Isomerized gutta-percha elastomers, methods of making and using the same

Abstract

The application provides an isomerized eucommia elastomer and a preparation method and application thereof. The isomerized eucommia elastomer forms cis-isoprene structure in the molecular chain through self-isomerization reaction. By regulating the content of cis structure, the regulation of the regularity of the molecular chain is realized, so that the isomerized eucommia rubber no longer crystallizes at room temperature and exhibits high elasticity. Meanwhile, the suitable regularity enables the isomerized eucommia rubber to have self-reinforcing capacity and exhibit excellent mechanical strength. The application also provides a preparation method and application of the isomerized eucommia elastomer. The isomerization modification of the eucommia rubber is carried out by using a mercapto compound or a disulfide compound under the initiation of a free radical initiator. The high-performance isomerized eucommia rubber elastomer material obtained by the application does not change the original chemical structure and polarity of the eucommia rubber, has similar structure and performance to natural rubber, can make up for the problem of insufficient yield of natural rubber, and has wide application prospects in the fields of tires, conveyor belts, sealing rings, wearable devices and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of elastomer material preparation, and particularly relates to an isomerized eucommia elastomer and a preparation method and application thereof. BACKGROUND

[0002] Eucommia rubber is a bio-based polymer material, and its structural formula is trans-1,4-polyisoprene, which is an isomer of natural rubber. In the structural formula of natural rubber, two methylenes are on the same side of the double bond, and the content of cis is very high. Therefore, the molecular chain regularity of natural rubber is moderate, and the natural rubber has both high elasticity and tensile crystallization self-reinforcing ability. However, in the structural formula of eucommia rubber, two methylenes are on different sides of the double bond, and the regularity is better than that of natural rubber. This makes eucommia rubber easily crystallize at room temperature, and eucommia rubber behaves as a hard plastic, which cannot be directly used as an elastomer material.

[0003] Natural rubber has excellent comprehensive performance and plays an extremely important role in the rubber industry. However, the production of natural rubber is very limited and mainly relies on imports. Therefore, it is of great significance to develop a second natural rubber with excellent performance. Eucommia resources are abundant in China, and the planting area is wide. Eucommia rubber is similar in structure to natural rubber, and is expected to be used as a second natural rubber. However, eucommia rubber cannot be directly used as an elastomer because of its room temperature crystallization. Chemical modification must be performed to exhibit high elasticity. Patent CN108102034A discloses a preparation method of a graft copolymer of trans-1,4-polyisoprene grafted with cis-1,4-polyisoprene. By copolymerization, cis-isoprene structure is introduced into the molecular chain of eucommia rubber, thereby improving its elasticity. However, this method has complicated steps, low controllability, and large molecular weight, which greatly affects the performance of eucommia rubber itself. Therefore, modifying the molecular chain of eucommia rubber itself to reduce the crystallinity is an effective way.

[0004] At present, there are many methods for directly chemically modifying the molecular weight of eucommia rubber to prepare eucommia rubber elastomer materials. For example, patent CN110615901A provides a self-crosslinking shape memory eucommia rubber composite material and its preparation method and application. The carbon-carbon double bond of eucommia rubber is subjected to epoxidation reaction by using peroxide to obtain an epoxy eucommia rubber elastomer. CN110183551A provides a bio-based oil-resistant eucommia ester elastomer and its preparation method. Hydroxyl and ester groups are introduced into the molecular chain of eucommia rubber by ring-opening reaction to prepare a eucommia ester elastomer. CN110272510A provides a bio-based high-damping cyclized eucommia rubber and its preparation method and application. The carbon-carbon double bond of eucommia rubber is subjected to cyclization modification by using a halogenated catalyst to prepare a cyclized eucommia rubber elastomer material. However, the regularity of the molecular chain of eucommia rubber obtained by these modification methods is poor, and the eucommia rubber does not have self-reinforcing ability and has poor mechanical properties. Moreover, the modification process changes the chemical structure and polarity of eucommia rubber, which is not conducive to the use of eucommia rubber as a second natural rubber.

[0005] Therefore, how to transform eucommia rubber into elastomer without changing the chemical structure and polarity of eucommia rubber still faces challenges. SUMMARY

[0006] The present application aims to provide an isomerized eucommia elastomer and a preparation method and application thereof, by isomerization reaction of the molecular chain of eucommia rubber, the content of cis structure is increased, so that the crystallinity is regulated, and the eucommia rubber elastomer is endowed with high elasticity, self-reinforcing performance and other performances.

[0007] To achieve the above-mentioned purpose, the present application provides an isomerized eucommia elastomer, which forms cis-isoprene structure in the molecular chain through isomerization reaction. The present application breaks the inherent thinking of cyclization, grafting or copolymerization reaction in the prior art, regulates the content of cis structure in the molecular chain of eucommia rubber through isomerization reaction, and thus the preparation method is simple without introducing new raw materials and groups. Therefore, the high-performance isomerized eucommia rubber elastomer obtained has the same chemical structure and polarity as eucommia rubber, and has excellent elasticity and self-reinforcing performance, thereby providing a new idea for the preparation of high-performance eucommia rubber elastomer.

[0008] Further, the methyl characteristic peak of the cis-isoprene structure at 1.68 ppm in the nuclear magnetic hydrogen spectrum.

[0009] Further, the content of the cis-isoprene structure is 5mol%-40mol%, preferably 5mol%-20mol% or 20mol%-40mol%, preferably 6mol%-18mol%; more preferably 8mol%-20mol%, and more preferably 10mol%-20mol%. Research shows that within this range, the elasticity and mechanical properties of the obtained isomerized eucommia elastomer are better. In practical applications, the content of the cis-isoprene structure can be regulated according to the requirements of elasticity and strength, and is not limited thereto. The present application focuses on providing an effective way for the regulation of the crystallinity of eucommia rubber, and different eucommia rubber materials with different properties can be obtained by regulating the isomerization degree. For example, when the content of cis structure is higher, the mechanical properties are poor, but the elasticity is excellent, and it can be used in related fields with low strength requirements.

[0010] The present application also provides a preparation method of the isomerized eucommia elastomer, which comprises: dissolving eucommia rubber in an organic solvent to obtain a glue solution, and then performing isomerization reaction under the action of a catalyst and an initiator to obtain the isomerized eucommia elastomer. Specifically, after the reaction is completed, the isomerized eucommia elastomer is obtained by precipitation, washing and drying. Through isomerization reaction, the eucommia rubber no longer crystallizes at room temperature, and exhibits high elasticity; at the same time, it has self-reinforcing ability and exhibits excellent mechanical strength.

[0011] Further, the catalyst comprises one or more of mercapto compounds or disulfide compounds; the initiator is a free radical initiator; the catalyst is used in an amount of 1%-500% of the mass of the eucommia ulmoid gum, preferably 10%-100%; the initiator is used in an amount of 0.1%-5% of the mass of the eucommia ulmoid gum, preferably 0.5%-3%. Studies show that the preferred amount is easy to control, less side reactions, and no gel is produced. The present application uses mercapto compounds or disulfide compounds to isomerize and modify the eucommia ulmoid gum under the initiation of a free radical initiator, and reasonably controls the content of cis structure, realizes the regulation of the regularity of the molecular chain of the eucommia ulmoid gum without changing the chemical structure and polarity of the eucommia ulmoid gum, so that the eucommia ulmoid gum has excellent elasticity and self-reinforcing performance, and a high-performance isomerized eucommia elastomer comparable to natural rubber is obtained.

[0012] Further, the mercapto compounds comprise one or more of 4,6-diamino-2-mercapto pyrimidine, 4,5-diamino-6-hydroxy-2-mercapto pyrimidine, 2-(acetylamino)-3-mercapto propionamide, 1,4-butanediol di(mercaptoacetate), pentaerythritol tetra-mercaptoacetate, di(2-mercaptoethyl) adipate, 2-mercapto-octadecyl acetate, n-dodecyl mercaptan, thioglycerol, mercaptoacetic acid, mercaptoacetic acid methyl ester, mercaptoacetic acid ethyl ester, mercapto propionic acid, N-phenyl-3-mercapto propionamide, [4,5-dimethyl-2-(mercapto methyl) phenyl] methyl mercaptan, cyclohexyl 3-mercapto propionate, 2-(mercapto methyl) pentane diacid, 3-mercapto propionic acid, 1-mercapto-propan-2-ol, thiophenol, 1,3-propanedithiol, or the like; the disulfide compounds comprise one or more of 4,4'-dinitro diphenyl disulfide, 3,3'-dithio di-propionamide, 4,4'-[dithio bis(methylene)] di-pyridine, 8,8'-dithio di-octanoic acid, or the like. Preferably, the catalyst is one or more of n-dodecyl mercaptan, thioglycerol, mercaptoacetic acid, mercaptoacetic acid methyl ester, mercaptoacetic acid ethyl ester, mercapto propionic acid, which is cheaper and easier to obtain than other catalysts.

[0013] Further, the free radical initiator comprises one or more of azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobis isobutyrate, ammonium persulfate, potassium persulfate, benzoyl peroxide, t-butyl benzoyl peroxide, methyl ethyl ketone peroxide, benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone, tetramethyl Michler's ketone, tetraethyl Michler's ketone, methyl ethyl Michler's ketone, or the like.

[0014] Further, when the free radical initiator is a thermal initiator, the isomerization reaction is carried out at 60-100°C for 1-10h; when the free radical initiator is a photo initiator, the isomerization reaction is carried out under ultraviolet light for 10-300 minutes. Preferably, the reaction is carried out under 360nm ultraviolet light.

[0015] Furthermore, the organic solvent includes one or more of toluene, xylene, chlorobenzene, n-hexane, tetrahydrofuran, petroleum ether, and chloroform; and the mass concentration of eucommia gum in the glue solution is 0.1%-10%, preferably 1%-8%. When the glue solution concentration is controlled within this range, the glue solution viscosity is moderate, which is more conducive to the isomerization reaction.

[0016] The present invention also provides an application of an isomerized eucommia elastomer, wherein the isomerized eucommia elastomer is used for the preparation of tires, conveyor belts, sealing rings, and wearable devices.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The isomerized eucommia elastomer provided by the present invention increases the cis-structure content of eucommia gum by subjecting the eucommia gum molecular chain to a self-isomerization reaction, thereby regulating its crystallinity and obtaining eucommia gum elastomers with different properties. This invention does not require the introduction of new raw materials and groups, and therefore the chemical structure and polarity of the isomerized eucommia gum elastomer are the same as those of eucommia gum, providing a new approach for the preparation of high-performance eucommia gum elastomers.

[0019] 2. The present invention regulates the content of cis structure by regulating the degree of isomerization of eucommia gum, thereby obtaining an eucommia gum elastomer with both high elasticity and self-reinforcement properties. It is expected to replace natural rubber and has broad application prospects in the fields of tires, conveyor belts, sealing rings, wearable devices, etc.

[0020] 3. The present invention utilizes thiol or disulfide compounds to isomerize eucommia gum under the influence of a free radical initiator, and rationally regulates the cis-structure content. This allows for the regulation of the molecular chain regularity of eucommia gum without changing its chemical structure or polarity. This preparation method is simple and novel, highly controllable and operable, and is readily applicable to industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the isomerized eucommia gum elastomer prepared in Example 1 ( 1 H NMR);

[0023] Figure 2 1 is the stress-strain curve of the isomerized eucommia elastomer and natural rubber prepared in Example 2;

[0024] Figure 3 Tensile recovery curves of the isomerized eucommia elastomer prepared in Example 2 and natural rubber. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0026] The present application regulates the crystallinity of eucommia rubber by isomerization of the eucommia rubber itself, and obtains eucommia rubber elastomers with different properties. The high-elasticity and high-self-reinforcement eucommia rubber elastomers are mainly described below, but are not limited thereto.

[0027] Example 1

[0028] The preparation method of the high-performance isomerized eucommia rubber elastomer provided in the present embodiment comprises:

[0029] 10 g of eucommia rubber was dissolved in an organic solvent toluene to prepare a 3% solution, 3 g of n-dodecyl mercaptan, 200 mg of benzophenone were added, and the reaction was carried out under 360 nm ultraviolet light for 120 minutes. The high-performance isomerized eucommia rubber elastomer was obtained by ethanol precipitation, washing and drying.

[0030] The obtained eucommia rubber was characterized, and the results are shown in Figure 1 After modification, the methyl characteristic peak of the cis-isoprene structure at 1.68 ppm appeared. The content of the cis structure in the elastomer obtained in the present embodiment was 11.3 mol%.

[0031] Example 2

[0032] The preparation method of the high-performance isomerized eucommia rubber elastomer provided in Example 2 comprises:

[0033] 10 g of eucommia rubber was dissolved in an organic solvent toluene to prepare a 3% solution, 3 g of n-dodecyl mercaptan, 200 mg of benzophenone were added, and the reaction was carried out under 360 nm ultraviolet light for 120 minutes. The high-performance isomerized eucommia rubber elastomer was obtained by ethanol precipitation, washing and drying.

[0034] The obtained elastomer has a methyl characteristic peak of the cis-isoprene structure at 1.68 ppm, and the content of the cis structure is 12.6 mol%.

[0035] Effect verification:

[0036] To compare the performance of the high performance isomerized gutta-percha obtained in Example 2 with that of natural rubber, the two rubbers were vulcanized according to the following formulation:

[0037] Zinc oxide 5 parts, stearic acid 2 parts, accelerator D 0.5 part, accelerator CZ 0.5 part, antioxidant 4010 1 part, sulfur 1 part;

[0038] The vulcanization time was the positive vulcanization time (t 90 ) determined by a vulcanization instrument, and the vulcanization pressure was 15 MPa.

[0039] The results were as follows:

[0040] As shown in Table 1, the high performance isomerized gutta-percha obtained in Example 2 had a tensile strength of 15.5 MPa and an elongation at break of 1370%, which were comparable to those of natural rubber. Figure 2 As shown in Table 2, the high performance gutta-percha obtained in Example 2 had a strain recovery rate of 97% after being stretched to 300% and then stress was removed, which was comparable to that of natural rubber.

[0041] Figure 3 As shown in Table 2, the high performance gutta-percha obtained in Example 2 had a strain recovery rate of 97% after being stretched to 300% and then stress was removed, which was comparable to that of natural rubber.

[0042] Example 3

[0043] The method for preparing the high performance isomerized gutta-percha elastomer provided in Example 3 comprises:

[0044] 10 g of gutta-percha was dissolved in an organic solvent dimethylbenzene to form a 2% solution, 2 g of methyl mercaptoacetate and 100 mg of azobisisoheptyl nitrile were added, and the mixture was reacted at 70°C for 5 h. The high performance isomerized gutta-percha was obtained by precipitation with ethanol, washing, and drying.

[0045] The obtained elastomer had a methyl characteristic peak of cis-isoprene structure at 1.68 ppm, and the content of cis structure was 13.1 mol%.

[0046] Example 4

[0047] The method for preparing the high performance isomerized gutta-percha elastomer provided in Example 4 comprises:

[0048] 10 g of gutta-percha was dissolved in an organic solvent dimethylbenzene to form a 2% solution, 2 g of methyl mercaptoacetate and 100 mg of azobisisoheptyl nitrile were added, and the mixture was reacted at 70°C for 5 h. The high performance isomerized gutta-percha was obtained by precipitation with ethanol, washing, and drying.

[0049] The obtained elastomer had a methyl characteristic peak of cis-isoprene structure at 1.68 ppm, and the content of cis structure was 13.1 mol%.

[0050] Example 5

[0051] ​The preparation method of the high-performance isomerized eucommia gum elastomer provided in Example 5 comprises:

[0052] 10g of Eucommia gum was dissolved in organic solvent petroleum ether to prepare a 5% solution, 6g of thioglycerol and 200mg of tetramethyl Michler's ketone were added, and the mixture was reacted under 360nm ultraviolet light for 60 minutes. The mixture was precipitated with ethanol, washed and dried to obtain high-performance isomerized Eucommia gum.

[0053] The obtained elastomer had a characteristic peak of methyl group of cis-isoprene structure at 1.68 ppm, and the content of cis structure was 15.1 mol%.

[0054] Example 6

[0055] The preparation method of the high-performance isomerized eucommia gum elastomer provided in Example 6 comprises:

[0056] 10g of eucommia gum is dissolved in an organic solvent, n-hexane, to prepare a 3.5% solution, 10g of n-dodecanethiol and 100mg of tetramethyl Michler's ketone are added, and the mixture is reacted under 360nm ultraviolet light for 90 minutes. The mixture is precipitated with ethanol, washed, and dried to obtain high-performance eucommia gum.

[0057] The obtained elastomer had a characteristic peak of methyl group of cis-isoprene structure at 1.68 ppm, and the content of cis structure was 16.6 mol%.

[0058] Comparative Example 1

[0059] This comparative example provides a method for modifying eucommia gum, which differs from Example 2 in that the reaction time is 30 minutes.

[0060] The obtained elastomer had a characteristic peak of methyl group of cis-isoprene structure at 1.68 ppm, and the content of cis structure was 5.6 mol%.

[0061] Comparative Example 2

[0062] This comparative example provides a method for modifying Eucommia gum, which differs from Example 2 in that the reaction time is 360 minutes.

[0063] The obtained elastomer had a characteristic peak of methyl group of cis-isoprene structure at 1.68 ppm, and the content of cis structure was 25.3 mol%.

[0064] Effect test:

[0065] The isomerized eucommia gum obtained in Examples 1-6 and Comparative Examples 1-2 was tested using the testing method described in Example 2. The results are shown in Table 1.

[0066] Table 1 Mechanical properties of isomerized eucommia gum elastomer vulcanizates prepared in Examples 1-6 and Comparative Examples 1-2

[0067]

[0068]

[0069] 1. According to the results in Table 1, the isomerized eucommia elastomers obtained in Examples 1-6 have both high elasticity and self-reinforcing properties, and are closer to natural rubber.

[0070] 2. Although the reaction conditions in Comparative Example 1 are the same as those in Example 2, the reaction time is too short, the content of cis structure is low, and the material will still crystallize at room temperature, so the elastic recovery is only 55%.

[0071] 3. Although the reaction conditions in Comparative Example 2 are the same as those in Example 2, the reaction time is too long, the content of cis structure is too high, the regularity of the molecular chain is poor, and the material does not have self-reinforcing ability, so the tensile strength is only 2.3 MPa.

[0072] The above examples and comparative examples can show that the method of the present application can isomerize eucommia rubber to different degrees, and the isomerization degree can be controlled by adjusting the reaction time. The isomerization degree is closely related to the properties of eucommia rubber. When it is needed for other applications, a eucommia rubber elastomer with a higher isomerization degree can be obtained, for example, when the content of cis structure continues to increase in Comparative Example 2, the elastic recovery rate is still high, and the strength and elongation at break decrease. Such a material can be suitable for other applications in fields where strength is not required, and still falls within the scope of the present application.

[0073] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing an isomerized Eucommia ulmoides elastomer, characterized in that: include: Dissolving eucommia gum in an organic solvent to obtain a glue solution, and then performing an isomerization reaction under the action of a catalyst and an initiator to obtain the isomerized eucommia elastomer, wherein the isomerized eucommia elastomer forms a cis-isoprene structure in its molecular chain through a self-isomerization reaction; The catalyst is a thiol compound; the initiator is a free radical initiator; the amount of the catalyst is 10%-100% of the mass of the eucommia gum; the amount of the initiator is 0.5%-3% of the mass of the eucommia gum; The content of the cis-isoprene structure is 10 mol%-20 mol%; The chemical structure and polarity of the obtained isomerized eucommia elastomer are the same as those of eucommia gum.

2. The method for preparing the isomerized Eucommia ulmoides elastomer according to claim 1, wherein: The thiol compounds include one or more of 4,6-diamino-2-mercaptopyrimidine, 4,5-diamino-6-hydroxy-2-mercaptopyrimidine, 2-(acetylamino)-3-mercaptopropionamide, 1,4-butanediol di(mercaptoacetate), pentaerythritol tetramercaptoacetate, di(2-mercaptoethyl) adipate, 2-mercapto-octadecyl acetate, n-dodecyl mercaptan, thioglycerol, mercaptoacetic acid, methyl mercaptoacetate, ethyl mercaptoacetate, mercaptopropionic acid, N-phenyl-3-mercaptopropionamide, [4,5-dimethyl-2-(mercaptomethyl)phenyl]methanethiol, cyclohexyl 3-mercaptopropionate, 2-(mercaptomethyl)pentanediolic acid, 3-mercaptopropionic acid, 1-mercaptoprop-2-ol, thiophenol, and 1,3-propanediol.

3. The method for preparing the isomerized Eucommia ulmoides elastomer according to claim 1, wherein: The free radical initiator includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, ammonium persulfate, potassium persulfate, benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, tetramethyl Michler's ketone, tetraethyl Michler's ketone, and methyl ethyl Michler's ketone.

4. The method for preparing the isomerized Eucommia ulmoides elastomer according to claim 3, wherein: When the free radical initiator is a thermal initiator, the isomerization reaction is carried out at 60° C.-100° C. for 1-10 hours; when the free radical initiator is a photoinitiator, the isomerization reaction is carried out under ultraviolet light for 10-300 minutes.

5. The method for preparing the isomerized Eucommia ulmoides elastomer according to any one of claims 1 to 4, characterized in that: The organic solvent includes one or more of toluene, xylene, chlorobenzene, n-hexane, tetrahydrofuran, petroleum ether, and chloroform; and the mass concentration of eucommia gum in the glue solution is 0.1%-10%.

6. The method for preparing the isomerized Eucommia ulmoides elastomer according to claim 5, characterized in that: The mass concentration of Eucommia gum in the glue solution is 1%-8%.

7. An isomerized Eucommia ulmoides elastomer, characterized in that: The isomerized eucommia elastomer is prepared by the preparation method according to any one of claims 1 to 6. The isomerized eucommia elastomer forms a cis-isoprene structure in its molecular chain through a self-isomerization reaction.

8. The isomerized Eucommia ulmoides elastomer according to claim 7, characterized in that There is a characteristic peak of methyl group of cis-isoprene structure at 1.68 ppm in the H NMR spectrum.

9. An isomerized Eucommia ulmoides elastomer prepared by the preparation method of the isomerized Eucommia ulmoides elastomer according to any one of claims 1 to 6 or a use of the isomerized Eucommia ulmoides elastomer according to any one of claims 7 to 8, characterized in that: The isomerized eucommia elastomer is used for the preparation of tires, conveyor belts, sealing rings and wearable devices.

Images