Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2002-03-29
2003-03-25
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C156S330000, C156S331100, C156S331400, C156S331700, C524S417000, C524S414000, C524S706000, C525S438000, C525S440030, C525S454000, C525S528000, C528S060000, C528S051000, C528S065000, C528S066000, C528S073000, C528S076000, C528S080000, C528S083000, C528S085000, C528S905000
Reexamination Certificate
active
06538095
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a solvent-free two-component curable adhesive composition for lamination and a process of lamination. In further detail, the present invention relates to a solvent-free two-component curable adhesive composition for lamination useful in producing materials for packaging food, beverages, medicines, and others, and to a process of lamination.
BACKGROUND OF THE INVENTION
Composite laminated films comprising metal foil such as aluminum foil have been widely used as materials for packaging food, beverages, medicines, and others. These composite laminated films can be obtained by gluing at least one side of metal foil and a plastic film of any kind together using an adhesive.
To be concrete, when bonding films to the both sides of metal foil, at first, a first plastic film is adhered to one side of the metal foil (first laminating step) and the resultant laminated foil is rolled up. The composite laminated film once rolled up is then paid out, and another plastic film is bonded to the other side of the metal foil (second laminating step). Thereafter, the resultant laminated film is rolled up again. If necessary, in some cases, the laminated metal foil is laminated with still another plastic film (e.g., third laminating step, forth laminating step).
Up to now, an organic solvent-based two-component curable adhesive being the blend of a polyisocyanate compound and at least one member selected from a polyester polyol, a polyether polyol, and a polyurethane polyol has been used as the above-described adhesive for lamination.
In recent years, for improving working environment and as a result of restrictions on the use of solvents, there is a gradual transition from the use of organic solvent-based adhesives to the use of solvent-free adhesives, and adhesive compositions being blends of a polyol component and a polyisocyanate component have come into use as solvent-free adhesives for lamination.
Conventional solvent-free adhesives, however, have the drawback of, when a roll of the laminated film after the first laminating step is left alone, permeating through the minute pinholes of metal foil and causing blocking. This leads to the problem that the composite film breaks while being rolled out or during the second laminating step. The thinner the metal foil (e.g., aluminum foil) is, the higher the rate of occurrence of such trouble is. In addition, a laminating operation under certain conditions (e.g., in the case where the composite film after the first laminating step is rolled up at a higher tension, the case where a solvent-free two-component adhesive is cured at high temperatures, the case where the amount of an adhesive applied is large) is liable to be faced with such problem.
SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide a solvent-free two-component curable adhesive composition for lamination capable of preventing the occurrence of blocking caused by an adhesive seeped through metal foil, and a process of lamination.
Another object of the present invention is to provide a solvent-free two-component curable adhesive composition for lamination capable of preventing the occurrence of blocking even in the case where metal foil such as aluminum foil is thin, and a process of lamination.
Still another object of the present invention is to provide a solvent-free two-component curable adhesive composition for lamination which is, even in the case of lamination under severe conditions, capable of inhibiting the occurrence of blocking, and a process of lamination.
The inventors of the present invention made intensive studies to achieve the above objects, and finally found that the use of a solvent-free two-component curable adhesive composition for lamination, which comprises a polyol component and a polyisocyanate component and has a specific viscosity, inhibits the occurrence of blocking due to the seepage of the adhesive through metal foil. The present invention was accomplished based on the above finding.
That is, the solvent-free two-component curable adhesive composition of the present invention comprises (A) a polyol component and (B) a polyisocyanate component, and the viscosity of the mixture at 80° C. immediately after the time the components (A) and (B) are mixed together is not less than 900 mPa·s. The component (A) may be a polyester polyol which can be obtained from a polyhydric alcohol and at least one member selected from the group consisting of an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid. The number average molecular weight of the component (A) may be not less than 800 (particularly, 800 to 5,000), or the viscosity of the component (B) at 25° C. may be not less than 20,000 mPa·s (particularly, 20,000 to 1,000,000 mPa·s). The component (B) is at least one member selected from: (B1) a reaction product of a polyisocyanate and at least one member selected from a polyhydric alcohol, a polyester polyol, a polyether polyol, a polycarbonate polyol, and a polyurethane polyol; and (B2) a polyisocyanate derivative. Particularly, the component (B) is one containing a derivative of at least one diisocyanate selected from the group consisting of araliphatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates and may have a plurality of terminal isocyanate groups. The equivalent ratio of the isocyanate group of the component (B) to the hydroxyl group of the component (A) (NCO/OH) is about 0.4 to 10 (particularly, 0.5 to 5). The composition of the present invention may further comprise an adhesion improving agent (particularly, a coupling agent or an oxygen acid of phosphorus, epoxy resin). Moreover, the composition of the present invention may be a composition for laminating metal foil having a thickness of 5 to 15 &mgr;m with a plastic film.
The present invention further includes a process for laminating metal foil with a plastic film using the above composition.
DETAILED DESCRIPTION OF THE INVENTION
Polyol Component (A)
As the polyol component, there can be used at least one member selected from the group consisting of a polyester polyol, a polyether polyol, a polycarbonate polyol, and a polyurethane polyol, etc. There is no particular restriction as to the form (e.g., linear-, branched-chain) of the polyol component provided that the viscosity of the mixture immediately after the time the components (A) and (B) are mixed together is 900 mPa·s or higher.
The polyester polyol can be obtained through such a conventional esterification reaction as a condensation reaction between a polybasic acid and a polyhydric alcohol, a transesterification reaction between an alkyl ester of a polybasic acid and a polyhydric alcohol, a ring-opening polymerization reaction between a lactone and a polyhydric alcohol and/or a polybasic acid.
Exemplified as the polybasic acid or its alkyl ester are aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic diacid, and dimeric acid; alicyclic dicarboxylic acids such as hexahydrophthalic acid and tetrahydrophthalic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; dialkyl esters thereof (e.g., C
1-6
alkyl esters), and mixtures thereof.
Examples of the polyhydric alcohol are alkanediols (e.g., C
2-40
alkane or aliphatic diols of low molecular weight such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3,3′-dimetylolheptane, 1,9-nonanediol, 1,10-decanediol, 12-hydroxystearyl alcohol, and hydrogenated dimer diols); polyoxyalkylene glycols (e.g., poly(oxyC
2-4
alkylene)glycols such as diethylene glycol, triethylene glycol, polyoxyethylene glycol, dipropylene glycol, polyoxypropylene glycol, and polyoxytetramethylene glycol, and copolymers of C
2-4
alkylene oxides); alkylene oxide adducts of bisphenol A or hydrogenated bisphenol A; polyols (e.g., glycerol, trimethylolpropane, pentaerythritol
Igarashi Sachio
Imai Akihiro
Morimoto Taiji
Mitsui Takada Chemicals Inc.
Sergent Rabon
Wenderoth , Lind & Ponack, L.L.P.
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