JPS63120785A - Reactive hot-melt adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which can develop adhesive power when in use without deterioration of the initial adhesive strength, by using as its principal constituents a thermoplastic rubber and a urethane prepolymer containing a specified mixed polyol and polyisocyanate. CONSTITUTION:An adhesive composition composed mainly of a thermoplastic rubber and a urethane prepolymer containing a polyisocyanate and a mixed polyol comprising a hydroxyl-terminated hydrocarbon polyol and a polyoxybutylene glycol. The urethane prepolymer content of the composition is preferably 20-70wt%. The weight ratio of the hydroxyl-terminated hydrocarbon polyol to the polyoxybutylene glycol is preferably 80/20-20/80.

Description

DETAILED DESCRIPTION OF THE INVENTION ■ Industrial Application Field The present invention relates to hot melt adhesives, which have particularly high heat resistance, perform initial adhesion with hot melt, secure main adhesive strength over time through urethane reaction, and cure. Reactive hot-melt adhesives with highly elastic properties.Related to acids.

■ Conventional technology and its problems Conventionally, hot-melt adhesives and reactive adhesives are known.

Hot-melt adhesives are applied by heating and melting with an applicator, and instantaneous initial adhesive strength is obtained by cooling and solidifying after crimping, and has the property of being easy to work with, but the adhesive strength at high temperatures is poor. It has decreased significantly, and there is a limit to the range of its use as an adhesive. As a hot melt adhesive,
Generally EVA type, polyolefin type (LDPE, A
PP, etc.) Block copolymer polymer system (S15. SO5
, 5EBS, 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 electronics, and transportation, but commercially available hot melt adhesives are thermoplastic polymers, so they have limited heat resistance. The scope of use for each application is non-structural adhesives.

Particularly in the field of product assembly, he is interested in workability that takes advantage of hot melt's characteristic initial adhesive strength.
It is currently unusable due to a significant drop in adhesive strength at high temperatures.

On the other hand, reactive adhesives have adhesive strength at high temperatures and are used as structural adhesives. However, generally well-known reactive adhesives such as epoxy, urethane, and acrylic have no initial adhesive strength at all during operation, and it takes a long time to undergo a curing reaction and obtain adhesive strength, which is a problem.

For this reason, various reactive hot melt adhesives that have both the instantaneous initial adhesive strength of hot melt adhesives and the heat resistance strength of reactive adhesives have been studied (Japanese Patent Publication No. 51-30898, Japanese Patent Publication No. 51-47735, Japanese Patent Publication No. 51-47735, Kaisho 61-115977, etc.).

The reactive hot-melt adhesive disclosed in Japanese Patent Publication No. 51-30898 consists of an ethylene-vinyl acetate copolymer, a urethane prepolymer, and a tackifier.

The initial adhesive strength of such reactive hot melt adhesives is exerted by the thermoplastic resin, and the adhesive strength at high temperatures is ensured through reaction over time, but the disadvantage is that the cured product lacks elasticity. .

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

Under such circumstances, there is a strong desire to improve the heat resistance of moisture-curable reactive hot melt adhesives.

■ Purpose of the Invention The purpose of the present invention is to solve the conventional drawbacks of hot melt adhesives, and to solve the problems of hot melt adhesives without losing the initial adhesive strength, which is a characteristic of hot melt adhesives, when applied with an applicator. It is an object of the present invention to provide a reactive hot melt adhesive composition whose melt is moisture cured and whose cured product is elastic and can be used as a semi-structural or structural adhesive.

■ Structure of the Invention The present invention is a reaction method characterized in that the main components are a urethane prepolymer containing a mixed polyol of a terminal hydroxyl group hydrocarbon polyol and polyoxybutylene glycol, a polyisocyanate, and a thermoplastic rubber. A type hot melt adhesive composition is provided.

Here, the content of the urethane prepolymer is 20 to 7
The reactive hot melt adhesive composition is 0ffl% and/or the weight ratio of the terminal hydroxyl group hydrocarbon polyol and the polyoxybutylene glycol is 80/
The ratio is preferably 20 to 20/80.

Further, the reactive hot melt adhesive composition is one in which the polyoxybutylene glycol is modified with ethylene oxide, and the urethane prepolymer has an equivalent ratio of hydroxyl groups to isocyanate groups (NCOloH) of 1.8 to 3.
．． Reactive hot melt adhesive compositions having a 0.0% reactive hot melt adhesive composition are preferred.

The configuration of the present invention will be explained in detail below.

(1) Thermoplastic rubber The thermoplastic rubber composition of the present invention consists of a thermoplastic rubber such as a thermoplastic block copolymer, a tackifier, a wax, a plasticizer, a filler, and an antioxidant (anti-aging agent). This is a composition consisting of one or more selected types.

As the thermoplastic rubber, a thermoplastic block copolymer is preferable, and effective examples include isoprene-styrene block copolymer (51S), butadiene-styrene block copolymer (SO5), and its hydrogenated polymer (SEBS). In particular, hydrogenated block copolymer polymers are preferred.

Since such thermoplastic rubber compositions exhibit hydrophobicity, hydrophobic tackifiers and plasticizers are generally used as compounding agents. Therefore, hot melt adhesives using thermoplastic rubber compositions have strong hydrophobicity as a whole.

Tackifiers include rosin, rosin derivatives, terpene resins,
Terpene-phenolic resins, petroleum resins (aliphatic, aromatic, copolymerized, cyclic and hydrogenated petroleum resins),
Coumaron-indene resin etc. are considered, but considering the reactivity with urethane, rosin and rosin derivatives are
Hydrogenated rosin, hydrogenated rosin glycerin ester, hydrogenated rosin pentaerythritol, and disproportionated rosin obtained by eliminating the active hydrogen of avicenoic acid type rosin by esterification, etc., or by eliminating some or all of the double bonds. Rosin, polymerized rosin, etc. are preferred. Tackifiers may be used alone or in blends.

The terpene resin is preferably a hydrogen-enriched terpene resin.

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

Petroleum resins include, in particular, hydrogenated resins consisting of C5 fraction, C9 fraction, C5-C9 fraction copolymerization, etc., styrene resins, copolymer resins of styrene and hydrocarbons (Cs, C9), and hydrogenated resins thereof. Resins are preferred.

The amount of the tackifier added 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 reactive hot melt will have little effect on adhesion to adherends, improved cohesive force, lowered viscosity (at high temperatures), etc.
If it exceeds 800 parts by weight, the rubber loses its elasticity and becomes brittle.

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

The amount of wax added is 20 to 500 parts by weight based on 100 parts by weight of the base polymer. Less than 20 parts by weight improves cohesive force of reactive hot melt, lowers viscosity (at high temperature),
Setting effects are lost, and rubber elasticity is lost when the amount exceeds 500 parts by weight.

Examples of plasticizers include phthalate esters, aliphatic dibasic acid esters, glycol esters, phosphate esters, epoxy plasticizers, and hydrocarbon plasticizers (liquid paraffin, liquid polybutadiene, etc.).

Particularly effective are hydrocarbon plasticizers such as liquid paraffin, polybutene, and liquid polybutadiene.

The amount of plasticizer added is 20 to 500 fi 1 part per 100 parts by weight of the base polymer. Less than 20 parts by weight,
With reactive hot melts, it is difficult to obtain a hot melt composition with a viscosity range that can be worked with an applicator;
If fifi is exceeded, the cohesive force of the reactive hot melt is small, and the initial adhesive force and adhesive force are small.

The filler is general rubber, plastic, or adhesive,
Use a general filling reinforcing agent that is added to sealants. For example, calcium carbonate, barium sulfate, talc,
There are clay, titanium oxide, carbon black, white carbon, etc.

As the anti-aging agent, hindered phenols can be used.

(2) Mixed polyol One of the features of the present invention is that in order to improve the compatibility between the thermoplastic rubber composition and the urethane prepolymer described above, a hydroxyl-terminated hydrocarbon-based polyol and a polyoxybutylene glycol are mixed. It is to use a polyol in a urethane prepolymer.

This was discovered by the following research results by the inventors.

In general, the compatibility of a thermoplastic rubber composition with a polyol such as ethylene glycol, which constitutes a urethane prepolymer, and a urethane prepolymer consisting of pure MDI (diphenylmethane diisocyanate) is influenced by the skeletal structure of the polyol. It's easy. Therefore, when the skeleton structure of the polyol is hydrocarbon, the compatibility is the best, followed by polyether and then polyester. However, sufficient compatibility cannot be obtained at the above polyether levels.

On the other hand, urethane prepolymers of hydrocarbon polyols are well compatible with thermoplastic rubber compositions, but their moisture curing speed is very slow and in some cases they do not cure. The reason for this is thought to be that the entire system is hydrophobic and the rate of moisture permeation is extremely low.

Therefore, in order to improve moisture curability without impairing compatibility with the thermoplastic rubber composition, it is necessary to replace a portion of the urethane prepolymer of the hydrocarbon polyol with a moisture curable urethane prepolymer. When replacing a urethane prepolymer with a polymer polyol, it shows relatively compatibility, but the urethane prepolymer still separates at around room temperature, which is insufficient to form a moisture-curing reactive hot melt adhesive. It is.

The present inventors took a cue from polymer polyols and discovered that they have a skeleton structure that is more hydrophobic than polymer polyols, and
As a result of intensive research into polyols in which urethane prepolymers have excellent moisture curability, 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 polyol and polyoxybutylene glycol in the urethane prepolymer, thereby creating a novel one-component moisture absorbent material. A curable adhesive composition was obtained.

('a) Hydrocarbon-terminated polyol Hydrocarbon-terminated polyol is a hydrocarbon-based polyol that has a hydrocarbon skeleton and a hydroxyl group at the end, and is a polymer of butadiene, hydroxyl-terminated polybutadiene (abbreviated as PBD),
Polyisoprene with terminal hydroxyl groups (PI) is a polymer of isoprene.
(abbreviated as F) are representative examples. Hydrocarbon moieties other than those mentioned above include polystyrene/butadiene, polynitrile/butadiene, polychloroprene, etc., and some are hydrogenated to eliminate double bonds in the hydrocarbon moiety.

(b) Polyoxybutylene glycol The polyoxybutylene glycol (PBG) of the present invention is:
Reaction initiator (initiator) R+0H) I! l to butylene oxide (to) I, -(:11□- to H-CH2
) is pre-polymerized and is represented by the following general formula.

Usually m=2 to 8, preferably m=2 to 4.

R+f)H) m is, for example, ethylene glycol or diethylene glycol when m = 2, glycerin or trimethylolpropane when m = 3, pentaerythritol when m = 4, sorbitol when m = 6, and sulfur when m = 8. Close is well known.

The average molecular weight of PBG is determined by n, and the average number of functional groups is determined by m.

In addition, if the average molecular weight of PBG is low, the compatibility will decrease, so the average molecular weight is preferably 400 or more, and if the average molecular weight exceeds 6,000, the moisture curability will decrease, so 6,000
The following are desirable.

In order to improve moisture curability, it is preferable to use modified PBG in which ethylene oxide ((:ll2-CH2) or propylene oxide (C)lzll:11 CH2) is blotter polymerized at the terminal of PBG or randomly polymerized with butylene oxide. It is effective to use However, as the amount of modification increases, the hydrophilicity becomes stronger and the compatibility with the thermoplastic rubber composition decreases. Therefore, the amount of modification is preferably 18% or less.

In order to improve the compatibility with the thermoplastic rubber composition, when synthesizing the urethane prepolymer, it is necessary to increase the ratio of the terminal hydroxyl group hydrocarbon polyol/PBG, and to improve the moisture curing property, the terminal hydroxyl group It is important to reduce the ratio of hydrocarbon polyol/PBG. The ratio of terminal hydroxyl group hydrocarbon type polyol/PBG that satisfies the compatibility and curability of the composition of the present invention is 20/80 to 8.
The range is 0/20 (parts by weight).

The reason why moisture curing progresses even if the ratio of the terminal hydroxyl group hydrocarbon polyol, which has poor moisture curing properties, is relatively high is that when the PBG urethane prepolymer reacts with atmospheric moisture, the amino groups (
-N)12) and carbon dioxide gas are generated, and the generated amino groups react with the isocyanate of the urethane prepolymer of the hydrocarbon polyol, and it is presumed that polymerization progresses.

. It is also known that the produced amino group has a catalytic effect and acts as an internal neutralization catalyst for carbamic acid.

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

-NGO+ 1+2 0 →-NIICOOI+(
carbamic acid) -NI+2 + -NCO→-N++coNo- (polymerization) (urea bond) The present invention is characterized in that the polyol constituting the urethane prepolymer is a mixture of a hydrocarbon polyol and PBG. It goes without saying that the use of other polyols and low molecular weight diols in order to improve heat resistance, moisture curing properties, adhesion and other properties is covered by this patent.

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

Using ethylene glycol, diethylene glycol, glycerin, trimethylol-propane, pentaerythritol, sorbitol, ethylene diamine, diethylene diamine sorbitol, sucrose, etc. as a polymerization initiator,
Polyoxypropylene glycol (PPG) made by addition polymerization of propylene oxide or ethylene oxide
Polymer polyols made by graft polymerizing styrene and acrylonitrile to PPG-based polyols,
Polyether polyols such as polytetramethylene glycol, which is a ring-opening polymer of tetrahydrofuran.

These include adipate polyols which are dehydrated condensation products of adipic acid and low-molecular diols, lactone polyols produced by ring-opening polymerization of ε-caprolactone, and natural polyester polyols such as mustard oil.

(3) Polyisocyanate The polyisocyanate components that constitute the urethane prepolymer together with the above mixed polyol include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and bitolylene diisocyanate (TDI).
ODI), isophorone diisocyanate (IPDI)
, xylylene diisocyanate (MDI), etc., which are normally used for urethane resins, can be used, but considering moisture curing speed, industrial price, safety and health, etc., MDI
Preferred are polyisocyanates.

MDI-based polyisocyanates include pure MDI, acid-modified MDI (also known as liquid MDI), and crude MDI.
MDI and liquid 14DI are preferred. Of course, it is not a problem to use various types of polyisocyanates together.

When synthesizing urethane prepolymer, (-NGO)
/ (-OH) equivalent ratio is important. (-Neo)/
(-0) 1) When the equivalent ratio is less than 1.8, ML formation of the urethane prepolymer occurs as the equivalent ratio decreases, resulting in an increase in viscosity and a lack of thermal stability. Also, the equivalence ratio is 1
．． As the value increases to 8 or higher, the thermal stability of the urethane prepolymer improves, but free polyisocyanate (single substance)
increases, (-N(:O)/(-OH) equivalent ratio = 3
If it exceeds 20%, the compatibility with the thermoplastic rubber composition is unfavorable. Furthermore, if the amount of free polyisocyanate increases, the rapid reaction with moisture will cause rapid generation of carbon dioxide gas, which will not be able to dissipate in time during moisture curing, resulting in air bubbles. Therefore (-NC:O)/ (-O
H) The equivalent ratio is preferably from 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,
Although the initial adhesive strength decreases, the heat resistance of the cured product improves.

Initial adhesive strength is important for the adhesive composition of the present invention,
The content of the urethane prepolymer is preferably 70% by weight or less, preferably 60% by weight or less. On the other hand, if the content of the urethane prepolymer decreases, the heat-resistant adhesive strength will decrease and the value of the composition of the present invention will diminish.
It is preferably 0% by weight or more.

Therefore, the content of the urethane prepolymer is preferably 20% to 70% by weight, preferably 30% to 60% by weight.

The composition of the present invention is composed of each of the above-mentioned compositions, but it is also possible to add a portion of a generally commercially available thermoplastic polymer depending on the purpose of use. Examples of this thermoplastic polymer include the generally well-known ethylene-vinyl acetate copolymer (EVA) and modified polymers thereof, and ethylene-ethyl acrylate copolymer (EEA).
) and modified polymers thereof, butyl rubber (IIR), ethylene-propylene copolymers, etc. can be blended with the base polymer.

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

The composition of the present invention is heated at 190°C to 200°C for about 1 hour.
Adding a tackifier, plasticizer, etc. to the above-mentioned (1) thermoplastic rubber base using a high shear mixer, such as a kneader,
After thoroughly kneading and cooling to 80 to 120°C, (3) urethane prepolymer is added and kneaded for about 30 minutes in a nitrogen gas atmosphere. When the temperature of the urethane prepolymer reaches 90° C. or higher, allophanate bonds are formed over time, and the urethane prepolymer becomes bulky. This results in an increase in viscosity.

Therefore, it is preferable to first prepare a thermoplastic rubber composition, and then add and knead the urethane prepolymer at 90°C or lower.

When applying the composition of the present invention using a gun, it is important to keep the temperature of the composition below 120°C, preferably below 90°C. Further, it is important to adjust the viscosity of the composition (viscosity at the coating temperature of 10,000 ps to 300,000 ps) so that it can be coated at 120°C or lower, preferably 90°C or lower.

<Example> This will be explained in more detail below using Examples.

(Example-1) Thermoplastic rubber (styrene/isoprene/styrene block copolymer: Shell Chemical, Cariflex TR-11
07) 100 parts, tackifier (aliphatic cyclic hydrocarbon: Arayo Forestry Chemical, Alcon p-90) 400 parts, plasticizer (Nisseki Chemical Nippon Seki Polybutene +1V-300) 100
After putting the mixture into a horizontal kneader, the mixture was kneaded at 190° C. for 60 minutes under vacuum to prepare a mixture (A).

On the other hand, polybutadiene (PBD) with terminal hydroxyl groups has a hydroxyl value of 46 and an average molecular ffi of 2800 (Idemitsu Petrochemical;
40 parts of difunctional polyoxybutylene glycol (PBG) (hydroxyl value 56) and 60 parts of difunctional polyoxybutylene glycol (PBG) (hydroxyl value 56) were placed in a reaction vessel and subjected to vacuum hydrophilic treatment at 110°C for 4 hours. Next, dry nitrogen gas was filled in and the temperature was controlled at 80°C. Furthermore,
Pure-MDI (MO chemical: l5ONATE 125M)
23.3 parts (NOC1011 equivalent ratio = 2.0) was added from the inlet and reacted for 5 hours in a nitrogen gas atmosphere.
A urethane prepolymer with a CO% of 3.0% and a viscosity of 2200 ps (20° C.) was prepared.

Next, 50% of the mixture (A) was placed in a horizontal niegu whose temperature was controlled at 80°C.
and 50 parts of urethane prepolymer were weighed and kneaded for 15 minutes under vacuum to prepare a reactive hot melt adhesive composition.

Next, the weight ratio of POD/PBG was adjusted to 10010.90/
10.80/20, 60/40.20/80, 10
An adhesive composition was prepared in the same manner except that the adhesive composition was changed to /90 and O/100.

The adhesive composition of Example 1 was evaluated as follows.

■) Compatibility After kneader mixing, visual evaluation was performed.

Mixture (A) partially remained in granular form (x), opaque to translucent, and granular matter slightly remained (△).

Transparent state without particulate matter (○).

2) Curing properties: Place the mold in an iron mold (150 x 150
A reactive hot melt adhesive heated to 80°C is heated to a gun (A
It was shot to a thickness of about 2011 nm using a DOS hot shot gun. Leave it naturally for 6 days at 20℃ and 65RH,
I looked at the hardening state.

Deep uncured (X), The deep part is semi-hardened (△), Deep hardening (0) 3) Air bubbles The curing state and the presence of bubbles were confirmed and evaluated at the same time.

There are many bubbles (×), There are some air bubbles (Δ), No bubbles ○) The results are shown in Table 1.

Table-1 ($1) gels during prepolymer synthesis.

From the results in Table 1, the weight ratio of the terminal hydroxyl group hydrocarbon polyol and polyoxybutylene glycol is 80,720.
~20/80 indicates good compatibility and curability.

(Example-2) Ethylene oxide was addition-polymerized to PBG, and modified PBG (bifunctional group) with an ethylene oxide content of 7%, 18%, and 30% and an average molecular weight of about 3000, butylene oxide and ethylene oxide were Random polymerization, ethylene oxide content 18%, and average molecular weight approximately 300
0 modified PBG and unmodified PB with an average molecular weight of about 3000.
PBD/modified PUG (or unmodified PBG
) Weight ratio = 50750 of each pure -MDI urethane prepolymer (-N(:0/-OH equivalent ratio = 2.0) 5
I made different types.

Example-1, in mixture (A), Cauliflex T
R-1107 to Kraton G-1657 (Shell Chemical)
(Styrene-ethylene-butylene-styrene block copolymer) was replaced with a mixture (B).

Next, the weight ratio of mixture (B) and urethane prepolymer was set to 5.
0750, 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 whose temperature was controlled to 80°C, mold a metal mold (30φX10 (depth) (m/m)) whose temperature was controlled to 80°C.
The sample was filled with a reactive hot melt adhesive and allowed to stand in a 65R11 $ atmosphere at 20°C for 11 days with the top surface open to the atmosphere, then cut and the cured thickness at the center was measured. Note that bubbles and compatibility were evaluated in the same manner as in Example-1.

Table 2 (Example 3) Ethylene oxide content 7%, average molecular weight approximately 3000
using modified PBG with a weight ratio of PBD/modified PBG of 40.
760 (average hydroxyl value 40.8), -NCO/
-OH equivalent ratio 1.8, 2.2, 2.5, 2.7
, 3.0, and 4.0 pure MDI urethane prepolymers were synthesized. The NC0% and viscosity of the urethane prepolymer were measured and shown in Table 3 as initial values. The thermal stability of these urethane prepolymers was determined at 80°C, 100°C, and 120°C.
The samples were left at each temperature for 3 days and their NCO% viscosity was measured and evaluated. The results are shown in Table-3. The viscosity was measured using an E-type rotational viscometer (manufactured by Tokyo Keiki).

Next, reactive hot melt adhesives having a mixture (B)/urethane prepolymer weight ratio of Example 2 of 70/30 and 50150 were prepared in the same manner as Example 1, and the compatibility, curability, and air bubbles were determined. Evaluation was made in the same manner as in Example-1. Display the results -
4.

Table 4 From the results in Tables 3 and 4, it is clear that in the synthesis of urethane prepolymers, the equivalent ratio of hydroxyl groups to isocyanate groups (
It can be seen that the urethane prepolymer has good thermal stability when the NCO/OH) is 1.8 to 3.0.

(Example-4) Ethylene oxide content 7%, average molecular weight approximately 3000
PBD/modified P modified type 86 weight ratio 40760MDI urethane prepolymer (-NCO/
- times equivalent ratio = 2.0) and the mixture (B) of Example-2, the content of the urethane prepolymer was 0.10.2
0.30, 40.60, and 80.100% by weight of each reactive hot melt adhesive composition (0% and 100% are blanks) were prepared, and the initial adhesive strength (at 25°C), which is the effect of the hot melt adhesive, was prepared. ), and the heat-resistant adhesive strength (SO°C), which is the effect of the reactive hot melt adhesive, was measured.

l) Adhesive sample on a white painted steel plate (25.4 width x 200 mm) at 80°C.
Apply the reactive hot melt adhesive composition to a thickness of about 1 mm using a temperature-controlled gun, and immediately apply it to the paper (JIS cotton canvas 6).
No.) was placed and lightly crimped with a stitcher roll.

The composition was left to cool down to 25° C., and the adhesive strength obtained 60 minutes after application was defined as the initial adhesive strength. or,
After natural curing for 6 days at 20° C. in a 65 RH atmosphere, it was aged at 60° C. for 24 hours to obtain a heat-resistant adhesive strength sample.

2) Measurement of adhesive strength was performed using an Autograph (manufactured by Shimadzu: Model P-100) and a 180° peel test at a peel rate of 200 mm/win. A knife blade was used to expose the white painted steel plate surface during the measurement.

3) The results are shown in Figure 1. In the figure, the Q mark indicates material failure, the * mark indicates interfacial peeling on the white painted steel plate side, the Δ mark indicates thin layer material failure on the canvas side, and the mu mark indicates interfacial peeling on the canvas side.

From the above results, the urethane prepolymer using a mixed polyol of a terminal hydroxyl hydrocarbon polyol and polyoxybutylene glycol has good compatibility with thermoplastic rubber, good curability as an adhesive composition, and a cured product. It can be seen that there are no air bubbles inside.

Furthermore, if 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 can have both high initial adhesive strength and high heat-resistant adhesive strength.

<Effects of the Invention> The present invention is a composition containing a urethane prepolymer using a special mixed polyol and a thermoplastic rubber, and has an adhesive mechanism in which initial adhesion is performed using hot melt and main adhesion is performed using urethane. We were able to develop early adhesion (temporary adhesion), which is difficult with normal adhesives, and were able to develop full adhesion over time during practical use.

Furthermore, an adhesive composition was obtained in which the heat resistance, which is a drawback of thermoplastic rubber hot melt adhesives, was improved and the cured product had high elasticity.

[Brief explanation of the drawing]

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 hot melt adhesive characterized in that its main components are a urethane prepolymer containing a mixed polyol of a terminal hydroxyl group hydrocarbon polyol and polyoxybutylene glycol, a polyisocyanate, and a thermoplastic rubber. Composition. (2) The content of the urethane prepolymer is 20 to 70
% by weight of the reactive hot melt adhesive composition according to claim 1. (3) The weight ratio of the terminal hydroxyl group hydrocarbon polyol and the polyoxybutylene glycol is 80/20 to 2.
0/80 of the reactive hot melt adhesive composition according to claim 1 or 2. (4) The reactive hot melt adhesive composition according to any one of claims 1 to 3, wherein the oxybutylene glycol is modified with ethylene oxide. (5) The reactive type according to any one of claims 1 to 4, wherein the urethane prepolymer has an equivalent ratio of hydroxyl groups to isocyanate groups (NCO/OH) of 1.8 to 3.0. Hot melt adhesive composition.