Preparation method of heat-resistant stable granules suitable for PVC (polyvinyl chloride)

Abstract

The invention relates to the field of PVC (polyvinyl chloride) composite granules, and discloses a preparation method of PVC heat-resistant stable granules. The preparation method comprises the following steps: S1, preparing the silicon dioxide filler by adopting a sol-gel method; s2, a vinyl chloride monomer, N-butoxy methacryloyl and waterborne polyurethane are taken to be mixed and crosslinked, and the modified PVC resin is obtained. And S3, adding a silicon dioxide filler while blending and cross-linking. And S4, stirring and mixing the modified PVC resin, the antioxidant, the stabilizer and the lubricant to form slurry. And S5, performing melt extrusion, wherein fine-bundle-shaped materials are formed in a sieving nozzle before extrusion. And S6, the fine-bundle-shaped materials enter a horizontal stirring machine to be broken to form particles. And S7, sieving the particles, and molding to obtain the polyvinyl chloride particles. According to the present invention, the polyvinyl chloride particle material with characteristics of good water resistance and good heat resistance can be prepared, the chemical reaction degradation caused by water can be avoided, the retention time of the high temperature section in the whole preparation process is short, and the probability of polyvinyl chloride thermal decomposition dechlorination can be reduced.

Description

Technical Field

[0001] The invention relates to the field of PVC composite granules, in particular to a preparation method suitable for PVC heat-resistant and stable granules. Background Art

[0002] PVC is a synthetic plastic resin formed by free radical polymerization of vinyl chloride monomer. PVC resin is a hard and tough material. Its decomposition temperature is very close to the plasticizing temperature, and its mechanical strength is poor. Therefore, it is impossible to directly use PVC resin to mold products. Instead, it is necessary to add toughening agents, stabilizers and fillers to improve the performance. After PVC granules are made, they are processed into various products. PVC granules are widely used in flame-retardant plastic films, wires and cables, disposable plastic packaging and plastic products, drainage pipes, plastic toys, shopping bags, gloves, cling film and artificial leather.

[0003] Now, referring to the invention patent with application number 202311691747.1, special granules for high temperature resistant and impact resistant rigid polyvinyl chloride corrugated pipes and their preparation method, in the preparation process, in order to improve the toughness of the material, a toughening agent is added, resulting in the product being highly toxic and not environmentally friendly. In addition, since polyvinyl chloride will thermally decompose and release hydrogen chloride at 100-120°C, the preparation process is not environmentally friendly. Summary of the invention

[0004] In view of the above shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing heat-resistant and stable PVC polyvinyl chloride granules to obtain polyvinyl chloride granules with good waterproofness and heat resistance, thereby improving the environmental friendliness of the preparation process.

[0005] A method for preparing heat-resistant and stable granules of PVC polyvinyl chloride comprises the following steps: S1 is a silica filler prepared by a sol-gel method and is ready for use; S2 takes vinyl chloride monomer, N-butoxymethyl acryloyl and waterborne polyurethane and mixes and crosslinks them to obtain modified PVC resin; S3 adds silica filler while blending and crosslinking; S4: taking modified PVC resin, antioxidant, stabilizer and lubricant, stirring and mixing to form a slurry; S5: the slurry is fed into a twin-screw extruder for melt extrusion, and is passed through a sieve before extrusion to form a thin bundle of materials; S6 The thin bundles of materials enter the horizontal mixer and are broken into particles; The S7 particles are sieved and then molded to obtain polyvinyl chloride pellets.

[0006] As a further improvement of the above solution, the preparation of the silica filler is specifically operated as follows: S11 Mix the silicate ester and absolute ethanol in a volume ratio of 1:10 - 15, stir evenly at room temperature to obtain a mixed solution, add cetyltrimethylammonium bromide to the mixed solution, and stir at 30 - 60 °C until completely dissolved; S12 Drop deionized water into the solution obtained in S11 at a rate of 5 - 10 ml / min under magnetic stirring conditions, adjust the pH of the solution to 3 - 5, and age the obtained solution at room temperature for 8 - 12 h to obtain a gel; S13 Place the gel in a muffle furnace for calcination to remove cetyltrimethylammonium bromide. The calcination temperature is 400 - 500 °C, the calcination time is 1 - 2 h. After the calcination product is taken out and washed with absolute ethanol until neutral, it is placed in a constant temperature drying oven and dried at 60 - 80 °C, and then ground and filtered in sequence to obtain nano-silica powder.

[0007] As a further improvement of the above solution, the dosage standard of cetyltrimethylammonium bromide is: add 1 - 3 g of cetyltrimethylammonium bromide to every 10 ml of silicate ester.

[0008] As a further improvement of the above solution, the weight ratio of the vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane resin is 1 - 2:0.5 - 1:0.2 - 0.6. In the present invention, the modified PVC resin obtained by blending and crosslinking vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane is used as the resin matrix of the target product PVC polyvinyl chloride. Among them, the hydrophilic groups of the waterborne polyurethane form hydrogen bonds with water molecules, increasing the solubility and stability of the polymer in water. The active groups in the waterborne polyurethane undergo crosslinking reactions with N-butoxymethyl methacrylate and vinyl chloride monomer to form a three-dimensional network structure, significantly improving the water resistance and mechanical strength of the material. And, introducing silica to form hydrophobic groups to further improve the waterproof performance, so as to achieve the effect of improving the water resistance and comprehensive performance of the prepared modified PVC resin. During the aforementioned crosslinking process, no harmful gases such as formaldehyde are released, making the preparation process environmentally friendly and non-polluting to the environment.

[0009] As a further improvement of the above solution, the method for blending and crosslinking to obtain the modified PVC resin is specifically operated as follows: S21 Take vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane resin and mix them to obtain a resin stock solution; S22 Dilute ammonium persulfate with deionized water to obtain an initiator; S23 Take 10% of the resin stock solution and 10% of the initiator and add them to the reaction kettle, stir and mix for 10 min, then introduce steam into the reaction kettle and raise the temperature in the kettle to 80 °C, and carry out a polymerization reaction at 80 °C for 20 - 40 min; S24 was maintained at a temperature of 80 °C, and the remaining resin stock solution and initiator were continuously added dropwise for 4 h. The addition was stopped when the conversion rate reached 99.5% to obtain a polymerization product, i.e., modified PVC resin.

[0010] In the present invention, a two-stage polymerization method is adopted, so that 10% of the resin stock solution and 10% of the initiator are pre-reacted for a period of time, making the subsequent added resin stock solution and initiator react more fully, thereby improving the conversion rate.

[0011] As a further improvement of the above solution, the weight ratio of the silica filler to the waterborne polyurethane resin is 1:1 to 3.

[0012] As a further improvement of the above solution, during the process of stirring and mixing to form a slurry, the stirring temperature is 80 to 90 °C.

[0013] As a further improvement of the above solution, the antioxidant is any one of BHT, BHA, DTPD, and IPPD. In the present invention, an antioxidant is added to prevent the resin material from undergoing an oxidation reaction, so that the PVC polyvinyl chloride pellets can resist thermal-oxidative degradation.

[0014] As a further improvement of the above solution, the stabilizer includes calcium soap, zinc soap, and polyols. In the present invention, a stabilizer is added to coordinate and bind with the unstable chlorine atoms in the polyvinyl chloride molecules, displace the unstable allyl chloride atoms or tertiary carbon chloride atoms, eliminate the degradation initiation sites, and improve the light and heat stability of the PVC polyvinyl chloride pellets. In the present invention, a binary composite heat stabilizer system of calcium soap + zinc soap is added in a synergistic manner. Calcium soap and zinc soap combine with chlorine atoms to form metal chlorides, while polyols transfer the chlorine atoms to calcium soap to regenerate zinc soap, and cooperate synergistically to obtain a good stabilizing effect.

[0015] As a further improvement of the above solution, the lubricant is any one of glycerol partial fatty acid ester, fatty acid composite ester, polyethylene wax, and oxidized polyethylene wax. In the present invention, the purpose of adding a lubricant is to reduce the cohesive force between polymer molecular chains, accelerate melting, reduce the melt viscosity of the resin, make it flow more easily during the processing, and form a lubricating film between the resin and the surface of the processing equipment to reduce friction and wear, thereby reducing processing losses.

[0016] As a further improvement of the above solution, the compression ratio of the conical twin-screw of the twin-screw extruder is 3.5 to 5.0, the screw speed is 30 to 50 r / min, and the extrusion temperature is 150 to 180 °C.

[0017] As a further improvement of the above solution, the rotation speed of the horizontal mixer is 30 to 60 r / min; the sieved particles roll in the pelletizing pan to form polyvinyl chloride pellets.

[0018] As a further improvement of the above solution, the weight parts composition of the PVC granules is as follows: 50-80 parts of modified PVC resin, 7-12 parts of silica filler, 2-5 parts of antioxidant, 1-7 parts of stabilizer, and 1-3 parts of lubricant.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: In the present invention, a modified PVC resin obtained by blending and crosslinking vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane is used as the resin matrix of the target product PVC polyvinyl chloride. Among them, the hydrophilic groups of the waterborne polyurethane form hydrogen bonds with water molecules, increasing the solubility and stability of the polymer in water. The active groups in the waterborne polyurethane undergo crosslinking reactions with N-butoxymethyl methacrylate and vinyl chloride monomer to form a three-dimensional network structure, significantly improving the water resistance and mechanical strength of the material. Moreover, the introduction of silica forms hydrophobic groups to further improve the waterproof performance, thereby achieving the effect of improving the water resistance and comprehensive performance of the prepared modified PVC resin. During the aforementioned crosslinking process, no harmful gases such as formaldehyde are released, making the preparation process environmentally friendly and non-polluting to the environment.

[0020] In the present invention, the stabilizer used is a binary composite heat stabilizer system with synergistic cooperation of calcium soap + zinc soap. Calcium soap and zinc soap combine with chlorine atoms to form metal chlorides, while polyols transfer chlorine atoms to calcium soap to regenerate zinc soap, achieving good stabilization effects through synergistic cooperation.

[0021] The PVC granules prepared by the present invention have good waterproofness and heat resistance, can avoid chemical reaction degradation caused by moisture, and moreover, the residence time in the high-temperature section during the entire preparation process is short, which can reduce the probability of thermal decomposition and dechlorination of polyvinyl chloride.

[0022] In the preparation of PVC granules by the present invention, the ingredients used are environmentally friendly, and the crosslinking modification method is adopted to improve the plasticity of the material without introducing toxic toughening agents. Specific Embodiments

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following will further elaborate on the present invention in combination with embodiments. The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. It should be understood that the following description is only used to explain the present invention and is not used to limit the present invention.

[0024] As used herein, the terms "comprising", "including", "containing" or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or apparatus containing the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article or apparatus.

[0025] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed individually. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise specified, the range is intended to include its end values and all integers and fractions within the range.

[0026] The following provides a detailed description of specific embodiments of the present invention. Example 1

[0027] The example provides a preparation method applicable to heat-resistant stable pellets of PVC (polyvinyl chloride), characterized by including the following steps: S1 Prepare silica filler by the sol-gel method for later use.

[0028] The preparation of silica filler is specifically operated as follows: S11 Mix silicate ester and absolute ethanol in a volume ratio of 1:10, stir evenly at room temperature to obtain a mixed solution, add cetyltrimethylammonium bromide to the mixed solution, and stir at 30°C until completely dissolved. The dosage standard of cetyltrimethylammonium bromide is: add 1 - 3 g of cetyltrimethylammonium bromide per 10 ml of silicate ester. S12 Drop deionized water into the solution obtained in S11 at a rate of 8 ml / min under magnetic stirring conditions, adjust the pH of the solution to 5, and age the obtained solution at room temperature for 10 h to obtain a gel. S13 Place the gel in a muffle furnace for calcination to remove cetyltrimethylammonium bromide. The calcination temperature is 400°C, and the calcination time is 1 h. After taking out the calcination product and washing it with absolute ethanol until neutral, place it in a constant temperature drying oven and dry it at 60°C, and then successively carry out grinding and filtration to obtain nano-silica powder.

[0029] S2 Take vinyl chloride monomer, N-butoxymethyl methacrylate, and waterborne polyurethane and blend and crosslink them in a ratio of 1.5:0.8:0.5 to obtain a modified PVC resin.

[0030] The method for blending and crosslinking to obtain the modified PVC resin is specifically operated as follows: S21 Take vinyl chloride monomer, N-butoxymethyl acrylamide, and aqueous polyurethane resin and mix them to obtain a resin stock solution. S22 Dilute ammonium persulfate with deionized water to obtain an initiator. S23 Take 10% of the resin stock solution and 10% of the initiator and add them to a reaction kettle. After stirring and mixing for 10 min, introduce steam into the reaction kettle and raise the temperature in the kettle to 80 °C, and carry out a polymerization reaction at 80 °C for 30 min. S24 Keep the temperature at 80 °C, continue to dropwise add the remaining resin stock solution and initiator, and the dropping time is 4 h. Stop dropping when the conversion rate reaches 99.5% to obtain a polymerization product, that is, the modified PVC resin.

[0031] S3 While blending and crosslinking, add silica filler, and the weight ratio of the silica filler to the aqueous polyurethane resin is 1:2.

[0032] S4 Take 50 parts of the modified PVC resin, 2 parts of BHT, 1 part of stabilizer, and 1 part of glycerol fatty acid ester, and stir and mix them at 80 °C to form a slurry. In this example, the added BHT belongs to phenolic antioxidants, which have high stability and antioxidant properties, and can effectively prevent the resin material from undergoing oxidation reactions, so that the PVC polyvinyl chloride pellets can resist thermal oxygen degradation. The stabilizer includes calcium soap, zinc soap, and polyols. In this example, a binary composite heat stabilizer system with the synergistic combination of calcium soap + zinc soap is added. Calcium soap and zinc soap combine with chlorine atoms to form metal chlorides, while polyols transfer chlorine atoms to calcium soap to regenerate zinc soap, and through synergistic cooperation, a good stabilizing effect is obtained.

[0033] S5 Feed the slurry into a twin-screw extruder for melt extrusion. Before extrusion, it passes through a sieve nozzle to form a fine bundle of materials. The compression ratio of the conical twin screws of the twin-screw extruder is 3.5, the screw speed is 30 r / min, and the extrusion temperature is 160 °C.

[0034] S6 The fine bundle of materials enters a horizontal mixer with a rotation speed of 30 - 60 r / min and is broken to form particles.

[0035] S7 The particles are sieved and then roll in a balling pan to form polyvinyl chloride pellets.

[0036] The polyvinyl chloride pellets prepared by the preparation method of this example have the following weight composition: 50 parts of modified PVC resin, 7 parts of silica filler, 2 parts of BHT, 1 part of stabilizer, and 1 part of glycerol fatty acid ester. Example 2

[0037] The example provides a preparation method suitable for heat-resistant stable pellets of PVC polyvinyl chloride, which is characterized by including the following steps: S1 Prepare silica filler by the sol-gel method for later use.

[0038] Preparation of silica filler, and the specific operation is as follows: S11 Mix silicate ester and absolute ethanol at a volume ratio of 1:10, stir evenly at room temperature to obtain a mixed solution, add cetyltrimethylammonium bromide to the mixed solution, and stir at 30 °C until completely dissolved. The dosage standard of cetyltrimethylammonium bromide is: add 1 - 3 g of cetyltrimethylammonium bromide for every 10 ml of silicate ester. S12 Drop deionized water into the solution obtained in S11 at a rate of 8 ml / min under magnetic stirring conditions, adjust the pH of the solution to 5, and age the obtained solution at room temperature for 10 h to obtain a gel. S13 Place the gel in a muffle furnace for calcination to remove cetyltrimethylammonium bromide. The calcination temperature is 400 °C, and the calcination time is 1 h. After the calcination product is taken out and washed with absolute ethanol until neutral, it is placed in a constant temperature drying oven and dried at 60 °C, and then ground and filtered in sequence to obtain nano-silica powder.

[0039] S2 Take vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane and blend and crosslink them in a ratio of 1.5:0.8:0.5 to obtain modified PVC resin.

[0040] The method for blending and crosslinking to obtain the modified PVC resin, and the specific operation is as follows: S21 Take vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane resin and mix them to obtain a resin stock solution. S22 Dilute ammonium persulfate with deionized water to obtain an initiator. S23 Take 10% of the resin stock solution and 10% of the initiator and add them into a reaction kettle, stir and mix for 10 min, then introduce steam into the reaction kettle and raise the temperature in the kettle to 80 °C, and carry out a polymerization reaction at 80 °C for 30 min. S24 Keep the temperature at 80 °C, continue to drop the remaining resin stock solution and initiator, and the dropping time is 4 h. When the conversion rate reaches 99.5%, stop dropping to obtain a polymerization product, that is, modified PVC resin.

[0041] S3 While blending and crosslinking, add silica filler, and the weight ratio of silica filler to waterborne polyurethane resin is 1:2.

[0042] S4 Take 60 parts of modified PVC resin, 3 parts of BHA, 2 parts of stabilizer and 2 parts of fatty acid composite ester, and stir and mix them at 80 °C to form a slurry. In this embodiment, the added BHA belongs to phenolic antioxidants, which have high stability and antioxidant properties, and can effectively prevent the resin material from undergoing oxidation reactions, so that the PVC polyvinyl chloride pellets can resist thermal oxygen degradation. The stabilizer includes calcium soap, zinc soap and polyols. In this embodiment, a binary composite heat stabilizer system of calcium soap + zinc soap in synergistic cooperation is added. Calcium soap and zinc soap combine with chlorine atoms to form metal chlorides, while polyols transfer chlorine atoms to calcium soap to regenerate zinc soap, and cooperate synergistically to obtain a good stabilizing effect.

[0043] The slurry described in S5 is fed into a twin-screw extruder and melt-extruded. Before extrusion, it passes through a sieve nozzle to form a fine-beam-shaped material. The compression ratio of the conical twin screws of the twin-screw extruder is 3.5, the screw speed is 30 r / min, and the extrusion temperature is 160 °C.

[0044] S6 The fine-beam-shaped material enters a horizontal mixer with a rotation speed of 30 - 60 r / min and is broken to form particles.

[0045] S7 After sieving, the particles roll in a pelletizing pan to form polyvinyl chloride pellets.

[0046] The polyvinyl chloride pellets prepared by the preparation method of this example have the following weight parts composition: 60 parts of modified PVC resin, 8 parts of silica filler, 3 parts of BHA, 2 parts of stabilizer, and 2 parts of fatty acid composite ester. Example 3

[0047] The example provides a preparation method applicable to heat-resistant stable pellets of PVC polyvinyl chloride, which is characterized by including the following steps: S1 Prepare silica filler by the sol-gel method and set aside.

[0048] The preparation of silica filler is specifically operated as follows: S11 Mix silicate ester and absolute ethanol according to a volume ratio of 1:10, stir evenly at room temperature to obtain a mixed solution, add cetyltrimethylammonium bromide to the mixed solution, and stir at 30 °C until completely dissolved. The dosage standard of cetyltrimethylammonium bromide is: add 1 - 3 g of cetyltrimethylammonium bromide to every 10 ml of silicate ester. S12 Deionized water is dripped into the solution obtained in S11 at a rate of 8 ml / min under magnetic stirring conditions, adjust the pH of the solution to 5, and the obtained solution is aged at room temperature for 10 h to obtain a gel. S13 Place the gel in a muffle furnace for calcination to remove cetyltrimethylammonium bromide. The calcination temperature is 400 °C, the calcination time is 1 h. After the calcination product is taken out and washed with absolute ethanol until neutral, it is placed in a constant-temperature drying oven and dried at 60 °C, and then ground and filtered in sequence to obtain nano-silica powder.

[0049] S2 Take vinyl chloride monomer, N-butoxymethylacrylamide, and waterborne polyurethane and blend and crosslink them according to a ratio of 1.5:0.8:0.5 to obtain modified PVC resin.

[0050] The method for obtaining the modified PVC resin by blending and crosslinking is specifically operated as follows: S21 Take vinyl chloride monomer, N-butoxymethyl acrylamide, and aqueous polyurethane resin and mix them to obtain a resin stock solution. S22 Dilute ammonium persulfate with deionized water to obtain an initiator. S23 Take 10% of the resin stock solution and 10% of the initiator and add them to a reaction kettle. After stirring and mixing for 10 min, introduce steam into the reaction kettle and raise the temperature in the kettle to 80 °C. Polymerize at 80 °C for 30 min. S24 Keep the temperature at 80 °C, continue to dropwise add the remaining resin stock solution and initiator. The dropping time is 4 h. When the conversion rate reaches 99.5%, stop dropping to obtain a polymerization product, that is, the modified PVC resin.

[0051] S3 While blending and crosslinking, add silica filler. The weight ratio of silica filler to aqueous polyurethane resin is 1:2.

[0052] S4 Take 70 parts of modified PVC resin, 4 parts of DTPD, 3 parts of stabilizer, and 2 parts of polyethylene wax, and stir and mix at 80 °C to form a slurry. In this example, the added DTPD belongs to sulfide phenol antioxidants, which have good heat resistance and antioxidant properties, and can effectively prevent the oxidation reaction of epoxy resin at high temperature, so that the PVC polyvinyl chloride pellets can resist thermal oxygen degradation. The stabilizer includes calcium soap, zinc soap, and polyols. In this example, a binary composite heat stabilizer system with the synergistic cooperation of calcium soap + zinc soap is added. Calcium soap and zinc soap combine with chlorine atoms to form metal chlorides, while polyols transfer chlorine atoms to calcium soap to regenerate zinc soap, and through synergistic cooperation, a good stabilizing effect is obtained.

[0053] S5 Feed the slurry into a twin-screw extruder for melt extrusion. Before extrusion, it passes through a sieve nozzle to form a fine bundle of materials. The compression ratio of the conical twin screws of the twin-screw extruder is 3.5, the screw speed is 30 r / min, and the extrusion temperature is 160 °C.

[0054] S6 The fine bundle of materials enters a horizontal mixer with a rotation speed of 30 - 60 r / min and is broken to form particles.

[0055] S7 The particles are sieved and then roll in a balling pan to form polyvinyl chloride pellets.

[0056] The polyvinyl chloride pellets prepared by the preparation method of this example have the following weight composition: 70 parts of modified PVC resin, 9 parts of silica filler, 4 parts of DTPD, 3 parts of stabilizer, and 2 parts of polyethylene wax. Example 4

[0057] The example provides a preparation method suitable for heat-resistant and stable PVC polyvinyl chloride pellets, which is characterized by including the following steps: S1 Prepare silica filler by the sol-gel method and set it aside.

[0058] Preparation of silica filler is carried out as follows: S11 Mix silicate ester and absolute ethanol at a volume ratio of 1:10, stir evenly at room temperature to obtain a mixed solution, add cetyltrimethylammonium bromide to the mixed solution, and stir at 30 °C until completely dissolved. The dosage standard of cetyltrimethylammonium bromide is: add 1 - 3 g of cetyltrimethylammonium bromide for every 10 ml of silicate ester. S12 Drop deionized water into the solution obtained in S11 at a rate of 8 ml / min under magnetic stirring, adjust the pH of the solution to 5, and age the obtained solution at room temperature for 10 h to obtain a gel. S13 Place the gel in a muffle furnace for calcination to remove cetyltrimethylammonium bromide. The calcination temperature is 400 °C, and the calcination time is 1 h. After taking out the calcined product and washing it with absolute ethanol until neutral, place it in a constant temperature drying oven and dry it at 60 °C, and then carry out grinding and filtration in sequence to obtain nano-silica powder.

[0059] S2 Take vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane and blend and crosslink them in a ratio of 1.5:0.8:0.5 to obtain a modified PVC resin.

[0060] The method for blending and crosslinking to obtain the modified PVC resin is carried out as follows: S21 Take vinyl chloride monomer, N-butoxymethyl methacrylate and waterborne polyurethane resin and mix them to obtain a resin stock solution. S22 Dilute ammonium persulfate with deionized water to obtain an initiator. S23 Take 10% of the resin stock solution and 10% of the initiator and add them to a reaction kettle, stir and mix for 10 min, then introduce steam into the reaction kettle and raise the temperature in the kettle to 80 °C, and carry out a polymerization reaction at 80 °C for 30 min. S24 Keep the temperature at 80 °C, continue to dropwise add the remaining resin stock solution and initiator, and the dropping time is 4 h. When the conversion rate reaches 99.5%, stop dropping to obtain a polymerization product, that is, a modified PVC resin.

[0061] S3 While blending and crosslinking, add silica filler, and the weight ratio of silica filler to waterborne polyurethane resin is 1:2.

[0062] S4 Take 80 parts of modified PVC resin, 5 parts of IPPD, 4 parts of stabilizer and 3 parts of oxidized polyethylene wax, and stir and mix them at 80 °C to form a slurry. In this example, the added IPPD belongs to sulfide phenolic antioxidants, which have good heat resistance and antioxidant properties, and can effectively prevent the oxidation reaction of epoxy resin at high temperature, so that the PVC polyvinyl chloride pellets can resist thermal oxygen degradation. The stabilizer includes calcium soap, zinc soap and polyols. In this example, a binary composite heat stabilizer system of calcium soap + zinc soap is added in a synergistic manner. Calcium soap and zinc soap combine with chlorine atoms to form metal chlorides, while polyols transfer chlorine atoms to calcium soap to regenerate zinc soap, and cooperate synergistically to obtain a good stabilizing effect.

[0063] The slurry described in S5 is fed into a twin-screw extruder and melt-extruded. Before extrusion, it passes through a sieve nozzle to form a fine-beam-shaped material. The compression ratio of the conical twin screws of the twin-screw extruder is 3.5, the screw speed is 30 r / min, and the extrusion temperature is 160 °C.

[0064] The fine-beam-shaped material enters a horizontal mixer with a rotation speed of 30 - 60 r / min and is broken to form particles.

[0065] After sieving, the particles roll in a pelletizing pan to form PVC pellets.

[0066] The PVC pellets prepared by the preparation method of this example have the following weight parts composition: 80 parts of modified PVC resin, 10 parts of silica filler, 5 parts of IPPD, 4 parts of stabilizer, and 3 parts of oxidized polyethylene wax.

[0067] Taking commercially available PVC pellets as a comparative example below, the heat distortion temperature test and oxidation index test are carried out on the PVC pellets of Examples 1 - 4. The specific test process is not elaborated here. The test results are as follows: the heat distortion temperature of the comparative example is 200 °C and the oxidation index is 50%; the heat distortion temperature of Example 1 is 320 °C and the oxidation index is 39%; the heat distortion temperature of Example 2 is 310 °C and the oxidation index is 37%; the heat distortion temperature of Example 3 is 315 °C and the oxidation index is 38%; the heat distortion temperature of Example 4 is 320 °C and the oxidation index is 40%. The smaller the oxidation index, the better the antioxidant performance, and the higher the heat distortion temperature, the better the heat resistance. The above results prove that the preparation method of the present invention can prepare PVC pellets with good heat resistance and stability.

[0068] The above embodiments are only the preferred embodiments of the present invention. Any simple modification, modification, and substitution change made to the above embodiments based on the technical essence of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing heat-resistant and stable granules of PVC polyvinyl chloride, characterized in that: The following steps are involved: S1 is a silica filler prepared by a sol-gel method and is ready for use; S2 takes vinyl chloride monomer, N-butoxymethyl acryloyl and waterborne polyurethane and mixes and crosslinks them to obtain modified PVC resin; S3 adds silica filler while blending and crosslinking; S4: taking modified PVC resin, antioxidant, stabilizer and lubricant, stirring and mixing to form a slurry; S5: the slurry is fed into a twin-screw extruder for melt extrusion, and is passed through a sieve before extrusion to form a thin bundle of materials; S6 The thin bundles of materials enter the horizontal mixer and are broken into particles; The S7 particles are sieved and then molded to obtain polyvinyl chloride pellets.

2. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to claim 1, characterized in that: The preparation of the silica filler is specifically performed as follows: S11: mixing silicate and anhydrous ethanol in a volume ratio of 1:10-15, stirring at room temperature to obtain a mixed solution, adding hexadecyltrimethylammonium bromide to the mixed solution, and stirring at 30-60° C. until the mixed solution is completely dissolved; S12 deionized water was dripped into the solution obtained by S11 at a rate of 5-10 ml / min under magnetic stirring, and the pH of the solution was adjusted to 3-5. The obtained solution was aged at room temperature for 8-12 h to obtain a gel; S13: The gel is placed in a muffle furnace and calcined to remove hexadecyltrimethylammonium bromide. The calcination temperature is 400-500°C and the calcination time is 1-2 hours. The calcined product is taken out and washed with anhydrous ethanol until neutral. It is then placed in a constant temperature drying oven and dried at 60-80°C. It is then ground and filtered to obtain nano-silicon dioxide powder.

3. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to claim 2, characterized in that: The dosage standard of hexadecyltrimethylammonium bromide is: add 1~3g of hexadecyltrimethylammonium bromide to every 10ml of silicate.

4. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to claim 1, characterized in that: The weight ratio of the vinyl chloride monomer, N-butoxymethyl acryloyl and waterborne polyurethane resin is 1-2:0.5-1:0.2-0.

6.

5. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to claim 4, characterized in that: The method for obtaining the modified PVC resin by blending and cross-linking is specifically performed as follows: S21: vinyl chloride monomer, N-butoxymethyl acryloyl and waterborne polyurethane resin are mixed to obtain a resin stock solution; S22 is used to dilute ammonium persulfate with deionized water to obtain an initiator; S23: 10% of the resin stock solution and 10% of the initiator are added to the reactor, stirred and mixed for 10 minutes, steam is introduced into the reactor and the temperature in the reactor is raised to 80°C, and the polymerization reaction is carried out at 80°C for 20-40 minutes; S24 maintains a temperature of 80°C and continues to drip the remaining resin stock solution and initiator for 4 hours. When the conversion rate reaches 99.5%, the dripping is stopped to obtain a polymerization product, namely, modified PVC resin.

6. The method for preparing heat-resistant and stable granules suitable for PVC polyvinyl chloride according to claim 1, characterized in that: The weight ratio of the silica filler to the waterborne polyurethane resin is 1:1-3.

7. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to claim 1, characterized in that: During the stirring and mixing process to form the slurry, the stirring temperature is 80-90°C; The antioxidant is any one of BHT, BHA, DTPD and IPPD; the stabilizer includes calcium soap, zinc soap and polyols; the lubricant is any one of glycerol partial fatty acid ester, fatty acid complex ester, polyethylene wax and oxidized polyethylene wax.

8. The method for preparing heat-resistant and stable granules suitable for PVC polyvinyl chloride according to claim 1, characterized in that: The conical twin-screw compression ratio of the twin-screw extruder is 3.5-5.0, the screw speed is 30-50 r / min, and the extrusion temperature is 150-180°C.

9. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to claim 1, characterized in that: The rotation speed of the horizontal mixer is 30-60 r / min; the sieved particles roll in the ball-forming disk to form polyvinyl chloride pellets.

10. The method for preparing heat-resistant and stable granules of PVC polyvinyl chloride according to any one of claims 1 to 9, characterized in that: The polyvinyl chloride granules are composed of the following parts by weight: 50-80 parts of modified PVC resin, 7-12 parts of silicon dioxide filler, 2-5 parts of antioxidant, 1-7 parts of stabilizer and 1-3 parts of lubricant.