CN111944176A - Starch-plant-based bio-plastic sheet for packaging and preparation method thereof - Google Patents
Starch-plant-based bio-plastic sheet for packaging and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of biological plasticizing materials, in particular to a starch-plant-based biological plastic sheet for packaging and a preparation method thereof. According to the invention, the KH550 silane coupling agent is used for modifying the silica sol, so that the silica sol can be grafted to the starch, epichlorohydrin is used as a crosslinking agent and reacts with the modified silica sol in the process of crosslinking the starch, so that the silica sol is more firmly connected with the starch, and the crosslinked starch has a more stable structure, so that the water resistance and the tensile strength of the starch are improved, the straw fiber modified by hydrophobicity has good hydrophobic property, and the sheet material obtained by blending the straw fiber with the crosslinked starch has good tensile strength and water resistance.
Description
Technical Field
The invention relates to the technical field of biological plasticizing materials, in particular to a starch-plant-based biological plastic sheet for packaging and a preparation method thereof.
Background
Films made from polyvinyl chloride, polyethylene, polypropylene, polystyrene, and other resins are used for packaging, and as a film coating. Plastic packages and plastic package products have a larger share in the market, and particularly, composite plastic flexible packages are widely applied to the fields of food, medicine, chemical industry and the like, wherein the proportion of the plastic packages is the largest, such as beverage packages, quick-frozen food packages, steamed and cooked food packages, fast food packages and the like, and the plastic packages and the plastic package products bring great convenience to the life of people. However, since these films are difficult to degrade and put a great strain on the environment after use, the development and use of degradable packaging films are urgently needed for the sustainable development of the environment.
The conventional bioplastic is plastic produced by using natural substances such as starch and the like as a base under the action of microorganisms, and has renewability, so that the bioplastic is very environment-friendly. And biodegradable plastics refer to a type of plastics that are degraded by the action of microorganisms existing in the natural world, such as bacteria, molds (fungi), and algae. The ideal biodegradable plastic is a high molecular material which has excellent service performance, can be completely decomposed by environmental microorganisms after being discarded, and is finally inorganic to become a component of carbon circulation in nature. "paper" is a typical biodegradable material, while "synthetic plastics" is a typical polymeric material. Biodegradable plastics can be divided into completely biodegradable plastics and destructively biodegradable plastics. Destructive biodegradable plastics currently mainly comprise starch modified (or filled) polyethylene PE, polypropylene PP, polyvinyl chloride PVC, polystyrene PS, and the like. The completely biodegradable plastic is mainly prepared from natural polymers (such as starch, cellulose and chitin) or agricultural and sideline products by microbial fermentation or synthesis of biodegradable polymers, such as thermoplastic starch plastic, aliphatic polyester, polylactic acid, starch/polyvinyl alcohol and the like.
Biodegradable plastic films are the most common type of biodegradable plastic, and currently biodegradable plastic films mainly include both completely biodegradable plastics and destructively biodegradable plastics. Destructive biodegradable plastics currently mainly comprise starch modified (or filled) polyethylene PE, polypropylene PP, polyvinyl chloride PVC, polystyrene PS, and the like. The completely biodegradable plastic is mainly prepared from natural polymers (such as starch, cellulose and chitin) or agricultural and sideline products by microbial fermentation or synthesis of biodegradable polymers, such as thermoplastic starch plastic, aliphatic polyester, polylactic acid, starch/polyvinyl alcohol and the like. As more hydrophilic groups are contained in the completely degradable plastic, the completely degradable plastic is not water-resistant in the using process and is easy to hydrolyze in water environment, so that the packaging material loses the effect and the packaged articles are affected. Meanwhile, the completely degraded biological material has low tensile strength and large brittleness, thereby limiting the application range of the material.
Chinese patent publication No. CN110713624A discloses a starch-based cellulose degradable plastic film, which is prepared by the following method: adding polyvinyl alcohol into deionized water, heating in a water bath at 65 ℃, and stirring at a constant speed until a transparent solution is formed; adding corn amylose and deionized water into a beaker, heating and stirring for 30min, maintaining the temperature, adding the transparent solution prepared in the step S1, adjusting the pH to 4.5-5.0 to prepare a mixed solution, and adding modified silica sol; the invention adds hydroxypropyl methyl cellulose into deionized water, heats, mixes with the mixed solution added with modified silicon dioxide sol, adds glycerin, casts and uncovers the film to prepare the degradable plastic film.
Chinese patent publication No. CN108976482A discloses a method for preparing a plastic film, which comprises the following raw materials in parts by weight: 40-60 parts of starch, 30-40 parts of glycerol, 25-35 parts of polyvinyl alcohol, 4-6 parts of hydrophilic nano silicon dioxide, 3-5 parts of antioxidant, 4-6 parts of solubilizer and 1-3 parts of catalyst. The invention uses the nano silicon dioxide as the filler and the reinforcing agent to improve the strength of the degradable plastic, thereby leading the degradable plastic to have good tensile strength.
Although the above patents are improved in water resistance and tensile strength, respectively, there is still a problem that the water resistance and tensile strength cannot be improved correspondingly at the same time.
Disclosure of Invention
Aiming at the problem that the existing biodegradable plastic film is poor in tensile strength and water resistance, the invention provides a starch-plant-based bioplastic sheet for packaging and a preparation method thereof.
In order to solve the problems, the invention adopts the following technical scheme:
a method of preparing a starch-plant based bio-plastic sheet for packaging comprising the steps of:
(1) adding water glass into acetic acid solution, adjusting the pH value to 3-4, soaking for 2-4h, adjusting the pH value to be neutral, adding a silane coupling agent for modification, and continuously stirring for 0.5-1h to obtain modified silica sol;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding rotation speed to be 800-1000r/min, heating to 50-70 ℃ to grind the starch to a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 1-2h, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 2-6h at the temperature of 50-80 ℃ and the pressure of 1.5-2.5MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber;
(4) adding 50-60 parts by weight of the crosslinked starch obtained in the step (2), 5-10 parts by weight of a plasticizer, 3-5 parts by weight of a filler, 0.05-1 part by weight of an ultraviolet absorber and 40-50 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
The silane coupling agent is mainly used for glass fiber reinforced plastics, and the molecular structural formula of the silane coupling agent is generally Y-R-Si (OR)3(wherein Y is an organofunctional group, SiOR is a siloxy group). The siloxy group is reactive with inorganic species and the organofunctional group is reactive or compatible with organic species. Thus, when a silane coupling agent intervenes between the inorganic and organic interfaces, a bonding layer of organic matrix-silane coupling agent-inorganic matrix may be formed. Wherein the silane coupling agent KH-550 is a low molecular organosilicon compound with a special structure and a general formula of the low molecular organosilicon compound is RSiX3Wherein R represents an active functional group having affinity or reactivity with a polymer molecule, such as oxy, mercapto, vinyl, epoxy, amido, aminopropyl, etc., and X represents an alkoxy group capable of hydrolysis, such as halogen, alkoxy, acyloxy, etc. In the coupling process, firstly, X radical water forms silanol, and then the silanol reacts with hydroxyl on the surface of inorganic powder particles to form hydrogen bonds and is condensed into a-SiO-M covalent bond (M represents the surface of the inorganic powder particles). Meanwhile, silanol of each molecule of silane is mutually associated and oligomerized to form a film with a net structure to cover the surfaces of the powder particles, so that the surfaces of the inorganic powder are organized. Further, in the step (1), the silane coupling agent is a KH550 silane coupling agent; the adding amount of the silane coupling agent is 3-5% of the mass of the water glass.
Further, the mass fraction of the modified silica sol in the step (1) is 8-10%.
Further, in the step (2), the crosslinking agent is epichlorohydrin; the catalyst is sodium hydroxide. The invention takes the gelatinized modified starch as the raw material, sodium hydroxide as the catalyst and epichlorohydrin as the cross-linking agent to prepare the cross-linked starch, thereby improving the strength and the water resistance of the starch.
Further, the raw materials in the step (2) comprise the following components in parts by weight: 20-40 parts of starch, 10-15 parts of water, 4-8 parts of glycerol, 3-5 parts of modified silica sol, 0.5-2 parts of cross-linking agent and 0.1-0.3 part of catalyst.
Cellulose is a macromolecular polysaccharide composed of glucose, which is the main component of plant cell walls, and hemicellulose is a heteromultimer composed of several different types of monosaccharides, which are five-carbon sugars and six-carbon sugars, including xylose, arabinose, mannose, galactose, and the like. It is bound to the surface of cellulose microfibrils and is interconnected, these fibers constituting a rigid interconnected network of cells. The straw fiber is the most common and economical type of cellulose, and can be recycled, so that the pollution of burning to the environment is reduced. Further, in the step (3), the straw fiber is selected from one of corn straw fiber, soybean straw fiber and rice straw fiber.
Further, in the step (3), the raw materials in parts by weight are as follows: 10-20 parts of straw fiber, 0.5-1 part of caustic alkali, 10-20 parts of chloromethane and 0.4-0.8 part of propylene oxide.
Further, in the step (4), the plasticizer is one or a combination of more than two of dioctyl phthalate, tricresyl phosphate and dioctyl sebacate; the filler is talcum powder; the light absorber is a light stabilizer, and the light stabilizer is selected from one of a basf light stabilizer 2020 and a basf light stabilizer 1100 or a mixture of the basf light stabilizer and the basf light stabilizer in a mass ratio of 1: 1. The light stabilizer can capture free radicals in the material, block chain reaction of light and oxygen aging, ensure that the free radicals can not continuously damage molecular chains, effectively protect macromolecules, avoid the problems of yellowing, reduction of glossiness, reduction of physical properties and the like, and strengthen the weather resistance of products. It is often added into plastic, paint, cosmetics, etc. to prevent the light degradation caused by long-term exposure to light.
The invention also provides a starch-plant-based bioplastic sheet for packaging, which is prepared by the preparation method of the starch-plant-based bioplastic sheet for packaging. According to the invention, the starch and the modified silica sol are blended and then crosslinked by using epichlorohydrin, so that the strength and the water resistance of the starch are improved, then the hydrophobic modified cellulose is continuously added, and the mixture is granulated and then tabletted to obtain the plastic sheet for packaging.
According to the invention, the KH550 silane coupling agent is used for modifying the silica sol, so that the silica sol can be grafted to the starch, epichlorohydrin is used as a crosslinking agent and reacts with the modified silica sol in the process of crosslinking the starch, so that the silica sol is more firmly connected with the starch, and the crosslinked starch has a more stable structure, so that the water resistance and tensile strength of the starch are improved, the straw fiber modified by hydrophobicity has good hydrophobic property, and the packaging plastic film obtained by blending the straw fiber with the crosslinked starch has good tensile strength and water resistance.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1a method for preparing a starch-plant based bio-plastic sheet for packaging:
(1) adding water glass into acetic acid solution, adjusting the pH value to be 3, soaking for 3h, adjusting the pH value to be neutral, adding a silane coupling agent accounting for 4% of the mass of the water glass for modification, and continuously stirring for 1h to obtain modified silica sol with the mass fraction of 9%; the silane coupling agent is KH550 silane coupling agent;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding speed to be 900r/min, heating to 60 ℃ to grind the starch to be in a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 2 hours, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch; the cross-linking agent is epichlorohydrin; the catalyst is sodium hydroxide; the weight parts of the raw materials are as follows: 30 parts of starch, 12 parts of water, 6 parts of glycerol, 4 parts of modified silica sol, 1 part of cross-linking agent and 0.2 part of catalyst;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 4 hours at the temperature of 70 ℃ and the pressure of 2MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber; the straw fiber is selected from corn straw fiber; the weight parts of the raw materials are as follows: 15 parts of straw fiber, 0.8 part of caustic alkali, 15 parts of chloromethane and 0.6 part of propylene oxide;
(4) adding 55 parts by weight of the crosslinked starch obtained in the step (2), 8 parts by weight of a plasticizer, 4 parts by weight of a filler, 0.5 part by weight of a light absorber and 45 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules; the plasticizer is dioctyl phthalate; the filler is talcum powder; the light absorber is a light stabilizer selected from a basf light stabilizer 2020;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
Example 2a method of preparing a starch-plant based bio-plastic sheet for packaging:
(1) adding water glass into acetic acid solution, adjusting the pH value to be 4, soaking for 4h, adjusting the pH value to be neutral, adding a silane coupling agent accounting for 5% of the mass of the water glass for modification, and continuously stirring for 1h to obtain modified silica sol with the mass fraction of 10%; the silane coupling agent is KH550 silane coupling agent;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding rotation speed to be 800r/min, heating to 50 ℃ to grind the starch to be in a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 1h, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch; the cross-linking agent is epichlorohydrin; the catalyst is sodium hydroxide; the weight parts of the raw materials are as follows: 40 parts of starch, 10 parts of water, 8 parts of glycerol, 5 parts of modified silica sol, 1 part of cross-linking agent and 0.2 part of catalyst;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 3 hours at the temperature of 75 ℃ and the pressure of 1.5MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber; the straw fiber is selected from rice straw fiber; the weight parts of the raw materials are as follows: 10 parts of straw fiber, 1 part of caustic alkali, 16 parts of chloromethane and 0.6 part of propylene oxide;
(4) adding 60 parts by weight of the crosslinked starch obtained in the step (2), 5 parts by weight of a plasticizer, 4 parts by weight of a filler, 0.1 part by weight of a light absorber and 50 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules; the plasticizer is dioctyl sebacate; the filler is talcum powder; the light absorber is a light stabilizer selected from a BASF light stabilizer 1100;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
Example 3 a method of preparing a starch-plant based bio-plastic sheet for packaging:
(1) adding water glass into acetic acid solution, adjusting the pH value to 3.5, soaking for 2h, adjusting the pH value to be neutral, adding a silane coupling agent accounting for 5% of the mass of the water glass for modification, and continuously stirring for 0.8h to obtain modified silica sol with the mass fraction of 8%; the silane coupling agent is KH550 silane coupling agent;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding rotation speed to be 800r/min, heating to 55 ℃, grinding the starch to be in a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine, continuously grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuously adding a cross-linking agent and a catalyst, after grinding reaction for 2 hours, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch; the cross-linking agent is epichlorohydrin; the catalyst is sodium hydroxide; the weight parts of the raw materials are as follows: 25 parts of starch, 13 parts of water, 6 parts of glycerol, 4 parts of modified silica sol, 1 part of cross-linking agent and 0.3 part of catalyst;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 5 hours at the temperature of 60 ℃ and the pressure of 1.8MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber; the straw fiber is selected from soybean straw fiber; the weight parts of the raw materials are as follows: 18 parts of straw fiber, 0.9 part of caustic alkali, 18 parts of chloromethane and 0.7 part of propylene oxide;
(4) adding 58 parts by weight of the crosslinked starch obtained in the step (2), 8 parts by weight of a plasticizer, 3 parts by weight of a filler, 0.5 part by weight of a light absorber and 49 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules; the plasticizer is a combination of dioctyl phthalate and tricresyl phosphate; the filler is talcum powder; the light absorber is a mixture of light stabilizers selected from the group consisting of a basf light stabilizer 2020 and a basf light stabilizer 1100;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
Example 4a method of preparing a starch-plant based bio-plastic sheet for packaging:
(1) adding water glass into acetic acid solution, adjusting the pH value to be 4, soaking for 3h, adjusting the pH value to be neutral, adding a silane coupling agent accounting for 5% of the mass of the water glass for modification, and continuously stirring for 1h to obtain modified silica sol with the mass fraction of 10%; the silane coupling agent is KH550 silane coupling agent;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding speed to 850r/min, heating to 55 ℃ to grind the starch to be in a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 2 hours, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch; the cross-linking agent is epichlorohydrin; the catalyst is sodium hydroxide; the weight parts of the raw materials are as follows: 35 parts of starch, 13 parts of water, 6 parts of glycerol, 4 parts of modified silica sol, 2 parts of cross-linking agent and 0.2 part of catalyst;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 5 hours at the temperature of 75 ℃ and the pressure of 1.8MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber; the straw fiber is selected from corn straw fiber; the weight parts of the raw materials are as follows: 15 parts of straw fiber, 1 part of caustic alkali, 18 parts of chloromethane and 0.7 part of propylene oxide;
(4) adding 60 parts by weight of the crosslinked starch obtained in the step (2), 8 parts by weight of a plasticizer, 5 parts by weight of a filler, 1 part by weight of a light absorber and 48 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules; the plasticizer is a combination of dioctyl phthalate and dioctyl sebacate; the filler is talcum powder; the light absorber is a light stabilizer selected from a basf light stabilizer 2020;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
Example 5 a method of preparing a starch-plant based bio-plastic sheet for packaging:
(1) adding water glass into acetic acid solution, adjusting the pH value to be 3, soaking for 3h, adjusting the pH value to be neutral, adding a silane coupling agent accounting for 5% of the mass of the water glass for modification, and continuously stirring for 1h to obtain modified silica sol with the mass fraction of 8%; the silane coupling agent is KH550 silane coupling agent;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding rotation speed to 950r/min, heating to 65 ℃ to grind the starch to a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 2 hours, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch; the cross-linking agent is epichlorohydrin; the catalyst is sodium hydroxide; the weight parts of the raw materials are as follows: 40 parts of starch, 14 parts of water, 6 parts of glycerol, 4 parts of modified silica sol, 1 part of cross-linking agent and 0.2 part of catalyst;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 5 hours at the temperature of 70 ℃ and the pressure of 1.8MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber; the straw fiber is selected from rice straw fiber; the weight parts of the raw materials are as follows: 14 parts of straw fiber, 0.9 part of caustic alkali, 15 parts of chloromethane and 0.6 part of propylene oxide;
(4) adding 59 parts by weight of the crosslinked starch obtained in the step (2), 8 parts by weight of a plasticizer, 4 parts by weight of a filler, 0.8 part by weight of a light absorber and 48 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules; the plasticizer is a combination of dioctyl phthalate and tricresyl phosphate; the filler is talcum powder; the light absorber is a light stabilizer selected from a basf light stabilizer 2020;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
Example 6 a method of preparing a starch-plant based bio-plastic sheet for packaging:
(1) adding water glass into acetic acid solution, adjusting the pH value to be 3, soaking for 4h, adjusting the pH value to be neutral, adding a silane coupling agent accounting for 4% of the mass of the water glass for modification, and continuously stirring for 0.8h to obtain modified silica sol accounting for 8% of the mass fraction; the silane coupling agent is KH550 silane coupling agent;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding rotation speed to be 880r/min, heating to 60 ℃ to grind the starch to be in a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 2 hours, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch; the cross-linking agent is epichlorohydrin; the catalyst is sodium hydroxide; the weight parts of the raw materials are as follows: 28 parts of starch, 13 parts of water, 7 parts of glycerol, 4 parts of modified silica sol, 2 parts of cross-linking agent and 0.2 part of catalyst;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 5 hours at the temperature of 70 ℃ and the pressure of 2MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber; the straw fiber is selected from rice straw fiber; the weight parts of the raw materials are as follows: 18 parts of straw fiber, 0.7 part of caustic alkali, 14 parts of chloromethane and 0.6 part of propylene oxide;
(4) adding 58 parts by weight of the crosslinked starch obtained in the step (2), 8 parts by weight of a plasticizer, 4 parts by weight of a filler, 0.6 part by weight of a light absorber and 47 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules; the plasticizer is dioctyl phthalate; the filler is talcum powder; the light absorber is a light stabilizer selected from a BASF light stabilizer 1100;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
Comparative example 1
Unmodified silica sol was used. The remaining raw materials and processes were identical to those of example 1.
Comparative example 2
The rest of the raw materials and process were identical to example 1, using non-hydrophobically modified straw fibers.
And (3) correlation detection:
the tensile strength and the tensile elongation at break of the plastic sheet are determined according to GB1040 plastic tensile property test method.
The test method comprises the following steps:
1. tensile property test
The tensile strength and tensile elongation at break of the plastic sheet were measured in accordance with GB1040 "test method for tensile Properties of plastics", and the test pieces were 1A dumbbell-shaped, and the results are shown in Table 1.
2. Water resistance test
The dumbbell-shaped plastic sheets 1A prepared in comparative examples 1-2 and examples 1-6 according to GB1040 method for testing tensile properties of plastics were stored in water at 35 ℃ for 24 hours, and the tensile strength and tensile elongation at break of the plastic sheets were again measured according to the requirements of tensile properties tests, and the results are shown in Table 1.
Table 1 shows the results of the tensile property test and the water resistance test of examples 1 to 6 and comparative examples 1 to 2
As can be seen from table 1, in comparative example 1, since the silica sol is not modified, the silica sol can only physically penetrate into the starch, and the obtained sheet has low tensile strength and low elongation at break, while in comparative example 2, the cellulose is not modified, and after a water resistance test, the cellulose is easy to absorb water, so that the tensile strength and elongation at break are rapidly reduced.
Claims (9)
1. A method of making a starch-plant based bio-plastic sheet for packaging, comprising the steps of:
(1) adding water glass into acetic acid solution, adjusting the pH value to 3-4, soaking for 2-4h, adjusting the pH value to be neutral, adding a silane coupling agent for modification, and continuously stirring for 0.5-1h to obtain modified silica sol;
(2) adding starch, water and glycerol into a grinding dispersion machine, grinding, controlling the grinding rotation speed to be 800-1000r/min, heating to 50-70 ℃ to grind the starch to a gelatinized state, then adding the modified silica sol obtained in the step (1) into the grinding dispersion machine to continue grinding and dispersing, fully mixing the modified silica sol and the gelatinized starch, continuing adding a cross-linking agent and a catalyst, after grinding reaction for 1-2h, adjusting the pH value to be neutral, discharging, drying and crushing to obtain cross-linked starch;
(3) adding the straw fiber into a high-pressure reaction kettle, continuously adding caustic alkali, chloromethane and epoxypropane, reacting for 2-6h at the temperature of 50-80 ℃ and the pressure of 1.5-2.5MPa, decompressing and adjusting the pH value to be neutral, washing with ethanol and water, and drying to obtain hydrophobic straw fiber;
(4) adding 50-60 parts by weight of the crosslinked starch obtained in the step (2), 5-10 parts by weight of a plasticizer, 3-5 parts by weight of a filler, 0.05-1 part by weight of a light absorber and 40-50 parts by weight of the hydrophobic straw fiber obtained in the step (3) into an internal mixer, and mixing, cooling and granulating to obtain uniformly dispersed granules;
(5) and (3) tabletting the granules obtained in the step (4) through a calendering machine to obtain the starch-plant-based bioplastic sheet for packaging.
2. The method for preparing a starch-plant based bio-plastic sheet for packaging according to claim 1, wherein in the step (1), the silane coupling agent is KH550 silane coupling agent; the adding amount of the silane coupling agent is 3-5% of the mass of the water glass.
3. The method of preparing a starch-plant based bio-plastic sheet for packaging according to claim 1, wherein: the mass fraction of the modified silica sol in the step (1) is 8-10%.
4. The process for preparing a starch-plant based bio-plastic sheet for packaging according to claim 1, wherein said cross-linking agent in step (2) is epichlorohydrin; the catalyst is sodium hydroxide.
5. The preparation method of the starch-plant based bio-plastic sheet for packaging according to claim 1, wherein the raw materials in the step (2) comprise, by weight: 20-40 parts of starch, 10-15 parts of water, 4-8 parts of glycerol, 3-5 parts of modified silica sol, 0.5-2 parts of cross-linking agent and 0.1-0.3 part of catalyst.
6. The method for preparing a starch-plant based bio-plastic sheet for packaging according to claim 1, wherein the straw fiber in step (3) is selected from one of corn straw fiber, soybean straw fiber, and rice straw fiber.
7. The preparation method of the starch-plant based bio-plastic sheet for packaging according to claim 1, wherein in the step (3), the weight parts of the raw materials are as follows: 10-20 parts of straw fiber, 0.5-1 part of caustic alkali, 10-20 parts of chloromethane and 0.4-0.8 part of propylene oxide.
8. The method for preparing a starch-plant based bio-plastic sheet for packaging according to claim 1, wherein in the step (4), the plasticizer is one or a combination of two or more of dioctyl phthalate, tricresyl phosphate and dioctyl sebacate; the filler is talcum powder; the light absorber is one or a mixture of light stabilizers selected from a basf light stabilizer 2020 and a basf light stabilizer 1100.
9. A starch-plant based bio-plastic sheet for packaging prepared by the method for preparing a starch-plant based bio-plastic sheet for packaging of any one of claims 1 to 8.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113563134A (en) * | 2021-09-09 | 2021-10-29 | 苏农（广德）生物科技有限公司 | Preparation method of compound fertilizer convenient for rice growth regulation |
| CN113583466A (en) * | 2021-07-22 | 2021-11-02 | 湖北嘉鑫环保新材料科技有限公司 | Moderate cross-linked starch biodegradable plastic and preparation method thereof |
| CN114753184A (en) * | 2022-05-16 | 2022-07-15 | 四川轻化工大学 | Water-based coating paint for food packaging paper and preparation method thereof |
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2020
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113583466A (en) * | 2021-07-22 | 2021-11-02 | 湖北嘉鑫环保新材料科技有限公司 | Moderate cross-linked starch biodegradable plastic and preparation method thereof |
| CN113563134A (en) * | 2021-09-09 | 2021-10-29 | 苏农（广德）生物科技有限公司 | Preparation method of compound fertilizer convenient for rice growth regulation |
| CN114753184A (en) * | 2022-05-16 | 2022-07-15 | 四川轻化工大学 | Water-based coating paint for food packaging paper and preparation method thereof |
| CN114753184B (en) * | 2022-05-16 | 2023-02-17 | 四川轻化工大学 | Water-based coating paint for food packaging paper and preparation method thereof |
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