JP2022065596A - Rubber composition production method, re-crosslinked rubber, tire, and rubber industrial product - Google Patents

Abstract

To provide a liquid hydrocarbon production method that makes it possible to produce liquid hydrocarbons of increased molecular weight at a high decomposition rate even under mild conditions, and a re-crosslinked rubber, a tire, and a rubber industrial product obtainable from a rubber composition produced by the production method.SOLUTION: A liquid hydrocarbon production method includes heating a crosslinked rubber at 300°C or less in a reaction solvent that has a boiling point of 230°C or less and contains an aldehyde having a hydrocarbon group with a carbon number of 2 or greater, thereby producing a rubber composition that contains a liquid hydrocarbon.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a rubber composition, recrosslinked rubber, a tire and a rubber industrial product.

From the viewpoint of environment and resource saving, it is considered to recycle the crosslinked rubber and reuse it as a new crosslinked rubber.
For example, Patent Document 1 discloses a method for obtaining a rubber composition containing a liquid hydrocarbon by heating a crosslinked rubber at 300 ° C. or lower in a reaction solvent containing a primary alcohol having 2 or more carbon atoms. ..

International Publication No. 2019/160088

However, although the method described in Patent Document 1 can recover liquid hydrocarbons in high yield even under mild conditions, further studies are required to obtain liquid hydrocarbons having a high molecular weight.

The present invention is obtained from a method for producing a rubber composition capable of producing a liquid hydrocarbon having a higher molecular weight at a high decomposition rate even under mild conditions, and a rubber composition produced by the production method. The object is to provide re-crosslinked rubber, tires and rubber industrial products, and it is an object to solve the object.

<1> A rubber composition containing a liquid hydrocarbon is prepared by heating a crosslinked rubber at 300 ° C. or lower in a reaction solvent containing an aldehyde having a boiling point of 230 ° C. or lower and having a hydrocarbon group having 2 or more carbon atoms. A method for producing a rubber composition to be obtained.

<2> The method for producing a rubber composition according to <1>, wherein the hydrocarbon group has 3 to 16 carbon atoms.
<3> The method for producing a rubber composition according to <1> or <2>, wherein the hydrocarbon group has 6 to 10 carbon atoms.
<4> The method for producing a rubber composition according to any one of <1> to <3>, wherein the hydrocarbon group is a linear saturated aliphatic group.
<5> The method for producing a rubber composition according to any one of <1> to <4>, wherein the aldehyde contains nonanal.

<6> The method for producing a rubber composition according to any one of <1> to <5>, wherein the crosslinked rubber is heated at 150 to 250 ° C.
<7> The method for producing a rubber composition according to any one of <1> to <6>, wherein the crosslinked rubber is a crosslinked product of a rubber component containing 50 to 100% by mass of a diene rubber.
<8> The method for producing a rubber composition according to any one of <1> to <7>, wherein the crosslinked rubber contains vulcanized rubber.

<9> A re-crosslinked rubber obtained by re-cross-linking a rubber composition produced by the method for producing a rubber composition according to any one of <1> to <8>, wherein the rubber composition is: The liquid hydrocarbon produced by the method for producing a rubber composition according to any one of <1> to <7> is contained as a rubber component, and the content of the liquid hydrocarbon in the rubber component is 1 to 100. Re-crosslinked rubber which is mass%.

<10> The tire made of the recrosslinked rubber according to <9>.
<11> A rubber industrial product made of the recrosslinked rubber according to <9>.

According to the present invention, from a method for producing a rubber composition capable of producing a liquid hydrocarbon having a higher molecular weight at a high decomposition rate even under mild conditions, and a rubber composition produced by the production method. The obtained re-crosslinked rubber, tires and rubber industrial supplies can be provided.

<Manufacturing method of rubber composition>
In the method for producing a rubber composition of the present invention, a crosslinked rubber is heated at 300 ° C. or lower in a reaction solvent containing an aldehyde having a boiling point of 230 ° C. or lower and a hydrocarbon group having 2 or more carbon atoms to be liquid carbonized. It has a step of obtaining a rubber composition containing hydrogen (hereinafter, may be referred to as a “decomposition step”).
The method for producing a rubber composition of the present invention may include, in addition to the decomposition step, a drying step of drying the reaction product obtained in the decomposition step.
Further, the liquid hydrocarbon contained in the rubber composition produced by the production method of the present invention is a rubber molecule constituting the crosslinked rubber, and varies depending on the composition of the crosslinked rubber, but when the crosslinked rubber derived from waste tire is used. , Usually includes natural rubber, styrene-butadiene copolymer rubber and the like. The term "liquid" means that it is easily solubilized in a liquid state or petroleum components (alcohol, diethyl ether, tetrahydrofuran, etc.) at room temperature (25 ° C.) and atmospheric pressure (0.1 MPa) to become a liquid state.

According to the method for producing a rubber composition of the present invention, a bond between carbon atoms derived from rubber molecules constituting the crosslinked rubber (carbon-carbon bond), a heteroatom derived from the carbon atom and the crosslinking agent (oxygen atom, sulfur atom, etc.) It is considered that the bond is cleaved by heat and solvent effects in the bond with (for example, carbon-sulfur bond), and a radical and / or a new bond is generated. It is considered that hydrogen atoms released from aldehydes having a hydrocarbon group having two or more carbon atoms are attracted to the highly reactive radical species generated by these cleavages to stop the radical reaction. It is considered that an aldehyde having a hydrocarbon group having 2 or more carbon atoms is more likely to be hydrogenated than an alcohol, is more likely to cause a termination of the radical reaction, and is more likely to cause a termination of the radical reaction. Further, the oxygen in the autoclave can be consumed by oxidizing the primary aldehyde to a primary carboxylic acid with respect to the oxygen required for breaking the main chain of the rubber molecule. As a result, since the cleavage of the main chain is suppressed, it is considered that a liquid hydrocarbon having a higher molecular weight than the conventional one can be obtained at a high decomposition rate.
Hereinafter, the details of the method for producing the rubber composition of the present invention will be described.

[Cross-linked rubber]
The crosslinked rubber is a crosslinked product of a rubber component.
The rubber component that is the raw material of the crosslinked rubber may be either a diene-based rubber or a non-diene-based rubber.
Examples of the diene-based rubber include at least one selected from the group consisting of natural rubber (NR) and synthetic diene-based rubber.
Examples of the synthetic diene rubber include polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and butyl halide rubber. , Acryloni Little-butadiene rubber (NBR) and the like.
Examples of the non-diene rubber include butyl rubber, ethylene propylene rubber, urethane rubber, silicone rubber, acrylic rubber and the like.
These rubber components may be used alone or in combination of two or more.

Among the above, since diene-based rubber is generally used for rubber products such as tires, it is preferable that the rubber component contains 50% by mass or more of diene-based rubber. That is, the crosslinked rubber is preferably a crosslinked product having a rubber component containing 50 to 100% by mass of diene rubber. The rubber component more preferably contains 70% by mass or more of diene-based rubber, and further preferably contains 90% by mass or more of diene-based rubber. Further, the diene-based rubber is preferably at least one selected from the group consisting of natural rubber, polyisoprene rubber and styrene-butadiene copolymer rubber.

The cross-linking agent of the rubber component is not particularly limited, and is, for example, a sulfur-based cross-linking agent, an organic peroxide-based cross-linking agent, an acid cross-linking agent, a polyamine cross-linking agent, a resin cross-linking agent, a sulfur compound-based cross-linking agent, and an oxime-nitrosoamine-based cross-linking agent. Agents and the like can be mentioned.
Since a sulfur-based cross-linking agent (vulcanizing agent) is usually used as the rubber component of tires and the like, the cross-linked rubber preferably contains a vulcanized product vulcanized with a vulcanizing agent, that is, vulcanized rubber. ..
By heating the vulture rubber at 300 ° C. or lower in a reaction solvent containing an aldehyde having a hydrocarbon group having 2 or more carbon atoms, the carbon-sulfur bond mainly constituting the molecular structure of the vulnerable rubber is heated. The hydrogen atom released from the aldehyde having a hydrocarbon group having 2 or more carbon atoms is attracted to the highly reactive radical species generated by the cleavage, and the radical is attracted. The reaction is thought to stop.
The content of the vulcanized rubber in the crosslinked rubber is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and the crosslinked rubber is the vulcanized rubber. (The content is 100% by mass) is particularly preferable.

(filler)
The crosslinked rubber may contain a filler.
Tires generally contain a reinforcing filler such as carbon black or silica in order to improve various functions such as tire durability and wear resistance.
As the filler, either silica or carbon black may be used alone, or both silica and carbon black may be used.

The silica is not particularly limited, and can be used depending on the application, such as general grade silica and special silica surface-treated with a silane coupling agent or the like. As the silica, for example, wet silica is preferably used.
The carbon black is not particularly limited and may be appropriately selected depending on the intended purpose. The carbon black is preferably, for example, FEF, SRF, HAF, ISAF, SAF grade.
The content of the filler in the crosslinked rubber is preferably 20 to 100 parts by mass, more preferably 30 to 90 parts by mass with respect to 100 parts by mass of the rubber component.

In addition to the rubber component and the above-mentioned filler, the crosslinked rubber contains, if necessary, a compounding agent usually used in the rubber industry, such as a softener, stearic acid, an antioxidant, zinc oxide, and a vulcanization accelerator. It may be a crosslinked product obtained by cross-linking the rubber composition contained therein. Tires generally include vulcanized rubber obtained by vulcanizing a rubber composition containing these formulations.

[Reaction solvent]
The reaction solvent contains an aldehyde having a boiling point of 230 ° C. or lower and having a hydrocarbon group having 2 or more carbon atoms.
By selecting an aldehyde having a hydrocarbon group having a boiling point of 230 ° C. or lower and a carbon number of 2 or more as the reaction solvent, the cross-linking point of the cross-linked rubber is decomposed, but the breaking of the main chain of the rubber molecule is suppressed. , The molecular weight of the recovered liquid hydrocarbon can be maintained high. This is considered to be because oxidative deterioration occurs when alcohol is used as the reaction solvent, but oxidative deterioration is unlikely to occur with aldehydes.
If the hydrocarbon group of the aldehyde has less than 2 carbon atoms, the molecular weight of the recovered liquid hydrocarbon cannot be maintained high.
The hydrocarbon group preferably has 3 to 16 carbon atoms, more preferably 4 to 14 carbon atoms, and preferably 4 to 12 carbon atoms from the viewpoint of maintaining a higher molecular weight of the recovered liquid hydrocarbon. It is more preferably to 10.

The boiling point of the reaction solvent is 230 ° C. or lower at room temperature (25 ° C.) and atmospheric pressure (0.1 MPa).
If the boiling point of the reaction solvent exceeds 230 ° C, purification becomes difficult. The lower limit of the boiling point is not particularly limited, and it is usually higher than 80 ° C. and preferably liquid at 25 ° C.
The boiling point of the reaction solvent is preferably 85 ° C. or higher, more preferably 90 ° C. or higher, further preferably 95 ° C. or higher, further preferably 100 ° C. or higher, and even 105 ° C. or higher. It is even more preferable to have. The boiling point of the reaction solvent is preferably 225 ° C. or lower, more preferably 220 ° C. or lower.

The hydrocarbon group contained in the aldehyde is not particularly limited as long as it has a boiling point of 230 ° C. or lower and has 2 or more carbon atoms, and examples thereof include an aliphatic group and an aromatic group.
The aliphatic group may be linear or branched, and may be a saturated aliphatic group or an unsaturated aliphatic group. The aliphatic group includes, for example, an ethyl group, a 1-propyl group, a 1-butyl group, a 2-butyl group, a tert-butyl group, a 1-pentyl group, a 2-methyl-1-pentyl group, a 1-hexyl group and 1 -Heptyl group, 1-octyl group, 1-nonyl group, 1-decyl group, 1-dodecyl group; vinyl group, propenyl group and the like can be mentioned.
Examples of the aromatic group include a phenyl group and a naphthyl group.
As the aldehyde having a hydrocarbon group having 2 or more carbon atoms, one kind may be used alone, or two or more kinds may be used in combination. Further, it is not particularly limited except that it has the above-mentioned hydrocarbon group, and may further have a substituent such as a halogen atom, an alkoxy, an amino group, a nitro group, a sulfonyl group and a hydroxy group. The alkyl group (R) in alkoxy (RO-) preferably has 1 to 8 carbon atoms.

Specific examples of the aldehyde having a hydrocarbon group having a boiling point of 230 ° C. or lower and a carbon number of 2 or more include an aldehyde having a propyl group (propanol), an aldehyde having a butyl group (butanal), and a pentyl group. Aldehyde having a hexyl group (hexanal), aldehyde having a heptyl group (heptanal), aldehyde having an octyl group (octanal), aldehyde having a nonyl group (nonanal), aldehyde having a decyl group (decalal) ), Aldehydes having a phenyl group (benzaldehyde, cinnamaldehyde, etc.) and the like. The side chain may have an alkyl group, and in the case of an aldehyde having a phenyl group, for example, alkyl cinnamaldehyde can be mentioned, and amyl cinnamaldehyde is particularly preferable. If there are isomers, they are included.
As the aldehyde having a boiling point of 230 ° C. or lower and having a hydrocarbon group having 2 or more carbon atoms, a solvent of each company's reagent manufacturer such as Tokyo Chemical Industry Co., Ltd. or Fujifilm Wako Pure Chemical Industries, Ltd. may be used.

The boiling point of the reaction solvent can be confirmed from the catalogs of the reagent manufacturers of each company, and can also be confirmed from various books such as "Chemical Dictionary" of Tokyo Kagaku Dojinsha and "Chemical Handbook" of Maruzen.
For example, according to the catalog of Tokyo Kasei Kogyo Co., Ltd., the boiling point of 1-hexanal is 131 ° C, the boiling point of 1-heptanal is 155 ° C, the boiling point of 1-octanal is 170 ° C, and the boiling point of 1-nonanal is 192 ° C, 1-. Decanal has a boiling point of 208 ° C. and benzaldehyde has a boiling point of 179 ° C.

Among the above, the hydrocarbon group is preferably an aliphatic group, more preferably a saturated aliphatic group, and further preferably a linear saturated aliphatic group from the viewpoint of maintaining a higher molecular weight of the recovered liquid hydrocarbon. ..
Specifically, the aldehyde having a hydrocarbon group having a boiling point of 230 ° C. or lower and having 2 or more carbon atoms is an aldehyde having a hexyl group (hexanal), an aldehyde having a heptyl group (heptanal), and an aldehyde having an octyl group. It is preferably at least one selected from the group selected from (octanal) and an aldehyde having a nonyl group (nonanal), and an aldehyde having a nonyl group (nonanal) is more preferable.

The reaction solvent may consist of an aldehyde having a boiling point of 230 ° C. or lower and having a hydrocarbon group having 2 or more carbon atoms, or may contain another solvent in addition to the aldehyde, but is a liquid hydrocarbon. From the viewpoint of increasing the decomposition rate of the aldehyde, it is preferable that the aldehyde having a hydrocarbon group having a boiling point of 230 ° C. or lower and a hydrocarbon group having 2 or more carbon atoms is the main component of the reaction solvent.
Here, the main component means that the boiling point in the reaction solvent is 230 ° C. or lower, and the content of the aldehyde having a hydrocarbon group having 2 or more carbon atoms exceeds 50% by volume, and the boiling point in the reaction solvent. The content of the aldehyde having a hydrocarbon group having 2 or more carbon atoms is preferably 70% by volume or more, more preferably 90% by volume or more, and more preferably 100% by volume or more. There may be.

In the decomposition step, the ratio (Vs / Wg) of the reaction solvent to the volume [mL] (Vs) of the reaction solvent and the mass [mg] (Wg) of the crosslinked rubber is preferably 0.001 / 1/1 to 1/1. , More preferably, it is preferably used in the range of 0.005 / 1 to 0.1 / 1.
By using the reaction solvent in the above range, the solvolysis reaction is further promoted, sufficient hydrogen atoms are supplied to the crosslinked rubber, the recombination of radicals generated by thermal decomposition is suppressed, and the crosslinked rubber is efficiently decomposed. can do.

[Reaction conditions in the decomposition process]
(temperature)
In the decomposition step, the crosslinked rubber and the reaction solvent are heated at 300 ° C. or lower.
By setting the heating temperature to 300 ° C. or lower, energy saving is excellent, and a decrease in decomposition rate due to side reactions or the like can be suppressed. The heating temperature in the decomposition step may be referred to as the decomposition temperature. By heating the crosslinked rubber at a lower temperature, the reaction involving the solvent can be prioritized and the crosslinked rubber can be decomposed. The heating temperature is preferably 150 ° C. or higher, more preferably 155 ° C. or higher, further preferably 160 ° C. or higher, further preferably 180 ° C. or higher, and further preferably 250 ° C. or lower, more preferably 240 ° C. or lower. , 230 ° C. or lower is further preferable, 220 ° C. or lower is further preferable, and 210 ° C. or lower is even more preferable.

(Disassembly time)
In the decomposition step, the time for heating the crosslinked rubber (decomposition time) is preferably 30 minutes to 20 hours, more preferably 60 minutes to 18 hours from the viewpoint of sufficiently advancing the decomposition reaction of the crosslinked rubber. .. When the crosslinked rubber does not contain a filler, the decomposition time can be 240 minutes or less, preferably 180 minutes or less.

(pressure)
In the decomposition step, the pressure applied to the crosslinked rubber and the reaction solvent is not particularly limited.
From the viewpoint of the reaction rate of the decomposition reaction of the crosslinked rubber and the viewpoint of resource saving and energy saving, it is preferably 0.1 to 2.0 MPa (G), more preferably 0.1 to 1.5 MPa (G). preferable. The unit "MPa (G)" means that the pressure is a gauge pressure.
When the pressure is 2.0 MPa (G) or less, it is difficult to reduce the molecular weight of the liquid hydrocarbon, and when it is 0.1 MPa (G) or more, the reaction solvent easily permeates the crosslinked rubber and the reaction rate is increased. Easy to raise.

(atmosphere)
The reaction atmosphere in the decomposition step of 300 ° C. or lower is not particularly limited, and the reaction may proceed in a gas atmosphere consisting of an inert gas such as argon gas or nitrogen gas (hereinafter, simply referred to as an inert gas atmosphere). , The reaction may proceed in a gas atmosphere composed of air (hereinafter, simply referred to as an air atmosphere), or the reaction may proceed in a mixed gas atmosphere of air and an inert gas. When an inert gas is used, two or more kinds of inert gases may be mixed and used.
From the viewpoint of decomposing the crosslinked rubber with a lighter facility and promoting low energy, the crosslinked rubber is preferably heated in an aerobic environment, that is, in an oxygen-containing atmosphere, and has an atmosphere of a gas containing air. It is more preferable to heat underneath, and it is further preferable to heat under an air atmosphere.

[Drying process]
The method for producing a rubber composition of the present invention preferably includes a drying step of drying a reaction product (rubber composition containing a liquid hydrocarbon) obtained in the decomposition step.
The reaction product may be blown with warm air at, for example, 100 to 150 ° C. The warm air may be air or an inert gas such as nitrogen gas.

As described above, the crosslinked rubber contains liquid hydrocarbons by heating at 300 ° C. or lower in a reaction solvent containing an aldehyde having a boiling point of 230 ° C. or lower and having a hydrocarbon group having 2 or more carbon atoms. A rubber composition is obtained. The rubber composition thus obtained may be referred to as a "decomposition-produced organic substance". The rubber composition (decomposition-produced organic substance) generally contains a liquid product containing a liquid hydrocarbon obtained by thermal decomposition of a crosslinked rubber, as well as a solid content remaining without decomposition. Further, when a waste tire is used as the crosslinked rubber, the tire usually contains a filler, so that the solid content also contains a filler.
In the case of isoprene rubber (IR), the raw rubber before vulcanization generally has a weight average molecular weight (Mw) of about 1.2 million, a number average molecular weight (Mn) of about 400,000, and a styrene-butadiene copolymer rubber. In the case of (SBR), the weight average molecular weight (Mw) is generally about 400,000 and the number average molecular weight (Mn) is about 100,000. The closer the Mw and Mn of the obtained liquid hydrocarbons are to these values, the closer the rubber having a molecular chain similar to that of the raw material rubber is obtained.
The liquid hydrocarbons Mw and Mn can be measured, for example, by gel permeation chromatography (GPC).

The liquid hydrocarbon produced by the above method can be used for regeneration of crosslinked rubber.
Further, for the regeneration of the crosslinked rubber, not only the liquid hydrocarbon alone is used as a raw material, but also the rubber composition obtained in a state where the liquid hydrocarbon and the solid content obtained in the decomposition step are mixed, that is, the rubber composition obtained in the decomposition step. The rubber composition may be used as a raw material for recycled rubber without separating the liquid hydrocarbon from the rubber.
As described above, the rubber composition obtained by the method for producing a rubber composition of the present invention is a recycled rubber that can recycle crosslinked rubber (recrosslinked rubber), and the method for producing a rubber composition of the present invention is a recycled rubber. It is a manufacturing method of. However, the rubber composition (recycled rubber) in the present invention does not include powdered rubber obtained by crushing vulcanized rubber into powder.

<Re-crosslinked rubber>
The recrosslinked rubber of the present invention is a recrosslinked rubber obtained by recrosslinking a rubber composition produced by the method for producing a rubber composition of the present invention, and the liquid hydrocarbon contained in the rubber composition is used as a rubber component. The content of the liquid hydrocarbon in the rubber component is 1 to 100% by mass.
That is, the recrosslinked rubber of the present invention is a recrosslinked product of a rubber composition containing a liquid hydrocarbon obtained by thermal decomposition of the crosslinked rubber as a rubber component, and the rubber component contains at least 1% by mass of the liquid hydrocarbon. It may be 100% by mass. The content of the liquid hydrocarbon in the rubber component may be 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more. There may be. The content of the liquid hydrocarbon in the rubber component may be 70% by mass or less, 60% by mass or less, or 50% by mass or less.

When the content of the liquid hydrocarbon in the rubber component is less than 100% by mass, the other rubber components used together with the liquid hydrocarbon are not particularly limited. In addition, other rubber components used together with liquid hydrocarbons may be referred to as pure rubber components.
The pure rubber component is the above-mentioned rubber component mentioned as the rubber component which is the raw material of the crosslinked rubber. Among them, at least one selected from the group consisting of natural rubber (NR) and synthetic diene rubber is preferable, and at least one selected from the group consisting of natural rubber, polyisoprene rubber, polybutadiene rubber and styrene-butadiene copolymer rubber. Is more preferable.

The rubber composition used as a raw material for the recrosslinked rubber of the present invention includes a filler, a vulcanizing agent, a vulcanization accelerator, a softening agent, stearic acid, an antiaging agent, and zinc oxide, in addition to a rubber component containing a liquid hydrocarbon. Etc. may be included.
As described above, the rubber composition produced by the method for producing a rubber composition of the present invention remains without decomposition in addition to the liquid product containing the liquid hydrocarbon obtained by the thermal decomposition of the crosslinked rubber. It contains solids, which may also include fillers.
The rubber composition used as a raw material for the recrosslinked rubber may contain solid content remaining without decomposition. By producing the re-crosslinked rubber by using the liquid hydrocarbon obtained by the thermal decomposition of the crosslinked rubber and the solid content remaining without decomposition, the environmental burden can be further reduced.
The conditions for recrosslinking the rubber composition produced by the method for producing a rubber composition of the present invention are not particularly limited.
The re-crosslinked rubber of the present invention may be a re-vulcanized rubber in which a rubber component containing a liquid hydrocarbon is vulcanized with a vulcanizing agent.

<Tire>
The tire of the present invention is made of the recrosslinked rubber of the present invention.
By constructing the tire by using the re-crosslinked rubber obtained by re-crosslinking the rubber composition containing the liquid hydrocarbon obtained by the thermal decomposition of the cross-linked rubber, the tire can be made into a tire having a small environmental load.
The tire may be obtained by cross-linking after molding using an uncross-linked rubber composition depending on the type and member of the tire to be applied, or may be semi-cross-linked from the uncross-linked rubber composition once through a preliminary cross-linking step or the like. After obtaining the rubber, the rubber may be used for molding, and then further cross-linked to obtain the rubber. As the gas to be filled in the tire, an inert gas such as nitrogen, argon or helium can be used in addition to normal air or air having an adjusted oxygen partial pressure.

<Rubber industrial products>
The rubber industrial product of the present invention comprises the recrosslinked rubber of the present invention.
Examples of rubber industrial products include automobile parts excluding the above tires, hose tubes, anti-vibration rubbers, conveyor belts, crawlers, cables, sealing materials, ship parts, building materials and the like. By constructing the rubber industrial product by using the recrosslinked rubber of the present invention, it can be made into an industrial product having a small environmental load.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for the purpose of exemplifying the present invention and do not limit the present invention in any way.

<Preparation of vulcanized rubber>
The following vulcanized rubber was prepared as the vulcanized rubber.
Vulcanized rubber (IR): Vulcanized rubber obtained by vulcanizing polyisoprene rubber Vulcanized rubber (SBR): Vulcanized rubber obtained by vulcanizing styrene-butadiene copolymer rubber Vulcanized rubber (vulcanized rubber) NR): Vulcanized rubber obtained by vulcanizing a rubber composition containing at least natural rubber and carbon black.

<Manufacturing of liquid hydrocarbon A>
[Example 1a]
(Disassembly process)
0.4 g of vulcanized rubber (IR) in the form of small pieces of about 1 mm and 5 mL of 1-nonanal were put into an autoclave (pressure resistant container manufactured by EYELA, trade name "HIP-30L"). The inside of the autoclave was sealed, the autoclave was placed in a heating container (manufactured by EYELA, personal organic synthesizer Chemistation, trade name "PPV-CTRL1"), and the input was heated at 200 ° C. for 2 hours in an air atmosphere. After the heating was completed, the heating container was returned to room temperature (25 ° C.) with cooling water, and the reaction product was brought to room temperature.

(Drying process)
The reaction product obtained in the decomposition step was dried using a spray-type test tube concentrator (manufactured by EYELA, trade name "MGS-3100") under the condition of nitrogen flow at 130 ° C., and the decomposition-produced organic substance of Example 1a was obtained. Got

[Examples 2a to 6a, Comparative Examples 1a to 5a]
The decomposition step and the drying step were carried out in the same manner as in Example 1a except that the reaction solvent was replaced with the solvent shown in Table 1, and the decomposition-generated organic substances of Examples 2a to 6a and Comparative Examples 1a to 5a were obtained.

<Manufacturing of liquid hydrocarbon B>
[Examples 1b to 3b]
Except for changing the heating temperature and heating time of the input material in the decomposition step of Example 1a from 200 ° C. and 2 hours to the reaction conditions shown in Table 2, the decomposition step and the drying step were carried out in the same manner, and Example 1b The decomposition product organic substance of ~ 2b was obtained.
In addition, Table 2 shows the results of Example 3b under the same conditions as in Example 1a for comparison.

<Manufacturing of liquid hydrocarbon C>
[Examples 1c to 5c]
As the vulcanized rubber, the vulcanized rubber (SBR) was used instead of the vulcanized rubber (IR), and the reaction solvent shown in Table 3 was used as the reaction solvent. The drying step was advanced to obtain the decomposition product organic substances of Examples 1c to 5c.

[Comparative Example 1c]
Except for using vulcanized rubber (SBR) instead of vulcanized rubber (IR) as the vulcanized rubber, the decomposition step and the separation step were proceeded in the same manner as in Comparative Example 1a, and the decomposition-generated organic substance of Comparative Example 1c was obtained. Obtained.

[Comparative Example 2c]
As the vulcanized rubber, the decomposition product organic substance of Comparative Example 2c was obtained in the same manner as in Comparative Example 2a except that the vulcanized rubber (SBR) was used instead of the vulcanized rubber (IR).

[Comparative Example 3c]
As the vulcanized rubber, the decomposition product organic substance of Comparative Example 3c was obtained in the same manner as in Comparative Example 3a except that the vulcanized rubber (SBR) was used instead of the vulcanized rubber (IR).

<Analysis of decomposition-generated organic matter>
The decomposition product organics obtained in Examples and Comparative Examples were dissolved in tetrahydrofuran and analyzed by gel permeation chromatography (GPC). From the analysis results, the solubilization rate and the weight average molecular weight (Mw) of the decomposition-produced organic matter were measured. In addition, a calibration curve was prepared using a solution of pure rubber components having different concentrations in tetrahydrofuran. The liquid hydrocarbon in tetrahydrofuran was quantified using a calibration curve, and the decomposition rate was calculated.

The conditions for GPC measurement are as follows.
-Column: Tosoh Corporation Manufacturing: TSKgel GMHXL
・ Eluent: Tetrahydrofuran ・ Flow rate: 1 mL / min
・ Temperature: 40 ℃
・ Detector: RI

In Table 1, the weight average molecular weight (Mw) obtained in Comparative Example 1a was set to 100.0, and the weight average molecular weights (Mw) of Examples 1a to 6a and Comparative Examples 2a to 5a were indexed. Further, the decomposition rate obtained in Comparative Example 1a was set to 100.0, and the decomposition rates of Examples 1a to 6a and Comparative Examples 2a to 5a were indexed.

In Table 2, the weight average molecular weight (Mw) obtained in Comparative Example 1a was set to 100.0, and the weight average molecular weight (Mw) of Examples 1b to 3b was indexed. Further, the decomposition rate obtained in Comparative Example 1a was set to 100.0, and the decomposition rates of Examples 1b to 3b were indexed.

In Table 3, the weight average molecular weight (Mw) obtained in Comparative Example 1c was set to 100.0, and the weight average molecular weights (Mw) of Examples 1c to 5c and Comparative Examples 2c to 3c were indexed. Further, the decomposition rate obtained in Comparative Example 1c was set to 100.0, and the decomposition rates of Examples 1c to 5c and Comparative Examples 2c to 3c were indexed.
The results are shown in Tables 1 to 3.

<Manufacturing of liquid hydrocarbon D>
[Example 1d]
In Example 1a, the vulcanized rubber (IR) was changed to the vulcanized rubber (NR); the heating time (decomposition time) of the input was changed from 2 hours to the time shown in Table 4, and the decomposition was carried out in the same manner. The process was performed. Then, purification for removing the solvent was carried out, and the drying step was advanced to obtain the decomposition product organic substance of Example 1d.

[Comparative Example 1d]
In Comparative Example 1a, the vulcanized rubber (IR) was changed to the vulcanized rubber (NR); the reaction solvent was changed from 1-heptanol to 1-octanol; the heating time (decomposition time) of the input was changed from 6 hours to the time shown in Table 4. The decomposition step and the separation step were carried out in the same manner except for the changes, respectively, to obtain the decomposition product organic substance of Comparative Example 1d.

[Comparative Example 2d]
In Comparative Example 1a, the vulcanized rubber (IR) was changed to the vulcanized rubber (NR); the reaction solvent was changed from 1-heptanol to 1-octanol; the heating time (decomposition time) of the input was changed from 6 hours to the time shown in Table 4. The decomposition step and the separation step were carried out in the same manner except for the changes, respectively, to obtain the decomposition product organic substance of Comparative Example 2d.

<Manufacturing of revulcanized rubber>
A rubber composition was prepared according to the contents shown in Table 5 and vulcanized to obtain a vulcanized rubber.

The details of the components shown in Table 5 are as follows.
NR: Natural rubber carbon black: SAF grade 6C: Anti-aging agent, N-phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Nocrack 6C"
DM: Vulcanization accelerator, di-2-benzothiazolyl disulfide, manufactured by Sanshin Kagaku Kogyo Co., Ltd., trade name "Sun Cellar DM"
NS: Vulcanization accelerator, Nt-butyl-2-benzothiadylsulfenamide, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Noxeller NS"
DPG: Vulcanization accelerator, 1,3-diphenylguanidine, manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Sun Cellar D"

<Analysis of decomposition-generated organic matter>
The produced decomposition product organic matter was analyzed by the same method as that of Example 1a, and the weight average molecular weight (Mw) and the decomposition rate were measured and shown in Table 4 as three significant figures.
The molecular weight shown in Table 4 means, for example, 271 × 10 ³ in the case of Example 1d, that is, 271,000.

<Characteristic evaluation of vulcanized rubber>
The tensile strength and loss tangent (tan δ) of each vulcanized rubber were evaluated for Comparative Examples 1e to 5e, Example 1e, and Example 2e, and are shown in Table 5.

1. 1. Tensile Strength The tensile strength of each vulcanized rubber was evaluated from the viewpoint of breaking strength (TB; Tensile strength at Break). The breaking strength was measured as the maximum tensile force required to break the vulcanized rubber by 100% elongation at room temperature (23 ° C.) ° C. based on JIS K 6251 (2017).
The obtained breaking strength value was expressed exponentially with the breaking strength value of Comparative Example 1e as 100. The larger the exponential value, the higher the breaking strength of the vulcanized rubber.

2. 2. Loss tangent (tanδ)
The loss tangent (tan δ) of each vulcanized rubber was measured using a viscoelasticity measuring device (manufactured by Leometrics) under the conditions of a temperature of 50 ° C., a strain of 10%, and a frequency of 15 Hz. The obtained value of tan δ was expressed exponentially with the reciprocal value of tan δ of Comparative Example 1e as 100. The larger the index value, the better the low heat generation of the vulcanized rubber.

As can be seen from Tables 1 to 3, in Examples, a rubber composition containing a liquid hydrocarbon having a higher molecular weight can be produced with a higher decomposition rate than in Comparative Examples.
Further, as can be seen from Table 4, the vulcanized rubber produced from the rubber composition containing the liquid hydrocarbon of the example is compared with the vulcanized rubber produced from the rubber composition containing the liquid hydrocarbon of the comparative example. It can be seen that even when 70 parts by mass was added (Example 2e), the tensile strength was maintained at a high level, and tan δ was also maintained.

Claims (11)

A rubber composition obtained by heating a crosslinked rubber at 300 ° C. or lower in a reaction solvent containing an aldehyde having a boiling point of 230 ° C. or lower and having a hydrocarbon group having 2 or more carbon atoms to obtain a rubber composition containing a liquid hydrocarbon. Manufacturing method of goods. The method for producing a rubber composition according to claim 1, wherein the hydrocarbon group has 3 to 16 carbon atoms. The method for producing a rubber composition according to claim 1 or 2, wherein the hydrocarbon group has 6 to 10 carbon atoms. The method for producing a rubber composition according to any one of claims 1 to 3, wherein the hydrocarbon group is a linear saturated aliphatic group. The method for producing a rubber composition according to any one of claims 1 to 4, wherein the aldehyde contains nonanal. The method for producing a rubber composition according to any one of claims 1 to 5, wherein the crosslinked rubber is heated at 150 to 250 ° C. The method for producing a rubber composition according to any one of claims 1 to 6, wherein the crosslinked rubber is a crosslinked product of a rubber component containing 50 to 100% by mass of a diene rubber. The method for producing a rubber composition according to any one of claims 1 to 7, wherein the crosslinked rubber contains vulcanized rubber. A recrosslinked rubber obtained by recrosslinking a rubber composition produced by the method for producing a rubber composition according to any one of claims 1 to 8, wherein the liquid hydrocarbon contained in the rubber composition is used. A recrosslinked rubber contained as a rubber component and having a content of the liquid hydrocarbon in the rubber component of 1 to 100% by mass. The tire made of the recrosslinked rubber according to claim 9. A rubber industrial product made of the recrosslinked rubber according to claim 9.