1. A self-plasticizing starch, characterized in that the starch comprises, in parts by weight:

2. a self-plasticizing starch as defined in claim 1 wherein said starch is at least one of corn starch, potato starch, tapioca starch, sweet potato starch, mung bean starch.

3. A self-plasticizing starch and its preparation method as claimed in claim 1 or 2 characterised in that the coupling agent is isopropyl tri (dioctyl pyrophosphato acyloxy) titanate.

4. A self-plasticizing starch and its preparation method as claimed in claim 3 wherein said talc is a crystal nucleating agent selected from 3000 mesh.

5. The self-plasticizing starch and the preparation method thereof as claimed in claim 4, characterized in that the antioxidant is one or two of 1010 antioxidant, 300 antioxidant or 168 antioxidant.

6. The self-plasticizing starch and the preparation method thereof as claimed in claim 5, characterized in that the lubricant is polyethylene wax or oxidized polyethylene wax.

7. The self-plasticizing starch and the preparation method thereof of claim 6, characterized in that the plasticizer is at least one of glycerol, polyethylene glycol and acetyl tributyl citrate.

8. The self-plasticizing starch and the preparation method thereof as claimed in claim 7, characterized in that the volume ratio of polyethylene glycol and glycerol is 2:1 when the polyethylene glycol and glycerol compound plasticizer is adopted.

9. A method for preparing self-plasticizing starch is characterized by comprising the following steps,

s1: putting starch into a high-speed mixer pot, and dropwise adding a coupling agent diluted by 1:1 with water in a stirring state at a stirring speed of 1200rpm, wherein the dropwise adding is completed within 33-5 min;

s2: adding titanium dioxide, talcum powder, an antioxidant, zinc stearate, a lubricant and a plasticizer, and stirring at the stirring speed of 1200rpm for 4-5 min to obtain a pre-grinding material;

s3: adding the pre-ground material into a superfine grinding machine, grinding and mixing to 200-325 meshes, and sending the mixture to a powder collector through pipeline air to obtain the homogenized self-plasticizing starch.

Background

With the excessive exploitation and utilization of petrochemical resources, the storage capacity of the petrochemical resources is reduced year by year, and meanwhile, a large amount of disposable non-degradable plastic products are used, so that garbage is continuously formed, and particularly, a large amount of non-degradable garbage causes great negative effects on soil and environment. There is an urgent need to develop and promote biodegradable & compostable materials to alleviate the current environmental pressures.

The ecological civilization construction is the fundamental great idea of the eternal development of Chinese nationality, the promotion of ecological civilization construction is increased, the ecological environment problem is solved, the sustainable development of plastic raw materials and products is promoted, the recyclable, easily-recycled and degradable guide is realized, the technological innovation strength is increased, the development performance reaches the standard, the green and environment-friendly plastic materials and products are economically applicable, the green low-carbon production is developed, the plastic waste recycling is improved, the energy utilization ratio is increased, the green product is promoted, a green factory is adopted, a green park is adopted, the construction of a green supply chain system is realized, the novel green and environment-friendly functional material is expanded, and the application range of degradable plastics in the fields of disposable plastic packaging, shopping bags, food packaging, agricultural films and the like is included. The environment-friendly plastic product packaging method has the advantages that the environment is advocated actively, the consumption of disposable plastic products which are not easy to recycle is greatly reduced, the guiding work in the fields of e-commerce, express delivery, take-out and the like is realized, the scientific and reasonable solution is found by taking recyclable, easy to recycle and degradable as a guide, the popular science knowledge publicity is made, the plastic is used scientifically, the sanitation classification recycling is made, the good atmosphere participating in the whole society together is created, and the win, pollution, prevention, control and attack combat can be achieved in a continuous effort.

Recently, the nations, the provinces and the cities have been in successive sales and forbidden to use non-degradable disposable packaging bags and tableware, which is favorable for further promoting the trend of the requirement of biodegradable plastics. Currently, biodegradable polyesters mainly include: PLA, PBAT, PBS, PHA, PPC and the like, but the price of degradable plastics is higher, which mainly causes the problem of raw material supply, the supply of the raw materials of the degradable plastics is tense, the cost price is more than twice of that of common plastics, and in order to accelerate the degradation speed of the biological plastics, increase the capacity and reduce the cost, the filling type biological decomposition plastics are favored. Most fillers of the bioplastic are calcium carbonate, talcum powder and starch, but the filling of the calcium carbonate and the talcum powder can only increase the capacity, the addition amount is basically 5-20%, and although the addition of a large amount can further reduce the cost, the fluidity of a melt is poor, the processing performance is reduced, and the mechanical property is obviously reduced. The starch can be degraded, compatibilized and cost-reduced, and the key is the thermoplasticity of the starch. Therefore, the starch filled type biodegradable plastic is the most fully researched and applied biodegradable plastic at home and abroad at present, the starch serving as the filler can be raw starch, physically modified starch or chemically modified starch, or a copolymer formed by reacting with a monomer, and the raw starch, the physically modified starch or the chemically modified starch can be blended with the biodegradable plastic to prepare a required product. In order to create a resource-saving and environment-friendly society, starch-based bioplastic must be rapidly developed as a most advantageous bio-based material.

Disclosure of Invention

The present invention is directed to solving the above problems and providing a self-plasticizing starch and a method for preparing the same.

The invention realizes the purpose through the following technical scheme:

a self-plasticizing starch comprising, in parts by weight:

in the invention, preferably, the starch is at least one of corn starch, potato starch, tapioca starch, sweet potato starch and mung bean starch.

Preferably, the coupling agent is isopropyl tris (dioctyl pyrophosphato acyloxy) titanate.

In the invention, the talcum powder is preferably used as a crystallization nucleating agent and is selected to be 3000 meshes.

Preferably, the antioxidant is one or two of 1010 antioxidant, 300 antioxidant or 168 antioxidant.

Preferably, the lubricant is polyethylene wax or oxidized polyethylene wax.

Preferably, the plasticizer is at least one of glycerol, polyethylene glycol and acetyl tributyl citrate.

According to the invention, the volume ratio of the polyethylene glycol to the glycerol is preferably 2:1 when the polyethylene glycol and glycerol compound plasticizer is adopted.

A preparation method of self-plasticizing starch comprises the following steps,

s1: putting starch into a high-speed mixer pot, and dropwise adding a coupling agent diluted by 1:1 with water in a stirring state at a stirring speed of 1200rpm, wherein the dropwise adding is completed within 33-5 min;

s2: adding titanium dioxide, talcum powder, an antioxidant, zinc stearate, a lubricant and a plasticizer, and stirring at the stirring speed of 1200rpm for 4-5 min to obtain a pre-grinding material;

s3: adding the pre-ground material into a superfine grinding machine, grinding and mixing to 200-325 meshes, and sending the mixture to a powder collector through pipeline air to obtain the homogenized self-plasticizing starch.

The invention has the beneficial effects that:

according to the invention, a certain amount of plasticizer is added to weaken the hydrogen bond effect in starch molecules and greatly reduce the glass transition temperature of the starch molecules, so that the plasticizing processing of the starch is realized, polyethylene glycol is an environment-friendly plasticizer, a polyethylene glycol molecular chain is a flexible connecting segment, and after the polyethylene glycol is added, the flexibility of the resin molecular chain can be improved, the motion capability of the resin molecular chain is increased, the free volume is increased, and the Tg reduction of the resin can be improved; meanwhile, the talcum powder serving as a micromolecule is convenient to be in resin, and can promote the molecular bond movement of the resin, so that the crystallization is promoted.

Detailed Description

The invention is further illustrated below:

a self-plasticizing starch comprising, in parts by weight:

further, the starch is at least one of corn starch, potato starch, cassava starch, sweet potato starch and mung bean starch.

Further, the coupling agent is isopropyl tri (dioctyl pyrophosphato acyloxy) titanate.

Furthermore, the talcum powder is used as a crystallization nucleating agent and is selected to be 3000 meshes.

Further, the antioxidant is one or two of 1010 antioxidant, 300 antioxidant or 168 antioxidant.

Further, the lubricant is polyethylene wax or oxidized polyethylene wax.

Further, the plasticizer is at least one of glycerol, polyethylene glycol and acetyl tributyl citrate.

Further, when the polyethylene glycol and glycerol compound plasticizer is adopted, the volume ratio of the polyethylene glycol to the glycerol is 2: 1.

A preparation method of self-plasticizing starch comprises the following steps,

s1: putting starch into a high-speed mixer pot, and dropwise adding a coupling agent diluted by 1:1 with water in a stirring state at a stirring speed of 1200rpm, wherein the dropwise adding is completed within 33-5 min;

s2: adding titanium dioxide, talcum powder, an antioxidant, zinc stearate, a lubricant and a plasticizer, and stirring at the stirring speed of 1200rpm for 4-5 min to obtain a pre-grinding material;

s3: adding the pre-ground material into a superfine grinding machine, grinding and mixing to 200-325 meshes, and sending the mixture to a powder collector through pipeline air to obtain the homogenized self-plasticizing starch.

The invention prepares the self-plasticizing starch by a solid phase method crushing mode combining mechanics and mechanochemistry, modifies the starch by mechanical effect, improves the compatibility, the fluidity and the self-plasticizing property of the starch, blends and processes the self-plasticizing starch and bio-based plastics, is used for biodegradable and compostable products, improves the processing performance compared with the original starch, improves the mechanical property, increases the addition amount, prepares the self-plasticizing starch, has simple process and easy operation, and is beneficial to realizing large-scale industrial production and application.

Example 1

A preparation method of self-plasticizing starch comprises the following steps,

s1: putting 95 parts of corn starch into a high-speed mixer pot, diluting 0.7 part of coupling agent and 1:1 parts of water, slowly adding the coupling agent and the water into the starch at the stirring speed of 1200rpm, and stirring for 4 min;

s2: sequentially adding 1.2 parts of talcum powder, 10100.2 parts of antioxidant, 1680.4 parts of antioxidant, 0.2 part of zinc stearate, 0.2 part of oxidized polyethylene wax, 2.0 parts of polyethylene glycol glycerol composite plasticizer (the volume ratio of polyethylene glycol to glycerol is 2:1) and 0.1 part of titanium dioxide under stirring, and stirring at the stirring speed of 1200rpm for 4min to obtain a pre-grinding material;

s3: and (3) adding the pre-ground material into an ultrafine grinding machine for grinding, adjusting the size of a gap between an inclined blade of a screen of the grinding machine and a taper shell to be 200 meshes of powder granularity, and discharging the material from a powder collector of the grinding machine after grinding the material to obtain a self-plasticizing starch finished product.

Example 2

A preparation method of self-plasticizing starch comprises the following steps,

s1: putting a starch mixture of 80 parts of corn starch and 15 parts of cassava starch into a high-speed mixer pot, diluting 0.7 part of coupling agent with 1:1 of water, slowly adding the diluted coupling agent into the starch mixture at a stirring speed of 1200rpm, and stirring for 5 min;

s2: sequentially adding 1.2 parts of talcum powder, 3000.6 parts of antioxidant, 0.2 part of zinc stearate, 0.2 part of oxidized polyethylene wax, 2.0 parts of polyethylene glycol-glycerol composite plasticizer (the volume ratio of polyethylene glycol to glycerol is 2:1) and 0.1 part of titanium dioxide under stirring, and stirring at the stirring speed of 1200rpm for 5min to obtain a pre-grinding material;

s3: and (3) adding the pre-ground material into an ultrafine grinding machine for grinding, adjusting the size of a gap between an inclined blade of a screen of the grinding machine and a taper shell to be 325 meshes of powder granularity, and discharging the material from a powder collector of the grinding machine after grinding the material to obtain a self-plasticizing starch finished product.

In order to change the natural property of starch, increase the performance and introduce new characteristics, the self-plasticizing starch preparation process adopts the method of grinding, kneading, homogenizing and modifying, and combines solid-phase mechanics and mechanochemistry to prepare the self-plasticizing starch body. The self-plasticizing starch grinding, kneading, homogenizing and modifying equipment selects a high-speed mixer and an ultrafine grinder, the high-speed mixer is used for activating starch and uniformly mixing the starch and the auxiliaries, and the key is that the ultrafine grinder is used for grinding, kneading and homogenizing the starch and the auxiliaries. The blades of the superfine pulverizer rotate at a high speed of 1200r/min to generate centrifugal force, materials are thrown onto the box walls of the blade boxes under the action of the centrifugal force to be impacted and crushed, starch molecular chains are broken, meanwhile, starch fine powder is conveyed to the top of a conveying tower by utilizing high-speed air generated by the blades, the powder with different particle sizes is separated, larger particles which cannot reach the fineness enter a material returning device and are conveyed to a main machine again through a spiral conveying device to be continuously ground and rubbed, and finally, the qualified fine powder enters a powder collector to be collected, so that solid-phase mechanical and mechanochemical grinding and homogenizing are completed. The material fineness is controlled by adjusting the size of a gap between an inclined blade of the screen and the cone shell so as to solve the problem that biodegradable materials are difficult to process and realize the plasticization of starch/PLA, PBAT, PBS, PHA, PPC and other blending materials.

The self-plasticizing starch is subjected to experiments, a formula optimized in industrialization and a unique grinding and rubbing process, the capacity of an incompatible polymer mixture is increased by a mechanochemical effect generated in the process of crushing starch particles, and the plasticizing and viscosity of biodegradable resin are not matched with the effective mixing of a blend system, so that the filling amount of the prepared self-plasticizing starch in filling biodegradable plastic is greatly increased, the plasticizing time is shortened, the processing performance is ensured, the cost is reduced, and the degradation speed is accelerated under the condition of ensuring the quality of a product. The influencing factors of the degradation rate of the self-plasticizing starch mainly comprise temperature, humidity, pH value, water, bacterial colonies, microorganisms, animals and plants and the like which are used for accelerating the degradation rate in the use environment. In the degradation environment of agricultural production and land burial, the chain segment of starch-based plastic is broken, the mechanical property of the material is reduced, the starch-based plastic is gradually broken into fragments, and the fragments are decomposed into glucose micromolecules under the action of microorganisms and various enzymes, and the final products are CO2 and water.

The size of the starch particle size directly affects the uniformity of the starch dispersion in the matrix and the properties of the product. The finer the starch granule, the better the dispersion, the higher the mechanical property of the material, see table 1, because of the yield and cost problem, the size of the self-plasticizing starch granule of the invention is 200-350 mesh, which is enough to reach the national standard of the product, therefore, the starch solid phase grinding and rubbing process is an excellent choice.

TABLE 1 influence of PBAT/self-plasticizing starch particle size on mechanical Properties

Note: PBAT/self-plasticizing starch 70/30

Compared with the traditional plastic products, the self-plasticizing starch-based material and the products have the advantages that:

a. performance: has the same or similar performance with the traditional plastic products;

b. and (3) environmental protection: the self-plasticizing starch-based plastic and products have the advantages of saving petroleum resources, reducing carbon dioxide emission, being completely biodegradable and compostable, and realizing harmless treatment of garbage;

c. safety: the self-plasticizing starch-based material and the product do not contain harmful substances such as bisphenol A, heavy metals and the like, meet the national food-grade plastic standard, and have no influence on the health of operators in the whole production process;

d. the production process comprises the following steps: the production process is mild, high pressure, toxicity, harm and noise are avoided, three wastes are not discharged, and green products are produced;

e. cost: the self-plasticizing starch-based decomposed plastic product is slightly higher than common plastic in cost due to the influence of the price of the biodegradable polyester.

In conclusion, the invention can weaken the hydrogen bond action in starch molecules by adding a certain amount of plasticizer, greatly reduce the glass transition temperature, thereby realizing the plasticizing processing of the starch, wherein the polyethylene glycol is an environment-friendly plasticizer, the polyethylene glycol molecular chain is a flexible connecting segment, and after the polyethylene glycol is added, the flexibility of the resin molecular chain can be improved, the motion capability of the resin molecular chain is increased, the free volume is increased, so the Tg reduction of the resin can be improved; meanwhile, the talcum powder serving as a micromolecule is convenient to be in resin, and can promote the molecular bond movement of the resin, so that the crystallization is promoted.

As will be realized, the invention is capable of other and different modifications and its several details are capable of modifications in various obvious respects, all without departing from the spirit and scope of the present invention.