WO2018164540A1 - Thermoplastic polymer particles - Google Patents

Abstract

Provided are thermoplastic polymer particles having an aspect ratio of 1.00 or more and less than 1.05, and a sphericity of 0.95 to 1.00. The thermoplastic polymer particles are formed from a thermoplastic polymer resin in a continuous matrix phase. The thermoplastic polymer particles show a peak cold crystallization temperature (T_cc) at a temperature between a glass transition temperature (T_g) and the melting point (T_m) in a differential scanning calorimetry (DSC) curve which is derived from an elevated temperature analysis at 10℃/min by differential scanning calorimetry.

Description

Thermoplastic polymer particles

This application is filed with Korean Patent Application No. 10-2017-0030178 filed March 9, 2017, Korean Patent Application No. 10-2017-0030179 filed March 9, 2017, and Korean Patent Application No. 10-2017 dated September 18, 2017 -0119573, and the benefit of priority based on Korean Patent Application No. 10-2018-0027661 dated March 8, 2018, including all content disclosed in the documents of that Korean Patent Application as part of this specification.

The present invention relates to thermoplastic polymer particles.

Polymeric resins in the form of particles are used in various ways throughout the industry. Such polymer resin particles are manufactured through a process of granulating a polymer resin raw material.

In general, a method for granulating a thermoplastic polymer resin includes a grinding method represented by freeze grinding; A solvent dissolution precipitation method in which a solution is dissolved in a high temperature solvent and then cooled to precipitate or dissolved in a solvent and then precipitated by adding a poor solvent; And a melt kneading method in which a thermoplastic resin particle is obtained by mixing the thermoplastic resin and the incompatible resin in a mixer to form a composition having the thermoplastic resin and the incompatible resin in the continuous phase, and then removing the incompatible resin.

When preparing the particles through the grinding method, there is a problem that it is difficult to ensure particle uniformity of the manufactured thermoplastic polymer resin particles. In addition, since liquid nitrogen is used during cooling of the grinding method, it costs more than the particle obtaining process. When a compounding step of adding a pigment, an antioxidant, or the like to the thermoplastic polymer raw material is added, the compounding process proceeds in a batch manner, thereby lowering the productivity compared to the continuous particle obtaining process. When the particles are manufactured by the solvent dissolution precipitation method and the melt kneading method, there is a problem that other components such as a solvent may be detected as impurities in addition to the thermoplastic resin particles. When impurities are mixed in the process, it is difficult to produce particles composed of purely thermoplastic polymer resin, and there is a high possibility of causing deformation of physical properties and shapes of the particles, and it is difficult to finely control them.

Due to the above-described problems, it is not possible to produce thermoplastic polymer resin particles having suitable physical properties for application to products by conventional methods. Accordingly, there is a need in the art for thermoplastic polymer resin particles having improved physical properties by improving conventional methods.

[Preceding technical literature]

[Patent Documents]

 (Patent Document 1) Japanese Unexamined Patent Publication No. 2001-288273

(Patent Document 2) Japanese Unexamined Patent Publication No. 2000-007789

(Patent Document 3) Japanese Unexamined Patent Publication No. 2004-269865

The present invention is to extrude the thermoplastic polymer resin, and to atomize the extruded resin in contact with air, and then cooled to produce the thermoplastic polymer particles, thereby effectively preventing the incorporation of impurities other than the resin component in the particles, the particles are widely It is an object of the present invention to provide a thermoplastic polymer particle that can be controlled to have physical properties that can be utilized.

According to the first aspect of the invention,

In the present invention, the aspect ratio calculated by the following formula 1 is 1.00 or more and less than 1.05,

It provides a thermoplastic polymer particles having a sphericity of 0.95 to 1.00 calculated by the following formula (2).

[Calculation 1]

Aspect ratio = major axis / minor axis

[Calculation 2]

Roundness = 4 × area / (π × long axis ^ 2)

In one embodiment of the invention, the thermoplastic polymer particles are formed in a continuous matrix (matrix) phase from the thermoplastic polymer resin.

In one embodiment of the present invention, the thermoplastic polymer particles have a glass transition temperature (T _g ) and melting point (DS) in a DSC curve derived from an elevated temperature analysis of 10 ° C./min by differential scanning calorimetry (DSC). At temperatures between T _m ), a peak of cold crystallization temperature (T _cc ) appears.

In one embodiment of the present invention, the thermoplastic polymer is polylactic acid (PLA, Poly lactic acid), thermoplastic polyurethane (TPU, Thermoplastic Polyurethane), polyethylene (PE, Polyethylene), polypropylene (PP, Polypropylene), polyether Polyether sulfone (PES), polymethyl methacrylate (PMMA, Poly (methyl methacrylate)), ethylene vinyl-alcohol polymer (EVOH, Ethylene Vinyl-Alcohol Copolymer) and at least one polymer selected from the group consisting of a combination thereof.

In one embodiment of the present invention, the particle diameter of the thermoplastic polymer particles is 1 to 1000㎛.

According to a second aspect of the invention,

The present invention comprises the steps of supplying a thermoplastic polymer resin to the extruder; Supplying the extruded thermoplastic polymer resin and air to a nozzle, contacting the thermoplastic polymer resin and air to granulate the thermoplastic polymer resin, and then discharging the granulated thermoplastic polymer resin; And cooling the thermoplastic polymer particles by supplying the discharged thermoplastic polymer particles to a cooler, and then obtaining the cooled thermoplastic polymer particles.

Since the thermoplastic polymer particles according to the present invention have an almost spherical shape, the handling and processing characteristics of the particles are excellent. Since the thermoplastic polymer particles are formed in a continuous matrix form from the thermoplastic polymer resin and there are almost no impurities in the particles, there is little defect in a product manufactured by processing the particles. In addition, since the thermoplastic polymer particles exhibit a cold crystallization temperature (T _cc ) peak in the DSC curve, when the particles are heated and processed, thermal energy is generated by heat generation, and thus the particles may be easily processed even with a small supply of thermal energy. .

1 is an image schematically showing the shape of the thermoplastic resin particles of the present invention.

2 is a process flowchart schematically showing a method of manufacturing thermoplastic polymer particles according to the present invention.

3 is a cross-sectional view of a nozzle discharge portion showing a supply position of a thermoplastic polymer resin and air to a nozzle according to an embodiment of the present invention.

Embodiments provided according to the present invention can all be achieved by the following description. It is to be understood that the following description describes preferred embodiments of the invention, and the invention is not necessarily limited thereto.

In the following specification, for the numerical range, the expression "to" is used to include both the upper and lower limits of the range, and when not including the upper limit or the lower limit, "less than", " The expression "greater than", "less than" or "greater than" is used.

The present invention provides thermoplastic polymer particles that could not be obtained by conventional particle production methods. Hereinafter, the thermoplastic polymer particles according to the present invention will be described in detail.

Thermoplastic polymer particles

The present invention provides thermoplastic polymer particles having a shape close to a spherical shape. In the present invention, the shape of the particles is evaluated in the following aspect ratio and roundness, and the closer the aspect ratio and sphericity to 1, the closer the shape of the particles is interpreted. The aspect ratio is calculated by the following formula (1).

[Calculation 1]

Aspect ratio = major axis / minor axis

In addition, the sphericity degree is calculated by the following formula (2).

[Calculation 2]

Roundness = 4 × area / (π × long axis ^ 2)

In order to explain the above formula in more detail, FIG. 1 schematically shows a thermoplastic polymer particle. According to Figure 1, the "long axis" in the formula 1 and 2 means the longest distance among the vertical distance (d) between two parallel tangents of the 2D image (cross section) of the thermoplastic polymer particles, "short axis" is It means the shortest distance among the vertical distance (d) between two parallel tangents of the 2D image (cross section) of the thermoplastic polymer particles. In addition, in Formula 2, "area" means a cross-sectional area including the long axis of the thermoplastic polymer particles. FIG. 1 illustrates an area A as an example when the vertical distance d between two parallel tangent planes of the thermoplastic polymer particles is a long axis.

According to one embodiment of the invention, the thermoplastic polymer particles according to the invention may have an aspect ratio of 1.00 or more and less than 1.05, more specifically 1.02 or more and less than 1.05, and may have a spherical shape of 0.95 to 1.00, more specifically 0.98 to 1.00 May have a degree. When the shape of the thermoplastic polymer particles satisfies the above-described aspect ratios and sphericity ranges, the flowability and uniformity of the thermoplastic polymer particles are increased, so that the particles are easily handled, and the products produced by the particles also have defects such as internal voids. This is suppressed and the quality is improved.

The numerical values according to Formulas 1 and 2 can be measured by image processing of thermoplastic polymer particles using ImageJ (National Institutes of Health (NIH))-converting them into binary images and quantifying the degree of sphericalness of individual particles- Do.

The thermoplastic polymer particles according to the present invention are particles formed in a continuous matrix from the thermoplastic polymer resin. Forming into a continuous matrix from the thermoplastic polymer resin means forming the thermoplastic polymer resin in a continuous dense structure without additional components. By extruding the thermoplastic polymer resin, melting and granulating the melt with air, the thermoplastic polymer particles are continuously produced with a dense structure. In contrast, according to the conventional manufacturing method, particles are formed by adding additional components or particles are formed through a discontinuous process of cooling and pulverization, so that particles are not formed on a continuous matrix.

Particles formed in a continuous matrix from the thermoplastic polymer resin have a high purity since impurities are not incorporated in the manufacturing process of the particles. Here, “impurity” means components other than the thermoplastic polymer which may be incorporated in the preparation of the particles. Exemplary impurities include a solvent for dispersing the thermoplastic polymer resin, a heavy metal component included in the grinding or grinding process, and an unreacted monomer included in the polymerization process. According to one embodiment of the present invention, the impurity content of the thermoplastic polymer particles of the present invention may be 50 ppm or less, preferably 20 ppm or less, more preferably 5 ppm or less.

In addition, the particles may additionally have other properties as well as purity. One of these characteristics is that the thermoplastic polymer particles are separated from the glass transition temperature (T _g ) and the melting point (T _m ) in a DSC curve derived from an elevated temperature analysis of 10 ° C./min by differential scanning calorimetry (DSC). The peak of the cold crystallization temperature (T _cc ) appears at the temperature. Thermoplastic polymer particles are spherical solid particles at room temperature. When the particles are temperature-analyzed using a differential scanning calorimeter, the thermoplastic polymer particles have a peak of cold crystallization temperature (T _cc ) at a temperature between the glass transition temperature (T _g ) and the melting point (T _m ), This means that the thermoplastic polymer particles generate heat before melting. Peak of cold crystallization temperature (T _cc) used herein refers to only the peak of cold crystallization temperature (T _cc) appears when the first temperature elevation analysis of the thermoplastic polymer particles, and the internal structure of the particles by the subsequent repeated temperature rise modification As The peak of the cold crystallization temperature (T _cc ) that may occur is not included in the properties of the particles described herein. If it has a peak of the cold crystallization temperature (T _cc ) by repeated elevated temperature, because the energy for the repeated elevated temperature is consumed, there is no advantage in terms of energy when processing the particles. According to one embodiment of the invention, the cold crystallization temperature (T _cc ) is shown in the 30% to 70% section between the glass transition temperature (T _g ) and the melting point (T _m ). In this section, 0% is the glass transition temperature (T _g ), and 100% is the melting point (T _m ). In addition, according to the DSC curve, the thermoplastic polymer particles may have a difference (ΔH1-ΔH2) of 3 to 100 J / g between an endothermic amount (ΔH1) and a calorific value (ΔH2). In this case, when the heat processing is performed using the thermoplastic polymer particles, it is possible to obtain an advantage that processing at a low temperature is possible compared to the processing temperatures of conventional thermoplastic polymer particles.

In the present invention, the thermoplastic polymer is not particularly limited, but according to one embodiment of the present invention, the thermoplastic polymer is polylactic acid (PLA), thermoplastic polyurethane (TPU, Thermoplastic Polyurethane), polyethylene (PE, Polyethylene) ), Polypropylene (PP, Polypropylene), polyether sulfone (PES), polymethyl methacrylate (PMMA, Poly (methyl methacrylate)), ethylene vinyl-alcohol polymer (EVOH, Ethylene Vinyl-Alcohol Copolymer) and At least one polymer selected from the group consisting of combinations thereof.

The particle diameter of the thermoplastic polymer particles may be freely adjusted during the preparation of the particles by the manufacturing method according to the present invention, but the physical properties of the thermoplastic polymer particles may be adjusted to 1 to 1000 μm, more specifically 1 to 500 μm. Considering the handleability together, it can be preferably utilized.

The thermoplastic polymer particles having the above characteristics are produced by the following production method. Hereinafter, a method of manufacturing the thermoplastic polymer particles according to the present invention will be described in detail.

Manufacturing method of thermoplastic polymer particles

Figure 2 schematically shows a process flow diagram for the manufacturing method. The manufacturing method is a step of extruding by supplying a thermoplastic polymer resin to the extruder (S100); Supplying the extruded thermoplastic polymer resin and air to a nozzle, contacting the thermoplastic polymer resin and air to granulate the thermoplastic polymer resin, and then discharging the granulated thermoplastic polymer resin (S200); And cooling the thermoplastic polymer particles by supplying the discharged thermoplastic polymer particles to a cooler, and then obtaining the cooled thermoplastic polymer particles (S300). Hereinafter, each step of the manufacturing method will be described in detail.

In order to manufacture the thermoplastic polymer particles according to the present invention, first, the thermoplastic polymer resin, which is a raw material, is fed to an extruder and extruded. By extruding the thermoplastic polymer resin, the thermoplastic polymer resin has suitable physical properties for processing the particles in the nozzle. The thermoplastic polymer resin used as a raw material is not particularly limited as long as it is a material that can be granulated according to the manufacturing method of the present invention. However, the thermoplastic polymer resin has a weight average molecular weight (Mw) of 10,000 to 200,000 g / mol in consideration of the proper physical properties of the manufactured particles. It may be desirable. According to one embodiment of the invention, the thermoplastic polymer resin is polylactic acid (PLA, Poly lactic acid), thermoplastic polyurethane (TPU, Thermoplastic Polyurethane), polyethylene (PE, Polyethylene), polypropylene (PP, Polypropylene), poly It may be a resin selected from the group consisting of ether sulfone (PES, Polyether sulfone), polymethyl methacrylate (PMMA, Poly (methyl methacrylate)), ethylene vinyl-alcohol polymer (EVOH, Ethylene Vinyl-Alcohol Copolymer) and combinations thereof. .

The extruder supplied with the thermoplastic polymer resin heats and pressurizes the thermoplastic polymer resin to control physical properties such as viscosity of the thermoplastic polymer resin. The type of the extruder is not particularly limited as long as it can be adjusted to suitable physical properties for granulation at the nozzle. According to one embodiment of the invention, the extruder may be used a twin screw extruder for efficient extrusion. The interior of the extruder may be maintained at 150 to 450 ℃, preferably 170 to 400 ℃, more preferably 200 to 350 ℃. When the internal temperature of the extruder is less than 150 ° C., the viscosity of the thermoplastic polymer resin is high, which is not suitable for granulation at the nozzle, and the flowability of the thermoplastic polymer resin in the extruder is not efficient for extrusion. In addition, when the internal temperature of the extruder is higher than 450 ° C., the flowability of the thermoplastic polymer resin is high, so that efficient extrusion is possible, but it is difficult to control fine physical properties when the thermoplastic polymer resin is granulated in the nozzle.

The extrusion amount of the thermoplastic polymer resin may be easily set in consideration of the size of the extruder to control the physical properties of the thermoplastic polymer resin. According to one embodiment of the invention, the thermoplastic polymer resin is extruded at a rate of 1 to 10 kg / hr. The extruded thermoplastic polymer resin may have a viscosity of 0.5 to 20 Pa · s, preferably 1 to 15 Pa · s, more preferably 2 to 10 Pa · s. If the viscosity of the thermoplastic polymer resin is less than 0.5 Pa · s, it is difficult to process the particles at the nozzle. If the viscosity of the thermoplastic polymer resin is more than 20 Pa · s, the flowability of the thermoplastic polymer resin at the nozzle is low, resulting in poor processing efficiency. The extruded thermoplastic polymer resin may have a temperature of 150 to 450 ° C.

The thermoplastic polymer resin extruded in the extruder is supplied to the nozzle. Together with the thermoplastic polymer resin, air is also supplied to the nozzle. The air contacts the thermoplastic polymer resin in the nozzle to granulate the thermoplastic polymer resin. Hot air is supplied to the nozzle to properly maintain the physical properties of the thermoplastic polymer resin. According to one embodiment of the invention, the temperature of the air may be 250 to 600 ℃, preferably 270 to 500 ℃, more preferably 300 to 450 ℃. If the temperature of the air is less than 250 ° C or more than 600 ° C, when the thermoplastic polymer particles are manufactured from the thermoplastic polymer resin, the physical properties of the surface contacted with the air may be changed in an undesirable direction, thereby causing a problem. In particular, when the temperature of the air exceeds 600 ℃ excessive heat is supplied to the contact surface with the air may cause decomposition of the polymer on the surface of the particles.

The thermoplastic polymer resin and the air supplied to the nozzle may have a suitable size and shape of the thermoplastic polymer particles, and the feeding position is set so that the formed particles may be evenly dispersed. Figure 3 shows a cross-sectional view of the nozzle discharge portion, the supply position of the thermoplastic polymer resin and air according to an embodiment of the present invention will be described in detail with reference to FIG. For the detailed description herein, the position of the nozzle is expressed as "injection part", "discharge part", "end part", and the like. The "injection part" of the nozzle means the position where the nozzle starts, and the "discharge part" of the nozzle means the position where the nozzle ends. In addition, the "end" of a nozzle means the position from two thirds of a nozzle to a discharge part. Here, the zero point of the nozzle is the injection portion of the nozzle, and one point of the nozzle is the discharge portion of the nozzle.

As shown in FIG. 3, the cross section perpendicular to the flow direction of the thermoplastic polymer resin and air is circular. The air is supplied through a first air stream 40 supplied to the center of the circle and a second air stream 20 supplied to the outer portion of the circle, and the thermoplastic polymer resin is connected to the first air stream 40. Supplied between the second air streams 20. Each supply flow (the thermoplastic polymer resin stream 30, the first air stream 40 and the second air stream 20) from when the thermoplastic polymer resin and air are supplied to the inlet of the nozzle to just before the discharge part of the nozzle It is separated by the structure inside the nozzle. Immediately before the discharge portion of the nozzle, the thermoplastic polymer resin stream and the second air stream are combined to make contact with the thermoplastic polymer resin and air, whereby the thermoplastic polymer resin is granulated. Alternatively, the first air stream is separated by the nozzle internal structure from the thermoplastic polymer stream and the second air stream until the thermoplastic polymer resin and the air are discharged from the nozzle. The first air stream prevents the particles of the thermoplastic polymer resin granulated by the second air stream from sticking to the discharge portion of the nozzle, and evenly distributes the discharged particles before discharge to the cooler after discharge from the nozzle. .

The thermoplastic polymer resin extruded from the extruder are all supplied to the above-described position of the nozzle, and the flow rate of air supplied to the nozzle can be adjusted according to the flow rate of the extruded thermoplastic polymer resin. According to one embodiment of the invention, the air is supplied to the nozzle at a flow rate of 1 to 300m ³ / hr, preferably 30 to 240m ³ / hr, more preferably 60 to 180m ³ / hr. Air is supplied separately from the first air stream and the second air stream within the flow rate range of the air. As described above, the thermoplastic polymer resin is granulated by the second air stream, and the ratio of the thermoplastic polymer resin and the second air stream as well as the temperature of the second air stream may determine the physical properties of the particles. According to one embodiment of the present invention, the ratio of the cross-sectional area of the thermoplastic polymer resin and the second air flow is 1: 1 to 10: 1, preferably 1.5: 1 to 8: 1, more preferably based on the discharge cross section of the nozzle. Preferably 2: 1 to 6: 1. When the ratio of the thermoplastic polymer resin and the second air flow is controlled within the above range, it is possible to produce thermoplastic polymer particles of appropriate size and shape with high usability.

Since the thermoplastic polymer resin is granulated in the nozzle, the inside of the nozzle is controlled to a temperature suitable for the thermoplastic polymer resin to be granulated. Since the sudden rise in temperature can change the structure of the polymer in the thermoplastic polymer resin, the temperature from the extruder to the discharge portion of the nozzle can be raised step by step. Therefore, the internal temperature of the nozzle is set in a range higher than the internal temperature of the extruder on average. Since the temperature for the distal end of the nozzle is defined separately below, the internal temperature of the nozzle herein means the average temperature of the rest of the nozzle except for the distal end of the nozzle, unless otherwise specified. According to one embodiment of the invention, the interior of the nozzle may be maintained at 250 to 450 ℃. If the internal temperature of the nozzle is less than 250 ℃, sufficient heat is not transmitted to the thermoplastic polymer resin to satisfy the physical properties when granulated, if the internal temperature of the nozzle is more than 450 ℃ excessive heat is supplied to the thermoplastic polymer resin to improve the structure of the polymer Can change.

The distal end of the nozzle may be maintained at a temperature higher than the average temperature inside the nozzle to improve the external and internal properties of the resulting particles. The temperature of the distal end of the nozzle may be determined between the glass transition temperature (T _g ) and the pyrolysis temperature (T _d ) of the thermoplastic polymer, specifically, according to the following equation (3).

[Calculation 3]

Terminal Temperature = Glass Transition Temperature (T _g ) + (Pyrolysis Temperature (T _d ) -Glass Transition Temperature (T _g )) × A

Here, A may be 0.5 to 1.5, preferably 0.65 to 1.35, more preferably 0.8 to 1.2. If A is less than 0.5, it is difficult to expect the improvement of the external and internal properties of the particles as the temperature rises at the distal end of the nozzle. If A is greater than 1.5, the heat substantially transferred to the thermoplastic polymer at the distal end of the nozzle is excessively increased. The structure of the thermoplastic polymer can be modified. The glass transition temperature and pyrolysis temperature may vary depending on the type of polymer, degree of polymerization, structure, and the like. According to one embodiment of the present invention, a thermoplastic polymer having a glass transition temperature of -40 to 250 ° C and a glass transition temperature of 270 to 500 ° C may be used. Since the distal end of the nozzle is kept higher than the average temperature of the nozzle, in some cases the distal end of the nozzle may be provided with additional heating means.

The thermoplastic polymer particles discharged from the nozzle are supplied to the cooler. The nozzle and the cooler may be spaced apart, in which case the discharged thermoplastic polymer particles are primarily cooled by ambient air before being supplied to the cooler. The nozzle discharges not only thermoplastic polymer particles but also high temperature air, and by separating the nozzle and the cooler, the hot air can be discharged to the outside instead of the cooler, thereby increasing the cooling efficiency in the cooler. According to one embodiment of the invention, the cooler is positioned 100 to 500 mm, preferably 150 to 400 mm, more preferably 200 to 300 mm apart from the nozzle. When the separation distance is shorter than the distance, a large amount of high-temperature air is injected into the cooling chamber to lower the cooling efficiency. When the separation distance is longer than the distance, the cooling by the surrounding air becomes large and rapid cooling by the cooling chamber. This can't be done. In addition, when the thermoplastic polymer particles are discharged from the nozzle, the injection angle may be 10 to 60 °, and when the thermoplastic polymer particles are discharged at the angle, the effect of the separation between the nozzle and the cooler may be doubled.

The cooler may cool the thermoplastic polymer particles by supplying low temperature air into the cooler to contact the air with the thermoplastic polymer particles. The low temperature air forms a rotary airflow in the cooler, and the residence time of the thermoplastic polymer particles in the cooler can be sufficiently secured by the rotary airflow. The flow rate of the air supplied to the cooler may be adjusted according to the supply amount of the thermoplastic polymer particles, and according to one embodiment of the present invention, the air may be supplied to the cooler at a flow rate of 1 to 10 m ³ / min. The air may preferably have a temperature of -30 to -20 ℃. By supplying the cryogenic air into the cooler as compared to the thermoplastic polymer particles supplied to the cooler, the thermoplastic polymer particles are rapidly cooled to maintain the internal structure of the hot thermoplastic polymer particles at the time of discharge. When the thermoplastic polymer particles are actually applied for the production of the product, the thermoplastic polymer particles are reheated again, wherein the reheated thermoplastic polymer has properties favorable for processing. The thermoplastic polymer particles cooled by low temperature air are cooled to 40 ° C. or lower and discharged, and the discharged particles are collected through a cyclone or a bag filter.

Hereinafter, preferred examples are provided to aid in understanding the present invention, but the following examples are provided only for better understanding of the present invention, and the present invention is not limited thereto.

Example

Example  1: according to the manufacturing method of the present invention Polylactic acid  Preparation of Particles

Polylactic acid resin (Natureworks, 2003D, Mw: about 200,000g / mol, glass transition temperature (T _g ): about 55 ° C, pyrolysis temperature (T _d ): about 300 ° C) 100% by weight of twin screw extruder (diameter (D ) = 32 mm, length / diameter (L / D) = 40). The twin screw extruder was subjected to extrusion by setting at a temperature condition of about 220 ° C. and an extrusion amount condition of about 5 kg / hr. The extruded polylactic acid resin has a viscosity of about 10 Pa.s, and the extruded polylactic acid resin has a nozzle set to an internal temperature of about 300 ° C. and an end temperature of about 350 ° C. (A value according to formula 3 is about 1.2). Supplied to. In addition, air of about 350 ° C. was supplied to the nozzle at a flow rate of about 1 m ³ / min. The air was supplied to the center and the outer portion of the nozzle cross section, and the extruded polylactic acid resin was supplied between the center and the outer portion of the nozzle to which the air is supplied. The cross-sectional ratio of extruded polylactic acid supplied between the air supplied to the periphery and the air-fed core and the periphery was about 4.5: 1. The polylactic acid resin supplied to the nozzle was atomized in contact with the hot air, and the atomized particles were ejected from the nozzle. The spray angle from the nozzle was about 45 ° and the sprayed particles were supplied to a cooling chamber (diameter D = 1,100 mm, length L = 3500 mm) spaced about 200 mm from the nozzle. In addition, the cooling chamber was controlled to form a rotary airflow by injecting air at −25 ° C. at a flow rate of about 6 m ³ / min before the injected particles were supplied. Particles sufficiently cooled down to 40 ° C. in the cooling chamber were collected via cyclone or bag filter.

Example  2: preparation of thermoplastic polyurethane particles according to the preparation method of the present invention

The thermoplastic polyurethane resin as a starting material a ^{(Lubrizol, Pearlthane TM D91M80, Mw} : about 160,000g / mol, a glass transition temperature (T _g):: about -37 ℃, the thermal decomposition temperature (T _d) of about 290 ℃) 100% by weight Particles were prepared in the same manner as in Example 1 except for the use.

Comparative example  1: freeze grinding Polylactic acid  Preparation of Particles

The same polylactic acid resin as in Example 1 was fed to a screw feeder through a hopper. Water was removed while moving the raw material through the screw, and then the raw material was introduced into a grinder supplied with liquid nitrogen at -130 ° C. The grinder was a pin crusher type grinder was used. Particle size was controlled via grinding size crystal pins. The particles atomized through the mill were collected through the cyclone.

Experimental Example  1: Evaluation of Physical Properties of Particles

The physical properties of the particles prepared according to Examples 1 and 2 and Comparative Example 1 are shown in Table 1 below.

	Average particle diameter (㎛) 1 )	Aspect ratio 2 )	Spherical degree 3 )
Example 1	14.2	1.02 ± 0.01	0.98 ± 0.01
Example 2	102.6	1.01 ± 0.01	0.99 ± 0.01
Comparative Example 1	10.8	1.43 ± 0.41	0.74 ± 0.18

1) Derived the average particle diameter of the powder, which is an aggregate of particles, using ImageJ (National Institutes of Health (NIH)) at room temperature. The major axis of each particle is the particle size, and the number average value of each particle diameter is the average particle diameter for the aggregate of particles.

2), 3) Analysis of particle formation by image processing-converting into binary image and quantifying the degree of spherical shape of individual particles-using the same apparatus, and calculating the aspect ratio and the degree of sphericity by Equations 1 and 2.

According to Table 1, the thermoplastic polymer particles according to Examples 1 and 2 have a shape close to a sphere by measuring the aspect ratio and the sphericity degree close to 1, whereas the thermoplastic polymer particles according to Comparative Example 1 have an aspect ratio and a sphere shape. The degree of saturation was slightly different from 1, so it did not have a near-spherical shape.

As in Comparative Example 1, the thermoplastic polymer particles prepared by the conventional freeze-pulverization method do not satisfy the aspect ratio and the degree of sphericity close to the sphere, so that the thermoplastic polymer particles of Examples 1 and 2 when the thermoplastic polymer particles are later handled Not easy

Experimental Example  2: DSC  analysis

The particles prepared according to Examples 1 and 2 and Comparative Example 1 are shown in Table 2 by DSC analysis. Specifically, the DSC curve was obtained by using a differential scanning calorimeter (DSC, Perkin-Elmer, DSC8000) to increase the temperature from 0 ° C to 200 ° C at a temperature increase rate of 10 ° C / min. The difference between glass transition temperature (T _g ), melting point (T _m ), cold crystallization temperature (T _cc ), and endothermic amount (ΔH1) and calorific value (ΔH2) was derived from each DSC curve.

	T g (℃)	T m (℃)	T cc (℃)	ΔH1-ΔH2 (J / g)
Example 1	55	140	98	36
Example 2	-37	136	34	6
Comparative Example 1	59	146	-	42

According to Table 2, the thermoplastic polymer particles of Example 1 showed a cold crystallization temperature peak at 98 ℃, the thermoplastic polymer particles of Example 2 appeared a cold crystallization temperature peak at 34 ℃, Comparative Example 1 It was confirmed that the thermoplastic polymer particles of did not exhibit such a cold crystallization temperature peak.

Further, in Example 1, the difference between the endothermic amount ΔH1 and the calorific value ΔH2 is about 36 J / g. In Example 2, the endothermic amount ΔH1 and the calorific value ΔH2 It was confirmed that the difference appeared about 6J / g. Unlike Example 1, it was confirmed that the difference between the heat absorbing amount (ΔH1) and the calorific value (ΔH2) was about 42 J / g. This is understood to have a relatively high calorific value since the polylactic acid particles of Example 1 have a property of generating heat before the particles are melted by cold crystallization.

When the thermoplastic polymer particles have cold crystallization temperature peaks as in Examples 1 and 2, when the heat processing is performed using these particles, the thermoplastic polymer particles may have an advantage of being able to be processed at a low temperature compared to the processing temperature of the thermoplastic polymer particles of Comparative Example 1. Can be.

Comparative example  2: according to the solvent polymerization method Polylactic acid  Preparation of Particles

Lactic acid was added to the xylene solvent, followed by stirring. Then, a tin-based catalyst and a polyol were added thereto and polymerized at a temperature of about 140 ° C. The polymer was dissolved in chloroform, precipitated in methanol, and dried to prepare polylactic acid particles having a size of 10 μm.

Comparative example  3: Preparation of thermoplastic polyurethane particles according to solvent polymerization method

Prepolymer was synthesized by adding an ester or ether-based polyol to a dimethylformamide solvent, followed by diisocyanate. Subsequently, at a temperature of 80 ° C., a reactive monomolecular diol or diamine-based chain extender was added to finally prepare a thermoplastic polyurethane particle having a size of 400 μm.

Experimental Example  3: Impurity Analysis in Particles

The impurity content of the particles prepared according to Example 1 and Comparative Examples 2 and 3 is shown in Table 3 below. Specifically, the residual solvent in the particles was measured through a GC / FID apparatus (manufacturer: Agilent, model name: 7890A), and the heavy metals in the particles were measured by an ICP / MS apparatus (manufacturer: Perkinelmer, model name: Nexion300). The impurity content of Table 3 is the sum of the content of the residual solvent and the content of heavy metals in the particles.

	Impurity Content (ppm)
Example 1	3
Comparative Example 2	61
Comparative Example 3	53

According to Table 3, the particles of Comparative Examples 2 and 3 have a significantly higher content of impurities compared to the particles of Example 1 due to the residual solvent in the particles because the solvent is used in the preparation of the particles. On the contrary, the particles of Example 1 contained little impurities such as a residual solvent except for a small amount of impurities introduced from the apparatus during the preparation of the particles.

All simple modifications and variations of the present invention will fall within the scope of the present invention, and the specific scope of protection of the present invention will be clarified by the appended claims.

[Description of the code]

d: vertical distance of two parallel tangent planes

A: Area

10: nozzle

20: second air flow

30: thermoplastic polymer resin flow

40: first air flow

Claims (6)

1. The aspect ratio calculated by the following formula 1 is not less than 1.00 and less than 1.05,

   Thermoplastic polymer particles having a degree of sphericity of 0.95 to 1.00 calculated by the following Formula 2.

   [Calculation 1]

   Aspect ratio = major axis / minor axis

   [Calculation 2]

   Roundness = 4 × area / (π × long axis ^ 2)
2. The method according to claim 1,

   The thermoplastic polymer particles are thermoplastic polymer particles, characterized in that formed in a continuous matrix (matrix) phase from the thermoplastic polymer resin.
3. The method according to claim 2,

   The impurity content of the thermoplastic polymer particles is characterized in that 50ppm or less thermoplastic polymer particles.
4. The method according to claim 1,

   The thermoplastic polymer particles were cold crystallized at a temperature between the glass transition temperature (T _g ) and the melting point (T _m ) in a DSC curve derived from an elevated temperature analysis of 10 ° C./min by differential scanning calorimetry (DSC). A thermoplastic polymer particle characterized by the appearance of a peak of temperature (T _cc ).
5. The method according to claim 1,

   The thermoplastic polymer is polylactic acid (PLA), thermoplastic polyurethane (TPU, Thermoplastic Polyurethane), polyethylene (PE, Polyethylene), polypropylene (PP, Polypropylene), polyether sulfone (PES, Polyether sulfone), poly Thermoplastic polymer particles, characterized in that at least one polymer selected from the group consisting of methyl methacrylate (PMMA, Poly (methyl methacrylate)), ethylene vinyl alcohol (EVOH, Ethylene Vinyl-Alcohol Copolymer) and combinations thereof.
6. The method according to claim 1,

   The thermoplastic polymer particles have a particle diameter of 1 to 1000 μm.

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