WO2023287221A1

WO2023287221A1 - Method for manufacturing plate-like polymer powder

Info

Publication number: WO2023287221A1
Application number: PCT/KR2022/010286
Authority: WO
Inventors: 김태엽; 조상호
Original assignee: 엑시노 주식회사
Priority date: 2021-07-16
Filing date: 2022-07-14
Publication date: 2023-01-19
Also published as: KR102529791B1; KR20230012880A

Abstract

Disclosed is a method for making a polymer powder into a plate-like form. A method for a plate-like form according to an embodiment comprises the steps of: preparing a polymer powder; and making the prepared polymer powder into a plate-like form through mechanical milling.

Description

Manufacturing method of plate-shaped polymer powder

The present invention relates to the production of low-density polymer powders, and more particularly, to a method for producing plate-like polymer powders by flattening spherical or amorphous polymer powders.

With the advancement of information and communication technology, portable electronic devices are continuously being made lighter and smaller. For example, a tablet computer or a notebook computer, including a smart phone, is gradually becoming lighter in weight and thinner in spite of increasingly high functionality and high specifications. To this end, research and development on materials that can support light-thin and short-circuiting for the main body of the product as well as internal electronic components, adhesives or films for bonding or mounting them are continuously being pursued.

Among various technological factors for realizing light, thin, and compact portable electronic devices, the importance of a conductive adhesive material for mounting and bonding electronic components such as highly integrated IC chips on a circuit board is continuously increasing. Due to the nature of these conductive adhesives used in electronic devices, not only high conductivity is required, but also performance such as thermal conductivity and formability along with electromagnetic wave shielding ability is required. In particular, in order to support thin, thin and short electronic devices, the importance of low-density characteristics such as conductive adhesives and conductive films is gradually increasing.

In general, a conductive adhesive or conductive film is manufactured by molding a paste or mixture of a metal powder having high electrical conductivity, such as silver, copper, nickel, or zinc, with an organic binder (synthetic resin), into a film form. However, metal powder is basically a material with high density, so there is a limit to weight reduction, and dispersion stability is poor, as well as stability over time, so when precipitation occurs over time, there is a problem of poor uniformity. Due to this, the thickness of the conductive adhesive or the conductive film is non-uniform, the surface is rough, and the conductive properties are not satisfied locally.

In order to solve the disadvantages of these metal powders, various methods have been proposed. For example, a method of lowering the density by manufacturing a hollow metal powder or using a plastic ball instead of a metal powder has been proposed. In the latter case, by applying electroless metal plating to the surface of a plastic ball made of, for example, PolyStyrene (PS), PolyMethyl MethAcrylate (PMMA), Arcylonitrile Butadiene Styrene (ABS), PolyOxy Methylene (POM), PolyAcryloNitrile (PAN), etc. Low density is achieved while maintaining conductivity.

However, in the conventional method of plating metal on plastic balls, low density of the powder is possible by using a base material core material with low density, but the shape of the particles is spherical and the contact between the particles becomes a point contact to realize high conductivity. There are limits.

[Prior art literature]

(Patent Document 1) Korean Patent Registration No. 10-1718158

One problem to be solved by the present invention is to provide a method for producing a plate-shaped polymer powder capable of preparing a spherical or amorphous polymer powder in a plate-shaped form with a large contact area between particles.

A method for preparing a plate-shaped polymer powder according to an embodiment of the present invention for solving the above problems includes preparing a polymer powder and mechanically milling the prepared polymer powder to plate it.

According to one aspect of the embodiment, the polymer powder is polyacrylonitrile (PolyAcryloNitrile, PAN), polymethyl methacrylate (PolyMethyl MethAcrylate, PMMA), polystyrene (PolyStyrene, PS), polyethylene (PolyEthylene, PE) and It may be formed of one or more copolymers selected from the group consisting of polypropylene (PP).

According to another aspect of the embodiment, the polymer powder may have a spherical or amorphous shape with an average particle diameter of 1 to 60 μm.

Further, the plate-shaped polymer powder produced as a result of the plate-forming step has a length of a long axis of 2 to 150 μm and a thickness of 0.2 to 2 μm, and a ratio of the length of the long axis to the thickness may be 10 to 300.

In the plate-forming step, the prepared polymer powder may be mechanically milled using one or more methods selected from among a ball mill method, an attrition mill method, and a beads mill method. In this case, in the plate-forming step, a solvent may be included during the process in order to increase the mixing and dispersing effect of the polymer powder, and the solvent is methanol, ethanol, 1,2-propanol (1 ,2-propanol), ethylene glycol, glycerol, and the like may be selected from one or more alcohols. In addition, depending on the type of polymer powder, mechanical milling may be performed at a temperature higher than room temperature in order to increase the milling effect.

According to the above-described embodiments of the present invention, spherical or amorphous polymer powder can be easily and inexpensively manufactured into plate-like polymer powder having a desired thickness-to-diameter (or major axis length).

In addition, the plate-shaped polymer powder prepared in this way can be used to prepare a conductive powder having excellent conductivity and low density through a subsequent process of coating with metal.

1 is a flowchart showing a method of manufacturing low-density plate-like conductive powder according to an embodiment of the present invention.

2a and 2b are SEM images of the prepared spherical polymer powder, and FIG. 2b is an enlarged portion of FIG. 2a.

3a and 3b are SEM pictures of the plate-shaped polymer powder according to Experimental Example 3, and FIG. 3b is an enlarged portion of FIG. 3a.

4a and 4b are SEM images of the plate-shaped polymer powder according to Experimental Example 7, and FIG. 4b is an enlarged portion of FIG. 4a.

5a and 5b are SEM pictures of the plate-shaped polymer powder according to Experimental Example 13, and FIG. 5b is an enlarged portion of FIG. 5a.

6a and 6b are SEM images of the plated polymer powder according to Comparative Example 1, and FIG. 6b is an enlarged portion of FIG. 6a.

7a and 7b are SEM images of the plated polymer powder according to Comparative Example 2, and FIG. 7b is an enlarged portion of FIG. 7a.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Terms and words used in this specification are terms selected in consideration of functions in the embodiments, and the meanings of the terms may vary depending on the intention or practice of the invention. Therefore, the terms used in the embodiments to be described later, when specifically defined in the present specification, follow the definition, and when there is no specific definition, they should be interpreted as meanings generally recognized by those skilled in the art.

A method for producing a plate-like polymer powder according to an embodiment of the present invention includes a process of preparing a spherical and/or amorphous polymer powder and a process of mechanically milling the prepared polymer powder into a plate shape under predetermined process conditions. include The plate-shaped polymer powder thus prepared can be used to manufacture plate-shaped low-density conductive powder by coating a metal through a subsequent process.

1 is a flowchart showing a method for manufacturing a plate-like polymer powder according to an embodiment of the present invention.

Referring to FIG. 1, first, a polymer powder to be plated is prepared (S10). There is no particular limitation on the type of polymer powder. For example, the polymer powder is polyacrylonitrile (PolyAcryloNitrile, PAN), polymethyl methacrylate (PolyMetahyl MethAcrylate, PMMA), polystyrene (PS), polyethylene (PolyEthylene, PE) and polypropylene (PolyPropylene, PP). It may be one copolymer selected from the group consisting of, or a mixture in which two or more copolymers are mixed. Preferably, the polymer powder is polyacrylonitrile. Polyacrylonicryl polymer powder has excellent ductility compared to other types of polymer powder and is easier to plate.

And the prepared polymer powder has a three-dimensional shape, such as a spherical and/or amorphous shape. For example, when the spherical polymer powder is plate-shaped by mechanical milling in step S20 to be described later, it has a circular or elliptical shape with a thin thickness, so it is easy to control the shape of the powder even if it is plate-shaped. In addition, when coated with metal, a wider contact area can be secured between circular or elliptical powders, and there is an advantage in that the deviation of the contact area between the powders is small.

For example, the spherical polymer powder may have an average particle diameter of 1 μm to 60 μm. Preferably, the polymer powder preferably has an average particle diameter of 3 to 15 μm. When the average particle diameter of the polymer powder is smaller than 3 μm, it is not easy to coat the polymer with metal even if it is plate-shaped, and it is difficult to secure a large contact area between the powders. On the other hand, when the average particle diameter of the polymer powder is greater than 15 μm, the particle size greatly increases after plate-shaping, making it difficult to evenly distribute the powder during manufacture of pastes or films, as well as making it difficult to thin and refine the product.

Subsequently, the prepared polymer powder is mechanically milled and plated under predetermined process conditions (S20). Here, "mechanical milling" refers to flattening by physically applying impact and/or pressure to polymer powder using a milling machine commonly used to make fine powder. In general, metal particles, paints, grains, etc. are broken into smaller particles (powder) when using a milling machine. However, in the case of a polymer powder, its shape is easily deformed rather than split into smaller sizes even when an impact or pressure is applied due to its material properties (eg, ductility). More specifically, in the case of spherical polymer powder, when mechanical milling is performed using a milling machine, it can be flattened by impact or pressure and plated into a circular or elliptical shape.

Here, there is no particular limitation on the type of milling machine for performing mechanical milling. For example, the milling machine may be a device for mechanically milling using one or more methods selected from among a ball mill method, an attrition mill method, and a beads mill method. Depending on the milling conditions such as the size of the ball used, the rotational speed, and the processing time, the milling device (ie, the milling method used in the milling machine) can be selectively used. According to an embodiment of the present invention, it is preferable to perform the plate forming step (S20) using the attrition mill method in consideration of the ball size, rotational speed, productivity, and the like.

According to an embodiment of the present invention, the mechanical milling in step S20 is preferably performed in a state in which the polymer powder is dispersed in a predetermined solvent. When the polymer powder is dispersed in a solvent, mixing and dispersing effects of the polymer powder can be enhanced, and more uniform milling is possible. Since the polymer powder is hydrophobic and has a lower density than water, it does not disperse well in water. Therefore, it is preferable to use an organic solvent instead of water for dispersing the polymer powder. However, when an organic solvent is used as a dispersion, the polymer powder may be dissolved depending on its type, so an organic solvent of a type in which the polymer powder does not dissolve well should be used.

More specifically, polymer powders such as polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polystyrene (PS), polyethylene (PE) or polypropylene (PP) are not easily soluble in alcohol. Therefore, the organic solvent used in the mechanical milling process in step S20 is preferably alcohol. For example, the alcoholic organic solvent may be methanol, ethanol, 1,2-propanol, ethylene glycol, glycerol, or a mixture thereof. can In this case, since the polymer powder is not easily dissolved in the organic solvent and is uniformly dispersed, it is possible to plate the particle size uniformly without damaging the polymer powder.

However, since the above-mentioned polymer powder can be easily dissolved in ketones (e.g., acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, etc.) It is preferable not to use it as a solvent. If ketones are used as a solvent, the polymer powder is dissolved and the base material may be damaged when the milling machine is used for a long time.

According to one embodiment of the present invention, the mechanical milling process of step S20 may be performed at a temperature of 10° C. or higher, but the temperature should be lower than the boiling point of the solvent used. In this case, depending on the type of polymer powder, it is preferable to perform the milling at a temperature higher than room temperature (25° C.) in order to increase the milling effect. For example, high-strength polymer powders such as polymethyl methacrylate (PMMA) have low ductility and can easily break the powder during mechanical milling. Therefore, the temperature is maintained high during the milling process to increase the ductility of the powder, thereby increasing the platelet efficiency. can increase In this case, the mechanical milling process is preferably performed at room temperature lower than the boiling point of the organic solvent, for example, 25 to 75°C. If the process temperature is less than 25 ° C., the ductility of the polymer powder is not increased, so the polymer powder can be easily broken. On the other hand, when the process temperature is 75° C. or higher, it may be difficult to perform the milling process for a long time because the solvent is evaporated and the amount is reduced during the mechanical milling process.

In addition, it is preferable to perform this mechanical milling process at a predetermined rotational speed (rpm) for a predetermined time so that more powder can be plated. For example, the mechanical milling process is preferably performed at 200 to 600 rpm for about 10 to 60 minutes. When the rotational speed is too small or the process time is too short, there is a concern that only a part of the polymer powder introduced is plated. On the other hand, if the rotation speed is too high, there is a concern that the polymer powder is not plated and pulverized, and if the process time is too long, not only is it a factor that lowers productivity, but also the polymer powder is dissolved in an organic solvent. There is a risk that this may be damaged.

And the size of the ball used in the mechanical milling process is 0.5 to 4mm, preferably 1 to 3mm. If the size of the ball is too small (for example, 1 mm or less), it is difficult to flatten the polymer powder as a whole and it is easy to break the polymer powder due to partial impact. On the other hand, if the size of the ball is too large (eg, 4 mm or more), the impact applied by the ball is great, so the polymer powder is also easy to break.

As such, in step S20, when the plate-forming process is performed on the polymer powder using a mechanical milling method under predetermined process conditions (ie, the above-described process temperature, rotational speed, and/or ball size, etc.), the spherical polymer powder The silver is plated to form a plate-like polymer powder. For example, when spherical polymer powder having an average particle diameter of 1 to 60 μm is plated using a ball mill method, a bead mill method, or an attrition mill method, the length of the long axis (or diameter) is 2 to 150 μm and the thickness is 0.2 μm. As ~2 μm, a platelet polymer powder with a length to thickness ratio of 10 to 300 can be made.

In this way, when the plate-like polymer powder is produced, it can be used to prepare a low-density plate-like polymer powder by coating a conductive metal material on its surface. To this end, the metal to be coated is silver (Ag), copper (Cu), nickel (Ni), tin (Sn), gold (Au), aluminum (Al), bismuth (Bi), iron (Fe) or cobalt (Co ), or a mixture of two or more metals.

There is no particular limitation on the method of coating the surface of the plate-like polymer powder with a conductive metal material, and any technique known for coating a metal material on the polymer powder may be used. For example, according to the method disclosed in Patent Document 1 (Korean Patent Registration No. 10-1718158) or Patent Document 3 (Korean Patent Publication No. 10-2020-0113461), metal is deposited on the surface of the plate-shaped polymer powder by electroless plating. The material may be coated.

Alternatively, a predetermined coating solution containing metal ions to be coated is prepared, plate-shaped polymer powder is added to the prepared coating solution, and then the solution is stirred for a predetermined period of time to form a corresponding metal material on the surface of the polymer powder. It can also be coated. To this end, the coating solution includes a complexing agent and a reducing agent together with metal ions (metal precursors) so that metal ions can be bound to the surface of the polymer powder by a redox reaction during stirring. Here, the complexing agent serves to form a complex compound of metal ions. Since the produced metal complex has a lower redox potential than pure metal ions, a rapid reduction reaction of metal ions is suppressed to form a uniform metal coating layer.

And, if necessary, the coating solution may further contain a pH adjuster so that the oxidation-reduction reaction can occur smoothly by the reducing agent. According to one embodiment of the present invention, in this case, the hydrogen ion concentration (pH) of the coating solution is preferably 7 or more and 12 or less.

Further, the metal layer formed on the surface of the polymer powder may be formed in a single layer or in multiple layers. In the latter case, the multiple metal layers need not necessarily be of the same kind of metal, but may be of different kinds of metal.

The plate-shaped low-density conductive powder prepared according to the embodiment of the present invention has a significantly lower density than the conventional metal conductive powder. For example, in the case of silver (Ag), the density is 10.49 g / cm3, in the case of copper (Cu), the density is 8.93 g / cm3, in the case of nickel (Ni), the density is 8.8 g / cm3, etc., but the result of step S30 The conductive powder made of (conductive powder in FIG. 2A) has a tap density of 2.5 g/cm3 or less regardless of the type of metal 4 coated on the surface of the plate-like polymer powder 2.

In addition, the plate-shaped low-density conductive powder prepared according to the embodiment of the present invention can be mixed with a polymer resin to be prepared in the form of a conductive paste, film, or sheet, and the plate-shaped low-density conductive powder prepared according to the embodiment itself or mixed with other conductive powders and can be used.

Hereinafter, experimental examples and comparative examples according to the above-described embodiments of the present invention will be described. However, the experimental examples described below are intended to specifically illustrate or explain the above-described embodiments of the present invention, and the embodiments of the present invention are not limited by the experimental examples described later.

Experimental Examples 1 to 13

Experimental Examples 1 to 13 are examples of the process of plate-forming the polymer powder according to the above-described embodiment of the present invention, respectively. More specifically, first, a spherical polymer powder having a particle diameter of 3 to 15 μm is prepared (see Table 1). 2a and 2b are SEM images of the spherical polymer powder prepared according to Experimental Example 3, and FIG. 2b is an enlarged portion of FIG. 2a. Then, a ball with a diameter of 1 to 3 mm is put into the stirrer of the attrition milling device, and then ethanol and polymer powder are mixed at a weight ratio of 10: 1 (eg, 200 g of ethanol and 20 g of polymer powder), It is put into the agitator of the milling device. Subsequently, the stirrer is rotated to plate the polymer powder. In this experimental example, milling was performed at 200 rpm, 400 rpm, or 600 rpm for 10 minutes, 20 minutes, 40 minutes, or 60 minutes, respectively, to prepare a plate-shaped polymer powder having a powder size (long axis length of the plate-shaped powder) of 10 to 20 μm.

Figures 3a and 3b are SEM pictures of the plate-shaped polymer powder prepared according to the process conditions of Experimental Example 3 in Table 1 below, and Figure 3b is an enlarged portion of Figure 3a. And Figures 4a and 4b are SEM pictures of the plated polymer powder prepared according to the process conditions of Experimental Example 7 in Table 1 below, Figure 4b is an enlarged portion of Figure 4a, Figures 5a and 5b As an SEM picture of the plate-shaped polymer powder prepared according to the process conditions of Experimental Example 13 in Table 1 below, FIG. 5B is an enlarged portion of FIG. 5A.

Comparative Examples 1 and 2

Comparative Examples 1 and 2 are also examples of the process of plate-forming the polymer powder, but some process conditions are different from those of Experimental Examples 1 to 13 described above (see Table 1). More specifically, in the case of Comparative Example 1, compared to Experimental Example 4 using a 1 mm ball, the size of the ball is larger as 5 mm. And in the case of Comparative Example 2, the ball size is 2 mm, but the milling speed is 800 rpm.

6a and 6b are SEM pictures of the plate-shaped polymer powder prepared according to the process conditions of Comparative Example 1 in Table 1 below, and FIG. 6b is an enlarged portion of FIG. 6a. And Figures 7a and 7b are SEM pictures of the plate-shaped polymer powder prepared according to the process conditions of Comparative Example 2 in Table 1 below, and Figure 7b is an enlarged portion of Figure 7a.

Table 1 shows the process conditions used in the plate-forming process of Experimental Examples 1 to 13 and Comparative Examples 1 and 2, that is, the diameter of the polymer powder (polymer size), the size of the ball (ball size), and the rotation speed of the stirrer (milling speed) And it is shown by comparing the process conditions and the result of Particle Size Analysis (PSA) of the plated polymer powder according to the experiment while changing some of the milling time. In Table 1, the particle sizes corresponding to 10%, 50%, and 90% of the volume accumulation from the smaller particle size side in the particle size distribution are indicated as D10, D50, and D90, respectively. And the item Span is a value of (D90-D10)/D50, showing the degree of uniformity of the size distribution of the polymer powder.

Referring to Table 1 and FIGS. 3A to 5B, it can be seen that as the ball size and milling time increase, the polymer particles are plated and the particle size (e.g., the particle size corresponding to the particle size D50) increases. can In addition, as the size of the ball increases, the size of the particle increases, but the uniformity (span) of the particle decreases, and damage occurs to the outer portion of the plate-shaped polymer particle. In addition, referring to Figures 6a to 7b, when the ball size, rotation speed, milling time is too large, for example, as in Comparative Example 1, the size of the ball is 4 mm or more (eg, 5 mm) or Comparative Example As shown in 2, when the rotation speed exceeds 600 rpm (eg, 800 rpm), it can be seen that the polymer particles are broken and it is difficult to plate them.

Although the present invention has been described in detail with preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is possible.

The plate-shaped polymer powder prepared according to the present invention can be used for manufacturing highly reliable conductive adhesives, conductive films, and the like.

Claims

preparing polymer powder; and

A method of plate-forming a polymer powder comprising the step of mechanically milling the prepared polymer powder into a plate shape.
According to claim 1,

The polymer powder is polyacrylonitrile (PolyAcryloNitrile, PAN), polymethyl methacrylate (PolyMetahyl MethAcrylate, PMMA), polystyrene (PS), polyethylene (PolyEthylene, PE) and polypropylene (PolyPropylene, PP). A method for plate-forming a polymer powder, characterized in that it is formed of at least one copolymer selected from the group consisting of:
According to claim 1 or 2,

The polymer powder has a spherical or amorphous shape with an average particle diameter of 1 to 60 μm,

The plate-shaped polymer powder produced as a result of the plate-forming step has a length of a long axis of 2 to 150 μm and a thickness of 0.2 to 2 μm, and a ratio of the length of the long axis to the thickness is 10 to 300. A method for plate-forming polymer powders.
According to claim 1 or 2,

The plate-forming step is characterized by mechanically milling the prepared polymer powder using at least one method selected from a ball mill method, an attrition mill method and a beads mill method A method for plate-forming polymer powders.
According to claim 4,

The plate-forming step is one selected from alcohols including methanol, ethanol, 1,2-propanol, ethylene glycol and glycerol A method of plate-forming a polymer powder, characterized in that mechanical milling is performed in a state in which the prepared polymer powder is dispersed in the above solvent.