JPH0765026B2 - Reactive hot melt adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hot-melt adhesive, which has particularly high heat resistance, performs initial adhesion by hot-melt, and can secure the main adhesive force over time by a urethane reaction and cure. The present invention relates to a reactive hot melt adhesive composition having a high elasticity.

II Conventional technology and its problems Conventionally, hot melt type and reactive type adhesives are known.

The hot-melt adhesive is applied by heating and melting with an applicator, and after the pressure bonding, it is cooled and solidified to obtain the initial adhesive strength instantaneously, and the workability is good, but the adhesive strength at high temperature is It is remarkably reduced, and the range of use as an adhesive is limited. As the hot melt adhesive, generally, EVA type, polyolefin type (LDPE, APP, etc.) block copolymer type (SIS, SBS, SEBS, etc.), butyl rubber type, polyamide type, polyester type, etc. are commercially available.

Hot melt adhesives are widely used in various industries such as paper, bookbinding, packaging, textiles, furniture woodworking, light electric power, transportation, etc., but commercially available hot melts are thermoplastic polymers and have limited heat resistance. The range of use for each application is non-structural adhesives.

Especially in the field of product assembly, I am interested in workability that takes advantage of the initial adhesive strength of hotmelt.
It is in a situation where it cannot be used because the adhesive strength significantly decreases at high temperatures.

On the other hand, the reactive adhesive has adhesive strength at high temperature and is used as a structural adhesive. However, generally known reactive adhesives such as epoxies, urethanes, and acrylics have no initial adhesive strength at the time of work, and it takes a long time for a curing reaction to obtain an adhesive force.

Therefore, various reactive hot melt adhesives having both a hot melt type instantaneous initial adhesive force and a reactive type heat resistant strength have been studied (Japanese Patent Publication Nos. 51-30898 and 51-4).
7735, JP-A-61-115977, etc.).

The reactive hot melt type adhesive disclosed in JP-B-51-30898 is composed of an ethylene-vinyl acetate copolymer, a urethane prepolymer and a tacky fire.

Such a reactive hot-melt adhesive has an initial adhesive force exerted by the thermoplastic resin, and the adhesive force at a high temperature is secured by the reaction over time, but it has a drawback that the cured product lacks elasticity. .

On the other hand, when considering adhesives for automobiles, hot melt adhesives whose main components are thermoplastic rubber, a tackifier, and a plasticizer are widely used for side moldings, lamps, housings, and the like. However, since the softening point of thermoplastic rubber-based hot melt adhesives is as low as 70 to 120 ° C, the adhesive strength is almost zero at temperatures around 60 ° C. Automotive adhesives are required to have heat resistance of 80 ° C, depending on the location.

Under such circumstances, improvement in heat resistance of a moisture-curing type reactive hot melt adhesive has been earnestly desired.

III Object of the Invention The object of the present invention is to solve the conventional drawbacks of hot-melt adhesives, and to prevent the initial adhesive strength, which is a characteristic of hot-melts, from being deteriorated during hot-melt application with an applicator, and after application and pressure bonding, hot It is an object of the present invention to provide a reactive hot melt adhesive composition in which the melt is moisture-cured and the cured product has elasticity and can be used as a semi-structural or structural adhesive.

IV Structure of the Invention The present invention is characterized in that a mixed polyol of a terminal hydroxyl group hydrocarbon-based polyol and polyoxybutylene glycol, a urethane prepolymer obtained by reacting a polyisocyanate, and a thermoplastic rubber are main components. A reactive hot melt adhesive composition is provided.

Here, the content of the urethane prepolymer is 20-70 wt% reactive hot melt adhesive composition and / or, the weight ratio of the terminal hydroxyl group hydrocarbon-based polyol and the polyoxybutylene glycol is 80 / It should be between 20 and 20/80.

Further, the reaction type hot melt adhesive composition in which the polyoxybutylene glycol is modified with ethylene oxide, the urethane prepolymer, the equivalent ratio of hydroxyl groups and isocyanate groups (NCO / OH) is 1.8 to 3.0. Reactive hot melt adhesive compositions are preferred.

The constitution of the present invention will be described in detail below.

(1) Thermoplastic rubber The thermoplastic rubber composition of the present invention includes thermoplastic rubbers such as thermoplastic block copolymers and tackifiers, waxes, plasticizers, fillers, and antioxidants (antiaging agents). It is a composition consisting of one or more selected from the following.

As the thermoplastic rubber, a thermoplastic block copolymer is preferable, and isoprene-styrene block copolymer (SIS), butadiene-styrene block copolymer (SBS) and its hydrogenated polymer (SEBS) are effective. And a hydrogenated block copolymer is particularly preferable.

Since such a thermoplastic rubber composition exhibits hydrophobicity, a hydrophobic tackifier and a plasticizer are generally used as a compounding agent. Therefore, the hot mel adhesive using the thermoplastic rubber composition has strong hydrophobicity as a whole.

Tackifiers include rosin, rosin derivatives, terpene resins,
Terpene-phenol resin, petroleum resin (aliphatic, aromatic, copolymerization, alicyclic and hydrogenated petroleum resin),
Although coumarone-indene resin and the like are considered, in consideration of reactivity with urethane, rosin and rosin derivative eliminate active hydrogen of abithienoic acid type rosin by esterification or the like, or partially or wholly the double bond. Hydrogenated rosin, hydrogenated rosin glycerin ester, hydrogenated rosin pentaerythritol, disproportionated rosin, polymerized rosin and the like obtained by erasing are preferable. The tackifier is used alone or in a blend of a plurality thereof.

The terpene resin is preferably a hydrogenated terpene resin.

The terpene-phenol resin is a tackifier obtained by copolymerizing terpenes and phenols, and the terpene / phenol molar ratio is preferably 1.0 to 3.0.

Petroleum resins include hydrogenated resins having a composition such as C ₅ cut, C ₉ cut, C ₅ -C ₉ cut copolymerization, etc., and styrene resins, and copolymers of styrene and hydrocarbons (C ₅ , C ₉ ). Polymerized resins and hydrogenated resins thereof are preferred.

The addition amount of the tackifier is 30 to 800 parts by weight based on 100 parts by weight of the base polymer. If it is less than 30 parts by weight, the effect on the adhesion to the adherend as a reactive hot melt, the improvement of cohesive force, the reduction of viscosity (at high temperature), etc. is small, and
If it exceeds the weight part, the rubber elasticity disappears and it becomes brittle.

Examples of the wax include paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polymerized wax, low molecular weight polyethylene, low molecular weight polypropylene, some modified waxes, atactic polypropylene and the like.

The amount of wax added is 20 to 500 parts by weight based on 100 parts by weight of the base polymer. If it is less than 20 parts by weight, the effect of improving the cohesive force of the reactive hot melt, lowering the viscosity (at high temperature), setting, etc. is lost, and if it exceeds 500 parts by weight, the rubber elasticity is lost.

Plasticizer is ethyl phthalate, aliphatic dibasic acid ester,
Glycol ester, phosphoric acid ester, epoxy plasticizer, hydrocarbon plasticizer (liquid paraffin liquid polybutadiene etc.) and the like. Hydrocarbon-based plasticizers such as liquid paraffin, polybutene, and liquid polybutadiene are particularly effective.

The amount of plasticizer added is 2 per 100 parts by weight of the base polymer.
0 to 500 parts by weight. If it is less than 20 parts by weight, it is difficult to obtain a hot melt composition having a viscosity range in which the reactive hot melt can work with an applicator, while if it exceeds 500 parts by weight, the cohesive force of the reactive hot melt is small and the initial adhesive strength and adhesion The power is small.

The filler is a general rubber, plastic, or adhesive,
A general filling reinforcing agent added to the sealing agent is used. For example, calcium carbonate, barium sulfate, talc,
Examples include clay, titanium oxide, carbon black, and white carbon.

As the antiaging agent, hindered phenols can be used.

(2) Mixed Polyol One of the characteristics of the present invention is that in order to improve the compatibility between the above-mentioned thermoplastic rubber composition and the urethane prepolymer, a mixed polyol of a hydroxyl group-terminated hydrocarbon-based polyol and polyoxybutylene glycol. Is used for the urethane prepolymer.

This has been revealed by the following research results by the present inventors.

Generally, the compatibility of the polyol such as ethylene glycol, which constitutes the urethane prepolymer, and the urethane prepolymer composed of pure-MDI (diphenylmethane diisocyanate) and the thermoplastic rubber composition is easily influenced by the skeleton structure of the polyol. . Therefore, when the skeleton structure of the polyol is hydrocarbon, the compatibility is the best, followed by polyether and polyester in this order. However, at the above polyether level, sufficient compatibility cannot be obtained.

On the other hand, the urethane prepolymer of the hydrocarbon-based polyol is well compatible with the thermoplastic rubber composition, but has a very low moisture curing rate and does not cure in some cases. This is probably because the entire system is hydrophobic and the moisture vapor transmission rate is very low.

Therefore, in order to improve the moisture curability without impairing the compatibility with the thermoplastic rubber composition, it is necessary to replace a part of the urethane prepolymer of the hydrocarbon-based polyol with the moisture curable urethane prepolymer. When it is replaced with a urethane prepolymer using polymer polyol, it is relatively compatible, but the urethane prepolymer still separates at around room temperature, which is insufficient to form a moisture-curing reaction hot melt adhesive. Is.

The present inventors have a skeleton structure having a stronger hydrophobicity than the polymer polyol with the polymer polyol as a hint, and
As a result of diligent research on a polyol in which the urethane prepolymer has excellent moisture curing properties, polyoxybutylene glycol (hereinafter abbreviated as PBG) having the following molecular structure was obtained.

That is, the present invention improves the compatibility between the thermoplastic rubber composition and the urethane prepolymer by using a mixed polyol of a terminal hydroxyl group hydrocarbon-based polyol and polyoxybutylene glycol as a component of the urethane prepolymer, and a new one-component liquid A moisture-curable adhesive composition is obtained.

(A) Hydroxyl Hydroxyl Hydroxyl of Terminal Hydroxyl Hydroxyl Hydroxyl of Hydroxyl Hydroxyl is a hydrocarbyl polyol having a skeleton of hydrocarbon and having a hydroxyl group at the terminal. It is a polymer of butadiene and polyhydroxyl terminal polybutadiene (abbreviated as PBD) and isoprene. Typical examples of the polymer include a terminal hydroxyl group polyisoprene (abbreviated as PIP) and the like. Hydrocarbon moieties other than those mentioned above include polystyrene / butadiene, polynitrile / butadiene, polychloroprene and the like, and some of them are hydrogenated to eliminate double bonds in the hydrocarbon moieties.

(B) Polyoxybutylene glycol Polyoxybutylene glycol (PBG) of the present invention comprises a reaction initiator (initiator) ROH) _m and butylene oxide. Is an addition polymerized product and is represented by the following general formula. m =
It is usually 2 to 8, and preferably m = 2 to 4.

ROH) _m is, for example, ethylene glycol or diethylene glycol when m = 2, glycerin when m = 3,
Trimethylolpropane, pentaerythritol when m = 4, sorbitol when m = 6, and sucrose when m = 8 are well known.

The average molecular weight of PBG is determined by n, and the average number of functional groups is determined by m.
Also, since the compatibility decreases when the average molecular weight of PBG is low, the average molecular weight is preferably 400 or more, and the average molecular weight is 6000.
If it exceeds, the moisture curing property will decrease, so 6000 or less is desirable.

In order to improve the moisture curing property, ethylene oxide is preferable. Or propylene oxide It is effective to use a modified PBG obtained by performing block polymerization or random polymerization with butylene oxide at the terminal of PBG. However, as the amount of modification increases, the hydrophilicity increases, and the compatibility with the thermoplastic rubber composition decreases. Therefore, the modification amount is preferably 18% or less.

In order to improve the compatibility with the thermoplastic rubber composition, a urethane prepolymer is synthesized, that is, a hydroxyl group-terminated hydrocarbon-based polyol and a mixed polyol of polyoxybutylene glycol (PBG) are reacted with the isocyanate described below. In the case of
It is important to increase the ratio of / PBG and to decrease the ratio of terminal hydroxyl group-based hydrocarbon polyol / PBG in order to improve the moisture curability. Hydroxyl-terminated polyol based on terminal hydroxyl group / P satisfying both compatibility and curability of the composition of the present invention
The BG ratio is in the range of 20 / 80-80 / 20 (parts by weight).

Moisture curing progresses even if the ratio of the terminal hydroxyl group-based hydrocarbon polyol, which is inferior in moisture curability, is relatively high, because the PBG urethane prepolymer reacts with moisture in the air to give amino groups (-
It is presumed that NH ₂ ) and carbon dioxide gas are generated, the generated amino groups react with the isocyanate of the urethane prepolymer of the hydrocarbon-based polyol, and the polymerization proceeds. Further, it is known that the produced amino group has a catalytic action and also acts as an internal neutralizing catalyst for carbamic acid.

The reaction mechanism is considered to be based on the following formula.

The present invention is characterized in that the polyol constituting the urethane prepolymer is a mixture of a hydrocarbon-based polyol and PBG, but in order to improve various properties such as weather resistance, heat resistance, moisture curability, adhesiveness, etc. Needless to say, the polyol and the low-molecular-weight diol are used in combination, and are included in this patent.

As other polyols, the following are well known as general polyols constituting urethane prepolymers.

A polymerization initiator such as ethylene glycol, diethylene glycol, glycerin, trimethylol-propane, pentaerythritol, sorbitol, ethylenediamine, diethylenediamine sorbitol, and sucrose is used as a polymerization initiator, and propylene oxide or ethylene oxide-added polyoxypropylene glycol (PB
G) -based polyols, polymer polyols obtained by graft-polymerizing styrene and acrylonitrile on PPG-based polyols,
Polyether-based polyols such as polytetramethylene glycol, which is a ring-opening polymer of tetrahydrofuran.

Examples thereof include adipate-based polyols, which are dehydration-condensation polymers of adipic acid and low-molecular-weight diols, lactone-based polyols obtained by ring-opening polymerization of ε-caprolactone, and polyester-based polyols such as natural castor oil.

(3) Polyisocyanate Tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), vitolylene diisocyanate (TODI), isophorone diisocyanate (IPDI), xylylene diisocyanate is used as a polyisocyanate component constituting the urethane prepolymer together with the above mixed polyol. Although isocyanates (XDI) and the like which are usually used for urethane resins can be used, MDI-based polyisocyanates are preferable in consideration of the moisture curing rate, industrial price, safety and hygiene.

Pure MDI, decarboxylation modified MD for MDI polyisocyanate
There are I (also known as liquid MDI) and crude-MDI, but pure-MDI and liquid MDI are preferable in order to obtain the thermal stability of the urethane prepolymer. Of course, it is not possible to use various polyisocyanates together.

(-NCO) / when synthesizing urethane prepolymer
The (-OH) equivalent ratio is important. If the (-NCO) / (-OH) equivalent ratio is less than 1.8, the urethane prepolymer will increase in amount as the equivalent ratio decreases, resulting in an increase in viscosity and a lack of thermal stability. Further, as the equivalent ratio becomes 1.8 or more, the thermal stability of the urethane prepolymer is improved,
The amount of free polyisocyanate (single unit) increases, and (-NC
If the O) / (-OH) equivalent ratio exceeds 3, the compatibility with the thermoplastic rubber composition is unfavorable. Further, when the amount of free polyisocyanate becomes large, a rapid reaction with water causes a rapid generation of carbon dioxide gas, so that when the moisture is cured, the carbon dioxide gas cannot be dissipated in time, which causes bubbles to be mixed. Therefore, the (-NCO) / (-OH) equivalent ratio is preferably 1.8 to 3.0.

Further, various properties of the composition of the present invention can be adjusted by changing the content of the urethane prepolymer in the thermoplastic rubber composition. As the urethane prepolymer content increases, the thermoplastic rubber composition portion decreases and the initial adhesive strength decreases, but the heat resistance of the cured product improves. The initial adhesive strength is important for the adhesive composition of the present invention, and the content of the urethane prepolymer is 70% by weight or less, preferably 60% by weight or less. On the contrary, when the content of the urethane prepolymer is small, the heat-resistant adhesive strength is lowered, and the value as the composition of the present invention is diminished. Therefore, the content of the urethane prepolymer is 20% by weight or more, preferably 30% by weight or less.
Weight% or more is preferable. Therefore, the content of the urethane prepolymer is 20% by weight to 70% by weight, preferably 30% by weight.
60% by weight is good.

The composition of the present invention comprises each of the above-mentioned compositions, and it is possible to add a part of a commercially available thermoplastic polymer to the composition according to the purpose of use. Examples of the thermoplastic polymer include, for example, generally well-known ethylene-vinyl acetate copolymer (EVA) and its modified polymer, ethylene-ethyl acrylate copolymer (EEA) and its modified polymer, butyl rubber (IIR), ethylene.・
A propylene copolymer polymer or the like can be blended with the base polymer.

Next, production and construction of the reactive hot melt adhesive composition of the present invention will be described.

The composition of the present invention was well kneaded at 190 ° C. to 200 ° C. for about 1 hour with the above-mentioned thermoplastic rubber base (1), a heat-separation imparting agent and a plasticizer using a high shear mixer such as a kneader. Then, after cooling to 80 to 120 ° C., (3) urethane prepolymer is added in a nitrogen gas atmosphere and kneading is performed for about 30 minutes. When the temperature of the urethane prepolymer rises above 90 ° C, allophanate bonds are formed over time, and the urethane prepolymer is increased in quantity. As a result, the viscosity increases.

Therefore, it is preferable that the thermoplastic rubber composition is first prepared and the urethane prepolymer is added and kneaded at 90 ° C. or lower.

The point of practicing the composition of the present invention is to set the temperature of the composition to 120 ° C. or lower, preferably 90 ° C. or lower before coating with a gun. Also, 120 ° C or lower, preferably 90
It is important to adjust the viscosity of the composition (viscosity at the coating temperature is 10,000 ps to 300,000 ps) so that the composition can be coated at a temperature of not more than ° C.

<Examples> Examples will be described in more detail below.

(Example-1) Thermoplastic rubber (styrene / isoprene / styrene block copolymer: shell chemistry, Califlex TR-1107)
100 parts, tackifier (aliphatic cyclic hydrocarbon: Arakawa Hayashi Chemical, Alcon p-90) 400 parts, plasticizer (Nisseki Chemical: Nisseki Polybutene HV-300) 100 parts into a horizontal kneader, The mixture was kneaded under vacuum at 190 ° C for 60 minutes to prepare a mixture (A).

On the other hand, terminal hydroxyl group polybutadiene (PBD) having a hydroxyl value of 46 and average molecular weight of 2800 (Idemitsu Petrochemical; R-45HT) 40 parts, bifunctional polyoxybutylene glycol (PBG) (hydroxyl value 5
6) 60 parts was placed in a reaction kettle and vacuum dehydrated at 110 ° C. for 4 hours. Then, dry nitrogen gas was enclosed and the temperature was adjusted to 80 ° C.
Furthermore, 23.3 copies of pure-MDI (MD formation: ISONATE 125M) (NOC /
OH equivalent ratio = 2.0) Add from the inlet and react for 5 hours in a nitrogen gas atmosphere, NCO% = 3.0%, viscosity 2200ps (20
(° C) urethane prepolymer was made.

Next, 50 parts of the mixture (A) and 50 parts of urethane prepolymer were weighed and put into a horizontal kneader whose temperature was adjusted to 80 ° C., and kneading was performed under vacuum for 15 minutes to prepare a reactive hot melt adhesive composition.

Then, the weight ratio of PBD / PBG is 100/0, 90/10, 80/20, 60/4
An adhesive composition was prepared in the same manner by changing to 0, 20/80, 10/90, 0/100.

The adhesive composition of Example 1 was evaluated as follows.

1) Compatibility After the kneaders were mixed, they were visually evaluated.

Part of the mixture (A) remains granular (x), opaque to translucent state, and a small amount of granules remains (△).

Transparent state No particulate matter (○).

2) Curability A reactive hot-melt adhesive heated to 80 ° C is placed in a gun (ADOS) on an iron mold (150 × 150 × 2 (thickness) (m / m)) that is open to the atmosphere and whose temperature is adjusted to 80 ° C in advance. It was shot with a hot shot gun) to a thickness of about 2 mm. 6 at 20 ℃ and 66RH
After allowing to stand for a day, the cured state was observed.

Deep part uncured (x), deep part semi-cured (△), deep part cured (○) 3) Bubbles The presence of bubbles was confirmed and evaluated simultaneously with the cured state.

Table 1 shows the results with many bubbles (x), some bubbles (△), and no bubbles (◯).

From the results in Table-1, the weight ratio of the terminal hydroxyl group hydrocarbon-based polyol and the polyoxybutylene glycol is 80/20 to 20 /.
A value of 80 indicates good compatibility and curability.

(Example-2) Ethylene oxide was subjected to addition polymerization with PBG to give ethylene oxide contents of 7%, 18%, 30% and an average molecular weight of about 30.
Modified PBG of 00 (bifunctional group), butylene oxide and ethylene oxide are randomly polymerized, and modified PBG of ethylene oxide content 18% and average molecular weight of about 3000 and unmodified PBG of average molecular weight of about 3000 are used for PBD / modified Five types of each pure -MDI urethane prepolymer (-NCO / -OH equivalent ratio = 2.0) with PBG (or unmodified PBG) weight ratio = 50/50 were prepared.

In Example-1, Mixture (A), Califlex TR
-1107 by Kraton G-1657 (Shell Chemistry) (Styrene-Ethylene Butylene Styrene Block Copolymer)
A mixture (B) which was replaced by

Next, the weight ratio of the mixture (B) to the urethane prepolymer is 50.
/ 50, a reactive hot melt adhesive was prepared in the same manner as in Example-1, and the compatibility, curability and bubble state were evaluated.

The evaluation was performed as follows, and the results are shown in Table-2.

Using the gun controlled to 80 ° C, fill the metal mold (30φ × 10 (depth) (m / m)) controlled to 80 ° C with the reactive hot melt adhesive, and open the upper surface to the atmosphere. State, 20
After leaving it to stand at 65 ° C. in a 65 RH atmosphere for 11 days, it was cut and the cured thickness of the central part was measured. The bubbles and compatibility were evaluated in the same manner as in Example-1.

(Example-3) Using a modified PBG having an ethylene oxide content of 7% and an average molecular weight of about 3000, a PBD / modified PBG weight ratio of 40/60 (average hydroxyl value 40.8), a -NCO / -OH equivalent ratio of 1.8, 2.2, 2.5, 2.7,
3.0 and 4.0 pure MDI urethane prepolymers were synthesized.
The NCO% and viscosity of the urethane prepolymer were measured.
The initial value is shown. The thermal stability of these urethane prepolymers was evaluated by measuring the temperature (NCO% viscosity) after allowing them to stand at each temperature of 80 ° C., 100 ° C. and 120 ° C. for 3 days. The results are shown in Table-3. The viscosity was measured using an E-type rotational viscometer (manufactured by Tokyo Keiki).

Next, a reactive hot melt adhesive having a mixture (B) / urethane prepolymer weight ratio of Example-2 of 70/30 and 50/50 was prepared in the same manner as in Example-1, and the compatibility, curability, and bubbles Was evaluated in the same manner as in Example-1. The results are shown in Table-4.

From the results of Table 3 and Table 4, it can be seen that in the synthesis of the urethane prepolymer, when the equivalence ratio (NCO / OH) of the hydroxyl group and the isocyanate group is 1.8 to 3.0, the thermal stability of the urethane prepolymer is good. .

(Example-4) Pure-MDI urethane prepolymer having a PBD / modified PBG weight ratio of 40/60 (-NCO / -OH equivalent ratio = 2.0) using a modified PBG having an ethylene oxide content of 7% and an average molecular weight of about 3000. ) And the mixture (B) of Example-2, and the content of the urethane prepolymer is 0, 10, 20, 30, 40, 60, 80, 100% by weight of each reactive hot melt adhesive composition (0. % And 100% were made blank, and the initial adhesive strength (at 25 ° C atmosphere), which is the effect of the hotmelt adhesive, and the heat resistant adhesive strength (80 ° C), which is the effect of the reactive hotmelt adhesive, were measured.

1) Adhesion sample About 1 mm of the reactive hot melt adhesive composition was applied on a white painted steel plate (25.4 width × 200 mm) using a gun whose temperature was adjusted to 80 ° C.
It was applied thickly, immediately put on a sailcloth (JIS cotton canvas No. 6), and lightly crimped with a stitcher roll. The composition was allowed to stand naturally so that it was cooled to 25 ° C., and the adhesive strength after 60 minutes from application was taken as the initial adhesive strength. Further, after naturally curing in an atmosphere of 20 ° C. and 65 RH for 6 days, it was aged at 60 ° C. for 24 hours to obtain a heat resistant adhesive strength sample.

2) Measurement The adhesive strength was measured by using an autograph (P-100 type manufactured by Shimadzu), and a 180 ° peeling test was performed at a peeling speed of 200 mm / min. A knife blade was used in order to expose the white coated steel plate surface for the measurement.

3) Results The results are shown in Fig. 1. In the figure, ○ indicates material destruction, ● indicates white-coated steel sheet side interface delamination, Δ indicates canvas-side thin layer material destruction, and ▲ indicates canvas-side interface delamination.

From the above results, the urethane prepolymer using the mixed polyol of the terminal hydroxyl group hydrocarbon-based polyol and the polyoxybutylene glycol has good compatibility with the thermoplastic rubber and good curability as an adhesive composition in the cured product. You can see that there are no bubbles.

Further, when the content of the urethane prepolymer in the adhesive composition is 20 to 70% by weight, preferably 30 to 60% by weight, the composition of the present invention having high initial adhesive strength and high heat resistant adhesive strength can be obtained.

<Effects of the Invention> The present invention is a composition having a urethane prepolymer using a special polyol and a thermoplastic rubber, and is usually formed by an adhesive mechanism in which initial adhesion is performed by hot melt and main adhesion is performed by urethane. It was possible to develop early adhesive strength (temporary adhesion), which is difficult with the adhesive of No. 3, and it was possible to express the actual adhesive strength at the time of practical use due to aging.

Further, an adhesive composition was obtained in which the heat resistance, which is a drawback of the thermoplastic rubber-based hot melt adhesive, was improved and the cured product was highly elastic.

[Brief description of drawings]

FIG. 1 is a graph showing the measurement results of the initial adhesive strength and heat resistant adhesive strength of the composition of Example 4.

Claims (5)

[Claims] 1. A reactive type comprising, as a main component, a urethane prepolymer obtained by reacting a mixed polyol of a hydroxyl group-terminated hydrocarbon polyol and polyoxybutylene glycol, a polyisocyanate, and a thermoplastic rubber. Hot melt adhesive composition. 2. The content of the urethane prepolymer is 20 to
The reactive hot melt adhesive composition according to claim 1, which is 70% by weight. 3. A polyol having a hydrocarbon group having a terminal hydroxyl group,
The weight ratio of the polyoxybutylene glycol is 80/20 to 2
The reactive hot melt adhesive composition according to claim 1 or 2, which is 0/80. 4. The method according to claim 1, wherein the oxybutylene glycol is modified with ethylene oxide.
Item 5. A reactive hot melt adhesive composition according to any one of items 3 to 3. 5. The reactive hot melt according to any one of claims 1 to 4, wherein the urethane prepolymer has an equivalent ratio (NCO / OH) of hydroxyl groups to isocyanate groups of 1.8 to 3.0. Adhesive composition.