Polycarbodiimide compound, aqueous resin composition, and food packaging container

Abstract

The present invention provides: a polycarbodiimide compound which enables the achievement of an aqueous resin composition that is capable of forming a coating film (layer) having water resistance and adhesion, which are good enough to withstand use in food packaging applications; an aqueous resin composition which contains this polycarbodiimide compound; and a food packaging container which is provided with a layer that is formed from this aqueous resin composition. A polycarbodiimide compound (A) which is represented by general formula (1). (In the formula, each R1 represents a residue that is obtained by removing a functional group that is reactive with an isocyanate from a hydrophilic compound which has the functional group that is reactive with an isocyanate; each R2 represents a divalent residue that is obtained by removing isocyanate groups from an aliphatic diisocyanate compound; R3 represents a divalent residue that is obtained by removing hydroxyl groups from a glycol compound that has 2 or 3 carbon atoms; X represents a group that is formed by a reaction between the hydrophilic compound and the aliphatic diisocyanate compound; n1 represents a number from 1 to 10; n2 represents a number from 1 to 10; p represents a number from 2 to 4; and the plurality of R1 moieties and R2 moieties are respectively the same as or different from each other.)

Description

[Technical field]

[0001] The present invention relates to a polycarbodiimide compound, an aqueous resin composition, and a food packaging container. [Background technology]

[0002] Conventionally, as a means for improving various physical properties such as the strength, water resistance, and durability of aqueous resin coating films, a method has been adopted in which a crosslinking agent such as a carbodiimide compound capable of reacting with a functional group (e.g., a carboxyl group) of the aqueous resin to form a crosslinked structure is used in combination (see, for example, Patent Documents 1 and 2).

[0003] Although the above-mentioned aqueous resin coating films have been used in many fields, such as paints, inks, fiber treatment agents, adhesives, and coating agents, they have not been used for food packaging. As described above, the above-mentioned aqueous resin coating films have not been used for food packaging, and therefore their water resistance and adhesion (e.g., water resistance when immersed in high-temperature water and adhesion after immersion) have not reached a level sufficient to withstand use for food packaging. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-047225 A [Patent Document 2] JP 2002-363250 A Summary of the Invention [Problem to be solved by the invention]

[0005] Under the above circumstances, there has been an increasing demand for the use of aqueous resin coatings for food packaging, but there has been a problem in that the water resistance and adhesion have not yet reached a level sufficient for use in food packaging.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a polycarbodiimide compound capable of obtaining an aqueous resin composition capable of forming a coating film (layer) having water resistance and adhesion sufficient to withstand use in food packaging, an aqueous resin composition containing the polycarbodiimide compound, and a food packaging container having a layer made of the aqueous resin composition. [Means for solving the problem]

[0007] As a result of intensive research aimed at solving the above problems, the present inventors have found that the above problems can be solved by using a polycarbodiimide compound (A) having a specific structure as a crosslinking agent. The present invention has been completed based on this finding.

[0008] That is, the present invention provides the following [1] to

[12] . [1] A polycarbodiimide compound (A) represented by the following general formula (1): [ka] (In the formula, R 1 represents a residue obtained by removing a functional group capable of reacting with isocyanate from a hydrophilic compound having a functional group capable of reacting with isocyanate, and R 2 represents a divalent residue obtained by removing an isocyanate group from an aliphatic diisocyanate compound, and R 3 represents a divalent residue obtained by removing a hydroxyl group from a glycol compound having 2 or 3 carbon atoms. X represents a group formed by the reaction of the hydrophilic compound with the aliphatic diisocyanate compound. n1 represents a number from 1 to 10, n2 represents a number from 1 to 10, and p represents a number from 2 to 4. 1 and R 2 may be the same or different.) [2] The polycarbodiimide compound (A) according to the above [1], wherein the glycol compound is at least one of ethylene glycol and propylene glycol. [3] The polycarbodiimide compound (A) according to the above [1] or [2], wherein the diisocyanate compound is at least one of dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate. [4] The polycarbodiimide compound (A) according to any one of the above [1] to [3], which has a carbodiimide equivalent of 640 or less. [5] An aqueous resin composition comprising the polycarbodiimide compound (A) according to any one of the above [1] to [4] and an aqueous resin. [6] The aqueous resin composition according to [5] above, wherein the aqueous resin is at least one selected from the group consisting of aqueous polyurethane resins, acrylic resins, polyester resins, and rubber-based latex resins. [7] The aqueous resin composition according to [6] above, wherein the aqueous resin is at least one selected from the group consisting of aqueous polyurethane resins, acrylic resins, and polyester resins. [8] The aqueous resin composition according to any one of the above [5] to [7], further comprising at least one selected from water and a hydrophilic solvent. [9] The aqueous resin composition according to any one of the above [5] to [8], wherein the aqueous resin contains a carboxyl group, and an equivalent ratio of the carbodiimide group of the polycarbodiimide compound (A) to the carboxyl group of the aqueous resin is 0.1 to 2.0.

[10] A food packaging container comprising a layer made of the aqueous resin composition according to any one of [5] to [9] above.

[11] The food packaging container described in

[10] above, having the layer as an outermost layer.

[12] The food packaging container described in

[10] above, which has the layer as an adhesive layer. Effect of the Invention

[0009] According to the present invention, it is possible to provide a polycarbodiimide compound capable of obtaining an aqueous resin composition capable of forming a coating film (layer) having water resistance and adhesion sufficient to withstand use in food packaging, an aqueous resin composition containing the polycarbodiimide compound, and a food packaging container having a layer made of the aqueous resin composition. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram illustrating the evaluation criteria for water resistance in the examples. [Diagram 2] FIG. 2 is a diagram illustrating the evaluation criteria for adhesion evaluation in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Polycarbodiimide compound (A)] The polycarbodiimide compound (A) of the present invention is characterized by being represented by the following general formula (1): The polycarbodiimide compound (A) of the present invention forms a crosslinked structure with an aqueous resin described below, and can improve the water resistance, adhesion, etc. of a coating film of the aqueous resin, making it suitable for use in food packaging.

[0012] [ka] (In the formula, R 1 represents a residue obtained by removing a functional group capable of reacting with isocyanate from a hydrophilic compound having a functional group capable of reacting with isocyanate, and R 2 represents a divalent residue obtained by removing an isocyanate group from an aliphatic diisocyanate compound, and R 3 represents a divalent residue obtained by removing a hydroxyl group from a glycol compound having 2 or 3 carbon atoms. X represents a group formed by the reaction of the hydrophilic compound with the aliphatic diisocyanate compound. n1 represents a number from 1 to 10, n2 represents a number from 1 to 10, and p represents a number from 2 to 4. 1 and R 2 may be the same or different.)

[0013] <R 2 > In the above general formula (1), R 2represents a divalent residue obtained by removing an isocyanate group from an aliphatic diisocyanate compound. Here, the aliphatic diisocyanate compound includes an alicyclic diisocyanate compound. Specific examples of the aliphatic diisocyanate compound include hexamethylene diisocyanate (an aliphatic diisocyanate compound having two primary isocyanate groups), cyclohexane-1,4-diisocyanate (an aliphatic diisocyanate compound having two secondary isocyanate groups), isophorone diisocyanate (an aliphatic diisocyanate compound having one primary isocyanate group and one secondary isocyanate group), dicyclohexylmethane-4, Examples of such isocyanate compounds include 4'-diisocyanate (an aliphatic diisocyanate compound having two secondary isocyanate groups), methylcyclohexane diisocyanate (1-methylcyclohexane-2,4-diyl diisocyanate) (an aliphatic diisocyanate compound having two secondary isocyanate groups), and 2,5(2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane (an aliphatic diisocyanate compound having two primary isocyanate groups). Among these, from the viewpoints of ease of synthesis of the polycarbodiimide compound and storage stability of the synthesized polycarbodiimide compound, dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate are preferred, and from the viewpoint of storage stability of the synthesized polycarbodiimide compound, dicyclohexylmethane-4,4'-diisocyanate is more preferred. Incidentally, an aliphatic diisocyanate compound having only secondary or higher isocyanate groups is more preferable than an aliphatic diisocyanate compound having a primary isocyanate group. Among the aliphatic diisocyanate compounds having a primary isocyanate group, a suitable example is isophorone diisocyanate, which has not only a primary isocyanate group but also a secondary isocyanate group. In this specification, a "primary isocyanate group" refers to an isocyanate group in which the carbon atom to which the isocyanate group is directly bonded is a primary carbon atom, and a "secondary isocyanate group" refers to an isocyanate group in which the carbon atom to which the isocyanate group is directly bonded is a secondary carbon atom.

[0014] <R 1 > In the above general formula (1), R 1 represents a residue obtained by removing a functional group capable of reacting with isocyanate from a hydrophilic compound having a functional group capable of reacting with isocyanate. The hydrophilic compound is preferably at least one selected from the group consisting of the following general formulae (2), (3), (4), and (5), and from the viewpoint of improving the solubility or dispersibility of the polycarbodiimide compound (A) in water or a hydrophilic solvent, is more preferably at least one selected from the group consisting of the following general formulae (2) and (3), is even more preferably the following general formula (2), and is particularly preferably at least one selected from the group consisting of polyethylene glycol monomethyl ether, polyethylene glycol mono-2-ethylhexyl ether, and polyethylene glycol monolauryl ether.

[0015] R 4 O-(CH2-CHR 5 -O) m -H (2) In the formula, R 4 is an alkyl group having 1 to 12 carbon atoms (preferably an alkyl group having 1 to 4 carbon atoms), R 5 is a hydrogen atom or a methyl group, and m is an integer of 4 to 30. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a t-butyl group. R 4 is preferably a methyl group, and R 5 is preferably a hydrogen atom. m is an integer of 4 to 30, and from the viewpoint of improving the affinity between the polycarbodiimide compound (A) and the carboxyl group-containing aqueous resin, is preferably an integer of 4 to 22, and more preferably an integer of 8 to 15.

[0016] (R 6 )2-NR 7 -OH (3) In the formula, R 6 is an alkyl group having 1 to 6 carbon atoms, R 7 is an alkylene group having 1 to 10 carbon atoms or a polyoxyalkylene group. R 6 Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, a cyclohexyl group, etc. Among these, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a s-butyl group, an isobutyl group, and a t-butyl group are preferable. R 7 Examples of the alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, a propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, a nonamethylene group, and a decamethylene group. The hydrogen atom of the alkylene group may be substituted with a monovalent hydrocarbon group such as a methyl group. R 7 As the alkyl group, an ethylene group, a propylene group, a tetramethylene group, and a pentamethylene group are preferable.

[0017] (R 8 )2-NR 9 -NH2(4) In the formula, R 8 is an alkyl group having 1 to 6 carbon atoms, R 9 is an alkylene group having 1 to 10 carbon atoms or a polyoxyalkylene group. R 8 The alkyl group having 1 to 6 carbon atoms is the same as the above R 6Among these, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, and a t-butyl group are preferable. R 9 The alkylene group having 1 to 10 carbon atoms is the above-mentioned R 7 The same can be mentioned. R 9 As the alkyl group, an ethylene group, a propylene group, a tetramethylene group, and a pentamethylene group are preferable.

[0018] H.O.R. 10 -SO3M (5) In the formula, R 10 represents an alkylene group having 1 to 10 carbon atoms, and M represents an alkali metal such as Na or K. R 10 The alkylene group having 1 to 10 carbon atoms is the above-mentioned R 7 Among these, a methylene group and an ethylene group are preferred.

[0019] <R 3 > In the general formula (1), R 3 represents a divalent residue obtained by removing a hydroxyl group from a glycol compound having a carbon number of 2 or 3. The glycol compound having a carbon number of 2 or 3 is preferably at least one of ethylene glycol and propylene glycol. In the above glycol compounds, those with one carbon atom are difficult to obtain industrially and are not suitable for practical use. Conversely, those with a carbon atom number of more than 3 (an integer of 4 or more) contain a large amount of glycol components in the molecule, resulting in a decrease in the concentration of the carbodiimide to be reacted.

[0020] In the general formula (1), X represents a group formed by the reaction of the hydrophilic compound with the aliphatic diisocyanate compound. For example, when the hydrophilic compound is represented by the general formula (2), (3), or (5), X represents a group represented by the following general formula (6), and when the hydrophilic compound is represented by the general formula (4), X represents a group represented by the following general formula (7).

[0021]

change

[0022]

change

[0023] <n1> In the general formula (1), n1 is not particularly limited as long as it is a number from 1 to 10, but is preferably a number from 1 to 5, more preferably a number from 1 to 4, and particularly preferably a number from 1 to 3. If n1 in the general formula (1) exceeds 10, the hydrophilicity of the polycarbodiimide compound (A) decreases, making it difficult to disperse it in water, and therefore difficult to use it as an aqueous crosslinking agent.

[0024] <n2> In the general formula (1), n2 is not particularly limited as long as it is a number from 1 to 10, but is preferably a number from 1 to 5, more preferably a number from 1 to 4, and particularly preferably a number from 1 to 3. If n2 in the general formula (1) exceeds 10, the hydrophilicity of the polycarbodiimide compound (A) decreases, making it difficult to disperse it in water, and therefore difficult to use it as an aqueous crosslinking agent.

[0025] In the general formula (1), p is not particularly limited as long as it is 2 to 4, but is preferably 2 to 3, and more preferably 2. If p in the general formula (1) is less than 2, water resistance and PET adhesion are reduced, and if it exceeds 4, the hydrophilicity of the polycarbodiimide compound (A) is reduced, making it difficult to disperse it in water, and therefore difficult to use it as an aqueous crosslinking agent.

[0026] The polycarbodiimide compound (A) is preferably used by dissolving or dispersing in at least one selected from water and hydrophilic solvents.

[0027] The carbodiimide (NCN) equivalent of the polycarbodiimide compound (A) is not particularly limited, but is preferably not more than 640, more preferably not more than 600, and even more preferably not more than 550. In this specification, the term "carbodiimide (NCN) equivalent" means "molecular weight of polycarbodiimide compound (A) / number of "carbodiimide (N=C=N) structures" present in one molecule of polycarbodiimide compound (A)", and from the viewpoint of improving the crosslinking performance of the polycarbodiimide compound, the smaller the equivalent, the more preferable.

[0028] <Method for producing polycarbodiimide compound (A)> The method for producing the polycarbodiimide compound (A) of the present invention is characterized by comprising the following steps (a) and (b): Step (a): A step of subjecting an aliphatic diisocyanate compound to a carbodiimidization reaction in the presence of a catalyst to obtain a polycarbodiimide (Y) having isocyanate groups at both ends. Step (b): reacting a hydrophilic compound having a functional group capable of reacting with an isocyanate in an amount of 0.33 equivalents or less relative to the total amount of isocyanate groups at both ends of the polycarbodiimide (Y), the polycarbodiimide (Y), and a glycol compound having 2 or 3 carbon atoms. In the present invention, the glycol compound functions as a chain extender for the polycarbodiimide (Y).

[0029] <<Process (a)>> In the step (a), an aliphatic diisocyanate compound is subjected to a carbodiimidization reaction in the presence of a catalyst to obtain a polycarbodiimide (Y) having isocyanate groups at both ends. As the aliphatic diisocyanate compound, the compounds listed in the section [Polycarbodiimide compound (A)] can be used. Examples of catalysts used in the carbodiimidization reaction include phospholene oxides such as 1-phenyl-2-phospholene-1-oxide, 3-methyl-1-phenyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, and 3-phospholene isomers thereof. Among these, 3-methyl-1-phenyl-2-phospholene-1-oxide is preferred from the viewpoint of reactivity. The amount of the catalyst used in the production method of the polycarbodiimide compound (A) is usually 0.01 to 2.0 parts by mass based on 100 parts by mass of the diisocyanate compound used for carbodiimidization.

[0030] The carbodiimidization reaction can be carried out without a solvent or in a solvent. Examples of solvents that can be used include alicyclic ethers such as tetrahydroxyfuran, 1,3-dioxane, and dioxolane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; halogenated hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene, percrene, trichloroethane, and dichloroethane; and cyclohexanone. These may be used alone or in combination of two or more. When the reaction is carried out in a solvent, the concentration of the diisocyanate compound is preferably from 5 to 55% by mass, more preferably from 5 to 20% by mass.

[0031] The conditions for the carbodiimidization reaction are not particularly limited, but are preferably 40 to 250° C., more preferably 80 to 195° C., and are preferably 1 to 30 hours, more preferably 5 to 25 hours. When the reaction is carried out in a solvent, the temperature is preferably from 40° C. to the boiling point of the solvent.

[0032] The polymerization degrees n1 and n2 of the polycarbodiimide compound (A) are not particularly limited as long as they are numbers from 1 to 10. From the viewpoint of facilitating dissolution or dispersion of the polycarbodiimide compound (A) in water or a hydrophilic solvent, they are preferably numbers from 1 to 5, more preferably numbers from 1 to 4, and particularly preferably numbers from 1 to 3.

[0033] <<Process (b)>> In the step (b), a hydrophilic compound having a functional group capable of reacting with an isocyanate in an amount of 0.33 equivalents or less relative to the total amount of isocyanate groups at both ends of the polycarbodiimide (Y), the polycarbodiimide (Y), and a glycol compound having 2 or 3 carbon atoms are reacted with each other. The method of reacting the polycarbodiimide (Y) obtained in step (a), the hydrophilic compound, and the glycol compound is not particularly limited, and examples thereof include (i) a method of reacting the polycarbodiimide (Y) with a specific amount of the hydrophilic compound, and reacting the polycarbodiimide (Z) having a hydrophilic group at the end with the glycol compound having 2 or 3 carbon atoms, (ii) a method of reacting the compound obtained by reacting the polycarbodiimide (Y) with the glycol compound having 2 or 3 carbon atoms with the hydrophilic compound, and (iii) a method of simultaneously reacting the polycarbodiimide (Y), the hydrophilic compound, and the glycol compound having 2 or 3 carbon atoms. Among these, the method (i) is preferred from the viewpoint of controlling the reaction from proceeding locally to increase the molecular weight.

[0034] Specifically, the method according to (i) comprises a step (b1) of reacting the polycarbodiimide (Y) obtained in the step (a) with a hydrophilic compound having a functional group capable of reacting with an isocyanate in an amount of 0.33 equivalents or less relative to the total amount of isocyanate groups at both ends of the polycarbodiimide (Y) to obtain a polycarbodiimide (Z) having a hydrophilic group at its end, and a step (b2) of reacting the polycarbodiimide (Z) obtained in the step (b1) with a glycol compound having 2 or 3 carbon atoms to chain-extend the polycarbodiimide (Z) to obtain a polycarbodiimide compound (A).

[0035] In step (b1), the polycarbodiimide (Y) obtained in step (a) is reacted with a hydrophilic compound having a functional group capable of reacting with an isocyanate in an amount of 0.33 equivalents or less relative to the total amount of isocyanate groups present at both ends of the polycarbodiimide (Y) to introduce a hydrophilic group into the end of the polycarbodiimide (Y). As the hydrophilic compound, the hydrophilic compounds listed in the section [Polycarbodiimide compound (A)] can be used. The amount of the hydrophilic compound used is preferably 0.2 to 0.33 equivalents, more preferably 0.25 to 0.33 equivalents, relative to the functional group equivalent of the total amount of isocyanate groups at both ends of the polycarbodiimide (Y). By keeping the amount at 0.33 equivalents or less, it is possible to control side reactions and obtain the desired polycarbodiimide compound (A) in the step (b2) described below.

[0036] The reaction conditions are not particularly limited, but it is preferable to heat and hold the mixture at a temperature of preferably 50 to 200°C, more preferably 100 to 180°C, and then add the hydrophilic compound and further carry out the reaction at about 80 to 200°C for about 0.5 to 5 hours.

[0037] In the step (b2), the polycarbodiimide (Z) obtained in the step (b1) is reacted with a glycol compound having 2 or 3 carbon atoms to chain-extend the polycarbodiimide (Z). As the glycol compound having 2 or 3 carbon atoms, the glycol compounds having 2 or 3 carbon atoms listed in the section [Polycarbodiimide compound (A)] can be used. The amount of the glycol compound having 2 or 3 carbon atoms used is preferably 0.67 to 0.8 equivalents, more preferably 0.67 to 0.75 equivalents, relative to the functional group equivalent of the total amount of isocyanate groups at both ends of the polycarbodiimide (Y) obtained in step (a). By setting the amount within these ranges, it is possible to suppress the unreacted polycarbodiimide (Y) obtained in step (b1) and the unreacted glycol compound having 2 or 3 carbon atoms, and to obtain the desired polycarbodiimide compound (A).

[0038] The reaction conditions are not particularly limited, but the reaction temperature is preferably about 80 to 200° C., and the reaction time is preferably about 0.5 to 5 hours.

[0039] In addition, the chain extension unit p of the polycarbodiimide compound (A) is not particularly limited as long as it is 2 to 4, but from the viewpoint of facilitating dissolution or dispersion of the polycarbodiimide compound (A) in water or a hydrophilic solvent, it is preferably 2 to 3, more preferably 2.

[0040] By containing the polycarbodiimide compound (A) obtained in this manner, the aqueous resin composition described later can be formed into a coating film (layer) having water resistance and adhesion sufficient for use in food packaging.

[0041] [Aqueous resin composition] The aqueous resin composition of the present invention is characterized by containing the polycarbodiimide compound (A) represented by general formula (1) of the present invention and an aqueous resin.

[0042] <Water-based resin> The aqueous resin used in the present invention is not particularly limited, but preferably has a carboxyl group. Examples of the aqueous resin include aqueous polyurethane resin, acrylic resin, polyester resin, rubber-based latex resin, etc., and these resins can be preferably used. Among them, from the viewpoint of exerting the effects of the present invention, aqueous polyurethane resin, acrylic resin, and polyester resin are preferred. These resins may be used alone or in combination of two or more kinds.

[0043] <<Water-based polyurethane resin>> Examples of the aqueous polyurethane resin include a resin obtained by reacting a carboxyl group-containing urethane prepolymer obtained from polyols, carboxyl group-containing polyols, and a polyisocyanate compound with a neutralizing agent and a chain extender in the presence of an organic solvent or water, and then removing the solvent under reduced pressure.

[0044] -Polyols- The polyols that are raw materials for the aqueous polyurethane resin include polymers or copolymers of low molecular weight polyols, specifically, polyether polyols, polyester polyols, polycarbonate polyols, polyether ester polyols, polycarbonate ester polyols, polycarbonate ether polyols, etc. These may be used alone or in combination of two or more.

[0045] -Carboxyl group-containing polyols- The carboxyl group-containing polyols, which are raw materials for the above-mentioned aqueous polyurethane resin, are compounds that contain two or more hydroxyl groups and one or more carboxyl groups in one molecule, and preferably contain a compound having two hydroxyl groups and one carboxyl group in one molecule. Examples of the carboxyl group-containing polyols include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid, N,N-bishydroxyethylglycine, N,N-bishydroxyethylalanine, 3,4-dihydroxybutanesulfonic acid, and 3,6-dihydroxy-2-toluenesulfonic acid. Among them, from the viewpoint of availability, dimethylolalkanoic acid is preferred, and 2,2-dimethylolpropionic acid is more preferred. These may be used alone or in combination of two or more.

[0046] In addition to the polyols and the carboxyl group-containing polyols, other polyols can be used as raw materials for the aqueous polyurethane resin, if necessary. The other polyols can be used without any particular limitation as long as they are other than the polyols exemplified as the polyols and the carboxyl group-containing polyols.

[0047] -Polyisocyanate compounds- The polyisocyanate compound that is the raw material of the aqueous polyurethane resin is not particularly limited, and specific examples thereof include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate, 4,4'-diphenylenemethane diisocyanate (MDI), 2,4-diphenylmethane diisocyanate, 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl- Aromatic polyisocyanate compounds such as 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 1,5-naphthylene diisocyanate, 4,4',4''-triphenylmethane triisocyanate, m-isocyanatophenylsulfonyl isocyanate, p-isocyanatophenylsulfonyl isocyanate; ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, etc. Aliphatic polyisocyanate compounds such as 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate; Examples of the polyisocyanate include alicyclic polyisocyanate compounds such as sophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanatoethyl)-4-dicyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate. These polyisocyanate compounds may be used alone or in combination of two or more.

[0048] The polyisocyanate compound generally has two isocyanate groups per molecule, but polyisocyanates having three or more isocyanate groups, such as triphenylmethane triisocyanate, can also be used as long as the aqueous polyurethane resin does not gel. Among the above polyisocyanate compounds, from the viewpoints of controlling reactivity and imparting strength, 4,4'-diphenylenemethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI) are preferred.

[0049] -Neutralizer- Examples of the neutralizing agent include organic amines such as trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, N-methyldiethanolamine, N-phenyldiethanolamine, dimethylethanolamine, diethylethanolamine, N-methylmorpholine, pyridine, and 2-(dimethylamino)-2-methyl-1-propanol; ammonia; etc. Among the above, organic amines are preferred, tertiary amines are more preferred, and triethylamine and 2-(dimethylamino)-2-methyl-1-propanol are particularly preferred.

[0050] - Chain extender - Examples of the chain extender include compounds reactive with isocyanate groups, specifically amine compounds such as ethylenediamine, 1,4-tetramethylenediamine, 2-methyl-1,5-pentanediamine, 1,4-butanediamine, 1,6-hexamethylenediamine, 1,4-hexamethylenediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 1,3-bis(aminomethyl)cyclohexane, xylylenediamine, piperazine, adipoylhydrazide, hydrazine, 2,5-dimethylpiperazine, diethylenetriamine, and triethylenetetramine; diol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol; polyalkylene glycols such as polyethylene glycol; water; and the like. Among these, amine compounds are preferred, and ethylenediamine is more preferred. These may be used alone or in combination of two or more.

[0051] <<Acrylic resin>> Examples of the acrylic resin include acrylic resins obtained by copolymerizing a polymerizable unsaturated carboxylic acid or anhydride thereof, an acrylic monomer other than a (meth)acrylic acid ester or (meth)acrylic acid, and, if necessary, α-methylstyrene, vinyl acetate, or the like, by a polymerization method such as emulsion polymerization, solution polymerization, or bulk polymerization. Specific examples of the polymerizable unsaturated carboxylic acid and its anhydride include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and its anhydride. Examples of the (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. Examples of acrylic monomers other than (meth)acrylic acid include (meth)acrylamide and (meth)acrylonitrile.

[0052] <<Polyester resin>> Examples of the polyester resin include polyester resins obtained by chain extension of a polyester glycol having a hydroxyl group at its terminal and a tetracarboxylic dianhydride through an esterification reaction.

[0053] <<Rubber-based latex resin>> Examples of the rubber-based latex resin include natural rubber-based latex resins having a carboxyl group and synthetic rubber-based latex resins having a carboxyl group.

[0054] When the aqueous resin contains a carboxyl group, the equivalent ratio of the carbodiimide group of the polycarbodiimide compound (A) to the carboxyl group of the aqueous resin is not particularly limited, and is preferably 0.1 to 2.0. By making it 0.1 or more, the effect of adding the carbodiimide compound (A) can be obtained, and by making it 2.0 or less, the carbodiimide compound (A) does not remain in excess, and deterioration of performance due to the excess carbodiimide compound (A) can be suppressed.

[0055] The acid value of the aqueous resin varies depending on the type and molecular weight of the resin, but is usually 1 to 100 mgKOH / g, and preferably 5 to 70 mgKOH / g. The acid value is measured according to JIS K 0070:1992. In addition, when the aqueous resin contains a carboxyl group, the "acid value" means the acid value of the resin solid content based on the carboxyl group.

[0056] When 1 mol of carbodiimide groups in the polycarbodiimide compound (A) is reacted with 1 mol of carboxyl groups in the aqueous resin, it is preferable to contain the polycarbodiimide compound (A) and the aqueous resin in an amount that satisfies the following formula (2). Solid content (g) of polycarbodiimide compound (A) = (acid value of water-based resin (mgKOH / g) / (56.11 × 1000)) × carbodiimide equivalent × solid content of water-based resin (g) (2)

[0057] The aqueous resin composition of the present invention preferably further contains at least one selected from water and a hydrophilic solvent.

[0058] <Hydrophilic Solvent> Examples of hydrophilic solvents include polyalkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; polyalkylene glycol dialkyl ethers such as diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol Examples of the polyalkylene glycol monoalkyl ether acetates include diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; polyalkylene glycol diacetates such as ethylene glycol diacetate and propylene glycol diacetate; polyalkylene glycol monophenyl ethers such as ethylene glycol monophenyl ether and propylene glycol monophenyl ether; and monoalcohols such as propanol, butanol, hexanol, and octanol.

[0059] <Additives> In addition, the aqueous resin composition of the present invention may contain additives such as pigments, fillers, leveling agents, surfactants, dispersants, UV absorbers, antioxidants, flame retardants, and colorants, as required.

[0060] The total content of the aqueous resin and the polycarbodiimide compound (A) contained in the solid content of the aqueous resin composition is preferably 80 to 100 mass %, more preferably 85 to 100 mass %, and further preferably 95 to 100 mass %.

[0061] The viscosity of the aqueous resin composition of the present invention varies depending on the type and molecular weight, but is generally preferably 20 to 500 mPa s, and more preferably 30 to 300 mPa s. The viscosity can be determined by measurement using a B-type viscometer.

[0062] [Food packaging containers] The food packaging container of the present invention includes a layer made of the above-mentioned aqueous resin composition. Here, the food packaging container may include a layer made of the aqueous resin composition as an outermost layer, or may include a layer made of the aqueous resin composition as an adhesive layer. Food packaging containers may contain additives as necessary, as long as the effects of water resistance and adhesion are not impaired and the safety standards applicable to food packaging containers are met, from the standpoint of the performance required for the application.

[0063] In this specification, the food packaging container includes food utensils and food container packaging. Examples of food utensils include bowls, plates, lunch boxes, cups, chopsticks, spoons, knives, forks, kitchen knives, cutting boards, bowls, etc. Examples of food container packaging include laminated films (laminates), cups, bottles, bags, trays, capsules, retort pouches, wrapping films, etc. Food packaging containers may be disposable or may be reused. Here, when the food packaging container is disposable, it is preferable that the food packaging container contains biodegradable plastic from the viewpoint of reducing the burden on the environment due to disposal. In addition, it does not matter whether the food in the food packaging container is solid or liquid.

[0064] <Laminate film (laminate)> When a laminate film (laminate) is used for food (especially for retort), it is required to have water resistance and adhesion, and it is preferable that the laminate film further satisfy the following requirements: (i) it is safe (Food Sanitation Act, FDA, etc.), (ii) it is tasteless and odorless, (iii) it has sufficient heat resistance, (iv) it has excellent moisture resistance and oxygen barrier properties, (v) it can be completely sealed by heat sealing, and (vi) it has suitable strength (sealing strength, puncture resistance, pressure resistance, etc.). The basic structure of a laminate film (laminate) is, for example, a base substrate / adhesive layer / barrier layer / adhesive layer / sealant structure. Examples of the base material include a stretched polyethylene terephthalate film (hereinafter sometimes referred to as PET), a stretched nylon film (hereinafter sometimes referred to as ON), and the like. Examples of the adhesive layer include an adhesive layer made of the aqueous resin composition of the present invention and an adhesive layer made of a heat seal material. Examples of the barrier material include aluminum foil (hereinafter sometimes referred to as AL foil), modified EVOH resin, polyvinylidene chloride (PVDC), and the like. Examples of sealants include an outermost layer made of the aqueous resin composition of the present invention, a non-oriented film mainly composed of a propylene-ethylene block copolymer (CPP), and a linear low-density polyethylene (LLDPE). Specific examples of the laminate film (laminate) configuration include (i) PET / AL foil / CPP, (ii) PET / ON / AL foil / CPP, (iii) PET / AL foil / ON / CPP, (iv) ON / CPP, (v) PET / AL foil / outermost layer made of the aqueous resin composition of the present invention, (vi) PET / ON / AL foil / outermost layer made of the aqueous resin composition of the present invention, (vii) PET / AL foil / ON / outermost layer made of the aqueous resin composition of the present invention, (viii) ON / outermost layer made of the aqueous resin composition of the present invention, etc. Here, an adhesive layer made of the aqueous resin composition of the present invention may be used as the adhesive layer between the respective components. Examples of methods for producing a laminate film (laminate) include the usual dry lamination method in which the constituent films of the laminate film (laminate) are bonded together using an adhesive, but a method in which a resin is extruded and directly laminated may also be used. The laminate film (laminate) is used after being processed into bags such as flat bags and standing pouches, with the sealant applied as a sealing layer on the inner surface of the bag. In addition, the layer structure of these laminate films (laminates) is appropriately selected according to the required characteristics of the packaging bag, such as barrier performance to ensure the shelf life of the packaged food, size to accommodate the weight of the contents, low-temperature impact resistance, visibility of the contents, etc.

[0065] <Top surface layer> The outermost layer of the food packaging container of the present invention is not particularly limited as long as it is a layer made of the aqueous resin composition of the present invention, and is preferably used, for example, as a sealant present on the outermost surface of the above-mentioned laminate film (laminate).

[0066] <Adhesive layer> The adhesive layer provided in the food packaging container of the present invention is not particularly limited as long as it is a layer made of the aqueous resin composition of the present invention, and is suitably used, for example, as an adhesive layer (crosslinking agent) for interlayer bonding between a polyethylene terephthalate film (PET) and a nylon stretched film (ON), or an adhesive layer (crosslinking agent) for interlayer bonding between a polyethylene terephthalate film (PET) and an aluminum foil (AL foil). EXAMPLES

[0067] EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the embodiments described in the examples.

[0068] (Production Example 1) Production of polycarbodiimide-containing liquid (crosslinking agent 1) 100 parts by mass of dicyclohexylmethane-4,4'-diisocyanate (HMDI) and 0.5 parts by mass of a carbodiimidization catalyst (3-methyl-1-phenyl-2-phospholene-1-oxide) were placed in a reaction vessel equipped with a reflux condenser and a stirrer, and stirred at 190°C for 6 hours under a nitrogen stream to obtain isocyanate-terminated poly(4,4'-dicyclohexylmethanecarbodiimide) (degree of polymerization = 3). The obtained isocyanate-terminated poly(4,4'-dicyclohexylmethanecarbodiimide) was subjected to infrared absorption (IR) spectrum measurement using an infrared spectrophotometer (FT / IR-6100 manufactured by JASCO Corporation) at a wavelength of 2150 cm -1 Absorption peaks due to carbodiimide groups before and after were confirmed. Next, the isocyanate-terminated poly4,4'-dicyclohexylmethanecarbodiimide obtained above was allowed to cool to 120°C, and 63.5 parts by mass of polyethylene glycol monomethyl ether (PEGME) (average molecular weight 1000) (0.33 equivalents relative to the functional group equivalent of the total amount of isocyanate groups at both ends of the isocyanate-terminated poly4,4'-dicyclohexylmethanecarbodiimide) was added as an end-capping agent, and the mixture was heated to 150°C and reacted for about 1 hour with stirring. After that, 3.9 parts by mass of ethylene glycol (0.67 equivalents relative to the functional group equivalent of the total amount of isocyanate groups at both ends of the isocyanate-terminated poly4,4'-dicyclohexylmethanecarbodiimide) was added as a chain extender, and the mixture was reacted for about 1 hour with stirring. Infrared absorption (IR) spectrum measurement: wavelength 2200-2300 cm -1 After confirming that the absorption of the isocyanate group had disappeared, a polycarbodiimide compound was obtained. This was cooled to about 80° C., and water was added to obtain a pale yellow, transparent polycarbodiimide-containing liquid (crosslinking agent 1) with a solid content of 40% by mass.

[0069] (Production Examples 2, 3, 3-2, 4-7, 9-15) Production of polycarbodiimide-containing liquid (crosslinking agent 2, 3, 3-2, 4-7, 9-15) Polycarbodiimide-containing liquids (crosslinking agents 2, 3, 3-2, 4 to 7, 9, 11 to 15) were obtained in the same manner as in Production Example 1, except that the diisocyanate compound, organic compound (end-capping agent), diol compound (chain extender), and solvent were changed to the types shown in Tables 1A and 1B. In addition, in Production Example 10, since the polycarbodiimide compound was not dispersed in water, a polycarbodiimide-containing liquid could not be obtained (Comparative Example 9).

[0070] (Production Example 8) Production of polycarbodiimide-containing liquid (crosslinking agent 8) 100 parts by mass of dicyclohexylmethane-4,4'-diisocyanate (HMDI) and 0.5 parts by mass of a carbodiimidization catalyst (3-methyl-1-phenyl-2-phospholene-1-oxide) were placed in a reaction vessel equipped with a reflux condenser and a stirrer, and stirred at 190°C for 10 hours under a nitrogen stream to obtain isocyanate-terminated poly4,4'-dicyclohexylmethanecarbodiimide (degree of polymerization = 8). The obtained isocyanate-terminated poly(4,4'-dicyclohexylmethanecarbodiimide) was subjected to infrared absorption (IR) spectrum measurement using an infrared spectrophotometer (FT / IR-6100 manufactured by JASCO Corporation) at a wavelength of 2150 cm -1 Absorption peaks due to carbodiimide groups before and after were confirmed. Next, the isocyanate-terminated poly(4,4'-dicyclohexylmethanecarbodiimide) obtained above was allowed to cool to 120°C, and 84.7 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 1000) was added as a terminal blocking agent to this, and the reaction was allowed to proceed for another hour while stirring at the same temperature. The reaction was then heated again to 150°C and allowed to proceed for another 5 hours while stirring. After that, infrared absorption (IR) spectroscopy was performed to measure the amount of the isocyanate-terminated poly(4,4'-dicyclohexylmethanecarbodiimide at a wavelength of 2200 to 2300 cm. -1 After confirming that the absorption of the isocyanate group had disappeared, a polycarbodiimide compound was obtained. This was cooled to about 80°C, and water was added to obtain a pale yellow transparent polycarbodiimide-containing liquid (crosslinking agent 8) with a solid content of 40%.

[0071] (Examples 1 to 3, 3-2, 4 to 8, and Comparative Examples 1 to 8) The polycarbodiimide-containing liquid (crosslinking agent) produced in Production Examples 1 to 3, 3-2, and 4 to 15 was mixed and stirred with the aqueous resin-containing liquid shown in Tables 1A and 1B in the amounts shown in Tables 1A and 1B to prepare aqueous resin compositions.

[0072] Details of each component used in the preparation of the aqueous resin composition and shown in Tables 1A and 1B are as follows. [Diisocyanate Compound] ·HMDI: Dicyclohexylmethane-4,4'-diisocyanate IPDI: Isophorone diisocyanate TDI: Toluene diisocyanate (mixture of 2,4-TDI (80% by mass) and 2,6-TDI (20% by mass)) HMDI+IPDI: A mixture of dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate (molar ratio 1:1) [Diol compound (chain extender)] EG: Ethylene glycol (molecular weight: 62.07) PG: Propylene glycol (molecular weight: 76.09) BD: 1,4-butanediol (molecular weight: 90.12) PPG(2000): Polypropylene glycol (molecular weight: 2000) ·PCD(2000): Polycarbonate diol (molecular weight: 2000) ·PCLD(2000): Polycaprolactone diol (molecular weight: 2000) [Organic compounds (end-capping agents)] PEGME(550): Polyethylene glycol monomethyl ether (weight average molecular weight: 550) PEGME(1000): Polyethylene glycol monomethyl ether (weight average molecular weight: 1000) PEGMEHE: Polyethylene glycol mono-2-ethylhexyl ether (molecular weight: approx. 482) PEGMLE: Polyethylene glycol monolauryl ether (molecular weight: approx. 1066) HPSS: Sodium hydroxypropanesulfonate (molecular weight: 162.14) 〔solvent〕 NMP + water: A mixture of 1-methyl-2-pyrrolidone (NMP) and water (mass ratio 1:1) [Water-based resin] MD-1480: Toyobo Co., Ltd., water-based polyester resin, acid value 3mg / KOHmg, solid content 25% by mass AC-261P: The Dow Chemical Company, water-based acrylic resin, acid value 15mg / KOHmg, solid content 50% by mass

[0073] The aqueous resin compositions prepared in Examples 1 to 3, 3-2, 4 to 8 and Comparative Examples 1 to 8 were evaluated under the measurement conditions shown below. The evaluation results are shown in Tables 1A and 1B.

[0074] <Evaluation items> First, the aqueous resin compositions prepared in Examples 1 to 3, 3-2, 4 to 8 and Comparative Examples 1 to 8 were applied to a PET substrate (thickness: 100 μm) whose surface had been degreased with acetone using a bar coater #4, and dried at 120° C. for 5 minutes to form a 3 μm dried coating (coating). The coating test pieces on which the coating was formed were used as evaluation samples in the following water resistance test and adhesion test. (1) Water resistance test (immediately after removal, after drying for 24 hours) The obtained coating film test piece was placed in a highly accelerated life tester ("EHS-210M", manufactured by Espec Corporation, thermo-hygrostat; temperature 120°C, relative humidity 100%) and subjected to a moist heat treatment for 0.5 hours. The degree of whitening of the coating surface of the coating test piece taken out of the highly accelerated life test apparatus was visually observed immediately after taking out and after drying for 24 hours, and was evaluated according to the evaluation criteria shown in Figure 1 (left: good (whitening rate: 10% or less), center: acceptable (whitening rate: over 10% and 50% or less), right: poor (whitening rate: over 50% and 100% or less)). The results are shown in Tables 1A and 1B. In Tables 1A and 1B, the results are expressed as good, acceptable, or poor.

[0075] (2) Adhesion test The adhesion test was performed in accordance with JIS5600-5-6:1999 (cross-cut method). Specifically, on the test surface of the coating film test piece (coating film test piece that had been subjected to the water resistance evaluation test (after drying for 24 hours) in (1) above, 11 cuts (1 mm interval between cuts) reaching the base material (PET substrate) were made using a cutter knife, creating 25 grids. Tape "Cellotape (registered trademark)" (manufactured by Nichiban Co., Ltd., adhesive strength 3.9 N / cm) was firmly pressed onto the grids, and the end of the tape was peeled off at an angle of 45° in one go, and the state of the grids was evaluated according to the evaluation criteria shown in FIG. 2 (6-level classification from 0 to 5 in the JIS standard shown below). Tables 1A and 1B show the results of the adhesion evaluation. It can be said that the smaller the classification number, the better the adhesion of the coating film. <Evaluation Classification> 0: The edges of the cut are completely smooth and there is no peeling on any of the grid lines. 1: Small separations of the coating at the intersections of cuts. The cross-cut area affected is not significantly more than 5%. 2: The coating has delaminated along the edges of cuts and / or at intersections. Clearly more than 5% but not more than 15% of the cross-cut area is affected. 3: The coating has partially or completely spalled along the edges of the cuts and / or has partially or completely spalled various areas of the mesh. Cross-cut areas are clearly more than 15% but not more than 35% affected. 4: The coating has partially or completely peeled off significantly along the edges of the cuts and / or partially or completely peeled off in several sections. Cross-cut areas not appreciably more than 65% affected. 5: Any degree of peeling that cannot be classified as category 4.

[0076] [Table 1A]

[0077] [Table 1B]

[0078] As can be seen from the evaluation results shown in Tables 1A and 1B, it was found that by using the polycarbodiimide compound (A) of the present invention (Examples 1 to 3, 3-2, 4 to 8), it is possible to obtain an aqueous resin composition capable of forming a coating film (layer) having water resistance and adhesion sufficient for use in food packaging. Moreover, by comparing Example 1 and Example 4, it is understood that the degree of polymerization (n1 and n2) is preferably 3 or less. Moreover, by comparing Example 1 and Example 5, it is clear that the value of p is preferably 3 or less. Furthermore, by comparing Example 1 with Examples 6 and 7, it is found that dicyclohexylmethane-4,4'-diisocyanate (HMDI) is more preferable as the aliphatic diisocyanate compound than isophorone diisocyanate (IPDI). Furthermore, it is understood from Example 8 that a water-based acrylic resin can be used as the water-based resin.

Claims

1. The composition contains a polycarbodiimide compound (A) represented by the following general formula (1) and an aqueous resin, The aqueous resin contains a carboxyl group, an equivalent ratio of the carbodiimide groups of the polycarbodiimide compound (A) to the carboxyl groups of the aqueous resin is 1.1 to 2.0; The aqueous resin composition has an acid value of 1 to 100 mgKOH / g. [Formula 1] (In the formula, R １ represents a residue obtained by removing a functional group capable of reacting with isocyanate from a hydrophilic compound having a functional group capable of reacting with isocyanate, R ２ represents a divalent residue obtained by removing an isocyanate group from an aliphatic diisocyanate compound, R ３ represents a divalent residue obtained by removing a hydroxyl group from a glycol compound having 2 or 3 carbon atoms. X represents a group formed by the reaction of the hydrophilic compound with the aliphatic diisocyanate compound. n1 represents a number from 1 to 10, n2 represents a number from 1 to 10, and p represents a number from 2 to 4. １ and R ２ may be the same or different.)

2. The aqueous resin composition according to claim 1 , wherein the glycol compound is at least one of ethylene glycol and propylene glycol.

3. 3. The aqueous resin composition according to claim 1, wherein the aliphatic diisocyanate compound is at least one of dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate.

4. An aqueous resin composition described in any one of claims 1 to 3, wherein the carbodiimide equivalent of the polycarbodiimide compound (A) is 640 or less.

5. The aqueous resin composition according to any one of claims 1 to 4, wherein the aqueous resin is at least one selected from the group consisting of an aqueous polyurethane resin, an acrylic resin, a polyester resin, and a rubber-based latex resin.

6. The aqueous resin composition according to claim 5 , wherein the aqueous resin is at least one selected from the group consisting of an aqueous polyurethane resin, an acrylic resin, and a polyester resin.

7. The aqueous resin composition according to any one of claims 1 to 6, further comprising at least one selected from water and a hydrophilic solvent.

8. A food packaging container comprising a layer made of the aqueous resin composition according to any one of claims 1 to 7.

9. The food packaging container according to claim 8 , comprising the layer as an outermost surface layer.

10. The food packaging container according to claim 8 , wherein the layer is provided as an adhesive layer.

Images