CN111763365B - Antibacterial fresh-keeping material containing nano-silver and preparation method thereof - Google Patents
Antibacterial fresh-keeping material containing nano-silver and preparation method thereof Download PDFInfo
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- CN111763365B CN111763365B CN202010693836.XA CN202010693836A CN111763365B CN 111763365 B CN111763365 B CN 111763365B CN 202010693836 A CN202010693836 A CN 202010693836A CN 111763365 B CN111763365 B CN 111763365B
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- C08J5/18—Manufacture of films or sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
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- B29D22/003—Containers for packaging, storing or transporting, e.g. bottles, jars, cans, barrels, tanks
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- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
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- C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
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- C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
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- C08J2433/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
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- C08J2471/00—Characterised by the use of polyethers obtained by reactions forming an ether link in the main chain; Derivatives of such polymers
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
- C08K5/41—Compounds containing sulfur bound to oxygen
- C08K5/42—Sulfonic acids; Derivatives thereof
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- C08K9/00—Use of pretreated ingredients
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract
The invention belongs to the technical field of preparation of fresh-keeping materials, and particularly relates to an antibacterial fresh-keeping material containing nano-silver and a preparation method thereof. The invention provides a fresh-keeping material containing nano-silver, which comprises the following components in parts by weight: 80-100 parts of polyethylene, 20-30 parts of dispersing agent, 5-12 parts of adhesive and 3-10 parts of composite nano silver powder. The antibacterial preservative film or preservative bag containing nano-silver provided by the invention can efficiently and broadly inhibit the growth of various pathogenic microorganisms, has excellent sterilization and mildew resistance, effectively prevents the loss, oxidation, putrefaction or degradation of fresh water or oil of food, prolongs the shelf life and improves the quality guarantee effect.
Description
Technical Field
The invention belongs to the technical field of preparation of fresh-keeping materials, and particularly relates to an antibacterial fresh-keeping material containing nano-silver and a preparation method thereof.
Background
The preservative film and the preservative bag are mainly used for occasions such as microwave oven food heating, refrigerator food preservation, fresh and cooked food packaging and the like, can effectively prevent pollution of dust in food and air, can prevent bacteria from entering, and further play a role in preservation. At present, various preservative films and preservative bags exist in the market, but the preservative films and the preservative bags can only play a role in preventing bacteria from entering for a short time and cannot play a role in inhibiting bacteria and killing bacteria. Over time, the food will decay and deteriorate. Some PVC preservative films mainly used for outer packaging contain a di (2-ethylhexyl) adipate (DEHA) plasticizer which is not allowed by relevant national standards, and when the preservative films containing DEHA are subjected to grease or high temperature (over 100 ℃), the plasticizer is easily released and brings harm to health after food enters human bodies.
The nano silver has high-efficiency broad-spectrum antibacterial performance, high safety and no toxic or side effect. The antibacterial activity of the nano-silver is achieved by releasing Ag + By the use of these Ag + By binding to organic functional groups such as thiol, amide, hydroxyl, carboxyl, etc., DNA replication is disturbed, microbial proteins are denatured, and bacterial cells are destroyed. Since the beginning of this century, the antibacterial properties of nano-silver have been extensively and deeply studied, and a series of research results show that nano-silver exhibits a certain antibacterial activity against gram-positive bacteria, gram-negative bacteria, fungi and viruses.
The bactericidal mechanism of silver ions is shown in the following: silver ion (Ag) + ) Upon contact with the bacteria, the proteins that cause the bacteria are destroyed, causing the bacteria to die. The contact principle is based on electrical adsorption, since the cell membrane carries a negative charge, and silver ions (Ag) + ) The silver ion has positive charge, and the silver ion and the positive charge generate electric adsorption to enable the silver ion and the positive charge to be firmly combined, and the silver ion penetrates through cell membranes and enters into the bacterial body to generate chemical reaction with sulfur amino (-SH) on proteins in the bacterial body: this reaction causes protein coagulation, which destroys the activity of bacterial synthetases, interferes with the synthesis of bacterial DNA, and causes the bacteria to lose division and proliferation capacity and die. At the same time Ag + The binding of proteins also destroys the respiratory system, the substance transport system, and in addition, the Ag due to the bacteria + Has higher redox performance, so the bacteria can be released from the thallus after being killed, and can generate oxidation reaction with other organic bacteria to kill germs again, thereby generating the bactericidal and antibacterial effects repeatedly.
However, some preservative films and preservative bags containing silver ions in the prior art can not effectively prevent the silver ions from being oxidized, so the preservative films and the preservative bags can be made into dark yellow. In Japan and other countries, glass powder and zirconium phosphate are used as carriers of silver and added into master batches to manufacture freshness protection bags or freshness protection films, but combustion residues in the freshness protection bags or the freshness protection films do not meet the standard requirements and have poor antibacterial effect, so the freshness protection films can not be applied to freshness protection plastic bag film products.
Therefore, a preservative film or a preservative bag with excellent antibacterial performance is urgently needed to be developed, and the nano silver is dissolved into the preservative film or the preservative bag to enable the preservative film or the preservative bag to have the functions of preservation, antibiosis and the like, and can be applied to preservation of vegetables, fruits and food.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide an antibacterial fresh-keeping material containing nano-silver and a preparation method thereof. The antibacterial preservative film or the preservative bag containing the nano-silver can efficiently and broadly inhibit the growth of various pathogenic microorganisms, has excellent sterilization and mildew resistance, effectively prevents the fresh food from being oxidized, rotten or degraded, prolongs the shelf life and improves the quality guarantee effect.
The technical scheme of the invention is as follows:
an antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 80-100 parts of polyethylene, 20-30 parts of dispersing agent, 5-12 parts of adhesive and 3-10 parts of composite nano silver powder.
Further, the antibacterial and fresh-keeping material containing nano-silver comprises the following components in parts by weight: 90 parts of polyethylene, 25 parts of dispersing agent, 8 parts of adhesive and 6 parts of composite nano-silver powder.
Further, the preparation steps of the composite nano silver powder are as follows:
s1, taking rice straws, cleaning, chopping into short stems with the length of 2-4 cm, drying at the temperature of 60-80 ℃, crushing, and sieving with a 60-mesh sieve;
s2, soaking the dried rice straws obtained in the step S1 in a sodium hydroxide solution with the mass fraction of 15% at room temperature in a weight ratio of 1: 5-12, and washing and drying after 24 hours; then treating the rice straw fiber with 2 mass percent of sodium hydroxide and 15 mass percent of sodium chlorite solution for 3 hours at the temperature of 100 ℃ in a weight ratio of 1: 3-6, cooling, washing and drying to obtain rice straw fiber powder;
s3, adding the rice straw fiber powder obtained in the step S2 into a silver nitrate solution with the mass fraction of 10%, uniformly stirring, introducing nitrogen gas with the introduction amount of 3-5L/min, introducing for 10-20 min, sealing, irradiating for 10-15 min under ultraviolet light, performing centrifugal separation after irradiation to obtain a precipitate, putting the precipitate into an oven, and drying at the temperature of 70-80 ℃ for 6-8 h to obtain the composite nano-silver powder.
Furthermore, in the step of preparing the composite nano silver powder, the weight ratio of the rice straw fiber powder added in the step S3 to the 10% silver nitrate solution is (1-5): 30.
Further, the dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to a weight ratio of 7-13: 2-5.
Furthermore, the dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to the weight ratio of 11: 4.
Further, the adhesive is one or more of polyvinyl alcohol, sodium alginate, sodium silicate, polyacrylic acid and hydroxymethyl cellulose.
In addition, the invention also provides a preparation method of the antibacterial and fresh-keeping material containing the nano-silver, which comprises the following steps:
(1) putting polyethylene, a dispersing agent and an adhesive into a plastic refining machine, and heating for 20-30 min at 130-150 ℃ to obtain a plasticized hot material;
(2) slowly pouring composite nano silver powder onto the plasticized hot material obtained in the step (1), quickly stirring to well mix the composite nano silver powder with the hot material, then putting the mixture into an oven, and drying at the temperature of 70-85 ℃ to obtain a mixed material;
(3) extruding and granulating the mixed material obtained in the step (2) by a double-screw granulator to prepare antibacterial master batches;
(4) carrying out blow molding on the antibacterial master batch obtained in the step (3) by using a single-screw blow molding machine to form a film, so as to obtain a preservative film;
(5) and (4) carrying out hot-pressing adhesion on the preservative film obtained in the step (4) at the temperature of 140-300 ℃, and shearing into the preservative bag with the required specification.
Further, the temperature of the twin-screw granulator in the step (3) is set to be 150-180 ℃, the feeding speed of a hopper is 8-15 m/min, the rotating speed of the twin-screw is 100-150 r/min, and the granulating speed is 3-7 m/min.
Further, the temperature of the single-screw blow molding machine in the step (4) is set to be 150-190 ℃, and the rotating speed of the single screw is 40-60 r/min.
The antibacterial fresh-keeping material containing nano-silver provided by the invention has the advantages that the fresh-keeping film and the fresh-keeping bag have antibacterial effects on the original basis by adding the composite nano-silver powder taking natural plant fibers as the carrier, in addition, the silver is a natural mineral substance existing in the nature, has a broad-spectrum antibacterial effect, is long in antibacterial time and free of toxic and side effects on a human body, the antibacterial fresh-keeping material containing nano-silver is used for storing foods such as fruits and vegetables, the invasion of external bacteria can be prevented, the bacteria in the fresh-keeping bag can be killed, the storage period of the foods is greatly prolonged, and the use of preservatives can be reduced. The added rice straw fiber and the nano-silver are compounded, so that the oxygen transmission rate of the prepared fresh-keeping material is lower, and the antibacterial performance detection test data also shows that the antibacterial fresh-keeping material containing the nano-silver can better inhibit the growth of aerobic bacteria on the surface of food, effectively slow down the deterioration of the food and prolong the fresh-keeping period of the food.
The nano-silver-containing antibacterial fresh-keeping material provided by the invention is added with the dispersing agent which is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to a certain proportion, so that the added composite nano-silver powder can be stably dispersed in the material without agglomeration, aggregation and flocculation of the composite nano-powder can be prevented, and the tensile strength and elongation at break of the prepared nano-silver-containing fresh-keeping material are further improved.
Compared with the prior art, the antibacterial and fresh-keeping material containing nano-silver provided by the invention has the following advantages: (1) the invention provides an antibacterial fresh-keeping material containing nano-silver, which is characterized in that the nano-silver is dissolved into plastic master batches through a special process, then the plastic master batches containing the nano-silver are re-produced through a plastic screw granulator, and a fresh-keeping film or a fresh-keeping bag meeting the requirements is produced through a formula, so that the plastic master batches have good antibacterial performance, the growth of 650 harmful bacteria and microorganisms is effectively inhibited, the freshness and the quality guarantee period of food are increased, and the perishable and difficultly preserved food is easier to store.
(2) The invention provides an antibacterial preservative film or a preservative bag containing nano silver, which solves the problems that residues in a combustion test exceed the standard and do not meet the standard when traditional silver antibacterial master batches are added into the preservative film or the preservative bag, and the combustion residues do not have toxic and harmful gases and pungent odor and residual toxic and harmful substances through detection, so that the national standard is completely met.
Detailed Description
The present invention is further illustrated by the following description of specific embodiments, which are not intended to limit the invention, and various modifications and improvements can be made by those skilled in the art based on the basic idea of the invention, but the invention is within the protection scope of the invention.
Wherein, the reagents used in the invention are all common reagents which can be purchased from common reagent production and sale companies.
Example 1 an antibacterial and freshness-retaining material containing nano silver
The antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 80 parts of polyethylene, 20 parts of dispersing agent, 5 parts of adhesive and 3 parts of composite nano-silver powder.
The preparation steps of the composite nano silver powder are as follows:
s1, washing rice straws, cutting into short stems with the length of 2cm, drying at the temperature of 60 ℃, crushing, and sieving with a 60-mesh sieve;
s2, soaking the dried rice straws obtained in the step S1 in a sodium hydroxide solution with the mass fraction of 15% at room temperature in a weight ratio of 1: 5, and washing and drying after 24 hours; then treating the mixture for 3 hours by using sodium hydroxide with the mass fraction of 2% and sodium chlorite solution with the mass fraction of 15% at the weight ratio of 1:3 under the condition of 100 ℃, cooling, washing and drying to obtain rice straw fiber powder;
s3, adding the rice straw fiber powder obtained in the step S2 into a silver nitrate solution with the mass fraction of 10%, uniformly stirring, introducing nitrogen with the introduction amount of 3L/min, introducing for 10min, sealing, illuminating for 10min under ultraviolet light, performing centrifugal separation after illumination to obtain a precipitate, putting the precipitate into an oven, and drying at 70 ℃ for 6h to obtain the composite nano-silver powder.
In the preparation step of the composite nano silver powder, the weight ratio of the rice straw fiber powder added in the step S3 to the 10% silver nitrate solution is 1: 30.
The dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to a weight ratio of 7: 5.
The adhesive is composed of polyvinyl alcohol and sodium alginate according to the weight ratio of 1: 1.
The preparation method of the antibacterial fresh-keeping material containing the nano-silver comprises the following steps:
(1) putting polyethylene, a dispersing agent and an adhesive into a plastic mixer, and heating for 20min at 130 ℃ to obtain a plasticized hot material;
(2) slowly pouring the composite nano-silver powder onto the plasticized hot material obtained in the step (1), quickly stirring to well mix the composite nano-silver powder with the hot material, then putting the mixture into an oven, and drying at the temperature of 70 ℃ to obtain a mixed material;
(3) and (3) extruding and granulating the mixed material obtained in the step (2) through a double-screw granulator to prepare the antibacterial master batch, wherein the temperature of the double-screw granulator is set to be 150 ℃, the feeding speed of a hopper is 8m/min, the rotating speed of the double screws is 100r/min, and the granulating speed is 3 m/min.
(4) Carrying out blow molding on the antibacterial master batch obtained in the step (3) through a single-screw extrusion blow molding machine to form a film, so as to obtain a preservative film; the temperature of the single-screw extrusion blow molding machine is set to be 150 ℃, and the rotating speed of the single screw is 40 r/min.
(5) And (4) hot-pressing and bonding the preservative film obtained in the step (4) at 140 ℃, and cutting into the preservative bags with required specifications.
Example 2 an antibacterial and freshness-retaining material containing nano-silver
The antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 90 parts of polyethylene, 25 parts of dispersing agent, 8 parts of adhesive and 6 parts of composite nano silver powder.
The preparation steps of the composite nano silver powder are as follows:
s1, washing rice straws, cutting into short stems with the length of 3cm, drying at 70 ℃, crushing, and sieving with a 60-mesh sieve;
s2, soaking the dried rice straws obtained in the step S1 in 15% of sodium hydroxide solution at room temperature in a weight ratio of 1: 8, and washing and drying after 24 hours; then treating the mixture for 3 hours by using sodium hydroxide with the mass fraction of 2% and sodium chlorite solution with the mass fraction of 15% at the weight ratio of 1: 5 under the condition of 100 ℃, cooling, washing and drying to obtain rice straw fiber powder;
s3, adding the rice straw fiber powder obtained in the step S2 into a silver nitrate solution with the mass fraction of 10%, uniformly stirring, introducing nitrogen with the introduction amount of 4L/min, introducing for 15min, sealing, illuminating for 12min under ultraviolet light, performing centrifugal separation after illumination to obtain a precipitate, putting the precipitate into an oven, and drying at the temperature of 75 ℃ for 7h to obtain the composite nano-silver powder.
In the preparation step of the composite nano silver powder, the weight ratio of the rice straw fiber powder added in the step S3 to the 10% silver nitrate solution is 3: 30.
The dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to the weight ratio of 11: 4.
The adhesive is composed of polyvinyl alcohol, sodium alginate and polyacrylic acid according to the weight ratio of 1:1: 1.
The preparation method of the antibacterial fresh-keeping material containing the nano-silver comprises the following steps:
(1) putting polyethylene, a dispersing agent and an adhesive into a plastic refining machine, and heating at 140 ℃ for 25min to obtain a plasticized hot material;
(2) slowly pouring the composite nano-silver powder onto the plasticized hot material obtained in the step (1), quickly stirring to well mix the composite nano-silver powder with the hot material, then putting the mixture into an oven, and drying at the temperature of 80 ℃ to obtain a mixed material;
(3) and (3) extruding and granulating the mixed material obtained in the step (2) through a double-screw granulator to prepare the antibacterial master batch, wherein the temperature of the double-screw granulator is set to be 160 ℃, the feeding speed of a hopper is 12m/min, the rotating speed of the double screws is 130r/min, and the granulating speed is 5 m/min.
(4) Carrying out blow molding on the antibacterial master batch obtained in the step (3) through a single-screw extrusion blow molding machine to form a film, so as to obtain a preservative film; the temperature of the single-screw extrusion blow molding machine is set to be 170 ℃, and the rotating speed of the single screw is 50/min.
(5) And (4) carrying out hot-pressing adhesion on the preservative film obtained in the step (4) at 260 ℃, and cutting into the preservative bags with required specifications.
Example 3 an antibacterial and freshness-retaining material containing nano-silver
The antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 100 parts of polyethylene, 30 parts of dispersing agent, 12 parts of hydroxymethyl cellulose and 10 parts of composite nano silver powder.
The preparation steps of the composite nano silver powder are as follows:
s1, washing rice straws, cutting into short stems with the length of 4cm, drying at 80 ℃, crushing, and sieving with a 60-mesh sieve;
s2, soaking the dried rice straws obtained in the step S1 in 15% sodium hydroxide solution at room temperature according to the weight ratio of 1: 12, and washing and drying after 24 hours; then treating the mixture for 3 hours by using sodium hydroxide with the mass fraction of 2% and sodium chlorite solution with the mass fraction of 15% at the weight ratio of 1: 6 under the condition of 100 ℃, cooling, washing and drying to obtain rice straw fiber powder;
s3, adding the rice straw fiber powder obtained in the step S2 into a silver nitrate solution with the mass fraction of 10%, uniformly stirring, introducing nitrogen gas with the introduction amount of 5L/min, introducing for 20min, sealing, illuminating for 15min under ultraviolet light, performing centrifugal separation after illumination to obtain a precipitate, putting the precipitate into an oven, and drying at the temperature of 80 ℃ for 8h to obtain the composite nano-silver powder.
In the step of preparing the composite nano silver powder, the weight ratio of the rice straw fiber powder added in the step S3 to the 10% silver nitrate solution is 5: 30.
The dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to a weight ratio of 13: 2.
The preparation method of the antibacterial fresh-keeping material containing the nano-silver comprises the following steps:
(1) putting polyethylene, a dispersing agent and hydroxymethyl cellulose into a plastic mixer, and heating for 30min at 150 ℃ to obtain a plasticized hot material;
(2) slowly pouring composite nano silver powder onto the plasticized hot material obtained in the step (1), quickly stirring to well mix the composite nano silver powder with the hot material, then putting the mixture into an oven, and drying at the temperature of 85 ℃ to obtain a mixed material;
(3) and (3) extruding and granulating the mixed material obtained in the step (2) through a double-screw granulator to prepare the antibacterial master batch, wherein the temperature of the double-screw granulator is set to be 180 ℃, the feeding speed of a hopper is 15m/min, the rotating speed of the double screws is 150r/min, and the granulating speed is 7 m/min.
(4) Carrying out blow molding on the antibacterial master batch obtained in the step (3) through a single-screw extrusion blow molding machine to form a film, so as to obtain a preservative film; the temperature of the single-screw extrusion blow molding machine is set to be 190 ℃, and the rotating speed of the single screw is 60 r/min.
(5) And (5) carrying out hot-pressing bonding on the preservative film obtained in the step (4) at 300 ℃, and cutting into the preservative bags with required specifications.
Comparative example 1 antibacterial and fresh-keeping material containing nano-silver
The antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 90 parts of polyethylene, 25 parts of sodium dodecyl sulfate, 8 parts of an adhesive and 6 parts of composite nano silver powder.
The preparation procedure of the composite nano silver powder was similar to that of example 2.
The adhesive is composed of polyvinyl alcohol, sodium alginate and polyacrylic acid according to the weight ratio of 1:1: 1.
The preparation method of the antibacterial and fresh-keeping material containing the nano-silver is similar to that of the embodiment 2.
The difference from the embodiment 2 is that no fatty alcohol-polyoxyethylene ether is added in the dispersing agent.
Comparative example 2 antibacterial and fresh-keeping material containing nano-silver
The antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 90 parts of polyethylene, 25 parts of dispersing agent, 8 parts of adhesive and 6 parts of composite nano-silver powder.
The preparation procedure of the composite nano silver powder was similar to that of example 2.
The dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to the weight ratio of 1: 1.
The adhesive is composed of polyvinyl alcohol, sodium alginate and polyacrylic acid according to the weight ratio of 1:1: 1.
The preparation method of the antibacterial and fresh-keeping material containing the nano-silver is similar to that of the embodiment 2.
The difference from the embodiment 2 is that the dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to the weight ratio of 1: 1.
Comparative example 3 antibacterial fresh-keeping material containing nano silver
The antibacterial fresh-keeping material containing nano-silver comprises the following components in parts by weight: 90 parts of polyethylene, 25 parts of dispersing agent, 8 parts of adhesive and 6 parts of nano-silver powder.
The dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to the weight ratio of 11: 4.
The adhesive is composed of polyvinyl alcohol, sodium alginate and polyacrylic acid according to the weight ratio of 1:1: 1.
The preparation method of the antibacterial fresh-keeping material containing the nano-silver comprises the following steps:
(1) putting polyethylene, a dispersing agent and an adhesive into a plastic mixer, and heating for 25min at 140 ℃ to obtain a plasticized hot material;
(2) slowly pouring nano-silver powder onto the plasticized hot material obtained in the step (1), quickly stirring to well mix the nano-silver powder with the hot material, then putting the mixture into an oven, and drying at the temperature of 80 ℃ to obtain a mixed material;
(3) and (3) extruding and granulating the mixed material obtained in the step (2) through a double-screw granulator to prepare the antibacterial master batch, wherein the temperature of the double-screw granulator is set to be 160 ℃, the feeding speed of a hopper is 12m/min, the rotating speed of the double screws is 130r/min, and the granulating speed is 5 m/min.
(4) Carrying out blow molding on the antibacterial master batch obtained in the step (3) through a single-screw extrusion blow molding machine to form a film, so as to obtain a preservative film; the temperature of the single-screw extrusion blow molding machine is set to be 170 ℃, and the rotating speed of the single screw is 50/min.
(5) And (4) carrying out hot-pressing adhesion on the preservative film obtained in the step (4) at 260 ℃, and cutting into the preservative bags with required specifications.
The difference from the example 2 is that the nano silver powder added in the composition is common commercial nano silver powder.
Test example I, Performance test
1. Test materials: the preservative films containing nano silver prepared in the examples 1 to 3 and the comparative examples 1 to 3.
2. The test method comprises the following steps:
(1) tensile strength and elongation at break: according to the method of GB/T1040.3-2006 test conditions for determination of tensile Properties of plastics for the third part of films and sheets;
(2) oxygen permeability determination: according to GB/T1038-2000 pressure difference method for testing gas permeability of plastic films and sheets;
(3) combustion residue ratio: according to GB/T9345.1-2008 determination of Plastic Ash.
3. Test results
Table 1 results of performance testing
| Group of | Example 1 | Example 2 | Example 3 | Comparative example 1 | Comparative example 2 | Comparative example 3 |
| Tensile Strength (MPa) | 62.5 | 63.3 | 62.7 | 33.1 | 32.5 | 57.5 |
| Elongation at Break (%) | 9.48 | 10.05 | 9.57 | 6.42 | 6.33 | 7.28 |
| Oxygen transmission rate (cm) 3 /m 2 ·d·Pa) | 0.092 | 0.087 | 0.089 | 0.106 | 0.119 | 1.43 |
| Combustion residual ratio (%) | 10.3 | 9.5 | 9.8 | 11.3 | 11.2 | 10.7 |
As can be seen from Table 1, compared with comparative examples 1 to 3, the preservative films containing nano-silver prepared in examples 1 to 3 have greatly improved tensile strength and elongation at break, so that the preservative films prepared by the invention can obviously improve flexibility and mechanical strength by adding a dispersing agent which is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether in a certain proportion. Meanwhile, the preservative film containing nano silver prepared in the embodiments 1 to 3 has a lower oxygen transmission rate than that of the preservative film prepared in the comparative example 3 (adopting common commercially available nano silver powder), and can effectively slow down the chemical change of food and inhibit the growth of aerobic bacteria on the surface of food. The rice straw fiber and the nano-silver are compounded, so that the oxygen transmission rate of the prepared preservative film or preservative bag is lower, the food deterioration is effectively slowed, and the food preservation period is prolonged. Moreover, the preservative film containing nano-silver prepared in the embodiments 1 to 3 has a lower combustion residue rate, and the combustion residue has no toxic and harmful gas and pungent smell, does not have residual toxic and harmful substances, and meets the national standard.
Test example two, antimicrobial Property measurement
1. Test materials: the preservative films containing nano silver prepared in the examples 1 to 3 and the comparative examples 1 to 3.
2. The test method comprises the following steps: in order to detect the antibacterial performance of the preservative film containing nano-silver, Escherichia coli and staphylococcus aureus are used as experimental bacteria, activated bacteria liquid is diluted to a certain concentration, a proper amount of bacteria liquid is uniformly coated on inactivated plate agar, the preservative film containing nano-silver prepared in examples 1-3 and comparative examples 1-3 and a commercially available common preservative film are cut into a circle with the diameter of 10mm, the circle is placed under an ultraviolet lamp for double-sided sterilization for 2 hours, then the circle is horizontally placed on the coated plate, the circle is cultured for 48 hours at 37 ℃ after sealing, the bacterial growth condition around the preservative film is observed by adopting an antibacterial ring method, and a transparent antibacterial ring is measured by a vernier caliper.
3. Test results
The test results are shown in table 2.
TABLE 2 results of the antibacterial property test
As can be seen from Table 2: compared with the preservative films containing nano-silver prepared in the groups of comparative examples 1 to 3, the preservative films containing nano-silver prepared in the groups of examples 1 to 3 have excellent antibacterial property, excellent inhibition effect on escherichia coli and staphylococcus aureus, and capability of remarkably slowing down the rot and mildew rate of fruits and vegetables, wherein the group of example 2 has the best effect, the diameters of inhibition zones are respectively 24.6mm and 28.4mm, and the overall effect is better than that of a commercially available common preservative film, and the preservative film is the best embodiment of the invention. While the components of the dispersant are changed in the comparative examples 1-2, and the composite nano silver powder prepared by the invention is not added in the comparative example 3, the inhibition effect on escherichia coli and staphylococcus aureus is obviously reduced.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Those skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (8)
1. An antibacterial fresh-keeping material containing nano-silver is characterized by comprising the following components in parts by weight: 80-100 parts of polyethylene, 20-30 parts of dispersing agent, 5-12 parts of adhesive and 3-10 parts of composite nano silver powder; the fresh-keeping material comprises a fresh-keeping film and a fresh-keeping bag;
the preparation steps of the composite nano silver powder are as follows:
s1, taking rice straws, cleaning, chopping the rice straws into short stems with the length of 2-4 cm, drying the stems at the temperature of 60-80 ℃, crushing the stems, and sieving the stems with a 60-mesh sieve;
s2, soaking the dried rice straws obtained in the step S1 in a sodium hydroxide solution with the mass fraction of 15% at room temperature in a weight ratio of 1: 5-12, and washing and drying after 24 hours; then treating the rice straw fiber with 2 mass percent of sodium hydroxide and 15 mass percent of sodium chlorite solution for 3 hours at the weight ratio of 1: 3-6 at the temperature of 100 ℃, cooling, washing and drying to obtain rice straw fiber powder;
s3, adding the rice straw fiber powder obtained in the step S2 into a silver nitrate solution with the mass fraction of 10%, uniformly stirring, introducing nitrogen gas with the introduction amount of 3-5L/min, introducing for 10-20 min, sealing, irradiating for 10-15 min under ultraviolet light, performing centrifugal separation after irradiation to obtain a precipitate, putting the precipitate into an oven, and drying at the temperature of 70-80 ℃ for 6-8 h to obtain composite nano-silver powder;
the dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether according to a weight ratio of 7-13: 2-5.
2. The antibacterial fresh-keeping material containing nano-silver as claimed in claim 1, which is characterized by comprising the following components in parts by weight: 90 parts of polyethylene, 25 parts of dispersing agent, 8 parts of adhesive and 6 parts of composite nano-silver powder.
3. The antibacterial and refreshing material containing nano silver as claimed in claim 1, wherein in the step of preparing the composite nano silver powder, the weight ratio of the rice straw fiber powder added in the step S3 and the 10% silver nitrate solution is (1-5): 30.
4. The antibacterial and refreshing material containing nano-silver as claimed in claim 1 or 2, wherein the dispersing agent is composed of sodium dodecyl sulfate and fatty alcohol-polyoxyethylene ether in a weight ratio of 11: 4.
5. The antibacterial and fresh-keeping material containing nano-silver as claimed in claim 1 or 2, wherein the binder is one or more of polyvinyl alcohol, sodium alginate, sodium silicate, polyacrylic acid, and hydroxymethyl cellulose.
6. The method for preparing the nano-silver-containing antibacterial fresh-keeping material according to any one of claims 1 to 5, characterized in that the preparation steps are as follows:
(1) putting polyethylene, a dispersing agent and an adhesive into a plastic refining machine, and heating for 20-30 min at 130-150 ℃ to obtain a plasticized hot material;
(2) slowly pouring the composite nano-silver powder onto the plasticized hot material obtained in the step (1), quickly stirring to well mix the composite nano-silver powder with the hot material, then putting the mixture into an oven, and drying at the temperature of 70-85 ℃ to obtain a mixed material;
(3) extruding and granulating the mixed material obtained in the step (2) by a double-screw granulator to prepare antibacterial master batches;
(4) carrying out blow molding on the antibacterial master batch obtained in the step (3) by using a single-screw blow molding machine to form a film, so as to obtain a preservative film;
(5) and (5) carrying out hot-pressing adhesion on the preservative film obtained in the step (4) at 140-300 ℃, and shearing into preservative bags with required specifications.
7. The method for preparing the antibacterial and refreshing material containing nano-silver according to claim 6, wherein the temperature of the twin-screw granulator in the step (3) is set to be 150-180 ℃, the feeding speed of a hopper is 8-15 m/min, the rotating speed of the twin-screw is 100-150 r/min, and the granulating speed is 3-7 m/min.
8. The method for preparing the antibacterial and refreshing material containing nano silver according to claim 6, wherein the temperature of the single-screw blow molding machine in the step (4) is set to be 150-190 ℃, and the rotating speed of the single screw is 40-60 r/min.
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