KR20210063108A - Ethylene vinyl acetate copolymer for extrusion coating with excellent processability and manufacturing method the same - Google Patents

Abstract

Disclosed are a polypropylene-based resin composition with improved barrier properties while maintaining rigidity and transparency without a laminated structure or adhesive coating to improve barrier properties, and a molded article using the same. The present invention provides the polypropylene-based resin composition, which comprises: 70 to 98 wt% of a polypropylene random copolymer comprising ethylene; 1 to 20 wt% of a polypropylene random terpolymer comprising ethylene and butene; and 1 to 10 wt% of dicyclopentadiene, and the molded article using the same.

Description

Ethylene vinyl acetate copolymer for extrusion coating with excellent processability and a manufacturing method therefor {ETHYLENE VINYL ACETATE COPOLYMER FOR EXTRUSION COATING WITH EXCELLENT PROCESSABILITY AND MANUFACTURING METHOD THE SAME}

The present invention relates to an ethylene vinyl acetate copolymer and a method for producing the same, and more particularly, to an ethylene vinyl acetate copolymer for extrusion coating and a method for producing the same.

In the case of general low-density polyethylene for extrusion coating and lamination, ethylene vinyl acetate resin is used for paper coating and kraft paper coating for waterproofing purposes, and is widely used for lamination and thermal bonding purposes such as plastic films.

Basically, the higher the molecular weight distribution (MWD), the less the extrusion load due to the low molecular weight shows a relatively stable flow characteristic in the extruder, and the high melt tension during T-Die casting due to the high molecular weight. It has a tendency to have excellent neck-in characteristics.

However, in recent years, as productivity has become more important, the draw-down characteristic has emerged as a more important processing property. Therefore, it is important to have a high discharge amount while receiving a load in the extruder due to a narrow molecular weight distribution characteristic, and to secure a drawdown property by having a small high molecular weight region. That is, the draw-down characteristic due to the existing wide molecular weight distribution and high molecular weight tends to be inhibited, and balancing the high molecular weight acts as an important factor in controlling the resin properties. In addition, if it has an excessively wide distribution of low molecular weight, die build-up may occur during T-Die casting, making it difficult to form a coating film.

On the other hand, in the case of the ethylene vinyl acetate copolymer provided by the conventional autoclave process, the molecular weight distribution is relatively wide, so it has the advantage that it can be advantageously designed in terms of neck-in characteristics or extrusion processability by melt tension, but it has relatively low draw-down characteristics. If a modifier is added to reinforce it, the properties of the part can be adjusted, but there is a difficulty in balancing the high molecular weight. On the other hand, in the case of the ethylene vinyl acetate copolymer provided by the tubular process, the drawdown characteristic is excellent because the molecular weight distribution is relatively narrow, but the melt strength is inferior to the resin provided in the autoclave process due to the characteristics of the resin, so coating such as neck-in characteristics It shows disadvantages in machinability.

Korean Patent Publication No. 2019-0022642 and US Patent Publication No. 2014-0303309 are high-pressure polymerization methods for forming ethylene-based polymers, and the reactor configuration includes a tubular reactor, an autoclave reactor, or both a tubular reactor and an autoclave reactor. However, it does not mention specific reactor conditions for improving neck-in and draw-down properties in the production of ethylene vinyl acetate copolymer.

Korean Patent Registration No. 19759696 relates to a method for separating components of a reactor off-gas and a related reactor system, wherein the reactor system may include a high-pressure tubular reactor and/or an autoclave reactor and may be used in the production of polyolefin polymers. Although the reactor system is disclosed, the polymerization reaction of low density polyethylene is only described in detail, but also specific reactor conditions for improving neck-in and draw-down properties in the production of ethylene vinyl acetate copolymer are not mentioned.

Japanese Patent Application Laid-Open No. 2002-080652 discloses an ethylene vinyl acetate copolymer prepared in an autoclave-type polymerization reactor or a tubular polymerization reactor, but does not mention the combined use of the polymerization reactor and improvement of processability due to this. .

The present invention intends to propose a specialized reactor condition for providing an ethylene vinyl acetate copolymer having excellent processability, particularly, both neck-in and draw-down properties, which are opposite properties, in the production of an ethylene vinyl acetate copolymer.

In order to solve the above problems, the present invention, (a) polymerization of an ethylene monomer and a vinyl acetate monomer in an autoclave reactor in the presence of a polymerization initiator and a modifier for controlling molecular weight distribution; and (b) adding the polymer polymerized in step (a) and the unreacted monomer to a tubular reactor to continuously polymerize it; provides a method for preparing an ethylene vinyl acetate copolymer comprising.

In addition, the autoclave reactor has a pressure of 1,700 to 2,200 kgf/cm 2 , an upper temperature of 140 to 170° C. and a lower temperature of 185 to 225° C., and the tubular reactor has a pressure of 1,700 to 2,200 kgf/cm 2 and a temperature of 185 It provides a method for producing an ethylene vinyl acetate copolymer, characterized in that to 225 ℃.

In addition, prepared by the above method, the melt index (ASTM D1238, 125 ℃, 2.16 kg load) is 10 to 25 g / 10 min, the vinyl acetate content is 10 to 30 wt%, the molecular weight distribution (MWD, Mw / Mn) Ethylene vinyl acetate copolymers having 4 to 6 and Z average molecular weights from 130,000 to 200,000 are provided.

In addition, it provides an ethylene vinyl acetate copolymer prepared by the above method and having a neck-in ratio of 25% or less, a maximum processing speed of 100 m/min or more, and an adhesive strength of 40 kgf/cm 2 or more, measured according to the following method.

[Method of measuring neck-in ratio]

Using an extrusion coating machine with a discharge width of 450 mm, the ethylene vinyl acetate copolymer prepared above is coated on a biaxially stretched polypropylene film at a die temperature of 230 ° C. When molding to a coating thickness of 20 μm at an extrusion coating processing speed of 60 m/min Calculate the coating width to the discharge width of the neck-in ratio as {1-(coating width/discharge width)}*100.

[Method of measuring maximum processing speed]

Using an extrusion coating machine with a discharge width of 450 mm, the resin discharge rate is fixed at 700 g/min, and the ethylene vinyl acetate copolymer is coated on a biaxially stretched polypropylene film at a die temperature of 230° C. and check the processing speed at the point when the resin flow is broken and coating is not performed.

[Measuring method of adhesive strength]

After coating the ethylene vinyl acetate copolymer on a biaxially stretched polypropylene film (40 μm thickness), lamination on a black paper substrate printed with ink printing at 100° C. and a speed of 3 m/min. Using a universal tensile tester, Load Cell 100 The adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured under the conditions of N and a speed of 200 mm/min.

According to the present invention, through the multi-process application of sequentially performing the autoclave process and the tubular process, the molecular weight distribution of the ethylene vinyl acetate copolymer is maximized, and the polymerization degree and high molecular weight reduction can be controlled by controlling the reactor pressure and temperature. By making this possible, as a result, the high molecular weight region is reduced and the molecular weight distribution is narrow, so that it is possible to prepare an ethylene vinyl acetate copolymer excellent in both neck-in and draw-down properties.

In addition, in the multi-polymerization process, it is possible to prepare an ethylene vinyl acetate copolymer having excellent adhesive strength, which is a post-processing property, by controlling the flowability and vinyl acetate content of the ethylene vinyl acetate copolymer.

Hereinafter, the present invention will be described in detail through preferred embodiments. Prior to this, terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors appropriately explain the concept of terms in order to explain their own invention in the best way. Based on the principle that it can be defined, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention. Accordingly, since the configuration of the embodiments described in the present specification is only the most preferred embodiment of the present invention and does not represent all the technical spirit of the present invention, various equivalents and modifications that can be substituted for them at the time of the present application It should be understood that there may be

The present inventors have found that it is difficult to satisfy both neck-in and draw-down properties in post-processing due to opposite molecular weight characteristics in the case of a single process using an autoclave reactor or a tubular reactor in the production of a conventional ethylene vinyl acetate copolymer, and autoclave Even in the multi-process that combines a reactor and a tubular reactor, the specific reactor conditions are not presented, so we faced a situation in which it is not easy to solve a problem through process control and as a result of repeated research, the autoclave process and the tubular process were sequentially performed. It is possible to control the molecular weight characteristics of the ethylene vinyl acetate copolymer by proceeding to the ethylene vinyl acetate copolymer, and furthermore, the molecular weight distribution of the ethylene vinyl acetate copolymer is maximized by controlling the pressure and temperature of each reactor, and the high molecular weight region is reduced while narrowing the molecular weight distribution. It was found that it is possible to have an ethylene vinyl acetate copolymer excellent in both neck-in properties and draw-down properties, resulting in the present invention.

Accordingly, the present invention comprises the steps of: (a) polymerizing an ethylene monomer and a vinyl acetate monomer in an autoclave reactor in the presence of a polymerization initiator and a modifier for controlling molecular weight distribution; and (b) adding the polymer polymerized in step (a) and the unreacted monomer to a tubular reactor to continuously polymerize it; discloses a method for preparing an ethylene vinyl acetate copolymer comprising.

In the present invention, in manufacturing the ethylene vinyl acetate copolymer, the molecular weight distribution (MWD, Mw/Mn) is maximized through the multi-process application of the autoclave process and the tubular process sequentially. It is possible to relatively easily control the molecular weight distribution by widening the reduction control range. In addition, it is possible to obtain a narrow molecular weight distribution by controlling the reactor temperature and pressure to maximize the effect of reducing the high molecular weight region. Therefore, it is possible to realize excellent drawdown properties with a relatively small high molecular weight region and narrow molecular weight distribution characteristics compared to the ethylene vinyl acetate copolymer provided in a single autoclave process, and compared to the ethylene vinyl acetate copolymer provided through a single tubular process. It is possible to provide a copolymer having an excellent neck-in property while having an equivalent drawdown property. In addition, it is possible to improve the adhesion strength of the ink with the printed paper by controlling the flowability and vinyl acetate content along with controlling the molecular weight properties.

In the present invention, the autoclave reactor may have a pressure of 1,700 to 2,200 kgf/cm 2 , an upper temperature of 140 to 170° C. and a lower temperature of 185 to 225° C., preferably a pressure of 1,850 to 2,050 kgf/cm 2, upper The temperature can be set at 145 to 165°C and the lower temperature at 195 to 215°C. Here, the upper temperature and lower temperature of the autoclave reactor mean temperatures measured by temperature sensors (thermocouples) installed at the highest stage of the reactor and the lowest stage of the reactor, respectively.

If the autoclave reactor pressure is less than 1,700 kgf / ㎠, a lot of long-chain branches of the ethylene vinyl acetate copolymer are generated, the Z average molecular weight is increased, the drawdown property in terms of processability may be reduced, and the reactor pressure is 2,200 kgf / cm 2 If it exceeds the limit operating value of the autoclave reactor, production stability may be problematic, long chain branches become too small, the Z average molecular weight becomes small, and the neck-in characteristics in terms of processability may be deteriorated.

In addition, in the autoclave reactor, if the upper temperature is less than 140 ° C, the long chain branches of the ethylene vinyl acetate copolymer are reduced, the Z average molecular weight is reduced, the neck-in characteristics in terms of processability may be lowered, and the upper temperature of the reactor is 170 ° C. When it exceeds, the long-chain branching of the ethylene vinyl acetate copolymer increases, resulting in an increase in the average molecular weight of Z, and the drawdown property may decrease in terms of processability.

In addition, if the lower temperature of the autoclave reactor is less than 185 ℃, the production load may be lowered, and if it exceeds 225 ℃, there may be a problem in the stability of the reactor. Drawdown properties may be deteriorated.

An initiator for initiating polymerization is used in the autoclave reactor. Although there is no limitation on the type of polymerization initiator used, two or more peroxides may be preferably used to achieve the object of the present invention, and from the viewpoint of the activity suitable for the reaction temperature, for example, at the upper part of the reactor, t -butyl peroxy Neo having an input decanoate (t -butyl peroxyneodecanoate), and the lower part of the de-can inject the butylperoxy isobutyrate (di-t-butyl peroxyisobutyrate) - t.

In addition, a modifier for controlling molecular weight distribution is used in the autoclave reactor. Although there is no limitation on the type of modifier used, 1-butene, 2-butene, isobutylene and The same C4 series olipine hydrocarbon may be selected. In this case, the amount of the modifier is preferably 120 to 200 kg/hr, more preferably 140 to 180 kg/hr. When the amount of the modifier input is less than 120 kg/hr, it may be difficult to control the molecular weight distribution by the modifier, and when it exceeds 200 kg/hr, the production of low molecules is maximized, so that the melt index and density increase, and the Z average 　 molecular weight decrease occurs. , which may result in a decrease in neck-in properties in terms of workability.

In polymerizing the ethylene vinyl acetate copolymer, the vinyl acetate monomer is added together with the ethylene monomer to the autoclave reactor, and may be added in an amount of 10 to 30% by weight based on the final copolymer, preferably 15 to 23% by weight. % content can be added. If the vinyl acetate content is less than 10% by weight, adhesive properties may be inferior, and if it exceeds 30% by weight, cross-linking gel is highly likely to occur in the T-Die extruder, and due to excessively high adhesive properties, the coating process It can be difficult to apply.

The ethylene vinyl acetate copolymer firstly polymerized in the autoclave reactor is a continuous reaction process, and the primary polymerized polymer and unreacted monomer are added to the tubular reactor installed at the rear end of the autoclave, and an additional process is performed.

By the additional reaction through the tubular reactor, ethylene vinyl acetate copolymer at a level of 1 to 10% by weight, 10% by weight or more depending on process conditions may be additionally produced, and through the secondary polymerization process through the tubular reactor The molecular weight distribution of the ethylene vinyl acetate copolymer is wider, and the output and production load are increased.

In the present invention, the tubular reactor has a pressure of 1,700 to 2,200 kgf / ㎠ and a reactor temperature of 185 to 225 ℃ in consideration of the neck-in and draw-down properties according to the generation of appropriate long-chain branches of the ethylene vinyl acetate copolymer. Preferably, the pressure may be set at 1,850 to 2,050 kgf/cm 2 and the reactor temperature at 195 to 215° C.

If the tubular reactor pressure is less than 1,700 kgf / ㎠, a lot of long-chain branches of the ethylene vinyl acetate copolymer are generated, so the Z average molecular weight increases, and the drawdown property in terms of processability may decrease, and the reactor pressure is 2,200 kgf / ㎠ If it exceeds, the long-chain branching becomes too small, the Z average molecular weight becomes small, and the neck-in characteristic in terms of workability may be deteriorated.

In addition, in the tubular reactor, when the temperature is less than 185 ° C, the reaction activity is lowered, so the improvement of properties and increase in the production load according to the additional reaction may be insignificant, and if it exceeds 225 ° C, the reaction activity is not stable, and high pressure, high temperature reaction This may cause safety issues.

An initiator for initiating polymerization may be added to the tubular reactor. Although there is no limitation on the type of polymerization initiator to be added, preferably two or more peroxides may be used to achieve the object of the present invention, and in terms of activity suitable for the reaction temperature, for example, t -butyl peroxybenzoate ( t -butyl peroxybenzoate), t -butyl- peroxy-3,5,5,-trimethylhexanoate ( t- butyl peroxy-3,5,5-trimethylhexanoate), t -butyl peroxyisobutyrate ( t-butyl peroxyisobutyrate), t-butyl-peroxypivalate (t -butyl peroxypivalate) it may be added to an initiator such as a combination of two or more.

The ethylene vinyl acetate copolymer prepared through the continuous polymerization process of the autoclave reactor and the tubular reactor has a melt index (ASTM D1238, 125°C, 2.16 kg load) of 10 to 25 g/10 min, molecular weight distribution (MWD, Mw) /Mn) may be 4 to 6, the Z average molecular weight may be 130,000 to 200,000, and as described above, the vinyl acetate content may be 10 to 30 wt%.

When the melt index of the ethylene vinyl acetate copolymer is less than 10 g/10 min, the neck-in property is excellent, but the draw-down property is greatly reduced, so that the processing stability during T-Die coating is poor, so high-speed processing may be difficult, and 25 g/ If it exceeds 10 minutes, the draw-down characteristic is relatively improved, but the neck-in characteristic is inferior, and thus the productivity may decrease during T-Die coating processing.

In addition, when the molecular weight distribution (MWD, Mw/Mn) of the ethylene vinyl acetate copolymer is less than 4, the extrusion load increases during extrusion processing and the neck-in property may be deteriorated in terms of processability, and when the molecular weight distribution exceeds 6, processability In this case, the draw-down characteristic may be deteriorated. Similarly, when the Z average molecular weight of the ethylene vinyl acetate copolymer is less than 130,000, the neck-in property may be deteriorated, and when it exceeds 200,000, the draw-down property may be deteriorated.

Meanwhile, the ethylene vinyl acetate copolymer according to the present invention may be a copolymer having a suitable melt index and vinyl acetate content depending on the coating and lamination processing speed conditions.

Coating and lamination processing can be performed using a conventional extrusion coating technique, and the ethylene vinyl acetate copolymer is put into an extrusion device and discharged as a T-die as a melt, which runs through a cooling roll and a nip roll below. coated on the substrate. At this time, the extruder melting temperature may be set to 130 to 240 ℃, T-Die temperature may be set to 210 to 240 ℃. Films of various materials may be applied to the substrate traveling through the cooling roll and the nip roll, for example, a polyethylene terephthalate (PET) film, a biaxially stretched polypropylene (BOPP) film, and the like may be selected.

Here, the running speed may be set variously from 80 m/min to 300 m/min, and the characteristics of the 　ethylene vinyl acetate copolymer may be classified and provided according to the running speed. That is, the ethylene vinyl acetate copolymer for medium and low speed, which can be provided at a running speed of 80 to 150 m/min, has a melt index of 13 to 17 g/10 min and a vinyl acetate content of 16 among the copolymers provided under the aforementioned polymerization conditions. A copolymer of from 20 wt % to 20 wt % can be preferably applied, and the high-speed ethylene vinyl acetate copolymer, which can be provided at a level of 150 to 300 m/min, has a melt index of 18 to 22 g/10 min and a vinyl acetate content of 16 to 22% by weight of the copolymer may be preferably applied.

According to the present invention as described above, it is possible to prepare an ethylene vinyl acetate copolymer excellent in both neck-in and draw-down properties in terms of processability.

Specifically, the ethylene vinyl acetate copolymer prepared according to the present invention may have a neck-in ratio of 25% or less and a maximum processing speed of 100 m/min or more, measured according to the following method.

[Method of measuring neck-in ratio]

Using an extrusion coating machine with a discharge width of 450 mm, the ethylene vinyl acetate copolymer prepared above is coated on a biaxially stretched polypropylene film at a die temperature of 230 ° C. When molding to a coating thickness of 20 μm at an extrusion coating processing speed of 60 m/min Calculate the neck-in ratio by measuring the coating width compared to the discharge width by measuring the coating width.

[Method of measuring maximum processing speed]

The maximum processing speed was measured at 35 rpm of the screw of the extrusion coating machine during extrusion coating using the ethylene vinyl acetate copolymer.

In addition, according to the present invention, it is possible to prepare an ethylene vinyl acetate copolymer excellent in adhesive strength, which is a post-processing property.

The ethylene vinyl acetate copolymer is provided to the consumer as a final product through an extrusion coating process and a post-processing process. For example, the ethylene vinyl acetate copolymer coated on a biaxially oriented polypropylene film is laminated with ink printed paper. will go through processing. In this case, the physical adhesion of the printed paper is important due to the chemical adhesion of the ink used for printing and the relatively high roughness of the paper. Therefore, it is important to have an appropriate melt index and vinyl acetate copolymer content in the range where extrusion processing is possible. The ethylene vinyl acetate copolymer prepared according to the present invention may have an adhesive strength of 40 kgf/cm 2 or more measured according to the following method.

[Measuring method of adhesive strength]

After coating the ethylene vinyl acetate copolymer on a biaxially stretched polypropylene film (40 μm thickness), lamination on a black paper substrate printed with ink printing at 100° C. and a speed of 3 m/min. Using a universal tensile tester, Load Cell 100 The adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured under the conditions of N and a speed of 200 mm/min.

In addition, according to the present invention, since process sensitivity is reduced by including a multi-process in which the autoclave process and the tubular process are continuously performed, processability and productivity can be improved. That is, the production method according to the present invention has an hourly production rate of 1 to 20%, preferably 5 to 20%, more preferably 10 to 20%, compared to a single process of polymerization only with an autoclave reactor or a single process of polymerization with only a tubular reactor It can be improved by 20%.

Hereinafter, the present invention will be described in more detail through specific examples and comparative examples.

Example 1

Compress the pressure to 50 kgf/cm2 while inputting the recirculated gas through a purge gas compressor, and ethylene gas and vinyl acetate monomers are introduced from the primary compressor, and the pressure is 250 kgf/cm2 and maintained at 1,600 kgf/cm 2 in a secondary compressor (Hyper Compressor).

Ethylene gas and vinyl acetate monomer compressed under high pressure in the secondary compressor were put into the autoclave reactor, the reactor pressure was set to 1900 kgf/cm 2 , the reactor upper temperature was set to 150 °C, and the reactor lower temperature was set to 200 °C, and the modifier was 1 -Butene was added at 160 kg/hr. The polymerization initiator is diluted with a hydrocarbon reactor upper portion t - butyl peroxyneodecanoate (t -butyl peroxyneodecanoate) input to, and the lower part di - t - butylperoxy isopropyl butyrate In the (di- t -butyl peroxyisobutyrate) did. The ethylene vinyl acetate copolymer, unreacted ethylene gas, and acetate monomer from the autoclave reactor were directly introduced into the tubular reactor, and further reaction was performed at a reactor pressure of 1,900 kgf/cm 2 and a reactor temperature of 200°C. In the tubular reactor, the polymerization initiator t-butyl peroxybenzoate (t -butyl peroxybenzoate), and t-butyl-peroxy -3,5,5-trimethyl hexanoate (t -butyl peroxy-3,5, 5-trimethylhexanoate) was added. Ethylene vinyl acetate copolymers having the melt index, vinyl acetate content, and molecular weight characteristics of Table 1 below were prepared by controlling the residence time, etc. together with the pressure and temperature conditions of the autoclave reactor and the tubular reactor.

Examples 2 to 8 and Comparative Examples 1 to 2

An ethylene vinyl acetate copolymer was prepared in the same manner as in Example 1, except that the polymerization conditions in Example 1 were changed as shown in Table 1 below.

Test example

The physical properties, processability and adhesive strength of the prepared ethylene vinyl acetate copolymer were measured in the following manner, and the results are shown in Table 1 below.

[How to measure]

(1) Melt flow index (MI)

It was measured at 125° C. and a load of 2.16 kg according to ASTM D1238.

(2) vinyl acetate content

A content obtaining the area and the peak area ratio of the vinyl acetate 580-670㎝ ^{-1 -1} 1980-2090㎝ of reference peak (Peak) was calculated by measuring by FT-IR Nicolet instrument Corporation.

(3) molecular weight characteristics (molecular weight distribution (MWD, Mw/Mn), Z average molecular weight)

It was measured by GPC analysis according to ASTM D3536.

(4) Neck-in ratio

Using an extrusion coating machine with a discharge width of 450 mm, the ethylene vinyl acetate copolymer prepared above is coated on a biaxially stretched polypropylene film at a die temperature of 230 ° C. When molding to a coating thickness of 20 μm at an extrusion coating processing speed of 60 m/min The neck-in ratio was calculated by measuring the coating width compared to the discharge width by measuring the coating width.

(5) Maximum machining speed

In order to identify the drawdown characteristics, the maximum processing speed at 35 rpm of the screw of the extrusion coating machine was measured during the extrusion coating.

(6) Adhesive strength

After coating the ethylene vinyl acetate copolymer on a biaxially oriented polypropylene film (40 μm thick), it was applied to a black paper substrate printed by ink printing at 100° C. and a speed of 3 m/min. After lamination as a condition, the adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured under the conditions of Load Cell 100 N and speed 200 mm/min using a universal tensile tester.

(7) production load

The hourly production in each Example and Comparative Example was automatically measured through the control panel of the manufacturing facility.

Referring to Table 1, first, the autoclave process and the tubular process are sequentially performed according to the present invention, but when the reactor pressure and temperature, the melt index, and the vinyl acetate content are adjusted in preferred ranges (Examples 1 and 2), high molecular weight It can be seen that as the area is reduced, it has a narrow molecular weight distribution, which has excellent neck-in and draw-down properties, and further exhibits excellent adhesive strength.

In contrast, in the case of manufacturing in a single process, not in the multi-process of the autoclave reactor and the tubular reactor, when manufacturing in a single process of the autoclave reactor (Comparative Example 1), it exhibits insufficient drawdown properties due to the high Z average molecular weight characteristics, It can be seen that the production load is reduced, and when the tubular reactor is manufactured in a single process (Comparative Example 2), the neck toughness and drawdown properties are equivalent to those of Example 2, but the adhesive strength is lowered and the production load is reduced. have.

However, even if the multi-process of autoclave reactor and tubular reactor is applied, it is confirmed that it is difficult to realize satisfactory processing characteristics or adhesive strength characteristics if the pressure or temperature conditions of the reactor or the vinyl acetate (VA) content are slightly out of the desired range. do.

That is, when the pressure of the autoclave reactor and the tubular reactor is somewhat low (Examples 3 and 4), the molecular weight distribution is wide and high molecular weight characteristics are shown, and as a result, the neck-in characteristics are excellent but the draw-down characteristics are lowered. Able to know.

In addition, when the temperatures of the autoclave reactor and the tubular reactor are somewhat low or high (Examples 5 and 6), the molecular weight distribution or the Z average molecular weight does not satisfy desirable physical properties, resulting in neck-in characteristics and drawdown characteristics. It can be seen that the result was biased toward a specific processing property in terms of balance, and when the temperature of the reactor was somewhat low (Example 5), the production load was reduced due to the decrease in the reaction temperature.

In addition, when the vinyl acetate content is somewhat low (Example 7), the adhesive strength property is reduced, and when the vinyl acetate content is somewhat high (Example 8), the drawdown property is significantly reduced due to oxidative crosslinking in the extruder due to the high vinyl acetate content. it can be seen that

The preferred embodiments of the present invention have been described in detail above. The description of the present invention is for illustrative purposes only, and those of ordinary skill in the art to which the present invention pertains will be able to understand that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Accordingly, the scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims are included in the scope of the present invention. should be interpreted

Claims (4)

(a) polymerizing an ethylene monomer and a vinyl acetate monomer in an autoclave reactor in the presence of a polymerization initiator and a modifier for controlling molecular weight distribution; and
(b) continuously polymerizing the polymer and unreacted monomers polymerized in step (a) by introducing them into a tubular reactor;
A method for producing an ethylene vinyl acetate copolymer comprising a. The method of claim 1,
The autoclave reactor has a pressure of 1,700 to 2,200 kgf/cm 2 , an upper temperature of 140 to 170° C. and a lower temperature of 185 to 225° C., and the tubular reactor has a pressure of 1,700 to 2,200 kgf/cm 2 and a temperature of 185 to 225 Ethylene vinyl acetate copolymer manufacturing method, characterized in that ℃. It is prepared by the method of claim 1, and has a melt index (ASTM D1238, 125°C, 2.16 kg load) of 10 to 25 g/10 min, a vinyl acetate content of 10 to 30% by weight, and a molecular weight distribution (MWD, Mw/Mn) Ethylene vinyl acetate copolymers having 4 to 6 and Z average molecular weights from 130,000 to 200,000. An ethylene vinyl acetate copolymer prepared by the method of claim 1 and having a neck-in ratio of 25% or less, a maximum processing speed of 100 m/min or more, and an adhesive strength of 40 kgf/cm 2 or more, measured according to the following method:
[Method of measuring neck-in ratio]
Using an extrusion coating machine with a discharge width of 450 mm, the ethylene vinyl acetate copolymer prepared above is coated on a biaxially stretched polypropylene film at a die temperature of 230 ° C. When molding to a coating thickness of 20 μm at an extrusion coating processing speed of 60 m/min Calculate the coating width to the discharge width of the neck-in ratio as {1-(coating width/discharge width)}*100.
[Method of measuring maximum processing speed]
Using an extrusion coating machine with a discharge width of 450 mm, the resin discharge rate is fixed at 700 g/min, and the ethylene vinyl acetate copolymer is coated on a biaxially stretched polypropylene film at a die temperature of 230° C. and check the processing speed at the point when the resin flow is broken and coating is not performed.
[Method of measuring adhesive strength]
After coating the ethylene vinyl acetate copolymer on a biaxially oriented polypropylene film (40 μm thick), it was applied to a black paper substrate printed by ink printing at 100° C. and a speed of 3 m/min. After lamination as a condition, the adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured under the conditions of Load Cell 100 N and speed 200 mm/min using a universal tensile tester.