JPH06271832A - Reactive hot-melt type adhesive - Google Patents

Abstract

PURPOSE:To obtain a reactive hot-melt type adhesive capable of solving fragility of adhesive itself at an initial stage curing by moisture, including a crystalline polyester in the molecule so as to have non-adhesiveness and capable of facilitat ing handling operation after applying the adhesive. CONSTITUTION:This reactive hot-melt type adhesive consists essentially of an isocyanate group-containing urethane prepolymer obtained by reacting a urethane prepolymer obtained by reacting a crystalline polyester diol with a diisocyanate compound with a low-molecular weight diol or a terminal isocyanate group-containing urethane prepolymer obtained by reacting a diisocyanate oligomer obtained by reacting a low-molecular weight diol with a diisocyanate compound with a crystalline polyester dial and further reacting the reactional product with a diisocyanate compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-curable reactive hot melt adhesive containing a polyester urethane prepolymer as a main component, and more particularly to a reactive hot melt adhesive excellent in initial cohesive force. It is a thing.

[0002]

2. Description of the Related Art Conventionally, in a moisture-curable reactive hot-melt adhesive, a reactive compound containing a urethane prepolymer having an isocyanate group at a terminal as a main component, which is obtained by reacting a crystalline polyester diol with a diisocyanate compound, is used. The crystallinity of the hot-melt adhesive can be used to improve the initial adhesive force, and since it is non-adhesive, the workability can be improved.

For example, JP-A-62-181375 discloses a mixture of a polyester diol obtained from a glycol having 2 to 4 carbon atoms and a dicarboxylic acid, a polyester diol obtained from a glycol having 5 to 10 carbon atoms and a dicarboxylic acid. An adhesive comprising a urethane prepolymer obtained by reacting a polyester diol and a diisocyanate compound is disclosed, and JP-A-2-88686 discloses an adhesive obtained by reacting a linear aliphatic polyester diol with a polyisocyanate. Adhesives based on urethane prepolymers are disclosed.

[0004]

[Problems to Solve the Problem] However, since the above-mentioned adhesive containing a urethane prepolymer as a main component is non-adhesive, it is possible to stack the adhesive after applying the adhesive and improve workability. Although it has an advantage, it has a drawback that the adhesive itself becomes brittle in the initial stage of curing by moisture, and there is a problem in the initial adhesive strength.

An object of the present invention is to provide a reactive hot melt type adhesive having an improved initial adhesive strength of an adhesive containing a urethane prepolymer as a main component obtained by reacting a polyester diol and a diisocyanate compound.

[0006]

Means for Solving the Problems As a result of extensive studies to solve the above problems, a urethane prepolymer obtained by reacting a crystalline polyester diol of the following formula 1 with a diisocyanate compound has 2 to 10 carbon atoms. Using a urethane prepolymer having an isocyanate group obtained by reacting a low molecular weight diol as a main component of a reactive hot melt adhesive (Invention 1), or having 2 to 1 carbon atoms
No. 0, a diisocyanate oligomer obtained by reacting a diisocyanate compound with a crystalline polyester diol of the following formula 1 is obtained, and a polyester urethane oligomer having an isocyanate group is further reacted with a diisocyanate compound. The present invention has been completed by finding that the prepolymer as a main component of the reactive hot melt type adhesive (Invention 2) can eliminate the brittleness of the adhesive itself in the initial stage.

[0007]

[Chemical 2]

The crystalline polyester diol represented by the above formula 1 used in the present invention is a reaction of one or more linear aliphatic dicarboxylic acids with one or more linear aliphatic diols. It is a product.

As the above-mentioned straight-chain aliphatic dicarboxylic acid,
Adipic acid, pimelic acid, suberic acid, azelaic acid,
Examples thereof include sebacic acid, nonamethylenedicarboxylic acid, decamethylenedicarboxylic acid, undecamethylenedicarboxylic acid, dodecamethylenedicarboxylic acid and the like.

Examples of the straight-chain aliphatic diol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8. -Octanediol, 1,9-nonanediol, 1,10-
Decanediol and the like can be mentioned. These aliphatic diols can be obtained alone or as a mixture of two or more kinds.

Examples of the diisocyanate compound used in the present invention include 4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, tolylene diisocyanate, 4,4'-biphenylene diisocyanate and 1,5-octylene diisocyanate. However, from the viewpoint of safety, 4,4′-diphenylmethane diisocyanate (MDI) is preferably used.
MDI is a commercially available purified MDI or crude MD.
Any of I and carboimide-modified MDI may be used.

Further, the number of carbon atoms used in the present invention is 2 to 1.
The diol of 0 is preferably a linear aliphatic glycol, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol. , 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and the like.

Other diols that can be used include molecular aliphatic glycols such as neopentyl glycol and ether diols such as diethylene glycol and triethylene glycol, but the crystallinity of the polyester diol is lowered. It is not so preferable because it causes it.

In the production of the urethane prepolymer having an isocyanate group at the terminal in the present invention 1, NC of the crystalline polyester diol and the diisocyanate compound are used.
The O / OH ratio is 1.2 to 2.5, preferably 1.5 to 2.
It is 0.

The NCO / OH ratio of the diol having 2 to 10 carbon atoms and the diisocyanate compound in the diisocyanate oligomer of the second invention is 1.2 to 2.5, preferably 1.5 to 2.2.

If the NCO / OH ratio is less than 1.2, the molecular weight of the urethane prepolymer obtained will be too large and the melt viscosity will be very high. Also, NCO /
When the OH ratio is larger than 2.5, the residual amount of the diisocyanate monomer increases, and the low molecular weight diol added later is lost to the reaction with the residual diisocyanate monomer.

In obtaining the isocyanate group-containing urethane prepolymer in the present invention 1, a urethane prepolymer having an isocyanate group at the terminal and a carbon number of 2 to 10 are used.
The NCO / OH ratio of the diol is 1.2 to 50, preferably 2 to 20.

The NCO / OH ratio of the diisocyanate oligomer of the polyester urethane oligomer having an isocyanate group at the terminal and the crystalline polyester diol represented by the above formula 1 in the present invention 2 is 1.2 to 5.
It is 0, preferably 2 to 20.

When the NCO / OH ratio is less than 1.2, the molecular weight of the urethane prepolymer obtained becomes too large and the melt viscosity becomes very high. Also, NCO /
When the OH ratio is larger than 50, the effect of adding the low molecular weight diol becomes small.

The NCO / OH ratio of the polyester urethane oligomer having an isocyanate group at the end and the diisocyanate compound in the urethane prepolymer having an isocyanate terminal group in the present invention 2 is 1.5 to 2.5, preferably 1.8 to 2. It is 2.

When the NCO / OH ratio is less than 1.5, the molecular weight of the urethane prepolymer obtained becomes too large, and the melt viscosity becomes very high. Also, NCO /
When the OH ratio is larger than 2.5, the amount of residual diisocyanate monomer becomes large, which is not preferable.

In the invention 2, the diisocyanate used to obtain the diisocyanate oligomer from the diol having 2 to 10 carbon atoms and the diisocyanate used to obtain the urethane prepolymer containing an isocyanate group from the diol having 2 to 10 carbon atoms are the same. Or different types may be used.

The reactive hot-melt adhesive in the present invention contains a urethane prepolymer obtained from a crystalline polyester diol as a main component, but is optionally obtained from an amorphous polyester diol, polyether diol or polyolefin diol. A urethane prepolymer, a thermoplastic elastomer, a tackifying resin, a plasticizer, a catalyst, a filler, a dye, a pigment and the like may be added.

[0024]

[Function] By adding a low molecular weight diol, a part or all of the urethane prepolymer having an isocyanate group at the terminal becomes a high molecular weight to increase the cohesive force of the adhesive and eliminate the brittleness of the adhesive itself. To be done.

[0025]

EXAMPLES Examples and comparative examples of the present invention will be shown below. Example 1 1000 g of polyhexamethylene adipate (molecular weight 2500, hydroxyl value 42) and carbodiimide-modified diphenylmethane diisocyanate (Isonate 143L, manufactured by Mitsubishi Kasei Dow Co., Ltd.) were mixed so that the ratio of NCO groups / OH groups was 2.0. However, under a nitrogen stream, 100
A urethane prepolymer was obtained by reacting at 3 ° C for 3 hours. To this urethane prepolymer, 14.6 g of 1,6-hexanediol was added so that the ratio of NCO groups / OH groups was 3, and the reaction was further continued for 2 hours to obtain a reactive hot-melt adhesive. This reactive hot-melt adhesive solidified when cooled to room temperature and lost its tackiness.

This reactive hot melt adhesive was
The composition was heated and melted at 0 ° C. and applied on a canvas at a rate of about 100 g / m ² , and then immediately pressed and adhered to a birch material. After leaving it for 10 minutes at room temperature to fully solidify the reactive hot-melt adhesive, it is cut into a width of 25 mm and a pulling speed of 200 mm /
The 180 ° peel strength at the initial stage of adhesion was measured in minutes. The result was 3.0 kgf / 25 mm.

Example 2 A mixture of 600 g of polyhexamethylene adipate (molecular weight 2500, hydroxyl value 42) and 400 g of polyhexamethylene sebacate (molecular weight 3500, hydroxyl value 30) and diphenylmethane diisocyanate (Isonat).
e125M, Mitsubishi Kasei Dow Co., Ltd.) NCO group / O
The mixture was mixed so that the ratio of H groups was 2.0, and reacted at 100 ° C. for 3 hours under a nitrogen stream to obtain a urethane prepolymer. To this urethane prepolymer, 7.8 g of 1,6-hexanediol was added so that the ratio of NCO group / OH group was 5, and the mixture was further reacted for 2 hours to obtain a reactive hot melt adhesive. This reactive hot-melt adhesive solidified when cooled to room temperature and lost its tackiness. Using this reactive hot melt adhesive, the 180 ° peel strength at the initial stage of adhesion was measured in the same manner as in Example 1. The result was 3.5 kgf / 25 mm.

Example 3 7.8 g of 1,6-hexanediol and diphenylmethane diisocyanate (Isonate 125M, manufactured by Mitsubishi Kasei Dow Co., Ltd.) were mixed so that the ratio of NCO groups / OH groups was 2.0, and nitrogen was mixed. A diisocyanate oligomer was obtained by reacting at 100 ° C. for 3 hours under an air stream. To this diisocyanate oligomer, a mixture of 600 g of polyhexamethylene adipate (molecular weight 2500, hydroxyl value 42) and 400 g of polyhexamethylene sebacate (molecular weight 3500, hydroxyl value 30) heated at 100 ° C. and having an NCO group / OH group ratio was prepared. The mixture was added so as to have a concentration of 0.2 and further reacted for 2 hours to obtain a polyester urethane oligomer having a hydroxyl group at the terminal, and a mixture of polyhexamethylene adipate and polyhexamethylene sebacate. To this, carboimide-modified diphenylmethane diisocyanate (Millionate MTL, manufactured by Nippon Urethane Co., Ltd.) was added so that the ratio of NCO groups / OH groups was 2.0, and the reaction was continued for another 3 hours to form a hot reactive urethane prepolymer. A melt type adhesive was obtained. This reactive hot-melt adhesive solidified when cooled to room temperature and lost its tackiness. Using this reactive hot melt adhesive,
The 180 ° peel strength at the initial stage of adhesion was measured in the same manner as in Example 1. The result was 3.3 kgf / 25 mm.

Example 4 14.6 g of 1,6-hexanediol and diphenylmethane diisocyanate (Isonate 125M, manufactured by Mitsubishi Kasei Dow Co., Ltd.) were used in an NCO group / OH group ratio of 2.0.
And mixed at 100 ° C under a nitrogen stream for 3
The reaction was carried out for a time to obtain a diisocyanate oligomer. To this diisocyanate oligomer, polyhexamethylene adipate (molecular weight 2500,
Hydroxyl value 42) 1000 g was added so that the ratio of NCO group / OH group was 0.3, and the reaction was further continued for 2 hours to obtain a polyester urethane oligomer having a hydroxyl group at the terminal,
A mixture of polyhexamethylene adipates was obtained. Diphenylmethane diisocyanate (Isonate 1
25M, manufactured by Mitsubishi Kasei Dow Co., Ltd.) was added so that the ratio of NCO group / OH group was 2.0, and the mixture was further reacted for 3 hours to obtain a reactive hot melt type adhesive composed of urethane prepolymer. . This reactive hot-melt adhesive solidified when cooled to room temperature and lost its tackiness. Using this reactive hot melt adhesive, the 180 ° peel strength at the initial stage of adhesion was measured in the same manner as in Example 1. The result is 3.1k
It was gf / 25 mm.

Comparative Example 1 1000 g of polyhexamethylene adipate (molecular weight 2500, hydroxyl value 42) and carbodiimide-modified diphenylmethane diisocyanate (Isonate 143 L,
Mitsubishi Kasei Dow Co., Ltd.) was mixed so that the ratio of NCO groups / OH groups was 2.0, and 100
A urethane prepolymer was obtained by reacting at 3 ° C. for 3 hours, and this was used as a reactive hot melt adhesive. This reactive hot-melt adhesive solidified when cooled to room temperature and lost its tackiness. Using this reactive hot melt adhesive, the 180 ° peel strength at the initial stage of adhesion was measured in the same manner as in Example 1. The result was 1.8 kgf / 25 mm.

Comparative Example 2 A mixture of 600 g of polyhexamethylene adipate (molecular weight 2500, hydroxyl value 42) and 400 g of polyhexamethylene sebacate (molecular weight 3500, hydroxyl value 30) and diphenylmethane diisocyanate (Isonat).
e125M, manufactured by Mitsubishi Kasei Dow Co., Ltd.) with NCO group / OH
The mixture was mixed so that the ratio of the groups was 2.0, and the mixture was reacted at 100 ° C. for 3 hours under a nitrogen stream to obtain a urethane prepolymer, which was used as a reactive hot melt adhesive. This reactive hot-melt adhesive solidified when cooled to room temperature and lost its tackiness. Using this reactive hot melt adhesive, the 180 ° peel strength at the initial stage of adhesion was measured in the same manner as in Example 1. The result was 2.0 kgf / 25 mm.

[0032]

According to the adhesive of the present invention, the brittleness of the adhesive itself at the initial stage of curing is eliminated, and an adhesive having a strong initial adhesive force can be obtained. Further, the polyester diol in the molecule becomes non-tacky due to crystallization, and the handling work after application of the adhesive becomes easy.

Claims (2)

[Claims] 1. A terminal obtained by reacting one or more crystalline polyester diols represented by the following formula 1 with a diisocyanate compound under an NCO / OH ratio of 1.2 to 2.5. A urethane prepolymer having an isocyanate group is added with a diol having 2 to 10 carbon atoms in NCO /
Reactive hot melt type adhesive containing as a main component an isocyanate group-containing urethane prepolymer obtained by reacting at an OH ratio of 1.2 to 50. 2. A diisocyanate oligomer obtained by reacting a diol having 2 to 10 carbon atoms with a diisocyanate compound at an NCO / OH ratio of 1.2 to 2.5 and 1 represented by the following formula 1. And two or more crystalline polyester diols having an NCO / OH ratio of 1.2 to 2
To the polyester urethane oligomer having a hydroxyl group at the terminal, which is obtained by reacting so as to have an NCO / OH ratio of 1.5 to 2.5.
Reactive Hot Melt Adhesive Mainly Containing Urethane Prepolymer Containing Terminal Isocyanate Group Obtained by Reacting