1. The preparation method of the starch-based dry powder is characterized by comprising the following steps:

(1) puffing the plant seeds rich in starch in a puffing machine to obtain a starch-based puffed body;

(2) and crushing the starch-based puffed body into powder to obtain the starch-based dry powder.

2. The method of claim 1, further comprising the step of drying the dry starch-based powder.

3. The method of claim 2, wherein the moisture content of the dried starch-based powder after drying is less than 5% by weight.

4. The preparation method of the starch-based dry powder is characterized by comprising the following steps:

(1) puffing the plant seeds rich in starch in a puffing machine to obtain a starch-based puffed body;

(2) drying the starch-based puffed body;

(3) and (3) crushing the starch-based puffed body to obtain powdery starch-based dry powder.

5. The method of preparing a dry, starch-based powder according to claim 4, wherein the moisture content of the dried starch-based puffed mass in step (2) is less than 5% wt.

6. The method for preparing the dry starch-based powder according to claim 4, wherein the drying method in the step (2) is hot air drying.

7. Melt mixing any one of the starch-based dry powders prepared according to claims 1-6 with plastic masterbatches to produce starch-based plastic articles.

8. Melt-mixing the starch-based dry powder prepared according to any one of claims 1 to 6 with plastic master batches, and granulating to obtain starch-based plastic master batches.

Background

The plastic is a material with low price and good service performance, and is widely applied in industry and life. However, the raw materials for plastics are mainly derived from petroleum, natural gas, coal, and the like. Because of their non-regenerability and excessive carbon dioxide emissions, the use of plastic raw materials and plastic products has become increasingly restricted with increasing environmental requirements and the enforcement of environmental policies. Therefore, in the field of plastics, it is becoming a trend in the field to seek renewable raw materials that reduce carbon dioxide emissions. In the prior art, biomass such as starch, wood powder, bamboo powder and the like is added into petroleum-based materials such as PP, PE, PVC and the like, so that the use amount of the petroleum-based materials is reduced and the carbon emission is reduced. However, starch contains a large amount of water (about 13% of commercial starch) and is extremely difficult to remove in plastic processing, so that the product quality is reduced or the addition cost is high; in addition, wood flour, bamboo powder and other plant fibers and lignins have high ductility and toughness, so that fine equipment and high energy consumption are required to obtain fineness required for processing, and the wood flour, bamboo powder and other plant fibers are mixed with PP, PE and the like, so that the smaller the particle size is, the better the quality is. In this way, although the use of petroleum-based plastics can be reduced by adding wood flour, bamboo flour, or the like during the processing of some plastic products, the cost is often higher than that of petroleum-based plastics, and the large-scale application of petroleum-based plastics is limited. Some starch-rich plant seeds, such as corn, wheat, sorghum, etc., have the potential to be used in the plastic field because they contain large amounts of starch. However, these seeds contain components such as vegetable protein and vegetable fiber in addition to starch and lignin powder, which are single components, and thus the processing thereof is more difficult. This is a technology that has not been found in the prior art for directly processing the plant seeds rich in starch and applying the plant seeds to the field of plastics.

Disclosure of Invention

In order to directly apply low-cost, renewable and natural plant grains rich in starch to the field of plastics, the invention provides a preparation method of starch-based dry powder, which is characterized by comprising the following steps:

(1) puffing the plant seeds rich in starch in a puffing machine to obtain a starch-based puffed body;

(2) and crushing the starch-based puffed body into powder to obtain the starch-based dry powder.

Preferably, the method further comprises the step of drying the starch-based dry powder.

Preferably wherein the moisture content of the dried starch-based powder after drying is less than 5% wt.

Also provides another preparation method of the starch-based dry powder, which is characterized by comprising the following steps:

(1) puffing the plant seeds rich in starch in a puffing machine to obtain a starch-based puffed body;

(2) drying the starch-based puffed body;

(3) and (3) crushing the starch-based puffed body to obtain powdery starch-based dry powder.

Preferably wherein the moisture content of the starch-based puffed body after drying in step (2) is less than 5% wt.

Preferably, the drying method in step (2) is hot air drying.

The invention also provides a method for preparing the starch-based plastic product by melting and mixing the starch-based dry powder and the plastic master batch.

The invention also provides a method for preparing the starch-based plastic master batch by melting and mixing the starch-based dry powder and the plastic master batch and granulating.

The invention is further illustrated below:

starch-rich plant seed

The plant seeds rich in starch refer to crop fruits such as corn grains, wheat grains, sorghum grains, mung beans, red beans and the like. The main components of the fruits of these crops include starch, water, protein, fiber, etc.

The table shows the contents of the components of several crop grains disclosed in starch chemistry and technology (chemical industry publishers):

table one:

name of article	Moisture content	Starch	Protein	Fat	Fiber
						Corn (corn)	16.7	71.3	9.91	4.45	9.5
(sorghum)	15.5	74.1	11.1	3.7	2.6
						Wheat (Triticum aestivum L.)	15	68	14	1.5	8
Rice	16	70	8	3	1

It can be seen from the table that the starch content of the various grains in the table is more than 60%.

The starch-rich plant seed grain of the invention refers to a plant seed grain with a starch content of more than 50% in the seed grain. The main components of the soybean are soybean oil and protein, and the content of starch is only about 10%, so the soybean and the like do not belong to the plant seeds rich in starch.

In addition, water was analyzed to be present in the starch, protein and fiber of the plant seeds listed in Table one, wherein the water content in the starch was about 12-15%; the water content of the protein is about 8-10%; the water content of the fiber is about 10%.

Due to the existence of starch and water in the plant seeds, necessary conditions are provided for the expansion of the plant seeds. Wherein water acts as a bulking agent during bulking.

Secondly, an innovative point of the invention lies in the treatment of the starch in the seed grain (in the case of maize, the same applies hereinafter)

The main component of corn is starch, and therefore, the treatment of starch is the key objective of the invention. Applicants have discovered that water is present in corn starch in two forms: one is free water, which is loosely bound to the starch molecules. When dried, free water can be dried more easily from within the starch; the other is bound water, which is represented by the fact that water and starch molecules are bound into fixed hydrate in the form of hydrogen bonds. When starch is dried by conventional means, bound water is difficult to separate from starch due to the action of hydrogen bonds unless additional large amounts of energy are expended. The reason why the water content of the existing starch is difficult to remove after being reduced to 13% is due to the influence of bound water. In addition, the prior art teaches that the texture of starch granules can be divided into two parts: one part is a crystalline region and the other part is an amorphous region. The applicant believes that, in the crystalline region, moisture is present predominantly in the form of bound water; the water in the amorphous region is present primarily as free water. The conventional drying method cannot completely remove water because the crystallization area of starch cannot be destroyed.

The innovation point of the invention is that the crystalline region inside the starch granule is changed into the amorphous region, the crystalline water is exclusively changed into free water, and then the free water is dried and removed. In this way, the moisture in the starch can be dried off very easily compared to the prior art.

In contrast, the technical means adopted by the invention is to puff the starch. Puffing is the process of heating (e.g. over 100 deg.C) and pressurizing starch containing a certain amount of water, then instantaneously releasing the pressure, at which time the water in the starch is released by vaporization, thus resulting in the starch being instantaneously puffed.

The invention relates to equipment for puffing.

The bulking machine is a single-screw or double-screw extruder, is common equipment and is commonly applied to the fields of food and feed. Compared with extruders used in the plastic field, such as a granulator and the like, the rotation speed of the bulking machine is slightly higher, which is approximately in the range of 100-1000 revolutions, and can also be higher, and the selection of the speed is related to the bulking pressure and the size of a die opening required by the process, other parameters of the bulking machine and the like.

The bulking machine can be provided with a temperature heating device and can also heat the material by means of heat generated in the rotating process. The working temperature of the bulking machine is set to meet the bulking requirement.

The change of the corn starch after being puffed is as follows:

first, the presence state of starch changes: after being expanded by an expander, the starch is changed into porous and fluffy blocks from powder. The fluffy, porous morphology would be very beneficial for drying of starch versus dry powder.

Secondly, the internal structure of the starch is changed: when the starch is expanded, under the plasticizing action of water as a plasticizer and high temperature and pressure of an expander, the crystalline structure inside the starch granules is broken, so that the starch granules are promoted to be converted from a crystalline state to an amorphous state. The internal structure of the solid block after expansion is in an amorphous state through experimental analysis.

Thirdly, the moisture in the starch is volatilized and removed while the starch is expanded. Tests prove that the water content of the expanded starch is about 4-6 percent and is far lower than the water content of commercial starch.

One test example is that when the puffing of corn with 15.2% moisture content is finished, the moisture content is measured to be 5.12%; after drying at 110 ℃ for 20 minutes in a drying oven, the moisture content was found to be 0.63%, less than 1%.

The following table shows the drying data (drying time and water content) of a commercial corn starch and a dry starch-based powder of the present invention in the same dryer (starting mass: 100 g; drying temperature of the dryer: 110 ℃ C.; water content: mass%).

Watch two

Time (minutes)	0	10	20	30	40	70	100
								Commercial starch	13.15	11.43	8.39	6.41	5.36	2.31	2.1
Corn dry powder	8.23	4.65	0.85	0.02	0	0	0

As can be seen from Table II, the moisture content of the dried corn flour is less than that of the commercial starch; compared with starch, the moisture in the corn dry powder is easier to remove, the effect is good, and the consumed time is short.

Thirdly, another innovation point of the invention is that the plant seeds are expanded, and tissues including seed coats and the like are also more easily refined.

The components of the plant seed grains rich in starch mainly include starch, but also include components such as coarse fiber, fine fiber, protein, fat, and the like. The presence of these components, particularly the fibres of the seed coat fraction, can cause great difficulties in the powdering process of the plant seeds. In addition, the presence of moisture in the seed coat or the like further enhances the toughness. The existing technical means are difficult to refine and obtain powder with smaller granularity. The reason for the large particle size of corn flour on the market (typically below 50 mesh) is that.

The technical means of the invention can overcome the difficulties. The seeds are expanded in an expander, so that not only the structure of starch is changed, but also the fiber, protein and the like of the seeds are changed: firstly, the moisture content is reduced after puffing: before puffing, the water content of the corn seed coat is 10 percent, and the water content after puffing is about 5 percent; secondly, the structure has also changed: after extrusion and expansion by an expander, the spatial structure of the fiber, protein and the like is damaged, so that the water holding capacity and toughness of the fiber or protein are reduced; furthermore, starch, protein, fiber and the like are mixed together by extrusion, which further reduces the mutual connection among fibers, reduces the toughness and plasticity thereof, increases brittleness, and makes it easier to obtain finer particles by machining. If the corn puffed body with the water content of about 5.4 percent is put in a pulverizer, fine powder of 150 meshes can be easily obtained; the less the moisture content of the corn puffed body is, the smaller the crushed particles are, and the lower the energy consumption is; in a fine mill, when the corn puffed is dried to 2%, fines in excess of 600 mesh can be easily obtained. If the same machine is used to process corn, it is not possible to obtain a meal of the same fineness.

The prior art shows that when starch, bamboo powder, wood powder and the like are mixed with PE, PP and other plastics for processing, the mechanical property of the combined product is related to the content and water of the starch, the bamboo powder and the wood powder, and the particle sizes of the starch, the bamboo powder and the wood powder are related. The smaller the water content is, the better the comprehensive mechanical property is; the smaller the particle size of the powder is, the better the comprehensive mechanical properties are. Compared with starch, bamboo powder, wood powder and the like, the starch-based dry powder can achieve very low water content and smaller particle size. Thus, when the starch-based dry powder is mixed with plastics such as PP, PE and the like, a combination with better mechanical properties can be obtained.

Fourthly, another innovation point of the invention is that the plant seeds are directly processed into powder without separating the epidermis, starch, protein and the like of the plant seeds according to the traditional process.

Therefore, the processing technology is simplified, and the cost is greatly saved. The price of the existing commercial corn is about 2700 Yuan/ton, and the market price of the starch-based dry powder under the invention is about 3000-Yi 3200 Yuan/ton through preliminary estimation. And the market price of the existing starch is about 3900 yuan/ton. The price of the starch-based dry powder is lower than that of starch, and commercial starch does not have the low water content, amorphous property and ultrafine property of the starch-based dry powder of the present invention.

And fifthly, the starch-based dry powder is an application type new material.

According to the preceding analysis, the applicant defines a starch-based dry powder as: the plant seeds rich in starch are puffed and crushed to obtain powder. Starch is mixed with protein, cellulose and the like in the internal organization structure of the starch-based dry powder particles, and the starch is mainly in an amorphous state, so that the moisture content of the dry powder is smaller than that of the existing starch, generally less than 10%, and if the dry powder is dried, the moisture content can be less than 5% or even less than 1%. The current market does not find the same commodities as the starch-based dry powder for sale; in the prior art, no technology is found for directly processing plant seeds rich in starch into powder to be applied to the fields of plastics and the like.

Application of starch-based dry powder

As an unprecedented material with the characteristics of biomass, the starch-based dry powder has an amorphous state with ultralow water content, ultra-small granularity and an internal structure, so that the starch-based dry powder can be applied to the field of plastics and other fields.

1. As a plastic filler

Because of low water content, when the starch-based dry powder is used as a filling material to be combined with traditional plastics (such as PP and PE), compared with starch, the starch-based dry powder has better compatibility and more competitive price advantage, and experiments show that if the adding amount is 30%, when the water content in the starch-based dry powder is more than 5%, the mechanical property of the combination is obviously smaller than that of the PE material due to the existence of water; when the water content is less than 5%, the mechanical property of the combination is obviously improved; when the moisture content is less than 1%, the strength of the starch-based dry powder to PE conjugate will exceed that of PE itself. Furthermore, because the starch structure in the starch-based dry powder is mainly an amorphous structure, compared with the common starch, the product formed by combining the starch-based dry powder and the plastic has better mechanical properties. Therefore, the starch-based dry powder is applied to the field of plastics as a filler, and can completely replace part of petroleum-based plastic raw materials, so that the cost is reduced, and the carbon emission is reduced.

The third table shows the mechanical property of the corn dry powder (30%) and PE (70%) of a certain manufacturer after mixing and melting:

watch III

As can be seen from the third table, when the dried corn flour with the water content of 9% is added into PE, each index of the mechanical property of PE is greatly weakened; when the water content is reduced to 5%, although the impact toughness and the elongation at break are weakened, the weakening degree is not more than 50%, and the strength is strengthened and exceeds the strength of PE; when the water content is reduced to 1%, the strength is further enhanced, and the impact toughness and the fracture strength are also increasingly closer to PE itself. It follows that the moisture content of the starch-based dry powder has a greater influence on the mechanical properties of the molten product.

The starch-based dry powders are bound to PP, PE, etc. in the same manner as starch is bound to PP, PE, etc. The conventional method is to mix and granulate the starch-based dry powder and granules of PP, PE and the like to obtain mixed master batches, and then to process plastic products by the mixed master batches.

When the equipment conditions allow, the starch-based dry powder and plastic master batches such as PP, PE and the like can be simultaneously added into equipment (such as a plate extruder), and are melted and mixed in the equipment, and a plastic product is directly obtained at a die orifice of the equipment. The equipment is conventional plastic processing equipment, but a powder feeding device is arranged.

2. Other applications

Besides the field of plastics, the starch-based dry powder can be applied to various fields due to the amorphous structure in the starch-based dry powder particles and the fine particle property of fibers and the like: such as tablet binders in the pharmaceutical industry, fluid loss additives in the petroleum industry, and the like.

The water solubility of starch-based dry powders is very good compared to the water insolubility of commercial starch. Therefore, the product can be applied to the food industry, such as instant food for the old and children. As a new application type material, the starch-based dry powder can be applied in more and more fields in the future.

Has the advantages that:

1. the invention provides a novel starch-based dry powder which can be applied to the field of plastics;

2. compared with wood powder and bamboo powder, the starch-based dry powder has low cost and is easy to process;

3. the starch-based dry powder has ultra-low water content, smaller granularity and excellent binding performance with plastics.

Best mode for carrying out the invention

Example 1

The puffing machine is a corn puffing machine produced by Shengde mechanical factory in Wenling of Zhejiang province, the power is 5.5KW, and the rotating speed is 400-. Corn is freely purchased in the market. Starting the puffing machine, puffing the corn into a strip-shaped corn puffed body by the puffing machine, and measuring that the moisture of the corn puffed body is 5.59%; crushing the corn puffed body in flour to obtain corn dry powder, wherein the particle size of the corn dry powder is 110-130 meshes by measurement.

Example 2

The puffing machine is a corn puffing machine produced by Shengde mechanical factory in Wenling of Zhejiang province, the power is 55KW, and the rotating speed is 400-. Corn is freely purchased in the market. Starting the puffing machine, puffing the corn into a strip-shaped corn puffed body by the puffing machine, and measuring that the moisture of the corn puffed body is 5.59%; 200g of the corn puffed material is crushed into particles with a particle size of about 0.5-2mm, 200g of the corn dry powder is put into a drying oven to be dried at a drying temperature of 110 ℃ for 20 minutes, and the moisture content is measured to be 0.46%.

Example 3

The puffing machine is a corn puffing machine produced by Shengde mechanical factory in Wenling of Zhejiang province, the power is 5.5KW, and the rotating speed is 400-. Corn is freely purchased in the market. The puffing machine is started, the puffing machine puffs the corns into strip-shaped corn puffed bodies, and the moisture of the corn puffed bodies is measured to be 5.59%. 200g of the corn puffed material was pulverized into pellets having a particle size of about 1 to 5mm, and dried in a drying oven at a drying temperature of 110 ℃ for 20 minutes to obtain a moisture content of 0.33%.

Example 4

The puffing machine is a corn puffing machine produced by Shengde mechanical factory in Wenling of Zhejiang province, the power is 5.5KW, and the rotating speed is 400-. Corn is freely purchased in the market. Starting the puffing machine, puffing the corn into a strip-shaped corn puffed body by the puffing machine, and measuring that the moisture of the corn puffed body is 5.59%; drying 10kg of the corn puffed body in a drying oven at 110 ℃ for 20 minutes to obtain a water content of 0.35%; pulverizing in jet mill of type F3 to obtain superfine dried corn powder of 320 meshes.

Example 5

The puffing machine is a corn puffing machine produced by Shengde mechanical factory in Wenling of Zhejiang province, the power is 5.5KW, and the rotating speed is 400-. Corn is freely purchased in the market. Starting the puffing machine, puffing the corn into a strip-shaped corn puffed body by the puffing machine, and measuring that the moisture of the corn puffed body is 5.59%; and (3) drying the corn puffed body by blowing through a hot air dryer at the hot air temperature of 110-120 ℃ for 15 minutes to obtain the corn puffed body with the moisture of 0.61 percent. Crushing the dried corn puffed body in a flour mill to obtain corn dry powder, wherein the particle size of the corn dry powder is measured to be 180-220 meshes.

Example 6

300 g of the dry powder obtained in example 5 and 700 g of LPE were simultaneously fed into a molding machine, which was an experimental extruder, heated at 80 ℃, 130 ℃, 135 ℃ and die sizes of 1mm and 30mm, and extruded to obtain a starch-based PE sheet.

Example 7

300 g of the dry powder obtained in example 4 was taken and charged into a granulation extruder together with 700 g of LPE, the extruder was heated at 80 ℃, 130 ℃, 135 ℃ and the die diameter was 3 mm. And granulating by a granulator after extrusion.

Cutting the granules, taking a material with the length of 200mm, cooling, and measuring the tensile strength and the elongation of the material in a tensile testing machine, wherein the tensile strength and the elongation are respectively as follows: 25 MPa; 324 percent. The above examples are also applicable to starch-based pellets such as sorghum and wheat, and the respective measured values are slightly different from those of corn.