Biodegradable PVC composite material and preparation method thereof

Abstract

The invention discloses a biodegradable PVC (polyvinyl chloride) composite material and a preparation method thereof, belongs to the technical field of PVC material processing, and aims to solve the technical problems that the flame retardant property and mechanical strength of a PBAT (poly (butylene adipate-co-terephthalate)) enhanced biodegradable PVC composite material need to be further improved and the decomposition property of PVC is poor in the prior art. The composite PVC material is prepared from the following components in parts by weight: 80 to 90 parts of modified PBAT, 14 to 19 parts of modified polysiloxane, 35 to 45 parts of modified PVC, 10 to 12 parts of diacetyl epoxy vegetable oil glyceride and 5 to 7 parts of additive, and through mutual cooperation of the modified PVC, the modified polysiloxane and the modified PBAT, not only is the biodegradability of the composite PVC effectively improved, but also the service life of the composite PVC material is prolonged, and the service life of the composite PVC material is prolonged. And the used modified PVC can be decomposed under ultraviolet light, so that the influence of the PVC material on environmental pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of PVC material processing, and particularly relates to a biodegradable PVC composite material and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC), as a widely used plastic material, is widely used in fields such as wire and cable, film, and soft sheet due to its excellent physical properties and processing properties. However, traditional PVC materials are often difficult to degrade after use, resulting in a large amount of plastic waste accumulation, causing serious environmental pollution. Especially when treating PVC waste by landfilling, it not only occupies a large amount of land resources but also generates leachate and greenhouse gases, causing long-term harm to the soil and atmospheric environment.

[0003] In the prior art, a Chinese patent with the publication number CN1037107C discloses a biodegradable plastic and a manufacturing method thereof, which is a mixture prepared by adding modified starch, plasticizer, and other functional additives to a synthetic polymer polyolefin. This plastic can be used to produce plastic products with traditional blown film equipment or injection molding equipment. Its physical and chemical properties are close to those of pure PVC and PE, but the cost is greatly reduced, and it has good biodegradability, which can reduce the pollution caused by residual plastics to the environment.

[0004] However, the above patent content improves the degradation performance by mixing biodegradable starch materials into the PVC material. However, PVC itself is difficult to be degraded by the action of microorganisms, resulting in environmental pollution caused by the long-term existence of PVC materials. PBAT is a commonly used thermoplastic biodegradable material, but it is easy to burn, resulting in a decrease in the flame retardant performance of the prepared composite PVC material after mixing with PVC. Moreover, the chemical property differences between materials will also form weak interfaces in the mixed material, leading to a decrease in the mechanical strength of the mixed material.

[0005] In view of the technical defects in this regard, a solution is proposed now. Summary of the Invention

[0006] The purpose of the present invention is to provide a biodegradable PVC composite material and a preparation method thereof, which are used to solve the technical problems that the flame retardant performance and mechanical strength of the PBAT-reinforced biodegradable PVC composite material in the prior art need to be further improved and the decomposition performance of PVC is poor.

[0007] The object of the present invention can be achieved by the following technical scheme: a biodegradable PVC composite material, comprising the following components in parts by weight: 80-90 parts of modified PBAT, 14-19 parts of modified polysiloxane, 35-45 parts of modified PVC, 10-12 parts of diacetyl epoxy vegetable oil glyceride and 5-7 parts of additives;

[0008] Modified PVC is processed by the following steps:

[0009] A1. Add PVC and pretreatment solution into a reactor and stir. Raise the temperature of the reactor to reflux and keep the reaction temperature for 3-4 hours. Post-treat to obtain pretreated PVC.

[0010] The synthetic reaction mechanism of pretreated PVC is:

[0011] During the reaction, the nucleophilic amino groups on the aminooctapolyethylene glycol hydroxyl molecules in the pretreatment solution attack the halogen atoms on the PVC chain, causing a nucleophilic substitution reaction, and modifying the PVC molecular chain with hydroxyl-terminated polyethylene glycol to obtain pretreated PVC.

[0012] A2. The pretreated PVC, modified titanium dioxide and dispersant are mixed evenly and added into a twin-screw extruder for melt extrusion and granulation to obtain modified PVC.

[0013] Furthermore, in step A1, the amount ratio of the PVC and the pretreatment solution is 1g:16mL, the pretreatment solution is composed of aminooctapolyethylene glycol hydroxyl and tetrahydrofuran at 1g:40mL, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, methanol is added to the reactor, the reactor is stirred for 30-50min, filtered, the filter cake is washed with methanol 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 50-60°C, and vacuum dried to constant weight to obtain pretreated PVC.

[0014] Furthermore, in step A2, the weight ratio of the pretreated PVC, modified titanium dioxide and dispersant is 100:12-15:3-5, and the dispersant is composed of stearate and polyethylene sodium in a weight ratio of 1:2.

[0015] Further, the modified titanium dioxide is processed by the following steps:

[0016] B1, adding 1-hydroxycyclohexyl phenyl ketone and acetone into a nitrogen-protected reactor and stirring, raising the temperature of the reactor to 45-50° C., adding isocyanate propyl triethoxysilane solution dropwise into the reactor, and after the addition is complete, heat-retaining the reaction for 60-80 minutes, and post-treating to obtain modified triethoxysilane;

[0017] The synthetic reaction formula of modified triethoxysilane is:

[0018]

[0019] The synthesis reaction mechanism of the modified triethoxysilane is as follows:

[0020] During the reaction process, the hydroxyl group on the 1-hydroxycyclohexyl phenyl ketone molecule undergoes a condensation reaction with the isocyanate group on the isocyanatopropyltriethoxysilane molecule, grafting and modifying the 1-hydroxycyclohexyl phenyl ketone molecule onto the triethoxysilane to prepare the modified triethoxysilane. The mass spectrometry analysis data of the modified triethoxysilane are: m / z: 451.2378 (100.0%), 452.2411 (24.9%), 452.2374 (5.1%), 453.2336 (3.3%), 453.2433 (3.0%), 453.2401 (1.3%), 453.2417 (1.2%).

[0021] B2. Add nano-titanium dioxide, modified triethoxysilane, KH-560, and N,N-dimethylformamide into the reaction kettle, ultrasonically disperse for 30 - 50 min, then turn on the stirring, raise the temperature of the reaction kettle to 60 - 70 °C, add the catalyst solution into the reaction kettle, keep the temperature for reaction for 2 - 3 h, and perform post-treatment to obtain the modified titanium dioxide.

[0022] The synthesis reaction mechanism of the modified titanium dioxide is as follows:

[0023] Under alkaline conditions, the siloxane bond on the modified triethoxysilane and KH-560 molecules hydrolyzes to form silanol groups, which undergo a condensation reaction with the active hydroxyl groups on the surface of the nano-titanium dioxide, forming a modification of 1-hydroxycyclohexyl phenyl ketone and epoxy functional groups on the surface of the nano-titanium dioxide to prepare the modified titanium dioxide.

[0024] Furthermore, in step B1, the dosage ratio of the 1-hydroxycyclohexyl phenyl ketone to the isocyanatopropyltriethoxysilane is 1 mol:1 mol, the dosage ratio of the 1-hydroxycyclohexyl phenyl ketone to acetone is 1 g:7 mL, the isocyanatopropyltriethoxysilane solution is composed of isocyanatopropyltriethoxysilane and acetone according to a weight ratio of 1:3, and the post-treatment includes: after the reaction is completed, distill off acetone under reduced pressure to obtain the modified triethoxysilane.

[0025] Further, in step B2, the dosage ratio of the nano-titanium dioxide, modified triethoxysilane, KH-560, N,N-dimethylformamide and the catalyst solution is 7 g: 3 g: 1 g: 40 mL: 8 mL. The catalyst solution is a 0.3 - 0.5 mol / L sodium hydroxide solution. The post-treatment includes: after the reaction is completed, the temperature of the reaction kettle is reduced to room temperature, and then suction filtration is carried out. The filter cake is washed with purified water until it is neutral and then dried by suction. The filter cake is transferred to a drying oven at a temperature of 65 - 75 °C and vacuum dried to a constant weight to obtain modified titanium dioxide.

[0026] Further, the modified polysiloxane is obtained by the following steps:

[0027] C1. Add dimethyl [3-[(hydroxymethyl)amino]-3-oxopropyl]phosphonate and toluene into a reaction kettle protected by nitrogen and stir. Add 3-isocyanatopropene into the reaction kettle. The temperature of the reaction kettle is raised to 50 - 60 °C and kept warm for reaction for 50 - 70 min. After post-treatment, modified dimethyl phosphonate is obtained.

[0028] The synthesis reaction formula of the modified dimethyl phosphate is:

[0029]

[0030] The synthesis reaction mechanism of the modified dimethyl phosphate is:

[0031] During the reaction, the hydroxyl group on the molecule of dimethyl [3-[(hydroxymethyl)amino]-3-oxopropyl]phosphonate undergoes a condensation reaction with the isocyanate group on the molecule of 3-isocyanatopropene, forming an olefin double bond modification on the molecule of dimethyl [3-[(hydroxymethyl)amino]-3-oxopropyl]phosphonate, and the modified dimethyl phosphonate is prepared. The mass spectrometry data of the modified dimethyl phosphate are: m / z: m / z: 294.0981(100.0%), 295.1014(10.8%), 296.1023(1.2%).

[0032] C2. Add 2,4,6,8-tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, aminopropylmethyldiethoxysilane, 1,1,3,3-tetramethyldisiloxane and a catalyst into the reaction kettle and stir. The temperature of the reaction kettle is raised to 85 - 95 °C and kept warm for reaction for 4 - 6 h. After post-treatment, polysiloxane is obtained.

[0033] The synthesis reaction formula of the polysiloxane is:

[0034]

[0035] The synthesis reaction mechanism of the polysiloxane is:

[0036] During the synthesis process, using 1,1,3,3-tetramethyldisiloxane as the end-capping agent, under the catalysis of a catalyst, 2,4,6,8-tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, aminopropylmethyldiethoxysilane, and 1,1,3,3-tetramethyldisiloxane undergo hydrolysis and then condensation to form -Si-O-Si- bonds, and a long siloxane chain segment modified with amino and silicon hydride is prepared.

[0037] C3. Add polysiloxane, toluene, modified dimethyl phosphate, and a catalyst into a reaction kettle and stir. Raise the temperature of the reaction kettle to 80 - 90 °C, keep the temperature for reaction for 4 - 5 h, and perform post-treatment to obtain modified polysiloxane.

[0038] The synthesis reaction formula of the modified polysiloxane is:

[0039]

[0040] In the formula:

[0041]

[0042] The synthesis reaction mechanism of the modified polysiloxane is:

[0043] During the reaction process, using chloroplatinic acid as the catalyst, the olefin double bond on the modified dimethyl phosphonate molecule undergoes a hydrosilylation reaction with the silicon hydride on the polysiloxane molecular chain segment, and a modified dimethyl phosphonate modification is formed on the polysiloxane chain segment to obtain the modified polysiloxane.

[0044] Furthermore, in step C1, the dosage ratio of [3-[(hydroxymethyl)amino]-3-oxopropyl]-dimethyl phosphonate to 3-isocyanatopropene is 1 mol:1 mol, and the dosage ratio of [3-[(hydroxymethyl)amino]-3-oxopropyl]-dimethyl phosphonate to toluene is 1 g:5 mL. The post-treatment includes: after the reaction is completed, raise the temperature of the reaction kettle to 75 - 85 °C, distill off toluene under reduced pressure to obtain the modified dimethyl phosphonate.

[0045] Furthermore, in step C2, the weight ratio of 2,4,6,8-tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, aminopropylmethyldiethoxysilane, 1,1,3,3-tetramethyldisiloxane, and the catalyst is 7:3:2:1:0.5. The catalyst is 50 - 60 wt% sulfuric acid. The post-treatment includes: after the reaction is completed, lower the temperature of the reaction kettle to room temperature, wash the reaction product with purified water until it is neutral, then raise the temperature of the product system to 90 - 100 °C, and distill off low-boiling impurities under reduced pressure to obtain the polysiloxane.

[0046] Further, in step C3, the dosage ratio of the polysiloxane, toluene, modified dimethyl phosphate, and catalyst is 5 g: 30 mL: 1 g: 0.02 g. The catalyst is chloroplatinic acid. The post-treatment includes: after the reaction is completed, the temperature of the reaction kettle is lowered to room temperature, purified water is added to the reaction kettle, stirred for 10 - 15 min, allowed to stand for liquid separation, the organic phase is transferred to a rotary evaporator at 80 - 90 °C, and the solvent is removed under reduced pressure to obtain the modified polysiloxane.

[0047] Further, the preparation method of the modified PBAT is: uniformly mix PBAT, glycidyl methacrylate, and initiator, and then add them to an internal mixer at 185 - 195 °C, knead for 15 - 18 min, and discharge to obtain the modified PBAT.

[0048] The synthesis reaction mechanism of the modified PBAT is:

[0049] During the preparation process, the free radicals generated by the initiator attack the methylene group on the PBAT molecular chain and the olefin double bond on the glycidyl methacrylate molecule to form free radicals, and then through free radical polymerization reaction, glycidyl methacrylate is modified onto the PBAT molecular chain to prepare the modified PBAT.

[0050] Further, the weight ratio of the PBAT, glycidyl methacrylate, and initiator is 100:7:1, and the initiator is diisopropylbenzene peroxide.

[0051] The present invention also provides a preparation method of a biodegradable PVC composite material. The preparation method of the biodegradable PVC composite material is: add the modified PBAT, modified polysiloxane, modified PVC, diacetyl epoxy vegetable oil glyceride, and additive to a twin-screw extruder, melt and extrude into a molding die, and cool and form to obtain the composite PVC.

[0052] Further, the additive is composed of a dispersant, a lubricant, an antioxidant, and a colorant in a weight ratio of 5:3:2:3. The dispersant is a stearate, the lubricant is one or more of butyl stearate, oleamide, and ethylene bisstearamide, the antioxidant is one or more of antioxidant DPPD, antioxidant PPD, and antioxidant H, the colorant is one or more of titanium dioxide, cadmium red, iron oxide trioxide, carbon black, and chrome yellow. The temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are 210 °C, 215 °C, 220 °C, 220 °C, 220 °C, and 225 °C in sequence, and the main shaft speed of the twin-screw extruder is 18 - 20 rpm.

[0053] The present invention has the following beneficial effects:

[0054] 1. The biodegradable PVC composite material of the present application prepares modified titanium dioxide by surface modification of nano-titanium dioxide with modified triethoxysilane and KH-560. 1-Hydroxycyclohexyl phenyl ketone is used as a photosensitizer, which adsorbs on the surface of nano-titanium dioxide to enhance the light absorption of nano-titanium dioxide. When irradiated with sufficient light energy, the photosensitizer is excited to generate free electrons that are injected into the conduction band of titanium dioxide, realizing the effective separation of photo-generated carriers and improving the photocatalytic activity to accelerate the degradation rate of PVC. The epoxy groups on the surface of the modified titanium dioxide molecule serve as active sites and react with the hydroxyl groups on the hydroxyl-terminated octaethylene glycol chain segment modified on the modified PVC molecular chain under high-temperature conditions to form cross-linking and intercalation, anchoring the modified titanium dioxide on the PVC molecular chain to prevent its migration from the PVC molecular chain.

[0055] 2. The biodegradable PVC composite material of the present application prepares modified PBAT by modifying PBAT and modifying epoxy groups on the PBAT molecular chain. Under high-temperature conditions, the epoxy groups modified on the modified PBAT molecular chain, the polyamino groups contained in the modified polysiloxane molecular chain, and the epoxy groups or oxygen-containing groups on the diacetylated epoxy oleic acid glyceride molecule undergo ring-opening condensation to increase the degree of intermolecular cross-linking and construct a three-dimensional cross-linked network structure. The hydroxyl-terminated octaethylene glycol chain segment modified on the modified PVC molecule increases the flexibility and polarity of the modified PVC molecular weight. Using diacetylated epoxy oleic acid glyceride as a compatibilizer enhances the compatibility between the modified PVC and PBAT, thereby improving the mechanical strength of the material.

[0056] 3. The biodegradable PVC composite material of the present application grafts and modifies dimethyl phosphonate with good flame retardancy on the polysiloxane chain segment. The modified dimethyl phosphonate is evenly distributed in the composite PVC along with the modified polysiloxane. PVC itself is a flame-retardant material, and the modification of dimethyl phosphonate further improves the flame retardancy of the composite PVC. Moreover, polysiloxane itself has excellent heat resistance and oxidation resistance, can remain stable at high temperatures, form a protective silicon-oxygen layer, isolate oxygen and heat, thereby slowing down the combustion rate of the composite PVC material and improving the flame retardancy of the PVC composite material. Detailed implementation manners

[0057] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0058] In the present application:

[0059] The PVC is selected from the polyvinyl chloride powder of Arkema;

[0060] The amino octaethylene glycol hydroxyl is NH2-PEG8-OH, with a molecular weight of 369.45 and a purity of 97.00%;

[0061] The acid value of diacetyl epoxy vegetable oil glyceride is 0.8 - 1.2 mg / g (calculated as potassium hydroxide), and the epoxy group is 5 - 8%.

[0062] Example 1

[0063] A preparation method of modified PVC for a biodegradable PVC composite material in this example includes the following steps:

[0064] A1. Preparation of modified titanium dioxide

[0065] Weigh: 49.5 g of isocyanatopropyltriethoxysilane and acetone are mixed evenly according to a weight ratio of 1:3 to obtain an isocyanatopropyltriethoxysilane solution for standby;

[0066] Weigh: 40.9 g of 1-hydroxycyclohexyl phenyl ketone and 286.3 mL of acetone are added to a reaction kettle under nitrogen protection and stirred. The temperature of the reaction kettle is raised to 45 °C, and the above-prepared isocyanatopropyltriethoxysilane solution is added dropwise to the reaction kettle. After the addition is complete, keep the temperature for reaction for 60 min, and remove acetone by reduced pressure distillation to obtain modified triethoxysilane;

[0067] Weigh: 140 g of nano-titanium dioxide, 60 g of modified triethoxysilane, 20 g of KH-560, and 800 mL of N,N-dimethylformamide are added to the reaction kettle, ultrasonically dispersed for 30 min, then switched to stirring. The temperature of the reaction kettle is raised to 60 °C, 160 mL of 0.3 mol / L sodium hydroxide solution is added to the reaction kettle, and the temperature is kept for reaction for 2 h. The temperature of the reaction kettle is lowered to room temperature, filtered by suction. The filter cake is washed with purified water until neutral and then dried by suction. The filter cake is transferred to a drying oven at 65 °C and vacuum dried to constant weight to obtain modified titanium dioxide.

[0068] A2. PVC pretreatment

[0069] Mix the amino octaethylene glycol hydroxyl and tetrahydrofuran evenly at a ratio of 1 g:40 mL to obtain a pretreatment solution;

[0070] Weigh: 100 g of PVC and 1600 mL of the pretreatment solution are added to the reaction kettle and stirred. The temperature of the reaction kettle is raised to reflux, and the temperature is kept for reaction for 3 h. The temperature of the reaction kettle is lowered to room temperature, 3200 mL of methanol is added to the reaction kettle, and the temperature is kept for stirring for 30 min. Filter by suction. The filter cake is washed with methanol 3 times and then dried by suction. The filter cake is transferred to a drying oven at 50 °C and vacuum dried to constant weight to obtain pretreated PVC.

[0071] A3. Preparation of Modified PVC

[0072] Mix the stearate and sodium polyvinyl alcohol evenly according to the weight ratio of 1:2 to obtain a dispersant;

[0073] Weigh according to parts by weight: 100 parts of pretreated PVC, 12 parts of modified titanium dioxide, and 3 parts of dispersant. After mixing evenly, add them to a twin-screw extruder. The temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are 200°C, 210°C, 210°C, 210°C, 210°C, and 215°C in sequence. Set the main shaft speed to 18 rpm, and melt-extrude and pelletize through the twin-screw extruder to obtain modified PVC.

[0074] Example 2

[0075] A preparation method of modified PVC for a biodegradable PVC composite material in this example includes the following steps:

[0076] A1. Preparation of Modified Titanium Dioxide

[0077] Weigh: 49.5 g of isocyanatopropyltriethoxysilane and acetone are mixed evenly according to the weight ratio of 1:3 to obtain an isocyanatopropyltriethoxysilane solution for standby;

[0078] Weigh: 40.9 g of 1-hydroxycyclohexyl phenyl ketone and 286.3 mL of acetone are added to a reaction kettle under nitrogen protection and stirred. The temperature of the reaction kettle is raised to 47°C, and the above-prepared isocyanatopropyltriethoxysilane solution is added dropwise to the reaction kettle. After the addition is completed, keep the temperature for reaction for 70 min, and distill off acetone under reduced pressure to obtain modified triethoxysilane;

[0079] Weigh: 140 g of nano-titanium dioxide, 60 g of modified triethoxysilane, 20 g of KH-560, and 800 mL of N,N-dimethylformamide are added to the reaction kettle, ultrasonically dispersed for 40 min, then switched to stirring, the temperature of the reaction kettle is raised to 65°C, 160 mL of 0.4 mol / L sodium hydroxide solution is added to the reaction kettle, keep the temperature for reaction for 2.5 h, lower the temperature of the reaction kettle to room temperature, filter by suction, wash the filter cake with purified water until neutral and then drain it by suction, transfer the filter cake to a drying oven at 70°C, and vacuum dry to constant weight to obtain modified titanium dioxide.

[0080] A2. PVC Pretreatment

[0081] Mix amino octaethylene glycol hydroxyl and tetrahydrofuran evenly according to 1 g:40 mL to obtain a pretreatment solution;

[0082] Weigh: 100 g of PVC and 1600 mL of the pretreatment solution, add them to a reaction kettle and stir. Raise the temperature of the reaction kettle to reflux, keep the temperature for 3.5 h, then lower the temperature of the reaction kettle to room temperature. Add 3200 mL of methanol to the reaction kettle, keep the temperature and stir for 40 min, then carry out suction filtration. Wash the filter cake with methanol three times and then drain it. Transfer the filter cake to a drying oven at 55 °C and dry it under vacuum until constant weight to obtain pretreated PVC.

[0083] A3. Preparation of modified PVC

[0084] Mix stearate and sodium polyvinyl alcohol evenly according to a weight ratio of 1:2 to obtain a dispersant.

[0085] Weigh according to parts by weight: 100 parts of pretreated PVC, 13 parts of modified titanium dioxide and 4 parts of dispersant. Mix them evenly and then add them to a twin-screw extruder. The temperatures of the six temperature zones of the twin-screw extruder from the feeding end to the discharging end are 200 °C, 210 °C, 210 °C, 210 °C, 210 °C, and 215 °C in sequence. Set the main shaft speed to 19 rpm, and carry out melt extrusion and pelletizing through the twin-screw extruder to obtain modified PVC.

[0086] Example 3

[0087] A preparation method of modified PVC for a biodegradable PVC composite material in this example includes the following steps:

[0088] A1. Preparation of modified titanium dioxide

[0089] Weigh: 49.5 g of isocyanatopropyltriethoxysilane and mix it evenly with acetone according to a weight ratio of 1:3 to obtain an isocyanatopropyltriethoxysilane solution for standby.

[0090] Weigh: 40.9 g of 1-hydroxycyclohexyl phenyl ketone and 286.3 mL of acetone, add them to a reaction kettle under nitrogen protection and stir. Raise the temperature of the reaction kettle to 50 °C, and dropwise add the above-prepared isocyanatopropyltriethoxysilane solution for standby to the reaction kettle. After dropping, keep the temperature for 80 min, and remove acetone by reduced pressure distillation to obtain modified triethoxysilane.

[0091] Weigh: 140 g of nano-titanium dioxide, 60 g of modified triethoxysilane, 20 g of KH-560, and 800 mL of N,N-dimethylformamide, add them to a reaction kettle, carry out ultrasonic dispersion for 50 min, then switch to stirring. Raise the temperature of the reaction kettle to 70 °C, add 160 mL of 0.5 mol / L sodium hydroxide solution to the reaction kettle, keep the temperature for 3 h, lower the temperature of the reaction kettle to room temperature, carry out suction filtration, wash the filter cake with purified water until neutral and then drain it. Transfer the filter cake to a drying oven at 75 °C and dry it under vacuum until constant weight to obtain modified titanium dioxide.

[0092] A2. PVC pretreatment

[0093] Mix 1 g of amino octaethylene glycol hydroxyl and 40 mL of tetrahydrofuran evenly to obtain a pretreatment solution;

[0094] Weigh: 100 g of PVC and 1600 mL of the pretreatment solution, add them to a reaction kettle and stir. Heat the temperature of the reaction kettle to reflux, keep the temperature for 4 h, then lower the temperature of the reaction kettle to room temperature. Add 3200 mL of methanol to the reaction kettle, keep the temperature and stir for 50 min, then filter. Wash the filter cake with methanol three times and then drain it. Transfer the filter cake to a drying oven at 60 °C and vacuum dry it to constant weight to obtain pretreated PVC.

[0095] A3. Preparation of modified PVC

[0096] Mix stearate and sodium polyvinyl alcohol evenly at a weight ratio of 1:2 to obtain a dispersant;

[0097] Weigh according to parts by weight: 100 parts of pretreated PVC, 15 parts of modified titanium dioxide and 5 parts of dispersant. Mix them evenly and then add them to a twin-screw extruder. The temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are 200 °C, 210 °C, 210 °C, 210 °C, 210 °C, and 215 °C in sequence. Set the main shaft speed to 20 rpm, and melt extrude and pelletize through the twin-screw extruder to obtain modified PVC.

[0098] Example 4

[0099] A preparation method of a biodegradable PVC composite material in this example includes the following steps:

[0100] S1. Preparation of modified dimethyl phosphonate

[0101] Weigh: 211.2 g of [3-[(hydroxymethyl)amino]-3-oxopropyl]-dimethyl phosphonate and 1126.5 mL of toluene, add them to a reaction kettle under nitrogen protection and stir. Add 83.1 g of 3-isocyanatopropene to the reaction kettle. Heat the temperature of the reaction kettle to 50 °C and keep the temperature for 50 min. Then heat the temperature of the reaction kettle to 75 °C and distill off toluene under reduced pressure to obtain modified dimethyl phosphonate.

[0102] S2. Preparation of modified polysiloxane

[0103] Weigh: 70 g of 2,4,6,8-tetramethylcyclotetrasiloxane, 30 g of octamethylcyclotetrasiloxane, 20 g of aminopropylmethyldiethoxysilane, 10 g of 1,1,3,3-tetramethyldisiloxane and 5 g of 50 wt% sulfuric acid and add them to a reaction kettle for stirring. Raise the temperature of the reaction kettle to 85 °C, keep the temperature for reaction for 4 h, then lower the temperature of the reaction kettle to room temperature. After washing the reaction product with purified water until it is neutral, transfer the product to a rotary evaporator, raise the temperature of the heat exchange medium to 90 °C, and distill off low-boiling impurities under reduced pressure to obtain polysiloxane;

[0104] Weigh: 100 g of polysiloxane, 600 mL of toluene, 20 g of modified dimethyl phosphonate and 0.4 g of chloroplatinic acid and add them to a reaction kettle for stirring. Raise the temperature of the reaction kettle to 80 °C, keep the temperature for reaction for 4 h, then lower the temperature of the reaction kettle to room temperature. Add 300 mL of purified water to the reaction kettle, stir for 10 min, let it stand for liquid separation, transfer the organic phase to a rotary evaporator, set the temperature of the heat exchange medium to 80 °C, and distill off the solvent under reduced pressure to obtain modified polysiloxane.

[0105] S3. Prepare modified PBAT

[0106] Weigh by weight: 100 parts of PBAT, 7 parts of glycidyl methacrylate and 1 part of dicumyl peroxide, mix them evenly and then add them to an internal mixer at a temperature of 185 °C, knead for 15 min, discharge to obtain modified PBAT.

[0107] S4. Prepare composite PVC

[0108] Weigh by weight: 5 parts of calcium stearate, 3 parts of butyl stearate, 2 parts of antioxidant DPPD, 3 parts of cadmium red, mix them evenly to obtain an additive;

[0109] Weigh by weight: 80 parts of modified PBAT, 14 parts of modified polysiloxane, 35 parts of modified PVC prepared in Example 1, 10 parts of diacetyl epoxy vegetable oil glyceride and 5 parts of the additive, add them to a twin-screw extruder. The temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are 210 °C, 215 °C, 220 °C, 220 °C, 220 °C, 225 °C in sequence. Set the main shaft speed to 18 rpm, melt and extrude through the twin-screw extruder into a molding die, cool and form to obtain composite PVC.

[0110] Example 5

[0111] A preparation method of a biodegradable PVC composite material in this example includes the following steps:

[0112] S1. Prepare modified dimethyl phosphonate

[0113] Weigh: 211.2 g of dimethyl [3-[(hydroxymethyl)amino]-3-oxopropyl]phosphonate and 1126.5 mL of toluene, add them to a reaction kettle protected by nitrogen and stir. Then add 83.1 g of 3-isocyanatopropene to the reaction kettle. Raise the temperature of the reaction kettle to 55 °C and keep the temperature for 60 min. Then raise the temperature of the reaction kettle to 80 °C and distill off toluene under reduced pressure to obtain modified dimethyl phosphonate.

[0114] S2. Prepare modified polysiloxane

[0115] Weigh: 70 g of 2,4,6,8-tetramethylcyclotetrasiloxane, 30 g of octamethylcyclotetrasiloxane, 20 g of aminopropylmethyldiethoxysilane, 10 g of 1,1,3,3-tetramethyldisiloxane and 5 g of 55 wt% sulfuric acid, add them to a reaction kettle and stir. Raise the temperature of the reaction kettle to 90 °C and keep the temperature for 5 h. Then lower the temperature of the reaction kettle to room temperature. After washing the reaction product with purified water until neutral, transfer the product to a rotary evaporator. Raise the temperature of the heat exchange medium to 95 °C and distill off low-boiling impurities under reduced pressure to obtain polysiloxane.

[0116] Weigh: 100 g of polysiloxane, 600 mL of toluene, 20 g of modified dimethyl phosphonate and 0.4 g of chloroplatinic acid, add them to a reaction kettle and stir. Raise the temperature of the reaction kettle to 85 °C and keep the temperature for 4.5 h. Then lower the temperature of the reaction kettle to room temperature. Add 300 mL of purified water to the reaction kettle, stir for 13 min, let it stand for liquid separation, transfer the organic phase to a rotary evaporator, set the temperature of the heat exchange medium to 85 °C and distill off the solvent to obtain modified polysiloxane.

[0117] S3. Prepare modified PBAT

[0118] Weigh by weight parts: 100 parts of PBAT, 7 parts of glycidyl methacrylate and 1 part of dicumyl peroxide, mix them evenly and then add them to an internal mixer at 190 °C, knead for 17 min, discharge to obtain modified PBAT.

[0119] S4. Prepare composite PVC

[0120] Weigh by weight parts: 5 parts of zinc stearate, 3 parts of oleamide, 2 parts of antioxidant PDD and 3 parts of iron(III) oxide, mix them evenly to obtain an additive.

[0121] Weigh by parts by weight: 85 parts of modified PBAT, 16 parts of modified polysiloxane, 40 parts of modified PVC prepared in Example 2, 11 parts of diacetyl epoxy vegetable oil glyceride, and 6 parts of additive assistant, and add them to a twin-screw extruder. The temperatures of the 6 temperature zones of the twin-screw extruder from the feeding end to the discharging end are 210 °C, 215 °C, 220 °C, 220 °C, 220 °C, and 225 °C in sequence. Set the main shaft speed to 19 rpm, melt and extrude through the twin-screw extruder into a forming die, cool and form to obtain composite PVC.

[0122] Example 6

[0123] A preparation method of a biodegradable PVC composite material in this example includes the following steps:

[0124] S1. Prepare modified dimethyl phosphonate

[0125] Weigh: 211.2 g of [3-[(hydroxymethyl)amino]-3-oxopropyl]-dimethyl phosphonate and 1126.5 mL of toluene, add them to a reaction kettle under nitrogen protection and stir. Add 83.1 g of 3-isocyanatopropene to the reaction kettle. The temperature of the reaction kettle rises to 60 °C, keep the temperature for reaction for 70 min, the temperature of the reaction kettle rises to 85 °C, and toluene is removed by reduced pressure distillation to obtain modified dimethyl phosphonate.

[0126] S2. Prepare modified polysiloxane

[0127] Weigh: 70 g of 2,4,6,8-tetramethylcyclotetrasiloxane, 30 g of octamethylcyclotetrasiloxane, 20 g of aminopropylmethyldiethoxysilane, 10 g of 1,1,3,3-tetramethyldisiloxane, and 5 g of 60 wt% sulfuric acid, add them to a reaction kettle and stir. The temperature of the reaction kettle rises to 95 °C, keep the temperature for reaction for 6 h, the temperature of the reaction kettle drops to room temperature. After washing the reaction product with purified water until neutral, transfer the product to a rotary evaporator, raise the temperature of the heat exchange medium to 100 °C, and remove low-boiling impurities by reduced pressure distillation to obtain polysiloxane;

[0128] Weigh: 100 g of polysiloxane, 600 mL of toluene, 20 g of modified dimethyl phosphonate, and 0.4 g of chloroplatinic acid, add them to a reaction kettle and stir. The temperature of the reaction kettle rises to 90 °C, keep the temperature for reaction for 5 h, the temperature of the reaction kettle drops to room temperature. Add 300 mL of purified water to the reaction kettle, stir for 15 min, let it stand for liquid separation, transfer the organic phase to a rotary evaporator, set the temperature of the heat exchange medium to 90 °C, and remove the solvent by reduced pressure distillation to obtain modified polysiloxane.

[0129] S3. Prepare modified PBAT

[0130] Weigh by parts by weight: 100 parts of PBAT, 7 parts of glycidyl methacrylate, and 1 part of dicumyl peroxide. After mixing evenly, add them to an internal mixer at a temperature of 195°C, knead for 18 minutes, discharge the material, and obtain modified PBAT.

[0131] S4. Prepare composite PVC

[0132] Weigh by parts by weight: 5 parts of magnesium stearate, 3 parts of ethylene bisstearamide, 2 parts of antioxidant H, and 3 parts of chrome yellow. Mix evenly to obtain an additive

[0133] Weigh by parts by weight: 90 parts of modified PBAT, 19 parts of modified polysiloxane, 45 parts of modified PVC prepared in Example 3, 12 parts of diacetyl epoxy vegetable oil glyceride, and 7 parts of the additive. Add them to a twin-screw extruder. The temperatures of the 6 temperature zones of the twin-screw extruder from the feed end to the discharge end are 210°C, 215°C, 220°C, 220°C, 220°C, and 225°C in sequence. Set the main shaft speed to 20 rpm, melt and extrude through the twin-screw extruder into a molding die, cool and form to obtain composite PVC.

[0134] Comparative Example 1

[0135] The difference between this comparative example and Example 6 is that when preparing the modified PVC used, in step A1, modified triethoxysilane was not added.

[0136] Comparative Example 2

[0137] The difference between this comparative example and Example 6 is that when preparing the modified PVC used, step A2 was cancelled, and the PVC in step A2 was used to replace the pretreated PVC in step A3.

[0138] Comparative Example 3

[0139] The difference between this comparative example and Example 6 is that step S1 was cancelled, and the polysiloxane in step S2 was used to replace the modified polysiloxane in step S4.

[0140] Comparative Example 4

[0141] The difference between this comparative example and Example 6 is that step S3 was cancelled, and the PBAT in step S3 was used to replace the modified PBAT in step S4.

[0142] Comparative Example 5

[0143] The difference between this comparative example and Example 6 is that in step S4, diacetyl epoxy vegetable oil glyceride was not added.

[0144] Performance test:

[0145] The biodegradation rate of the composite PVC specimens prepared in Examples 1-3 and Comparative Examples 1-5 and the weight-average relative molecular mass reduction rate of the modified PVC in the specimens were determined with reference to the standard GB / T 20197-2006 "Definition, Classification, Marking and Degradation Performance Requirements for Degradable Plastics".

[0146] The tensile strength and tensile strain of the composite PVC specimens prepared in Examples 1-3 and Comparative Examples 1-5 were determined with reference to the standards GB / T 1040.1-2018 "Plastics - Determination of tensile properties - Part 1: General principles" and GB / T 1040.2-2022 "Plastics - Determination of tensile properties - Part 2: Test conditions for moulded and extruded plastics".

[0147] The vertical burning grade of the composite PVC specimens prepared in Examples 1-3 and Comparative Examples 1-5 was determined with reference to the standard GB / T 2408-2021 "Plastics - Determination of burning behaviour - Horizontal and vertical methods". The specific test results are shown in Table 1 below.

[0148] Table 1 - Data Sheet for Performance Detection of Specimens

[0149]

[0150] Data Analysis:

[0151] By comparing and analyzing the data in Table 1 above, the biodegradation rate of the PVC composite material prepared in the present invention reaches 58.6%, the tensile strength reaches 26.91 MPa, the tensile strain reaches 365.3%, the vertical burning grade reaches V-0, and the weight-average relative molecular mass reduction rate of the ultraviolet decomposition of the modified PVC used reaches 28.33%. All the performance detection data are better than those of the comparative examples. Therefore, in the present invention, after modifying the PVC material, it is combined with modified polysiloxane and modified PBAT, which not only effectively improves the biodegradation performance of the composite PVC material, but also improves the mechanical strength and flame retardancy of the composite PVC material. Moreover, the modified PVC used in the composite PVC can degrade in the ultraviolet environment, which can effectively reduce the impact of the PVC material on environmental pollution.

[0152] The above content is only an example and illustration of the structure of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

[0153] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

[0154] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not elaborate on all details, nor do they limit the present invention to only the specific implementation manners. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the relevant art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A biodegradable PVC composite material, characterized in that, By weight parts, it includes the following components: 80 - 90 parts of modified PBAT, 14 - 19 parts of modified polysiloxane, 35 - 45 parts of modified PVC, 10 - 12 parts of diacetyl epoxy vegetable oil glyceride, and 5 - 7 parts of additive; The modified PVC is obtained by the following steps: A1. Add PVC and the pretreatment solution into a reaction kettle and stir. Raise the temperature of the reaction kettle to reflux, keep the temperature for reaction for 3 - 4 h, and perform post - treatment to obtain pretreated PVC; A2. Mix the pretreated PVC, modified titanium dioxide, and dispersant evenly, then add them into a twin - screw extruder for melt extrusion and pelletizing to obtain modified PVC.

2. A biodegradable PVC composite material according to claim 1, characterized in that, In step A1, the dosage ratio of PVC to the pretreatment solution is 1 g:16 mL, and the pretreatment solution is composed of amino octaethylene glycol hydroxyl and tetrahydrofuran in a ratio of 1 g:40 mL; in step A2, the weight ratio of the pretreated PVC, modified titanium dioxide, and dispersant is 100:12 - 15:3 - 5, and the dispersant is composed of stearate and sodium polyvinyl in a weight ratio of 1:

2.

3. A biodegradable PVC composite material according to claim 1, characterized in that, The modified titanium dioxide is obtained by the following steps: B1. Add 1 - hydroxycyclohexyl phenyl ketone and acetone into a reaction kettle under nitrogen protection and stir. Raise the temperature of the reaction kettle to 45 - 50 °C, and dropwise add isocyanatopropyltriethoxysilane solution to the reaction kettle. After dropping, keep the temperature for reaction for 60 - 80 min, and perform post - treatment to obtain modified triethoxysilane; B2. Add nano - titanium dioxide, modified triethoxysilane, KH - 560, and N,N - dimethylformamide into a reaction kettle, perform ultrasonic dispersion for 30 - 50 min, then turn to stirring. Raise the temperature of the reaction kettle to 60 - 70 °C, add the catalyst solution to the reaction kettle, keep the temperature for reaction for 2 - 3 h, and perform post - treatment to obtain modified titanium dioxide.

4. A biodegradable PVC composite according to claim 3, characterized in that, In step B1, the dosage ratio of 1 - hydroxycyclohexyl phenyl ketone to isocyanatopropyltriethoxysilane is 1 mol:1 mol, the dosage ratio of 1 - hydroxycyclohexyl phenyl ketone to acetone is 1 g:7 mL, and the isocyanatopropyltriethoxysilane solution is composed of isocyanatopropyltriethoxysilane and acetone in a weight ratio of 1:3; in step B2, the dosage ratio of nano - titanium dioxide, modified triethoxysilane, KH - 560, N,N - dimethylformamide, and the catalyst solution is 7 g:3 g:1 g:40 mL:8 mL, and the catalyst solution is 0.3 - 0.5 mol / L sodium hydroxide solution.

5. A biodegradable PVC composite according to claim 1, characterized in that, The modified polysiloxane is obtained by the following steps: C1. Add [3 - [(hydroxymethyl)amino] - 3 - oxopropyl] - phosphonic acid dimethyl ester and toluene into a reaction kettle under nitrogen protection and stir. Add 3 - isocyanatopropene to the reaction kettle, raise the temperature of the reaction kettle to 50 - 60 °C, keep the temperature for reaction for 50 - 70 min, and perform post - treatment to obtain modified phosphonic acid dimethyl ester; C2. Add 2,4,6,8 - tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, aminopropylmethyldiethoxysilane, 1,1,3,3 - tetramethyldisiloxane, and a catalyst into a reaction kettle and stir. Raise the temperature of the reaction kettle to 85 - 95 °C, keep the temperature for reaction for 4 - 6 h, and perform post - treatment to obtain polysiloxane; C3. Add polysiloxane, toluene, modified dimethyl phosphate, and a catalyst into a reaction kettle and stir. Raise the temperature of the reaction kettle to 80 - 90 °C, keep the temperature for reaction for 4 - 5 h, and perform post-treatment to obtain modified polysiloxane.

6. The biodegradable PVC composite material according to claim 5, wherein, In step C1, the dosage ratio of [3 - [(hydroxymethyl)amino] - 3 - oxopropyl] - dimethyl phosphonate to 3 - isocyanatopropene is 1 mol:1 mol, and the dosage ratio of [3 - [(hydroxymethyl)amino] - 3 - oxopropyl] - dimethyl phosphonate to toluene is 1 g:5 mL; in step C2, the weight ratio of 2,4,6,8 - tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, aminopropylmethyldiethoxysilane, 1,1,3,3 - tetramethyldisiloxane, and the catalyst is 7:3:2:1:0.5, and the catalyst is 50 - 60 wt% sulfuric acid; in step C3, the dosage ratio of the polysiloxane, toluene, modified dimethyl phosphate, and the catalyst is 5 g:30 mL:1 g:0.02 g, and the catalyst is chloroplatinic acid.

7. A biodegradable PVC composite according to claim 1, characterized in that, The preparation method of modified PBAT is as follows: Mix PBAT, glycidyl methacrylate, and an initiator evenly and then add them into an internal mixer at a temperature of 185 - 195 °C, knead for 15 - 18 min, and discharge to obtain modified PBAT.

8. A biodegradable PVC composite material according to claim 7, characterized in that, The weight ratio of the PBAT, glycidyl methacrylate, and the initiator is 100:7:1, and the initiator is diisopropyl peroxide.

9. The preparation method of a biodegradable PVC composite material according to any one of claims 1-8, characterized in that, The preparation method of the biodegradable PVC composite material is as follows: Add modified PBAT, modified polysiloxane, modified PVC, diacetyl epoxy oleic acid glyceride, and an additive into a twin - screw extruder, melt - extrude into a forming die, and cool and form to obtain composite PVC.

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