WO2023127699A1

WO2023127699A1 - Modified vinyl alcohol polymer and method for producing same

Info

Publication number: WO2023127699A1
Application number: PCT/JP2022/047467
Authority: WO
Inventors: 心之介芥川; 啓之小西; 一俊三島
Original assignee: 株式会社クラレ
Priority date: 2021-12-27
Filing date: 2022-12-22
Publication date: 2023-07-06
Also published as: TW202334251A

Abstract

The modified vinyl alcohol polymer according to the present invention contains a structure α represented by formula (I), wherein the content ratios a (mol%), b₁ (mol%), b₂ (mol%), and c (mol%) for the individual monomer units, with reference to the total monomer units in the structure α, satisfy formulas (1), (2), and (3).　(1) 1 ≤ a ≤ 40; (2) 1 ≤ c ≤ 15; (3) 35 ≤ (b₁ + b₂) ≤ 98

Description

Modified vinyl alcohol polymer and method for producing the same

The present invention relates to a modified vinyl alcohol polymer and a method for producing the same.

A vinyl alcohol polymer (hereinafter sometimes abbreviated as "PVA") is one of the few water-soluble polymers with crystallinity. Utilizing its excellent water solubility and film properties (strength, oil resistance, film-forming properties, oxygen gas barrier properties, etc.), PVA is used as an emulsifier, suspending agent, surfactant, fiber processing agent, various binders, and paper processing agents. , adhesives, films, etc.

PVA has poor moldability due to its high crystallinity. PVA with reduced crystallinity is known to improve molding workability. For example, PVA with reduced crystallinity by lowering the degree of saponification is manufactured and sold. However, it has been pointed out that PVA with a reduced degree of saponification is degraded in its original features such as oxygen gas barrier properties, mechanical properties, and thermal stability. For the above reasons, it is difficult to achieve molding processability, oxygen gas barrier properties, mechanical properties, and thermal stability at the same time.

For example, Patent Document 1 describes PVA containing 2-methylene-1,3-propane-diol (DAMP). According to Patent Literature 1, the PVA is excellent in water solubility, film physical properties at high humidity, low foaming properties in an aqueous solution, and viscosity stability. However, there is no disclosure or suggestion that such PVA has oxygen barrier properties and melt moldability in addition to such properties.

Patent Document 2 describes a vinyl alcohol polymer containing ethylene and 3,4-diacetoxy-1-butene (DAB). It is described that the polymer described in Patent Document 2 is excellent in oxygen barrier properties at high humidity, appearance and strength in addition to melt moldability. However, it does not disclose or suggest that the polymer is excellent in water solubility and biodegradability.

Patent Document 3 describes a vinyl alcohol polymer containing an α-olefin having 2 or more carbon atoms and methallyl alcohol. PVA described in Patent Document 3 is disclosed to be impermeable to oxygen and excellent in solvent solubility. However, it is stated that such PVA has a low equilibrium water absorption, ie, low water solubility.

Patent Document 4 describes a melt molding method in which PVA containing an olefin having 3 or 4 carbon atoms is mixed with water. The PVA described in Patent Document 4 only discloses that the softening temperature and the melt viscosity are significantly lowered.

However, the modified vinyl alcohol polymers described in Patent Documents 1 to 4 have a common problem that they have not been able to achieve a high degree of both moldability and water solubility. Specifically, when these modified vinyl alcohol polymers are formed into the form of a packaging material as an oxygen barrier film, for example, after coating an aqueous solution on a base film, heat is applied to seal the contents. In the sealing process, it may be necessary to set the heat sealing temperature high. Therefore, the base material is limited to materials having heat resistance, and it may be difficult to provide a versatile resin film.

JP 2013-177576 A JP 2004-359965 A Japanese Patent Publication No. 2005-514083 Japanese Patent Publication No. 49-032657

An object of the present invention is to solve the above-mentioned problems, and to provide a modified vinyl alcohol polymer that maintains the good water solubility and oxygen barrier properties of PVA and has excellent moldability, and a method for producing the same. intended to provide

The present invention includes the following inventions.
[1] Containing a structure α represented by the following formula (I), the content ratios a (mol%), b ₁ (mol%), and b ₂ of each monomer unit with respect to all monomer units in the structure α (mol%) and c (mol%) satisfying the following formulas (1) to (3), a modified vinyl alcohol polymer,
1≤a≤40 (1)
1≤c≤15 (2)
35≦(b ₁ +b ₂ )≦98 (3)

[in the formula (I),
R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom or an optionally branched alkyl group,
the total number of carbon atoms constituting R ¹ , R ² , R ³ and R ⁴ is 1 to 3;
R ⁵ and R ^5′ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms,
R ⁶ is a hydrogen atom, or —(CH ₂ ) _m —R ⁹ in which at least one hydrogen atom may be substituted with R ⁸ (wherein R ⁹ and R ⁸ are each independently a hydroxyl group, formyl an oxy group or an acyloxy group having 2 to 10 carbon atoms, and m is an integer of 1 to 5),
R ⁷ has at least one hydrogen atom optionally substituted with R ¹¹ and is at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH ₂ ) _n —R ¹⁰ (wherein R ¹⁰ and R ¹¹ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and n is an integer of 1 to 5 and R ⁶ and R ⁷ together are at least two, which may be the same or different, selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; containing one group];
[2] The modified vinyl alcohol polymer according to [1], wherein the formula (I) is represented by the following formula (I-1),

[In formula (I-1), a, b ₁ , b ₂ , b ₁ +b ₂ , c, R 1 , R ² , R ³ , R ⁴ , R ⁵ , R ⁵ ^′ , R ⁹ , R ¹⁰ , m and n are each independently as defined in said formula (I)];
[3] The modified vinyl alcohol polymer according to [1], wherein the formula (I) is represented by the following formula (I-2),

[In the formula (I-2),
R ^7′ has at least one hydrogen atom optionally substituted with R ¹¹ and at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH ₂ ) _n —R ¹⁰ (wherein R ¹⁰ and R ¹¹ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and together they are a hydroxyl group; formyloxy and an acyloxy group having 2 to 10 carbon atoms; and at least two groups which may be the same or different and are selected from the group consisting of;
a, b ₁ , b ₂ , b ₁ +b ₂ , c, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ^5′ are each independently as defined in said formula (I) ];
[4] The modified vinyl alcohol polymer according to any one of [1] to [3], which has a number average degree of polymerization of 200 to 5000;
[5] In the formula (I),
R ⁵ and R ^5′ are each independently a hydroxyl group or an acetyloxy group;
R ⁶ is a hydrogen atom, or —(CH ₂ ) _m —R 9′ in which at least one hydrogen atom may be substituted with R ⁸ ^′ (wherein R ^9′ and R ^8′ are each independently , a hydroxyl group or an acetyloxy group, and m is an integer of 1 to 5),
R ⁷ has at least one hydrogen atom optionally substituted with R ^11′ and at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH ₂ ) _n —R ^10′ (wherein R ^10′ and R ^11′ are each independently a hydroxyl group or an acetyloxy group and n is an integer from 1 to 5), and The modified vinyl alcohol polymer according to any one of [1] to [4], wherein a, b ₁ , b ₂ , and c are each independently defined in formula (I);
[6] The modified vinyl alcohol polymer according to any one of [1] to [5], which has a saponification degree of 50 to 99.99 mol%;
[7] A method for producing a modified vinyl alcohol polymer,
Copolymerizing an olefinic monomer containing a polymerizable unsaturated bond and having 3 to 5 carbon atoms, a vinyl ester monomer, and a hydroxyl group-containing monomer,
The vinyl ester monomer is
A compound represented by the following formula (II):

[wherein R ⁵ is a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms], and a compound represented by the following formula (III):

[In formula (III), R ^5′ is a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms]
At least one compound selected from the group consisting of
provided that in formulas (II) and (III), R ⁵ and R ^5' may be the same or different;
A compound in which the hydroxyl group-containing monomer is represented by the following formula (IV):

[In the formula (IV),
R ⁶ is a hydrogen atom, or —(CH ₂ ) _m —R ⁹ in which at least one hydrogen atom may be substituted with R ⁸ (wherein R ⁹ and R ⁸ are each independently a hydroxyl group, formyl an oxy group or an acyloxy group having 2 to 10 carbon atoms, and m is an integer of 1 to 5),
R ⁷ has at least one hydrogen atom optionally substituted with R ¹¹ and has at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH ₂ ) _n —R ¹⁰ (wherein R ¹⁰ and R ¹¹ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and n is an integer of 1 to 5; and R ⁶ and R ⁷ together are at least two, which may be the same or different, selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; including groups]
, manufacturing method.

According to the present invention, it is possible to provide a modified vinyl alcohol polymer that maintains good water solubility and excellent barrier properties against oxygen, while also having excellent moldability, and a method for producing the same. In addition, the heat sealing temperature of the film produced from the polymer of the present application is kept low, and the enlargement and/or complication of equipment is not particularly required for molding. As a result, it is possible to provide containers and packaging materials suitable for storing products such as foodstuffs that are susceptible to deterioration by oxygen, such as multilayer films and multilayer containers.

(Modified vinyl alcohol polymer)
The modified vinyl alcohol polymer of the present invention has the following formula (I):

That is, the olefin-based monomer unit represented by the following formula (I-(a)), the vinyl ester-based monomer unit represented by the following formula (I-(b ₁ )), the following formula ( It is composed of a vinyl ester monomer unit represented by I-(b ₂ )) and a hydroxyl group-containing monomer unit represented by the following formula (I-(c)).

In formula (I) and formula (I-(a)), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom or an optionally branched alkyl group, and R ¹ , R The total number of carbon atoms constituting each of ² , R ³ and R ⁴ is 1 to 3, ie 1, 2 or 3. Here, the optionally branched alkyl group that can constitute each of R ¹ , R ² , R ³ and R ⁴ is a linear or branched alkyl group having 1 to 3 carbon atoms, for example , methyl group, ethyl group, n-propyl group and isopropyl group.

In Formula (I), Formula (I-(b ₁ )) and Formula (I-(b ₂ )), R ⁵ and R ^5′ each independently represent a hydroxyl group, a formyloxy group or a C 2-10 group. acyloxy group. Here, the acyloxy group having 2 to 10 carbon atoms that can constitute each of R ⁵ and R ^5′ has 2 to 10, preferably 2 to 3 carbon atoms, which may contain a carbon-carbon double bond. straight-chain, branched-chain and cyclic acyl groups having any number. Specific examples of the acyloxy group having 2 to 10 carbon atoms include an ethanoyloxy group (acetyloxy group), a propanoyloxy group, a butanoyloxy group, an isobutanoyloxy group, a pentanoyloxy group, and an isopentyloxy group. noyloxy group, pivaloyloxy group, hexanoyloxy group, heptanoyloxy group, octanoyloxy group, nonanoyloxy group, decanoyloxy group, lactoyloxy group, glyceroyloxy group, tropoyloxy group, cyclohexanecarbonyloxy group, benzoyloxy group salicyloyloxy, anisoyloxy, vanilloyloxy, veratroyloxy, and galloyloxy groups. In the present invention, R ⁵ and R ^5' constituting formula (I) may be the same or different.

In formula (I) and formula (I-(c) ⁾ , R ⁶ is a hydrogen atom, or —(CH ₂ ) _m —R ⁹ (wherein R ⁸ and R ⁹ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and m is 1 to 5, preferably 1 to 2 is an integer). Here, the acyloxy groups having 2 to 10 carbon atoms that can constitute each of R ⁸ and R ⁹ are each independently the acyloxy groups having 2 to 10 carbon atoms that can constitute each of R ⁵ and R ^5′. It is the same as the base.

In formula (I) and formula (I-(c)), R ⁷ is a hydroxyl group, at least one hydrogen atom of which may be substituted with R ¹¹ ; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms. —(CH ₂ ) _n —R ¹⁰ (wherein R ¹⁰ and R ¹¹ are each independently a hydroxyl group, a formyloxy group, or a C 2-10 and n is an integer of 1 to 5, preferably 1 to 2). Here, the acyloxy groups having 2 to 10 carbon atoms that can constitute each of R ¹⁰ and R ¹¹ are each independently the acyloxy groups having 2 to 10 carbon atoms that can constitute each of R ⁵ and R ^5′. It is the same as the base.

Here, in formula (I) and formula (I-(c)), R ⁶ and R ⁷ together are selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; It also includes at least two groups which may be the same or different.

Here, as used herein, "the two groups X ¹ and X ² together comprise at least two groups Y ¹ which may be the same or different" means both groups X ¹ and X ² , or It refers to the state in which at least two groups Y ¹ are included as part of the constituent part in either the substituents X ¹ or X ² . That is, in this context (a) at least one group Y ¹ is included among the members of the group X ¹ and at least one group Y ¹ is included among the members of the group X ² so that they collectively contain at least two groups Y ¹ ; (b) at least two groups Y ¹ are contained in the constituent parts of group ^{X 1} ^and ^{and (c) no group Y 1} ^is included among the constituent parts of the group X ¹ and ^the group X at least two groups Y ¹ are included in the constituent parts of ² so that they collectively include at least two groups Y ¹ ;

For example, in formula (I) and formula (I-(c)) above, R ⁶ and R ⁷ may together contain two hydroxyl groups as part of their constituent moieties.

Furthermore, in the modified vinyl alcohol polymer of the present invention, the contents of the monomer units constituting the formula (I) are a (mol %), b ₁ (mol %), b ₂ (mol %), and c (mol %) satisfy the following relationships (1) to (3):
1≤a≤40 (1)
1≤c≤15 (2)
35≦(b ₁ +b ₂ )≦98 (3)

In one embodiment, a satisfies the following relationship (1′):
1≦a≦30 (1′)

Alternatively, in one embodiment, a satisfies the following relationship (1″):
1≦a≦20 (1″)

In one embodiment, c above satisfies the following relation (2′):
1≦c≦10 (2′)

Alternatively, in one embodiment, c above satisfies the following relationship (2″):
1≦c≦8 (2′)

In one embodiment, (b ₁ +b ₂ ) above satisfies the following relational expression (3′):
40≦(b ₁ +b ₂ )≦98 (3′)

Alternatively, in one embodiment, c above satisfies the following relationship (b ₁ +b ₂ ) satisfies the following relationship (3″):
45≦(b ₁ +b ₂ )≦98 (3″)

In a further embodiment, b1 and b2 of each monomeric unit comprising formula (I) above satisfies formula (3), (3′) or (3″) above, and the following relationship (4): and satisfy (5):
0≦b ₁ ≦98 (4)
0≦b ₂ ≦98 (5)

Alternatively, in a further embodiment, b1 and b2 of each monomeric unit constituting formula (I) above satisfies formula (3), (3′) or (3″) above, and the following relational expression: 4′) and (5′) are satisfied:
1≦b ₁ ≦98 (4)
1≦b ₂ ≦98 (5)

In one embodiment, the modified vinyl alcohol polymer of formula (I) of the present invention is represented by the following formula (I-1):

In formula (I-1), a, b ₁ , b ₂ , b ₁ +b ₂ , c, R 1 , R ² , R ³ , R ⁴ , R ⁵ , R ⁵ ^′ , R ⁹ , R ¹⁰ , m and Each n is independently as defined in formula (I).

Alternatively, in one embodiment, the modified vinyl alcohol polymer of formula (I) of the present invention is represented by the following formula (I-2):

In formula (I-2), R ^7′ is from the group consisting of a hydroxyl group, at least one hydrogen atom of which may be substituted with R ¹¹ ; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH ₂ ) _n —R ¹⁰ having at least one selected group (wherein R ¹⁰ and R ¹¹ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms; formyloxy ^; and acyloxy having 2 to ¹⁰ carbon atoms; together contain two hydroxyl groups and n is an integer from 1 to 5), a, b ₁ , b ₂ , b ₁ +b ₂ , c, R ^{1 , R 2} ^, R ³ , R ⁴ , R ⁵ , and R ^5′ are each independently as defined in the formula (I), and in the above formula (I-2), each of R ¹⁰ and R ¹¹ having 2 to 10 carbon atoms is The acyloxy groups having 2 to 10 carbon atoms are the same as the acyloxy groups having 2 to 10 carbon atoms that can independently constitute each of the above R ⁵ and R ^5' .

Alternatively, in one embodiment, in the modified vinyl alcohol polymer of the present invention, R ⁵ and R ^5′ in formula (I) are each independently a hydroxyl group or an acetyloxy group.

In a further embodiment, the modified vinyl alcohol-based polymer of the present invention is represented by formula (I) wherein ^R6 is a hydrogen atom, or at least one hydrogen atom (e.g., one hydrogen atom) is substituted with ^R8' . —(CH ₂ ) _m —R ^9′ (wherein R ^8′ and R ^9′ are each independently a hydroxyl group or an acetyloxy group, and m is an integer of 1 to 5). and R ⁷ has at least one hydrogen atom optionally substituted with R ^11′ and has at least one hydroxyl group, formyloxy group or acyloxy group having 2 to 10 carbon atoms —(CH ₂ ) _n —R ^10′ (wherein R ^10′ and R ^11′ are each independently a hydroxyl group or an acetyloxy group, n is an integer of 1 to 5, preferably 1 to 2), and R ⁶ and R ⁷ together contain at least two groups, which may be the same or different, selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms. For example, ^R6 and ^R7 may together contain two hydroxyl groups.

In one embodiment, the modified vinyl alcohol polymer of formula (I) of the present invention is represented by the following formula (I'):

In formula (I′), R ^5″ is a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and is a, b ₁ , b ₂ , b ₁ +b ₂ , c, R ¹ , R ² , R ³ , R ⁴ , R ⁶ and R ⁷ are each independently as defined in the formula (I). The acyloxy group having 2 to 10 carbon atoms that can constitute R ^5″ is It is the same as the acyloxy group having 2 to 10 carbon atoms that can constitute R ⁵ or R ^5' in the above formula (I).

In a further embodiment, the modified vinyl alcohol polymer of formula (I') above is represented by the following formula (I'-1):

In formula (I′-1), a, b ₁ , b ₂ , b ₁ +b ₂ , c, R ¹ , R ² , R ³ , R ⁴ , R ^5″ , R ⁹ , R ¹⁰ , m and n are Each is as independently defined in said formula (I) or (I').

Alternatively, in a further embodiment, the modified vinyl alcohol polymer of formula (I') above is represented by the following formula (I'-2):

In formula (I′-2), R ^7″ is a group consisting of a hydroxyl group in which at least one hydrogen atom may be substituted with R ¹¹ ; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —( ^CH ₂ ) _n —R ¹⁰ ^having at least one group selected from formyloxy group; and acyloxy group having 2 to ¹⁰ carbon atoms; ¹¹ together contain two hydroxyl groups, and n is an integer from 1 to 5), a, b ₁ , b ₂ , b ₁ +b ₂ , c, R ¹ , R ² , R ³ , R ⁴ , and Each R ^5″ is independently as defined in the formula (I) or (I′). In the above formula (I′-2), the number of carbon atoms that can constitute each of R ¹⁰ and R ¹¹ The acyloxy groups having 2 to 10 are each independently the same as the acyloxy groups having 2 to 10 carbon atoms that can constitute R ⁵ or R ^5' in formula (I) above.

The modified vinyl alcohol polymer of formula (I) of the present invention preferably has a number average degree of polymerization (Pn) of 200 to 5,000, more preferably 200 to 4,000, and even more preferably 300 to 3,000. If the modified vinyl alcohol polymer has a Pn of less than 200, it may not have sufficient strength when formed into a film, for example. If the Pn of the modified vinyl alcohol polymer exceeds 5,000, industrial production of the modified vinyl alcohol copolymer may become difficult, or the stability of the coating solution may deteriorate, and the workability of the film may deteriorate. . Pn is calculated by the following formula (S ₁ ) after measuring the number average molecular weight (Mn) of the polymer by, for example, high performance liquid chromatography (HPLC).

Although the degree of saponification of the modified vinyl alcohol polymer of formula (I) of the present invention is not particularly limited, it is preferably 50 to 99.99 mol %. If the degree of saponification is less than 50 mol %, sufficient water vapor barrier properties may not be obtained. The degree of saponification is more preferably 70 mol% or more, more preferably 80 mol% or more. On the other hand, those with a degree of saponification exceeding 99.99 mol % may be difficult to obtain industrially. The degree of saponification is more preferably 99.95 mol% or less, even more preferably 99.90 mol% or less. In the present invention, the degree of saponification is defined by DS shown in the following formula (S ₂ ), and specifically calculated from the measurement results of ¹ H-NMR.

The modified vinyl alcohol polymer of the present invention can be copolymerized with the olefin monomer, vinyl ester monomer, and hydroxyl group-containing monomer within a range that does not inhibit the effects of the present invention. A structural unit derived from an ethylenically unsaturated monomer may also be included. Examples of such ethylenically unsaturated monomers include acrylic acid and its salts; unsaturated monomers having an acrylate ester group; methacrylic acid and its salts; and unsaturated monomers having a methacrylate ester group. acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts (eg quaternary salts); methacrylamide, N - methyl methacrylamide, N-ethyl methacrylamide, methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts (eg 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; 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 compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane and allyl chloride; maleic acid , itaconic acid, fumaric acid and the like, and salts or esters thereof; vinylsilane compounds such as vinyltrimethoxysilane; isopropenyl acetate and the like.

The modified vinyl alcohol polymer of the present invention may also contain a carboxyl group, a sulfonic acid group, an amino group and/or a salt thereof within the range that does not impair the performance of the present invention. may be modified to have a side chain or a molecular end. The amount of modification with carboxyl groups, sulfonic acid groups, amino groups and/or salts thereof is, for example, 0.05 to 10 mol % based on the total monomer units of the modified vinyl alcohol polymer of the present invention.

(Polymerization method of modified vinyl alcohol polymer)
The modified vinyl alcohol polymer of the above formula (I) is not necessarily limited, but can be produced, for example, by copolymerizing an olefin monomer, a vinyl ester monomer and a hydroxyl group-containing monomer.

In the production method of the present invention, the olefinic monomer contains a polymerizable unsaturated bond and has 3 to 5 carbon atoms, preferably 3 to 4 carbon atoms. Examples of olefinic monomers include propylene, 1-butene, 2-butene (ie cis-2-butene and trans-2-butene), isobutene, 1-pentene, 2-pentene (ie cis-2 -pentene and trans-2-pentene), 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene. Propylene is preferred because it is versatile and readily available.

In the production method of the present invention, the vinyl ester monomer is composed of a compound represented by the following formula (II), a group consisting of compounds represented by the following formula (III), or a combination thereof. .

In formula (II) and formula (III), R ⁵ and R ^5′ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms. Here, the acyloxy group having 2 to 10 carbon atoms that can constitute each of R ⁵ and R ^5′ in formula (II) and formula (III) is the number of carbon atoms that can constitute R ⁵ in formula (I) above. The same is true for acyloxy groups with 2-10. In formulas (II) and (III), R ⁵ and R ^5' may be the same or different.

Examples of vinyl ester monomers represented by formulas (II) and (III) include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl isovalerate, Vinyl pivalate, vinyl caproate, vinyl enanthate, vinyl caprylate, vinyl pelargonate, vinyl caprate, vinyl lactate, vinyl tropicate, vinyl cyclohexanoate, vinyl benzoate, vinyl salicylate, vinyl anisate, vanillic acid, gallic acid Examples include vinyl acid and vinyl versatate. Either the vinyl ester-based monomer represented by the formula (II) or the vinyl ester-based monomer represented by the formula (II) because of its high versatility and easy availability, Alternatively, both are preferably vinyl acetate.

In the production method of the present invention, the hydroxyl group-containing monomer is represented by the following formula (IV).

In formula (IV), R ⁶ is a hydrogen atom, or —(CH ₂ ) _m —R ⁹ in which at least one hydrogen atom may be substituted with R ⁸ (wherein R ⁸ and R ⁹ are each independently is a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and m is an integer of 1 to 5, preferably 1 to 2). Here, the acyloxy group having 2 to 10 carbon atoms that can constitute R ⁹ is the same as the acyloxy group having 2 to 10 carbon atoms that can constitute each of R ⁵ and R ^5′ in the above formula (I). be.

In formula (IV), R ⁷ has at least one hydrogen atom optionally substituted with R ¹¹ and is selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH ₂ ) _n —R ¹⁰ having at least one group (wherein R ¹⁰ and R ¹¹ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and n is an integer of 1 to 5, preferably 1 to 2), and R ⁶ and R ⁷ together are selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; It also includes at least two groups which may be the same or different. Here, each of the acyloxy groups having 2 to 10 carbon atoms that can constitute each of R ¹⁰ and R ¹¹ independently has 2 carbon atoms that can constitute each of R ⁵ and R ^5′ in the above formula (I). The same is true for acyloxy groups with ∼10.

Examples of hydroxyl group-containing monomers represented by formula (IV) include 1,3-diacetoxy-2-methylenepropane (DAMP), 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyl and ronyloxy-2-methylenepropane. DAMP is preferred because the hydroxyl group-containing monomer itself can be easily produced.

The copolymerization of the olefin-based monomer, the vinyl ester-based monomer, and the hydroxyl group-containing monomer is carried out using any polymerization method of batch polymerization, semi-batch polymerization, continuous polymerization, or semi-continuous polymerization. may As the polymerization method, known methods such as bulk polymerization method, solution polymerization method, suspension polymerization method and emulsion polymerization method can be employed. For example, a bulk polymerization method or a solution polymerization method, in which the polymerization proceeds without solvent or in a solvent such as alcohol, may be employed. Employment of an emulsion polymerization method is one of the options for obtaining a modified vinyl alcohol polymer with a high degree of polymerization.

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

For example, a known polymerization initiator can be used for copolymerizing the olefin-based monomer, the vinyl ester-based monomer, and the hydroxyl group-containing monomer. The type of polymerization initiator to be used can be appropriately selected according to the polymerization method. Examples of such polymerization initiators include azo initiators, peroxide initiators, and redox initiators.

Examples of azo initiators include 2,2-azobisisobutyronitrile, 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(4-methoxy-2,4-dimethyl valeronitrile).

Examples of peroxide-based initiators include peroxydicarbonate-based compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; t-butyl peroxyneodecanate, perester compounds such as α-cumyl peroxyneodecanate and acetyl peroxide; acetylcyclohexylsulfonyl peroxide; 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate and the like. When peroxide-based initiators are used, potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like may be used in combination with the above initiators.

Examples of redox initiators include combinations of the above peroxide initiators and reducing agents such as sodium hydrogensulfite, sodium hydrogencarbonate, tartaric acid, L-ascorbic acid, and Rongalit.

The amount of polymerization initiator used is not necessarily limited because it varies depending on the type of polymerization catalyst used in combination, but the amount can be arbitrarily adjusted by those skilled in the art according to, for example, the polymerization rate. For example, the amount of the polymerization initiator to be used is preferably 0.01 to 0.2 mol %, more preferably 0.02 to 0.15 mol %, relative to the vinyl ester monomer of the above formula. By using a polymerization initiator in an amount within this range with respect to the vinyl ester-based monomer of the above formula, the olefin-based monomer, the vinyl ester-based monomer, and the hydroxyl group-containing monomer can be carried out more efficiently. Although the polymerization temperature is not particularly limited, for example, room temperature to about 150° C. is appropriate, and a temperature of 40° C. or higher and the boiling point or lower of the solvent used can be preferably selected.

In the production method of the present invention, the copolymerization may be carried out in the presence of a chain transfer agent to the extent that the effects of the present invention are not impaired.

Examples of chain transfer agents include aldehydes such as acetaldehyde and propynaldehyde; ketones such as acetone and methyl ethyl ketone; mercaptans such as 2-hydroxyethanethiol; phosphinates such as sodium phosphinate monohydrate. mentioned. The amount of the chain transfer agent to be added to the polymerization reaction solution can be determined according to the chain transfer coefficient of the chain transfer agent and the degree of polymerization of the desired modified vinyl alcohol polymer. 0.1 to 10 parts by mass per part is preferred.

In the production method of the present invention, the copolymer obtained above may be saponified. At this time, vinyl ester units derived from vinyl ester monomers in the copolymer are converted to vinyl alcohol units. At the same time, an ester bond derived from the hydroxyl group-containing monomer is also hydrolyzed and converted to a 1,3-diol structure. Thus, different kinds of ester groups can be hydrolyzed simultaneously by one saponification reaction.

A known method can be adopted as such a saponification method. Saponification is usually carried out in an alcoholic or hydroalcoholic solution. Alcohols preferably used at this time are, for example, lower alcohols such as methanol and ethanol, preferably methanol. The alcohol or hydroalcohol used for saponification may contain other solvents such as acetone, methyl acetate, ethyl acetate, benzene, etc. up to 40% by weight of the alcohol. Catalysts used for saponification include, for example, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, alkali catalysts such as sodium methylate, and acid catalysts such as mineral acids. A temperature of, for example, 20 to 120° C. is set during the saponification. When a gel-like product precipitates as the saponification progresses, washing and drying may be performed after pulverizing the product.

Thus, the modified vinyl alcohol polymer of the present invention can be produced.

(resin composition)
The modified vinyl alcohol polymer of the present invention can be used alone, or can be used as a resin composition by blending other copolymers and/or additives.

Examples of other copolymers include polyvinyl alcohol and ethylene-vinyl alcohol copolymers that do not contain a hydroxyl group-containing monomer unit represented by the above formula (Ic). Examples of other additives include inorganic salts, organic salts, crosslinkers, solvents, UV absorbers, antioxidants, antistatic agents, plasticizers, fungicides, and preservatives, and combinations thereof. . The contents of other copolymers and other additives are not particularly limited, and suitable amounts can be selected by those skilled in the art.

The resin composition of the present invention can be molded, for example, in the form of a heat-sealable packaging material (for example, a resin film) due to the water-solubility and barrier properties of the modified vinyl alcohol polymer contained as a component. At that time, the heat sealing temperature can be set relatively low as compared with the case of using conventional PVA. As a result, the resin composition of the present invention can provide a versatile resin film without requiring large or complicated equipment.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. "%" and "parts" in the following examples and comparative examples represent "% by mass" and "parts by mass", respectively, unless otherwise specified.

(Calculation of contents a, b ₁ , b ₂ and c of each monomer unit)
Using a nuclear magnetic resonance apparatus "LAMBDA 500" manufactured by JEOL Ltd., ¹ H-NMR of the modified vinyl alcohol polymers obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were analyzed in deuterated dimethyl sulfoxide. , measured at 27 ° C., the content of each monomer unit in the polymer (content of each monomer unit constituting the above formula (I)) a (mol%), b ₁ (mol%), b ₂ (mol %) and c (mol %) were quantified.

(degree of saponification)
The vinyl ester-based monomer unit of formula (I-(b ₁ )), the vinyl ester-based monomer unit of formula (I-(b ₂ )), and the formula Focusing on the hydroxyl group-containing monomer units of (I-(c)), the number of moles of hydroxyl groups and the number of moles of ester groups constituting R ⁵ , R ^5′ , R ⁶ and R ⁷ of these monomer units was calculated from the ¹ H-NMR measurement results of the polymer, and the degree of saponification (DS) of the polymer was obtained according to the following formula (S ₂ ):

(Number average degree of polymerization)
The number average molecular weight (Mn) of the obtained modified vinyl alcohol polymer was measured using a size exclusion high performance liquid chromatography device "HLC-8320GPC" manufactured by Tosoh Corporation. The measurement conditions are as follows.
Column: HFIP column "GMHHR-H (S)" manufactured by Tosoh Corporation 2 series connection Standard sample: polymethyl methacrylate 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 through a filter with an opening diameter of 0.45 μm)
Injection volume: 10 μL
Detector: RI
The number average degree of polymerization Pn of the polymer was calculated by the following formula (S ₁ ).

(Oxygen gas barrier property)
A modified vinyl alcohol polymer aqueous solution having a concentration of 10% by mass was prepared from the modified vinyl alcohol polymer prepared in Examples and Comparative Examples, and filtered and centrifuged to remove foreign substances and air bubbles. Next, using a bar coater, the surface of a base PET film having a thickness of 12 μm was coated with the aqueous solution of the modified vinyl alcohol polymer obtained above at room temperature, and dried with a hot air dryer at 60° C. to obtain a base. A multilayer film consisting of a PET film (12 μm) and a modified vinyl alcohol polymer layer (about 20 μm) was obtained. After the obtained multilayer film was conditioned at a temperature of 20° C. and a relative humidity of 90% for 5 days, the oxygen permeation of the multilayer film was measured using an oxygen gas permeation measuring device OX-TRAN 2/21 (manufactured by Mocon Co., Ltd.). The value A ₁ [cc/(m ² ·day · atm)] was measured as the amount (OTR).

The film thickness of the multilayer film after the measurement was measured using an electromagnetic film thickness gauge SAMAC-PRO manufactured by Sanko Electronics Laboratory Co., Ltd., and the obtained thickness was defined as T (μm). After obtaining F ₁ from the following formula (S ₃ ), the formula (S ₄ ) is used to calculate the oxygen transmission rate (OTR) of the modified vinyl alcohol polymer layer when the thickness is 20 μm. A ₂ [cc/(m ² ·day · atm)] was obtained.

The meaning of each symbol in formulas (S ₃ ) and (S ₄ ) is as follows.
・ Thickness of modified vinyl alcohol polymer layer: T-12 (μm)
・ OTR actual value of the entire multilayer film: A ₁ [cc/(m ² ·day · atm)]
- OTR of modified vinyl alcohol polymer layer: F ₁ [cc/(m ² ·day · atm)]
・ OTR actual measurement value of base PET film: F ₂ [cc/(m ² · day · atm)]
- OTR after conversion of the thickness of the modified vinyl alcohol polymer layer to 20 μm: A ₂ [cc/(m ² ·day · atm)].

(Water soluble)
A modified vinyl alcohol polymer aqueous solution having a concentration of 10% by mass was prepared from the modified vinyl alcohol polymer prepared in Examples and Comparative Examples, cast on a PET film, and dried at 20° C. and 50% RH for 1 week. , to obtain a single-layer film having a thickness of 100 μm by peeling from the PET film. The monolayer film thus obtained was cut into a size of 3 cm×4 cm, and the mass (M ₁ ) was measured. The film was then immersed in water (100 mL) at 60° C. for 1 hour, then taken out and vacuum dried at 40° C. for 3 days. The mass (M ₂ ) of this film was then measured. From the obtained masses before and after immersion (M ₁ and M ₂ ), the dissolution rate YS (%) was calculated from the following formula (S ₅ ) by comparing with the mass before immersion, and according to the following criteria. The water solubility of the modified vinyl alcohol polymer layer in the multilayer film was evaluated.

<Evaluation Criteria for Water Solubility>
○: The elution rate was 20% or more, and it was judged that the modified vinyl alcohol polymer layer in the obtained film had good water solubility.
x: The elution rate was less than 20%, and the modified vinyl alcohol polymer layer in the obtained film was judged to be poor in water solubility.

(Heat sealability)
The monolayer film prepared for the above water-solubility evaluation was stored in a thermo-hygrostat at 20° C. and 50% RH for 5 days to condition the humidity. Then, the two films thus humidity-conditioned were cut into pieces each having a size of 1.5 cm×5.0 cm. And in a 50% RH atmosphere, using a heat sealer ("heating temperature control electric sealer OPL-200-10" manufactured by Fuji Impulse Co., Ltd.), the upper crimped part (10 mm), the lower crimped part (10 mm), and the crimping force A portion of the laminated film was heat-sealed at various temperatures under conditions of about 0.6 MPa for 1 second. After that, the breaking strength or peel strength of the obtained heat-sealed portion was measured at a test speed of 300 mm / min by T peel (180 degree peel test) with a width of 15 mm, and when the strength could exceed 5 N / 15 mm The lowest value of the set temperatures was taken as the heat sealing temperature.

(Biodegradable)
Using the modified polyvinyl alcohol polymers produced in Examples and Comparative Examples as samples, biodegradability was evaluated according to the biodegradability evaluation method described in ISO14851. That is, 20 mg of activated sludge (obtained from the sewage treatment plant on the day of the start of the test) and 20 mg of the sample were added to 200 ml of the inorganic medium liquid, and Oxitop (pressure sensor type BOD measuring device manufactured by WTW) was used for 49 days at 22 ° C. By measuring the amount of oxygen consumed by biodegradation during this culture period, the biodegradation rate SB (%) was calculated from the following formula (S ₆ ), and biodegradability was determined according to the following criteria. was evaluated.

<Biodegradability evaluation criteria>
O: The biodegradation rate was 50% or more, and the biodegradability of the obtained modified polyvinyl alcohol polymer was judged to be good.
x: The biodegradation rate was less than 50%, and the obtained modified polyvinyl alcohol polymer was judged to be inferior in biodegradability.

(Example 1: Production of modified vinyl alcohol polymer (E1))
Into a 5 L pressurized reactor equipped with an agitator, nitrogen inlet, propylene inlet, initiator addition and solution feed, 1.3 kg vinyl acetate, 1.2 kg methanol and 1,3-diacetoxy-2-methylene were charged. 0.016 kg of propane (DAMP) was charged, the temperature was raised to 60° C., and nitrogen bubbling was performed for 30 minutes to replace the inside of the system with nitrogen.

On the other hand, as a feed solution, a solution of DAMP dissolved in methanol with a concentration of 42 g/L was prepared and bubbled with nitrogen gas. Further, an initiator solution having a concentration of 20 g/L was separately prepared by dissolving 2,2-azobis(isobutyronitrile) as a radical polymerization initiator in methanol, and nitrogen gas was bubbled through the solution to replace it with nitrogen.

After that, propylene was introduced into the pressurized reactor so that the reactor pressure was 0.35 MPa. After adjusting the inner temperature of the pressurized reactor to 60° C., 500 mL of an initiator solution separately prepared and nitrogen-substituted was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 60° C., and the methanol solution of DAMP separately prepared and nitrogen-substituted was fed to continue the polymerization. After confirming that the rate of polymerization reached 30% by periodic sampling, the polymerization was terminated by cooling. The amount of the methanol solution of DAMP (concentration: 42 g/L) fed until the termination of the polymerization was 240 mL in total.

After depropylene was removed by opening the pressurized reaction tank, nitrogen gas was bubbled to complete depropylene. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of modified propylene-vinyl acetate copolymer (hereinafter also referred to as "modified PVAc"). After that, 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). saponification was carried out at 40° C. (20% modified PVAc concentration in the saponification solution, 0.2 molar ratio of sodium hydroxide to vinyl acetate units in the modified PVAc). About 1 minute after the addition of sodium hydroxide, the reactant gelled, and it was taken out and pulverized with a pulverizer, left at 40° C. for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added. Any remaining sodium hydroxide was neutralized.

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, left at room temperature for 3 hours, and washed. After repeating the washing operation a total of three times, the saponified product obtained by deliquoring by centrifugation was allowed to stand in a dryer at 70° C. for 2 days to obtain a dried modified vinyl alcohol polymer (E1). rice field.

The production conditions of the modified vinyl alcohol polymer (E1) are shown in Table 1, and the contents a, b ₁ , b ₂ and c of the monomer units of the polymer (E1), the number average degree of polymerization Pn, the saponification Table 2 shows the degree, biodegradability, oxygen gas barrier property, water solubility, and heat sealability of the multilayer film obtained using the polymer (E1).

(Examples 2-7 and Comparative Examples 1-7)
The amount of vinyl acetate and methanol charged, the type of gas and gas pressure during polymerization, the type of monomer used during polymerization and polymerization conditions such as the amount of monomer added, and/or sodium hydroxide relative to the vinyl acetate unit during saponification Various modified vinyl alcohol polymers (E2) to (E7) and (C1) were prepared in the same manner as in Example 1, except that the saponification conditions such as the molar ratio of were changed to the conditions shown in Table 1. ~ (C7) were produced. Table 1 shows these production conditions, and Table 2 shows the evaluation results of the polymer and the multilayer film using the polymer.

As shown in Tables 1 and 2, the modified polyvinyl alcohol polymers (E1) to (E7) produced in Examples 1 to 7 all have excellent biodegradability, and when laminated on a multilayer film, oxygen It can be seen that all of gas barrier properties, water solubility and heat sealing properties were excellent.

On the other hand, with the unmodified polyvinyl alcohol (C1) of Comparative Example 1, the multilayer film had a low oxygen gas barrier property and a high heat-sealable temperature. In addition, the ethylene-vinyl alcohol copolymer (C2) of Comparative Example 2, which has an ethylene unit content a of 8 mol% and does not contain a hydroxyl group-containing monomer unit, has an oxygen gas barrier property as compared with Comparative Example 1. Although improved, the heat seal temperature was still high. Furthermore, the ethylene-vinyl alcohol copolymer (C3) of Comparative Example 3, which has an ethylene unit content a of 8 mol% and a content c (derived from DAMP) of 3 mol%, further has oxygen gas barrier properties. Although improved, the heat seal temperature was still high.

In a multilayer film using a propylene-vinyl alcohol copolymer (C4) having an olefinic monomer unit content a of 10 mol% and containing no hydroxyl group-containing monomer units, oxygen barrier properties and heat sealing properties but had low water solubility and biodegradability.

In the case of using the vinyl alcohol copolymer (C5) of Comparative Example 5, which does not contain olefinic monomer units and has a hydroxyl group-containing monomer content c (derived from DAB) of 3 mol%, water-soluble and excellent biodegradability, but the oxygen barrier property was low and the heat sealing temperature was high.

The propylene-vinyl alcohol copolymer of Comparative Example 6 (C6 ) was excellent in heat-sealing properties, but poor in oxygen barrier properties, water solubility and biodegradability.

The propylene-vinyl alcohol copolymer of Comparative Example 7 (C7 ) was excellent in water solubility and heat-sealing properties, but poor in oxygen barrier properties and biodegradability.

The resin composition of the present invention is useful, for example, for packaging various products in technical fields such as the food and beverage field, pet food field, oil and fat industry field, and pharmaceutical field.

Claims

Including the structure α represented by the following formula (I), the content ratios a (mol%), b 1 (mol%), b 2 (mol%) of each monomer unit with respect to all monomer units in the structure α ), and c (mol %) satisfy the following formulas (1) and (3).
1≤a≤40 (1)
1≤c≤15 (2)
35≦(b 1 +b 2 )≦98 (3)

[in formula (I), R 1 , R 2 , R 3 and R 4 are each independently a hydrogen atom or an optionally branched alkyl group;
the total number of carbon atoms constituting R 1 , R 2 , R 3 and R 4 is 1 to 3;
R 5 and R 5′ are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms,
R 6 is a hydrogen atom, or —(CH 2 ) m —R 9 in which at least one hydrogen atom may be substituted with R 8 (wherein R 9 and R 8 are each independently a hydroxyl group, formyl an oxy group or an acyloxy group having 2 to 10 carbon atoms, and m is an integer of 1 to 5),
R 7 has at least one hydrogen atom optionally substituted with R 11 and is at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH 2 ) n —R 10 (wherein R 10 and R 11 are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and n is an integer of 1 to 5 and R 6 and R 7 together are at least two, which may be the same or different, selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; including one group]
The modified vinyl alcohol polymer according to claim 1, wherein the formula (I) is represented by the following formula (I-1).

[In formula (I-1), a, b 1 , b 2 , b 1 +b 2 , c, R 1 , R 2 , R 3 , R 4 , R 5 , R 5 ′ , R 9 , R 10 , m and n are each independently as defined in said formula (I)]
The modified vinyl alcohol polymer according to claim 1, wherein the formula (I) is represented by the following formula (I-2).

[In the formula (I-2),
R 7′ has at least one hydrogen atom optionally substituted with R 11 and at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH 2 ) n —R 10 (wherein R 10 and R 11 are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and together they are a hydroxyl group; formyloxy and an acyloxy group having 2 to 10 carbon atoms; and at least two groups which may be the same or different and are selected from the group consisting of;
a, b 1 , b 2 , b 1 +b 2 , c, R 1 , R 2 , R 3 , R 4 , R 5 , and R 5′ are each independently as defined in said formula (I) ]
The modified vinyl alcohol polymer according to any one of claims 1 to 3, which has a number average degree of polymerization of 200 to 5,000.
In the formula (I),
R 5 and R 5′ are each independently a hydroxyl group or an acetyloxy group;
R 6 is a hydrogen atom, or —(CH 2 ) m —R 9′ in which at least one hydrogen atom may be substituted with R 8 ′ (wherein R 9′ and R 8′ are each independently , a hydroxyl group or an acetyloxy group, and m is an integer of 1 to 5),
R 7 has at least one hydrogen atom optionally substituted with R 11′ and at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; —(CH 2 ) n —R 10′ (wherein R 10′ and R 11′ are each independently a hydroxyl group or an acetyloxy group and n is an integer from 1 to 5), and 5. The modified vinyl alcohol polymer according to any one of claims 1 to 4, wherein a, b1 , b2 , and c are each independently defined in formula (I).
The modified vinyl alcohol polymer according to any one of claims 1 to 5, which has a saponification degree of 50 to 99.99 mol%.
A method for producing a modified vinyl alcohol polymer, comprising:
Copolymerizing an olefinic monomer containing a polymerizable unsaturated bond and having 3 to 5 carbon atoms, a vinyl ester monomer, and a hydroxyl group-containing monomer,
The vinyl ester monomer is
A compound represented by the following formula (II):

[wherein R 5 is a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms], and a compound represented by the following formula (III):

[In formula (III), R 5′ is a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms]
At least one compound selected from the group consisting of
provided that in formulas (II) and (III), R 5 and R 5' may be the same or different;
A compound in which the hydroxyl group-containing monomer is represented by the following formula (IV):

[In the formula (IV),
R 6 is a hydrogen atom, or —(CH 2 ) m —R 9 in which at least one hydrogen atom may be substituted with R 8 (wherein R 9 and R 8 are each independently a hydroxyl group, formyl an oxy group or an acyloxy group having 2 to 10 carbon atoms, and m is an integer of 1 to 5),
R 7 has at least one hydrogen atom optionally substituted with R 11 and has at least one group selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms. —(CH 2 ) n —R 10 (wherein R 10 and R 11 are each independently a hydroxyl group, a formyloxy group or an acyloxy group having 2 to 10 carbon atoms, and n is an integer of 1 to 5; and R 6 and R 7 together are at least two, which may be the same or different, selected from the group consisting of a hydroxyl group; a formyloxy group; and an acyloxy group having 2 to 10 carbon atoms; including groups]
, manufacturing method.