WO2021177573A1

WO2021177573A1 - Process for preparing ethylene copolymer that is easy to extrude and granulate

Info

Publication number: WO2021177573A1
Application number: PCT/KR2020/019389
Authority: WO
Inventors: 전성해; 김라연; 김지성; 김학민; 박제훈; 허은정
Original assignee: 한화솔루션 주식회사
Priority date: 2020-03-04
Filing date: 2020-12-30
Publication date: 2021-09-10
Also published as: KR102565861B1; KR20210112067A

Abstract

The present invention relates to a process for preparing an ethylene copolymer through a copolymerization reaction and extrusion and granulation steps using raw materials comprising ethylene and α-olefin, and relates to a process for preparing an ethylene copolymer that is easy to extrude and granulate, in which the temperature of a copolymer resin to be introduced into an extruder is lowered in advance, thereby enabling the copolymer resin to be maintained in strand form at the rear of the extruder and be easily extruded and granulated. To this end, the present invention provides a process for preparing an ethylene copolymer, the process comprising: a preparation step of preparing raw materials comprising ethylene and α-olefin; a copolymerization step of copolymerizing the raw materials to prepare a copolymer resin composition; an impurity removal step of removing impurities by allowing the prepared copolymer resin composition to pass through a separation unit, and preparing a copolymer resin; an extrusion step of introducing and extruding the prepared copolymer resin into/through an extruder; and a granulation step of granulating the extruded copolymer resin, wherein, before the copolymer resin is introduced into the extruder, a cooling step before extrusion of lowering the temperature of the copolymer resin is performed.

Description

Manufacturing process of ethylene copolymer that is easy to extrude and granulate

The present invention relates to a method for producing an ethylene copolymer that is easy to extrude and granulate. In the process of extruding/granulating a copolymer of ethylene and alpha olefin, by controlling the temperature during the manufacturing process, the copolymer resin is It relates to a manufacturing method that can maintain the shape of the strand). In more detail, by injecting cold raw materials into the separator at the last stage or by lowering the temperature of the polymer introduced into the extruder in advance through a heat exchanger, the copolymer resin can maintain its strand form at the rear end of the extruder even for low-density and high-MI resins. It relates to a manufacturing process of an ethylene copolymer to facilitate extrusion and granulation.

In general, the manufacturing process of an ethylene copolymer is made through a step of preparing a copolymer resin composition by copolymerizing a compound such as ethylene and an alpha olefin, removing a solvent or impurities from the prepared copolymer resin composition, and then extruding. At this time, the extruded copolymer may be additionally subjected to a granulation step.

The extruder is generally an extruder using a plunger and an extruder using a screw, but it is preferable to use a screw extruder in the manufacturing process of the ethylene copolymer. In a screw extruder, the contents are advanced through a screw, and the advanced contents are shaped as they pass through an orifice-like structure called a die.

As it passes through the die, the ethylene copolymer is extruded in the form of a strand, and by re-granulating it, a desired product can be manufactured.

On the other hand, the shape of the strands of the copolymer discharged through the die may not be maintained. In particular, in the case of a resin having a low density and a high MI (melt index), extrusion and granulation are more difficult for the above reasons.

Melt index (MI) is an index expressed also as melt index or MFR (melt flow rate), and represents the flow rate when the melt is extruded under certain conditions, and represents the melt viscosity of the thermoplastic polymer. The unit is expressed in g/10min.

On the other hand, in order to prevent the problem that the shape of the strand of the copolymer passing through the die is not maintained, it is necessary to lower the temperature of the prepared copolymer. There is a practical limit to the temperature being lowered to the extent that the shape of the copolymer can be maintained inside the extruder. Therefore, it is necessary to discharge the copolymer to a temperature at which extrusion/granulation is easy at the rear of the extruder by lowering the temperature in advance before the copolymer is introduced into the extruder.

Korean Patent No. 10-1493531, which is a prior document, discloses a manufacturing apparatus having a separation vessel and an extruder for manufacturing an ethylene copolymer containing olefins such as ethylene and 1-butene. However, there is a difference in the polymerization method, and the method for solving the problem for overcoming the difficulty of granulation and the point that the strand shape is maintained at the rear of the extruder and the effect thereof are not disclosed, so it is still for the ease of extrusion / granulation method is required.

Another prior document, Korean Patent No. 10-1378892, discloses a method for producing an ethylene-octene copolymer, and discloses a process through a gas-liquid separator, an extruder, and a heat exchanger. However, the heat exchanger is used in the recirculation step, and the purpose for the ease of extrusion and granulation is not disclosed, and the location, purpose, and effect of the heat exchanger are also different, so that the strand shape is still maintained at the rear of the extruder. /A method for ease of granulation is required.

[Prior art literature]

[Patent Literature]

(Patent Document 1) Republic of Korea Patent Publication No. 10-1493531

(Patent Document 2) Republic of Korea Patent Publication No. 10-1378892

An object of the present invention is to solve all of the above problems.

An object of the present invention is to provide a series of manufacturing processes up to extrusion and granulation at the same time as preparing an ethylene copolymer containing ethylene and alpha olefin.

An object of the present invention is to allow the copolymer resin discharged from the rear of the extruder to maintain the strand shape by controlling the temperature of the copolymer resin composition injected into the extruder.

An object of the present invention is to make it possible to relatively lower the temperature of the rear end of the extruder for easy extrusion/granulation even in the case of a resin having a low density and a high MI.

The characteristic configuration of the present invention for realizing the characteristic effects of the present invention to be described later while achieving the object of the present invention as described above is as follows.

The method for producing an ethylene copolymer that is easy to extrude and granulate according to the present invention includes a preparation step of preparing a raw material containing ethylene and alpha olefin, a copolymerization step of preparing a copolymer resin composition by copolymerizing the raw material, and the prepared Removing impurities by passing the copolymer resin composition through a separation unit, removing impurities to prepare a copolymer resin, extruding the prepared copolymer resin by putting it into an extruder, and granulating the extruded copolymer resin In the manufacturing process of an ethylene copolymer comprising; a granulation step,

It is characterized in that the pre-extrusion cooling step of lowering the temperature of the copolymer resin before introducing the copolymer resin into the extruder is performed.

According to the present invention, the alpha olefin is propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1- It may be at least one selected from dodecene, 1-tetradecene, and 1-hexadecene.

According to the present invention, based on 100 parts by weight of ethylene, 10 to 40 parts by weight of the alpha olefin may be included.

According to the present invention, the separation unit may include a plurality of separators.

According to the present invention, at least one of the separators may return a portion of the input copolymer resin composition to be reused in the copolymerization reaction.

According to the present invention, the cooling step before extrusion may include a first pre-extrusion cooling step of lowering the temperature of the copolymer resin composition injected into the separator of the last stage in the separator of the last stage.

According to the present invention, the cooling step before the first extrusion may be made by introducing a hydrocarbon gas having 4 or less carbon atoms into the separator of the last stage.

According to the present invention, the hydrocarbon gas may be introduced at -40 to 100 ℃.

According to the present invention, the cooling step before the first extrusion may lower the temperature of the copolymer resin composition in the separator of the last stage to 100 to 200 °C.

According to the present invention, the pre-extrusion cooling step may include a second pre-extrusion cooling step of lowering the pre-extrusion temperature of the copolymer resin by providing a heat exchanger between the separation unit and the extruder.

According to the present invention, the heat exchanger may lower the temperature of the copolymer resin to 100 to 200 °C.

According to the present invention, it may further include a cooling step of cooling the copolymer passing through the extruder.

According to the present invention, the cooling step may cool the temperature of the copolymer to a temperature of 50 to 150 ℃.

In the manufacturing process of the ethylene copolymer, which is easy to extrude and granulate according to the present invention, the copolymer resin prepared through the copolymerization reaction is lowered to an appropriate temperature in advance before being introduced into the extruder so that the strand shape can be maintained at the rear of the extruder. And, furthermore, it can be made to facilitate extrusion and granulation.

In addition, it may be possible to accurately supply the required energy by setting the temperature of the copolymer resin composition before input to the extruder, which can maintain the strand shape at the rear end of the extruder.

1 is a view showing a flowchart of an ethylene copolymer manufacturing process that is easy to extrude and granulate according to the present invention.

2 is a graph expressing the correlation between the maximum die temperature and MI.

3 is a photograph of an example of manufacturing a resin according to whether or not a cooling step before extrusion is included.

The inventor can select or define appropriate terms or words in describing the invention, and in this case, the terms or words used are not limited to the meanings commonly used, but rather the intention of the inventor is taken into consideration. It should be interpreted so as to conform to the technical idea embodied in the invention.

Accordingly, the terms or words used in the present specification and claims cannot be regarded as being limited to their commonly used meanings. The above-described content is merely a preferred embodiment of the present invention, and will not represent or limit all of the present technical idea, so there may be examples corresponding to easily replaceable elements and equivalent ranges from the standpoint of those skilled in the art.

Hereinafter, on the basis of the above-mentioned principle, the manufacturing process of the ethylene copolymer, which is easily extruded and granulated according to the present invention, will be described in detail.

As shown in FIG. 1, the manufacturing process of an ethylene copolymer that is easy to extrude and granulate according to the present invention is a preparation step of preparing a raw material containing ethylene and alpha olefin, and copolymerizing the raw material to prepare a copolymer resin composition A copolymerization step to prepare, passing the prepared copolymer resin composition through a separation unit to remove impurities, removing impurities to prepare a copolymer resin, an extrusion step of injecting the prepared copolymer resin into an extruder and extruding, and the A granulation step of granulating the extruded copolymer resin may be included, and a pre-extrusion cooling step of lowering the temperature of the copolymer resin before introducing the copolymer resin into the extruder may be further included.

The preparation step is a step of preparing a raw material containing ethylene and alpha olefin for the copolymerization reaction. Olefin refers to all unsaturated hydrocarbon compounds containing one double bond between carbons in a molecule, and belongs to the alkene series. In the present invention, an alpha olefin is used, and the alpha olefin is an olefin in which a double bond is positioned at the alpha (1) carbon. Among them, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene and at least one alpha olefin selected from 1-hexadecene. said propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene and By using at least one alpha olefin selected from 1-hexadecene, an ethylene copolymer having an excellent impact resistance effect can be obtained.

Meanwhile, 10 to 40 parts by weight of the selected alpha olefin may be included based on 100 parts by weight of ethylene. When ethylene and alpha olefin are used in a mixing ratio other than this, a _{problem in impact resistance or melting point (T m} ) may be too low.

After the raw materials are prepared, a copolymerization step of preparing a copolymer resin composition by copolymerizing the raw materials is performed. The copolymerization reaction may be prepared by a solution polymerization method or a slurry polymerization method, and examples of the solvent include C _5-12 aliphatic hydrocarbon solvents such as pentane, hexane, heptane, nonane, decane and isomers thereof; aromatic hydrocarbon solvents such as toluene and benzene; hydrocarbon solvents substituted with chlorine atoms such as dichloromethane and chlorobenzene; mixtures thereof, and the like, but are not limited thereto.

The copolymer resin composition prepared through the copolymerization reaction may contain impurities such as isomers, volatiles, and solvents. Accordingly, an impurity removal step of extracting a high-purity copolymer resin from the copolymer resin composition by removing these impurities is performed.

The step of removing impurities may be performed by passing the prepared copolymer resin composition through a separation unit. The separation unit may consist of a plurality of separators, preferably a series of separators consisting of two to three separators. The at least one separator may be configured to return a portion of the input copolymer resin composition for reuse in the copolymerization reaction. Therefore, it is possible to control the purity of the copolymer resin that has passed through the separation unit.

The prepared copolymer resin is introduced into an extruder and undergoes an extrusion step in which it is extruded. That is, the copolymer resin passes through the extruder to become a copolymer having the required physical properties. The extruder may preferably be a screw-type extruder. The extruder may include a hopper to which the copolymer resin is supplied, a screw for advancing the supplied copolymer resin, and a die plate (die) through which the moved copolymer resin is passed and extruded. The die is a configuration in which a hollow of a specific shape and a small size is formed, and as the copolymer resin passes through the die, it can have physical properties such as a required diameter.

Afterwards, the copolymer extruded through the extruder may be finally subjected to a granulation step.

On the other hand, when the molecular weight of the product is low, the polymer strand shape of the ethylene copolymer resin drawn out from the rear end of the extruder may not be maintained. In this case, the extrusion and granulation steps may be difficult or impossible. Also, in the case of a resin having a low density and a high melt index (MI), the same phenomenon may occur.

Therefore, it is necessary to relatively lower the temperature of the rear end of the extruder in order to prevent this phenomenon. Here, the temperature at the rear end of the extruder is referred to as a die temperature.

Here, the relationship between the maximum die temperature for maintaining the strand shape of the ethylene copolymer resin, the density of the copolymer resin, and MI is shown in Table 1 below, and when expressed as an equation, Equation 1 follows.

[Table 1]

[Equation 1]

In addition, FIG. 2 is a graph showing the correlation between the maximum die temperature and MI according to the above equation. That is, since an ethylene copolymer having required physical properties can be prepared by controlling the die temperature, it is essential to have a means for controlling the die temperature.

However, in general, the temperature of the ethylene copolymer resin withdrawn from the separation unit may be 200° C. or higher. That is, when the separation unit is composed of a plurality of separators, the temperature withdrawn from the last separator may be generally 200° C. or higher.

In this case, when the ethylene copolymer is introduced into the extruder at a temperature of 200° C. or higher, there is a limit to cooling the ethylene copolymer resin to a required temperature by removing heat only inside the extruder. Therefore, it is necessary to lower the temperature of the ethylene copolymer resin introduced into the extruder in advance.

To this end, in the manufacturing process of the ethylene copolymer, which is easily extruded and granulated according to the present invention, a pre-extrusion cooling step of lowering the temperature of the copolymer resin before introducing the copolymer resin into the extruder may be further performed.

In the cooling step before extrusion, the temperature of the copolymer resin composition input to the separation unit in the impurity preparation step is lowered in advance in the last separation unit, or a heat exchanger is provided between the separation unit and the extruder to transfer the temperature of the copolymer resin to the extruder. It can be lowered before input. Of course, one of the two means may be selectively employed, or both means may be employed as needed.

Detailed description of the pre-extrusion cooling step, the present invention may further include a first pre-extrusion cooling step of lowering the temperature of the copolymer resin composition put into the last stage separator in the last stage separator. That is, in the case of lowering the temperature of the copolymer resin composition in the separation unit, if the separation unit consists of a plurality of separators, it is preferable to lower the temperature of the copolymer resin composition input to the separator of the last stage. In this case, the copolymer resin composition inside the separator of the last stage may be lowered to a temperature of 100 to 200° C. and then introduced into the extruder. In this case, the temperature of the copolymer resin composition input to the separator of the last stage may be lowered by introducing a low-temperature hydrocarbon gas having 4 or less carbon atoms into the separator of the last stage. Preferably, the low-temperature hydrocarbon gas having 4 or less carbon atoms may be -40 to 100°C.

Meanwhile, the present invention may further include a second pre-extrusion cooling step of lowering the pre-extrusion temperature of the copolymer resin by providing a heat exchanger between the separation unit and the extruder as described above. In this case, the heat exchanger may lower the temperature of the copolymer resin to 100 to 200°C.

The extrusion step is a step in which the copolymer resin is introduced into an extruder and extruded through a die. In addition, the manufacturing process of the ethylene copolymer according to the present invention may further include a granulation step of granulating the copolymer resin extruded through an extruder. In addition, if necessary, a cooling step of cooling the copolymer prepared during the process of passing through the extruder may be further included. In the cooling step, since the temperature of the copolymer passing through the extruder die is preferably 50 to 150° C., it is preferable to cool the temperature of the copolymer to 50 to 150° C. through the cooling step. If the extruded copolymer is not cooled, the shape of the polymer strand may not be maintained or the shape of the granulated pellet may be non-uniform.

Hereinafter, a preferred embodiment of the manufacturing process of the ethylene copolymer that is easy to extrude and granulate according to the present invention will be described in detail.

실시예: 압출 전 냉각 단계 포함Example: Including Cooling Step Before Extrusion

Copolymerization of ethylene and 1-octene was carried out under a continuous solution process using a metallocene catalyst. Specifically, in a 2.0L continuous solution polymerization reactor (CSTR), copolymerization was performed under conditions ^{of 150 o C and 90 bar using an n-hexane solvent.} Hydrogen was used as a chain transfer agent for molecular weight control, and triisobutylaluminum was used as a scavenger. After the ethylene-octene copolymer resin composition produced through the copolymerization reaction passes through a plurality of gas-liquid separators, the volatile material is lowered to less than 1% by weight. The ethylene-octene copolymer resin composition passed through the last separator passed through the heat exchanger and sent to the extruder to be collected as solid pellets through a pelletizer.

Through the above process, three types of ethylene-octene copolymers having the properties shown in Table 2 below were finally produced at 2 kg per hour.

[Table 2]

비교예: 압출 전 냉각 단계 미포함Comparative Example: Without cooling step before extrusion

An ethylene-octene copolymer having the same physical properties as Sample 3 was produced in the same manner as in Example except that the pre-extrusion cooling step of cooling before introducing the copolymer resin to the extruder was not included.

실험예 1: 최대 다이 온도 측정Experimental Example 1: Maximum die temperature measurement

The maximum die temperature that can be extruded and granulated by controlling the coolant temperature of the heat exchanger between the separator and the extruder so that the ethylene-octene copolymer that has passed through the extruder die in the manufacturing process of the above example can maintain the strand shape is shown in Table 3 below. . As shown in Table 2, in order to lower the ethylene-octene copolymer to a die temperature suitable for extrusion and granulation, cooling through a heat exchanger is required in addition to cooling inside the extruder.

실험예 2: 불량률의 측정Experimental Example 2: Measurement of defective rate

The defective rates of the Examples and Comparative Examples were measured and shown in Table 3. At this time, the normally prepared ethylene copolymer has the same shape as the normal resin of FIG. 3 , and the defective products included in the defective rate have the same shape as the defective resin of FIG. 3 .

[Table 3]

As mentioned above, although the present invention has been described in detail with preferred embodiments, the scope of the technical idea of the present invention is not limited to these embodiments. Accordingly, various modifications or equivalent ranges of embodiments may exist within the scope of the technical spirit of the present invention. Therefore, the scope of the technical idea according to the present invention should be interpreted by the claims, and the technical idea within the equivalent or equivalent scope should be interpreted as belonging to the scope of the present invention.

Claims

A preparation step of preparing a raw material containing ethylene and alpha olefin;

a copolymerization step of preparing a copolymer resin composition by copolymerizing the raw materials;

removing impurities by passing the prepared copolymer resin composition through a separation unit, and removing impurities to prepare a copolymer resin;

an extrusion step of extruding the prepared copolymer resin by inputting it into an extruder; and

In the manufacturing process of an ethylene copolymer comprising; a granulation step of granulating the extruded copolymer resin,

Pre-extrusion cooling step of lowering the temperature of the copolymer resin before injecting the copolymer resin into the extruder; Extrusion and granulation easy method for producing an ethylene copolymer, characterized in that performed.
According to claim 1,

The alpha olefin is propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1- A method for producing an ethylene copolymer that is easily extruded and granulated with at least one selected from tetradecene and 1-hexadecene.
According to claim 1,

With respect to 100 parts by weight of ethylene, the alpha olefin is a method for preparing an ethylene copolymer that is easy to extrude and granulate, wherein 10 to 40 parts by weight is included.
According to claim 1,

The separation unit is a method for producing an ethylene copolymer that is easy to extrude and granulate comprising a plurality of separators.
5. The method of claim 4,

At least one of the separators is a method for producing an ethylene copolymer that is easy to extrude and granulate by returning a portion of the input copolymer resin composition to be reused in the copolymerization reaction.
5. The method of claim 4,

The cooling step before extrusion,

A method for preparing an ethylene copolymer that is easy to extrude and granulate, comprising a first cooling step before extrusion of lowering the temperature of the copolymer resin composition input to the separator of the last stage in the separator of the last stage.
7. The method of claim 6,

The cooling step before the first extrusion is a method of producing an ethylene copolymer that is easy to extrude and granulate by adding a hydrocarbon gas having 4 or less carbon atoms into the separator of the last stage.
8. The method of claim 7,

The hydrocarbon gas is a method for producing an ethylene copolymer, which is easily extruded and granulated at a temperature of -40 to 100 °C.
7. The method of claim 6,

The first cooling step before extrusion is a method for producing an ethylene copolymer that is easy to extrude and granulate by lowering the temperature of the copolymer resin composition in the separator of the last stage to 100 to 200°C.
According to claim 1,

The cooling step before extrusion,

A method for producing an ethylene copolymer that is easy to extrude and granulate, comprising a second pre-extrusion cooling step of lowering the pre-extrusion temperature of the copolymer resin by providing a heat exchanger between the separation unit and the extruder.
11. The method of claim 10,

The heat exchanger lowers the temperature of the copolymer resin to 100 to 200 °C.
According to claim 1,

A method for producing an ethylene copolymer that is easy to extrude and granulate further comprising a cooling step of cooling the copolymer passing through the extruder.
13. The method of claim 12,

The cooling step is a method for producing an ethylene copolymer that is easy to extrude and granulate by cooling the temperature of the copolymer to a temperature of 50 to 150 °C.