JP7420706B2 - resin composition - Google Patents

Description

The present invention relates to a resin composition used for food packaging containers, etc., a coating made by coating paper or film with the resin composition, a method for producing the same, a multilayer structure including the coating, and the coating. Alternatively, a packaging material made of the multilayer structure is provided.

Conventionally, resin compositions containing modified starch and polyvinyl alcohol have been widely used in containers for packaging foods because of their excellent biodegradability (for example, Japanese Patent No. 4782284).

Patent No. 4782284

Among the containers for packaging these foods, there are many containers that use a coating made by coating paper or film with the resin composition, and the coating is required to have high oxygen barrier properties. Ru. On the other hand, the coated article is manufactured by coating a resin composition discharged from a die outlet of an extruder onto a paper or film conveyed by a take-up machine, for example. However, according to the inventor's study, the resin composition that can ensure high oxygen barrier properties has low fluidity and has a low draw ratio expressed as the maximum take-up speed with respect to the flow rate at the die exit, so it is difficult to improve productivity. I found out that I can't do it.

Therefore, the objects of the present invention are a resin composition capable of forming a coating having a high maximum draw ratio during production and excellent oxygen barrier properties, a coating and a method for producing the same, and a multilayer structure including the coating. , and to provide a packaging material comprising the coating or the multilayer structure.

As a result of intensive studies to solve the above problems, the present inventors discovered a resin containing a modified starch (A) containing a hydrophobic group and having an amylose content of 45% by mass or more, and polyvinyl alcohol (B). It was discovered that the above problems could be solved by adjusting the content of modified starch (A) to 40 to 98 parts by mass and the content of polyvinyl alcohol (B) to 2 to 60 parts by mass in the composition, and completed the present invention. I let it happen.

[1] A resin composition containing a modified starch (A) containing a hydrophobic group and having an amylose content of 45% by mass or more, and polyvinyl alcohol (B),
Based on a total of 100 parts by mass of modified starch (A) and polyvinyl alcohol (B), the content of modified starch (A) is 40 to 98 parts by mass, and the content of polyvinyl alcohol (B) is 2 to 60 parts by mass. Parts by mass of the resin composition.
[2] The modified starch (A) is different from the high amylose modified starch (A-1) having an amylose content of 50% by mass or more and the high amylose modified starch (A-1), and has a hydrophobic group. The resin composition according to [1], comprising a hydrophobically modified starch (A-2) having the following.
[3] The resin composition according to [2], wherein the hydrophobically modified starch (A-2) has an amylose content of less than 50% by mass.
[4] The resin composition according to any one of [1] to [3], wherein the hydrophobic group is a modified group with a hydrophobic compound having 6 to 24 carbon atoms.
[5] The high amylose modified starch (A-1) is at least one selected from etherified starch having a hydroxyalkyl group and esterified starch having a carboxylic anhydride modified group, [2] to [ 4]. The resin composition according to any one of [4].
[6] The hydrophobically modified starch (A-2) is selected from etherified starch having a glycidyl ether modifying group having 6 to 24 carbon atoms and esterified starch having a carboxylic acid anhydride modifying group having 6 to 24 carbon atoms. The resin composition according to any one of [2] to [5], which is at least one selected resin composition.
[7] The hydrophobically modified starch (A-2) has a viscosity of 1000 cP or less when a 15% by mass aqueous solution is gelatinized by stirring at 95°C for 5 minutes and then cooled to 30°C, [2] The resin composition according to any one of ~[6].
[8] The polyvinyl alcohol (B) according to any one of [1] to [7], has a viscosity of 1 to 50 mPa·s at 20°C as a 4% aqueous solution measured in accordance with JIS Z 8803. Resin composition.
[9] A coated article obtained by coating paper or a film with the resin composition according to any one of [1] to [8].
[10] A multilayer structure comprising the coating according to [9].
[11] A packaging material comprising the coating according to [9] or the multilayer structure according to [10].
[12] Using an extruder, the resin composition according to any one of [1] to [8] is coated onto a film or paper conveyed by a take-up machine, and in this step, the resin composition according to the formula (1 )
Draw ratio = (take-up speed of take-off machine) / (flow rate at die exit of extruder) (1)
The method for producing a coating according to [9], wherein the draw ratio represented by is 5 to 20.

The resin composition of the present invention has a high maximum draw ratio during production and can form a coating with excellent oxygen barrier properties, so it can be suitably used as a material for food packaging, containers, etc.

A schematic diagram of a twin-screw extruder used in Examples is shown.

[Resin composition]
The resin composition of the present invention contains modified starch (A) and polyvinyl alcohol (B).
<Modified starch (A)>
The modified starch (A) contains a hydrophobic group and has an amylose content of 45% by mass or more. The resin composition of the present invention has good drawability and can improve maximum draw ratio and adhesion, especially by containing modified starch (A). In this specification, take-up property refers to the property that the resin composition can be coated without tearing when the resin composition discharged from the die outlet of the extruder is coated onto the transported paper or film. "Improved take-up properties" means that the resin composition can be coated easily without tearing even when paper or film is conveyed at high speed. Furthermore, in this specification, adhesion refers to the adhesion between the paper or film in the coating and the resin composition.

Starch that is a raw material for modified starch (A) includes, for example, starch derived from cassava, corn, potato, sweet potato, sago, tapioca, sorghum, bean, bracken, lotus, water chestnut, wheat, rice, oat, arrowroot, pea, etc. It may be. Among these, from the viewpoint of amylose content, the starch used as a raw material for the modified starch (A) is preferably a starch derived from corn or cassava, and more preferably a starch derived from corn. The modified starch (A) may be composed of one or more types of starch.

Modified starch (A) contains hydrophobic groups. A hydrophobic group refers to an atomic group that has a low affinity for water. The hydrophobic group contained in the modified starch is not particularly limited, but is preferably a modified group by a hydrophobic compound (sometimes referred to as a hydrophobic compound modified group). When the modified starch (A) contains a hydrophobic compound-modified group, the resin composition has good drawability, and the maximum draw ratio and adhesion are likely to be improved. The hydrophobic group is preferably introduced into the starch through a reaction between the hydroxyl group contained in the starch and the reactive group of the hydrophobic compound, and more preferably, the hydrophobic group is bonded to the starch through etherification, esterification, or amidation. preferable. Furthermore, before or simultaneously with the modification, the starch may be treated to reduce or increase its molecular weight by a known method such as decomposition with an acid or oxidation.

The hydrophobic compound is preferably a hydrophobic compound having 6 to 24 carbon atoms from the viewpoint of reducing pseudo-crosslinking due to hydrogen bonding between starches and easily improving drawability, maximum draw ratio, and adhesion. The number of carbon atoms is more preferably 7 to 24, and even more preferably 8 to 18.
In a preferred embodiment of the invention, the hydrophobic compound is a hydrophobic compound containing aliphatic and/or aromatic groups having 6 to 24, preferably 7 to 20, more preferably 8 to 18 carbon atoms. This aspect is advantageous from the viewpoint of maximum draw ratio and adhesion.

The hydrophobic compound preferably contains at least one reactive group selected from the group consisting of, for example, a halogen group, a halohydrin group, an epoxy group, a glycidyl group, an acid anhydride group, and an amino group.

When a hydrophobic group is etherified, that is, bonded to starch by an ether bond, the reactive group contained in the hydrophobic compound may be, for example, a halogen group, a halohydrin group, an epoxy group, a glycidyl group, and the hydrophobic compound is Preferably, it is a hydrophobic compound having 6 to 24 carbon atoms. Specifically, hydrophobic compounds include cetyl bromide, lauryl bromide; epoxidized soybean fatty alcohol, epoxidized flaxseed fatty alcohol; allyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, decane glycidyl ether, lauryl phenyl glycidyl ether, Examples include glycidyl ethers having 2 to 24 carbon atoms, preferably glycidyl ethers having 6 to 24 carbon atoms, such as myristoyl glycidyl ether, cetyl glycidyl ether, palmityl glycidyl ether, stearyl glycidyl ether, and linolyl glycidyl ether.

When a hydrophobic compound is esterified, that is, bonded to starch by an ester bond, the reactive group contained in the hydrophobic compound may be, for example, an acid anhydride group, and the hydrophobic compound has 6 to 6 carbon atoms. 24, preferably a carboxylic acid anhydride having 7 to 20 carbon atoms. Specifically, examples of carboxylic anhydrides include alkanoic acid carboxylic anhydrides such as octanoic acid anhydride, decanoic acid anhydride, lauric acid acetic anhydride, and myristic acid acetic anhydride; alkyl or alkenyl succinic anhydrides; , alkyl or alkenyl dicarboxylic acid anhydrides such as alkyl or alkenyl maleic anhydride. Among these, alkyl or alkenyl dicarboxylic acid anhydrides are preferred from the viewpoint of easily improving drawability, maximum draw ratio, and adhesion, such as octenylsuccinic anhydride, nonylsuccinic anhydride, decylsuccinic anhydride, dodecenylsuccinic anhydride, Octenyl maleic anhydride, nonyl maleic anhydride, decyl maleic anhydride, and dodecenyl maleic anhydride are more preferred, and octenyl succinic anhydride or octenyl maleic anhydride is even more preferred.

When a hydrophobic compound is amidated, that is, bonded to starch by an amide bond, the reactive group contained in the hydrophobic compound may be, for example, an amino group, and the hydrophobic compound has 6 to 24 carbon atoms. Aliphatic amines containing saturated or unsaturated hydrocarbon groups can be suitably used, which may contain branched chains, but are preferably linear. Specifically, aliphatic amines include n-dodecylamine, n-hexadecylamine, n-octadecylamine, cocoa amine, tallow amine, hydrogenated N-tallow-1,3-diaminopropane, N-hydrogenated tallow-1, Examples include 3-diaminopropane and N-oleyl-1,3-diaminopropane. The modified starch (A) may be composed of one or more hydrophobic groups, preferably hydrophobic compound-modified groups.

Among these hydrophobic compounds, glycidyl ethers having 6 to 24 carbon atoms and glycidyl ethers having 6 to 24 carbon atoms are preferred from the viewpoint of reducing pseudo-crosslinking caused by starch hydrogen bonds and easily improving drawability, maximum draw ratio, and adhesion. At least one selected from 24 carboxylic acid anhydrides is preferred, carboxylic acid anhydrides having 6 to 24 carbon atoms are more preferred, and alkyl or alkenyldicarboxylic acid anhydrides having 6 to 24 carbon atoms are even more preferred.

In the modified starch (A), the average number of modified hydroxyl groups per glucose unit [referred to as degree of substitution (DS)] is preferably 1.0×10 ⁻⁴ or more, more preferably 5.0×10 ⁻⁴ Above, more preferably 1.0×10 ⁻³ or more, preferably 1.0×10 ⁻¹ or less, more preferably 2.0×10 ⁻² or less, even more preferably 1.5×10 ⁻² or less , particularly preferably 1.0×10 ⁻² or less. When the degree of substitution (DS) is within the above range, it is advantageous in terms of drawability, maximum draw ratio, and adhesion.

The modified starch (A) may contain a hydrophilic group in addition to the hydrophobic group. A hydrophilic group refers to an atomic group that has a high affinity for water. The hydrophilic group contained in the modified starch (A) is not particularly limited, but it is a modified group by a hydrophilic compound (sometimes referred to as a hydrophilic compound modified group) from the viewpoint of easily inhibiting the aging of the starch after molding. It is preferable. The hydrophilic group is preferably introduced into the starch through a reaction between the hydroxyl group contained in the starch and the reactive group of the hydrophilic compound, and is more preferably bonded to the starch through etherification, esterification, or amidation. preferable. Furthermore, before or simultaneously with the chemical modification, the starch may be treated to reduce or increase its molecular weight by a known method such as decomposition with an acid or oxidation.

Examples of hydrophilic compounds include alkylene oxides having 2 to 5 carbon atoms such as ethylene oxide, propylene oxide, and butylene oxide; halogenated carboxylic acids having 2 to 5 carbon atoms such as chloroacetic acid; Alkyl halides such as methyl chloride; Carboxylic acid anhydrides having 2 to 5 carbon atoms such as maleic anhydride and phthalic anhydride; Oxo acid salts such as sodium nitrate and sodium phosphate; 2-diethylaminoethyl chloride; , 3-epoxypropyltrimethylammonium chloride and the like. Hydrophilic compounds may be used alone or in combination of two or more. Among these, from the viewpoint of reactivity with starch, hydrophilic compounds having 2 to 5 carbon atoms are preferred, and hydrophilic compounds containing an aliphatic group and/or aromatic group having 2 to 5 carbon atoms are more preferred. More preferably, it is at least one selected from alkylene oxides having 2 to 5 carbon atoms and carboxylic acid anhydrides having 2 to 5 carbon atoms.

The modified starch (A) has an amylose content of 45% by mass or more, preferably 50% by mass or more, more preferably 55% by mass or more, and preferably 80% by mass or less. When the amylose content of the modified starch (A) is at least the above-mentioned lower limit, it is easy to improve film-forming properties, take-up properties, maximum draw ratio, and adhesion, and it is also easy to improve moldability of the resin composition. In this specification, the amylose content can be measured, for example, by the iodine coloring method described in "Starch 50 No. 4 158-163 (1998)". Here, when the modified starch (A) is composed of two or more types of modified starches, the amylose content of the modified starch (A) is the average amylose content obtained by weighting the amylose content of the two or more types of modified starches. means quantity.

In a preferred embodiment of the present invention, the modified starch (A) is different from the high amylose modified starch (A-1) having an amylose content of 50% by mass or more, and the high amylose modified starch (A-1), It also consists of a hydrophobically modified starch (A-2) having a hydrophobic group. This embodiment is advantageous from the viewpoint of easily increasing the drawability of the resin composition, and easily improving the maximum draw ratio and adhesion.

<High amylose modified starch (A-1)>
High amylose modified starch (A-1) is a modified starch having an amylose content of 50% by mass or more. The amylose content of the high amylose modified starch (A-1) is preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 65% by mass or more, particularly preferably 70% by mass or more, and preferably It is 90% by mass or less. When the amylose content of the high amylose modified starch (A-1) is equal to or higher than the above lower limit, it is easy to improve film-forming properties, take-off properties, maximum draw ratio, and adhesion, and the molding processability of the resin composition is also improved. Cheap.

Examples of the starch that can be used as a raw material for the high amylose modified starch (A-1) include those exemplified above as the starch that can be used as a raw material for the modified starch (A). The high amylose modified starch (A-1) may be composed of one or more types of starch.

The high amylose modified starch (A-1) may be, for example, a modified starch containing a hydrophobic group and/or a hydrophilic group as described in the section <Modified starch (A)>, and the modified starch containing the hydrophilic group It is preferable that Specifically, the high amylose modified starch (A-1) is preferably at least one selected from the group consisting of, for example, etherified starch, esterified starch, cationized starch, and crosslinked starch.

Etherified starches include, for example, alkyl etherified starches such as methyl etherified starches, preferably alkyl etherified starches having 2 to 5 carbon atoms; carboxyalkyl etherified starches such as carboxymethyl etherified starches, preferably carbon atoms. Carboxymethyl etherified starch having a number of 2 to 5; etherified starch having a hydroxyalkyl group such as a hydroxyethylene group, a hydroxypropylene group, or a hydroxybutylene group (hydroxyalkyl etherified starch), preferably a hydroxyl starch having 2 to 5 carbon atoms. Examples include etherified starch having an alkyl group; allyl etherified starch, preferably allyl etherified starch having 2 to 5 carbon atoms. Hydroxyalkyl etherified starch having 2 to 5 carbon atoms can be obtained, for example, by reaction of starch with alkylene oxide having 2 to 5 carbon atoms, such as ethylene oxide, propylene oxide, butylene oxide.

Examples of esterified starch include esterified starch having a carboxylic acid modified group such as esterified starch having a structural unit derived from acetic acid (also referred to as esterified starch having a structural unit derived from carboxylic acid); Esterified starch with a carboxylic anhydride-modified group, such as esterified starch with a structural unit derived from phthalic anhydride, esterified starch with a structural unit derived from octenylsuccinic anhydride, etc. Starch (also referred to as esterified starch having a structural unit derived from a carboxylic acid anhydride); Esterified starch having a structural unit derived from an oxoacid such as nitrate-esterified starch, phosphate-esterified starch, urea-phosphate-esterified starch; Examples include xanthate-esterified starch; acetoacetate-esterified starch.

Examples of the cationized starch include a reaction product of starch and 2-diethylaminoethyl chloride, a reaction product of starch and 2,3-epoxypropyltrimethylammonium chloride, and the like.

Examples of the crosslinked starch include formaldehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphoric acid crosslinked starch, acrolein crosslinked starch, and the like.

Among these, high amylose-modified starch (A-1) is selected from the viewpoint of easily improving film-forming properties, drawability, maximum draw ratio, and adhesion. esterified starch having a hydroxyalkyl group having 2 to 5 carbon atoms and an ester having a carboxylic acid anhydride modified group having 2 to 5 carbon atoms. More preferably, it is at least one selected from modified starches. Note that the resin composition of the present invention may contain one or more types of high amylose modified starch (A-1). Further, in the high amylose modified starch (A-1), the average number of modified hydroxyl groups per glucose unit [referred to as degree of substitution (DS)] is preferably 0.05 to 2. In addition, in this specification, the number of carbon atoms described before "starch" refers to the carbon atoms of a group substituted for one hydroxyl group in starch (a group formed by modifying one hydroxyl group in starch). represents a number. For example, etherified starch having a hydroxyalkyl group having 2 to 5 carbon atoms indicates the number of carbon atoms in the hydroxyalkyl group formed by modifying one hydroxyl group in the starch.

The water content in the high amylose modified starch (A) is preferably 10 to 15% by mass based on the mass of the high amylose modified starch (A).

A commercially available high amylose modified starch (A-1) can be used. Typical commercial products of high amylose modified starch (A-1) include ECOFILM (registered trademark), GELOSE (registered trademark) A939, etc. available from Ingredion and National Starch & Chemical Company.

<Hydrophobically modified starch (A-2)>
The hydrophobically modified starch (A-2) is a modified starch different from the high amylose modified starch (A-1). Examples of the starch that can be used as a raw material for the hydrophobically modified starch (A-2) include those exemplified above as the starch that can be used as a raw material for the modified starch (A). The hydrophobically modified starch (A-2) may be composed of one or more types of starch.

Hydrophobically modified starch (A-2) contains a hydrophobic group. The hydrophobic group is not particularly limited, but is preferably a modified group with a hydrophobic compound. The hydrophobic group and hydrophobic compound are the same as those described in the section <Modified starch (A)>. Specifically, the hydrophobically modified starch (A-2) is preferably at least one selected from the group consisting of, for example, etherified starch, esterified starch, and amidated starch, including etherified starch having 6 to 24 carbon atoms. More preferably, it is at least one selected from the group consisting of starch, esterified starch having 6 to 24 carbon atoms, and amidated starch having 6 to 24 carbon atoms.

The etherified starch is preferably an etherified starch having a modified group with a hydrophobic compound, and as the hydrophobic compound, the hydrophobic group is bonded to the starch by etherification in the section <Modified starch (A)>. Examples of hydrophobic compounds used in this case include those listed below. The esterified starch is preferably an esterified starch having a modified group with a hydrophobic compound, and as the hydrophobic compound, the hydrophobic group is bonded to the starch by esterification in the section <Modified starch (A)>. Examples of hydrophobic compounds used in this case include those listed below. The amidated starch is preferably an amidated starch having a modified group with a hydrophobic compound, and as the hydrophobic compound, a hydrophobic group is bonded to the starch by amidation in the section of <Modified starch (A)>. Examples of hydrophobic compounds used in this case include those listed below.

Among these, hydrophobically modified starch (A-2) is an etherified starch (derived from glycidyl ether) having a glycidyl ether modified group having 6 to 24 carbon atoms, from the viewpoint of easily improving take-up speed, maximum draw ratio, and adhesion. (etherified starch having a structural unit derived from carboxylic anhydride) and esterified starch having a carboxylic anhydride-modified group having 6 to 24 carbon atoms (esterified starch having a structural unit derived from a carboxylic anhydride) It is preferable that

The amylose content of the hydrophobically modified starch (A-2) is particularly limited if the average amylose content of the high amylose modified starch (A-1) and the hydrophobically modified starch (A-2) is 45% by mass or more. However, it is preferably less than 50% by mass, more preferably 40% by mass or less, even more preferably 30% by mass or less, particularly preferably 20% by mass or less, preferably 0.1% by mass or more, more preferably 1% by mass. % or more, more preferably 3% by mass or more. When the amylose content of the hydrophobically modified starch (A-2) is within the above range, it is advantageous in terms of drawability, maximum draw ratio, and adhesion.

The hydrophobically modified starch (A-2) has a viscosity of preferably 1000 cP or less, more preferably 500 cP or less, when a 15% by mass aqueous solution is gelatinized by stirring at 95 °C for 5 minutes and then cooled to 30 °C. It is preferably 300 cP or less, particularly preferably 100 cP or less, most preferably 50 cP or less, and preferably 10 cP or more. When the viscosity is below the above upper limit, the take-up properties, maximum draw ratio and adhesion can be easily improved, and when the viscosity is above the above lower limit, the water solubility of the molded product can be reduced. The viscosity of the hydrophobically modified starch (A-2) can be measured using a viscometer, for example, by the method described in Examples.

The water content in the hydrophobically modified starch (A-2) is preferably 10 to 15% by mass based on the mass of the hydrophobically modified starch (A-2).

As the hydrophobically modified starch (A-2), commercially available starch may be used, or starch having a predetermined amylose content may be produced by modifying it with a hydrophobic compound using a conventional method. Good too.

In the resin composition of the present invention, the ratio of the high amylose modified starch (A-1) and the hydrophobically modified starch (A-2) is as follows: ) may be adjusted as appropriate so that the average amylose content is 45% by mass or more. In a preferred embodiment of the present invention, the content of the high amylose modified starch (A-1) is preferably 0.1 part by mass or more, more preferably 1 part by mass of the hydrophobically modified starch (A-2). 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, particularly preferably 2.0 parts by mass or more, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5.0 parts by mass. Parts by mass or less. When the content of the high amylose modified starch (A-1) relative to the content of the hydrophobically modified starch (A-2) is at least the above lower limit, the oxygen barrier property is easily improved, and when it is at most the above upper limit, Easy to improve pullability, maximum draw ratio, and adhesion.

<Polyvinyl alcohol (B)>
The resin composition of the present invention contains polyvinyl alcohol (B). The degree of saponification of polyvinyl alcohol (B) is preferably 80 to 99.8 mol%. When the degree of saponification of polyvinyl alcohol (B) is within the above range, sufficient strength and oxygen barrier properties are likely to be obtained. The degree of saponification is more preferably 85 mol% or more, still more preferably 88 mol% or more. In this specification, the degree of saponification refers to the molar fraction of hydroxyl groups to the total of hydroxyl groups and ester groups in polyvinyl alcohol (B).

Polyvinyl alcohol (B) can further contain monomer units other than vinyl alcohol units. Examples of other monomer units include monomer units derived from ethylenically unsaturated monomers. Ethylenically unsaturated monomers include α-olefins such as ethylene, propylene, n-butene, isobutylene, and 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylic ester group; methacrylic acid and its salts; unsaturated monomers having a methacrylic acid ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and its salts, acrylamide propyl dimethyl Amines and salts thereof (e.g. quaternary salts); methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propane sulfonic acid and salts thereof, methacrylamide propyldimethylamine and salts thereof (e.g. quaternary salts); Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane, etc. Vinyl ethers; Vinyl cyanides such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride and vinyl fluoride; Vinylidene halides such as vinylidene chloride and vinylidene fluoride; Allyl acetate, 2,3-diacetoxy- Allyl compounds such as 1-allyloxypropane and allyl chloride; Unsaturated dicarboxylic acids and their salts or esters such as maleic acid, itaconic acid, and fumaric acid; Vinylsilyl compounds such as vinyltrimethoxysilane, isopropenyl acetate; Vinyl formate, acetic acid Vinyl, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl carrylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. Vinyl ester monomers are exemplified. Furthermore, monomer units derived from unsaturated monomers that have not been saponified are also included in the other monomer units. The content of other monomer units is preferably 10 mol% or less, more preferably 5 mol% or less.

The method for producing polyvinyl alcohol (B) is not particularly limited. For example, a method can be mentioned in which a vinyl alcohol monomer and another monomer are copolymerized, and the resulting copolymer is saponified to convert it into vinyl alcohol units. Examples of polymerization methods for copolymerization include batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. Examples of the polymerization method include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. A known method can be applied to saponify the copolymer. For example, the copolymer can be dissolved in alcohol or hydrous alcohol. The alcohol that can be used at this time is preferably a lower alcohol such as methanol or ethanol.

The viscosity of polyvinyl alcohol (B) at 20°C of a 4% aqueous solution measured in accordance with JIS Z 8803 is preferably 1 mPa·s or more, more preferably 2 mPa·s or more, still more preferably 3 mPa·s or more, and preferably is 45 mPa·s or less, more preferably 35 mPa·s or less. When the viscosity of polyvinyl alcohol (B) is within the above range, sufficient strength and oxygen barrier properties are likely to be obtained. In addition, the said viscosity of polyvinyl alcohol (B) can be measured using a viscometer, for example, by the method described in an Example.

<Resin composition>
The resin composition of the present invention contains the modified starch (A) and the polyvinyl alcohol (B), and the modified starch (A) is based on a total of 100 parts by mass of the modified starch (A) and the polyvinyl alcohol (B). ) is 40 to 98 parts by mass, and the content of polyvinyl alcohol (B) is 2 to 60 parts by mass, making it possible to form a coating with excellent maximum draw ratio and oxygen barrier properties during production. Furthermore, the coating can also exhibit good biodegradability. Therefore, the resin composition of the present invention can be suitably used as a material for containers for packaging foods.

The content of modified starch (A) is 40 parts by mass or more, preferably 50 parts by mass or more, more preferably 60 parts by mass or more, based on the total of 100 parts by mass of modified starch (A) and polyvinyl alcohol (B). , more preferably 70 parts by mass or more, and 98 parts by mass or less, preferably 95 parts by mass or less, more preferably 90 parts by mass or less, still more preferably 85 parts by mass or less. When the content of modified starch (A) is at least the above-mentioned lower limit, the drawability, maximum draw ratio, and adhesion are easily improved, and when it is at most the above-mentioned upper limit, the oxygen barrier property is easily improved.

The content of polyvinyl alcohol (B) is 2 parts by mass or more, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, based on the total of 100 parts by mass of modified starch (A) and polyvinyl alcohol (B). , more preferably 15 parts by mass or more, and 60 parts by mass or less, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. When the content of polyvinyl alcohol (B) is at least the above-mentioned lower limit, the oxygen barrier property is easily improved, and when it is below the above-mentioned upper limit, the take-up property, maximum draw ratio, and adhesion are easily improved.

In the resin composition of the present invention, the total proportion of modified starch (A) and polyvinyl alcohol (B) is preferably 10% by mass or more, more preferably 40% by mass or more, and more preferably 40% by mass or more, based on the mass of the resin composition. It is preferably 60% by mass or more, particularly preferably 80% by mass or more, and preferably 98% by mass or less. When the total ratio of modified starch (A) and polyvinyl alcohol (B) is within the above range, the maximum draw ratio, adhesion and oxygen barrier properties can be improved.

The resin composition of the present invention may further contain a fatty acid having 12 to 22 carbon atoms and/or a fatty acid salt thereof. Examples of fatty acids having 12 to 22 carbon atoms and their fatty acid salts include stearic acid, calcium stearate, sodium stearate, palmitic acid, lauric acid, myristic acid, linoleic acid, and behenic acid. Among these, stearic acid, calcium stearate, and sodium stearate are preferred from the viewpoint of processability. Fatty acids having 12 to 22 carbon atoms and fatty acid salts thereof can be used alone or in combination.

When the resin composition of the present invention contains a fatty acid having 12 to 22 carbon atoms and/or a fatty acid salt thereof, the content in the resin composition is preferably 0.00% based on the mass of the resin composition. The amount is preferably 0.01 to 3% by weight, more preferably 0.03 to 2% by weight, and even more preferably 0.1 to 1% by weight. When the content of the fatty acid having 12 to 22 carbon atoms and/or its fatty acid salt is within the above range, it tends to be advantageous in terms of processability.

The resin composition of the present invention may further contain clay. Clays include synthetic or natural layered silicate clays such as montmorillonite, bentonite, beidellite, mica, hectorite, saponite, nontronite, sauconite, vermiculite, ladykite, magadite, kenyaite, stevensite, volkons. Examples include Koito. Clays can be used alone or in combination.

When the resin composition of the present invention contains clay, the content in the resin composition is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass based on the mass of the resin composition. %, more preferably 0.5 to 2% by mass. When the clay content is within the above range, it tends to be advantageous in terms of transparency and strength.

The resin composition of the present invention can further contain a plasticizer from the viewpoint of film-forming properties. Examples of plasticizers include water, sorbitol, glycerol, maltitol, xylitol, mannitol, glycerol trioleate, epoxidized linseed oil, epoxidized soybean oil, tributyl citrate, acetyltriethyl citrate, glyceryl triacetate, 2,2 , 4-trimethyl-1,3-pentanediol diisobutyrate, polyethylene oxide, and polyethylene glycol. Plasticizers can be used alone or in combination. Among these plasticizers, water is preferred from the viewpoint of obtaining good film-forming properties and coating properties.

The water content (water content) in the resin composition is preferably 3 to 20% by mass, more preferably 4 to 20% by mass, based on the mass of the resin composition, from the viewpoint of film-forming properties and oxygen barrier properties of the resin composition. It is 18% by weight, more preferably 7 to 15% by weight. When the water content is within the above range, the resin composition can exhibit excellent film-forming properties, and the adhesion and oxygen barrier properties of the coating will be good. The water content is the water content measured for 30 minutes at a temperature of 130° C. using a heat-drying moisture meter after conditioning the humidity at a temperature of 23° C. and a relative humidity of 50% for two weeks.

The resin composition of the present invention may optionally contain fillers, processing stabilizers, weathering stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, and other heat-resistant additives. Additives such as plastic resins, lubricants, fragrances, antifoaming agents, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization rate retardants, etc. can be included.

The resin composition of the present invention may be in the form of pellets and films or sheets. When the resin composition of the present invention is used as a film or sheet, the thickness of the film is generally 5 to 100 μm, and the thickness of the sheet is generally 100 μm to 1000 μm. Further, the film or sheet may be a single layer or a multilayer.

[Method for manufacturing resin composition]
The resin composition of the present invention comprises at least a step (1) of mixing the modified starch (A) and polyvinyl alcohol (B) to obtain a mixture, a step (2) of extruding the mixture, and a step of extruding the extruded mixture. It can be manufactured by a method including the step (3) of cooling and drying.

Step (1) is a step of mixing at least modified starch (A) and polyvinyl alcohol (B), and optionally includes other components such as the above-mentioned fatty acid having 12 to 22 carbon atoms and/or its fatty acid salt, the above-mentioned The clay, the plasticizer, and the additive can be mixed together.

Step (1) is usually performed using an extruder. In the extruder, each component is subjected to shear stress by a screw and homogeneously mixed while being heated by the application of external heat to the barrel.

As the extruder, for example, a twin screw extruder can be used. The twin screw extruder may be either co-rotating or counter-rotating. The screw diameter may be, for example, 20 to 150 mm, and the ratio L/D of extruder length (L) to screw diameter (D) may be, for example, 20 to 50. The rotation speed of the screw is preferably 80 rpm or more, more preferably 100 rpm or more. Further, the extrusion pressure is preferably 5 bar (0.5 MPa) or higher, more preferably 10 bar (1.0 MPa) or higher. Each component can be introduced directly into the extruder. Alternatively, these components may be premixed using a mixer and then introduced into the extruder.

In step (1), from the viewpoint of film-forming properties and oxygen barrier properties of the resin composition, the lower limit is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 10% by mass or more, particularly preferably 15% by mass or more, most preferably 20% by mass or more, the upper limit is preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less of plasticizer, preferably is preferably mixed with water. Here, the mass of the mixture indicates the total mass of the mixture containing the plasticizer. In step (1), a plasticizer may be introduced at the initial stage of extrusion, and may be introduced before the heating temperature is reached, for example, when the temperature is 100° C. or lower. Modified starch (A) can be subjected to a cooking treatment using a combination of moisture, heat, and shear stress to form gelatin (gel). Furthermore, by separately introducing a plasticizer, preferably water, a water-soluble polymer such as polyvinyl alcohol (B) can be dissolved, the resin composition can be softened, and the modulus and brittleness can be reduced.

In step (1), the cooking treatment is performed by heating preferably to a temperature of higher than 100°C and lower than or equal to 150°C, more preferably higher than or equal to 115°C and lower than or equal to 140°C. Here, the cooking process is a process of crushing starch granules and gelling them. Heating can be accomplished by externally applying heat to the extruder barrel. By applying a stepwise temperature to each barrel, it can be heated to the desired temperature. When the cooking process is performed at a temperature higher than 120° C., it is advantageous in terms of processability.

The cooked mixture is preferably forced toward the die while reducing the temperature to preferably 85-120°C, more preferably 90-110°C to prevent foaming. Additionally, by evacuating the barrel, foaming can be prevented and water can be removed.

The residence time in the extruder can be set depending on the temperature profile and screw speed, and is preferably 1 to 2.5 minutes.

In the step (2) of extruding the mixture, the molten mixture that has been pushed through the extruder while being melt-kneaded is extruded from the die. The temperature of the die is preferably 85-120°C, more preferably 90-110°C.

In step (3) of cooling and drying the extruded mixture (melt), the mixture (melt) can be extruded into a film or a strand.

When extruding the mixture into a film, the mixture can be extruded from a film-forming die and then cooled and dried while being wound up with a take-up roller. Cooling between the die and the rollers is preferred to prevent the mixture from sticking to the rollers. For drying, the roll may be heated and dehumidified air may be supplied during winding. Dehumidified air can be used to expand the film as it exits the die in the case of a blown tube method. Talc can also be entrained in the air stream to prevent blocking of the film.

When extruding the mixture into strands, the strands can be made into pellets by extruding through a multi-hole strand nozzle and cutting with a rotary cutter. In order to prevent pellets from sticking together, vibration can be applied periodically or constantly, and moisture in the pellets can be removed using hot air, dehumidified air, or an infrared heater.

[Coating and its manufacturing method]
The present invention includes a coated article formed by coating paper or a film with the resin composition of the present invention. Since the coating of the present invention contains the resin composition, it has a high maximum draw ratio during production, has high productivity, and also has excellent oxygen barrier properties and biodegradability. Furthermore, since the coating of the present invention has a high maximum draw ratio of the resin composition during manufacture, it also has excellent adhesion between the paper or film and the resin composition. This is thought to be because the viscosity of the resin composition is low and, for example, the resin composition easily penetrates between paper fibers.

When coating paper with the resin composition, the paper is not particularly limited, and includes, for example, kraft paper, high-quality paper, imitation paper, glassine paper, parchment paper, synthetic paper, white paperboard, manila ball, milk carton base paper, and cup paper. Examples include base paper, ivory paper, and white silver paper. The thickness of the paper in the coating is not particularly limited, and is preferably 1 to 500 μm, more preferably 10 to 300 μm. When the thickness of the paper in the coated article is within the above range, the take-up speed during production of the coated article can be increased, and productivity can be easily improved.

When coating a film with the resin composition, the film is not particularly limited, and examples include polyethylene terephthalate (PET) film, biaxially oriented polypropylene (BOPP) film, polyethylene (PE) film (preferably low density polyethylene (LDPE) ) film) and polylactic acid film. The thickness of the film in the coating is not particularly limited, and is preferably 1 to 500 μm, more preferably 10 to 300 μm, and even more preferably 50 to 100 μm.

The thickness of the resin composition in the coating of the present invention is preferably 1 to 300 μm, more preferably 5 to 100 μm, and still more preferably 10 to 50 μm. When the thickness of the resin composition in the coating is within the above range, good film formability and oxygen barrier properties are likely to be obtained.

The maximum draw ratio during production of the coating of the present invention, that is, the maximum draw ratio of the resin composition, is preferably 5 or more, more preferably 8 or more, even more preferably 10 or more, and preferably 30 or less, more preferably It is 25 or less, more preferably 20 or less. When the maximum draw ratio is within the above range, a coating having excellent adhesion between the paper or film and the resin composition and excellent oxygen barrier properties can be obtained with high productivity.
Note that the maximum draw ratio is expressed by the following formula.
(Maximum draw ratio) = (Maximum draw speed) / (Flow speed at extruder die exit)
(Flow rate at the die outlet of the extruder) = (Discharge amount) / ((Lip opening) x (Die width))
The maximum take-up speed is the conveyance speed of the paper or film ( The maximum speed at which the melt curtain of the resin composition does not tear from the edge even after increasing the take-up speed (take-up speed) in 1.0 m/min increments and holding it for 10 seconds is shown. The amount of resin composition discharged from the die outlet of the extruder, the lip opening degree, and the die width may be adjusted as appropriate. The maximum draw ratio can be determined by measuring, for example, the method described in Examples. In addition, since the maximum draw ratio changes depending on the characteristics of the resin composition, it can also be said to be a specific parameter that the resin composition has.
Here, the units of each of the items described in the above formula are (maximum take-up speed) [m/s], (flow velocity at the die outlet of the extruder) [m/s], (discharge amount) [m ³ /s], (lip opening degree) [m] and (die width) [m], and (maximum draw ratio) is [unitless].

The oxygen permeability (mL 20 μm/m ² atm 24 hr) of the coating of the present invention at 23° C. and 50% RH is preferably 8.0 or less, more preferably 5.0 or less, still more preferably 4. It is 0 or less, particularly preferably 3.0 or less, even more preferably 2.0 or less, and most preferably 1.0 or less. When the oxygen permeability in the coating is below the above upper limit, excellent oxygen barrier properties can be exhibited. Further, the oxygen permeability (mL・20 μm/m ²・atm・24 hr) is usually 0.1 or more. The oxygen permeability of the coating can be measured by an oxygen permeation measuring device after storing it at 23° C. and 50% RH for two weeks and adjusting the humidity, for example, by the method described in the Examples. Furthermore, in this specification, "improved oxygen barrier properties" indicates that oxygen permeability is reduced, and "excellent oxygen barrier properties" indicates that oxygen permeability is low.

The coating of the present invention can exhibit excellent adhesion between the paper or film and the resin composition. The adhesion strength (N/15 mm) of the coating of the present invention is preferably 2.0 or more, more preferably 3.0 or more, still more preferably 4.0 or more, particularly preferably 5.0 or more. Further, the adhesion strength (N/15 mm) is usually 10.0 or less. The adhesion strength can be measured using a tensile tester after being stored at 23° C. and 50% RH for two weeks to control the humidity, for example, by the method described in Examples.

The method for producing the coating of the present invention is not particularly limited as long as it is a method that allows paper or film to be coated with the resin composition. In a preferred embodiment, the coated article of the present invention can be produced by a method including a step (referred to as step (A)) of using an extruder to coat the resin composition on a film or paper conveyed by a take-up machine. .

In one embodiment of the present invention, in step (A), the resin composition, preferably in the form of pellets, absorbs a certain amount of water, and then the resulting water-containing pellets are fed into an extruder. The water content (water content) in the water-containing pellet is preferably 0.1 to 50% by mass, more preferably 10 to 45% by mass based on the mass of the water-containing pellet. Examples of the extruder include a single screw extruder and a twin screw extruder. The screw diameter of the extruder is, for example, 20 to 150 mm, the ratio L/D of the extruder length (L) to the screw diameter (D) is, for example, 15 to 50, and the rotational speed of the screw is preferably 80 rpm or more, More preferably, the speed is 100 rpm or more. The cylinder temperature in the extruder may be, for example, 80-120°C, preferably 90-110°C.

The resin composition introduced into the extruder is plasticized and discharged from the die outlet. On the other hand, the paper or film is conveyed by a take-up machine, preferably a roller-type take-up machine. A coated article is obtained by coating the transported paper or film with the resin composition discharged from the die outlet. The obtained coating may be pressed onto a base material using, for example, a pressure roll, and then wound up into a roll using a winder. Note that in this specification, "coating" may be referred to as "coat."

In step (A), formula (1)
Draw ratio = (take-up speed of take-off machine) / (flow rate at die exit of extruder) (1)
It is preferable that the draw ratio expressed by is 5 to 20. When a coated article is manufactured with such a draw ratio, productivity is improved and a coated article with excellent adhesion and oxygen barrier properties is easily obtained. Note that the flow rate at the die outlet of the extruder is expressed as (discharge amount)/((lip opening degree)×(die width)), as described above. When expressing the discharge amount in terms of mass per unit time, the discharge amount is preferably 1 to 500 kg/hr, more preferably 5 to 200 kg/hr, and the lip opening is preferably 0.01 to 5 mm, more preferably The die width is preferably 100 to 3000 mm, more preferably 200 to 2000 mm.

[Multilayer structure and packaging material]
The present invention encompasses multilayer structures that include the coatings of the present invention. The multilayer structure of the invention may contain layers other than the coating, such as film, paper or adhesive. These layers can be used alone or in combination. Although the multilayer structure of the present invention has a plurality of layers, the number of layers is not particularly limited, and may be, for example, 3 to 10 layers. Examples of the film and paper include those exemplified as the film and paper described in the [Coating] section, respectively.

Examples of adhesives that may be included in the multilayer structure include acrylic adhesives, urethane adhesives, epoxy adhesives, vinyl acetate adhesives, ethylene-vinyl acetate adhesives, vinyl chloride adhesives, and silicone adhesives. Examples include adhesives, nitrile cellulose adhesives, phenolic adhesives, polyvinyl alcohol adhesives, melamine adhesives, styrene adhesives, and the like.

In a preferred embodiment of the present invention, the multilayer structure has a layer structure in which film/adhesive/resin composition/paper/adhesive/film are laminated in this order. In this embodiment, the type of film or paper is not particularly limited, but the film is preferably a polyethylene film.

The present invention includes a packaging material comprising the coating or multilayer structure of the present invention. Since the packaging material has excellent oxygen barrier properties, adhesion properties, and biodegradability, it can be suitably used as a food packaging material.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

・吐出量：２０ｋｇ／ｈｒ
・ダイス：４５０ｍｍ幅コートハンガーダイ、リップ開度０．２ｍｍ
・ダイス－キャストロール間の距離（エアーギャップ）：１５０ｍｍ
・紙：日本製紙社製 白銀（無塗工紙、厚み７０μｍ）<Test method>
(1) Measurement of maximum draw ratio Water was added to the pellet-shaped resin compositions obtained in Examples and Comparative Examples until the amount was 35% by mass based on the mass of the resin composition. When adding water, the pellets were stirred for 15 minutes using a tumbler mixer while being added in multiple portions to prevent the pellets from sticking to each other and to uniformly absorb water throughout the pellets. After stirring, the mixture was placed in a sealed polyethylene bag to prevent moisture from evaporating and left at room temperature for 6 hours. The above-mentioned moisture content was confirmed by measuring at 130° C. for 60 minutes using a heat-drying moisture meter “HR73” manufactured by Mettler Toledo.
The above-mentioned water-containing pellets were put into a single-screw extruder shown in Table 1 below, extruded from a film-forming die, and coated on paper conveyed by a roller-type take-off machine. The resulting coating was immediately pressed onto the base material using a pressure roll, and then wound up into a roll using a winder.
・Single-screw extruder: Extruder made by Plastic Engineering Research Institute (40 mm diameter, L/D = 25)
·Preset temperature:

・Discharge amount: 20kg/hr
・Dice: 450mm width coat hanger die, lip opening 0.2mm
・Distance between die and cast roll (air gap): 150mm
・Paper: Nippon Paper Industries, white silver (uncoated paper, thickness 70μm)

Under conditions of a constant discharge amount, the paper conveyance speed was increased from 1.0 m/min to 1.0 m/min increments, and the maximum speed at which the melt curtain did not tear from the edge even after holding for 10 seconds was recorded as the maximum pick-up speed. . The maximum draw ratio was calculated based on the formula below.
(Maximum draw ratio) = (Maximum draw speed) / (Flow speed at extruder die exit)
(Flow rate at die outlet of extruder) = (discharge amount) / ((lip opening) x (die width))

(2) Measurement of oxygen permeability After storing the coatings obtained in Examples and Comparative Examples at 23°C and 50% RH for two weeks and controlling the humidity, they were attached to an oxygen permeation measuring device and the oxygen permeability was measured. did. The measurement conditions were as follows.
Device: “MOCON OX-TRAN2/20” manufactured by Modern Control
Temperature: 23℃
Humidity on oxygen supply side and carrier gas side: 50%RH
Oxygen pressure: 1.0 atm
Carrier gas pressure: 1.0 atm

(3) Evaluation of adhesion to paper The coatings obtained in Examples and Comparative Examples were stored at 23°C and 50% RH for two weeks to condition the humidity, and then cut into strips of 15 mm x 100 mm. The adhesion strength between the paper and the resin composition (resin layer) was measured by pulling the resin composition peeled from the paper.
Equipment: Instron 3367, load cell maximum load 1kN
Temperature: 23℃
Humidity: 50%RH
Peeling surface angle: 180°

(4) Viscosity measurement method of hydrophobically modified starch (A-2) The moisture content of hydrophobically modified starch (A-2) in Examples and Comparative Examples was measured using a heat drying moisture meter “HR73” manufactured by Mettler Toledo. The dry mass was determined by heating at 130° C. for 30 minutes. An aqueous solution was prepared to have a dry mass of 15% by mass, and gelatinized by stirring at 95°C for 5 minutes using NS's "Rapid Viscocity Analyzer TecMaster", and then cooled to 30°C. The viscosity was measured and defined as the viscosity (30° C.) of a 15% by mass aqueous solution of hydrophobically modified starch (A-2).

(5) Viscosity measurement method for polyvinyl alcohol (B) In accordance with JIS Z 8803 (falling ball viscometer) and JIS K 6726 (polyvinyl alcohol test method), 4% aqueous solutions of polyvinyl alcohol in Examples and Comparative Examples were prepared. Then, the viscosity at 20°C was measured using a Hebler viscometer, and was defined as the viscosity (at 20°C) of a 4% aqueous solution of polyvinyl alcohol (B).

(6) Material used <High amylose modified starch (A-1)>
- ECOFILM (registered trademark): corn starch modified with propylene oxide, amylose content 70% by weight, obtained from Ingredion - Gelose A939 (registered trademark): corn starch modified with propylene oxide, amylose content 80% by weight, Obtained from National Starch and Chemical Company

<Hydrophobically modified starch (A-2)>
By applying the following chemical modification method to low amylose starch, OSA modified starches a to c shown in Table 2 as hydrophobically modified starches and PO modified starches d and e as hydrophilically modified starches were obtained. Note that the unmodified starch f is a starch to which no chemical modification method has been applied.

(Octenylmaleic anhydride (OSA) modification method)
In a 2 L plastic beaker, 500 g of raw starch and 750 ml of tap water were put into a slurry. The slurry was mixed with a stirrer while the pH was adjusted to 7.5 by adding 3% sodium hydroxide solution. Stirring was continued while adding 15 g of octenyl maleic anhydride (OSA) in three portions every 30 minutes. The pH was maintained at 7.5 by adding 3% sodium hydroxide solution. The reaction was stirred until sodium hydroxide consumption ceased (less than 1 ml consumed in 10 minutes). The starch was then filtered through Waltman No. 1 filter paper and the resulting starch was washed with 750 ml of tap water. The starch was then reslurried in 500 ml of water and 25% hydrochloric acid was added to adjust the pH to 5.5. The slurry was filtered again, washed with an additional 750 ml of water, and air dried to less than 15% moisture to produce OSA modified starch.

(Propylene oxide (PO) modification method)
4 g of solid sodium hydroxide was dissolved in 750 g of tap water and mixed until completely dissolved. 50g of sodium sulfate was then added to the water and mixed until dissolved. 100 g of raw starch was then quickly added to the stirred aqueous mixture and mixed until homogeneous. Various levels of propylene oxide were added to the starch slurry and mixed for 1-2 minutes. The slurry was then transferred into a 2L plastic bottle and sealed. The bottle and contents were then placed in a preheated mixing cabinet set at 40°C and stirred for 18 hours. After the reaction was complete, the slurry was adjusted to pH 3 with dilute sulfuric acid and mixed for 30 minutes. Dilute sodium hydroxide solution was then added to adjust the pH to 5.5-6.0. Recovery by filtration was then carried out and the starch cake obtained was washed with water (3 x 250 ml) and spread on a bench to air dry. In this way, PO modified starch was produced. PO modified starch is a hydrophilically modified starch (modified starch having a hydrophilic modified group) and does not have a hydrophobic group.

<Polyvinyl alcohol (B)>
・ELVANOL (registered trademark) 71-30: polyvinyl alcohol resin, degree of saponification 99 mol% or more, viscosity 27-33 mPa・s (20°C, 4% aqueous solution), obtained from Kuraray Co., Ltd. ・ELVANOL (registered trademark) 90-50: polyvinyl Alcohol resin, saponification degree 99 mol% or more, viscosity 12-15 mPa・s (20°C, 4% aqueous solution), obtained from Kuraray Co., Ltd. Kuraray Poval (registered trademark) 22-88: polyvinyl alcohol resin, saponification degree 88 mol%, viscosity 22 mPa・s (20°C, 4% aqueous solution), obtained from Kuraray Co., Ltd. ・Kuraray Poval (registered trademark) 5-88: polyvinyl alcohol resin, degree of saponification 88 mol%, viscosity 5 mPa・s (20°C, 4% aqueous solution), Kuraray Co., Ltd. Obtained from Kuraray Poval (registered trademark) 3-98: polyvinyl alcohol resin, degree of saponification 98 mol%, viscosity 3 mPa・s (20°C, 4% aqueous solution), obtained from Kuraray Co., Ltd.

<Example 1>
(Resin composition)
As raw materials, ECOFILM (registered trademark) (7.35 kg), OSA modified starch a (2.45 kg), and ELVANOL71-30 (200 g) were mixed for 2 hours in a tumbler mixer, and the resulting mixture was mixed with a liquid pump connected. It was then subjected to a twin-screw extruder. FIG. 1 shows a schematic diagram of the twin screw extruder used in Example 1, and the screw diameter, L/D ratio, rotation speed, operating method, and temperature profile (Table 3) of the extruder are shown below.

Screw diameter: 27mm
L/D ratio: 48
Screw rotation speed 500 rpm
Operating method: Co-rotation (meshing self-wiping) method

Specifically, the resulting mixture was fed into the barrel through the hopper in C1 at a rate of 3.5 kg/hour via the gravimetric feeder of a twin-screw extruder. Water was injected into the barrel through a liquid pump (L) at C4 at a flow rate of 26 g/min. The temperature range from C5 to C9 is the cooking zone and complete gelatinization was completed within these zones. The strand die is after C11. The resin composition was extruded from a multi-hole strand nozzle and cut with a rotary cutter to form the strand into a pellet shape. Since the pellets contained excess moisture, the moisture was removed using hot air, dehumidified air, or an infrared heater while constantly applying vibrations to prevent sticking.

(Coating)
By the same method as described in [(1) Measurement of maximum draw ratio] above, a coating was prepared by coating paper with a resin composition so that the coating thickness was 20 μm at the maximum draw ratio.

<Example 2>
The same procedure as in Example 1 was carried out, except that ECOFILM (registered trademark) (6.75 kg), OSA modified starch a (2.25 kg), and ELVANOL71-30 (registered trademark) (1.00 kg) were used as raw materials. A resin composition and a coating were obtained.

<Example 3>
The same procedure as in Example 1 was carried out, except that ECOFILM (registered trademark) (5.25 kg), OSA modified starch a (1.75 kg), and ELVANOL71-30 (registered trademark) (3.00 kg) were used as raw materials. A resin composition and a coating were obtained.

<Example 4>
The same procedure as in Example 1 was carried out, except that ECOFILM (registered trademark) (3.75 kg), OSA modified starch a (1.25 kg), and ELVANOL71-30 (registered trademark) (5.00 kg) were used as raw materials. A resin composition and a coating were obtained.

<Example 5>
A resin composition and a coating were obtained in the same manner as in Example 2, except that ELVANOL (registered trademark) 90-50 was used as polyvinyl alcohol (B).

<Example 6>
A resin composition and a coating were obtained in the same manner as in Example 2, except that Kuraray Poval (registered trademark) 22-88 was used as polyvinyl alcohol (B).

<Example 7>
A resin composition and a coating were obtained in the same manner as in Example 2, except that Kuraray Poval (registered trademark) 5-88 was used as polyvinyl alcohol (B).

<Example 8>
A resin composition and a coating were obtained in the same manner as in Example 2, except that Kuraray Poval (registered trademark) 3-98 was used as polyvinyl alcohol (B).

<Example 9>
The same procedure as in Example 1 was carried out, except that ECOFILM (registered trademark) (5.40 kg), OSA modified starch a (3.60 kg), and ELVANOL71-30 (registered trademark) (1.00 kg) were used as raw materials. A resin composition and a coating were obtained.

<Example 10>
The procedure was the same as in Example 1, except that ECOFILM (registered trademark) (8.10 kg), OSA modified starch a (0.90 kg), and ELVANOL71-30 (registered trademark) (1.00 kg) were used as raw materials. A resin composition and a coating were obtained.

<Example 11>
A resin composition and a coating were obtained in the same manner as in Example 2, except that OSA modified starch b was used as the hydrophobically modified starch (A-2).

<Example 12>
A resin composition and a coating were obtained in the same manner as in Example 2, except that OSA modified starch c was used as the hydrophobically modified starch (A-2).

<Example 13>
A resin composition and a coating were obtained in the same manner as in Example 2, except that Gelose A939 (registered trademark) was used as the high amylose modified starch (A-1).

<Comparative example 1>
A resin composition and a coating were obtained in the same manner as in Example 1, except that ECOFILM (registered trademark) (10.00 kg) was used as the raw material.

<Comparative example 2>
A resin composition was obtained in the same manner as in Example 1 except that OSA modified starch a (10.00 kg) was used as the raw material. Moreover, the resin composition could not be formed into a film.

<Comparative example 3>
A resin composition was obtained in the same manner as in Example 1, except that OSA modified starch a (9.00 kg) and ELVANOL71-30 (registered trademark) (1.00 kg) were used as raw materials. Moreover, the resin composition could not be formed into a film.

<Comparative example 4>
A resin composition and a coating were obtained in the same manner as in Example 1, except that ECOFILM (registered trademark) (7.50 kg) and OSA modified starch a (2.50 kg) were used as raw materials.

<Comparative example 5>
A resin was prepared in the same manner as in Example 1, except that ECOFILM (registered trademark) (7.42 kg), OSA modified starch a (1.57 kg), and ELVANOL71-30 (registered trademark) (100 g) were used as raw materials. A composition and a coating were obtained.

<Comparative example 6>
The same procedure as in Example 1 was carried out, except that ECOFILM (registered trademark) (2.25 kg), OSA modified starch a (0.75 kg), and ELVANOL71-30 (registered trademark) (7.00 kg) were used as raw materials. A resin composition was obtained. Moreover, the resin composition could not be formed into a film.

<Comparative example 7>
A resin composition and a coating were obtained in the same manner as in Example 2, except that PO modified starch d was used in place of the hydrophobically modified starch (A-2).

<Comparative example 8>
A resin composition and a coating were obtained in the same manner as in Example 2, except that PO modified starch e was used in place of the hydrophobically modified starch (A-2).

<Comparative example 9>
A resin composition and a coating were obtained in the same manner as in Example 2, except that unmodified starch f was used instead of hydrophobically modified starch (A-2).

<Comparative example 10>
The same procedure as in Example 1 was carried out, except that ECOFILM (registered trademark) (3.60 kg), OSA modified starch a (5.40 kg), and ELVANOL71-30 (registered trademark) (1.00 kg) were used as raw materials. A resin composition was obtained. Moreover, the resin composition could not be formed into a film.

<Comparative example 11>
A resin composition was obtained in the same manner as in Comparative Example 10, except that Gelose A939 (registered trademark) was used as the high amylose modified starch (A-1). Moreover, the resin composition could not be formed into a film.

Measurement results of viscosity (30°C) in a 15% by mass aqueous solution of hydrophobically modified starch (A-2) after gelatinization treatment, mixing ratio of high amylose modified starch (A-1) and hydrophobically modified starch (A-2) and the measurement results of the average amylose content, the amount of polyvinyl alcohol (B) added, the degree of saponification, and the viscosity (20°C) in a 4% aqueous solution, the maximum draw ratio of the coating, the oxygen permeability, and the relationship between the paper and the resin composition. Table 4 shows the evaluation results of adhesion.

As shown in Table 4, it was confirmed that the coatings obtained in Examples 1 to 13 had a high maximum draw ratio during production and a low oxygen permeability. On the other hand, it was confirmed that Comparative Examples 1 to 11 were inferior to Examples 1 to 13 in terms of maximum draw ratio, oxygen permeability, or both. Therefore, it was found that the coating of the present invention had a high maximum draw ratio during production and had excellent oxygen barrier properties. Furthermore, it was found that the coatings obtained in Examples 1 to 13 had excellent adhesion between the paper and the resin composition.

Claims (10)

A resin composition comprising a modified starch (A) containing a hydrophobic group and having an amylose content of 45% by mass or more, and polyvinyl alcohol (B),
Based on a total of 100 parts by mass of modified starch (A) and polyvinyl alcohol (B), the content of modified starch (A) is 40 to 98 parts by mass, and the content of polyvinyl alcohol (B) is 2 to 60 parts by mass. mass part ,
The modified starch (A) is different from the high amylose modified starch (A-1) having an amylose content of 50% by mass or more and the high amylose modified starch (A-1), and is a hydrophobic starch having a hydrophobic group. Consisting of modified starch (A-2),
The resin composition, wherein the hydrophobic group is a modified group with a hydrophobic compound having 6 to 24 carbon atoms . The resin composition according to claim 1 , wherein the hydrophobically modified starch (A-2) has an amylose content of less than 50% by mass. The high amylose modified starch (A-1) is at least one selected from etherified starch having a hydroxyalkyl group and esterified starch having a carboxylic anhydride modified group, according to claim 1 or 2. Resin composition. The hydrophobically modified starch (A-2) is selected from etherified starch having a glycidyl ether modifying group having 6 to 24 carbon atoms and esterified starch having a carboxylic acid anhydride modifying group having 6 to 24 carbon atoms. The resin composition according to any one of claims 1 to 3 , which is at least one type. The hydrophobically modified starch (A-2) has a viscosity of 1000 cP or less when a 15% by mass aqueous solution is gelatinized by stirring at 95° C. for 5 minutes and then cooled to 30° C. Any of the resin compositions. The resin composition according to any one of claims 1 to 5 , wherein the polyvinyl alcohol (B) has a viscosity of 1 to 50 mPa·s at 20°C as a 4% aqueous solution measured according to JIS Z 8803. A coated article obtained by coating paper or a film with the resin composition according to any one of claims 1 to 6 . A multilayer structure comprising a coating according to claim 7 . A packaging material comprising the coating according to claim 7 or the multilayer structure according to claim 8 . The method comprises a step of using an extruder to coat the resin composition according to any one of claims 1 to 6 on a film or paper conveyed by a take-up machine, and in the step, formula (1)
Draw ratio = (take-up speed of take-off machine) / (flow rate at die exit of extruder) (1)
The method for producing a coating according to claim 7 , wherein the draw ratio represented by is 5 to 20.

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