JP2009167283A - Thermally responsive aba tri-block polymer and aqueous coating composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ABA tri-block polymer which is dissolvable in water or dispersible in water at a normal temperature, having a stimulation responsive property capable of being used as various functional materials, and a thermally responsive thickening agent composition containing the same. <P>SOLUTION: This ABA tri-block polymer consisting of the block A which is a polymer having the ≥40°C lower limit of critical solution temperature to water, and the block B which is a polymer having the higher lower limit of critical temperature than that of the block A by ≥20°C, or a water soluble polymer is provided, wherein starting monomers of the blocks A and the B have a vinyl ether structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ABA triblock polymer that can be used as various functional materials and has a stimulus responsiveness and is soluble in water at room temperature, and an aqueous coating composition containing it as a thickener. In particular, according to the present invention, since the block segment of the ABA triblock polymer has LCST (Lower Critical Solution Temperature: LCST), it has a high fluidity at normal temperature, and it becomes a state in which there is no drasticity to fluidity due to heating. The present invention relates to an aqueous coating composition using the polymer as a thickener by utilizing the properties.

  The use of stimuli-responsive substances as industrially available functional materials has been widely studied. Among them, there are many organic materials that are put to practical use, such as leuco dyes and liquid crystal temperature indicating materials, which have thermal properties, in response to heat, which is one of the most common forms of stimulation, that is, thermal response.

  On the other hand, in the field of polymer synthetic chemistry, so-called living polymerization has been studied as a means for synthesizing polymer materials with controlled structures. At present, the existence of living polymerization is known for each type of polymerization where the growth species are radical, cation, and anion, and it is possible to precisely control the polymerization.

A structure in which a polymer having a narrow molecular weight distribution is blocked or grafted can be obtained by living polymerization. In view of this, attempts have been made to use a functional material having controlled stimulus response characteristics by using a stimulus responsive polymer as a block polymer. Non-Patent Documents 1 and 2 are reviews of stimuli-responsive polymers, and mention is also made of the block polymers described here.
: Sadato Aoshima, Polymer, 46, 497-502 (1997) : Sadato Aoshima, Polymer Journal, Vol. 63, pp. 71-85 (2006).

  Patents have also been filed with the technical feature of using stimulus-responsive polymers with controlled structures. Patent Document 1 discloses a polymer gel film using a heat-responsive graft polymer. Patent Document 2 discloses a composition containing an ABC type block polymer containing at least one stimulus-responsive block. In addition, the composition is used as an ink composition, an image forming method using the composition, and the like. Is disclosed.

Patent Document 3 discloses that when Patent Document 2 is used particularly in an aqueous solvent, it becomes a material excellent in dispersion stability. In the detailed description of Patent Documents 2 and 3, it is described that the state of the system undergoes a “critical change” by stimulation, and for example, a sol-gel change due to temperature is caused as a preferable change. Further, it is described that the temperature causing the critical change is about 20 ° C. for polyethoxyethyl vinyl ether and about 70 ° C. for polymethoxyethyl vinyl ether.
: JP-A-06-157589 : JP 2003-119342 A : Japanese Unexamined Patent Application Publication No. 2007-23297.

  However, it is essential that the composition using the block polymer described in Patent Documents 2 and 3 is a composition that contains a block polymer, a solvent, and a coloring material to form a micelle, and the block polymer is ABC type. It is preferable that. Further, there is no description of an ABA triblock polymer that becomes a heat-sensitive aqueous solution or water dispersion by itself without requiring the third component. Further, there is no description of using such an ABA triblock polymer as a thickener in so-called water-based paints.

  An ABA triblock polymer having heat sensitivity and water solubility at room temperature and an aqueous coating composition containing it as a thickener are obtained.

As a result of intensive studies, the inventors have found that an ABA triblock polymer in which the A block segment has a lower critical solution temperature (LCST) and is soluble in water at room temperature, and the aqueous solution has high fluidity at room temperature. It has been found that when heated, it is dramatically in a state of no viscosity to fluidity, and it can be used as a heat-responsive thickener in water-based paints. That is, the present invention
1. A polymer having a lower critical solution temperature with respect to water of 40 ° C. or higher and lower than 80 ° C., a polymer having a lower critical solution temperature that is 20 ° C. higher than the A block, or a polymer that dissolves in water at any temperature of 100 ° C. or lower. An ABA triblock polymer consisting of a certain B block, wherein the starting monomers of the A block and B block are vinyl ether structures.
2. Item 2. The ABA triblock polymer according to Item 1, wherein the molecular weights of both the A block and the B block are 4000 or more.
3. Item 3. The ABA triblock polymer according to Item 1 or 2, wherein the ABA triblock polymer is synthesized by a living cationic polymerization method using a bifunctional initiator.
4). Heat sensitive responsive thickening that is water-soluble at room temperature, and that the A block is hydrophobized by raising the temperature above the lower critical solution temperature of the A block to form a network due to hydrophobic interaction, thereby increasing the viscosity of the liquid. Item 3. An aqueous solution or dispersion of an ABA triblock polymer according to Item 1 or 2, which exhibits behavior.
5. An aqueous coating composition comprising the aqueous solution or dispersion of the ABA triblock polymer according to claim 4. Is disclosed.

  The triblock polymer of the present invention has a very simple structure and is easy to manufacture. Moreover, the thickener which melt | dissolved it in water has heat-sensitive response by itself.

  In addition, since the lower critical solution temperature can be adjusted by selecting the monomer of the A block, the triblock polymer of the present invention can be used by designing the thickening temperature according to the use conditions.

  By using the aqueous solution or aqueous dispersion of the triblock polymer of the present invention as a thickener in a water-based paint, it is possible to suppress secondary sagging that has been a problem in the past with a bake-curing-type water-based paint. Can be greatly improved.

  Hereinafter, the ABA triblock polymer of the present invention will be described in detail.

ABA triblock polymer
The ABA triblock polymer (hereinafter sometimes referred to as “triblock polymer”) used in the present invention is synthesized using a vinyl ether structure monomer as a starting monomer, and has a lower critical solution temperature of 40 ° C. or higher with respect to water. An ABA triblock polymer comprising a polymer A block and a polymer having a lower critical solution temperature 20 ° C. or higher than the A block or a B block which is a water-soluble polymer.

A block:
The A block is a polymer that is water-soluble at room temperature (usually higher than 20 ° C. and lower than 35 ° C. as an aqueous solution temperature) and becomes hydrophobic at the lower critical solution temperature (40 ° C. or more and less than 80 ° C.). As a vinyl ether monomer exhibiting such characteristics as a single homopolymer, for example, 2-methoxyethyl vinyl ether (lower critical solution temperature is 63 ° C.) can be mentioned as a preferable one. A block having a desired lower critical solution temperature is synthesized as long as it satisfies the condition that the A block is hydrophilic at room temperature and becomes hydrophobic and precipitates at the lower critical solution temperature (40 ° C. or more and less than 80 ° C.). In combination with other hydrophilic vinyl ether monomers such as p-methoxytriethylene glycol vinyl ether (lower critical solution temperature is 90 ° C.), and highly hydrophobic monomers such as isobutyl vinyl ether and 2-ethoxyethyl vinyl ether It may be used.

B block:
On the other hand, the B block is a polymer having a lower critical solution temperature that is 20 ° C. or more higher than the lower critical solution temperature of the A block, or a so-called water-soluble polymer that dissolves in water at an arbitrary temperature of 100 ° C. or less. As the vinyl ether monomer, any homopolymer alone having such characteristics can be used without any problem. For example, examples of the water-soluble monomer include 2-hydroxymethyl vinyl ether, 2-hydroxyethyl vinyl ether, and the like, and vinyl alcohol can also be used as the vinyl ether in a broad sense. Incidentally, these monomers can also be regarded as monomers whose lower critical solution temperature is so high that it cannot be measured without thermal decomposition of the polymer. Even a monomer having a lower critical solution temperature can be used alone if the lower critical solution temperature is 20 ° C. or more higher than that of the A block. For example, when 2-methoxyethyl vinyl ether (lower critical solution temperature is 63 ° C.) is used for the A block, p-methoxytriethylene glycol vinyl ether (lower critical solution temperature is 90 ° C.) can be used for the B block. . Further, the lower critical solution temperature can be set to a higher temperature by copolymerizing these monomers and the above-mentioned water-soluble monomers. In these cases, the B block is hydrophilic at room temperature and becomes hydrophobic and precipitates at a temperature 20 ° C. higher than the lower critical solution temperature (40 ° C. or higher) of the A block.

  In short, the triblock polymer used in the present invention may be a single constituent monomer or a combination of two or more types as long as the affinity for water satisfies the essential properties described above. In particular, the combination of a plurality of vinyl ether monomers in both the A block and the B block is preferable because the lower critical solution temperature can be set to a desired temperature according to the application.

  Moreover, in such an ABA triblock polymer, the size of each block (= block molecular weight) is preferably 4000 or more, and it is more preferable that there is no difference between the molecular weight of the A block and the molecular weight of the B block. If the molecular weights of the A block and B block are less than 4000, sufficient viscosity may not be obtained at a temperature exceeding the lower critical solution temperature of the A block. In addition, when there is a large difference in molecular weight between the B block and the A block, the effect of developing the viscosity may be small.

  In the ideal living polymerization, the molecular weight of the polymer to be produced = number average molecular weight = weight average molecular weight, but in reality, a slight molecular weight distribution is generated and the number average molecular weight ≦ weight average molecular weight is often obtained. In the present specification, unless otherwise specified, “molecular weight” indicates a number average molecular weight.

  The triblock polymer of the present invention is dissolved in water to form an aqueous solution at room temperature due to the solubility effect of the A block and B block. When the concentration of the triblock polymer is above a certain level, the aqueous solution of this triblock polymer becomes hydrophobic when the liquid temperature is higher than the lower critical solution temperature of the A block, which is 40 ° C. or higher. A partial aggregation structure is formed by the action, and the polymers form a network in water. Therefore, this triblock polymer aqueous solution or aqueous dispersion becomes very viscous (that is, acts as a thickener).

  At this time, it seems that the molecular weight of the A block needs to be larger than a certain level in order to aggregate from the dissolved state and develop a hydrophobic interaction. In the present invention, the thickening effect is observed when the molecular weight of the A block is 4000 or more. It was done.

  If the B block has a lower critical solution temperature that is 20 ° C. or more higher than the lower critical solution temperature of the A block, the liquid is further raised by 20 ° C. or more by heating or the like, so that it is higher than the lower critical solution temperature of the B block. By increasing the temperature, the B block also loses solubility and aggregates. For this reason, the network formed by the partially aggregated structure of the A block disappears, and the fluidity of the liquid becomes high again.

  Here, the lower critical solution temperature of the A block and the B block can be set to a desired temperature by combining the lower critical solution temperature with known monomers. However, the lower critical solution temperature of the polymer is additive but not linear, so the composition that gives the desired lower critical solution temperature is determined by copolymerizing multiple monomers in advance and measuring the lower critical solution temperature. It takes time and effort. However, the lower critical solution temperatures of the A block and the B block can be freely set thereby, and the use range of the triblock polymer is greatly expanded.

  A block or B block may be formed by copolymerization. As a method of determining the lower critical solution temperature of the block in such a case, the viscosity of the dilute aqueous solution of the copolymer itself constituting the block is about 1 to 5% by mass from room temperature using a temperature variable viscosity measuring device. The temperature is measured while the temperature is increased, and the temperature at which the viscosity rapidly decreases, that is, the peak temperature of the differential viscosity curve can be determined as the lower critical solution temperature. As a simpler method, the transparency of the aqueous solution can be visually confirmed while raising the temperature, and the cloud point temperature (the liquid becomes cloudy due to the aggregation of the polymer) can be set as the lower critical solution temperature.

  Thus, ABA triblock polymer consisting of A block with lower critical solution temperature and B block with lower critical solution temperature or water-soluble has high fluidity at room temperature when diluted in water, and viscosity greatly increases with increasing liquid temperature. When the B block also has a lower critical solution temperature, it acts as a heat-responsive thickener composition whose fluidity is increased again by further heating.

Synthesis method of triblock polymer
The triblock polymer of the present invention can be synthesized without any problem as long as it is a method capable of synthesizing the block polymer, but it is preferably synthesized by a living cationic polymerization method from the viewpoint of simplicity of the procedure and stability of the process.

The method of synthesizing the triblock polymer of the present invention by the living cationic polymerization method can be appropriately carried out according to the book. For example, in “Chapter 2.5 Cationic Polymerization” in “Experimental Chemistry Course Vol. 26 Polymer Chemistry (5th Edition)” (edited by the Chemical Society of Japan, published by Maruzen Co., Ltd.) Eight cases are introduced. In the case of the ABA triblock polymer of the present invention, the method described in Non-Patent Document 3 or 4 by the inventors of the present invention uses a bifunctional initiator to form a B trunk polymer having growth ends at both ends. This is a method of synthesizing and then growing the A block on both sides at the same time, which is reasonable and preferable because block polymerization can be completed in two stages.
： Hirahara et al., Polymer Preprints, Japan., 53, p416 (2004) Hirahara et al., Polymer Preprints, Japan., 54, p421 (2005) At this time, the molecular weight of the A block and the B block can be determined by gel exclusion chromatography (GPC). That is, the reaction solution obtained by extracting a small amount of the molecular weight of only the B block is polymerized with methanol and subjected to GPC measurement using tetrahydrofuran as a developing solvent to determine the number average molecular weight Mn and the molecular weight distribution (Mw / Mn). Next, the same value is measured for the triblock polymer after A blocks are formed on both ends. The molecular weight of the A block can be calculated by the following formula 1. (Mn measured later-Mn of B block measured earlier) / 2 (Formula 1) Note) "HLC8120GPC" (manufactured by Tosoh Corporation) was used for GPC measurement. As the columns, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (both manufactured by Tosoh Corporation, trade name) were used, Mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: RI.

  The molecular weight of the triblock polymer is preferably 12,000 to 500,000, more preferably 20,000 to 200,000. If it is smaller than 12000, the thickening effect may be small, and if it is larger than 500,000, it may not be sufficiently dissolved or dispersed in water at room temperature.

  In synthesizing a triblock polymer, when a plurality of monomers are copolymerized with a living cation in order to obtain a desired lower critical solution temperature as an A block and / or a B block, appropriate measures are required. In living cationic polymerization, the structure selectivity of a monomer newly added to an active terminal coordinated with a counter ion is very high. When the entire monomer mixture is charged and polymerized, a random copolymer polymer corresponding to the mixing ratio of the monomers can be obtained by ordinary radical copolymerization, but in the case of ionic copolymerization, particularly living cation copolymerization, the same monomer There may occur a case where the polymer has a long sequence and a structure with a high blocking property and exhibits a plurality of lower critical solution temperatures instead of the desired single lower critical solution temperature or does not clearly indicate the lower critical solution temperature. In order to obtain a copolymer chain in which the monomers are sufficiently mixed, the monomers are not added all at once as in the usual living cationic polymerization, but the monomer mixture is dropped little by little to extend the copolymerized chain little by little. It is preferable to take a method. A block having a desired lower critical solution temperature can be synthesized by adding such a device to the synthesis method.

How to use thermosensitive thickener composition
The heat-responsive thickener comprising the ABA triblock polymer of the present invention is a liquid having a high fluidity at room temperature, and is heated or touched to a high temperature part to cause hydrophobic interaction. Since it thickens by pseudo gelation, it can be used as an emergency treatment for burns, for example, by containing a drug. It can also be used as a hair dryer treatment as a cosmetic.

As a particularly preferred application, an aqueous solution or aqueous dispersion of this triblock polymer (which may contain a pigment, a surfactant or the like) may be added to a general baking curable aqueous paint, which may be either a one-pack type or a two-pack type. As the sticking agent, it is preferable to add 0.1 to 20 parts of triblock polymer as a solid content with respect to 100 parts by weight of the binder solid content of the paint.
The water-based paint blended with the triblock polymer of the present invention has a low viscosity of the paint at the time of painting and after painting when applied at room temperature, and therefore can form a smooth coating surface with excellent flowability of the coating film, A process of raising the temperature for baking at a temperature sufficiently higher than 40 ° C. (120 ° C. to 200 ° C., in particular, often 120 ° C. to 150 ° C. in general baking-curable water-based paints). Thus, the viscosity rises before and after the temperature set as the lower critical solution temperature of the A block, so that the flow of the applied paint, so-called “secondary sagging” can be prevented, and a highly finished coating surface can be obtained.

  The water-based paint described here contains the organic solvent, extender pigment, color pigment, glittering material, catalyst, and various additives that are commonly used in paints in addition to the binder that is the main ingredient and water that is the diluent. It may be included.

  The binder is a general term for a base resin and a curing agent. As the base resin, acrylic resin, polyester resin, alkyd resin, urethane resin or the like is used. These resins have a reactive functional group that can be subjected to a crosslinking reaction with the curing agent. As such a reactive functional group, a hydroxyl group is the most common, but other examples include a carboxy group, a carboxylic acid group, an oxirane group, and an amino group.

  The curing agent is a generic term for substances capable of undergoing a crosslinking reaction with the reactive functional group. The curing agent may be a relatively low molecular weight compound or a resin. Examples of the curing agent that reacts with a hydroxyl group include melamine compounds or melamine resins, polyisocyanates, epoxy resins, and resins having alkoxysilyl groups. Curing agents that react with carboxy groups include hydrazine or hydrazides, curing agents that react with carboxylic acid groups include epoxy resins, and curing agents that react with oxirane groups react with polycarboxylic acid compounds and polyamines with amino groups. A typical example of the curing agent is an epoxy resin.

  Additives include coating surface conditioners, light absorbers, antioxidants, dispersants, fungicides, and anti-sagging agents. If the water-based paint does not contain or contain a color pigment, it is a very small amount and the coating film shows transparency, clear paint, if it contains a color pigment, enamel paint, glittering material (and color pigment if necessary) ) Is sometimes called metallic paint.

  As described above, by including the ABA triblock polymer of the present invention, it is possible to obtain a water-based paint having both coating workability and finished surface finish.

  As described above, the ABA triblock polymer of the present invention can impart a preferable temperature / viscosity characteristic to various household goods as a thermosensitive thickener. In particular, by containing it, an aqueous coating composition having both coating workability and finished surface finish can be obtained.

Hereinafter, the present invention will be described in more detail with reference to synthesis examples, examples and comparative examples. However, the present invention is not limited by these. “Part” and “%” are both based on mass.

Synthesis of ABA triblock polymer
Starting monomer
2-Ethoxyethyl vinyl ether (hereinafter abbreviated as EOVE), 2-methoxyethyl vinyl ether (hereinafter abbreviated as MOVE), and p-methoxytriethylene glycol vinyl ether (hereinafter abbreviated as TEGMEVE) were obtained from Maruzen Petrochemical Co., Ltd. A thing was used.
solvent
Commercial solvents such as hexane, toluene, methanol, dichloromethane, etc. were used for the synthesis.
Raw material pretreatment
All the monomers and solvents used in the synthesis were dehydrated with molecular sieves (monomers, nonpolar solvents) or calcium chloride (methanol) and then purified by distillation.

Preparation of polymerization starting seed solution
The polymerization starting species was synthesized by reacting 1 mol of cyclohexanedimethanol divinyl ether (manufactured by Nippon Carbide Industries Co., Ltd., trade name CHDVE) and 4 mol of acetic acid at 60 ° C. for 8 hours. Excess acetic acid was distilled off under reduced pressure, and polymerization initiation seed 1 was obtained by recrystallization from hexane. The polymerization initiating species 1 was sufficiently dried under reduced pressure and then diluted with toluene to give a 40 mM / L solution for use in the synthesis of the ABA triblock polymer.

Preparation of polymerization initiator solution
Ethyl aluminum sesquichloride as a polymerization initiator was diluted with toluene immediately before use without purification of the trade name EASC manufactured by Nippon Alkyl Aluminum Co., Ltd., and cooled to 0 ° C. to obtain a 1 M / L solution. And used for the synthesis of ABA triblock polymer.

Synthesis of ABA triblock polymer ABA triblock polymer with reference to “Chapter 2.5 Cationic Polymerization” of “Experimental Chemistry Course Vol. 26 Polymer Chemistry (5th Edition)” (edited by Chemical Society of Japan, published by Maruzen Co., Ltd.) Synthesized.

Production Example 1
MOVE-TEGMEVE-MOVE triblock polymer
A glass reaction vessel equipped with a stirrer and thermometer and sufficiently heated and dried to remove adsorbed water was purged with nitrogen, and then 51.3 g of toluene, 8.8 g of ethyl acetate, 19.0 g of TEGMEVE (100 mM), polymerization started 10.0 ml of seed solution (0.4 mM of starting seed) was added and cooled to 0 ° C. with good stirring. Polymerization was started by adding 2.0 ml of 1M-EASC solution (2.0 mM ethylaluminum sesquichloride), and the reaction was allowed to proceed by stirring at 0 ° C. for 3 hours to synthesize B component of the ABA triblock polymer. A part of the solution in the middle of the reaction was extracted and injected into a large amount of 0.3 wt% methanol solution of ammonia to stop the reaction, and GPC measurement was used to trace changes in the reaction rate and molecular weight of TEGMEVE. At the time when 90 mol% or more of TEGMEVE was consumed (the number average molecular weight of the B component at this time was 47000), 16.3 g (160 mM) of A component was added, and further at 24 ° C. for 21 to 24 hours. The reaction was allowed to proceed with stirring. When the MOVE was consumed, 80 ml of a 0.3 wt% methanol solution of ammonia was added and the mixture was vigorously stirred to terminate the polymerization. Diluted by adding dichloromethane to the mixed solution after stopping the reaction, 3 times with 0.6 N hydrochloric acid, 1 time with deionized water, 1 time with 0.5 N aqueous sodium hydroxide solution, 3 times with deionized water Washed in this order. Subsequently, the volatile matter was distilled off under reduced pressure to obtain a target MOVE-TEGMEVE-MOVE triblock polymer (Polymer 1). The molecular weight and molecular weight distribution of the obtained polymer were measured by GPC. Mn was 88000, Mw was 110000, and Mw / Mn was 1.25.

Production Example 2
MOVE-TEGMEVE-MOVE triblock polymer
A glass reaction vessel equipped with a stirrer and a thermometer and sufficiently heated and dried to remove adsorbed water was purged with nitrogen, and then 52.2 g of toluene, 8.8 g of ethyl acetate, TEGMEVE 38.0
g (200 mM) and 10.0 ml of the polymerization initiating seed solution (0.4 mM initiating seed) were added, and the mixture was cooled to 0 ° C. with good stirring. The polymerization was started by adding 2.0 ml of 1 M-EASC solution (2.0 mM ethylaluminum sesquichloride), and the reaction was allowed to proceed by stirring at 0 ° C. for 3 hours to synthesize B component of the ABA triblock polymer. A part of the solution in the middle of the reaction is extracted, a part of the solution in the middle of the reaction is extracted, and the reaction is stopped by injecting a large amount of ammonia into a 0.3 wt% methanol solution, and the reaction rate of MOVE using GPC measurement And the change of molecular weight was followed. At the time when 90% by mole or more of MOVE was consumed (the number average molecular weight of the B component was 97000 at this time), 8.2 g (80 mM) of the A component was added, and further at 23 ° C. for 23 to 23 hours. The reaction was allowed to proceed with stirring. When MOVE was consumed, 120 ml of a 0.3 wt% methanol solution of ammonia was added and the mixture was vigorously stirred to terminate the polymerization. Diluted by adding dichloromethane to the mixed solution after stopping the reaction, 3 times with 0.6 N hydrochloric acid, 1 time with deionized water, 1 time with 0.5 N aqueous sodium hydroxide solution, 3 times with deionized water Washed in this order. The volatile matter was then distilled off under reduced pressure to obtain the target product, MOVE-TEGMEVE-MOVE triblock polymer (Polymer 2). The molecular weight and molecular weight distribution of the obtained polymer were measured by GPC. Mn was 119000, Mw was 150,000, and Mw / Mn was 1.26.

Production Examples 3 to 10
Polymers 3 to 10 were obtained in the same manner as in Production Examples 1 and 2 except for the blending amounts and reaction time shown in Table 1.

  The properties of the produced ABA block polymer are shown in Table 2.

Evaluation of thermal sensitivity
Production of emulsion In a 4-neck flask with a capacity of 2 liters, 38.5 parts of deionized water and 0.1 part of Newcol 707SF (manufactured by Nippon Emulsifier Co., Ltd., an anionic surfactant having a polyoxyethylene chain, non-volatile content of 30%) were added. In addition, after nitrogen substitution, the temperature was kept at 85 ° C. In this, 52.3 parts of deionized water, 30 parts of methyl methacrylate, 10 parts of styrene, 20 parts of n-butyl acrylate, 30 parts of 2-ethylhexyl acrylate, 10 parts of hydroxyethyl acrylate, 1.6 parts of Newcol 707SF are emulsified. Add 3% of the pre-emulsion and 25% of 10.4 parts of a solution of 0.4 parts of ammonium persulfate in 10 parts of deionized water, 20 minutes after the addition, the remaining pre-emulsion and the remaining An aqueous ammonium persulfate solution was added dropwise over 4 hours. After completion of the dropping, this was further maintained at 85 ° C. for 2 hours, and then allowed to cool to room temperature to obtain an acrylic resin emulsion I having a solid content of 50%.

Example 1
1.5 g of the polymer 1 obtained in Production Example 1 was dissolved in 17.0 g of deionized water to obtain a transparent and viscous solution 1 at room temperature. The emulsion 1 of Example 1 was obtained by adding all of Solution 1 to 100 g of Emulsion I obtained above and mixing well.

Examples 2-6 and Comparative Examples 1-4
Except for the formulation shown in Table 3, the emulsion compositions of Examples 2 to 7 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 above.

Comparative Example 4
Comparative Example 4 was prepared by adding 1.6 g of commercially available urethane-associated reocon agent “Adecanol UH-756VF” (manufactured by ADEKA, 32% aqueous solution) and 13.2 g of deionized water to 100 g of Emulsion I.

Comparative Example 5
Comparative Example 5 was obtained by adding only 13.6 g of deionized water to 100 g of Emulsion I.

Evaluation of thermal sensitivity
About Examples 1-7 and Comparative Examples 1-5, the temperature change of the viscosity was measured and the thermal sensitivity was evaluated. Viscosity was measured using a cone and plate viscometer “Rheostress RS150” (trade name, manufactured by HAAKE) at a shear rate of 5 sec ⁻¹ (30 ° C., 50 ° C., 70 ° C.). Table 4 shows the thermal response thickening evaluation (below) along with the value of viscosity (Pa · sec) at each temperature.
○: There is an increase in viscosity between 30 ° C and 50 ° C or between 50 ° C and 70 ° C.
X: The viscosity decreases as the temperature increases.

Evaluation of water-based paint
Production of water-based paint Examples 8-14 and Comparative Examples 6-10
Instead of Emulsion I in Table 3 above, a baking-curing water-based enamel paint “Asuka Bake TW-400 Black” (manufactured by Kansai Paint Co., Ltd., water-based emulsion paint, acrylic resin / melamine resin system) to a solid content concentration of 50% Aqueous paints of Examples 8 to 14 and Comparative Examples 6 to 10 were produced in the same manner as in Examples 1 to 7 and Comparative Examples 1 to 5 except that 100 g of the prepared product was used.

Evaluation of paint workability and surface finish
As an object to be coated, a cold-rolled steel sheet (size: 7.5 × 15 × 0.2 cm) surface-treated with “Palbond # 3030” (manufactured by Nihon Parkerizing Co., Ltd., zinc phosphate type), “Electron No. 9200 "(manufactured by Kansai Paint Co., Ltd., epoxy-based cationic electrodeposition paint) is electrodeposited so as to have a dry film thickness of 20 μm, and further on this," Amilak N-2 Sealer "(manufactured by Kansai Paint Co., Ltd., Aminopolyester resin-based intermediate coating material) coated with 30 μm was used. Furthermore, the colored paints of Examples and Comparative Examples were electrostatic spray-coated in an environment where the viscosity was adjusted to about 30 seconds (Ford Cup # 4, 20 ° C.) and the relative humidity was 70% at a temperature of 25 ° C. did. The coating film thickness was 45 ± 5 μm based on the cured coating film.
The coated plate was left horizontally and pre-dried at 80 ° C. for 5 minutes. Then, it fixed to the state which stood 70-80 degree | times from the horizontal surface using the coating plate stand, and baked for 20 minutes at 150 degreeC using the hot air dryer. The sagging property and finish of the coated plate after baking were evaluated.

Sauce
○: There is no sagging mark on the coated surface, and it is cured uniformly.
X: Sagging occurs on the painted surface.

Finish
○: The coated surface is free from turbidity, flares and irregularities, and is finished well.
X: The coating surface is turbid or has any flaming or unevenness, resulting in poor finish.
In addition, the thing with sagging property x was not evaluated.

  The evaluation results are shown in Table 6.

Claims (5)

A polymer having a lower critical solution temperature with respect to water of 40 ° C. or higher and lower than 80 ° C., a polymer having a lower critical solution temperature that is 20 ° C. higher than A block, or a polymer that is soluble in water at any temperature of 100 ° C. or lower. An ABA triblock polymer consisting of a certain B block, wherein the starting monomers of the A block and B block are vinyl ether structures. The ABA triblock polymer according to claim 1, wherein the molecular weights of both the A block and the B block are 4000 or more. The ABA triblock polymer according to claim 1 or 2, wherein the ABA triblock polymer is synthesized by a living cationic polymerization method using a difunctional initiator. Heat sensitive responsive thickening that is water-soluble at room temperature, and that the A block is hydrophobized by raising the temperature above the lower critical solution temperature of the A block to form a network due to hydrophobic interaction, thereby increasing the viscosity of the liquid. An aqueous solution or dispersion of an ABA triblock polymer according to claim 1 or 2, characterized in that it exhibits behavior. An aqueous coating composition comprising the aqueous solution or dispersion of the ABA triblock polymer according to claim 4.