JPH05214311A - Moisture-curable hot melt type polyurethane adhesive - Google Patents

Abstract

PURPOSE:To provide the subject adhesive comprising a specific active isocyanate group-containing urethane prepolymer and increased in the moisture-curing rate without deteriorating the storage stability of the adhesive. CONSTITUTION:The objective adhesive comprises an active isocyanate group- containing urethane prepolymer obtained by reacting (C) an excessive amount of a polyisocyanate compound with (A) a polyester polyol (a number-average mol.wt. of 2000-5000) comprising 1,6-hexamethylene adipate polymer, 1,6- hexamethylene terephthalate polymer or their mixture and with (B) a polyether diol having an ethylene oxide content of 50-80mol.% and a number-average mol.wt. of 1000-5000 and comprising the random or block copolymer of a >=3C alkylene glycol with ethylene glycol.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a moisture-curable hot-melt polyurethane adhesive, and more specifically, an active isocyanate group-containing urethane obtained by reacting a specific polyester polyol and polyether diol with an excess of a polyisocyanate compound. The present invention relates to a heat-melting type polyurethane adhesive characterized by comprising a prepolymer and accelerating a moisture curing rate without impairing storage stability.

[0002]

2. Description of the Related Art A hot-melt type polyurethane adhesive exhibits a certain degree of adhesive strength (initial adhesive strength) at the initial stage of bonding due to cooling and solidification of the adhesive itself. However, if a temperature higher than the melting temperature is applied again at that stage, the adhesive is remelted and the adhesive strength is lost. For this reason, the hot-melt polyurethane adhesive must have sufficient durability (heat resistance) even at such a re-melting temperature, and must be subjected to rapid moisture curing at the initial stage of bonding.

By the way, as a moisture-curable, heat-melting type polyurethane adhesive, an adhesive comprising an active isocyanate group-containing urethane prepolymer obtained by the reaction of a polyester polyol and an excess polyisocyanate compound is known. However, as a polyester polyol, 1,6-hexanediol adipate-based and 1,6-hexanediol
Since the hexanediol terephthalate-based polyester polyol has high hydrophobicity, the rate of moisture penetration into the resulting urethane prepolymer is slow, resulting in a slow moisture curing rate. Therefore, in order to obtain the desired excellent heat resistance, it was usually necessary to carry out curing curing for at least one week.

Therefore, in order to increase the moisture curing rate, attempts have been made to use a moisture curing accelerating catalyst. However, since the moisture permeation rate of the polyester polyol is still slow, the expected effect is rarely obtained. , Further impair storage stability, or melting temperature during use
The curing reaction excessively progresses (generally around 100 ° C.), which causes new problems such as skinning in the storage tank and gelation in the coating machine.

[0005]

[Means for Solving the Problems] The inventors of the present invention have made earnest studies for the purpose of accelerating the moisture curing reaction while solving the problems of deterioration of storage stability or skinning or gelation during use. However, they have found that the intended purpose can be achieved by using a specific polyether diol in addition to the polyester polyol as the polyol component of the urethane prepolymer, and have completed the present invention.

That is, the present invention is a polyester polyol comprising a 1,6-hexanediol adipate type or a 1,6-hexanediol terephthalate type or a mixture thereof, and a random or block of C ₃ or more alkylene glycol and ethylene glycol. Active isocyanate group-containing urethane prepolymer obtained by reacting an excess polyisocyanate compound with a polyether diol having an ethylene oxide content of 50 to 80 mol% and a number average molecular weight of 1000 to 5000, which is a copolymer (hereinafter, NCO content (Referred to as prepolymer)
The present invention provides a moisture-curable heat-melting polyurethane-based adhesive characterized by comprising:

The polyester polyol used in the present invention is a 1,6-hexanediol adipate-based or 1,6-hexanediol phthalate-based polyester polyol (1 obtained by reacting 1,6-hexanediol with adipic acid or terephthalic acid). Number of hydroxyl groups (OH) in molecule 2 to 4, number average molecular weight 2000 to 500
0), and a mixture of one or two of these is used.

The polyether diol, which is a random or block copolymer of C ₃ or more alkylene glycol and ethylene glycol used in the present invention, is specifically a low molecular weight active hydrogen compound having two or more active hydrogens.
(For example, diols such as ethylene glycol, propylene glycol, butylene glycol, 1,6-hexanediol, amines such as ammonia, methylamine, ethylamine, propylamine, butylamine)
Alkylene oxide in the presence of one or more of
(Propylene oxide, butylene oxide, etc.) and a bifunctional one of a random or block copolymer obtained by ring-opening polymerization of ethylene oxide, particularly an ethylene oxide content of 50 to 80 mol%, preferably 60 to 80 mol %, And number average molecular weight 1000 to 5
000, preferably 2000 to 4000 are used. When the ethylene oxide content is less than 50 mol%, the compatibility with the polyester polyol is poor, and when it exceeds 80 mol%, there is a problem in storage stability. If the number average molecular weight is less than 1000, the obtained NCO-containing prepolymer gels at the time of melting (around 100 ° C), and
If it exceeds 000, the reaction rate decreases. The amount of the polyether diol used is usually 5 to 20 parts with respect to 100 parts (parts by weight, the same applies hereinafter) of the polyester polyol.
Parts, preferably 5 to 15 parts. 5
If it is less than 20 parts, the desired effect of promoting moisture curing cannot be obtained, and if it exceeds 20 parts, the initial adhesive strength tends to decrease.

The NCO-containing prepolymer in the present invention comprises the above polyester polyol and polyether diol and an excess amount of the polyisocyanate compound, that is, the active isocyanate group (NCO) of the polyisocyanate compound relative to the OH of the polyester polyol and polyether diol. 1 to 70, for example, at a ratio of 1.3 ≦ NCO / OH ≦ 10, 70 to 110.
It is produced by reacting at ℃ for several hours, usually NCO
The content is adjusted to 1 to 15% (% by weight, the same applies hereinafter). In this reaction, a usual catalyst, plasticizer or solvent may be used.

As the above polyisocyanate compound,
Aliphatic polyisocyanates such as hexamethylene diisocyanate and lysine methyl ester diisocyanate, alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate and hydrogenated tolylene diisocyanate, tolylene diisocyanate (TDI), diphenyl Aromatic isocyanates such as methane diisocyanate (MDI), naphthylene diisocyanate, xylylene diisocyanate, and mixtures thereof. Particularly preferred polyisocyanate compounds are aromatic polyisocyanates, and MDI and the like are preferably used.

The moisture-curable hot-melt polyurethane adhesive according to the present invention comprises the NCO-containing prepolymer described above, and if necessary, a conventional filler, plasticizer, solvent,
An appropriate amount of antiaging agent, pigment, etc. may be blended.

[0012]

The adhesive of the present invention having the above constitution is N
By using a specific polyether diol that imparts hygroscopicity as the polyol component of the CO-containing prepolymer, it is possible to cause a rapid moisture curing reaction, and
It is possible to avoid deterioration of storage stability due to the moisture curing accelerating catalyst or skinning or gelation during use.

[0013]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Examples 1 and 2 and Comparative Example 1 NCO-containing prepolymer The number of parts of 1,6-hexanediol adipate polyester diol (number average molecular weight 3000) and polyether diol [ethylene oxide (EO)] shown in Table 1 below.
MD content of 70 mol% and number average molecular weight of 3000]
I is added so that NCO / OH = 2.0 and reacted at 80 ° C. for 3 hours to obtain an NCO-containing prepolymer having an NCO content shown in Table 1.

Performance test Compatibility of the above NCO-containing prepolymers (○ is good, × is not compatible) and initial adhesive strength (○ is shear adhesive strength 5 kg / cm.
² or more) and 100 ° C. heat resistance after 24 hours at 20 ° C. (∘ is good without softening, × is remelting), and the results are shown in Table 1.

[0015]

[Table 1] Actual Examples Comparative Example 1 2 1 Polyester diol 100 100 100 100 Polyether diol 10 20- NCO content (%) 2.03 2.16 2.10 Compatibility ○ ○ − Initial adhesion ○ ○ ○ 100 ℃ heat resistance ○ ○ × (20 ℃ × 24 hours)

Example 3 This example is carried out using polyether diols having different EO contents. 1,6-hexanediol adipate polyester diol (number average molecular weight 3000) 10
0 parts and 20 parts of polyetherdiol (number average molecular weight 3000) having an EO content shown in Table 2 below were mixed with MDI
CO / OH = 2.0, and reacted at 80 ° C. for 3 hours to obtain NCO-containing prepolymers No. 1 to 5,
Compatibility and initial adhesive strength and 1 after 24 hours at 20 ° C
The results of heat resistance at 00 ° C are also shown in Table 2.

[0017]

[Table 2] No. 1 2 3 4 5 E O content 0 10 30 50 70 70 (mol%) Compatibility × × × ○ ○ Initial adhesive force − − − ○ ○ 100 ° C Heat resistance − − − ○ ○ (20 ° C × 24 hours) In Table 2, Nos. 1 to 3 are comparative examples, and No. 5 is the same as Example 2. No. 1 EO content of 0 mol% means 100% of propylene oxide.

Example 4 This example is carried out using polyether diols having different number average molecular weights. 1,6-hexanediol adipate polyester diol (number average molecular weight 3000)
MD to 100 parts and 20 parts of polyether diol (EO content 50 mol%) having the number average molecular weight shown in Table 3 below.
I was added so that NCO / OH = 2.0 and reacted at 80 ° C. for 3 hours to give NCO-containing prepolymer Nos. 6-9.
, Compatibility and state after melting at 100 ° C. for 3 hours (◯ is good, × is gelling), initial adhesive strength and 20 ° C. × 2
Table 3 also shows the result of 100 ° C. heat resistance after 4 hours.

[0019]

[Table 3] No. 6 7 8 9 Number average molecular weight 500 1000 3000 3000 5000 Compatibility ○ ○ ○ ○ 100 ° C molten state × ○ ○ ○ Initial adhesive strength − ○ ○ ○ 100 ° C heat resistance − ○ ○ ○ (20 ° C × 24 hours) No. 6 of Table 3 is an example for comparison, and No. 8 is the same as No. 4 of Example 3.

Example 5 100 parts of 1,6-hexanediol adipate polyester diol (number average molecular weight 3500) and polyether diol (EO content 70 mol%, number average molecular weight 30)
(00) to 20 parts of MDI so that NCO / OH = 2.0 and reacted at 80 ° C. for 3 hours to obtain an NCO-containing prepolymer, which has compatibility and 100 ° C. molten state and initial adhesive strength and When the heat resistance at 100 ° C. after 24 hours at 20 ° C. was judged, all were good.

Claims (3)

[Claims] 1. A polyester polyol comprising a 1,6-hexanediol adipate type, a 1,6-hexanediol terephthalate type or a mixture thereof.
And a polyether diol having a content of ethylene oxide of 50 to 80 mol% and a number average molecular weight of 1,000 to 5,000, which is a random or block copolymer of alkylene glycol having C ₃ or more and ethylene glycol, and a number average molecular weight of 1,000 to 5,000, are reacted with an excess polyisocyanate compound. A moisture-curable heat-melting polyurethane-based adhesive comprising the obtained urethane prepolymer containing an active isocyanate group. 2. The adhesive according to claim 1, wherein the polyester polyol has a number average molecular weight of 2000 to 5000. 3. The adhesive according to claim 1, wherein the amount of the polyether diol used is 5 to 20 parts by weight based on 100 parts by weight of the polyester polyol.