Similarly, for the purpose of improving the gas barrier properties, an inorganic-based thin film layer of, for example, silicon oxide or aluminum oxide may be provided on the plastic base physically or chemically using a vapor deposition method without any limitation.

In addition, the base may be a molded product, such as a final film, sheet, or container, or this coating can also be provided in advance to a preformed product to be formed into a container. Examples of such a preformed body can include bottomed or bottomless tubular parisons for biaxial stretch blow molding, pipes for direct blow molding, sheets for vacuum forming, pressure forming, and plug-assist forming, or films for heat seal lids or bag making.

Anchor Coat Layer

For the anchor coat layer formed on a surface of the base as necessary, an anchor coat layer used in a gas barrier laminate and known in the art, the anchor coat layer including a polyurethane-based resin including a polyol and an isocyanate compound can be used; however, the anchor coat layer including a polyurethane-based resin and a silane coupling agent, the anchor coat layer proposed by the present inventors, is preferable.

Polyurethane-Based Resin

For the polyurethane-based resin constituting the anchor coat layer, a known polyurethane-based resin that has been used as an anchor coat layer in the art can be used; in an embodiment of the present invention, however, a polyurethane-based resin with a glass transition temperature (Tg) of 80° C. or higher and particularly in a range of 80 to 120° C. is desirably used. With a polyurethane resin with a glass transition temperature lower than the above range, the anchor coat layer would have poor heat resistance compared to the one with a polyurethane resin with a glass transition temperature in the above range, and the gas barrier layer would have a crack when heating causes a difference in a contraction ratio between the anchor coat layer and the gas barrier layer, and this may reduce the barrier properties.

The polyol component, which is the main agent of the polyurethane-based resin, can be exemplified by glycols, polyester polyols, polyether polyols, acrylic polyols, or their urethane-modified products, but in particular, a glycol is preferably used.

The glass transition temperature of the polyester polyol is preferably from −50° C. to 100° C. and more preferably from −20° C. to 80° C. In addition, the number average molecular weight of these polyester polyols is preferably from 50 to 100000 and more preferably from 50 to 80000.

Examples of the glycol include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, neopentyl glycol, and 1,6-hexanediol.

Examples of the polyvalent carboxylic acid include aromatic polyvalent carboxylic acids, such as isophthalic acid, terephthalic acid, and naphthalene dicarboxylic acid; and aliphatic polyvalent carboxylic acids, such as adipic acid, azelaic acid, sebacic acid, and cyclohexane dicarboxylic acid.

For the isocyanate component, which is a curing agent for the polyurethane-based resin, an aromatic diisocyanate, an alicyclic diisocyanate, an aliphatic diisocyanate, or the like can be used.

The aromatic diisocyanate can be exemplified by a tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate, or their mixtures) (TDI), a phenylene diisocyanate (m-, p-phenylene diisocyanate or their mixtures), 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), a diphenylmethane diisocyanate (4,4′-, 2,4′-, or 2,2′-diphenylmethane diisocyanate, or their mixtures) (MDI), 4,4′-toluidine diisocyanate (TODI), and 4,4′-diphenyl ether diisocyanate.

The aromatic aliphatic diisocyanate can be exemplified by a xylene diisocyanate (1,3- or 1,4-xylene diisocyanate, or their mixtures) (XDI), a tetramethylxylene diisocyanate (1,3- or 1,4-tetramethylxylene diisocyanate, or their mixtures) (TMXDI), and ω,ω′-diisocyanate-1,4-diethylbenzene.

Examples of the alicyclic diisocyanate can include 1,3-cyclopentene diisocyanate, a cyclohexane diisocyanate (1,4-cyclohexane diisocyanate or 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), a methylene bis(cyclohexyl isocyanate) (4,4′-, 2,4′-, or 2,2′-methylene bis(cyclohexyl isocyanate)) (hydrogenated MDI), a methylcyclohexane diisocyanate(methyl-2,4-cyclohexane diisocyanate or methyl-2,6-cyclohexane diisocyanate), and a bis(isocyanatomethyl)cyclohexane (1,3- or 1,4-bis(isocyanatomethyl)cyclohexane, or their mixtures) (hydrogenated XDI).

Examples of the aliphatic diisocyanate can include trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, or 1,3-butylene diisocyanate), hexamethylene diisocyanate, pentamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocianatomethyl caffeate.

The polyisocyanate component that can also be used include: a polyfunctional polyisocyanate compound, such as isocyanurate, biuret, or allophanate, derived from the polyisocyanate monomer; or a polyfunctional polyisocyanate compound containing a terminal isocyanate group obtained by a reaction with a trifunctional or higher polyol compound, such as trimethylolpropane or glycerin.

The polyisocyanate component preferably has a glass transition temperature (Tg) of 50° C. or higher and a number average molecular weight (Mn) of 400 or greater, and in particular, a glass transition temperature (Tg) of 60° C. or higher and a number average molecular weight (Mn) of 500 or greater.

In an embodiment of the present invention, among the above isocyanate components, a xylene diisocyanate is preferably used.

Silane Coupling Agent

For the silane coupling agent used in the anchor coat layer, an epoxy silane-based coupling agent can be preferably used.

Such an epoxy silane-based coupling agent that can be used include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropyltrimethoxysilane.

Other examples of the silane coupling agent include tetramethoxysilane, tetraethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-isocyanatopropyltriethoxysilane, which can be used as necessary.

In addition, for the purpose of improving hot water resistant adhesion, these silane coupling agents can be subjected to hydrolysis to allow the condensation reaction to proceed. Such silane coupling agents may be used.

Composition for Forming Anchor Coat Layer

In an embodiment of the present invention, a composition for forming an anchor coat layer preferably contains the polyurethane-based resin and the silane coupling agent. In addition, the composition for forming an anchor coat layer may be either a water-based or solvent-based composition; however, the composition is desirably an aqueous composition, and thus the polyurethane-based resin to be used is desirably a water-soluble or water-dispersible polyurethane.

The composition for forming an anchor coat layer preferably contains an epoxy silane compound in an amount from 1 to 60 parts by mass relative to 100 parts by mass (solid content) of the polyurethane-based resin. The epoxy silane compound contained in an amount less than the above range would fail to satisfy crack resistance performance during drying compared to the epoxy silane compound contained in an amount in the above range; on the other hand, the epoxysilane compound contained in an amount greater than the above range would have a difficulty in further improving the adhesion and may rather impair hot water resistance.

In addition, for an aqueous medium, the composition for forming an anchor coat layer can contain an aqueous medium known in the art or an organic solvent, such as an alcohol, a polyhydric alcohol, or a derivative of them, which are similar to those used in the composition for forming a gas barrier layer.

In addition to the above components, the composition for forming an anchor coat layer may contain a known component, such as a curing accelerator catalyst; a filler; a softener; an anti-aging agent; a stabilizer; an adhesion promoter; a leveling agent; an antifoaming agent; a plasticizer; an inorganic filler; a tackifying resin; a fiber; a colorant, such as a pigment; or a usable time extender.

Method of Manufacturing Gas Barrier Laminate

In a method of manufacturing a gas barrier laminate according to an embodiment of the present invention, the composition for forming a gas barrier layer described above can be applied directly to at least one surface of the base described above, but preferably, the composition for forming an anchor coat layer is applied prior to applying the composition for forming a gas barrier layer.

A coat weight of the composition for forming an anchor coat layer is determined according to the contents of the polyurethane-based resin and the silane coupling agent in the composition and may not be specified unconditionally, but the composition is preferably applied to be in a range from 0.05 to 1.00 g/m²and particularly from 0.10 to 0.50 g/m²based on a solid content weight of the coating film. The anchor coat applied in an amount less than the above range may fail to adhere the anchor coat layer to the base compared to the anchor coat applied in an amount in the above range; on the other hand, the anchor coat applied in an amount greater than the above range would reduce economic efficiency.

The composition for forming an anchor coat layer applied onto the base body is dried at a temperature of 80 to 140° C. for 1 to 60 seconds to remove a solvent in the composition although the conditions depend on the composition to be used and the coat weight. This enables the anchor coat layer to be formed economically without affecting the base even if the base includes a plastic with a low melting point, such as a polypropylene.

The composition for forming a gas barrier layer is then applied onto the composition for forming an anchor coat layer in a dry state after the solvent removal. A coat weight of the composition for forming a gas barrier layer is determined according to the contents of the zirconium oxide and the phosphoric acid compound in the composition and may not be specified unconditionally, but the composition is preferably applied to be in a range from 0.05 to 2.0 g/m²and particularly from 0.3 to 1.0 g/m²based on a solid content weight of the coating film. The composition applied in an amount less than the above range would fail to provide sufficient barrier properties. On the other hand, the composition applied in an amount greater than the above range would only reduce economic efficiency but provide no special advantage.

The composition for forming a gas barrier layer is then heated at a temperature of 80 to 220° C., particularly of 140 to 220° C., for 1 second to 10 minutes to form the gas barrier layer although the conditions depend on the composition of the zirconium oxide and the phosphoric acid compound in the composition to be used and the coat weight. This reduces a difference in contraction due to heating of the gas barrier layer and the anchor coat layer and can improve the cracking resistance of the gas barrier layer as well as significantly improve the interlayer adhesion between the gas barrier layer and the anchor coat layer, and prevents peeling of the gas barrier layer from the base also when the gas barrier laminate is subjected to retort sterilization.

The application and drying or heating of the composition for forming an anchor coat layer and the composition for forming a gas barrier layer can be performed by methods known in the art.

The application method is not limited to the following, but the compositions can be applied, for example, by spray coating, immersion, or a bar coater, a roll coater, or a gravure coater.

In addition, the drying or heating can be performed by oven drying (heating), infrared heating, high-frequency heating, or the like.

EXAMPLES

The present invention will be further described by the following experimental examples, but the present invention is not limited in any way by the following examples. Various measurement methods and evaluation methods of the experimental examples are as follows.

Experimental Example 1

For a barrier coat paint, a zirconium oxide sol (Zirconia Sol ZSL-10T, available from Daiichi Kigenso Kagaku Kogyo Co., Ltd., amorphous zirconium oxide, solid content (in terms of ZrO₂) of 10%, particle size D (50) of 15 nm) was used as a metal oxide, and a water/methanol solvent was used to adjust a solid content to 4.2% and a ratio of water/methanol to 75/25. To the mixture, as additives, nitric acid (Wako Pure Chemical Industries, Ltd.) was added to give an acid content mass of 18 phr relative to a solid content of the zirconia sol (in terms of ZrO₂) and phosphoric acid (Wako Pure Chemical Industries, Ltd., concentration of 85%) was added to give a non-volatile content of phosphoric acid of 97 phr relative to a solid content of the zirconia sol (in terms of ZrO₂). The mixture was stirred for a predetermined time and used as a barrier coat paint.

Gas Barrier Laminate: Method for Producing Sample

A sample of the gas barrier laminate was performed as follows using the barrier coat paint produced. The barrier coat paint described above was applied onto a plastic base with a thickness of 12 μm (Lumirror P60, available from Toray Advanced Film Co., Ltd.) with a coat weight of 1.0 g/m²using a bar coater, heated and dried in a box oven at 220° C. for 10 minutes, and a sample of the gas barrier laminate was obtained.

Gas Barrier Laminate Film Laminate: Method for Producing Sample

A laminated laminate sample for gas barrier property evaluation was produced by applying a urethane-based adhesive (Takenate A-315/Takenate A-50 available from Mitsui Chemicals, Inc.) in a coat weight of 4.0 g/m²onto the barrier coat surface of the gas barrier laminate described above with a bar coater, drying in a dryer, and then laminating a unstretched polypropylene film with a thickness of 50 μm, and a gas barrier laminate film laminate shown in Experimental Example 1 was obtained.

Experimental Example 2

A gas barrier laminate and a gas barrier laminate film laminate were obtained in the same manner as in Experimental Example 1 except that phosphoric acid of the barrier coat paint was blended in an amount of 113 phr in Experimental Example 1.

Experimental Example 3

A gas barrier laminate and a gas barrier laminate film laminate were obtained in the same manner as in Experimental Example 1 except that phosphoric acid of the barrier coat paint was blended in an amount of 136 phr in Experimental Example 1.

Experimental Example 4

A gas barrier laminate and a gas barrier laminate film laminate were obtained in the same manner as in Experimental Example 1 except that phosphoric acid of the barrier coat paint was blended in an amount of 151 phr in Experimental Example 1.