JP2020105305A - Resin composition - Google Patents

Abstract

To provide a resin composition which has a high maximum draw ratio during production and can form a coating excellent in an oxygen barrier property.SOLUTION: A resin composition contains (A) a modified starch that comprises a hydrophobic group and has an amylose content of 45 mass% or more and (B) a polyvinyl alcohol. Based on 100 pts.mass of the total of the modified starch (A) and the polyvinyl alcohol (B), the content of the modified starch (A) is 40-98 pts.mass and the content of the polyvinyl alcohol (B) is 2-60 pts.mass.SELECTED DRAWING: None

Description

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

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

Japanese Patent No. 4782284

Among the containers for packaging these foods, there are many containers that use a coating formed by coating the resin composition on paper or film as a material, and the coating requires a high oxygen barrier property. It On the other hand, the coating is produced, for example, by coating the paper or film conveyed by a take-up machine with the resin composition discharged from the die outlet of the extruder. However, according to the study by the present inventors, a resin composition capable of ensuring a high oxygen barrier property has low fluidity, and has a low draw ratio represented by the maximum take-up speed with respect to the flow rate at the die outlet, which improves productivity. I knew I couldn't.

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

As a result of intensive studies to solve the above problems, the present inventor has made a resin containing a modified starch (A) containing a hydrophobic group and having an amylose content of 45% by mass or more, and a polyvinyl alcohol (B). In the composition, when the content of the modified starch (A) is adjusted to 40 to 98 parts by mass and the content of the polyvinyl alcohol (B) is adjusted to 2 to 60 parts by mass, it is found that the above problems can be solved, and the present invention is completed. Let

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

Since the resin composition of the present invention can form a coating having a high maximum draw ratio during production and an excellent oxygen barrier property, it can be suitably used as a material for food packaging and containers.

1 shows a schematic view of the twin-screw extruder used in the examples.

[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. When the resin composition of the present invention contains the modified starch (A) in particular, the take-up property becomes good, and the maximum draw ratio and the adhesiveness can be improved. Incidentally, in the present specification, the retrievable property is a property that, when the conveyed paper or film is coated with the resin composition discharged from the die outlet of the extruder, the resin composition can be coated without tearing. The improvement in the take-off property means that the resin composition can be easily coated without tearing even when the paper or film is conveyed at high speed. Further, in the present specification, the adhesiveness means the adhesiveness between the paper or film in the coating and the resin composition.

The starch which is a raw material of the modified starch (A) is, for example, a starch derived from cassava, corn, potato, sweet potato, sago, tapioca, sorghum, bean, bracken, lotus, jade, wheat, rice, oats, arrowroot, pea, etc. May be Among these, from the viewpoint of amylose content, the starch that is a raw material of the modified starch (A) is preferably starch derived from corn (corn) or cassava, and more preferably starch derived from corn. The modified starch (A) may be composed of one kind or two or more kinds of starch.

The modified starch (A) contains a hydrophobic group. The hydrophobic group refers to an atomic group having a low affinity for water. The hydrophobic group contained in the modified starch is not particularly limited, but is preferably a group modified by a hydrophobic compound (sometimes referred to as a hydrophobic compound modified group). When the modified starch (A) contains a hydrophobic compound-modifying group, the resin composition has good take-off properties, and the maximum draw ratio and the adhesion are likely to be improved. The hydrophobic group is preferably introduced into starch by reacting a hydroxyl group contained in starch with a reactive group of a hydrophobic compound, and more preferably bound to starch by etherification, esterification or amidation. preferable. Further, before or simultaneously with the modification, a treatment for decreasing or increasing the molecular weight of starch may be carried out by a known method such as decomposition with 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 bond between starches and easily improving the take-up property, the maximum draw ratio and the adhesiveness. The number of carbon atoms is more preferably 7 to 24, further preferably 8 to 18.
In a preferred embodiment of the present invention, the hydrophobic compound is a hydrophobic compound containing an aliphatic and/or aromatic group having 6 to 24 carbon atoms, preferably 7 to 20 carbon atoms, 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 the 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 It is preferably a hydrophobic compound having 6 to 24 carbon atoms. Specifically, as the hydrophobic compound, cetyl bromide, lauryl bromide; epoxidized soybean fatty alcohol, epoxidized linseed fatty alcohol; allyl glycidyl ether, propyl glycidyl ether, butyl glycidyl ether, decane glycidyl ether, lauryl phenyl glycidyl ether, Examples thereof include glycidyl ethers having 2 to 24 carbon atoms such as myristoyl glycidyl ether, cetyl glycidyl ether, palmityl glycidyl ether, stearyl glycidyl ether, and linoleyl glycidyl ether, and preferably glycidyl ether having 6 to 24 carbon atoms.

When the hydrophobic compound is esterified, that is, bound 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 10 carbon atoms. 24, preferably C 7-20 carboxylic acid anhydrides are preferred. Specific examples of the carboxylic acid anhydride include alkanoic acid carboxylic acid anhydrides such as octanoic acid acetic acid anhydride, decanoic acid acetic acid anhydride, lauric acid acetic acid anhydride and myristic acid acetic acid anhydride; alkyl or alkenyl succinic acid anhydrides. , Alkyl or alkenyl dicarboxylic acid anhydrides such as alkyl or alkenyl maleic anhydride. Among these, from the viewpoint of easily collecting, maximum draw ratio and adhesion, alkyl or alkenyl dicarboxylic acid anhydride is preferable, octenyl succinic anhydride, nonyl succinic anhydride, decyl succinic anhydride, dodecenyl succinic anhydride, Octenyl maleic anhydride, nonyl maleic anhydride, decyl maleic anhydride, dodecenyl maleic anhydride are more preferable, and octenyl succinic anhydride or octenyl maleic anhydride is still more preferable.

When a hydrophobic compound is amidated, that is, bound 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. An aliphatic amine containing a saturated or unsaturated hydrocarbon group can be preferably used, and the aliphatic amine may contain a branched chain, but is preferably a straight chain. Specifically, as the aliphatic amine, n-dodecylamine, n-hexadecylamine, n-octadecylamine, cocoamine, tallowamine, hydrogenated N-tallow-1,3-diaminopropane, N-hydrogenated tallow-1, Examples thereof include 3-diaminopropane and N-oleyl-1,3-diaminopropane. The modified starch (A) may be composed of one kind or two or more kinds of hydrophobic groups, preferably a hydrophobic compound modifying group.

Among these hydrophobic compounds, glycidyl ether having 6 to 24 carbon atoms and 6 to 24 carbon atoms are preferable from the viewpoint of easily reducing the pseudo-crosslinking due to hydrogen bond of starch to improve the take-up property, the maximum draw ratio and the adhesiveness. At least one selected from 24 carboxylic acid anhydrides is preferable, a carboxylic acid anhydride having 6 to 24 carbon atoms is more preferable, and an alkyl or alkenyl dicarboxylic acid anhydride having 6 to 24 carbon atoms is further preferable.

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. Or more, more preferably 1.0×10 ⁻³ or more, preferably 1.0×10 ⁻¹ or less, more preferably 2.0×10 ⁻² or less, further preferably 1.5×10 ⁻² or less. And particularly preferably 1.0×10 ⁻² or less. When the substitution degree (DS) is in the above range, it is advantageous in terms of take-up property, maximum draw ratio, and adhesion.

The modified starch (A) may contain a hydrophilic group in addition to the hydrophobic group. The hydrophilic group refers to an atomic group having a high affinity for water. The hydrophilic group contained in the modified starch (A) is not particularly limited, but is a modified group by a hydrophilic compound (may be 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 starch by reacting a hydroxyl group contained in starch with a reactive group of a hydrophilic compound, and more preferably bonded to starch by etherification, esterification or amidation. preferable. Further, before or simultaneously with the chemical modification, a treatment for decreasing or increasing the molecular weight of starch may be performed by a known method such as decomposition with acid or oxidation.

Examples of the hydrophilic compound 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; and odors having 2 to 5 carbon atoms. Alkyl halides such as methyl halide; maleic anhydride, phthalic anhydride and other carboxylic acid anhydrides having 2 to 5 carbon atoms; oxo acid salts such as sodium nitrate and sodium phosphate; 2-diethylaminoethyl chloride; 2 , 3-epoxypropyltrimethylammonium chloride and the like. Among these, at least one selected from an alkylene oxide having 2 to 5 carbon atoms and a carboxylic acid anhydride having 2 to 5 carbon atoms is preferable from the viewpoint of reactivity with starch.

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 lower limit, the film-forming property, the take-up property, the maximum draw ratio and the adhesiveness are likely to be improved, and the moldability of the resin composition is also easily improved. In the present specification, the amylose content can be measured, for example, by the iodine coloration method described in “Starch 50 No. 4 158-163 (1998)”. Here, when the modified starch (A) is composed of two or more kinds of modified starch, the amylose content of the modified starch (A) is the average amylose content obtained by weighted average of the amylose contents of the two or more kinds of modified starch. 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), And it consists of hydrophobically modified starch (A-2) having a hydrophobic group. This mode is advantageous from the viewpoint that the take-up property of the resin composition can be easily improved, and the maximum draw ratio and the adhesiveness can be easily improved.

<High amylose modified starch (A-1)>
The 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, further preferably 65% by mass or more, particularly preferably 70% by mass or more, and preferably It is 90 mass% or less. When the amylose content of the high amylose-modified starch (A-1) is at least the above lower limit, the film-forming property, the take-up property, the maximum draw ratio and the adhesiveness are easily improved, and the moldability of the resin composition is also improved. Cheap.

Examples of the starch as the raw material of the high amylose modified starch (A-1) include those exemplified above as the starch as the raw material of the modified starch (A). The high amylose-modified starch (A-1) may be composed of one kind or two or more kinds 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 described in the section of <modified starch (A)>, and a modified starch containing the hydrophilic group. Is preferred. Specifically, the high amylose-modified starch (A-1) is preferably at least one selected from the group consisting of etherified starch, esterified starch, cationized starch and crosslinked starch.

Examples of the etherified starch include alkyl etherified starch such as methyl etherified starch, preferably alkyl etherified starch having 2 to 5 carbon atoms; carboxyalkyl etherified starch such as carboxymethyl etherified starch, preferably carbon atom. Carboxymethyl etherified starch having a number of 2 to 5; etherified starch having a hydroxyalkyl group such as hydroxyethylene group, hydroxypropylene group and hydroxybutylene group (hydroxyalkyl etherified starch), preferably hydroxy having 2 to 5 carbon atoms An etherified starch having an alkyl group; an allyl etherified starch, preferably an allyl etherified starch having 2 to 5 carbon atoms. The hydroxyalkyl etherified starch having 2 to 5 carbon atoms can be obtained by reacting an alkylene oxide having 2 to 5 carbon atoms such as ethylene oxide, propylene oxide and butylene oxide with starch.

Examples of the esterified starch include esterified starch having a carboxylic acid modifying 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); derived from maleic anhydride. Esterification having a carboxylic acid anhydride-modifying group such as esterified starch having a structural unit of, an esterified starch having a structural unit derived from phthalic anhydride, and an esterified starch having a structural unit derived from octenylsuccinic anhydride Starch (also referred to as esterified starch having a structural unit derived from carboxylic acid anhydride); esterified starch having a structural unit derived from oxo acid such as nitrate esterified starch, phosphoric acid esterified starch, and urea phosphoric acid esterified starch; Examples include xanthate esterified starch; acetoacetate esterified starch and the like.

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

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

Among them, the high amylose-modified starch (A-1) is an etherified starch having a hydroxyalkyl group and a carboxylic acid anhydride-modified group from the viewpoint of easily improving the film-forming property, take-up property, maximum draw ratio and adhesion. It is preferably at least one selected from esterified starches having ##STR5## and has an etherified starch having a hydroxyalkyl group having 2 to 5 carbon atoms and an ester having a carboxylic acid anhydride modifying group having 2 to 5 carbon atoms. More preferably, it is at least one selected from modified starch. The resin composition of the present invention may contain one or more high amylose-modified starch (A-1). 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 the present specification, the number of carbon atoms described before “starch” is the carbon atom of a group in which one hydroxyl group in starch is substituted (a group formed by modifying one hydroxyl group in starch). Represents a number. For example, an etherified starch having a hydroxyalkyl group having 2 to 5 carbon atoms indicates the number of carbon atoms of a 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 mass% with respect to the mass of the high amylose modified starch (A).

What is marketed as high amylose modified starch (A-1) can be used. Examples of typical commercial products of the high amylose modified starch (A-1) include ECOFILM (registered trademark), GELOSE (registered trademark) A939, etc., which are available from Ingredion or National Starch & Chemical Company.

<Hydrophobic modified starch (A-2)>
The hydrophobic modified starch (A-2) is a modified starch different from the high amylose modified starch (A-1). Examples of the starch as the raw material of the hydrophobic modified starch (A-2) include those exemplified above as the starch as the raw material of the modified starch (A). The hydrophobically modified starch (A-2) may be composed of one or more starches.

The 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 the hydrophobic compound are the same as the hydrophobic group and the hydrophobic compound described in the section of <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, and etherified with 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 modifying group with a hydrophobic compound, and as the hydrophobic compound, the hydrophobic group is bound to the starch by etherification in the section <modified starch (A)>. Examples of the hydrophobic compound used in this case include those mentioned above. The esterified starch is preferably an esterified starch having a modifying group with a hydrophobic compound, and as the hydrophobic compound, the hydrophobic group is bound to the starch by etherification in the section of <modified starch (A)>. Examples of the hydrophobic compound used in this case include those mentioned above. The amidated starch is preferably an amidated starch having a modification group with a hydrophobic compound, and as the hydrophobic compound, the hydrophobic group is bonded to the starch by amidation in the section of <modified starch (A)>. Examples of the hydrophobic compound used in this case include those mentioned above.

Among these, the hydrophobically modified starch (A-2) is an etherified starch (derived from glycidyl ether) having a glycidyl ether modifying group having 6 to 24 carbon atoms from the viewpoint of easily improving the take-up speed, the maximum draw ratio and the adhesion. At least one selected from the group consisting of an etherified starch having a structural unit of 4) and an esterified starch having a carboxylic acid anhydride modifying group having 6 to 24 carbon atoms (an esterified starch having a structural unit derived from a carboxylic acid anhydride). Is preferred.

The amylose content of the hydrophobic modified starch (A-2) is particularly limited as long as the average amylose content of the high amylose modified starch (A-1) and the hydrophobic 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, further 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, and 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 take-up property, maximum draw ratio and adhesion.

The hydrophobically modified starch (A-2) has a viscosity of preferably 15OcP or less, more preferably 500cP or less, when a 15 mass% aqueous solution is stirred at 95°C for 5 minutes to gelatinize 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 less than the above upper limit, the take-up property, maximum draw ratio and adhesion are likely to be improved, and when the viscosity is more than 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, and can be measured, for example, by the method described in the examples.

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

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

In the resin composition of the present invention, the ratio of high amylose modified starch (A-1) and hydrophobic modified starch (A-2) is such that the high amylose modified starch (A-1) and the hydrophobic modified starch (A-2). ) And the average amylose content may be adjusted to 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, and more preferably 1 part by mass of the hydrophobic 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, still more preferably 5.0 parts by mass or less. It is below the mass part. When the content of the high amylose modified starch (A-1) with respect to the content of the hydrophobic modified starch (A-2) is at least the above lower limit, the oxygen barrier property is easily improved, and when the content is at most the above upper limit, It is easy to improve the take-up property, maximum draw ratio and adhesion.

<Polyvinyl alcohol (B)>
The resin composition of the present invention contains polyvinyl alcohol (B). The degree of saponification of the polyvinyl alcohol (B) is preferably 80 to 99.8 mol %. When the saponification degree of the polyvinyl alcohol (B) is within the above range, sufficient strength and oxygen barrier property are easily obtained. The degree of saponification is more preferably 85 mol% or more, further preferably 88 mol% or more. In addition, in this specification, a saponification degree says the molar fraction of the hydroxyl group with respect to the total of the hydroxyl group and ester group in polyvinyl alcohol (B).

The polyvinyl alcohol (B) may further include other monomer units other than the vinyl alcohol unit. Examples of the other monomer unit include a monomer unit derived from an ethylenically unsaturated monomer. Examples of the ethylenically unsaturated monomer include α-olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and salts thereof; unsaturated monomers having an acrylate group; methacrylic acid. And salts thereof; unsaturated monomers having a methacrylic acid ester group; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N,N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and salts thereof, acrylamidopropyl dimethyl Amine and its salts (for example, quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts (for example, 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 such as maleic acid, itaconic acid and fumaric acid and salts or esters thereof; 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 carlylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. A vinyl ester monomer is exemplified. In addition, a monomer unit derived from an unsaturated monomer that is not saponified is also included in the other monomer units. The content of the other monomer unit 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, there may be mentioned a method of copolymerizing a vinyl alcohol monomer and another monomer, and saponifying the resulting copolymer to convert it into a vinyl alcohol unit. Examples of the polymerization method at the time of copolymerization include batch polymerization, semi-batch polymerization, continuous polymerization and semi-continuous polymerization. Examples of the polymerization method include known methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method and an emulsion polymerization method. A known method can be applied to the saponification of the copolymer. For example, it can be carried out in a state where the copolymer is 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 polyvinyl alcohol (B) has a viscosity at 20° C. of a 4% aqueous solution measured according to JIS Z 8803, which is preferably 1 mPa·s or more, more preferably 2 mPa·s or more, further 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 the polyvinyl alcohol (B) is within the above range, sufficient strength and oxygen barrier property are easily obtained. The above-mentioned viscosity of polyvinyl alcohol (B) can be measured using a viscometer, and can be measured, for example, by the method described in Examples.

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

The content of the modified starch (A) is 40 parts by mass or more, preferably 50 parts by mass or more, and more preferably 60 parts by mass or more, based on the total 100 parts by mass of the modified starch (A) and the polyvinyl alcohol (B). , More preferably 70 parts by mass or more, 98 parts by mass or less, preferably 95 parts by mass or less, more preferably 90 parts by mass or less, and further preferably 85 parts by mass or less. When the content of the modified starch (A) is at least the above lower limit, the take-off property, the maximum draw ratio and the adhesiveness are easily improved, and when it is at most the above 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, and more preferably 10 parts by mass or more, based on 100 parts by mass of the modified starch (A) and polyvinyl alcohol (B). , More preferably 15 parts by mass or more, 60 parts by mass or less, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less. When the content of the polyvinyl alcohol (B) is at least the above lower limit, the oxygen barrier property is easily improved, and when it is at most the above upper limit, the take-off property, the maximum draw ratio and the adhesiveness are easily improved.

In the resin composition of the present invention, the total ratio of the modified starch (A) and the polyvinyl alcohol (B) is preferably 10% by mass or more, 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 the modified starch (A) and the polyvinyl alcohol (B) is in the above range, the maximum draw ratio, the adhesiveness and the oxygen barrier property 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 the fatty acid having 12 to 22 carbon atoms and the fatty acid salt thereof 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 preferable from the viewpoint of workability. The fatty acids having 12 to 22 carbon atoms and the fatty acid salts thereof can be used alone or in combination of two or more.

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. It is 0.01 to 3% by mass, more preferably 0.03 to 2% by mass, and further preferably 0.1 to 1% by mass. When the content of the fatty acid having 12 to 22 carbon atoms and/or the fatty acid salt thereof 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. Examples of the clay include synthetic or natural layered silicate clays, such as montmorillonite, bentonite, beidellite, mica, hectorite, saponite, nontronite, sauconite, vermiculite, ladykite, magadaite, kenyaite, stevensite, and volcons. Examples include Koito. Clay can be used alone or in combination of two or more kinds.

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

The resin composition of the present invention may further contain a plasticizer from the viewpoint of film formability. Examples of the plasticizer 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, polyethylene glycol. The plasticizers can be used alone or in combination of two or more. Among these plasticizers, water is preferable 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, and more preferably 4 to 20% by mass with respect to the mass of the resin composition from the viewpoint of film-forming property and oxygen barrier property of the resin composition. 18% by mass, more preferably 7 to 15% by mass. When the water content is within the above range, the resin composition can exhibit excellent film-forming properties, and the adhesiveness of the coating and the oxygen barrier property are improved. The water content is the water content measured at a temperature of 130° C. for 30 minutes using a heat-drying moisture content meter after conditioning the humidity for 2 weeks at a temperature of 23° C. and a relative humidity of 50%.

The resin composition of the present invention, if necessary, a filler, a processing stabilizer, a weather resistance stabilizer, a colorant, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a flame retardant, and other heat. Additives such as plastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, release agents, reinforcing agents, cross-linking agents, fungicides, preservatives, crystallization speed retarders, 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 monolayer or a multilayer.

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

The step (1) is a step of mixing at least the modified starch (A) and the polyvinyl alcohol (B), and optionally other components such as the fatty acid having 12 to 22 carbon atoms and/or the fatty acid salt thereof, 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 with a screw, and is uniformly mixed while being heated by applying external heat to the barrel.

As the extruder, for example, a twin screw extruder can be used. The twin screw extruder may be co-rotating or counter-rotating. The screw diameter may be, for example, 20 to 150 mm, and the ratio L/D of the extruder length (L) to the 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. The extrusion pressure is preferably 5 bar (0.5 MPa) or more, more preferably 10 bar (1.0 MPa) or more. Each of the components can be directly introduced into the extruder. In addition, a premixed product of each of these components using a mixer may be introduced into the extruder.

In step (1), the lower limit is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably from the viewpoint of film-forming property and oxygen barrier property of the resin composition. 10 mass% or more, particularly preferably 15 mass% or more, most preferably 20 mass% or more, and the upper limit is preferably 50 mass% or less, more preferably 45 mass% or less, further preferably 40 mass% or less, preferably Is preferably mixed with water. Here, the mass of the mixture indicates the total mass of the mixture containing the plasticizer. In the step (1), the plasticizer may be introduced in the initial stage of extrusion, and the plasticizer can be introduced before reaching the heating temperature, for example, at 100° C. or lower. The modified starch (A) can be gelatinized by subjecting it to a cooking treatment by a combination of moisture, heat and shear stress. Further, 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 the step (1), heating is preferably performed at a temperature higher than 100° C. and 150° C. or lower, more preferably 115° C. or higher and 140° C. or lower to perform cooking treatment. Here, the cooking treatment is a treatment in which starch granules are crushed and gelled. Heating can be accomplished by externally applying heat to the extruder barrel. By applying a gradually changing temperature to each barrel, it is possible to heat up to the target temperature. When the cooking treatment is performed at a temperature higher than 120° C., it is advantageous in terms of workability.

To prevent foaming, the cooked mixture is preferably pushed towards the die while lowering to a temperature of preferably 85-120°C, more preferably 90-110°C. Further, by exhausting from the barrel, it is possible to prevent foaming and remove water.

The residence time in the extruder can be set according to the temperature profile and the 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 the step (3) of cooling and drying the extruded mixture (melt), the mixture (melt) can be extruded into a film or strand.

When the mixture is extruded into a film, the mixture can be extruded from a film forming die and then cooled and dried while being wound by 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 warmed or dehumidified air may be supplied during winding. Dehumidified air can be used to inflate the film as it exits the die in the blown tube process. Talc can also be entrained in the air stream to prevent blocking of the film.

When the mixture is extruded into a strand, the strand can be extruded from a multi-hole strand nozzle and cut with a rotary cutter to form the strand into a pellet. In order to prevent sticking of the pellets, vibration can be periodically or constantly applied to remove water in the pellets by hot air, dehumidified air or an infrared heater.

[Coating and its manufacturing method]
The present invention includes a coating material obtained by coating the resin composition of the present invention on paper or a film. Since the coating material of the present invention contains the resin composition, it has a high maximum draw ratio during production, high productivity, and is excellent in oxygen barrier property and biodegradability. Further, the coated article of the present invention has a high maximum draw ratio of the resin composition at the time of production, and therefore has excellent adhesion between the paper or film and the resin composition. It is considered that this is because the viscosity of the resin composition is low and, for example, the resin composition easily penetrates between the fibers of the paper.

When the resin composition is coated on paper, the paper is not particularly limited, and examples thereof include kraft paper, high-quality paper, imitation paper, glassine paper, parchment paper, synthetic paper, white paperboard, Manila balls, milk carton base paper, cups. 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 coating is within the above range, the take-up speed during the production of the coating can be increased, and the productivity can be improved easily.

When the resin composition is coated on the film, the film is not particularly limited, and examples thereof include a polyethylene terephthalate (PET) film, a biaxially oriented polypropylene (BOPP) film, a polyethylene (PE) film (preferably low density polyethylene (LDPE). ) Films) and polylactic acid films. 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 further preferably 50 to 100 μm.

The thickness of the resin composition in the coating material of the present invention is preferably 1 to 300 μm, more preferably 5 to 100 μm, and further preferably 10 to 50 μm. When the thickness of the resin composition in the coating is in the above range, good film-forming property and oxygen barrier property are easily obtained.

The maximum draw ratio at the time of producing the coating material of the present invention, that is, the maximum draw ratio of the resin composition is preferably 5 or more, more preferably 8 or more, further preferably 10 or more, 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, it is possible to obtain a coating having excellent adhesiveness between the paper or film and the resin composition and an oxygen barrier property with high productivity.
The maximum draw ratio is represented by the following formula.
(Maximum draw ratio) = (Maximum drawable speed) / (Velocity at the die exit of the extruder)
(Flow velocity at the die outlet of the extruder)=(Discharge amount)/((Lip opening)×(Die width))
The maximum retrievable speed is the paper or film conveyed by the take-off machine, when the resin composition discharged from the die outlet of the extruder is coated, under the condition of a constant discharge amount, the paper or film conveyance speed ( The take-up speed) is increased by 1.0 m/min, and the maximum speed at which the melt curtain of the resin composition does not tear from the end even after holding for 10 seconds is shown. The discharge amount of the resin composition from the die outlet of the extruder, the lip opening, and the die width may be appropriately adjusted. The maximum draw ratio can be determined by measuring, for example, by the method described in the example. Since the maximum draw ratio changes depending on the characteristics of the resin composition, it can be said to be a specific parameter of the resin composition.
Here, each unit of the items described in the above formula is (maximum drawable speed) [m/s], (flow velocity at die exit of extruder) [m/s], (discharge amount) [m ³ /S], (lip opening) [m] and (die width) [m], and (maximum draw ratio) is [no unit].

The oxygen permeability of the coating of the present invention at 23° C. and 50% RH (mL·20 μm/m ² ·atm·24 hr) is preferably 8.0 or less, more preferably 5.0 or less, and further preferably 4. It is 0 or less, particularly preferably 3.0 or less, more preferably 2.0 or less, and most preferably 1.0 or less. When the oxygen permeability of the coating is less than or equal to the above upper limit, excellent oxygen barrier properties can be exhibited. 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 amount measuring device after being stored at 23° C. and 50% RH for 2 weeks to adjust the humidity, and can be measured, for example, by the method described in Examples. Further, in the present specification, an improvement in oxygen barrier property means that the oxygen permeability is reduced, and an excellent oxygen barrier property means that the oxygen permeability is low.

The coating material 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 material of the present invention is preferably 2.0 or more, more preferably 3.0 or more, still more preferably 4.0 or more, and particularly preferably 5.0 or more. The adhesion strength (N/15 mm) is usually 10.0 or less. The adhesive strength can be measured using a tensile tester after being stored at 23° C. and 50% RH for 2 weeks to adjust the humidity, and can be measured, for example, by the method described in Examples.

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

In one embodiment of the present invention, in step (A), a resin composition, preferably a resin composition in the form of pellets, is allowed to absorb a specific amount of water, and then the obtained water-containing pellets are charged into an extruder. The water content (water content) in the water-containing pellets is preferably 0.1 to 50 mass% and more preferably 10 to 45 mass% with respect to the mass of the water-containing pellets. 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) and the screw diameter (D) is, for example, 15 to 50, and the rotation speed of the screw is preferably 80 rpm or more, More preferably, it is 100 rpm or more. The cylinder temperature in the extruder may be, for example, 80 to 120°C, preferably 90 to 110°C.

The resin composition charged in 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-out machine. A coated product is obtained by coating the conveyed paper or film with the resin composition discharged from the die outlet. The obtained coated product may be pressed against the substrate with a pressure roll or the like and wound into a roll by a winder. In the present specification, "coating" may be referred to as "coat".

In the step (A), the formula (1)
Draw ratio = (take-off speed of take-up machine) / (flow rate of die exit of extruder) (1)
The draw ratio represented by is preferably 5 to 20. When the coated product is produced with such a draw ratio, the productivity is improved, and the coated product having excellent adhesion and oxygen barrier property is easily obtained. The flow rate at the die outlet of the extruder is represented by (discharge amount)/((lip opening)×(die width)) as described above. When the discharge amount is expressed by 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 It is 0.1 to 1 mm, and the die width is preferably 100 to 3000 mm, more preferably 200 to 2000 mm.

[Multilayer structure and packaging material]
The present invention includes a multilayer structure including the coating of the present invention. The multilayer structure of the present invention can include layers other than coatings, such as films, papers or adhesives. These layers can be used alone or in combination of two or more. The multilayer structure of the present invention has a plurality of layers, but the number of layers is not particularly limited and may be, for example, 3 to 10 layers. Examples of the film and the paper include those exemplified as the film and the paper described in the section of [Coating].

Examples of the adhesive 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 thereof include adhesives, nitrile cellulose-based adhesives, phenol-based adhesives, polyvinyl alcohol-based adhesives, melamine-based adhesives and styrene-based adhesives.

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

The present invention includes a coating material of the present invention or a packaging material comprising a multilayer structure. Since the packaging material is excellent in oxygen barrier property, adhesiveness and biodegradability, it can be suitably used as a packaging material for food.

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

<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 content became 35% by mass with respect to the mass of the resin composition. During the addition of water, in order to prevent the pellets from sticking to each other and to absorb the water uniformly throughout the pellets, the mixture was stirred for 15 minutes with a tumbler mixer while adding water in several batches. After stirring, the mixture was placed in a polyethylene bag so as not to evaporate water, sealed, and allowed to stand at room temperature for 6 hours. The above-mentioned water content was confirmed by measuring at 130° C. for 60 minutes using a heat drying type water content meter “HR73” manufactured by METTLER TOLEDO.
The above water-containing pellets were put into a single-screw extruder shown in Table 1 below, extruded from a die for film formation, and coated on paper conveyed by a roller type take-up machine. The coated material obtained by coating was immediately pressed against the substrate with a pressure roll, and then wound into a roll with a winder.
・Single screw extruder: Extruder manufactured by Plastic Engineering Laboratory (40 mm diameter, L/D=25)
·Preset temperature:
・Discharge rate: 20 kg/hr
・Die: 450mm width coat hanger die, lip opening 0.2mm
・Die-cast roll distance (air gap): 150mm
・Paper: NIPPON PAPER CO., LTD. white silver (uncoated paper, thickness 70 μm)

Under the condition of a constant discharge amount, the paper conveyance speed was increased from 1.0 m/min to 1.0 m/min in increments of 1.0 m/min, 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 take-off speed. .. The maximum draw ratio was calculated based on the following formula.
(Maximum draw ratio) = (Maximum drawable speed) / (Velocity at the die exit of the extruder)
(Flow velocity at the die outlet of the extruder)=(Discharge amount)/((Lip opening)×(Die width))

(2) Measurement of oxygen permeability The coatings obtained in Examples and Comparative Examples were stored at 23° C. and 50% RH for 2 weeks to adjust the humidity, and then attached to an oxygen permeability measuring device to measure oxygen permeability. did. The measurement conditions were as follows.

(3) Evaluation of Adhesion to Paper The coated materials obtained in Examples and Comparative Examples were stored at 23° C. and 50% RH for 2 weeks to control the humidity, and then cut into 15 mm×100 mm strips. The adhesive strength between the paper and the resin composition (resin layer) was measured by pulling the resin composition peeled from the sheet.

(4) Method for measuring viscosity of hydrophobically modified starch (A-2) The moisture content of the hydrophobically modified starch (A-2) in Examples and Comparative Examples was measured using a heat drying moisture meter "HR73" manufactured by METTLER TOLEDO. It measured by heating at 130 degreeC for 30 minute(s), and calculated|required the dry mass. An aqueous solution was prepared so as to have a dry mass of 15% by mass, and gelatinized by stirring at 95°C for 5 minutes using "Rapid Viscocity Analyzer TecMaster" manufactured by NSP, and then cooled to 30°C. The viscosity at that time was measured and defined as the viscosity (30° C.) in a 15 mass% aqueous solution of the hydrophobically modified starch (A-2).

(5) Method for measuring viscosity of polyvinyl alcohol (B) According to JIS Z 8803 (falling ball viscometer) and JIS K 6726 (testing method for polyvinyl alcohol), 4% aqueous solutions of polyvinyl alcohol in Examples and Comparative Examples are prepared. Then, the viscosity at 20° C. was measured using a Hebrew viscometer, and the viscosity (20° C.) in a 4% aqueous solution of polyvinyl alcohol (B) was used.

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

<Hydrophobic modified starch (A-2)>
The hydrophobic modified starch shown in Table 2 was obtained by applying the following chemical modification method to the low amylose starch. The unmodified starch f is a starch to which the chemical modification method is not applied.

(Propylene oxide (PO) modification method)
4 g of solid sodium hydroxide was dissolved in 750 g of tap water and mixed until completely dissolved. Then 50 g of sodium sulfate was 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 uniform. Various levels of propylene oxide were added to the starch slurry and mixed for 1-2 minutes. The slurry was then transferred to a 2L plastic bottle and encapsulated. 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 then mixed for 30 minutes. Then dilute sodium hydroxide solution was added to adjust pH to 5.5-6.0. It was then collected by filtration and the resulting starch cake was washed with water (3 x 250 ml), spread on a bench and air dried. This produced a PO-modified starch.

(Octenyl maleic anhydride (OSA) modification method)
Into a 2 L plastic beaker, 500 g of raw starch and 750 ml of tap water were placed to make a slurry. The slurry was mixed with a stirrer while adjusting the pH to 7.5 by adding 3% sodium hydroxide solution. Stirring was continued while adding 15 g of octenyl maleic anhydride (OSA) every 30 minutes in three portions. The pH was maintained at 7.5 by adding 3% sodium hydroxide solution. The reaction was stirred until consumption of sodium hydroxide ceased (consumption was less than 1 ml in 10 minutes). The starch was then filtered through a Waltman #1 filter paper and the resulting starch washed with 750 ml tap water. The starch was then reslurried in 500 ml 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 make an OSA modified starch.

<Polyvinyl alcohol (B)>
-ELVANOL (registered trademark) 71-30: polyvinyl alcohol resin, saponification degree 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 mPas. -S (20°C, 4% aqueous solution), obtained from Kuraray-Kuraray Poval (registered trademark) 5-88: polyvinyl alcohol resin, saponification degree 88 mol%, viscosity 5 mPa-s (20°C, 4% aqueous solution), Kuraray Obtained from Kuraray Poval (registered trademark) 3-98: Polyvinyl alcohol resin, saponification degree 98 mol%, viscosity 3 mPa·s (20° C., 4% aqueous solution), obtained from Kuraray Co., Ltd.

<Example 1>
(Resin composition)
ECOFILM (registered trademark) (7.35 kg), OSA modified starch a (2.45 kg), and ELVANOL71-30 (200 g) were mixed as raw materials in a tumbler mixer for 2 hours, and the obtained mixture was connected to a liquid pump. Was subjected to the 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.

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

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

<Example 2>
Same as Example 1 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. To obtain a resin composition and a coating.

<Example 3>
As in Example 1, 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. To obtain a resin composition and a coating.

<Example 4>
As in Example 1, 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. To obtain a resin composition and a coating.

<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 the 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 the 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 the 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 the polyvinyl alcohol (B).

<Example 9>
Same as Example 1 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. To obtain a resin composition and a coating.

<Example 10>
Same as 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. To obtain a resin composition and a coating.

<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 hydrophobic 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 hydrophobic 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 coated product were obtained in the same manner as in Example 1 except that ECOFILM (registered trademark) (10.00 kg) was used as a 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 a raw material. Also, 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 the raw materials. Also, 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>
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 coating were obtained.

<Comparative example 6>
As in Example 1, 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. To obtain a resin composition. Also, 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 as the hydrophobic 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 as the hydrophobic 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 the unmodified starch f was used as the hydrophobically modified starch (A-2).

<Comparative Example 10>
As in Example 1, 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. To obtain a resin composition. Also, 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). Also, the resin composition could not be formed into a film.

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

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 the maximum draw ratio, the oxygen permeability, or both. Therefore, it was found that the coating of the present invention has a high maximum draw ratio during production and excellent oxygen barrier properties. Furthermore, it was also found that the coatings obtained in Examples 1 to 13 have excellent adhesion between the paper and the resin composition.

Claims (12)

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),
The modified starch (A) content is 40 to 98 parts by mass, and the polyvinyl alcohol (B) content is 2 to 60, based on the total of 100 parts by mass of the modified starch (A) and the polyvinyl alcohol (B). Resin composition which is a mass part. The modified starch (A) is different from the high amylose modified starch (A-1) and the high amylose modified starch (A-1) having an amylose content of 50% by mass or more, and a hydrophobic group having a hydrophobic group. The resin composition according to claim 1, comprising the modified starch (A-2). The resin composition according to claim 2, wherein the hydrophobically modified starch (A-2) has an amylose content of less than 50% by mass. The resin composition according to claim 1, wherein the hydrophobic group is a modified group with a hydrophobic compound having 6 to 24 carbon atoms. The high amylose modified starch (A-1) is at least one kind selected from etherified starch having a hydroxyalkyl group and esterified starch having a carboxylic acid anhydride modified group. The resin composition according to. The hydrophobic 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 anhydride modifying group having 6 to 24 carbon atoms. The resin composition according to claim 2, which is at least one kind. 7. The hydrophobically modified starch (A-2) has a viscosity of 1000 cP or less when cooled to 30° C. after gelatinizing a 15 mass% aqueous solution by stirring at 95° C. for 5 minutes. The resin composition according to any of the above. The said polyvinyl alcohol (B) is the resin composition in any one of Claims 1-7 whose viscosity in 20 degreeC of a 4% aqueous solution measured based on JISZ8803 is 1-50 mPa*s. A coated article obtained by coating the resin composition according to any one of claims 1 to 8 on paper or a film. A multilayer structure comprising the coating according to claim 9. A packaging material comprising the coating according to claim 9 or the multilayer structure according to claim 10. A step of coating the resin composition according to any one of claims 1 to 8 on a film or paper conveyed by a take-off machine using an extruder, wherein the formula (1) is used.
Draw ratio = (take-off speed of take-up machine) / (flow rate of die exit of extruder) (1)
The method for producing a coated article according to claim 9, wherein the draw ratio represented by is 5 to 20.