JPH07118622A - Hot-melt adhesive composition - Google Patents

Abstract

PURPOSE:To provide the moist-hardening type hot-melt adhesive composition possible of melting at relatively low temperatures, having a low viscosity in a molten state and good in coating workability, rapidly solidifiable after coated and laminated with resultant good initial adhesive force manifestation, also presenting the final adhesive force and heat-resistant creep characteristics after moist-hardened. CONSTITUTION:The objective adhesive composition comprises (1) an active NCO group-contg, urethane prepolymer prepared by reaction of a polyisocyanate compound with >=50wt.% of (A) a crystalline polyester polyol 3000-10000 in number-average molecular weight and (2) another active NCO group-contg. urethane prepolymer prepared by reaction of a polyisocyanate compound with >=10wt.% of (B) a crystalline polyester polyol 1000-3000 in number-average molecular weight, or comprises a third active NCO group-contg. urethane prepolymer prepared by reaction of a polyisocyanate compound with a mixed polyester polyol composed of >=50wt.% of the component A and >=10wt.% of the component B.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a moisture-curable hot melt adhesive composition.

[0002]

2. Description of the Related Art Generally, a moisture-curable hot melt adhesive contains a urethane prepolymer having a relatively low molecular weight as a main component, is heat-melted by heating and is applied to one adherend by a roll or the like, and then adhered to the other adherent. It is intended to be bonded to the body and to react with moisture in the adherend or in the air to obtain a strong adhesive force.

Moisture-curable hot-melt adhesives are required to have such properties that they can be melted by heat at a temperature as low as possible and that the melt has a low viscosity. And exhibiting an initial adhesive force, and exhibiting excellent final adhesive force and heat creep resistance after a moisture reaction.

However, it is contrary to the fact that the melt can be heat-melted at a low temperature and the melt has a low viscosity, and that it rapidly solidifies after coating and pasting to exhibit good initial strength development and initial adhesive strength. It is difficult to obtain a moisture-curable hot melt adhesive that satisfies these requirements at the same time.

For example, as an example of a moisture-curable hot melt adhesive, the melting point is 30 to 60 ° C. and the molecular weight is 800 to 8
000 polyester diol 70 to 98 parts by weight and a urethane prepolymer obtained by reacting 2 to 30 parts by weight of a polyester diol having a melting point of 65 to 150 ° C. and a molecular weight of 600 to 8000 with polyisocyanate have been proposed. (JP-A-3-152112)
However, this moisture-curable hot melt adhesive has a melting point of 65.
Since a polyester diol having a molecular weight of 600 to 8000 at ~ 150 ° C is used together, the initial adhesive strength is good, but a heat melting temperature of 100 ° C or higher is required. For example, heat resistance such as soft vinyl chloride resin. When a sheet of a thermoplastic resin having a low heat resistance is used as an adherend, there is a problem that the adherend is deformed or broken and cannot be suitably used.

Another example of a moisture-curable hot melt adhesive is a urethane prepolymer obtained by reacting a polyisocyanate with a highly crystalline polyester polyol and a non-crystalline polyol as polyol components. Has been proposed (JP-A-3-2859).
No. 82, Japanese Patent Laid-Open No. 4-8787), all of which use an amorphous polyol component.
There is a problem in that initial strength development and initial adhesive strength are poor, and practicability is poor.

[0007]

In order to solve the above-mentioned conventional problems, the present invention can be suitably used for an adherend which can be heat melted at a low temperature and has low heat resistance, and the melt has a low viscosity. Moisture-curing type that has good coating workability, rapidly solidifies after coating and pasting, and exhibits good initial strength development and initial adhesive strength, and exhibits excellent final adhesive strength and heat-resistant creep after moisture curing. It is an object to provide a hot melt adhesive composition.

[0008]

In order to achieve such an object, the moisture-curable hot melt adhesive composition according to the invention of claim 1 has a number average molecular weight of 3,000 to 3,000.
An active NCO group-containing urethane prepolymer obtained by reacting 50% by weight or more of a crystalline polyester polyol of 10000 with a polyisocyanate compound, and 10% by weight or more of a crystalline polyester polyol having a number average molecular weight of 1000 to 3000 It is essential to contain an active NCO group-containing urethane prepolymer obtained by reacting with an isocyanate compound, and thereby the above object is achieved.

The moisture-curable hot melt adhesive composition according to the invention of claim 2 has a number average molecular weight of 30.
Crystalline polyester polyol having a number average molecular weight of 1,000 to 3,000 and a weight average molecular weight of 1,000 to 3,000.
It is essential to contain an active NCO group-containing urethane prepolymer obtained by reacting a mixed polyester polyol consisting of 10% by weight or more of the crystalline polyester polyol and a polyisocyanate compound, whereby the above object is achieved. To be achieved.

The crystalline polyester polyol referred to herein is a polyester polyol having a melting point of 20 ° C. or higher when measured by a differential thermal analysis method.

The active NCO group-containing urethane prepolymer (hereinafter referred to as "urethane prepolymer") constituting the moisture-curable hot melt adhesive composition of the present invention has a number average molecular weight of 3000-10000
And 50% by weight or more of the crystalline polyester polyol (hereinafter referred to as “polyester polyol A”) and a polyisocyanate compound are reacted with the urethane prepolymer (hereinafter referred to as “urethane prepolymer A”), and A urethane prepolymer obtained by reacting 10% by weight or more of a crystalline polyester polyol having an average molecular weight of 1,000 to 3,000 (hereinafter referred to as "polyester polyol B") with a polyisocyanate compound (hereinafter, "urethane prepolymer B"). It is also possible to obtain a polyisocyanate by using a mixed polyester polyol in which 50% by weight or more of the polyester polyol A and 10% by weight or more of the polyester polyol B are mixed in advance as described in claim 2. May be obtained by reacting with a compound

The polyester polyol A used in the present invention has a number average molecular weight of 3,000 to 10,000, and the polyester polyol B has a number average molecular weight of 10.
It is from 00 to 3000.

When the number average molecular weight of the polyester polyol A exceeds 10,000, the melt viscosity of the obtained hot melt adhesive composition is increased and the coating workability is deteriorated.
When the number average molecular weight of the polyester polyol B is less than 1000, the active NCO group concentration in the obtained hot melt adhesive composition becomes high, foaming occurs after coating, and sufficient adhesive strength is not expressed.

The types of the polyester polyols A and B used in the present invention are not particularly limited, but in order to increase the crystallinity, one dicarboxylic acid having an even number of carbons and the number of carbons A polyester polyol obtained by reacting with an even number of one kind of diol is preferable.

Examples of the dicarboxylic acid having an even number of carbon atoms include succinic acid, adipic acid and sebacic acid,
Examples of the diol having an even number of carbon atoms include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,8-octanediol.

Various polyester polyols A and B can be obtained by changing the combination of the above dicarboxylic acid and diol.

As an example of a preferable combination of the number average molecular weight of the polyester polyol A and the dicarboxylic acid and the diol obtained, when the number average molecular weight is 3000 to 4000, adipic acid, sebacic acid and the like, 1,6-hexanediol, A combination of 1,8-octanediol and the like can be mentioned. When the number average molecular weight is 4000 to 6000, adipic acid, sebacic acid, etc. and 1,4-butanediol, 1,6
Examples include a combination of hexanediol and the like. When the number average molecular weight is 6000 to 10000, a combination of succinic acid, adipic acid and the like, ethylene glycol, 1,4-butanediol and the like can be mentioned. Regarding the polyester polyol B, there are no particular restrictions on the combination of such number average molecular weight and dicarboxylic acid and diol.

The polyisocyanate compound used in the present invention has two or more isocyanate groups in the molecule. The type of the polyisocyanate compound is
Although not particularly limited, a bifunctional organic polyisocyanate compound is preferable, and examples thereof include tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), isophorone diisocyanate, hexamethylene diisocyanate, xylidene diisocyanate, Hydrogenated xylidene diisocyanate and the like are preferably used. In the present invention, so-called crude industrial grades (for example, crude TDI, crude MDI, etc.) may be used as these polyisocyanate compounds.

When the urethane prepolymer is prepared, the equivalent ratio of the polyester polyol to the polyisocyanate compound is preferably 1.2 to 2.8 equivalents of the polyisocyanate compound to 1 equivalent of the polyester polyol. Compound 1.5-2.
5 equivalents are more preferred.

If the equivalent ratio of the polyisocyanate compound to 1 equivalent of the polyester polyol is less than 1.2 equivalents, the molecular weight of the urethane prepolymer obtained will be high, so the coating temperature of the hot melt adhesive composition will exceed 90 ° C. In the case of an adherend having a low heat resistance such as a soft vinyl chloride resin sheet, it is damaged and cannot be applied. vice versa,
When the equivalent ratio of the polyisocyanate compound exceeds 2.8 equivalents, unreacted polyisocyanate compound remains excessively in the obtained urethane prepolymer, which is not preferable for safety and hygiene.

In the present invention, the content of unreacted isocyanate groups in the urethane prepolymer obtained as described above is preferably in the range of 2.0 to 8.0% by weight based on all adhesive components.

If the content of unreacted isocyanate groups is less than 2.0% by weight based on all the adhesive components, the resulting hot melt adhesive composition will have insufficient heat-resistant creep property, and conversely 8.0% by weight. If it exceeds%, the resulting hot-melt adhesive composition coating foams and sufficient adhesive strength cannot be obtained.

The method for obtaining the urethane prepolymer by reacting the polyester polyol with the polyisocyanate compound is not particularly limited and may be a known method. For example, as described above, a desired urethane prepolymer can be obtained by reacting at a temperature of 60 to 160 ° C. for 1 to 20 hours under a dry air reflux with the equivalent ratio of the polyisocyanate compound to the polyester polyol being excessive. I can.

The urethane prepolymer constituting the moisture-curable hot melt adhesive composition of the present invention comprises, as described in claim 1, 50% by weight or more of polyester polyol A and 10% by weight or more of polyester polyol B alone. A mixed urethane prepolymer obtained by reacting with a polyisocyanate compound to prepare urethane prepolymers A and B, and mixing these two types of urethane prepolymers, or 50 as described in claim 2.
It is necessary that the urethane prepolymer is obtained by reacting a mixed polyester polyol obtained by mixing 10% by weight or more of the polyester polyol A and 10% by weight or more of the polyester polyol B with the polyisocyanate compound.

In Claims 1 and 2, when the polyester polyol A is less than 50% by weight, the melting temperature and the coating temperature of the obtained hot-melt adhesive composition become high, so that the soft vinyl chloride resin sheet It cannot be applied to adherends having low heat resistance.

Further, in claims 1 and 2, when the polyester polyol B is less than 10% by weight, the resulting hot melt adhesive composition has insufficient heat resistance and creep resistance.

The hot melt adhesive composition of the present invention comprises:
If necessary, a tackifying resin that does not react with an active NCO group,
You may mix additives, such as a softener and a stabilizer.

The moisture-curable hot melt adhesive composition of the present invention thus obtained is heated and melted by a known applicator such as a roll equipped with a heating device, a knife coater, and a hand gun, and then one of them is applied. The adhesive work can be completed by being applied to the body and immediately being attached to the other adherend.

[0029]

The moisture-curable hot melt adhesive composition obtained by the present invention contains a urethane prepolymer as a main component, which is obtained from two types of crystalline polyester polyols having a relatively low melting temperature of crystals of about 60 ° C. or lower. So
It can be melt-coated at a temperature of 90 ° C. or lower, and can be suitably used for an adherend having low heat resistance such as a soft vinyl chloride resin sheet.

The number average molecular weight is 3,000 to 10,000.
Since it contains a urethane prepolymer obtained from a relatively large crystalline polyester polyol, the crystallization rate is fast, and the solidification rate after melt coating is also fast, so that the initial strength development and the initial adhesion are excellent, and the number average molecular weight is 1000
Since it contains a urethane prepolymer obtained from a crystalline polyester polyol having a relatively small value of up to 3000, the content of urethane bonds after moisture curing becomes high, and excellent final adhesive strength and heat creep resistance are exhibited.

[0031]

EXAMPLES In order to explain the present invention in more detail, examples will be given below. In the examples, "part" is "part by weight".
Means

(Example 1)

(A ) Moisture-curable hot melt adhesive composition
Product Preparation As shown in Example 1 of Table 1, adipic acid and 1,6
To 4 parts of 4,4-diphenylmethane diisocyanate (MDI) was added to 1000 parts of polyester polyol A having a number average molecular weight of 5000 and a hydroxyl value of 23.6, which was obtained by reacting with hexanediol, and added with nitrogen reflux at 110. A urethane prepolymer A was synthesized by carrying out a heating reaction at ℃ for 3 hours. Next, the number average molecular weight 2 obtained by reacting adipic acid with 1,6-hexanediol
000, Polyester Polyol B having a hydroxyl value of 56.8
MDI167.2 parts was added to 600 parts, and urethane prepolymer B was synthesized in the same manner as in the case of urethane prepolymer A to obtain two kinds of urethane prepolymers A and B.
Got 700 parts of the obtained urethane prepolymer A and 300 parts of the obtained urethane prepolymer B were mixed to obtain a moisture-curable hot melt adhesive composition.

( B) Preparation of Sample for Evaluation The obtained moisture-curable hot melt adhesive composition was
Coating thickness is 30μm using coating roll heated to ℃
Was coated on one surface of a soft vinyl chloride resin sheet so as to be the same as the above, and immediately bonded to one surface of a medium quality fiberboard (MDF) to prepare an evaluation sample having a width of 25 mm.

( C) Evaluation The following items were evaluated using the obtained moisture-curable hot melt adhesive composition and evaluation sample, and the results are shown in Table 3.

Crystal melting temperature : Using a differential thermal analyzer, the hot melt adhesive composition was heated from 0 ° C. to 150 ° C. at a rate of 5 ° C./min in a dry nitrogen atmosphere, and showed the maximum endotherm. The temperature was used as the crystal melting temperature (° C).

Melt viscosity : The viscosity of the hot-melt adhesive composition was measured from 90 ° C. to 120 ° C. every 10 ° C. in a dry nitrogen atmosphere using a B type rotational viscometer, and the melt viscosity (mPa) at each temperature was measured. ) Got.

Coating temperature : When the hot melt adhesive composition is coated with a roll, the heating temperature of the roll is 85 ° C. to 130 ° C.
The soft vinyl chloride resin sheet was coated by setting every 5 ° C. up to 5 ° C., and the coating temperature (° C.) was defined as the lowest temperature at which the soft vinyl chloride resin sheet could be coated without adversely affecting the surface. The acceptance standard of the coating temperature is 90 ° C or lower.

Activation temperature : A soft vinyl chloride resin sheet coated with the obtained hot-melt adhesive composition so as to have a coating thickness of 30 μm was heated from 65 ° C. to 100 ° C.
After leaving for 2 minutes in a heating oven set to a temperature of ℃,
It was bonded to MDF, and the activation temperature (° C.) was defined as the lowest temperature at which the normal adhesive force described below is developed. The activation temperature acceptance criterion is 70 ° C or lower.

Initial strength development time: Using the sample obtained in the preparation of the sample for evaluation, a width of 2 every 15 seconds after bonding.
A 100g load is hung on one end of a 5mm soft vinyl chloride resin sheet in a 180 degree angle peeling direction, and 20 ° C-65% RH.
The sample was left for 24 hours or more in the above atmosphere, and the initial strength development time (minutes) was defined as the shortest time after bonding until no peeling occurred. The acceptance criterion for the initial strength development time is within 2 minutes.

Normal-state adhesive strength : The sample obtained in the preparation of the sample for evaluation was allowed to stand in an atmosphere of 20 ° C.-65% RH for 24 hours, and then pulled at an autograph of 50 mm /
The 180-degree angle peel strength (kg / 25 mm) was measured in minutes. The acceptance criteria for normal adhesive strength is 3.5 kg / 25 mm
That is all.

Heat-resistant creep : The sample obtained in the preparation of the sample for evaluation was left in an atmosphere of 20 ° C.-65% RH for 24 hours, and a load of 400 g was applied to one end of a soft vinyl chloride resin sheet having a width of 25 mm for 180 hours. Hanging in the angle peeling direction,
The peeling distance (mm) after 24 hours of standing at 60 ° C. was measured. The heat-resistant creep acceptance criteria is 5 mm or less.

(Examples 2-3, Comparative Example 1)

Polyester polyols A and B were prepared from combinations of dicarboxylic acids and diols having the compositions shown in Table 1 and reacted with MDI in the same manner as in Example 1 to synthesize urethane prepolymers A and B, respectively. did. Next, urethane prepolymers A and B were mixed in the respective compounding parts as shown in Table 1 to obtain three kinds of moisture-curable hot melt adhesive compositions.

[0045]

[Table 1]

Table 3 shows the results of evaluating various performances of the obtained three kinds of moisture-curable hot melt adhesive compositions in the same manner as in Example 1.

(Example 4)

As shown in Example 4 in Table 2, 700 parts of polyester polyol A having a number average molecular weight of 5,000 and a hydroxyl value of 23.6, obtained by reacting adipic acid with 1,6-hexanediol, and adipine Number average molecular weight 2 obtained by reacting an acid with 1,6-hexanediol
000, Polyester Polyol B having a hydroxyl value of 56.8
To 1000 parts of the mixed polyester polyol obtained by mixing with 300 parts, MDI166.2 parts was added, and the mixture was heated and reacted under nitrogen reflux at 110 ° C. for 3 hours to synthesize a urethane prepolymer, and moisture-curable hot melt. An adhesive composition was obtained.

Various properties of the obtained moisture-curable hot melt adhesive composition were evaluated in the same manner as in Example 1 and the results are shown in Table 3.

(Examples 5 to 9, Comparative Example 2)

Six kinds of mixed polyester polyols were prepared by mixing the polyester polyols A and B obtained by the combination of the dicarboxylic acid and the diol having the composition shown in Table 2, and each mixed polyester polyol was the same as in Example 4. Was reacted with the polyisocyanate compound to synthesize 6 types of urethane prepolymers to obtain 6 types of moisture-curable hot melt adhesive compositions.

Table 3 shows the results of evaluation of various performances of the resulting 6 kinds of moisture-curable hot melt adhesive compositions in the same manner as in Example 1.

Comparative Examples 3 to 4 Two kinds of polyester polyols obtained by combining dicarboxylic acids and diols having the compositions shown in Table 2 were reacted with a polyisocyanate compound in the same manner as in Example 4 to obtain two kinds of polyester polyols. A urethane prepolymer was synthesized to obtain two types of moisture-curable hot melt adhesive compositions.

Table 3 shows the results of evaluating various performances of the two types of moisture-curable hot melt adhesive compositions obtained in the same manner as in Example 1.

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

As described above, the hot-melt adhesive composition according to the present invention can be heat-melted at 90 ° C. or lower, so that it can be applied to an adherend having low heat resistance such as a soft vinyl chloride resin sheet without any problem. In addition, it has excellent initial strength development, initial adhesive strength, final adhesive strength, and heat creep resistance.

Claims (2)

[Claims] 1. An active N obtained by reacting 50% by weight or more of a crystalline polyester polyol having a number average molecular weight of 3,000 to 10,000 with a polyisocyanate compound.
CO group-containing urethane prepolymer and number average molecular weight of 1
A hot melt adhesive composition comprising an active NCO group-containing urethane prepolymer obtained by reacting 10% by weight or more of a crystalline polyester polyol of 000 to 3000 and a polyisocyanate compound. 2. A crystalline polyester polyol having a number average molecular weight of 3,000 to 10,000 and 50% by weight or more,
It is characterized by containing an active NCO group-containing urethane prepolymer obtained by reacting a mixed polyester polyol consisting of 10% by weight or more of a crystalline polyester polyol having a number average molecular weight of 1000 to 3000 and a polyisocyanate compound. Hot melt adhesive composition.