Composition containing polyvinyl alcohol polymer

Abstract

Provided is a novel combination of polyvinyl alcohol polymer (for example, a composition containing a PVA polymer). A polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant are combined. Such a combination (such as a composition) can be suitably used as a dispersion stabilizer (dispersant) or the like.

Description

Composition containing polyvinyl alcohol polymer

[0001] The present invention relates to a composition containing a polyvinyl alcohol polymer (vinyl alcohol polymer) that can be suitably used as a dispersion stabilizer [or dispersant, for example, a dispersion stabilizer for suspension polymerization of a vinyl monomer (particularly vinyl chloride monomer)], a method for producing the same, and a method for producing a vinyl polymer [particularly a vinyl chloride polymer (resin)] using the polyvinyl alcohol polymer (or dispersion stabilizer).

[0002] The industrial production of vinyl chloride resins is generally carried out by batch suspension polymerization, in which vinyl monomers such as vinyl chloride are dispersed in an aqueous medium in the presence of a dispersion stabilizer, and polymerization is carried out using an oil-soluble polymerization initiator. Factors in the polymerization process that determine the quality of vinyl chloride resins include the conversion rate, the ratio of aqueous medium to monomer, polymerization temperature, the type and amount of polymerization initiator, the type of polymerization vessel, the stirring speed, and the type and amount of dispersion stabilizer, among which the dispersion stabilizer has the greatest effect.

[0003] The role of a dispersion stabilizer in suspension polymerization to obtain a vinyl chloride resin is to disperse a monomer in an aqueous medium, form stable droplets, regulate the size of the droplets that repeatedly disperse and coalesce, and control the coagulation tendency of the polymerized particles. Therefore, the performance required of such a dispersion stabilizer includes: <1> controlling the particle size of the obtained vinyl chloride resin particles within an appropriate range, <2> increasing the plasticizer absorption of the obtained vinyl chloride resin particles to improve moldability, and <3> adjusting the porosity of the obtained vinyl chloride resin particles within a certain range to facilitate removal of residual monomers.

[0004] That is, the dispersion stabilizer is required to exhibit excellent dispersing power and to control the particle size, particle shape, etc. of the vinyl chloride resin to an appropriate state, for example.

[0005] As the dispersion stabilizer, polyvinyl alcohol resins (or polymers, hereinafter sometimes abbreviated as PVA polymers, PVA, etc.), cellulose derivatives, etc. are generally used alone or in appropriate combination.

[0006] For example, Non-Patent Document 1 describes a method of using, as a dispersion stabilizer for suspension polymerization of vinyl chloride, a PVA having a viscosity-average degree of polymerization of 2000 and a degree of saponification of 88 mol % or 80 mol %, which is considered to have high emulsifying power, or a PVA having a viscosity-average degree of polymerization of 600 to 700 and a degree of saponification of about 70 mol %.

[0007] "Poval", Polymer Publishing Association, 1981

[0008] As mentioned above, PVA is used as a dispersion stabilizer (dispersant), but according to the investigations of the present inventors, further improvements are required in PVA as well.

[0009] For example, PVA with a relatively low degree of saponification (e.g., around 70 mol%) is less hydrophilic than PVA with a higher degree of saponification, making it difficult to prepare an aqueous solution (aqueous liquid). In addition, a 4% aqueous solution of PVA has a low cloud point (e.g., around 30°C), and there is a risk of PVA precipitating (separating) if the aqueous solution is stored in a tank or the like at a temperature equal to or higher than the cloud point.

[0010] Furthermore, the polymerization temperature of vinyl chloride monomer is generally 40 to 70°C, which is a temperature above the cloud point of PVA. Therefore, when the aqueous PVA solution is added to the polymerizer (hot water at 40 to 70°C), it is necessary to prevent the PVA from precipitating in the polymerizer.

[0011] Thus, PVA as a dispersion stabilizer (such as a dispersion stabilizer for suspension polymerization) is required to have not only the inherent performance as a dispersion stabilizer but also ease of preparation of an aqueous solution, stability of the aqueous solution (and further dispersibility in warm water), and the like. However, it becomes more difficult to maintain these properties as the degree of saponification of PVA decreases or the degree of polymerization of PVA increases.

[0012] Under these circumstances, the present inventors attempted to introduce units derived from itaconic acid into PVA in the hope of improving hydrophilicity. However, this resulted in a decrease in the inherent performance as a dispersion stabilizer (for example, destabilization of the polymerization, an increase in the particle size of the resulting vinyl chloride resin, and a tendency for the plasticizer absorption to decrease), possibly due to a decrease in surface activity. It was extremely difficult to achieve ease of preparation of an aqueous solution, stability of the aqueous solution, dispersibility in warm water, etc., while maintaining the performance as a dispersion stabilizer.

[0013] In view of the above points, an object of the present invention is to provide a novel combination (for example, composition) of polyvinyl alcohol-based polymers.

[0014] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that a combination of a specific PVA-based polymer and a surfactant (particularly an ionic surfactant such as an anionic surfactant) (or a combination thereof, for example, a composition containing them) is useful as a dispersion stabilizer (for example, a dispersion stabilizer for suspension polymerization), etc., and have completed the present invention through further research.

[0015] That is, the present invention relates to the following inventions, etc. [1] A composition containing a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond (a polyvinyl alcohol (A) having a polymerizable unsaturated bond) and a surfactant (or a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond containing a surfactant; the same applies hereinafter to a composition). [2] The composition according to [1], wherein the polyvinyl alcohol-based polymer (A) has a proportion of polymerizable unsaturated bonds of 3 μmol / g or more. [3] The composition according to [1] or [2], wherein the polyvinyl alcohol-based polymer (A) has a proportion of polymerizable unsaturated bonds of 5 to 500 μmol / g. [4] The composition according to any of [1] to [3], wherein the polyvinyl alcohol-based polymer (A) contains an acetal skeleton (a) having a polymerizable unsaturated bond. [5] The composition according to any one of [1] to [4], wherein the polyvinyl alcohol-based polymer (A) contains an acetal skeleton (a) having a polymerizable unsaturated bond, and the acetal skeleton (a) includes a skeleton represented by the following formula (a1): (wherein R' represents a group having a polymerizable unsaturated bond.) [6] The composition according to any one of [1] to [5], wherein the polyvinyl alcohol-based polymer (A) contains an acetal skeleton (a) having a polymerizable unsaturated bond, the acetal skeleton (a) includes a skeleton represented by the formula (a1), and the content of the acetal skeleton (a) is 0.05 to 5 mol% per monomer unit. [7] The composition according to any one of [1] to [6], wherein the polyvinyl alcohol-based polymer (A) has a degree of saponification of 50 to 90 mol%. [8] The composition according to any one of [1] to [7], wherein the polyvinyl alcohol-based polymer (A) has a degree of polymerization of 160 to 3,000. [9] The composition according to any one of [1] to [8], wherein the surfactant contains an ionic surfactant.

[10] The composition according to any one of [1] to [9], wherein the surfactant contains an anionic surfactant.

[11] The composition according to any one of [1] to

[10] , wherein the proportion of the surfactant relative to the total amount of the polyvinyl alcohol-based polymer (A) and the surfactant is 0.1 to 10% by mass.

[12] The composition according to any one of [1] to

[11] , wherein a 4% by mass aqueous solution has a cloud point (for example, the cloud point of a 4% by mass aqueous solution is 25°C or higher).

[13] A method for producing a composition containing a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond and a surfactant (or the composition according to any one of [1] to

[12] ), the method comprising a step of mixing the polyvinyl alcohol-based polymer (A) and the surfactant.

[14] An aqueous liquid containing a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond, a surfactant, and water.

[15] The aqueous liquid according to

[14] , wherein the surfactant contains an anionic surfactant, and the proportion of the surfactant relative to the total amount of the polyvinyl alcohol-based polymer (A) and the surfactant is 0.1 to 10% by mass.

[16] A dispersion stabilizer (dispersant) comprising a combination of a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond and a surfactant.

[17] A dispersion stabilizer (dispersant) comprising a composition containing a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond and a surfactant.

[18] The agent according to

[16] or

[17] , wherein the surfactant contains an anionic surfactant, and the proportion of the surfactant relative to the total amount of the polyvinyl alcohol polymer (A) and the surfactant is 0.1 to 10% by mass.

[19] The agent according to any one of

[16] to

[18] , which is a dispersion stabilizer (dispersant) for polymerization.

[20] The agent according to any one of

[16] to

[19] , which is a dispersion stabilizer (dispersant) for suspension polymerization.

[21] The agent according to any one of

[16] to

[20] , which is a dispersion stabilizer for suspension polymerization of a vinyl monomer containing vinyl chloride.

[22] A method for producing a vinyl polymer, comprising polymerizing a vinyl monomer in the presence of a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant {for example, adding (e.g., dissolving or dispersing) the polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond to an aqueous medium in the presence of the surfactant, and polymerizing the vinyl monomer [for example, polymerizing (suspension polymerization) in an aqueous solvent]}.

[23] A method for producing a vinyl polymer, comprising polymerizing a vinyl monomer (e.g., polymerizing in an aqueous solvent) in the presence of a composition containing a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant.

[24] The method according to

[22] or

[23] , wherein the surfactant contains an anionic surfactant, and the proportion of the surfactant relative to the total amount of the polyvinyl alcohol polymer (A) and the surfactant is 0.1 to 10 mass%.

[25] The method according to any one of

[22] to

[24] , wherein the polymerization is suspension polymerization (polymerization in an aqueous medium).

[26] The method according to any one of

[22] to

[25] , wherein a vinyl monomer containing vinyl chloride is suspension polymerized (polymerization in an aqueous medium).

[0016] The present invention provides a novel combination of PVA-based polymers. Specifically, such a combination may be a combination (use in combination) of a specific PVA-based polymer and a surfactant, and may be in the form of, for example, a composition (a composition containing a PVA-based polymer and a surfactant).

[0017] In one embodiment of such a combination (composition, etc.), the composition can efficiently provide the performance required for a dispersion stabilizer (dispersant), etc. For example, a resin (e.g., a vinyl polymer such as a vinyl chloride resin) can be efficiently obtained that has excellent polymerization stability, an average particle size within an appropriate range, and sufficient plasticizer absorption.

[0018] In another embodiment of the combination (composition, etc.) of the present invention, it is possible to easily prepare an aqueous liquid (particularly an aqueous solution) at a predetermined temperature [for example, a temperature that generally includes room temperature or ambient temperature, such as 20°C or higher (e.g., 20 to 50°C, 25 to 40°C)] (and further, to achieve excellent storage stability, dispersibility in warm water, etc. of the aqueous solution).

[0019] In particular, the combination (composition, etc.) of the present invention can achieve (achieve) such easy preparation of an aqueous solution (and further achieve excellent storage stability and warm water dispersibility of the aqueous solution) while providing (ensuring) the performance as a dispersion stabilizer, etc., as described above.

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments. However, the present invention is not limited to the preferred embodiments described below.

[0021] The present invention can provide a combination (e.g., composition) of specific PVA-based polymers. Such a combination (e.g., composition) is useful as a dispersion stabilizer (dispersant, particularly a dispersion stabilizer for suspension polymerization). Therefore, the present invention can also provide such a dispersion stabilizer. The combination or dispersion stabilizer may contain the specific PVA-based polymer (and / or surfactant) alone or in combination of two or more types. The present invention will be described in detail below.

[0022] <Combination> The combination (combination, combined thing, composition) of the present invention is a combination (use in combination) of a specific polyvinyl alcohol-based polymer (A) (hereinafter, may be referred to as a PVA-based polymer (A) or PVA (A), etc.) with a surfactant.

[0023] In such a combination, the form in which the PVA polymer (A) and the surfactant are combined is not particularly limited, but typically, they may be in the form of a composition.

[0024] Therefore, the present invention also includes such a composition (a composition containing a PVA-based polymer (A) and a surfactant). Although the composition depends on the form in which the PVA-based polymer (A) and the surfactant are present, it may usually be (or may be) a PVA-based polymer (A) containing a surfactant.

[0025] Hereinafter, such a combination may be collectively referred to as a composition, regardless of whether it is in the form of a composition or not.

[0026] In the composition (combination), the polyvinyl alcohol polymer (A) may be used alone or in combination of two or more kinds.Similarly, the surfactant may be used alone or in combination of two or more kinds.

[0027] [Polyvinyl Alcohol Polymer (A)] The PVA polymer (A) (polyvinyl alcohol (A) having a polymerizable unsaturated bond) has a polymerizable unsaturated bond. Examples of the polymerizable unsaturated bond include a double bond (unsaturated double bond) and a triple bond (unsaturated triple bond). The polymerizable unsaturated bond may usually be a double bond (particularly, a carbon-carbon double bond) [or may contain at least a double bond (particularly, a carbon-carbon double bond)].

[0028] In the PVA polymer (A), the proportion of polymerizable unsaturated bonds can be selected within a range of, for example, about 1 μmol / g or more (e.g., 2 μmol / g or more), preferably 3 μmol / g or more, and more preferably 5 μmol / g or more (e.g., 8 μmol / g or more, 10 μmol / g or more, 12 μmol / g or more, 15 μmol / g or more, 20 μmol / g or more).

[0029] In the PVA-based polymer (A), the upper limit of the proportion of polymerizable unsaturated bonds is not particularly limited, and may be, for example, 3000 μmol / g or less, 2000 μmol / g or less, 1000 μmol / g or less, 800 μmol / g or less, 600 μmol / g or less, 500 μmol / g or less, 450 μmol / g or less, or 400 μmol / g or less.

[0030] The proportion of polymerizable unsaturated bonds can be set within a range that is an appropriate combination of the lower limit and upper limit of the above range (the same applies to the ranges hereinafter).

[0031] Typically, the proportion of polymerizable unsaturated bonds in the PVA polymer (A) may be about 1 to 2000 μmol / g, preferably about 3 to 1000 μmol / g, and more preferably about 5 to 500 μmol / g.

[0032] In the PVA-based polymer (A), the proportion of polymerizable unsaturated bonds may satisfy the skeleton proportion described below [for example, the proportion of acetal skeleton (a) (e.g., 0.001 mol % or more, 0.05 to 5 mol %, 0.1 to 3 mol %, 0.2 to 2 mol %, etc., per monomer unit)].

[0033] When the content of polymerizable unsaturated bonds (e.g., unsaturated double bonds) is within the above range, the effects of the present invention can be efficiently achieved. In particular, if the content is not too small (e.g., 5 μmol / g or more), it is preferable because, when used in suspension polymerization, it is easy to achieve excellent polymerization stability, suppress scale adhesion to a polymerization vessel, and prevent the particle size of the obtained vinyl resin from becoming coarse. On the other hand, if the content of polymerizable unsaturated bonds (e.g., unsaturated double bonds) is not too large (e.g., 500 μmol / g or less), it is easy to obtain a vinyl resin with high plasticizer absorption, and it is therefore preferable.

[0034] The polymerizable unsaturated bonds contained in the PVA-based polymer (A) can be detected or quantified (their content (content ratio) can be determined) by, for example, bromine titration. The bromine titration method is not particularly limited, but utilizes a reaction between bromine and the polymerizable unsaturated bonds (unsaturated double bonds, etc.) contained in the PVA-based polymer (A). The amount of polymerizable unsaturated bonds (unsaturated double bonds, etc.) (μmol / g) contained in the PVA-based polymer (A) can be calculated from the amount (mol) of bromine reacted with the polymerizable unsaturated bonds (unsaturated double bonds, etc.) contained in the PVA-based polymer (A).

[0035] The PVA-based polymer (A) is not particularly limited, but may preferably contain an acetal skeleton (a) having a polymerizable unsaturated bond (for example, an ethylenically unsaturated double bond) as an embodiment having a polymerizable unsaturated bond.

[0036] (Acetal Skeleton (a)) In the acetal skeleton (a), the number of polymerizable unsaturated bonds is not particularly limited as long as it is 1 or more (for example, 1 to 5, 1 to 3, 1 to 2, 1, etc.).

[0037] In the acetal skeleton (a), the acetal may be either a cyclic acetal or an acyclic (chain) acetal, and preferably a cyclic acetal.

[0038] A typical acetal skeleton having a polymerizable unsaturated bond includes a skeleton (structural unit) represented by the following formula (a1): Therefore, the acetal skeleton (a) may include a skeleton represented by the following formula (a1).

[0039] (In the formula, R′ represents a group having a polymerizable unsaturated bond.)

[0040] In the above formula (a1), R' is a group having a polymerizable unsaturated bond. R' may be a polymerizable unsaturated bond group itself, or may be a group containing a polymerizable unsaturated bond (e.g., a hydrocarbon group). The group having a polymerizable unsaturated bond may have a substituent in addition to the polymerizable unsaturated bond. The substituent can be appropriately selected depending on the type of group having a polymerizable unsaturated bond and is not particularly limited, and examples thereof include a hydroxyl group, a halogen atom, an acyl group, an ester group, an alkoxy group, a nitro group, a substituted amino group, and a group different from the base group (e.g., an aromatic group such as an aryl group). The substituent may be used alone or in combination of two or more types.

[0041] Examples of the group having a polymerizable unsaturated bond [particularly a double bond (ethylenic double bond)] include a group having one polymerizable unsaturated bond {for example, an alkenyl group [for example, a hydrocarbon group (which may have a substituent) having 2 or more carbon atoms (for example, 2 to 30, preferably 2 to 14, more preferably about 2 to 10 carbon atoms), such as a vinyl group, allyl group, propenyl group (1-propenyl group, 2-propenyl group, etc.), butenyl group, pentenyl group, 6-methyl-5-hexenyl group, decenyl group, 2-(dimethylamino)vinyl group, cyclohexenyl group, or 2-phenylethenyl group], and the like}, a group having two or more polymerizable unsaturated bonds {for example, an alkadienyl group [for example, a 1,3-pentadienyl group, 2,6-dimethyl Examples of the alkyl group include hydrocarbon groups (hydrocarbon groups which may have a substituent, for example, an alkapolyenyl group) such as an alkadienyl group having 4 or more carbon atoms (for example, about 4 to 30, preferably about 4 to 14, and more preferably about 4 to 10) such as aryl-1,5-hexadienyl group, cyclohexadienyl group, and propenylcyclohexenyl group, an alkatrienyl group (for example, an alkatrienyl group having 6 or more carbon atoms (for example, about 6 to 30, and preferably about 6 to 24)), an alkatetraenyl group (for example, an alkatetraenyl group having 8 or more carbon atoms (for example, about 8 to 30, and preferably about 8 to 24)), and an alcapentaenyl group (for example, an alcapentaenyl group having 10 or more carbon atoms (for example, about 10 to 30, and preferably about 10 to 24)).

[0042] The acetal skeleton having a polymerizable unsaturated bond {for example, a group represented by formula (a1) (or R'-<) in formula (a1)} may be derived from a corresponding carbonyl compound (for example, an aldehyde, its acetal, or a ketone), in particular, an aldehyde [for example, R'CHO (an aldehyde in which R' is a hydrocarbon group having a polymerizable unsaturated bond)]. The carbonyl compound may have a substituent, as described above.

[0043] Examples of such carbonyl compounds include alkenals [e.g., acrolein, crotonaldehyde, methacrolein, 3-butenal, 3-methyl-2-butenal, 2-methyl-2-butenal, 2-pentenal, 3-pentenal, 4-pentenal, 2-hexenal, 3-hexenal, 4-hexenal, 5-hexenal, 2-ethylcrotonaldehyde, 2-methyl-2-pentenal, 3-( dimethylamino)acrolein, 10-undecenal, myristolein aldehyde, palmitolein aldehyde, olein aldehyde, elaidin aldehyde, vaccen aldehyde, gadolein aldehyde, erucaldehyde, nervon aldehyde, linoleic aldehyde, citronellal, cinnamaldehyde, and other alkenals having 3 to 15 carbon atoms, preferably alkenals having 3 to 10 carbon atoms], alkadienals [e.g., Alkadienals having 5 to 15 carbon atoms, such as 2,4-pentadienal, 2,4-hexadienal, 2,6-nonadienal, citral, and perillaldehyde, preferably alkadienals having 5 to 10 carbon atoms], alkatrienals [for example, linolenic aldehyde, eleostearic aldehyde, and other alkatrienals having 7 to 30 carbon atoms, preferably alkatrienals having 7 to 25 carbon atoms], alkatetraenals [for example, sucralose, Examples include unsaturated aldehydes (particularly monoaldehydes) such as alktetraenals having 9 to 30 carbon atoms, such as thearidone aldehyde and arachidone aldehyde, and alkpentaenals having 11 to 30 carbon atoms, preferably alkpentaenals having 11 to 25 carbon atoms, and ketones and acetals corresponding thereto. When the carbonyl compound has isomers (e.g., cis-trans isomers), both isomers (e.g., both cis and trans isomers) are included.

[0044] As described above, acetals, which are condensates of aldehydes and alcohols, can also be used as carbonyl compounds. The acetals are not particularly limited, but examples thereof include condensates of aldehydes and primary alcohols (e.g., methanol).

[0045] These carbonyl compounds can be used alone or in combination of two or more.

[0046] From the viewpoint of water solubility and the like, the carbonyl compound is preferably composed of a monocarbonyl compound (monoaldehyde, etc.), and even when a polyvalent carbonyl compound (for example, a polyvalent aldehyde such as a dialdehyde) is used, it is often used in a small amount or at a level that ensures water solubility and the like.

[0047] The acetal skeleton having a polymerizable unsaturated bond (e.g., the acetal skeleton represented by the formula (a1)) may be a skeleton that can be introduced via a hydroxy group, and may be, for example, an acetal skeleton derived from (introduced via) two adjacent hydroxy groups (e.g., hydroxy groups of a vinyl alcohol unit). For example, when a carbonyl compound having a polymerizable unsaturated bond (aldehyde, ketone, etc.) is used, a PVA-based polymer (A) having an acetal skeleton (a) having a polymerizable unsaturated bond can be obtained by acetalizing two adjacent OH groups in a PVA-based polymer with the carbonyl compound having a polymerizable unsaturated bond.

[0048] The PVA polymer (A) may have one or more types of acetal skeletons having a polymerizable unsaturated bond, either singly or in combination.

[0049] The content of the acetal skeleton (a) [or polymerizable unsaturated bond, for example, a skeleton represented by formula (a1)] per monomer unit in the PVA-based polymer (A) may be selected from a range of about 0.001 mol % or more (e.g., 0.005 mol % or more), for example, 0.01 mol % or more, preferably 0.05 mol % or more, more preferably 0.1 mol % or more, particularly 0.2 mol % or more, or may be 10 mol % or less [e.g., 8 mol % or less (e.g., 5 mol % or less, 3 mol % or less), preferably 2 mol % or less, more preferably 1 mol % or less].

[0050] As mentioned above, these ranges (upper and lower limits) may be combined appropriately to select a range (for example, 0.01 to 3 mol %, 0.05 to 5 mol %, etc.).

[0051] Specifically, the content of the acetal skeleton (a) (or polymerizable unsaturated bond) per monomer unit in the PVA-based polymer (A) may be about 0.05 to 5 mol %, preferably about 0.1 to 3 mol %, and more preferably about 0.2 to 2 mol %.

[0052] The content of 1 mol % refers to the case where one acetal skeleton (a) (e.g., a skeleton represented by formula (a1)) is present per 100 monomer units (e.g., the total of monomer units such as vinyl alcohol units and vinyl ester units).

[0053] When the content is within the above range, the performance as a dispersant (dispersion stabilizer) can be efficiently realized (for example, a vinyl chloride resin having excellent polymerization stability, an appropriate average particle size, excellent plasticizer absorption, etc. can be efficiently obtained).

[0054] In addition, by not setting the upper limit too high, it becomes easier to improve the preparation properties of the aqueous solution, storage stability, and dispersibility in warm water.

[0055] The method for measuring the content of the acetal skeleton (a) is not particularly limited, but for example, it can be measured using NMR. １ It may be measured by H-NMR and analyzing signals derived from polymerizable unsaturated bonds (such as ethylenic double bonds) in the acetal skeleton (a).

[0056] The PVA polymer (A) may have another acetal skeleton (acetal group, acetal unit) that does not belong to the category of the acetal skeleton (a). Such another acetal skeleton may be a skeleton of the formula (a1) in which R' is a group not having a polymerizable unsaturated bond (e.g., an aliphatic group, an aromatic group, etc.). Examples of such a group include an aliphatic group [e.g., an alkyl group (e.g., a C alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, etc.], １－３０ alkyl group), cycloalkyl group (e.g., cyclopentyl group, cyclohexyl group, etc.) ３－２０ cycloalkyl groups, etc.)], aromatic groups [for example, aryl groups (for example, C groups such as phenyl groups, naphthyl groups, etc. ６－２０ aryl groups, etc.].

[0057] The method for introducing such another acetal skeleton is not particularly limited, and any conventional method can be used, for example, a method of acetalizing the PVA polymer (C) with an aldehyde corresponding to the other acetal skeleton. In such a method, the other acetal skeleton is usually formed from two adjacent vinyl alcohol units.

[0058] Examples of such aldehydes include aliphatic aldehydes such as alkanals [e.g., acetaldehyde, propionaldehyde, butanal, pentanal, hexanal, heptanal, octanal, nonanal, decanal, undecanal, dodecanal, 2-methylbutanal, 2-ethylbutanal, 2-methylpentanal, and 2-ethylhexanal] and cycloalkanecarbaldehydes [e.g., cyclopentanecarboxaldehyde and cyclohexanecarboxaldehyde]; and aromatic aldehydes such as arenecarbaldehydes (e.g., benzaldehyde and naphthaldehyde).

[0059] The PVA polymer (A) contains at least a vinyl alcohol unit, and may contain both the vinyl alcohol unit and an unhydrolyzed (unsaponified) unit [for example, a vinyl ester unit (or a unit derived from a vinyl ester monomer, for example, a vinyl acetate unit)].

[0060] The PVA polymer (A) may contain other units (units other than those exemplified above, such as vinyl alcohol units, unhydrolyzed units, and acetal skeletons (a)) as necessary. Examples of such units include units derived from other monomers exemplified in the section on the PVA polymer (B) described below.

[0061] When the PVA-based polymer (A) contains units derived from such other monomers, the content of the units derived from the other monomers in the PVA-based polymer (A) may be, for example, 20% by mass or less (e.g., 15% by mass or less), 10% by mass or less (e.g., 8% by mass or less), 5% by mass or less (e.g., 3% by mass or less, 2% by mass or less, 1% by mass or less), etc.

[0062] The degree of saponification of the PVA-based polymer (A) (or the proportion of vinyl alcohol units in the units derived from the monomer in the PVA-based polymer (A)) may be, for example, 20 mol % or more (e.g., 25 mol % or more), preferably 30 mol % or more (e.g., 35 mol % or more), more preferably 40 mol % or more (e.g., 45 mol % or more), particularly preferably 50 mol % or more (e.g., 55 mol % or more, 60 mol % or more).

[0063] The upper limit of the saponification degree of the PVA polymer (A) may be, for example, 95 mol% or less (e.g., 93 mol% or less), preferably 90 mol% or less (e.g., 88 mol% or less), and more preferably 85 mol% or less (e.g., 80 mol% or less).

[0064] Specifically, the saponification degree of the PVA polymer (A) may be, for example, about 20 to 90 mol % (e.g., 50 to 90 mol %), preferably about 55 to 85 mol %, and more preferably about 60 to 80 mol %.

[0065] A degree of saponification that is not too low is preferable because it provides excellent aqueous solution preparation, storage stability, and warm water dispersibility, whereas a degree of saponification that is not too high is preferable because it facilitates the efficient production of vinyl chloride resins that exhibit excellent performance as dispersants (for example, excellent polymerization stability, an appropriate average particle size, and high plasticizer absorption).

[0066] The saponification degree can be determined, for example, by the method for measuring the saponification degree of PVA specified in JIS K 6726.

[0067] The viscosity (20°C) of a 4% by mass aqueous solution of the PVA polymer (A) is not particularly limited, and may be selected from the range of, for example, about 1 mPa s or more (e.g., 1.5 mPa s or more), and may be 2 mPa s or more (e.g., 2.2 mPa s or more), preferably 2.5 mPa s or more (e.g., 2.7 mPa s or more), and more preferably 3 mPa s or more (e.g., 3.2 mPa s or more, 3.4 mPa s or more, 3.6 mPa s or more).

[0068] The upper limit of the viscosity (20°C) of a 4% by mass aqueous solution of the PVA polymer (A) is not particularly limited, and may be selected from a range of about 2000 mPa or less (e.g., 1500 mPa s or less, 1000 mPa s or less, 500 mPa s or less), typically about 300 mPa s or less (e.g., 250 mPa s or less, 200 mPa s or less, 150 mPa s or less, 120 mPa s or less, 100 mPa s or less, 80 mPa s or less, 50 mPa s or less), or may be 30 mPa s or less (e.g., 20 mPa s or less), preferably 15 mPa s or less (e.g., 10 mPa s or less), more preferably 9 mPa s or less (e.g., 8 mPa s or less).

[0069] Specifically, the viscosity (20°C) of a 4% by mass aqueous solution of the PVA polymer (A) may be, for example, about 1 to 500 mPa s (e.g., 2 to 300 mPa s, 1 to 100 mPa s, 2 to 100 mPa s, 2.5 to 30 mPa s), or about 20 mPa or less (e.g., 3 to 15 mPa s, 3.2 to 10 mPa s, 3.4 to 9 mPa s, 3.6 to 8 mPa s).

[0070] The (average) degree of polymerization of the PVA-based polymer (A) is not particularly limited, and may be, for example, 100 or more (e.g., 120 or more), preferably 150 or more (e.g., 160 or more), and more preferably 180 or more (e.g., 200 or more, 220 or more, 250 or more, 280 or more, 300 or more).

[0071] The upper limit of the (average) degree of polymerization of the PVA-based polymer (A) is not particularly limited, and may be selected within a range of, for example, about 10,000 or less (e.g., 8,000 or less, 5,000 or less), and may be 3,000 or less (e.g., 2,500 or less), preferably 2,000 or less (e.g., 1,500 or less), and more preferably 1,000 or less (e.g., 800 or less).

[0072] Specifically, the (average) degree of polymerization of the PVA polymer (A) may be, for example, about 120 to 3,000 (eg, 200 to 2,000), preferably about 250 to 1,500, and more preferably about 300 to 1,000.

[0073] If the viscosity of a 4% by mass aqueous solution of the PVA polymer (A) or the degree of polymerization is not too small, it is advantageous in terms of polymerization stability, suppression of scale adhesion, suppression of coarsening of the resulting vinyl resin, etc. On the other hand, if the viscosity of a 4% by mass aqueous solution or the degree of polymerization is not too large, it is advantageous in terms of excellent preparation properties of the aqueous solution, storage stability, and dispersibility in warm water, etc.

[0074] The viscosity of a 4% by mass aqueous solution (20°C) can be determined, for example, by the method specified in JIS K 6726. The degree of polymerization can be determined, for example, by the method specified in JIS K 6726, or can be a calculated (converted) value based on another analytical method [for example, a calculated (converted) value based on the viscosity of a 4% by mass aqueous solution].

[0075] [Surfactant] Examples of the surfactant include ionic surfactants (anionic surfactants, cationic surfactants, amphoteric surfactants, etc.), and nonionic surfactants.

[0076] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0077] Examples of anionic surfactants include carboxylic acid surfactants [for example, carboxylic acid or its salt (e.g., sodium dodecanoate, sodium oleate, potassium laurate, sodium myristate, fatty acid salts), sulfo group-containing carboxylic acid ester or its salt (e.g., sodium bis(2-ethylhexyl)-sulfosuccinate, etc.), N-acylamino acid or its salt (e.g., sodium N-lauroylsarcosinate, sodium cocoyl glutamate, etc.), polyoxyethylene alkyl ether carboxylic acid or its salt (e.g., polyoxyethylene lauryl ether sodium acetate), etc.], sulfate ester surfactants [for example, sulfate ester or its salt (e.g., sodium dodecyl sulfate), etc.], sulfonic acid surfactants [for example, sulfuric acid ester or its salt (e.g., sodium dodecyl sulfate), etc.], and the like. Examples of suitable surfactants include activators [for example, alkanesulfonic acids or salts thereof (e.g., sodium dodecanesulfonate, etc.), alkylarenesulfonic acids or salts thereof (e.g., alkylbenzenesulfonic acids or salts thereof such as sodium octylbenzenesulfonate and sodium dodecylbenzenesulfonate), arenesulfonic acids or salts thereof (e.g., arene mono- or polysulfonic acids or salts thereof such as trisodium naphthalenetrisulfonate), etc.], phosphate ester surfactants [for example, alkylphosphates or salts thereof (e.g., sodium monodecyl phosphate, laurylphosphate, sodium laurylphosphate), polyoxyethylene alkyl ether phosphates or salts thereof (e.g., sodium polyoxyethylene lauryl ether phosphate)], etc.

[0078] Examples of cationic surfactants include quaternary ammonium salt surfactants [e.g., tetraalkylammonium salts (e.g., tetramethylammonium chloride, hexadecyltrimethylammonium bromide, didecyldimethylammonium chloride, etc.), aralkyltrialkylammonium salts (e.g., benzalkonium chloride, etc.), benzethonium chloride, etc.], alkylamine salt surfactants (e.g., mono- to trimethylamine hydrochloride, etc.), and pyridinium salt surfactants (e.g., cetylpyridinium chloride, etc.).

[0079] Examples of amphoteric surfactants include alkyl betaine surfactants (e.g., lauryl dimethyl amino acetic acid betaine), fatty acid amidopropyl betaine surfactants (e.g., cocamidopropyl betaine), alkyl imidazole surfactants (e.g., 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine), amino acid surfactants (e.g., sodium lauroyl glutamate, lauroyl methyl-β-alanine, etc.), and amine oxide surfactants (e.g., lauryl dimethylamine N-oxide, etc.).

[0080] Specific examples of the surfactant [ionic surfactant (e.g., anionic surfactant)] include alkyl sulfonic acids, alkenyl sulfonic acids, alkyl benzene sulfonic acids, alkyl sulfates, polyoxyalkylene alkyl ether sulfates, dialkyl sulfosuccinates, monoalkyl sulfosuccinates, alkyl sulfoacetic acids, α-sulfofatty acid methyl esters, N-acyl-N-methyl taurines, monoalkyl phosphates, dialkyl phosphates, polyoxyethylene alkyl ether phosphates, linear saturated carboxylic acids, linear unsaturated carboxylic acids, alkyl aromatic carboxylic acids, N-acyl amino acids, polyoxyalkylene alkyl ether acetic acids, and salts thereof.

[0081] Furthermore, the surfactant [ionic surfactant (for example, anionic surfactant)] may specifically be a surfactant (compound) represented by the following formula (I):

[0082] R-X-Y (I) [In formula (I), R represents an alkyl group (e.g., a linear or branched alkyl group having 4 to 29 carbon atoms) or an alkenyl group (e.g., a linear or branched alkenyl group having 4 to 29 carbon atoms). X represents a single bond or a linking group, and Y represents an ionic group.]

[0083] The number of carbon atoms in the alkyl group represented by R is, for example, 4 to 29, more preferably 6 to 24, and still more preferably 8 to 20. The alkyl group may be linear or branched. Examples of such alkyl groups include an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, a t-butyl group, an n-pentyl group, an i-pentyl group, a t-pentyl group, a neo-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetra ... Examples thereof include a decyl group, an n-pentadecyl group, a 2-hexyloctyl group, an n-hexadecyl group, a 2-hexyldecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-icosyl group, an n-henicosyl group, an n-docosyl group, an n-tricosyl group, an n-tetracosyl group, an n-pentacosyl group, an n-hexacosyl group, an n-heptacosyl group, an n-octacosyl group, and an n-nonacosyl group.

[0084] The number of carbon atoms in the alkenyl group represented by R is, for example, 4 to 29, more preferably 6 to 24, and even more preferably 8 to 20. The alkenyl group may be linear or branched. Examples of such alkenyl groups include ethenyl, n-propenyl, i-propenyl, n-butenyl, i-butenyl, sec-butenyl, t-butenyl, n-pentenyl, n-hexenyl, n-octenyl, n-nonenyl, n-decenyl, n-dodecenyl, n-tetradecenyl, n-hexadecenyl, n-heptadecenyl, n-octadecenyl, n-icosenyl, n-docosenyl, n-tetracosenyl, n-hexacosenyl, and n-nonacosenyl.

[0085] Examples of the ionic group Y include a carboxyl group, a sulfonic acid group, a phosphate group, and salts (groups) thereof, with the salts of the carboxyl group, the salts of the sulfonic acid group, and the salts of the phosphate group being preferred. Here, examples of the counter cation in each of the above salts include cations of alkali metals such as sodium and potassium; cations of alkaline earth metals such as calcium and barium; and ammonium ions. Among these, the sodium cation is preferred from the viewpoint of availability.

[0086] The above-mentioned X is a single bond or a linking group. The linking group is not particularly limited, but examples thereof include an ether group (—O—), a (poly)oxyalkylene group [for example, a group represented by —(AO)n- (wherein A is an alkylene group, and n is an integer of 1 or more)], a (poly)oxyalkyleneoxy group [for example, a group represented by —O—(AO)n- (wherein A is an alkylene group, and n is an integer of 1 or more)], an unsaturated bond-containing group [for example, an aliphatic group (hydrocarbon group, etc.) containing an unsaturated bond, such as an alkenylene group (for example, a vinylene group (—CH═CH—))], an aromatic group (for example, a phenylene group), an ester group, an amide group (and further, a group containing at least one of these), and the like.

[0087] Examples of the compound represented by formula (I) above, when Y is a carboxyl group or a salt thereof, include a chain saturated carboxylic acid or a salt thereof, a chain unsaturated carboxylic acid or a salt thereof, an alkyl aromatic carboxylic acid or a salt thereof, an N-acyl amino acid or a salt thereof, and a polyoxyalkylene alkyl ether acetic acid or a salt thereof.

[0088] When Y is a sulfonic acid group or a salt thereof, examples of the sulfonic acid group include alkyl sulfates or salts thereof, alkenyl sulfates or salts thereof, polyoxyalkylene alkyl ether sulfates or salts thereof, alkyl sulfonic acids or salts thereof, alkenyl sulfonic acids or salts thereof, alkyl aromatic sulfonic acids or salts thereof, dialkyl sulfosuccinic acids or salts thereof, monoalkyl sulfosuccinic acids or salts thereof, alkyl sulfoacetic acids or salts thereof, α-sulfofatty acid methyl esters or salts thereof, and N-acyl-N-methyl taurine or salts thereof.

[0089] When Y is a phosphate group or a salt thereof, examples of the phosphate include monoalkyl phosphates or salts thereof, dialkyl phosphates or salts thereof, and polyoxyethylene alkyl ether phosphates or salts thereof.

[0090] Examples of nonionic surfactants include ether surfactants [e.g., alkyl ether surfactants (e.g., polyoxyalkylene alkyl ethers such as polyoxyethylene dodecyl ether, polyoxyethylene oleyl ether, and polyoxyethylene polyoxypropylene lauryl ether), alkyl aryl ether surfactants (e.g., alkyl phenyl ether surfactants) (e.g., polyoxyalkylene alkyl aryl ethers such as polyoxyethylene octyl phenyl ether and polyoxyethylene alkyl phenyl ether), alkenyl aryl ether surfactants (e.g., allyl phenyl ether surfactants) (e.g., polyoxyalkylene allyl aryl ethers such as polyoxyalkylene allyl phenyl ether)], ester surfactants [e.g., aliphatic ester (e.g., alkyl ester) surfactants (e.g., alkyl alcohol ethoxylate, higher alcohol propoxylate, alkyl alcohol ethoxylate propoxylate), mono- or polyol fatty acid esters such as polyoxyethylene laurate, glycerin monostearate, sucrose fatty acid esters, and sorbitan fatty acid esters, etc.], amine-type (e.g., alkylamine-type) surfactants (e.g., polyoxyalkylene fatty amines such as polyoxyethylene lauryl amino ether), amide-type (e.g., alkylamide-type) surfactants [e.g., polyoxyalkylene fatty acid amides (e.g., polyoxyethylene lauric acid amide), etc.], alkanolamide-type surfactants (e.g., oleic acid diethanolamide, stearic acid diethanolamide), polypropylene glycol ether-type surfactants [e.g., polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxypropylene ethers (e.g., alkyl ethers such as polyoxyethylene polyoxypropylene lauryl ether), etc.], and higher alcohols (e.g., oleyl alcohol, stearyl alcohol, etc.).

[0091] The surfactants may be used alone or in combination of two or more.

[0092] Preferred surfactants include ionic surfactants, and among them, at least one selected from anionic surfactants and amphoteric surfactants (particularly, anionic surface surfactants (e.g., salt-type anionic surfactants such as carboxylates and alkylarenesulfonates) are preferred).

[0093] By using such a surfactant, the effects of the present invention can be easily achieved efficiently (for example, the ease of preparing an aqueous solution, the stability of the aqueous solution, and the dispersibility in warm water can be easily improved).

[0094] Therefore, the surfactant may contain (or may consist of) an ionic surfactant (e.g., at least one selected from an anionic surfactant and an amphoteric surfactant, particularly an anionic surfactant).

[0095] In such cases, the surfactant may consist solely of an ionic surfactant (e.g., at least one selected from an anionic surfactant and an amphoteric surfactant, particularly an anionic surfactant), or may be used in combination with a nonionic surfactant.

[0096] In such cases, the proportion of the ionic surfactant (e.g., at least one selected from anionic surfactants and amphoteric surfactants, particularly anionic surfactants) in the total surfactants may be, for example, 10% by mass or more (e.g., 20% by mass or more), preferably 30% by mass or more (e.g., 40% by mass or more), more preferably 50% by mass or more (e.g., 60% by mass or more), or may be 70% by mass or more (e.g., 80% by mass or more, 90% by mass or more, 95% by mass or more, 100% by mass, etc.).

[0097] In the combination (composition, etc.), the proportion of the surfactant (amount to be combined, content) may be selected from a range of about 0.00001% by mass or more (e.g., 0.0001% by mass or more) relative to the total amount (total) of the PVA-based polymer (A) and the surfactant, and may be about 0.001% by mass or more (e.g., 0.005% by mass or more), preferably 0.01% by mass or more (e.g., 0.03% by mass or more), more preferably 0.05% by mass or more (e.g., 0.1% by mass or more), or may be 0.15% by mass or more (e.g., 0.2% by mass or more, 0.25% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 1% by mass or more), etc.

[0098] The upper limit of the surfactant ratio (combined amount, content) may be, for example, about 30% by mass or less (e.g., 20% by mass or less), 15% by mass or less (e.g., 12% by mass or less), preferably 10% by mass or less (e.g., 8% by mass or less), more preferably 5% by mass or less (e.g., 4% by mass or less), or 3% by mass or less (e.g., 2.5% by mass or less, 2% by mass or less, 1.5% by mass or less, 1.2% by mass or less, etc.) based on the total amount (total) of the PVA-based polymer (A) and the surfactant. By setting the ratio as described above (e.g., not too small and / or not too large), the effects of the present invention can be efficiently realized. For example, by setting the ratio not too large, when used as a dispersion stabilizer, the performance as a dispersion stabilizer can be efficiently realized (e.g., a vinyl chloride resin having excellent polymerization stability, an appropriate average particle size, and excellent plasticizer absorption can be efficiently obtained). By setting the ratio not too small, the ease of preparation of an aqueous solution, storage stability, and dispersibility in warm water can be improved. As will be described later, when the PVA-based polymer and the surfactant are used as a dispersant or the like, the PVA-based polymer and the surfactant can be used separately. However, when the composition (PVA-based polymer) contains the surfactant in such a ratio, the function of the combination of the PVA-based polymer and the surfactant can be efficiently exhibited or realized when used as a dispersant or the like, without the need to add a new surfactant or to determine the timing of addition.

[0099] A 4% by mass aqueous solution of the composition (or the PVA-based polymer (A) combined with a surfactant) may have a cloud point. In such a case, the cloud point of the 4% by mass aqueous solution of the composition (or the PVA-based polymer (A) combined with a surfactant) may be selected from a range of about 15° C. or higher (e.g., 16° C. or higher), and may be 17° C. or higher (e.g., 18° C. or higher, 19° C. or higher), preferably 20° C. or higher (e.g., more than 20° C., 22° C. or higher, 23° C. or higher, 24° C. or higher), more preferably 25° C. or higher (e.g., 26° C. or higher, 27° C. or higher, 28° C. or higher, 29° C. or higher), particularly 30° C. or higher (e.g., 31° C. or higher, 32° C. or higher, 33° C. or higher, 34° C. or higher).

[0100] The lower limit of the cloud point of a 4% by mass aqueous solution of the composition (or the PVA-based polymer (A) in combination with a surfactant) may be selected, for example, from a range of about 15°C or higher (e.g., 16°C or higher), and may be 17°C or higher (e.g., 18°C ​​or higher, 19°C or higher), preferably 20°C or higher (e.g., more than 20°C, 22°C or higher, 23°C or higher, 24°C or higher), more preferably 25°C or higher (e.g., 26°C or higher, 27°C or higher, 28°C or higher, 29°C or higher), particularly 30°C or higher (e.g., 31°C or higher, 32°C or higher, 33°C or higher, 34°C or higher).

[0101] The upper limit of the cloud point of a 4% by mass aqueous solution of the composition (or the PVA-based polymer (A) in combination with a surfactant) is not particularly limited, and may be, for example, 75° C., 70° C., 65° C., 60° C., 55° C., or 50° C. Typically, the cloud point of a 4% by mass aqueous solution of the PVA-based polymer (A) may be, for example, 25 to 50° C.

[0102] Such a cloud point provides excellent preparation properties and storage stability of the aqueous solution.

[0103] The cloud point of the composition (or the PVA polymer (A) combined with a surfactant) can be adjusted by, for example, the degree of saponification and polymerization of the PVA polymer (A), the type and content of the surfactant, etc.

[0104] <Aqueous Liquid> The combination (composition, etc.) may be used as a dispersion stabilizer (dispersant) or the like as it is, or may be used as an aqueous liquid by dissolving it in water (at least water). Such an aqueous liquid may contain the PVA polymer (A), a surfactant, and water (at least water as a solvent). The aqueous liquid may be, for example, one in which the PVA polymer (A) is dispersed or dissolved in water as a dispersoid.

[0105] The content of the PVA polymer (A) in the aqueous liquid is not particularly limited, and may be selected from a range of, for example, about 0.01% by mass or more (e.g., 0.1% by mass or more), about 1% by mass or more (e.g., 2% by mass or more, 3% by mass or more), or about 80% by mass or less (e.g., 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less).

[0106] In the aqueous liquid, the content of the surfactant is not particularly limited, and may be selected from a range of, for example, about 0.00001% by mass or more (e.g., 0.0001% by mass or more), about 0.001% by mass or more (e.g., 0.002% by mass or more, 0.003% by mass or more, 0.005% by mass or more, 0.01% by mass or more), or about 10% by mass or less (e.g., 5% by mass or less, 3% by mass or less, 2% by mass or less, 1% by mass or less, 0.5% by mass or less).

[0107] The aqueous liquid may have good stability.

[0108] The aqueous liquid may contain a water-soluble organic solvent from the viewpoint of improving storage stability. Examples of water-soluble organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; esters such as methyl acetate and ethyl acetate; and glycol derivatives such as ethylene glycol, ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether. Two or more of these organic solvents may be mixed and used.

[0109] When a water-soluble organic solvent is contained, the proportion of the water-soluble organic solvent relative to the entire solvent may be, for example, 70% by mass or less (e.g., 60% by mass or less), preferably 50% by mass or less, and more preferably 30% by mass or less. In particular, from the viewpoint of environmental considerations and improving workability, the content of the organic solvent is preferably 5% by mass or less relative to the entire solvent or aqueous liquid.

[0110] The aqueous liquid is not particularly limited and can be produced by mixing the PVA-based polymer (A), a surfactant, and water (at least water as a solvent). For example, the aqueous liquid may be produced by simultaneously or stepwise mixing the PVA-based polymer (A), the surfactant, and water (at least water as a solvent). In the mixing, either or both of the PVA-based polymer (A) and the surfactant may be prepared as aqueous liquids in advance. For example, the aqueous liquid may be prepared by mixing the PVA-based polymer (A) with a previously prepared aqueous liquid containing a surfactant. Alternatively, the aqueous liquid containing the surfactant and the aqueous liquid containing the PVA-based polymer (A) may be separately prepared, and then these (and, if necessary, water (at least water as a solvent)) may be mixed together to prepare the aqueous liquid.

[0111] <Method for producing composition and PVA-based polymer (A)> The method for producing the composition is not particularly limited, and the composition may be produced by mixing the PVA-based polymer (A) with the surfactant (and other components as necessary). For example, the PVA-based polymer (A) powder and the surfactant powder may be mixed as they are, or the PVA-based polymer (A) and the surfactant may be mixed in a dissolved or dispersed state in a solvent, and then the solvent may be dried to obtain the composition.

[0112] The method for producing the PVA polymer (A) is not particularly limited. For example, the PVA polymer (A) can be obtained by acetalizing a PVA polymer (B) (polyvinyl alcohol (B)) with an aldehyde having a polymerizable unsaturated bond or the like. The method for producing the PVA polymer (B) is not particularly limited, and a conventionally known method can be used. The PVA polymer (B) and the acetalization step will be described in detail below.

[0113] [PVA-Based Polymer (B)] The PVA-based polymer (B) is not particularly limited, but for example, a PVA-based polymer obtained by saponifying (reacting) a vinyl ester-based polymer [saponified product of vinyl ester-based polymer (polymer containing vinyl ester-based monomers as a polymerization component)] can be used.

[0114] The vinyl ester polymer can be obtained by polymerizing at least a vinyl ester monomer (polymerizing it as a polymerization component). The polymerization method is not particularly limited, and may be any conventionally known method, such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. In consideration of controlling the degree of polymerization and the saponification reaction performed after polymerization, solution polymerization using methanol as a solvent or suspension polymerization using water or water / methanol as a dispersion medium is preferred, but is not limited thereto.

[0115] The vinyl ester monomer usable in the polymerization is not particularly limited, but examples thereof include fatty acid vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl caprylate, and vinyl versatate, and these vinyl ester monomers can be used alone or in combination. Among these, vinyl acetate is preferred from an industrial viewpoint.

[0116] When polymerizing a vinyl ester-based monomer, the vinyl ester-based monomer may be copolymerized with other monomers as long as the effects of the present invention are achieved. In other words, the polymerization components of the vinyl ester-based polymer may contain a vinyl ester-based monomer and other monomers. Examples of other monomers that can be used include, but are not limited to, α-olefins (e.g., ethylene, propylene, n-butene, isobutylene, etc.), (meth)acrylic acid and its salts, (meth)acrylic acid esters [e.g., (meth)acrylic acid alkyl esters (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, etc.], and the like. １－２０ alkyl, etc.)], (meth)acrylamide, (meth)acrylamide derivatives (for example, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide, etc.), vinyl ethers (for example, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc. １－２０ alkyl vinyl ethers, etc.), nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl halides (e.g., vinyl chloride, vinyl fluoride, etc.), vinylidene halides (e.g., vinylidene chloride, vinylidene fluoride, etc.), allyl compounds (e.g., allyl acetate, allyl chloride, etc.), vinylsilyl compounds (e.g., vinyltrimethoxysilane, etc.), fatty acid alkenyl esters (e.g., isopropenyl acetate, etc.), etc. These other monomers can be used alone or in combination.

[0117] When other monomers are used, the content of the other monomers may be appropriately selected depending on the monomers to be used, etc., and may be, for example, 0.1 to 20 mass % or the like relative to the total amount of the polymerization components.

[0118] Furthermore, during polymerization of vinyl ester monomers, a chain transfer agent may be present in order to adjust the degree of polymerization of the resulting vinyl ester polymer, etc. The chain transfer agent is not particularly limited, but examples thereof include aldehydes such as acetaldehyde, propionaldehyde, butylaldehyde, and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone, and cyclohexanone; mercaptans such as 2-hydroxyethanethiol, dodecyl mercaptan, 3-mercaptopropionic acid, mercaptosuccinic acid, and sodium 3-mercapto-1-propanesulfonate; and organic halogens such as carbon tetrachloride, trichloroethylene, and perchloroethylene.

[0119] The amount of the chain transfer agent to be added is determined depending on the chain transfer constant of the chain transfer agent to be added and the degree of polymerization of the desired vinyl ester polymer, but is generally preferably 0.1 to 10% by mass based on the total amount of the polymerization components.

[0120] The vinyl ester polymer obtained as described above is subjected to a saponification reaction to produce a PVA polymer (B).

[0121] The method for saponifying the vinyl ester polymer is not particularly limited, and may be any conventionally known method. For example, alcoholysis or hydrolysis using an acidic catalyst such as an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid, or an organic acid such as formic acid, acetic acid, oxalic acid, or p-toluenesulfonic acid can be used. Examples of solvents used in the saponification 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 can be used alone or in combination of two or more.

[0122] If a gel-like product precipitates as the saponification reaction proceeds, the gel-like product can be pulverized and dried to obtain the PVA polymer (B). It is preferable to neutralize the remaining catalyst before drying. When a basic catalyst is used, an acidic substance such as acetic acid or phosphoric acid is used as the neutralizing agent. When an acidic catalyst is used, an alkaline substance such as sodium hydroxide or potassium hydroxide is used.

[0123] Drying may be performed in an oxidizing atmosphere such as air, or in an inert atmosphere (e.g., nitrogen). The drying temperature may be room temperature (natural drying), or may be heated or high temperature. From the viewpoint of efficient drying, the drying temperature may usually be 30°C or higher, 35°C or higher, 40°C or higher, 45°C or higher, 50°C or higher, 55°C or higher, 60°C or higher, 70°C or higher, etc. The upper limit of the drying temperature is not limited, and may be, for example, 200°C, 180°C, 160°C, 150°C, 140°C, 130°C, 120°C, 110°C, 100°C, etc.

[0124] From this viewpoint, drying is preferably carried out in an inert atmosphere, and it is also preferable to dry at a temperature that is not too high (for example, 120°C or less, less than 120°C, 115°C or less, 110°C or less, 100°C or less, 70 to 110°C, etc.).

[0125] The drying time is not particularly limited and can be selected depending on the drying temperature, etc., and may be, for example, about 1 to 12 hours.

[0126] [Acetalization] The method for acetalizing the PVA polymer (B) with a carbonyl compound (aldehyde, etc.) having a polymerizable unsaturated bond is not particularly limited, and a known acetalization method can be used. The PVA polymer (A) can be obtained by acetalizing the PVA polymer (B) with a carbonyl compound having a polymerizable unsaturated bond.

[0127] In the acetalization, the amount of the carbonyl compound used is not particularly limited, and may be, for example, about 0.05 to 50 parts by mass, preferably about 0.1 to 20 parts by mass, and more preferably about 0.2 to 10 parts by mass, relative to 100 parts by mass of the PVA polymer (B).

[0128] The acetalization reaction is preferably carried out in the presence of an acidic catalyst, which is not particularly limited, but includes, for example, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, oxalic acid, and p-toluenesulfonic acid.

[0129] The amount of the acid catalyst used is not particularly limited, but is, for example, 0.1 to 10 parts by mass per 100 parts by mass of the PVA polymer (B).

[0130] Specific examples of the acetalization method include: (i) a method in which a vinyl ester polymer is saponified in a solvent such as methanol with a basic catalyst such as sodium hydroxide to obtain a solution of a PVA polymer (B), and then an aldehyde or the like and an acidic catalyst are added to acetalize the polymer, followed by neutralization with a basic substance to obtain a solution of a PVA polymer (A); (ii) a method in which a vinyl ester polymer is saponified in a solvent such as methanol in the presence of an acidic catalyst as a saponification catalyst to obtain a PVA polymer (B), and then an aldehyde or the like is added to acetalize the polymer using the same acidic catalyst as used in the saponification reaction, followed by neutralization with a basic substance to obtain a solution of a PVA polymer (A); (i) a method in which a vinyl ester polymer is subjected to simultaneous saponification and acetalization in a solvent in the presence of an acidic catalyst and an aldehyde, etc., followed by neutralization with a basic substance to obtain a solution of the PVA polymer (A); (iv) a method in which an aldehyde, etc., is added to an aqueous solution of the PVA polymer (B), reacted in the presence of an acidic catalyst, and then neutralized with a basic substance to obtain an aqueous solution of the PVA polymer (A); (v) a method in which an aldehyde, etc., is added directly to a slurry or powder of the PVA polymer (B), or a liquid in which the aldehyde, etc., is dissolved or dispersed in an organic solvent or water, is added, reacted in the presence of an acidic catalyst, followed by neutralization with a basic substance, and then excess solvent is removed to obtain the PVA polymer (A). In the methods (i) to (iv), a surfactant is added to the resulting solution or aqueous liquid, followed by mixing, to obtain a solution (aqueous liquid) containing the PVA polymer and the surfactant. The solvent from this solution (aqueous liquid) can then be evaporated to obtain the aforementioned composition (solid). In the method (v), a mixture containing a PVA-based polymer and a surfactant can be obtained by adding and mixing a surfactant before removing the solvent. Alternatively, the above-mentioned composition can be obtained by adding a surfactant after obtaining the PVA-based polymer (A) (after removing the solvent). The surfactant may be dissolved in an appropriate solvent and then added to the PVA-based polymer (A), or may be added to the PVA-based polymer (A) in powder form (solid form). In the methods (i) to (v), the method for converting the PVA-based polymer into an aqueous liquid and the methods for saponification, neutralization, dissolution, dispersion, and drying are not particularly limited, and conventional methods can be used.

[0131] The basic substance used for neutralization is not particularly limited, but examples thereof include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

[0132] The pH of the reaction solution during the acetalization reaction is preferably 3.0 or less from the viewpoint of reaction rate, more preferably 1.0 or less. The pH of the reaction solution after neutralization is preferably 4.7 to 9.0, more preferably 7.0 to 8.5.

[0133] The PVA polymer (A) may be dried in the same manner as the PVA polymer (B). The drying conditions [drying atmosphere, drying temperature, drying time (e.g., 1 to 12 hours)] and preferred embodiments (and the reasons therefor) are the same as those described above [for example, drying in an inert atmosphere such as nitrogen at a not too high temperature (e.g., 70 to 110°C)].

[0134] <Applications, Method for Producing Vinyl Polymer, etc.> The combination (composition, etc.) of the present invention can be used for various applications (for example, dispersants, film applications, etc.), but as described above, it can be suitably used particularly as a dispersion stabilizer [or dispersant, for example, a dispersion stabilizer (dispersant) for polymerization (for example, suspension polymerization)].

[0135] Such a dispersion stabilizer may be a combination of a PVA-based polymer and a surfactant, but is not necessarily a composition thereof. For example, when using a dispersion stabilizer (e.g., during polymerization, in a solvent), the PVA-based polymer and the surfactant may coexist (the PVA-based polymer and the surfactant may be used in combination). The PVA-based polymer and the surfactant may be added separately or as a composition. When added separately, it is preferable to add the PVA-based polymer in the presence of the surfactant. For example, the PVA-based polymer and the surfactant may be added simultaneously, or the PVA-based polymer may be added after the surfactant is added. In particular, to fully utilize the function of the surfactant, it is preferable to add the PVA-based polymer after the surfactant is added. Furthermore, when added separately, at least a portion (partial or all) of the surfactant may be present. When a portion of the surfactant is added (the surfactant is added stepwise), the remaining surfactant may be added simultaneously with the PVA-based polymer, before the addition of the PVA-based polymer, or after the addition of the PVA-based polymer, preferably simultaneously with the addition of the PVA-based polymer or before the addition (particularly before the addition). On the other hand, if the PVA-based polymer and the surfactant are used in a composition, the functions of the combination can be efficiently exhibited or realized without having to consider the timing of adding each component. Therefore, from the viewpoint of process efficiency and the like, the composition can be preferably used among the combinations. Therefore, hereinafter, a method for producing a vinyl-based polymer by using the dispersion stabilizer of the present invention [or a combination (composition, etc.), the same applies hereinafter] or by polymerizing (particularly, suspension polymerization) a vinyl-based monomer using the dispersion stabilizer will be described.

[0136] Suspension polymerization is a polymerization method in which, for example, an insoluble vinyl monomer and an oil-soluble polymerization initiator are added to an aqueous medium, and the mixture is stirred to form minute droplets containing the vinyl monomer, and polymerization is carried out in these droplets. The aqueous medium that can be used here is not particularly limited, and examples thereof include water, aqueous solutions containing various additives, and mixed solvents of water and an organic solvent that is compatible with water.

[0137] The combination (composition, etc.) of the present invention can be used as a dispersion stabilizer when carrying out suspension polymerization of a vinyl monomer. The vinyl monomer is not particularly limited, but is preferably, for example, a vinyl monomer that is generally applied to suspension polymerization, such as vinyl chloride, vinylidene chloride, styrene, acrylic acid ester, methacrylic acid ester, vinyl acetate, acrylonitrile, etc., and among them, vinyl chloride monomer is particularly preferred.

[0138] Examples of vinyl chloride monomers include vinyl chloride monomer (vinyl chloride) and mixtures of vinyl chloride monomer with other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl chloride monomer include vinylidene chloride, vinyl acetate, ethylene, propylene, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, styrene, vinylalkoxysilane, maleic acid, hydroxyalkyl acrylate, allyl sulfonic acid, vinyl sulfonic acid, and the like.

[0139] Therefore, the dispersion stabilizer is suitable for suspension polymerization of vinyl monomers including vinyl chloride monomers (particularly vinyl chloride), and can be particularly suitably used for homopolymerization of vinyl chloride by suspension polymerization. It can also be used for binary or multi-component copolymerization of vinyl chloride with one or more known monomers copolymerizable with vinyl chloride by suspension polymerization, and can be particularly suitably used as a dispersion stabilizer in copolymerization of vinyl chloride with vinyl acetate by suspension polymerization.

[0140] A vinyl chloride resin can be obtained by suspension polymerization of vinyl monomers including vinyl chloride. In producing the vinyl chloride resin, it is preferable that vinyl chloride accounts for 50 to 100 mol % (or 50 to 100 mass %) of the total amount of vinyl monomers used.

[0141] The polymerization initiator in the suspension polymerization of vinyl monomers may also be a known one, and examples thereof include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as benzoyl peroxide, t-butyl peroxyneodecanoate, α-cumyl peroxyneodecanoate, and t-butyl peroxydecanoate; peroxides such as acetylcyclohexylsulfonyl peroxide and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; azo compounds such as 2,2′-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and azobis(4-methoxy-2,4-dimethylvaleronitrile); benzoyl peroxide; and lauroyl peroxide. These may also be used in combination with potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like.

[0142] The main role of a dispersion stabilizer in suspension polymerization of a vinyl monomer is to stabilize droplets consisting of the vinyl monomer and its polymer and to prevent polymer particles formed from the droplets from fusing together to form large agglomerates, but the dispersion stabilizer of the present invention has excellent dispersibility and can form stable droplets with a small amount used, thereby preventing the formation of agglomerates due to the above-mentioned fusing. Note that "stabilized droplets" means that fine droplets of approximately uniform size are stably dispersed in the dispersion medium for suspension polymerization.

[0143] In the suspension polymerization of a vinyl monomer, the amount of the dispersion stabilizer of the present invention [or the PVA polymer (A) or the total amount of the PVA polymer (A) and a surfactant] used is not particularly limited, but is usually 5 parts by mass or less, preferably 0.005 to 1 part by mass, and more preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the vinyl monomer. The dispersion stabilizer of the present invention (PVA polymer and / or surfactant in combination) is generally dissolved in a dispersion medium for suspension polymerization by a conventional method before charging the vinyl monomer, as with a conventional dispersion stabilizer.

[0144] As described above, the dispersion stabilizer of the present invention (a dispersion stabilizer comprising a combination of the PVA-based polymer (A) and a surfactant) may be added (mixed) to a polymerization system either separately or as a composition thereof. Even when the PVA-based polymer (A) and a surfactant are added (mixed) separately (coexisting in the polymerization system), the PVA-based polymer (A) can be efficiently dissolved or dispersed in the polymerization system (in an aqueous medium) by the surfactant (coexisting surfactant). The dispersion stabilizer [composition and components (PVA-based polymer and surfactant)] may be added to the polymerization system in a solid state (such as a powder) or in a non-solid state [for example, dissolved or dispersed in a solvent (for example, as an aqueous liquid)].

[0145] As a dispersion stabilizer for suspension polymerization of vinyl monomers, the dispersion stabilizer of the present invention may be used alone, or other dispersion stabilizers may be used in combination. Examples of such other dispersion stabilizers include known dispersion stabilizers used in suspension polymerization of vinyl monomers such as vinyl chloride in an aqueous medium, such as PVA having an average degree of polymerization of 100 to 4,500 and a degree of saponification of 30 to 100 mol %, modified PVA polymers other than those of the present invention, water-soluble cellulose ethers such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, water-soluble polymers such as gelatin, oil-soluble emulsions such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, and ethylene oxide propylene oxide block polymers, and water-soluble emulsifiers such as polyoxyethylene glycerin oleate and sodium laurate. These other dispersants may be used alone or in combination of two or more.

[0146] In the present invention, the dispersion stabilizer may be a combination of the dispersion stabilizer of the present invention and one or more PVA polymers different from the PVA polymer (A) (e.g., different in degree of polymerization or degree of saponification). For example, a PVA polymer having high dispersion stability and a degree of polymerization of 1,700 or more may be used in combination with a PVA polymer having a degree of polymerization of 1,000 or less, and one or more of these may be the PVA polymer (A).

[0147] In suspension polymerization using the dispersion stabilizer of the present invention, it is also possible to use various known dispersing aids [secondary dispersing agents (dispersion stabilizers)] in combination. As such a dispersing aid, a low-saponification PVA having a saponification degree of preferably 30 to 60 mol%, more preferably 35 to 55 mol%, is used. Furthermore, as the dispersing aid, a PVA having an average polymerization degree of preferably 160 to 900, more preferably 200 to 500, is used.

[0148] In addition to the dispersing aid, various additives known in the suspension polymerization of vinyl compounds, such as chain transfer agents, polymerization inhibitors, pH adjusters, scale inhibitors, and crosslinking agents, may be used in combination.

[0149] The polymerization temperature in suspension polymerization is not limited and can be arbitrarily selected depending on the type of vinyl monomer used, the target polymerization degree of the polymer, the polymerization yield, etc., but is usually preferably 40 to 70° C. The polymerization time is also not particularly limited and may be appropriately set depending on the target polymerization yield, etc.

[0150] The vinyl polymer obtained by the production method of the present invention described above can be processed into various molded articles, etc. In particular, vinyl chloride resins, for example, have an average particle size within an appropriate range and can be efficiently obtained as those with excellent plasticizer absorption, and are often favorably processable into various molded articles.

[0151] The present invention will be described in more detail and specifically below with reference to examples, but the present invention is not limited to these examples. In the following examples and comparative examples, "%" and "parts" mean "% by mass" and "parts by mass" unless otherwise specified.

[0152] First, methods for evaluating PVA-based polymers, methods for measuring the cloud point of an aqueous solution of a PVA-based polymer composition (or a PVA-based polymer), methods for evaluating storage stability, and methods for evaluating vinyl chloride polymers (vinyl chloride resins) in the present examples are described below.

[0153] (Method for Measuring Degree of Polymerization) The measurement was carried out in accordance with the method specified in JIS K 6726.

[0154] (Method for measuring the degree of saponification) The measurement was carried out in accordance with the method specified in JIS K 6726.

[0155] (Method for measuring the content of polymerizable unsaturated bonds in a PVA-based polymer) A 0.5 mol / L acetic acid solution of bromine was added dropwise to an aqueous solution prepared by dissolving 5 g of a PVA-based polymer in 150 g of pure water in an Erlenmeyer flask, and titration was carried out until the color of bromine (yellow) ceased to disappear. The amount of bromine (μmol) required for titration was divided by the weight (g) of the PVA to calculate the content (μmol / g) of polymerizable unsaturated bonds in the PVA.

[0156] (Acetal skeleton content) Dissolved in d6-DMSO (dimethyl sulfoxide) solvent, １ Measurement was performed by H-NMR, and the content of acetal groups per monomer unit was calculated from the signal intensity of the signal derived from the polymerizable unsaturated bond (such as an ethylenic double bond) contained in the acetal skeleton (a).

[0157] (Method for measuring the cloud point of an aqueous solution) A 4% aqueous solution was placed in a quartz cell with an optical path length of 10 mm, and the transmittance at 430 nm was continuously measured at a temperature increase rate of 2°C / min from a temperature of 15°C. The temperature at which the transmittance became 50% of that of the blank (pure water) was defined as the cloud point.

[0158] (Method for evaluating storage stability of aqueous solution) A beaker containing a 4% aqueous solution was placed in a thermostatic water bath at 30°C, and the state of the aqueous solution after 24 hours was visually inspected and evaluated according to the following criteria: ◯: The aqueous solution remained homogeneous. Δ: The aqueous solution separated into two layers. ×: The aqueous solution did not become an aqueous solution (could not be prepared).

[0159] (Evaluation of Vinyl Chloride Polymer) The vinyl chloride polymer was evaluated for average particle size, plasticizer absorption, and amount of scale adhesion as follows.

[0160] <Average particle size> The particle size distribution was measured using a low tap type vibrating sieve (using a JIS sieve) to determine the average particle size.

[0161] <Plasticizer Absorption> The obtained resin was placed in a cylindrical container with glass fiber packed at the bottom, and excess dioctyl phthalate (hereinafter abbreviated as DOP) was added. The resin was left for 30 minutes to allow the DOP to penetrate the resin. The resin was then centrifuged at 3,000 rpm to remove excess DOP, and the weight of the resin was measured to calculate the DOP absorption per 100 parts of polymer. A larger DOP absorption indicates better plasticizer absorption and superior molding processability.

[0162] <Scale Adhesion Amount> After the polymer slurry was taken out of the polymerizer, the state of scale adhesion on the inner wall of the polymerizer was visually observed and evaluated according to the following criteria: ⊚: No or almost no scale adhesion; ◯: Little scale adhesion; ×: Significant white scale adhesion

[0163] Example 1 Synthesis of PVA Polymer (B) A reactor equipped with a stirrer, a condenser, a nitrogen gas inlet, and an initiator inlet was pre-charged with 55 parts of methanol and 45 parts of vinyl acetate monomer. The system was heated to 60°C while flowing nitrogen gas through the system, and 5 parts of a 1% methanol solution of 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN) was added as an initiator to initiate polymerization. The system was maintained at 60°C during polymerization, and 90 parts of vinyl acetate monomer was continuously added over 4 hours starting immediately after the start of polymerization while flowing nitrogen gas through the system. One part of a 1% methanol solution of ADVN was added at 1 hour and two hours after the start of polymerization. When the reaction yield of vinyl acetate reached 85%, the system was cooled to terminate the polymerization. Methanol vapor was added to the resulting polymer to distill off the remaining vinyl acetate monomer, yielding a 50% methanol solution of polyvinyl acetate. Next, 14 parts of methyl acetate and 5 parts of a 3% methanol solution of sodium hydroxide were added to 100 parts of the 50% methanol solution of polyvinyl acetate obtained above, and the mixture was thoroughly mixed to carry out a saponification reaction at 40° C. The resulting gel-like substance was pulverized, neutralized with acetic acid, and then dried. Analysis revealed that a powder of PVA-based polymer (B) having a saponification degree of 71 mol % and a polymerization degree (average polymerization degree) of 600 was obtained.

[0164] (Synthesis of PVA-based polymer (A)) 100 parts of the powder of the PVA-based polymer (B) obtained above was immersed in a mixed solvent of 150 parts of methanol and 300 parts of methyl acetate, and 1.9 parts of cinnamaldehyde was added. The mixture was maintained at 50°C for 1 hour, and then 5 parts of a 50% methanol solution of p-toluenesulfonic acid was added and reacted at 50°C for 1 hour. The mixture was then neutralized with 10 parts of a 5% methanol solution of sodium hydroxide. The pH after neutralization was 7.5. The solvent was then removed by centrifugation, and the mixture was dried at 80°C for 5 hours under a nitrogen atmosphere to obtain a PVA-based polymer (A). The analytical values ​​of this PVA-based polymer (A) were a saponification degree of 72 mol% and a polymerization degree of 600. Bromine titration revealed that the double bond content was 80 μmol / g. Furthermore, the acetal group content per monomer unit was 0.46 mol%.

[0165] (Preparation of Composition) The obtained PVA polymer (A) and sodium dodecyl sulfate were placed in a bag so that the content of sodium dodecyl sulfate in the composition (relative to the total amount of these) was 1.0%, and the bag was shaken to mix well, thereby obtaining a composition (PVA polymer composition). A 4% aqueous solution of the obtained composition had a cloud point of 41°C, and its storage stability was evaluated as good (the 4% aqueous solution remained homogeneous even after being stored at 30°C for 24 hours).

[0166] (Suspension Polymerization of Vinyl Chloride) Using the PVA polymer composition obtained above as a dispersion stabilizer (dispersant), suspension polymerization of vinyl chloride was carried out under the following conditions. 120 parts of deionized water and 1.5 parts of a 4% aqueous solution of the PVA polymer composition obtained above (0.06 parts of the PVA polymer composition per 100 parts of vinyl chloride monomer) were charged into a pressure-resistant stainless steel polymerization reactor. Next, the pressure inside the polymerization reactor was reduced to 50 mmHg using a vacuum pump. After degassing, 100 parts of vinyl chloride monomer and 0.06 parts of t-butyl peroxyneodecanoate as a polymerization initiator were charged, followed by stirring and heating. Suspension polymerization was carried out while maintaining the internal temperature of the polymerization reactor at 57°C, and the polymerization reaction was terminated when the vinyl chloride conversion reached 88%. Unreacted monomer was recovered using a vacuum trap, and the polymer slurry was withdrawn from the polymerization reactor, dehydrated, and dried to obtain a vinyl chloride polymer (vinyl chloride resin). The evaluation results of the PVA polymer composition and the vinyl chloride resin are shown in Table 1.

[0167] [Examples 2 to 13, 20] PVA-based polymer compositions were obtained in the same manner as in Example 1, except that the type and content of the surfactant added to the PVA-based polymer (A) were changed as shown in Table 1. Using the PVA-based polymer compositions, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 to obtain vinyl chloride polymers. The evaluation results of the PVA-based polymer compositions and the vinyl chloride resins are shown in Table 1. The types of surfactants were those shown in Table 2 (the same applies hereinafter).

[0168] Examples 14 to 19 PVA-based polymers (A) shown in Table 1 were synthesized in the same manner as in Example 1, except that the polymerization conditions for the PVA-based polymer (A), the saponification conditions, the type and amount of aldehyde used in the acetalization reaction, etc. were appropriately changed. Subsequently, PVA-based polymer compositions were obtained in the same manner as in Example 1, except that the type and content of surfactant added to the PVA-based polymer (A) were changed as shown in Table 1. Using the PVA-based polymer compositions, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 to obtain vinyl chloride polymers. The evaluation results of the PVA-based polymer compositions and the vinyl chloride resins are shown in Table 1.

[0169] Comparative Example 1 A PVA polymer composition was obtained in the same manner as in Example 1, except that the PVA polymer (A) was changed to a PVA polymer (B) containing no double bond. The evaluation results of the PVA polymer composition and the vinyl chloride resin are shown in Table 1.

[0170] Comparative Example 2 Except for changing the PVA polymer (A) to a PVA polymer (B) containing no double bond and not using a surfactant, evaluation and suspension polymerization were carried out in the same manner as in Example 1. The evaluation results of the PVA polymer and the vinyl chloride resin are shown in Table 1.

[0171] Comparative Example 3 A partially saponified product of itaconic acid-vinyl acetate copolymer (degree of polymerization 600, degree of saponification 72 mol%, amount of itaconic acid modification 0.3 mol%) was synthesized as the PVA-based polymer (A). Evaluation and suspension polymerization were carried out in the same manner as in Example 1, except that the PVA-based polymer (A) was replaced with the partially saponified product of vinyl acetate-itaconic acid copolymer synthesized above and no surfactant was used. The evaluation results of the PVA-based polymer and the vinyl chloride resin are shown in Table 1.

[0172]

[0173]

[0174] Example 21 A vinyl chloride polymer was obtained by suspension polymerization of vinyl chloride in the same manner as in Example 1, except that 1.485 parts of a 4% aqueous solution of a PVA polymer and 0.015 parts of a 4% aqueous solution of a surfactant (sodium dodecylbenzenesulfonate) were used instead of 1.5 parts of the 4% aqueous solution of the PVA polymer composition (i.e., the PVA polymer and the surfactant were used without being combined into a composition (mixture)). The order of charging into the stainless steel polymerization reactor was the aqueous solution of the surfactant followed by the 4% aqueous solution of the PVA polymer. The evaluation results of the vinyl chloride resin were the same as those of Example 1 shown in Table 1.

[0175] Example 22 0.0002 parts of sodium dodecyl sulfate powder was dissolved in water, and then 0.0198 parts of the PVA polymer powder obtained in Example 1 was added and mixed to obtain an aqueous liquid (aqueous solution) with a total concentration of the PVA polymer and sodium dodecyl sulfate of 4%. Then, vinyl chloride was suspension polymerized in the same manner as in Example 1, except that the obtained aqueous solution was used instead of the 4% aqueous solution of the PVA polymer composition used in Example 1, to obtain a vinyl chloride polymer. The evaluation results of the vinyl chloride resin were similar to those of Example 1 shown in Table 1.

[0176] The present invention provides a novel combination of specific PVA-based polymers (e.g., a composition containing a PVA-based polymer and a surfactant). Such a combination (composition) can be suitably used as a dispersion stabilizer (dispersant), etc.

Claims

A composition containing a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant.

2. The composition according to claim 1, wherein the polyvinyl alcohol polymer (A) has a proportion of polymerizable unsaturated bonds of 3 μmol / g or more.

2. The composition according to claim 1, wherein the polyvinyl alcohol polymer (A) has a proportion of polymerizable unsaturated bonds of 5 to 500 μmol / g. 　 The composition according to claim 1, wherein the polyvinyl alcohol polymer (A) contains an acetal skeleton (a) having a polymerizable unsaturated bond. 　 The polyvinyl alcohol polymer (A) contains an acetal skeleton (a) having a polymerizable unsaturated bond, The composition according to claim 1, wherein the acetal skeleton (a) comprises a skeleton represented by the following formula (a1): (In the formula, R′ represents a group having a polymerizable unsaturated bond.) 　 The polyvinyl alcohol polymer (A) contains an acetal skeleton (a) having a polymerizable unsaturated bond, The acetal skeleton (a) contains a skeleton represented by the formula (a1), 2. The composition according to claim 1, wherein the content of the acetal skeleton (a) is 0.05 to 5 mol % per monomer unit.

2. The composition according to claim 1, wherein the polyvinyl alcohol polymer (A) has a degree of saponification of 50 to 90 mol %.

2. The composition according to claim 1, wherein the degree of polymerization of the polyvinyl alcohol polymer (A) is 160 to 3,000. 　 The composition of claim 1 , wherein the surfactant comprises an ionic surfactant. 　 The composition of claim 1 , wherein the surfactant comprises an anionic surfactant.

2. The composition according to claim 1, wherein the proportion of the surfactant is 0.1 to 10% by mass based on the total amount of the polyvinyl alcohol polymer (A) and the surfactant. 　 The composition according to claim 1, wherein the cloud point of a 4% by weight aqueous solution is 25°C or higher. 　 A method for producing a composition containing a polyvinyl alcohol-based polymer (A) having a polymerizable unsaturated bond and a surfactant, the method comprising a step of mixing the polyvinyl alcohol-based polymer (A) with the surfactant. 　 An aqueous liquid containing a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond, a surfactant, and water. 　 The aqueous liquid according to claim 14, wherein the surfactant contains an anionic surfactant, and the proportion of the surfactant relative to the total amount of the polyvinyl alcohol-based polymer (A) and the surfactant is 0.1 to 10 mass%. 　 A dispersion stabilizer comprising a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant in combination. A dispersion stabilizer comprising a composition containing a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant. 　 The agent according to claim 16 or 17, wherein the surfactant contains an anionic surfactant, and the proportion of the surfactant relative to the total amount of the polyvinyl alcohol-based polymer (A) and the surfactant is 0.1 to 10 mass%.

18. The agent according to claim 16 or 17, which is a dispersion stabilizer for polymerization.

18. The agent according to claim 16 or 17, which is a dispersion stabilizer for suspension polymerization. 　 The agent according to claim 16 or 17, which is a dispersion stabilizer for suspension polymerization of vinyl monomers including vinyl chloride. 　 A method for producing a vinyl polymer, comprising polymerizing a vinyl monomer in the presence of a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant. 　 A method for producing a vinyl polymer, comprising polymerizing a vinyl monomer in the presence of a composition containing a polyvinyl alcohol polymer (A) having a polymerizable unsaturated bond and a surfactant. 　 The method according to claim 22 or 23, wherein the surfactant contains an anionic surfactant, and the proportion of the surfactant relative to the total amount of the polyvinyl alcohol-based polymer (A) and the surfactant is 0.1 to 10 mass%.

24. The method of claim 22 or 23, wherein the polymerization is a suspension polymerization.

24. The method according to claim 22 or 23, wherein a vinyl monomer including vinyl chloride is suspension polymerized.

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