KR20160092288A - Method for manufacturing Ethylene Vinyl Acetate Copolymer and Ethylene Vinyl Acetate Copolymer manufactured by the same - Google Patents

Abstract

The present invention relates to a method for producing an ethylene vinyl acetate copolymer based on a high-pressure radical polymerization method in a tubular reactor. The present invention further relates to an ethylene vinyl acetate copolymer produced by the production method. More specifically, the present invention relates to a method for producing an ethylene vinyl acetate copolymer which exhibits improved viscoelasticity and high melt tension, by carrying out a polymerization while varying the composition ratio of a vinyl acetate monomer injected into a first monomer inlet and a second monomer inlet respectively. The ethylene vinyl acetate copolymer produced thereby is particularly suitable for foaming and extrusion coating.

Description

    TECHNICAL FIELD The present invention relates to a method for producing an ethylene vinyl acetate copolymer and an ethylene vinyl acetate copolymer produced by the method,

The present invention relates to a process for producing an ethylene vinyl acetate copolymer in a tubular reactor and an ethylene vinyl acetate copolymer produced by the process, and more particularly, to a process for producing an ethylene vinyl acetate copolymer, To an ethylene vinyl acetate copolymer having a high melt tension and improved viscoelastic properties. The ethylene vinyl acetate copolymers thus prepared are particularly suitable for foaming and extrusion coating applications.

The ethylene vinyl acetate copolymer (hereinafter, referred to as 'EVA') resin produced by the high-pressure radical polymerization method is excellent in properties such as excellent elasticity, transparency and adhesiveness and is thus widely used for films, foaming and coating . Methods for producing EVA resins by high-pressure radical polymerization are roughly divided into two processes, one is a tubular reactor and the other is an autoclave reactor, and the basic production method is known.

The product manufactured in the tubular reactor is excellent in adhesion, gloss and transparency compared to the product manufactured in the autoclave reactor, but is characterized in that a long chain branch is less formed than the product manufactured in the autoclave reactor The melt tension is lowered and the viscoelastic property is lowered. In the case of foaming and extrusion coating applications where the melt tension and viscoelastic properties are particularly important in the use of EVA resins, the tubular reactor product has a disadvantage in that the processability and finished product performance are significantly lowered.

 When used for foaming, optimum melt tension, melt flow (MI) is required to form a stable, fine foam. In general, a resin having a higher content of vinyl acetate monomer (hereinafter referred to as VA) in an EVA resin is superior in stretchability and excellent in elasticity, while a lower VA content has a higher melt tension and a lower compression ratio (Compression set) can be secured. Because of these properties, foaming companies often use blends of high VA content EVA resins and low VA content EVA resins instead of using a single EVA resin with a constant VA content. However, EVA produced commercially is limited in selection because of its limited VA content and MI, and it is difficult to expect foam properties to be improved due to process increase due to blend operation and degradation of dispersibility.

In the case of EVA products for extrusion coating, if the melt tension is low, there is a large amount of neck-in of the film when the T-die coating is applied, so there are many parts to be cut off at both ends of the film, resulting in economical loss. Which is a problem in producing a high quality product. In addition, when the coating speed is increased, the necking-in becomes worse and the productivity of the coating is lowered because the coating speed can not be increased.

US Patent No. 3,875,134 discloses a technique for improving workability by connecting an autoclave reactor and a tubular reactor. However, this method has a disadvantage in that the reaction apparatus is complicated and the tubular reaction is dependent on the autoclave reaction, thereby lowering transparency, which is an advantage of tubular reaction. In Japanese Patent (5-339318), a technique of improving the neck-in characteristics using multifunctional peroxide has been disclosed. However, since PO is sensitive to the reaction, it is difficult to control the physical properties by increasing or decreasing the amount thereof arbitrarily.

An object of the present invention is to provide a process for producing an ethylene vinyl acetate copolymer having a high melt tension and improved viscoelastic properties by a high-pressure radical polymerization method in a tubular reactor.

The present invention provides a process for preparing an ethylene vinyl acetate copolymer by injecting an ethylene monomer and a vinyl acetate monomer in a tubular reactor, the process comprising the steps of:

A first step of injecting the vinyl acetate monomer through at least two or more monomer injection ports;

A second step of polymerizing the vinyl acetate monomer introduced into the first monomer inlet of the two or more monomer injection ports in a one-stage reactor;

A third step in which the vinyl acetate monomer charged into the second monomer inlet of the two or more monomer injection ports is mixed with the monomer and polymer of the first stage; And

And a fourth step in which the monomer and the polymer of the third step are polymerized in a two-stage reactor,

The absolute value of the difference between the content of the vinyl acetate monomer injected into the first monomer injection port and the content of the vinyl acetate monomer injected into the second monomer injection port in the two or more monomer injection ports is 1 to 30% Wherein the vinyl acetate monomer is injected in such a manner that the vinyl acetate monomer is injected.

According to the EVA resin production method of the present invention, it is possible to easily provide an EVA copolymer having a high melt tension and improved viscoelastic characteristics in a tubular reactor.

1 is a conceptual diagram showing an outline of an embodiment of a manufacturing facility according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

The method for producing an ethylene vinyl acetate copolymer according to the present invention is a method for producing an ethylene vinyl acetate copolymer by injecting an ethylene monomer and a vinyl acetate monomer in a tubular reactor wherein the vinyl acetate monomer is fed through at least two or more monomer injection ports A first step of injecting; A second step of polymerizing the vinyl acetate monomer introduced into the first monomer inlet of the two or more monomer injection ports in a one-stage reactor; A third step in which the vinyl acetate monomer charged into the second monomer inlet of the two or more monomer injection ports is mixed with the monomer and polymer of the first stage; And a fourth step in which the monomer and the polymer of the third step are polymerized in a two-stage reactor, wherein the content of the vinyl acetate monomer injected into the first monomer inlet of the two or more monomer injection ports and the content of the vinyl acetate monomer injected into the second monomer inlet The vinyl acetate monomer is injected so that the absolute value of the difference in the content of the vinyl acetate monomer to be injected is 1 wt% to 30 wt%.

According to an embodiment of the present invention, the vinyl acetate monomer may be heated to a temperature of 100 to 300 ° C after the first step. If the reaction temperature is lower than 100 ° C, the initial reaction rate becomes too slow, the conversion to EVA is lowered, ultrahigh molecular weight chains are formed, desired molecular weight and molecular weight distribution can not be obtained, and gelation may occur. If the polymerization temperature exceeds 300 ° C, decomposition reaction of vinyl acetate occurs, and the stability of the reactor may be deteriorated.

According to an embodiment of the present invention, after the fourth step, additional polymerization may be further performed in at least one reactor. This is because it is more preferable because it can broaden the molecular weight distribution and improve the neck in and melt strength.

In the process for producing an ethylene vinyl acetate copolymer of the present invention, it is preferable that 60 to 97% by weight of the ethylene monomer and 3 to 40% by weight of the vinyl acetate unit are added. When the amount of the ethylene monomer is more than 97% by weight or the amount of the vinyl acetate monomer is less than 3% by weight, it is not preferable to apply it to the foaming application because of the lack of elasticity and flexibility and the amount of the ethylene monomer Is less than 60% by weight or the amount of the vinyl acetate monomer is more than 40% by weight is not preferable because polymerization is difficult.

The polymerization temperature is preferably 100 占 폚 to 300 占 폚, and more preferably 125 占 폚 to 280 占 폚. If the polymerization temperature is less than 100 占 폚, the initial reaction rate is too slow to lower the conversion to EVA, and an ultrahigh molecular weight chain is formed, which results in undesirable molecular weight and molecular weight distribution, which is undesirable. If the polymerization temperature is higher than 300 ° C, decomposition reaction of vinyl acetate occurs, and the reactor is corroded, resulting in a concern about stability.

If the polymerization pressure is less than 2000 kg / cm < 2 >, the reaction efficiency of the initiator deteriorates and the reaction becomes insufficient or the temperature tends to increase to the desired polymerization temperature, which is preferable If it is more than 3000 kg / cm 2, generation of a long-chain branch is inhibited and melt tension is lowered, which is not preferable.

The residence time in the reactor is preferably from 1 to 10 minutes. If the residence time is less than 1 minute, the conversion to EVA is low and the molecular weight distribution is widened to limit melt tension and improve viscoelastic properties, If it is more than 10 minutes, EVA which has been exposed to high temperature is decomposed, the polymer properties are lost, and an excessively reacted polymer chain generates a gel, which is not preferable.

In the EVA resin production method of the present invention, the ethylene monomer and the vinyl acetate monomer to be fed into the reactor are fed in at least two or more portions. In the high-pressure radical reaction, the reactivity ratio of ethylene monomer to vinyl acetate monomer is almost equal to 1: 1.05, so that EVA is polymerized at a rate substantially similar to that of the injected monomer (Reference).

Figure 1 illustrates a process diagram of a tubular reactor. FIG. 1 is a diagram for illustrating the present invention in more detail, and the present invention is not limited to the arrangement of corresponding process drawings. In the present invention, the ratio of the ethylene monomer to the vinyl acetate monomer entering the reactor through the first monomer inlet 6 and the ratio of the ethylene monomer to the vinyl acetate monomer entering the second monomer inlet 7 are different.

The major part of the tubular polymerization reaction can be divided into a compressor, a reactor, a separator and an extruder as shown in Fig. The purified ethylene monomer 1 and vinyl acetate monomers 3 and 4 in the gaseous phase are compressed to about 200 to 300 kg / cm 2 in the primary compressor 2, (5) to 1,000 to 3,000 kg / cm < 2 > and then introduced into the reactor together with the reaction initiator (14-17) or the molecular weight regulator. The reaction is controlled by maintaining a predetermined pressure, temperature (100 to 300 ° C) and time condition in the reactor, and then the reaction product containing the ethylene vinyl acetate copolymer is polymerized in the high pressure separator 10 and the low pressure separator 11, The ethylene vinyl acetate copolymer separated from the reaction monomer and separated through the low pressure separator is cut into a pellet through an extruder and packaged as a product. The monomer may be injected into the tubular reactor in one or more places. FIG. 1 shows a method of injecting monomer into two places and polymerizing the monomer in four stages. The monomer is injected into the first monomer injection port 6 and heated to an appropriate reaction temperature through the preheater 8 and then enters the first stage reactor 14 and thereafter to be polymerized. Separately, the compressed monomer is injected through the second monomer inlet 7, heated to an appropriate reaction temperature through the preheater 8, mixed with the first monomer inlet monomer / polymer, and then mixed with the second monomer inlet / And polymerization is carried out. Then, the polymerization is carried out in a three-stage reactor (after 16) and a four-stage reactor (after 17).

More specifically, the absolute value (ms) of the difference between the ratio (%) by weight of the vinyl acetate monomer in the total monomer of the first monomer inlet and the ratio (%) by weight of the vinyl acetate monomer in the total monomer at the second monomer inlet ) Is not less than 1% and not more than 30%. There are two ways to make the difference in the monomer ratios: let s be larger than m, and let m be larger than s. If the difference between the monomer ratios m and s is less than 1%, the vinyl acetate content of the EVA polymerized in the first stage reactor and the second stage reactor and the subsequent three stage or fourth stage reactor are all equal, so that the melt tension is not improved. If the difference between m and s exceeds 30%, the difference in the content of vinyl acetate in the EVA polymerized in the EVA produced in the one-stage reactor and the two-stage reactor and the subsequent three-stage and four-stage reactor is large, And the melt strength is lowered by phase separation, which is not preferable.

According to an embodiment of the present invention, the method may further include adding a concentration of 50 to 3,000 ppm of the polymerization initiator before the second step, or the second step and the fourth step.

In the EVA resin production method of the present invention, when the addition concentration of the peroxide initiator is less than 50 ppm, the reaction temperature during polymerization is low and the conversion to EVA is low and the molecular weight is not easily controlled. There is a possibility that the resin is decomposed due to a high reaction temperature at the time of reaction, and decomposition of vinyl acetate causes acetic acid to corrode the reactor.

Specific examples of the dialkyl peroxy dicarbonate compound that can be used as a polymerization initiator in the present invention include Di (2-ethylhexyl) peroxy-dicarbonate and Di-butyl peorxy-dicarbonate, and alkyl peroxypivalate Specific examples of the compound include t-Amyl peroxypivalate and t-Butyl peroxypivalate. Specific examples of the alkyl peroxyalkylhexanoate compound include t-Amyl peroxy-2-ethylhexanoate, t-Butyl peroxy -2-ethylhexanoate and tert-butyl peroxy-3,5,5-trimethylhexanoate. Specific examples of the dialkyl peroxide compound include Dt-butyl peroxide and Di-t-Amyl peroxide .

The peroxide initiator mixture to be used in the present invention may be at least one selected from the group consisting of dialkyl peroxydicarbonate (a), alkylperoxy pivalate compound (b), alkylperoxyalkylhexanoate compound (c) and dialkyl peroxide type (D): e: f: g: h where e, f, g and h are at least one member selected from the group consisting of 0 to 8.0, and it is preferable that none of them is 0. When the mixing weight ratio between the peroxide initiators is out of the above range, it is not preferable to control the molecular weight easily.

In order to achieve still another object of the present invention, there is provided an EVA resin for foaming use which has a high melt tension and an improved viscoelastic property. The EVA resin preferably has a VA content of 10 to 40% by weight, a melt index of 1 to 10 g / 10 minutes as measured at 190 占 폚 under a load of 2.16 kg, more preferably a VA content of 15 to 40% The melt index is 1 to 10. When the VA content of the EVA resin is less than 3% by weight, stretchability, elasticity and adhesiveness are deteriorated. When the VA content exceeds 40% by weight, polymerization and production are not possible due to the nature of the tubular reactor. If the melt index of the EVA resin is less than 0.3 g / 10 min, the processability is deteriorated. If the EVA resin exceeds 50 g / 10 min, the melt tension decreases and production is difficult due to limitations of the extruder.

In order to achieve still another object of the present invention, there is provided an EVA resin for extrusion coating which has a high melt tension and an improved viscoelastic property. The EVA resin preferably has a VA content of 5 to 40% by weight, a melt index of 10 to 40 g / 10 min as measured at 190 占 폚 under a load of 2.16 kg, more preferably a VA content of 10 to 25% The index is 12-30. When the VA content of the EVA resin is less than 5% by weight, the adhesive strength is lowered, which is undesirable. When the VA content is more than 40% by weight, blocking effect occurs in the coating film. When the melt index is less than 5, the flowability is poor and the coating is not good. When the melt index is more than 40, it is difficult to use for the coating because of the deepening of the neck phosphorus.

In the present invention, additives may be added to the extent that the nature of the invention is not impaired. These additives include hindered phenol antioxidants, phosphite antioxidants, lactone antioxidants, ethanol amine antioxidants, HALS antioxidants, UV stabilizers, UV fog agents, neutralizers, anti-blocking agents, slip agents, .

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

Example 1

The ethylene vinyl acetate copolymer was polymerized in the tubular reactor according to the method of the present invention under the conditions shown in Table 1. The reaction temperature was polymerized under the conditions shown in Table 1 within the range of from a minimum of 100 占 폚 to a maximum of 300 占 폚, and was manufactured at a reaction pressure of 2650 kg / cm2. The ratio (m) of the vinyl acetate monomer at the first monomer inlet is 12 wt%, and the ratio (s) of the vinyl acetate monomer at the second monomer inlet is 22 wt%. The absolute value of the difference in the monomer ratio is 10%.

Since the reactivity between ethylene and VA is almost 1: 1, EVA of 12% VA at stage 1 and 17% VA at stage 2 were polymerized to produce an average VA of 15%. 1,200 ppm of a mixture of peroxy-dicarbonate, t-Butyl peroxy pivalate, t-Butyl peroxy-2-ethylhexanoate and tert-butyl peroxy-3,5,5-trimethylhexanoate (20/20/30/30) The EVA resin was prepared by polymerization under the reaction pressure of 2650 kg / cm 2 and the reaction temperature of 235 ° C. in a tubular reactor. Propylene was used as a molecular weight regulator and 44 kg / h was injected.

Example 2

The polymerization conditions were the same as in Example 1 except that the ratio (m) of the vinyl acetate monomer at the first monomer inlet was 20.9 wt%, the ratio (s) of the vinyl acetate monomer at the second monomer inlet was 17.1 wt% Was 3.8% by weight in terms of absolute value.

Example 3

Polymerization was carried out in the same manner as in Example 1 except that the ratio (m) of the vinyl acetate monomer in the first monomer inlet was 23.9 wt%, the ratio (s) of the vinyl acetate monomer in the second monomer inlet was 21.1 wt% Was 2.8% by weight.

Example 4

The polymerization conditions were as in Example 1, the polymerization pressure was 2300 kg / cm 2, the ratio (m) of the vinyl acetate monomer in the first monomer inlet was 23.0 wt%, the ratio of the vinyl acetate monomer in the second monomer inlet s) was 15.8% by weight, and the absolute value of the difference in the monomer ratio was 7.2% by weight.

Comparative Example 1

Polymerization was carried out in the same manner as in Example 1 except that the ratio (m) of the vinyl acetate monomer at the first monomer inlet and the ratio (s) of the vinyl acetate monomer at the second monomer inlet were the same 15 wt%.

Comparative Example 2

Polymerization was carried out in the same manner as in Example 1 except that the ratio (m) of the vinyl acetate monomer at the first monomer inlet and the ratio (s) of the vinyl acetate monomer at the second monomer inlet were both 18 wt%. .

Comparative Example 3

Polymerization was carried out in the same manner as in Example 1 except that the ratio (m) of the vinyl acetate monomer at the first monomer inlet and the ratio (s) of the vinyl acetate monomer at the second monomer inlet were both 22 wt%. .

Comparative Example 4

Polymerization was carried out in the same manner as in Example 4 except that the ratio (m) of the vinyl acetate monomer at the first monomer inlet and the ratio (s) of the vinyl acetate monomer at the second monomer inlet were both 18 wt%.

The physical properties of the EVA resin prepared under the conditions of the above Examples and Comparative Examples were measured by the following physical property measuring methods, and the results are shown in Table 2 below. The EVA resin thus prepared was molded into films according to the following film production conditions, and the properties thereof were evaluated. The results are also shown in Table 2 below.

How to measure property

The physical properties of the EVA resin prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were measured by the following methods and standards.

1) Measurement of melt flow index: Measured according to ASTM D 1238 at 190 캜, 2.16 kg.

2) Measurement of VA content: Measured by Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR).

3) Melt strength (SMER): Measured by pulling the molten resin at 160 ° C at an acceleration of 1 mm / sec at a piston speed of 10 mm / min. (Chamber temperature: 100 DEG C, Die L32 D2)

4) Neck In: We measured the neck-in of the processed film by changing the take-up speed at 180 ° with an OCS casting machine.

division Example Comparative Example One 2 3 4 One 2 3 4 One-stage reactor Early
Temperature (℃) 136 136 135 141 141 138 133 141 Best
Temperature (℃) 251 245 236 275 274 250 237 275 Two-stage reactor Best
Temperature (℃) 271 258 236 275 274 265 236 274 Three-stage reactor Best
Temperature (℃) 271 255 234 272 275 264 237 272 4-stage reactor Best
Temperature (℃) 253 235 221 261 263 235 223 259 Propylene injection amount (kg / h) 44 0 0 15 26 0 0 50 The amount of ethylene monomer injected (T / h) 13.7 13.2 12.4 15.7 14.8 13.5 12.5 15.8 VA dose (T / h) 4.31 5.56 6.42 6.43 4.26 5.68 6.42 6..44 Main stream VA ratio (m), (% by weight) 12.0 20.9 23.9 23.0 15 18 22 18 Side stream VA ratio (s), (wt%) 22.0 17.1 21.1 15.8 15 18 22 18 Note - The difference in the side VA ratio,
(ms) 10.0 3.8 2.8 7.2 0 0 0 0 Polymerization pressure (kg / cm2) 2650 2650 2650 2300 2650 2650 2650 2300 Production (ton / hr) 15.4 15.5 15.4 18.4 15.8 16.3 15.5 18.4

Example Comparative Example One 2 3 4 One 2 3 4 Melt Index (g / 10 min) 1.95 2.1 2.9 14.5 1.74 2.0 3.0 15.6 VA content (% by weight) 14.7 18.6 22.1 18.1 15.1 18.2 22.2 17.5 Melt tension (mN) 106 119 81 - 97 102 73 - Neck-in (mm) 16 21 - 19 18 23 - 22

As shown in the above Tables 1 and 2, in the case of the EVA resin of the examples prepared by the method of the present invention, the melt tension was increased, and the film made of the EVA resin of Examples was made of the EVA resin of Comparative Examples The film neck-in was significantly reduced compared to the film.

1. Fresh ethylene injection 2. B / P Compressor
3. VA main inlet 4. VA side inlet
5. Hyper compressor 6. First monomer inlet
7. Second monomer inlet 8. Pre-heater
9. After cooler 10. HPS
11. LPS 12. Low pressure recycle
13. High pressure recycle 14. Peroxide inlet
15. Second stage Peroxide inlet 16. Third stage Peroxide inlet
17. Four-stage Peroxide inlet

Claims (8)

A method for producing an ethylene vinyl acetate copolymer by injecting an ethylene monomer and a vinyl acetate monomer in a high-pressure tubular reactor,
A first step of injecting the vinyl acetate monomer through at least two or more monomer injection ports;
A second step of polymerizing the vinyl acetate monomer introduced into the first monomer inlet of the two or more monomer injection ports in a one-stage reactor;
A third step in which the vinyl acetate monomer charged into the second monomer inlet of the two or more monomer injection ports is mixed with the monomer and polymer of the first stage; And
And a fourth step in which the monomer and the polymer of the third step are polymerized in a two-stage reactor,
The absolute value of the difference between the content of the vinyl acetate monomer injected into the first monomer injection port and the content of the vinyl acetate monomer injected into the second monomer injection port in the two or more monomer injection ports is 1 to 30% Wherein the vinyl acetate monomer is injected in such a manner that the vinyl acetate monomer is injected. The method according to claim 1,
Wherein the vinyl acetate monomer is heated to a temperature of 100 to 300 DEG C after the first step. The method according to claim 1,
And further polymerizing the copolymer in at least one or more stages of the reactor after the fourth step. The method according to claim 1,
Wherein the polymerization in the second and fourth steps is performed at a temperature of 100 to 300 DEG C under a pressure of 2000 to 3000 kg / cm < 2 > for 1 to 10 minutes. The method according to claim 1,
Wherein the ethylene monomer is 60 to 97% by weight and the vinyl acetate monomer is 3 to 40% by weight. The method according to claim 1,
Further comprising the step of adding 50 to 3,000 ppm of the polymerization initiator before the second step, or the second step and the fourth step,
Wherein the polymerization initiator is selected from the group consisting of a dialkyl peroxy dicarbonate compound (a), an alkylperoxy pivalate compound (b), an alkylperoxy ethylhexanoate compound (c) and a dialkyl peroxide compound (d) At least one peroxide initiator selected,
F, g, and h are included in the range of 0 to 8.0, where e, f (g) and h , g, h is not 0 in the formula (I). An ethylene vinyl acetate copolymer produced by the process for producing ethylene vinyl acetate according to any one of claims 1 to 6,
Wherein the ethylene vinyl acetate has a melt flow index of 1 to 10 (190 DEG C, 2.16 kg), the vinyl acetate content is 15 to 40 wt%
Ethylene vinyl acetate copolymer used for foaming. An ethylene vinyl acetate copolymer produced by the process for producing ethylene vinyl acetate according to any one of claims 1 to 6,
Wherein the ethylene vinyl acetate has a melt flow index of 5 to 40 (190 DEG C, 2.16 kg), the vinyl acetate content is 10 to 25 wt%, and is used for extrusion coating.

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