A method for improving the dispersibility of nano zinc oxide in polybutylene adipate / terephthalate resin

Abstract

The invention provides a method for improving the dispersibility of nano zinc oxide in poly (butylene adipate / terephthalate) resin. The modified nano zinc oxide is prepared by ultrasonically modifying the nano zinc oxide with polyacrylic acid having a neutralization degree of 50-70% and performing centrifugal spray drying. The modified nano zinc oxide is then mixed with the poly (butylene adipate / terephthalate) resin, thereby effectively improving the dispersibility of the nano zinc oxide in the poly (butylene adipate / terephthalate) resin and ensuring the mechanical properties and waterproof properties of the poly (butylene adipate / terephthalate) resin composite material.

Description

Technical field:

[0001] The invention relates to the technical field of degradable plastics, and more specifically to a method for improving the dispersibility of nano zinc oxide in poly(butylene adipate / terephthalate) resin. Background technology:

[0002] Polybutylene adipate-terephthalate (PBAT) is a biodegradable material and a copolyester of aliphatic and aromatic groups. It is prepared by the polycondensation of butylene adipate (PBA) and butylene terephthalate (PBT). It combines the excellent degradation properties of aliphatic polyesters with the good mechanical properties of aromatic polyesters.

[0003] With the increasing prominence of environmental issues and the domestic restrictions on the use of non-degradable plastics, biodegradable materials have attracted more and more attention. PBAT has become one of the most active biodegradable materials in biodegradable plastic research due to its excellent flexibility. However, the presence of aromatic polyester PBT segments in the PBAT molecular chain leads to a relatively slow degradation rate of PBAT; and the application of this biodegradable polymer is limited by relatively high cost and poor mechanical properties. One way to reduce the overall material cost and improve mechanical properties is to combine biodegradable polymers with cheap inorganic or organic fillers.

[0004] As an inorganic filler, nano zinc oxide not only reduces the overall material cost and improves mechanical properties, but also has certain antibacterial ability, so nano zinc oxide is often used as an inorganic antibacterial agent. Since the surface of nano zinc oxide contains a large number of hydroxyl radicals, it has poor compatibility with PBAT; in addition, due to its own large surface energy and surface tension, it is easy to produce particle agglomeration during use. Therefore, only by dispersing and modifying nano zinc oxide can the role of nano zinc oxide in PBAT be truly brought into play.

[0005] Nano zinc oxide can be modified by silane coupling agent, polyacrylic acid, polystyrene, polymethyl methacrylate, long-chain fatty acid (stearic acid, oleic acid, etc.). Patent CN116515036B discloses a polymer material for coating nano zinc oxide. The preparation method of the monomer in this method is: add dimethylaminoethyl methacrylate (DM), solvent, and polymerization inhibitor into a reactor, stir and mix, heat and reflux; add 1,3-propane sultone, react, take out the solid after the reaction, wash and dry, and obtain monomer A. The overall process of the monomer is complicated and the cost is high.

[0006] Therefore, obtaining an effective dispersion and modification technology for nano zinc oxide is an important basis for expanding its application range. Summary of the invention:

[0007] The present invention intends to provide a method for improving the dispersibility of nano zinc oxide in polybutylene adipate / terephthalate resin, so as to overcome the problems of high cost and insufficient dispersibility of the modification method of nano zinc oxide in the prior art.

[0008] To achieve the above purpose, the technical ideas adopted by the present invention are as follows:

[0009] The modified nano zinc oxide is prepared by using polyacrylic acid with a neutralization degree of 50-70% to perform ultrasonic reaction modification and centrifugal spray drying on nano zinc oxide, and then the modified nano zinc oxide is mixed with poly (butylene adipate / terephthalate) resin to improve the dispersibility of the nano zinc oxide in the poly (butylene adipate / terephthalate) resin.

[0010] The technical solution of the present invention comprises the following steps:

[0011] (1) dispersing nano zinc oxide in deionized water to form a suspension;

[0012] (2) adding polyacrylic acid with a neutralization degree of 50-70% to the suspension obtained in step (1); subjecting the mixture to ultrasonic reaction, filtering, washing and spray drying to obtain modified nano zinc oxide;

[0013] (3) Evenly mix the modified nano zinc oxide and poly (butylene adipate / terephthalate) resin; the amount of nano zinc oxide used is 3-8% of the mass of the poly (butylene adipate / terephthalate) resin.

[0014] Preferably, the mass ratio of nano zinc oxide to deionized water in step (1) of the present invention is 1:(10-20).

[0015] Preferably, the preparation method of polyacrylic acid with a neutralization degree of 50-70% in step (2) of the present invention is: selecting an acrylic acid solution with a neutralization degree of 50-70%, reacting it at 50-70° C. for 1-2 hours under the action of a catalyst to synthesize a polyacrylic acid solution with a neutralization degree of 50-70%, and drying it at 70-90° C. to constant weight to obtain polyacrylic acid with a neutralization degree of 50-70%.

[0016] Further, the preparation method of the acrylic acid solution with a neutralization degree of 50-70% is: according to the desired neutralization degree, a corresponding molar amount of NaOH solution is slowly added dropwise to the acrylic acid solution in an ice water bath at 0-5°C, followed by a neutralization reaction for 1-2 hours to obtain an acrylic acid solution with a corresponding neutralization degree. The mass concentration of the acrylic acid solution is 30-40%, and the mass concentration of the NaOH solution is 20-40%.

[0017] Furthermore, the catalyst is one or more of potassium persulfate, ammonium persulfate, and hydrogen peroxide; the amount of the catalyst used is 0.5-1% of the amount of acrylic acid used.

[0018] Preferably, the amount of acrylic acid used in step (2) is 3%-10% of the mass of the nano zinc oxide.

[0019] Preferably, the conditions of the ultrasonic reaction in step (2) are: ultrasonic frequency of 20-30 kHz, ultrasonic power of 150-300 W, ultrasonic time of 0.5-1 h, and ultrasonic temperature of 30-50° C.

[0020] Preferably, the washing conditions in step (2) are washing with ethanol and deionized water respectively.

[0021] Preferably, the spray drying conditions in step (2) are high-speed centrifugal spray drying, with an inlet temperature of 200-250°C, an outlet temperature of 80-90°C, and an atomizer speed of 11000-13000 rpm.

[0022] In the present invention, nano zinc oxide is modified by using polyacrylic acid with a certain degree of neutralization, so that the retained carboxyl groups can fully react with the active hydroxyl groups on the surface of nano zinc oxide, and at the same time, the sodium ions generated by neutralization are adsorbed on the surface of zinc oxide, so that the effective radius of the particles is increased, the repulsion between the particles is increased, and the attraction between the particles is greatly reduced, thereby achieving the effect of improving the dispersibility.

[0023] When polyacrylic acid with a low neutralization degree is used, the number of sodium ions adsorbed on the surface of zinc oxide is too small, and the effective radius between particles is insufficient; when polyacrylic acid with a high neutralization degree is used, insufficient carboxyl content will lead to excessive active hydroxyl groups remaining in nano zinc oxide, resulting in poor dispersibility of the modified nano zinc oxide in PBAT. At the same time, the present invention can fully ensure that the carboxyl group and the active hydroxyl group react by reacting under ultrasonic conditions.

[0024] Since the potential of the dispersion of nano zinc oxide is the lowest under neutral conditions, the particles are prone to sedimentation due to agglomeration. Therefore, the ultrasonic reaction time of the nano zinc oxide in the present invention should not be too long to avoid agglomeration and sedimentation. At the same time, the centrifugal spray drying method can play a good role in dispersing the particles, thereby improving the dispersion effect of nano zinc oxide in PBAT.

[0025] After testing, it is found that the particle size distribution of the nano zinc oxide prepared by the present invention is uniform; the mechanical properties of the composite film prepared by dispersing the modified nano zinc oxide in PBAT are higher than those of the unmodified or other modified nano zinc oxide / PBAT composite film, indicating that the modification method in the present invention is more suitable for the composite system of PBAT.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses polyacrylic acid with a neutralization degree of 50-70% to perform ultrasonic reaction modification on nano zinc oxide, thereby ensuring good dispersibility of nano zinc oxide in PBAT and ensuring the mechanical properties of the PBAT composite material.

[0028] 2. The present invention controls the duration of the ultrasonic reaction, thereby ensuring the adequacy of the reaction and avoiding the instability caused by a too long reaction time.

[0029] 3. The present invention dries the modified nano zinc oxide by high-speed centrifugal spray drying. Compared with the ordinary drying method, it can ensure that the nano zinc oxide modified with polyacrylic acid is not agglomerated, thereby ensuring the mechanical properties of the PBAT composite material. Specific implementation method:

[0030] In order to make the purpose, technical scheme and advantages of the present invention more clear, the technical scheme of the present invention is further described below through specific implementation methods. Those skilled in the art should know that the embodiments are only to help understand the technical content and technical effects of the present invention and should not be regarded as limiting the present invention.

[0031] The sources of the components of the following embodiments and comparative examples are as follows:

[0032] Nano zinc oxide was purchased from Beijing Mairida Technology Co., Ltd., model number M244315, purity 99%, particle size ≤100 nm.

[0033] Acrylic acid was purchased from Beijing Mairuida Technology Co., Ltd., model number M184805, purity > 99%.

[0034] Polybutylene adipate-terephthalate (PBAT) was purchased from Guangdong Jinfa Technology Co., Ltd., model EBAG-262, density 1.25-1.35 g / cm 3 , melting point is 90-130℃.

[0035] The raw materials used in the embodiments of the present invention or the comparative examples are all commonly used reagents in the chemical field, all purchased from mainstream manufacturers in the market, and do not represent that the raw materials must be produced by the above-mentioned manufacturers. As long as it is conventional raw material, it can play the expected role without particular restrictions. If specific conditions or operating methods are not described in the present embodiment or the comparative examples, it can be obtained according to the conditions or operating methods commonly used in the art.

[0036] Prepare polyacrylic acid with a neutralization degree of 30%, 50%, 70%, and 90% respectively for use; taking the preparation of 50% polyacrylic acid as an example:

[0037] (1) preparing 100 g of an acrylic acid solution with a mass concentration of 36%, slowly adding 25 g of a NaOH solution with a mass concentration of 40% at 5° C., and continuing the reaction for 1 hour after the addition is complete to prepare an acrylic acid solution with a neutralization degree of 50%;

[0038] (2) adding 0.18 g of potassium persulfate to the obtained acrylic acid solution with a neutralization degree of 50%, and reacting at 60° C. for 2 h to prepare a polyacrylic acid solution with a neutralization degree of 50%;

[0039] (3) The polyacrylic acid solution was dried at 80° C. to a constant weight to prepare polyacrylic acid with a neutralization degree of 50%.

[0040] According to the required neutralization degree, a corresponding molar amount of NaOH solution is subjected to neutralization reaction with acrylic acid to obtain polyacrylic acid with a neutralization degree of 30%, 70%, and 90%, respectively.

[0041] Example 1

[0042] (1) Dispersing 100 g of nano zinc oxide into 1 L of deionized water to obtain a suspension;

[0043] (2) adding 5 g of polyacrylic acid with a neutralization degree of 50%; reacting at an ultrasonic frequency of 30 kHz, an ultrasonic power of 300 W, and an ultrasonic temperature of 30° C. for 1 h; filtering, washing with ethanol, and washing with deionized water, and then high-speed centrifugal spray drying to obtain modified nano zinc oxide; the spray dryer inlet temperature was set at 220° C., the outlet temperature was set at 90° C., and the atomizer speed was 11000 rpm;

[0044] (3) 5 parts by mass of modified nano zinc oxide and 100 parts by mass of PBAT were mixed uniformly, and extruded and granulated by a twin-screw extruder to prepare ZnO / PBAT blended granules. The extrusion temperatures of zones 1 to 6 of the extruder were 110, 120, 130, 130, 120, and 120° C., respectively, and the die temperature was 120° C. The pellets were cut with cold air, dried, and sealed for later use.

[0045] Example 2

[0046] (1) Dispersing 100 g of nano zinc oxide into 1 L of deionized water to obtain a suspension;

[0047] (2) adding 5 g of polyacrylic acid with a neutralization degree of 70%; reacting at an ultrasonic frequency of 25 kHz, an ultrasonic power of 200 W, and an ultrasonic temperature of 50° C. for 0.5 h; filtering, washing with ethanol, and washing with deionized water, and then high-speed centrifugal spray drying to obtain modified nano zinc oxide; the spray dryer inlet temperature was set at 220° C., the outlet temperature was set at 90° C., and the atomizer speed was 11000 rpm;

[0048] (3) 6 parts by mass of modified nano zinc oxide and 100 parts by mass of PBAT were mixed uniformly, and extruded and granulated by a twin-screw extruder to prepare ZnO / PBAT blended granules. The extrusion temperatures of zones 1 to 6 of the extruder were 110, 120, 130, 130, 120, and 120° C., respectively, and the die temperature was 120° C. The pellets were cut into pellets using cold air, dried, and sealed for later use.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that 5 g of polyacrylic acid with a neutralization degree of 30% is added in step (2).

[0051] Comparative Example 2

[0052] The difference from Example 2 is that 5 g of polyacrylic acid with a neutralization degree of 90% is added in step (2).

[0053] Comparative Example 3

[0054] The difference from Example 1 is that in step (2), the ultrasonic reaction time is increased from 1 h to 2 h; and the drying method is replaced by hot air drying at 90° C. to constant weight.

[0055] Manufacturing example

[0056] Preparation of PBAT nanocomposite film by tape casting: The nano ZnO / PBAT blended pellets in Examples 1-2 and Comparative Examples 1-3 were vacuum dried at 50°C for 2h, and composite films were prepared by tape casting, wherein the mold temperature was 140°C, the speed of the polishing roll and the casting roll was 2m / min, and the speed of the traction roll was 2.2m / min.

[0057] Mechanical properties and water absorption are both means of evaluating the dispersion effect of the nano zinc oxide / PBAT composite material, so the mechanical properties and water absorption properties of the manufacturing example were tested.

[0058] Mechanical properties test

[0059] The tensile strength and elongation at break of the PBAT nanocomposite film samples in the manufacturing example were tested according to the standard GB / T1040.3-2006. The film was cut into (10mm×160mm) specification samples, the clamp spacing was 40mm, the tensile speed was 200mm / min, the test was repeated 5 times, and the average value was taken to obtain the tensile strength and elongation at break.

[0060] Water absorption performance test

[0061] The PBAT nanocomposite film sample in the manufacturing example was placed in a blast drying oven at 80°C for 24 hours to remove free water from the sample. When the sample was left to stand at room temperature in the drying oven, the sample was weighed and recorded as M1. The sample was immersed in distilled water. After soaking at room temperature for 24 hours, the sample was taken out and the water attached to the surface of the sample was wiped off with absorbent paper and weighed, recorded as M2. The water absorption rate L = (M2-M1) / M1*100%. High water absorption indicates that the dispersion of nano zinc oxide in the PBAT nanocomposite film is not good, and the agglomeration phenomenon and film voids increase; on the contrary, low water absorption indicates that the dispersion of nano zinc oxide in the PBAT nanocomposite film is less, the agglomeration phenomenon and the film voids are less.

[0062] Table 1. Test results of tensile strength and elongation at break of samples of examples and comparative examples

[0063]

[0064]

[0065] From the comparison between the embodiment and comparative examples 1-2, when polyacrylic acid with too low or too high neutralization degree is selected as the modifier, the dispersion of nano zinc oxide in PBAT will be insufficient, resulting in gaps and holes in the composite material, resulting in reduced mechanical strength and increased water absorption.

[0066] From the comparison between the embodiment and comparative example 3, when the ultrasonic time is too long, the system becomes unstable, and eventually the nano zinc oxide appears to be aggregated. Meanwhile, ordinary hot air drying cannot achieve a good dispersion effect, and eventually leads to a decrease in mechanical strength and an increase in water absorption.

[0067] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for improving the dispersibility of nano zinc oxide in polybutylene adipate / terephthalate resin, characterized in that: The steps include: (1) dispersing nano zinc oxide in deionized water to form a suspension; (2) adding polyacrylic acid with a neutralization degree of 50-70% to the suspension obtained in step (1); subjecting the suspension to ultrasonic reaction, filtering, washing and spray drying to obtain modified nano zinc oxide; (3) Evenly mix the modified nano zinc oxide and poly (butylene adipate / terephthalate) resin; the amount of nano zinc oxide used is 3-8% of the mass of the poly (butylene adipate / terephthalate) resin.

2. The method according to claim 1, characterized in that In step (1), the mass ratio of nano zinc oxide to deionized water is 1:(10-20).

3. The method according to claim 1, characterized in that The preparation method of polyacrylic acid with a neutralization degree of 50-70% in step (2) is as follows: selecting an acrylic acid solution with a neutralization degree of 50-70%, reacting it at 50-70° C. for 1-2 hours under the action of a catalyst to synthesize a polyacrylic acid solution with a neutralization degree of 50-70%, and drying it at 70-90° C. to constant weight to obtain polyacrylic acid with a neutralization degree of 50-70%.

4. The method according to claim 3, characterized in that The preparation method of an acrylic acid solution with a neutralization degree of 50-70% is as follows: according to the required neutralization degree, a corresponding molar amount of NaOH solution is slowly added dropwise to the acrylic acid solution in an ice water bath at 0-5°C, followed by a neutralization reaction for 1-2 hours to obtain an acrylic acid solution with a corresponding neutralization degree.

5. The method according to claim 4, characterized in that: The mass concentration of the acrylic acid solution is 30-40%, and the mass concentration of the NaOH solution is 20-40%.

6. The method according to claim 3, characterized in that The catalyst is one or more of potassium persulfate, ammonium persulfate and hydrogen peroxide; the amount of the catalyst used is 0.5-1% of the mass of acrylic acid.

7. The method according to claim 1, characterized in that In step (2), the amount of acrylic acid used is 3%-10% of the mass of nano zinc oxide.

8. The method according to claim 1, characterized in that The conditions of the ultrasonic reaction in step (2) are: ultrasonic frequency of 20-30 kHz, ultrasonic power of 150-300 W, ultrasonic time of 0.5-1 h, and ultrasonic temperature of 30-50° C.

9. The method according to claim 1, characterized in that: The washing conditions in step (2) are washing with ethanol and deionized water respectively.

10. The method according to claim 1, characterized in that The spray drying conditions in step (2) are high-speed centrifugal spray drying, with an inlet temperature of 200-250°C, an outlet temperature of 80-90°C, and an atomizer speed of 11000-13000 rpm.

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