JPH0548765B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing a novel hydrophilic-hydrophobic thermoreversible polymer having a high molecular weight. More specifically, the present invention provides a high-strength material that becomes insoluble in water by heating and can be used for light shields, temperature sensors, adsorbents, toys, interior decorations, textile printing agents, displays, separation membranes, mechanochemical materials, etc. The present invention relates to a method for producing a hydrophilic-hydrophobic thermoreversible polymer. Prior Art Some water-soluble polymer compounds exhibit a special reversible dissolution behavior in which they precipitate and become cloudy above a certain temperature (transition temperature or cloud point) in an aqueous solution state, and dissolve and become transparent below that temperature. Yes, this compound is called a hydrophilic-hydrophobic thermoreversible polymer compound, and in recent years it has been used as a light-shielding material in greenhouses, chemical laboratories, etc.
It has started to attract attention as a temperature sensor, etc. So far, such thermoreversible polymer compounds include partially saponified polyvinyl acetate (Kagaku to Kogyo, Vol. 27, p. 84, published in 1974), polyvinyl methyl ether (J. of Colloid and Interface Sci.
35, p. 77, published in 1971), methylcellulose (J.of Appl.Polym.Sci., vol. 24, p. 1073, published in 1979), polyethylene oxide (J.of Appl.
Polym Sci., vol. 1, p. 56, published in 1959), polyvinylmethyloxazolidinone (Fed.Proc.
Suppl., Vol. 15, p. S-24, published in 1964) and polyacrylamide derivatives (Fiber and Polymer Materials Research Institute Research Report, No. 144, p. 7, published in 1984). Among polyacrylamide derivatives, poly(N-isopropylacrylamide) has high thermal response sensitivity. However, even if the above-mentioned polymer compounds, including poly(N-isopropylacrylamide), were to be used for separation membranes, mechanochemical materials, etc., their range of application was inevitably limited due to the low strength of the materials. . In order to improve the strength of polymeric materials, increasing their molecular weight is an essential condition. Problems to be Solved by the Invention Under these circumstances, the purpose of the present invention is to expand the scope of use of poly(N-isopropylacrylamide) by creating a material that is strong and insoluble in water by heating. An object of the present invention is to provide a novel method for producing a hydrophilic-hydrophobic thermoreversible polymer having a high molecular weight. Means for Solving the Problems As a result of extensive research, the present inventors have determined that N-isopropylacrylamide has the general formula CH ₃ COOC _o
High molecular weight (intrinsic viscosity at 27°C in tetrahydrofuran of 1.00 or more) characterized by radical polymerization at 0 to 40°C using an alkyl acetate represented by H _2o+1 (n is an integer of 2 to 6) as a solvent. Poly(N
The inventors have discovered that the above object can be achieved by a method for producing (-isopropylacrylamide), and have completed the present invention based on this knowledge. That is, the present invention provides N-isopropylacrylamide with the general formula CH ₃ COOC _o H _2o+1 (n is an integer from 2 to 6).
Using an alkyl acetate represented by as a solvent, 0 to
High molecular weight poly(N-isopropylacrylamide) characterized by radical polymerization at 40℃
The present invention provides a method for producing a hydrophilic-hydrophobic thermoreversible polymer that has strong material strength and becomes insoluble in water upon heating. The N-isopropylacrylamide homopolymer used in the present invention is a hydrophilic-hydrophobic thermoreversible polymer, and its transition temperature is approximately 29°C to 33°C, depending on the molecular weight and aqueous solution concentration. . A specific method for producing a hydrophilic-hydrophobic thermoreversible polymer by radical polymerizing N-isopropylacrylamide is to synthesize N-isopropylacrylamide with the general formula CH ₃ COOC _o H _2o+1 (n is 2 to 6). A solution polymerization method of diluting with an alkyl acetate solvent represented by an integer) can be adopted. The polymerization mode at that time is radical polymerization. Methods for starting polymerization include (1) using a polymerization initiator, (2) irradiation with light such as ultraviolet rays and visible light, (3) methods using heat, and (4) ionizing methods such as radiation, electron beams, and plasma. A method such as irradiation with energy rays can be adopted. The polymerization initiator has the ability to initiate radical polymerization and has the general formula
Any material may be used as long as it is soluble in the alkyl acetate solvent represented by CH ₃ COOC _o COOC _o H _2o+1 (n is an integer of 2 to 6), such as organic peroxides and azo compounds.
Specifically, benzoyl peroxide, acetyl peroxide, azobisisobutyronitrile, etc. can be used. It is also possible to use two or more of the above polymerization initiators in combination. In this case, the amount of the polymerization initiator added is in the range of 0.001 to 5% by weight, preferably 0.001 to 2% by weight, based on the vinyl compound. General formula used in the present invention CH ₃ COOC _o H _2o+1
The alkyl acetate represented by (n is an integer of 2 to 6) is
Specifically, ethyl acetate, n-propyl acetate, acetic acid
iso-propyl, n-butyl acetate, iso-butyl acetate, sec-butyl acetate, tert-butyl acetate, n-amyl acetate, iso-amyl acetate, sec-amyl acetate, tert-amyl acetate, n-hexyl acetate, etc. I can give it to you. N-isopropylacrylamide is soluble in alkyl acetate represented by the general formula CH ₃ COOC _o H _2o+1 (n is an integer from 2 to 6), but poly(N-isopropylacrylamide) is difficult to dissolve in the above alkyl acetate. The larger n becomes, the smaller the solubility becomes. In the present invention, the general formula CH ₃ COOC _o H _2o+1
A commonly known radical polymerization method can be used by dissolving N-isopropylacrylamide in an alkyl acetate solvent represented by (n is an integer of 2 to 6) to obtain a solution having a concentration of 1 to 80% by weight. The alkyl acetate solvent represented by the general formula CH ₃ COOC _o H _2o+1 (n is an integer of 2 to 6) is a good solvent for N-isopropylacrylamide, but its homopolymer poly(N-isopropylacrylamide) It is a poor solvent for In the present invention, the reaction temperature is in the range of 0 to 40°C, preferably 20 to 30°C. In the present invention, the general formula which is a poor solvent for poly(N-isopropylacrylamide) is
When a polymerization reaction is carried out in an alkyl acetate solvent represented by CH ₃ COOC _o H _2o+1 (n is an integer from 2 to 6), poly(N-isopropylacrylamide) becomes white fine particles as the reaction progresses. Precipitate. The resulting polymer has a molecular weight of, for example, a limiting viscosity [η] of 1.00 or more at 27° C. in a tetrahydrofuran solution. Generally, when a polymerization initiator is used, reaction conditions such as a low initiator concentration and a low reaction temperature produce a high molecular weight polymer. The relationship between the intrinsic viscosity [η] and the molecular weight M _o in a tetrahydrofuran solution at 27°C is expressed by the following equation. [η]=9.59×10 ⁻⁵ M _o ^0.65 The molecular weight of poly(N-isopropylacrylamide) with an intrinsic viscosity of [η]=1.00 at 27° C. in tetrahydrofuran solution corresponds to 1.52×10 ⁶ . Effects of the Invention The hydrophilic-hydrophobic thermoreversible polymer with high molecular weight obtained by the novel production method of the present invention is characterized by strong material strength, and can be used as a light shielding body, a temperature sensor, and an adsorbent. Furthermore, it can be used in toys, interiors, textile printing agents, displays, separation membranes, mechanochemical materials, etc. For example, molded articles such as fibers crosslinked with the polymer of the present invention can be used as mechanochemical materials, and articles laminated on a transparent plate in the form of an aqueous solution or in the form of a hydrous gel or microcapsules can be used as a mechanochemical material. It is suitable as a light shield for automatically preventing indoor temperature from rising more than necessary due to direct light. Examples 1 to 8 Using various alkyl acetates as polymerization solvents, add N-isopropylacrylamide to 20 ml of alkyl acetate.
Add 2.0g, put this in an ampoule, degas it under reduced pressure using liquid nitrogen, seal the tube, and irradiate the dose rate to 3.9.
γ-ray irradiation from cobalt 60 was carried out at ×10 ⁴ R/hr for 2 hours at a temperature of 24°C to cause a reaction. As the polymerization reaction progressed, poly(N-isopropylacrylamide) was precipitated. After the reaction, n-hexane was added to separate and collect the polymer. In Examples 1 to 8, about 2.0 g of poly(N-isopropylacrylamide) was obtained. This polymer was made into a tetrahydrofuran solution, and its viscosity was measured at 27°C using an Ubbelohde viscometer. The thermoreversibility of this polymer in water was investigated. The transition temperature was determined from the light transmittance associated with the temperature change of the aqueous solution. That is, an aqueous polymer solution with a concentration of 1% by weight was prepared, and using a spectrophotometer with a temperature controller, the light transmittance at a wavelength of 500 nm was measured while raising the temperature at a rate of 1°C/min, and the transition temperature was determined. This light transmittance was determined from the temperature T _L at which the light transmittance was 0.5 of the initial transmittance. These results are shown in Table 1.

【table】

[Table] Examples 9 to 11 Using various alkyl acetates as polymerization solvents, add N-isopropylacrylamide to 20 ml of alkyl acetate.
Add 2.0g of asobisisobutyronitrile, put it into an ampoule, degas it under reduced pressure using liquid nitrogen, seal the tube, and incubate in a constant temperature bath at 30°C for 12 hours.
It was soaked for some time to react. As the polymerization reaction progressed, poly(N-isopropylacrylamide) was precipitated. After the reaction, add n-hexane to separate the polymer,
Recovered. The polymerization reaction results of Examples 9 to 11 are shown in Table 2.

[Table] Viscosity and transition temperature were determined using the same method as in Examples 1 to 8. These results are shown in Table 3. Further, the transmittance-temperature curve of the aqueous polymer solution of Example 10 is shown in FIG. Among these, the solid line is the data when the temperature is rising, and the dotted line is the data when the temperature is falling.

【table】 [Brief explanation of the drawing]

FIG. 1 shows a transmittance-temperature curve of a 1% by weight aqueous solution of the polymer of Example 10 according to the method of the present invention.

Claims (1)

[Claims] 1 N-isopropylacrylamide with the general formula
A polymer with a high molecular weight characterized by radical polymerization at 0 to 40°C using an alkyl acetate represented by CH ₃ COOC _o H _2o+1 (n is an integer of 2 to 6) as a solvent (limited at 27°C in tetrahydrofuran). (viscosity 1.00 or more)
A method for producing poly(N-isopropylacrylamide).