KR100867984B1 - Laser sintering powders using nylon 6, Manufacturing method thereof and molded product obtained from the same powder - Google Patents

Abstract

The present invention relates to the production of a powder for laser sintering and to a molded article sintered using the powder. Conventional laser sintering polymer powder was nylon 11 or nylon 12, the present invention was prepared by the laser sintering powder dry drying and shape control (spherization) using nylon 6, the prepared nylon 6 powder The powder for laser sintering having excellent moldability and mechanical properties was prepared by mixing and sintering with nylon 11 or nylon 12, which is a polymer powder that was frequently used in the process.

Nylon 6, powder for laser sintering, SLS (Selective Laser Sintering), toy rate, sinterability, formability, mechanical properties

Description

Laser sintering powders using nylon 6, a method of manufacturing the same and a molded article using the same {Laser sintering powders using nylon 6, Manufacturing method etc. and molded product obtained from the same powder}

1 is a SEM photograph showing the shape of a molded article (a) using nylon 12 alone and a molded article (b) sintered by mixing 1: 1 with nylon 12 and nylon 6.

2 is a graph comparing tensile strength of molded articles (a) using nylon 12 alone and molded articles (b) mixed by sintering nylon 12 and nylon 6 in a 1: 1 ratio.

The present invention relates to a nylon powder used as a material of a three-dimensional laser replicator, and more particularly, to a powder for laser sintering, characterized in that used by mixing nylon 6 and nylon 11 or nylon 12.

3D laser duplicator is a next generation machine that can duplicate the real three-dimensionally unlike the existing two-dimensional planar copier. It is called SLS (Selective Laser Sintering), Selective Laser Sintering Process and the equipment used is called Solid Freeform Fabrication System (SFFS), Arbitrary Shape Manufacturing Equipment. The driving sequence of the digital 3D replicator using the SLS method is to put the polymer powder for laser sintering into the feed room and preheat it for a predetermined time. The preheated powder in the feed room is unrolled to a constant thickness using a roller and moved to the build room, where laser sintering occurs. The powder transferred to the buildroom is heat treated at a temperature higher than the feedroom, preferably slightly below the melting point (m.p) of the powder and sintered only through the laser to produce the desired shape.

The production of products using this equipment requires polymers for laser sintering. There are various kinds of materials sintered by laser, but appropriate materials should be used according to the function of the product to be made or the characteristics of the physical replicator equipment. The process for producing molded articles using powders is described in detail in US Pat. No. 6,136,948 and WO 96/06881, filed by DTM. In the case of the polymer powder for laser sintering, 10-2003-0072060 filed by Degusa, Germany, added titanium dioxide to obtain a molded article having better elasticity when using only nylon 12, and 10-2003-0055535 to obtain organic carboxylic acid. It was added to prepare a nylon powder having a constant solution viscosity. 10-2005-7024944, filed by Rhodia Nylon Intermediate, France, has also invented a method of preparing a powder, including dispersing in an inert liquid using monomers and polymerizing monomers.

Various polymer materials have been developed as the sintering materials applied to date, and polystyrene, polyacrylate, nylon (polyamide), polyethylene, polypropylene, polyacetate, etc., in particular, nylon 11 or 12 is the most commonly used. This is because 12 has excellent mechanical and chemical properties, good abrasion resistance and toughness, light weight, excellent cold resistance and moldability, and non-toxic properties.

However, the above nylon 11 or 12 is relatively expensive compared to nylon 6 and the physical properties are also low, so the development is to produce a polymer powder using nylon 6. However, in the case of nylon 6, since the melting point is higher than 40 ℃ and severely deformed by heat compared to nylon 12, it is difficult to use it alone as a powder for laser sintering. In addition, due to its high hygroscopicity, the sintering of the sintered molded product may occur as the moisture is vaporized by the laser during sintering in a state containing moisture. However, when using a mixture of nylon 11 or 12 and nylon 6 can compensate for these disadvantages, the present invention sought a method to make use of the advantages while complementing the disadvantages of each nylon.

The present invention is to compensate for the above-mentioned disadvantages, by lowering the material price of the laser polymer sintering powder currently developed by adding nylon 6, which is relatively inexpensive and superior mechanical properties than nylon 11 or 12, the laser produced thereby An object is to increase the moldability and physical properties of the polymer powder for sintering. More specifically, the present invention prepares nylon 6, which is a laser sintering powder having an average particle diameter of 20 to 100 µm, preferably 40 to 70 µm, and a toy ratio of 0.6 to 0.9, and mixes it with nylon 12, which is widely used. It is an object to produce a polymer sintered powder excellent after the sintering molding by physical properties using nylon 12 alone.

The present invention for achieving the above object is first made of a powder having a particle size and a toy ratio similar to that of nylon 12 which is a conventional laser sintering powder through dry freeze grinding, and the prepared powder for conventional sintering By sintering and molding with nylon 12, which is a powder, the stack of sintered bodies is more stably formed than when sintering with only nylon 12, and the surprising effect of remarkably increasing tensile strength is found to complete the present invention.

Specifically, the present invention has a difficulty in preparing a powder by polymerization or recrystallization because nylon 6 has a melting point of about 40 ° C. higher than that of nylon 12 and a high hydrophilic group content. Therefore, nylon 6 is pulverized by dry freezing, and after the treatment, nylon 6, a powder for laser sintering having an average particle diameter of 20 to 100 μm, preferably 40 to 70 μm, and a toy ratio of 0.6 to 0.9, is prepared. The present invention was completed by confirming that the polymer sintered powder having excellent physical properties than that of nylon 12 was prepared by mixing and sintering molding with nylon 12, which was used a lot.

In general, the lamination height of the filler particles during laser sintering is performed at about 50 to 200 μm, so the particle size distribution of the laser sintering powder is 20 to 100 μm, preferably 40 to 70 μm. In the case of particle size distribution, the filling density between powder particles increases as the uniformity increases, and the surface area decreases as the toy rate increases, so that uniform heat transfer is possible during preheating or laser sintering, which is advantageous for producing a stable sintered molded product.

Therefore, in the process of carrying out the present invention, nylon 6, which is a powder for laser sintering, has a particle size distribution of 20 to 100 μm, more preferably 40 to 70 μm through dry freeze grinding, and focuses on manufacturing to increase the toy rate. In addition, the present invention was achieved by preventing distortion of the molded article due to the characteristic difference between nylon 12 and nylon 6 during sintering molding after mixing with existing nylon 12.

When manufacturing a powder using nylon 6 and a method of increasing the physical properties of the sintered molded article by addition thereof,

a) preparing pellets of nylon 6 into powder using a dry freeze grinding method;

b) heat treating nylon 6 made of powder to increase the toy rate;

c) mixing the heat treated nylon 6 powder with nylon 11 or nylon 12 powder;

Characterized in that it comprises a.

More specifically

a) pelletizing nylon 6 in liquid form using liquid nitrogen and pulverizing it through a high speed rotor grinder (Japan Seishin, IMPELLER MILL IMP 400) to prepare a powder;

b) increasing the toy rate by stirring nylon 6 made of powder with heat at 65-220 ° C. between the heat deflection temperature and the melting point;

c) uniformly mixing the powder having a higher toy rate through a mixer and sintering and molding through a CO 2 laser;

It includes, more preferably

a) When the pelletized nylon 6 is frozen using liquid nitrogen and ground through a high speed rotor grinder (Japan Seishin, IMPELLER MILL IMP 400), sieve is used to freeze large particles again. Continuously grinding until the desired particle size distribution is 20 to 100 µm, preferably 40 to 70 µm;

b) The powder having a desirable particle size distribution is stirred at 65-220 ° C., more preferably 100-200 ° C., between the heat deflection temperature and the melting point, or stirred in the water to increase the toy rate to 0.6-0.9. Putting glass beads to increase the toy ratio;

c) uniformly mixing the powder having a higher toy rate through a mixer, preheating in a feed room and sintering molding through a CO 2 laser in a pre-heated state at a temperature of 5 to 10 ° C. below the melting point of the powder in the build room;

The physical properties of the powder prepared and are measured using UTM.

The following describes each step used in the production method of the present invention in detail.

In the present invention, the powder for laser sintering was used by mixing nylon 11 or nylon 12 and nylon 6. More preferably, it is preferable to use nylon 12, and the nylon 11 or nylon 12 can be used by any manufacturing method as long as it has a toy ratio of 0.7 or more and a particle size distribution of 40 ~ 70㎛, polymerization Or those prepared by recrystallization are used. For example, DuraForm® PA, a powder being developed and supplied by 3D Systems, Inc., can be used.

Nylon 6 is prepared by using a nylon 6 in a pellet (such as BASF Ultramid b3s) to produce a powder having a high toy rate using the dry freeze grinding method according to the present invention. As with all polymers, nylon 6 is flexible due to heat, so simple grinding does not yield the desired particle size distribution. This is because in general grinding, excessive heat is generated by the friction force between the grinder and the particles, and the particles and the particles, and because of this, nylon 6 becomes soft and does not grind, and thus a desired particle size distribution cannot be obtained.

Therefore, in the present invention, the nylon 6 in the pellet state is frozen to the inside using liquid nitrogen, and more precisely, it is pulverized using a grinder, more specifically, a high speed rotor type grinder (Japan Seishin, IMPELLER MILL IMP 400). The reason why the high speed rotor type grinder is used is that it is easy to obtain powder of several micrometers (μm) size by the ultra-fine grinding of soft resin, which has been difficult to grind up to now, due to the interaction between the high speed rotor and the corrugated liner. to be.

The powder obtained by one cycle of pulverization has a particle size distribution of 10 to 400 μm, an average particle size of 100 to 200 μm, strictly 150 μm, so that the particle size of the powder for laser sintering through sieve is not more than 100 μm. Preferably, the powder of 70 μm or more is pulverized repeatedly until the desired particle size is 20 to 100 μm, more preferably 40 to 70 μm.

When preparing a powder having a particle size of 20 ~ 100㎛ through the pulverization it is necessary to increase the toy rate through heat treatment because the shape of the powder is very irregular. The higher the toy ratio, the better the smoothness and fluidity, so that the powder can receive heat evenly during preheating and the surface of the molded part can be smoothed during laser sintering. Improving the surface shape of the sintered molded article means that no additional pore or process of the finished molded article is required, and thus serves to lower the manufacturing cost industrially.

The post-treatment to increase the toy rate is to agitate the powder at 65 ~ 220 ℃, more precisely 100 ~ 200 ℃ between the heat deflection temperature and the melting point, or to put the powder into water and increase the toy rate by surface tension. give. At this time, if glass beads are added and stirred together, a larger toy ratio can be improved. In the case of heat treatment temperature, when the temperature is low, the value of the improved toy rate is low, and when the temperature is high, the value of the toy rate is high.

In the case of nylon 6 used in the present invention, the toy ratio of the nylon powder obtained through dry freeze grinding is 0.5 to 0.6, so the shape is uneven, so that the temperature between the heat deformation temperature and the melting point (mp) can be obtained in order to obtain a desirable laser sintering powder material. Phosphorus was stirred at 65 ~ 220 ℃, more precisely, the powder was stirred at 100 ~ 200 ℃, the toy rate was 0.6 ~ 0.9, it was raised to 0.76 ~ 0.84 by putting in 100 ℃ water and stirred.

As described above, in the present invention, the toy rate is preferably used in the sintering molding as a precondition for easy sintering. A powder for laser sintering molding is prepared due to a toy ratio of 0.7 or more obtained through heat treatment and a particle size distribution of 40 to 70 μm.

In the present invention, when the powder mixed with nylon 11 or nylon 12 is used as a powder for laser sintering, the molding is performed very stably even by sintering molding by slightly adjusting the preheating temperature or laser power. The strength is very improved. Since nylon 6 has a composition similar to that of nylon 11 or nylon 12, it is possible to develop a product that can significantly improve the mechanical properties of molded products because of its low molding process parameters and acts as a polymer filler. Could get

In the present invention, when the nylon 6 and the nylon 11 or nylon 12 is mixed when the nylon 6 is more than nylon 11 or nylon 12 sintering is performed, but the lamination is not good or the warping phenomenon of the molded product is unstable molding Therefore, it is preferable to use nylon 6 and nylon 11 or nylon 12 in a 0.2 to 1: 1 weight ratio, more preferably in a 0.2 to 0.4: 1 weight ratio, more preferably in a ratio of 1: 1. In this case, intact sintering was performed and an increase in physical properties such as tensile strength was observed.

In the present invention, the sintering molding is preferably using a laser, more preferably using a CO 2 laser. The sintering molding is pre-heated in the feed room of the sintering equipment, and sintered through the CO 2 laser in a pre-heated state at a temperature of 5 ~ 10 ℃ lower than the melting point of the powder in the build room.

After the preheating of the machine and the powder is finished, the laser is sintered to the desired shape.It is not relevant for single layer, but if you want to make three-dimensional by pairing several layers, use a roller to flatten on the powder sintered to a certain lamination thickness. Powder should be applied and sintering should be performed repeatedly. Repeatedly sintered three-dimensional molded articles are stored for 30 minutes or more without being taken out immediately to prevent deformation.

Hereinafter, the present invention will be described with reference to Examples for the specific description of the present invention, but the present invention is not limited to the following Examples.

Example 1

1) Preparation of Nylon 6 Powder

Pelletized nylon 6 (Ultramid b3s from BASF Korea) was frozen using liquid nitrogen and subjected to primary grinding using a high-speed rotor type mill (Japan Seishin, IMPELLER MILL IMP 400). A powder having a particle size of 70 μm or more through sieve was obtained by repeatedly grinding to obtain a powder having a particle size of 40 μm to 70 μm, which is a desired particle size.

The nylon 6 powder obtained through dry freeze grinding was placed in a beaker and heat was applied at 200 ° C. At this time, the nylon 6 was changed from glass to rubber by heat. Nylon 6 turned into a rubber phase was stirred for 4 hours using a stirrer to increase the toy rate.

The particle size distribution and the improved toy ratio of the powder obtained through the heat treatment are shown in Table 1 below.

2) using nylon 6 and nylon 12 mixed powder Molded  Produce

Nylon 6 (DuraForm® PA manufactured by 3D System, Inc., with a mean particle diameter of 50 μm and a toy rate of 0.7˜0.9) was sintered by mixing nylon 6 with an improved toy ratio obtained through the experiment in a weight ratio of 1: 1. When the mixed powder of nylon 12 and nylon 6 in the above ratio is put into the feed room of the laser sintering equipment (SFFS equipment of the Korea Institute of Machinery and Materials) and the nitrogen gas is added, the internal temperature of the machine becomes 178 ℃, the sintering temperature. Preheated to The film was laminated to a thickness of 100 μm using a roller, and then sintered using a CO 2 laser.

The physical properties of the three-dimensional molded article thus obtained were measured and shown in Table 1 below.

Example 2

Through the same manufacturing process as described in Example 1, it was prepared in the same manner as in Example 1 except that the stirring time was changed to 8 hours. The particle size distribution and the improved toy ratio of the obtained powder are shown in Table 1 below.

In addition, a molded product was prepared in the same manner as in Example 1, and the results are shown in Table 1 below.

Example 3

Through the same manufacturing process as described in Example 1, it was prepared in the same manner as in Example 1 except that the stirring time was changed to 12 hours or more. The particle size distribution and the improved toy ratio of the obtained powder are shown in Table 1 below.

In addition, a molded article was prepared in the same manner as in Example 1, and the results are shown in Table 1, and are shown in FIGS. 1 and 2.

Example 4

Nylon 6 (Ultramid b3s, BASF Korea) obtained through dry freeze grinding of the same method as Example 1 was placed in a beaker containing water at 100 ° C. for the purpose of using surface tension. After heating for 4 hours while applying a heat to remove the moisture by using an oven to prepare a powder with improved toy rate. The particle size distribution and the improved toy ratio of the obtained powder are shown in Table 1 below.

In addition, a molded product was prepared in the same manner as in Example 1, and the results are shown in Table 1 below.

Example 5

The same process as in Example 4 was conducted except that the stirring time was changed to 8 hours. The particle size distribution and the improved toy ratio of the obtained powder are shown in Table 1 below.

In addition, a molded product was prepared in the same manner as in Example 1, and the results are shown in Table 1 below.

Example 6

The same process as in Example 4 was carried out, except that the stirring time was changed to 12 hours. The particle size distribution and the improved toy ratio of the obtained powder are shown in Table 1 below.

In addition, a molded product was prepared in the same manner as in Example 1, and the results are shown in Table 1 below.

Comparative Example 1

1) Preparation of nylon 6 powder without post-treatment

Pelletized nylon 6 (Ultramid b3s from BASF Korea) was frozen using liquid nitrogen and subjected to primary grinding using a high-speed rotor type mill (IMPELLER MILL IMP 400, Seishin, Japan). A powder having a particle size distribution of 40 to 70 µm (average particle diameter: 53 µm) was prepared, and heat treatment was not performed to increase a toy ratio.

2) using nylon 6 and nylon 12 mixed powder Molded  Produce

The nylon 6 powder was sintered by mixing nylon 12 (DuraForm® PA, manufactured by 3D System, having an average particle diameter of 50 μm and a toy ratio of 0.7˜0.9) in a weight ratio of 1: 1. When the mixed powder of nylon 12 and nylon 6 in the above ratio is put into the feed room of the laser sintering equipment (SFFS equipment of the Korea Institute of Machinery and Materials) and the nitrogen gas is added, the internal temperature of the machine becomes 178 ℃, the sintering temperature. Preheated to and laminated to a thickness of 100㎛ using a roller and then sintered using a CO 2 laser.

As a result, when sinter molding, the powder must be repeatedly spread through the roller. When the roller moves, not only the powder but also the sintered molded product is pushed and moved, so that the three-dimensional molding is impossible. It is considered that even if the powder having the same particle size distribution has a low toy rate, there may be a large number of powders over 70 μm and there is difficulty in lamination because sintering is not performed smoothly. Obtained physical properties are shown in Table 1 below.

Comparative Example 2

1) Preparation of nylon 6 powder by lowering the heat treatment temperature to the heat deformation temperature

The nylon 6 powder obtained in the same manner as in Comparative Example 1 was heated at 60 ° C., which is lower than the heat deformation temperature, and stirred for 12 hours or more. The synergistic effect of the obtained powder was almost unchanged as compared with the non-heat-treated powder.

2) using nylon 6 and nylon 12 mixed powder Molded  Produce

The nylon 6 powder obtained through the experiment was sintered by mixing nylon 12 (DuraForm® PA of 3D System Co., Ltd., having an average particle diameter of 50 μm and a toy ratio of 0.7 to 0.9) in a weight ratio of 1: 1. When the mixed powder of nylon 12 and nylon 6 in the above ratio is put into the feed room of the laser sintering equipment (SFFS equipment of the Korea Institute of Machinery and Materials) and the nitrogen gas is added, the internal temperature of the machine becomes 178 ℃, the sintering temperature. Preheated to and laminated to a thickness of 100㎛ using a roller and then sintered using a CO 2 laser.

Obtained physical properties are shown in Table 1 below.

Comparative Example 3

When sintered using only nylon 12

Put the nylon 12 (DuraForm® PA from 3D System Co., Ltd. with an average particle diameter of 50 µm and a toy ratio of 0.7 ~ 0.9) into the feed room of the laser sintering equipment (SFFS equipment of the Korea Institute of Machinery & Materials) and put the nitrogen gas in the machine. It preheated until internal temperature became 178 degreeC which is a sintering temperature.

The film was laminated to a thickness of 100 μm using a roller, and then sintered using a CO 2 laser.

The physical properties of the three-dimensional molded article thus obtained were measured. The obtained physical properties are shown in FIGS. 1 and 2.

TABLE 1

* Shape (toy rate) = (vertical diameter / horizontal diameter) of the powder particles

* The average particle size was measured with a laser diffraction size analyzer (HELOS / RODOS of Sympatec GmbH, Germany).

* Tensile strength was measured by a universal testing machine (UTM: 810 System of MTS System Corporation, USA).

The present invention has a similar composition to supplement the properties of nylon 12, a powder material for laser sintering, and has a low cost and good properties. Since the same nylon can be obtained, it is possible to supply a powder material for laser sintering without difficulty in sintering molding without adding a coupling agent or the like.

In addition, the present invention can provide a method for producing a powder having a high toy ratio using nylon 6 commercially available in pellet form, nylon 6 powder prepared according to the production method of the present invention is suitable for use as a laser powder It can be used as the laser sintering powder which has the average particle diameter and the toy rate and is mixed with nylon 12 to improve tensile strength and formability.

Claims (12)

delete delete delete a) preparing pellets of nylon 6 into powder using a dry freeze grinding method; b) preparing a powder having a toy ratio of 0.6 to 0.9 by stirring nylon 6 made of powder with heat at 65 to 220 ° C. between a heat deflection temperature and a melting point; c) mixing the heat treated nylon 6 powder with nylon 11 or nylon 12 powder; Method for producing a powder for laser sintering comprising a. a) preparing pellets of nylon 6 into powder using a dry freeze grinding method; b) adding nylon 6 prepared as a powder to water at 65-220 ° C., stirring to prepare a powder having a toy rate of 0.6 to 0.9, and then drying it; c) mixing the heat treated nylon 6 powder with nylon 11 or nylon 12 powder; Method for producing a powder for laser sintering comprising a. The method of claim 5, The method of manufacturing a powder for laser sintering, characterized in that the glass beads are added when stirring. delete delete A molded article characterized by sintering molding using a CO 2 laser using a mixed powder of nylon 6 and nylon 11 or nylon 12 prepared by the method of any one of claims 4 to 6. The method of claim 9, The sintering molding is pre-heated in the feed room of the sintering equipment, the molded body characterized in that the sintering molding through the CO 2 laser in a pre-heated state at a temperature 5 ~ 10 ℃ lower than the melting point of the powder in the build room. Laser sintering, characterized in that the nylon 6 powder having an average particle diameter of 20 ~ 100㎛ manufactured by dry freeze pulverization method and nylon 11 or nylon 12 having a toy ratio of 0.6 to 0.9 in a 0.2 to 1: 1 weight ratio powder. delete

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