Specification
Title of Invention: Ethylene/alpha-olefin copolymer with excellent electrical insulation properties
technical field
[One]
Cross-Citation with Related Applications
[2]
This application claims the benefit of priority based on the Korean Patent Application 2020-0046027 dated April 16, 2020, and all contents disclosed in the documents of the Korean patent applications are incorporated as a part of this specification.
[3]
[4]
technical field
[5]
The present invention relates to an ethylene/alpha-olefin copolymer having high volume resistance and light transmittance, and a method for preparing the same.
[6]
background
[7]
While global environmental problems and energy problems are getting more and more serious, solar cells are attracting attention as a means of generating energy that does not cause environmental pollution and depletion. When a solar cell is used outdoors, such as on the roof of a building, it is generally used in the form of a solar cell module. In order to obtain a crystalline solar cell module at the time of manufacturing a solar cell module, a protective sheet for a solar cell module (front side protection member) / solar cell encapsulant / crystalline solar cell element / solar cell encapsulant / protective sheet for solar cell module (back side) protection member) in the order of In addition, at the time of manufacturing a thin-film solar cell module, it laminates|stacks in order of the thin film type solar cell element/solar cell sealing material/protective sheet for solar cell modules (back surface side protection member). As the solar cell encapsulant, an ethylene/vinyl acetate copolymer or an ethylene/alpha-olefin copolymer, which is generally excellent in transparency, flexibility, and adhesion, is used.
[8]
On the other hand, although the solar cell module is generally used for a long period of time outside, problems such as performance degradation due to various external stimuli are continuously observed. In particular, it is urgent to solve the PID (Potential Induced Degradation) phenomenon found in the form of high-output power plants.
[9]
In a large-capacity power generation system that obtains a high voltage by connecting a plurality of solar cell modules, the volume resistance of the encapsulant decreases as the temperature and humidity of the installed place increase, and a potential difference occurs between the solar cell and the frame. As a result, toward the end of the array in which several solar cell modules are connected in series, the potential difference between the solar cell and the frame increases. A phenomenon in which leakage current is generated in the presence of such a potential difference and the power generation efficiency is rapidly reduced is referred to as a PID phenomenon.
[10]
Under the above background, it is required to develop an ethylene/alpha-olefin copolymer capable of continuously preventing the PID phenomenon by improving the volume resistance without reducing the light transmittance.
[11]
[12]
[Prior art literature]
[13]
[Patent Literature]
[14]
(Patent Document 1) Japanese Patent Application Laid-Open No. 2010-258439
[15]
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[16]
An object of the present invention is to provide an ethylene/alpha-olefin copolymer that can be usefully used as an insulating material due to its high volume resistance and a method for preparing the same.
[17]
means of solving the problem
[18]
In order to solve the above problems, the present invention provides an ethylene/alpha-olefin copolymer satisfying the following conditions (a) to (d).
[19]
(a) a density of 0.85 to 0.89 g/cc;
[20]
(b) the molecular weight distribution is 1.8 to 2.3;
[21]
(c) melt index (Melt Index, MI, 190 ℃, load condition of 2.16 kg) is 1 to 100 dg / min; and
[22]
(d) The Full Width at Half Maximum (FWHM) of the crystallization peak that appears when the crystallization temperature is measured by Cross-Fractionation Chromatography (CFC) is 15 or more.
[23]
Effects of the Invention
[24]
The ethylene/alpha-olefin copolymer of the present invention has a high crystallinity distribution and thus has a small free volume, thereby exhibiting excellent volume resistance and excellent electrical insulation properties. .
[25]
Modes for carrying out the invention
[26]
Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.
[27]
The terms or words used in the description and claims of the present invention should not be construed as being limited to their ordinary or dictionary meanings, and the inventor appropriately defines the concept of the term in order to best describe his invention. Based on the principle that can be done, it should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention.
[28]
[29]
[Ethylene/alpha-olefin copolymer]
[30]
The ethylene/alpha-olefin copolymer of the present invention is characterized in that the following conditions (a) to (d) are satisfied.
[31]
(a) a density of 0.85 to 0.89 g/cc;
[32]
(b) the molecular weight distribution is 1.8 to 2.3;
[33]
(c) melt index (Melt Index, MI, 190 ℃, load condition of 2.16 kg) is 1 to 100 dg / min; and
[34]
(d) The Full Width at Half Maximum (FWHM) of the crystallization peak that appears when the crystallization temperature is measured by Cross-Fractionation Chromatography (CFC) is 15 or more.
[35]
[36]
The present invention relates to an ethylene/alpha-olefin copolymer exhibiting excellent electrical insulation properties due to high volume resistance. Specifically, the ethylene/alpha-olefin copolymer of the present invention is used as a catalyst by mixing the transition metal compound represented by Chemical Formula 1 and Chemical Formula 2 during preparation. Since it is difficult to introduce an alpha-olefin-based monomer, there is a tendency to produce a high-density copolymer, and since a large amount of alpha-olefin can be introduced into the transition metal compound represented by Formula 2, the polymer (elastomer) in the ultra-low-density region is also can be prepared, the two transition metal compounds have different copolymerizability of incorporating an alpha-olefinic monomer when used alone, respectively.
[37]
The ethylene/alpha-olefin copolymer of the present invention prepared by using a mixed composition thereof as a catalyst has both a low-density region in which a large amount of alpha-olefinic monomer is mixed and a high-density region in which a small amount of alpha-olefin-based monomer is incorporated. As a copolymer, it has a wide crystallinity distribution and contains a small amount of free volume, and thus has excellent electrical insulation properties due to low charge mobility.
[38]
[39]
The ethylene/alpha-olefin copolymer of the present invention is a low-density polymer having a density ranging from 0.85 to 0.89 g/cc, wherein the density may mean a density measured according to ASTM D-792. More specifically, the density may be 0.850 g/cc or more, 0.860 g/cc or more, or 0.870 g/cc or more, or 0.874 g/cc or more, and 0.890 g/cc or less, or 0.880 g/cc or less, 0.878 g It can be less than or equal to /cc.
[40]
If the density is out of the above range, there may be a problem in that the volume resistance or light transmittance of the ethylene/alpha-olefin copolymer is lowered.
[41]
In general, the density of the ethylene/alpha-olefin copolymer is affected by the type and content of the monomer used during polymerization, the degree of polymerization, and the like, and in the case of the copolymer, it is greatly affected by the content of the comonomer. In this case, as the content of the comonomer increases, a low-density ethylene/alpha-olefin copolymer can be prepared, and the content of the comonomer can be introduced into the copolymer may depend on the inherent copolymerizability of the catalyst.
[42]
The copolymer of the present invention is a copolymer prepared by using the compound represented by Chemical Formulas 1 and 2 as a catalyst, and exhibits a low density as described above, and as a result, excellent processability can be exhibited.
[43]
[44]
The ethylene/alpha-olefin copolymer of the present invention has a narrow molecular weight distribution (MWD) in the range of 1.8 to 2.3. More specifically, the molecular weight distribution may be 1.80 or more, 1.90 or more, 2.30 or less, 2.20 or less, 2.10 or less, and 2.05 or less.
[45]
In general, when two or more kinds of monomers are polymerized, the molecular weight distribution increases, and as a result, impact strength and mechanical properties are reduced, and there is a possibility that a blocking phenomenon may occur. In particular, since the polymerizability of the monomer is different for each catalyst, the molecular weight of the final polymer is affected depending on the type of catalyst. There is a problem that the molecular weight distribution also becomes wider.
[46]
In order to prevent a decrease in the crosslinking characteristics, impact strength, mechanical properties, etc. of the copolymer, an appropriate amount of hydrogen is added during the polymerization reaction to narrow the molecular weight distribution, thereby preventing the β-hydride elimination reaction from arbitrarily occurring in the polymer chain. And it is possible to induce a uniform termination reaction by adding hydrogen. In this case, since the weight average molecular weight and melt index of the copolymer tend to decrease according to the hydrogen input, the catalyst structure affects the weight average molecular weight and melt index. It is necessary to determine the appropriate type of catalyst and the amount of hydrogen input within a range that can take both the unique characteristics and the effect of reducing the molecular weight distribution according to the hydrogen input.
[47]
In consideration of the above points, in the present invention, as described below, the transition metal compound represented by Formula 1 and the transition metal compound represented by Formula 2 were mixed and used as a catalyst and an optimal amount of hydrogen was added while preparing, It has a narrow molecular weight distribution within the above-described range, preventing deterioration of crosslinking properties, impact strength, mechanical properties, etc., while exhibiting high volume resistance and electrical insulation.
[48]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) are polystyrene equivalent molecular weights analyzed by gel permeation chromatography (GPC), and the molecular weight distribution can be calculated from a ratio of Mw/Mn.
[49]
또한, 본 발명의 에틸렌/알파-올레핀 공중합체는 중량평균 분자량(Mw)이 40,000 내지 150,000 g/mol일 수 있다. 구체적으로, 상기 중량평균 분자량은 45,000 g/mol 이상, 50,000 g/mol 이상, 또는 60,000 g/mol 이상일 수 있고, 130,000 g/mol 이하, 100,000 g/mol 이하, 또는 90,000 g/mol 이하일 수 있다.
[50]
[51]
본 발명의 에틸렌/알파-올레핀 공중합체는 용융 지수(Melt Index, MI, 190℃, 2.16kg 하중 조건)가 1 내지 100 dg/min이다. 구체적으로, 상기 용융 지수는 1 dg/min 이상, 2 dg/min 이상, 3 dg/min 이상, 또는 4 dg/min 이상일 수 있고, 100 dg/min 이하, 20 dg/min 이하, 또는 15 dg/min 이하일 수 있다.
[52]
상기 용융 지수가 1 dg/min 미만일 경우 높은 부하로 인해 생산 속도가 떨어지게 될 수 있고, 용융 지수가 100 dg/min 초과일 경우 에틸렌/알파-올레핀 공중합체의 체적저항이나 광 투과율이 저하되거나, 필름 성형이 어려워 태양전지용 봉지재 조성물 등의 사용이 적합하지 않은 문제가 있다.
[53]
[54]
또한, 상기 에틸렌/알파-올레핀 공중합체는 190℃, 2.16 kg 하중 조건에서 측정한 용융 지수(MI 2.16)에 대한 190℃, 10 kg 하중 조건에서 측정한 용융 지수(MI 10) 값인 용융 유동 지수(MFRR, Melt Flow Rate Ratio, MI 10/MI 2.16)가 8.0 이하일 수 있고, 구체적으로 4.0 이상, 4.2 이상, 4.5 이상, 8.0 이하, 7.0 이하, 6.8 이하일 수 있다. 용융 유동 지수는 공중합체의 장쇄 분기 정도의 지표가 되며, 본 발명의 에틸렌/알파-올레핀 공중합체는 전술한 물성들과 함께 상기 용융 유동 지수를 만족함으로써 우수한 물성으로 태양전지용 봉지재 조성물 등에 적합하게 적용될 수 있다.
[55]
특히, 상기와 같이 본 발명의 에틸렌/알파-올레핀 공중합체가 1 내지 100 dg/min의 낮은 용융 지수를 가질 때, 상기와 같이 8.0 이하의 낮은 용융 유동 지수를 가질 수 있다. 본 발명의 공중합체는 이와 같이 용융 지수와 용융 유동 지수가 낮기 때문에, 공중합체의 분자량이 높으며 장쇄 분지 함량이 적어 가교도가 우수한 특징이 있다.
[56]
The conventional copolymer has such a low melt index and melt flow index, and at the same time, it is difficult to have a wide crystallinity distribution because the full width at half maximum (FWHM) of the crystallization peak, which will be described later, is 15 or more. In the present invention, Formula 1 and A copolymer was prepared by adding an appropriate amount of hydrogen while using the compound represented by Formula 2 as a catalyst, and the melt flow index was decreased because the polymerization was terminated due to the addition of hydrogen, so that the end of the copolymer was saturated and long chain branches were not formed. By using heterogeneous catalysts with different crystallinity characteristics while having low characteristics, a copolymer with a wide crystallinity distribution was prepared at the same time.
[57]
[58]
The ethylene/alpha-olefin copolymer of the present invention has a Full Width at Half Maximum (FWHM) of 15 or more when the crystallization temperature is measured by Cross-Fractionation Chromatography (CFC). Here, the peak width at half maximum is a value derived from a crystallinity distribution graph plotted as a dW/dT value according to temperature measured in a bivariate distribution by cross-fractionation chromatography.
[59]
The cross-fractionation chromatography is a method that combines Temperature Rising Elution Fractionation (TREF) and Gel Filtration Chromatography (GPC). It is a kind of method.
[60]
Specifically, a high-temperature sample solution in which an ethylene/alpha-olefin copolymer is completely dissolved in a solvent is injected into a column filled with an inert carrier, the temperature of the column is lowered to attach the sample to the surface of the filler, While flowing ortho dichlorobenzene, gradually increase the temperature of the column. The concentration of the copolymer eluted at each temperature is detected, and the component eluted at each temperature is sent to GPC online for each fraction at the same time to obtain a chromatogram, and the molecular weight distribution of each component is calculated therefrom. At this time, since the higher the crystallinity of the elution component, the higher the elution temperature. Therefore, the crystallinity distribution of the copolymer can be known by finding the relationship between the elution temperature and the elution amount (wt%) of the ethylene/alpha-olefin copolymer.
[61]
The ethylene/alpha-olefin copolymer of the present invention has a high FWHM value of 15 or more, which indicates that the crystallinity distribution of the copolymer is high. It is high, and it shows excellent insulation.
[62]
In order to prepare an ethylene/alpha-olefin copolymer having excellent volume resistance and light transmittance as in the present invention, it is important to increase the FWHM value and narrow the molecular weight distribution. FWHM is related to the uniformity of crystallinity according to the copolymerizability in which the alpha-olefinic monomer is incorporated, and the molecular weight distribution is related to the uniformity of the chain length according to the growth rate of ethylene, etc. In the case of site, the molecular weight distribution is narrow due to constant chain growth, but in the same principle, the copolymerizability is constant and the crystallinity distribution is narrow and the FWHM value is small. It is difficult to prepare the resulting copolymers.
[63]
On the other hand, in the present invention, an ethylene/alpha-olefin copolymer having a high FWHM value of 15 or more and a narrow molecular weight distribution of 1.8 to 2.3 by mixing and using heterogeneous catalysts having similar ethylene growth rates and different copolymerizability. has been manufactured
[64]
Specifically, the FWHM value may be 15 or more, 16 or more, 16.5 or more, 16.8 or more, 50 or less, 40 or less, 30 or less, 25 or less, or 21 or less.
[65]
[66]
In addition, the ethylene/alpha-olefin copolymer of the present invention may have a melting temperature (Melting Temperature, Tm) of 70° C. or less. More specifically, the melting temperature may be 50 °C or higher, 55 °C or higher, 58 °C or higher, and 70 °C or lower, 68 °C or lower, 67 °C or lower. By having a melting temperature in such a temperature range, excellent thermal stability may be exhibited.
[67]
In addition, the ethylene / alpha-olefin copolymer of the present invention may have a crystallization temperature (Crystallization Temperatur, Tc) of 70 ℃ or less, 60 ℃ or less, 55 ℃ or less, 51 ℃ or less, 30 ℃ or more, 35 ℃ or more, 40 ℃ or more, it may be 42°C or more. This low crystallization temperature is due to the non-uniform distribution and high crystallinity distribution of the comonomer in the ethylene/alpha-olefin copolymer, and by having the above temperature range, excellent volume resistance and electrical insulation can be exhibited.
[68]
The melting temperature and crystallization temperature may be measured using a Differential Scanning Calorimeter (DSC). Specifically, the copolymer is heated to 150° C. and maintained for 5 minutes, then lowered to 20° C., and then the temperature is increased again. At this time, the rate of rise and fall of the temperature is controlled at 10°C/min, respectively, and the result measured in the section where the second temperature rises is the melting temperature, and the result measured in the section where the temperature is decreased is the crystallization temperature. can do.
[69]
[70]
The ethylene/alpha-olefin copolymer of the present invention is prepared by copolymerizing ethylene and an alpha-olefin-based monomer. In this case, the alpha-olefin, which means a portion derived from the alpha-olefin-based monomer in the copolymer, is C4 to C20. of alpha-olefins, specifically propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene , 1-tetradecene, 1-hexadecene, 1-eicosene, and the like, may be used alone or as a mixture of two or more thereof.
[71]
Among them, the alpha-olefin may be 1-butene, 1-hexene, or 1-octene, and preferably 1-butene, 1-hexene, or a combination thereof.
[72]
In addition, the content of the alpha-olefin in the ethylene/alpha-olefin copolymer may be appropriately selected within the range satisfying the above-described physical property requirements, and specifically, more than 0 to 99 mol% or less, or 10 to 50 mol% may be, but is not limited thereto.
[73]
[74]
[Method for producing ethylene/alpha-olefin copolymer]
[75]
The ethylene/alpha-olefin copolymer of the present invention as described above includes a step of polymerizing ethylene and an alpha-olefinic monomer in the presence of a catalyst composition comprising a transition metal compound represented by the following Chemical Formulas 1 and 2 It can be prepared by a manufacturing method characterized in that.
[76]
[Formula 1]
[77]

[78]
상기 화학식 1에서,
[79]
R 1은 수소; 탄소수 1 내지 20의 알킬; 탄소수 3 내지 20의 사이클로알킬; 탄소수 2 내지 20의 알케닐; 탄소수 1 내지 20의 알콕시; 탄소수 6 내지 20의 아릴; 탄소수 7 내지 20의 아릴알콕시; 탄소수 7 내지 20의 알킬아릴; 또는 탄소수 7 내지 20의 아릴알킬이고,
[80]
R 2 및 R 3은 각각 독립적으로 수소; 할로겐; 탄소수 1 내지 20의 알킬; 탄소수 3 내지 20의 사이클로알킬; 탄소수 2 내지 20의 알케닐; 탄소수 7 내지 20의 아릴알킬; 탄소수 1 내지 20의 알킬아미도; 또는 탄소수 6 내지 20의 아릴아미도이고,
[81]
R 4 및 R 5는 각각 독립적으로 수소; 탄소수 1 내지 20의 알킬; 탄소수 3 내지 20의 사이클로알킬; 탄소수 6 내지 20의 아릴; 또는 탄소수 2 내지 20의 알케닐이고,
[82]
R 6 To R 9 are each independently hydrogen; alkyl having 1 to 20 carbon atoms; cycloalkyl having 3 to 20 carbon atoms; aryl having 6 to 20 carbon atoms; or alkenyl having 2 to 20 carbon atoms,
[83]
Two or more adjacent to each other among R 6 to R 9 may be connected to each other to form a ring,
[84]
Q 1 is Si, C, N, P or S,
[85]
M 1 is Ti, Hf or Zr,
[86]
X 1 and X 2 are each independently hydrogen; halogen; alkyl having 1 to 20 carbon atoms; alkenyl having 2 to 20 carbon atoms; aryl having 6 to 20 carbon atoms; alkylaryl having 7 to 20 carbon atoms; arylalkyl having 7 to 20 carbon atoms; alkylamino having 1 to 20 carbon atoms; or arylamino having 6 to 20 carbon atoms;
[87]
[Formula 2]
[88]

[89]
In Formula 2,
[90]
R 10 is hydrogen; alkyl having 1 to 20 carbon atoms; cycloalkyl having 3 to 20 carbon atoms; alkenyl having 2 to 20 carbon atoms; alkoxy having 1 to 20 carbon atoms; aryl having 6 to 20 carbon atoms; arylalkoxy having 7 to 20 carbon atoms; alkylaryl having 7 to 20 carbon atoms; or arylalkyl having 7 to 20 carbon atoms,

Claims
[Claim 1]
An ethylene/alpha-olefin copolymer satisfying the following conditions (a) to (d): (a) having a density of 0.85 to 0.89 g/cc; (b) having a molecular weight distribution of 1.8 to 2.3; (c) melt index (Melt Index, MI, 190 ℃, load condition of 2.16 kg) is 1 to 100 dg / min; And (d) Cross-fractionation chromatography (Cross-Fractionation Chromatography, CFC), the full width at half maximum (FWHM) of the crystallization peak appearing when the crystallization temperature is measured by 15 or more.
[Claim 2]
The ethylene/alpha-olefin copolymer according to claim 1, wherein the melt index is 2 to 20 dg/min.
[Claim 3]
The ethylene/alpha-olefin copolymer according to claim 1, wherein the full width at half maximum of the crystallization peak is 16 to 50.
[Claim 4]
The ethylene/alpha-olefin copolymer according to claim 1, wherein the melting temperature is 70°C or less.
[Claim 5]
The ethylene/alpha-olefin copolymer according to claim 1, wherein the weight average molecular weight (Mw) is 40,000 to 150,000 g/mol.
[Claim 6]
The method according to claim 1 , Melt Flow Rate Ratio (MFRR, Melt Flow Rate Ratio, MI 10 / that is a value of the melt index (MI 10 , 190 ° C, 10 kg load condition) to the melt index (MI 2.16 , 190 ° C., 2.16 kg load condition) MI 2.16 ) is 8.0 or less.
[Claim 7]
The ethylene/alpha-olefin copolymer according to claim 1, wherein the crystallization temperature is 70°C or less.
[Claim 8]
The method according to claim 1, wherein the alpha-olefin is propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1 -Dodecene, 1-tetradecene, 1-hexadecene and 1- ethylene / alpha-olefin copolymer comprising at least one selected from the group consisting of eicosene.
[Claim 9]
The ethylene/alpha-olefin copolymer according to claim 1, wherein the alpha-olefin is contained in an amount greater than 0 and 99 mol% or less compared to the copolymer.