JP2005232297A - Acrylic polymer fine particle and plastisol composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a plastisol composition useful for obtaining a molded product having excellent recovery from deformation; and to provide an acrylic polymer fine particle for constituting the plastisol composition. <P>SOLUTION: The acrylic polymer fine particle has at least one tanδ peak in each range of ≤-10°C and ≥60°C in a chart of temperature dependency of a dynamic viscoelasticity when a sheet-shaped testing piece is prepared and the viscoelasticity thereof is measured by the following measuring method: the measuring method comprising adding 100 pts. mass of diisononyl phthalate to 100 pts. mass of the acrylic polymer fine particles, homogeneously mixing and dispersing the diisononyl phthalate, casting the resultant mixture so as to have 2 mm thickness, heating the cast product at 150°C for 20 min to provide the sheet-shaped testing piece, and measuring the dynamic viscoelasticity of the testing piece at 1 Hz frequency within the range of -50 to 150°C. The plastisol composition contains the polymer fine particles. The article is obtained from the plastisol composition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to acrylic polymer fine particles useful for obtaining a molded article having excellent deformation recovery properties, and a plastisol composition containing the acrylic polymer fine particles.

  Vinyl chloride plastisol (hereinafter abbreviated as PVC sol) obtained by dispersing vinyl chloride polymer particles in a plasticizer is a low-viscosity paste that is easy to process and gives a molded product that can be deformed by heating. Widely used in various industrial fields. However, in recent years, problems derived from chlorine have been highlighted, and the use of vinyl chloride sol is regarded as a problem. For example, hydrogen chloride gas generated when incinerating a PVC sol product significantly damages the incinerator and causes acid rain, causing environmental destruction. Furthermore, there is a concern as a cause of the generation of highly toxic dioxins.

  Therefore, in recent years, an acrylic plastisol (hereinafter abbreviated as “acrylic sol”) using acrylic polymer fine particles instead of vinyl chloride sol has been proposed. For example, Patent Document 1 proposes an acrylic sol using acrylic polymer fine particles having a core-shell structure. Patent Document 2 also proposes an acrylic sol. In addition, many proposals regarding acrylic sol have been made so far.

  However, molded articles obtained from acrylic sols according to these proposals are inferior in deformation recovery and cannot be used in fields where a high level of deformation recovery is required. In order to improve this point, the proposal which mix | blends urethane-type resin with acrylic sol is made | formed (for example, refer patent document 3). However, the urethane-based resin has problems such as reducing the thixotropy of the acrylic sol and remarkably reducing the workability during coating.

In the prior art, it is difficult to achieve a high level of deformation recovery with an acrylic polymer alone. In particular, when a high level is also required for the storage stability of the acrylic sol, it is extremely difficult to increase both the storage stability and the deformation recovery property. Furthermore, even when a high level is required for the strength of the molded body, it is extremely difficult to make both this and the deformation recovery property high. That is, it is difficult to realize excellent deformation recovery itself, and it is further difficult to achieve both storage stability and strength.
International Publication No. 00/01748 Pamphlet Japanese Patent No. 1390600 Japanese Patent No. 1518354

  An object of the present invention is to provide a plastisol composition useful for obtaining a molded article having excellent deformation recovery properties, and acrylic polymer fine particles for constituting the plastisol composition. Another object of the present invention is to provide a plastisol composition and acrylic polymer fine particles capable of achieving both excellent deformation recovery properties of the molded product and maintenance of storage stability and strength (such as tensile strength). It is to provide.

  As a result of intensive studies on the above-described problems of the prior art, the present inventors have found that an acrylic polymer that gives a tan δ peak to each of a specific low temperature side and a specific high temperature side in the viscoelasticity of the molded body. The inventors have found that the above problems can be solved by using fine particles, and have completed the present invention.

That is, in the present invention, when a sheet-like test piece is prepared by the following measurement method and the dynamic viscoelasticity is measured, the tan δ peak is −10 ° C. or lower and 60 ° C. or higher in the temperature dependence chart of the dynamic viscoelasticity. At least one each is an acrylic polymer fine particle characterized in that it exists.
[Measurement Method] 100 parts by mass of acrylic polymer fine particles are added with 100 parts by mass of diisononyl phthalate, mixed and dispersed homogeneously, cast to a thickness of 2 mm, and heated at 150 ° C. for 20 minutes to obtain a sheet-like test piece. The dynamic viscoelasticity of the test piece is prepared and measured in the range of −50 to 150 ° C. at a frequency of 1 Hz.

  Furthermore, the present invention provides a plastisol composition comprising the above-mentioned acrylic polymer fine particles; an article obtained from the plastisol composition; and an automobile underbody coat, an automobile body sealer or an automobile mastic adhesive obtained from the plastisol composition. It is an agent.

  In the present invention, since a tan δ peak is imparted to a specific low temperature side and a tan δ peak is imparted to a specific high temperature side, and a molded product having at least two tan δ peaks is obtained, it is obtained from an acrylic polymer. It is possible to improve the deformation recovery which has been a problem of the plastisol composition to be obtained, and at the same time, it is possible to simultaneously maintain the storage stability and strength (such as tensile strength). Therefore, the industrial significance of the present invention and the effect on global environmental conservation are significant.

  For example, an acrylic plastisol composition can be obtained by blending the acrylic polymer fine particles of the present invention with a plasticizer and, if necessary, an additive. This plastisol composition can be processed into various shaped articles by heating. As described above, the molded body obtained by using the acrylic polymer fine particles of the present invention is extremely excellent in deformation recovery compared to the conventional one. In addition, the deformation recovery property is evaluated by using a tensile hysteresis test in which a certain amount of elongation strain is applied or released by a tensile tester, and the area between the forward path and the return path of the strain-stress curve (SS curve). It is implemented by the method of calculating from the ratio. Specifically, it evaluated by the method as described in the Example explained in full detail later.

  The acrylic polymer fine particles of the present invention are characterized in that at least one tan δ peak is present at −10 ° C. or lower and 60 ° C. or higher, respectively, in a temperature dependence chart of dynamic viscoelasticity by a specific measuring method. . Here, when the tan δ peak is not below −10 ° C., sufficient strength is obtained, but the deformation recovery property is low. Also, when the tan δ peak is not above 60 ° C., a certain degree of deformation recovery is obtained, but since there is no strong restraining component, a high level of deformation recovery is not obtained, and since the strength is low, it easily breaks. End up. In addition, the higher the ratio (D1 / D2) of the maximum tan δ value (D1) of −10 ° C. or lower and the maximum tan δ value (D2) of 60 ° C. or higher is, the better the deformation recovery is.

  Specifically, the dynamic viscoelasticity is measured by adding 100 parts by mass of diisononyl phthalate to 100 parts by mass of acrylic polymer fine particles, mixing and dispersing uniformly, casting to 2 mm thickness, and 150 ° C. × 20 minutes. A sheet-like test piece is produced by heating the above, and the test piece is carried out at a frequency of 1 Hz in a range of −50 to 150 ° C.

  The method for producing such acrylic polymer fine particles exhibiting a specific dynamic viscoelasticity is not particularly limited, and there are many methods. For example, there is a method in which a large amount of a polymerization initiator is added or a chain transfer agent is administered when the shell of the core-shell polymer is polymerized. By these methods, the physical contribution of the flexible core component is greatly increased, so it is considered that the deformation recovery property is dramatically improved. In particular, when D1 / D2 is 0.5 or more, the deformation recovery property is remarkably improved, and the applicable range of application is expanded.

Furthermore, it is preferable that the acrylic polymer fine particles have little change in viscosity over time of the dispersion. Specifically, with respect to the viscosity of the dispersion obtained by adding 100 parts by mass of diisononyl phthalate to 100 parts by mass of the acrylic polymer fine particles and uniformly mixing and dispersing, the shear rate at 25 ° C. within 2 hours after the preparation of the dispersion. an initial viscosity measured at 20s ^-1 (η1), and further stores 10 days this at 35 ° C., then the ratio of the viscosity measured at a shear rate of 20s ^-1 again returned to 25 ℃ (η2) (η2 / η1) is preferably 2.0 or less. In this case, excellent deformation recovery can be realized and storage stability can be maintained.

  The method for producing such acrylic polymer fine particles exhibiting such specific viscosity characteristics (η2 / η1) is not particularly limited, and there are many methods. Examples thereof include a method for significantly increasing the polarity of the particle surface of the core-shell polymer, and a method for adding a large amount of a water-soluble salt polymerization initiator when the shell is polymerized.

  The above-mentioned acrylic polymer fine particles showing dynamic viscoelasticity and viscosity characteristics are not particles having a uniform structure but particles having a certain layer (or phase) structure. It is impossible to achieve such dynamic viscoelasticity with uniformly structured particles. Examples of a preferable structure include a core-shell structure or a multistage structure composed of a plurality of polymer layers having different compositions, or a gradient structure in which the polymer composition changes continuously. By effectively using these particle structures, the dynamic viscoelasticity can be easily controlled.

  Examples of monomers that can be used to obtain acrylic polymers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) ) (Meth) acrylates of linear alkyl alcohols such as acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate; (meth) of cyclic alkyl alcohols such as cyclohexyl (meth) acrylate Acrylates: methacrylic acid, acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, methacrylic acid 2-succinoloyloxyethyl-2-methacryloyloxyethyl succinic acid, methacrylic acid 2-malenoyloxyethyl-2 -Methacryloy Carboxyl group-containing monomers such as ruoxyethylmaleic acid, methacrylic acid 2-phthaloyloxyethyl-2-methacryloyloxyethylphthalic acid, methacrylic acid 2-hexahydrophthaloyloxyethyl-2-methacryloyloxyethylhexahydrophthalic acid; Sulfonic acid group-containing monomers such as allylsulfonic acid; Phosphoric acid group-containing (meth) acrylates such as 2- (meth) acryloyloxyethyl acid phosphate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Hydroxyl group-containing (meth) acrylates such as acrylate; carbonyl group-containing (meth) acrylates such as acetoacetoxyethyl (meth) acrylate; N-dimethylaminoethyl (meth) acrylate, N-diethylamino ester Amino group-containing (meth) acrylates such as til (meth) acrylate; and the like. However, the present invention is not limited to these examples.

  The method for producing the acrylic polymer fine particles is not particularly limited, and examples thereof include an emulsion polymerization method, a soap-free polymerization method, a suspension polymerization method, a fine suspension polymerization method, and a dispersion polymerization method. Of these, emulsion polymerization and soap-free polymerization are preferred. According to these methods, it is easy to control the particle structure such as the core-shell structure. However, the present invention is not limited to these methods.

  The acrylic polymer fine particles may have any properties or structure as a dry powder. For example, a large number of primary particles obtained by polymerization may be aggregated to form aggregated particles (secondary particles), and higher-order structures are also possible. However, in the case of such an agglomerated structure, it is preferable that the primary particles are not firmly bonded to each other and are loosely aggregated. This is because fine and uniform dispersion of the primary particles in the plasticizer is achieved.

  The plastisol composition of the present invention includes the acrylic polymer fine particles of the present invention described above. Specifically, a plastisol composition can be obtained by, for example, blending and uniformly dispersing a plasticizer and, if necessary, an additive with respect to the acrylic polymer fine particles.

  As the plasticizer, typically, diisononyl phthalate is used as in the method of measuring dynamic viscoelasticity. However, other than these, for example, dialkyl phthalates such as dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, diisononyl phthalate and diisodecyl phthalate; alkyl benzyl phthalates such as butyl benzyl phthalate; alkyl aryl phthalates; Dibenzyl phthalate; diaryl phthalate; triaryl phosphates such as tricresyl phosphate; phosphate esters such as trialkyl phosphates and alkylaryl phosphates; aliphatic dibasic acid esters such as adipine dibutyl; dibutyl glycol adipate Ether-containing compounds such as polyester plasticizers, soybean oil plasticizers such as epoxidized soybean oil, and the like can be used as plasticizers. These plasticizers can be used alone or in combination of two or more plasticizers. The blending amount of the plasticizer is preferably 50 to 300 parts by mass, more preferably 60 to 200 parts by mass with respect to 100 parts by mass of the acrylic polymer fine particles.

  For plastisol compositions, calcium carbonate, aluminum hydroxide, pearlite, clay, colloidal silica, mica powder, quartz sand, diatomaceous earth, kaolin, talc, bentonite, glass powder, aluminum oxide, fly ash, shirasu balloon, if necessary You may mix | blend fillers, such as. The purpose, type, amount, etc. of the filler are arbitrary. Further, the filler may be subjected to a surface treatment or the like.

  In addition, if necessary, pigments such as titanium oxide and carbon black, further diluents such as mineral terpenes and mineral spirits, further antifoaming agents, antifungal agents, deodorants, antibacterial agents, surfactants, lubricants, ultraviolet rays Absorbers, fragrances, foaming agents, leveling agents, adhesives and the like can be freely blended.

  The acrylic plastisol composition of the present invention can be widely used in fields of application where a conventional vinyl chloride sol has been used. Specifically, automotive undercoats, automotive body sealers, automotive mastic adhesives, tile carpet backing materials, cushion floors, wallpaper, steel plate paints, toys, gloves, food samples, shoes, building materials, various adhesives, various sealers, Gaskets, waterproof sheets, automobile inner layer skin materials, canvas, table cloths, synthetic leather, erasers, screen printing paints, and the like. Among them, since an automobile undercoat is particularly required to have chipping resistance, an acrylic sol excellent in deformation recovery as in the present invention is suitable. In addition, since an automobile body sealer and a mastic adhesive are required to follow high-speed deformation (vibration), an acrylic sol excellent in deformation recovery as in the present invention is suitable.

  Hereinafter, the present invention will be specifically described according to examples.

[Preparation of polymer fine particles (A1)]
100 g of pure water is put into a 500 ml four-necked flask equipped with a thermometer, nitrogen gas introduction tube, stirring rod, dropping funnel, and cooling tube, and nitrogen gas is thoroughly bubbled for 30 minutes to dissolve dissolved oxygen in the pure water. Replaced. Next, after stopping the aeration of nitrogen gas, the temperature was raised to 80 ° C. while stirring at 200 rpm. When the internal temperature reached 80 ° C., 0.01 g of potassium persulfate dissolved in 5.0 g of pure water was added all at once. Next, a mixture solution in which a monomer (methyl methacrylate 36.0 g, n-butyl methacrylate 34.0 g) and an emulsifier (1.0 g of sodium dioctylsulfosuccinate per 100 g of monomer) were uniformly dissolved as a first drop was added at a rate of 20 g / hr. Then, stirring was continued at 80 ° C. for 1 hour to obtain a core polymer latex.

  Further, 0.20 g of potassium persulfate dissolved in 10.0 g of pure water was added to the core polymer latex at once. Next, as a second drop, a mixed solution in which the monomer (methyl methacrylate 28.7 g, methacrylic acid 1.3 g) and the emulsifier (sodium dioctylsulfosuccinate 1.0 g per 100 g monomer) were uniformly dissolved was added at a rate of 20 g / hr. Then, stirring was continued at 80 ° C. for 1 hour to obtain a core-shell polymer latex.

  After cooling the core-shell polymer latex to room temperature, it is spray-dried at an inlet temperature of 170 ° C., an outlet temperature of 65 ° C., and an atomizer speed of 25000 rpm using a spray dryer (L8 type, manufactured by Okawara Chemical Co., Ltd.). Combined fine particles (A1) were obtained.

[Preparation of polymer fine particles (A2)]
Polymer fine particles (A2) were prepared in the same manner as in the case of the polymer fine particles (A1) except that the monomer compositions of the first drop and the second drop were changed to the compositions shown in Table 1, respectively. That is, the amount of emulsifier added to the monomer, the dropping rate of the monomer, the spray drying conditions, and the like are the same as in the case of the polymer fine particles (A1).

[Preparation of polymer fine particles (A3)]
Polymer fine particles (A1) except that the monomer composition of the first and second drops was changed to the composition shown in Table 1 and that the potassium persulfate solution was not dropped immediately before the second drop. Polymer fine particles (A3) were prepared in the same manner as in the above.

[Preparation of polymer fine particles (A4)]
Polymer fine particles (A4) were prepared according to the method for producing polymer fine particles exemplified as (A3) in the examples of the pamphlet of International Publication No. 00/01748.

[Preparation of polymer fine particles (A5) and (A6)]
The polymer fine particles (A5) and the polymer fine particles (A6) are the same as the polymer fine particles (A4) except that the monomer compositions of the first drop and the second drop are changed to the compositions shown in Table 1, respectively. Was prepared.

[Examples 1-3 and Comparative Examples 1-3: Preparation of plastisol compositions]
100 parts by mass of diisononyl phthalate (DINP) as a plasticizer per 100 parts by mass of each polymer fine particle shown in Table 2 was added and defoamed with a vacuum mixer (ARV-200, manufactured by Sinky Corporation) for 10 seconds at atmospheric pressure And mixing for 50 seconds under reduced pressure to 20 mmHg) to obtain a uniform plastisol composition. For the obtained plastisol composition, the following items were evaluated. The evaluation results are shown in Table 2.

(Storage stability (η2 / η1))
After preparing the plastisol composition, the viscosity was measured at 25 ° C. within 2 hours (initial viscosity η1). Furthermore, this was stored in a constant temperature room at 35 ° C. for 10 days, returned to 25 ° C., and the viscosity was measured again (viscosity η2 after storage). These viscosities were measured by casting the plastisol composition onto a Teflon-treated iron plate (thickness: about 1 mm) to a thickness of about 2 mm, and heating it in a gear oven at 150 ° C. for 20 minutes. The molded body was used as a test piece for viscosity measurement, and an EMD viscometer (manufactured by Toki Sangyo Co., Ltd., cone angle: 3 °) was used at a measurement temperature of 25 ° C. and a shear rate of 20 s ⁻¹ . From the values of the initial viscosity η1 and the post-storage viscosity η2 measured in this way, “η2 / η1” was calculated as storage stability and evaluated according to the following criteria.
“◎”: η2 / η1 is less than 2.
“◯”: η2 / η1 is 2 or more and less than 6.
“×”: η2 / η1 is 6 or more (or η2 cannot be measured).

(Viscoelasticity measurement (tan δ peak temperature, tan δ1 / tan δ2))
The sheet-like molded body obtained as described above was cut into a strip shape having a width of 10 mm and a length of 20 mm, and a viscoelasticity measuring device (manufactured by UBM, Rheosol-G3000) was used at a frequency of 1 Hz, − The dynamic viscoelasticity was measured over 50 to 150 ° C. (temperature increase rate: 4 ° C./min) (gripping part: 5 mm each). The twist angle was automatically adjusted by changing the hardness of the material. One or more tan δ peaks were observed in the obtained temperature dependence chart of dynamic viscoelasticity, and “tan δ1” and “tan δ2” were taken from the low temperature side, and the temperature giving each peak was read.

  There are cases where tan δ does not draw a clear two peak and shows a broad distribution, but in that case, if there is a region that is clearly seen as a shoulder, it is the peak, and there is no obvious shoulder Considered that the two tan δ's almost coincided. Further, the heights of the respective peaks of tan δ1 and tan δ2 were read from the chart, and the ratio was calculated as “tan δ1 / tan δ2”. The higher this value is, the higher the ratio of the soft component that contributes to the mechanical properties in the sheet-like molded product, and the rubber-like properties become particularly remarkable when tan δ1 / tan δ2 is 0.5 or more.

(tensile strength)
The sheet-like molded body obtained as described above was cut into a dumbbell-shaped No. 2 mold according to the method described in JIS K-7113, and a tensile breaking strength was measured with a Tensilon measuring instrument. evaluated. The test speed was 200 mm / min, the load cell rating was 1000 N, and the environmental temperature when measured was 25 ° C.
“◎”: 3.0 MPa or more.
“◯”: 1.5 MPa or more and less than 3.0 MPa.
“X”: less than 1.5 MPa.

(Deformation recovery rate)
The sheet-like molded body obtained as described above was cut into a strip shape of 15 mm × 80 mm, and a tensile deformation hysteresis test was performed using a Tensilon measuring machine. Here, the tensile speed was 50 mm / min, the displacement was 40% in terms of elongation, and the measurement temperature was 25 ° C. This hysteresis test was repeated 5 times in succession, but the area (S1) given by the SS curve in the forward path (during tension) and the area given by the SS curve in the return path (during return) (S2). ) And hysteresis storage rate = S2 / S1 × 100 (%) was calculated, and this was used as an index for deformation recovery, and evaluated according to the following criteria.
“◎”: Hysteresis storage 60% or more.
"(Circle)": Hysteresis storage 40% or more and less than 60%.
"X": Hysteresis storage is less than 40%.

（各例の考察）
実施例１は、用いるモノマー類は従来技術と同等であるが、軟質成分の比率を増量するとともに、ラテックス粒子表面の極性を大幅に上げる等、従来にない重合技術を用いることで、変形回復性と貯蔵安定性を同時に高いレベルで両立することを可能にした例である。実施例１の粘弾性チャートを図１に示す。このチャートから明らかなように、成形体中のｔａｎδは明瞭な２つのピークを形成しており、そのうち低温側のピークは十分に低い温度域に出現している。これにより成形体はゴム的な回復性を有しており、表２に記載に通り変形回復性は極めて良好であった。また同時に、高温側のｔａｎδピークは十分に高い温度域に出現しており、高い抗張力を維持することも可能であった。また、ラテックス粒子の表面極性を大幅にアップすることで、プラスチゾル貯蔵時の粘度上昇を従来にないレベルで抑制することが出来た。

(Consideration of each example)
In Example 1, the monomers used are the same as in the prior art, but the deformation recovery properties are improved by using an unprecedented polymerization technique such as increasing the ratio of the soft component and greatly increasing the polarity of the latex particle surface. It is an example that makes it possible to achieve both high and storage stability at the same time. The viscoelasticity chart of Example 1 is shown in FIG. As is apparent from this chart, tan δ in the molded body forms two distinct peaks, of which the peak on the low temperature side appears in a sufficiently low temperature range. As a result, the molded article had rubber-like recoverability, and the deformation recovery ability was very good as shown in Table 2. At the same time, the tan δ peak on the high temperature side appeared in a sufficiently high temperature range, and it was possible to maintain a high tensile strength. In addition, by greatly increasing the surface polarity of latex particles, an increase in viscosity during plastisol storage could be suppressed to an unprecedented level.

  Example 2 is an example in which the core portion of the polymer fine particles (A1) is further softened. Although the viscoelasticity chart is omitted, two clear tan δ peaks appeared as in FIG. The resulting molded article had very good deformation recovery and high tensile strength. In addition, the increase in viscosity of plastisol could be significantly suppressed.

  Example 3 is an example in which the core part of the polymer fine particles (A1) is further softened, but the polarity of the particle surface is not increased so much. Also in this case, two clear tan δ peaks appeared in the viscoelasticity chart as in FIG. However, since the polarity of the particle surface was not sufficiently increased, the tan δ peak on the high temperature side was not as high as in Examples 1 and 2. Although the deformation recovery property of the obtained molded body is very good, the tensile strength is slightly low as compared with Examples 1 and 2. However, this level is sufficiently practical. The increase in viscosity of plastisol is slightly lower than that in Examples 1 and 2, but it is at a sufficiently practical level.

  Comparative Example 1 is a trial of an example described in the pamphlet of International Publication No. 00/01748, which is a typical prior art. A viscoelasticity chart of Comparative Example 1 is shown in FIG. When a plastisol was prepared from the acrylic core-shell structure particles of the prior art and the sheet-like molded body was measured, tan δ observed in the viscoelasticity measurement of the molded body appeared on the low-temperature side and the high-temperature side sufficiently separated. (See FIG. 2). Further, the deformability of the molded product was low. Therefore, it was confirmed that excellent deformation recovery was not obtained in the case where tan δ on the low temperature side was not sufficiently low as in this comparative example.

  Comparative Example 2 is an example for confirming the possibility of improving the deformation recovery property by softening the core portion of the core-shell polymer fine particles of Comparative Example 1, that is, by reducing tan δ on the low temperature side as much as possible. In this example, as shown in Table 2, the tan δ on the low temperature side decreased to −15 ° C., but the tan δ peak on the high temperature side also decreased to 36 ° C. As a result, the deformation recovery property of the molded product is not bad, but the tensile strength is extremely low, which is insufficient as practical performance. Moreover, the storage stability of plastisol also decreased, and it was also possible to confirm the problem of the prior art that it was impossible to achieve both deformation recovery properties.

  Comparative Example 3 is an example for confirming the possibility of improving the deformation recovery property by hardening the core portion of the core-shell polymer fine particles of Comparative Example 1, that is, by increasing tan δ on the high temperature side as much as possible. In this example, as shown in Table 2, the tan δ on the high temperature side rose to 89 ° C, but the tan δ peak on the low temperature side also rose to -6 ° C. As a result, although the tensile strength was not bad, the deformation recovery property was extremely low.

2 is a viscoelasticity chart in Example 1. 3 is a viscoelasticity chart in Comparative Example 1.

Claims (5)

When a sheet-like test piece was prepared by the following measurement method and its dynamic viscoelasticity was measured, at least one tan δ peak was −10 ° C. or lower and 60 ° C. or higher in the temperature dependence chart of dynamic viscoelasticity. Acrylic polymer fine particles characterized by being present.
[Measurement Method] 100 parts by mass of acrylic polymer fine particles are added with 100 parts by mass of diisononyl phthalate, mixed and dispersed homogeneously, cast to a thickness of 2 mm, and heated at 150 ° C. for 20 minutes to obtain a sheet-like test piece. The dynamic viscoelasticity of the test piece is prepared and measured in the range of −50 to 150 ° C. at a frequency of 1 Hz. The viscosity of a dispersion obtained by adding 100 parts by mass of diisononyl phthalate to 100 parts by mass of acrylic polymer fine particles and mixing and dispersing it uniformly was measured at 25 ° C. and a shear rate of 20 s ⁻¹ within 2 hours after the preparation of the dispersion. The ratio (η2 / η1) between the initial viscosity (η1) and the viscosity (η2) measured at a shear rate of 20 s ⁻¹ after being stored at 35 ° C. for 10 days and then returned to 25 ° C. is 2. The acrylic polymer fine particle according to claim 1, which is 0 or less.   A plastisol composition comprising the acrylic polymer fine particles according to claim 1.   An article obtained from the plastisol composition of claim 3.   An underbody coat for automobiles, a body sealer for automobiles or a mastic adhesive for automobiles obtained from the plastisol composition according to claim 3.

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