JP2001172601A - Hot melt adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hot melt adhesive composition reducing melt viscosity without damaging its original adhesion performance, improving workability, usable for more general purposes. SOLUTION: This hot melt adhesive composition comprises a structural unit excluding a reactive unsaturated bond, and includes a resin composition having a heat reversible cross-link formed by reacting a basic metal compound and a polyurethane resin having a carboxyl and excluding ester bond.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-melt adhesive composition, and more particularly, to a hot-melt adhesive composition having a low melt viscosity and excellent workability without impairing adhesion to various adherends. About things.

[0002]

2. Description of the Related Art In recent years, with the need to respond to environmental pollution and resource saving on a global scale, hot-melt adhesives are rapidly polluting because they have no pollution, labor saving and excellent workability. Demand is growing. In particular, the main EVA (ethylene-vinyl acetate copolymer) -based hot melt adhesive is inexpensive, has a low melt viscosity, and is excellent in workability, and is therefore used in, for example, bookbinding, packaging, and woodworking fields. .

However, with the expansion of the application range of hot-melt adhesives, diversification of adherends, and sophistication of required performance, EVA-based hot-melt adhesives cannot be applied in many cases due to insufficient adhesive strength. It has become. In such cases, other types of adhesives such as SIS (styrene-isoprene resin) adhesives, polyamide adhesives, and polyester adhesives have been actively studied and used.

For example, polyester-based hot melt adhesives generally have excellent thermal stability when melted, have good adhesion to various adherends, heat resistance and cold resistance, as well as chemical resistance and electrical properties. The adhesiveness is particularly good when the adherend is made of a polyester material, a vinyl chloride material, or a metal. Therefore, polyester-based hot melt adhesives are used for adhesive interlining for fibers, wiring boards for automobiles, shield boards, interiors of automobiles, etc. by utilizing this feature.

However, conventional polyester hot-melt adhesives generally have high melt viscosities and are therefore extremely difficult to process and work, and have poor wettability and permeability to adherends, which may cause poor adhesion. At present, its use is limited. Therefore, in order to obtain a strong adhesive force, apply it at a high temperature and then press it as soon as possible,
At that time, the pressure must be increased, or a special coating machine is required at the time of coating.

Accordingly, as a technique for reducing the melt viscosity, a technique of polymer molecule design by controlling the composition and molecular weight of polyester has been proposed. (Japanese Patent 54
No. -17997, JP-A-55-43118, JP-A-59-22796
No. 8, JP-A-2-140283, etc.). However, in these conventional methods, reducing the melt viscosity leads to a decrease in adhesiveness, and has a problem that the balance between adhesiveness and melt viscosity cannot be maintained at a high level.

Further, Japanese Patent Application Laid-Open Nos. 62-32167 and 6-19
No. 46 proposes a technique for reducing the melt viscosity by adding a low molecular weight polyethylene or a terpene resin. However, at the present time, it is impossible to achieve a high level of adhesiveness and melt viscosity at the same time.

[0008] As described above, in the conventional hot melt adhesive, no effective means has been found which can achieve both the adhesiveness and the melt viscosity at a high level. This is the actual situation.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hot melt adhesive composition which can reduce the melt viscosity without impairing the adhesive performance, improve workability, and can be used for more general purposes. To provide.

[0010]

Means for Solving the Problems The present inventors have studied hot-melt adhesives and found that a hot-melt adhesive composition having a specific crosslinked structure can solve the above-mentioned problems. It was completed.

The hot melt adhesive composition according to claim 1 comprises a polyurethane resin comprising a structural unit containing no reactive unsaturated bond, having a carboxyl group and containing no ester bond, and a basic metal compound. To form a thermoreversible cross-linking bond at the carboxyl group.

The hot melt adhesive composition according to claim 2 is characterized in that, in the hot melt adhesive composition according to claim 1, the polyol compound forming a urethane bond in the polyurethane resin does not contain an ester bond. Features.

[0013] The hot melt adhesive composition according to claim 3 is the hot melt adhesive composition according to claim 1 or 2, wherein the polyisocyanate compound forming a urethane bond in the polyurethane resin is an aromatic isocyanate compound. It is characterized by being.

According to a fourth aspect of the present invention, there is provided a hot-melt adhesive composition according to any one of the first to third aspects, wherein the carboxyl group is 50 to 1500 eq / 10 ⁶ g in the resin. Characterized in that it is contained in an amount of

According to a fifth aspect of the present invention, there is provided the hot melt adhesive composition according to the fourth aspect, wherein the basic metal compound is contained in an amount of 0.2 to 0.2% based on the amount of carboxyl groups in the resin. It is characterized by being mixed 4.0 times equivalent.

A hot-melt adhesive composition according to claim 6 is a glass of the resin composition having the thermoreversible cross-link formed in the hot-melt adhesive composition according to any one of claims 1 to 5. The transition temperature is −30 to 20 ° C.

According to a seventh aspect of the present invention, there is provided the hot melt adhesive composition according to any one of the first to sixth aspects, wherein the thermoreversible cross-linking is an ionic bond. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described by way of preferred embodiments. The hot melt adhesive composition of the present invention comprises a structural unit containing no reactive unsaturated bond, has a carboxyl group, and is thermally reversible with a basic metal compound in the carboxyl group portion of the polyurethane resin containing no ester bond. Crosslinks are formed.

It is necessary for the polyurethane resin to be composed of structural units containing no reactive unsaturated bond from the viewpoint of viscosity stability at the time of hot melting, and to have a carboxyl group to form the above-mentioned thermoreversible crosslink. And the absence of an ester bond is necessary in order to develop low melt viscosity characteristics.

The polyurethane resin is produced by a known method by reacting a polyol compound containing no ester bond, a carboxyl group-containing diol compound and a polyisocyanate compound.

Examples of the polyol compound containing no ester bond include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and neopentyl glycol. 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, trimethylolethane, trimethylolpropane, pentaerythritol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, silicon-modified polyether, urethane-modified poly Polyethers such as ethers, epoxy resin-modified polyols, polycarbonate diols, acrylic polyols, polybutadiene polyols, etc. are used alone or in combination of two or more. Rukoto can.

The carboxyl group-containing diol compounds include glyceric acid, glycolic acid, lactic acid, malic acid, dihydroxytartaric acid, 2,2-dimethylolvaleric acid,
2-dimethylolpropionic acid and dimethylolbutanoic acid are used, and in particular, 2,2-dimethylolpropionic acid is preferable from the viewpoint of economic efficiency.

As the polyisocyanate compound, for example, tolylene diisocyanate, diphenylmethane-
4,4′-diisocyanate, xylylene diisocyanate, naphthalene-1,5-diisocyanate, p-phenylene diisocyanate, dibenzyl diisocyanate, diphenyl ether diisocyanate, m- or p-tetramethyl xylylene diisocyanate, or triphenylmethane triisocyanate And aromatic di- or triisocyanate monomers, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane-4, 4 '
And aliphatic or alicyclic diisocyanate monomers such as diisosinate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate. In addition, trifunctional or higher polyisocyanates based on these various monomers include:
Various modified polyisocyanates such as polyisocyanurate-type polyisocyanate and burette-type polyisocyanate are exemplified. Among these, aromatic isocyanates are preferable as the polyisocyanate compound forming a urethane bond from the viewpoint of adhesiveness.

Although the amount of the carboxyl group contained in the resin is not particularly limited, it is preferably 50 to 1500 e in the resin from the viewpoint of forming a crosslinked structure and adhesiveness.
q / 10 ⁶ g, more preferably 100 to 1000 eq /
It should be contained in 10 ⁶ g (measured by sodium hydroxide titration method).

When the content of the carboxyl group is 50 eq / 10
If it is less than ⁶ g, the density of crosslinks obtained by the reaction with the basic metal compound is low, the cohesive strength is low, and sufficient adhesiveness cannot be obtained. On the other hand, when the content of the carboxyl group is 150
If it is larger than 0 eq / 10 ⁶ g, the density of the crosslinks obtained by the reaction with the basic metal compound is high, but the internal stress at the time of bonding becomes high, so that sufficient adhesiveness cannot be obtained.

The number average molecular weight of the thus obtained resin comprising a structural unit containing no reactive unsaturated bond and having a carboxyl group has a number average molecular weight of from 1,000 to 20,000 in view of adhesiveness and melt viscosity characteristics. Are preferred (measured by gel permeation chromatography).

In the present invention, the carboxyl group of the polyurethane resin comprising a structural unit containing no such reactive unsaturated bond and having a carboxyl group and containing no ester bond is further modified with a basic metal compound. It is necessary to crosslink. The cross-linking form is a thermo-reversible cross-linking at a carboxyl group of the polyurethane resin. This bond is a bond having a small binding energy because it is a cross-linking bond due to an ionic bond.Therefore, it is easily broken when heat is applied, and is restored when cooled.
That is, it exhibits thermoreversible properties.

Specifically, a phenomenon occurs in which the temperature dependence of the melt viscosity increases, and when the temperature exceeds 120 ° C., the cross-linking is broken to lower the viscosity of the adhesive and improve the workability. When the temperature is lower than 120 ° C., cross-linking is formed and the adhesive strength is increased. Thereby, at the required bonding temperature, the cohesive force of the adhesive is high, and the adhesiveness to various adherends is good. On the other hand, at the adhesive application temperature, that is, at the melting temperature, the viscosity is low, and the workability is good.

The temperature dependency of the melt viscosity, which is an index of the thermoreversible cross-linking property, is determined by comparing the melt viscosity at 200 ° C.
If expressed as a ratio of 0 ° C. melt viscosity, a hot melt adhesive having the ratio of 100 or more, preferably 200 or more is preferable, and thus such thermoreversible cross-linking is performed with respect to the amount of carboxyl groups in the resin. 0.2 to basic metal compound
It is preferably formed by mixing 4.0 equivalents, preferably 0.5 to 2.5 equivalents.

As the basic metal compound which can exhibit such features, various basic metal compounds can be used as long as a thermoreversible cross-linking is formed and the temperature dependence of the melt viscosity becomes large. it can.

For example, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, aluminum hydroxide, etc. Hydroxide, beryllium oxide, magnesium oxide, calcium oxide, strontium oxide,
Oxides such as barium oxide and aluminum oxide can be used. Among these, a metal compound having two or more valences is preferable in that the temperature dependence of the melt viscosity increases.

In order to form the above-mentioned thermoreversible cross-linking, a basic metal compound is added to a resin comprising a structural unit containing no reactive unsaturated bond and having a carboxyl group, at 20 to 250 ° C. It is obtained by reacting.
When the viscosity of the reaction system is high, a solvent that dissolves both the resin and the basic metal compound if necessary is used in combination,
A method of removing the solvent later may be used. Alcohol or the like is used as such a solvent.

The hot melt adhesive composition of the present invention has a glass transition temperature of-
It is preferably 30 to 20 ° C. Such a glass transition temperature is measured by differential scanning calorimetry (DSC). If the temperature is lower than −30 ° C., the adhesiveness at high temperatures is poor, and 2
If the temperature is higher than 0 ° C., on the contrary, the adhesiveness at a low temperature will deteriorate.

In using the hot-melt adhesive composition of the present invention, the hot-melt adhesive composition obtained by the above-mentioned reaction is used in the form of powder, flake, chip, tape, string or film. 1) A method of applying a hot-melt adhesive composition in a molten state on an adherend using an adhesive applicator and cooling and solidifying the mixture, 2) Hot-melt the adherend. The most suitable method can be adopted depending on the conditions of use, the object to be bonded, and the like, such as a method in which the adhesive composition is heated and fused while holding the adhesive composition.

In particular, in the above method 1), before bonding, the substrate coated with the hot melt adhesive composition of the present invention may be temporarily stacked or wound, so that the surface coated with the adhesive is not coated. Often comes in contact with the surface. For such a reason, the hot melt adhesive in the present invention is such that the adhesive-coated surface and the non-coated surface do not stick at the time of contact,
It has the property of being non-adhesive (tack-free).

The hot melt adhesive composition of the present invention may contain various additives within a range usually used by those skilled in the art as long as the object of the present invention can be achieved.

Examples of such additives include terpene resins, rosin derivatives, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, alicyclic hydrocarbon resins, polymers of unsaturated hydrocarbons, coumarone indene resins, Resins that have a viscosity reducing effect such as styrene resins and petroleum hydrocarbon resins, plasticizers such as phthalic acid ester, adipic acid ester, sebacic acid ester, azelaic acid ester, and phosphoric acid ester, montan wax, polyethylene wax, and polypropylene wax And fillers such as wax, barium sulfate, calcium carbonate, calcium sulfate, magnesium silicate, magnesium carbonate, alumina, quartz powder and silica. Further, if necessary, a coloring agent, a heat stabilizer,
A light stabilizer and the like may be added.

[0038]

The present invention will be described below with reference to the following examples and comparative examples. In Examples and Comparative Examples, “parts” means “parts by weight” and “%” means “% by weight”. The hydroxyl value is
In the method of acetylation in a pyridine solvent, the amount of isocyanate was measured by back titration of the excess amine with hydrochloric acid.

Example 1 440 g (0.44 mol) of polytetramethylene glycol having a number average molecular weight of 1,000, 80 g (0.60 mol) of 2,2-dimethylolpropionic acid, and diphenylmethane-
240 g (0.96 mol) of 4,4'-diisocyanate
And a urethanization reaction was carried out at 80 to 90 ° C. under a nitrogen stream, and the reaction was continued until the residual isocyanate amount became 5% or less of the charged isocyanate amount. Take this,
As a result of analyzing the acid value, it was 800 eq / 10 ⁶ g.
Next, with respect to 100 parts by weight of the resin, 2.4 parts of magnesium oxide (1.5 times equivalent of the COOH group of the resin, 90 g)
(0.23 mol)) and reacted at 180 ° C. for 1 hour. This was cooled to room temperature to obtain a flaky hot melt adhesive composition of the present invention.

Example 2 Polypropylene glycol 44 having a number average molecular weight of 1,000
A hot melt adhesive composition of the present invention was obtained in the same manner as in Example 1, except that 0 g (0.44 mol) was used as a polyol compound for the urethane reaction.

Example 3 440 g (0.15 mol) of polytetramethylene glycol having a number average molecular weight of 1,000 and 1,4-butanediol 2
A hot melt adhesive composition of the present invention was obtained in the same manner as in Example 1, except that 6.1 g (0.29 mol) of the polyol compound used in the urethane reaction was used.

Example 4 Magnesium oxide was replaced with magnesium hydroxide, and the amount added was changed to 3.5 parts (1.5 equivalents, 14.1 g (0.24 mol) based on the COOH group of the resin). except,
In the same manner as in Example 1, a hot melt adhesive composition of the present invention was obtained.

Example 5 Magnesium oxide was replaced with calcium oxide, and the amount added was 1.7 parts (1.5 equivalents to COOH groups of the resin,
A hot melt adhesive composition of the present invention was obtained in the same manner as in Example 1 except that the amount was changed to 7.0 g (0.25 mol).

Example 6 Magnesium oxide was replaced with calcium hydroxide, and the amount added was changed to 2.2 parts (1.5 times equivalent to COOH group of the resin, 9.3 g (0.25 mol)). Except for the above, a hot melt adhesive composition of the present invention was obtained in the same manner as in Example 1.

Comparative Example 1 A hot melt adhesive composition was obtained in the same manner as in Example 1 except that no magnesium oxide was added.

Comparative Example 2 Magnesium oxide was replaced with Denacol EX-411 (Nagara Kasei Kogyo Co., Ltd., epoxy equivalent: 231), and the added amount was 28.3 parts (1.5 equivalents based on the COOH group of the resin).
114g), except that it was changed to 114 g).
A hot melt adhesive composition was prepared. As a result, a sample having no fluidity was obtained.

Comparative Example 3 Magnesium oxide was replaced with Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate content: 13%), and the amount added was 18.8 parts (1.5 equivalents to the OH group of the resin, 7 equivalents).
A hot melt adhesive composition was prepared in the same manner as in Example 1 except that the composition was changed to 6 g). As a result, a sample having no fluidity was obtained.

[0048]Comparative Example 4 52 g (0.84 mol) of ethylene glycol, 1,4-
A stirrer for 114 g (1.26 mol) of butanediol,
Heating device, thermometer, fractionation device and inlet for inert gas
Into a stainless steel reactor having
The temperature was raised to 60 ° C. Then, 196 g of terephthalic acid
(1.18 mol) and di-n-butyltin oxide as a catalyst
Side 0.15g (6 × 10^-Four mol)
The temperature at the top of the fractionator should not exceed 100 ° C
While removing the condensed water generated outside the system,
Gradually raise the contents to 230 ° C to carry out the esterification reaction.
went. The amount of condensed water generated is 90% or more of the theoretical amount
Thereafter, the content was cooled to 180 ° C., and adipic acid 1
20 g (0.82 mol) were charged, and nitrogen gas was
While removing condensed water generated by the flow out of the system, 230
The esterification reaction was continued for 6 hours at that temperature.
This gave a polyester resin. The polyester resin
As a result of analysis and analysis of the hydroxyl value and the acid value, the hydroxyl value was 3
95 eq / 10 ⁶ g, acid value is 10 eq / 10⁶ g
Was. This as it is as a hot melt adhesive composition
evaluated.

Comparative Example 5 A hydroxyl value of 395 eq / produced in the same manner as in Comparative Example 4.
To 100 parts of a polyester resin having 10 ⁶ g and an acid value of 10 eq / 10 ⁶ g, YS polystar T was applied in the same manner as in Example 1.
30 parts of -100 (terpene phenol resin manufactured by Yasuhara Chemical Co., Ltd.) was added to obtain a hot melt adhesive composition.

Comparative Example 6 Polybutadiene diol 440 having a number average molecular weight of 1,000
A hot melt adhesive composition was obtained in the same manner as in Example 1, except that g (0.44 mol) was used as the polyol compound for the urethane reaction.

Comparative Example 7 Polycarbonate diol 44 having a number average molecular weight of 1,000
A hot melt adhesive composition was obtained in the same manner as in Example 1, except that 0 g (0.44 mol) of the polyol compound used in the urethane reaction was used.

Comparative Example 8 440 g (0.44 mol) of polytetramethylene glycol having a number average molecular weight of 1,000, 2.7 g (0.02 mol) of 2,2-dimethylolpropionic acid, and diphenylmethane-4,4'-diisocyanate 90 0.0 g (0.36 m
ol), except that the hot melt adhesive composition was obtained in the same manner as in Example 1.

Comparative Example 9 440 g (0.44 mol) of polytetramethylene glycol having a number average molecular weight of 1,000, 320.3 g (2.39 mol) of 2,2-dimethylolpropionic acid, 637 of diphenylmethane-4,4'-diisocyanate 0.5 g (2.
55 mol), except that it was changed to 55 mol).
A hot melt adhesive composition was obtained.

Table 1 shows the resin composition, acid value, molecular weight, composition of the adhesive composition, and glass transition temperature obtained in Examples 1 to 6 and Comparative Examples 1 to 9.

[0055]

[Table 1]

[0056]

[Test Example] (Preparation of Sample for Measuring Adhesive Strength) Using a heat press machine, the above adhesive sample was heated at 180 ° C. for 1 hour.
After rolling for 5 minutes, a hot melt adhesive film having a thickness of 50 μm was obtained. This adhesive film was sandwiched between a single-sided corona-treated biaxially stretched PET film having a thickness of 100 μm such that the corona-treated surface became the adhesive surface. Then, using a heated heat sealer, bonding was performed at 180 ° C. for 2 seconds at 2 kg / cm ² . This was cut to a width of 15 mm to obtain a sample for measuring adhesive strength.

(Evaluation of Physical Properties of Adhesive Composition) With respect to each sample obtained above, the adhesive strength to PET, melt viscosity, and tack-free property were evaluated under the following conditions. Table 2 shows the evaluation results. 1) Adhesive strength At a temperature of -5 ° C, 20 ° C, and 50 ° C, a tensile speed of 10
A 90 ° peel test was performed at 0 mm / min.

2) Melt viscosity Melt viscosity was measured by a capillary extrusion method using a flow tester CFT-100D (manufactured by Shimadzu Corporation).

3) Tack-free property Evaluation was made by hand feeling. A five-point ranking was performed as follows. 5: No tackiness at all. 4: Slightly sticky. 3: Slightly sticky. 2: There is strong tackiness. 1: There is very strong tackiness.

[0060]

[Table 2]

[0061]

The hot-melt adhesive composition of the present invention comprises:
The workability is greatly improved by reducing the melt viscosity without impairing the adhesiveness to various adherends, and it can be used for a wide range of uses, for example, as a coating agent for ink binders and conductive paints.

Claims (7)

[Claims] 1. A polyurethane resin having a carboxyl group and containing no ester bond, comprising a structural unit containing no reactive unsaturated bond, is reacted with a basic metal compound, and the carboxyl group is heated. A hot melt adhesive composition comprising a resin composition having a reversible cross-linkage formed. 2. The hot melt adhesive composition according to claim 1, wherein the polyol compound forming a urethane bond in the polyurethane resin does not contain an ester bond. 3. The hot melt adhesive composition according to claim 1, wherein the polyisocyanate compound forming a urethane bond in the polyurethane resin is an aromatic isocyanate compound. 4. The method according to claim 1, wherein the carboxyl group is contained in the resin.
The hot melt adhesive composition according to any one of claims 1 to 3, wherein the hot melt adhesive composition is contained in an amount of 1 to 1500 eq / 10 ⁶ g. 5. The hot melt adhesive composition according to claim 4, wherein the basic metal compound is added in an amount of 0.2 to 4.0 times equivalent to the amount of carboxyl group in the resin. . 6. The hot melt adhesive according to claim 1, wherein a glass transition temperature of the resin composition on which the thermoreversible cross-linking is formed is −30 to 20 ° C. Composition. 7. The hot melt adhesive composition according to claim 1, wherein the thermoreversible cross-linking is an ionic bond.