JPS619478A - Polyurethane adhesive - Google Patents

Abstract

PURPOSE:To provide a polyurethane adhesive which causes neither whitening nor shrinking by crystallization and has excellent adhesion and resistance to hydrolysis and mold, containing a polyurethane contg. a specified group in the molecule as a main component. CONSTITUTION:The titled polyurethane adhesive contains a polyurethane contg. a group of the formula in the molecule as its main component. The polyurethane contg. the group of the formula can be obtd. by reacting a polyol contg. the group of the formula, such as poly(beta-methyl--sigma-valerolactone)polyol, with an org. polyisocyanate such as tolyene diisocyanate, optionally in the presence of a chain extender such as butanediol. The polyurethane adhesive is suitable for use in bonding packaging materials such as food and medical packaging materials and structural materials such as building materials, automobile parts, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel polyurethane adhesive, particularly a polyurethane adhesive useful as an adhesive for metals, plastics, wood, rubber, and the like. More specifically, it relates to polyurethane adhesives that do not cause crystal whitening or crystal shrinkage, have excellent adhesion to a wide range of adherends, and have excellent hydrolysis resistance and mold resistance. It is.

Generally, polyester-based polyurethane adhesives have superior adhesive strength compared to polyether-based polyurethane adhesives.

However, on the other hand, the current situation is that applications requiring hydrolysis resistance, mold resistance, and flexibility are subject to limitations due to problems of crystal whitening and crystal shrinkage. Furthermore, in recent years, multilayer composite films made of several layers of plastic films such as cellophane, polyethylene, polypropylene, nylon, polyester, PVC, EVAL, Surlyn, etc., and metal foils such as aluminum foil have been developed as packaging materials for foods, etc. Although polyurethane adhesives are widely used and are often used to bond these films, it has been pointed out that their adhesive strength is not necessarily sufficient.

By using a polyurethane adhesive made of polyurethane, the adhesive force is greatly improved, and even with a flexible polyurethane composition, it exhibits good adhesion without problems such as crystal whitening or crystal shrinkage, and is resistant to hydrolysis. The present invention was completed based on the discovery that the properties and mold resistance were improved to an extent that was completely unimaginable with conventional polyester-based polyurethanes, and that all of the conventional problems were solved at once.

Since the polyurethane adhesive obtained by the present invention has the above-mentioned features, particularly preferred applications include adhesion of packaging materials for foods and pharmaceuticals, construction materials, electrical appliances, etc. car,
Examples include adhesion of structural materials such as tanks.

Furthermore, a major feature of the polyurethane adhesive of the present invention is that it has greater adhesive strength than other polyester polyurethanes. In general, polyurethanes made from adipate-based polyesters have poorer adhesion to various adherends than polycaprolactone-based polyurethanes. Since the polyester polyol having polyurethane used in the present invention is liquid and does not crystallize, the polycaprolactone-based polyester polyol is a liquid polyester polyol, so it can be used as a solvent-free adhesive, especially for structures such as metals and plastics. The polyurethane adhesive of the present invention is particularly preferred in cases where solvent-free adhesives, pollution, and hygiene are strictly required. This polyol is manufactured by using a polyol having an average molecular weight of 300 to 1000, specifically, (rivoli(β-methyl-δ-valerolactone) polyol or (2) An average molecular weight of 300 obtained by ring-opening copolymerization of a polyol mixture containing this or (5) β-methyl-δ-valerolactone as one component.
~10,000 block or random copolymer polyols. As a specific example of case (3) above,
When using a polyol introduced by ring-opening copolymerization of ε-caprolactone and β-methyl-δ-valerolactone, or when using a special polymer polyol such as adipate polyester polyol and β-methyl-δ-valerolactone. Examples include cases where it is used. These (2), (
3) When it has, the effects of the present invention can be sufficiently obtained.

In the case of (2) above, typical examples of polyols that can be used in combination with poly(β-methyl-δ-valerolactone) polyol include polycaprolactone polyol, polybutylene adipate polyol, polyethylene adipate polyol, polyethylene propylene acypate polyol, and polyhexane. Examples include adipate polyols. In the case of (5) above, ε-caprolactone is a typical example of a monomer that can be copolymerized with β-methyl-δ-valerolactone.

Note that poly(β-methyl-δ-valerolactone) polyol is obtained by ring-opening polymerization of β-methyl-δ-valerolactone with a low-molecular polyhydric alcohol such as ethylene glycol or butanediol.

Poly(ε-caprolactone) obtained by a similar method
Polyols and polyester polyols obtained by condensation polymerization of diols and dicarboxylic acids generally have a high melting point of 30 to 60"C and have a strong tendency to crystallize. Therefore, polyurethanes obtained from these polyols have soft segments. These polyols tend to cause crystal hardening of the components, resulting in loss of elasticity, and their high melt viscosity can impede workability when synthesizing polyurethane. However, poly(β-methyl-δ-valerolactone) polyol Since it is itself an amorphous polymer and a liquid with extremely low viscosity at room temperature, it does not have the above-mentioned drawbacks.

Further, as for the operation method for obtaining the polyurethane adhesive, a known urethanization reaction technique is used. For example, after mixing a polyol and, if necessary, a low-molecular-weight compound having an active hydrogen atom and heating it to about 40 to 100°C, the active water of these compounds has a ratio of the number of elementary atoms to the NGO group of 1.2.
A polyisocyanate compound having a ratio of ~0.8 is added and reacted at 50 to 150°C to obtain a polyurethane having isocyanate groups or hydroxyl groups at the ends. These reactions can be carried out in various organic solvents or without solvent. For example, in the case of polyurethane adhesives that require a certain degree of high molecular weight, such as film adhesives, it is preferable to use a solvent with low toxicity and a low boiling point.
An example is ethyl acetate.

Examples include methyl ethyl ketone, acetone, toluene, methyl cellosolve acetate, ethyl cellosolve acetate, cyclohexane, methyl isobutyl ketone, dioxane, cyclohexanone, tetrahydrofuran, dimethyl formamide, and the like.

The amount of the solvent used is preferably 1.0 to 15 times the solid content of the polyurethane obtained.

In cases where the use of a solvent is not preferred, such as in the case of adhesives for films used in food packaging, a method is used in which a liquid prepolymer is reacted to cure and adhere at the same time. For example, when the terminal group of a liquid prepolymer is a hydroxyl group, a method is adopted in which triincyanate (1:5 adduct of trimethylolpropane and tolylene diisocyanate) is added and cured. When the polymer has terminal isocyanate groups, a method of curing by adding amine, triol, etc. is used.

As is well known in the industry, structural adhesives are used for wood and other materials, such as moisture-curable prepolymers, which are used as sb, liquid type, and two-part adhesives, which are used in combination with amines or polyols. is necessary.

As the structural adhesive, for example, a polyol with 0 trifunctional terminals obtained by ring-opening polymerization of β-methyl-δ-valerolactone using trimethylolpropane (TMP) as an initiator is used. When curing and adhering simultaneously by mixing analyte or triisocyanate, or tolylene diinocyanate and trifunctional terminal OH polyol prepared by ring-opening polymerization of β-methyl-δ-valerolactone using TMP as an initiator. There is a case where a reacted trifunctional terminal incyanate prepolymer is used, and the prepolymer is cured and bonded at the same time. In the latter case, a method of crosslinking and curing with diol, diamine, water, etc. is used.

Furthermore, for food packaging and structural adhesives, the type of adherend imposes restrictions on the use of solvents, determines whether they should be isocyanate-terminated or hydroxyl-terminated, and how much molecular weight is required. It is a matter of course that it is a thing.

Examples of the organic polyisocyanate used in the polyurethane adhesive of the present invention include diphenylmethane diisocyanate), 2.4-) 1) 7-diisocyanate, 2,6-tolylene diisocyanate, and phenylene diisocyanate. ), 1.5-1-7 ethylene diisocyanate, 5.3'-dichloro-4,4'-diphenylmethane diisocyanate, xylylene diisocyanate,
Examples include aromatic diisocyanates such as toluylene diisocyanate, and aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, inphorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hydrogenated xylylene diisocyanate.

Further examples of curing agents include trifunctional isocyanates, that is, adducts of the above-mentioned isocyanates with glycerin and trimethylolpropane. Polyisocyanates may be used alone or in combination.

Furthermore, in the synthesis of polyurethane, low molecular weight compounds having two or more active hydrogen atoms are usually used as chain extenders, and these active hydrogen atom compounds can also be used in the present invention. Representative examples of these active hydrogen atom-containing compounds include, for example, t, ethylene glycol, butanediol, glopylene glycol, 1,6-
Diols such as hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, bis(β-hydroxyethyl)terephthalate, xylene glycol, water, hydrazine, ethylenediamine, propylene diamine, xylene Examples include diamine, isophorone diamine, piperazine, phenylene diamine, tolylene diamine, adipic dihydrazide, isophthalic acid dihydrazide, and the like, and these compounds may be used alone or in combination. Furthermore, if necessary, a -valent low molecular weight alcohol, low molecular weight amine, etc. can also be used as a modifying agent.

The present invention will be specifically explained below using examples.

Further, the polyol, polyincyanate, and chain extender that are raw materials for polyurethane used in the examples are shown using abbreviations, and the relationship between the abbreviations and the compounds is as follows.

Examples 1 to 3, Comparative Examples 1 to 7 Polyurethane adhesives were manufactured using the raw materials shown in Table 1. That is, a polyol, a polyisocyanate, and a chain extender were reacted in ethyl acetate to a solid content of 40% by weight to obtain a polyurethane having terminal hydroxyl groups. For 100 parts of this polyurethane solution, add 5 to 7.
Mix 5 parts of polyester film (CPET) and polypropylene film (CPET) and dilute with ethyl acetate to make a 20% solution and use a laminator to obtain a coating amount of 5.09/d.
P, surface corona treatment) and cured at 40"C for 3 days, followed by adhesive strength (tensile speed n.

mw/mix, T-shaped peeling), etc. were measured.

Table 1 Table 2 (*1) Appearance after 60 days of immersion in 100℃ hot water (*
2) Released in a mixed medium of 4 types of mold including Aspergillus-aybowi (5 [1°C x 24 days)] (*3) Comparative procedure amendment document December 21, 1982, assuming the adhesive strength of PBA-based polyurethane to be 1 Day

Claims (1)

[Claims] -O・CH_2・CH_2・▲mathematical formula, chemical formula,
There are tables, etc.▼・CH_2・▲There are mathematical formulas, chemical formulas, tables, etc.▼Polyurethane adhesive made of polyurethane with groups.