JP3066465B2 - Method for manufacturing shape memory resin molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing an aqueous solution at a temperature not higher than a predetermined temperature, which is separated from water with the passage of time and maintaining the same shape. The present invention relates to a method for producing a molded article having properties capable of being molded into a compact.

[0002]

2. Description of the Related Art If there is a substance such as a rubber balloon that can be freely expanded or reduced while maintaining a predetermined shape, the cavity is filled with this substance and used, and if it is no longer needed, it is removed. It is very convenient because it can be easily taken out by reducing it in the cavity. However, regarding the resin molding,
No one having such properties is known. On the other hand,
Shape memory alloys are known to exhibit similar properties.However, no matter how the shape is deformed, the shape can be expanded simply by restoring the original shape when the temperature exceeds a predetermined temperature. And shrinking cannot be done. By the way, in recent years,
Thermosensitive polymers whose behavior with respect to water reversibly changes depending on temperature have come to attract widespread attention as one type of functional materials, such as nonionic surfactant adsorbents, thermosensitive light-shielding agents,
The development of applications as temperature-sensitive thickeners, anti-staining agents, marine antifouling materials, artificial muscles, drug delivery system materials, etc. is being studied.

Some types of N-alkylacrylamide-based polymers or copolymers are soluble in water at a predetermined temperature or lower, but become insoluble in water at a higher temperature. It is known that the compound exhibits a reversible property-water-insoluble reversible change, and attempts have been made to use this property as a light-shielding material (Japanese Patent Application Laid-Open No. 58-78758).

Further, an aqueous solution of a copolymer of N-isopropylacrylamide and another N-substituted acrylamide has a property of causing a phase transition based on a coil-globule transition, and separates into two phases at a transition temperature or higher. It is known that a non-uniform distribution occurs in the concentration of copolymer molecules and a fine pattern is formed, thereby exhibiting strong light scattering ["J. Phys. Chem.", Vol. 93, No. 331.
1 (1989), "Polymer Papers," Vol. 46 (7), Page 437 (1989), Journal, Vol. 47 (6), Page 467 (1990)].

[0005] Separately, if the gel is left alone, a phenomenon in which water is naturally separated and the volume shrinks is called syneresis. Although it is known as a phenomenon of sweating the surface, no N-alkylacrylamide-based polymer or copolymer exhibiting such a syneresis phenomenon has heretofore been known.

[0006]

SUMMARY OF THE INVENTION The present invention has the property that water is released over time at a predetermined temperature or higher to reduce its size while maintaining its shape, and at a temperature lower than that temperature it is dissolved in water to form an aqueous solution. The purpose of the present invention is to provide a method for manufacturing a resin molded article.

[0007]

SUMMARY OF THE INVENTION The present inventor has proposed that certain N
-It has been found that a polymer or copolymer of a substituted acrylamide exhibits a syneresis phenomenon, and that a molded article whose size can be reduced while maintaining its shape can be realized by using this syneresis phenomenon. Based on this, the present invention has been accomplished.

That is, the present invention relates to an aqueous solution containing a monomer mixture consisting of 60 to 100 mol% of N-propyl acrylamide and 40 to 0 mol% of N-butyl acrylamide. At a temperature above its transition temperature in the presence of a radical polymerization initiator at 27 ° C.
The polymer or copolymer is prepared by performing intra-micellar polymerization or copolymerization until the intrinsic viscosity [η] of the methanol solution at 2.0 becomes 2.0 or more, and is converted into an aqueous solution at a temperature lower than the transition temperature into a predetermined form. It is intended to provide a method for producing a shape-memory resin molded article, which is characterized in that after pouring, the temperature is raised to a temperature not lower than the transition temperature and solidified, and then removed from a mold.

The polymer or copolymer of the present invention has a hydrophilic property
It has a temperature that shows a reversible change in hydrophobicity, that is, a transition temperature, and solidifies by releasing water when it becomes hydrophobic at or above the transition temperature,
While maintaining the original shape, that is, any corresponding cross section shrinks with time while showing a similar shape. And below this transition temperature, it becomes hydrophilic and dissolves in water to become an aqueous solution.

The above-mentioned copolymer needs to be composed of only N-propylacrylamide units or N-propylacrylamide units and N-butylacrylamide units. Copolymers having a similar structure, for example, N
Those composed of N-propyl methacrylamide unit and N-butyl acrylamide unit or N-propyl acrylamide unit and N-butyl methacrylamide unit cannot be made high molecular weight or become insoluble in water, so that the syneresis phenomenon occurs. And the compact cannot be reduced while maintaining its shape.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer or copolymer from which a molded article is formed in the method of the present invention may be composed of only N-propylacrylamide units or N-propylacrylamide units and N-propylacrylamide units.
-Butylacrylamide unit, and the propyl group of the N-propylacrylamide unit and the butyl group of the N-butylacrylamide unit may be any of linear, branched or cyclic. That is, the propyl group may be any of an n-propyl group, an isopropyl group and a cyclopropyl group, and the butyl group may be an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, a cyclobutyl group. Any of a propylmethyl group and a methylcyclopropyl group may be used.

Accordingly, the polymer or copolymer from which the molded article is formed in the method of the present invention is at least one selected from Nn-propylacrylamide units, N-isopropylacrylamide units and N-cyclopropylacrylamide units. One type of structural unit or this structural unit, and Nn-butylacrylamide unit, N-isobutylacrylamide unit, N-sec-butylacrylamide unit, N-tert-butylacrylamide unit, N-cyclobutylacrylamide unit, N- It is composed of at least one structural unit selected from a cyclopropylmethyl unit and an N-methylcyclopropylacrylamide unit.

In the method of the present invention, 60 to 100 mol% of the N-propylacrylamide unit and the N-propylacrylamide unit are used.
It is necessary to mold using a polymer or copolymer consisting of 40 to 0 mol% of butylacrylamide units. Those having more N-butylacrylamide units become insoluble in water at practical temperatures.

These polymers or copolymers may be N-propylacrylamide, ie, Nn-propylacrylamide, N-isopropylacrylamide or N-cyclopropylacrylamide, or N-butylacrylamide, ie, Nn-butylacrylamide. By polymerizing or copolymerizing acrylamide, N-isobutylacrylamide, N-sec-butylacrylamide, N-tert-butylacrylamide, N-cyclobutylacrylamide, N-cyclopropylmethylacrylamide, or N-methylcyclopropylacrylamide Manufactured. N-propylacrylamide and N-butylacrylamide used at this time may be used alone or as a mixture of two or more monomers.

In the polymerization or copolymerization of N-propylacrylamide alone or N-propylacrylamide with N-butylacrylamide, water is used as a reaction medium, usually in the presence of a cationic surfactant or an anionic surfactant. Can be carried out in the same manner as in the case of radical polymerization of As the concentration of the total amount of monomer in water,
A range of 2 to 15% by weight is suitable.

As the above-mentioned cationic surfactant, for example, trimethyl stearyl ammonium chloride, trimethyl cetyl ammonium chloride, trimethyl cetyl ammonium bromide, trimethyl n-tetradecylammonium chloride and the like are used. Ammonium salts can also be used.

Examples of the anionic surfactant include sodium dodecylbenzenesulfonate,
Alkylbenzene sulfonates such as sodium n-octylbenzenesulfonate, sulfates such as sodium nonylphenol sulfate, and conventional anionic surfactants such as sodium dioctylsulfosuccinate and sodium dodecylsulfate are used. These cationic surfactants or anionic surfactants may be used alone or in combination of two or more.

These cationic surfactants or anionic surfactants are added to water as a reaction medium at a concentration higher than the critical micelle concentration. Although the monomer N-propylacrylamide and N-butylacrylamide are both insoluble in water, the presence of these surfactants at or above the critical micelle concentration allows them to be uniformly dispersed in the reaction medium.

In order to start the polymerization, according to a conventionally known radical polymerization method, for example, irradiation with radiation or electron beam,
Heating is performed in the presence of a radical polymerization initiator, or light irradiation is performed in the presence of a photosensitizer. Of these methods, a particularly advantageous method is heating in the presence of a radical polymerization initiator. The radical polymerization initiator at this time is not particularly limited as long as it is a water-soluble one. Such materials include, for example, ammonium persulfate, potassium persulfate,
Redox initiators such as hydrogen peroxide, peroxides such as tert-butyl hydroperoxide, sulfites, bisulfites, and ceric ammonium nitrate; 2,2'-
Azobis-2-amidinopropane hydrochloride, 2,2'-azobis-2,4-dimethylvaleronitrile, 4,4'-
Azo compounds such as azobis-4-cyanovaleric acid and salts thereof can be used. These radical polymerization initiators may be used alone or in combination of two or more, and the amount used is usually from 0.01 to 100% by weight based on the total amount of the monomers. %, Preferably in the range of 0.05 to 8% by weight. The polymerization temperature is
The temperature is usually in the range of 0 to 100 ° C. and higher than the transition temperature of the aqueous polymer solution formed by polymerization, although it depends on the type of the monomer and the initiator used.

In this case, a polymerization reaction takes place in the micelle, and a polymer or copolymer can be obtained efficiently. After completion of the polymerization, the reaction solution is cooled to a temperature lower than the transition temperature, and the micelle structure is destroyed by further adding methanol or ethanol. When the aqueous solution is heated to the transition temperature or higher, the polymer becomes hydrophobic and precipitates. The precipitated polymer is dissolved in pure water and heated to precipitate the polymer. By repeating this operation, a polymer or copolymer from which the surfactant and unreacted monomer have been completely removed can be obtained.

In the method of the present invention, the polymer or copolymer thus obtained is dissolved in water at a temperature lower than the hydrophobization-hydrophilization transition temperature to form an aqueous solution. And then solidified by elevating the temperature to or above the transition temperature to produce a shape-memory resin molded article. At this time, the concentration of the polymer or copolymer in the aqueous solution is selected in the range of 0.5 to 5.0% by weight, preferably 1.0 to 3.0% by weight. Also, once the compact has been reduced to the transition temperature or lower, it dissolves in water and becomes an aqueous solution, so that it can be molded again to restore it to its original shape.

[0022]

The resin molded product obtained by the method of the present invention, when left at a temperature above the transition temperature, releases water and shrinks while maintaining its original shape, and when kept below the transition temperature, it dissolves in water. Since it becomes an aqueous solution, it can be easily filled when necessary into a cavity having a narrow opening and a complicated shape, and can be easily removed when unnecessary. In addition, let it be formed into the shape of animals and characters,
By coloring, it can be used as a toy.

[0023]

Next, the present invention will be described in more detail by way of examples.

Reference Example 1 500 g of distilled water, 24.55 g of N-isopropylacrylamide, N-tert were placed in a 1000 ml Erlenmeyer flask equipped with a V-tube equipped with a capillary stopper and a condenser.
4.78 g of -butylacrylamide and 1.76 g of sodium harddodecylbenzenesulfonate were added, and nitrogen gas was passed vigorously for 30 minutes. Next, add 0.07 g of ammonium persulfate and stir under a nitrogen stream.
The polymerization was started by heating to 60 ° C. After polymerization at 60 ° C. for 2 hours, air was blown to stop the polymerization, and a copolymer was produced.

The copolymer was purified in the same manner as in Example 1 to obtain 25.99 g of a copolymer from which the surfactant and the unreacted monomer had been completely removed. The molar ratio of N-isopropylacrylamide units to t-butylacrylamide units in this copolymer was 84.2: 14.
It was 8. Next, 2 of a methanol solution of this copolymer was prepared.
The intrinsic viscosity and the transition temperature at 7 ° C. were determined in the same manner as in Example 1, and were 3.20 and 24 ° C., respectively.

Next, regarding this polymer, the polymer 0.1.
5213 mg of distilled water 34.3455 g (1.5% by weight)
Aqueous solution) was placed in a sample tube and dissolved at 10 ° C. to prepare this aqueous solution. Keep this in a 50 ° C thermostat for 24 hours,
Let the water out. It shrank while keeping the shape similar to the shape of the container. The weight of the shrunk molded product was 3.8 g.

Example 1 200.46 g of distilled water and N were placed in a 500 ml Erlenmeyer flask equipped with a V-tube equipped with a capillary stopper and a condenser.
9.09 g of -isopropylacrylamide and 0.70 g of sodium dodecylbenzenesulfonate were added, and nitrogen gas was passed vigorously for 30 minutes. Next, 0.051 g of ammonium persulfate was added, and the mixture was heated to 60 ° C. while stirring under a nitrogen stream to initiate polymerization. After polymerization at 60 ° C. for 2 hours, air was blown in to stop the polymerization, and a polymer was produced.

After the polymerization is completed, a small amount of methanol is added to destroy the micelle structure, and when this aqueous solution is heated to a temperature higher than the transition temperature, the polymer becomes hydrophobic and precipitates. Since the polymer thus obtained is present in the micelle, it has a low viscosity. When this is cooled below the transition temperature, the polymer in the micelle breaks the micelle structure and becomes an aqueous solution. When this aqueous solution is heated above the transition temperature, the polymer becomes hydrophobic,
Precipitates. The precipitated polymer was dissolved in pure water and heated to precipitate the polymer, thereby obtaining 9.02 g of a polymer from which the surfactant and the unreacted monomer were completely removed.

Next, this copolymer was used as a methanol solution, and the viscosity was measured at 27 ° C. using an Ubbelohde viscometer to find the intrinsic viscosity, which was 2.90. Further, the transition temperature was determined from the measurement of the light transmittance accompanying the temperature change of the aqueous solution. That is, an aqueous solution having a concentration of 1% by weight was prepared, and the temperature was raised at a rate of 1 ° C. /
The light transmittance at a wavelength of 500 nm was measured. The transition temperature was 30.5 ° C. as the temperature (T _L ) at which the light transmittance became の of the initial transmittance.

Next, 0.3310 g of this polymer was placed at 10 ° C.
Was dissolved in 14.0048 g of distilled water to prepare a 2.3% by weight aqueous solution, and a circular petri dish having a diameter of 27 mm was used as a mold, poured into this, and formed into a cylinder having a height of 25.0 mm. This was placed in a thermostat at 60 ° C. together with the petri dish, and observed, a thickening phenomenon was first observed. Then, the gel was gradually gelled while maintaining the shape of the cylinder, and was taken out after 24 hours. 6mm
Column was obtained.

Example 2 A 500 ml Erlenmeyer flask equipped with a V-tube equipped with a capillary stopper and a condenser was charged with 200 g of distilled water and Nn-
9.67 g of propylacrylamide, 1.91 g of N-tert-butylacrylamide and 0.70 g of sodium harddodecylbenzenesulfonate were added, and nitrogen gas was passed vigorously for 30 minutes. Next, 0.05 g of ammonium persulfate was added, and while stirring under a nitrogen stream, 60 g was added.
C. to initiate the polymerization. After polymerization was performed at 60 ° C. for 2 hours, air was blown in to stop the polymerization, and a copolymer was formed.

The purification of the polymer was carried out in the same manner as in Example 1. 11.50 g of a copolymer from which the surfactant and unreacted monomers were completely removed were obtained. N in this copolymer
The molar ratio of -n-propylacrylamide units to t-butylacrylamide units was 85:15.

Next, the methanol solution of the copolymer
The intrinsic viscosity and the transition temperature at 7 ° C. were determined in the same manner as in Example 1 and found to be 3.00 and 19 ° C., respectively.

Next, 0.3715 g of this copolymer was added to 10
A 2.3% by weight aqueous solution was prepared by dissolving in 15.6960 g of distilled water at ℃. This was poured into a dog-shaped mold to obtain a dog-shaped molded body. The molded body was placed in a thermostat at 60 ° C. and observed. As a result, the phenomenon of thickening was first observed, and then the gel was gradually gelled while maintaining the shape of the dog. Reduced to

Example 3 500 g of distilled water, 50.92 g of N-isopropylacrylamide, and N-tert were placed in a 1000 ml Erlenmeyer flask equipped with a V-tube equipped with a capillary stopper and a condenser.
6.35 g of -butylacrylamide and 1.75 g of sodium harddodecylbenzenesulfonate were added, and nitrogen gas was passed vigorously for 30 minutes. Next, 0.055 g of ammonium persulfate was added, and the mixture was heated to 60 ° C. while stirring under a nitrogen stream to initiate polymerization. After polymerization was performed at 60 ° C. for 2 hours, air was blown in to stop the polymerization, and a copolymer was formed.

The purification of the polymer was carried out in the same manner as in Example 1. 57.10 g of a copolymer from which the surfactant and the unreacted monomer were completely removed were obtained. N in this copolymer
The molar ratio between -isopropylacrylamide units and t-butylacrylamide units was 90:10.

Next, the methanol solution of the copolymer
The intrinsic viscosity and the transition temperature at 7 ° C. were determined in the same manner as in Example 1, and were 3.80 and 26 ° C., respectively.

Next, 0.2678 g of this copolymer was added to 10
Dissolved in 13.2991 g of distilled water at 1.degree.
A weight% aqueous solution was prepared, and a circular Petri dish having a diameter of 27 mm was used as a mold and poured into the dish to form a column having a height of 23.7 mm. When this was placed in a thermostat at 60 ° C. together with a petri dish and observed, a thickening phenomenon was first observed. Then, the gel was gradually gelled while maintaining the shape of the cylinder, and was taken out after 24 hours. An 8 mm cylinder was obtained.

Reference Example 2 The reduced product obtained in Example 2 was put into a glass beaker with water and kept at 10 ° C., and gradually dissolved to form an aqueous solution.

Comparative Example In a 2000 ml Erlenmeyer flask equipped with a V-tube equipped with a capillary stopper, 792.90 g of methanol and N-
203.69 g of isopropylacrylamide, N-te
25.44 g of rt-butylacrylamide and 0.50 g of azobisisobutyronitrile were added, and the mixture was heated to 60 ° C. in a nitrogen gas atmosphere to initiate polymerization. 2.5 at 60 ° C
After polymerization was carried out for an hour, air was blown in to stop the polymerization, thereby forming a copolymer.

The purification of the polymer was performed in the same manner as in Example 1. 169.98 g of a copolymer from which the surfactant and unreacted monomers were completely removed were obtained. The molar ratio between N-isopropylacrylamide units and t-butylacrylamide units in this copolymer was 90:10.

Next, the methanol solution of the copolymer
The intrinsic viscosity and the transition temperature at 7 ° C were determined in the same manner as in Example 1, and were 1.32 and 26.5 ° C, respectively.

Next, the copolymer was heated at 10 ° C. for 1 hour.
A weight% aqueous solution was prepared. This aqueous solution was poured into a petri dish and kept in a thermostat at 50 ° C. for 10 hours. As a result, only a clouding phenomenon was observed, and no reduction in the size of the molded product was observed.

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Claims (1)

(57) [Claims] 1. N-propylacrylamide 60 to 10
A cationic surfactant or an anionic surfactant is added to an aqueous solution containing a monomer mixture consisting of 0 mol% and N-butylacrylamide at 40 to 0 mol% at a concentration higher than the critical micelle concentration to initiate radical polymerization. A polymer or copolymer is prepared by performing intra-micellar polymerization or copolymerization in the presence of an agent at a temperature equal to or higher than its transition temperature until the intrinsic viscosity [η] of the methanol solution at 27 ° C. becomes 2.0 or higher. A method for producing a shape-memory resin molded article, comprising: pouring an aqueous solution at a temperature lower than the transition temperature into a predetermined mold, and then raising the temperature to a temperature equal to or higher than the transition temperature to solidify, and then removing the molded article from the mold. .