JP2013018965A - Vinyl alcoholic polymer, and aqueous solution containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vinyl alcohol polymer providing a film excellent in water resistance and binder performance, and having sufficient water solubility and viscosity stability also in a neutral region; and to provide an aqueous solution containing the same.SOLUTION: The vinyl alcohol polymer contains a monomer unit having a group represented by formula (1), and satisfies expression (I): 370≥P≥S≥6,000. The PVA preferably further satisfies expressions (II): 200≥P≥4,000 and (III): 0.1≥S≥10, wherein P: a viscosity average polymerization degree, and S: a content (mol%) of the monomer unit.

Description

  The present invention relates to a vinyl alcohol polymer having a silyl group and an aqueous solution containing the same.

  A vinyl alcohol polymer represented by polyvinyl alcohol (hereinafter sometimes abbreviated as “PVA”) is known as a water-soluble synthetic polymer, and is a raw material for vinylon which is a synthetic fiber, a paper processing agent. It is widely used for fiber processing agents, adhesives, stabilizers for emulsion polymerization and suspension polymerization, inorganic binders, films and the like. In particular, PVA is superior to other water-soluble synthetic polymers in strength properties and film-forming properties. By utilizing these properties, clear coating agents for improving the surface properties of paper, binders in pigment coating, etc. It is heavily used as.

  In order to further enhance the properties of such PVA, PVA with various modifications has been developed. As one of the modified PVA, silyl group-containing PVA can be mentioned. This silyl group-containing PVA is particularly excellent in water resistance and adhesion to inorganic substances. However, the silyl group-containing PVA is (a) difficult to dissolve unless an alkali or acid such as sodium hydroxide is added when preparing an aqueous solution, and (b) the viscosity stability of the prepared aqueous solution is low. There are inconveniences such as lowering.

  Therefore, water solubility and the like are improved by setting the product (P × S) of the viscosity average degree of polymerization (P) and the content of the monomer unit having a silyl group (S: mol%) within a certain range. A silyl group-containing PVA obtained has been proposed (see Japanese Patent Application Laid-Open No. 2004-43644). However, in this silyl group-containing PVA, the upper limit of the product (P × S) is set to 370, and the content of the monomer unit having a silyl group is increased to enhance the characteristics as the silyl group-containing PVA. And the trade-off relationship between improving water solubility and the like has not been resolved. That is, as described in paragraph 0009 of the above publication, when the product (P × S) is 370 or more, it may not be dissolved unless an alkali or acid is added when preparing an aqueous solution of silyl group-containing PVA. It has the disadvantage of being. That is, it cannot be said that the silyl group-containing PVA sufficiently solves the above-mentioned disadvantages.

JP 2004-43644 A

  The present invention has been made based on the above-described circumstances, and is a vinyl alcohol polymer having excellent water resistance and binder performance of the resulting film, and sufficient water solubility and viscosity stability even in a neutral region. An object of the present invention is to provide an aqueous solution containing such a vinyl alcohol polymer.

（式（１）中、Ｒ^１は、水素原子又は炭素数１〜５のアルキル基である。Ｒ^２は、アルコキシル基、アシロキシル基又はＯＭで表される基である。Ｍは、水素原子、アルカリ金属又はアンモニウム基である。Ｒ^３及びＲ^４は、それぞれ独立して、水素原子又はアルキル基である。Ｒ^１〜Ｒ^４で表されるアルキル基、アルコキシル基及びアシロキシル基が有する水素原子は、酸素原子又は窒素原子を含有する置換基で置換されていてもよい。ｍは、０〜２の整数である。ｎは、３以上の整数である。Ｒ^１〜Ｒ^４がそれぞれ複数存在する場合、複数存在する各Ｒ^１〜Ｒ^４は、独立して上記定義を満たす。）
３７０≦Ｐ×Ｓ≦６，０００ ・・・（Ｉ）
Ｐ：粘度平均重合度
Ｓ：上記単量体単位の含有率（モル％） The invention made to solve the above problems is
A vinyl alcohol polymer containing a monomer unit having a group represented by the following formula (1) and satisfying the following formula (I).

(In Formula (1), R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ² is an alkoxyl group, an acyloxyl group, or a group represented by OM. M is a hydrogen atom, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group, each of which represents an alkyl group, an alkoxyl group or an acyloxyl group represented by R ^{1 to} R ^4. May be substituted with a substituent containing an oxygen atom or a nitrogen atom, m is an integer of 0 to 2. n is an integer of 3 or more, and there are a plurality of R ^{1 to} R ⁴ , respectively. In the case, a plurality of each R ^{1 to} R ⁴ independently satisfy the above definition.)
370 ≦ P × S ≦ 6,000 (I)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

  The PVA includes a monomer unit having a group represented by the above formula (1), and has a structure in which a silyl group is connected to a main chain via an alkylene group having 3 or more carbon atoms. For this reason, according to the said PVA, even if the modification amount of a silyl group is raised, the fall of water solubility and viscosity stability is suppressed. Moreover, according to the PVA, since the product (P × S) of the viscosity average degree of polymerization (P) and the content (S) of the monomer unit is in the above range, the amount of silyl group modification can be increased. And a film excellent in water resistance and binder performance can be obtained.

It is preferable that the PVA further satisfies the following formulas (II) and (III).
200 ≦ P ≦ 4,000 (II)
0.1 ≦ S ≦ 10 (III)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

  Thus, by setting the viscosity average degree of polymerization (P) and the content of the monomer units (S) in the above ranges, the water solubility and viscosity stability, and the water resistance and binder performance of the resulting film are improved. Can do.

  N in the above formula (1) is preferably an integer of 6 or more and 20 or less. By setting n in the above range, the content of the crosslinking agent used in combination with the vinyl alcohol polymer can be reduced, and even when no crosslinking agent is used, the water resistance and binder performance of the resulting film are obtained. Can be fully demonstrated.

（式（２）中、Ｒ^１〜Ｒ^４、ｍ及びｎの定義は、式（１）と同様である。Ｘは、直接結合、２価の炭化水素基又は酸素原子若しくは窒素原子を含む２価の有機基である。Ｒ^５は、水素原子又はメチル基である。） The monomer unit is preferably represented by the following formula (2).

(In formula (2), the definitions of R ^{1 to} R ⁴ , m and n are the same as those in formula (1). X represents a direct bond, a divalent hydrocarbon group, an oxygen atom or a nitrogen atom 2. R ⁵ is a hydrogen atom or a methyl group.)

  When the monomer unit has a structure represented by the formula (2), the various performances can be further enhanced.

X in the above formula (2) is —CO—NR ⁶ — * (R ⁶ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. * Is a group represented by the above formula (1). It is preferably represented by the following: Thus, when the monomer unit has an amide structure at a position away from the silyl group, water solubility and viscosity stability can be further improved while maintaining the performance derived from the silyl group.

  X in the above formula (2) is represented by —CO—NH— * (* represents a bonding site with the group represented by the above formula (1)), and n is an integer of 12 or less. Good. By setting the monomer unit to such a structure, the performance of the PVA such as water solubility and viscosity stability can be further enhanced, and the production of the PVA can be easily performed.

  The aqueous solution of the present invention contains 4% by mass or more and 20% by mass or less of the vinyl alcohol polymer, and has a pH of 4 or more and 8 or less. The aqueous solution has a high concentration of the modified PVA and can provide a film having excellent water resistance and binder performance. Moreover, since the aqueous solution has high viscosity stability and the pH is in the above range, it is excellent in handleability.

  As described above, the vinyl alcohol polymer of the present invention is excellent in water resistance and binder performance of the resulting film, and has sufficient water solubility and viscosity stability even in the neutral region. Moreover, the aqueous solution of the present invention has a high viscosity stability and can provide a film excellent in water resistance and binder performance.

  Hereinafter, embodiments of the vinyl alcohol polymer and the aqueous solution of the present invention will be described in detail.

<PVA>
The PVA of the present invention contains a monomer unit having a group represented by the above formula (1). That is, the PVA is a copolymer including a monomer unit having a group represented by the above formula (1) and a vinyl alcohol unit (—CH ₂ —CHOH—), and further another monomer unit. You may have.

In the above formula (1), ^{R 1} is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group.

R ² is a group represented by an alkoxyl group, an acyloxyl group, or OM. M is a hydrogen atom, an alkali metal, or an ammonium group ( ⁺ NH ₄ ). Examples of the alkoxyl group include a methoxy group and an ethoxy group. Examples of the acyloxyl group include an acetoxy group and a propionyloxy group. Examples of the alkali metal include sodium and potassium. Among these groups represented by R ² , an alkoxyl group or a group represented by OM is preferable, and an alkoxyl group having 1 to 5 carbon atoms and a group represented by OM in which M is hydrogen or an alkali metal are more preferable. A methoxy group, an ethoxy group, and a group represented by OM in which M is sodium or potassium are more preferable.

R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include the above-described alkyl groups having 1 to 5 carbon atoms. R ³ and R ⁴ are preferably a hydrogen atom or a methyl group.

The hydrogen atom which the alkyl group, alkoxyl group, and acyloxyl group represented by R ^{1 to} R ⁴ have may be substituted with a substituent containing an oxygen atom or a nitrogen atom. Examples of the substituent containing an oxygen atom include an alkoxyl group and an acyloxyl group. In addition, examples of the substituent containing a nitrogen atom include an amino group and a cyano group.

In ^the case where R 1 to R ⁴ is present in plural, each ^R 1 to R ⁴ that there are two or more, independently meets the above definition.

m is an integer of 0 to 2, and 0 is preferable. When m is 0, that is, the monomer unit has three R ² groups, the effect of modification can be further enhanced.

n is an integer of 3 or more. The upper limit of n is not particularly limited, but is, for example, 20 and is preferably 12. The PVA has a structure in which n in the formula (1) is 3 or more, that is, the silyl group is connected to the main chain via an alkylene group having 3 or more carbon atoms, so that the amount of modification of the silyl group can be reduced. Even if it raises, the fall of water solubility and viscosity stability is suppressed. The reason why such an effect appears is not sufficiently elucidated, but, for example, an alkylene group having 3 or more carbon atoms that exhibits hydrophobicity decreases the hydrolysis rate of Si—R ² and inhibits the reaction in an aqueous solution. This is presumed to be caused.

  Further, n is more preferably an integer of 6 or more. By setting n in such a range, the content of the crosslinking agent usually used in combination with the vinyl alcohol polymer can be reduced, and the water resistance of the resulting film can be obtained even when no crosslinking agent is used. Property and binder performance can be sufficiently exhibited.

  The specific structure of the monomer unit is not particularly limited as long as it has a group represented by the above formula (1), but is preferably represented by the above formula (2).

In formula (2), the definitions of R ^{1 to} R ⁴ , m and n are the same as in formula (1). These preferred groups or numerical ranges are also the same as those in the formula (1).

  X is a direct bond, a divalent hydrocarbon group, or a divalent organic group containing an oxygen atom or a nitrogen atom. When the monomer unit has a structure represented by the above formula (2), various performances such as water solubility and viscosity stability, water resistance of the resulting film and binder performance can be further enhanced.

  Examples of the divalent hydrocarbon group include a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms and a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include a methylene group, an ethylene group, and a propylene group. A phenylene group etc. can be mentioned as said C6-C10 bivalent aromatic hydrocarbon group. Examples of the divalent organic group containing an oxygen atom include an ether group, an ester group, a carbonyl group, an amide group, and a group in which these groups are connected to a divalent hydrocarbon group. Examples of the divalent organic group containing a nitrogen atom include an imino group, an amide group, and a group in which these groups are connected to a divalent hydrocarbon group.

Among the groups represented by X, a divalent organic group containing an oxygen atom or a nitrogen atom is preferable, a group containing an amide group is more preferable, and —CO—NR ⁶ — * (R ⁶ is a hydrogen atom or a carbon atom) It is an alkyl group of formulas 1 to 5. * is more preferably a group represented by the bonding site with the group represented by the above formula (1). As described above, the monomer unit has a polar structure, preferably an amide structure, at a position away from the silyl group, thereby improving water solubility and viscosity stability while maintaining the performance derived from the silyl group. it can. As the above R ^6, enhance more the function, and is preferably a hydrogen atom from the viewpoint of can be manufactured of the PVA easily, the R ⁶ is a hydrogen atom, n is 3 to 12 integer It is more preferable that

R ⁵ is a hydrogen atom or a methyl group.

  As said monomer unit, what is represented by following formula (3) is still more preferable.

In the above formula (3), the definitions of R ¹ , R ² , R ⁵ , X and m are the same as in the above formula (2). These preferred groups or numerical ranges are also the same as those in the above formula (2).

In the above formula (3), R ³ ′ and R ⁴ ′ are each independently a hydrogen atom or an alkyl group. Examples of the alkyl group include the above-described alkyl groups having 1 to 5 carbon atoms. R ³ ′ and R ⁴ ′ are preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom. The hydrogen atom contained in the alkyl group represented by R ³ ′ and R ⁴ ′ may be substituted with a substituent containing an oxygen atom or a nitrogen atom. Examples of the substituent containing an oxygen atom include an alkoxyl group and an acyloxyl group. In addition, examples of the substituent containing a nitrogen atom include an amino group and a cyano group. When there are a plurality of R ³ ′ and R ⁴ ′, a plurality of R ³ ′ and R ⁴ ′ satisfy the above definition independently.

  In the above formula (3), n ′ is an integer of 1 or more. The upper limit of n is not particularly limited, but is 18 for example and 10 is preferable. Furthermore, n is more preferably an integer of 4 or more. By setting n in such a range, the content of the crosslinking agent usually used in combination with the vinyl alcohol polymer can be reduced, and the water resistance of the resulting film can be obtained even when no crosslinking agent is used. Property and binder performance can be sufficiently exhibited.

When the monomer unit is represented by the above formula (3), various functions of the PVA can be expressed more effectively. The reason for this is not clear, but it is presumed that the above-described function of reducing the hydrolysis rate of Si—R ² and inhibiting the reaction in the aqueous solution is more effectively exhibited.

The PVA satisfies the following formula (I).
370 ≦ P × S ≦ 6,000 (I)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

The viscosity average degree of polymerization (P) is measured according to JIS-K6726. That is, when the PVA has a saponification degree of less than 99.5 mol%, it is re-saponified to a saponification degree of 99.5 mol% or more, purified, and then the intrinsic viscosity [η] (unit: measured in water at 30 ° C.) (unit: (Deciliter / g) can be obtained by the following equation.
P = ([η] × 1000 / 8.29) ^{(1 / 0.62)}

The content of the monomer unit (S: mol%) can be obtained from proton NMR of the vinyl ester polymer before saponification. Here, when the proton NMR of the vinyl ester polymer before saponification is measured, the vinyl ester polymer is purified by reprecipitation with hexane-acetone, and the monomer having an unreacted silyl group is contained in the polymer. The body is sufficiently removed and then dried at 90 ° C. under reduced pressure for 2 days, and then dissolved in CDCl ₃ solvent for analysis.

The product (P × S) of the viscosity average degree of polymerization (P) and the content (S) of the monomer units corresponds to the number of the monomer units per 100 molecules. When this product (P × S) is less than the above lower limit, various properties derived from silyl groups such as water resistance and binder performance of the film obtained by the PVA cannot be sufficiently exhibited. On the contrary, when this product (P × S) exceeds the above upper limit, water solubility and viscosity stability are lowered. The product (P × S) preferably satisfies the following formula (I ′), and more preferably satisfies the following formula (I ″).
400 ≦ P × S ≦ 3,000 (I ′)
500 ≦ P × S ≦ 2,000 (I ″)

The PVA preferably further satisfies the following formulas (II) and (III).
200 ≦ P ≦ 4,000 (II)
0.1 ≦ S ≦ 10 (III)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)

  Thus, by setting the viscosity average degree of polymerization (P) and the content of the monomer units (S) in the above ranges, the water solubility and viscosity stability, and the water resistance and binder performance of the resulting film are improved. Can do.

Furthermore, in the viscosity average polymerization degree (P), it is more preferable to satisfy the following formula (II ′), and it is more preferable to satisfy the following formula (II ″).
500 ≦ P ≦ 3,000 (II ′)
1,000 ≦ P ≦ 2,400 (II ″)

  When the viscosity average degree of polymerization (P) is less than the lower limit, the water resistance, binder performance, etc. of the resulting film may be lowered. Conversely, when the viscosity average degree of polymerization (P) exceeds the above upper limit, water solubility, viscosity stability, etc. may be reduced.

Moreover, in the content rate (S) of the monomer unit, it is more preferable to satisfy the following formula (III ′), and it is more preferable to satisfy the following formula (III ″).
0.25 ≦ S ≦ 6 (III ′)
0.5 ≦ S ≦ 5 (III ″)

  When the content rate (S) of the monomer unit is less than the lower limit, the water resistance, binder performance, and the like of the resulting film may be deteriorated. Conversely, when the viscosity average degree of polymerization (P) exceeds the above upper limit, water solubility, viscosity stability, etc. may be reduced.

  Although there is no restriction | limiting in particular as the saponification degree of the said PVA, 80 mol% or more is preferable, 90 mol% or more is more preferable, 95 mol% or more is further more preferable, 97 mol% or more is especially preferable. When the saponification degree of the PVA is less than the above lower limit, the water resistance and the like of the resulting film may be lowered. In addition, although there is no restriction | limiting in particular as an upper limit of the saponification degree of the said PVA, when productivity etc. are considered, it is 99.9 mol%, for example. Here, the saponification degree of PVA says the value measured according to the method of JIS-K6726.

<Method for producing PVA>
The method for producing the PVA is not particularly limited. For example, a copolymer obtained by copolymerizing a vinyl ester monomer and a monomer having a group represented by the above formula (1) ( It can be obtained by saponifying a vinyl ester polymer).

  Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Among these, vinyl acetate is preferable.

  In addition, for the purpose of adjusting the viscosity average polymerization degree (P) of the obtained PVA at the time of copolymerization of the monomer having a group represented by the above formula (1) and a vinyl ester monomer, Polymerization may be carried out in the presence of a chain transfer agent as long as the gist of the present invention is not impaired. As chain transfer agents, aldehydes such as acetaldehyde and propionaldehyde; ketones such as acetone and methyl ethyl ketone; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-hydroxyethanethiol, n-dodecanethiol, Examples include mercaptans such as mercaptoacetic acid and 3-mercaptopropionic acid; halogens such as tetrachloromethane, bromotrichloromethane, trichloroethylene, and perchloroethylene.

  As a monomer which has group represented by the said Formula (1), the compound represented, for example by following formula (4) can be mentioned. By using a compound represented by the following formula (4), finally, a PVA containing a monomer unit having a group represented by the above formula (2) can be easily obtained.

In formula (4), the definitions of R ^{1 to} R ⁵ , X, m, and n are the same as in formula (2). These preferred groups or numerical ranges are also the same as those in the formula (2).

  Examples of the compound represented by the above formula (4) include 3- (meth) acrylamidopropyltrimethoxysilane, 4- (meth) acrylamidobutyltrimethoxysilane, 8- (meth) acrylamideoctyltrimethoxysilane, 6- (meta ) Acrylamide hexyltrimethoxysilane, 12- (meth) acrylamide dodecyltrimethoxysilane, 18- (meth) acrylamide octadecyltrimethoxysilane, 3- (meth) acrylamidepropyltriethoxysilane, 3- (meth) acrylamidopropyltributoxysilane , 3- (meth) acrylamidopropylmethyldimethoxysilane, 3- (meth) acrylamidopropyldimethylmethoxysilane, 3- (meth) acrylamide-3-methylbutyltrimethoxysilane, 4- (meth) Acrylamide-4-methylbutyltrimethoxysilane, 4- (meth) acrylamide-3-methylbutyltrimethoxysilane, 5- (meth) acrylamide-5-methylhexyltrimethoxysilane, 4-pentenyltrimethoxysilane, 5-to Examples include xenyl trimethoxysilane.

  Examples of the method for copolymerizing the vinyl ester monomer and the monomer having the group represented by the formula (1) include a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. A well-known method is mentioned. In particular, when the polymerization temperature is lower than 30 ° C., an emulsion polymerization method is preferable, and when the polymerization temperature is 30 ° C. or higher, a bulk polymerization method performed without solvent or a solution polymerization method performed using a solvent such as alcohol is used. Usually adopted.

  In the case of the emulsion polymerization method, examples of the solvent include water, and lower alcohols such as methanol and ethanol may be used in combination. Moreover, a well-known emulsifier can be used as an emulsifier. As an initiator for copolymerization, a redox initiator using iron ions, an oxidizing agent and a reducing agent in combination is preferably used for controlling the polymerization. In the case of the bulk polymerization method or the solution polymerization method, the reaction method can be carried out by either a batch method or a continuous method. When the copolymerization reaction is carried out using the solution polymerization method, examples of the alcohol used as the solvent include lower alcohols such as methanol, ethanol, and propanol. Examples of the initiator used for the copolymerization reaction in this case include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 1,1′-azobis ( Azo initiators such as cyclohexane-1-carbonitrile) and 2,2′-azobis (N-butyl-2-methylpropionamide); peroxide initiators such as benzoyl peroxide and n-propyl peroxycarbonate And known initiators. Although there is no restriction | limiting in particular about the polymerization temperature at the time of performing a copolymerization reaction, The range of 5 to 50 degreeC is suitable.

  In the case of this copolymerization reaction, a copolymerizable monomer can be copolymerized as necessary as long as the gist of the present invention is not impaired. Examples of such monomers include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; carboxylic acids such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, or the like Derivatives; acrylic acid or salts thereof, acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate; methacrylic acid or salts thereof, methyl methacrylate, ethyl methacrylate, n-methacrylate Methacrylic acid esters such as propyl and isopropyl methacrylate; Acrylamide derivatives such as acrylamide, N-methylacrylamide and N-ethylacrylamide; Methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide and N-ethylmethacrylamide; Vinyl ethers such as ru vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether; hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1,4-butanediol vinyl ether; Allyl ethers; allyl ethers such as propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate; 3-buten-1-ol, 4-penten-1-ol, 5 -Hydroxyl-containing α-olefins such as hexen-1-ol, 7-octen-1-ol, 9-decene-1-ol, 3-methyl-3-buten-1-ol; , Monomers having a sulfonic acid group such as allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid; vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine , Having a cationic group such as vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine And monomers. The amount of these monomers used varies depending on the purpose and application of use, but is usually 20 mol% or less, preferably 10 mol, based on all monomers used for copolymerization. % Or less.

  The vinyl ester polymer obtained by the copolymerization is then saponified in a solvent according to a known method and led to PVA.

  As the catalyst for the saponification reaction, an alkaline substance is usually used, and examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. The amount of the alkaline substance used is preferably in the range of 0.004 to 0.5 in terms of a molar ratio based on the vinyl ester monomer unit in the vinyl ester polymer. More preferably, it is in the range of 0.05. Further, this catalyst may be added all at once in the early stage of the saponification reaction, or a part thereof may be added in the early stage of the saponification reaction, and the rest may be added in the middle of the saponification reaction.

  Examples of the solvent that can be used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide, and the like. Of these solvents, methanol is preferred. Further, in the use of methanol, the water content in methanol is preferably adjusted to 0.001 to 1% by mass, more preferably 0.003 to 0.9% by mass, and particularly preferably 0.005 to 0.8% by mass. It is good to be.

  The saponification reaction is preferably performed at a temperature of 5 to 80 ° C, more preferably 20 to 70 ° C. The time required for the saponification reaction is preferably 5 minutes to 10 hours, more preferably 10 minutes to 5 hours. The saponification reaction can be carried out in either a batch method or a continuous method. If necessary, the remaining saponification catalyst may be neutralized after completion of the saponification reaction. Examples of usable neutralizing agents include organic acids such as acetic acid and lactic acid, and ester compounds such as methyl acetate. Can do.

  The PVA obtained by the saponification reaction can be washed as necessary. Examples of the cleaning liquid used in this cleaning include lower alcohols such as methanol, lower fatty acid esters such as methyl acetate, and mixtures thereof. A small amount of water, alkali, acid, or the like may be added to these cleaning liquids.

<Applications>
The PVA can be stored and transported in a powder state. Moreover, when using the said PVA, it can be used with the state of a powder, or the state melt | dissolved or disperse | distributed to liquids, such as water. When the PVA is used as an aqueous solution, the PVA can be dispersed in water and then heated with stirring to obtain a uniform aqueous solution. According to the PVA, a uniform aqueous solution can be obtained without adding an alkali or acid such as sodium hydroxide to water.

  The PVA can be dissolved in water without adding an alkali or acid such as sodium hydroxide when preparing this aqueous solution. (2) Excellent viscosity stability in the aqueous solution state (3) When mixed with an inorganic material to form a film, the film has excellent binder power with the inorganic material, and (4) the formed film has excellent water resistance. Therefore, the PVA can be used, for example, as a paper coating agent. In addition to this, the PVA can be used in various applications utilizing the function of a functional group such as a hydroxyl group, a vinyl ester group, and a silyl group. Applications include, for example, paper sizing agents, fiber finishing agents, dyes, glass fiber coating agents, metal and glass surface coating agents, coating agents such as antifogging agents, wood, paper, aluminum foil, plastics. Adhesives such as non-woven fabric binders, fibrous binders, binders for building materials such as gypsum board and fiberboard, thickeners for various emulsion adhesives, additives for urea resin adhesives, additives for cement and mortar, hot Various adhesives such as melt-type adhesives and pressure-sensitive adhesives, dispersants for emulsion polymerization of various ethylenically unsaturated monomers such as ethylene, vinyl acetate and vinyl chloride, stabilizers for pigment dispersion such as paints and adhesives , Dispersion stabilizers for suspension polymerization of various ethylenically unsaturated monomers such as vinyl chloride, vinylidene chloride, styrene, (meth) acrylic acid, vinyl acetate, fibers, films, sheets, Molds for pipes, tubes, water-soluble fibers, provisional films, etc., additives for hydrophilicity to hydrophobic resins, compounding agents for synthetic resins such as composite fibers, films and other additives for moldings, soil conditioners, soil stability An agent etc. can be mentioned.

  The vinyl acetal polymer obtained by acetalizing the PVA with an aldehyde compound such as acetaldehyde or butyraldehyde is useful for applications such as safety glass interlayers, ceramic binders, ink dispersants, and photosensitive materials. is there.

<Aqueous solution>
The aqueous solution of the present invention contains 4% by mass or more and 20% by mass or less of the PVA, and has a pH of 4 or more and 8 or less. The method for preparing the aqueous solution is as described above for the use of the PVA.

  The aqueous solution may contain other components in addition to the PVA and water. Examples of other components include alcohols such as ethanol, other solvents such as diethyl ether, alkalis such as sodium hydroxide and ammonia, acids such as hydrochloric acid, inorganic particles such as silica, titanium dioxide, clay, and calcium carbonate. Can be mentioned.

  The aqueous solution has a high concentration of the modified PVA and can provide a film having excellent water resistance and binder performance. The aqueous solution is also excellent in viscosity stability. Furthermore, since the aqueous solution has a pH in the above range, it is excellent in handleability. Therefore, the said aqueous solution can be used suitably for each use etc. which were mentioned above as a use of the said PVA.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the following examples and comparative examples, unless otherwise specified, parts and% represent parts by mass and mass%, respectively.

In addition, the monomer (monomer A) which has the silyl group used by the Example and the comparative example is as follows.
MAmPTMS: 3-methacrylamideamidopropyltrimethoxysilane MAmPTES: 3-methacrylamideamidopropyltriethoxysilane MAmBTMS: 4-methacrylamidobutyltrimethoxysilane MAmOTMS: 8-methacrylamidooctyltrimethoxysilane MAmDDTMS: 12-methacrylamidododecyltrimethoxysilane MAmODTMS: 18-methacrylamidooctadecyltrimethoxysilane AMBTMS: 3-acrylamido-3-methylbutyltrimethoxysilane 4-PTMS: 4-pentenyltrimethoxysilane VMS: vinyltrimethoxysilane MAMTMTS: methacrylamidomethyltrimethoxysilane AMPTMS: 2 -Acrylamide-2-methylpropyltrimethoxysilane

[Production of silyl group-containing PVA]
PVA is produced by the following method, the degree of saponification, the content of monomer units having a group represented by the above formula (1) (S) (in some examples, monomer units having a silyl group) Content) and viscosity average degree of polymerization (P). Moreover, according to the following evaluation methods, the performance of the film and the binder strength with inorganic substances were evaluated.

[Analysis method of PVA]
Analysis of PVA was performed according to the method described in JIS-K6726 unless otherwise specified.

[Example 1] Production of PVA1 Into a 6 L separable flask equipped with a stirrer, reflux condenser, nitrogen inlet, comonomer dropping port and initiator addition port, 1,500 g of vinyl acetate, 500 g of methanol, the above formula (1 ) MAmPTMS 1.87 g as a monomer (monomer A) having a group represented by) was charged, and the inside of the system was purged with nitrogen for 30 minutes while carrying out nitrogen bubbling. Further, a comonomer solution having a concentration of 8% was prepared by dissolving MAmPTMS in methanol as a delay solution, and nitrogen substitution was performed by bubbling nitrogen gas. The temperature of the reactor was increased, and when the internal temperature reached 60 ° C., 0.8 g of 2,2′-azobisisobutyronitrile (AIBN) was added to initiate polymerization. The delay solution was added dropwise to polymerize the monomer composition (ratio of vinyl acetate and monomer A (MAmPTMS)) in the polymerization solution at a constant rate for 2.7 hours at 60 ° C. and then cooled to stop the polymerization. . The total amount of comonomer solution (sequentially added solution) added until the polymerization was stopped was 99 g. Further, the solid content concentration when the polymerization was stopped was 29.0%. Subsequently, an unreacted vinyl acetate monomer is removed while sometimes adding methanol under reduced pressure at 30 ° C., and a methanol solution containing 40% of polyvinyl acetate (PVAc) having a group represented by the above formula (1) Got. Furthermore, a methanol solution containing 10% by mass of methanol and sodium hydroxide was added so that the molar ratio of sodium hydroxide to the vinyl acetate unit in PVAc was 0.04 and the solid content concentration of PVAc was 30% by mass. In this order, with stirring, the saponification reaction was started at 40 ° C. A gel was formed in about 5 minutes after the addition of the alkaline solution. This gel-like material was pulverized with a pulverizer and allowed to stand at 40 ° C. for 1 hour to allow saponification to proceed. Then, methyl acetate was added to neutralize the remaining alkali. After confirming the completion of neutralization using a phenolphthalein indicator, the mixture was filtered to obtain a white solid. Methanol was added thereto, and the mixture was allowed to wash at room temperature for 3 hours. After repeating the above washing operation three times, the white solid obtained by centrifugal drainage was left in a dryer at 65 ° C. for 2 days to obtain PVA1 having a group represented by the above formula (1). PVA1 had a viscosity average polymerization degree (P) of 1,700 and a saponification degree of 98.6 mol%.

The content of the monomer unit having the group represented by the above formula (1) of the obtained PVA1 (content of the monomer unit having a silyl group) is the proton NMR of PVAc which is a precursor of this PVA. I asked for it. Specifically, after reprecipitation purification of the obtained PVAc was sufficiently performed three times or more with n-hexane / acetone, drying was performed under reduced pressure at 50 ° C. for 2 days to prepare a PVAc for analysis. This PVAc was dissolved in CDCl ₃ and measured at room temperature using 500 MHz proton NMR (JEOL GX-500). From the peak α (4.7 to 5.2 ppm) derived from the main chain methine of the vinyl acetate unit and the peak β (3.4 to 3.8 ppm) derived from the methyl of the methoxy group of the monomer A unit, the following formula is obtained. The content (S) of the monomer unit having a group represented by the formula (1) was calculated. In PVA1, the content (S) was 0.5 mol%. The results of analyzing the obtained PVA are shown in Table 1.
Content of monomer unit having group represented by formula (1) (S: mol%)
= {(Peak area of β / 9) / (peak area of α + (peak area of β / 9))} × 100

[Examples 2-31 and Comparative Examples 1-22] Production of PVA2-PVA53 Polymerization conditions such as the amount of vinyl acetate and methanol charged, the type and amount of monomer A added, the concentration of PVAc during saponification, and water relative to vinyl acetate units PVA2 to PVA53 were obtained in the same manner as in Example 1 except that the saponification conditions such as the molar ratio of sodium oxide were changed as shown in Tables 1 and 2. Tables 1 and 2 show the results of analysis for each obtained PVA.

[Examples 32-66 and Comparative Examples 23-46] Preparation of aqueous solution About PVA1-PVA53, PVA aqueous solution was prepared so that it might become a predetermined density | concentration and pH. The viscosity stability of the PVA aqueous solution, the water resistance of the film, the water resistance of the film containing an inorganic substance, and the binder strength between the PVA and the inorganic substance were evaluated by the following evaluation methods. Table 3 shows the type of PVA used, the pH of the aqueous solution, and the evaluation results.

[Viscosity stability of PVA aqueous solution]
An 8% PVA aqueous solution was prepared and allowed to stand in a 20 ° C. constant temperature bath, and the viscosity immediately after the temperature of the PVA aqueous solution reached 20 ° C. and the viscosity after 7 days were measured. A value obtained by dividing the viscosity after 7 days by the viscosity immediately after the temperature of the PVA aqueous solution reached 20 ° C. (viscosity after 7 days / viscosity immediately after) was determined and determined according to the following criteria.
A: Less than 2.5 times.
B: 2.5 times or more and less than 3.0 times.
C: 3.0 times or more and less than 5.0 times.
D: 5.0 times or more, but the PVA aqueous solution is not gelled.
E: The PVA aqueous solution loses fluidity and gels.

[Water resistance of film]
A 4% PVA aqueous solution was prepared and cast at 20 ° C. to obtain a film having a thickness of 40 μm. The obtained film was cut into a size of 10 cm in length and 10 cm in width to prepare a test piece. After this test piece was immersed in distilled water at 20 ° C. for 24 hours, it was taken out (collected), the water adhering to the surface was wiped off with gauze, and the mass at the time of water swelling was measured. The test piece whose weight during water swelling was measured was dried at 105 ° C. for 16 hours, and then the weight during drying was measured. Here, a value obtained by dividing the mass at the time of water swelling by the mass at the time of drying was obtained, and this was taken as the degree of swelling (times), and was judged according to the following criteria.
S: Less than 3.0 times.
A: 3.0 times or more and less than 5.0 times.
B: 5.0 times or more and less than 8.0 times.
C: 8.0 times or more and less than 10.0 times.
D: 10.0 times or more.
E: The immersed test piece cannot be collected.

[Water resistance of coatings containing inorganic substances]
A 20% aqueous dispersion of colloidal silica (manufactured by Nissan Chemical Industries: Snowtex ST-O) was prepared so that a 4% PVA aqueous solution was prepared and the mass ratio based on the solid content of PVA / colloidal silica was 100/10. After the addition, the film was cast at 20 ° C. to obtain a film having a thickness of 40 μm. The obtained film was cut into a size of 10 cm in length and 10 cm in width to prepare a test piece. After this test piece was immersed in distilled water at 20 ° C. for 24 hours, it was taken out (collected), the water adhering to the surface was wiped off with gauze, and the mass at the time of water swelling was measured. The test piece whose weight during water swelling was measured was dried at 105 ° C. for 16 hours, and then the weight during drying was measured. Here, a value obtained by dividing the mass at the time of water swelling by the mass at the time of drying was obtained, and this was taken as the degree of swelling (times), and was judged according to the following criteria.
A: Less than 3.0 times.
B: 3.0 times or more and less than 5.0 times.
C: 5.0 times or more and less than 8.0 times.
D: 8.0 times or more and less than 10.0 times.
E: It is 10.0 times or more, or the immersed test piece cannot be collected.

[Binder strength of PVA and inorganic substances]
Silica (manufactured by Mizusawa Chemical Co., Ltd .: Mizukasil P78D) and 0.2% of a dispersant (manufactured by Toagosei Chemical Industry Co., Ltd .: Aron T40) are dispersed in water with a homomixer, and a 20% aqueous dispersion of silica. Was prepared. To this silica aqueous dispersion, an aqueous PVA solution adjusted to 8% is added so that the mass ratio based on the solid content of silica / PVA is 100/20, and the above-mentioned silica and PVA are added by adding a necessary amount of water. A silica-dispersed PVA aqueous solution with a total concentration of 15% was obtained.

The obtained silica-dispersed PVA aqueous solution was applied to the surface of the fine paper with a basis weight of 60 g / m ² using a wire bar. Thereafter, the quality paper was dried at 100 ° C. for 3 minutes using a hot air dryer to obtain a sample for evaluation. The coating amount on high-quality paper (sample for evaluation) after drying was 11 g / m ² .

About the sample for evaluation, using an IGT print aptitude tester (manufactured by Kumagai Riki Kogyo Co., Ltd.), the measurement was performed at a printing pressure of 50 kg / cm ² , and the printing speed (cm / sec) was used as the binder strength between PVA and inorganic matter, and the binder strength was evaluated according to the following criteria. In the measurement using an IGT printability tester, IGT pick oil M (manufactured by Dainippon Ink & Chemicals, Inc.) was used and a spring drive B mechanism was adopted.
A: 260 cm / sec or more.
B: 220 cm / sec or more and less than 260 cm / sec.
C: 180 cm / sec or more and less than 220 cm / sec.
D: 140 cm / sec or more and less than 180 cm / sec.
E: Less than 140 cm / sec.

  As shown in Table 3, the PVA (PVA 1 to 31) obtained in Examples 1 to 31 has high water solubility, viscosity stability, water resistance of the obtained film, and binder performance (binder strength). It turns out that it is excellent. Here, if the viscosity stability is D or more, it is assumed that the viscosity stability is practically sufficient, and that the other three items are C or more is an excellent evaluation. Furthermore, the viscosity average degree of polymerization (P) of PVA, the degree of saponification, the structure of the monomer unit, the content (S), the product of the viscosity average degree of polymerization (P) and the content (S) (P × S), and an aqueous solution The aqueous solutions of Examples 32, 38, 42, 45, 47, 50-52, 56, 60-63, 65, and 66, which specified the pH of, were viscosity stable, water resistance of the resulting film and binder performance ( (Binder strength) is particularly excellent (viscosity stability is evaluated as C or higher, and among the other three items, two or more items are A or higher and the other is B). For example, the aqueous solutions of Examples 33, 34, 37, 41, 43, 44, 46, 48, 49, 53 to 55, and 57 to 59 have a slight decrease in viscosity stability and water resistance of the obtained film. I understand. This is due to a decrease in the viscosity average degree of polymerization (P) and saponification degree, and a product (P × S) of the viscosity average degree of polymerization (P) and the content rate (S) being small or large. In Examples 35, 36, 39, and 40, the pH of the aqueous solution is acidic or alkaline, so that the water resistance and binder strength of the film are reduced. In Example 64, since the alkylene group connecting the silyl group and the main chain has a long carbon number of 18, the hydrophobic group interaction becomes too strong, and the viscosity stability is considered to be lowered.

On the other hand, when PVA does not satisfy the prescribed requirements (Comparative Examples 23 to 46), it can be seen that water solubility, viscosity stability, water resistance performance of the film and binder performance (binder power) are lowered. In addition, when Example 32 (PVA1) is compared with Comparative Example 36 (PVA43) and Comparative Example 38 (PVA45), the pH of the aqueous solution, the viscosity average degree of polymerization (P), the degree of saponification, and the content rate (S) (S ) Is almost the same value, the water resistance and binder strength of the film are good in Example 32, and the viscosity stability is good in Example 32. The reason for this is not fully understood. However, in PVA1 of Example 32, (1) the mobility of the silyl group is high due to the presence of an alkylene group having 3 or more carbon atoms connecting the main chain and the silyl group. The film has excellent water resistance and binder strength. (2) In addition, in aqueous solution, the alkylene group reduces the rate of hydrolysis of Si—R ² or inhibits the reaction, so that the viscosity stability is improved. Conceivable.

  The PVA of the present invention comprises a coating agent for paper, an internal sizing agent, a fiber processing agent, a dye, a glass fiber coating agent, a metal or glass surface coating agent, a coating agent such as an antifogging agent, wood, paper, and aluminum foil. Adhesives such as plastics, nonwoven fabric binders, fibrous binders, binders for building materials such as gypsum board and fiberboard, thickeners for various emulsion adhesives, additives for urea resin adhesives, additives for cement and mortar , Various adhesives such as hot melt adhesives, pressure sensitive adhesives, dispersants for emulsion polymerization of various ethylenically unsaturated monomers such as ethylene, vinyl acetate, vinyl chloride, pigment dispersions such as paints, adhesives, etc. Stabilizer, dispersion stabilizer for suspension polymerization of various ethylenically unsaturated monomers such as vinyl chloride, vinylidene chloride, styrene, (meth) acrylic acid, vinyl acetate, fiber, film, Molds for plastics, pipes, tubes, water-soluble fibers, provisional films, etc., additives for hydrophilicity to hydrophobic resins, compounding agents for synthetic resins such as composite fibers, films and other additives for moldings, soil conditioners It can be used as a soil stabilizer.

Claims (7)

A vinyl alcohol polymer containing a monomer unit having a group represented by the following formula (1) and satisfying the following formula (I).

(In Formula (1), R ¹ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ² is an alkoxyl group, an acyloxyl group, or a group represented by OM. M is a hydrogen atom, R ³ and R ⁴ are each independently a hydrogen atom or an alkyl group, each of which represents an alkyl group, an alkoxyl group or an acyloxyl group represented by R ^{1 to} R ^4. May be substituted with a substituent containing an oxygen atom or a nitrogen atom, m is an integer of 0 to 2. n is an integer of 3 or more, and there are a plurality of R ^{1 to} R ⁴ , respectively. In the case, a plurality of each R ^{1 to} R ⁴ independently satisfy the above definition.)
370 ≦ P × S ≦ 6,000 (I)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%) The vinyl alcohol polymer according to claim 1, further satisfying the following formulas (II) and (III).
200 ≦ P ≦ 4,000 (II)
0.1 ≦ S ≦ 10 (III)
P: Viscosity average degree of polymerization S: Content of the monomer unit (mol%)   The vinyl alcohol polymer according to claim 1 or 2, wherein n in the formula (1) is an integer of 6 or more and 20 or less. The vinyl alcohol polymer according to claim 1, wherein the monomer unit is represented by the following formula (2).

(In formula (2), the definitions of R ^{1 to} R ⁴ , m and n are the same as those in formula (1). X represents a direct bond, a divalent hydrocarbon group, an oxygen atom or a nitrogen atom 2. R ⁵ is a hydrogen atom or a methyl group.) X in the above formula (2) is —CO—NR ⁶ — * (R ⁶ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. * Is a group represented by the above formula (1). The vinyl alcohol polymer according to claim 4, wherein the vinyl alcohol polymer is represented by:   X in the above formula (2) is represented by —CO—NH— * (* represents a bonding site with the group represented by the above formula (1)), and n is an integer of 12 or less. Item 5. A vinyl alcohol polymer according to Item 4.   An aqueous solution containing the vinyl alcohol polymer according to any one of claims 1 to 6 in an amount of 4% by mass to 20% by mass and a pH of 4 to 8.