JPH10259214A - Melt moldable polyvinyl alcohol and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyvinyl alcohol capable of being melted and molded, excellent in heat resistance, without using a plasticizer, etc. SOLUTION: A polyvinyl alcohol is reacted through dehydration with an aliphatic hydrocarbon group-containing boronic acid while removing water caused by the reaction out of the system so that at least a part of the hydroxyl group of the polyvinyl alcohol is reacted with the aliphatic hydrocarbon group- containing boronic acid group and blocked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol which can be melt-molded without using a plasticizer or the like and has excellent heat resistance and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as P
The fibers are abbreviated as VA), for example, gel spinning represented by coagulation spinning and boric acid cross-linking spinning, wet spinning from a PVA aqueous solution using water as a solvent, and high-concentration PVA aqueous solution extruded with an extruder and spun into the air. It is well known that a PVA film is formed by casting from a PVA aqueous solution. However, the above method is disadvantageous in terms of operability in view of the fact that the spinning speed is very slow, that a large amount of an organic solvent to be used for the purpose of coagulation is required, and that the apparatus and the solvent recovery method are taken into consideration. Also, P
VA is very difficult to melt due to intermolecular hydrogen bonding due to its own many hydroxyl groups, and furthermore, its melting point and decomposition temperature are very close to each other. It has been impossible.

On the other hand, PVA has recently been used as a roofing material as a substitute for asbestos. However, PV
Since A is inferior in heat resistance, it has a problem of flowing or decomposing during roofing molding, and improvement of this problem has been strongly desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyvinyl alcohol which can be melt-molded without using a plasticizer or the like and which has excellent heat resistance and a method for producing the same. .

[0005]

Means for Solving the Problems The present invention achieves the above object, and comprises reacting at least a part of the hydroxyl groups of PVA (A) with boronic acid (B) having an aliphatic hydrocarbon group to form PVA. A melt-moldable PVA characterized by introducing a boronic acid group having an aliphatic hydrocarbon group, and a reaction between PVA (A) and a boronic acid (B) having an aliphatic hydrocarbon group. Melt-moldable PVA characterized by performing a dehydration reaction while removing water out of the system
Of the present invention.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The PVA (A) used in the present invention is a polymer containing 10 mol% or more, preferably 30 mol% or more, more preferably 50 mol% or more of vinyl alcohol units, and is usually a homopolymer of vinyl ester or vinyl ether. And copolymers are hydrolyzed (saponification, alcoholysis, etc.). Here, as the vinyl ester, vinyl acetate is mentioned as a representative example, and in addition, vinyl formate, vinyl propionate, vinyl pivalate, vinyl valerate, vinyl caprate, vinyl benzoate and the like are also exemplified. Examples of the vinyl ether include t-butyl vinyl ether and benzyl vinyl ether.

The PVA (A) used in the present invention may contain the following monomer units. These monomer units include olefins other than ethylene, such as propylene, 1-butene, and isobutene; unsaturated acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and maleic anhydride; Mono- or dialkyl esters of 1 to 18; acrylamide, having 1 to 18 carbon atoms
Acrylamides such as N-alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or an acid salt or a quaternary salt thereof; methacrylamide, N-alkylmethacrylamide having 1 to 18 carbon atoms, N, Methacrylamides such as N-dimethylmethacrylamide, 2-methacrylamidepropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or an acid salt or a quaternary salt thereof; N-vinylpyrrolidone, N-vinylformamide, N-vinyl N-vinylamides such as acetamide; allyl compounds such as allyl acetate, allyl alcohol and 8-hydroxy-1-octene; vinyl cyanides such as acrylonitrile and methacrylonitrile; alkyl vinyl ethers having 1 to 18 carbon atoms; alkoxyalkyl vinyl ethers Which vinyl ethers; vinyl chloride, vinyl fluoride, a vinylidene chloride, vinyl halides or vinylidene fluoride; dimethyl allyl alcohol, vinyl ketones, and the like.

The average degree of polymerization of PVA (A) used in the present invention (hereinafter, abbreviated as degree of polymerization) is not particularly limited.
50 to 30,000 is preferred, 50 to 10,000 is more preferred, and 10
0 to 5,000 is particularly preferred.

The boronic acid (B) having an aliphatic hydrocarbon group used in the present invention is a compound in which an aliphatic hydrocarbon group (R) and a boronic acid group are formed by a carbon-boron bond.
Here, the aliphatic hydrocarbon group (R) is a linear or branched alkyl group having 1 to 18 carbon atoms. The boronic acid group is represented by the following formulas (1), (2) and (3).

[0010]

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[0011]

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[0012]

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In the formula, X is an aliphatic hydrocarbon group having 1 to 20 carbon atoms (such as a linear or branched alkyl group or an alkenyl group) or an alicyclic hydrocarbon group (such as a cycloalkyl group,
And Y is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an amino group or an amide group similar to X.

Specific examples of the boronic ester group represented by the above formula (2) include a boronic acid methyl ester group, a boronic acid ethyl ester group, a boronic acid propyl ester group,
Boronic acid isopropyl ester group, boronic acid butyl ester group, boronic acid hexyl ester group, boronic acid cyclohexyl group, boronic acid ethylene glycol ester group,
And a boronic acid propylene glycol ester group. Further, as specific examples of the boronic acid represented by the above formula (3), Y is a lower hydrocarbon group such as a methyl group, an ethyl group, a propyl group, a butyl group, a 1-methylpropyl group, a pentyl group, and a hexyl group. Are shown. Representative examples include a methylboronic acid group, an ethylboronic acid group, and a butylboronic acid group.

The boronic acid (B) having an aliphatic hydrocarbon group used in the present invention comprises the above-mentioned aliphatic hydrocarbon group (R) and the above-mentioned aliphatic hydrocarbon group (R).
Formulas (1), (2) and (3) by bonding to the boronic acid group, typical examples of which include methylboronic acid, ethylboronic acid, butylboronic acid, hexylboronic acid, methylboronic acid ethyl ester Butylboronic acid methyl ester, butylboronic acid isopropyl ester, methylbutylboronic acid, dibutylboronic acid, and the like.

The PVA of the present invention is obtained by a dehydration reaction between PVA (A) and a boronic acid (B) having an aliphatic hydrocarbon group. In the reaction, PVA (A) and boronic acid (B) are used.
Both are performed by dissolving in an organic solvent. As the solvent, both are soluble and non-water-soluble solvents are desirable. Examples of the solvent include dimethyl sulfoxide, dimethylformamide, triethylenediamine, piperazine,
1,3-dimethyl-2-imidazolidinone and the like can be used. In the reaction, it is desirable to remove the water generated by the reaction out of the system.For example, a solvent that azeotropes with water, such as benzene, is added, and the water generated by the reaction is azeotropically removed during the reaction. Is desirable. The reaction temperature varies depending on the type of PVA (A) and boronic acid (B) used, but is preferably 100 to 150 ° C.

The boron-containing PVA of the present invention comprises
It is preferable that the reaction amount of the component (B) is 0.02 to 0.2 mol per monomer unit of the component (A),
More preferably, the amount is 0.05 mol or more and 0.1 mol or less.
In the dehydration reaction, both OH of PVA (A) and boronic acid (B) are used.
It is considered that the dehydration bond is formed between the group and the group. Specifically, it is considered that H of the PVA (A) and OH of the boronic acid (B) are separated to form water and bond.

A property of the PVA of the present invention is that it can be melt molded. For example, when a film is formed by melt molding, the PVA of the present invention softens and melts in the range of 190 to 240 ° C., so that the film can be formed at a temperature of 200 to 260 ° C.

Another characteristic of the PVA of the present invention is that it has excellent heat resistance. It is known that the decomposition temperature of conventional PVA is about 260 ° C., but the PVA of the present invention is provided with boronic acid,
The effect of the presence of boron raises the decomposition temperature to above about 300 ° C.

If the PVA of the present invention is left in water or methanol at room temperature after melt molding, hydrolysis and the like will occur, and most of the boronic acid will come off the PVA and return to the state of PVA (A). It is also possible to remove the reacted boronic acid from the film or fiber once melt-molded and use it as a PVA-based film or fiber. The decomposition temperature of this PVA is P
Unlike VA (A), the temperature was about 300 ° C. due to the residual boron that could not be completely removed physically or chemically.

The PVA obtained as described above is reacted with boronic acid to temporarily block the hydroxyl groups of the PVA, thereby cutting off intermolecular hydrogen bonds to make it meltable and formable. The presence also improves the heat resistance, and the temperature difference between the melting point and the decomposition temperature increases, which facilitates molding by a conventionally used melt molding method or the like.

[0022]

The present invention will be described below in detail with reference to examples. The measuring method and measuring conditions of each item in the examples are as follows. (1) Reaction Amount of Boronic Acid Having an Aliphatic Hydrocarbon Group Evaluated from a 1H-NMR spectrum measured at 30 ° C. in a deuterated dimethyl sulfoxide solvent using a VRX200 type NMR apparatus manufactured by Varian Corporation. (2) Melting point and decomposition temperature of PVA Using DSC7 manufactured by PERKINELMER, the temperature rise and fall rates were each
It was measured at 10 ° C / min. (3) Meltability of PVA Using a FP80 hot stage manufactured by METTlER, a sample heated at a rate of 10 ° C./min was visually observed under an optical microscope to confirm the possibility of developing a molten state. (4) Thickness It was measured with a micrometer.

Example 1 10 g of PVA having a degree of polymerization of 2,000 and a degree of saponification of 99% was added to 500 ml of dimethyl sulfoxide and completely dissolved by stirring at 70 ° C. for 1 hour. Thereafter, when the temperature of the solution reached room temperature, 2.3 g of butylboronic acid dissolved in 10 ml of dimethyl sulfoxide was added to the PVA solution with stirring.
At the same time, benzene 180 was also added for the purpose of azeotropically dehydrating water produced by the reaction. Thereafter, water was azeotropically removed with benzene while stirring the solution, and the reaction was continued at 120 to 140 ° C. for 5 hours. After completion of the reaction, isopropyl alcohol was added to collect the precipitate, which was washed with ethanol, and dried at 60 ° C. under vacuum to obtain boronic acid-containing PVA.

When the performance of the obtained PVA was measured, it was found that butylboronic acid was contained per monomer unit of PVA.
0.1 mol reaction, its melting point is 208 ℃, decomposition temperature is
300 ° C. This PVA was completely melted at 230 ° C. This PVA is represented by the following formula at the reaction site of butylboronic acid.

[0025]

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The obtained PVA was heated at 230 ° C. under a pressure of 10 kg / c by a hot press using a spacer having a thickness of 100 μm.
The film was hot-pressed with m ² to prepare a film having a thickness of 100 μm, a length of 50 mm and a width of 5 mm.

The PVA film was allowed to stand in methanol for 24 hours while continuing to stir, and an attempt was made to remove reacted butylboronic acid. The determination as to whether or not butylboronic acid could be removed was made based on the presence or absence of a peak (0.8 ppm) derived from the methyl group of butylboronic acid in the 1H-NMR spectrum.
As a result, there was no peak derived from the methyl group of butylboronic acid in the 1H-NMR spectrum of the film after the methanol treatment. The decomposition temperature of this film is
300 ° C.

Example 2 In Example 1, the amount of butylboronic acid reacted with PVA was 1.
The reaction was carried out in the same manner as in Example 1 except that the amount was changed to 15 g to obtain the desired PVA. When each performance of the obtained PVA was measured, butylboronic acid reacted 0.05 mol per monomer unit of the PVA, the melting point was 215 ° C., and the decomposition temperature was 300 ° C. The PVA was completely melted at 240 ° C. The obtained PVA was heated at 240 ° C. under a pressure of 10 kg / c by a hot press using a spacer having a thickness of 100 μm.
The film was hot-pressed with m ² to prepare a film having a thickness of 100 μm, a length of 50 mm and a width of 5 mm.

The PVA film was allowed to stand in methanol for 24 hours while continuing stirring, and an attempt was made to remove reacted butylboronic acid. The determination as to whether or not butylboronic acid could be removed was made based on the presence or absence of a peak (0.8 ppm) derived from the methyl group of butylboronic acid in the 1H-NMR spectrum.
As a result, there was no peak derived from the methyl group of butylboronic acid in the 1H-NMR spectrum of the film after the methanol treatment. The decomposition temperature of this film is
300 ° C.

Example 3 The reaction was carried out in the same manner as in Example 1, except that 1.36 g of PVA was reacted with methylboronic acid. P obtained
When each performance of VA was measured, methylboronic acid was PV
The reaction was carried out in 0.1 mol per monomer unit of A, and the melting point was 218 ° C and the decomposition temperature was 290 ° C. The PVA was completely melted at 240 ° C. This obtained PV
A was hot-pressed with a hot press at 240 ° C and a pressure of 10 kg / cm ² using a spacer with a thickness of 100 μm.
A film having a length of 50 mm and a width of 5 mm was prepared.

The PVA film was left in methanol for 24 hours while continuing stirring, and an attempt was made to remove the reacted methylboronic acid. The determination as to whether or not methylboronic acid could be removed was made based on the presence or absence of a peak (0.8 ppm) derived from the methyl group of methylboronic acid in the 1H-NMR spectrum.
As a result, there was no peak derived from the methyl group of methylboronic acid in the 1H-NMR spectrum of the film after the methanol treatment. The decomposition temperature of this film is
290 ° C.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that 2.77 g of phenylboronic acid was reacted with PVA. When the performances of the obtained PVA were measured, phenylboronic acid was reacted in an amount of 0.1 mol per monomer unit of the PVA. The melting point was 192 ° C and the decomposition temperature was 290 ° C.
Even when the temperature was raised to 290 ° C, it did not melt at all and could not be melt-molded by itself.

Comparative Example 2 The reaction was carried out in the same manner as in Example 1 except that PVA was reacted with 1.40 g of boronic acid. Because the boronic acid cross-linked three-dimensionally during the reaction, the polymer solution gelled, and the desired PVA could not be obtained.

[0034]

As is clear from the above description, the PVA of the present invention can be melt-molded and has higher heat resistance than conventional PVA, so that the fiber or film can be easily molded by a general-purpose melt molding machine. is there. The boronic acid reacted can be removed simply by leaving the obtained fiber or film in water or methanol, and the heat resistance of polyvinyl alcohol after removing boronic acid is higher than that of general pure polyvinyl alcohol. Is also excellent. from these things,
It is suitable for applications where conventional polyvinyl alcohol has been used, particularly for applications such as roofing materials that require heat resistance.

Claims (2)

[Claims] 1. A method in which at least a part of hydroxyl groups of a polyvinyl alcohol (A) is reacted with a boronic acid (B) having an aliphatic hydrocarbon group to introduce a boronic acid group having an aliphatic hydrocarbon group into the polyvinyl alcohol. A melt-moldable polyvinyl alcohol, comprising: 2. A melt-moldable polyvinyl, characterized in that a polyvinyl alcohol (A) and a boronic acid (B) having an aliphatic hydrocarbon group are subjected to a dehydration reaction while removing water generated by the reaction outside the system. A method for producing alcohol.