阅读说明：本技术 乙烯醋酸乙烯酯共聚物及其制备方法 (Ethylene-vinyl acetate copolymer and preparation method thereof ) 是由 俞在明 孙昌奎 尹普相 金珍佑 林贤傧 朴仙雅 李贞旻 崔秉斗 于 2020-11-19 设计创作，主要内容包括：本发明提供一种乙烯醋酸乙烯酯共聚物及其制备方法,其中公开用于在制备乙烯醋酸乙烯酯共聚物时提供加工性、尤其作为相反性质的颈缩性及垂伸性均优异的乙烯醋酸乙烯酯共聚物的特殊的反应器条件。本发明的乙烯醋酸乙烯酯共聚物制备方法包括：步骤a,在聚合引发剂及用于调节分子量分布的改性剂的存在下,使乙烯单体及醋酸乙烯酯单体在高压釜反应器中聚合；以及步骤b,通过将在所述步骤a中聚合的聚合物及未反应单体加入到管式反应器而连续地进行聚合。(The invention provides an ethylene-vinyl acetate copolymer and a preparation method thereof, wherein special reactor conditions for providing the ethylene-vinyl acetate copolymer with excellent processability, particularly necking property and sagging property which are opposite properties, when the ethylene-vinyl acetate copolymer is prepared are disclosed. The preparation method of the ethylene-vinyl acetate copolymer comprises the following steps: a, polymerizing ethylene monomers and vinyl acetate monomers in an autoclave reactor in the presence of a polymerization initiator and a modifier for adjusting molecular weight distribution; and a step b of continuously performing polymerization by feeding the polymer polymerized in the step a and unreacted monomers into a tubular reactor.)

1. A method for preparing ethylene-vinyl acetate copolymer comprises the following steps:

a, polymerizing ethylene monomers and vinyl acetate monomers in an autoclave reactor in the presence of a polymerization initiator and a modifier for adjusting molecular weight distribution; and

step b, continuously performing polymerization by adding the polymer polymerized in the step a and unreacted monomers to a tubular reactor.

2. The method of producing an ethylene-vinyl acetate copolymer according to claim 1,

the pressure of the autoclave reactor was 1,700kgf/cm²To 2,200kgf/cm²The upper temperature is 140 ℃ to 170 ℃, the lower temperature is 185 ℃ to 225 ℃, and the pressure of the tubular reactor is 1,700kgf/cm²To 2,200kgf/cm²The temperature is 185-225 ℃.

3. An ethylene vinyl acetate copolymer prepared by the process of claim 1 having a melt index of 10g/10 min to 25g/10 min, a vinyl acetate content of 10 wt% to 30 wt%, a molecular weight distribution MWD, as expressed by Mw/Mn, of 4 to 6, and a Z-average molecular weight of 130,000 to 200,000, measured at 125 ℃ under a 2.16kg load, based on ASTM D1238.

4. An ethylene vinyl acetate copolymer prepared by the method of claim 1, having a neck-in ratio of 25% or less, a maximum processing speed of 100m/min or more, and an adhesive strength of 40kgf/cm, measured according to the method²In the above-mentioned manner,

[ necking ratio measuring method ]

The ethylene vinyl acetate copolymer prepared was coated on a biaxially stretched polypropylene film at a die temperature of 230 ℃ using an extrusion coating machine having a discharge width of 450mm, the ratio of the coating width to the discharge width at the time of molding at an extrusion coating processing speed of 60m/min and a coating thickness of 20 μm was calculated, and the necking ratio was calculated using {1- (coating width/discharge width) × 100},

[ method for measuring maximum processing speed ]

The ethylene-vinyl acetate copolymer was coated on a biaxially stretched polypropylene film at a die temperature of 230 ℃ with the resin discharge amount fixed at 700g/min using an extrusion coating machine having a discharge width of 450mm, the coating condition was confirmed by increasing the processing speed, and the processing speed was also confirmed when the film was not coated due to the disruption of the resin flow,

[ method for measuring adhesive Strength ]

After coating the ethylene vinyl acetate copolymer on a biaxially stretched polypropylene film at a thickness of 40 μm, the film was laminated to a black paper substrate printed by ink printing at 100 ℃ and a speed of 3m/min, and then the adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured using a universal tensile tester under a weight sensor of 100N and a speed of 200 mm/min.

Technical Field

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

Background

General low-density polyethylene or ethylene vinyl acetate resin for extrusion coating and lamination is used for a paper coating, a kraft paper coating, and the like for waterproof use, and is widely used for a plastic film and the like for lamination and thermal bonding use.

Basically, from the viewpoint of molecular weight distribution characteristics, the wider the Molecular Weight Distribution (MWD), the smaller the extrusion load due to low molecular weight, the more stable flow characteristics are exhibited In the extruder, and the higher the molecular weight, the more excellent the Neck-In (Neck-In) characteristics due to high Melt tension (Melt tension) tend to be at the time of T-die casting.

However, as productivity has become important in recent years, drawdown (Draw down) characteristics have been regarded as more important processability. Therefore, it is important to ensure drawdown properties by having a narrow molecular weight distribution characteristic, while bearing a load in the extruder, a high discharge rate and having a small high molecular weight region. That is, since the conventional broad molecular weight distribution and high molecular weight hinder the drawdown characteristics, it is important to balance the high molecular weight to adjust the resin characteristics. In addition, when the molecular weight is too low in a broad distribution, build-up (Die build-up) may occur during T-Die casting, and it may be difficult to form a film by coating.

In addition, in the case of an ethylene vinyl acetate copolymer provided by a conventional autoclave process, although there is an advantage that a molecular weight distribution is relatively wide and a favorable design can be made in terms of necking property or extrusion processability due to melt tension, a drawdown property is relatively low, and if a modifier is added to enhance the drawdown property, although the properties of the corresponding portion can be adjusted, there is a problem that it is difficult to maintain a high molecular weight balance. On the contrary, in the case of the ethylene vinyl acetate copolymer provided by the tubular process, although the molecular weight distribution is relatively narrow and the drawdown property is excellent, the melt tension is inferior to that of the resin provided by the autoclave process in the resin property, and the property such as the neck-in property and the like are exhibited disadvantageously.

In addition, a high pressure polymerization method using a reactor structure of a tubular reactor, an autoclave reactor or two reactors including a tubular reactor and an autoclave reactor for forming an ethylene-based polymer is disclosed in korean laid-open patent No. 2019-0022642 and U.S. published patent No. 2014-0303309, but specific reactor conditions for improving necking and sagging when an ethylene vinyl acetate copolymer is prepared are not mentioned.

Korean patent No. 1975696 relates to a method for separating components of reactor off-gas and a related reactor system, which discloses a reactor system that may include a high pressure pipe type reactor and/or an autoclave reactor and is available when polyolefin polymer is prepared, but only describes a polymerization reaction of low density polyethylene in detail, and does not mention specific reactor conditions for improving necking and sagging when ethylene vinyl acetate copolymer is prepared.

Japanese laid-open patent No. 2002-080652 discloses an ethylene-vinyl acetate copolymer produced by using an autoclave-type polymerizer or a tubular polymerizer, but does not mention the use of a combination of polymerizers and the improvement of processability caused thereby.

Disclosure of Invention

The present invention is to provide a specific reactor condition for providing an ethylene vinyl acetate copolymer excellent in processability, particularly in neck-in property and drawdown property which are contradictory properties, when the ethylene vinyl acetate copolymer is produced.

In order to solve the above problems, the present invention provides a method for preparing an ethylene vinyl acetate copolymer, comprising: a, polymerizing ethylene monomers and vinyl acetate monomers in an autoclave reactor in the presence of a polymerization initiator and a modifier for adjusting molecular weight distribution; and a step b of continuously performing polymerization by feeding the polymer polymerized in the step a and unreacted monomers into a tubular reactor.

Further, there is provided a method for producing an ethylene-vinyl acetate copolymer, characterized in that the pressure of the autoclave reactor is 1,700kgf/cm²To 2,200kgf/cm²The upper temperature is 140 ℃ to 170 ℃, the lower temperature is 185 ℃ to 225 ℃, and the pressure of the tubular reactor is 1,700kgf/cm²To 2,200kgf/cm²The temperature is 185-225 ℃.

Further, there is provided an ethylene vinyl acetate copolymer prepared by the above method, having a melt index of 10g/10 min to 25g/10 min, a vinyl acetate content of 10 wt% to 30 wt%, a molecular weight distribution MWD of 4 to 6, represented by Mw/Mn, and a Z-average molecular weight of 130,000 to 200,000, measured at 125 ℃ under a 2.16kg load, based on ASTM D1238.

Further, there is provided an ethylene vinyl acetate copolymer produced by the above method, having a neck-in ratio of 25% or less, a maximum processing speed of 100m/min or more, and an adhesive strength of 40kgf/cm, measured according to the method described below²The above.

[ necking ratio measuring method ]

The ethylene vinyl acetate copolymer prepared was coated on a biaxially stretched polypropylene film at a die temperature of 230 ℃ using an extrusion coating machine having a discharge width of 450mm, the ratio of the coating width to the discharge width at the time of molding at an extrusion coating processing speed of 60m/min and a coating thickness of 20 μm was calculated, and the necking ratio was calculated using {1- (coating width/discharge width) × 100 }.

[ method for measuring maximum processing speed ]

The ethylene vinyl acetate copolymer was coated on a biaxially stretched polypropylene film at a die temperature of 230 ℃ using an extrusion coater having a discharge width of 450mm with a resin discharge amount fixed at 700g/min, and the coating condition was confirmed by increasing the processing speed, and the processing speed was also confirmed when the film was not coated due to the disruption of the resin flow.

[ method for measuring adhesive Strength ]

After coating the ethylene vinyl acetate copolymer on a biaxially stretched polypropylene film at a thickness of 40 μm, it was laminated to a black paper substrate printed by ink printing at 100 ℃ and a speed of 3m/min, and then the adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured using a universal tensile tester under a Load Cell 100N of 100N and a speed of 200 mm/min.

According to the present invention, by applying a multi-process in which an autoclave process and a tubular process are sequentially performed, the decrease in polymerization degree and high molecular weight can be adjusted by adjusting the pressure and temperature of the reactor in a state where the molecular weight distribution of the ethylene-vinyl acetate copolymer is maximized, and as a result, the ethylene-vinyl acetate copolymer having a narrow molecular weight distribution while the high molecular weight region is decreased, and having excellent necking properties and elongation properties can be produced.

Further, by controlling the fluidity and vinyl acetate content of the ethylene vinyl acetate copolymer in the multi-polymerization process, an ethylene vinyl acetate copolymer excellent in post-processability, that is, adhesive strength can be produced.

Detailed Description

The present invention will be described in detail below with reference to preferred embodiments. It should be noted that the terms or words used in the present specification and claims should not be construed as limited to the meanings commonly or dictionary, and should be construed as meanings and concepts conforming to the technical idea of the present invention on the basis of the principle that the inventor can appropriately define the concept of the terms in order to describe his own invention in the best way. Therefore, it should be understood that the configuration of the embodiment described in the present specification is merely the most preferable embodiment of the present invention, and does not represent the entire technical idea of the present invention, and various equivalents and modifications that can replace the above-described embodiment may exist at the stage of the present application.

In the conventional production of ethylene-vinyl acetate copolymer, when a single process using an autoclave reactor or a tubular reactor is used, it is difficult to satisfy both necking property and drawdown property in post-processing due to the opposite molecular weight characteristics, and a multi-process combining an autoclave reactor and a tubular reactor does not provide specific reactor conditions, and it is difficult to solve the problem by process adjustment. The present inventors have paid attention to the above-mentioned facts and circumstances and have found, as a result of repeated studies, that an ethylene vinyl acetate copolymer having excellent neck-in properties and drawdown properties can be produced by adjusting the molecular weight characteristics of the ethylene vinyl acetate copolymer by sequentially performing an autoclave process and a tubular process, and further having a narrow molecular weight distribution while minimizing the molecular weight distribution of the ethylene vinyl acetate copolymer by adjusting the pressure and temperature of each reactor, and have completed the present invention.

Therefore, the invention discloses a preparation method of an ethylene-vinyl acetate copolymer, which comprises the following steps: a, polymerizing ethylene monomers and vinyl acetate monomers in an autoclave reactor in the presence of a polymerization initiator and a modifier for adjusting molecular weight distribution; and a step b of continuously performing polymerization by feeding the polymer polymerized in the step a and unreacted monomers into a tubular reactor.

In the preparation of ethylene vinyl acetate copolymer in the present invention, the molecular weight distribution (MWD, Mw/Mn) is maximized by applying a multi-process of sequentially performing an autoclave process and a tubular process, thereby increasing the reduction range of the high molecular weight region regulated by the modifier, and thus the molecular weight distribution can be relatively easily regulated. In addition, a narrower molecular weight distribution can be obtained by adjusting the reactor temperature and pressure to maximize the high molecular weight region reducing effect. Accordingly, it is possible to provide a copolymer having a relatively small high molecular weight region and a relatively narrow molecular weight distribution characteristic compared to an ethylene vinyl acetate copolymer provided by an autoclave single process, thereby achieving excellent drawdown and having excellent neck-in characteristics while having equivalent drawdown as compared to an ethylene vinyl acetate copolymer provided by a tubular single process. Furthermore, by controlling the fluidity and vinyl acetate content while adjusting the molecular weight characteristics, the adhesive strength with the ink-printed paper can be improved.

In the present invention, the pressure of the autoclave sensor may be set to 1,700kgf/cm²To 2,200kgf/cm²The upper temperature may be set at 140 ℃ to 170 ℃ and the lower temperature may be set at 185 ℃ to 225 ℃, and preferably, the pressure may be set at 1,850kgf/cm²To 2,050kgf/cm²The upper temperature may be set at 145 ℃ to 165 ℃ and the lower temperature may be set at 195 ℃ to 215 ℃. Here, the upper temperature and the lower temperature of the autoclave reactor refer to temperatures measured by temperature sensors (thermal sensors) respectively provided at the highest position end and the lowest position end of the reactor.

If the pressure of the autoclave reactor is less than 1,700kgf/cm²When the reactor pressure is more than 2,200kgf/cm, a large amount of long chain branches of the ethylene-vinyl acetate copolymer may be formed, the Z-average molecular weight may be increased, and the drawdown property may be lowered in view of the processability²There is a possibility that a problem may occur in production stability due to the approach to the limit operation value of the autoclave reactor, and the long chain branch becomes too small and the Z-average molecular weight becomes small, and the necking property may be degraded in processability.

Further, when the upper temperature of the autoclave reactor is less than 140 ℃, the Z-average molecular weight decreases due to the decrease of the long chain branches of the ethylene vinyl acetate copolymer, and there is a possibility that the neck-in property is lowered, and when the upper temperature of the autoclave reactor is more than 170 ℃, the Z-average molecular weight increases due to the increase of the long chain branches of the ethylene vinyl acetate copolymer, and there is a possibility that the drawdown property is lowered.

Further, if the lower temperature of the autoclave reactor is less than 185 ℃, a reduction in production load may be caused, and if the lower temperature of the autoclave reactor exceeds 225 ℃, a problem may occur in terms of reactor stability, and drawdown may be reduced in terms of processability due to an increase in the Z-average molecular weight of the ethylene vinyl acetate copolymer.

An initiator for initiating polymerization is used in the autoclave reactor. Although the kind of the polymerization initiator used is not limited, in order to achieve the object of the present invention, preferably two or more peroxides may be used, and from the viewpoint of meeting the reaction temperature, for example, t-butyl peroxyneodecanoate (t-butyl peroxidocecanoate) may be added to the upper portion of the reactor, and di-t-butyl peroxyisobutyrate (di-t-butyl peroxiisobutoxide) may be added to the lower portion.

In addition, a modifier for adjusting the molecular weight distribution is used in the autoclave reactor. Although the kind of the modifier to be used is not limited, an olefinic hydrocarbon of C4 series such as 1-butene (1-butene), 2-butene (2-butene), isobutylene (iso-butene) can be selected in consideration of the achievement of the object of the present invention and the reactor conditions. In this case, the modifier is preferably added in an amount of 120kg/hr to 200kg/hr, more preferably 140kg/hr to 180 kg/hr. If the amount of the modifier added is less than 120kg/hr, it may be difficult to adjust the molecular weight distribution by the modifier, and if the amount of the modifier added exceeds 200kg/hr, the melt index and density increase and the Z-average molecular weight decrease due to the maximization of the production of low molecules, thereby possibly deteriorating the necking property in terms of processability.

In polymerizing ethylene vinyl acetate copolymer, vinyl acetate monomer is fed to the autoclave reactor along with ethylene monomer, wherein the vinyl acetate monomer may be added in an amount of 10 to 30% by weight, preferably 15 to 23% by weight of the final copolymer. If the vinyl acetate content is less than 10 wt%, the adhesive property may be deteriorated, and if the vinyl acetate content exceeds 30 wt%, the crosslinked Gel (Gel) may be generated in the T-die extruder with high possibility, and it may be difficult to apply to the coating process due to excessively high adhesive property.

In the case of the ethylene vinyl acetate copolymer once polymerized in the autoclave reactor, as a continuous reaction process, a once polymerized polymer and unreacted monomers are fed into a tubular reactor disposed at the rear stage of the autoclave to perform an additional process.

By the additional reaction performed by the tubular reactor, about 1 to 10% by weight of ethylene vinyl acetate copolymer can be further produced, and more than 10% by weight of ethylene vinyl acetate copolymer can be further produced according to the process conditions, and by the secondary polymerization process by the tubular reactor, the molecular weight distribution of ethylene vinyl acetate copolymer becomes broader, increasing productivity and production load.

In the present invention, the pressure in the tubular reactor may be set to 1,700kgf/cm in consideration of the necking property, the drawdown property, etc. due to the formation of a moderate long chain branch of the ethylene vinyl acetate copolymer²To 2,200kgf/cm²The reactor temperature may be set at 185 ℃ to 225 ℃, and preferably, the pressure may be set at 1,850kgf/cm²To 2,050kgf/cm²The reactor temperature may be set at 195 ℃ to 215 ℃.

If the pressure in the tubular reactor is less than 1,700kgf/cm²When the reactor pressure exceeds 2,200kgf/cm, the Z-average molecular weight becomes large due to the formation of a large amount of long chain branches of the ethylene-vinyl acetate copolymer, which may result in a decrease in the drawability²When the number of long-chain branches is too small, the Z-average molecular weight is small, and the neck-in property may be deteriorated in processability.

Further, if the temperature of the tubular reactor is less than 185 ℃, the improvement of characteristics and the increase of production load due to additional reaction may be slight due to the decrease of reactivity, and if the temperature of the tubular reactor exceeds 225 ℃, the reactivity may be unstable, and there may be a problem in stability due to high-pressure and high-temperature reaction.

An initiator for initiating polymerization may be added to the tubular reactor. Although the kind of the polymerization initiator to be added is not limited, in order to achieve the object of the present invention, it is preferable to use two or more peroxides, and from the viewpoint of the activity degree corresponding to the reaction temperature, for example, initiators such as t-butyl peroxybenzoate (t-butyl peroxybenzoate), t-butyl peroxy-3,5,5-trimethylhexanoate (t-butyl peroxy3, 5,5-trimethylhexanoate), t-butyl peroxyisobutyrate (t-butyl peroxyisobutryate), t-butyl peroxypivalate (t-butyl peroxypivalate), and the like may be added in combination.

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

When the melt index of the ethylene vinyl acetate copolymer is less than 10g/10 min, although the neck-in property is excellent, the drawdown property is greatly reduced, and high-speed processing may be difficult due to reduced processing stability in T-die coating, and when the melt index of the ethylene vinyl acetate copolymer is more than 25g/10 min, the drawdown property is relatively greatly improved, but the neck-in property is deteriorated, and the productivity may be reduced in T-die coating processing.

If the molecular weight distribution (MWD, Mw/Mn) of the ethylene-vinyl acetate copolymer is less than 4, the extrusion load during extrusion processing becomes large, and the neck-in property may be lowered in processability, and if the molecular weight distribution is more than 6, the drawdown property may be lowered in processability. Similarly, if the Z-average molecular weight of the ethylene vinyl acetate copolymer is less than 130,000, the neck-in property may be reduced, and if the Z-average molecular weight of the ethylene vinyl acetate copolymer is more than 200,000, the drawdown property may be reduced.

In addition, for the ethylene vinyl acetate copolymer of the present invention, a copolymer having an appropriate melt index and vinyl acetate content can be used according to coating and lamination process speed conditions.

The coating and lamination processes may be performed using conventional extrusion coating techniques by feeding ethylene vinyl acetate copolymer to an extrusion device and ejecting it as a melt to a T-die for coating onto a substrate traveling through a lower chill roll and nip roll. At this time, the melting temperature of the extruder may be set to 130 ℃ to 240 ℃ and the temperature of the T-die may be set to 210 ℃ to 240 ℃. The substrate traveling through the cooling roll and the nip roll may be a film made of various materials, for example, polyethylene terephthalate (PET) film, biaxially oriented polypropylene (BOPP) film, or the like may be selected.

Here, the walking speed may be set to various speeds of 80 m/min to 300 m/min, and the characteristics of the ethylene-vinyl acetate copolymer may be provided by differentiating the walking speed. That is, as for the medium and low speed ethylene vinyl acetate copolymer which can be provided at a level of a traveling speed of 80 m/min to 150 m/min, it is preferable to use a copolymer having a melt index of 13g/10 min to 17g/10 min and a vinyl acetate content of 16 wt% to 20 wt% among the copolymers provided under the aforementioned polymerization conditions, and as for the high speed ethylene vinyl acetate copolymer which can be provided at a level of 150 m/min to 300 m/min, it is preferable to use a copolymer having a melt index of 18 g/min to 20 g/min and a vinyl acetate content of 16 wt% to 22 wt%.

According to the present invention, an ethylene-vinyl acetate copolymer excellent in both necking property and drawdown property in processability can be produced.

Specifically, for the ethylene vinyl acetate copolymer produced by the present invention, the neck-in ratio measured according to the method described below may be 25% or less, and the maximum processing speed may be 100m/min or more.

[ necking ratio measuring method ]

The prepared ethylene vinyl acetate copolymer was coated on a biaxially stretched polypropylene film at a die temperature of 230 ℃ using an extrusion coating machine having a discharge width of 450mm, the coating width at the time of molding at an extrusion coating processing speed of 60m/min and a coating thickness of 20 μm was measured, and the ratio of the coating width to the discharge width was measured to calculate a necking ratio.

[ method for measuring maximum processing speed ]

In the extrusion coating with the ethylene vinyl acetate copolymer, the maximum processing speed at 35rpm of the screw rotation speed of the extrusion coating machine was measured.

Further, according to the present invention, an ethylene-vinyl acetate copolymer excellent in adhesive strength as post-processing physical properties can be produced.

The ethylene vinyl acetate copolymer is supplied to consumers as a final product after an extrusion coating process through a post-processing process, for example, the ethylene vinyl acetate copolymer coated to a biaxially stretched polypropylene film and the ink-printed paper are subjected to a lamination process. In this case, the substrate characteristics of the printed paper are important for the physical adhesion due to the chemical adhesion of the ink used in the printing and the relatively high roughness characteristics of the paper. Therefore, an appropriate melt index and vinyl acetate copolymer content in a range capable of performing an extrusion processing operation are important. For the ethylene vinyl acetate copolymer prepared by the present invention, the adhesive strength measured according to the above method may be 40kgf/cm²The above.

[ method for measuring adhesive Strength ]

After coating the ethylene vinyl acetate copolymer (thickness: 40 μm) on a biaxially stretched polypropylene film, the biaxially stretched polypropylene film was laminated on a black paper substrate printed by ink printing at 100 ℃ and a speed of 3m/min, and then the adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured by a universal tensile tester under a weight sensor of 100N and a speed of 200 mm/min.

Further, according to the present invention, since the process sensitivity is decreased due to the multi-process including the continuous autoclave process and the tubular process, the manufacturability and productivity can be improved. That is, the production method of the present invention can improve the production amount per hour by 1% to 20%, preferably by 5% to 20%, and more preferably by 10% to 20% as compared with a single process in which polymerization is performed using only an autoclave reactor or a single process in which polymerization is performed using only a tubular reactor.

The present invention will be described in more detail below with reference to specific examples and comparative examples.

Example 1

While the recycle gas was fed through a Purge gas compressor (Purge gas compressor), the pressure was compressed to 5.0kgf/cm²The ethylene gas and the vinyl acetate monomer were fed into a Primary Compressor (Primary Compressor) and the pressure was set at 250kgf/cm²The pressure was maintained, and 1,600kgf/cm was maintained in a secondary Compressor (Hyper Compressor)²The state of (1).

Ethylene gas compressed at a high pressure in a secondary compressor and a vinyl acetate monomer were charged into an autoclave reactor, and the reactor pressure was set to 1,900kgf/cm²The temperature of the upper portion of the reactor was set to 150 ℃ and the temperature of the lower portion of the reactor was set to 200 ℃ and 160kg/hr of 1-butene was added as a modifier. The polymerization initiator was diluted with hydrocarbon, t-butyl peroxyneodecanoate (t-butyl peroxyneodecanoate) was fed to the upper portion of the reactor, and di-t-butyl peroxyisobutyrate (di-t-butyl peroxyisobutryate) was fed to the lower portion of the reactor. The ethylene-vinyl acetate copolymer discharged from the autoclave reactor, unreacted ethylene gas and an acetate monomer were directly charged into a tubular reactor under a reactor pressure of 1,900kgf/cm²And carrying out an additional reaction at a reactor temperature of 200 ℃. In a tubular reactor, t-butyl peroxybenzoate (t-butyl peroxybenzoate) and t-butyl peroxy-3,5,5-trimethylhexanoate (t-butyl peroxyy-3, 5,5-trimethylhexanoate) were added as polymerization initiators. Ethylene vinyl acetate copolymers having the melt index, vinyl acetate content and molecular weight characteristics of table 1 below were prepared by adjusting 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 produced in the same manner as in example 1, except that the polymerization conditions of example 1 were changed to those described in table 1 below.

Test examples

The ethylene vinyl acetate copolymer prepared was measured for physical properties, processability and adhesive strength by the following methods, and the results thereof are shown in table 1 below.

[ measuring method ]

(1) Melt Index (MI, Melt flow Index)

Measurements were made at 125 ℃ under a 2.16kg load based on ASTM D1238.

(2) Vinyl acetate content

The Peak value was determined by measuring with a FT-IR instrument from Nicolet corporation to find 1980-2090cm as a reference Peak value (Peak)^-1Area of (d) and 580-670cm as the peak of vinyl acetate^-1The ratio of the areas of (a) to (b), from which the content is calculated.

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

Measurement was performed by using GPC (gel permeation chromatography) analysis method based on ASTM D3536.

(4) Necking ratio

The prepared ethylene vinyl acetate copolymer was coated on a biaxially stretched polypropylene film at a die temperature of 230 ℃ using an extrusion coating machine having a discharge width of 450mm, the coating width at the time of molding at an extrusion coating processing speed of 60m/min and a coating thickness of 20 μm was measured, and the ratio of the coating width to the discharge width was measured to calculate a necking ratio.

(5) Maximum working speed

In order to understand the drawdown characteristics, the maximum processing speed at 35rpm of the screw rotation speed of the extrusion coating machine was measured while the extrusion coating was performed.

(6) Adhesive strength

After coating the ethylene vinyl acetate copolymer (thickness: 40 μm) on a biaxially stretched polypropylene film, the biaxially stretched polypropylene film was laminated on a black paper substrate printed by ink printing at 100 ℃ and a speed of 3m/min, and then the adhesive strength between the paper and the ethylene vinyl acetate copolymer was measured by a universal tensile tester under a weight sensor of 100N and a speed of 200 mm/min.

(7) Production load

The amount of production per hour in each of examples and comparative examples was automatically measured by a Control panel (Control panel) of the preparation apparatus.

[ Table 1]

Referring to table 1, it is understood that, first, when the autoclave process and the tubular process are sequentially performed according to the present invention, and the reactor pressure and temperature, the melt index, and the vinyl acetate content are adjusted to the preferred ranges (examples 1 and 2), the high molecular weight region is reduced and the molecular weight distribution is narrow, so that the neck-in property and the drawdown property are excellent, and the adhesive strength is further excellent.

On the other hand, in the case of the multi-process production using a single process without using an autoclave reactor and a tubular reactor, respectively, it was found that, in the case of the single process production using an autoclave reactor (comparative example 1), drawdown property was not sufficient and production load was reduced due to the high Z-average molecular weight characteristic, and in the case of the single process production using a tubular reactor (comparative example 2), drawdown property and drawdown property were on the same level as in example 2, but adhesive strength was reduced and production load was reduced.

However, even if a multi-process of an autoclave reactor and a tubular reactor is applied, when the pressure or temperature conditions of the reactor, or the Vinyl Acetate (VA) content slightly deviates from the preferred range, it is confirmed that it is difficult to achieve satisfactory processing characteristics or adhesive strength characteristics.

That is, it was found that when the pressure in the autoclave reactor and the tubular reactor was slightly low (examples 3 and 4), the molecular weight distribution was broad, and high molecular weight characteristics were exhibited, and as a result, the drawdown characteristics were reduced although the neck-down characteristics were excellent.

Further, it was found that when the temperatures of the autoclave reactor and the tubular reactor were slightly low or high (examples 5 and 6), the molecular weight distribution and the Z-average molecular weight did not satisfy preferable physical properties, and as a result, the balance between the neck-in property and the drawdown property was biased to specific processability, and when the temperature of the reactor was slightly low (example 5), the reaction temperature was lowered, and the production load was reduced.

It is also found that the adhesive strength characteristics are reduced when the vinyl acetate content is slightly low (example 7), and that the drawability is significantly reduced when the vinyl acetate content is slightly high (example 8) because of the oxidative crosslinking in the extruder due to the high vinyl acetate content.

The preferred embodiments of the present invention have been described in detail. The present invention has been described for illustrative purposes, and it will be appreciated by those skilled in the art that the present invention can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the scope of the present invention is not limited to the description of the above embodiments, but is defined by the scope of the appended claims, and all changes and modifications derived from the meaning and range of the claims and their equivalents are intended to be included in the scope of the present invention.