Waterproof starch section bar and preparation method and application thereof
Technical Field
The invention belongs to the technical field of starch materials, and particularly relates to a waterproof starch section bar and a preparation method and application thereof.
Background
The current plastic products have the advantages of low cost, various varieties, good performance and the like, are widely applied to various fields and appear in daily life of people. The plastic products bring many negative problems while facilitating the life of people, not only consume non-renewable petroleum resources, but also cause huge environmental pressure because most of the plastic products are not degradable, and particularly cause serious environmental pollution because of the large accumulation of disposable plastic products.
The starch material, such as thermoplastic starch material, is a high molecular raw material derived from natural plants, is a degradable and renewable natural resource, has better plastic processability and biocompatibility, and has lower cost than plastic. From the economic and green environmental protection perspectives, the starch material has great potential to replace common plastics, especially in the packaging field or disposable daily life products, such as disposable straws, lunch boxes, water cups and the like. Since these products do not have high mechanical properties required for the material, the starch material is fully competent and the starch itself is edible for packaging food with safety. However, starch materials, such as thermoplastic starch materials in particular, have their own distinct weaknesses in the use as packaging materials or as disposable articles of daily use-water resistance and water absorption, which substantially completely limit the packaging of food products by thermoplastic starch materials. The water resistance of thermoplastic starch materials has been studied, and more reports are made at present only to improve the sensitivity to water, but no waterproof and water-resistant thermoplastic starch materials are obtained.
The soybean oil is a natural material derived from vegetable oil, and the modified epoxy soybean oil acrylate obtained by modification has the characteristics of degradability, no toxicity and low cost and is a widely used additive; meanwhile, the liquid epoxy soybean oil acrylate has three double-bond functional groups and can be cured through free radical polymerization to form solid resin with strong water resistance and low water absorption. However, the hydrophilic thermoplastic starch material and the hydrophobic epoxidized soybean oil acrylate cannot be uniformly blended, and particularly, the cured epoxidized soybean oil acrylate is easy to phase separate from the hydrophilic starch material, so that the material cannot be molded.
At present, the preparation of Starch/epoxy soybean oil acrylate waterproof materials by a coating method has been reported (Meng L, Li S, Yang W, Simons R, Yu L, Liu H, et al, improvement of Interfacial Interaction between hydrophobic Starch Film and Hydrophilic Biodegradable coating. ACS Sustainable Chem Eng 2019; 7 (10): 9506-14), wherein a thermoplastic Starch material is prepared, then a cross-linking agent or a compatilizer is coated on the surface, then epoxy soybean oil acrylate is further coated on the surface, and then the epoxy soybean oil acrylate is cured to form the waterproof Starch material. The coating method used when the waterproof starch material is prepared by the method is an intermittent production mode, has complex process and is not suitable for industrial production; and because the thermoplastic starch material is difficult to coat a waterproof layer after being made into the section bar and is difficult to carry out forming processing after being made into the waterproof starch sheet/film material, namely forming processing and waterproof coating are difficult to complete, the method is not suitable for preparing the section bar, and the use space of the starch material is seriously reduced.
Provides a waterproof starch material which can be directly molded and processed and a method thereof, and has important environmental and economic significance.
Disclosure of Invention
In view of the above, the present invention provides a waterproof starch material, which has the advantages of water resistance, water resistance and direct molding treatment; the invention also provides a preparation method and application of the waterproof starch material.
In order to achieve the purpose of the invention, the invention provides the following technical scheme:
the invention provides a waterproof starch section which is prepared from 20-40 wt.% of oil-water mixture and the balance of starch;
the oil-water mixture is prepared from the following raw materials in percentage by mass:
the sum of the mass percentages of the raw materials in the oil-water mixture is 100%.
Preferably, the emulsifier is one or more of sodium stearoyl lactylate, calcium stearoyl lactylate, diacetyl tartaric acid esters of monoglycerides, sucrose fatty acid esters and distilled monoglycerides.
Preferably, the photoinitiator is 2-methyl-1- (4-methylthiophenyl) -2-morpholine-1-one, 1-hydroxycyclohexyl phenyl ketone or 2-hydroxy-2-methyl-1-phenyl-1-propanone.
The invention also provides a preparation method of the waterproof starch section bar in the technical scheme, which comprises the following steps:
providing an oil-water mixture;
blending and extruding the oil-water mixture and starch to obtain the thermoplastic starch material;
and sequentially carrying out molding and ultraviolet curing treatment on the thermoplastic starch material to obtain the waterproof starch section.
Preferably, the temperature of the blending extrusion is 40-100 ℃.
Preferably, the blending extrusion equipment is a twin-screw extruder.
Preferably, the molding is injection molding, hot press molding, cast film forming or extrusion molding.
Preferably, the ultraviolet light power of the ultraviolet light curing treatment is 8-100W; the time of the ultraviolet curing treatment is 30-60 s.
The invention also provides the application of the waterproof starch section material in the technical scheme or the waterproof starch section material prepared by the preparation method in the technical scheme in the field of living products.
The invention provides a waterproof starch section which is prepared from 20-40 wt.% of oil-water mixture and the balance of starch; the oil-water mixture is prepared from the following raw materials in percentage by mass: 4.5-50% of epoxidized soybean oil acrylate; 0.5-5% of an emulsifier; 0.1-2% of a photoinitiator; 43-94.9% of water; the sum of the mass percentages of the raw materials in the oil-water mixture is 100%.
In the invention, part of the epoxidized soybean oil acrylate macromolecules can be combined with the emulsifier to promote the epoxidized soybean oil acrylate to show hydrophilicity, so that the hydrophilic fragments on the molecular chain of the epoxidized soybean oil acrylate can be fully mixed and combined with starch molecules, the water absorption of the waterproof starch profile can be reduced, and the mechanical property of the waterproof starch profile can be enhanced; the hydrophobic segments existing in the molecular chain of the epoxy soybean oil acrylate are automatically distributed on the surface of starch molecules during blending, and are mixed with the epoxy soybean oil acrylate which is not emulsified by the emulsifier and gathered on the surface of the starch, so that the compatibility of the hydrophobic epoxy soybean oil acrylate and hydrophilic starch is obviously improved, and the hydrophobic epoxy soybean oil acrylate is tightly linked to the surface of the hydrophilic starch through the emulsified epoxy soybean oil acrylate to form a waterproof liquid oil layer. Meanwhile, the liquid epoxy soybean oil acrylate and the thermoplastic starch material have the physical characteristics of being capable of being mixed and repeatedly subjected to thermoplastic molding, so that the waterproof starch material is favorably ensured to have molding capacity, and the contained photoinitiator is favorable for directly crosslinking and curing the epoxy soybean oil acrylate in the waterproof starch section bar and the epoxy soybean oil acrylate oil layer on the surface in situ in the ultraviolet curing process, so that the mechanical property of the waterproof starch section bar is obviously enhanced, and the waterproof high-performance section bar is directly molded and produced.
The experimental result shows that compared with the common starch material, the waterproof starch section provided by the invention has the water resistance time of only 5min, the waterproof starch section provided by the invention has the water resistance time of more than 1 day, and has good plastic processing performance, good mechanical performance and excellent service performance.
The invention also provides a preparation method of the waterproof starch section bar in the technical scheme, which comprises the following steps: providing an oil-water mixture; blending and extruding the oil-water mixture and starch to obtain a thermoplastic starch material; and sequentially carrying out molding and ultraviolet curing treatment on the thermoplastic starch material to obtain the waterproof starch section. The invention is beneficial to fully mixing the fragments of the emulsified hydrophilic epoxy soybean oil acrylate molecules with starch and remaining the mixture in the thermoplastic starch material through blending extrusion, the fragments of the epoxy soybean oil acrylate molecules with hydrophobicity and the epoxy soybean oil acrylate with hydrophobicity which is not emulsified are automatically distributed on the surface of the thermoplastic starch material in the blending extrusion process, the compatibility of the hydrophobic epoxy soybean oil acrylate and the hydrophilic starch is improved in the process, and the hydrophobic epoxy soybean oil acrylate is closely linked on the surface of the hydrophilic starch material to form a liquid oil layer; in addition, the liquid epoxidized soybean oil acrylate and the thermoplastic starch material have the physical characteristics of being capable of being mixed and repeatedly subjected to thermoplastic forming, so that the starch material containing the liquid epoxidized soybean oil acrylate is favorably ensured to have the thermoplastic forming capability. In the ultraviolet curing process, under the action of a photoinitiator, the ultraviolet curing is favorable for combining the epoxy soybean oil acrylate in the thermoplastic starch material with starch and carrying out in-situ crosslinking and curing in the thermoplastic starch material, the water absorption of the thermoplastic starch material is reduced, the mechanical property of the thermoplastic starch material is improved, meanwhile, the ultraviolet curing is favorable for curing the epoxy soybean oil acrylate oil layer on the surface of the thermoplastic starch material to form a waterproof film, the direct contact between water and the thermoplastic starch material is isolated, the waterproof property of the waterproof starch material is obviously improved, the mechanical property of the waterproof starch material is further improved, and the waterproof starch material or the waterproof starch section bar is directly prepared.
Detailed Description
The invention provides a waterproof starch section which is prepared from 20-40 wt.% of oil-water mixture and the balance of starch;
the oil-water mixture is prepared from the following raw materials in percentage by mass:
the sum of the mass percentages of the raw materials in the oil-water mixture is 100%.
In the present invention, the starting components for the preparation are commercially available products well known to those skilled in the art, unless otherwise specified.
In the invention, the preparation raw material of the waterproof starch section comprises 20-40 wt.% of oil-water mixture, preferably 24-36%, and more preferably 28-32%.
In the invention, the oil-water mixture comprises the following preparation raw materials in percentage by mass:
the sum of the mass percentages of the raw materials in the oil-water mixture is 100%.
The oil-water mixture comprises 4.5-50% by mass of epoxidized soybean oil acrylate, preferably 10-45% by mass of epoxidized soybean oil acrylate, and more preferably 15-40% by mass of epoxidized soybean oil acrylate.
The oil-water mixture comprises 0.5-5% of emulsifier by mass, preferably 1-4.5% of emulsifier by mass, more preferably 1.5-4% of emulsifier by mass, and even more preferably 2-3.5% of emulsifier by mass. In the present invention, the emulsifier is preferably one or more of sodium stearoyl lactylate, calcium stearoyl lactylate, diacetyl tartaric acid ester of monoglycerides, sucrose fatty acid esters and distilled monoglycerides, more preferably one or more of sodium stearoyl lactylate, calcium stearoyl lactylate, diacetyl tartaric acid esters of monoglycerides and sucrose fatty acid esters, and still more preferably sodium stearoyl lactylate, calcium stearoyl lactylate or diacetyl tartaric acid esters of monoglycerides. In the invention, the emulsifier can be combined with part of the epoxidized soybean oil acrylate to promote the molecule segment of the epoxidized soybean oil acrylate to be changed from hydrophobicity to hydrophilicity, so that the partial epoxidized soybean oil acrylate and the starch are well blended and connected, and further, the partial epoxidized soybean oil acrylate is favorably embedded into the waterproof starch section bar so as to enhance the waterproofness, the water absorbability and the mechanical property of the waterproof starch section bar; meanwhile, the emulsifier is beneficial to promoting the uniform blending of the epoxidized soybean oil acrylate and water, and improving the viscous state of the epoxidized soybean oil acrylate, so that the epoxidized soybean oil acrylate is beneficial to realizing good blending with starch in a liquid form.
The oil-water mixture comprises 0.1-2% of photoinitiator, preferably 0.4-1.7%, more preferably 0.7-1.4%, and even more preferably 0.9-1.2% by mass. In the present invention, the photoinitiator is preferably 2-methyl-1- (4-methylthiophenyl) -2-morpholine-1-one, 1-hydroxycyclohexylphenylketone or 2-hydroxy-2-methyl-1-phenyl-1-propanone. In the invention, the photoinitiator is beneficial to realizing the curing of the epoxy soybean oil acrylate, and is further beneficial to obtaining the waterproof starch section with waterproof performance and capable of being molded.
The oil-water mixture comprises, by mass, 43-94.9% of water, preferably 48-90%, more preferably 55-85%, and even more preferably 60-80%. The water used in the present invention is not particularly limited, and may be water known to those skilled in the art, specifically tap water, deionized water or distilled water.
Besides the oil-water mixture, the raw materials for preparing the waterproof starch profile also comprise the balance of starch. In the present invention, the starch is preferably one or more of potato starch, corn starch, tapioca starch, wheat starch and modified starch; the modified starch is preferably one or more of potato starch, corn starch, tapioca starch or wheat starch obtained by modifying through etherification, esterification or hydroxypropylation crosslinking.
The invention also provides a preparation method of the waterproof starch section bar in the technical scheme, which comprises the following steps:
providing an oil-water mixture;
blending and extruding the oil-water mixture and starch to obtain the thermoplastic starch material;
and sequentially carrying out molding and ultraviolet curing treatment on the thermoplastic starch material to obtain the waterproof starch section.
In the invention, the components in the preparation method are consistent with those in the waterproof starch section bar in the technical scheme, and are not described again.
The present invention provides oil and water mixtures. According to the invention, the epoxidized soybean oil acrylate, the emulsifier, the photoinitiator and water are preferably fully mixed to obtain an oil-water mixture. The mixing method of the present invention is not particularly limited, and a mixing method known to those skilled in the art may be used. According to the invention, the oil-water mixture is prepared firstly, so that the partial emulsification effect of the emulsifier on the epoxy soybean oil acrylate is ensured, the partial epoxy soybean oil acrylate has hydrophilicity, and the good blending of the partial epoxy soybean oil acrylate (which is emulsified) and the starch is realized.
After an oil-water mixture is obtained, the oil-water mixture and starch are subjected to blending extrusion treatment to obtain the thermoplastic starch material. In the invention, the blending extrusion equipment is preferably a double-screw extruder, and the length-diameter ratio of the double-screw extruder is preferably (30-40): 1, more preferably (32-38): 1, and preferably (34-36): 1; the width of the die head of the double-screw extruder is preferably 50-500 mm, more preferably 100-450 mm, and further preferably 150-400 mm. In the invention, the rotation speed of the blending and extruding screw is preferably 60-240 rpm, more preferably 100-200 rpm, and still more preferably 130-170 rpm. In the invention, the sampling flow rate of the oil-water mixture in the blending extrusion is preferably 20-80 mL/min, more preferably 30-70 mL/min, and still more preferably 40-60 mL/min. In the invention, the equipment for adding the oil-water mixture in the blending extrusion is preferably a plunger pump. In the invention, the sampling flow rate of the starch is preferably 1-50 kg/h, more preferably 5-45 kg/h, and still more preferably 10-40 kg/h. In the invention, the equipment for adding starch in the blending extrusion is preferably a double-screw weight-loss type feeder. In the invention, the temperature of the blending extrusion is preferably 40-100 ℃; specifically, the temperature of the seven sections of the screw of the blending extruder from the feed port is set to 40 ℃, 60 ℃, 90 ℃, 80 ℃ and 70 ℃ in sequence, and the temperature of the die head is set to 70 ℃ as in the embodiment of the invention.
According to the invention, by the method of preparing the oil-water mixture firstly and then mixing the oil-water mixture and the starch, the defect that epoxy soybean oil acrylate cannot be tightly connected with starch molecules through the emulsifier due to the fact that micromolecule emulsifier is completely wrapped by macromolecular starch molecules when all preparation raw materials of the waterproof starch material are directly extruded and mixed together is avoided, the emulsifying effect of the emulsifier on the epoxy soybean oil acrylate and the connection contribution of the emulsifier on the epoxy soybean oil acrylate/starch are ensured, and further the good mixing of the epoxy soybean oil acrylate and the starch is ensured.
After the thermoplastic starch material is obtained, the thermoplastic starch material is molded to obtain the primary section. In the present invention, the molding is preferably injection molding, hot press molding, cast film forming or extrusion molding. The process of injection molding, hot press molding and extrusion molding is not particularly limited in the present invention, and may be a process of injection molding, hot press molding and extrusion molding well known to those skilled in the art. In the present invention, the molding treatment apparatus is preferably an extrusion molding machine, an injection molding machine, or a hot press molding machine.
After the primary section bar is obtained, the invention carries out ultraviolet curing treatment on the primary section bar to obtain the waterproof starch section bar. In the invention, the ultraviolet light power of the ultraviolet light curing treatment is preferably 8-100W, more preferably 15-90W, and further preferably 20-85W. In the invention, the time of the ultraviolet curing treatment is preferably 30-60 s, more preferably 32-55 s, and still more preferably 35-50 s. In the present invention, the ultraviolet curing apparatus is preferably an ultraviolet curing machine.
The invention also provides the application of the waterproof starch section material in the technical scheme or the waterproof starch section material prepared by the preparation method in the technical scheme in the field of living products.
In the invention, the application is preferably that the thermoplastic starch material is directly molded into a shape of a living product and then subjected to ultraviolet curing treatment to obtain the waterproof starch section. In the present invention, the living article is preferably a package or a straw; the package is preferably a lunchbox or drinking cup.
In order to further illustrate the present invention, the following examples are provided to describe the waterproof starch shapes and the preparation method and application thereof in detail, but they should not be construed as limiting the scope of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The reagents used in example 1 are all commercially available.
Fully mixing 50 wt.% of epoxidized soybean oil acrylate, 5 wt.% of sodium stearoyl lactylate as an emulsifier, 2 wt.% of 2-hydroxy-2-methyl-1-phenyl-1-acetone as a photoinitiator and 43 wt.% of water to obtain an oil-water mixture;
after an oil-water mixture is obtained, blending and extruding the obtained oil-water mixture and starch (the mass percentage of the oil-water mixture is 40%) by using a double-screw extruder to obtain a thermoplastic starch material, wherein the temperature of seven sections of the double-screw extruder is set as follows: the temperature from the charging opening is 40 ℃, 60 ℃, 90 ℃, 80 ℃ and 70 ℃ in sequence, the die head temperature is 70 ℃, and blending extrusion is carried out after the temperature is stabilized at the set temperature; the rotating speed of the double-screw extruder is 60 rpm; adding the oil-water mixture into a double-screw extruder by using a plunger pump, wherein the sample injection flow is 20 mL/min; and adding starch into a double-screw extruder by using a double-screw weight loss type feeding machine, wherein the sample injection flow rate is 20kg/h, and thus obtaining the thermoplastic starch material.
After the thermoplastic starch material is obtained, directly utilizing a molding device (an injection molding machine) to carry out molding processing to obtain a primary section; and after the primary section is obtained, carrying out ultraviolet curing on the obtained primary section by using an ultraviolet curing machine, wherein the ultraviolet power is 8W, and the ultraviolet curing time is 60s, so as to obtain the waterproof starch section.
The mechanical properties of the waterproof starch profile obtained in example 1 were tested according to ASTM D3983-98, and the test results were: young's modulus is 96MPa, and elongation at break is 30%.
Example 2
Fully mixing 4.5 wt.% of epoxidized soybean oil acrylate, 0.5 wt.% of emulsifier diacetyl tartaric acid monoglyceride, 0.1 wt.% of photoinitiator 2-hydroxy-2 methyl-1-phenyl-1-acetone and 94.9 wt.% of water to obtain an oil-water mixture;
after an oil-water mixture is obtained, blending and extruding the obtained oil-water mixture and starch (the mass percentage of the oil-water mixture is 20%) by using a double-screw extruder to obtain a thermoplastic starch material, wherein the temperature of seven sections of the double-screw extruder is set as follows: the temperature from the charging opening is 40 ℃, 60 ℃, 90 ℃, 80 ℃ and 70 ℃ in sequence, the die head temperature is 70 ℃, and blending extrusion is carried out after the temperature is stabilized at the set temperature; the rotating speed of the double-screw extruder is 240 rpm; adding the oil-water mixture into a double-screw extruder by using a plunger pump, wherein the sample injection flow is 80 mL/min; and adding starch into a double-screw extruder by using a double-screw weight loss type feeding machine, wherein the sample injection flow is 50kg/h, so as to obtain the thermoplastic starch material.
After the thermoplastic starch material is obtained, directly utilizing a forming device (a hot-press forming machine) to carry out forming processing to obtain a primary section; and after the primary section is obtained, carrying out ultraviolet curing on the obtained primary section by using an ultraviolet curing machine, wherein the ultraviolet power is 100W, and the ultraviolet curing time is 30s, so as to obtain the waterproof starch section.
The mechanical properties of the waterproof starch profile obtained in example 2 were tested according to ASTM D3983-98, and the test results were: young's modulus 52MPa, elongation at break 60%.
Comparative example 1
Raw starch was used as comparative material.
The waterproof starch section obtained in examples 1-2 and the starch material in comparative example 1 were tested for waterproof performance by the following method:
the test method comprises the following steps: soaking a sample to be tested in sufficient water, taking out after soaking for a certain time, wiping off water on the surface of the material of the sample to be tested by using absorbent paper, and performing a tensile test according to the ASTM D5938 standard, wherein the mechanical property of the sample to be tested is not changed when the tensile strength is greater than 80% of that of the sample which is not soaked, and the sample to be tested is water-resistant at the moment.
Tests prove that the water-resistant time of the starch material provided in the comparative example 1 is less than 5min, and the water-resistant time of the waterproof starch section provided in the embodiments 1-2 is more than 1 day, so that the waterproof starch section provided by the invention has excellent waterproof and water-resistant properties and can completely meet the requirements of living products with molding requirements.
The experimental results show that the waterproof starch section provided by the invention has excellent waterproof and water-resistant performances, and the water-resistant time is longer than 1 day; the section bar can be processed, and the section bar processing and the waterproof performance can be considered at the same time; the mechanical strength of the product is good, and the product can meet the mechanical strength requirements of living products such as straws, packing boxes and beverage cups; the main components are starch and epoxy soybean oil acrylate, so that the biodegradable polyester film has biodegradable performance, and is safe and environment-friendly; and the cost is low, and the preparation method is safe, simple and easy to master, and is suitable for industrial continuous production. In conclusion, the waterproof starch profile provided by the invention has great commercial application value and economic value.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.