FULLY BIO-BASED, HIGHLY FILLED LIGNIN-RUBBER MASTERBATCH, METHOD FOR PREPARING SAME, AND USE THEREOF

Abstract

The present invention discloses a fully bio-based, highly filled lignin-rubber masterbatch, a method for preparing same, and use thereof. The lignin-rubber masterbatch is prepared by a method comprising: (1) reacting a lignin, acetic acid, and oleic acid in the presence of a catalyst to give a modified lignin; and (2) blending the modified lignin and a rubber, and granulating to give the lignin-rubber masterbatch. The highly filled lignin-rubber masterbatch prepared by the present invention can replace the conventional reinforcing agent carbon black and provide a better reinforcing effect and higher mechanical properties for rubber materials. The present invention can also reduce the rubber content of the rubber composite materials while retaining the mechanical properties, thus featuring cost-efficiency.

Claims

1. A lignin-rubber masterbatch prepared by a method comprising: (1) reacting a lignin, acetic acid, and oleic acid in the presence of a catalyst to give a modified lignin; and (2) blending the modified lignin and a rubber, and granulating to give the lignin-rubber masterbatch; in step (1), the mass-to-mole ratio of the lignin to the total amount of acetic acid and oleic acid is 1 g:8.2-18.2 mol; the molar ratio of acetic acid to oleic acid is 1:0.5-3; the catalyst is any one of N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, or a combination thereof; the mass-to-mole ratio of the lignin to the catalyst is 1 g:5.7-11.2 mmol.

2. The lignin-rubber masterbatch according to claim 1, wherein in step (1), the mass-to-mole ratio of the lignin to the total amount of acetic acid and oleic acid is 1 g:10.2-16.2 mol; the molar ratio of acetic acid to oleic acid is 1:1-2.5; the mass-to-mole ratio of the lignin to the catalyst is 1 g:6.7-10.2 mmol.

3. The lignin-rubber masterbatch according to claim 1, wherein in step (1), the catalyst is a combination of N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine; the molar ratio of N,N-dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 2-4:1.

4. The lignin-rubber masterbatch according to claim 1, wherein in step (1), the solvent of the reaction is N,N-dimethylformamide; the mass-to-volume ratio of the lignin to the solvent is 1 g:11-23 mL.

5. The lignin-rubber masterbatch according to claim 1, wherein in step (1), the temperature of the reaction is 20-30 C.

6. The lignin-rubber masterbatch according to claim 1, wherein in step (2), the modified lignin accounts for 10%-90% of the total mass of the modified lignin and the rubber.

7. The lignin-rubber masterbatch according to claim 1, wherein in step (2), the blending is conducted in an open mill or an internal mixer; the temperature of the blending is 60-120 C.

8. The lignin-rubber masterbatch according to claim 1, wherein the rubber comprises one or more of styrene butadiene rubber, cis-polybutadiene rubber, natural rubber, ethylene propylene rubber, ethylene propylene diene monomer rubber, and butyl rubber.

9. A method for preparing a lignin-rubber masterbatch, comprising: (1) reacting a lignin, acetic acid, and oleic acid in the presence of a catalyst to give a modified lignin; and (2) blending the modified lignin and a rubber, and granulating to give the lignin-rubber masterbatch; in step (1), the mass-to-mole ratio of the lignin to the total amount of acetic acid and oleic acid is 1 g:8.2-18.2 mol; the molar ratio of acetic acid to oleic acid is 1:0.5-3; the catalyst is any one of N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, or a combination thereof.

10. The method according to claim 9, wherein in step (1), the mass-to-mole ratio of the lignin to the total amount of acetic acid and oleic acid is 1 g:10.2-16.2 mol; the molar ratio of acetic acid to oleic acid is 1:1-2.5; the mass-to-mole ratio of the lignin to the catalyst is 1 g:6.7-10.2 mmol.

11. The method according to claim 9, wherein in step (1), the catalyst is a combination of N,N-dicyclohexylcarbodiimide and 4-dimethylaminopyridine; the molar ratio of N,N-dicyclohexylcarbodiimide to 4-dimethylaminopyridine is 2-4:1.

12. The method according to claim 11, wherein in step (1), the solvent of the reaction is an organic solvent.

13. The method according to claim 9, wherein in step (1), the solvent of the reaction is N,N-dimethylformamide.

14. The method according to claim 9, wherein in step (1), the mass-to-volume ratio of the lignin to the solvent is 1 g:11-23 mL.

15. The method according to claim 9, wherein in step (1), the temperature of the reaction is 20-30 C.

16. The method according to claim 9, wherein in step (2), the modified lignin accounts for 10%-90% of the total mass of the modified lignin and the rubber.

17. The method according to claim 9, wherein in step (2), the blending is conducted in an open mill or an internal mixer; preferably, the temperature of the blending is 60-120 C.

18. The method according to claim 9, wherein the rubber comprises one or more of styrene butadiene rubber, cis-polybutadiene rubber, natural rubber, ethylene propylene rubber, ethylene propylene diene monomer rubber, and butyl rubber.

19. Use of the lignin-rubber masterbatch according to claim 1 in preparing a rubber composite material.

20. The use according to claim 19, comprising: (i) mixing the lignin-rubber masterbatch with a rubber to give a rubber compound; and (ii) subjecting the rubber compound obtained in step (i) and an additive to mixing, milling, and compression molding to give the rubber composite material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further illustrated in detail with reference to the following accompanying drawing and detailed description, from which the advantages in the above and/or other aspects of the present invention will become more apparent.

[0045] FIG. 1 illustrates the water contact angles of the modified lignins obtained in Example 1, Comparative Example 1 and Comparative Example 2.

[0046] FIG. 2 illustrates the SEM photographs of the rubber masterbatches obtained in Example 1, Comparative Example 1 and Comparative Example 2.

DETAILED DESCRIPTION

[0047] In the following examples, the experimental methods are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

[0048] In the following examples, the lignin is alkali lignin, unless otherwise specified.

Example 1

[0049] The lignin and a mixture of acetic acid and oleic acid (in a molar ratio of 1:2) were added to 360 mL of DMF in a mass-to-mole ratio of 20 g:284 mol. The mixture was stirred at room temperature for 20 min until complete dissolution. N,N-dicyclohexylcarbodiimide (DCC, 28.4 g, 137.6 mmol) was then added to the reaction system. The system was degassed with nitrogen for 5 min. 4-Dimethylaminopyridine (DMAP, 5.6 g, 45.8 mmol) was added to 15 mL of DMF, and the mixture was then slowly added to the reaction system. The reaction system was stirred at room temperature for 48 h and filtered to remove by-product ethyl N,N-dichlorocarbamate (DCU) to give a black filtrate. The black filtrate was added to an aqueous HCl solution to give a precipitate. The precipitate was separated by filtration to give a brown filter cake, and the brown filter cake was dried in vacuum at 50 C. for 24 h to give modified lignin 1 (85% yield);

[0050] The modified lignin obtained in step (1) was milled by a jet mill to a d50 of about 2 m;

[0051] The natural rubber was masticated and banded in an open mill. 300 parts of the modified lignin filler were added as per 100 parts of the natural rubber by mass for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give a modified lignin 1\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the fully bio-based, highly filled lignin 1\natural rubber masterbatch.

[0052] According to the formulation in Table 1, the fully bio-based, highly filled lignin\natural rubber masterbatch obtained in step (3) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00001 TABLE 1 Formulation of natural rubber composite material in Example 1 Component Ratio 1 Natural rubber 25.0% 2 Fully bio-based, highly filled lignin 65.0% 1\natural rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Example 2

[0053] The lignin and a mixture of acetic acid and oleic acid (in a molar ratio of 1:1) were added to 300 mL of DMF in a mass-to-mole ratio of 20 g:284 mol. The mixture was stirred at room temperature until complete dissolution. N,N-dicyclohexylcarbodiimide (DCC, 117 mmol) was then added to the reaction system. The system was degassed with nitrogen for 5 min. 4-Dimethylaminopyridine (DMAP, 36.5 mmol) was added to 15 mL of DMF, and the mixture was then slowly added to the reaction system. The reaction system was stirred at room temperature for 48 h and filtered to remove by-product ethyl N,N-dichlorocarbamate (DCU) to give a black filtrate. The black filtrate was added to an aqueous HCl solution to give a precipitate. The precipitate was separated by filtration to give a brown filter cake, and the brown filter cake was dried in vacuum at 50 C. for 24 h to give modified lignin 2;

[0054] The modified lignin obtained in step (1) was milled by a jet mill to a d50 of about 2 m;

[0055] The natural rubber was masticated and banded in an open mill. 300 parts of the modified lignin filler were added as per 100 parts of the natural rubber by mass for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give a modified lignin 2\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the fully bio-based, highly filled lignin 2\natural rubber masterbatch.

[0056] According to the formulation in Table 2, the fully bio-based, highly filled lignin 2\natural rubber masterbatch obtained in step (3) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00002 TABLE 2 Formulation of natural rubber composite material in Example 2 Component Ratio 1 Natural rubber 25.0% 2 Fully bio-based, highly filled lignin 65.0% 2\natural rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Example 3

[0057] The lignin and a mixture of acetic acid and oleic acid (in a molar ratio of 2:1) were added to 300 mL of DMF in a mass-to-mole ratio of 20 g:284 mol. The mixture was stirred at room temperature until complete dissolution. N,N-dicyclohexylcarbodiimide (DCC, 117 mmol) was then added to the reaction system. The system was degassed with nitrogen for 5 min. 4-Dimethylaminopyridine (DMAP, 36.5 mmol) was added to 15 mL of DMF, and the mixture was then slowly added to the reaction system. The reaction system was stirred at room temperature for 48 h and filtered to remove by-product ethyl N,N-dichlorocarbamate (DCU) to give a black filtrate. The black filtrate was added to an aqueous HCl solution to give a precipitate. The precipitate was separated by filtration to give a brown filter cake, and the brown filter cake was dried in vacuum at 50 C. for 24 h to give modified lignin 3;

[0058] The modified lignin obtained in step (1) was milled by a jet mill to a d50 of about 2 m;

[0059] The natural rubber was masticated and banded in an open mill. 300 parts of the modified lignin filler were added as per 100 parts of the natural rubber by mass for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give a modified lignin 3\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the fully bio-based, highly filled lignin 3\natural rubber masterbatch.

[0060] According to the formulation in Table 3, the fully bio-based, highly filled lignin\natural rubber masterbatch obtained in step (3) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00003 TABLE 3 Formulation of natural rubber composite material in Example 3 Component Ratio 1 Natural rubber 25.0% 2 Fully bio-based, highly filled lignin 65.0% 3\natural rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Example 4

[0061] An enzymatically digested lignin and a mixture of acetic acid and oleic acid (in a molar ratio of 1:2) were added to 360 mL of DMF in a mass-to-mole ratio of 20 g:284 mol. The mixture was stirred at room temperature for 20 min until complete dissolution. N,N-dicyclohexylcarbodiimide (DCC, 28.4 g, 137.6 mmol) was then added to the reaction system. The system was degassed with nitrogen for 5 min. 4-Dimethylaminopyridine (DMAP, 5.6 g, 45.8 mmol) was added to 15 mL of DMF, and the mixture was then slowly added to the reaction system. The reaction system was stirred at room temperature for 48 h and filtered to remove by-product ethyl N,N-dichlorocarbamate (DCU) to give a black filtrate. The black filtrate was added to an aqueous HCl solution to give a precipitate. The precipitate was separated by filtration to give a brown filter cake, and the brown filter cake was dried in vacuum at 50 C. for 24 h to give modified lignin 4;

[0062] The modified lignin obtained in step (1) was milled by a jet mill to a d50 of about 2 m;

[0063] The natural rubber was masticated and banded in an open mill. 300 parts of the modified lignin filler were added as per 100 parts of the natural rubber by mass for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give a modified lignin 4\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the fully bio-based, highly filled lignin 4\natural rubber masterbatch.

[0064] According to the formulation in Table 4, the fully bio-based, highly filled lignin 4\natural rubber masterbatch obtained in step (3) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00004 TABLE 4 Formulation of natural rubber composite material in Example 4 Component Ratio 1 Natural rubber 25.0% 2 Fully bio-based, highly filled lignin 4\natural 65.0% rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Example 5

[0065] An organosolv lignin and a mixture of acetic acid and oleic acid (in a molar ratio of 1:1.5) were added to 300 mL of DMF in a mass-to-mole ratio of 20 g:244 mol. The mixture was stirred at room temperature until complete dissolution. N,N-dicyclohexylcarbodiimide (DCC, 117 mmol) was then added to the reaction system. The system was degassed with nitrogen for 5 min. 4-Dimethylaminopyridine (DMAP, 36.5 mmol) was added to 15 mL of DMF, and the mixture was then slowly added to the reaction system. The reaction system was stirred at room temperature for 48 h and filtered to remove by-product ethyl N,N-dichlorocarbamate (DCU) to give a black filtrate. The black filtrate was added to an aqueous HCl solution to give a precipitate. The precipitate was separated by filtration to give a brown filter cake, and the brown filter cake was dried in vacuum at 50 C. for 24 h to give modified lignin 5;

[0066] The modified lignin obtained in step (1) was milled by a jet mill to a d50 of about 2 m;

[0067] The natural rubber was masticated and banded in an open mill. 300 parts of the modified lignin filler were added as per 100 parts of the natural rubber by mass for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give a modified lignin 5\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the fully bio-based, highly filled lignin 5\natural rubber masterbatch.

[0068] According to the formulation in Table 5, the fully bio-based, highly filled lignin 5\natural rubber masterbatch obtained in step (3) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00005 TABLE 5 Formulation of natural rubber composite material in Example 5 Component Ratio 1 Natural rubber 25.0% 2 Fully bio-based, highly filled lignin 5\natural 65.0% rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Comparative Example 1

[0069] A dry original lignin was milled by a jet mill to a d50 of about 2 m for later use;

[0070] The natural rubber was masticated and banded in an open mill. 300 parts of the original lignin filler were added as per 100 parts of the natural rubber for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give an original lignin\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the original lignin\natural rubber masterbatch.

[0071] According to the formulation in Table 6, the original lignin \natural rubber masterbatch obtained in step (2) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00006 TABLE 6 Formulation of natural rubber composite material in Comparative Example 1 Component Ratio 1 Natural rubber 25.0% 2 Original lignin/natural 65.0% rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Comparative Example 2

[0072] The natural rubber was masticated and banded in an open mill. 300 parts of a carbon black filler were added as per 100 parts of the natural rubber for blending. The mixing temperature was 100 C., the mixture was mixed until a constant weight to give a carbon black\natural rubber masterbatch (300:100). The mixed masterbatch was granulated in a screw extruder to give the carbon black\natural rubber masterbatch.

[0073] According to the formulation in Table 7, the carbon black\natural rubber masterbatch obtained in step (1) was mixed with the natural rubber to give a rubber compound, wherein the mixing temperature was 100 C., and the time was 15 min. The obtained rubber compound was added into the open mill for banding, before naphthenic oil, sulfur, stearic acid, and PEG-4000 were added. The mixture was mixed at 25 C. for 10 min, milled 5 times, and subjected to compression molding on a plate vulcanizing press at 160 C. for 20 min to give the natural rubber composite material.

TABLE-US-00007 TABLE 7 Formulation of natural rubber composite material in Comparative Example 2 Component Ratio 1 Natural rubber 25.0% 2 Carbon black/natural 65.0% rubber masterbatch 3 Naphthenic oil 4.0% 4 Stearic acid 1.0% 5 Sulfur 2.5% 6 PEG-4000 2.5%

Tests of the Examples and Comparative Examples

[0074] Contact angle test: The modified lignins and the original lignin were tested for the contact angle on a contact angle tester SDC-200. The results are shown in Table 8 and FIG. 1.

[0075] DSC test: The modified lignins and the original lignin were tested for the glass transition temperature (Tg) on a differential scanning calorimeter DZ-DSC300. The results are shown in Table 9.

[0076] SEM test: The morphology of the rubber composite material was characterized on a Hitachi S4800 scanning electron microscope at an accelerating voltage of 20 kV. The results are shown in FIG. 2.

[0077] Tensile test: The stress at a given elongation, tensile strength, elongation at break, and Shore-A hardness of the vulcanized rubbers were respectively determined according to national standards GB/T 528-2009, GB/T 528-1998, GB/T 531-1999, and GB/T 3512-2001, and the mechanical properties were tested on a UTM6104 electronic universal tester. The mechanical properties are shown in Table 10.

TABLE-US-00008 TABLE 8 Contact angles of lignin and modified lignins in Examples 1-5 and Comparative Example 1 Modified Modified Modified Modified Modified Original lignin 1 lignin 2 lignin 3 lignin 4 lignin 5 lignin Contact 111 103 102 106 115 70 angle

TABLE-US-00009 TABLE 9 Tg of lignin and modified lignins in Examples 1-5 and Comparative Example 1 Modified Modified Modified Modified Modified Original lignin 1 lignin 2 lignin 3 lignin 4 lignin 5 lignin Tg 30.2 C. 58.5 C. 91.4 C. 32.5 C. 28.6 C. 153 C.

TABLE-US-00010 TABLE 10 Mechanical properties of rubber composite materials of Examples 1-5 and Comparative Examples 1 and 2 Example Example Example Example Example Comparative Comparative 1 2 3 4 5 Example 1 Example 2 Tensile 26.53 24.42 23.56 23.94 25.43 20.87 23.48 Strength (MPa) Elongation 479.52 461.25 452.25 466.3 470.25 408.26 452.82 at break Stress at 2.31 2.26 2.21 1.99 2.41 2.05 2.25 100% elongation (MPa) Stress at 13.13 12.07 12.54 13.12 13.13 12.42 12.54 300% elongation (MPa) Permanent 13.08 12.21 11.96 12.51 12.16 10.21 11.17 tensile deformation Hardness 64 60 61 62 64 55 59 (Shore A)

[0078] The test results show that: from the contact angles of the original lignins and the modified lignins in Examples 1, 2 and 3 and Comparative Examples 1 and 2, the contact angles of the modified lignins were significantly increased compared with those of the original lignins, suggesting a greatly improved hydrophobicity and a better dispersibility in rubbers. Also, by comparing the glass transition temperatures of the modified lignins and the original lignins, the glass transition temperatures of the modified lignins were significantly reduced along with the increase of the proportion of oleic acid, and particularly, the modified lignin 1 greatly improves the convenience of the rubber processing process. The rubber masterbatch prepared from the modified lignin has the best performance, and the mechanical properties such as tensile strength, stress at a given elongation, and the like are better than those of the rubber masterbatch prepared from carbon black (Comparative Example 2), indicating that a cross-linking network is formed between the modified lignin and the rubber which significantly improves the compatibility and provides the rubber masterbatch with better performance. From the SEM graphs, it can be seen that modified lignins were dispersed in the rubber masterbatch uniformly due to the introduction of oleic acid, while the original lignins significantly aggregated in the rubber masterbatch, resulting in remarkable reductions in mechanical properties.

[0079] The natural rubber composite materials prepared in Examples 4 and 5 have similar performance as that of Example 1, with mechanical properties such as tensile strength, stress at a given elongation, and the like superior to those of the rubber masterbatch prepared from carbon black and excellent thermal properties and lower glass transition temperatures, thus greatly improving the thermal stability of the rubber products.

[0080] The above examples only illustrate several embodiments of the present invention for the purpose of detailed description, and should not be construed as limiting the scope of the present invention. It should be noted that various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit of the present invention, and such modifications and improvements shall fall within the scope of the present invention. Therefore, the protection scope of the present invention is determined by the claims.