WO2021210555A1

WO2021210555A1 - Modified vinyl-alcohol-based polymer

Info

Publication number: WO2021210555A1
Application number: PCT/JP2021/015246
Authority: WO
Inventors: 啓之小西; 由貴清水; 佐和子小林; 彰久綿島
Original assignee: 株式会社クラレ
Priority date: 2020-04-14
Filing date: 2021-04-13
Publication date: 2021-10-21
Also published as: TW202146480A; JP2023085574A

Abstract

This modified vinyl-alcohol-based polymer is represented by the following formula (I), wherein the contents, a (mol%), b (mol%), and c (mol%), of the respective monomer units with respect to all the monomer units satisfy the following relationships (1)-(3). Such modified vinyl-alcohol-based polymer is excellent in terms of barrier property, water solubility, and melt shapability. Coating materials including said modified vinyl-alcohol-based polymer bring about excellent production efficiency when applied and can form films retaining high water-vapor barrier properties.　(1) 10≤a≤20 (2) 1≤c≤15 (3) [100-(a+c)]×0.9≤b≤[100-(a+c)] [In formula (I), X, Y, and Z each independently represent a hydrogen atom, a formyl group, or an alkanoyl group having 2-10 carbon atoms.]

Description

Modified vinyl alcohol polymer

The present invention relates to a vinyl alcohol-based polymer having a gas barrier property, which is suitably used for packaging, particularly as a film for food packaging, and a coating agent using the same.

Oxygen gas barrier film and packaging materials using it are well known. Aluminum (hereinafter sometimes abbreviated as "Al") foil is an example of a material having an oxygen gas barrier property, but since pinholes are likely to occur, the aluminum foil alone cannot be used except in special cases. Therefore, the aluminum foil is often used as an intermediate layer of the laminated film. The gas barrier property of this laminated film is good, but there are drawbacks such as the contents cannot be seen because it is opaque and it is difficult to recycle.

As other oxygen gas barrier films, a single-layer film of polyvinylidene chloride (hereinafter sometimes abbreviated as "PVDC") and a film coated with PVDC are known. In particular, the latter is widely used as a food packaging material that requires a barrier property against oxygen gas and water vapor. PVDC has almost no hygroscopicity and maintains good gas barrier properties even under high humidity, so it is coated on various substrates. As the base material, for example, films such as biaxially stretched polypropylene (OPP), biaxially stretched nylon (ON), biaxially stretched polyethylene terephthalate (OPET), and cellophane are used. The laminated film in which the base material is coated with PVDC has a gas barrier property, and is used for packaging various foods such as dried products and water products. However, these packaging materials are discarded as general waste from households after use, but since it is difficult to recycle the laminated film containing the PVDC layer by melt molding, the movement of non-use is spreading.

As an oxygen gas barrier film compatible with recycling, a film formed by forming a thin film on a substrate film by depositing a metal oxide has been proposed. For example, Patent Document 1 discloses a gas barrier film as a packaging material for water foods, which is provided with a thin film mainly composed of silicon oxide and having a specific gravity of 1.80 to 2.20 on at least one side of a plastic base material. Has been done. However, there is a problem that the film is easily cracked when bent and the barrier performance is easily lost.

Further, a polyvinyl alcohol (hereinafter sometimes abbreviated as "PVA") film is also well known as an oxygen gas barrier film. The PVA film has a very good oxygen gas barrier property when the amount of moisture absorption is small, but has a hygroscopic property, and the water vapor barrier property is not sufficient, so that the use tends to be limited. Further, an ethylene-vinyl alcohol copolymer obtained by copolymerizing ethylene in order to reduce hygroscopicity has been proposed. For example, Patent Document 2 states that the viscosity average degree of polymerization is 100 to 1000, the ratio Pw / Pn of the weight average degree of polymerization Pw to the number average degree of polymerization Pn is 2.4 or more, and the number of carbon atoms is 4 or less. A coating agent for a gas barrier made of a polyvinyl alcohol-based polymer containing 2 to 19 mol% of an olefin unit is disclosed. However, the resin used for the coating agent has problems such as poor solubility in water, poor stability in an aqueous solution state, and easy generation of agglomerates.

Further, Patent Document 3 describes that the modified vinyl alcohol-based polymer having a 1,3-diol structure in the main chain is excellent in water solubility and water resistance of the film, and is also excellent in thermoforming property. However, the polymer has insufficient melt moldability, water vapor barrier property, or water solubility, and it is difficult to satisfy all of them. Moreover, when used as a coating agent, the solid content concentration In some cases it was difficult to increase. Further, Patent Document 4 discloses an ethylene-vinyl ester-based copolymer saponified product containing a structural unit having an ethylene structural unit of 10 mol% or more and less than 20 mol% and having a primary hydroxyl group in a side chain. .. However, the polymer is used for a hose for hydrogen gas, a storage container, etc., and there is no description about the water vapor barrier property, and there is no description about using the polymer as an aqueous solution.

JP-A-6-344492 Japanese Patent Application Laid-Open No. 2000-204311 JP 2015-34262 JP 2016-69481

The present invention has been made to solve the above problems, and provides a modified vinyl alcohol polymer having excellent barrier properties, water solubility and melt moldability, and also having excellent productivity when used as a coating agent. The purpose is to provide. In particular, it is an object of the present invention to suppress a decrease in water vapor barrier property, which has been a problem of a film using a vinyl alcohol-based polymer having hygroscopicity.

As a result of diligent studies by the present inventors, it was found that the above problems can be solved by the embodiments described below, and the present invention has been completed.

The above problem is represented by the following formula (I), and the contents a (mol%), b (mol%) and c (mol%) of each monomer unit with respect to all the monomer units are represented by the following formula (1). This is solved by providing a modified vinyl alcohol-based polymer that satisfies the above (3).
10 ≦ a ≦ 20 (1)
1 ≦ c ≦ 15 (2)
[100- (a + c)] × 0.9 ≦ b ≦ [100- (a + c)] (3)

[In formula (I), X, Y and Z each independently represent a hydrogen atom, a formyl group or an alkanoyl group having 2 to 10 carbon atoms. ]

The number average degree of polymerization Pn of the modified vinyl alcohol polymer is preferably 200 to 950.

It is also preferable that a and c satisfy the following formula (4).
ac ≤ 10 (4)

It is also preferable that X, Y and Z are independently hydrogen atoms or acetyl groups.

It is also preferable that the degree of saponification of the modified vinyl alcohol polymer is 90 to 99.99 mol%.

A coating agent containing the modified vinyl alcohol-based polymer and a solvent, wherein the solvent is composed of at least one of water or an aliphatic alcohol having 1 to 4 carbon atoms, is a preferred embodiment of the present invention. A more preferred embodiment is a multilayer film obtained by applying the coating agent to a base film.

The above problem is also solved by providing a composition containing a modified vinyl alcohol-based polymer and sodium acetate in an amount of 0.01 to 2% by mass.

The modified vinyl alcohol polymer of the present invention is excellent in barrier property, water solubility and melt moldability. The coating agent using the modified vinyl alcohol-based polymer is excellent in productivity at the time of coating, and the formed film maintains a high water vapor barrier property.

The modified vinyl alcohol polymer of the present invention is represented by the following formula (I).

The modified vinyl alcohol-based polymer of the present invention contains an ethylene unit [unit shown at the left end of formula (I)]. The ethylene unit can impart a high barrier property to the polymer, and can impart a high water vapor barrier property particularly even under high humidity.

The modified vinyl alcohol-based polymer of the present invention contains a monomer unit containing X in the side chain [unit shown in the center of formula (I)] (hereinafter, may be referred to as a monomer unit containing X). do. The monomer unit containing X can impart water solubility and water vapor barrier property to the polymer.

The modified vinyl alcohol-based polymer of the present invention may be referred to as a monomer unit containing Y and Z in the side chain [unit shown at the right end of the formula (I)] (hereinafter, referred to as a monomer unit containing Y and Z). There is). By containing the monomer unit containing Y and Z, the crystallinity of the polymer is lowered, so that the handleability such as water solubility, viscosity stability and melt moldability is improved. On the other hand, usually, when the crystallinity decreases, the barrier property of the vinyl alcohol polymer decreases, but surprisingly, the modified vinyl alcohol polymer of the present invention can maintain the barrier property, and particularly high water vapor even under high humidity. Maintain barrier properties. The effect is that the monomer unit containing Y and Z contains one quaternary carbon constituting the main chain of the modified vinyl alcohol polymer, so that the mobility is low, and Y and Y in the monomer unit It is considered that this is due to the high hydrogen bonding force derived from Z.

In formula (I), X, Y and Z each independently represent a hydrogen atom, a formyl group or an alkanoyl group having 2 to 10 carbon atoms. When X, Y or Z is a hydrogen atom, the formula (I) has a hydroxyl group, and when X, Y or Z is a formyl group or an alkanoyl group, the formula (I) has an ester group. .. The alkanoyl group is preferably an alkanoyl group having 2 to 5 carbon atoms, and an acetyl group, a propanoyl group, a butanoyl group and the like are exemplified as suitable ones. Of these, the acetyl group is particularly suitable. It is preferable that X, Y and Z are all hydrogen atoms or contain hydrogen atoms.

The monomer unit containing X is usually obtained by saponifying the vinyl ester unit in the polymer. It is preferable that the modified vinyl alcohol-based polymer contains a vinyl alcohol unit in which X is a hydrogen atom as the monomer unit containing X. Further, it is also preferable that the modified vinyl alcohol polymer contains a vinyl ester unit in which X is a formyl group or an alkanoyl group having 2 to 10 carbon atoms as the monomer unit containing X. Further, as the monomer unit in which the modified vinyl alcohol polymer contains X, both a vinyl alcohol unit in which X is a hydrogen atom and a vinyl ester unit in which X is a formyl group or an alkanoyl group having 2 to 10 carbon atoms are used. It is more preferable to include it.

When a monomer unit containing X is obtained through saponification, the vinyl ester unit is preferably a vinyl acetate unit in consideration of the availability of the monomer and the production cost. For example, when a polymer having a vinyl acetate unit is partially saponified, the monomer unit containing X contains both a vinyl alcohol unit in which X is a hydrogen atom and a vinyl acetate unit in which X is an acetyl group. A polymer can be obtained.

The content of the vinyl alcohol unit in the modified vinyl alcohol polymer is preferably 80 to 99.99 mol% with respect to the total amount of the monomer units containing X. The content is more preferably 90 mol% or more, further preferably 95 mol% or more. On the other hand, the content is more preferably 99.95 mol% or less, further preferably 99.90 mol% or less.

The content of the vinyl ester unit in the modified vinyl alcohol polymer is preferably 0.01 to 20 mol% with respect to the total amount of the monomer unit containing X. The content is more preferably 0.05 mol% or more, still more preferably 0.10 mol% or more. On the other hand, the content is more preferably 10 mol% or less, further preferably 5 mol% or less.

The monomer unit containing Y and Z can also be produced by copolymerizing an unsaturated monomer unit having a 1,3-diester structure and then saponifying it, or a non-saturated monomer unit having a 1,3-diol structure. It can also be produced by copolymerizing saturated monomer units. It is preferable that the modified vinyl alcohol-based polymer contains a unit of a hydrogen atom in Y and Z as a monomer unit containing Y and Z. It is also preferable that the modified vinyl alcohol polymer contains a unit in which Y is a hydrogen atom and Z is a formyl group or an alkanoyl group having 2 to 10 carbon atoms as the monomer unit containing Y and Z. Further, it is also preferable that the modified vinyl alcohol polymer contains a unit in which Y and Z are a formyl group or an alkanoyl group having 2 to 10 carbon atoms as the monomer unit containing Y and Z. Further, in the modified vinyl alcohol-based polymer, Y and Z are hydrogen atom units, Y is a hydrogen atom, and Z is a formyl group or an alkanoyl group having 2 to 10 carbon atoms as monomer units containing Y and Z. It is more preferable to include all the units in which Y and Z are formyl groups or alkanoyl groups having 2 to 10 carbon atoms.

For example, when a polymer having 1,3-diacetoxy-2-methylenepropane (DAMP) unit is partially saponified to obtain a monomer unit containing Y and Z, the monomer unit containing Y and Z is used. Obtain a polymer containing a unit in which Y and Z are hydrogen atoms, a unit in which Y is a hydrogen atom and Z is an acetyl group, and a unit in which Y and Z are a formyl group or an alkanoyl group having 2 to 10 carbon atoms. be able to.

The content of the hydrogen atom among Y and Z in the modified vinyl alcohol polymer with respect to the total amount of Y and Z is preferably 80 to 99.99 mol%. The content is more preferably 90 mol% or more, further preferably 95 mol% or more. On the other hand, the content is more preferably 99.95 mol% or less, further preferably 99.90 mol% or less.

The total content of Y and Z having a formyl group and an alkanoyl group having 2 to 10 carbon atoms is 0.01 to 20 mol% with respect to the total amount of Y and Z in the modified vinyl alcohol polymer. Is preferable. The content is more preferably 0.05 mol% or more, still more preferably 0.10 mol% or more. On the other hand, the content is more preferably 10 mol% or less, further preferably 5 mol% or less.

The bonding form of each monomer unit represented by the formula (I) is not particularly limited, and the modified vinyl alcohol-based polymer of the present invention may be a random copolymer or a block copolymer. , A graft copolymer may be used, but a random copolymer is preferable from the viewpoint of easy production.

In the present invention, the contents a (mol%), b (mol%) and c (mol%) of each monomer unit with respect to all the monomer units in the modified vinyl alcohol polymer are the following formulas (1) to It is necessary to satisfy (3).
10 ≦ a ≦ 20 (1)
1 ≦ c ≦ 15 (2)
[100- (a + c)] × 0.9 ≦ b ≦ [100- (a + c)] (3)

A in the above formulas (1) and (3) is the content rate (mol%) of ethylene units with respect to all monomer units. The content rate a is 10 to 20 mol%. When the content a is 10 mol% or more, good water vapor barrier property can be obtained. From this viewpoint, the content a is preferably 11 mol% or more, more preferably 12 mol% or more, further preferably 13 mol% or more, particularly preferably 14 mol% or more, and most preferably. It is 15 mol% or more. On the other hand, when the content of ethylene unit a is 20 mol% or less, the water solubility is enhanced, so that a stable solution can be obtained. The content a is preferably 19 mol% or less, more preferably 18 mol% or less, and particularly preferably 17 mol% or less. The contents a, b and c can be determined by a nuclear magnetic resonance (NMR) method.

C in the above formulas (2) and (3) is the content ratio (mol%) of the monomer units including Y and Z with respect to all the monomer units. The content c is 1 to 15 mol%. When the content c is 1 mol% or more, the water solubility of the modified vinyl alcohol polymer is increased, and when it is used as an aqueous solution, the viscosity stability is improved and foaming is difficult. Further, since the modified vinyl alcohol polymer can be melt-molded at a low temperature, it is excellent in decomposition resistance during thermoforming. Further, the strength of the obtained film under high humidity is improved. From these viewpoints, the content c is preferably 1.5 mol% or more, more preferably 2 mol% or more, further preferably 3 mol% or more, particularly preferably 4 mol or more, and most. It is preferably 4.5 mol% or more. On the other hand, when the content c exceeds 15 mol%, the polymerization rate is remarkably lowered, so that it tends to be difficult to synthesize industrially. The content c is preferably 12 mol% or less, and more preferably 10 mol% or less.

Reference numeral b in the above formula (3) is the content rate (mol%) of the monomer unit containing X with respect to all the monomer units. That is, according to the above formula (3), in the modified vinyl alcohol-based polymer of the present invention, 90 mol% or more of the monomer units other than the ethylene unit and the monomer unit containing Y and Z is X. It becomes a monomer unit containing. Examples of the monomer unit containing X include a vinyl alcohol unit and a vinyl ester unit. If the formula (3) is not satisfied, the water vapor barrier property becomes insufficient. The following formula (3') is preferably satisfied, and more preferably the following formula (3 ") is satisfied.
[100- (a + c)] x 0.95 ≤ b ≤ [100- (a + c)] (3')
[100- (a + c)] x 0.98 ≤ b ≤ [100- (a + c)] (3 ")

In the present invention, it is preferable that a and c satisfy the following formula (4). As a result, the water solubility of the modified vinyl alcohol polymer is further enhanced. This is water-soluble by increasing the content c of the monomer unit containing Y and Z and satisfying the following formula (4) even when the content a of the ethylene unit having a relatively high hydrophobicity is high. This is because it can be improved.
ac ≤ 10 (4)

The number average degree of polymerization Pn of the modified vinyl alcohol-based polymer of the present invention is preferably 200 to 950. When Pn is 200 or more, the strength of the film obtained from the modified vinyl alcohol-based polymer of the present invention is improved. Pn is more preferably 300 or more, still more preferably 350 or more. On the other hand, when Pn is 950 or less, the viscosity of the solution of the modified vinyl alcohol-based polymer does not become too high, so that the solution stability is further improved. Pn is more preferably 800 or less, still more preferably 600 or less. The number average degree of polymerization Pn and the weight average degree of polymerization Pw of the modified vinyl alcohol polymer are measured by gel permeation chromatography (GPC). Specifically, Pn is obtained by the method described in the examples. At this time, measurement is carried out at 40 ° C. using monodisperse polymethylmethacrylate (PMMA) as a standard and hexafluoroisopropanol (HFIP) containing 20 mmol / liter sodium trifluoroacetate as a mobile phase. Pn can be adjusted by, for example, the amount of solvent when a polymer is produced by radical polymerization or the addition of a chain transfer agent.

The weight average degree of polymerization Pw of the modified vinyl alcohol-based polymer of the present invention is preferably 300 to 2000. When Pw is 300 or more, the strength of the film obtained from the modified vinyl alcohol-based polymer of the present invention is improved. Pw is more preferably 350 or more, still more preferably 400 or more, and most preferably 450 or more. On the other hand, when Pw is 2000 or less, the viscosity of the solution of the modified vinyl alcohol-based polymer does not become too high, so that the solution stability is further improved. Pw is more preferably 1500 or less, still more preferably 1300 or less, and most preferably 950 or less. Pw can be adjusted by, for example, the amount of solvent when a polymer is produced by radical polymerization or the addition of a chain transfer agent.

The saponification degree of the modified vinyl alcohol polymer of the present invention is not particularly limited, but is preferably 80 to 99.99 mol%. If the saponification degree is less than 80 mol%, sufficient water vapor barrier property may not be obtained. The degree of saponification is more preferably 90 mol% or more, further preferably 95 mol% or more. On the other hand, those having a saponification degree of more than 99.99 mol% may be difficult to obtain industrially. The degree of saponification is more preferably 99.95 mol% or less, further preferably 99.90 mol% or less. In the present invention, the saponification degree is defined by the DS represented by the following formula (5), and specifically, it is calculated from the measurement result of NMR.
DS = [(total number of moles of hydrogen atom among X, Y and Z) / (total number of moles of X, Y and Z)] × 100 (5)
Here, "the total number of moles of X, Y and Z that are hydrogen atoms" indicates the number of moles of the hydroxyl group, and "the total number of moles of X, Y and Z" is the total number of moles of the hydroxyl group and the ester group. Is shown.

The method for producing the modified vinyl alcohol polymer of the present invention is not particularly limited. For example, ethylene, a vinyl ester represented by the following formula (II), and a modified ethylene-vinyl ester copolymer represented by the following formula (IV) by radical polymerization of an unsaturated monomer represented by the following formula (III). After obtaining, there is a method of polymerizing it. The bonding form of each monomer unit in the modified ethylene-vinyl ester copolymer represented by the following formula (IV) is not particularly limited, and the copolymer may be a random copolymer or a block copolymer. It may be a graft copolymer or a graft copolymer, but a random copolymer is preferable from the viewpoint of easy production.

In formula (II), R ¹ represents a hydrogen atom or an alkyl group having 1 to 9 carbon atoms. The alkyl group preferably has 1 to 4 carbon atoms. Examples of the vinyl ester represented by the formula (II) include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatic acid, vinyl caproate and the like. Vinyl acetate is particularly preferred from an economic point of view.

In formula (III), R ² and R ³ independently represent a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, respectively. The alkyl group preferably has 1 to 4 carbon atoms. Examples of the unsaturated monomer represented by the formula (III) include 1,3-diacetoxy-2-methylenepropane (DAMP), 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyronyloxy. -2-Methylenepropane and the like. Of these, 1,3-diacetoxy-2-methylenepropane (DAMP) is preferably used because it is easy to produce.

[In formula (IV), R ¹ , R ² and R ³ are the same as in formulas (II) and (III). In formula (IV), a represents the content of ethylene units (mol%), b represents the content of vinyl ester-derived units represented by formula (II) (mol%), and c represents the content of formula (III). The content rate (mol%) of the unit derived from the unsaturated monomer represented by is shown. ]

A modified ethylene-vinyl ester copolymer represented by the formula (IV) by copolymerizing ethylene, a vinyl ester represented by the above formula (II), and an unsaturated monomer represented by the above formula (III). The polymerization method for producing the above may be any of batch polymerization, semi-batch polymerization, continuous polymerization, and semi-continuous polymerization. Further, as the polymerization method, known methods such as a massive polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be adopted. A massive polymerization method or a solution polymerization method in which the polymerization proceeds without a solvent or in a solvent such as alcohol is usually adopted. When obtaining a modified ethylene-vinyl ester copolymer having a high degree of polymerization, the adoption of an emulsion polymerization method is one of the options.

The solvent used in the solution polymerization method is not particularly limited, but alcohol is preferably used, and for example, lower alcohols such as methanol, ethanol, and propanol are more preferably used. The amount of the solvent used in the polymerization reaction solution may be selected in consideration of the viscosity average degree of polymerization of the target modified vinyl alcohol polymer and the chain transfer of the solvent, and the solvent contained in the reaction solution and all the monomers. The mass ratio with and (solvent / total monomer) is selected from the range of 0.01 to 10, preferably 0.05 to 3.

The polymerization initiator used when copolymerizing ethylene, the vinyl ester represented by the above formula (II), and the unsaturated monomer represented by the above formula (III) is a known polymerization initiator, for example. It is selected from an azo-based initiator, a peroxide-based initiator, and a redox-based initiator according to the polymerization method. Examples of the azo-based initiator include 2,2-azobisisobutyronitrile, 2,2-azobis (2,4-dimethylvaleronitrile), and 2,2-azobis (4-methoxy-2,4-dimethylvaleronitrile). Nitrile). Examples of the peroxide-based initiator include percarbonate-based compounds such as diisopropylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethylperoxydicarbonate; t-butylperoxyneodecanate, α. -Perester compounds such as cumyl peroxyneodecanate and acetyl peroxide; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and the like. Potassium persulfate, ammonium persulfate, hydrogen peroxide and the like may be used in combination with the above initiator. The redox-based initiator is, for example, a polymerization initiator that is a combination of the above-mentioned peroxide-based initiator and a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, and longalit. The amount of the polymerization initiator used varies depending on the polymerization catalyst and cannot be unconditionally determined, but is adjusted according to the polymerization rate. The amount of the polymerization initiator used is preferably 0.01 to 0.2 mol%, more preferably 0.02 to 0.15 mol%, based on the vinyl ester represented by the above formula (II). The polymerization temperature is not particularly limited, but is appropriately about room temperature to 150 ° C., preferably 40 ° C. or higher and lower than the boiling point of the solvent used.

When copolymerizing ethylene, the vinyl ester represented by the above formula (II), and the unsaturated monomer represented by the above formula (III), a chain is provided as long as the effect of the present invention is not impaired. Copolymerization may be carried out in the presence of a transfer agent. Examples of the chain transfer agent include aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; and phosphinates such as sodium phosphinate monohydrate. .. Of these, aldehydes and ketones are preferably used. The amount of the chain transfer agent added to the polymerization reaction solution is determined according to the chain transfer coefficient of the chain transfer agent and the degree of polymerization of the target modified ethylene-vinyl ester copolymer, but is generally determined by the above formula (II). 0.1 to 10 parts by mass is preferable with respect to 100 parts by mass of the vinyl ester shown.

The modified ethylene-vinyl ester copolymer thus obtained can be saponified to obtain the modified vinyl alcohol-based polymer of the present invention. At this time, the vinyl ester unit derived from the vinyl ester represented by the formula (II) in the copolymer is converted into a vinyl alcohol unit. In addition, the ester bond derived from the unsaturated monomer represented by the formula (III) is also hydrolyzed at the same time and converted into a 1,3-diol structure. In this way, different types of ester groups can be hydrolyzed at the same time by a single saponification reaction.

As a saponification method for the modified ethylene-vinyl ester copolymer, a known method can be adopted. The saponification reaction is usually carried out in a solution of alcohol or hydrous alcohol. The alcohol preferably used at this time is a lower alcohol such as methanol and ethanol, and particularly preferably methanol. The alcohol or hydrous alcohol used in the saponification reaction may contain other solvents such as acetone, methyl acetate, ethyl acetate and benzene as long as it is 40% by mass or less by mass. The catalyst used for saponification is, for example, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methylate, or an acid catalyst such as mineral acid. The temperature at which saponification is performed is not limited, but is preferably in the range of 20 to 120 ° C. When a gel-like product is precipitated as the saponification progresses, the product can be pulverized, washed and dried to obtain a modified vinyl alcohol-based polymer.

The modified vinyl alcohol-based polymer of the present invention includes ethylene, the vinyl ester represented by the above formula (II), and the unsaturated monomer represented by the above formula (III) as long as the effects of the present invention are not impaired. It may contain structural units derived from other ethylenically unsaturated monomers copolymerizable with. Examples of such ethylenically unsaturated monomers include α-olefins such as propylene, n-butene, isobutylene, and 1-hexene; allyl acid and salts thereof; and unsaturated monomers having an allyl ester group. Methacrylic acid and its salts; Unsaturated monomers having a methacrylic ester group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamide propanesulfonic acid and its salts, Acrylpropyl dimethylamine and its salts (eg, quaternary salts); methalkylamide, N-methylmethacrylamide, N-ethylmethacrylate, methallylamide propanesulfonic acid and its salts, methacrylicamidopropyldimethylamine and its salts (eg, quaternary). Salt); 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-vinyloxy Vinyl ethers such as propane; vinyl cyanide 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 -Allyl compounds such as diacetoxy-1-allyloxypropane and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid and salts or esters thereof; vinylsilane compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like. Can be mentioned.

The modified vinyl alcohol polymer of the present invention may have a carboxyl group, a sulfonic acid group, an amino group or a salt thereof at the side chain or the molecular terminal as long as the performance of the present invention is not impaired. The amount of modification is usually 0.05 to 10 mol% with respect to all the monomer units of the modified vinyl alcohol-based polymer of the present invention.

The modified vinyl alcohol-based polymer of the present invention may be used alone, but it can also be used as a composition by blending other copolymers and additives. Examples of other copolymers include polyvinyl alcohol and ethylene-vinyl alcohol copolymers that do not contain monomer units containing Y and Z. Examples of other additives include inorganic salts, organic salts, cross-linking agents, solvents, ultraviolet absorbers, antioxidants, antistatic agents, plasticizers, fungicides, preservatives and the like. Two or more of these may be used in combination.

Examples of the composition include a composition containing the modified vinyl alcohol-based polymer of the present invention and sodium acetate. The content of sodium acetate in the composition at this time is preferably 0.01 to 2% by mass, more preferably 0.02 to 1% by mass, still more preferably 0.03 to 0.5% by mass. Most preferably, it is 0.35 to 0.45% by mass. When the content is in such a range, the water vapor barrier property is further improved. The modified vinyl alcohol-based polymer of the present invention and sodium acetate may be mixed to form a composition, or the sodium acetate produced in the saponification step during the production of the modified vinyl alcohol-based polymer of the present invention may be left and used. good.

Examples of the composition include a composition containing the modified vinyl alcohol-based polymer of the present invention and a known cross-linking agent. Water resistance can be imparted to the composition by including a cross-linking agent. Examples of the cross-linking agent include epoxy compounds, isocyanate compounds, aldehyde compounds, silica compounds, aluminum compounds, boron compounds, zirconium compounds and the like, and silica compounds such as colloidal silica and alkyl silicates and zirconium compounds are preferably used. The content of the cross-linking agent in the composition is not particularly limited as long as it does not impair the characteristics of the present invention, but is usually 1 to 60 parts by mass with respect to 100 parts by mass of the modified polyvinyl alcohol-based polymer. If the content of the cross-linking agent exceeds 60 parts by mass, the water vapor barrier property may be adversely affected. The cross-linking agent may coexist with the sodium acetate described above.

The content of the modified vinyl alcohol polymer in the composition is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 50% by mass or more, and particularly preferably 60% by mass or more.

Another preferred embodiment of the composition is a coating agent. The coating agent is a coating agent containing the modified vinyl alcohol-based polymer of the present invention and a solvent, and the solvent comprises at least one of water or an aliphatic alcohol having 1 to 4 carbon atoms.

The concentration of the modified vinyl alcohol polymer in the coating agent is not particularly limited, but is preferably 5 to 50% by mass. If the concentration is less than 5% by mass, the drying load may increase. The concentration is more preferably 8% by mass or more, further preferably 10% by mass or more. On the other hand, when the concentration exceeds 50% by mass, the viscosity becomes too high and the handleability may become a problem.

The aliphatic alcohol is not particularly limited as long as it is water-soluble, but methanol, ethanol, isopropyl alcohol, n-propyl alcohol and the like are preferably used. From the viewpoint of further increasing the solubility of the modified vinyl alcohol-based polymer, it is preferable that the solvent used for the coating agent is water or a mixed solution of water and the aliphatic alcohol. From the same viewpoint, the upper limit of the ratio of the aliphatic alcohol to the total solvent in the coating agent is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 20% by mass or less. Yes, particularly preferably 10% by mass or less. On the other hand, when the coating agent contains the aliphatic alcohol, the lower limit of the content thereof is not particularly limited, but is preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 2 It is mass% or more.

The coating agent may contain additives other than the modified vinyl alcohol polymer and the solvent. Preferred examples of other additives include surfactants, leveling agents and the like. The content of the modified vinyl alcohol-based polymer and the components other than the solvent in the coating agent is usually 30% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less.

The temperature of the coating agent at the time of coating is preferably 20 to 80 ° C. As the coating method, known methods such as a gravure roll coating method, a reverse gravure coating method, a reverse roll coating method, and a Meyer bar coating method are preferably used.

A multilayer film formed by applying the coating agent to a base film is a more preferred embodiment of the present invention.

Examples of the base film include polyolefin films, polyester films, polyamide films and the like. As these base films, those conventionally known are preferably used, and the structure of the base films such as syndiotactic and isotactic is not limited.

The thickness of the layer containing the modified vinyl alcohol polymer formed by applying the coating agent is not particularly limited, but is usually 0.1 to 30 μm.

A known anchor coat layer may be provided between the layer containing the modified vinyl alcohol polymer and the base film.

After applying the coating agent to the base film, stretching, heat treatment, etc. can be freely applied. The draw ratio, heat treatment temperature, etc. differ depending on the base film, but may be in a known range.

After forming a layer containing the modified vinyl alcohol-based polymer on the base film, a heat-sealing resin layer may be further formed on the layer containing the modified vinyl alcohol-based polymer. The heat-sealed resin layer is usually formed by an extrusion laminating method or a dry laminating method. Examples of the heat-sealed resin include polyethylene such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), polypropylene, ethylene-vinyl acetate copolymer, and ethylene / α-olefin random common weight. Known heat-sealing resins such as coalesced and ionomer are used.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "%" and "parts" in Examples and Comparative Examples represent "mass%" and "parts by mass", respectively.

[ ^{1 1} H-NMR]
Primary structure of modified vinyl alcohol-based polymer (hereinafter, may be simply referred to as polymer) [Contents of each monomer unit a (mol%), b (mol%), c (mol%) and degree of saponification (Mole%)] was ^{quantified by 500 MHz 1} H-NMR. ¹ DMSO-d6 was used as the solvent for the polymer during 1 H-NMR measurement.

[Number average degree of polymerization and weight average degree of polymerization]
The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer were measured using a size exclusion high performance liquid chromatograph "HLC-8320GPC" manufactured by Tosoh Corporation. The measurement conditions are as follows.
Column: HFIP-based column "GMHRH-H (S)" manufactured by Tosoh Corporation, connected in series Standard sample: Polymethylmethacrylate Solvent and mobile phase: Sodium trifluoroacetate-HFIP solution (concentration 20 mM)
Flow rate: 0.2 mL / min
Temperature: 40 ° C
Sample solution concentration: 0.1% by mass (filtered with a 0.45 μm opening diameter filter)
Injection volume: 10 μL
Detector: RI

The number average degree of polymerization Pn and the weight average degree of polymerization Pw of the polymer were calculated by the following formulas.
Pn = Mn × 100 / (28 × a + 44 × b + 88 × c)
Pw = Mw × 100 / (28 × a + 44 × b + 88 × c)

[Saponification degree]
The degree of saponification was determined from the result of measuring the polymer by ^{1 1 H-NMR.}

[Water vapor barrier property]
An aqueous polymer solution having a concentration of 10% was prepared, coated on a PET film, dried at 60 ° C. for 1 hour, and peeled off from the PET film to obtain a single-layer film having a thickness of 30 μm. With reference to JIS Z0208: 1976 Moisture Permeability Test Method (Cup Method) for Moisture-Proof Packaging Materials, the amount of water vapor that passed through the film per unit time at 40 ° C. and 90% RH was adsorbed on calcium chloride in the cup. After obtaining by measuring the mass of water, the moisture permeability (g · 30 μm / [m ² · day]) was calculated from the obtained value. The value at the time when the value was measured at predetermined time intervals and became stable was adopted (the average value of n = 2).

[Melting formability]
Polymer pellets were produced by extruding under the following molding temperature conditions, and the minimum temperature at which the polymer could be melt-molded and the decomposition resistance at that temperature were evaluated based on the following criteria. The set temperature (cylinder portion) was adjusted in the range of 180 to 240 ° C. according to the type of polymer, and the lowest temperature at which melt molding was possible within the range was adopted as the molding temperature.
・ Pelletization condition Extruder: Labplast mill screw manufactured by Toyo Seiki Seisakusho Co., Ltd .: 2-axis same direction, 25 mmφ, L / D = 26
Discharge rate: 3.0 kg / hr
Set temperature (cylinder): 180-240 ° C
Set temperature (die part): 130 ° C
A: No smoke was emitted during molding, and no decomposition odor was generated.
B: Smoke was emitted to the extent that it could be molded, but no decomposition odor was generated.
C: Smoke was emitted during molding, and a decomposed odor was also generated.

[Water solubility of film]
A polymer aqueous solution having a concentration of 10% was prepared, cast on a PET film, dried at 20 ° C. for 1 week, further dried in a vacuum dryer for 16 hours, and peeled from the PET film to a thickness of 100 μm. A single layer film was obtained. 100 mL of ion-exchanged water was added to a 100 mL beaker and the temperature was controlled to 60 ° C. The elution rate of the modified vinyl alcohol polymer into the aqueous layer after immersing the film (size: 30 mm × 40 mm, thickness 100 μm) in the ion-exchanged water for 1 hour without stirring was measured and evaluated in the following three steps. bottom.
A: The elution rate was 70% or more.
B: The elution rate was 30% or more and less than 70%.
C: The elution rate was less than 30%.

[Solution concentration]
After putting 25 g of the powdered polymer and 75 g of ion-exchanged water into a 200 mL beaker and stirring the mixture at 90 ° C. for 2 hours with a magnetic stirrer, the state of the solution was observed and evaluated in the following three stages. ..
A: It completely dissolved and became a transparent aqueous solution.
B: It became a transparent aqueous solution, but significant thickening was observed and it became difficult to stir.
C: Undissolved component remained and became cloudy.

[Film strength]
An aqueous solution of a vinyl alcohol-based polymer having a concentration of 10% was prepared, cast on a PET film, and then dried at 20 ° C. for 1 week to obtain a film having a thickness of about 40 μm. The obtained film is cut into strips of 10 mm x 80 mm, and the humidity is adjusted at 20 ° C. and 70% humidity for one week. Then, using AG-IS manufactured by Shimadzu Corporation, the distance between chucks is 50 mm and the tensile speed. A tensile test was performed under the condition of 500 mm / min to determine the elongation at break. In addition, each sample was measured 5 times, the average value was calculated, and it was evaluated according to the following evaluation criteria.
A: 140% or more B: 90% or more and less than 140% C: less than 90%

[Sodium acetate content]
The amount of sodium acetate was measured using an ICP emission spectrophotometer. Specifically, after drying the polymers obtained in each Example and Comparative Example, 0.1 g of the dried sample is precisely weighed in a stainless steel container, 20 mL of water is added, and the temperature is 90 ° C. or higher for 2 hours. It was heated and melted. The obtained solution was diluted with ion-exchanged water in a range of up to 100 times. The Na element content was measured and converted to sodium acetate content by quantitatively analyzing the above aqueous solution at a Na wavelength of 818.326 nm using an ICP emission spectroscopic analyzer (“iCAP6500” manufactured by Thermo Fisher Scientific). ..

[Example 1]
(Manufacturing of modified vinyl alcohol polymer)
1.2 kg of vinyl acetate, 1.4 kg of methanol and 1,3-diacetoxy-2-methylenepropane (1.2 kg of vinyl acetate, 1.4 kg of methanol and 1,3-diacetoxy-2-methylenepropane) in a 5 L pressurized reaction vessel equipped with a stirrer, a nitrogen inlet, an ethylene inlet, an initiator addition port and a solution feed port. 0.049 kg of DAMP) was charged, the temperature was raised to 60 ° C., and then nitrogen was replaced in the system by nitrogen bubbling for 30 minutes.

Separately, a 42 g / L solution in which DAMP was dissolved in methanol was prepared for the feed solution, and bubbling was performed with nitrogen gas. Further, a solution of 2,2-azobis (isobutyronitrile) dissolved in methanol as a radical polymerization initiator at a concentration of 20 g / L was separately prepared, and bubbling with nitrogen gas was performed to replace nitrogen.

Next, ethylene was introduced into the pressurized reaction vessel so that the reaction vessel pressure was 0.8 MPa. After adjusting the internal temperature of the pressurized reaction vessel to 60 ° C., 120 mL of the above-mentioned initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 60 ° C., and a methanol solution of DAMP was fed to carry out the polymerization. After confirming that the polymerization rate was 40%, the mixture was cooled to stop the polymerization. The total feed amount of the methanol solution of DAMP (concentration 42 g / L) until the polymerization was stopped was 880 mL.

After opening the pressurized reaction vessel to deethylene, nitrogen gas was bubbled to completely deethylene. Then, the unreacted vinyl acetate monomer was removed under reduced pressure to prepare a methanol solution of a modified ethylene-vinyl acetate copolymer (hereinafter, also referred to as “modified PVAC”). Next, 62.0 parts by mass of sodium hydroxide methanol solution (concentration 15.0%) was added to 438 parts by mass of a methanol solution of modified PVAC prepared by adding methanol (100 parts by mass of modified PVAC in the solution). Then, saponification was carried out at 40 ° C. (modified PVAC concentration of 20% in the saponified solution, molar ratio of sodium hydroxide to vinyl acetate unit in the modified PVAC was 0.2). About 1 minute after the addition of the alkali, the gelled system was pulverized with a pulverizer and left at 40 ° C. for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali.

After confirming the completion of neutralization using a phenolphthalein indicator, a mixed solvent of 900 g of methanol and 100 g of water was added to the white solid saponified product obtained by filtration, and the mixture was allowed to stand at room temperature for 3 hours for washing. After repeating the above washing operation three times, the saponified product obtained by centrifugal deflation was left in a dryer at 70 ° C. for 2 days to obtain a dried modified vinyl alcohol-based polymer.

The obtained modified vinyl alcohol polymer has a number average degree of polymerization Pn of 420, a weight average degree of polymerization Pw of 770, a saponification degree of 99.1 mol%, an ethylene unit content a of 11.4 mol%, and is derived from DAMP. The content of the unit c was 5.4 mol%, and the content of sodium acetate was 0.067 mass%. The total content b of the vinyl acetate unit and the vinyl alcohol unit was 83.2 mol%. The water vapor barrier property, thermoformability, water solubility, solution concentration and film strength of the modified vinyl alcohol polymer were evaluated. The results are shown in Table 2.

[Examples 2 to 7, Comparative Examples 1 to 5]
Table 1 shows polymerization conditions such as the amount of vinyl acetate and methanol charged, ethylene pressure during polymerization, amount of comonomer added during polymerization, and molar ratio of sodium hydroxide to vinyl acetate unit during saponification. Various modified vinyl alcohol-based polymers were produced by the same method as in Example 1 except that the polymer was changed to.

The content of ethylene unit a is in the range of 10 to 20 mol%, and the content of content c of the monomer unit containing Y and Z (unit derived from DAMP) is in the range of 1 to 15 mol%. A modified vinyl alcohol-based polymer of the present invention (Examples 1 to 7) maintained water solubility, and the obtained film had a high water vapor barrier property due to its low moisture permeability. Moreover, since the viscosity of the aqueous solution of these modified vinyl alcohol-based polymers increased slowly even when the concentration was increased, it is useful as a coating agent and is also excellent in productivity as a coating agent. Further, the modified vinyl alcohol-based polymer can be melt-molded at a low temperature, and there is no problem of decomposition.

On the other hand, unmodified polyvinyl alcohol (Comparative Example 1) has a low water vapor barrier property and a high temperature at which it can be melt-molded, resulting in decomposition. The ethylene-vinyl alcohol copolymer (Comparative Example 2) having an ethylene unit content a of 6.5 mol% was deteriorated in water solubility and solution concentration as compared with Comparative Example 1, but as compared with Comparative Example 1. Decomposition resistance has improved. Further, although the water vapor barrier property was improved as compared with Comparative Example 1, a sufficient value could not be obtained.

The polymers of Comparative Examples 3 and 4 contain monomer units (units derived from DAMP) containing Y and Z, but have a low vapor barrier property because the ethylene unit content a is less than 10 mol%. rice field. In the polymer of Comparative Example 5, since the content a of the ethylene unit is 10 mol% or more, the vapor barrier property is excellent, but the content c of the monomer unit (unit derived from DAMP) containing Y and Z. Since the content is less than 1 mol%, the water solubility is low, and when the concentration of the aqueous solution of the polymer is increased, the viscosity is remarkably increased.

Claims

It is represented by the following formula (I), and the contents a (mol%), b (mol%) and c (mol%) of each monomer unit with respect to all the monomer units are represented by the following formulas (1) to (3). A modified vinyl alcohol-based polymer that satisfies the above.
10 ≦ a ≦ 20 (1)
1 ≦ c ≦ 15 (2)
[100- (a + c)] × 0.9 ≦ b ≦ [100- (a + c)] (3)

[In formula (I), X, Y and Z each independently represent a hydrogen atom, a formyl group or an alkanoyl group having 2 to 10 carbon atoms. ]
The modified vinyl alcohol-based polymer according to claim 1, wherein the number average degree of polymerization Pn is 200 to 950.
The modified vinyl alcohol-based polymer according to claim 1 or 2, wherein a and c satisfy the following formula (4).
ac ≤ 10 (4)
The modified polyvinyl alcohol-based polymer according to any one of claims 1 to 3, wherein X, Y and Z are independently hydrogen atoms or acetyl groups.
The modified vinyl alcohol-based polymer according to any one of claims 1 to 4, which has a saponification degree of 90 to 99.99 mol%.
A composition containing the modified vinyl alcohol-based polymer according to any one of claims 1 to 5 and 0.01 to 2% by mass of sodium acetate.
A coating agent containing the modified vinyl alcohol-based polymer according to any one of claims 1 to 5 and a solvent, wherein the solvent comprises at least one of water or an aliphatic alcohol having 1 to 4 carbon atoms. ,Coating agent.
A multilayer film obtained by applying the coating agent according to claim 7 to a base film.