LU501327B1

LU501327B1 - Method for preparing highly hydrophobic starch-based straws

Info

Publication number: LU501327B1
Application number: LU501327A
Authority: LU
Inventors: Chao Yuan; Wei Gao; Bo Cui; Li Guo; Bin Yu; Zhengzong Wu; Pengfei Liu
Original assignee: Shanke Gongda Shandong Tech Co Ltd
Priority date: 2022-01-25
Filing date: 2022-01-25
Publication date: 2022-08-09

Abstract

Disclosed is a method for preparing a highly hydrophobic starch-based straw, belonging to the technical field of agricultural product processing. A starch-based straw is prepared herein by an extrusion method with starch, water and nano-silica as raw materials. A hydrophobic modification treatment is performed on surfaces inside and outside the straw with hexamethyl-disilazane steam; and a stable Si-O-Si(CH3)3 structure formed between hexamethyl-disilazane and nano-silica is utilized to firmly graft the three hydrophobic methyl groups on the surfaces of the straw, thereby reducing the sensitivity of the starch-based straw to water molecules and enhancing the hydrophobic properties. The present disclosure overcomes the defects of the existing non-plastic straws which are easy to absorb water and to be softened, and even dissolved in hot beverages. The prepared starch-based straw is featured by good hydrophobic properties, strong mechanical properties, high temperature resistance and non-deformation when immersed in hot beverages.

Description

METHOD FOR PREPARING HIGHLY HYDROPHOBIC STARCH-BASED

STRAWS Field of the Invention The present disclosure belongs to the technical field of agricultural product processing, and particularly relates to a method for preparing a highly hydrophobic starch-based straw.

Background of the Invention With the development of science and technology, plastic straws have been widely used. Currently, most of the plastic straws sold on the market are made by polyethylene (PE) or polypropylene (PP) as a base material. But the PE/PP-based straws are difficult to be decomposed under natural conditions. Therefore, such kind of straw causes the degree of environmental pollution second only to plastic bags, and has been questioned in food safety. Hence, the development of an environmental friendly straw derived from renewable resources has become one of the research hotspots in straw products industry.

Starch is considered as one of the most potential natural biodegradable materials due to its abundance, cheapness, renewability and biodegradability. However, there are many problems, such as, poor hydrophobic properties and low mechanical strength in the existing starch-based straws; especially the starch-based straw is easy to absorb water and to be softened, even dissolved when it is used in hot beverages.

Nano-silica is a kind of nano-filler widely used in material modification.

Nano-silica has non-bonded hydroxyl groups on the surface, and shows a three-dimensional chain structure in the molecular state and thus, can form hydrogen bonds on its surface; moreover, and hydroxyl groups in starch are combined to form -Si-O-C-bonds, which can enhance the degree of crystallinity of the starch-based straw, improve the mechanical properties of straw, and weaken the water absorption of the starch-based straw. Hexamethyl-disilazane can be reacted with hydroxyl groups inside alcohols or phenols to produce trimethylalkoxysilane; trimethylalkoxysilane can form a -Si-O-C-bond when it is blended with starch, and can also be reacted with nano-silica quickly to form a more stable -Si-O-Si- bond, such that the silane of the three methyl groups can be finally grafted onto the surface of the starch-based straw. Exposure of the three methyl groups to the surface of the straw can reduce surface energy, increase the surface roughness of the straw and thus, exhibits better hydrophobic properties. Hexamethyl-disilazane is a volatile liquid at room temperature. Hence, hexamethyl-disilazane steam may be conveniently used to perform a modification treatment on the surface of materials. The hydrophobic modification by a steaming process can uniformly act on the surface of materials, especially suitable for irregular and multi-surface materials, thus greatly facilitating the industrial waterproof post-treatment of starch-based straws.

To sum up, it is of great significance to develop a method for preparing an environment-friendly starch-based straw with strong hydrophobic properties, high-temperature soaking resistance and good mechanical properties by adding nano-silica and hexamethyl-disilazane for hydrophobic modification treatment via a steaming process.

Summary of the Invention Directed to the problems of poor hydrophobic properties, low mechanical strength and easy softening and dissolving in hot beverages existing in the prior art, the present disclosure provides a highly hydrophobic starch-based straw and a preparation method thereof. The prepared starch-based straw has good hydrophobic properties, high mechanical strength and high-temperature soaking resistance.

The present disclosure 1s achieved by the following technical solution: a method for preparing a highly hydrophobic starch-based straw, including the following steps of: (1) mixing: adding starch and nano-silica to a high-speed mixer, opening an additive valve, and slowly adding water to the high-speed mixer for stirring at a low speed; after adding water, closing the valve and stirring the materials rapidly; opening a discharge valve, bagging and standing the mixed materials; (2) extrusion treatment: uniformly feeding the materials obtained in the step (1) into a twin-screw extrusion set via a single-screw feeding system, and setting a feeding screw speed, an extrusion screw speed, and temperatures from a zone one to a zone four in a barrel of the extrusion set; performing extrusion via a molding die head to form a tube blank; (3) cutting: cooling the tube blank obtained in the step (2) by a blower provided on a conveying device, and then performing cutting treatment after cooling; (4) hydrophobic modification by a steaming process: placing the straw cut in the step (3) into a closed container containing sufficient amount of hexamethyl-disilazane solution, and putting the closed container to a drying oven, performing a hydrophobic modification on the surface of the straw using hexamethyl-disilazane steam, and cooling to room temperature after the reaction to obtain a highly hydrophobic starch-based straw.

Further, the nano-silica of the step (1) is used in an amount of 2-10% of the starch, and the water is used in an amount of 25-40% of the starch.

Further, the stirring at a low speed of the step (1) is performed at 120-300 r/min, and the stirring time is 5-10 min; the rapidly stirring is performed at a speed of 600-960 r/min, and the stirring time is 5-10 min.

Further, in step (2), the feeding screw speed is 12-30 r/min, the extrusion screw speed 1s 30-90 r/min, and the temperatures from a zone one to a zone four in a barrel of the extrusion set are 80-90°C, 85-105°C, 90-120°C, and 100-110°C.

Further, the drying oven in the step (4) has a temperature of 30-50°C.

Further, the steam treatment time in the step (4) is 1-4 h.

In the present disclosure, provided is a highly hydrophobic starch-based straw prepared by the preparation method.

In this present disclosure, nano-silica and hydroxyl groups of starch are bound to form -Si-O-C-bonds, thus further forming a network structure and enhancing the degree of crystallinity of the starch-based straw and improving its mechanical properties. Moreover, a stable Si-O-Si(CHs3)s structure formed between hexamethyl-disilazane and nano-silica is utilized to firmly graft the three hydrophobic methyl groups on the surface of the straw, thereby improving the sensitivity of the starch-based straw to water molecules and enhancing the hydrophobic properties of the straw.

Beneficial effects

(1) In the present disclosure, a hexamethyl-disilazane steaming process is used to perform a hydrophobic modification treatment on the surfaces inside and outside the starch-based straw, which can effectively improve the hydrophobic properties of the straw and enhance the soaking-proof properties of the straw.

(2) In the present disclosure, a straw is prepared using starch as a base material, which is environmentally friendly, degradable and reduces white pollution. Detailed Description of the Embodiments For a further understanding of the present disclosure, preferred embodiments of the present disclosure will be described below with reference to the examples. But it is to be understood that these descriptions are merely illustrative of the features and advantages of the present disclosure and are not to be construed as limiting the present disclosure.

Example 1 (1) Mixing: corn starch and nano-silica accounting for 4% of the amount of starch were added to a high-speed mixer, and an additive valve was opened, and water accounting for 30% of the amount of starch was slowly added to the high-speed mixer, then, the above materials were stirred at a low speed (180 r/min) for 8 mins; after adding water, the valve was closed and the materials were stirred rapidly (600 r/min) for 10 mins; a discharge valve was opened, and the mixed materials were bagged and subjected to standing; (2) extrusion treatment: the materials obtained in the step (1) were uniformly fed

© LU501327 into a twin-screw extrusion set through a single-screw feeding system, where the feeding screw speed was set to 18 r/min, the extrusion screw speed was set to 60 r/min, and temperatures from a zone one to a zone four in a barrel of the extrusion set were set to 85°C, 90°C, 105°C and 100°C, and the materials were extruded through a molding die head to form a tube blank; (3) cutting: the tube blank obtained in the step (2) was cooled by a blower provided on a conveying device, and then subjected to cutting treatment after cooling; (4) hydrophobic modification by a steaming process: the straw cut in the step (3) was placed into a closed container containing sufficient amount of hexamethyl-disilazane solution, and the closed container was put to a drying oven, where a temperature of the drying oven was set to 40°C; hydrophobic modification was performed on the surface of the straw using hexamethyl-disilazane steam for 2 h, and the straw was cooled to room temperature after the reaction to obtain a highly hydrophobic starch-based straw.

Example 2 (1) Mixing: corn starch and nano-silica accounting for 5% of the amount of starch were added to a high-speed mixer, and an additive valve was opened, and water accounting for 35% of the amount of starch was slowly added to the high-speed mixer, then, the above materials were stirred at a low speed (240 r/min) for 5 mins; after adding water, the valve was closed and the materials were stirred rapidly (720 r/min) for 8 mins; a discharge valve was opened, and the mixed materials were bagged and subjected to standing; (2) extrusion treatment: the materials obtained in the step (1) were uniformly fed into a twin-screw extrusion set through a single-screw feeding system, where the

’ LU501327 feeding screw speed was set to 24 r/min, the extrusion screw speed was set to 78 r/min, and temperatures from a zone one to a zone four in a barrel of the extrusion set were set to 80°C, 100°C, 115°C and 105°C, and the materials were extruded through a molding die head to form a tube blank; (3) cutting: the tube blank obtained in the step (2) was cooled by a blower provided on a conveying device, and then subjected to cutting treatment after cooling; (4) hydrophobic modification by a steaming process: the straw cut in the step (3) was placed into a closed container containing sufficient amount of hexamethyl-disilazane solution, and the closed container was put to a drying oven, where a temperature of the drying oven was set to 45°C; hydrophobic modification was performed on the surface of the straw using hexamethyl-disilazane steam for 3 h, and the straw was cooled to room temperature after the reaction to obtain a highly hydrophobic starch-based straw.

Example 3 (1) Mixing: corn starch and nano-silica accounting for 8% of the amount of starch were added to a high-speed mixer, and an additive valve was opened, and water accounting for 32% of the amount of starch was slowly added to the high-speed mixer, then, the above materials were stirred at a low speed (300 r/min) for 7 mins; after adding water, the valve was closed and the materials were stirred rapidly (900 r/min) for 6 mins; a discharge valve was opened, and the mixed materials were bagged and subjected to standing; (2) extrusion treatment: the materials obtained in the step (1) were uniformly fed into a twin-screw extrusion set through a single-screw feeding system, where the feeding screw speed was set to 30 r/min, the extrusion screw speed was set to 72 r/min,

and temperatures from a zone one to a zone four in a barrel of the extrusion set were set to 80°C, 95°C, 120°C and 100°C, and the materials were extruded through a molding die head to form a tube blank; (3) cutting: the tube blank obtained in the step (2) was cooled by a blower provided on a conveying device, and then subjected to cutting treatment after cooling; (4) hydrophobic modification by a steaming process: the straw cut in the step (3) was placed into a closed container containing sufficient amount of hexamethyl-disilazane solution, and the closed container was put to a drying oven, where a temperature of the drying oven was set to 50°C; hydrophobic modification was performed on the surface of the straw using hexamethyl-disilazane steam for 2.5 h, and the straw was cooled to room temperature after the reaction to obtain a highly hydrophobic starch-based straw.

Example 4 (1) Mixing: corn starch and nano-silica accounting for 7% of the amount of starch were added to a high-speed mixer, and an additive valve was opened, and water accounting for 30% of the amount of starch was slowly added to the high-speed mixer, then, the above materials were stirred at a low speed (120 r/min) for 9 mins; after adding water, the valve was closed and the materials were stirred rapidly (780 r/min) for 6 mins; a discharge valve was opened, and the mixed materials were bagged and subjected to standing; (2) extrusion treatment: the materials obtained in the step (1) were uniformly fed into a twin-screw extrusion set through a single-screw feeding system, where the feeding screw speed was set to 12 r/min, the extrusion screw speed was set to 42 r/min, and temperatures from a zone one to a zone four in a barrel of the extrusion set were

’ LU501327 set to 90°C, 95°C, 115°C and 110°C, and the materials were extruded through a molding die head to form a tube blank;

(3) cutting: the tube blank obtained in the step (2) was cooled by a blower provided on a conveying device, and then subjected to cutting treatment after cooling;

(4) hydrophobic modification by a steaming process: the straw cut in the step (3) was placed into a closed container containing sufficient amount of hexamethyl-disilazane solution, and the closed container was put to a drying oven, where a temperature of the drying oven was set to 40°C; hydrophobic modification was performed on the surface of the straw using hexamethyl-disilazane steam for 4 h, and the straw was cooled to room temperature after the reaction to obtain a highly hydrophobic starch-based straw.

Claims

1. A method for preparing a highly hydrophobic starch-based straw, comprising the following steps of: (1) mixing: adding starch and nano-silica to a high-speed mixer, opening an additive valve, and slowly adding water to the high-speed mixer for stirring at a low speed; after adding water, closing the valve and stirring the materials rapidly, opening a discharge valve, bagging and standing the mixed materials; (2) extrusion treatment: uniformly feeding the materials obtained in the step (1) into a twin-screw extrusion set via a single-screw feeding system, and setting a feeding screw speed, an extrusion screw speed, and temperatures from a zone one to a zone four in a barrel of the extrusion set; performing extrusion via a molding die head to form a tube blank; (3) cutting: cooling the tube blank obtained in the step (2) by a blower provided on a conveying device, and then performing cutting treatment after cooling; (4) hydrophobic modification by a steaming process: placing the straw cut in the step (3) into a closed container containing sufficient amount of hexamethyl-disilazane solution, and putting the closed container to a drying oven, performing hydrophobic modification on the surface of the straw using hexamethyl-disilazane steam, and cooling to room temperature after the reaction to obtain a highly hydrophobic starch-based straw.

2. The preparation method according to claim 1, wherein the nano-silica of the step (1) is used in an amount of 2-10% of the starch, and the water is used in an amount of 25-40% of the starch.

3. The preparation method according to claim 1, wherein the stirring at a low speed of the step (1) is performed at 120-300 r/min, and the stirring time is 5-10 min; the rapidly stirring is performed at a speed of 600-960 r/min, and the stirring time is 5-10 min.

4. The preparation method according to claim 1, wherein in the step (2), the feeding screw speed is 12-30 r/min, the extrusion screw speed is 30-90 r/min, and the temperatures from a zone one to a zone four in a barrel of the extrusion set are 80-90°C, 85-105°C, 90-120°C, and 100-110°C .

5. The preparation method according to claim 1, wherein the drying oven in the step (4) has a temperature of 30-50°C.

6. The preparation according to claim 1, wherein the steam treatment time in the step (4) is 1-4 h.

7. A highly hydrophobic starch-based straw prepared by the preparation method of any one of claims 1-6.