JP4441850B2 - Solvent-free moisture-curable hot-melt urethane resin composition - Google Patents

Description

  The present invention relates to a solventless moisture-curable hot-melt urethane resin composition excellent in viscosity stability in a state where it is heated and melted for a long time and excellent in crosslinking reactivity with moisture (water).

A reactive hot melt resin composition is one that can be used as an adhesive or coating material by heating and melting a resin having a solid reactivity at room temperature, and has many excellent features. In recent years, many expectations have been received from the industrial world, and its practical application has been promoted.
For example, the reactive hot-melt resin composition is solvent-free and does not require a drying step, and thus has a feature that the application and bonding speed can be increased (for example, a line speed of about 40 m / min). Compared with solvent-based adhesives and water-based adhesives, productivity can be dramatically improved. In addition, it does not release the solvent to the atmosphere, and further, since no drying process is required, it can reduce carbon dioxide emissions by saving energy, and is attracting attention as an environmentally friendly adhesive. .

  Among such reactive hot melt resin compositions, those that have received particular attention and are used in the industry are isocyanate group-containing hot melt urethane prepolymers, which are the main components of many reactive hot melt resin compositions. It is used. The reactive hot melt resin composition mainly composed of this isocyanate group-containing hot-melt urethane prepolymer is crosslinked with moisture contained in the substrate in which it is used, such as moisture (moisture) in the air or a wooden substrate. A reaction is caused to develop the final adhesive strength.

  For such a reactive hot melt resin composition, the cross-linking reactivity that influences the overall bonding process time is very important. In recent years, from the viewpoint of productivity, the line speed for bonding various substrates using a reactive hot melt resin composition has been greatly increased. For example, bonding is performed at a high speed of about 40 m / min. It has been broken. However, even if they are bonded together, sufficient adhesive strength cannot be obtained instantaneously. The isocyanate group-containing hot-melt urethane prepolymer undergoes a crosslinking reaction with water in the environment, so that the final adhesive strength can be obtained to some extent. Time, which depends on the crosslinking reactivity of the urethane prepolymer.

  In the conventional reactive hot melt resin composition, this crosslinking reactivity is poor and a long time may be required for the crosslinking reaction. For example, in a low temperature environment in winter, 4 to 5 until the final adhesive strength is obtained. It may take many days, and in this case, there is no point in bonding at a high speed, and a problem arises in the storage space of the base material after bonding. Therefore, when designing a reactive hot melt resin composition, the cross-linking reactivity is an important factor.

  The isocyanate group-containing hot melt urethane prepolymer is obtained by reacting polyol and polyisocyanate as raw materials, and the polyisocyanate is in consideration of the crosslinking reactivity and safety. In many cases, an aromatic polyisocyanate having a low vapor pressure is used.

  Among these diphenylmethane diisocyanates, those in which the isocyanate group is located in the para position are useful because they have high reactivity and exhibit good crosslinking reactivity when used as a reactive hot melt resin. Due to its properties, it reacts with urethane bonds and urea bonds existing in the prepolymer itself even under moisture-free conditions to form allophanate bonds and burette bonds, respectively. As a result, the molecular weight tends to increase and the viscosity of the system tends to increase. There is.

  The reactive hot melt resin is generally used after being heated and melted at 100 to 130 ° C. When the above-mentioned high molecular weight occurs at the time of heating and melting, the viscosity increases with time, and the coating amount changes. Problems such as a change in wettability with respect to the substrate occur, and in an extreme case, a serious problem occurs in production that gelation occurs inside the melting apparatus or the coating apparatus and it cannot be used.

As a countermeasure for this problem, a method for suppressing polymerization due to a side reaction at the time of melting of the reactive hot melt resin has been studied.
For example, there is a technique of using a low-reactivity aliphatic polyisocyanate as a polyisocyanate that is a raw material of a urethane prepolymer in order to prevent a thickening over time due to a side reaction at the time of melting of a reactive hot melt resin. . However, such aliphatic polyisocyanates have low practical reactivity due to poor crosslinking reactivity when used as reactive hot melt resins because of low reactivity at room temperature.

Specifically, after bonding the substrates using the reactive hot melt resin composition, for example, after 2-3 hours, cutting or drilling is performed on the shape of each member used. Actually, in cutting and drilling, a considerable amount of heat is applied to the work piece, so that the crosslinking reaction has not progressed and the heat resistance is still insufficient. Adhesion failure occurs.
Further, since the vapor pressure of aliphatic polyisocyanate is generally higher than that of diphenylmethane diisocyanate, it has a problem in terms of safety.

  In addition, as a polyisocyanate that is a raw material of the urethane prepolymer, a method of using tolylene diisocyanate having an isocyanate group having low reactivity in aromatic polyisocyanate or 2,4′-diphenylmethane diisocyanate has been proposed, As in the case of aliphatic polyisocyanates, there is a problem that the crosslinking reactivity is low. In addition, in the case of tolylene diisocyanate, there is also a safety problem due to the high vapor pressure.

  In addition, improvement of crosslinking reactivity under room temperature conditions by addition of a crosslinking accelerator to the reactive hot melt resin has been studied, but conventionally used crosslinking accelerators, for example, amine-based catalysts such as diethylenetriamine, Alternatively, metal-based catalysts such as dibutyltin dilaurate improve the cross-linking reactivity at room temperature, but at the same time have the adverse effect of promoting a side reaction during melting of the reactive hot melt resin, which is a practical problem. It was.

  A polyurethane reactive hot melt adhesive using a urethane prepolymer and a morpholine ether-based crosslinking catalyst such as 2,2′-dimorpholinodiethyl ether or di (2,6-dimethylmorpholinoethyl) ether (For example, Patent Document 1) has been reported to be relatively effective in improving the thermal stability during melting and the crosslinking reaction rate. However, although these morpholine ether crosslinking catalysts have some effect in improving the crosslinking reaction rate, the effect is not sufficient, and the amount of catalyst is increased to improve the crosslinking reactivity to a practically sufficient level. In such a case, there was a problem that thickening during melting was likely to occur.

Furthermore, the moisture curable adhesive composition comprising an isocyanate group-containing compound, an organic phosphorus compound, and a morpholine compound has good storage stability at room temperature and thermal stability at the time of heat melting, and rapid moisture curing. There is a report that it is possible to develop the property and excellent adhesive strength (for example, Patent Document 2).
However, such a moisture curable adhesive composition does not have a great effect on the thermal stability of the organophosphorus compound, and when the added amount is small, the effect of improving the thermal stability at the time of melting is poor. Therefore, when the amount of addition of the organic phosphorus compound is increased in order to improve the thermal stability at the time of melting, the organic phosphorus compound acts as a plasticizer, so that the heat resistance is delayed and the heat resistance is remarkable. A drop occurs. Further, the organic phosphorus compound has a problem that durability is lowered in order to promote hydrolyzability .

  As described above, if the cross-linking reactivity is improved, the problem of thickening over time due to side reactions during heat-melting becomes significant, and the conventional reactive hot melt resin composition has cross-linking reactivity and heat stability. There was nothing that could satisfy both performances.

US Pat. No. 5,550,191 JP 2001-262113 A

  An object of the present invention is a solventless, moisture-curable, hot-melt urethane resin composition that has high crosslinking reactivity at room temperature, has little time-dependent thickening due to side reactions during heat-melting, and has excellent thermal stability. Is to provide.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have obtained a composition obtained by adding a morpholine ether-based crosslinking catalyst as a crosslinking accelerator to an isocyanate group-containing hot melt urethane prepolymer under room temperature conditions. Although there is an improvement in cross-linking reactivity, there is a problem of thermal stability in which the composition is markedly thickened or gelled when heated and melted. The present invention has been completed by finding out that it is possible to suppress the thickening at the time of heating and melting while maintaining excellent crosslinking reactivity.

  When the specific sulfur atom-containing organic acid constituting the present invention is added alone to an isocyanate group-containing hot-melt urethane prepolymer that does not contain a morpholine ether-based crosslinking catalyst, it has thermal stability contrary to the above effect. In spite of adverse effects on the crosslinking reactivity under room temperature conditions, the excellent effect of the present invention is unexpectedly expressed when used in combination with a morpholine ether crosslinking catalyst. Of nature.

That is, the present invention is selected from the group consisting of an isocyanate group-containing hot melt urethane prepolymer (A) having a softening point in the range of 40 to 120 ° C. , a morpholine ether-based crosslinking catalyst (B), and sulfonic acids and sulfinic acids. at least one a of comprising sulfur atom-containing organic acid (C) as an essential component solvent-free moisture-curable hot melt urethane resin composition, the solvent-free moisture-curable hot melt isocyanate groups of the urethane resin composition The content is 2.0 to 2.2% by weight, solvent-free, solid or viscous at normal temperature, melts when heated, and can be applied, and agglomerates again by cooling. The present invention provides a solventless, moisture-curable hot-melt urethane resin composition characterized by having a property of exerting a force .

The matters necessary for carrying out the present invention are described below.
The solventless moisture-curable hot-melt urethane resin composition of the present invention is an isocyanate group-containing hot-melt urethane prepolymer (A) (hereinafter referred to as urethane prepolymer (A)), morpholine ether-based crosslinking catalyst (B). And a sulfur atom-containing organic acid (C) as an essential component.

  The urethane prepolymer (A) used in the present invention is a compound having in its molecule an isocyanate group that can form a crosslinked structure by reacting with moisture present in the air or in the substrate on which it is applied. It has solid or viscous properties at room temperature. In general, what is called a urethane prepolymer has a relatively low molecular weight, but those skilled in the art also have a number average molecular weight (Mn) of tens of thousands, which is also called a urethane prepolymer. Also, urethane prepolymers having a number average molecular weight (Mn) of tens of thousands can be used.

  The number average molecular weight (Mn) of the urethane prepolymer (A) is preferably in the range of 500 to 30,000, more preferably in the range of 1,000 to 10,000. If the number average molecular weight of the urethane prepolymer is within such a range, a solventless moisture-curable hot melt urethane resin composition excellent in fluidity and workability can be obtained.

The urethane prepolymer (A) used in the present invention has both properties of moisture crosslinking reactivity (moisture curability) and hot melt property.
The moisture cross-linking reactivity of the urethane prepolymer (A) is derived from the cross-linking reaction initiated by the reaction of the isocyanate group of the urethane prepolymer and moisture (water), and is caused by the isocyanate group of the urethane prepolymer. It is a property to do.

  On the other hand, the hot-melt property of the urethane prepolymer (A) is a property resulting from the molecular structure of the urethane prepolymer to be selected. It is solid at room temperature but can be melted and applied by heating. It is a property that solidifies and develops adhesiveness when cooled.

  Hot melt is a general term for properties or substances that are solid or viscous at room temperature, but melt and become fluid or liquid when heated. For example, hot melt typified by ethylene vinyl acetate is generally used. Are known. Hot melt is a solvent-free and solid or viscous property at room temperature, but when heated, it melts and becomes ready for coating, and has the property of generating cohesive force again upon cooling. It is useful as a solventless adhesive or coating material.

Hot melt properties are closely related to the softening point. Generally, the lower the softening point of the urethane prepolymer used, the better the workability. Conversely, the higher the softening point, the better the adhesive strength.
The softening point of the urethane prepolymer (A) used in the present invention is in the range of 40 to 120 ° C. If the softening point of the urethane prepolymer is within the range, the workability is good and the adhesive strength is excellent. A solvent-type moisture-curable hot-melt urethane resin composition is obtained. In addition, the softening point as used in the field of this invention means the temperature which begins to heat flow and loses cohesive force, when the temperature of a urethane prepolymer is raised.

  Examples of the method for adjusting the softening point of the urethane prepolymer (A) include (1) a method for adjusting the molecular weight of the urethane prepolymer, and (2) a polyalkylene of the polyester polyol when a polyester polyol is used as a raw material. An adjustment method by chain crystallinity, (3) an adjustment method by introduction of an aromatic ring using a polyol or polyisocyanate, (4) an adjustment method by the content of urethane bonds, and the like can be employed. These adjustment methods can be used alone or in combination.

  In the method (1) for adjusting the softening point of the urethane prepolymer (A), the softening point generally tends to increase as the molecular weight of the urethane prepolymer increases. In addition, adjustment of the molecular weight of a urethane prepolymer can employ | adopt methods, such as adjustment by the molar ratio of polyisocyanate and a polyol, use of high molecular weight polyol, for example, and there is no restriction | limiting in particular.

  In the method (2) for adjusting the softening point of the urethane prepolymer (A), generally, the larger the number of carbon atoms in the polyalkylene chain of the crystalline polyester polyol, the more crystals of the urethane prepolymer (A) obtained. The softening point tends to increase, and the softening point tends to increase as the amount of the crystalline polyester polyol used increases.

In the method (3) for adjusting the softening point of the urethane prepolymer (A), the softening point tends to increase as the content of the aromatic ring in the urethane prepolymer increases.
Moreover, in (4) of the adjustment method of the softening point of the said urethane prepolymer (A), there exists a tendency for a softening point to raise normally, so that there is much content of a urethane bond.

  In the urethane prepolymer (A), the polyol and polyisocyanate are in a state in which the equivalent ratio of the isocyanate group of the polyisocyanate to the hydroxyl group of the polyol (hereinafter referred to as isocyanate group / hydroxyl group equivalent ratio) exceeds 1 (that is, , And an isocyanate group is in an excess state.).

  The equivalent ratio of isocyanate group / hydroxyl group of the urethane prepolymer (A) is preferably in the range of 1.1 to 5.0, more preferably in the range of 1.5 to 3.0. Within such a range, the resulting solvent-free moisture-curable hot-melt urethane resin composition has an appropriate range of melt viscosity and good processability, and excellent initial cohesive strength and adhesive strength. Can do.

  Examples of polyols that can be used in producing the urethane prepolymer (A) include polyester polyols, polyether polyols, polycarbonate polyols, acrylic polyols, polyolefin polyols, castor oil polyols, and the like. These mixtures or copolymers may be mentioned.

As a polyester-type polyol which can be used when manufacturing the said urethane prepolymer (A), the condensate of a polyhydric alcohol and a polybasic acid can be used. Examples of the polyhydric alcohol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethyl-1,3- Propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, Cyclohexane-1,4-dimethanol ; one or two or more of ethylene oxide adduct or propylene oxide adduct of bisphenol A can be used.

Examples of the polybasic acid that can be used in the production of the polyester polyol include succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, One or more of phthalic acid, isophthalic acid, terephthalic acid, hexahydroisophthalic acid and the like can be mentioned.
In addition, a polymer obtained by ring-opening polymerization of γ-butyrolactone, ε-caprolactone, etc. using the polyhydric alcohol as an initiator can also be used.

Moreover, as a polyether-type polyol which can be used when manufacturing the said urethane prepolymer (A), the said polyhydric alcohol or the said polyester-type polyol is used as an initiator, ethylene oxide, propylene oxide, butylene oxide. And a polymer obtained by ring-opening polymerization of one or more of styrene oxide and the like.
Moreover, ring-opening addition polymerization products, such as (gamma) -butyrolactone and (epsilon) -caprolactone, to the said polyether-type polyol can also be used.

  Furthermore, as the polycarbonate-based polyol that can be used in producing the urethane prepolymer (A), the polyhydric alcohol is condensed with one or more of diaryl carbonate, dialkyl carbonate, and alkylene carbonate. Examples include poly (alkylene carbonate) diol obtained by the reaction.

  Examples of the polyisocyanate that can be used in producing the urethane prepolymer (A) include aromatic polyisocyanates such as diphenylmethane diisocyanates, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate, hexamethylene diisocyanate, and lysine. Examples thereof include aliphatic polyisocyanates such as diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate, and alicyclic polyisocyanates.

  Among them, the urethane prepolymer (A) having an isocyanate group derived from diphenylmethane diisocyanate at the molecular terminal has a fast moisture cross-linking reaction and a low vapor pressure at the time of heating and melting and low toxicity. Of the polyisocyanates, diphenylmethane diisocyanates are particularly preferred.

  Examples of the diphenylmethane diisocyanates (hereinafter also referred to as MDI) include 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, a mixture of 4,4′-diphenylmethane diisocyanate and 2,4′-diphenylmethane diisocyanate, and carbodiimide. Examples thereof include modified diphenylmethane diisocyanate and crude diphenylmethane diisocyanate.

As a method for producing the urethane prepolymer (A) used in the present invention, various known and commonly used methods can be employed.
For example, a method in which a predetermined amount of a polyol from which water has been removed is dropped onto a raw polyisocyanate and heated until the hydroxyl group of the polyol is substantially eliminated, or conversely, a raw polyisocyanate is added to a predetermined amount of polyol from which water has been removed. And a method of reacting until the hydroxyl group of the polyol substantially disappears. Although this reaction can be carried out without a solvent, it may be removed after reacting in an organic solvent. When reacting in an organic solvent, the type of organic solvent used is not particularly limited as long as it does not inhibit the reaction. For example, an organic solvent such as ethyl acetate, n-butyl acetate, methyl ethyl ketone, or toluene is used. Is possible. However, when reacting using an organic solvent, it is necessary to remove the organic solvent by, for example, a solvent removal method represented by heating under reduced pressure during or after the reaction.

Further, when synthesizing the urethane prepolymer (A), additives such as a urethanization reaction catalyst and a stabilizer, if necessary, can be used for the purpose of the present invention in terms of viscosity stability during heating and melting and room temperature conditions. It can also be used as long as the moisture crosslinking reactivity is not impaired.
Additives such as these urethanization reaction catalysts and stabilizers can be appropriately added at any stage of the reaction.

  Examples of the urethanization reaction catalyst include nitrogen-containing compounds such as triethylamine, triethylenediamine, or N-methylmorpholine, organic acid metal salts such as potassium acetate, zinc stearate, or tin octylate, or dibutyltin dilaurate. An organometallic compound or the like can be used.

  Examples of the stabilizer include ultraviolet absorbers such as benzotriazole compounds, benzophenone compounds, phenyl salicylate compounds, and cyanoacrylate compounds, or antioxidants such as hindered phenol compounds and hindered amine compounds. Stabilizers can be used.

  Next, the morpholine ether crosslinking catalyst (B) used in the present invention will be described. The morpholine ether-based crosslinking catalyst (B) contributes to the improvement of moisture crosslinking reactivity under room temperature conditions of the solventless moisture-curable hot melt urethane resin composition in the present invention.

  As the morpholine ether-based crosslinking catalyst (B) constituting the present invention, specifically, a compound represented by the following general formula (X) can be used.

(In the formula, R ¹ and R ² represent hydrogen or an alkyl group, and n represents a positive integer.)

  In the solventless moisture-curable hot melt urethane resin composition of the present invention, the amount of the morpholine ether-based crosslinking catalyst (B) can be appropriately set according to the target moisture crosslinking reactivity. Preferably it is the range of 0.05-5.0 weight% with respect to the weight of a polymer (A), More preferably, it is the range of 0.2-3.0 weight%. If the addition amount of the morpholine ether crosslinking catalyst is within such a range, it is possible to achieve both moisture crosslinking reactivity at a relatively low temperature such as room temperature and excellent thermal stability.

As the morpholine ether-based crosslinking catalyst (B) used in the present invention, it is excellent in moisture crosslinking reactivity and heat stability and is easily available. Morpholino diethyl ether or di (2,6-dimethylmorpholinoethyl) ether represented by the following structural formula (2) is particularly preferred.
2,2′-Dimorpholinodiethyl ether or di (2,6-dimethylmorpholinoethyl) ether may be used alone or in combination, and the mixing ratio of both is not particularly limited.

Next, the sulfur atom containing organic acid (C) which comprises this invention is demonstrated.
In the present invention, the sulfur atom-containing organic acid (C) contributes to an improvement in the thermal stability of the solventless moisture-curable hot-melt urethane resin composition when heated and melted.

The sulfur atom-containing organic acid (C) used in the present invention is at least one sulfur atom-containing organic acid selected from the group consisting of sulfonic acids and sulfinic acids.
Examples of the sulfonic acids include methanesulfonic acid, ethanesulfonic acid, methanedisulfonic acid, 1,2-ethanedisulfonic acid, 2-hydroxy-1-ethanesulfonic acid, sulfoacetic acid, 2-amino-1-ethanesulfonic acid, and trifluoro. Aliphatic sulfonic acids such as lomethanesulfonic acid and aromatic sulfonic acids such as benzenesulfonic acid, o- or m- or p-toluenesulfonic acid, and other substituted benzenesulfonic acids can be used.

Moreover, as said sulfinic acid, ethane sulfinic acid etc. can be used. Among these, methanesulfonic acid and ethanesulfonic acid are preferable because the effect of improving the thermal stability during heating and melting is particularly excellent. These sulfur atom-containing organic acids may be used alone or in combination of two or more.
Note that sulfinic acid is also a sulfonic acid precursor and can be converted to sulfonic acid by heating.

  The amount of the sulfur atom-containing organic acid (C) used in the solventless moisture-curable hot-melt urethane resin composition of the present invention is preferably 0.005 to 3.3 based on the weight of the urethane prepolymer (A). It is in the range of 0% by weight, more preferably in the range of 0.02 to 0.1% by weight. When the sulfur atom-containing organic acid is used in such a range, a solventless moisture-curable hot-melt urethane resin composition having excellent thermal stability during heating and melting can be obtained.

The solvent-free moisture-curable hot-melt urethane resin composition of the present invention includes, for example, rosin resin, rosin ester resin, hydrogenated rosin ester resin, terpene resin, terpene phenol resin, water as necessary. hydrogenated terpene resins; also, as a petroleum resin, C ₅ based aliphatic resin, C ₉ aromatic resins, and C ₅ based tackifier such as C ₉ based copolymer resin,

For example, dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, diisooctyl phthalate, diisodecyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, trioctyl phosphate, epoxy plasticizer, toluene-sulfoamide, chloroparaffin, adipic acid ester, castor oil, etc. Plasticizers,

For example, stabilizers such as hindered phenol compounds, benzotriazole compounds, hindered amine compounds, fillers such as silicic acid derivatives, talc, metal powder, calcium carbonate, clay, carbon black, dyes, pigments, fluorescent whitening agents , Silane coupling agents, waxes, urethanization reaction catalysts, foam stabilizers and other additives, thermoplastic resins, etc., are selected singly or plurally depending on the purpose and added within a range that does not impair the purpose of the present invention. Can be used.

  The solventless moisture-curable hot-melt urethane resin composition of the present invention has excellent moisture crosslinking reactivity at room temperature, and is excellent in thermal stability because it has little viscosity increase with time during heating and melting. . For this reason, when using the solvent-free moisture-curable hot melt urethane resin composition of the present invention using a coating apparatus by heating and melting, there is no harmful effect due to thickening, and it is excellent in coating workability and performance. For example, it can be used for a wide range of applications such as adhesives, pressure-sensitive adhesives, coating materials, binders, sealing agents, and paints.

  Hereinafter, the present invention will be described more specifically by way of examples. In the following, all parts and% are based on weight unless otherwise specified. In addition, the properties, thermal stability, and moisture crosslinking reactivity under room temperature conditions (substitute evaluation was performed with heat-resistant creep characteristics) of the resin compositions of Examples and Comparative Examples were measured under the following conditions. The results are shown in Tables 1 and 2.

[Measuring method of melt viscosity]
Melt viscosity (mPa · s) at 125 ° C. of a solvent-free moisture-curable hot-melt urethane resin composition using an ICI cone-plate rotational viscometer (cone diameter: φ19.5 mm, cone angle: 2.0 °) Was measured.

[Measurement method of isocyanate group content (% by weight)]
The isocyanate group content (% by weight) of the solventless moisture-curable hot-melt urethane resin composition was measured by an appropriate method.

[Measurement method of thermal stability]
A solvent-free, moisture-curable hot-melt urethane resin composition is filled in a metal can with an internal volume of 200 ml, and is visually observed for gelation after being left in an oven at 120 ° C. for 18 hours and 36 hours in a sealed state. did. Moreover, the melt viscosity (mPa * s) in 125 degreeC after time-lapse was measured about what has not reached gelatinization.

[Measurement method of heat-resistant creep characteristics]
As a substitute evaluation method for moisture cross-linking reactivity under room temperature conditions, heat-resistant creep characteristics were measured according to the following procedure.
Using a test piece in which an olefin decorative sheet and medium density wood board (MDF, Middle Density Fiber Boards) are bonded together via a solvent-free moisture-curable hot-melt urethane resin composition, heat-resistant creep characteristics are obtained by the following method. evaluated.
Apply a solvent-free moisture-curable hot-melt urethane resin composition heated to a 50 μm thick olefin decorative sheet on a hot plate with a surface temperature of 80 ° C. to a thickness of 40 μm, and bond an MDF plate to the coated surface. Then, after performing a roll press at a linear pressure of 10 kg / cm, it was cut into a width of 25 mm to prepare an adhesion processing test piece.

Immediately after the preparation of the adhesion test piece, each test piece after standing for 1 hour, standing for 2 hours, standing for 3 hours, and standing for 4 hours at room temperature (23 ° C., relative humidity: 65%) was placed on one end of the olefin decorative sheet. In addition, a heat resistant creep test was conducted by leaving it to stand in an oven at 60 ° C. for 1 hour in a state where a load of 500 g / 25 mm was vertically suspended in a 90-degree angle peeling direction. The deviation distance (mm) from the initial suspension position was measured over time. Those with a deviation distance of 5 mm or less were determined to be acceptable.
Since the initial creep characteristics at 60 ° C. were improved by the progress of the crosslinking reaction under room temperature conditions (23 ° C., relative humidity 65%), a test was conducted as a substitute evaluation of moisture crosslinking reactivity under room temperature conditions.

Example 1
500 parts of polyester polyol obtained by reacting adipic acid having a number average molecular weight of 3000 and 1,6-hexanediol in a 1 liter four-necked flask, and reacting neopentyl glycol having a number average molecular weight of 1000 and terephthalic acid. The polyester polyol obtained by reacting 250 parts of the polyester polyol obtained by reacting sebacic acid having a number average molecular weight of 3500 with 1,6-hexanediol was heated to 120 ° C. under reduced pressure to obtain a moisture content of 0.05. Dehydrated to%.
After cooling to 70 ° C., 207 parts of 4,4′-diphenylmethane diisocyanate was added, and then the temperature was raised to 90 ° C. and reacted for 3 hours until the isocyanate group content became constant to obtain a urethane prepolymer.

  After completion of the reaction, 4.8 parts of 2,2′-dimorpholinodiethyl ether (trade name: U-CAT 2041, manufactured by San Apro) and 0.5 part of methanesulfonic acid were added and stirred uniformly. A solventless moisture-curable hot melt urethane resin composition was obtained. Table 1 shows the properties of the obtained solventless moisture-curable hot-melt urethane resin composition. The melt viscosity at 125 ° C. in an ICI cone-plate rotational viscometer was 11000 mPa · s, and the isocyanate group content was 2.1% by weight.

<< Examples 2 to 5 >>
A urethane prepolymer was synthesized according to the composition shown in Table 1 by the same operation as in Example 1. After completion of the reaction, the additives shown in Table 1 were added according to the indicated addition amount. Table 1 shows the properties of the obtained solvent-free moisture-curable hot-melt urethane resin composition of the present invention.
In Tables 1 and 2, isonate 143LJ (trademark, manufactured by Mitsubishi Chemical Corporation) is carbodiimide-modified diphenylmethane diisocyanate.

<< Comparative Example 1 >>
500 parts of polyester polyol obtained by reacting adipic acid having a number average molecular weight of 3000 and 1,6-hexanediol in a 1-liter four-necked flask having the same composition as in Example 1 and neopentyl glycol having a number average molecular weight of 1000 250 parts of a polyester polyol obtained by reacting terephthalic acid with terephthalic acid, 250 parts of a polyester polyol obtained by reacting sebacic acid having a number average molecular weight of 3500 with 1,6-hexanediol is heated to 120 ° C. under reduced pressure. Then, it was dehydrated until the water content became 0.05%.
After cooling to 70 ° C., 240 parts of isonate 143LJ [carbodiimide-modified diphenylmethane diisocyanate, manufactured by Mitsubishi Chemical Corporation] was added, and the mixture was heated to 90 ° C. and reacted for 3 hours until the isocyanate group content became constant. A group-containing urethane prepolymer was obtained.

  After completion of the reaction, 5.0 parts of 2,2′-dimorpholinodiethyl ether (U-CAT 2041, manufactured by San Apro) was added and stirred uniformly to obtain a solventless moisture-curable hot melt urethane resin composition. The obtained hot-melt urethane resin composition had a melt viscosity at 125 ° C. of 14,000 mPa · s with an ICI corn plate type rotational viscometer and an isocyanate group content of 2.1% by weight.

<< Comparative Example 2 >>
An isocyanate group-containing urethane prepolymer was obtained in the same manner as in Comparative Example 1. After completion of the reaction, 0.5 part of methanesulfonic acid was added and stirred uniformly to obtain a solventless moisture-curable hot melt urethane resin composition. The obtained hot melt urethane resin composition had a melt viscosity at 125 ° C. of 15000 mPa · s with an ICI corn plate type rotational viscometer and an isocyanate group content of 2.1% by weight.

<< Comparative Example 3 >>
An isocyanate group-containing urethane prepolymer was obtained in the same manner as in Comparative Example 1. After completion of the reaction, 0.6 parts of 89% phosphoric acid and 5.0 parts of 2,2′-dimorpholinodiethyl ether (U-CAT 2041, manufactured by San Apro) were added and stirred uniformly to obtain a solventless moisture-curable hot melt urethane. A resin composition was obtained. The melt viscosity at 125 ° C. of the obtained hot melt urethane resin composition measured with an ICI type cone plate type rotational viscometer was 13000 mPa · s, and the isocyanate group content was 2.1% by weight.

According to the present invention, a solventless moisture-curable hot-melt urethane resin composition having excellent moisture cross-linking reactivity under room temperature conditions and little increase in viscosity over time during heat-melting and excellent thermal stability. Can be provided.

Claims (4)

Containing at least one sulfur atom selected from the group consisting of an isocyanate group-containing hot melt urethane prepolymer (A) having a softening point in the range of 40 to 120 ° C., a morpholine ether-based crosslinking catalyst (B), and sulfonic acids and sulfinic acids A solventless moisture-curable hot-melt urethane resin composition containing an organic acid (C) as an essential component, and the isocyanate group content in the solvent-free moisture-curable hot-melt urethane resin composition is 2.0 to 2 solventless moisture curable hot melt urethane resin composition, wherein the .2 percent by weight. The solvent-free moisture-curable hot-melt urethane resin composition according to claim 1, wherein the isocyanate group-containing hot-melt urethane prepolymer (A) is a urethane prepolymer having an isocyanate group derived from diphenylmethane diisocyanate at a molecular end. object. 2. The solventless moisture-curable hot water according to claim 1, wherein the morpholine ether crosslinking catalyst (B) is 2,2′-dimorpholinodiethyl ether and / or di (2,6-dimethylmorpholinoethyl) ether. Melt urethane resin composition. The solvent-free moisture-curable hot-melt urethane resin composition according to claim 1, wherein the sulfur atom-containing organic acid (C) is methanesulfonic acid and / or ethanesulfonic acid.