MODIFIED LIGNIN REINFORCED RUBBER AND PREPARATION METHOD THEREFOR

Abstract

A modified lignin reinforced rubber is obtained by subjecting a lignin to composite modification by a compound containing a carbon-carbon double bond, a compound containing a sulfur element and a compound capable of blocking a hydroxyl; the lignin is modified with the compound containing the carbon-carbon double bond, and the contained double bond and an olefin in the rubber generate a bonding effect, which improves a binding force between the lignin and the rubber; furthermore, by modifying the lignin with the compound containing the sulfur element, the lignin contains a certain amount of the element sulfur, which improves an interaction between the lignin and the rubber, improves properties of the rubber, and reduces the use of a vulcanizing agent, and further increases a replacement amount of the lignin to carbon black.

Claims

1. A preparation method for a modified lignin reinforced rubber, wherein the modified lignin is obtained by subjecting a lignin to composite modification by a compound containing a carbon-carbon double bond, a compound containing a sulfur element and a compound capable of blocking a hydroxyl.

2. The preparation method for the modified lignin reinforced rubber according to claim 1, wherein the lignin is one or a combination of a plurality of alkali lignin, soda lignin, organic solvent lignin and enzymatic hydrolysis lignin.

3. The preparation method for the modified lignin reinforced rubber according to claim 1, wherein the compound containing the carbon-carbon double bond is a compound containing any one of vinyl, acrylic, butadiene, oleic, linoleic, linolenic, arachidonic and dienyl phthalate groups.

4. The preparation method for the modified lignin reinforced rubber according to claim 2 or 3, wherein the compound containing the carbon-carbon double bond is a long-chain compound containing no less than five carbon atoms.

5. The preparation method for the modified lignin reinforced rubber according to claim 1, wherein the compound containing the sulfur element is any one or a combination of a plurality of sulfhydryl silane coupling agent shown in formula I, bis[3-(triethoxysilyl)propyl]tetrasulfide, mercaptan, potassium persulfate, mercaptobenzothiazole, brimstone and tetramethyl thiuram monosulfide; ##STR00002## wherein, R.sub.1, R.sub.2 and R.sub.3 are independently selected from —O—R.sub.6; wherein, R.sub.6 is selected from alkyl, alkenyl, aryl or aralkyl; R.sub.4 is selected from —(CH.sub.2).sub.n—; wherein, n is any integer selected from 1 to 10; and R.sub.5 is selected from H, CN or (C═O)—R.sup.6; wherein, R.sup.6 is selected from branched or unbranched, saturated or unsaturated aliphatic, aromatic or mixed aliphatic/aromatic monovalent C1-C30 hydrocarbyl groups.

6. The preparation method for the modified lignin reinforced rubber according to claim 1, wherein the compound capable of blocking the hydroxyl is one or a combination of a plurality of silane coupling agent, titanate coupling agent and aluminate coupling agent.

7. The preparation method for the modified lignin reinforced rubber according to claim 1, wherein the preparation method for the modified lignin is: adding the compound containing the carbon-carbon double bond and the compound containing the sulfur element for modification first, and then adding the compound capable of blocking the hydroxyl for modification.

8. The preparation method for the modified lignin reinforced rubber according to claim 1, wherein the rubber is any one of natural rubber, butyl rubber and styrene butadiene rubber.

9. The preparation method for the modified lignin reinforced rubber according to claim 1, comprising the following steps of: (1) adding the modified lignin, a rubber, carbon black, a vulcanizing agent and a vulcanizing aid into an internal mixer for mixing to obtain a rubber compound; and (2) after the rubber compound obtained in step (1) is placed in an open mill for repeated thinning, measuring a vulcanization properties of the rubber compound by a rubber vulcameter, and then hot-pressing and molding the rubber compound by a vulcanizing press.

10. The preparation method for the modified lignin reinforced rubber according to claim 7, wherein in step (1), a mass ratio of the modified lignin to the rubber, the carbon black, the vulcanizing agent and the vulcanizing aid is (2-50):100:(1-20):(0.5-2.5):(0.5-10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 shows water contact angles of lignin modified by different coupling agents.

[0060] FIG. 2 shows properties of rubbers in Embodiment 4.

DETAILED DESCRIPTION

[0061] The present invention can be better understood from the following embodiments. However, those skilled in the art will easily understand that the contents described in the embodiments are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0062] The detection method in this embodiment was as follows:

[0063] Water contact angle test: pre-dried lignin samples were pressed into uniform slices by an infrared tablet press, and water contact angles of the sample slices were measured by a contact angle meter.

[0064] Particle size test: the dried lignin samples were added into water according to a solid-liquid ratio of 1:50, dispersed by ultrasonic for 30 minutes, and then a proper amount of the mixture was taken and dropwise added into a laser particle size analyzer for particle size analysis.

[0065] Tensile properties of rubber were tested on a UTM6104 electronic universal testing machine according to GB/T528-2009.

[0066] Rubber hardness testing method: a spline was placed on a Shore durometer A, and a handle was downwards pressed to make the durometer contact with the sample horizontally, and read the durometer in one second.

Embodiment 1: Preparation of Modified Lignin (Impregnation Method)

[0067] According to Table 1, a compound containing a carbon-carbon double bond and a compound containing a sulfur element were weighed, stirred evenly, and added with ethanol, wherein concentrations of the compound containing the carbon-carbon double bond and the compound containing the sulfur element were both 2 g/mL to obtain a first solution. According to Table 1, a compound capable of blocking a hydroxyl was weighed, and added with ethanol, wherein a concentration of this compound was 2 g/ml, to obtain a second solution. If the compound the containing the carbon-carbon double bond, the compound containing the sulfur element and the compound capable of blocking the hydroxyl listed in Table 1 do not need to be dissolved in ethanol, the compounds could be used directly, and dosages of these compounds were controlled according to the description in the following two paragraphs.

[0068] The first solution was dropwise added in 10 g of enzymatic hydrolysis lignin (the dosage of the compound containing the carbon-carbon double bond and the compound containing the sulfur element were both 2 wt % of that of the enzymatic hydrolysis lignin), and then dropwise added with ethanol (about 8 mL) until the lignin reached an infiltrated state, thoroughly mixed, and stood for 30 minutes. The modified lignin was put into a vacuum drying oven, dried at 60° C. in vacuum to completely volatilize the ethanol, and then pulverized for 2 minutes with a pulverizer.

[0069] The second solution was dropwise added in the pulverized material (the dosage of the compound capable of blocking the hydroxyl was 4 wt % of that of the enzymatic hydrolysis lignin), and then dropwise added with ethanol until the lignin reached the infiltrated state, thoroughly mixed, and stood for 30 minutes. The modified lignin was put into a vacuum drying oven, dried at 60° C. in vacuum to completely volatilize the ethanol, and then pulverized for 1 minute with a pulverizer.

TABLE-US-00001 TABLE 1 Compound containing Serial a carbon-carbon Compound containing a Compound capable of No. double bond sulfur element blocking a hydroxyl 1 Zinc acrylate Tetramethyl thiuram Vinyltriacetoxysilane monosulfide Zinc acrylate Tetramethyl thiuram Diisobutoxy(ethylacetoacetate)titanate 2 monosulfide Zinc acrylate Tetramethyl thiuram Isopropyl 3 monosulfide dioleic(dioctylphosphate)titanate 4 Zinc acrylate Tetramethyl thiuram Vinyltriacetoxysilane monosulfide 5 Zinc acrylate 2-mercaptobenzothiazole Vinyltriacetoxysilane 6 Zinc acrylate Bis[3- Vinyltriacetoxysilane (triethoxysilyl)propyl]tetrasulfide 7 Zinc acrylate 3- Vinyltriacetoxysilane mercaptopropyltriethoxysilane 8 Zinc acrylate (3- Vinyltriacetoxysilane mercaptopropyl)trimethoxysilane 9 Vinyltrimethoxysilane 2-mercaptobenzothiazole Vinyltriacetoxysilane 10 Vinyltris(2- 2-mercaptobenzothiazole Vinyltriacetoxysilane methoxyethoxy)silane 11 Isopropyl trioleyl 2-mercaptobenzothiazole Vinyltriacetoxysilane titanate 12 Vinyltrimethoxysilane 2-mercaptobenzothiazole / 13 Vinyltrimethoxysilane / Vinyltriacetoxysilane 14 / 2-mercaptobenzothiazole Vinyltriacetoxysilane 15 Vinyltrimethoxysilane / / 16 / 2-mercaptobenzothiazole / 17 / / Vinyltriacetoxysilane

[0070] The results were analyzed according to Table 2 and FIG. 1: [0071] (1) The contact angle of the enzymatic hydrolysis lignin was tested. As can be seen from Table 2, the contact angles of the modified lignin are all increased in comparison to the contact angle of the unmodified lignin, which was 62°. [0072] (2) Compared with other modifications, the hydroxyl was not blocked in Examples 1-12, and the contact angle of the modified lignin was 80°, which was lower than that of other embodiment in Embodiment 1, indicating that it was very necessary to use the compound that can block the hydroxyl for modification. Examples 1-1 to 1-3 used different compounds to block the hydroxyl of the enzymatic hydrolysis lignin, and contact angles of the three embodiments were similar. [0073] (3) Embodiments 1-4 to 1-8 studied influences of different sulfides on the contact angle. The results showed that different sulfides had no significant influence on the contact angles except for Examples 1-7 and 1-8, because a silane coupling agent was used in Embodiments 1-7 and 1-8, which contained sulfhydryl and silane at the same time, and had a certain function of blocking the hydroxyl. [0074] (4) In Embodiments 1-9 to 1-11, different compounds containing carbon-carbon double bonds were used for modification, and vinyltriacetoxysilane was used to block hydroxyl. Compared with an acrylic acid, these three examples used long chains containing double bonds for modification, and the contact angle of the modified enzymatic hydrolysis lignin was obviously improved, especially in Embodiment 1-9, the contact angle thereof reached 101, which showed that the polarity of the lignin was greatly improved.

TABLE-US-00002 TABLE 2 Serial No. Contact angle 0 (unmodified enzymatic hydrolysis lignin) 62° 1 93° 2 89° 3 93° 4 94° 5 95° 6 94° 7 104°  8 105°  9 101°  10 96° 11 98° 12 80° 13 85° 14 81° 15 77° 16 63° 18 78°

Embodiment 2: Preparation of Modified Lignin (Airflow Modification Method)

[0075] According to the serial numbers 4, 9, 10 and 12 in Table 1, a first solution and a second solution were prepared in the same way as in Embodiment 1.

[0076] Enzymatic hydrolysis lignin was sprayed into a pulverizing cavity by high-pressure air at about 100° C., and at the same time, the first solution (flow rate was 40 mL/min) was sprayed into the pulverizing cavity through an atomizing nozzle, and a rotating speed of an air classification wheel was 2,000 rpm, running for 2 minutes; then, the second solution (flow rate was 40 mL/min) was sprayed into the pulverizing cavity through the atomizing nozzle, and a rotating speed of an air classification wheel was 2,000 rpm, running for 3 minutes; and then the lignin was separated by a cyclone separator to obtain four kinds of modified lignin, namely ligni4, lignin9, lignin10 and lignin12. Particle sizes of the modified lignin were tested by S3500 laser particle size analyzer by American Microtrac, and D50 of the four were 1.6 μm, 1.4 μm, 1.7 μm and 2.3 μm respectively. However, in Embodiment 1, the particle size of the modified lignin prepared by the same method was higher than these four particle sizes. It follows that the particle size of the lignin can be further reduced by air flow pulverization, which is more conducive to the application of the lignin in the rubber.

Embodiment 3: Preparation of Lignin Reinforced Rubber

[0077] (1) 10 g of enzymatic hydrolysis lignin (particle size was pulverized to 2.1 μm by air flow), the lignin4, the lignin9, the lignin10 and the lignin12 prepared in Embodiment 2, and the lignin13 and the lignin14 (the serial No. 13 and the series number 14 in Table 1) prepared according to Embodiment 2, 40 g of natural rubber, 10 g of high wear-resistant carbon black N330, 1 g of sulfur, 0.6 g of N-cyclohexylbenzothiazole-2-sulphenamide, 2 g of zinc oxide and 0.8 g of stearic acid were respectively taken and added into an internal mixer in turn, and mixed at 100° C. for 20 minutes. [0078] (2) The rubber compound obtained in step (1) was put in an open mill and thinned for 7 times, and a vulcanization property of the rubber compound was measured by a rubber vulcanizer to obtain that an optimum curing time t90 at 180° C. was 3 minutes, and then the rubber compound was hot-pressed and molded by a vulcanizing press at 180° C. for 3 minutes, and the obtained rubbers were respectively named as Ru-lignin, Ru-lignin4, Ru-lignin9 and Ru-lignin10, Ru-lignin12, Ru-lignin13 and Ru-lignin14. The detection results of the rubbers were as shown in Table 3.

TABLE-US-00003 TABLE 3 Properties of vulcanized rubber 300% 100% Elonga- stress at stress at Tensile tion definite definite Tensile strength at break elongation elongation set Hard- (MPa) (%) (MPa) (MPa) (%) ness Ru-lignin 7.9 340 2.9 1.3 2.2 63 Ru-lignin4 27.93 861 6.2 3.4 11.1 81 Ru-lignin9 28.9 864 7.2 3.9 11.5 82 Ru-lignin10 26.3 862 6.1 3.4 10.5 78 Ru-lignin12 20.1 755 4.7 1.9 7.8 70 Ru-lignin13 15.9 693 3.8 1.5 6.7 65 Ru-lignin14 18.7 731 4.1 1.8 7.4 68

[0079] It can be seen from Table 3 that under the same particle size, compared with the unmodified lignin, the properties of the rubber prepared after being modified by the lignin are greatly improved. Compared with the lignin lignin12, the lignin13 and the lignin14 with the hydroxyl not blocked, the ligni4, the lignin13 and the lignin14 modified by three compounds at the same time can significantly improve the properties of the rubber after increasing the contact angle. Meanwhile, the lignin4 is modified by zinc acrylate with double bonds. Although a chain length of the zinc acrylate is not as long as that of vinyltrimethoxysilane, the zinc acrylate is beneficial to vulcanization with the rubber, so the zinc acrylate can also achieve a similar effect as the lignin9.

Embodiment 4

[0080] In the same way as the preparation method for the Ru-lignin9 in Embodiment 3, the natural rubber was changed into butyl rubber and neoprene rubber. Properties of the rubber prepared by the butyl rubber were tested, and a tensile strength, an elongation at break, a 300% stress at definite elongation, a 100% stress at definite elongation, a tensile set and a hardness of the rubber were 27.8 MPa, 870%, 7.5 MPa, 3.6 MPa, 11.7% and 79 respectively. Properties of the rubber prepared by the neoprene rubber were tested, and a tensile strength, an elongation at break, a 300% stress at definite elongation, a 100% stress at definite elongation, a tensile set and a hardness of the rubber were 18.3 MPa, 578%, 5.8 MPa, 4.4 MPa, 3.9% and 65 respectively. It follows that, compared with the natural rubber, the modified lignin prepared by the present invention is not suitable for polar neoprene rubber.

Comparative Example 1: Preparation Method in Other Sequences

[0081] The modified lignin was prepared according to the formulation of serial No. 9 in Table 1. The same preparation method as in Embodiment 2 was adopted, except that the sequence of the first solution and the second solution was changed to obtain the modified lignin lignin91.

[0082] The modified lignin was prepared according to the formulation of serial No. 9 in Table 1. The same preparation method as in Embodiment 2 was adopted, except that the first solution and the second solution were mixed. That is, enzymatic hydrolysis lignin was sprayed into a pulverizing cavity by high-pressure air at about 100° C., and the mixed solution of the first solution and the second solution (flow rate was 40 mL/min) was sprayed into the pulverizing cavity by an atomizing nozzle, and a rotating speed of an air classification wheel was 2,000 rpm, running for 5 minutes, and then separated by a cyclone separator to obtain the modified lignin lignin92.

[0083] In the same way as the preparation method for the Ru-lignin9 in Embodiment 3, the lignin9 was respectively changed into the lignin91 and the lignin92 respectively to obtain rubbers Ru-lignin9l and Ru-lignin92. Properties of the rubber were detected. It can be seen from Table 4 that compared with the preparation sequence of the present invention, after the first solution and the second solution are changed in sequence, namely, the hydroxyl is blocked first, and then the compound containing the sulfur element and the compound containing the double bond are used for modification, and the properties of the rubber are worse than that of using the three together.

TABLE-US-00004 TABLE 4 300% 100% Elonga- stress at stress at Tensile tion definite definite Tensile strength at break elongation elongation set Hard- (MPa) (%) (MPa) (MPa) (%) ness Ru-lignin9 28.9 864 7.2 3.9 11.5 80 Ru-lignin91 20.0 786 4.9 2.6 8.1 70 Ru-lignin92 21.1 805 5.2 2.5 7.9 72

Comparative Example 4

[0084] The modified lignin was prepared respectively according to the substances in the formulation of serial No. 9 in Table 1. The same preparation method as in Embodiment 2 was adopted, that is, three compounds were prepared into solutions to obtain solutions of three compounds; enzymatic hydrolysis lignin was sprayed into a pulverizing cavity by high-pressure air at about 100° C., and the solutions of the three compounds (flow rate was 40 mL/min) were sprayed into the pulverizing cavity by an atomizing nozzle respectively, and a rotating speed of an air classification wheel was 2,000 rpm, running for 5 minutes, and then separated by a cyclone separator to obtain the modified lignin lignin93 (modified by vinyltrimethoxysilane), the lignin94 (modified by 2-mercaptobenzothiazole) and the lignin95 (modified by vinyltriacetoxysilane).

[0085] In the same way as the preparation method for the Ru-lignin9 in Embodiment 3, the lignin9 was respectively changed into the lignin93, the lignin94 and the lignin95 respectively to obtain rubbers Ru-lignin93, Ru-lignin94 and Ru-lignin95. Properties of the rubber were detected, and the results were seen in Table 5. It can be seen from Table 5 that although the properties are improved to some extent, the improvement effect is small, and the present invention can achieve a good effect only when the three are used at the same time.

TABLE-US-00005 TABLE 5 Tensile strength Elongation at break (MPa) (%) Hardness Ru-lignin9 28.9 864 80 Ru-lignin93 12.6 408 68 Ru-lignin94 13.8 415 68 Ru-lignin93 12.9 410 70

Embodiment 5

[0086] In the same way as the preparation method of Ru-lignin9 in Embodiment 3, the dosages of the lignin9 were changed to 20 parts, 30 parts, 40 parts and 50 parts respectively, and the prepared rubbers were respectively named as Ru-lignin9-20, Ru-lignin9-30, Ru-lignin9-40 and Ru-lignin9-50. Moreover, in the same way as the preparation method of Ru-lignin12 in Embodiment 3, the dosages of the lignin12 were changed to 20 parts, 30 parts, 40 parts and 50 parts respectively, and the prepared rubbers were respectively named as Ru-lignin12-20, Ru-lignin12-30, Ru-lignin12-40 and Ru-lignin12-50. The detection results were shown in FIG. 2. It can be seen from the figure that the dosage of the lignin9 can reach 50 parts. Although the properties of the Lignin 9 decrease at the dosage of 50 parts, the properties are still higher than the original dosage of 10 parts, while the properties of the Ru-lignin12 decrease at the dosage of 30 parts with the increase of the dosage of the lignin12. Therefore, after the modifier with long chain and double bonds is selected by the present invention to modify the lignin, the properties of the rubber can be significantly improved, and the replacement amount of the lignin to the carbon black can be further improved.

[0087] The present invention provides the ideas and methods of the modified lignin reinforced rubber and the preparation method therefor. There are many methods and ways to realize the technical solutions. The above is only the preferred embodiments of the present invention. It should be pointed out that those of ordinary skills in the art can make some improvements and embellishments without departing from the principle of the present invention, and these improvements and embellishments should also be regarded as falling with the scope of protection of the present invention. All the unspecified components in the embodiments can be realized by the prior art.