Self-reinforced starch-based multifunctional materials and processing method thereof

Abstract

Disclosed is a processing method of a self-reinforced starch-based multifunctional material, and belongs to the technical field of starch deep processing. The processing method takes bulk starch as a base material, including the following steps: firstly reacting starch nanoparticles with an organic acid anhydride reagent and adding a bacteriostatic agent to prepare composite nanoparticles, then mixing the composite nanoparticles with the bulk starch, an etherifying agent, a crosslinking agent, a plasticizer and the like, and finally preparing a starch-based multifunctional material by dry extrusion modification combined with a starch-based nanoparticle assembly and reinforcement technology. The method of the disclosure is simple and convenient in step, mild and controllable in reaction, and continuous and green in production. The obtained product has good mechanical properties, high barrier properties and high antibacterial properties, can be applied to many fields such as food, textiles, daily chemicals and medicine, and has a broad market prospect.

Claims

1. A method of manufacturing a self-reinforced starch-based multifunctional material, which comprises: (a) mixing starch nanoparticles, each having a particle size of 20 nm to 100 nm, and an organic acid anhydride reagent in an aqueous solution, wherein the organic acid anhydride reagent is 0.5% to 10% of the starch nanoparticles by mass, wherein the starch nanoparticles are derived from natural plant glycogen, animal glycogen, synthetic polymer dendritic sugar chains, or starch nanocrystals, each having a molecular weight of 10.sup.5 to 10.sup.7 g/mol, (b) adjusting pH to 8 to 12, thereby forming a mixed solution, (c) reacting the mixed solution at 30° C. to 55° C. for 2 hours to 10 hours, thereby forming a reacted solution, (d) blending 0.1 wt % to 0.5 wt % of an antibacterial agent into the reacted solution, thereby forming a blend, (e) drying the blend to thereby prepare composite nanoparticles, (f) preparing a composition according to the proportion of each material added, in parts by weight, by mixing 100 parts of bulk starch, 20 parts to 60 parts of the composite nanoparticles, 2 parts to 5 parts of an etherifying agent, 2 parts to 5 parts of a crosslinking agent, and 2 parts to 5 parts of a plasticizer, (g) adjusting the composition formed in step (g) of step (f) to a moisture content of 10 wt % to 25 wt %; and (h) feeding the composition into a twin-screw extruder, wherein three heating zones of the twin-screw extruder of material kneading, melting plasticization, and modification molding are 60° C. to 90° C., 90° C. to 120° C., and 110° C. to 130° C., respectively, and wherein the twin-screw extruder has a screw speed of 100 r/min to 200 r/min, thereby obtaining the self-reinforced starch-based multifunctional material.

2. The method according to claim 1, wherein: the organic acid anhydride reagent comprises one or more of: succinic anhydride, maleic anhydride, acetic anhydride, stearic anhydride and citric anhydride; and the antibacterial agent comprises one or more of nisin, lysozyme, chitin, ε-polylysine, natamycin, thymol, eugenol, and Gemini quaternary ammonium salt.

3. The method according to claim 1, wherein the bulk starch comprises cereal starch, potato starch, or legume starch.

4. The method according to claim 1, wherein the bulk starch comprises one or more of corn starch, wheat starch, potato starch, tapioca starch, rice starch, sweet potato starch, and mung bean starch.

5. The method according to claim 1, wherein: the etherifying agent comprises one or more of ethylene oxide, propylene oxide, methyl chloride, 2-chloroethanol, epichlorohydrin, acrylamide, dimethylsulfuric acid, monohalogenated carboxylic acid, and cationic amine reagents; the cross-linking agent comprises one or more of aliphatic dihalogen compounds, tripolyphosphates, sodium trimetaphosphate, citrate, organic mixed acid anhydride, urea, dimethylolurea, dimethylol ethylene urea, acrolein, and succinic aldehyde; and the plasticizer comprises one or more of water, glycerin, ethylene glycol, sorbitol, and xylitol.

6. The method according to claim 3, wherein: the etherifying agent comprises one or more of ethylene oxide, propylene oxide, methyl chloride, 2-chloroethanol, epichlorohydrin, acrylamide, dimethylsulfuric acid, monohalogenated carboxylic acid, and cationic amine reagents; the cross-linking agent comprises one or more of aliphatic dihalogen compounds, tripolyphosphates, sodium trimetaphosphate, citrate, organic mixed acid anhydride, urea, dimethylolurea, dimethylol ethylene urea, acrolein and succinic aldehyde; and the plasticizer comprises one or more of water, glycerin, ethylene glycol, sorbitol, and xylitol.

7. The method according to claim 5, wherein the monohalogenated carboxylic acid is monochloroacetic acid.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 is an electron micrograph of the self-reinforced starch-based multifunctional material obtained in Example 1.

DETAILED DESCRIPTION

(2) The content of the disclosure will be further clarified below with examples, but the content protected by the disclosure is not limited to the following examples.

(3) Molecular weight determination: The molecular weight is determined by a combined system of high performance liquid phase exclusion chromatography, a multi-angle laser light scattering detector and a differential refractive index detector. The wavelength λ of a He—Ne laser source in the multi-angle laser scattering detector is 632.8 nm. A Shodx OHpak SB-806 chromatographic column is used, a 0.1 mol/L NaNO.sub.3 solution is used as a mobile phase, and the flow rate is 0.2 mL/min. The refractive index increment is set to dn/dc=0.138.

(4) Particle size determination: A sample to be tested is prepared into a 0.1% (w/v) solution, and particle size distribution is determined with a Malvern Zetasizer Nano ZS analyzer at 25° C.

(5) Amylose content determination: A reference is made to the method in GB/T 15683-2008 Determination of Amylose Content of Rice for analysis.

(6) Tensile strength determination: A reference is made to the method in the national standard GB/T 1040.2-2006 Determination of Plastic Tensile Properties Part 2: Test Conditions of Molded and Extruded Plastics for analysis.

(7) Moisture resistance determination: A reference is made to the method in GB/T 26253-2010 Determination of Water Vapor Transmission Rate of Plastic Films and Sheets, Infrared Detector Method for analysis.

(8) Determination of broad-spectrum antibacterial rate: Food-borne spoilage bacteria such as Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Salmonella typhimurium (S. typhimurium), and Listeria monocytogenes (L. monocytogenes) are streaked on nutrient agar and cultured at 37° C. for 12 h, and then single colonies are selected. Then the single colonies are incubated for 12 h at 37° C. in nutrient broth, plate count is performed, and a certain amount of bacteria is pipetted into 100 mL of nutrient broth (finally 10.sup.7 CFU/mL). Then an appropriate amount of the self-reinforced starch-based multifunctional material is put for culturing in a constant temperature incubator at 37° C. OD.sub.600 values of the sample at 0 h, 4 h, 6 h, 8 h, 10 h, 12 h and 24 h are measured, and plate count is performed on the sample cultured for 12 h to determine the antibacterial rate. The determination is performed in triplicate for each group of samples, and the calculation formula is as follows:

(9) $\mathrm{Antibacterial}\mathrm{rate}\left(\%\right)=\frac{\begin{array}{c}\mathrm{Bacterial}\mathrm{count}\mathrm{of}\mathrm{control}\mathrm{sample}-\\ \mathrm{Recycled}\mathrm{Bacterial}\mathrm{count}\end{array}}{\mathrm{Recycled}\mathrm{bacterial}\mathrm{count}\mathrm{of}\mathrm{sample}}\times 100.$

(10) The corn glycogen and the synthetic polymer dendritic sugar chains can be prepared by referring to: Ming Miao, Microbial Starch-Converting Enzymes: Recent Insights and Perspectives, Comprehensive Reviews in Food Science and Food Safety 2018, 17: 1238-1260; The oyster glycogen was purchased from Sigma company.

Example 1

(11) Corn glycogen (3.1×10.sup.7 g/mol, particle size 82 nm) and acetic anhydride were mixed in an aqueous solution. The mass fraction of the acetic anhydride relative to the corn glycogen was 1%. The pH was adjusted to 12, the mixed solution was placed at 30° C. to react for 10 h, and 0.1% chitin was added for aggregating and drying to prepare composite nanoparticles. According to the proportion of each material added (weight percentage), 100 parts of corn starch (amylose content 51%), 40 parts of the composite nanoparticles, 2 parts of epichlorohydrin, 5 parts of urea, and 3 parts of glycerin were mixed, and the moisture content was adjusted to 15%. A twin-screw extruder was used as a reactor, the temperatures of three heating zones of material kneading, melting plasticization, and modification molding were set at 60° C., 95° C., and 130° C. separately, the screw speed was set as 150 r/min, and a dry extrusion reaction was performed to obtain a self-reinforced starch-based multifunctional material, the electron micrograph of which is shown in FIG. 1.

(12) The obtained target product self-reinforced starch-based multifunctional material has a tensile strength of 34 MPa, a moisture resistance of 4.6 g/(m.sup.2×24 h), and a broad-spectrum antibacterial rate of 98.2%.

Example 2

(13) Oyster glycogen (7.2×10.sup.6 g/mol, particle size 67 nm) and citric anhydride were mixed in an aqueous solution. The mass fraction of the citric anhydride relative to the oyster glycogen was 5%. The pH was adjusted to 11, the mixed solution was placed at 50° C. to react for 4 h, and 0.3% nisin was added for aggregating and drying to prepare composite nanoparticles. According to the proportion of each material added (weight percentage), 100 parts of tapioca starch (amylose content 36%), 20 parts of the composite nanoparticles, 5 parts of monochloroacetic acid, 3 parts of citrate, and 4 parts of sorbitol were mixed, and the moisture content was adjusted to 20%. A twin-screw extruder was used as a dry reactor, the temperatures of three heating zones of material kneading, melting plasticization, and modification molding were set at 90° C., 100° C., and 110° C. separately, the screw speed was set as 120 r/min, and extrusion was performed to obtain a self-reinforced starch-based multifunctional material.

(14) The obtained target product self-reinforced starch-based multifunctional material has a tensile strength of 29 MPa, a moisture resistance of 5.1 g/(m.sup.2×24 h), and a broad-spectrum antibacterial rate of 99.4%.

Example 3

(15) Synthetic polymer dendritic sugar chains (8.2×10.sup.5 g/mol, particle size 44 nm) and stearic anhydride were mixed in an aqueous solution. The mass fraction of the stearic anhydride relative to the synthetic polymer dendritic sugar chains was 8%. The pH was adjusted to 9, the mixed solution was placed at 45° C. to react for 6 h, and 0.5% ε-polylysine was added for aggregating and drying to prepare composite nanoparticles. According to the proportion of each material added (weight percentage), 100 parts of rice starch (amylose content 42%), 60 parts of the composite nanoparticles, 4 parts of methyl chloride, 2 parts of ethylene glycol dimethacrylate, and 4 parts of ethylene glycol were mixed, and the moisture content was adjusted to 18%. A twin-screw extruder was used as a dry reactor, the temperatures of three heating zones of material kneading, melting plasticization, and modification molding were set at 65° C., 90° C., and 120° C. separately, the screw speed was set as 160 r/min, and extrusion was performed to obtain a self-reinforced starch-based multifunctional material.

(16) The obtained target product self-reinforced starch-based multifunctional material has a tensile strength of 32 MPa, a moisture resistance of 4.1 g/(m.sup.2×24 h), and a broad-spectrum antibacterial rate of 99.0%.

(17) When the starch nanoparticles, organic acid anhydrides, antibacterial agents, bulk starch, etherifying agents, crosslinking agents, plasticizers and the like in the above examples are replaced with other materials described in the disclosure, self-reinforced starch-based multifunctional materials can also be prepared and have a tensile strength of greater than 25 MPa, a moisture resistance of less than 6.0 g/(m.sup.2×24 h), and a broad-spectrum bacteriostatic rate of greater than 95%.

Comparative Example 1

(18) Referring to Example 1, when composite nanoparticles were not prepared, according to the proportion of each material added (weight percentage), 100 parts of corn starch (amylose content 51%), 2 parts of epichlorohydrin, 5 parts of urea, 3 parts of glycerin and 4 parts of bacteriostatic chitin were mixed, and the moisture content was adjusted to 15%. A twin-screw extruder was used as a reactor, the temperatures of three heating zones of material kneading, melting plasticization, and modification molding were set at 60° C., 95° C. and 130° C. separately, the screw speed was set as 150 r/min, and a dry extrusion reaction was performed to obtain a material.

(19) After testing, the material has a tensile strength of 21 MPa, a moisture resistance of 6.7 g/(m.sup.2×24 h), and a broad-spectrum antibacterial rate of 57%.

Comparative Example 2

(20) Referring to Example 1, when no chitin was added to the composite nanoparticles, according to the proportion of each material added (weight percentage), 100 parts of corn starch (amylose content 51%), 40 parts of the composite nanoparticles, 2 parts of epichlorohydrin, 5 parts of urea and 3 parts of glycerin were mixed, and the moisture content was adjusted to 15%. A twin-screw extruder was used as a reactor, the temperatures of three heating zones of material kneading, melting plasticization, and modification molding were set at 60° C., 95° C. and 130° C. separately, the screw speed was set as 150 r/min, and a dry extrusion reaction was performed to obtain a material.

(21) After testing, the material has a tensile strength of 27 MPa, a moisture resistance of 5.9 g/(m.sup.2×24 h), and a broad-spectrum antibacterial rate of 0%.

Comparative Example 3

(22) Referring to Example 1, the mass fraction of the acetic anhydride added in the preparation of the composite nanoparticles was replaced with 0%, 0.2%, and 30%, respectively, to obtain the corresponding starch-based material properties. The properties of the products obtained are shown in Table 1.

(23) TABLE-US-00001 TABLE 1 Properties of products obtained with different amounts of organic acid anhydride reagent Mass fraction Tensile Moisture Broad-spectrum of organic acid strength resistance antibacterial anhydride reagent MPa g/(m.sup.2 × 24 h) rate %  0% 23 6.3 70 0.2%  26 6.6 87 30% 26 6.1 91

Comparative Example 4

(24) Referring to Example 1, the mass fraction of moisture in the dry extrusion reaction was controlled to 0%, 5% and 40%, respectively, to obtain the corresponding starch-based material properties. The properties of the products obtained are shown in Table 2.

(25) TABLE-US-00002 TABLE 2 Properties of the products prepared under different mass fractions of moisture in the dry extrusion reaction Tensile Moisture Broad-spectrum Mass fraction strength resistance antibacterial of moisture MPa g/(m.sup.2 × 24 h) rate % 0% 22 5.9 96 5% 24 5.6 95 40%  17 6.6 85

Comparative Example 5

(26) Referring to Example 1, when no epichlorohydrin was added, a material was obtained by dry extrusion reaction.

(27) After testing the properties of the starch-based material, the tensile strength is 16 MPa, the moisture resistance is 6.3 g/(m.sup.2×24 h), and the broad-spectrum antibacterial rate is 96%.

Comparative Example 6

(28) Referring to Example 1, when no urea was added, a material was obtained by dry extrusion reaction.

(29) After testing the properties of the starch-based material, the tensile strength is 23 MPa, the moisture resistance is 6.1 g/(m.sup.2×24 h), and the broad-spectrum antibacterial rate is 97%.

(30) Although the disclosure has been disclosed as above in preferred examples, it is not intended to limit the disclosure. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure. Therefore, the protection scope of the disclosure should be defined by the claims.