JP5128966B2 - A heat-responsive ABA triblock polymer and an aqueous coating composition containing the same. - Google Patents

Description

The present invention relates to an ABA triblock polymer that can be used as various functional materials and that is heat-responsive and can be dissolved or dispersed in water at room temperature, and an aqueous coating composition containing it as a thickener.
In particular, according to the present invention, the block segment of the ABA triblock polymer has a lower critical solution temperature (LCST), so that it is not viscous to fluid at room temperature and dramatically fluidized by heating. The present invention relates to an aqueous coating composition using the polymer as a thickener by utilizing the property of increasing the viscosity.

  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 poly-2-ethoxyethyl vinyl ether and about 70 ° C. for poly-2-methoxyethyl 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-soluble or water-dispersible 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 B block segment has a lower critical solution temperature (LCST) and can be dissolved or dispersed in water at room temperature is viscous to fluid at room temperature. It has been found that it can be used in water-based paints as a heat-sensitive thickener that is in a non-existent state and dramatically increases its fluidity upon heating. That is, the present invention
1. A block length of the A block is 1/5 or less of the block length of the B block, and the lower critical solution temperature for water is 20 ° C. or lower. ℃ consists in is cold water soluble or water-dispersible polymer a is B block over the molecular weight of a ABA triblock polymer of 7000 to 500,000, starting monomers of the a block and the B block is a vinyl ether structure, B The block is made of polyvinyl ether, an ABA triblock polymer.
2. The ABA triblock polymer according to claim 1 , wherein the ABA triblock polymer is synthesized by a living cationic polymerization method using a bifunctional initiator.
3. Acts as an associative thickener having a hydrophobic-water-soluble-hydrophobic structure at room temperature, and when the temperature rises above the lower critical solution temperature of the B block, the entire polymer changes to hydrophobic and the viscosity decreases. The aqueous solution or aqueous dispersion of the ABA triblock polymer according to claim 1, wherein the ABA triblock polymer exhibits a heat-sensitive response behavior.
4). An aqueous coating composition comprising the aqueous solution or aqueous dispersion of the ABA triblock polymer according to claim 3 .

  The triblock polymer of the present invention has a very simple structure and is relatively easy to manufacture. Further, a thickener obtained by dissolving or dispersing it in water has a heat-sensitive response, and can be used for a heat transfer fluid, a heat medium (for example, a heat-filling agent for a warm ship pad), and the like.

  Further, since the lower critical solution temperature of the triblock polymer of the present invention can be adjusted by selecting the monomer of the B block, for example, a mixture containing the aqueous dispersion is a jelly-like or viscous liquid at room temperature, It can be designed to exhibit characteristics that dramatically increase fluidity at a relatively low desired temperature that is slightly higher than body temperature.

  By adding such a thickener to foods such as baby food for infants and nutritional food for nursing care, it can be easily absorbed and ingested. Moreover, by adding to a chemical | medical agent, it can be set as the oral chemical | drug | medicine which is easy to take, or the patch and wound disinfectant with good skin absorbability.

  In addition, when the lower critical solution temperature is set to a relatively high temperature, it can be added to cosmetics to make it difficult to leave makeup, and it can be easily removed by washing your face with hot water, It can also be used as a detergent for dwelling and water around like mold remover that wants to stay on the treated surface for a long time.

  And by blending the aqueous solution or aqueous dispersion of the triblock polymer of the present invention as a thickener in the aqueous paint, the viscosity of the applied paint is high when applied at room temperature, and the coating film slips down on the vertical surface. The so-called “sagging” is prevented, and by increasing the temperature, the fluidity of the surface is smoothed due to a sudden drop in viscosity before and after the desired temperature. It eliminates the fine “spray eyes” in spray coating and the “vortex pattern” that is a slightly large uneven pattern caused by the volatilization of the solvent, and obtains a highly finished coating surface. Thus, it is possible to achieve both painting workability and finished surface finish.

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

Triblock polymer
The triblock polymer used in the present invention is synthesized using a monomer having a vinyl ether structure as a starting monomer, and is a polymer having a lower critical solution temperature (LCST) of 20 ° C. or lower with respect to water. It is an ABA triblock polymer comprising an A block which is a hydrophobic polymer and a B block which is a polymer having a lower critical solution temperature of 40 ° C. or higher with respect to water.

A block:
The A block is hydrophobic at room temperature (the temperature of the aqueous solution is higher than 20 ° C. and lower than 35 ° C.). Here, even if the A block has a lower critical solution temperature, the temperature is 20 ° C. or less, and the block is hydrophobic at room temperature. As the constituent monomer, any monomer that exhibits such properties as a single polymer can be used without any problem, and typical examples thereof include various known monomers such as styrene. In the present invention, stable living cations are used. Use of vinyl ether monomer exhibiting polymerizability, among them, isobutyl vinyl ether (non-water-soluble = hydrophobic), 2-ethoxyethyl vinyl ether (lower critical solution temperature is 20 ° C., hydrophobic at higher solution temperature) Can be mentioned as preferred. In addition, water-soluble monomers such as hydroxymethyl vinyl ether and 2-hydroxyethyl vinyl ether and vinyl alcohol as a water-soluble monomer in a broad sense are combined with the above-mentioned monomers such as isobutyl vinyl ether and 2-ethoxyethyl vinyl ether. If the synthesized A block exhibits hydrophobicity at room temperature, it can be used in the quantitative range.

B block:
On the other hand, the B block is hydrophilic at room temperature and becomes hydrophobic and precipitates at the lower critical solution temperature (40 ° C. or higher). Examples of vinyl ether monomers that exhibit such properties alone include 2-methoxyethyl vinyl ether (lower critical solution temperature is 63 ° C.), p-methoxytriethylene glycol vinyl ether (lower critical solution temperature is 90 ° C.), and the like. It can be mentioned as preferable.
In order to synthesize a B block having a desired lower critical solution temperature, as long as it satisfies the condition that the B block is hydrophilic at normal temperature and becomes hydrophobic and precipitates at the lower critical solution temperature (40 ° C. or higher). Hydrophobic monomers such as vinyl ether and 2-ethoxyethyl vinyl ether (having the effect of lowering the lower critical solution temperature) and water-soluble monomers such as 2-hydroxymethyl vinyl ether, 2-hydroxyethyl vinyl ether and vinyl alcohol may be used in combination. Good (water-soluble monomers have the effect of raising the lower critical solution temperature).

  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 as the B block is preferable because the lower critical solution temperature can be set to a desired temperature according to the application.

  Further, in the ABA triblock polymer, the size of each block (hereinafter referred to as the block length. This is the number of monomers constituting the block) is the sum of the block lengths of the A blocks at both ends than the block length of the B block. It is preferable to be small, and it is more preferable that the sum of the block lengths of the A blocks is 1/5 or less of the block length of the B blocks. Thus, since the size of the B block is large with respect to the A block, the affinity of the triblock polymer for water is superior to the characteristics of the B block.

  The triblock polymer of the present invention dissolves or disperses in water at room temperature due to the solubility effect of the B block. At this time, when the concentration of the triblock polymer is more than a certain level, the A blocks exhibiting hydrophobicity have a partially aggregated structure due to hydrophobic interaction with each other, and the polymers form a network in water. Therefore, this triblock polymer aqueous solution or aqueous dispersion becomes very viscous at room temperature (that is, acts as a thickener).

  By raising the liquid temperature by heating or the like to a temperature higher than the lower critical solution temperature of the B block, the B block loses solubility and aggregates. For this reason, the network formed by the A block having a partially aggregated structure as a chain portion obtained by extending the B block, which has been formed at room temperature, disappears, and the viscosity of the liquid decreases and the fluidity increases.

  Here, the lower critical solution temperature of 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 temperature of the B block can be freely set by this, and the range of use of this triblock polymer is greatly expanded.

  As a method for determining the lower critical solution temperature, the viscosity of a dilute polymer aqueous solution having a concentration of about 1 to 5% by mass is measured while raising the temperature from room temperature using a temperature variable viscosity measuring device, 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, when diluted in water, the ABA triblock polymer of the present invention acts as a thickener at room temperature, and acts as a thermosensitive thickener whose viscosity is greatly reduced by increasing the liquid temperature.

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 performed according to the book. For example, in “Chapter 2.5 Cationic Polymerization” of “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).

The characteristic of living cationic polymerization is the number of moles of polymerization initiating species = the number of moles of the polymer to be produced, and all the produced polymers have the same block length (= molecular weight).
The block lengths of the A block and the B block are determined by the number of moles of the polymerization initiating species and the number of moles of monomers used for the A block and the B block. That is,
Block length of A block = Na / 2Ni (Formula 1)
Here, Na is the total number of moles of the A block monomer charged at the time of synthesis, and Ni is the number of moles of the bifunctional initiator. The sum of the block lengths of the A blocks at both ends of the ABA triblock polymer is Na / Ni.
On the other hand, the block length of the B block = Nb / Ni (Formula 2)
Here, Nb is the total number of moles of the B block monomer charged at the time of synthesis.

  As described above, in the ABA triblock polymer of the present invention, the B block is preferably larger than the A block, and the block length of the B block is more preferably 5 times or more the sum of the block lengths of the A block. For example, when there are A blocks each having a block length of 10 at both ends, the sum of the block lengths of the A blocks is 20, and the block length of the B block is preferably 20 or more, more preferably 100 or more.

  The molecular weight of the ABA triblock polymer of the present invention can be determined by gel exclusion chromatography (GPC). That is, the living polymerization reaction solution is terminated with methanol, GPC is measured using tetrahydrofuran as a developing solvent, and the average molecular weight Mn and the molecular weight distribution (Mw / Mn) are determined.

  In the examples of the present invention, “HLC8120GPC” (manufactured by Tosoh Corporation) is used, and the columns are “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, “TSKgel G-2000HXL” (all Also, GPC measurement was performed under the conditions of mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 ml / min, detector: RI.

  The molecular weight of the triblock polymer is preferably from 7,000 to 500,000, more preferably from 15,000 to 200,000. If it is less than 7000, the thickening effect may be small, and if it is more than 500,000, it may not be sufficiently dissolved or dispersed in water at room temperature.

  When synthesizing a triblock polymer, if a plurality of monomers are to be copolymerized with a living cation in order to obtain a desired lower critical solution temperature as the 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 ordinary living cationic polymerization, but the monomer mixture is dropped little by little and the copolymerized chain is extended little by little. It is preferable to take a method. By adding such a device to the synthesis method, it is possible to synthesize a B block having a desired lower critical solution temperature.

How to use thermosensitive thickener
The heat-responsive thickener comprising the ABA triblock polymer of the present invention is a jelly-like or viscous liquid at room temperature, and the mixture in which it is added is added to foods such as baby food for infants and nutritional food for care can do. In this case, a food or nutritional substance that is water-soluble and / or stably dispersed in water may be mixed in an aqueous solution or aqueous dispersion of ABA triblock polymer as a heat-responsive thickener. It can also be used as a drug, and the drug may be mixed in advance with an aqueous solution or aqueous dispersion of an ABA triblock polymer as a heat-responsive thickener.

  In addition, since it can be used in cosmetics or as a detergent, a pigment, a surfactant, or the like may be mixed in an aqueous solution or aqueous dispersion of an ABA triblock polymer as a heat-responsive thickener.

A particularly preferred use of the ABA triblock polymer is to use an aqueous solution or an aqueous dispersion of this ABA triblock polymer (which may be mixed with a pigment, a surfactant, etc.) as a thickener in an aqueous coating material. By blending 0.1 to 20 parts of this triblock polymer as a solid content with respect to 100 parts by weight of the binder solid content of the paint, the viscosity of the applied paint is high when applied at room temperature, and it is applied on the vertical surface. It is possible to prevent so-called “sag” that the film is slipped off.
When drying or heating, the surface is smoothed due to a sudden drop in viscosity before and after the desired temperature when the temperature is raised, and "brush eyes" during brush painting, "roller eyes" during roller coating, spray It eliminates the fine “spray eyes” in painting and the “vortex pattern” that is a slightly large uneven pattern caused by solvent volatilization, resulting in a highly finished coating surface. In this way, it is possible to obtain a water-based paint that achieves both coating workability and finished surface finish. At this time, the base water-based paint may be a one-pack type or a two-pack type, and may be a lacquer type or a thermosetting type.

  In addition to water, which is a binder and diluent, water-based paints contain organic solvents, extender pigments, colored pigments, glittering materials, catalysts, and various additives that are commonly used as paints. Also good. Here, the additive includes a coating surface conditioner, a light absorber, an antioxidant, a dispersant, a fungicide, a sagging inhibitor, and the like. 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.

When the water-based paint is a lacquer type, it is often painted with brushes or rollers, but the surface after painting is heated with a hot air dryer (dryer), electric heater, infrared heater, etc. It can be erased to smooth the surface of the coating.
In the case of thermosetting type, which is often used for industrial coatings, spray coating is often performed. By setting the lower critical solution temperature of block B of the block polymer to above the spray coating temperature (room temperature) and below the baking temperature, It is possible to achieve both prevention, spraying and vortex pattern elimination.

  As described above, the ABA triblock polymer of the present invention can give a preferable temperature / viscosity characteristic as a heat-responsive thickener to various daily goods using water as a medium mainly used at around normal temperature. In particular, a water-based coating composition containing the same can achieve both coating workability and finished surface finish.

Hereinafter, the present invention will be described in more detail with reference to production 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
Isobutyl vinyl ether (hereinafter abbreviated as IBVE) is Kyowa Hakko Chemical Co., Ltd., 2-ethoxyethyl vinyl ether (hereinafter abbreviated as EOVE), 2-methoxyethyl vinyl ether (hereinafter abbreviated as MOVE), p-methoxytriethylene glycol vinyl ether. (Hereinafter abbreviated as TEGMEVE), those obtained from Maruzen Petrochemical Co., Ltd. were 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
IBVE-MOVE-IBVE triblock polymer
The inside of a glass reaction vessel equipped with a stirrer and a thermometer and sufficiently heated and dried to remove adsorbed water was replaced with nitrogen, and then 43.9 g of toluene, 8.8 g of ethyl acetate, 24.5 g of MOVE (240 mM), polymerization 10.0 ml of starting seed solution (0.4 mM 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. The block length of the B component is 600. A part of the solution in the middle of the reaction was extracted and poured into a 0.3 wt% methanol solution of a large amount of ammonia to stop the reaction, and the change in MOVE reaction rate and molecular weight was followed using GPC measurement. When 90 mol% or more of MOVE was consumed, IBVE 1.6 g (16 mM) as component A was added, and the reaction was further stirred by stirring at 0 ° C. for 24 to 26 hours. The block length (one side) of the A component (IBVE) is 20. When IBVE was consumed, 80 ml of a 0.3 wt% methanol solution of ammonia was added and stirred vigorously 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 IBVE-MOVE-IBVE triblock polymer (Polymer 1). The molecular weight and molecular weight distribution of the obtained polymer were measured by GPC. Mn was 66000, Mw was 77000, and Mw / Mn was 1.17.

Production Example 2
IBVE-MOVE-IBVE 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 51.9 g of toluene, 8.8 g of ethyl acetate, 16.3 g of MOVE (160 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 1 M-EASC solution (2.0 mM ethylaluminum sesquichloride), and the reaction was allowed to proceed by stirring at 0 ° C. for 3 hours 30 minutes to synthesize B component of the ABA triblock polymer. . The block length of the B component is 400. 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. When 90% by mole or more of MOVE was consumed, IBVE 0.8 g (8.0 mM) as component A was added, and the reaction was further stirred by stirring at 0 ° C. for 24 to 26 hours. The block length (one side) of the A component (IBVE) is 10. When IBVE 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, IBVE-MOVE-IBVE triblock polymer (Polymer 2). The molecular weight and molecular weight distribution of the obtained polymer were measured by GPC. Mn was 43,000, Mw was 49000, and Mw / Mn was 1.14.

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.

感熱応答性の評価
エマルションの製造
容量２リットルの４つ口フラスコに、脱イオン水３８．５部、Ｎｅｗｃｏｌ７０７ＳＦ（日本乳化剤社製、ポリオキシエチレン鎖を有するアニオン性界面活性剤、不揮発分３０％）０．１部を加え、窒素置換後、８５℃に保った。この中に、脱イオン水５２．３部、メチルメタクリレート３０部、スチレン１０部、ｎ−ブチルアクリレート２０部、２−エチルヘキシルアクリレート３０部、ヒドロキシエチルアクリレート１０部、Ｎｅｗｃｏｌ７０７ＳＦ１．６部をエマルション化してなるプレエマルションの３％分及び０．４部の過硫酸アンモニウムを１０部の脱イオン水に溶解させた溶液１０．４部の２５％分を添加し、添加２０分後から残りのプレエマルション及び残りの過硫酸アンモニウム水溶液を４時間かけて滴下した。 滴下終了後、これをさらに２時間８５℃に保持した後、常温まで放冷して固形分５０％のアクリル樹脂エマルションＩを得た。

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, 30% nonvolatile content) 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 2-7 and Comparative Examples 1-3
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 evaluation (below) along with the viscosity (Pa · sec) value at each temperature.
○: Viscosity at 50 ° C. is greatly reduced (viscosity is 1/3 or less) compared to viscosity at 30 ° C., or viscosity at 70 ° C. is significantly higher than viscosity at 50 ° C. (viscosity is 1/3 or less) Decrease).
X: Viscosity at 30 ° C., 50 ° C., and 70 ° C. does not change greatly.

Evaluation as water-based paint
The emulsion compositions of Examples 1 to 7 and Comparative Examples 1 to 5 were applied, and the coating workability and the finish of the coated surface when forcedly heated were evaluated.

Using a straight brush on an A4 size tin plate (200 mm x 300 mm x 0.3 mm) that has been thoroughly degreased using a thinner and then thoroughly dried, use a straight brush to adjust the wet coating amount to 12 g. The emulsion composition was applied by moving the brush in only one direction while measuring the weight. At this time, coating workability was evaluated.
○: The coating liquid has a suitable viscosity and is easy to paint.
(Triangle | delta): It is hard to apply a little because the coating liquid viscosity is insufficient.
X: The coating liquid flows and cannot be brushed.

After leaving in a horizontal state at room temperature for 5 minutes, it was placed in a drying furnace heated to 80 ° C. and forcedly dried for 15 minutes, and then the coated plate was taken out to evaluate the state of the coating film surface. (Excluding those with a coating workability of x above.)
A: The surface of the coating film is smooth and no brush eyes remain.
X: Brush eyes remain on the entire coated plate.

  The evaluation results are shown in Table 5.

Claims (4)

A block length of the A block is 1/5 or less of the block length of the B block, and the lower critical solution temperature for water is 20 ° C. or lower. ℃ consists in is cold water soluble or water-dispersible polymer a is B block over the molecular weight of a ABA triblock polymer of 7000 to 500,000, starting monomers of the a block and the B block is a vinyl ether structure, B The block is made of polyvinyl ether, an ABA triblock polymer. The ABA triblock polymer according to claim 1 , wherein the ABA triblock polymer is synthesized by a living cationic polymerization method using a bifunctional initiator.   Acts as an associative thickener having a hydrophobic-water-soluble-hydrophobic structure at room temperature, and when the temperature rises above the lower critical solution temperature of the B block, the entire polymer changes to hydrophobic and the viscosity decreases. The aqueous solution or aqueous dispersion of the ABA triblock polymer according to claim 1, wherein the ABA triblock polymer exhibits a heat-sensitive response behavior. An aqueous coating composition comprising the aqueous solution or aqueous dispersion of the ABA triblock polymer according to claim 3 .