JP2001072728A - Block polymer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermally stable diblock polymer having a heatresponsive component, which polymer comprises a product prepared by bonding a PVA polymer component to a component of a polymer that can give an aqueous solution having a cloud point through an ether linkage. SOLUTION: Also a triblock polymer of an ABA type (wherein A is a component of a polymer that can give an aqueous solution having a cloud point, B is a PVA polymer component, and B is bonded to each A through an ether linkage) is a thermally stable one. It is desirable that the polymer that can give an aqueous solution having a cloud point is a polyalkenyl ether type polymer desirably having structural units of the formula, wherein R1 is H or CH3; R2 is H or a monovalent organic group; and n is 1-10 when R2 is H or is 0-10 when R2 is H. Each of the block polymers is produced by adding a polymerization stop being a PVA polymer having an OH group on at least either terminal during the polymerization or after the reaction in synthesizing a polyalkenyl ether type polymer by a cationic polymerization process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) polymer component and an aqueous solution comprising a polymer component having a cloud point, wherein both components are linked via an ether bond. The present invention relates to a linked block polymer and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a means for imparting useful properties to a polymer, a general-purpose polymer is modified, a functional group or a reactive group is added, or a functional group or a reactive group is added from the beginning. Various methods have been proposed, such as polymerization or copolymerization of a monomer having a group, or bonding of a heterogeneous polymer as a second component to a polymer chain in a graft or block manner. Of these, the most common method is to bond a heterogeneous polymer, which is the second component, to the polymer chain in a graft or block manner, and many proposals have been made on so-called graft polymer or block polymer production techniques. As a method for synthesizing a block polymer containing a PVA-based polymer as one component, for example, radical polymerization of various monomers using polyvinyl acetate having a thiol group at a terminal as a chain transfer agent is followed by saponification to block copolymer. A method for synthesizing a polymer (JP-A-59-189111)
Publication No.) is reported. Among these, in particular, a block polymer composed of a PVA-based polymer component and a polymer component in which an aqueous solution has a cloud point is a functional polymer obtained by imparting stimulus responsiveness to a PVA-based polymer which is a typical water-soluble resin. It has a very high industrial value.

Examples of a block polymer comprising a PVA-based polymer component and a polymer component having an aqueous solution having a cloud point include polyalkenyl ethers having a thiol group at the terminal and poly (N-isopropyl (meth) acrylamides). A method of synthesizing a block polymer by subjecting vinyl acetate to radical polymerization and saponifying the compound by using as a chain transfer agent (see JP-A-6-136036) has been reported. However, the block polymer obtained by applying this method is thermally unstable because the PVA-based polymer component and the polymer component having an aqueous solution having a cloud point are bonded via S (sulfur group). Yes, there is a problem that coloring is easy during drying or heating.

In recent years, a so-called living polymerization method has been found as a method for synthesizing a block polymer comprising a PVA-based polymer component and a polyalkenyl ether component having an aqueous solution having a cloud point (Japanese Patent Laid-Open No. 62-257910). JP, JP-A-62-257911, JP-A-1-1
No. 08202, JP-A-1-108203), a benzyl vinyl ether and another alkenyl ether are block-copolymerized and debenzylated by using this method, so that the PVA component and the polyalkenyl ether component are decomposed. A method for synthesizing a block polymer is known. However, this method has a problem that it is difficult to synthesize in large quantities because sodium radicals in liquid ammonia are used for debenzylation.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermally stable block polymer comprising a PVA-based polymer component having no above-mentioned problems and a polymer component having an aqueous solution having a cloud point. It is to provide a method.

[0006]

As a result of intensive studies to solve the above-mentioned problems, a PVA-based polymer component (B component) was obtained.
And an aqueous solution comprising a polymer component (A component) having a cloud point, and an AB type diblock polymer or an ABA type triblock polymer in which both components are connected via an ether bond achieves the above object. And completed the present invention.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described in more detail. The PVA-based polymer component (component B) constituting one component of the block polymer of the present invention usually comprises a vinyl alcohol unit and a vinyl ester unit. As vinyl ester units, vinyl acetate, vinyl pivalate,
Units derived from bulky vinyl esters of side chains such as vinyl formate or vinyl esters of high polarity are usually selected.

The degree of saponification of the PVA polymer component is usually 7
0 mol% or more is preferable, 90 mol% or more is more preferable, and 95 mol% or more is further preferable. Here, the degree of saponification indicates the ratio of a vinyl alcohol unit after saponification to a unit that can be converted into a vinyl alcohol unit by saponification of a vinyl ester unit, and the residue is a vinyl ester unit.

The PVA-based polymer component may have various copolymerized monomer units for the purpose of modifying the PVA-based polymer component as long as the effects of the present invention are not impaired. Examples of such a copolymerized monomer unit include olefins such as ethylene, propylene, 1-butene, and isobutene;
Acrylic acid and its salts, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, Acrylates such as dodecyl acrylate, octadecyl acrylate, methacrylic acid and salts thereof,
Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, methacrylic acid Methacrylic esters such as octadecyl, acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts and quaternary salt,
Acrylamide derivatives such as N-methylolacrylamide and its derivatives, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N, N
Methacrylamide derivatives such as dimethyl methacrylamide, diacetone methacrylamide, methacrylamidopropanesulfonic acid and salts thereof, methacrylamidopropyldimethylamine and salts thereof and quaternary salts, N-methylol methacrylamide and derivatives thereof, methyl vinyl ether, Ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, benzyl vinyl ether, dodecyl vinyl ether, vinyl ethers such as stearyl vinyl ether, acrylonitrile, nitriles such as methacrylonitrile, vinyl chloride,
Vinyl halides such as vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts and esters; itaconic acid and its salts and esters; vinylsilyl such as vinyltrimethoxysilane Examples include units derived from compounds, isopropenyl acetate, and the like. Of these, units derived from ethylene are preferred. The use ratio of these copolymerized monomers is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 0 to 15 mol%, more preferably 0 to 10 mol%.

[0010] The degree of polymerization of the component comprising the PVA-based polymer is appropriately selected depending on the use of the finally obtained block polymer, but is preferably 500 or more, more preferably 1,000 or more, and still more preferably 2,000 or more. That is all. Further, from the viewpoint of the viscosity of the aqueous solution and the processing characteristics such as film forming property and stretching, it is preferably 30,000 or less. Here, the polymerization degree is a viscosity average polymerization degree determined according to JIS K-6726.

The stereoregularity of the PVA-based polymer component in the present invention is not particularly limited, but is preferably an atactic structure or a syndiotactic structure close to an atactic structure, and more preferably an atactic structure.

The other component (component (A)) in the block polymer of the present invention, the polymer component whose aqueous solution has a cloud point, is not particularly limited as long as the polymer aqueous solution has a cloud point. Among them, those having a cloud point of an aqueous polymer solution of 0 to 100 ° C. are preferable, and those having a cloud point of 20 to 95 are preferable.
C. is more preferable, 30 to 95C is more preferable, and 30 to 80C is more preferable. The cloud point of these aqueous polymer solutions is determined by a temperature controller,
A 1% by weight aqueous solution of a polymer is placed in a UV cell equipped with a thermocouple and a stirrer, and the light transmittance at 500 nm when the temperature is increased (or decreased) at a rate of 1 ° C./min is from 100% to 0%. (Or from 0% to 100%).

Specific examples of the polymer component in which the aqueous solution has a cloud point include a polyalkenyl ether-based polymer having a structural unit represented by the following general formula (1) (Preprints of the Society of Polymer Science, vol. No. 6, P. 1710).

[0014]

Embedded image

(Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a monovalent organic group. When R ² is a hydrogen atom, n represents an integer of 1 to 10, When R ² is a monovalent organic group, n represents an integer of 0 to 10.)

R ² in the general formula (1) represents a hydrogen atom or a monovalent organic group. As a monovalent organic group,
Organic groups having 1 to 10 carbon atoms are preferred, and organic groups having 1 to 5 carbon atoms are more preferred. Examples include an alkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkoxyalkyl group, an aryloxyalkyl group, and the like. They may be substituted by hetero groups.

Examples of the polyalkenyl ether polymer include those obtained by polymerizing one or more alkenyl ethers among the alkenyl ethers represented by the following general formula (2). be able to. Also,
A block copolymer obtained by polymerizing one or two or more alkenyl ethers, adding another alkenyl ether, and further polymerizing the alkenyl ether may also be used.

[0018]

Embedded image

(Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a monovalent organic group. When R ² is a hydrogen atom, n represents an integer of 1 to 10, When R ² is a monovalent organic group, n represents an integer of 0 to 10.)

R ² in the above formula (2) represents a hydrogen atom or a monovalent organic group. As the monovalent organic group, an organic group having 1 to 10 carbon atoms is preferable, and an organic group having 1 to 5 carbon atoms is more preferable. For example, an alkyl group, an aryl group,
Aralkyl groups, alkenyl groups, alkoxyalkyl groups,
And an aryloxyalkyl group. They may be substituted by hetero groups.

Examples of the alkenyl ether represented by the above general formula (2) include, for example, methyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, propoxyethyl vinyl ether, butoxyethyl vinyl ether, 2-methoxyethoxyethyl vinyl ether, 2-ethoxy. Ethoxyethyl vinyl ether, 2-methoxy-2-ethoxyethoxyethyl vinyl ether, 2-ethoxy-2-ethoxyethoxyethyl vinyl ether, phenoxyethyl vinyl ether, methoxyethylpropenyl ether, ethoxyethylpropenyl ether, propoxyethylpropenyl ether, butoxyethylpropenyl ether, 2-methoxyethoxyethylpropenyl ether, 2-ethoxyethoxyethylpropenyl Ether, 2-methoxy-2-ethoxyethoxy ethyl propenyl ether, 2-ethoxy-2-ethoxyethoxy ethyl propenyl ether,
Phenoxyethyl propenyl ether and the like.

The number average molecular weight (Mn) of the polymer whose aqueous solution has a cloud point is appropriately selected depending on the use of the finally obtained block polymer.
1,000,000, more preferably 1,000 to 5
00,000. Further, gel permeation chromatography (GP) of a polymer whose aqueous solution has a cloud point
C) The ratio (Mw) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) determined from the standard polystyrene calibration curve by the method
/ Mn) is preferably from 1.0 to 10.0, and more preferably from 1.0 to 5.0.

When a polyalkenyl ether polymer is selected as a polymer whose aqueous solution has a cloud point, and the living cationic polymerization method described later is used as a method for synthesizing this component, the molecular weight of the polymer is determined by the monomer Since it is almost uniquely determined by the molar ratio with the agent, the molecular weight of the polymer can be controlled over a wide range by changing the ratio of the amounts of the monomer and the polymerization initiator used. The number average molecular weight (Mn) of the polyalkenyl ether polymer obtained by living cationic polymerization is appropriately selected depending on the use of the finally obtained block polymer, but is preferably from 500 to 1,000,000. Preferably it is 1,000-500,000. The weight average molecular weight (Mw) and the number average molecular weight (Mw) of the obtained polymer obtained from the standard polystyrene calibration curve by the GPC method.
The ratio (Mw / Mn) to n) is usually in the range of 1.0 to 1.3, and more preferably in the range of 1.0 to 1.25.

The method for producing a block polymer of the present invention is a block polymer comprising a PVA-based polymer component and a polymer component having an aqueous solution having a cloud point, wherein both components are connected via an ether bond. The method is not particularly limited as long as it can be manufactured efficiently.

When the polyalkenyl ether is synthesized by the cationic polymerization method of the alkenyl ether represented by the general formula (2), a PVA polymer having a hydroxyl group at one end or both ends or polyvinyl as a terminator for the polymerization is used. The block polymer of the present invention can be efficiently obtained by coexisting the ester polymer during the polymerization or by adding it after the polymerization reaction.

The method of introducing a hydroxyl group into one end or both ends of the PVA polymer is not particularly limited, but for example, the following method is used.

First, as a method for introducing a hydroxyl group into the terminal of the PVA-based polymer, it is preferable to use so-called living polymerization, since the hydroxyl group can be introduced into the terminal of the polymer at a desired ratio. For example, trimethylsilyl group, t-butyl group, a polymerization initiator having introduced a hydroxyl group protected by a benzyl group, etc., living cationic polymerization of t-butyl vinyl ether, benzyl vinyl ether, vinyl ethers such as trimethylsilyl vinyl ether, etc., to carry out living cationic polymerization of these monomers. After obtaining a homopolymer or a random copolymer or a block copolymer composed of two or more of these monomers, the protected hydroxyl group of the polymerization initiator is deprotected, and further, or simultaneously, the vinyl ether side By converting the chain into a hydroxyl group, a hydroxyl group can be introduced into one end of each polymer with high accuracy. Alternatively, after obtaining a homopolymer of these monomers, or a random copolymer or a block copolymer of two or more of these monomers by living cationic polymerization, a trimethylsilyl group, a t-butyl group, a benzyl group By adding a compound having a hydroxyl group protected by, for example, and a free hydroxyl group at the same time, the hydroxyl group can be introduced into one end of each polymer with high accuracy. Furthermore, by performing both methods simultaneously, hydroxyl groups can be introduced into both terminals of the polymer with high accuracy.

If the living radical polymerization, which has been actively studied in recent years, is used as the living polymerization, it is not necessary to protect the hydroxyl group as in the case of the living cationic polymerization in order to proceed with the polymerization. Hydroxyl groups can be introduced at both ends. For example, a vinyl ester is subjected to living radical polymerization by a polymerization initiator having a hydroxyl group introduced thereto to obtain a homopolymer of these monomers, or a random copolymer or a block copolymer of two or more of these monomers. This makes it possible to introduce a hydroxyl group into one end of each polymer with high accuracy. Alternatively, after obtaining a homopolymer of these monomers, or a random copolymer or a block copolymer composed of two or more of these monomers by living radical polymerization, for example, containing a hydroxyl group such as hydroxyethyl methacrylate The hydroxyl group can be introduced into one end of each polymer with high accuracy even by adding a radically polymerizable monomer to the growing end of the polymer in an equivalent amount. Furthermore, a hydroxyl group can be introduced into both ends of the polymer with high accuracy by performing both methods simultaneously. In addition, hydroxyl groups can be introduced into both ends of these polymers by performing radical polymerization of these monomers using hydrogen peroxide as a chain transfer agent.

Next, a method for obtaining a polyalkenyl ether-based polymer component by a cationic polymerization method will be described.
The cationic polymerization initiator used herein is not particularly limited as long as it is a compound that generates a carbonium ion from the alkenyl ether that is a monomer, and is added to the second and third monomers to promote polymerization. Specifically, protic acids (sulfuric acid, phosphoric acid, hydrochloric acid, hydrobromic acid, nitric acid, hydrogen fluoride, hydrogen iodide, acetic acid and chlorinated products thereof, trifluoroacetic acid, p-toluenesulfonic acid, etc.), metal oxides And other solid acids (chromium oxide, phosphorus oxide, titanium oxide, aluminum oxide, cobalt oxide, manganese oxide, molybdenum oxide, silica-alumina, vanadium oxide, aluminum sulfate, iron sulfate, chromium sulfate, etc.), halogens (iodine, bromine) , Chlorine, iodine bromide, iodine chloride, bromine chloride), metal halides (beryllium, magnesium, zinc, cadmium, mercury, boron, aluminum Bromide, gallium, titanium,
Zirconium, tin, phosphorus, antimony, niobium, bismuth, thallium, uranium, rhenium, iron and other bromides, chlorides or fluorides; organometallic compounds (aluminum or zinc alkyl compounds; magnesium alkyl compounds called Grignard reagents) ) And stable carbonium ions (salts such as triphenylmethylcarbonium ion and tropylium ion). Among these polymerization initiators, a metal-containing polymerization initiator includes, as necessary, a compound that generates a proton (water, a hydroxy compound such as an alcohol, a protonic acid, or the like), or a compound that generates a carbonium ion ( Alkyl halides) are added as cocatalysts.

Here, as a cationic polymerization method for synthesizing a PVA-based polymer, it is easy to control the molecular weight, composition, and structure, and it is easy to obtain a uniform polymer having a narrow molecular weight distribution and composition distribution. Living cation polymerization is preferred because of high blocking efficiency with coalescence.

The living cationic polymerization initiator is not particularly limited as long as the cationic polymerization of alkenyl ether proceeds in a living manner. For example, JP-A-60-2
HI / I ₂ -based polymerization initiator reported in JP 28509, JP-A-61-103654, 62-
257910, JP-A-1-108202,
JP-A-1-108203 and JP-A-4-318
Polymerization initiators and the like, which are obtained by combining an organic aluminum compound and an additive such as an ether or an ester, which are reported in JP-A-004, are preferably used.

The number average molecular weight (Mn) of the block polymer of the present invention is a polymer obtained by re-acetylating the PVA component.
It is preferably from 000 to 1,000,000. The number average molecular weight (Mn) of the block polymer of the present invention is GPC
It is measured by the method and determined by standard polystyrene conversion. The degree of saponification of the vinyl alcohol component can be determined by ¹ H-NMR quantification of acetate residue.

The block polymer of the present invention has a wide range of properties by adjusting the composition and molecular weight of both components. Further, since it has a heat-sensitive response function different from PVA such as an increase in aqueous solution viscosity near the temperature at which the polymer used as one component in the block polymer exhibits a cloud point, a dispersant, It is suitable for use as a processing agent for resins, paper, fibers and the like. Further, it is also suitable for use as a component constituting a water-based ink, a water-based paint, a water-based adhesive or the like, or as a base polymer.

[0034]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A glass container provided with a three-way cock was prepared, replaced with nitrogen, and heated in a nitrogen gas atmosphere to remove water adsorbed in the glass container. In a container, t-butyl vinyl ether (0.76 molar (hereinafter abbreviated as M)), THF (1.0 M),
-Trimethylsiloxyethyl acetate (4.0 mmol (hereinafter abbreviated as mM)) and hexane,
When the temperature in the system reaches -20 ° C, Et _1.5 AlCl
_{A 1.5} (20 mM) hexane solution was added to initiate polymerization. After 57 hours, hydrochloric acid-methanol was added for deprotection.
Further, after washing with a 0.6 N hydrochloric acid aqueous solution to remove the initiator residue and neutralizing with a dilute sodium hydroxide aqueous solution, the reaction solution is concentrated and dried under reduced pressure to obtain a poly (t-containing hydroxyl group at one end). Butyl vinyl ether). The polymerization rate was 96%, the terminal hydroxyl group introduction rate determined by ¹ H-NMR was 95%, and the degree of polymerization after deprotection with hydrogen bromide and conversion to PVA was 179. Next, a glass container provided with a three-way cock was separately prepared, and after replacement with nitrogen, the mixture was heated in a nitrogen gas atmosphere to remove adsorbed water in the glass container. In a container, 2-methoxyethyl vinyl ether (0.38M), ethyl acetate (1.0M), 1-butoxyethyl acetate (4.
(0 mM) and toluene. When the temperature in the system reached 0 ° C., a toluene solution of Et _1.5 AlCl _1.5 (20 mM) was added to initiate polymerization. After 1.8 hours, a toluene solution of the above-mentioned poly (t-butyl vinyl ether) as a reaction terminator (10% by weight (hereinafter abbreviated as wt%))
Was added so that the number of terminal hydroxyl groups of poly (t-butyl vinyl ether) was twice as large as that of Et _1.5 AlCl _1.5 , and the reaction was stopped. A few hours after stopping the reaction, methanol was added, and the solution was further diluted with dichloromethane, and then the initiator residue was removed by washing with water. Thereafter, the solution was concentrated and dried under reduced pressure to collect a produced block polymer. Further, in order to confirm the molecular weight of the poly (2-methoxyethyl vinyl ether) component in the block polymer, the polymerization was stopped by adding methanol instead of poly (t-butyl vinyl ether), and the resulting poly (2-methoxyethyl vinyl ether) was obtained. After collecting vinyl ether), the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by GPC was 1.1, and Mn was 8,000. Next, 1.0 g of the obtained block polymer composed of poly (t-butyl vinyl ether) and poly (2-methoxyethyl vinyl ether) is dissolved in 100 ml of toluene, and hydrogen bromide gas is blown in a 0 ° C. ice bath while blowing. Stir well. About 10 minutes after the start of the reaction, the produced PVA / poly (2-methoxyethyl vinyl ether) block polymer was precipitated and the inside of the system became cloudy. After blowing hydrogen bromide gas for further 20 minutes, the precipitated polymer was separated by filtration, neutralized and washed with ammoniacal methanol and methanol, and dried under reduced pressure to obtain a PVA / poly (2-methoxyethyl vinyl ether) block polymer. I got From the analysis of dissolved components in the filtrate, it was found that under the above-mentioned conditions, the homopolymer of poly (2-methoxyethyl vinyl ether) was about 10%, and the remaining 90% was a block polymer with polyvinyl alcohol. The structure of the block polymer was confirmed by ¹ H-NMR. Further, the degree of saponification of the vinyl alcohol unit was measured by ¹ H-NMR and found to be 99%.
The obtained polymer was placed in a hot air drier at 180 ° C. for 30 minutes.
After standing for a minute, no coloring or odor was observed. The solubility of the block polymer before saponification was soluble in methanol, benzene, toluene, ethyl acetate, chloroform and the like, and partially dissolved in water. On the other hand, the saponified block polymer became soluble in water at room temperature, and became partially soluble in methanol. In addition, the aqueous solution of the block polymer after saponification had a heat-responsive property, and was dissolved almost completely at room temperature, but became rapidly clouded at 70 ° C. as the temperature was increased. The cloudy solution returned to its original state at approximately the same 70 ° C. when the temperature was lowered. On the other hand, when the aqueous solution was heated to 0 ° C., gelation caused by the polyvinyl alcohol unit in the block polymer occurred, the solution became cloudy, and a precipitate was formed when left for a long time.

Comparative Example 1 A glass container equipped with a three-way cock was prepared, and after replacement with nitrogen, pressure was applied in a nitrogen gas atmosphere to remove adsorbed water in the glass container. 2-Methoxyethyl vinyl ether 20 in a container
0 ml, 200 ml of ethyl acetate, and 1540 ml of toluene as a polymerization solvent were added, and 0.84 ml of trifluoroacetic acid was added.
20 ml of a mixture of 1.5 ml of 2-vinyloxyethylthioacetate and 1.5 ml of toluene in 25 ml of toluene was added. When the temperature in the system reached 0 ° C., Et _1.5 AlCl _1.5 (1.
(0M) in a toluene solution (40 ml) was added to initiate polymerization. After 4 hours, the polymerization was stopped with 20 ml of methanol.
In this case, the conversion was 100% (by gas chromatography), and the number average molecular weight (Mn) was 22,000. In addition, the terminal thiol group of the polymer was reacted with excess iodine in an aqueous solution, and the remaining iodine was titrated with sodium thiosulfate to quantify the content of the terminal thiol group. The introduction ratio of the thiol group was 109%, indicating that the thiol group was quantitatively introduced. Then, vinyl acetate (VAc) 24
0 g was dissolved in 60 g of methanol, and replaced with nitrogen.
C., and a methanol solution of 0.0434 g of AIBN was added as an initiator. Immediately after that, a methanol solution of poly 2-methoxyethyl vinyl ether having a thiol group at one end obtained by the above-mentioned method (119 g / liter) ) Was added dropwise at a rate of 1.7 ml / 5 minutes to carry out polymerization. After 110 minutes, the polymerization was stopped, and the polymer obtained by precipitating in hexane was vacuum-dried, whereby a yield of 81 g of the polymer was obtained. The resulting polymer was dissolved in methanol (concentration: 20%), and [NaOH] /
NaO so that [VAc] = 0.05 (molar ratio).
By adding a methanol solution of H and saponifying at 40 ° C., a block polymer in which a PVA unit and a poly (2-methoxyethyl vinyl ether) unit were bonded via S (sulfur group) was obtained. The degree of saponification of the PVA component of the block polymer was 99.9 mol% as measured by ¹ H-NMR, and the ratio of vinyl alcohol units to 2-methoxyethyl vinyl ether units in the block polymer was 21/1 (molar ratio). ), 9.1 / 1 (weight ratio). The number average molecular weight (Mn) of the copolymer obtained by re-acetylating the obtained block polymer is 113,000,
The weight average molecular weight (Mw) was 60,000, and Mw / Mn was 1.67. When the obtained polymer was left in a 180 ° C. hot air drier for 30 minutes, it was colored brown and odor was generated.

[0037]

According to the present invention, it is possible to provide a thermally stable block polymer having a thermosensitive polymer component which is industrially highly useful and a method for producing the same. .

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J026 HA10 HA25 HA32 HA39 HB10 HB25 HB32 HB39 HB45 HB47 HB49 HE01 HE02 4J100 AD02P AE03Q AE09Q BA02Q BA04Q BA05Q BA06Q BC43Q CA04 CA25 CA27 DA01 DA61 FA08 JA34 JA01 JA03

Claims (8)

[Claims] 1. A polyvinyl alcohol-based polymer component,
A diblock polymer, wherein the aqueous solution comprises a polymer component having a cloud point, and both components are connected via an ether bond. 2. An ABA-type triblock wherein a polyvinyl alcohol polymer is a component B, an aqueous solution of the polymer having a cloud point is a component A, and each component is connected via an ether bond. polymer. 3. The block polymer according to claim 1, wherein the polymer whose aqueous solution has a cloud point is a polyalkenyl ether polymer. 4. The block polymer according to claim 3, wherein the polyalkenyl ether polymer is a polyalkenyl ether polymer having a structural unit represented by the following general formula (1). Embedded image (Wherein, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a monovalent organic group. When R ² is a hydrogen atom, n represents an integer of 1 to 10, and R ² represents In the case of a monovalent organic group, n represents an integer of 0 to 10.) 5. A ratio (Mw) between a weight average molecular weight (Mw) and a number average molecular weight (Mn) of a polyalkenyl ether polymer.
The block polymer according to claim 3 or 4, wherein w / Mn) is from 1.0 to 1.3 and the number average molecular weight (Mn) is 500 or more. 6. When a block polymer comprising a polyvinyl alcohol-based polymer component and a polyalkenyl ether-based polymer component is produced, a polyalkenyl ether-based polymer is synthesized by a cationic polymerization method, and a polymerization terminator is provided. A polyvinyl alcohol polymer containing a hydroxyl group at one or both ends of the polymer, a homopolymer of vinyl ester or a copolymer of vinyl ester, or a saponified product of these vinyl ester polymers coexist during polymerization. Or a method for producing a block polymer, which is added after a polymerization reaction. 7. When a block polymer comprising a polyvinyl alcohol-based polymer component and a polyalkenyl ether-based polymer component is produced, the polyalkenyl ether-based polymer is synthesized by a cationic polymerization method, and a terminator for this polymerization is used. A method for producing a block polymer, characterized in that an ethylene / vinyl ester copolymer having a hydroxyl group at one or both ends of the polymer or a saponified product thereof is added during polymerization or added after the polymerization reaction. . 8. The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyalkenyl ether polymer obtained by the cationic polymerization method is from 1.0 to 1.0.
The method for producing a block polymer according to claim 6 or 7, wherein the number average molecular weight (Mn) is 1.3 or more and 500 or more.