阅读说明：本技术 一种菠萝叶纤维素基载纳米TiO2抗菌保鲜膜制备方法 (Pineapple leaf cellulose-based nano TiO2Preparation method of antibacterial preservative film ) 是由 庄志凯 杜嵇华 李明福 何俊燕 黄涛 连文伟 张劲 于 2020-06-10 设计创作，主要内容包括：本发明属于保鲜膜制备技术领域,公开了一种菠萝叶纤维素基载纳米TiO<Sub>2</Sub>抗菌保鲜膜制备方法,包括：利用乳化剪切方式使菠萝叶纤维素溶解在含抗菌金属离子的溶液中,添加制备的纳米TiO<Sub>2</Sub>抗菌剂,搅拌均匀后加入铸膜液原料共混,并加热搅拌溶解,得到含有纳米TiO<Sub>2</Sub>抗菌剂的铸膜液；在玻璃板上用玻璃棒进行超滤膜的刮制,利用凝胶相转化的方式制备得到所述菠萝叶纤维素基载纳米TiO<Sub>2</Sub>抗菌保鲜膜。本发明将纳米TiO<Sub>2</Sub>加入到菠萝叶纤维膜中制备复合抗菌纤维膜,对提高本单位固体废弃物资源化学科领域中材料化研究方向的科技创新能力,保持菠萝叶纤维开发利用研究的国际领先地位具有重要意义。(The invention belongs to the technical field of preservative film preparation, and discloses a pineapple leaf cellulose-based nano TiO carrier 2 The preparation method of the antibacterial preservative film comprises the following steps: dissolving pineapple leaf cellulose in solution containing antibacterial metal ions by using an emulsifying and shearing mode, and adding the prepared nano TiO 2 The antibacterial agent is added with the raw materials of the casting solution after being evenly stirred, and is heated, stirred and dissolved to obtain the nano TiO-containing material 2 A casting solution of an antibacterial agent; scraping an ultrafiltration membrane on a glass plate by using a glass rod, and preparing the pineapple leaf fiber by using a gel phase inversion modeVitamin-based nano TiO 2 An antibacterial preservative film. The invention uses nano TiO 2 The composite antibacterial fiber membrane is added into the pineapple leaf fiber membrane to prepare the composite antibacterial fiber membrane, and has important significance for improving the technological innovation capability of the material-oriented research direction in the unit solid waste resource subject field and maintaining the international leading position of the development and utilization research of the pineapple leaf fiber.)

1. Pineapple leaf cellulose-based nano TiO₂The preparation method of the antibacterial preservative film is characterized in that the pineapple leaf cellulose based nano TiO is loaded₂The preparation method of the antibacterial preservative film comprises the following steps:

step one, soaking nano TiO₂Formation of TiO₂Soaking in water, and adding TiO₂Placing the soaking solution in an ultrasonic dispersion instrument for ultrasonic dispersion treatment by using ultrasonic waves;

the ultrasonic dispersion treatment method comprises the following steps:

(1.1) mixing TiO₂The soaking solution is placed in a placing bottle of an ultrasonic dispersion instrument and is in surface contact with an oxygenation catalyst in the placing bottle;

(1.2) starting an ultrasonic bar and a refrigerator of the ultrasonic dispersion instrument to oxygenate the TiO with the catalyst₂Carrying out ultrasonic dispersion on the soak solution under the action of an ultrasonic bar, and controlling the temperature of a placing bottle by using a refrigerator in the ultrasonic dispersion process;

step two, the dispersed TiO obtained in the step one₂Adding metal salt containing antibacterial metal ions into the soaking solution, mixing and dissolving, and fully stirring to obtain a mixed solution A;

step three, carrying out solid-liquid separation on the mixed liquid A obtained in the step two, drying, roasting and grinding the obtained solid to obtain the finished product of nano TiO₂An antibacterial agent;

the solid-liquid separation method of the mixed liquid comprises the following steps:

(3.1) stirring the obtained mixed solution A by using a stirring device, naturally stopping stirring after a period of time, and standing the mixed solution A;

(3.2) placing the mixed solution A after standing into a water storage container, and sequentially flowing through a coarse filter screen, a fine filter screen and an air bag plate to enter a storage tank;

(3.3) continuously repeating the step (3.2) for three times;

step four, dissolving pineapple leaf cellulose in a solution containing antibacterial metal ions by using an emulsifying and shearing mode, and adding the nano TiO obtained in the step three₂The antibacterial agent is evenly stirred to obtain a mixed solution B;

step five, blending the raw materials of the membrane casting solution with the mixed solution B obtained in the step four, heating, stirring and dissolving to obtain the membrane casting solution containing nano TiO₂A casting solution of an antibacterial agent;

the heating, stirring and dissolving comprises:

detecting the temperature of the mixed solution by using a temperature sensor, if so, judging whether the temperature of the solution reaches a heating interruption threshold value, and if so, controlling a heating device to interrupt heating; if not, judging whether the concentration of the solution reaches a heating preset temperature or not, and if so, stopping heating; if the preset heating temperature is not reached, controlling the heating device to continue heating until the preset heating temperature is reached, simultaneously utilizing a timer to carry out heating timing, and stopping heating when the preset heating time is reached;

pouring the casting solution obtained in the fifth step on a glass plate with the thickness of 15 multiplied by 25cm, and scraping an ultrafiltration membrane by using a glass rod;

seventhly, pre-evaporating the glass plate with the film coating in the air at room temperature, immersing the glass plate in a coagulating bath to perform gel phase conversion on the high molecular polymer in the casting solution on the glass plate, and separating out the high molecular polymer on the surface of the glass plate to obtain the pineapple leaf cellulose based nano TiO carrier₂An antibacterial preservative film.

2. The pineapple leaf cellulose-based nano TiO of claim 1₂The preparation method of the antibacterial preservative film is characterized in that in the step one, the nano TiO is₂The soaking time is 30-50 min, and the soaking temperature is 20-40 ℃.

3. The pineapple leaf cellulose-based nano TiO of claim 1₂Preparation method of antibacterial preservative filmThe method is characterized in that in the step one, the ultrasonic dispersion time is 20-50 min.

4. The pineapple leaf cellulose-based nano TiO of claim 1₂The preparation method of the antibacterial preservative film is characterized in that in the second step, the antibacterial metal ions are one or a combination of more of silver, zinc, copper and decorative metal ions; the antibacterial metal ions are the combination of two metal ions of silver and zinc, or the combination of two metal ions of silver and copper, or the combination of three metal ions of silver, zinc and copper.

5. The pineapple leaf cellulose-based nano TiO of claim 1₂The preparation method of the antibacterial preservative film is characterized in that in the second step, sulfuric acid or nitric acid is selected for suspension liquid in stirring to adjust the pH value to be 3-7, the stirring temperature is 50-75 ℃, and the stirring time is 6-8 hours.

6. The pineapple leaf cellulose-based nano TiO of claim 1₂The preparation method of the antibacterial preservative film is characterized in that in the third step, the drying temperature of the solid is 80-125 ℃, and the drying time is 1.5-3 hours; and roasting the dried solid at the temperature of 500-600 ℃ for 3-6 h, and grinding the roasted solid by using a ball mill.

7. The pineapple leaf cellulose-based nano TiO of claim 1₂The preparation method of the antibacterial preservative film is characterized in that in the fifth step, the raw materials of the film casting liquid are composed of 20-25 parts by mass of high molecular polymer, 10-15 parts by mass of pore-foaming agent and the balance of solvent.

8. The pineapple leaf cellulose-based nano TiO as claimed in claim 7₂The preparation method of the antibacterial preservative film is characterized in that the high molecular polymer is polyether sulfone (PES) and polyvinylidene fluoride (PVDF); the pore-foaming agent is polyvinylpyrrolidone (PVP); the solvent is N, N-dimethylacetamide (DMAc) and N, N-Dimethylformamide (DMF).

9. The pineapple leaf cellulose-based nano TiO of claim 1₂The preparation method of the antibacterial preservative film is characterized in that in the seventh step, the pre-evaporation temperature is 100-120 ℃, and the pre-evaporation time is 30-40 s.

10. The pineapple leaf cellulose-based nano TiO of claim 1₂And the preparation method of the antibacterial preservative film is characterized in that in the seventh step, the coagulating bath is deionized water, and the temperature is controlled to be 30-25 ℃.

Technical Field

The invention belongs to the technical field of preservative film preparation, and particularly relates to a pineapple leaf cellulose-based nano TiO carrier₂A method for preparing an antibacterial preservative film.

Background

At present, China is a big agricultural country, and the varieties and the yield of fruits and vegetables are the first world and are one of the prop industries of national economy. For a long time, agricultural production in China attaches importance to prenatal and prenatal management, neglects postpartum fresh-keeping storage and causes great economic loss. With the increasing living standard and the demand for high quality of food, food needs to be kept fresh for a longer time under more complicated conditions and to retain flavor and nutrients. The food fresh-keeping requires that the original form and biochemical characteristics of the food are kept, the growth of microorganisms and biochemical reaction of enzymes in the food are inhibited, and the food is prevented from being rotten and deteriorated. The development of food preservation technology has great significance in promoting the processing and circulation of agricultural products, ensuring the food quality safety, improving the national standard of living and the like.

In recent years, plastic packaging materials are widely used as food packaging materials and the 'white pollution' caused by preservation to the environment is widely paid attention to. Most of the preservative films sold in the market are prepared by taking ethylene as a raw material through polymerization reaction. Preservative films can be divided into three major categories: the first is polyethylene, abbreviated as PE; the second is polyvinyl chloride, PVC for short; the third is polyvinylidene chloride, abbreviated as PVDC. Researches show that the PVC preservative film is easy to degrade when meeting oil, heat, cold and the like and enters a human body along with food, so that the endocrine of a mild person is influenced, and the breast cancer, the congenital defect of a newborn or the male reproductive disorder and other diseases are caused by a severe person. Therefore, the plastic packaging is replaced by the preservative film prepared from the novel material, and the new trend of food preservation development is formed.

Pineapple, one of the four big tropical fruits. China is mainly distributed in provinces such as Guangdong, Guangxi, Hainan, Fujian and Yunnan. The pineapple leaf fiber is fiber extracted from pineapple leaves, belongs to vein fiber, and has the basic properties of moisture absorption and release, good heat conductivity and the like of common hemp fiber, and also has excellent natural sterilization, peculiar smell removal and mite expelling functions. Scientists have diligently made efforts on the research on the antibacterial function of the hemp fiber, and the research shows that the action mechanism of the natural antibacterial function of the hemp fiber mainly comprises three aspects: (1) the hemp fiber is in a porous structure, has large internal specific surface area and a plurality of holes and gaps, is rich in oxygen and inhibits the growth and the propagation of anaerobic bacteria; (2) hemp fibers may contain antibacterial substances such as phenols and derivatives thereof, thereby inhibiting or killing microorganisms; (3) because of the combined action of the hemp fiber structure and the contained components, the growth and the reproduction of the microorganisms are inhibited or the microorganisms are killed. Therefore, the material has attracted much attention and has become one of the hot spots of the research in the field of materials in recent years. Nearly 1000 million tons of pineapple leaves are abandoned or burned every year in China, so that a large amount of resources are wasted and the environment is polluted, the pineapple leaves are effectively developed and utilized, a new high-quality functional material is provided for the food packaging industry, the problem of source of regenerated cellulose fiber vitamin production raw materials is solved, the contradiction between resource supply and demand is relieved, and the method is an important way for realizing resource recycling.

Food preservation techniques are mainly divided into three main categories: first, chemical preservation techniques. Including traditional chemical preservation methods (vinegar preservation, salt preservation, sugar preservation), adsorption and protection type preservatives, and immersion, smoke and smearing type preservatives. Chemically synthesized preservatives, their toxicity and potential danger to the human body have attracted serious attention. Second, biological preservation technology. The preservation is mainly carried out by utilizing genetic genes and biological control, namely, modifying genetic information by utilizing DNA recombination and operation technology. The natural sugar galactose in the plant cell wall of the scientific household of the American Ministry of agriculture is injected into the immature tomatoes to generate chain reaction and generate ripening hormone, so that the tomatoes are ripened without damaging the quality and the taste of the tomatoes, the loss of the tomatoes during harvesting, transportation, sale and storage is greatly reduced, and the long-term fresh keeping of the tomatoes is realized. However, the food preserved by the biotechnology changes the natural properties of the food, and the safety of the food needs to be further verified. Thirdly, physical preservation technology. Comprises the fresh-keeping technologies of refrigeration, frozen storage, air-conditioned storage, pressure regulation, electron, ionization, irradiation and the like. The safety of radiation storage on fruits and vegetables needs further research.

At present, the most studied technology is chemical preservation technology, and the antibacterial preservation of agricultural products is mainly realized by adding an antibacterial agent. The antibacterial agent is a substance capable of inhibiting the development of microorganisms such as bacteria and fungi or inhibiting the growth of microorganisms. The main developed and applied at present are 4 classes of organic antibacterial agents, inorganic antibacterial agents, natural antibacterial agents and macromolecular antibacterial agents. The antibacterial food preservative film is a functional film which is prepared by adding an antibacterial agent into a film material, utilizing the antibacterial action of metal ions and achieving the aims of antibiosis and preservation through the actions of slow release, photocatalysis and the like. In the research aspect of antibacterial food preservative films, Japan is the most active country, and in 90 th Japan of 20 th century, dozens of preservative films have been developed and used for preserving fruits and vegetables. In addition to Japan, the research of antibacterial food preservative films in Europe and America has made great progress. China began to turn to the research of modified atmosphere, antibacterial and other functional food preservative films after 90 s in the 20 th century. At present, various antibacterial food preservative films such as a nanometer mildew-proof preservative film, a nanometer preservative film and the like are developed, the antibacterial performance of the films is excellent, the mechanical strength is improved to different degrees compared with that of a common plastic film, and the application prospect is good.

The information shows that the inorganic antibacterial agent widely used in the antibacterial material is a silver-based antibacterial agent, which has high bactericidal performance, but is easy to change color when exposed to light or stored, and is separated from the material to be harmful to human body. In addition, because of the activity of silver, redox reaction is easy to occur to cause yellowing of plastic color, and the problems all bring adverse effects to the application of the material.

TiO is found in the Tokyo university Tengjingdao Zhao and Qiaogehren professor in 1997₂Having photocatalytic activity in the presence of light orPhotocatalytic antimicrobial agents have been developed rapidly since environmental energy can decompose microorganisms and their toxins produced. Materials that can be used as photocatalytic antimicrobial agents are mainly n-type semiconductors. TiO 2₂Is the most commonly used photocatalysis type antibacterial agent at present, in particular the anatase type. TiO 2₂Is an inorganic component, has no toxicity, no odor, no irritation, good thermal stability and heat resistance, is white, does not change color at high temperature, does not decompose, and has the advantages of good immediate effect, strong antibacterial capability, wide antibacterial spectrum, long-lasting antibacterial effect and the like. Currently, most of the commonly used antibacterial agents are ultrafine TiO₂The antibacterial agent is better effect, and the nanometer TiO is₂An antibacterial agent. Nano TiO 2₂The antibacterial effect is better, and compared with the common antibacterial material, the added nano antibacterial material prepared by nano level has the advantages of aging resistance, high temperature resistance, excellent comprehensive performance, stable antibacterial property, long time and the like, the application range is expanded, and the application level is improved.

At present, TiO is available at home and abroad₂The research on filling the antibacterial preservative film into the polymer is not many. Reported that nano TiO developed by Nanometric Material research institute of Qingdao chemical industry institute₂The antibacterial agent is added into PP, and the antibacterial rate is excellent through the antibacterial experiment test; xuruifen et al reported that anatase type nano TiO is adopted₂The antibacterial plastic is prepared by surface coating treatment and adding into resins such as PE and the like, and has long-acting broad-spectrum antibacterial effect; chenli et al by adding TiO in the resin₂The functional materials such as the master batch and the like are developed into the high-strength oxygen-resistant nano Fuji apple preservative film, and test results show that the nano particles are added to obviously improve the tensile strength of the film and reduce the permeability of oxygen and water vapor without influencing CO almost₂The penetration amount of the apple preservative has good effect when being used for preserving Fuji apples. With the development of the technique of combining organic polymer and inorganic substance to make film, the material prepared by mixing organic substance and nano inorganic substance combines the advantages of the two substances, and the aspect is also widely concerned and researched.

The pineapple leaf is rich in resources, and provides conditions for large-scale production of fiber raw materials. The first is the resource advantage. It is used as a waste resource and can be recycled every year; the second is the quality advantage. The pineapple leaf cellulose content is about 60 percent, is similar to that of needle-leaved wood and broad-leaved wood which are used as raw materials for producing viscose fiber in the prior art, but has lower lignin content than wood, and has the condition of film preparation. Scientific researchers at the university of Kebangsan Malaysia of Malaysia utilize pineapple leaves as fiber raw materials for pulping and papermaking, the physical and mechanical properties, the sulfate pulping performance, the pulp yield and the pulp fiber characteristics of pineapple leaf fibers are tested, the pineapple leaves and the fibers processed by the pineapple leaves are used as samples, the traditional sulfate cooking is adopted, the pulp yield is 2 l% -30% under various pulping conditions, and the strength property, particularly the tensile strength, of pulp is good. However, the pineapple leaf fiber has no natural antibacterial special function, and the research on the aspect of food preservative films is not carried out. The research of agricultural product processing research institute of tropical agricultural academy of China Weixiaoyi, and the like, clove oil is added into a pineapple leaf fiber film to prepare an antibacterial composite film, pork is subjected to fresh-keeping packaging, and the fresh-keeping performance of the pork is researched by analyzing the change of the appearance, the weight loss rate, the pH change and the change of the total number of bacterial colonies of the pork in the storage process. The result shows that the clove oil/pineapple leaf fiber antibacterial composite membrane can enable pork to keep good sensory quality, the weight loss rate and the pH value of the pork are not changed greatly, the total number of bacterial colonies rises very slowly, the growth of microorganisms can be effectively inhibited, and the shelf life can be prolonged by 3-5 days compared with that of a polyethylene membrane sold in the market. Third, a functional advantage. The pineapple leaf fiber has the functions of natural sterilization, peculiar smell removal, mite control and the like, and if the pineapple leaf fiber is prepared into renewable cellulose, the characteristic can be still kept or improved, the added value of the pineapple leaf fiber is greatly improved, and the pineapple leaf fiber is incomparable with other materials.

In view of the development trend, the development of the antibacterial food preservative film is coming to the golden period, the development trend of the antibacterial food preservative film is diversified in the following functions, and future antibacterial food preservative film researches convert from single metal ion dissolution type, non-dissolution type, far infrared ray antibacterial mode and the like to functional food preservative films integrating a plurality of antibacterial modes into a whole. The nano-grade and composite antibacterial material has unique physical properties and high activity, so that the nano-grade of the antibacterial material gradually becomes the main development direction of the antibacterial agent, and the corresponding antibacterial preservative film also develops towards the nano-grade of the antibacterial material. The microporous structure of the film is the material basis of the technology, and the addition of the antibacterial agent influences the microporous structure and the mechanical properties of the plastic film. The research of the antibacterial food preservative film comprehensively considers performance indexes such as antibacterial property, air conditioning, mechanical strength and the like in a future period of time, and realizes the combination of the performance. In a word, with the development of food science and technology and the requirement of consumers on the high quality of food, the antibacterial food package can inhibit the microbial contamination on the surface of the food, improve the safety of the food, prolong the shelf life of the food, and has wide application prospect in the future food package market.

Through the above analysis, the problems and defects of the prior art are as follows: the existing silver-based antibacterial agent is easy to discolor when being illuminated or stored, and is separated out from the material to be unfavorable for human body. In addition, because of the activity of silver, redox reaction is easy to occur to cause yellowing of plastic color, and the problems all bring adverse effects to the application of the material.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a pineapple leaf cellulose-based nano TiO carrier₂A method for preparing an antibacterial preservative film.

The invention is realized by the following steps that the pineapple leaf cellulose based nano TiO is loaded₂Preparation method of antibacterial preservative film, wherein nano TiO is loaded on pineapple leaf cellulose₂The preparation method of the antibacterial preservative film comprises the following steps:

step one, soaking nano TiO₂Formation of TiO₂Soaking in water, and adding TiO₂Placing the soaking solution in an ultrasonic dispersion instrument for ultrasonic dispersion treatment by using ultrasonic waves;

the ultrasonic dispersion treatment method comprises the following steps:

(1.1) mixing TiO₂The soaking solution is placed in a placing bottle of an ultrasonic dispersion instrument and is in surface contact with an oxygenation catalyst in the placing bottle;

(1.2) starting an ultrasonic bar and a refrigerator of the ultrasonic dispersion instrument to oxygenate the TiO with the catalyst₂SoakingThe liquid is subjected to ultrasonic dispersion under the action of an ultrasonic bar, and the temperature of a placing bottle is controlled by a refrigerator in the ultrasonic dispersion process;

step two, the dispersed TiO obtained in the step one₂Adding metal salt containing antibacterial metal ions into the soaking solution, mixing and dissolving, and fully stirring to obtain a mixed solution A;

step three, carrying out solid-liquid separation on the mixed liquid A obtained in the step two, drying, roasting and grinding the obtained solid to obtain the finished product of nano TiO₂An antibacterial agent;

the solid-liquid separation method of the mixed liquid comprises the following steps:

(3.1) stirring the obtained mixed solution A by using a stirring device, naturally stopping stirring after a period of time, and standing the mixed solution A;

(3.2) placing the mixed solution A after standing into a water storage container, and sequentially flowing through a coarse filter screen, a fine filter screen and an air bag plate to enter a storage tank;

(3.3) continuously repeating the step (3.2) for three times;

step four, dissolving pineapple leaf cellulose in a solution containing antibacterial metal ions by using an emulsifying and shearing mode, and adding the nano TiO obtained in the step three₂The antibacterial agent is evenly stirred to obtain a mixed solution B;

step five, blending the raw materials of the membrane casting solution with the mixed solution B obtained in the step four, heating, stirring and dissolving to obtain the membrane casting solution containing nano TiO₂A casting solution of an antibacterial agent;

the heating, stirring and dissolving comprises:

detecting the temperature of the mixed solution by using a temperature sensor, if so, judging whether the temperature of the solution reaches a heating interruption threshold value, and if so, controlling a heating device to interrupt heating; if not, judging whether the concentration of the solution reaches a heating preset temperature or not, and if so, stopping heating; if the preset heating temperature is not reached, controlling the heating device to continue heating until the preset heating temperature is reached, simultaneously utilizing a timer to carry out heating timing, and stopping heating when the preset heating time is reached;

pouring the casting solution obtained in the fifth step on a glass plate with the thickness of 15 multiplied by 25cm, and scraping an ultrafiltration membrane by using a glass rod;

seventhly, pre-evaporating the glass plate with the film coating in the air at room temperature, immersing the glass plate in a coagulating bath to perform gel phase conversion on the high molecular polymer in the casting solution on the glass plate, and separating out the high molecular polymer on the surface of the glass plate to obtain the pineapple leaf cellulose based nano TiO carrier₂An antibacterial preservative film.

Further, in the step one, the nano TiO₂The soaking time is 30-50 min, and the soaking temperature is 20-40 ℃.

Further, in the step one, the ultrasonic dispersion time is 20-50 min.

Further, in the second step, the antibacterial metal ions are one or a combination of more of silver, zinc, copper and decorative metal ions; the antibacterial metal ions are the combination of two metal ions of silver and zinc, or the combination of two metal ions of silver and copper, or the combination of three metal ions of silver, zinc and copper.

Further, in the second step, sulfuric acid or nitric acid is selected for the suspension liquid in stirring to adjust the pH value to 3-7, the stirring temperature is 50-75 ℃, and the stirring time is 6-8 hours.

Further, in the third step, the drying temperature of the solid is 80-125 ℃, and the drying time is 1.5-3 hours; and roasting the dried solid at the temperature of 500-600 ℃ for 3-6 h, and grinding the roasted solid by using a ball mill.

Further, in the fifth step, the raw materials of the casting solution consist of, by mass, 20-25 parts of a high molecular polymer, 10-15 parts of a pore-forming agent and the balance of a solvent.

Further, the high molecular polymer is polyether sulfone (PES) and polyvinylidene fluoride (PVDF); the pore-foaming agent is polyvinylpyrrolidone (PVP); the solvent is N, N-dimethylacetamide (DMAc) and N, N-Dimethylformamide (DMF).

Further, in the seventh step, the pre-evaporation temperature is 100-120 ℃, and the pre-evaporation time is 30-40 s.

Further, in the seventh step, the coagulating bath is deionized water, and the temperature is controlled to be 30-25 ℃.

By combining all the technical schemes, the invention has the advantages and positive effects that: the pineapple leaf cellulose-based nano TiO provided by the invention₂The preparation method of the antibacterial preservative film comprises the step of mixing nano TiO₂The preparation of the composite membrane with the pineapple leaf cellulose is carried out, the physical characteristics and the antibacterial and fresh-keeping performance of the membrane forming material are researched, and the analysis and the comparison with a pure pineapple leaf cellulose membrane are carried out, so as to clarify whether the pineapple leaf cellulose has antibacterial property and base-loaded nano TiO after the membrane forming₂The antibacterial effect of the composite film is the possibility of being used as a novel food fresh-keeping material, and the industrial application of the pineapple leaf fiber is expanded. The invention uses nano TiO₂The composite antibacterial fiber membrane is added into the pineapple leaf fiber membrane to prepare the composite antibacterial fiber membrane, and has important significance for improving the technological innovation capability of the material-oriented research direction in the unit solid waste resource subject field and maintaining the international leading position of the development and utilization research of the pineapple leaf fiber.

Drawings

FIG. 1 shows pineapple leaf cellulose-based nano TiO provided by the embodiment of the invention₂A flow chart of a preparation method of the antibacterial preservative film.

FIG. 2 shows pineapple leaf cellulose-based nano TiO provided by the embodiment of the invention₂A schematic diagram of a preparation method of the antibacterial preservative film.

Fig. 3 is a flow chart of an ultrasonic dispersion method provided by an embodiment of the invention.

FIG. 4 is a flow chart of a mixed liquid solid-liquid separation method provided by the embodiment of the invention.

FIG. 5 shows pineapple leaf cellulose-based nano TiO provided by the embodiment of the invention₂The water flux of the antibacterial preservative film is compared with that of the common antibacterial preservative film.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Aiming at the problems in the prior art, the invention provides a pineapple leaf cellulose-based nano TiO carrier₂The invention relates to a preparation method of an antibacterial preservative film, which is described in detail below with reference to the accompanying drawings.

As shown in figure 1, the pineapple leaf cellulose-based nano TiO provided by the embodiment of the invention₂The preparation method of the antibacterial preservative film comprises the following steps:

s101, soaking the nano TiO₂Formation of TiO₂Soaking in water, and adding TiO₂And (5) placing the soaking solution in an ultrasonic dispersion instrument for ultrasonic dispersion treatment.

S102, dispersed TiO obtained in S101₂And adding metal salt containing antibacterial metal ions into the soaking solution, mixing and dissolving, and fully stirring to obtain a mixed solution A.

S103, carrying out solid-liquid separation on the mixed liquid A obtained in the step S102, drying, roasting and grinding the obtained solid to obtain the finished product of nano TiO₂An antibacterial agent.

S104, dissolving pineapple leaf cellulose in a solution containing antibacterial metal ions by using an emulsifying and shearing mode, and adding the nano TiO obtained in the step S103₂And (4) uniformly stirring the antibacterial agent to obtain a mixed solution B.

S105, blending the raw materials of the casting solution with the mixed solution B obtained in the S104, heating, stirring and dissolving to obtain the nano TiO-containing material₂And (3) a casting solution of an antibacterial agent.

S106, pouring the casting solution obtained in S105 on a glass plate of 15X 25cm, and scraping the ultrafiltration membrane by using a glass rod.

S107, pre-evaporating the glass plate with the film coating in the air at room temperature, immersing the glass plate in a coagulating bath to perform gel phase conversion on the high molecular polymer in the casting solution on the glass plate, and separating out the high molecular polymer on the surface of the glass plate to obtain the pineapple leaf cellulose based nano TiO₂An antibacterial preservative film.

In step S101, the nano TiO provided in the embodiment of the present invention₂The soaking time is 30-50 min, and the soaking temperature is 20-40 ℃.

In step S101, the ultrasonic dispersion time provided by the embodiment of the invention is 20-50 min.

As shown in fig. 3, in step S101, the ultrasonic dispersion method provided by the embodiment of the present invention includes:

s201, mixing TiO₂The soaking solution is placed in a placing bottle of an ultrasonic dispersion instrument and is in surface contact with an oxygenation catalyst in the placing bottle;

s202, starting an ultrasonic bar and a refrigerator of the ultrasonic dispersion instrument, and oxygenating the TiO with the catalyst₂The soak solution is subjected to ultrasonic dispersion under the action of an ultrasonic bar, and the temperature of the placing bottle is controlled by a refrigerator in the ultrasonic dispersion process.

In step S102, the antibacterial metal ions provided by the embodiment of the present invention are one or a combination of more of silver, zinc, copper, and decorative metal ions; the antibacterial metal ions are the combination of two metal ions of silver and zinc, or the combination of two metal ions of silver and copper, or the combination of three metal ions of silver, zinc and copper.

In step S102, sulfuric acid or nitric acid is selected to adjust the pH value of the suspension during stirring to 3-7, the stirring temperature is 50-75 ℃, and the stirring time is 6-8 hours.

As shown in fig. 4, in step S103, the method for solid-liquid separation of a mixed liquid according to the embodiment of the present invention includes:

s301, stirring the obtained mixed solution A by using a stirring device, naturally stopping stirring after a period of time, and standing the mixed solution A;

s302, placing the standing mixed solution A into a water storage container, and sequentially flowing through a coarse filter screen, a fine filter screen and an air bag plate to enter a storage tank;

s303, repeating step S302 three times continuously.

In step S103, the drying temperature of the solid provided by the embodiment of the invention is 80-125 ℃, and the drying time is 1.5-3 h; and roasting the dried solid at the temperature of 500-600 ℃ for 3-6 h, and grinding the roasted solid by using a ball mill.

In step S105, the raw material of the casting solution provided in the embodiment of the present invention is composed of, by mass, 20 to 25 parts of a high molecular polymer, 10 to 15 parts of a pore-forming agent, and the balance of a solvent.

The high molecular polymer provided by the embodiment of the invention is polyether sulfone (PES) and polyvinylidene fluoride (PVDF); the pore-foaming agent is polyvinylpyrrolidone (PVP); the solvent is N, N-dimethylacetamide (DMAc) and N, N-Dimethylformamide (DMF).

In step S105, the heating, stirring and dissolving provided by the embodiment of the present invention includes:

detecting the temperature of the mixed solution by using a temperature sensor, if so, judging whether the temperature of the solution reaches a heating interruption threshold value, and if so, controlling a heating device to interrupt heating; if not, judging whether the concentration of the solution reaches a heating preset temperature or not, and if so, stopping heating; if the preset heating temperature is not reached, controlling the heating device to continue heating until the preset heating temperature is reached, simultaneously utilizing a timer to heat and time, and stopping heating when the preset heating time is reached.

In step S107, the pre-evaporation temperature provided by the embodiment of the invention is 100-120 ℃, and the pre-evaporation time is 30-40S.

In step S107, the coagulation bath provided by the embodiment of the present invention is deionized water, and the temperature is controlled to be 30 to 25 ℃.

The present invention will be further described with reference to the following examples.