KR102184390B1 - Prediction method of durability of the resin composition for piping - Google Patents

Abstract

This application is a method for evaluating long-term durability of a resin for piping, and unlike conventional FNCT evaluation methods that take a long time, the content of tie molecule, entanglement molecular weight (M _e ), and content of ultra-high molecular weight components It is possible to provide a method for predicting the long-term durability of a pipe resin in a short time by a simple formula calculation using.

Description

Prediction method of durability of the resin composition for piping}

The present application relates to a method for predicting long-term durability of a resin for piping or a composition comprising the resin.

Since pipes for piping used for heating pipes and the like are installed inside the building, they must have excellent long-term durability so as not to leak water due to cracks. Well-known methods for evaluating long-term durability of piping pipes include ISO 9080 and ISO 16770. ISO 9080 is a method of measuring the crack occurrence time according to the temperature and pressure of water passing through a pipe for at least 1 year, and extrapolating this to estimate the pressure expected to generate cracks after 50 years. Products certified for long-term durability under ISO 9080 have an environmental stress cracking resistance of about 2,000 hours or more as measured by the Full Notch Creep Test (FNCT) according to ISO 16770 at 4.0 MPa stress and 80°C temperature. That is, according to the above method, the product has durability such that the sample is broken only after 2,000 hours or more has elapsed. However, there is a problem that it takes at least 3 months to 1 year or more to perform the above two methods. Therefore, there is a need for a method of predicting long-term durability as an attribute so that the product development time can be shortened by selecting a sample for measuring long-term durability among various samples in the product development stage.

An object of the present application is to provide a method for predicting long-term durability of a resin composition for piping within a short time.

Another object of the present application is to provide a method of comparing and evaluating long-term durability with respect to a plurality of resin compositions for piping.

Another object of the present application is to provide a resin composition for a heating tube excellent in environmental stress cracking resistance.

All of the above and other objects of the present application can be solved by the present application described in detail below.

One example related to the present application, the present application relates to a method of predicting or evaluating long-term durability of a resin composition for piping.

In the present application, the sample to be predicted or evaluated may be a resin or a resin composition including other components. In addition, in the present application, the term resin (composition) for piping may refer to a resin (composition) used for a pipe forming a moving path of fluid, etc., and may mainly refer to a resin (composition) for heating pipes. .

The long-term durability prediction method of the present application uses a tie molecule, an entanglement molecular weight (M _e ), and a mass average molecular weight (M _w ) as factors predicting long-term durability.

In the present application, a tie molecule, which is one of the factors used in predicting long-term durability, refers to a polymer connecting crystals of an amorphous polymer resin. In amorphous polymers, crystals having a lamellar structure are formed by chain folding below the crystallization temperature. At this time, when a polymer structure capable of making defects in the crystal structure, for example, an α-olefin or a long chain branch (LCB), exists, the corresponding portion cannot form a crystal and remains amorphous. On the other hand, since a lamellar can be formed in a portion where the α-olefin or LCB structure does not exist, one polymer chain can form a crystalline-amorphous-crystalline structure. In such a structure, the amorphous portion plays a role of connecting the crystal and the crystal, and this is referred to as a tie-molecular. The higher the molecular weight of the polymer and the longer the length of the polymer chain, the greater the probability of forming tie molecules. As described above, the higher the content of tymolecule, the stronger the connection between the crystal structures, and it is considered that generation and propagation of cracks becomes difficult. In consideration of this point, in the present application, the content of Thai molecule is used as a factor in predicting long-term durability. In this case, the content of thai molecule refers to a% ratio, that is, weight %, of the polymer forming the thai molecule based on the weight of 100 of the total polymer included in the resin composition. The content of tie molecule can be determined as described below.

The entanglement molecular weight (M _e ), which is another one of the factors used in the method of the present application, is that one polymer chain is entangled with a surrounding polymer or itself to form an entanglement point that functions as a physical crosslink. When present, it means the average molecular weight between these entanglement points. As the molecular weight of the polymer increases and the length of the polymer chain increases, the probability of generating an entanglement point increases, so that the entanglement molecular weight decreases. As the entanglement molecular weight decreases, the degree of entanglement of the polymer increases, and it is considered that the resistance to external force increases. In consideration of this point, in the present application, the entangled molecular weight is used as one of the factors for predicting long-term durability. The entanglement molecular weight can be determined as described below.

Another factor used in the prediction of long-term durability of the present application is the content of ultra-high molecular weight components. At this time, the ultra-high molecular weight refers to a case where the mass average molecular weight (Mw) is more than 1 million, and the content of the ultra-high molecular weight component is the% ratio of the polymer having a mass average molecular weight of 1 million or more based on the weight of the total polymer included in the resin composition, That means weight percent. As the content of the ultra-high molecular weight component increases, the number of polymers with a longer polymer chain length increases, and thus it is thought that the entanglement of the polymer chain or the content of tymolecule increases. In consideration of this point, in the present application, the content of the ultra-high molecular weight component is used as a factor in predicting long-term durability. The content of the ultra-high molecular weight component can be measured as described below.

According to the present application, which uses the above factor to measure the long-term durability of a resin composition as a sample, even if a small amount of a sample is used, the long-term durability of the resin composition can be predicted or evaluated in a short time.

Specifically, the method according to the present application may predict or evaluate the long-term durability of the resin composition as a sample by using the following equation.

[Equation]

Long-term durability predicted value of the resin composition = ax (X) ^b x (Y) ^c x (K) ^d

In the above equation, a=386,600, b=4.166, c=-1.831, and d=1.769. In addition, each of X, Y, and Z is a value related to molecular properties that can be measured in the resin composition as a sample. Specifically, X is the content of the tie molecule (wt%), Y is the entanglement molecular weight (g/mol), and Y is the content (wt%) of a component having a mass average molecular weight (Mw) of 1 million or more. Means. At this time, X, Y, and Y are used as non-dimensional constants excluding units.

The inventors of the present application said that the predicted value for long-term durability calculated according to the above equation is very similar to the environmental stress crack resistance evaluation result measured by the full notch creep test (FNCT) according to ISO 16770 at actual 4.0 MPa and 80°C. Confirmed. Therefore, if the long-term durability predicted value of the resin composition as a sample is calculated according to the present application, the long-term durability of the resin composition for piping can be predicted within a short time without performing durability evaluation over a long period of time such as ISO 9080 or ISO 16770, or Can be evaluated.

In the present application, the calculation of the predicted value of long-term durability may be performed for a plurality of samples. In this case, it can be determined that the long-term durability of the sample having the largest calculated value is the best.

In the present application, a sample to be predicted or evaluated for long-term durability, that is, a resin composition, may include a homopolymer formed from one type of monomer component and/or a copolymer formed from a plurality of different monomer components. I can. In addition, the resin composition may include one or more homopolymers or copolymers.

In one example, the resin composition as a sample may include polyolefin. The kind of polyolefin is not particularly limited. For example, the polyolefin may be a polymer formed from ethylene, butylene, propylene, and/or α-olefinic monomers. The kind of the α-olefin monomer is not particularly limited. For example, 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-octadecene, or 1-eicosene may be used, but is not particularly limited thereto.

According to an example of the present application, a method capable of predicting long-term durability of a pipe resin within a short time may be provided using a small amount of sample. In addition, according to the present application, since long-term durability of the piping resin can be evaluated in a short time, a polymer structure having excellent long-term durability can be usefully designed, and a sample worth measuring actual long-term durability can be selected in a short time. Can increase the efficiency of the product development stage and shorten the development time.

1 is a graph showing the correlation between the measured FNCT values for the resins used in the preparation examples and the predicted FNCT values calculated for the resins of each example of the present application corresponding to the preparation examples.

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

Related physical properties measured in the following experimental examples were measured according to the following method.

<Measurement 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 4.0 MPa stress and 80°C temperature. Specifically, the specimen for performing the FNCT is a rectangular parallelepiped having a size of 10 X 10 X 100 mm, obtained by milling a plate material having a thickness of 15 mm. Thereafter, notches having a depth of 1.5 mm were formed on the four sides of the specimen, and a stress of 4.0 MPa was applied to the specimen in a 10% Igepal solution at 80°C, and the time taken until fracture occurred in the specimen was measured. Based on the measured time, the properties of the resin were qualitatively classified based on the following criteria.

<Qualitative classification of FNCT measured values>

-Over 2,000 hours: Excellent

-1,500 to less than 2,000 hours: somewhat excellent

-1,000 hours to less than 1,500 hours: Moderate

-400 hours to less than 1,000 hours: somewhat bad

-Less than 400 hours: bad

* Content of tie molecule : The molecular weight distribution, melting point (Tm), and mass fraction crystallinity were calculated by the following method, and the content of tie molecule was calculated from these values.

-Molecular weight distribution: Using Agilent's PL-SP260, dissolve 10 mg of a sample to be measured in 1,2,4-Trichlorobenzene containing 0.0125% BHT for 10 hours at 160°C for 10 hours and pretreat it, and then pretreat with high temperature GPC (Gel Permeation Chromatography) A GPC curve was obtained using phosphorus PL-GPC220.

-Melting point and mass fraction crystallinity: 5 mg of the sample to be measured is put on Al Pan, covered with Al Lid, and then punched and sealed, and heated from 50°C to 190°C at 10°C/min using DSC Q20 of TA (Cycle 1) After isothermal at 190° C. for 5 minutes, cooled to 50° C. at 10° C./min, isothermal at 50° C. for 5 minutes, and heated again at 10° C./min to 190° C. (Cycle 2). The melting point and mass fraction crystallinity were calculated from the temperature (Tm) and area (ΔH) of the peak of the DSC curve in the range of 60°C to 140°C in Cycle 2.

Tm: temperature of the DSC curve peak

Mass fraction crystallinity: ΔH/293.6 X 100 (293.6: ΔH in case of 100% Crystal)

-Calculation of Thai Molecular Content: The content of Thai Molecular was calculated from the area of the Thai Molecular distribution graph, where the x-axis is the molecular weight M and the y-axis is expressed as n·P·dM. The graph is calculated from the GPC curve and DSC measurement results. With respect to the y-axis, n is the number of polymers having a molecular weight of M, and can be obtained as (dw/dlogMw)/M from the data of the GPC curve in which the x-axis is logMw and the y-axis is dw/dlogMw. In addition, P is the probability that a polymer having a molecular weight of M forms a tie molecule, and can be calculated from Equations 1 to 3 below, and dM is an interval between data on the x-axis (molecular weight M) of the GPC curve.

[Equation 1]

In Equation 1, r is the end to end distance of a random coil, b ² is 3/2r ² , and l _c is the crystal thickness from Equation 2 below. It is calculated|required, and l _a is calculated|required from following Formula 3 as an amorphous thickness.

[Equation 2]

In Equation 2, T ^o _m is 415K, σ _e is 60.9 x 10 ^-3 J/m ² , and Δh _m is 2.88 x 10 ³ J/m ³ .

[Equation 3]

In Equation 3, ρ _c is the density of crystalline, 1,000 kg/m ³ , ρ _a is the density of amorphous phase, 852 kg/m ³ , and ω ^c is the mass fraction crystallinity (weight fraction crystallinity) is confirmed from DSC results.

* Calculation of entanglement molecular weight (M _e ) : Storage of each sample under conditions of 150 ℃ to 230 ℃ temperature, 0.05 to 500 rad/s each frequency (Angular Frequency), 0.5% strain using a rotary rheometer The elastic modulus and the loss modulus were measured, and the entanglement molecular weight was calculated according to the following theoretical formula from the plateau elastic modulus (G _N ⁰ ) obtained here. However, in the following theoretical formula, ρ is the density (kg/m ³ ), R is the gas constant (8.314 Pa·m ³ /mol·K), and T is the absolute temperature (K).

[Theoretical]

M _e = (ρRT) / G _N ⁰

* Measurement and calculation of the content of ultra-high molecular weight components: From the result of analyzing the molecular weight distribution of the sample, the area ratio (%) of the portion having a molecular weight of 1 million or more relative to the total area was calculated.

* Long-term durability predicted value : The values obtained from the above were substituted into the following equation to calculate a long-term durability predicted value.

[Equation]

Long-term durability predicted value of the resin composition = ax (X) ^b x (Y) ^c x (K) ^d

However, in the above equation, a = 386,600, b = 4.166, c =-1.831, d = 1.769, each of X, Y, and Z is the content of thymolecule in the resin composition as a sample (wt%), The entanglement molecular weight (g/mol) and the mass average molecular weight (Mw) mean the content (wt%) of a component having 1 million or more. However, in the above equation, X, Y, and Y are used as non-dimensional constants excluding units.

Based on the predicted value calculated from the above equation, the properties of the resin were qualitatively classified based on the following criteria.

<Qualitative classification of predicted values>

-Over 2,000: Excellent

-1,500 to less than 2,000: somewhat superior

-1,000 to less than 1,500: moderate

-400 to less than 1,000: somewhat bad

-Less than 400: bad

Manufacturing example

A resin, which is a measurement object for long-term durability, was prepared as follows. And, the time was measured according to the FNCT (Full Notch Creep Test). The results are shown in Table 1.

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

Preparation Example 2: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9392 g/cm ³ And MI was 0.34.

Preparation Example 3: A resin was prepared in the same manner as in Preparation Example 1, except that the feed rate of the raw material was adjusted differently. The density of the prepared resin is 0.9358 g/cm ³ And MI was 0.75.

Preparation Example 4: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9359 g/cm ³ And the MI was 0.47.

Preparation Example 5: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9363 g/cm ³ And MI was 0.27.

Preparation Example 6: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9396 g/cm ³ And MI was 0.32.

Preparation Example 7: A resin was prepared in the same manner as in Preparation Example 1, except that the feed rate of the raw material was adjusted differently. The density of the prepared resin is 0.9365 g/cm ³ And MI was 0.60.

Preparation Example 8: A resin was prepared in the same manner as in Preparation Example 3, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9367 g/cm ³ And the MI was 0.47.

Preparation Example 9: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9369 g/cm ³ And MI was 0.38.

Preparation Example 10: A resin was prepared in the same manner as in Preparation Example 1, except that the input rate of the raw material was adjusted differently. The density of the prepared resin is 0.9364 g/cm ³ And MI was 0.48.

Preparation Example 11: Density of 0.9362 g/cm ³ And, except that the MI measured under the same conditions was 0.43, a resin was prepared in the same manner as in Preparation Example 1.

Preparation Example 12: Density of 0.9363 g/cm ³ And, except that the MI measured under the same conditions was 0.26, a resin was prepared in the same manner as in Preparation Example 1.

Preparation Example 13: Density of 0.9362 g/cm ³ And, except that the MI measured under the same conditions was 0.44, a resin was prepared in the same manner as in Preparation Example 1.

Preparation Example 14: Density of 0.9357 g/cm ³ And, except that the MI measured under the same conditions was 0.25, a resin was prepared in the same manner as in Preparation Example 1.

Preparation Example 15: Density is 0.9363 g/cm ³ And, except that the MI measured under the same conditions was 0.39, a resin was prepared in the same manner as in Preparation Example 1.

Example

Example One

For the sample prepared in Preparation Example 1, the content of Thai molecule, the entanglement molecular weight, and the content of the ultra-high molecular weight component were measured according to the above method, and the predicted value related to long-term durability was calculated by substituting it into the equation according to the present application. . The results are shown in Table 2.

Example 2 to 15

In each of Examples 2 to 15, in the same manner as in Example 1, except that the resin prepared according to Preparation Examples 2 to 15 was used, the content of the Thai molecule, the entanglement molecular weight, and the content of the ultra-high molecular weight component were measured. , Durability-related predicted values were calculated.

[Table 1]

[Table 2]

Comparing the measured FNCT values in Table 1 with the dimensionless calculated values in Table 2, it can be seen that the numerical values are very similar. In addition, it can be seen that the measured value and the calculated value can be evaluated very similarly even on a qualitative classification basis. In fact, it is also confirmed in FIG. 1 that the X-axis and Y-axis have a strong linear relationship. That is, the durability prediction method of the present application may replace the existing FNCT measurement method. In other words, the method according to the present application can evaluate the durability of the pipe resin (composition) within a short period of time only by measuring the molecular weight, etc., even without passing through a test period of several months or more.

Claims (6)

It is a method for predicting long-term durability of a resin composition for piping,
Long-term durability prediction method of a resin composition for piping using the following equation:
[Equation]
Long-term durability predicted value of the resin composition = ax (X) ^b x (Y) ^c x (K) ^d
However, in the above equation, a = 386,600, b = 4.166, c =-1.831, d = 1.769, each of X, Y, and Z is the content of thymolecule in the resin composition as a sample (wt%), The entanglement molecular weight (g/mol) and the mass average molecular weight (Mw) mean the content (wt%) of a component having 1 million or more. However, in the above equation, X, Y, and Y are used as non-dimensional constants excluding units. delete The method of claim 1, wherein the longer the long-term durability predicted value calculated through the equation is larger, the longer the long-term durability of the resin composition to be evaluated is determined to be superior. The method of claim 1, wherein a predicted long-term durability value is calculated according to the above equation for a plurality of resin compositions, and the calculated values are compared. The method for predicting long-term durability of a piping resin according to any one of claims 1, 3, or 4, wherein the resin composition contains a polyolefin resin. The method of claim 5, wherein the polyolefin resin is a polymer of ethylene, butylene, propylene, or α-olefin-based monomers.

Images