JP7470403B2 - Moisture-curing hot melt adhesive - Google Patents

Description

The present invention relates to a moisture-curing hot melt adhesive.

In recent years, there has been a demand for improved fire resistance in architectural structures. In the event of a fire, the base material that constitutes the architectural structure burns and collapses due to the heat of the fire, creating gaps through which flames can penetrate and cause the fire to spread.

Although it has been proposed to construct the base material from a non-combustible material, the base material deteriorates significantly due to the heat during a fire, and is no longer able to retain its shape, collapsing, making it impossible to adequately prevent the spread of fire.

Traditionally, decorative sheets that have been colored or otherwise decorated have been attached to the surfaces of base materials such as furniture, exterior materials, and interior materials using adhesives to impart design features, and in order to improve the fire resistance of the base material, a metal sheet has been placed between the base material and the decorative sheet.

However, the process of laminating a metal sheet onto the surface of a base material using an adhesive, and then laminating a decorative sheet onto the metal sheet using an adhesive, is complicated, resulting in low manufacturing efficiency and insufficient fire resistance of the base material.

Patent document 1 discloses an additive mixture that improves the dimensional stability of plastic molded bodies in the event of a fire, the additive mixture containing at least one acid-forming substance, at least one carbon-donating compound, and at least one particulate metal.

JP 2001-270998 A

However, the additive mixture cannot meet the needs for improving the fire resistance of conventionally used substrates, and there is a demand for improving the fire resistance of conventionally used substrates. Furthermore, the additive mixture has the problem of being highly viscous and poorly coatable.

The present invention provides a moisture-curing hot melt adhesive that can adhere decorative sheets to the surfaces of conventionally used general-purpose substrates (e.g., furniture, exterior and interior materials, etc.), improves the heat resistance of the substrate, and further has low viscosity and excellent coatability.

The moisture-curable hot melt adhesive of the present invention contains a urethane prepolymer which is a reaction product of a polyol and a polyisocyanate and contains an isocyanate group at its terminal, and a glass frit;
The glass frit is characterized by containing glass frit (A) which does not contain a phosphoric acid component as a main component and contains an alkali component in an amount of 15 mass % or less and/or glass frit (B) which contains a phosphoric acid component as a main component and contains an alkali component in an amount of 25 mass % or less.

The moisture-curing hot melt adhesive of the present invention can stably attach and integrate a desired component onto an adherend, and produces a cured product with excellent heat resistance. Therefore, when the adherend is a base material that constitutes a building structure, the adhesive can protect the adherend from heat during a fire, prevent the adherend from deteriorating or collapsing despite the heat of the fire, and prevent the spread of the fire.

In addition, the moisture-curing hot melt adhesive of the present invention contains a specific glass frit, so it has low viscosity and excellent coatability.

The moisture-curable hot melt adhesive of the present invention is
a urethane prepolymer which is a reaction product of a polyol and a polyisocyanate and contains an isocyanate group at its terminal;
and a glass frit,
The glass frit contains glass frit (A) which does not contain a phosphoric acid component as a main component and contains an alkali component in an amount of 15 mass % or less and/or glass frit (B) which contains a phosphoric acid component as a main component and contains an alkali component in an amount of 25 mass % or less.

[Urethane prepolymer]
The moisture-curing hot melt adhesive contains a urethane prepolymer which is a reaction product of a polyol and a polyisocyanate and contains an isocyanate group at the end.

The urethane prepolymer contained in the moisture-curing hot melt adhesive is obtained by reacting a polyol with a polyisocyanate, and a preferred example of the urethane prepolymer is one that has isocyanate groups at both ends of the molecular chain.

A polyol is a compound having two or more hydroxyl groups in one molecule. Preferred examples of polyols include polyester polyols, polycaprolactone polyols, polyether polyols, polyalkylene polyols, and polycarbonate polyols, with polyester polyols and polyether polyols being preferred, and polyester polyols and polyether polyols being more preferred. These polyols may be used alone or in combination of two or more.

The polyester polyol is not particularly limited, and examples thereof include polyester polyols obtained by condensation polymerization of polycarboxylic acids and polyols. The polycarboxylic acids are not particularly limited, and examples thereof include dicarboxylic acids such as succinic acid, terephthalic acid, isophthalic acid, dodecanedioic acid, 1,5-naphthalic acid, 2,6-naphthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecamethylenedicarboxylic acid. Among these, linear dicarboxylic acids are preferred as the polycarboxylic acids. Linear dicarboxylic acids can be used to obtain moisture-curable hot melt adhesives with excellent adhesion under normal conditions.

The linear dicarboxylic acid preferably has 4 or more carbon atoms, more preferably 4 to 12. It is particularly preferable that the linear dicarboxylic acid has an even number of carbon atoms. Specific examples of such linear dicarboxylic acids include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Linear dicarboxylic acids having an even number of carbon atoms from 4 to 12 have high crystallinity, and therefore can improve the adhesive strength of moisture-curing hot melt adhesives made using such linear dicarboxylic acids after moisture curing.

The polyol is not particularly limited, and examples thereof include propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, and cyclohexanediol. The polycarboxylic acids and polyols may be used alone or in combination of two or more kinds.

The hydroxyl value of the polyester polyol can improve the normal adhesiveness of the moisture-curing hot melt adhesive and can reduce the melt viscosity of the moisture-curing hot melt adhesive, so it is preferably 2 to 300 mgKOH/g, more preferably 20 to 200 gKOH/g, more preferably 25 to 150 gKOH/g, and even more preferably 26 to 100 gKOH/g.

In the present invention, the hydroxyl value of a polyol refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl groups when 1 g of polyol is acetylated (JIS K0070:1992 2.1(5)). Specifically, it can be measured by acetylating the hydroxyl groups in the polyol with acetic anhydride, and then titrating the unused acetic anhydride with potassium hydroxide (JIS K0070:1992 3.1 (neutralization titration method)).

As the polyester polyol, crystalline polyester polyol and amorphous polyester polyol are preferred, and it is preferable to include crystalline polyester polyol and amorphous polyester polyol.

The crystalline polyester polyol is preferably a condensation polymer of a polycarboxylic acid having 2 to 14 carbon atoms excluding the carbon in the carboxy group (-COOH) and a polyol having 2 to 8 carbon atoms. That is, the crystalline polyester polyol is preferably a polymer obtained by condensation polymerization of a polycarboxylic acid having 2 to 14 carbon atoms excluding the carbon in the carboxy group and a polyol having 2 to 8 carbon atoms through an ester reaction between the carboxyl group of the polycarboxylic acid and the hydroxyl group of the polyol. The condensation polymerization reaction of the polycarboxylic acid and the polyol may be carried out using a general-purpose method. The number of carbon atoms excluding the carbon in the carboxy group, as specified for the polycarboxylic acid, refers to the number of carbon atoms obtained by subtracting the total number of carbons in all the carboxy groups from the total number of carbons contained in the molecule.

In the polycarboxylic acid, the number of carbon atoms excluding the carbon in the carboxy group is preferably 2 to 14, and more preferably 10 to 12. If the number of carbon atoms excluding the carbon in the carboxy group is 2 or more, the crystallinity of the crystalline polyester polyol is improved, and the initial adhesiveness of the moisture-curing hot melt adhesive is improved, which is preferable. If the number of carbon atoms excluding the carbon in the carboxy group is 14 or less, the normal adhesiveness of the moisture-curing hot melt adhesive is improved, which is preferable.

The polycarboxylic acid is preferably a dicarboxylic acid (HOOC-R ¹ -COOH). When the polycarboxylic acid is a dicarboxylic acid, the melt viscosity of the moisture-curable hot melt adhesive can be reduced. The carbon number of R ¹ is preferably 2 to 14, and more preferably 10 to 12. When the carbon number of R ¹ is within the above range, the normal adhesiveness of the moisture-curable hot melt adhesive is improved.

R ¹ is preferably an aliphatic chain, more preferably a linear aliphatic chain. When R ¹ is an aliphatic chain, the crystallinity of the crystalline polyester polyol is improved, and the initial adhesiveness of the moisture-curable hot melt adhesive is improved, which is preferable. When R ¹ is linear, the crystallinity of the crystalline polyester polyol is improved, and the initial adhesiveness of the moisture-curable hot melt adhesive is improved, which is preferable. R ¹ being linear means that carbon is bonded in a straight line without branching. R ¹ is preferably a linear alkylene group (-CnH ₂ n-). However, n is a natural number.

The polycarboxylic acid having 2 to 14 carbon atoms excluding the carbon in the carboxy group (-COOH) is not particularly limited, and examples thereof include sebacic acid, decamethylenedicarboxylic acid (1,10-decanedicarboxylic acid), and 1,14-tetradecanedicarboxylic acid, with sebacic acid and decamethylenedicarboxylic acid being preferred. The polycarboxylic acids may be used alone or in combination of two or more kinds.

The carbon number of the polyol is preferably 2 to 8, and more preferably 2 to 6. If the carbon number of the polyol is 2 or more, the crystallinity of the crystalline polyester polyol is improved, and the initial adhesion of the moisture-curing hot melt adhesive is improved, which is preferable. If the carbon number of the polyol is 8 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, which is preferable.

The polyol is preferably a dihydric alcohol (HO- ^R2 -OH). If the polyol is a dihydric alcohol, the melt viscosity of the moisture-curable hot melt adhesive can be reduced. The carbon number of ^R2 is preferably 2 to 8, and more preferably 2 to 6. If the carbon number of ^R2 is within the above range, the normal adhesiveness of the moisture-curable hot melt adhesive is improved.

R ² is preferably an aliphatic chain, more preferably a linear aliphatic chain. When R ² is an aliphatic chain, the crystallinity of the crystalline polyester polyol is improved, and the initial adhesiveness of the moisture-curable hot melt adhesive is improved, which is preferable. When R ² is linear, the crystallinity of the crystalline polyester polyol is improved, and the initial adhesiveness of the moisture-curable hot melt adhesive is improved, which is preferable. R ² being linear means that carbon is bonded in a straight line without branching. R ² is preferably a linear alkylene group (-CmH ₂ m-). However, m is a natural number. m is preferably an even number, since the crystallinity of the crystalline polyester polyol is improved, and the initial adhesiveness of the moisture-curable hot melt adhesive is improved.

The polyol having 2 to 8 carbon atoms is not particularly limited, and examples thereof include 1,2-ethanediol (ethylene glycol), 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol. 1,6-hexanediol and 1,2-ethanediol (ethylene glycol) are preferred, and 1,6-hexanediol is more preferred. The polyols may be used alone or in combination of two or more kinds.

Crystalline polyester polyols are crystalline. Crystalline polyester polyols are polyester polyols that have a heat absorption amount (hereinafter sometimes simply referred to as "heat absorption amount") of 10 cal/g (40 J/g) or more in the melting curve measured at a heating rate of 10°C/min in differential scanning calorimetry (DSC) as specified in JIS K7121.

The number average molecular weight of the crystalline polyester polyol is preferably 1000 to 20000, more preferably 1500 to 10000, more preferably 1800 to 7000, more preferably 2000 to 6000, more preferably 2500 to 5000, more preferably 3000 to 4500, and more preferably 3200 to 4000. When the number average molecular weight of the crystalline polyester polyol is 1000 or more, the initial adhesion and normal adhesion of the moisture-curing hot melt adhesive are improved. When the number average molecular weight of the crystalline polyester polyol is 20000 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, which is preferable.

In the present invention, the number average molecular weight of a polyol refers to a value measured as follows. The number average molecular weight of a polyol can be measured using gel permeation chromatography (GPC). Specifically, a sample solution is prepared by dissolving a sample in tetrahydrofuran (THF) so that the concentration is 1.0% by mass. This sample solution is used to measure the number average molecular weight of the polyol by GPC using a refractive index detector with standard polystyrene as the standard.

As a measuring device, for example, a system consisting of an LC-9A liquid delivery device, an RID-6A refractive index detector, a CTO-6A column oven, and a C-R4A data analyzer (all manufactured by Shimadzu Corporation) can be used. As a GPC column, for example, three GPC-805 (exclusion limit 4 million) and one GPC-804 (exclusion limit 400,000) (all manufactured by Shimadzu Corporation) can be connected in this order. The measurement conditions are as follows: sample injection volume 25 μL (liters), eluent tetrahydrofuran (THF), liquid delivery rate 1.0 mL/min, and column temperature 45°C.

The hydroxyl value of the crystalline polyester polyol is preferably 20 to 50 mgKOH/g, more preferably 25 to 45 mgKOH/g, and particularly preferably 30 to 35 mgKOH/g. When the hydroxyl value of the crystalline polyester polyol is 20 mgKOH/g or more, the normal adhesiveness of the moisture-curing hot melt adhesive is improved. When the hydroxyl value of the crystalline polyester polyol is 50 mgKOH/g or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, improving the coatability.

In the polyol, the content of crystalline polyester polyol is preferably 15 to 35 mass%, more preferably 18 to 33 mass%, and even more preferably 20 to 30 mass%. When the content of crystalline polyester polyol is 15 mass% or more, the initial adhesion of the moisture-curing hot melt adhesive is improved. When the content of crystalline polyester polyol is 35 mass% or less, the normal adhesion of the moisture-curing hot melt adhesive is improved.

Amorphous polyester polyol is a condensation polymer of polycarboxylic acid and polyol. In other words, amorphous polyester polyol is a polymer obtained by condensation polymerization of polycarboxylic acid and polyol through an ester reaction between the carboxyl group of the polycarboxylic acid and the hydroxyl group of the polyol.

The polycarboxylic acid is not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, 1,5-naphthalic acid, 2,6-naphthalic acid, cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decamethylenedicarboxylic acid, and dodecamethylenedicarboxylic acid. Adipic acid, terephthalic acid, and isophthalic acid are preferred, terephthalic acid and isophthalic acid are more preferred, and terephthalic acid and isophthalic acid are preferred. The polycarboxylic acid may be used alone or in combination of two or more kinds.

The polyol is not particularly limited, and examples thereof include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, diethylene glycol, cyclohexanediol, etc., with 1,6-hexanediol, ethylene glycol and neopentyl glycol being preferred, ethylene glycol and neopentyl glycol being more preferred, and it is preferable to include ethylene glycol and neopentyl glycol. The polyols may be used alone or in combination of two or more kinds.

Amorphous polyester polyol is a polyester polyol that has an endothermic heat of less than 2.5 cal/g (10 J/g) in the melting curve measured at a heating rate of 10°C/min in differential scanning calorimetry (DSC) as specified in JIS K7121.

The number average molecular weight of the amorphous polyester polyol is preferably 1000 to 6000, more preferably 1100 to 4000, and even more preferably 1200 to 3500. When the number average molecular weight of the amorphous polyester polyol is 1000 or more, the initial adhesive strength of the moisture-curing hot melt adhesive is improved. When the number average molecular weight of the amorphous polyester polyol is 6000 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, improving the coatability.

The hydroxyl value of the non-crystalline polyester polyol is preferably 20 to 150 mgKOH/g, more preferably 30 to 120 mgKOH/g, and particularly preferably 50 to 100 mgKOH/g. When the hydroxyl value of the non-crystalline polyester polyol is 20 mgKOH/g or more, the normal adhesiveness of the moisture-curing hot melt adhesive is improved. When the hydroxyl value of the non-crystalline polyester polyol is 150 mgKOH/g or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced.

In the polyol, the content of the amorphous polyester polyol is preferably 15 to 35 mass%, more preferably 18 to 33 mass%, and even more preferably 20 to 30 mass%. When the content of the amorphous polyester polyol is 15 mass% or more, the normal adhesiveness of the moisture-curing hot melt adhesive is improved. When the content of the amorphous polyester polyol is 35 mass% or less, the normal adhesiveness of the moisture-curing hot melt adhesive is improved.

Examples of polycaprolactone polyols include polycaprolactone polyols obtained by ring-opening addition polymerization of a lactone compound to a polyol. Examples of polyols include the same polyols as those described above for polyester polyols. Examples of lactone compounds include β-propiolactone, pivalolactone, δ-valerolactone, ε-caprolactone, methyl-ε-caprolactone, dimethyl-ε-caprolactone, and trimethyl-ε-caprolactone.

The polyether polyol is not particularly limited. As the polyether polyol, a polymer containing a repeating unit represented by the general formula: HO-(R ³ -O)p-H (wherein R ³ represents an alkylene group having 1 to 14 carbon atoms, and p is a positive integer representing the number of repeating units) and a polyether polyol obtained by addition reaction of an alkylene oxide (e.g., ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, etc.) to the active hydrogen portion of the bisphenol A molecular skeleton are preferable. The main chain skeleton of the polyether polyol may be composed of only one type of repeating unit, may contain two or more types of repeating units, or may contain two or more types of polymer blocks. The polyether polyol may be used alone or in combination of two or more types.

Examples of the main chain skeleton [-(R ³ -O)p-] of the polymer containing a repeating unit represented by the above-mentioned general formula: HO-(R ³ -O)p-H include polyethylene oxide, polypropylene oxide, polybutylene oxide, polytetramethylene oxide, polyethylene oxide-polypropylene oxide copolymer, polypropylene oxide-polybutylene oxide copolymer, etc. Among these, polypropylene oxide and polyethylene oxide-polypropylene oxide copolymer are preferred because they improve the normal adhesiveness of the moisture-curable hot melt adhesive.

As polyether polyols obtained by addition reaction of alkylene oxide to the active hydrogen moiety of the bisphenol A molecular skeleton, polyether polyols obtained by addition reaction of propylene oxide to the active hydrogen moiety of the bisphenol A molecular skeleton and polyether polyols obtained by addition reaction of ethylene oxide to the active hydrogen moiety of the bisphenol A molecular skeleton are preferred because they improve the normal adhesiveness of moisture-curing hot melt adhesives.

The number average molecular weight of the polyether polyol is preferably 500 to 7000, more preferably 600 to 6000, more preferably 650 to 5000, more preferably 700 to 4000, more preferably 750 to 3000, and particularly preferably 760 to 2500. When the number average molecular weight of the polyether polyol is 500 or more, the normal adhesiveness of the moisture-curing hot melt adhesive is improved, which is preferable. When the number average molecular weight of the polyether polyol is 7000 or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the coatability can be improved.

The hydroxyl value of the polyether polyol is preferably 50 to 300 mgKOH/g, more preferably 80 to 180 mgKOH/g, and particularly preferably 100 to 150 mgKOH/g. When the hydroxyl value of the polyether polyol is 50 mgKOH/g or more, the normal adhesiveness of the moisture-curing hot melt adhesive is improved. When the hydroxyl value of the polyether polyol is 300 mgKOH/g or less, the melt viscosity of the moisture-curing hot melt adhesive can be reduced, and the coatability can be improved.

In the polyol, the content of polyether polyol is preferably 20% by mass or more, more preferably 30% by mass or more, and more preferably 45% by mass or more. In the polyol, the content of polyether polyol is preferably 70% by mass or less, more preferably 60% by mass or less, and more preferably 55% by mass or less. When the content of polyether polyol is 20% by mass or more, the normal adhesiveness of the moisture-curing hot melt adhesive is improved. When the content of polyether polyol is 70% by mass or less, the initial adhesiveness of the moisture-curing hot melt adhesive is improved.

Examples of polyoxyalkylene modified products of bisphenol A include polyether polyols obtained by addition reaction of alkylene oxides with active hydrogen moieties such as hydroxyl groups of the bisphenol A skeleton. Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, and isobutylene oxide. It is preferable that both ends of the bisphenol A skeleton are each modified with 1 to 10 moles of one or more alkylene oxides in monomer units.

Examples of polyalkylene polyols include polybutadiene polyols, hydrogenated polybutadiene polyols, and hydrogenated polyisoprene polyols.

Examples of polycarbonate polyols include polyhexamethylene carbonate polyol and polycyclohexanedimethylene carbonate polyol.

The polyol preferably contains polyester polyol and polyether polyol, since this improves the normal adhesiveness of the moisture-curing hot melt adhesive and reduces the melt viscosity of the moisture-curing hot melt adhesive, and more preferably contains crystalline polyester polyol, amorphous polyester polyol and polyether polyol.

Polyisocyanates are compounds that have two or more isocyanate groups in one molecule. Examples of polyisocyanates include 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4-diphenylmethane diisocyanate (2,4-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), carbodiimide-modified diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, carbodiimidized diphenylmethane polyisocyanate, tolylene diisocyanate (TDI, 2,4-, 2,6-, or mixtures thereof), xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate (N DI), tetramethylxylene diisocyanate, phenylene diisocyanate, hexamethylene diisocyanate (HDI), dimer acid diisocyanate, norbornene diisocyanate, lysine diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate. These polyisocyanates may be used alone or in combination of two or more.

Of these, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, and 2,2'-diphenylmethane diisocyanate are preferred because they improve the normal state adhesion of moisture-curing hot melt adhesives. And among polyisocyanates, diphenylmethane diisocyanate is preferably used because it can impart superior normal state adhesion to moisture-curing hot melt adhesives.

A preferred method for synthesizing urethane prepolymers is to heat polyol to 80-120°C to melt it, dehydrate the resulting melt under reduced pressure, and then add polyisocyanate to the melt in a nitrogen atmosphere to react the polyol with the polyisocyanate.

When synthesizing the urethane prepolymer, it is preferable to set the molar ratio ([NCO]/[OH]) of the sum of the isocyanate groups (NCO) in the polyisocyanate to the sum of the hydroxyl groups (OH) in the polyol to 1.5 to 4.0. When the molar ratio ([NCO]/[OH]) is 1.5 or more, the viscosity of the moisture-curing hot melt adhesive can be suppressed and the coatability can be improved. When the molar ratio ([NCO]/[OH]) is 4.0 or less, foaming of the moisture-curing hot melt adhesive after moisture curing is suppressed, which is preferable.

[Glass frit]
The moisture-curing hot melt adhesive contains a specific glass frit. The moisture-curing hot melt adhesive contains a specific glass frit, so that the cured product produced by moisture curing has excellent heat resistance. Furthermore, the moisture-curing hot melt adhesive is inhibited from gelling over time, has excellent storage stability, and has a low viscosity and excellent coatability.

The glass frit can be obtained _{by adjusting the components in a predetermined ratio, such as B2O3, P2O5, ZnO, SiO2 , Bi2O3 , Al2O3 , BaO , CaO , MgO, MnO2, ZrO2, TiO2, CeO2, SrO, V2O5 , SnO2 , Li2O , Na2O , K2O ,} CuO, and _Fe2O3 . The glass frit may be used alone or in combination of two or _more kinds.

The glass frit contains glass frit (A) which does not contain a _phosphoric acid component ( _P2O5 ) as a main component and contains an alkaline component of 15 mass% or less, and/or glass frit ( _B ) which contains a phosphoric acid component ( _P2O5 ) as a main component and contains an alkaline component of 25 mass% or less.

In the present invention, the term "main component" refers to the component that is contained in the largest amount among the components that constitute the glass frit. When there are multiple components that are contained in the largest amount, each component is referred to as _the "main component". The term "phosphate component" refers to _P2O5 . The term "alkali component" refers to _Li2O , _Na2O , and _K2O .

The glass frit (A) does not contain a _phosphoric acid component ( _P2O5 ) as a main component and contains an alkali component of 15 mass% or less. In the glass frit (A), the alkali component (total amount of _Li2O , _Na2O and _K2O ) is 15 mass% or less, preferably 12 mass% or less, more preferably 10 mass% or less, more preferably 1 mass% or less, and more preferably 0.5 mass% or less. When the alkali component is 15 mass% or less, the moisture-curable hot melt adhesive is inhibited from gelling over time and has excellent storage stability, and the viscosity is also kept low and the adhesive has excellent coatability.

The softening point of the glass constituting the glass frit (A) is preferably 600° C. or higher,
More preferably, the softening point is 620°C or higher, and more preferably, 670°C or higher. The softening point of the glass constituting the glass frit (A) is preferably 1000°C or lower, more preferably 900°C or lower, and more preferably 850°C or lower. When the softening point of the glass constituting the glass frit (A) is 600°C or higher, the moisture-curable hot melt adhesive is excellent in storage stability because gelation over time is suppressed, and the viscosity is also suppressed to be low, so that the adhesive has excellent coatability. The softening point of the glass constituting the glass frit is the temperature at which the viscosity of the glass is 107.6 dPa·s (log η=7.6).

The glass frit (B) is mainly composed of _phosphoric acid ( _P2O5 ) and contains 25 mass% or less of an alkaline component. The amount of the alkaline component in the glass frit (B) is relatively larger than that in the glass frit (A), because the glass frit (B) contains phosphoric acid, which is an acidic component, as the main component.

In the glass frit (B), the alkali component (total amount of _Li2O , _Na2O and _K2O ) is 25 mass% or less, preferably 20 mass% or less, more preferably 15 mass% or less, and more preferably 10 mass% or less. When the alkali component is 25 mass% or less, the moisture-curable hot melt adhesive is prevented from gelling over time and has excellent storage stability, and the viscosity is kept low and the adhesive has excellent coatability.

In the moisture-curing hot melt adhesive, the glass frit content is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and more preferably 100 parts by mass or more, per 100 parts by mass of the urethane prepolymer. The glass frit content is preferably 210 parts by mass or less, more preferably 170 parts by mass or less, and more preferably 150 parts by mass or less, per 100 parts by mass of the urethane prepolymer. When the glass frit content is 50 parts by mass or more, the heat resistance of the cured product of the moisture-curing hot melt adhesive is improved. When the glass frit content is 210 parts by mass or less, the melt viscosity of the moisture-curing hot melt adhesive is reduced, and the coatability is improved.

[Additive]
The moisture-curable hot melt adhesive contains a urethane prepolymer and a glass frit, but may contain additives other than the urethane prepolymer and the glass frit.

Additives are not particularly limited as long as they do not impair the physical properties of the moisture-curable hot melt adhesive, and examples include tackifiers, oils, plasticizers, thermoplastic resins, curing catalysts, stabilizers, fillers, antioxidants, light stabilizers, UV absorbers, colorants, flame retardants, fragrances, pigments, dyes, and polymers having hydrolyzable silyl groups. The additives may be used alone or in combination of two or more.

Examples of tackifiers include rosin-based resins, terpene-based resins, aliphatic petroleum resins, and aromatic petroleum resins. The ring and ball softening point of the tackifier is preferably 90 to 150°C. The ring and ball softening point refers to the temperature measured in accordance with JAI-7-1999 (Japan Adhesives Industry Association standard). Tackifiers may be used alone or in combination of two or more types.

Examples of oils include process oil, extender oil, softener, naphthenic oil, and paraffinic oil. The oils may be used alone or in combination of two or more.

Examples of plasticizers include phosphate esters such as tributyl phosphate and tricresyl phosphate, phthalate esters such as dioctyl phthalate, fatty acid-basic acid esters such as glycerin monooleate, fatty acid dibasic acid esters such as dioctyl adipate, aliphatic esters such as butyl oleate and methyl acetyl ricinoleate, trimellitic acid esters, hydrocarbon oils such as chlorinated paraffin, alkyl diphenyls, and partially hydrogenated terphenyls, process oils, epoxidized soybean oil, epoxy plasticizers such as epoxy benzyl stearate, vinyl polymers obtained by polymerizing vinyl monomers, and esters of polyalkylene glycols such as diethylene glycol dibenzoate, triethylene glycol dibenzoate, and pentaerythritol esters. Plasticizers may be used alone or in combination of two or more.

Examples of thermoplastic resins include polyvinyl acetate, polystyrene derivatives, polyisobutene, polyolefins, polyalkylene oxides, polyurethanes, polyamides, natural rubber, polybutadiene, polyisoprene, nitrobutadiene rubber (NBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), hydrogenated nitrobutadiene rubber (hydrogenated NBR), hydrogenated styrene-butadiene-styrene block copolymer (hydrogenated SBS), hydrogenated styrene-isoprene-styrene block copolymer (hydrogenated SIS), and hydrogenated styrene-ethylene-butylene-styrene block copolymer (hydrogenated SEBS). Thermoplastic resins may be used alone or in combination of two or more.

Curing catalysts are used to improve the moisture reactivity of moisture-curing hot melt adhesives. Examples of catalysts that can be used include amine-based curing catalysts and tin-based curing catalysts. There is no particular limitation on the amine-based curing catalyst, but morpholine-based compounds are preferred. Specific examples of morpholine-based compounds include 2,2'-dimorpholinodiethyl ether, bis(2,6-dimethylmorpholinoethyl)ether, bis(2-(2,6-dimethyl-4-morpholino)ethyl)-(2-(4-morpholino)ethyl)amine, bis(2-(2,6-dimethyl-4-morpholino)ethyl)-(2-(2,6-diethyl-4-morpholino)ethyl)amine, tris(2-(4-morpholino)ethyl)amine, tris(2-(4-morpholino)propyl)amine, tris(2-(4-morpholino)butyl)amine, tris(2-(2,6-dimethyl-4-morpholino)ethyl ... Examples of the tin-based curing catalyst include, but are not limited to, stannous acid, dibutyltin dilaurate, dibutyltin dioctate, dibutyltin diacetate, dioctyltin dilaurate, dioctyltin dioctate, dioctyltin diacetate, and stannous dioctanoate. The curing catalyst may be used alone or in combination of two or more.

The stabilizer is not particularly limited, but an organic phosphorus compound is preferable. Examples of organic phosphorus compounds include tricresyl phosphate, triethyl phosphate, tributyl phosphate, tris(2-ethylhexyl)phosphate, tributoxyethyl phosphate, triphenyl phosphate, octyl diphenyl phosphate, tris(isopropylphenyl)phosphate, cresyl diphenyl phosphate, triphenyl phosphite, triphenyl phosphine, triphenyl phosphine oxide, and aromatic phosphoric acid condensation ester. Among them, organic phosphorus compounds that are solid at room temperature are preferable, and triphenyl phosphite, triphenyl phosphine, triphenyl phosphine oxide, and aromatic phosphoric acid condensation ester are more preferable. The organic phosphorus compound can improve the thermal stability of the moisture-curable hot melt adhesive without decreasing the curing speed of the moisture-curable hot melt adhesive. The stabilizer may be used alone or in combination of two or more kinds.

Examples of fillers include silica, talc, clay, calcium carbonate, magnesium carbonate, anhydrous silicon, hydrated silicon, calcium silicate, titanium dioxide, carbon black, bentonite, organic bentonite, shirasu balloons, glass microballoons, organic microballoons formed from phenolic resins and vinylidene chloride resins, and particles formed from resins such as PVC (polyvinyl chloride) and PMMA (polymethyl methacrylate). The fillers may be used alone or in combination of two or more.

Examples of antioxidants include monophenol-based antioxidants, bisphenol-based antioxidants, and polyphenol-based antioxidants. The antioxidants may be used alone or in combination of two or more.

As the light stabilizer, for example, a hindered amine light stabilizer is preferably used. Among them, a hindered amine light stabilizer in which the amine portion is a tertiary amine is more preferable. As the light stabilizer, for example, N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, decanedioic acid bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl)ester, reaction product of 1,1-dimethylethyl hydroperoxide and octane, bis(1,2,2,6,6, -pentamethyl-4-piperidyl [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, and bis(1-octyloxy-2,2,6,6tetramethyl-4-piperidyl)sebacate. The light stabilizers may be used alone or in combination of two or more.

Examples of ultraviolet absorbents include benzotriazole-based ultraviolet absorbents and benzophenone-based ultraviolet absorbents. The ultraviolet absorbents may be used alone or in combination of two or more kinds.

[Moisture-curing hot melt adhesive]
During synthesis of the above-mentioned urethane prepolymer, a moisture-curable hot melt adhesive containing a urethane prepolymer and a glass frit containing glass frit (A) and/or glass frit (B) can be produced by adding glass frit (A) and/or glass frit (B) together with polyisocyanate to a melt of a polyol.

The glass frit contains specific glass frit (A) and/or glass frit (B), which can largely prevent the urethane prepolymers produced from crosslinking with each other and curing, and the resulting moisture-curable hot melt adhesive has excellent storage stability, low viscosity, and excellent coatability.

We will explain how to use moisture-curing hot melt adhesive. First, remove the moisture-curing hot melt adhesive from its storage container, such as an aluminum pack.

Next, the moisture-curing hot melt adhesive is heated to 100-130°C to melt it, and then the molten moisture-curing hot melt adhesive is applied to the adherend. Another adherend is placed on top of the moisture-curing hot melt adhesive applied to the adherend, and the two adherends are placed together with the moisture-curing hot melt adhesive between them.

The moisture-curing hot melt adhesive is then left for 120 to 168 hours, preferably in an environment at 20 to 25°C and a relative humidity of 50 to 60%. The urethane prepolymer contained in the moisture-curing hot melt adhesive undergoes a crosslinking reaction due to moisture in the air and/or the adherend, hardening the moisture-curing hot melt adhesive and bonding the two adherends together. Since the hot melt adhesive has excellent normal-state adhesive strength after curing, the two adherends are stably bonded together over a long period of time.

Furthermore, the cured product of the moisture-curing hot melt adhesive has excellent heat resistance, and the adherend is effectively protected from heat during a fire by the cured product, which has excellent fire resistance, minimizing the loss of mechanical strength due to heat.

[Cosmetic materials]
The moisture-curable hot melt adhesive is preferably used in the production of a decorative material, and is preferably used to bond and integrate a substrate and a decorative sheet.

The composition of the decorative material is not particularly limited, and examples include the compositions of conventionally known decorative materials. For example, a decorative material in which a substrate and a decorative sheet are bonded together with a moisture-curing hot melt adhesive can be mentioned.

Since the moisture-curing hot melt adhesive has the above-mentioned structure, it has excellent adhesion under normal conditions, which is a basic performance required of a moisture-curing hot melt adhesive.

The melt viscosity of the moisture-curing hot melt adhesive is preferably 40,000 mPa·s or less at 120°C. When the melt viscosity of the moisture-curing hot melt adhesive is 40,000 mPa·s or less, it has excellent coating properties. The melt viscosity of the moisture-curing hot melt adhesive is the melt viscosity measured at a temperature of 120°C and a rotation speed of 20 rpm using a B-type viscometer in accordance with the Japan Adhesives Industry Association standard JAI-7-1999. An example of a B-type viscometer is commercially available from Brookfield under the product name "B-type Viscometer Digital Rheometer DVII (Rotor No. 29)".

One example of a method for producing a decorative material is to heat a moisture-curing hot melt adhesive to 70-160°C to melt it, then apply it to one of the substrate or decorative sheet, and then overlay the other substrate or decorative sheet on the applied moisture-curing hot melt adhesive to produce a laminate, which is then cured to cure the moisture-curing hot melt adhesive, thereby forming an adhesive layer and obtaining a decorative material in which the substrate and decorative sheet are bonded together by the adhesive layer.

Methods for applying the heated and melted moisture-curing hot melt adhesive to a substrate or decorative sheet include a roll coater, spray coater, T-die coater, and knife coater.

In addition, before curing the laminate, it is preferable to apply roll pressing, flat pressing, belt pressing, etc. to the laminate to press the substrate, moisture-curing hot melt adhesive, and decorative sheet together.

Examples of substrates used in decorative materials include synthetic resin boards made of synthetic resins such as polyvinyl chloride resin, vinylidene chloride resin, polyethylene resin, polypropylene resin, polystyrene resin, ABS resin, polyamide resin, polyester resin, polyurethane resin, polyvinyl alcohol resin, ethylene-vinyl acetate copolymer resin, chlorinated polypropylene resin, and melamine resin; wood such as natural wood, plywood, medium density fiberboard (MDF) particle board, hard fiberboard, semi-hard fiberboard, and laminated lumber; and inorganic boards. In the substrate, the surface to be bonded and integrated with the adhesive layer may be subjected to plasma treatment, electrocoating treatment with acrylic resin or melamine acrylic resin, and primer treatment such as anodizing, as necessary. In addition to grooves, curved surfaces such as R and reverse R may be formed on the substrate.

Examples of decorative sheets include sheets made of synthetic resins such as polyester, nylon, polystyrene, polycarbonate, vinyl chloride, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyethylene, and polypropylene, and papers. The decorative sheets may be enhanced in decorativeness by adding colors or patterns to their surfaces.

The decorative material of the present invention is preferably used as exterior and interior materials and furniture, such as flooring, wooden door frames and panels, window frames, thresholds, handrails, baseboards, moldings, kitchens, and closets.

In the decorative material, the cured product of the moisture-curing hot melt adhesive that bonds the substrate and the decorative sheet together has excellent heat resistance. Therefore, in the event of a fire, the substrate is protected from the heat by the cured product of the moisture-curing hot melt adhesive, minimizing the loss of mechanical strength due to heat, and in the event of a fire, the adherend retains its shape and is prevented from collapsing. Therefore, in the event of a fire, gaps may be created due to the collapse of the adherend, and the spread of fire through these gaps can be effectively prevented.

The present invention will be described in more detail below using examples, but the present invention is not limited to these.

First, we will provide details of each component used in the manufacture of the moisture-curable hot melt adhesive in the examples and comparative examples described below.

[Polyol]
Polyester polyol 1 (crystalline polyester polyol, polyester polyol obtained by condensation polymerization of sebacic acid (carbon number: 10) and 1,6-hexanediol (number average molecular weight: 3500, product name "HS 2H-350S" manufactured by Toyokuni Oil Co., Ltd., hydroxyl value: 32 mgKOH/g, endothermic heat: 25 cal/g)
Polyester polyol 2 (amorphous polyester polyol, a polyester polyol obtained by condensation polymerization of a polyol containing ethylene glycol and neopentyl glycol and a polyol containing terephthalic acid and isophthalic acid (number average molecular weight: 1250, product name "HS 2F-125P" manufactured by Toyokuni Oil Co., Ltd., hydroxyl value: 88 mg KOH / g, endothermic amount: 2 cal / g)
Polyether polyol (polypropylene glycol (number average molecular weight: 1000, AGC product name "Exenol 1020", hydroxyl value: 112 mg KOH / g)

[Polyisocyanate]
4,4'-diphenylmethane diisocyanate (4,4'-MDI)

[Glass frit]
Glass frit (A1) (not mainly composed of phosphoric acid component and containing 10% by mass of alkaline component, manufactured by Takara Standard Co., Ltd., product name "CK0133", softening point: 820°C)
Glass frit (A2) (not mainly composed of phosphoric acid component and containing 10% by mass of alkaline component, manufactured by Takara Standard Co., Ltd., product name "CY5401", softening point: 681°C)
Glass frit (A3) (not mainly composed of phosphoric acid and containing 0% by mass of alkali, manufactured by Takara Standard Co., Ltd., product name "CY0037", softening point: 627°C)
Glass frit (B1) (mainly composed of phosphoric acid component and 25% by mass of alkali component, manufactured by Takara Standard Co., Ltd., product name "VQ0028", softening point: 430°C)
Glass frit (C1) (mainly composed of phosphoric acid component and 30% by mass of alkali component, manufactured by Takara Standard Co., Ltd., product name "VY0144", softening point: 404°C)
Glass frit (C2) (mainly composed of phosphoric acid and containing 30% by mass of alkali, manufactured by Takara Standard Co., Ltd., product name "VY0047", softening point: 396°C)
Glass frit (C3) ( not mainly composed of phosphoric acid component and containing 10% by mass of alkaline component, manufactured by Takara Standard Co., Ltd., product name "CY0086", softening point: 569°C)
Glass frit (C4) ( not mainly composed of phosphoric acid and containing 5% by mass of alkaline component, manufactured by Takara Standard Co., Ltd., product name "CY0113", softening point: 562°C)

[filler]
・Calcium carbonate (product name "P30" manufactured by Toyo Fine Chemical Co., Ltd.)

[Feldspar]
Feldspar (average particle size: 5 μm, nepheline syenite, manufactured by Shiraishi Calcium Co., Ltd., product name "Nespar")

[Dehydrating agent]
Monoisocyanate (p-toluenesulfonyl isocyanate, product name "Additive Ti" manufactured by OMG)

(Flame retardants)
- Phosphate ester (manufactured by Daihachi Chemical Industry Co., Ltd., product name "PX-200")

(Examples 1 to 4, Comparative Examples 1 to 6)
The polyol, glass frit, calcium carbonate, feldspar and phosphate ester in the amounts shown in Table 1 were placed in a 1-liter four-neck flask equipped with a stirring blade, heated to 140° C. and melted to obtain a molten raw material composition.

The obtained raw material composition was subjected to a dehydration treatment under a reduced pressure of 133.3 Pa (1 mmHg) or less, and then the flask was purged with nitrogen gas and the raw material composition was cooled to 80°C. Next, a specified amount of 4,4'-diphenylmethane diisocyanate shown in Table 1 was added to the raw material composition in the flask.

After stirring the contents of the flask for 3 hours under a nitrogen gas atmosphere to allow the reaction to proceed, the specified amount of monoisocyanate shown in Table 1 was added to the flask to obtain a moisture-curing hot melt adhesive containing a urethane prepolymer and glass frit that contain isocyanate groups at the ends.

The content of each component in the resulting moisture-curable hot melt adhesive is shown in Table 2.

The melt viscosity of the resulting moisture-curable hot melt adhesive at 120°C was measured as described above, and the results are shown in Table 2.

The storage stability, normal adhesion, initial adhesion, and heat resistance of the obtained moisture-curing hot melt adhesive were measured as described below, and the results are shown in Table 2.

(Storage Stability)
The moisture-curable hot melt adhesive was left for 14 days in an atmosphere of 23°C and 50% relative humidity. The melt viscosity of the moisture-curable hot melt adhesive after leaving it was measured at 120°C in the manner described above. The moisture-curable hot melt adhesives of Comparative Examples 1 to 4 and 6 were cured, and the melt viscosity could not be measured.

(Normal adhesion)
The moisture-curing hot melt adhesive was heated to 120°C to melt it, and then the molten moisture-curing hot melt adhesive was applied to one side of a flat rectangular olefin sheet (thickness 180 μm) with a coating thickness of 50 μm. The olefin sheet was then superimposed on a non-combustible board whose surface temperature was adjusted to 40°C, with the moisture-curing hot melt adhesive interposed therebetween, and a rubber roll was rolled on the olefin sheet to pressure-bond the olefin sheet and the non-combustible board to obtain a test piece.

Comparative Examples 1 to 4 and 6 significantly increased in viscosity over time after heating and melting, so test specimens could not be prepared.

Next, the test piece was left in an environment with a temperature of 23°C and a relative humidity of 55% for one hour, allowing the moisture-curing hot melt adhesive to cool and solidify. After that, the test piece was left in an environment with a temperature of 23°C and a relative humidity of 55% for one week, allowing the moisture-curing hot melt adhesive to moisture cure. The olefin sheet was then peeled off from the non-flammable board at a peel angle of 180 degrees and a peel speed of 200 mm/min, and the average peel strength at this time was measured as "normal adhesive strength (N/25 mm)."

(Initial Adhesion)
The moisture-curable hot melt adhesive was heated to 120° C. and melted. The molten moisture-curable hot melt adhesive was applied to the entire surface of one side of a flat rectangular (150 cm long x 50 cm wide) polyolefin resin sheet having a thickness of 180 μm, to a coating thickness of 50 μm.

Next, a polyolefin resin sheet was fully overlapped on the surface of a plate-shaped non-flammable board whose surface temperature was kept at 40°C, with the moisture-curing hot melt adhesive facing the substrate side, and then a rubber roll was rolled over the olefin sheet to press the olefin sheet and the non-flammable board together to obtain a test specimen. After that, the test specimen was left in an environment of 23°C temperature and 55% relative humidity for 30 minutes, after which the polyolefin resin sheet was peeled off from the surface of the plate-shaped substrate, and the peeling state was visually observed. Cases in which the surface layer of the substrate experienced material failure were noted as "material failure", and cases in which the moisture-curing hot melt adhesive experienced cohesive failure were noted as "cohesive failure".

Comparative Examples 1 to 4 and 6 were unable to be used to prepare test specimens because the viscosity increased significantly over time after heating and melting.

(Heat resistance)
Test pieces were prepared in the same manner as in the evaluation of normal adhesion. The obtained test pieces were cut into flat squares with sides of 50 mm to prepare test specimens. The test pieces were heated in an electric furnace at 800°C for 30 minutes. After the heated test pieces were removed from the electric furnace and left at room temperature for 3 hours, the appearance of the test pieces was visually observed and judged based on the following criteria. Note that in Comparative Examples 1 to 4 and 6, the viscosity increased significantly over time after heating and melting, so test pieces could not be prepared.

◯: The test piece maintained its shape.
×: The shape of the test piece was distorted.

Claims (1)

The polyurethane prepolymer is a reaction product of a polyol and a polyisocyanate and contains an isocyanate group at its terminal, and contains a glass frit.
The above-mentioned glass frit is a moisture-curable hot melt adhesive characterized in that it contains glass frit (A) which does not contain a phosphoric acid component as a main component , an alkali component of 15 mass% or less, and a softening point of 600°C or higher, and/or glass frit (B) which contains a phosphoric acid component as a main component and an alkali component of 25 mass% or less.