JPH0425989B2 - - Google Patents

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, etc. More specifically, it relates to polyurethane adhesives that do not cause crystal whitening or crystal shrinkage, have excellent adhesive strength to a wide range of adherends, and have excellent hydrolysis resistance and mold resistance. It is. In general, 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, cellophane, polyethylene, polypropylene, nylon,
Multilayer composite films, which are made by laminating several layers of plastic films such as polyester, PVC, EVAL, and Surlyn, and metal foils such as aluminum foil, have been developed and are widely used, and polyurethane adhesives are often used to bond these films together. However, it has been pointed out that the adhesive strength is not necessarily sufficient. As a result of various studies to solve these shortcomings, the present inventor found that

By using a polyurethane adhesive made of polyurethane having a [Formula] group, adhesive strength is greatly improved, and even with a flexible polyurethane composition, it exhibits good adhesion without problems such as crystal whitening or crystal shrinkage. The hydrolysis resistance and mold resistance have also been improved to a degree that is completely unimaginable with conventional polyester polyurethane.
The present invention has been completed by discovering that the conventional problems can be solved all 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 medical products, and adhesion of structural materials such as building materials, electrical equipment, automobiles, and tanks. etc. can be mentioned. 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. The polyurethane used in the present invention has adhesive strength comparable to polycaprolactone-based polyurethane and

The polyester polyol having the group [Formula] is liquid and does not crystallize, making it very advantageous as an adhesive compared to polycaprolactone-based polyurethane. Also

[Formula] Since the polyester polyol having the group is a liquid polyester polyol, it is a solvent-free adhesive, especially a structural adhesive for metals and plastics, and is free from pollution.
The polyurethane adhesive of the present invention is particularly preferred in cases where solvent-free adhesives are strictly required from a sanitary standpoint, and its significance is significant. within the molecule

[Formula] A polyurethane adhesive made of polyurethane having a group is specifically produced by using a polyol having an average molecular weight of 300 to 100,000 and having a group having the above structure.
Specifically, ring-opening copolymerization using (1) poly(β-methyl-δ-valerolactone) polyol, (2) polyol mixture containing it, or (3) β-methyl-δ-valerolactone as one component is performed. Examples include block or random copolymerized polyols having an average molecular weight of 300 to 100,000. the above
As a specific example of case (3), when ε-caprolactone and β-methyl-δ-valerolactone are obtained by ring-opening copolymerization, the molecule is randomly or blocked.

Examples include the case where a polyol into which a group of [Formula] has been introduced is used, and the case where a block polymer polyol made of an adipate polyester polyol and β-methyl-δ-valerolactone is used. In the case of these (2) and (3), the polyol component contains 20% by weight, especially 40% by weight or more.

[Formula] When the compound has a group, the effects of the present invention can be sufficiently obtained. Typical examples of polyols that can be used in combination with poly(β-methyl-δ-valerolactone) polyol in the case of (2) above include polycaprolactone polyol,
Examples include polybutylene adipate polyol, polyethylene adipate polyol, polyethylene propylene adipate polyol, polyhexane adipate polyol, and the like. In the case of (3) above, ε-caprolactone is a typical example of a monomer that can be copolymerized with β-methyl-δ-valerolactone. In addition, poly(β-methyl-δ-valerolactone)
The 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) polyols obtained by similar methods and polyester polyols obtained by condensation polymerization of diols and dicarboxylic acids generally have a high melting point of 30 to 60°C and a strong tendency to crystallize. Polyurethanes obtained from polyols tend to suffer from crystal hardening of the soft segment component, resulting in loss of elasticity.Furthermore, these polyols have high melt viscosity, which can impede workability when synthesizing polyurethane. methyl-δ-valerolactone)
Polyols are themselves amorphous polymers;
Moreover, since it is a liquid with extremely low viscosity at room temperature, it does not have the above-mentioned drawbacks. Furthermore, as for the operation method for obtaining the polyurethane adhesive, a known urethanization reaction technique is used. For example, by mixing a polyol and, if necessary, a low-molecular compound having an active hydrogen atom,
After heating to 100℃, a polyisocyanate compound with a ratio of active hydrogen atoms to NCO groups of these compounds in a ratio of 1.2 to 0.8 is added and reacted at 50 to 150℃ to form a polyisocyanate compound having an isocyanate group or a hydroxyl group at the end. Use polyurethane. 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 solvents with low toxicity and low boiling points, such as ethyl acetate, methyl ethyl ketone, acetone, toluene, etc. , methyl cellosolve acetate, ethyl cellosolve acetate, cyclohexane, methyl isobutyl ketone,
Examples include dioxane, cyclohexanone, tetrahydrofuran, dimethylformamide, and the like. The amount of 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 desirable, such as in the case of adhesives for films for food packaging, a method is used in which a liquid prepolymer is reacted and cured, and at the same time, the adhesive is bonded. For example, when the terminal group of a liquid prepolymer is a hydroxyl group, a method of adding triisocyanate (1:3 adduct of trimethylolpropane and tolylene diisocyanate, etc.) and curing is adopted; When the prepolymer has terminal isocyanate groups, a method of curing by adding an amine, triol, etc. is used. As is well known in the industry, structural adhesives are moisture-curable prepolymers used for wood, etc., and can be used as a one-component type or as a two-component type in combination with an amine or polyol. be. At this time, of course, the prepolymer

[Formula] It is necessary that the group is incorporated. As a structural adhesive, for example, β-methyl-
A trifunctional terminal OH polyol obtained by ring-opening polymerization of δ-valerolactone is used, and diisocyanate or triisocyanate is mixed with this to cure and adhere at the same time, or β-valerolactone is used as an initiator. -Methyl-δ-valerolactone A trifunctional terminal OH polyol produced by ring-opening polymerization is reacted with tolylene diisocyanate to form a trifunctional terminal isocyanate prepolymer, which is then cured and bonded at the same time. However, in the latter case, a method of crosslinking and curing with diols, diamines, water, etc. is used. Furthermore, for food packaging and structural adhesives, there are restrictions on the use of solvents depending on the type of adherend, whether it should be isocyanate-terminated or hydroxyl-terminated, and how much molecular weight is required. It is a matter of course that it is something that can be determined. Examples of the organic polyisocyanate used in the polyurethane adhesive of the present invention include diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, phenylene diisocyanate, and 1,5-tolylene diisocyanate.
- Aromatic diisocyanates such as naphthylene diisocyanate, 3,3'-dichloro-4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, toluylene diisocyanate,
Examples include aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hydroxylated 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-containing compounds can also be used in the present invention. Typical examples of these active hydrogen atom-containing compounds include ethylene glycol, butanediol, propylene glycol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, bis Diols such as (β-hydroxyethyl) terephthalate and xylylene glycol,
Examples include water, hydrazine, ethylene diamine, propylene diamine, xylylene diamine, isophorone diamine, piperazine, phenylene diamine, tolylene diamine, adipic acid dihydrande, isophthalic acid dihydrande, etc. These compounds can be used alone or in combination. Good too. Furthermore, if necessary, a monohydric low-molecular alcohol, a low-molecular amine, or the like may be used as a modifying agent. The present invention will be specifically explained below using Examples.
Furthermore, the polyols, polyisocyanates, and chain extenders used as raw materials for polyurethane used in the Examples are shown using abbreviations, and the relationship between the abbreviations and the compounds is as follows.

[Table] Examples 1 to 3, Comparative Examples 1 to 7 Polyurethane adhesives were manufactured using the raw materials shown in Table 1. i.e. polyol, polyisocyanate and chain extender at 40% by weight in ethyl acetate.
The mixture was reacted to form a solid content to obtain a polyurethane with terminal hydroxyl groups. Add 5 to 7.5 parts of Coronate L to 100 parts of this polyurethane solution, dilute to 20% solution with ethyl acetate, and use a laminator to coat polyester film (PET) and polypropylene film at a coating amount of 3.0 g/ ^m2 . (CPP, surface corona treatment) was glued together and cured for 3 days at 40℃, and then the adhesive strength (tensile speed 300mm/mm, T
Mold peeling) etc. were measured.

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Claims (1)

[Claims] A polyurethane adhesive comprising a polyurethane having a group represented by the formula in one molecule.