JPH04253785A - Reactive adhesive composition - Google Patents

Abstract

PURPOSE:To provide a reactive adhesive compsn. which exhibits excellent storage stability and deblocking at relatively low temp. and is a hot-melt type adhesive which is easily treated at low viscosity, exhibits heat resistance after adhesion and curing and has various excellent effects for adhesion of automobile-related uses, construction material, wooden furnitures, eectric uses, etc., in the same time way as an unblocked reactive hot-melt adhesive. CONSTITUTION:A reactive adhesive compsn. having a number-average mol. wt. of 600-20,000 and a melt viscosity at 110 deg.C of 100 Pa.s or smaller and contg. a prepolymer having isocyanate groups at its terminals as a main ingredient, wherein the isocyanate gruops are blocked with a compd. having an active hydrogen group.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a hot-melt product that has excellent storage stability, can be disassembled from blocks at relatively low temperatures, has a low viscosity, is easy to handle, and has excellent heat resistance after adhesive hardening. The present invention relates to reactive adhesive compositions of the type.

0002

BACKGROUND OF THE INVENTION Conventionally used adhesives include hot-melt adhesives, solvent-based adhesives, and reactive adhesives. Hot-melt adhesives do not use solvents and require heating and melting during bonding, but do not require drying equipment and can be applied to the adherend and then pressed for the time required for cooling and solidification. There is an advantage that the gluing work can be completed. For this reason, it is widely used as a general-purpose adhesive. However, hot melt adhesives are based on thermoplastic resins, and therefore have low heat resistance and are limited in adhesive strength, chemical resistance, creep properties, etc.

On the other hand, reactive adhesives have excellent heat resistance, adhesive strength, etc. because they form a three-dimensional structure through crosslinking. However, it requires some time to solidify, and therefore has the disadvantage that it cannot provide the instant adhesive strength that hot melt adhesives can provide immediately after application.

[0004] For this reason, in recent years, reactive hot melt adhesives have been developed that combine the instant adhesive properties of hot melt adhesives with the high heat resistance and adhesive strength of reactive adhesives, which incorporate reactivity such as moisture curing. It is being considered. The reaction at this time is low energy cost because curing proceeds at room temperature. Characteristics of such reactive hot melt adhesives include that they are cross-linked, so they have excellent heat resistance and solvent resistance, and have good adhesive strength.They can also be applied at low temperatures, making them suitable for adhesion to many adherends. There is sex. As the adhesive used in this case, a prepolymer having an isocyanate group at the end is usually considered.

[0005]

[Problems to be Solved by the Invention] However, since moisture-curing adhesives react with moisture in the atmosphere, they must be stored in a closed container. Therefore, storage stability is poor, and there are problems in handling such as workability during manufacturing and use.

[0006]

[Means for solving the problem] Therefore, the present inventors
When the storage stability was improved by blocking the isocyanate groups of the urethane prepolymer, an adhesive in which block dissociation occurred at 120 to 180 was obtained. In other words, the present invention is mainly composed of a urethane prepolymer having a number average molecular weight of 600 to 20,000, a melt viscosity at 110° C. of 100 Pa·s or less, and having an isocyanate group at the end. This is a reactive adhesive composition characterized in that it is blocked with a compound having an active hydrogen group.

[0007] The urethane prepolymer compound having an isocyanate group at the end used in the present invention is obtained by a normal addition reaction of a polyol compound and an isocyanate compound, and does not have to be a completely linear chain, but has thermoplastic properties. and the average molecular weight is 600 to 20,000,
The melt viscosity at 110° C. is 100 Pa·s or less.

[0008] In the present invention, the polyol component used in the urethane prepolymer preferably has a hydroxyl group at its terminal. Specific compounds include dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, subecic acid, and sebacic acid, and ethylene glycol, diethylene glycol, 1,3-propanediol, and 1,4-butane diol. Polyester polyol obtained by reaction with aliphatic diol such as diol, 1,5-pentadiol, 1,6-hexanediol. and polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

[0009] As the isocyanate component, diphenylmethane diisocyanate, tolylene diisocyanate,
Examples include diisocyanate compounds such as hexamethylene diisocyanate and isophorone diisocyanate.

[0010] As the blocking agent, general activated hydrogen compounds are used, such as phenolic blocking agents such as phenol, cresol, nitrophenol, chlorophenol, ethylphenol, and oxybiphenyl, and ε-caprolactam. lactam blocking agents such as acetaldoxime, acetoxime, methyl ethyl ketone oxime, diacetyl monoxime, cyclohexanoxime, amyl alcohol, lauryl alcohol,
Examples include alcohol-based blocking agents such as benzyl alcohol and methoxymethanol. Among these, those having a melting point of 150°C or lower and a boiling point of 100°C or higher are particularly preferred.

[0011] For blocking of urethane prepolymer,
It is obtained by reacting the above urethane prepolymer with a blocking agent in a conventional manner. This reaction can be carried out in a solvent that does not contain active hydrogen or in the absence of a solvent.

[0012]If the urethane prepolymer used in the present invention has a melt viscosity of more than 100 Pa·s at 110°C, handling at low temperatures becomes difficult, which is not preferable. If the number average molecular weight is less than 600, the adhesiveness will be extremely reduced, which is undesirable.
If it is larger than 20,000, the melt viscosity becomes high, which not only makes handling difficult, but also reduces the properties as a reactive hot melt, which is not preferable. Block dissociation in the present invention can be carried out by a conventional method, and can easily proceed by heating and stirring at a predetermined temperature for a certain period of time.

The reactive adhesive composition of the present invention may contain curing/dissociation catalysts, plasticizers, tackifiers, various fillers, pigments, waxes, etc. as long as the properties of the composition of the present invention are not lost. Additives used in moisture-curing urethane adhesives, such as moisture removers and storage stabilizers, may also be added. Examples and comparative examples are described below.

[0014]

[Example 1] 196 parts by weight (hereinafter abbreviated as parts) of polyester diol with a number average molecular weight of 4,000 obtained by the reaction of subesic acid and 1,4-butanediol, and polytetra with a number average molecular weight of 1,000. 84 parts of methylene ether glycol and 73 parts of 4,4-diphenylmethane diisocyanate were reacted at 110°C for 2 hours to obtain a urethane prepolymer having isocyanate groups at the ends. This urethane prepolymer has a melt viscosity of 9 at 110°C.
It was Ps・s. To this was added 36 parts of ε-caprolactam as a blocking agent, and the mixture was reacted at 110° C. for 3 hours to obtain a reactive adhesive composition of the present invention. The end point of the blocking reaction was confirmed by the disappearance of absorption by isocyanate groups in the IR spectrum. The physical properties of the obtained reactive adhesive composition of the present invention were measured using methods 1 to 4 below.

[Table 1] Hereinafter, for Example 2 and Comparative Examples 1 to 3,
Measure in the same manner and show the results.

(1). Peel Adhesive Strength A solution obtained by disassociating blocks of the reactive adhesive composition of the present invention was applied to a 25 mm wide aluminum foil (thickness 50 μm), a 25 mm cloth was attached to this, and the mixture was heated at 23° C. and at a humidity of 5 μm.
A sample for measurement was prepared by leaving it at 0% for a predetermined period of time. This sample was measured at a peeling speed of 200 mm/min. (2). A sample for measurement was prepared by laminating a block-dissociated solution with a shear adhesive strength (1) on 25 x 100 mm of magnolia wood with an overlap of 25 x 12 mm, and leaving it at a temperature of 23° C. and a humidity of 50% for a predetermined period of time. This sample was sheared at a rate of 10 mm/min.
Measured in. (3). A load of 500 g was applied to the sample obtained at peel failure temperature and shear failure temperature (2), and 5
Measure the breakdown temperature when the temperature is increased at ℃/min. (4). Storage Stability The solution viscosity of the reactive adhesive of the present invention at 110°C was measured and the results are shown below. ○ - No thickening, △ - Thickening but no problem in use, ×
- Cannot be used for gelling.

[0016]

Example 2 A urethane prepolymer was synthesized in the same manner as in Example 1. In this, methyl ethyl ketoxime 2
Two parts were reacted at 110° C. for 2 hours to obtain an adhesive of the present invention. Thereafter, evaluation tests were conducted in the same manner as in Example 1.

[0017]

[Comparative Example 1] 182 parts of polyester diol with a number average molecular weight of 5,600 obtained by the reaction of subesic acid and 1,4-butanediol, 78 parts of polytetramethylene ether glycol with a number average molecular weight of 3,000, 32 parts of 4-diphenylmethane diisocyanate at 110°C
A urethane prepolymer having isocyanate groups at the terminals was obtained by reacting for a period of time. The melt viscosity of this prepolymer at 110° C. was 180 Pa·s. This was reacted with 10 parts of methyl ethyl ketoxime at 110° C. for 4 hours, but the blocking reaction was not completed.

[0018]

[Comparative Example 2] 16 parts of ε-caprolactam was added to the same urethane prepolymer as in Comparative Example 1, and the mixture was reacted at 140°C for 3 hours to obtain a blocked compound. However, when this compound was deblocked, the regeneration rate of isocyanate groups was unstable, making it unsuitable for use as an adhesive.

[0019]

[Comparative Example 3] Polyester diol 1 with a number average molecular weight of 4,000 obtained by reaction of subesic acid with 1,4-
96 parts, 84 parts of polytetramethylene ether glycol with a number average molecular weight of 1,000, and 73 parts of 4,4-diphenylmethane diisocyanate were reacted at 110°C for 2 hours to produce a moisture-curing urethane adhesive having an isocyanate group at the end. Obtained. Hereinafter, measurements were performed in the same manner as in Example 1, and the results were reported.

It is shown in [Table 1].

[0020]

[Table 1]

[0021]

Effects of the Invention The reactive adhesive composition of the present invention has a low block dissociation temperature of 120 to 180°C and a low melt viscosity, so it can be applied at low temperatures and has fast adhesive properties equivalent to hot melt adhesives. It also has heat resistance and high adhesive strength as a crosslinking adhesive. In addition, due to the stabilization of physical properties by forming blocks, workability and storage stability have been significantly improved, making handling easier.

Claims (1)

[Claims] Claim 1: A urethane prepolymer having a number average molecular weight of 600 to 20,000, a melt viscosity at 110°C of 100 Pa·s or less, and having an isocyanate group at the end, the isocyanate group being A reactive adhesive composition characterized in that it is blocked with a compound having an active hydrogen group.