KR102317520B1 - Thermoplastic polyurethane particles and method for preparing the same - Google Patents

Abstract

The present invention provides thermoplastic polyurethane particles formed in a continuous matrix phase from a thermoplastic polyurethane resin and having a particle diameter of 1 μm to 100 μm. The thermoplastic polyurethane particles have an average particle diameter (D ₅₀ ) of 20 to 50 μm, a cumulative volume 10% particle diameter (D ₁₀ ) of 5 to 15 μm, and a cumulative volume 90% particle diameter (D _{90) of 40 to 80 μm} ) has The thermoplastic polyurethane particles have a D value representing the particle distribution of 5 to 20.

Description

Thermoplastic polyurethane particles and manufacturing method thereof

The present invention relates to thermoplastic polyurethane particles and a method for preparing the same.

Thermoplastic polyurethane particles are used in various industrial fields such as cosmetics, fillers for paints and coatings, hot melt adhesives, heat-molded products, and polymerized toners. In particular, the thermoplastic polyurethane particles having a small diameter of less than 100 μm are used for 3D printing products manufactured by SLS (Selective Laser Sintering) method, color cosmetics, and the like. In order for the small-diameter thermoplastic polyurethane particles to be utilized for the above purpose, the size and shape of the basically manufactured particles should be uniformly prepared, and the better the flowability and dispersibility of the particles, the higher the quality of the manufactured product.

In order to prepare such small-diameter thermoplastic polyurethane particles, the following three methods have been mainly used in the prior art. Specifically, the method for producing the thermoplastic polyurethane particles includes a pulverization method represented by freeze pulverization; a solvent dissolution precipitation method of dissolving in a high temperature solvent and then cooling to precipitate, or dissolving in a solvent and then adding a poor solvent to precipitate; and a melt-kneading method in which a thermoplastic resin is mixed with a thermoplastic resin and an incompatible resin in a mixer to form a composition having a thermoplastic resin and an incompatible resin in a continuous phase in a dispersed phase, and then the incompatible resin is removed to obtain thermoplastic resin particles.

When the particles are manufactured through the pulverization method, it is difficult to ensure uniformity in the size and shape of the manufactured thermoplastic polyurethane particles. In addition, since liquid nitrogen is used for cooling of the pulverization method, higher costs are required compared to the particle obtaining process, and when a compounding process of adding pigments, antioxidants, etc. Therefore, the productivity is lowered compared to the continuous particle obtaining process. When the particles are prepared through the solvent dissolution precipitation method and the melt kneading method, there may be a problem that other components such as a solvent may be detected as impurities in addition to the thermoplastic resin particles. The problem may be more serious as the amount of impurities may be higher. Due to the above-described problems, when the small-diameter thermoplastic polyurethane particles prepared by the conventional method are applied to 3D printing products and color cosmetics, the quality of the product is deteriorated.

Therefore, in the technical field, there is a need for thermoplastic polyurethane particles with improved particle properties to be suitable for application to 3D printing products and color cosmetics.

Japanese Laid-Open Patent Publication No. 2001-288273 Japanese Laid-Open Patent Publication No. 2000-007789 Japanese Laid-Open Patent Publication No. 2004-269865

An object of the present invention is to provide thermoplastic polyurethane particles having excellent physical properties when manufacturing 3D printing products and color cosmetics.

According to a first aspect of the present invention,

The present invention provides thermoplastic polyurethane particles formed in a continuous phase from a thermoplastic polyurethane resin and having a particle diameter of 1 to 100 μm.

In one embodiment of the present invention, the thermoplastic polyurethane particles have an average particle diameter (D ₅₀ ) of 20 to 50㎛.

In one embodiment of the present invention, the thermoplastic polyurethane particles have a cumulative volume of 10% particle diameter (D ₁₀ ) of 5 to 15㎛.

In one embodiment of the present invention, the thermoplastic polyurethane particles have a cumulative volume of 90% particle diameter (D ₉₀ ) of 40 to 80㎛.

In one embodiment of the present invention, the thermoplastic polyurethane particles have a D value of 5 to 20 calculated by Equation 1 below.

[Formula 1]

Here, D ₁₀ is a particle diameter of 10% of the cumulative volume, D ₅₀ is an average particle diameter, and D ₉₀ is a particle diameter of 90% of the cumulative volume.

In one embodiment of the present invention, the impurity content of the thermoplastic polyurethane particles is 50 ppm or less.

_{In one embodiment of the present invention, the thermoplastic polyurethane particles have a glass transition temperature (T g} ) and a melting point in a DSC curve derived from a temperature rise analysis of 10 ° C / min by Differential Scanning Calorimetry (DSC) The peak of the cold crystallization temperature (T _cc ) is shown at a temperature between (T _{m ).}

In one embodiment of the present invention, the thermoplastic polyurethane particles have an aspect ratio calculated by the following formula 2 is 1.00 or more and less than 1.05,

The degree of sphericity calculated by Equation 3 below is 0.95 to 1.00.

[Formula 2]

Aspect ratio = major axis/minor axis

[Formula 3]

Roundness=4×area/(π×long axis^2).

In one embodiment of the present invention, the thermoplastic polyurethane particles have a compressibility of 7 to 15% calculated by Equation 4 below.

[Formula 4]

Compression degree = (compressed bulk density - relaxed bulk density) / compressed bulk density x 100.

In one embodiment of the present invention, the thermoplastic polyurethane particles have a compressed bulk density ^{of 0.4 to 0.45 g/cm 3 .}

In one embodiment of the present invention, the thermoplastic polyurethane particles have a flow time of 10 to 20 seconds.

According to a second aspect of the present invention,

The present invention comprises the steps of (1) extruding by supplying a thermoplastic polyurethane resin to the extruder;

(2) supplying the extruded thermoplastic polyurethane resin and air to the nozzle, contacting the thermoplastic polyurethane resin with air to make the thermoplastic polyurethane resin particles, and then discharging the granulated thermoplastic polyurethane resin; and

(3) supplying the discharged thermoplastic polyurethane particles to a cooler to cool the thermoplastic polyurethane particles, and then provides a method for producing the thermoplastic polyurethane particles comprising the step of obtaining the cooled thermoplastic polyurethane particles.

In one embodiment of the present invention, the extruded thermoplastic polyurethane resin supplied to the nozzle in step (2) has a melt viscosity of 0.5 to 20 Pa·s.

In one embodiment of the present invention, air is supplied to the center and the outer portion based on the cross section of the nozzle in step (2), and the extruded thermoplastic polyurethane resin is supplied between the center and the outer portion to which air is supplied. .

In one embodiment of the present invention, based on the cross section at the discharge part of the nozzle in step (2), the air supplied to the outer portion and the extruded thermoplastic polyurethane supplied between the center and the outer portion to which the air is supplied The cross-sectional area ratio of the resin is 4:1 to 6:1.

In one embodiment of the present invention, the inside of the nozzle in step (2) is maintained at 250 to 350 ℃.

In one embodiment of the present invention, in the step (2), the discharge portion of the nozzle is maintained at a temperature calculated by Equation 5 below.

[Formula 5]

Discharge part temperature = glass transition temperature (T _g ) + (decomposition temperature (T _d ) - glass transition temperature (T _g ))×B

In Equation 5, the glass transition temperature and the decomposition temperature are values for the thermoplastic polyurethane, and B is 0.5 to 1.5.

The thermoplastic polyurethane particles according to the present invention have physical properties suitable for the manufacture of 3D printing products and color cosmetics, and the quality of the applied products can be improved.

1 is an image schematically showing the shape of the thermoplastic polyurethane particles of the present invention.
2 is a process flow diagram schematically showing a method for producing a thermoplastic polyurethane particle according to the present invention.
3 is a cross-sectional view of a nozzle discharge unit showing a supply position of a thermoplastic polyurethane resin and air to the nozzle according to an embodiment of the present invention.

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

In the following specification, with respect to the numerical range, the expression "to" is used to include both the upper and lower limits of the range, and when it does not include the upper or lower limits, "less than", " The expressions "more than", "less than" or "more than" are used.

The present invention provides thermoplastic polyurethane particles having properties suitable for use in 3D printing products and color cosmetics that could not be obtained by conventional particle manufacturing methods. Hereinafter, the thermoplastic polyurethane particles according to the present invention will be described in detail.

Thermoplastic polyurethane particles

The present invention provides thermoplastic polyurethane particles prepared by atomizing a thermoplastic polyurethane resin by contacting it with air after extrusion. The method for producing thermoplastic polyurethane particles according to the present invention is an improved method compared to the conventional pulverization method, solvent dissolution precipitation method, and melt kneading method. Explain.

The thermoplastic polyurethane particles according to the present invention have a particle diameter of 1 to 100 μm, more specifically 5 to 80 μm. When the particles have a particle diameter of less than 1 μm, the thermoplastic polyurethane particles are excessively dispersed, so it is difficult to realize the particle properties of the thermoplastic polyurethane in the product, and when the particles have a particle diameter of more than 100 μm, the particles are too large For example, when applied to cosmetics, etc., it is not suitable because the spreadability is deteriorated. _{The thermoplastic polyurethane particles have an average particle diameter (D 50} ) (or 50% cumulative volume particle diameter) of 20 to 50 μm, more specifically, 25 to 40 μm. It is possible to uniformly disperse a product material, such as a color cosmetic, in which the particles satisfy the average particle diameter of the above-mentioned range while maintaining an appropriate distance between the materials. _{The thermoplastic polyurethane particles have a particle diameter (D 10} ) of 10% of the cumulative volume of 5 to 15 μm, more specifically 7 to 12 μm. The thermoplastic polyurethane particles have a 90% cumulative volume particle diameter (D ₉₀ ) of 40 to 80 μm, more specifically 50 to 70 μm. In the present specification, the particle size distribution of the thermoplastic polyurethane particles was measured by a wet method using a particle size analyzer (Microtrac, S3500), and the specific method will be described in Examples below. Here, D ₁₀ , D ₅₀ , and D ₉₀ mean particle diameters corresponding to 10%, 50%, and 90% of the cumulative volume percentage in the cumulative volume distribution of the particles, respectively. Regarding the particle size distribution of the thermoplastic polyurethane particles, the thermoplastic polyurethane particles according to the present invention have a D value of 5 to 20, more specifically 10 to 15, and the D value is calculated by the following formula 1.

[Formula 1]

The D value quantifies where the particles having a larger cumulative volume of 90% particle diameter (D ₉₀ ) and a particle having a smaller cumulative volume 10% particle diameter (D ₁₀ ) are located based on the particles having an average particle diameter (D _{50 ).} is one value. Here, particles having a relatively large particle diameter serve to support particles having an average particle diameter when applied together with particles having an average particle diameter, and particles having a relatively small particle diameter when applied together with particles having an average particle diameter It serves to fill the voids between particles with As the value of D is smaller, the particle diameters are distributed closer to the average particle diameter, and as the D value is larger, the particle diameters of the particles are distributed farther from the average particle diameter. If the D value is small, the ratio of particles close to the average particle diameter increases, so it is difficult to obtain the effect due to the diversity of particle sizes. On the other hand, if the D value is large, the ratio of particles far to the average particle diameter increases, difficult to apply Average particle size When the particles satisfy the D value in the above-mentioned range, large particles and small particles are distributed in an appropriate ratio around the average particle diameter, and excellent physical properties can be exhibited when applied to 3D printing products and color cosmetics. .

In the present invention, the shape of the particle is evaluated in the following aspect ratio (aspect ratio) and roundness (roundness), the closer the aspect ratio and sphericity (roundness) to 1, the shape of the particle is interpreted as closer to a spherical shape. The aspect ratio is calculated by Equation 2 below.

[Formula 2]

Aspect ratio = major axis/minor axis

In addition, the sphericity is calculated by Equation 3 below.

[Formula 3]

Roundness=4×area/(π×long axis^2)

In order to describe the above calculation formula in detail, Fig. 1 schematically shows the thermoplastic polyurethane particles is provided. According to FIG. 1, in Equations 2 and 3, the “long axis” means the longest distance among the vertical distances (d) between two parallel tangents of the 2D image (cross-section) of the thermoplastic polyurethane particles, and the “short axis” is It means the shortest distance among the vertical distances (d) between two parallel tangents of the 2D image (cross-section) of the thermoplastic polyurethane particles. In addition, in Equation 3, “area” means a cross-sectional area including the long axis of the thermoplastic polyurethane particles. 1 shows an area (A) as an example of a case in which the vertical distance (d) between two parallel tangent planes of the thermoplastic polyurethane particles is a long axis.

According to one embodiment of the present invention, the thermoplastic polyurethane particles according to the present 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, 0.95 to 1.00, more specifically 0.98 to 1.00. It may have a sphericity. When the shape of the thermoplastic polyurethane particles satisfies the above-mentioned aspect ratio and sphericity range, the flowability and uniformity of the thermoplastic polyurethane particles increase, so that the particles are easy to handle in application to 3D printing products and color cosmetics, The 3D printing products and color cosmetics to which the particles are applied may have improved quality due to the excellent flowability and dispersibility of the particles.

Numerical values according to Equations 2 and 3 can be measured by image processing the image of the thermoplastic polyurethane particles using ImageJ (National Institutes of Health (NIH)) - After converting to a binary image, quantifying the degree of spheroidization of individual particles - possible.

The thermoplastic polyurethane particles according to the present invention are particles formed in a continuous matrix phase from a thermoplastic polyurethane resin. Formed from the thermoplastic polyurethane resin into a continuous matrix phase means that the thermoplastic polyurethane resin forms a continuous dense structure without additional components. By extruding the thermoplastic polyurethane resin, melting and then granulating the melt with air, the thermoplastic polyurethane particles are continuously produced with a dense structure. On the other hand, according to the conventional manufacturing method, since particles are formed by adding additional ingredients or particles are formed through a discontinuous process of cooling and grinding, particles are not formed in a continuous matrix.

The particles formed into a continuous matrix from the thermoplastic polyurethane resin have high purity because impurities are not incorporated in the process of manufacturing the particles. Here, "impurities" means components other than the thermoplastic polyurethane that may be incorporated during the manufacture of the particles. Exemplary impurities include a solvent for dispersing the thermoplastic polyurethane 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 polyurethane 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. _{As one of these characteristics, the thermoplastic polyurethane particles are between the glass transition temperature (T g} ) and the melting point (T _m ) in the DSC curve derived from the analysis of the temperature increase of 10 ° C / min by Differential Scanning Calorimetry (DSC). The peak of the cold crystallization temperature (T _cc ) appears at the temperature of . Thermoplastic polyurethane particles are spherical solid particles at room temperature. When the temperature rise analysis of these particles using a differential scanning calorimeter, the fluidity gradually increases as the temperature rises. At this time, the thermoplastic polyurethane particles have a peak of the cold crystallization temperature (T _{cc ) at a temperature between the glass transition temperature (T g} ) and the melting point (T _m ), which is soon before the thermoplastic polyurethane particles are melted. It means that it has a heat-generating characteristic. According to one embodiment of the present invention, the cold crystallization temperature (T _cc ) appears in the 30% to 70% section between the glass transition temperature (T _g ) and the melting point (T _{m ).} In the above 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 difference (ΔH1-ΔH2) between the endothermic amount (ΔH1) and the heating value (ΔH2) of the thermoplastic polymer particles may be 3 to 100 J/g. Due to these characteristics, when the thermoplastic polyurethane particles are used in a heating process, it is possible to obtain an advantage that can be processed at a low temperature compared to the processing temperature of the same type of thermoplastic polyurethane particles.

The thermoplastic polyurethane particles of the present invention have a high degree of compression compared to conventional thermoplastic polyurethane particles. The degree of compressibility may be calculated by Equation 4 below. According to one embodiment of the present invention, the thermoplastic polyurethane particles have a degree of compression of 7 to 15%.

[Formula 4]

Compressibility = (P-R)/P×100

In Equation 4, P denotes compressed bulk density, and R denotes relaxed bulk density.

As described above, since the thermoplastic polyurethane particles according to the present invention have good flowability, the voids between the particles can be well filled, and accordingly, the degree of compression is higher than that of the thermoplastic polyurethane particles produced by other manufacturing methods. maintain. The degree of compressibility of the thermoplastic polyurethane particles can affect the quality of the product in the manufacture of the product through the particles. In the case of using the thermoplastic polyurethane particles having a certain degree of compression as in the present invention, in the case of a molded article, it may have an effect of minimizing voids that may occur in the product, and in the case of products such as cosmetics, the gap between the skin and the product Compressibility can be improved. According to one embodiment of the present invention, the thermoplastic polyurethane particles have a compressed bulk density ^{of 0.4 to 0.45 g/cm 3 .} The compressed bulk density has a lower numerical value than the thermoplastic polyurethane particles produced by other manufacturing methods, which means that the thermoplastic polyurethane particles according to the present invention having a high sphericity and a uniform particle size distribution are constant between the particles even after compression. This is because it can have pores of any size.

The thermoplastic polyurethane particles according to the present invention have a flow time of 10 to 20 seconds. The flow time is a numerical value indicating the fluidity of the powder. The short flow time means that the frictional resistance between the particles is small, and when the frictional resistance between the particles is small, it is easy to handle the particles. The thermoplastic polyurethane particles according to the present invention can maintain an appropriate level in terms of flow time, so that it is easy to handle the particles when applying the particles.

The thermoplastic polyurethane particles having the above-described characteristics are prepared by the following manufacturing method. Hereinafter, a method for producing the thermoplastic polyurethane particles according to the present invention will be described in detail.

Method for producing thermoplastic polyurethane particles

2 schematically shows a process flow chart for the manufacturing method. The manufacturing method comprises the steps of supplying a thermoplastic polyurethane resin to an extruder and extruding (S100); supplying the extruded thermoplastic polyurethane resin and air to the nozzle, contacting the thermoplastic polyurethane resin with air to make the thermoplastic polyurethane resin particles, and then discharging the granulated thermoplastic polyurethane resin (S200); and supplying the discharged thermoplastic polyurethane particles to a cooler to cool the thermoplastic polyurethane particles, and then obtaining the cooled thermoplastic polyurethane particles (S300). Hereinafter, each step of the manufacturing method will be described in detail.

In order to manufacture the thermoplastic polyurethane particles according to the present invention, the thermoplastic polyurethane resin as a raw material is first supplied to an extruder and extruded. By extruding the thermoplastic polyurethane resin, the thermoplastic polyurethane resin has properties suitable for particle processing in the nozzle. The thermoplastic polyurethane resin used as a raw material may preferably have a weight average molecular weight (Mw) of 10,000 to 200,000 g/mol in consideration of appropriate physical properties of the prepared particles.

The extruder to which the thermoplastic polyurethane resin is supplied controls physical properties such as viscosity of the thermoplastic polyurethane resin by heating and pressurizing the thermoplastic polyurethane resin. The type of the extruder is not particularly limited as long as it is possible to adjust the physical properties suitable for granulation in the nozzle. According to one embodiment of the present invention, the extruder may be a twin screw extruder for efficient extrusion. The inside of the extruder may be preferably maintained at 150 to 300 ℃, preferably 170 to 270 ℃, more preferably 200 to 250 ℃. If the internal temperature of the extruder is less than 150° C., the viscosity of the thermoplastic polyurethane resin is high, which is not suitable for particle formation in the nozzle, and the flowability of the thermoplastic polyurethane resin in the extruder is low, which is not efficient for extrusion. In addition, if the internal temperature of the extruder is more than 300 ℃, the flowability of the thermoplastic polyurethane resin is high, so that efficient extrusion is possible, but it is difficult to control fine physical properties when the thermoplastic polyurethane resin is granulated in the nozzle.

The extrusion amount of the thermoplastic polyurethane resin can be easily set in consideration of the size of the extruder to control the physical properties of the thermoplastic polyurethane resin. According to one embodiment of the present invention, the thermoplastic polyurethane resin is extruded at a rate of 1 to 10 kg/hr. The viscosity of the extruded thermoplastic polyurethane resin may be 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 polyurethane resin is less than 0.5 Pa·s, it is difficult to process the particles in the nozzle, and if the viscosity of the thermoplastic polyurethane resin is more than 20 Pa·s, the flowability of the thermoplastic polyurethane resin in the nozzle is low, resulting in poor processing efficiency. The temperature of the extruded thermoplastic polyurethane resin may be 150 to 250 ℃.

The extruded thermoplastic polyurethane resin in the extruder is fed to the nozzle. Along with the thermoplastic polyurethane resin, air is also supplied to the nozzle. The air contacts the thermoplastic polyurethane resin in the nozzle to granulate the thermoplastic polyurethane resin. In order to properly maintain the properties of the thermoplastic polyurethane resin, high-temperature air is supplied to the nozzle. According to one embodiment of the present invention, the temperature of the air may be 250 to 450 ℃, preferably 260 to 400 ℃, more preferably 270 to 350 ℃. When the temperature of the air is less than 250 ° C. or more than 450 ° C., when the thermoplastic polyurethane particles are produced from the thermoplastic polyurethane resin, the physical properties of the surface in contact with the air may be changed in an undesirable direction, which is a problem. In particular, when the temperature of the air exceeds 450 °C, excessive heat is supplied to the contact surface with the air, which may cause the decomposition of the thermoplastic polyurethane on the surface of the particles.

The thermoplastic polyurethane resin and air supplied to the nozzle are set so that the thermoplastic polyurethane particles can have an appropriate size and shape, and the formed particles can be evenly dispersed. 3 is a cross-sectional view of the nozzle discharge part, and the supply position of the thermoplastic polyurethane resin and air according to an embodiment of the present invention will be described in detail with reference to FIG. For a detailed description herein, the position of the nozzle is expressed as “injection part”, “discharge part”, and “end part”. 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 "distal end" of the nozzle means the position from the two-thirds point of the nozzle to the discharge portion. Here, point 0 of the nozzle is the injection part of the nozzle, and point 1 of the nozzle is the discharge part of the nozzle.

As shown in FIG. 3 , a cross section perpendicular to the flow direction of the thermoplastic polyurethane 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 part of the circle, and the thermoplastic polyurethane resin is a first air stream 40 and the second air stream 20 is supplied. Each supply stream (thermoplastic polyurethane resin stream 30, first air stream 40 and second air stream 20) from the time the thermoplastic polyurethane resin and air are supplied to the inlet part of the nozzle to just before the outlet part of the nozzle ) are separated by the structure inside the nozzle. Immediately before the discharge portion of the nozzle, the thermoplastic polyurethane resin stream and the second air stream are combined to bring the thermoplastic polyurethane resin into contact with the air, whereby the thermoplastic polyurethane resin is granulated. In contrast, the first air stream is separated from the thermoplastic polyurethane resin stream and the second air stream by the nozzle internal structure until the thermoplastic polyurethane resin and air are discharged from the nozzle. The first air flow prevents the particles of the thermoplastic polyurethane resin granulated by the second air flow from sticking at the discharge part of the nozzle, and the role of evenly dispersing the discharged particles before being supplied to the cooler after discharge from the nozzle is do.

All of the thermoplastic polyurethane resin extruded from the extruder is supplied to the above-described position of the nozzle, and the flow rate of air supplied to the nozzle may be adjusted according to the flow rate of the extruded thermoplastic polyurethane resin. According to one embodiment of the present invention, the air is supplied to the nozzle at a flow rate of ^{1 to 300 m 3} /hr, preferably 30 to 240 m ³ /hr, more preferably 60 to 180 m ^{3 /hr.} Within the flow rate range of the air, air is supplied separately into a first air stream and a second air stream. As described above, the thermoplastic polyurethane resin is granulated by the second air stream, and the ratio of the thermoplastic polyurethane 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 cross-sectional area ratio of the thermoplastic polyurethane resin and the second air flow based on the cross-section of the discharge part of the nozzle may be 4:1 to 6:1, preferably 4.3:1 to 5:1. have. When the ratio of the thermoplastic polyurethane resin and the second air flow is adjusted within the above range, it is possible to manufacture thermoplastic polyurethane particles of an appropriate size and shape with high utility in 3D printing products and color cosmetics.

Since the thermoplastic polyurethane resin is granulated in the nozzle, the inside of the nozzle is adjusted to a temperature suitable for the thermoplastic polyurethane resin to be granulated. Since the rapid increase in temperature may change the structure of the thermoplastic polyurethane, the temperature from the extruder to the discharge portion of the nozzle may be increased in stages. 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 separately defined below, the internal temperature of the nozzle in this specification 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 present invention, the inside of the nozzle may be maintained at 250 to 350 ℃. If the internal temperature of the nozzle is less than 250 ℃, sufficient heat to satisfy the physical properties when granulating the thermoplastic polyurethane resin is not transmitted, and if the internal temperature of the nozzle is more than 350 ℃, excessive heat is supplied to the thermoplastic polyurethane resin, The structure of urethane can be changed.

The distal end of the nozzle may be maintained at a temperature higher than the average temperature inside the nozzle in order to improve the external and internal properties of the generated particles. The temperature of the distal end of the nozzle _{may be determined between the glass transition temperature (T g} ) and the thermal decomposition temperature (T _d ) of the thermoplastic polyurethane, specifically, it may be determined according to Equation 5 below.

[Formula 5]

End temperature = glass transition temperature (T _g ) + (thermal decomposition temperature (T _d ) - glass transition temperature (T _g ))×B

Here, B may be 0.5 to 1.5, preferably 0.65 to 1.35, more preferably 0.8 to 1.2. When B is less than 0.5, it is difficult to expect improvement of the external and internal physical properties of the particles according to the temperature rise of the distal end of the nozzle. Thus, the structure of the thermoplastic polyurethane may be deformed. The glass transition temperature and thermal decomposition temperature may vary depending on the type of polymer, polymerization degree, structure, and the like. According to one embodiment of the present invention, the thermoplastic polyurethane of the present invention has a glass transition temperature of -40 to -20 ℃, a thermoplastic polyurethane having a thermal decomposition temperature of 250 to 350 ℃ may be used. Since the distal end of the nozzle is maintained above the average temperature of the nozzle, the distal end of the nozzle may optionally be provided with additional heating means.

The thermoplastic polyurethane particles discharged from the nozzle are supplied to the cooler. The nozzle and the cooler may be spaced apart, and in this case, the discharged thermoplastic polyurethane particles are primarily cooled by ambient air before being supplied to the cooler. In the nozzle, not only the thermoplastic polyurethane particles but also high-temperature air are discharged. By separating the nozzle and the cooler, the high-temperature air can be discharged to the outside instead of the cooler, so that the cooling efficiency in the cooler can be increased. According to one embodiment of the present invention, the cooler is positioned 100 to 500 mm, preferably 150 to 400 mm, more preferably 200 to 300 mm spaced 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 and the cooling efficiency is low. This cannot be done. In addition, the injection angle when discharging the thermoplastic polyurethane particles from the nozzle may be 10 to 60 °, when discharging the thermoplastic polyurethane particles at the corresponding angle, the effect due to the separation of the nozzle and the cooler can be doubled.

The cooler may cool the thermoplastic polyurethane particles by supplying low-temperature air into the cooler and bringing the air into contact with the thermoplastic polyurethane particles. The low-temperature air forms a rotating airflow in the cooler, and the residence time of the thermoplastic polyurethane particles in the cooler can be sufficiently secured by the rotating airflow. The flow rate of the air supplied to the cooler may be adjusted according to the supply amount of the thermoplastic polyurethane 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 °C. By supplying cryogenic air into the cooler compared to the thermoplastic polyurethane particles supplied to the cooler, the thermoplastic polyurethane particles are rapidly cooled and the internal structure of the high-temperature thermoplastic polyurethane particles can be properly maintained when discharged. When the thermoplastic polyurethane particles are actually applied for the production of products, they are reheated again. At this time, the reheated thermoplastic polyurethane has properties advantageous for processing. The thermoplastic polyurethane particles cooled by low-temperature air are cooled to 40° C. or less and discharged, and the discharged particles are collected through a cyclone or a bag filter.

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are only provided for easier understanding of the present invention, and the present invention is not limited thereto.

Example

Example One

100% by weight of a thermoplastic polyurethane resin (Lubrizol, Pearlthane ^TM _{D91M80, Mw: about 160,000 g} /mol, glass transition temperature (T g ): about -37°C, pyrolysis temperature (T _d ): about 290°C) was mixed with a twin-screw extruder (Diameter (D) = 32 mm, length/diameter (L/D) = 40). The twin screw extruder was set at a temperature of about 220° C. and an extrusion amount of about 5 kg/hr to perform extrusion. The extruded thermoplastic polyurethane resin has a viscosity of about 5 Pa·s, and the extruded thermoplastic polyurethane resin is heated to an internal temperature of about 300°C and an end temperature of about 300°C (the B value according to Equation 5 is about 1.03). It was supplied to the set nozzle. In addition, air at 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 cross section of the nozzle, and the extruded thermoplastic polyurethane resin was supplied between the center and the outer portion of the nozzle to which air is supplied. The cross-sectional area ratio of the air supplied to the outer portion and the extruded thermoplastic polyurethane supplied between the air-supplied central portion and the outer portion was about 4.5:1. The thermoplastic polyurethane resin supplied to the nozzle was atomized by contact with hot air, and the atomized particles were sprayed from the nozzle. The injection angle from the nozzle was about 45°, and the injected particles were supplied to a cooling chamber (diameter (D) = 1,100 mm, length (L) = 3,500 mm) spaced about 200 mm from the nozzle. In addition, the cooling chamber was adjusted to form a rotational airflow by injecting ^{air at -25°C at a flow rate of about 6m 3 /min before the injected particles were supplied.} Particles sufficiently cooled to 40° C. or less in the cooling chamber were collected through a cyclone or a bag filter.

comparative example One

Thermoplastic polyurethane particles were prepared in the same manner as in Example 1, except that the temperature of the distal end was adjusted to 124° C. (the B value according to Equation 5 was about 0.49).

comparative example 2

Thermoplastic polyurethane particles were prepared in the same manner as in Example 1, except that the temperature of the distal end was adjusted to 470° C. (the B value according to Equation 5 was about 1.55).

comparative example 3

The same thermoplastic polyurethane resin as in Example 1 was supplied to a screw feeder through a hopper. Moisture was removed while moving the raw material through the screw, and then the raw material was introduced into a pulverizer supplied with liquid nitrogen at -130°C. As the crusher, a pin crusher type crusher was used. The particle size was controlled through a grinding size pin. Particles atomized through the grinder were collected through a cyclone.

comparative example 4

Thermoplastic polyurethane particles were prepared in the same manner as in Example 1, except that the cross-sectional area ratio of the air supplied to the outer portion and the extruded thermoplastic polyurethane supplied between the central portion and the outer portion supplied with air was 3.5:1.

comparative example 5

Thermoplastic polyurethane particles were prepared in the same manner as in Example 1, except that the cross-sectional area ratio of the air supplied to the outer portion and the extruded thermoplastic polyurethane supplied between the central portion and the outer portion supplied with air was 6.5:1.

Experimental example One

The particle size distribution of the thermoplastic polyurethane particles prepared according to Example 1 and Comparative Examples 1 to 5 was measured and shown in Table 1 below. Specifically, the particle size distribution was measured by the following two steps.

1) Sample pretreatment: Put about 0.003wt% of a powder sample in ethanol, set it to 30% of the maximum amplitude using a 50Watt/30kHz ultrasonic disperser, and disperse the powder sample in the ethanol by excitation for about 120 seconds.

2) Measurement of particle size distribution: Measure particle size distribution according to ISO 13320 standard.

particle size distribution D ₁₀ (μm) D ₅₀ (μm) D ₉₀ (μm) D Example 1 10 28 60 12.42 Comparative Example 1 550 800 1150 4.17 Comparative Example 2 1.2 8 16.5 48.73 Comparative Example 3 8 45 68 33.92 Comparative Example 4 195 232 325 3.38 Comparative Example 5 2.5 15 30.5 40.13

According to Table 1, the particle diameter of the particles prepared according to Example 1 is not biased in a larger or smaller direction based on the average particle diameter, unlike the particle diameters of the particles prepared according to Comparative Examples 2, 3 and 5, D ₅₀ It can be seen that the ratio of /D ₁₀ and D ₉₀ /D _{50 remains similar.} In addition, the particle diameter of the particles prepared according to Example 1 is not too large unlike the particle diameters of the particles prepared according to Comparative Examples 1 and 4, and the ratio of D ₅₀ /D ₁₀ and D ₉₀ /D ₅₀ is at least a certain level ( It can be confirmed that it is maintained at about 2 to 3).

When the particles have the same particle size distribution as the particles prepared according to Example 1, it is possible to effectively compensate for the disadvantages of having only an average particle size when applied to a product.

Experimental example 2

The physical properties of the particles prepared according to Example 1 and Comparative Example 3 were measured and shown in Table 2 below.

Average particle size ^{1 )} (㎛) aspect ratio ^{2 )} Sphericity ^{3 )} Relaxed bulk density ^{4 )} (g/cm ³ ) Compressed Bulk Density ^{5 )} (g/cm ³ ) Compression degree ^{6 )} (%) Falling time ^{7 )} (s) Example 1 28 1.02±0.02 0.98±0.02 0.401 0.435 7.8 18 Comparative Example 3 45 1.44±0.35 0.71±0.25 0.45 0.46 2.2 21

1) Average particle diameter: D ₅₀ value was measured by the method of Experimental Example 1. 2), 3) Aspect ratio and sphericity: Image processing using the same device - After converting to a binary image, quantifying the degree of spheronization of individual particles - By The formation of particles was analyzed, and the aspect ratio and sphericity were derived by Equations 2 and 3.

4) Relaxed Bulk Density: Calculate the mass per unit volume by measuring the mass when the particles are quietly filled in a 100ml cylinder (average of 5 repeated measurements).

5) Compressed bulk density: The cylinder filled with particles according to 1) is arbitrarily compressed by tapping 10 times with a constant force, and then the mass is measured to calculate the mass per unit volume (average value measured repeatedly 5 times).

6) Compressibility (%)=(P-R)/P×100, P: particle compressed bulk density, R: particle relaxed bulk density.

7) Flow time: After filling a 100ml cylinder with particles, pour it into the KS M 3002 apparent specific gravity measuring device funnel, open the outlet, and measure the time it takes for the sample to come out completely (average value measured 5 times).

According to Table 2, the particles of Example 1 have a smaller diameter and uniform particle distribution compared to the particles of Comparative Example 3. In addition, the particles of Example 1 have a high degree of sphericity compared to the particles of Comparative Example 3, thereby securing a certain space during compression, and thus have a low compressed bulk density. The particles of Example 1 have a low compressive bulk density and a high degree of compression, so that when used in a molded article, it can have the effect of minimizing voids that may occur in a product, and when used in products such as cosmetics, it can Compressibility can be improved.

Experimental example 3

DSC analysis of the particles prepared according to Example 1 and Comparative Example 3 is shown in Table 3 below. Specifically, using a differential scanning calorimeter (DSC, Perkin-Elmer, DSC8000), the temperature was raised from 0 °C to 200 °C under a temperature increase rate of 10 °C/min to obtain a DSC curve. Glass transition temperature (T _g ), melting point (T _m ), cold crystallization temperature (T _cc ), and the difference between endothermic value (ΔH1) and calorific value (ΔH2) were derived from each DSC curve.

T _g (℃) T _m (℃) T _cc (℃) ΔH1-ΔH2 (J/g) Example 1 -37 136 36 6 Comparative Example 3 -34 140 - -

It was confirmed that the thermoplastic polyurethane particles of Example 1 showed a cold crystallization temperature peak at 36° C., whereas the thermoplastic polyurethane particles of Comparative Example 3 did not exhibit such a cold crystallization temperature peak. Furthermore, in the case of Example 1, it was confirmed that the difference between the endothermic amount (ΔH1) and the calorific value (ΔH2) was about 6 J/g.

When the thermoplastic polyurethane particles have a cold crystallization temperature peak as in Example 1, when heat-processing using these particles, it can have an advantage that it can be processed at a low temperature compared to the processing temperature of the thermoplastic polyurethane particles of Comparative Example 3 .

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will become apparent from the appended claims.

d: perpendicular distance between two parallel tangent planes
A: area
10: nozzle
20: second air flow
30: thermoplastic polyurethane resin flow
40: first air flow

Claims (17)

A method for producing thermoplastic polyurethane particles, comprising:
The manufacturing method is
(1) supplying a thermoplastic polyurethane resin to the extruder and extruding;
(2) supplying the extruded thermoplastic polyurethane resin and air to the nozzle, contacting the thermoplastic polyurethane resin with air to make the thermoplastic polyurethane resin particles, and then discharging the granulated thermoplastic polyurethane resin; and
(3) supplying the discharged thermoplastic polyurethane particles to a cooler to cool the thermoplastic polyurethane particles, and then obtaining cooled thermoplastic polyurethane particles,
Method for producing thermoplastic polyurethane particles, characterized in that the distal end of the nozzle in step (2) is maintained at a temperature calculated by the following formula 5:

[Formula 5]
End temperature = glass transition temperature (T _g ) + (decomposition temperature (T _d ) - glass transition temperature (T _g ))×B

In Equation 5, the glass transition temperature and the decomposition temperature are values for the thermoplastic polyurethane, and B is 0.5 to 1.5.
The method according to claim 1,
The method for producing thermoplastic polyurethane particles, characterized in that the extruded thermoplastic polyurethane resin supplied to the nozzle in step (2) has a melt viscosity of 0.5 to 20 Pa·s.
The method according to claim 1,
In step (2), based on the cross section of the nozzle, air is supplied to the central part and the outer part, and the extruded thermoplastic polyurethane resin is supplied between the central part and the outer part to which air is supplied. manufacturing method.
4. The method according to claim 3,
Based on the cross-section at the discharge part of the nozzle in step (2), the cross-sectional area ratio of the air supplied to the outer part and the extruded thermoplastic polyurethane resin supplied between the central part and the outer part to which the air is supplied is 4:1 to Method for producing thermoplastic polyurethane particles, characterized in that 6:1.
The method according to claim 1,
The method for producing thermoplastic polyurethane particles, characterized in that the inside of the nozzle in step (2) is maintained at 250 to 350 ℃.
As a thermoplastic polyurethane particle prepared by the manufacturing method according to claim 1,
Formed in a continuous matrix phase from a thermoplastic polyurethane resin,
Thermoplastic polyurethane particles having a particle diameter of 1 to 100 μm.
7. The method of claim 6,
The thermoplastic polyurethane particles are thermoplastic polyurethane particles, characterized in that having _{an average particle diameter (D 50 ) of 20 to 50㎛.}
7. The method of claim 6,
The thermoplastic polyurethane particle is a thermoplastic polyurethane particle, characterized in that it has a cumulative volume of 10% particle diameter (D _{10 ) of 5 to 15㎛.}
7. The method of claim 6,
The thermoplastic polyurethane particles are thermoplastic polyurethane particles, characterized in that it has a cumulative volume of 90% particle diameter (D ₉₀ ) of 40 to 80㎛.
7. The method of claim 6,
The thermoplastic polyurethane particles are thermoplastic polyurethane particles, characterized in that the D value calculated by the following formula 1 is 5 to 20:

[Formula 1]

Here, D ₁₀ is a particle diameter of 10% of the cumulative volume, D ₅₀ is an average particle diameter, and D ₉₀ is a particle diameter of 90% of the cumulative volume.
7. The method of claim 6,
The thermoplastic polyurethane particles, characterized in that the impurity content of the thermoplastic polyurethane particles is 50ppm or less.
7. The method of claim 6,
The thermoplastic polyurethane particles are cooled at a temperature between the _{glass transition temperature (T g} ) and the melting point (T _m ) in the DSC curve derived from the analysis of the temperature increase of 10 ° C / min by Differential Scanning Calorimetry (DSC) Thermoplastic polyurethane particles, characterized in that the peak of the crystallization temperature (T _{cc ) appears.}
7. The method of claim 6,
The thermoplastic polyurethane particles have an aspect ratio of 1.00 or more and less than 1.05 calculated by the following formula 2,
Thermoplastic polyurethane particles having a sphericity of 0.95 to 1.00 calculated by the following formula 3:

[Formula 2]
Aspect ratio = major axis/minor axis

[Formula 3]
Roundness=4×area/(π×long axis^2).
7. The method of claim 6,
The thermoplastic polyurethane particles are thermoplastic polyurethane particles, characterized in that the degree of compression calculated by the following formula 4 is 7 to 15%:

[Formula 4]
Compression degree = (compressed bulk density - relaxed bulk density) / compressed bulk density x 100.
15. The method of claim 14,
The thermoplastic polyurethane particles are thermoplastic polyurethane particles, characterized in that having a compressed bulk density ^{of 0.4 to 0.45 g / cm 3 .}
7. The method of claim 6,
The thermoplastic polyurethane particles are thermoplastic polyurethane particles, characterized in that having a flow time of 10 to 20 seconds. delete

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