Method of setting measurement temperature and method of measuring residual dipolar coupling constant
By setting a measurement temperature based on the thermal degradation susceptibility of diene-based vulcanized rubber compositions, the method effectively reduces thermal effects, allowing for accurate measurement of the residual dipole interaction constant and crosslink density.
Patent Information
- Application Number
- JP2023199045
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-11-24
- Publication Date
- 2025-06-05
AI Technical Summary
Existing methods for measuring the residual dipole interaction constant in diene-based vulcanized rubbers face challenges due to thermal degradation, which alters the crosslinked structure and makes it difficult to evaluate the sample accurately.
A method for setting a measurement temperature based on the susceptibility of the diene-based vulcanized rubber composition to thermal degradation, using the swelling degree as an index to minimize thermal effects and ensure accurate crosslink density analysis.
This approach allows for the reduction of thermal degradation effects, enabling accurate measurement of the residual dipole interaction constant and reflecting the crosslink density more accurately in the analysis results.
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Abstract
Description
[Technical field]
[0001] The present invention relates to a method for setting a measurement temperature and a method for measuring a residual dipole interaction constant. [Background technology]
[0002] For diene-based vulcanized rubbers such as NR and SBR, the residual dipole interaction constant (D res A method is known in which the measurement of the temperature is performed at a uniform measurement temperature (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] Macromolecules,(US),2020,53,p.11166-11177 Summary of the Invention [Problem to be solved by the invention]
[0004] In the above literature, the measurement principle is to measure at high temperatures, extracting the effect of reduced mobility due to the constraints of crosslinking without being affected by the mobility of the polymer itself, and to obtain the crosslink density index D res Therefore, it is desirable to measure at high temperatures.
[0005] However, when measurements are performed at high temperatures, the crosslinked structure itself may change due to thermal degradation of the sample, making it impossible to evaluate the sample in the state that is originally intended for analysis, etc. For this reason, it is desirable to set a measurement temperature for each sample that is less susceptible to thermal degradation according to the polymer type, etc.
[0006] An object of the present invention is to provide a method for setting a measurement temperature for a residual dipole interaction constant, and a method for measuring a residual dipole interaction constant, which can solve the above problems and reduce the effects of thermal degradation. [Means for solving the problem]
[0007] The present invention relates to a method for setting a measurement temperature in measuring the residual dipole interaction constant of a diene-based vulcanized rubber composition, the measurement temperature being set based on the susceptibility of the composition to thermal degradation. Effect of the Invention
[0008] According to the present invention, a measurement temperature capable of reducing the influence of thermal degradation is set for each sample, and the residual dipole-dipole interaction constant can be measured. [Brief description of the drawings]
[0009] [Figure 1] 1 is a graph showing a multiple quantum enhancement curve obtained by 1H multiple quantum NMR. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] <How to set the measurement temperature> In the setting method of the present disclosure, the residual dipole interaction constant (D res In the measurement of the thermal degradation, the measurement temperature is set based on the susceptibility of the composition to thermal degradation. This makes it possible to set a measurement temperature that can reduce the effects of thermal degradation for each diene-based vulcanized rubber composition.
[0011] In the above-mentioned setting method, for example, for a diene-based vulcanized rubber composition for which the residual dipole interaction constant is to be measured, the degree of thermal degradation can be measured by changing the temperature when measuring the residual dipole interaction constant, and the temperature at which the effect of thermal degradation falls within an acceptable range can be set as the measurement temperature for the residual dipole interaction constant.
[0012] Although there is no limitation on the index of thermal degradation, it is preferable to use the swelling degree (SWELL) in terms of being easy to grasp the change in the crosslinking structure. That is, in the above setting method, it is preferable to set the measurement temperature based on the swelling degree of the diene vulcanized rubber composition. The swelling degree is a volume swelling degree measured by a toluene swelling method.
[0013] When the degree of swelling is used as an index of thermal degradation, it is preferable to set the measurement temperature so that the rate of change in the degree of swelling before and after the measurement of the residual dipole interaction constant is preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. The lower limit is not limited, but may be 0%. The rate of change in swelling degree is calculated according to the following formula. Swelling rate change (%) = {|(D res Swelling degree after measurement)-(D res Swelling degree before measurement)| / (D res Swelling degree before measurement) × 100
[0014] In the above setting method, further, D is determined based on the susceptibility of the diene-based vulcanized rubber composition to thermal degradation. res The measurement time may be set to 100%. As an index of thermal deterioration, an index similar to the measurement temperature may be used. The measurement temperature may be set first, and then an appropriate measurement time may be set at that temperature.
[0015] In the above setting method, the measurement temperature (and measurement time) may be set in consideration of the mobility of the polymer itself of the diene vulcanized rubber composition. This allows the crosslink density to be accurately reflected in the analysis results while reducing the influence of thermal degradation.
[0016] In the above setting method, the upper limit of the measurement temperature (and the measurement time) may be set based on the susceptibility of the diene vulcanized rubber composition to thermal degradation, and the lower limit of the measurement temperature (and the measurement time) may be set based on the mobility of the polymer itself.
[0017] The diene rubber used in the diene vulcanized rubber composition is not limited, and common rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), etc. are usable. Of these, NR, BR, and SBR are preferred.
[0018] The diene-based vulcanized rubber composition is vulcanized with a vulcanizing agent such as sulfur or a vulcanization accelerator. The sulfur and vulcanization accelerator are not particularly limited, and general ones can be used.
[0019] The diene-based vulcanized rubber composition may also contain fillers and other additives, which likewise may be conventional.
[0020] <Method for measuring residual dipole interaction constant> In the measurement method of the present disclosure, the residual dipole interaction constant of a diene-based vulcanized rubber composition is measured at a measurement temperature set by the above-mentioned setting method.
[0021] When the glass transition point (Tg) of the diene rubber used in the diene vulcanized rubber composition is less than -60°C, the measurement temperature is preferably 30°C or higher and 100°C or lower, more preferably 90°C or lower, even more preferably 80°C or lower, even more preferably 75°C or lower, more preferably 40°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher. By setting the measurement temperature in this manner, the influence of thermal degradation can be further reduced and the crosslink density can be more accurately reflected in the analysis results.
[0022] Examples of diene rubbers having a Tg of less than -60°C include NR, IR, and BR.
[0023] When the Tg of the diene rubber used in the diene vulcanized rubber composition is -60°C or higher, the measurement temperature is preferably 50°C or higher and 120°C or lower, more preferably 110°C or lower, even more preferably 100°C or lower, more preferably 60°C or higher, even more preferably 70°C or higher, and may be 90°C or higher. By setting the measurement temperature in this manner, the influence of thermal degradation can be further reduced and the crosslink density can be more accurately reflected in the analysis results.
[0024] An example of the diene rubber having a Tg of -60°C or higher is SBR.
[0025] When a diene rubber having a Tg of less than -60°C is used in combination with a diene rubber having a Tg of -60°C or higher, the measurement temperature is preferably 50°C or higher and 100°C or lower, more preferably 90°C or lower, even more preferably 80°C or lower, even more preferably 75°C or lower, and more preferably 60°C or higher, even more preferably 70°C or higher. By setting the measurement temperature in this manner, the influence of thermal degradation can be further reduced and the crosslink density can be more accurately reflected in the analysis results.
[0026] The Tg of rubber is a value measured by differential scanning calorimetry (DSC) at a temperature rise rate of 10° C. / min in accordance with JIS K7121.
[0027] In the above measurement method, the measurement time is preferably 1.5 hours or less, more preferably 1.3 hours or less, and even more preferably 1.2 hours or less, and is preferably 0.5 hours or more, and more preferably 0.8 hours or more. By setting the measurement temperature in this manner, the influence of thermal degradation can be further reduced and the crosslink density can be more accurately reflected in the analysis results.
[0028] Residual dipole interaction constant (D res ) can be measured, for example, by using a solid-state NMR method. As described in JP 2014-85309 A, D res Since there is a good correlation between D and crosslink density, res By measuring the crosslink density, it is possible to evaluate the crosslink density.
[0029] Here, as described in the publication, the residual dipole interaction constant (D res ) means that the remaining 1 The magnitude of the coupling between H, 1 H- 1 This means the magnitude of the interaction between H, and when the interaction is large, D res The value of is large, and the smaller the value of D res The value of becomes smaller.
[0030] Dres For example, as described in the above publication, 1 It can be obtained from the transverse magnetization decay curve obtained by H-NMR measurement. The solid echo method, the Hahn echo method, the CPMG method, etc. are known as methods for obtaining the transverse magnetization decay curve. res In order to accurately determine
[0031] The decay parameter of the transverse magnetization decay curve measured by the Hahn echo method is the transverse relaxation time constant (T 2 ) and the residual dipole interaction constant (D res ) Therefore, when fitting the transverse magnetization decay curve, it is necessary to separate the transverse relaxation time constant and the residual dipolar interaction constant.
[0032] The transverse magnetization decay curve can be transformed into the following equation for fitting, for example. In the following equation, it is assumed that the rubber composition is composed of three components A, B, and C. res.A , D res.B are the D of the A component, respectively. res , B component D res Also, M(t) is the magnetization strength at a certain time t, and M(0) is the initial magnetization strength.
number
[0033] The transverse relaxation time constant can also be measured by other methods. In the case of a rubber composition, taking into account the speed of the rubber polymer chain motion, the transverse relaxation time constant (T 2 ) = relaxation time constant at spin lock (T 1ρ ) is approximately true in principle. 1ρ By measuring the value, T 2 It is possible to substitute as:
[0034] The procedure for determining the residual dipole interaction constant by the method using the transverse magnetization decay curve can be summarized as follows (1) to (3). (1) A transverse magnetization decay curve is obtained by the Hahn echo method. (2)T 1ρ (Relaxation time constant during spin lock) is calculated. (3) T 2 =T 1ρ Assuming that, D res Request.
[0035] The molecular structure in rubber is amorphous. 1 H- 1 The H-distance is not uniform. Therefore, 1 H- 1 The magnitude of the H-H interaction is also considered to be not uniform but to have a distribution. Therefore, it is preferable to analyze the residual dipole-dipole interaction constant by introducing a distribution function. For example, the following formula can be used as the distribution function. In the following formula, F(S) is the frequency, β A means a constant related to the distribution width. Also, R A is the R in the fitting function of the transverse magnetization decay curve mentioned above. A , R Am means the average value.
number
[0036] The device used for NMR measurement is preferably a low magnetic field NMR device, specifically, an NMR device of 50 MHz or less. Of commercially available types, a 20 MHz NMR device is preferable. In a high magnetic field, the analysis of the transverse magnetization decay curve may become complicated or may not be possible due to the influence of chemical shift. In addition, if it is less than 20 MHz, the signal becomes weak, and the analysis may become complicated or may not be possible.
[0037] D res The method for finding this is as follows: 1 It is also possible to use H multiple quantum NMR, which allows measurements with small amounts of sample and provides excellent data accuracy.
[0038] 1The H multiple quantum NMR method is described, for example, in Saalwachter et al. Journal of Chemical Physics. 119(6). 3468-3482. (Document A) 1 This corresponds to H multiple-quantum nuclear magnetic resonance, etc.
[0039] 1 The 1 H multiple quantum NMR method can be carried out, for example, according to the method described in II. EXPERIMENT, B. NMR spectroscopy in the above-mentioned document A, and a multiple quantum enhancement curve (FIG. 1) can be obtained by this method.
[0040] 1 The multiple quantum enhancement curve obtained by the H multiple quantum NMR method has a residual dipolar interaction constant (D res ) and the standard deviation (σ) of the residual dipole interaction constant.
[0041] The multiquantum increase curve can be transformed into, for example, the following formula (I) and fitted. nDQ means the theoretical curve of the multiquantum growth curve. DQ is one of the experimental variables related to time.
number
[0042] 1 The procedure for determining the residual dipole interaction constant by H multiple quantum NMR method is summarized as follows (1) to (2). (1) 1 A multiple quantum enhancement curve is obtained by 1 H multiple quantum NMR method. (2) For the experimental multiquantum growth curves, the residual dipole-dipole coupling constant (D res ) and the standard deviation (σ) of the residual dipole interaction constant are used as variables to perform fitting with the theoretical curve of the above formula (I).
[0043] As mentioned above, the molecular structure in rubber is amorphous.1 H- 1 The H-distance is not uniform. Therefore, 1 H- 1 The magnitude of the H-H interaction is also not uniform, but is thought to have a distribution. Therefore, it is preferable to perform the analysis taking the distribution into account. In the above formula (I), the analysis is performed assuming the distribution.
[0044] 1 There are no particular limitations on the device used for the H multiple quantum NMR method, but the irradiation magnetic field strength is preferably 75 kHz or more (more preferably 100 kHz).
[0045] The diene-based vulcanized rubber composition measured in the present disclosure is not particularly limited, but may be one sampled from a rubber product such as a tire, or may be one sampled from a tire. EXAMPLES
[0046] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.
[0047] <Preparation of Diene-Based Vulcanized Rubber Composition> The various chemicals used in the examples will be collectively described below. NR:SVR-L (Tg -70℃) BR: BR150B (cis content 96% by mass) manufactured by Ube Industries, Ltd. (Tg -85°C) SBR: SBR1502 (solution polymerization SBR) manufactured by Sumitomo Chemical Co., Ltd. (Tg -56°C) Carbon black: Show Black N220 (N) manufactured by Cabot Japan Co., Ltd. 2 SA:111m 2 / g, DBP absorption: 115ml / 100g) Zinc oxide: Zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia made by NOF Corporation Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
[0048] According to the compounding recipe in Table 1, rubber, carbon black, and additives (sulfur, vulcanization accelerator, zinc oxide, and stearic acid) were mixed in a kneader, and then pressed at 150°C to obtain a diene-based vulcanized rubber composition. The vulcanization time was T100 measured with a Curelastometer (registered trademark).
[0049] [Table 1]
[0050] <Evaluation of thermal effects> (Variable temperature D by low-field time-domain NMR res measurement) Using a Bruker Minispec mq20 (measurement frequency: 19.65 MHz) manufactured by Bruker Corporation, the diene vulcanized rubber composition was measured at each temperature under the conditions shown in Table 2. 1 H-NMR measurements were performed to obtain multiple quantum enhancement curves. The MQ method was used for the measurement pulse. The irradiation magnetic field strength was set to 100 kHz.
[0051] The obtained multiquantum increase curve was fitted with the theoretical curve of the above formula (I).
[0052] [Table 2]
[0053] The obtained D res Value and D res The distribution is shown in Table 3.
[0054] (Measurement of swelling degree (SWELL)) D at each temperature res The diene vulcanized rubber composition after the measurement of the volume swelling degree was then immersed in a sufficient amount of toluene solvent at room temperature for 24 hours to 72 hours, and the volume swelling degree was measured. The results are shown in Table 3.
[0055] [Table 3]
[0056] From the above results, D is observed at 100℃ or higher for NR, 120℃ or higher for BR, and 140℃ or higher for SBR. res The values decreased or the distribution increased, and the SWELL values also increased, indicating that there was a thermal effect (thermal degradation) on the sample at the above temperatures. Therefore, in order to reduce the effect of thermal degradation, it is necessary to set the measurement temperature lower than the above temperature.
[0057] The present invention (1) is a method for setting a measurement temperature in measuring the residual dipole interaction constant of a diene-based vulcanized rubber composition, the measurement temperature being set based on the susceptibility of the composition to thermal degradation.
[0058] The present invention (2) relates to the method according to the present invention (1), in which the measurement temperature is set based on the swelling degree of the composition.
[0059] The present invention (3) is a method for measuring the residual dipole interaction constant, which comprises measuring the residual dipole interaction constant of a diene-based vulcanized rubber composition at a measurement temperature set by the method according to the present invention (1) or (2).
[0060] The present invention (4) relates to the measurement method according to the present invention (3), in which the glass transition point of the diene rubber used in the composition is lower than -60°C, and the measurement temperature is 30°C or higher and 100°C or lower.
[0061] The present invention (5) relates to the measurement method according to the present invention (3), in which the glass transition point of the diene rubber used in the composition is -60°C or higher, and the measurement temperature is 50°C or higher and 120°C or lower.
[0062] The present invention (6) is a measurement method optionally combined with any of the present inventions (3) to (5), in which the measurement time is 1.5 hours or less.
Claims
1. A method for setting a measurement temperature in measuring the residual dipole interaction constant of a diene-based vulcanized rubber composition, the measurement temperature being set based on the susceptibility of the composition to thermal degradation.
2. 2. The method according to claim 1, wherein the measurement temperature is set based on the swelling degree of the composition.
3. A method for measuring a residual dipole interaction constant, comprising measuring the residual dipole interaction constant of a diene-based vulcanized rubber composition at a measurement temperature set by the method according to claim 1 or 2.
4. The method according to claim 3, wherein the glass transition point of the diene rubber used in the composition is lower than -60°C, and the measurement temperature is 30°C or higher and 100°C or lower.
5. The method according to claim 3, wherein the glass transition point of the diene rubber used in the composition is -60°C or higher, and the measurement temperature is 50°C or higher and 120°C or lower.
6. 4. The method according to claim 3, wherein the measurement time is 1.5 hours or less.