KR100435518B1 - The production of spherical polyethylene particle by emulsion crystallization - Google Patents

Abstract

The present invention relates to a method for producing a polyethylene spherical powder with improved productivity, and more particularly, to completely dissolving polyethylene in a good solvent to form a transparent homogeneous solution and to a polyethylene in a separate container. A non-solvent which is not soluble at all is mixed with a polyethylene solution and cooled to below the crystallization temperature of polyethylene, thereby inducing phase separation between the good solvent and the non-solvent to obtain a densely produced emulsion, and using the washing solvent to form particles. By dissolving and removing the good solvent and the non-solvent remaining in the product, an independent spherical polyethylene particle having a uniform particle size distribution is produced. Unlike the conventional manufacturing method, the production of a polymerization catalyst is unnecessary and the manufacturing cost is reduced by simplifying the process. The present invention relates to a method for producing polyethylene spherical powder with improved productivity, and an apparatus thereof. .

Description

Production method of polyethylene spherical powder with improved productivity and apparatus therefor {The production of spherical polyethylene particle by emulsion crystallization}

The present invention relates to a method for producing a polyethylene spherical powder with improved productivity, and more particularly, to completely dissolving polyethylene in a good solvent to form a transparent homogeneous solution and to a polyethylene in a separate container. A non-solvent which is not soluble at all is mixed with a polyethylene solution and cooled to below the crystallization temperature of polyethylene, thereby inducing phase separation between the good solvent and the non-solvent to obtain a densely produced emulsion, and using the washing solvent to form particles. By dissolving and removing the good solvent and the non-solvent remaining in the product, an independent spherical polyethylene particle having a uniform particle size distribution is produced. Unlike the conventional manufacturing method, the production of a polymerization catalyst is unnecessary and the manufacturing cost is reduced by simplifying the process. The present invention relates to a method for producing polyethylene spherical powder with improved productivity, and an apparatus thereof. .

Conventional polyethylene atomization uses catalysts to control shape and size. Korean Patent Publication No. 4086 has proposed a method for preparing a catalyst for producing spherical polyolefin particles. A magnesium chloride compound was used as a support for the catalyst, and a Ziegler-Natta spherical catalyst was prepared having a polydispersity of 1.01 to 1.2 having a particle size of 40 to 80 µm. As a result of ethylene polymerization with the prepared catalyst, polyethylene particles having a polydispersity of 1.02 to 1.3 with a particle size of 300 to 800 µm could be produced. In addition, Korean Patent No. 145240 used γ-alumina as a support, and prepared a catalyst impregnated with titanium. The catalyst had a particle diameter of 30 to 40 µm, and spherical particles of 300 to 650 µm were prepared as a result of ethylene polymerization.

However, the conventional polymerization method is harsh, the reaction conditions are not presented in the sub-micron several micrometers range. In addition, there is a problem of a polymerization catalyst production method and a separation problem.

Conventional methods for preparing powders of polymers synthesized by bulk polymerization were to separate and collect powders of a certain size through a mechanical grinding device such as a ball mill, but the disadvantage of the powder manufacturing method is that the bulk polymers are mechanically It takes a long time to grind, and there is a possibility of contamination by other foreign substances and physical change of particles due to grinding energy. In addition, the shape of the particles cannot be controlled by grinding, and other additional processes are required to obtain a powder having an appropriate particle size distribution and size.

Therefore, due to the low productivity and high manufacturing cost caused by mechanical grinding, the mechanical grinding method for mass production is practically impossible to use.

On the other hand, the representative TIPS (Thermally Induced Phase Separation) method is a method for producing particles by inducing phase separation between the polymer and the solvent while completely dissolving the polymer in a solvent, cooling to below the crystallization temperature of the polymer.

Cheol-rim Choi et al. In Korea Patent No. 148831 describes polyethylene terephthalate, a thermoplastic polymer, as a diglycidyl derivative, such as neopentyl glycol diglycidyl ether, polypropylene glycol diglycidyl ether, carbonic monoglycidyl ether, or phenol ether. After dissolving in a phase separation solvent such as a derivative, the mixture was cooled and a spherical powder having a size of 6 to 10 µm was obtained. In addition, by using the same method in Korean Patent No. 127095, nylon 6 and nylon 6,6 were dissolved in glycerin and ethylene glycol to prepare spherical particles having 8-20 μm after quenching.

WHHou et al. [WHHou, TBLloyd, Journal of Applied Polymer Science, 45, 1783 (1992)] dissolve nylon 6, nylon 6,6 in a theta solvent, a formic acid / water mixture, ethanol, and then quench Spherical particles ranging from 4 to 12 μm were prepared.

As a study on polypropylene, there is a research published by H. Matsuyama in Polymer (41, 8673 (2000)). They dissolved polypropylene in a concentration of 0.05 to 0.1% in diphenyl ether and methyl salicylate, and then cooled to 10 DEG C per minute to obtain a spherical powder. The approximate size was 0.6 to 0.97 mu m. However, no studies on polyethylene have been conducted.

In addition, as a technique for showing the difference in the mechanism of the production of emulsion in the US Patent No. 4,110,529 to prepare a spherical porous polyacrylonitrile particles by dispersing the polymer solution in a non-solvent. Nevertheless, anisotropic particles were produced in which the pore distribution was concentrated in the particle center, and since the surface of the particles was difficult to control, it was difficult to produce particles that could be used for size exclusion chromatography (SEC), which is a practical use. In addition, this invention does not mention the manufacture of dense particle | grains.

Complementing the shortcomings of the patent, US Pat. No. 5,314,923 discloses a method for producing isotropic polyacrylonitrile particles. DMSO, DMF, and dimethyl sulfone, which do not cause chemical modification of the polymer, were selected as solvents, and urea, water, propylene glycol, and ethylene glycol were selected as the emulsifying nonsolvent.

On the other hand, the particle generation research results for the vinyl-based polymer containing a double bond and the carbon-based polymer containing a carbonyl group, such as polyethylene. Here, the vinyl polymer containing a carbonyl group is, for example, alkyl methacrylate such as methyl methacrylate, methacrylic acid.

In 1978, Naito dissolved a copolymer of methacrylic acid-methyl methacrylate and acrylic acid-methyl methacrylate in a solvent consisting of secondary-butanol or tert-butanol and ethyl acetate as a hydrophobic organic solvent. Dispersed in water in the presence of the active agent to obtain porous particles of about 3 to 5 ㎛. The purpose of Naito's manufacture of polymer particles was to increase the storage performance of photosensitive materials by coating polymers to prevent static or particle adhesion between surfaces of photosensitive materials such as silver halides.

Polyethylene can be found in most organic solvents at room temperature, unlike polyamide, polymethylmethacrylate, polystyrene, and polyvinyl alcohol, which have been studied until now in the Polymer handbook (4th ed.) By Brandrup and Immergut. It is not soluble in water, and when the temperature is increased, it is soluble in xylene, halogenated hydrocarbons, ketones and aliphatic esters. Using this property, Korean Patent No. 2001-13416 discloses a patent for producing porous polyolefin particles. Solvents used herein are alkanes, cycloalkanes, aromatic hydrocarbons, polycyclic aromatic compounds, and the like. Water, acetone, and methanol were selected as nonsolvents to be emulsified. In order to control the size of the porous polyolefin particles in the non-solvent, a surfactant was added, and the prepared polyolefin particle size was a relatively large porous particle of 0.5 to 12 mm.

In addition, a method using a nucleating agent for inducing secondary nucleation is disclosed in Korean Patent Publication No. 1999-0071923. The disclosed patent does not control the shape of the particles, but produces a narrow distribution of porous particles, and does not mention the production of dense particles.

In the literature published so far, a method for producing porous particles by a method of emulsifying a polymer solution in a non-solvent is disclosed.

Yarovoy dissolves Ultrahigh Molecular Weight Polyethylene (UHMWPE) in Decalin of 3,000,000 to 6,000,000 Molecular Weight, mixes it with non-solvent tetraglyme, and rapidly quench it as a homogenizer and rapidly quench 0.11. Particles ranging from ˜0.85 μm were prepared [YKYarovoy, G. Baran, SL Wunder, R. Wang, Journal of Biomedical Materials Research, 53, 152 (2000)]. However, it failed to control the formation of particles, there is a problem that the particle production conditions are made in harsh conditions (polyethylene melting temperature 160 ℃, cooling temperature -70 ℃).

Therefore, the present inventors conducted a study to solve the disadvantages caused by mechanical grinding method or polymerization, the phase separation between the good solvent and the non-solvent according to the temperature without generating waste, excessive energy consumption, excess chemicals The present invention was completed by producing spherical polyethylene particles using.

Accordingly, an object of the present invention is to provide a method for producing polyethylene spherical powder through emulsion crystallization and a continuous batch device.

Figure 1 is a schematic diagram of a continuous batch device according to the production of polyethylene spherical powder of the present invention.

[Description of Major Symbols in Drawing]

1: good solvent dissolving device

2: non-solvent heating device

3: uptake type stirred crystallizer

4: strainer

5: separator

Figure 2 shows a scanning electron micrograph (magnification 2500) of the low density polyethylene spherical particles prepared according to Example 1.

Figure 3 shows a scanning electron microscope magnification (magnification 10000) of the low density polyethylene spherical particles prepared according to Example 1.

Figure 4 shows a scanning electron micrograph (magnification 1000) of the low density polyethylene spherical particles prepared according to Example 2.

Figure 5 shows a scanning electron microscope magnification (magnification 10000) of the low density polyethylene spherical particles prepared according to Example 2.

Figure 6 shows a scanning electron micrograph (magnification 1000) of the low density polyethylene spherical particles prepared according to Example 3.

Figure 7 shows a scanning electron microscope magnification (magnification 10000) of the low density polyethylene spherical particles prepared according to Example 3.

Figure 8 shows a scanning electron microscope magnification (magnification 10000) of the low density polyethylene spherical particles prepared according to Example 4.

Figure 9 shows a scanning electron microscope magnification (magnification 10000) of the low density polyethylene spherical particles prepared according to Example 5.

The present invention

1) dissolving polyethylene in a good solvent to form a transparent homogeneous solution;

2) heating the non-solvent having no solubility in polyethylene in a separate container of step 1) to a temperature above the polyethylene melting point;

3) mixing the polyethylene homogeneous solution of 1) with the heated nonsolvent of 2);

4) cooling the mixture to below the crystallization temperature of polyethylene to form an emulsion; And

5) After separating and filtering the polyethylene particles in the emulsion, characterized in that the method for producing a polyethylene spherical powder consisting of the step of drying by removing the good solvent and non-solvent remaining in the washing solvent.

It also includes the continuous and batch devices of FIG. 1.

The present invention will be described in more detail as follows.

The present invention forms a transparent homogeneous solution by completely dissolving polyethylene in a good solvent and at the same time a non-solvent having no solubility in polyethylene is mixed with the polyethylene solution and cooled to below the crystallization temperature of the polyethylene. By inducing phase separation to obtain a densely produced emulsion, and using a washing solvent to dissolve and remove the good solvent and non-solvent remaining in the particles to produce independent spherical polyethylene particles with a uniform particle size distribution, Unlike the above, there is no need to prepare a polymerization catalyst and a method and apparatus for producing a polyethylene spherical powder having improved productivity by reducing manufacturing costs through a simplified process.

First, various types of polyethylene are possible as starting materials, but do not meet the polyethylene waste, contaminated polyethylene, and product conditions for most polyethylenes, including commercial UHMWPE, LLDPE, HDPE, MDPE, LDPE, ULDPE, VLDPE, and for recycling purposes. The non-standard polyethylene is also possible to produce spherical particles through the manufacturing method according to the present invention.

Therefore, the kind of polyethylene is not important in particle production, Preferably low density polyethylene or high density polyethylene is used.

Referring to the step of preparing a polyethylene spherical powder according to the present invention as follows.

In step 1), 0.1-50% by weight of polyethylene is dissolved in the good solvent at 20-200 ° C. in the good solvent dissolving device 1 of the continuous batch device of FIG. 1 to obtain a transparent homogeneous solution. At this time, if the concentration of polyethylene is less than 0.1% by weight of polyethylene particles are small, there is a problem that is difficult to recover, if more than 50% by weight there is a problem in the injection of polyethylene, if the reaction temperature at the time of dissolution is difficult to dissolve less than 100 ℃ There is a problem, and if it exceeds 200 ° C, there is a problem in the operation of the process, which is not preferable.

Step 2) is carried out in a container separate from step 1), there is no solubility in polyethylene in the non-solvent heating device (2) of the continuous batch device of Figure 1 attached to the good solvent and phase separation behavior depending on the temperature The visible nonsolvent is heated at a temperature above the polyethylene melting point. At this time, the temperature above the polyethylene melting point is specifically 100 to 200 ℃.

On the other hand, the good solvent selection criteria of polyethylene suitable for the present invention is as follows.

① The boiling point of good solvent should be more than melting point of polyethylene based on the melting point of polyethylene.

② Above the melting point, polyethylene and good solvent should form a completely transparent homogeneous solution.

③ Do not cause chemical deformation such as oxidation or decomposition at high temperature.

④ It should be less toxic during process operation.

⑤ To produce emulsification according to temperature, polyethylene solution and non-solvent mixture should not be mixed at low temperature and should be mixed at high temperature.

Therefore, in the present invention, it is preferable to use linear alkanes such as decanol, dodecanol, and the like or mixtures thereof, which are good solvents having strong hydrogen bonding properties and affinity for polyethylene.

In addition, suitable non-solvent selection criteria for causing emulsification with temperature are as follows.

① Polymer solution and non-solvent mixture should not be mixed at low temperature and should be mixed at high temperature.

② There should be no solubility for polymers.

③ It should not cause chemical transformation such as oxidation or decomposition.

④ It should be less toxic under process conditions.

Thus, as a non-solvent for polyethylene, having affinity with a polymer solvent, dihydric alcohols such as diethylene glycol, triethylene glycol, tetraethylene glycol, ethylene glycol, derivatives thereof, or mixtures thereof are preferred, but are not limited thereto. It is not.

In the step 3), when the polyethylene homogeneous solution and the non-solvent are mixed in the aeration type stirred crystallizer 3, the good solvent and the non-solvent are completely mixed to form a transparent solution. The mixing ratio of the polyethylene homogeneous solution and the non-solvent is 1: 2 to 1: 150 (weight ratio) is preferable. At this time, if the mixing ratio of the polyethylene homogeneous solution and the non-solvent is less than 1: 150 (weight ratio), there is a problem of phase separation between the non-solvent and the good solvent, and if it exceeds 1: 2 (weight ratio), there is a problem of interparticle aggregation due to the instability of the emulsion. .

In step 4), when the mixture is stirred at 100 to 1000 rpm and cooled to below the polyethylene crystallization temperature at a rate of 0.1 to 10 ° C. per minute, a polyethylene emulsion is formed by phase separation between good solvent and non-solvent. The polyethylene crystallization temperature is 50 to 100 ℃. The polyethylene in the emulsion crystallizes and finally becomes particles of suitable shape. In general, the relationship between the particle size produced and the emulsion produced is represented by Equation 1 in a paper published by Garside in Powder Technology (63, 235 (1991)).

Where ρ _L and ρ _S are the density of the liquid and solid phases, respectively, d _p is the diameter of the particles and d _e is the diameter of the emulsion.

Therefore, it is determined that a polymer powder having various sizes can be prepared according to the selection of a suitable crystallization material and a solvent, a stirring method, and a temperature.

The final step is to separate the emulsion and filter it in the filter 4 of the continuous batch device of Figure 1 attached, and then to completely dissolve and remove the good solvent and non-solvent remaining in polyethylene to obtain a spherical powder Drying recovers uniform spherical polyethylene particles. At this time, available washing solvents are water, acetone, methanol, ethanol or mixtures thereof. In the separator 5 of the continuous batch device, the solvent and the non-solvent mixture remaining after the filtration are separated and recycled back to the good solvent dissolving device 1 and the non-solvent heating device 2.

When the spherical polyethylene particles are manufactured by the above-described manufacturing method and apparatus, the preparation of the polymerization catalyst is unnecessary, and the productivity can be improved and the manufacturing cost can be reduced by simplifying the process.

The spherical powder thus prepared has a diameter of 0.1 to 200 μm, which is useful for chromatographic fixation, catalyst carriers, standard particles and the like.

Hereinafter, the present invention will be described in detail based on the following examples, but the present invention is not limited thereto.

Example 1

In the good solvent dissolving apparatus 1, low-density polyethylene (LDPE) was made 0.5% in dodecanol, and then dissolved until completely dissolved at 138 ° C. 150 g of diethylene glycol, prepared at the same temperature, in the non-solvent heater 2 was transferred to an aeration type stirred crystallizer 3 and 9 g of the dissolved polymer solution was injected. The diethylene glycol and LDPE mixture was cooled to 38 ° C. under 530 rpm stirring, adjusting to 3 ° C. per minute. In the course of cooling, diethylene glycol and dodecanol were phase separated and an opaque emulsion was obtained. After the temperature reached 38 ° C., the crystal solution was filtered through a filter 4 to obtain spherical low density polyethylene. After washing off the dodecanol and diethylene glycol which remain | survived in polyethylene with acetone sufficiently, it dried. The average diameter of the spherical low density polyethylene particles obtained in this example was 1.8 µm.

Example 2

Under the same conditions as in Example 1, the injection amount was 11 g. The average diameter of the spherical low density polyethylene particles obtained in this example was 0.78 µm.

Example 3

Under the same conditions as in Example 1, the nonsolvent was triethylene glycol, and the amount of the nonsolvent was 100 g. The injection amount of the polymer solution was 6.71 g. The average diameter of the spherical low density polyethylene particles obtained in this example was 1.53 µm.

Example 4

Under the same conditions as in Example 1, the nonsolvent was triethylene glycol, and the amount of the nonsolvent was 100 g. The injection amount of the polymer solution was 8.5 g. The average diameter of the spherical low density polyethylene particles obtained in this example was 1.38 µm.

Example 5

Under the same conditions as in Example 1, the non-solvent was triethylene glycol, and the injection amount was 9.78 g. The average diameter of the spherical low density polyethylene particles obtained in this example was 1.54 µm.

Example 6

Ultra-high molecular weight polyethylene (UHMWPE) was made 0.1% to dodecanol in the good solvent dissolving apparatus 1, and then dissolved until completely dissolved at 160 ° C. 150 g of diethylene glycol prepared at the same temperature in the non-solvent heater 2 was transferred to an aeration type stirred crystallizer 3 and 2 g of the dissolved polymer solution was injected. The diethylene glycol and LDPE mixture was cooled to 38 ° C. under 530 rpm stirring, adjusting to 3 ° C. per minute. In the course of cooling, diethylene glycol and dodecanol were phase separated and an opaque emulsion was obtained. After the temperature reached 38 ° C., the crystal solution was filtered through a filter 4 to obtain spherical low density polyethylene. Dodecanol and diethylene glycol remaining in polyethylene were sufficiently washed with acetone and dried. The average diameter of the spherical low-density polyethylene particles obtained in this example was 2.1 µm.

As described above, the method for producing the spherical polyethylene particles according to the present invention does not require surfactants or initiators necessary for the production of existing polymer particles such as emulsion polymerization, and is advantageous in terms of excessive chemical use or low energy consumption. Useful for chromatography, stationary phases, catalyst carriers, standard particles and the like.

Claims (14)

1) dissolving polyethylene in a good solvent to form a transparent homogeneous solution; 2) heating the non-solvent having no solubility in polyethylene in a separate container of step 1) to a temperature above the polyethylene melting point; 3) mixing the polyethylene homogeneous solution of 1) with the heated nonsolvent of 2); 4) cooling the mixture to below the crystallization temperature of polyethylene to form an emulsion; And 5) After the separation and filtration of the emulsion, a method for producing a product improved polyethylene spherical powder, characterized in that consisting of the step of removing the remaining good solvent and non-solvent in the washing solvent. The method according to claim 1, wherein the polyethylene concentration of 1) is 0.1 to 50% by weight. The method according to claim 1, wherein the polyethylene is dissolved in a good solvent at a temperature of 20 to 200 ° C. The method according to claim 1, wherein the good solvent of 1) is linear alkanols. 5. The method of claim 1, wherein the solvent is decanol, dodecanol, or a mixture thereof. The method according to claim 1, wherein the temperature above the polyethylene melting point of 2) is in the range of 100 to 200 ° C. The method according to claim 1, wherein the non-solvent of 2) is a dihydric alcohol. 8. The method of claim 1, wherein the non-solvent is ethylene glycol, diethylene glycol, triethylene glycol, derivatives thereof, or mixtures thereof. The method according to claim 1, wherein the mixing ratio between the polyethylene homogeneous solution and the non-solvent of 3) is 1: 2 to 1: 150 (weight ratio). The method according to claim 1, wherein the mixture of 4) is cooled to 0.1 to 10 ° C. per minute while stirring at 100 to 1000 rpm. The method for producing polyethylene spherical powder according to claim 1, wherein the polyethylene crystallization temperature of 4) is 50 to 100 ° C. The method according to claim 1, wherein the washing solvent of 5) is water, acetone, methanol, ethanol alone or a mixture thereof. The method of claim 1, wherein the diameter of the spherical powder is 0.1 to 200 ㎛ production method of the polyethylene spherical powder with improved productivity. Good solvent dissolving device (1) for injecting polyethylene and dissolving it in good solvent (1), nonsolvent heating device (2) for heating non-solvent without solubility in polyethylene, and aeration-type stirring for mixing good solvent and non-solvent A continuous batch device comprising a crystallizer (3), a filter (4) for recovering spherical polyethylene particles, and a separator (5) for recycling the remaining polyethylene.