Temperature-sensitive particles

Abstract

To provide temperature-sensitive fine particles which can be added to various resin materials and can impart temperature-sensitivity.SOLUTION: Temperature-sensitive fine particles are composed of a side chain crystalline polymer which is crystallized at a temperature lower than a melting point and exhibits flowability at a temperature equal to or higher than the melting point. The side chain crystalline polymer may contain (meth)acrylate having a linear alkyl group having 14 or more carbon atoms as a monomer component. The temperature-sensitive fine particles may have an average particle size of 0.1-50 μm. The temperature-sensitive fine particles does not need to contain an organic solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to temperature-sensitive fine particles. [Background technology]

[0002] Side-chain crystalline polymers are known that are thermosensitive and reversibly change between a crystalline state and a fluid state in response to temperature changes (see, for example, Patent Document 1). Conventional side-chain crystalline polymers such as those described in Patent Document 1 are often synthesized in organic solvent systems and are often processed into the form of tapes or the like for use in adhesive applications. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-251923 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide temperature-sensitive fine particles that can be added to various resin materials and can impart temperature sensitivity. [Means for solving the problem]

[0005] As a result of extensive research into solving the above problems, the inventors have found a solution comprising the following configuration, and have completed the present invention. (1) Thermosensitive particles made of a side-chain crystalline polymer that crystallizes at a temperature below the melting point and exhibits fluidity at a temperature equal to or higher than the melting point. (2) The thermosensitive fine particles according to (1) above, wherein the side-chain crystalline polymer contains, as a monomer component, a (meth)acrylate having a linear alkyl group having 14 or more carbon atoms. (3) The thermosensitive fine particles according to (1) or (2) above, which have an average particle size of 0.1 to 50 μm. (4) The ratio [(storage modulus G' at melting point -10°C) / (storage modulus G' at melting point +10°C)] is 1 × 10 2 The thermosensitive fine particles according to any one of (1) to (3) above. (5) The thermosensitive fine particles according to any one of (1) to (4) above, which do not contain an organic solvent. (6) The thermosensitive fine particles according to any one of (1) to (5) above, which are a thermosensitivity imparting agent. (7) The thermosensitive fine particles according to any one of (1) to (6) above, which are used for dimming. [Effects of the Invention]

[0006] According to the present invention, it is possible to add the composition to various resin materials and obtain the effect of imparting temperature sensitivity to the resin materials. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph showing the results of measuring the storage modulus G′ in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Thermosensitive fine particles> Hereinafter, a detailed description will be given of the temperature-sensitive fine particles (hereinafter sometimes referred to as "fine particles") according to one embodiment of the present invention.

[0009] The fine particles of this embodiment are made of a side-chain crystalline polymer that crystallizes at a temperature below the melting point and exhibits fluidity at a temperature equal to or higher than the melting point.

[0010] The above-described configuration allows the polymer to be added to various resin materials and provides the effect of imparting temperature sensitivity. Specifically, the above-described side-chain crystalline polymer is a polymer having a melting point. The melting point is the temperature at which a specific portion of a polymer that was initially aligned in an orderly arrangement becomes disordered through an equilibrium process. It is a value obtained by measuring the melting point using a differential scanning calorimeter (DSC) at a rate of 10°C / min. The side-chain crystalline polymer crystallizes at temperatures below the melting point and undergoes a phase transition at temperatures above the melting point, exhibiting fluidity. In other words, the side-chain crystalline polymer has a temperature sensitivity that reversibly changes between a crystalline state and a fluid state in response to temperature changes. Since the microparticles are made of such a side-chain crystalline polymer, they possess a temperature sensitivity derived from the side-chain crystalline polymer.

[0011] Here, when the side-chain crystalline polymer is formed into a fine particle shape, it becomes less susceptible to the influence of the type and proportion of the base resin (hereinafter sometimes referred to as "base resin"), and the dispersion state of the side-chain crystalline polymer in the base resin is less likely to change, making it possible to add it to various resin materials and to impart temperature sensitivity derived from the side-chain crystalline polymer. Furthermore, by adding the fine particles of this embodiment to a resin material, it becomes possible to control and express physical properties of the base resin, such as elastic modulus control, optical property control, gas permeability control, surface modification, and heat storage / heat release function, depending on the temperature.

[0012] The melting point of the side-chain crystalline polymer is preferably 20 to 100°C. The melting point can be adjusted, for example, by changing the composition of the monomer components that constitute the side-chain crystalline polymer. To give a specific example, the melting point can be adjusted by changing the length of the side chain in the side-chain crystalline polymer. Increasing the length of the side chain tends to increase the melting point.

[0013] The side-chain crystalline polymer contains a (meth)acrylate having a linear alkyl group with 14 or more carbon atoms as a monomer component. In the (meth)acrylate having a linear alkyl group with 14 or more carbon atoms, the linear alkyl group with 14 or more carbon atoms functions as a side-chain crystalline moiety in the side-chain crystalline polymer. In other words, the side-chain crystalline polymer is a comb-shaped polymer having a linear alkyl group with 14 or more carbon atoms in its side chain, and crystallizes when this side chain is aligned in an orderly arrangement by intermolecular forces or the like. Note that the above-mentioned (meth)acrylate refers to acrylate or methacrylate. The upper limit of the carbon number is preferably 50 or less.

[0014] Examples of (meth)acrylates having a linear alkyl group having 14 or more carbon atoms include cetyl (meth)acrylate, stearyl (meth)acrylate, eicosyl (meth)acrylate, behenyl (meth)acrylate, etc. The exemplified (meth)acrylates may be used alone or in combination of two or more.

[0015] The monomer component constituting the side chain crystalline polymer may contain other monomers copolymerizable with a (meth)acrylate having a linear alkyl group having 14 or more carbon atoms. Examples of other monomers include monofunctional monomers and polyfunctional monomers. That is, the side chain crystalline polymer may contain a monofunctional monomer or a polyfunctional monomer as a monomer component.

[0016] Examples of monofunctional monomers include (meth)acrylates having an alkyl group having 1 to 12 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, lauryl (meth)acrylate, and 2-ethylhexyl acrylate, as well as acrylic acid. The monofunctional monomers exemplified above may be used alone or in combination of two or more. When it is desired to add a function in addition to temperature sensitivity, any monomer that is copolymerizable with a (meth)acrylate having a linear alkyl group having 14 or more carbon atoms and has that function can be freely copolymerized.

[0017] The polyfunctional monomer can function as a component that crosslinks the side-chain crystalline polymer. It is preferable to use a polyfunctional monomer from the viewpoints of maintaining the dispersion state during use, suppressing deformation, and maintaining repeatability of function. That is, the side-chain crystalline polymer preferably contains a polyfunctional monomer as a monomer component. The polyfunctional monomer has two or more, preferably two to four, radically polymerizable double bonds in the molecule. Examples of the polyfunctional monomer include bifunctional (meth)acrylate, trifunctional (meth)acrylate, and tetrafunctional (meth)acrylate. Specific examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, polyethylene glycol 200 di(meth)acrylate, and ethoxylated bisphenol A di(meth)acrylate. The polyfunctional monomers exemplified above may be used alone or in combination of two or more. The polyfunctional monomer may be at least one selected from a difunctional (meth)acrylate, a trifunctional (meth)acrylate, and a tetrafunctional (meth)acrylate.

[0018] The composition of the side chain crystalline polymer may be, for example, 20 to 100 parts by weight of a (meth)acrylate having a linear alkyl group with 14 or more carbon atoms, 0 to 40 parts by weight of a monofunctional monomer, and 0 to 10 parts by weight of a polyfunctional monomer.

[0019] The average particle size of the fine particles is preferably 0.1 to 50 μm, more preferably 1.5 to 50 μm. This configuration makes it easy to control the dispersion state of the fine particles in the base resin. The average particle size is a value obtained by image processing of a scanning electron microscope (SEM) photograph. More specifically, the average particle size is a value obtained by taking an SEM photograph of the fine particles using an SEM, randomly extracting 30 fine particles from the SEM photograph, and calculating the average value.

[0020] The shape of the fine particles is preferably spherical. This configuration makes it easier for the fine particles to be dispersed stably in the base resin. The fine particles may contain particles having a sphericity of 0.7 or more, preferably at a number average ratio of 70% or more, more preferably 70 to 100%. In this case, the dispersion of the fine particles in the base resin is stabilized. Sphericity is the ratio of the minor axis to the major axis. The sphericity and sphericity distribution are values ​​obtained by image processing of SEM photographs. The upper limit of the sphericity is not particularly limited, but may be 0.99 or less.

[0021] The ratio [(storage modulus G' at melting point - 10°C) / (storage modulus G' at melting point + 10°C)] is preferably 1 x 10 2 or more, more preferably 1×10 2 ~1×10 7 According to this configuration, the side-chain crystalline polymer undergoes a steep transition from a crystalline state to a fluid state at the melting point, making it easy to control and manifest physical properties of the base resin, such as elastic modulus control, optical property control, gas permeability control, surface modification, and heat storage / heat release function, by temperature.

[0022] The storage modulus G' at the melting point -10°C is preferably 1 x 10 6 ~1×10 9 The storage modulus G' at the melting point +10°C is preferably 1 x 10 2 ~1×10 5 The storage modulus G' is a value obtained by measurement using a dynamic viscoelasticity measuring device. The storage modulus G' can be adjusted, for example, by changing the composition of the monomer components that make up the side-chain crystalline polymer.

[0023] The microparticles preferably do not contain an organic solvent. This configuration eliminates the influence of compatibility with the base resin, making it easier to stabilize the dispersion state of the microparticles in the base resin. Furthermore, solvent resistance is improved, making it less likely to bleed out. Polymerizing the monomer components without using an organic solvent allows the microparticles to be free of organic solvents.

[0024] The microparticles may be obtained by aqueous polymerization of a monomer component. A surfactant (emulsifier) ​​may be used when polymerizing the monomer component. In this case, the resulting side-chain crystalline polymer may contain a surfactant. In other words, the side-chain crystalline polymer may contain a surfactant.

[0025] The microparticles can be suitably used as a temperature-sensitivity imparting agent. That is, according to this embodiment, temperature sensitivity can be imparted to a resin material by the simple method of adding microparticles to the resin material. Examples of base resins include polyethylene terephthalate resin, polyvinyl chloride resin, ethylene-methyl methacrylate copolymer resin, polycarbonate, methyl methacrylate resin, acrylic resin, epoxy resin, polyamide resin, polyurethane, polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer resin (EVA), and polyolefin-based resin. Examples of polyolefin-based resins include polyethylene resin. Note that the base resin is not limited to the examples given above. The microparticles can also be added to inks and the like.

[0026] The fine particles can be suitably used for various purposes. For example, the fine particles may be used for adhesion, light control, plasticizer, mold release, surface modification, volatile gas permeability, etc. The uses of the fine particles are not limited to those exemplified above.

[0027] (for dimming) Next, the case where the fine particles are used for light control will be described. The fine particles can be added to the base resin of the light control film to make it transparent or opaque, i.e., to express the light control function (turbidity change) in the light control film. In addition, adding the fine particles to the base resin of the light control film has the effect of being able to control the transparency or opacity of the light control film by temperature.

[0028] Specifically, photochromic mixtures that utilize the difference in the temperature dependence of the refractive index between a base resin and an additive have been known (see, for example, Japanese Patent Application Laid-Open No. 51-132241). These photochromic mixtures are transparent when the difference in refractive index is small, and become opaque, such as cloudy, when the difference in refractive index is large. Therefore, they change from transparent at room temperature to opaque at high temperatures. However, because the above-mentioned photochromic mixtures do not have an inflection point, the change is sluggish and difficult to detect unless there is a large temperature difference. In addition, it is difficult to control the change temperature, and even if it could be controlled, it is difficult to maintain the properties of the base resin.

[0029] The refractive index of the microparticles of this embodiment changes (decreases) rapidly (abruptly) near the melting point. Therefore, for example, if the refractive index of the microparticles at temperatures below the melting point is set to a value close to that of the base resin, the two refractive indices will be close at temperatures below the melting point, and the difference between the two will become larger at temperatures above the melting point. Therefore, a light-control film containing the microparticles (hereinafter sometimes referred to as a "thermosensitive light-control film") will be transparent at temperatures below the melting point and opaque at temperatures above the melting point. Thus, the microparticles of this embodiment utilize the temperature sensitivity of the side-chain crystalline polymer as well as the change in the optical properties (refractive index) of the side-chain crystalline polymer, allowing the transparency and opacity of the light-control film to be controlled by temperature. Furthermore, the change between transparency and opacity is more abrupt than that of conventional light-control mixtures. Furthermore, the microparticles of this embodiment are less likely to degrade the properties of the base resin. The refractive index of the microparticles of this embodiment can be adjusted by the copolymerization material, making it possible to control the transparency and opacity of a base resin with any refractive index.

[0030] The temperature at which a thermosensitive light-controlling film changes from transparent to opaque can be controlled by the melting point of the side-chain crystalline polymer. The degree of opacity (turbidity), such as cloudiness, can be controlled by the composition of the monomer components that make up the side-chain crystalline polymer and the blending ratio of the base resin and microparticles. A thermosensitive light-controlling film can alternate between transparency and opacity because the side-chain crystalline polymer reversibly changes between a crystalline state and a fluid state in response to temperature changes. The transparency and opacity (light-controlling function) of a thermosensitive light-controlling film need only be visible to the naked eye.

[0031] The refractive index of the fine particles is, for example, 1.480 to 1.520 at temperatures below the melting point and 1.440 to 1.495 at temperatures equal to or higher than the melting point. The refractive index is a value measured with an automatic refractometer. The refractive index of the fine particles is not limited to the numerical range exemplified above. The refractive index of the fine particles may be set according to the refractive index of the base resin.

[0032] The difference (absolute value) between the refractive index at a temperature below the melting point and the refractive index at a temperature equal to or higher than the melting point of the fine particles is 0.010 or more, preferably 0.010 to 0.070, which makes it easy for the temperature-sensitive light control film to change significantly from transparent to opaque.

[0033] When the fine particles are used for photochromic purposes, a refractive index-adjusting monomer may be included in the monomer components constituting the side chain crystalline polymer. The refractive index-adjusting monomer may be a monomer having a refractive index of 1.300 to 1.600. Examples of the refractive index-adjusting monomer include 2-(O-phenylphenoxy)ethyl acrylate (refractive index: 1.577), 2-propenoic acid (3-phenoxyphenyl) methyl ester (refractive index: 1.566), 1-naphthyl acrylate (refractive index: 1.595), acrylamide (refractive index: 1.515), hydroxyacrylamide (refractive index: 1.515), EO-modified bisphenol A diacrylate (refractive index: 1.537), acrylamide (refractive index: 1.515), 2,2,2-trifluoroethyl acrylate (refractive index: 1.348), and methacryl-modified polydimethylsiloxane (refractive index: 1.408). The refractive index-adjusting monomers listed above may be used alone or in combination of two or more. The refractive index adjusting monomer is contained in the monomer component constituting the side chain crystalline polymer at a ratio of preferably 40% by weight or less, more preferably 1 to 30% by weight.

[0034] When the microparticles are for photochromic use, the composition of the side-chain crystalline polymer may be, for example, 20 to 100 parts by weight of a (meth)acrylate having a linear alkyl group with 14 or more carbon atoms, 0 to 40 parts by weight of a monofunctional monomer, 0 to 10 parts by weight of a polyfunctional monomer, and 0 to 30 parts by weight of a refractive index adjusting monomer.

[0035] The microparticles may be added in a proportion that allows the thermosensitive light-control film to exhibit the temperature sensitivity derived from the side-chain crystalline polymer. In other words, the thermosensitive light-control film may contain the microparticles in a proportion that allows the light-control function due to the microparticles to be obtained. The content of the microparticles is, for example, 5 to 45% by weight. The content of the base resin is, for example, 55 to 95% by weight. Note that the weight ratio of the base resin to the microparticles may be greater than that of the microparticles in the thermosensitive light-control film. Specifically, the weight ratio of the base resin to the microparticles may be base resin:microparticles=95:5 to 55:45. The respective contents of the microparticles and base resin are not limited to the numerical ranges exemplified above.

[0036] At temperatures below the melting point, the difference (absolute value) between the refractive index of the microparticles and the refractive index of the base resin may be less than 0.020, preferably 0.001 or more and less than 0.020. At temperatures above the melting point, the difference (absolute value) between the refractive index of the microparticles and the refractive index of the base resin may be 0.020 or more, preferably 0.020 to 0.050. In these cases, the temperature-sensitive light-control film significantly changes from transparent to opaque. For example, when an ethylene-methyl methacrylate copolymer resin (or methyl methacrylate resin) is used as the base resin, the refractive index of the base resin is 1.480 to 1.520 at temperatures below the melting point and 1.450 to 1.500 at temperatures above the melting point.

[0037] Examples of base resins for the temperature-sensitive light control film include polyethylene terephthalate resin, polyvinyl chloride resin, ethylene-methyl methacrylate copolymer resin, polycarbonate, methyl methacrylate resin, polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer resin (EVA), and polyolefin-based resins. Examples of polyolefin-based resins include polyethylene resins. Examples of polyethylene resins include linear low-density polyethylene resin (LLDPE) and low-density polyethylene resin (LDPE). Two or more types of base resins may be mixed and used. The weight-average molecular weight of the base resin is not particularly limited.

[0038] The thickness of the temperature-sensitive light-control film is preferably 10 to 500 μm, more preferably 40 to 150 μm. The temperature-sensitive light-control film is not limited to a film shape, but includes a film shape or a sheet shape as long as the effect of this embodiment is not impaired. In other words, the temperature-sensitive light-control film may be referred to as a temperature-sensitive light-control sheet.

[0039] In the above-described embodiment, the thermosensitive light-controlling film is transparent at temperatures below the melting point and opaque at temperatures equal to or higher than the melting point. However, the transparency and opaqueness of the thermosensitive light-controlling film can be reversed. That is, the thermosensitive light-controlling film may be opaque at temperatures below the melting point and transparent at temperatures equal to or higher than the melting point. When constructing such a thermosensitive light-controlling film, the refractive index of the microparticles at temperatures below the melting point may be set to a value far from the refractive index of the base resin, and the refractive index of the microparticles at temperatures equal to or higher than the melting point may be set to a value close to the refractive index of the base resin.

[0040] (for plasticizers) Next, the case where the fine particles are used as a plasticizer will be described. When a general plasticizer is added to a resin material to improve its processability at high temperatures, the properties at room temperature (for example, a temperature range of -20 to 40°C) also deteriorate.

[0041] The fine particles of this embodiment are added to improve the processability of resin materials at high temperatures, but their properties at room temperature are not easily degraded. Furthermore, by adjusting the melting point, plasticity can be imparted at any temperature. Therefore, for example, the molding processability, such as reducing the torque of an extruder, can be improved while maintaining the properties of the resin material at room temperature.

[0042] The weight ratio of the base resin to the fine particles may be 9:1 to 1:9. The fine particles alone may be used as the plasticizer, or a general-purpose resin such as polyethylene resin to which the fine particles have been added may be used as the plasticizer.

[0043] <Method for producing thermosensitive particles> Next, a method for producing thermosensitive fine particles according to one embodiment of the present invention will be described.

[0044] In this embodiment, the fine particles are obtained by polymerizing the monomer components constituting the side-chain crystalline polymer. Examples of the polymerization method for the monomer components include emulsion polymerization, suspension polymerization, and mini-emulsion polymerization. During the polymerization, for example, an aqueous medium, a surfactant, a polymerization initiator, and the like may be used.

[0045] For example, an aqueous medium and a surfactant may be added to the monomer components to prepare a mixed solution, the mixed solution may be stirred by a stirring means to turn the monomer components into particles, and then a polymerization initiator may be further added to polymerize the monomer components.

[0046] Examples of the stirring means include a homogenizer. The stirring conditions may be, for example, a rotation speed of 5,000 to 20,000 rpm, a stirring time of 1 to 20 minutes, and a liquid temperature of 40 to 90° C. The liquid temperature during polymerization of the monomer components may be, for example, 40 to 90° C.

[0047] The aqueous medium may be, for example, water, etc. The amount of the aqueous medium added is preferably 50 to 90% by weight relative to 100% by weight of the total of the monomer components and the aqueous medium.

[0048] Examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, reactive surfactants, etc. The amount of surfactant added is preferably 0.5 to 7 parts by weight in terms of solid content per 100 parts by weight of the monomer component.

[0049] Examples of the polymerization initiator include persulfates and azo compounds. Specific examples include potassium persulfate, 2,2'-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate, 2,2'-Azobis(2-methylpropionamidine)dihydrochloride, and Lauroyl peroxide. The amount of the polymerization initiator added is preferably 0.05 to 2 parts by weight per 100 parts by weight of the monomer components.

[0050] The present invention will be described in detail below with reference to synthesis examples and examples, but the present invention is not limited to the following synthesis examples and examples.

[0051] (Synthesis examples 1-7: Temperature-sensitive fine particles) First, the monomers shown in Table 1 were added to a reaction vessel in the proportions shown in Table 1. The monomers shown in Table 1 are as follows. C18A: Stearyl acrylate C16A: Cetyl acrylate C12A: Lauryl acrylate AA: acrylic acid Multifunctional monomer (A): Trimethylolpropane triacrylate Multifunctional monomer (B): 1,6-hexanediol diacrylate HRD-01: 2-(O-phenylphenoxy)ethyl acrylate, a refractive index adjusting monomer manufactured by Nisshoku Techno Fine Chemical Co., Ltd.

[0052] Next, an aqueous medium and a surfactant were added to the reaction vessel to obtain a mixed solution. Water was used as the aqueous medium. The surfactants added were as follows: Synthesis Example 1: Adeka Reactive Anionic Surfactant "Adeka Reasoap SR-10" Synthesis Examples 2 to 7: Aqualon AR-10, a reactive anionic surfactant manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0053] The amount of aqueous medium added was 80% by weight based on 100% by weight of the total of the monomer components and aqueous medium, and the amount of surfactant added was 1 part by weight in terms of solid content based on 100 parts by weight of the monomer components.

[0054] Next, the mixture was stirred by a stirring means to convert the monomer component into particles under the following stirring conditions. Stirring means: AS ONE homogenizer (main body: AHG-160D, rotor: HT1025) Rotation speed for synthesis examples 1 and 2: 15,000 rpm Rotation speed for synthesis examples 3 to 7: 7500 rpm Stirring time: 5 minutes Liquid temperature: 40℃

[0055] Finally, a polymerization initiator was added to the reaction vessel to polymerize the monomer components to obtain thermosensitive particles. The aqueous medium was then removed by suction filtration and vacuum drying. The polymerization initiators added were as follows: Synthesis example 1: 2,2'-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate Synthesis examples 2~7: Lauroyl peroxide

[0056] The amount of the polymerization initiator added was 1 part by weight relative to 100 parts by weight of the monomer components. The liquid temperature during polymerization of the monomer components was as follows. Synthesis example 1: 65℃ Synthesis examples 2-7: 67℃

[0057] The average particle size and melting point were measured for the thermosensitive microparticles obtained in Synthesis Examples 1 to 7. The storage modulus G' was also measured for Synthesis Example 1. The measurement methods are shown below, and the results are also shown in Table 1.

[0058] (Average particle size) SEM photographs (magnification: 1000 times) of the fine particles were taken using an SEM, and the obtained SEM photographs were subjected to image processing to randomly extract 30 fine particles, and the average value was calculated.

[0059] (Melting Point) Measurement was performed using a DSC under the condition of 10°C / min.

[0060] (storage modulus G') Using a Thermo Scientific dynamic viscoelasticity measuring device "HAAKE MARSIII," the frequency was set to 1 Hz, the load to 3.00 N, and the heating rate to 5°C / min. The temperature was lowered from 60°C to 0°C, and then the storage modulus G' at the melting point -10°C and at the melting point +10°C was measured during the temperature increase from 0 to 100°C. The measurement results were also used to calculate the ratio [(storage modulus G' at melting point -10°C) / (storage modulus G' at melting point +10°C)].

[0061] [Table 1]

[0062] [Example 1] <Preparation of test specimens> First, polyethylene resin and the fine particles obtained in Synthesis Example 1 were mixed at a weight ratio of polyethylene resin:fine particles=7:3.

[0063] The mixture was then kneaded and formed into a 1 mm thick sheet to obtain a test piece. The kneading was carried out using a Labo Plastomill manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of 150°C x 15 minutes.

[0064] <Evaluation> The storage modulus G' of the obtained test piece was measured in the same manner as in the above-mentioned synthesis example. The results are shown in Figure 1.

[0065] [Comparative Example 1] A test piece was obtained by molding the polyethylene resin alone used in Example 1 into a sheet having a thickness of 1 mm. The storage modulus G' of this test piece was then measured in the same manner as in Example 1. The results are shown in Figure 1.

[0066] As is clear from Figure 1, Example 1 has a storage modulus G' similar to that of Comparative Example 1 at temperatures below the melting point, but at temperatures above the melting point, the storage modulus G' is lower than that of Comparative Example 1, demonstrating a softening function. These results demonstrate that the use of temperature-sensitive microparticles makes it possible to control and manifest physical properties such as the elastic modulus of the base resin by temperature. It also demonstrates that the temperature-sensitive microparticles can be used as plasticizers, etc.

[0067] [Examples 2 to 7] <Preparation of thermosensitive light-control film> First, the base resin and the microparticles obtained in Synthesis Examples 2 to 7 were mixed in the combinations shown in Table 2. The weight ratio of the base resin to the microparticles was base resin:microparticles=90:10.

[0068] The base resins used were as follows: EVA: Tosoh's "Ultrasen 630" LLDPE: Tosoh's "Nipolon L T240F"

[0069] Next, the mixture was kneaded at 150°C for 15 minutes using a Laboplastomill manufactured by Toyo Seiki Seisaku-sho, Ltd. The kneaded mixture was then molded using a press set at 140°C to obtain a light-control film with a thickness of 100 μm.

[0070] <Evaluation> The light control functions of the light control films obtained in Examples 2 to 7 were evaluated. Specifically, the light control films were first visually observed at room temperature (20°C). As a result, the light control films were transparent. Next, the light control films were heated with a dryer to a temperature above the melting point (melting point + 5°C) and visually observed. As a result, the light control films became cloudy. The light control films were then cooled back to room temperature and visually observed. As a result, the light control films changed to transparency. As is clear from these results, Examples 2 to 7 are transparent at temperatures below the melting point and opaque at temperatures above the melting point. It is also clear that Examples 2 to 7 alternate between transparency and opaqueness.

[0071] The haze is shown in Table 2. A haze of less than 15% was transparent, and a haze of 15% or more was cloudy. The haze was measured using a spectrophotometer "CM3600" manufactured by Konica Minolta.

[0072] The refractive indices of the base resin and the fine particles at 20°C and melting point + 5°C are shown in Table 2. The refractive indices were measured using an automatic refractometer "Abbemat 350" manufactured by Anton Paar.

[0073] [Table 2]

Claims

1. The polymer comprises a side chain crystalline polymer that crystallizes at a temperature below the melting point and exhibits fluidity at a temperature equal to or higher than the melting point, the side-chain crystalline polymer contains, as monomer components, a (meth)acrylate having a linear alkyl group having 14 or more carbon atoms and a polyfunctional monomer; the polyfunctional monomer is at least one selected from the group consisting of a difunctional (meth)acrylate, a trifunctional (meth)acrylate, and a tetrafunctional (meth)acrylate; dried particles, The average particle size is 1.5 to 50 μm, The temperature-sensitive fine particles have a difference (absolute value) between the refractive index at a temperature below the melting point and the refractive index at a temperature equal to or higher than the melting point of 0.010 or more.

2. The thermosensitive fine particles according to claim 1 , which do not contain an organic solvent.

3. The thermosensitive fine particles according to claim 1 or 2, which are a thermosensitivity imparting agent.

4. The thermosensitive fine particles according to any one of claims 1 to 3, which are used for dimming.

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