KR102244068B1 - Preparation method of ethylene vinyl acetate - Google Patents

Abstract

The present invention relates to a method for producing an ethylene vinyl acetate copolymer having a sufficient tensile strength while containing a high content of vinyl acetate using an autoclave reactor.

Description

Production method of ethylene vinyl acetate copolymer {PREPARATION METHOD OF ETHYLENE VINYL ACETATE}

The present invention relates to a method for producing an ethylene vinyl acetate copolymer having a narrow molecular weight distribution and sufficient tensile strength while containing a high content of vinyl acetate using an autoclave reactor.

Ethylene vinyl acetate is a copolymer of ethylene and vinyl acetate. Depending on the content of vinyl acetate, the range of use is very wide, from hard materials to soft materials such as hot melt adhesives. It has this excellent feature.

In addition, ethylene vinyl acetate has a thermoplastic polymer or rubbery character, has excellent electrical insulation and voltage resistance, and has excellent transparency, barrier properties, adhesion, and UV properties. It is widely used for tapes, adhesives, various sheets, and the like, and has recently been expanding its use area with a protective film for photovoltaic devices such as solar cells.

In general, the ethylene vinyl acetate copolymer can be prepared by injecting ethylene and vinyl acetate into an autoclave reactor or a tubular reactor at an appropriate ratio into the reactor, and polymerizing under high temperature/high pressure conditions. At this time, if the amount of vinyl acetate input to the reactor increases, some vinyl acetate may act as a chain transfer agent, and eventually the molecular weight of ethylene vinyl acetate decreases and the melt index (MI) increases, resulting in tensile strength and There is a limit to the deterioration of the same mechanical properties.

Therefore, in the case of the existing ethylene vinyl acetate copolymer with a high vinyl acetate content, it has excellent flexibility and elasticity, but causes a problem of deteriorating mechanical properties and workability, so it is used for wires, foaming, compounds, etc. There was a limit.

Accordingly, while maintaining a high content of vinyl acetate required for ethylene vinyl acetate for use in wires, foaming, compounds, etc., a novel ethylene vinyl acetate copolymer having sufficient tensile strength by controlling polymerization conditions is maintained. Research on the method is still needed.

The present invention is to provide a method for producing an ethylene vinyl acetate copolymer having a narrow molecular weight distribution and sufficient tensile strength while containing a high content of vinyl acetate using an autoclave reactor.

The present invention comprises the step of polymerizing an ethylene monomer and a vinyl acetate monomer in an autoclave reactor in the presence of a low temperature initiator and a high temperature initiator,

The polymerization step is characterized in that the autoclave reactor (the highest temperature at the bottom of the reactor)-(the input gas temperature) is controlled at 130 to 170°C, and is carried out at a pressure of 1800 bar or more. Provides.

Hereinafter, a method for preparing an ethylene vinyl acetate copolymer according to a specific embodiment of the present invention will be described in more detail.

According to one embodiment of the invention, in the presence of a low temperature initiator and a high temperature initiator, comprising the step of polymerizing an ethylene monomer and a vinyl acetate monomer in an autoclave (Autoclave) reactor,

The polymerization step is characterized in that the autoclave reactor (the highest temperature at the bottom of the reactor)-(the input gas temperature) is controlled at 130 to 170°C, and is carried out at a pressure of 1800 bar or more. Can be provided.

In the case of the existing ethylene vinyl acetate copolymer having a high vinyl acetate content, the present inventors have excellent flexibility and elasticity, but a problem of deteriorating mechanical properties and workability is caused, so there is a limit to use it for purposes such as wires. Recognizing that, while maintaining a high content of vinyl acetate required for ethylene vinyl acetate, research was conducted on a new method for preparing an ethylene vinyl acetate copolymer having sufficient tensile strength.

As a result, when a low-temperature initiator and a high-temperature initiator are mixed and the polymerization conditions in the autoclave are controlled, an ethylene vinyl acetate copolymer having a narrow molecular weight distribution and excellent tensile strength while containing a high content of vinyl acetate can be prepared. It was confirmed through an experiment and the invention was completed.

Ethylene vinyl acetate copolymer can be prepared in an autoclave or tubular reactor.In general, ethylene vinyl acetate prepared in an autoclave reactor has a wide molecular weight distribution, and ethylene vinyl acetate prepared in a tubular reactor. Is characterized by a narrow molecular weight distribution, and it is common to select and manufacture a reactor according to the application.

However, in the case of using an autoclave reactor in which back-mixing takes place, since it is possible to maintain a uniform and high reaction temperature, higher vinyl than in the case of using a tubular reactor in which mixing occurs by turbulent plug flow. There is an advantage of producing an ethylene vinyl acetate copolymer having an acetate content.

Therefore, the manufacturing method of the above embodiment uses an autoclave reactor, but is a method of controlling polymerization conditions such as an applied initiator, temperature, and pressure in the reactor, and the molecular weight distribution is narrow even when the autoclave reactor is used, and tensile strength, etc. It is possible to prepare an ethylene vinyl acetate copolymer having excellent mechanical properties.

More specifically, the manufacturing method of the embodiment includes the step of polymerizing an ethylene monomer and a vinyl acetate monomer in an autoclave reactor in the presence of a low temperature initiator and a high temperature initiator.

In the following specification, the low-temperature initiator refers to an initiator capable of initiating and/or accelerating the reaction between the ethylene monomer and the vinyl acetate monomer at a temperature of 100 to 160°C, and the high-temperature initiator refers to the reaction at 160°C to 230°C. It refers to an initiator capable of initiating and/or accelerating at a temperature of.

In general, when only one initiator is used in the manufacture of an ethylene vinyl acetate copolymer, the initiator cannot react when the operating temperature is too low, and when the reaction temperature is too high, the initiator is decomposed before polymerization of the copolymer, resulting in an initiator efficiency. Fall or run away reactions can occur.

Therefore, when using a mixture of a low-temperature initiator and a high-temperature initiator as an initiator, as in the method for producing the ethylene vinyl acetate copolymer of the above embodiment, the operating temperature range (for example, (the highest temperature at the bottom of the reactor)-(injection By widening the gas temperature)), the production of ethylene vinyl acetate having a narrow molecular weight distribution can be increased.

In addition, the low-temperature initiator and the high-temperature initiator may be mixed and used in a weight ratio of about 5:95 to 90:10, preferably about 20:80 to 70:30.

The low-temperature initiator has a characteristic capable of initiating a polymerization reaction at a temperature lower than a general high-pressure radical polymerization reaction temperature, for example, DIPND (1,4-di (2-neodecanoylperoxyisopropyl) benzene), CUPND (Cumylperoxy neodecanoate). , SBPC(Di(sec-butyl) peroxydicarbonate), NBPC(Di(n-butyl)peroxydicarbonate), EHP(Di(2-ethylhexyl) peroxydicarbonate), TAPND(Tert-amylperoxyneodecanoate) and TBPND(Tert-butyl peroxyneodecanoate) One or more compounds selected from the group may be used.

In addition, the high-temperature initiator has a characteristic capable of initiating a polymerization reaction at a temperature higher than a general high-pressure radical polymerization reaction temperature, for example, TAPPI (Tert-amylperoxy pivalate), TBPPI (Tert-butylperoxy pivalate), INP ( Di(3,5,5-trimethylhexanoyl) peroxide), TAPEH (Tert-amylperoxy 2-ethylhexanoate), TBPEH (Tert-butylperoxy 2-ethylhexanoate), TBPIB (Tert-butylperoxy-isobutyrate), TBPIN (Tert-butylperoxy-3, At least one compound selected from the group consisting of 5,5-trimethylhexanoate) and TBPA (Tert-butylperoxyacetate) may be used.

In addition, the low-temperature initiator and the high-temperature initiator may be used by diluting the initiator stock solution in a hydrocarbon solvent in an amount of 20 to 80 wt%, preferably 30 to 70 wt%. At this time, as the hydrocarbon solvent, for example, one or more selected from the group consisting of n-decane, n-octane, iso-dodecane, and iso-octene may be used, or an Isopar-based solvent, which is a commercial product of a mixture of hydrocarbons, may be used. .

In addition, the polymerization step is performed by controlling the pressure of the autoclave reactor, the temperature of the input gas, the maximum temperature at the bottom of the reactor, and the maximum temperature at the top of the reactor. Can be reduced, the molecular weight distribution can be narrowed, and the tensile strength can be increased.

The temperature of the input gas of the autoclave reactor refers to an average of the temperature measured between a portion divided for distribution of the input gas to each stage of the reactor and a portion connected to the reactor. In addition, the maximum temperature at the bottom of the reactor and the maximum temperature at the top of the reactor mean the temperatures measured by the thermocouple installed at the lowest position of the reactor and the highest end of the reactor, respectively.

In particular, the (highest temperature at the bottom of the reactor)-(input gas temperature) of the autoclave reactor is a reaction condition related to the conversion rate, which is the rate at which the monomer is converted to a polymer, the molecular weight distribution of the polymerized copolymer, and the content of short and long chain branches. By controlling the (highest temperature at the bottom of the reactor)-(input gas temperature) at about 130 to 170°C, preferably at about 130 to 165°C, an ethylene vinyl acetate copolymer having mechanical properties such as more excellent tensile strength is obtained. It can be prepared by conversion.

In addition, the temperature of the input gas may be about 10 to 60 ℃, preferably about 20 to 50 ℃. When the temperature of the input gas is lower than 10℃, it is difficult to control the polymerization heat of the autoclave, which is an adiabatic reactor, and a lost reaction may occur. When the temperature of the input gas is higher than 60℃, the polymerization conversion rate is lowered and thus the production cost is reduced. It is not desirable.

In addition, the maximum temperature at the bottom of the autoclave reactor may be about 170 to 230°C, preferably about 180 to 220°C. When the maximum temperature at the bottom of the reactor is lower than 170°C, the polymerization conversion rate is lowered, which is not preferable in terms of production cost, and when the maximum temperature at the bottom of the reactor is higher than 230°C, the run away reaction is caused by the problem of thermal stability of the vinyl acetate monomer. Can occur.

In addition, the maximum temperature at the top of the autoclave reactor may be about 120 to 180°C, preferably about 130 to 170°C. When the maximum temperature at the top of the reactor is lower than 120℃, it is difficult to control the reaction temperature and a lost reaction may occur. When the maximum temperature at the top of the reactor is higher than 180℃, the amount of initiator for polymerization of the target polymer increases. It is not desirable in terms of production cost.

In addition, the polymerization step may be carried out at a pressure of about 1800 bar or more, preferably about 1800 to 2000 bar. When the pressure in the reactor is low, less than 1800 bar, the amount of initiator for the polymerization of the target polymer increases, which is not preferable in terms of production cost, and when it is higher than 2000 bar, it is difficult to control in terms of polymerization stability, resulting in a lost reaction or a run away reaction. This can happen.

And, in the manufacturing method of the ethylene vinyl acetate copolymer of the embodiment, the vinyl acetate monomer is included in about 15 to 30 parts by weight, preferably about 26 to 30 parts by weight, based on 100 parts by weight of the sum of the ethylene monomer and the vinyl acetate monomer. can do.

As described above, if a low-temperature initiator and a high-temperature initiator are mixed and the polymerization conditions in the autoclave reactor are controlled, ethylene having a narrow molecular weight distribution and excellent tensile strength even though the content of the vinyl acetate monomer is high (15 to 30 parts by weight). It is possible to prepare a vinyl acetate copolymer.

According to the method for producing an ethylene vinyl acetate copolymer using the autoclave reactor of the present invention, it is possible to prepare an ethylene vinyl acetate copolymer having a narrow molecular weight distribution and excellent tensile strength while containing a high content of vinyl acetate.

The invention will be described in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

Examples and Comparative Examples

An ethylene vinyl acetate copolymer was prepared in an autoclave reactor under the process conditions shown in Table 1 below, and MWD and MI of the prepared ethylene vinyl acetate copolymer were measured and shown by the following method.

(1) MI (melting index): It was measured with a load of 2.16 kg at 125° C. according to ASTM D1238.

(2) Molecular weight distribution: It was measured using size exclusion chromatography (SEC).

Process conditions Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 VA content (wt%) 28 28 28 28 28 Initiator EHP, TBPND, TBPPI TBPND, TBPPI TBPND, TBPPI EHP, TBPPI TBPND, TBPPI Pressure (bar) 1940 1940 1940 1880 1880 Input gas temperature (℃) 45 40 40 25 10 Reactor top temperature (℃) 150 150 150 150 155 Reactor bottom temperature (℃) 180 190 200 200 200 Maximum temperature at the bottom of the reactor-Input gas temperature (℃) 135 150 160 175 190 MWD 3.1 3.6 3.7 4.1 - MI(g/10min) 3.2 4.0 4.1 6.5 -

As shown in Table 1, in the autoclave reactor as in the above example, a low-temperature initiator and a high-temperature initiator were used together, and (the maximum temperature at the bottom of the reactor)-(input gas temperature) was controlled to 130 to 170°C. It can be seen that the ethylene vinyl acetate copolymer exhibits a low melt index value even though the vinyl acetate content is as high as 28%.

On the other hand, in the case of the comparative example in which (the maximum temperature at the bottom of the reactor)-(input gas temperature) was not controlled at 130 to 170°C, an ethylene vinyl acetate copolymer having a higher melting index compared to the example was prepared (Comparative Example 1) , When the temperature of the input gas was too low, a Lost reaction occurred (Comparative Example 2).

Claims (8)

In the presence of a low temperature initiator and a high temperature initiator, comprising the step of polymerizing ethylene monomer and vinyl acetate monomer in an autoclave reactor,
The polymerization step is characterized in that the autoclave reactor (the highest temperature at the bottom of the reactor)-(the input gas temperature) is controlled at 130 to 170°C, and is carried out at a pressure of 1800 bar or higher. .
The method of claim 1,
The low-temperature initiator and the high-temperature initiator are mixed in a weight ratio of 5:95 to 90:10.
The method of claim 1,
The low-temperature initiators are DIPND (1,4-di (2-neodecanoylperoxyisopropyl)benzene), CUPND (Cumylperoxy neodecanoate), SBPC (Di (sec-butyl) peroxydicarbonate), NBPC (Di (n-butyl) peroxydicarbonate), EHP (Di (2-ethylhexyl) peroxydicarbonate), TAPND (Tert-amylperoxyneodecanoate) and TBPND (Tert-butyl peroxyneodecanoate) at least one compound selected from the group consisting of, ethylene vinyl acetate copolymer production method.
The method of claim 1,
The high-temperature initiators are TAPPI (Tert-amylperoxy pivalate), TBPPI (Tert-butylperoxy pivalate), INP (Di(3,5,5-trimethylhexanoyl) peroxide), TAPEH (Tert-amylperoxy 2-ethylhexanoate), TBPEH (Tert-butylperoxy pivalate). Ethylene vinyl acetate, which is one or more compounds selected from the group consisting of 2-ethylhexanoate), TBPIB (Tert-butylperoxy-isobutyrate), TBPIN (Tert-butylperoxy-3,5,5-trimethylhexanoate) and TBPA (Tert-butylperoxyacetate). Method of making coalescence.
The method of claim 1,
A method for producing an ethylene vinyl acetate copolymer, characterized in that the temperature of the input gas is 10 to 60°C.
The method of claim 1,
The method for producing an ethylene vinyl acetate copolymer, characterized in that the maximum temperature at the bottom of the autoclave reactor is 170 to 230°C.
The method of claim 1,
The method for producing an ethylene vinyl acetate copolymer, characterized in that the maximum temperature at the top of the autoclave reactor is 120 to 180°C.
The method of claim 1,
The vinyl acetate monomer is characterized in that 15 to 30 parts by weight based on 100 parts by weight of the total of the ethylene monomer and the vinyl acetate monomer, the method for producing an ethylene vinyl acetate copolymer.