DESCRIPTION

MOISTURE-CURABLE HOT MELT ADHESIVE

Cross-Reference to Related Applications

[0001]

This application claims benefit under Paris Convention of Japanese Patent Application No. 2013-245045 filed on November 27, 2013, incorporated herein by reference in its entirety .

Technical Field

[0002]

The present invention relates to a moisture-curable hot melt adhesive, and particularly to a moisture-curable hot melt adhesive which has high initial adhesive strength and long open time.

Background Art

[0003]

A moisture-curable hot melt adhesive is employed in various fields such as building interior materials (or building materials) and electronic materials. The

moisture-curable hot melt adhesive contains a urethane prepolymer having an isocyanate group at the end. Initial adhesion is generally produced by coating both adherends (or a base material and an adherend) with the adhesive in a hot molten state, followed by cooling and solidifying.

Thereafter, adhesive force, heat resistance, and the like are improved by moisture curing caused by cross-linking isocyanate groups with moisture in atmospheric air, and increasing the molecular weight of the urethane prepolymer.

[0004]

One of performances (or properties) required to the moisture-curable hot melt adhesive includes initial

adhesive strength (initial cohesive force) . Means for increasing the initial adhesive strength includes a method in which a thermoplastic resin is mixed in the moisture- curable hot melt adhesive, and a method in which high crystallinity is imparted to the urethane prepolymer using a polyesterpolyol .

[0005]

Patent Document 1 discloses that initial adhesive strength of a urethane hot melt adhesive is improved by adding an acrylic resin (see [claim 8] and [0024] of Patent Document 1) . However, the initial adhesive strength of the moisture-curable hot melt adhesives of Patent Document 1 was not sufficiently satisfactory to users.

[0006] Patent Document 2 discloses a moisture-curable hot melt adhesive to which an acrylic polymer having an alicyclic structure was added. In recent years, users' requirements for the moisture-curable hot melt adhesive become more severe. When a hard board such as a melamine decorative board is laminated using the moisture-curable hot melt adhesive of Patent Document 2, the melamine decorative board may sometimes cause lifting due to the insufficient initial adhesive strength.

[0007]

Patent Document 3 discloses that a moisture-curable hot melt adhesive containing a urethane prepolymer having high crystallinity obtained using a polyesterpolyol is produced and this adhesive is useful for lamination of a melamine decorative board (see [claim 1] and [0005] of

Patent Document 3). The moisture-curable hot melt adhesive of Patent Document 3 exhibits very short open time, although the initial adhesive strength is sufficiently improved. The short open time of the moisture-curable hot melt adhesive will lead to early solidification of the adhesive, which makes it difficult to laminate a base material and an adherend.

[0008]

When a hard board such as a melamine decorative board is laminated, an adhesive having sufficiently high initial adhesive strength is required. However, since the adhesive having high initial adhesive strength exhibits short open time, there has never been found a moisture-curable hot melt adhesive which is excellent in balance between both performances, and is also excellent in initial adhesive strength and workability.

[0009]

Patent Document 1: JP 2011-202172 A

Patent Document 2: JP 2012-241182 A

Patent Document 3: JP 2010-084109 A

Summary of Invention

Problems to be Solved by the Invention

[0010]

The present invention has been made so as to solve such a problem, and an object thereof is to provide a moisture-curable hot melt adhesive which has high initial adhesive strength and long open time.

Means for Solving the Problems

[0011]

The present inventors have intensively studied and found, surprisingly, that it is possible to obtain a moisture-curable hot melt adhesive, which is excellent not only in initial adhesive strength but also in adhesive strength after curing, and also has open time suitable for operation (work or process) , by using a specific amount of a specific monomer diol . Thus, the present invention has been completed.

[0012]

That is, the present invention provides, in an aspect, a novel moisture-curable hot melt adhesive obtainable by using :

(A) an acrylic polymer having an alicyclic structure;

(B) a polyetherpolyol ;

(C) a crystalline polyesterpolyol ;

(D) dodecanediol ; and

an isocyanate compound, wherein

the (D) dodecanediol is used in an amount of 0.5 to 4.0 part by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the

isocyanate compound.

[0013]

In an embodiment of the present invention, a moisture- curable hot melt adhesive, wherein the (A) acrylic polymer having an alicyclic structure is used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the

isocyanate compound, is provided.

In another embodiment of the present invention, a moisture-curable hot melt adhesive, wherein the isocyanate compound is used in an amount of 15 to 35 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound, is provided.

[0014]

In a preferred embodiment of the present invention, a moisture-curable hot melt adhesive, wherein the (B) polyetherpolyol includes a polyoxyalkylene glycol having a number average molecular weight of 400 to 8,000, is provided.

In a more preferred embodiment of the present

invention, a moisture-curable hot melt adhesive, which has plural melting points after curing, at least one of the melting points existing in a temperature range of 50 to 100 °C and at least one of the melting points existing in a temperature range of 150 to 200 °C, is provided.

Effects of the Invention

[0015]

The moisture-curable hot melt adhesive of the present invention is obtainable by using (A) an acrylic polymer having an alicyclic structure,- (B) a polyetherpolyol ; (C) a crystalline polyesterpolyol ,- (D) dodecanediol ; and an isocyanate compound; and the (D) dodecanediol is used in an amount of 0.5 to 4.0 part by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound, and thus the obtained moisture- curable hot melt adhesive is excellent in initial adhesive strength (initial cohesive force) and has a certain length of open time, and is also excellent in adhesion after curing.

[0016]

The moisture-curable hot melt adhesive of the present invention is more excellent in balance between initial adhesive strength and open time, when the (A) acrylic polymer having an alicyclic structure is used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound.

The moisture-curable hot melt adhesive of the present invention is more excellent in balance between coatability (viscosity) and the amount of the remaining isocyanate, when the isocyanate compound is used in an amount of 15 to 35 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the

isocyanate compound.

[0017]

The moisture- curable hot melt adhesive of the present invention is excellent in balance between coatability

(viscosity) and adhesive strength after curing, when the (B) polyetherpolyol includes a polyoxyalkylene glycol having a number average molecular weight of 400 to 8,000.

The moisture-curable hot melt adhesive of the present invention is excellent in balance between initial adhesive strength and length of open time, when the adhesive has plural melting points after curing, and at least one of the melting points exists in a temperature range of 50 to 100 °C and at least one of the melting points exists in a

temperature range of 150 to 200 °C.

[0018]

When base materials are laminated each other using the moisture-curable hot melt adhesive of the present

invention, because of excellent balance between length of the open time and the initial adhesive strength, it is easy to perform a coating operation and the adhesive is quickly cured after the coating operation, and thus the base material becomes less likely to peel off after curing the adhesive. The moisture-curable hot melt adhesive of the present invention is suitable to laminate a melamine decorative board in the field of building materials.

Brief Description of Drawings

[0019]

Fig. 1 shows a DSC chart when a melting point of a moisture-curable hot melt adhesive according to the present invention (Example 7) was measured after curing.

Fig. 2 shows a DSC chart when a melting point of a moisture-curable hot melt adhesive of a prior art

(Comparative Example 3) was measured after curing.

Description of Embodiments

[0020]

The moisture-curable hot melt adhesive according to the present invention is obtainable by using (A) an acrylic polymer having an alicyclic structure; (B) a

polyetherpolyol ,- (C) a crystalline polyesterpolyol ; (D) dodecanediol , and an isocyanate compound, and contains a "urethane prepolymer having an isocyanate group at the end" .

[0021]

As used herein, the "urethane prepolymer having an isocyanate group at the end" usually refers to those interpreted as a "urethane prepolymer" (hereinafter also simply referred to as a "urethane prepolymer") , and is obtainable by reacting (B) a polyetherpolyol ; (C) a

crystalline polyesterpolyol ; and (D) dodecanediol , and an isocyanate compound according to a conventionally known method .

[0022]

In the present invention, the (D) dodecanediol is used in an amount of 0.5 to 4.0 parts by weight based on 100 parts by weight of the total of the components (A) to (D) and the isocyanate compound. The (D) dodecanediol is preferably used in an amount of 0.5 to 3.5 parts by weight, more preferably 1.0 to 3.5 parts by weight, and most preferably 1.5 to 3.5 parts by weight. When the component (D) is used in the amount within the above-mentioned range, the initial adhesive strength of the moisture-curable hot melt adhesive is improved, which leads to more satisfactory balance between the magnitude of the initial adhesive strength and the open time, resulting in more suitable workability.

[0023]

In the present invention, the component (A) is

preferably used in an amount of 5 to 20 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound. The component (A) is more preferably used in an amount of 10 to 20 parts by weight, particularly preferably 14 to 20 parts by weight, and most preferably 15 to 18 parts by weight. When the component (A) is used in the amount within the above range, the moisture-curable hot melt adhesive is more excellent in balance between the initial adhesive strength and the open time.

[0024]

In the present invention, the isocyanate compound is preferably used in an amount of 15 to 35 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound. The isocyanate compound is more preferably used in an amount of 15 to 30 parts by weight, particularly preferably 15 to 25 parts by weight, and most preferably 17 to 22 parts by weight. When the isocyanate compound is used in the amount within the above range, the viscosity of the moisture- curable hot melt adhesive can be a value within an optimum range for coating, thus decreasing the amount of the remaining isocyanate compound.

[0025]

In the present invention, the (A) acrylic polymer having an alicyclic structure refers to an acrylic polymer based on an ester of acrylic acid and/or methacrylic acid, and is a polymer having an alicyclic structure. Generally, a monomer comprising a monomer having an alicyclic

structure and an ethylenic double bond (hereinafter also referred to as an " (a) monomer having an alicyclic

structure") is subjected to radical polymerization (or addition polymerization) , thus making it possible to preferably obtain the acrylic polymer having an alicyclic structure in the side chain. When the monomer contains an aromatic ring, it is not included in the monomer having an alicyclic structure.

[0026]

Such (a) monomer having an alicyclic structure and an ethylenic double bond is preferably an (a) (meth) acrylic acid derivative having an alicyclic structure (hereinafter also referred to as an "(a) (meth) acrylic acid

derivative") .

[0027]

The (a) (meth) acrylic acid derivative includes, for example, (meth) acrylates having an alicyclic structure, such as cyclohexyl (meth) acrylate , isobornyl

(meth) acrylate, and dicyclopentanyl (meth) acrylate , and is preferably at least one selected from these

(meth) acrylates . Particularly, isobornyl methacrylate and cyclohexyl methacrylate are preferable, and cyclohexyl methacrylate is most preferable. The (A) acrylic polymer will have an alicyclic structure based on a chemical structure derived from these alicyclic compounds.

[0028]

As used herein, the " (meth) acrylic acid derivative" means both a methacrylic acid derivative and an acrylic acid derivative. When simply referred to as a "methacrylic acid derivative", methacrylic acid per se may be included. When simply referred to as an "acrylic acid derivative", acrylic acid per se may be included.

[0029]

In the present invention, the (A) acrylic polymer is obtainable by homopolymerizing the (a) (meth) acrylic acid derivative, which is the above-mentioned (a) monomer having an alicyclic structure, and is preferably a copolymer of the (a) (meth) acrylic acid derivative with the other monomer having an ethylenic double bond (hereinafter also referred to as the " (a' ) other monomer") .

[0030]

As used herein, the " (a' ) other monomer having an ethylenic double bond" refers to a monomer other than the monomer having an alicyclic structure, and examples of such other monomer include a monomer having an aromatic ring and an ethylenic double bond (hereinafter also referred to as a "monomer having an aromatic ring") , a monomer having no cyclic structure and having an ethylenic double bond

(hereinafter also referred to as a "monomer having no cyclic structure", and the like.

[0031]

The (a' ) other monomer having an ethylenic double bond is preferably a monomer having no cyclic structure, and more preferably a (meth) acrylic acid derivative having no cyclic structure.

[0032]

In a preferred embodiment of the present invention, the (A) acrylic polymer may be produced by copolymerizing the monomer having an alicyclic structure with the

(meth) acrylic acid derivative having no cyclic structure.

[0033]

Examples of the (meth) acrylic acid derivative having ho cyclic structure include an (a') (meth) acrylic acid derivative which may have a chain- like structure (capable of being branched) in which carbon atoms are connected in a chain-like state. Such (a') (meth) acrylic acid derivative is distinguishable as follows:

an (a') (meth) acrylic acid derivative which has an alkyl group having 6 or more carbon atoms, an (a') (meth) acrylic acid derivative which has an alkyl group having less than 6 carbon atoms,

(a') (meth) acrylic acid, and

the (a') other (meth) acrylic acid derivative.

[0034]

Examples of the (a') (meth) acrylic acid derivative which has an alkyl group having 6 or more carbon atoms include a (meth) acrylic acid ester such as n-hexyl

(meth) acrylate , n-octyl (meth) acrylate , 2-ethylhexyl

(meth) acrylate , decyl (meth) acrylate , dodecyl (or lauryl) (meth) acrylate , and stearyl (meth) acrylate ; and

a (meth) acrylic acid amide (or (meth) acrylamides) such as N-hexylacrylic acid amide and N-octylacrylic acid amide.

[0035]

The (meth) acrylic acid ester is preferably a

(meth) acrylic acid alkyl ester, and the (meth) acrylic acid amide is preferably a (meth) acrylic acid alkylamide .

[0036]

The alkyl group having 6 or more carbon atoms may be either a linear alkyl group (for example, n-hexyl and n- octyl, etc.) or a branched alkyl group (for example, 2- ethylhexyl , etc . ) , or may be an alkyl group having a substituent (for example, hydroxyl group, an amino group, carboxyl group, glycidyl group, (meth) acryloyl group, and methoxy group, etc.) or not, and preferably has no

substituent .

[0037]

The (a') (meth) acrylic acid derivative which has an alkyl group having 6 or more carbon atoms preferably includes the (meth) acrylic acid ester which has an alkyl group having 6 or more carbon atoms. These (meth) acrylic acid derivatives may be used alone, or a plurality of

(meth) acrylic acid derivatives may be used in combination.

[0038]

Examples of the (a') (meth) acrylic acid derivative which has an alkyl group having less than 6 carbon atoms include :

a (meth) acrylic acid ester such as methyl (meth)acryl- ate, ethyl (meth) acrylate , n-propyl (meth) acrylate ,

isopropyl (meth) acrylate , n-butyl (meth) acrylate , isobutyl (meth) acryl-ate , and t-butyl (meth) acrylate ;

a (meth) acrylic acid amide such as N, N-dimethylacrylic acid amide, N-butylacrylic acid amide, and N-propylacrylic acid amide; and

the other derivative such as 2 - (meth) acryloyloxyethyl- succinic acid.

[0039]

The (meth) acrylic acid ester is preferably a (meth) acrylic acid alkyl ester, and the (meth) acrylic acid amide is preferably a (meth) acrylic acid alkylamide.

[0040]

The alkyl group having less than 6 carbon atoms may be either an alkyl group having a chain- like structure (for example, methyl, ethyl and propyl, etc.), or a linear alkyl group (for example, n-propyl and n-butyl, etc.) , or a branched alkyl group (for example, isobutyl and t-butyl, etc.) , or may be an alkyl group having a substituent (for example, hydroxyl group, an amino group, carboxyl group, glycidyl group, (meth) acryloyl group, and methoxy group, etc.) or not, and preferably has no substituent.

[0041]

The (a') (meth) acrylic acid derivative which has an alkyl group having less than 6 carbon atoms preferably includes the (meth) acrylic acid ester which has an alkyl group having less than 6 carbon atoms. These (meth) acrylic acid derivatives may be used alone, or a plurality of

(meth) acrylic acid derivatives may be used in combination.

[0042]

The (a') (meth) acrylic acid includes at least one selected from acrylic acid and methacrylic acid. Examples of the "(a') other (meth) acrylic acid derivative" include acrylonitrile , methacrylonitrile , acrylamide, methacrylamide , and the like. These other

(meth) acrylic acid derivatives may be used alone, or a plurality of other (meth) acrylic acid derivatives may be used in combination.

[0043]

In the present invention, the (A) acrylic polymer may contain an aromatic ring as long as the objective moisture- curable hot melt adhesive is obtainable, and the aromatic ring is provided by using a monomer having an aromatic ring.

Examples of the monomer having an aromatic ring include :

a (meth) acrylic acid aryl ester such as benzyl (meth) - acrylate, phenoxyethyl (meth) acrylate , and 4 -hydroxyphenyl (meth) acrylate ;

a (meth) acrylic acid amide such as 3 , 5 -dimethyl -4 - hydroxybenzyl (meth) acrylic acid amide;

phenyl ester and/or benzyl ester of crotonic acid, maleic acid, fumaric acid, and itaconic acid etc; and

styrene, alkylstyrene , and the like.

[0044]

In an embodiment of the present invention,

the (A) acrylic polymer includes a copolymer of the (a) (meth) acrylic acid derivative which is a monomer having an alicyclic structure with the (a') (meth) acrylic acid derivative which may have a chain- like structure,

the (a) (meth) acrylic acid derivative preferably includes cyclohexyl (meth) acrylate, and more preferably cyclohexyl methacrylate , and

the (a') (meth) acrylic acid derivative preferably includes at least one selected from the group consisting of methyl (meth) acrylate , butyl (meth) acrylate , hydroxyethyl (meth) acrylate , and (meth) acrylic acid, more preferably at least one selected from the group consisting of methyl methacrylate, butyl methacrylate, and methacrylic acid, and particularly preferably methyl methacrylate, butyl

methacrylate, and methacrylic acid.

[0045]

Therefore, the (A) acrylic polymer in the present invention most preferably includes a copolymer of

cyclohexyl methacrylate, methyl methacrylate, butyl

methacrylate, and methacrylic acid.

[0046]

The method of producing the (A) acrylic polymer can be used without any particular limitation as long as the objective moisture-curable hot melt adhesive is obtainable. Usually, the acrylic polymer can be produced by using solution polymerization, bulk polymerization, suspension polymerization, and the like.

[0047]

In the present invention, the glass transition

temperature (Tg) of the (A) acrylic polymer is preferably 60 °C or higher, preferably 160 °C or lower, more preferably 70 to 120 °C, and particularly preferably 80 °C to 100 °C. When the Tg is 60 °C or higher, the initial adhesive

strength of the finally obtained "moisture-curable hot melt adhesive" is improved.

[0048]

Since the (A) acrylic polymer is obtained by

polymerizing a monomer containing the " (a) monomer having an alicyclic structure" and, if necessary, the " (a' ) other monomer having no alicyclic structure", the Tg of the (A) acrylic polymer is determined by kinds of the (a) monomer and the " (a' ) other monomer" used optionally, and a mixing ratio (parts by weight) of the (a) monomer to the " (a' ) other monomer" .

[0049]

In order to design the acrylic polymer having desired Tg, both the " (a) monomer" and the " (a' ) other monomer" are generally used. A glass transition temperature (Tg) of a copolymer which is obtained by polymerizing a monomer mixture containing the (a) monomer and the (a' ) other monomer is considered. Taking a glass transition

temperature of a homopolymer of each monomer of the (a) monomer and the (a' ) other monomer in the monomer mixture thereof (hereinafter also referred to as a "Tg of a

homopolymer") into consideration, a mixing ratio (parts by weight) of the (a) monomer to the " (a' ) other monomer" is decided.

[0050]

Specifically, the "Tg of an acrylic polymer" can be determined by calculating using a calculation formula (1) of a theoretical Tg of the acrylic polymer:

1/Tg = Cl/Tgl + C2/Tg2 + · · · + Cn/Tgn: (1)

where Tg in the calculation formula (1) denotes a

theoretical Tg of the acrylic polymer, Cn denotes a weight percentage of the nth monomer n contained in the monomer mixture, Tgn denotes a Tg of a homopolymer of the nth monomer n, and n denotes the number of monomers

constituting the acrylic polymer and is a positive integer.

[0051]

Values disclosed in a literature can be used as the Tg of the homopolymer of the monomer. It is possible to refer, as such literature, for example, the following literatures: Acrylic Ester Catalogue of Mitsubishi Rayon Co., Ltd. (1997 Version); and edited by Kyozo Kitaoka, "Shin Kobunshi Bunko 7, Guide to Synthetic Resin for

Coating Material", Kobunshi Kankokai, published in 1997, pp.168-169.

[0052]

An example of design of the Tg of the above-mentioned acrylic polymer will be described below.

When cyclohexyl (meth) acrylate (hereinafter also referred to as "CHMA") of which homopolymer has a Tg of 83 °C is used as the (a) monomer in an amount of 40 to 67 parts by weight based on 100 parts by weight of the monomer mixture, it is possible to use, as the "(a') other

monomer", for example, a monomer of which homopolymer has a Tg of 95 °C or higher in an amount of 20 to 30 parts by weight based on 100 parts by weight of the monomer mixture, and a monomer of which homopolymer has a Tg of -50 °C or lower in an amount of 13 to 30 parts by weight based on 100 parts by weight of the monomer mixture.

[0053]

More specifically, it is possible to obtain an (A) acrylic polymer showing a theoretical Tg of 10 to 60 °C by using 40 to 67 parts by weight of the above-mentioned CHMA, 20 to 30 parts by weight of methyl methacrylate

(hereinafter also referred to as "MMA", whose homopolymer has a Tg of 105 °C) and/or styrene (hereinafter also referred to as "St", whose homopolymer has a Tg of 100°C), of which homopolymers have a Tg of 95 °C or higher as the "(a') other monomer", and 13 to 30 parts by weight of 2- ethylhexyl acrylate (hereinafter also referred to as

"2EHA", whose homopolymer has a Tg of -85 °C) and/or butyl acrylate (hereinafter also referred to as "BA", whose homopolymer has a Tg of -54 °C) , of which homopolymers have a Tg of -50°C or lower as the "(a') other monomer", and then polymerizing the mixture of these monomers.

[0054]

Examples of the "(a) monomer" include, in addition to CHMA, for example, dicyclopentanyl methacrylate (whose homopolymer has a Tg of 175°C) . Examples of the (a') other monomer include, in addition to MMA and St, for example, acrylamide (whose homopolymer has a Tg of 153 °C), acrylic acid (hereinafter also referred to as "AA", whose

homopolymer has a Tg of 106°C), methacrylic acid

(hereinafter also referred to as "MAA", whose homopolymer has a Tg of 130°C), acrylonitrile (whose homopolymer has a Tg of 100°C) , and maleic acid (whose homopolymer has a Tg of 130°C) . Examples of the "monomer of which homopolymer has a Tg of -50 °C or lower" include, in addition to 2EHA and BA, dodecyl methacrylate (whose homopolymer has a Tg of -65°C) . [0055]

A value disclosed in Acrylic Ester Catalogue of

Mitsubishi Rayon Co., Ltd. (1997 Version) was used as the value of the Tg of the homopolymer of CHMA, and values disclosed in "Shin Kobunshi Bunko 7, Guide to Synthetic

Resin for Coating Material", Kobunshi Kankokai, published in 1997, pp.168-169 were used for MMA, St, 2EHA, BA, AA, MAA, acrylamide, acrylonitrile , maleic acid, and dodecyl methacrylate .

[0056]

In the present invention, weight average molecular weight (Mw) of the (A) acrylic polymer having an alicyclic structure is preferably from 5,000 to 1,000,000, more preferably 30,000 to 250,000, and particularly preferably from 40,000 to 60,000. When the Mw of the acrylic polymer (A) is within the above range, a moisture-curable hot melt adhesive having more excellent initial adhesive strength is obtained.

[0057]

As used herein, the Mw refers to a value measured by gel permeation chromatography (GPC) . More specifically, the Mw refers to a value measured by using the below- mentioned GPC apparatus and measuring method. 600E

manufactured by Waters Corporation was used as a GPC apparatus, and RI (Waters410) was used as a detector. Two LF-804 manufactured by Shodex were used as a GPC column. A sample was dissolved in tetrahydrofuran and the obtained solution was allowed to flow at a flow rate of 1.0 ml/min and a column temperature of 40 °C to give a observed data, and then the objective Mw was determined by conversion of the observed data using a calibration curve which is obtained by using polystyrene having a monodisperse

molecular weight as a standard reference material.

[0058]

In the present invention, the (B) polyetherpolyol is not particularly limited, as long as it has a number average molecular weight (Mn) of 400 or more and preferably 8,000 or less as measured by the previous GPC measurement, is usually interpreted as a polyetherpolyol, and the objective moisture-curable hot melt adhesive of the present invention is obtainable. When the number average molecular weight of the (B) polyetherpolyol is 400 or more, the moisture-curable hot melt adhesive exhibits more

satisfactory balance between the initial cohesive force and the open time, and thus the adhesion after curing is improved.

[0059]

Examples of the (B) polyetherpolyol include polyoxy- tetramethylene glycol (PTMG) , polyoxypropylene glycol (PPG), polyoxyethylene glycol (PEG), and the like. The polyetherpolyol more preferably includes polyoxypropylene glycol. These polyetherpolyols can be used alone or in combination.

[0060]

In the present invention, the component (B) is preferably used in an amount of 10 to 50 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound. The component (B) is more preferably used in an amount of 20 to 50 parts by weight, particularly preferably 25 to 40 parts by weight, and most preferably 27 to 35 parts by weight. When the component (B) is used in the amount within the above range, the moisture-curable hot melt adhesive is more excellent in balance between the initial adhesive strength and the open time of the moisture-curable hot melt

adhesive .

[0061]

In the present invention, the (C) crystalline

polyesterpolyol generally refers to those called a

crystalline polyesterpolyol, and more particularly refers to a polyesterpolyol having a melting point.

In the present invention, the melting point of the crystalline polyesterpolyol is preferably 55 °C or higher, preferably 120 °C or lower, more preferably 60 °C or higher, more preferably 100 °C or lower, and most preferably 60 °C to 75 °C. When the melting point is 55 °C or higher, the initial adhesive strength of the moisture-curable hot melt adhesive is more improved.

[0062]

As used herein, the melting point means a value measured by a differential scanning calorimeter (DSC) . By the differential scanning calorimeter, difference in calorie between a measurement sample and a standard

reference material is measured and the melting point of the measurement sample is calculated. Specifically, a peak top of an endothermic peak observed was regarded as the melting point, when the temperature is raised from -50°C to 220°C at a rate of 10°C/minute.

The urethane prepolymer according to the present invention may have a chemical structure derived from the amorphous polyesterpolyol as long as the prepolymer has a chemical structure derived from the crystalline

polyesterpolyol .

[0063]

The amorphous polyesterpolyol generally refers to those called an amorphous polyesterpolyol, and more particularly refers to a polyesterpolyol which has no melting point and has only a glass transition temperature.

The crystalline polyesterpolyol is easily

distinguished from the amorphous polyesterpolyol even by DSC. The melting point of the crystalline polyesterpolyol is observed as an endothermic peak during the temperature rise by the measurement of DSC, and is observed as an exothermic peak during the temperature fall.

[0064]

Since the melting point of the amorphous

polyesterpolyol is not clearly observed when measuring by DSC, it is possible to distinguish from the crystalline polyesterpolyol .

In general, the crystalline polyesterpolyol is white opaque in a solid state, whereas the amorphous polyesterpolyol is transparent .

[0065]

The "polyol" according to the present invention includes a crystalline polyesterpolyol and a

polyetherpolyol , and may also include, for example, an amorphous polyesterpolyol .

Examples of the crystalline polyesterpolyol and amorphous polyesterpolyol include an aliphatic

polyesterpolyol and an aromatic polyesterpolyol. [0066]

The aliphatic polyesterpolyol is obtainable by the reaction between an aliphatic dicarboxylic acid and a diol . The diol is preferably a low molecular weight diol.

Examples of the diol include low molecular weight diols having 2 to 12 carbon atoms, such as ethylene glycol, 1-methylethylene glycol, 1 -ethylethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentyl glycol, 2- methyl -1, 3 -propanediol, cyclohexanedimethanol , and 2,4- dimethyl-1 , 5 -pentanediol . These diols can be used alone or in combination.

As used herein, the low molecular weight diol has a number average molecular weight of less than 400.

Examples of the aliphatic dicarboxylic acid include adipic acid, sebacic acid, azelaic acid, and decamethylene- dicarboxylic acid. These aliphatic dicarboxylic acids may be used alone, or two or more aliphatic dicarboxylic acids may be used in combination. Examples of the aliphatic polyesterpolyol includes polyhexamethylene adipate (PHMA) , polyhexamethylene sebacate (PHMS) , polyhexamethylene dodecanate (PHMD) , and polybutylene adipate (PBA) .

[0067]

The aromatic polyesterpolyol is preferably obtained by reacting an aromatic poly- (or di-) carboxylic acid with the above-mentioned diol . Examples of the aromatic poly- (or di-) carboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, and the like. These aromatic poly- (or di-) carboxylic acids may be used alone, or two or more aromatic poly- (or di-) carboxylic acids may be used in combination. Examples of the aromatic

polyesterpolyol include polyalkylene phthalates,

polyalkylene isophthalates , and polyalkylene

terephthalates .

[0068]

In the present invention, the component (C) is

preferably used in an amount of 10 to 50 parts by weight based on 100 parts by weight of the total weight of the components (A) to (D) and the isocyanate compound. The component (C) is more preferably used in an amount of 10 to 40 parts by weight, particularly preferably 15 to 40 parts by weight, and most preferably 18 to 30 parts by weight. When the component (C) is used in the amount within the above range, the moisture-curable hot melt adhesive is more excellent in balance between the initial adhesive strength and the open time.

[0069]

In the present invention, (D) dodecanediol which is a monomer diol is used in the production of the moisture- curable hot melt adhesive. The (D) dodecanediol is not particularly limited to bonding patterns of carbon

skeletons and substitution positions of hydroxyl groups as long as the moisture-curable hot melt adhesive of the present invention can be produced. For example, the dodecanediol may be either 1 , 2 -dodecanediol or 1,12- dodecanediol .

[0070]

The (D) dodecanediol may be used, together with the other low molecular weight diol . Examples of the low molecular weight diol include, in addition to dodecanediol, the above-mentioned diols to be used as the raw material of the aliphatic polyesterpolyol , for example, low molecular weight diols having 2 to 12 carbon atoms, such as ethylene glycol, 1-methylethylene glycol, 1-ethylethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentyl glycol, 2 -methyl - 1 , 3 -propanediol , cyclohexanedimethanol , and 2 , 4 -dimethyl- 1 , 5 -pentanediol .

As used herein, the low molecular weight diol has a number average molecular weight of less than 400.

[0071]

There is no particular limitation on the isocyanate compound in the present invention as long as the objective urethane prepolymer can be obtained, and the isocyanate compound which is used in conventional production of polyurethanes may be used. The isocyanate compound

preferably has from 1 to 3 isocyanate groups per molecule on average, and is particularly preferably a difunctional isocyanate compound, so-called diisocyanate compound. The isocyanate compounds can be used alone, or two or more isocyanate compounds can be used in combination.

[0072]

Examples of the "isocyanate compound" include ethylene diisocyanate , ethylidene diisocyanate , propylene

diisocyanate , butylene diisocyanate, hexamethylene

diisocyanate, toluene diisocyanate, cyclopentylene 1,3- diisocyanate, cyclohexylene 1 , 4 -diisocyanate , cyclohexylene 1 , 2 -diisocyanate , 4 , 4 ' -diphenylmethane diisocyanate, 2,2'- diphenylpropane 4 , 4 ' -diisocyanate , p-phenylene

diisocyanate, m-phenylene diisocyanate, xylylene

diisocyanate, 1 , 4 -naphthylene diisocyanate, 1 , 5 -naphthylene diisocyanate, diphenyl -4 , 4 ' -diisocyanate , azobenzene 4,4'- diisocyanate , diphenylsulfone 4 , 4 ' -diisocyanate ,

dichlorohexamethylene diisocyanate, furfurylidene

diisocyanate, 1 -chlorobenzene-2 , 4 -diisocyanate , and the like. These isocyanate compounds can be used alone or in combination.

[0073]

In producing the "urethane prepolymer" according to the present invention, a monool and a monoisocyanate can be used, and also a trifunctional polyol and a trifunctional isocyanate can be used as long as the objective urethane prepolymer can be obtained. It is preferred to produce using a difunctional polyol (diol) and a difunctional isocyanate (diisocyanate) .

[0074]

It is more preferred that the "urethane prepolymer" is produced by reacting a difunctional polyol with a

difunctional isocyanate from the viewpoint of control of the thermal stability and a production method (and a production process thereof) of the obtainable moisture- curable hot melt adhesive. It is preferred to use 2 mol of the difunctional isocyanate based on 1 mol of the

difunctional polyol, since the objective urethane

prepolymer can be produced comparatively easily.

[0075]

The ratio (NCO/OH) of the number of isocyanate groups in the isocyanate compound to the number of OH groups contained in the components (B) , (C) , and (D) is preferably 1.5 to 2.4, and more preferably 1.6 to 2.2, and particularly preferably 1.7 to 2.0.

[0076]

The moisture-curable hot melt adhesive according to the present invention contains the (A) acrylic polymer and the above-mentioned "urethane prepolymer" produced by using the (B) polyetherpolyol , the (C) crystalline

polyesterpolyol , the (D) dodecanediol, and the isocyanate compound. There is no particular limitation on the

production method as long as the objective moisture-curable hot melt adhesive is obtainable.

Specifically, the moisture-curable hot melt adhesive may be produced by mixing the "urethane prepolymer"

produced in advance with the (A) acrylic polymer, or the moisture-curable hot melt adhesive may be produced by mixing the (A) acrylic polymer with the (B) polyether polyol, the (C) crystalline polyester polyol , the (D) dodecanediol and the isocyanate compound as precursors of the urethane prepolymer, and then reacting the components (B) , (C) and (D) with the isocyanate compound in the presence of the (A) acrylic polymer.

[0077]

The moisture-curable hot melt adhesive of the present invention exhibits plural melting points after curing, and any one of the melting points exhibits a temperature from 50 to 100°C and another any one of them exhibits a

temperature from 150 to 200 °C. When the melting point is measured by a differential scanning calorimeter (DSC) , a peak top of an endothermic peak appears from 50 to 100°C, and a peak top of an endothermic peak also appears from 150 to 200 °C. The measurement conditions using the

differential scanning calorimeter (DSC) are the same as those mentioned previously.

The moisture-curable hot melt adhesive of the present invention is excellent in initial cohesive force and adhesion after curing and exhibits open time prolonged to some extent due to having plural melting points.

[0078]

The moisture-curable hot melt adhesive according to the present invention can contain other additives as long as the additives do not exert an adverse influence on the reaction of the polyol with the isocyanate compound to form the urethane prepolymer, and the objective moisture-curable hot melt adhesive of the present invention can be obtained. There is no particular limitation on timing of the addition of the additives to the moisture-curable hot melt adhesive, as long as the objective moisture-curable hot melt adhesive of the present invention can be obtained. The additives may be added, for example, together with the polyol and the isocyanate compound in synthesizing the urethane

prepolymer. Alternatively, first, the polyol may be reacted with the isocyanate compound to synthesize the urethane prepolymer, and then the additives may be added.

[0079]

The "additives" are not particularly limited, as long as they are usually used in a moisture-curable hot melt adhesive and the objective moisture-curable hot melt adhesive of the present invention can be obtained.

Examples of the additives include a plasticizer, an antioxidant, a pigment, a photostabilizer, a flame

retardant, a catalyst, a wax, and the like.

[0080]

Examples of the "plasticizer" include dioctyl

phthalate, dibutyl phthalate, dioctyl adipate, mineral spirit, and the like.

Examples of the "antioxidant" include a phenol -based antioxidant, a phosphite-based antioxidant, a thioether- based antioxidant, an amine-based antioxidant, and the like.

Examples of the "pigment" include titanium oxide, carbon black, and the like.

[0081]

Examples of the "photostabilizer" include benzotriazole , hindered amine, benzoate, benzotriazole, and the like.

Examples of the "flame retardant" include a halogen- based flame retardant, a phosphorous-based flame retardant, an antimony-based flame retardant, a metal hydroxide-based flame retardant, and the like.

[0082]

Examples of the "catalyst" include metal-based

catalysts such as tin-based catalysts (trimethyltin

laurate, trimethyltin hydroxide, dibutyltin dilaurate, and dibutyltin maleate, etc.), lead-based catalysts (lead oleate, lead naphthenate, and lead octoate, etc.), and other metal-based catalysts (naphthenic acid metal salts such as cobalt naphthenate) and amine-based catalysts such as triethylene-diamine , tetramethylethylenediamine ,

tetramethylhexylene-diamine , diazabicycloalkenes ,

dialkylaminoalkylamines , and the like.

Examples of the "wax" include waxes such as paraffin wax and microcrystalline wax.

[0083]

The moisture-curable hot melt adhesive according to the present invention is solid at a normal temperature (15 to 30 °C) and can be used in the fields where a moisture- curable hot melt adhesive has hitherto been used. It can be also used in exterior materials and interior materials for building materials to which higher initial adhesive strength is required, floorings, bonding (adhering or attaching) and profile wrapping of a decorative sheet to a base material, and the like.

[0084]

The above moisture-curable hot melt adhesive is suited in bonding a decorative material, as a building interior material, to the floor. The use is not limited to bonding to the floor, and it can be also used to bond a decorative sheet to the other base material. Therefore, the moisture- curable hot melt adhesive of the present invention can also be used for woodworking, paper processing, fiber

processing, popular use, and the like.

[0085]

In the present invention, the moisture-curable hot melt adhesive can be used in the same manner as a

conventional moisture-curable hot melt adhesive, and there is no particular limitation on the usage. For example, in bonding an adherend to a base material, the moisture- curable hot melt adhesive may be applied to the base material side and/or the adherend side.

[0086]

The "adherend" may be a usually used adherend, and examples thereof include, but are not limited to, a film, a sheet, and the like.

The film may be either colorless or colored, or either transparent or opaque, and examples thereof include films made of a polyolefin resin, a polyester resin, an acetate resin, a polystyrene resin, a vinyl chloride resin, and the like. Examples of the polyolefin resin include

polyethylene and polypropylene, and examples of the

polyester resin include polyethylene terephthalate .

[0087]

Examples of the decorative sheet include:

sheets made of plastic materials such as a rigid or semi-rigid vinyl chloride resin, a polyolefin resin, and a polyester resin;

boards obtainable by slicing a wood into a sheet; and decorative papers subjected to various decorative printings .

[0088]

In the present invention, it is possible to use "base materials" which are usually used, and examples thereof include, but are not limited to:

woody materials such as a plywood (for example, a lauan plywood) , a medium density fiberboard (MDF) , a particle board, a solid wood (or natural wood) , and a woody fiber board;

inorganic materials such as a cement board, a gypsum plaster board, and an autoclaved lightweight concrete (ALC) ; and

plastic materials such as a melamine resin, a vinyl chloride resin, a polyolefin resin, and a polyester resin.

The moisture-curable hot melt adhesive of the present invention is suited for the production of a laminate using a flat and hard plate made of a plastic material.

[0089]

A laminated product obtainable by bonding an adherend and a base material using the moisture-curable hot melt adhesive according to the present invention can be

specifically employed in various fields such as building materials, electronic materials and automobiles. It is not necessary to use a special apparatus so as to produce the laminated product, and the laminated product can be

produced by using generally known production apparatuses including a conveyer, a coater, a press, a heater and a cutter. For example, the laminated product can be produced by the following procedure. While allowing a base material and an adherend to flow on a conveyer, the base material or adherend is coated with the moisture-curable hot melt adhesive according to the present invention using a coater. The coating temperature is controlled to a predetermined temperature by a heater. The adherend and the base

material are laminated with each other through the

moisture-curable hot melt adhesive by slightly pressing the adherend against the base material using a press. Then, the laminated adherend and base material are left standing to cool and allowed to flow by the conveyer as they are, thereby solidifying the moisture-curable hot melt adhesive. Then, the base material laminated with the adherend is cut into an appropriate size by a cutter.

[0090]

The moisture-curable hot melt adhesive according to the present invention has high initial adhesive strength and high adhesive strength after curing, and has a certain length of open time. Therefore, it is easy to apply the adhesive, and the adhesive also exhibits satisfactory productive efficiency, and thus peeling becomes less likely to occur between the base material and the adherend of the obtained laminated product even if the times elapses.

It is also possible for an operator to apply the adhesive without using a coater to produce the laminated product .

Examples [0091]

The present invention will be described below by way of Examples and Comparative Examples. These Examples are merely for illustrative purposes and are not meant to be limiting on the present invention.

[0092]

Weight average molecular weights (Mw) of acrylic polymers (A-l) to (A-3) having an alicyclic structure, and weight average molecular weights (Mw) of acrylic polymers (A' -4) to (A' -5) having no alicyclic structure, and number average molecular weights (Mn) of (B) polyetherpolyols are values measured and converted by gel permeation

chromatography (GPC) . Molecular weights of components (C) , (C ) , (D) , and (D' ) are cited from catalogues of raw materials.

Glass transition temperatures (Tg) of the components are calculated according to the compositions of the

monomers, respectively. The glass transition temperatures were calculated using the previously mentioned calculation formula.

Melting points (M. P) of the components are measured by differential scanning calorimeter (DSC) , respectively. The measurement conditions are as mentioned previously.

[0093] Acrylic Polymer

(A) Acrylic polymer having an alicyclic structure

(A-1) Acrylic polymer having a cyclohexyl structure, a weight average molecular weight ( w) of 50,000, and a glass transition temperature (Tg) of 75 °C

(A-2) Acrylic polymer having a cyclohexyl structure, a weight average molecular weight (Mw) of 50,000, and a glass transition temperature (Tg) of 85 °C

(A-3) Acrylic polymer having an isobornyl structure, a weight average molecular weight (Mw) of 50,000, and a glass transition temperature (Tg) 140 °C

[0094]

(A' ) Acrylic polymer having no alicyclic structure

(A' -4) Acrylic polymer obtained from only an (a') (meth) acrylic acid derivative having no alicyclic structure (manufactured by Mitsubishi Rayon Co., Ltd., BR113 (product name) having Mw of 35,000 and a glass transition

temperature (Tg) of 75 °C)

(A' -5) Acrylic polymer obtained from only an (a') (meth) acrylic acid derivative having no alicyclic structure (manufactured by Mitsubishi Rayon Co., Ltd., BR113 (product name) having Mw of 60,000 and a glass transition

temperature (Tg) of 50 °C

Synthesis of the above-mentioned acrylic polymers (A- 1) to (A-3) are mentioned below.

[0095]

(B) Polyetherpolyol

(B-l) Polyoxypropylene glycol (manufactured by Dai- ichi Kogyo Seiyaku Co., Ltd., HIFLEX D2000 (product name) having a hydroxyl value of 56 (mgKOH/g) and a number average molecular weight (Mn) of 3,000)

(B-2) Polyoxypropylene glycol (manufactured by Dai- ichi Kogyo Seiyaku Co., Ltd., HIFLEX D400 (product name) having a hydroxyl value of 280 (mgKOH/g) and a number average molecular weight (Mn) of 486)

[0096]

(C) Crystalline polyesterpolyol

(C-l) Crystalline polyhexamethylene adipate

(manufactured by HOKOKU CORPORATION HS 2H-351A (product name) having a melting point of 60 °C, a hydroxyl value of 32 (mgKOH/g) , and a number average molecular weight (Mn) of 3 , 500)

(C-2) Crystalline polyhexamethylene sebacate

(manufactured by HOKOKU CORPORATION HS 2H-350S (product name) having a melting point of 70 °C, a hydroxyl value of 32 (mgKOH/g) , and a number average molecular weight (Mn) of 3,500)

(C-3) Crystalline polyhexamethylene dodecanate (manufactured by UBE INDUSTRIES, LTD. ETERNACOLL 3010 (product name) having a melting point of 74 °C, a hydroxyl value of 32 (mgKOH/g) , and a number average molecular weight (Mn) of 3,500)

(C-4) Crystalline polyesterpolyol (manufactured by

Evonik Industries, DYNACOLL 7340 having a melting point of 102°C, hydroxyl value of 32 (mgKOH/g), and a number average molecular weight of (Mn) of 3,500)

(C -5) Amorphous polyesterpolyol (manufactured by Asahikawa Kagaku Co., Ltd. or Xuchuan Chemical (Suzhou)

Co., Ltd.), PES0001 (product name) having no melting point, a hydroxyl value of 56 (mgKOH/g), and a number average molecular weight (Mn) of 2,000)

[0097]

(D) Dodecanediol

(D-l) 1 , 12 -dodecanediol (manufactured by Ube

Industries, Ltd. 1 , 12 -dodecanediol (product name), melting point of 83 °C, molecular weight of 202)

(D'-2) 1, 10-decanediol (manufactured by HOKOKU

CORPORATION, 1 , 10 -decanediol (product name) having a melting point of 72 °C, and a molecular weight of 174)

(D'-3) 1 , 6-hexanediol (manufactured by Ube Industries, Ltd., 1 , 6 -hexanediol (product name) having a melting point of 40°C, and a molecular weight of 118) (D'-4) 1 , 4 -cyclohexanedimethanol (manufactured by Eastman Chemical Company, 1 , 4 -cyclohexanedimethanol

(product name) , having no melting point (above room

temperature) , and a molecular weight of 144)

[0098]

Isocyanate Compound

4 , 4 ' -diphenylmethanediisocyanate (hereinafter also referred to as " DI") (manufactured by Nippon Polyurethane Industry Co., Ltd., MILLIONATE MT (product name))

Other Additives

Initiator

Azobisisobutyronitrile (AIBN, manufactured by Otsuka Chemical Co., Ltd.)

[0099]

<Synthesis of Acrylic Polymer (A) >

An (a) (meth) acrylic acid derivative having an

alicyclic structure was mixed with an (a') (meth) acrylic acid derivative which has no cyclic structure and may have a chain- like structure, and then the mixture was

polymerized to produce the acrylic polymers (A-l) to (A-3) .

The (a) (meth) acrylic acid derivatives and the (a') (meth) acrylic acid derivatives, which serve as raw

materials of the (A) acrylic polymer, are shown below.

[0100] (a-1) Cyclohexyl methacrylate

(a-2) Isobornyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., IB-X (product name))

(a' -3) Methyl methacrylate

(a' -4) Butyl methacrylate

(a' -5) Methacrylic acid

The production of the acrylic polymer (A-1) will be described in detail below.

(a-1) Cyclohexyl methacrylate 150 g

(a' -3) Methyl methacrylate 120 g

(a' -4) Butyl methacrylate 30 g

(a' -5) Methacrylic acid 1.5 g

[0101]

The (a) monomer was mixed with the (a' ) monomers in the above weights to prepare 301.5 g in total of a monomer mixed solution. In a 2L reaction vessel, 549 g of the (B- 1) polyetherpolyol was charged and 50 g of the above- mentioned monomer mixed solution was added to the same reaction vessel, and also 4.0 g of azobisisobutyronitrile (AIBN) as a polymerization initiator was added to the same reaction vessel.

After attaching a stirring blade, a reflux condenser tube and a thermometer to the reaction vessel, the same reaction vessel was immersed in a warm bath at 80 °C and the polymerization reaction was initiated while stirring the mixed solution in the vessel. After about 20 minutes from generation of reaction heat, the remainder of the above- mentioned monomer mixed solution was added dropwise over about 2 hours .

After 30 minutes from the completion of the dropwise addition, 0.15 g of AIBN was added every 30 minutes for three times, followed by stirring at 90 °C for 2 hours. After the completion of the stirring, the prepared acrylic polymer solution was removed from the reactor. The concentration of the acrylic polymer prepared solution was 35.7% by weight .

[0102]

Production of Acrylic Polymers (A-2) to (A-3)

After mixing an (a) monomer with (a' ) monomers according to the compositions shown in Table 1 to obtain a monomer mixture, the acrylic polymers (A-2) to (A-3) were produced in the same manner as in the (A-l) .

The commercially available products (A' -4) to (A' -5) were used as they are provided. The compositions of the (A-l) to (A' -5) are shown in Table 1. [0103]

[Table

[0104]

<Production of Moisture-Curable Hot Melt Adhesive>

Examples 1 to 8 and Comparative Examples 1 to 5

Components (A) to (D) and an isocyanate compound were mixed according to the compositions shown in Tables 2 to 3 to produce moisture-curable hot melt adhesives.

Specifically, the components (A) to (D) were charged in a reaction vessel and stirred under reduced pressure for 1 hour. After removing moisture, the isocyanate compound (4 , 4 ' -diphenylmethanediisocyanate) was added at the same temperature, followed by stirring under reduced pressure for 2 hours to obtain moisture-curable hot melt adhesives, respectively.

The numerical values of the acrylic polymers (A) disclosed in Tables 2 to 3 are numerical values (values in terms of the solid content) after removal of the solvent, respectively.

[0105]

[Table 2]

[0106]

[Table 3]

[0107]

In order to evaluate performances before curing of the moisture-curable hot melt adhesives of Examples and Comparative Examples, open time, yield stress of an

adhesive film before curing, dynamic creep, and presence or absence of lifting (or releasing) of a melamine board were measured.

In order to evaluate adhesion after curing of the moisture-curable hot melt adhesives, a material breakage ratio of plywood was measured.

In order to evaluate coating performance, the

viscosity was measured and the melting point after curing was also measured. Test procedures and evaluation criteria are shown below.

[0108]

<Performance before Curing (Test for Open Time) >

Plywoods kept and warmed in an incubator at 25 °C for 12 hours or more were used as a material for test. The moisture-curable hot melt adhesives of Examples and

Comparative Examples were melted at 120 °C, and the plywoods were coated with the adhesives by a roll coater in a coating amount of 60 g/m ² , respectively. The open time was determined by measuring the time until tack disappears from just after coating by finger touch. Evaluation criteria of the open time are as follows.

A: 40 Seconds or more

B: 20 Seconds or more and less than 40 seconds C: Less than 20 seconds

[0109]

<Performance before Curing (Yield Stress of Adhesive Film before Curing) >

The moisture-curable hot melt adhesives of Examples and Comparative Examples were melted at 120 °C to produce 1 mm thick resin plates, followed by cooling to room

temperature, respectively. Immediately after cooling, the resin plates were formed into a form of dumbbell (defined in ASTM D1708) by punching. After 5 minutes and 10 minutes, yield point stress was measured using Autograph AGS-J, manufactured by Shimadzu Corporation. Testing speed was 100 mm/minute. Evaluation criteria are shown below. A: 1.5 MPa or more

B: 1.0 MPa or more and less than 1.5 MPa

C: 0.5 MPa or more and less than 1.0 MPa

D: Less than 0.5 MPa

[0110]

<Performance before Curing (Dynamic Creep Test) >

Paper strips measuring 50 mm in width, 500 mm in length, and 0.1 mm in thickness were coated with the moisture-curable hot melt adhesives of Examples and

Comparative Examples melted at 120 °C in a width of 25 mm and a thickness of 0.1 mm, and then the paper strips were laminated to a glass plate preheated to 120 °C, respectively. After attaching temperature sensors to the glass plates, the laminates were air-cooled at room

temperature, respectively. When the temperatures of the glass plates reach 55 °C, a load was applied by suspending 100 g of a weight at the end of each of the laminated paper strips. While the laminates were air-cooled, a peeling distance was measured when the temperature of each of the glass plates is within a range of 34 to 35 °C. Evaluation criteria are as follows.

A: Less than 1 mm

B: 1 mm or more and less than 3 mm

C : 3 mm or more

[0111]

<Performance before Curing (Lifting of Melamine Board at 35°C) >

Plywoods and curved melamine boards (0.6 mm in

thickness) kept and warmed in an incubator at 35 °C for 12 hours or more were used for a test. The moisture-curable hot melt adhesives of Examples and Comparative Examples were melted at 120 °C, and the plywoods were coated with the adhesives using a roll coater in a coating amount of 60 g/m ² , respectively. After thirty seconds just from the coating, the plywoods were laminated with the melamine board, followed by pressing using a roll press, respectively. The laminated melamine board and plywood was left to stand in an incubator at 35°C for 24 hours, it was confirmed whether or not lifting of the curved portion of the melamine board from the plywood occurs. Evaluation criteria are as follows.

A: No lifting

B: Lifting occurs

[0112]

<Adhesion after Curing (Breakage Ratio of Plywood

Material) >

Plywoods and curved melamine boards (0.6 mm in

thickness) kept and warmed in an incubator at 35 °C for 12 hours or more were used for a test. The moisture-curable hot melt adhesives of Examples and Comparative Examples were melted at 120 °C, and the sides of the plywoods were coated with the adhesives using a roll coater in a coating amount of 60 g/m ² , respectively. After thirty seconds from the coating, the plywoods were laminated with the melamine · boards, followed by pressing using a roll press,

respectively. The laminated melamine board and plywood was aged in an incubator at 25 °C for 72 hours. After aging, the melamine board was forcibly peeled off from the

plywood, and then a material breakage ratio of the plywood (proportion of a damaged surface of the plywood, showing the proportion of the portion where adhesion between the plywood and the adhesive is smaller than the strength inside the adhesive) was visually judged (or observed) . Evaluation criteria are as follows.

A: 80% or more

B: 50% or more and less than 80%

C: Less than 50%

[0113]

<Measurement of Viscosity>

Using a viscometer (manufactured by Brookfield

Engineering Laboratories) , melt viscosity was measured. Specifically, a predetermined amount (10.5 g) of a molten moisture-curable hot melt adhesive was poured into a viscosity tube and a spindle was inserted into a

viscometer. After the adhesive was left to stand at 120 °C for 30 minutes, the melt viscosity was measured at 120°C.

[0114]

<Melting Point after Curing>

After curing the moisture-curable hot melt adhesives of Examples and Comparative Examples, the cured adhesives were used as measurement samples and then a difference in heat quantity between the sample and a standard substance a-alumina was measured using DSC. Specifically, the temperature was raised from -50°C to 220°C at 10°C/minute and a peak top of an endothermic peak observed was regarded as a melting point. The value of the peak top is shown in Table 2. When no endothermic peak was observed (or

confirmed), "-" is shown in Table 3.

[0115]

As shown in Tables 2 to 3 , the moisture-curable hot melt adhesives of Examples exhibit long open time before curing and high initial adhesion (cohesive force) , since the adhesives are obtained from four components of the components (A) to (D) , and the isocyanate compound. The moisture-curable hot melt adhesives are also excellent in adhesion after curing.

[0116]

As shown in Fig. 1, with regard to the moisture- curable hot melt adhesives of Examples 1 to 8 , a peak top of an endothermic peak is observed within a temperature range of 50 to 100°C, and a peak top of an endothermic peak is further observed within a temperature range of 150 to 200°C.

On the other hand, as shown in Fig. 2, with regard to the moisture-curable hot melt adhesives of Comparative Examples 1 to 5 and Comparative Example 7, a peak top of an endothermic peak is observed within a temperature range of 50 to 100 °C, but no peak top of an endothermic peak is observed within a temperature range of 150 to 200 °C.

Industrial Applicability

[0117]

The present invention provides a moisture-curable hot melt adhesive. The moisture-curable hot melt adhesive according to the present invention can be used in exterior materials and interior materials for building materials, floorings, bonding (adhering or attaching) and profile wrapping of a decorative sheet to a base material, and the like, and is therefore particularly effective for flat lamination of hard boards such as a melamine decorative board.