TWI654211B - Method for producing ethylene/vinyl acetate copolymer resin and ethylene/vinyl acetate copolymer resin produced by the method - Google Patents

Abstract

The invention provides a method for producing ethylene / vinyl acetate copolymer (EVA) resin. The method uses a tube reactor, which includes at least two reactors; and a method for producing the same by using the method. Production of EVA resin. The production method of the EVA resin comprises: injecting an ethylene monomer and a vinyl acetate monomer into a reactor in a restrictive manner, the reactor is coupled to the monomer injection hole; adding a peroxide to start And a polymerization reaction at a temperature of 170-300 ° C and an air pressure of 2000-3000 kg / cm ² for 2-20 minutes. Therefore, an EVA resin having a high crosslinking density and a high crosslinking speed, which is used as a foamed resin or a wire resin, can be easily manufactured.

Description

Production method of ethylene / vinyl acetate copolymer resin and ethylene / vinyl acetate copolymer resin produced by the method

The present invention relates to a method for producing an ethylene / vinyl acetate copolymer (EVA) resin, which is limited to a method for injecting monomers in a tube reactor, and an EVA resin produced by the method The EVA resin has a high crosslinking density and a high crosslinking rate.

Ethylene / vinyl acetate copolymer (EVA) is a copolymer resin with a wide range of industrial applications. Compared with polyethylene (PE), EVA has several advantages, including: according to the low crystallinity of vinyl acetate content and a wide range of use, from lightweight materials to soft materials, such as hot melt adhesives, with low temperature Performance and excellent impact resistance.

However, EVA also has several disadvantages, including: low chemical resistance, poor processability (due to increased adhesion with increasing vinyl acetate content), poor mechanical properties, and when used with a foamed product Reduced pull strength when used. To overcome these shortcomings, a process system that improves mechanical properties by partially crosslinking EVA is widely used. Improved processability by partially crosslinking EVA During the process of manufacturing physical properties, the cross-linking density and cross-linking speed of EVA resin significantly affect the processing and physical properties of the final product, which is a very important factor.

An embodiment of the present invention provides a method for producing an ethylene / vinyl acetate copolymer (EVA) resin, which has excellent cross-linking characteristics.

An embodiment of the present invention also provides an ethylene / vinyl acetate copolymer (EVA) resin, which has excellent cross-linking characteristics.

The above and other aspects of the present invention will be described or made apparent in the description of the following exemplary embodiments.

According to one aspect of the present invention, it provides a method for producing an ethylene / vinyl acetate copolymer (EVA) resin. The method uses: a tubular reactor, which includes at least two reactors; a monomer An injection hole, which is coupled to one end of the tubular reactor; and an EVA resin ejector, which is coupled to the other end of the tubular reactor, the method comprising: The monomer and vinyl acetate monomer are injected only into the reactor coupled to the monomer injection hole.

As described above, in a method according to an embodiment of the present invention, when it is applied to a crosslinking process by restricting a monomer injection method restrictively, it can be processed to exhibit excellent crosslinking characteristics. EVA resin.

In addition, the EVA resin system produced by the method according to an embodiment of the present invention can exhibit excellent characteristics, including high crosslink density and excellent mechanical characteristics and processability. Therefore, an EVA resin used as a foamed resin or a wire resin can be easily provided.

The above information disclosed in this background section is only used to enhance the understanding of the background of the technology, and therefore it may contain information that is not already familiar to those of ordinary skill in the technical field to which this invention belongs in this country. .

The above and other features of the present invention will become more apparent through its detailed exemplary embodiments and with reference to the accompanying drawings, in which: [Fig. 1] depicts Examples 1-4 and A graph of the measured shear thinning index (STI) value versus the MI (measured at 2.16 kg at 190 ° C) of the EVA resin produced in Comparative Examples 1-4, which uses an advanced Rheometric expansion system (Advanced Rheometric Expansion System, ARES) rheometer, measured under the conditions of frequency scanning, 180 ℃ and strain 10%.

Hereinafter, examples of the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this way, they can be easily manufactured and used by those with ordinary knowledge in the technical field to which the present invention belongs.

The invention provides a method for producing an ethylene / vinyl acetate copolymer (EVA) resin. The method uses: a tubular reactor comprising at least two reactors; a monomer injection hole which is coupled to One end of the tubular reactor; and an EVA resin ejector coupled to the other end of the tubular reactor. The method includes: limiting an ethylene monomer and a vinyl acetate monomer in a restrictive manner. The body is injected only into the reactor coupled to the monomer injection hole.

In the production method of the EVA resin according to the present invention, when the ethylene monomer and vinyl acetate monomer system injected into the reactor are additionally injected into other reactors or systems other than the reactor connected to the monomer injection hole When reacting in an autoclave reactor, it is difficult to improve the cross-linking speed and cross-linking density due to the STI values of the products that increase with the same VA composition and MI.

In a tubular reactor composed of two or more reactors, a reactor connected to the monomer injection hole is called a first-stage reactor, and a subsequent reactor is called a second-stage reactor. Reactors, third-stage reactors, and so on, based on the number of reactors.

According to an embodiment of the present invention, the ethylene monomer and the vinyl acetate monomer are preferably injected at a ratio of 60 to 90: 10 to 40 by weight. If the content of ethylene monomer in the EVA resin is greater than 90% by weight or the content of vinyl acetate monomer is less than 10% by weight, it will exhibit insufficient elasticity and flexibility, making the EVA resin unsuitable for use as a hair Foam resin or a wire resin. In addition, when the content of the ethylene monomer injected into the tubular reactor is less than 60 wt% or the content of the vinyl acetate monomer is more than 40 wt%, the polymerization reaction on the EVA resin will be difficult to proceed, which is not desirable.

According to an embodiment of the present invention, the method for producing an EVA resin further includes: adding a polymerization reaction initiator. The polymerization reaction initiator may include: at least one selected from the group consisting of C4-C40 dialkylperoxy dicarbonate-based compounds including di (2-ethylhexyl) peroxydicarbonate (di (2-ethylhexyl) peroxy-dicarbonate), di-butyl peroxy-dicarbonate, C4-C20 alkylperoxy pivalate-based compounds include tertiary T-amyl peroxypivalate, t-butyl peroxypivalate, C4-C20 alkylperoxy alkylhexanoate- based compounds) including t-amyl peroxy-2-ethyl hexanoate, t-amyl peroxy-2-ethyl hexanoate, t-amyl peroxy-2-ethyl hexanoate (t-butyl peroxy-2-ethyl hexanoate) and tert-butyl peroxy-3,5,5-trimethylhexanoate and C4 ~ C20 bis Dialkyl peroxide-based compounds include groups consisting of di-t-butyl peroxide and di-t-amyl peroxide .

The peroxy polymerization initiator used in the present invention is preferably added at a concentration of 50 to 3,000 ppm. The peroxy polymerization initiator includes at least one selected from the group consisting of (A) dialkyl peroxydi Carbonate-based compounds (dialkylperoxy dicarbonate-based compound), (B) alkylperoxy pivalate-based compounds, (C) alkylperoxy ethyl caproate-based compounds (alkylperoxy ethyl hexanoate-based compound) and (D) a dialkyl peroxide-based compound. If the added concentration of the peroxygen initiator is less than 50 ppm, the reaction temperature during the polymerization reaction is low, resulting in a low turnover rate to EVA, and it is not easy to control the molecular weight of the peroxygen initiator, This is not ideal. If the added concentration of the peroxygen initiator is more than 3,000 ppm, the reaction temperature during the polymerization reaction is high, which causes the EVA resin to be easily decomposed, and because the reactor is corroded by the decomposed vinyl acetate, acetic acid is generated. This is not ideal.

According to an embodiment of the present invention, the polymerization reaction temperature is preferably in a range of 170 to 300 ° C. If the polymerization reaction temperature is lower than 170 ° C, the turnover rate of EVA becomes low, and it is difficult to achieve a desired molecular weight and a desired molecular weight distribution, which is not desirable. If the polymerization reaction temperature is higher than 300 ° C, a decomposition reaction will occur and the reactor will be corroded, thereby undesirably reducing stability.

In addition, the polymerization pressure is preferably in the range of 2000 to 3000 kg / cm ² . If the polymerization reaction pressure is lower than 2000 kg / cm ² , the reaction is insufficient to occur or the work stability is lowered, which is not desirable. If the polymerization pressure is higher than 3000 kg / cm ² , a high-pressure pump may limit performance, and thus undesirably reduces stability.

In addition, the polymerization reaction time is preferably in the range of 2 to 20 minutes. If the polymerization reaction time is shorter than 2 minutes, the turnover rate of EVA is low and the molecular weight is small, which is not desirable. If the polymerization reaction time is longer than 20 minutes, it will not be easy to control the polymerization pressure, and gel formation may occur, which is not desirable.

In order to achieve the objective of the present invention, the present invention provides an EVA resin produced by the method for producing an EVA resin according to the present invention.

According to an embodiment of the present invention, the MI value of the EVA resin measured when filled at 2.16 kg at 190 ° C is in the range of 0.5 to 30 g / 10 min, and an Advanced Rheometric Expansion System (ARES) is used. Rheometer, under conditions of frequency sweep, 180 ° C and strain of 10%, the shear thinning index (STI) value measured for this MI is greater than 13.987 * MI ^-0.75 and less than 26.956 * MI ^-0.687 ( ^13.987 * MI ^-0.75 <STI <26.956 * MI ^-0.687 ).

If the MI system of the EVA resin is less than 0.5 g / 10min, the processability is poor and undesired. If the MI system of the EVA resin is greater than 30 g / 10min, the melt tension system decreases and exhibits poor cross-linking characteristics, which is not desirable.

Using an ARES rheometer, under the conditions of frequency sweep, 180 ° C and 10% strain, the STI value measured for this MI is preferably greater than 13.987 * MI ^-0.75 and less than 26.956 * MI ^-0.687 ( ^13.987 * MI ^-0.75 <STI <26.956 * MI ^-0.687 ). If the STI value is less than 13.987 * MI ^-0.75 , the cross-linking speed is too high, so that premature curing or coking may occur, or an unpleasant appearance (such as gel formation) may easily occur. If the STI value is greater than 26.956 * MI ^-0.687 , it will be difficult to achieve the ideal crosslinking density and high crosslinking speed.

In the present invention, additives may be added unless they will hinder the nature or essence of the present invention. The additives may include: a hindered phenol-based antioxidant, a phosphite-based antioxidant, a lactone-based antioxidant, and an ethanolamine group Antioxidant (ethanol amine-based antioxidant), a hindered amine light stabilizer-based antioxidant (HALS-based antioxidant), an ultraviolet stabilizer (UV stabilizer), an ultraviolet absorbent (UV absorbent), a neutralizer (neutralizer ), An anti-blocking agent, a slipping agent, a nucleating agent, a pigment, and so on.

The EVA resin according to the present invention is excellent in electrical insulation characteristics and withstand voltage characteristics, so that it can be ideally used for a tube, a wire covering, and the like. In addition, foamed products are manufactured using the viscoelastic properties of EVA, which are used in insoles to absorb impact, electrical insulation products, tapes, sheets and the like.

Hereinafter, the present invention will be further described in detail with reference to the following examples, which are provided as exemplary illustrations of the present invention and are not intended to limit the scope of the present invention.

Example 1

A tubular reactor having two continuously connected reactors was used, and 82% by weight of ethylene monomer and 18% by weight of vinyl acetate single system were produced with a limitation by the production method of EVA resin according to the present invention. In a sexual way, only one of the monomer injection holes of a reactor is injected. Subsequently, di (2-ethylhexyl) peroxy-dicarbonate and tert-butylperoxypivalate were mixed at a ratio of (20/20/30/30). (t-butylperoxypivalate), t-butyl peroxy-2-ethyl hexanoate, and t-butylperoxy-2-ethyl hexanoate ( tert-butyl peroxy-3,5,5-trimethylhexanoate) was added at a concentration of 1200 ppm as a radical generating catalyst, and then a high-pressure pump for polymerization was used at a polymerization pressure of 2650 kg / cm ² Under the conditions of a polymerization reaction temperature of 235 ° C and a polymerization reaction time of 3 minutes, it was transferred to the tubular reactor, thereby producing an EVA resin according to the present invention.

Example 2

74wt% of ethylene monomer and 26wt% of vinyl acetate single system were injected into a reactor in only one monomer injection hole in a restrictive manner, and propionaldehyde was added at a concentration of 70ppm as a A chain transfer agent, which is a molecular weight adjuster, thereby producing an EVA resin under the same polymerization conditions as in Example 1.

Example 3

72% by weight of ethylene monomer and 28% by weight of vinyl acetate single system were injected into a single monomer injection hole of a reactor in a restrictive manner, except that the polymerization temperature was 190 ° C, thereby An EVA resin according to the present invention was produced under the same polymerization conditions as in Example 1.

Example 4

67% by weight of ethylene monomer and 33% by weight of vinyl acetate single system were injected into one of the reactor's monomer injection holes in a restrictive manner, and propionaldehyde was added at a concentration of 70ppm as a A chain transfer agent, which is a molecular weight modifier, except that the polymerization reaction temperature is 180 ° C., thereby producing the EVA resin according to the present invention under the same polymerization reaction conditions as in Example 1.

Comparative Example 1

82wt% ethylene monomer and 18wt% vinyl acetate single system are injected into the monomer injection hole of the first-stage reactor and the unit of the second-stage reactor at a ratio of 50 to 50 in a partial manner. The body was injected into the hole, whereby an EVA resin was produced under the same polymerization conditions as in Example 1.

Comparative Example 2

74wt% ethylene monomer and 26wt% vinyl acetate single system were injected into the monomer injection hole of the first-stage reactor and the unit of the second-stage reactor in a one-by-one manner at a ratio of 50 to 50. The body was injected into the hole, whereby an EVA resin was produced under the same polymerization conditions as in Example 2.

Comparative Example 3

A traditional EVA resin production method using a one-tube reactor is applied to 72% by weight of ethylene monomer and 26% by weight of vinyl acetate monomer, thereby producing EVA that is commercially available from Arkema 28-03 products.

Comparative Example 4

A traditional EVA resin production method using an autoclave reactor is applied to 67 wt% of ethylene monomer and 33 wt% of vinyl acetate monomer, thereby producing EVA that is commercially available from Lotte Chemical VC710 products.

Various physical properties of the EVA resin produced under the conditions of the examples and comparative examples were measured by the following measurement methods, and the measurement results are shown in Table 1.

Test example: measurement of physical characteristics

Various physical properties of the EVA resin produced in Examples 1-4 and Comparative Examples 1-4 were measured in the following manner and standards:

1) VA content: VA content is measured by Differential Scanning Calorimeter (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR).

2) Melt Index (MI): The MI value is measured according to ASTM D1238 at 2.16 kg at 190 ° C.

3) Shear thinning index (STI): STI is measured using an ARES rheometer under the conditions of frequency sweep, 180 ° C and 10% strain, and by using a shear rate of 0.1 The value (w0.1 / w100) obtained by dividing the viscosity at the shear rate by 100 at the shear rate is used.

4) Cross-linking density and cross-linking speed: 2wt% dicumyl peroxide (DCP) as a cross-linking agent was added to the EVA resin produced in the examples and comparative examples, and the product obtained The compound was kneaded at 80 ° C for 5 minutes, then granulated at 90 ° C, and a curing curve of the compound was obtained using an Oscillating Disk Rheometer (ODR) at 180 ° C. In order to measure the crosslinking speed, the delta torque (MH-ML) value representing the difference between the minimum torque value (ML) and the maximum torque value (MH) is usually defined as the crosslinking density And the time when the torque value corresponds to 10% from the minimum torque value to the △ torque (MH-ML) value and the time when the torque value corresponds to 90% from the minimum torque value to the △ torque (MH-ML) value are respectively Defined as coking time (T10) and appropriate cross-linking time (T90).

5) Appearance: After cross-linking, the cross-linked product is observed by naked eyes, and the surface roughness and gel formation are identified.

As shown in Table 1 and Figure 1, the STI values of the EVA resins produced in Examples 1 to 4 were measured relative to the MI using an ARES rheometer under conditions of frequency sweep, 180 ° C, and 10% strain , And the measured STI values are greater than 13.987 * MI ^-0.75 and less than 26.956 * MI ^-0.687 , which is ^13.987 * MI ^-0.75 <STI <26.956 * MI ^-0.687 . The compounds prepared from the EVA resins produced in Examples 1 to 4 used the same amount of crosslinking agent, and their crosslinking characteristics were evaluated. The evaluation results show that these EVA resins have improved cross-linking density and cross-linking speed compared to the comparative examples, and have good appearance characteristics.

Although the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it should be understood that the present invention has the following technical scope without departing from the spirit and scope of the invention as defined by the following patent application scope: Knowledge can usually be changed in many forms and details.

Claims (7)

An ethylene / vinyl acetate copolymer (EVA) resin, in which an Advanced Rheometric Expansion System (ARES) rheometer is used. The frequency sweep, 180 ° C and strain (strain) 10%, the shear thinning index (STI) value measured for the Melt Index (MI) of the EVA resin is greater than 13.987 * MI ^-0.75 and less than 26.956 * MI- ^0.687 , in which the method for producing the ethylene / vinyl acetate copolymer (EVA) resin is used: a tube reactor comprising at least two reactors, wherein the at least two reactors are continuously connected; A monomer injection hole, which is coupled to the first-stage reactor in the at least two reactors; and an EVA resin ejector, which is coupled to the last-stage reactor in the at least two reactors, The method includes: injecting an ethylene monomer and a vinyl acetate monomer into only the first stage reactor coupled to the monomer injection hole in the at least two reactors. The EVA resin according to claim 1, wherein the ethylene monomer and the vinyl acetate single system are injected at a ratio of 60 to 90: 10 to 40 by weight. The EVA resin according to claim 1, wherein the method for producing the EVA resin further comprises a step of adding (A) a C4-C40 dialkylperoxydicarbonate-based compound (a) at a concentration of 50 to 3,000 ppm. dicarbonate-based compound) as a polymerization reaction initiator, and at least one selected from (B) C4 ~ C20 alkylperoxy pivalate-based compounds, (C) C4 ~ C20 alkyl Initiation of another polymerization reaction of a group consisting of alkylperoxy alkyl hexanoate-based compound and (D) C4 ~ C20 dialkyl peroxide-based compound Agent. The EVA resin according to claim 1, wherein the polymerization initiator is at least one selected from the group consisting of di (2-ethylhexyl) peroxy-dicarbonate, dibutyl Di-butyl peroxy-dicarbonate, t-amyl peroxypivalate, t-butyl peroxypivalate, t-amyl peroxypivalate T-amyl peroxy-2-ethyl hexanoate, t-butyl peroxy-2-ethyl hexanoate, and t-butyl peroxy-2-ethyl hexanoate Tert-butyl peroxy-3,5,5-trimethylhexanoate, di-t-butyl peroxide and di-t-pentyl peroxide A group of di-t-amyl peroxide. The EVA resin according to claim 1, wherein the tubular reactor is subjected to polymerization under the conditions of a polymerization temperature of 170 to 300 ° C, a polymerization pressure of 2000 to 3000 kg / cm ² and a polymerization time of 2 to 20 minutes. The EVA resin according to claim 1, wherein the EVA resin has a Melt Index (MI) of 0.5 to 30 g / 10 min (190 ° C, 2.16 kg). The EVA resin according to claim 1, wherein the EVA resin is used as a foamed resin or a wire resin.