JP4377299B2 - Process for producing polyvinyl alcohol rich in syndiotacticity with regulated molecular weight - Google Patents

Description

  The present invention relates to a vinyl ester polymer and polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) whose primary structure is controlled, and methods for producing them. In particular, the present invention relates to vinyl ester polymers and PVA with a regulated molecular weight distribution (ratio of weight average molecular weight to number average molecular weight) and high syndiotacticity, and methods for producing them.

  In general, vinyl ester polymers and PVA obtained by saponifying the same are polymers useful for applications such as molded products such as fibers and films, and have mechanical strength, flow characteristics, thermal stability, and other resins. Various studies have been made from the viewpoints of compatibility, plasticization efficiency, dispersion stabilizing effect, and the like.

For example, as a method for obtaining vinyl ester polymers and PVA with controlled stereoregularity in order to improve crystallinity and improve heat resistance, strength, etc. Polym. Sci. , Part A, Vol. 24, p. 3225, 1986 (Non-patent Document 1), JP-A-11-147913 (Patent Document 1), and the like have been reported.

  On the other hand, it is important to control the molecular weight and molecular weight distribution of the polymer in order to improve the function and performance of the polymer. Living radical polymerization or the like is known as the method. If living radical polymerization is used as a method for obtaining a vinyl ester polymer, it is possible to control the molecular weight, control the molecular weight distribution, control the molecular end groups, etc., and obtain a block copolymer. Further, by saponifying the obtained vinyl ester polymer, it is possible to obtain PVA having a controlled molecular weight, molecular weight distribution and molecular end groups, or a block copolymer containing PVA as one component.

For example, Japanese Patent No. 3377916 (Patent Literature 2), Japanese Patent Application Laid-Open No. 2003-160605 (Patent Literature 3), WO 098/01478 (Patent Literature 4), Macromolecules.
Volume 36, page 9346, 2003 (Non-Patent Document 2) and the like have reported living radical polymerization of vinyl acetate and the like.

  As described above, various studies have been conducted to improve the physical properties of vinyl ester polymers and PVA. However, as the needs of users are becoming increasingly sophisticated and diversified, the above various physical properties are simultaneously satisfied. There is a need for more functional vinyl ester polymers and PVA.

JP-A-11-147913 Japanese Patent No. 3377916 JP 2003-160605 A International Publication No. 098/01478 Pamphlet (Special Table 2000-515181) J. et al. Polym. Sci. Part A, 24, 3225, 1986. Macromolecules 36, 9346, 2003

  Therefore, the problem of the present invention is that the vinyl ester polymer or PVA has good heat resistance, mechanical strength, flow characteristics, thermal stability, compatibility with other resins, plasticization efficiency, dispersion stability effect, etc. The object is to provide a vinyl ester polymer and PVA having physical properties and high functionality.

  The inventors of the present invention have made extensive studies for the purpose of controlling the primary structure of the vinyl ester polymer, and the molecular weight and molecular weight distribution are regulated, and at the same time, the vinyl ester polymer having a high syndiotacticity or As a result of further research, the present invention has been completed by paying attention to the fact that PVA can solve the above problems.

  That is, in the present invention, the molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] is 1.05 to 1.5, and the syndiotacticity (doublet) is 54% or more. And a vinyl ester polymer.

  The present invention also relates to the vinyl ester polymer, wherein the vinyl ester polymer is polyvinyl acetate.

（式中、Ｒ_１およびＲ_２は、各々その一部が塩素原子で置換されていてもよいフッ素化炭化水素基を示し、Ｒ_３は、炭化水素基、フッ素化炭化水素基、フッ素原子、塩素原子または水素原子を示す。）で表され、かつｐＫａが４以上１０未満であるフッ素含有分枝アルコール中、ヨウ素化合物の存在下でビニルエステル系単量体をラジカル重合することにより得られる、前記ビニルエステル系重合体に関する。 Furthermore, the present invention provides the following formula:

(In the formula, R ₁ and R ₂ each represents a fluorinated hydrocarbon group, a part of which may be substituted with a chlorine atom, and R ₃ represents a hydrocarbon group, a fluorinated hydrocarbon group, a fluorine atom, Obtained by radical polymerization of a vinyl ester monomer in a fluorine-containing branched alcohol having a pKa of 4 or more and less than 10 in the presence of an iodine compound. The present invention relates to the vinyl ester polymer.

Further, in the present invention, the molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] is 1.05 to 1.5, and the syndiotacticity (doublet) is 54% or more. It relates to polyvinyl alcohol.

  Furthermore, the present invention relates to polyvinyl alcohol obtained by saponifying the vinyl ester polymer.

（式中、Ｒ_１およびＲ_２は、各々その一部が塩素原子で置換されていてもよいフッ素化炭化水素基を示し、Ｒ_３は、炭化水素基、フッ素化炭化水素基、フッ素原子、塩素原子または水素原子を示す。）で表され、かつｐＫａが４以上１０未満であるフッ素含有分枝アルコール中、ヨウ素化合物の存在下でビニルエステル系単量体をラジカル重合する、ビニルエステル系重合体の製造方法に関する。 The present invention also provides the following formula:

(In the formula, R ₁ and R ₂ each represents a fluorinated hydrocarbon group, a part of which may be substituted with a chlorine atom, and R ₃ represents a hydrocarbon group, a fluorinated hydrocarbon group, a fluorine atom, A vinyl ester heavy polymer which radically polymerizes a vinyl ester monomer in a fluorine-containing branched alcohol having a pKa of 4 or more and less than 10 in the presence of an iodine compound. The present invention relates to a method for manufacturing coalescence.

The present invention, R _1, R ₂ and R ₃ is each a fluorinated hydrocarbon group having 1 to 3 carbon atoms, a process for the production of the vinyl ester polymer.

  The present invention also provides the method for producing a vinyl ester polymer, wherein the fluorine-containing branched alcohol is 1,1,1,3,3,3-hexafluoro-2- (trifluoromethyl) -2-propanol. About.

  Furthermore, the present invention relates to a method for producing the vinyl ester polymer, wherein the iodine compound has at least one bond selected from the group consisting of a carbon-iodine bond, a hydrogen-iodine bond, and a halogen-iodine bond in the molecule.

  The present invention also relates to a method for producing the vinyl ester polymer, wherein the vinyl ester monomer is a vinyl ester monomer having 3 to 20 carbon atoms.

  Furthermore, the present invention relates to a method for producing the vinyl ester polymer, wherein the vinyl ester monomer is vinyl acetate.

In the present invention, the molar ratio of the iodine compound to the vinyl ester monomer is 5 × 10 ^{−4 to} 0.1, and the molar ratio of the radical polymerization initiator to the iodine compound is 0.1 to 5. Further, the present invention relates to a method for producing the vinyl ester polymer, wherein a vinyl ester monomer, an iodine compound, and a radical polymerization initiator are blended to perform radical polymerization.

Furthermore, this invention relates to the manufacturing method of polyvinyl alcohol which saponifies the vinyl ester polymer obtained by the said manufacturing method.

  In the vinyl ester polymer or PVA obtained by the present invention, not only the molecular weight and molecular weight distribution are regulated, but also syndioctacy is simultaneously controlled. It is possible to provide materials with excellent mechanical strength, flow characteristics, thermal stability, compatibility with other resins, plasticization efficiency, dispersion stability, etc. that cannot be obtained at all. It can be said that it produces an immense effect.

  The pKa of the fluorine-containing branched alcohol used in the production method of the present invention is preferably in the range of 4 or more and less than 10. If pKa is too large, the hydrogen bond strength with the side chain carbonyl group is weak, so the tacticity is not so high. On the other hand, an alcohol having a pKa that is too small is inappropriate because it has high reactivity and may cause a reaction with a monomer.

  Moreover, it is possible to precisely control the primary structure of the polymer by radical polymerization of the vinyl ester monomer in the presence of an iodine compound. In this case, the iodine compound has an action as a chain transfer agent, and it is considered that a polymer having a controlled molecular weight, molecular weight distribution, and terminal group can be obtained by polymerization having living characteristics.

  According to the present invention, it is possible to produce a vinyl ester polymer having controlled molecular weight, molecular weight distribution, and terminal groups and rich in syndiotacticity, and further, the molecular weight, molecular weight distribution, and terminal groups are controlled, and PVA rich in otaku can be produced. These are useful as materials excellent in mechanical strength, flow characteristics, thermal stability, compatibility with other resins, plasticization efficiency, dispersion stability and the like.

により表わされるフッ素含有分枝アルコールおいて、式中のＲ_１およびＲ_２は、各々炭化水素基の炭素原子に結合する水素原子の一部または全部がフッ素原子により置換されたフッ素化炭化水素基、あるいは炭化水素基の炭素原子に結合する水素原子の一部が塩素原子により置換され、かつ残りの水素原子の少くとも一部がフッ素原子により置換された塩素化フッ素化炭化水素基である。 [1] Method for producing vinyl ester polymer The following formula:

In the fluorine-containing branched alcohol represented by the formula, R ₁ and R ₂ are each a fluorinated hydrocarbon group in which some or all of the hydrogen atoms bonded to the carbon atom of the hydrocarbon group are substituted with fluorine atoms. Or a chlorinated fluorinated hydrocarbon group in which some of the hydrogen atoms bonded to the carbon atoms of the hydrocarbon group are substituted with chlorine atoms, and at least some of the remaining hydrogen atoms are substituted with fluorine atoms.

The number of carbon atoms of R ₁ and R ₂ is not particularly limited, but is preferably 10 or less, more preferably 6 or less, and still more preferably from the viewpoints of synthesis and availability, polymerization reaction stability and selectivity, and the like. Is 1-3. When R ₃ is a hydrocarbon group or a fluorinated hydrocarbon group, the hydrogen atom bonded to these carbon atoms may be substituted with a chlorine atom, and the number of carbon atoms and the degree of substitution of fluorine atoms are R ₁ and it may be the same as in the case of R _2.

Examples of fluorine-containing branched alcohols having R ₁ , R ₂ and R ₃ include 1,1,1,3,3,3-hexafluoro-2- (trifluoromethyl) -2-propanol, 1,1 , 1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 1,1,1,3,3,3 Hexafluoro-2-phenyl-2-propanol, 1-chloro-1,1,3,3,3-pentafluoro-2- (trifluoromethyl) -2-propanol, 1,1,1,3,3 , 3-hexafluoro-2- (trichloromethyl) -2-propanol and the like.

  The pKa of the fluorine-containing branched alcohol is desirably in the range of 4 or more and less than 10. For alcohols with a large pKa, such as methanol (pKa = 16), tert-butanol (pKa = 19), 2,2,2-trifluoroethanol (pKa = 12.4), etc. The tacticity is not so high because the hydrogen bond strength with the group is weak. Further, even when acetic acid having an appropriate pKa (pKa = 4.8) or bulky pivalic acid (pKa = 5.0) is used, the tacticity may not be so high. This is because hydrogen bonds between carboxylic acids are possible, hydrogen bonds with carbonyl groups on the monomer side chain are lowered, and these carboxylic acids are insufficient in bulk, including electrostatic repulsion. It is estimated to be. On the other hand, if the pKa is too small, it may react with the monomer as in the case of trifluoroacetic acid (pKa = 0.23), which is inappropriate.

  As the fluorine-containing branched alcohol used in the present invention, 1,1,1,3,3,3-hexafluoro-2- (trifluoromethyl) -2-propanol (pKa = 5. 2), 1-chloro-1,1,3,3,3-pentafluoro-2- (trifluoromethyl) -2-propanol (pKa = 5.3), 1,1,1,3,3,3 -Hexafluoro-2-methyl-2-propanol (pKa = 9.6), 1,1,1,3,3,3-hexafluoro-2-propanol (pKa = 9.3) and the like are preferable.

  The amount of the fluorine-containing branched alcohol used in the polymerization of the vinyl ester monomer is preferably about 10 to 90% by volume, more preferably about 30 to 80% by volume with respect to the volume of the polymerization solution.

  As the vinyl ester monomer, a vinyl ester monomer having 3 to 20 carbon atoms is preferable. Examples of such a monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, n- Examples include vinyl caproate, vinyl isocaproate, vinyl octoate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl trimethyl acetate, vinyl chloroacetate, vinyl trichloroacetate, vinyl trifluoroacetate, and vinyl benzoate. These may be used alone or in combination of two or more. Among these, it is particularly preferable to use vinyl acetate.

  The production method of the present invention is not limited to homopolymerization or copolymerization of vinyl ester monomers, and it is also possible to copolymerize monomers other than vinyl ester monomers in combination. For example, α-olefins such as ethylene, propylene and isobutene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and maleic anhydride, or salts thereof, mono- or dialkyl esters, acrylonitrile, methacrylonitrile , Acrylamide, methacrylamide, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, vinyl ethers such as n-butyl vinyl ether, N-vinylformamide, N-vinylacetamide, N-methyl-N-vinyl A small amount of N-vinylamides such as acetamide, N-vinyl-2-caprolactam, N-vinyl-2-pyrrolidone, vinyl chloride, vinylidene chloride, vinyl sulfonic acid or a salt thereof should be present in the polymerization solution. Possible it is.

  The vinyl ester polymer of the present invention can be obtained by radical polymerization of the vinyl ester monomer in the presence of an iodine compound. The entire amount of the vinyl ester monomer may be added to the polymerization solution from the beginning, or may be added sequentially as the polymerization proceeds.

  Examples of the iodine compound used in the present invention include compounds having in the molecule at least one bond selected from the group consisting of a carbon-iodine bond, a hydrogen-iodine bond, and a halogen-iodine bond.

  Examples of the iodine compound having a carbon-iodine bond include alkyl iodide, perfluoroalkyl iodide, and phenyl iodide. Specific examples of the alkyl iodide include iodomethane, iodoethane, iodopropane, iodobutane, diiodomethane, 1,2-diiodoethane, iodoform, chloroiodomethane, iodoacetonitrile, iodoacetic acid, 1,6-diiodohexane, iodoacetamide, iodine Examples of the product include an addition reaction between hydrogen fluoride and an alkene. Specific examples of the alkene include vinyl ester monomers such as vinyl acetate; vinyl ether monomers such as isobutyl vinyl ether; styrene monomers. Moreover, as a method of addition reaction of hydrogen iodide and alkene, a method of mixing anhydrous hydrogen iodide with alkene at a low temperature or the like can be mentioned.

  Specific examples of perfluoroalkyl iodide include iodoperfluoropropane, 1-iodoperfluorohexane, 1-iodoperfluorooctane, 1,2-diiodoperfluoroethane, 1,4-diiodoperfluoro Examples include butane and 1,6-diiodoperfluorohexane. Specific examples of phenyl iodide include iodobenzene and 2-iodoethylbenzene.

  Examples of the iodine compound having a hydrogen-iodine bond include hydrogen iodide. Examples of the iodine compound having a halogen-iodine bond include iodine monochloride, iodine trichloride, iodine monobromide, and the like.

  An iodine compound may be used independently or may use 2 or more types together. Among the above iodine compounds, more preferably, iodoform, diiodomethane, alkyl iodide such as iodoacetonitrile, 1-iodoperfluorohexane, 1,4-diiodoperfluorobutane, 1,6-diiodoperfluorohexane, etc. Perfluoroalkyl iodide, an adduct of hydrogen iodide and alkene, hydrogen iodide and the like.

  In particular, from the viewpoint of controlling the number average molecular weight, it is preferable to use iodoform as the iodine compound. In the reaction in the presence of an iodine compound, the number average molecular weight can be predicted on the assumption that one molecule of polymer is produced from one molecule of iodine compound. When iodoform is used as the iodine compound, the predicted value (by calculation) agrees well with the obtained polymer result, so that the number average molecular weight of the polymer can be precisely controlled.

  The amount of iodine compound added can be appropriately determined according to the molecular weight of the polymer to be obtained, but if the amount of iodine compound is too small, the structure of the polymer cannot be controlled, and If the amount is too large, a polymer cannot be obtained. Therefore, it is preferably added at a rate of 0.0001 to 0.2 mol with respect to 1 mol of the vinyl ester monomer, and a proportion of 0.0005 to 0.1 mol. It is more preferable to add at. The method for adding the iodine compound is not particularly limited, but it is preferably added to the polymerization system before the start of the polymerization from the viewpoint of control of the molecular weight distribution and ease of operation.

  Examples of the radical polymerization method in the present invention include use of a radical polymerization initiator; use of a photosensitizer and irradiation of light; irradiation of radiation, laser light, light, etc .; heating and the like. Is preferably a method using a radical polymerization initiator.

  The radical polymerization initiator is not particularly limited as long as it can generate a radical and react with a vinyl ester monomer and an iodine compound to cause a polymerization reaction, but preferably heat, light, radiation, It is selected from compounds that generate radicals by the action of redox chemical reaction or the like. Preferable examples of the radical polymerization initiator include azo compounds, organic peroxides, inorganic peroxides, organometallic compounds, photosensitizers, redox polymerization initiators, and the like.

  Examples of the azo compound include azobisisobutyronitrile (hereinafter referred to as AIBN), azobisisobutyric acid ester, hyponitrite and the like. Examples of the organic peroxide include benzoyl peroxide (hereinafter referred to as BPO), lauroyl peroxide, dicumyl peroxide, dibenzoyl peroxide, and the like. Examples of inorganic peroxides include potassium persulfate and ammonium persulfate.

  Examples of the redox polymerization initiator include hydrogen peroxide-ferrous iron system, BPO-dimethylaniline system, cerium (IV) salt-alcohol system, and the like. Examples of the organometallic compound include compounds containing Group 2 and Group 3 metals and lead. An initiator that generates radicals by a combination of trialkylborane-oxygen, trialkylaluminum-oxygen, or the like can also be used. Among these polymerization initiators, it is particularly preferable to use AIBN, trialkylborane-oxygen or the like.

  In the case of radical polymerization by light, a photosensitizer such as an azo compound, a peroxide, a carbonyl compound, a sulfur compound, or a dye may be added.

  The above radical polymerization initiators may be used alone, or two or more of them may be used in combination as long as the polymerization does not adversely affect the progress of polymerization. In addition, radical polymerization may be used in combination of a plurality of methods, for example, after the polymerization is advanced to some extent by the action of heat and then the polymerization is completed by light.

  The amount of the radical polymerization initiator used is not particularly limited as long as it is an amount capable of initiating polymerization. However, when the amount is small, the polymerization reaction is slow and the polymerization rate is low. Therefore, 0.02-20 mol is preferable with respect to 1 mol of the iodine compound used, More preferably, it is 0.05-10 mol. In particular, it is preferable to use a radical initiator in the range of 0.1 to 5 mol with respect to 1 mol of the iodine compound.

  Moreover, 0.00005-0.5 mol is preferable with respect to 1 mol of vinyl ester monomers, and, as for the usage-amount of a radical polymerization initiator, More preferably, it is 0.0001-0.2 mol.

  The polymerization temperature varies depending on the type of radical polymerization reaction and is not particularly limited, but is preferably in the range of −100 ° C. to 60 ° C. If the polymerization temperature is too high, syndiotacticity is lowered, which is not preferable. On the other hand, if the polymerization temperature is too low, the polymerization reactivity is extremely lowered and the productivity is insufficient, which is not preferable.

  It has been confirmed that many of the starting ends of the vinyl ester polymer obtained by the present invention are an iodine group-derived alkyl group, perfluoroalkyl group, phenyl group, etc., and most of the growing ends are iodine. Yes. Therefore, by using an iodine compound having a functional group, the functional group can be introduced at the end of the polymer. Moreover, it is also possible to convert into other functional groups using the reactivity of the terminal functional group or iodine. These end-functional polymers can be used as macromonomer synthesis and crosslinking points, and can be used as compatibilizers, block polymer raw materials, and the like.

  In order to improve the stability of the vinyl ester polymer, methanol, ammoniacal methanol, lithium borohydride, etc. may be added to the polymerization system when the polymerization is stopped, and iodine present at the growth terminal of the polymer may be eliminated. Good. Further, the obtained polymer may be irradiated with ultraviolet rays in the presence of isopentane or the like to stabilize iodine with hydrogen.

  After obtaining a vinyl ester polymer, it is also possible to obtain a block copolymer by adding another monomer to the polymerization system for polymerization. In addition to block copolymers of different vinyl ester monomers, it is also possible to obtain block copolymers of vinyl ester monomers and styrene, acrylic or methacrylate monomers.

  As the iodine compound, it is also possible to obtain a multi-branched polymer by using an iodine compound having a plurality of iodines that can participate in polymerization, or by adding a small amount of various divinyl monomers in the late stage of polymerization and crosslinking. is there.

  As a vinyl ester polymer, a polymer having a functional group at the terminal can be obtained, and by using such a terminal group, synthesis of a macromonomer, use as a crosslinking point, synthesis of a block polymer, etc. can be performed. . By such a block polymer, a polymer that expresses new physical properties different from the homopolymerization of the monomer can be obtained.

[2] Polyvinyl alcohol production method Partially saponified PVA or PVA having a predetermined degree of saponification can be obtained by partially or fully saponifying the obtained vinyl ester polymer.

  A known method may be used as a saponification method for the vinyl ester polymer. For example, PVA can be obtained by saponification by using an alkaline substance such as sodium hydroxide or potassium hydroxide as a saponification catalyst and mixing with a vinyl ester polymer in a solvent. In that case, you may saponify, distilling off the produced | generated carboxylic acid ester. The saponification catalyst may be added all at the beginning of the saponification reaction or may be added during the reaction. The ultimate saponification degree can be calculated, for example, by analyzing the remaining carboxylic acid group by alkali titration such as sodium hydroxide. The solvent for the saponification reaction is not particularly limited, but methanol, methyl acetate, dimethyl sulfoxide, dimethylformamide and the like can be used. Of these, methanol is particularly preferred. As the cleaning liquid, methanol, acetone, methyl acetate, ethyl acetate, hexane, water or the like can be used, and a cleaning liquid mainly containing methanol is preferable.

  The obtained PVA can be converted into various polymers using the reactivity of the hydroxyl group possessed by the PVA, the hydrogen bonding ability, etc., or used as a compatibilizing agent. In particular, polyvinyl acetal can be obtained by acetalization by a conventional method.

[3] Vinyl ester polymer / polyvinyl alcohol The vinyl ester polymer of the present invention has a molecular weight distribution (Mw / Mn) of 1.05 to 1.5, preferably 1.05 to 1.45. Moreover, the syndiotacticity (doublet) is 54% or more, preferably 57% or more. Vinyl ester polymers having a molecular weight distribution of less than 1.05 are practically difficult to produce. On the other hand, when the molecular weight distribution exceeds 1.5, for example, the proportion of low molecular weight components becomes extremely high, and it becomes difficult to improve adhesiveness, mechanical strength, flow characteristics, and the like.

  The molecular weight of the vinyl ester polymer can be adjusted by the concentration of the iodine compound. Specifically, the number average molecular weight is preferably 500 to 500,000, more preferably 1,000 to 200,000. When the number average molecular weight is too small, the function as a polymer is not exhibited, and when the number average molecular weight is too large, handling becomes difficult. In order to narrow the molecular weight distribution of the vinyl ester polymer and increase the syndiotacticity (doublet), the number average molecular weight is particularly preferably 1,000 to 50,000.

  The preferred ranges of the molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] and syndiotacticity (doublet) of polyvinyl alcohol obtained by saponifying a vinyl ester polymer are as described above. The same as in the case of the vinyl ester polymer. PVA with a syndiotacticity of less than 54% is not sufficient in heat resistance, strength and the like, as in PVA obtained by saponifying a vinyl ester polymer obtained by ordinary radical polymerization.

  As described above, according to the method of the present invention, the molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] is 1.05 to 1.5, and syndiotacticity (doublet) is It is possible to produce a polyvinyl ester polymer of 54% or more. Further, by saponifying the polyvinyl ester polymer, the molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] is 1.05 to 1.5, and syndiotacticity (double It is possible to produce PVA with a child) of 54% or more. The obtained PVA is suitable for a high-strength, high-modulus material, a high heat-resistant material, and the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. In addition, the measuring method used for the Example and the comparative example is as follows.
<Polymerization rate>
Measurement was performed by gas chromatography (GC-8A, manufactured by Shimadzu Corporation, column: PEG20M, 10% Chromosorb W80 / 100AW-DMSC) using n-hexane as an internal standard.
<Molecular weight and molecular weight distribution>
The number average molecular weight (Mn) and the weight average molecular weight (Mw) are determined by gel permeation chromatography (GPC) [GPC: manufactured by Shodex, column: “KF-806L and KF-803” manufactured by Shodex, solvent: THF]. Measured in terms of polystyrene. The molecular weight distribution (MW / Mn) was calculated from the number average molecular weight (Mn) and the weight average molecular weight (Mw) measured above.
<Syndio Tacticity>
The proton NMR of PVA was measured with a 400 MHz NMR apparatus (manufactured by Varian), the ratio (%) of triplets (mm / mr / rr) was determined, and syndiotacticity (doublet) (%) from the following formula: Was calculated.
Syndiotacticity (doublet) = rr + (mr / 2)

Example 1
Under a nitrogen atmosphere, 1,1,1,3,3,3-hexa-1, so that AIBN is 102 mmol / L, ethyl 2-iodo-2-methylpropanoate is 51 mmol / L, and vinyl acetate is 5.1 mol / L. A fluoro-2- (trifluoromethyl) -2-propanol solution was prepared and polymerized at 20 ° C. under ultraviolet irradiation with a high-pressure mercury lamp. The molecular weight of polyvinyl acetate obtained by reprecipitation in ether after 8 hours (polymerization rate 25%) and 48 hours (polymerization rate 99%) was determined by GPC. Mn) was 1,800, molecular weight distribution (MWD) was 1.50, Mn after 48 hours was 10,700, and MWD was 1.41. Further, the polyvinyl acetate obtained after 48 hours was dissolved in methanol and alkali saponified to obtain PVA, and the syndiotacticity (doublet) was determined from proton NMR measurement of PVA, and it was 57%. . The composition of the polymerization solution is shown in Table 1, and the properties of the obtained PVA are shown in Table 2.

Example 2
In a nitrogen atmosphere, 1,1,1,3,3,3-tributylboron was 102 mmol / L, ethyl 2-iodo-2-methylpropanoate was 51 mmol / L, and vinyl acetate was 5.1 mol / L. A hexafluoro-2- (trifluoromethyl) -2-propanol solution was prepared, air was introduced into the reaction system, and polymerization was performed at −40 ° C. for 1, 4, and 19 hours. The molecular weight of polyvinyl acetate obtained by reprecipitation in ether after 1 hour (26% polymerization rate), 4 hours (53% polymerization rate), and 19 hours (94% polymerization rate) was determined by GPC. However, the Mn after 1 hour was 7,300, and the MWD was 1.40. The polyvinyl acetate obtained after 1 hour was dissolved in methanol and alkali saponified to obtain PVA. It was 63.3% when the tacticity (duplex) was calculated | required. The composition of the polymerization solution is shown in Table 1, and the properties of the obtained PVA are shown in Table 2.

Comparative Example 1
Under a nitrogen atmosphere, prepare a methanol solution so that AIBN is 102 mmol / L, ethyl 2-iodo-2-methylpropanoate is 51 mmol / L, and vinyl acetate is 5.1 mol / L. The reaction was carried out at 20 ° C. for 48 hours, but polyvinyl acetate was not obtained.

Comparative Example 2
Under a nitrogen atmosphere, prepare a methanol solution such that tributylboron is 102 mmol / L, ethyl 2-iodo-2-methylpropanoate is 51 mmol / L, and vinyl acetate is 5.1 mol / L, and air is introduced into the reaction system. The reaction was carried out at −40 ° C. for 19 hours, but no polyvinyl acetate was obtained.

Comparative Example 3
Under a nitrogen atmosphere, the 1,1,1,3,3,3-hexafluoro-2- (trifluoromethyl) -2-propanol solution was adjusted so that AIBN was 102 mmol / L and vinyl acetate was 5.1 mol / L. The polymer was prepared and polymerized at 20 ° C. under ultraviolet irradiation with a high-pressure mercury lamp. When the molecular weight of polyvinyl acetate obtained by reprecipitation in ether after 48 hours (polymerization rate 90%) was determined by GPC, Mn was 68,300 and MWD was 1.80. The obtained polyvinyl acetate was dissolved in methanol and alkali saponified to obtain PVA, and syndiotacticity (duplex) was determined from proton NMR measurement of PVA. As a result, it was 62.5%. The composition of the polymerization solution is shown in Table 1, and the properties of the obtained PVA are shown in Table 2.

Claims (6)

In 1,1,1,3,3,3-hexafluoro-2- (trifluoromethyl) -2-propanol , in the presence of ethyl 2-iodo-2-methylpropanoate , the vinyl ester monomer was A vinyl having a molecular weight distribution [weight average molecular weight (Mw) / number average molecular weight (Mn)] of 1.05 to 1.5 and a syndiotacticity (doublet) of 54% or more. A method for producing an ester polymer. The method for producing a vinyl ester polymer according to claim 1 , wherein the vinyl ester monomer is a vinyl ester monomer having 3 to 20 carbon atoms. The method for producing a vinyl ester polymer according to claim 1 or 2 , wherein the vinyl ester monomer is vinyl acetate. The molar ratio of ethyl 2-iodo-2-methylpropanoate to vinyl ester monomer was 5 × 10 ^{−4 to} 0.1, and the mole of radical polymerization initiator relative to ethyl 2-iodo-2-methylpropanoate. as the ratio is 0.1-5, vinyl ester monomers, radical polymerization by blending 2-iodo-2-methyl propanoate and a radical polymerization initiator, any one of claims 1 to 3, A method for producing a vinyl ester polymer as described in 1. The method for producing a vinyl ester polymer according to any one of claims 1 to 4, wherein the polymerization reaction is performed at -100 ° C to 20 ° C. Saponifying vinyl ester-based polymer obtained by the production method according to any one of claims 1 to 5, the production method of the polyvinyl alcohol.