JPH10176001A - Regeneration of vulcanized rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for regenerating a vulcanized rubber, capable of providing a regenerated rubber molded article excellent in appearance and quality and consuming a large amount of waste vulcanized rubber, by adding a solvent to a vulcanized rubber into a swollen state. SOLUTION: (B) A solvent is added to (A) a vulcanized rubber, which is made into a swollen state. Then heat and shear stress are simultaneously applied to the component A in the swollen state to give a regenerated rubber. The component B is removed from the regenerated rubber. Waste material such as rubber tire is used as the component A. An ethylene-propylene-diene terpolymer is preferable as the kind of the rubber. Toluene, hexane, etc., are used as the component B. The heating is carried out at 150-350 deg.C and shear stress is applied by using a twin-screw extruder, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for reclaiming vulcanized rubber applied to the reuse of waste vulcanized rubber.

[0002]

2. Description of the Related Art Conventionally, as a method of reusing waste vulcanized rubber such as waste of rubber molded products made of vulcanized rubber such as old tires, offcuts and defective products generated in the process of manufacturing rubber molded products,
There is known a method for producing a rubber molded product by the following method. After finely pulverizing the waste vulcanized rubber, it is added to the new unvulcanized rubber. Then, this is made into a rubber molded product by a usual vulcanization and molding method.

Further, a regenerant is added to the finely ground waste vulcanized rubber and heat-treated for about 5 hours in an autoclave at a temperature of 150 to 250 ° C. After that, it is refined with a finishing roll machine to make recycled rubber rich in plasticity. The reclaimed rubber is mixed with a new unvulcanized rubber, and then subjected to ordinary vulcanization and molding methods to form a rubber molded product.

[0004]

However, the above-mentioned reproducing method has the following problems. First, in the former method,
Although the vulcanized rubber is finely pulverized, it is contained in the rubber molded product as it is. Therefore, during the above vulcanization and molding, the vulcanized rubber is exposed on the surface of the rubber molded product, thereby deteriorating the appearance quality of the rubber molded product.

[0005] In the latter method, the waste heat vulcanized rubber is desulfurized to some extent by the heat treatment. However, the waste heat vulcanized rubber cannot be completely removed by the heat treatment as described above. For this reason, as in the former method, the undesulfurized rubber is exposed on the surface of the rubber molded product during the vulcanization and molding, thereby deteriorating the appearance quality.

On the other hand, when the amount of the waste vulcanized rubber or the reclaimed rubber added to the new unvulcanized rubber is limited to about 10% by weight of the whole rubber molded product, the appearance quality of the rubber molded product deteriorates. Can be prevented. However, for recycling of wastes that generate a large amount of waste vulcanized rubber, such as automobile tires, the digestible amount of the waste vulcanized rubber is limited, and the above method is not suitable.

[0007] In view of the above problems, the present invention aims to provide a method for molding a vulcanized rubber which can obtain a reclaimed rubber molded article having excellent appearance quality and has a high digestible amount of waste vulcanized rubber. Things.

[0008]

According to a first aspect of the present invention, a solvent is added to a vulcanized rubber to form a swollen state, and then heat and shear are simultaneously applied to the vulcanized rubber in the swollen state. ,
A method for regenerating a vulcanized rubber, comprising forming a reclaimed rubber and then removing the solvent from the reclaimed rubber.

The vulcanized rubber to be regenerated by the regeneration method according to the present invention is a mixture of raw rubber, which is an aggregate of long chain organic compounds having a carbon main chain, mixed with sulfur or a sulfur compound, It shows a substance in which various kinds of sulfur cross-links such as a monosulfide bond, a disulfide bond, and a polysulfide bond are formed between them to exhibit properties of an elastomer or rubber. There are also vulcanized rubbers in which the sulfur cross-links are formed between side chains, not between carbon main chains.

[0010] Examples of the chain organic compound include natural rubber, butadiene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, styrene-butadiene rubber, EPDM (ethylene propylene diene terpolymer), acrylic rubber, acrylonitrile-butadiene rubber. And the like.

The vulcanized rubber to be reclaimed by the reclaiming method of the present invention includes used waste materials such as rubber tires, weather strips, hoses, etc., unnecessary scrap materials generated during molding, and defective molded products. And the like.

The type of the vulcanized rubber is EP
DM and butyl rubber are particularly suitable for the regeneration method according to the present invention. These rubbers have a large sulfur crosslinking bond formed between the carbon main chains, that is, a large difference in the breaking energy between the sulfur crosslinking point and the carbon main chain, and can improve the degree of decomposition without breaking the carbon main chain. it can.

The solvent may be any solvent as long as it has good compatibility with the vulcanized rubber to be regenerated and can swell the vulcanized rubber. Specific examples include aromatic hydrocarbons such as benzene, toluene,
Ethylbenzene, styrene, xylene, mesitylene, etc.
As aliphatic hydrocarbons, pentane, hexane, heptane,
Octane, nonane, decane, isooctane, petroleum ether, dicyclopentadiene, ethylidene norbornene,
Other examples include ethylidene norbornane, dichloromethane, chloroform, carbon tetrachloride and the like.

Among the above-mentioned substances, particularly preferred are toluene, hexane and the like. These solvents are very compatible with the vulcanized rubber and can extend the carbon backbone with a small amount. Also, since the boiling point is low, it is convenient from the viewpoint of eliminating the solvent after regeneration.

Next, the above-mentioned swelling refers to a state where the network structure formed by the carbon main chain and the sulfur cross-linking point in the vulcanized rubber is wider than the normal state as shown in FIG. . Preferably, the volume of the polymer component in the vulcanized rubber in the swollen state is at least twice the volume in the unswelled state.

Next, it is preferable that the temperature at the time of the heating be a temperature at which a cutting reaction at a sulfur crosslinking point of the vulcanized rubber proceeds. However, a high temperature at which the cleavage of the carbon main chain proceeds is not desirable. In addition, since the thermal stability of the sulfur crosslinking point is reduced by applying a shearing force during the heating, the sulfur crosslinking point can be cut at a lower temperature as the shearing force increases. Specifically, the heating is 150
Although it is desirable to carry out at a temperature of from 350C to 350C, the temperature range varies depending on the type of vulcanized rubber. For example, EPDM
In this case, the temperature is preferably from 220 ° C to 330 ° C.

The above-mentioned shearing force is applied by so-called kneading, and may be such that some force is applied to the vulcanized rubber. Examples of the device to which the above shearing force can be applied include a single screw extruder, a twin screw extruder, a Henschel mixer, and a rubber roll.

In the expression "simultaneous application of heat and shearing force", "simultaneously" means that shearing force is simultaneously applied while heating, but after heating is completed,
This includes the case where a shearing force is applied while the temperature of the vulcanized rubber (the sulfur cross-linking point is gradually being cut off) is within the temperature range where the sulfur cross-linking point can be cut. It also includes the case where heat and shear force are applied alternately.

As a method for removing the above-mentioned solvent,
Any method may be used as long as the solvent can be removed. Specific examples include vacuum drying, natural drying by standing, and heat drying at normal pressure. The removal of the solvent may be performed after the application of the heating and the shearing force, or may be gradually performed during the application. Further, the removal of the solvent may not be 100%, that is, may not be complete, as long as it does not adversely affect the physical properties of the recycled rubber molded product obtained by this recycling method.
It may remain.

When the recycled rubber according to the present invention is molded, vulcanization is performed at the same time. At this time, a new material, unvulcanized rubber, can be mixed with the recycled rubber as appropriate, and molding can be performed. Alternatively, molding can be performed using only the recycled rubber at 100%. In addition, at the time of the molding, additives generally used for rubber molded articles, carbon black, fillers, organic additives, and the like can be added.

The operation of the present invention will be described below. In the method for regenerating a vulcanized rubber according to the present invention, a solvent is added to the vulcanized rubber to cause swelling, and heat and shearing force are simultaneously applied to the swollen rubber. Fig. 1 (a)
As shown in the figure, vulcanized rubber 10 which is shrunk under normal conditions
Is stretched as shown in FIG. 1 (b). By applying a shearing force to the vulcanized rubber 10 in this state, the carbon main chain 11 has already been sufficiently elongated, so that the shearing force concentrates on the sulfur crosslinking point 12 having a relatively weak bonding force. Act.

Therefore, the bond distance of the sulfur bridging point 12 becomes long, and becomes very unstable thermally as compared with a normal state. In the present invention, since heat is applied simultaneously with the shearing force, as shown in FIG. 1 (c), the sulfur crosslinking points 12 are efficiently cut, and the vulcanized rubber 10 is largely desulfurized and regenerated. It becomes rubber 1.

For reference, FIG. 2 shows a case where a shearing force is applied to the vulcanized rubber 10 which is not swelled.
(A) and (b) show. In this case, by applying a shearing force, the vulcanized rubber 10 is in a state in which the carbon main chain 11 shown in FIG. 2B is extended from the state in which the carbon main chain 11 shown in FIG. Becomes However, the cutting force is consumed in extending the carbon main chain 11 and does not reach the point where the sulfur crosslinking point 12 becomes unstable.

Further, since the vulcanized rubber 10 loses the shearing force, there is a possibility that the carbon main chain 11 which has been once expanded may be contracted again. As described above, even if heat is applied to the vulcanized rubber in the non-swelling state, the sulfur cross-linking points are not efficiently cut, and the undesulfurized portion largely remains in the treated recycled rubber. Such undesulfurized rubber is exposed on the surface of the reclaimed rubber molded product and causes a deterioration in the appearance quality.

As described above, since the reclaimed rubber regenerated by the regenerating method according to the present invention has a small amount of undesulfurized portion, a reclaimed rubber molded product having excellent appearance quality is obtained when molded into a reclaimed rubber molded product. be able to. In addition, since it is sufficiently desulfurized, even when a new rubber unmolded rubber is not added and a recycled rubber molded article is made using only the recycled rubber, its physical properties are different from those of a normal rubber molded article. Absent. For this reason, it is possible to efficiently recycle unnecessary items, wastes, and the like made of a large amount of vulcanized rubber.

As described above, according to the present invention, it is possible to obtain a reclaimed rubber molded product having excellent appearance quality and to provide a method for molding a vulcanized rubber having a high digestible amount of waste vulcanized rubber. Can be.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A method for reclaiming vulcanized rubber according to an embodiment of the present invention will be described with reference to FIGS. Vulcanized rubber 10 of this example
In the regenerating method (1), as shown in FIGS. 1A and 1B, a solvent is added to the vulcanized rubber 10 to bring it into a swollen state. Next, as shown in FIG. 1 (c), heat and shear are simultaneously applied to the vulcanized rubber 10 in the swollen state,
The crosslinked points 12 in the vulcanized rubber 10 are cut to form the recycled rubber 1. Next, the solvent is removed from the recycled rubber 1, and then the recycled rubber 1 is vulcanized and molded.
Recycled rubber molded products.

Next, the performance of Samples 1 to 3, which are recycled rubber molded articles according to the present invention, will be described together with Comparative Samples C1, C2 and Reference Sample 1. First, samples 1 to 3 will be described. The same amount (by weight) of toluene was added to the pulverized material of the scrap material of the weather strip made of sulfur-vulcanized EPDM to obtain a swollen state.

Next, the pulverized material in the swollen state is introduced into a twin-screw extruder having a screw diameter of 30 mm and a screw length of 1200 mm, and subjected to a regeneration treatment under the treatment conditions shown in Table 1.
Recycled rubber according to Samples 1 to 3 was obtained. In addition, the above-mentioned toluene was in front of the above-mentioned twin-screw extruder, and the degree of vacuum was
Was removed by a vacuum vent.

Next, two types of reclaimed rubber molded articles were prepared for each sample using the reclaimed rubbers of the samples 1 to 3. One of the two types of recycled rubber molded products is a recycled rubber molded product prepared using only recycled rubber, that is, a rubber composition having a value of 100% by weight in each table.
The other is a reclaimed rubber molded product made from a rubber material obtained by equally mixing the reclaimed rubber and the new unvulcanized rubber in a weight ratio, that is, the value of the reclaimed rubber compounding ratio in each table is 50% by weight.
belongs to.

In producing the recycled rubber molded article, 0.5 parts by weight of sulfur, 1.7 parts by weight of zinc oxide, and 0 parts by weight of stearic acid were added to 100 parts by weight of the recycled rubber or 100 parts by weight of the rubber raw material. 0.37 parts by weight, 0.67 parts by weight of Noxeller TT (trade name of Ouchi Shinko Chemical Industry Co., Ltd., compound name: tetramethylthiuram disulfide), Noxeller M (trade name of Ouchi Shinko Chemical Industry Co., Ltd., compound name 2)
-Mercaptobenzothiazole) in an amount of 0.17 parts by weight. This mixture was press-molded at a temperature of 160 ° C. to obtain a recycled rubber molded product.

Then, the hardness of the obtained recycled rubber molded product was measured according to JIS K6301. In addition, tensile strength,
The breaking elongation was measured according to JIS K6301. Further, the surface quality of the reclaimed rubber molded product was determined according to ASTM D2663-89.
It went according to. The surface quality was evaluated on a five-point scale, with 5 being the highest. The above measurement results are shown in Table 1.

Next, the comparative sample C1 will be described. The same pulverized scraps as in Samples 1 to 3 were prepared. next,
With the above pulverized material as it is (that is, not swelled), a screw diameter of 30 mm and a screw length of 1200 m
m into a twin-screw extruder and subjected to a regeneration treatment under the treatment conditions shown in Table 2 to obtain a recycled rubber for C1. Two types of recycled rubber molded articles were obtained from the obtained recycled rubber in the same manner as in Samples 1 to 3. And the hardness of the recycled rubber molded product,
Tensile strength, elongation at break, and surface quality were measured in the same manner as Samples 1 to 3, and are shown in Table 2.

Next, the comparative sample C2 will be described. The same amount (weight) of toluene was added to the ground material of the same offcuts as in Samples 1 to 3 to swell. Next, the pulverized material in the swelling state was heated at a temperature of 20 ° C using an autoclave.
Heat at 0 ° C for 5 hours under no shearing force.
The recycled rubber according to Comparative Sample C2 was used. After the completion of the reaction, the toluene was removed under reduced pressure using a vacuum dryer.

From the obtained reclaimed rubber, two types of reclaimed rubber molded articles were obtained in the same manner as in samples 1 to 3. The hardness, tensile strength, elongation at break, and surface quality of this recycled rubber molded product were measured in the same manner as in Samples 1 to 3, and are shown in Table 2.

As a reference sample 1, an ordinary new material unvulcanized rubber (however, made of EPDM in this example) was used.
Vulcanization and molding were carried out under the same conditions as when the above-mentioned recycled rubber molded article was prepared to obtain a rubber molded article. The hardness, tensile strength, elongation at break, and surface quality of this rubber molded product were measured in the same manner as in Samples 1 to 3, and are shown in Table 2.

As shown in Tables 1 and 2, the physical properties of the recycled rubber molded products according to Samples 1 to 3 were almost the same as those of the rubber molded product according to Reference Sample 1. In addition, the surface quality was all excellent at 5. On the other hand, the comparative sample C1 did not swell the pulverized material of the vulcanized rubber offcuts, so the physical properties were the same as those of the reference sample 1, but the surface quality was poor.
Moreover, since the comparative sample C2 was subjected to the regeneration treatment without applying a shearing force, the physical properties were poor and the surface quality was also poor.

The operation and effect of the method for regenerating vulcanized rubber according to this embodiment will be described. In the playback method according to this example,
A solvent is added to the vulcanized rubber to cause swelling, and heat and shear are simultaneously applied to the swollen vulcanized rubber. Fig. 1
As shown in FIG. 1A, the carbon main chain 11 constituting the vulcanized rubber 10 which is normally contracted is stretched as shown in FIG. 1B. In the vulcanized rubber 10 in this state,
Since the carbon backbone 11 has already been sufficiently stretched by applying a shearing force, the shearing force acts on the sulfur bridging points 12 having a relatively weak bonding force.

Therefore, the bond distance of the sulfur bridging point 12 becomes long, and becomes very unstable thermally as compared with a normal state. In this example, since heat is applied simultaneously with the shearing force, as shown in FIG. 1C, the sulfur crosslinking points 12 are efficiently cut, and the vulcanized rubber 10 is largely desulfurized and regenerated. It becomes rubber 1.

As described above, since the reclaimed rubber regenerated by the above-mentioned regenerating method has a small amount of undesulfurized portion, when the reclaimed rubber molded product is subjected to re-vulcanization and molding, the reclaimed rubber molded product having excellent appearance quality is obtained. Can be obtained.

Further, since it is sufficiently desulfurized, even when a reclaimed rubber molded article is formed by using only the reclaimed rubber without adding the new unvulcanized rubber, the physical properties of the reclaimed rubber molded article are not changed. It is not different from the product. For this reason, it is possible to efficiently recycle unnecessary items, wastes, and the like made of a large amount of vulcanized rubber.

[0042]

[Table 1]

[0043]

[Table 2]

Embodiment 2 In this embodiment, the same test as in the embodiment is performed on a waste vulcanized rubber made of butyl rubber. Samples 4 to 6 and comparative samples C3 and C4 according to this example will be described. First, samples 4 to 6 will be described. To the pulverized waste sulfur-vulcanized butyl rubber, the same amount (weight) of toluene was added,
Swelled. Next, the pulverized product in the swollen state is introduced into a twin-screw extruder similar to that of the first embodiment, and regenerated under the processing conditions shown in Table 2 to obtain a regenerated rubber for samples 4 to 6. Was. The removal of toluene was performed in the same manner as in Example 1.

Then, in the same manner as in the first embodiment, two types of recycled rubber molded articles were used as the recycled rubber. Then,
The hardness, tensile strength, elongation at break,
The surface quality was measured in the same manner as in Example 1 and described in Table 3.

In Comparative Sample C3, the same pulverized product as in Samples 4 to 6 was introduced into a twin-screw extruder without swelling in the same manner as Comparative Sample C1 in Embodiment 1, and the treatment shown in Table 4 was carried out. The rubber was regenerated under the conditions to produce recycled rubber. Then, the recycled rubber was made into two types of recycled rubber molded articles in the same manner as in the first embodiment. Next, the hardness, tensile strength, elongation at break, and surface quality of the obtained recycled rubber molded product were measured in the same manner as in Example 1 and described in Table 4.

In Comparative Sample C4, the same pulverized material as in Samples 4 to 6 above was swelled, and heated and regenerated without applying a shear force using an autoclave as in Comparative Sample C2 in Embodiment 1. It is rubber.

The reclaimed rubber was made into two types of reclaimed rubber products in the same manner as in the first embodiment. Then,
The hardness, tensile strength, elongation at break,
The surface quality was measured in the same manner as in Example 1 and described in Table 4.

As reference sample 2, an ordinary new material unvulcanized rubber (however, in the case of this example, made of butyl rubber)
Was vulcanized and molded under the same conditions as those for producing the above-mentioned reclaimed rubber molded product to obtain a rubber molded product. The hardness, tensile strength, elongation at break, and surface quality of this rubber molded product were measured in the same manner as in Example 1 and described in Table 4.

As shown in Tables 3 and 4, Samples 4 to 6
The physical properties of the reclaimed rubber molded product according to Comparative Example 2 were comparable to those of the rubber molded product according to Reference Sample 2. In addition, the surface quality was all excellent at 5. On the other hand, the comparative sample C3 did not swell the pulverized material as the waste vulcanized rubber, so that the physical properties were the same as those of the reference sample 2, but the surface quality was poor. In addition, the comparative sample C4 was regenerated without applying a shearing force, and thus had poor physical properties and poor surface quality.

[0051]

[Table 3]

[0052]

[Table 4]

[0053]

As described above, according to the present invention, it is possible to obtain a recycled rubber molded article having excellent appearance quality and to provide a method for molding a vulcanized rubber having a high digestible amount of waste vulcanized rubber. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing (a) a state of a carbon main chain of a vulcanized rubber in a first embodiment, and (b) a state of a carbon main chain of a vulcanized rubber which has been swollen (extended) by a solvent. Explanatory drawing showing a state, (c) Explanatory drawing showing a state in which recycled rubber is obtained from vulcanized rubber by applying heat and shearing force.

2 (a) is an explanatory view showing the state of the carbon main chain of the vulcanized rubber, and FIG. 2 (b) is an explanatory view showing the state of the carbon main chain of the vulcanized rubber expanded by a shearing force.

[Explanation of symbols]

 1. . . Recycled rubber, 10. . . Vulcanized rubber,

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Makoto Mori 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. (72) Inventor Hirotaka Okamoto Hirotaka Okamoto, Aichi-gun No. 41, Yokomichi, Toyota Central Research Institute, Inc. (72) Inventor Arimitsu Usuki 41, Chuo, Yoji, Nagakute-cho, Aichi-gun, Aichi Prefecture, Japan No. 41 Inside Toyota Central Research Institute, Inc. (72) Inventor: Norio Sato Aichi 41, Chuo-ku, Yokomichi, Nagakute-machi, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. (72) Inventor Yasuyuki Yasuyuki 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Masao Owaki Aichi Prefecture 1 Toyota Town, Toyota City Inside Toyota Motor Corporation (72) Inventor Hidetada Honda Hata 1, Toyoda Gosei Co., Ltd. No. 1 Toyoda Gosei Co., Ltd.

Claims (1)

[Claims] 1. A solvent is added to a vulcanized rubber to make it a swollen state, and then the vulcanized rubber in the swollen state is
A method for regenerating vulcanized rubber, comprising applying heat and shear force simultaneously to form a reclaimed rubber, and then removing the solvent from the reclaimed rubber.