KR20180055561A - Ethylene vinyl acetate and molded article produced therefrom - Google Patents

Abstract

The present invention relates to an ethylene vinyl acetate copolymer and a molded article produced therefrom. To this end, in the ethylene vinyl acetate copolymer, content of vinyl acetate is 25-35 wt%, a melt index (measured by a load of 2.16 kg at 125°C based on ASTM D1238) is 2-6 g/10min, long chain branch (LCB) content is less than or equal to 2 per 1000 carbon atoms, and a polydispersity index (PDI) is 2-4. According to the present invention, it is possible to provide ethylene vinyl acetate copolymers having a low PDI and sufficient tensile strength while ensuring high content of vinyl acetate.

Description

TECHNICAL FIELD [0001] The present invention relates to an ethylene vinyl acetate copolymer, and a molded article produced therefrom. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to ethylene vinyl acetate copolymers having a high content of vinyl acetate but having a narrow molecular weight distribution and a sufficient tensile strength.

Ethylene Vinyl Acetate is a copolymer of ethylene and vinyl acetate and has a wide range of applications from hard materials to flexible materials such as hot melt adhesives depending on the content of vinyl acetate. It has a lower crystallinity than polyethylene, low temperature characteristics and impact resistance This is an excellent feature.

Ethylene vinyl acetate has a thermoplastic polymer or rubber character and is excellent in electrical insulation and dielectric strength and is excellent in transparency, barrier property, adhesive property, and UV characteristic. Therefore, it can be used as a tube, a packaging material, Tapes, adhesives, various sheets, and the like. In recent years, the protective film for photoelectric devices such as solar cells has been widely used.

Generally, the ethylene vinyl acetate copolymer can be prepared by injecting ethylene and vinyl acetate into an autoclave reactor or a tubular reactor at an appropriate ratio and polymerizing at a high temperature / high pressure. At this time, when the content of vinyl acetate added to the reactor is increased, some vinyl acetate may act as a chain transfer agent, resulting in a lower molecular weight of ethylene vinyl acetate, a higher melt index (MI) There is a limit to the deterioration of the same mechanical properties.

Therefore, in the case of the conventional ethylene vinyl acetate copolymer having a high vinyl acetate content, flexibility and elasticity are excellent, but mechanical properties and processability are lowered, and the use thereof is limited there was.

Accordingly, there is still a need for research on an ethylene vinyl acetate copolymer having a sufficient tensile strength while maintaining a high content of vinyl acetate required for ethylene vinyl acetate for use in applications such as wire and foaming.

The present invention is intended to provide an ethylene vinyl acetate copolymer having a high content of vinyl acetate and a narrow molecular weight distribution and a sufficient tensile strength.

The present invention is characterized in that the content of vinyl acetate is 25 to 35% by weight,

A melt index (measured according to ASTM D 1238 at 2.16 kg load at 125 캜) of 2 to 6 g / 10 min,

The content (LCB) of the long chain branch is 2 or less per 1,000 carbon atoms,

And an ethylene vinyl acetate copolymer having a molecular weight distribution (PDI) of 2 to 4.

The present invention also provides a molded article produced from the ethylene vinyl acetate copolymer.

DETAILED DESCRIPTION OF THE INVENTION The ethylene vinyl acetate copolymer according to a specific embodiment of the present invention and a molded article produced therefrom will be described in detail below.

According to one embodiment of the invention, the content of vinyl acetate is 25 to 35% by weight,

A melt index (measured according to ASTM D 1238 at 2.16 kg load at 125 캜) of 2 to 6 g / 10 min,

The content (LCB) of the long chain branch is 2 or less per 1,000 carbon atoms,

An ethylene vinyl acetate copolymer having a molecular weight distribution (PDI) of 2 to 4 is provided.

The ethylene vinyl acetate copolymer of one embodiment of the present invention can exhibit excellent flexibility, elasticity, tensile strength, and the like by including vinyl acetate in a relatively high content of about 25 to 35% by weight, or about 25 to 30% by weight.

The ethylene vinyl acetate copolymer has a low melt index (measured according to ASTM D1238 at 125 DEG C under a load of 2.16 kg) of about 2 to 6 g / 10 min. Generally, when the content of vinyl acetate in the ethylene vinyl acetate copolymer is increased, some vinyl acetate may act as a chain transfer agent, resulting in a lower molecular weight of ethylene vinyl acetate, a higher melt index (MI) The ethylene vinyl acetate copolymer of the embodiment has vinyl acetate content of about 25% by weight or more. However, by adjusting the polymerization conditions so as to have a low melt index, the ethylene vinyl acetate copolymer having mechanical properties such as tensile strength Can be kept excellent.

And, the content of long chain branch (LCB) of the ethylene vinyl acetate copolymer is about 2 or less per 1,000 carbon atoms. The content of the long chain branch is related to the molecular weight distribution and the tensile strength property of the ethylene vinyl acetate copolymer. When the content of the long chain branch is small, as in the copolymer of the embodiment, it has a narrow molecular weight distribution and high tensile strength And can be very preferably used for applications such as wire and foaming.

On the other hand, the content (LCB) of the long-chain branch is measured using ¹³ C-NMR. Specifically, the sample was dissolved in a solvent of TCE-d2 (1,1,2,2-Tetrachloroethane-d2), subjected to ¹³ C-NMR and analyzed for the number of branches having 6 or more carbon atoms per 1,000 carbon atoms The sum is measured in a manner that calculates.

Also, the ethylene vinyl acetate copolymer has a narrow molecular weight distribution (PDI) of about 2 to 4, or about 2 to 3.5. The molecular weight distribution (PDI) means the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn), and if the molecular weight distribution exceeds 4, the tensile strength decreases.

The ethylene vinyl acetate copolymer may have a tensile strength (measured according to ASTM D638) of about 120 to 200 kg / cm 2, preferably about 150 to 200 kg / cm 2.

The ethylene vinyl acetate copolymer may have a weight average molecular weight (Mw) of about 80,000 to 100,000 g / mol, preferably about 80,000 to 90,000 g / mol, and a number average molecular weight (Mn) of about 20,000 to 30,000 g / mol, preferably about 23,000 to 28,000.

The molecular weight distribution (PDI), the weight average molecular weight, and the number average molecular weight were measured using Size Exclusion Chromatography (SEC).

On the other hand, the ethylene vinyl acetate copolymer of the embodiment can be produced by polymerizing an ethylene monomer and a vinyl acetate monomer in an autoclave reactor in the presence of a low-temperature initiator and a high-temperature initiator.

The step of polymerizing can be carried out at a pressure of 1800 bar or more while controlling the (maximum reactor bottom temperature) - (inlet gas temperature) of the autoclave reactor to 140 to 160 ° C.

As can be seen from the following examples and the like, two or more initiators including a low-temperature initiator and a high-temperature initiator are used together, and the polymerization conditions such as the temperature and the pressure of each part of the reactor are controlled so that the content of the vinyl acetate , The melt index, the content of the long-chain branch, and the molecular weight distribution can be produced.

In the case where two or more initiators including a low-temperature initiator and a high-temperature initiator are not used, or the polymerization conditions are different, the ethylene vinyl acetate finally produced does not have a low melt index within the above-mentioned range, The content of the branch may not meet the above-mentioned range.

A more detailed description of the method for producing ethylene vinyl acetate in the above embodiment is as follows.

The ethylene vinyl acetate copolymer can be produced in an autoclave or a tubular reactor. Generally, the ethylene vinyl acetate produced in the autoclave reactor has a wide molecular weight distribution and the ethylene vinyl acetate produced in the tubular reactor Has a narrow molecular weight distribution and is generally produced by selecting a reactor according to the application.

However, in the case of using an autoclave reactor in which back-mixing occurs, it is possible to maintain a uniform and high reaction temperature. Therefore, compared to a tubular reactor in which mixing is performed by turbulent plug flow, It is possible to produce an ethylene vinyl acetate copolymer having an acetate content.

Therefore, the production method of this embodiment uses the autoclave reactor, and the polymerization conditions such as the temperature and the pressure in the reactor are controlled. Even though the autoclave reactor is used, the molecular weight distribution is narrow and mechanical properties such as tensile strength The excellent ethylene vinyl acetate copolymer can be produced.

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

In the following description, the low temperature initiator refers to an initiator capable of initiating and / or promoting the reaction between the ethylene monomer and the vinyl acetate monomer at a temperature of from 100 to 160 ° C, Quot; refers to an initiator that can initiate and / or promote at a temperature of about < RTI ID = 0.0 >

Generally, when only one initiator is used in the production of an ethylene vinyl acetate copolymer, the initiator does not react when the operating temperature is too low, and when the reaction temperature is too high, the initiator is decomposed before the copolymer is polymerized, A fall or run away reaction can occur.

Therefore, when a low-temperature initiator and a high-temperature initiator are mixed with an initiator as in the method for producing an ethylene vinyl acetate copolymer of one embodiment, the temperature range in which the apparatus can be operated (for example, the maximum temperature at the bottom of the reactor) Gas temperature) can be increased to increase the production amount of ethylene vinyl acetate having a high molecular weight with a narrow molecular weight distribution.

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

The low-temperature initiator is capable of initiating a polymerization reaction at a temperature lower than a normal high-pressure radical polymerization reaction temperature. For example, 1,4-di (2-neodecanoylperoxyisopropyl) benzene, cumylperoxy neodecanoate (CUPND) , SBPC (di-sec-butyl) peroxydicarbonate, Di (n-butyl) peroxydicarbonate, Di (2-ethylhexyl) peroxydicarbonate, TAPND (Tert-amylperoxyneodecanoate) and TBPND (tert-butyl peroxyneodecanoate) May be used.

The high temperature initiator has a characteristic of being capable of initiating polymerization reaction at a temperature higher than a normal high-pressure radical polymerization reaction temperature. For example, TAPPI (tert-amylperoxy pivalate), TBPPI (tert-butylperoxy pivalate) Tert-butylperoxy 2-ethylhexanoate (TBPEH), tert-butylperoxy-isobutyrate (TBPIB), tert-butylperoxy-3 (TBPIN) 5,5-trimethylhexanoate) and TBPA (tert-butylperoxyacetate) may be used.

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

The step of polymerizing may be carried out by controlling the pressure of the autoclave reactor, the temperature of the introduced gas, the maximum temperature at the lower end of the reactor, and the maximum temperature at the upper end of the reactor so that the content of the long chain branch and the short chain branch of the ethylene vinyl acetate copolymer The molecular weight distribution can be narrowed, and the tensile strength can be increased.

The temperature of the input gas in the autoclave reactor means the average of the temperatures measured between the portion where the input gas is divided to be distributed to each end of the reactor and the portion connected to the reactor. The highest temperature at the lower end of the reactor and the highest temperature at the upper end of the reactor refer to the temperature measured by the thermocouple installed at the lowest position of the reactor and the highest position of the reactor, respectively.

In particular, the (reactor bottom maximum temperature) - (inlet gas temperature) of the autoclave reactor is the reaction condition related to the conversion ratio, ie, the rate at which the monomer is converted to the polymer, The ethylene vinyl acetate copolymer having a higher tensile strength can be produced at a high conversion rate by controlling the temperature to about 140 to 160 ° C.

The temperature of the introduced gas may be about 10 to 60 ° C, preferably about 20 to 50 ° C. When the temperature of the introduced gas is lower than 10 캜, polymerization reaction is unstable, and when the temperature of the introduced gas is higher than 60 캜, the conversion rate is lowered and the production cost of the product is increased.

The lower end maximum temperature of the autoclave reactor may be about 170 to 230 캜, preferably about 180 to 220 캜. When the lower end maximum temperature of the reactor is lower than 170 ° C, the polymerization conversion rate is lowered, which is not preferable from the viewpoint of production cost. When the lower end maximum temperature of the reactor is higher than 230 ° C, run away reaction is caused by the thermal stability problem of the vinyl acetate monomer Lt; / RTI >

The uppermost peak temperature of the autoclave reactor may be about 120 to 180 ° C, preferably about 130 to 170 ° C. When the uppermost peak temperature of the reactor is as low as less than 120 ° C, it is difficult to control the reaction temperature and a lost reaction may occur. When the peak uppermost temperature of the reactor is higher than 180 ° C, the amount of the initiator used for polymerizing the target polymer is increased It is not preferable from the viewpoint of production cost.

Further, the polymerizing step can be carried out at a pressure of about 1800 bar or more, preferably about 1800 to 2000 bar. When the pressure of the reactor is as low as below 1800 bar, the amount of the initiator for the target polymer polymerization increases, which is not preferable from the viewpoint of production cost. When the pressure is higher than 2000 bar, Can occur.

In the process for producing an ethylene vinyl acetate copolymer of the above embodiment, the vinyl acetate monomer is contained in an amount of about 25 to 35 parts by weight, preferably about 25 to 30 parts by weight per 100 parts by weight of the sum of the ethylene monomer and the vinyl acetate monomer can do.

According to another embodiment of the present invention, a molded article produced from the ethylene vinyl acetate copolymer may be provided. As described above, the content of vinyl acetate is 25 to 35% by weight, the melt index (measured according to ASTM D1238 at a load of 2.16 kg at 125 캜) is 2 to 6 g / 10 min, the content of long chain branch (LCB) Ethylene vinyl acetate copolymer having a molecular weight distribution (PDI) of not more than 2 per 1,000 carbon atoms and having a molecular weight distribution (PDI) of 2 to 4 has excellent processability and tensile strength. Thus, the ethylene vinyl acetate copolymer is superior to a conventional molded product made of ethylene vinyl acetate The field is wide.

In addition to ethylene vinyl acetate according to the present invention, the molded article may contain at least one selected from the group consisting of antioxidants, plasticizers, antistatic agents, nucleating agents, flame retardants, lubricants, impact modifiers, fluorescent brighteners, ultraviolet absorbers, pigments and dyes May be further included.

The ethylene vinyl acetate according to the present invention and other additives are well mixed using a mixer and then extruded by an extruder to prepare pellets. The pellets are dried and then injected by an injection molding machine Step < / RTI >

According to the present invention, it is possible to provide an ethylene vinyl acetate copolymer having a high content of vinyl acetate, a narrow molecular weight distribution and a sufficient tensile strength.

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

Example  And Comparative Example

An ethylene vinyl acetate copolymer was prepared using an autoclave reactor under the conditions as shown in Table 1 in the presence of one kind of low-temperature initiator and one kind of high-temperature initiator. In Comparative Example 2, a commercially available ethylene vinyl acetate copolymer product (HH 1828, Hanwha Chemical).

Process conditions Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 VA content (wt%) 27.2 27.4 27.9 27.6 27.4 27.3 Pressure (bar) 1940 1930 1930 1930 1880 - Reactor top temperature (° C) 150 150 150 150 150 - Reactor bottom maximum temperature - Input gas temperature (℃) 140 143 145 148 165 - Conversion Rate (%) 12.2 12.5 12.7 13.0 14.5 -

Experimental Example

The properties of the ethylene vinyl acetate copolymers of Examples 1 to 4 and Comparative Examples 1 and 2 prepared above were measured by the following methods and are shown in Table 2.

(1) MI (melt index): measured according to ASTM D1238 at 125 占 폚 at a load of 2.16 kg.

(2) LCB: A copolymer sample was dissolved in a solvent of TCE-d2 (1,1,2,2-Tetrachloroethane-d2) and subjected to ¹³ C-NMR, and a branched branch having 6 or more carbon atoms per 1,000 carbon atoms And the sum was calculated.

(3) Molecular weight distribution (PDI) and weight average molecular weight (Mw): The size was measured using exclusion chromatography (SEC).

(4) Tensile Strength: The sample of the copolymer was formed into a 2 mm thick sheet using hot press equipment, and then measured with UTM equipment according to ASTM D638.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 MI (g / 10 min) 3.3 3.6 4.2 4.8 5.0 3.4 LCB (/ 1,000C) 1.3 1.4 1.6 1.5 2.5 2.5 PDI 3.1 3.1 3.2 3.3 3.8 3.7 Tensile strength (kg / cm 2) 191 189 169 141 115 135 Mw 86,800 84,200 84,800 85,600 88,400 97,500

As shown in Table 2, the ethylene vinyl acetate copolymer according to the present invention has a low melt index and a long chain branch content of less than 2 per 1,000 carbon atoms, even though the content of vinyl acetate is 25 wt% But also has a narrow molecular weight distribution.

Claims (4)

The content of vinyl acetate is 25 to 35% by weight,
A melt index (measured according to ASTM D 1238 at 2.16 kg load at 125 캜) of 2 to 6 g / 10 min,
The content (LCB) of the long chain branch is 2 or less per 1,000 carbon atoms,
Ethylene vinyl acetate copolymer having a molecular weight distribution (PDI) of 2 to 4.
The method according to claim 1,
Ethylene vinyl acetate copolymer having a tensile strength (measured according to ASTM D638) of 120 to 200 kg / cm2.
The method according to claim 1,
An ethylene vinyl acetate copolymer having a weight average molecular weight of 80,000 to 100,000 g / mol and a number average molecular weight of 20,000 to 30,000 g / mol.
A molded article produced from the ethylene vinyl acetate copolymer of any one of claims 1 to 3.