Preparation of nanoscale hydrophobic starch and its reinforcement of styrene-butadiene rubber

Abstract

The application belongs to the technical field of polymer materials, and discloses a preparation method of nanoscale hydrophobic starch, nanoscale hydrophobic starch and application and reinforced styrene-butadiene rubber based on the same. The preparation method adopts a nanometer precipitation method to perform nanometer treatment on starch and then perform hydrophobic modification, so as to obtain nanoscale hydrophobic starch. The nanoscale hydrophobic starch is applied to the reinforcement of styrene-butadiene rubber, the nanoscale crystalline starch is dispersed in the styrene-butadiene rubber in a nanoscale, has a micro-nano island structure, and improves the modulus and strength of the reinforcing body; through efficient hydrophobic modification, the interface strength is further increased, and the water absorption of the starch is reduced, so that the defects of performance reduction of the styrene-butadiene rubber caused by water absorption and swelling of the starch during use are overcome; after the reinforcement, the mechanical properties of the styrene-butadiene rubber are obviously improved, the tensile strength is increased by more than 110%, the elongation at break is increased by 59%, and the 100% modulus and the 300% modulus are also obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and specifically relates to a method for preparing nano-scale hydrophobic starch, the nano-scale hydrophobic starch and its applications, and styrene-butadiene rubber based thereon. Background Technology

[0002] Styrene-butadiene rubber (SBR) is a synthetic rubber copolymerized from butadiene and styrene. Its molecular structure is linear, and the presence of benzene rings gives SBR better physical and chemical properties than polypropylene rubber, making it widely used in automotive parts, seals, medical devices, transportation, and communications. Currently, the main reinforcing materials for SBR are carbon black and precipitated silica. However, the production of precipitated silica requires a large amount of energy; carbon black is a fossil resource and non-renewable, and its production process poses health problems for workers. Therefore, it is necessary to find renewable reinforcing agents that align with green development strategies.

[0003] Starch has excellent biodegradability; the carbon dioxide and water produced during degradation can return to nature without causing environmental pollution. In addition, starch also has excellent biocompatibility, mechanical properties, and processability, and has broad application prospects in many fields such as biomedicine, textiles and clothing, plastic packaging, agriculture, forestry, animal husbandry and fishery. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a method for preparing nano-scale hydrophobic starch.

[0005] Another object of the present invention is to provide nanoscale hydrophobic starch prepared by the above method.

[0006] Another object of the present invention is to provide applications of the above-mentioned nano-sized hydrophobic starch, particularly in reinforcing styrene-butadiene rubber.

[0007] Another object of the present invention is to provide a reinforced styrene-butadiene rubber based on the above-mentioned nano-scale hydrophobic starch.

[0008] The objective of this invention is achieved through the following solution:

[0009] A method for preparing nanoscale hydrophobic starch, using a nanoprecipitation method, includes the following specific steps:

[0010] (1) Starch nano-sizing: The starch suspension was gelatinized once, and then amylase was added under heat for enzymatic hydrolysis. After refrigeration, it was heated again for secondary gelatinization. The system was then added to an ethanol solution to separate and obtain nano-sized starch.

[0011] (2) Hydrophobic modification: Nano-sized starch was added to hexadecyltrimethoxysilane hydrolysate and stirred to react. After separation and drying, it was heated under an inert atmosphere to obtain nano-sized hydrophobic starch.

[0012] In step (1), the concentration of the starch suspension can be 10-15 wt%. It is obtained by dispersing starch in water.

[0013] In step (1), the starch can be any conventional starch in the art, such as tapioca starch, corn starch, potato starch, etc.

[0014] In step (1), the gelatinization treatment, whether the process is the same or different, can be carried out at 90-98℃. The gelatinization time, whether the process is the same or different, can be 20-120 min. Gelatinization is preferably carried out in a constant temperature water bath. Continuous stirring is preferably performed during the gelatinization process.

[0015] In step (1), the insulation temperature can be 50-60℃.

[0016] In step (1), the amount of amylase added can be 7-10 ASPU / g starch.

[0017] In step (1), the amylase can be any enzyme commonly used in the art, such as α-amylase, β-amylase, isoamylase, etc.

[0018] In step (1), the enzymatic hydrolysis time can be 6-10 hours.

[0019] In step (1), the refrigeration treatment can be carried out at 2-6℃; the treatment time can be 12-48h.

[0020] In step (1), the volume ratio of ethanol to water in the ethanol solution can be 3:2-5:0.

[0021] In step (2), the mass ratio of nano-sized starch to hydrolysate can be 5:100-10:100.

[0022] In step (2), the mass concentration of hexadecyltrimethoxysilane in the hydrolysate can be 2.5-5‰.

[0023] In step (2), the pH of the hydrolysate can be 4-6. The pH of the system can be adjusted by using an acid, such as hydrochloric acid, acetic acid, sulfuric acid, or a mixture thereof.

[0024] Furthermore, the hydrolysate can be obtained by adding hexadecyltrimethoxysilane (HDS) to an aqueous ethanol solution.

[0025] Furthermore, the hydrolysate can be obtained by adding hexadecyltrimethoxysilane (HDS) to an aqueous ethanol solution and hydrolyzing at pH 4-6 for 1-4 hours.

[0026] Furthermore, the volume ratio of ethanol to water in the ethanol-water solution can be 2:3-4:1.

[0027] In step (2), the drying process can be vacuum drying at room temperature.

[0028] In step (2), the heating treatment can be carried out at 100-120℃; the treatment time can be 1-5h.

[0029] The preparation method and separation of the present invention can be carried out by conventional methods, such as centrifugation, for example, centrifugation at 5000-10000 rpm for 1-30 min.

[0030] The preparation method of this invention is simple and mild, and the prepared nano-sized hydrophobic starch has small particle size and stable properties, effectively solving the problem of severe sticking of existing nano-sized starch during alcohol precipitation.

[0031] The present invention also provides a nanoscale hydrophobic starch prepared by the above method.

[0032] The present invention also provides the application of the above-mentioned nano-scale hydrophobic starch in reinforcing styrene-butadiene rubber.

[0033] The present invention also provides a reinforcing styrene-butadiene rubber, the components of which contain the above-mentioned nano-sized hydrophobic starch.

[0034] The nano-sized hydrophobic starch of this invention achieves a small particle size distribution through nano-sizing treatment, while having a large number of active groups such as hydroxyl groups distributed on the surface. Then, through acid hydrolysis and HDS modification, it fully combines with HDS to form hydrophobic starch. When applied to the reinforcement of styrene-butadiene rubber (SBR), nano-sized crystalline starch improves the modulus and strength of the reinforcement. Its nanoscale dispersion within SBR, exhibiting a micro-nano island structure, results in excellent reinforcement. Through efficient hydrophobic modification, long-chain lipids are introduced onto the starch surface, further increasing interfacial strength while reducing starch water absorption, overcoming the defect of SBR performance degradation caused by starch swelling during use. The long-chain hydrophobic groups on its surface have good compatibility with SBR, improving the dispersion of starch within the rubber groups, thus forming a uniformly dispersed reinforcing structure in the rubber matrix. Simultaneously, it retains a large number of surface-active groups, significantly improving the physical and mechanical properties of SBR (non-polar rubber). This effectively solves the problem of weak interfacial bonding between starch and non-polar rubber, resulting in a significant improvement in the mechanical properties of the reinforced SBR. Tensile strength increases by over 110%, elongation at break increases by 59%, and stresses at 100% and 300% of their maximum tensile strength are also significantly improved.

[0035] This invention uses starch to reinforce styrene-butadiene rubber (SBR). Starch, as a low-cost renewable resource, can reduce costs when used as a reinforcing filler in SBR. It is also completely biodegradable and environmentally friendly. The resulting reinforced SBR exhibits significantly improved performance and can be applied in various fields such as automotive parts, seals, medical devices, transportation, and communications. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figures 1-2 The image shows an electron microscope image of the nano-sized starch prepared in Example 1.

[0038] Figure 3 The image shows the hydrophobic angle of the nano-sized hydrophobic starch prepared in Example 1.

[0039] Figure 4 This is a picture of gelatinized starch in a comparative example.

[0040] Figure 5 This is a cross-sectional electron microscope image of sample 1. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, all materials involved in the following embodiments are commercially available. Unless otherwise specified, all methods described are conventional methods.

[0042] Styrene-butadiene rubber: SBR-1502, Kunlun; hexadecyltrimethoxysilane: 16415-12-6, Aladdin; starch, stearic acid, zinc oxide and other reagents are all commercially available industrial products.

[0043] Example 1

[0044] (1) Starch nano-sizing: A starch aqueous suspension with a mass concentration of 15% was placed in a 98℃ constant temperature water bath and stirred for 30 min to obtain a translucent starch paste. The temperature of the constant temperature water bath was lowered to 58℃, and 10 ASPU / g α-amylase was added for further enzymatic hydrolysis for 6 h. The system was then refrigerated at 4℃ for 24 h, and then subjected to secondary gelatinization in a 98℃ constant temperature water bath for 1 h to obtain a secondary starch paste. The secondary starch paste was poured into a large amount of ethanol-water aqueous solution (ethanol-water volume ratio 4:1) and nano-sized starch was obtained. The prepared nano-sized starch was scanned by electron microscopy, and the results are shown in the figure. Figures 1-2As shown in the figure, the present invention prepares nanoscale starch particles with uniform particle size distribution and that are not easily aggregated.

[0045] (2) Hydrophobic modification of nano-starch: The pH of an ethanol-water solution (ethanol-water volume ratio 4:1) was adjusted to 4 using acid. Hexadecyltrimethoxysilane (HDS) was added at a mass concentration of 2.5‰, and the mixture was stirred and hydrolyzed for 2 hours to obtain a hydrolysate. Five parts by mass of nano-sized starch were added to 100 parts by mass of the above hydrolysate, and the mixture was stirred and reacted for 2 hours. After centrifugation, the mixture was vacuum dried at room temperature to remove water and ethanol. Then, it was heated to 120℃ for 2 hours under a nitrogen atmosphere to obtain nano-sized hydrophobic starch. The hydrophobic angle of the prepared nano-sized hydrophobic starch was measured, and the results are shown in […]. Figure 3 As can be seen from the figure, the nanoscale hydrophobic starch prepared by this invention has excellent hydrophobic properties.

[0046] Example 2

[0047] (1) Starch nanoparticle formation: A 10% starch aqueous suspension was placed in a 95℃ constant temperature water bath and stirred for 40 min to obtain a translucent starch paste. The temperature of the constant temperature water bath was lowered to 58℃, and 7 ASPU / g β-amylase was added for further enzymatic hydrolysis for 6 h. The system was then refrigerated at 4℃ for 48 h, and then subjected to secondary gelatinization at 95℃ constant temperature water bath for 0.5 h to obtain a secondary starch paste. The secondary starch paste was poured into a large amount of ethanol solution and separated to obtain nano-sized starch. Electron microscopy of the prepared nano-sized starch showed that the nano-sized starch particles prepared by this invention had a uniform particle size distribution and were not prone to agglomeration.

[0048] (2) Hydrophobic modification of nano-starch: The pH of an ethanol-water solution (ethanol-water volume ratio 4:1) was adjusted to 5 with acid, and hexadecyltrimethoxysilane (HDS) was added at a mass concentration of 2.5‰. The mixture was stirred and hydrolyzed for 2 hours to obtain a hydrolysate. Five parts by mass of nano-sized starch were added to 100 parts by mass of the above hydrolysate and stirred for 2 hours. The mixture was centrifuged, vacuum dried at room temperature to remove water and ethanol, and then heated to 120°C for 2 hours under a nitrogen atmosphere to obtain nano-sized hydrophobic starch. The hydrophobic angle of the prepared nano-sized hydrophobic starch was measured, and the results showed that the nano-sized hydrophobic starch prepared by this invention has excellent hydrophobic properties.

[0049] Example 3

[0050] (1) Starch nano-sizing: A starch aqueous suspension with a mass concentration of 12% was placed in a 92℃ constant temperature water bath and stirred for 60 min to obtain a translucent starch paste. The temperature of the constant temperature water bath was lowered to 58℃, and 9 ASPU / g of isoamylase was added for further enzymatic hydrolysis for 6 h. The system was then refrigerated at 4℃ for 36 h, and then subjected to secondary gelatinization in a 92℃ constant temperature water bath for 1 h to obtain a secondary starch paste. The secondary starch paste was poured into a large amount of ethanol aqueous solution (ethanol-water volume ratio 3:2) and separated to obtain nano-sized starch. Electron microscopy of the prepared nano-sized starch showed that the nano-sized starch particles prepared by this invention had a uniform particle size distribution and were not prone to agglomeration.

[0051] (2) Hydrophobic modification of nano-starch: The pH of an ethanol-water solution (ethanol-water volume ratio 4:1) was adjusted to 6 with acid, and hexadecyltrimethoxysilane (HDS) was added at a mass concentration of 3‰. The mixture was stirred and hydrolyzed for 2 hours to obtain a hydrolysate. Six parts by mass of nano-sized starch were added to 100 parts by mass of the above hydrolysate and stirred for 2 hours. The mixture was centrifuged, vacuum dried at room temperature to remove water and ethanol, and then heated to 120°C for 2 hours under a nitrogen atmosphere to obtain nano-sized hydrophobic starch. The hydrophobic angle of the prepared nano-sized hydrophobic starch was measured. The hydrophobic angle of the nano-sized hydrophobic starch remained above 100° within 300 seconds, indicating that the nano-sized hydrophobic starch prepared in this invention has excellent hydrophobic properties.

[0052] Comparative Example 1

[0053] A 15% (w / w) starch aqueous suspension was placed in a 98°C constant temperature water bath and stirred for 30 minutes to obtain a translucent starch paste. The temperature of the constant temperature water bath was then lowered to 58°C, and 10 ASPU / g α-amylase was added. Enzymatic hydrolysis continued for 6 hours. The hydrolyzed product was then directly poured into a large amount of ethanol aqueous solution. The nano-starch particles would stick together and be unable to separate due to excessive viscosity. (See...) Figure 4 .

[0054] Comparative Example 2

[0055] (1) Starch nanoparticle formation: A 10% starch aqueous suspension was placed in a 95℃ constant temperature water bath and stirred for 40 min to obtain a translucent starch paste. The temperature of the constant temperature water bath was lowered to 58℃, and 7 ASPU / g β-amylase was added for further enzymatic hydrolysis for 6 h. The system was then refrigerated at 4℃ for 48 h, and then subjected to secondary gelatinization at 95℃ constant temperature water bath for 0.5 h to obtain a secondary starch paste. The secondary starch paste was poured into a large amount of ethanol solution and separated to obtain nano-sized starch. Electron microscopy of the prepared nano-sized starch showed that the nano-sized starch particles prepared by this invention had a uniform particle size distribution and were not prone to agglomeration.

[0056] (2) Hydrophobic modification of nano starch: The pH of the ethanol-water solution (ethanol-water volume ratio 4:1) was adjusted to 5 with acid solution, and bis-[γ-(triethoxysilyl)propyl]tetrasulfide (Si69) was added to it at a mass concentration of 2.5‰. The mixture was stirred and hydrolyzed for 2 hours to obtain the hydrolysate. 5 parts by mass of nano starch were added to 100 parts by mass of the above hydrolysate and stirred for 2 hours. The mixture was centrifuged, vacuum dried at room temperature to remove water and ethanol, and then heated to 120℃ for 2 hours under a nitrogen atmosphere to obtain Si69 modified starch.

[0057] To test the reinforcing effect of the nano-hydrophobic starch of this invention on styrene-butadiene rubber (SBR), the preparation of reinforced SBR according to a conventional formula included the following steps: The closed-type mixing mill was adjusted to 30 rpm and the temperature was set to 30°C. Under these conditions, 100 parts of SBR, 5 parts of zinc oxide, 2 parts of stearic acid, and the hydrophobic nano-starch of Example 1 were added every 0.5 min. The rubber compound was then placed in an open-type mixing mill and passed through it three times. 0.5 parts of accelerator DM were added; after passing through it three times, 1 part of accelerator CZ was added; after passing through it three times, 1.5 parts of sulfur were added. The mixture was then sheeted and left to stand for 9 hours before being vulcanized for 40 min at 150°C in a flat vulcanizing apparatus.

[0058] Styrene-butadiene rubber (SBR) samples 1-3 were obtained by reinforcing with different amounts of hydrophobic nano-starch from Example 1. SBR without starch modification served as a blank control, while SBR with unmodified starch or modified starch from Comparative Example 2 served as controls. The unmodified starch strongly adhered to the rotor and inner wall of the internal mixer and could not be blended with the SBR.

[0059] The tensile strength, elongation at break, stress at 100% elongation, and stress at 300% elongation of the prepared styrene-butadiene rubber material were tested. The test results are detailed in Table 1. The cross-section of sample 1 was observed using a scanning electron microscope; the results are shown in Table 1. Figure 5 .

[0060] Table 1

[0061] Sample 1 Sample 2 Sample 3 Blank comparison Comparative Example 2 Starch / parts by weight 10 20 30 / 20 Tensile strength / MPa 3.33±0.32 4.27±0.60 3.54±0.42 2.00±0.13 2.43±0.32 Elongation at break / % 451±82 517±62 451±63 325±8 402±27 100% constant tensile stress / MPa 1.16±0.3 1.33±0.04 1.50±0.03 0.97±0.04 1.11±0.01 300% constant tensile stress / MPa 2.12±0.02 2.29±0.05 2.38±0.03 1.86±0.07 1.50±0.07

[0062] Note: Unmodified starch has poor compatibility with styrene-butadiene rubber and cannot be mixed to obtain a reinforcing sample, therefore no performance data is available.

[0063] Depend on Figure 5As can be seen, the present invention prepares nanoscale modified starch, which is uniformly dispersed in the styrene-butadiene rubber matrix at the nanoscale and exhibits excellent compatibility. Combined with the data in the table, it can be seen that after nano-sizing and hydrophobic modification, the starch of the present invention can not only be effectively and uniformly dispersed in the styrene-butadiene rubber matrix, but also act as a reinforcing agent to improve the matrix strength of the styrene-butadiene rubber; after reinforcement, the mechanical properties of the styrene-butadiene rubber are significantly improved, with tensile strength increasing by more than 110%, elongation at break increasing by 59%, and significant increases in 100% and 300% constant elongation stresses.

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing nanoscale hydrophobic starch, wherein the starch is prepared by a nanoprecipitation method, characterized in that... The specific steps include the following: (1) Starch nano-sizing: The starch suspension was gelatinized once, and then amylase was added under heat for enzymatic hydrolysis. After refrigeration, it was heated again for secondary gelatinization. The system was then added to an ethanol solution and separated to obtain nano-sized starch. (2) Hydrophobic modification: Nano-sized starch was added to hexadecyltrimethoxysilane hydrolysate and stirred to react. After separation and drying, it was heated under an inert atmosphere to obtain nano-sized hydrophobic starch. In step (1), the temperature for heat preservation is 50-60℃; the enzymatic hydrolysis time is 6-10h; and the cold storage treatment is carried out at 2-6℃ for 12-48h.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of the starch suspension is 10-15 wt%; the amount of amylase added is 7-10 ASPU / g starch.

3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of nano-sized starch to hydrolysate is 5:100-10:

100.

4. The preparation method according to claim 1, characterized in that: The mass concentration of hexadecyltrimethoxysilane in the hydrolysate is 2.5-5‰.

5. The preparation method according to claim 1, characterized in that: In step (2), the hydrolysate is obtained by adding hexadecyltrimethoxysilane to an aqueous ethanol solution and hydrolyzing it at pH 4-6 for 1-4 hours.

6. The preparation method according to claim 1, characterized in that: In step (2), the heat treatment is carried out at 100-120℃; the treatment time is 1-5h.

7. A nanoscale hydrophobic starch, characterized in that... The preparation method according to any one of claims 1-6 is obtained.

8. The application of the nano-sized hydrophobic starch according to claim 7 in reinforcing styrene-butadiene rubber.

9. A reinforcing styrene-butadiene rubber, characterized in that... The component contains the nano-sized hydrophobic starch as described in claim 7.

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