Method for predicting long-term durability of resin composition for piping and olefinic polymer used for resin for piping

Abstract

A method for evaluating long-term durability of a resin for piping is provided. Unlike the conventional FNCT evaluation method requiring a long period of time, the method disclosed herein is capable of predicting long-term durability of a resin for piping in a short time, by a simple calculation using a content of tie molecules, an entanglement molecular weight (M.sub.e) and a content of ultrahigh molecular weight components. In addition, the olefinic polymer is configured to have a predetermined relationship in relation to the content of tie molecules, the entanglement molecular weight (M.sub.e) and the content of ultrahigh molecular weight components, whereby the polymer of the present application can be used in the manufacture of a heating pipe requiring excellent long-term durability.

Claims

1. A method for predicting long-term durability of a resin composition for piping comprising: collecting data of the resin composition, the data comprising a content (wt %) of tie molecules, an entanglement molecular weight (M.sub.e), and a content (wt %) of a component having a mass average molecular weight (M.sub.w) of 1,000,000 or more; and using Equation below to determine a value of long-term durability of the resin composition:
Long-term durability predicted value of resin composition=a×(X).sup.b×(Y).sup.c×(Z).sup.d  [Equation] wherein, a=386,600, b=4.166, c=−1.831, and d=1.769, X, Y and Z represent, in the resin composition, the content (wt %) of tie molecules, the entanglement molecular weight (M.sub.e), and the content (wt %) of the component having the mass average molecular weight (M.sub.w) of 1,000,000 or more, respectively, where X, Y and Z are used as dimensionless constants excluding their respective units.

2. The method according to claim 1, further comprising: determining the value of long-term durability by calculating through the Equation to evaluate a long-term durability of the resin composition.

3. The method according to claim 1, further comprising: comparing the value of long-term durability determined by calculating through the Equation for each resin composition of a plurality of resin compositions.

4. The method according to claim 1, wherein the resin composition comprises a polyolefin resin.

5. The method according to claim 4, wherein the polyolefin resin is a polymer of ethylene, butene, propylene or α-olefin monomers.

6. The method of claim 1, wherein the long-term durability is excellent when the long term durability predicted value of the resin composition calculated from the Equation is greater than 2000.

7. The method of claim 1, wherein the long term durability predicted value of the resin composition calculated from the Equation has a linear correlation with a value measured from a full notch creep test (FNCT).

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGURE is a graph showing the correlation between FNCT measured values of the resin used in a Preparation Example and FNCT predicted values calculated for each resin of the present application examples corresponding to the Preparation Example.

BEST MODE

(2) Hereinafter, the present application will be described in detail through examples. However, the protection scope of the present application is not limited by the following examples.

Experimental Example 1: Experimental Example on Long-Term Durability Prediction

(3) The relevant physical properties and the like measured in the following experimental examples were measured according to the following methods.

(4) Measuring Method FNCT (full notch creep test) measured value: For the resins of Preparation Examples 1 to 15 prepared below, a full notch creep test was performed according to ISO 16770 at a stress of 4.0 MPa and a temperature of 80° C. Specifically, a specimen for performing the FNCT was a rectangular parallelepiped having a size of 10×10×100 mm, which was obtained by milling a plate having a thickness of 15 mm. Then, notches having a depth of 1.5 mm were formed on four sides of the specimen, a stress of 4.0 MPa was applied to the specimen in a 10% Igepal solution at 80° C., and then the time taken until the specimen was broken was measured. Based on the measured time, the properties of the resins were qualitatively classified according to the following criteria.

(5) <Qualitative Classification of FNCT Measured Values> above 2,000 hours: excellent 1,500 hours to less than 2,000 hours: somewhat excellent 1,000 hours to less than 1,500 hours: normal 400 hours to less than 1,000 hours: somewhat poor less than 400 hours: poor Content of tie molecules: The molecular weight distribution, melting point (Tm) and mass fraction crystallinity were calculated in the following methods, and the content of tie molecules was calculated from these values.

(6) Molecular weight distribution: 10 mg of a sample to be measured was dissolved in 1,2,4-trichlorobenzene containing 0.0125% of BHT at 160° C. for 10 hours and pretreated using PL-SP260 from Agilent, and a GPC curve was obtained using PL-GPC220 as GPC (gel permeation chromatography) for high temperature.

(7) Melting point and mass fraction crystallinity: 5 mg of a sample to be measured was placed on an Al pan, covered with an Al lid, and then punched and sealed, and it was heated from 50° C. to 190° C. at 10° C./min using DSC Q20 from TA (Cycle 1), and cooled to 50° C. at 10° C./min after isothermal treatment at 190° C. for 5 minutes, and then heated again to 190° C. at 10° C./min after isothermal treatment at 50° C. for 5 minutes (Cycle 2). The melting point and mass fraction crystallinity were calculated from the temperature (Tm) and area (ΔH) of the DSC curve peak in the range of 60° C. to 140° C. in Cycle 2.

(8) Tm: temperature of DSC curve peak

(9) Mass fraction crystallinity: ΔH/293.6×100 (293.6: ΔH at 100% crystal)

(10) Content calculation of tie molecules: The content of tie molecules was calculated from the area of the tie molecule distribution graph in which the x-axis was the molecular weight M and the y-axis was represented by n.Math.P.Math.dM. The corresponding graph is calculated from the GPC curve and DSC measurement results. With regard to the y-axis, n is the number of the polymer molecules having a molecular weight of M, which can be obtained as (dw/d log Mw)/M from the data of the GPC curve in which the x-axis is log Mw and the y-axis is dw/d log Mw. In addition, the P is a probability that the polymer molecules having a molecular weight of M form tie molecules, which can be calculated from the following equations 1 to 3, and the dM is an interval between the x-axis data (molecular weight M) of the GPC curve.

(11) $\begin{array}{cc}P=\frac{1}{3}\frac{{\int }_{2l_c+l_c}^{\infty }{r}^2\exp \left(-b^2{r}^2\right)\mathrm{dr}}{{\int }_0^{\infty }{r}^2\exp \left(-b^2{r}^2\right)\mathrm{dr}}& \left[\mathrm{Equation}1\right]\end{array}$

(12) In Equation 1 above, r is an end-to-end distance of a random coil, b.sup.2 is 3/2r.sup.2, le is a crystal thickness, which is obtained from Equation 2 below, and l.sub.a is an amorphous thickness, which is obtained from Equation 3 below.

(13) $\begin{array}{cc}{T}_m=T_m^o\left(1-\frac{2{\sigma }_e}{\Delta h_m{l}_c}\right)& \left[\mathrm{Equation}2\right]\end{array}$

(14) In Equation 2 above, T°.sub.m is 415K, σ.sub.e is 60.9×10.sup.−3 J/m.sup.2, and Δh.sub.m is 2.88×10.sup.3 J/m.sup.3.
l.sub.a=ρ.sub.cl.sub.c(1−ω.sup.c)/ρ.sub.aω.sup.c  [Equation 3]

(15) In Equation 3 above, pc is a crystal density, which is 1,000 kg/m.sup.3, ρ.sub.a is a density of amorphous phase, which is 852 kg/m.sup.3, ω.sup.c is weight fraction crystallinity, which is confirmed from DSC results. Calculation of entanglement molecular weight (Me): Using a rotary rheometer, a storage elastic modulus and a loss elastic modulus of each sample were measured under conditions of a temperature of 150° C. to 230° C., an angular frequency of 0.05 to 500 rad/s and a strain of 0.5%, and from the plateau elastic modulus (GN0) thus obtained, the entanglement molecular weight was calculated according to Theoretical Equation below. However, in Theoretical Equation below, p means a density (kg/m.sup.3), R is the gas constant (8.314 Pa.Math.m.sup.3/mol.Math.K) and T is the absolute temperature (K).
M.sub.e=(ρRT)/G.sub.N.sup.0  [Theoretical Equation] Content measurement and calculation of ultrahigh molecular weight component: In the molecular weight distribution analysis result of the sample, the area ratio (%) of the portion having a molecular weight of 1,000,000 or more relative to the total area was calculated. Long-term durability predicted value: The predicted value of long-term durability was calculated by substituting the values obtained from the above into the following equation.
Long-term durability predicted value of resin composition=a×(X).sup.b×(Y).sup.c×(Z).sup.d  [Equation]

(16) However, in Equation above, a=386,600, b=4.166, c=−1.831, and d=1.769, X, Y and Z mean, in a resin composition as a sample, a content (wt %) of tie molecules, an entanglement molecular weight (g/mol) and a content (wt %) of a component having a mass average molecular weight (Mw) of 1,000,000 or more, respectively. At this time, in Equation above, X, Y and Z are used as dimensionless constants excluding the units.

(17) Based on the predicted value calculated from Equation above, the characteristics of the resin were classified qualitatively by the following criteria.

(18) <Qualitative Classification of Predicted Values> above 2,000: excellent 1,500 to less than 2,000: somewhat excellent 1,000 to less than 1,500: normal 400 to 1,000: somewhat poor less than 400: poor

PREPARATION EXAMPLES

(19) A resin as a target for long-term durability measurement was prepared as follows. Then, the time was measured according to the FNCT (full notch creep test). The results are shown in Table 1.

(20) Preparation Example 1: In a hexane slurry CSTR process, the resin was polymerized while supplying ethylene, hydrogen and 1-butene at a predetermined input rate using a metallocene catalyst. The prepared resin had a density of 0.9396 g/cm.sup.3 as measured according to ASTM D 1505 and an MI (melt index) of 0.26 as measured under conditions of 190° C. and 2.16 kg/10 min according to ASTM D 1238.

(21) Preparation Example 2: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9392 g/cm.sup.3 and the MI was 0.34.

(22) Preparation Example 3: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9358 g/cm.sup.3 and the MI was 0.75.

(23) Preparation Example 4: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9359 g/cm.sup.3 and the MI was 0.47.

(24) Preparation Example 5: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9363 g/cm.sup.3 and the MI was 0.27.

(25) Preparation Example 6: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9396 g/cm.sup.3 and the MI was 0.32.

(26) Preparation Example 7: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9365 g/cm.sup.3 and the MI was 0.60.

(27) Preparation Example 8: A resin was prepared in the same manner as in Preparation Example 3, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9367 g/cm.sup.3 and the MI was 0.47.

(28) Preparation Example 9: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9369 g/cm.sup.3 and the MI was 0.38.

(29) Preparation Example 10: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9364 g/cm.sup.3 and the MI was 0.48.

(30) Preparation Example 11: A resin was prepared in the same manner as in Preparation Example 1, except that the density was 0.9362 g/cm.sup.3 and the MI measured under the same conditions was 0.43.

(31) Preparation Example 12: A resin was prepared in the same manner as in Preparation Example 1 except that the density was 0.9363 g/cm.sup.3 and the MI measured under the same conditions was 0.26.

(32) Preparation Example 13: A resin was prepared in the same manner as in Preparation Example 1, except that the density was 0.9362 g/cm.sup.3 and the MI measured under the same conditions was 0.44.

(33) Preparation Example 14: A resin was prepared in the same manner as in Preparation Example 1, except that the density was 0.9357 g/cm.sup.3 and the MI measured under the same conditions was 0.25.

(34) Preparation Example 15: A resin was prepared in the same manner as in Preparation Example 1, except that the density was 0.9363 g/cm.sup.3 and the MI measured under the same conditions was 0.39.

Examples

Example 1

(35) For the sample prepared in Preparation Example 1, the content of tie molecules, the entanglement molecular weight, and the content of the ultrahigh molecular weight component were measured according to the above methods, and the predicted value concerning long-term durability was calculated by substituting them into Equation according to the present application. The result is as shown in Table 2.

Examples 2 to 15

(36) The contents of tie molecules, the entanglement molecular weights and the contents of the ultrahigh molecular weight components were measured and the predicted values concerning the durability were calculated, in the same manner as in Example 1, except that in Examples 2 to 15, the resins prepared in accordance with Preparation Examples 2 to 15 in this order were used, respectively.

(37) TABLE-US-00001 TABLE 1 Preparation FNCT measured value Example (hour) Remark 1 2310 Excellent 2 376 Poor 3 59 Poor 4 206 Poor 5 2000 Excellent 6 1710 Somewhat excellent 7 244 Poor 8 285 Poor 9 416 Somewhat poor 10 114 Poor 11 138 Poor 12 1537 Somewhat excellent 13 155 Poor 14 1354 Normal 15 168 Poor

(38) TABLE-US-00002 TABLE 2 Content of ultrahigh Content molecular Long-term of tie weight durability molecules Me component predicted Example (%) (g/mol) (%) value Remark 1 12.4 13900 2.8 2226 Excellent 2 10.6 19500 2.4 474 Somewhat poor 3 9.6 36700 2.0 71 Poor 4 11.2 25600 2.6 418 Somewhat poor 5 11.3 15800 3.7 1958 Somewhat excellent 6 8.2 11700 5.2 1629 Somewhat excellent 7 9.5 35900 1.2 29 Poor 8 9.8 28200 1.2 51 Poor 9 9.5 23300 1.6 106 Poor 10 10.2 25100 1.3 86 Poor 11 11.0 23800 1.8 231 Poor 12 11.2 12500 2.8 1770 Somewhat excellent 13 10.6 25300 1.6 144 Poor 14 11.9 15100 2.3 1138 Normal 15 11.8 22800 1.4 215 Poor

(39) Comparing the FNCT measured values in Table 1 with the dimensionless calculated values in Table 2, it can be seen that their values are very similar. Then, it can be confirmed that the measured values and the calculated values can be evaluated very similarly even in the qualitative classification. Actually, it is also confirmed in FIGURE that the X-axis and the Y-axis have a strong linear correlation. That is, the durability prediction method of the present application can replace the conventional FNCT measurement method. In other words, the method according to the present application can evaluate the durability of the resin (composition) for piping in a short time only by measuring the molecular weight and the like, even without going through a testing period of several months or more.

Experimental Example 2: Confirmation of Suitability as Polymer for Heater-Piping

(40) The relevant physical properties and the like measured in the following experimental examples were measured according to the following methods.

(41) Measuring Method FNCT (full notch creep test) measured value: For the polymers of Preparation Examples 1 to 14 prepared below, a full notch creep test was performed according to ISO 16770 at a stress of 4.0 MPa and a temperature of 80° C. Specifically, a specimen for performing the FNCT was a rectangular parallelepiped having a size of 10×10×100 mm, which was obtained by milling a plate having a thickness of 15 mm. Then, notches having a depth of 1.5 mm were formed on four sides of the specimen, a stress of 4.0 MPa was applied to the specimen in a 10% Igepal solution at 80° C., and then the time taken until the specimen was broken was measured. Based on the measured time, the properties of the resins were qualitatively classified according to the following criteria.

(42) <Qualitative Classification of FNCT Measured Values> above 2,000 hours: excellent 1,500 hours to less than 2,000 hours: somewhat excellent 1,000 hours to less than 1,500 hours: normal 400 hours to less than 1,000 hours: somewhat poor less than 400 hours: poor Content of tie molecules: The molecular weight distribution, melting point (Tm) and mass fraction crystallinity were calculated in the following methods, and the content of tie molecules was calculated from these values. Molecular weight distribution: 10 mg of a sample to be measured was dissolved in 1,2,4-trichlorobenzene containing 0.0125% of BHT at 160° C. for 10 hours and pretreated using PL-SP260 from Agilent, and a GPC curve was obtained using PL-GPC220 as GPC (gel permeation chromatography) for high temperature. Melting point and mass fraction crystallinity: 5 mg of a sample to be measured was placed on an Al pan, covered with an Al lid, and then punched and sealed, and it was heated from 50° C. to 190° C. at 10° C./min using DSC Q20 from TA (Cycle 1), and cooled to 50° C. at 10° C./min after isothermal treatment at 190° C. for 5 minutes, and then heated again to 190° C. at 10° C./min after isothermal treatment at 50° C. for 5 minutes (Cycle 2). The melting point and mass fraction crystallinity were calculated from the temperature (Tm) and area (ΔH) of the DSC curve peak in the range of 60° C. to 140° C. in Cycle 2.

(43) Tm: temperature of DSC curve peak

(44) Mass fraction crystallinity: ΔH/293.6×100 (293.6: ΔH at 100% crystal) Content calculation of tie molecules: The content of tie molecules was calculated from the area of the tie molecule distribution graph in which the x-axis was the molecular weight M and the y-axis was represented by n.Math.P.Math.dM. The corresponding graph is calculated from the GPC curve and DSC measurement results. With regard to the y-axis, n is the number of the polymer molecules having a molecular weight of M, which can be obtained as (dw/d log Mw)/M from the data of the GPC curve in which the x-axis is log Mw and the y-axis is dw/d log Mw. In addition, the P is a probability that the polymer molecules having a molecular weight of M form tie molecules, which can be calculated from the following equations 1 to 3, and the dM is an interval between the x-axis data (molecular weight M) of the GPC curve.

(45) $\begin{array}{cc}P=\frac{1}{3}\frac{{\int }_{2l_c+l_c}^{\infty }{r}^2\exp \left(-b^2{r}^2\right)\mathrm{dr}}{{\int }_0^{\infty }{r}^2\exp \left(-b^2{r}^2\right)\mathrm{dr}}& \left[\mathrm{Equation}1\right]\end{array}$

(46) In Equation 1 above, r is an end-to-end distance of a random coil, b.sup.2 is 3/2r.sup.2, l.sub.c is a crystal thickness, which is obtained from Equation 2 below, and l.sub.a is an amorphous thickness, which is obtained from Equation 3 below.

(47) $\begin{array}{cc}{T}_m=T_m^o\left(1-\frac{2{\sigma }_e}{\Delta h_m{l}_c}\right)& \left[\mathrm{Equation}2\right]\end{array}$

(48) In Equation 2 above, T°.sub.m is 415K, ae is 60.9×10.sup.−3 J/m.sup.2, and Δh.sub.m is 2.88×10.sup.3 J/m.sup.3.
l.sub.a=ρ.sub.cl.sub.c(1−ω.sup.c)/ρ.sub.aω.sup.c  [Equation 3]

(49) In Equation 3 above, ρ.sub.c is a crystal density, which is 1,000 kg/m.sup.3, ρ.sub.a is a density of amorphous phase, which is 852 kg/m.sup.3, ω.sup.c is weight fraction crystallinity, which is confirmed from DSC results. Calculation of entanglement molecular weight (M.sub.e): Using a rotary rheometer, a storage elastic modulus and a loss elastic modulus of each sample were measured under conditions of a temperature of 150° C. to 230° C., an angular frequency of 0.05 to 500 rad/s and a strain of 0.5%, and from the plateau elastic modulus (GN0) thus obtained, the entanglement molecular weight was calculated according to Theoretical Equation below. However, in Theoretical Equation below, p means a density (kg/m.sup.3), R is the gas constant (8.314 Pa.Math.m.sup.3/mol.Math.K) and T is the absolute temperature (K).
M.sub.e=(ρRT)/G.sub.N.sup.0  [Theoretical Equation] Content measurement and calculation of ultrahigh molecular weight component: In the molecular weight distribution analysis result of the sample, the area ratio (%) of the portion having a molecular weight of 1,000,000 or more relative to the total area was calculated.

Preparation Examples

(50) Preparation Example 1: In a hexane slurry CSTR process, the resin was polymerized while supplying ethylene, hydrogen and 1-butene at a predetermined input rate using a metallocene catalyst capable of producing a bimodal molecular weight distribution. The prepared resin had a density of 0.9365 g/cm.sup.3 as measured according to ASTM D 1505 and an MI (melt index) of 0.02 as measured under conditions of 190° C. and 2.16 kg/10 min according to ASTM D 1238.

(51) Preparation Example 2: A resin was prepared in the same manner as in Preparation Example 1, except that a metallocene catalyst of a different kind from that of Preparation Example 1 was used. The density of the prepared resin was 0.9396 g/cm.sup.3 and the MI was 0.26.

(52) Preparation Example 3: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9392 g/cm.sup.3 and the MI was 0.34.

(53) Preparation Example 4: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9358 g/cm.sup.3 and the MI was 0.75.

(54) Preparation Example 5: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9363 g/cm.sup.3 and the MI was 0.27.

(55) Preparation Example 6: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9396 g/cm.sup.3 and the MI was 0.32.

(56) Preparation Example 7: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9365 g/cm.sup.3 and the MI was 0.60.

(57) Preparation Example 8: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9367 g/cm.sup.3 and the MI was 0.47.

(58) Preparation Example 9: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9369 g/cm.sup.3 and the MI was 0.38.

(59) Preparation Example 10: A resin was prepared in the same manner as in Preparation Example 2, except that the input rate of the raw materials was controlled differently. The density of the prepared resin was 0.9364 g/cm.sup.3 and the MI was 0.48.

(60) Preparation Example 11: A resin was prepared in the same manner as in Preparation Example 2, except that the density was 0.9362 g/cm.sup.3 and the MI measured under the same conditions was 0.43.

(61) Preparation Example 12: A resin was prepared in the same manner as in Preparation Example 2, except that the density was 0.9363 g/cm.sup.3 and the MI measured under the same conditions was 0.26.

(62) Preparation Example 13: A resin was prepared in the same manner as in Preparation Example 2, except that the density was 0.9362 g/cm.sup.3 and the MI measured under the same conditions was 0.44.

(63) Preparation Example 14: A resin was prepared in the same manner as in Preparation Example 2, except that the density was 0.9363 g/cm.sup.3 and the MI measured under the same conditions was 0.39.

Examples

(64) For the sample prepared in each of Preparation Examples, the content of tie molecules, the entanglement molecular weight and the content of the ultrahigh molecular weight component were measured according to the above methods. Alternatively, for the sample prepared in each of Preparation Examples above, the environmental stress crack resistance measured by FNCT was measured. The results are as shown in Table 3.

(65) TABLE-US-00003 TABLE 3 Content of ultrahigh Content molecular of tie weight molecules Me component FNCT Example (%) (g/mol) (%) (hour) Remark 1 12.2 1400 10.2 6500 Excellent 2 12.4 13900 2.8 2310 Excellent 3 10.6 19500 2.4 376 Poor 4 9.6 36700 2.0 59 Poor 5 11.3 15800 3.7 2000 Excellent 6 8.2 11700 5.2 1710 Somewhat excellent 7 9.5 35900 1.2 244 Poor 8 9.8 28200 1.2 285 Poor 9 9.5 23300 1.6 416 Somewhat poor 10 10.2 25100 1.3 114 Poor 11 11.0 23800 1.8 138 Poor 12 11.2 12500 2.8 1534 Somewhat excellent 13 10.6 25300 1.6 155 Poor 14 11.8 22800 1.4 168 Poor

(66) Referring to Table 3 above, it can be seen that if at least two conditions of the conditions defined in the present application are satisfied, a polymer for heater-piping having excellent long-term durability can be designed.