TW201710349A - One-step modified hydrophobic thermoplastic starch-based biodegradable material and method for preparing same the impact strength and the tensile strength of the prepared product is highly retained - Google Patents

Abstract

The present invention discloses a one-step modified hydrophobic thermoplastic starch-based biodegradable material and a method for preparing same. The method comprises the following steps: (1) adding and mixing starch, a plasticizer and a preplasticizing dispersant according to a mass ratio of 1:(0.1~0.5):(0.5~1) to obtain a starch mixture I; (2) mixing a blend of an enhancer, a plasticizer and a preplasticizing dispersant according to a mass ratio of (0.0005 ~ 0.01): (0.5 ~ 10): (0.5 ~ 10) with the starch mixture I to obtain a starch mixture II; (3) after adjusting the pH value of the starch mixture II, reacting with a modifier to obtain a gelling starch; (4) after removing preplasticizing dispersant using in step (1) and step (2), granulizing the gelling starch. The preparation method of the present invention is simple, the impact strength and the tensile strength of the prepared product is highly retained and the hydrophobicity of hte prepared product is well maintained after being stored for a long period of time.

Description

One-step modified hydrophobic thermoplastic starch-based biodegradable material and preparation method thereof

The invention relates to the field of polymer materials, in particular to a one-step modified hydrophobic thermoplastic starch-based biodegradable material and a preparation method thereof.

The depletion of petroleum resources, increasing prices and environmental pollution have contributed to the development of biomass materials, renewable resources and energy. Nowadays, the natural polymer science, which is completely separated from petroleum resources in the field of polymers, is developing rapidly and plays a decisive role in the survival, health and sustainable development of mankind. Biodegradable materials have become the focus of research because they can be degraded by the action of natural microorganisms.

Starch is a kind of degradable natural polymer widely used at present. It has the advantages of wide source, low price and easy biodegradation, and plays an important role in the field of biodegradable materials. The traditional thermoplastic starch (TPS) processing method is mainly based on mechanical/heating mixed plasticized starch, and the prepared thermoplastic starch generally has poor mechanical and water resistance properties, thus limiting its use as a material. To this end, domestic and foreign scholars have done a lot of research in order to improve the usability of thermoplastic starch.

In order to solve the problem of loss of usability of starch-based biodegradable plastic products due to water absorption, researchers have improved the water resistance of thermoplastic starch by various methods. Chinese patent CN 101418081 B describes a method for esterifying the surface of a thermoplastic starch product by subjecting a thermoplastic starch product having an esterifying agent (alkenyl succinic anhydride) on the surface to a certain temperature for a certain period of time for esterification. The agent reacts with the hydroxyl groups on the molecular chain of the starch to form esterified layers of different thicknesses and different degrees of substitution on the surface of the article. Chinese patents CN 1273522 C and CN 1038422 C both use modified starches such as oxidized starch, crosslinked starch, ethoxylated starch and acetate starch to produce shaped articles and films, in which the molded articles and films have excellent physical and mechanical properties. Properties (such as modulus higher than 4.9 × 10 ⁸ Pascals, yield strength up to 3.9 × 10 ⁷ Pascal) and insoluble in water. Chinese patent CN 1036659 C describes the addition of a crosslinking agent and other chemical modifiers, such as divalent or polyvalent carboxylic acids and/or their anhydrides, hydrazine halides and/or guanamines of divalent or polyvalent carboxylic acids, etc. Improve the hydrophobic properties of thermoplastic starch. Chinese patent CN 1190448 C and Chinese patent CN 1192040 C describe the addition of a hydrophobic reaction reagent having a hydrocarbon group of 4 to 24 carbon atoms to improve the hydrophobic properties of the thermoplastic starch. Chinese patent CN 103980684 A describes a toughened and water-resistant starch plastic and a preparation method thereof. The thermoplastic starch is mixed with polylactic acid, thermoplastic polyurethane and antioxidant in proportion to obtain a starch plastic with good toughness and good water resistance. Chinese patent CN 1336936 A describes a process for preparing a hydrophobic starch by etherifying, esterifying or acetylating a root or tuber starch or a derivative thereof with a substituent of an alkenyl chain of 4 to 24 carbon atoms. Chinese patent CN 101225117 A describes the preparation of hydrophobic thermoplastic starch with alkenyl succinic anhydride, which has a long aliphatic hydrocarbon chain (C _12-18 ) and a five-membered anhydride ring which reacts with a hydroxyl group in the starch to form an ester bond. The introduced long aliphatic hydrocarbon chain not only has excellent hydrophobicity, but also has good internal plasticization. Chinese patent CN 101328285 A describes a preparation method of hydrophobized thermoplastic starch, which is mixed with alkyl ketene dimer (AKD) into a high-speed mixer and extruded through a screw to obtain a hydrophobized thermoplastic starch, since AKD has A long aliphatic hydrocarbon chain (C _14-16 ) and a quaternary lactone ring which react with a hydroxyl group in the starch to form a strong hydrophobic β-carbonyl ester bond. Chinese patent CN 1303870 A describes a method for hydrophobically modifying, degrading hydrated granular starch prepared by crosslinking starch and epichlorohydrin. Chinese patent CN 1850892 A describes mixing starch and aliphatic polyester, adding a ratio of surface grafted polylactic acid starch to make a fully degradable starch-based composite, and surface grafting polylactic acid as a blending system. The compatibilizer in the mixture improves the compatibility between the hydrophilic starch and the hydrophobic fatty polyester material, and has excellent processing properties, water resistance and acid and alkali resistance. Chinese patent CN 103044719 A describes mixing and mixing oxidized starch and elastic particles, and then washing and drying after centrifugation. After pulverization, an elastic particle-oxidized starch coating material with a mesh number greater than 50 mesh is obtained, which is combined with plasticizer and lubrication. The agent is mechanically mixed, and finally extruded and granulated by an extruder. The obtained thermoplastic starch plastic has good hydrophobic property, and the surface contact angle thereof is increased from 37.5° of pure starch to 108°, which is nearly 3 times. The surface contact angle is greater than 90°, achieving the purpose of thermoplastic starch plastic hydrophobicity. Chinese patent CN 101302321 A describes mixing and stirring starch, plasticizer, maleic anhydride, t-butyl peroxide and dioctyl maleate, and then subjecting the water and the mixture together for extrusion reaction, and cooling to obtain a master batch. Then, the masterbatch and the secondary plasticizer and glutaraldehyde are stirred and granulated by a high-speed kneader, and the obtained thermoplastic starch has obvious improvement in heat resistance, water resistance and physical properties.

Summarizing the above patents, the surface of the starch is hydrophobized, most of which only have hydrophobic properties after surface modification, and no actual impact on the mechanical strength of the starch after long-term aging (water absorption) test. In addition, studies on tensile, impact strength and retention of thermoplastic starch have rarely been reported.

The technical problem to be solved by the present invention is that in the process of preparing the thermoplastic starch-based biodegradable composite material in the prior art, most of the thermoplastic starch surface is hydrophobized and modified, and the hydrophobic property is general, and the actual test is not performed for a long time. The effect of (water absorption) on its mechanical strength, as well as the rarely reported defects in TPS tensile, impact strength, and retention rates, provides a one-step modified hydrophobic thermoplastic starch-based biota that is completely different from the prior art. Degradable materials and preparation methods thereof. The invention can be used in starch In the gelation process, a modifier is added to carry out a one-step modification reaction, and the preparation method is simple; the obtained starch-based biodegradable material has high retention rate of impact strength and tensile strength, and has a high retention rate during long-term placement. Better hydrophobicity.

The present invention solves the above technical problems through the following technical solutions.

The invention provides a method for preparing a one-step modified hydrophobic thermoplastic starch-based biodegradable material, which comprises the following steps: (1) mass ratio of starch, plasticizer and pre-plasticizing dispersant to 1: (0.1~) 0.5): (0.5~1) mixed uniformly to obtain starch mixture I; (2) will contain mass ratio (0.0005~0.01): (0.5~10): (0.5~10) enhancer, plasticizer and The blend of the pre-plasticized dispersant is uniformly mixed with the starch mixture I to obtain a starch mixture II, wherein the reinforcing agent is a bacterial cellulose fiber, and the mass ratio of the reinforcing agent to the starch is (0.0005-0.01). ): (50~100); (3) adjusting the pH of the starch mixture II in the step (2) to 3-6, and mixing with the modifier to obtain a starch gel, wherein the mixed reaction The temperature is 70 to 120 ° C, the time is 10 to 40 minutes, and the modifier is a hydrophobic reactant; (4) the starch gelatin removal step (1) and the step (2) in the step (3) After pre-plasticizing the dispersant, granulation is carried out.

The starch used in the step (1) is conventional in the art, and is preferably selected from natural starch and/or starch modified by a starch modifier. The natural starch is conventional in the art and is preferably selected from one or more of corn starch, wheat starch, sweet potato starch, potato starch and tapioca starch, more preferably tapioca starch. The starch modifier is conventional in the art, and is preferably selected from one or more of a carboxylic acid, an acid anhydride, a hydrazine halide and a guanamine. The carboxylic acid is preferably selected from the group consisting of citric acid, acetic acid, and malic acid. And one or more of the succinic acid, the acid anhydride is preferably acetic anhydride and/or maleic anhydride, and the hydrazine halide is preferably hydrazine. Chlorine, and the guanamine is preferably selected from one or more of the group consisting of formamide, N-methylformamide and dimethylacetamide.

In the step (1), the mixing is preferably carried out in a mechanical mixer to cut and disperse and mix, and more preferably in a mechanical mixer, cutting and dispersing and mixing for 0.5 to 1 hour, and the best system is cut and mixed and mixed in a mechanical mixer for 1 hour.

In the step (1) and the step (2), the plasticizer generally refers to a plasticizer conventionally used in the field of preparing a thermoplastic starch-based biodegradable material, preferably selected from the group consisting of ethylene glycol, glycerol, and dimethyl. One or more of the hydrazine and urea, more preferably glycerol.

In the step (1) and the step (2), the pre-plasticized dispersant is generally a liquid reagent which allows the starch and the plasticizer to be uniformly dispersed and dispersed under certain conditions, preferably selected from the group consisting of ethanol, water and methanol. One or more, more preferably water.

In the step (1), the starch, the plasticizer and the pre-plasticized dispersant in the starch mixture I preferably have a mass of 1: (0.1 to 0.3): (0.7 to 0.9), more preferably 1: 0.2:0.8.

In the step (2), the quality of the reinforcing agent, the plasticizer and the pre-plasticizing dispersing agent in the blend is preferably (0.0005 to 0.0015): (0.5 to 1.5): (0.5 to 1.5), more preferably The ground is 0.001:1:1.

In the step (2), the mass of the enhancer and the starch in the starch mixture II is preferably (0.015 to 0.025): (98 to 100), more preferably 0.02: 100.

As is common in the art, "bacterial cellulose fibers" are defined as cellulose synthesized by microorganisms such as Acetobacter, Agrobacterium, Rhizobium, and Sarcina. Collectively.

In the step (2), the bacterial cellulose fiber is selected from the group consisting of unmodified bacterial cellulose fibers and/or modified bacterial cellulose fibers. Among them, unmodified bacterial cellulose fibers are generally Refers to natural bacterial cellulose fibers.

Wherein, the modified bacterial cellulose fiber generally refers to a bacterial cellulose fiber modified by a bacterial cellulose fiber modifier, and the bacterial cellulose fiber modifier is preferably an alcohol and/or an acid anhydride, and the alcohol is preferably selected from the group consisting of One or more of n-butanol, ethylene glycol, glycerol, polyvinyl alcohol, polyethylene glycol, and ethylene-vinyl alcohol, preferably selected from the group consisting of maleic anhydride, succinic anhydride, acetic anhydride, propionic anhydride, and One or more of phthalic anhydride.

Preferably, the modified bacterial cellulose fiber is obtained by heating a mixture of an alcohol and an acid anhydride of a molar ratio (1 to 10): (1 to 10) at a temperature of 0 to 200 ° C for 1 to 200. Minutes, after the two substances are dissolved, add 0.1~10% of the total mass of the alcohol and the anhydride, and heat to the reaction temperature of 50~200 °C to carry out the reaction. The reaction time is in the range of 1 to 480 minutes to obtain the terminal carboxyl group. Product; cut unmodified bacterial cellulose fiber into small pieces, add alkaline solution with a concentration of 1% to 20% by mass, swell for 1 to 120 minutes at 0~100 °C, then rinse with water and then bake Dry, then mixed with the above-mentioned product having a terminal carboxyl group, and added one or more of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid, and reacted under mechanical stirring at a pH of 1 to 7 and a temperature of 0 to 200 ° C. Modified bacterial cellulose fibers can be obtained in 1 to 200 minutes.

More preferably, the modified bacterial cellulose fiber is obtained by adding a molar ratio of 1:1 acetic anhydride and ethylene glycol to a stirrer and heating and stirring at a temperature of 100 ° C for 100 minutes. After the two materials are dissolved, a catalyst of p-toluenesulfonic acid in an amount of 5% by weight based on the total mass of acetic anhydride and ethylene glycol is added, followed by heating to a reaction temperature of 100 ° C to carry out a reaction for 100 minutes, and finally a terminal carboxyl group is obtained. Light yellow clear liquid product. The bacterial cellulose fiber was cut into small pieces, added with a 10% by mass sodium hydroxide solution, and swelled at a temperature of 50 ° C for 60 minutes, followed by repeated washing with water, followed by drying, and then with the aforementioned pale yellow clarified liquid product Mix and add a small amount of concentrated sulfuric acid at a pH of 4 and a temperature of 100 ° C The reaction was carried out under mechanical stirring for 100 minutes to obtain a modified bacterial cellulose fiber.

In the step (2), the length of the bacterial cellulose fiber is preferably from 0.1 to 1 μm. The bacterial cellulose fiber preferably has a diameter of 20 to 100 nm.

In the step (2), preferably, the blend is uniformly mixed, then allowed to stand, and then uniformly mixed with the starch mixture I; more preferably, the blend is first dispersed and mixed in a dispersing machine. Evenly, then stand still, and then mix well with the starch mixture I; optimally, the mixture is first dispersed and dispersed in a dispersing machine for 1 to 2 hours, and then allowed to stand for 4 to 8 hours, and then mixed with the starch. The liquid I was uniformly mixed; further preferably, the blend was first dispersed and mixed in a disperser for 2 hours, allowed to stand for 6 hours, and then uniformly mixed with the starch mixture I.

In the step (3), preferably, the pH is adjusted by using a pretreatment agent, and the pretreatment agent is preferably selected from one or more selected from the group consisting of citric acid, acetic acid, acetic anhydride, malic acid, azelaic acid and maleic anhydride. More preferably, it is citric acid.

In the step (3), preferably, the pH is adjusted to 3 to 6, and more preferably to 4 to 5.

In the step (3), the hydrophobic reactant refers to a chemical reaction reagent which can chemically react with starch under certain conditions to reduce the hydrophilic group on the surface of the starch molecule and increase the hydrophobic property of the starch, and is preferably selected from water-soluble. The polyaldehyde substance is more preferably one or more selected from the group consisting of glyoxal, succinaldehyde, glutaraldehyde and adipaldehyde. The hydrophobic reactant may also be selected from sodium trimetaphosphate and/or sodium hexametaphosphate. The hydrophobic reactant is preferably present in the form of an aqueous solution, and in the aqueous solution of the hydrophobic reactant, the mass percentage of the hydrophobic reactant is preferably from 20 to 40%, more preferably 25%.

In the step (3), the modifier is preferably added in an amount of from 0.1 to 32 phr, more preferably from 0.1 to 2 phr, most preferably from 0.5 phr or 2 phr. Here, 0.1 to 32 phr means that the amount of the modifier added to 100 parts by mass of the starch mixture II is 0.1 to 32 parts by mass.

In the step (3), the mixing reaction is generally carried out in a mixer, and the temperature is preferably from 70 to 100 ° C, more preferably from 90 ° C, and the mixing reaction time is preferably from 15 to 25 minutes, more preferably from 20 minutes.

In the step (4), the operation of removing the pre-plasticized dispersant in the step (1) and the step (2) is conventional in the chemical field, and it is preferred to dry the starch gelate. When the hydrophobic reactant is present in the form of an aqueous solution, the aqueous solution of the hydrophobic reactant can be dehydrated while drying.

The drying temperature is preferably 0 to 100 ° C, more preferably 60 to 100 ° C; the drying time is preferably 0.5 to 50 hours, more preferably 2 to 50 hours; drying is preferably carried out according to the following steps: The starch gelatin is first dried in a blast drying oven or an infrared direct drying oven, and then placed in a vacuum drying oven or a dew point drying oven to dry.

The drying temperature of the blast drying oven or the infrared direct drying oven is preferably 75 to 85 ° C, more preferably 80 ° C; the drying time of the blast drying oven or the infrared direct drying oven is preferably 23 to 25 Hours, preferably 24 hours. The drying temperature of the vacuum drying box or the dew point drying box is preferably 0 to 100 ° C, more preferably 60 to 100 ° C, and most preferably 80 ° C; the drying time of the vacuum drying oven or the dew point drying oven is preferably 4 to 30 The hour is preferably 10 to 30 hours, and the best is 24 hours.

In the step (4), granulation is preferably carried out in an internal mixer or a screw extruder, more preferably in a screw extruder.

In the step (4), a compatibilizer may be further added during the granulation. The compatibilizer is preferably selected from one or more of maleic anhydride, succinic anhydride, acetic anhydride, propionic anhydride and phthalic anhydride, more preferably maleic anhydride. The mass of the compatibilizer and the starch gelate from which the pre-plasticized dispersant is removed is preferably (0 to 1): (5 to 10).

In the step (4), when granulation is carried out, preferably, it may be further added Degradation material. The biodegradable material is preferably a biodegradable aliphatic polyester material and/or a biodegradable aliphatic and aromatic copolyester material, more preferably selected from the group consisting of polylactic acid, polysuccinic acid/terephthalic acid. One or more of a glycol ester, polysuccinic acid/adipic acid-butylene glycol ester, poly(adipic acid)/butylene terephthalate and polycaprolactone, and most preferably polylactic acid. The quality of the biodegradable material and the starch gelatin which removes the pre-plasticized dispersant is preferably (0.5 to 5): (5 to 10).

A coloring agent may also be added to the preparation method of the present invention, and the coloring agent is preferably a metal oxide, more preferably titanium dioxide. The colorant and the quality of the starch are preferably (0.1 to 20): 100, more preferably (0.5 to 5): 100, most preferably 2: 100. When the colorant is added, it is preferably added after the operation of removing the pre-plasticized dispersant in the step (1) and the step (2) in the step (4) and before the granulation.

The present invention also provides a hydrophobic thermoplastic starch-based biodegradable material obtained by the above production method.

In a preferred embodiment of the present invention, after the injection molded spline is placed at 20 ° C / 50% relative humidity for 56 and 168 days, the tensile strength retention rate can reach 93.3% and 72.5%, and the impact strength retention rate. Up to 62.9% and 37.1%. In another preferred embodiment of the invention, it has good hydrophobic properties: water absorption after 3.3 hours is 3.3%, and water absorption after 624 hours is 7.1%.

The above preferred conditions can be arbitrarily combined on the basis of the common knowledge in the technical field, that is, the preferred embodiments of the present invention are obtained.

The reagents and starting materials used in the present invention are commercially available.

The positive effects of the present invention are:

1. The invention can add a modifier to a one-step modification reaction in the gelation process under the condition of sufficient water, and the hydrophobic type can be prepared by using a conventional thermoplastic processing equipment. The powder-based biodegradable material has a simple preparation method.

2. The starch-based biodegradable material prepared by the invention has high retention rate and tensile strength, and has good hydrophobicity during long-term placement.

1 is a graph showing the tensile strength as a function of standing time of a starch-based degradable biocomposite of Example 1, Example 2 and Comparative Example 1 at 20 ° C / 50% relative humidity. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2.

2 is a graph showing the relationship between the initial tensile strength of the starch-based degradable biocomposite of Example 1, Example 2, and Comparative Example 1 and the amount of glutaraldehyde added. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2.

3 is a graph showing the relationship between the impact strength and the standing time of the starch-based degradable biocomposites of Example 1, Example 2 and Comparative Example 1 at 20 ° C / 50% relative humidity. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2.

4 is a graph showing the relationship between the initial impact strength of the starch-based degradable biocomposite of Example 1, Example 2, and Comparative Example 1 and the amount of glutaraldehyde added. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2.

5 is a graph showing the change of water content with the standing time of the starch-based degradable biocomposite of Example 1, Example 2 and Comparative Example 1 under the condition of 20 ° C / 50% relative humidity. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2.

Fig. 6 is a graph showing the relationship between the initial moisture content of the starch-based degradable biocomposite of Example 1, Example 2 and Comparative Example 1 and the amount of glutaraldehyde added. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2.

7 is a starch-based degradable biocomposite material of Example 1, Example 3 and Example 4. The tensile strength as a function of standing time at 20 ° C / 50% relative humidity. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4.

Figure 8 is a graph showing the relationship between initial tensile strength and pH of the starch-based degradable biocomposites of Example 1, Example 3 and Example 4. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4.

Fig. 9 is a graph showing the relationship between the impact strength and the standing time of the starch-based degradable biocomposites of Example 1, Example 3 and Example 4 under the conditions of 20 ° C / 50% relative humidity. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4.

Figure 10 is a graph showing the relationship between initial impact strength and pH of the starch-based degradable biocomposites of Example 1, Example 3, and Example 4. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4.

Figure 11 is a graph showing the change of water content with the standing time of the starch-based degradable biocomposites of Example 1, Example 3 and Example 4 under the condition of 20 ° C / 50% relative humidity. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4.

Figure 12 is a graph showing the relationship between initial moisture content and pH of the starch-based degradable biocomposites of Example 1, Example 3 and Example 4. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4.

The invention is further illustrated by the following examples, which are not intended to limit the invention. The experimental methods in the following examples which do not specify the specific conditions are selected according to conventional methods and conditions, or according to the product specifications.

The percentages, parts, and the like used in the following examples, unless otherwise specified, refer to the mass percentage and mass parts of the materials.

[Example 1]

The starch-based biodegradable material was prepared in the formulation ratio of Table 1 below.

(1) The tapioca starch, glycerin and water were mixed at a mass ratio of 5:1:4 to form a starch suspension, and the starch suspension was placed in a mechanical mixer for dispersion for 1 hour to obtain a starch mixture I.

(2) Dispersing a blend of natural bacterial cellulose fibers, glycerol and water having a mass ratio of 0.001:1:1 in a dispersing machine for 2 hours, allowing to stand for 6 hours, and then mixing with the starch obtained in the step (1) I mixed the starch mixture II. Wherein, the mass ratio of the natural bacterial cellulose fiber to the tapioca starch is 0.02:100; the length of the natural bacterial cellulose fiber is 0.1 to 1 μm; and the diameter is 20 to 100 nm.

(3) After adjusting the pH of the starch mixture II obtained in the step (2) to 4 by using citric acid, 0.5 phr of an aqueous solution of glutaraldehyde is added, and then placed in a mechanical stirrer and stirred at a temperature of 90 ° C for 20 minutes. Starch gelatin.

(4) The starch gelatin obtained in the step (3) is placed in a blast drying oven and dehydrated at a temperature of 80 ° C for 48 hours, then dehydrated in a vacuum drying oven at 80 ° C for 24 hours, titanium dioxide is added, and extruded in a screw extruder. Granulation, injection molding to obtain the finished product.

[Example 2]

The starch-based biodegradable material was prepared in the formulation ratio of Table 1 below. The conditions were the same as in Example 1 except that the amount of the aqueous solution of glutaraldehyde was different.

[Example 3]

The starch-based biodegradable material was prepared in the formulation ratio of Table 1 below. The conditions were the same as in Example 1 except that the pH of the starch suspension was adjusted to 3 with citric acid.

[Example 4]

The starch-based biodegradable material was prepared in the formulation ratio of Table 1 below. The conditions were the same as in Example 1 except that the pH of the starch suspension was adjusted to 6 with citric acid.

[Example 5]

The starch-based biodegradable composite was prepared in the formulation ratios of Table 1 below. The conditions were the same as in Example 1 except that the modified bacterial cellulose fiber was added instead of the natural bacterial cellulose fiber. Among them, the preparation method of the modified bacterial cellulose fiber is as follows:

Acetic anhydride and ethylene glycol were added to a stirrer at a molar ratio of 1:1, and the mixture was heated and stirred at a temperature of 100 ° C for 100 minutes. After the two materials are dissolved, a catalyst of p-toluenesulfonic acid in an amount of 5% by weight based on the total mass of acetic anhydride and ethylene glycol is added, followed by heating to a reaction temperature of 100 ° C to carry out a reaction for 100 minutes, and finally a terminal carboxyl group is obtained. Light yellow clear liquid product. The bacterial cellulose fiber was cut into small pieces, added with a 10% by mass sodium hydroxide solution, and swelled at a temperature of 50 ° C for 60 minutes, followed by repeated washing with water, followed by drying, and then with the aforementioned pale yellow clarified liquid product The mixture was mixed, and a trace amount of concentrated sulfuric acid was added thereto, and the reaction was carried out by mechanical stirring at a pH of 4 and a temperature of 100 ° C for 100 minutes to obtain a modified bacterial cellulose fiber.

[Comparative Example 1]

The starch-based biodegradable material was prepared in the formulation ratio of Table 1 below. The conditions were the same as in Example 1 except that the aqueous solution of glutaraldehyde was not added and the pH was not adjusted with citric acid.

[Comparative Example 2]

The starch-based biodegradable composite was prepared in the formulation ratios of Table 1 below. The conditions were the same as in Example 1 except that the pH of the starch suspension was adjusted to 2 with citric acid.

[Comparative Example 3]

The starch-based biodegradable composite was prepared in the formulation ratios of Table 1 below. The conditions were the same as in Example 1 except that the pH of the starch suspension was adjusted to 7 with citric acid.

The performance parameters of the composites prepared in Comparative Example 1 and Examples 1, 2, and 5 were shown in Table 2 and Figures 1-6.

It can be seen from Table 2 that the tensile strength retention and the impact strength retention rate after the injection molding of the inventive examples 1, 2, and 5 are placed at 20 ° C / 50% relative humidity for 56 days and 168 days. Significantly higher than Comparative Example 1, the water content was significantly lower than Comparative Example 1. Further, in Example 5 in which the modified bacterial cellulose fiber was added, the tensile strength retention ratio, the impact strength retention ratio, and the moisture content of the sample prepared in Example 1 to which the natural bacterial cellulose fiber was added were not significantly different.

1 is a graph showing the tensile strength as a function of standing time of a starch-based degradable biocomposite of Example 1, Example 2 and Comparative Example 1 at 20 ° C / 50% relative humidity. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2. As can be seen from Fig. 1, when the product of Comparative Example 1 in which glutaraldehyde was not added was left for 14 days, the tensile strength was remarkably lowered, while in Examples 1 and 2, the decrease was slow. The tensile strength of Comparative Example 1 was significantly lower than that of Examples 1 and 2 when placed for 84 days.

2 is a graph showing the relationship between the initial tensile strength of the starch-based degradable biocomposite of Example 1, Example 2, and Comparative Example 1 and the amount of glutaraldehyde added. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2. It can be seen from Fig. 2 that the initial tensile strength decreases as the glutaraldehyde content increases.

3 is a graph showing the relationship between the impact strength and the standing time of the starch-based degradable biocomposites of Example 1, Example 2 and Comparative Example 1 at 20 ° C / 50% relative humidity. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2. As can be seen from Fig. 3, the impact strength of the product of Comparative Example 1 in which no glutaraldehyde was added was significantly greater than that of Examples 1 and 2. The impact strength of Comparative Example 1 was significantly lower than that of Examples 1 and 2 when placed for 84 days.

4 is a graph showing the relationship between the initial impact strength of the starch-based degradable biocomposite of Example 1, Example 2, and Comparative Example 1 and the amount of glutaraldehyde added. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2. As can be seen from Figure 4, the initial impact strength and The amount of glutaraldehyde added has little to do with.

5 is a graph showing the change of water content with the standing time of the starch-based degradable biocomposite of Example 1, Example 2 and Comparative Example 1 under the condition of 20 ° C / 50% relative humidity. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2. As can be seen from Fig. 5, the product of Comparative Example 1 in which no glutaraldehyde was added was significantly longer than the examples 1 and 2 with the extension of the standing time. The hydrophobic properties of the product of Example 1 showed a water absorption of 3.3% after 96 hours and a water absorption of 7.1% after 624 hours.

Fig. 6 is a graph showing the relationship between the initial moisture content of the starch-based degradable biocomposite of Example 1, Example 2 and Comparative Example 1 and the amount of glutaraldehyde added. Here, Δ is Comparative Example 1, □ is Example 1, and ▽ is Example 2. It can be seen from Fig. 6 that as the content of glutaraldehyde increases, the initial water content first decreases and then stabilizes.

The performance parameters of the composites prepared in Comparative Examples 2, 3 and Examples 1, 3, and 4 were shown in Table 3 and Figures 7-12.

It can be seen from Table 3 that the tensile strength retention rates of the injection molded splines of Examples 1, 3, and 4 after 28 days of placement were all above 25%, and the retention of impact strength was above 35%. Since the pH values of Comparative Examples 1 and 2 were not within the limits of the present invention, the retention of the tensile strength and the retention of the impact strength after the injection molding of the injection molded sample were significantly lower, and the moisture content was higher.

Figure 7 is a graph showing the tensile strength versus time of a starch-based degradable biocomposite of Examples 1, 3, and 4 at 20 ° C / 50% relative humidity. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4. As is clear from Fig. 7, when the pH is 5, the tensile strength is the largest.

Figure 8 is a graph showing the relationship between initial tensile strength and pH of the starch-based degradable biocomposites of Examples 1, 3, and 4. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4. As can be seen from Fig. 8, as the pH increases, the initial tensile strength first increases and then decreases.

Figure 9 is a graph showing the impact strength of the starch-based degradable biocomposites of Examples 1, 3, and 4 at 20 ° C / 50% relative humidity as a function of standing time. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4. As can be seen from Fig. 9, when the pH is 5, the impact strength is the largest.

Figure 10 is a graph showing the relationship between initial impact strength and pH of the starch-based degradable biocomposites of Examples 1, 3, and 4. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4. It can be seen from Fig. 9 that the initial impact strength gradually decreases as the pH value increases.

Figure 11 is a graph showing the change of water content with the standing time of the starch-based degradable biocomposites of Examples 1, 3 and 4 under the condition of 20 ° C / 50% relative humidity. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4. As can be seen from Fig. 11, when the pH is 5, the water content is the lowest.

Figure 12 is a starch-based degradable biocomposite of Examples 1, 3, and 4 A plot of initial moisture content versus pH. Here, Δ is Example 3, □ is Example 1, and ▽ is Example 4. As can be seen from Fig. 12, the water content increases first with a decrease in pH.

[Example 6]

The starch-based biodegradable material was prepared in the formulation ratios of Table 4 below. In this example, the starch gelled product after drying in a vacuum drying oven was first blended with 25 wt% of polylactic acid before extrusion granulation by adding titanium dioxide. Other control conditions are the same as in the first embodiment.

[Example 7]

The starch-based biodegradable material was prepared in the formulation ratios of Table 4 below. In the present embodiment, the starch gelled product dried in the vacuum drying oven was first blended with 50% by weight of polylactic acid before the titanium dioxide extrusion granulation was added. Other control conditions are the same as in the first embodiment.

[Example 8]

The starch-based biodegradable material was prepared in the formulation ratios of Table 4 below. In this example, the starch gelled product after drying in a vacuum drying oven was first blended with 25 wt% of polylactic acid and 0.4 phr of maleic anhydride before adding titanium dioxide by extrusion granulation. The percentage is relative to the weight percentage of the starch, and the 0.4 phr means that 100 parts by mass of the starch contains 0.4 part of maleic anhydride. Other control conditions are the same as in the first embodiment.

The performance parameters of the composites prepared in Examples 6 to 8 were tested in the performance test.

As can be seen from Table 5, in Example 6 and Example 7, in the case where the pH of the starch suspension was 4, the glutaraldehyde-modified thermoplastic starch was blended with 25 wt% and 50 wt% of polylactic acid. The initial tensile strength of the splines can reach 24.6 MPa and 38.9 MPa, respectively. After the finished product was placed at 60 ° C / 50% relative humidity for 56 days and 168 days, the tensile strength of Example 6 was still retained at 82.5% and 66.7%, and the tensile strength of Example 7 was still retained at 93.3% and 72.5. %. In Example 8, when the thermoplastic starch prepared by modifying the tapioca starch with glutaraldehyde is blended with 25 wt% of polylactic acid and 0.4 phr of maleic anhydride, the initial tensile strength of the obtained spline is 26.6 MPa; Tensile strength remained 86.8% and 67.3% after leaving the finished product for 56 days and 168 days at °C/50% relative humidity.

Claims (10)

A method for preparing a hydrophobic thermoplastic starch-based biodegradable material, characterized in that it comprises the following steps: (1) a starch, a plasticizer and a pre-plasticized dispersant according to a mass ratio of 1: (0.1 to 0.5): 0.5~1) mixing evenly to obtain starch mixture I; (2) containing reinforcing agent, plasticizer and pre-plasticized dispersion with mass ratio (0.0005~0.01): (0.5~10): (0.5~10) The blend of the mixture is uniformly mixed with the starch mixture I to obtain a starch mixture II, wherein the reinforcing agent is a bacterial cellulose fiber, and the mass ratio of the reinforcing agent to the starch is (0.0005~0.01): (50 ~100); (3) After adjusting the pH value of the starch mixture II in the step (2) to 3-6, the mixture is reacted with a modifier to obtain a starch gelatinized product, wherein the temperature of the mixed reaction is 70~ 120 ° C, time is 10 to 40 minutes, and the modifier is a hydrophobic reactant; (4) pre-plasticized dispersion in the starch gelatin removal step (1) and step (2) from the step (3) After the agent, granulation is carried out. The preparation method of claim 1, wherein the starch is selected from the group consisting of natural starch and/or starch modified by a starch modifier; and/or, in the step (1), the mixing system is placed in a mechanical mixer to cut and disperse; And/or, in step (1) and step (2), the plasticizer is selected from one or more of ethylene glycol, glycerol, dimethyl hydrazine, and urea; and/or, step (1) And in step (2), the pre-plasticizing dispersant is selected from one or more of ethanol, water and methanol; and/or, in step (2), the bacterial cellulose fiber is selected from unmodified bacteria Cellulose fibers and/or modified bacterial cellulose fibers. The preparation method of claim 2, wherein the natural starch is selected from the group consisting of corn starch, One or more of wheat starch, sweet potato starch, potato starch and tapioca starch; and/or the starch modifier is selected from one or more of a carboxylic acid, an acid anhydride, a hydrazine halide and a decylamine; the carboxylic acid is selected from the group consisting of One or more of citric acid, acetic acid, malic acid and azelaic acid; the anhydride is acetic anhydride and/or maleic anhydride; the guanidine halide is ruthenium chloride; the guanamine is selected from the group consisting of formamide and N-methyl One or more of methotrexate and dimethylacetamide; and/or, in step (1), the mixing system is cut and dispersed in a mechanical mixer for 0.5 to 1 hour; and/or the modified bacterial cellulose The fiber is a bacterial cellulose fiber modified by a bacterial cellulose fiber modifier, and the bacterial cellulose fiber modifier is an alcohol and/or an acid anhydride selected from the group consisting of n-butanol, ethylene glycol, glycerin, and polyethylene. One or more of an alcohol, polyethylene glycol, and ethylene-vinyl alcohol selected from one or more of maleic anhydride, succinic anhydride, acetic anhydride, propionic anhydride, and phthalic anhydride; the modified bacterial fiber The fiber is obtained by the following steps: molar ratio (1~10): (1~10) alcohol and The mixture of the acid anhydride is heated and stirred at a temperature of 0 to 200 ° C for 1 to 200 minutes. After the two materials are dissolved, 0.1 to 10% of the total mass of the alcohol and the acid anhydride is added, and the reaction temperature is 50 to 200 ° C to carry out the reaction. The reaction time is in the range of 1 to 480 minutes to obtain a product having a terminal carboxyl group; the unmodified bacterial cellulose fiber is cut into small pieces, and an alkaline solution having a mass percentage of 1 to 20% is added at a temperature of 0 to 100. Swell at °C for 1~120 minutes, then rinse with water and then dry, then mix with the above-mentioned product with terminal carboxyl group, and add one or more of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid at pH 1~ 7 and the temperature is 0 ~ 200 ° C under the conditions of mechanical stirring for 1 to 200 minutes to obtain modified bacterial cellulose fibers. The preparation method of claim 1, wherein in the step (1), the mass ratio of the starch, the plasticizer and the pre-plasticized dispersant in the starch mixture I is 1: (0.1 to 0.3): (0.7~0.9); and/or, in step (2), the mass ratio of the reinforcing agent, plasticizer and pre-plasticizing dispersant in the blend is (0.0005~0.0015): (0.5~1.5): (0.5~1.5); and/or, in the step (2), the mass ratio of the enhancer to the starch in the starch mixture II is (0.015 to 0.025): (98 to 100). The preparation method of claim 1, wherein, in the step (2), the bacterial cellulose fiber has a length of 0.1 to 1 μm; and/or the bacterial cellulose fiber has a diameter of 20 to 100 nm; and/or, the step ( 2), the blend is firstly mixed uniformly, and then allowed to stand, and then uniformly mixed with the starch mixture I; preferably, the blend is first placed in a dispersing machine, dispersed and uniformly mixed, and then allowed to stand. Further, the starch mixture I is uniformly mixed; more preferably, the blend is first dispersed and dispersed in a dispersing machine for 1 to 2 hours, and then allowed to stand for 4 to 8 hours, and then uniformly mixed with the starch mixture I. The preparation method of claim 1, wherein in the step (3), the pH is adjusted by using a pretreatment agent selected from the group consisting of citric acid, acetic acid, acetic anhydride, malic acid, azelaic acid and maleic anhydride. And one or more; and/or, in step (3), the pH is adjusted to 4 to 5; and/or, in step (3), the hydrophobic reactant is selected from the group consisting of polyaldehydes dissolved in water, Sodium trimetaphosphate and/or sodium hexametaphosphate, the polyaldehyde species being selected from one or more of glyoxal, succinaldehyde, glutaraldehyde and adipaldehyde, and the hydrophobic reactant is in the form of an aqueous solution There is, in the aqueous solution of the hydrophobic reactant, the mass percentage of the hydrophobic reactant is 20 to 40%. The preparation method of claim 1, wherein, in the step (3), the modifier is added in an amount of 0.1 to 32 phr, preferably 0.1 to 2 phr; And/or, in the step (3), the temperature of the mixing reaction is 70 to 100 ° C; and/or, in the step (3), the mixing reaction time is 15 to 25 minutes. The preparation method of claim 1, wherein in the step (4), the operation of removing the pre-plasticized dispersant in the step (1) and the step (2) is performed by drying the starch gelate; wherein, the drying temperature It is preferably 0 to 100 ° C, more preferably 60 to 100 ° C; the drying time is preferably 0.5 to 50 hours, more preferably 2 to 50 hours; the drying is carried out by the following steps: presetting the starch gel After drying in a blast drying oven or an infrared direct drying oven, it is then placed in a vacuum drying oven or a dew point drying oven; wherein the drying temperature of the blast drying oven or the infrared direct drying oven is 75 to 85 ° C, the time is 23~25 hours; the drying temperature of the vacuum drying box or the dew point drying box is preferably 0 to 100 ° C, more preferably 60 to 100 ° C, and the time is preferably 4 to 30 hours, more preferably 10 to 30 hours; Or, in the step (4), the granulation system is carried out in an internal mixer or a screw extruder. The preparation method of claim 1, wherein in the step (4), a compatibilizer is added during granulation; the compatibilizer is selected from the group consisting of maleic anhydride, succinic anhydride, acetic anhydride, propionic anhydride, and phthalic acid One or more of the acid anhydrides; the mass ratio of the compatibilizer to the starch gelate of the pre-plasticized dispersant is (0~1): (5~10); and/or, in step (4), Further, when the granulation is performed, the biodegradable material is further added; the biodegradable material is preferably a biodegradable aliphatic polyester material and/or a biodegradable aliphatic and aromatic copolyester material, and more preferably selected from the group consisting of One of lactic acid, polybutylene succinate/butylene terephthalate, polysuccinic acid/adipic acid-butylene glycol ester, poly(adipic acid)/butylene terephthalate and polycaprolactone Or a plurality of; the mass ratio of the biodegradable material to the starch gelate removing the pre-plasticized dispersant is (0.5 to 5): (5 to 10); and/or, in step (4), the removal step (1) And after the pre-plasticized dispersant in step (2) And adding a coloring agent before granulation, the coloring agent is preferably a metal oxide, more preferably titanium dioxide; the coloring agent and the quality of the starch are preferably (0.1-20): 100, more preferably (0.5-5) :100. A hydrophobic thermoplastic starch-based biodegradable material obtained by the production method of any one of claims 1 to 9.