Method for preparing degradable rubber by taking liquid rubber as raw material

Abstract

The invention discloses a method for preparing degradable rubber by taking liquid rubber as a raw material, which is characterized in that hydroxyl-terminated liquid rubber and / or carboxyl-terminated liquid rubber are / is taken as the raw material, and the degradable rubber is prepared through polycondensation and transesterification. The synthesized rubber has excellent mechanical properties and degradation and recycling properties, and has important significance for realizing green synthesis and economic circulation of rubber.

Description

Technical Field

[0001] The invention relates to the technical field of degradable materials and rubber synthesis, and in particular to a method for preparing degradable rubber using liquid rubber as a raw material. Background Art

[0002] Rubber products are made of natural or synthetic rubber as raw materials, with some additives such as vulcanizers, vulcanization accelerators, antioxidants, reinforcing fillers, etc., and are processed. At present, the output of synthetic rubber has far exceeded that of natural rubber, among which styrene-butadiene rubber has the largest output. Rubber products are widely used in people's production and life, and with the continuous development of my country's industry, agriculture, transportation, oil extraction and other fields, its demand is increasing. However, the pollution problem of waste rubber comes with it. Since nitrile rubber, butadiene rubber, styrene-butadiene rubber, etc. are not degradable, the "black pollution" problem caused by waste rubber is becoming more and more serious. Therefore, the recycling of waste rubber and the development of degradable rubber are of great significance.

[0003] There are several common methods for the biodegradable modification of rubber: one is to add decomposition promoters such as PGA and glycolide to the rubber matrix, but the rubber residues promoted by the decomposition promoter are large, which is not conducive to subsequent recycling and reuse, and will also lead to a decrease in the mechanical properties of the rubber composite material. The second is to construct dynamic reversible covalent bonds between rubbers for cross-linking, and then to achieve recycling and degradation by removing the cross-linking under specific conditions. The degradation conditions of this method are harsh and will also lead to a decrease in the mechanical properties of the rubber composite material. The third is to use small molecular bio-based dibasic acids and diols to copolymerize in different ratios to obtain degradable polyester rubber to replace traditional rubber, but this method has a single raw material and it is difficult to find a suitable ratio. Summary of the invention

[0004] In order to overcome the problems of poor degradation and recycling ability, great difficulty in degradation, and great differences in mechanical properties between the existing biodegradable rubber and traditional rubber, the present invention provides a method for preparing biodegradable rubber using liquid rubber as raw material, by periodically introducing ester bonds on the rubber main chain and utilizing the inherent hydrolyzability of the ester bonds to give it multiple decomposition pathways, and to enable the biodegradable rubber to have better mechanical properties.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] The present invention first discloses a method for preparing degradable rubber using liquid rubber as raw material, comprising the following steps:

[0007] Step 1, uniformly mixing the hydroxyl-terminated liquid rubber and the dibasic acid, adding a catalyst, heating and stirring the reaction under an argon atmosphere, cooling to room temperature, and obtaining a carboxyl-terminated rubber; or uniformly mixing the carboxyl-terminated liquid rubber and the diol, adding a catalyst, heating and stirring the reaction under an argon atmosphere, cooling to room temperature, and obtaining a hydroxyl-terminated rubber;

[0008] Step 2: Add the catalyst again to the carboxyl-terminated rubber or hydroxyl-terminated rubber obtained in step 1, and heat and stir the reaction under vacuum conditions to obtain the degradable rubber.

[0009] Furthermore, the molecular weight of the hydroxyl-terminated liquid rubber or the carboxyl-terminated liquid rubber is in the range of 400-10,000.

[0010] Furthermore: the dibasic acid is selected from one of substituted or unsubstituted aliphatic dibasic acid with 2-10 carbon atoms, 2,5-furandicarboxylic acid and terminal carboxyl liquid rubber; the diol is selected from one of substituted or unsubstituted aliphatic diol with 2-10 carbon atoms, 2,5-furan dimethanol, polylactic acid diol and terminal hydroxyl liquid rubber.

[0011] Furthermore, the catalyst is a mixture of one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, antimony trioxide, antimony glycolate, antimony acetate, stannous octoate, stannous chloride and stannous oxide in any proportion.

[0012] Further: in step 1, the molar ratio of the hydroxyl-terminated liquid rubber to the dibasic acid is 1:1-1.5, and the molar ratio of the carboxyl-terminated liquid rubber to the diol is 1:1-1.5; the amount of the catalyst added in step 1 is 1×10 of the molar amount of the hydroxyl-terminated liquid rubber or the carboxyl-terminated liquid rubber raw material. -4 -5×10 -4 The amount of catalyst added in step 2 is 0.5×10 of the molar amount of the hydroxyl-terminated liquid rubber or carboxyl-terminated liquid rubber raw material. -4 -2.5×10 -4 The molar amount of the hydroxyl-terminated liquid rubber or the carboxyl-terminated liquid rubber is measured by the ratio of its weight to its molar mass.

[0013] Further: In step 1, the method of heating and stirring the reaction is: adjusting the heating rate so that the reaction system gradually heats up to 150-180°C in 1.5-2.5h, and keeping the temperature for 8-12h. In step 2, the method of heating and stirring the reaction is: adjusting the heating rate so that the reaction system gradually heats up to 200-230°C in 1.5-2.5h, and keeping the temperature for 4-6h. By controlling the heating rate, the internal exothermic reaction can be avoided from being too intense, thereby avoiding the product cross-linking caused by the reaction of the double bond groups in the rubber with the catalyst.

[0014] The general structural formula of the degradable rubber prepared according to the above preparation method can be expressed as:

[0015]

[0016] Among them: R1 comes from the raw material terminal hydroxyl liquid rubber or diol, and R2 comes from the raw material terminal carboxyl liquid rubber or dibasic acid.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. The present invention utilizes macromolecular hydroxyl-terminated liquid rubber and / or carboxyl-terminated liquid rubber to prepare degradable rubber, and a rich variety of raw materials are available. For example, the hydroxyl-terminated liquid rubber can be selected from hydroxyl-terminated cis-1,1-butadiene rubber, hydroxyl-terminated nitrile rubber, hydroxyl-terminated natural rubber or hydroxyl-terminated styrene-butadiene rubber, and the carboxyl-terminated liquid rubber can be selected from carboxyl-terminated cis-1,1-butadiene rubber, carboxyl-terminated nitrile rubber, carboxyl-terminated natural rubber or carboxyl-terminated styrene-butadiene rubber. Different types of liquid rubbers can be used to prepare degradable rubbers with various block structures, so that the performance of the obtained rubber has a wide adjustable range and a wide range of applications.

[0019] 2. The mechanical properties of the degradable rubber synthesized by the present invention are similar to those of traditional rubber, and it has good degradation and recycling performance. Degradation can be achieved by adding the rubber to an alkaline or acidic mixed system of water and alcohol (such as methanol or ethanol) and heating it, and the small molecules obtained by degradation can be used sustainably. Therefore, the degradable rubber prepared by the present invention is a green and sustainable polymer, which is of great significance to the realization of green synthesis and economic circulation of rubber. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is the NMR image of the degradable polyester rubber prepared in Example 1 of the present invention;

[0022] Figure 2 This is an infrared image of the degradable polyester rubber prepared in Example 1 of the present invention;

[0023] Figure 3 This is the NMR image of the degradable polyester rubber prepared in Example 2 of the present invention;

[0024] Figure 4 This is an infrared image of the degradable polyester rubber prepared in Example 2 of the present invention;

[0025] Figure 5 This is the NMR image of the degradation product of the degradable polyester rubber obtained in Example 2 of the present invention;

[0026] Figure 6 This is an infrared image of the degradation product of the degradable polyester rubber prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] The technical scheme of the present invention is described in detail below through specific examples. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0028] Example 1

[0029] This embodiment prepares the degradable rubber according to the following steps:

[0030] (1) Add hydroxy-terminated nitrile rubber (8.0 g, 6 mmol, 1350 g / mol) and succinic acid (1.1 g, 9 mmol) to a three-necked reaction bottle, and add tetraisopropyl titanate (170 μg, 0.6 μmol). Install a stirrer at the middle port and 90° exhaust joints at the two side ports. Replace the atmosphere in the bottle with argon. Keep flowing argon through the three-necked bottle, place the reaction bottle in a sand bath, slowly heat it to 150°C (total heating time 2 h), keep it warm for 10 hours, and then cool it to room temperature to obtain a yellow low molecular weight carboxyl-terminated rubber product.

[0031] (2) Add low molecular weight carboxyl-terminated rubber (5 g) to a three-necked reaction bottle, and add tetraisopropyl titanate (100 μg, 0.35 μmol). Install a stirrer at the middle port and 90° exhaust joints at the two side ports. Replace the atmosphere in the bottle with argon. Place the reaction bottle in a sand bath, slowly heat it up, and start vacuuming when the temperature reaches 100°C until the temperature stabilizes at 200°C (total heating time 2h). Continue vacuuming for 5 hours to obtain a light yellow biodegradable rubber. The product structure is shown below:

[0032]

[0033] Figure 1 and Figure 2 The following are the NMR and IR spectra of the biodegradable polyester rubber. In the NMR spectrum, a new signal peak appears at a chemical shift of 4.10 ppm, representing the methylene signal connected to the ester group in the product, indicating the presence of the ester group and the successful synthesis of the product. In the IR spectrum, a new signal peak appears at 1735 cm -1 A strong signal peak appears, which is the signal peak of the C=O double bond in the ester group, once again proving that the product was successfully synthesized.

[0034] Example 2

[0035] This embodiment prepares the degradable rubber according to the following steps:

[0036] (1) Add carboxyl-terminated nitrile rubber (5.0 g, 1.5 mmol, 3250 g / mol) and 1,5-pentanediol (0.234 g, 2.25 mmol) to a three-necked reaction bottle, and add tetraisopropyl titanate (4.26 mg, 0.15 μmol). Install a stirrer at the middle port and 90° exhaust joints at the two side ports. Replace the atmosphere in the bottle with argon. Keep flowing argon through the three-necked bottle, place the reaction bottle in a sand bath, slowly heat it to 150°C (total heating time 2 h), keep it warm for 10 hours, and then cool it to room temperature to obtain a yellow low molecular weight hydroxyl-terminated rubber product.

[0037] (2) Add low molecular weight hydroxyl-terminated rubber (5 g) to a three-necked reaction bottle, and add tetraisopropyl titanate (2.13 mg, 0.075 μmol). Install a stirrer in the middle port and 90° exhaust joints on both sides. Replace the atmosphere in the bottle with argon. Place the reaction bottle in a sand bath, slowly heat it up, and start vacuuming when the temperature reaches 100°C until the temperature stabilizes at 200°C (total heating time 2h), and continue vacuuming for 5 hours. Finally, a light yellow biodegradable rubber is obtained. The product structure is shown below:

[0038]

[0039] Figure 3 and Figure 4 The following are the NMR and IR spectra of the biodegradable polyester rubber. In the NMR spectrum, a new signal peak appears at the chemical shift of 4.09 ppm, representing the methylene signal connected to the ester group in the product, indicating the presence of the ester group and the successful synthesis of the product. In the IR spectrum, a new signal peak appears at 1735 cm -1 A strong signal peak appears, which is the signal peak of the C=O double bond in the ester group, once again proving that the product was successfully synthesized.

[0040] (3) The obtained degradable rubber (0.5 g) was added to a 150 mL thick-walled pressure-resistant bottle, 50 mL of a mixed solution of ethanol and water (ethanol: water = 49:1) was added, and then 2.5 g of potassium hydroxide was added, and the mixture was placed in an oil bath at 80° C. and heated and stirred for 4 hours. After 4 hours, the mixture was cooled to room temperature, the upper clear layer was aspirated, the precipitated potassium hydroxide was removed, the supernatant was dried by rotary evaporation, and the dried product was subjected to NMR and IR spectrum measurement. Figure 5 and Figure 6 The following are the NMR spectrum and IR spectrum of the degradable polyester rubber after degradation. Figure 3 contrast, Figure 5In the NMR spectrum, the signal peak at the chemical shift of 4.09 ppm disappeared. This signal peak represents the methylene signal connected to the ester group in the product. Its disappearance indicates the disappearance of the ester group and the successful degradation of the degradable rubber. Figure 6 In the infrared spectrum of the degradable rubber before degradation, the infrared -1 A strong signal peak appears, which is the signal peak of the C=O double bond in the ester group. The signal peak disappears after degradation, indicating that the ester group disappears, proving that the ester bond of the degradable rubber is broken and the degradation is successful.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing degradable rubber using liquid rubber as raw material, characterized in that: The steps include: Step 1, uniformly mixing the hydroxyl-terminated liquid rubber and the dibasic acid, adding a catalyst, heating and stirring the reaction under an argon atmosphere, cooling to room temperature, and obtaining a carboxyl-terminated rubber; or uniformly mixing the carboxyl-terminated liquid rubber and the diol, adding a catalyst, heating and stirring the reaction under an argon atmosphere, cooling to room temperature, and obtaining a hydroxyl-terminated rubber; Step 2: Add the catalyst again to the carboxyl-terminated rubber or hydroxyl-terminated rubber obtained in step 1, and heat and stir the reaction under vacuum conditions to obtain the degradable rubber.

2. The method according to claim 1, characterized in that: The molecular weight of the hydroxyl-terminated liquid rubber or the carboxyl-terminated liquid rubber is in the range of 400-10,000.

3. The method according to claim 1, characterized in that: The dibasic acid is selected from one of substituted or unsubstituted aliphatic dibasic acid with 2-10 carbon atoms, 2,5-furandicarboxylic acid and carboxyl-terminated liquid rubber; the diol is selected from one of substituted or unsubstituted aliphatic diol with 2-10 carbon atoms, 2,5-furan dimethanol, polylactic acid diol and hydroxyl-terminated liquid rubber.

4. The method according to claim 1, characterized in that: The catalyst is a mixture of one or more of tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, antimony trioxide, antimony glycolate, antimony acetate, stannous octoate, stannous chloride and stannous oxide in any proportion.

5. The method according to claim 1, characterized in that: In step 1, the molar ratio of the hydroxyl-terminated liquid rubber to the dibasic acid is 1:1-1.5, and the molar ratio of the carboxyl-terminated liquid rubber to the diol is 1:1-1.

5.

6. The method according to claim 1, characterized in that The amount of catalyst added in step 1 is 1×10 of the molar amount of the hydroxyl-terminated liquid rubber or carboxyl-terminated liquid rubber raw material. -4 -5×10 -4 The amount of catalyst added in step 2 is 0.5×10 of the molar amount of the hydroxyl-terminated liquid rubber or carboxyl-terminated liquid rubber raw material. -4 -2.5×10 -4 .

7. The method according to claim 1, characterized in that In step 1, the method of heating and stirring the reaction is: adjusting the heating rate so that the reaction system is gradually heated to 150-180° C. in 1.5-2.5 hours, and the reaction is kept warm for 8-12 hours.

8. The method according to claim 1, characterized in that In step 2, the method of heating and stirring the reaction is: adjusting the heating rate so that the reaction system is gradually heated to 200-230° C. in 1.5-2.5 hours, and the reaction is kept warm for 4-6 hours.

9. A degradable rubber obtained by the preparation method according to any one of claims 1 to 8.

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