JPH05271639A - Moisture-curing hot-melt polyurethane adhesive - Google Patents

Abstract

PURPOSE:To provide a hot-melt polyurethane adhesive having the rate of moisture curing increased without detriment to its storage stability, low melt viscosity, high initial strength and low-modules/high-elongation properties. CONSTITUTION:This adhesive comprises an active-isocyanate-containing urethane prepolymer obtained by reacting an excess of a polyisocyanate compound with a quaternary mixture comprising a polyester polyol comprising a linear aliphatic diol and a linear aliphatic dicarboxylic acid, a polyether diol of an ethylene oxide content of 50-90mol% and a number-average molecular weight of 1000-5000 which is a random or block copolymer of a 3C or higher alkylene glycol with ethylene glycol, an ethylene/vinyl acetate copolymer of a vinyl acetate content of 30-60mol%, and a rosin ester.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a moisture-curable hot-melt polyurethane adhesive, more specifically, a four-component mixture obtained by adding an ethylene-vinyl acetate copolymer and a rosin ester to a specific polyester polyol and polyether diol. On the other hand, it consists of an active isocyanate group-containing urethane prepolymer obtained by reacting an excess polyisocyanate compound, and can accelerate the moisture curing rate without impairing storage stability, and further has a low viscosity during melting and an initial strength. The present invention relates to a moisture-curable heat-melting polyurethane-based adhesive which is highly flexible and relatively soft (hereinafter, referred to as modulus) -high elongation physical property after moisture curing.

[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 a high hydrophobicity, the moisture penetration rate into the resulting urethane polymer is slow, resulting in a slow moisture curing rate. Therefore, in order to obtain the desired excellent heat resistance, it is usually 1
Hardening curing for more than a week was required.

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.

Further, an adhesive comprising an active isocyanate group-containing urethane prepolymer obtained by reacting the above-mentioned 1,6-hexanediol adipate-based or 1,6-hexanediol terephthalate-based polyester polyol with an excess of a polyisocyanate compound is crystalline. It is already well known that it has high properties, low viscosity when melted, and high crystallization rate, so that the initial strength is rapidly expressed, but the physical properties after moisture curing are hard and high strength. On the other hand, it is fragile and the elongation characteristics deteriorate. Therefore, although it is easy to adapt to bonding for structural applications, it is not suitable for bonding applications of different materials that require low modulus and high extensibility.

On the other hand, an adhesive having a low modulus and a high elongation property has been proposed in order to adapt it to the application of bonding such dissimilar materials. For example, as a part or all of the alcohol component of the polyester polyol, a diol having a small carbon number such as ethylene glycol, propylene glycol, or 1,4-butanediol, or 1,4-neopentyl glycol or 1,4-hexanediol. By using a diol having a side chain such as, it has been attempted to lower the crystallinity of the resulting urethane prepolymer containing an active isocyanate group and lower the cohesive force as an adhesive to lower the modulus. The strength is lost.

Further, a high molecular weight polyester resin having a molecular weight of 8,000 to 25,000, or a high molecular weight elastomer such as an ethylene-vinyl acetate copolymer or an ethylene-acrylic acid copolymer is used as a main component, and a urethane prepolymer is used as a crosslinking component. A combination of relatively high initial strength, low-modulus-high-extension heat-melting polyurethane adhesive has been proposed, but although it has high initial strength, it has a degree of adhesion peculiar to elastomers. However, there is a limit to the initial creep resistance, the viscosity at the time of melting is high, and a coating operation at a high temperature of 120 to 180 ° C. is required.

[0008]

Therefore, the present inventors have
While solving the problems of deterioration of storage stability or skinning or gelation during use, the purpose is to accelerate the moisture curing reaction, and further, the viscosity at melting is low and the initial strength is high, and low modulus-high elongation. As a result of intensive studies to provide a moisture-curable heat-melting polyurethane adhesive having physical properties, the above-mentioned 1,6-hexanediol adipate-based straight-chain aliphatic diol and straight-chain aliphatic dicarboxylic acid were used. A four-component mixture obtained by adding a polyester polyol consisting of an acid and a specific polyether diol to an ethylene-vinyl acetate copolymer as an elastomer component and a rosin ester as a compatibilizing agent for the polyester polyol and the ethylene-vinyl acetate copolymer. By reacting excess polyisocyanate compound to form urethane prepolymer, The present invention has been completed by finding that a specific adhesive can be obtained.

That is, the present invention is a polyester polyol consisting of a linear aliphatic diol and a linear aliphatic dicarboxylic acid, a random or block copolymer of C ₃ or more alkylene glycol and ethylene glycol, and an ethylene oxide content of 50. ˜80 mol% and a number average molecular weight of 1000-5000, a polyether diol,
Urethane prepolymer containing an active isocyanate group obtained by reacting an excess polyisocyanate compound with a four-component mixture of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 30 to 60 mol% and a rosin ester.
(Hereinafter referred to as NCO-containing prepolymer) A moisture-curable heat-melting polyurethane adhesive is provided.

The polyester polyol used in the present invention is a linear aliphatic diol (for example, formula: HOROH [in the formula, R is-(CH ₂ ) ₂ -,-(CH ₂ ) ₃ -,-(CH ₂ ) _{4
-, - (CH 2) 5} -, - (CH 2) 6 -, - (CH 2) 10 -, -
_{(CH 2) 20 -, -} (CH 2) 2 -O- (CH 2) 2 - or - (C
H ₂ ) ₂ —O— (CH ₂ ) ₂ —O— (CH ₂ ) ₂ —] are preferred, and diols having 4 to 9 carbon atoms are preferred) and linear aliphatic dicarboxylic acids (for example, Adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and other dicarboxylic acids having 6 to 10 carbon atoms are preferred. Polyester polyols obtained by the reaction (2 to 4 hydroxyl groups (OH) in one molecule, Number average molecular weight 2000-500
0), and a mixture of one or two of these is used.

The polyether diol used in the present invention, which is a random or block copolymer of C ₃ or more alkylene glycol and ethylene glycol, 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 ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) in the present invention contributes to impart rubber elasticity to the obtained NCO-containing prepolymer and has a vinyl acetate content of 30 to 60 mol%, preferably 40%. ~ 50 mol% is used. When the vinyl acetate content is less than 30 mol%, the compatibility with the polyester polyol is lowered, and when it exceeds 60 mol%, the compatibility is improved but the rubber property peculiar to EVA is lost. The amount of EVA used is usually selected in the range of 2 to 30 parts, preferably 5 to 20 parts, relative to 100 parts of the polyester polyol. If it is less than 2 parts, the desired effect of imparting rubber elasticity cannot be obtained, and if it exceeds 30 parts, the initial strength tends to decrease and the heat resistance after moisture curing also decreases.

The rosin ester used in the present invention refers to an ester of rosin or hydrogenated rosin and a polyhydric alcohol (for example, pentaerythritol, glycerol, triethylene glycol, etc.), particularly a melting temperature of 70 to 1
Those having 20 ° C. are preferred. The rosin ester functions as a compatibilizing agent for the above polyester polyol and EVA, and the amount used is usually Polyester Polyol 1
It may be selected in the range of 2 to 30 parts, preferably 3 to 20 parts relative to 00 parts. If it is less than 2 parts, the desired compatibility effect cannot be obtained, and if it exceeds 30 parts, the rubber elasticity of the adhesive is lost, and the heat resistance after moisture curing tends to be lowered.

The NCO-containing prepolymer in the present invention comprises a four-component mixture of polyester polyol, polyether diol, EVA and rosin ester in the above-specified proportions and an excess polyisocyanate compound, that is,
OH of polyester polyols and polyether diols (and OH which may be present in EVA)
On the other hand, the polyisocyanate compound has an active isocyanate group (NCO) of more than 1, for example, 1.3 ≦
It is produced by reacting at 70 to 110 ° C. for several hours at a ratio of NCO / OH ≦ 10, and usually has an NCO content of 1
It is adjusted to -15% (wt%, the same applies below). 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 heat-melting polyurethane adhesive according to the present invention is composed of the above NCO-containing prepolymer, and if necessary, usual fillers, plasticizers, solvents,
An appropriate amount of antiaging agent, pigment, etc. may be blended.

[0017]

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. In addition, EVA via polyester polyol herodin ester
Has been required from the past because of the good compatibility, it becomes possible to perform coating work at a temperature of around 100 ° C. due to the decrease in viscosity during melting, and also to secure high initial strength and low modulus-high elongation physical properties. It can be adapted for bonding applications of dissimilar materials.

[0018]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Examples 1 and 2 and Comparative Examples 1 and 2 NCO-containing prepolymers 1,6-hexanediol adipate polyester diol (Adeka New Ace Y6-30, manufactured by Asahi Denka Kogyo Co., Ltd., number average) in the number of parts shown in Table 1 below. Molecular weight 3000),
Polyether diol (Asahi Denka Kogyo KK, polyether PR-3007, ethylene oxide content 70 mol%, number average molecular weight 3000), vinyl acetate content EVA (manufactured by Mitsui DuPont Polychemical, EVAflex EV) -45X) and a disproportionated rosin ester having a melting temperature of 100 ° C. (manufactured by Arakawa Chemical Co., Ltd., super ester A
-100), MDI was added so that NCO / OH = 2.0, and the mixture was reacted at 80 ° C. for 3 hours.
A CO-containing NCO-containing prepolymer is obtained.

Performance test Compatibility of the NCO-containing prepolymers described above (○ is good, ×
Are not compatible with each other), the bonding time at 20 ° C, the initial bonding strength (○
Is good with a shear adhesive strength of 5 kg / cm ² or more), and 20 ° C ×
Heat resistance at 100 ° C after 24 hours (○ means good without softening, × means remelting) and 50% modulus (kg / cm) as cured physical properties
² ), breaking strength (dumbbell physical properties, kg / cm ² ) and elongation
The judgment results of (%) are also shown in Table 1.

[0020]

Table 1 Examples Comparative Examples 1 2 12 Polyester diol 100 100 100 100 100 Polyether diol 10 5 10-EVA 10 5 10 10 Rosin ester 10 5-10 NCO content (%) 2.10-2.272 0.06 Compatibility ○ ○ × ○ Bondable time (seconds) 90 to 180 90 to 180 −90 to 120 Initial adhesive strength ○ ○ − ○ 100 ° C heat resistance ○ ○ − × (20 ° C × 24 hours) 50% modulus 70 ^{85 - 80 (kg / cm 2} ) strength at break 200 200 - 250 (kg / cm 2) elongation (%) 600 550 - 500

Example 3 In the production of the NCO-containing prepolymer of Example 1, 100 parts of a polyester diol consisting of a diol and a dicarboxylic acid shown in the following Table 2 (both molecular weights are shown) were used as the polyester diol, and the other 3 components and blending amount were used. In the same manner, MDI was similarly reacted to obtain NCO-containing prepolymers (Nos. 1 to 4), and the same performance test as described above was performed. The results are shown in Table 3 below (note that No. 4 is a comparison. For example).

[0022]

TABLE 2 No. 1 2 3 4 diol 1,6 〃 1,9 2-methyl-1,8 Njioru diol - Okutanji ol dicarboxylic acids adipic acid sebacic acid, adipic acid 〃 molecular weight 3500 3500 4000 4000 NCO content Amount (%) 2.10 2.10 1.64 1.64

[0023]

[Table 3] No. 1 2 3 4 4 Compatibility ○ ○ ○ ○ Bonding time (sec) 90 to 180 45 to 90 45 to 90 3 minutes or more Initial adhesive strength ○ ○ ○ × 100 ℃ heat resistance ○ ○ ○ ○ ( 20 ° C x 24 hours) 50% modulus 70 80 80 35 (kg / cm ² ) Breaking strength 200 150 150 135 145 (kg / cm ² ) Elongation rate (%) 600 400 400 450 700

Claims (6)

[Claims] 1. A polyester polyol comprising a straight-chain aliphatic diol and a straight-chain aliphatic dicarboxylic acid, a random or block copolymer of C ₃ or more alkylene glycol and ethylene glycol, and an ethylene oxide content of 50 to 80 mol%. And a number average molecular weight of 1,000 to
5000 polyether diol, vinyl acetate content 30
To 60 mol% of ethylene-vinyl acetate copolymer and a four component mixture of rosin ester, and a moisture-curable urethane prepolymer obtained by reacting an excess polyisocyanate compound. Heat-melting type polyurethane adhesive. 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. 4. The adhesive according to claim 1, wherein the rosin ester has a melting temperature of 70 to 120 ° C. 5. The amount of ethylene-vinyl acetate copolymer used is 2 to 100 parts by weight of polyester polyol.
The adhesive according to any one of claims 1 to 4, which is 30 parts by weight. 6. The adhesive according to claim 1, wherein the amount of the rosin ester used is 2 to 30 parts by weight based on 100 parts by weight of the polyester polyol.