Preparation and application of oligomer modified maleopimaric acid

Abstract

The invention relates to a preparation and application method of low polymer modified maleopimaric acid, which prepares the low polymer modified maleopimaric acid and uses the low polymer modified maleopimaric acid as an additive for thermoplastic starch plastics, and belongs to the fields of high-value utilization of forest chemicals and biodegradable plastics. The method comprises the following steps: firstly, preparing maleopimaric acid by using industrial-grade maleated rosin, then modifying maleopimaric acid by using an oligomer polyethylene glycol 400 (PEG400), further uniformly mixing the PEG400 modified maleopimaric acid with starch and glycerol, and extruding by using a single (or double) screw extruder to obtain the PEG400 modified maleopimaric acid enhanced thermoplastic starch plastic. According to the method, under the condition that a small amount of (0.3-1.5 parts) PEG400 modified maleopimaric acid is added, the strength and toughness of the thermoplastic starch plastic can be synchronously improved, the tensile strength is improved by about 20-100%, and the elongation at break is improved by about 40-94%. Besides, the PEG400 modified maleopimaric acid serving as a novel rosin derivative also has certain antibacterial property, so that the prepared thermoplastic starch plastic can be applied to the fields of food packaging, disposable tableware or medical supplies and the like.

Description

Technical Field

[0001] The invention belongs to the field of high-value utilization of forest chemicals and biodegradable plastics, and relates to the preparation of oligomer-modified maleopimaric acid and the application of the oligomer-modified maleopimaric acid in biodegradable plastics. Background Art

[0002] Vigorously developing bio-based and biodegradable plastics and reducing the use of petroleum-based plastics is one of the scientific and technological issues that need to be urgently addressed in the economic and social development of mankind. As a biodegradable natural polymer, starch has advantages not only in terms of source and price, but also in terms of its renewability, environmental pollution-free and biodegradability, which makes it widely used in the field of biodegradable plastics.

[0003] Adding plasticizers to starch to prepare thermoplastic starch plastics is one of the hot topics of research and development at home and abroad. At present, the commonly used plasticizers in thermoplastic starch plastics are polyols and polyamines or amides. Commonly used polyols such as glycerol, after being mixed with starch and extruded, can make thermoplastic starch have a certain tensile strength and elongation at break. In comparison, polyamines or amides can form stronger hydrogen bonds with the hydroxyl groups on starch macromolecules, thereby having higher tensile strength. However, the accompanying problem is that thermoplastic starch plastics become brittle, that is, the toughness decreases, which is manifested as a significant decrease in elongation at break.

[0004] Adding other fillers to thermoplastic starch can enhance the mechanical properties of thermoplastic starch. For example, rosin, as a forest chemical product, has a wide source, low cost, and has broad application prospects as a degradable and environmentally friendly material. Using two double bonds and one carboxyl group in rosin, modified rosin and rosin derivatives are prepared respectively, which can be mainly used as reinforcing phases or phase interface modifiers in composite materials. Therefore, giving full play to the structural characteristics and advantages of rosin can effectively improve the mechanical, water resistance, antibacterial and aging properties of composite materials. Patent No. CN113717441A discloses a method, a starch-based nanocomposite material synergistically modified with sodium rosin acid and cellulose nanocrystals and a preparation method thereof. The invention mixes sodium rosin acid, cellulose nanocrystals and starch evenly to prepare a film liquid, and casts the film liquid on a glass dish to prepare a composite material. However, the prepared composite material has poor tensile strength, which is lower than 10 MPa. In patent CN117887149A, maleic rosin urea complex is used to toughen thermoplastic starch plastic, which can maintain a high tensile strength of the thermoplastic starch plastic and significantly improve toughness, but the maximum elongation at break is only 11.3%. Summary of the invention

[0005] In order to solve the technical problem in the prior art that while improving the tensile strength of thermoplastic starch plastics, the elongation at break is reduced, resulting in increased brittleness of the material, the inventor unexpectedly found that using polyethylene glycol 400 (PEG400) modified maleopimaric acid as an additive can better maintain and improve the tensile strength of thermoplastic starch plastics, while significantly improving the elongation at break. Based on the above findings, the present invention was completed.

[0006] Therefore, the present invention first provides a method for preparing PEG400 modified maleopimaric acid.

[0007] The present invention also provides the use of the PEG400 modified maleopimaric acid as a thermoplastic starch plastic additive.

[0008] Specifically, the oligomer-modified maleopimaric acid of the present invention is used to prepare thermoplastic starch plastics, which is composed of the following components by weight:

[0009] Starch 100

[0010] Glycerin 30~40

[0011] PEG400 modified maleopimaric acid 0.3~1.5

[0012] The specific method adopted by the present invention is:

[0013] 1) Preparation of maleopimaric acid and PEG400-modified maleopimaric acid

[0014] Weigh 15-20 parts of maleic rosin, dissolve it in about 50 parts of anhydrous ethanol, add saturated sodium hydroxide ethanol solution, adjust the pH value of the solution to 10-12, and stir and heat at 65-70°C for 2-3 hours. After the solution is cooled, filter to obtain a precipitate, and wash it with anhydrous ethanol. Dissolve the washed precipitate in a small amount of ultrapure water, add dilute hydrochloric acid, adjust the pH of the solution to 3-5, and obtain a precipitate. Filter and wash the precipitate, put it into a vacuum drying oven at 40-50°C, and dry it for 10-14 hours to obtain maleopimaric acid.

[0015] Weigh 2-4 parts of the maleopimaric acid prepared above and 8-10 parts of PEG400, add them into a round-bottom flask, add 0.5-1 parts of 4-dimethylaminopyridine (DMAP) as a catalyst, stir and heat at 110-120° C. for 3-4 hours to obtain a brown-red viscous liquid, which is PEG400-modified maleopimaric acid.

[0016] 2) Preparation of PEG400 modified maleopimaric acid reinforced thermoplastic starch plastics

[0017] Take 100 parts of starch, add 30-40 parts of glycerol and 0.3-1.5 parts of PEG400 modified maleopimaric acid, and mix them evenly; extrude into strips in a single screw extruder, with a barrel temperature of 115-125° C., a die temperature of 105-115° C., and a rotation speed of 40-50 r / min; perform hot pressing in a hot press at 110-120° C. to obtain a PEG400 modified maleopimaric acid reinforced thermoplastic starch plastic film.

[0018] The advantages of the present invention are:

[0019] 1) As a renewable forest chemical product, natural rosin has a wide source and low cost. After modification, it is added to thermoplastic starch plastics. The addition amount is small and will not significantly increase the cost of thermoplastic starch plastics. It has good market application prospects;

[0020] 2) PEG400 is a low molecular weight oligomer with relatively low cost, and a small amount of addition will not have a significant effect on the degradation of thermoplastic starch plastics;

[0021] 3) PEG400 modified maleopimaric acid can significantly improve the tensile strength of modified thermoplastic starch plastics and also improve the elongation at break of modified thermoplastic starch plastics;

[0022] 4) PEG400 modified maleopimaric acid has certain antibacterial properties and can be used in food packaging or medical materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Preparation mechanism of maleopimaric acid and PEG400 modified maleopimaric acid

[0024] Figure 2 IR spectra of maleopimaric acid, PGE400 and PEG400 modified maleopimaric acid

[0025] As attached Figure 2 As shown in Figure 2, PEG400 modified maleopimaric acid has a peak at 1770 cm -1 A new absorption peak appeared at 3420 cm-1, which corresponds to the stretching vibration absorption peak of the ester group generated by the reaction; -1 There is also a broad absorption peak at 2915cm -1 The absorption peak at 1691cm corresponds to the stretching vibration absorption peak of the methyl group in maleopimaric acid; -1 The absorption peak at 1084 cm corresponds to the stretching vibration absorption peak of C=C in maleopimaric acid; -1The absorption peaks at correspond to the stretching vibration peaks of CO at the terminal hydroxyl group in PEG400. These absorption peaks in PEG400-modified maleopimaric acid indicate that maleopimaric acid reacts with PEG400.

[0026] Figure 3 Maleopimaric acid and PEG400 modified maleopimaric acid and H NMR spectra

[0027] As attached Figure 3 , Chemical shifts of hydrogen at the indicated positions of PEG400-modified maleopimaric acid, the chemical shift at 4.12 corresponds to the -CH 2 -The chemical shift of hydrogen (i.e. Figure 3 The hollow square corresponds to the hydrogen chemical shift at the position); the chemical shift at 3.51 corresponds to the -CH 2 -The chemical shift of hydrogen (i.e. Figure 3 The hollow circle in the middle corresponds to the chemical shift of hydrogen at the position corresponding to the hydroxyl group at the end of the PEG400 molecular chain (i.e., the attached Figure 3 The hollow triangle in the middle corresponds to the chemical shift of hydrogen at the position corresponding to the position of the hollow triangle in the middle); the chemical shift at 12.13 corresponds to the chemical shift of hydrogen at the carboxyl group in maleopimaric acid (i.e. Figure 3 The chemical shift of hydrogen at the position corresponding to the solid triangle in the figure): The chemical shift at 5.34 corresponds to the chemical shift of hydrogen on the C=C double bond in maleopimaric acid (i.e. Figure 3 The chemical shift at 2.36 corresponds to the chemical shift of the hydrogen on the methine in maleopimaric acid (i.e. Figure 3 These all indicate that PEG400 reacts with maleopimaric acid, but the chemical shift at 12.13 does not completely disappear, indicating that only a portion of the carboxyl groups on maleopimaric acid react with PEG400.

[0028] Figure 4 Scanning electron microscope images of the cross-section of the thermoplastic starch plastic film prepared in Examples 1, 2, 3, 4 and Comparative Example 1

[0029] Note: The test was conducted using the MTS\SANS CMT4000 universal testing machine of MTS Industrial Systems (China) Co., Ltd. The film size was 40×10×0.7 mm and the tensile rate was 50 mm / min. DETAILED DESCRIPTION

[0030] The present invention will be further understood from the following illustrative examples. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0031] Embodiment 1:

[0032] 1) Preparation of maleopimaric acid and PEG400-modified maleopimaric acid

[0033] Weigh 16g of maleic rosin, dissolve it in about 50ml of anhydrous ethanol, add saturated sodium hydroxide ethanol solution, adjust the pH value of the solution to 10, and stir and heat at 68°C for 2.5h. After the solution is cooled, filter to obtain a precipitate, and wash it with anhydrous ethanol. Dissolve the washed precipitate in a small amount of ultrapure water, add dilute hydrochloric acid dropwise, adjust the pH of the solution to 3, and obtain a precipitate. Filter the precipitate and wash it with ultrapure water. Put the washed precipitate into a vacuum drying oven at 45°C and dry it for 12h to obtain maleopimaric acid.

[0034] Weigh 3 g of the maleopimaric acid prepared above and 9 g of PEG400, add them into a round-bottom flask, add 0.5 g of DMAP as a catalyst, stir and heat at 110° C. for 3 h to obtain a brown-red viscous liquid, which is PEG400-modified maleopimaric acid.

[0035] 2) Preparation of PEG400 modified maleopimaric acid reinforced thermoplastic starch plastics

[0036] Weigh 100 g of starch, add 35 g of glycerol and 0.3 g of PEG400 modified maleopimaric acid, and mix them evenly; extrude into strips in a single-screw extruder, with a barrel temperature of 120° C., a head mold temperature of 115° C., and a rotation speed of 40 r / min; and perform hot pressing at 110° C. with a hot press to obtain a PEG400 modified maleopimaric acid reinforced thermoplastic starch plastic film.

[0037] Embodiment 2:

[0038] 1) Preparation of maleopimaric acid and PEG400-modified maleopimaric acid

[0039] Preparation of maleopimaric acid and PEG400-modified maleopimaric acid Reference method of step (1) in Example 1

[0040] 2) Preparation of thermoplastic starch plastic modified by PEG400-modified maleopimaric acid

[0041] Weigh 100 g of starch, add 35 g of glycerol and 0.6 g of PEG400 modified maleopimaric acid, and mix them evenly; extrude into strips in a single-screw extruder, with a barrel temperature of 120° C., a head mold temperature of 115° C., and a rotation speed of 40 r / min; and perform hot pressing at 110° C. with a hot press to obtain a PEG400 modified maleopimaric acid reinforced thermoplastic starch plastic film.

[0042] Embodiment 3:

[0043] 1) Preparation of maleopimaric acid and PEG400-modified maleopimaric acid

[0044] Preparation of maleopimaric acid and PEG400 modified maleopimaric acid Reference method of step (1) in Example 1

[0045] 2) Preparation of thermoplastic starch plastic modified by PEG400-modified maleopimaric acid

[0046] Weigh 100 g of starch, add 35 g of glycerol and 0.9 g of PEG400 modified maleopimaric acid, and mix them evenly; extrude into strips in a single-screw extruder, with a barrel temperature of 120° C., a head mold temperature of 115° C., and a rotation speed of 40 r / min; and perform hot pressing at 110° C. with a hot press to obtain a PEG400 modified maleopimaric acid reinforced thermoplastic starch plastic film.

[0047] Embodiment 4:

[0048] 1) Preparation of maleopimaric acid and PEG400-modified maleopimaric acid

[0049] Preparation of maleopimaric acid and PEG400-modified maleopimaric acid Reference method of step (1) in Example 1

[0050] 2) Preparation of thermoplastic starch plastic modified by PEG400-modified maleopimaric acid

[0051] Weigh 100 g of starch, add 35 g of glycerol and 1.2 g of PEG400 modified maleopimaric acid, and mix them evenly; extrude into strips in a single-screw extruder, with a barrel temperature of 120° C., a head mold temperature of 115° C., and a rotation speed of 40 r / min; and perform hot pressing at 110° C. with a hot press to obtain a PEG400 modified maleopimaric acid reinforced thermoplastic starch plastic film.

[0052] Comparative Example 1: (No PEG400 modified maleopimaric acid was added, only glycerol plasticized thermoplastic starch plastic)

[0053] Weigh 100g starch and 35g glycerol and mix them evenly; extrude them into strips in a single-screw extruder with a barrel temperature of 120°C, a die temperature of 115°C, and a rotation speed of 40r / min; hot-press the obtained strips at 110°C using a hot press to obtain a glycerol-plasticized thermoplastic starch plastic film.

[0054] Table 1

[0055]

[0056] Table 1 shows the test data of the dosage of each component and the strength (tensile strength) and toughness (elongation at break) of each embodiment and comparative example sample. The results show that the strength and toughness of the modified thermoplastic starch plastic prepared by the present invention using 0.3 to 1.2 parts of PEG400 modified maleopimaric acid are improved by about 18 to 100% in tensile strength and about 4094% in elongation at break compared with the comparative example (without adding PEG400 modified maleopimaric acid). In addition, the attached Figure 4 The scanning electron microscope images of the fracture surface of the thermoplastic starch plastic film further provide evidence, indicating that 0.3-1.2 parts of PEG400 modified maleopimaric acid can form a uniform and stable interaction with the thermoplastic starch matrix, and as the amount of PEG400 modified maleopimaric acid added gradually increases, the fracture surface gradually becomes rough and uneven, which is consistent with the change of elongation at break in Table 1. Among all the embodiments, the embodiment 3 has the highest strength and toughness.

Claims

1. This invention is a preparation and application of oligomer-modified maleopimaric acid, characterized in that: The preparation of oligomer-modified maleopimaric acid and its application in thermoplastic starch plastics is carried out according to the following steps: Weigh 15 to 20 parts of maleic rosin, dissolve it in about 50 parts of anhydrous ethanol, add saturated sodium hydroxide ethanol solution, adjust the pH value of the solution to 10 to 12, stir and heat at 65 to 70° C. for 2 to 3 hours, and after the solution is cooled, filter to obtain a precipitate, wash it with anhydrous ethanol, dissolve the washed precipitate in a small amount of ultrapure water, add dilute hydrochloric acid dropwise, adjust the pH value of the solution to 3 to 5, obtain a precipitate, filter and wash the precipitate, put it into a vacuum drying oven at 40 to 50° C., and dry it for 10 to 14 hours to obtain maleopimaric acid; Weigh 2-4 parts of the maleopimaric acid prepared above and 8-10 parts of polyethylene glycol 400 (PEG400), add them into a round-bottom flask, add 0.5-1 parts of 4-dimethylaminopyridine (DMAP) as a catalyst, stir and heat at 110-120° C. for 3-4 hours to obtain a brown-red viscous liquid, which is PEG400-modified maleopimaric acid; Take 100 parts of starch, add 30-40 parts of glycerol and 0.3-1.5 parts of PEG400 modified maleopimaric acid, mix evenly, extrude into strips in a single screw extruder, the barrel temperature is 115-125° C., the head mold temperature is 105-115° C., the rotation speed is 40-50 r / min, and hot pressing is performed at 110-120° C. using a hot press to obtain a PEG400 modified maleopimaric acid reinforced thermoplastic starch plastic film.

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