JP2015113411A - Adhesive for food packaging film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for a food packaging film which, when laminating a plastic film to produce a food packaging film, causes no film separation and further which, after subjecting a food packaging bag produced from the food packaging film to a sterilization treatment, can maintain film appearance for a long period.SOLUTION: Provided is an adhesive for a food packaging film containing a urethane resin obtained by compounding a polyol component (A), an isocyanate component (B), and an aromatic compound (C) having both of a phenolic hydroxyl group and a carboxyl group or an ester group. The adhesive has excellent peeling strength and excellent resistance to contents. Therefore, this adhesive is very suitable as an adhesive for bonding the food packaging film.

Description

  The present invention relates to an adhesive for food packaging films.

  The food packaging film is a composite laminate film, and is composed of various plastic films having a thickness of about 5 to 100 μm and / or metal foil. Examples of the plastic film include polyolefin films such as polyethylene and polypropylene (PP), copolymers of olefins, polyvinyl chloride, polyvinylidene chloride, polyester and polyamide, and examples of the metal foil include aluminum and Metal foils, such as stainless steel, can be illustrated.

  These plastic films and metal foils are characterized by properties such as strength, water resistance, moisture permeability resistance, oxygen resistance resistance and heat resistance. Therefore, by laminating two or more kinds of films as required, a high-performance food packaging film that cannot be obtained by a single film can be provided. As an adhesive used for producing a food packaging film, a urethane adhesive is mainly mentioned. Patent Documents 1 to 3 disclose that a food packaging film is manufactured by laminating a plastic film using a urethane adhesive.

  Patent Document 1 discloses an adhesive for food packaging film in which an oxygen acid of phosphorous, a carboxylic acid, an anhydride thereof, and an epoxy resin are blended in a urethane resin (see Patent Document 1 [Claim 1] [Example]). . Patent Document 2 discloses a urethane adhesive containing an oxygen acid of phosphorus and a silane coupling agent (see Patent Document 2 [Claim 1] [Table 1]). Patent Document 3 discloses a urethane adhesive obtained by reacting a partially acid-modified polyol and a polyisocyanate (see Patent Document 3 [Claim 1] [Table 1]).

Patent Documents 1 to 3 disclose urethane adhesives with improved peel strength, heat resistance and acid resistance. These urethane adhesives are all suitable for laminating a plastic film or the like to produce a food packaging film.
However, in recent years, adhesives for food packaging films have been applied to the appearance of packaging films after a certain period of time after the contents (for example, food) are put into food packaging bags made from food packaging films and sterilized. It is required to have no influence, that is, to have excellent content resistance. Since the urethane adhesives of Patent Documents 1 to 3 contain an epoxy resin, a silane coupling agent, and various acid components, the peel strength (content does not exist) is improved, but the content resistance is insufficient. .

Japanese Patent No. 2683937 JP 2002-3813 A JP-A-2005-132902

  This invention was made in order to solve this subject, and when the subject laminated | stacks a plastic film and manufactured the film for food packaging (laminate film), there is no peeling of a film, and also for food packaging An object of the present invention is to provide an adhesive for food packaging film that can maintain the appearance of the film over a long period of time (excellent in resistance to contents) after the contents are put into a food packaging bag manufactured from a film and sterilized.

  As a result of intensive investigations to solve the above problems, the present inventors have produced a urethane adhesive using an aromatic compound having a specific structure, resulting in a urethane adhesive having high peel strength and excellent content resistance. The inventors have found that the present invention can be obtained and have completed the present invention.

The present invention, in one aspect,
(A) polyol component,
Provided is an adhesive for a food packaging film containing a urethane resin obtained by blending (B) an isocyanate component and (C) an aromatic compound having a phenolic hydroxyl group and a carboxyl group or an ester group.
A food packaging film can be suitably produced using such an adhesive.

In one aspect of the present invention, there is provided an adhesive for a food packaging film, wherein (C) the aromatic compound includes at least one selected from gallic acid, gallic acid alkyl ester, and tannic acid.
In another aspect of the present invention, there is provided an adhesive for food packaging film, wherein (A) the polyol component contains a polyester polyol and / or a polyester polyurethane polyol.

In a preferred embodiment of the present invention, there is provided an adhesive for food packaging films, wherein (B) the isocyanate component contains a polyfunctional isocyanate compound derived from an alicyclic diisocyanate compound and / or an aliphatic diisocyanate compound.
In a further preferred embodiment of the present invention, 0.01 to 10.0 parts by weight of (C) aromatic compound is used with respect to 100 parts by weight of the total weight of (A) polyol component, (B) isocyanate component and (C) aromatic compound. An adhesive for food packaging film is provided.

The adhesive according to the present invention includes a urethane resin obtained by blending an aromatic compound having a carboxyl group or an ester group with (A) a polyol component, (B) an isocyanate component, and (C) a phenolic hydroxyl group. Excellent peel strength and excellent content resistance. Therefore, this adhesive is very suitable as an adhesive for adhering food packaging films.
The food packaging film produced using the food packaging film adhesive of the present invention does not peel off the film, and can maintain its appearance even after being sterilized and left at 60 ° C. for 2 weeks.

When the (C) aromatic compound contains at least one selected from gallic acid, gallic acid alkyl ester, and tannic acid, the content resistance of the food packaging film adhesive is further improved.
When the (A) polyol component contains polyester polyol and / or polyester polyurethane polyol, the content resistance of the food packaging film adhesive is further improved.

When the (B) isocyanate component contains a polyfunctional isocyanate compound derived from an alicyclic diisocyanate compound and / or an aliphatic diisocyanate compound, the heat resistance of the adhesive for food packaging films is further improved.
The adhesive for food packaging film comprises 0.01 to 10.0 parts by weight of (C) aromatic compound relative to 100 parts by weight of the total weight of (A) polyol component, (B) isocyanate component and (C) aromatic compound. When blended, content resistance is further improved.

It is sectional drawing which shows one Embodiment of the food packaging film of this invention.

  The adhesive for food packaging films according to the present invention comprises (A) a polyol component, (B) an isocyanate component, and (C) an aromatic compound having a carboxyl group or ester group and a phenolic hydroxyl group (hereinafter referred to as “(C) aroma”. A urethane resin obtained by blending a “group compound”).

  The “urethane resin” according to the present invention is not particularly limited by the blending order and blending method of the components (A) to (C) as long as the target adhesive can be obtained. Even if the urethane resin is obtained by simultaneously blending three components of (A) a polyol component, (B) an isocyanate component, and (C) an aromatic compound, the urethane resin is composed of the component (A) or the component (C). Either one may be reacted in advance with the component (B), and then the remaining one component may be blended, but the component (A) and the component (C) are mixed in advance, and the mixture is ( What is blended with the component B) is more preferred.

The reaction of the component (A), the component (C) and the component (B) can be performed by a known method. Although the urethane resin can be produced by reacting the components (A) to (C) in a solvent, the components (A) to (C) can also be reacted without using a solvent.
It is also possible to produce a urethane resin by producing an NCO-terminated urethane prepolymer using a polyol and excess isocyanate and reacting it with a short-chain polyol.

In the present invention, “(A) polyol component” is not particularly limited as long as it can obtain the target food packaging film adhesive of the present invention and does not adversely affect the production (or synthesis) of urethane resin. .
The component (A) may be a polyol generally used for obtaining a urethane resin. For example, a polyester polyol, an acrylic polyol, a polyether polyol, a polyether ester polyol, a polyester polyurethane polyol, a polyether polyurethane polyol, And modified products of these polyols.

In the present invention, the “polyester polyol” is a “main chain type” polyester, and refers to a compound having an ester bond and a hydroxyl group in the “main chain”. This hydroxyl group is usually located at the end of the main chain and acts as a functional group that reacts with an isocyanate group.
The polyester polyol is generally obtained by a condensation polymerization reaction between a low molecular polyol, a dicarboxylic acid and an anhydride thereof.

  Examples of such dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, and 2-methyladipic acid. 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid Examples include acids, trimellitic acid, trimesic acid and cyclohexanedicarboxylic acid. These are used alone or in combination.

  Examples of the carboxylic acid anhydride include acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride. These can be used alone or in combination.

As the low-molecular polyol, those having 1 to 3 functional groups are preferable, and bifunctional polyols, so-called diols are particularly preferable. Low molecular polyols can be used alone or in combination.
Examples of the diol include ethylene glycol, 1-methylethylene glycol, 1-ethylethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentylglycol, Low molecular weight diols such as 2-methyl-1,3-propanediol, cyclohexanedimethanol, 2,4-dimethyl-1,5-pentanediol and 2,4-dibutyl-1,5-pentanediol are included. In particular, at least one selected from ethylene glycol, diethylene glycol, butanediol, hexanediol, and neopentyl glycol may be used.

“Acrylic polyol” refers to a compound obtained by an addition polymerization reaction of a (meth) acrylate having a hydroxyl group, and has an ester bond in a “side chain”.
In the present invention, the “acryl polyol” may be a homopolymer of a (meth) acrylate having a hydroxyl group or a copolymer with “another polymerizable monomer”. The hydroxyl group of the acrylic polyol reacts with the isocyanate group.

  Examples of the “(meth) acrylate having a hydroxyl group” include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, glycerol mono (meth) acrylate and 4-hydroxy A butyl acrylate etc. can be illustrated.

The “other polymerizable monomers” are “radical polymerizable monomers having an ethylenic double bond” other than “(meth) acrylate having a hydroxyl group”. Specifically, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dicyclopentanyl (meth) Examples include acrylate, isobornyl (meth) acrylate, styrene, vinyltoluene and the like.
In the present invention, examples of the “polyether polyol” include polyoxytetramethylene glycol (PTMG), polyoxypropylene glycol (PPG), and polyoxyethylene glycol (PEG).

The “polyether polyurethane polyol” is a product obtained by urethanizing the polyether polyol by extending the chain length with an isocyanate compound.
“Polyester polyurethane polyol” is obtained by extending the chain length of the polyester polyol with an isocyanate compound and urethanizing it.
The “polyether ester polyol” is a polyol having both an ester group and an ether group in the main chain.

  "(B) Isocyanate component" according to the present invention includes, for example, aliphatic isocyanate, aromatic isocyanate and alicyclic isocyanate, and as long as the adhesive for food packaging film intended by the present invention can be obtained, It is not particularly limited. However, in view of the fact that the present invention is an adhesive for food packaging films, it is not preferable to use an aromatic isocyanate that may generate an aromatic amine that is a carcinogenic substance. The isocyanate component does not contain only aromatic isocyanate.

  In the present invention, the (B) isocyanate component does not mean that it is composed only of aliphatic isocyanate and / or alicyclic isocyanate. As long as the adhesive for food packaging film intended by the present invention can be obtained, that is, it does not adversely affect the peel strength and content resistance of the adhesive for food packaging film of the present invention, and elution of aromatic amines is confirmed. Insofar as it is not, the (B) isocyanate component may contain an aromatic isocyanate.

In this specification, “aliphatic isocyanate” is a compound having a chain-like hydrocarbon chain in which an isocyanate group is directly bonded to the hydrocarbon chain, and having no cyclic hydrocarbon chain. Refers to a compound. The “aliphatic isocyanate” may have an aromatic ring, but the aromatic ring is not directly bonded to the isocyanate group.
In the present specification, the aromatic ring is not included in the cyclic hydrocarbon chain.

The “alicyclic isocyanate” is a compound that has a cyclic hydrocarbon chain and may have a chain hydrocarbon chain. The isocyanate group may be directly bonded to the cyclic hydrocarbon chain or may be directly bonded to the chain-like hydrocarbon chain that may be included. The “alicyclic isocyanate” may have an aromatic ring, but the aromatic ring and the isocyanate group are not directly bonded.
“Aromatic isocyanate” refers to a compound having an aromatic ring and having an isocyanate group directly bonded to the aromatic ring. Therefore, even if an aromatic ring is present in the molecule, the compound in which the isocyanate group is not directly bonded to the aromatic ring is classified as an aliphatic isocyanate or an alicyclic isocyanate.

Therefore, for example, 4,4′-diphenylmethane diisocyanate (OCN—C ₆ H ₄ —CH ₂ —C ₆ H ₄ —NCO) corresponds to an aromatic isocyanate because the isocyanate group is directly bonded to the aromatic ring. . On the other hand, for example, xylylene diisocyanate (OCN—CH ₂ —C ₆ H ₄ —CH ₂ —NCO) has an aromatic ring, but the isocyanate group is not directly bonded to the aromatic ring, but is bonded to the methylene group. Corresponds to aliphatic isocyanates. The aromatic ring may be condensed with two or more benzene rings.

  Examples of the aliphatic isocyanate include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (hereinafter referred to as HDI), 1,6-diisocyanato-2,2,4. Examples thereof include trimethylhexane, methyl 2,6-diisocyanatohexanoate (lysine diisocyanate), and 1,3-bis (isocyanatomethyl) benzene (xylylene diisocyanate) (hereinafter referred to as XDI).

  Examples of the alicyclic isocyanate include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate) (hereinafter referred to as IPDI), 1,3-bis (isocyanatomethyl) cyclohexane (water). Examples thereof include hydrogenated xylylene diisocyanate), bis (4-isocyanatocyclohexyl) methane (hydrogenated diphenylmethane diisocyanate) and 1,4-diisocyanatocyclohexane.

Examples of the aromatic isocyanate include 4,4′-diphenylmethane diisocyanate (hereinafter referred to as MDI), toluene diisocyanate (hereinafter referred to as TDI), p-phenylene diisocyanate, and m-phenylene diisocyanate.
These isocyanate compounds can be used alone or in combination.

  In the present invention, (B) the isocyanate component preferably contains at least one selected from HDI, IPDI, XDI and modified products thereof, and isocyanurate of 1,6-diisocyanatohexane (HDI), isophorone More preferably, it contains at least one selected from a trimethylolpropane adduct of diisocyanate (IPDI) and a trimethylolpropane adduct of xylylene diisocyanate (XDI). (B) When an isocyanate component contains the said isocyanate, since it becomes difficult to volatilize and the aromatic amine which is a carcinogenic substance does not elute, it is environmentally preferable. Furthermore, the content resistance property of the adhesive for food packaging films is also improved.

In the present invention, the aromatic compound (C) has a carboxyl group or an ester group and a phenolic hydroxyl group.
In the present specification, “phenolic hydroxyl group” means a hydroxyl group directly bonded to an aromatic ring.

In this specification, a carboxyl group (—COOH) refers to a hydrophilic functional group in which one hydroxy group is bonded to a carbon atom by a single bond and an oxygen atom is bonded by a double bond. The carboxyl group can include a carboxylate group (—COO ⁻ ) in which hydrogen of the hydroxyl group is dissociated. Here, the paired cation is not particularly limited as long as the adhesive of the present invention can be obtained, and examples thereof include sodium ion, potassium ion, and magnesium ion.
In the present specification, the ester group is represented by (—COOR), in which hydrogen of the above carboxyl group is replaced with R. R represents an alkyl group or an aryl group.

Specific examples of the aromatic compound (C) are shown below, but the present invention is not limited to the following specific examples. (C) As a preferable embodiment of the aromatic compound,
Gallic acid;
Gallic acid alkyl esters such as methyl gallate, ethyl gallate and propyl gallate; and tannic acid, aminosalicylic acid, hydroxyphenylacetic acid, hydroxyphenylacetic acid methyl, salicylic acid, methyl salicylate, hydroxybenzoic acid, hydroxyhydroxybenzoic acid, diphenol Other acids and esters, such as acid and mycophenolate mofetil.

  As embodiment of this invention, it is preferable that (C) aromatic compound contains at least 1 sort (s) chosen from gallic acid, a gallic-acid alkylester, and tannic acid, and it is most preferable that gallic acid is included especially.

As embodiment of this invention, it is preferable to use 0.01-10.0 weight part of (C) aromatic compound per 100 weight part of total weight of (A)-(C) (in solid content conversion), ( It is more preferable to use 0.01 to 5.0 parts by weight of C) aromatic compound, and it is particularly preferable to use 0.1 to 2.0 parts by weight of (C) aromatic compound.
When the aromatic compound (C) is used within the above range, the peel strength and content resistance of the food packaging film adhesive of the present invention are further improved.

  The adhesive for food packaging films of the present invention may contain other components in addition to the components (A) to (C). Examples of the “other components” include a solvent, a tackifier resin, a pigment, a plasticizer, a catalyst, and an adhesion promoter.

  Examples of the “tackifying resin” include styrene resins, terpene resins, aliphatic petroleum resins, aromatic petroleum resins, rosin esters, acrylic resins, and polyester resins (excluding polyester polyols). Tackifying resins generally have a molecular weight of less than 1500 g / mol, in particular a low molecular weight of less than 1000 g / mol. The addition amount of the tackifying resin is preferably 0 to 50 parts by weight and more preferably 30 parts by weight or less with respect to 100 parts by weight of the total weight of the adhesive for food packaging film.

“Pigments” include, for example, nanopigments based on TiO ₂ , SiO ₂ , FeO ₃ , similar oxides and oxyhydrates. These pigments usually preferably have a particle size of 500 nm or less, and more preferably have a particle size of less than 100 nm.
Examples of “plasticizer” include white oil, naphthene mineral oil, paraffin hydrocarbon oil, polypropylene oligomer, polybutene oligomer, polyisoprene oligomer, hydrogenated polyisoprene oligomer, hydrogenated polybutadiene oligomer, phthalate, adipate, benzoate ester, vegetable oil, animal oil And derivatives thereof. Vegetable oils, animal oils and derivatives thereof are generally more preferable in view of using the adhesive of the present invention for the production of food packaging films because they can be generally used in foods and are considered to be safer.

  “Catalysts” include metal catalysts such as tin catalysts (trimethyltin laurate, trimethyltin hydroxide, dibutyltin dilaurate, dibutyltin maleate, etc.), lead-based catalysts (lead oleate, lead naphthenate, lead octenoate, etc.) ), Other metal catalysts (such as naphthenic acid metal salts such as cobalt naphthenate), and amine-based catalysts such as triethylenediamine, tetramethylethylenediamine, tetramethylhexylenediamine, diazabicycloalkenes, and dialkylaminoalkylamines Etc. can be illustrated.

Examples of the “adhesion promoter” include silane compounds. Known organofunctional silanes such as (meth) acryloxy functionality, epoxy functionality, amine functionality and non-reactive substituted silanes can be used as adhesion promoters. Examples are vinyltrialkoxysilane, alkyltrialkoxysilane, tetraalkoxysilane, 3-acryloxypropyltrialkoxysilane, 3-methacryloxypropyltrialkoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxy. Silane, 3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-glycidyloxymethyltrimethoxysilane, 3-glycidyloxymethyltriethoxysilane and 2-glycidyloxyethyl Such as trimethoxysilane.
As an embodiment of the present invention, it is preferable that 0.1 to 5 parts by weight of an adhesion promoter is included with respect to 100 parts by weight of the total weight of the adhesive for food packaging films.

  The adhesive for food packaging films of the present invention can be produced by mixing the components (A), (B) and (C) as described above. In some cases, other components may be mixed. The mixing method is not particularly limited as long as the adhesive for food packaging film targeted by the present invention can be obtained. The order of mixing the components is not particularly limited. The adhesive for food packaging films according to the present invention can be produced without requiring a special mixing method and a special mixing order. And the obtained adhesive agent for food packaging films is excellent in both peel strength and content resistance.

Since the adhesive for food packaging films of the present invention is applied to the film at 15 to 100 ° C., it should have a low viscosity in this temperature range. The viscosity of the adhesive for food packaging films is preferably 500 mPas or less as measured using a (Brookfield viscometer) in consideration of applicability.
The food packaging film of the present invention is a laminate film produced using the above-described adhesive for food packaging film. Examples of the film include a film in which a metal layer is formed on a plastic substrate and a film in which a metal layer is not formed.

When producing a food packaging film, the food packaging film adhesive of the present invention is applied to the film. As a coating method, for example, various methods such as gravure coating, wire bar coating, air knife coating, die coating, lip coating, and comma coating can be used. A plurality of films coated with the adhesive for food packaging film of the present invention can be bonded together to produce a food packaging film.
When apply | coating the adhesive agent for food packaging films to a film, it is preferable that it is 1-100 g / m < ² >, and, as for an application quantity, it is more preferable that it is 2-35 g / m < ² >.

Although one form of the food packaging film of this invention is illustrated in FIG. 1, this invention is not limited to these forms.
FIG. 1 shows a cross-sectional view of the food packaging film 10. The food packaging film 10 is a laminate (laminate) including one metal foil 14 and two plastic films 12 and 13, and the plastic film 12 is formed on both surfaces of the metal foil 14 using the adhesive layer 11. And 13 are bonded. More specifically, for example, the plastic film 12 is preferably a polyethylene terephthalate (PET) film, the film 13 is preferably a polyolefin film, more preferably a PP film, and a CPP film. Most preferably, a metal foil 14 is inserted between them. The metal foil 14 is, for example, an aluminum foil. The film 12 and the metal foil 14, and the film 13 and the foil 14 are bonded together by the food packaging film adhesive layer 11.

  Examples of laminated films include plastic films such as polyethylene terephthalate, nylon, polyethylene, polypropylene and polyvinyl chloride; metal foils such as aluminum foil; vapor deposition films such as metal vapor deposition films and silica vapor deposition films; and stainless steel, iron and copper And metal films such as lead. The thickness is preferably 5 to 200 μm in the case of a plastic film, for example.

A food packaging bag can be manufactured by heat-sealing the food packaging film of the present invention, for example. The food packaging bag can contain food.
The food to be included is, for example, food that has been sterilized by heating and heating (that is, retort food), and examples of the retort food include curry, stew, meat sauce, and soup.
The food packaging film of the present invention is preferably used for producing a packaging bag for enclosing a retort food, a so-called retort pouch.
Since the food packaging film of the present invention is manufactured with the above-mentioned adhesive for food packaging film, the film is difficult to peel off, and the film appearance is changed even after two weeks after sterilization of the contents. Therefore, the content resistance is superior compared to conventional food packaging films.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example and a comparative example, these examples are for demonstrating this invention, and do not limit this invention at all.

<Synthesis Example of (A) Polyol Component and (B) Isocyanate Component>
Synthesis Example 1 (A1) Synthesis of Polyester Polyol 265.8 g of isophthalic acid, 23.6 g of 1,6-hexanediol and 244.1 g of diethylene glycol were charged, and an esterification reaction was performed at 180 to 220 ° C. for 6 hours. After distilling off a predetermined amount of water, 131.5 g of adipic acid was added, and an esterification reaction was further performed at 180 to 220 ° C. for 6 hours. After distilling a predetermined amount of water, 0.15 g of tetra (isopropyl) titanate was added, the pressure was gradually reduced, and a transesterification reaction was carried out at 200 to 250 ° C. for 3 hours to obtain a number average molecular weight of 8,000 and a hydroxyl value of 14.0 mgKOH. / G of (A1) polyester polyol was obtained. Ethyl acetate was added to (A1) polyester polyol to obtain a (A1) polyester polyol solution having a nonvolatile content of 50% by weight.

Synthesis Example 2 (A2) Synthesis of Polyester Polyol 265.8 g of isophthalic acid, 40.3 g of ethylene glycol, 67.7 g of neopentyl glycol and 118.2 g of 1,6-hexanediol were charged and esterified at 180 to 220 ° C. for 6 hours. Reaction was performed. After distilling a predetermined amount of water, 73.1 g of adipic acid was added, and the esterification reaction was further performed at 180 to 220 ° C. for 6 hours. After distilling out a predetermined amount of water, 0.15 g of tetra (isopropyl) titanate was added, the pressure was gradually reduced, and the ester exchange reaction was carried out at 200 to 250 ° C. for 3 hours to obtain a number average molecular weight of 10,000 and a hydroxyl value of 11.2 mgKOH. / G of (A2) polyester polyol was obtained. Ethyl acetate was added to the (A2) polyester polyol to obtain a (A2) polyester polyol solution having a nonvolatile content of 50% by weight.

Synthesis Example 3 (A3) Synthesis of Polyester Polyurethane Polyol 265.8 g of isophthalic acid, 74.5 g of ethylene glycol and 239.7 g of neopentyl glycol were charged, and an esterification reaction was performed at 180 to 220 ° C. for 2 hours. After distilling off a predetermined amount of water, 262.9 g of sebacic acid was added, and an esterification reaction was further performed at 180 to 220 ° C. for 2 hours. After distilling a predetermined amount of water, 0.15 g of tetra (isopropyl) titanate was added and the pressure was gradually reduced, and excess ethylene glycol was removed from the system at 200 to 250 ° C. for 2 hours to obtain a polyester polyol. It was. 300 g of this polyester polyol was heated and dehydrated at 120 ° C. and then reacted at 130 ° C. with 21.0 g of isophorone diisocyanate (NCO / OH = 0.7) until the NCO group disappeared, and the number average molecular weight was 10,000. A (A3) polyester polyurethane polyol having a hydroxyl value of 10.0 mgKOH / g was obtained. Ethyl acetate was added to (A3) polyester polyol to obtain a (A3) polyester polyurethane polyol solution having a nonvolatile content of 50% by weight.

Synthesis Example 4 (A4) Synthesis of Polyether Polyurethane Polyol 500 g of polyoxypropylene glycol (number average molecular weight 1,000), 93.9 g of dipropylene glycol, 188.0 g of toluene diisocyanate, 335 g of ethyl acetate and tin octylate as a urethanization catalyst 0.15 g of the mixed solution was reacted at 65 ° C. for 8 hours. Thereafter, 13.4 g of trimethylolpropane was added, and the mixture was further reacted for 2 hours to obtain a (A4) polyether polyurethane polyol having a number average molecular weight of 6,000 and a hydroxyl value of 21.0 mgKOH / g. Ethyl acetate was added to the (A4) polyether polyurethane polyol to obtain a (A4) polyether polyurethane polyol solution having a nonvolatile content of 70% by weight.

Synthesis Example 5 (B4) Synthesis of NCO-terminated urethane prepolymer 265.8 g of isophthalic acid and 265.3 g of diethylene glycol were charged and an esterification reaction was performed at 180 to 220 ° C. for 3 hours. After distilling a predetermined amount of water, 119.9 g of adipic acid was added, and the esterification reaction was further performed for 3 hours. After distilling off a predetermined amount of water, 0.15 g of tetra (isopropyl) titanate was added and the pressure was gradually reduced, followed by further reaction at 200 to 250 ° C. for 3 hours to obtain a polyester polyol. After 300 g of this polyester polyol was heated and dehydrated at 120 ° C. under reduced pressure, 65.0 g of isophorone diisocyanate (NCO / OH = 2.0) and 0.80 g of tin octylate as a urethanization catalyst were added, and at 130 ° C. for 3 hours. The reaction was performed to obtain a (B4) NCO-terminated urethane prepolymer having a number average molecular weight of 5,000 and NCO% = 4.0%. Ethyl acetate was added to the (B4) NCO-terminated urethane prepolymer to obtain a (B4) NCO-terminated urethane prepolymer solution having a nonvolatile content of 50% by weight.

Synthesis Example 6 (A6) Synthesis of Partially Acid-Modified Polyol 265.8 g of isophthalic acid, 40.3 g of ethylene glycol, 67.7 g of neopentyl glycol, and 118.2 g of 1,6-hexanediol were charged at 200 to 230 ° C. for 6 hours. An esterification reaction was performed. After distilling a predetermined amount of water, 73.1 g of adipic acid was added, and the esterification reaction was further performed for 6 hours. After distilling off a predetermined amount of water, the pressure was gradually reduced and the esterification reaction was carried out at 230 to 250 ° C. for 5 hours to obtain a polyester polyol. After 300 g of this polyester polyol was heated to 120 ° C. and dehydrated under reduced pressure, 10.3 g of isophorone diisocyanate (NCO / OH = 0.75) was reacted at 130 ° C. until the NCO group of isophorone diisocyanate disappeared, A polyester polyurethane polyol having a number average molecular weight of 14,000 and a hydroxyl value of 8.0 mgKOH / g was obtained. To 300 g of this polyester polyurethane polyol, 2.9 g of trimellitic anhydride and 6.2 g of ethylene glycol bisanhydro trimellitate were added and reacted at 180 ° C. for 2 hours to obtain (A6) a partially acid-modified polyol. Ethyl acetate was added to the (A6) partially acid-modified polyol to obtain a (A6) partially acid-modified polyol solution having a nonvolatile content of 50% by weight.

  (A1) to (A4) and (A6) obtained in Synthesis Examples 1 to 6, (A5) General-purpose diethylene glycol, (B) Isocyanate component, (C) Aromatic compounds are blended and used in Examples and Comparative Examples An adhesive for food packaging film was produced. (B) component and (C) component which are the raw materials of the adhesive agent for food packaging films are described below.

(B) Isocyanate component (B1) 1,6-diisocyanatohexane (HDI) isocyanurate (Sumidule N3300 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd., NCO% = 21.8%)
(B2) TMP (trimethylolpropane) adduct of xylylene diisocyanate (XDI), 75 wt% ethyl acetate solution (Takenate D-110N (trade name) manufactured by Mitsui Chemicals, NCO% = 11.5)
(B3) TMP adduct of isophorone diisocyanate (IPDI), 75 wt% ethyl acetate solution (Takenate D-140N (trade name), NCO% = 10.5 manufactured by Mitsui Chemicals)
(B4) NCO-terminated urethane prepolymer solution of Synthesis Example 5

(C) Aromatic compound (C1) Gallic acid (gallic acid anhydrous (trade name))
(C2) Tannic acid (C3) Ethyl gallate (C4) Propyl gallate (C5) Aminosalicylic acid (4-aminosalicylic acid (trade name))
(C6) 3,4-hydroxyphenylacetic acid (C'7) benzoate (C'8) resorcinol (C'9) 85 wt% orthophosphoric acid (phosphoric acid _-d 3, 85% solution (trade name))
(C'10) Phthalic anhydride (phthalic anhydride (trade name))
(C'11) Epoxy resin (Mitsubishi Chemical Corporation, jER1002 (trade name))
(C′12) 3-Glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403 (trade name))
All of (C1) to (C′10) were manufactured by Wako Pure Chemical Industries. In addition, the product name is the same as the compound name if there is no description of the product name.

  Using the above components, the following food packaging film adhesives of Examples 1 to 17 and Comparative Examples 1 to 10 were produced, and their performance was evaluated. A manufacturing method and an evaluation method are shown below.

<Synthesis of adhesive for food packaging film>
(A) component, (B) component, and (C) component are mix | blended by the ratio (solid content conversion) as described in a table | surface, Furthermore, appropriate amount ethyl acetate is mixed and stirred, and solid content 30 weight% solution is prepared. Manufactured.
Specifically, first, after (C) the aromatic compound was stirred and mixed with the (A) polyol component and completely dissolved, (B) the isocyanate component and ethyl acetate were added, and the mixture was further stirred and mixed. did.

<Production of composite film>
At normal temperature, the adhesives of Examples and Comparative Examples were applied to a PET film with an applicator so that the solid content weight was 4.0 (g / m ² ), and the solvent was stripped off. Bonded to the surface.
Next, after applying an adhesive to the surface of the corona-treated surface of the CPP (unstretched polypropylene) film in the same manner as described above, and evaporating the solvent, it was bonded to the aluminum foil side of the two-layer product prepared earlier. A film was prepared.
Then, this composite film was cured at 50 ° C. for 4 days, and the adhesive composition was cured to obtain the intended three-layer composite film.

<Evaluation>
Evaluation of the adhesive for food packaging films was performed by the following method.

1. Peel strength test A 300 mm x 15 mm test piece was cut out from the above three-layer composite film, and a tensile strength tester (Tensilon RTM-250 (trade name) manufactured by Orientec Co., Ltd.) was used at a temperature of 23 ° C and a relative humidity of 50. %, A T-type peel test was performed at a peel rate of 300 mm / min, and the peel strength (N / 15 mm) of the aluminum foil / CPP film was measured. About each Example and the comparative example, intensity | strength was measured 5 times and the average value was shown to the table | surface.

2. Content resistance test A 14 cm x 28 cm packaging bag was produced from the above three-layer composite film using a heat sealer. On the other hand, cereal vinegar (manufactured by Tamanoi vinegar) / salad oil (manufactured by Riken) / tomato ketchup (manufactured by Kikkoman) at a weight ratio of 1/1/1 was mixed with stirring to obtain a mixture. This mixture was used as the contents of the packaging bag. 100 g of this content was filled into a packaging bag, the bag lid was heat sealed, and the packaging bag was completely sealed. The completely sealed packaging bag was subjected to pressurized hot water sterilization using a sterilization tester under the conditions of 121 ° C., 30 minutes, and 0.20 MPa. Then, the packaging bag was cut open and a test piece of 300 mm × 15 mm was cut out. The peel strength (N / 15 mm) between the aluminum foil / CPP film of the test piece was measured by the same method as the peel strength test described above, and the appearance of the film immediately after sterilization was visually evaluated.

The appearance evaluation results immediately after sterilization of the aluminum foil / CPP film are shown in (2-1) of Tables 1 to 3, and the peel strength immediately after sterilization is shown in (2-2) of Tables 1 to 3. The criteria for the appearance evaluation (2-1) of the film immediately after sterilization are shown below.
◎: No abnormality ○: Part of the aluminum surface is corroded but not delaminated.
Δ: The entire aluminum surface is corroded but not delaminated.
X: Corrosion was observed on the entire aluminum surface, and some delamination was observed.
XX: Corrosion was observed on the entire aluminum surface and it was severely delaminated.

  Moreover, after storing the packaging bag after the above-mentioned sterilization treatment with a thermostat of 60 ° C. for 2 weeks, the appearance of the aluminum foil / CPP film was visually evaluated (2-3). The criteria for the appearance evaluation (2-3) of the film after storage at 60 ° C. for 2 weeks are the same as the criteria for the appearance evaluation (2-1) of the film immediately after sterilization.

※1：各成分の量は、（Ａ）〜（Ｃ）の固形分の合計１００重量部当たりの重量を示す。

* 1: The amount of each component indicates the weight per 100 parts by weight of the total solid content of (A) to (C).

※1：各成分の量は、（Ａ）〜（Ｃ）の固形分の合計１００重量部当たりの重量を示す。

* 1: The amount of each component indicates the weight per 100 parts by weight of the total solid content of (A) to (C).

※1：各成分の量は、（Ａ）〜（Ｃ）の固形分の合計１００重量部当たりの重量を示す。

* 1: The amount of each component indicates the weight per 100 parts by weight of the total solid content of (A) to (C).

As Tables 1-2 show, since the adhesives for food packaging films of Examples 1 to 17 were obtained from the three components (A) to (C), they were excellent in peel strength and content resistance. The three-layer composite films of Examples 1 to 17 show no delamination even after sterilization and after storage at 60 ° C. for 2 weeks.
On the other hand, since the adhesive for food packaging films of Comparative Examples does not contain the component (C) as shown in Table 3, the content resistance is inferior to the Examples. In particular, the three-layer composite film of the comparative example clearly shows delamination after sterilization and after storage at 60 ° C. for 2 weeks.

  The present invention provides an adhesive for food packaging films. The adhesive for food packaging films according to the present invention is suitable for producing a food packaging film excellent in content resistance, particularly a retort pouch.

  10: Food packaging film, 11: Adhesive layer, 12: Plastic (PET) film, 13: Plastic (PP) film, 14: Metal (aluminum) foil

Claims (5)

(A) polyol component,
(B) An adhesive for a food packaging film containing a urethane resin obtained by blending an isocyanate component and (C) an aromatic compound having both a phenolic hydroxyl group and a carboxyl group or an ester group.   (C) The adhesive for food packaging films of Claim 1 in which an aromatic compound contains at least 1 sort (s) chosen from gallic acid, a gallic acid alkylester, and tannic acid.   (B) The adhesive for food packaging films of Claim 1 or 2 in which an isocyanate component contains the polyfunctional isocyanate compound induced | guided | derived from an alicyclic diisocyanate compound and / or an aliphatic diisocyanate compound.   2. (C) Aromatic compound 0.01-10.0 weight part is mix | blended with respect to 100 weight part of total weight of (A) polyol component, (B) isocyanate component, and (C) aromatic compound. The adhesive for food packaging films according to any one of -3.   The food packaging film manufactured using the adhesive agent for food packaging films in any one of Claims 1-4.

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