WO2023002992A1

WO2023002992A1 - Moisture-curable polyurethane hot-melt adhesive

Info

Publication number: WO2023002992A1
Application number: PCT/JP2022/028089
Authority: WO
Inventors: 明佳眞田; 寛女奥泉; 一弥佐々木
Original assignee: 大日精化工業株式会社
Priority date: 2021-07-21
Filing date: 2022-07-19
Publication date: 2023-01-26
Also published as: CN117651749A; JP2023016602A; JP7112573B1; TW202305083A; JP2023016691A; TWI828242B

Abstract

A moisture-curable polyurethane hot-melt adhesive which comprises a urethane prepolymer having terminal isocyanate groups and obtained by reacting a polyisocyanate ingredient at least including a modification of an aliphatic diisocyanate with a polyol ingredient, wherein the average number of isocyanate functional groups in the polyisocyanate ingredient is 2.0-3.0 and the polyol ingredient contains a tri- or higher-functional polyol in an amount of 1-8 mass% with respect to the polyol ingredient.

Description

Moisture curable polyurethane hot melt adhesive

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

Moisture-curing polyurethane hot-melt adhesives are non-solvent adhesives that are solid at room temperature. They are heated and melted, applied to a base material, bonded to another base material, and then hardened by moisture. Although it is an environmentally friendly adhesive because it does not use a solvent, the light-resistant non-yellowing polyurethane hot-melt resin has a problem of odor caused by the raw material isocyanate remaining in the adhesive.

In order to solve this problem, Patent Document 1 uses an allophanate group-containing polyisocyanate produced by a specific production method, so that storage stability, weather resistance, etc. are good, and especially less odor during adhesion work. A solventless moisture cure adhesive is disclosed.

In addition, Patent Document 2 discloses a one-pack curing solution containing at least one polyisocyanate component and titanium oxide selected from the group consisting of aliphatic polyisocyanates, araliphatic polyisocyanates, and derivatives thereof. A mold solventless adhesive is disclosed.

In addition, Patent Document 3 discloses a method for producing a moisture-curable polyurethane prepolymer in which the residual monomer content is reduced and foaming of the cured product is suppressed.

Japanese Patent Application Laid-Open No. 2003-201460 JP 2009-280735 A Japanese Patent No. 5853295

However, in Patent Document 1, the heat-resistant creep resistance was not sufficient, and the performance was insufficient as an adhesive mainly for synthetic imitation leather. In this way, if the heat creep resistance is poor, for example, when post-processing shoes, the sole and upper are bonded together under the conditions of a load of 3 kg and 150 to 160 ° C., and when processing clothing, they are bonded together with seam tape. Since it is necessary to perform at 160 to 170 ° C., there is a problem that the synthetic leather is easily peeled off.

In addition, in Patent Document 2, the breaking elongation tends to be relatively small, and when it is used as an adhesive for synthetic imitation leather, the texture of the leather, as well as the cold bending resistance and flexibility, may be inferior. .
Furthermore, in Patent Document 3, there is a problem that not only heat creep resistance but also workability (for example, initial hardening property) is low.

Therefore, the present invention has excellent heat resistance, workability, stability over time, and adhesive strength, while premised on the fact that it has excellent light resistance and little odor during work, and is used for synthetic imitation leather. The purpose of the present invention is to provide a moisture-curing polyurethane hot-melt adhesive excellent in leather-like texture and flexibility.

The above objects are achieved by the present invention described below. That is, the present invention is as follows.
[1] A moisture-curable polyurethane hot-melt adhesive obtained from a reaction between a polyisocyanate component containing at least a modified aliphatic diisocyanate and a polyol component and containing a urethane prepolymer having terminal isocyanate groups, wherein the polyisocyanate A moisture-curable polyurethane hot melt wherein the average functional number of isocyanate groups in the component is 2.0 to 3.0, and the polyol component contains 1 to 8% by mass of a trifunctional or higher polyfunctional polyol in the polyol component. glue.
[2] The moisture-curable polyurethane hot-melt adhesive according to [1], which has a gel fraction of 85% or more.
[3] The moisture-curable polyurethane hot-melt adhesive according to [1] or [2], wherein the modified aliphatic diisocyanate contains an allophanate-type diisocyanate.
[4] The moisture-curable polyurethane hot-melt adhesive according to any one of [1] to [3], wherein the modified aliphatic diisocyanate includes a diisocyanate adduct of a diol.
[5] The moisture-curable polyurethane hot-melt adhesive according to any one of [1] to [4], wherein the modified aliphatic diisocyanate contains a nurate-type polyisocyanate.
[6] The moisture-curable polyurethane hot-melt adhesive according to [5], containing 10 to 37 mol % of the nurate-type polyisocyanate in the polyisocyanate component.
[7] The moisture-curable polyurethane hot-melt adhesive according to any one of [1] to [6], which has a thermal softening point of 175° C. or higher after curing.
[8] The moisture-curable polyurethane hot melt adhesive according to any one of [1] to [7], which has a breaking elongation at 25° C. of 300 to 1,000% after curing.
[9] The moisture-curable polyurethane hot-melt adhesive according to any one of [1] to [8], further comprising an isocyanate cross-linking agent.
[10] The moisture-curable polyurethane hot-melt adhesive according to [9], wherein the isocyanate-based cross-linking agent is a modified aliphatic diisocyanate.

According to the present invention, it is premised that it is excellent in light resistance and has little odor during work, and is excellent in heat creep resistance, workability (initial solidification property), stability over time, and adhesive strength. It is possible to provide a moisture-curable polyurethane hot-melt adhesive that is excellent in leather texture and flexibility when used for leather.

FIG. 4 is a schematic explanatory diagram illustrating the form of a sample used in evaluation of Examples. It is an explanation explaining the form of the gear oven used in the evaluation of the examples.

A moisture-curable polyurethane hot-melt adhesive according to one embodiment (this embodiment) of the present invention is obtained by reacting a polyisocyanate component containing at least a modified aliphatic diisocyanate with a polyol component, and has an isocyanate group at its end. Contains urethane prepolymer.
Here, the average functionality of the isocyanate groups in the polyisocyanate component is 2.0 to 3.0, and the polyol component contains 1 to 8% by mass of trifunctional or higher polyfunctional polyol.
The urethane prepolymer is a reaction product obtained by reacting the polyisocyanate component and the polyol component, and may contain other components during the reaction.

In this embodiment, by using a specific modified aliphatic diisocyanate as described later, it has excellent light resistance, can reduce odor during work, and introduces a trifunctional or higher polyfunctional polyol to improve the leather texture. A non-yellowing, odorless, moisture-curing polyurethane hot-melt adhesive that maintains the I found what I can offer.
Hereinafter, the moisture-curable polyurethane hot-melt adhesive according to this embodiment will be described in detail.

(Polyisocyanate component)
As described above, in the present embodiment, a modified aliphatic diisocyanate is included as a polyisocyanate component. By containing the modified aliphatic diisocyanate, good light resistance and odor reduction can be achieved.

The modified aliphatic diisocyanate in the present embodiment means an isocyanurate of an aliphatic diisocyanate (nurate-type polyisocyanate: for example, "TKA100" manufactured by Asahi Kasei Corporation, "D376N" manufactured by Mitsui Chemicals, Inc., "D376N" manufactured by Vencolex Co., Ltd. IDT-70B”, etc.), allophanate derivatives of aliphatic diisocyanates (allophanate-type diisocyanates: for example, “A201H” manufactured by Asahi Kasei Corporation, “C-2770” manufactured by Tosoh Corporation, etc.), aliphatic diisocyanates Biuret form (biuret type diisocyanate: for example, "24A-100" manufactured by Asahi Kasei Corp.), or adduct form of aliphatic diisocyanate and polyol (adduct type diisocyanate: for example, "D201" manufactured by Asahi Kasei Corp.) , a diisocyanate adduct of a diol such as “D-160N” manufactured by Mitsui Chemicals, Inc.).
In the present embodiment, as the modified aliphatic diisocyanate, allophanate-type diisocyanate alone or at least containing allophanate-type diisocyanate is preferable from a practical viewpoint.

Examples of the aliphatic diisocyanate, which is a raw material component of the modified aliphatic diisocyanate, include 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 1,5-pentamethylene diisocyanate.
In addition, an unmodified polyisocyanate can be used in combination as long as there is no problem with the effect of the present invention.

Here, the isocyanurate is a trimer of diisocyanate. An allophanate compound is obtained by adding a diisocyanate to a urethane group formed by the reaction of a diisocyanate and an alcohol. A buret form is obtained by adding a diisocyanate to a urea group formed by a reaction of a diisocyanate with water or an amine. Adducts are obtained by adding diisocyanates to polyhydric alcohols.

In the present embodiment, the average functionality of the isocyanate groups in the polyisocyanate component is 2.0 to 3.0, preferably 2.0 to 2.8, and preferably 2.0 to 2.4. more preferred. If the average functional group number is less than 2.0, sufficient physical properties of the film cannot be obtained after curing. inferior in quality.

The average functional number of isocyanate groups in the polyisocyanate component represents the number of isocyanate functional groups when using one type of modified aliphatic diisocyanate, and when using a plurality of modified aliphatic diisocyanates, each aliphatic diisocyanate It represents the total number obtained by multiplying the number of functional groups of the modified product by the molar ratio (mol%) in the polyisocyanate component.
For example, when 50 mol% of a bifunctional aliphatic diisocyanate modified product and 50 mol% of a trifunctional aliphatic diisocyanate modified product are combined, the average number of functional groups is 2 × 0.5 + 3 × 0.5 = 2.5. . In addition, when the calculation result includes a number below the second decimal place, the second decimal place is rounded off.

As a preferred aspect of the modified aliphatic diisocyanate according to the present embodiment, it is more preferable to include any one of the following combinations from the viewpoint of more reliably exhibiting the effects attributed to the modified aliphatic diisocyanate.
(1) a combination of an allophanate-type diisocyanate and an adduct-type diisocyanate (especially a diol diisocyanate adduct) (2) a combination of two or more different allophanate-type diisocyanates (3) an allophanate-type diisocyanate and/or an adduct-type diisocyanate ( In particular, a combination of a diol diisocyanate adduct) and a nurate-type polyisocyanate

In the case of the combination of (1) and (2) above, that is, allophanate-type diisocyanates (e.g., "A201H", "C-2770", etc. described above) and adduct-type diisocyanates (in particular, diisocyanate adducts of diols, e.g. , the already described "D201", etc.), or when combining two or more different allophanate-type diisocyanates in structure (for example, the previously described "A201H" and "C-2770" are combined) , 30:70 to 70:30 (mixing ratio of polyisocyanate components=molar ratio), more preferably 60:40 to 40:60 (molar ratio).

In addition, in the case of the combination of (3) above, that is, allophanate-type diisocyanate and/or adduct-type diisocyanate (especially diol diisocyanate adduct), nurate-type polyisocyanate (e.g., the above-mentioned "TKA100", "D376N etc.), the nurate-type polyisocyanate is preferably 10 to 37 mol %, more preferably 15 to 32 mol %, of the total polyisocyanate component. When the mixing ratio of the nurate-type polyisocyanate is 10 to 37 mol %, the desired leather texture and cold bending resistance can be easily obtained.
Nurate-type polyisocyanates include those using 1,6-hexamethylene diisocyanate and 1,5-pentamethylene diisocyanate. 1,5-pentamethylene diisocyanate nurate-type polyisocyanate is preferred in view of the fact that the heat resistance is increased and high durability is obtained.

In addition, although unmodified polyisocyanate can be used in combination to the extent that there is no problem with the effect of the present invention, the proportion of the aliphatic diisocyanate modified product in the total polyisocyanate component is preferably 95 mol% or more, and 98 mol%. is more preferable. When the amount is 95 mol % or more, the effect (particularly, the odor reduction effect) attributed to the modified aliphatic diisocyanate can be exhibited more reliably.

(Polyol component)
As described above, the polyol component contains 1 to 8% by mass of tri- or higher polyfunctional polyol. If the polyfunctional polyol is less than 1% by mass, sufficient heat creep resistance required as an adhesive for synthetic leather applications cannot be obtained, and if it exceeds 8% by mass, stability over time, leather texture and flexibility decreases. The content of polyfunctional polyol is preferably 1 to 5% by mass, more preferably 2 to 4% by mass.
In this way, a specific amount of trifunctional or higher polyol component is blended in any of the combinations (1) to (3) of the polyisocyanate components in which the modified aliphatic diisocyanate is blended in an appropriate ratio as described above. As a result, the effect of improving the thermal softening point can be satisfactorily expressed, and as a result, an adhesive having both heat resistant creep resistance and texture (cold flex resistance) can be obtained.

Trifunctional or higher polyfunctional polyols include glycerin, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, polyethylenetriol, polypropylenetriol, polyoxypropylenetriol, polyoxy Ethylene triol, polyoxyethylene propylene triol and the like can be mentioned.
Among them, trimethylolpropane and polyoxypropylenetriol are preferred, and trimethylolpropane is more preferred, from the viewpoint of good gel fraction or heat resistant creep resistance.

The polyfunctional polyol preferably has a number average molecular weight of 100 to 1,000, more preferably 100 to 200, from the viewpoint of good heat-resistant creep resistance, gel fraction, and the like.
When the number average molecular weight is 100 to 1000, good synthesis stability is maintained, and expected effects can be easily obtained.

Polyols other than trifunctional or higher polyfunctional polyols include bifunctional polyols used in polyurethanes, examples of which include polycarbonate polyols, polyether polyols, polyester polyols, polylactone polyols, polyolefin polyols, polymethacrylate diols, and polysiloxane polyols. is mentioned.
The bifunctional polyol preferably has a number average molecular weight of 500 to 6000, more preferably 700 to 4000. Examples thereof include the following.

(1) Polycarbonate Polyol Polycarbonate polyols include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, and these diols. Random/block copolymers and the like are included.

(2) Polyether polyol Polyether polyols include those obtained by polymerizing or copolymerizing any of alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) and heterocyclic ethers (tetrahydrofuran, etc.). . Specific examples include polyethylene glycol, polypropylene glycol, polyethylene glycol-polytetramethylene glycol (block or random), polytetramethylene ether glycol and polyhexamethylene glycol.

(3) Polyester polyol Polyester polyols include aliphatic dicarboxylic acids (e.g., succinic acid, adipic acid, sebacic acid, glutaric acid and azelaic acid), and aromatic dicarboxylic acids (e.g., isophthalic acid and terephthalic acid). ) and low molecular weight glycols (e.g., ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentyl glycol and 1,4-bishydroxymethylcyclohexane).
Specifically polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene/butylene adipate diol, polyneopentyl/hexyl adipate diol, poly-3-methylpentane adipate diol and polybutylene and isophthalate diol.

(4) Polylactone polyol Examples of polylactone polyol include polycaprolactone diol and poly-3-methylvalerolactone diol.
(5) Polyolefin Polyol Examples of polyolefin polyol include polybutadiene glycol, polyisoprene glycol, and hydrogenated products thereof.
(6) Polymethacrylate Diol Polymethacrylate diols include α,ω-polymethyl methacrylate diol and α,ω-polybutyl methacrylate diol.
(7) Polysiloxane polyol As the polysiloxane polyol, dimethylpolysiloxane is preferred. Since it can impart lubricity, it is particularly useful when used as a coating agent.

These polyols can be used alone or in combination of two or more.

In this specification, the "number average molecular weight" is the polystyrene-equivalent number average molecular weight (Mn), which can be usually determined by gel permeation chromatography (GPC).

The moisture-curable polyurethane hot-melt adhesive according to the present embodiment is a urethane preform having an isocyanate group at its end, which is obtained by reacting a polyisocyanate component containing at least the above-mentioned modified aliphatic diisocyanate with the above-mentioned polyol component. Although it contains a polymer, the urethane prepolymer specifically contains these polyisocyanate component and polyol component, and if necessary, a chain extender and the like, and the equivalent ratio of the isocyanate group to the hydroxyl group (NCO/OH) is 1. Manufactured by reacting at 40 to 150° C. (preferably 60 to 110° C.) with a formulation of 5 to 2.0 by a one-shot method or a multistage method until the reaction product reaches the theoretical NCO%. be able to.

As described above, the equivalent ratio (NCO/OH) between the isocyanate group of the isocyanate component and the hydroxyl group of the polyol component is preferably 1.5 to 2.0, more preferably 1.3 to 2.2. When the equivalent ratio (NCO/OH) is from 1.5 to 2.0, gels do not occur and the viscosity suitable for processing can be obtained.

Moreover, a short-chain diol, a short-chain diamine, etc. are mentioned as a chain extender.
The short-chain diol is a compound having a number average molecular weight of less than 500, and includes ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,4-butylene glycol, Aliphatic glycols such as 6-hexamethylene glycol and neopentyl glycol and their alkylene oxide low molar adducts (number average molecular weight less than 500), 1,4-bishydroxymethylcyclohexane and 2-methyl-1,1-cyclohexane di Alicyclic glycols such as methanol and their alkylene oxide low molar adducts (number average molecular weight less than 500), aromatic glycols such as xylylene glycol and their alkylene oxide low molar adducts (number average molecular weight less than 500), Compounds such as bisphenols such as bisphenol A, thiobisphenols and sulfonebisphenols and their alkylene oxide low molar adducts (number average molecular weight less than 500), and alkyldialkanolamines such as C1-C18 alkyldiethanolamines. Diols containing ionic groups such as carboxyl groups, sulfo groups, phosphoric acid groups and amino groups can also be used.

Short chain diamines include aliphatic diamine compounds such as ethylenediamine, trimethylenediamine, hexamethylenediamine and octamethylenediamine, phenylenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4,4′-methylenebis (phenylamine), aromatic diamine compounds such as 4,4′-diaminodiphenyl ether and 4,4′-diaminodiphenyl sulfone, cyclopentanediamine, cyclohexyldiamine, 4,4-diaminodicyclohexylmethane, 1,4-diaminocyclohexane and Alicyclic diamine compounds such as isophorone diamine, hydrazines such as hydrazine, carbodihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, phthalic acid dihydrazide, and the like.

Also, in the above production method, a catalyst can be used as necessary. For example, salts of metals and organic and inorganic acids such as dibutyltin laurate, dioctyltin laurate, stannus octoate, lead octoate, tetra-n-butyl titanate, and organometallic derivatives, organic amines such as triethylamine, diaza bicycloundecene-based catalysts, and the like.

The urethane prepolymer according to this embodiment is preferably reacted without using an organic solvent. Thereby, a solventless urethane prepolymer can be obtained.

The NCO% (isocyanate group content) of the resin component (urethane prepolymer) according to the present embodiment is preferably 2 to 4%, and 2.5 to 3.5% from the viewpoint of workability and leather texture. 7% is more preferred.
The NCO % is a theoretical value obtained by calculation and can be obtained by the following formula.
NCO% (theoretical value) = [(mixed amount of isocyanate) x (NCO% of isocyanate) x (1-NCO/OH)/(NCO/OH)]/[mixed amount of isocyanate + blended amount of polyol + additive Amount of]

The moisture-curable polyurethane hot-melt adhesive of the present embodiment preferably contains 90% by mass or more of the urethane prepolymer described above, and more preferably consists of polyurethane prepolymer (that is, 100% by mass).

Here, the moisture-curable polyurethane hot-melt adhesive of this embodiment preferably contains 90% by mass or more of the urethane prepolymer described above, and if it is less than 100% by mass, it further contains an isocyanate-based cross-linking agent. By including an isocyanate-based cross-linking agent, it is possible to prevent delamination between adherends due to the adhesive, compared to the case where the isocyanate-based cross-linking agent is not included.

When an isocyanate-based cross-linking agent is contained, the content of the isocyanate-based cross-linking agent in the moisture-curable polyurethane hot-melt adhesive of the present embodiment is preferably 10% by mass or less with respect to the urethane prepolymer. It is more preferably up to 7% by mass, and even more preferably 1 to 5% by mass.

The isocyanate-based cross-linking agent is preferably a modified aliphatic diisocyanate, and specific examples thereof include the above-described modified aliphatic diisocyanate.
The modified aliphatic diisocyanate of the urethane prepolymer described above and the isocyanate-based cross-linking agent of the present embodiment may be the same or different.

The NCO% (isocyanate group content) of the resin component (when it contains a urethane prepolymer and a cross-linking agent) according to the present embodiment is preferably 2 to 4% from the viewpoint of workability and leather texture. More preferably 2.5 to 3.7%.
Incidentally, the NCO% when the urethane prepolymer and the cross-linking agent are contained is a theoretical value obtained by calculation, and can be obtained by the following formula.
NCO% (theoretical value) = [(NCO% of urethane prepolymer) x (amount of urethane prepolymer) + (NCO% of cross-linking agent) x (amount of cross-linking agent)]/[(amount of urethane prepolymer + cross-linking) amount of agent)]

A moisture-curable polyurethane hot-melt adhesive containing an isocyanate-based cross-linking agent can be prepared by adding a predetermined amount of an isocyanate-based cross-linking agent after preparing the urethane prepolymer described above and mixing by stirring or the like.

Further, in the moisture-curable polyurethane hot-melt adhesive of the present embodiment, if necessary, a thermoplastic polymer, a tackifying resin, a catalyst, a pigment, an antioxidant, a light stabilizer, an ultraviolet absorber, a surfactant, Flame retardants, fillers, foaming agents, etc. may be blended in appropriate amounts.

Various light stabilizers can be used here, and hindered amine light stabilizers are preferred.
When a specific amount of a hindered amine light stabilizer is added to the urethane prepolymer of the present invention as described above, excellent effects such as improvement in gel fraction and shortening of curing time can be obtained.

Hindered amine light stabilizers include, for example, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethylpiperidine-4- yl), tetrakis(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl) ) 1,2,3,4-butane tetracarboxylate, (mixed 2,2,6,6-tetramethyl-4-piperidyl/tridecyl) 1,2,3,4-butane tetracarboxylate, (mixed 1, 2,2,6,6-pentamethyl-4-piperidyl/tridecyl) 1,2,3,4-butanetetracarboxylate, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1, 3,8-Triazaspiro[4.5]decane-2,4-dione and the like can be used. Among them, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate is preferred.
In addition, these compounds may be used independently or may be used in combination of 2 or more types.

Also, the moisture-curable polyurethane hot-melt adhesive of the present embodiment is preferably for synthetic imitation leather, that is, an adhesive for synthetic imitation leather.

The moisture-curable polyurethane hot-melt adhesive of this embodiment can easily bond adherends together by applying it to the surfaces of adherends. Examples of the adherend include substrates of metals and non-metals (polycarbonate, glass, etc.) in addition to the above substrates for synthetic imitation leather.

Here, the gel fraction of the moisture-curable polyurethane hot-melt adhesive of this embodiment is preferably 85% or more, more preferably 90% or more.

When the gel fraction is 85% or more, heat creep resistance, alcohol resistance, and workability (curing speed) can be improved. To increase the gel fraction, for example, the aforementioned hindered amine light stabilizer can be added to the urethane prepolymer. From the viewpoint of obtaining the desired effect (high gel fraction, shortening of curing time, etc.), the amount added is preferably 0.2 to 1.0% by mass, more preferably 0.2 to 0.5%, relative to the urethane prepolymer. % by mass is more preferred. The gel fraction can be measured by the method described in Examples.

The heat softening point (thermosetting temperature) of the moisture-curable polyurethane hot-melt adhesive of this embodiment after curing is preferably 175°C or higher, more preferably 185 to 220°C.

When the heat softening point after curing is 175° C. or higher, the heat creep resistance, weather resistance, heat resistance, and resistance to industrial washing are improved. The improved weather resistance and heat resistance make it possible to use it as an adhesive for vehicle exterior members, and the improved industrial washing resistance makes it possible to use it for sanitary materials that require high-temperature sterilization.
The thermal softening point can be measured by the method described in Examples. In the present specification, the heat softening point and the elongation at break described below are measured after heat curing, and "after curing" means after disappearance of NCO is confirmed by IR measurement.

The breaking elongation at 25° C. after curing of the moisture-curable polyurethane hot-melt adhesive of this embodiment is preferably 300 to 1000%, more preferably 400 to 800%. If the elongation at break is 300% or more, the synthetic leather can have good flexibility. When the elongation at break is 1,000% or less, deterioration in heat creep resistance and adhesive strength is suppressed, and good functions as an adhesive are likely to be exhibited.
The breaking elongation can be measured by the method described in Examples.

The present invention will be described in more detail with examples and comparative examples below, but the present invention is not limited to these. In addition, "parts" below indicate parts by mass, and "%" indicates mass%. In the table, (numbers in parentheses) indicate "molar ratio (mol%) in the polyisocyanate component".

The materials used are as follows.
(1) Polyester polyol TPEP85: adipic acid/1,4-butanediol (60/40 mol%) (number average molecular weight 2000, manufactured by Daisei Chemical (2) Polyether polyol PTMG1000: number average molecular weight 1000, Mitsubishi Chemical ( Co., Ltd. PPG1000: number average molecular weight 1000, Asahi Glass Co., Ltd. (3) trifunctional polyol T-700: polyoxypropylene triol, number average molecular weight 700, Mitsui Chemicals Co., Ltd. TMP: trimethylolpropane, Number average molecular weight 134, manufactured by Mitsubishi Gas Chemical Company, Inc.

(4) Polyisocyanate component A201H: Duranate A201H, 1,6-hexamethylene diisocyanate modified allophanate-type diisocyanate, weight average molecular weight 488.4, NCO% = 17.2, Asahi Kasei Co., Ltd. D201: Duranate D201 , 1,6-hexamethylene diisocyanate modified diisocyanate adduct of diol, weight average molecular weight 558.2, NCO% = 15.9, manufactured by Asahi Kasei Co., Ltd. TKA100: Nurate polyisocyanate of hexamethylene diisocyanate, weight average Molecular weight 578, Asahi Kasei Co., Ltd. C-2770: Allophanate-type diisocyanate of hexamethylene diisocyanate, weight average molecular weight 437.5, Tosoh Corporation D376N: Nurate-type polyisocyanate of 1,5-pentane diisocyanate, weight average Molecular weight 536.1, manufactured by Mitsui Chemicals Co., Ltd. HDI: hexamethylene diisocyanate, manufactured by Asahi Kasei Co., Ltd. Note that the above "A201H" and "C-2770" are both allophanate-type diisocyanates of hexamethylene diisocyanate. They differ from each other in average molecular weight, structure, and the like.

(5) Light stabilizer HALS (hindered amine light stabilizer): CHISORB770 (LS770, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate)

[Example 1]
Into a glass reaction vessel equipped with a stirrer, a thermometer, a gas inlet, etc., 55 parts of polyester polyol (TPEP85), 45 parts of polyether polyol (PTMG1000), and a trifunctional or higher polyfunctional polyol ( T-700) 3.0 parts, 30 parts of Duranate A201H and 30 parts of Duranate D201 as polyisocyanate components are mixed, dehydration treatment is performed by heating and depressurizing the inside of the reaction vessel, and nitrogen gas is further introduced. The mixture was sealed and the internal temperature was kept at 110° C., and the mixture was stirred for 120 minutes for reaction to obtain a urethane prepolymer having an NCO/OH ratio of 1.7. Next, a light stabilizer was added so as to be 0.3% (0.3% relative to the resin) with respect to the obtained urethane prepolymer, and the mixture was stirred for 30 minutes.

[Examples 2 to 10, Comparative Examples 1 to 10]
A urethane prepolymer was obtained in the same manner as in Example 1 except that the types and formulations of the polyol component and the polyisocyanate component were as shown in Tables 1 and 2 below. In Examples 3 to 8 and 10 and Comparative Examples 1 to 10, no light stabilizer was added after synthesizing the urethane polymer.

The following evaluations were performed using the urethane prepolymers obtained in Examples and Comparative Examples. The results are shown in Tables 1 and 2.

[Gel fraction and resin physical properties]
(Production of film for evaluation)
The urethane prepolymer of each example was melted at 100° C. and coated on release paper so that the film thickness after coating would be 50 to 70 μm. Thereafter, as an aging step, the film was aged for 60 hours under an environment of a temperature of 40° C. and a relative humidity of 60%, and further stored at room temperature (20° C.) for 1 day to obtain an evaluation film with release paper.
This evaluation film is used to evaluate the gel fraction and the physical properties of the resin.

<Gel fraction>
A film for evaluation obtained by peeling off the release paper was cut into a size of 8 cm×8 cm, and the weight (Wa) was measured. The weighed film was immersed in each of MEK (methyl ethyl ketone) and toluene, sealed with a lid, left at 25°C for 2 hours, and then completely dried at 70°C. The weight (Wb) of the completely dried film was measured. The gel fraction was calculated by the formula (Wb)/(Wa)×100. 85% or more for both MEK and toluene is acceptable.

<20% modulus, 100% modulus, 300% modulus, breaking strength and breaking elongation>
For the film for evaluation obtained by peeling off the release paper, a dumbbell-shaped test piece was punched according to JIS3, and an Autograph AGS-J manufactured by Shimadzu Corporation was used to measure the temperature at room temperature (25 ° C.), 20% modulus, 100% modulus, 300% modulus (ML (MPa)), breaking strength (MPa) and breaking elongation (%) were measured. In this evaluation, the higher the breaking strength, the higher the strength of the film. Further, the elongation at break is preferably 300 to 1000% as an adhesive for synthetic imitation leather.
The 300% modulus of Comparative Examples 3 and 5 are indicated by "-" in Table 2 because the films did not stretch to 300% (hard) and there are no measured values.

<Thermal softening point>
The thermal softening point was measured using an evaluation film (width 1.5 cm, length 6 cm) obtained by peeling off the release paper.
Specifically, first, as shown in FIG. 1, clips 12 are attached to the top and bottom of the evaluation film 10, and the clips 12 are further fixed with Sellotape (registered trademark). A sample 16 was prepared by attaching a weight 14 that applies a load of cm ² . In addition, 2 cm in the central longitudinal direction of the evaluation film 10 is not covered with Sellotape (registered trademark).

Next, as shown in FIG. 2, the clip 12 of the sample 16 to which the weight 14 was not attached was attached to the rotating disk 22 of the gear oven 20 . After that, while rotating the rotating disk 22 at 5 rpm, the temperature inside the gear oven 20 was raised from room temperature at a rate of 3° C./min. The temperature (° C.) at which the evaluation film 10 was cut or stretched twice was taken as the thermal softening point.
In this evaluation, the higher the thermal softening point (thermal softening temperature), the higher the resistance (heat resistance) as a film.

[Evaluation of Adhesive]
<Heat resistant creep resistance>
As a creep test, a constant load was applied to the test piece for a long time at high temperature, and the amount of deformation and the time until fracture were measured. Specifically, the following 1) to 8) were carried out.

1) The moisture-curable PUR-HM resin (urethane prepolymer in each example) to be tested and the coated bar were preheated in an oven at 110°C.
2) PUR-HM resin was applied to the PU resin surface of the wet film-formed cloth (A) at a 200 μgap (thickness of 200 μm), and immediately bonded to the PU resin surface of the wet film-formed cloth (B).
As the wet film-forming fabric (A) and the wet film-forming fabric (B), a polyurethane resin compound liquid (Rezamin CU-4340NS (PU resin solid content 30%, large manufactured by Nissei Kagaku Kogyo Co., Ltd.) is diluted with DMF to a solid content of 15%) is applied, solidified in a water tank, DMF is removed, and then dried. A synthetic imitation leather having a porous layer having a thickness of 800 to 1000 μm after drying formed thereon was used.
3) After curing the laminated product at 25° C./60% RH for 24 hours, the heat resistance was measured according to the following procedure.
4) The oven was set to 170°C. Also, the bonded product was cut to a width of 3 cm and a length of 12 cm or more to obtain a test piece.
5) The end of the test piece was peeled off at the bonded surface, clamps were attached and fixed to the wet film-formed cloth (A) side and the wet film-formed cloth (B) side, respectively, and a weight of 3 kg was hung on one side.
6) After placing the test sample in an oven at 170°C and hanging the test sample, the oven door was quickly closed.
7) After closing the door, let stand for 5 minutes.
8) After 5 minutes had passed, the test piece was immediately taken out and left at 170°C for 5 minutes to observe the peeled length and peeled state, and evaluated according to the following evaluation criteria. In addition, 0 is a pass.

[Evaluation criteria]
○: Peeled length of less than 2 cm, peeled state is substrate destruction △: Peeled length of 2 cm or more and less than 5 cm, peeled state is substrate destruction ×: Peeled length of 5 cm or more, or wet PU resin layer peeled off

<Processing performance (initial hardening property)>
The urethane prepolymers obtained in Examples and Comparative Examples were melted at 100° C. and coated on release paper so as to have a film thickness of 50 to 70 μm. At 40° C., the uncoated surface of the same substrate was adhered every 30 seconds for up to 5 minutes. The processing (initial solidification) performance was evaluated based on the feeling of resistance when peeling off the bonded base material by hand and the amount of resin adhered to the base material.
◯: No resistance during peeling and no adhesion, passing the test.
Δ: There is resistance during peeling, but there is no adhesion. The evaluation is inferior to ○.
x: There is resistance at the time of peeling, and there is also adhesion, so it is disqualified.

(Production and evaluation of synthetic imitation leather)
(Formation of epidermis layer)
For synthetic imitation leather skin, Rezamin NE-8875-30 (manufactured by Dainichiseika Kogyo Co., Ltd.), a solvent-type urethane resin, and Seika Seven BS-780 (Dainichiseika Kogyo Co., Ltd.) as a coloring agent for synthetic imitation leather )), and methyl ethyl ketone (MEK) and dimethylformamide (DMF) as diluent solvents. After uniformly applying a coating amount of 250 μm / wet on release paper with a bar coater, dry at 120 ° C. for 5 minutes. A skin layer having a thickness of 40 to 50 μm was obtained.

(Preparation of standard synthetic imitation leather for evaluation of leather texture)
100 parts by mass of Lezamin UD-8351NT (polyurethane resin adhesive, manufactured by Dainichiseika Kogyo Co., Ltd.), C-50 cross-linking agent (isocyanate cross-linking agent, Dainichiseika Kogyo Co., Ltd.) is added to the skin layer formed on the release paper. Co., Ltd.) was coated so as to form an adhesive layer having a thickness of 100 μm and was pre-dried at 80° C. for 2 minutes. ) were pressure-bonded at a laminate roll temperature of 40°C. Then, it was aged at 50° C./48 hours to obtain a standard synthetic imitation leather for flexibility evaluation.

(Production of synthetic imitation leather according to Examples 1 to 10 and Comparative Examples 1 to 10)
The polyurethane prepolymers obtained in Examples and Comparative Examples are heated to 100° C. and coated on the skin layer formed on the release paper so that the coating thickness is 100 μm, and the base fabric (fabric) is laminated. Pressure bonding was performed at a roll temperature of 30°C. As an aging step, the mixture was aged for 5 days under an environment of a temperature of 40° C. and a relative humidity of 60%. A synthetic imitation leather for evaluation was prepared by peeling from the release paper and using a polyurethane prepolymer.

<Leather texture>
The softness of each synthetic imitation leather obtained for evaluation was compared with the standard synthetic imitation leather as a reference, and the evaluation index was as follows. In addition, if the evaluation is ◯, it is acceptable.
○: As soft as standard synthetic imitation leather (accepted as leather texture)
×: Significantly harder than standard synthetic imitation leather (failed as leather texture)

<Cold Flexibility Test>
Each synthetic imitation leather obtained above was used as a test sheet with a width of 50 mm and a length of 150 mm (evaluation range: 100 mm). ), a bending test was performed under a -10°C environment, with a stretching and bending range of 72 to 108%, and at a low temperature of -10°C. The evaluation indices were as follows. In addition, if the evaluation is ◯, it is acceptable.
○: -10°C, 30,000 times or more ×: -10°C, less than 30,000 times

<Stability over time: Pot Life>
The urethane prepolymers obtained in Examples and Comparative Examples were melted at 100° C., and the change in viscosity over time and sedimentation were visually evaluated under the conditions of 100° C. for 24 hours (useable level is ◯).
◯: No sediment, viscosity change less than +100%.
x: Presence of sediment, viscosity change of +100% or more.
The viscosity was measured under the following conditions.
(Viscosity measurement)
Using a BM type viscometer (Tokyo Keiki Seisakusho), rotor No. The viscosity of each urethane prepolymer was measured under the conditions of 4/30 rpm/100°C.

<Odor>
The urethane prepolymers obtained in Examples and Comparative Examples were placed in 250 ml pound cans, heated at 100° C. for 2 hours, and then each of the 10 panelists opened the lid and checked the odor. The evaluation criteria are as follows (○ indicates a practical level).
◯: All 10 people did not sense an odor.
x: 5 or more out of 10 people felt the odor.

<Film Formability>
The urethane prepolymers obtained in Examples and Comparative Examples were heated to 100° C. and coated on release paper K8P(01) to a coating thickness of 100 μm. Immediately after coating, the film was kept at 40°C for 10 minutes. The film-forming property was evaluated based on the presence or absence of continuity of the coating film after 10 minutes (◯ indicates a practical level).
○: Continuity of coating film maintained ×: Repelling or shrinkage of coating film

<Curing time>
The urethane prepolymers obtained in Examples and Comparative Examples were melted at 100° C., coated on release paper so as to give a film thickness of 50 to 70 μm after coating, and then stored under conditions of 40° C./60 RH%. IR measurement was performed every 12 hours, and the time at which NCO disappeared was taken as the curing time. The curing time was measured only for Examples 1, 3 and 8-10.

<Adhesion strength>
On the resin layer surface, which is the upper surface of the skin layer of the evaluation synthetic imitation leather used in the evaluation of <leather texture> described above, press a hot melt tape for 1 minute with an iron at 140 ° C., 1 hour. After cooling to room temperature, the base fabric was peeled off from the skin adhered to the hot-melt tape, and the strength was measured with an autograph to determine the adhesive strength. In addition, as an adhesive for synthetic imitation leather, a measured value of 1.2 kgf/cm or more is preferable.

"NCO % in resin component" in Tables 1 and 2 is NCO % in the obtained urethane prepolymer.

[Example 11]
Into a glass reaction vessel equipped with a stirrer, a thermometer, a gas inlet, etc., 55 parts of polyester polyol (TPEP85), 45 parts of polyether polyol (PTMG1000), and a trifunctional or higher polyfunctional polyol ( T-700) 3.0 parts, 30 parts of Duranate A201H and 30 parts of Duranate D201 as polyisocyanate components are mixed, dehydration treatment is performed by heating and depressurizing the inside of the reaction vessel, and nitrogen gas is further introduced. The mixture was sealed and the internal temperature was kept at 110° C., and the mixture was stirred for 120 minutes for reaction to obtain a urethane prepolymer having an NCO/OH ratio of 1.7. Next, a light stabilizer is added to the obtained urethane prepolymer so as to be 0.3% (0.3% relative to the resin), and further to 2.0% (2.0% relative to the resin). TKA-100 (HDI nurate) was added as an isocyanate-based cross-linking agent and stirred for 30 minutes to prepare a moisture-curable polyurethane hot-melt adhesive.
Moisture-curable polyurethane hot-melt adhesives were subjected to the evaluation described above and the delamination test described below. Table 3 shows the results.

<Delamination test>
1) The moisture-curable PUR-HM resin to be tested (the moisture-curable polyurethane hot-melt adhesives of Example 11 and Examples 12-15 below) and the coated bar were preheated in an oven at 110°C.
2) PUR-HM resin is applied at 200 μ Gap (thickness 200 μm) on the skin layer obtained in (Formation of skin layer) of (Preparation and evaluation of synthetic imitation leather), and immediately the already described After bonding to the PU resin surface of the wet film-formed cloth (B), the bonded product was cured at 40° C./60% RH for 48 hours.
3) A hot-melt tape is crimped to the resin layer surface, which is the upper surface of the skin layer of the laminated product, with an iron at 140 ° C. for 1 minute, and after cooling to room temperature for 1 hour, the base fabric and the skin adhered to the hot-melt tape. was peeled off, and the strength was measured with an autograph.
Further, as a reference for peel strength, strength was measured in the same manner for Example 1 as well.

Each example was evaluated for delamination strength using the following evaluation index. Table 3 shows the results.
A: The delamination strength was improved by 10% or more compared to Example 1.
B: The delamination strength was the same as in Example 1 or less than 10% even if improved. C: The delamination strength was lower than in Example 1.

[Examples 12 to 15]
A moisture-curable polyurethane hot-melt adhesive was prepared in the same manner as in Example 11, except that the isocyanate-based cross-linking agent was changed to the following cross-linking agent.
As the isocyanate-based cross-linking agent, Example 12 uses "24A-100" manufactured by Asahi Kasei Co., Ltd., and Example 13 uses "D376N" manufactured by Mitsui Chemicals, Inc., manufactured by Vencolex. Example 14 uses "IDT-70B", and Example 15 uses "D-160N" manufactured by Mitsui Chemicals, Inc.
The same evaluations and tests as in Example 11 were performed using the moisture-curable polyurethane hot-melt adhesive. Table 3 shows the results.

"NCO% in the resin component" in Table 3 is the NCO% when the obtained urethane prepolymer and the cross-linking agent are included.

The moisture-curable polyurethane hot-melt adhesive of this embodiment can be used for synthetic imitation leather, that is, for synthetic imitation leather substrates. It can also be used for substrates (polycarbonate, glass, etc.). In addition, due to its excellent heat resistance, it can be expected to be applied to vehicle exterior parts and sanitary materials that require high-temperature sterilization.

10 evaluation film 12 clip 14 weight 16 sample 20 gear oven 22 turntable

Claims

A moisture-curable polyurethane hot-melt adhesive obtained from the reaction of a polyisocyanate component containing at least a modified aliphatic diisocyanate and a polyol component and containing a urethane prepolymer having terminal isocyanate groups,
The average functional number of isocyanate groups in the polyisocyanate component is 2.0 to 3.0,
A moisture-curable polyurethane hot-melt adhesive, wherein the polyol component contains 1 to 8% by mass of a trifunctional or higher polyfunctional polyol.
The moisture-curable polyurethane hot-melt adhesive according to claim 1, which has a gel fraction of 85% or more.
The moisture-curable polyurethane hot-melt adhesive according to claim 1 or 2, wherein the modified aliphatic diisocyanate contains an allophanate-type diisocyanate.
The moisture-curable polyurethane hot-melt adhesive according to any one of claims 1 to 3, wherein the modified aliphatic diisocyanate contains a diisocyanate adduct of a diol.
The moisture-curable polyurethane hot-melt adhesive according to any one of claims 1 to 4, wherein the modified aliphatic diisocyanate contains a nurate-type polyisocyanate.
The moisture-curable polyurethane hot-melt adhesive according to claim 5, which contains 10 to 37 mol% of the nurate-type polyisocyanate in the polyisocyanate component.
The moisture-curable polyurethane hot-melt adhesive according to any one of claims 1 to 6, which has a thermal softening point of 175°C or higher after curing.
The moisture-curable polyurethane hot-melt adhesive according to any one of claims 1 to 7, which has a breaking elongation at 25°C of 300 to 1,000% after curing.
The moisture-curable polyurethane hot-melt adhesive according to any one of claims 1 to 8, further comprising an isocyanate-based cross-linking agent.
10. The moisture-curable polyurethane hot-melt adhesive according to claim 9, wherein the isocyanate-based cross-linking agent is a modified aliphatic diisocyanate.