JPH06128552A - Reactive hot-melt adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an moisture-curing adhesive excellent in initial tack and heat resistance and comprising a specified urethane prepolymer, a styrene copolymer rubber and/or a tackifying resin. CONSTITUTION:The composition comprises an NCO-containing urethane prepolymer, desirably one obtained by reacting a polyester polyol (e.g. a polyester diol obtained by reacting adipic acid and isophthalic acid with 1,4-butanediol) with a polyisocyanate compound (e.g. diphenylmethane diisocyanate), a styrene copolymer rubber, desirably a block copolymer (e.g. a PS-polybutadiene-PS block copolymer) and/or a tackifying resin (e.g. an alicyclic saturated hydrocarbon resin).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a moisture curable reactive hot melt adhesive composition based on a urethane prepolymer.

[0002]

2. Description of the Related Art Moisture-curing reactive hot melt adhesive compositions containing urethane urepolymer as a main component are widely used for applications such as panels for building materials and interior materials for automobiles. Its characteristic is that it is a pollution-free system like ordinary hot melt adhesives and reacts with moisture in the air or the adherend within about 24 to 48 hours after bonding, and has a higher heat resistance than ordinary hot melt adhesives. Is to obtain the sex.

[0003]

However, since the polyurethane prepolymer lacks thermal stability, the temperature during application must be 150 ° C. or lower, preferably 140 ° C. or lower. Further, the polyurethane prepolymer has a higher viscosity at the time of melting as compared with the polyolefin-based material used in a usual hot melt adhesive, and the upper limit of the viscosity that can be applied under the above temperature condition, for example, 100,000C.
In order to make P or less, the molecular weight must be suppressed to 10,000 or more, preferably 5,000 or less. For this reason, the adhesive strength immediately after bonding remains at a low level because the cohesive strength due to the low molecular weight is insufficient even if the crystallinity inherent to polyurethane is highly utilized. On the other hand, a usual hot melt adhesive has a drawback that the adhesive strength at a temperature of about 50 ° C. to 60 ° C. cannot be put to practical use because an appropriate adhesive strength can be obtained from the initial stage of adhesion, but it is non-reactive.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the drawbacks of the moisture-curable reactive hot melt adhesive containing a polyurethane prepolymer as a main component as described above and to provide an adhesive composition having an excellent adhesive strength from the initial stage. To provide things.

[0005]

MEANS FOR SOLVING THE PROBLEMS The present inventors have found that a polyurethane prepolymer and a styrene copolymer rubber, which is one of the main components in a conventional hot melt adhesive, and / or a tackifying resin are There is a certain degree of compatibility, and by this mixing, the characteristics as the original reactive hot melt adhesive, particularly the adhesive strength at 50 to 60 ° C. are not significantly reduced in practical use, and the initial adhesive strength is improved. The present invention has been completed. This compatibility is not always sufficient, and what should be transparent at the time of melting is cloudy, but partially compatible with it, resulting in a sea-island structure or an IPN structure, and no separation occurs on an industrial level. Compatibility was obtained throughout the melt, after cooling. A feature of the present invention is that the solidification time can be adjusted almost freely by selecting each material and mixing ratio. That is, from about 1 minute, physical solidification hardly occurs, and it is possible to adjust to a type that solidifies for the first time by a moisture curing reaction. Moreover, since the viscoelastic element is added to the initial adhesive force, the polyurethane prepolymer alone It was able to be improved drastically than in the case of. The adhesive composition of the present invention and its action will be described below. (A) Urethane Prepolymer As the urethane prepolymer used in the present invention, a urethane prepolymer having an isocyanate group at the terminal obtained by reacting various polyols with a polyisocyanate compound is used. As the polyol, one kind or two or more kinds of materials having one or more hydroxyl groups such as materials obtained by adding hydroxyl groups to rubber such as polyester, polyether and butadiene are used. Among these polyols, it is particularly preferable to use polyester polyol as the main component from the viewpoint of improving the initial adhesive strength and adaptability to a wide range of adherends. Examples of this are known dihydric alcohols such as ethylene glycol, 1.4-butanediol, 1.6-hexanediol, 1.8-octanediol and neopentyl glycol, and divalent carboxylic acids such as adipic acid and suberic acid. Polyester polyols can be exemplified by reacting with azelaic acid, sebacic acid, isophthalic acid and the like. The crystallinity of the urethane prepolymer obtained by combining these alcohols and acids depends, but the crystallinity is not so important factor. As the polyether polyol, those synthesized from ordinary ethylene glycol, propylene glycol, neopentyl glycol and the like are used. Examples of polyisocyanate compounds include:
There are diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and modified products thereof, and one or more of these are used. The [NCO] / [OH] equivalent ratio is preferably 1.5 to 4.0. If it is less than 1.5, the viscosity of the obtained prepolymer becomes too large, and if it exceeds 4.0, foaming significantly occurs at the time of moisture curing, and the adhesive strength is lowered.
The properties of the polyurethane prepolymer thus obtained do not necessarily have to be solid at room temperature, and if the adhering force immediately after hot melt adhesion can be appropriately obtained by the styrene copolymer rubber and / or the tackifying resin to be mixed. ,
The property is not particularly limited. (B) Styrenic Copolymer Rubber and Tackifying Resin In the composition of the present invention, a styrene copolymer rubber is used to improve the initial adhesive strength. As examples thereof, in addition to SBR and SIR of random copolymer rubber, ABA block copolymers, AB block copolymers and A- (BA) _n-
B block copolymer [where A is a polystyrene block or poly α-methylstyrene block, B is a polyolefin block for rubber (eg hydrogenated or unhydrogenated polyisoprene or polybutadiene block), and n is 2-50. ], Specifically, a polystyrene-polyisoprene-polystyrene block copolymer having a molecular weight of 7,000 to 200,000 (styrene content 14 to 50% by weight), a molecular weight of 7,000 to 150,000.
Polystyrene-polybutadiene-polystyrene block copolymer (styrene content 20-50% by weight), polystyrene having a molecular weight of 50,000-100,000-hydrogenated polybutadiene-polystyrene block copolymer (styrene content 10-40% by weight), etc. Is mentioned. The tackifying resin is used as a pair with a styrene rubber copolymer, and is mixed with a urethane prepolymer to improve compatibility, control of solidification time, and improvement of initial adhesive strength. Examples thereof include rosin acid ester, terbene resin, aliphatic hydrocarbon resin, cyclopentamine resin, ketone resin, and its polymer in the case of being polymerizable, and its hydrogenated resin in the case of being hydrogenable. However, it is not particularly limited. (C) Other Additives The adhesive composition of the present invention may be appropriately mixed with antioxidants, fillers, pigments and the like other than the above-mentioned materials, if necessary. (D) The compounding ratio of the adhesive-containing urethane prepolymer to the styrene-based copolymer rubber and / or the tackifying resin is 99/1.
To 50/50, preferably 97/3 to 60/40. When the molecular weight is high, the effect of the initial adhesive strength is large even with a small amount, and when the molecular weight is low, it is necessary to have a large amount. When the amount is out of the above range, the initial adhesive strength cannot be improved, and when the amount is more than the above range, moisture curing becomes insufficient and heat resistance is deteriorated. The mixing with is not particularly limited, and the necessary adhesive composition can be obtained by a known method by heat melting and mixing. (E) Adhesion method As in the case of a normal reactive hot-melt adhesive, a method of applying hot-melt state to one or both sides of an adherend and immediately adhering, or a method of adhering by reheating after application is possible. is there.

[0006]

EXAMPLES Examples will be given below to more specifically show the present invention.

[0007]

Example 1 Diphenylmethane diisocyanate was added to a polyester diol obtained by reacting adipic acid / isophthalic acid = 80/20 with 1.4 butanediol in an equivalent ratio [NCO] / [OH] = 2.1 / 1. Then, they were reacted to obtain a urethane prepolymer. (Molecular weight = 3,20
0) On the other hand, 30 parts of alicyclic saturated hydrocarbon (Arcon P-125 manufactured by Arakawa Chemical Co., Ltd.) was added to 100 parts of SBS (molecular weight = 20,000).
The parts were melt mixed to obtain a mixture. These = 90
/ 10 was mixed to obtain an adhesive. The viscosity of this adhesive at 140 ° C is 30,000 CP and 100 g on cotton cloth (No. 10).
/ M ² application, immediately with chip board 0.5k / cm ²
Adhesion was performed with pressure of 10 seconds. The initial adhesive strength (after 5 minutes at room temperature) is 2 kg / cm, and after 24 hours it is 4 kg / cm.
It was a partial breakage of the chip board in cm. Similarly, the adhesive strength at 60 ° C. after 24 hours was 1.5 kg / cm. The adhesive strength at this time was measured at 50 mm / min by a 180 ° peeling method from cotton cloth.

[0008]

Example 2 A urethane prepolymer (molecular weight = 3,800) was prepared in the same manner as in Example 1 except that a polyol obtained by reacting adipic acid with ethylene glycol / neopentyl glycol = 40/60 was used. Obtained. Meanwhile S
100 parts of EBS (molecular weight = 30,000) and terpene-styrene resin (YS resin, manufactured by Yasuhara Chemical Co.)
50 parts were melt mixed to obtain a mixture. these/
= 90/10 were mixed to obtain an adhesive. The viscosity of this adhesive was 20,000 CP at 130 ° C. When evaluated in the same manner as in Example 1, the initial adhesive force was 2.2 kg / cm and the adhesive force after 24 hours was 3.5 kg / cm. It was 2.5 kg / cm at 60 ° C.

[0009]

Example 3 A polyester acid was obtained by reacting adipic acid with 1.6 hexanediol. This one
To 100 parts, 5 parts of polypropylene glycol and 7 parts of SB copolymer rubber (molecular weight = 50,000) are melt mixed, and tolylene diisocyanate is added at an equivalence ratio [NCO] / [OH].
= 1.9 / 1 to obtain an adhesive composition composed of a urethane polymer containing a styrene copolymer rubber.
This canvas (No. 10) was applied to a thickness of 200 g / m ² , cooled and solidified, and then superposed on a stainless steel plate having a thickness of 1 mm and heat-bonded at 80 ° C. for 30 seconds at a pressure of 1 kg / cm ² . . The initial adhesive strength was 1.5 kg / cm and after 24 hours it was 1.8 kg / cm. Also, at 60 ° C, 1.3k
It was g / cm.

[0010]

Comparative Examples 1 to 3 Tables 1 show the results of the same tests as Comparative Examples 1 to 3 using the adhesive compositions obtained by removing the styrene-based copolymer rubber and the tackifying resin in Examples 1 to 3, respectively. .

[0011]

Comparative Examples 4 to 6 The results of the same tests as Comparative Examples 4 to 6 except that the application temperature of the adhesive composition excluding the urethane prepolymer was 180 ° C. in Examples 1 to 3 are shown in Table 2. Shown in.

[0012]

[Effect] According to the present invention, the initial adhesive strength, which is a serious drawback of the moisture-curing type reactive hot melt adhesive containing a urethane prepolymer as a main component, can be significantly improved, and the adhesiveness in the industrial world is improved. After adhering the object, even if it is moved to the next step, it is possible to eliminate partial floating and peeling of the adherend,
Moreover, the heat resistance of the moisture-curable adhesive is essentially not impaired.

Claims (5)

[Claims] 1. A reactive hot melt adhesive composition comprising a urethane prepolymer having an isocyanate group, a styrene copolymer rubber, and / or a tackifying resin. 2. The adhesive composition according to claim 1, wherein the urethane prepolymer is obtained by reacting a polyester polyol and a polyisocyanate compound. 3. The adhesive composition according to claim 2, wherein the styrene copolymer rubber is a block copolymer. 4. The adhesive composition according to claim 1 or 2, wherein the styrene copolymer rubber is a hydrogenated block copolymer rubber. 5. The adhesive composition according to claim 1, wherein the total amount of the styrene copolymer rubber and the tackifying resin is 2 to 30%.