Method for producing polyolefin powder

Abstract

A method for producing a polyolefin powder. The present invention relates to a method for producing a polyolefin ultrafine powder and a polyolefin ultrafine powder produced by the production method. Specifically, a polyolefin melt is produced by mixing and heating a polyolefin resin and a xylene mixed solvent, and then the polyolefin melt is cooled and crystallized. And performing a reduced pressure wet pulverization step in which the crystallized reactant is subjected to wet pulverization and drying together with the solvent, and a step in which ultrafine pulverization is performed by dry pulverization, thereby providing an ultrafine polyolefin powder having an average particle size of approximately 30 [mu] m or less. According to the present invention, the xylene mixed solvent is used as the mixed solvent for melting the polyolefin resin, and the manufactured ultrafine polyolefin powder can be applied to the field of general-purpose materials such as buildings, civil engineering, chemical products and the like, and particularly has physical properties beneficial to manufacturing of secondary battery electrodes.

Description

Technical Field

[0001] This invention relates to a polyolefin powder with a small and uniform size at the micrometer level and a method for manufacturing the same. The polyolefin powder according to the invention has an average particle size and physical properties that are not only applicable to general material fields such as construction, civil engineering and chemical products, but also effectively applicable to the manufacture of secondary battery electrodes. Background Technology

[0002] Polyolefin polymer resins such as polypropylene (PP) and polyethylene (PE) are inexpensive and easy to process, making them representative general-purpose plastic materials widely used in films, sheets, pipes, and fibers.

[0003] The technology of micronizing general-purpose polyolefin polymer resins as described above into micron-sized particles and applying them to entirely new fields is attracting attention.

[0004] Existing methods for producing polyolefin resin powder involve feeding resin particles of 3–5 mm in size into a specific pulverizer equipped with blades, and repeatedly cutting, grinding, and polishing them at high speed to obtain powder. However, unlike metals and inorganic materials, polyolefin resins are plastic elastomers, which are difficult to mechanically pulverize due to their inherent elasticity. This makes it difficult to produce micron-sized fine particles and also results in low production yields.

[0005] In particular, for polypropylene, it is difficult to obtain powder of the required size through ordinary mechanical crushing. Therefore, a cryogenic crushing method is adopted, in which the polyolefin resin is cooled to below its brittle temperature by means of liquid nitrogen or dry ice and then crushed. However, the powder produced by the cryogenic crushing method described above still has the problems of large particle size, uneven particle size distribution, irregular particle shape and high manufacturing cost.

[0006] Prior technology documents

[0007] Patent documents

[0008] (Patent Document 0001) Korean Patent Registration No. 1418786 (July 7, 2014) Summary of the Invention

[0009] The present invention aims to solve the problems existing in the prior art as described above by providing a method for manufacturing micro-fine polyolefin powder with uniform particle shape, average particle size, and particle size distribution in micrometer units.

[0010] Therefore, after producing a polyolefin melt by mixing a xylene mixed solvent and a polyolefin resin raw material adjusted to a specific composition ratio, the melt is crystallized and chemically pulverized, followed by a mechanical pulverization process under optimal conditions, thereby producing ultrafine polyolefin powder with an average particle size of less than 30 μm in micrometers.

[0011] As one embodiment of the present invention for solving the problems existing in the prior art as described above, a method for manufacturing polyolefin ultrafine powder can be provided, comprising: a melting step of heating a polyolefin molten liquid after mixing a polyolefin resin with a xylene mixed solvent; a crystallization step of cooling the polyolefin molten liquid to produce a crystallized mixture; a vacuum wet pulverization step of stirring under reduced pressure in order to simultaneously perform pulverization and drying on the crystallized mixture obtained in the crystallization step; and a dry pulverization step of dry pulverizing the powder after vacuum wet pulverization to pulverize the average particle size to less than 30 μm.

[0012] The polyolefin resin is preferably polyethylene and / or polypropylene.

[0013] The xylene mixed solvent may include: xylene; C6-8 aromatic components including ethylbenzene, benzene and toluene, but excluding xylene; and non-aromatic components not included in xylene and the C6-8 aromatic components.

[0014] Within the xylene mixed solvent, the C6-8 aromatic component may comprise less than 80 wt%.

[0015] In addition, the stirring speed in the vacuum wet grinding step can exceed 380 rpm, the gauge pressure in the vacuum wet grinding step is -0.05 to -0.1 MPa, and the heating temperature in the melting step is preferably 120 to 140°C.

[0016] The micronization step can be performed once, or repeated at least twice.

[0017] As another embodiment of the present invention, a polyolefin ultrafine powder can be provided, which is manufactured by the method described above, and the average particle size of the polyolefin ultrafine powder after the micronization step is 30 μm or less.

[0018] As another embodiment of the present invention, a secondary battery electrode comprising the polyolefin ultrafine powder as described above can be provided.

[0019] The polyolefin ultrafine powder manufactured by the multi-stage polyolefin particle manufacturing method of the present invention, which organically combines chemical crushing engineering and mechanical crushing engineering, has an average particle size of less than 30 μm and a uniform particle distribution. Therefore, in addition to general materials fields such as construction, civil engineering and chemical products, it can also be effectively applied to the manufacture of secondary battery electrodes. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the manufacturing process of polyolefin ultrafine powder according to one embodiment of the present invention. Detailed Implementation

[0021] Before proceeding with a detailed description of the preferred embodiments of the present invention, it should be understood that the terms or words used in this specification and claims should not be limited to their general or dictionary meanings, but should be interpreted as meanings and concepts consistent with the technical ideas of the present invention.

[0022] Throughout this description, when a part is described as "including" a constituent element, it does not mean that other constituent elements are excluded, but rather that other constituent elements may be included, unless otherwise expressly stated to the contrary.

[0023] Throughout this specification, regarding the use of "%" to indicate the concentration of a particular substance, unless otherwise stated, solid / solid means (weight / weight)%, solid / liquid means (weight / weight)%, and liquid / liquid means (weight / weight)%.

[0024] In each step, unless a specific order is explicitly stated in the context, the steps may be executed in a different order than that stated. That is, the steps may be executed in the same order as stated, may be executed simultaneously, or may be executed in the reverse order.

[0025] The embodiments of the present invention will now be described. However, the scope of the present invention is not limited to the preferred embodiments described below, and those skilled in the art to which this invention pertains may implement it in various different modifications based on the description in the specification.

[0026] This invention relates to a method for manufacturing ultrafine polyolefin powder, providing a method different from existing mechanical pulverization methods to produce ultrafine polyolefin powder with micron-level dimensions and uniform size. The ultrafine polyolefin powder according to this invention is applicable to general materials fields such as construction, civil engineering, and chemical products, and is particularly effective in the manufacture of secondary battery electrodes.

[0027] The method for manufacturing polyolefin ultrafine powder according to the present invention includes: a melting step of heating a polyolefin melt after mixing a polyolefin resin with a xylene mixed solvent; a crystallization step of cooling the polyolefin melt to produce a crystallized mixture; a vacuum wet pulverization step of stirring under reduced pressure in order to simultaneously perform pulverization and drying on the crystallized mixture obtained in the crystallization step; and a dry pulverization step of dry pulverizing the powder after vacuum wet pulverization to pulverize the average particle size to less than 30 μm.

[0028] The polyolefin resin may be polyethylene and / or polypropylene. For example, it may contain one or more selected from low-density polyethylene, high-density polyethylene, linear low-density polyethylene, homopolymer polypropylene, block polypropylene, and atactic polypropylene, but the polyolefin resins used are not limited thereto.

[0029] The xylene mixed solvent may include: xylene; ethylbenzene, benzene and toluene, but not the C6-8 aromatic components of xylene; and non-aromatic components not included in xylene and the aromatic components.

[0030] Xylene is an aromatic hydrocarbon with a chemical structure similar to benzene, and it consists of three isomers. Xylene is used as a solvent in various industries due to its high solubility, but it has the disadvantage of rapid evaporation.

[0031] The C6-8 aromatic component refers to an aromatic substance having 6 to 8 carbon atoms, including ethylbenzene, benzene, and toluene but excluding xylene. That is, in this specification, the term "C6-8 aromatic component" means "an aromatic substance having 6 to 8 carbon atoms, including ethylbenzene, benzene, and toluene but excluding xylene." The C6-8 aromatic component may include ethylbenzene, benzene, and toluene; as an example, the C6-8 aromatic component may be composed of ethylbenzene, benzene, and toluene.

[0032] As described above, the C6-8 aromatic component should be contained in the xylene mixed solvent at a concentration of less than 80 wt%. Because the boiling point of the C6-8 aromatic component is relatively lower than that of xylene, if the content of the C6-8 aromatic component exceeds 80 wt%, the solubility of the C6-8 aromatic component in the polyolefin resin will decrease during the melting process of mixing and heating the polyolefin resin with the xylene mixed solvent. Due to the aforementioned problems, it becomes difficult to manufacture polyolefin ultrafine powders to the required size, and the powder strength deviation will increase, potentially leading to larger particle sizes. Therefore, it is preferable that the C6-8 aromatic component be contained in the xylene mixed solvent at a concentration of less than 80 wt%.

[0033] The melting step involves heating a mixture of polyolefin resin and xylene solvent to produce a molten polyolefin liquid. In this step, the amounts of polyolefin resin and xylene solvent are not specifically limited; they can be mixed in appropriate amounts according to the type and characteristics of the polyolefin resin.

[0034] In this step, heating can be performed to melt the polyolefin resin, and the heating temperature can be 120-140°C. If the heating temperature is below this range, the polyolefin resin may not be fully melted. If the heating temperature exceeds this range, the rheological properties may change due to the rapid evaporation of xylene solvent, making it difficult to produce sufficiently fine polyolefin ultrafine powder in subsequent steps. Therefore, melting at the temperature described above is preferable.

[0035] In this step, stirring can be performed to ensure uniform melting, and the stirring conditions are not subject to any special limitations.

[0036] The crystallization step involves cooling the molten polyolefin to produce a crystallized mixture. The cooling temperature is not particularly limited; for example, cooling can be performed between 10 and 80°C. Through the cooling process described above, polyolefin can precipitate, thereby producing polyolefin powder. In this step, stirring can be performed during cooling to precipitate polyolefin powder of more uniform size; the stirring conditions are not particularly limited.

[0037] The reduced pressure wet pulverization step involves simultaneously pulverizing and drying the crystallized mixture by stirring it under reduced pressure. This step allows the solvent contained in the crystallized mixture to evaporate, thereby obtaining polyolefin powder.

[0038] The purpose of stirring in this step is to uniformly adjust the size of the obtained polyolefin powder while promoting solvent evaporation by stirring the crystallized mixture. The stirring speed can exceed 380 rpm, and is preferably above 480 rpm, and more preferably above 580 rpm.

[0039] If the stirring speed is too slow, it may be impossible to obtain sufficiently uniform polyolefin powder in this step, resulting in the particle size of the polyolefin powder obtained in the final step increasing to hundreds of micrometers, thus causing the problem of not being able to produce ultrafine powder. Therefore, it is advisable to stir under the stirring conditions described above.

[0040] In this step, stirring can be performed under reduced pressure, which allows for faster evaporation of the xylene mixed solvent, thereby producing ultrafine powder more efficiently. The gauge pressure for this reduced pressure is preferably -0.05 to 0.1 MPa. Exceeding this range may make it difficult to produce sufficiently small and uniform polyolefin ultrafine powder.

[0041] After the depressurized wet pulverization step described above, if residual solvent is still present, a drying step for solvent removal can be performed. In this step, the drying method is not particularly limited.

[0042] Next, a micro-pulverization step is performed to pulverize the powder, which has undergone vacuum wet milling, into an average particle size of less than 30 μm. This step involves pulverizing the powder under dry conditions using a high-speed rotating blade without any water or solvent. Through this step, ultrafine polyolefin powder with an average particle size of less than 30 μm can be produced.

[0043] In this step, to produce ultrafine powder with the particle size described above, the blade rotation speed is preferably 3,000–6,000 rpm, the internal temperature of the pulverizer is preferably 30–60°C, and the feed rate is 30–60 g / min. The micro-pulverization step described above can be performed once, or it can be repeated two or more times.

[0044] Through the process described above, ultrafine polyolefin powder with an average particle size of less than 30 μm can be produced. The method for producing ultrafine polyolefin powder according to the present invention is different from the existing method. It can produce ultrafine polyolefin powder with a very fine average particle size and uniform particle size. Moreover, it has the advantages of low manufacturing difficulty, high productivity and excellent yield.

[0045] The present invention includes ultrafine polyolefin powder with an average particle size of less than 30 μm, produced by the method described above according to one embodiment of the present invention.

[0046] Furthermore, the present invention includes a secondary battery electrode comprising the ultrafine polyolefin powder.

[0047] The specific functions and effects of the present invention will be described below through an embodiment of the invention. However, this is only a preferred embodiment of the present invention, and the scope of the claims is not limited by the embodiment.

[0048]

Example 1

[0049] Manufacturing of polyolefin melt

[0050] In a 5L three-necked flask reaction vessel equipped with a stirrer, 10 wt% polypropylene (homogeneous polypropylene with a specific gravity of 0.90) was added as a polyolefin resin, and 90 wt% xylene was added as a solvent. While stirring the mixture at 300 rpm, the temperature was increased and the mixture was held at 140°C for 60 minutes to melt the polypropylene into the xylene solvent, thereby producing a polyolefin melt.

[0051] As the xylene mixed solvent, a mixed solvent comprising 94.5 wt% xylene, 5.3 wt% C6-8 aromatic components (a mixture of ethylbenzene, benzene, and toluene) and 0.2 wt% non-aromatic components is prepared and used.

[0052] Manufacturing of crystallized mixtures

[0053] The polyolefin melt is cooled to room temperature to perform a crystallization process, thereby producing a crystallized mixture.

[0054] Manufacturing of polyolefin powder

[0055] The crystallized mixture was pulverized in a depressurized chamber, thereby performing depressurized pulverization that simultaneously performs drying and wet pulverization. The blades can rotate inside the depressurized chamber to pulverize and dry the contents, and a stirring speed of 580 rpm is maintained during depressurized pulverization, while wet depressurized pulverization is performed at a gauge pressure of -0.1 MPa for a residence time of 120 minutes.

[0056] The residual xylene mixed solvent is removed by drying the pulverized material after the depressurization wet pulverization process, and polypropylene ultrafine powder is produced by dry pulverizing the polypropylene powder after removing the xylene mixed solvent.

[0057] Dry grinding employs a method of grinding raw materials by feeding them into a rotating body and a stationary body equipped with multiple blades, using the high-speed rotating blades to grind the raw materials. Dry grinding was carried out under the conditions of a rotation speed of 5,000 rpm, an internal temperature of 50°C in the grinder, and a raw material feed rate of 50 g / min.

[0058]

Example 2

[0059] Except for changing the composition of the xylene mixed solvent to 80.5 wt% xylene, 19.3 wt% C6-8 aromatic components and 0.2 wt% other non-aromatic components, polypropylene ultrafine powder was produced by the same process as in Example 1.

[0060]

Example 3

[0061] Except for changing the composition of the xylene mixed solvent to 49.0 wt% xylene, 50.9 wt% C6-8 aromatic components and 0.1 wt% other non-aromatic components, polypropylene ultrafine powder was produced by the same process as in Example 1.

[0062]

Example 4

[0063] Except for changing the composition of the xylene mixed solvent to 35.0 wt% xylene, 64.9 wt% C6-8 aromatic components and 0.1 wt% other non-aromatic components, polypropylene ultrafine powder was produced by the same process as in Example 1.

[0064]

Comparative Example 1

[0065] Except for changing the composition of the xylene mixed solvent to 19.3 wt% xylene, 80.6 wt% C6-8 aromatic components and 0.1 wt% other non-aromatic components, polypropylene ultrafine powder was produced by the same process as in Example 1.

[0066] [Comparative Example 2]

[0067] Except that the xylene mixed solvent was replaced with 100 wt% of C6-8 aromatic components consisting of ethylbenzene, benzene, and toluene, polypropylene ultrafine powder was produced by the same process as in Example 1.

[0068]

Experimental Example 1

[0069] The particle size of the polypropylene ultrafine powders of Examples 1-4 and Comparative Examples 1 and 2, which were dry-milled, was measured multiple times using a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical), and the particle size is recorded in Table 1 in the form of "mean particle size ± standard deviation".

[0070] Table 1

[0071]

[0072] As can be confirmed from Examples 1 to 8 in Tables 1 and 2, ultrafine polyolefin powder with an average particle size of less than 30 μm can be produced by sequentially performing the chemical pulverization (reduced pressure wet pulverization) and mechanical pulverization processes according to the present invention. In particular, it can be confirmed that during the production of the polypropylene melt for chemical pulverization, the average size of the final particles obtained by the same process increases with the increase of the content of C6-8 aromatic components (see Examples 1 to 4).

[0073] Meanwhile, it can be confirmed that in order to produce ultrafine polyolefin powder with an average particle size of less than 30 μm, the C6-8 aromatic components in the xylene mixed solvent should be less than 80 wt% (see Examples 1 to 4 and Comparative Example 1 in Table 1).

[0074] The reason for the above-mentioned result is estimated to be that, in the composition of the xylene mixed solvent, the content of C6-8 aromatic components, including ethylbenzene, benzene and toluene, which have relatively low boiling points compared to xylene, is high. Therefore, the dissolving power of the C6-8 aromatic components of polypropylene resin is reduced during the heating process of the melting step in the production of polypropylene melt.

[0075] That is, the results in Table 1 confirm that the average particle size increases and the particle size distribution widens because the dissolving power of the polypropylene melt decreases. It can also be confirmed that in order to produce ultrafine polyolefin powder with an average particle size of less than 30 μm, the content of C6-8 aromatic components in the xylene mixture should be less than 80 wt%.

[0076] [Example 5 to Comparative Example 8]

[0077] In the polypropylene melt manufacturing step of Example 1, the amounts of polypropylene as a polyolefin resin and xylene mixed solvent were changed as shown in Table 2 below, and the polypropylene ultrafine powders of Examples 5 to 8 were manufactured through the same process as in Example 1.

[0078] The xylene mixture used at this time consists of 94.5 wt% xylene, 5.3 wt% C6-8 aromatic components, and 0.2 wt% other non-aromatic components.

[0079] [Comparative Example 3]

[0080] In Comparative Example 3, polypropylene and xylene mixed solvent were used in the same proportions as in Example 5, except that the composition of the xylene mixed solvent was changed to 19.9 wt% xylene, 80.0 wt% C6-8 aromatic components and 0.1 wt% other non-aromatic components. Polypropylene ultrafine powder was produced by the same method as in Example 5.

[0081] Comparative Examples 4 to 6

[0082] In Comparative Examples 4 to 6, polypropylene and xylene mixed solvents were used in the same proportions as in Examples 6 to 8, wherein the composition of the xylene mixed solvent was changed as shown in Table 2 below, and polypropylene ultrafine powder was produced.

[0083]

Experimental Example 2

[0084] The particle size of the polypropylene ultrafine powders of Examples 5-8 and Comparative Examples 3-6, which were dry-milled, was measured multiple times using a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical), and the particle size is recorded in Table 1 in the form of "mean particle size ± standard deviation".

[0085] Table 2

[0086]

[0087] Table 2 confirms that as the polypropylene resin content increases, the final particle size increases slightly. However, the xylene content in the xylene mixture (i.e., the content excluding C6-8 aromatic components and non-aromatic components) has a greater impact. In particular, while ultrafine powders with an average particle size of less than 30 μm were produced in Examples 5-8, larger powders (at least twice the size of the examples) were formed in Comparative Examples 3-6. This confirms that, as in Experimental Example 1, the C6-8 aromatic component content in the xylene mixture should ideally be less than 80 wt%.

[0088] Furthermore, even when the content of C6-8 aromatic components is below 80 wt%, insufficient polypropylene content or excessive xylene mixed solvent content can lead to increased average particle size and decreased production yield. Therefore, to produce ultrafine polypropylene powder, it is preferable to use 5–50 wt% polypropylene resin and 95–50 wt% xylene mixed solvent. In particular, it has been confirmed that mixing polypropylene resin and xylene mixed solvent at a weight ratio of 1:1 to 45 is preferable.

[0089] [Example 9 and Comparative Example 10]

[0090] The polypropylene ultrafine powder of Example 9 was manufactured according to the same manufacturing method as the polyolefin powder manufacturing method of Example 1, and the same polypropylene ultrafine powder as Example 9 was manufactured, except that the gauge pressure in the reduced pressure condition was changed to -0.05 MPa to manufacture Example 10.

[0091] [Comparative Examples 7 to 10]

[0092] Polypropylene ultrafine powders were produced in the same manner as in Example 9, including Comparative Example 7, which omitted the depressurization step in the wet depressurization process, and Comparative Examples 8, 9, and 10, which only adjusted the stirring speed to 380 rpm, 190 rpm, and 60 rpm, respectively.

[0093]

Experimental Example 3

[0094] The particle size of polypropylene powders from Examples 9, 10, and 7-10 that only completed the reduced pressure wet pulverization step, as well as the particle size of polypropylene ultrafine powders that completed the drying and dry pulverization steps, were measured multiple times using a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical). The results are recorded in Table 1 as “mean particle size ± standard deviation”.

[0095] Table 3

[0096]

[0097] Referring to the experimental results in Table 3, it can be confirmed that both the decompression conditions and the rotation speed in the decompression wet grinding step affect the final average particle size, with the rotation speed having a greater impact. In particular, when no decompression conditions were applied as described in Comparative Example 7, the particle size increased by more than 1.5 times compared to Examples 9 and 10, where decompression conditions were applied under the same conditions. This confirms that a pressure condition below atmospheric pressure (gauge pressure of -0.05 to -0.1 MPa) is required inside the decompression wet grinding chamber.

[0098] Furthermore, the results of Example 9 and Comparative Examples 8 to 10 confirm that the final average particle size decreases as the rotational speed increases. Therefore, a rotational speed of at least 380 rpm or more, or 480 rpm or more, is preferable, and most preferably 580 rpm or more.

Claims

1. A method for manufacturing ultrafine polyolefin powder, comprising: The melting step involves mixing polyolefin resin with xylene mixed solvent and then heating the mixture to produce a polyolefin melt. A crystallization step that produces a crystallized mixture by cooling the polyolefin melt; A vacuum wet pulverization step is performed by stirring under reduced pressure in order to simultaneously pulverize and dry the crystallized mixture obtained in the crystallization step. as well as, The powder that has undergone depressurized wet milling is then subjected to dry milling to reduce the average particle size to less than 30 μm.

2. The method for manufacturing polyolefin ultrafine powder according to claim 1, characterized in that: The polyolefin resin is polyethylene and / or polypropylene.

3. The method for manufacturing polyolefin ultrafine powder according to claim 1, The xylene mixed solvent includes: Xylene; It contains ethylbenzene, benzene, and toluene, but does not contain the C6-8 aromatic components of xylene; as well as, Non-aromatic components not included in xylene and the C6-8 aromatic components.

4. The method for manufacturing polyolefin ultrafine powder according to claim 3, characterized in that: Within the xylene mixed solvent, the C6-8 aromatic component comprises less than 80 wt%.

5. The method for manufacturing polyolefin ultrafine powder according to claim 1, characterized in that: The stirring speed in the vacuum wet pulverization step exceeds 380 rpm.

6. The method for manufacturing polyolefin ultrafine powder according to claim 1, characterized in that: The gauge pressure in the depressurized wet pulverization step is -0.05 to -0.1 MPa.

7. The method for manufacturing polyolefin ultrafine powder according to claim 1, characterized in that: The heating temperature in the melting step is 120–140°C.

8. The method for manufacturing polyolefin ultrafine powder according to claim 1, characterized in that: The micronization step may be performed once, or repeated at least twice.

9. A polyolefin ultrafine powder, The particles are manufactured by the method according to any one of claims 1 to 8, and the average particle size is less than 30 μm.

10. A secondary battery electrode, It contains the polyolefin ultrafine powder according to claim 9.

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