Method for producing resin particles and drying device

Abstract

To provide a method for producing resin particles, which can suppress generation of coarse particles.SOLUTION: Provided is a method for producing resin particles, comprising a drying step where resin particles in a wet state, which undergo a phase transition by pressure, are dried by being passed through a drying tube together with a first gas without recycling. The drying tube comprises: a supply port where the resin particles are supplied into the drying tube; a gas discharge port where a second gas is discharged towards the resin particles which pass through the drying tube; and a discharge port where the resin particles are discharged from the drying tube. The discharge speed of the second gas, discharged from the gas discharge port, is 50 m / s or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing resin particles and a drying apparatus used in the method for manufacturing the resin particles.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing toner particles in which toner particles generated in an aqueous dispersion medium are washed, dehydrated, and the obtained wet toner particles are dried by a drying means. The drying means is a method of drying using an air flow with a wind speed of 15 m / s or more. When the ratio of particles having a particle size of 0.6 μm to 2.0 μm in the particle size distribution based on the equivalent circle diameter of the toner particles before drying is A, and the ratio of particles having a particle size of 0.6 μm to 2.0 μm in the particle size distribution based on the equivalent circle diameter of the toner particles after drying is B, drying is performed so as to satisfy the relationship B < 0.9A. The total cross-sectional area of the discharge path of the air flow of the drying means is C (m 2 ), and when the cross-sectional area of the main maximum path of the air flow is D (m 2 ), the relationship 0.09 < C / D < 0.15 is satisfied. The drying means has a loop-type air flow heating pipe and a plurality of cyclone collection parts, and the plurality of cyclone collection parts are connected in parallel, and a classifier is not provided between the loop-type air flow heating pipe and the cyclone repair part. A method for manufacturing toner particles is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present disclosure is to provide a method for producing resin particles, which includes a drying step in which wet resin particles that undergo a phase transition due to pressure are dried by circulating them together with a gas through a drying tube, or a drying step in which wet resin particles that undergo a phase transition due to pressure are dried by passing them through a drying tube together with a first gas without circulating them, wherein the drying tube has a gas outlet that discharges a second gas toward the resin particles passing through the drying tube, and which can suppress the generation of coarse particles compared to when the discharge speed of the second gas is less than 50 m / s. [Means for solving the problem]

[0005] Specific means for solving the above problems include the following aspects.

[0006] <1> a drying step of drying wet resin particles that undergo a phase transition under pressure by passing the wet resin particles together with a first gas through a drying tube without circulating the resin particles; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, The method for producing resin particles, wherein the second gas is discharged from the gas discharge port at a discharge speed of 50 m / s or more. <2> a drying step of drying wet resin particles that undergo a phase transition under pressure by passing the wet resin particles together with a first gas through a drying tube without circulating the resin particles; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, A method for producing resin particles, wherein the difference Δ(V2-V1) between the velocity V1 of the first gas passing through the drying tube and the discharge velocity V2 of the second gas discharged from the gas discharge port is 40 m / s or more.

[0007] <3> The drying tube has two or more gas outlets. <1> or <2> 1. A method for producing resin particles according to claim 1. <4> The discharge speed of the second gas discharged from the two or more gas discharge ports is 100 m / s or more, <3> 1. A method for producing resin particles according to claim 1. <5> a flow rate Q1 of the first gas passing through the drying tube and a total flow rate Q2 of the second gas discharged from the gas discharge port satisfy the relationship Q2 / (Q1+Q2)≧0.9; <3> or <4> 1. A method for producing resin particles according to claim 1. <6> a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfying the relationship d / D≦0.25; <1> ~ <5> 10. The method for producing resin particles according to any one of the above. <7> a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfying the relationship d / D≦0.20; <6> 1. A method for producing resin particles according to claim 1.

[0008] <8> The method further includes a recovery step of recovering the resin particles discharged from the drying tube in a recovery section, The temperature T1 of the second gas discharged from the gas discharge port is 50°C or more and 70°C or less, and the temperature T2 in the recovery section is 20°C or more and 40°C or less. <1> ~ <7> 10. The method for producing resin particles according to any one of the above. <9> The recovery unit is equipped with a bag filter, and the linear velocity of the gas passing through the filter in the bag filter is 0.1 m / s or less. <8> 1. A method for producing resin particles according to claim 1. <10> The resin particles that undergo a phase transition due to pressure are particles that satisfy the following formula 1: <1> ~ <9> 10. The method for producing resin particles according to any one of the above. Formula 1: 8℃≦T A -T B (In formula 1, T A is the temperature at which the viscosity is 10,000 Pa s under a pressure of 1 MPa, and T B is the temperature at which the viscosity is 10,000 Pa·s under a pressure of 10 MPa.

[0009] <11> a drying section that dries wet resin particles that undergo a phase transition under pressure by passing the resin particles together with a first gas through a drying tube without circulating the resin particles; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, A drying device, wherein the second gas is discharged from the gas discharge port at a discharge speed of 50 m / s or more. <12> a drying section that dries wet resin particles that undergo a phase transition under pressure by passing the resin particles together with a first gas through a drying tube without circulating the resin particles; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, A drying apparatus, wherein the difference Δ(V2-V1) between the velocity V1 of the first gas passing through the drying tube and the discharge velocity V2 of the second gas discharged from the gas discharge port is 40 m / s or more.

[0010] <13> The drying tube has two or more gas outlets. <11> or <12> The drying device according to claim 1. <14> The discharge speed of the second gas discharged from the two or more gas discharge ports is 100 m / s or more, <13> The drying device according to claim 1. <15> a flow rate Q1 of the first gas passing through the drying tube and a total flow rate Q2 of the second gas discharged from the gas discharge port satisfy the relationship Q2 / (Q1+Q2)≧0.9; <13> or <14> The drying device according to claim 1. <16> a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfying the relationship d / D≦0.25; <11> ~ <15> 10. The drying apparatus according to claim 9, wherein the drying apparatus is a drying apparatus for drying a semiconductor device. <17> a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfying the relationship d / D≦0.20; <16> The drying device according to claim 1.

[0011] <18> a recovery unit that recovers the resin particles discharged from the drying tube, The temperature T1 of the second gas discharged from the gas discharge port is 50°C or more and 70°C or less, and the temperature T2 in the recovery section is 20°C or more and 40°C or less. <11> ~ <17> 10. The drying apparatus according to claim 9, wherein the drying apparatus is a drying apparatus for drying a semiconductor device. <19> The recovery unit is equipped with a bag filter, and the linear velocity of the gas passing through the filter in the bag filter is 0.1 m / s or less. <18> The drying device according to claim 1. <20> The resin particles that undergo a phase transition due to pressure are particles that satisfy the following formula 1: <11> ~ <19> 10. The drying apparatus according to claim 9, wherein the drying apparatus is a drying apparatus for drying a semiconductor device. Formula 1: 8℃≦T A -T B (In formula 1, T A is the temperature at which the viscosity is 10,000 Pa s under a pressure of 1 MPa, and T B is the temperature at which the viscosity is 10,000 Pa·s under a pressure of 10 MPa.

[0012] <21> a drying section that dries wet resin particles that undergo a phase transition under pressure by passing the resin particles together with a first gas through a drying tube without circulating the resin particles; The drying device includes a loop-shaped pipe, a supply unit that supplies the resin particles into the loop-shaped pipe, a gas discharge unit that discharges a second gas toward the resin particles passing through the loop-shaped pipe, a discharge unit that discharges the resin particles from the loop-shaped pipe, and a closing plate that closes the circulation of the resin particles within the loop-shaped pipe. [Effects of the Invention]

[0013] <1> or <10> According to the invention, a method for producing resin particles can be provided which includes a drying step of circulating wet resin particles that undergo a phase transition due to pressure together with a gas through a drying tube to dry them, or a drying step of passing wet resin particles that undergo a phase transition due to pressure through a drying tube together with a first gas without circulating them, the drying tube having a gas discharge port that discharges a second gas toward the resin particles passing through the drying tube, and which can suppress the generation of coarse particles compared to when the discharge speed of the second gas is less than 50 m / s. <2> According to the invention, a method for producing resin particles can be provided which includes a drying step in which wet resin particles that undergo a phase transition due to pressure are circulated together with a gas through a drying tube to dry them, or a drying step in which wet resin particles that undergo a phase transition due to pressure are dried by passing them through a drying tube together with a first gas without circulating them, wherein the drying tube has a gas outlet that discharges a second gas toward the resin particles passing through the drying tube, and the difference Δ(V2-V1) between the speed V1 of the first gas passing through the drying tube and the discharge speed V2 of the second gas discharged from the gas outlet is less than 40 m / s.

[0014] <3> According to the invention, it is possible to provide a method for producing resin particles that can suppress the generation of coarse particles compared to when the drying tube has one gas discharge port. <4> According to the present invention, a method for producing resin particles can be provided that can suppress the generation of coarse particles compared to when the discharge speed of the second gas discharged from two or more gas discharge ports is, in part, less than 100 m / s. <5> According to the invention, a method for producing resin particles can be provided that can suppress the generation of coarse particles compared to when the flow rate Q1 of the first gas passing through the drying tube and the total flow rate Q2 of the second gas discharged from the gas discharge port satisfy the relationship Q2 / (Q1+Q2)<0.9. <6> According to the present invention, a method for producing resin particles can be provided that can suppress the generation of coarse particles compared to when the maximum diameter D of the drying tube and the maximum diameter d of the gas discharge port satisfy the relationship d / D>0.25. <7> According to the present invention, a method for producing resin particles can be provided that can suppress the generation of coarse particles compared to when the maximum diameter D of the drying tube and the maximum diameter d of the gas discharge port satisfy the relationship d / D>0.20. <8> According to the invention, a method for producing resin particles can be provided which further includes a recovery step of recovering resin particles discharged from the drying tube in a recovery section, and which can suppress the generation of coarse particles compared to when the temperature T1 of the second gas discharged from the gas discharge port is less than 50°C or more than 70°C and the temperature T2 in the recovery section is less than 20°C or more than 40°C. <9> According to the present invention, it is possible to provide a method for producing resin particles that can suppress the generation of coarse particles compared to when the recovery section is equipped with a cyclone.

[0015] <11> or <20> According to the invention, a drying device can be provided which is equipped with a drying section that circulates wet resin particles that undergo a phase transition due to pressure through a drying tube together with a gas to dry them, or which is equipped with a drying section that dries wet resin particles that undergo a phase transition due to pressure by passing them through a drying tube together with a first gas without circulating them, and the drying tube has a gas discharge port that discharges a second gas toward the resin particles passing through the drying tube, and which can suppress the generation of coarse particles compared to when the discharge speed of the second gas is less than 50 m / s. <12> According to the invention, a drying device can be provided which is equipped with a drying section that circulates wet resin particles that undergo a phase transition due to pressure through a drying tube together with a gas to dry them, or which is equipped with a drying section that dries wet resin particles that undergo a phase transition due to pressure by passing them through a drying tube together with a first gas without circulating them, and the drying tube has a gas outlet that discharges a second gas toward the resin particles passing through the drying tube, and which can suppress the generation of coarse particles compared to when the difference Δ(V2-V1) between the speed V1 of the first gas passing through the drying tube and the discharge speed V2 of the second gas discharged from the gas outlet is less than 40 m / s.

[0016] <13> According to the invention, it is possible to provide a drying device that can suppress the generation of coarse particles compared to a case in which the drying tube has one gas outlet. <14> According to the invention, a drying device can be provided that can suppress the generation of coarse particles compared to when the discharge speed of the second gas discharged from two or more gas discharge ports is, in part, less than 100 m / s. <15> According to the invention, it is possible to provide a drying device that can suppress the generation of coarse particles compared to a case where the flow rate Q1 of the first gas passing through the drying tube and the total flow rate Q2 of the second gas discharged from the gas discharge port satisfy the relationship Q2 / (Q1+Q2)<0.9. <16> According to the invention, it is possible to provide a drying device that can suppress the generation of coarse particles compared to when the maximum diameter D of the drying tube and the maximum diameter d of the gas discharge port satisfy the relationship d / D>0.25. <17> According to the invention, it is possible to provide a drying device that can suppress the generation of coarse particles compared to when the maximum diameter D of the drying tube and the maximum diameter d of the gas discharge port satisfy the relationship d / D>0.20. <18> According to the invention, a drying device can be provided which further includes a recovery section that recovers resin particles discharged from the drying tube in the recovery section, and which can suppress the generation of coarse particles compared to when the temperature T1 of the second gas discharged from the gas discharge port is less than 50°C or more than 70°C and the temperature T2 in the recovery section is less than 20°C or more than 40°C. <19> According to the invention, it is possible to provide a drying device that can suppress the generation of coarse particles compared to when the recovery section is equipped with a cyclone.

[0017] <21> It is possible to provide a drying device that can suppress the generation of coarse particles compared to a device equipped with a drying section that circulates wet resin particles that undergo a phase transition under pressure together with gas within a drying tube to dry them. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing an example of a drying section and a recovery section in a drying device according to the present disclosure, which performs the drying step and the recovery step in the method for producing resin particles according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing another example of the drying section of the drying device according to the present disclosure, which performs the drying step in the method for producing resin particles according to the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing another example of the drying section of the drying device according to the present disclosure, which performs the drying step in the method for producing resin particles according to the present disclosure. [Figure 4] FIG. 4 is a partially enlarged configuration diagram for explaining the maximum diameter D of the drying tube and the maximum diameter d of the gas discharge port. DETAILED DESCRIPTION OF THE INVENTION

[0019]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0020] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0021] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0022] When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0023] In the present disclosure, the term "(meth)acrylic" means either "acrylic" or "methacrylic."

[0024] <Method of manufacturing resin particles> The method for producing resin particles may include a drying step of drying wet resin particles. One method for drying wet resin particles is to circulate the wet resin particles together with a gas through a loop-shaped drying tube. However, when resin particles that undergo a phase transition due to pressure are used as wet resin particles in the above drying method, the resin particles may fuse together due to their properties, resulting in the generation of coarse particles. Here, the term "coarse particles" refers to aggregates formed by fusion of resin particles, and refers to particles that do not pass through a standard sieve with 20 μm openings as specified in JIS Z 8801-1:2006.

[0025] Therefore, the present inventors have conducted extensive research into methods for drying wet resin particles that undergo phase transition under pressure, and have come to the following findings. That is, the present inventors have found that the generation of coarse particles can be suppressed by including a drying process in which wet resin particles that undergo a phase transition under pressure are dried by passing them through a drying tube together with a first gas without circulating them, the drying tube having a gas outlet that discharges a second gas toward the resin particles passing through the drying tube, and by setting the discharge speed of the second gas discharged from the gas outlet to 50 m / s or more, or by setting the difference Δ(V2-V1) between the speed V1 of the first gas passing through the drying tube and the discharge speed V2 of the second gas discharged from the gas outlet to 40 m / s or more.

[0026] <First embodiment of the method for producing resin particles / First embodiment of the drying device> A first embodiment of the method for producing resin particles according to the present disclosure includes a drying step in which wet resin particles that undergo a phase transition under pressure are dried by passing them through a drying tube together with a first gas without circulating them, wherein the drying tube has a supply port for supplying resin particles into the drying tube, a gas outlet for ejecting a second gas toward the resin particles passing through the drying tube, and an outlet for discharging the resin particles from the drying tube, and the second gas ejected from the gas outlet has an ejection speed of 50 m / s or more. Furthermore, a first embodiment of the method for producing resin particles according to the present disclosure is carried out in a drying device (first embodiment of the drying device according to the present disclosure) that includes a drying section that dries wet resin particles that undergo a phase transition under pressure by passing them through a drying tube together with a first gas without circulating them, the drying tube having a supply port that supplies the resin particles into the drying tube, a gas outlet that ejects a second gas toward the resin particles passing through the drying tube, and an outlet that discharges the resin particles from the drying tube, and the second gas ejected from the gas outlet has an ejection speed of 50 m / s or more. Here, the discharge speed of the second gas discharged from the gas discharge port means the flow speed of the second gas at the gas discharge port.

[0027] <Second embodiment of the method for producing resin particles / Second embodiment of the drying device> A second embodiment of the method for producing resin particles according to the present disclosure includes a drying step in which wet resin particles that undergo a phase transition under pressure are dried by passing them through a drying tube together with a first gas without circulating them, wherein the drying tube has a supply port for supplying resin particles into the drying tube, a gas outlet for discharging a second gas toward the resin particles passing through the drying tube, and an outlet for discharging the resin particles, and the difference Δ(V2-V1) between the speed V1 of the first gas passing through the drying tube and the discharge speed V2 of the second gas discharged from the gas outlet is 40 m / s or more. In addition, a second embodiment of the method for producing resin particles according to the present disclosure is carried out in a drying device (second embodiment of the drying device according to the present disclosure) that includes a drying section that dries wetted resin particles that undergo a phase transition under pressure by passing them through a drying tube together with a first gas without circulating them, and the drying tube includes a supply port that supplies resin particles into the drying tube, a gas outlet that discharges a second gas toward the resin particles passing through the drying tube, and an outlet that discharges the resin particles from the drying tube, and the difference Δ(V2-V1) between the speed V1 of the first gas passing through the drying tube and the discharge speed V2 of the second gas discharged from the gas outlet is 40 m / s or more. Here, the velocity V1 of the first gas passing through the drying tube means the flow velocity of the first gas just before the second gas mixes with the first gas inside the drying tube, and the discharge velocity V2 of the second gas discharged from the gas discharge port means the flow velocity of the second gas at the gas discharge port.

[0028] <Third embodiment of the drying device> A third embodiment of the drying apparatus according to the present disclosure is a drying apparatus comprising a drying section that dries wet resin particles that undergo a phase transition under pressure by passing them through a drying tube together with a first gas without circulating them within the drying tube, the drying tube comprising a loop-shaped pipe, a supply section that supplies resin particles into the loop-shaped pipe, a gas discharge section that discharges a second gas toward the resin particles passing through the loop-shaped pipe, a discharge section that discharges the resin particles from within the loop-shaped pipe, and a closing plate that closes the circulation of the resin particles within the loop-shaped pipe.

[0029] In the present disclosure, unless otherwise specified, when the term "the method for producing resin particles according to the present disclosure" is used, it refers to both the first and second embodiments described above. Furthermore, in this disclosure, when the term "drying device according to the present disclosure" is used without any particular specification, it refers to all of the above-mentioned first embodiment, second embodiment, and third embodiment. In the following, resin particles in a wet state that undergo a phase transition due to pressure will also be referred to as "particles to be dried" as appropriate, and when describing resin particles themselves that undergo a phase transition due to pressure, regardless of whether they are wet or not, they will also be referred to as "pressure-responsive particles" as appropriate.

[0030] In the resin particle manufacturing method and drying apparatus according to the present disclosure, the particles to be dried pass through the drying tube together with the first gas without circulating. Here, "without circulating" means that the particles to be dried move with the flow of the first gas (i.e., the airflow) and pass through the interior region of the drying tube from the supply port to the discharge port only once. Note that the above "without circulating" allows for localized retention and backflow of the particles within the drying tube. Thus, in the present disclosure, the particles to be dried pass through the drying tube together with the first gas only once and are discharged from the drying tube. This eliminates collisions between dried particles and wet particles, which occurs in methods in which wet particles are circulated through a loop-shaped drying tube together with the gas. Resin particles that undergo a pressure-sensitive phase transition (i.e., pressure-responsive particles) can undergo fusion due to collisions between resin particles, which can result in the generation of coarse particles. According to the method for producing resin particles disclosed herein, the particles to be dried are passed through the drying tube together with the first gas without being circulated, which is presumably effective in suppressing the generation of coarse particles caused by collisions between dried particles and wet particles.

[0031] Hereinafter, with reference to FIG. 1, a drying device according to the present disclosure that performs the drying step in the method for producing resin particles according to the present disclosure will be described. FIG. 1 is a schematic diagram showing an example of a drying section and a recovery section in a drying device according to the present disclosure, which performs the drying step and the recovery step in the method for producing resin particles according to the present disclosure. The drying apparatus shown in FIG. 1 includes a drying section 100A that dries particles to be dried by passing them through a drying tube together with a first gas without circulating them, and a recovery section 200 that recovers the particles to be dried discharged from the drying tube. The drying device shown in FIG. 1 includes a drying tube 10A according to the third embodiment of the present disclosure.

[0032] 1, the drying section 100A includes a drying tube 10A configured such that the interior of the loop piping is closed with a closing plate to prevent the particles to be dried from circulating within the loop piping. The drying tube 10A includes a loop piping 11A, a supply unit 12 that supplies the particles to be dried together with a first gas into the loop piping 11A, a second gas discharge nozzle (an example of a gas discharge unit) 14 that discharges a second gas toward the particles to be dried passing through the loop piping 11A, a discharge unit 16 that discharges the particles to be dried together with the gas from the loop piping 11A, and a closing plate 18 that closes the circulation of the particles to be dried within the loop piping 11A. In other words, the drying tube 10A is configured by providing the supply unit 12, the second gas discharge nozzle 14, the discharge unit 16, and the closing plate 18 in the loop piping 11A.

[0033] In the drying tube 10A, the "supply port that supplies resin particles into the drying tube" corresponds to the supply port 12a, which is an opening of the supply section 12, the "gas outlet that ejects a second gas toward resin particles passing through the drying tube" corresponds to the gas outlet 14a, which is an opening of the second gas ejection nozzle (an example of a gas outlet section) 14, and the "exhaust port that ejects resin particles from inside the drying tube" corresponds to the exhaust port 16a, which is an opening of the exhaust section 16.

[0034] 1, three gas discharge ports 14a are arranged side by side from the supply port 12a toward the discharge port 16a of the drying tube 10A, and three second gas discharge nozzles 14 are connected to the three gas discharge ports 14a, respectively. The drying section 100A is also provided with a second gas supply section 20 that covers the three gas discharge nozzles 14.

[0035] The particles to be dried are supplied to the supply port 12a by a supply machine (not shown). The particles to be dried that have been supplied to the supply port 12a are naturally sucked in the direction of the arrow shown in FIG. 1 due to a balance between suction (specifically, intake air) from the exhaust section 16 (specifically, exhaust port 16a) side in the drying tube 10A and the discharge of the second gas from the gas discharge port 14a into the drying tube 10A.

[0036] The second gas supplied to the second gas supply unit 20 has its temperature and humidity adjusted by passing through a dehumidifier, a discharge blower, a heater, etc. (not shown). For example, gas dehumidified by a dehumidifier is pushed out by a discharge blower, and then heated by a heater, and the low-humidity, high-temperature second gas is supplied to the second gas supply unit 20.

[0037] When the particles to be dried are supplied into the drying tube 10A from the supply port 12a together with the first gas, the particles form an aggregate (i.e., a mass of wet pressure-responsive particles) and flow intermittently or continuously toward the discharge port 16a. Here, the first gas forms an airflow (hereinafter also referred to as the main flow) that passes through the drying tube 10A from the supply port 12a to the discharge port 16a. The particles to be dried pass through the drying tube 10A along with this main flow. The drying tube 10A is constructed using a loop-type pipe 11A, but since the inside of the loop-type pipe 11A is blocked by a closing plate 18, the particles to be dried pass through the drying tube 10A together with the first gas without circulating.

[0038] The second gas discharged from the three gas outlets 14a hits the particles to be dried (specifically, aggregates of particles) passing through the drying tube 10A in the direction of gravity. The impact of the second gas on the aggregates of particles breaks them up, accelerating the drying of the particles. The particles to be dried (specifically, the individually broken particles) pass through the drying tube 10A in their original state, undergo drying, and become less moist. The particles are then discharged from the outlet 16a together with a gas containing the first and second gases (i.e., along with the airflow of the first and second gases). Specifically, the particles to be dried, which are continuously or intermittently supplied into the drying tube 10A, are broken up by the second gas, and are then entrained in the flow of the first and second gases, whereby moisture is transferred to the first and second gases, forming dried particles, which are then discharged from the outlet 16a. The drying section 100A has the above-described configuration, and thus the drying process of the particles to be dried is carried out continuously.

[0039] As shown in FIG. 1, the recovery section 200 is connected to the outlet 16a of the drying tube 10A and includes a transfer pipe 30 that transfers the dried particles and gas discharged from the outlet 16a of the drying tube 10A, and a bag filter 40 that separates the dried particles and gas transferred via the transfer pipe 30 and recovers the dried particles.

[0040] The dried particles and gas discharged from the outlet 16 a of the drying tube 10 A are transferred to the bag filter 40 via the transfer pipe 30 . The dry particles transferred to the bag filter 40 are captured by the filter 42. The gas that flows into the bag filter 40 together with the dry particles passes through the filter 42 and is discharged from an exhaust port connected to the intake side of an exhaust blower (not shown). In this way, the dry particles and the gas are separated into solid and gas in the bag filter 40.

[0041] The dried particles captured by air filtration in filter 42 of bag filter 40 may have a further decrease in moisture content because they are exposed to air while being captured on the surface of filter 42. In this way, the dried particles may be further dried in bag filter 40 equipped with filter 42. The dried particles captured by air filtration in filter 42 are discharged and collected from collection port 44 at the bottom of bag filter 40.

[0042] In the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure, the drying section is not limited to the configuration of drying section 100A shown in Fig. 1. The drying section in the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure may be drying section 100B equipped with drying tube 10B as shown in Fig. 2, or drying section 100C equipped with drying tube 10C as shown in Fig. 3.

[0043] The drying section 100B shown in FIG. 2 differs from the drying section 100A shown in FIG. 1 only in that it includes a drying tube 10B with a different structure instead of the drying tube 10A. The drying tube 10B has a supply port 12a through which particles to be dried are supplied into the drying tube 10B together with a first gas, a gas outlet 14a through which a second gas is discharged toward the particles passing through the drying tube 10B, and an outlet 16a through which the particles to be dried together with the gas are discharged from the drying tube 10B. The drying tube 10B is configured by a non-loop piping 11B having a supply section 12 and an outlet 16, and a gas discharge nozzle 14. Similar to the drying section 100A shown in FIG. 1, the drying section 100B has three gas outlets 14a arranged in a row from the supply port 12a to the outlet 16a of the drying tube 10B, and three second gas discharge nozzles 14 are connected to each of the three gas outlets 14a. Furthermore, the drying section 100B is provided with a second gas supply section 20 that covers the three gas discharge nozzles .

[0044] The particles to be dried are naturally sucked into the drying tube 10B together with the first gas in the direction of the arrow shown in Figure 2 due to a balance between suction (specifically, intake air) from the exhaust section 16 (specifically, exhaust port 16a) side of the drying tube 10B and the discharge of the second gas from the gas discharge port 14a into the drying tube 10B. When the particles to be dried are supplied into the drying tube 10B from the supply port 12a together with the first gas, they form an aggregate of particles to be dried (i.e., a mass of wet pressure-responsive particles) and flow intermittently or continuously toward the exhaust port 16a. Here too, the particles to be dried pass through the drying tube 10B without circulating, accompanied by the airflow (i.e., main flow) of the first gas passing through the drying tube 10B from the supply port 12a to the exhaust port 16a.

[0045] The second gas discharged from the three gas outlets 14a hits the particles to be dried (specifically, aggregates of particles to be dried) passing through the drying tube 10B in a direction perpendicular to the direction of gravity. When the second gas hits the aggregates of particles to be dried, the aggregates are broken up and the drying of the particles is promoted. The particles to be dried after being hit by the second gas (specifically, the particles to be dried in an individually broken up state) pass through the drying tube 10B as they are, whereby the drying progresses, and the particles are discharged from the outlet 16a together with the gas containing the first gas and the second gas (i.e., along with the airflow of the first gas and the second gas). The drying section 100B has the above-described configuration, and thus the drying process of the particles to be dried is continuously carried out.

[0046] The drying section 100C shown in FIG. 3 differs from the drying section 100A shown in FIG. 1 only in that it includes a drying tube 10C with a different structure instead of the drying tube 10A. The drying tube 10C has a supply port 12a through which particles to be dried are supplied into the drying tube 10C together with a first gas, a gas outlet 14a through which a second gas is discharged toward the particles passing through the drying tube 10C, and an outlet 16a through which the particles to be dried together with the gas are discharged from the drying tube 10C. The drying tube 10C is configured by a non-loop piping 11C having a supply section 12 and an outlet 16, and a gas discharge nozzle 14. Similar to the drying section 100 shown in FIG. 1, the drying section 100C has three gas outlets 14a arranged in a row from the supply port 12a to the outlet 16a of the drying tube 10C, and three second gas discharge nozzles 14 are connected to each of the three gas outlets 14a. Furthermore, the drying section 100C is provided with a second gas supply section 20 that covers the gas discharge nozzle .

[0047] The particles to be dried are naturally sucked into the drying tube 10C together with the first gas in the direction of the arrow shown in Figure 1 due to a balance between suction (specifically, intake air) from the exhaust section 16 (specifically, exhaust port 16a) side of the drying tube 10C and the discharge of the second gas from the gas discharge port 14a into the drying tube 10C. When the particles to be dried are supplied into the drying tube 10C from the supply port 12a together with the first gas, they form an aggregate of particles to be dried (i.e., a mass of wet pressure-responsive particles) and flow intermittently or continuously toward the exhaust port 16a. Here too, the particles to be dried pass through the drying tube 10C without circulating, accompanied by the airflow (i.e., main flow) of the first gas passing through the drying tube 10C from the supply port 12a to the exhaust port 16a.

[0048] The second gas discharged from the three gas outlets 14a hits the particles to be dried (specifically, aggregates of particles to be dried) passing through the drying tube 10C in the direction of gravity. When the second gas hits the aggregates of particles to be dried, the aggregates are broken up and the drying of the particles is promoted. The particles to be dried after being hit by the second gas (specifically, the particles to be dried in an individually broken up state) pass through the drying tube 10C in this state, whereby the drying progresses, and the particles are discharged from the outlet 16a together with the gas containing the first gas and the second gas (i.e., along with the airflow of the first gas and the second gas). The drying section 100C has the above-described configuration, and thus the drying process of the particles to be dried is continuously carried out.

[0049] In the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure, the collection section is not limited to the configuration of collection section 200 shown in Fig. 1. The collection section in the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure may be provided with a cyclone instead of a bag filter, or may be provided with both a bag filter and a cyclone. From the viewpoint of suppressing the generation of coarse particles, it is preferable that the collection section only includes a bag filter as a solid-gas separation means for separating the dried particles from the gas, as in the drying apparatus shown in Fig. 1. It is also preferable that the drying sections 100B and 100C shown in Figs. 2 and 3 are combined with a collection section equipped with a bag filter, as in collection section 200 shown in Fig. 1.

[0050] In the first embodiment of the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure, the second gas discharged from the gas discharge port has a discharge velocity (i.e., V2) of 50 m / s or more. Discharging the second gas at this discharge velocity efficiently breaks up aggregates of the particles to be dried and also promotes drying of the particles to be dried. From the viewpoint of suppressing the generation of coarse particles, the discharge speed of the second gas discharged from the gas discharge port is preferably 80 m / s or more, more preferably 100 m / s or more, and even more preferably 120 m / s or more. The upper limit of the discharge speed of the second gas discharged from the gas discharge port is preferably 300 m / s or less, and more preferably 250 m / s or less, from the viewpoint of reducing the load on the equipment and suppressing the generation of coarse particles.

[0051] In addition, in the second embodiment of the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure, as well as the third embodiment of the drying apparatus according to the present disclosure, the discharge speed of the second gas discharged from the gas discharge port is preferably 50 m / s or more, more preferably 80 m / s or more, even more preferably 100 m / s or more, and particularly preferably 120 m / s or more, from the viewpoint of suppressing the generation of coarse particles. The upper limit of the discharge speed of the second gas discharged from the gas discharge port is preferably 300 m / s or less, and more preferably 250 m / s or less, from the viewpoint of reducing the load on the equipment and suppressing the generation of coarse particles.

[0052] In a second embodiment of the method for producing resin particles and the drying apparatus according to the present disclosure, the difference Δ(V2-V1) between the velocity V1 of the first gas passing through the drying tube (i.e., the velocity V1 of the main flow) and the velocity V2 of the second gas discharged from the gas discharge port is 40 m / s or more. Such a velocity difference effectively breaks down aggregates of the particles to be dried and also promotes drying of the particles to be dried. The difference Δ(V2−V1) is preferably 70 m / s or more, and more preferably 90 m / s or more. The upper limit of the difference Δ(V2−V1) is preferably 290 m / s or less, and more preferably 240 m / s or less, from the viewpoint of reducing the load on the equipment and suppressing the generation of coarse particles. Here, the velocity V1 of the first gas passing through the drying tube is preferably 0.01 m / s or more and 10 m / s or less, and more preferably 0.02 m / s or more and 5 m / s or less.

[0053] In addition, in the first embodiment of the method for producing resin particles and the drying apparatus according to the present disclosure, as well as the third embodiment of the drying apparatus according to the present disclosure, the difference Δ(V2-V1) is preferably 40 m / s or more, more preferably 70 m / s or more, and even more preferably 90 m / s or more. Moreover, the upper limit of the difference Δ(V2−V1) is preferably 290 m / s or less, and more preferably 240 m / s or less, from the viewpoint of reducing the load on the equipment and suppressing the generation of coarse particles. Here too, the velocity V1 of the first gas passing through the drying tube is preferably 0.01 m / s or more and 10 m / s or less, and more preferably 0.02 m / s or more and 5 m / s or less.

[0054] In the resin particle manufacturing method and the drying apparatus according to the present disclosure, the number of gas outlets that the drying tube has is not particularly limited, and may be at least 1. From the viewpoint of suppressing the generation of coarse particles and effectively drying the particles to be dried, the drying tube preferably has two or more gas outlets, and more preferably has three or more gas outlets. From the viewpoint of equipment load, the upper limit of the number of gas outlet ports provided in the drying tube is preferably 10 or less, and more preferably 8 or less. The gas discharge port in the drying tube is preferably located within a distance from the supply port side to 0.6 times the entire length of the drying tube (i.e., the length from the supply port to the discharge port, the distance along a line passing through the center of the drying tube). When there are multiple gas discharge ports, it is preferable that all of them be located within a distance from the supply port side to 0.6 times the entire length of the drying tube, and it is particularly preferable that the distance between adjacent gas discharge ports be equal to or greater than the maximum diameter d of the gas discharge port.

[0055] In the resin particle manufacturing method and drying apparatus according to the present disclosure, when the drying tube has two or more gas outlets, the discharge speed of the second gas discharged from each of the two or more gas outlets is preferably 50 m / s or more, more preferably 80 m / s or more, and even more preferably 100 m / s or more. When the drying tube has two or more gas outlets, the discharge speeds of the second gas discharged from the two or more gas outlets may be the same or different. The upper limit of the discharge speed of the second gas discharged from the two or more gas discharge ports is preferably 300 m / s or less, and more preferably 250 m / s or less, from the viewpoint of reducing the load on the equipment and suppressing the generation of coarse particles.

[0056] In the resin particle manufacturing method and drying apparatus according to the present disclosure, from the viewpoint of suppressing the generation of coarse particles, it is preferable that the flow rate Q1 of the first gas passing through the drying tube and the total flow rate Q2 of the second gas discharged from the gas outlet satisfy the relationship Q2 / (Q1+Q2)≧0.9, and it is more preferable that they satisfy the relationship Q2 / (Q1+Q2)≧0.95.

[0057] Here, the velocity V1 (i.e., velocity V1 of the main flow) and flow rate Q1 of the first gas passing through the drying tube, and the discharge velocity V2 and flow rate Q2 of the second gas discharged from the gas discharge port are calculated as follows. First, the discharge blower is operated when supplying the second gas, and then air is sucked from the outlet side of the drying tube (for example, by operating the exhaust blower in the recovery section), and the flow rate of the first gas at the supply port of the drying tube and the flow rate of the second gas at the gas outlet port of the drying tube are each measured using a Pitot tube flow meter without supplying particles to be dried. The velocity V1 of the first gas passing through the drying tube is determined by dividing the flow rate of the first gas at the supply port of the drying tube measured as described above by the cross-sectional area of ​​the drying tube just before the second gas mixes with the first gas (specifically, the cross-sectional area at the position indicated by the dotted line P in the drying tube 10A (i.e., the loop-type piping 11A) at the connection with the gas outlet port 14a shown in Figure 4). The flow rate Q1 of the first gas passing through the drying tube is the flow rate of the first gas at the supply port of the drying tube measured as described above. The discharge velocity V2 of the second gas discharged from the gas discharge port is calculated by dividing the flow rate of the second gas at the gas discharge port in the drying tube measured as described above by the total area of ​​the gas discharge ports in the drying tube. Here, if there are multiple gas discharge ports, the discharge velocity at each gas discharge port is calculated, and the arithmetic mean value thereof is defined as the "discharge velocity V2 of the second gas discharged from the gas discharge port." The total flow rate Q2 of the second gas discharged from the gas outlets is the sum of the flow rates of the second gas at the gas outlets of the drying tube measured as described above. In other words, if there are multiple gas outlets, the flow rate at each gas outlet is measured, and the sum of these is defined as the "total flow rate Q2 of the second gas discharged from the gas outlets." 1 to 3, when the drying units 100A, 100B, and 100C include the second gas supply unit 20, the "discharge velocity V2 of the second gas discharged from the gas discharge port" may be calculated using the flow rate of the second gas at the supply port to the second gas supply unit 20 instead of the flow rate of the second gas at the gas discharge port in the drying tube. Also, the flow rate of the second gas at the supply port to the second gas supply unit 20 may be used as the "total flow rate Q2 of the second gas discharged from the gas discharge port."

[0058] In the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure, the speed of the gas moving within the drying tube preferably increases as the gas passes through the drying tube. Specifically, only the first gas is supplied to the supply port within the drying tube, and as the first gas moves through the drying tube, the second gas is ejected toward the particles to be dried, and the second gas merges with the first gas, so that the speed of the gas containing the first and second gases preferably increases above the speed of the first gas alone (i.e., the speed V1 of the first gas passing through the drying tube). After acceleration, the speed of the gas containing the first and second gases preferably approaches the ejection speed V2 of the second gas. Furthermore, by appropriately adjusting the flow rate Q1 of the first gas passing through the drying tube, the total flow rate Q2 of the second gas discharged from the gas outlet, the velocity V1 of the first gas passing through the drying tube, the discharge velocity V2 of the second gas discharged from the gas outlet, the number of gas outlets, the installation locations of the gas outlets, the direction of the gas outlets, etc., the movement velocity of the gas within the drying tube can be increased as it passes through the drying tube.

[0059] In the resin particle manufacturing method and drying device according to the present disclosure, it is preferable that the maximum diameter D of the drying tube and the maximum diameter d of the gas discharge port satisfy the relationship d / D≦0.25, and it is more preferable that the relationship d / D≦0.20. Furthermore, from the viewpoint of reducing the load on the equipment and suppressing the generation of coarse particles, it is preferable to satisfy 0.05≦d / D, and it is more preferable to satisfy 0.1≦d / D.

[0060] Here, as shown in FIG. 4, the maximum diameter D of the drying tube means the inner diameter at the largest position among the portions of the drying tube (for example, drying tube 10A in FIG. 4) through which the particles to be dried, the first gas, and the second gas pass, and the maximum diameter d of the gas outlet means the maximum value of the inner diameter of the gas outlet (the maximum length of a straight line drawn between any two points on the outline of the outlet). The maximum diameter D of the drying tube and the maximum diameter d of the gas outlet port are measured with a tape measure or vernier calipers. The maximum diameter D of the drying tube may be a value specified in the piping standard. Here, when there are multiple gas discharge ports, the maximum diameter of each gas discharge port is found, and the arithmetic mean value thereof is taken as the "maximum diameter d of the gas discharge port."

[0061] In the resin particle manufacturing method and drying apparatus according to the present disclosure, from the viewpoint of suppressing the generation of coarse particles, it is preferable that the temperature T1 of the second gas discharged from the gas discharge port is 50°C or higher and 70°C or lower, and that the temperature T2 in the recovery section is 20°C or higher and 40°C or lower, and it is more preferable that the temperature T1 is 55°C or higher and 65°C or lower, and that the temperature T2 is 30°C or higher and 40°C or lower. The temperature T1 of the second gas may be controlled by adjusting the heating temperature of the second gas, and the temperature T2 in the recovery section may be controlled by directly controlling the temperature in the recovery section, or by adjusting the supply amount and supply speed of the particles to be dried, the moisture content of the particles to be dried, or a combination of these.

[0062] Here, the temperature T1 of the second gas discharged from the gas discharge port and the temperature T2 inside the recovery section are calculated as follows. First, the discharge blower is operated when supplying the first gas, and the discharge blower is operated when supplying the second gas. Furthermore, air is sucked in from the outlet side of the drying tube, and while the particles to be dried are being supplied, the temperature at the gas outlet in the drying tube for the second gas and the temperature in the recovery section are each measured with a thermocouple. Here, when there are a plurality of gas discharge ports, the temperature at each gas discharge port is found, and the arithmetic mean value thereof is set as the "temperature T1 of the second gas discharged from the gas discharge port." As shown in Figures 1 to 3, when the drying sections 100, 100A, and 100B are equipped with a second gas supply section 20, the temperature T1 of the second gas discharged from the gas discharge port may be obtained using the temperature at the supply port of the second gas to the second gas supply section 20 instead of the temperature at the gas discharge port in the drying tube of the second gas.

[0063] In the resin particle manufacturing method and the drying apparatus according to the present disclosure, as described above, the recovery section preferably includes a bag filter as a solid-gas separation means for separating the dried particles from the gas. In addition, from the viewpoint of further suppressing the generation of coarse particles, the linear velocity of the gas passing through the bag filter is preferably 0.1 m / s or less, and more preferably 0.05 m / s or less. The lower limit of the linear velocity of the gas passing through the bag filter may be set to 0.005 m / s or more, for example, from the viewpoint of equipment costs.

[0064] Here, the linear velocity of the gas passing through the bag filter is determined by dividing the value of flow rate Q1+flow rate Q2 by the total filtering area of ​​the filter.

[0065] According to the method for producing resin particles and the drying device of the present disclosure, it is preferable to dry the resin particles to a moisture content of less than 10% by mass, more preferably to a moisture content of 2% by mass or less.

[0066] [gas] The gas used in the method for producing resin particles according to the present disclosure and the drying apparatus according to the present disclosure is preferably air, but an inert gas such as nitrogen gas may be used as part or all of the air.

[0067] [Dried particles] The method for producing resin particles according to the present disclosure and the particles to be dried, which are applied to the drying apparatus according to the present disclosure, will be described. As described above, the particles to be dried are wet resin particles that undergo a phase transition due to pressure. A wet state means, for example, a moisture content of 10% by mass or more. The moisture content of the particles to be dried is preferably 15% by mass or more, more preferably 20% by mass or more, from the viewpoint of preventing the generation of coarse particles due to stress applied during dehydration. Furthermore, the moisture content of the particles to be dried is preferably 50% by mass or less, more preferably 40% by mass or less, from the viewpoint of drying efficiency. In other words, the moisture content of the particles to be dried is preferably 20% by mass or more and 40% by mass or less. Here, the moisture content is calculated by the formula: (amount of moisture in wet particles) / (mass of wet particles)×100.

[0068] The particles to be dried are resin particles that undergo a phase transition when subjected to pressure, i.e., pressure-responsive particles. In the method for producing resin particles and the drying apparatus according to the present disclosure, even when a pressure-responsive resin is used as the material to be dried, the generation of coarse particles is suppressed.

[0069] (Pressure-responsive particles) Pressure-responsive particles are particles that undergo a phase transition when pressure is applied. Specifically, pressure-responsive particles refer to particles that satisfy the following formula 1: Formula 1: 8℃≦T A -T B In formula 1, T A is the temperature at which the viscosity is 10,000 Pa s under a pressure of 1 MPa, and T B is the temperature at which the viscosity is 10,000 Pa·s under a pressure of 10 MPa.

[0070] Temperature difference (T A -T B ) is 10°C or more, preferably 15°C or more, and more preferably 20°C or more, from the viewpoint that the pressure-responsive particles are easily subjected to a phase transition due to pressure. A -T B The upper limit of the temperature is preferably 120°C or lower, more preferably 100°C or lower, and even more preferably 80°C or lower.

[0071] temperature T A The value of the temperature T is preferably 140°C or less, more preferably 130°C or less, even more preferably 120°C or less, and even more preferably 115°C or less. A The lower limit is preferably 60°C or higher, more preferably 80°C or higher, and even more preferably 85°C or higher. temperature T B The temperature T is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. B The upper limit of the temperature is preferably 85°C or less.

[0072] The temperature T at which the pressure-responsive particles exhibit a viscosity of 10,000 Pa s under a pressure of 1 MPa is used as an indicator of their susceptibility to phase transition due to pressure. A and the temperature T at which the viscosity reaches 10,000 Pa s under a pressure of 4 MPa. C temperature difference (T A -T C ) and the temperature difference (T A -T C ) is preferably 5°C or more. From the viewpoint that pressure-responsive particles are easily subjected to phase transition by pressure, A -T C ) is preferably 5°C or higher, more preferably 10°C or higher. Temperature difference (T A -T C ) is generally below 25°C.

[0073] Pressure-responsive particles respond to temperature differences (T A -T C ) is 5°C or higher, the temperature T C The temperature T is preferably 90°C or less, more preferably 85°C or less, and even more preferably 80°C or less. C The lower limit is preferably 60°C or higher.

[0074] temperature T A , temperature T B , and temperature T C The method for finding is as follows: The pressure-responsive particles are compressed to prepare a pellet-shaped sample. The pellet-shaped sample is set in a flow tester (Shimadzu Corporation, CFT-500), and the applied pressure is fixed at 1 MPa, and the viscosity at 1 MPa versus temperature is measured. From the obtained viscosity graph, it is found that the viscosity is 10 4 The temperature T when the temperature becomes Pa s A Except for changing the applied pressure from 1 MPa to 10 MPa, the temperature T A Similarly to the method according to the present invention, the temperature T B Except for changing the applied pressure from 1 MPa to 4 MPa, the temperature T A Similarly to the method according to the present invention, the temperature TC Determine the temperature T A and temperature T B temperature difference (T A -T B ) is calculated. A and temperature T C temperature difference (T A -T C ) is calculated.

[0075] Specifically, the pressure-responsive particles preferably contain a baroplastic resin. The baroplastic resin preferably includes at least two resins with different glass transition temperatures (Tg), or a resin having two glass transition temperatures in one molecule. Examples of such baroplastic resins include the resins described in paragraphs 0039 to 0111 of JP 2018-2889 A. Methods for producing pressure-responsive particles containing the above-mentioned two types of baroplastic resin include, for example, an emulsion aggregation method and a dissolution suspension method, and specifically include the production methods described in paragraphs 0128 to 0141 of JP 2018-2889 A.

[0076] Specifically, the pressure-responsive particles preferably contain a styrene-based resin containing styrene and other vinyl monomers as polymerization components, and a (meth)acrylic acid ester-based resin containing at least two types of (meth)acrylic acid esters as polymerization components, and have at least two glass transition temperatures, with the difference between the lowest and highest glass transition temperatures being 30°C or more. The pressure-responsive particles are prone to undergo phase transition due to pressure because they contain a "styrene-based resin containing styrene and other vinyl monomers as polymerization components" and a "(meth)acrylic acid ester-based resin containing at least two types of (meth)acrylic acid esters as polymerization components."

[0077] Preferred embodiments of the pressure-responsive particles will be described in detail below. In the following description, unless otherwise specified, "pressure-responsive particles" means "pressure-responsive particles that contain a styrene-based resin containing styrene and other vinyl monomers as polymerization components, and a (meth)acrylic acid ester-based resin containing at least two types of (meth)acrylic acid esters as polymerization components, and that have at least two glass transition temperatures, with the difference between the lowest and highest glass transition temperatures being 30°C or more." Furthermore, in the following description, unless otherwise specified, "styrene-based resin" means "styrene-based resin containing styrene and other vinyl monomers as polymerization components," and "(meth)acrylic acid ester-based resin" means "(meth)acrylic acid ester-based resin containing at least two types of (meth)acrylic acid esters as polymerization components."

[0078] As described above, the pressure-responsive particles preferably contain at least a styrene-based resin and a (meth)acrylic acid ester-based resin. The pressure-responsive particles may also contain a colorant, a release agent, and other additives.

[0079] The pressure-responsive particles preferably contain a styrene resin in an amount greater than the amount of the (meth)acrylic ester resin. The amount of the styrene resin is preferably 55% by mass or more and 80% by mass or less, more preferably 60% by mass or more and 75% by mass or less, and even more preferably 65% ​​by mass or more and 70% by mass or less, based on the total amount of the styrene resin and the (meth)acrylic ester resin.

[0080] (styrene resin) The pressure-responsive particles preferably contain a styrene-based resin containing styrene and other vinyl monomers as polymerization components.

[0081] The mass proportion of styrene in all the polymer components of the styrene-based resin is preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 75 mass% or more, from the viewpoint of suppressing fluidization of the pressure-responsive particles in an unpressurized state, and is preferably 95 mass% or less, more preferably 90 mass% or less, and even more preferably 85 mass% or less, from the viewpoint of forming pressure-responsive particles that are prone to phase transition under pressure. For the same reasons as above, the mass proportion of styrene in all the polymer components of the styrene-based resin is preferably 60 mass % or more and 95 mass % or less.

[0082] Examples of vinyl monomers other than styrene that constitute the styrene-based resin include styrene-based monomers other than styrene and acrylic monomers.

[0083] Examples of styrene-based monomers other than styrene include vinylnaphthalene; alkyl-substituted styrenes such as α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, and pn-dodecylstyrene; aryl-substituted styrenes such as p-phenylstyrene; alkoxy-substituted styrenes such as p-methoxystyrene; halogen-substituted styrenes such as p-chlorostyrene, 3,4-dichlorostyrene, p-fluorostyrene, and 2,5-difluorostyrene; and nitro-substituted styrenes such as m-nitrostyrene, o-nitrostyrene, and p-nitrostyrene. One type of styrene-based monomer may be used alone, or two or more types may be used in combination.

[0084] The acrylic monomer is preferably at least one acrylic monomer selected from the group consisting of (meth)acrylic acid and (meth)acrylic acid esters. Examples of the (meth)acrylic acid esters include (meth)acrylic acid alkyl esters, (meth)acrylic acid carboxy-substituted alkyl esters, (meth)acrylic acid hydroxy-substituted alkyl esters, (meth)acrylic acid alkoxy-substituted alkyl esters, and di(meth)acrylic acid esters. The acrylic monomers may be used alone or in combination of two or more.

[0085] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)methacrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of the carboxy-substituted alkyl (meth)acrylate include 2-carboxyethyl (meth)acrylate. Examples of hydroxy-substituted alkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the alkoxy-substituted alkyl (meth)acrylate include 2-methoxyethyl (meth)acrylate. Examples of di(meth)acrylic acid esters include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, and decanediol di(meth)acrylate.

[0086] Examples of the (meth)acrylic acid ester include 2-(diethylamino)ethyl (meth)acrylate, benzyl (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate.

[0087] Examples of other vinyl monomers constituting the styrene-based resin include, in addition to styrene-based monomers and acrylic monomers, (meth)acrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; and olefins such as isoprene, butene and butadiene.

[0088] From the viewpoint of forming pressure-responsive particles that readily undergo a phase transition upon pressure, the styrene-based resin preferably contains a (meth)acrylic acid ester as a polymerization component, more preferably a (meth)acrylic acid alkyl ester, even more preferably a (meth)acrylic acid alkyl ester having an alkyl group with 2 to 10 carbon atoms, still more preferably a (meth)acrylic acid alkyl ester having an alkyl group with 4 to 8 carbon atoms, and particularly preferably at least one of n-butyl acrylate and 2-ethylhexyl acrylate. From the viewpoint of forming pressure-responsive particles that readily undergo a phase transition upon pressure, the styrene-based resin and the (meth)acrylic acid ester-based resin preferably contain the same type of (meth)acrylic acid ester as a polymerization component.

[0089] The mass proportion of the (meth)acrylic acid ester in the total polymerization components of the styrene-based resin is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of suppressing fluidization of the pressure-responsive particles in an unpressurized state, and is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of forming pressure-responsive particles that readily undergo phase transition in response to pressure. The (meth)acrylic acid ester here is preferably a (meth)acrylic acid alkyl ester, more preferably a (meth)acrylic acid alkyl ester having 2 to 10 carbon atoms in the alkyl group, and even more preferably a (meth)acrylic acid alkyl ester having 4 to 8 carbon atoms in the alkyl group.

[0090] It is particularly preferable that the styrene-based resin contains at least one of n-butyl acrylate and 2-ethylhexyl acrylate as a polymerization component, and the total amount of n-butyl acrylate and 2-ethylhexyl acrylate in all polymerization components of the styrene-based resin is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of suppressing fluidization of pressure-responsive particles in an unpressurized state; and is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of forming pressure-responsive particles that are prone to phase transition when pressure is applied.

[0091] The weight average molecular weight of the styrene-based resin is preferably 3,000 or more, more preferably 4,000 or more, and even more preferably 5,000 or more, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied, and is preferably 60,000 or less, more preferably 55,000 or less, and even more preferably 50,000 or less, from the viewpoint of forming pressure-responsive particles that are prone to phase transition when subjected to pressure.

[0092] In this disclosure, the weight-average molecular weight (also referred to as "Mw") of a resin is measured by gel permeation chromatography (GPC). Molecular weight measurement by GPC is performed using a Tosoh HLC-8120GPC as the GPC apparatus, a Tosoh TSKgel SuperHM-M (15 cm) column, and tetrahydrofuran as the solvent. The weight-average molecular weight of the resin is calculated using a molecular weight calibration curve prepared using monodisperse polystyrene standard samples.

[0093] The glass transition temperature of the styrene-based resin is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied; and is preferably 110°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower, from the viewpoint of forming pressure-responsive particles that readily undergo phase transition when subjected to pressure.

[0094] In the present disclosure, the glass transition temperature of a resin is determined from a differential scanning calorimetry (DSC) curve obtained by DSC measurement. More specifically, it is determined according to the "extrapolated glass transition onset temperature" described in JIS K7121:1987 "Method for measuring transition temperatures of plastics."

[0095] The glass transition temperature of a resin can be controlled by the type and polymerization ratio of the polymerization components. The glass transition temperature tends to be lower as the density of flexible units such as methylene groups, ethylene groups, and oxyethylene groups contained in the main chain increases, and tends to be higher as the density of rigid units such as aromatic rings and cyclohexane rings contained in the main chain increases. In addition, the glass transition temperature tends to be lower as the density of aliphatic groups in the side chain increases.

[0096] The mass proportion of the styrene-based resin in the entire pressure-responsive particle is preferably 55 mass% or more, more preferably 60 mass% or more, and even more preferably 65 mass% or more, from the viewpoint of preventing the pressure-responsive particle from fluidizing when no pressure is applied, and is preferably 80 mass% or less, more preferably 75 mass% or less, and even more preferably 70 mass% or less, from the viewpoint of forming pressure-responsive particles that are prone to phase transition when pressure is applied.

[0097] ((Meth)acrylic ester resin) The pressure-responsive particles preferably contain a (meth)acrylic acid ester-based resin containing at least two types of (meth)acrylic acid esters as polymerization components.

[0098] The mass proportion of the (meth)acrylic acid ester in all the polymerization components of the (meth)acrylic acid ester-based resin is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 98 mass% or more, and particularly preferably 100 mass%.

[0099] Examples of the (meth)acrylic acid ester include (meth)acrylic acid alkyl ester, (meth)acrylic acid carboxy-substituted alkyl ester, (meth)acrylic acid hydroxy-substituted alkyl ester, (meth)acrylic acid alkoxy-substituted alkyl ester, and di(meth)acrylic acid ester.

[0100] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)methacrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of the carboxy-substituted alkyl (meth)acrylate include 2-carboxyethyl (meth)acrylate. Examples of hydroxy-substituted alkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Examples of the alkoxy-substituted alkyl (meth)acrylate include 2-methoxyethyl (meth)acrylate. Examples of di(meth)acrylic acid esters include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, and decanediol di(meth)acrylate.

[0101] Examples of the (meth)acrylic acid ester include 2-(diethylamino)ethyl (meth)acrylate, benzyl (meth)acrylate, and methoxypolyethylene glycol (meth)acrylate.

[0102] The (meth)acrylic acid ester may be used alone or in combination of two or more kinds.

[0103] As the (meth)acrylic acid ester, from the viewpoint of obtaining pressure-responsive particles that easily undergo a phase transition due to pressure, (meth)acrylic acid alkyl esters are preferred, (meth)acrylic acid alkyl esters having an alkyl group with 2 to 10 carbon atoms are more preferred, (meth)acrylic acid alkyl esters having an alkyl group with 4 to 8 carbon atoms are even more preferred, and n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. From the viewpoint of forming pressure-responsive particles that easily undergo a phase transition due to pressure, it is preferred that the styrene-based resin and the (meth)acrylic acid ester-based resin contain the same type of (meth)acrylic acid ester as polymerization components.

[0104] The mass proportion of the (meth)acrylic acid alkyl ester in all the polymerization components of the (meth)acrylic acid ester-based resin is preferably 90 mass % or more, more preferably 95 mass % or more, even more preferably 98 mass % or more, and even more preferably 100 mass % from the viewpoint of obtaining pressure-responsive particles that undergo phase transition under pressure. As the (meth)acrylic acid alkyl ester here, a (meth)acrylic acid alkyl ester having an alkyl group with 2 to 10 carbon atoms is preferred, and a (meth)acrylic acid alkyl ester having an alkyl group with 4 to 8 carbon atoms is more preferred.

[0105] The mass ratio of the two (meth)acrylic acid esters with the largest mass proportions among the at least two (meth)acrylic acid esters contained as polymerization components in the (meth)acrylic acid ester-based resin is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and even more preferably 60:40 to 40:60, from the viewpoint of obtaining pressure-responsive particles that undergo a phase transition due to pressure.

[0106] Of the at least two (meth)acrylic acid esters contained as polymerization components in the (meth)acrylic acid ester-based resin, the two with the largest mass proportions are preferably (meth)acrylic acid alkyl esters. The (meth)acrylic acid alkyl esters herein are preferably (meth)acrylic acid alkyl esters having an alkyl group with 2 to 10 carbon atoms, and more preferably (meth)acrylic acid alkyl esters having an alkyl group with 4 to 8 carbon atoms.

[0107] When the two (meth)acrylic acid esters having the largest mass proportions among the at least two (meth)acrylic acid esters contained as polymerization components in the (meth)acrylic acid ester-based resin are (meth)acrylic acid alkyl esters, the difference in the number of carbon atoms in the alkyl groups of the two (meth)acrylic acid alkyl esters is preferably 1 or more and 4 or less, more preferably 2 or more and 4 or less, and even more preferably 3 or 4, from the viewpoint of obtaining pressure-responsive particles that undergo a phase transition due to pressure.

[0108] From the viewpoint of obtaining pressure-responsive particles that undergo a phase transition due to pressure, the (meth)acrylic acid ester resin preferably contains n-butyl acrylate and 2-ethylhexyl acrylate as polymerization components, and it is particularly preferred that the two (meth)acrylic acid esters having the largest mass proportions among the at least two types of (meth)acrylic acid esters contained as polymerization components in the (meth)acrylic acid ester resin are n-butyl acrylate and 2-ethylhexyl acrylate. The total amount of n-butyl acrylate and 2-ethylhexyl acrylate in the total polymerization components of the (meth)acrylic acid ester resin is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 98 mass% or more, and even more preferably 100 mass%.

[0109] The (meth)acrylic acid ester resin may contain a vinyl monomer other than (meth)acrylic acid ester as a polymerization component. Examples of vinyl monomers other than (meth)acrylic acid ester include (meth)acrylic acid; styrene; styrene-based monomers other than styrene; (meth)acrylonitrile; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; and olefins such as isoprene, butene and butadiene. These vinyl monomers may be used alone or in combination of two or more.

[0110] When the (meth)acrylic acid ester-based resin contains a vinyl monomer other than a (meth)acrylic acid ester as a polymerization component, the vinyl monomer other than a (meth)acrylic acid ester is preferably at least one of acrylic acid and methacrylic acid, and more preferably acrylic acid.

[0111] The weight average molecular weight of the (meth)acrylic acid ester resin is preferably 100,000 or more, more preferably 120,000 or more, and even more preferably 150,000 or more, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied; and is preferably 250,000 or less, more preferably 220,000 or less, and even more preferably 200,000 or less, from the viewpoint of forming pressure-responsive particles that easily undergo phase transition when subjected to pressure.

[0112] The glass transition temperature of the (meth)acrylic acid ester resin is preferably 10°C or lower, more preferably 0°C or lower, and even more preferably -10°C or lower, from the viewpoint of forming pressure-responsive particles that easily undergo phase transition when subjected to pressure; and is preferably -90°C or higher, more preferably -80°C or higher, and even more preferably -70°C or higher, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied.

[0113] The mass proportion of the (meth)acrylic acid ester resin in the entire pressure-responsive particle is preferably 20 mass% or more, more preferably 25 mass% or more, and even more preferably 30 mass% or more, from the viewpoint of forming pressure-responsive particles that are prone to phase transition when subjected to pressure, and is preferably 45 mass% or less, more preferably 40 mass% or less, and even more preferably 35 mass% or less, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied.

[0114] The total amount of styrene-based resin and (meth)acrylic acid ester-based resin contained in the pressure-responsive particles is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass, based on the total amount of the pressure-responsive particles.

[0115] (Other resins) The pressure-responsive particles may contain, for example, polystyrene, or non-vinyl resins such as epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, and modified rosin. These resins may be used alone or in combination of two or more.

[0116] (Various additives) The pressure-responsive particles may contain, as necessary, colorants (e.g., pigments, dyes), release agents (e.g., hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, candelilla wax, etc.; synthetic or mineral / petroleum waxes such as montan wax; ester waxes such as fatty acid esters, montan acid esters), charge control agents, etc.

[0117] When the pressure-responsive particles are to be transparent, the amount of colorant in the pressure-responsive particles is preferably 1.0 mass % or less relative to the entire pressure-responsive particles, and the smaller the amount, the better from the viewpoint of increasing the transparency of the pressure-responsive particles.

[0118] (Structure of pressure-responsive particles) The internal structure of the pressure-responsive particles is preferably a sea-island structure, and the sea-island structure preferably has a sea phase containing a styrene-based resin and an island phase containing a (meth)acrylic ester-based resin dispersed in the sea phase. The specific form of the styrene-based resin contained in the sea phase is as described above. The specific form of the (meth)acrylic ester-based resin contained in the island phase is as described above. Island phases not containing a (meth)acrylic ester-based resin may be dispersed in the sea phase.

[0119] When the pressure-responsive particles have a sea-island structure, the average diameter of the island phases is preferably 200 nm or more and 500 nm or less. When the average diameter of the island phases is 500 nm or less, the pressure-responsive particles are likely to undergo phase transition due to pressure, and when the average diameter of the island phases is 200 nm or more, the pressure-responsive particles have excellent mechanical strength (for example, strength that makes them resistant to deformation when stirred in a developing device). From these perspectives, the average diameter of the island phases is more preferably 220 nm or more and 450 nm or less, and even more preferably 250 nm or more and 400 nm or less.

[0120] Methods for controlling the average diameter of the island phases in the sea-island structure within the above range include, for example, increasing or decreasing the amount of (meth)acrylic acid ester-based resin relative to the amount of styrene-based resin in the method for producing pressure-responsive particles described below, or increasing or decreasing the time for which the temperature is maintained at a high temperature in the step of fusing and coalescing the aggregated resin particles.

[0121] The sea-island structure is confirmed and the average diameter of the island phase is measured by the following method. The pressure-responsive particles are embedded in epoxy resin, sliced ​​using a diamond knife or similar, and stained with osmium tetroxide or ruthenium tetroxide in a desiccator. The stained sections are then observed under a scanning electron microscope (SEM). The sea and island phases of the sea-island structure are distinguished by the degree of staining of the resin by osmium tetroxide or ruthenium tetroxide, and this is used to confirm the presence or absence of a sea-island structure. 100 island phases are randomly selected from the SEM image, and the longest diameter of each island phase is measured. The average of the longest diameters of the 100 islands is used as the average diameter.

[0122] The pressure-responsive particles may be pressure-responsive mother particles with a single layer structure, or pressure-responsive particles with a core-shell structure having a core and a shell layer covering the core. From the viewpoint of preventing the pressure-responsive particles from fluidizing in an unpressurized state, the pressure-responsive particles preferably have a core-shell structure.

[0123] When the pressure-responsive particles have a core-shell structure, the core preferably contains a styrene-based resin and a (meth)acrylic ester-based resin, from the viewpoint of facilitating phase transition under pressure. Furthermore, the shell layer preferably contains a styrene-based resin, from the viewpoint of suppressing fluidization of the pressure-responsive particles in an unpressurized state. The specific form of the styrene-based resin is as described above. The specific form of the (meth)acrylic ester-based resin is as described above.

[0124] When the pressure-responsive particles have a core-shell structure, it is preferable that the core portion has a sea phase containing a styrene-based resin and an island phase containing a (meth)acrylic ester-based resin dispersed in the sea phase. The average diameter of the island phase is preferably within the range described above. Furthermore, in addition to the core portion having the above-mentioned configuration, it is preferable that the shell layer contains a styrene-based resin. In this case, the sea phase and shell layer of the core portion have a continuous structure, making it easy for the pressure-responsive particles to undergo phase transition due to pressure. The specific form of the styrene-based resin contained in the sea phase and shell layer of the core portion is as described above. The specific form of the (meth)acrylic ester-based resin contained in the island phase of the core portion is as described above.

[0125] Examples of resins contained in the shell layer include polystyrene, and non-vinyl resins such as epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, and modified rosin. These resins may be used alone or in combination of two or more.

[0126] The average thickness of the shell layer is preferably 120 nm or more, more preferably 130 nm or more, and even more preferably 140 nm or more, from the viewpoint of suppressing deformation of the pressure-responsive particles, and is preferably 550 nm or less, more preferably 500 nm or less, and even more preferably 400 nm or less, from the viewpoint of facilitating phase transition of the pressure-responsive particles due to pressure.

[0127] The average thickness of the shell layer is measured by the following method. The pressure-responsive particles are embedded in epoxy resin, sliced ​​using a diamond knife or similar, and stained with osmium tetroxide or ruthenium tetroxide in a desiccator. The stained sections are then observed under a scanning electron microscope (SEM). Ten pressure-responsive particle cross sections are randomly selected from the SEM images, and the shell layer thickness is measured at 20 points per pressure-responsive particle, the average value is calculated, and the average of the 10 pressure-responsive particles is used as the average thickness.

[0128] The volume average particle diameter (D50v) of the pressure-responsive particles is preferably 4 μm or more, more preferably 5 μm or more, and even more preferably 6 μm or more, from the viewpoint of ease of handling the pressure-responsive particles, and is preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 9 μm or less, from the viewpoint of ease of phase transition of the entire pressure-responsive particles due to pressure.

[0129] The volume-average particle diameter (D50v) of pressure-responsive particles was measured using a Coulter Multisizer II (Beckman Coulter) with a 100 μm aperture. Pressure-responsive particles (0.5 mg to 50 mg) were dispersed in 2 mL of a 5% by mass aqueous solution of sodium alkylbenzene sulfonate. This was then mixed with 100 mL to 150 mL of electrolyte (ISOTON-II, Beckman Coulter) and dispersed for 1 minute using an ultrasonic disperser. The resulting dispersion was used as the sample. The particle diameters of 50,000 particles with diameters between 2 μm and 60 μm in the sample were measured. The volume-average particle diameter (D50v) was determined as the particle diameter at 50% cumulative concentration in the volume-based particle size distribution, calculated from the smallest diameter.

[0130] (Favorable properties of pressure-responsive particles) The pressure-responsive particles have at least two glass transition temperatures, one of which is presumed to be the glass transition temperature of a styrene-based resin, and the other is presumed to be the glass transition temperature of a (meth)acrylic acid ester-based resin.

[0131] The pressure-responsive particles may have three or more glass transition temperatures, but the number of glass transition temperatures is preferably 2. Examples of a form in which the pressure-responsive particles have two glass transition temperatures include a form in which the resins contained in the pressure-responsive particles are only styrene-based resins and (meth)acrylic acid ester-based resins, and a form in which the content of other resins other than styrene-based resins and (meth)acrylic acid ester-based resins is low (for example, a form in which the content of other resins is 5% by mass or less of the entire pressure-responsive particles).

[0132] The pressure-responsive particles have at least two glass transition temperatures, and the difference between the lowest and highest glass transition temperatures is preferably 30° C. or more. From the viewpoint of facilitating a phase transition of the pressure-responsive particles due to pressure, the difference between the lowest and highest glass transition temperatures is more preferably 40° C. or more, even more preferably 50° C. or more, and even more preferably 60° C. or more. The upper limit of the difference between the lowest and highest glass transition temperatures is, for example, 140° C. or less, 130° C. or less, or 120° C. or less.

[0133] The lowest glass transition temperature exhibited by the pressure-responsive particles is preferably 10°C or lower, more preferably 0°C or lower, and even more preferably -10°C or lower, from the viewpoint of enabling the pressure-responsive particles to easily undergo phase transition due to pressure, and is preferably -90°C or higher, more preferably -80°C or higher, and even more preferably -70°C or higher, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied.

[0134] The highest glass transition temperature of the pressure-responsive particles is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher, from the viewpoint of preventing the pressure-responsive particles from fluidizing when no pressure is applied; and is preferably 70°C or lower, more preferably 65°C or lower, and even more preferably 60°C or lower, from the viewpoint of facilitating phase transition of the pressure-responsive particles due to pressure.

[0135] In the present disclosure, the glass transition temperature of the pressure-responsive particles is determined from a differential scanning calorimetry (DSC) curve obtained by DSC measurement. More specifically, it is determined according to the "extrapolated glass transition onset temperature" described in JIS K7121:1987 "Method for measuring the transition temperature of plastics."

[0136] [Method for producing pressure-responsive particles] The pressure-responsive particles may be produced by either a dry production method (e.g., a kneading and pulverization method) or a wet production method (e.g., an aggregation and coalescence method, a suspension polymerization method, a dissolution and suspension method). There are no particular limitations on these production methods, and any known production method may be used. Among these, it is preferable to obtain pressure-responsive particles by the aggregation and coalescence method.

[0137] When the pressure-responsive particles are produced by the aggregation and coalescence method, for example, a step of preparing a styrene-based resin particle dispersion liquid in which styrene-based resin particles containing a styrene-based resin are dispersed (a styrene-based resin particle dispersion liquid preparation step); a step of polymerizing a (meth)acrylic acid ester-based resin in a styrene-based resin particle dispersion to form composite resin particles containing a styrene-based resin and a (meth)acrylic acid ester-based resin (composite resin particle formation step); a step of aggregating the composite resin particles in the composite resin particle dispersion liquid in which the composite resin particles are dispersed to form aggregated particles (aggregated particle forming step); Pressure-responsive particles are produced through a step of heating the aggregated particle dispersion in which the aggregated particles are dispersed, fusing and coalescing the aggregated particles to form pressure-responsive mother particles (fusion and coalescence step).

[0138] Each step will be described in detail below. The following describes a method for obtaining pressure-responsive particles that do not contain a colorant or a release agent. Colorants, release agents, and other additives may be used as needed. When the pressure-responsive particles contain a colorant and a release agent, a composite resin particle dispersion, a colorant particle dispersion, and a release agent particle dispersion are mixed together, and then a fusion and coalescence process is carried out. The colorant particle dispersion and the release agent particle dispersion can be prepared, for example, by mixing the materials and then performing a dispersion process using a known disperser.

[0139] - Styrene-based resin particle dispersion preparation process - The styrene-based resin particle dispersion is, for example, a dispersion in which styrene-based resin particles are dispersed in a dispersion medium using a surfactant.

[0140] Examples of the dispersion medium include aqueous media such as water, alcohols, etc. These may be used alone or in combination of two or more.

[0141] Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. Among these, anionic surfactants are preferred. The surfactants may be used alone or in combination of two or more.

[0142] Examples of a method for dispersing styrene-based resin particles in a dispersion medium include a method in which the styrene-based resin and the dispersion medium are mixed and stirred using a rotary shear homogenizer, a ball mill with media, a sand mill, a dyno mill, or the like to disperse the mixture.

[0143] Another method for dispersing styrene-based resin particles in a dispersion medium is emulsion polymerization. Specifically, after mixing the polymerization components of the styrene-based resin with a chain transfer agent or a polymerization initiator, an aqueous medium containing a surfactant is further mixed and stirred to prepare an emulsion, and the styrene-based resin is polymerized in the emulsion. In this case, it is preferable to use dodecanethiol as a chain transfer agent.

[0144] The volume average particle size of the styrene-based resin particles dispersed in the styrene-based resin particle dispersion is preferably 100 nm or more and 250 nm or less, more preferably 120 nm or more and 220 nm or less, and even more preferably 150 nm or more and 200 nm or less. The volume average particle diameter of the resin particles contained in the resin particle dispersion is measured using a laser diffraction particle size distribution analyzer (e.g., LA-700 manufactured by Horiba, Ltd.), and the particle diameter at the cumulative 50% in the volume-based particle size distribution calculated from the smallest diameter side is defined as the volume average particle diameter (D50v).

[0145] The content of the styrene-based resin particles contained in the styrene-based resin particle dispersion is preferably 30% by mass or more and 60% by mass or less, and more preferably 40% by mass or more and 50% by mass or less.

[0146] -Composite resin particle formation process- A styrene-based resin particle dispersion and a polymerization component of a (meth)acrylic acid ester-based resin are mixed, and the (meth)acrylic acid ester-based resin is polymerized in the styrene-based resin particle dispersion to form composite resin particles containing the styrene-based resin and the (meth)acrylic acid ester-based resin.

[0147] The composite resin particles are preferably resin particles containing a styrene-based resin and a (meth)acrylic acid ester-based resin in a microphase-separated state. The resin particles can be produced, for example, by the following method.

[0148] A polymerization component of a (meth)acrylic ester resin (a group of monomers containing at least two types of (meth)acrylic esters) is added to a styrene-based resin particle dispersion, and an aqueous medium is added as needed. Next, while slowly stirring the dispersion, the temperature of the dispersion is heated to a temperature equal to or higher than the glass transition temperature of the styrene-based resin (for example, a temperature 10°C to 30°C higher than the glass transition temperature of the styrene-based resin). Next, while maintaining the temperature, an aqueous medium containing a polymerization initiator is slowly added dropwise, and stirring is continued for an additional long period of time ranging from 1 hour to 15 hours. In this case, ammonium persulfate is preferably used as the polymerization initiator.

[0149] Although the detailed mechanism is not entirely clear, it is speculated that when the above-mentioned method is adopted, the styrene-based resin particles are impregnated with the monomer and the polymerization initiator, and the (meth)acrylic acid ester is polymerized inside the styrene-based resin particles. As a result, it is speculated that composite resin particles are obtained in which the (meth)acrylic acid ester resin is contained inside the styrene-based resin particles, and the styrene-based resin and the (meth)acrylic acid ester resin form a microphase-separated state inside the particles.

[0150] The volume average particle size of the composite resin particles dispersed in the composite resin particle dispersion is preferably 140 nm or more and 300 nm or less, more preferably 150 nm or more and 280 nm or less, and even more preferably 160 nm or more and 250 nm or less.

[0151] The content of the composite resin particles contained in the composite resin particle dispersion is preferably 20% by mass or more and 50% by mass or less, and more preferably 30% by mass or more and 40% by mass or less.

[0152] -Agglomerated particle formation process- The composite resin particles are aggregated in the composite resin particle dispersion to form aggregated particles having a diameter close to that of the target pressure-responsive particles.

[0153] Specifically, for example, an aggregating agent is added to the composite resin particle dispersion, and the pH of the composite resin particle dispersion is adjusted to be acidic (for example, pH 2 or higher and 5 or lower), and a dispersion stabilizer is added as necessary. After that, the dispersion is heated to a temperature close to the glass transition temperature of the styrene-based resin (for example, the glass transition temperature of the styrene-based resin -30°C or higher and the glass transition temperature -10°C or lower), causing the composite resin particles to aggregate and form aggregated particles.

[0154] In the aggregated particle formation process, an aggregating agent is added to the composite resin particle dispersion at room temperature (e.g., 25°C) while stirring with a rotary shear homogenizer, the pH of the composite resin particle dispersion is adjusted to an acidic value (e.g., pH 2 or more and 5 or less), and a dispersion stabilizer may be added as needed, followed by heating.

[0155] Examples of the flocculant include a surfactant having an opposite polarity to that of the surfactant contained in the composite resin particle dispersion, an inorganic metal salt, and a divalent or higher metal complex. When a metal complex is used as the flocculant, the amount of surfactant used can be reduced, and charging properties can be improved. If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used together with the flocculant, and a chelating agent is preferably used as this additive.

[0156] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. The chelating agent may be a water-soluble chelating agent, such as hydroxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid), or aminocarboxylic acid (e.g., iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), or ethylenediaminetetraacetic acid (EDTA). The amount of the chelating agent added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the resin particles.

[0157] -Fusion / unification process- Next, the aggregated particle dispersion liquid in which the aggregated particles are dispersed is heated, for example, to a temperature equal to or higher than the glass transition temperature of the styrene-based resin (for example, a temperature 10°C to 30°C higher than the glass transition temperature of the styrene-based resin), to fuse and coalesce the aggregated particles and form pressure-responsive particles.

[0158] The pressure-responsive particles obtained through the above steps usually have a sea-island structure with a sea phase containing a styrene-based resin and an island phase containing a (meth)acrylic ester-based resin dispersed in the sea phase. In the composite resin particles, the styrene-based resin and the (meth)acrylic ester-based resin are in a state of microphase separation, and it is presumed that in the fusion and coalescence step, the styrene-based resins come together to form the sea phase, and the (meth)acrylic ester-based resins come together to form the island phase.

[0159] The average diameter of the island phases in the sea-island structure can be controlled, for example, by increasing or decreasing the amount of the styrene-based resin particle dispersion or the amount of at least two types of (meth)acrylic acid esters used in the composite resin particle formation step, or by increasing or decreasing the time for which the mixture is maintained at a high temperature in the fusion / coalescence step.

[0160] Pressure-responsive particles with a core-shell structure, for example, a step of further mixing the aggregated particle dispersion and the styrene-based resin particle dispersion after obtaining the aggregated particle dispersion, and aggregating the styrene-based resin particles so that the particles adhere to the surfaces of the aggregated particles, thereby forming second aggregated particles; a step of heating the second aggregate particle dispersion liquid in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles, thereby forming pressure-responsive particles having a core-shell structure; It is manufactured through this process. The pressure-responsive particles with a core-shell structure obtained through the above process have a shell layer containing a styrene-based resin. A shell layer containing another type of resin may be formed by using a resin particle dispersion in which other types of resin particles are dispersed instead of the styrene-based resin particle dispersion.

[0161] After the fusion and coalescence process is completed, the pressure-responsive particles formed in the solution are subjected to a washing process, a solid-liquid separation process, and a drying process to obtain pressure-responsive particles in a dried state. The washing step can be a known washing step, and may be, for example, a displacement wash using ion-exchanged water. The solid-liquid separation step can be a known solid-liquid separation step, and from the viewpoint of productivity, it is preferable to carry out suction filtration, pressure filtration, or the like.

[0162] The drying step may be the same as the drying step and drying device of the resin particle manufacturing method of the present disclosure, which are described above. By applying this drying step, the generation of coarse particles is suppressed, and dry pressure-responsive particles with few coarse particles can be obtained.

[0163] An external additive may be added to the dried pressure-responsive particles obtained as described above. The external addition of an external additive is carried out, for example, by adding the external additive to the obtained pressure-responsive particles in a dry state and mixing them. Mixing can be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, etc. Furthermore, if necessary, coarse particles may be removed using a vibrating sieve, an air sieve, etc.

[0164] -External additives- Examples of external additives for pressure-responsive particles include inorganic particles, such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, KO, Na2O, ZrO2, CaO·SiO2, KO·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4. The surfaces of the inorganic particles used as the external additive are preferably subjected to a hydrophobic treatment.

[0165] Further, examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate, and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers), and the like.

[0166] The total amount of external additives added is preferably 1.0 to 20.0 parts by mass, more preferably 1.0 to 10.0 parts by mass, and even more preferably 2.5 to 7.0 parts by mass, per 100 parts by mass of pressure-responsive particles. [Example]

[0167] Hereinafter, embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass.

[0168] <Preparation of pressure-responsive particles> Pressure-responsive particles were prepared as follows.

[0169] <Preparation of Resin Particles (A)> [Resin Particle Dispersion (1): Preparation of High Tg Resin] The following components were mixed and dissolved to prepare a solution. Styrene: 450 parts by mass n-Butyl acrylate: 150 parts by mass Acrylic acid: 12 parts by mass Dodecanethiol: 9 parts by mass

[0170] On the other hand, 20 parts of an anionic surfactant (DOWFAX2A1, manufactured by The Dow Chemical Company) was dissolved in 250 parts of ion-exchanged water, and the above solution was added to the solution, followed by dispersion and emulsification in a flask (monomer emulsion A). Furthermore, 3 parts of anionic surfactant (DOWFAX2A1, manufactured by Dow Chemical Company) was dissolved in 555 parts of ion-exchanged water, and the solution was charged into a polymerization flask. The polymerization flask was sealed, a reflux condenser was installed, and the polymerization flask was heated to 75° C. in a water bath with nitrogen injection and slow stirring, and maintained at that temperature. 9 parts by mass of ammonium persulfate was dissolved in 43 parts by mass of ion-exchanged water and added dropwise to the polymerization flask via a metering pump over 20 minutes, and then the monomer emulsion A was added dropwise via a metering pump over 200 minutes. Thereafter, the polymerization flask was maintained at 75°C for 3 hours while continuing to slowly stir, to complete the polymerization. This resulted in a resin particle dispersion (1) having a median particle diameter of 75 nm, a glass transition temperature of 51° C., a weight average molecular weight of 29,000, and a solid content of 42% by mass.

[0171] [Resin Particle Dispersion (2): Preparation of Low Tg Resin] The following components were mixed and dissolved to prepare a solution (2). Styrene: 100 parts n-Butyl acrylate: 500 parts Acrylic acid: 12 parts Dodecanethiol: 9 parts

[0172] On the other hand, 20 parts of an anionic surfactant (DOWFAX2A1, manufactured by The Dow Chemical Company) was dissolved in 250 parts of ion-exchanged water, and the solution (2) was added thereto, followed by dispersion and emulsification in a flask (monomer emulsion B). Furthermore, 3 parts of anionic surfactant (DOWFAX2A1, manufactured by Dow Chemical Company) was dissolved in 555 parts of ion-exchanged water, and the solution was charged into a polymerization flask. The polymerization flask was sealed, a reflux condenser was installed, and the polymerization flask was heated to 75°C in a water bath with gentle stirring while injecting nitrogen, and maintained at that temperature. 9 parts by mass of ammonium persulfate was dissolved in 43 parts by mass of ion-exchanged water and added dropwise to the polymerization flask via a metering pump over 20 minutes, followed by adding the monomer emulsion B dropwise via a metering pump over 200 minutes. Thereafter, the polymerization flask was maintained at 75°C for 3 hours with continued slow stirring to complete the polymerization. This resulted in a resin particle dispersion (2) having a median particle diameter of 50 nm, a glass transition temperature of 10° C., a weight average molecular weight of 26,000, and a solid content of 42% by mass.

[0173] [Preparation of Wet Resin Particles (A)] The components were mixed and dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50, manufactured by IKA) according to the formulation below, and then the flask was heated to 42°C in a heating oil bath while stirring. After holding at 42°C for 60 minutes, 100 parts by mass of resin particle dispersion (1) (21 parts by mass of resin) was added and gently stirred. Resin particle dispersion (1): 100 parts by mass (21 parts by mass of resin) Resin particle dispersion (2): 100 parts by mass (42 parts by mass of resin) Polyaluminum chloride: 0.15 parts by mass Ion-exchanged water: 300 parts by mass

[0174] Thereafter, the pH in the system was adjusted to 5.5 with 0.5 mol / L aqueous sodium hydroxide solution, and then the system was heated to 90° C. with continued stirring. During the temperature increase to 95° C., the pH in the system would normally drop to 4.5 or less, but here additional aqueous sodium hydroxide solution was added dropwise to maintain the pH above 5.0. After the reaction was completed, the mixture was cooled, filtered, washed with ion-exchanged water, and then subjected to solid-liquid separation using Nutsche suction filtration. The mixture was then redispersed in ion-exchanged water at 40°C and washed by stirring at 100 rpm using a stainless steel impeller for 15 minutes. This washing procedure was repeated three times, and after solid-liquid separation using Nutsche suction filtration, the water content of the solids was adjusted to 40% by mass. After further adjusting the water content of the solids, the solids were finely crushed using a granulator (coal mill) to obtain wet resin particles (A). The resin particles (A) correspond to pressure-responsive particles.

[0175] <Preparation of Resin Particles (B)> <Preparation of Dispersion Containing Styrene-Based Resin Particles> [Preparation of styrene-based resin particle dispersion (St1)] Styrene: 390 parts n-Butyl acrylate: 100 parts Acrylic acid: 10 parts Dodecanethiol: 7.5 parts The above materials were mixed and dissolved to prepare a monomer solution. Eight parts of an anionic surfactant (Dowfax2A1, manufactured by The Dow Chemical Company) was dissolved in 205 parts of ion-exchanged water, and the monomer solution was added thereto, dispersed and emulsified to obtain an emulsion. 2.2 parts of anionic surfactant (Dowfax 2A1, manufactured by The Dow Chemical Company) was dissolved in 462 parts of ion-exchanged water, and the solution was charged into a polymerization flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube. The mixture was heated to 73°C with stirring and maintained at that temperature. 3 parts of ammonium persulfate was dissolved in 21 parts of ion-exchanged water and added dropwise to the polymerization flask via a metering pump over 15 minutes, and then the emulsion was added dropwise via a metering pump over 160 minutes. The polymerization flask was then maintained at 75°C for 3 hours with slow stirring, and then allowed to cool to room temperature. This resulted in a styrene-based resin particle dispersion (St1) containing styrene-based resin particles, with a volume average particle size (D50v) of 174 nm, a weight average molecular weight measured by GPC (UV detection) of 49,000, a glass transition temperature of 54°C, and a solid content of 42%.

[0176] <Preparation of dispersion containing composite resin particles> [Preparation of Composite Resin Particle Dispersion (M1)] Styrene-based resin particle dispersion (St1): 1,190 parts (solid content: 500 parts) 2-Ethylhexyl acrylate: 250 parts n-Butyl acrylate: 250 parts Ion-exchanged water: 982 parts The above materials were charged into a polymerization flask, stirred at 25°C for 1 hour, and then heated to 70°C. 2.5 parts of ammonium persulfate was dissolved in 75 parts of ion-exchanged water, and the solution was added dropwise to the polymerization flask over 60 minutes via a metering pump. The polymerization flask was then maintained at 70°C for 3 hours with slow stirring, and then allowed to cool to room temperature. This resulted in a composite resin particle dispersion (M1) containing composite resin particles with a volume average particle size (D50v) of 219 nm, a weight average molecular weight measured by GPC (UV detection) of 219,000, and a solid content of 32%.

[0177] <Preparation of pressure-responsive particles> [Preparation of pressure-responsive particles] ·Composite resin particle dispersion (M1): 504 parts Ion-exchanged water: 710 parts Anionic surfactant (Dow Chemical Company, Dowfax2A1): 1 part The above materials were placed in a reaction vessel equipped with a thermometer and pH meter. The pH was adjusted to 3.0 by adding 1.0% aqueous nitric acid solution at 25°C. Then, 23 parts of 2.0% aqueous aluminum sulfate solution were added while dispersing using a homogenizer (IKA Ultra Turrax T50) at 5,000 rpm. The reaction vessel was then equipped with a stirrer and a heating mantle. The temperature was increased at a rate of 0.2°C / min up to 40°C, and then at a rate of 0.05°C / min after 40°C. The particle size was measured every 10 minutes using a Multisizer II (aperture diameter 50 μm, Beckman Coulter). When the volume average particle size reached 5.0 μm, the temperature was maintained, and 170 parts of styrene-based resin particle dispersion (St1) were added over 5 minutes. After the addition, the mixture was held at 50°C for 30 minutes, after which the pH of the slurry was adjusted to 6.0 by adding 1.0% aqueous sodium hydroxide solution. Next, the temperature was raised to 90°C at a rate of 1°C / min while adjusting the pH to 6.0 every 5°C, and then maintained at 90°C. When the particle shape and surface properties were observed using an optical microscope and a field emission scanning electron microscope (FE-SEM), coalescence of the particles was confirmed after 10 hours, so the container was cooled to 30°C over 5 minutes with cooling water. The cooled slurry was passed through a nylon mesh with 15 μm openings to remove coarse particles, and the slurry that passed through the mesh was filtered under reduced pressure using an aspirator. The solids remaining on the filter paper were crushed as finely as possible by hand and added to ion-exchanged water (30°C) in an amount 10 times the solid content and stirred for 30 minutes. The mixture was then filtered under reduced pressure using an aspirator. The solids remaining on the filter paper were crushed as finely as possible by hand and added to ion-exchanged water (30°C) in an amount 10 times the solid content. After stirring for 30 minutes, the mixture was again filtered under reduced pressure using an aspirator, and the electrical conductivity of the filtrate was measured. This procedure was repeated until the electrical conductivity of the filtrate reached 10 μS / cm or less, and the solids were washed. After washing, the water content of the solids was adjusted to 40% by mass, and the solids were further crushed in a particle sizer (coal mill) to obtain wet resin particles (B). The resin particles (B) correspond to pressure-responsive particles.

[0178] [Example 1] The wet resin particles (A) were applied to a drying device as shown in Fig. 1 and dried under the drying conditions shown in Table 1.

[0179] The particle size of the dried resin particles (A) was measured, and the volume average particle size D50 was 6.5 μm and the volume average particle size distribution index GSDv was 1.23. The shape factor SF1 of the resin particles (A) was found to be 130 by observing the shape with Luzex. In addition, the temperature difference (T A -T B ) was measured and found to be 35°C.

[0180] [Examples 2 to 18] Drying was carried out using a drying device in the same manner as in Example 1, except that the drying conditions were changed as appropriate according to Table 1 or Table 2.

[0181] [Example 19] Drying was carried out in a drying device in the same manner as in Example 1, except that the wet resin particles (A) were replaced with wet resin particles (B). When the particle size of the resin particles (B) after drying was measured, the volume average particle size D50 was found to be 8.0 μm. In addition, the temperature difference (T A -T B ) was measured and found to be 40°C.

[0182] <Measurement> The drying conditions shown in Tables 1 and 2 were measured by the methods already described. The results are shown in Tables 1 and 2.

[0183] <Evaluation> (Suppression of generation of coarse particles) The dried resin particles were sieved using a standard sieve with a mesh size of 20 μm as specified in JIS Z 8801-1:2006, and the weight ratio of particles that did not pass through the sieve (i.e., coarse particles) to the total amount of dried resin particles was defined as the amount of coarse particles [mass%]. The ability to suppress the generation of coarse particles was classified according to the following criteria. The results are shown in Table 1 or Table 2. G1: The amount of coarse particles was 0.1% by mass or less. G2: The amount of coarse particles was more than 0.1% by mass and 0.5% by mass or less. G3: The amount of coarse particles was more than 0.5% by mass and 1.0% by mass or less. G4: The amount of coarse particles was more than 1.0 mass% and 1.5 mass% or less. G5: The amount of coarse particles exceeded 1.5% by mass.

[0184] (White spots) To 50 parts of the dried resin particles, 1.5 parts of hydrophobic silica (TS720, manufactured by Cabot Corporation) was added, and the mixture was mixed in a sample mill to obtain a toner with external additives. Then, using a ferrite carrier with an average particle size of 35 μm coated with 1% by mass of polymethyl methacrylate (manufactured by Soken Chemical Industries, Ltd.), the above-mentioned externally added toner was weighed so that the toner concentration was 8% by mass, and both were stirred and mixed in a ball mill for 5 minutes to prepare an electrostatic image developer.

[0185] A modified image forming apparatus DocuCentre C7550I manufactured by FUJIFILM Business Innovation Co., Ltd. was prepared, and the electrostatic image developer obtained by the above method was placed in the magenta position of the image forming apparatus, and a commercially available cyan toner developer manufactured by FUJIFILM Business Innovation Co., Ltd. was placed in the cyan position. Using this image forming apparatus, in an environment of 30°C and 85% RH, a toner weight per unit area of ​​1 g / m 2 The result was a solid image of dried resin particles superimposed on a solid image of cyan, and 1,000 sheets of A4 paper were printed in succession. The 1,000 printed images were visually inspected for the presence or absence of white spots in the image and classified according to the following criteria. If coarse particles are present in the dried resin particles, white spots will occur when a solid cyan image is transferred onto the solid image of the dried resin particles. Therefore, it can be said that the fewer white spots there are in the image, the fewer coarse particles there are in the dried resin particles. The results are shown in Table 1 or Table 2. G1: No white spots in the image G2: White spots appear on 1 to 5 images G3: White spots appear on 6 to 10 sheets G4: White spots appear on 11 or more images

[0186] [Table 1]

[0187] [Table 2]

[0188] As is clear from Tables 1 and 2, the production of coarse particles is suppressed in the resin particle production methods of the Examples compared to the resin particle production methods of the Comparative Examples. [Explanation of symbols]

[0189] 10A, 10B, 10C: drying tube, 11A: loop type piping, 11B, 11B: non-loop type piping, 12: supply section, 12a: supply port, 14: second gas discharge nozzle, 14a: gas discharge port, 16: discharge section, 16a: discharge port, 18: closing plate, 20: second gas supply section, 30: transfer piping, 40: bag filter, 42: filter, 44: recovery port, 100A, 100B, 100C: drying section, 200: recovery section

Claims

1. a drying step of drying the wet resin particles that undergo a phase transition under pressure by passing them together with a first gas through a drying tube without circulating them; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, The method for producing resin particles, wherein the second gas is discharged from the gas discharge port at a discharge speed of 50 m / s or more.

2. a drying step of drying the wet resin particles that undergo a phase transition under pressure by passing them together with a first gas through a drying tube without circulating them; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, a difference Δ(V2-V1) between a velocity V1 of the first gas passing through the drying tube and a discharge velocity V2 of the second gas discharged from the gas discharge port is 40 m / s or more.

3. The method for producing resin particles according to claim 1 or 2, wherein the drying tube has two or more gas outlets.

4. The method for producing resin particles according to claim 3 , wherein the second gas is discharged from two or more of the gas discharge ports at a discharge speed of 100 m / s or more.

5. 5. The method for producing resin particles according to claim 3, wherein a flow rate Q1 of the first gas passing through the drying tube and a total flow rate Q2 of the second gas discharged from the gas discharge port satisfy a relationship of Q2 / (Q1+Q2)≧0.

9.

6. The method for producing resin particles according to any one of claims 1 to 5, wherein a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfy the relationship d / D≦0.

25.

7. The method for producing resin particles according to claim 6, wherein a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfy the relationship d / D≦0.

20.

8. The method further includes a recovery step of recovering the resin particles discharged from the drying tube in a recovery section, The method for producing resin particles according to any one of claims 1 to 7, wherein a temperature T1 of the second gas discharged from the gas discharge port is 50°C or higher and 70°C or lower, and a temperature T2 in the recovery section is 20°C or higher and 40°C or lower.

9. The method for producing resin particles according to claim 8, wherein the recovery section includes a bag filter, and the linear velocity of the gas passing through the bag filter is 0.1 m / s or less.

10. The method for producing resin particles according to any one of claims 1 to 9, wherein the resin particles that undergo a phase transition due to pressure satisfy the following formula 1: Formula 1: 8℃≦T Ａ -T Ｂ (In formula 1, T Ａ is the temperature at which the viscosity is 10,000 Pa s under a pressure of 1 MPa, and T Ｂ is the temperature at which the viscosity is 10,000 Pa s under a pressure of 10 MPa.)

11. a drying section that dries wet resin particles that undergo a phase transition under pressure by passing the resin particles together with a first gas through a drying tube without circulating the resin particles; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, a drying device, wherein the second gas is discharged from the gas discharge port at a discharge speed of 50 m / s or more;

12. a drying section that dries wet resin particles that undergo a phase transition under pressure by passing the resin particles together with a first gas through a drying tube without circulating the resin particles; the drying tube has a supply port for supplying the resin particles into the drying tube, a gas discharge port for discharging a second gas toward the resin particles passing through the drying tube, and a discharge port for discharging the resin particles from inside the drying tube, a difference Δ(V2-V1) between a velocity V1 of the first gas passing through the drying tube and a discharge velocity V2 of the second gas discharged from the gas discharge port is 40 m / s or more.

13. 13. The drying apparatus according to claim 11, wherein the drying tube has two or more gas outlets.

14. The drying device according to claim 13 , wherein the second gas discharged from the two or more gas discharge ports each has a discharge speed of 100 m / s or more.

15. 15. The drying device according to claim 13 or 14, wherein a flow rate Q1 of the first gas passing through the drying tube and a total flow rate Q2 of the second gas discharged from the gas discharge port satisfy a relationship of Q2 / (Q1+Q2)≧0.

9.

16. 16. The drying device according to claim 11, wherein a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfy a relationship of d / D≦0.

25.

17. 17. The drying device according to claim 16, wherein a maximum diameter D of the drying tube and a maximum diameter d of the gas discharge port satisfy a relationship of d / D≦0.

20.

18. a recovery unit that recovers the resin particles discharged from the drying tube, The drying device according to any one of claims 11 to 17, wherein a temperature T1 of the second gas discharged from the gas discharge port is 50°C or higher and 70°C or lower, and a temperature T2 in the recovery section is 20°C or higher and 40°C or lower.

19. 19. The drying apparatus according to claim 18, wherein the collection section includes a bag filter, and the linear velocity of the gas passing through the bag filter is 0.1 m / s or less.

20. The drying device according to any one of claims 11 to 19, wherein the resin particles that undergo a phase transition due to pressure are particles that satisfy the following formula 1: Formula 1: 8℃≦T Ａ -T Ｂ (In formula 1, T Ａ is the temperature at which the viscosity is 10,000 Pa s under a pressure of 1 MPa, and T Ｂ is the temperature at which the viscosity is 10,000 Pa s under a pressure of 10 MPa.)

21. a drying section that dries wet resin particles that undergo a phase transition under pressure by passing the resin particles together with a first gas through a drying tube without circulating the resin particles; the drying pipe comprises a loop-shaped pipe, a supply unit that supplies the resin particles into the loop-shaped pipe, a gas discharge unit that discharges a second gas toward the resin particles passing through the loop-shaped pipe, a discharge unit that discharges the resin particles from the loop-shaped pipe, and a closing plate that closes the circulation of the resin particles in the loop-shaped pipe, A drying device, wherein the second gas is discharged from a gas discharge port, which is an opening of the gas discharge portion, at a discharge speed of 50 m / s or more.

22. A drying unit is provided which dries wet resin particles that undergo a phase transition under pressure by passing them through a drying tube together with a first gas without circulating them, the drying pipe comprises a loop-shaped pipe, a supply unit that supplies the resin particles into the loop-shaped pipe, a gas discharge unit that discharges a second gas toward the resin particles passing through the loop-shaped pipe, a discharge unit that discharges the resin particles from the loop-shaped pipe, and a closing plate that closes the circulation of the resin particles in the loop-shaped pipe, a difference Δ(V2-V1) between a velocity V1 of the first gas passing through the loop piping and a discharge velocity V2 of the second gas discharged from a gas discharge port which is an opening of the gas discharge section is 40 m / s or more.

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