JP5717098B2 - Thermoresponsive resin particles and method for producing the same - Google Patents

Description

  The present invention relates to a thermoresponsive resin particle. More specifically, the present invention relates to a thermally responsive resin particle that can be widely used as a biomaterial, a medical material, a sanitary material, an industrial material, etc., and has a shape restoring property due to a temperature change, and a method for producing the same. is there.

  The shape memory material that shows shape restoration properties can fix the deformed shape by cooling the molded body by applying a predetermined temperature and then cooling it. By heating again, the shape of the molded body before deformation Is a material that can be restored. Conventionally, shape memory alloys and shape memory resins are known as shape memory materials.

  Compared to shape memory alloys, shape memory resin can be easily processed into complex shapes and has excellent moldability, high shape recovery rate, light weight, free coloring, low cost, etc. Have. Known shape memory resins include norbornene resins, crystalline block copolymers made of polystyrene and butadiene, and shape memory polyurethane elastomer moldings.

  Patent Document 1 describes a shape that exhibits shape memory by impregnating a non-thermoplastic elastomer having no shape memory with a resin having a glass transition temperature or a melting point higher than that of the non-thermoplastic elastomer. A memory resin is disclosed.

  Patent Document 2 discloses a weight-average particle size of 0.1 to 10 μm made of a shape memory resin such as polynorbornene, a crystalline styrene-transbutadiene block copolymer, and a hydrogenated crystalline styrene-butadiene copolymer. A shape memory resin emulsion comprising shape memory resin emulsion particles, a surfactant, and water is disclosed.

  Patent Document 3 discloses a three-dimensional paint containing spherical powder obtained by pulverizing a shape memory polymer having a glass transition point higher than the atmospheric temperature at the time of painting.

  Patent Document 4 includes a rubber and a crystalline non-polymer compound, and after preparing an intermediate kneaded product in which the rubber and the non-polymer compound are finely phase-separated in a state where the non-polymer compound is crystallized, A shape memory rubber molded article having shape memory properties by crosslinking the rubber is disclosed.

  However, although all of the shape memory resins disclosed in Patent Documents 1 to 4 undergo volume changes such as swelling and shrinkage at a specific temperature, the shape memory properties that are expressed are not high, and the original shape by heat Restorability to shape (shape self-restoration) was not sufficient.

JP 2004-10820 A Japanese Patent Publication No. 7-47642 JP-A-2-123174 JP 2009-24169 A

  The present invention has been made in view of the above-described conventional problems, and the purpose thereof is a thermoresponsive resin excellent in shape self-restoration by heat (characteristic showing shape change close to reversible shape change due to heat). It is to provide particles and a method for producing the same.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present application have compressed until the diameter reaches 40 to 50%, and the glass transition temperature of the thermoresponsive resin particles + 30 ° C. (the glass transition of the thermoresponsive resin particles) A heat-responsive resin particle having a diameter recovery rate of 80% or more based on the diameter before compression when heated for 60 seconds at a temperature higher by 30 ° C. than the temperature. The present inventors have found that the shape self-restoration by heat is excellent and have accomplished the present invention.

In order to solve the above-mentioned problem, the thermoresponsive resin particles of the present invention are compressed until the diameter is 40 to 50%, and are heated at the glass transition temperature of the thermoresponsive resin particles + 30 ° C. for 60 seconds. The diameter recovery rate is 80% or more based on the diameter before compression.
Thermoresponsive resin particles, at least one selected from the group consisting of (meth) acrylic acid ester-based polymerizable monomers, (meth) acrylamide-based polymerizable monomers, and (meth) acrylamide derivatives Polymeric matrix comprising a monomer mixture copolymer of (meth) acrylic monomer and a crosslinkable monomer having two or more carbon-carbon double bonds having polymerizable properties in the molecule And the acrylic liquid polymer contained in the polymer matrix, the crosslinkable monomer is a polyfunctional (meth) acrylate derivative, and the acrylic liquid polymer has a weight average molecular weight of 1000. Is an acrylic liquid polymer that is liquid at room temperature with a glass transition temperature of 0 ° C. or less, and the content of the acrylic liquid polymer is It is in the range of 5 to 100 parts by weight with respect to 100 parts by weight of the polymer matrix made of a polymer, and the amount of the crosslinkable monomer used is 100 parts by weight of the (meth) acrylic monomer. It is within the range of 0.3 to 10 parts by weight, and the glass transition temperature of the thermoresponsive resin particles is 14.0 to 52.8 ° C.

  In order to solve the above-mentioned problem, the method for producing the thermoresponsive resin particles of the present invention is a method for producing the thermoresponsive resin particles of the present invention, and is a (meth) acrylate-based polymerizable monomer. Body, at least one selected from the group consisting of (meth) acrylamide-based polymerizable monomers, and (meth) acrylamide derivatives, and a crosslink having two or more carbon-carbon double bonds having polymerizability in the molecule It is characterized by suspension polymerization of a mixture containing a monomer mixture containing a polymerizable monomer, an acrylic liquid polymer, and a radical polymerization initiator in a medium in which the mixture does not dissolve.

  The heat-responsive resin particles of the present invention are compressed until the diameter reaches 40 to 50%, and the restoration rate of the diameter when heated for 60 seconds at the glass transition temperature + 30 ° C. of the heat-responsive resin particles is Since it is 80% or more based on the diameter, it is excellent in shape self-restoration by heat.

  Such heat-responsive resin particles, for example, when applied to various paints such as automatic paints, impart to the paint film the property of repairing scratches on the paint film surface by heat stimulation. Excellent scratch resistance can be imparted to the coating film. Therefore, for example, when the coating film to which such heat-responsive resin particles are added is damaged, the coating film is repaired by heating the scratched portion of the coating film with a heat source such as a dryer. Can do. In addition, when such heat-responsive resin particles are added to a light diffusion film as a light diffusion agent for a light diffusion film (used for liquid crystal displays, etc.), the surface of the light diffusion film is damaged by heat stimulation. Can provide the light diffusing film with the property of repairing and impart excellent scratch resistance to the light diffusing film.

  Moreover, the thermoresponsive resin particle of this invention can be used suitably also as an easily peelable adhesive. In addition, the thermoresponsive resin particles of the present invention are general resin particle applications, such as tactile sensation improvers or slipperiness improvers used in cosmetics such as foundations, and antiblocking agents used in plastic films such as polyolefin films. Also, it can be suitably used as various spacers (gap retaining materials).

  According to the production method of the present invention, the diameter according to the present invention is compressed until the diameter reaches 40 to 50%, and the restoration rate of the diameter when the thermoresponsive resin particles are heated at the glass transition temperature + 30 ° C. for 60 seconds is compressed. Thermally responsive resin particles that are 80% or more based on the previous diameter and excellent in heat self-restoring can be easily obtained. Moreover, according to the manufacturing method of this invention, the thermoresponsive resin particle with high transparency maintenance property can be obtained.

  The present invention will be described more specifically below.

  The heat-responsive resin particles of the present invention are compressed until the diameter reaches 40 to 50%, and the diameter of the heat-responsive resin particles when heated at the glass transition temperature + 30 ° C. for 60 seconds is the standard before compression. The recovery rate (hereinafter referred to as “restoration rate by heating after compression”) is 80% or more. As for the heat-responsive resin particle of this invention, it is more preferable that the restoration rate by the heating after compression is 90% or more. Thereby, the thermoresponsive resin particle excellent in the shape self-restoration by heat | fever can be implement | achieved.

  Further, the thermoresponsive resin particles of the present invention are compressed until the diameter becomes 40 to 50%, and the glass transition temperature of the thermoresponsive resin particles is −20 ° C. (20 than the glass transition temperature of the thermoresponsive resin particles). It is preferable that the change rate of the diameter when heated at 60 ° C. for 60 seconds is 0 to 20% based on the diameter immediately after compression. By satisfying such physical properties, the thermoresponsive resin particles of the present invention can restore the thermoresponsive resin particles that have been compressed at the timing at which they are to be restored. In particular, the thermoresponsive resin particles of the present invention are compressed until the diameter reaches 40 to 50%, and the rate of change in diameter when left at room temperature (25 ° C.) is 0 based on the diameter immediately after compression. More preferably, it is -20%.

  Moreover, it is preferable that the average particle diameter of the thermoresponsive resin particle of this invention is 1 micrometer-2000 micrometers.

  The restoration rate and the average particle diameter of the heat-responsive resin particles after compression can be measured as follows when the average particle diameter of the heat-responsive resin particles is 200 μm or more.

  First, the center of the thermally responsive resin particles is obtained in a projection view obtained by projecting the thermally responsive resin particles with a digital microscope VHX-100 manufactured by Keyence Corporation at a magnification of 100 times. The average value of the major axis and the minor axis passing through the center of gravity is taken as the average particle diameter of the thermoresponsive resin particles before compression.

  Next, the thermo-responsive resin particles are sandwiched with a caliper under a glass transition temperature of −20 ° C. and 60% RH and compressed, and the scale of the caliper (the diameter along the compression direction of the thermo-responsive resin particles) is confirmed. However, it is compressed until the scale of calipers is 40-50% of the particle diameter.

  Thereafter, the compression is released, and the heat-responsive resin particles are held for 60 seconds in a glass transition temperature of −20 ° C. and a 60% RH environment. The particle diameter is obtained, and the rate of change in the average particle diameter of the thermoresponsive resin particles is confirmed.

  Next, the thermally responsive resin particles compressed and crushed on a hot plate set to a temperature 30 ° C. higher than the glass transition temperature of the thermally responsive resin particles are allowed to stand for 60 seconds (under a 60% RH environment).

  The center of gravity of the thermally responsive resin particles is obtained from the projection obtained by projecting the thermally responsive resin particles after heating with a digital microscope VHX-100 manufactured by Keyence Corporation. The average value of the major axis and the minor axis that passes is defined as the average particle diameter of the heat-responsive resin particles after heating.

  The ratio (B / A × 100) of the average particle diameter (B) of the heat-responsive resin particles after heating to the average particle diameter (A) of the heat-responsive resin particles before compression is defined as a restoration rate. The restoration rate may be measured for a plurality of (for example, 50) thermoresponsive resin particles, and an average value of the restoration rates obtained by the measurement may be used as the restoration rate.

  On the other hand, the recovery rate and the average particle diameter of the heat-responsive resin particles after compression can be measured as follows when the average particle diameter of the heat-responsive resin particles is less than 200 μm.

  The heat-responsive resin particles are compressed to 40 to 50% using a micro compression tester (“MCT series” manufactured by Shimadzu Corporation). That is, first, the heat-responsive resin particles are placed on the lower pressure plate of the micro compression tester and photographed with a microscope (“Side Observation Kit for Micro Compression Tester MCT” manufactured by Shimadzu Corporation). The center of gravity of the thermally responsive resin particles is obtained in the projected view, and the average value of the major axis and the minor axis passing through the center of gravity of the thermally responsive resin particles is defined as the average particle diameter of the thermally responsive resin particles before compression.

  Next, for one of the thermoresponsive resin particles on the lower pressure plate, the load is 0.072500 gf / sec using the upper pressure indenter (planar indenter made of diamond), and the load is the maximum load (test force). ) A load is applied downward in the vertical direction until reaching 1.00 gf, and the thermally responsive resin particles are compressed until the diameter along the vertical direction of the thermally responsive resin particles reaches 40 to 50% before compression. Thereafter, the compression is released, and the mixture is held in a Tg-20 ° C., 60% RH environment for 60 seconds, and the average particle size of the thermoresponsive resin particles is obtained in the same manner as the above-described measurement method of the average particle size. The rate of change in the average particle size of the resin particles is confirmed.

  Next, the thermally responsive resin particles compressed and crushed on a hot plate set at a temperature 30 ° C. higher than the Tg of the thermally responsive resin particles are allowed to stand for 60 seconds (under a 60% RH environment).

  In the projection obtained by projecting the thermally responsive resin particles after heating with a microscope (“Side Observation Kit for Micro Compression Tester MCT” manufactured by Shimadzu Corporation) at a magnification of 100 times, The center of gravity is obtained, and the average value of the major axis and the minor axis passing through the center of gravity of the thermoresponsive resin particles is defined as the average particle diameter of the thermoresponsive resin particles after heating.

  The ratio (B / A × 100) of the average particle diameter (B) of the heat-responsive resin particles after heating to the average particle diameter (A) of the heat-responsive resin particles before compression is defined as a restoration rate. The restoration rate may be measured for a plurality of (for example, 50) thermoresponsive resin particles, and an average value of the restoration rates obtained by the measurement may be used as the restoration rate.

  The upper presser indenter may be of a size suitable for the particle size of the thermoresponsive resin particles. For example, an upper presser indenter having a diameter of 50 μm can be used.

Although the thermoresponsive resin particles of the present invention can take various forms, it is easy to realize the thermoresponsive resin particles having a recovery rate of 80% or more after heating according to the present invention. is preferably Netsu応 answer resin particles according to the present embodiment explained.

The thermoresponsive resin particles of the present invention are at least one selected from the group consisting of (meth) acrylic acid ester polymerizable monomers, (meth) acrylamide polymerizable monomers, and (meth) acrylamide derivatives. Copolymerization of a monomer mixture containing a seed (hereinafter also referred to as a (meth) acrylic monomer) and a crosslinkable monomer having two or more carbon-carbon double bonds having polymerizability in the molecule A polymer matrix composed of a combination and an acrylic liquid polymer contained in the polymer matrix are included. In the thermoresponsive resin particles of the present invention , it is presumed that the copolymer forming the polymer matrix takes a form including a liquid polymer.

According to the configuration of the present invention, it is possible to easily realize the thermoresponsive resin particles having a recovery rate of 80% or more by heating after compression according to the present invention. Moreover, the thermoresponsive resin particles of the present invention further have an excellent feature of high transparency maintenance.

  In the present specification, “(meth) acryl” means acryl or methacryl, and “(meth) acrylate” means acrylate or methacrylate.

  The (meth) acrylic acid ester-based monomer is a (meth) acrylic acid ester having one polymerizable carbon-carbon double bond in the molecule and compatible with an acrylic liquid polymer. If there is no particular limitation, it can be used. Examples of the (meth) acrylate-based polymerizable monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) Tert-butyl acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, (meth) acrylic Benzyl acid, 1-adamantyl (meth) acrylate can be used. Each of these (meth) acrylic acid ester-based polymerizable monomers may be used alone or in combination of two or more. As the (meth) acrylic acid ester-based polymerizable monomer, a branched alkyl (meth) acrylate such as isobutyl (meth) methacrylate, tert-butyl (meth) acrylate or the like is used alone or branched. It is preferable to use a combination of an alkyl (meth) acrylate and another (meth) acrylic ester polymerizable monomer.

  Examples of the (meth) acrylamide polymerizable monomer include N-alkyl (meth) acrylamide and (meth) acrylamide. Each of these (meth) acrylamide polymerizable monomers may be used alone or in combination of two or more.

  Any (meth) acrylamide derivative may be used without particular limitation as long as it has one polymerizable carbon-carbon double bond in the molecule and is compatible with an acrylic liquid polymer. Examples of the (meth) acrylamide derivative include N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, N-pentoxymethyl (meth) acrylamide, N-hexyloxymethyl (meth) acrylamide, N-heptoxymethyl (meth) acrylamide, N-octoxymethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-propoxy N-alkoxyalkyl (meth) acrylamides such as ethyl (meth) acrylamide and N-butoxyethyl (meth) acrylamide may be mentioned. Each of these (meth) acrylamide derivatives may be used alone or in combination of two or more. As said (meth) acrylic-type monomer, N-alkoxyalkyl (meth) acrylamide is preferable and branched alkoxyalkyl (meth) acrylates, such as N-isobutoxymethyl (meth) acrylamide, are more preferable.

Carbon having a polymerizable within the molecule - crosslinkable monomer having two or more carbon double bonds, such as 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth ) Acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol adipate di (meta) ) Acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, N, N′-methylenebis (meth) acrylamide, N, N′-ethylenebis (meth) acrylamide, etc. Functional type; trimethylolpropane tri (meta Trifunctional type such as acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate; diglycerin tetra (meth) acrylate, pentaerythritol tetra (meth) tetrafunctional such acrylate; Ru polyfunctional (meth) acrylate derivatives der such.

  The amount of the crosslinkable monomer having two or more carbon-carbon double bonds having a polymerizable property in the molecule is 0.3 to 10 with respect to 100 parts by weight of the (meth) acrylic monomer. It is preferably within the range of parts by weight.

  The monomer mixture includes other vinyl monomers other than (meth) acrylic monomers and crosslinkable monomers for the purpose of increasing the compatibility between the monomer mixture and the acrylic liquid polymer. A monomer may be added as appropriate. When another vinyl monomer is added to the monomer mixture, the copolymer is a copolymer of a (meth) acrylic monomer, another vinyl monomer and a crosslinkable monomer. It becomes the composition which did.

  As said other vinyl-type monomer, what has one carbon-carbon double bond which has polymerizability in a molecule | numerator should just be mentioned, for example, (meth) acrylic acid, styrene, p-methylstyrene, (alpha), -Those having a polymerizable alkenyl group (broadly-defined vinyl group) such as methylstyrene and vinyl acetate. Each of these other vinyl monomers may be used alone or in combination of two or more.

The acrylic-based liquid polymer used in the heat-responsive resin particles of the present invention are those liquid at normal temperature, as long as it is compatible with the monomer mixture, can be used. The acrylic liquid polymer over is an acrylic based liquid polymer in liquid glass transition temperature (Tg) of 0 ℃ or less. As a result, it is possible to realize thermoresponsive resin particles having higher mechanical strength, better reversible shape self-restoration by heat, and higher transparency maintenance. In addition, when the glass transition temperature (Tg) of the acrylic liquid polymer exceeds 0 ° C., the acrylic liquid polymer is solidified and difficult to prepare, and heat-responsive resin particles having high flexibility cannot be realized. Sometimes. If heat-responsive resin particles having high flexibility cannot be realized, it becomes difficult to realize heat-responsive resin particles that are further excellent in shape self-restoration by heat.

The acrylic liquid polymer over has a weight average molecular weight (Mw) of 1,000 to 50,000, and a glass transition temperature (Tg) of an acrylic liquid polymers are liquid at room temperature is 0 ℃ or less. As a result, it is possible to realize thermoresponsive resin particles having higher mechanical strength, better reversible shape self-restoration by heat, and higher transparency maintenance.

  The acrylic liquid polymer may be a non-functional acrylic liquid polymer having no functional group in its structure, and has a functional group such as a hydroxyl group, a carboxyl group, an epoxy group, or an alkoxysilyl group in the structure. An acrylic liquid polymer containing a group may be used and can be selected as necessary. These may be used alone or in combination.

  Examples of the acrylic liquid polymer include products marketed under the trade names listed below, and can be arbitrarily selected from the products listed below.

  Examples of the non-functional acrylic liquid polymer include a product group having a product group name “ARUFON (registered trademark) UP series” manufactured by Toagosei Co., Ltd. (Registered trademark) UP-1000 ”,“ ARUFON (registered trademark) UP-1010 ”,“ ARUFON (registered trademark) UP-1020 ”,“ ARUFON (registered trademark) UP-1021 ”,“ ARUFON (registered trademark) UP- 1061 "," ARUFON (registered trademark) UP1080 "," ARUFON (registered trademark) UP-1110 "," UP-1170 ", and" ARUFON (registered trademark) UP-1190 ". In addition, as a non-functional acrylic liquid polymer, a polyflow series manufactured by Kyoeisha Chemical Co., Ltd. can be suitably used.

  Examples of the acrylic liquid polymer containing a hydroxyl group include a product group having a product group name of “ARUFON (registered trademark) UH series” manufactured by Toagosei Co., Ltd. ARUFON (registered trademark) UH-2000 "," ARUFON (registered trademark) UH-2032 ", and" ARUFON (registered trademark) UH-2041 "are classified into products. Moreover, as an acrylic liquid polymer containing a hydroxyl group, Act Flow (registered trademark) series UMB-1001, UME-1001, UMM-1001, UT-1001, UT-3001, UMB-2005, UME manufactured by Soken Chemical Co., Ltd. -2005 etc. can also be used suitably.

  Examples of the acrylic liquid polymer containing an epoxy group include a product group with a product group name “ARUFON (registered trademark) UG series” manufactured by Toagosei Co., Ltd. The products are classified into products having the product names “ARUFON (registered trademark) UG-4000” and “ARUFON (registered trademark) UG-4010”.

  Examples of the acrylic liquid polymer containing an alkoxysilyl group include a product group having a product name of “ARUFON (registered trademark) US series” manufactured by Toagosei Co., Ltd., and the product group depends on quality and properties. , “ARUFON (registered trademark) US-6110”, “ARUFON (registered trademark) US-6120”, and “ARUFON (registered trademark) US-6170”. Further, as an acrylic liquid polymer containing an alkoxysilyl group, Actflow (registered trademark) series AS-300, AS-301 and the like manufactured by Soken Chemical Co., Ltd. can be suitably used.

  In addition, as the acrylic liquid polymer, a product commercially available under the trade name “Jonkrill (registered trademark)” from BASF Japan Ltd. may be used.

The content of the acrylic liquid polymer in the heat-responsive resin particles of the present invention, with respect to the co comprising a polymer a polymer matrix 100 parts by weight, Ru der range of 5 to 100 parts by weight. In this case, it is possible to realize thermoresponsive resin particles having higher mechanical strength, better shape self-restoration due to heat, no volume change due to water, and high transparency maintenance. When the acrylic liquid polymer is less than 5 parts by weight with respect to 100 parts by weight of the polymer matrix, the strength of the thermoresponsive resin particles becomes too high, and it becomes difficult to obtain high flexibility, and the shape self-restoration by heat It becomes difficult to realize heat-responsive resin particles that are more excellent in properties. On the other hand, when the amount of the acrylic liquid polymer is more than 100 parts by weight with respect to 100 parts by weight of the polymer matrix, the strength of the heat-responsive resin particles becomes weak and handling of the heat-responsive resin particles becomes difficult.

Furthermore, the thermoresponsive resin particles of the present invention may contain various additives as necessary. Examples of the additive include an antioxidant, a stabilizer, a pH adjuster, a fragrance, a surfactant, a colorant, and a dye.

[Method for producing thermoresponsive resin particles]
The thermoresponsive resin particles of the present invention are at least one selected from the group consisting of (meth) acrylic acid ester polymerizable monomers, (meth) acrylamide polymerizable monomers, and (meth) acrylamide derivatives. A monomer mixture containing a seed (meth) acrylic monomer and a crosslinkable monomer having two or more carbon-carbon double bonds having polymerizability in the molecule, an acrylic liquid polymer, and radical polymerization A mixed solution containing an initiator can be easily obtained by a production method in which the mixture is suspension-polymerized in a medium in which the mixed solution is not dissolved (a medium in which the mixed solution is insoluble), and the monomer mixture is polymerized and crosslinked. . In the mixed solution, (meth) acrylic acid ester-based polymerizable monomer, (meth) acrylamide-based polymerizable monomer, and at least one (meth selected from the group consisting of (meth) acrylamide derivatives ) An acrylic monomer, a crosslinkable monomer having two or more carbon-carbon double bonds having polymerizability in the molecule, an acrylic liquid polymer, and a radical polymerization initiator are uniformly mixed and dissolved. It is preferable.

  The radical polymerization initiator used in these production methods is not particularly limited, and examples thereof include benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroper Oil-soluble peroxides such as oxide and tert-butyl hydroperoxide; oil-soluble azo compounds such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile) Is mentioned. Each of these radical polymerization initiators may be used alone or in combination of two or more.

  The amount of the radical polymerization initiator used is preferably in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the total amount of the (meth) acrylic monomer and the crosslinkable monomer. .

  Moreover, you may add a dispersing agent and / or surfactant to the reaction system of suspension polymerization in these manufacturing methods. Examples of the dispersant include poorly water-soluble inorganic salts such as calcium phosphate and magnesium pyrophosphate; water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and polyvinyl pyrrolidone. Each of these dispersants and surfactants may be used alone or in combination of two or more.

  Examples of the surfactant include an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. Examples of the anionic surfactant include fatty acid salts such as sodium oleate; alkyl sulfates such as sodium lauryl sulfate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; alkylnaphthalene sulfonates; Examples include salts. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, and glycerin fatty acid ester. Is mentioned. Examples of the amphoteric surfactant include lauryl dimethylamine oxide.

  Each of these dispersants and surfactants may be used alone or in combination of two or more. From the point that the dispersion stability of the monomer mixture in the medium can be further improved, a dispersant of a poorly water-soluble phosphate such as calcium phosphate and magnesium pyrophosphate, and an anion such as alkyl sulfate and alkyl benzene sulfonate It is preferable to use in combination with a surfactant.

  The amount of the dispersant used is preferably in the range of 0.5 to 30 parts by weight with respect to 100 parts by weight of the total amount of the monomer mixture and the liquid polymer. The amount of the surfactant used is preferably in the range of 0.01 to 0.2 parts by weight with respect to 100 parts by weight of a medium (for example, an aqueous medium) in which the mixed solution does not dissolve.

  The polymerization reaction includes an oil phase containing the above mixed liquid (and a non-polymerizable organic solvent or the like used as necessary), a medium in which the mixed liquid is not dissolved (and a dispersant used as necessary, a surface activity) A second phase containing an agent or the like (a phase in which the oil phase does not dissolve, for example, an aqueous phase), and the oil phase is dispersed in the second phase and then heated while stirring. Can start. The second phase (for example, the aqueous phase) is preferably used in an amount of 100 to 1000 parts by weight with respect to 100 parts by weight of the oil phase.

  It is preferable to use an aqueous medium as the medium in which the mixed solution does not dissolve. Examples of the aqueous medium include water and a mixture of water and a water-soluble organic solvent (for example, a lower alcohol (alcohol having 5 or less carbon atoms)).

  The polymerization temperature is preferably in the range of 40 to 90 ° C. The polymerization time while maintaining the reaction system at the polymerization temperature is usually about 1 to 10 hours. The average particle size of the thermoresponsive resin particles can be appropriately controlled by adjusting the mixing ratio of the oil phase and the aqueous phase, the amount of dispersant used, the amount of surfactant used, the stirring conditions, the dispersion conditions, and the like.

  The oil phase is preferably dispersed as fine droplets in the second phase (for example, an aqueous phase). As a method of dispersing the oil phase as fine droplets in the aqueous phase, a method using a stirring force such as a propeller blade, a method using a homogenizer, a gap between a rotating blade and a machine wall, or a gap between rotating blades And a method using an emulsifying disperser utilizing high shear (shearing force), a method using an ultrasonic disperser, a method using a high-pressure jet disperser, and the like. For example, in the case of a method using a homogenizer, when the rotation speed of the homogenizer is large and the dispersion time is long, the obtained droplet diameter tends to be small, and the particle diameter of the obtained thermoresponsive resin particles tends to be small.

  After completion of the polymerization reaction, the dispersant is decomposed and removed with an acid, if desired, filtered if desired, washed with water if desired, dehydrated if desired, and dried if desired. The desired thermoresponsive resin particles can be obtained by carrying out pulverization if desired, and classification if desired. The thermoresponsive resin particles may be isolated by a known method from a medium (for example, an aqueous medium) in which the mixed solution is not dissolved.

  In order to prevent coalescence of the obtained thermoresponsive resin particles, an inorganic powder is attached to the surface of the obtained thermoresponsive resin particles, or an appropriate amount of the inorganic powder is combined with the thermoresponsive resin particles. Or the like, and the heat-responsive resin particles may be used. Examples of the inorganic powder include silica, alumina, titania, zirconia, ceria, iron oxide, and zinc oxide.

  The inorganic powder preferably has an average particle size within a range of 1/10000 to 1/100 of the average particle size of the thermoresponsive resin particles, and the average particle size of the thermoresponsive resin particles It is more preferable to have an average particle diameter in the range of 1 / 3,000 to 1/900. Specifically, the average particle size of the inorganic powder is preferably in the range of 1 to 100 nm, more preferably in the range of 2 to 50 nm, and in the range of 10 to 15 nm. Most preferred.

  Furthermore, the amount of the inorganic powder used is preferably in the range of 0.1 to 5% by weight with respect to the total amount of the inorganic powder and the thermoresponsive resin particles, and is preferably 1.0 to 3.0. More preferably, it is in the range of% by weight.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

  First, in the examples and comparative examples, the glass transition temperature (Tg) measurement method, the resin particle shape restoration property evaluation method (40% to 50% compression after Tg + 30 ° C. restoration rate measurement method by heating), and The method for measuring the average particle diameter will be described.

[Evaluation of Resilience of Resin Particle Shape (Measurement of Restoration Ratio by Heating at Tg + 30 ° C. after 40-50% Compression)]
(1) Measuring method of glass transition temperature (Tg) The glass transition point (Tg) was measured by the method described in JIS K7121: 1987 "Method for measuring plastic transition temperature". However, the temperature conditions were measured under the following conditions. Using a differential scanning calorimeter DSC6220 (made by SII NanoTechnology Co., Ltd.), about 6 mg of sample is filled so that there is no gap at the bottom of the aluminum measurement container, and alumina is supplied under a nitrogen gas flow rate of 30 ml / min. Used as a reference material, heated from 30 ° C. to 120 ° C. at a heating rate of 10 ° C./min, held at temperature for 10 minutes, cooled from 120 ° C. to −60 ° C. at a cooling rate of 10 ° C./min, and heated for 10 minutes. After the heat treatment to be held, the midpoint glass transition temperature was calculated from the DSC curve obtained when the temperature was raised to 120 ° C. at a rate of 10 ° C./min under a nitrogen gas flow rate of 30 ml / min. This midpoint glass transition temperature was determined from the standard (9.3 “How to determine glass transition temperature”).

(2) Measurement method of average particle diameter and evaluation method of shape restoration property (restoration rate) In a projection view obtained by projecting resin particles with a digital microscope VHX-100 manufactured by Keyence Corporation at a magnification of 100 times The center of gravity of the resin particles was determined, and the average value of the major axis and the minor axis passing through the center of gravity of the resin particles was taken as the average particle diameter of the resin particles before compression.

  Next, the resin particles are sandwiched with a caliper under a Tg-20 ° C., 60% RH environment and compressed, and the caliper scale (diameter along the compression direction of the resin particles) is confirmed, and the scale of the caliper has a particle diameter. It was compressed until it became 40 to 50%. The ratio of the scale after compression to the scale of calipers before compression was taken as the compressibility of the resin particles, and the value is shown in Table 1.

  Thereafter, the compression is released, the resin particles are held for 60 seconds in a Tg-20 ° C., 60% RH environment, and the average particle size of the resin particles is determined in the same manner as in the method for measuring the average particle size described above. The rate of change in average particle size was confirmed.

  Next, the resin particles compressed and crushed on a hot plate set at a temperature 30 ° C. higher than the Tg of the resin particles were allowed to stand for 60 seconds (under a 60% RH environment).

  The resin particle after the heating is photographed with a digital microscope VHX-100 manufactured by Keyence Co., Ltd., and the center of the resin particle is obtained in a projection view, and the average value of the major axis and the minor axis passing through the center of gravity of the resin particle. Was the average particle size of the resin particles after heating.

  In addition, the ratio (B / Ax100) of the average particle diameter (B) of the resin particle after a heating with respect to the average particle diameter (A) of the resin particle before compression was made into the restoration rate. In this example and comparative example, the restoration rate was measured for 50 resin particles, and the average value of the restoration rate by these measurements is shown in Table 1.

[Example 1]
66.5 g of isobutyl methacrylate (trade name “Acryester IB”, manufactured by Mitsubishi Rayon Co., Ltd.) as a (meth) acrylate-based polymerizable monomer, and a carbon-carbon double bond having polymerizability in the molecule 1,9-nonanediol dimethacrylate (trade name “Light Ester 1,9-ND”, manufactured by Kyoeisha Chemical Co., Ltd.) as a crosslinkable monomer having 2 or more, and a weight average molecular weight of 3000 30 g of an epoxy group-containing acrylic liquid polymer (manufactured by Toagosei Co., Ltd., trade name “ARUFON (registered trademark) UG-4000”, glass transition temperature Tg = −61 ° C.) and 2,2 ′ as a radical polymerization initiator -2 g of azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed and stirred to obtain a monomer compounded liquid (mixed liquid). Also, 60 g of a 5 wt% aqueous solution of polyvinyl alcohol (saponification degree 88%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GH-17”) was dissolved in 240 g of ion-exchanged water, and 300 g of a 1 wt% aqueous polyvinyl alcohol solution was dissolved. Got.

  Next, the obtained monomer compounded solution and 300 g of the above 1 wt% polyvinyl alcohol aqueous solution were put into a glass separable flask having an internal volume of 500 ml, and the internal temperature of the separable flask was stirred while stirring at a stirring speed of 170 rpm. After raising the temperature to 65 ° C. and carrying out suspension polymerization under the condition of 65 ° C. over 3 hours, the internal temperature of the separable flask was further raised to 80 ° C. and taking 1 hour under the condition of 80 ° C. Suspension polymerization was performed. After returning the internal temperature of the separable flask to room temperature, resin particles were obtained by isolating the solid content from the contents of the separable flask.

  About the obtained resin particle, the average particle diameter and glass transition temperature Tg (intermediate point) were measured by the above-mentioned measuring method, and the shape restoration property by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

[Example 2]
The amount of isobutyl methacrylate (trade name “Acryester IB” manufactured by Mitsubishi Rayon Co., Ltd.) was changed to 75 g, and 1,9-nonanediol dimethacrylate (trade name “Light Ester 1,9” manufactured by Kyoeisha Chemical Co., Ltd.) was used. -ND ") was changed to 4.0 g, and the epoxy group-containing acrylic liquid polymer (trade name“ ARUFON (registered trademark) UG-4000 ”manufactured by Toagosei Co., Ltd.) was changed to 20 g. Except for this, resin particles were obtained in the same manner as in Example 1.

  About the obtained resin particle, the particle diameter and glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

Example 3
Resin particles were obtained by the same method as in Example 2 except that the stirring speed was changed from 170 rpm to 250 rpm.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

Example 4
The amount of isobutyl methacrylate (trade name “Acryester IB” manufactured by Mitsubishi Rayon Co., Ltd.) was changed to 85.5 g, and 1,9-nonanediol dimethacrylate (trade name “Light Ester 1” manufactured by Kyoeisha Chemical Co., Ltd.) was used. , 9-ND "")) was changed to 4.5 g, and the amount of non-functional acrylic liquid polymer (trade name “ARUFON (registered trademark) UG-4000” manufactured by Toagosei Co., Ltd.) was changed to 10 g. Resin particles were obtained in the same manner as in Example 1 except for changing to.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

Example 5
Resin particles were obtained by the same method as in Example 4 except that the stirring speed was changed from 170 rpm to 100 rpm.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

Example 6
As (meth) acrylic acid ester-based polymerizable monomer, instead of 66.5 g of isobutyl methacrylate (trade name “Acryester IB” manufactured by Mitsubishi Rayon Co., Ltd.), isobutyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., product) Resin particles were obtained in the same manner as in Example 1 except that 46.5 g of the name “Acryester IB”) and 20 g of methyl methacrylate (trade name: Acryester M, manufactured by Mitsubishi Rayon Co., Ltd.) were used.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

Example 7
Other than using 66.5 g of tert-butyl methacrylate (trade name: Light Ester TB, manufactured by Kyoeisha Chemical Co., Ltd.) instead of 66.5 g of isobutyl methacrylate as the (meth) acrylate-based polymerizable monomer. Obtained resin particles in the same manner as in Example 1.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

Example 8
Instead of 66.5 g of isobutyl methacrylate as the (meth) acrylic acid ester-based polymerizable monomer, isobutoxymethylacrylamide (manufactured by MRC Unitech Co., Ltd., product) as (meth) acrylamide and / or (meth) acrylamide derivative Resin particles were obtained in the same manner as in Example 1 except that 66.5 g of name: IBMA) was used.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. As a result of the evaluation, the obtained resin particles were found to be the thermoresponsive resin particles of the present invention having a glass transition temperature after compression of 40 to 50% + a recovery rate by heating at 30 ° C of 80% or more. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

[Comparative Example 1]
Use of non-functional acrylic liquid polymer (trade name “ARUFON (registered trademark) UG-4000” manufactured by Toagosei Co., Ltd.) and use of isobutyl methacrylate (trade name “IBMA” manufactured by Mitsubishi Rayon Co., Ltd.) Example except that the amount was changed to 95 g and the amount of 1,9-nonanediol dimethacrylate (Kyoeisha Chemical Co., Ltd., trade name “Light Ester 1,9-ND”) was changed to 5.0 g. 1 was used to obtain resin particles.

  About the obtained resin particle, the average particle diameter and the glass transition temperature (Tg (intermediate point)) were measured by the above-mentioned measuring method, and the shape recoverability by a temperature change was evaluated by the above-mentioned evaluation method. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

[Comparative Example 2]
Without using 1,9-nonanediol dimethacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name “Light Ester 1,9-ND”), isobutyl methacrylate (made by Mitsubishi Rayon Co., Ltd., trade name “Acryester IB”) Resin particles were obtained in the same manner as in Example 1 except that the amount of) was changed to 70 g.

  About the obtained resin particle, the average particle diameter was measured by the above-mentioned measuring method, and the shape recoverability by temperature change was evaluated by the above-mentioned evaluation method. The measurement results and the evaluation results are shown in Table 1 together with the blending amounts of the respective components used for the production of the resin particles.

[Comparative Example 3]
Non-functional acrylic liquid polymer having a weight average molecular weight of 1,700 (produced by Toagosei Co., Ltd., trade name “ARUFON (registered trademark) UG-4000”, Tg = −61 ° C.) 30 g instead of containing epoxy group Resin was prepared in the same manner as in Example 1 except that 30 g of an acrylic flake polymer (trade name “ARUFON (registered trademark) UG-4035” manufactured by Toagosei Co., Ltd., Tg = 52 ° C. (catalog value)) was used. Attempts were made to produce particles. However, resin particles could not be produced. Table 1 shows the amount of each component used in Comparative Example 3.

  In Table 1, PVA represents polyvinyl alcohol.

  From Table 1, the thermoresponsive resin particles of the present invention (Examples 1 to 8) are compared with the thermoresponsive resin particles outside of the scope of the present invention (Comparative Examples 1 to 3) after 40 to 50% compression. The glass has a high recovery rate by heating at a glass transition temperature of + 30 ° C. and has excellent shape self-restoration by heat.

Claims (4)

Diameter is compressed to 40 to 50% recovery rate of diameter when heated for 60 seconds with a glass transition temperature of + 30 ° C. of the heat-responsive resin particles is 80% or more size before compression as standard heat Responsive resin particles,
At least one (meth) acrylic monomer selected from the group consisting of (meth) acrylic acid ester polymerizable monomers, (meth) acrylamide polymerizable monomers, and (meth) acrylamide derivatives And a polymer matrix comprising a copolymer of a monomer mixture containing a crosslinkable monomer having two or more carbon-carbon double bonds having a polymerizable property in the molecule, and
Including an acrylic liquid polymer contained in the polymer matrix;
The crosslinkable monomer is a polyfunctional (meth) acrylate derivative,
The acrylic liquid polymer is a liquid acrylic liquid polymer having a weight average molecular weight of 1000 to 50000 and a glass transition temperature of 0 ° C. or less at room temperature,
The acrylic liquid polymer content is in the range of 5 to 100 parts by weight with respect to 100 parts by weight of the polymer matrix made of the copolymer,
The amount of the crosslinkable monomer used is in the range of 0.3 to 10 parts by weight with respect to 100 parts by weight of the (meth) acrylic monomer,
The heat-responsive resin particles, wherein the heat-responsive resin particles have a glass transition temperature of 14.0 to 52.8 ° C. The heat-responsive resin particle according to claim 1,
When the diameter of the thermoresponsive resin particles is compressed to 40 to 50% and heated at a glass transition temperature of −20 ° C. for 60 seconds, the change rate of the diameter is 0 to 20% based on the diameter immediately after compression. A heat-responsive resin particle characterized by being. The thermally responsive resin particle according to claim 1 or 2,
Thermoresponsive resin particles having an average particle size of 1 to 2000 μm. It is a manufacturing method of the thermoresponsive resin particle of any one of Claims 1-3 ,
At least one (meth) acrylic monomer selected from the group consisting of (meth) acrylic acid ester polymerizable monomers, (meth) acrylamide polymerizable monomers, and (meth) acrylamide derivatives And a monomer mixture containing a crosslinkable monomer having two or more carbon-carbon double bonds having polymerizability in the molecule, an acrylic liquid polymer, and a radical polymerization initiator, A method for producing heat-responsive resin particles, wherein suspension polymerization is performed in a medium in which the mixed solution is not dissolved.