JP5170758B2 - Water-soluble block copolymer and dilatancy composition for inducing dilatancy - Google Patents

Description

The present invention relates to a water-soluble block copolymer that induces dilatancy to an aqueous solution system, and a dilatancy composition. The present invention also relates to a composition that gels by flow. The water-soluble block copolymer and composition of the present invention are useful as impact absorbers, other aqueous viscosity regulators, and gelling compositions by flow. In the present invention, the dilatancy means that the viscosity increases due to flow and the fluidity decreases.

A water-soluble polymer aqueous solution generally decreases in viscosity under high shear. On the other hand, a liquid containing fine particles may exhibit dilatancy that increases in viscosity under high shear. Patent Document 1 reports a dilatancy property for a system of fine particles, a dispersant, and a liquid. Patent Document 2 and Non-Patent Document 1 have reports on the dilatancy of oil droplets and water-soluble polymer systems, but both are heterogeneous systems containing oil droplets and the like. There is a problem that it is necessary to emulsify and stabilize oil droplets by adding an agent.
Japanese Patent No. 3922370 Patent No. 4098967 THE JOURNAL OF CHEMICAL PHYSICS 127 No. 144450

An object of the present invention is to provide a water-soluble block copolymer that induces dilatancy to an aqueous solution system, and an aqueous solution composition that exhibits dilatancy and has excellent stability. Another object of the present invention is to provide an aqueous solution composition that gels by flow.

A water-soluble block copolymer having the same ionic block at both ends and a nonionic hydrophilic block at the center, and an ion having an ionicity opposite to that of the water-soluble block copolymer It was found that a uniform aqueous polymer solution containing a water-soluble polymer exhibits dilatancy. In addition, a water-soluble block copolymer having the same ionic block at both ends and a nonionic hydrophilic block in the central portion, and an ionicity opposite to that of the water-soluble block copolymer It has been found that a uniform aqueous polymer solution containing an ionic water-soluble polymer has gelation by flow.

The water-soluble block copolymer for inducing dilatancy of the present invention exhibits dilatancy in an aqueous system when added to an aqueous solution containing an ionic water-soluble polymer having an opposite charge. This composition is homogeneous, does not require a dispersion stabilizer, a surfactant and the like, has excellent storage stability, and exhibits dilatancy even at a low concentration of 1% or less. In addition, when no flow stimulus is applied, the solution is a low-viscosity uniform aqueous solution. However, when the flow stimulus is applied, the solution rapidly has a high viscosity, the fluidity is lowered, and gelation occurs.

Hereinafter, the present invention will be described in further detail. In the present invention, the ionic block refers to a portion composed of ionic monomer units, or a portion where ionic monomer units and nonionic hydrophilic monomer units are mixed. The portion consisting of ionic monomer units may be a block formed from a mixture of different types of monomers as long as they are of the same ionic type, and the portion consisting of nonionic hydrophilic monomer units is also of a different type. It may be a block generated from a mixture of monomers. In the present invention, the nonionic hydrophilic block refers to a portion composed of a nonionic hydrophilic monomer unit. The portion composed of the nonionic hydrophilic monomer unit may be a block formed from a mixture of different types of monomers.

A water-soluble block copolymer having the same ionic block at both ends and a nonionic hydrophilic block at the central portion is used for living anionic polymerization, atom transfer radical polymerization, nitroxide mediated polymerization, reversible addition / desorption. It can be obtained by chain transfer polymerization (Reverseable Addition-Fragmentation Chain Transfer Polymerization, hereinafter abbreviated as RAFT polymerization). Hereinafter, the case of RAFT polymerization will be described in detail.

RAFT polymerization is carried out by adding a RAFT polymerization chain transfer agent to a normal radical polymerization reaction system. Usually, a RAFT polymerization chain transfer agent containing a dithioester group, a trithiocarbonate group or the like is used. Of these, water-soluble ones are preferred, and examples thereof include 4-cyanopentanoic acid dithiobenzoate, S-Ethyl-S ′-(α, α′-dimethyl-α “-acetic acid) -trithiocarbonate. In addition to these, it is also possible to use bisdithioesters and bistrithiocarbonates.

Among the monomers used during polymerization, examples of anionic monomers include (meth) acrylic acid, itaconic acid, maleic acid, styrene sulfonic acid, acrylamide 2-methylpropane sulfonic acid, and salts thereof. can give. Of these, acrylic acid and its salts are more preferred.

Among the cationic monomers, examples of tertiary amino group-containing cationic monomers include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl. (Meth) acrylamide and salts thereof may be mentioned. Examples of quaternary ammonium base-containing cationic monomers include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloyl. Examples thereof include aminopropyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride, diallyldimethylammonium chloride and the like. Examples of the primary amine include allylamine, and examples of the secondary amine include diallylmethylamine.

Examples of nonionic hydrophilic monomers are (meth) acrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, hydroxyethylacrylamide, vinylpyrrolidone, vinylformamide, vinylacetamide, glycerol (meth) acrylate, hydroxyethyl (meth) An acrylate etc. are mentioned. Acrylamide is more preferable because of ease of polymerization.

For the initiation of polymerization, a radical polymerization initiator is used. These initiators are preferably water-soluble and can be polymerized in any of azo, redox and peroxide systems. Examples of water-soluble azo initiators include 2,2′-azobis (2-methylpropionamidine) dichloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] And hydrogen chloride, 4,4′-azobis (4-cyanovaleric acid), and the like. Examples of redox systems include a combination of ammonium persulfate and sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine and the like. Further, examples of peroxides include ammonium or potassium persulfate, hydrogen peroxide, and the like. Of these, water-soluble azo initiators are preferred.

  The polymerization conditions are usually appropriately determined according to the monomer used, the polymerization initiator, and the like. As temperature, it carries out in the range of 0-100 degreeC. The polymerization is usually carried out in three stages. During the first stage polymerization, polymerization of a mixture of an ionic monomer (mixture) and a nonionic hydrophilic monomer (mixture) is performed. Polymerization of only an ionic monomer (mixture) may be used. The ionic monomer (mixture) may be a single type or a mixture of plural types of ionic monomers having the same ionicity. The nonionic hydrophilic monomer (mixture) may be a single type or a mixture of a plurality of types. A chain transfer agent and a polymerization initiator are added to an aqueous solution of a mixture of an ionic monomer (mixture) and a nonionic hydrophilic monomer (mixture), and the first polymerization is started after the system is sufficiently purged with nitrogen. . The polymerization time is about 1 to 30 hours. If necessary, it is preferable to adjust the pH by adding hydrochloric acid or the like. The amount of the chain transfer agent is about 20 to 20000 ppm based on the polymerizable monomer used throughout the entire polymerization. If it is less than this, the progress of the polymerization is slow, and if it is more than this range, the molecular weight of the resulting polymer becomes too small. The amount of the polymerization initiator is about 5 to 100 mol% with respect to the chain transfer agent. After the first polymerization is sufficiently completed, a nonionic hydrophilic monomer and water as necessary are added, a polymerization initiator is further added, and after the system is sufficiently purged with nitrogen, the second polymerization is started. The polymerization time is about 1 to 30 hours. The amount of the polymerization initiator is about 5 to 100% with respect to the amount of the chain transfer agent added during the first polymerization. After the second polymerization is sufficiently completed, an ionic monomer (mixture) and a nonionic hydrophilic monomer (mixture) are added, a polymerization initiator is further added, and the system is sufficiently purged with nitrogen. 3 polymerization is started. Polymerization of only an ionic monomer (mixture) may be used. The polymerization time is about 1 to 30 hours. The amount of the polymerization initiator is about 5 to 100% with respect to the amount of the chain transfer agent added during the first polymerization. Although there is no restriction | limiting in particular in the whole quantity of a polymerizable monomer, About 5 to 30% of the whole is preferable if the viscosity and economical efficiency of the finally produced aqueous solution are considered. After the first and second polymerizations, it is possible to remove unreacted monomers by a dialysis method, a precipitation method, an extraction method or the like.

The amount of the ionic monomer used during the first polymerization and the third polymerization is preferably 1 mol% or more based on the total amount of monomers. If it is less than this, the dilatancy property is lowered. Further, the ratio of the number of moles of nonionic hydrophilic monomers and the number of moles of ionic monomers used during the first polymerization and the third polymerization is as follows.
0 ≦ (number of moles of nonionic hydrophilic monomer) / (number of moles of ionic monomer) ≦ 5
It is preferable to satisfy. When it is larger than 5, dilatancy is lowered. The first polymerization and the third polymerization may be polymerization of only an ionic monomer (mixture). The number of moles of the monomer (mixture) used in the second polymerization is the number of moles of the monomer (mixture) used in the first polymerization and the single amount used in the third polymerization. It is preferable to be equal to or greater than the sum of the number of moles of the body (mixture). If it is less than this, the dilatancy property is lowered. The types of ionic monomers in the first and third polymerizations may be different as long as they are the same ionic. The molecular weight of the finally obtained copolymer is preferably 5,000 to 3,000,000. More preferably, it is 10,000 to 3 million. In order to obtain a molecular weight larger than this, it is necessary to reduce the addition amount of the RAFT polymerization chain transfer agent and the polymerization initiator. In this case, however, problems such as a long time for polymerization occur. The molecular weight can be controlled by the amount of RAFT polymerization chain transfer agent.

It is also possible to use bisdithioesters and bistrithiocarbonates as RAFT polymerization chain transfer agents. When these are used, the water-soluble block copolymer of the present invention can be obtained by two-stage polymerization.

In order to develop dilatancy, the ionic polymer combined with the water-soluble block copolymer is an ionic water-soluble polymer having an ionic property opposite to that of the water-soluble block copolymer. For example, it can be obtained by polymerizing the ionic monomer by an ordinary method, or copolymerizing the ionic monomer and the nonionic hydrophilic monomer by an ordinary method. In addition, natural ionic polymers and those obtained by introducing ionic groups into natural polymers may be used.

The mixing ratio of the water-soluble block copolymer and the ionic water-soluble polymer that is counterionic in an aqueous solution is particularly preferably in the range of 20 to 80:80 to 20 by weight. If it is smaller or larger than this range, the dilatancy is lowered. The concentration of the water-soluble block copolymer and the ionic polymer in the aqueous solution is preferably 0.001 to 20% by weight. When the amount is 0.001% by weight or less, the dilatancy is lowered, and when it is 20% by weight or more, the viscosity becomes high even when no flow stimulus is applied. More preferably, it is 0.01 weight%-1 weight%. Further, a water-miscible solvent such as methanol or ethanol may be contained in the aqueous solution to such an extent that the solubility of the block copolymer and the ionic water-soluble polymer is not lowered.

(Example)
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to a following example, unless the summary is exceeded. In the examples, the viscosity was measured using a Brookfield viscometer with a rotation speed of 100 rpm and a No. 2 rotor (measured at 25 ° C.).

To a four-necked 300 ml separable flask equipped with a stirrer, reflux condenser, and nitrogen inlet tube was added 1.67 g of 60% aqueous acrylic acid solution, 12.0 g of 1N-NaOH, and 0.005 g of 4-cyanopentanoic acid dithiobenzoate. A mixed solution. While maintaining the temperature at 20 ° C., nitrogen was introduced from the nitrogen introduction tube while stirring, and the system was purged with nitrogen. Next, 0.1 g of 1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution was added, and the flask was heated to a temperature of 50 ° C. 1 polymerization was started. The first polymerization reaction was completed after 8 hours. After cooling to room temperature, 16 g of 50% aqueous acrylamide solution, 18.4 g of deionized water, 1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution 0.1 g And heated to a temperature of 50 ° C. to initiate the second polymerization. After 16 hours, the second polymerization reaction was completed. After cooling to room temperature, 1.67 g of 60% aqueous acrylic acid solution, 50 g of deionized water, 1 g of 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution 0.1 g The third polymerization was started by adding and heating to a temperature of 50 ° C. The third polymerization was terminated after 22 hours. The resulting product is designated as water-soluble block copolymer 1.

A methacryloyloxyethyltrimethylammonium chloride homopolymer (p-MMCQ, weight average molecular weight of 900,000 by MALS) was dissolved in deionized water to 1%. The water-soluble block copolymer 1 was dissolved in deionized water so as to be 1%. After mixing 2 g of 1% p-MMCQ aqueous solution and 2 g of 1% water-soluble block copolymer 1 aqueous solution, 36 g of demineralized water was added to dilute the total concentration to 0.1%. When the viscosity after standing for 1 day was measured, it was 4.8 mPa · s (measured at 25 ° C., the same applies hereinafter). Next, it was put into a 50 mL sample bottle, the viscosity measured after shaking for 5 seconds at an amplitude of about 10 cm and a frequency of 4 times / S was 38.4 mPa · s, and the viscosity increased 8 times. Moreover, a transparent solid substance adhered to the wall of the sample bottle, and a part of the gel was generated.

To a four-necked 300 ml separable flask equipped with a stirrer, reflux condenser, and nitrogen inlet tube was added 1.67 g of 60% aqueous acrylic acid, 12.0 g of 1N-NaOH, and 0.01 g of 4-cyanopentanoic acid dithiobenzoate. A mixed solution. While maintaining the temperature at 20 ° C., nitrogen was introduced from the nitrogen introduction tube while stirring, and the system was purged with nitrogen. Next, 0.2 g of 1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution was added, and the flask was heated to a temperature of 50 ° C. 1 polymerization was started. The first polymerization reaction was completed after 8 hours. After cooling to room temperature, 16 g of 50% acrylamide aqueous solution, 68.4 g of deionized water, 1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution 0.2 g And heated to a temperature of 50 ° C. to initiate the second polymerization. After 16 hours, the second polymerization reaction was completed. After cooling to room temperature, 1.67 g of 60% aqueous acrylic acid solution, 0.2 g of 1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution was added, and the temperature was adjusted. The third polymerization was started by heating to 50 ° C. The third polymerization was terminated after 22 hours. The resulting product is designated as water-soluble block copolymer 2.

After mixing 3 g of 1% p-MMCQ aqueous solution and 6 g of 1% water-soluble block copolymer 2 aqueous solution, 36 g of demineralized water was added to dilute the total concentration to 0.2%.
The viscosity after standing for 1 day was measured and found to be 4.8 mPa · s. Next, it was put in a 50 mL sample bottle, the viscosity measured after shaking for 5 seconds at an amplitude of about 10 cm and a frequency of 4 times / S was 41.1 mPa · s, and the viscosity increased 8.6 times. Moreover, a transparent solid substance adhered to the wall of the sample bottle, and a part of the gel was generated.

1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution was 0.1 g, and the amount of acrylic acid added during the third polymerization was 3.3 g. Polymerization was carried out under the same conditions as in Example 3. The obtained product is designated as water-soluble block copolymer 3.

After mixing 0.8 g of 1% p-MMCQ aqueous solution and 1.2 g of 1% water-soluble block copolymer 3 aqueous solution, 38 g of demineralized water was added to dilute to a total concentration of 0.05%. . The viscosity after standing for 1 day was measured and found to be 8.7 mPa · s. Next, it was put into a 50 mL sample bottle, the viscosity measured after shaking for 5 seconds with an amplitude of about 10 cm and a frequency of 4 times / S was 21.1 mPa · s, and the viscosity increased 2.4 times.
Moreover, a transparent solid substance adhered to the wall of the sample bottle, and a part of the gel was generated.

(Comparative Example 1)
In a four-neck 300 ml separable flask equipped with a stirrer, reflux condenser, and nitrogen inlet tube, 3.4% 60% acrylic acid aqueous solution, 12.0 g 1N-NaOH, 16.0 g 50% aqueous acrylamide solution, 67.7 g deionized water Was added to obtain a uniform mixed solution. While maintaining the temperature at 20 ° C., nitrogen was introduced from the nitrogen introduction tube while stirring, and the system was purged with nitrogen. Next, 1.0 g of 1% 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride aqueous solution was added, and the flask was heated to a temperature of 50 ° C. to polymerize. Was started. The polymerization was terminated after 10 hours.
The resulting product is referred to as random copolymer 1.

(Comparative Example 2)
A methacryloyloxyethyltrimethylammonium chloride homopolymer (p-MMCQ, weight average molecular weight of 900,000 by MALS) was dissolved in deionized water to 1%. Random copolymer 1 of Comparative Example 1 was dissolved in deionized water to 1%. After mixing 2 g of 1% p-MMCQ aqueous solution and 2 g of 1% random copolymer 1 aqueous solution, 36 g of demineralized water was added and diluted so that the total concentration was 0.1%. A cloudy precipitate was formed and showed no viscosity.

Claims (3)

A water-soluble block copolymer having the same ionic block at both ends and a nonionic hydrophilic block at the center, and an ion having an ionicity opposite to that of the water-soluble block copolymer A dilatant composition containing a water- soluble polymer and water . A water-soluble block copolymer having the same ionic block at both ends and a nonionic hydrophilic block at the center, and an ion having an ionicity opposite to that of the water-soluble block copolymer A composition that contains a water- soluble polymer and water and gels by flow. In the water-soluble block copolymer, the number of moles of an ionic monomer in one ionic block is a, the number of moles of a nonionic hydrophilic monomer is b, and the central nonionic hydrophilic block is The number of moles of the nonionic hydrophilic monomer in the inside is c, the number of moles of the ionic monomer in the other ionic block is d, and the number of moles of the nonionic hydrophilic monomer is e. When
a / (a + b + c + d + e) ≧ 0.01,
d / (a + b + c + d + e) ≧ 0.01,
0 ≦ b / a ≦ 5, 0 ≦ e / d ≦ 5,
c ≧ (a + b + d + e)
The composition according to claim 1 or 2 .