. The summary of each evaluation is described below.

[0114]

<Adhesion: coated carton>

(Sample preparation)

A hot melt adhesive melted at 180°C was applied to a carton having the surface coated with an agent. The application amount was 2 g/m.

[0115]

The cartons were laminated under conditions with a setting time of 1 second, an open time of 1 second, and a pressing pressure of 1 kg/25 cm ² . The lamination was cut into a sample with a length of 5 cm and a width of 2.5 cm for evaluation.

(Evaluation method) The prepared sample was aged in a thermostatic chamber set at 23°C with a humidity of 50% for 24 hours, and then the laminated cartons were forcibly detached by hand under the same atmosphere. The proportion of broken area to the entire adhesion area of the carton was defined as material breakage rate, and the state of breakage was evaluated.

[0116]

oo: Material breakage rate was more than 80%.

o: Material breakage rate was 65 to 80%.

X· Material breakage rate was less than 65%.

[0117]

<Adhesion: Corrugated cardboard>

(Sample preparation)

A hot melt adhesive melted at 180°C was applied to K liner corrugated cardboards with an application amount of 2 g/m, and the corrugated cardboards were laminated under conditions with a setting time of 10 seconds, an open time of 3 seconds, and a pressing pressure of 1 kg/25 cm ² . The lamination was cut into a sample with a length of 5 cm and a width of 2.5 cm for evaluation.

(Evaluation method)

The prepared sample was aged in a thermostatic chamber set at 23°C with a humidity of 50% for 24 hours, and then forcibly detached by hand under the same atmosphere. The proportion of broken area to the entire adhesion area of K liner corrugated cardboard was defined as material breakage rate (proportion of broken material), and the state of breakage was evaluated.

[0118]

oo: Material breakage rate was more than 80%.

o: Material breakage rate was 60% to 80%.

Material breakage rate was 40% or more and less than 60%.

x: Material breakage rate was less than 40%.

[0119]

<Adhesion: PET>

(Sample preparation)

A hot melt adhesive melted at 180°C was applied to a polyethylene terephthalate (PET) film. The application amount was 2 g/m. The PET films were laminated under conditions with a setting time of 1 second, an open time of 1 second, and a pressing pressure of 1 kg/25 cm ² . The lamination was cut into a sample with a length of 5 cm and a width of 2.5 cm for evaluation.

(Evaluation method)

The prepared sample was aged in a thermostatic chamber set at 23°C with a humidity of 50% for 24 hours, and then a 90° peel test was performed under the same atmosphere with a tensile tester.

[0120]

oo: 1 kg/inch or more

o: 0.5 kg/inch or more and less than 1 kg/inch

x: less than 0.5 kg/inch

[0121]

<Stringing properties>

A hot melt adhesive was intermittently applied to an adherend disposed 20 cm away in vertical direction from the tip of a hot melt gun. The state of a falling object between the hot melt gun and the adherend was visually observed for evaluation of stringing properties.

(Measurement conditions)

Temperature setting: 180°C for all of tank, hose, and nozzle

Nozzle diameter: 14/1000 inch

Nozzle: 1-orifice (number of discharging port: 1) and 4-orifice (number of discharging port: 4)

Application pressure: 0.4 MPa

Application shot number: 350 shots/5 minutes for 1-orifice, and 70 shots/1 minute for 4-orifice

00: Falling objects were in particle form.

o: Falling objects were mostly in particle form and sparsely in string form.

Δ: Falling objects were mixed in particle form and in string form,

x: Falling objects were in string form.

[0122]

<Thermal Stability>

The thermal stability was visually determined by a change in appearance after 20 g of the hot melt adhesive was placed in a 70 mL glass bottle and allowed to stand in a dryer oven at 180°C for 24 hours.

[0123] oo: Phase separation, carbonized product or ring (a degraded product of the hot melt adhesive deposited in a ring shape) was not observed.

o: Phase separation, carbonized product and a ring were very slightly observed.

Δ: Phase separation, carbonized product and a ring were slightly observed, x: Phase separation, carbonized product and a ring were observed.

[0124]

[Table 1]

Ex.= Example

[0125] [Table 2]

ConvEx. = Comparative Example

[0126]

As shown in Table 1, the hot melt adhesives in Examples 1 to 12 include all the five components of the (A) component, the (B) component, the (C) component, the (D) component, and the (E) component, so as to have reduced stringing and excellent adhesion to paper substrates such as cartons and corrugated cardboards and adhesion to PET films. Furthermore, the hot melt adhesives in Examples 1 to 12 have excellent thermal stability due to good compatibility among the respective components, and are environmentally preferred due to inclusion of the component (B).

[0127]

As shown in Table 2, the hot melt adhesives in Comparative Examples 1 to 6 lack any of the (A) component, the (B) component, the (C) component, the (D) component, and the (E) component. All of the hot melt adhesives in Comparative Examples 1 to 6 caused "stringing". The results proved that the inclusion of all the 5 components (A) to (E) allows for reduction in stringing. Furthermore, the hot melt adhesives in Comparative Examples have inferior adhesion and thermal stability compared to the ones in Examples.

Industrial Applicability

[0128]

The present invention provides a hot melt adhesive and a paper product to which the hot melt adhesive is applied. Among the paper products, the present invention is particularly effective in products made from thick paper such as corrugated cardboards and cartons.