阅读说明：本技术 一种高强度的可降解塑料膜及其制备方法 (High-strength degradable plastic film and preparation method thereof ) 是由 吴建宏 洪建东 吴雨薇 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种高强度的可降解复合膜及其制备方法,包括以下质量比成分：100份酯化淀粉、10-50份增强剂、2-9份交联剂、6-33份塑化剂,所述酯化淀粉的酯化度不超过0.2,所述酯化淀粉包括以下成分淀粉、冰乙酸、乙酸酐和浓硫酸,其物质的量比为1：3：3：0.1。采用上述技术方案,通过淀粉乙酰基化改性,制的不同取代度的淀粉醋酸酯,在添加适量的增强剂聚乙烯醇、乙二醛、丙三醇,进而得到力学性能更好的生物降解复合膜。(The invention discloses a high-strength degradable composite membrane and a preparation method thereof, wherein the high-strength degradable composite membrane comprises the following components in percentage by mass: 100 parts of esterified starch, 10-50 parts of reinforcing agent, 2-9 parts of cross-linking agent and 6-33 parts of plasticizer, wherein the esterification degree of the esterified starch is not more than 0.2, the esterified starch comprises the following components of starch, glacial acetic acid, acetic anhydride and concentrated sulfuric acid, and the mass ratio of the components is 1: 3: 3: 0.1. by adopting the technical scheme, starch acetate with different substitution degrees is prepared by performing acetylation modification on starch, and a proper amount of reinforcing agents including polyvinyl alcohol, glyoxal and glycerol are added, so that the biodegradable composite membrane with better mechanical property is obtained.)

1. A high-strength degradable composite membrane is characterized by comprising the following components in percentage by mass: 100 parts of esterified starch, 10-50 parts of reinforcing agent, 2-9 parts of cross-linking agent and 6-33 parts of plasticizer, wherein the esterification degree of the esterified starch is not more than 0.2, the esterified starch comprises the following components of starch, glacial acetic acid, acetic anhydride and concentrated sulfuric acid, and the mass ratio of the components is 1: 3: 3: 0.1.

2. the high-strength degradable composite film according to claim 1, wherein the esterified starch is starch acetate, the degree of esterification of the starch acetate is 0.1, the reinforcing agent is polyvinyl alcohol, the crosslinking agent is glyoxal, and the plasticizer is glycerol.

3. The high-strength degradable composite membrane according to claim 2, which comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 3-8 parts of glyoxal and 8-30 parts of glycerol.

4. The high-strength degradable composite membrane according to claim 2, which comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 5.6 parts of glyoxal and 8-30 parts of glycerol.

5. The high-strength degradable composite membrane according to claim 2, which comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 5.6 parts of glyoxal and 20 parts of glycerol.

6. A method for preparing a high-strength degradable composite film according to any one of claims 1 to 5, wherein the method comprises the steps of

S1, adding starch, glacial acetic acid, acetic anhydride and a catalyst concentrated sulfuric acid in sequence according to the mass ratio to perform acetylation reaction to prepare esterified starch;

s2, dissolving the prepared esterified starch in water, and gelatinizing the esterified starch for 1 hour at the temperature of 92 ℃;

s3, adding polyvinyl alcohol, glyoxal and glycerol according to the mass ratio, and stirring at 85 ℃; reacting for 0.5 hour;

s4, casting the film at 70 ℃ and drying the film for 3 hours at 80 ℃;

and S5, placing the uncovering film in an environment with the humidity of 65% for 7 days.

7. The method for preparing the high-strength degradable composite membrane according to claim 6, wherein in step S1, stirring and mixing are performed by a stirrer with a rotation speed of 600r/min under a constant temperature environment of 85 ℃, the reaction is performed for 1 hour, then the natural cooling is performed, the mixture is poured into distilled water after the cooling is completed until the white precipitate is completely separated out, the white precipitate is washed to be neutral, and then the white precipitate is screened by a 200-mesh screen, dried and ground, so as to obtain the esterified starch.

Technical Field

The invention relates to the technical field of plastic films, in particular to a high-strength degradable composite film and a preparation method thereof.

Background

Because the degradable plastics have the advantages of wide raw material sources, degradability, no environmental pollution and the like, more and more researches are focused on the degradable materials. The main purpose of developing the degradable plastics is to solve the problem of environmental pollution caused by plastic wastes. It can be degraded into carbon dioxide and water under specific environment, and does not cause pollution to the environment.

The common degradable plastics mainly comprise two types of photodegradable plastics and biodegradable plastics. Biodegradable plastics have developed over decades, with biodegradable plastics becoming the predominant form. In the biodegradable plastic, starch-based plastic accounts for a large part of the degradable plastic. Starch is a natural polymer compound, and has certain plasticity through molecular modification, so that the starch is regarded as one of the most potential research objects in the field of degradable materials.

However, since a large number of hydroxyl groups in native starch cause extremely strong hydrogen bonds in and between molecules, it is poor in thermoplasticity and is a thermally unstable substance. And the mechanical strength of such a composite film is insufficient.

Disclosure of Invention

According to the defects of the prior art, the invention provides the high-strength degradable composite membrane and the preparation method thereof, which can be rapidly degraded, and have better thermal stability and higher mechanical strength.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a high-strength degradable composite membrane comprises the following components in percentage by mass: 100 parts of esterified starch, 10-50 parts of reinforcing agent, 2-9 parts of cross-linking agent and 6-33 parts of plasticizer, wherein the esterification degree of the esterified starch is not more than 0.2, the esterified starch comprises the following components of starch, glacial acetic acid, acetic anhydride and concentrated sulfuric acid, and the mass ratio of the components is 1: 3: 3: 0.1.

preferably, the esterified starch is starch acetate, the degree of esterification of the starch acetate is 0.1, the reinforcing agent is polyvinyl alcohol, the crosslinking agent is glyoxal, and the plasticizer is glycerol.

Preferably, the composition comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 3-8 parts of glyoxal and 8-30 parts of glycerol.

Preferably, the composition comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 5.6 parts of glyoxal and 8-30 parts of glycerol.

Preferably, the composition comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 5.6 parts of glyoxal and 20 parts of glycerol.

The invention also discloses a preparation method of the high-strength degradable composite membrane, which comprises the following steps

S1, adding starch, glacial acetic acid, acetic anhydride and a catalyst concentrated sulfuric acid in sequence according to the mass ratio to perform acetylation reaction to prepare esterified starch;

s2, dissolving the prepared esterified starch in water, and gelatinizing the esterified starch for 1 hour at the temperature of 92 ℃;

s3, adding polyvinyl alcohol, glyoxal and glycerol according to the mass ratio, and stirring at 85 ℃; reacting for 0.5 hour;

s4, casting the film at 70 ℃ and drying the film for 3 hours at 80 ℃;

and S5, placing the uncovering film in an environment with the humidity of 65% for 7 days.

Preferably, in step S1, stirring and mixing the starch solution at a constant temperature of 85 ℃ by a stirrer at a rotation speed of 600r/min, reacting for 1 hour, naturally cooling, pouring the cooled product into distilled water until the white precipitate is completely separated out, washing the white precipitate to neutrality, sieving the white precipitate with a 200-mesh sieve, drying and grinding the white precipitate to obtain the esterified starch.

The invention has the following characteristics and beneficial effects:

by adopting the technical scheme, starch acetate with different substitution degrees is prepared by performing acetylation modification on starch, and a proper amount of reinforcing agents including polyvinyl alcohol, glyoxal and glycerol are added, so that the biodegradable composite membrane with better mechanical property is obtained.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a diagram showing the content of polyvinyl alcohol versus the mechanical properties of a composite film;

FIG. 2 is a schematic diagram of the mechanical properties of a composite membrane according to the content of glycerol;

FIG. 3 is a schematic diagram of glyoxal content versus mechanical properties of a composite membrane;

FIG. 4 is a schematic diagram of the degree of esterification of esterified starch versus the mechanical properties of a composite film

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

Example 1

The invention provides a high-strength degradable composite membrane, which comprises the following components in percentage by mass: 100 parts of esterified starch, 10-50 parts of reinforcing agent, 2-9 parts of cross-linking agent and 6-33 parts of plasticizer, wherein the esterification degree of the esterified starch is not more than 0.2, the esterified starch comprises the following components of starch, glacial acetic acid, acetic anhydride and concentrated sulfuric acid, and the mass ratio of the components is 1: 3: 3: 0.1.

further, the esterified starch is starch acetate, the reinforcing agent is polyvinyl alcohol, the cross-linking agent is glyoxal, and the plasticizer is glycerol.

In the technical scheme, starch acetate with different substitution degrees is prepared by performing acetylation modification on starch, and a proper amount of reinforcing agents including polyvinyl alcohol, glyoxal and glycerol are added, so that the biodegradable composite membrane with better mechanical property, improved compactness, reduced crystallinity and improved thermal stability is obtained.

Specifically, the original starch/PVA composite film had a strong crystallization peak at 2 θ of 19.56 ° and a small crystallization peak at 2 θ of 21.32 °, indicating crystallinity. The SA/PVA composite film has a diffuse broad peak at the 2 theta of 20.36 degrees, which shows that the rheological form of the polymer is changed along with the increase of the esterification degree, the crystallinity of the starch is destroyed, and the crystallinity is reduced. The crystallinity of the cassava native starch/PVA composite membrane is 4.13%, and the crystallinity of the SA/PVA composite membrane is 2.39%.

Example 2

This example differs from example 1 in that the degree of esterification of the starch acetate is 0.1.

As shown in fig. 4, the tensile strength and elongation at break of the composite film are all improved with the improvement of the esterification degree, and when the esterification degree reaches about 0.1, the tensile strength and elongation at break both reach the maximum, which greatly improves the practicability; meanwhile, as the esterification degree is continuously improved, the esterified starch and the system have a phase separation phenomenon, so that the mechanical property of the composite membrane is reduced, and when the esterification degree is 0.2, the phase separation phenomenon is serious and the membrane can hardly be formed. Therefore, the degree of esterification of starch acetate in this example was selected to be 0.1.

Example 3

In the embodiment, the paint comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 3-8 parts of glyoxal and 8-30 parts of glycerol.

As shown in fig. 1, as the amount of the polyvinyl alcohol is increased, the tensile strength of the composite film is increased, and the elongation at break is increased and then decreased, which shows the skeleton effect of the polyvinyl alcohol in the composite film, when the amount of the polyvinyl alcohol is 40 parts, that is, the total amount of the polyvinyl alcohol is 40% of the total amount of the esterified starch, the pull-string strength of the composite film is not increased greatly, and the elongation at break reaches the maximum value. In addition, the price of the polyvinyl alcohol is 5-8 times of that of the starch, the performance and the production cost of the composite film are comprehensively considered, and the dosage of the polyvinyl alcohol is preferably 40%.

Example 4

In the embodiment, the paint comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 5.6 parts of glyoxal and 8-30 parts of glycerol.

As shown in fig. 2, when the amount of glyoxal is small, the tensile strength and the elongation at break of the composite membrane become larger as the amount of glyoxal increases, and at this time, a large number of cross-linked chains are formed due to the reaction between glyoxal and hydroxyl, so that the strength of the macromolecular chains is improved, and the acting force between molecules is increased. However, after the glyoxal reaches a certain dosage, a network structure is formed among molecules, a large number of cross-linked chains limit the sliding among the molecules, so that the macromolecular chains are not easy to orient under the action of external force, and the residual glyoxal which is not reacted in the film plays a similar role as an inert material, so that the tensile strength and the elongation at break are reduced. Therefore, the mechanical property of the composite membrane is improved by crosslinking to a certain degree; excessive crosslinking affects the spatial structure of system molecules, and the mechanical property is reduced. Therefore, the amount of the glyoxal is 5.6 parts, namely 4% of the total amount of the esterified starch and the polyvinyl alcohol.

Example 5

In the embodiment, the paint comprises the following components in percentage by mass: 100 parts of esterified starch, 40 parts of polyvinyl alcohol, 5.6 parts of glyoxal and 20 parts of glycerol.

As shown in fig. 3, as the amount of glycerol is increased, the tensile strength of the composite film increases and then decreases, and the elongation at break increases. The reason is that: the use amount of glycerol is increased, the number of hydroxyl groups in unit volume is increased, the number of combined water molecules is also increased, so that the content of esterified starch and polyvinyl alcohol in the composite membrane is relatively reduced, the interaction between molecules is weakened, the compactness of the composite membrane is reduced, the structure is deteriorated, and the breaking elongation of the composite membrane is improved. When the consumption of the glycerol is low, the bonding effect between starch molecules is strong, but the composite film is hard and crisp due to too little bound water; when the amount of the glycerol is more, the formed film is soft and smooth. The glycerol is selected from 20 parts, namely 14 percent of the total amount of the esterified starch and the polyvinyl alcohol.

Example 6

The invention also discloses a preparation method of the high-strength degradable composite membrane, which comprises the following steps

S1, adding starch, glacial acetic acid, acetic anhydride and a catalyst concentrated sulfuric acid in sequence according to the mass ratio to perform acetylation reaction to prepare esterified starch;

s2, dissolving the prepared esterified starch in water, and gelatinizing the esterified starch for 1 hour at the temperature of 92 ℃;

s3, adding polyvinyl alcohol, glyoxal and glycerol according to the mass ratio, and stirring at 85 ℃; reacting for 0.5 hour;

s4, casting the film at 70 ℃ and drying the film for 3 hours at 80 ℃;

and S5, placing the uncovering film in an environment with the humidity of 65% for 7 days.

Further, in the step S1, stirring and mixing the materials in a stirrer with a rotation speed of 600r/min at a constant temperature of 85 ℃, reacting for 1 hour, naturally cooling, pouring the mixture into distilled water after cooling until the white precipitate is completely separated out, washing the white precipitate to be neutral, sieving the white precipitate with a 200-mesh sieve, drying and grinding the white precipitate to obtain the esterified starch.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments, including the components, without departing from the principles and spirit of the invention, and still fall within the scope of the invention.