Hydroxyl-containing bio-based ethylene propylene rubber and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to hydroxyl-containing bio-based ethylene propylene rubber and a preparation method thereof. The hydroxyl-containing bio-based ethylene propylene rubber comprises the following three blocks: # imgabs 0 #, # imgabs 1 # and # imgabs 2 #; x is equal to 1-500, y is equal to 1-500, and z is equal to 1-500. The preparation method of the hydroxyl-containing bio-based ethylene propylene rubber provided by the invention is simple and convenient, and is suitable for industrial large-scale production. The hydroxyl-containing bio-based ethylene propylene rubber prepared by adopting the preparation method disclosed by the invention is excellent in heat resistance, aging resistance and mechanical property, has relatively good cohesiveness and oil resistance, and has relatively high practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a bio-based ethylene propylene rubber containing hydroxyl groups and a preparation method thereof. Background Art

[0002] Hydroxyl groups are highly reactive groups. Introducing them into materials not only improves their oil resistance but also reacts with compounds such as anhydrides, carboxylic acids, and isocyanate, thereby giving the materials greater functionality and application potential. However, traditional methods for introducing hydroxyl groups into rubber materials have many limitations.

[0003] In the prior art, a common method is to dissolve epoxy elastomer in tetrahydrofuran solution and add zirconium tetrachloride to carry out ring-opening reaction. Although this method can introduce hydroxyl groups to a certain extent, the hydroxyl content of the obtained product is usually no more than 10%. When the hydroxyl content is too high, the product easily forms a gel and loses its utilization value. Another method is to introduce hydroxyl groups into elastomers containing double bonds by click chemistry, but this method also has the problem of complex post-processing. Therefore, the traditional method has obvious deficiencies in the efficiency and application range of hydroxyl group introduction, and it is urgent to develop a more efficient modification method.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] Epoxy natural rubber is a modified natural rubber whose oil resistance is improved by the presence of epoxy groups. However, the numerous double bonds in its backbone are susceptible to crosslinking or chain scission reactions under the influence of heat, oxygen, and light. Hydrogenation can significantly improve its thermal properties. The present inventors unexpectedly discovered that, compared to other butadiene-based rubbers, isoprene-based rubber, due to the presence of pendant methyl groups in its backbone, exhibits unique reactivity during hydrogenation. When hydrogenated using a precious metal rhodium catalyst, butadiene rubber primarily exhibits selective hydrogenation of double bonds, while isoprene rubber undergoes not only double bond hydrogenation but also conversion of epoxy groups to hydroxyl groups. Based on this characteristic, the present inventors hydrogenated epoxy natural rubber (ENR). This process eliminates unsaturated double bonds in the backbone, significantly improving the material's resistance to thermal oxidative aging. Furthermore, it directly converts epoxy groups to hydroxyl groups, eliminating the complex ring-opening step required with zirconium tetrachloride in traditional methods.

[0006] In addition, the rubber prepared based on this method has an alternating structure of ethylene and propylene groups, and the main chain contains a large number of hydroxyl groups. It is an EPDM rubber with a special structure. Because its raw material is a renewable green resource, a bio-based EPDM rubber that does not rely on petroleum resources is prepared.

[0007] Based on this, the present invention has the following technical solutions: In a first aspect, the present invention provides a hydroxyl-containing bio-based EPDM rubber comprising the following three blocks: 、 and ;x=1~500, y=1~500, z=1~500.

[0008] Preferably, the hydroxyl content in the hydroxyl-containing bio-based EPDM rubber is less than 20%.

[0009] Preferably, x:y+z=70~95:5~30.

[0010] Preferably, the segment Accounting for 70%~95% of rubber, chain segments and chain segments It accounts for 5% to 30% of rubber.

[0011] In the present invention, the raw rubber of the hydroxyl-containing bio-based EPDM rubber has a peel strength greater than 3N / mm, a tensile strength greater than 20MPa, and heat resistance and aging resistance comparable to those of EPDM rubber.

[0012] In a second aspect, the present invention provides a method for preparing the hydroxyl-containing bio-based EPDM rubber, comprising: dissolving epoxidized natural rubber in an organic solvent, adding a catalyst to carry out a hydrogenation reaction; the catalyst contains precious metal rhodium, and the rhodium content is 10wt% to 100wt%.

[0013] The present invention finds that a specific hydrogenation catalyst is used to carry out a hydrogenation reaction on epoxy natural rubber containing side methyl groups to eliminate double bonds on the epoxy rubber, thereby achieving the effect of improving its thermodynamic properties. During this process, epoxy is converted into hydroxyl groups in a 1:1 ratio. The resulting saturated rubber main chain has a large number of hydroxyl groups, which can give the rubber better bonding properties. The prepared saturated rubber has excellent tensile properties and excellent oil resistance, and its thermal properties are comparable to those of traditional EPDM rubber, and has high practical application value.

[0014] In the present invention, the rhodium content in the catalyst is any value among 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt%, 100wt% or a numerical range with any two of the above values as endpoints.

[0015] Preferably, the amount of the catalyst is 0.3% to 5% of the mass of the epoxidized natural rubber.

[0016] Preferably, the hydroxyl groups are converted from epoxy groups, and the epoxy degree of the epoxidized natural rubber is below 25; preferably, the content of epoxy groups in the epoxidized natural rubber is 5% to 25%.

[0017] Preferably, the reaction temperature of the hydrogenation reaction is 80-130° C., and the reaction pressure is 3-6 MPa.

[0018] Preferably, the organic solvent is one or more of toluene, xylene, chlorobenzene, n-hexane, petroleum ether and tetrahydrofuran.

[0019] Preferably, the preparation method of the epoxidized natural rubber comprises: mixing natural latex and a stabilizer, and then adding peroxide and an organic acid to carry out an epoxidation reaction to obtain the epoxidized natural rubber.

[0020] More preferably, the stabilizer is one or more of sodium lauryl sulfate, nonylphenol polyoxyethylene ether and isomeric decanol polyoxyethylene ether; more preferably, the amount of the stabilizer added is 0.5% to 3% of the mass of the dry rubber; More preferably, the organic acid is one or more of formic acid, acetic acid and m-chloroperbenzoic acid; more preferably, the amount of the organic acid added is 0.1% to 0.8% of the double bond molar content.

[0021] Preferably, the preparation method of the hydroxyl-containing bio-based EPDM rubber comprises: S1: diluting natural rubber latex with water to a solid content of 23-28% to obtain natural rubber latex; then mixing the natural rubber latex with a stabilizer, adding peroxide and an organic acid to carry out an epoxidation reaction, and after the reaction, flocculating with ethanol, washing, and drying to obtain epoxidized natural rubber; S2: dissolving the epoxy natural rubber having an epoxy degree of 5 to 25 in chlorobenzene, adding a noble metal rhodium catalyst, exhausting the air and heating to carry out a hydrogenation reaction; controlling the reaction temperature to be 90 to 130° C. and the pressure to be 3 to 6 MPa; after the reaction is completed, using ethanol to precipitate the rubber, and then drying.

[0022] Preferably, the degree of hydrogenation of the hydroxyl-containing bio-based EPDM rubber is greater than 70%; more preferably, the degree of hydrogenation of the hydroxyl-containing bio-based EPDM rubber is greater than 99%.

[0023] In the present invention, a catalyst is added to an epoxy natural rubber solution for hydrogenation. When the degree of hydrogenation is above 70%, a hydroxyl-containing bio-based EPDM rubber can be obtained. When the degree of hydrogenation is above 99%, the properties of the elastomer will undergo a significant change, and a hydroxyl-containing bio-based EPDM rubber with better thermal properties, mechanical properties, and oil resistance can be obtained.

[0024] Based on this, the technical solution of the present invention has the following beneficial effects: The present invention provides a simple and convenient method for preparing a hydroxyl-containing bio-based EPDM rubber, suitable for large-scale industrial production. The hydroxyl-containing bio-based EPDM rubber obtained using the present invention exhibits excellent heat resistance, aging resistance, and mechanical properties, as well as good adhesion and oil resistance, and has high practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] Figure 1 This is the H-NMR spectrum of the hydroxyl-containing bio-based EPDM rubber prepared in Example 1. Compared with the ENR spectrum, the characteristic peak of the epoxy group at 2.7 ppm and the characteristic peak of the double bond at 5.2 ppm disappeared, indicating that the hydrogenation reaction was successful.

[0027] Figure 2 This is the low-temperature DSC spectrum of hydroxyl-containing bio-based EPDM rubber.

[0028] Figure 3 The thermal properties of bio-based EPDM rubber with different hydrogenation degrees at a hydroxyl content of 12% and its comparison with EPDM rubber, including TGA spectra and DTG spectra.

[0029] Figure 4 Comparison of tensile properties between hydroxyl-containing bio-based EPDM rubber and EPDM rubber.

[0030] Figure 5 The oil resistance of hydroxyl-containing bio-based EPDM rubber and EPDM rubber is compared. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0032] In the present invention, if specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the field or in the product specifications were used. Instruments and the like used, for which the manufacturer is not specified, are all conventional products that can be purchased through regular channels. The raw materials used in the present invention are all readily available in the domestic market.

[0033] Example 1 This embodiment provides a hydroxyl-containing bio-based EPDM rubber, the structural formula of which is , where x=1-500, y=1-500, z=1-500; segment Accounting for 70%~95% of rubber, chain segments and chain segments It accounts for 5% to 30% of rubber.

[0034] This embodiment further provides a method for preparing a bio-based EPDM rubber containing hydroxyl groups, comprising the following steps: Step 1: Deionized water was added to the natural rubber latex to dilute the solid content to 25%. The molar ratio of carbon-carbon double bond: formic acid: hydrogen peroxide was 1:0.55:0.55. The mixture was reacted at 40°C for 4 hours and 8 hours, respectively. The mixture was flocculated and washed three times with ethanol, and dried at 50°C to obtain ENR-1 with an epoxy group content of 11.9% and ENR-2 with an epoxy group content of 20%, respectively.

[0035] Step 2: ENR-1 epoxidized natural rubber with an epoxy group content of 11.9% was prepared into a 3% chlorobenzene solution. A precious metal rhodium catalyst (3% by weight of the epoxidized natural rubber) was added to the reactor. The air was evacuated and the temperature was increased. The reaction was carried out under a hydrogen pressure of 3 MPa and a reaction temperature of 120°C for 7 hours. After the reaction, the rubber was precipitated in ethanol and dried at 50°C for 24 hours. The hydrogenation degree of the obtained product was characterized by proton nuclear magnetic resonance spectroscopy, which showed a hydrogenation degree of 99% and a hydroxyl content of 12%.

[0036] Example 2 This example provides a method for preparing a hydroxyl-containing bio-based EPDM rubber. The method differs from Example 1 only in that the ENR-1 epoxidized natural rubber, which has an epoxy group content of 11.9%, is replaced with an equal amount of ENR-2 epoxidized natural rubber, which has an epoxy group content of 20%. The resulting product was characterized by proton nuclear magnetic resonance spectroscopy to determine its degree of hydrogenation, which showed a degree of hydrogenation of 99% and a hydroxyl content of 20%.

[0037] Example 3 This example provides a method for preparing bio-based EPDM rubber containing hydroxyl groups. The only difference from Example 1 is that the amount of catalyst used is 1.5% of the mass of the epoxidized natural rubber, and the obtained product has a hydrogenation degree of 90% and a hydroxyl content of 12%.

[0038] Example 4 This example provides a method for preparing bio-based EPDM rubber containing hydroxyl groups. The only difference from Example 1 is that the amount of catalyst used is 1.2% of the mass of the epoxidized natural rubber, and the obtained product has a hydrogenation degree of 70% and a hydroxyl content of 12%.

[0039] Example 5 This example provides a method for preparing a hydroxyl-containing bio-based EPDM rubber. The only difference from Example 1 is that the amount of catalyst used is 0.8% of the mass of the epoxidized natural rubber. The resulting product has a hydrogenation degree of 40%, a hydroxyl content of 6.6%, and a residual epoxy content of 5.4%.

[0040] Example 6 This example provides a method for preparing a hydroxyl-containing bio-based EPDM rubber. The only difference from Example 1 is that the amount of catalyst used is 2% of the mass of the epoxidized natural rubber. The resulting product has a hydrogenation degree of 40%, a hydroxyl content of 6.6%, and a residual epoxy content of 5.4%.

[0041] Comparative Example 1 This comparative example provides a method for preparing a hydroxyl-containing bio-based EPDM rubber, which differs from Example 1 only in that the reaction temperature is 80° C., the obtained product has a hydrogenation degree of 22.9%, a hydroxyl content of 0%, and a residual epoxy content of 12%.

[0042] Comparative Example 2 This comparative example provides a method for preparing a bio-based EPDM rubber containing hydroxyl groups. The method differs from Example 1 only in that: Step 1 is omitted, the natural rubber is prepared as a 3% chlorobenzene solution, the catalyst amount is 3% of the mass of the natural rubber, the reaction temperature is 120°C, the reaction time is 7 hours, and the obtained product has a hydrogenation degree of 98% and is free of hydroxyl groups.

[0043] Comparative Example 3 This comparative example provides a method for preparing bio-based EPDM rubber containing hydroxyl groups. The method differs from Example 1 only in that the catalyst is replaced with a ruthenium catalyst at a catalyst dosage of 0.5 wt %. The resulting product has a hydrogenation degree of 99% and is free of hydroxyl groups.

[0044] Comparative Example 4 This comparative example provides a method for preparing a bio-based EPDM rubber containing hydroxyl groups. The only difference between the comparative example and Example 1 is that the epoxy natural rubber is replaced by epoxy nitrile rubber, and the obtained product has no hydroxyl groups.

[0045] Test case performance test The nuclear magnetic hydrogen spectrum of the hydroxyl-containing bio-based EPDM rubber prepared in Example 1 is shown in Figure 1 Compared with ENR, the characteristic peak of epoxy group at 2.7ppm and the characteristic peak of double bond at 5.2ppm disappeared, indicating that the hydrogenation reaction was successful. Figure 1 The H-NMR characterization proved the success of the hydrogenation reaction and the preparation of bio-based EPDM rubber containing hydroxyl groups in the chain.

[0046] The low temperature DSC spectra of the hydroxyl-containing bio-based EPDM rubber prepared in Examples 1 and 2 are shown in FIG. Figure 2 .

[0047] The thermal properties of bio-based EPDM rubber with different hydrogenation degrees and EPDM rubber prepared in Example 1 are compared with those of EPDM rubber. Figure 3 , the left picture is the TGA spectrum, and the right picture is the DTG spectrum.

[0048] The tensile properties of the hydroxyl-containing bio-based EPDM rubber prepared in Examples 1 and 2 are compared with those of the EPDM rubber. Figure 4 .

[0049] The oil resistance of the hydroxyl-containing bio-based EPDM rubber prepared in Examples 1 and 2 is compared with that of the EPDM rubber. Figure 5 .

[0050] The peeling performance of the hydroxyl-containing bio-based EPDM rubber prepared in the example was compared with that of the commercially available EPDM rubbers EPDM4045 and EPDM4703. The test results are shown in Table 1: Table 1

[0051] It can be seen that the bio-based EPDM rubber prepared by this method has good bonding properties.

[0052] like Figure 2 As shown, the hydroxyl-containing bio-based EPDM rubber prepared in Examples 1 and 2 and the natural rubber of Comparative Example 2 were subjected to DSC tests at low temperature, indicating that the hydroxyl-containing bio-based EPDM rubber improved the crystallization of natural rubber at low temperature.

[0053] Figure 3 It can be seen that the thermal properties of the hydroxyl-containing bio-based EPDM rubber and EPDM rubber with different hydrogenation degrees prepared in Examples 1, 3, and 4 are compared. The results show that the hydroxyl groups in the chain are stable, and when the hydrogenation degree is above 99%, the heat resistance of the hydroxyl-containing bio-based EPDM rubber is comparable to that of EPDM rubber.

[0054] Figure 4 The comparison of tensile properties shows that the hydroxyl-containing bio-based EPDM rubber with a hydrogenation degree of more than 99% has better tensile strength and elongation at break.

[0055] Figure 5 The oil resistance test shows that the hydroxyl-containing bio-based EPDM rubber with a hydrogenation degree of more than 99% has better oil resistance.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A bio-based EPDM rubber containing hydroxyl groups, characterized in that: It consists of the following three blocks: 、 and ;x=1~500, y=1~500, z=1~500.

2. The hydroxyl-containing bio-based EPDM rubber according to claim 1, characterized in that The hydroxyl content of the bio-based EPDM rubber containing hydroxyl groups is less than 20%.

3. The hydroxyl-containing bio-based EPDM rubber according to claim 1 or 2, characterized in that: x:y+z=70~95:5~30.

4. The method for preparing the hydroxyl-containing bio-based EPDM rubber according to any one of claims 1 to 3, characterized in that: include: The epoxy natural rubber is dissolved in an organic solvent, and a catalyst is added to carry out a hydrogenation reaction; the catalyst contains precious metal rhodium, and the rhodium content is 10wt% to 100wt%.

5. The method for preparing the hydroxyl-containing bio-based EPDM rubber according to claim 4, characterized in that: The amount of the catalyst used is 0.3% to 5% of the mass of the epoxy natural rubber.

6. The method for preparing the hydroxyl-containing bio-based EPDM rubber according to claim 4 or 5, characterized in that: The hydroxyl groups are obtained by converting epoxy groups, and the epoxy degree of the epoxy natural rubber is less than 25; preferably, the content of epoxy groups in the epoxy natural rubber is 5% to 25%.

7. The method for preparing the hydroxyl-containing bio-based EPDM rubber according to any one of claims 4 to 6, characterized in that: The reaction temperature of the hydrogenation reaction is 80-130° C., and the reaction pressure is 3-6 MPa.

8. The method for preparing a hydroxyl-containing bio-based EPDM rubber according to any one of claims 4 to 7, characterized in that: The organic solvent is one or more of toluene, xylene, chlorobenzene, n-hexane, petroleum ether and tetrahydrofuran.

9. The method for preparing a hydroxyl-containing bio-based EPDM rubber according to any one of claims 4 to 8, characterized in that: The preparation method of the epoxidized natural rubber comprises: adding peroxide and organic acid to natural rubber latex to carry out epoxidation reaction to obtain the epoxidized natural rubber; Preferably, the organic acid is one or more of formic acid, acetic acid and m-chloroperbenzoic acid; more preferably, the amount of the organic acid added is 0.1% to 0.8% of the double bond molar content.

10. The method for preparing a hydroxyl-containing bio-based EPDM rubber according to any one of claims 4 to 9, characterized in that: include: S1: diluting natural rubber latex with water to a solid content of 23-28% to obtain natural rubber latex; then mixing the natural rubber latex with a stabilizer, adding peroxide and an organic acid to carry out an epoxidation reaction, and after the reaction, flocculating with ethanol, washing, and drying to obtain epoxidized natural rubber; S2: dissolving the epoxy natural rubber having an epoxy degree of 5 to 25 in chlorobenzene, adding a noble metal rhodium catalyst, exhausting the air and heating to perform a hydrogenation reaction; controlling the reaction temperature to be 80 to 130° C. and the pressure to be 3 to 6 MPa; after the reaction is completed, using ethanol to precipitate the rubber, and then drying; Preferably, the degree of hydrogenation of the hydroxyl-containing bio-based EPDM rubber is greater than 70%; more preferably, the degree of hydrogenation of the hydroxyl-containing bio-based EPDM rubber is greater than 99%.

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