JP6387053B2 - Method for producing ethylene vinyl acetate copolymer resin for solar cell encapsulant sheet and resin produced by the method - Google Patents

Description

  In the production of an ethylene vinyl acetate copolymer (EVA) resin used for a solar cell encapsulant sheet in a tubular reactor, the present invention relates to the type and content of initiator, the weight ratio of the initiator mixture, and polymerization. The present invention relates to a method for producing an EVA resin capable of reducing the vinyl acetate content in the resin by limiting the conditions, maintaining the sunlight transmittance and transparency, and reducing the amount of acetic acid generated, and the EVA resin produced by this method .

  Solar cell modules used for photovoltaic power generation usually use an ethylene vinyl acetate copolymer (EVA) resin sheet on both sides to protect the cells, and additionally a transparent glass substrate on the side where sunlight is incident And on the opposite side, it is laminated with a sheet excellent in gas barrier properties and weather resistance. In the laminating method, the transparent glass substrate, the EVA sheet, the cell, the EVA sheet, and the gas barrier sheet are laminated, and then heated and crosslinked under a specific temperature and pressure to be bonded. The EVA sheet is made by mixing various additives such as a crosslinking agent, a crosslinking aid, a silane coupling agent, an antioxidant, a light stabilizer, and an ultraviolet absorber with the EVA resin, and then the melting point of the EVA copolymer resin or higher. It is manufactured by melt-kneading in a temperature range that is equal to or lower than the decomposition temperature of the organic peroxide as the agent.

  Generally, the EVA sheet for solar cell encapsulant is used to protect the cell from external impact, and also plays a role of transmitting sunlight transmitted through the glass to the cell without loss of sunlight. The ability to transmit to the cell as is is required. Therefore, the EVA resin used for the solar sealing material is required to have high transparency and high light transmittance.

  Solar modules must be used for 20 years or longer, so long-term durability is required. Among them, a sealing material that protects cells is the most problematic. The ethylene vinyl acetate resin used for the sealing material requires a VA content above a certain level to ensure transparency. However, during long-term use, acetic acid is generated by being decomposed by moisture penetration, heat and ultraviolet rays. become. Therefore, many efforts have been made in the industry to solve the problem caused by the encapsulant according to the long-term use of the solar module.

  As a conventional technique, in Korean Patent Laid-Open No. 10-2010-0123505, olefin resin is used as a sealing material, and the moisture permeability is low and the electrical insulation is excellent. However, transparency is higher than that of EVA resin. In order to ensure transparency, the copolymer content must be at a very high level, so that there is a problem that the economy is very low. Further, in this case, the melting point (Tm) is very low, and bubbles are not successfully removed during the lamination process, resulting in a high module failure rate. Japanese Patent No. 47774050 discloses a method of improving transparency by a method using an ionomer. However, simply using an ionomer as a component of the sealing material cannot ensure light transmittance. For example, general-purpose zinc ionomers tend to have lower light transmittance than Na ionomers and Mg ionomers, particularly in the region from 400 nm to 600 nm, which is the center of the visible region. In this connection, Na ionomer and Mg ionomer have a relatively low degree of adhesion to the back surface protection sheet (so-called back sheet), so there is a high risk of peeling, which is basically more expensive and economical than existing EVA resins. There were low disadvantages.

Korean Published Patent No. 10-2010-0123505 Japanese Patent No. 47774050

  The object of the present invention to solve the above problems is to reduce the vinyl acetate (VA) content of the ethylene vinyl acetate copolymer (EVA) resin to reduce the moisture barrier characteristics of the EVA resin and acetic acid during long-term use. Provided is a method for producing an ethylene vinyl acetate copolymer resin for a solar cell encapsulant sheet that reduces the generation amount and improves the long-term durability of the module and is excellent in light transmittance and long-term durability when the solar module is commercialized. There is.

  Another object of the present invention is a solar cell encapsulating having excellent transparency and light transmittance produced by the above method, low moisture permeability, low acetic acid generation level, high electric resistance and excellent long-term durability. An object of the present invention is to provide an ethylene vinyl acetate copolymer resin for a material sheet.

In order to achieve the above object, the present invention includes a step of charging a mixed reactor comprising 72 to 80% by weight of ethylene monomer and 20 to 28% by weight of vinyl acetate monomer into a tubular reactor;
Adding a polymerization initiator comprising three or more peroxide polymerization initiators;
Wherein the polymerization temperature 190-300 ° C., polymerization pressure 2,500~3,000kg f / cm ^2, and performing polymerization under the conditions of polymerization time 2-10 minutes, and
The peroxide polymerization initiator, a (A) alkyl peroxy-ethylhexanoate compound or an alkyl group having 5 to no 4 carbon number having an alkyl peroxy group containing an alkyl group of 5 to carbon number is not 4 alkyl peroxy alkyl peroxy trimethyl hexanoate based compounds with, (B) to carbon number is not 4 alkyl peroxy pivalate compound having an alkyl peroxy group containing an alkyl group of 5, and (C) a char containing A mixture of alkylperoxyneodecanoate compounds having an alkylperoxy group containing an alkyl group having a prime number of 4 to 5;
The mixing weight ratio of the peroxide-based polymerization initiator is (A) :( B) :( C) = 50-80: 10-20: 10-30, and the ethylene vinyl acetate copolymer resin is characterized in that A manufacturing method is provided.

  According to the method for producing an ethylene vinyl acetate copolymer (EVA) resin of the present invention, it has excellent transparency and light transmittance, low moisture permeability, low acetic acid generation level, high electrical resistance, and long-term durability. An excellent resin for solar cell encapsulant can be easily provided.

It is a graph which shows the light transmittance (%) of the solar cell sealing material sheet | seat manufactured with the ethylene vinyl acetate copolymer resin which concerns on the Example and comparative example of this invention.

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

A step of introducing 72 to 80% by weight of ethylene monomer and 20 to 28% by weight of vinyl acetate monomer into a tubular reactor, a step of adding a polymerization initiator containing three or more peroxide polymerization initiators, and a polymerization temperature And a step of polymerizing under conditions of 190 to 300 ° C., a polymerization pressure of 2,500 to 3,000 kg / cm ² , and a polymerization time of 2 to 10 minutes, wherein the peroxide polymerization initiator comprises (A) an alkyl group An alkylperoxyethylhexanoate compound having 4 to 5 carbon atoms or an alkylperoxytrimethylhexanoate compound having 4 to 5 carbon atoms in the alkyl group, and (B) an alkyl group having 4 to 5 carbon atoms. Alkyl peroxypivalate-based compounds and (C) alkyl peroxyneodecanoate having an alkyl group having 4 to 5 carbon atoms Ethylene vinyl, which is a mixture of compounds, and the mixing weight ratio of the peroxide polymerization initiator is (A) :( B) :( C) = 50-80: 10-20: 10-30 A method for producing an acetate copolymer resin is provided.

  In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, the ethylene monomer and vinyl acetate monomer are charged into a tubular reactor.

  In the tubular reactor, peroxide used as an initiator for the polymerization reaction is injected into the tubular reactor, and then the reaction is started. The polymerization temperature rapidly rises due to reaction heat from the position where the peroxide is injected, and ethylene monomer, vinyl acetate monomer and the produced polymer flow along the tubular reactor, and cooling water flows from the wall surface. The heat is controlled by heat exchange with the reaction temperature. The polymer and the unreacted monomer are finally discharged to the reactor outlet and separated, and the resin in pellet form is obtained through an extruder.

  In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, the ethylene monomer content is desirably 72 to 80% by weight. Thereby, the content of the vinyl acetate monomer in the resin is determined, and the content of the vinyl acetate monomer is preferably 20 to 28% by weight.

  If the vinyl acetate content is less than 20% by weight, the transparency is lowered and the processability is lowered, and the resulting film is hard and may cause damage to the cell during module production. If it exceeds 28% by weight, not only the electrical insulation property is deteriorated, but also the water permeability is increased, the amount of acetic acid generated is increased, the solar module is seriously damaged, and the long-term use performance is deteriorated. Absent.

In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, the peroxide polymerization initiator is preferably added at a concentration of 1,000 to 3,000 ppm with respect to the mixed monomer . When the concentration of the peroxide-based initiator is less than 1,000 ppm, the reaction temperature is low at the time of polymerization, the conversion rate to EVA is low, and molecular weight control is not easy. In this case, the reaction temperature is high at the time of polymerization and the resin may be decomposed, and there is a problem in stability such as generation of acetic acid that decomposes vinyl acetate and corrodes the reactor, which is not desirable.

  In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, as a specific example of an alkyl peroxyethyl hexanoate compound or an alkyl peroxy trimethyl hexanoate compound used for the peroxide polymerization initiator T-Amyl peroxy-2-ethylhexanoate, t-Butyl peroxy-2-ethylhexanoate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-Amylperoxy-3,5,5-trihex, etc. T-Butyl peroxy-2-ethylhexanoate and t-butyl peroxy-3,5,5-trimethylhex ananoate.

  Specific examples of alkyl peroxypivalate compounds include t-Amyl peroxypivalate, t-Butyl peroxypivalate, and the like. Specific examples of alkyl peroxyneodecanoate compounds include t-Amyl peroxynate. and neodecanoate, tert-buty peroxide neodecanoate, and the like.

  The peroxide polymerization initiator is preferably tert-butyl peroxy-2-ethyl hexanoate (TBPO), tert-butyl peroxy-3,5,5-trimethyl hexanoate (TBPIN), or tert-butyl tert. ), Tert-butyl peroxynedecanoate (TBND), and the like. Each peroxide is diluted with a paraffin solvent, and each peroxide is mixed and used.

  The peroxide polymerization initiator used in the present invention is an alkyl peroxyethyl hexanoate compound having an alkyl group having 4 to 5 carbon atoms or an alkyl peroxy having an alkyl group having 4 to 5 carbon atoms. The mixing weight ratio of the trimethylhexanoate compound, the alkyl peroxypivalate compound having 4 to 5 carbon atoms in the alkyl group, and the alkyl peroxyneodecanoate compound having 4 to 5 carbon atoms in the alkyl group is 50 It is preferable to be in the range of ˜80: 10 to 20: 10-30, and when the mixing weight ratio between the peroxide initiators is out of the above range, it is not desirable because the molecular weight adjustment is not easy.

  More specifically, in the method for producing an EVA copolymer resin of the present invention, the peroxide polymerization initiator is used by mixing at least three peroxide polymerization initiators, and any one of the mixtures is used. It is mixed in a weight ratio of other peroxide initiators to peroxide initiators at 1: a: b: c. Here, a, b, and c are determined in the ranges of 0.1 ≦ a ≦ 0.9, 0.1 ≦ b ≦ 0.9, and 0.1 ≦ c ≦ 0.9, respectively. When the weight ratio between the peroxide polymerization initiators is out of the above range, it is not desirable because the molecular weight cannot be easily adjusted.

  In order to achieve the object of the present invention, TBPO is preferably selected and used more preferably, and the weight ratio of TBPO: TBPV: TBND: TBPIN is 1: 0.1 to 0.5: 0.1 to 0.7: It is more desirable to be in the range of 0.1 to 0.3.

  In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, the polymerization temperature is preferably 190 to 300 ° C.

  If the polymerization temperature is less than 190 ° C., the conversion rate to EVA is low and the desired molecular weight and molecular weight distribution cannot be obtained, and if it exceeds 300 ° C., it is difficult to obtain the desired molecular weight, causing a decomposition reaction and a reactor. It is not desirable due to concerns about stability such as corrosion.

In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, the polymerization pressure is preferably 2,500 to 3,000 kg / cm ² . If the polymerization pressure is less than 2,500 kg / cm ² , the reaction is insufficient or the work stability is lowered, which is undesirable, and if it exceeds 3,000 kg / cm ² , there is a problem in stability due to the performance limit of the high-pressure pump. Is undesirable.

  In the method for producing an ethylene vinyl acetate copolymer resin of the present invention, the polymerization time is preferably 2 to 10 minutes. If the polymerization time is less than 2 minutes, the conversion rate to EVA resin is low and the molecular weight is low, which is undesirable. If it exceeds 10 minutes, pressure control is not easy and gel is generated, which is undesirable.

  This invention provides the ethylene vinyl acetate copolymer resin manufactured with the manufacturing method of the ethylene vinyl acetate copolymer resin for solar cell sealing material sheets.

  The ethylene vinyl acetate copolymer resin produced according to the present invention has a Z average molecular weight (Mz) of 200,000 to 250,000 g / mol, and a molecular weight distribution (Mw / Mn) of 3.0 to 4.0. According to ASTM D1238, the melt index measured at 190 ° C. under a 2.16 kg load is 1 to 30 (g / 10 min).

  In the present invention, the ethylene vinyl acetate copolymer resin preferably has a Z average molecular weight (Mz) of 200,000 to 250,000 g / mol.

  When the EVA resin has a Z average molecular weight (Mz) of less than 200,000 g / mol, it is difficult to satisfy the mechanical properties, and when it exceeds 250,000 g / mol, the transparency is poor and a gel is generated. As a result, the light transmittance is lowered.

  In the present invention, the molecular weight distribution (Mw / Mn) of the ethylene vinyl acetate copolymer resin is preferably 3.0 to 4.0. If the molecular weight distribution is less than 3.0, the load during the extrusion process is high, and the neck-in phenomenon after the die (Die) causes severe problems, and if it exceeds 4.0, the transparency is poor. The light transmittance will be reduced.

  In the present invention, the Mz / Mw of the ethylene vinyl acetate copolymer resin is 2.0 to 2.5. If the Mz / Mw is less than 2.0, the load during the extrusion process is high and it is difficult to satisfy the mechanical properties, and if it exceeds 2.5, the light transmittance is lowered.

  In the present invention, the ethylene vinyl acetate copolymer resin has a melt index of 1 to 30 (g / 10 minutes) under conditions of 190 ° C. and 2.16 kg according to ASTM D1238, and less than 1 (g / 10 minutes). If it exceeds 30 (g / 10 minutes), the resin melted during laminating flows out between the glass substrate and the back sheet (back sheet).

  In the present invention, the content of the vinyl acetate (VA) is preferably 20 to 28% by weight relative to the total weight of the ethylene vinyl acetate copolymer resin composition, and if it is less than 20% by weight, the haze is high. As a result, the light transmittance is low and it is difficult to use for a solar cell encapsulating material. There is.

  In the present invention, the ethylene vinyl acetate copolymer resin preferably has a light transmittance of 90% or more at 400 to 750 nm. The light transmittance is generally a value measured after glass lamination, and the higher the vinyl acetate monomer content, the easier it is to achieve 90% or more.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, the scope of the present invention is not limited to this.

[Example 1]
Injecting 76% by weight of ethylene monomer and 24% by weight of vinyl acetate monomer into a tubular reactor, and using tert-butyl peroxy-2-ethylhexanoate (TBPO), tert-butyl peroxypivalate (TBPV), tert-butyl as radical generating initiators. The weight ratio of peroxyneodecanoate (TBND), tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPIN) was 1: 0.2: 0.4: 0.1, and the ethylene and vinyl acetate monomer ratio was 1800 ppm. Polymerization conditions with a high pressure pump pumped to a tubular reactor and a polymerization pressure of 2650 kg / cm ² , a polymerization temperature of 240 ° C., and a polymerization time of 5 minutes The EVA resin was manufactured at

[Example 2]
76% by weight of ethylene monomer and 24% by weight of vinyl acetate monomer were injected into a tubular reactor, and tert-butyl peroxy-2-ethylhexanoate (TBPO), tert-butyl peroxypivalate (TBPV), tert-butyl peroxyneodec as a radical generating catalyst. (TBND), tert-butyl peroxide-3,5,5-trimethylhexanoate (TBPIN) in a weight ratio of 1: 0.4: 0.6: 0.1 to 1500 ppm of ethylene and vinyl acetate monomer and high pressure Polymerization conditions by pumping a pump to a tubular reactor, polymerization pressure 2650 kg / cm ² , polymerization temperature 200 ° C., polymerization time 5 minutes The EVA resin was manufactured at

[Comparative Example 1]
The polymerization conditions were the same as in Example 1, and tert-butyl peroxide-2-ethylhexanoate (TBPO), tert-butyl peroxypivalate (TBPV), tert-butyl peroxynedecanoate (TBND), tBtyx tert-butyl tert-butyl tert-butyl tert-butyl tert-butyl tert-butyl tert-butyl tert The weight ratio of the mixture of 5,5-trimethylhexanoate (TBPIN) was 1: 1: 0: 0, the ethylene and vinyl acetate monomer ratio was 1600 ppm, and the high pressure pump was pumped to a tubular reactor to superpose the polymerization pressure of 2650 kg / An EVA resin was produced under the polymerization conditions of cm ² , polymerization temperature of 240 ° C., and polymerization time of 5 minutes.

[Comparative Example 2]
72% by weight of ethylene monomer and 28% by weight of vinyl acetate monomer were injected into a tubular reactor, and tert-butyl peroxy-2-ethylhexanoate (TBPO), tert-butyl peroxypivalate (TBPV), tert-butyl peroxyneode was used as a radical generating catalyst. (TBND), the weight ratio of the mixture of tert-butyl peroxide-3,5,5-trimethylhexanoate (TBPIN) was 1: 0.2: 0.4: 0.1, and Di-tert-Butyl peroxide (DTBP) ) Is added to the mixture at a 0.3 weight ratio relative to tert-butyl peroxide-2-ethylhexanoate (TBPO), and then the entire mixture is Ren and Application tubular reactor a high pressure pump as a vinyl acetate monomer compared 1400ppm (tubular reactor) pumping the polymerization pressure 2650kg / cm ^2, the polymerization temperature 240 ° C., the EVA resin at the polymerization conditions of the polymerization time of 5 minutes Manufactured.

[Comparative Example 3]
82% by weight of ethylene monomer and 18% by weight of vinyl acetate monomer were injected into a tubular reactor, and tert-butyl peroxy-2-ethylhexanoate (TBPO), tert-butyl peroxypivalate (TBPV), tert-butyl peroxyneodec as a radical generating catalyst. (TBND), tert-butyl peroxy-3,5,5-trimethylhexanoate (TBPIN) at a weight ratio of 1: 0.2: 0.4: 0.1, and the total mixture was 1800 ppm relative to ethylene and vinyl acetate monomer. The high pressure pump was pumped to a tubular reactor so that the polymerization pressure was 2700 kg / cm ² , the polymerization temperature was 250 ° C., An EVA resin was produced under polymerization conditions of a polymerization time of 5 minutes.

[Comparative Example 4]
Comparison was made using a commercial EVA resin produced by a conventional EVA resin production method utilizing an autoclave reactor (VA content of USI, 28% by weight, product name: UE2828 product).

  The physical properties of the EVA resin produced under the conditions of the examples and comparative examples were measured by the following physical property measurement method, and the results and the physical properties relating to sunlight were evaluated by molding a sheet using the produced EVA resin. The results are shown in Table 2 below.

[Physical property measurement method]
Various physical properties of the EVA resins produced in Examples 1-2 and Comparative Examples 1-4 were measured by the following methods and standards.
1) Melt flow index measurement: Measured by ASTM D1238 at 190 ° C. and 2.16 kg.
2) VA content measurement: Measured by Fourier Transform Infrared Spectroscopy (FT-IR).
3) Measurement of average molecular weight (Mw, Mn and Mz): Measured by gel permeation chromatography.
4) Transparency: 450 microsheet haze was measured and compared. The smaller the haze value, the more transparent.
5) Light transmittance: The light transmittance in the 900 to 200 nm region was measured using UV-vis-spectrometer. The specimen was manufactured by laminating a sheet manufactured by the following extruder with a glass for low iron solar light on both sides of the sheet and then laminating at 150 ° C.
6) Volume resistivity (electrical insulating property): Measured by ASTM D257 (voltage is 1,000 V) using an electric resistance measuring instrument.
7) Acetic acid generation amount: 1 g of sheet was placed in a vial together with 10 ml of water and sealed, then placed in an 85 ° C. oven and after 1500 hours, I. The amount of acetic acid generated was measured using C (Ion Chromatography).

[Film production conditions]
The EVA resins of Examples 1 and 2 and Comparative Examples 1 to 4 were a single screw extruder having a screw diameter of 40 mm and a T-die width of 400 mm. The extruder temperature was 100 ° C. and the screw rotation speed was 50 rpm. Thus, a sheet type film having a thickness of 450 μm was manufactured.

  As shown in Table 2 above, in the case of the EVA resin of Example manufactured by the method of the present invention, the VA content is around 24% by weight and the molecular weight distribution (Mw / Mn) is 4.0 or less. The Mz / Mw value is 2.5 or less, and the Mz value is 250,000 g / mol or less.

  In this connection, if the VA content is high, the transparency and light transmittance are high and suitable for a solar cell encapsulant, but the acetic acid generation rate due to the decomposition of vinyl acetate increases rapidly with long-term use. As a result, the long-term performance deteriorates.

  In the case of Comparative Examples 2 and 4, the content of vinyl acetate in the resin was 28% by weight and the light transmittance showed a high level. However, the amount of acetic acid generated after 1500 hours at 85 ° C. was twice that of Example 1. It turns out that it is above.

  The light transmittance required for a solar cell encapsulant is generally 90% or more in measured values after glass lamination, but this is easier to achieve as the VA content is higher.

  When the VA content is 28% by weight as in Comparative Examples 2 and 4, the light transmittance shows a level of 90% or more. However, when the VA content is low as in Comparative Example 3, the amount of acetic acid generated is drastically reduced, which is advantageous from the viewpoint of durability, but the light transmittance is also drastically reduced. It turns out that it is difficult to apply to. In addition, the light transmittance and haze of the resin are affected by the molecular weight distribution and high molecular weight of the resin. As seen from Comparative Examples 2 and 4 and Example 1 and Comparative Example 1, even if the VA content is the same, if the MWD, Mz / Mw, and Mz values are low, a low haze value and a high light transmittance may be exhibited. I understand. In Comparative Example 3, it can be seen that when the ethylene content exceeds 80% by weight, the amount of acetic acid generated is very low, but the haze and light transmittance show undesirable results.

  As can be seen from Tables 1 and 2, the type and content of peroxides used as initiators during polymerization in the present invention are limited, and the molecular weight distribution and Mz and Mz / Mw values are limited within a certain range under specific polymerization conditions. In this case, it has been found that even if the VA content of the EVA resin is lowered, the same light transmittance as before the VA content is lowered can be maintained.

  Therefore, the above-mentioned method makes it possible to dramatically reduce the amount of acetic acid generated without damaging the relative transparency and light transmittance of the resin having the same VA content, thereby improving the durability of the solar cell. I understand that.

Claims (3)

Charging a tubular reactor with a mixed monomer comprising 72 to 80% by weight of ethylene monomer and 20 to 28% by weight of vinyl acetate monomer;
Adding a polymerization initiator comprising three or more peroxide polymerization initiators;
Wherein the polymerization temperature 190-300 ° C., polymerization pressure 2,500~3,000kg f / cm ^2, and performing polymerization under the conditions of polymerization time 2-10 minutes, and
The peroxide polymerization initiator, a (A) alkyl peroxy-ethylhexanoate compound or an alkyl group having 5 to no 4 carbon number having an alkyl peroxy group containing an alkyl group of 5 to carbon number is not 4 alkyl peroxy alkyl peroxy trimethyl hexanoate based compounds with, (B) to carbon number is not 4 alkyl peroxy pivalate compound having an alkyl peroxy group containing an alkyl group of 5, and (C) a char containing A mixture of alkylperoxyneodecanoate compounds having an alkylperoxy group containing an alkyl group having a prime number of 4 to 5;
The mixing weight ratio of the peroxide-based polymerization initiator is (A) :( B) :( C) = 50-80: 10-20: 10-30, and the ethylene vinyl acetate copolymer resin is characterized in that Production method.   The peroxide-based polymerization initiators include tert-butyl peroxy-2-hydroxy (TBPO), tert-butyl peroxynevalate (TBND), tert-butyl peroxynedecanoate (TPND), and tert-butyl trimethyl-5 (TPND). The weight ratio of the peroxide-based polymerization initiator is TBPO: TBPV: TPND: TBPIN = 1: 0.1 to 0.5: 0.1 to 0.7: 0. It is 1-0.3, The manufacturing method of the ethylene vinyl acetate copolymer resin of Claim 1 characterized by the above-mentioned. The method for producing an ethylene vinyl acetate copolymer resin according to claim 1, wherein the polymerization initiator is added at a concentration of 1,000 to 3,000 ppm with respect to the mixed monomer .