JPS61287931A - Production of thermoreversible high-molecular crosslinked molding - Google Patents

Abstract

PURPOSE:To produce a crosslinked molding having thermoplasticity, being insoluble in water and being capable of retaining its shape, by radical- polymerizing a specified acrylamide derivative and an N-methylolacrylamide and molding and crosslinking the polymer. CONSTITUTION:1mol of a compound of the formula is mixed with 1mol or below of an N-methylolacrylamide, and the mixture is radical-polymerized in a state of solution. The obtained copolymer is molded and then crosslinked by heating. In the formula, R1 is H or methyl and R2 is n-propyl or isopropyl. To copolymerize a compound of the formula with N-methylolacrylamide, it is necessary to perform the copolymerization in a solvent in which the monomers can be dissolved homogeneously. Examples of such solvents include water, alcohols and N,N-diethylacetamide. In order to give a NW suitable for processing into a molding to this copolymer, it is preferable to produce it so that it has an intrinsic viscosity [eta], as measured in, for example, a methanol solution at 30 deg.C, of about 0.01-6.0.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a crosslinked molded article of an acrylic copolymer having thermoreversible properties. More specifically, the present invention is a molded article that has thermoreversible properties such that it becomes cloudy when heated above a certain temperature in water, but becomes transparent when heated below that temperature, and is insoluble in water and capable of retaining its original shape. , light shielding bodies for greenhouses, show windows, etc.
The present invention relates to a method for producing a novel material that can be widely used as adsorbents, toys, water-breathing bodies, coating materials, separation membranes, mechanochemical materials, etc.

Conventional technology When made into an aqueous solution, a predetermined temperature (transition temperature or cloud point)
Water-soluble polymer compounds that precipitate and become cloudy at above temperatures, but dissolve and become transparent at temperatures below that temperature, are usually called thermoreversible polymers, and their reversibility can be used to make them into light shielding materials, adsorbents, etc. Applications are being considered.

Until now, N-alkyl-substituted acrylamide or methacrylamide polymers have been known as thermoreversible acrylic polymers. However, even if this acrylic thermoreversible polymer is molded into a desired shape, it dissolves in water at low temperatures and cannot maintain its shape, so its uses are naturally limited.

In addition to acrylic polymers, many thermoreversible polymers have been proposed, but none have been known to become cloudy at high temperatures and transparent at low temperatures while maintaining a predetermined shape.

On the other hand, a copolymer of N-isopropylacrylamide and N-methylolacrylamide is known as a material for diffusion transfer photographic paper (U.S. Pat. No. 3,42
No. 1,893), it was completely unknown that this had thermoreversible properties or that it could be used as a crosslinked product.

Problems to be Solved by the Invention An object of the present invention is to provide a method for producing an acrylic polymer crosslinked molded product that has thermoreversible properties, is insoluble in water, and can retain its shape. It is.

Means for Solving the Problems The present inventors have conducted extensive research in order to develop a material that has thermoreversible properties and can maintain its shape even at any temperature when molded. As a result, it was discovered that the object could be achieved by crosslinking a copolymer obtained from N-propylacrylamide and N-methylolacrylamide, and based on this knowledge, the present invention was accomplished.

That is, the present invention provides an amount that does not exceed 1 mole per mole of the compound represented by the general formula % (in which R2 is a hydrogen atom or a methyl group, and R2 is an n-propyl group or an isopropyl group). Provided is a method for producing a thermoreversible polymer crosslinked molded article, which comprises adding N-methylol acrylamide, radically polymerizing it in a solution state, molding the resulting copolymer, and then crosslinking it by heating. It is.

In the process according to the invention it is necessary to use not more than 1 mol, preferably from 0.002 to 1 mol, of N-methylolacrylamide per mol of compound of general formula (I). If this amount is small, insolubilization will be insufficient when crosslinked, and if this amount exceeds 1 mol, the polymer will become water-soluble and will not exhibit thermoreversible properties.

In the method of the present invention, in order to copolymerize the compound of general formula (I) and N-methylolacrylamide, it is necessary to use a solvent that can uniformly mix the monomers. Examples of such solvents include water, alcohol, N,N-diethylacetamide, dimethyl sulfoxide, acetone, dioxane, tetrahydrofuran, benzene, chloroform, carbon tetrachloride, and the like. These solvents may be used alone or in combination of two or more.

In the method of the present invention, 1 monomer is added to these solvents.
It is dissolved at a concentration of ~100% by weight and subjected to radical polymerization in a solution state. This radical polymerization may be carried out by heating in the presence of a common radical polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, peracetic acid, etc., or by radiation or light irradiation.

This copolymer has an intrinsic viscosity [η] of 0.01 to 6.0 at 30°C in chloroform or methanol solution, for example, in order to have a molecular weight suitable for processing into molded bodies.
It is preferable to manufacture the material to a degree of 0.1 to 3.0.

Next, the copolymer thus obtained is molded by a conventional method such as a casting method or a wet spinning method, and then
By dry heating, it is made into a water-insoluble molded product.

The crosslinking conditions at this time depend on the composition of the copolymer, the reaction temperature and reaction time used, but in general, the more N-methylolacrylamide units there are, the lower the reaction temperature and the reaction time. is shorter, and those with fewer N-methylolacrylamide units require a higher reaction temperature and longer reaction time. Usually, the reaction temperature is 100-2
00°C, reaction time is within the range of 1 to 500 minutes.

The transition temperature of the copolymer depends on the molar ratio of each monomer unit, and shifts toward higher temperatures as the proportion of N-methylolacrylamide increases. Therefore, by changing this molar ratio, the transition temperature can be adjusted as desired.

On the other hand, the thermal response and sensitivity of this copolymer decrease as the proportion of N-methylolacrylamide increases;
Since the rate of this decrease is small, the thermal response sensitivity is good overall.

Example Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Copolymers having various composition ratios were produced by changing the combined amounts of N-methylolacrylamide and N-isopropylacrylamide. Using azobisisobutyronitrile as a polymerization initiator, a methanol solution with a concentration of 5 Da/-2
0 m/ was added to a monomer solution having a predetermined composition and concentration, and the reaction was carried out at a reaction temperature of 50° C. for 14 hours. After the reaction, the reaction solution was made into an acetone solution, precipitated in diethyl ether, and the polymer was recovered. The N-methylolacrylamide fraction in the copolymer was calculated assuming a polymerization rate of 100.

The transition temperature of the obtained thermoreversible polymer was determined from the change in light transmittance with the temperature of its aqueous solution.

That is, a polymer aqueous solution with a concentration of 1% was prepared, set in a spectrophotometer with temperature control, and heated at a rate of 1°C/1°C.
When the change in light transmittance at a wavelength of 500 nm is measured while raising the temperature at min., the results shown in FIG. 1 are obtained.

In this figure, the transition temperature is when the light transmittance is 1/2 of the initial transmittance.
It was decided based on the following points.

Table 1 summarizes the amount of monomer charged, the N-methylolacrylamide fraction in the copolymer, and the transition temperature in each experiment.

Table 1 From these results, it was found that the copolymer obtained had excellent thermal response sensitivity and the transition temperature could be varied over a wide range depending on the content of N-methylolacrylamide in the copolymer.

In addition, the sample from Jikkenya 3 was molded into a film and heated to 150°C.
When dry heating was carried out for 1 hour, a crosslinked product was obtained which remained in the same shape as before heating.

Example 2 Copolymers having various composition ratios were produced by changing the combined amounts of N-methylolacrylamide and N-n-propylacrylamide. Using azobisisobutyronitrile as a polymerization initiator, a methanol solution 25- of the solution having a concentration of 5 m9/ml was added to a monomer solution having a predetermined composition and concentration, and the reaction was carried out at a reaction concentration of 50°C for 400 hours. After the reaction, it was made into a methanol solution and precipitated in diethyl ether to recover the polymer. The N-methylolacrylamide fraction in the copolymer was calculated assuming a polymerization rate of 100.

The transition temperature was determined by the method of Example 1.

Table 2 summarizes the relationship between the amount of monomer charged, the N-methylolacrylamide fraction in the copolymer, and the transition temperature in each experiment.

Table 2 These results show that, as in Example 1, N- in the copolymer
It was found that the transition temperature could be varied over a wide range depending on the methylol acrylamide content.

In addition, the sample of Experiment 415 was formed into a film, and 150
When dry heated at ℃ for 1 hour, the shape before heating was maintained and crosslinked.

Example 3 Copolymers having various composition ratios were produced by changing the combined amounts of N-methylolacrylamide and N-inpropylmethacrylamide. Using azobisisobutyronitrile as a polymerization initiator, 20 ml of a methanol solution with a concentration of 5 ml/ml was added to a monomer solution with a predetermined composition and concentration, and the mixture was reacted at a reaction temperature of 50° C. for 70 hours. After the reaction, the methanol solution was made into an acetone solution, and the polymer was recovered by precipitation in diethyl ether. The N-methylolacrylamide fraction in the copolymer was calculated assuming a polymerization rate of 100%. The transition temperature was determined by the method of Example 1.

Table 3 summarizes the relationship among the amount of monomer charged, the N-methylolacrylamide fraction in the copolymer, and the transition temperature in each experiment.

Table 3 From these results, it was found that similarly to Example 1, the transition temperature could be varied over a wide range depending on the content of N-methylolacrylamide in the copolymer.

In addition, a sample of experimental flat plate 21 was molded into a film shape, and 150
When heated at ℃ for 1 hour, the shape before heating was maintained and crosslinked.

Example 4 Methanol solution (concentration 5W/
ml) 100m7! was placed in an ampoule, degassed under reduced pressure using liquid nitrogen, and the upper part was sealed with a burner.

This was placed in a constant temperature bath at 50°C and left to polymerize for 24 hours. After the reaction, the container was opened and methanol was removed under reduced pressure. Furthermore, this was made into an acetone solution and precipitated in diethyl ether to recover the polymer. The N-methylolacrylamide fraction in the copolymer was 10.7. The transition temperature of this 1% aqueous copolymer solution was 36.0°C. Also,
The ultimate viscosity of this copolymer was [η]=0.48 based on the constant viscosity '113 at 30° C. as a chloroform solution.

This copolymer was dissolved in acetone, poured onto a Teflon plate, and air-dried to create a film. Table 4 shows the relationship between the treatment conditions and the crosslinking state when this film-like molded product was subjected to dry heat treatment.

Table 4 ×: Dissolved in water (uncrosslinked) 〇 Undissolved in water (crosslinked) As is clear from Table 4, by subjecting a film-like molded product to heat treatment, it can easily become a crosslinked molded product. can do.

Effects of the Invention The thermoreversible polymer crosslinked molded product obtained by the method of the present invention has a thermoreversible property of becoming cloudy in water above a predetermined temperature and becoming transparent below a predetermined temperature, and is non-water soluble. Since it can maintain its original shape, it can be widely used as mechanochemical materials, light shielding materials, adsorbents, toy materials, separation membranes, etc.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between light transmittance and temperature for an aqueous solution of a copolymer of N-isopropylacrylamide and N-methylolacrylamide, and Figure 2 is a copolymer solution of N-n-propylacrylamide and N-methylolacrylamide. It is. Patent applicant Director of the Agency of Industrial Science and Technology Todoroki Transmittance rate (%) Dense volume 3

Claims (1)

[Claims] 1 General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R_1 is a hydrogen atom or a methyl group, R_2 is n-
N- in an amount not exceeding 1 mole per mole of the compound represented by
A method for producing a thermoreversible polymer crosslinked molded article, which comprises adding methylol acrylamide, performing radical polymerization in a solution state, molding the resulting copolymer, and then heating to crosslink it.