Modified vinyl alcohol-based polymer, aqueous solution, and method for producing modified vinyl alcohol-based polymer

Abstract

The present application provides a modified vinyl alcohol polymer having excellent water solubility, viscosity stability in aqueous solution, and film water resistance. The modified vinyl alcohol polymer has a group represented by the following formula (1). In formula (1), R 1 is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group represented by -OM. M is an alkali metal or an alkaline earth metal. R 2 is a group containing a siloxane structure. n is an integer of 1 to 3.

Description

Technical Field

[0001] This disclosure relates to modified vinyl alcohol polymers, aqueous solutions, and methods for manufacturing modified vinyl alcohol polymers. Background Technology

[0002] Vinyl alcohol polymers (hereinafter sometimes abbreviated as "PVA") are synthetic resins obtained by saponifying vinyl ester polymers. PVA is water-soluble and is used as a raw material for synthetic fibers, membrane materials, emulsifiers and dispersants, adhesives, etc.

[0003] As vinyl alcohol polymers containing silyl groups, vinyl alcohol polymers having specific silyl groups are disclosed in Patent Documents 1 and 2.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-043817

[0007] Patent Document 2: Japanese Patent Application Publication No. 2004-091774 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Vinyl alcohol polymers containing silyl groups exhibit excellent water resistance and strong adhesion to inorganic materials in the films obtained from their aqueous solutions. However, due to the high reactivity of silyl groups, vinyl alcohol polymers containing silyl groups sometimes suffer from reduced water solubility and decreased viscosity stability of the solution.

[0010] The purpose of this disclosure is to provide a modified vinyl alcohol polymer with excellent water solubility, viscosity stability of aqueous solutions, and water resistance of films; a method for manufacturing such a modified vinyl alcohol polymer; and an aqueous solution containing such a modified vinyl alcohol polymer.

[0011] means for solving problems

[0012] Through in-depth research, the inventors discovered that the above-mentioned problems can be solved by modifying vinyl alcohol polymers with groups having specific structures, thus completing this invention.

[0013] That is, the present invention includes the following disclosed solutions.

[0014] [1] A modified vinyl alcohol polymer having the groups shown in formula (1) below;

[0015] [Chemistry 1]

[0016]

[0017] In equation (1) above, R 1 It is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a hydroxyl group, or a group indicated by -OM. M is an alkali metal or an alkaline earth metal. R 2 This refers to a group containing a siloxane structure. n is an integer from 1 to 3. In R 1 In the case of multiple Rs, multiple Rs 1 Choose either the same or different. In R 2 In the case of multiple Rs, multiple Rs 2 Choose either the same or different.

[0018] [2] According to the modified vinyl alcohol polymer of [1], wherein the above R 2 The group is shown in formula (2) below;

[0019] [Chemistry 2]

[0020]

[0021] In equation (2) above, multiple R 3 Each group is independently an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a phenyl group, a benzyl group, a haloalkyl group having 1 to 8 carbon atoms, a halophenyl group, an aminoalkyl group having 1 to 8 carbon atoms, a mercaptoalkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group indicated by -OQ. Q is an alkali metal or an alkaline earth metal.

[0022] [3] According to [1] or [2], the modified vinyl alcohol polymer, wherein the content of the above-mentioned siloxane structure in the modified vinyl alcohol polymer is 0.001 mol% or more relative to all monomer units;

[0023] [4] A modified vinyl alcohol polymer according to any one of [1] to [3], wherein the content of the siloxane structure in the modified vinyl alcohol polymer is 50 mol% or more relative to all monomer units derived from monomers containing silane.

[0024] [5] Modified vinyl alcohol polymers having monomer units derived from silyl-containing monomers and modified with silane coupling agents;

[0025] [6] According to [5] the modified vinyl alcohol polymer, wherein the amount of modification of the silane coupling agent relative to all monomer units of the modified vinyl alcohol polymer is 0.001 mol% or more.

[0026] [7] According to [5] or [6], the modified vinyl alcohol polymer, wherein the amount of modification of the silane coupling agent relative to all monomer units derived from silyl-containing monomers in the modified vinyl alcohol polymer is 50 mol% or more.

[0027] [8] A method for manufacturing modified vinyl alcohol polymers, comprising a step of saponifying a modified vinyl ester polymer having silane groups in the presence of a silane coupling agent.

[0028] [9] An aqueous solution containing any one of the modified vinyl alcohol polymers in [1] to [7].

[0029] Invention Effects

[0030] According to this disclosure, a modified vinyl alcohol polymer with excellent water solubility, viscosity stability of aqueous solutions, and water resistance of films can be provided; a method for manufacturing such a modified vinyl alcohol polymer; and an aqueous solution containing such a modified vinyl alcohol polymer. Detailed Implementation

[0031] <Modified vinyl alcohol polymers>

[0032] Vinyl alcohol polymers (PVA) are polymers that contain vinyl alcohol units as monomer units. PVA is obtained by saponifying vinyl ester polymers synthesized from vinyl ester monomers used as raw materials. In addition to vinyl alcohol units, saponified PVA may also contain vinyl ester units.

[0033] Furthermore, regarding PVA, by saponifying copolymers formed by copolymerizing vinyl ester monomers (which are its raw material monomers) with other monomers, PVA containing monomer units other than vinyl alcohol units and vinyl ester units can be produced; by reacting specific chemical species with PVA during or after saponification, PVA with specific functional groups can be produced. In this disclosure, such PVA is sometimes referred to as a "modified vinyl alcohol polymer (modified PVA)," and the raw material monomers of PVA containing monomer units other than the aforementioned vinyl alcohol units and vinyl ester units, i.e., monomers other than vinyl ester monomers, are referred to as "modifying species." Additionally, in this disclosure, the (modified) vinyl ester polymer before saponification of the (modified) PVA is sometimes referred to as a "precursor" of the (modified) PVA. It should be noted that "modified vinyl ester polymer" here refers to a vinyl ester polymer containing monomer units other than vinyl ester units.

[0034] The modified vinyl alcohol polymer (modified PVA) disclosed herein has the groups shown in the following formula (1).

[0035] [Chemistry 3]

[0036]

[0037] In equation (1) above, R 1 It is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a hydroxyl group, or a group indicated by -OM. M is an alkali metal or an alkaline earth metal. R 2 This refers to a group containing a siloxane structure. n is an integer from 1 to 3. In R 1 In the case of multiple Rs, multiple Rs 1 Choose either the same or different. In R 2 In the case of multiple Rs, multiple Rs 2 Choose either the same or different.

[0038] By incorporating the groups shown in Formula (1) into the modified PVA, the water solubility of the modified PVA, the viscosity stability of the aqueous solution of the modified PVA, and the water resistance of the film formed from the modified PVA are improved. The reason for this may not be clear, but it can be speculated that it is because: by incorporating the groups shown in Formula (1) into the modified PVA, the volume around the highly reactive sites containing silicon atoms (e.g., silanol sites) increases, and the interaction between the highly reactive sites containing silicon atoms in the modified PVA and the vinyl alcohol sites is moderately weakened.

[0039] In this disclosure, "siloxane structure" refers to a structure (-O-Si-) formed by the bonding of one oxygen atom and one silicon atom. A siloxane structure can be referred to as a siloxane bond. The types of atoms bonded to the three bonds of the four connecting bonds of the silicon atom constituting a siloxane structure that are not bonded to the oxygen atom constituting the siloxane structure are not particularly limited. The types of atoms bonded to the two connecting bonds of the oxygen atom constituting a siloxane structure that are not bonded to the silicon atom constituting the siloxane structure are also not particularly limited. Preferably, the two connecting bonds of the oxygen atom constituting a siloxane structure that are not bonded to the silicon atom constituting the siloxane structure are also bonded to other silicon atoms. These other silicon atoms are preferably silicon atoms represented by Si in formula (1).

[0040] As R 1 The alkyl groups with 1 to 8 carbon atoms shown can be exemplified by methyl, ethyl, propyl, butyl, etc. The number of carbon atoms in the alkyl group is preferably 1 to 4, more preferably 1 or 2.

[0041] As R 1 Examples of alkoxy groups having alkyl groups with 1 to 8 carbon atoms include methoxy, ethoxy, propoxy, and butoxy. The number of carbon atoms in the alkyl group of this alkoxy group is preferably 1 to 4, more preferably 1 or 2.

[0042] Examples of alkali metals represented by M include sodium and potassium. Examples of alkaline earth metals represented by M include magnesium and calcium.

[0043] When n in equation (1) is 1 or 2, there are 1 or 2 R 1 Preferably, it contains an alkoxy, hydroxyl, or -OM group of an alkyl group having 1 to 8 carbon atoms. Additionally, R 1 Preferably, it is an alkoxy group, hydroxy group, or a group represented by -OM with an alkyl group having 1 to 8 carbon atoms.

[0044] As R in equation (1) 2 The indicated group (including groups with a siloxane structure) is preferably a group in which the oxygen atom constituting the siloxane structure is bonded to the silicon atom represented by Si in formula (1), and more preferably a group represented by formula (2) below. As R 2 The indicated group can be other groups that contain multiple siloxane structures (e.g., polysiloxane chains).

[0045] [Chemistry 4]

[0046]

[0047] In equation (2) above, multiple R 3 Each group is independently an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a phenyl group, a benzyl group, a haloalkyl group having 1 to 8 carbon atoms, a halophenyl group, an aminoalkyl group having 1 to 8 carbon atoms, a mercaptoalkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group indicated by -OQ. Q is an alkali metal or an alkaline earth metal.

[0048] As R 3 Alkyl groups with 1 to 20 carbon atoms shown can be listed as R 1 Examples of alkyl groups having 1 to 8 carbon atoms, and other similar groups. As R 3 The number of carbon atoms in the alkyl group is preferably 1 to 8, more preferably 1 to 4, and even more preferably 1 or 2.

[0049] As R 3 The alkoxy groups having alkyl groups having 1 to 8 carbon atoms shown can be listed as R 1 Examples of alkoxy groups, such as those having alkyl groups with 1 to 8 carbon atoms, are shown. As R 3 The alkoxy group shown has 1 to 4 carbon atoms in its alkyl group, more preferably 1 or 2.

[0050] As R 3 Examples of alkenyl groups with 2 to 5 carbon atoms include vinyl, allyl, and 2-methylallyl. As R 3The number of carbon atoms in the alkenyl group shown is preferably 2 to 4, more preferably 2.

[0051] As R 3 The halogens present in alkyl halogens and phenyl halogens with 1 to 8 carbon atoms include fluorine, chlorine, and bromine.

[0052] As R 3 Examples of aminoalkyl groups with 1 to 8 carbon atoms include aminomethyl, 2-aminoethyl, and 3-aminopropyl. As R 3 The number of carbon atoms in the aminoalkyl group shown is preferably 1 to 4.

[0053] As R 3 Examples of mercaptoalkyl groups with 1 to 8 carbon atoms include mercaptomethyl, 2-mercaptoethyl, and 3-mercaptopropyl. As R 3 The number of carbon atoms in the mercaptoalkyl group shown is preferably 1 to 4.

[0054] Examples of alkali metals represented by Q include sodium and potassium. Examples of alkaline earth metals represented by Q include magnesium and calcium.

[0055] The three R's in equation (2) 3 Preferably, it contains alkoxy groups. As one of the three R groups in formula (2) 3 The number of alkoxy groups in the formula is preferably 1 or 2. From the viewpoint of viscosity stability, the three R groups in formula (2) are preferred. 3 The number of alkoxy groups in the formula is preferably 1. From the viewpoint of membrane water resistance, the three R groups in formula (2) are... 3 The number of alkoxy groups in the sample is preferably 2.

[0056] In formula (1), n ​​is preferably 1 or 2, and more preferably 1.

[0057] The lower limit of the content of the group shown in formula (1) in the modified PVA relative to all monomer units is sometimes preferably 0.001 mol%, more preferably 0.005 mol%, further preferably 0.01 mol%, even more preferably 0.05 mol%, even more preferably 0.10 mol%, and particularly preferably 0.16 mol%. Furthermore, the upper limit of the content of the group shown in formula (1) relative to all monomer units is not particularly limited, and can be, for example, 0.30 mol% or 0.25 mol%. Additionally, in the modified PVA of, for example, an embodiment described later, the content of the group shown in formula (1) can be the same as the amount of silane modification. That is, for example, all monomer units derived from silane-containing modified species introduced into the modified PVA can have the group shown in formula (1).

[0058] In this disclosure, a "monomer unit" refers to the smallest repeating unit derived from a monomer and having a portion comprising the main chain. A monomer unit may be formed from only one monomer, or it may be formed from one monomer and one or more other compounds (e.g., silane coupling agents described later).

[0059] The lower limit of the content of the siloxane structure (-O-Si-) in the modified PVA relative to all monomer units is sometimes preferably 0.001 mol%, more preferably 0.005 mol%, even more preferably 0.01 mol%, even more preferably 0.05 mol%, even more preferably 0.10 mol%, and particularly preferably 0.16 mol%. Furthermore, the upper limit of the content of the siloxane structure relative to all monomer units is not particularly limited; for example, it can be 0.30 mol% or 0.25 mol%.

[0060] The lower limit of the content of the group shown in formula (2) in modified PVA relative to all monomer units is sometimes preferably 0.001 mol%, more preferably 0.005 mol%, even more preferably 0.01 mol%, even more preferably 0.05 mol%, even more preferably 0.10 mol%, and particularly preferably 0.16 mol%. In addition, the upper limit of the content of the group shown in formula (2) relative to all monomer units is not particularly limited, for example, it can be 0.30 mol%, or it can be 0.25 mol%. It should be noted that when R2 in the above formula (1) is the group shown in formula (2), as long as no other modifications are performed, the content of the group shown in formula (2) is usually equal to the content of the siloxane structure.

[0061] The groups or siloxane structures represented by formula (1) in modified PVA can be modified by, for example... 1 ¹H-NMR is used for determination. For example, in the case of modified PVA of this disclosure as described later, i.e., modified PVA obtained by saponifying a copolymer of vinyl acetate and vinyltrimethoxysilane in the presence of methyltrimethoxysilane, the determination can be made by... 1 The siloxane structure was confirmed by measuring the structure derived from methyltrimethoxysilane in the modified PVA using ¹H-NMR. An example of the specific determination method is shown below. For a sample obtained by dissolving the modified PVA in D₂O, the siloxane structure was determined using 400 MHz. 1 When measured by ¹H-NMR at room temperature, the peak derived from the methine in the vinyl alcohol unit is assigned to 3.3–4.2 ppm (integral value α), and the peak derived from the methyl group in the methyltrimethoxysilane structure is assigned to around -0.5–0.5 ppm (integral value β). Based on the integral values ​​α and β, the content of the methyltrimethoxysilane-derived structure, i.e., the siloxane structure, relative to all monomer units can be calculated using the following formula (I).

[0062] The content (mol%) of the siloxane structure (derived from the structure of methyltrimethoxysilane) = {(β / 3) / (α+β / 3)} × 100···(I)

[0063] The content obtained using the above method is equal to the content of the Si-O-Si structure. Furthermore, in the case of modified PVA obtained by saponifying a copolymer of vinyl acetate and vinyltrimethoxysilane in the presence of methyltrimethoxysilane, the content of the siloxane structure relative to all monomer units obtained using the above method is equal to the content of the groups shown in formula (2) relative to all monomer units. Furthermore, in the case of modified PVA obtained by saponifying a copolymer of vinyl acetate and vinyltrimethoxysilane in the presence of methyltrimethoxysilane, based on steric hindrance and other relationships, it can be considered that two or more methyltrimethoxysilanes are unlikely to react with one monomer unit derived from vinyltrimethoxysilane. That is, it can be considered that n in formula (1) usually reaches 1. Therefore, it can be considered that the content of the siloxane structure relative to all monomer units obtained by the above method is substantially equal to the content of the groups shown in formula (1) relative to all monomer units.

[0064] The modified PVA in this disclosure typically comprises monomer units having the groups shown in formula (1) above. Examples of monomer units having the groups shown in formula (1) below include, for example, the monomer unit shown in formula (3) below.

[0065] [Chemistry 5]

[0066]

[0067] In equation (3), R 4 It can be a hydrogen atom or a methyl group. R 5 It is a single bond or a divalent linker. R 6 The group is represented by the formula (1) above.

[0068] As R 5 The divalent linking groups shown can be exemplified by, for example, -(CH2). m -(m is an integer from 1 to 4), -CONR 7 -(CH2) q -(R 7 It can be a hydrogen atom or a methyl group. q is an integer from 0 to 4, etc. Additionally, a divalent linker can be added above -(CH2). m -and the above-CONR 7 -(CH2) q The carbon-carbon bonds of the groups shown contain -O- and -NR-. 8 -(R 8 A divalent group containing heteroatoms, such as a hydrogen atom or a methyl group.

[0069] A preferred embodiment of the modified PVA in this disclosure is a modified PVA obtained by saponifying a modified vinyl ester polymer (hereinafter also referred to as a "silyl-modified vinyl ester polymer") obtained by copolymerizing a silyl-containing monomer (hereinafter also referred to as a "silyl-containing monomer" or "silyl-containing modified species") with a vinyl ester monomer in the presence of a silane coupling agent, thereby introducing the group shown in formula (1) into the side chain of the PVA. That is, a modified PVA having monomer units derived from silyl-containing monomers and modified using a silane coupling agent is also a form of modified PVA in this disclosure.

[0070] In this disclosure, "silyl group" refers to the group represented by -SiH3, and a group in which one or more of the three hydrogen atoms of the group represented by -SiH3 are replaced by other atoms or substituents. From the viewpoint of reactivity, silyl groups are preferably those having a hydroxyl group or a group that has a hydroxyl group (such as an alkoxy group) that can be formed by hydrolysis.

[0071] The lower limit of the modification amount of the silane coupling agent in modified PVA relative to all monomer units is sometimes preferably 0.001 mol%, more preferably 0.005 mol%, further preferably 0.01 mol%, even more preferably 0.05 mol%, even more preferably 0.10 mol%, and particularly preferably 0.16 mol%. Furthermore, the upper limit of the modification amount of the silane coupling agent in modified PVA relative to all monomer units is not particularly limited; for example, it can be 0.30 mol% or 0.25 mol%.

[0072] The amount of modification by the silane coupling agent refers to the amount of silane coupling agent bonded. Specifically, the amount of modification by the silane coupling agent in modified PVA relative to all monomer units refers to the number of structures derived from the silane coupling agent in the modified PVA relative to the total number of monomer units. For example, in the case of modified PVA obtained by saponifying the copolymer of vinyl acetate and vinyltrimethoxysilane in the presence of methyltrimethoxysilane, if one methyltrimethoxysilane as a silane coupling agent is bonded, one structure derived from methyltrimethoxysilane is formed. Therefore, the content (mol%) of siloxane structures (structures derived from methyltrimethoxysilane) relative to all monomer units, calculated using the above formula (I), is equal to the amount of modification by the silane coupling agent relative to all monomer units (mol%).

[0073] The lower limit of the silane modification amount in modified PVA is sometimes preferably 0.05 mol%, more preferably 0.08 mol%, and even more preferably 0.1 mol%. Furthermore, the upper limit of the silane modification amount is sometimes preferably 1.0 mol%, more preferably 0.8 mol%, and even more preferably 0.5 mol%. By setting the silane modification amount within the above range, there is a tendency to exhibit the effects of silane more effectively, and there is a tendency for the resulting modified PVA to have better water solubility. It should be noted that the silane modification amount of modified PVA in this disclosure refers to the content of all monomer units in the modified PVA derived from silane-containing monomers (silane-containing modified species) relative to all monomer units.

[0074] All monomer units derived from silyl-containing monomers include monomer units derived from silyl-containing monomers that have not been modified with a silane coupling agent, and monomer units derived from silyl-containing monomers that have been modified with a silane coupling agent. That is, a monomer unit having the group shown in formula (1) above is also one of the monomer units derived from silyl-containing monomers. In addition, monomer units derived from silyl-containing monomers also include monomer units that have undergone modification other than modification based on a silane coupling agent, such as hydrolysis.

[0075] The amount of silane modification in modified PVA can be, for example... 1 It can be determined by H-NMR, for example, by using 1 ¹H-NMR is used to determine the silyl-modified vinyl ester polymer, the precursor of modified PVA, thereby enabling the determination of the silyl modification content of the modified PVA. For example, when using vinyltrimethoxysilane as the silyl-containing modifying species in modified PVA, the amount of silyl modification can be determined using… 1 ¹H-NMR analysis of the precursor of this modified PVA, namely the silyl-modified vinyl ester polymer, can also determine the amount of silyl modification. An example of the specific determination method is shown below. The silyl-modified vinyl ester polymer used as the sample is purified by reprecipitation at least three times using a mixed solution of n-hexane and acetone, and then dried under reduced pressure at 80°C for 3 days to prepare the modified vinyl ester polymer for analysis. Next, this modified vinyl ester polymer for analysis is dissolved in DMSO-d6 and measured at 20°C. 1 H-NMR (400MHz). The amount of silane modification can be calculated using the measured peaks of the vinyl ester unit derived from the chain methylene protons (integral value A: 4.5–5.2 ppm) and the peaks of the silane (trimethoxysilane) derived from the methyl protons (integral value B: 3.4–3.6 ppm) using the following formula (II).

[0076] Silyl modification amount (mol%) = {(B / 9) / (A+B / 9)}×100···(II)

[0077] The lower limit of the content of the groups shown in formula (1), the groups shown in formula (2), or the siloxane structure in the modified PVA relative to all monomer units derived from the silyl-containing monomer can be, for example, 40 mol%, preferably 50 mol%, more preferably 60 mol%. Similarly, the lower limit of the modification amount of the silane coupling agent relative to all monomer units derived from the silyl-containing monomer in the modified PVA can be, for example, 40 mol%, preferably 50 mol%, more preferably 60 mol%. In this case, the monomer units derived from the silyl-containing monomer are modified by the silane coupling agent in a larger proportion, and therefore, the effect of modification based on the silane coupling agent can be particularly fully utilized. The upper limit of the content of the groups shown in formula (1), the groups shown in formula (2), or the siloxane structure in the modified PVA relative to all monomer units derived from the silyl-containing monomer, and the upper limit of the modification amount of the silane coupling agent relative to all monomer units derived from the silyl-containing monomer in the modified PVA can be, for example, 100 mol%. Sometimes, multiple silane coupling agents react with monomer units derived from monomers containing silane groups. Therefore, the content of the group or siloxane structure shown in formula (2) above in the modified PVA relative to all monomer units derived from monomers containing silane groups, and the amount of modification of the silane coupling agent relative to all monomer units derived from monomers containing silane groups in the modified PVA, can exceed 100 moles.

[0078] The modified PVA disclosed herein may contain monomer units derived from vinyl ester monomers (vinyl alcohol units and vinyl ester units) and monomer units derived from silyl-containing monomers, as well as monomer units derived from other monomers. For example, the modified PVA described in a preferred embodiment of this disclosure contains ethylene units. The content of ethylene units in the modified PVA relative to all monomer units (ethylene modification amount) is sometimes preferably less than 20 mol%, more preferably less than 10 mol%. By setting the ethylene modification amount to the above range, the water solubility of the modified PVA is sometimes improved. The lower limit of the content of ethylene units in the modified PVA relative to all monomer units (ethylene modification amount) may be, for example, 0.1 mol%, or 1 mol%. When the ethylene modification amount is above the above lower limit, the water resistance of the resulting film can be further improved.

[0079] When modified PVA contains ethylene units, the amount of ethylene modification can be, for example... 1 The amount can be determined by H-NMR. For example, by using the same method as described above for determining the amount of silane modification. 1H-NMR is used to determine the amount of ethylene modification in the precursor of modified PVA, namely the modified vinyl ester polymer.

[0080] The lower limit of the proportion of vinyl alcohol units in the modified PVA of this disclosure relative to all monomer units is sometimes preferably 35 mol%, more preferably 50 mol%, even more preferably 70 mol%, even more preferably 80 mol%, and particularly preferably 90 mol%. On the other hand, the upper limit of the proportion of the above-mentioned vinyl alcohol units is sometimes preferably 99.95 mol%.

[0081] The content of monomer units other than those derived from vinyl ester monomers, monomer units derived from silyl-containing monomers, and ethylene units in the modified PVA disclosed herein is preferably 10 mol%, more preferably 1 mol% or 0.1 mol%, relative to all monomer units. In this case, the effects of silyl-based modification can be more fully utilized.

[0082] The viscosity-uniform polymerization degree of the modified PVA is preferably 100 or more and less than 5,000. The lower limit of the viscosity-uniform polymerization degree of the modified PVA is sometimes more preferably 200, further preferably 500, even more preferably 1,000, and even more preferably 2,000. Furthermore, the upper limit of the viscosity-uniform polymerization degree of the modified PVA is sometimes more preferably 4,000, and even more preferably 3,000. By setting the viscosity-uniform polymerization degree to the above range, there is a tendency for it to be easier to manufacture and for the mechanical properties of the film to be superior. The viscosity-uniform polymerization degree is a value obtained by measurement according to JIS K 6726:1994. Specifically, when the degree of saponification of the modified PVA is less than 99.5 mol%, for modified PVA obtained by saponification to a degree of saponification of 99.5 mol% or more, the viscosity-uniform polymerization degree is obtained using the intrinsic viscosity [η] (L / g) measured in water at 30°C, and using the following formula.

[0083] P=([η]×10 4 / 8.29) (1 / 0.62)

[0084] The lower limit of the degree of saponification of modified PVA is sometimes preferably 30 mol%, more preferably 65 mol%, even more preferably 70 mol%, even more preferably 80 mol%, even more preferably 85 mol%, and particularly preferably 90 mol%. On the other hand, the upper limit of the degree of saponification of the modified PVA is sometimes preferably 99.99 mol%, more preferably 99.0 mol%, and even more preferably 98.5 mol%. By setting the degree of saponification of modified PVA within the above range, there is a tendency to further improve the effect of improving water solubility and to manufacture modified PVA more stably in industry. The degree of saponification of modified PVA can be determined using the method described in JIS K 6726:1994.

[0085] <Preparation Method of Modified Vinyl Alcohol-Based Polymers>

[0086] The method for manufacturing modified PVA disclosed herein includes a step of saponifying a modified vinyl ester polymer having a silane group in the presence of a silane coupling agent.

[0087] Furthermore, a preferred embodiment of the method for manufacturing modified PVA disclosed herein includes: a step (polymerization step) of copolymerizing a silyl-containing monomer (a silyl-containing modified species) with a vinyl ester monomer to obtain a silyl-modified vinyl ester polymer; and a step (saponification step) of saponifying the silyl-modified vinyl ester polymer (a silyl-containing modified vinyl ester polymer) in the presence of a silane coupling agent. For example, by saponifying the silyl-modified vinyl ester polymer in the presence of a silane coupling agent as described above, a siloxane structure can be introduced into the resulting modified PVA, and a modified PVA having the group shown in formula (1) can be obtained. The silyl-containing modified species and the silane coupling agent can be the same or different chemical species.

[0088] [Polymerization Process]

[0089] The modified vinyl ester polymers that serve as precursors to the modified PVA of this disclosure can be manufactured by polymerizing vinyl ester monomers with silane-containing monomers or other monomers using existing known methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and dispersion polymerization. From the viewpoint of improving the effectiveness of this disclosure, solution polymerization using lower alcohols is preferred. The lower alcohol is not particularly limited, but is preferably an alcohol with 3 or fewer carbon atoms, such as methanol, ethanol, propanol, or isopropanol, and more preferably methanol. Regarding the polymerization operation, any polymerization method, including batch, semi-batch, and continuous polymerization, can be used.

[0090] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pentanoate, vinyl tert-carboxylate, vinyl hexanoate, vinyl octanoate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. Vinyl acetate is preferred.

[0091] The monomer containing silane (a modified species containing silane) preferably has the structure shown in the following formula (4).

[0092] [Chemistry 6]

[0093]

[0094] In equation (4), here, R 11 It is a functional group with polymerizable multiple bonds. R 12 and R 13 Each is independently an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an acetoxy group. R 14 It is an alkyl, aromatic hydrocarbon, or acetyl group having 1 to 8 carbon atoms.

[0095] As R 11 The functional groups shown are polymerizable multi-bonded groups, preferably groups having carbon-carbon unsaturated double bonds, such as vinyl, allyl, styrene, (meth)acryloylalkyl, etc.

[0096] As R 12 and R 13 Preferably, it is an alkoxy group having an alkyl group having 1 to 8 carbon atoms, more preferably an alkoxy group having an alkyl group having 1 to 4 carbon atoms, and further, an alkyl group having 1 or 2 carbon atoms.

[0097] As R 14 The aromatic hydrocarbon groups shown can include phenyl, tolyl, naphthyl, etc., with phenyl being preferred. As R 14 Preferably, it is an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and further preferably an alkyl group having 1 or 2 carbon atoms.

[0098] Examples of monomers containing silyl groups (modified species containing silyl groups) include, for example, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, allyltrimethoxysilane, allylmethyldimethoxysilane, allyldimethylmethoxysilane, allyltriethoxysilane, allylmethyldiethoxysilane, allyldimethylethoxysilane, vinyltri(β-methoxyethoxy)silane, vinylisobutyldimethoxysilane, vinylethyldimethoxysilane, and vinylmethoxydibutoxysilane. Alkane, Vinyl dimethoxybutoxysilane, Vinyl tributoxysilane, Vinyl methoxydihexyloxysilane, Vinyl dimethoxyhexyloxysilane, Vinyl trihexyloxysilane, Vinyl methoxydioctyloxysilane, Vinyl dimethoxyoctyloxysilane, Vinyl trioctyloxysilane, Vinyl methoxydilauoxysilane, Vinyl dimethoxylauoxysilane, Vinyl dimethoxydioleoxysilane, Vinyl dimethoxyoleoxysilane, 3-(methyl)acrylamide-propyltrimethoxysilane, 3-(methyl)acrylamide-propyltriethoxysilane, 3-(methyl)acrylamide-propyltri(β-methoxyethoxy)silane, 2 1-(methyl)acrylamide-ethyltrimethoxysilane, 2-(methyl)acrylamide-2-methylpropyltrimethoxysilane, 2-(methyl)acrylamide-isopropyltrimethoxysilane, N-(2-(methyl)acrylamide-ethyl)-aminopropyltrimethoxysilane, (3-(methyl)acrylamide-propyl)-oxypropyltrimethoxysilane, 3-(methyl)acrylamide-propyltriacetoxysilane, 2-(methyl)acrylamide-ethyltriacetoxysilane, 4-(methyl)acrylamide-butyltriacetoxysilane, 3-(methyl)acrylamide-propyltripropionyl Oxykrylyl silanes, such as 2-(meth)acrylamide-2-methylpropyltriacetoxysilane, N-(2-(meth)acrylamide-ethyl)-aminopropyltriacetoxysilane, 3-(meth)acrylamide-propylisobutyldimethoxysilane, 2-(meth)acrylamide-ethyldimethylmethoxysilane, 3-(meth)acrylamide-propylmethyldiacetoxysilane, 2-(meth)acrylamide-2-methylpropylhydrodimethoxysilane, 3-(N-methyl-(meth)acrylamide)-propyltrimethoxysilane, 2-(N-ethyl-(meth)acrylamide)-ethyltriacetoxysilane, and styryltrimethoxysilane, are among the preferred options, considering ease of industrial manufacturing and low cost.

[0099] It should be noted that when the monomer containing silyl groups has acyl groups such as acetoxy groups (e.g., R in formula (4) above), 12 Or R13 The case of acetoxy and R 14 In the case of acetyl groups, monomer units with hydroxyl groups are usually formed through hydrolysis. The hydroxyl group may also be in a salt state. Among these, monomer units in modified PVA may exist in the form of acyl groups such as acetoxy groups.

[0100] Furthermore, the modified PVA of this disclosure may copolymerize monomers other than vinyl ester monomers and silyl-containing monomers, without prejudice to the spirit of this disclosure. Examples of other monomers include, for instance, α-olefins such as ethylene, propylene, n-butene, and isobutene; (meth)acrylic acid and its salts; (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate; (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, diacetone (meth)acrylamide, and (meth)acrylamide. Acrylamide compounds, including acrylamide propanesulfonic acid and its salts, (meth)acrylamide propyl dimethylamine and its salts or quaternary ammonium salts, N-hydroxymethyl (meth)acrylamide and its derivatives; vinyl ethers, including methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitrile compounds, including acrylonitrile and methacrylonitrile; halogenated vinylides, including vinyl chloride and vinyl fluoride; vinylidene halogenated vinylides, including vinylidene chloride and vinylidene fluoride; allyl acetate, allyl chloride, and other allyl compounds; unsaturated dicarboxylic acids, including maleic acid, itaconic acid, and fumaric acid, and their salts or esters; and isopropyl acetate, etc. These can be used alone or in combination of two or more. The copolymerization amount of other monomers (the amount of modification of other monomers) is preferably less than 10 mol%. It should be noted that in this disclosure, "(meth)acryloyl" refers to the general term for methacryloyl and acryloyl groups.

[0101] The polymerization initiator used in the polymerization can be selected from known initiators (e.g., azo initiators, peroxide initiators, redox initiators, etc.). Examples of azo initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylpentanonitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile). Examples of peroxide initiators include percarbonate compounds such as di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as tert-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, and tert-butyl peroxyneodecanate; acetylcyclohexylsulfonyl peroxide; and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetic acid ester. Initiators can be prepared by combining these initiators with potassium persulfate, ammonium persulfate, hydrogen peroxide, etc. Examples of redox initiators include those obtained by combining the aforementioned peroxides with reducing agents such as sodium bisulfite, sodium bicarbonate, tartaric acid, L-ascorbic acid, and sodium silicate. In copolymerization at high temperatures, discoloration due to the decomposition of vinyl ester monomers is sometimes observed. In such cases, to prevent discoloration, an antioxidant such as tartaric acid can be added to the polymerization system at a concentration of approximately 1–100 ppm relative to the vinyl ester monomers.

[0102] The polymerization temperature is not particularly limited, but is preferably 0–180°C, more preferably 20–160°C, and even more preferably 30–150°C. When polymerization is carried out below the boiling point of the solvent used in the polymerization process, both vacuum boiling polymerization (polymerization under reduced pressure while the solvent boils) and atmospheric pressure non-boiling polymerization (polymerization under normal pressure without the solvent boiling) can be selected. Alternatively, when polymerization is carried out above the boiling point of the solvent used in the polymerization process, both pressurized non-boiling polymerization (polymerization under pressure without the solvent boiling) and pressurized boiling polymerization (polymerization under pressure while the solvent boils) can be selected.

[0103] In one embodiment of this disclosure, where the modified PVA comprises ethylene units (i.e., ethylene-modified PVA), the preferred manufacturing method is to copolymerize ethylene under pressure in the presence of vinyl ester monomers and silane-containing monomers. The ethylene pressure within the polymerization reactor is not particularly limited, but is sometimes preferably 0.01–2.0 MPa, more preferably 0.05–1.0 MPa, and even more preferably 0.1–0.65 MPa. The polymerization rate of the vinyl ester monomers at the outlet of the polymerization reactor is not particularly limited, but is sometimes preferably 5–90%, more preferably 15–85%.

[0104] [Saponification process]

[0105] In a preferred embodiment of this disclosure, the modified PVA is obtained by saponifying a silane-modified vinyl ester copolymer obtained by copolymerizing a vinyl ester monomer with a silane-containing monomer in the presence of a silane coupling agent. Examples of saponification methods include alcoholysis or hydrolysis using alkaline catalysts such as sodium hydroxide, potassium hydroxide, or sodium methoxide, or acidic catalysts such as p-toluenesulfonic acid. Examples of solvents that can be used in this reaction include alcohols such as methanol and ethanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl ethyl ketone; and aromatic hydrocarbons such as benzene and toluene. These solvents can be used alone or in combination of two or more. Using methanol or a methanol / methyl acetate mixture as the solvent and sodium hydroxide as the catalyst for saponification is simple and therefore preferred.

[0106] Silane coupling agents are chemical species capable of incorporating the group shown in formula (1) above. Silane coupling agents can be, for example, modified species containing silane (monomers containing silane) having the structure shown in formula (4) above, or silane coupling agents having the structure shown in formula (5) below, or mixtures thereof.

[0107] [Chemistry 7]

[0108]

[0109] In equation (5), multiple R 3 R in equation (2) 3 The meanings are the same. R 15 It is an alkoxy group or a hydroxyl group having 1 to 5 carbon atoms in an alkyl group.

[0110] R in equation (5) 3 The specific form and suitable form are the same as R in equation (2). 3 The specific form and suitable form are the same. As R 15 Preferably, it is an alkoxy group, more preferably an alkoxy group having 1 or 2 carbon atoms.

[0111] Examples of silane coupling agents include trimethylsilanol, methoxytrimethylsilane, dimethyldimethoxysilane, methyltrimethoxysilane, ethoxytrimethylsilane, diethoxydimethylsilane, triethoxymethylsilane, tetraethoxysilane, propoxytrimethylsilane, dipropoxydimethylsilane, tripropoxymethylsilane, tetrapropoxysilane, isopropoxytrimethylsilane, diisopropoxydimethylsilane, triisopropoxymethylsilane, tetraisopropoxysilane, butoxytrimethylsilane, dibutoxydimethylsilane, tributoxymethylsilane, tetrabutoxymethylsilane, and tetrabutoxytrimethylsilane. Silane, isobutoxytrimethylsilane, diisobutoxydimethylsilane, triisobutoxymethylsilane, tetraisobutoxysilane, tert-butoxytrimethylsilane, di-tert-butoxydimethylsilane, tri-tert-butoxymethylsilane, tetra-tert-butoxysilane, phenoxytrimethylsilane, diphenoxydimethylsilane, triphenoxymethylsilane, tetraphenoxysilane, methoxytriethylsilane, dimethoxydiethylsilane, trimethoxyethylsilane, ethoxytriethylsilane, diethoxydiethylsilane, triethoxyethylsilane, methoxytripropylsilane, dimethyl... Trimethoxypropylsilane, trimethoxypropylsilane, ethoxytripropylsilane, diethoxydipropylsilane, triethoxypropylsilane, trimethoxybutylsilane, trimethoxyheptylsilane, trimethoxyhexylsilane, trimethoxyoctylsilane, trimethoxydecylsilane, trimethoxydodecylsilane, trimethoxytetradecylsilane, trimethoxyoctadecylsilane, trimethoxyphenylsilane, trimethoxybenzylsilane, triethoxybutylsilane, triethoxyheptylsilane, triethoxyhexylsilane, triethoxyoctylsilane, triethoxydecylsilane Triethoxydodecylsilane, triethoxytetradecylsilane, triethoxyoctadecylsilane, phenyltriethoxysilane, triethoxybenzylsilane, mercaptomethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-bromopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, mercaptomethyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 3-chloropropyltriethoxysilane, 3-bromopropyltriethoxysilane, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, etc. Among these, methoxytrimethylsilane, dimethoxydimethylsilane, methyltrimethoxysilane, ethoxytrimethylsilane, diethoxydimethylsilane, triethoxymethylsilane, and vinyltrimethoxysilane are particularly suitable.

[0112] <Aqueous solution>

[0113] The aqueous solution disclosed herein contains the modified PVA of this disclosure. The aqueous solution may contain a small amount of organic solvent, or may contain a small amount of water-insoluble organic or inorganic particles. The concentration of the modified PVA in the aqueous solution is preferably 1-30% by mass.

[0114] <Applications>

[0115] The modified PVA disclosed herein can be used for a variety of purposes. Examples are given below, but are not limited thereto.

[0116] (1) Applications of dispersants: Dispersant stabilizers for pigments contained in coatings, adhesives, etc.; dispersant stabilizers and dispersing aids for suspension polymerization of various vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, (meth)acrylate, and vinyl acetate.

[0117] (2) Applications of coating agents: paper coating agents, sizing agents, fiber processing agents, leather finishing agents, coatings, anti-fogging agents, anti-metal corrosion agents, brightening agents for galvanizing, antistatic agents.

[0118] (3) Applications of adhesives: adhesives, bonding agents, wet adhesives, various bonding agents, additives for cement or mortar.

[0119] (4) Applications of emulsifiers: emulsifiers for emulsion polymerization, post-emulsifiers for asphalt, etc.

[0120] (5) Uses of flocculants: Flocculants for suspended solids and dissolved solids in water, and flocculants for metals.

[0121] (6) Paper processing applications: paper strength enhancer, oil / solvent resistance enhancer, smoothness improver, surface gloss improver, sealant, barrier agent, lightfastness enhancer, hydration resistant agent, dye / color developer dispersant, adhesion improver, adhesive.

[0122] (7) Agricultural uses: pesticide binders, pesticide spreading agents, agricultural mulching agents, soil conditioners, ablation inhibitors, pesticide dispersants

[0123] (8) Medical / cosmetic applications: granulating binders, coating agents, emulsifiers, patches, adhesives, film preparation substrates, film forming agents

[0124] (9) Uses of viscosity modifiers: thickeners, rheology modifiers

[0125] (10) Membrane applications: water-soluble membranes, polarizing films, barrier films, packaging films for fiber products, seed health tablets, vegetation tablets, seed tapes, moisture-absorbing films.

[0126] (11) Applications of molded products: fibers, pipes, tubes, leak-proof membranes, lace and frayed edges made with water-soluble fibers and sponges.

[0127] (12) Gel applications: medical gels, industrial gels

[0128] (13) Post-reaction applications: Post-reaction applications with low molecular weight organic compounds, high molecular weight organic compounds, and inorganic compounds.

[0129] Example

[0130] The present invention will now be described in more detail by way of examples, but the present invention is not limited in any way by these examples. It should be noted that, in the following examples and comparative examples, unless otherwise specified, "parts" and "%" represent parts by mass and percentage by mass, respectively.

[0131] [Silyl modification amount of modified PVA]

[0132] The amount of silane modification in modified PVA is from 1 The H-NMR spectrum is used to determine the composition. For example, in the case of modified PVA manufactured using vinyltrimethoxysilane as a silyl-containing modifying species, the following steps are followed: First, as the test sample, the precursor of the modified PVA, namely the silyl-modified vinyl ester polymer, is subjected to reprecipitation purification at least three times using a mixed solution of n-hexane and acetone, and then dried under reduced pressure at 80°C for 3 days to prepare the analytical modified vinyl ester polymer. The obtained analytical modified vinyl ester polymer is dissolved in DMSO-d6 and measured at 20°C. 1 H-NMR (400MHz). The amount of silane modification was calculated using the measured peaks of the vinyl ester unit derived from the chain methylene protons (integral value A: 4.5–5.2 ppm) and the peaks of the silane (trimethoxysilane) derived from the methyl protons (integral value B: 3.4–3.6 ppm) using the following formula (II).

[0133] Silyl modification amount (mol%) = {(B / 9) / (A+B / 9)}×100···(II)

[0134] [Ethylene modification amount of modified PVA]

[0135] The ethylene modification amount of the modified PVA7 described below was determined using the same method as the silane modification amount mentioned above, based on the precursor of the modified PVA7. 1 The result can be obtained using H-NMR.

[0136] [Content of siloxane structures in modified PVA]

[0137] The content of siloxane structure in modified PVA is utilized 1 The determination was performed using ¹H-NMR. For example, in the case of modified PVA1 described later, the obtained modified PVA1 was dissolved in D₂O and analyzed using 400 MHz. 1When measured by ¹H-NMR at room temperature, the peak derived from the methine in the vinyl alcohol unit is assigned to 3.3–4.2 ppm (integral value α), and the peak derived from the methyl group in the methyltrimethoxysilane structure is assigned to around -0.5–0.5 ppm (integral value β). Using these integral values ​​α and β, the content of the methyltrimethoxysilane-derived structure, i.e., the siloxane structure, relative to all monomer units is calculated using the following formula (I).

[0138] The content of siloxane structures (mol%) = {(β / 3) / (α+β / 3)}×100···(I)

[0139] It should be noted that the content of the siloxane structure obtained by the above method is equal to the content of the group shown in formula (2) and the amount of modification by the silane coupling agent. In addition, it can be considered that the content of the siloxane structure obtained by the above method is essentially equal to the content of the group shown in formula (1).

[0140] [Viscosity-uniform degree of polymerization of modified PVA]

[0141] The viscosity-uniform degree of polymerization of modified PVA was determined according to JIS K 6726:1994. Specifically, for modified PVA obtained by saponification to a degree of saponification of 99.5 mol% or more, the viscosity-uniform degree of polymerization was calculated using the intrinsic viscosity [η] (L / g) measured in water at 30°C, when the degree of saponification was less than 99.5 mol%.

[0142] P=([η]×10 4 / 8.29) (1 / 0.62)

[0143] [Degree of saponification of modified PVA]

[0144] The degree of saponification of modified PVA was determined according to JIS K 6726:1994.

[0145] [The insoluble components of modified PVA]

[0146] Prepare a 500mL flask equipped with a stirrer and reflux condenser in a water bath set to 20°C. Add 285g of distilled water and start stirring at 300rpm. Weigh 15g of modified PVA and slowly add it to the flask. After adding all the modified PVA (15g), immediately allow approximately 30 minutes to raise the water bath temperature to 95°C. Once the temperature reaches 95°C, continue stirring at 300rpm for 60 minutes to dissolve the PVA. Filter the undissolved particles using a 63μm mesh metal filter. Thoroughly wash the filter with 90°C warm water to remove any adhering solution, then dry the filter in a 120°C desiccant for 1 hour. Calculate the percentage of insoluble components based on the mass of undissolved particles collected, as the insoluble component (%). This insoluble component is an indicator of water solubility; a lower insoluble component indicates better water solubility. Specifically, based on the insoluble components, the following criteria are used for evaluation, and in case A or B, it is judged to have excellent water solubility.

[0147] A: Less than 0.5%

[0148] B: 0.5% or more but less than 2.0%

[0149] C: 2.0% or more

[0150] Viscosity of modified PVA aqueous solution

[0151] Prepare a 300mL flask equipped with a stirrer and reflux condenser in a water bath at room temperature. Add 192g of distilled water and start stirring at 300rpm. Weigh 8g of modified PVA and slowly add it to the flask. After all 8g of modified PVA has been added, immediately allow approximately 30 minutes to raise the water bath temperature to 95°C. Once the temperature inside the flask reaches 90°C, continue dissolving the PVA by stirring at 300rpm for 2 hours. Then, bring the water bath temperature back to room temperature and cool the flask while stirring slowly. Transfer the resulting aqueous solution to a 100mL sample tube and measure the viscosity at 20°C and 60rpm using a Type B viscometer (manufactured by Toki Sangyo Co., Ltd.). This viscosity is then recorded as the viscosity immediately after dissolution (mPa·s). Next, store the aqueous solution at 5°C for 48 hours, and then measure the viscosity at 20°C using the same method as above. This viscosity is recorded as the viscosity after storage (mPa·s). The difference between the viscosity after storage and the viscosity immediately after dissolution is an indicator of viscosity stability; the smaller the viscosity difference, the better the viscosity stability. Specifically, based on the viscosity difference, the following criteria are used for evaluation: In A... + In cases A or B, it is judged to have excellent viscosity stability.

[0152] A + Less than 1 MPa·s

[0153] A: Above 1 mPa·s and below 5 mPa·s

[0154] B: Above 5 mPa·s and below 10 mPa·s

[0155] C: Above 10 mPa·s

[0156] [Membrane swelling degree]

[0157] A 4% (w / w) aqueous solution of modified PVA was prepared using the same method as described above. This aqueous solution was cast at 20°C to obtain a membrane with a thickness of 50 μm. The resulting membrane was cut into 10 cm long and 10 cm wide pieces to prepare test pieces. These test pieces were immersed in distilled water at 20°C for 24 hours, then removed and recovered. The surface moisture was wiped off with gauze, and the mass at which water swelling occurred was measured. Next, the test pieces after measuring the mass at which water swelling occurred were dried at 105°C for 16 hours, and the mass after drying was measured. Here, the mass at which water swelling occurred was divided by the mass after drying, and this value was used as the membrane swelling degree (%), serving as an indicator of the membrane's water resistance. The lower the membrane swelling degree, the better the membrane's water resistance. Specifically, based on the membrane swelling degree, the evaluation was conducted according to the following criteria: In A... + In cases A or B, the membrane is judged to have excellent water resistance.

[0158] A + :300% or less

[0159] A: More than 300% but less than 400%

[0160] B: More than 400% but less than 500%

[0161] C: Over 500%

[0162] <Example 1>

[0163] [Manufacturing of Modified PVA1]

[0164] 850g of vinyl acetate, 150g of methanol, and 1.6g of vinyltrimethoxysilane (a silyl-containing modifier) ​​were added to a 3L reactor equipped with a stirrer, reflux condenser, nitrogen inlet, comonomer dropper, and initiator inlet. Nitrogen purging was performed on the system for 30 minutes while simultaneously introducing nitrogen gas. Separately, a 10% comonomer solution was prepared by dissolving vinyltrimethoxysilane in methanol as a delay solution, and nitrogen purging was performed on this solution as well. The reactor was heated until the internal temperature reached 60°C. 0.2g of 2,2'-azobisisobutyronitrile (AIBN) was added to initiate polymerization. The delay solution was added dropwise to maintain a constant monomer composition (vinyl acetate to vinyltrimethoxysilane ratio) in the polymerization solution. After polymerization at 60°C for 3 hours, 0.4g of hydroquinone was added, and the reactor was cooled to stop polymerization. The total amount of comonomers (containing silyl-modified species) added until polymerization was stopped was 2.6 g. Furthermore, the solids concentration at polymerization stop was 24.8%, and the polymerization rate was 30%. Next, unreacted vinyl acetate monomers were removed by continuously adding methanol at 50°C under reduced pressure, yielding a methanol solution (concentration 35%) of the silyl-modified vinyl acetate polymer. Then, 3.17 g of methyltrimethoxysilane as a silane coupling agent was added to 571.4 g of the methanol solution of the silyl-modified vinyl acetate polymer prepared by adding methanol (containing 200.0 g of the silyl-modified vinyl acetate polymer in the solution) and thoroughly mixed. Finally, 27.9 g of an alkaline solution (a 10% methanol solution of sodium hydroxide) was added for saponification (the concentration of the silyl-modified vinyl acetate polymer in the saponification solution was 25%, the molar ratio of the silane coupling agent to the vinyl acetate unit was 1.0 mol%, and the molar ratio of sodium hydroxide was 3.0 mol%). Approximately one minute after the addition of the alkaline solution, a gel-like substance was formed. This substance was then pulverized and saponified at 40°C for one hour. 500g of methyl acetate was added to neutralize the remaining alkali. After confirming neutralization with phenolphthalein indicator, the mixture was filtered to obtain a white solid. 2,000g of methanol was added to this solid, and the mixture was left to wash at room temperature for three hours. This washing process was repeated three times. The resulting white solid, obtained by centrifugation, was then dried at 65°C for two days to obtain modified PVA1. The modified PVA1 had a viscosity-average degree of polymerization of 2,500, a degree of saponification of 98.5 mol%, a silane modification amount of 0.30 mol%, and a siloxane structure content of 0.20 mol%. The water solubility, viscosity stability of aqueous solutions, and membrane water resistance of the obtained modified PVA1 were evaluated. The results are shown in Table 2.

[0165] <Examples 2-5, Comparative Example 1>

[0166] [Manufacturing of modified PVA2-6]

[0167] As shown in Table 1, the polymerization conditions (amount of vinyl acetate, amount of methanol, type and amount of silane-containing modifier, and polymerization rate) and saponification conditions (type and amount of silane coupling agent, and molar ratio of sodium hydroxide to the modified vinyl ester polymer) were varied. Except for these variations, modified PVAs 2 through 6 were prepared using the same procedures as in Example 1 for the preparation of modified PVA 1. The analytical results of the obtained modified PVAs are shown in Table 2. Furthermore, the water solubility, viscosity stability of aqueous solutions, and water resistance of the films were evaluated for the obtained modified PVAs 2 through 6 in the same manner as in Example 1. The results are shown in Table 2.

[0168] <Example 6>

[0169] [Manufacturing of Modified PVA7]

[0170] 2760 g of vinyl acetate, 240 g of methanol, and 6.4 g of vinyltrimethoxysilane (a silyl-containing modifier) ​​were added to a 5 L pressurized reactor equipped with a stirrer, nitrogen inlet, ethylene inlet, initiator inlet, and delayed solution inlet. After heating to 60 °C, the system was purged with nitrogen for 30 minutes. Then, ethylene was introduced into the reactor at a pressure of 0.32 MPa. The temperature in the polymerization tank was adjusted to 60 °C, and 0.3 g of 2,2'-azobisisobutyronitrile (AIBN) was injected to begin polymerization. During polymerization, ethylene was introduced while simultaneously injecting a 5% (w / w) methanol solution of vinyltrimethoxysilane, maintaining the reactor pressure at 0.32 MPa and the polymerization temperature at 60 °C. After 4 hours, when the polymerization rate reached 25%, cooling was performed to stop the polymerization. The total amount of vinyltrimethoxysilane methanol solution added until the polymerization was complete was 90 ml. Next, modified PVA7 was produced by saponification under the conditions described in Table 1, using the same method as in Example 1. The analytical and evaluation results of the modified PVA7 are shown in Table 2.

[0171] [Table 1]

[0172]

[0173] [Table 2]

[0174]

[0175] As shown in Table 2, the modified PVAs of Examples 1-6 exhibit excellent water solubility, viscosity stability of aqueous solutions, and membrane water resistance. On the other hand, the modified PVA2 of Comparative Example 1, which was manufactured without the use of a silane coupling agent during saponification, may have been due to the absence of the group shown in Formula (1). Therefore, it had a high proportion of insoluble components and poor water solubility, making it impossible to perform physical property tests regarding viscosity stability and membrane water resistance.

Claims

1. A modified vinyl alcohol-based polymer having a group represented by the following formula (1), In the above formula (1), R 1 is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group represented by -OM; M is an alkali metal or an alkaline earth metal; R 2 is a group represented by the following formula (2) containing a siloxane structure; n is an integer of 1 to 3; and R 1 is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group represented by -OM; M is an alkali metal or an alkaline earth metal; R 1 is a group represented by the following formula (2) containing a siloxane structure; n is an integer of 1 to 3; and R 2 is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group represented by -OM; M is an alkali metal or an alkaline earth metal; R 2 is a group represented by the following formula (2) containing a siloxane structure; n is an integer of 1 to 3; and R In the above formula (2), the plurality of R 3 each independently is an alkyl group having 1 to 20 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a phenyl group, a benzyl group, a haloalkyl group having 1 to 8 carbon atoms, a halophenyl group, a mercaptoalkyl group having 1 to 8 carbon atoms, a hydroxyl group, or an -OQ group, and the plurality of R 3 In the above formula (2), the number of the alkoxy groups in the 3 R 3 is an integer of 1 to 3; and Q is an alkali metal or an alkaline earth metal.

2. The modified vinyl alcohol-based polymer according to claim 1, wherein, The content of the siloxane structure in the modified vinyl alcohol-based polymer is 0.001 mol% or more with respect to the total monomer units.

3. The modified vinyl alcohol-based polymer according to claim 1 or 2, wherein, The content of the siloxane structure in the modified vinyl alcohol-based polymer is 50 mol% or more with respect to the total monomer units derived from the monomer containing a silyl group.

4. A modified vinyl alcohol-based polymer having a monomer unit derived from a monomer containing a silyl group and modified with a silane coupling agent, the monomer containing a silyl group is a group represented by the following formula (4), the silane coupling agent is a group represented by the following formula (4') or the following formula (5), In the above formula (4), R 11 is a functional group having a polymerizable multiple bond; R 12 and R 13 are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, or an acetoxy group; R 14 is an alkyl group having 1 to 8 carbon atoms, an aromatic hydrocarbon group, or an acetyl group; In the above formula (4'), R 11 is a functional group having a polymerizable multiple bond; R 12 is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, or an acetoxy group; R 13 is an alkoxy group having an alkyl group having 1 to 8 carbon atoms; R 14 is an alkyl group having 1 to 8 carbon atoms, an aromatic hydrocarbon group, or an acetyl group; In the above formula (5), the plurality of R 3 each independently is an alkyl group having 1 to 20 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a phenyl group, a benzyl group, a haloalkyl group having 1 to 8 carbon atoms, a halophenyl group, a mercaptoalkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group represented by -OQ, the plurality of R 3 comprising the above alkoxy group, 3 R 3 in the formula (5) is an integer of 1 to 3; Q is an alkali metal or an alkaline earth metal; R 15 is an alkoxy group having an alkyl group having 1 to 5 carbon atoms, or a hydroxyl group.

5. The modified vinyl alcohol polymer according to claim 4, wherein, The modification amount of the silane coupling agent in the modified vinyl alcohol-based polymer is 0.001 mol% or more with respect to the total monomer units.

6. The modified vinyl alcohol-based polymer according to claim 4 or 5, wherein, The modification amount of the silane coupling agent in the modified vinyl alcohol-based polymer is 50 mol% or more with respect to the total monomer units derived from the monomer containing a silyl group.

7. A method for producing a modified vinyl alcohol-based polymer, comprising: a step of copolymerizing a monomer containing a silyl group and a vinyl ester-based monomer to obtain a modified vinyl ester-based polymer having a silyl group; and a step of saponifying the modified vinyl ester-based polymer having a silyl group in the presence of a silane coupling agent, the monomer containing a silyl group is a group represented by the following formula (4), the silane coupling agent is a group represented by the following formula (4) or the following formula (5), In the above formula (4), R 11 is a functional group having a polymerizable multiple bond; R 12 and R 13 are each independently an alkyl group having 1 to 8 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, or an acetoxy group; R 14 is an alkyl group having 1 to 8 carbon atoms, an aromatic hydrocarbon group, or an acetyl group; In the above formula (5), the plurality of R 3 each independently is an alkyl group having 1 to 20 carbon atoms, an alkoxy group having an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a phenyl group, a benzyl group, a haloalkyl group having 1 to 8 carbon atoms, a halophenyl group, an aminoalkyl group having 1 to 8 carbon atoms, a mercaptoalkyl group having 1 to 8 carbon atoms, a hydroxyl group, or a group represented by -OQ, the plurality of R 3 comprises the above alkoxy group, 3 R 3 in the formula (5) is an integer of 1 to 3; Q is an alkali metal or an alkaline earth metal; and R 15 is an alkoxy group having an alkyl group having 1 to 5 carbon atoms, or a hydroxyl group.

8. An aqueous solution containing the modified vinyl alcohol-based polymer according to any one of claims 1 to 6.

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