Method for quantifying component in rubber composition

Abstract

To provide a method for quantifying components in a rubber composition that is excellent in versatility of components to be quantified while ensuring quantitative property.SOLUTION: A method for quantifying components in a rubber composition, comprises at least an extraction step of obtaining an extract containing extract components from the rubber composition using an organic solvent, a concentration step of obtaining a concentrate of the extract components by distilling off the organic solvent from the extract, a thermal analysis step of performing a thermogravimetric analysis of the concentrate to obtain a thermogravimetric curve, and a quantification step of reading a weight loss ratio corresponding to components to be quantified from the thermogravimetric curve.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for quantifying components in a rubber composition. [Background technology]

[0002] Rubber compositions are used in many rubber products, such as pneumatic tires, etc. In order to understand and improve the performance of rubber products, it is important to have a technique for quantifying the amounts of components contained in the rubber products.

[0003] The following Patent Document 1 describes a method for quantifying a component in a rubber composition, in which the component to be quantified is a component that is kneaded with the rubber component, and the quantification is based on the ratio of the peak area of ​​a peak derived from the standard sample to the peak area of ​​a peak derived from the component to be quantified in a chromatogram obtained by drying a solvent extract of a rubber composition containing a standard sample and analyzing the solvent extract with a pyrolysis gas chromatograph mass spectrometer.

[0004] The following Patent Document 2 describes a method for individually quantifying the content of each resin component in a paste containing a plurality of resin components and an inorganic powder, the method comprising: a dissolving step of mixing the paste with an organic solvent to dissolve the plurality of resin components; a separation step of separating the inorganic powder from the solution obtained in the dissolving step to form a resin solution containing the plurality of resin components; a measurement step of measuring the resin solution by pyrolysis gas chromatography to obtain peak area values ​​of pyrolysis products specific to each resin component generated by pyrolysis of each resin component; a quantification step of calculating the content in the paste from the peak area values ​​obtained in the measurement step based on a calibration curve showing the correlation between the content and the peak area value of the specific pyrolysis product for each resin component; and a drying step between the separation step and the measurement step, in which the resin solution is heated at a temperature equal to or higher than the boiling point of the organic solvent and equal to or lower than the pyrolysis temperature of the plurality of resin components, dried, the organic solvent is volatilized, and a dry product containing the plurality of resin components is formed. In the measurement step, the dry product is measured by pyrolysis gas chromatography. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6665629 [Patent Document 2] Patent No. 6950494 Summary of the Invention [Problem to be solved by the invention]

[0006] As a result of intensive research by the present inventors, it was found that the above-mentioned conventional quantitative determination method cannot accurately determine the components to be quantified unless information on the components to be quantified (such as their chemical structure and behavior during control measurement) is known in advance, and therefore the components to be quantified are limited. Therefore, it was found that there is room for further improvement in the above-mentioned conventional quantitative determination method with respect to the versatility of the components to be quantified.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a method for quantifying components in a rubber composition, which is highly versatile in terms of the components to be quantified while ensuring quantitative accuracy.

[0008] The above-mentioned problems can be solved by the following configuration: That is, the present invention relates to a method for quantifying a component in a rubber composition, comprising at least an extraction step of obtaining an extract containing an extract component from the rubber composition using an organic solvent, a concentration step of obtaining a concentrate of the extract component by distilling off the organic solvent from the extract, a thermal analysis step of performing a thermogravimetric analysis of the concentrate to obtain a thermogravimetric curve, and a quantification step of reading a weight loss ratio corresponding to the component to be quantified from the thermogravimetric curve.

[0009] Of the above-mentioned method (1) for quantifying a component in a rubber composition, the method (2) for quantifying a component in a rubber composition in which the component to be quantified is a non-volatile component is preferred.

[0010] In the above-mentioned method (2) for quantifying a component in a rubber composition, the method (3) for quantifying a component in a rubber composition in which the non-volatile component is a hydrocarbon resin is preferable.

[0011] In any one of the above quantitative determination methods (1) to (3) for a component in a rubber composition, when the ratio of the amount of the extract of the concentrate when the total amount of the rubber composition in the concentrating step is taken as 100 mass%, and after the thermal analysis step, the thermogravimetric curve is differentiated to identify a component that undergoes a weight loss in a high temperature region, and in the quantitative determination step, the ratio γ (mass%) of the amount of the component blended in the rubber composition is calculated by the following formula (2): γ=α×β / 100 (2) The quantitative determination method (4) of the components in the rubber composition, which is calculated based on the above, is preferred.

[0012] In any one of the above methods (1) to (4) for quantifying a component in a rubber composition, the method (5) for quantifying a component in a rubber composition, in which the thermal analysis step is carried out in an inert gas atmosphere, is preferred.

[0013] In the above-mentioned method (4) or (5) for quantifying a component in a rubber composition, a method (6) for quantifying a component in a rubber composition is preferred, in which the peak top temperature of a differential curve of a thermogravimetric curve corresponding to the component that loses weight in a high temperature region is 250°C or higher. Effect of the Invention

[0014] In particular, rubber compositions used in pneumatic tires often contain non-volatile components such as hydrocarbon resins, and in order to understand and improve the performance of rubber products, it is important to have a technique for quantifying the amount of components contained in rubber products, particularly the amount of non-volatile components such as hydrocarbon resins. Although there is a technique for extracting non-volatile components such as hydrocarbon resins by solvent extraction and specifying the amount of the components based on the amount extracted, the extracted components contain many other components such as antioxidants and oils in addition to the desired components, and this technique has the problem of being unable to accurately specify the amount of the desired components.

[0015] On the other hand, in the present invention, an extraction step is carried out in which an extract containing an extract component is obtained from a rubber composition using an organic solvent, and then the organic solvent is distilled off from the extract to obtain a concentrate of the extract component (concentration step). The present invention further includes at least a thermal analysis step in which a thermogravimetric analysis is carried out on the concentrate to obtain a thermogravimetric curve, and a quantification step in which a weight loss rate corresponding to the component to be quantified is read from the thermogravimetric curve. This makes it possible to more accurately quantitate the amount of a desired component compared to the prior art.

[0016] In particular, in the present invention, when the ratio of the amount of the concentrate extracted in the concentrating step is taken as 100 mass %, the thermogravimetric curve is differentiated after the thermal analysis step to identify components that undergo weight loss in a high temperature range, and the ratio of the weight loss of the components in the high temperature range in the quantitative determination step is taken as β (mass %). The ratio γ (mass %) of the amount of the components blended in the rubber composition is calculated using the following formula (2): γ=α×β / 100 (2) The amount of the desired component can be determined more accurately when the amount of the component to be determined is calculated based on the above formula. Note that, in the differential curve of the thermogravimetric curve, the peak top temperature of the peak corresponding to the component to be determined is 250° C. or higher, which is preferable because the amount of the component can be determined more accurately.

[0017] The present invention is preferable when quantifying the amount of a non-volatile component, particularly a hydrocarbon resin, as a desired component, because the components to be quantified are more versatile than those in the prior art.

[0018] The present invention is preferable because it improves quantitative accuracy when quantifying the amount of non-volatile components, particularly hydrocarbon resins, in the case of quantifying the components of a rubber composition after vulcanization (vulcanized rubber) as a rubber composition. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing an example of the results of thermogravimetric analysis (thermogravimetric curve) of a concentrate of an extract obtained by extracting a rubber composition using chloroform as an organic solvent. [Diagram 2]FIG. 1 is a diagram showing the relationship between the quantitative results (mass%) and the actual blend amount (mass%) for the quantitative method according to the present invention and the conventional extraction method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention relates to a method for quantifying components in a rubber composition, and includes at least: (i) an extraction step of obtaining an extract containing the extract from the rubber composition using an organic solvent, (ii) a concentration step of obtaining a concentrate of the extract by distilling off the organic solvent from the extract, (iii) a thermal analysis step of performing a thermogravimetric analysis of the concentrate to obtain a thermogravimetric curve, and (iv) a quantification step of reading the weight loss rate corresponding to the component to be quantified from the thermogravimetric curve. Each step will be described below.

[0021] (i) Extraction process In the extraction step, an organic solvent is used to obtain an extract containing an extract component from a rubber composition, more preferably a rubber composition after vulcanization. The organic solvent is a solvent that is usually used for extracting a rubber composition, specifically, for example, chloroform, 1,2-dichloroethane, toluene, acetone, tetrahydrofuran, methanol, ethanol, 2-propanol, ethyl acetate, etc. Among these, in the present invention, it is preferable to use chloroform. The conditions for obtaining an extract containing an extract component from a rubber composition using an organic solvent are not particularly limited, but from the viewpoint of performing the subsequent concentration step more easily and further increasing the quantitative accuracy, it is preferable to perform the extraction step at a ratio of 0.5 to 3.0 g of the rubber composition to 50 to 200 ml of the organic solvent. In addition, the conditions for extracting the rubber composition with an organic solvent are not particularly limited, and can be carried out, for example, by the Soxhlet extraction method. The Soxhlet extraction time can be exemplified as about 4 to 8 hours.

[0022] (ii) Concentration process After the extraction step, the organic solvent is distilled off from the extract to obtain a concentrate of the extracted components (concentration step). The method for concentrating the extract is not limited, and examples of the method include a method in which the organic solvent is distilled off by drying the extract under reduced pressure.

[0023] In the conventional extraction method, the amount of the component extracted through the extraction and concentration steps (extracted amount of concentrate) is regarded as the amount actually blended in the rubber composition. On the other hand, in the method for quantifying the components in a rubber composition according to the present invention, it is possible to derive a blending amount closer to the actual blending amount than the amount of the extracted component based on information obtained in the following thermal analysis and quantification steps. The thermal analysis and quantification steps will be described below.

[0024] (iii) Thermal analysis process In the thermal analysis step, a thermogravimetric analysis (hereinafter, simply referred to as "TGA") of the concentrate is performed to obtain a thermogravimetric curve. FIG. 1 shows an example of the results of a thermogravimetric analysis (thermogravimetric curve) of a concentrate of an extract component obtained by extracting a rubber composition using chloroform as an organic solvent. In FIG. 1, the horizontal axis indicates the heating time (Time (kmin)), and the right vertical axis indicates the thermal weight loss (TG (%)). Curve A shows a thermogravimetric curve, in which the thermal weight loss (TG) is 0.0 when the heating time (Time) is 0.000, and the weight loss gradually progresses with heating, and when the heating time (Time) passes 0.800, the weight loss is 0.0. From this point on, the thermal weight loss (TG) becomes almost constant (-99.3%). The inner left vertical axis indicates the heating temperature (Temp (°C)). Curve B indicates a heating curve, which is approximately 100°C when the heating time elapsed (Time) is 0.000, and finally rises to 600°C. The outer left vertical axis indicates the thermal weight loss per unit time (DTG (μg / min)). Curve C indicates a differential curve of the thermogravimetric curve (curve A), and has two maximum peaks between 0.400 and 0.500, and between 0.600 and 0.700, when the heating time elapsed (Time) is 0.

[0025] In the present invention, from the viewpoint of preventing the components to be quantified from being oxidized and more accurately measuring the thermal weight loss, it is preferable that the atmosphere in which the thermal analysis step is carried out is an inert gas atmosphere.

[0026] (iv) Quantification process In the quantification step, the weight loss ratio corresponding to the component to be quantified is read from the thermogravimetric curve obtained in the thermal analysis step. In the present invention, the weight loss ratio (β (mass%)) of the component in the high temperature region is preferably read in the quantification step. In the following, an example will be described in which the component to be quantified in the present invention is a non-volatile component whose peak top temperature in the differential curve of the thermogravimetric curve is 250°C or higher. The differential curve of the thermogravimetric curve obtained in the thermal analysis step has two maximum peaks, of which the maximum peak on the high temperature side indicates that the weight loss of the non-volatile component is progressing. On the other hand, the maximum peak on the low temperature side indicates that the weight loss of other low temperature volatile components, for example, organic compounding agents in vulcanized rubber, is progressing. That is, in the example shown in this figure, taking into account the overlap of the two maximum peaks, the weight loss ratio from 286.5°C to 441.9°C is the weight loss ratio (β (mass%)) of the non-volatile component in the high temperature region.

[0027] As far as the inventors know, a method for quantifying components in a rubber composition, particularly a rubber composition after vulcanization, which includes a thermal analysis step of performing thermogravimetric analysis of a concentrate to obtain a thermogravimetric curve, is a method for quantifying components in a rubber composition that includes a thermal analysis step of performing thermogravimetric analysis of a concentrate to obtain a thermogravimetric curve.

[0028] In particular, in the present invention, in the concentrating step, the ratio of the amount of the concentrate extracted when the total amount in the rubber composition is taken as 100 mass % is taken as α (mass %), and after the thermal analysis step, the thermogravimetric curve is differentiated to identify components that undergo weight loss in a high temperature region. In the quantification step, the ratio of the weight loss of the components in the high temperature region is taken as β (mass %). In this case, the ratio γ (mass %) of the amount of the components blended in the rubber composition is calculated based on the following formula (2): γ=α×β / 100 (2) is preferable because it is excellent in quantitative determination of non-volatile components.

[0029] In the present invention, the components contained in the rubber composition, more preferably the rubber composition after vulcanization, and to be quantified are preferably those having a peak top temperature of 250° C. or higher in the differential curve of the thermogravimetric curve. It is preferable that the components to be quantified are those having a peak top temperature of 250° C. or higher in the differential curve of the thermogravimetric curve, because more accurate quantification can be achieved. Such components can be said to be non-volatile components, and the non-volatile components are preferably hydrocarbon resins. EXAMPLES

[0030] The present invention will be explained more specifically below by describing examples thereof.

[0031] First, rubber compositions were prepared according to compounding Nos. 1 to 7, which had compounding ratios shown in Table 1. Information on each component shown in Table 1 is as follows. SBR; Product name "HPR840", manufactured by ENEOS Materials BR: Product name "BR730", manufactured by ENEOS Materials Co., Ltd. CB: Product name "Diablack N339", manufactured by Mitsubishi Chemical Corporation Silica: Product name "Nipsil AQ", manufactured by Nippon Silica Kogyo Co., Ltd. Cp agent: Product name "NXT SILANE", manufactured by Momentive Performance Materials Processing aid: Product name "AFLUX 16", manufactured by LANXESS Wax; Product name: OZOACE-2701, manufactured by Nippon Seiro Co., Ltd. Stearic acid: product name "Stearic acid N-50", manufactured by NOF Corporation Zinc oxide: Product name: "Zinc oxide type 2", manufactured by Sakai Chemical Industry Co., Ltd. 6PPD; product name "Nocrac 6C", manufactured by Ouchi Shinko Chemical Industry Co., Ltd. TMDQ: Product name "ANTIOXIDANT TMQ", manufactured by Kemai Chemical Co., Ltd. Non-volatile components (hydrocarbon resins) (i) C9-C5 resin (weight loss onset differential peak top temperature (367°C) in TGA measurement); product name "Petrotac 90", manufactured by Tosoh Corporation (ii) Terpene resin (weight loss onset differential peak top temperature (360°C) in TGA measurement); trade name "Sylvatraxx 4150", manufactured by Kraton Chemical Co. (iii) Styrene resin (weight loss onset differential peak top temperature (368°C) in TGA measurement); trade name "Sylvatraxx4401", manufactured by Kraton Chemical Co. DPG: Trade name "Soccinol DG", manufactured by Sumitomo Chemical Co., Ltd. CBS: Product name "Noccela CZ-G", manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: Product name: "Oil treatment 150 mesh powder sulfur", manufactured by Tsurumi Chemical Industry Co., Ltd.

[0032] [Table 1]

[0033] In Table 1, "actual amount of hydrocarbon resin (mass %)" is the total amount (mass %) of the non-volatile components (hydrocarbon resins), "C9-C5 resin," "terpene resin," and "styrene resin," when the total amount of the rubber composition after vulcanization is taken as 100 mass %.

[0034] First, the amounts of non-volatile components (hydrocarbon resins) in Compounds No. 1 to No. 7 were quantified based on the quantitative determination method based on the amount of extraction ("Extraction method" in FIG. 2), which is a conventional technique. Specifically, an extract containing the extract was obtained from the rubber compositions after vulcanization of Compounds No. 1 to No. 7 using chloroform (organic solvent) (extraction step), and the chloroform was distilled off from the extract to obtain a concentrate of the extract (concentration step). The amounts of non-volatile components (hydrocarbon resins) quantified based on the amount (mass%) of the concentrate of the extract are shown in the column of "Quantitative results (mass%) of the amount of hydrocarbon resin quantified based on the quantitative determination method based on the amount of extraction ("Extraction method" in FIG. 2)" in Table 1.

[0035] Next, the amount of non-volatile components (hydrocarbon resins) in Compound No. 1 to Compound No. 7 was quantified based on the quantification method according to the present invention ("present invention" in FIG. 2). Specifically, an extract containing the extract component was obtained from the rubber composition after vulcanization of Compound No. 1 to Compound No. 7 using chloroform (organic solvent) (extraction step), and the chloroform was distilled off from the extract to obtain a concentrate of the extract component (concentration step). The amount of non-volatile components (hydrocarbon resins) (proportion of the extracted amount of the concentrate) quantified based on the amount of the concentrate of the extract component was defined as α (mass %). The α (mass %) is the same as the quantification result (mass %) of the amount of the hydrocarbon resin quantified based on the extraction method. Next, the concentrate was subjected to thermogravimetric analysis to obtain a thermogravimetric curve (thermal analysis step), and the weight loss ratio corresponding to the component to be quantified was read from the thermogravimetric curve (quantification step). After the thermal analysis step, the thermogravimetric curve was differentiated to identify the components that had lost weight in the high temperature range. In the quantification step, the proportion of weight loss of the components in the high temperature range was designated as β (mass%), and the proportion of the blended amount of the non-volatile component (hydrocarbon resin) γ (mass%) was calculated by multiplying α by β. The results are shown in Table 1 under the heading "Quantification based on the quantification method according to the present invention ("Present invention" in FIG. 2)." The quantitative results of the amount of hydrocarbon resin blended are shown in the column "γ=α×β / 100".

[0036] Figure 2 shows the relationship between the quantification results and the actual blended amount for the quantification method of the present invention and the extraction method of the prior art. As shown in Table 1 and Figure 2, it can be seen that in the extraction method, the blended amount of the hydrocarbon resin is quantified to be higher than the actual blended amount for all vulcanized rubbers of the rubber compositions of Compounding No. 1 to Compounding No. 7. On the other hand, in the quantification method of the present invention, the component amount close to the actual blended amount (mass%) of the hydrocarbon resin is derived for all vulcanized rubbers of the rubber compositions of Compounding No. 1 to Compounding No. 7, and it can be seen that the quantification method of the present invention is a method for quantifying components in a rubber composition after vulcanization with excellent quantitative ability.

Claims

1. A method for quantifying components in a rubber composition, comprising the steps of: A method for quantifying a component in a rubber composition, comprising at least the steps of: an extraction step of obtaining an extract containing an extract component from the rubber composition using an organic solvent; a concentration step of obtaining a concentrate of the extract component by distilling off the organic solvent from the extract; a thermal analysis step of performing a thermogravimetric analysis of the concentrate to obtain a thermogravimetric curve; and a quantification step of reading a weight loss ratio corresponding to the component to be quantified from the thermogravimetric curve.

2. 2. The method for quantifying components in a rubber composition according to claim 1, wherein the components to be quantified are non-volatile components.

3. 3. The method for quantifying components in a rubber composition according to claim 2, wherein the non-volatile component is a hydrocarbon resin.

4. a ratio of an extracted amount of the concentrate to a total amount of the rubber composition in the concentrating step being 100 mass % is defined as α (mass %), After the thermal analysis step, the thermogravimetric curve is differentiated to identify a component that undergoes a weight loss in a high temperature region. In the quantification step, when the percentage of weight loss of the component in the high temperature region is defined as β (mass%), The ratio γ (mass%) of the amount of the component blended in the rubber composition is calculated based on the following formula (2): γ=α×β / 100 (2) The method for quantifying components in a rubber composition according to claim 1, wherein the content of each component in the rubber composition is calculated based on the above formula.

5. 2. The method for quantitatively determining components in a rubber composition according to claim 1, wherein the thermal analysis step is carried out in an inert gas atmosphere.

6. 5. The method for quantitatively determining a component in a rubber composition according to claim 4, wherein the component exhibiting a weight loss in a high temperature region has a peak top temperature of 250° C. or higher in a differential curve of a thermogravimetric curve corresponding to the component.

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