JPH06136036A - Block copolymer - Google Patents

Abstract

PURPOSE:To produce a block copolymer capable of preparing an aqueous solution exhibiting a low temperature-dependent viscosity and useful as a treatment agent for a resin, paper, a fiber, etc., by polymerizing a vinyl ester in the presence of a specified polymer and subsequently saponifying the resultant polymer. CONSTITUTION:A vinyl ester such as vinyl acetate is polymerized in the presence of a polymer such as poly-2-methoxyethyl vinyl ether containing a terminal thiol group and capable of preparing an aqueous solution exhibiting a cloud point and the resultant polymer is subsequently saponified, thus producing the objective copolymer composed of a PVA component and a polymer component an aqueous solution of which exhibits a cloud point and having a structure where both the components are bonded through a sulfide linkage.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a polyvinyl alcohol component and an aqueous solution comprising a polymer component having a cloud point.
The present invention relates to a block copolymer in which the temperature dependence of the viscosity of an aqueous solution is small and a method for producing the same.

[0002]

2. Description of the Related Art A method for synthesizing a block copolymer having crystalline polyvinyl alcohol as one component is a method in which polyvinyl acetate having a thiol group at a terminal is used as a chain transfer agent, and various monomers are radically polymerized. A method of synthesizing by saponification is known (JP-A-59-189111).

As a method for synthesizing a block copolymer composed of a polyvinyl alcohol component and a polyalkenyl ether component having a cloud point, a so-called living polymerization method (Japanese Patent Laid-Open No. 62-257910, Japanese Laid-Open Patent Publication No. 62-2)
No. 57911, JP-A-1-108202, JP-A-1-108203), and using this method, block copolymerization of benzyl vinyl ether with other alkenyl ether, followed by debenzylation A method for synthesizing a block copolymer composed of a polyvinyl alcohol component and a polyalkenyl ether component is known. However, this method has a problem in that it is difficult to synthesize a large amount because sodium bromide in hydrogen bromide gas or liquid ammonia is used for debenzylation. In addition, since polyvinyl alcohol obtained by debenzylation reaction of polybenzyl vinyl ether has an isotactic structure, it is compared with polyvinyl alcohol having an atactic structure obtained by saponifying conventional polyvinyl acetate. It has been reported that the crystallinity, heat resistance and water resistance are poor (K. Fujii, J. Po.
lym. Sci. , Part D, 5, 431 (197).
1)). That is, hitherto, a block copolymer having a polyvinyl alcohol component having a property as a crystalline polymer as one component has not been known.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a block copolymer having a small temperature dependence of the viscosity of an aqueous solution, which comprises a polyvinyl alcohol component which does not have the above-mentioned problems and a polymer component whose aqueous solution has a cloud point. A polymer and a method for producing the same.

[0005]

As a result of intensive studies for solving the above-mentioned problems, a block copolymer in which a polyvinyl alcohol component and an aqueous solution consist of a polymer component having a cloud point, and both components are linked by a sulfide bond. And a method for producing the above block copolymer, which comprises polymerizing vinyl esters in the presence of a polymer having a thiol group at the terminal and having an aqueous solution having a cloud point, and then saponifying the produced polymer. The present invention has been completed and the present invention has been completed.

The block copolymer of the present invention is a block copolymer in which the polyvinyl alcohol component and the aqueous solution consist of a polymer component having a cloud point, and both components are linked by a sulfide bond. Polyvinyl alcohol (hereinafter,
The component (sometimes abbreviated as PVA) comprises a vinyl alcohol unit and a vinyl ester unit, and the degree of saponification thereof is preferably 70 mol% or more, and 90 mol%
The above is more preferable, and 95 mol% or more is more preferable.
The stereoregularity of the PVA component in the present invention is not particularly limited, but an atactic structure or a syndiotactic structure close to an atactic structure is preferable, and an atactic structure is more preferable. The polymer component whose aqueous solution has a cloud point in the present invention is not particularly limited as long as the aqueous polymer solution has a cloud point in the temperature range of 0 to 100 ° C, and among them, the cloud point of the aqueous polymer solution is 20 to. The temperature is preferably 95 ° C, more preferably 30 to 95 ° C, even more preferably 30 to 80 ° C. The cloud point of these polymer aqueous solutions is 500 nm when 1% by weight aqueous solution of the polymer is put into a UV cell equipped with a temperature controller, a thermocouple and a stirrer and the temperature is raised or lowered at a rate of 1 ° C./min. Light transmittance is 100
It was calculated from the temperature changing from 0% to 0% (or 0% to 100%).

Specific examples of the polymer component in which the aqueous solution has a cloud point include polyalkenyl ethers represented by the following chemical formulas 1 and 2 (Proceedings of the Polymer Society of Japan, vol. 40, N.
o. 6, P. 1710) and poly N-isopropyl acrylamide (poly N-isopropyl methacrylamide)
(J. Phys. Chem., 93, 3311 (198
9)) and the like.

[0008]

[Chemical 1]

(In the formula, R ↑ 1 represents a hydrogen atom or a methyl group, and R ↑ 2 represents a hydrogen atom or a monovalent organic group (preferably an organic group having 1 to 10 carbon atoms, more preferably 1 to 10 carbon atoms). 5 is an organic group), and n is an integer of 0 to 10.)

[0010]

[Chemical 2] (In the formula, R ↑ 3 represents a hydrogen atom or a methyl group.)

The number average molecular weight of the polymer component of the aqueous solution of the present invention having a cloud point is not particularly limited, but it is 500.
To 1,000,000 are preferable, and 1000 to 100,000
Is more preferable. The number average molecular weight of the polymer component in which the aqueous solution of the present invention has a cloud point is determined by size exclusion chromatography.
And standard polystyrene conversion.

The block copolymer of the present invention is obtained by polymerizing vinyl esters in the presence of a polymer having a thiol group at the terminal and an aqueous solution having a cloud point, and then saponifying the produced polymer. To be In the method for producing a block copolymer of the present invention, a chain transfer agent has a thiol group at the terminal, and a specific example of the polymer having an aqueous solution has a cloud point is a polyalkenyl ether having a thiol group at the terminal and Poly N-having a thiol group at the end
Examples include isopropyl acrylamide. As the alkenyl ether, those having an oxyethylene chain in the side chain represented by the following chemical formula 3 are preferable.

[0013]

[Chemical 3]

(In the formula, R ↑ 4 represents a hydrogen atom or a methyl group, R ↑ 5 represents a hydrogen atom or a monovalent organic group, and n represents an integer of 0 to 10.) 5
Is a monovalent organic group (preferably an organic group having 1 to 10 carbon atoms,
More preferably, it represents an organic group having 1 to 5 carbon atoms, and examples thereof include an alkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkoxyalkyl group and an aryloxyalkyl group. They may be substituted with a hetero group. The above alkenyl ether units may be used alone or in combination of two or more. Also, one or two
A block copolymer obtained by polymerizing at least one alkenyl ether and then further polymerizing by adding another alkenyl ether may be used. Specific examples of the alkenyl ether include methyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, propoxyethyl vinyl ether, butoxyethyl vinyl ether, 2
-Methoxyethoxyethyl vinyl ether, 2-ethoxyethoxyethyl vinyl ether, 2-methoxy-2-ethoxyethoxyethyl vinyl ether, 2-ethoxy-2-ethoxyethoxyethyl vinyl ether, phenoxyethyl vinyl ether, methoxyethylpropenyl ether, ethoxyethylpropenyl ether, propoxyethylpropenyl ether, Examples thereof include butoxyethyl propenyl ether, 2-methoxyethoxyethyl propenyl ether, 2-ethoxyethoxyethyl propenyl ether, 2-methoxy-2-ethoxyethoxyethyl propenyl ether, 2-ethoxy-2-ethoxyethoxyethyl propenyl ether and phenoxyethyl propenyl ether.

The polyalkenyl ether having a thiol group at one end of the present invention can be obtained by the following method. Polymerization is performed with an addition compound of an alkenyl ether having a thiocarbonyl ester bond in the side chain represented by the following Chemical formula 4 and a proton-supplying compound represented by the following Chemical formula 5 as a polymerization initiation terminal.

[0016]

[Chemical 4]

(In the formula, R ↑ 6 represents a hydrogen atom or a methyl group, and R ↑ 7 represents an alkyl group such as a methyl, ethyl, propyl, butyl or phenyl group or an aryl group (preferably an alkyl group having 1 to 10 carbon atoms). A group or an aryl group,
More preferably, it shows a C1-C5 alkyl group or aryl group, and n shows the integer of 1-5. )

[0018]

[Chemical 5] (In the formula, X represents an anionic group.)

Specific examples of the compound of Chemical formula 5 include sacrificial acid, acetic acid, propionic acid, butyric acid, pivalic acid, fluoroacetic acid, chloroacetic acid, bromoacetic acid, difluoroacetic acid, dichloroacetic acid, dibromoacetic acid, trifluoroacetic acid, trichloroacetic acid. Acetic acid, tribromoacetic acid, hydrogen chloride, hydrogen bromide, hydrogen iodide, phosphoric acid dialkyl ester, phosphoric acid monoalkyl ester, methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, phenol and the like can be mentioned. Among them, acetic acid, Trifluoroacetic acid is particularly preferred.

The alkenyl ether is polymerized by the conventionally known living cationic polymerization method (Japanese Patent Laid-Open No. 228509/1985).
No. 61-103654, 62-257.
910, JP-A-1-108202, and JP-A1-1.
No. 08203) which can be used with a Lewis acid or protonic acid initiator, an additive and a solvent, and the polymerization temperature is preferably 60 ° C. or lower, particularly preferably + 40 ° C. or lower. When synthesizing a polyalkenyl ether having a thiol group at one end, monohydric alcohols are usually used as a polymerization terminator. The content of the alkenyl ether unit is not particularly limited, but is preferably 50 mol% or more, more preferably 70 mol% or more, and further preferably 90 mol% or more.

The poly N-isopropylacrylamide having a thiol group at one end of the present invention is the same as the conventionally known method for producing a polyvinyl alcohol-based polymer having a thiol group at the end (JP-A-59-187003). Can be synthesized by.

The block copolymer of the present invention is obtained by polymerizing vinyl esters in the presence of a polymer having a thiol group at the terminal and having an aqueous solution having a cloud point, and then saponifying the resulting polymer. To be Examples of vinyl esters used in the present invention include vinyl acetate, vinyl benzoate, vinyl pivalate, vinyl trifluoroacetate and the like. As the polymerization method in the invention, generally known polymerization methods such as bulk polymerization, solution polymerization, pearl polymerization and emulsion polymerization can be used. The addition amount to the polymerization system of the polymer having a thiol group at the end and having a cloud point in the aqueous solution is not particularly limited, and is appropriately selected depending on the physical property value of the target block copolymer. . The polymerization in the present invention is carried out using a usual radical polymerization initiator. Examples of the radical polymerization initiator include 2,2′-azobisisobutyronitrile (hereinafter abbreviated as AIBN), benzoyl peroxide, lauroyl peroxide, diisopropyl peroxycarbonate, potassium persulfate, and ammonium persulfate. .

The number average molecular weight of the block copolymer in the present invention is preferably 5,000 to 1,000,000 in a polymer obtained by reacetylating a polyvinyl alcohol component. The molecular weight of the block copolymer of the present invention is measured by size exclusion chromatography and determined by standard polystyrene conversion. The degree of saponification of the vinyl alcohol component can be determined by quantifying the acetic acid ester residue by 1 ↑ H-NMR.

The block copolymer of the present invention has a wide range of properties by controlling the composition and molecular weight of both components. Even at low temperature, the viscosity of the aqueous solution is PV
P that is lower than A and that temperature dependence of viscosity is small, etc.
Since it has properties different from VA, it is suitable for use as a processing agent for dispersants, resins, papers, fibers and the like.

[0025]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. Synthesis Example 1 A glass container equipped with a three-way stopcock was prepared, and after nitrogen substitution, pressure was applied under a nitrogen gas atmosphere to remove adsorbed water in the glass container. 2-methoxyethyl vinyl ether 200 in the container
ml, 200 ml of ethyl acetate, and 1540 ml of toluene as a polymerization solvent were added, 20 ml of a solution prepared by mixing 0.84 ml of trifluoroacetic acid and 1.5 ml of 2-vinyloxyethyl thioacetate in 25 ml of toluene was added, and the system temperature was 0 ° C. Et ↓ 1.5 AlCl ↓ 1.
Polymerization was started by adding 40 ml of a 5 (1.0 M) toluene solution. After 4 hours, the polymerization was stopped with 20 ml of methanol. In this case, the polymerization rate was 100% (by gas chromatography), and the number average molecular weight was Mn = 22000 in terms of standard polystyrene measured by size exclusion chromatography in tetrahydrofuran at 55 ° C.
Further, the terminal thiol group of the polymer was reacted with an excess of iodine in an aqueous solution, and the remaining iodine was titrated with sodium thiosulfate to quantify the content of the thiol group at the terminal, and the result was that The introduction rate of thiol groups is 10
It was 9% and it was found that the thiol group was quantitatively introduced.

Example 1 Vinyl acetate (240 g) was dissolved in methanol (60 g), the atmosphere was replaced with nitrogen and the temperature was raised to 60 ° C., and AIBN was used as an initiator.
Immediately after adding 0.0434 g of a methanol solution, poly-2-methoxyethyl vinyl ether having a thiol group at one end obtained in Synthesis Example 1 (number average molecular weight M
n = 22000, functionality f = 1.0
The methanol solution of 9) (119 g / l) was added to 1.7.
Polymerization was performed by dropwise addition at a rate of ml / 5 minutes. 1
After 10 minutes, the polymerization was stopped, and the polymer obtained by precipitating in hexane was vacuum dried to obtain 81 g of a polymer. The produced polymer is dissolved in methanol (concentration 20%), and [NaOH] / [VAc] = 0.05
A methanol solution of NaOH was added so as to have a (molar ratio) and saponified at 40 ° C. to obtain a block copolymer (hereinafter sometimes abbreviated as B1).
According to 1 ↑ H-NMR of the block copolymer, the degree of saponification of the PVA component was 99.9 mol%, and the ratio of vinyl alcohol unit to 2-methoxyethyl vinyl ether unit in the block copolymer was 21/1. (Molar ratio), 9.1 / 1
(Weight ratio). With respect to the copolymer obtained by re-acetylating the obtained block copolymer, the polystyrene-reduced number average molecular weight Mn = 11 determined from size exclusion chromatography measured at 55 ° C. in tetrahydrofuran.
3000, weight average molecular weight Mw = 60000, Mw / M
It was n = 1.67.

Example 2 240 g of vinyl acetate was dissolved in 60 g of methanol, the atmosphere was replaced with nitrogen, the temperature was raised to 60 ° C., and AIBN was used as an initiator.
Immediately after adding 0.0651 g of methanol solution, a methanol solution of poly-2-methoxyethyl vinyl ether having a thiol group at one end (number average molecular weight Mn = 21,000, functionality f = 1.07) (1
(57 g / l) was added dropwise at a rate of 3.5 ml / 5 minutes to polymerize for 254 minutes, and then saponified under the same conditions as in Example 1, yielding 99 g, Mn = 600.
0, Mw = 114000, Mw / Mn = 1.89, saponification degree 99.9%, vinyl alcohol in the block copolymer
A polymer (hereinafter, sometimes abbreviated as B2) having a ratio of the unit of 2-methoxyethyl vinyl ether to 5.5 / 1 (molar ratio) and 2.4 / 1 (weight ratio) was obtained.

Example 3 The temperature change of the viscosity of the aqueous solution (9 to 10 wt%) of the block copolymers obtained in Examples 1 and 2 was measured by an E-type viscometer. The result is shown in FIG. PVA homopolymer shown for comparison (Kuraray, trade name: PVA-
EC, degree of polymerization 1700, degree of saponification 99.8% or more) and PVA homopolymer (manufactured by Kuraray, trade name: PVA-11)
7, the degree of polymerization is 1700, and the degree of saponification is 98.5 mol%), the change in viscosity with temperature is small.

Example 4 A tensile test was conducted on the film obtained by casting the aqueous solution of the block copolymer obtained in Example 1 and Example 2. The results are shown in Table 1.

[0030]

[Table 1]

From Table 1, it is clear that the polymer obtained in Example 1 has the same elastic modulus and tensile strength as PVA homopolymer (PVA-EC).

[0032]

As is clear from the above examples, the block copolymer of the present invention has a
Since the temperature dependence of the viscosity of the aqueous solution is low and the film strength is similar to that of PVA homopolymer, the resin,
Since it is considered that it can be used as an ideal processing agent for paper, fibers, etc., it has extremely high industrial value. Further, according to the production method of the present invention, a block copolymer of a PVA component and a polymer component whose aqueous solution has a cloud point, which has been difficult to synthesize in the past, can be synthesized by a relatively simple method.

[Brief description of drawings]

FIG. 1 shows the temperature dependence of the aqueous solution viscosity of a block copolymer of a PVA component and a 2-methoxyethyl vinyl ether component.

[Explanation of symbols]

● PVA homopolymer (Kuraray, trade name: PVA-
117, degree of polymerization 1700, degree of saponification 98.5 mol%, concentration 10 wt%), Δ Polymer obtained in Example 1 (B1, concentration 10 wt%)
%), (2) Polymer obtained in Example 2 (B2, concentration 10 wt
%), PVA homopolymer (Kuraray, trade name: PVA-
EC, degree of polymerization 1700, degree of saponification 99.8% or more, concentration 9 wt%) PVA homopolymer (manufactured by Kuraray, trade name: PVA-
117, degree of polymerization 1700, degree of saponification 98.5 mol%, concentration 9 wt%)

Claims (2)

[Claims] 1. A block copolymer in which a polyvinyl alcohol component and an aqueous solution consist of a polymer component having a cloud point, and both components are linked by a sulfide bond. 2. The method according to claim 1, wherein after the vinyl ester is polymerized in the presence of a polymer having a thiol group at the terminal and the aqueous solution has a cloud point, the produced polymer is saponified. A method for producing a block copolymer.