JP2005231091A - Recycled rubber manufacturing method and method and apparatus for evaluating characteristics of recycled rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a recycled rubber having rubber characteristics capable of withstanding practicality independently as a raw material of a recycled rubber extrusion molded product. <P>SOLUTION: Recycling treatment is applied to pulverized pieces of a vulcanized rubber put in a hermetically closed kneader by applying shearing force to them to impart flowability and plasticity thereto. A kneading finish time is preset on the basis of a value of apparent activation energy in the unvulcanized state being the original state of the vulcanized rubber. The recycled rubber is taken out of the hermetically closed kneader after the load torque of the hermetically closed kneader during recycling treatment exceeds a peak but during a period until the kneading finish time starting from the peak time of the load torque elapses. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing recycled rubber for reusing waste vulcanized rubber and a characteristic evaluation method and characteristic evaluation apparatus related thereto, and in particular, using apparent activation energy of unvulcanized recycled rubber as a parameter, The present invention relates to a manufacturing method, a characteristic evaluation method, and a characteristic evaluation apparatus for a recycled rubber which are managed for conditions for regeneration (desulfurization or depolymerization).

  When recycling waste vulcanized rubber, such as rubber molded products made of vulcanized rubber such as old tires of automobiles, weather strips, scraps or defective products generated in the manufacturing process of those rubber molded products In general, after pulverizing the waste vulcanized rubber, it is regenerated by performing a desulfurization treatment for cutting the sulfur bridges. Then, a recycled rubber molded product is obtained by kneading, vulcanizing, molding and the like with a vulcanizing agent using the recycled rubber.

  As a technique for recycling this kind of waste vulcanized rubber, for example, a technique described in Patent Document 1 has been proposed in addition to an old bread recycling method.

In the technique described in Patent Document 1, a waste vulcanized rubber containing carbon black or added in advance is made into a so-called molten state by performing regeneration (desulfurization) treatment under specific temperature conditions and specific shear stress. It is based on that.
Japanese Patent No. 3272623

  However, even a vulcanized rubber premised on containing carbon black can always be put to practical use only by so-called kneading for desulfurization under specific temperature conditions and specific shear stress. It is difficult to get just recycled rubber. Therefore, in order to form a recycled rubber product that can withstand practical use, it is often necessary to mix more or less new unvulcanized rubber with the recycled rubber, which limits the amount of waste vulcanized rubber consumed. Not only that, it is impossible to achieve the true recycling of waste vulcanized rubber, and there is still room for improvement as a technology for manufacturing recycled rubber.

  The present invention has been made paying attention to such a problem, and as a raw material for a recycled rubber molded product, a recycled rubber having rubber properties that can be practically used alone can be produced. The present invention intends to provide a technology for producing recycled rubber that can be reused as a raw material for molded products.

  The invention according to claim 1 is a method for producing a reclaimed rubber, in which a shearing force is applied to a vulcanized rubber put in a closed kneader to give fluidity and plasticity, and a regeneration treatment is performed. The kneading finish time was set in advance based on the apparent activation energy value in the unvulcanized state, which is the original state of the rubber, and the load torque of the closed kneader during the regeneration process exceeded the peak. The recycled rubber is taken out from the hermetic kneader after and until the above-mentioned kneading finishing time starting from this peak time elapses.

In this case, as described in claim 2, the value of the apparent activation energy in the unvulcanized state, which is the original state of the vulcanized rubber, is Ea _0, and the apparent value of the recycled rubber in the unvulcanized state When the value of the activation energy of Ea is Ea, the apparent finishing energy Ea in the unvulcanized state of the recycled rubber satisfies the relationship of 0.8 × Ea ₀ ≦ Ea ≦ Ea ₀ with the above-mentioned kneading finishing time. It is desirable to set the end.

  Further, in order to efficiently impart fluidity and plasticity by applying a shearing force to the vulcanized rubber, it is not preferable that too little or too much vulcanized rubber is charged into the closed kneader. As described in No. 3, it is desirable to carry out a regeneration treatment after putting a crushed rubber crushed piece into a hermetic kneader with a volume filling rate of 70 to 90%.

  The apparent activation energy is a parameter derived from the temperature dependence of the viscosity of the viscoelastic material, as will be described later. Therefore, here, the apparent activation energy is used as an index indicating the structural change caused by the kneading of the rubber compound. Use.

  On the other hand, when paying attention to the load torque of the closed kneading machine in the process of regenerating vulcanized rubber, the load torque is very low and relatively constant in the initial stage after the start of the process, but the predetermined time has passed. When the load torque elapses, the load torque suddenly increases and reaches a peak value. After reaching the peak value, the load torque gradually decreases again, and finally the load torque is about 30% of the peak value as described later. Will stabilize.

  The inventor found that there is a large correlation between the elapsed time from the peak load torque and the apparent activation energy, and conducted various experiments.

As a result, for example, the apparent activation energy value of the vulcanized rubber in the unvulcanized state, which is the original state of the vulcanized rubber, is Ea ₀ , and the regenerated rubber is apparent in the unvulcanized state. When the activation energy value of Ea is Ea, the final activation time Ea has a timing at which the apparent activation energy Ea in the unvulcanized state of the recycled rubber satisfies the relationship of 0.8 × Ea ₀ ≦ Ea ≦ Ea ₀ The reclaimed rubber is sealed after the load torque of the closed kneader during the regeneration process has passed the peak and before the above-mentioned kneading finish time starting from the peak time has elapsed. It has been found that a recycled rubber having physical properties sufficient to withstand practical use can be obtained by taking it out of the kneading machine.

  At the same time, there is a corresponding correlation between the apparent activation energy and the physical properties and extrudability of the recycled rubber. With this apparent activation energy, the recycled rubber obtained by the previous production method. It was found that the normality of the tensile strength and elongation, the extrusion processability variation of extrusion processability, and the appearance of the recycled rubber extruded product can also be evaluated to determine the suitability.

  Invention of Claim 4 was specified as a manufacturing method using the evaluation method of the recycled rubber based on this apparent activation energy, Comprising: Manufacturing of the recycled rubber in any one of Claims 1-3 The method is assumed.

  In addition, in the regeneration process step, the regeneration process is performed under the conditions set in advance for the regeneration process condition including at least the kneading finishing time. Measure the viscoelasticity of the recycled rubber in the sulphated state to determine the apparent activation energy value of the recycled rubber, and compare and collate the calculated apparent activation energy value with the preset allowable range. As a result, when the obtained apparent activation energy value does not satisfy the set allowable range, the regeneration process condition including the kneading finishing time is changed.

  Therefore, in the invention according to the fourth aspect, as described above, a recycled rubber having physical properties that can withstand practical use alone can be obtained more reliably, and the reliability of the physical properties of the recycled rubber is improved. It will be even higher.

  The invention described in claim 5 more specifically specifies the method for evaluating recycled rubber based on the apparent activation energy, and has the following requirements (a) and (b): A method for evaluating properties of recycled rubber.

  (A) The shearing force applied to the unvulcanized recycled rubber produced by the production method according to any one of claims 1 to 3 is controlled, and based on the stress that reacts to the shearing force, Measurement process for obtaining complex viscosity.

  (B) The temperature and gas constant at the time of the above measurement are T and R, the viscosity is η, and the complex viscosity is η * (η), respectively, and the Arrhenius type equation (Andrad ) A step of calculating the apparent activation energy Ea of the recycled rubber based on the formula (1).

η = Aexp (Ea / RT) (1)
However,
Ea: Abbreviation for Activation Energy, apparent activation energy of compound viscosity (flow) (KJ / mol)
Then, at least one of physical properties and extrudability of the recycled rubber is evaluated based on the apparent activation energy Ea.

  In this case, as described in claim 6, an allowable value of the apparent activation energy Ea that can be molded in the extrusion molding process for each of a plurality of types of recycled rubber having different vulcanized rubber blends before regeneration. A range is set in advance, and by comparing and collating the calculated apparent activation energy Ea with the set allowable range of the corresponding recycled rubber, at least one of physical properties and extrusion processability of the recycled rubber is determined. It is desirable to determine suitability.

  More preferably, as described in claim 7, whether or not the physical properties of the recycled rubber and the extrusion processability are appropriate is determined based on the apparent activation energy Ea. It is assumed that at least one of strength and elongation, and the determination item related to extrusion processability is at least one of variation in extrusion discharge amount and appearance of a recycled rubber molded product.

  In addition, the invention described in claim 8 is the one in which the technique described in claim 5 is specified and specified as a physical property evaluation apparatus, and includes the following means (a1) to (d1). .

  (A1) Controlling the shear force applied to the unvulcanized reclaimed rubber produced by the production method according to any one of claims 1 to 3, and based on the stress acting against the shear force, the reclaimed rubber Means for obtaining the complex viscosity of

  (B2) The temperature and gas constant at the time of the above measurement are T and R, the viscosity is η, and the complex viscosity is η * (η), respectively, and an Arrhenius type equation (Andrad ) The calculation means for calculating the value of the apparent activation energy Ea of the recycled rubber based on the formula (1).

η = Aexp (Ea / RT) (1)
However,
Ea: Abbreviation for Activation Energy, apparent activation energy of compound viscosity (flow) (KJ / mol)
(C1) Storage means in which the allowable range of the apparent activation energy Ea that can be molded in the extrusion molding process is preset and stored for each of a plurality of types of recycled rubber having different vulcanized rubber blends before regeneration. .

  (D1) By comparing and collating the apparent activation energy Ea calculated by the calculation means with the allowable range of the corresponding recycled rubber set and stored in the storage means, the physical properties of the recycled rubber and the extrusion processability A determining means for determining suitability of at least one of them.

  Therefore, in the inventions according to the fifth to eighth aspects, the physical properties and extrudability of a so-called recycled rubber extruded product made from recycled rubber can be more accurately evaluated.

  According to the first aspect of the present invention, the reprocessing time of the reclaimed rubber is managed based on the apparent activation energy, so that it can be sufficiently put into practical use without mixing a new rubber material. Recycled rubber with physical properties that can withstand high temperatures can be obtained. Recycled rubber itself has high reliability in physical properties, as well as dramatically increases the range of uses and applications of recycled rubber. As a result, more effective utilization of rubber material resources can be achieved.

  In particular, as described in claim 2, the value of the apparent activation energy in the unvulcanized state, which is the original state of the vulcanized rubber, and the value of the apparent activation energy in the unvulcanized state of the recycled rubber The reclaimed rubber itself is limited by limiting the volume filling rate of the pulverized rubber crushed pieces to a specific range, as described in claim 3. In addition to improving the quality of the product, the reliability of the physical properties becomes even higher.

  According to the invention described in claim 4, when the apparent activation energy value of the recycled rubber obtained by the regeneration process does not satisfy the set allowable range, the regeneration process condition is changed, thereby In addition to the same effects as those of the inventions described in Items 1 to 3, the recycled rubber itself also has higher physical property reliability.

  According to the inventions described in claims 5 to 8, by using the apparent activation energy as an evaluation parameter, the physical properties and extrusion processability of the obtained recycled rubber are accurately predicted with high reliability. In addition to improving the reliability of the evaluation results, it can greatly contribute to the improvement of the recycled rubber productivity and the quality of the recycled rubber extruded product.

  Table 1 shows, for example, No. 1 made from an EPDM compound extruded product, which is a vulcanized rubber. No. 1-7 recycled rubber compound A samples were manufactured, Samples of recycled rubber compound A 1 to 7 were actually extruded into a predetermined shape as a recycled rubber extruded product, and the normal properties and extrusion processability (extrusion moldability) of the recycled rubber extruded product were evaluated. Results are shown.

  Here, compound A in Table 1 refers to a compound in an unvulcanized and vulcanized state of an EPDM compound material used as a raw material for regeneration, and recycled rubber compound A refers to a compound A extruded product (vulcanized rubber). ) Is a compound of recycled rubber obtained by regeneration treatment. Then, as described above, the recycled rubber compound A is No. according to the conditions during the regeneration process. 1-No. 7 as a sample of recycled rubber compound A.

  In addition, No. Among samples of recycled rubber compound A of Nos. 1 to 7, No. 1 having the conditions of the present invention. 1-No. No. 5 which does not satisfy the conditions of the present invention other than the sample of No. 5 as an example. There are 6 and 7 samples as comparative examples.

  First, the following experiment was conducted on the recycled rubber compound A in order to make the manufacturing method of the recycled rubber that is the basis of the present embodiment more concrete.

  First, an EPDM compound extruded product, which is a waste vulcanized rubber, is pulverized in advance, and then the pulverized vulcanized rubber is sealed in a closed kneader (for example, Labo Plast Mill 10C 100 type, B600 manufactured by Toyo Seiki Co., Ltd. (blade shape)). Was introduced into the chamber of the Banbury type)). Then, when the kneading machine is started, a regeneration process (desulfurization process) is performed by applying shearing force to the pulverized vulcanized rubber inside the chamber to promote fluidization and plasticization. After a predetermined time, the obtained recycled rubber compound A was taken out of the chamber and cooled. In addition, since the material itself self-heats due to the shearing force, other positive heating is not performed. Recycled desulfurized rubber, that is, recycled rubber compound A was obtained by the above operation. The chamber temperature was room temperature, and the rotational speed of the kneader was 100 rpm.

In the process of regenerating vulcanized rubber, when attention is paid to the load torque of the closed kneader together with the temperature change, as shown in FIG. 1, the load torque is extremely low and constant at the initial stage after the start of the process. although the objects, when a predetermined time has elapsed the load torque is abruptly elevated peaks and T _1, the since reaching its peak value T ₁ drops gradually again load torque, eventually peak It stabilizes with a load torque T ₂ (= 0.3 × T ₁ ) of about 30% of the value T ₁ .

Therefore, in Table 1, no. 1-No. In the production of samples of reclaimed rubber compound A, shown as 7, using a temperature-torque chart such as Figure 1 monitors the load torque in real time, after the load torque peaked T _1, the peak After a predetermined time (3 to 20 minutes) has elapsed from the time point T _1, 1-No. A sample of the recycled rubber compound A is taken out from the kneader chamber. The predetermined time from the peak T ₁ time point here is defined as a kneading finish time starting from the peak time of the load torque in FIG.

  Subsequently, the obtained No. 1-No. For example, 1.7 phr of a thiazole accelerator, 2.5 phr of a thialium accelerator, 2.5 phr of sulfur, and 1 phr of sulfur were added to each sample of the recycled rubber compound A of No. 7 as the same vulcanization system as that of Compound A in an open roll. And No. 1-No. Each sample of No. 7 was vulcanized together with press molding to produce a sheet having a thickness of 2 mm and a size of 30 cm × 30 cm as a recycled rubber extruded product.

  Here, there is a concept of apparent activation energy as an index indicating the structural change caused by kneading of viscoelastic materials represented by rubber compounds, and this apparent activation energy depends on the temperature of the viscosity of the viscoelastic material. Therefore, there is a correlation between the physical properties of the reclaimed rubber, the apparent activation energy, and the load torque of the above-mentioned closed kneader in the regeneration treatment of the vulcanized rubber as described above. There will be.

Therefore, no. 1-No. For each of the samples, viscoelasticity measurement described later was performed for each state before vulcanization and after vulcanization, and apparent activation energy Ea was calculated for each sample. Table 1 shows No. before and after vulcanization. 1-No. 7 and the apparent activation energy Ea of each sample, and the apparent activation energies Ea ₀ and Ea before and after vulcanization of the rubber compound A that is the raw material for regeneration, The value of Ea / Ea ₀ in the sulfur state is shown.

The calculation of the apparent activation energy Ea (including Ea ₀ , hereinafter the same) in Table 1 is performed using “RPA2000 manufactured by Alpha Technologies, Inc.” as a viscoelasticity measuring machine. 1-No. 7 Measure the complex viscosity η * (η) of each sample. Then, the value of the apparent activation energy Ea is calculated by substituting that value into the following equation (1).

Calculation method: Arrhenius type (Andrade's formula)
η = Aexp (Ea / RT) (1)
However,
η: Viscosity Ea: Apparent activation energy (KJ / mol)
T: Temperature R: Gas constant

  Similarly, no. 1-No. The Mooney viscosity (Vm) of each sample of No. 7 in the unvulcanized state was measured, and as described above, No. 7 as a recycled rubber extrusion molded product vulcanized into a sheet shape. 1-No. For each sample of No. 7, a tensile test was performed based on the C2 grade of JIS K 6313 (standard for recycled rubber other than natural rubber and tire), which is a standard for recycled rubber, and tensile strength (MPa) and elongation (maximum elongation) as normal properties. ) (%) Was measured.

  Moreover, the extrusion discharge amount variation (extrusion discharge amount variation rate) (%) in Table 1 is, for example, a screw having a screw rotation speed of 20 rpm and a extrusion port 1a having a shape as shown in FIG. Use No. The weight variation of the discharge weight (number of samples n = 100) per minute when each of the samples 1 to 7, that is, the recycled rubber extruded product was extruded, was determined by the following formula (2).

Extrusion discharge amount variation rate (%) = {(maximum discharge amount (g) −minimum discharge amount (g)) / average discharge amount (g)} × 100 (2)
In addition, the dimension of each part of the extrusion shape in FIG. 1 is a = 6mm, b = 2mm, c = 11mm, d = 11mm, e = 3mm, f = 7mm, g = 7mm, h = 4mm. And the extrusion discharge amount variation rate (%) was 3% or less as “OK”.

  At the same time, no. The appearance appearance of each of the samples 1 to 7 after extrusion vulcanization was subjected to sensory evaluation by visual inspection and touch.

The graph of FIG. 1-No. 7 is a plot of the relationship between the time (min) from the peak load torque of each sample and the value of the apparent activation energy Ea in the vulcanized state. Similarly, the graph of FIG. 1-No. 7 is a plot of the relationship between the time (min) from the peak load torque of each sample and the value of Ea / Ea ₀ in the unvulcanized state. The parameter Ea / Ea ₀ is set to No. 1-No. No. 7 represents the degree to which the properties of the recycled rubber material of each sample are close to the rubber material that is the raw material for regeneration.

As is apparent from FIGS. 1-No. 7 shows that there is a large correlation between the time from the peak load torque of each sample 7 and the apparent activation energy Ea. That is, No. 1 as a comparative example in Table 1. As seen in samples 6 and 7, when the value of Ea / Ea ₀ is larger than 1, it means that the temperature dependency is higher than the original new material, and the variation in extrusion discharge amount is extremely worsened. However, it is not suitable for extrusion molding. Accordingly, in order to use the recycled rubber compound as a material for extrusion molding (compound), the regeneration process is stopped before the value of Ea / Ea ₀ of the recycled rubber compound during the regeneration process exceeds 1, and the chamber of the kneader is used. Means you have to take it out of.

Actually, as apparent from Table 1 and FIG. 3, the range in which the value of Ea / Ea ₀ is 0.8 to 1, that is, No. In the samples 3 and 5, the tensile strength is about 80% of the original material, that is, the rubber material used as a raw material for recycling. As shown in Table 1, JIS K 6313 (standard for recycled rubber other than natural rubber and tire) Therefore, even if a recycled rubber extruded product is molded with the recycled rubber alone, it is sufficiently practical.

On the other hand, when the value of Ea / Ea ₀ deviates from the range of 0.8 to 1, When the value of Ea / Ea ₀ is less than 0.8 as in the samples 1 and 2, the physical properties will be lowered. Even if Ea / Ea ₀ = 0.669 as in the sample No. 1, the tensile strength is 3.5 MPa, which satisfies the C2 grade of JIS K 6313 described above.

On the other hand, when the value of Ea / Ea ₀ deviates from the range of 0.8 to 1, When the value of Ea / Ea ₀ greatly exceeds 1 as in samples 6 and 7, the tensile strength, which is a physical property, is extremely deteriorated. For example, no. When Ea / Ea ₀ = 1.185 as in the sample No. 6, the tensile strength becomes 2.5 MPa, and the C2 grade of JIS K 6313 described above is not satisfied.

From the above, in this embodiment, the absolute condition is that the relationship between Ea and Ea ₀ satisfies the relationship of 0.8Ea ₀ ≦ Ea ≦ Ea ₀ as described above.

  Further, regarding the elongation which is a physical property, all samples shown in Table 1, that is, No. Although each sample of 1 to 7 satisfies the C2 grade of JIS K 6313 (120% or more), the elongation required for automotive weather strips and door glass runs that are representative of extruded products. Is generally 200% or more, and the sample Nos. Shown in Table 1 as examples are shown. If the value is 1 to 5, the required characteristics are sufficiently satisfied.

The variation in extrusion discharge amount shown in Table 1 is also correlated with the value of Ea / Ea ₀ described above, and when the value of Ea / Ea ₀ exceeds 1, the variation in extrusion discharge amount is extremely deteriorated and is 3% or less. No. in which the value of Ea / Ea ₀ is 1.185 in spite of the “OK” range. Sample No. 6 is 5.1% and Ea / Ea ₀ is 1.318. In the sample No. 7, it becomes 10.3%, which shows that there is a clear correlation between the two.

Further, regarding the appearance appearance evaluation of each sample which is a recycled rubber extruded product, as is clear from Table 1, when the value of Ea / Ea ₀ is less than 0.8, No. The roughness of the surface of the extrusion-molded product becomes remarkable as in the samples 1 and 2, and the mixing of powder that is not completely plasticized is recognized in part, and conversely the value of Ea / Ea ₀ exceeds 1. No. As in the samples 6 and 7, the surface of the extruded product was sticky, and so-called oil bleeding was observed.

From these results, No. 1 in Table 1 was obtained. When the samples 1 to 7 were evaluated comprehensively, No. 1 shown as an example. When the value of Ea / Ea ₀ is less than 0.8 as in the samples 1 and 2, a rough feeling is recognized on the surface of the recycled rubber extruded product after vulcanization, or a part thereof is completely plasticized. Although the appearance of the powder after the vulcanization is slightly deteriorated, the required properties are satisfied with respect to the tensile strength and the variation in the extrusion discharge amount. When the value of Ea / Ea ₀ exceeds 1 as in samples 6 and 7, the required properties are not satisfied in terms of tensile strength, variation in extrusion discharge amount, and appearance after vulcanization. In other words, when the value of Ea / Ea ₀ described above is in the range of 0.8-1 In the case of the samples 3, 4 and 5, the tensile strength, the variation in the extrusion discharge amount, and the appearance after vulcanization all satisfy the required characteristics and become the most preferable.

FIG. 1 to 7 shows the relationship between the apparent activation energy Ea and the tensile strength, and as described above, the value of Ea / Ea ₀ is in the range of 0.8 to 1, that is, The most preferred No. It can be understood that the samples 3 to 5 have higher tensile strengths, and the physical properties and the extrudability evaluation based on the value of Ea / Ea ₀ are appropriate.

  In this way, with the apparent activation energy value, it can be judged whether or not the recycled rubber has been sufficiently recycled by itself, and at the same time, the recycled rubber can be used as a compound for extrusion molding. It will be possible to judge whether it is possible.

  In Table 2, as in Table 1, No. 1 made from an EPDM compound extruded product, which is a vulcanized rubber, is used. No. 8 to 10 samples of recycled rubber compound B were produced, Results of 8 to 10 samples of recycled rubber compound B being actually extruded into a predetermined shape as a recycled rubber extruded product, and evaluation of normal properties and extrusion processability (extrusion moldability) of the recycled rubber extruded product Indicates.

  Here, compound B in Table 2 refers to a compound in an unvulcanized and vulcanized state of EPDM compound material that is a raw material for regeneration as in Table 1, and recycled rubber compound B is compound B extrusion. This refers to a compound of recycled rubber obtained by reprocessing using a molded product (vulcanized rubber) as a raw material. Then, as described above, the recycled rubber compound B is No. according to the conditions during the regeneration process. It is subdivided as 8-10 recycled rubber compound B samples.

  In addition, No. Among samples of recycled rubber compound B of 8-10, No. having the conditions of the present invention. Samples Nos. 8 and 9 were used as examples, and No. There are 10 samples as comparative examples.

  First, an EPDM compound extrusion molded product, which is a waste vulcanized rubber, is pulverized in advance, and the pulverized vulcanized rubber is placed in a chamber of a closed kneader (eg, GK-5E internal mixer manufactured by Mitsubishi Heavy Industries, Ltd.). I put it in. Then, when the kneading machine is started, a regeneration process (desulfurization process) is performed by applying shearing force to the pulverized vulcanized rubber inside the chamber to promote fluidization and plasticization. After a predetermined time, the obtained recycled rubber compound B was taken out of the chamber and cooled. In this case as well, the material itself self-heats due to the shearing force, and other positive heating is not performed. Recycled desulfurized rubber, that is, recycled rubber compound B, was obtained by the above operation. The chamber temperature was room temperature, and the rotational speed of the kneader was 70 rpm.

  And in Table 2, No. The same evaluation as in Table 1 was performed on the recycled rubber compound B samples shown as 8 to 10.

From these results, No. 2 in Table 2 was obtained. When each sample of 8-10 was comprehensively evaluated, No. shown as an example. As in sample 8, when the value of Ea / Ea ₀ is less than 0.8, the surface of the recycled rubber extruded product after vulcanization has a rough feeling or is not completely plasticized partially. Although the appearance of the body after vulcanization is slightly deteriorated due to the mixing of the body, the required properties are satisfied with respect to the tensile strength and the variation in the extrusion discharge amount. When the value of Ea / Ea ₀ exceeds 1, as in sample 10, the required properties are not satisfied in terms of tensile strength, variation in extrusion discharge amount, and appearance after vulcanization. In other words, No. in which the value of Ea / Ea0 is in the range of 0.8 to 1. In the case of No. 9, it can be seen that the tensile strength, the variation in the amount of extrusion discharge, and the appearance after vulcanization all satisfy the required characteristics and become the most preferable.

  Here, when rubber regeneration is performed using a closed kneader as shown in the previous experimental example, the volume filling rate (vol%) of the material in the chamber of the closed kneader greatly affects the degree of regeneration. To do. Therefore, an experiment was conducted to see how the volume filling rate (vol%) of the material with respect to the chamber actually affects the physical properties and extrudability of the recycled rubber. The results are shown in Table 3.

  Here, No. 1 as an example of Table 3. Sample No. 3-3 is No. 1 in Table 1. No. 3 which is exactly the same as the sample of No. 3 (recycled rubber compound A), and other examples. 3-2 and 3-4 and No. as a comparative example. For samples 3-1 and 3-5, no. For the sample of 3-3, only the volume filling rate of the material with respect to the chamber of the closed kneader at the time of the regeneration treatment is varied, and the time from the peak of the load torque is constant for 5 minutes, The other conditions are the same as in Table 1. The kneader used in the experiment was the same as that used in the experiment of Table 1 (Toyo Seiki Lab Plast Mill 10C 100 type, B600 (blade shape is Banbury type)).

As is apparent from Table 3, when the volume filling rate of the material is in the range of 70 to 90 (vol%), that is, No. shown as an example. In 3-2, 3-3 and 3-4, the value of Ea / Ea ₀ described above is in the range of 0.8 to 1, and at the same time the tensile strength is about 8 MPa, which is sufficiently practical. The characteristics are shown. On the other hand, when the volume filling rate is 65 (vol%), In the case of the sample of 3-1, the material in the chamber of the hermetic kneader only became powder and was not regenerated. Furthermore, when the volume filling rate is 95 (vol%), In the case of the sample 3-5, the material in the upper part in the chamber of the hermetic kneader remained, and was not mixed or regenerated.

  FIG. 6 shows an example of a viscoelasticity test apparatus for calculating the apparent activation energy described above. In FIG. 6, reference numeral 1 denotes a viscoelasticity measuring machine. The viscoelasticity measuring machine 1 is a temperature-controlled sample chamber for storing a sample to be measured, a shearing force by controlling the vibration frequency and vibration amplitude of the sample. And a converter that detects reaction torque and converts it into an electrical signal. In the sample chamber, a sample to be measured, that is, a recycled rubber compound before vulcanization manufactured by the above-described closed kneader is accommodated (this apparatus is shown in Table 1 for example). It is also possible to measure the Ea value of rubber in the vulcanized state).

  Reference numeral 2 denotes an A / D converter that converts an analog signal corresponding to the reaction torque output from the viscoelasticity measuring device 1 into a digital signal. Reference numeral 3 denotes an information processing apparatus that stores a signal from the A / D converter 2 and performs processing by reading the stored data after the measurement is completed.

  Among the information processing devices 3, there is an Ea arithmetic device 4, which calculates a complex viscosity η * (η) based on data (data corresponding to reaction torque) in which the output of the A / D converter 2 is stored. It has a function of calculating the apparent activation energy Ea from the η * (η) based on the equation (1) described above.

Reference numeral ₅ denotes a storage device that stores in advance, for example, the above-described relationship of 0.8Ea ₀ ≦ Ea ≦ Ea ₀ as a setting allowable range as a range of Ea values that can be molded in the extrusion molding process for each material. In this storage device 5, when it is assumed that extrusion molding is performed under specific conditions for each recycled rubber compound having a different composition of EPDM compound as a raw material for recycling, the tensile strength and elongation, which are physical properties, or after extrusion molding The setting allowable range of the Ea value that will satisfy the required characteristics such as the appearance appearance of the sheet and the variation in the extrusion discharge amount is set and stored after being empirically or experimentally obtained in advance.

  6 compares the setting allowable range of the Ea value calculated by the Ea calculation device 4 and the Ea value stored in the storage device 5, in addition to physical properties of the material such as tensile strength and elongation, variation in extrusion discharge amount and appearance. It is an arithmetic unit that determines the suitability of extrusion processability (extrusion formability). Reference numeral 7 denotes a storage device that stores the calculation result in the calculation device 6 together with the calculation result in the Ea calculation device 4.

  The calculation of the apparent activation energy Ea in the viscoelasticity testing apparatus in FIG. 6 and the suitability determination thereof are executed according to the procedure of the flowchart in FIG. This flowchart is executed as a CPU program of the viscoelasticity testing apparatus shown in FIG.

In FIG. 7, first, as a preparation stage, a specific sample manufactured in the previous recycled rubber manufacturing process, that is, an unvulcanized recycled rubber compound (here, for example, sample a) is used as a test machine (measurement of viscoelasticity in FIG. 1). machine 1) to the set (step S _1), after preheating the sample a and viscoelastic measuring instrument 1 (step S _2), to start the test (step S _3).

After starting the test, the tester control (steps S ₄ and S ₅ ) described on the right side of the flowchart and the data storage (steps S ₆ and S ₇ ) described on the left side are performed in parallel.

In Step S _4, the viscoelasticity measuring machine 1 of FIG. 6, any temperature, vibration frequency relative to the sample a, enter the shear force in the vibration amplitude, detects the output torque of the reaction. This is performed until predetermined data collection is completed (step S ₅ ). In step S ₆ , the test collection data is A / D converted and stored in the storage device. This is performed until predetermined data collection is completed (step S ₇ ).

When the data collection is completed, in step S _8, reads the stored data, calculates the * complex viscosity eta (eta) from the output torque. Then, to calculate the activation energy Ea apparent performs operation based on equation (1) previously described in the next step S _9.

On the other hand, in step S ₁₀ , the sample a is selected from the range of Ea values that can be formed by extrusion (set allowable range) for each material (recycled rubber compound having a different composition of EPDM compound that is a raw material for regeneration). call those falling, in step S _11, compared with the allowable setting range of extrudable Ea values for calculation values of Ea and sample a for the samples a, collating, actually extruded the samples a Evaluation and judgment of physical properties and extrudability when it is assumed to be performed.

As a result, if the calculated value of Ea is within a pre-stored allowable Ea value setting range for extrusion molding, the physical property and extrusion processability of the sample a based on the Ea value are determined as “OK” ( step S _12), the other, as long as the calculated value of Ea is out of extrudable set tolerance, physical properties and extrudability of the sample a by Ea values is determined to be "NG" (step S ₁₃₎ . That is, as described above based on the data in Tables 1 to 3, the Ea value of a specific recycled rubber compound as sample a and the tensile strength that is the physical property of a recycled rubber extruded product made from the recycled rubber compound. Since there is a close correlation between elongation and elongation, in steps S _{11 to} S ₁₃ , the suitability of physical properties is determined simultaneously with the evaluation of the extrusion processability of the sample a.

  FIG. 8 shows a manufacturing management flowchart to which the present invention is applied.

  That is, FIG. 8 shows the apparent activation energy by exchanging information between the information processing device 3 of FIG. 6 and the control device 8 of the closed kneader for the regeneration process in the mass production process of recycled rubber. An example is shown in which the determination result based on Ea is immediately fed back to the kneader.

First performed in step S _21, putting pulverized pieces of vulcanized rubber in a chamber of the internal mixer, the reproduction processing by the reproducing processing conditions are previously set according to the type of vulcanized rubber, reclaimed rubber A compound (referred to here as sample a) is obtained (step S ₂₂ ). The regeneration process condition refers to the time (kneading finishing time) and the number of rotations from the peak time of the load torque described above.

Then, for example, viscoelasticity measurement similar to that of FIG. 7 is performed by the viscoelasticity measuring device 1 of FIG. 6, and data necessary for calculating the Ea value is collected (step S ₂₃ ). Then, it calculates the activation energy Ea apparent based on the foregoing equation (1) in step S _24.

In step S ₂₅ , the calculated value of Ea obtained in step S ₂₄ is compared with the preset allowable range of the Ea value of sample a to determine whether the physical properties and extrudability of sample a are appropriate. I do. As a result, if the calculated value of Ea is within the preset allowable range of the Ea value, it is determined that the physical property and extrudability of the sample a are “OK” (step S ₂₆ ), and the state is unchanged. It is determined to be adopted as an extrusion material (step S ₂₇ ).

On the other hand, the comparison of step S _25, the result of the comparison, if the calculated value of Ea for Sample a is determined to be outside the allowable setting range, inadequate for physical properties and extrudability of the sample a itself extrusion Is determined, and an instruction to change the regeneration processing condition is issued. Then, the regeneration processing conditions such as the time from the peak time of the load torque described above are changed.

  Thus, using the apparent activation energy Ea that enables evaluation of physical properties and extrusion processability of recycled rubber, recycled rubber extrusion using the recycled rubber compound as a raw material while manufacturing the recycled rubber compound It is possible to perform production management when extruding a molded product.

The graph which shows the relationship between the time in the manufacturing process of recycled rubber, load torque, and temperature. Explanatory drawing which shows the extrusion port shape for evaluating the extrusion discharge amount dispersion | variation, when performing extrusion molding using a reproduction | regeneration rubber compound. Graph showing the relationship between the apparent activation energy of the time and unvulcanized硫再raw rubber compound from the peak of the load torque (Ea / Ea _0). The graph which shows the relationship between the time from the peak of load torque, and the apparent activation energy Ea of a vulcanized reclaimed rubber compound. The graph which shows the relationship between the apparent activation energy Ea of a vulcanized recycled rubber compound, and tensile strength. The block circuit diagram for calculating the apparent activation energy Ea by a viscoelasticity test. The flowchart which shows the procedure for calculating the apparent activation energy Ea in FIG. 6 is a flowchart when the functions and procedures of FIGS. 6 and 7 are applied to the production management of recycled rubber.

Claims (8)

While applying shearing force to the vulcanized rubber put in a closed kneader to give fluidity and plasticity,
Based on the value of the apparent activation energy in the unvulcanized state that is the original state of the vulcanized rubber, the kneading finish time is set in advance,
The reclaimed rubber is taken out from the closed kneader after the load torque of the closed kneader during the regeneration process has passed the peak and before the above kneading finish time starting from this peak. A method for producing recycled rubber characterized by the above. When the apparent activation energy value in the unvulcanized state which is the original state of the vulcanized rubber is Ea ₀ and the apparent activation energy value in the unvulcanized state of the recycled rubber is Ea,
The end of the kneading finish time is set at a timing at which the apparent activation energy Ea of the recycled rubber in an unvulcanized state satisfies a relationship of 0.8 × Ea ₀ ≦ Ea ≦ Ea _0. Item 2. A method for producing recycled rubber according to Item 1.   The method for producing a reclaimed rubber according to claim 1 or 2, wherein the regenerated treatment is performed after the pulverized rubber crushed pieces are introduced into the closed kneader with a volume filling ratio of 70 to 90%. In the regeneration process step, the regeneration process is performed under the conditions set in advance for the regeneration process condition including at least the kneading finishing time,
Measure the viscoelasticity of the unvulcanized recycled rubber obtained by the regeneration process to determine the apparent activation energy value of the recycled rubber,
When the obtained apparent activation energy value is compared with the preset allowable setting range and the obtained apparent activation energy value does not satisfy the allowable setting range, the finishing time is determined. The method for producing a reclaimed rubber according to any one of claims 1 to 3, wherein the regenerating treatment conditions including A method for evaluating at least one of physical properties and extrudability of recycled rubber produced by the production method according to claim 1,
A measurement step of controlling the shear force applied to the unvulcanized reclaimed rubber and determining the complex viscosity of the reclaimed rubber based on the stress that reacts to the shear force;
The temperature and gas constant at the time of the above measurement are T and R, the viscosity is η, and the complex viscosity is η * (η), respectively, and the Arrhenius type equation (Andrad's equation) representing the temperature dependence of the viscoelastic material ) Calculating the apparent activation energy Ea of the recycled rubber based on (1);
η = Aexp (Ea / RT) (1)
However,
Ea: Abbreviation for Activation Energy, apparent activation energy of compound viscosity (flow) (KJ / mol)
Including
A method for evaluating properties of recycled rubber, comprising evaluating at least one of physical properties and extrusion processability of recycled rubber based on the apparent activation energy Ea. For each of a plurality of types of recycled rubber having different vulcanized rubber formulations before regeneration, an allowable range of the apparent activation energy Ea that can be molded in the extrusion process is set in advance,
By comparing and comparing the calculated apparent activation energy Ea with the set allowable range of the corresponding recycled rubber, it is characterized in that the suitability of at least one of the physical properties and extrusion processability of the recycled rubber is determined. The method for evaluating characteristics of recycled rubber according to claim 5. Based on the apparent activation energy Ea, the physical properties of the recycled rubber and the suitability of the extrudability are determined.
The determination item related to physical properties is at least one of tensile strength and elongation, and the determination item related to extrusion processability is at least one of variation in extrusion discharge amount and appearance of recycled rubber extruded products. The method for evaluating characteristics of recycled rubber according to claim 6. An apparatus for evaluating at least one of physical properties and extrudability of recycled rubber produced by the production method according to claim 1,
A measuring means for controlling the shear force applied to the unvulcanized reclaimed rubber and obtaining the complex viscosity of the reclaimed rubber based on the stress that reacts to the shear force;
The temperature and gas constant at the time of the above measurement are T and R, the viscosity is η, and the complex viscosity is η * (η), respectively, and the Arrhenius type equation (Andrad's equation) representing the temperature dependence of the viscoelastic material ) Calculating means for calculating the value of the apparent activation energy Ea of the recycled rubber based on (1);
η = Aexp (Ea / RT) (1)
However,
Ea: Abbreviation for Activation Energy, apparent activation energy of compound viscosity (flow) (KJ / mol)
A storage means in which the allowable range of the apparent activation energy Ea that can be molded in the extrusion molding process is preset and stored for each of a plurality of types of recycled rubber having different vulcanized rubber compositions before regeneration,
By comparing and collating the apparent activation energy Ea value calculated by the calculation means with the permissible range of the corresponding recycled rubber set and stored in the storage means, at least one of the physical properties and extrusion processability of the recycled rubber A determination means for determining the suitability of either one;
An apparatus for evaluating the characteristics of recycled rubber, comprising:

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