KR20240041048A - Method and Apparatus for Neck-in prediction of polymer - Google Patents

Abstract

The present invention relates to a method and prediction device for predicting the neckiness of a polymer sample. The present invention can predict the neckiness of a polymer sample in advance with a small amount of sample, without the complicated process of modeling the polymer sample and performing numerical analysis according to the finite element method. Highly accurate results can be obtained.

Description

Neck-in prediction method and prediction device for polymer samples {Method and Apparatus for Neck-in prediction of polymer}

The present invention relates to a method and prediction device for predicting neckin of a polymer sample.

Polymers are used for a variety of purposes, including films, injection molding, electrical and electronic products, and fibers, and many types of polymer films used in daily life are manufactured through the extrusion process. The extrusion process includes a cast film process in which polymers are melted at a specific temperature and stretched uniaxially at a constant speed, and a blown film process in which air is injected and stretched biaxially (bi-axially). The Blown Film process is a representative example. When producing film through the cast film process, the film is extruded through an extrusion die. The film is inevitably produced smaller than the die size, resulting in processing instability that causes the film to shrink. This phenomenon is caused by Neckin. It is called -in, neck-in).

The neckkin phenomenon is largely influenced by the viscoelastic properties of the polymer. For example, when the elasticity of the polymer is high, the neckiness of the film is offset due to recovery, but when the elasticity is low, the neckiness of the polypropylene film appears relatively large due to insufficient recovery. The greater the elasticity of the polymer, the more the neckkin phenomenon can be partially offset due to the recovery power of the polymer itself, but the neckkin phenomenon cannot be completely eliminated.

Due to the necking phenomenon of the film, polymer films produced in sizes smaller than the extrusion die specifications have a direct impact on product productivity and unit cost. In addition, since the film must be cut due to the instability of thickening at both ends of the film, called edge beads, the actual usable size becomes narrower than the width of the film where necking occurs.

Therefore, it is important to predict and measure this neckin phenomenon in advance. Until now, in order to measure the neckiness of polymer films, they were actually extruded using actual extruders and cast film equipment, but there were disadvantages in that extrusion required a large amount of samples and took a lot of time. Therefore, there is a need for technology that can predict the degree of necking in a short period of time with a small amount of polymer before processing the polymer into a film.

Patent Document 1. Korean Patent No. 10-1975004

The present invention was created to solve the problems described above, and the purpose of the present invention is to provide a method and prediction device for predicting neckin of a polymer sample that can predict the neckin rate only with a small amount of polymer sample and its loss tangent (tanδ) information. is to provide.

One aspect of the present invention includes (i) measuring the dynamic viscoelasticity of a polymer sample to obtain a loss tangent (tanδ); and (ii) predicting the Neckin rate using the loss tangent (tanδ) of the polymer sample.

Another aspect of the present invention is a measuring unit that measures the dynamic viscoelasticity of a polymer sample and determines the loss tangent (tanδ); and a calculation unit that predicts the Neckin rate using the loss tangent (tanδ) of the polymer sample.

The present invention uses the correlation between the elasticity index and Neckin among the rheological properties of polymers to confirm the size of the film that can be produced within up to 2 hours through simple measurement and calculation without a large amount of samples before starting the process, and by comparing Neckin's prediction and Together, rheological properties can be measured. In addition, by understanding the characteristics of the polymer film in advance, it is possible to reduce costs and check in advance whether it is suitable for the intended use.

Figure 1 shows the results of curve fitting the rheological properties of polypropylene measured in Example 1 of the present invention according to the Phan-Tien-Tanner model.
Figure 2 shows the prediction of the neck-in phenomenon of the film as a result of simulating film processing using Ansys' Polyflow S/W.
Figure 3 shows the correlation between the neckin rate of the polymer measured in Examples 1 to 5 of the present invention and the neckin rate measured with Polyflow S/W.

Hereinafter, the present invention will be described in more detail with the accompanying drawings and examples.

As explained earlier, in the process of processing polymers into films, it was impossible to completely eliminate the Neckin phenomenon, in which the width of the polymer film being manufactured becomes narrower than the extrusion die, and it had a direct impact on the productivity and unit cost of the polymer film being manufactured. . Accordingly, a technology was required to predict in advance the extent to which necking occurs, but the conventional method for predicting the necking phenomenon had the limitation of requiring a large amount of polymer film and requiring a long measurement time.

Accordingly, the present invention provides a method of measuring the dynamic viscoelasticity of a polymer sample to obtain the loss tangent (tanδ) and using this to predict the Neckin ratio of the polymer sample.

The loss tangent is a value that can be easily obtained by measuring the dynamic viscoelasticity of a polymer sample. If the loss tangent value is derived under preset conditions, the Neckin ratio can be predicted by simple calculation, so it has the advantage of being very simple to measure.

In addition, the measurement method of the present invention using loss tangent (tanδ) has the advantage of enabling more precise measurement because the storage modulus and loss modulus can be considered simultaneously. The neckin ratio of a polymer is closely related to dynamic viscoelasticity because when the elasticity of the polymer is large, the neckin phenomenon is partially offset by the recovery force. The neckin ratio measured by the measurement method of the present invention is linearly proportional to the loss tangent (tanδ). It was confirmed that it corresponded very well to .

More specifically, one aspect of the present invention includes the steps of (i) measuring the dynamic viscoelasticity of a polymer sample to obtain a loss tangent (tanδ); and (ii) predicting the Neckin rate using the loss tangent (tanδ) of the polymer sample.

Hereinafter, each step of the method for predicting neckin of a polymer sample of the present invention will be described in more detail.

(i) Measuring the dynamic viscoelasticity of the polymer sample and calculating the loss tangent (tanδ)

First, measure the dynamic viscoelasticity of the polymer sample for which you want to measure the Neckin ratio, and obtain the loss tangent (tanδ) value from this.

The dynamic viscoelasticity may be measured with a rheometer.

The loss tangent (tanδ) means the loss modulus divided by the storage modulus, and is expressed in the equation below.

Here, tanδ is the loss tangent, G ′ is the storage modulus, and G ″ is the loss modulus.

The dynamic viscoelasticity may be performed by a frequency change test (Frequency Sweep) method, which is measured by changing each frequency.

According to one embodiment, the dynamic viscoelasticity may be loss modulus and storage modulus.

That is, in step (i), the loss modulus and storage modulus of the polymer sample according to each frequency are measured to obtain the loss tangent (tanδ) according to each frequency.

The polymer sample may preferably be made of polypropylene. The polypropylene resin may refer to any one of homo polypropylene, impact polypropylene, and ethylene-polypropylene rubber. Since polypropylene is a polymer with a linear structure, there is no extensional thickening phenomenon, so it has the advantage of making it easy to predict the neck-in phenomenon of the film.

In step (i), the dynamic viscoelasticity may be measured at 165 to 260°C, preferably 170 to 250°C, more preferably 180 to 240°C, and most preferably 190 to 220°C. If the dynamic viscoelasticity measurement temperature is less than 165°C, it is undesirable because the polymer may not be in a molten state or a load may occur on the device used to measure dynamic viscoelasticity. Conversely, if it exceeds 260°C, the polymer sample may deteriorate and lose its inherent properties. It is difficult to measure, and measurement accuracy may decrease.

In step (i), the dynamic viscoelasticity is 0.01 to 150 rad/s, preferably 0.05 to 130 rad/s, more preferably 0.08 to 120 rad/s, and most preferably 0.1 to 100 rad/s. It may be measured in a range.

In particular, if the respective frequency range for dynamic viscoelasticity measurement is less than 0.1 rad/s, it takes a lot of measurement time, and when measuring storage modulus and loss modulus, noise generation increases and the dynamic viscoelastic properties of the polymer sample are not properly reflected. It may not be possible. Conversely, if the speed exceeds 100 rad/s, the measurement sample may deviate from the measurement position due to normal force, thereby reducing measurement accuracy.

In step (i), the dynamic viscoelasticity may be measured at a strain of 1 to 12%, preferably 2 to 10%, more preferably 3 to 8%, and most preferably 4 to 6%. When measuring dynamic viscoelasticity, if the strain is less than 1%, the force applied to the measurement sample is small and does not cause sufficient deformation in the sample, which may reduce measurement accuracy. Conversely, if it exceeds 12%, the strain is excessive and the linear viscoelasticity section can escape.

When the dynamic viscoelasticity is performed by the frequency sweep method, the tanδ value according to the frequency (rad/s) is obtained. However, in the actual polymer film manufacturing process, there is a difference because it is performed by setting the shear rate, not the frequency, as the process condition. Therefore, it is more desirable to convert the frequency (ras/s) to the shear rate (1/s) to obtain the tanδ value according to the shear rate. In this case, the frequency can be converted to the shear rate according to the Cox-Merz rule.

The loss tangent (tanδ) is at a shear rate of 60 to 150 1/s, preferably 70 to 130 1/s, more preferably 80 to 120 1/s, and most preferably 90 to 110 1/s. It may be a loss tangent (tanδ) value. If the loss tangent (tanδ) is a loss tangent (tanδ) value at a shear rate of less than 60 1/s, the measurement accuracy may be low because it is a value at a lower shear rate than actual processing conditions, and conversely, if it exceeds 150 1/s. The loss tangent (tanδ) value measured at a shear rate of may be a value at a higher shear rate than actual processing conditions and may not represent actual processing conditions.

(ii) Predicting the neck-in rate (%) using the loss tangent (tanδ) of the polymer sample.

Next, the Neckin rate is derived using the loss tangent (tanδ) obtained previously.

In this specification, neckin ratio refers to the width of the film reduced after extrusion relative to the width of the existing polymer film, and can be expressed in equation (1) below.

식 (1)

Equation (1)

The step of predicting the neckin ratio of the polymer sample may be performed by substituting tan δ of the polymer sample into Equation 1 below.

[Equation 1]

tan δ=A·Neckin rate (%)-B

(In Equation 1 above, A is a real number from 0.01 to 0.04, and B is a real number from 0.5 to 1.2.)

It was confirmed that the Neckin ratio can be easily calculated by substituting the loss tangent (tanδ) of the polymer sample previously obtained into Equation 1 defined above. The method for predicting neckin of a polymer sample according to the present invention is to model the polymer sample and obtain results with high accuracy and actual neckin rate in a very simple way using Equation 1 without numerical analysis according to the finite element method. There are advantages.

In particular, although not explicitly described in the following Examples and Comparative Examples, in the method for predicting the neckin of a polymer sample according to the present invention, the neckin rate of the polymer sample was measured under different conditions.

As a result, measurement accuracy was excellent regardless of the melt index of the polymer sample only when all of the following conditions were satisfied.

The material of the polymer sample is polypropylene,

In step (i), the dynamic viscoelasticity is measured at 190 to 220 ° C,

In step (i), the dynamic viscoelasticity is measured in the respective frequency range of 0.1 to 100 rad/s,

In step (i), dynamic viscoelasticity is measured at a strain of 4 to 6%,

In step (i), the loss tangent (tanδ) is the loss tangent (tanδ) value at a shear rate of 90 to 110 1/s,

Step (ii) may be performed by substituting tan δ of the polymer sample into Equation 1 below.

[Equation 1]

tan δ=A·Neckin rate (%)-B

(In Equation 1 above, A is a real number from 0.01 to 0.04, and B is a real number from 0.5 to 1.2.)

However, if any of the above conditions are not satisfied, the measurement may or may not be accurate depending on the melt index of the polymer sample, which reduces measurement reliability, and the first order value derived from the linear approximation of the loss tangent value to the Neckin rate The coefficient of determination (R ² ) of the function had a value of less than 0.8.

Meanwhile, another aspect of the present invention includes a measuring unit that measures the dynamic viscoelasticity of a polymer sample and determines the loss tangent (tanδ); and an arithmetic unit that predicts the Neckin rate using the loss tangent (tanδ) of the polymer sample.

The polymer sample may preferably be made of polypropylene.

The dynamic viscoelasticity may be measured at 165 to 260 °C, preferably 170 to 250 °C, more preferably 180 to 240 °C, and most preferably 190 to 220 °C.

The dynamic viscoelasticity is measured in the respective frequency range of 0.01 to 150 rad/s, preferably 0.05 to 130 rad/s, more preferably 0.08 to 120 rad/s, and most preferably 0.1 to 100 rad/s. You can.

The dynamic viscoelasticity may be measured at a strain of 1 to 12%, preferably 2 to 10%, more preferably 3 to 8%, and most preferably 4 to 6%.

The loss tangent (tanδ) is at a shear rate of 60 to 150 1/s, preferably 70 to 130 1/s, more preferably 80 to 120 1/s, and most preferably 90 to 110 1/s. It may be a loss tangent (tanδ) value.

The calculation unit may predict the Neckin ratio by substituting the loss tangent (tan δ) of the polymer sample into Equation 1 below.

[Equation 1]

tan δ=Aneckkin rate (%)-B

(In Equation 1 above, A is a real number from 0.01 to 0.04, and B is a real number from 0.5 to 1.2.)

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

Examples 1 to 5

(1) Frequency sweep analysis

Using a rheometer (ARES-G2) from TA Instruments, companies A (Example 1), Company B (Example 2), Company C (Example 3), and Company D (Example 3) each had a melt index (MI) of 4. Frequency sweep analysis was conducted on commercial homopolypropylene polymers from Example 4) and Company E (Example 5). The analysis temperature was 200°C, each frequency range was 0.1~100 rad/s, and the strain was 5%, and each frequency was converted to shear rate according to the Cox-Merz rule. Next, the loss tangent (tanδ) value at 100 1/s (shear rate), which is a general shear strain range transmitted to the film during film production, was calculated and shown in Table 1 below.

classification Loss tangent (tanδ) Example 1 0.7309 Example 2 0.6755 Example 3 0.6987 Example 4 0.6683 Example 5 0.6578

(2) Neckin rate prediction

The Neckin rate was predicted according to Equation 1 below using the loss tangent (tanδ) value, and the results are shown in Table 2.

[Equation 1]

tan δ=A·Neckin rate (%)-B

(In Equation 1 above, A is 0.0253 and B is 0.8383.)

Experiment example

The neckin ratio was measured for the homo polypropylene used in Examples 1 to 5 by the following method.

Using Ansys' Polyflow S/W, neck-in during cast film processing was analyzed. Using the rheological properties (storage modulus, loss modulus, viscosity) measured in the above Frequency Sweep analysis, curve fitting was performed in five multi-modes to fit the Phan-Thien-Tanner Model, a viscoelastic model (Figure 1), and through this, a viscoelastic model was created. Extrusion processing analysis was performed by securing the coefficients. When the stretching speed compared to the extrusion speed was 13 (DR=13), the film width at the part where the chill roll would be located was checked and the neckin ratio was calculated and shown in Table 2.

Figure 1 shows the results of curve fitting the rheological properties of polypropylene measured in Example 1 of the present invention according to the Phan-Tien-Tanner model.

Figure 2 shows the prediction of the neck-in phenomenon of the film as a result of simulating film processing using Ansys' Polyflow S/W.

Figure 3 shows the correlation between the neckin rate of the polymer measured in Examples 1 to 5 of the present invention and the neckin rate measured with Polyflow S/W.

Table 2 below shows the results of comparing the neckin rate measured in the above example and the neckin rate analyzed using Polyflow S/W.

classification Neckin rate according to examples Neckin rate measured with Polyflow S/W Example 1 62.02 60.16 Example 2 59.83 59.58 Example 3 60.75 60.34 Example 4 59.55 59.71 Example 5 59.13 59.37

As shown in FIG. 3 and Table 2, the neckin rate measured in the examples tends to generally match the neckin rate measured with Polyflow S/W, confirming that highly reliable measurement is possible.

Claims (15)

(i) measuring the dynamic viscoelasticity of the polymer sample to obtain the loss tangent (tanδ); and
(ii) predicting the neckin rate using the loss tangent (tanδ) of the polymer sample. The method of claim 1, wherein the polymer sample is made of polypropylene. The method of claim 1, wherein in step (i), the dynamic viscoelasticity is measured at 165 to 260 °C. The method of claim 1, wherein in step (i), the dynamic viscoelasticity is measured in an angular frequency range of 0.01 to 150 rad/s. The method of claim 1, wherein in step (i), the dynamic viscoelasticity is measured at a strain of 1 to 12%. The method of claim 1, wherein in step (i), the loss tangent (tanδ) is a loss tangent (tanδ) value at a shear rate of 60 to 150 1/s. The method of claim 1, wherein step (ii) is performed by substituting tan δ of the polymer sample into Equation 1 below.
[Equation 1]
tan δ=A·neckin rate (%)-B
(In Equation 1 above, A is a real number from 0.01 to 0.04, and B is a real number from 0.5 to 1.2.) According to paragraph 1,
The material of the polymer sample is polypropylene,
In step (i), the dynamic viscoelasticity is measured at 190 to 220 ° C,
In step (i), the dynamic viscoelasticity is measured in the respective frequency range of 0.1 to 100 rad/s,
In step (i), dynamic viscoelasticity is measured at a strain of 4 to 6%,
In step (i), the loss tangent (tanδ) is the loss tangent (tanδ) value at a shear rate of 90 to 110 1/s,
Step (ii) is a method for predicting neckin of a polymer sample, characterized in that it is performed by substituting tan δ of the polymer sample into Equation 1 below.
[Equation 1]
tan δ=A·neckin rate (%)-B
(In Equation 1 above, A is a real number from 0.01 to 0.04, and B is a real number from 0.5 to 1.2.) A measuring unit that measures the dynamic viscoelasticity of the polymer sample and calculates the loss tangent (tanδ); and
An arithmetic unit that predicts the Neckin rate using the loss tangent (tanδ) of the polymer sample. The apparatus for predicting neckin of a polymer sample according to claim 9, wherein the polymer sample is made of polypropylene. The apparatus for predicting neckin of a polymer sample according to claim 9, wherein the dynamic viscoelasticity is measured at 165 to 260 °C. The apparatus of claim 9, wherein the dynamic viscoelasticity is measured in an angular frequency range of 0.01 to 150 rad/s. The apparatus of claim 9, wherein the dynamic viscoelasticity is measured at a strain of 1 to 12%. The Neckin prediction device of claim 9, wherein the loss tangent (tanδ) is a loss tangent (tanδ) value at a shear rate of 60 to 150 1/s. The apparatus of claim 9, wherein the calculation unit predicts the Neckin rate by substituting the loss tangent (tan δ) of the polymer sample into Equation 1 below.
[Equation 1]
tan δ=A·neckin rate (%)-B
(In Equation 1 above, A is a real number from 0.01 to 0.04, and B is a real number from 0.5 to 1.2.)